FR2604673A1 - HYDRAULIC BRAKE PRESSURE GENERATOR FOR MOTOR VEHICLE BRAKING SYSTEM - Google Patents

Abstract

THE INVENTION PROVIDES A BRAKING PRESSURE GENERATOR WHICH INCLUDES AN AMPLIFIER PISTON 22 FOR ACTIVATING A BRAKING MASTER CYLINDER 1, AND IN WHICH AN AUXILIARY PRESSURE IN AN AMPLIFIER CHAMBER 25 CAN BE APPLIED AUDIT AMPLIFIER PISTON 22. TO MAINTAIN THE REACTION FORCE AT A LOW LEVEL WHEN THE BRAKING PRESSURE GENERATOR IS ACTUATED, A PRESSURE REDUCTION VALVE 46 IS LOCATED UPSTREAM OF THE VALVE MECHANISM 28, 29 OF THE BRAKE PRESSURE GENERATOR, A THROUGH WHICH THE AMPLIFIER CHAMBER 25 CAN BE CONNECTED TO A SOURCE OF HIGH PRESSURE 49 INCLUDING A PRESSURE ACCUMULATOR 61, THE PRESSURE OF THE AMPLIFIER CHAMBER 25 CAN BE APPLIED TO THE CONTROL PISTON 55 OF THE BOOSTER VALVE 46 TO DECREASE PRESSURE REDUCTION.

Description

-1- The present invention relates to a pressure generator

  braking for a hydraulic vehicle braking system

  bile, comprising an amplifier piston which is intended for action-

  a brake master cylinder to which an auxiliary hydraulic pressure prevailing in an amplifier chamber can be applied.

  including an actuating mechanism which cooperates with the piston

  tone amplifier and a valve device which is intended to com-

  apply auxiliary pressure which can be actuated by a relative movement between the amplifier piston and the mechanism

  actuator, and comprising a double seat valve by means of

  diary of which the amplifier can be connected to a tank

  without pressure or at a high pressure source with accumulated

pressure reader.

  Brake pressure generators of the type described below

  above have a high efficiency, require a low implementation of

  means and are characterized by satisfactory convenience of use.

  They are particularly suitable for braking systems of motor vehicles equipped with a device for regulating the brake slip and, due to the presence of a pressure accumulator,

  they are particularly well protected against failures.

  In practice, a brake pressure generator powered

  by a high pressure source has already proved to be advantageous (request

  German patent 31.08 908) and included, to control the auxiliary pressure, a slide valve operable by

  by means of a double lever and by the relative displacement between

  be the amplifier piston and the actuation mechanism. Although this design mode admits reduced reaction forces to initiate braking, its manufacture requires significant mechanical and financial means because the precision requirements imposed on the

  manufacture of the valve seat and the force transmission by the

vier are high.

  To reduce the means used, in a generator

  braking pressure of the type described above in accordance with the request

  German Patent No. 34 40 991, the valve device comprises two seat valves which are connected in series mechanically, which are - 2 -

  implanted in the amplifier piston and which can be action-

  born together by a control piston. However, this system pre-

  has a downside that due to the work surface

  high pressure valve seat hydraulics, at which pressure

  ion from the accumulator is applied, a high reaction force is produced which affects operating comfort and

  control of reduced braking forces.

  The present invention therefore aims to provide a general-

  braking pressure sensor of the type indicated above which, while retaining the structural advantage that constitutes the

  valves fitted with seat valves, has a reduced response force.

  According to the invention, this object is achieved in that a pressure reduction valve is located on the connecting ciliite situated between the source of pressure liquid and the valve device, the pressure of the amplifier chamber being applied to the piston of

  command to decrease the pressure reduction. Due to the pre-

  sence of the pessin rexdticn valve and the brakes are in the released position in which the amplifier chamber communicates with the tank without pressure, the pressure existing at the inlet of the

  brake pressure generator is reduced until a low

  ble reaction force is produced. As soon as the pressure generator

  brake pressure is activated, the auxiliary pressure which increases in the amplifier chamber decreases the pressure reduction,

  so that the entire accumulator pressure prevailing at the in-

  The brake pressure generator is available to pro-

  add an auxiliary pressure. In addition, the design of the brake pressure generator according to the invention has the advantage of simplicity, dmans the nare has the valve of pssion redatina does not require the implementation of any significant means of construction and o . she

  can be easily integrated into the brake pressure generator.

  In addition, it is advantageous that, when the brakes are in po-

  sition released, the valve drirAticndepressicnretirelahatepressicn

  charging the pressure accumulator, so that the mo-

  Yen seals arranged on the high pressure side of the brake pressure generator are only subjected to a comparatively low pressure load. This increases the life of the sealing means; in addition, when the brakes are in the released position, losses due to leakage likely to occur

  when the pressure accumulator drains, are noticeably ridiculous

  your. Preferably, the valve of reiticrn deressicn doxrd ue valve has seat which can close the entry communicating with the source of high pressure, which makes it possible to obtain, using simple structural means, a valve which, when the brakes are find in position

  released, permanently seals the connection between the

  pressure accumulator and the brake pressure generator and

  thus prevents a gradual increase in pressure reduction

  at the input of the brake pressure generator.

  In accordance with one embodiment of the invention, the valve for reworking the pressure valve so that the seat valve closes in the direction of flow and the control piston is subjected in the direction of valve closing, under pressure

  initial and, in the opening direction of the valve, at an elastic force

  pressure and pressure in the amplifier chamber. In order to guarantee that, when the brakes are applied, the pressure relief valve opens so that the circumstances are resolved, it can also be provided, in accordance with the invention, that the force

  elastic exceeds the pressure force exerted, in the direction of closing

  ture, on the closing element of the seat valve.

  According to another embodiment of the invention, the design can be simplified in that the control piston acts against the initial pressure and the pressure of the amplifier chamber by means of hydraulic working faces. identical. In addition, it has been found that the brake pressure generator makes it possible to obtain an interesting actuation curve and an advantageously reduced reaction force if the coefficient of

  pressure relief valve pressure equal or greater than

  less than 10 when the amplifier chamber is without pressure.

  The various objects and characteristics of the invention are-

  will now be detailed in the description which follows, made to

  -4- By way of nonlimiting example, with reference to the appended figure which represents, in longitudinal section, a hydraulic system of

  braking for a motor vehicle, comprising a pressure generator

  sion d brakes conform to the invatin eture valve of pesscn.

  The brake pressure generator shown includes a

  master cylinder 1 which can be actuated by a hydraulic amplifier

  forceful. Master cylinder 1 includes a working chamber

  3 comprising a connection bore 4 to which a first circuit is connected

  braking circuit 5 for actuating two wheel brakes 6, 7

of a motor vehicle.

  The master cylinder 1 is of conventional design and includes

  a master cylinder piston 8 which is guided in a cylindrical bore

  drique 9 so as to slide axially there, giqi supports a cup

  seal 10 and which, by means of a compression spring

  sion 11, is biased in the direction of release of the brakes. The-

  compression spring 11 is supported on a spring cup-12

  in which a valve plunger 13 is mounted, one of the ends of which

  mites (on the right in the figure) supports a closing element which cooperates with a bore 15 made in the master cylinder piston 8 to form a so-called central valve through which, when the

  brakes are in the released position, the working chamber 3

  provided with a chamber 16 connected to a pressureless reservoir 19 via a case connection 17 and a pressure line 18. In addition, the master cylinder piston 8 is provided with axial bores 20 which lead from chamber 16 at the rear of sealing tube 10 and which allow excess pressure liquid to pass from chamber 16 into the working chamber bypassing

  the lip of the sealing cup 10.

  The hydraulic power amplifier mainly comprises

  tiel, an amplifier piston 22 which is guided in a housing bore 21, the cylindrical side face of the amplifier piston being interrupted by a piston stage 23. By means of its larger diameter section, the piston amplifier 22 delimits a circumferential annular chamber 24 and, using the stage of

  piston 23, it forms, with the housing bore 21, an amber chamber

  amplifier 25. Inside the amplifier piston 22 is provided

  a closing piston 27 provided with an axial bore 26 whose port

  central tion has a shoulder forming a closure element

  valve 28 which, when the brakes are in the position

  released shown, is held in abutment against a valve seat 29

  by a compression spring 30. The closing piston 27 is

  rotated by an annular chamber 31 which is hydraulically connected to the circumferential annular chamber 24 through radial bores 32, 33. The master cylinder piston 8 is supported on the piston

  amplifier 22 via a rod 34.

  In addition, a control piston 36 which can be actuated by a brake pedal 35 is arranged in the amplifier piston 22

  and can move relative to the latter, a front panel supports

  both in this case a closure element 37 of spherical design

  that engaging in the amplifier chamber 25. In the sense of

  release of the brakes, the control piston 36 is subjected to ac-

  tion of a compression spring 38 which rests on the valve seat

  29 fixed to the amplifier piston 22. The closing element 37 co-

  operates with a valve seat 39 formed by the end of the closing piston 27 which passes through the valve seat 29. Since it is

  applied against the valve seat 39, the closing element 37 blo-

  that the opening of the axial bore 26 made in the closing piston

  27 and thus isolates the amplifier chamber 25 from the chamber 16

  which communicates with the axial bore 26 through holes 40.

  A connection bore 41 starts from the chamber 25 of the amplifier.

  force generator 2 and is connected to a second braking circuit 42 which

  allows two other wheel brakes 43, 44 to be actuated from the vehicle

  tomobile. In addition, the amplifier chamber 25 communicates, by

  via a connecting pipe 45, with a return valve

  d = tiadn e presion 46 which is implanted if link connection 47 leading from a connection bore 48, which opens into the circumferential annular chamber 24, to a high pressure source 49 which ensures

  supplying the force amplifier 2 with pressure liquid.

  The tosiom re & otia valve 46 has a seat valve 50 which closes in the direction of flow and which is provided with a closing element 51 of spherical design which cooperates with a valve seat 52 secured to the housing. . The seat valve 50 makes it possible to isolate a valve inlet chamber 53, which communicates with the high pressure source 49, from a valve outlet chamber 54 which communicates with the connection bore 48 of the amplifier. force 2. The valve outlet chamber 54 is delimited by a control piston 55

  a pin 56 of which is applied against the closing element 51.

  The control piston 55 isolates the valve outlet chamber 54 from a control chamber 57 which communicates with the connection pipe 45 and which contains a prestressed compression spring 58 exerting an elastic force on the control piston 55 in the direction of the valve outlet chamber 54, the amplitude of the elastic force

  being sufficient to overcome the hydraulic closing force ma-

  ximum able to act on the closing element 51.

  The high pressure source 49 comprises a pump 59 which is driven by a motor and which charges a pressure accumulator 61

  from the reservoir 19 through a non-return valve 60, the device

  positive pump drive can be switched on

  of the accumulator charging pressure.

  The operating mode of the braking system described is as follows:

  When the brakes are in the released position re-

  presented, the braking circuit 5 communicates, through the valve

  open central 14, 15, with the chamber 16 which is connected, by the

  through the pressure line 18, to the non-pressure tank 19. The control piston 36 is in the extreme withdrawal position in which the closing element 37 is detached from the seat

  valve 39, so that the braking circuit 42 also communicates

  ment with the chamber 16 through the open axial bore 26 and the bore..40. In the closed position, the valve closing element 28

  is applied against the valve seat 29, so that the chamber an-

  ring 31 is kept closed. The pressure in the room

  annular bre 31, in the annular -circferential chamber which precedes it and in the valve outlet chamber 54 is maintained, by in ii xde lavalve de rreitsnde pssicn 46, at the reduction level - 7 - the lowest because the chamber 57, just like the room

  of amplifier 25, is without pressure. The total accumulating pressure

  high pressure source 49 reigns only in the chamber

  input from. valve 53 and is retained there by the closed seat valve 50.

  As soon as the brake pedal 35 is actuated to initiate braking, the control piston 36 is first moved, which has the effect of pushing the closing element 37 against the valve seat 39 and isolating the chamber of amplifier 25 of chamber 16. So that pressure can be established in amplifier chamber 25 to apply the brakes, the valve closing element 28 is

  detached from its valve seat 29. To this end, in addition to the relative force

  low compression spring 30, it is especially necessary

  to overcome the hydraulic closing force produced by the appli-

  cation of a pressure on the differential surface located between the cross sections D2 and Dl. Since the pressure of the

  annular chamber 31 is significantly reduced by the over-valve

  pressure 46, the hydraulic closing force is also not very high, so that the valve closing member 28 can

  be opened by exerting a relatively weak force. As soon as the

  valve closing ment 28 is open and the annular chamber 31 is connected to the amplifier chamber 25, the pressure of the

  amplifier chamber 25 increases to push the amplifier piston

  cator 22 as well as the master cylinder piston 8 in the direction of

  operation. The amplifier piston 22 begins to move as soon as the pressure increases because, since the pressure in the circumferential chamber 24 is reduced, the friction resistance

  is weak on the sealing elements 62, 63, 64 of the piston

  planner. As soon as the central valve 14, 15 is closed, the pressure which

  prevails in the amplifier chamber 25 and in the working chamber

  vail 3 of master cylinder 1 increases to cause actuation

wheel brakes 6, 7, 43, 44.

  In addition, the pressure rise in the amplifier chamber

  cator 25 causes a reduction in the pressure reduction via the recticn valve dc pssicn46, because this pnsion57 - 8 - is added to the compression spring 58, so that the seat valve cannot adopt a closed position only if the pressure increases accordingly in the valve outlet chamber 54. Since the control piston 55 has identical working faces on both sides, the closing of the pressure relief valve is only possible if the prevailing pressure in the valve outlet chamber 54 is greater, by the value resulting from the quotient of the elastic force of the compression spring 58 by the transverse face of the piston

  control 55, to that prevailing in the control chamber 57. By cons

  sequent, the presenn 46 r6drticn valve always has tiarae to supply to

  force amplifier 2, on the input side, higher pressure

  lower, by the value indicated above, than the pressure produced in the amplifier chamber 25, which guarantees in each actuation phase a good reactivity of the pressure generator

  braking. As soon as the difference between the pressure prevailing on the

  force amplifier and that produced in the amplifier chamber falls below the value indicated above, the pressure relief valve remains constantly open. This can occur at higher actuation pressures and no longer presents

  inconvenience to the actuation process.

  When the brakes are released, the pistons and valve of the

  brake pressure generator are returned to the initial position

  tial shown, the pressures passing through the chamber 16 me-

  of the tank 19. being reduced. As this operation also

  The effect of once again removing the pressure in the control chamber 57, the reduced pressure predetermined by the elastic force of the compression spring 58 is adjusted in the valve outlet chamber 54 d lavalve de r icn d pssimn 46, which again advantageously reduces the reaction forces in the event of reactivation of the

  brake pressure generator.

- 9 -

Claims (6)

  1. Brake pressure generator for a hy-   motor vehicle braking hydraulics, comprising an amplifier piston which is intended to actuate a master cylinder of   braking to which auxiliary hydraulic pressure can be applied   binding in an amplifier chamber, comprising an actuating mechanism which cooperates with the amplifier piston and a   valve device which is intended to control the pressure aUxi-   linked and which can be actuated by a relative displacement between the amplifier piston and the actuation mechanism, and comprising   a double seat valve through which the amplifia-   tor can be connected to a pressureless tank or to a high pressure source comprising a pressure accumulator, characterized in that a pressure retaining valve (46) is located on the connection pipe (47) located between the source pressure fluid (49) and the   valve device (28, 29), the pressure in the amplifier chamber   tor (25) being applied to a control piston (55) to reduce the pressure reduction.   2. Brake pressure generator in accordance with the claim   cation 1, cats in that p: ssicn nrctn valve (46) includes a seat valve (50) which can close the communicating inlet (53) with the high pressure source.   3. Brake pressure generator in accordance with the claim   cation 1 or 2, characterized in that the seat valve (50) closes in the direction of flow, and in that the control piston (55)   is subjected, in the direction of closure of the valve, to the initial pressure   tial and, in the opening direction of the valve, to the force of a -res-   kind of. compression (58) and the pressure prevailing in the chamber amplifier (25).   4. Brake pressure generator conforming to the claim   cation 3, characterized in that the elastic force of the compression spring   pressure (58) exceeds the pressure force exerted, in the direction of   closure, on the closure element (51) of the seat valve (50). - 1O - 2604673   5. Brake pressure generator conforming to one   conch of the preceding claims, characterized in that the pis-   control tone (55) acts against the initial pressure and the pressure of the amplifier chamber (25) by means of identical hydraulic working faces.   6. Brake pressure generator conforming to one   conch of the preceding claims, characterized in that the coef-   pressure reduction factor is equal to or greater than- 10 if the   amplifier chamber (25) is pressureless.