FR2606348A1 - HYDRAULIC BRAKE SYSTEM WITH A BRAKE AND TRACTION SLIDING CONTROL DEVICE FOR A MOTOR VEHICLE - Google Patents

Abstract

THIS SYSTEM INCLUDES A BRAKE PRESSURE GENERATOR 1-12-17 PEDAL ACTED AND CONSISTS OF A BRAKE MASTER CYLINDER 1, A DRIVE AMPLIFIER 12 AND A PRESSURE SOURCE 17, AND ALSO INCLUDES 22-23-25-26-27-28 VALVES ASSOCIATED WITH THE VL-VR-HA WHEEL BRAKES, THESE VALVES BEING CONTROLLED BY THE SLIP CONTROL DEVICE. FOLLOWING THE INVENTION, THERE IS PROVIDED, MOUNTED DOWNSTREAM FROM THE PRESSURE SOURCE 17, A PRESSURE REDUCTION VALVE 32 WHICH IS CONTROLLED EITHER BY THE PRESSURE IN CHAMBER 15 OF THE AMPLIFIER, OR BY THE PRESSURE IN THIS CHAMBER 15 OF THE AMPLIFIER BECOMES WEAK BY A PREFIXED FORCE SUCH AS THE PRESSURE IN THE OUTPUT CHAMBER 31 OF THIS PRESSURE REDUCING VALVE 32 CORRESPONDS EITHER TO THE PRESSURE IN CHAMBER 15 OF THE AMPLIFIER, OR TO A PRESSURE EQUIVALENT TO THIS PREFIXED FORCE.

Description

The present invention relates to a hydraulic braking system

  comprising a brake and traction slip control device for use on a motor vehicle and having a brake pressure generator actuated by a pedal and consisting of a brake master cylinder, a brake booster force and a source of pressure, and also includes valves associated with the wheel brakes,

  these valves being controlled by the slip control device.

  DE-A-3338826.1 discloses a braking system

  including slip control in which at least the cy-

  wheel lenght of the driving wheels communicate with the working chambers

  brake master cylinder, and in which, in the case of a

  braking glide, these working chambers communicate with the amplifier chamber via an inlet chamber, whereas in the case of traction slip

  communicate directly with the pressure source.

  In order to ensure a pressure supply of the type indicated above,

  above, a combination of three 2-way / 2-way valves (per

  example 4 of the cited patent application). The need for valves is

  important, which implies the risk that, in the event of a valve failure, the desired pressurized fluid

slip regulation.

  This is why the present invention aims to reduce the need for

  care in valves. Moreover, in the case of a regulation of the slip of

  traction, it must be possible to have a braking pressure which is

  dependent on the pressure fluctuations of the potential pressure source

  exist. It is also planned to achieve this result without

additional ves.

  For this purpose, the subject of the invention is a hydraulic braking system of the type in question, characterized in that a pressure reduction valve is provided downstream of the pressure source and is controlled either by pressure ruling in the amplifier chamber,

  either - if the pressure in this chamber of the amplifier becomes low -

  by a prefixed force such as the pressure prevailing in the chamber of

  output of this pressure reduction valve corresponds either to the pressure

  amplifier chamber, or at this prefixed force.

  In the practice of the invention, it may be advantageously provided that the configuration of the pressure reduction valve is such that the end face of the valve piston delimits, on one of its sides, the control chamber, while it is the front face of the control piston which delimits it on the other side, whereas a force prefixed, for example a force exerted by a spring, is applied on the face of this

  control piston which is turned away from the control chamber.

  In order to allow the control piston to act on the valve piston, if there is no pressure in the control chamber, or only a low pressure, a pushbutton can be provided by means of which the piston of

  control can be placed in abutment on the valve piston, so as to allow

  put for example the spring force to act on this valve piston.

  In order to ensure that, in the case of the lowest possible pressures prevailing in the control chamber, the control piston is pushed away from the valve piston, it can be expected that the size of the front surface of the this control piston is larger than the one

  of the front surface of the valve piston.

  Advantageously, the piston can be in the form of

  me of a shutter cone, whose converging face is integral with a guide piston. Its conical surface can be placed in abutment on a sealing seat, while the base of the sealing cone projects into the outlet chamber and the converging portion of this closure cone delimits

  with the guide piston the inlet chamber.

  In order to be able to submit to a leak test. the seal of the valve piston, it is possible to provide a stepped piston which can be placed in abutment on the valve piston by its smallest stage and limit the control chamber by its largest stage, while the interstage chamber communicates with the tank without

pressure.

  In order to safeguard a pressure supply at least

  drive wheels in the case of slippage control, the control valve

  pressure ducting is provided between the pressure source and a main valve, this main valve opening, in the case of slip control, so as to send the pressure, through an inlet chamber, into the chambers at which the cylinders are connected at least

brakes driving wheels.

  For this purpose, advantageously, the inlet chamber of the pressure reduction valve is connected to the pressure source, while the outlet chamber is connected to the main valve and the chamber

  control is connected to the amplifier chamber.

  Other features and advantages of the invention will emerge

  of the following description, by way of non-limiting example and in re-

  in the accompanying drawing in which, for a particular embodiment of the invention, the figure is a sectional view of the master brake cylinder, the amplifier coupled upstream thereof and the reduction valve.

  of pressure, with their incorporation into a braking system.

  The brake pressure generator comprises a brake master cylinder 1 in the bore 2 of which are guided two pistons 3 and 4, which thus forms two working chambers 5 and 6. It is provided, interposed with

  upstream of these working chambers 5 and 6, an entrance chamber 7 which

  with these working chambers via central valves

  8, 9 and sealing cups 10, 11 acting as anti-leaking valves

return.

  A braking force amplifier 12 is coupled upstream of the master cylinder 1. An amplifier piston 13 is guided in a bore 14 which, by its face facing away from the master cylinder, defines the chamber

amplifier 15.

  This amplifier chamber 15 communicates, via a pressure control means 16, with the pressure source 17 which

  is essentially composed of a pump 18 and an accumulator 19.

  Front wheel brakes communicate via

  20, 21 with the working chambers 5, 6 of the master cylinder.

  brake liner, electromagnetic valves normally open 22, 23 being interposed in these pressure lines. The brake cylinders of the rear wheels communicate via a pipe 24 with the

  amplifier chamber, a normally open valve 25 being

posed on this conduct.

  The brake cylinders of the wheels are connected to a fuel tank.

  thought 29 through the normally closed magnetic valves

26, 27, 28.

  The inlet chamber 7 is connected, via the main valve S30, either to the compensation tank 29, or to a chamber of

  output 31 of a pressure reducing valve 32.

  This pressure reduction valve 32 comprises a piston of

  The guide piston 35 is guided in a sealed manner in a bore 36 of the valve housing 37. The conical surface 38 may be sealingly disposed in abutment.

  on a sealing seat 39. The inlet chamber 40 of the reduction valve

  a controllable pressure relief 32 is provided between the piston of

  35 and this conical surface 38. This inlet chamber 40 communicates with

  than directly with the accumulator 19.

  The base surface of the cone protrudes into the outlet chamber 31 which as explained above - communicates with the valve

main 30.

  It is provided, coupled to the guide piston 35, a stepped piston 41 which is such that it is arranged a chamber between its stages 42 which communicates

  with the compensation tank 29.

  This stepped piston 41 defines a control chamber 43 which is

  killed in another bore portion 44 of the housing 37 and which is delimited by the control piston 45. This control chamber 43 communicates with the chamber 15 of the force amplifier 12. The control piston 45 acts on the valve body 33 via a pusher 46 and the piston

  Step 41. A force is applied to this control piston 45 by means of a

  Compression lot 47 which bears on the bottom of the case.

  The brake system and the pressure reduction valve work as follows: In the case of a deceleration in which there is still no need for slip control, some pressure develops

  in the amplifier chamber 15 via the system of con-

  brake pressure control 16 which acts on the pistons 3 and 4 by

  intermediate of the amplifier piston 13, which leads to the development

  some pressure in working chambers 5 and 6.

  Via the open valves 22, 23, 25, the pressure

  these working chambers 5, 6 and in the amplification chamber

  15 is transmitted to the wheel cylinders.

  At the same time, the pressure also develops in the control chamber 43 of the reduction valve 32 as this chamber communicates with the amplifier chamber 15. The control piston 45 is thus pushed back against the the force of the spring 47, away from the stepped piston 41, and therefore the valve piston 33. Therefore, the pressure from the amplifier chamber 15 is applied to the valve piston as a function of the surface transverse of the bore 36, which causes the valve seat 39 to exit from this valve piston 33 by its surface 38, to such an extent that it develops in the outlet chamber 31 a

  pressure corresponding to the pressure prevailing in the amplification chamber.

  tor. This pressure is sent to the main valve 30 interconnecting the inlet chamber 7 and the compensation tank 29, which valve is

in its closed position.

  In the event of an imminent blockage, for example of the left front wheel, this tendency is recorded by a detector (not shown), while a slip control device (not shown) causes the valve 22 to move to its position. lock and the valve 26 in its position

  open, thereby allowing pressurized fluid to flow out of the cylinder.

  wheel brake drum to the compensation tank 29 to enable

  be a reduction of the pressure in this wheel brake cylinder. This will re-accelerate the wheel and prevent this wheel from blocking. To achieve a

  further deceleration of the wheel, the valves 20, 22 return to their position.

  initially, so that pressure is again applied to the cylinders

  brake wheels. To compensate for the loss of fluid under pressure, it is necessary to connect the wheel brake cylinders directly to the pressure source. This is achieved by a new change of position of

  the main valve 30 so that the pressurized fluid flows

  holding the accumulator 19 into the working chambers 5, 6, via the pressure reducing valve 32 of the inlet chamber 7 and respectively the sealing cups 10, 11 and central valves

  8, 9. The pressure to which the fluid under pressure is subjected is

  undermined by the reduction valve and the pressure of the

indicator 15 provided.

  In the case of traction slip control, the function

  the system is as follows:

  As the brakes are not actuated, no pressure is

  veloppe in the amplifier chamber 15, and therefore in the chamber

  The piston 45 is displaced by the force of the spring 47 so as to come, with its pusher 46, in abutment with the stepped piston 41. The latter transmits the force of the spring to the valve piston 33. A pressure corresponding to this spring force is

  therefore develops in the outer chamber.

  If the slip control device now detects the fact that, for example, the left front wheel tends to pack, first the valves 22, 26 change position and the main valve 30

  opens, so that the reduced pressure of the accumulator

  described above, in work rooms 5, 6 through

  6. Due to the return of the valve 22 to its previous position, the reduced pressure of the accumulator is applied to the wheel brake cylinder of the left front wheel. Due to the closing and opening of the valves 22, 26, this left front wheel always suffers

  deceleration to the extent that we are just avoiding a package

this wheel.

  Thanks to the pressure reduction valve 32, one thus obtains that,

  in the case of brake slip regulation, a pressure corresponding to

  at the pressure prevailing in the amplifier chamber 15 is made

  available for wheel brakes, whereas in the case of traction slip control, the reduced pressure of the accumulator

  is fur.ie to these wheel brakes.

IDIJÄCATIONS

  1. Hydraulic brake system comprising a device for

  brake and traction slip regulation for use in a motor vehicle comprising a brake pressure generator (1-12-17) operated by the pedal and comprising a brake master cylinder (1), a force amplifier (12) and a pressure source (17), and which also has associated valves (22-23-2526-27-28)

  the wheel brakes (VL-VR-HA), these valves being controlled by the

  sliding control device, characterized in that a pressure reduction valve (32) is provided downstream of the pressure source (17) and is controlled by the pressure in the chamber (15).

  of the amplifier, or - if the pressure in that chamber (15) of the

  plyer becomes weak - by a prefixed force such as pressure

  in the outlet chamber (31) of this pressure reducer valve

  sion (32) corresponds either to the pressure of the chamber (15) of the ampli-

  tor, at a pressure equivalent to this prefixed force.

  Braking system according to Claim 1, characterized in that the control chamber (43) of the pressure reducing valve (32) is defined on one of its sides by the valve piston (33). and is delimited, on its other side, by the control piston (45), whereas a force prefixed, for example a force exerted by a spring, is applied on the face of this control piston (45) which is turned the opposite of the

control room.

  Braking system according to Claim 2, characterized in that, by means of a pusher (46), the control piston (45) can

  be placed in abutment with the valve piston (33).

  Braking system according to any one of claims 2

  or 3, characterized in that the front surface of the control piston (45)

  is larger than the front surface of the valve piston (33).

  Braking system according to one of claims 2

  at 4, characterized in that the valve piston (33) consists of a guide piston (35) and a valve cone (33) whose converging face is

  integral with this guide piston and whose conical surface (38) is sus-

  it can be placed in abutment on a sealing seat (39).

  Braking system according to claim 5, characterized in that the base of the closing cone (33) protrudes into the outlet chamber (31) and the convergent portion of the closing cone (33) delimits with the

  guide piston (35) the inlet chamber (40).

  Braking system according to any one of claims 2

  to 6, characterized in that a stepped piston (41) is capable of being placed in abutment on the valve piston by its smallest stage and delimits the

  control room (43> by its largest floor, while the room

  between stages (42) communicates with the tank without pressure.

  Braking system according to any one of claims 1,

  6 or 7, characterized in that at least the wheel brake cylinders of

  drive wheels communicate with the work chambers (5, 6) of the master

  brake cylinder, while, via an inlet chamber (7) 10 and a main valve (30) opening in the case of brake or traction slip regulation, these work rooms communicate

  with the pressure reducing valve (32).

  9. Braking system according to claim 8 taken in combination

  sound with one of claims 6 or 7, characterized in that the valve

  (30) communicates with the outlet chamber (31) of the pressure reducing valve (32), the inlet chamber being connected to the pressure source (17) and the control chamber (43) being connected to bedroom

amplifier (15).