Whatever the car, dear friends, incredibly luxurious or spartan-budget, in its depths there is always a single basic process - the transmission of torque from the engine to the wheels. They take part in it various nodes and units, each of which bears a certain share of responsibility for our comfortable and moderately fast movement on the roads. And the main gear of the car is the unit thanks to which the wheels of the vehicle spin and we gain an unforgettable feeling of flight, even at a super low altitude.

So, the main transmission of a car is a unit, without which the efforts of the engine and gearbox would be a waste of energy. Why? The fact is that it is she who is responsible for transmitting torque from the directly driving wheels.

In addition, rotation, as a rule, still needs to change direction - from longitudinal (along the axis of the car) to transverse in order to get to the wheels. And all this is performed, in fact, by one gear mechanism, also known as gear reducer. In addition to everything, the gear ratios are selected in such a way as to increase the torque of the motor.

Where is?

Purpose final drive We seem to have found out the car, now it would be nice to find it. Doing this can be a difficult task, because the location of this unit can be different and depends on the type of machine drive and the imagination of the development engineers.

Fortunately, the flight of thoughts here is limited by the number of axes. So, for example, if we have front-wheel drive, then in this case it is worth looking for the main gear of the car in the gearbox along with, in vehicles with rear driving wheels - directly in the rear axle. If, then choose one of the above options.

Variety of final drives

As we already understood, the final drive of a car is a very serious unit. It is clear that for such a responsible task that is entrusted to him, a reliable and at the same time uncomplicated engineering solution, and then they opened for designers wide open spaces for action. Let's look at the types of final drives of cars. Depending on the number of gears, this unit can be like this:

• single;
• double.

The first type is a combination of two gear parts - the drive and driven gears. It is most common among passenger cars mobiles and small cargo vehicles. Double final drives have, as you might guess, several pairs of gears, and are usually used where an increase in the gear ratio is necessary, for example, in buses and special equipment.

The picture would be incomplete without mentioning the types of gear connections used. There are many of them, and the following are distinguished:

• cylindrical;
• hypoid;
• conical;
• worm-type

The cylindrical final drive of a car is the most popular type for a configuration with front-wheel drive, as well as a transversely mounted engine and gearbox. It uses, as the name suggests, cylindrical helical, spur or chevron gears. The gear ratio of such units ranges from 3.5 to 4.2 - this is no longer possible, since the dimensions and noise from operation increase enormously.

No less popular, but true for classic rear-wheel drive vehicles, are the so-called hypoid gears. Their key feature are curved teeth, due to which it is possible to transmit torque of large values.

In addition, the gears in this case can be offset relative to each other, which allows, for example, to lower the floor level in the car. The main gear of a car of this type has a gear ratio in the range of 3.5-4.5.

As for conical and worm gears, then they are less common. You can see the final drive of these types of vehicles at various techniques with rear drive wheels, but due to their design features, they are currently used less and less. The disadvantages of the former include big sizes and noise, and the latter require high precision in manufacturing, which entails extra costs.

Well, dear readers of our blog, we got acquainted with the purpose of the final drive of a car, found out what this unit could be and where it is located. In the next publication we will look at another, no less important unit of the machine. Which? Subscribe to us and be among the first to know about it!

One of the main elements of the transmission is the main gear. Next, the main gear design, classification and maintenance are discussed.

Definition

This part is one of the transmission mechanisms designed to increase torque and transmit it to the wheels.

Location

The main gear is usually located in the drive axle housing or in the gearbox. Thus, on rear-wheel drive models it is located in the crankcase rear axle, on cars with front-wheel drive - in the gearbox.

Classification

These parts are divided based on several design features.

According to the drive mechanism used, they are divided into chain and gear, also called gear drives.

According to the number of pairs of gears involved in meshing, gears are classified into single and double.

Options of the first type include drive and driven bevel gears. Such mechanisms are used both passenger cars, and on trucks.

A double gear has a double set of gears. It includes conical and cylindrical parts. This is required to increase the gear ratio, so it is usually used on trucks mobile phones

The main gear of the second type can be central or spaced.

In the first case, the mechanism is located in the drive axle housing. There are one- and two-stage options. Two-stage mechanisms provide for changing pairs of gears to vary the torque. These devices are equipped with heavy and tracked vehicles.

The separate transmission is partly installed in the axle, partly in the hub of the drive wheel pair in the form of wheel reducers. Such mechanisms are relevant for SUVs and trucks off-road, as they allow you to increase ground clearance.

Also, main gears are classified according to the type of gear engagement into three options.

Depending on the number of axles, through and non-through gears are used. Mechanisms of the first type are equipped three-axle vehicles with two axle drive. For biaxial machines, non-pass options are used.

Based on the type of gear connection, single-type transmissions are classified into cylindrical, worm, hypoid, and canonical.

The first type of transmission has gears with herringbone, straight or oblique teeth. The currently most common front-wheel drive models with a transversely mounted engine are equipped with such mechanisms.

Models with manual transmission can have up to three primary shafts. In this case, each of them is equipped with a drive gear. All of them are connected to one slave.

Among other designs, the most widely used is the hypoid (spiroid) main gear. Its gears have straight or oblique teeth. They can be coaxial or offset up or down. The complex shape of the teeth provides a large meshing area, making this final drive designed for high torque. Consequently, it is used on cars and trucks with a classic layout.

The main gear of the canonical type is characterized largest sizes and noise level.

Worm gears involve a worm transmitting torque to a worm wheel. Based on the location of the worm, they are divided into options with lower and upper placement. In any case, the driven wheel has large diameter and oblique teeth. And the worm in various designs changes. It can be globoid or cylindrical in shape, right or left in the direction of the thread lines, multi-start or single-start in terms of the number of thread grooves, with an Archimedean, involute or convolute profile in the shape of the thread groove. Worm gears are used extremely rarely due to labor intensity and high cost production (usually in multi-axle models with a through final drive and in winches).

Chain-type main drives have two sprockets. The leader is set to input shaft The driven gearbox is combined with the drive wheel hub. They are used on motorcycles.

The planetary gearbox of bicycles is more complex. It is built into the drive wheel, and the driven sprocket is connected to its gears, and through them to the wheel.

Subtype chain transmission is belt. Its difference is the presence of reinforced timing belt instead of a chain. This mechanism is most often used on scooters and motorcycles with a CVT. Its driven pulley is connected to the hub of the drive wheel, and the variator itself represents the main gear.

Installation Features

The main gear of the car is combined with the differential in a single design. Motorcycles with shaft drives do not have a differential. On models with a sidecar and two-wheel drive, it is represented by a separate mechanism connecting the two main gears.

Service

During the operation of the vehicle, it is necessary to properly maintain the transmission. Maintenance this mechanism consists of checking the fastening of its crankcase, maintaining the oil level and monitoring its leakage, checking and adjusting the bearings.

Malfunctions are indicated by such signs as noises during acceleration, when cornering, when starting to move, and oil leaks. In such cases, repair of the main gear is required.

The highest gear ratio that can be obtained using a single gear transmission, is limited by the diameter of the driven gear. In order for the gear ratio to be greater than 6.7, use main double gears . They allow provide almost any gear ratio and create through gears provided by the transmission design. Main double gears are installed on cars heavy lifting capacity, when the overall transmission ratio must be significant as torques are transmitted large size. In the main double gear, the torque is increased sequentially by two pairs of gears, one of which is bevel and the other is cylindrical. The total gear ratio of a double gear is equal to the product of the gear ratios of the component pairs.

The central main double transmission of ZIL vehicles consists of the following elements:

A driving bevel gear manufactured as one piece with a shaft that receives torque from cardan transmission;
driven bevel gear with spiral teeth, which is attached to the flange intermediate shaft rivets;
an intermediate shaft with a helical spur gear (drive), manufactured as one piece with the shaft;
driven cylindrical helical gear, which is bolted to the differential box housing, consisting of left and right cups.

The drive bevel gear shaft is supported by roller bearings located in a cup bolted to the main gear housing. The intermediate shaft of the drive cylindrical gear is supported by tapered roller bearings, which are located in the side covers of the main gear housing. To adjust the bearings, shims are provided. The differential box rotates on two tapered roller bearings covered with caps. These roller bearings are adjusted with special nuts.

The drive axle of the ZIL vehicle and the main double gears of the ZIL:

1 - flange; 2 - cuff; 3, 15, 18 and 32 - covers; 4 - washer; 5 - sealing gasket; 6, 9, 14 and 24 and 31 - roller bearings; 7 - glass; 8 - adjusting washers; 10 and 13 - shims; 11 - bevel drive gear; 12 - bevel driven gear; 16 - cylindrical drive gear; 17- final drive housing; 19 and 29 - support washers; 20-right differential cup; 21 - cylindrical driven gear; 22 - semi-axial gear; 23 - left differential cup; 25 - adjusting nut; 26 - axle shaft; 27 - axle housing; 28 - satellite; 30 - cross; 33 - spacer sleeve.

LABORATORY WORK No. 15

Topic: “Purpose, design and principle of operation of the main gear and differential”

Goal of the work: study of the purpose, structure and principle of operation of the main gear and differential.

General provisions

On most modern cars The transmission includes one or more (according to the number of drive axles) main gears and a corresponding number of cross-axle differentials. In addition, on vehicles with several drive axles (drive axles), center differentials can be installed.

The final drive on a car performs two functions:

1) speed matching crankshaft engine and drive wheels and the resulting constant increase in torque transmitted to the drive wheels;

2) changing the direction of the torque vector in accordance with the layout of the car (for example, rotating the torque vector by 90° with a longitudinal engine).

Differential is a vehicle transmission mechanism that distributes the torque supplied to it between the shafts and allows them to rotate at unequal angular speeds.

The cross-wheel differential serves for kinematic misalignment of the wheels of one axle when the vehicle moves around corners or over uneven surfaces.

Center differential serves for kinematic misalignment of wheels different axes when the vehicle moves over uneven surfaces or when the speed changes, as well as for constant distribution of torque between axles in a certain ratio all-wheel drive cars mobiles.

main gear

When the car moves, torque from the engine crankshaft is transmitted to the gearbox and then, through the main gear and differential, to the drive wheels. The final drive allows you to increase or decrease torque wheel-transferable car and simultaneously reduce and accordingly increase the speed of rotation of the wheels.

The gear ratio in the main gear is selected in such a way that the maximum torque and rotation speed of the drive wheels are in the most optimal values ​​for specific car. In addition, the final drive is very often the object of car tuning.

In fact, the main gear is nothing more than a gear reduction gear in which the drive gear is connected to secondary shaft The gearbox, and the driven one - with the wheels of the car. According to the type of gear connection, the main gears differ into the following: varieties:

· cylindrical– in most cases it is used on cars with a transverse engine and gearbox and front-wheel drive;

· conical– used very rarely, as it is large in size and high level noise;

· hypoid– the most popular type of final drive, which is used on most cars with classic rear wheel drive. The hypoid gear is small in size and low level noise;

· worm– practically not used on cars due to the complexity of production and high cost.

It is also worth noting that front- and rear-wheel drive vehicles have different location main gear. IN front wheel drive cars with a transverse gearbox and power unit, the cylindrical main gear is located directly in the gearbox housing. In cars with classic rear-wheel drive, the main gear is installed in the drive axle housing and is connected to the gearbox via cardan shaft. In functionality hypoid transmission rear wheel drive car also includes a 90-degree rotation due to bevel gears. Despite Various types and the location and purpose of the main gear remains unchanged.

Scheme of operation of the main transmission of a car
1 - flange; 2 - drive gear shaft; 3 - drive gear; 4 - driven gear; 5 - driving (rear) wheels; 6 - axle shafts; 7 - final drive housing

Differential

Differential- this is a mechanism that allows (if necessary) the driving wheels of a car to rotate with at different speeds. What is it for? When driving in a straight line, the wheels travel the same distance, but when turning, the outer wheel travels a longer path than the inner wheel. Therefore, in order to “keep up” with the car, the outer wheel must rotate faster.

Differential device simple - a housing, a satellite axis and two satellites (gears). The housing is attached to the driven gear main couple and rotates with her. The satellites mesh with the axle gears, which directly rotate the wheels.

In this design, the satellites transmit more torque to the axle shaft that has less resistance to rotation. That is, with higher speed the wheel will rotate, which is easier for the differential to spin. When driving in a straight line, the wheels are loaded equally, the differential divides the torque equally, and the satellites do not rotate around their axis. When turning, the inner wheel is loaded more, the outer wheel is unloaded. Therefore, the satellites begin to rotate around the axis, twisting the less loaded wheel, thereby increasing its rotation speed.

But this feature of the differential sometimes leads to very unpleasant consequences. If, for example, one of the wheels hits a slippery surface, the differential will only rotate that one, completely ignoring the wheel that has normal contact with the road. That is, the car will “slip”.

To combat this phenomenon, differential locks are used. Many locking methods have been invented - from simple mechanical to sophisticated electronic ones.

The transmission in the design of the car ensures the change and transmission of rotation from power plant to the drive wheels. This component includes a number of components, including the final drive of the vehicle.

Purpose, design features

The main task of this element is to change the torque before applying it to the wheel drive. The gearbox does the same, but it has the ability to change gear ratios by engaging certain gears. Despite the presence of a gearbox in the design of the car, the torque output from it is small, and the rotation speed of the output shaft is high. If you transfer rotation directly to the drive wheels, the resulting load will “crush” the engine. In general, the car simply will not budge.

The final drive of the car provides increased torque and reduced rotation speed. But unlike a gearbox, its gear ratio is fixed.

The location of the final drive using the example of a conventional manual transmission

This transmission on a passenger car is a conventional single-stage constant mesh gearbox, consisting of two gears of different diameters. The drive gear is small in size and is connected to the gearbox output shaft, that is, rotation is supplied to it. The driven gear is much larger in size and the resulting rotation is applied to drive shafts wheels

The gear ratio is the ratio of the number of gear teeth in the gearbox. For passenger cars this parameter is in the range of 3.5-4.5, and for trucks it reaches 5-7.

The higher the gear ratio (the greater the number of teeth on the driven gear relative to the drive gear), the higher the torque supplied to the wheels. In this case, the tractive effort will be greater, but the maximum speed will be lower.

The main gear ratio is selected based on operational indicators power plant, as well as other transmission components.

The final drive design directly depends on the design features of the car itself. This gearbox can be either a separate unit installed in its own housing (rear-wheel drive models) or be part of the gearbox design (cars with front-wheel drive).

Final drive in a rear-wheel drive car

As for some all-wheel drive cars, they may use a different layout. If in such a car the location of the power plant is transverse, then the main gear of the front axle is included in the design of the gearbox, and the rear axle is located in a separate housing. In a car with a longitudinal layout, the main gears on both axles are separated from the gearbox and transfer case.

In models with a separate main gear, this gearbox performs one more task - it changes the angle of rotation by 90 degrees. That is, the gearbox output shaft and wheel drive shafts are perpendicular.

Audi front axle final drive location

IN front-wheel drive models, where the main gear is part of the gearbox design, these shafts have a parallel arrangement, since there is no need to change the direction angle.

A number of trucks use two-stage gearboxes. It is noteworthy that their design may be different, but greatest distribution received a so-called spaced layout, which uses one central gearbox and two wheeled (on-board) gearboxes. This design allows you to significantly increase the torque and, accordingly, the traction force on the wheels.

The peculiarity of the gearbox is that it evenly divides the rotation into both drive shaft. For straight-line motion, this condition is normal. But when cornering, the wheels of the same axle travel different distances, so it is necessary to change the rotation speed of each of them. This is the job of the differential used in the transmission design (it is installed on the driven gear). As a result, the main gear supplies rotation to the drive shafts not directly, but through the differential.

Types and their applicability

The main characteristic of the main gears is the type of gears and the type of tooth engagement between them. The following types of gearboxes are used on cars:

1. Cylindrical
2. Conical
3. Hypoid
4. Worm

Main gear types

Spur gears are used in the final drives of front-wheel drive cars. The absence of the need to change the direction of rotation allows the use of such a gearbox. The teeth on the gears are oblique or chevron.

The gear ratio for such gearboxes is in the range of 3.5-4.2. A larger gear ratio is not used, since this requires increasing the size of the gears, which is accompanied by an increase in the noise level of the transmission.

Conical, hypoid and worm gear are used where it is necessary not only to change the gear ratio, but also to change the direction of rotation.

Bevel gearboxes are usually used on trucks. Their peculiarity comes down to the fact that the gear axes intersect, that is, they are on the same level. In such gears, oblique or curved teeth are used. This type of gearbox is not used on passenger cars due to significant overall dimensions and increased noise.

On rear-wheel drive cars, a different type is most often used - hypoid. Its peculiarity is that the gear axes are shifted. Due to the location of the drive gear lower relative to the driven axis, it is possible to reduce the dimensions of the gearbox. Moreover, this type of transmission is characterized by increased resistance to loads, as well as smooth and silent operation.

Worm gears are the least common and are practically not used on cars. The main reason for this is the complexity and high cost of manufacturing the components.

Primary requirements. Modern tendencies

The main gears are subject to many requirements, the main ones being:

• Reliability;
• Minimal maintenance required;
• High efficiency indicators;
• Smooth and silent;
• Minimum possible overall dimensions.

Naturally, there is no ideal option, so designers have to look for compromises when choosing the type of final drive.

It is not yet possible to abandon the use of final drives in transmission designs, so all developments are aimed at increasing performance indicators.

It is noteworthy that changing the operating parameters of the gearbox is one of the main types of transmission tuning. By installing gears with a changed gear ratio, you can significantly influence the dynamics of the car, maximum speed, fuel consumption, load on the gearbox and power unit.

Finally, it is worth mentioning the design features robotic gearboxes With double clutch, which also affects the main gear design. In such gearboxes, paired and unpaired gears are separated, so there are two secondary shafts at the output. And each of them transmits rotation to its own drive gear of the main gear. That is, in such gearboxes there are two driving gears, and only one driven gear.

DSG gearbox diagram

This design feature allows you to make the gear ratio on the gearbox variable. To do this, only drive gears with different numbers of teeth are used. For example, when using a number of unpaired gears, to increase traction, a gear is used that provides a larger gear ratio, and the gear of a paired row has a lower value of this parameter.