FR2565186A1 - Brake servo valve with antiskid control - Google Patents

Abstract

The open brake circuit is controlled directly by the pedal operated control valve and links the servo pressure to the brakes. The closed circuit is operated in the anti-skid control via a control solenoid valve with a pressure control on a master piston. The pressure modulation in the closed brake circuit is via a control circuit. This has an additional cylinder adjacent to themain brake cylinder and has a control piston mechanically linked to the master brake piston by a thrust rod.

Description

 The present invention relates to a brake booster and in particular a multi-circuit brake booster with an affected anti-lock device (ABS), a racing simulator and a brake valve for applying pressure from a source.

 Boosters, including those with several circuits, are well known (patent applications of the Federal Republic of Germany published under the numbers 25 31 264, 29 25 478 and 31 51 292). These known booster brakes are produced with a closed braking circuit and a second braking circuit usually open. The open braking circuit is charged directly by the accumulator pressure from a source, applied by a control or braking valve. If the pressure source fails, the open braking circuit becomes a closed braking circuit. The open brake system usually includes an annular piston, mounted on a plunger actuated by the brake pedal.

 There is a need for brake booster inserted in the ABS concept with an anti-blocker (ABS), so as to be usable also for ABS functions, at least indirectly, in the form of an integrated component, thus making it possible to produce a mixed "brake booster" system. "(ABS integrated) at significantly reduced costs and equipment, for acceptable anti-blocker power.

 According to an essential characteristic of the invention, in the case of at least two braking circuits, namely an open braking circuit (II), to which the pressure of a braking valve (18) is applied, and a circuit closed braking (I), ABS pressure regulation takes place in said closed braking circuit by the controlled action of a pressure on its piston (3) to control the cylinder. Ie brake booster according to the invention has the following advantage: at least some of the ABS regulation functions - pressure increase, pressure maintenance and / or pressure drop - are transferred to the brake booster, which thus has a dual function.

The invention has the following particular advantage: in the case of the pressure drop resulting from an appropriate ABS signal, the corresponding piston of the master cylinder is pushed back into the brake booster by an appropriate intensity control force, produced by the application of the fluid under the pressure of the accumulator, so that the speed of reduction of the pressure is higher in the case of ABS, in particular at low braking pressures. In addition to the braking pressure, the force exerted by a spring is a return component usually acting on the movement of the piston; these two components can however be relatively low in the low pressure range, so that the resulting pressure drop speed is too low for ABS regulation, in particular at low temperatures. The invention remedies this and provides in this case special case an additional auxiliary piston, integrated into the brake booster and acting by an appropriate additional force on the movement of the master cylinder piston.

 The invention also has the following advantage: also for low pressures, the pedal push-button is produced and arranged with respect to the master cylinder piston reacting to ABS control signals so as to produce a contact on the modulation range pressure, thus making it possible to obtain, if necessary in ABS, direct pressure modulation for reaction on the pedal plunger and consequently on the brake pedal. The driver of the vehicle thus receives direct information via the brake pedal on the intervention of ABS regulation functions.

 The invention also has the advantage of being protected against faults and of not having any opening of closed braking circuits, even for ABS functions. A failure of the pressure source produces a multiplication discontinuity, but the failure of the open circuit does not entail any appreciable reduction in the pedal stroke. Another advantage lies in the locking of the pedal push-button and the primary piston, which is crossed by said push-button and assigned to the open braking circuit, to which a brake valve directly applies pressure from the source.

The invention provides a perfectly functional combination of brake booster and ABS with an acceptable power of all the components and simultaneously a significant reduction in the number of components.
ABS required, including speed sensors and electromagnetic valves, and where appropriate also control channels, while fully maintaining stability, maneuverability and safety braking stroke. The invention is applicable both to a conventional division of the braking circuits, that is to say separately for the front and rear axles, and to a division of the braking circuits diagonally, in which for example the brake cylinders of the front wheel are assigned to different brake circuits.

 The control of the pressure modulation for ABS can be carried out according to known regulation algorithms and can be supplemented if necessary by signals from stroke sensors, detecting the translation of the pistons of the master cylinder for regulation.

 A preferred exemplary embodiment comprises a sequential control valve in the case of separate regulation of the rear axle, the two wheel brake cylinders of which are thus regulated by a single channel; on the other hand, in the event of failure of the braking circuit supplying the pressure for this regulation, a valve reversal is produced mechanically by probing the piston of the master cylinder of said circuit, so as to be able to apply at least the full wheel to a rear wheel brake pressure of the second brake circuit.

 Other characteristics and advantages of the invention will be better understood with the aid of the detailed description below of exemplary embodiments and of the appended drawings in which FIG. 1 is the schematic section of a first exemplary embodiment of a booster according to the invention with external control valve; and FIG. 2 shows a second embodiment of a brake booster for producing the four-channel EBS for dividing the braking circuits diagonally.

 ! .a re 1 represents a brake booster with a tandem master cylinder 10 with two circuits, coaxially which is disposed a pusher 12 actuated by a brake pedal 11. The tandem master cylinder 10 is stepped, but may also include a bore of constant diameter for the two pistons 13 (of the closed brake circuit I) and 14 (of the open brake circuit II). The entire device shown in FIG. 1 includes a pressure source 20, the hydraulic booster 30 and a group of valves 40 mounted downstream of the booster for carrying out regulation functions. ABS, the pressure supply between the booster and the various wheel brake cylinders front left (VL), front right (VR) and towards the rear axle (HA), or separately for the right rear (HR) and the rear left (HL), s' even performing in the case of normal braking by the electromagnetic valves ABS of group 40, reversed on the passage position in this case. The electromagnetic ABS valves are produced, unless specified below, so as to adapt appropriately, depending on the condition of the road surface or the behavior of the wheels, the braking pressure in the two circuits (I) and (II), with division, if necessary, at the brake cylinders of the various wheels, using an electronic control circuit. logic to which the input signals of at least one wheel sensor are applied.

 It goes without saying that the example of brake booster shown in Figure 1 does not limit the application of the invention, which is on the contrary applicable to all possible embodiments of brake booster racing simulator, in which a reduction in the fluid pressure in the event of ABS intervention is possible by controlled retraction of a piston of the master cylinder.

 The rear or primary piston 14 of the master cylinder 10 is annular and ttaversed by a pusher 12 which the brake pedal actuates by means of a plate 15. The annular piston is movable in the corresponding part of the master cylinder and delimits by its inner face a first pressure chamber 16, which a channel 17 connects to a brake or control valve 17 of the brake booster. In the embodiment shown, the control valve 18 is external to the axis of the tandem master cylinder 10, but parallel to the latter. The operation of the control valve and of the pedal plunger is carried out by the brake, by means of the plate 15, on which is further fixed a pin 19 which can interact with a first position monitoring switch 52 to determine the position of the pedal. The plate 19 also serves as a support, by the intermediary of a racing spring 21, to a slide 22 with elastic support for the operation of the control valve 18, so that the known function of a racing simulator is obtained in this case by the application of the pressure from the accumulator from the source 20 to the working chamber 16 of the open braking circuit II. The pressure source 20 comprises a pump 23 and an accumulator 24, and is connected to the brake valve 18 by a hydraulic connection pipe 25 and a non-return valve 26.

 The front piston 13 of the master cylinder of the closed braking circuit I, in the initial position shown in the figure, keeps a connection open (breather 27) between a reserve or make-up container 28 and its chamber 29 in the master cylinder . This chamber is connected by a hydraulic pressure line a to the closed braking circuit I.

 According to another important characteristic of the invention, means are provided for the rapid return of the piston 13 to master the cylinder of the closed braking circuit I in the case of the intervention of ABS regulation functions, and are advantageously made so that the full pressure of the accumulator acts on an active surface, assigned to the piston 13 of the master cylinder, for the rapid return and the corresponding pressure reduction in the various wheel brake cylinders connected to the closed brake circuit I.

 The exemplary embodiment shown comprises an auxiliary circuit 31 for applying the pressure of the accumulator; this circuit consists of an additional pressure chamber 32, disposed on and preferably integrated into the tandem master cylinder 10, and in which an auxiliary piston 33 is held by a banded spring 34 in the position shown. The auxiliary piston 33 carries an extension 35 in the form of a rod which passes through a partition 36, disposed between the chamber 29 of the master cylinder and its pressure chamber 32, and live applied at 37 on the piston 13 of the master cylinder.

The auxiliary circuit is completed by an electromagnetic reversing valve 38 which is arranged in the vicinity of the group of valves.
ABS 40 and produced so as to apply, in the event of a desired pressure drop in the braking circuit I, full pressure from the accumulator to the pressure gauge 32 by a pipe 25 'for bypassing the pressure of the accumulator.

 In the usual way for normal braking, the pressure applied to the primary pressure chamber 16 by the brake valve 18 loads the piston 13 of the master cylinder of the closed brake circuit I; an extension 12a of the pedal plunger is simultaneously placed at a small distance from a posterior pressure piece 13e of the piston 13 of the master cylinder, so that in the event of failure of the source, a pressure can be established at least in the closed braking circuit I for emergency braking.

 The constitution and arrangement of the group 40 ABS control valves are as follows. The open braking circuit II contains an electromagnetic distributor 3/3 39 which, taking into account the particular suitability of the assembly according to FIG. 1 for the conventional division of the braking circuits, is responsible in this case for the joint realization of the three functions of different ABS regulation for the rear axle HA.A single reversing valve, i.e. a 2/2 electromagnetic distributor 41a, 41b, is provided for each front wheel brake cylinder VL and VR; the electromagnetic valve 38 switching the auxiliary circuit of the control piston is finally a 3/2 electromagnetic distributor, produced consequently so as either to apply the pressure of the accumulator to the pressure chamber 33 of the auxiliary circuit, or - in the case normal braking - to connect this pressure chamber to the return line.

 It is superfluous to specify the ABS regulation functions of the rear axle, which take place in a known manner. When an ABS control signal for a drop in pressure appears in the closed brake circuit I, the 3/2 electromagnetic distributor 38 is reversed in the auxiliary circuit and the pressure of the accumulator acts on the auxiliary piston 33, which pushes back then the master cylinder piston 13 of said braking circuit with an appropriate force and speed, so as to produce the desired pressure reduction.

It goes without saying that, according to the ABS control signals, the pressure reduction can be carried out in the two control channels, in which case the 2/2 electromagnetic distributors remain in the passage position, or in a single channel, the distributor electromagnetic 2/2 corresponding 41a or 41b then being inverted on the holding position. It can thus be seen that the three ABS regulation functions can be performed separately for each front wheel brake cylinder VL and VR, with a view to a desired modulation of the pressure and by integration of the brake booster, that is to say in the case of the exemplary embodiment according to FIG. 1 in the direction of a three-channel ABS with a conventional division of the braking circuits.

 It goes without saying that the analog or digital output signals of the position sensor S2 and of the position sensor S1 assigned to the piston 13 of the master cylinder can be used for the determination of the pressure modulation operations and / or the detection of brake circuit failure.

It is furthermore within the scope of the invention to close the primary side of the piston 13 of the master cylinder with respect to the pressure chamber 16, using a partition crossed for example by an extension of the pedal plunger. , and to apply pressure in another way to the additional pressure chamber thus formed on the primary side of the piston 13. A preferred embodiment finally consists in locking the annular piston 14 and the pedal push-button 12 which passes through it in the event of failure of the accumulator pressure and as a function of the latter, for example by providing locking means with radial, direct mobility or by means of additional adjustment pistons subjected to the action of the pressure of the accumulator, and establishing for safety of connection a link between the annular piston and the pedal pusher 12 in the event of defect of the pressure of the accumulator, which reaches the annular piston by an a2 channel internal to the rps
In the exemplary embodiment shown, and for low pressures, the master cylinder piston 13 comes into contact with the pedal plunger when the auxiliary piston acts on said piston 13 in the direction of reducing pressure, consequently ABS regulation functions; 1 results in a pressure modulation directly detectable by the driver in the form of a corresponding vibration of the brake pedal, when the driver keeps the brake valve 18 depressed and the intervention of the ABS regulation functions applies the end rear of the master cylinder piston 13 on the extension of the pedal plunger.

 In the exemplary embodiment according to FIG. 2, the principle of constitution of the brake booster is identical to that of the exemplary embodiment according to FIG. 1, so that a detailed description is superfluous. The same references are used for the same parts having identical functions.

 The group 40 'of ABS valves is different and is suitable by its realization with four channels for the division of the braking circuits in diagonal The distribution of the channels can be carried out as indicated on the outputs of the pressure lines of the group of valves 40', i.e. the 3/3 electromagnetic distributor 39 'is used for the regulation of the right front wheel brake cylinder (VR) and the output of the electromagnetic distributor 2/2 41a' directly modulates the pressure of the wheel brake cylinder front left (VL). The parallel derivation then again contains another 2/2 41bu electromagnetic distributor, connected to the braking circuit I and responsible in this case for all of the ABS regulation functions for maintaining and raising the pressure on the axle. The pressure applied by the brake circuit I is transmitted to the rear wheel brake cylinder HR by a standard pressure regulator 43 interposed and one side of an additional sequential control valve 44, while the pressure towards the other rear wheel brake cylinder HL is certainly derived from the (open) brake circuit II by a bypass line 45, but also subjected to the control action of the right rear wheel brake cylinder.

 The operation of the sequential control valve 44 is such that a reduction in the pressure on the left side of the latter (towards the wheel brake cylinder HR) is accompanied by a corresponding drop in pressure in the brake cylinder wheel HL (common ABS pressure modulation for the rear axle), by a displacement of the piston 44a of the valve 44 and the resulting closure of the valve 44b on the right side.

 Such a sequential control valve requires a bypass valve in the event of a brake circuit I failure, so that the rear wheel HL of the brake circuit II receives full brake pressure. This result is obtained by arranging in another pressure line 45 ′, derived on the braking circuit II, an additional hydraulic valve 46, which is actuated by the feeler 47 of the position sensor S1 ′, by means of a pusher 46a (and a bent lever 48), so that when the piston 13 of the master cylinder reaches the left limit position, which is equivalent to a failure of the braking circuit, the position of its inclined plane determined by the feeler 47 opens the hydraulic bypass valve 46 and that the pressure of the braking circuit II is transmitted directly to the left rear wheel brake cylinder, avoiding the closing valve 44b of the sequential control valve.

 Of course, various modifications can be made by those skilled in the art to the principle and to the devices which have just been described only by way of nonlimiting examples, without departing from the scope of the invention.

Claims (9)

Claims 1. Brake booster, and in particular multi-circuit brake booster with an affected anti-lock device (ABS), a racing simulator and a brake valve for applying pressure from a source, said brake booster being characterized in that in the case at least two braking circuits, namely an open braking circuit (II), to which the pressure of a brake valve (18) is applied, and a closed braking circuit (I), an ABS pressure regulation s 'performs in said closed braking circuit by commanded action of a pressure on its master cylinder piston (13). 2. Brake booster according to claim 1, characterized in that the pressure regulation in the closed braking circuit (I) is effected by an auxiliary hydraulic circuit (31), controlled by a reversing valve (38) in the case of ABS regulation functions. 3. Brake booster according to claim 2, characterized in that the auxiliary hydraulic circuit (31) consists of an additional working cylinder, disposed on the master cylinder (10) and containing an adjustment piston (33) which, by the Intermediate of a pressure rod (35) similar to a piston rod and sealed, acts mechanically on the piston (13) of the master cylinder of the closed brake circuit (I). 4. Brake booster according to one of claims 2 or 3, characterized in that the additional hydraulic working cylinder on the master cylinder (10) of the brake booster (30) comprises a pressure chamber (32) to which the electromagnetic distributor 3/2 dtinversion ( 38) assigned to the ABS control valves of an ABS valve group (40) applies the full pressure of the accumulator in the event of an ABS pressure reduction signal in the wheel brake cylinders (VL, VR; HR, HL) connected to said braking circuit (I). 5. Brake booster according to any one of claims 1 to 4, characterized in that the primary side of the piston (13) of the master cylinder of the closed brake circuit (I) is charged by the pressure applied by the brake valve (18) to a pressure chamber (16) of the open braking circuit (II), the pressure of the accumulator applied in the case of ABS regulation functions acting at least indirectly on the other side; and the primary side of the piston (13) of the master cylinder of the closed braking circuit (I) also presents a predetermined distance, if necessary very small, to the pusher (12) of the brake pedal (11) passing through the piston primary, made in the form of an annular piston (1S), so that the pressure modulations appearing in the closed braking circuit (I) are perceptible to the driver in the form of vibrations, via the brake pedal. 6. Brake booster according to any one of claims 1 to 5, characterized in that a 3/3 electromagnetic distributor (39) is inserted in the open braking circuit (II? As ABS control valve of the rear axle and two distributors 2/2 electromagnetic (41a, 41b) are inserted in the closed brake circuit (I) to perform transmission and pressure maintenance functions in each front wheel brake cylinder (VL, VR). 7. Brake booster according to any one of claims 1 to 6, characterized in that for a division of the braking circuits diagonally, the electromagnetic circuit 3/3 t39 ') in the open braking circuit (II) is assigned to a cylinder of front wheel brake (VR) and one of the 2/2 solenoid valves (41a ') inserted in the closed brake circuit (I) is assigned to the other front wheel brake cylinder (VL), the second solenoid valve 2 / 2 (41b ') being used for the rear axle with maintenance of the pressure reduction functions by the pressure control of the auxiliary circuit. 8. Brake booster according to claim 7, characterized in that the second 2/2 electromagnetic distributor (41b ') of the closed brake circuit (I) transmits pressure to an affected rear wheel brake cylinder (HR) via d '' a standard pressure regulator (43) and on one side a sequential control valve (44), the other side of which transmits the pressure from the open brake circuit (II) to the other wheel brake cylinder rear LHL) via a shut-off valve (44b). 9. Brake booster according to one of claims 8 or 9, characterized in that a hydraulic bypass valve (46) is provided for in the event of a brake circuit failure (I), is actuated by a stroke sensor pusher ( feeler 47) of the piston (13) for mastering the closed brake circuit (I), then transmits the pressure of the brake circuit (II) to the affected rear wheel brake cylinder (HL), avoiding the closing valve (44b ) in the sequential control valve (44).