GST-90 hydraulic drive (Figure 1.4) includes axial-plunger units: adjustable hydraulic pump with a gear pump of feeding and a hydraulic distributor; Unregulated hydraulic motor assembly with a valve box, a fine filter with a vacuum, pipelines and hoses, and a tank for working fluid.
Shaft 2 The hydraulic pump rotates in two roller bearings. A block of cylinders planted on the shaft slot 25 , in the holes of which plungers move. Each plunger with a spherical hinge is connected to the fifth, which rests on the support located on the inclined washer 1 . The washer is connected to the hydraulic pump housing using two roller bearings, and due to this can be changed the tilt of the washer relative to the pump shaft. Changing the angle of inclination of the washer occurs under the action of the effort of one of two servo-cylinders 11 whose pistons are connected to the puck 1 With the help of thrust.
Inside the servo-cylinders there are springs acting on pistons and installing the washer so that the support located in it has been perpendicular to the shaft. Along with the cylinder block rotates an appropriate bottom, moving along the distributor, fixed on the rear lid. The holes in the distributor and the appropriate day periodically connect the operating chambers of the cylinder block with highways that bind hydraulic pump with hydraulic motor.
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Figure 1.4 - GST-90 hydraulic diagram: 1 - washer; 2 - the output shaft of the pump; 3 - reversible adjustable pump; 4 - hydrolynia management; 5 - control lever; 6 - spool control of the lulley position; 7 8 - Pump fuel; 9 - check valve; 10 - safety valve Significant systems; 11 - servoscillide; 12 - filter; 13 - vacuummeter; 14 - Hydrobac; 15 - heat exchanger; 16 - spool; 17 - overflow valve; 18 - the main safety valve of high pressure; 19 - Hydrolynia low pressure; 20 - High pressure hydrolynium; 21 - drainage hydrolynium; 22 - unregulated motor; 23 - the output shaft of the hydraulic motor; 24 - inclined hydraulic washer; 25 - cylinder block; 26 - link link; 27 - end seal |
Spherical plunger hinges and sliding stains are lubricated under the pressure of the working fluid.
The inner plane of each unit is filled with the working fluid and is an oil bath for mechanisms running in it. The leakage of the hydraulic aggregate are also coming into this cavity.
The pump fasteners are attached to the rear end surface of the hydraulic pump 8 Six-type, the shaft of which is connected to the hydraulic pump shaft.
Pump feeding sucks the working fluid from the tank 14 And gives it:
- in hydraulic pump through one of the check valves;
- into the control system through the hydrodistributor in quantities limited by the bib.
On the casing pump 8 Safety valve is located 10 which opens with the increase in pressure developed by the pump.
Hydraulic distributor 6 It serves to distribute fluid flow in the control system, that is, to direct it to one of two servo-cylinders, depending on the change of the lever position 5 or locking the liquid in the servoscilliter.
The hydraulic distributor consists of a housing, a spool with a return spring, located in a glass, a control lever with a spring forces, and a lever 5 and two crashes 26 which bind a spool with control lever and inclined washer.
Hydromotor device 22 Similar to the pump device. The main differences are as follows: the plunger spits when rotating the shaft slide on the inclined washer 24 having a permanent angle of inclination, and therefore the mechanism of its turn with the hydraulic distributor is absent; Instead of a pump feeding to the rear end surface of the hydromotor, the valve box is attached. Hydromotor hydraulic pump connected with two pipelines (Hydron pumps-Gitzromotor highways). According to one of the mains, the flow of working fluid under high pressure moves from hydraulic pump to the hydraulic pressure, on the other - under low pressure is returned back.
In the valve box case there are two high pressure valves, overflow valve 17 And Spool 16 .
The feeding system includes a feed pump 8 as well as reverse 9 , Safety 10 and overflow valves.
The feeding system is designed to supply the working fluid of the control system, providing minimum pressure in the hydraulic pump highways, compensating for leaks in hydraulic pump and hydromotor, constant mixing of the working fluid circulating in the hydraulic pump and hydromotor, with a liquid in the tank, removal from heat parts.
High pressure valves 18 Hydraulic drive: from overload, cross-country working fluid from high-pressure highway in low pressure housing. Since highways are two and each of them in the process of work can be a high-pressure high pressure, then high pressure valves are also two too. Overflow valve 17 Must be released excess the working fluid from the low pressure highway, where it is constantly fed to the pump.
Shovel 16 In the valve box connects the overflow valve to the "hydraulic pump hydraulic motor" highway, in which the pressure will be less.
When the valves are triggered by the supply system (safety and overflow), the resulting working fluid falls into the inner cavity of the units, where, mixing with leaks, the drainage pipes enters the heat exchanger 15 and further to the tank 14 . Due to the drainage device, the working fluid takes the heat from the driving parts of the hydraulic units. A special end sealing of the shaft prevents the leakage of the working fluid from the inner cavity of the aggregate. The tank serves as a reservoir for the working fluid, has an inside partition separating it to the drain and suction cavity, is equipped with a level pointer.
Filter of fine cleaning 12 The extraneous particles is delayed with a vacuum. The filter element is made of nonwoven material. The degree of contamination of the filter is judged by the testimony of a vacuum.
The engine rotates the hydraulic pump shaft, and, consequently, the associated cylinder block and the pump shaft feed. The feed pump sucks the working fluid from the tank through the filter and serves it in the hydraulic pump.
In the absence of pressure in the servo-cylinder springs, located in them, set the washer so that the plane of the support in it (washers) is perpendicular to the shaft axis. In this case, when rotating the cylinder block, the plunger fifth will slide along the support, without causing the axial movement of the plungers, and the hydraulic pump will not send the working fluid into the hydraulic motor.
From the adjustable hydraulic pump in the process of operation, you can get a different amount of fluid (feed) supplied in one turn. To change the hydraulic pump feed, you must turn the hydraulic distributor lever, which is kinematically connected to the washer and spool. The latter, moving, will send a working fluid that comes from the pump to the control system into one of the servo-cylinders, and the second servoscillide is connected to the cavity of the drain. The first servo-cylinder piston rendered under the action of the production fluid will begin moving, turning the washer, moving the piston in the second servoscilliter and squeezing the spring. The washer turning into the position given by the hydrodistrator lever will move the spool until it returns it to the neutral position (with this position, the output of the working fluid from the servo-cylinders is closed with spool belts).
When the cylinder block rotates, the fifth sliding along the inclined support will cause the movement of plungers in the axial direction, and as a result, there will be a change in the volume of chambers formed by holes in the cylinder block and plungers. Moreover, half cameras will increase its volume, another half is reduced. Thanks to the holes in the appropriate day and the distributor, these cameras are alternately connected to the "Hydraulic Hydromotor" highways.
In the chamber that increases its volume, the working fluid comes from the low pressure highway, where the feed pump is supplied through one of the check valves. The rotating cylinder block, the working fluid, located in the chambers, is transferred to another highway and is supplanted with plungers, creating high pressure. According to this highway, the liquid falls into the working chambers of the hydraulic driver, where its pressure is transmitted to the end surfaces of the plungers, causing them to move them in the axial direction and, thanks to the interaction of Plungers with an inclined washer, causes the block of cylinders to rotate. Having passed the working chambers of the hydraulic motor, the working fluid will be released into the low pressure highway, at which part of it will return to the hydraulic pump, and the excess via the spool and the overflow valve will flow into the inner cavity of the hydraulic motor. In the overload of the hydraulic pressure, the high pressure in the hydraulic pump highway may increase until the high-pressure valve opens, which is moving the working fluid from high pressure high pressure line to the low pressure highway, bypassing the hydraulic engine.
The GST-90 volume hydraulic guide allows simpler to change the transfer ratio: for each turnover of the shaft, the hydraulic motor consumes 89 cm 3 of the working fluid (excluding leaks). Such a number of working fluid hydraulic pump can be given over one or more, the revolutions of its drive shaft depending on the angle of the washer tilt. Consequently, changing the flow of hydraulic pump, you can change the speed of the movement of the machines.
To change the direction of movement of the machine, it is enough to tilt the washer in the opposite direction. The reversing hydraulic pump with the same rotation of its shaft will change the direction of flow of the working fluid in the high-pressure hydraulic pump triggers on the opposite (that is, the low pressure high pressure will become a high-pressure highway, and high pressure housing is a low-pressure trunk). Consequently, to change the direction of movement of the machine, a lever of the hydraulic distributor is necessary to rotate in the opposite direction (from the neutral position). If you remove the effort from the hydraulic distributor lever, then the puck under the action of the springs will return to the neutral position, in which the plane of the support in it will become perpendicular to the shaft axis. Plungers will not move in the axial direction. The supply of working fluid will stop. Self-propelled machine will stop. In the highways "Hydroonasos-hydromotor" pressure will become the same.
A spool in the valve box under the action of centering springs will take a neutral position in which the overflow valve will not be connected to any of the highways. The entire liquid supplied to the feed pump, through the safety valve will be drained into the inner cavity of the hydraulic pump. With uniform motion self-propelled machine In the hydraulic pump and the hydromotor, it is only necessary to compensate for leakage, therefore a significant part of the working fluid, supplied to the feed pump, will be superfluous, and it will have to be released through the valves. In order for the excess of this fluid to use to remove heat, through the valves produced heated, the hydraulic motor, and the cooled - from the tank. To this end, the overflow valve of the feed system, located in the valve box on the hydraulic engine, is configured to a slightly smaller pressure than the fused on the casing case. Due to this, when the pressure is exceeded in the feeding system, the overfit valve will open and will release the heated fluid released from the hydromotor. Next, the fluid from the valve falls into the inner cavity of the unit, from where the drainage pipelines through the heat exchanger is sent to the tank.
In the hydraulic switching stepless transmissions, the torque and power from the drive link (pump) on the slave (hydromotor) is transmitted by liquid through pipelines. Power N, kW, fluid flow is determined by the production of H, M, M3 / s:
N \u003d HQPG / 1000,
where p is the density of the liquid.
Hydraulic transfers do not possess internal automatism, SAU is required to change the gear ratio. However, for the hydraulic transmission, the reverse mechanism is not needed. Reverse proof is provided by a change in the pump connection with the injection lines and return the fluid, which causes the hydraulic val to rotate in the opposite direction. With an adjustable pump, you do not need a coupling of the start of movement.
Hydraulic transmissions (as well as power) compared with frictional and hydrodynamic have much broader layout. They can be part of a combined hydromechanical gearbox with a sequential or parallel compound with a mechanical gearbox. In addition, they can be part of a combined hydromechanical transmission, when the hydromotor is installed before the main transmission - Fig. A (preserved the leading bridge with the main transmission, differential, semi-axes) or in two or in all wheels, hydraulic motors are installed - Fig. A (they are complemented by gearboxes that perform the functions of the main transmission). In any case, the hydraulic system is closed, and the feed pump is enabled to maintain overpressure in the return line. Due to the loss of energy in pipelines, it is usually considered to be appropriate to the use of hydro-pump transmission at a maximum distance between the pump and the hydraulic motor 15 ... 20 m.
Fig. Transmission circuits with hydraulic volumes or with electrical transmissions:
a - when using motor-wheels; b - when using a leading bridge; N - pump; Um - hydromotor; G - generator; EM - electric motor
Currently, hydraulic transmissions are used on small amphibious cars, such as "Jigger" and "Moul", on cars with active semi-trailers, on small series of heavy trucks ( full mass up to 50 tons) dump trucks and experienced city buses.
The widespread use of hydraulic transmissions is constrained mainly by their high cost and not enough high efficiency (about 80 ... 85%).
Fig. Schemes of hydraulic hydraulic drive:
a - radial-piston; b - axial piston; e - eccentricity; y - block of inclination block
Of the variety of bulk hydromachins: screw, gear, paddle (girlfriends), piston - for automotive hydraulic transmissions mainly find the use of radial-piston (Fig. A) and axial-piston (Fig. B) hydromachines. They allow you to use high working pressure (40 ... 50 MPa) and can be adjustable. The change in the supply of (consumption) of the fluid is provided in radial-piston hydromens by the change in eccentricity e, in axial-piston corners.
Losses in bulk hydromachines are divided into bulk (leakage) and mechanical, the latter are hydraulic losses. Losses in the pipeline are divided into friction loss (they are proportional to the length of the pipeline and the square of the fluid velocity during turbulent flow) and local (expansion, narrowing, turn turning).
Hydraulic transmission - Collapse hydraulic devicesallowing to connect the source of mechanical energy (engine) with executive mechanisms Machines (car wheels, machine spindle, etc.). The hydrotransmission is also called hydraulic transmission. As a rule, in hydraulic transmission, energy is transmitted by fluid from the pump to hydromotor (turbine).
In the presented video, a hydraulic motion was used as a output level. In the hydrostatic transmission, the hydraulic motor of the rotational motion is used, but the principle of operation is still based on the law. In the hydrostatic drive of rotational action, the working fluid is supplied from the pump to the motor. At the same time, depending on the working volumes of hydromachins, the moment of rotation of the shafts may change. Hydraulic transmission possesses all the advantages hydraulic drive: high power transmitted, the possibility of implementing large gear ratios, implementation of stepless regulation, the possibility of transmitting power to movable, moving machine elements.
Methods for regulation in hydrostatic transmission
Adjusting the speed of the output shaft in the hydraulic transmission can be carried out by changing the volume of the working pump (volumetric control), or by setting the choke or the flow controller (parallel and consistent throttle). The figure shows a hydrotransmission with a volumetric control with a closed circuit.
Hydrotransmission with closed contour
Hydraulic transmission can be implemented by closed type (closed loop), in this case there is no hydraulic tank in the hydraulic system connected to the atmosphere.
In the hydraulic systems of a closed type, the regulation of the rotational speed of the shaft can be carried out by changing the pump working volume. As a pump-motors in the hydrostatic transmission most often used.
Open contour hydrotransmission
Open Called the hydraulic system connected to the tank, which is reported to the atmosphere, i.e. The pressure over the free surface of the working fluid in the tank is equal to the atmospheric. In the hydrotransissions of the open type it is possible to implement volumetric, parallel and consistent throttle. The following figure shows a hydrostatic transmission with an open circuit.
Where hydrostatic transmissions are used
Hydrostatic transmissions Use in machines and mechanisms where it is necessary to implement the transmission of high power, create a high moment on the output shaft, to carry out stepless speed control.
Hydrostatic transmissions are widely used. in mobile, road construction techniques, excavators of bulldorators, on rail transport - in locomotives and traveling machines.
Hydrodynamic transmission
In hydrodynamic transmissions for power transmission, turbines are used. The working fluid in hydraulic transmissions is supplied from the dynamic pump to the turbine. Most often in the hydrodynamic transmission, blade pumping and turbine wheel are used, located directly opposite each other, in such a way that the fluid comes from the pumping wheel immediately to the turbine percentage of pipelines. Such devices combining the pump and turbine wheel are called hydromefts and torque converters, which, despite some similar elements in the design, have a number of differences.
Hydromefta
Hydrodynamic transmission consisting of pumping and turbine wheelinstalled in the general crankcase called hydromuft. The moment on the outlet shaft of the hydraulic clutch is equal to the moment on the input shaft, that is, the hydromefta does not allow you to change the torque. In the hydraulic transmission, power transmission can be carried out through a hydraulic coupling, which will ensure the smoothness of the stroke, the smooth increase in the torque, reduced shock loads.
Hydrotransformer
Hydrodynamic transmission, which includes pumping, turbine and reactor wheels, placed in a single housing is called a torque converter. Thanks to the reactor, hydrotector Allows you to change the torque on the output shaft.
Hydrodynamic transmission in a tetatic gearbox
The most famous example of the use of hydraulic transmission is automatic car gearboxin which hydromefta or hydrotransformer can be installed. Due to the higher efficiency of the hydrotransformer (compared to hydromefta), it is installed on most modern cars from automatic box Transmissions.
The article discusses the development of the transmission of tracked bulldozers of the class 10 ... 15 T on the caterpillar.
To start a little story. The very concept of "bulldozer" originated at the end of the XIX century. And meant the powerful force overcoming any barriers. TO crawler tractors This concept began to attribute in the 1930s, figuratively characterizing the power of the tracked machine with a metal shield fixed with a metal shield moving the ground. As a base, an agricultural tractor with a main feature was originally used - a crawler move, providing maximum grip with the soil. The caterpillar is defined as an endless rail. For the invention, it, as well as all key fundamental discoveries, were attributed by Russian scientists. One of the first patents is registered in Russia around 1885.
One of the features caterpillar stroke It is the possibility of turning due to the disconnection of one of the tracks, or its blocking, or its inclusion in the opposite. In fig. 1 shows a typical scheme of the mechanical transmission, which was used in the first tracked bulldozers and are still used.
The advantages of this scheme - simplicity of the design of aggregates, kpd. More than 95%, low cost and minimum time spent on repairs.
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During the rapid growth of the global economy in 1955-1965. and the development of technologies of machining and the chemical industry parallel to several manufacturers of tracked bulldozers were used by a hydromechanical transmission (GMT). It was built on the basis of the hydrotransformer (GTR), which by that time widespread on diesel locomotives. The GMT on the bulldozers was in demand primarily in a heavy class: more than 15 tons, and is characterized by the possibility of obtaining the maximum moment on zero speed, i.e., with the maximum clutch of the caterpillars with the soil and the maximum resistance of the moved mass of the soil. The only and critical drawback in addition to technological complexity remained high mechanical losses - 20 ... 25% at a single-stage GTR used in the overwhelming majority on tracked bulldozers using GMT. The scheme of the hydromechanical transmission is presented in Fig. 2.
The advantages of this scheme - Maximum possible traction on caterpillars, simpler control compared to mechanical transmission, elastic connection of the excavator engine.
The need to use expensive planetary KP and onboard gearboxes is caused by a higher torque transmission than in a mechanical transmission, up to two times. The GMT scheme today uses the leading manufacturers of tracked Bulldozers Komatsu and Caterpillar. Only Chelyabinsky tractor factory It provides a significant share of mechanical transmissions, more than 50 years releasing a practically not changed copy of the Caterpillar 1960s.
The next technological stage of the development of the transmission of tracked bulldozers was the use of the "Hydron pump (GG) - hydraulic engineer (GM)" under the general term "hydrostatic transmission" (GST). The beginning of a wide use of GNG GM was laid by the military when improving the actuators of artillery guns, where the high speed of moving the moving parts having a considerable inertial mass, which excluded the use of tight mechanical communication was required.
The transmission of this type today is predominantly distributed on the special equipment of medium and heavy class: the hydrostatic transmission apply all the leaders of the excavator technology market. The use of GTS in excavators is associated with the performance of the main work by actuating mechanisms with the hydraulic framework. The spread of GTS also contributed to the improvement of technology of machining and widespread synthetic oilsproduced under predetermined use parameters, and in addition, the development of microelectronics, which allowed to implement complex GST control algorithms. The scheme of the hydrostatic transmission is presented in Fig. 3.
The advantages of this scheme:
- high kpd - more than 93%;
- the maximum possible traction on the caterpillars is higher than that of the GMT, due to smaller losses;
- best maintainability due to the minimum number of units and their unification different manufacturers, mostly not producing ready-made tracked bulldozers;
- it also provides the minimum cost of aggregates;
- the maximum simple control of one joystick, allowing without refinement to implement remote control, including with the help of radio communication;
- elastic connection of the excavator engine;
- small dimensionswhat allows you to use the released space under hinged equipment;
- the possibility of a macrocontroller of the state of the entire transmission one by one parameter - the temperature of the working fluid;
- the maximum possible maneuverability is the zero radius of the reversal due to the antiquities of the tracks;
- the possibility of 100% power take-off on the hydraulic attachment equipment from the standard hydraulic pump;
- the possibility of cheap software, as well as technological upgrades in the near future due to the elementary transition to working fluid with new properties obtained on the basis of nanotechnology.
An indirect confirmation of such advantages is the choice of GST leader of German manufacturers of special equipment by Liebherr as a basic in the design of all special equipment, including tracked bulldozers. Table of all advantages, disadvantages and features of operation different types Transmissions, including the "New" for Caterpillar and actually implemented in 1959 by the factory for the DT-250 Electromechanical Transmission bulldozer, is shown on the website www.tm10.ru DST-Ural plant.
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Of course, readers drew attention to the preferences of the authors of the article. Yes, we make our choice in favor of the GTS and believe that it is such a decision to overcome the technological lag of the leaders of the production of special equipment in Russia and tear away from the Eastern neighbor - China, applying to a slight absorption of our bulldozers market. The new TM bulldozer with a transmission on the components of the BOSSH REXROTH class of thrust 13 ... 15 tons will be represented by DST-Urals in July. The working mass of the new bulldozer will remain 23.5 tons, power - 240 hp And the maximum thrust is 25 tons, which with a 5% lag corresponds to the analogue Liebherr Pr744 (24, 5 tons, 255 hp). Once again we recall the existing possibilities of domestic engineering. For example, we first in world practice applied the scheme of carts on swing carriages in the 10th grade of tracked bulldozers on the serial release. Prior to that, it was possible to afford it manufacturers only in the heavy class of these machines weighing more than 30 tons, where prices are several times higher. The market price of the TM10 bulldozer on swing carriages with hydrostatic transmission is planned no more than 4.5 million rubles.
Hydrostatic transfers
During the first two decades of existence automotive industry A number of hydraulic studies were proposed, in which the fluid under pressure generated by the pump operated by the engine flows through the hydraulic engine. As a result of moving, under the action of fluid, the working bodies of the hydromotor to its shaft is supplied. The liquid, of course, carrys some kinetic energy supply, however, since it comes out of the hydromotor at the same speed with which it enters it, the magnitude of the kinetic energy does not change and, therefore, does not participate in the transmission of power.
A single type of hydraulic studies appeared somewhat later, in which both rotating elements are placed in one crankcase - and the wheel of the pump, leading the fluid, and the turbine, in the blades of which the moving liquid is hidden. In such transmissions, the liquid comes out of the channels between the blades of the slave element with a much smaller absolute speed than enters them, and the power is transmitted through the liquid in the form of kinetic energy.
Thus, two types of hydraulic arms should be distinguished: hydrostatic or volume transmissions in which the energy is transmitted to the fluid pressure acting on moving pistons or blades, and hydrodynamic transmissions in which the energy is transmitted by increasing the absolute fluid velocity in the pump wheel and reduce absolute speed in turbine
Transmission of motion or power using fluid pressure with great success is used in a number of regions. An example of successful use of such gears are hydraulic systems Modern machines. Other examples are the hydraulic drives of the steering mechanisms of the courts and the management of gun tower towers of combat boxes. From the point of view of applying on cars, the most favorable property of the hydrostatic transmission is the possibility of stepless change of gear ratio. To do this, only a pump is needed, in which the volume described by the pistons in one turnover of the shaft can be smoothly changed during operation. Another advantage of hydrostatic transmission is the simplicity of receipt rear stroke. In most constructions, the movement of the control organ further corresponding to the zero speed, and the transfer ratio, equal to infinity, causes rotation in the opposite direction with gradually increasing speed.
Use of oil as a working "fluid. Translated the term "hydraulic" means the use of water as a working fluid. However, in practice, using this term, usually imply the use of any fluid for transmitting motion or power. In hydraulic transmissions of all types are used mineral oilsSince they protect the mechanism from corrosion and simultaneously provide its lubricant. Usually use low-viscosity oils, since the internal losses increase with an increase in viscosity. However, the less viscosity, the harder it is to prevent the leakage of the working fluid.
The use of hydrostatic gears on cars has never come out of the experiment stage. However, some successes were achieved in the use of these transmissions on railway transport. At the exhibition vehicle In the German city of Seddin, held in the mid-20s, on seven of the eight demonstrated maneuver diesel locomotives were installed. These transmissions are very convenient to manage. Since they allow you to get any gear ratio, the engine can always work with the number of revolutions per minute, which corresponds to the highest to. P. D.
One of the serious shortcomings that prevent the use of hydrostatic gears on vehicles is the dependence of them to. P. D. From speed. The literature published data according to which the maximum to. P. D. Similar gear reaches 80%, which is quite acceptable. However, it is necessary to keep in mind that the maximum to. P. D. Is always achieved at low operating speeds.
Dependence to. P. D. From speed. In the hydrostatic gears, turbulent fluid flow occurs, and with a turbulent movement of the loss (heat release), the third degree of speed is directly proportional to the third degree of speed, while the power transmitted power changes directly in proportion to the flow rate. Therefore, with an increase in the flow rate to. P. D. Quickly falls. Most of the well-known data on the C. P. hydrostatic gear refers to the speed of rotation, significantly less than 1000 rpm (usually 500-700 rpm); If you use similar transmissions to work with the engine, the normal speed of rotation of the crankshaft of which is over 2000 rpm, then to. p. d. will be unacceptable low. Of course, a gear gearbox can be installed between the engine and the hydrostatic transmission pump. However, this transmission would complicate another unit, and the low-speed pump and the hydraulic motor would be overhaul. Another disadvantage is to use in hydrostatic transmissions of high pressures that reach up to 140 kg! CM2, in which, naturally, is very difficult to prevent leakage of the working fluid. Moreover, all parts that are exposed to such pressures must be very durable.
Hydrostatic transmissions did not get distribution in cars by no means because they did not pay attention to them. A number of American and European firms who have sufficient technical and cash, engaged in the creation of hydrostatic gears, in most cases, having to use the transmission on vehicles. However, as far as the author is known, cargo cars with hydrostatic gears did not enrolled in production. In cases where firms produced hydrostatic transmissions for some time, they found them sales in other engineering industries, where high speed of rotation and low weight are not mandatory applications. Several ingenious designs of hydrostatic transmissions were proposed, two of which are described below.
Transmission of Manley. One of the first car hydrostatic gears created in the United States is Mainie's transfer. It was invented by Charles Manley, a Pioneer Employee of the Langlei Aid and Chairman of the Society of American Automotive Engineers. The transfer consisted of a five-cylinder radial piston pump with variable strokes of pistons and a five-cylinder radial piston hydromotor with a constant piston running; The pump connected with the hydraulic motor two pipelines. When the direction of rotation changes, the injection pipe has become sucking, and vice versa; With a decrease in the stroke of the pump piston to zero, the hydraulic engine operated the role of the brake. To prevent damage to the mechanism from excessive pressure, a safety valve opened at a pressure of 140 kg / cm2 was used.
The longitudinal section of the transfer of Mainie is presented in Fig. 1. The pump and the hydraulic motor were located coaxially next to each other, forming a single compact unit. On the left is the incision of one of the pump cylinders. The gap between the piston and the cylinder was very small, and the pistons did not have sealing rings. The lower heads of the rods did not cover the crank, but had the form of sectors and retained with two rings located on both sides of the connecting rod. The change in the stroke of the pump piston was carried out with the help of the eccentrics installed on the crankshaft shaft. During the operation of the aggregate, the crankshaft and the eccentrics remained fixed, and the cylinder block rotated around the axis of Eccentric E. On the figure, the mechanism is shown in a position corresponding to the maximum move of the piston equal to the amount of radius of crank and eccentricity of its eccentric; The cylinders rotate around the axis E, and the pistons of the pump - around the axis R. to reduce the stroke of the pistons, the eccentric turns around the axis E in one direction, and the crank is around the axis in the opposite direction; Due to this, the angular position of the crank remains unchanged, and the distribution mechanism continues to work as before. Management is carried out with the help of two worm wheels installed on the eccentric, one of which is planted freely, the second is fixed. Free sitting worm wheel connected with crankshaft By means of a gear that is reinforced on the colleague shaft, which engages with internal teeth, made on a worm wheel. Wormwood wheels are in engaging with worms connected by two cylindrical gears. Thus, the worms are always rotated in opposite directions, and the transmission was designed so that the angular movements of the eccentric and the crank were equal in the absolute value are opposite to the direction. If the eccentric and crank rotated at an angle of 90 °, the course of the piston of the pump became zero. Eccentric distribution mechanism was installed at an angle of 90 ° to the shoulder of the crank. The hydromotor differs from the pump only by the fact that it does not have a mechanism for changing the piston running. Both the pump and the hydromotor have spool valves, controlled by eccentric.
Fig. 1. Hydrostatic transfer Mainie:
1 - pump; 2 - hydromotor.
Fig. 2. Eccentric management of Menley's transfer.
Transmission of Mainic, intended for use on a cargo car with a carrying capacity of 5 g gasoline engine With a capacity of 24 liters. from. At 1200 rpm, there was a pump with cylinders with a diameter of 62.5 mm and the maximum stroke of the pistons of 38 mm. The pump worked for two hydromotors (one for each leading wheel). With the working volume of the five-cylinder pump, equal to 604 cm3 to transmit 24 liters. from. At 1200 rpm, at the maximum progress, the pistons required a pressure of 14 kg / cm2. When driving, Mainic in the laboratory, it was found that peak to. P. D. Took place at 740 rpm of the pump shaft and amounted to 90.9%. With a further increase in the speed of rotation to. P. D. Dropped sharply and already at 760 rpm amounted to only 81.6%.
Fig. 3. Hydrostatic gear gear.
Transmission of Jenna. Jenny's hydraulic frame has long been built by Waterbury Tul Company for various industries; In particular, she was also installed on trucksAvtomotris and locomotives. This transfer consists of a multi-cylinder porseless pump with a swinging washer and variable stroke and the same hydraulic transmission, but with a constant piston. The longitudinal section of the aggregate is presented in Fig. 144. The difference in the pump and hydrometer device is only that in the first slope of the swinging washer can change, and in the second - cannot. Pump and hydromotor shafts perform each from one end. Each shaft relies on the sliding bearing in the crankcase and on the roller bearing in the camshaft. A cylinder block is attached to the inner end of each shaft, which has nine holes forming cylinders. The axes of these cylinders are parallel to the axis of rotation and are at an equal distance from it. When the cylinder heads are rotated, the cylinder head slide across the camshaft. The holes in the head of each cylinder are periodically communicated with one of the two windows in the distribution plate, made on the circle arc; Thus, the supply and production of the working fluid is carried out. The length of each window on the arc is about 125 °, and since the cylinder message with the channel in the stove begins from the moment when the hole in the cylinder head begins to combine with the window, and continues until the window in the stove is blocked by the edge of the opening, then The discovery phase is about 180 °.
The springs installed on the shafts are used to press the cylinder blocks to the distribution plate at a time when the load is not transmitted. When transferring the load, the contact is provided by fluid pressure. Cylinder blocks are installed on the shafts in such a way that they can slide and slightly swing on them. This provides a dense adjacent of the cylinder block to the distribution plate even with some inaccuracies of manufacture, as well as in the case of wear.
The gap between the piston and the cylinder is 0.025 mm, and the piston do not have any sealing devices. Each piston is connected to a hinged ring by means of a rod with spherical heads. The body of the connecting rod has a longitudinal hole, and the hole is also made in the bottom of each piston. Thus, the connecting rod heads are lubricated by oil from the main flow of fluid and the pressure under which the oil is supplied to the support surfaces, in proportion to the load. Each swinging washer is attached to the shafts through cardanic hinges Thus, that when it rotates together with the shaft, its rotation plane can be any angle with the shaft axis. In the pump, the angle of inclination of the swinging washer can vary in the range from 0 to 20 ° in any direction. This is achieved using the control handle associated with the rotating bearing jack. In the hydraulic engine, the bearing nest is rigidly attached to the Carder at an angle of 20 °.
In cases where the swinging washer is a straight angle with the shaft, when the cylinder block rotates, the piston will not move in the cylinders; Accordingly, there will be no oil supply. But as soon as the angle between the swinging washer and the axis of the shaft will be changed, the piston will begin to move in the cylinders. Throughout one half of the turnover, the oil is suused through the hole in the distribution plate; During the second half of turnover, the oil is injected through the injection hole in the camshaft.
The oil supplied under pressure in the hydraulic motor causes the piston of the hydromotor to move, and the forces acting on the swinging washer through the connecting rods are caused to rotate the cylinder block and its shaft. In the case when the angle of inclination of the pumping washer of the pump is equal to the angle of inclination of the swinging washer of the hydraulico, the latter shaft will rotate at the same speed as the shaft 'of the pump; Reducing the rotational speed of the hydraulic shaft can be achieved by reducing the angle between the pumping of the pump and the shaft.
In the transmission built for automotive engine with a capacity of 150 l., E., K. P. D. At 25% load and maximum speed rotation was 65%, and when maximum load - 82%. The transfer of this type has a significant weight; The unit given as an example had a proportion of 11.3 kg per 1 liter. from. Transmitted power.
TO Manager: - Automotive clutch
