DE102010038328A1 - Braking system for motor vehicles - Google Patents

Abstract

The brake system has a main cylinder which is connected at wheel brake circuits and a piston (11) which is coupled with a brake pedal (9) by a pressure rod transmitting actuating force. Another piston (12) is provided which limits a hydraulic chamber at which a brake circuit is connected. A third piston (13) is provided which is actuated by the former piston. A ring surface (35) formed on the third piston is larger than the front surface of the former piston. The ring surface limits a retention area (17).

Description

• • einem Hauptzylinder, an den Bremskreise angeschlossen sind,
• • einem ersten Kolben, der über eine Betätigungskräfte übertragende Druckstange mit einem Bremspedal gekoppelt ist,
• • einem zweiten Kolben, der eine hydraulische Kammer begrenzt, an die ein Bremskreis angeschlossen ist,
• • einem dritten Kolben, der vom ersten Kolben betätigbar ist, und der in eine kraftübertragende Verbindung mit dem zweiten Kolben bringbar ist,
• • mit einer Simulationseinrichtung mit mindestens einem elastischen Element, die in der Betriebsart „Brake-by-wire” dem Fahrzeugführer ein angenehmes Pedalgefühl vermittelt,
• • mit einem mit hydraulischem Druck beaufschlagbaren Zwischenraum zwischen dem zweiten Kolben und dem dritten Kolben, wobei eine Druckbeaufschlagung des Zwischenraums den zweiten und den dritten Kolben in entgegen gesetzter Richtung belastet,
• • mit einem vom dritten Kolben begrenzten, hydraulischen, mittels eines Sperrventils absperrbaren Rückhalteraum, mit dem bei Bedarf eine Bewegung des dritten Kolbens in Betätigungsrichtung verhindert wird,
• • mit einer Druckbereitstellungseinrichtung, die den Druck im Zwischenraum steuert,
• • mit einem unter Atmosphärendruck stehenden Druckmittelvorratsbehälter, der mit dem Zwischenraum hydraulisch verbindbar ist,
• • sowie mit einer elektronischen Steuer- und Regeleinheit.

The invention relates to a brake system for motor vehicles, which can be controlled in a "brake-by-wire" mode both by the driver and independently of the driver, preferably operated in the "brake-by-wire" mode and operated in at least one fallback mode can, in which only the operation by the driver is possible, with

• A master cylinder to which brake circuits are connected,
• A first piston, which is coupled to a brake pedal via an actuating force transmitting push rod,
• A second piston defining a hydraulic chamber to which a brake circuit is connected,
• A third piston which can be actuated by the first piston and which can be brought into a force-transmitting connection with the second piston,
• • with a simulation device with at least one elastic element, which gives the driver a pleasant pedal feel in the "brake-by-wire" operating mode,
• • with a pressurizable intermediate space between the second piston and the third piston, wherein pressurization of the intermediate space loads the second and the third piston in the opposite direction,
• • with a limited by the third piston, hydraulic, shut-off by means of a check valve retaining space, with the movement of the third piston is prevented in the direction of actuation, if necessary,
• 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 an electronic control unit.

A brake system of the type mentioned is from the international patent application of the applicant WO 2008/025797 A1 known. As the person skilled in the publication can see, remains in the preferred mode "brake-by-wire" of the third or the retaining piston after a slight movement, which is made possible by the flexibility of the sealing elements sealing it. When applying the intermediate space with braking system pressure, the third or the retaining piston can move back by the mentioned way, so that undesirable in particular in rapid and repeated pressure changes in the space by a hard abutment of the third and the retaining piston to a stop formed in a housing Pedal vibrations and structure-borne noise are caused.

It is therefore an object of the present invention, a brake system of to improve the type mentioned above in such a way that said Issues of noise and pedal vibration largely be eliminated.

These The object is achieved according to the invention that a retention piston bounding the third piston trained annular surface is greater than the end face of the first piston.

to Concretization of the inventive concept is provided that a in a flow direction lockable hydraulic connection between the retention space and the pressure medium reservoir is provided.

at an advantageous development of the subject invention is in the hydraulic connection an electrically actuated, normally open (SO) 2/2-way valve inserted, the in energized switching state, the function of a pressure medium reservoir closing check valve met.

to Detection of an operating force acting on the brake pedal provides an advantageous development of the invention that in third and the retaining piston formed a hydraulic pressure chamber is.

The familiar pedal feeling, especially in the "Brake-by-wire" mode the driver by the features of the claim 4 mediated, after which the hydraulic pressure chamber in lockable Connection with a hydraulic simulator chamber is available from a hydraulic simulator piston is limited, with the Pedal travel simulator forming elements in force-transmitting Connection stands.

One Turn off the simulator function, especially in a fallback mode is required, in another advantageous embodiment of Invention thereby allows the connection of the hydraulic Pressure chamber with the hydraulic simulator chamber by means of a electrically operated simulator release valve can be released is that in the de-energized switching state, the function of a Simulator chamber closing check valve Fulfills.

An increase in operational safety is achieved in another embodiment of the subject invention in that between the retaining space and the hydraulic pressure chamber, a first hydraulic connection and a second hydraulic connection are provided, the pa are connected in parallel, wherein in the first connection an electrically operable, normally closed (SG) 2/2-way valve and in the second connection, a central valve is arranged, which is actuated by a differential path between the first and the third and the retaining piston ,

The Central valve has one in the third or retaining piston trained sealing seat and a valve closing body on, in a release position of the brake pedal of a Lifting member formed on the first piston lifted from its sealing seat is.

Further advantageous embodiments of the invention Brake system are listed in the subclaims 9 to 15.

The The present invention will become more apparent from an embodiment explained in more detail with reference to the accompanying schematic drawing, whose only figure is the structure of an advantageous embodiment of the brake system according to the invention shows.

The braking system according to the invention shown in the drawing consists essentially of an actuating device 1 , a pressure supply device 2 in which the actuating unit and the pressure supply device form a brake booster, as well as a master brake cylinder or tandem master cylinder operatively connected downstream of the brake booster 3 , its pressure chambers 20 . 21 with the chambers under atmospheric pressure of a first pressure medium reservoir 16 are connectable. On the other hand, to the pressure chambers 20 . 21 Connected wheel brake circuits I, II, with the interposition of a known ABS or ESP hydraulic unit or a controllable Radbremsdruckmodulationsmodul 4 the wheel brakes 5 . 6 . 7 . 8th supply a motor vehicle with hydraulic pressure medium. The actuating device 1 in a housing 50 is arranged, to which the tandem master cylinder 3 is connected via a brake pedal 9 controllable, that via an actuating rod 10 with a first piston 11 the actuator 1 is operatively connected. The actuating travel of the brake pedal 9 is by means of a displacement sensor 19 captures the path of the first piston 11 relative to the housing 50 sensed. For the same purpose, however, an unillustrated angle of rotation sensor can be used which determines the angle of rotation of the brake pedal 9 detected. The first piston 11 is in a third piston 13 sealed slidably guided, in which he a pressure chamber 14 limited, which is a compression spring 15 the brake pedal is de-energized 9 the first piston 11 to rest on one in the third piston 13 trained stop 45 brings. One with the reference numeral 43 designated pressure sensor is used to detect the in the pressure chamber 14 built up pressure. Alternatively or additionally, in the area of the push rod 10 or the brake pedal 9 a pedal return spring may be provided. The third or the retaining piston 13 is designed as a stepped piston whose smaller stage the first and the primary piston of the tandem master cylinder 3 forms. Between a second piston 12 , the floating piston of the tandem master cylinder 3 is a gap 20 limited, the same time a first or primary pressure chamber of the master cylinder 3 forms, to which the first brake circuit I is connected. To a secondary pressure chamber 21 of the tandem master cylinder, that of the second piston 12 is limited, the second brake circuit II is connected. The formation of the second or the third or of the retaining piston 13 is made such that by applying the intermediate or the primary pressure chamber 20 with a hydraulic pressure of the third piston 13 at one in the housing 50 trained stop 47 is held while the same pressure by the first brake circuit I is forwarded. In addition, with the same pressure, the second and the secondary piston 12 acted upon in the sense of a pressure build-up in the second brake circuit II.

As can be seen from the schematic illustration in the single figure, the third or the restraining piston limits 13 in the case 50 a hydraulic chamber or a retention space 17 whose function is explained in the following text. One at the third or retaining piston 13 trained, the retention room 17 limiting annular surface 35 is preferably designed to be larger than the end face of the first piston 11 , To the hydraulic retention room 17 is a first line 34 connected via a normally closed (SG) shut-off valve 23 with a second line 24 connected to the previously mentioned pressure chamber 14 connected. A second, for the first connection 34 parallel second hydraulic connection 38 also connects the retention room 17 with the pressure chamber 14 , wherein the second connection by means of a central valve 39 can be locked. The central valve 39 has one in the retaining piston 13 trained seal seat 40 on, with which a valve closing body 41 cooperates, in the closing direction of the central valve by a valve closing spring 48 is biased. This is the central valve 39 controlled by a relative displacement of the first piston 11 towards the third and the retaining piston 13 actuated by the valve closing body 41 in a release position of the brake pedal 9 from one on the first piston 11 trained driver from his tight seat 40 is lifted off. The retention room 17 is via a lockable in a flow direction connection 36 with a second pressure medium reservoir 18 or a separate chamber 18 a pressure medium reservoir's 16 . 18 connected, the or the actuator 1 assigned. The barrier of the mentioned connection 36 is preferably used an electrically actuated, preferably normally open (SO) 2/2-way valve 22 in the actuated switching state, the function of a second pressure medium reservoir 18 closing check valve met.

Furthermore, it can be seen from the drawing that the previously mentioned pressure chamber 14 via a lockable connection line 37 , to the above-mentioned hydraulic connection 24 connected with a simulator chamber 25 communicating from a simulator piston 26 is limited. The simulator piston acts 26 with a simulator pen 27 and one of the simulator spring 27 parallel elastomer spring 28 together. The simulator chamber forms 25 , the simulator piston 26 , the simulator pen 27 as well as the elastomer spring 28 a pedal travel simulator, which provides the vehicle operator with the usual pedal feel that corresponds to a common brake pedal characteristic when operating the brake system in the preferred "brake-by-wire" mode. This means that with low brake pedal travel, the resistance increases slowly and increases disproportionately with a larger brake pedal travel. To dampen the movement of the simulator piston 26 not shown, for example pneumatic damping means may be provided. The hydraulic connection line 37 between the simulator chamber 25 and the pressure chamber 14 is by means of a simulator-free valve 33 can be released or shut off, the function of a simulator in the illustrated unactuated switch position 25 closing check valve met. The first piston 11 , the return spring 15 , the hydraulic chamber 14 , the hydraulic connection 24 respectively. 37 , the simulator chamber 25 , the simulator piston 26 , the simulator springs 18 and 27 , As well as the damping means not shown together form a simulation device, which together with the second pressure fluid reservoir 18 , the retention chamber 17 , the valves 22 . 23 and the associated hydraulic connections is associated with a simulation and retention pressure medium circuit which is completely separated from the wheel brake circuits I, II.

The aforementioned electrohydraulic pressure supply device 2 consists essentially of a hydraulic cylinder-piston arrangement 29 and an electromechanical actuator 30 For example, which is formed by an electric motor with a reduction gear, the translational movement of a hydraulic piston 31 guaranteed, so in a pressure room 51 the hydraulic cylinder-piston arrangement 29 a hydraulic pressure is built up. The detection of the rotor position and the travel of the electromechanical actuator 30 serves a rotor position sensor 42 , The electromechanical actuator 30 is powered by a not shown, known electrical energy storage with energy. The pressure room 51 is on the one hand via an annulus 46 to the gap 20 connected and on the other hand with the pressure medium reservoir under atmospheric pressure 16 connectable. Here are the pressure supply device 2 and the gap 20 associated with the first brake circuit I, which is completely separated from both the second brake circuit II and the first-mentioned simulation and retention pressure medium circuit. A pressure sensor 32 serves to capture the from the pressure supply device 2 provided or in the annulus 46 prevailing pressure.

The previously mentioned check valve 22 allows a shut-off of the retention space 17 opposite the separate chamber 18 the pressure medium reservoir of the pressure chamber 14 , causing a movement of the third piston 13 is essentially prevented in the direction of actuation. A small movement in the context of the compliance of the retention space 17 sealing gaskets is still possible, which would lead to the disadvantages mentioned in the prior art, if not at the same time the Zuschaltventil 23 would be pressed. In the actuated state, however, connects the Zuschaltventil 23 the pressure chamber 14 with the retention room 17 , so that in both rooms the same pressure prevails. This pressure exerts two force effects on the third or retaining piston: in the retention space 17 over the ring surface 35 against the direction of actuation and in the pressure chamber 14 via a surface corresponding to the cross-sectional area of the first piston in the actuating direction. According to the invention, the annular surface 35 of the third piston 13 greater than the cross-sectional area of the first piston 11 such that the force effect resulting from the two said forces is the third or restraining piston 13 against the direction of actuation of the in the housing 50 trained stop 47 presses, regardless of a yielding of the retention space 17 sealing gaskets or a compression of the retention space 17 enclosed pressure medium volume.

The said elements is a separate electronic control unit 44 The acquisition of sensor data, the processing of this data, the exchange of data with other control units, the control of the electromechanical actuator 30 , as well as the brake lights of the vehicle is used.

in the The following text will describe the operation of the invention Brake system explained in more detail in connection with the drawing.

A first operating mode corresponds to the purely electrical, so-called "brake-by-wire" mode, in which all components of the brake system are intact and working properly. In this mode is used to build up a hydraulic pressure in the space 20 the electromechanical actuator 30 controlled, so that of the pressure-providing device 2 provided or in their cylinder-piston arrangement 29 generated pressure over the annulus 46 the gap 20 is supplied. By the action of the pressure, which is passed on via the first brake circuit I to the wheel brakes associated with this brake circuit, the third piston 13 in addition to the mentioned restraint by the pedal pressure in the retention space 17 at the stop 47 held and the second master brake cylinder piston 12 shifted to the left, whereby pressure is built up in the second brake circuit II. For the purpose of keeping pressure, the piston 31 the piston-cylinder arrangement 29 held firmly in the activated position.

For a pressure reduction, the piston 31 the cylinder-piston arrangement 29 driven back. In this case, pressure medium flows from the intermediate space 20 over the annulus 46 back to the pressure room 51 , For complete reduction of the pressure to atmospheric pressure level eventually the compound 49 between the pressure room 51 the cylinder-piston arrangement 29 and the pressure fluid reservoir 16 open.

The process of controlling the electromechanical actuator 30 is from the electronic control unit 44 performed so that the pressure in the space 20 a target pressure value is approximated. This desired pressure value results on the one hand from a detected actuation component of the brake pedal 9 and, on the other hand, a foreign operation component. The operating component of the brake pedal 9 is from the actuation of the brake pedal 9 or the first piston 11 and from the hydraulic pressure in the pressure chamber 14 determined by means of the pressure sensor 43 is detected and the operating force of the brake pedal 9 is proportional.

In a second mode of operation caused by a fault in the electronics or by the absence of any of the hydraulic pressure supply means 2 generated pressure is equivalent and corresponds to a fallback level, is not an electronically controlled pressure build-up in the intermediate space 20 possible. In this operating mode, the brake system can be actuated purely mechanically. The retaining piston 13 moves from its stop under the influence of a brake pedal actuation 47 away, so build in the space 20 a pressure on. The operation of the master cylinder 3 is done exclusively with the muscle power of the driver.

By The present invention will be a simply constructed brake system achieved when in a "brake-by-wire" mode the brake pedal characteristic not from 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 regulatory activities the braking system such as anti-skid control, traction control or Driving stability control can be disturbed.

The brake system according to the invention also has the Advantage that no complex hydraulic components as pump, hydraulic accumulator and slide valve are needed. As the only hydraulic components are compared to the straight mentioned components simple and inexpensive elastomer-sealed Pistons and cylinders, as well as the millions of times proven in brake technology 2/2 solenoid valves used. The invention allows the use of a mechatronic actuator, both from a electrical place energy storage as well as directly from an electrical Vehicle electrical system can be fed.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - WO 2008/025797 A1 [0002]

Claims (15)

Brake system for motor vehicles, which is in a "brake-by-wire" mode both by the driver and independently of the driver can be controlled, preferably in the "brake-by-wire" mode is operated and can be operated in at least one fallback mode, in the only operation by the driver is possible, with a master cylinder ( 3 ), are connected to the wheel brake circuits (I, II), • a first piston ( 11 ), which via an actuating forces transmitting push rod ( 10 ) with a brake pedal ( 9 ), a second piston ( 12 ) defining a hydraulic chamber to which a brake circuit is connected, a third piston ( 13 ) from the first piston ( 11 ) is operable, and in a force-transmitting connection with the second piston ( 12 ) can be brought, • a simulation device with at least one elastic element ( 27 . 28 ), which gives the driver a pleasant pedal feel in the "brake-by-wire" operating mode, • a space which can be acted upon with hydraulic pressure ( 20 ) between the second piston ( 12 ) and the third piston ( 13 ), wherein a pressurization of the gap ( 20 ) the second piston ( 12 ) and the third piston ( 13 ) in the opposite direction, • one of the third piston ( 13 ) limited, hydraulic, by means of a check valve ( 22 ) lockable retention space ( 17 ), with the movement of the third piston ( 13 ) is prevented in the actuating direction, • a pressure-providing device ( 2 ), the pressure in the space ( 20 ), • a pressurized medium storage tank (below atmospheric pressure) ( 16 ), with the space ( 20 ) is hydraulically connectable, and • an electronic control unit ( 4 ), characterized in that the retention space ( 17 ) limiting, on the third piston ( 13 ) formed annular surface ( 35 ) is larger than the end face of the first piston ( 11 ). Brake system according to claim 1, characterized in that a lockable in a flow direction hydraulic connection ( 36 ) between the retention space ( 17 ) and a pressure medium reservoir ( 16 . 18 ) is provided. Brake system according to claim 2, characterized in that in the hydraulic connection ( 36 ) an electrically operated, normally open (SO) 2/2-way valve ( 22 ) is inserted, which in energized switching state, the function of a pressure medium reservoir ( 16 . 18 ) closing check valve met. Brake system according to one of claims 1 to 3, characterized in that in the third piston ( 13 ) a hydraulic pressure chamber ( 14 ) is formed, the detection of a brake pedal ( 9 ) acting actuating force is used. Brake system according to claim 4, characterized in that the hydraulic pressure chamber ( 14 ) in lockable connection with a hydraulic simulator chamber ( 25 ) from a hydraulic simulator piston ( 26 ) associated with the elements forming the pedal travel simulator ( 27 . 28 ) is in force-transmitting connection. Brake system according to claim 5, characterized in that the connection of the hydraulic pressure chamber ( 14 ) with the hydraulic simulator chamber ( 25 ) by means of an electrically operated simulator-free valve ( 33 ), which in the unactuated switching state has the function of a simulator chamber ( 25 ) closing check valve met. Braking system according to one of claims 1 to 6, characterized in that between the retention space ( 17 ) and the hydraulic pressure chamber ( 14 ) a first hydraulic connection ( 24 . 34 ) and a second hydraulic connection ( 38 ) are provided, which are connected in parallel, wherein in the first connection ( 24 . 34 ) an electrically actuated, normally closed (SG) 2/2-way valve ( 23 ) and in the second compound ( 38 ) a central valve ( 39 ) arranged by a differential path between the first ( 11 ) and the third piston ( 13 ) is operable. Brake system according to claim 7, characterized in that the central valve ( 39 ) one in the third piston ( 13 ) formed sealing seat ( 40 ) and a valve closing body ( 41 ), which in a release position of the brake pedal ( 9 ) of one on the first piston ( 11 ) trained driver from his tight seat ( 40 ) is lifted off. Braking system according to one of claims 1 to 8, characterized in that between the third piston ( 13 ) and the first piston ( 11 ) axial stops ( 45 ) are formed, which limit the relative displacement of the two pistons to each other in both axial directions. Braking system according to one of claims 1 to 9, characterized in that the pressure supply device ( 2 ) by a cylinder-piston arrangement ( 29 ) is formed whose piston ( 31 ) by an electromechanical actuator ( 30 ) is operable. Braking system according to one of claims 1 to 10, characterized in that the intermediate space ( 20 ) a first or a primary pressure chamber of the master cylinder ( 3 ). Braking system according to claim 11, characterized in that a depression of the brake pedal ( 9 ), processed electronically and in an activation of the pressure-providing device ( 2 ) is implemented. Braking system according to claim 12, characterized in that that the depression of the brake pedal over a the pedal travel and / or a pedal force representing Measured variable is detected. Braking system according to claim 13, characterized in that the size representing the pedal travel is the travel of the first piston ( 11 ) and by a piston travel sensor ( 19 ) is detected. Braking system according to claim 13 or 14, characterized in that the size representing the pedal force of the pressure in the pressure chamber ( 14 ), which is controlled by a pressure sensor ( 43 ) is detected.

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