GB2246608A

GB2246608A - Anti-lock brake system for automotive vehicles

Info

Publication number: GB2246608A
Application number: GB9113662A
Authority: GB
Inventors: Frank Meyer
Original assignee: Alfred Teves GmbH
Current assignee: Continental Teves AG and Co OHG
Priority date: 1990-08-01
Filing date: 1991-06-25
Publication date: 1992-02-05
Anticipated expiration: 2011-06-25
Also published as: DE4024384A1; GB9113662D0; JPH04230455A; FR2665407A1; GB2246608B

Abstract

In order to reduce the cost of manufacture and assembly of an anti-lock-controlled brake system for automotive vehicles in which the movable wall (6) of a vacuum booster (1) is movable independently of the input member (3) of the booster and which has means for positioning the input member in anti-lock control to isolate disturbing pressure pulsations, the pressure chambers (7, 8) of a master cylinder (2) can be shut off in anti-lock control and a hydraulic modulator chamber (53) provided within the master cylinder (2) and confined by a modulator piston (51) connected with the movable wall (6) in a power-transmitting manner is connected instead to the wheel brakes. The modulator chamber (53) is normally connected to a reservoir. <IMAGE>

Description

1 Th ANTI-LOCKCONTROLLED BRAKE SYSTEM FOR AUTOMOTIVE VEHICLES is invention

relates to an anti- lock-control led brake system for automotive vehicles.

More specifically, the invention relates to such brake systems of the kind comprising an actuating unit including a master brake cylinder, preferably a tandem master cylinder, having primary and secondary pressure chambers confined by primary and secondary master cylinder pistons, and a vacuum brake power booster connected upstream of the master brake cylinder and actuatable by means of an input member, wheel brake cylinders connected to the pressure chambers of the master brake cylinder via hydraulic lines, and a central electronic control unit the inputs of which are fed with output signals of sensors detecting the rotational behaviour of the wheels to be braked and the control signals of which, in the event of anti-lock control, control pressure medium wheel valves inserted into hydraulic lines and connected upstream of the wheel brake cylinders, a movable wall within the vacuum brake power booster housing and separating a vacuum chamber, ventilatable in the event of anti-lock control, from a working chamber being movable independently of the input member and communicating with the primary master cylinder piston in a power-transmitting manner.

Such a brake system and its actuating unit, is known from Applicant's prior German Patent Application No.

2 P4005584.1. As regards the subject matter of the prior application, a hydraulic chamber co-operating with the input member of the vacuum brake power booster is provided in order to generate a retaining force in the event of antilock control, which force will counteract the actuating force. Communication of the hydraulic chamber with a pressureless hydraulic fluid reservoir can be shut off by means of an electromagnetically-operable shut-off valve. The chamber is formed by an annular chamber provided between the surface of the master brake cylinder and an intermediate piece arranged co-axially with regard to the master cylinder and is confined by a locking piston which can be displaced by the movable wall of the vacuum brake power booster. In the brake release position, the two pressure chambers of the is master brake cylinder communicate with the hydraulic fluid reservoir, with communication being shut off by means of central valves upon application.

The complicated structure of the known actuating unit, involving considerable cost of manufacture and assembly, must be considered a particular disadvantage of this unit. The adjustment of all the operationally relevant dimensions, or rather the adaptation of the existing coaxial dimensions (master cylinder diameter, inside and outside diameters of the locking piston or inside diameter of the intermediate piece), is also very complicated and requires a great many operations. A further disadvantage resides in the considerable size of the vacuum brake power booster which, in particular, is due to the vacuum failure occurring during control. The pulsations ensuing in case of control and felt at the actuating pedal are also considered negative.

It is thus an object of the present invention to provide an antilockcontro 1 led brake system of the kind referred to above which can be manufactured in a particularly cost-saving manner. Further, all the operationally relevant dimensions allow of easy adjustment. A further object consists in eliminating the pressure 1 i i 1 i i i i 1 j J 1 i j 3 pulsations occurring during control and f elt at the brake pedal.

According to the present invention an anti-lockcontrolled brake system for automotive vehicles comprising an actuating unit including a master brake system having primary and secondary pressure chambers confined by primary and secondary master cylinder pistons, and a vacuum brake power booster connected upstream of the master brake cylinder and actuatable by means of an input member, wheel brake cylinders connected to the pressure chambers of the master brake cylinder via hydraulic lines, a nd a central electronic control unit the inputs of which are f ed with output signals of sensors detecting the rotational behaviour of the wheels to be braked and the control signals of which, in the event of anti-lock control, control pressure medium wheel valves inserted into hydraulic lines and connected upstream of the wheel brake cylinders, a movable wall within the vacuum brake power booster housing and separating a vacuum chamber, ventilatable in the event of anti-lock control, from a working chamber being movable independently of the input member and communicating with the primary master cylinder piston in a power-transmitting manner, characterised in that the pressure chambers can be shut off or interrupted in the event of anti-lock control and in that a hydraulic modulator chamber is provided within the master cylinder and confined by a modulator piston coupled to the movable wall in a power- transmitting manner and the modulator chamber is alternatively connectible to a pressureless hydraulic fluid reservoir or to the wheel brakes.

A particularly compact design of the brake system is achieved in an advantageous embodiment of this invention in which the modulator chamber is formed by an annular chamber arranged upstream of the primary pressure chamber and confined by the primary piston and in which the modulator piston comprises an annular piston and is guided by the primary piston.

i 1 i 4 In order to ensure that the same pressures are built up in all the wheel brake cylinders connected to the individual pressure chambers of the master brake cylinder an advantageous further development provides that, between outlets of the shut-off valves a hydraulic arrangement is connected which produces a pressure compensation whilst, simultaneously, the two pressure chambers are separated from each other.

In order to give the driver an idea of the action of a force corresponding to the reaction force resulting from the hydraulic pressure prevailing in the master cylinder in another embodiment of the invention the primary piston has on the end thereof facing the brake power booster a cylindrical recess in which an elastic reaction disc is arranged, the input member and the movable wall supporting themselves on the disc the first directly and the latter via a power transmission sleeve.

By way of example an embodiment of the present invention will now be described with reference to the accompanying drawing in which:

Figure 1 is a schematic representation of an antilock-controlled brake system for automotive vehicles according to this invention; and Figure 2 is an axial sectional view of an actuating unit used in the brake system according to Figure 1.

In the two figures of the drawing, like reference numerals are assigned to corresponding components of the system.

Referring firstly to Figure 1 this shows an anti- lock-controlled brake system for automotive vehicles with a vacuum brake power booster 1 connected in a manner known per se with a brake pedal 3 via an input member 4. On the side of the vacuum brake power booster 1 remote fromt he input member 4, a master brake cylinder 2 is provided having primary and secondary pressure chambers 7,8, respectively, communicating with a hydraulic fluid reservoir 5.

The primary pressure chamber 7, confined by a primary i 1 i 1 1 i 1 1 i 1 i i master cylinder piston 9 is connected with the wheel brake cylinders of two wheel brakes 22,23 associated, for example with the vehicle rear axle by way of a first hydraulic line 11 and two wheel valves 14,24 designed as 2/2-way valves and usually accommodated in a valve block. A first hydraulic shut-off valve 44 is connected into line 11 and comprises an electromagnetically-operable 2/2-way valve which provides hydraulic shut- off of the primary pressure chamber 7 in case of anti-lock control.

By means of a second hydraulic line 13 having a second shut-off valve 45 connected therein, wheel brake cylinders of the two wheel brakes 20,21 having respective wheel valves 47,48 connected upstream thereof, and associated for example with the vehicle front axle are connected to the secondary pressure chamber 8 confined by a secondary master cylinder piston 10. The second shut-off valve 45, like the first hydraulic shut-off valve 44 comprises an electromagnetically-operable 2/2- way valve.

A third hydraulic line 46 proceeding from a hydraulic modulator chamber provided within the master cylinder housing is connected to the inlet of a hydraulic 3/2-way valve 19 which enables an alternative communication to be made between the modulator chamber and the hydraulic fluid reservoir 5 by way of line 85 or between the modulator chamber and the brakes 20,21 which may be associated with either of the two vehicle axles, by way of line 86.

Each front and rear axle brake 20,21,22,23 has associated with it a sensor 25,26,27,28 connected with a central electronic control unit 33 via a corresponding signal line 29,30,31,32. Via control lines 34,35,36,37,38 and 88, the electronic control unit 33 is connected with the wheel valves 47,48,14,24, the two shut-off valves 44,45 and the hydraulic 3/2-way valve 19 in order to actuate the valves in dependence on the sensor signals.

A pneumatic 3/2-way valve 42 actuatable by the central electronic control unit 33 is connected to the master- cyl inder-s ide working chamber of the vacuum brake 6 power booster 1 via a pneumatic line 43. The 3/2-way valve 42 alternatively connects the aforementioned working chamber with a vacuum source 12 through a non-return valve 41 or with the atmosphere.

In order that the same hydraulic pressure are applied to the wheel brake cylinders from the individual pressure chambers 7,8 of the master cylinder 2 when braking is initiated a hydraulic arrangement 15 is provided which produces a pressure compensation between the two pressure chambers 7,8. As can be gathered f rom Figure 1, the arrangement 15 consists of two hydraulic chambers 17,18 separated from each other by a piston 16 having limited displacement. The chambers 17 and 18 are connected to the respective outlet sides of the shut-off valves 45 and 44 by means of hydraulic lines 39 and 40, 11. Within the scope of this invention it is contemplated that both the shut-off valves 44,45 and the 3/2-way valve 19 will be accommodated in the aforementioned valve block. The same applies to the hydraulic arrangement 15 which may also be integrated into -20 the housing of the master brake cylinder 2.

The vacuum brake power booster 1 of the assembly unit shown in Figure 2 has two shell-shaped housing parts 58,59 secured together on their open sides and forming a booster housing 70. Housing part 58 shown on the left in Figure 1 and provided with a pneumatic connection is fixed to tandem master brake cylinder 2 whereas a control housing 72 accommodating a control valve 63 is slidingly and sealedly guided in the right-hand housing part 59, with the control valve 63 being arranged to be actuated by a valve piston 64 connected with the input member 4.

As can readily be understood from the drawing, the represented vacuum brake power booster 1 is a tandem-version brake power booster. A partition wall 77 subdivides its housing 70 into two pneumatic chambers 61 and 71. Pneumatic chamber 71 represented on the right of the drawing is subdivided into a first vacuum chamber 50 and a first working chamber 60 by means of a first movable wall 6 1 i 1 1 7 arranged therein and consisting of a diaphragm disc 74 and an abutting rolling diaphragm 75. In the pneumatic chamber 61 a second movable wall 79 confines a second vacuum chamber 80, communicating with the first vacuum chamber 50, as well as confining a second working chamber 81 communicating with the first working chamber 60 which, during a normal braking action, can be ventilated by means of the control valve 63.

The housing part 59 is preferably provided with radial ribs 78 confining ventilation channels connecting the two working chambers 60,81. Partition wall 77 supports itself on the ribs 78 and is restrained axially by means of a retaining ring 52 clamped at its edge in the area where the two housing parts 58,59 are joined together.

The transmission of the boosting force, generated by the second movable wall 79, to the control housing 72 is achieved by means of a metallic sleeve 57 extending through the partition wall 77 in a sealed manner. The metallic sleeve 57 accommodates a return spring 49 which supports itself at one end on the master-cylinder-side housing part 58 and at its other end on a supporting plate 56 axially abutting the control housing 72. The spring 49 accordingly serves for resetting the two movable walls 6,79.

Supporting plate 56 prevents a seal from being displaced. This seal which in the illustrated example is sealing cup 69 seals the valve piston 64 relative to the control housing 72.

Within the housing of master cylinder 2, the primary piston 9 in conjunction with the wall of the cylinder bore, forms an annular chamber arranged upstream of the primary pressure chamber 7 and serving as hydraulic modulator chamber 53 in accordance with the present invention.

Modulator chamber 53 to which line 46 of Figure 1 will be connected via connection 76 of the chamber 53 is confined by a modulator piston 51 which takes the form of an annular piston, preferably guided on the surface of the primary piston 9 and supporting itself in the axial direction on the control housing 72 by means of the 8 X supporting plate 56, under the action of a pre-stressing spring 55. Pre- stressing spring 55 is clamped between a supporting surface on the master cylinder housing and a spring retainer 82 fastened on the end of the modulator piston 51 and is arranged co-axially within the booster housing 70 relative to the sleeve 57 and the return spring 49.

The transmission of the boosting force to the primary piston 9 is effected by means of a tubular power transmission element 54 guided within the modulator piston 51 and effectively supporting itself at one end on the primary piston 9 and abutting the supporting plate 56 at the other end.

The support of the power transmission element 54 on the primary piston 9 is effected by means of a power transmission sleeve 83 guided within a cylindrical recess 87 of the primary piston 9. The power transmission sleeve 83 co-operates with an elastic reaction disc 84 arranged in front of the sleeve 83. The power transmission sleeve 83 -20 receives the end of an axial extension 65 of the valve piston 64. The end of extension 65 abuts against the reaction disc 84 and the abutting surface area of the extension end together with the annular surface area of the end of the power transmission sleeve 83 also abutting the reaction disc 84, determining the transmission ratio of the represented actuating unit. In the following, the mode of operation of the brake system for automotive vehicles represented in Figure 1 will be described with more particular reference to Figure 2. 30 During a normal braking operation, where the two shut-off valves 44,45 of the system remain open and the pneumatic 3/2-way valve 42 connects the vacuum chambers 50 and 80 of the vacuum brake power booster 1 with the vacuum source 12, the build-up and decrease of pressure will take place as in any known actuating unit consisting of a master brake cylinder and a vacuum brake power booster connected upstream thereof. The displacement of the modulator piston j j i i i 1 1 9 1 1 51 in the actuating direction will cause the pressure medium volume enclosed in the modulator chamber 53 to be displaced into the hydraulic fluid reservoir 5 via the line 46 and the hydraulic 3/2-way valve 19 remaining in its first operating position as illustrated, the hydraulic arrangement 15 producing a pressure compensation between the two pressure chambers 7 and 8 of the master cylinder 2.

If any one of sensors 25 to 28 detects a wheel lockup during a braking operation the central electronic control unit 33 will generate change-over signals effecting a simultaneous change- over of the shut-off valves 44,45 as well as of the hydraulic 3/2-way valve 19 so that the two pressure chambers 7,8 will be shut off and the primary piston 9 and the input member 4 coupled to the brake pedal 3, will be halted. The change-over of the hydraulic 3/2-way valve 19 will cause communication between the modulator chamber 53 and the pressureless hydraulic fluid reservoir 5 to be shut off or interrupted but will establish communication between the modulator chamber 53 and line 86 leading to either of the two brake circuits (20,21). At the same time, the electronic control unit will change over the pneumatic 3/2-way valve 42 so that the movable walls 6 and 79 of the vacuum brake power booster 1 will no longer be subjected to force and the pressure, prevailing in the wheel brakes 20,21, can be decreased directly by the resetting motion of the modulator piston 51. The decrease of the pressure supplied to the wheel brakes 22,23 can take place by a displacement of piston 16 of the hydraulic compensation arrangement 15.

The following advantages are achieved by the present invention:

a) there is no depression of the brake pedal through its b) full travel in case of a vacuum failure; the pressure build-up during control by means of the boosting-force-applied modulator piston can easily be adapted to vehicle conditions by appropriate dimensioning of the annular surface of the modulator v 1 piston so that the existing series size of the vacuum brake power booster can be maintained; C) the driver will immediately become aware of any shut off valve failure.

1 1 1 j 1 i i i 0

Claims

CLAIMS:

1. An anti-lock-controlled brake system for automotive vehicles comprising an actuating unit including a master brake system having primary and secondary pressure chambers confined by primary and secondary master cylinder pistons, and a vacuum brake power booster connected upstream of the master brake cylinder and actuatable by means of an input member, wheel brake cylinders connected to the pressure chambers of the master brake cylinder via hydraulic lines,a nd a central electronic control unit the inputs of which are fed with output signals of sensors detecting the rotational behaviour of the wheels to be braked and the control signals of which, in the event of anti-lock control, control pressure medium wheel valves inserted into hydraulic lines and connected upstream of the wheel brake cylinders, a movable wall within the vacuum brake power booster housing and separating a vacuum chamber, ventilatable in the event of anti-lock control, from a working chamber being movable independently of the input member and communicating with the primary master cylinder piston in a power-transmitting manner, characterised in that the pressure chambers (7,8) can be shut off or interrupted in the event of anti-lock control and in that a hydraulic modulator chamber (53) is provided within the master cylinder (2) and confined by a modulator piston (51) coupled to the movable wall (6) in a power-transmitting manner and the modulator chamber (53) is alternatively connectible to a pressureless hydraulic fluid reservoir (5) or to the wheel brakes (20,21).

2. An anti-lock-controlled brake system for automotive vehicles as claimed in claim 1, characterised in that the modulator chamber (53) is formed by an annular chamber arranged upstream of the primary pressure chamber (7) and confined by the primary piston (9) and in that the modulator piston (51) comprises an annular piston which is guided by the primary piston (9).

3. An anti-lock-controlled brake system for automotive vehicles as claimed in claim 1 or claim 2, 12 j characterised in that the alternative connection of the modulator chamber (53) with either the hydraulic fluid reservoir (5) or the wheel brakes (20,21) is established by means of an electromagnetically-operable hydraulic 3/2-way valve (19).

4. An anti-lock-controlled brake system for automotive vehicles as claimed in any preceding claim, characterised in that the shut-off of the pressure chambers (7,8) is accomplished by means of hydraulic shut-off valves (44,45).

5. An anti-lock-controlled brake system for automotive vehicles as claimed in claim 4, characterised in that the shut-off valves (44,45) comprise electromagnetically-operable 2/2-way valves.

6. An anti-lock-controlled brake system for automotive vehicles as claimed in claim 4 or claim 5, characterised in that between outlets of the shut-off valves (44,45), a hydraulic arrangement (15) is connected which produces a pressure compensation whilst simultaneously, the.20 two pressure chambers (7,8) are separated from each other.

7. An anti-lock-controlled brake system for automotive vehicles as claimed in any preceding claim, characterised in that, under the action of a pre-stressing spring (55), the modulator piston (51) is supported on a supporting plate (56) axially abutting on a control valve housing (72).

8. An anti-lock-controlled brake system for automotive vehicles as claimed in any preceding claim, characterised in that power transmission between the movable wall (6,79) and the primary piston (9) takes place by means of a tubular power transmission element (54).

9. An anti-lock-controlled brake system for automotive vehicles as claimed in any one of the preceding claims, characteirsed in that, the primary piston (9) has on an end thereof facing the brake power booster (1), a cylindrical recess (87) which accommodates an elastic reaction disc (84) on which the input member (3,65) and the 9 p ll j i 1 i 1 1 I i i i i 1 i 1 1 j i i i r 1 i t 13 movable wall (6,79) support themselves, the first directly and the latter via a power transmission sleeve (83).

10. An anti-lock-controlled brake system for automotive vehicles as claimed in claim 8 and 9, characterised in that the power transmission element (54) is arranged between the movable wall (6) and the power transmission sleeve (83).

11. An anti-lock-controlled brake system for automotive vehicles substantially as hereinbefore described 10 with reference to the accompanying drawings.

Published 1992 at The Patent Office, Concept House. Cardiff Road, Newport, Gwent NP9 IRH. Further copies may be obtained from,QWes Branch. Unit 6. Nine Mile Point. Cwmfelinfach, Cross Keys, Newport. NP1 7HZ. Printed by Multiplex techniques'ltd, St Mary Cray, Kent.