Beginner drivers sometimes think that the most important quality that has motorcycle engines is the amount of horsepower, and believe that the tool will ride well, only possessing a power of more than a hundred forces. However, in addition to this indicator, there are many characteristics affecting the quality of the motor operation.
Types of motorcycle engines
There are two-stroke and four-stroke motors, the principle of operation is somewhat different.
Also on motorcycles, different number of cylinders are installed.
In addition to the native carburetor motor, you can often find injection units. And if the first type of motorcyclists are used to correcting independently, then the injection engine with a straight injection system with their own hands is already problematic. It has long been produced even with an electric motor. The article will consider the characteristics of the motorcycle engine of the carburetor type.
How the engine works
In the last type there is a minimum number of elements, thanks to which the crankshaft can rotate faster. Therefore, DOHC is becoming increasingly distributed.
Four-stroke engines have a more complex design compared to the two-stroke, as they have a gas distribution mechanism that is missing from the two-stakeholders. Nevertheless, they have become widely distributed due to the cost-effectiveness and less harmful effects on the environment.
Motorcycle engines most often are single, two and four-cylinder. But there are aggregates and with three, six and ten cylinders. The cylinders are in line - longitudinal or transverse, horizontal opposite, V-shaped and L-shaped. The working volume of motors usually have no higher than one and a half thousand cubes these motorcycles. Engine power - from one hundred and fifty to one hundred eighty horsepower.
Motor oil
Lubrication is necessary to ensure that excessive friction does not arise between the parts of the motor. It is implemented using motor oils having a resistant structure from exposure to high temperatures and low viscosity at low indicators. In addition, they do not form a nagar, are not aggressive to plastic and rubber details.
Oils are mineral, semi-synthetic and synthetic. The semi-synthetic and synthetics are more expensive, but these kinds prefer more, as it is believed that they are more useful for the engine. For the two-strokes and quottrats, various types of oils apply. They also differ in the degree of forsing.
"Wet" and "Dry" Carter
In use three ways to supply oil:
splashing;
pressure supply.
Moreover, most rubbing steam are lubricated under pressure from the oil pump. But there are also those that are lubricated by the oil mist forming due to splashing the crank-connecting mechanism, as well as the parts to which the oil flocks through the channels and grooves. At the same time, the pallet of the crankcase serves as a reservoir. It is called "wet" in this case.
In other motorcycles, a "dry" crankcase system is provided, where the oil is pumped into the tank in one section, and the other is fed under pressure to friction places.
In the dudgetnists, the lubricant occurs with oil, which is in fuel pairs. It is mixed with gasoline pre-, or in the inlet pipe it is supplied by a pump-dispenser. This last species was called the "Solid Grease system". It is especially common in foreign motors. In Russia, the system enters the engine of the Motorcycle "Izh Planet 5" and "Zid 200 courier".
Cooling system
When the fuel in the engine burns, heat is highlighted, from which almost thirty-five percent goes to the useful work, and the rest is dissipated. At the same time, if the process is ineffective, the parts in the cylinder overheat, which can lead to their encoffin and damage. So that this does not happen, the cooling system is used, which is air and liquid depending on the type of motor.
Air cooling system
In this system, the details are cooled due to counter air. Sometimes for better operation of the surface of the cylinder of its heads make ribbed. Sometimes forced cooling is used with a fan with a mechanical or electric drive. The four-strokes also carefully cooled the oil, for which the surface of the crankcase is increased and installed special radiators.
Liquid cooling system
The option is similar to what is installed on vehicles. The coolant here performs antifreeze, which is low-cost (from minus forty to minus sixty degrees Celsius) and high-boiling (from one hundred twenty to one hundred thirty degrees Celsius). In addition, antifreeze is achieved anti-corrosion and lubricating effect. Clean water in this capacity cannot be used.
Overheating of the cooling system can be caused by overloading or contamination of surfaces that take heat. Also, individual elements can be broken, because of which the fluid is found. Therefore, the cooling work must constantly monitor.
Supply system
As fuel for carburetor motorcycles, gasoline is used, an octane number of which is not lower than 93.
Motorcycle engines have a power system that includes a fuel tank, a crane, filter, air filter and carburetor. Gasoline is located in a tank, which in most cases is installed above the motor in order to grant in the carburetor. In other cases, it can be served using a special pump or vacuum drive. The latter can be found on the two-strokes.
In the fuel tank, there is a lid with a special hole where the air goes. In many foreign motorcycles, however, the air falls through coal tanks. And some have a lock on the lid.
Thanks to the fuel crane, fuel is prevented.
Through the air filter in the carburetor enters the air. The filter is three species.
The motorcycle driven by the internal combustion engine is a high-speed two-wheeled vehicle. On the device, motorcycles are divided into single (Fig. 1) and with a stroller (Fig. 2). Depending on the purpose of the motorcycles are road, sports and special.
Fig. 1. Road motorcycle "Sunrise"
Two more intermediates between the motorcycle and the bike of mechanical vehicles are available: Motovibics and mopeds.
Fig. 2. Road motorcycle with a carriage Izh "Jupiter"
Depending on the engine capacity of the engine cylinders, motorcycles are divided: on ultralight (50-100 cm 3), light (125-250 cm 3), medium (350-5 cm 3) and heavy (over 500 cm 3).
Below are the main data of road motorcycles.
Motorcycle has the following mechanisms and systems: an engine with its maintenance systems, lubricants, cooling and ignition, power transmission, driving part, control mechanisms.
Engine Converts thermal energy into mechanical, which, with a number of mechanisms, makes a motorcycle in motion.
Power transmission (Fig. 3) Throws the engine to the lead wheel developed on the crankshaft. It includes: front transmission, clutch, gearbox and rear gear.
There are three types of power transmission: chain, cardan and straight.
Chain transmission (Fig. 4, a) transmits a torque or torque of the engine with a motor circuit with a grip, and through it the gearbox, from where the rear chain on the drive wheel of the motorcycle.
When cardan transmission (Fig. 4, b), the torque from the crankshaft is transmitted through the adhesion directly the gearbox, from where with the help of a cardan shaft and the main transmission to the leading motorcycle wheel.
The direct transmission consists of a gear transmission (motor), which through the clutch mechanism and gearbox transmits an effort to the shaft, which is simultaneously the axis of the wheel.
Chassis Provides a motorcycle movement and serves as a core for fastening its main mechanisms. It includes a frame, anterior fork, wheels with tires, saddle, trunk, footboard, stand, mud shields and trailed stroller.
Control mechanisms Designed to control the motorcycle while driving, as well as for the operation of its units and appliances. Control mechanisms include: steering, brakes and controls.
Motorcycle engine, moped, scooter, quad bike, snowmobile and other similar Moto technique is an aggregate transforming thermal energy of combustable fuel into mechanical work, with which any motor vehicle (and not only) can move. In this article, more designed for beginner moto-technology lovers, I will try to describe everything in detail everything is connected with the internal combustion engine installed on the serial moto-technique.
Of course, it is impossible to describe absolutely all types of engines in one article, and it is impossible to make an immense, but it is not necessary, since I have understood the principle of operation of the simplest motorcycle engine (two-stroke and four-stroke) any moto-lover will later learn to deal with almost any motor, even Modern.
As mentioned above, internal combustion engines are installed on the motorcycle of all world manufacturers, in which the heat energy of the combustable gasoline is converted into mechanical work, to rotate the rear wheel.
Below I will describe the principle of operation and the general device of the motorcycle engine (internal combustion engine).
Principle of operation (workflow) and motorcycle engine device.
When we open a gas tank cranch (on modern motorcycles there is an automatic vacuum crane), then the fuel enters the float chamber of a motorcycle carburetor. Next, we give the movement of the piston with the help of a kickstarter (or by pressing the electro-starter button) and the piston movement creates a discharge in the cylinder and a combustible mixture begins to flow from the carburetor, consisting of a petrol gasoline looped through the air filter and vapor.
The combustible mixture begins to mix with the remnants of the exhaust gases (if the motor recently worked) and the working mixture is formed, which is compressed in the combustion chamber using the piston and then the compressed mixture is flammable at the desired torque (2-3 mm to VTT) using sparks on
Gas pressure from the combustible fuel begins to expand and move the piston down, and in turn it transmits motion through and on the motorcycle engine crankshaft. At the same time, the progressive-straightforward movement of the piston (thanks to the device of the cranked mechanism) is converted into a rotational motion, which through motor transmission and transmission (transmission) transmits the rear wheel rotation, which moves the motorcycle (or other Moto-technique). 
Well, the transformation of the thermal energy of the combustible fuel into mechanical work is and is the workflow of the internal combustion engine, while noted above, the engine piston moves in the cylinder down-top (about the pistons in more detail). And the extreme points at the top and at the bottom, which occupies the piston when moving in the motor cylinder are called the dead dots - the upper and lower (NTT and NMT).
The upper dead point is the year the piston is at the top of the combustion chamber, that is, when the piston is removed as much as possible from the crankshaft axis. Well, the lower dead point - when the piston is at the bottom - that is, it is minimally removed from the axis. Well, the distance from the upper dead point to the bottom is called the workflow of the piston, and the process that occurs in one piston stroke is called a tact.
Based on the above, if the workflow of the motorcycle engine (or other vehicle) is performed in two piston strokes, then such an engine is called a two-stroke. Well, if the workflow is performed for four piston strokes, then such a motor is called four-stroke. In more detail about the two-stroke and four-stroke engines, I will write below, but for now you should write several more important points regarding both types of engines.
The volume that is formed on the piston is when it is in the upper dead point, is called the volume of the combustion chamber (or the volume of the compression chamber). And the smaller this volume, the higher the degree of compression of the engine (about the degree of compression I will also say below), and more maximum engine speeds and the more high octane gasoline is required to work such a motor.
And the volume of the engine cylinder, from the bottom dead point to the top (full stroke of the piston), is called the working volume of the cylinder and is measured in cubic centimeters in the CIS countries and Europe, and in cubic inches (Inces) in America. If the engine is not single-cylinder, but has several cylinders (multi-cylinder), then the production volume of the multi-cylinder engine is considered the sum of the volumes of all cylinders.
By the way, the working volume of multi-cylinder ground engines is measured not only in cubic centimeters, it is easier to consider it in liters (and called the engine litter). And the sum of the working volume of the cylinder and the volume of the combustion chamber is considered the total volume of the cylinder. Well, the ratio of the total volume of the cylinder to the volume of the combustion chamber is called the degree of compression.
Well, another concept associated with motors and which are most interested in - it is power. The capacity is called the work, which is performed per unit of time and is measured in horsepower.
motorcycle engine: A - single-cylinder two-stroke, b - oxidate four-stroke engine of the Urals and Dnipro, in - two-cylinder two-stroke engine type Izh-Jupiter, 1 - cylinder, 2 - piston, 3 - rod, 4 - crankshaft, 5 - Carter.
The motorcycle engine (or other vehicle) has a crank shaft, referred to as the crankshaft (see Figure 1) of the gas distribution mechanism, the lubrication system, power supply and ignition system, and the cooling system (air or liquid) and all these systems will be described In this article, or references to other articles, as I make no sense to repeat what is already on the site.
But at first we will look at the workflow of two and four-stroke engine and wonder what they differ.
Workflow and features of a two-stroke motorcycle engine.
In the two-stroke engine of internal combustion, the workflow is carried out in just two piston strokes - see Figure 2 and gas distribution is performed using a piston. The two-stroke engine work process is carried out so: when the piston moves up, then the purge (bypass) and the outlet window are open, and the intake window is closed by the piston.
Two-stroke motorcycle engine - work process
At the same time, the cylinder of the two-stroke engine is carried out by the process of the crankcase from the fresh mixture and the release of exhaust gases. And at the end of the piston stroke (see Figure 2 b) a compression of the working mixture of air and gasoline vapor in the cylinder is made, and in the engine crankcase, the intake of fresh mixture occurs. Well, further, a compressed piston, the working mixture is flammable at the right moment with a spark plug and further combustion of a compressed mixture.
Expanding the gases are pressured on the piston and it moves down (see Figure 2 B), performing a working stroke, while purging (bypass) and exhaust windows are closed, and the inlet window is open. Further, in the cylinder of the two-stroke motorcycle engine, the combustion of the working mixture ends and the piston continues to move downwards.
In the two-stroke motor crankcase, the intake of the fresh mixture and moving down the piston closes the inlet window and the preliminary compression of the combustible mixture begins in the crankcase (see the same figure 2 V).
Then, in the second half of the stroke of the piston down, purging (bypass) and the outlet windows are open (see Figure 2 A), and the intake window is closed by the piston. In this case, the purge occurs, with which the fresh combustible mixture contributes to cleaning the cylinder from the exhaust gases that go through the open outlet window (windows). Well, again, in the two-stroke engine crankcase, a preliminary compression of a combustible mixture is performed and it is shown to the cylinder (cylinder bypassing in the cylinder is shown by arrows in Figure 2 A).
By the way, purging in two-stroke engines (by the location of the windows) can be transverse and return-loop. Transverse purge is when the bypass and exhaust windows are located opposite each other (diametrically opposite). And on old engines on the piston's donkey there was a special comb (a peculiar reflector on the piston), with which the fresh mixture is directed upwards and displaces from the cylinder of Motograde exhaust gases.
The cylinder of the two-stroke motorcycle engine: 1 - intake canal, 2 - exhaust pipe, 3 - bypass (purge) channel.
Later, on more modern two-stroke engines from the ridge, they refused, as the turnover increased and the more light piston was already required (and his ridge was dried). Well, the ridge turned out to be unnecessary, since they began to use the return-loop two-channel (or multi-channel) purge (see Figure 3).
With such a purge, as can be seen from Figure 3, graduation and purge windows began to position on one side of the cylinder and the fresh combustible mixture reflected by the return flow, blows out the exhaust gases.
The workflow of the four-stroke motorcycle engine.
As it is clear from the title, in the four-stroke engine, the workflow occurs for four piston strokes, and the workflow (all tacts) is shown in Figure 4. But first it should be said that the main difference between the four-stroke engine from the two-stroke lies not only in the number of clocks, and also In the fact that in the four-stroke motor, gas distribution is carried out not by the piston (as in a two-stroke engine), but using the valve mechanism.
Four-stroke motorcycle engine - workflow.
More modern and forced motors have not two, but four valves for each cylinder, but we will talk about the system of gas distribution a little later. And first consider in detail the workflow of the four-stroke motorcycle engine.
The first tact is the intake tact, in which the piston in the cylinder moves down from the NTC to NMT. In this case, the intake valve and the combustible mixture comes through it into the engine cylinder, and the exhaust valve is closed.
The second beat is a compression tact. When the piston passes the bottom dead point and start moving up to the NTC, the second tact begins - the compression tact of the working mixture. By this point, the intake valve managed to close and the exhaust valve also remains closed (both valves are closed and a combustible mixture is compressed).
Well, almost at the very end of the compression tact, when the piston did not reach the VMT (approximately 2 - 3 mm, all motors have a slightly different arc angle) There is a discharge between the electrodes and the electric spark is a compressed combustible mixture.
The third beat is expansion tact - work move. A compressed combustible mixture is quickly burning, combustible gases are expanding and pushing the piston down (from NTT to NMT) at the same time, the work move is happening, that is, the third tact of expansion and work. And it is in the third tact that the energy of the combustible fuel combustible in mechanical work occurs.
The fourth tact is a release tact, in which the piston moves from NMT to the VMT and at the same time the intake valve remains closed, and the graduation is already opening. With a fully open exhaust valve and, when approached up, the piston is removed from the cylinder and the combustion chamber of the exhaust gases into the environment.
Disadvantages and advantages of single-cylinder four-stroke motorcycle engine.
Four-dimensional single-cylinder engines have both pros and cons.
Their disadvantages should be noted:
- They work jolts (a little uneven, although there is its own chip in it) since from all four closures, for two crankshaft turns, there is only one worker tact, in which the engine makes work. And with the other three auxiliary tacks, the energy is consumed and therefore four-stroke engines have a slightly smaller power than the two-stroke (with the same parameters).
- There is an intermittent processes of filling fresh fuel mixtures and exhaust exhaust gases. And each of these processes is carried out throughout one of the four clocks, and then stops. This worsens cleaning from exhaust gases and also worsens the filling of fresh fuel mixture.
- It is not enough quickly to increase the number of revolutions and from this have insufficient eating (with the same parameters compared to two-stroke motor). But on modern motors, thanks to more valves (and cylinders), some of the disadvantages are almost completely eliminated.
And advantages of four motorcycle engines (and vehicles) should be noted the main:
- Much better efficiency, compared with more voracious two-stroke engines.
- A greater rings and piston resource (as there are no windows in the cylinder) and more easy repair.
- Increased motorcycle or other motorcycle motorcycles increases, since four-dimensional single-cylinder motors have a good traction on the bottoms, despite their uneven work, especially on small turns (shoes).
- More environmentally friendly engines (compared to the two-stakeholders, which are already prohibited and do not fit into the euro norms).
Let's start with a crank-connecting mechanism. This mechanism not only perceives the large pressure expanding with the combustion of the working mixture of gases, but the main purpose of this mechanism is the transformation of the straight movement of the piston in the cylinder into the rotational motion of the crankshaft.
Also, the motorcycle engine consists of a cylinder, its heads, piston C, connecting rod, flywheel, crankshaft (the same crank) and crankcase.
Cylinder Engine Designed to direct the movement of the piston. Together with the piston and cylinder head, it forms a closed chamber, in which the workflow occurs.
Cylinder Motorcycle Ural with a neckline below the oil-cutting tube.
Cylinders made of cast-iron castings, and more modern from aluminum alloys, with inserted cast-iron sleeves. And the most modern cylinders do not have a cast-iron sleeve, and the aluminum cylinder is coated with a wear-resistant Nicarile coating, or even more modern (applied by electroplating).
The inner surface of the cylinder is polished to reduce the friction, and for better oil retention on the walls of the cylinder - it is choning (about the honing of the cylinder of the motorcycle, and about the restoration of nicarial cylinder).
The cylinders of the two-stroke engines in the sleeve have windows that overlook the bypass, intake and outlet channels. Also on the cylinders of the two-stroke engines there is a nozzle (or two nozzles) with a thread (or flange), for fastening the outlet pipe, as well as there is an flange for fastening the carburetor (on the modern two-strokes, the carburetor flange is directly on the crankcase, and not on the cylinder, since The inlet of the combustible mixture occurs through the petal valve directly to the cavity of the crankcase.
And the cylinders of four-stroke motors are missing windows and channels, since the gas distribution occurs in the engine head using the valve mechanism (I will write the gas distribution system below).
Cylinder head It is made of aluminum alloy and is attached from above on the engine cylinder. The inner surface of the head, in the area of \u200b\u200bdocking with a cylinder, has a spherical surface and forms a combustion chamber, in which there is a threaded hole for the ignition candle.
Two-stroke motorcycle engines have a simple design, and besides the edge for cooling, the candle hole and the spherical combustion chamber in them there is nothing more (well, the plane for docking with the engine cylinder).
And the heads of the cylinders of four-stroke engines are more complex according to the design, since it has a gas distribution mechanism. There are also intake and exhaust channels, there are still valves, the relief supports for the valve drive, the holes for the roding (there are no rod holes (there are no rods on more modern rods, since the valves are opened directly from camshaft camshafts).
For the docking of the bottom plane of the head and the upper plane of the cylinder, a perfectly smooth surface is made and a copper gasket is used when assembling, and on the multi-cylinder engines, a gasket of a reinforced canvas is used, saturated with graphite.
Piston (or pistons) motorcycle engine, or any other technology is one of the most important details, as it perceives significant loads from the pressure of gases, as well as transmits an effort from the pressure of expanding gases to the connecting rod, and in addition, the piston moves in a cylinder at high speed (especially Maximum revs).
Motorcycle Engine Piston: 1 - Compression Ring, 2 - Rodyshko Piston, 3 - Piston Finger, 4 - Returning Ring, 5 - Barley, 6 - Schitun, 7 - Piston Skirt.
The engine's piston is shown in Figure 5 and has a bottom, skirt and bugs, but the bottom can be convex, flat or shaped. The convex bottom is considered more durable, reduces the nagaro formation, but four-dimensional motors in a convex bottom have to make lines for valves.
Flat bottom less durable, but make it easier. Well, the shaped bottom of the piston was made in the 50s - 60 years of the last century and was used on the two-stroke motors of some motorcycles and scooters (for example, VP-150 or VP-150M) and was made in the form of a ridge reflector (see Figure 2 above), providing a transverse blowing in Old two-stroke engines.
The piston has grooves (two, three in two-stroke, or three, four grooves in four-stroke motors) in which piston rings are installed using special devices. And the piston finger is inserted into the holes of the bobbies 5, which is put on the top head of the rod.
The motorcycle engine piston or other equipment has not just a smooth shape of the cylinder. Since in the engine's work process, all parts, including the piston heated and of course expand (thermal expansion). And the piston is heated and expands unequal throughout its length, because at the top it is heated more, and hence it is expanding more, and at the bottom less.
Well, in order to provide the same working gap between the piston and the walls of the engine cylinder, the piston is made a bit cone (to the bottom cone expands). And in the area of \u200b\u200bBreaki, the piston makes a little oval. The cone and oval are made within the limits of the hectare and geometry of the cone and the oval depends on the material from which the piston is manufactured.
Piston rings 1 is shown in Figure 5 and in the figure on the right, just below (on the improvement of the piston rings) put in the grooves of the piston and the rings are compression and oil-oil. Compression rings seal the gap between the piston and the walls of the cylinder, and the oil separable piston rings are used only in four-stroke motor, to remove excess engine oil, which through the holes in the oil-leaf rings and the piston merge back into the engine crankcase.
1 - Cylinder, 2 - Ring, 3 - Property.
Well, in order for the piston rings to be elastic, when they are making a billet, the ring is cut, then a certain gap is made, then compressed in a special mandrel and processed again. The location on the ring in the area of \u200b\u200bthe cut is called the lock, well, the gap in the castle in the piston rings should be no more than 0.1 - 0.5 mm (there are a little more heavy motors).
To eliminate the breakthrough of gases during the operation of the motor, the piston rings are installed on the piston so that the castles of the rings are not located one below the other (for example, if there are three rings, then the locks are located under 120º relative to each other). And in order to exclude the berths of the rings in the grooves and the breakdown of them from entering the windows in two-stroke engines, in the grooves of the pistons of the two-strokes, locking pins will be pressed.
And so that the ring is more densely, at the ends of the locks from the inside, the shading is cut out. Rings made of special gray cast iron, and on some motors (for example, sports) rings are made of high-quality steel and the top ring is chromat.
Piston finger 3 (see Figure 5) Designed for a piston and connecting rod hinged. The finger is made of high-quality steel and its outer surface is undergoing quenching and cementation to eliminate rapid wear. Well, in order to prevent the axial displacement of the finger in the bobbs, they make special grooves in which stop rings from elastic steel are inserted (in some engines, where the finger is pressed in bugs with tension, stop rings are not used).
Rod. Shown in Figure 5 under the number 6, as well as in the photo on the right. It is very detailed about the connecting rods and what they are, I wrote a separate article and you can read it. Well, in this article I will write only the main one.
The rod in the motorcycle engine, and in any internal combustion engine connects the piston with the crankshaft and consists of the top head of the connecting rod, which through (or needle bearing) and the piston finger joined the piston. The rod consists of a rod (as a rule of a height), well, from the bottom head, which is connected to the crankshaft neck through the sliding bearing (liner) or through the rolling bearing.
If the lower head of the rod is indefinitive, it is connected to the crankshaft (with a finger) with a roller rolling bearing (like most domestic two-stroke motorcycles and mopeds). On engines that have an oil pump and a pressure lubricant system, the lower head is made by the connector (of two halves) and is tightened by bolts and nuts, and the sliding bearings are used as bearings - so-called thin-walled.
To lubricate the lower and top head of the connecting rod in two-stroke engines, oil is used in a mixture with gasoline. And in engines with liners, the oil is supplied to the bottom head (and inserts) under the pressure generated by the oil pump (for example, both in the majority of foreign cars with four-stroke motors), and the oil is supplied to the top head with splashing.
A high-quality surface for a piston finger, b - the coarse surface due to irregularities is quickly covered by corrosion.
On some motorcycles (for example, domestic K-750, Ural, M-72), the lubricant of the lower heads of the rods is produced, received by splashing into special oil-trap crankshafts, of which the oil, under the action of centrifugal forces, goes through specially drilled channels to Rolling cakes and roller bearings of the lower head of the rod.
Flywheel. The engine flywheel is intended for uniform rotation of the crankshaft, as well as to facilitate the start of the engine and the motorcycle start. In four-stroke motorcycle engines, the flywheel is a separate detail located on the crankshaft conical pinion and also the flywheel is the basis for fastening the clutch mechanism.
On the balancing of the crankshaft along with the flywheel (in the garage conditions), I wrote a separate article that you can read. Well, in two-stroke engines, the flywheel is an integral part of the crankshaft (the so-called crankshaft cheeses, or counterweight).
The crankshaft it serves as an engine for the perception of effort from the piston (or pistons, if the engine is multi-cylinder) and the connecting rod, converting the transmissive movement of the piston into the rotational motion of the motor transmission and then transmissive transmission, and further on the drive wheel of the motorcycle, or another vehicle . How to choose a crankshaft in the store and not to buy a fake, I described in detail.
Crankshaft of a two-cylinder domestic opposite engine (K-750, M-72)
Crankshafts are whole (cast or forged, for example, in the Dnipro motorcycle engine) - on most motorcycles with four-dimensional multi-cylinder engines, which in the lower head roller are used crankshaft.
Also crankshafts are composite (for example, both on the Ural motorcycle and on most of the two-tone domestic motorcycles and mopeds). Composite crankshafts use if roller rolling bearings are installed in the bottom head of the roller. In detail about the extension of the resource and repair of the composite crankshaft, I described in detail here in.
The crankshaft of the motorcycle engine (and other motorcycles) has indigenous cakes (so-called trimps), as well as connecting rod cervix (the so-called finger of the lower head of the rod), well, and cheeks and counterweights that equilibrate the rotating masses of the crank mechanism.
On most domestic (and some imported) two-stroke motor turbines, counterweight and flywheels are made in the form of one solid part. Well, the connecting rod neck (the lower head of the rod) and the two cheeks form a detail called crank (or a crank-connecting mechanism).
On engines, in which roller rolling rolling rolling bearings are used in the lower head of the connecting roller shafts. Compounds in which parts are compressed with each other. For example, on the IL planet engines, sunrise, Minsk (and other single-cylinder two-stroke domestic motors) crankshafts consist of two flywheels, rod cervical (finger) and two rooted necks) crankshaft).
Well, the crankshafts in two-cylinder two-stroke domestic motorcycles (for example) consist of two shafts, which are connected by a massive flywheel. Also crankshafts of most mopeds and scooters (both imported and domestic) consist of two pitch with counterweights, one rod cervix and two native crankshaft necks.
All these shafts are compressed and for replacing the worn roller bearing, only disassembled with the overhaul of the crankshaft, which you can read or the second article by clicking on the link above.
Crankcase. Carter serves to mount almost all parts of the engine, a crank-connecting rod mechanism, cylinder (or cylinder block in multi-cylinder engines), gas distribution mechanism, for fastening the gearbox and for motor transmission, and of course to protect all internal parts from dust, water and water and mud.
Polished Opposite Engine Carter (and gearbox).
Motorcycle Carters are dry type (for example, at Motorcycles Harley Davidson - the photo above), in which the oil pump and the oil tank are located separately from the crankcase (about such more). And there are wet type, in which the oil pump is located inside the crankcase, and the engine oil is located in the pallet under the crankcase and such motors are most common (all domestic four-stroke engines and many imported).
But it should be noted that the two-stroke engines the crankresses are so-called pumping chambers where a combustible mixture of the carburetor comes, in the crankcase, the mixture is pre-compressed and then enters the engine cylinder. And therefore, the carters of the two-stroke engines must have increased tightness (always a working crankshaft seal) and have a message with the atmosphere only during the supply of a combustible mixture of the carburetor.
It should also be clarified that two-stroke dual-cylinder engines (for example, domestic Izh Jupiter engines) in the crankcase there are two separated chambers for each of the cylinders. These two separated cameras are well isolated from each other, in order not to break the gas distribution in each single cylinder.
When the engine is running in the crankcase, an increased pressure is created and that the engine oil is not supplanted outside (for example, through the plane of the crankcase connector, fuel and drain plugs, bearings and shafts, screws, etc.) between the crankcase planes, between the flanges of cylinders and their heads, between The plugs and other parts are set by the sealing gaskets, and the bearings of the crankshaft are installed and the glands are installed (about the crankshaft seals, and the camshaft seal).
When installing the seals, they are installed so that the spring, the compacting edge, is located on the part of the increased pressure (from the side of the inner cavity of the crankcase). Well, to increase the tightness of the drain and fuse plugs, gaskets (rubber rods) are installed under them and after drain or pouring the plug oil tightly tighten.
Motorcycle engine gas distribution mechanism.
This mechanism provides inlet to the cylinder (or in cylinders) of the engine of fresh combustible mixture and the release of exhaust gases. In the two-stroke engines of motorcycles, scooters and mopeds (scooters), tight-blanched gas distribution using a piston. And in four-stroke engines, gas distribution is carried out using the valve mechanism.
Blipped gas distribution. This gas distribution is carried out on two-stroke engines and here, as noted above, the inlet of the combustible mixture, as well as the cross-step of its engine crankcase in the cylinder and the release of exhaust gases is carried out by the piston. The piston, as the spool opens and closes the windows when the top-down movement and thus adjusts the gas distribution in the two-stroke motor.
Valve gas distribution. With this gas distribution of the inlet of the combustible mixture and the release of exhaust gases occurs through the channels in the engine head and these channels open and close at the right moment using valves tightly adjacent to the seeds (valve seat - this is the supporting conical surface to which adjoins when closing the valve, plate Valve - about the shoes of the valves and the restoration of worn seats).
Valves (usually two on the cylinder) may have the lower location at which the valves are installed in the cylinder (for example, antique domestic M-72 or K-750 motors). Or the upper arrangement at which the valves are installed in the cylinder head, as on the motorcycle engine of the Dnieper or Ural, and in general, all modern motorcycle engines. And the most modern motors have not two valves, but four and even five.
The mechanism of gas distribution of the low-voltage motor motorcycle engine (type K-750): 1 - the crankshaft gear, 2 - gear of the camshaft, 3 - Valve's guide sleeve, 4 - valve, 5 - valve pusher, 6 - camshaft, 7 - cam.
At the bottom location (see Figure 6), the mechanism consists of inlets and exhaust valves with springs, and there is also a distributional shaft 6, the cams 7 of which pushers 5 are pressed with rotation, and those in turn are put on the end of the valve rod.
Well, the drive (rotation) of the camshaft is carried out with the help of gear 2, based on the camshaft, and rotates its gear 1, placed on the crankshaft. Gear 1 has twice the number of teeth than gear 2, and therefore the camshaft rotates twice as slower than the crankshaft.
At the top arrangement of the valves shown in Figure 7 (on more modern motorcycles), the valves are located in the head and besides the parts listed above there are still 3 and rods 3 (for example, both on the engines of the Urals and Dnipro).
The mechanism of gas distribution of the upper electoral engine with the bottom camshaft.
And on more involuntary most modern motorcycles, the rods and rocker groups are missing (since they would hang on large speeds), and the cam is pressed on the valve end (through or through hydraulic pushers).
Read more about the details of the gas distribution mechanism read below. 
4 or 7 valves (see Figures 6 and 7 above) are needed in the engine for opening or closing at the desired moments inlet and outlet channels in the head and the valve consists of a plate and a rod. The valve plate has a tapered chamfer, which in domestic motorcycle engines has 45 degrees relative to the valve rod. Well, the valve spring provides the landing plate of the valve on its saddle when closing, and holds the valve in the closed state.
Pushers 5 or 4 (see Figures 6 and 7 above) transmit a force from camshaft to the end of the valve rod (with a low-appaped mechanism), and with a topless mechanism, the pushers transmit force on the bar, and the rod is already through the adjusting bolt pushes the valve end. In more modern engines there are hydraulic pushers, which, under the action of oil pressure, automatically adjust the desired valve gap.
Pushers in lower motors on one side have a threaded hole for an adjusting bolt (for). And the pusher in the topless motors has a spherical tip for the support of the rod, and on the other hand, the pusher of both the low-tang-valve and topless motorcycle engine has a flat solid surface for support in the camshaft camshape.
When operating any engine, the valve rod and other parts are heated and due to thermal expansion of the valve rod extends. From this, the valve plate after heating will not be tightly lay down to his saddle and the normal will break. That this does not occur and the valves were tightly closed both in cold condition and after heating, between the valve and the pusher (or between the valve and the rocker) in the cold state, it is done with a thermal gap.
Camshaft Designed to open and closing intake and exhaust valves at the right moment (in a specific sequence). The camshaft, both the motorcycle engine and any other vehicle, has the same amount of cams as valves.
Also camshaft has support cakes, for planting in bearings (sliding or rolling) and a neck with a key groove to attach the drive gear 2 (see Figure 6 above).
In front of the camshaft of heavy domestic motorcycles there is a cam, for opening the contacts in the interrupter of the ignition distributor. There is also a supporting surface to embed a runner (rotor with weight of the ignition timing).
Also on the distribution shaft (on the other side) there is a worm gear of the oil pump drive (for example, in heavy domestic motorcycles K-750 M, M-72, M63). By the way, to increase the resource of the camshaft, it should be modified a little (read more about it here).
Rods - these details are not available on all engines, but only on motors with the lower arrangement of the camshaft (for example, on our domestic upper valve heavy motorcycles, the Urals and Dnipro). On more involuntary and modern engines with the arrangement of camshaft (or camshafts) in the head, the rods are absent as unnecessary.
The rods are duraluminum tubes or rods, at the ends of which are spacing steel and tempered tips with a spherical surface at the end. Response spherical surfaces are made at the ends of the rumor and the ends of the pushers in which the tips are based on the rudder.
The rockers are shown in figure 2 in Figure 7, just above and they serve to transmit effort from the rod to the end of the valve rod (for opening the valves) and are a two-bearing lever planted on the axis. At one end of the rocker, a threaded hole was made into which the adjusting screw with a lock nut is screwed down, and on the other there is a spherical support for the end of the rod end.
Well, on any motorcycle engine, or any other Moto-technology still has, as well as a lubricant system and a system that I will not write about this article, since I have written in several articles in several articles in several articles. which will be given a little below.
I will only say that the power system consists of, benzo-wire, benzo-kranel, fuel and air filters. In more modern motorcycles, the nutrition system is equipped with fuel injection and the maintenance of injection motorcycles
Well, the lubricant in two-dimensional domestic engines is the simplest, since gasoline is simply diluted with oil in a gas tank, and in more modern two-stroke engines there is a separate oil tank, from which the oil, with a plunger oil pump, is injected into the carburetor diffuser, where it is mixed with gasoline .
It seems to be everything, I hope this article about the motorcycle engine and all its systems will be useful for novice motorcyclists, success to everyone.
As you know, the internal combustion engines (DVS) are three types, namely the two-stroke, four-stroke and rotary. The latter are not very common but some motorcycle producers are still used (triumf).
General device and engine operation
Internal combustion engines (internal combustion engine) are installed on the motorcycles, in the cylinders of which the thermal energy of the combusting fuel turns into mechanical work. The reciprocating movement of the piston, perceiving the pressure of the gases, is converted into the rotation of the crankshaft by means of a crank-connecting mechanism, which consists of a cylinder, piston with rings, piston finger, connecting rod and crankshaft. The extreme positions of the piston moving in the cylinder are called dead dots - the upper dead point (NTT) and the bottom dead point (NMT). The distance from VST to NMT is called a piston move, and the formed space - the working volume of the cylinder (see 3). The full internal volume of the cylinder consists of the working volume and volume of the combustion chamber. The ratio of the total volume to the volume of the combustion chamber is called the degree of compression; What it is higher, the more efficiently the engine workflow occurs. Modern engines have a compression ratio of 9-10 units (sports models have greater values).
Piston internal combustion engine
Two- and four-stroke engine, the working process flow and the design design are somewhat different.
Four-stroke engines
In four-stroke engines, the working cycle occurs in four piston strokes (clock) and two crankshaft turns: inlet - the piston is lowered from the NTC and sucks the combustible mixture through the open intake valve; compression - the piston rises from NMT compresses the working mixture with the valves closed; Working - the mixture burns, igniting the electric spark, and the resulting gases, expanding, move the piston down (the piston move is called workers, because during it and useful work); Issue - moving up the piston pushes the spent gases through the open exhaust valve.
Four-stroke engine
Two-stroke engines
In two-stroke engines, one working cycle occurs in one crankshaft turnover. Another feature is the absence of valves (intake and graduation) with a mechanical drive. Their role is performed by the piston itself, opening and closing special windows and channels on the cylinder mirror, well, on some engines, a petal valve is installed on the inlet. The volume of the crankcase under the piston is also used in gas exchange.
Two-stroke engine workflow
When the piston moves up from NMT, an inlet of the working mixture occurs in the rowing space, and in the supravnev, first the outstanding of the exhaust gases remaining from the previous cycle, and later, when the windows are closed by the edge of the piston - compression. About the VMT mixture in the combustion chamber is flammified by electrical spark, which is generated between the electrodes of the candle. The burning fuel and air mixture expands and pushes the piston down - the working stroke occurs. Having dropped about 2/3 of its turn, the top edge of the piston opens the windows in the cylinder. The exhaust gases under pressure extend through the exhaust window to the exhaust pipe. Through other windows in the cylinder, fresh charge from the cavity of the crankcase, where the descending piston creates overpressure. This flowing of the mixture is called purge, and windows and channels are purged.
Modern two-stroke DVS have multichannel (3-7 channels) return-loop purge. In addition, the inlet to the cylinder is the reverse plate (petal) valve, which controls the cutter vacuum. During the intake to the Carter (the piston moves from NMT to the VTM), under the action of a vacuum in the pouring space of the valve plate, opens the passage of a combustible mixture from the carburetor. With the reverse movement of the piston (during purge), overpressure in the crankcase closes the valve plates, preventing the reverse ejection of the mixture from the crankcase in the carburetor. The petal valve improves the cylinder filling, increases the power and efficiency of the engine, especially on the small and average rotation frequencies of the crankshaft. Many engines also have a special mechanism that changes the height of the exhaust window (which means the duration of the output), depending on the rotation frequency of the engine of the engine (the so-called "controlled issue"). Despite the measures taken to improve the gas exchange of two-stroke engine, some of the mixture goes with the spent gases, which reduces their economy compared to four-strokes.
The workflow is both two- and four-stroke DVS occurs in the cylinder. The piston moves along the inner surface (mirror) of the cylinder or the plug-in sleeve. In modern engines, instead of steel or cast iron sleeves, carbide nickel-silicon compositions are used ("NAZYL"), sprayed directly on the aluminum base of the cylinder. Depending on the accepted type of cooling system, the cylinder shirts have edges (air cooling) or internal cavities for the coolant passage.
Piston Perceives the pressure of gases during the combustion of the working mixture. It consists of the upper and lower parts (respectively, the head and skirts) and the bunches of the fastening of the piston finger. The bottom shape is flat or convex, four-stroke engines in the bottom often make removing valves. In the piston skirt, the two-stroke engines are made of cutouts through which the combustible mixture passes, because these engines have a piston controls gas distribution (intake, purging and releasing).
Pistons of two-stroke (a) and four-stroke engines (b)
1 - piston head;
2 - samples under the valves;
3 - compression rings;
4 - scale ring;
5 - Burars fastening the piston finger;
6 - piston skirt;
7 - cutout under the purge window;
8 - oil cavity (refrigerator);
9 - cutout for an additional purge window
The head of the piston has thickened walls in which 1-3 compression rings made from special cast iron or steel are placed. These rings compact the gap between the piston and the cylinder mirror, are warm in the cylinder walls. Four-stroke engines, in addition to the compression rings, there is an oil surcharge ring on the piston, removing excess oil from the cylinder mirror.
Goes serve as a support for the piston finger, they have grooves for a locking ring and a hole for lubricating oil fog. Often in the zone of buses, on the outer surface of the piston, they make special recesses - refrigerators.
The skirt sends the movement of the piston. Due to the unequal thermal expansion of various parts of the piston of its outer surface, the complex shape is given: a barrel-shaped (conical) height and oval - around the circle. Pistons made of high-quality aluminum alloys with a large silicon content, withstanding high thermal and mechanical loads, and at the same time possessing a low expansion coefficient.
Piston finger Hinged joins the piston with a connecting rod. Typically, a floating flooring of the finger in the piston bosses and the top head of the connecting rod is, its fixation from axial displacements is carried out by spring retaining rings in bosses.
Shatun. Transmits an effort from the piston to the crankshaft and consists of a rod (of a height or elliptic section) and heads: upper and lower. Depending on the type of engine and the applied lubrication system, the connecting rod heads are performed with bearings. slides (with sleeves or liners) or rolling (roller, needle). When the sliding bearing (liner) is used in the bottom head, the head itself is executed. In the case of the use of a needle bearing, the head is performed by an indefinite and the bottom neck of the shaft will be pressed into the cheek.
Schituns
a - with the detachable lower head ("Dnipro");
b - with an in-no one's head ("Ural");
1 - connecting rod;
2 - connecting rod bolt;
3 - rod;
4 - the bearing separator of the lower head roller and rollers;
5 - Inserts
Crankshaft Perceives effort from the piston (through the connecting rod), converts it to rotational movement and then transmits the torque to the transmission. In addition, other systems and mechanisms are driven from the crankshaft: gas distribution mechanism (timing), oil pump (in four-stroke engine), the generator, the cooling system pump, balancing shafts. Depending on the number of engine cylinders and a structural circuit, the crankshaft may have one or more knees, each of which is formed by two checkers and rod cerv. Between the knees and at the edges of the shaft there are indigenous necks based on bearings.
Crankshafts are made of composite, or intimidate (solid). The type of bearings of its supports (indigenous shek) depends on the used lubrication system. To increase the smoothness of the engine operation (after all, only one stroke of the piston is a worker, and the rest are one at the two-stroke engine, and three of the four-stroke - require energy costs) crankshafts have a remote flywheel, massive cheeks and counterweight. In addition, many modern engines have special balancing shafts, driven by gear transmission from the crankshaft.
Crankshaft twin-cylinder engine
b - solid ("Dnipro");
1 - connecting rod with a slight head and roller bearings;
2 - counterweight;
3 D Motorcycle Engine
Four-stroke internal combustion engine. How it works?
Disassembly of the engine Honda CBR929RR (part 1).
The first part of the terrible video disassembly of the Honda CBR929RR motorcycle engine.
In the engine, someone settled and growls, rattling, knocking.
Dicks decided to find out who lives there and expel it.
To do this, unscrew all attachments: covers, generator, drive, etc.
The closer to "someone else's" - the worse ...
Crankcase perform a straight or with the plane of the connector (longitudinal, transverse). In four-stroke engines, the crankcase (or its pallet) is usually a tank for oil flowing from the lubricated parts. Many engines have a common crankcase with adhesion and gearbox. In two-stroke multi-cylinder engines, the volume of the crankcase of each cylinder must be separated from others, it complicates the design of the crankcase with the number of cylinders from two or more.
Tour distribution in four-stroke engine Controls the distribution (or cam) shaft, which rotates twice as slower than the crankshaft. When rotating the camshaft with its protrusions (cams) interacts with pushers, which directly or through the gear ratio (rocker, rocker) open valves (intake and graduation); Their closure occurs under the action of valve springs. Time periods when intake and exhaust valves are open are called gas distribution phases; They are agreed with the piston moves.
Four-stroke motor timing phase diagram
1 - opening of the inlet valve;
2 - closing the inlet valve;
3 - closing of the exhaust valve;
4 - opening of the exhaust valve;
angle "A" - overlapping valves
For a better filling of the cylinder of the combustible mixture, the inlet phase begin when the piston has not yet reached the VMT. With the further progress of the piston from VTT to the NMT, it sues through the open valve combustible mixture; Finish the inlet after the passage of NMT, when part of the mixture enters the inertia cylinder. The cleaning of the cylinder from the exhaust gases is also beginning at the end of the expansion stroke, when the piston has not yet reached NMT, but there is an overpressure in the cylinder. Then, when the piston from NMT, the piston pushes the exhaust gases. Close the exhaust valve after NTT to give parts of the exhaust gases to leave the inertia cylinder. Thus, there is a period of time when both valves are open, it is called "overlapping valves". Each model of the four-stroke engine has its optimal phases of gas distribution, which are specified in the plant of the camshaft camshaft profile. Some newest motorcycle engines have special devices to change the gas distribution phases depending on the rotation frequency of the crankshaft.
Multiple types are used on modern four-stroke Timing: OHV, OHC, DOHC.
Schemes of gas distribution mechanisms
|
a - OHV, |
7 - plate (tie); |
In the OHV scheme located in the cylinder head valves are given from the "lower" camshaft by pushers, rods and rockers; The design does not provide a clear operation of the mechanism at high frequencies of the crankshaft rotation. OHC type thrm engines have a "upper" camshaft acting on valve pushers by levers (rockers); The shaft is driven by a chain or a toothed belt. In modern multiclapped heads with 4-5 valves on the cylinder, two camshafts are used, each of which their cams directly affects the valve pushers (DOHC scheme). This design has a minimum of parts and because of this, the inertia of the valve drive is reduced, which makes it possible to increase the rotation frequency of the crankshaft of the engine, and hence its power; Mercus type DOHC are becoming more widespread.
Scheme of work Ohv.
Camshaft Speed \u200b\u200bfrom the crankshaft toothed, chain transmission or by means of a toothed belt. In the last two cases, engines have tensioners and chain calm (belt).
For the normal operation of the valve mechanism between the valve rod and its drive, there should always be a heat gap (0.05-0.15 mm). When there is no gap, the valves are closed loosely, as a result of which they burn and fail. With an increased gap, they are not fully open (power is lost) and, in addition, knock. Many engines of foreign motorcycles have the timing GRM with hydrocommovers (operating from pressure in the lubrication system) automatically supporting the required valve gaps. If such a system is not provided, the gap is regulated during the maintenance (then).
Four-stroke engines structurally complicated two-stroke, since they are additionally GRM and lubrication system. Nevertheless, since the 70s of the twentieth century, they have preferential distribution on motorcycles due to more "clean" combustion and better efficiency. Currently, in developed countries, motorcycles with two-stroke engines have limited use - these are old models, sports motorcycles and mopeds; In the foreseeable future, in particular in Europe, a complete cessation of the production of these engines is expected due to the extremely negative environmental impact.
Cylinders of motorcycle engines most often happens 1, 2 and 4, although there are 3-, 6- and even 10-cylinder. They have a variety of arrangements: row (longitudinal and transverse), V- and L-shaped, horizontal opposites. The operating volume of motorcycle engines usually does not exceed 1500 cm3, power 150-180 hp
Location of cylinders of modern motorcycles engines
|
a - single-cylinder two-stroke; |
e - four-stroke V-shaped with a transverse arrangement of the crankshaft; |
Engine lubrication and cooling systems
Lubrication parts of DVS are needed to reduce friction between them and remove heat. It is carried out by motor oils that have resistance to high temperatures in combination with a low viscosity at low temperatures (for a confident engine start). In addition, motor oils should not, when combustion, form a NAAR, should not be aggressive with respect to rubber seals and details from plastics. For lubrication are used mineral oils(derived from oil by distillation), semi-synthetic and synthetic. Semi-synthetic oilspresent a mixture of high-quality oil and synthetic base components. W. synthetic oils
the oil base is absent, due to effective antifriction additives increases (compared to mineral oils), the service life of the engine is facilitated by its launch at low temperatures. Despite a higher price, semi-synthetic and synthetic oils find more and more use. Special engine oils are manufactured, and they differ for engines differing in strata (two- and four-stroke) and the degree of forcing. For Russian motorcycles with four-stroke engines, automotive oils of various viscosities are used, with two-stroke - MHD-14, or foreign counterparts.
In four-stroke engines, three methods of supplying oil to rubbing surfaces are used: under pressure, spraying and gravity. Most friction pairs are lubricated under pressure generated by the oil pump. Other friction pairs are lubricated with oil mist, which is formed when spraying the oil droplets by moving parts of the crank-connecting mechanism. And finally, the third group of parts is lubricated with oil flowing through special channels and grooves. Carter (Carter Pallet) is usually an oil reservoir (the so-called "wet" crankcase - Fig. A).
Four-stroke engine lubrication systems
Some overseas motorcycles have system with "dry" crankcase (Fig. b), from which the oil first pumps down one of the pump sections into a separate oil tank, and the other section under pressure is supplied to the friction surfaces. The tank can be located in different places: near the engine, at the rear wheel or in the front of the frame.
The oil level in all lubrication systems are monitored using a probe (with minimum and maximum level marks) or through a special control hole. The operation of the engine with a reduced oil level is unacceptable.
The lubricant system contains an oil pump, an oil filter, valves (reverse and safety) and highways in the form of channels (tubes, drills in detail).
Four-stroke oil pumps There are plunger and gear types.
Types of oil pumps
a - plunger;
b - gear with outdoor gear gear;
in - with internal gear gear
Gears, the most common distribution consists of a hull in which one or two pairs of gears are located with outdoor or internal gearing; The gears are rotated from the engine crankshaft or camshaft. The oil enters the input cavity cavity, is captured by the gear teeth and is injected to the exhaust cavity.From the filters are the most common removable paper.
In two-stroke engineslubrication of rubbing pairs is carried out by oil in the form of small droplets in fuel pairs. The oil is mixed with gasoline or pre-in the tank (in the proportion of 1: 25-1: 50), or directly in the inlet pipe where it in the required quantity is supplied by a special dispenser pump. The last oil supply system is called "Separate lubrication system"It has preferential distribution on foreign two-stroke engines. In such systems, oil supply at low loads is brought to a 1: 200 ratio, which reduces exhaust smoke, reduces the total oil consumption and the formation of a car in the combustion chamber.
Two-stroke engine with a separate lubrication system
1 - oil tank;
2 - carburetor;
3 - gas cable separator;
4 - Gas handle;
5 - oil supply control cable;
6 - plunger pump-dispenser;
7 - hose, liner oil in the inlet
In systems with separate lubrication use pumps plunger type, resulting from a crankshaft or motor transmission. The oil is stored in a special tank and comes to the pump of gravity. The design includes a low oil leveling signal in the tank. The amount of oil supplied in the inlet pipe depends on the rotation frequency of the crankshaft; In some constructions, there is another adjustment of its performance - from the position of the "Gas" handle, for which the pump is connected to it a separate cable.
Cooling system
When combustion of fuel in the Cylinder, the engine is highlighted heat, part of which (about 35%) goes to the useful operation, the rest is dissipated into the environment. If the heat dissipation is not effective enough, the details of the cylinder-piston group are overheated, and due to their excessive expansion, as well as disruption of lubricant conditions, can occur and damage to parts. To prevent overheating, all motorcycle engines, regardless of the clue The cooling system is air or liquid.
Motorcycle DVS cooling systems
- I know that there are two-stroke and four-stroke engines, but I do not imagine the difference between them. And also say - "Internal combustion engine". Is this the same or something completely different?
So that our further reasoning is more understandable, let's first agree on terminology, at least about the basic concepts.
The internal combustion engine (internal combustion engine) is a mechanical device in which the chemical energy of the combusting fuel turns into a thermal, and then into mechanical. Fuel combustion occurs directly inside the engine, in the so-called combustion chamber formed by the cylinder and its head.
Working cycle The combination of workflows consistently occurring in the cylinder is called. Such processes are five: inlet, compression, combustion, expansion and release.
Piston - Detail of the engine that perceives the pressure of gases formed during the combustion of the fuel, and transmitting it pressure through the piston finger and the connecting rod on the crankshaft.
Cylinder - Detail inside which moves the piston. The inner surface of the cylinder is for the piston of the guide, the outer serves to remove heat.
Upper Dead Point (NMT) - Extreme top of the piston.
Lower dead dot (NMT) - Extreme lower piston position.
Tact (or stroke) - Move the piston from one extreme position to another. In one clock, the crankshaft turns 180 ° (on the half turn).
Cylinder work volume - The volume released by the piston when it moves from the NMT to NMT. Working volume is measured in cubic centimeters. For a single-cylinder engine, a working volume of one cylinder is and engine working volume. For multi-cylinder engines, the working volume is defined as the sum of the working volumes of cylinders. (Sometimes the working volume is called litter). In the formulas, the working volume is indicated by VH;
Volume of combustion chamber - This is the volume above the piston when it is found in the NWT. It is indicated by VC.
Full of cylinder Called the sum of the VH working volume and the volume of the combustion chamber VC.
Compression ratio Indicates how many times the volume of the working mixture is reduced in the cylinder when the piston is moved from NMT to the VMT.
Compression ratio (E) - The ratio of the total volume of the VA cylinder to the volume of the combustion chamber VC
Two-stroke engine - The internal combustion engine in which the full duty cycle occurs in two clocks or that the same thing is in one crankshaft turnover.
Four-stroke engine - The same, but the full duty cycle takes place for four clocks, that is, for two full turns of the crankshaft.
It is clear that these are not all the terms with which we would face in the future. And therefore, as we need, we will explain more and more new concepts. In the meantime, this is enough to go to the main thing: consider workflows and understand the engine device.
Working cycle
We will start his consideration from the four-stroke engine - it is easier to understand the processes.
The first stroke of the piston is used for inlet into the cylinder of a combustible mixture consisting of fuel vapor and air associated with a certain proportion. The combustible mixture comes through the open intake valve. This is the intake tact.
When the piston reaches NMT, the inlet valve will close the piston, moving in the opposite direction, starts to compress the mixture, making compression tact. When compressed, the mixture heats up and is actively mixed.
Near the VMT mixture is mounted and burning. In this case, the volume of gases increases many times, the pressure in the combustion chamber increases. The piston under the action of this pressure begins to move down, the expansion tact occurs - the only useful work move.
When the piston is located at NMT, the exhaust valve opens, and the spent gases begin to go out into the atmosphere. Moving to the VMT piston actively displaces them - there is a tact of release.
Then the whole cycle is repeated.
In the working cycle we considered, we believed that the intake valve was found at the position of the piston in the VMT, and the graduation opens when the piston is in NMT. In fact, in the real engine, everything is much more complicated.
Judge yourself - because the valve can not open instantly. For its full opening, some time is necessary for closing.
Therefore, the inlet valve is beginning to open before the piston arrival in the VMT is called the inlet advance. Accordingly, it closes after the arrival of the piston in NMT (inlet delay).
The same thing happens with the exhaust valve: it opens until the piston arrives in the NMT (release leads) and closes after the NTC (delaying release).
Periods of opening valves - they are usually measured in degrees of rotation of the crankshaft - are called the phases of gas distribution. Using this term now, we can say that the opening of the valves, with ahead and. Closing with delay increases the duration of the phases (expands the phases). As a result, the filling of the cylinder of the combustible mixture and cleaning it from the exhaust gases is improved, the engine power increases.
For clarity, the phase is usually depicted in the form of a circular chart (Fig. 22). Looking at her, even the unprepared viewer will see that there are periods when both valves are at the same time. These periods are customary to be called the ceiling of the valves. At this time, two processes occur at once: the charge of the cylinder is a fresh mixture and cleaning it from the exhaust gases. On the one hand, it is bad: some of the fresh charge literally "crashes into the pipe". On the other hand, the quality of fresh charge is improved and, it means, the combustion has become, the engine power increases.
1-inlet; 2 - compression; 3 - work move; 4 - release; 5 - inventing the intake; 6 - overlapping valves; 7 - retardation of release; 8 - ahead of release; 9 - lagging inlet.
Of the same reasons for increasing the capacity, the working mixture in the combustion chamber and to wait, obviously, it should not be at the time of the arrival of the piston, in the NTC, and much earlier (because the burning is the process, the same time requested). And not just "earlier", but with such a calculation, so that the start of the workstop coincides with the peak of pressure over the piston. This moment of the ignition advance for each engine is strictly individual. From its magnitude, the ease of starting, developing power and fuel efficiency of the engine depend on its magnitude.
- In the four-stroke engine, everything is simple: valves are open and closed, the mixture and gas and gases are released. But in the two-stroke motor, there are no valves, and it also works. How so?
True, the main difference between the two-stroke engine is just that it consists that he has no valves. But the process of gas distribution here proceeds in the same laws. Only "heads" all this ... Piston. Another difference is that the working process is about
it comes not only over the piston, as in a four-stroke motor, but also under the piston, in the so-called crank chamber, which in
there is a hermetic connection with this. And the third difference - in the device of the cylinder and head.
If the four-stake the cylinder is very simple, and the head is complex (in it, as a rule, valves are placed), then the two-way motor is the opposite: in the walls of the cylinder there are windows and channels of a complex configuration, and the head is simple.
What caused these differences, we will understand when we consider how the workflow proceeds in the two-stroke.
So, the piston moves up. As soon as its upper edge blocks the left blowing channel connecting the cylinder with a crank chamber, the cutter begins to form in the crankcase under the piston. While the right exhaust channel is still open, in the cylinder above the piston there is a release and purge. But as soon as the top edge of the piston blocks this channel, compression will begin.
Continuing to move up, the piston will open the right intake canal with its lower edge, and the crank chamber, a freshly combustible mixture of the carburetor begins to flow into the cavity. Start inlet.
At the moment when the piston approaches the NTC for the distance, the corresponding ignition advance (you already know about it), the spark discharge will set fire to the mixture compressed in the combustion chamber. The hot gases formed at the same time, seeking to expand, will make the piston, the inertia passed the NMT, rushing down. There will be a work move.
1 - inlet in Carter; 2 - compression in the crankcase; 3 - purge; 4 - release; 5 - compression in the cylinder; 6 - work move.
When the lower edge of the piston blocks the inlet window, compression will begin in the crank chamber (it is called preliminary). Pressure under the piston will increase to 1.25-1.5 kg / cm 2.
When the upper edge of the piston head, still going down, will open the final window that spent gases that preserved sufficient pressure will rush into the exhaust system. The release will begin.
By the time when the pressure above the piston becomes almost equal to atmospheric, the head of the piston will open the left blowing window. A combustible mixture is pre-squeezed in a crank chamber through the purge channel will head to the cylinder and fill it out, displacing the exhaust gases and partially mixing with them. At the same time, part of the fresh charge, it is clear to depart into the graduation window. (This is called "direct emission"). It will be blown.
It will end when the NMT has passed the piston starts moving up and block the purge window. The release will continue until the exhaust window is blocked.
If you try to build an already familiar phase diagram of gas distribution, then you will have to show two processes at the same time: one, which is on the piston, in the cylinder, and the other occurring under it, in a crank chamber. The result will be two charts, two rings. Internal typically depicts processes in the crankcase, outdoor - in the cylinder.
Charts, of course, have absolutely symmetric phases of gas distribution.
- If in the two-stroke engine work movement is twice as often as in the four-stroke, then the power should be twice as much with the same working volume? Or do I not understand something?
Well, of course, everything should be that way. In theory. And in practice it turns out differently.
Despite all the triggers of the designers, the cylinders of the two-stroke motors are still poorly cleaned from the exhaust gases. As a result, there are fewer blends in them - it means that the combustion process is worse.
In addition, some of the fresh mixture time to jump out in the graduation window, without working at all (remember "direct emission"?). And one of this circumstance increases fuel consumption by 20-30%. And there is still a "reverse emission", in the carburetor! On the motorcycles of the 50s and 1960s, which had simple mesh air filters, losses from return emissions were also a tangible value - up to 25% ...
In short, there is no double winnings in the power, how much try. And even on the toxicity of the "Two Pointer" is clearly "dirtier" of its four-stroke rival.
There could be the following question: "And why then ..?" It is not in my mail, but it is meant from the same time as the Scottish engineer Dougall Clerk in 1877 created a two-stroke engine so controversial with many vices - and now for more than a century not passing. And therefore will reply.
Then that the two-strokemother is much easier by the device. Easier to manufacture. Reliable. Easier to use. And cheaper. Agree - not so little. And if you take into account that the two-stroke engines are also continuously improved (according to the latest information, the Australian campaign "Orbital" developed a new principle of blowing the two-stroke engine, which displays this motor in fuel economy and power to one level with the best four-stroke samples), the dispute Between different motors, which lasts more than one decade, may never end.
Cylindropional group and crank-connecting mechanism
If someone from this long and a little bad name ran goosebumps, then this is in vain. In fact, the group includes only a cylinder and piston, and the "mechanism" combines only two nodes: the rod and crankshaft.
The cylinder is one of the main parts of the engine. The inner surface of the cylinder serves as a guide for the piston, and heat is allocated through the outer. The cylinder of the four-stroke engine is the easiest. It is usually made from a special cast iron. The inner surface, the "mirror", is processed to high accuracy and purity. Moreover, with the help of a special technology, a mesh of micro-robes, holding the lubricant and extend the service life of the cylinder is applied to this surface.
If the engine is cooled by the incident oncoming air flow, the outer surface of the cylinder is supplied with developed ribs that improve heat removal. If the cooling of the liquid - the "shirt" is arranged around the cylinder, in which the liquid circulates.
At the bottom of the cylinder there is a flange for fastening to the engine of the engine; In the top - stud for fastening the head.
This, of course, is only a common primitive scheme. At the grandfather's grandfather, a great set. Nor a motorcycle, then another design of the cylinder.
For example, cast iron, well-working on abrasion and alternating durability, the cylinders would be too heavy for the modern engine. And therefore, engineers came up with a "puff" option: only an internal thin-walled sleeve is made from the cast iron, and the outer shirt is from aluminum. And it turned out very cool. After all, aluminum has excellent thermal conductivity. And just this is required from the shirt.
The cylinder of the two-stroke engine is much more complicated. In it, as you remember, at different heights there are channels: intake, graduation and purge. And the purge channels can be several.
Since, for reasons, the cylinder reduction cylinders of two-stroke engines is also completely made by layers, then the windows in the sleeve must very accurately coincide with the windows in the shirt: if there is no such coincidence, the working processes will deteriorate sharply, the motorcycle will lose power and efficiency. Therefore, the athletes using two-stroke engines are often manually highlighted by the channels and give the input and output edges a special form that provides the best flow of a combustible mixture.
The purge of two-stroke engines at all times was given the most serious attention. The output of the channels into the cylinder was built under a strictly defined angle, the width and the height of the windows were carefully calculated. Sometimes for a better twist of the fuel-air mixture on the head of the piston, a special scallop reflector was even arranged, a deflector. And the types of purge received special names: transverse, return-loop, three-channel, cruciform, etc. Let's not stop at this. For you, novice motorcyclists, said enough to understand how important the purge for the two-stroke engine is important. And those who want to understand this deeper, will find other books.
- I read that there are two-cylinder engines with a volume of only 125 cm. Cube. And there are single-cylinders with a "pot" in 600 "cubes". Why is that?
From my birth and many, many years a motorcycle engine was predominantly single-cylinder. Unless in class 750 cm 3 and above the designers supplied it with a pair of cylinders. And even partly unwillingly: it was necessary to reckon with the fact that not every driver is physically able to overcome the resistance of the mixture compressible in such a volume, and turn the crankshaft when started.
Single-cylinder motors, both two-stroke and four-stroke, to this day are built in all countries of the world and are installed on motorcycles in cases where the simplicity of the device, reliability and low cost are deliberately main qualities.
These are mainly the motors of small cubes, a working volume up to 100-125 cm 3.
However, in recent years, a whole generation of single-cylinder 600-cubic motorcycles appeared abroad, such as Yamaha SRZ 660, Suzuki LS 650P, KTM 620 EGS, Honda XR 650L and them like. What is it caused? To figure out, let's start "from the stove."
It is known that the single-cylinder engine has many congenital vices. The main ones are impassableness, irregularity of torque, a tendency to vibrations on large revs, the tension of the thermal regime. Before, with the comparative slowness of the motors, these shortcomings were not so rushed into the eyes and you could put up with them. With increasing capacity, the situation began to exacerbate. And over time, the inclusion of the number of cylinders has clearly outlined. As a rule, the engines from 250 cm3 and above already have two and more cylinders. This crushing of the working volume made it possible to significantly raise the liter power by increasing the number of revolutions and the degree of compression.
It is estimated, however, that reduce the volume of one cylinder and increase their number to a certain limit. Such a limit of volume is considered 62 cm 3 and by number - eight. As an example, the once famous four-stroke four-cylinder 350-cubic engine racing motorcycle "East" (C-364) or four-stroke eight-cylinder (!) 500-cubic engine of the Italian race motorcycle "Guzzi". A further increase in the number of cylinders faces almost insurmountable layout difficulties and can only be justified in the case of a single or piece, as a last resort, execution. For serial motorcycles, two-, three- and four-cylinder motors are built.
No need to possess a rich imagination to understand that it is much easier and cheaper to make a single-cylinder 350-cubic engine than the same four-cylinder volume.
But not only simplicity and reliability explains the appearance in the west of the real wave of "large pots".
The fact is that the single-cylinder engine of a large volume for smoothing pulsations is supplied with a massive flywheel, which provides excellent uniformity of torque at very low revs. For a long time, this is a good quality completely destroyed by monstrous vibrations inherent in such a motor. But after this nuisance was learned to fight with the help of special balanced shafts, nothing could prevent the widespread spread of single-cylinder engines of large cubatures.
And then it has also turned out that for the "flashing" of urban traffic jams there is no better means than a special motorcycle: a narrow, easy-to-control, powerful, capable of dynamically accelerated, and in case of need - and drag in a stream with a pedestrian speed. Such motorcycles were called urban "enduro", and single-cylinder 600-cubic engineers were ideal for them: narrow, powerful, possessing the desired characteristics.
In general, the cylinders can be spent very long - because their number and location is always indicated as one of their first and most important characteristics of the motorcycle.
But we are forced to move on: our road is long, and we are still just at the very beginning!
The head of the cylinder in most modern two-stroke engines cast from aluminum alloy. The outer surface in the case of natural cooling is strongly finished. Inside there is a compression chamber, or, as it is more common, the combustion chamber.
There are several through holes for fastening it to the cylinder and one threaded, overlooking the combustion chamber - for the spark plug. Before many two-stroke engines in the head, another threaded hole for the decompressor valve was made. Now it is put in less often.
At the top-smelted four-stroke engines, the head is much more complicated: nests are made in it, guides and valve channels.
Often there is a camshaft with rockers: the head has nozzles for fastening the carburetor and the exhaust system.
The combustion chamber shape is different. But it is not arbitrary, because he strongly affects the quality of combustion. Previously, such forms were often used as a semi-spherical and jockey visor.
Now the camera was widely distributed, as if consisting of two spheres - it provides the most efficient combustion of the mixture.
- I was always surprised that in the characteristics of the engine, the number and location of the cylinders - and not a word about pistons. This is discrimination. Piston - the most important part ...
It's true. Cylinder passive. The piston perceives the pressure of hot gases of the burning mixture and through the piston finger and the connecting rod transmits it to the crankshaft. Moving reciprocally in the cylinder, it accelerates up to 100 times per second to the maximum speed and slows down to zero, experiencing huge inertial loads. Indeed, this is one of the most loaded engine parts.
Consider the structure of the piston (Fig. 26).
Piston of the two-stroke engine: 1 - bottom; 2-grooves for piston rings; 3 - piston skirt; 4 - Break; 5 - cutouts in the skirt; 6 - an odd purge channel window
It distinguishes the head with a bottom of 1 and skirt 3. In the skirt (it plays the role of the guide) there are special tides - bits with holes in which the piston finger is located.
On the side surface of the head, in its upper part, the grooves are flowing 2. Piston rings are installed in them.
The piston is directly exposed to the temperature effect on the side of hot gases. It is cooled well, only fresh mixture and through contact with a cylinder mirror.
Since the piston is cast from an aluminum alloy, then when heated it expands significantly. To not jin, the piston is installed in a cylinder with a gap. Moreover, the gap of the height of the piston is different: the head has the smallest diameter, the lower belt of the skirt is the greatest. In addition, the skirt is also oval in cross section: it is elongated in the plane perpendicular to the piston finger. Considering such a complex shape of the piston, it was agreed to measure its diameter in one place: under the lower piston ring. There are pistons for cylinders on this size.
Pistons of four-stroke nipped engines have a flat bottom. Upper flapned it is flat, with notches for valve protection.
Pistons of two-stroke engines, as you remember, not only compress the working mixture in the combustion chamber, but also control the inlet, release and purge. In the skirt of such a piston there are special cuts or windows corresponding to the configuration windows on the cylinder mirror. And in the grooves for piston rings, retained pins are installed, which do not allow the rings to rotate on the piston and the topics protect their joints from entering the window and from breakage.
Piston rings are cut, they are made of such grants of cast iron or steel, which have spring properties. Due to this ring, they are well adjacent to the cylinder mirror, sealing the gap between it and the piston. The rings on purpose are two species: sealing (or compression) and oil surplus. The two-stroke engine oil rings has no. On the four-stroke piston, such a ring is set below the sealing. When the piston moves, it removes the cylinder walls overly oil and drops it into the crankcase.
More than three rings on the piston are not set: the degree of seal increases little, and friction losses are growing noticeably.
The junction of the piston ring is called a lock. Castles are direct or oblique (at the four-stroke engine). On the piston of the two-stroke engine, the ring in the lock corresponds to the form and location of the locking pin.
Steel piston finger, hollow, thermally processed. In the bosses of the piston, it is most often installed on the so-called floating landing - that is, it can turn freely. However, hot landing is often used, when the finger is fixed in the buses and can only rotate in the sleeve. The axial movement of the finger limit the spring stop rings installed in the battles.
Before moving to another detail, distracting a little and talk about how the diameter of the cylinder and the stroke of the piston are connected.
It is not only interesting, but is directly related to further reasoning.
If you compare, for example, these motorcycle ratios of different years, then even a non-specialist will notice that the process of reducing the stroke of the piston continuously goes into the diameter. What is it caused?
First of all, the fact that the motorcycle becomes easier at the same time: the smallest surface of the cylinder is achieved with the ratio of the piston to the diameter 1. When the piston stroke decreases, the distance it passes, and, accordingly, the average speed, and This not only extends the lifetime of the piston, but also allows you to increase the rotation frequency of the crankshaft. It is not important to note: the magnitude of the average piston velocity has been almost unchanged for many years, since the increase in the speed of rotation immediately should immediately increase due to this.
For four-stroke engines, an increase in the diameter of the cylinder is also beneficial and because it allows you to use larger valves or, even better, increase their number. And this already affects the filling and also raises power. There is even such a term: "piston power". It is expressed by the relation in which the piston area appears, and allows you to judge the degree of engine forcing. You can increase this area by increasing the number of cylinders and reducing the ratio of the piston stroke to the diameter. In modern engines, this relationship is close to one. A decrease in it below 0.8 is completely inappropriate.
The crankshaft and the connecting rod form a crank-connecting mechanism. Its main purpose is the transformation of the reciprocating movement of the piston in the rotational motion of the crankshaft.
The simplest crankshaft single-cylinder engine consists of indigenous and connecting rods and cheeks. The rod cervix is \u200b\u200bcovered by the lower head of the connecting rod, on the indigenous shaft rotates in the bearings installed in the crankcase. The crankshafts of multi-cylinder four-stroke engines are often cast entirely from high-strength cast iron, and then the neck is mechanically processed.
As a rule, the shafts are unspeborified. Even in the case when the native cervix (semi-axis) and the connecting rod cervix connect with the cheeks in the hot condition. So, for example, the crankshaft "Urals" works
The domestic two-cylinder two-stroke engine "Izh-Jupiter" is essentially two single-cylinder engines, "combined with a common crankcase. Therefore, the crankshaft is two independent shafts connected by the remote flywheel. Incoming in the flywheel, native cervix are fixed with the swords, and the split flywheel is tightened Powerful bolt.
Flywheel is a massive disk, usually fixed at the end of the crankshaft. With a significant mass, and, consequently, inertia, the flywheel when rotating the crankshaft accumulates considerable energy, which is consumed during auxiliary clocks and smoothes the irregularity of the torque.
Typically, the flywheel of the four-stroke engine is located at the rear end of the crankshaft, leaving the crankcase, and is part of the clutch. On the outer rim of the flywheel, there are usually tags that help set the ignition and control the number of revolutions. If the engine has an electrical launch, the handwheel is handled the handwheel to the handwheel, to engage with the starter gear.
The connecting rod hinge piston with a crankshaft. In cross section, the connecting rod most often has a dive form. The most preferred material is steel. Structurally in the connecting rod distinguish the top head, body and lower head. The piston finger bearing is located in the upper head. Before, in most cases it was a bronze bushing. Now increasingly - needle bearing: it is more durable and reliable at high speed.
Bearing is also installed in the bottom head. Often its inner cable is the neck of the crankshaft itself, and the outer is a special thermally processed ring, pressed into the head of the connecting rod. Sometimes the bottom head is detachable - then inserts are installed in it.
Unlike rolling rolling bearing, this option is called the sliding bearing. So it is arranged, for example, the rod motorcycle "Dnipro".
Carter
As the frame connects all the units and nodes of the motorcycle into one whole units, so the Carter connects the Power Unit. Through the attachment points on the crankcase most often this unit is connected to the frame. Carter is cast from aluminum alloy. Its structures significantly reflects the nature of the engine of the engine.
For example, a four-stroke engine crankcase is most often a single calm casting for a crankshaft, cylinder fastening flanges, oil pump, filter, with oil tank, etc. In its front and rear walls, the holes for the installation of bearings and glands are flowing.
Two-stroke motorcycle cartresses are distinguished by the fact that they are common to the engine, clutch and gearbox (Fig. 28). For convenience, disassembly and assembly are usually made by split, consisting of two, three, or even more parts. Moreover, the plane of the connector can be both vertical (which is inherent in Russian motorcycles) and horizontal (which can often be seen on Japanese motorcycles).
1 - left lid; 2 - the plug of the oil-tank hole; 3 - gasket; 4 - left and right half of the crankcase; 5 - gearbox cover; 6 - right lid
In front of the filter engine crankcase, there is a crank chamber. Since it is involved in the gas distribution process, it has to be sealing. To this end, a rubber seal (gland) is installed in the left half of the crankcase, which prevents oil transmission oil from the cavity chamber from the oil transmission cavity, and in the right half of the gland that does not allow the atmospheric air into the crank chamber when it creates a vacuum.
Next to the crank chamber there are cavities in which the shafts and gears of the gearbox are placed, motor transmission and clutch. Carter halves are connected by screws. The seal between halves is provided by the purity of surface treatment and applying glue or sealant.
Additional covers covering the motor and main transmission are usually compacted by thin cardboard or paronite gaskets.
Gas distribution mechanism
- In the two-stroke motor, the owner is a piston, he controls the entire process. And how do the valves open and closed in the four-stroke engine?
Well, in the two-stroke engine, too, everything is not as simple as it may seem at first glance.
When we talked about the diagram and gas distribution phases, we called them symmetrical. It sounds beautiful and looks, but such phases are not perfect at all. Inputs at the same time, the intake of fresh mixture and the release of exhaust gases worsen efficiency and reduce the engine power. Therefore, tempting somehow split these processes in order to better clean the cylinders from gases and increase their filling with a fresh mixture. This would increase the liter power, that is, the power attributed to one liter of the working volume.
The most cunning systems of purge if they gave some result, then very insignificant.
And then a new idea appeared: put a spool on the inlet - something like a valve, which would increase the duration of the intake phase and exclude the so-called reverse release of the mixture into the carburetor. This device is also called a petal valve or reverse plate valve.
The first valve was simply an elastic steel plate, located across the flow of fresh mixture. He, first, rendered great resistance to this stream, secondly, quite quickly broke, not withstanding endless beggars - pulsations.
However, "Likha trouble is the beginning." There was time, new materials appeared, technologies were worked out. And now the already valves on the inlet have become serially installed on many motorcycle engines, including domestic. And this suggests up to 15% of fuel while improving the dynamic motorcycle indicators.
Inspired by success, the designers turned their eyes to the release - after all, there, too, the ugly leakage of the mixture occurs. And immediately appeared valves on the release; They were called power. But we will talk about them a little later.
In the meantime, back to the four-stroke engine and its system of gas distribution.
It is customary to distinguish between two types of mechanisms: upper flap and nizhnecladnaya.
In the first case, the valves are located in the cylinder head and are driven by the camshaft located below, with long pushers, rods and rocker. The disadvantages of this system began to manifest everything more clearly as the number of engine revolutions is grown. After all, even the easiest pushers have a mass, it means, inertia, and at some stage they began to delay. More precisely, they stopped accurately track camshaft camshaft profiles. Phases were disturbed, and it became a verdict of the topless mechanism.
In the lower valve timing, the valves are located in the cylinder body, the drive is carried out by rocker or pushers. Such a scheme turned out to be much more lively, since the mass of parts moving reciprocally, is small.
But it was killed in congenital vices: a very large surface of the combustion chamber provokes detonation, and the speed of motors with this scheme does not exceed 4500 rpm, which is unacceptable for today.
Much more popular on modern motorcycles, a diagram with the top arrangement of the valves, but still with the lower distribution-scrap, which received the OHV conditional designation according to the first letters of the English words Over Head Valve. In this embodiment, the engine can develop up to 7000 rpm.
When the camshaft was moved to the head and it became directly through the fishers to influence the valves (the scheme is called OHC), the motor has received the ability to "unwind" to 9000 rpm. This option was very popular in the 70s.
Finally, for very high-speed motors, an option was invented with two camshafts in the head - it is called DOHC (D is a double, that is, a double). There are also no returnable moving pushers or rods - and therefore the motors can develop up to 11-12 thousand rpm.
However, the spring, as it turned out, also possesses the "trigger time." And at some, even even very high frequencies of the camshaft rotation, it does not have time to squeeze. For such particularly complex cases, the so-called desmodromic mechanism is invented, in which the valves are closed and open under the action of cams, the springs in it are not at all (Fig. 30). This scheme came up with designers of the Italian company Ducati. And she justified her racing engine with a volume of 125 cm3 developed 16 thousand rpm and was very reliable at the same time. The disadvantage of this design is one: it is expensive in production and is complex. However, this does not interfere with the Italians to use it even on road motorcycles.
The most common scheme for gas distribution - DOHC. It employs most modern four-stroke engines. And more and more often instead of two valves, 4, 5 are used on the cylinder, and sometimes 6 valves. Due to this, the total passage section for the intake and release becomes greater, the cleaning and filling of cylinders improve. Smaller diameter valves are better cooled, their weight is smaller, it means that you can even raise the engine speed. Unfortunately, this complication of the design significantly increases the cost of the motorcycle and therefore does not apply in cases where the first place is cheap and simplicity.
- In car engines, the camshaft drive is carried out with a chain or strap. And how is this done in motorcycle engines?
The type of camshaft drive depends primarily on where the camshaft is located. If it is downstairs, in the crankcase, then everything is very simple: a fairly ordinary gear transmission. It provides the accuracy of the phases of gas distribution and very reliable.
If the shaft is in the head of the cylinders, then the drive gears becomes uncomfortable, very cumbersome. And he comes to shift a flourishing roller chain. Its advantages are obvious: it is easier, more compact and cheaper. But the disadvantages are just as obvious. The chain is wearing and draws, noticeably disrupted phases; Chain "Noise" and requires constant observation and care.
And therefore, like on car motors, on the motorcycles, instead of the chain, a toothed belt is used. He, of course, also wear out over time. But the price of the belt is small, and replace it at the appointed term - the case is not difficult.
Thus, we reviewed the main engine mechanisms and now go to the consideration of its systems. Their five: lubrication systems, cooling, nutrition, release and electrical equipment.
Lubrication system
The friction is the worst enemy of any mechanism, including the internal combustion engine. When rubbing surfaces are carefully processed, friction is less; With coarse processing of friction force, such values \u200b\u200bcan be achieved that the parts will be heated up to sintering and melting.
The essence and meaning of the lubrication process lies in the fact that the oil is fed between rubbing surfaces, forms an oil wedge and disjects these surfaces. Dry friction is replaced
liquid, which is hundreds of times less. In addition, the oil removes heat from the parts and carries out the wear area from the contact area.
In four-stroke engines, a closed circulation system of lubricant is traditionally used. At the same time, the oil from the crankcase is taken by the oil pump and under pressure is supplied to the root bearing of the crankshaft, the distribution shaft, pushers, rockers and some other parts, which are then reset back into the crankcase.
Under pressure, and partly due to the oil mist is lubricated the bearing of the lower head of the rod.
Motorcycle Lubrication System "Ural":
1 - oil pump; 2 - oil filter; 3 - reduction valve; 4 - oil supply channel to the left cylinder; 5 ~ oil supply channels in casing rods and cylinder heads; 6 - Holes in Piston Barbes for Finger Lubrication
In some cases, the cylinder mirror, the piston and the piston finger are lubricated by splashing the oil - then the system is called combined.
In the descriptions of foreign four-stroke motorcycles, the term "dry carter" is often found. This means that in this performance, the oil is stored in a separate oil tank, and after it works in the friction nodes and will be reset to the crankcase, with the help of the pump immediately again through the filter will go to its container.
The two-stroke engines were originally a separate lubricant system - it was their big plus that reduced the cost of the motorcycle as a whole. The oil in a certain proportion was mixed up to gasoline and in such a form was fed into the engine, lubricating all the tracks on the way.
The ratio of gasoline and oil in the mixture depended on the engine design and its status. For domestic motors, as a rule, it was necessary to add 400 ml of oil to 10 liters of fuel, that is, the ratio was 25: 1. In foreign two-stroke engines, where often the oil was signed separately, the ratio was 33: 1, and sometimes 50: 1.
With all its simplicity and attractiveness, this method of lubrication was a lot of flaws.
First, oil and gasoline have different density and even more different ability to evaporate. Therefore, falling into a crank chamber, the oil immediately settles on its walls, flows down, and much part does not participate in the process of lubrication.
Secondly, with this method of lubrication, it is important that gasoline and oil are thoroughly mixed - and this is not always done. And the consequences in case of poor mixing can be for the engine with the most severe.
In third, the oil in the mixture is supplied to rubbing pairs always in the same proportion that does not depend on the engine operation mode. This leads to a deliberate overflow of oil and, which is much worse, to the large allocation of harmful substances with combustion products.
In addition, the oil that falls together with gasoline into the combustion chamber is settled on the most heated parts of the engine and forms a thick layer of a nagar consisting of severe non-heavy resins. This layer worsens the cooling of the parts, primarily the head of the cylinder and the bottom of the piston, and can lead to a callery ignition and even extending the piston. (Calil ignition is an unfavorable process, in which the ignition of the mixture does not occur from the spark, and from the hot particles of a nagar or metal).
The Nagar is actively formed on the spark plug electrodes, increasing electrical resistance and worsening sparking up to full candle failure.
Agree, the shortcomings turned out so much that they were eclipsed by all the advantages of the "old good system". And the designers actively engaged in search of ways to improve the lubricant system, optimization. These searches led to the creation of the so-called separate lubricant system.
For the first time in domestic practice, it was serially used on the Motorcycle Izh- "Planet-Sport" in 1974. And the author was able to participate in its trials.
Then, when "PS" was removed from production, there was a rather long period of oblivion. And since 1994, a separate lubricant, surviving modernization, getting rid of childhood diseases, returned to serial Izhi and other motorcycles.
The system provides strictly dosed lubrication of the details of the cylinder-piston group and the crank-connecting-connecting mechanism. It consists of a separate oil tank placed in the left cover of the crankcase, but isolated from the clutch cavity; The size of the screw oil pump, oil pipelines, sprayers and the control cable connected to the gas handle. The main part of the system is the pump. It consists of the proper screw pump, a piston valve, dispenser and a diaphragm check valve.
Oil through the channel enters the pump housing, captured by its screw and is fed under the pump cover and further to the sensor valve. Under the pressure of oil, the piston, overcoming the force of the spring, departs from the saddle (at the same time it opens the electric contact and the lamp goes out on the instrument panel, showing that there is pressure in the lubrication system) and frees the oil pass to the dispenser.
Let's not stop in detail on the design of the dispenser. Let's just say that this device is connected with a cable with a "gas" handle and, depending on the position of the handle (and therefore, the engine mode) reduces or increases the supply of oil.
The diaphragm valve mentioned by us does not allow the oil from the line to drain back into the oil container during the non-working engine, it serves to regulate the minimum oil supply on the idle engine mode.
Again, lowering long and detailed descriptions of the processes that are unlikely to be appropriate in our book. "Let's say that when using a separate lubricant system, an oil / gasoline ratio is provided on 1: 100 in idle mode until 1:25 on the nominal capacity mode. And the average Operational relations range from 1:33 to 1:67. And this is not the limit: the designers claim that when using special oils for push-pull engines and some refinement of the pump, oil consumption can be reduced again in two!
It is clear that one use of separate lubrication does not yet solve all the problems of the two-stroke engine. But it is also clear that this is a very strong course. Therefore, in the 90s, for foreign motorcycles with two-stroke engines, a separate lubricant has become an almost mandatory element of the design.
