DE102004025638A1 - Braking system for motor vehicle has arrangement for coupling movements of second and third pistons activated depending on manner of operation of third piston in housing - Google Patents

Abstract

The system has a main cylinder (1), a first piston (2) coupled to a brake pedal (3), a second piston (4) that operates the main cylinder, a third piston (5), an elastic element (6) that transfers actuating forces from the pedal to the third piston and forms a pedal displacement simulator for providing feel in "brake0by-wire" mode, a pedal coupling arrangement and an intermediate chamber between the second and third positions. It has an arrangement for coupling the movements of the second and third positions activated depending on the manner of operation of the third piston in the housing.

Description

The The invention relates to a brake system for motor vehicles, the one Has master cylinder, can be connected to the wheel brake cylinder, a first piston that over transmit an actuating forces Push rod is coupled to a brake pedal, a second piston, which actuates the master cylinder, a third piston operable by the first piston, wherein at least an elastic element is provided, via the actuating forces from the brake pedal to the third piston are transmitted and that forms a pedal travel simulator, which in the mode "brake-by-wire" the driver pleasant pedal feel mediates, means for coupling the movements of the first and the third Pistons depending on be activated by the travel of the third piston in the housing, as well with a loadable by hydraulic pressure gap between the second and third pistons, wherein a pressurization of the gap the second and the third piston in eingegengesetzter Direction burdened.

In Automotive technology find brake-by-wire braking systems increasingly widespread. In these brake systems, the brake can also without active action of the driver due to electronic signals "foreign" operated become. These electronic signals can, for example, from a electronic stability program ESP or a distance control system ACC. comes it to an overlay such a foreign operation with a driver's confirmation, so feels the driver of the motor vehicle has a reaction in the brake pedal. This Retroactive effect on the brake pedal can for make the driver unfamiliar and uncomfortable, leaving the driver in a critical situation of road traffic the brake pedal not actuated in a situation adapted to this situation, as it is governed by the foreign operation the brake caused repercussion on the brake pedal is irritated.

A brake system of the type mentioned is from the EP 1 078 833 A2 known. A pressurization of the gap takes place in the operating mode "brake-by-wire" _ "third operating mode" by a second valve means which is electrically controlled and in a non-electronically controlled mode = "second operating mode" by a first valve means by the third When the high-pressure accumulator is emptied, this brake system falls back into a "first operating mode", in which the intermediate space is connected to the now unpressurised high-pressure accumulator via the valve devices when the third piston is displaced is and located in the intermediate space pressure medium volume can flow in this way. This process is associated with undesirable brake pedal travel loss.

It is therefore an object of the present invention, the pedal travel loss in the case of a sufficiently high pressure due to a lack of pressure Pressure means caused a fallback mode to be used from inexpensive To prevent producible agents or components. Go with it should be improvements regarding the manufacturability and the acoustic behavior of the brake system.

These Task is inventively characterized solved, that means for coupling the movements of the second and third Pistons are provided, which depend on the travel of the third piston in the housing to be activated.

at an advantageous development of the subject invention is the gap by means of a single hydraulic connection connected to an electrically controllable pressure supply module, being both a filling the space with pressure medium as well as an emptying over this Connection takes place.

In a preferred embodiment is the hydraulic connection depending on the travel of the third piston in the housing shut off.

A other advantageous development of the subject invention exists in that the means flow through the hydraulic connection from Prevent gap to the print delivery module.

there is preferably a portion of the hydraulic connection in the third Piston formed and has an orifice, which is fixed to the housing Cooperating sealing element. The housing-fixed sealing element is as Cuff seal formed in the direction of an inflow to Interspace can be overflowed.

at In another advantageous variant, the housing-fixed sealing element is not a sealing element that can not be flowed over formed, with a check valve a bypass of the sealing element in the direction of an inflow to Space allows.

In a further advantageous variant is the piston path-dependent prevention of leakage of pressure medium from the intermediate space achieved by a pressure supply module side shut-off of the hydraulic connection.

at Another advantageous embodiment of the invention is a elastic agent between effective the push rod and the third piston arranged.

at another embodiment of the subject invention is a hydraulic shut-off device for coupling the movements of the first one and the third piston, which depends on the travel of the third piston in the housing is activated. The shut-off device is characterized by a in third piston formed by the first piston limited chamber, the filled with pressure medium is and in the inactive state of the shut-off with a pressure medium reservoir communicates.

The contained in the shut-off hydraulic connections are preferably used as hydraulic throttle elements of the hydraulic damping of the Pedal travel. It is particularly advantageous if at least one of the hydraulic throttle elements a flow direction-dependent behavior having.

In a preferred embodiment a rotation angle sensor is provided for detecting the brake pedal position, whose output signal is supplied to an electronic control unit and the control of the pressure supply module is used. Besides that is It makes sense if a pressure sensor to capture the from the pressure supply module provided hydraulic pressure is provided, the output signal the electronic control unit is supplied.

A Another advantageous embodiment of the invention is that the pressure supply module an electrically driven high pressure pump contains. The pressure supply module preferably contains electrical controllable valves.

at another embodiment contains the pressure supply module a high-pressure hydraulic accumulator. In further advantageous embodiments of the invention, the pressure supply module contains an electropneumatic or electromechanical actuator.

at another advantageous development of the subject invention the electronic control unit is assigned to the pressure supply module.

at another advantageous embodiment of Subject of the invention is the connection of the pressure supply module executed with the gap as a hydraulic hose.

A Another advantageous embodiment of the invention is that the master cylinder an ABS control module is connected downstream. The ABS control module In this case, an ABS control and regulating electronics are preferably assigned.

at another embodiment of the subject invention form the electronic control unit and the ABS control and electronic control an assembly.

Of the Master brake cylinder can be designed as a tandem master cylinder, whose pistons have the same cross-sectional area as the third piston.

at another advantageous variant of the subject invention the master cylinder is designed as Twinhauptbremszylinder whose Piston in total have the same cross-sectional area as the third piston.

in the Following are examples of embodiments of the invention with reference to the attached schematic drawings explained in more detail. It demonstrate:

1 the structure of the brake system according to the invention according to a first embodiment,

2 the structure of a second embodiment of the invention of the brake system,

3 A third embodiment of the brake system according to the invention,

4 a fourth embodiment of the invention of the brake system, and

5 and 6 Variants of the pressure supply module, the brake systems according to 1 to 4 Can be used.

1 shows the brake system according to the invention. The brake system has a brake pedal 3 on, that over an operating rod 28 with a first piston 2 is operatively connected. The brake pedal travel can be via a rotation angle sensor 27 be recorded. The first piston 2 is in a third piston 5 arranged between the first and the third piston 5 a chamber 21 is formed, in which a compression spring 6 is arranged, which is the first piston 2 for installation on the third piston 5 brings. An elastic element 7 For example, an elastomeric block is wirkmä larly between the actuating rod 28 and the third piston 5 arranged and forms a pedal travel simulator, which gives the driver when operating the brake the usual pedal feel, which corresponds to a common brake pedal characteristic. This means that with low brake pedal travel, the resistance increases slowly and increases disproportionately with a larger brake pedal travel.

Furthermore, a second piston 4 provided, a master cylinder 1 actuated. In the example shown is the master cylinder 1 designed as a tandem master cylinder, in which the second piston 4 a fourth piston 10 is downstream. To the master cylinder 1 can have a controllable ABS control module 29 be connected to the wheel brakes of the vehicle, the ABS control module 29 an electronic control unit 30 can be assigned.

All pistons 2 . 4 . 5 . 10 are in a housing 8th accommodated, wherein the second, the third and the fourth piston in the illustrated embodiment have the same diameter or the same cross-sectional areas. Between the third piston 5 and the second piston 4 there is a gap 11 that by means of a hydraulic connection 12 with an electrohydraulic pressure supply module 13 connected, which is a pressurization of the gap 11 allows. The print delivery module 13 comprises a high-pressure accumulator serving as a hydraulic pressure source 9 , a motor-driven pump 14 to charge the high-pressure accumulator 9 , Pressure control valves 15 . 16 . 17 and a pressure medium reservoir 18 , Monitoring the in between space 11 Injected pressure is a pressure sensor 19 who is also in the print delivery module 13 can be integrated. The high-pressure accumulator 9 supports the high pressure pump 14 especially in those cases where pressure has to be built up in a short time, for example in a fast emergency braking, the high pressure pump 14 can not deploy immediately due to their inertia. The print delivery module 13 is an electronic control unit 21 associated, the output signals of the pressure sensor 19 are fed and the control of the motor-driven high-pressure pump 14 and the pressure control valves 15 - 17 serves.

About the connection 12 becomes the gap 11 pressurized, causing the second piston 4 the master cylinder 1 pressed and the third piston 5 to a stop 31 in the case 8th is pressed, on which the third piston 5 before operating the brake system. The stop 31 in the case 8th is not necessarily as shown on the dry side of the third piston 5 trained - just as well he can, for example, in the pressure medium-filled gap 11 be arranged. Various configurations are possible for the electrically controllable valves used for pressure control. For example, a slide valve could be used. A preferred valve configuration is that shown, in which three separately controllable poppet valves are used. A first pressure control valve 15 controls the pressure build-up, a second one 16 the pressure reduction. Both are preferably infinitely adjustable analog valves and closed in de-energized state. A third valve 17 provides the necessary for expansion processes due to temperature changes connection of the gap 11 with a pressure medium reservoir 18 ago. For this purpose, it is preferably designed as a switching valve and open in the de-energized state. Electrically connected, it is preferably connected to a monitoring unit within the electronics unit 21 of the print delivery module. If these during braking a critical error in a control module of the electronic unit 21 detects, it switches off the latter and brings so the pressure control valves 15 and 16 in their closed position. At the same time, the switching valve 17 energized and so provided for this error case blocking the gap 11 ensured. Even with a power failure, in which no solenoid valve is naturally controllable, the brake system remains manageable for the driver, as explained in the following statements: The temperature-dependent volume change of the pressure medium takes place comparatively slowly, so that the opening cross-section of the valve 17 can be kept very small. This measure ensures that if in case of power failure all valves 15 . 16 . 17 the illustrated de-energized switch position assume that in the space 11 located pressure medium only very slowly in the container 18 can escape. A sudden, the driver irritating pedal loss is thus excluded in the event of a power failure.

As the drawing continues to show, is a section 20 the hydraulic connection 12 in the third piston 5 designed so that its mouth with a in the housing 8th fixed sealing element 22 interacts. This will ensure that the hydraulic connection 12 depending on the travel of the third piston 5 in the case 8th is shut off. The housing-fixed sealing element 22 is formed in the example shown as a cuff seal, which is in the direction of an inflow to the gap 11 can be overflowed and in the actuated state of the brake system, a flow through the hydraulic connection 12 from the gap 11 to the print delivery module 13 prevented.

The previously mentioned, in the third piston 5 be bounded chamber 21 is part of a hydraulic shut-off device for coupling the movements of the first 2 and the third piston 5 , which depends on the travel of the third piston 5 in the case 8th is activated. For this purpose is between the chamber 21 and a master cylinder 1 associated pressure fluid reservoir 23 a hydraulic connection 24 provided, the one in the third piston 5 trained section 25 having its mouth with a second, also in the housing 8th fixed sealing element or a second sleeve seal 26 cooperates such that the hydraulic connection 24 depending on the travel of the third piston 5 in the case 8th is shut off. The hydraulic connections contained in the shut-off device can be used as hydraulic throttle elements for hydraulic damping of the pedal travel simulator 7 serve, wherein at least one of the hydraulic throttle elements may have a flow direction-dependent behavior.

In the first mode of operation, due to the lack of a hydraulic pressure supply module 13 generated pressure is characterized, the brake system can be actuated purely mechanically, the third piston 5 moves from its stop under the influence of a brake pedal actuation 31 away and move the second piston 4 by mechanical contact. The operation of the master cylinder 1 is done exclusively with muscle power.

In the second operating mode, ie in a hydraulic booster mode, by driving the pressure build-up valve 15 in the space 11 built up a pressure, by the action of the third piston 5 in the drawing is pushed to the left, while the second piston 4 is pressed to the right. For electronically controlled pressure reduction, the pressure reduction valve 16 energized. The pressure in the space 11 is sized so that it is sufficient, the third piston 5 against the over the push rod 28 transmitted pedal force at its stop 31 in the case 8th to keep. Otherwise, the pressure in the space 11 freely selectable, so that any desired dependence of the brake pressure can be programmed by the brake pedal operation. Unwanted pedal reactions are excluded. This electronic actuation pressure control has the advantage that its transmission behavior is freely selectable within the given by the technical data of pressure accumulator, pressure build-up and isolation valve dynamics. Therefore, a so-called Springerfunktion, ie jumping to a predetermined brake pressure value when tapping the brake pedal 3 , brake assist function, deceleration control, and autonomous braking, such as those required for ASR (Drive Slip Control), ESP (Electronic Stability Program), and ACC (Adaptive Cruise Control), can be realized by software measures. For this purpose, the driver specification in the form of a brake pedal operation, which is detected by displacement, force or other sensors and converted by a not explicitly shown computing unit by applying appropriate algorithms in Radbremsdrücke using the electronically switchable valves in the pressure supply module and the downstream ABS control module will be realized.

At the in 2 illustrated second embodiment of the invention serves to seal the gap 11 a non-overflowable sealing element, preferably as a sealing ring 32 is trained. A bypass of the sealing element 32 in the direction of an inflow of the pressure medium to the gap 11 gets through in the case 8th integrated check valve 33 allows.

At the in 3 illustrated third embodiment is a displacement sensor 35 provided that the relative displacement of the third piston 5 in the case 8th recorded and detected when leaving the stop 31 via a signal transmission path 35 at least the valve 17 locks, so no pressure fluid from the gap 11 in the container 18 can flow out.

At the in 4 illustrated fourth embodiment is the master cylinder 1 designed as a so-called twin main cylinder. The radii of the pistons arranged in parallel in this case 4 ' . 10 '' are preferably selected such that the sum of the cross-sectional areas of the two pistons of the cross-sectional area of the third piston 5 equivalent.

The 5 and 6 Finally show further variants of the above-mentioned pressure supply module 13 , This in 5 illustrated Druckbereitsstellungs module has an electropneumatic actuator 36 on, which can be carried out both as operated with negative pressure and positive pressure actuator and the hydraulic cylinder-piston assembly 38 is downstream. A pressure room 39 the cylinder-piston arrangement 38 on the one hand is about the already mentioned line 12 associated with that 1 described gap 11 and on the other hand with the interposition of a normally open switching valve 40 with a pressure medium reservoir 41 ,

In contrast, the in 6 illustrated Druckbereitsstellungsmodul an electromechanical actuator 37 on which a hydraulic cylinder-piston arrangement 42 downstream of the structure with the structure of the hydraulic cylinder-piston assembly 38 according to 5 entspre can. The electromechanical actuator 37 is essentially formed by an electric motor, by means of a transmission, not shown, the piston 43 the hydraulic cylinder-piston arrangement 42 actuated. The transmission, which is used to convert the rotational movement of the electric motor into a translational movement (so-called red-trans gear), is known to the person skilled in the art and can be formed, for example, by a screw drive.

By The present invention will be a simply constructed brake system achieved in which the brake pedal characteristic is not the operating state the rest of the brake system depends causing the pedal feel in a driver's braking neither by the simultaneous presence an external braking nor by other control activities of the braking system such as anti-skid control, traction control or driving stability control disturbed can be.

The Brake system has the further advantage that it is easier to set up is as conventional brake systems. Vehicles with an electronic stability control function (ESP), for example, need a special ESP hydraulic, which is more complicated than a normal one ABS hydraulics, as they have the ability, unlike ABS hydraulics for the construction of wheel brake pressures must have above the master cylinder pressure.

In vehicles with the brake system according to the invention a special ESP hydraulic superfluous - the inventive third-party hydraulic in conjunction with a conventional ABS system provides a far better function. Less electromagnetically actuated valves are needed than for conventional ESP hydraulics. In addition, the brake system according to the invention has a better energy balance and lower noise than a conventional ESP hydraulics, because there in ESP operation required pumping of brake fluid for He testify of back pressure on a pressure relief valve deleted. Also, compared to the cited prior art, an improvement in the noise performance can be achieved because within the housing 8th enclosed module, which is connected in the vehicle with the structure-borne noise-critical bulkhead, no noise-generating components such as valves, motors or pumps are arranged.

Claims (27)

Brake system for motor vehicles with • a master cylinder ( 1 ), are connectable to the wheel brake cylinder, • a first piston ( 2 ), which via an actuating forces transmitting push rod ( 28 ) with a brake pedal ( 3 ), a second piston ( 4 ), the master cylinder ( 1 ), a third piston ( 5 ), from the first piston ( 2 ) is operable, wherein at least one elastic element ( 6 . 7 ) is provided, via the actuating forces from the brake pedal ( 3 ) on the third piston ( 5 ) and that forms a pedal travel simulator, which gives the driver a pleasant pedal feel in the "brake-by-wire" mode of operation, means for coupling the movements of the first and third pistons, which depend on the travel of the third piston ( 5 ) in the housing ( 8th ), as well as with a space which can be subjected to hydraulic pressure ( 11 ) between the second ( 4 ) and third piston ( 5 ), wherein a pressurization of the gap ( 11 ) the second and third pistons ( 4 . 5 ) in the opposite direction, characterized in that means for coupling the movements of the second ( 4 ) and the third piston ( 5 ) are provided, which depend on the travel of the third piston ( 5 ) in the housing ( 8th ) to be activated. Brake system according to claim 1, characterized in that the intermediate space ( 11 ) by means of a single hydraulic connection ( 12 ) with an electrically controllable pressure supply module ( 13 ), which is both a filling of the gap ( 11 ) with pressure medium and its possible. Brake system according to claim 2, characterized in that the hydraulic connection ( 12 ) depending on the travel of the third piston ( 5 ) in the housing ( 8th ) is shut off, so that a flow through the hydraulic connection ( 12 ) from the gap ( 11 ) to the print delivery module ( 13 ) is prevented. Brake system according to claim 2 or 3, characterized in that a section ( 20 ) of the hydraulic connection ( 12 ) in the third piston ( 5 ) is formed and having an orifice, which with a housing-fixed sealing element ( 22 ) cooperates. Brake system according to claim 4, characterized in that the housing-fixed sealing element ( 22 ) is formed as a cuff seal, which in the direction of an inflow to the space ( 11 ) can be overflowed. Brake system according to claim 4, characterized in that a check valve ( 33 ) a bypass of the sealing element ( 32 ) in the direction of an inflow to the intermediate space ( 11 ). Brake system according to one of the preceding claims 1 to 3, characterized in that the means a sensor ( 34 ) for detecting the travel of the third piston ( 5 ) and a signal transmission path ( 35 ) to the print delivery module ( 13 ) and with displaced third piston ( 5 ) a pressure supply module-side barrier of the hydraulic connec tion ( 12 ) enable. Brake system according to one of claims 1 to 7, characterized in that the elastic element ( 6 ) Effectively between the push rod ( 28 ) and the third piston ( 5 ) is arranged. Brake system according to one of claims 1 to 8, characterized in that a hydraulic shut-off device for coupling the movements of the first ( 2 ) and the third piston ( 5 ) is provided, which depends on the travel of the third piston ( 5 ) in the housing ( 8th ) is activated. Brake system according to claim 9, characterized in that the shut-off device by a in the third piston ( 5 ) from the first piston ( 2 ) limited chamber ( 21 ) is formed, which is filled with pressure medium and in the inactivated state of the shut-off device with a pressure fluid reservoir ( 23 ). Brake system according to claim 9 or 10, characterized in that the hydraulic connections contained in the shut-off device as hydraulic throttle elements of the hydraulic damping of the pedal travel simulator ( 7 ) serve. Brake system according to claim 11, characterized in that in that at least one of the hydraulic throttle elements is a flow direction-dependent behavior having. Brake system according to one of the preceding claims, characterized in that a rotation angle sensor ( 27 ) is provided for detecting brake pedal position and movement whose output signal of an electronic control unit ( 21 ) and the control of the pressure supply module ( 13 ) serves. Brake system according to one of the preceding claims, characterized in that a pressure sensor ( 19 ) to capture the from the print delivery module ( 13 ) provided hydraulic pressure is provided, the output signal of the electronic control unit ( 21 ) is supplied. Brake system according to one of the preceding claims, characterized in that the pressure supply module ( 13 ) an electrically driven high pressure pump ( 14 ) contains. Brake system according to claim 15, characterized in that the pressure supply module ( 9 ) contains a hydraulic high-pressure accumulator. Brake system according to one of claims 1 to 14, characterized in that the pressure supply module ( 13 ) an electropneumatic actuator ( 36 ) contains. Brake system according to one of claims 1 to 14, characterized in that the pressure supply module ( 13 ) an electromechanical actuator ( 37 ) contains. Brake system according to one of claims 13 to 18, characterized in that the electronic control unit ( 21 ) the print delivery module ( 13 ) assigned. Brake system according to one of the preceding claims 1 to 19, characterized in that the Druckbereit position module ( 13 ) electrically controllable valves ( 15 . 16 . 17 ) contains. Brake system according to claim 7 and 20, characterized in that the electrically controllable valves ( 15 . 16 . 17 ) via the signal transmission path ( 35 ) are controllable. Brake system according to one of the preceding claims, characterized in that the connection ( 12 ) of the print delivery module ( 13 ) with the space ( 11 ) is designed as a hydraulic hose. Brake system according to one of the preceding claims, characterized in that the master brake cylinder ( 1 ) an ABS control module ( 29 ) is connected downstream. Brake system according to claim 23, characterized in that the ABS control module ( 29 ) an ABS control and regulating electronics ( 30 ) assigned. Brake system according to claims 13 and 24, characterized that the electronic control unit and the ABS control and regulation electronics Form assembly. Brake system according to one of claims 1 to 25, characterized in that the master cylinder ( 1 ) is designed as a tandem master cylinder whose piston ( 4 . 10 ) the same cross-sectional area as the third piston ( 5 ) exhibit. Brake system according to one of claims 1 to 25, characterized in that the master cylinder ( 1 ) is designed as a twin master cylinder whose piston ( 4 ' . 10 ' ) in sum the same cross-sectional area like the third piston ( 5 ) exhibit.