hydrostatic transmission- a hydraulic drive with a closed (closed) circuit, which includes one or more hydraulic pumps and motors. The most common application of hydrostatic transmission is the drive of machines on wheels or tracks - where the hydraulic drive is designed to transfer mechanical energy from drive motor to the executive body.

A hydrostatic transmission is a hydraulic drive with a closed (closed) circuit, which includes one or more hydraulic pumps and motors. In Russian and Soviet literature, a different name is used for such hydraulic drives - hydrostatic transmission. The most common application of a hydrostatic transmission is in the propulsion of wheeled or tracked machines - where the hydraulic drive is designed to transfer mechanical power from the drive motor to the axle, wheel or sprocket of the tracked vehicle, by controlling the pump flow and tractive power output by controlling the hydraulic motor.

Hydrostatic transmission has many advantages over mechanical transmission. One of the advantages is the simplification of the mechanical wiring around the machine. This allows you to get a gain in reliability, because often, under a heavy load on the car, the cardans do not withstand and you have to repair the car. AT northern conditions this happens even more often at low temperatures. By simplifying the mechanical wiring, it is also possible to free up space for auxiliary equipment. The use of a hydrostatic transmission can make it possible to completely remove the shafts and bridges, replacing them with a pumping unit and hydraulic motors with gearboxes built directly into the wheels. Or, in more simple version, hydraulic motors can be built into the bridge.

The first of the mentioned schemes, where hydraulic motors are built into the wheels, can be applied to wheeled vehicles, but more interesting is the variant of such a hydraulic drive for tracked vehicles. For such machines, Sauer-Danfoss has also developed a control system based on hydraulic pumps and hydraulic motors of the 90 series, H1 series and 51 series -. Microcontroller control allows you to provide comprehensive control over the machine, ranging from control diesel engine. During operation, the system ensures the synchronization of the sides for the rectilinear movement of the machine and the side turn of the machine using the steering wheel or electric joystick.

The second scheme mentioned above is used for tractors or other wheeled vehicles. This is a hydraulic drive, in which there is one hydraulic pump and one hydraulic motor built into the drive axle. To control the hydraulic drive, both mechanical or hydraulic control can be used, as well as the most Hi-tech electric control using the controller built into the hydraulic pump. The program for controlling such a hydraulic drive can also be in the MC024 microcontroller installed separately. As well as for “Dual Path”, it allows you to control not only the hydrostatic transmission, but also the engine according to CAN bus. Electric control allows for even smoother and more precise control of the speed of movement and traction power of the machine.

The disadvantage of hydrostatic transmission can be considered not high efficiency, which is much lower than that of mechanical transmission. However, compared to mechanical transmissions that include gearboxes, hydrostatic transmission is more economical and faster. This happens because at the moment manual switching gears have to be released and the accelerator pedal pressed. It is at this moment that the engine spends a lot of power, and the speed of the car changes jerkily. All this negatively affects both speed and fuel consumption. In a hydrostatic transmission, this process is smooth and the engine runs more economically, which increases the durability of the entire system.

For hydrostatic transmission, Sauer-Danfoss develops several series of hydraulic pumps and hydraulic motors. The most common in both Russian and foreign technology are adjustable axial piston. Their production began back in the 90s of the last century and now it is a fully debugged line of equipment that has a lot of advantages over the so-called GTS 90, produced by many domestic and foreign companies. The advantages include the compactness of the units, the possibility of making tandem pump units and all control options from mechanical to electro-hydraulic based on the microcontroller control of the PLUS+1 system.

In conjunction with the hydraulic pumps of the 90 series, adjustable axial piston pumps are often used. They may also have different ways of regulating the working volume. Proportional electric control allows you to smoothly adjust the power over the entire range. Discrete electric control allows you to work in low and high power modes, which is used either for various types of soil, or for driving on flat or hilly terrain.

The latest development of Sauer-Danfoss are the H1 series. circuit diagram their operation is similar to the 90 series hydraulic pumps and 51 series motors respectively. But in comparison with them, the design was worked out using the latest technologies. The number of parts has been reduced, which provides greater reliability, reduced dimensions. But the main difference from the old series can be considered the presence of only one control option - electric. it modern trend- use systems based on complex electronics, controllers. And the H1 series is completely designed for such modern requirements. One of the signs of this is the version of hydraulic pumps with an integrated controller mentioned above.

There are also axial piston hydraulic pumps and hydraulic motors of the 40 and 42 series, which are applicable in low power hydrostatic transmission, where the working volume of the hydraulic pump does not exceed 51 cm 3. Such hydraulic drives can be found in small utility harvesters, skid steer loaders, mowers and other small-sized equipment. Often, gerotor hydraulic motors can be used in such a hydraulic drive. So in Bobcat loaders they are used. For other equipment, gerotor hydraulic motors of the OMT, OMV series are applicable, and for completely light engineering.

Hydraulic transmission- a set of hydraulic devices that allow you to connect a source of mechanical energy (engine) with executive mechanisms machines (car wheels, machine spindle, etc.). Hydraulic transmission is also called hydraulic transmission. As a rule, in a hydraulic transmission, energy is transferred through a fluid from a pump to a hydraulic motor (turbine).

In the presented video, a translational hydraulic motor is used as the output link. The hydrostatic transmission uses a rotary motion hydraulic motor, but the principle of operation is still based on the law. AT hydrostatic drive rotary action working fluid is supplied from pump to motor. In this case, depending on the working volumes of hydraulic machines, the torque and frequency of rotation of the shafts can change. Hydraulic transmission has all the virtues hydraulic drive: high transmitted power, the possibility of implementing large gear ratios, the implementation of stepless regulation, the possibility of transferring power to moving, moving elements of the machine.

Methods of regulation in hydrostatic transmission

The speed control of the output shaft in the hydraulic transmission can be carried out by changing the volume of the working pump (volumetric control), or by installing a throttle or flow controller (parallel and sequential throttle control). The illustration shows a hydraulic transmission with closed loop volume control.

Closed Loop Hydraulic Transmission

Hydraulic transmission can be realized according to closed type(closed circuit), in this case there is no hydraulic tank connected to the atmosphere in the hydraulic system.

In hydraulic systems of a closed type, the speed of rotation of the shaft can be controlled by changing the working volume of the pump. Most often used as pump motors in hydrostatic transmission.

Open loop hydraulic transmission

open called hydraulic system connected to a tank that communicates with the atmosphere, i.e. the pressure above the free surface of the working fluid in the tank is equal to atmospheric pressure. In open-type hydraulic transmissions, it is possible to implement volumetric, parallel and sequential throttle control. The following figure shows an open loop hydrostatic transmission.

Where are hydrostatic transmissions used?

Hydrostatic transmissions are used in machines and mechanisms where it is necessary to realize the transmission of large powers, to create a high torque on the output shaft, to carry out stepless speed control.

Hydrostatic transmissions are widely used in mobile, road-building equipment, excavators, bulldozers, in railway transport - in diesel locomotives and track machines.

Hydrodynamic transmission

Hydrodynamic transmissions also use turbines to transmit power. The hydraulic fluid in hydraulic transmissions is supplied from the dynamic pump to the turbine. Most often in hydrodynamic transmission vaned pump and turbine wheels are used, located directly opposite each other, so that the liquid flows from the pump wheel directly to the turbine wheel, bypassing the pipelines. Such devices that combine the pump and turbine wheels are called fluid couplings and torque converters, which, despite some similar elements in the design, have a number of differences.

fluid coupling

hydrodynamic transmission consisting of pump and turbine wheel installed in a common crankcase are called fluid coupling. The moment on the output shaft of the hydraulic clutch is equal to the moment on input shaft, that is, the fluid coupling does not allow changing the torque. In a hydraulic transmission, power can be transferred via hydraulic clutch, which will provide smooth running, a smooth increase in torque, and a reduction in shock loads.

torque converter

Hydrodynamic transmission, which includes pump, turbine and reactor wheels placed in a single housing is called a torque converter. Thanks to the reactor torque converter allows you to change the torque on the output shaft.

Hydrodynamic transmission in an automatic transmission

The most famous example of hydraulic transmission application is car automatic transmission, in which a fluid coupling or torque converter can be installed. Due to the higher efficiency of the torque converter (compared to the fluid coupling), it is installed on most modern cars with automatic transmission gears.

Hydraulics, hydraulic drive / Pumps, hydraulic motors / What is a hydraulic transmission

Hydraulic transmission- a set of hydraulic devices that allow you to connect a source of mechanical energy (engine) with the actuators of the machine (wheels of a car, machine spindle, etc.). Hydraulic transmission is also called hydraulic transmission. As a rule, in a hydraulic transmission, energy is transferred through a fluid from a pump to a hydraulic motor (turbine).

Depending on the type of pump and motor (turbine), there are hydrostatic and hydrodynamic transmission.

hydrostatic transmission

Hydrostatic transmission is a volumetric hydraulic drive.

In the presented video, a translational hydraulic motor is used as the output link. The hydrostatic transmission uses a rotary motion hydraulic motor, but the principle of operation is still based on the law of the hydraulic lever. In a rotary hydrostatic drive, the working fluid is supplied from pump to motor. In this case, depending on the working volumes of hydraulic machines, the torque and frequency of rotation of the shafts can change. Hydraulic transmission has all the advantages of a hydraulic drive: high transmitted power, the possibility of implementing large gear ratios, the implementation of stepless regulation, the possibility of transferring power to moving, moving elements of the machine.

Methods of regulation in hydrostatic transmission

The speed control of the output shaft in the hydraulic transmission can be carried out by changing the volume of the working pump (volumetric control), or by installing a throttle or flow controller (parallel and sequential throttle control).

The illustration shows a hydraulic transmission with closed loop volume control.

Closed Loop Hydraulic Transmission

Hydraulic transmission can be realized according to closed type(closed circuit), in this case there is no hydraulic tank connected to the atmosphere in the hydraulic system.

In closed-type hydraulic systems, the speed of rotation of the hydraulic motor shaft can be controlled by changing the working volume of the pump. Axial piston machines are most often used as pump-motors in hydrostatic transmission.

Open loop hydraulic transmission

open called a hydraulic system connected to a tank that communicates with the atmosphere, i.e. the pressure above the free surface of the working fluid in the tank is equal to atmospheric pressure. In open-type hydraulic transmissions, it is possible to implement volumetric, parallel and sequential throttle control. The following figure shows an open loop hydrostatic transmission.

Where are hydrostatic transmissions used?

Hydrostatic transmissions are used in machines and mechanisms where it is necessary to realize the transmission of large powers, to create a high torque on the output shaft, to carry out stepless speed control.

Hydrostatic transmissions are widely used in mobile, road-building equipment, excavators, bulldozers, in railway transport - in diesel locomotives and track machines.

Hydrodynamic transmission

Hydrodynamic transmissions use dynamic pumps and turbines to transmit power. The hydraulic fluid in hydraulic transmissions is supplied from the dynamic pump to the turbine. Most often, hydrodynamic transmission uses paddle pump and turbine wheels located directly opposite each other, so that fluid flows from the pump wheel directly to the turbine wheel, bypassing the pipelines. Such devices that combine the pump and turbine wheels are called fluid couplings and torque converters, which, despite some similar elements in the design, have a number of differences.

fluid coupling

hydrodynamic transmission consisting of pump and turbine wheel installed in a common crankcase are called fluid coupling. The moment on the output shaft of the hydraulic clutch is equal to the moment on the input shaft, that is, the hydraulic clutch does not allow changing the torque. In a hydraulic transmission, power can be transmitted through a hydraulic clutch, which will provide smooth running, a smooth increase in torque, and a reduction in shock loads.

torque converter

Hydrodynamic transmission, which includes pump, turbine and reactor wheels placed in a single housing is called a torque converter. Thanks to the reactor torque converter allows you to change the torque on the output shaft.

Hydrodynamic transmission in an automatic transmission

The most famous example of hydraulic transmission application is car automatic transmission, in which a fluid coupling or torque converter can be installed.

Due to the higher efficiency of the torque converter (compared to the fluid coupling), it is installed on most modern cars with automatic transmission.

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mini tractors

Hydrostatic transmissions

The considered designs of transmissions of mini-tractors provide for a stepwise change in their speed and traction. For more full use traction capabilities, especially microtractors and microloaders, the use of continuously variable transmissions and, first of all, hydrostatic transmissions is of great interest. Such transmissions have the following advantages:
1) high compactness with a small weight and overall dimensions, which is explained by the complete absence or use of a smaller number of shafts, gears, couplings and other mechanical elements. In terms of mass per unit of power, the hydraulic transmission of a mini-tractor is commensurate, and at high operating pressures it surpasses a mechanical speed transmission (8-10 kg / kW for a mechanical speed transmission and 6-10 kg / kW for a hydraulic transmission of mini-tractors);
2) the possibility of implementing large gear ratios with volumetric regulation;
3) low inertia, providing good dynamic properties machines; the inclusion and reversal of the working bodies can be carried out for a fraction of a second, which leads to an increase in the productivity of the agricultural unit;
4) stepless speed control and simple control automation, which improves the working conditions of the driver;
5) independent arrangement of transmission units, which makes it possible to place them most expediently on the machine: a mini-tractor with hydraulic transmission can be arranged in the most rational way in terms of its functional purpose;
6) high protective properties transmission, i.e. reliable protection against overloads of the main engine and the drive system of the working parts due to the installation of safety and overflow valves.

The disadvantages of hydrostatic transmission are: lower than that of a mechanical transmission, the coefficient useful action; higher cost and the need to use quality working fluids with a high degree of purity. However, the use of unified assembly units (pumps, hydraulic motors, hydraulic cylinders, etc.), their organization mass production using modern automated technology can reduce the cost of hydrostatic transmission. Therefore, there is now an increasing transition to the mass production of tractors with hydrostatic transmission, and above all garden tractors, designed to work with active working bodies of agricultural machines.

For more than 15 years, the transmissions of microtractors have been using both the simplest schemes of hydrostatic transmissions with unregulated hydraulic machines and throttle speed control, as well as modern transmissions with volumetric regulation. The gear type pump with a constant displacement (unregulated supply) is attached directly to the diesel engine of the microtractor. As a hydraulic motor, where the oil flow injected by the pump rushes through the valve-distributing control device, a single-screw (rotary) hydraulic machine of the original design is used. Screw hydraulic machines compare favorably with gear ones in that they provide an almost complete absence of hydraulic flow pulsation, are small in size at high feed rates, and besides, they are silent in operation. Screw hydraulic motors for small

sizes are capable of developing high torques at low speeds and high speeds at low loads. However wide application screw hydraulic machines currently do not have due to low efficiency and high requirements for manufacturing accuracy.

The hydraulic motor is attached through a two-stage gearbox to the rear axle of the microtractor. The gearbox provides two modes of movement of the machine: transport and work. Within each of the modes, the speed of the microtractor is infinitely variable from 0 to maximum with the help of a lever, which also serves to reverse the machine.

When moving the lever away from the neutral position, the microtractor increases speed, moving forward, when turning in reverse direction reverse movement is provided.

At neutral position lever, oil does not enter the pipelines, and therefore, the hydraulic motor. The oil is sent from the control device directly to the pipeline and then to the oil cooler, oil tank with filter, and then returns to the pump through the pipeline. When the lever is in neutral position, the drive wheels of the microtractor do not rotate, since the hydraulic motor is turned off. When the lever is turned in the opposite direction, the oil bypass in the control device stops, and the direction of its flow in the pipelines is reversed. This corresponds to the reverse rotation of the hydraulic motor, and consequently, the movement of the microtractor in reverse.

In Bolens-Husky microtractors (Bolens-Husky, USA), a two-console foot pedal is used to control the hydrostatic transmission. In this case, pressing the pedal with the toe of the foot corresponds to the movement of the microtractor forward (position P), and the heel - movement back. The middle fixed position H is neutral, and the speed of the machine (forward and backward) increases as the pedal angle increases from its neutral position.

The appearance of the rear drive axle of the Case microtractor with the open cover of the two-stage gearbox, combined with the main gear and transmission brake. To combined crankcase rear axle casings of the left and right axle shafts are fixed on both sides, at the ends of which there are wheel mounting flanges. A hydraulic motor is installed in front of the left side wall of the crankcase, the output shaft of which is connected to input shaft gearboxes. At the inner ends of the semi-axes there are semi-axial spur gears with straight teeth engaged with the gear teeth of the gearbox. Between the gears there is a mechanism for blocking the semi-axes between themselves. The switching of operating modes of the hydroexchange transmission (gears in the gearbox) is carried out from a mechanism that allows you to set either the operating mode by engaging the gears, or the transport mode by engaging the gears. When changing the oil, the combined crankcase is emptied through a drain hole closed by a plug.

The system is based on an adjustable pump and an unregulated hydraulic motor. Pump and hydraulic motor - axial piston type. The pump supplies fluid through the main pipelines to the hydraulic motor. The pressure in the drain line is maintained by a make-up system consisting of an auxiliary pump, a filter, an overflow valve and check valves. The pump draws fluid from the hydraulic tank. The pressure in the pressure line is limited by safety valves. When the gear is reversed, the drain line becomes pressure (and vice versa), so two check valves and two safety valves are installed. Axial-piston hydraulic machines with the transfer of equal power compared to other hydraulic machines are most compact; their working bodies have a small moment of inertia.

The design of the hydraulic drive and axial-piston hydraulic machine is shown in fig. 4.20. A similar hydraulic transmission is installed, in particular, on Bobket microloaders. The diesel of the microloader drives the main and auxiliary make-up pumps (the auxiliary pump can be made gear). The liquid from the pump under pressure along the line enters through safety valves to hydraulic motors
which, through reduction gears, rotate the sprockets chain drives(not shown in the diagram), and from them - the drive wheels. The make-up pump supplies liquid from the tank to the filter.

Schematic hydraulic diagram

Reversible axial piston hydraulic machines (pump-motors) are of two types: with an inclined disk and with an inclined block. To

The pistons rest against the ends of the disk, which can rotate around an axis. For half a revolution of the shaft, the piston will move in one direction for a full stroke. The working fluid from the hydraulic motors (through the suction line) enters the cylinders. During the next half revolution of the shaft, the liquid will be pushed out by the pistons into the pressure line to the hydraulic motors. The make-up pump replenishes the leaks collected in the tank.

By changing the angle p of the disc inclination, the pump performance is changed at a constant shaft speed. When the disc is in a vertical position, the hydraulic pump does not pump liquid (its idle mode). When the disk is tilted in the other direction from the vertical position, the direction of the fluid flow changes to the opposite: the line becomes pressure, and the line becomes suction. The microloader gets reversed. Parallel connection of the hydraulic motors of the left and right side of the microloader to the pump gives the transmission the properties of a differential, and separate control of the tilting disks of the hydraulic motors makes it possible to change them relative speed, up to obtaining the rotation of the wheels of one side in the opposite direction.

In machines with an inclined block, the axis of rotation is inclined to the axis of rotation of the drive shaft at an angle p. The shaft and block rotate synchronously due to the use of cardan gear. The working stroke of the piston is proportional to the angle p. At p = 0, the piston stroke is zero. The cylinder block is tilted by a hydraulic servo.

A reversible hydraulic machine (pump-motor) consists of a pumping unit installed inside the housing. The case is closed by front and back covers. Connectors are sealed with rubber rings.

The pumping unit of the hydraulic machine is installed in the housing and fixed with retaining rings. It consists of drive shaft, rotating in bearings and seven pistons with connecting rods, a cylinder block centered by a spherical distributor and a central spike. The pistons are rolled on the connecting rods and installed in the block cylinders. The connecting rods are fixed in spherical sockets of the drive shaft flange.

The cylinder block, together with the central spike, is deflected at an angle of 25 ° relative to the axis of the drive shaft, therefore, with the synchronous rotation of the block and the drive shaft, the pistons reciprocate in the cylinders, sucking in and pumping working fluid through the channels in the distributor (when operating in pump mode). The distributor is fixed and fixed relative to the rear cover with a pin. The channels of the distributor coincide with the channels of the cover.

For one revolution of the drive shaft, each piston makes one double stroke, while the piston leaving the block sucks in the working fluid, and displaces it when moving in the opposite direction. The amount of working fluid pumped by the pump (pump flow) depends on the speed of the drive shaft.

When the hydraulic machine is operating in the hydraulic motor mode, the fluid flows from the hydraulic system through the channels in the cover and distributor into the working chambers of the cylinder block. Fluid pressure on the pistons is transmitted through the connecting rods to the drive shaft flange. At the point of contact of the connecting rod with the shaft, axial and tangential components of the pressure force arise. The axial component is perceived angular contact bearings, and the tangential one creates a torque on the shaft. The torque is proportional to the displacement and pressure of the hydraulic motor. When changing the amount of working fluid or the direction of its supply, the frequency and direction of rotation of the hydraulic motor shaft change.

Axial piston hydraulic machines are designed for high nominal and maximum pressure(up to 32 MPa), so they have an insignificant specific metal content (up to 0.4 kg/kW). The overall efficiency is quite high (up to 0.92) and is maintained when the viscosity of the working fluid is reduced to 10 mm2/s. The disadvantages of axial-piston hydraulic machines are high requirements for the purity of the working fluid and the accuracy of manufacturing the cylinder-piston group.

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Rice. Fig. 2. Car "Elite" designed by V. S. Mironov. 3. The drive of the leading hydraulic pump by the cardan shaft from the engine

cones to gear ratio changed steplessly, which was not in the first Russian car. This was not enough for our hero. He decided to invent an automatic machine that smoothly changes the gear ratio of the transmission depending on the engine crankshaft speed, and abandon the differential.

Mironov displayed the hard-won idea on the drawing (Fig. 1). According to his plan, the engine through the splined universal joint and reverse (a mechanism that, if necessary, changes the direction of rotation to the opposite) should rotate the drive shaft of the belt drive. A fixed pulley is fixed on it, and a movable pulley moves along it. At low engine speeds, the pulleys are moved apart, the belt does not touch them and therefore does not rotate. As the engine speed increases, the centrifugal mechanism pulls together the pulleys, squeezing the belt to a greater radius of rotation. Due to this, the belt is tensioned, rotates the driven pulleys, and they turn the wheels through the axle shafts. Belt tension shifts it between the driven pulleys by a smaller radius of rotation, while increasing the distance between the variator shafts. To maintain belt tension, the spring shifts the reverse along the guides. This reduces the gear ratio, and the speed of the car increases.

When the idea acquired real features, Vladimir prepared an application for an invention and sent it to the All-Union Research Institute of Patent Information (VNIIPI) of the USSR State Committee for Inventions and Discoveries, where on December 29, 1980, his priority for the invention was registered. Soon he was issued a copyright certificate No. 937839 “Stepless power transmission for Vehicle". Mironov had to test his invention, for this he decided to build a car with his own hands and by the beginning of 1983 he had made the car "Spring" ("TM" No. 8, 1983). In a non-V-belt variator: one for each wheel._

Due to the fact that the torque is approximately equally distributed between the drive wheels, the car did not skid. When cornering, the belts slipped slightly, replacing the differential with this. All this allowed the driver to feel

ENJOY MOVEMENT. The car quickly accelerated, went well both on asphalt and on a dirt road, delighting the designer. There was a weak point in it: belts. At first, it was necessary to shorten the ones obtained from combine operators, but because of the joints, they did not serve for a long time. Someone suggested: "Contact the manufacturer." And what? The trip to the factory of rubber products in the Ukrainian town of Bila Tserkva turned out to be successful.

Director of the enterprise V.M. Beskpinsky listened and immediately ordered to make 14 pairs of belts according to a given size. They did it, and for free! Vladimir brought them home, installed them, adjusted something and drove without breakdowns, regularly replacing both at once every 70 thousand km. With them, he rolled out everywhere and participated in nine All-Union “home-made” motor races, drove more than 10 thousand km in them. The car, with an engine from the VAZ-21011, easily kept a uniform speed in the column, accelerated to 145 km / h, did not skid on a dirty or snowy road. And all this thanks to the fact that it used

V-BELT TRANSMISSION.

Mironov wanted as many people as possible to use his invention. He even rode the "Spring" in Moscow, the technical director of VAZ V.M. Akoev and chief designer G. Mirzoev. Liked! Thanks to this, in 1984, a prototype was made at VAZ, based on the VAZ-2107 model. The work went well. It was supposed to complete the testing of the prototype and design new prototype with the transfer of Mironov. However, in the midst of preparatory work Akoev died, and Mir-zoev lost interest in the novelty. He did not show Vladimir the test reports,

sylap to the official of the Automotive Industry I.V. Korovkin, and he again sent him to explain himself to Mirzoev.

Not prone to despondency, our hero traveled everywhere in the "Spring", and he discovered its amazing properties. So, smoothly releasing the accelerator pedal, it was possible to slow down the engine, reducing the speed to five, or even three km / h. And when you turn on the reverse, it slowed down much faster. Due to this, he used the shoe brake only at low speed to completely stop the car. Having traveled more than 250 thousand km on Vesna, Mironov did not change brake pads. Incredible fact for a car.

Our hero was haunted by other ideas. One of them: all-wheel drive, both belt-driven and hydraulic. And he set about creating new car, on which he wanted to independently check these and other technical solutions. For him, it was supposed to be an experimental car, a kind of layout, but with good speed characteristics. Continuing to drive the "Spring" every day, Vladimir in 1990 made a one-volume car with full hydraulic drive and called it "Elite" (Fig. 2). The main thing in it was

STEPLESS HYDRO TRANSMISSION. In the Elite, the engine from the Volga GAZ-2410 was located in front and actuated the hydraulic pump (Fig. 3). The oil circulated through metal tubes with an inner diameter of 11 mm. There is a dispenser next to the driver, and a receiver in the trunk (Fig. 4). The car has no clutch, gearbox, cardan shaft, rear axle and differential. Weight savings - almost 200 kg.

In the middle position of the reverse lever, the oil flow is blocked, and it does not enter the driven pumps, so the vehicle does not move. In the “Forward” position of the reverser handle, the oil enters the pump through the dispenser and under pressure, having passed the reverse, into the hydraulic motors. Having done useful work in them,

In hydrostatic continuously variable transmissions, the torque and power from the driving link (pump) to the driven link (hydraulic motor) is transmitted by liquid through pipelines. The power N, kW, of the fluid flow is determined by the product of the head H, m, and the flow rate Q, m3/s:

N = HQpg / 1000,
where p is the density of the liquid.

Hydrostatic transmissions do not have internal automatism, to change gear ratio ACS is required. However, hydrostatic transmission does not require a reverse mechanism. Reverse is provided by changing the connection of the pump to the liquid discharge and return lines, which causes the hydraulic motor shaft to rotate in the opposite direction. With a variable pump, no start-up clutch is needed.

Hydrostatic transmissions (as well as electric transmissions) have much wider layout possibilities compared to friction and hydrodynamic ones. They may be part of a combination hydromechanical box gears in series or parallel connection with a mechanical gearbox. In addition, they may be part of a combined hydromechanical transmission when the hydraulic motor is installed in front of the main gear - fig. a (the drive axle with the main gear, differential, axle shafts was retained) or hydraulic motors are installed in two or all wheels - fig. a (they are supplemented with reducers that perform the functions main gear). In any case, the hydraulic system is closed, and a make-up pump is included in it to maintain overpressure in the return line. Due to energy losses in pipelines, it is usually considered expedient to use hydrostatic transmission with a maximum distance between the pump and the hydraulic motor of 15 ... 20 m.

Rice. Transmission schemes for vehicles with hydrostatic or electric transmissions:
a - when using motor-wheels; b - when using a driving axle; H - pump; GM - hydraulic motor; G - generator; EM - electric motor

Currently, hydrostatic transmissions are used on small amphibious vehicles, such as the Jigger and Mule, on vehicles with active semi-trailers, on small series of heavy-duty ( gross weight up to 50 tons) dump trucks and experimental city buses.

The widespread use of hydrostatic transmissions is constrained mainly by their high cost and insufficient high efficiency(about 80...85%).

Rice. Schemes of hydraulic machines of volumetric hydraulic drive:
a - radial piston; b - axial piston; e - eccentricity; y - the angle of inclination of the block

Of the whole variety of volumetric hydraulic machines: screw, gear, bladed (gate), piston - for automotive hydrostatic transmissions, radial piston (Fig. a) and axial piston (Fig. b) hydraulic machines are mainly used. They allow you to use high operating pressure(40 ... 50 MPa) and can be adjustable. The change in the supply (flow rate) of the liquid is provided for radial piston hydraulic machines by changing the eccentricity e, for axial piston hydraulic machines - the angle y.

Losses in volumetric hydraulic machines are divided into volumetric (leaks) and mechanical, the latter also include hydraulic losses. Losses in the pipeline are divided into friction losses (they are proportional to the length of the pipeline and the square of the fluid velocity in turbulent flow) and local (expansion, contraction, turn of the flow).

The article deals with the development of transmission crawler bulldozers thrust class 10 ... 15 tons on a caterpillar.

To start, a little history. The very concept of "bulldozer" arose at the end of the 19th century. and meant a powerful force that overcomes any barriers. To caterpillar tractors this concept began to be attributed in the 1930s, figuratively characterizing the power of a tracked vehicle with a metal shield fixed in front that moves the soil. As a base, an agricultural tractor was originally used with main feature- caterpillar track, providing maximum grip with the ground. A caterpillar is defined as an endless rail. Russian scientists were involved in its invention, as well as in all key fundamental discoveries. One of the first patents was registered in Russia around 1885.

One of the features crawler is the ability to turn by turning off one of the tracks, or blocking it, or turning it into a counter move. On fig. 1 shown typical scheme mechanical transmission, which was used on the first crawler bulldozers and is still used today.

Advantages of this scheme- simplicity of the design of the units, efficiency more than 95%, low cost and minimum costs time for repairs.

During the period of rapid growth of the world economy in 1955-1965. and the development of machining technologies and the chemical industry, in parallel, several manufacturers of crawler bulldozers have applied hydromechanical transmission (HMT). It was built on the basis of a torque converter (GTR), which by that time had become widespread on diesel locomotives. GMT on bulldozers was in demand primarily in the heavy class: more than 15 tons of thrust, and is characterized by the ability to obtain maximum torque at zero speed, i.e. with maximum grip of the caterpillar with the ground and maximum resistance of the moved soil mass. The only and critical drawback, in addition to technological complexity, was high mechanical losses - 20 ... The scheme of hydromechanical transmission is shown in fig. 2.

Advantages of this scheme- the maximum possible traction on the tracks, simpler control compared to a mechanical transmission, elastic connection between the engine and the caterpillar.

The need to use expensive planetary gearboxes and final drives is caused by the transfer of higher torque than in a mechanical transmission - up to two times. The GMT scheme is currently used by the leading manufacturers of caterpillar bulldozers Komatsu and Caterpillar. Only Chelyabinsk tractor plant provides a significant share of manual transmissions, producing a virtually unchanged copy of the Caterpillar of the 1960s for more than 50 years.

The next technological step in the development of the transmission of caterpillar bulldozers was the use of the “hydraulic pump (HP) - hydraulic motor (GM)” scheme under the general term “hydrostatic transmission” (HST). The beginning of the widespread use of GN-GM was laid by the military when improving the drives of artillery pieces, where it was required high speed movement of moving parts with a considerable inertial mass, which excluded the use of a rigid mechanical connection.

A transmission of this type is today predominantly common on medium and heavy class special equipment: hydrostatic transmission is used by all leaders in the excavator equipment market. The use of HTS in excavators is associated with the performance of their main work by actuators with hydraulic force transfer. The spread of GTS was also facilitated by the improvement of machining technologies and the widespread use synthetic oils produced under predetermined parameters of use, and in addition, the development of microelectronics, which made it possible to implement complex algorithms GTS management. The scheme of hydrostatic transmission is shown in fig. 3.

Advantages of this scheme:

• high efficiency - more than 93%;
• the maximum possible thrust on the tracks is higher than that of the GMT, due to lower losses;
• better maintainability due to the minimum number of units and their unification by different manufacturers, mainly not releasing ready-made caterpillar bulldozers;
• it also ensures the minimum cost of the units;
• the most simple control of one joystick, allowing without modifications to implement remote control, including by means of radio communication;
• elastic connection engine-caterpillar;
• small dimensions, which makes it possible to use the freed up space for attachments;
• the possibility of macro-control of the state of the entire transmission by one parameter - the temperature of the working fluid;
• maximum possible maneuverability - zero turning radius due to anti-travel tracks;
• the possibility of 100% power take-off for hydroficated attachments from a regular hydraulic pump;
• the possibility of cheap software and technological modernization in the near future due to an elementary transition to a working fluid with new properties obtained on the basis of nanotechnology.

An indirect confirmation of such advantages is the choice of GTS as a leader German manufacturers special equipment by Liebherr as a base in the design of all special equipment, including crawler bulldozers. Table of all the advantages, disadvantages and features of operation various types transmissions, including the "new" for Caterpillar and actually implemented back in 1959 by the ChTZ plant on the DET-250 bulldozer, the electromechanical transmission is listed on the website www.TM10.ru of the DST-Ural Plant.

Of course, readers paid attention to the preferences of the authors of the article. Yes, we are making our choice in favor of the GTS and we believe that such a solution will make it possible to overcome the technological backlog of the leaders in the production of special equipment in Russia and break away from the eastern neighbor - China, which claims to easily absorb our bulldozer market. The new TM bulldozer with a transmission based on Bosch Rexroth components with a thrust class of 13…15 tons will be presented by DST-Ural in July. The working weight of the new bulldozer will remain 23.5 tons, power - 240 hp. and maximum thrust - 25 tons, which, with a 5% lag, corresponds to the Liebherr PR744 analogue (24.5 tons, 255 hp). Once again, let us recall the existing possibilities of domestic mechanical engineering. For example, we were the first in the world practice to apply the scheme of bogies on swing carriages in the 10th class of caterpillar bulldozers on serial production. Prior to this, manufacturers could afford it only in the heavy class of these machines weighing more than 30 tons, where prices are several times higher. Market price bulldozer TM10 on swing carriages with hydrostatic transmission is planned no more than 4.5 million rubles.