DE3504417A1 - Device for preventing a creep movement of motor vehicles provided with automatic transmissions - Google Patents

Abstract

Device for preventing a creep movement of motor vehicles, which have an engine and a transmission connected in series with a fluid medium clutch and having a frictionally engaging element. The device has an engine load sensor for generating a fluid medium signal with a pressure representing the engine load, a control device provided between the frictionally engaging element and a fluid medium source, and a fluid medium line for feeding the fluid medium signal from the engine load sensor to the control device. The control device serves for controlling the power transmission capacity of the frictionally engaging element in a range from zero up to a predetermined value as a function of the pressure of the fluid medium signal supplied, in order to prevent creeping of the vehicle when the engine is not under load. In the fluid medium line, a selector valve is provided, which is capable of assuming a first position, in which a flow of the fluid medium signal in both directions from the engine load sensor to the control device and vice versa is possible, when the pressure of the fluid medium signal is less than a predetermined value, and which is capable of assuming a second position, in which a flow of the fluid medium signal is only possible from the engine load sensor to the control device, when the pressure of the fluid medium signal is greater than the predetermined value. <IMAGE>

Description

Device to prevent creeping movement of with

automatic transmissions provided motor vehicles The present The invention relates to a device for preventing creeping movements in motor vehicles with an automatic transmission according to the preamble of claim 1.

It is in particular such a device that can be made effective or ineffective without an impact on the friction element the clutch occurs, and in which the response from the operation of the accelerator pedal depends.

In motor vehicles that have a fluid coupling, such as for example a torque converter, automatic transmission provided can be due to a grinding torque of the torque converter without will forward movement or creeping movement of the driver occur when the vehicle is stationary when the shift lever is set in a driving range (forward position), thereby generating a load on the engine.

Such an engine load causes the engine speed to drop when idling, which can even lead to the engine stalling. To avoid this disadvantage, the driver must depress the accelerator pedal by an amount corresponding to the grinding torque to prevent the engine speed from dropping when idling. This is however, it is not desirable in terms of fuel economy. At idle the transmission should therefore be automatically brought into a neutral position, to avoid power transfer between the engine and the driving wheels, so that the driver the accelerator pedal for reasons of economy in terms of fuel consumption does not have to penetrate significantly. It is known that trained for this purpose, Devices preventing the vehicle from creeping also have the advantage that vibrations of the chassis can be reduced when the engine is idling, what especially effective for front-wheel drive vehicles.

Admittedly, the creeping of the vehicle can be reduced by reducing the torque transmission a friction element used to start the vehicle, for example one Coupling element, reduced essentially to zero when the vehicle is stopped will. However, the torque transfer decreases as a function of the engine load, i.e. the amount by which the accelerator pedal is depressed when the vehicle is started shall be. Especially when the driver is driving the vehicle in a small space, for example should drive between vehicles on the side of the road when parking, it is advisable to to let slip the clutch, so that a certain small amount of power over it which is proportional to a fine operation of the accelerator pedal. Will on the other hand, if the vehicle is started when the road is clear, the grinding period should be can be shortened to the minimum possible value to get the clutch as fast as possible to fully intervene. Would the clutch only then take effect when the engine speed has reached a high value, so this would cause an uncomfortable shock and early clutch wear.

Used to avoid one with a conventional device Vehicle equipped with crawling movements pressed the accelerator and then suddenly released into the idle position, the creeping movement is prevented Device operated immediately, so that on the entire system of engine and transmission abruptly no more torque acts, causing rubber elements rubbing against each other suddenly interrupt the rotational energy, resulting in an uncomfortable shock. In order to avoid this, the creeping motion preventing device is one provided a short time delay until the engine speed has decreased sufficiently after releasing the accelerator pedal.

It is also known the internal pressure in the clutch for the first time Increase gear as a function of stepping on the accelerator pedal. Appropriately should the pressure in the clutch cannot be reduced to zero, even if the the device preventing the creeping movement works.

Rather, the pressure should be regulated as close as possible to a pressure value but remains below this value, above which the clutch engages against the force of a return spring provided in the clutch. This is an engagement pressure Pe. However, the pressure in the clutch in this way previously to such a pressure which is close to the engagement pressure If the pressure value increases, such an increased pressure can be used in the subsequent setting of the shift lever in the neutral position or in the reverse position as residual pressure act so that the response of the clutch when actuated by the driver, specifically in cold weather.

The present invention is based on the object, a Device that can be used in a motor vehicle to avoid creeping movements indicate that is simply structured and that the power transfer of a to Starting the vehicle used friction element in exact dependence on a parameter indicating the engine load, for example the amount of pedaling of the accelerator pedal, allowed to regulate, to avoid an unpleasant blow by the rubbing Element to prevent a sudden release of the accelerator pedal and to get one to make the creeping movement-enabling state possible immediately when the accelerator pedal is suddenly kicked.

Such a device is intended to be an automatic transmission in enable the driver to turn the gearshift lever into a can switch to a neutral position or a reverse position.

This task is achieved with a device of the type mentioned at the beginning according to the invention by the features of the characterizing part of the claim 1 solved.

Refinements of the inventive concept are characterized in the subclaims.

The invention is explained below with reference to in the figures of the drawing illustrated embodiments explained in more detail. It shows: Fig. 1 a schematic Representation of an automatic transmission for motor vehicles, in which an inventive Device for preventing creeping movements can be used; Fig. 2 is a circuit diagram a hydraulic control system for an automatic transmission according to Fig. 1, in which a device according to the invention in the form of a first embodiment is provided; Fig. 3 is a diagram showing the working oil pressure characteristic of a Creeping movement preventing device according to Figure 2 can be seen; Fig. 4 a the Fig. 2 corresponding circuit diagram of a hydraulic control system in which a a creep preventing device according to a second embodiment the invention is provided; 5 shows a partial illustration of the hydraulic control system according to FIG. 4 with a valve preventing creeping movement in a position in which the creeping movement of the vehicle is prevented; and FIG. 6 is a partial illustration of the hydraulic control system according to FIG. 4, from which a three-way valve with a Shift delay function can be seen in a second position, which is taken when a suction pressure Pt rises above a predetermined value.

Fig. 1 shows schematically an automatic transmission for motor vehicles with four forward gears and one reverse gear, for a device according to the invention is provided. An engine E drives drive wheels W and W 'through a crankshaft 1, a torque converter T as a fluid coupling, an auxiliary transmission M and a differential Df in this order.

The torque converter T includes one coupled to the crankshaft 1 Pump 2, one to an input shaft 5 of the Auxiliary gear M coupled Turbine 3 and one coupled to a stator shaft 4a via a one-way clutch 7 Stand 4, the shaft 4a in turn being supported on the input shaft 5, so that it rotates with this.

A torque is applied hydraulically to the pump by the crankshaft 1 2 and then transferred to the turbine 3. If when transmitting the torque a torque gain occurs from the pump 2 to the turbine 3, the resulting reaction force generated by the stand 4 in a manner known per se.

At the right-hand end of the pump 2 (seen in Fig. 1) is a pump gear 8 is provided, by means of which an oil hydraulic pump P according to FIG. 2 is driven. At the On the right-hand end of the stator shaft 4a, a stator arm 4b is attached through which a control valve Vr shown in FIG. 2 is controlled.

The one output shaft 6 running parallel to the input shaft 5 having auxiliary transmission has a transmission gear device G1 for the first Gear, a transmission gear device G2 for the second gear, a transmission gear device G3 for third gear, a transmission gear device G4 for fourth gear and a transmission gear device Gr for the reverse gear, which are opposite each other between the input shaft and the output shaft 5, 6 are arranged. The transmission gear device G1 for the first gear has a clutch C1 for the first gear with the Input shaft 5 connectable driving gear 17 and a one-way clutch CO with the output shaft 6 connectable and with the driving gear 17 in engagement driven gear 18 occurs. The gear transmission device G2 for the second gear has a clutch C2 for second gear with the input shaft 5 connectable driving gear 19 and one attached to the output shaft 6 and with the driving gear 19 in Engaging driven Gear 20 on, while the transmission gear device G3 for third gear on on the input shaft 5 attached driving gear 21 and a clutch C3 for the third input can be connected to the output shaft 6 and to the driving shaft Gear 21 having engaged driven gear 22. The transmission gear device G 4 for fourth gear has a connection to the input shaft 5 via a clutch C4 For the fourth gear connectable driving gear 23 and one with the output shaft 6 connectable via a selector clutch Cs and with the driving gear 23 in Engaging driven gear 24 occurs.

The transmission gear device Gr for the reverse gear has a driving gear 25, which is connected to the driving gear 23 of the transmission gear device G4 is integrally formed for fourth gear. Furthermore, this transmission gear device Gr for the reverse gear, one that can be connected to the output shaft 6 via the selector clutch Cs driven gear 27 and one with the gears 25 and 27 in engagement Idler gear 26 on. The select clutch Cs is between the driven gears 24 and 27 arranged and has a selector sleeve S, which between a left or front position and a right or rear position in Fig. 1 displaceable is to the driven gear 24 or 27 with the output shaft 6 to selectively associate. The one-way clutch CO allows the drive torque from the engine E is transmitted solely to the drive wheels W, W ', the transmission being eiens Torque from the drive wheels W, W 'to the engine E is prevented.

If the clutch C1 for the first gear is engaged alone, while the selector sleeve S is held in the front position shown in FIG is, the driving gear 17 is connected to the input shaft 5, whereby the transmission gear device G1 for the first Gang formed so that the torque 5 is transmitted to the input shaft 6. Will the Clutch C2 is engaged for second gear while clutch C1 is engaged for the first gear is kept engaged, the driving gear 19 is with of the input shaft 5 connected, whereby the transmission gear device G2 for the second gear is formed, via which the torque from the input shaft 5 on the output shaft 6 is transmitted.

That is, even if the first-speed clutch C1 is engaged is located, the transmission gear device G2 for the second gear, the Third gear transmission gear device or the transmission gear device G4 for fourth gear are formed by the action of the one-way clutch CO, wherein the transmission gear device G1 for the first speed becomes ineffective. Will the clutch C2 disengaged for the second input and instead When the clutch C3 for the third speed is engaged, the driven one becomes the driven Gear 22 connected to the output shaft 6 to the transmission gear device G3 to form third gear while the driving gear 23 is connected to the input shaft 5 is connected to form the transmission gear device G4 for fourth speed, when clutch C3 is disengaged for third gear and clutch C4 is disengaged for fourth gear is engaged instead. On the other hand, the clutch C4 engaged for fourth gear alone, while the selector sleeve S is the Selector clutch Cs is pushed into the right or rear position, so are the driving gear 25 or the driven gear 27 with the input shaft 5 or the output shaft 6 connected to the drive gear device Gr for the Form reverse gear, thereby allowing a transfer of torque from the input shaft 5 to the output shaft 6 via the transmission gear device Gr for the reverse gear is made possible.

The torque transmitted to the output shaft 6 is then over an output gear 28 mounted on one end of the output shaft 6 to an enlarged one Transfer gear Dg of the differential Gf.

Fig. 2 shows a creeping motion preventing device according to a first embodiment of the invention, in which the hydraulic oil pump P operating oil from an oil tank R to supply pressure to flow medium lines 29 and 94. The pressure of the pressurized oil sucked in by the pump P is determined by the Control valve VR regulated to a specified value (hereinafter referred to as line pressure P1), after which the pressure regulated oil becomes a Hand slide valve Vm, a valve Vt that responds to the throttle valve opening and a regulator valve Vg is performed.

The controlled by the control valve Vr to a predetermined pressure value, Pressurized oil is then partially provided with a constriction 33 Inlet fluid line 34 introduced into the torque converter T to its Increase internal pressure to avoid blistering.

Is intended to be the anti-creeping device for a gasoline engine are used, the throttle opening responsive valve generates Vt as a parameter which is a measure of the output power of the engine E, an intake pressure Pt, which is the amount of depression of an unillustrated accelerator pedal of the engine E, i.e. the valve opening of a throttle valve, not shown, corresponds to which is arranged in the intake system of the engine E. This pressure becomes a test fluid line 48 transferred. The regulator valve Vg is from the output shaft 6 of the auxiliary gear M or the enlarged gear Dg of the differential Df driven to a Regulator pressure To produce Pg which is variable as a function of vehicle speed and to a test fluid line 49 is transmitted. The hand slide valve Vm is between a flow medium line extending from the flow medium line 94 39 and a flow medium line 40, and between a neutral one Position, drive range positions, such as positions D3 and D4, as well as a reverse position displaceable. If the manual slide valve Vm takes one of the drive range positions on, the flow medium lines 39 and 40 are in communication with one another. If the manual slide valve Vm is in the neutral position or the reverse position, the flow medium line 40 is thus connected to a discharge line 39 ', by the pressurized oil in the flow medium line 40 in the oil tank R. to dissipate. In a flow medium line extending from the flow medium line 40 41 is a creep preventing valve to be explained below 50 arranged, which is connected to a hydraulically actuating part of the clutch C1 for the first gear is connected as a frictional engagement element for starting the vehicle. The pressurized oil in the flow medium line 40 is not only over the anti-creep valve 50 to the first-speed clutch C1 but also to hydraulically operated parts of the clutches C2, C3 and C4 for the second, third and fourth gear in a selective manner depending on valves V1, V2 and V3 for shifting from first to second gear, from second to third Gear as well as from third to fourth gear, as will be done in the following is described.

The switching valves V1 to V3 each have a coil on their one end the combined forces of the suction pressure Pt and one not shown The spring and the other end of which the regulator pressure Pg acts. This coil will from a left or first position to a right or

second position pushed when the regulator pressure Pg the combined Forces of the suction pressure Pt and the spring with an increase in the regulator pressure Pg, i.e., an increase in vehicle speed. The forces of the springs the switching valves V1 to V3 are set to different values. Special takes the switching valve V1 for switching from first to second gear, that between the flow medium line 40 and one provided with a constriction 43 Flow medium line 42 is arranged, the first position shown, if the vehicle speed is low, causing the fluid line 42 of the flow medium line 40 is decoupled. If the switching valve V1 for the Shifting from first to second gear held in this position so gets the clutch C1 for the first speed alone is engaged to the gear ratio for first gear to be realized as long as the valve preventing creeping movements 50 is open.

When the vehicle speed increases, the switching valve V1 for shifting from first to second gear to the right or second position pushed so that the flow medium lines 40 and 42 are in communication with one another reach. In this case, the valve V2 stands for switching from the second to the third gear in the illustrated first position, so that the flow medium line 42 is in communication with a flow medium line 44, which is connected to the hydraulic actuating part of the clutch C2 for the second gear is connected. Although the Clutches C1 and C2 for the first and second gear in this case engaged stand, only the gear tooth device G2 is implemented for the second gear, to generate the gear ratio for the second gear while the transmission gear device G1 for the first gear with the clutch C1 held for the first gear is ineffective due to the action of the one-way clutch CO according to FIG.

Are clutches C3 and C4 for third and fourth gear in Engagement, the transmission gear devices G3 and G4 are correspondingly for the third and fourth gear realized alone while the transmission gear device G1 for the first gear with the clutch C1 held for the first gear is ineffective.

When the vehicle speed continues to increase, the switching valve becomes V2 for shifting from second to third gear to the right or second position pushed to the flow medium line 42 with a flow medium line 45 to bring in connection. In this case, the switching valve takes V3 for switching from third to fourth gear the shown left or first position, so that the flow medium line 45 is connected to a flow medium line 46 stands with the hydraulically actuating part of clutch C3 for the third Gear is connected, which enables this clutch to realize the gear ratio engaged for third gear.

The switching valve V3 for switching from the third to the fourth The gear changes to the right or second as the vehicle speed increases Position pushed, the flow medium line 45 with a hydraulic actuating part of the clutch C4 for the fourth gear connected flow medium line 47 comes into connection, so that the clutch C4 for the fourth gear for adjustment of the gear ratio for fourth gear comes into engagement. The one described above Embodiment of an automatic transmission is known per se.

The anti-creep valve 50, which is in the flow medium line 41 is arranged, has a via this flow medium line 41 with the flow medium line 40 connected inlet port 51 and one with the hydraulically operated Port 52 connected to the first gear clutch C1. A core 55 of the valve 50 has an end surface 55a with a larger diameter than that other end surface 55b, the pressure-receiving area of the first-mentioned surface is larger than that of the latter area. The end face 55a of the core 55 has one with a large-sized hole 56 and a small-sized hole 57 provided central part, the diameter of the hole 57 being smaller than the of the hole 56 is. In the other end face 55b, a central part is provided with a Hole 58 provided. An annular one provided in the outer peripheral surface of the core 55 Groove 59 connects inlet port 51 with outlet port 52 when core 55 assumes a first position shown. The annular groove 59 protrudes over small ones Holes (hereinafter referred to as "constrictions") 60 and 61 with holes 57 and 58 in connection. A one-way valve provided in hole 57 enables one Flow of the pressurized oil in only one direction from hole 57 to hole 56.

Between the end face 55a of the core 55 and an opposite one End surface of an end block 63, a pressure chamber 65 is formed, in the end block 63, a through hole 63a opening into the pressure chamber 65 (hereinafter referred to as "passage") is formed. In the hole 56 of the core 55 is a spring 64 is provided with one end against the end face of the hole 56 and with its other end presses against the opposite end face of the end block 63. The openings 51 and 52 are connected to one another via a flow medium line 67 Connection arranged parallel to the valve 50 preventing creeping movements and includes a one-way valve 68 that controls a flow of the pressurized oil only made possible in the direction from the outlet opening 52 to the inlet opening 51. The flow medium line 67 and the one-way valve 68 serve to keep the under pressure standing oil in clutch C1 for the first course into a zone lower pressure when the manual slide valve Vm from the front Position is moved to the neutral position or the rearward position, the internal pressure of the clutch C1 to directly break its engagement to decrease immediately.

Such an embodiment is particularly advantageous when the Viscosity of the operating oil is small, such as in cold weather the case is.

At an end closer to the end block 63, preventing creeping movements Valve 50, an electromagnetic valve 70 is mounted. A valve body 71 this Valve 70 is displaced by the urging force of a spring 72 to the passage 63a to close when a solenoid 73 is de-excited. The valve body 71 is attracted against the force of the spring 72 to open the passage 63a when the Lifting magnet 73 is excited, whereby the pressure chamber 65 with an opening 53 in connection got. The electromagnetic valve 70 is designed as a pipe valve in which the valve body 71 by the spring 72 in a position closing the passage 63a is pressed and in which the force of the spring 72 and the diameter d of the passage 63a have such values that the pressure in the pressure chamber 65 on one of the following The predetermined pressure still to be explained is maintained when the solenoid 73 is de-energized will. By choosing the spring force and the passage diameter, the electromagnetic Open the valve even with de-energized solenoid 73 when the pressure in the pressure chamber 65 exceeds the predetermined pressure value by an amount which is the difference corresponds to between the predetermined pressure and the pressure in the pressure chamber 65, whereby the pressure chamber 65 via the passage 63a with the opening 53 in communication got. The pressure chamber 65 can also be connected via a bypass flow medium line 54 come into communication with the opening 53, with a one-way valve in the line 54 66 is arranged, that one flow of pressurized oil only made possible in the direction from the opening 53 to the pressure chamber 65.

A test fluid line extending from the test fluid line 48 90 is via a shut-off valve 74 provided on the hand slide valve Vm with a Port 75a of a selector valve 75 connected, the shut-off valve 74 opens when the manual slide valve Vm is in one of the drive range positions. The selector valve 75 has a valve 50 which prevents creeping movements with the opening 53 of the creeping movement Opening 75b connected via a test fluid line 91. Another from the test fluid line 48 outgoing test fluid line 92 is with a test flow medium line running between the opening 53 and the selector valve 75 91 connected. A one-way valve 82 is provided in the test flow medium line 92, through which the pressurized oil is only in the direction of the test fluid line 48 can flow to the one-way valve 82.

The selector valve 75 has a body 76, one in part through a left end face of body 76 (seen in Fig. 2) defined pressure chamber 78 as well a spring 77 urging the body 76 toward the pressure chamber 78. The pressure chamber 78 is arranged so that it is connected to the test fluid line via a one-way valve 79 90 can communicate with the valve 79 a flow of the pressurized Oil only in the direction from the test flow medium line 90 to the pressure chamber 78 allows. Furthermore, the pressure chamber 78 is via a constriction 80 with the Test flow medium line 92 in connection.

In the outer peripheral surface of the body 76 of the selector valve 75 is a annular groove 76a is provided, which is arranged such that they the openings 75a and 75b brought together in connection when the body 76 in a first position shown. The body 76 is counteracted by the force of the spring 77 pressed the first position. When the pressure in the pressure chamber 78 is through the Force of the spring 77 exceeds the specified reference pressure Ps, the body 76 as seen in Fig. 2 to the right in a second position, whereby the Openings 75a and 75b are no longer in communication, so that the selector valve 75 is closed to the connection between the test fluid lines 90 and 91 to interrupt.

The selector valve 75 has in terms of its displacement of one closed position to an open position delaying the displacement Function which is brought about by the one-way valve 79 and the constriction 80.

Specifically, as the suction pressure Pt increases, this pressure is both above the one-way valve 79 and the constriction 80 transferred into the pressure chamber 78, whereby the selector valve 75 is closed immediately without delay to the test fluid line 90 to switch off from the test flow medium line 91. On the other hand, the suction pressure decreases Pt from, the pressurized oil in the pressure chamber 78 flows through the alone Constriction 80 with a lower flow rate. Is the suction pressure Pt due to the sudden closing of the throttle below the reference pressure Ps dropped, the selector valve 75 therefore remains temporarily closed State whereby the function delaying the shift is implemented. As executed, the one-way valve 79, the constriction 80 and the selector valve 75 act so together that they work as a retarding valve 81, the one-way valve 79 and the constriction 80 are formed in one piece with the selector valve 75.

Because of this configuration, these prevent creeping movements Valve 50 and the selector valve 75 via the only test fluid line 91 connected to each other. The selector valve 75 as well as the creeping movement preventing Valve 50, which is provided with a lifting magnet and an adjustment mechanism, can therefore be in different places, for example inside the gearbox and placed on the outer periphery thereof, thereby building up the entire creep movements preventing device is simplified.

A brake sensor 10Q is used to determine whether a not shown The vehicle's brake pedal is depressed or not, and generates a high signal Level when the brake pedal is depressed. For example, one can be used to switch it on and off Switches serving the brake lights can be used as brake sensor 100.

An engine speed sensor 101 detects the engine speed Ne, for example by counting the time interval between adjacent pulses of an ignition signal and generates a high level signal when the detected engine speed Ne is smaller than a predetermined speed Ns, this being slightly smaller than a predetermined one Speed, for example an idle speed, is.

The brake sensor 100 and the engine speed sensor 101 have input connections an AND gate 103 of a solenoid driver circuit 102 is connected. The AND gate 103 has an output terminal coupled to the base of a transistor Tr, its emitter grounded and its collector via a line 104 with a connection of the solenoid 73 of the electromagnetic valve 70 is connected. The other The lifting magnet 73 is connected via a line 105 to a line (not shown) Voltage source connected.

The following is the mode of action of the creeping movements preventive Valve 50 and the delay valve 81 described.

When the vehicle is running, they have the output signal from the brake sensor 100 and the engine speed sensor 101 have a low level, so that the transistor Tr is held locked to the solenoid 73 of the electromagnetic valve 70 not to arouse. In this case, the amount of trampling will not be shown accelerator pedal corresponding oil pressure or suction pressure Pt in the test flow medium lines 90 and 92 directed. If the suction pressure Pt is greater than the reference pressure Ps, then the delay valve 81 is closed, its body 76 as seen in FIG is shifted right to the test fluid line 91 from the test fluid line 90 disconnect. Therefore, the suction pressure Pt via the test fluid line can then 92, the one-way valve 82 and the test flow medium line 91 free to the pressure chamber 65 of the creeping movement preventing valve 50 are transmitted, however the pressurized oil in the pressure chamber 65 has no way of draining therefrom Chamber finds. In this case, the line pressure becomes P1 in the fluid line 41 partly via the constrictions 60 and 61 of the creeping movements Valve 50 onto opposite end surfaces 55a and 55b of body 55 transfer. This body 55 is therefore due to the difference in pressure-receiving Areas between the end faces 55a and 55b as well as due to the force of the spring 64 shifted down into the first position shown, whereby the opening 51 comes into connection with the opening 52 via the annular groove 59. The line pressure P1 is therefore on the hydraulically actuating part of the clutch via valve 50 C1 for first gear transmitted to bring it into engagement.

If the accelerator pedal is released and the brake pedal is depressed at the same time, to stop the vehicle, the suction pressure Pt increases with a decrease in the Depress the accelerator pedal. However, the delay valve 81 remains due to the Displacement retarding function temporarily in a closed state, whereby Impact due to abrupt release of the accelerator pedal can be prevented. Falls the engine speed Ne falls below the reference speed Ns, the output of the Engine speed sensor 101 inverted to a high level. In this case it is Output signal of the brake sensor 100 already inverted to a high level, there the brake pedal was pressed.

The AND gate 103 therefore generates a high level signal, whereby the transistor Tr is held in the conductive state, so that the electromagnetic Valve 70 is energized to open passage 63a.

At this time, the delay valve 81 is shown in FIG first position moved to the test fluid line 91 with the test fluid line 90 to bring in connection, whereby the pressurized oil in the pressure chamber 65 of the creeping movement preventing valve 50 via the then open passage 63a and test fluid lines 91 and 92 into the lower pressure zone exits to lower the pressure in the pressure chamber 65. The body 55 will therefore by the oil pressure acting on its end face 55b in the direction of an interruption the connection of the openings 51 and 52, i.e., as seen in Fig. 2 upwards, displaced, whereby the port 52 with a communicating with the oil tank R outlet port 69 comes into connection, so that the oil pressure in the Strömugnsmediumleitung 41 to of port 52, i.e. that of the hydraulically actuating part of clutch C1 for the oil pressure (clutch pressure) supplied to first gear is reduced. The on the Body 55 acting force that sen in Fig. 2 seen upwards increases, i.e. the clutch pressure then supplied to clutch C1 for first gear is regulated to a pressure Po set by the force of the spring 64. This Pressure Po is set to a value that is almost the same and slightly smaller as an engagement pressure Pe above which the first-speed clutch C1 engages to cause the vehicle to creep. This pressure will by the force of a not shown, in the clutch C1 for the first gear provided return spring. The first-speed clutch C1 therefore becomes held in a fully released state, causing creep of the vehicle is prevented when this stands.

The brake pedal is then used to start the vehicle in its initial position brought, the output signal of the brake sensor 100 is at a low level inverted.

The output of AND gate 103 then goes low on, whereby the transistor Tr is blocked, so that the electromagnetic valve 70 is de-excited.

Thus, the valve body 71 by the force of the spring 72 to Closing the passage 63a are displaced.

In this case, if the accelerator pedal is not depressed, the valve body begins 71 to be pushed upwards by the oil pressure present in the pressure chamber 65, when this oil pressure is greater than the set pressure by a predetermined pressure AP Po becomes so that the oil pressure in the pressure chamber 65 via the passage 63a, the test fluid line 91, the then open delay valve 81 and the test fluid line 90 can escape into the zone of lower pressure, reducing the oil pressure in the chamber 65 is regulated to a predetermined pressure Po + AP.

This means that the force of the spring 64 prevents the creeping movements Valve 50 by a value corresponding to the predetermined pressure AP and thus the on the hydraulic actuating part of the clutch T1 for the first Acting pressure from the set value Po to the specified pressure Po + AP is increased. Because of this increase in the oil pressure by the predetermined value AP can no ineffective stroke of the hydraulically actuating part of the clutch C1 for the occur first gear. This predetermined pressure AP can be small. By avoidance of the ineffective stroke, clutch C1 can be effectively kept in a state in which the vehicle can creep. In addition, a through the re-action of the brake pedal caused by the small shock Pressure difference P can be reduced to a minimum value. The one in the clutch C1 for the first gear existing clutch pressure P is represented by a curve I in Fig. 3 shown. In the same figure, a broken curve represents the engagement pressure Pe represents in which the force of the return spring to return a piston of the hydraulic operating part of the clutch C1 for the first speed with the internal pressure of the clutch C1 is in equilibrium.

When the internal pressure of the clutch C1 is greater than the engagement pressure Pe is, so the vehicle can crawl while not crawling, as stated above can if the first-mentioned pressure is smaller than the second-mentioned pressure.

If the accelerator pedal is then stepped on, the amount of stepping is reduced of the gas pedal corresponding suction pressure Pt via the test flow medium line 90 and the delay valve 81 as well as the test flow medium line 92 and the One-way valve 82 into the flow medium line 91 and then via the one-way valve 66 passed into the pressure chamber 65 of the valve 50 which prevents creeping movements, whereby the body 50 is pushed downward as seen in FIG. When the suction pressure Pt is less than the reference pressure Ps and thus the delay valve 81 is is in its open state, the body 55 becomes with an increase in the Suction pressure Pt shifted down so that the outlet port 52 is decoupled from the outlet opening 69 and only with the inlet opening 51 communicates. The clutch pressure P of the first-speed clutch C1 decreases therefore gradually increases according to a solid curve II in FIG. That creeping movements preventive valve 50 is usually operated with such an increase in suction pressure Pt moved to a position allowing creeping movements.

When the throttle opening increases beyond a predetermined opening Oo, so that the suction pressure Pt exceeds the reference pressure Ps, as shown in FIG. 3, so the delay valve 81 closes to the test fluid line 91 from the test flow medium line 90 to be decoupled. The one on the opposite End faces 55a and 55b of the body 55 of the anti-creep valve 50 acting pressure is therefore equal, whereby the body 55 due to the difference in the pressure-receiving area between the end surfaces 55a and 55b and the pressure force the spring 64 is displaced downward so that the opening 52 is full of the opening 51 came into contact.

The line pressure P1 in the flow medium line 41 is therefore on routed the hydraulically actuating part of clutch C1 for first gear, to increase the clutch pressure P to a level equal to the line pressure P1, as shown by the solid curve III in FIG. This will make the Torque transmission capacity of the clutch C1 for the first gear to a maximum Increased value to ensure effective engagement of clutch C1.

If the brake pedal is held down, it stays that way solenoid valve 60 as long as in an open position, as the engine speed Ne is smaller than the predetermined speed Ns. The clutch pressure P therefore becomes then according to a solid curve IV in FIG the pressure Po held. If the accelerator pedal is stepped on in this case, the clutch pressure is increased P changed according to the solid curve II, with further stepping on the accelerator pedal the increased oil pressure Pt from the test fluid line 91 via the passage 63a and the one-way valve 66 is passed to the pressure chamber 65.

As stated above, the delay valve 81 performs the displacement delaying function only when it is open. When the shift lever for example from the neutral position (N), in which the throttle valve normally closed and therefore the suction pressure Pt is equal to zero, in the drive range position (D4) shifted, the delay valve 81 is in an open state, so that the body 55 of the anti-creep valve 50 is immediately so displaced becomes that between the first-speed clutch C1 and the operating oil source running flow medium line 41 is blocked to an immediate intervention of clutch C1 and avoid gear shift shock.

Is the shut-off valve arranged in the test flow medium line 90 74 designed so that it only opens when the shift lever is in the Drive range position (D4) and closes when the shift lever closes is in a position different from the drive range position (D4), so the creeping of the vehicle can only be prevented when the shift lever is in the drive range position (D4).

FIG. 4 shows a device which prevents creeping movements according to FIG a second embodiment of the invention, in which the same reference numerals correspond Parts and elements denote which have the same functions as those of the device according to Fig. 3 have. For an explanation these parts and elements is therefore waived.

An outgoing from the flow medium line 40 and with the manual slide valve Vm on the outlet side of which the flow medium line 145 has creeping movements preventing valve 152 from being different in structure from valve 50 of FIG. 2, flow medium line 114 connected to a clutch C1 for the first gear tied together. A valve body 153 of the creep preventing valve 152 has an upper end face with a pressure receiving area larger than that a lower end face. An axially central part of the body 153 has in its outer circumferential surface an annular groove 162, which has a small hole 155 is in communication with a lower pressure chamber 161, which in turn is partly through the lower end face of the body 153 is formed. The upper end face of the body 153 partially defines an upper pressure chamber 160, in which one the valve body 153 in FIG. 4, permanently downwardly pressing spring 158 is arranged. These Spring 158 rests with its upper end on an adjusting screw 165 so that the Force of the spring 158 by axially adjusting the screw 165 to a desired one Value can be set. With 165a is a fastening nut for fixation the adjusting screw 158 denotes in a desired position, while 165b denotes a cover removable from the valve 152 to protect the adjusting screw 165 is.

Preventing creep of the inlet fluid line 145 Valve 152 goes from a bypass flow medium line 169, which via a Filter 164 and a restriction 154 continuous with the exit fluid line 114 is in communication. The upper pressure chamber 160 of the preventive creep The valve is continuously connected to an exit fluid line 159 Link, which in turn is connected to an opening 180a of a selector valve 170. One from the outlet flow medium line 11 4 outgoing feedback flow medium line 167 is arranged to have an electromagnetic valve 156 and a Flow medium line 166 with a drain line 163 preventing creeping movements Valve 152 is in communication. The connection between the feedback fluid line 167 and the drain line 163 is selectively made by the valve body 153 of the creeping movements preventive valve 152 formed and blocked.

The electromagnetic valve 156 is electrically connected to a solenoid drive circuit 102 'connected. The brake sensor 100, a vehicle speed sensor 182 as well as an engine cooling temperature sensor 183 are connected to respective input terminals of a AND gate 103 'of the solenoid driver circuit 102' connected. These feelers 100, 182 and 183 set predetermined conditions for triggering and ending the creeping movements preventive function corresponding to the sensors according to Fig. 2. The vehicle speed sensor 182 generates a high level signal when the vehicle speed is slower as a reference value, and is for example through one of a tachometer cable actuated magnets and a reed switch. The engine coolant temperature sensor 183 generates a high level signal when the temperature of the engine cooling water is greater than a reference value which, for example, is equal to or less than OOC is. This sensor can, for example, be an element made of thermoferrite material and a reed switch can be formed.

When the brake pedal is depressed, the vehicle speed is than the Reference value and at the same time the engine cooling water temperature greater than the reference value, so take that Output of AND gate -103 'has a high level on, whereby the transistor Tr conducts and thus the electromagnetic valve 156 is energized to the valve body 127 in the illustrated upper or open position to move. If one of the above conditions is not met, it will electromagnetic valve 156 de-energized, so that the valve body 157 its lower or occupies closed position.

The valve body 172 of the selector valve 170 is supported by a spring 172 seen in Fig. 4 always biased to the left. A spring chamber 177 becomes part formed by a right end face of the valve body 171. This chamber 177 is connected to a drain line 178. A pressure chamber 176 is partially through a left end face of the valve body 171 is formed. This chamber is about one formed by a test valve 174 and a constriction 173 parallel circle with a Flow medium line 146 connected, which supplies the suction pressure Pt. An axially central one Part of the valve body 171 has an annular shape in its outer peripheral surface Groove 172a that connects the opening 180a with an opening 180b when the valve body 171 is in an illustrated first position. The one from the test fluid line 48 outgoing flow medium line 146 is connected to the opening 180b, while with a flow medium line 179 extending from the flow medium line 146 an opening 180c, which in turn is permanently connected to the opening 180a in FIG Connection. A one-way valve 175 is provided in the flow medium line 179, so that the pressurized oil only in the direction of the flow medium line 146 can flow to opening 180c. The valve 170 also has an opening 180d, which is connected to the flow medium line 145, and via the annular Groove 171a communicates with the opening 180a when the valve body 171 is a right shown in Fig. 6 or occupies second position. at In this embodiment, the one-way valve 174, the constriction 173 and the Selector valve 170 in the sense of the effect of a delay valve 81 'together, the the valve 81 according to.

Fig. 2 corresponds.

The delay valve 81 'as well as the creeping movement preventing Valve 152 according to the second embodiment of the invention operate as follows: If the vehicle speed is lower than the reference value with the brake pedal depressed and the engine cooling water temperature is greater than the reference value, i.e., if the vehicle is in a condition that prevents creeping is to be, the electromagnetic valve 156 is in an energized state, with the valve body 157 pushed to the up or open position. Is in In this state, the suction pressure Pt in the flow medium line 146 is essentially equal to zero, the valve body 171 of the selector valve 170 is made by the pressing force the spring 172 is held in the left position, the flow medium line 146 in full communication with the flow medium line 159 via the annular groove 171a stands. The pressure in the upper pressure chamber 160 prevents creeping movements Valve 152 is therefore small. On the other hand, the line pressure becomes P1 from the fluid line 145 directly and / or through the flow medium line provided with the constriction 154 159 passed into the lower pressure chamber so that it hits the lower end surface of the valve body 153 acts, as a result of which it is shifted upwards. If the valve body 153 is around shifted a certain stroke upwards, so that arrives with the flow medium line 114 connected flow medium line 156 with the discharge line 163 in connection, while the inlet flow medium line 145 blocked by the valve body 153 will.

Because the line pressure acting on the lower end face of the valve body 153 P1 only via the constriction 154 of the flow medium line 159, the annular one Groove 152 and the small hole 155 is fed, the valve body in the in Fig. 5 held the equilibrium position shown, in which the opposite End faces of the valve body acting pressures are in equilibrium. Is moving the valve body 153 from the position shown in Fig. 5 upwards, occurs the operating oil in the annular groove 162 through the flow medium lines 167, 160, as well as the drain line 163, so that the oil pressure in the annular groove 162 and the lower pressure chamber 161 decreases. The valve body 153 is therefore after shifted below, so that it is the equilibrium position shown in Fig. 5 again occupies. On the other hand, if the valve body 153 takes a position below the position 5, the line pressure P1 from the flow medium line 145 becomes passed directly into the annular groove 172 to be in this and in the lower pressure chamber 161 to increase the pressure immediately, whereby the valve body 163 again in the equilibrium position according to FIG. 5 is brought. The clutch pressure P in the flow medium line 114 is therefore held by the valve 152 at the pressure Po, which is not high enough is to engage the clutch C1 for the first speed.

The clutch C1 is therefore kept in a released state to prevent the vehicle from crawling.

The setting of the pressure value Po is made by the pressure receiving Area of the lower end face of the valve body 153, the cross-sectional area of Restriction 154, line pressure P1, force of spring 158, etc. set, and can be increased by moving the adjusting screw 125 axially inwards Value can be adjusted so that the spring 158 is further compressed. By axial Moving the screw 165 outward can reduce the pressure on a small one Value can be set, whereby the pressing force of the neither 158 is reduced.

When the throttle valve to increase the suction pressure Pt in the flow medium line 146 is opened beyond a reference pressure Ps', the suction pressure thus increased becomes Pt introduced into the pressure chamber 176 of the selector valve 170 via the test valve 174, so that the valve body 171 against the force of the spring 172 to the right in the second Position according to FIG. 6 is shifted. The line pressure P1 in the flow medium line 145 is therefore now through the annular groove 171a of the selector valve 170 in the Flow medium line 159 initiated.

The line pressure P1 supplied from the flow medium line 145 is greater than the suction pressure Pt supplied by the flow medium line 146, so that the test valve 175 is therefore closed by the line pressure P1, whereby the suction pressure Pt in the flow medium line 146 via the test valve 175 of the Flow medium line 179 cannot be introduced into flow medium line 159 can.

The test pressure Pl is therefore instead of the suction pressure Pt in the flow medium line 159 initiated with almost no suction pressure Pt lost.

The selector valve 170 thus works as a function of the test signal from the suction pressure Pt supplied to the fluid line 146 to the line pressure P1 to be conducted into the flow medium line 159 when the suction pressure Pt is the specified Pressure exceeds Ps'. The line pressure thus introduced into the flow medium line 159 P1 is then introduced into the upper pressure chamber 160 via the opening 168, see above that the valve body 153 due to the difference in the pressure-receiving area between its upper and lower end faces and by the force of the spring 158 is immediately shifted downward, whereby the input fluid line 145 full of the original Flow medium line 114 in connection arrives and the clutch C1 for the first gear in a creeping movement enabling State is brought.

It is now assumed that the electromagnetic valve 156 at in the lower or closed position pushed valve body 157 is de-energized.

Is the suction pressure Pt in the flow medium line 146 substantially equal to zero and therefore the pressure in the flow medium line 159 becomes small the line pressure P1 in the input flow medium line 145 directly and / or via the shunt fluid line 169 to prevent creep Valve 152 passed and then over the annular groove 162 and the small hole 165 introduced into the lower pressure chamber 161 so that the line pressure P1 at the lower end face acts on the valve body 153 to move it up into the second Position according to FIG. 5 to press. With the valve body held in this position 153, the inlet flow medium line 145 is blocked by the valve body 153, so that the line pressure P1 is solely through the constriction 154 of the bypass fluid line 159, the annular groove 162 and the small hole 155 in the lower pressure chamber 161 is directed. However, there is the pressurized oil in the flow medium line 114 not via the flow medium line then blocked by valve body 157 167 can flow, the clutch C1 receives a line pressure for the first gear P1, which is greater than the engagement pressure Pe, so that this clutch in a one Creeping movement enabling state is brought.

If the suction pressure Pt in the flow medium line 146 increases via the Reference pressure increases, the line pressure P1 is now via the flow medium line 159 and the opening 168 is introduced into the upper pressure chamber 160, such as this has already been mentioned above. The valve body 153 is therefore due to the difference of the pressure-receiving area between its upper and lower end surfaces as well as due to the force of the spring 158 immediately shifted downwards. In this case it stands the inlet flow medium line 145 to the outlet flow medium line 114 in connection to keep the first-speed clutch C1 in the to maintain a state that enables a creeping movement.

When the brake pedal is released from its depressed state while the first-speed clutch C1 in a creep preventing state is held, the state of the clutch which enables a creeping movement becomes Cl recovered in the following way: While the clutch C1 is in a one If there is a creeping movement preventing state, the valve body 153 takes the creeping movements preventing valve 152 the second position shown in FIG. Will in this case the brake pedal released from its depressed state and therefore the electromagnetic Valve 156 for blocking the feedback fluid line 167 through the If valve body 157 is de-energized, line pressure P1 is increased via constriction 154 the bypass flow medium line 159 introduced into the flow medium line 1114, whereby the clutch pressure P in this fluid line 114 without a downward displacement of the valve body 153 is gradually increased beyond the engagement pressure Pe. on this becomes the creeping enabling state of the clutch C1 for gradually regained first gear.

However, if the accelerator pedal is then stepped on, the line pressure is increased P1 immediately via the selector valve 170 and the opening 168 in the sense described above introduced into the pressure chamber 160, so that the valve body 153 as a function the speed at which the accelerator pedal is depressed away down moved, whereby the pressure in the flow medium line 114 is increased immediately.

Let us now assume, for example, that the accelerator pedal is depressed, while the electromagnetic valve 156 is held in the energized state. Of the Inlet pressure Pt then increases by an amount equal to the amount of depression of the accelerator pedal when starting the vehicle with increasing incline. In an initial state when the accelerator pedal is depressed, the pressure in the upper pressure chamber 160 of the decreases Creep preventing valve 152 in this case proportionally with a Increase in the valve opening of the throttle valve to increase the clutch pressure P of the clutch Gradually increase C1 for first gear. Eventually the pressure is then on increases a value equal to the line pressure P1, thereby smooth starting of the vehicle is ensured. On the other hand, the throttle is used for a quick If the vehicle is suddenly opened, the line pressure P1 acts directly the valve body 153 of the creep preventing valve 152 around this valve body shift down, causing the clutch C1 for first gear immediately adopts a creeping movement-enabling state, thereby giving a good response the anti-creeping device for the purpose of an immediate start-up process is ensured by the vehicle driver.

On the other hand, if the accelerator pedal suddenly comes out of its depressed position released and therefore the suction pressure Pt in the flow medium line 146 suddenly is decreased, the oil pressure in the pressure chamber 176 of the selector valve 170 becomes gradually Derived via the constriction 173 alone, so that the valve body 171 as well as at valve 81 according to FIG. 2 can be gradually shifted to the left until finally the connection between the flow medium lines 145 and 159 is blocked by the valve body 171. Therefore, due to the effect of the Delay valve 81 'no impact occurs when the throttle valve closes abruptly.

The delay valve used in the first embodiment of FIG 81 can instead of the valve 81 'directly in the second embodiment according to FIG. 4 can be used. On the other hand, this can also be done in the second embodiment according to FIG Fig. 4 used delay valve 81 'in place of valve 81 in the first embodiment according to Eig. 2 can be used. In the first case, the suction pressure Pt alone is in the upper pressure chamber 160 of the anti-creep valve 152 is initiated, while in the latter case the line pressure P1 instead of the suction pressure P t in the pressure chamber 65 of the anti-creep valve 50 is initiated, when the suction pressure Pt exceeds the reference pressure Ps.

Although in the embodiments described above, the creeping movement of the vehicle by blocking the connection between the clutch C1 for the first gear and the operating oil source by means of the preventing movements Valve prevented. The anti-creep valve according to the invention however, it can also be used in a case where the hydraulic actuator Part of the clutch Cl for the first gear supplied pressurized oil into the Oil tank can be drained to prevent the vehicle from creeping.

Claims (12)

Device for preventing creeping movement of with automatic Geared motor vehicles Patent claims 1. Device for prevention a creeping movement of motor vehicles that have an engine, a fluid coupling, one coupled in series with this and one frictionally engaging element having transmission and a flow medium source for supplying an operating having flowing medium to the frictionally engaging element, with a Motor load sensor for generating a flow medium signal, the pressure of which is a measure for the engine load, with one between the frictionally engaged element and the flow medium source provided control device and with a flow medium signal from the engine load sensor to the control device conducting flow medium line, wherein the regulating device for regulating the power transmission capacity of the friction engaging element in a range from zero to a predetermined Value as a function of pressure of the flow medium signal is used to prevent the vehicle from creeping when the engine is in no-load condition is located, characterized by a selector valve provided in the flow medium line, which can assume a first position in which a flow of the fluid medium signal possible in both directions from the motor load sensor to the control device and vice versa is when the pressure of the flow medium signal is less than a predetermined value is, and which can assume a second position in which a flow of the flow medium signal is only possible from the engine load sensor to the control device if the pressure of the flow medium signal is greater than the specified value. 2. Apparatus according to claim 1, characterized in that the selector valve a decelerating device for reducing a displacement moving speed from the second to the first position when the pressure of the flow medium signal decreases has to a value which is smaller than the speed of the displacement movement from the second to the first position when the pressure of the flow medium signal increases is. 3. Apparatus according to claim 1, characterized by a second flow medium line for supplying the flow medium from the flow medium source to the selector valve for supplying the flow medium instead of the flow medium signal to the control device is used via the first-mentioned flow medium line when the selector valve is in the second Position is pushed. 4. Apparatus according to claim 1, characterized in that the control device has the following components: one to the fluid source coupled input fluid conduit, one frictionally engaging Element coupled output fluid line, a first and a second End face having valve body for selective connection and decoupling of the Inlet fluid line to or from the outlet fluid line, a first pressure chamber defined in part by the first end face of the valve body, to which a fluid pressure is supplied in the outlet fluid line, a pressure chamber partially defined by the second end face of the valve body, to which the pressure of the flow medium signal is supplied, a third, a constriction having flow medium line, which the flow medium pressure in the outlet flow medium line always introduces into the second pressure chamber, a spring which the valve body in pushes a direction in which the input fluid conduit with the output fluid conduit is connected, and a discharge line, via which the flow medium pressure in the outlet flow medium line can be diverted into a zone of lower pressure, when the valve body due to a difference in the fluid pressure between the first pressure chamber and the second pressure chamber, the amount of which corresponds to the amount, around which the valve body is biased, in a direction of disconnection of the Inlet fluid line biased by the output fluid line will. 5. Apparatus according to claim 4, characterized in that the third Flow medium line is formed in the valve body. 6. The device according to claim 4, characterized by one in the first-mentioned, between the control device and the selector valve running flow medium line arranged one-way valve, through which the flow medium only in the direction of Selector valve can flow to the control device, a second in the first-mentioned flow medium line one-way valve arranged parallel to the first one-way valve, via which the flow medium can only flow from the control device to the selector valve, and through an opening of the second one-way valve when the pressure of the flow medium in the direction of flow upstream of this valve is greater than the pressure of the flow medium in the direction of flow behind this valve, by an amount that is one exceeds the specified value. 7. The device according to claim 6 for a vehicle with a braking device and a second one-way valve in the form of an electromagnetic valve by a brake sensor to determine whether the braking device is effective or not, and through a driver circuit to open the electromagnetic valve, when the braking device is determined to be effective by the brake sensor, whereby the power transfer capacity of the frictionally engaged element in Depending on whether the braking device is effective or not, on different Values is set. 8. Apparatus according to claim 1, characterized in that the control device has the following components: an inlet flow medium line coupled to the flow medium source, an output fluid conduit coupled to the frictionally engaging element, a valve body having first and second end surfaces for selective communication and uncoupling development of the inlet flow medium line with the resp. from the exit fluid line, one in part through the first The end face of the valve body defines the first pressure chamber, which is a flow medium pressure is fed in the output fluid line, one in part through the second The end face of the valve body defines the second pressure chamber, which is the pressure of the flow medium signal is supplied, a third flow medium line provided with a constriction, which always connects the inlet fluid line with the outlet fluid line couples, a spring, which the valve body in one direction in terms of a connection the inlet fluid line presses with the outlet fluid line, and a drain line through which the fluid pressure in the exit fluid line can flow into a zone of lower pressure when the valve body due to a Difference in the flow medium pressure between the first pressure chamber and a second Pressure chamber, the amount of which corresponds to an amount by which the valve body is biased is, in one direction in the sense of a decoupling of the inlet flow medium line is biased by the exit fluid line. 9. Apparatus according to claim 8, characterized by a shut-off valve to block the drain line when the braking device through the brake sensor is determined to be effective. 10. Apparatus according to claim 8, characterized in that the control device an adjusting device for adjusting the size of the flow medium pressure in the Having outlet flow medium line, such that the power transmission capacity of the frictionally engaging element is substantially zero. 11-. Device according to claim 10, characterized in that the Adjusting device is used to adjust the spring force of the spring. 12. The device according to claim 1, characterized in that the control device a bypass flow medium line bridging them, which the frictional engaging element couples with the fluid source, and that in the A one-way valve is provided which has a flow bypass flow medium line of the flow medium only in the direction of the frictionally engaging Allows element to flow medium source.