WO2006061279A1

WO2006061279A1 - Pressure medium-operable vehicle brake system and method for controlling a pressure medium-operable vehicle brake system

Info

Publication number: WO2006061279A1
Application number: PCT/EP2005/055311
Authority: WO
Inventors: Tobias Fluck
Original assignee: Robert Bosch Gmbh
Priority date: 2004-12-10
Filing date: 2005-10-17
Publication date: 2006-06-15
Also published as: DE102004059649A1

Abstract

The invention relates to a pressure medium-operable vehicle brake system (10) and to a method for controlling a pressure medium-operable vehicle brake system. Pressure medium-operable vehicle brake systems comprise, for the operation thereof, a master brake cylinder (12) to which a wheel brake (18a, 18b) is connected. The latest sensor systems in motor vehicles are capable of anticipating an imminent collision of a vehicle with an obstacle. In order to minimize the collision energy in order to protect the driver and the vehicle occupants, the invention provides that the vehicle brake system (10) is equipped with an emergency brake (60). This emergency brake can be electronically activated independent from the driver and generates, immediately after its activation, a brake pressure which is sufficient for acting upon the wheel brakes (18a, 18b) and which is at a level higher than a brake locking pressure level under all operating conditions of the vehicle.

Description

Pressure-medium actuated vehicle brake system and method for controlling a fluid pressure actuated vehicle brake system

State of the art

The invention is based on a fluid pressure actuated vehicle brake system according to the features of claim 1 and a method for controlling a pressure medium actuated vehicle brake system according to the features of claim 8.

Druckmittelbetätigbare vehicle brake systems are well known. They have an operable by the driver master cylinder, which is connected via pressure medium lines leading to the wheel brakes of the vehicle. In modern motor vehicle brake systems, a wheel slip control device can be interposed between the master brake cylinder and the wheel brakes. This prevents targeted braking of the wheels, that in a braking operation, a

Acceleration or during normal driving on one of the wheels wheel slip occurs. Background is that with an occurrence of wheel slip usually a safety-critical driving condition of the vehicle is connected.

Figure 1 shows the hydraulic circuit diagram of a known druckmittelbetätigbaren

Vehicle brake system 10 with a foreign-actuated service brake and a muscle-operated auxiliary brake. Whose master cylinder 12 is connected with the interposition of a so-called hydraulic unit 14 via brake lines with wheel brakes 18a - d. The master cylinder 12 is actuated by the driver via a pedal-operated brake booster 20 by muscle power and supplies two brake circuits 16 with pressure medium. These brake circuits 16 are symmetrical in their construction, so that the following explanations have been limited to one of the brake circuits 16. Each brake circuit 16 branches within the hydraulic unit 14 in two brake circuit branches 16a and 16b, to each of which a wheel brake 18a and 18b is connected. In each brake circuit branch 16a, 16b is a

Pressure build-up valve 22a, 22b, which is the hydraulic brake 18a, 18b upstream. As pressure build-up valve 22a, 22b is an electromagnetically actuated 2/2-way proportional valve, which is held by a return spring in its normally open basic position. By electronic control, the pressure build-up valve 22a, 22b is actuated in the direction of its blocking position. Each pressure build-up valve 22a, 22b is a

Check valve 24a, 24b connected in parallel, which blocks in the direction of the master cylinder 12 to a wheel brake 18a, 18b and opens in the opposite direction to allow a rapid pressure reduction in the wheel brake 18a, 18b.

One of the wheel brake 18a, 18b downstream pressure-reducing valve 26a, 26b is in a

Return line 28 arranged. It is an electronically controllable 2/2-way switching valve, which is held by a return spring in its blocking position and can be switched by driving in its passage position. The return line 28 leads to the suction connection of a three individual pump pressure generator unit 30. In this return line 28 is a spring-loaded piston accumulator 32, which provides the pressure generator unit 30 when starting pressure medium available. The suction side of the pressure generator unit 30 is secured by a check valve 34, which prevents a return of pressure medium from the pressure generator unit 30 back into the wheel brakes 18a, 18b.

The high pressure side of the pressure generator unit 30 is connected via a hydraulic damping volume 36 and a downstream throttle 38 to the brake circuit 16 and that upstream of the pressure build-up valves 22a, 22b. Downstream of this junction is a switching valve 40, which is similar to the pressure build-up valves 22a, 22b executed. In trouble-free operation of the

Vehicle brake system causes an electronic control of this change-over valve 40, that a pressure medium connection from the master cylinder 12 to the wheel brake 18a, 18b is interrupted, so that a brake pressure can be built by the mentioned pressure generator unit 30 alone. Finally, one intake line 42 is still present per brake circuit 16, which connects the master cylinder 12 directly to the suction side of the pressure generator unit 30. The suction line 42 is controlled by a suction valve 44, which is designed as a normally closed, electromagnetically controllable 2/2-way switching valve. In trouble-free operation of the vehicle brake system, the pressure generator unit 30 sucks pressure fluid from a reservoir 46 coupled to the master brake cylinder 12 indirectly on account of the intake valve 44, which is then in its throughput position.

The electronic control of these housed in the hydraulic unit 14 components is performed by an electronic control unit 48, which u.a. from

Sensors detected speed signals of the vehicle wheels and pressure signals from the vehicle brake system 10 further processed. As already explained, the proviso applies to avoid occurring wheel slip by braking the corresponding wheels.

The described vehicle brake system 10 knows various operating states. In a service braking state, the pressure medium connection from the master cylinder 12 to the wheel brakes 18a, 18b of a brake circuit 16 is interrupted by the switching device 40 controlled by the control unit 48 and accordingly occupying its blocking position. The brake pressure is provided by the pressure generator unit 30, which for this purpose via the open intake valve 44 pressure fluid from the reservoir

46 sucks. A modulation of the brake pressure is effected by electronic control of the pressure build-up valves 22a, 22b, the pressure reduction valves 26a, 26b and the drive of the pressure generator unit 30th

If there is a fault in the vehicle brake system 10, then this is in the

Auxiliary brake operation switched. The valves are in their illustrated basic position. The switching valve 40 is opened, so that a hydraulic connection from the master cylinder 12 to the wheel brakes 18a, 18b of the brake circuit 16 is made. With the one actuation of the master cylinder 12 by the driver, a brake pressure is built up by muscle power in the wheel brakes 18a, 18b. The

Pressure generator unit 30 is therefore not necessary for brake pressure generation during the auxiliary brake operation; the intake valve 44 accordingly assumes its blocking position. - A -

In the case of an imminent, inevitable collision of the vehicle with an obstacle, which can be detected electronically, for example by means of a radar sensor present on the vehicle, it must be deviated from the proviso of avoiding wheel slip to the extent that now possible by the fastest possible minimization of collision energy possible damage from the vehicle occupants to avert. A necessary, short-term increase in brake pressure to blocking pressure level can not be represented with the known vehicle brake system 10 due to the lack of dynamics of the known pressure generator unit 30, especially not when the pressure generator unit 30 must be driven out of its rest state and / or the pressure medium due to a deep

Ambient temperature has high viscosity values.

A known solution of this problem illustrated in FIG. 2 is the use of a high-pressure accumulator 50 which can be preloaded by the pressure generator unit 30, but which additionally has to be integrated into the brake system 10 '. The shown in Figure 2

Vehicle brake system 10 'corresponds with the exception of what is described below in its construction of the vehicle brake system of Figure 1. So that a single high-pressure accumulator 50 is sufficient for both brake circuits 16', this is arranged in a pressure medium connection 52, the two brake circuits 16 'together. A connection of the brake circuits 16 'should be avoided for safety reasons as possible. In the deactivated state, the pressure medium connection 52 is therefore shut off by two additional solenoid valves 54 relative to the brake circuits 16 '. In addition to the additional need for solenoid valves 54, this arrangement has the further disadvantage that the summons of the high pressure accumulator 50 must be electronically monitored and this requires an additional pressure sensor 56 is required. To pressure medium under high

To store pressure permanently, a particularly effective sealing of the high-pressure accumulator 50 from the environment is required. In addition, the pressure generator unit 30 'must be designed constructively for a high-pressure construction. Since the pressure generating unit 30 'is an interface to the environment, it can be contaminated by gas stored in the high-pressure accumulator 50 pressure medium. With the

Activation of the high-pressure accumulator 50 can thus be contaminated with gas, the entire connected brake circuit 16 '.

Advantages of the invention In contrast, an object with the features of claim 1 has the advantage that by means of a relatively small additional construction effort an emergency brake can be displayed, which avoids the disadvantages explained above. An emergency brake designed according to the invention realizes high brake pressures in neglected short pressure buildup time and at the same time avoids a hydraulic connection between the two

Brake circuits of a vehicle brake system. The proposed emergency brake requires no effort to monitor their summons and does not involve the risk of continuous gas entry into the pressure medium outside its activation. The emergency brake is activated electronically and does not require additional control elements, such as electromagnetic valves. Further advantages or advantageous

Further developments of the invention will become apparent from the dependent claims or the description below.

Advantageously, the transmission of the pressure of the pressure generator of the emergency brake to the brake system via an easily representable cylinder / piston unit.

As a pressure generator is particularly suitable a pyrotechnic gas generator, as he is now installed, for example, for airbag filling in vehicle now in large quantities. In order not to increase the existing elasticity in the vehicle braking system due to the integration of an emergency brake, it is proposed that the piston of the cylinder / piston unit by means of a return element against a mechanical

End stop of his cylinder to press block. This end stop can be formed by a holding element for the pyrotechnic gas generator, so that there is no additional space required for this purpose. A guided in a cylinder piston can be radially sealed well, so that even when an activation of the emergency brake, a gas input into the vehicle brake system can be avoided. Is the

Vehicle brake system provided with a slip control, it has for this purpose a switched between the master cylinder and wheel brake hydraulic unit with a housing block which controls the brake pressure via an electronic control of solenoid valves and a drive of a pressure generator unit. Particularly space-saving can be the cylinder that form the cylinder / piston unit as a blind hole open to the outside in this hydraulic unit.

drawing The invention is illustrated in the drawing and explained in more detail in the following description. Figures 1 and 2 show hydraulic circuit diagrams of known from the prior art fluid-actuated vehicle brake systems 10, 10 ', as they were already explained above. FIG. 3 also illustrates a vehicle brake system 10 "according to the invention on the basis of a hydraulic circuit diagram, while FIG. 4 shows the structure of a cylinder / piston unit with inserted pyrotechnic gas generator on the basis of a longitudinal section.

Description of the embodiment

The vehicle brake system 10 "according to FIG. 3, with the exception of two differences, has the same structure as the motor vehicle brake system 10 according to FIG. 1 already described and known from the prior art. The first difference is that only one individual pressure generator is present per brake circuit, while FIG This difference is irrelevant with regard to the function of the vehicle brake system, in other words, individual pressure generators or multiple pressure generators may alternatively be provided.

The second difference is that the vehicle brake system 10 "according to FIG. 3 is equipped with one emergency brake 60 per brake circuit 16". The emergency brake 60 comprises a pyrotechnic gas generator 62, as used for example in large-scale airbag systems. This gas generator 62, which can trigger single-stage or multi-stage, can be activated by electronic control. The contacting can be done via cable, via a plug connection or via a direct contact. The gas generator 62 generates almost instantaneously after his electronic control a high-pressure gas volume. This gas volume acts on a piston 64 of a cylinder / piston unit 66, which in turn is in operative connection with a brake circuit 16 "of the vehicle brake system 10". Thus, the piston 64 converts the pneumatic pressure generated by the gas generator 62 into a hydraulic pressure within the vehicle brake system 10 "

Piston 64 is radially sealed within a cylinder 68 so that gas can not enter the conduit system of vehicle brake system 10 "by activation of gas generator 62. Sealing of piston 64 can be accomplished by one or more circumferential seals 69, or can be seal-free In the present embodiment, the emergency brake 60 between the switching valve 40 "and the pressure build-up valves 22a", 22b "connected to the vehicle brake system 10". By electronic control of the switching valve 40 ", connected to its switching to its blocking position, thus can be repercussions on the brake master cylinder 12" operatively connected brake pedal avoided due to a sudden pressure increase. As an alternative to the illustrated connection point, the emergency brake 60 could also be connected further downstream between the pressure increase valve 22a ", 22b" and the wheel brake 18a ", 18b" to the vehicle brake system 10 "or further upstream in the region between the master brake cylinder 12" and the changeover valve 40 ", However, as mentioned reactions to the brake pedal would bring with it.

The cylinder / piston unit 66 shown in Figure 4 can be designed to save space in the housing block of a hydraulic unit 14 (Figure 1). The cylinder 68 is formed by an open to the outside blind hole 71 which is sealed by a holding member 72. This holding element 72 is as in his

Outer diameter graduated plug formed, which is screwed to the blind hole 71, caulked, riveted, crimped, glued or the like. The holding member 72 forms a receptacle 74, in which the gas generator 62 is installed. By way of example, the gas generator 62 is screwed to the holding element 72, however, anchoring can also take place in one of the abovementioned types of fastening.

In the resulting cylinder interior, a piston 64 is guided axially movable. This piston 64, which may be made of plastic or metal divides the cylinder space in two mutually sealed pressure chambers 76, 78. For this purpose, there are circumferential seals 69 in the form of lip seals, which on both

Ends of the piston 64 are arranged in receptacles provided for this purpose. The first pressure chamber 78 is connected to the installation space of the gas generator 62, while the second pressure chamber 76 has a connecting channel 84 connection to a pressure-carrying line 82 of the vehicle brake system 10 "in this second pressure chamber 76, a spring element 86 is arranged, which is located at the bottom of

Blind hole 71 on the one hand and on the floor facing this end face of the piston 64 on the other hand supported. The spring element 86 pushes the piston 64 against a housing-fixed mechanical stop 88 on block. This unwanted mechanical elasticity due to the installation of the emergency brake 60 in an existing Vehicle stop system 10 "avoided The stop 88 is formed in front of the protruding into the interior of the blind hole 71 end face of the holding member 72.

With an electronic activation of the gas generator 62 via the control line 73 shown, the pressure chamber 78 is quasi-free filled with high-pressure gas. The pressurized by the gas pressure piston 64 moves against the restoring force of the spring element 86 and displaces hydraulic pressure fluid from the second pressure chamber 76. Thus, a correspondingly high pressure level builds up in the vehicle brake system 10 " Vehicle wheels necessary

Locking pressure level. When designing the gas generator 62, the tolerances, the mechanical elasticities and the maximum state of wear of the vehicle brake system 10 "are to be taken into account so that the blocking pressure level is reliably exceeded under all operating conditions of the vehicle and thus the maximum possible deceleration of the vehicle can be achieved an activation of the emergency brake 60 are ensured that then a modulation of the brake pressure is overridden by the controller 48.

The proposed cylinder / piston unit 66 is to be arranged within a housing block of a hydraulic unit 14 (FIG. 1) in such a way that in the installed position this

Hydraulic unit 14 is a self-venting of the hydraulic pressure chamber 76 takes place. According to FIG. 4, which shows this installation situation, the connecting channel 84 is placed at the highest possible location of the pressure chamber 76 for this purpose.

Of course, changes or additions to the described embodiment are conceivable without departing from the spirit of the invention.

Claims

claims

1. pressure medium operable vehicle brake system (10) with a master cylinder (12) for actuating the vehicle brake system by the driver, with a wheel brake (18 a, 18 b) which is hydraulically coupled to the master cylinder (12) and with a between the

Master brake cylinder (12) and the wheel brake (18a, 18b) connected independently of the driver activatable by electronic control emergency brake (60) which acts on the wheel brake (18a, 18b) immediately after their electronic control with a brake pressure level under all operating conditions of the vehicle is above a Radbremsblockierdruckniveaus.

2. Druckmittelbetätigbare vehicle brake system according to claim 1, characterized in that the emergency brake (60) has an electronically controllable pressure source (62) which is hydraulically connected via a cylinder / piston unit (66) to the vehicle brake system (10).

3. Druckmittelbetätigbare vehicle brake system according to claim 2, characterized in that the pressure source (62) is a pyrotechnic gas generator.

4. Druckmittelbetätigbare vehicle brake system according to claim 2 or 3, characterized in that a piston (64) of the cylinder / piston unit (66) in its normal position by a spring element (86) against a mechanical end stop (88) of a cylinder (68) Block is pressed.

5. Druckmittelbetätigbare vehicle brake system according to claim 4, characterized in that the end stop (88) by a holding part (72) for the gas generator (62) is formed, wherein the holding part (72) the cylinder (68) of the cylinder / piston unit ( 66) closes pressure-tight to the environment.

6. Druckmittelbetätigbare vehicle brake system according to one of claims 2 to 5, characterized in that the piston (64) by means of seals (69) gas-tight in its cylinder (68) is guided.

7. Druckmittelbetätigbare vehicle brake system according to one of claims 1 to 6, characterized in that the vehicle brake system (10) comprises a hydraulic unit (14) to which the master cylinder (12) and the wheel brake (18 a, 18 b) is connected, that the hydraulic unit ( 14) has a valve block with solenoid valves arranged thereon and a pressure generator (30) for modulating the brake pressure in the wheel brakes (18a, 18b) in order to avoid an occurring wheel slip and that the cylinder (68) of the cylinder / piston unit (66) as for Surrounding open blind hole (71) is formed on this valve block.

8. A method for controlling a fluid pressure actuated vehicle brake system (10) according to one of claims 1 to 7, which is equipped for slip control with a device for modulating the brake pressure (22, 26, 30, 40, 44) on the wheel brakes (18a, 18b) , characterized in that with an activation of the emergency brake (60), the means for modulating the brake pressure (22, 26, 30, 40, 44) is overridden.