FR2631596A1 - ANTI-LOCK REGULATION BRAKING SYSTEM FOR MOTOR VEHICLES - Google Patents

Abstract

This installation comprises a master cylinder 16 with at least one main piston 21, 22 for sending a brake pressure in at least one brake circuit I, II, a brake booster 36, which can also be used as a pressure modulator for anti-lock regulation. , with a servopiston 35 acting mechanically on the main piston 21, as well as an additional, independent modulating member 32 to modulate the braking pressure. In order to obtain a simple construction, the modulation member 32 is integrated in the master cylinder 16, so that the main piston 21 delimits a modulation chamber 31 which can be connected alternately to a pressure source 10 or to a point discharge 13 by a distributor system 33, 34. The servo piston 35 and the main piston 21 are mutually coupled, in translation, under the effect of a force.

Description

Z631596

  The invention starts from an actuated braking installation

  by a pressure fluid, from a hydraulic braking system

  liquefied or pneumatic for example, provided with an anti-

  blocking, for motor vehicles, comprising a master cylinder in which is guided at least one axially sliding main piston, serving to. send a brake pressure in at least one brake circuit, a brake force amplifier or brake booster, usable as a pressure modulator for anti-lock regulation and comprising a brake booster cylinder and a servo piston sliding in this cylinder and controlled by means of '' a brake valve by actuating the brake pedal, servo piston which acts mechanically on the master cylinder, thus

  an additional de-modulating organ - independent of the modula-

  pressure tor - to change the braking pressure, which has a modulating piston and a modulating chamber delimited by this piston and which can be connected alternately to a pressure source and to a point of discharge through a

distributor system.

  The pressure modulations produced during the regulation

  Anti-lock braking in the brake booster, used as a pressure modulator, are retransmitted, via the link between the servo piston and the brake pedal, on the latter and can be clearly perceived by the driver pressing the brake pedal. In order to reduce this reaction on the pedal, we have

  provided for an additional modulation device, independent of the modu-

  pressure regulator constituted by the brake booster, to change the brake pressure. In the case of a medium modulation range, i.e. for medium-sized pressure variations, the pressure modulation is produced exclusively

  by the modulator, while the servo piston is immobilized

  read in the axial position which it occupies at this moment, so that it cannot be moved in the direction of an establishment of

  pressure. On the other hand, in the case of a large extent of modulation-

  tion, the brake booster also comes into play as a modu-

braking pressure.

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  In a known braking system of the men-

  actuated at the start (DE-OS 36 12 793), the servo piston is connected to the main piston by means of a pressure rod which is simply applied freely against the servo piston in the axial direction. The modulating device is integrated in the brake booster. For this purpose, the modulating piston is rigidly connected to the pressure rod and shares the return chamber or opposing chamber in the brake booster cylinder, located at the end of the servo piston remote from the working chamber or pressure chamber, in two segments, of which this directed towards the servo piston forms the modulation chamber of the modulating member and is connected to the distributor system. To operate pressure modulations of a medium modulation range, the modulation chamber is relaxed or

  supplied with pressure by the appropriate control of the distribution system

  stopper, so that the modulating piston discharges or loads the main brake piston accordingly, via the pressure rod. The servo piston is then essentially decoupled from the movement of the pressure rod and retains the axial translational position it occupied before the start

anti-blocking regulation.

  In another known braking installation of the type mentioned at the start (DE-OS 34 44 828), the modulating member is

  housed in the master cylinder. The modulation piston is con-

  in this case, replaced by a second servo piston which serves to amplify

  cation of the braking force during braking and which

  delimits the modulation chamber, connected to the distributor system.

  Together with a pumping piston, the servo piston forms an assembly

  pistons arranged axially sliding on the main brake piston. The brake chamber is delimited

  by an annular end face of the pumping piston, joint-

  ment with the master cylinder. When moving in the direction of establishing a brake pressure, the pumping piston

  can drive the main piston by a complement link

  priceless forms. In the case of a pressure modulation of a medium modulation range, the main piston is blocked by the servo piston of the brake booster, hydraulically immobilized at the

2 631596

  position of axial translation which he occupied at the start of the process, while the assembly formed by the second servo piston and the pumping piston, under the effect of the system control

  valve, moves axially on the main brake piston

  cipal and thus produces a reduction or an increase in the

  brake pressure in the brake chamber.

  The invention aims in particular to avoid the drawbacks of

this state of the art.

  According to the invention, a braking installation as defined at the start is characterized in that the modulating member is integrated in the cylinder-block, so that the main piston constitutes at the same time the modulating piston and that it delimits by a piston face a cylindrical segment forming the modulation chamber in the master cylinder, and that the piston

  main and servo piston are mutually coupled, in trans-

lation, under the effect of a force.

  Such an installation has the advantage of providing a solution.

  tion technically simpler and economically more advantageous for the construction of the modulating member. The particular modulation piston is eliminated and the two-part production of the servo piston and the pressure rod in the brake booster cylinder is also eliminated. The invention also avoids a relatively complicated and expensive system of pistons arranged concentrically and movable relative to each other, similarly

  as the sealing problems posed by such a system. Comparati-

  With a main piston for a braking system operating without an additional modulating member, it suffices to make the main piston so that pressure can be applied.

  applied to its rear side away from the brake chamber.

  Other characteristics and advantages of the invention

  will emerge more clearly from the following description of a

  nonlimiting exemplary embodiment, as well as the single figure of the appended drawing which is a schematic representation of a hydraulic braking installation with anti-lock regulation for

a motor vehicle.

  The drawing schematically represents a hydraulic braking installation according to the invention, which is supplied by a hydraulic accumulator 10 charged to a predetermined pressure by a hydraulic pump 12 driven by an electric motor 11. The driving torque for the pump 12 can be also provided by a drive device present in any case in the vehicle, for example by the engine thereof, with the interposition of a transmission, for example belt. The pressure fluid, in this case brake fluid, is sucked by the pump 12 into a reservoir 13, into which the fluid then returns via various return lines. The braking installation comprises two brake circuits I and II which are separated from each other and are each supplied from a separate braking chamber 14 or 15 from a master cylinder 16. The circuit braking I delivers the braking pressure to the right front wheel VR and to the left rear wheel HL, while the braking circuit II supplies the left front wheel VL and the right rear wheel HR. Solenoid valves 17 to 20 for maintaining the brake pressure are "interposed in known manner in the brake lines leading to the cylinders of

  front and rear wheel brake.

  Two main pistons 21, 22 - in each of which a filling valve 23 or 24 is integrated - are arranged

  axially sliding one behind the other * in the master-

  cylinder 16. Each of the main pistons 21, 22 delimits a braking chamber 14 or 15 which can be filled with pressure fluid, through the coordinated filling valve 23 or 24, from a feed tank 25 which is in communication with the reservoir 13. When the main pistons 21, 22 have moved over a preset distance, the filling valves 23, 24 are closed, which cuts the connection with the feed tank 25. Each of the main pistons 21, 22 is loaded by a return spring 26 or 27 which rests on a stop 28 or 29 secured to the body of the master cylinder and tends to push the main coordinated piston 21 or 22 to its starting position. While the second main brake piston 22 is pressed by the spring of

  reminder 27 against the stop 28 - integral with the body of the master-

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  cylinder - for the return spring 26 acting on the first.

  main braking piston 21 and the second piston delimits the first braking chamber 14 by its end face 221, the first piston 21 is pressed by its return spring 26 against an axial plunger 30 which penetrates one end of the master -cylinder 16. The end face 211 of the first main piston 21 and the end wall 161 of the master cylinder delimit between them a cylindrical segment - from inside the master cylinder - which forms a modulation chamber 31 d 'A modulating member 32 intended to modulate the brake pressure during anti-lock regulation. The modulation chamber 31 is retained through a first controlled valve 33 to the reservoir 13 and it can be connected through a second controlled valve 34 to the hydraulic accumulator 10. The two valves 33, 34 are produced in the form of solenoid valves with two tracks and two positions; in the starting position or non-excited position, the first tap 33 is open and

the second tap 34 is closed.

  The pusher 30, axially movable through the end wall 161 of the master cylinder 16, wall in which this

  pusher is liquid-tight, is rigidly connected to a servo

  piston 35 forming part of a brake booster 36 which is assembled in an assembly with the master cylinder 16.- The servo piston 35 can

  slide axially and is guided in a cylinder 37 of the servo

  brake, which is connected in the direction of the axis to the master cylinder

  16. At its starting position shown in the drawing, the servo

  piston 35 is applied against a stop 38, integral with the body of the assembly, by the pusher 30 urged by the main piston 21. By its end 351 shown on the right in the drawing, the servo piston 35 delimits a pressure chamber or work 39, while its end 352 shown in

  left delimits an opposing room or reminder room 40.

  A brake valve 41, mechanically controlled by a brake pedal 42, is integrated in the servo piston 35. The valve 41 connects the working chamber 39 alternately to the reservoir 13 and to the accumulator 10. In known manner, the brake valve 41 is provided with a distribution drawer 44, having several holes

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  distribution, which is connected by a push rod 43 to the brake pedal 42 and is loaded, against a displacement produced from the pedal 42, by a weak return spring 45. The structure and the operation of the brake valve 41 are known and are described in detail in document DE-OS 34 44 828

for example.

  The brake booster 36 serves as a pressure modulator in the case of anti-lock regulation; for this purpose, its return chamber 40 can either be connected to the reservoir 13 or to an outlet 52 of the working chamber 39, or be closed by a configuration or distribution device composed of three controlled taps

  46, 47 and 48. Each of these taps is made up of an electro-

  two-way, two-position valve. The two taps 46 and 47

  are open to their starting position, where they are not excited.

  Tap 46 contains a constriction. The controlled valve 48 is closed at its starting position. It should also be noted that one of the tap connections 34 used in the working position or

  excitation of this tap, is not connected directly to the battery

  hydraulic mulator 10, but at the outlet 52 of the working chamber 39 of the brake booster 36 and which it communicates through this

chamber with accumulator 10.

  The braking installation which has just been described functions

as explained below.

  When the brake pedal 42 occupies its starting position, the return spring 45 maintains the drawer 44 in its starting position. The working chamber 39 of the brake booster 36 is connected through the distribution bores of the slide valve 44 and through a flow orifice 49 of the cylinder 37 of the brake booster to a return line (shown in dashed lines in the drawing) which opens into the reservoir 13. The actuation of the brake pedal 42 produces

  first, via the push rod 43, the

  ment of the drawer 44, which cuts the communication between the working chamber 39 and the flow orifice 49 and on the contrary establishes the connection of the working chamber 39 with an inlet 50 which is connected by an inlet pipe to the accumulator 10. Pressure fluid from the accumulator 10 now flows into the 7- working chamber 39. Part of the fluid flows through the non-return valve designated by 51 towards the outlet 52 of the chamber 39, outlet to which the controlled valve 34 is connected, occupying its closed position. Under the effect of the pressure established in the working chamber 39, the servo piston 35 is moved to the left, in the representation of the drawing, so that its pusher

  moves the main piston 21 in the same way. Moves it

  The servo piston 35 continues as long as the working chamber 39 remains connected to the accumulator 10. It stops when the drawer 44 cuts this connection as a result of its movement by

compared to servo piston 35.

  After translation over a short distance, the filling valve 23 in the main piston 21 is closed. The braking pressure being established in the braking chamber 14, moves the second main piston 22 in the same direction, so that the filling valve 24 also closes and a braking pressure is also established in the second chamber 15. The two brake pressures are sent to the two brake circuits I and II, therefore to the brake cylinders.

wheels.

  When, after the start of braking, the brake pedal 42 is applied with too much force, so that the wheel brakes are applied too tightly, causing the undesired slipping of one or more wheels, the anti-lock control between in action. The detection of the slip of one or more wheels by sensors, not shown, causes the generation of control signals for the distribution system composed of valves 33, 34 and 46, 48. The first control signal causes the switching of all the valves ordered. In the return chamber 40, a pressure is then established which displaces the servo piston slightly to the right in the drawing. Similarly, there is established in the modulation chamber 31, through the valve 34, a pressure which allows only a smaller movement of the main piston 21 in the same direction, therefore to the right in the drawing. The mutual coupling - produced by force - of the servo piston 35 and the main piston 21 is thus

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  deleted. Switching of the controlled valve 48 causes the

  ture of the return chamber 40, so that the servo piston 35 is locked in the translational position which it occupies at this time, because the pressures in the working chamber 39 and in the OS return chamber 40 are the same. The slippage of the wheel or wheels is compensated for, that is to say stopped, by modulations of

  pressure triggered in the modulation chamber 31 by the action-

  simultaneous operation of the controlled valves 33 and 34. Thus, the pressure in the modulation chamber 31 can be reduced and increased by pulses while the servo piston 35 and the brake pedal 42 are stationary, so that the braking pressure sent from pedal 42 finally decelerates without

vehicle slipping.

  During this anti-lock regulation, the braking pressure maintenance solenoid valves 17 to 20 connect only to the braking chambers 14, 15, at times, the wheel brake cylinders coordinated with wheels whose slip or risk of slip has been detected. The other wheel brake cylinders are cut off from the brake chambers 14, 15, during anti-lock regulation, by the solenoid valves 17 to 20 which have been

  switched to the brake pressure maintenance position.

  If the lowering of the braking pressure achievable by the modulating member 32 is not sufficient, the brake booster 36 is put into action as an additional pressure modulator. The valve 48 is then switched back to its passage position, with the result that an increasing return pressure is established in the return chamber 40 of the servo piston, pressure which displaces the latter in the direction of the reduction of the efforts of braking, so to the right in the drawing. The

  pusher 30 is removed in the same way, which allows movement

  most importantly of the main pistons 21, 22 in the direction of

  reduction of brake pressure.

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Claims (6)

  1.-Antilock regulation braking system for motor vehicles, comprising a master cylinder in   which is guided at least one axially sliding main piston   sant, used to send brake pressure to at least one brake circuit, a brake force amplifier or   brake booster, usable as a pressure modulator for the regulation   anti-lock and comprising a brake booster cylinder and a servo piston sliding in this cylinder and controlled by means of a   brake valve by actuating the brake pedal, servo   piston which acts mechanically on the master cylinder, as well as an additional modulating member - independent of the pressure modulator for changing the braking pressure, which has a modulation piston and a modulation chamber delimited by this piston and which can be alternately connected to a source of   pressure and to a point of discharge through a distribution system   tor, characterized in * that the modulating member (32) is integrated in the master cylinder (16), so that the main piston (21) constitutes at the same time the modulating piston and which it delimits by a piston face (211) a cylindrical segment   in the master cylinder (16), segment which forms the modulus   lation (31), and that the main piston (21) and the servo piston (35) are mutually coupled, in translation, under the effect of a strength.   2. Installation according to claim 1, characterized in that the distributor system comprises two controlled taps (33, 34) of which the first (33) is closed at its working position, where it is excited, and the second of which (34) is closed at its starting position, where it is not excited, that a connection of each of these   two commandls taps (33, 34) is connected to the master segment   cylinder (16) forming the modulation chamber (31), that the other connection of the first valve (33) is connected to a discharge point (13) and that the other connection of the second valve (34)   is connected to a pressure source (10). 631l596   3. Installation according to claim 1 or 2, character-   in that the servo piston (35) carries a plunger (30) extending   axially into the master cylinder (16) and the main piston (21) is pressed against the end of the pusher   (30) by a pressure spring (26).   4. Installation according to any one of the claims   1 to 3, characterized in that the servo piston (35) shares the interior   of the brake booster cylinder (37) into a working chamber (39), the pressure of which is controlled by the brake valve (41) and a return chamber (40) which can be selectively connected to the working chamber (39) or at a discharge point (13) by means   a distribution device (46-48). -   5. Installation according to claim 4, characterized in that the brake valve (41) is integrated in the servo piston (35) and is coupled to the brake pedal (42) for the selective connection of the working chamber ( 39) at the pressure source   (10) or at a discharge point (49, 13).   6. Installation according to any one of the claims   2 to 5, characterized in that the connection of the second valve (34) to the pressure source (10) passes through the working chamber (39) of the brake booster (36).