DE102016224934A1 - Master brake cylinder for a vehicle brake system and motor vehicle brake system - Google Patents

Abstract

Third party vehicle brake systems having vehicle brake systems require a pedal travel simulator. This is in the master cylinder (1) integrated.Dazu has the master cylinder (1) has a primary piston (3) which limits a primary chamber (5) and a pedal piston (10) to which a brake pedal via a pedal rod can be supported. Between the primary piston (3) and the pedal piston (10) is a spring chamber (12) in which a simulator spring (13) is located, which is supported on the one hand on the pedal piston (10) and on the other hand on the primary piston (3). The spring chamber (12) is in a lockable hydraulic connection with a pressure medium having reservoir (8) in Verbindung.Is blocked the connection, the spring chamber (12) is hydraulically closed, so that the non-compressible pressure medium contained therein as a rigid push rod When the connection is opened, the pedaling force applied to the pedal works against the simulator spring (13), giving each pedal travel a certain retroactive force on the pedal.

Description

The invention relates to a master cylinder for a vehicle brake system having an external brake pressure transducer, wherein the master cylinder at least one primary piston defining a primary chamber which is connectable to a brake circuit of the brake system, a pedal piston to which a brake pedal via a pedal rod can be supported, and a Spring chamber between the primary piston and the pedal piston, in which there is a simulator spring, which is supported on the one hand on the pedal piston and on the other hand on the primary piston. Furthermore, the invention relates to a motor vehicle brake system with an electrically controllable pressure supply device.

Et al in brake systems in which the master cylinder separated by means of isolation valves of its brake circuits and the pressure medium supply of the brake circuits is performed by the separate electronically controlled external brake pressure transducer, a pedal travel simulator is needed. The control of this third-party brake pressure transducer receives information about the pedal operation, in particular via the pedal travel, so that accordingly a wheel brake pressure can be adjusted and, if necessary, modulated in a slip-controlled manner.

These brake systems can also be used to perform an automatic brake operation independently of a pedal operation. In this case, the isolation valves are also closed, so that the brake circuits are separated from the master cylinder. The external brake pressure sensor then inputs pressure medium into the brake circuits, depending on the conditions of the automatic braking.

Such pedal travel simulators can be constructed structurally separate from the master cylinder. But there are also proposals to integrate them into the master cylinder.

Such a proposal is eg in the DE 102 23 799 A1 shown. This is behind the primary piston, which limits the primary chamber in the master cylinder, a spring chamber, which is bounded by a pedal piston, which acts directly on a coupled with the pedal pedal rod.

The primary piston has a rearward, pointing to the pedal piston hollow cylindrical extension, the pedal piston has a front, pointing to the primary piston hollow cylindrical extension: extension and extension are telescopically inserted into each other.

Within the spring chamber thus formed is a simulator spring, which is supported on the one hand on the primary piston and on the other hand on the pedal piston.

The two extensions may be mechanically interconnected to act as a unit in which the forces transmitted to the pedal piston by means of the pedal rod are transmitted directly to the primary piston so that actuation of the master cylinder is possible.

This is particularly important in the event that the control of the brake system fails and a conventional pedal operation is necessary, is displaced in the pressure medium from the master cylinder to the wheel brakes.

If the brake system is intact, ie the supply of the wheel brakes can be done with pressure medium from the separate external brake pressure transducer, the mechanical connection is released, so that the pedal piston can approach the primary piston.

This is the case when the isolation valves - as explained above - are closed, so the primary piston is hydraulically fixed in position.

The pedal force exerted on the pedal in this case works against the simulator spring, giving each pedal travel a certain retroactive force on the pedal. The simulator spring is designed so that its reaction as possible corresponds to the reaction occurring in a conventional braking.

However, a mechanical coupling of the two extensions is only complex to implement.

The invention is based on the task of achieving a simple coupling of the two pistons.

To achieve the object, the invention provides that the spring chamber is in a lockable hydraulic connection with a pressure medium containing reservoir.

If this connection is blocked, then the spring chamber is hydraulically closed, so that the non-compressible pressure medium contained therein acts like a rigid pressure rod between the pedal piston on the one hand and the primary piston on the other hand. As with a mechanical coupling, the forces transmitted to the pedal piston by means of the pedal rod are relayed to the primary piston so that conventional actuation of the master cylinder is possible.

The lockable connection can be realized most simply by the fact that in the lockable hydraulic connection, an electromagnetically actuated shut-off valve is located, which is normally closed. This has the advantage that in case of failure of the electronic control and thus the external brake pressure transducer, the shut-off valve is de-energized and the connection to the reservoir is closed. In such a situation, the desired conventional brake operation becomes possible.

When the external brake pressure sensor fails, the energy stored in the previously compressed simulator spring is also used to actuate the primary piston. As a result of this energy recovery, the wheel brakes can be filled with pressure medium from the main cylinder chamber and / or a brake pressure can already be generated.

So that there is no negative pressure in the spring chamber - namely, the check valve is normally closed in this situation - has pressure medium (brake fluid) to run out of the reservoir. For this purpose, a check valve is preferably connected in parallel to the check valve, which closes to the reservoir. About this check valve pressure fluid reaches the spring chamber.

Since a direct power transmission between piston rod and primary piston is possible by closing the valve, the traveler can generate the residual braking force, which is required beyond the already generated by the simulator spring braking force.

Preferably, the pedal piston is guided in the primary piston, which has a hollow cylindrical extension in the direction of the pedal piston.

Due to the combination with the energy recovery from the simulator spring less pedal travel with the same delay in case of failure of the power brake system is necessary.

To be able to establish a connection to the spring chamber by the extension, this preferably has a transverse bore, which opens in the basic position of the master cylinder in an annular groove on the inner circumferential surface of the master cylinder, which in turn is connected via the lockable hydraulic connection to the reservoir.

The invention further preferably provides that the primary chamber has a closable by a displacement of the primary piston connection to the reservoir, that the connection is closed when the primary piston, starting from its normal position has been moved to a closing path, and that the width of the annular groove greater than the closing distance of the primary piston.

In an intact brake system, the primary piston is fixed because the brake circuits are separated from the master cylinder and the primary chamber has interrupted the connection of the primary chamber to the reservoir after overcoming the closing path. Since the width of the annular groove corresponds at least to the closing path of the primary piston, the spring chamber communicates with the reservoir with the shut-off valve open, so that the pedal piston can be displaced against the fixed primary piston while compressing the simulator spring.

If the electronic control of the brake system fails, the primary piston moves beyond the closing path, so that after an additional primary piston the annular groove is covered by the primary piston and the spring chamber is hydraulically locked, even if the check valve should not fall back into its closed normally closed normal position.

However, the width and position of the annular groove can also be chosen so that, regardless of the position of the primary piston, the connection bore opens into the annular groove.

The additional primary piston travel also allows the energy stored in the simulator spring - as described above - to be used for brake actuation.

Since the pedal piston has a socket for the simulator spring, which would cover the transverse bore in the extension, the invention preferably further provides that on the inner circumferential surface of the extension of the primary piston, a further annular groove is formed, in which an existing in the extension transverse bore opens , And that the socket has at least one transverse bore which, regardless of the position of the pedal piston in the extension of the primary piston in the further annular groove.

Preferably, the further annular groove has a position and width, so that regardless of the position of the pedal piston to the primary piston there is a hydraulic connection from the spring chamber to the annular groove.

The invention also relates to a motor vehicle brake system with an electrically controllable pressure supply device as a third-party brake pressure generator and a master cylinder according to the invention.

In the following, the invention will be explained in more detail with reference to an embodiment. For this purpose, the single figure shows a schematic structure of a master cylinder according to the invention in the form of a tandem master cylinder.

In the master cylinder 1 are one behind the other a secondary piston 2 , which is designed as a floating piston, and a primary piston 3 arranged. The secondary piston 2 limited at the bottom of the master cylinder 1 a secondary chamber 4 , the primary piston 3 limits a primary chamber 5 extending between the front of the primary piston 3 and the back of the secondary piston 2 extends. At the two chambers 4 . 5 the brake circuits not shown here are connected to a brake system, which are in the brake circuits isolation valves, the chambers in the closed state 4 . 5 hydraulically lock.

Between the bottom of the master cylinder 1 and the secondary piston 2 and between the secondary piston 2 and the primary piston 3 extend return springs 6 . 7 , after a brake operation, the two pistons 2 . 3 to reset their basic positions shown in the figure.

The chambers 4 . 5 also have closable connections with a reservoir 8th in connection. The closing of the connections becomes for both chambers 4 . 5 each realized in that the secondary piston 2 and the primary piston 3 each act as a slide, the respective connection to the reservoir 8th cover when the two pistons 2 . 3 in the direction of actuation, ie in the sense of a reduction of the chambers 4 . 5 , are moved from a home position to a closing path.

In a hollow cylindrical extension 9 of the primary piston 3 is a pedal piston 10 sealed guided, at the rear end side of a pedal rod 11 is supported.

In the Sun within the extension 9 of the primary piston 3 formed spring chamber 12 there is a simulator spring 13 , on the one hand at the rear end face of the primary piston 3 and on the other hand supported on the front surface of the pedal piston 10.

The spring chamber 12 is also with the reservoir 8th via a check valve 14 in the form of a normally closed solenoid valve in conjunction. The check valve 14 is a check valve 15 connected in parallel, that to the reservoir 8th locks out.

The check valve 14 and the check valve 15 are to with a connection hole 17 in the master cylinder 1 connected, in turn, into an annular groove 16 in the inner circumferential surface of the master cylinder 1 empties.

In the extension 9 there is a transverse bore 20 in the basic position of the primary piston 3 in overlap lies with this annular groove 16 , In this way is a connection of the check valve 14 to the spring chamber 12 produced.

The width of the annular groove 16 is chosen so that at least over the closing path of the primary piston 3 - Starting from its basic position shown in the figure - relative to the master cylinder 1 a connection between the reservoir 8th and the annular groove 16 remains.

The width of the annular groove 16 but can be even larger, so even with an additional path of the primary piston 3 the connection between the reservoir 8th and the ring groove 16 remains to be able to exploit the energy stored in the simulator spring for a brake application can.

In an intact control of the brake system, the check valve 14 is switched to its open position, so that the spring chamber 12 has a connection to the reservoir. In addition, the master cylinder chambers are locked as soon as the primary and secondary pistons have passed through their respective closing paths. Because the location and width of the ring groove 18 is chosen so that it is not covered by the extension in this situation, the simulator spring can be compressed in this situation according to the pedal force.

If the power-brake system and its control fails, the check valve remains 14 because it is now de-energized, in its closed position, causing the connection of the spring chamber 12 to the reservoir 8th is closed. The purpose of this is the following: If this happens during braking and thus the brake circuits are opened, the spring chamber 12 hydraulically locked so that the pedal pressure without loss of travel to the primary piston 3 can be transferred.

However, it is conceivable that the check valve 14 Although it is de-energized, but still z. B. is unable to close due to a mechanical defect. In this case, the pedal forces are initially under compression of the simulator spring 13 the primary piston 3 move until the simulator spring 13 is completely compressed and the pedal piston strikes the primary piston or the primary piston the annular groove 16 completely covers.

The width of the other annular groove 18 but can also be chosen so that almost independent of the position of the pedal piston 10 in terms of the primary piston 3 there is always a connection of the further annular groove in the spring chamber.

At the front of the pedal piston 10 is a socket 19 for holding and aligning the simulator spring 13 , So that this the cross hole 20 does not cover and closes, opens the transverse bore 20 in another annular groove 18 on the inner surface of the extension 9 , Another transverse bore in the socket 19 This shows - regardless of the position of the pedal piston 10 - to the primary piston 3 in the further annular groove 18 , so that a steady connection of the spring chamber 12 to the other ring groove 18 consists.

Such a master cylinder 1 works as follows:

As long as the check valve 14 closed normally and thus the spring chamber 12 hydraulically locked, the primary piston 3 and the pedal piston act 10 as a unit, as a primary piston of a conventional master cylinder without integrated pedal travel simulator.

In a functioning brake system with the operation of the pedal, the check valve 14 opened and the isolation valves in the brake circuits closed. This is the secondary piston 2 and the primary piston 3 hydraulically in the master cylinder 1 fixed. To actuate the wheel brakes is pressure medium from a third-party brake pressure transducer according to the detected pedal travel and / or the pressure in the primary or secondary chamber 3 . 4 promoted in the brake circuits.

The pressure medium in the spring chamber 12 is doing over the open shut-off valve 14 to the reservoir 8th escape, leaving the simulator spring 13 can be compressed according to the pedal operation, wherein it returns to each pedal travel a certain counterforce according to their spring characteristic.

If, during such braking, the electronic control of the brake system fails, the isolation valves are opened and the check valve 14 closed. The chambers 4 . 5 of the master cylinder are thus connected to the brake circuits. This has the consequence that a displacement of the pedal piston 10 due to a pedal force acting on it, a displacement of the primary and secondary pistons 3 . 2 causes, whereby a further pressure build-up in the wheel brakes now with pressure medium from the master cylinder 1 he follows.

There is thus no loss of pedal travel. Rather, can be transferred directly from an electronically controlled braking in a conventional braking.

The diameter of the pedal piston 10 can be chosen arbitrarily, since it only serves to support the simulator spring. Because no specific area ratio of the primary piston 3 to the pedal piston 10 must be respected, the primary piston 3 vehicle type are provided individually with a diameter that is suitable for the brake system of the respective vehicle type.

LIST OF REFERENCE NUMBERS

1

Master Cylinder

2

secondary piston

3

primary piston

4

secondary chamber

5

primary chamber

6

Return spring

7

Return spring

8th

reservoir

9

renewal

10

pedal piston

11

pedal rod

12

spring chamber

13

simulator spring

14

check valve

15

check valve

16

ring groove

17

connection bore

18

ring groove

19

version

20

cross hole

21

cross hole

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10223799 A1 [0005]

Claims (10)

Master brake cylinder for a vehicle brake system having an external brake pressure transducer, the master brake cylinder (1) defining at least one primary piston (3) defining a primary chamber (5) which can be connected to a brake circuit of the brake system, a pedal piston (10) to which a pedal rod engages Brake pedal is supported, and a spring chamber (12) between the primary piston (3) and the pedal piston (10), in which there is a simulator spring (13) which is supported on the one hand on the pedal piston (10) and on the other hand on the primary piston (3) , characterized in that the spring chamber (12) is in a lockable hydraulic connection with a pressure medium containing reservoir (8). Master cylinder after Claim 1 , characterized in that in the lockable hydraulic connection, an electromagnetically actuated shut-off valve (14) which is normally closed. Master cylinder after Claim 2 , characterized in that parallel to the check valve (14), a check valve (15) is connected, which closes to the reservoir. Master brake cylinder according to one of the preceding claims, characterized in that the pedal piston (10) in the primary piston (3) is guided, which has a hollow cylindrical extension (9) in the direction of the pedal piston. Master cylinder after Claim 4 , characterized in that the master brake cylinder (1) has a connection bore (17) which opens into an annular groove (16) on the inner circumferential surface of the master cylinder (1) which is connected via the lockable hydraulic connection with the reservoir (8). Master cylinder after Claim 5 , characterized in that the primary chamber (5) has a closable by a displacement of the primary piston (3) connection to the reservoir, that the connection is closed when the primary piston has been moved from its basic position to a closing path, and that the Width of the annular groove (16) is greater than the closing distance of the primary piston (3). Master cylinder after Claim 6 , characterized in that the width and position of the annular groove (16) is chosen so that, regardless of the position of the primary piston (3), the connection bore opens into the annular groove. Master brake cylinder according to one of the preceding claims, characterized in that the pedal piston (10) has a socket (19) for the simulator spring (13) that on the inner circumferential surface of the extension of the primary piston, a further annular groove (18) is formed, in which in the extension existing transverse bore (20) opens, and that the socket (19) has at least one further transverse bore (21) which, regardless of the position of the pedal piston (10) in the extension (9) of the primary piston (3) in the further Ring groove (18) points. Master cylinder after Claim 8 , characterized in that the further annular groove (18) has a position and width, so that regardless of the position of the pedal piston (10) to the primary piston (3) there is a hydraulic connection from the spring chamber (12) to the annular groove (18). Motor vehicle brake system, in particular of the type "brake-by-wire", with an electrically controllable pressure supply device and a master cylinder according to one of Claims 1 to 9 ,

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