WO1992004213A1

WO1992004213A1 - Device for holding a vehicle stationary on a slope

Info

Publication number: WO1992004213A1
Application number: PCT/EP1991/001492
Authority: WO
Inventors: Lutz Weise; Hans Wupper; Hans-Wilhelm Bleckmann
Original assignee: Alfred Teves Gmbh
Priority date: 1990-09-01
Filing date: 1991-08-07
Publication date: 1992-03-19
Also published as: DE4027793A1

Abstract

Described is a device designed to hold a vehicle fitted with an electronic anti-blocking system on a slope. The device has electrically operated multi-way valves (6, 7, 22, 23, 28, 29) fitted in at least one hydraulic-fluid line leading from a brake-pressure source (1) to the inlet valves (12, 13, 14, 15). The multi-way valves are open in the normal position and can be switched over to a closed position. Fitted parallel to the multi-way valves are pressure-relief valves (20, 21, 24, 25, 20, 31). The multi-way valves act as vehicle-holding valves. When the brake-pressure source (1) is in the released position, electronic circuits (not shown) control the vehicle-holding valves (6, 7, 22, 23, 28, 29) in response to hold commands or hold signals and/or start up the hydraulic pump (8, 27) of an auxiliary pressure source (5, 26)

Description

Arrangement for holding a vehicle on an inclined road

The invention relates to an arrangement for holding a vehicle on an inclined road, in particular as a starting aid on the mountain, for motor vehicles with an anti-lock braking system, in which the wheel brakes are connected to a brake pressure sensor via inlet-outlet valve pairs, and in which A hydraulic pump supplies auxiliary pressure during an anti-lock control.

Starting off on the mountain is often difficult, at least for the inexperienced. Inadvertent rolling back or rolling forward often leads to collisions with not inconsiderable damage. In many situations, e.g. when driving in a traffic jam on an incline, the constantly repeated starting is tedious and requires all the attention. A starting aid is therefore of great use to relieve the driver.

From DE-OS 34 39 067 a stopping aid when starting on a mountain is already known, which is designed as an addition to a brake system with electronic anti-lock control and which already requires components for the anti-lock braking system, such as multi-way valves, wheel sensors and electronic circuits Keep the vehicle on the mountain. In this known starting aid, a spring-loaded check valve is inserted in the pressure medium path leading to the wheel brakes, which initially maintains a residual pressure when the brake is released, which is just sufficient to hold the vehicle on the mountain. enough. This check valve is connected in parallel with a normally blocked valve which is actuated when the accelerator pedal is actuated, thereby switching to passage and leading to a complete reduction in pressure in the brake.

The proper functioning of the multi-way valve reducing the residual pressure and the associated control circuit must of course be guaranteed, because otherwise the brake would be overloaded by the residual pressure with which the holding function is carried out when the vehicle is propelled. Furthermore, it must be ensured that the valve locked in the rest position switches over when the brake is actuated, so that brake pressure can reach the wheel brake unhindered.

The invention is based on the object of developing a holding aid for a vehicle with an electronic ABS which can be implemented with little additional effort, which does not impair the functional reliability of the brakes and which satisfies the different requirements which occur in practice.

It has been found that this object can be achieved with an arrangement of the type mentioned at the outset, the special feature of which is that in at least one of the pressure medium lines leading from the brake pressure sensor to the inlet valves, an electrically operable one, in the idle position on passage Switched and lockable switchable multi-way valve is arranged, which is a pressure relief valve in parallel and which serves as a holding valve, and that electronic circuit They are present which, in the release position of the brake pressure transmitter or when the brake is released, actuate the stop valve as a function of stop commands or stop signals and / or switch on the hydraulic pump.

According to the invention, a starting aid is thus created with minimal additional effort. Essentially, only a holding valve with a parallel pressure relief valve is inserted into the pressure medium line leading from the brake pressure sensor to one or more wheel brakes. In the idle state, this holding valve is switched to passage, so that the pressure medium path to the wheel brake remains open in the event of a failure of the electrical power supply, a cable break or the like, so that the brake function is not restricted. It is also advantageous that - after blocking the way to the brake pressure sensor - by switching on the hydraulic pump and, if necessary, by controlling the wheel valves, the brake pressure curve in the wheel brakes during the starting process is very precise to the respective requirements, e.g. the slope, driver behavior, etc., can be adjusted.

According to an advantageous embodiment of the invention, the arrangement is provided for a vehicle with anti-lock and traction control by brake intervention, with the traction control, namely for blocking the pressure medium path from the wheel brake of a driven wheel to the brake pressure transmitter, and the same multi-way valve can be used to hold the vehicle on the mountain. In this case, the additional effort is limited to a corresponding design or addition of the electronics. According to a further exemplary embodiment of the invention, the holding valves are arranged in the pressure medium paths in such a way that after the switching of these holding valves the pressure medium return flow from the wheel brakes of all wheels into the brake pressure transmitter is blocked. Activation of the auxiliary pressure source to hold the vehicle is not necessary in this case, even with a steep incline.

In other cases, it could be sufficient to arrange holding valves in such a way that after the valves respond, only the pressure medium return from the wheel brakes of the wheels of a vehicle axle or from the wheels of a diagonal is blocked. With such an arrangement, it could be expedient or even necessary to increase the brake pressure on these two wheels after the brake has been released by switching on the hydraulic pump in order to hold the vehicle. In most cases, however, maintaining the brake pressure on two wheels is sufficient to hold the vehicle.

Furthermore, an advantageous embodiment of the invention is that in a brake system with two hydraulically separate brake circuits, to which the wheel brakes of two vehicle wheels are connected - diagonally or axially - the pressure medium return from the wheel brakes via the outlet valves to the Suction sides of the hydraulic pump and to the inlet valves are each designed as a closed system. In this case, a holding valve is arranged in each brake circuit in such a way that after switching the holding valves by opening an outlet valve and switching on ^* the hydraulic pump, the brake pressure in the wheel brakes, the pressure medium path to the brake pressure transmitter blocked by the holding valve, increases. In this way, a starting aid can be implemented very easily even in vehicles with closed systems.

Finally, it is also provided according to the invention that the holding valves can be controlled as a function of signals which represent the shift position of the vehicle clutch, the shift position of the transmission, the wheel speeds or the like. The starting aid can be adapted very precisely to the respective circumstances by logically linking the individual signals.

Further features, advantages and possible uses of the invention will become apparent from the following illustration of exemplary embodiments with reference to the attached figures.

Show it

1 in a schematic representation, simplified, the essential hydraulic components and the brake pressure sensor of an anti-lock brake system with a starting aid according to the invention,

2 in the same representation, an embodiment for a brake system with anti-lock and traction control Fig. 3 in the same representation, an anti-lock brake system with closed hydraulic systems according to a further exemplary embodiment according to the invention.

According to the exemplary embodiment shown in FIG. 1, the brake system essentially consists of a brake pressure sensor 1, which in turn is composed of a tandem master cylinder 2 and a vacuum booster unit 3, a valve block 4, an auxiliary pressure source 5 and holding valves 6 and 7. The auxiliary pressure source 5 comprises an electric motor-driven hydraulic pump 8 with two hydraulically separated circuits 9, 10. At the master cylinder 2 is also a surge tank

11 connected, in which the suction sides of the hydraulic pump 8 also open.

In the valve block 8 are the intake and exhaust valves

12 - 15 or 16 - 19 of the individual wheels VL, HR, VR, HL accommodated. A brake pressure transmitter with diagonal brake circuit division is provided here. The left front wheel VL and the right rear wheel HR are connected to the brake circuit I, and the two other wheels VR, HL are connected to the brake circuit II.

A pressure limiting valve 20, 21 is connected in parallel to the two holding valves 6, 7, which responds as soon as the pressure difference between the auxiliary pressure and the pressure in the master cylinder exceeds a predetermined limit value, which is above the maximum required for holding the vehicle There is pressure. The inlet and outlet valves 12 - 19 and the holding valves 6, 7 are designed as electromagnetically operable multi-way valves, namely 2/2-way valves. The electronics for controlling these valves and for switching the motor M of the hydraulic pump 8 on and off, as well as the sensors, in particular wheel sensors, which supply the required information in the form of electrical signals for controlling the brake system, are for the sake of clarity not shown. The arrangement according to FIG. 1 works as follows:

As long as all wheels are running steadily and the traction help is not working, all valves 6, 7 and 12 - 19 are in the rest position shown. For anti-lock control, the valves in the valve block 4 and the hydraulic pump 8 are controlled in a known manner. This does not require any further explanation here.

The starting aid according to the invention comes into operation each time the brake is released or only when certain conditions are met. The traction help is required if, for example, a certain lane inclination is determined, if the vehicle rolls back or rolls, even though the clutch is released or the transmission interrupts the drive train. In these cases, when the brake is released, the holding valves 6, 7 are switched over, and thereby the discharge of pressure medium from the wheel brakes of the wheels VL, HR, VR, HL, which are connected to the master cylinder 2 via the holding valves 6, 7, initially is prevented. If necessary, could now by switching on the hydraulic pump 8, the brake pressure in the wheel brakes can be increased to ensure that the vehicle is kept on the mountain in any situation.

If the pressure supplied by the auxiliary pressure source 5 rises above the response value of the pressure limiting valves 20, 21, these respond.

As soon as the information processed in the electronics (not shown) shows that a start-up process is taking place, the brake pressure is reduced in a certain manner and at a certain speed by correspondingly actuating and switching back the holding valves 6, 7 that a "comfortable" starting process occurs.

In the exemplary embodiment of the invention according to FIG. 2, ASR valves 22, 23, namely 2/2-way valves required for traction control, are simultaneously used as holding valves of the starting aid according to the invention. Pressure limiting valves 24, 25 connected in parallel must be designed such that they only respond when the maximum brake pressure required for traction control is exceeded.

In contrast to the exemplary embodiment shown in FIG. 1, in the arrangement according to FIG. 2 - without using further holding valves, not shown - by actuating the holding valves 22, 23, the reduction of the brake pressure can only be achieved in the two wheels VL, VR prevented when releasing the brake. The ASR valves 22, 23, which also serve as holding valves here, are namely as is known, inserted into the brake lines in such a way that only the brake lines of the driven wheels, here the front wheels VL, VR, are separated from the master cylinder and can be pressurized during a traction control system. The wheel brakes of the driven wheels, here the rear wheels HR, HL, on the other hand, must remain depressurized in the ASR phase.

To compensate for the pressure reduction on the rear wheels HR, HL when releasing the brake and activating the holding aid, the brake pressure on the front wheels VL, VR can be increased in the exemplary embodiment according to FIG. 2 by switching on the hydraulic pump 8. In this way it is ensured that after releasing the brake and activating the holding aid, sufficient braking pressure is initially available to hold the vehicle. By activating or switching back the ASR and holding valves 22, 23, practically any desired brake pressure curve can be brought about when the starting aid is released.

For the sake of completeness, it should also be pointed out that by means of additional holding valves in the pressure medium lines leading from the master cylinder 2 to the inlet valves 13, 15 of the rear wheels HR, HL, the brake pressure in the wheel brakes of the rear wheels for holding, if required of the vehicle when starting off on a hill, ie when releasing the brake, could be kept constant. For reasons of cost - two additional 2/2-way valves with pressure limiting valves connected in parallel are required, this embodiment should be limited to special cases. 3 illustrates the structure or the hydraulic circuit of an arrangement of the type according to the invention for anti-lock braking systems with closed hydraulic circuits.

In this case too, the wheels VL, HR; VR, HL are diagonally assigned to the two brake circuits I ', II' of the master cylinder 2. In contrast to the previously described exemplary embodiments according to FIGS. 1 and 2, the pressure medium derived via the outlet valves 16 ', 17', 18 ', 19' for lowering the brake pressure is not, however, in the pressure medium expansion tank 11 ', but returned directly to an auxiliary pressure source 26 and to the suction sides of a two-circuit hydraulic pump 27. According to the invention, two holding valves 28, 29, which in turn have pressure-limiting valves 30, 31 in parallel, in each of the two pressure circuits leading from one of the two brake circuits I ', II' to one wheel, here to the front wheels, VL, VR telwegen inserted. The holding valves 28, 29 are arranged in the two pressure medium systems in such a way that after the valves respond, which leads to the switch into the blocking position, pressure medium flows out of the associated wheel VL or VR, as in the preceding examples and that also by switching on the auxiliary pressure source 26 and opening the exhaust valves 17 ', 19', the pressure in the wheel brakes of the wheels VL, VR, which are braked to hold the vehicle, can be increased. The arrangement according to the invention can therefore also be used without restriction for anti-lock brake systems with closed hydraulic systems. As an alternative to the embodiment shown in FIG. 3, the holding valves 28 and 29 could of course also be connected directly to the master cylinder 2, so that the brake pressure in all wheel brakes would be kept constant in the blocking position of the holding valves. In this case too, opening an outlet valve 16 'or 17'; 18 'or 19', closing the inlet valve 12 or 13; 14 or 15 and switching on the hydraulic pump 27, the brake pressure in the wheel brake of the "other" wheel of each brake circuit can be increased.

The operation of the arrangements according to FIGS. 2 and 3 is basically the same as the described operation of the arrangement according to FIG. 1.

Claims

1. Arrangement for holding a vehicle on a inclined road, in particular as a starting aid on the mountain, for motor vehicles with an anti-lock braking system in which the wheel brakes are connected to a brake pressure transmitter via inlet-outlet valve pairs and in which a Hy¬ during an anti-lock control Draulic pump supplies auxiliary pressure, characterized in that ¬ indicates that in at least one pressure medium path leading from the brake pressure sensor (1) to the inlet valve (12 - 15) there is an electrically actuable multi-way valve (6, 22, switched to passage and switchable to lock) , 23,28,29) is arranged, which is parallel to a pressure relief valve (20,21,24,25,30,31) and which serves as a holding valve, and that electronic circuits are available which are in the release position of the brake pressure transmitter ( 1) or when releasing the brake depending on stop commands or stop signals, control the stop valve (6,7,22,23,28,29) and / or switch on the hydraulic pump (8,27).

2. Arrangement according to claim 1, characterized in that it is provided for a vehicle with anti-lock control and traction control by brake intervention and that for the Drive slip control, namely for blocking the pressure medium path from the wheel brakes of a driven wheel (VL, VR) to the brake pressure transmitter (1), and for holding the vehicle on the mountain to the same multi-way valve (22, 23) can be used.

3. Arrangement according to claim 1 or 2, characterized ge ¬ indicates that the holding valves (6, 7) are arranged in the pressure medium paths such that after the response or switching of the holding valves, the pressure medium return flow from the wheel brakes of all wheels (VL, VR, HL, HR) in the brake pressure sensor (1) is locked.

4. Arrangement according to claim 1 or 2, characterized ge ¬ indicates that the holding valves (22,23,28,29) in the pressure medium paths are angeord¬ net that after the response of the holding valves, the pressure medium return flow from the wheel brakes of the wheels of a vehicle axle Is blocked.

5. Arrangement according to one or more of claims 1 -

4, characterized in that the brake pressure in the wheel brakes, the pressure medium paths to the brake pressure sensor (1) can be blocked by the holding valves (6, 7, 22, 23, 28, 29), can be increased by switching on the hydraulic pump (8, 27) .

6. Arrangement according to one or more of claims 1 -

5, characterized in that there are two hydraulically separate brake circuits, to which the wheel brakes of two vehicle wheels are attached. locks are that the pressure medium return from the wheel brakes via the outlet valves (17 ', 19') to the suction sides of the hydraulic pump (27) and to the inlet valves (12, 14) are designed as hydraulically closed systems and that in each brake circuit a holding valve ( 28, 29) is arranged in such a way that, after switching the holding valve (28, 29) by opening an outlet valve (17 ', 19') and switching on the hydraulic pump (27), the brake pressure in the wheel brakes, the pressure medium path to the brake pressure transmitter through the holding valve (28, 29) is blocked, increases.

7. Arrangement according to one or more of claims 1-6, characterized in that the holding valves (6,7,22,23,28,29) in dependence on signals indicating the switching position of the vehicle clutch, the switching position of the Gearboxes that reproduce wheel speeds and the like can be controlled.