WO2010139569A1

WO2010139569A1 - Brake system for motor vehicles

Info

Publication number: WO2010139569A1
Application number: PCT/EP2010/057095
Authority: WO
Inventors: Stefan A. Drumm; Steffen Linkenbach; Peter Rieth; Lothar Schiel
Original assignee: Continental Teves Ag & Co. Ohg
Priority date: 2009-06-05
Filing date: 2010-05-25
Publication date: 2010-12-09
Also published as: DE102009024033A1

Abstract

The invention relates to a brake system for motor vehicles which can be controlled either by the driver or independently of the driver in a brake-by-wire operating mode. The brake system is preferably operated in the brake-by-wire operating mode and can be operated in a first fallback mode with brake servo and in a second fallback mode without brake servo, in which two modes it can only be operated by the driver. In order to perform braking processes which make high demands on the dynamics of the brake system of the present invention, a high pressure reservoir (3) and a pressure valve arrangement (40) are provided, the latter having a first, i. e. a working connection (A), a second, i. e. a pressure supply connection (P) and a third, i. e. a return connection (T), wherein the working connection (A) is connected to the clear spacing (21), the pressure supply connection (P) is connected to the high pressure reservoir (3) and the return connection (T) is connected to the pressure supply device (2) and wherein the working connection (A) is connected to the pressure supply device (2) via a check valve (55) that closes in the direction of the pressure supply device (2).

Description

Brake system for motor vehicles

The invention relates to a brake system for motor vehicles, which is drivable in a "brake-by-wire" mode both by the driver and independently of the driver, preferably in the "brake-by-wire" mode is operated and in a first fallback mode, in a brake booster is available, and can be operated in a second mode without brake booster, in which only the operation by the driver is possible, with

A master cylinder having at least one master cylinder piston and connected to the wheel brake circuits,

A first piston, which is coupled to a brake pedal via an actuating force transmitting push rod,

A second piston, which is actuatable by the first piston and which can be brought into a force-transmitting connection with the master cylinder piston,

A simulation device with at least one elastic element, which gives the driver a pleasant pedal feel in the "brake-by-wire" operating mode,

A pressurizable intermediate space between the second piston and the master cylinder piston, wherein a pressurization of the intermediate space loads the second and the master cylinder pistons in opposite directions,

With a pressure supply device that controls the pressure in the intermediate space,

• with a pressurized medium storage container under atmospheric pressure, which is hydraulically connectable with the intermediate space, as well as

• with means for electrical regulation of the pressure in the intermediate space.

A brake system of the type mentioned is known from the international patent application of the applicant WO 2008/025797 Al. A hydraulic pressure for actuating the master cylinder is provided in the prior art brake system by an electro-hydraulic actuator forming the pressure supply device, which is driven by an electric motor. A disadvantage is felt in such brake systems, the fact that to overcome the rotational inertia of electric motor drives in highly dynamic operation electrical services are needed with reasonable means neither provided (vehicle electrical system load), still controlled (electronic effort), still implemented (special motors required) can be ,

It is therefore an object of the present invention to propose a brake system of the type mentioned, in which with reasonable effort highly dynamic braking operations can be performed.

This object is achieved with a brake system in which a high-pressure accumulator and a pressure regulating valve arrangement are provided, which have a first or a working connection, a second or a pressure supply connection, and a NEN third and a return port, wherein the working port to the intermediate space, the pressure supply port to the high pressure accumulator and the return port are connected via a hydraulic connection to the pressure supply device.

With the brake system according to the invention, all the brakes can be handled without any special demands on the dynamics with the electrohydraulic actuator, while additional means according to the invention are used for brakes with higher pressure build-up dynamics. Therefore, a smaller sized high-pressure accumulator is sufficient.

Further advantageous embodiments of the brake system according to the invention are listed in the subclaims.

The present invention will be explained in more detail below with reference to an exemplary embodiment with reference to the attached schematic drawings, wherein FIGS. 1 and 2 each show an exemplary embodiment of the brake system according to the invention.

The brake system according to the invention shown in the drawing consists essentially of an actuator 1, a pressure supply device 2, a high-pressure accumulator 3, wherein the actuating unit 1, the pressure supply device 2 and the high-pressure accumulator 3 form a brake booster, and a brake booster the effective downstream master cylinder or tandem master cylinder 4th , whose pressure chambers, not shown in Fig.l, are connectable to the chambers of a pressure fluid supply reservoir 11 which are under atmospheric pressure. On the other hand, wheel brake circuits I, II are connected to the pressure chambers, with the interposition of a hydraulic pump. gregats or a controllable Radbremsdruckmodulationsmo- module 9, the wheel brakes 5 - 8 supply a motor vehicle with hydraulic pressure medium. The Radbremsdruckmodulati- onsmodul 9 has the wheel brakes 5-8 upstream, unspecified pressure modulation valves that allow a Radbremsdruckmodulation the so-called. Multiplex principle, which is known in the art. Of course, as an alternative to the illustrated four-valve multiplex wheel brake pressure modulation module 9, it is also possible to use the known ABS wheel brake pressure modulation module with eight or the ESP wheel brake pressure modulation module with twelve valves. In addition, the brake system shown on an only schematically indicated electronic control unit 10. The actuating device 1, which is arranged in a housing 20, on or in which the tandem master cylinder 4 is connected or integrated, can be controlled via a brake pedal 12, which is operatively connected via an actuating rod 13 with a first piston 14 of the actuator 1. The actuating travel of the brake pedal 12 is detected by means of a displacement sensor 23 which senses the travel of the first piston 14. However, for the same purpose, a rotation angle sensor can be used which detects the rotation angle of the brake pedal 12. The first piston 14 defines in a second piston 15, a pressure chamber 16 which receives a compression spring 17 which brings the first piston 14 to bear against a stopper 22a formed in the housing 20 with the brake pedal 12 unactuated. Alternatively or additionally, a pedal return spring may be provided in the region of the push rod 13 or the brake pedal 12. The pressure chamber 16 is connected in the unactuated state of the actuator 1 with a chamber 30 of a second pressure medium reservoir 19 which is associated with the actuator 1. The second piston 15 cooperates with a third piston 18, which is the primary piston of the tandem master cylinder 4 forms, wherein between the second (15) and the third piston 18, a pressure booster piston, not shown, may be arranged. Between the second piston 15 and the master cylinder piston 18, a gap 21 is limited, acted upon by the application of a hydraulic pressure of the second piston 15 against the actuating direction and is held on a housing-fixed stop 22b, while the master cylinder piston 18 in terms of pressure buildup in the tandem master cylinder 4 is acted upon in the direction of actuation. A movement of the master cylinder piston 18 resulting from this load is detected by means of a second displacement sensor 38. The stop 22b of the second piston 15 in the housing and the abovementioned stop 22a of the first piston 14 are preferably, but not necessarily, formed by the same annular surface of the housing recess. In addition, the second piston 15 in the housing 20 defines a hydraulic chamber 31, the function of which will be explained in the following text.

Furthermore, it can be seen from the drawing that the above-mentioned pressure chamber 16 is connected via a lockable connection line 24 with a simulator chamber 25 in communication, which is bounded by a simulator piston 26. The simulator piston 26 cooperates with a simulator spring 27 and one of the simulator spring 27 connected in parallel elastomer spring 28. The simulator chamber 25, the simulator piston 26, the simulator spring 27 and the elastomer spring 28 form a pedal travel simulator, which gives the vehicle operator the usual pedal feel when operating the brake system, which corresponds to a customary brake pedal characteristic. This means that with low brake pedal travel, the resistance increases slowly and increases disproportionately with a larger brake pedal travel. For damping the movement of the simulator piston 26, not shown, for example be provided hydraulic or pneumatic damping means. The hydraulic connection line 24 between the simulator chamber 25 and the pressure chamber 16 and the chamber 30 of the second pressure medium reservoir 19 is shut off by means of a preferably electromagnetically actuated shut-off valve 32, whereby the pedal travel simulator is effectively switched off. The shut-off valve 32 in its first or inoperative position shown in the drawing fulfills the function of a check valve closing to the simulator chamber 25, while the connection line 24 is released when switching to its second switching position. In an alternative variant, the shut-off valve 32 is actuated hydraulically by the pressure provided by the high-pressure accumulator 3 (FIG. 2). The detection of the pressure introduced in the pressure chamber 16 is served by a pressure sensor, which is provided with the reference numeral 33.

The above-mentioned electrohydraulic pressure supply device 2 consists essentially of a hydraulic cylinder-piston assembly 34 and an electromechanical drive unit 35, which is formed for example by an electric motor with a mechanical transmission, which is a rotation of the electric motor in a translational movement of a hydraulic piston 36, so that in a pressure chamber 37 of the hydraulic cylinder-piston assembly 34, a hydraulic pressure is built up. The electromechanical drive unit 35 is powered by an electrical energy storage, not shown, with energy. The movement of the piston 36 is detected by means of a displacement sensor, which is provided with the reference numeral 60. The pressure chamber 37 is connected via hydraulic means to be explained later [an optional SO valve] to a hydraulic line section 61, which, as will be explained in more detail below, is also described below. tile with the gap 21 is connectable, so that by means of the electromechanical drive unit 35 in the space 21 pressure is buildable. In addition, the pressure chamber 37 is connected via a closing in the direction of the pressure chamber check valve 57 via a line section 56 to the high pressure accumulator 3, so that by means of the electromechanical drive unit 35 of the high-pressure accumulator 3 is loadable. The hydraulic line section 61 can be connected by means of a normally open (SO) 2/2-way valve 39 to a chamber of the second pressure medium reservoir 19 which is under atmospheric pressure, so that in a quiescent state of the brake system by a temperature expansion of the pressure medium in the pressure chamber 37, no unintentional pressure buildup occurs , A pressure sensor 62 serves to detect the pressure provided by the pressure supply device 2 or the pressure prevailing in the intermediate space 21.

Finally, as can be seen from the drawing, between the electrohydraulic actuator 2 or the high-pressure accumulator 3 on the one hand and the intermediate space 21 or the hydraulic (blocking) space 31, a pressure regulating valve arrangement 40 with a working port A, a pressure supply port P, a return port T and two control terminals C1 and C2 connected. The pressure regulating valve arrangement 40 is preferably designed in two stages and has an electrically controllable valve device or a pilot control stage 41, a double hydraulic controllable valve main stage, which is provided with the reference numeral 42, and a hydraulic drive stage, whose structure will be explained in the following description.

The pilot stage 41 consists of a series connection of an analog controllable, normally closed (SG) 2/2-way valve 43 and an analog controllable, de-energized open (SO) 2/2-way valve 44, wherein the hydraulic center tap 45 is connected between the two valves 43, 44 via a line section 45 to the drive port C2 and one of the driving pressures for the valve main stage 42 supplies. The hydraulic control stage is formed by a first control chamber 46, a first control piston 47, and a second control chamber 48 delimited by the control piston 47, which is connected to the control port C2 or to the abovementioned center tap 45 of the pilot control stage 41. On the other hand, the second control chamber 48 is delimited by a second control piston 49 which, together with a valve sleeve 50, delimits a tank connection chamber 51 into which the return connection T opens. At the second control piston 49, a valve body 53 is supported under bias of a compression spring 52, which cooperates with formed on the valve sleeve 50 control edges. The valve sleeve 50 together with the valve body 53, the aforementioned main stage 42 of the pressure regulating valve assembly 40th

Furthermore, the illustration in the drawing shows that the first control chamber 47 is connected to the above-mentioned hydraulic chamber 16 with the interposition of an electromagnetically actuated, normally open (SO) 2/2-way valve 54. The 2/2-way valve 54 in its energized switching position fulfills the function of a control chamber 47 closing check valve.

Meanwhile, the valve body 53 forms together with the valve sleeve 50, a pressure supply chamber 58, which communicates by means of the pressure supply port P with the aforementioned connecting line 56. The pressure supply chamber 58, which in the illustrated in the drawing unactuated position of the pressure control valve assembly 40 with the second piston 15 limited hydraulic (blocking ) Space 31 is connected by a displacement of the valve body 53 with a working pressure chamber 59, which is connected by means of a formed in the valve body 53 bore and two pressure medium channels with the return chamber 51.

Furthermore, the connections T and A of the pressure regulating valve arrangement 40 are connected to a check valve 55 which opens toward the working chamber A via which pressure medium can be displaced to the intermediate space 21, regardless of the position of the valve body 53 or the operating state of the pressure regulating valve arrangement 40.

The above-mentioned electronic control unit 10 serves on the one hand the detection of sensor data, the processing of these data, u. U. the exchange of data with other control units, and on the other hand, the control of the electromagnetically operable 2/2-way valves 32, 39, 43, 44, 54, the wheel brakes 5-8 upstream multiplexer pressure control valves and the electromechanical actuator 34, 35 and the brake lights of the vehicle.

In the illustrated in Fig. 2 the second embodiment of the brake system according to the invention, a flow of pressure medium from the gap 21 to the working port A of the pressure regulating valve assembly 40 is prevented by a displacement of the second piston 15 in the actuating direction. For this purpose, radial or axial bores 63, 64 are provided in the second piston 15, which communicate with the working port A of the pressure regulating valve arrangement 40 and which cooperate with a non-movable sealing collar 65. To overflow of said compound in the direction of space 21 is in addition to the direction in this direction opening sealing sleeve 65 a check valve 66 is provided. Another difference from the first embodiment shown in FIG. 1 is that in the line section 61 mentioned in connection with FIG. 1, a normally open (SO) 2/2-way valve is provided, which is provided with the reference numeral 67. Finally, Fig. 2 it can be seen that the shut-off of the simulator device serving shut-off valve 32 a is formed as a hydraulically actuated valve which is switchable by the pressure provided by the high-pressure accumulator 3 pressure.

In the following text, the operation of the brake system according to the invention in connection with the first embodiment shown in Fig. 1 will be explained in more detail.

A first operating mode corresponds to a purely electric, the so-called "brake-by-wire" mode, in which all components of the brake system are intact and working properly In this mode, to build up a hydraulic pressure in the space 21, the pressure control valve assembly 40 and electrohydraulic actuators 34, 35 are controlled, so that the pressure provided by the pressure supply device 2 or the pressure generated in its cylinder-piston arrangement 34 is supplied to the intermediate space 21. By the pressure effect as well as the effect of the hydraulic (blocking) space 31 acting pressure of the high-pressure accumulator 3, the second piston 15 is held on the stop 22b and the master cylinder piston 18 is displaced to the left, whereby a pressure build-up takes place in the master cylinder 4. The hydraulic pressure is thereby contained in the electronic control unit 10 via a controller the current supplied to the electric motor 35 regulated. For the purpose of keeping pressure, the piston 36 of the piston-cylinder assembly 34 is held firmly in the activated position. The inserted in the connection between the pressure chamber 37 and the pressure fluid reservoir 19, normally open 2/2-way valve 39 is switched both in the pressure build-up and when holding pressure in its closed switching position. In contrast, during braking, which make high demands on the dynamics, the valve body 53 of the pressure regulating valve assembly 40 so far moved to the left that on the one hand the connection between the return chamber 51 and the working chamber 59 shut off and on the other hand, the connection between the conduit 56 and the working chamber 59th is released, so that the intermediate space 21 is acted upon by the high pressure accumulator 3 provided hydraulic pressure.

For a pressure reduction of the piston 36 of the cylinder-piston assembly 34 is moved back. In this case, pressure medium from the gap 21 flows back into the pressure chamber 37. For complete reduction of the pressure to atmospheric pressure level, the previously mentioned 2/2-way valve 39 is opened, whereby a hydraulic connection to the pressure medium reservoir 19 is produced. In order to avoid a negative pressure in the intermediate space 21 or in the pressure chamber 36, the 2/2-way valve 39 is preferably designed such that it allows a pressure medium volume flow from the pressure medium reservoir 39 into the pressure chambers 21, 37 in the energized state.

The process of controlling the electrohydraulic actuator 34, 35 is performed by the electronic control and regulation unit 10 such that the pressure in the intermediate space 21 is approximated to a target pressure value. This desired pressure value results, on the one hand, from a detected actuation component of the brake pedal 12 and, on the other hand, from a third-party actuation component. The actuating component of the brake pedal 12 is derived from the actuation path of the brake pedal. dals 12 and the first piston 14 and from the hydraulic pressure in the pressure chamber 16, which is detected by means of the pressure sensor 33 and the operating force of the brake pedal 12 is proportional.

In a second operating mode, which is characterized by a fault in the electronics or by the absence of a pressure generated by the hydraulic pressure supply device 2 and corresponds to a fallback level, no electronically controlled pressure build-up in the intermediate space 21 is possible. In this operating mode, the brake system can be actuated purely mechanically. The pressure built up in the chamber 16 via the pedal actuates the pressure regulating valve arrangement 40 via the first control input C1, as a result of which pressure medium flows from the high-pressure accumulator 3 into the intermediate space 21. Upon a withdrawal of the pedal operation, the pressure fluid flows through the pressure control valve assembly 40 and the open valve 39 into the container 19. When the hydraulic energy supply de high-pressure accumulator 3 is exhausted, no pressure can be built up in the space 21, but also in the hydraulic (blocking) Room 31 is no longer pressurized.

Therefore, under the influence of a brake pedal operation, the second piston 15 moves away from its stopper 22 and displaces the master cylinder piston 18 by mechanical contact. The operation of the master cylinder 4 is done exclusively with muscle power of the driver.

The present invention achieves a simply constructed, highly efficient braking system in which in a "brake-by-wire" mode, the brake pedal characteristic does not depend on the operating state of the rest of the brake system, whereby the pedal feel in a driver's braking neither by the simultaneous presence of a foreign braking can still be disturbed by other control activities of the brake system, such as antilock braking, traction control or driving stability control.

Claims

claims

1. brake system for motor vehicles, which is controlled in a "brake-by-wire" mode by both the driver and independently of the driver, preferably in the "brake-by-wire" mode is operated and in a first fallback mode in which a Braking power is available, and can be operated in a second mode without brake booster, in which only the operation by the driver is possible, with

A master brake cylinder (4) having at least one master cylinder piston (18) and connected to the wheel brake circuits (I, II),

A first piston (14) which is coupled to a brake pedal (12) via an actuating rod (13) transmitting actuating forces,

A second piston (15) which can be actuated by the first piston (14) and which can be brought into a force-transmitting connection with the master cylinder piston (18),

A simulation device with at least one elastic element (27, 28), which gives the driver a pleasant pedal feel in the brake-by-wire mode,

A pressurizable intermediate space (21) between the second piston (15) and the master cylinder piston (18), wherein pressurization of the intermediate space (21) loads the second (15) and the master cylinder piston (18) in opposite directions,

With a pressure supply device (2) which controls the pressure in the intermediate space (21), • with a pressurized medium reservoir (11) under atmospheric pressure, with the intermediate space

(21) is hydraulically connectable, as well

With means for electrical regulation of the pressure in the interspace (21), characterized in that a high-pressure accumulator (3) and a pressure regulating valve arrangement (40) are provided which have a first or a working connection (A), a second or a pressure supply connection ( P) and a third or a return port (T), wherein the working port (A) to the intermediate space (21), the pressure supply port (P) to the high-pressure accumulator (3) and the return port (T) via a hydraulic connection (61 ) are connected to the pressure supply device (2).

2. Brake system according to claim 1, characterized in that between the working port (A) and the return port (T) in the direction of flow to the working port (A) opening towards check valve (55) is provided.

3. Brake system according to claim 1, characterized in that the hydraulic connection (61) between the working port (A) and the pressure supply device (2) by means of a storage charging valve (67) can be shut off.

4. Brake system according to claim 1 or 2, characterized in that a solenoid valve (39) for producing a lockable hydraulic connection between the return port (T) and the pressure medium reservoir

(11) is provided, said barrier only in Direction of an outflow to the pressure medium reservoir (11) is effective.

5. Brake system according to claim 1, 2 or 3, characterized in that the connection between the working port (A) and the intermediate space (21) by a movement of the second piston (15) in the actuating direction can be shut off in such a way that an outflow of Pressure medium from the intermediate space (21) is prevented while an inflow is always possible.

6. Brake system according to claim 5, characterized in that as means for piston-path-dependent shut-off bores (63, 64) are provided in the second piston (15) which cooperate with an associated sealing sleeve (65), while as a means for overflow of said compound in Direction gap (21) in addition to the opening in this direction sealing sleeve (65), a check valve (66) is provided.

7. Brake system according to at least one of claims 1 to 6, characterized in that the pressure supply device (2) by an electro-hydraulic actuator (34, 35) is formed.

8. Brake system according to claim 6, characterized in that the high-pressure accumulator (3) from the electro-hydraulic actuator (34, 35) is chargeable.

9. Brake system according to claim 8, characterized in that in a hydraulic connection (56) between the electro-hydraulic actuator (34, 35) and the high-pressure accumulator (3) to the high-pressure accumulator (3) towards open nendes check valve (57) is inserted.

10. Brake system according to claim 1 to 9, characterized in that the pressure regulating valve arrangement (40) by a first piston (14) in a second piston (15) limited pressure chamber (16) generated pressure and / or a pilot pressure is hydraulically actuated, wherein an electromagnetically operable valve means or a pilot stage (41 or 43, 44) for electronically controlling the pilot pressure for the pressure regulating valve arrangement (40) is provided.

11. Brake system according to claim 10, characterized in that the valve device or a pilot stage (41 or 43, 44) by a first analog controllable, normally closed (SG) 2/2-way valve (43) and a second, analog adjustable, normally open (SO) 2/2-way valve (44) is formed, the center tap (45) forms the control port (C).

12. Brake system according to at least one of claims 1 to 11, characterized in that the simulator device (25 - 28) to the second piston (15) limited pressure chamber (16) with the interposition of a Simulatorabsperrventils (32, 32 a) is connected.

13. Brake system according to claim 12, characterized in that the Simulatorabsperrventil (32 a) by the high-pressure accumulator (3) provided pressure is actuated.

14. A method for loading the high-pressure accumulator of a brake system according to one of the preceding claims 7 to 13, characterized in that at a pressure build-up in the pressure supply device (2) the accumulator charging valve (67) or the wheel brake circuits (I, II) are shut off.