DE1555428B1 - Control device for a continuously variable hydrostatic drive, especially for motor vehicles - Google Patents

Description

The invention relates to a control device for a stepless adjustable hydrostatic drive, especially for motor vehicles, the hydrostatic Drive one driven by a prime mover by means of a pump control valve has adjustable pump flow rate, which has a pressure and at least one closed hydraulic working circuit having a suction line acts on a hydrostatic motor with adjustable swallowing capacity, its output shaft or output shafts with the drive wheel or wheels is or are connected and when the actuation of a brake actuation device the pump control valve in the sense of reducing the set delivery rate the pump is influenced, and at the same time the drive wheel or the drive wheels decelerating friction brake or friction brakes is or are applied.

In a known design (French patent 1305 437) the braking forces act as pressure supplied by a master brake cylinder on a piston, the movement of which, however, does not exactly correspond to the movement of the brake control element acting on the master brake cylinder. This design therefore enables only a relatively rough regulation.

The invention is based on the object of making the regulation more sensitive to make, and is based on the knowledge that this can be achieved through precise coordination the control of the pump delivery rate can be achieved on the movement of the brake control member is.

This object is achieved according to the invention in that the pump control valve to adjust the delivery rate of the pump delivery rate in the sense of an increase the delivery rate of the pump due to the pressure of the hydraulic fluid from the suction line of the hydraulic working circuit and by the pressure of the hydraulic fluid in one Line that is proportional to the engine speed is biased and the actuation of the brake actuation device adjusts a valve that controls the pressure the hydraulic fluid in a control line modifies, whereby the pump control valve is resilient in terms of reducing the delivery rate of the pump. Since the Brake force exerted, which is a measure of the braking demand, in the sense of a reduction the pump delivery rate, and the pressure in the suction line, which is a measure of the response the brake is, acts in the sense of increasing the pump delivery rate, is the resulting position force acting on the control device of the pump the brake actuator proportional.

The brake linkage and the one that adjusts the drive machine act expediently Lever on the pump control valve via a common part.

In a further embodiment of the invention it is provided that the pump control valve additionally in the sense of a reduction in the delivery rate of the i pump by at least a spring is biased.

According to a further feature of the invention it is provided that the Brake linkage also acts on a brake valve in such a way that the initial Movement of the brake linkage from the position for released friction brake the brake valve moved to a position in which a pressure medium source with a high pressure chamber a brake actuating motor is connected and in this the game in the Operating linkage for the friction brake is added.

It is also advantageous if the drive engine speed proportional pressure at the pump control valve is counteracted by a lower pressure, which is fed via a line from a Venturi nozzle, through which one of the prime mover driven feed pump promotes, so that this pressure with increasing Drive machine speed drops.

According to a further feature of the invention it is provided that the Line with the return line downstream of a hydraulic working circuit lying switching valve is connected, all lines in an idle position of the hydraulic working group.

In a further embodiment of the invention, in a control device of this type, in which the swallowing capacity of the hydrostatic motor is variable by a motor lift control valve, which is acted upon by the pressure in the hydraulic working circuit in the sense of increasing the swallowing capacity of the hydrostatic motor, it is provided that pressure medium from the feed line and the return line of the hydraulic working circuit to associated control collars of a remote valve slide of the motor lift control valve of the hydrostatic motor, variable absorption capacity is passed and it is adjusted to increase the absorption capacity of the hydrostatic motor. As a result, there is a maximum fluid flow in the hydraulic working circuit under thrust conditions, through which a strong engine braking is achieved.

In such a control device it is further provided that the Motorhubsteuerventü for the hydrostatic motor of variable swallowing capacity has a valve slide consisting of two telescopically arranged parts and a line from the hydraulic working circuit is connected between the two parts to keep the two parts away from each other and impulse lines from the feed line and the return line next to adjacent control collars (b and a) of the one formed separately. Part of the valve slide are connected and at excessively high pressure in the hydraulic working circuit, the two valve slide parts can be moved against each other in order to establish the connection between the lines via an annular throttle point between the remote valve slide part and a correspondingly remote bore.

In the drawings, exemplary embodiments of control devices for a continuously variable hydrostatic drive according to the invention are shown. In the drawings, FIG. 1 is an embodiment of a control device of a hydrostatic drive according to the invention and FIG. 2 shows another embodiment of a control device of a hydrostatic drive according to the invention.

The control device of the hydrostatic drive according to FIG. 1 consists of a drive machine 9 which has a throttle valve for regulating the fuel supply and speed and is equipped with a speed limit controller 10 which limits the fuel supply and thus the maximum speed of the drive machine. The drive machine 9 drives a pump 12 of variable delivery rate of a hydrostatic transmission via a shaft 11, the working group containing supply and return lines with variable displacement hydrostatic motors 16 and 17 on the right side of the vehicle and variable displacement 18 hydrostatic motors on the left side of the vehicle and 19 is connected. The hydrostatic motors have output shafts 21 or 22 or 23 or 24, which are connected to the drive elements z. B. are connected to a vehicle. The pump and the hydrostatic motors of the hydrostatic transmission can be of any known type which deliver a pressure fluid when their shaft is driven and drive their shafts when a pressure fluid is supplied. The pump and the hydrostatic motors have stroke adjustment devices.

The illustrated hydrostatic motor is a typical example of a pump or a hydrostatic motor. The hydrostatic motor 17 has four piston-cylinder units 201 which are arranged in the usual manner in a ring. The fourth piston-cylinder unit 201 is located in the drawing behind the one drawn in the middle. Each of the pistons cooperates with the disk-shaped part of a swash plate 202. An engine feed line 28 is connected to an intake chamber 203 which communicates with intake ports in each cylinder. Each cylinder also has outlet openings which are connected to a common outlet chamber 204, which in turn is connected to a return line 29 . A channel 206 connects a controlled opening in each cylinder between the inlet and outlet openings of that cylinder with the closed end of the preceding cylinder. The spherical end of an arm of the swash plate 202 is connected in the form of a joint that can move in all directions with the piston of a lifting actuator motor 207 , which is rotatably seated on the output shaft 22. The output shaft 22 is rotatably supported in the housing. A stop 214 in the cylinder of HubsteHmotors 207 limits the movement of the control piston and ensures a minimum absorption capacity of the hydrostatic motor 17 flows to the hydrostatic motor 17 through the motor supply line 28 pressure fluid via the inlet chamber 203 as well, this is fed through the channels 206 sequentially to each cylinder, so that the hydrostatic motor 17 drives the output shaft 22 in the direction of arrow V.

The pump 12 is connected to the hydrostatic motors 16, 17, 18 and 19 by a closed hydraulic working circuit. When driven by the prime mover 9, the pump 12 conveys pressure fluid into a delivery line 26, which is connected to its motor feed line 28 via an arbitrarily actuated switching valve 27 when the associated hydrostatic motor is driven in the forward direction. In this case, the return line 29 of the hydrostatic motor is connected to a pump inlet line 31 via the switchover valve 27 . In the idling position shown, the switching valve 27 connects the delivery and pump inlet lines as well as the motor feed and return lines so that the hydrostatic transmission can idle. In the position for reverse running of the hydrostatic motors, the switching valve 27 connects the delivery line 26 with the return line 29 in order to drive the hydrostatic motor backwards, while the pressure fluid returns to the pump inlet line 31 via the motor feed line 28. The switching valve 27 has a cup-like valve housing 27a 27 b seals with openings in the side wall for connection of the delivery line 26, the motor feed line 28 and the pump inlet line 31 in the manner shown, and an opening in the center of the base for connecting the return line 29. A cover the upper surface of the valve housing and contains an L-shaped anal 27c, which optionally connects the openings for the pump inlet line 31 and the delivery line 26 with the return line 29 . If either the pump inlet line 31 or the conveyor line c with the return line 29 is connected 26 through the channel 27, the other is connected through the space in the cup-shaped valve housing with the motor feed line 28th In the neutral position of the changeover valve 27 of the channel 27 overlaps c partially the openings for the feed pipe 26 and the pump inlet line 31, so that all four lines are connected to each other in the transfer valve.

In order to compensate for losses of pressure fluid in the working circuit, fluid is fed from a sump 32 below the housing of the pump 12 via a suction line 33 by a feed pump 34. The feed pump 34 is driven by the engine 9 at a rate proportional to the engine speed RPM and promotes jerk liquid in a feed line 36. A with this connected safety valve 37 limits the pressure of the pressure fluid in the feed line to a maximum value, with excess pressure fluid to the intake pipe 33 or to the Sump 32 is derived. A heat exchanger 38 and a filter 39 are located in the delivery line 36 of the feed pump.

The delivery line 36 also contains a Venturi nozzle 41, with which hydraulic fluid of high and low regulator pressure is obtained. A line 42 is connected to the narrowest cross section of the Venturi nozzle 41 and supplies the hydraulic fluid at a low regulator pressure, which decreases with increasing flow velocity in the Venturi nozzle as a result of the increasing speed of the feed pump 34. Closely upstream of the Venturi nozzle 41, a line 43 is connected for taking off the pressure fluid from the high regulator pressure, which increases as the speed of the feed pump 34 increases. Feed valve A feed valve 46 is used to supply pressure fluid to the hydraulic working circuit. It contains a valve slide 47 with control collars a, b and c of the same diameter, which slide in a closed valve bore 48. When the hydrostatic motors are driven forward, the delivery line 26 is connected via a branch line 51 to the left end of the valve bore 48 so that pressure fluid acts on the control collar a with the pressure prevailing in the delivery line 26 and moves the valve slide into the position shown in which the delivery line 36 of the feed pump 34 is connected to a branch line 52 between the control collars a and b , via which pressure fluid reaches the pump inlet line 31. Branch lines 53 and 54 are blocked by the -Feiierbüiide a and -b. The Purnipeneinlaßleitung 31 has at the same point connected branch lines 56 and 57, of which the branch line 56 is connected to one end of the valve bore so that pressure fluid with the pressure prevailing in the pump inlet line 31 acts on the control collar. Since the pressure of the pressure fluid * in the pump inlet line 31 is significantly lower than the pressure of the pressure fluid in the delivery line 26 , the pressure fluid from the branch line 56 acting on the control collar c cannot overcome the pressure fluid of higher pressure from the delivery line 26 acting on the control collar a so that the valve position is not changed. The branch line 57 is connected between the control > un 'M , b' den b and c with a control line in which the pressure fluid is reduced to a lower value, e.g. B. 7.04 kg / cm2, is limited by a pressure relief valve 60. The high pressure pressure fluid from the delivery line 26 is connected to a control line 62 via the branch line 51, the valve bore 48 and a branch line 59 .

If the hydrostatic motors overtake the drive machine 9, the pressure of the hydraulic fluid in the return line 29 is higher than in the motor feed line 28. The higher pressure hydraulic fluid then acting on the control collar c via the branch line 56 moves the valve slide into the other end position, whereby it the The delivery line 36 of the feed pump 34 connects between the control collars a and b and the branch line 53 with the delivery line 26 carrying the pressure fluid at a lower pressure, through which the pressure fluid flows from the pump to the hydrostatic motor. The branch lines 57 and 52 connected to the pump inlet line 31 are blocked by the control collars b and c. The branch line 54 connects the delivery line 26 between the control collars b and c in order to feed through the control line 58 pressure fluid of low pressure, which is controlled by the pressure relief valve 60 so as not to exceed the value of 7.04 kg / cm2. The high pressure pressure fluid from the pump inlet line 31 is connected to a branch line 61 via the branch line 56 and the valve bore in order to control the control line 62. Pressure reducing valve The control line 62 is connected to a pressure reducing valve 63 , which supplies a control line 64 with hydraulic fluid at a pressure proportional to the pressure of the hydraulic fluid in the working circuit. This is, for example, one tenth (7.04 to 35.2 kg / cm2). The pressure reducing valve 63 has a valve slide 66 with control collars b and c of larger diameter in a valve bore 67 and a control collar a of smaller diameter in a valve bore. The control line 62 is connected to one end of the closed valve bore of smaller diameter, so that the pressure prevailing in it acts on the control collar a, while the control line 64 is connected to the other end of the valve bore 67 , so that the pressure prevailing in it on the Tax collar c acts. An outlet 68 is provided between the control collars a and b. If the pressure of the pressure fluid in the control line 64 is in the correct ratio to the pressure of the pressure fluid in the control line 62, the pressure fluid in the latter line, which acts on the control collar c, keeps the valve slide 66 in the position shown, in which the control collar c blocks a branch line 71 of the control line 62 . If the pressure of the pressure fluid in the control line 64 falls as a result of the consumption of pressure fluid or leaks, the control slide is moved to the right by the pressure of the pressure fluid in the control line 62, so that the control line 62 via its branch line 71 between the control connections b and c and a branch line 72 to which the control line 64 is connected. The pressure reducing valve 63 is not an outlet for the control line 64. Although a certain leak occurs in the system, correct operation is ensured, even if the reduction of the control pressure of the pressure fluid in the control line 64 lags behind if the pressure fluid drops . TV Valve An engine throttle dependent TV valve 76 provides pressurized fluid at a TV pressure that is proportional to the torque demand or engine throttle position. It has a valve slide 77 with control collars a and b and a piston 78 which slide in a valve bore 79 of uniform diameter. A lever 81, which is part of the engine throttle linkage, can be moved from the dashed position I for idling of the engine 9 to the fully marked position F for full engine throttle valve opening and works together with a head 82 of the piston 78 in order to pre-tension a valve slide 77 acting spring 83 to increase with increasing fuel supply to the prime mover 9. A spring 98 acting in the opposite direction on the valve slide 77 exerts a small restoring force which, when the engine throttle valve is in the idle position, ensures that the valve slide is returned to the assigned position. The space between the valve slide 77 and the piston 78 is relieved through an outlet 84. If the TV pressure of the pressure fluid in a line 87 corresponds to the engine throttle valve position, the pressure fluid supplied via a branch line 87 ' with the valve bore 79 acts with TV pressure on the left end of the control collar a and, together with the spring 98, maintains the preload of the spring 83 the scales. The valve slide is in the closed position and blocks a low-pressure control line 58 ' through the control collar a and an outlet 88 with the control collar b. With an increase in the preload of the spring or a decrease in the pressure fluid acting in the opposite direction with TV pressure, the valve slide 77 is moved to the left and connects the low-pressure control line 58 ' with the line 87, the outlet 88 being shut off. When the engine throttle valve is withdrawn in order to lower the IV jerk of the pressure fluid, the low-pressure control line 58 is shut off and the line 87 is connected to the outlet 38 . The TV pressure of the hydraulic fluid therefore increases proportionally to the increase in the engine throttle valve or the torque demand. Pump control valve The delivery rate of the pump 12 is controlled by a pump control valve 91 which contains a valve slide 92 with a small control collar a in a bore 93 and control collars b and c of the same diameter in a larger bore 94. In the idle position shown, the control line 64 is connected to a space between the control collars b and c and separated by the control collar b from a control line 96 to reduce the stroke and through the control collar c from a control line 97 to increase the stroke. The valve slide 92 is loaded to the left in the position for reducing the pump stroke by the spring 98, which lies between the valve slides 92 and 77 , and by the hydraulic fluid with TV pressure from the branch line 87 ', which also opens between these two valve slides so that the control line 64 is connected to the control line 96 for reducing the stroke. A control piston 101, which acts via a shaft 103 on the left end of the control collar a of the valve slide 92, slides in a coaxial bore 102, which is closed on both sides. The shaft 103 moves freely in an opening in the wall between the bores 93 and 102 and prevents pressure fluid from passing through. In the area of this wall, the bore 93 is provided with an outlet 104. On the left side of the control piston 101, the pressure fluid of the higher control pressure from the line 43, which increases with increasing engine speed and is always greater than the pressure of the pressure fluid of the low control pressure, which decreases with increasing engine speed, which is transmitted through the line 42 to the left side of the Control piston 101 is passed. The combined effect of the pressure fluids with the two control pressures causes the valve slide 92 to move to the right as the engine speed increases, so that the control line 64 is then connected to the control line 97 for increasing the stroke. The pump inlet line 31 is also connected to the space between the control collars a and b via a branch line 56 * in order to load the valve slide 92 in the direction of increasing the pump stroke. When the engine throttle valve is adjusted to increase the fuel supply to the prime mover 9 for the purpose of increased torque demand, the hydraulic fluid with TV pressure from the branch line 87 ' moves the valve slide 92 into the position of reducing the pump stroke, whereby the load on the prime mover is relieved so that it can catch up with speed . With increasing engine speed, the pressure of the pressure fluid of the high control pressure rises, while the pressure of the pressure fluid of the low control pressure drops, so that the valve slide 92 is moved into the position for increasing the pump stroke. Adjusting the engine throttle valve results in an increase in the engine speed and the pump delivery rate.

Brake valve The hydraulic fluid with TV pressure line 87 is connected via a brake valve 106 to a control line 107 when the friction brake is released. The brake valve 106 has a valve slide 108 with control collars a and b of the same diameter, which slide in a valve bore 109. A brake pedal is connected to the actuating end 111 of the brake valve via a brake linkage 110 , the valve slide 108 of which is held in the illustrated position 0 when the brake is released. In this position, the pressure fluid with TV pressure line 87 is connected between the control collars a and b to the control line 107 . If the brake is applied, the brake linkage moves the valve slide 108 in the direction of the position F for fully applied brake. In the initial movement of the valve spool 108 of the control collar locks b from the pressure fluid with TV pressure carrying line 87, while the control line 107 is connected to an outlet 112th As a result, the hydraulic fluid with TV pressure is shut off from the motor lift control valves. The valve slide 108 of the brake valve is here also moved against the head 82 of the valve slide 78 of the TV valve, so that the TV pressure in the hydraulic fluid increases with increasing application of the brake or higher braking demand. Motor lift control valves Each hydrostatic motor 16, 17 and 19 is assigned the motor lift control valve 116, 117 and 118 , respectively. The stroke reduction of the hydrostatic motors that are seated on at least one axis, for example the hydrostatic motors 16 and 18, is e.g. B. limited to a quarter of the swallowing capacity. Since the engine lift control valves are the same as each other, only one will be described. A motor lift control valve has a valve slide 121 with a control collar a of small diameter in a small valve bore 122, control collars b and c of medium size, of the same diameter in a valve bore 123 of a smaller diameter, and a large control collar d. An auxiliary valve slide 124 slides in a large valve bore 126. It has an inner bore 127, which is open on one side, for receiving the control collar d of the valve slide 121, which slides in this in a sealed manner. This forms a sealed chamber 130 . The relative movement of the control collar d to the auxiliary valve slide 124 is limited by a snap ring 128 which is seated at the open end of the inner bore of the auxiliary valve slide 124. On the opposite side, the auxiliary valve slide 124 carries a shaft 131 of smaller diameter which fits into a corresponding bore 132 and contains a channel 133 which opens into the bore 127. The valve bores 122, 123, 126 and the bore 132 in the valve housing 120 and the bore 127 in the auxiliary valve slide 124 are coaxial with one another. The motor feed line 28 contains a Venturi nozzle 136, to the narrowest cross section of which an impulse line 141 is connected. In this there is a pressure which is inversely proportional to the flow rate in the motor feed line 28. The pulse line 141 is connected to the valve bore 122 of the associated motor lift control valve, so that the pressure of the hydraulic fluid prevailing in it acts on the end of the control collar a. A similar Venturi nozzle 146 is provided in the branch lines of the return line 29 , in the narrowest cross section of which an impulse line 151 is connected. This impulse line is connected between the valve bores 122 and 123 , and the pressure of the hydraulic fluid acts on the differential area of the control collar b. This differential area of the control collar b is just as large as the acted upon area of the control collar a. The control line 64 is connected to the valve bore 123 between the control collars b and c when the engine lift control valve is in the normal position shown. When the valve slide is moved upward, the control line 64 is connected to a control line 156 for greater lift of the hydrostatic motor, while when the valve slide is moved downward, it is connected to a control line 161 for reducing the swallowing capacity. The fluid in the valve bore 126 between the valve slide 121 and the auxiliary valve slide 124 and the shoulder between the valve bores 126 and 123 is relieved through an outlet 125. The control line 107 is connected to the upper end of the valve bore 126 so that the pressure prevailing in it acts on the upper surface of the auxiliary valve slide 124. At all normal operating speeds, hydraulic fluid is fed with a regulator pulse pressure via a line 166 to the bore 132 and passes through the channel 133 into the sealed chamber 130 between the auxiliary valve slide 124 and the control collar d of the valve slide 121, so that these two valve parts are held in the extended position will. In this position, a shoulder 134 rests against the upper end of the valve bore 126 in order to limit the movement of both valve parts, whereby the control collar a is prevented from exiting the valve bore 122, whereby the two impulse lines 141 and 151 would be connected to one another. If the anti-engine speed exceeds a maximum value given for safety reasons, a regulator relay valve 167 relieves the load on the line 166 so that the valve slide 121 and the auxiliary valve slide 124 can move relative to one another. By reducing the length of the two valve parts, the impulse lines 141 and 151 are connected to one another, whereby hydraulic braking is initiated, as will be explained below.

The pressure of the pressure fluid in the impulse lines 141 and 151, which changes directly with the pressure and inversely proportional to the flow rate in the associated lines, acts on the control collars a and b of the valve slide 121 to move it into the position for increasing the swallowing capacity move. The pressurized fluid with TV pressure acting on the upper surface of the I-eleven valve slide 124 seeks to move the valve into the position for reducing the swallowing capacity.

The pressure of the hydraulic fluid in the working circuit is limited to a maximum value, for example 352 kg / CM2, by the motor lift control valves. If the pressure of the hydraulic fluid in the working circuit reaches this maximum value, then the pressures of the hydraulic fluids, which act on the control collars a and b of the valve slide 121, exert sufficient force to move the valve slide 121 into the auxiliary valve slide 124 by lowering the Overcome the pressure of the hydraulic fluid of, for example, 7.04 kg (cm2 in the chamber 130) and the control collar a is moved out of the valve bore 122 to the motor feed line 28 and the return line 29 with the low pressure, for example 7.04 kg / cm2 Connect line.

Regulator relay valve The regulator relay valve 167 has a valve slide 168 with control collars a and b which slide in a valve bore 169. A spring 171 loads the valve slide 168 in the direction of the position shown in which the control line 58 , which has low pressure fluid, is connected to the line 166 . If the regulator pulse pressure rises to a value that indicates that the drive machine is running at excessive speed, the hydraulic fluid with high control pressure from line 43 overcomes the pressure fluid with low control pressure from line 42 and the bias of spring 171, so that the Valve slide 169 is moved to the right. Then the control collar a blocks the control line 58 , while the line 166 is connected to an outlet 172 n-üt.

Mode of operation If the arbitrarily actuated switching valve 27 is in the idle position, the delivery line 26 and the pump inlet line 31 as well as the motor feed line 28 and the return line 29 are connected to one another, so that the pump 12 and all hydrostatic motors 16, 17, 18 and 19 are relieved . No power can then be transferred in any direction. The drive machine 9 is completely relieved in this case, and the output shafts of the transmission can rotate freely.

For forward travel, the switching valve 27 is adjusted to the forward travel position F in which the delivery line 26 is connected to the motor feed line 28 and the return line 29 is connected to the pump inlet line 31 . When the engine is idling and the engine throttle valve is set to idle, the pump control valve 91 is in the position for the small delivery rate of the pump, so that the pump 12, which is set to zero delivery rate, does not deliver any pressure fluid into the working circuit. The pump control valve 91 is held in this position by the spring 98 , since the very low control pressures of the pressure fluids that act on the control piston 101 and the pressure fluid with low, for example 7.04 kg7cm2, supplied through the branch line 56 ' and on the Pump inlet pressure acting on control collar b is insufficient to move the valve slide against the force of spring 98. At idle speed of the prime mover, the feed pump driven by the prime mover promotes an amount of liquid proportional to the machine speed, so that the amount of liquid flowing through the venturi 41 is only small and therefore there is only a small difference between the high and low control pressure. As a result, the force exerted on the control piston 101 is only small. The feed pump 34 fills the working circuit with hydraulic fluid at low pressure, for example 7.04 kg / cm2, via the feed line 36 and the feed valve 46, which acts on the small area of the control collar b via the branch line 56 '. These pressures, however, are insufficient to overcome the spring 98 so that the pump control valve remains in the position for Pumpenhubverringerung 91 and the pump 12 has zero flow.

To transfer power, the engine throttle is opened to add more fuel to the prime mover so that its speed increases, and the TV valve 76 is operated to increase TV pressure to the pressurized fluid in line 87 and branch line 87 ' form. The increasing TV pressure initially tries to reduce the delivery rate of the pump. However, since the increasing engine speed increases the control pressure enough to overcome the hydraulic fluid with TV pressure and the bias of the spring 98 , the pump control valve 91 is progressively moved to the position for maximum flow rate. As the engine throttle valve opening and engine speed increase, the TV pressure and the control pressure balance the pump control valve 91 so that the pump delivery rate is controlled so that the engine speed corresponding to the torque requirement, which is required by the engine throttle valve opening, is achieved with the best efficiency at each engine throttle valve opening .

The operation with partial service is carried out in the same way, but increased the pump delivery rate is only up to one proportional to the power requirement Value. At half power z. B. the pump delivery rate would be half the flow rate Increase at about a quarter of the engine throttle valve opening and then constant stay.

As the pump delivery rate increases, the volume of liquid that is fed from the pump to the hydrostatic motors increases. When the drive machine is idling, after the feed pump 34 has filled the working circuit and the control circuit, the motor lift control valves 116, 117, 118 and 119 set the associated hydrostatic motors to maximum absorption capacity. The control line 64 is therefore connected to the control lines 156 for high absorption capacity, and since the pressure of the hydraulic fluid controlled by the pressure limiting valve 60 has a low value, for example 7.04 kg / CM2, a pressure of the hydraulic fluid from the motor feed line 28 over-acts the Venturi nozzle 136 and the L-npulsleitung 141 to the end of the control collar a and a pressure of the pressure fluid from the return line 29 via the ventari nozzle 146 and the impulse line 151 to the control collar b to the engine lift control valve in the position for high absorption capacity of the hydrostatic motor keep. At this time, since the prime mover has no overspeed, the low control pressure of the hydraulic fluid in the control line 58 is reduced to a low value by the pressure limiting valve 60, e.g. B. 7.04 kg / cm2, controlled and passed through the regulator relay valve 167 and the line 166 to the chamber 130 of the Motorhubsteuerventils so that the valve slide 121 and the auxiliary valve slide 124 are in the extended position. The pressure of the hydraulic fluid acting in the chamber 130 also has a component which tends to move the valve slide into the position for reducing the swallowing capacity, but since the shaft 131 and the channel 133 located in it are very small in relation to the total area of the control collars a and b are, the force acting in this direction is relatively small, so that the pressures of the hydraulic fluids acting on the control collars a and b can move the valve slide into the position for high absorption capacity. The shoulder 134 rests against the end wall of the valve bore 126 and holds the control collar a in the valve bore 122, as a result of which a connection between the pulse lines 141 and 151 is prevented. When idling, the engine throttle valve is in the zero position or close to this zero position, so that the pressure fluid acting on the end of the valve bore 126 via the line 87 and the control line 107 with TV pressure on the auxiliary valve slide 124 does not trigger sufficient force, to move the motor lift control valve to the position for reducing the displacement. Under idle conditions, the engine lift control valve will therefore remain in the high displacement position of the hydrostatic engine.

If the engine throttle valve is opened further to increase the engine speed, the pump delivery rate and the liquid flow in the working circuit to the hydrostatic motors increases, so that the pressure of the hydraulic fluid in the working circuit is quickly increased to a maximum value, for example 352 kg / cm2, so that a large starting torque results. If the engine throttle valve is half opened, the pump delivery rate increases as explained above, and the hydrostatic motors accelerate the vehicle while increasing their speed, whereby the pressure of the hydraulic fluid in the working circuit initially drops quickly and then drops more slowly after a curve corresponding to the transmission torque curve. With forward drive, the pressure fluid at high pressure in the motor feed line 28 is connected to the impulse line 141 via the narrowest cross section of the Venturi nozzle 136 in order to form a pressure acting on the control collar a, which influences this in the sense of increasing the swallowing capacity of the hydrostatic motor. This pressure is proportional to the pressure of the hydraulic fluid in the working circuit and is inversely proportional to the fluid flow to the hydrostatic motor. The TV pressure of the hydraulic fluid, which increases as the engine throttle valve opening increases, acts on the auxiliary valve spool 124 to move the engine lift control valve to the position for reducing the displacement. In the lower range of the engine throttle valve position, for example at half the throttle opening, there is a pressure of the hydraulic fluid in the working circuit above a minimum value of, for example 105.6 kg / CM2, so that the pressure of the hydraulic fluid from the working circuit acting on the motor stroke control valve equals the TV pressure of the hydraulic fluid overcomes and the Motorhubsteuerventil holds in the position for increasing the swallowing capacity, so that the hydrostatic motor continues to work with full swallowing capacity. If the pressure of the hydraulic fluid in the working circuit falls below the mentioned value of 105.6 kg / CM2, the TV pressure of the hydraulic fluid overcomes the pressure of the hydraulic fluid from the working circuit, which acts on the motor stroke control valve, and moves it in the sense of a decrease the ability to swallow. When the engine throttle valve is fully open, the equalization of the TV pressure and the pressure from the working circuit at the engine stroke control valve will gradually reduce the engine absorption capacity between a middle engine throttle valve position, for example half the engine throttle valve opening and fully open engine throttle valve, in order to maintain a constant minimum pressure of 105.6 kg in the working circuit. With a lower engine throttle valve opening, a proportionally lower pressure of the hydraulic fluid in the working circuit is maintained by further reducing the engine absorption capacity. When operating with the engine throttle valve partially open, it is advantageous if two of the hydrostatic motors are not provided with the stop 214 so that their shoving capacity can be reduced to zero , thereby completely eliminating their drive. The absorption capacity reduction of the other hydrostatic motor pair, which has the stop 214, is limited to a lower value, for example a quarter of the possible absorption capacity, in order to enable a drive without freewheeling and to be able to drive the drive machine for braking purposes from the hydrostatic transmission.

For reverse drive, the switching valve 27 is moved to position R in order to connect the delivery line 26 to the return line 29 , so that the hydrostatic motors are driven in reverse. The motor feed line 28 then acts as a return line which is connected to the pump inlet line 31 via the switching valve 27. Since the return line 29 now carries the pressure fluid at a higher pressure, the pressure of the pressure fluid is obtained from the working circuit via the Venturi nozzle 146, which is connected to the return line 29 , and fed to the valve bore 126 via the pulse line 151. The pressure acts on the control collar b of the motor lift control valve. Otherwise, the hydrostatic drive works in the same way with reverse drive as with forward drive.

For normal braking, the brake pedal is depressed to move the brake linkage 110. This actuates the brake valve 106 in order to shut off the pressure fluid with TV pressure from the line 87 from the control line 107 and to relieve the control line 107. This eliminates the influence of the hydraulic fluid with TV pressure on the motor stroke control valve. The pressure of the hydraulic fluid from the working circuit, which acts on the control collars a and b of the motor lift control valve, moves the motor lift control valve into the position for maximum absorption capacity, so that the hydrostatic motors deliver a maximum flow rate as a result of the drive through the movement of the vehicle. The increased liquid flow from the hydrostatic motor increases the pressure in the return line 29, which is connected to the pump inlet line 31 via the switching valve 27 , so that the hydrostatic motor drives the pump 12 and thus the prime mover 9. The movement of the valve spool 108 of the Breinsenventils 106 also causes the end of the control collar a of the valve spool 108 of the TV valve starts up against the head 82 of the valve spool 78 76, so that the TV pressure of the pressure fluid in the branch line 87 proportional to the Breinsanforderung increases . This pressure at the pump control valve 91 , which indicates the braking request, effects its adjustment in the sense of the pump stroke reduction. The increased pressure in the pump inlet line 31 acts via the branch line 56 ' on the control collar b of the pump control valve 91 in order to counteract the increased braking demand force. Since the pressure in the branch line 56 is a measure of the braking effect of the braking caused by the prime mover and the TV pressure is a measure of the position of the brake pedal or the brake request, the pump control valve 91 adjusts the pump swallowing capacity so that the pump is the prime mover drives with a speed matched to the position of the brake pedal, so that an increased braking effect occurs when the brake pedal is depressed more strongly. If a higher braking force is desired, the brake pedal is depressed further to further increase the TV pressure of the hydraulic fluid, so that the pump control valve 91 further reduces the pump swallowing capacity, thereby increasing the pressure required to drive the prime mover at a regulated speed and the resulting. Increase braking torque. The maximum braking torque is limited by the maximum pressure of the hydraulic fluid on the hydrostatic motors. The full braking torque according to the design is therefore available at any vehicle speed. The prime mover is driven at a regulated speed if the braking period is longer, by one. to obtain maximum machine braking. In this way, a maximum breaking effect is achieved by the drive machine before further braking is achieved by distributing the heat into the control circuit, with a maximum inflow of cool liquid being ensured for a longer braking period. The heat generated by braking is distributed over this entire hydraulic circuit, i.e. not concentrated in a few places. The thermal inertia is therefore greater in the present case than with conventional brakes. However, sufficient cooling by the heat exchanger 38 and a supply of cool liquid through the feed valve 46 must be ensured. Since the pump speed is always in the upper range of the speed range during operation with machine braking and generally corresponds to the maximum machine speed at maximum braking, the regulating pressure of the hydraulic fluid acting on the pump control valve is essentially constant. Since, however, the control pressure influence on the pump control valve decreases with decreasing engine speed like the braking effect, the control pulse pressure also represents a preload proportional to the braking effect, which opposes the preload corresponding to the braking demand at the actuating end 111 of the brake valve.

Reaches the engine speed during the braking operation the regulated limit, g t 'switches the controller relay valve 167 the control pulse pressure of the pressure fluid in the line 166 to the outlet 172, so that the chamber 130 of the Motorhubsteuerventils is relieved. The two valve slides of the motor lift control valve pull together so that the control collar a is pulled out of the valve bore 122 and the pulse lines 141 and 151 are connected to one another. Hydraulic fluid then flows from the return line 29 carrying pressurized fluid via the impulse line 151 through the engine stroke control valve and the impulse line 141 to the engine feed line 28 carrying the pressurized fluid and reduces the fluid flow in the working circuit, so that less fluid is conveyed from the hydrostatic motors to the pump and the engine speed is reduced.

The Venturi nozzles, which serve to compensate, ensure a positive drive on each wheel in the event of unequal drive conditions. When propelled forward, the motor feed line 28 carries high pressure fluid to each of the hydrostatic motors. Each of these feed lines contains a Venturi nozzle 136, in the narrowest cross section of which the impulse line 141 is connected, which leads to the motor lift control valve of the associated hydrostatic motor and there acts on its control collar a. When the load on a driving hydrostatic motor drops, e.g. B. if an impeller of the vehicle loses the pulling effect, this hydrostatic motor catches up by the relief of speed, so that a high flow rate in the associated motor feed line 28 occurs. The flow through the Venturi nozzle 136 reduces the pressure of the hydraulic fluid in the impulse line 141, so that the pressure of the hydraulic fluid acting on the control collar a of the motor lift control valve drops, while the TV pressure of the hydraulic fluid acting on the auxiliary valve slide 124 remains constant. As a result, the engine lift control valve is moved in the direction of reducing the absorption capacity, as a result of which the power supplied to the overspeed hydrostatic motor is reduced. This lowering of the power supply to the overspeed hydrostatic motor supports the distribution of the load or achieves a better pulling effect. It also prevents power losses at the other hydrostatic motors that could result from the overflow of pressure fluid by the overspeed hydrostatic motor.

With reverse drive, the compensating Venturi nozzles will work in the same way with the exception that the supply of pressure fluid to the hydrostatic motors is now via the return line 29 , which also has a Venturi nozzle 146 in each branch, from which the impulse line 151 branches off. The pressure of the hydraulic fluid in this impulse line 151 acts on the control collar b of the associated motor lift control valve. If this pressure falls, the absorption capacity of the hydrostatic motor is reduced in the same way.

In this control device, the TV pressure, when driven forward and backward, balances the amount of liquid conveyed in the working circuit with the amount of liquid absorbed by each hydrostatic motor. The controller automatically selects the correct engine speed to obtain maximum efficiency at every engine throttle position and automatically controls the pump and hydrostatic motors over the entire operating range of the vehicle to maintain this engine speed. The Venturi nozzles used for compensation also produce a compensation effect between the wheels of an axle. If one of the hydrostatic motors or the wheel coupled to it is relieved, for example due to a loss of traction, the fluid flow is influenced, which enables a positive drive on each wheel. In addition, one of the hydrostatic motors is prevented from running away, since its speed is reduced by changing the amount of liquid supplied in order to achieve a better pulling effect on the associated impeller. The wheels having normal traction maintain their correct speed by maintaining the normal displacement of the hydrostatic motor, while the speed of the unloaded wheel is reduced by relatively reducing the absorption capacity of the associated hydrostatic motor.

The control device of the hydrostatic drive according to FIG. 2 consists of a drive machine 309 with a conventional engine throttle valve, which is provided by a linkage 309 ' for regulating the fuel supply and the speed. A speed limit controller 310 is also provided in order to limit the fuel supply and thus the speed to a maximum value. The drive machine 309 works via a shaft 311 on a hydrostatic transmission, the pump 312 of which drives it with a variable delivery rate. The pump 312 supplies a working circuit in which hydrostatic motors 316 and 317 located on the right-hand side of the vehicle with variable displacement and hydrostatic motors 318 and 319 disposed on the left-hand side of the vehicle with variable displacement are provided. The pump is connected to the hydrostatic motors by supply and return lines. Each hydrostatic motor has an output shaft 321 or 322 or 323 or 324, via which the vehicle wheels are driven. The pump and each hydrostatic motor have stroke adjustment devices.

The hydrostatic motor 316 shown in detail is a typical form of the pump and hydrostatic motors. The hydrostatic motor 316 has four piston-cylinder units 501, which are arranged in the usual manner in a ring around an axis that is coaxial with the output shaft 321. Each piston cooperates with the disk-shaped part of a swash plate 502 . An engine feed line 328 is connected to an intake chamber 503 which is in communication with intake ports of each cylinder. Each cylinder also has exhaust ports which communicate with a common exhaust chamber 504 which is connected to a return line 329 of the hydrostatic engine. A channel 506 connects a controlled port in each cylinder between its inlet and outlet ports to the closed end of the preceding cylinder. The swash plate 502 is mounted with the spherical end of an arm in the manner of an all-round movable joint in the cylinder of a lifting actuator motor 507 , which is rotatably seated on the output shaft 321. The output shaft 321 is rotatably supported in the housing of the hydrostatic motor. A stop 514 limits the movement of the actuating piston in the actuating cylinder in order to ensure a minimum absorption capacity of the hydrostatic motor. When pressure fluid is supplied via the motor feed line 328 , the pressure fluid flows from the inlet chamber 503 to the channels 506 in succession to the individual cylinders, so that the hydrostatic motor rotates and the output shaft 321 is driven forward in the direction of arrow V. The housing of the hydrostatic motor is connected to a sump 332 by a conduit 320 . The pump 312 is connected to the hydrostatic motors 316, 317, 318 and 31.9 through a closed working circuit. The pump 312 driven by the drive machine 309 conveys pressure fluid into a delivery line 326 which, when it is set for forward drive, is connected to the motor feed line 328 , which is connected to each of the hydrostatic motors, via a switching valve 327. The hydraulic fluid flowing back from the hydrostatic motor reaches a pump inlet line 331 via the return line 329 via the switching valve 327. In the idle position shown, the switching valve 327 connects the delivery and pump inlet lines as well as the motor feed and return lines so that the hydrostatic transmission can free-run. When the reversing valve 327 is set for reverse drive, the delivery line 326 is connected to the return line 329 , so that the hydrostatic motors are driven backwards, the returning liquid then flowing via the motor feed line 328 through the reversing valve 327 to the pump inlet line 331. The switching valve 327 has a cup-like valve housing 327 a with openings in the side walls to accommodate the delivery line 326, the motor feed line 328 and the pump inlet line 331 in the arrangement shown and an opening in the center of the base area for connecting the return line 329. A Deckel327b seals the open upper part of the valve housing, and includes an L-shaped channel 327 c, of optionally the openings for the Purapeneinlaßleitung 331 and the connecting Förderleitune, 326 with the opening in the base of the housing. If either the pump inlet line 331 or the delivery line 326 is connected to the return line 329 through the channel 327c , the other is connected to the motor feed line 328 through the space in the cup-shaped valve housing. In the neutral position of the changeover valve 327 of the channel 327 overlaps c partially the openings for the conveyor line 326 and the pump inlet line 331, whereby all four conduits are connected to each other in the transfer valve.

In order to establish the working circuit and to replace any leaks that may occur, liquid is supplied from the sump 332 , which is provided at the bottom of the housing of the pump 312 . A feed line 334 sucks in liquid via a suction line 333. The feed pump 334, which is driven by the drive machine 309 at a speed proportional to the drive machine speed, conveys pressure fluid into a delivery line 336 to which a safety valve 337 is assigned, which limits the pressure in the delivery line 336 to a maximum value and transfers excess pressure fluid to the suction line 333 or the sump 332 derives. A filter 339 is provided in the delivery line 336. The delivery line leads to a pressure reducing valve 363, which controls the pressure in the delivery line 336 and supplies excess pressure fluid to a feed line 335 , which leads via a heat exchanger 338 and a check valve 340 to a feed valve 346.

A Venturi nozzle 341 is provided in the delivery line 336 in order to form pressure fluid with a low and a high regulator pressure. A line 342 is connected to the narrowest cross section of the Venturi nozzle and supplies hydraulic fluid with a low regulator pressure, which decreases with increasing flow velocity in the Venturi nozzle as a result of increasing speed of the feed pump 334 or the engine speed. A line 343 is connected close upstream of the Venturi nozzle 341 and supplies hydraulic fluid with a high regulator pressure which increases with increasing speed of the feed pump or drive engine. Feed valve The feed valve 346, via which pressure fluid is fed into the working circuit, has a valve slide 347 with control collars a, b and c of the same diameter, which slide in a closed valve bore 348. In the forward drive position, the high pressure hydraulic fluid is the motor feed line 328 via branch lines 353 and 351! connected to the left end of the valve bore 348, and the pressure of the hydraulic fluid prevailing in it acts on the control collar a to move the valve slide into the position shown, in which the feed line 335 between the control collars a and b with a branch line 352 of the return line 329 is connected. Branch lines 353, 354 and 361 are blocked by the control collars a, b and c, respectively. The return line 329 has branch lines 356 and 356 branching off from the same point, of which the branch line 356 'is connected to one end of the valve bore so that the pressure of the pressure fluid in it acts on the control collar c. Since the pressure of the hydraulic fluid in the return line 329 is significantly lower than the pressure of the hydraulic fluid in the motor feed line 328, the pressure of the hydraulic fluid supplied via the branch lines 356 and 356 ' and acting on the control collar c is not able to apply the higher pressure to the Control collar a acting pressure of the hydraulic fluid from the motor feed line 328 to overcome. The valve slide 347 of the feed valve thus remains in its position. The branch line 356 is connected to a control line 358 between the control collars b and c, and the pressure of the pressure fluid in this control line is limited to a low value, for example 10.6 kg / cm2, by a pressure limiting valve 360. The high pressure hydraulic fluid from the motor feed line 328 is connected to a control line 362 via the branch lines 353 and 351 ', the valve bore 348 and a branch line 359 in order to act on the pressure reducing valve.

In the position of the switching valve 327 for reverse travel, the higher pressure of the pressure fluid prevails in the return line 329, which guides pressure fluid via the branch lines 356 and 356 ' to one end of the control collar c, around the valve slide 347 to the other end of the valve bore 348 to move, whereby the pressure fluid leading higher pressure branch line 361 of the control circuit is connected to the control line 362 to act on the pressure reducing valve. The feed line 335 is then connected between the control collars a and b with the line 353 to the motor feed line 328 , which now carries hydraulic fluid of lower pressure. The branch lines 359, 352 and 356 are blocked by the control collars a, b and c, respectively.

If the hydrostatic motors overtake the prime mover, there is a higher pressure in the return line 329 than in the motor feed line 328. Then the higher pressure in the branch line 356 moves the valve slide 347 into the opposite end position by acting on the control collar c, so that the same Connections as with reverse drive result. Pressure reducing valve The pressure reducing valve 363 controls the pressure of the hydraulic fluid in the delivery line 336, which is used to control the pump and motor stroke adjustment. The pressure reducing valve has a valve slide 364 in a valve bore 365. A shaft 366 with a stepped diameter, which may be part of the valve slide 364, extends into a valve bore 367 of smaller diameter. A control piston 368 is provided in a bore 369 and has a shaft 370 protruding into the valve bore 367 . A spring 371 in the bore 369 loads the control piston 368 so that the shaft 370 is in contact with the shaft 366 in order to load the valve slide 364 against the pressure of the pressure fluid from the delivery line 336 , which acts on the other end of the valve slide 364 to shut off feed line 335. When the pressure of the hydraulic fluid in the delivery line 336 increases , the pressure reducing valve opens and connects the delivery line 336 with the feed line 335. The spring regulates the pressure to a normal minimum value, for example 10.6 kg / cm2. The control line 362 is connected to the bore 367 between the shafts 366 and 370 and acts with a pressure fluid of high pressure, for example up to 352 kg / cm2, in order to make the preload springs ineffective and to regulate a main network pressure of the pressure fluid, which increases with increasing pressure of the Hydraulic fluid increases in the working circuit. The shaft has about a tenth of the pressure applied to the area of the valve slide, so that the main network pressure of the hydraulic fluid above the normal minimum value is one tenth of the higher pressure of the hydraulic fluid in the working circuit. Outlets 373 and 374 at the ends of the valve bore 365 and the bore 369 next to the narrow valve bore 367 are used for relief. A line 375 for taking up the play of a brake has a branch line to the end of the spring chamber of the bore 369, so that the pressure of the hydraulic fluid prevailing in this acts on the regulating piston 368 to increase the preload of the spring 371 , whereby the normal minimum pressure to a higher value , for example 35.2 kg / cm2, is regulated.

TV Valve A TV valve 376 provides hydraulic fluid at TV pressure that is proportional to the torque demand or the position of the engine throttle. It has a valve slide 377 with control collars a and b in a valve bore 378 and a piston 379 which protrudes into an enlarged bore 380. A lever 381, which is part of the engine throttle linkage, can be moved between a position 1 for engine idling to a position F for fully open engine throttle valves and works together with the piston 379 to increase the biasing force of a spring 383, which acts on the valve slide 377 Increase fuel supply to the prime mover. A spring 398 acts on the valve spool 377 in the opposite direction to exert a small restoring force which, under idle conditions, returns the valve spool to the closed engine throttle position. The space between the valve slide 377 and the piston 379 is relieved through an outlet 384. If the TV pressure in a line 387 carrying pressure fluid with TV pressure has the value corresponding to the position of the engine throttle valve, the pressure fluid with TV pressure, which is conducted via a branch line 386 to the valve bore 378 , acts on the left side of the control collar a and holds together the spring 398 the equilibrium to the bias of the spring 383. The valve slide 377 is in the position in which the control line 358 is blocked by the control collar a and an outlet 388 by the control collar b. With an increase in the preload or a decrease in the TV pressure of the pressure fluid, the valve slide 377 moves to the left and connects the control line 358 with the pressure fluid with the TV pressure line 387, while the outlet 388 is shut off. When the engine throttle valve is withdrawn in order to lower the TV pressure of the hydraulic fluid, the control line 358 is shut off and the hydraulic fluid with line 387 carrying TV pressure is connected to the outlet 388 . The TV pressure increases proportionally to the increase in the engine throttle valve opening or the torque demand. Pump control valve A pump control valve 391 controls the flow rate of the pump 312. It has a valve slide 392 with a small control collar a in a bore 393 and control collars b, c and d of the same diameter in a bore 394. In the idle position of the pump control valve, as shown is, the mouth of the delivery line 336 in the bore 394 is blocked by the control collar c. A control line 396 for reducing the pump delivery rate is connected to an outlet 399 between the control collars c and d . A line 397 for increasing the pump delivery rate is connected to an outlet 400 between the control collars a and b. The valve slide 392 is loaded to the left in the position for reducing the pump delivery rate by the spring 398 , which is arranged between the valve slide 392 and the valve slide 377 of the TV valve. Furthermore, the hydraulic fluid with TV pressure is fed from the branch line 386 between these two valve slides, so that the delivery line 336 is connected to the control line 396 for reducing the pump delivery rate. A regulating piston 401 is arranged in a coaxial bore 402 which is closed on both sides. The control piston 401 has a shaft 403 which acts on the left side of the control collar a of the valve slide 392. For this purpose, the shaft 403 passes freely through an opening in a wall 405 between the bores 393 and 402, the passage of pressure fluid between these bores being prevented. The bore 393 is also provided with an outlet 404 in the area of this wall. On the other hand, the control piston 401 has a shaft 403 'which protrudes into an open bore and is used to guide the control piston 401. At the same time, on both sides of the control piston 401, this results in areas that are acted upon by the same size. Since hydraulic fluid of higher regulator pressure from line 343 acts on the end surface of control piston 401 and increases with increasing machine speed and is also always greater than the low regulator pressure of one of the hydraulic fluid, which decreases with increasing machine speed, and via line 342 to the right Side of the control piston 401 is passed, the regulator pressure acts to the right to move the valve slide 392 into its position for increasing the pump delivery rate, in which the delivery line 336 is connected to the line 397 for increasing the pump delivery rate. The return line 329 is also connected to the space between the control collar a and b via a branch line. 352 'in order to act on the valve slide 392 in order to increase the pump delivery rate. With an enlargement of the engine throttle valve opening for the purpose of supplying a larger combustion. Amount of material to the drive machine 309 with increased torque demand, the hydraulic fluid with TV pressure from the branch line 386 moves the valve slide 392 into the position for reducing the pump delivery rate, so that the drive machine is relieved and the speed can catch up. As the engine speed increases, the high regulator pressure of the hydraulic fluid rises and moves the valve slide 392 into the position for increasing the pump delivery rate. The normal mode of operation when the engine throttle valve opening is increased. The end result is an increase in engine speed and pump flow.

Brake valve A brake valve 405 'has a regulator valve slide 406 with control collars a and b which slide in a valve bore 407, and a brake valve slide 408 which slides in a valve bore 409 of larger diameter which is relieved through an outlet 409'. If the brake pedal is depressed to operate the brakes, the brake linkage 410 moves the piston 379 of the TV valve 376 and the brake valve slide 408 from position D when the brakes are released to position E when the brakes are applied. The initial movement of the brake valve slide 408, for example over 2.5 cm, takes place against the force of an external spring 412 and causes the delivery line 336 to be connected to the line 375 via an annular groove 411 without the friction brakes being applied. As will be explained later, during this movement the TV valve initiates braking by the hydrostatic transmission. After this initial movement, the brake valve slide 408 comes to rest against an internal spring 41Z and causes an increase in the preload on the control slide 406, which is moved against the force of a spring 413. The pressure of the pressurized fluid for applying the brake is passed through a channel 406 'in a control collar of Re elventilschiebers 406 for aeschlossenen end 9 of the valve bore C 407th Hydraulic fluid at higher pressure from the motor feed line 328 or the return line 329 of the working group is closes through the Speiseventü the control line 358 zugeleitet.Bei the movement of the brake valve slide 408 for applying the brakes of the control collar b an outlet 414 and connects the control line 358 between the control coils A and b with a brake feed line 415 in order to obtain pressure fluid with a controlled brake pressure proportional to the actuation of the brake pedal during the second part of the movement. As indicated above, on the initial movement ', <the control valve spool supplies pressurized fluid at controlled pressure.

Engine lift control valves Each of the hydrostatic motors 316, 317, 318 and 31-9 is assigned an engine lift control valve 416, 417, 418 and 419, respectively. The reduction in the absorption capacity of the hydrostatic motors of at least one axle, for example the hydrostatic motors 316 and 318 , is limited to a lower value, for example to a quarter of the absorption capacity. Since the engine lift control valves are the same as each other, only one will be described. Each Motorhubsteuerventil has a valve spool 421 with a control collar a small diameter in a valve bore 422 corresponding to the small-diameter control Bunde b 'c and d mean, among themselves the same diameter in a valve bore 423 average diameter, and a control collar e large diameter. An auxiliary valve slide 424 slides in a large valve bore 427 which is open on one side and sealed the control collar d receives. This forms a sealed chamber 425 between the valve slide 421 and the auxiliary valve slide 424. The relative movement between the control collar d and the auxiliary valve slide 424 is limited by a snap ring 428 at the open end of the bore 427. The auxiliary valve slide 424 has on the opposite side a cup-like shaft 431 of smaller diameter, which protrudes into a narrow bore 432 and has a channel 433 in the side wall which opens into the bore 427. A regulating piston 436 is arranged in a bore 437 and has a shaft 438 on both sides. One end of the shaft 438 is guided in a bore 439 which is relieved by an outlet 441 in order to ensure the free movement of the control piston 436. The other end of the shaft is guided in a bore 442 and rests against the auxiliary valve slide 424. The space between this part of the stem 438 and the stem 431 of the auxiliary valve slide 424 is relieved by an outlet 443. The valve bores 422, 423 and 426 as well as the bores 432, 439 and 442 in the valve housing 420 and the bore 427 in the auxiliary valve slide 424 are coaxial with one another.

The connecting lines of the return line 329 with the individual hydrostatic motors each contain a Venturi nozzle 446, to the narrowest cross-section of which a first impulse line 451 is connected, in which the pressure fluid is inversely proportional to the flow velocity. A second impulse line 452 is connected between the venturi 446 and the hydrostatic motor to form pressurized fluid at a second pressure that is inversely proportional to the flow rate. The first pulse line 451 is connected to the bore 437 of the associated Motorhubsteuerventils, so - that acts in their prevailing pressure of the pressurized fluid on the right side of the control piston 436, and this applied to the motor in the sense of increasing the absorption capacity. The second impulse line 452 is connected in such a way that the pressure of the hydraulic fluid prevailing in it acts on the left side of the control piston 436 and acts on the engine stroke control valve in terms of the engine's absorption capacity. The pressures of the pressure fluids act on the control piston in order to increase the preload on the valve slide, so that as the return flow from the hydrostatic motor increases or the speed of the hydrostatic motor increases, a reduction in the engine's absorption capacity is initiated. As already mentioned, such a Venturi nozzle 446 with impulse lines 451 and 452 is assigned to each hydrostatic motor.

Each branch line of the motor feed line 328 to a hydrostatic motor has a branch line 453 which is connected to the valve bore 423 of the associated motor lift control valve, so that the pressure of the pressure fluid in it acts on the differential area of the control collar b. Each branch of the return line 329, which is connected to a hydrostatic motor, has a branch line 454 which is connected to the valve bore 422 in such a way that the pressure of the pressure fluid prevailing in it acts on the control collar a. The difference: area of the control collar b has the same size as the applied area of the control collar a. The pressure of the hydraulic fluid in the motor feed line as well as the return line loads the valve slide 421 in the sense of an increase in the absorption capacity. The delivery line 336 opens into the valve bore 423 - at a point that is blocked by the control collar c in the drawn center position of the valve slide. In this position of the valve slide 421, a control line 456 is also blocked to increase the swallowing capacity between the control collars b and c , while the control collar b shuts off an outlet 453 ', and a star line 461 is shut off to reduce the absorption capacity between the control collars c and d. The control collar d blocks an outlet 454 'in this position of the valve slide. When the valve slide is moved to the left, the delivery line 336 is connected to the control line 456 to increase the absorption capacity, while the control line 461 to reduce the absorption capacity is connected to the outlet 454 '. When the valve slide is moved to the right, however, the delivery line 336 is connected to the control line 461 to reduce the swallowing capacity and the line 456 is connected to the outlet 453 '. Outlet 454 'unloads valve bore 426.

An outlet 455 relieves the valve bore between the valve slide 421 and the auxiliary valve slide 424 and the shoulder between the valve bores 426 and 423. The hydraulic fluid with TV pressure line 387 is connected to the end of the valve bore 426 and acts on the shoulder 434 of the auxiliary valve slide 424 in the area of the shaft 431 in order to exert a pretension in the sense of a reduction in the ability to swallow. Hydraulic fluid with a regulator pulse pressure is fed in at all normal operating speeds via a line 466 which is connected to the valve bore 432 and via the channel 433 with the sealed chamber 425 between the auxiliary valve slide 424 and the control collar d of the valve slide 421 in connection with these two To hold valve members normally in the extended position shown. In this case the shoulder 434 rests against the upper end of the valve bore 426 and limits the movement of the two valve elements, so that the control collar a of the valve slide 421 cannot move out of the valve bore 422 and thus the branch lines 453 and 454 remain separated from one another. If the pressure exceeds a maximum value as a result of the prime mover, for example 352 kg7CM2, a regulator relay valve 467 relieves the line 466 so that the auxiliary valve slide 424 and the valve slide 421 can slide into one another, whereby the length of the valve slide is shortened. Then the branch lines 453 and 454 are connected to each other and effect hydraulic braking, as will be explained later.

In each of the motor lift control valves 416 to 419, the pressures of the hydraulic fluids, which change directly with the pressure of the hydraulic fluids in the associated motor feed or return line, act on the control collars b and a of the valve slide 421 in order to act on it to increase the swallowing capacity . The pressurized fluid with TV pressure, which acts on the upper surface of the auxiliary valve slide 424, tends to move the valve slide in the sense of a reduction in the swallowing capacity. The pressure of the hydraulic fluid from the Venturi nozzle 446 in the return line 329, which acts on the control piston 436, tries to increase the preload in the sense of a reduction in the absorption capacity when the return flow increases.

The pressure of the hydraulic fluid in the working circuit is limited to a maximum value, for example 352 kg / CM2, by the motor lift control valves. If the pressure of the hydraulic fluid in the working circuit reaches this maximum value, the pressures in the branch lines 454 and 453, which act on the control collars a and b of the valve slide 421, will exert a force large enough to push the control collar d into the auxiliary valve slide 424 , since they overcome the low pressure of the Druckflüsgkeit of 7.04 kg / CM2 in the chamber 425, for example. The control collar a is moved out of the valve bore 422, so that the motor feed line 328 carrying hydraulic fluid at a higher pressure is connected to the return line 329 carrying hydraulic fluid at a low pressure of, for example, 7.04 kg / cm2.

Regulator relay valve The regulator relay valve 467 has a valve slide 468 with control collars a and b which slide in a valve bore 469. A spring 471 loads the valve slide 468 in the direction of the position shown, in which the control line 358 is connected to the line 466 carrying the pressure fluid with regulator pulse pressure. If the regulator pulse pressure exceeds a value and thus indicates that the drive machine is running at excessive speed, the hydraulic fluid with high regulator pressure from line 343, which acts on control collar a, overcomes the hydraulic fluid with low regulator pressure from line 342 and the bias of the Spring 471, which act in the opposite direction on the control collar b , so that the valve slide 468 is adjusted and the control collar a shuts off the control line 358 and connects the pressure fluid with regulator impulse pressure line 466 between the control collars to an outlet 472. Starting pump A starting pump 476 driven by an electric motor has a suction line 477 and delivers through a pressure line 478 in which a check valve 479 is located. The starting pump 476 conveys into the feed line 336 of the feed pump 334 when the latter does not. Hydraulic fluid promotes, z. B. because the prime mover is not running or the feed pump 334 fails. The electric motor for the starting pump 476 is fed by a battery 481 and can be switched on by a switch 482. Brake Actuator Actuator The friction brakes are operated by hydraulic brake actuator actuators 483 which are controlled by the brake linkage 410 and the brake valve 405 '. The brake actuating motor 483 has a stepped piston 484 with a part a of larger diameter and a part b of smaller diameter. These parts of the piston run in corresponding cylinders 486 of larger and 487 of smaller diameter. A piston rod 488 attached to part b passes axially through the end wall of the cylinder 487 of smaller diameter to the outside. The line 375 is connected to the cylinder 487 so that the pressure of the hydraulic fluid prevailing in it acts on the small end face of the part b of the piston 484 and exerts a small force to eliminate the air gap within the brake. This force is sufficient to overcome a return spring 500 of the friction brake and can already exert an initially low braking force. Rapid absorption of the air clearance in the brake is made possible by a check valve 491, which permits a rapid exchange of fluid between a low-pressure chamber 492 and a high-pressure chamber 489 of the cylinder 486 of larger diameter. The brake feed line 415, in which the pressure of the hydraulic fluid is proportional to the brake pedal position, is connected to the high pressure chamber 489 of the cylinder 486 of larger diameter, and the pressure prevailing in it acts on the differential area of the piston a in order to apply a large force to apply the friction brake produce. The pressure in the high-pressure chamber keeps the check valve 491 closed, and when the brake is applied, the low-pressure chamber 492 is emptied via a low-pressure outlet valve 493 and an outlet 494. A check valve 495 is closed by the liquid contained in the low-pressure chamber. To reduce the brake pressure, the brake feed line 415 is connected to the outlet 414 through the Brernsen valve 405 '. The return springs 500 pull the piston 484 back, and the negative pressure that occurs in the low-pressure chamber, supported by gravity, draws liquid from the sump 332 via a line 496 and the non-return valve 495 into the low-pressure can 492 in order to keep it filled so that the non-return valve 491 can act to quickly eliminate the air gap in the brake the next time the brake is actuated.

The piston rod 488 operates conventional vehicle brakes. In the exemplary embodiment, the piston rod 488 is connected by a cable 497 to a brake cam 498 which acts on a brake band or a brake shoe 499. The return springs 500 are supported on a frame part and load the brake cam in the direction of its position when the brakes are released. A hand lever 488 ' articulated to the frame engages the piston rod 488 and can be used as an auxiliary brake lever. Mode of operation If the switching valve 327 is in the idle position, the delivery line 326 and the pump inlet line 331 as well as the motor feed line 328 and the return line 329 are connected to one another, so that the pump, 312 and all hydrostatic motors 316, 317, 318 and 319 are unloaded and power cannot be transmitted in any direction of rotation. This also completely relieves the load on the drive machine 309 and allows the output shafts or the wheels of a vehicle to run free.

For forward drive, the switching valve 327 is adjusted to position F, in which the delivery line 326 is connected to the motor feed line 328 and the return line 329 is connected to the pump inlet line 331 . When the drive machine 309 is idling and the machine throttle is in the idle position, the pump control valve 391 is in the position for stroke reduction, so that the pump 312 has zero delivery rate and does not convey any pressure fluid into the working circuit. The pump control valve 391 is held in this position by the spring 398 , since the very low regulator pressures of the pressure fluids act on the control piston 401 and the low, for example 7.04 kg / cm2, the pump inlet pressure of the pressure fluid, which via the line 356 ' on the control collar b acts, is not sufficient to move the valve slide against the spring 398 . When the engine 309 is idling, the feed pump 334 driven by it conveys a small amount of liquid proportional to the engine speed through the Venturi nozzle 341, so that only a small difference between the high and low regulator pressure of the hydraulic fluids and therefore only a slight force is exerted on the regulating piston 401. The feed pump 334 falls via the feed line 336 and the feed valve 346 to the working circuit with hydraulic fluid of low pressure, for example, 7.04 kg / cm.2, the, -over the line 352 ' to the small differential area of the control collar b of the valve slide 392 of the pump control valve 391 acts. These two pressures are insufficient to overcome spring 398 so that the valve spool of the pump control valve remains in its low flow position and the pump 312 has zero flow.

To transfer power, the engine throttle is opened to add more fuel to the engine 309 so that the engine speed increases. Here, the TV pressure of the hydraulic fluid in the line 387 is increased by the TV valve 376 . The increased TV pressure initially tries to reduce the pump delivery rate. The resulting increased engine speed, however, increases the regulator pressure of the hydraulic fluid enough to overcome the TV pressure of the hydraulic fluid and the spring 398 so that the pump control valve 391 increases the pump delivery. With increasing opening of the engine throttle valve and the engine speed, the TV pressure and the regulator pressure of the hydraulic fluids adjust the pump control valve 391 so that the pump delivery rate is regulated in such a way that the correct engine speed is maintained proportionally to the torque requirement according to the setting of the engine throttle valve and the prime mover with the best Efficiency works at every engine throttle position.

When operating with partial output, the same conditions apply, but the pump delivery rate is only increased up to a partial value proportional to the output requirement. For example, at half power, the pump delivery rate will increase to half the pump delivery rate at around a quarter of the engine throttle valve opening and then remain constant. With the increase in the pump delivery, the volume of liquid which is supplied from the pump to the hydrostatic motors 316 to 319 increased. When the working circuit is filled with the drive engine running idle by the feed pump 334, the motor lift control valves 416 to 419 have been brought into the position for large motor absorption capacity. In this position, the delivery line 336 is connected to the control line 456 for large absorption capacity, so that full absorption capacity is set. Since the pressure of the pressure fluid in the feed line 335 is controlled by the pressure relief valve 360 to a low value, namely 7.04 kg / cm2, and pressure fluid of this pressure from the motor feed line 328 via the branch line 453 to the end of the control collar b of the valve slide 421 of the Motor lift control valve and acts from the return line 329 via the branch line 454 on the control collar a of the valve slide 421, the motor lift control valve is in the position for large absorption capacity. At this time, since the prime mover has no overspeed, the low control pressure of the hydraulic fluid in the control line 358 is controlled by the pressure limiting valve 360 to the low value of 7.04 kg / CM2, for example, and by the regulator relay valve 467 and the hydraulic fluid with regulator pulse pressure leading line 466 is connected to the chamber 425 so that the valve slide 421 and the auxiliary valve slide 424 of the engine lift control valve are in the extended position. In this the shoulder 434 of the auxiliary valve slide 424 rests against the end wall of the valve bore 426, so that the control collar a remains in the valve bore 422 and prevents the connection of the two branch lines 453 and 454. When idling, the accelerator pedal is in the idling position or close to this position, so that the hydraulic fluid with TV pressure, which is conducted via the line 387 to the end of the valve bore 426 and which acts on the differential area of the auxiliary valve slide 424, does not exert sufficient force to operate the engine lift control valve move to the swallowing reduction position. The engine lift control valve therefore remains in the position for large swallowing capacity when idling.

If the engine throttle valve is opened to increase the engine speed, the pump delivery rate and the liquid flow through the hydraulic working circuit to the hydrostatic motors increase, the pressure of the hydraulic fluid in the working circuit being quickly increased to the maximum value, for example 352 kg / cm2, by the engine lift control valves , as explained above, whereby a high starting torque is available. If the engine throttle valve is moved up to a partial opening, for example half the throttle valve opening, the pump delivery rate increases and the hydrostatic motors accelerate the vehicle while increasing their speed. The pressure of the hydraulic fluid in the hydraulic working circuit then first drops rapidly and then more slowly according to a curve that corresponds to the torque curve of the drive.

With forward drive, the return line 329 is connected at the narrowest point of the Venturi nozzle 446 with the impulse line 451 and upstream of it with the first impulse line 452, so that pressures of the hydraulic fluids acting on the control piston 436 arise, which the engine stroke control valve in the direction of the position for reducing the Load the absorption capacity according to the flow in the return line of the hydrostatic motor. The TV pressure of the hydraulic fluid, which increases as the engine throttle valve opening increases, acts on the auxiliary valve slide 424 and loads the engine lift control valve in the sense of a reduction in the absorption capacity. In the lower range of the machine throttle valve adjustment, for example at half the throttle valve opening, when the pressure of the hydraulic fluid in the working circuit is above a minimum value, for example 105.6kg / CM2, the force derived from the working circuit and acting on the engine lift control valve is sufficient, the TV pressure of To overcome hydraulic fluid, and thus holds the engine lift control valve in the position for increasing the swallowing capacity, so that the hydrostatic motor has full swallowing capacity. If the pressure of the hydraulic fluid in the working circuit falls below the value of 105.6 kg / CM2, which occurs at around half full power, the TV pressure of the hydraulic fluid overcomes the pressure of the hydraulic fluid derived from the working circuit and adjusts the motor stroke control valve in order to reduce the absorption capacity . When the throttle valve is fully open, the balance between the TV pressure of the hydraulic fluid and the pressure of the hydraulic fluid in the working circuit on the engine stroke control valve causes a gradual reduction in the engine absorption capacity at a medium throttle valve opening, e.g. B. between half and full throttle opening in order to maintain a constant minimum pressure of the hydraulic fluid in the working circuit of 105.6 kg / CM2. With a smaller throttle valve opening, a proportionally lower pressure of the hydraulic fluid is maintained in the working circuit by further reducing the engine absorption capacity. When operating with the engine throttle valve partially open, it is advantageous if two of the hydrostatic motors can be set to zero absorption capacity and then do not cause any drive. The reduction in the absorption capacity of the other pair of hydrostatic motors on an axle is limited by the stops 514 to a low value, for example a quarter absorption capacity, in order to enable a permanent drive without freewheeling so that the drive machine can be driven by the hydrostatic motor for the purpose of braking .

- For reverse drive, the switching valve 327 is moved to position R, in which the delivery line 326 is connected to the return line 329, so that the hydrostatic motors are driven backwards. The motor feed line 328 serves to return the pressure fluid and is connected to the pump inlet line 331 via the switchover valve 327. Since the return line 329 carries hydraulic fluid at a higher pressure in this case, the pressure of the hydraulic fluid for the flow in the working circuit is fed to the engine stroke control valve via the venturi nozzle 446 in this line and the impulse lines 451 and 452 to the bore 437 in order to act on the control piston 436 of the engine stroke control valve. Although the impulse line 452 is downstream of the narrowest cross section of the Venturi nozzle 446 with reverse drive, the obtained pulse pressure of the hydraulic fluid is not so different and can be used as a measure of the fluid flow through the hydrostatic motor. All the more so since reverse drive rarely occurs. Otherwise, the drive in reverse drive works in the same way as in forward drive.

To operate the friction brake, the brake pedal is depressed to move the brake linkage 410. In the initial movement, for example cm 2.5 moves the Brernsgestänge 410 the brake valve slide 408 and 'connecting the conveyor line 336 to the line 375, so - that' acts in this prevailing pressure of the pressurized fluid to the piston 484 b and the game absorbs in the friction brake. At the same time there is a connection to the control piston 368 of the pressure reducing valve in order to increase the network pressure of the hydraulic fluid. During the initial movement, the valve slide 377 of the TV valve is also actuated in order to generate a pressure of the hydraulic fluid in the line 387 which is proportional to the movement of the brake pedal. The pressure of the hydraulic fluid from the working circuit acting on the control collars a and b of the motor lift control valve is above 70.4 kg / cm2 and is therefore sufficient to apply the pretension to the control piston 436 and the pressure in the hydraulic fluid with line 387 carrying the pressure overcome and move the motor lift control valves into the position for increasing the lift, so that the hydrostatic motors deliver a maximum amount of fluid at maximum lift as a result of the drive through the movement of the vehicle. The increased liquid delivery by the hydrostatic motors causes a flow of liquid under pressure in the return line 329, which is connected to the pump inlet line 331 via the switching valve 327 , so that the pump 312 and the prime mover 309 are driven by the hydrostatic motors. The movement of the brake pedal, which brings the brake linkage 410 into abutment against the piston 379 of the TV valve 376 , increases the pressure of the hydraulic fluid in the line 387 proportionally with the brake demand.

The TV pressure of the hydraulic fluid in the line 387 also acts on the pump control valve 391 in order to move it into the position for reducing the swallowing capacity. The increased pressure of the pressure fluid in the return line 329 as a result of the hydrostatic motors driven by the vehicle acts via the branch line 352 ' on the control collar b of the valve slide of the pump control valve 391 against the increased force proportional to the braking requirement. Since the pressure of the pressure fluid in the branch line 352 'is a measure of the braking effect exerted by the prime mover, and the TV pressure of the pressure fluid in the line 387 is a measure of the position of the brake pedal or the braking force requirement, the pump control valve is used 391 set the pump swallowing capacity so that the pump drives the prime mover at a speed that is matched to the position of the brake pedal. The braking effect is thus increased as the brake pedal is depressed further. If stronger braking is desired, the brake pedal is depressed further in order to further increase the pressure in the hydraulic fluid with line 387 carrying TV pressure, and the pump control valve 391 further reduces the pump swallowing capacity, whereby the pressure required to drive the prime mover is added to the hydraulic fluid Regulated speed is increased and thus also the resulting braking torque. The continued movement of the brake pedal brings the brake linkage 410 into the second movement range in which the brake valve slide 408 acts on the spring 412 'in such a way that the control valve slide 406 controls a pressure of the pressure fluid to the brake feed line 415, whereby the application of the friction brake is initiated. The further movement of the brake pedal increases the brake feed pressure of the hydraulic fluid in order to achieve an increased braking effect, whereby the hydraulic braking is increased at the same time. At the end of the brake pedal movement, the piston 379 comes to rest against the valve slide 377 of the TV valve, whereby the pump 312 is set to the lowest possible swallowing capacity. Then the pressure of the pressure liquid in the working circuit reaches the maximum value, namely 352 kg / cm2, and acts via the return line 329 and the branch line 454 to the control collar a of the valve spool 421 of the Motorhubsteuerventils, so that the pressure fluid is displaced from the chamber 425 and the Verrtilschieber the Motorhubsteuerventils slide into each other, whereupon a flow of liquid -from the return line 329 to the motor feed line 328 occurs in order to achieve a maximum braking effect. The maximum machine braking torque is limited by the maximum pressure of the hydraulic fluid in the hydrostatic motors. This means that the full designed braking torque is available at any vehicle speed. The prime mover is driven by the hydrostatic transmission at a regulated speed while braking continues in order to obtain maximum machine braking. At this speed, maximum braking effect is achieved by the hydrostatic motor by distributing the heat through the motor lift control valves and achieving maximum fluid flow. Additional hydraulic braking is achieved through the fluid transfer in the motor lift control valve. Since the heat generated during braking is transferred to the entire hydraulic circuit and is not restricted to a few parts of the same, the result is a thermal inertia that is higher than with conventional brakes. In the meantime, there must be sufficient cooling by the heat exchanger 338. The feed valve 346 controls pressurized fluid through the heat exchanger during braking, as described above. Since the pump speed is always in the upper speed range during machine braking and generally corresponds to the maximum machine speed with the greatest braking effect, the regulator pressure of the hydraulic fluid acting on the pump control valve is essentially constant. If, however, the load on the pump control valve due to the regulator pressure of the hydraulic fluid drops when the engine speed decreases, the regulator pressure of the hydraulic fluid results in a preload which is proportional to the braking effect and which opposes the preload corresponding to the braking requirement by the position of the brake rod 410. If the drive engine speed reaches the regulated limit value during braking, the regulator relay valve 467 connects the pressure fluid with regulator pressure line 466 to the outlet 472 in order to relieve the chamber 425 of the motor stroke control valve so that the two valve slides of the same-. pull together. Then the control collar a is pulled out of the valve bore 422 and connects the branch lines 453 and 454, so that the pressure fluid with higher pressure from the return line 329 via the branch line 454 through the engine lift control valve and the branch line 453 receives pressure fluid with the engine feed line 328 leading to the lower pressure . This overflow from the high pressure side of the hydraulic working circuit to the low pressure side via a throttled channel has an additional braking effect and reduces the flow in the working circuit, so that less fluid is pumped from the hydrostatic motors to the pump 312 and the engine speed is reduced.

The compensating ventari nozzles ensure a positive drive on each wheel in unequal traction conditions. If the drive is in forward drive, the motor feed line 328 supplies hydraulic fluid at high pressure to each of the hydrostatic motors. In the coming of each hydrostatic motor branch pipe a venturi 446 is provided in each whose narrowest cross section is connected to the pulse line 451, so that the act of the associated hydrostatic motor in this prevailing pressure of the pressurized fluid to the control piston 456 of the Motorhubsteuerventils. If the load on the driving hydrostatic motor drops, for example because the associated wheel loses traction, the speed of the hydrostatic motor increases as a result of the relief, and a large flow of fluid flows in the branch line of the return line 329 from this motor through the Venturi nozzle 446, whereby the pressure of the hydraulic fluid in the first impulse line 451 drops and the pressure of the hydraulic fluid in the second impulse line 452 to the engine lift control valve of the hydrostatic motor running at overspeed rises. The impulse pressure of the hydraulic fluid acting on the control piston is thereby reduced, while the TV pressure of the hydraulic fluid acting on the auxiliary valve slide 424 remains constant. The engine absorption capacity is therefore reduced proportionally to the current in the return line 329 and thus also the power supplied to this hydrostatic engine. This reduction in the power supplied to the unloaded and overspeed hydrostatic motor supports the distribution of the load in order to achieve a better pulling effect and prevents power losses at the other hydrostatic motors that could occur when the hydraulic fluid overflows through the overspeed hydrostatic motor.

With reverse drive, the compensating Venturi nozzles work in the same way, with the exception that the liquid is supplied to the hydrostatic motors via the return line 329 , in which the Ventari nozzle 446 is arranged in each branch to a hydrostatic motor first impulse line 451 feeds the pressure of the hydraulic fluid to the control collar b of the associated motor lift control valve. When this pressure of the hydraulic fluid at the motor stroke control valve drops, the TV pressure of the hydraulic fluid reduces the delivery rate of the motor in the same way.

The drive according to FIG. 2 has the same properties as those at the end of the description of the design according to FIG . 1 specified.

Claims (2)

Patent claims: 1. Control device for a continuously variable hydrostatic drive, in particular for motor vehicles, the hydrostatic drive having a pump driven by a prime mover, the delivery rate adjustable by means of a pump control valve, which has a closed hydraulic working circuit having a pressure and a suction line at least a hydrostatic motor, adjustable in its absorption capacity, is applied, the output shaft or the output shafts of which is or are connected to the drive wheel or the drive wheels and in which the pump control valve is influenced in the sense of a reduction in the set delivery rate of the pump when a pulley actuation device is operated, and at the same time the drive wheel or friction brake or friction brakes braking the drive wheels is or are applied, characterized in that the pump control valve (91 or 391) is used to adjust the delivery rate ge of the pump (12 or 312) in the sense of an increase in the delivery rate of the pump through the pressure of the hydraulic fluid from the suction line (pump inlet line 31 or return line 329) of the hydraulic working circuit (26, 28, 29, 31 or 326, 328, 329, 331) and is preloaded by the pressure of the hydraulic fluid in a line (43 and 343), which is proportional to the engine speed, and the actuation of the brake actuation device (brake linkage 110 or 410) creates a valve (brake valve 106 or TV valve 376 ) adjusts the pressure of the hydraulic fluid in a control line (107 or 387) changes , whereby the pump control valve (91 or 391) can be loaded in the sense of a reduction in the delivery rate of the pump. 2. Control reservoir device according to claim 1, characterized in that the brake linkage (110 or 410) and the lever (81 or 381) adjusting the drive machine (9 or 309 ) via a common part (head 82 or piston 379) act on the pump control valve (91 or 391) . 3. Control device according to den_ claims 1 and 2, characterized in that the pump control valve (91 or 391) additionally in the sense of a reduction in the delivery rate of the pump (12 or 312) by at least one spring (83 and 98 or 383 and 398 ) is preloaded. 4. Control device according to claim 1 and claim 2 or 3, characterized in that the brake linkage (410) additionally acts on a brake valve (405) in such a way that the initial movement of the brake linkage from the position (D) for released friction brake into a Moved position in which a pressure medium source (control line 358) is connected to a high pressure chamber (489) of a brake actuating servomotor (483) and in this the play in the actuating linkage for the friction brake (brake band 499) is absorbed. 5. Control device according to spoke 1 and one of claims 2 to 4, characterized in that the pressure proportional to the engine speed (line 43 or 343) on the pump control valve (91 or 391) counteracts a lower pressure, which is via a line (42 or respectively . 342) is fed from a Venturi nozzle (41 or 341) through which a feed pump (34 or 334) driven by the prime mover delivers, so that this pressure drops with increasing engine speed. 6. Control device according to claim 1 and one of claims 2 to 5, characterized - in that the conduit downstream of a is connected in the hydraulic working circuit (328, 329) change-over valve located (327) (branch line 352 ') to the return line (329) which in an idle position (N) connects all lines (pump inlet lines 331, return line 329, delivery line 326 and motor feed line 328) of the hydraulic working circuit with one another. 7. Control device according to claim 1 and one of claims 2 to 6, wherein the absorption capacity of the hydrostatic motor is variable by a motor lift control valve which is acted upon by the pressure in the hydraulic working circuit in the sense of increasing the absorption capacity of the hydrostatic motor, characterized in that Pressure medium from the feed line (delivery line 26 or motor feed line 328) and the return line (pump inlet line 31 or return line 329) of the hydraulic working circuit to assigned control collars (b and a) of a remote valve slide (121 or 421) of the motor lift control valve (116, 117, 118 and 119 or 416, 417, 418 and 419) of the hydrostatic motor (16, 17, 18 and 19 or 316, 317, 318 and 319) variable swallowing capacity and adjusts it to increase the swallowing capacity of the hydrostatic motor . 8. Steuervorrichtun- according to claims 1 and 7, characterized in that the motor lift control valve (116, 117, 118 and 119 or 416, 417, 418 and 419) for the hydrostatic motor (16, 17, 18 and 19 or 316, 317, 318 and 319 ) variable swallowing capacity has a valve slide (121, auxiliary valve slide 124 or 421, auxiliary valve slide 424) consisting of two telescopically arranged parts and a line (166 or 466) from the hydraulic working circuit is connected between the two parts in order to keep the two parts apart hold, and impulse lines from the feed line and the return line next to adjacent control collars (b and a) of a separate part of the valve slide are connected and, if the pressure in the hydraulic working circuit is excessively high, the two valve slide parts can be moved against each other to establish the connection between the lines via a annular throttle point between the remote valve slide part and egg ner to produce a corresponding stepped hole.