GB2242243A

GB2242243A - Automotive vehicle brake system with anti-locking device

Info

Publication number: GB2242243A
Application number: GB9026673A
Authority: GB
Inventors: Wilfried Wagner; Lothar Schiel; Nabfred Ryeffer; Hans-Juergen Beilfuss; Frank Meyer
Original assignee: Alfred Teves GmbH
Current assignee: Continental Teves AG and Co oHG
Priority date: 1990-03-21
Filing date: 1990-12-07
Publication date: 1991-09-25
Also published as: FR2659921A1; JPH04221264A; GB9026673D0; DE4009084A1

Abstract

In an automotive vehicle brake system with anti-locking device the movable wall (6) of a vacuum brake power booster (1) is movable independently of its input member (4) and the respective pistons (9, 10) of a master brake cylinder (2) are in power-transmitting connection with said input member (4) and with the movable wall (6), and the pressure chamber (7) oil the piston (9) can be shut off (by a valve 44) in the event of an anti-locking control action. The two pressure circuits (11, 13) of the master cylinder are balanced by a device (15). An optional device (19) allows a limited advance of the piston (9) on closure of the valve (44). <IMAGE>

Description

1 AUTOMOTIVE VEHICLE BRAKE SYSTEM WITH ANTI-LOCKING DEVICE The present

invention relates to an automotive vehicle brake system incorporating an anti-locking arrangement.

more specifically, the invention relates to such a brake system comprising a vacuum brake power booster which is actuatable by means of an input member and which has at least two power chambers which are separated from each other by a movable wall, the first chamber being connectible, by means of a pneumatic valve, either to a vacuum source or to the atmosphere, as desired, and the second chamber being connectable, by means of a control valve which is actuatable by the input member, either to the first chamber or to the atmosphere, with a hydraulic master brake cylinder succeeding the vacuum brake power booster and within which two separated pressure chambers are provided and connectible to a pressureless hydraulic fluid supply tank, the pressure chambers being defined by first and second pistons, wheel cylinders being connected to the pressure chambers through hydraulic lines, a central electronic control unit being provided to the input of which output signals of sensors monitoring the 'rotational behaviour of the wheels to be braked are supplied and the control signals from the unit, in the event of an anti-locking control action, controlling hydraulic fluid valves which are incorporated in at least one of the hydraulic lines and which precede the wheel cylinders, the movable wall of the vacuum brake power 2 booster being movable independently of the input member.

A brake system of the above kind is known, for example, from German Patent Application No. 3,814,222 published without examination. In the event of an antilocking control action, in order to bring to bear a retaining force contrasting the actuating force, a hydraulic chamber is envisaged in the subject matter of the above patent application which is in active connection with the input member of the vacuum brake power booster and whose connection to the pressureless hydraulic fluid supply tank is interruptible by means of a check valve being actuatable electromagnetically.

In particular, the elevated costs of manufacture and mounting costs of the actuating unit comprising the vacuum brake power booster and the tandem master cylinder, which costs are due to its sophisticated set-up are considered of disadvantage in the prior- art brake system.

It is, therefore, an object of the present invention to simplify substantially the set-up of such an automotive vehicle brake system with anti-locking device in order to reduce its costs of manufacture and its mounting costs.

According to the present invention there is provided an automotive brake system incorporating an anti-locking arrangement, the system comprising a vacuum brake power booster which is actuatable by means of an input member and which has at least two power chambers which are separated from each other by a movable wall, the first chamber being connectible to a vacuum source or to the atmosphere, as required by means of a pneumatic valve and the second chamber being connectible to the first chamber or to the atmosphere by means of a control valve which is actuatable by the input member, a hydraulic master brake cylinder which succeeds the vacuum brake power booster and within which two separated pressure chambers are provided which are connectible to a pressureless hydraulic fluid supply tank and which are defined, respect ively, by first and second pistons, wheel cylinders being connected to the pressure 3 chambers through hydraulic lines, the anti-locking arrangement of the system comprising a central electronic control unit to inputs of which output signals of sensors monitoring the rotational behaviour of wheels to be braked are supplied and control signals from the unit, in the event of an antilocking control action, control hydraulic fluid valves which are incorporated in at least one of the hydraulic lines and which precede the wheel cylinders, the movable wall of the vacuum brake power booster being movable independently of the input member, characterised in that the first piston defining the first pressure chamber is in power-transmitting connection with the input member and the second piston defining the second pressure chamber is in power-transmitting connection with the movable wall, and in that the first pressure chamber can be shut off in the event of an anti- locking control action.

In order to safeguard that equal pressures are being built up within all wheel cylinders which are connected to the individual pressure chambers of the master brake cylinder, it is envisaged in an advantageous development that a hydraulic arrangement is inserted between the pressure chambers which affords a pressure balance while separating simultaneously the two pressure chambers. 'The arrangement is preferably formed by two hydraulic chambers which are separated from each other by means of an intermediate piston.

In order totally to eliminate the falling-through travel of the input member which is due to the slide of the intermediate piston at the moment of shutting off the first pressure chamber, it is proposed in a further embodiment of the subject matter of the invention that the connection between the pressure chamber and the hydraulic chamber of the arrangement which is associated with it is designed so as to allow shut off.

In the event of an anti-locking control action taking place in the brake circuit connected to the first pressure chamber,. in order to eliminate the hydraulic pressure ruling 4 in that brake circuit, it is proposed according to another advantageous f eature of the invention that a connection which can be shut off is provided between the wheel cylinders and is linked to the first pressure chamber, on one hand, and the hydraulic fluid supply tank, on the other hand.

A substantially improved anti-locking control action is attained in a further particularly advantageous embodiment of the invention in that the hydraulic chamber of the arrangement which is associated with the second pressure chamber is linked directly to the second pressure chamber, whereas the connection between the first pressure chamber and the hydraulic chamber associated with it is realised by interposing the 2/2-way valve shutting off the first pressure chamber, the wheel cylinders being connected in pairs to the hydraulic chambers.

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

Figure 1 shows a diagrammatic representation of one embodiment of an automotive vehicle brake system with antilocking control device in accordance with the invention; and, Figure 2 shows a diagrammatic representation of another embodiment of an automotive vehicle brake system with anti- locking control device in accordance with the invention.

Corresponding components of the braking systems shown in Figures 1 and 2 of the drawings are provided with identical reference numerals.

Figure 1 shows an automotive vehicle brake system with anti-locking control device with a vacuum brake power booster 1 which is connected in known manner to a brake pedal 3 through an input member 4. On the side of the vacuum brake power booster 1 facing away from the input member 4, a master brake cylinder is provided having first and second pressure chambers 7,8 in connection with a 1 hydraulic f luid supply tank 5. The association with the vacuum brake power booster 1 of f irst and second pistons 9,10 confining he pressure chambers 7,8 is preferably arranged so that the first piston 9 confining the f irst pressure chamber 7 is directly connected to the input member 4 while the second piston 10 being preferably formed as an annular piston and arranged co-axially with the input member 4 is in power-transmitting connection with the movable wall 6 of the booster 1, so that it is exclusively subject to the boosting power of the vacuum brake power booster 1.

Wheel cylinders of the two wheel brakes 20.21, which are illustrated schematically and are associated, for example, with the rear axle of the automotive vehicle, are linked to the first pressure chamber 7 by means of a first hydraulic line 11 incorporating a preferably electromagnetically-actuatable first 2/2-way valve 44.

A second hydraulic line 13 links the second pressure chamber 8, through two solenoid valves 14,24 which are constructed as 2/2-way valves and which are customarily accommodated in a valve block, to the wheel cylinders of two further wheel brakes 22,23 which may be associated with the front axle.

A third hydraulic line 38 is provided which links the wheel cylinders of the rear axle brakes 20,21 to the hydraulic fluid supply tank 5 through a second 2/2-way valve 45.

Sensors 25,26,27, and 28 which are linked, through corresponding respective signal lines 29,30,31 and 32, to a central electronic control unit 33 are associated with the rear and the front wheel brakes 20,21,22 and 23. The central electronic control unit 33 is linked through control lines 34 f 35, 36 and 37 to respective solenoid valves 45 r 44 r 14 and 24 for the actuation of the valves depending on sensor signals received from the sensors.

A pneumatic 3/2-way valve 42 which is controllable by the central electronic control unit 33 and which connects the master cylinder-side power chamber of the vacuum brake 6 power booster 1 (throug.-. a non-return valve 41) either to a vacuum source 12 or to the atmosphere, as required, is linked to the aforesaid power chamber through a pneumatic.

line 43.

Finally, to allow the wheel cylinders connected to the individual pressure chambers 7,8 of the master cylinder 2 to be subjected to equal hydraulic pressures in the event of brake actuation, a hydraulic arrangement 15 is provided which affords a pressure balance between the two pressure chambers 7,8. As will be seen from the Figure, the arrangement 15 comprises two hydraulic chambers 17,18 which are separated from each other by a slidable piston 16 movable to a limited extent and which are linked by means of hydraulic lines 39,40 to the first and the second hydraulic lines 11 and 13, respectively. In one of the two lines 39,40, a third hydraulic 2/2-way valve 46 is inserted, the function of which will be explained in more detail in conjunction with the mode of operation of the automotive vehicle brake system of the present embodiment. It is contemplated that the three 2/2-way valves 44,45,46 may advantageously be accommodated within the aforementioned valve block. The same holds true of the hydraulic arrangement 15, which may, alternatively, be integrated in the housing of the master brake cylinder 2.

Referring now to the mode of operation of the automotive vehicle brake system of the invention illustrated in Figure 1, in the event of a normal braking operation during which the first and the third 2/2-way valves 44 and 46 remain open, the second 2/2-way valve 45 remains closed and the pneumatic 3/2-way valve 42 connects the master cylinder-side power chamber to the vacuum source 12. the pressure build-up and the pressure decrease take place as in a prior-art actuating unit being comprised of a master brake cylinder and a vacuum brake power booster preceding it.

If during a braking action a locking of one or both rear axle wheels is detected by one or both sensors 25,26, as the case may be, then the central electronic control unit il 7 33 will generate switch-over signals which bring about a simultaneous switch-over of the 2/2-way valves 44f45 and 46, so that the first pressure chamber 7 will be shut off and the brake pedal j will remain in the controlled position.

Simultaneously, the second 2/2-way valve 45 will he opened so that the pressure acting at the rear axle can be reduced through the open connection 38 toward the hydraulic fluid supply tank 5.

If, however, a locking of one or both front axle wheels is detected by the sensors 27 and/or 28, then there will take place a switch-over of the pneumatic 3/2-way valve 42 to atmosphere in addition to the switch-over of the two 2/2-way valves 44,46, so that the movable wall 6 of the vacuum brake power booster 1 will become powerless and the hydraulic pressure acting at the front axle will be reduced by the restoring movement of the movable wall 6 and the second piston 10.

In the embodiment of automotive vehicle brake system shown in Figure 2, a hydraulic cylinder 19 is arranged in parallel to the first 2/2-way valve 44 shutting off the first pressure chamber 7 and within the housing 49 of which a guided piston 51 is pre- stressed by means of a compression spring 52. In this embodiment, the two wheel cylinders 20,21 are linked to the first pressure chamber 7 by respective hydraulic electromagnetically actuatable 2/2-way valves 47 and 48 which are open when de-energised, while the hydraulic arrangement 15 mentioned in connection with Figure 1 is connected, on one side, to the line section 50 leading from the first 2/2-way valve 44 to the wheel valves 47,48 and, on the other side, directly to the second line 13. As a result of the described connecon of the hydraulic arrangement 15, a closed system is created in which the reduction of the hydraulic pressure which leads to a locking of the rear axle wheels takes place through the second pressure chamber 8 at the moment of the restoring movement of the movable wall 6 and the second piston 10. When the first 2/2-way valve 44 is being closed, the utilisation of 8 the hydraulic cylinder 19 affords a limited movement of the input member 4 in the direction of actuation which results in a limited opening of the control valve (not shown in the drawing) of the vacuum brake power booster and, thus, to a 5 pressure increase in the two brake circuits.

Finally, it may for safety reasons be advisable to arrange a further 2/2way valve, open when de-energised, in parallel with the first 2/2-way valve 44. A total failure of the brake system if the first 2/2-way valve 44 should fail to be opened at the end of the control action will be prevented by this provision.

1 1 1 9

Claims

CLAIMS:

1. An automotive brake system incorporating an antilocking arrangement, the system comprising a vacuum brake power booster which is actuatable by means of an input member and which has at least two power chambers which are separated from each other by a movable wall, the first chamber being connectible to a vacuum source or to the atmosphere, as required by means of a pneumatic valve and the second chamber being connectible to the first chamber or to the atmosphere by means of a control valve which is actuatable by the input member,, a hydraulic master brake cylinder which succeeds the vacuum brake power booster and within which two separated pressure chambers are provided which are connectible to a pressureless hydraulic fluid supply tank and which are defined, respectively, by first and second pistons, wheel cylinders being connected to the pressure chambers through hydraulic lines, the anti-locking arrangement of the system a central electronic control unit to inputs of which output signals of sensors monitoring the rotational behaviour of wheels to be braked are supplied and control signals from the unit, in the event of an antilocking control action, control hydraulic fluid valves which are incorporated in at least one of the hydraulic lines and which precede the wheel cylinders, the movable wall of the vacuum brake power booster being movable independently of the input member, characterised in that the first piston (9) defining the first pressure chamber (7) is in powertransmitting connection with the input member (4) and the second piston (10) defining the second pressure chamber (8) is in power-transmitting connection with the movable wall (6), and in that the first pressure chamber (7) can be shut off in the event of an anti-locking control action.

2. An automotive vehicle brake system as claimed in claim 1, characterised in that a hydraulic arrangement (15) is inserted between the pressure chambers (7,8) and affords a pressure balance while separating simultaneously the two pressure chambers (7,8).

1

3. An automotive vehicle brake system as claimed in claim 2, characterised in that the arrangement (15) is formed by two hydraulic chambers (17,18) which are separated from each other by means of an intermediate piston (16).

4. An automotive vehicle brake system as claimed in claim 3. characterised in that a connection (39,40) between the pressure chamber (7,8)'and the hydraulic chamber (17,18) of the arrangement (15) which is associated with it is configurated so as to allow it to be shut off.

5. An automotive vehicle brake system as claimed in claim 1, characterised in that a connection (38) which can be shut off is provided between wheel cylinders (20,21) and is linked to the first pressure chamber (7), on one hand.

and to the hydraulic fluid supply tank (5), on the other hand.

6. An automotive vehicle brake system as claimed in claim 4 or claim 5 or claims 4 and 5, characterised in that the shutting-off of the first pressure chamber (7) and the connection (38,39,40) takes place by means of electromagnetically actuatable 2/2-way valves (44,45,46) which are actuatable by the central electronic control unit (33).

7. An automotive vehicle brake system as claimed in claim 3, characterised in that the hydraulic chamber (18) of the arrangement (15) which is associated with the second pressure chamber (8) is directly connected to the second pressure chamber (8) while the connection between the first pressure chamber (7) and the hydraulic chamber (17) is realised by interposing a 2/2-way valve (44) shutting off the first pressure chamber (7), wheel cylinders (20,21,22,23) being connected in pairs to the hydraulic chambers (17,18).

8. An automotive vehicle brake system as claimed in claim 6, characterised in that a further electromagnetically actuatable 2/2-way valve is arranged in parallel with the 2/2-way valve (44) shutting off the first pressure chamber (7).

11

9. An automotive vehicle brake system as claimed in any one of the preceding claims, characterised in that the piston (10) defining the second pressure chamber (8) is constructed as an annular piston and is arranged coaxially 5 with the input member (4).

10. An automotive vehicle brake system as claimed in claim 6, the hydraulic fluid valves being arranged in a valve block, characterised in that both the hydraulic arrangement (15) and the 2/2-way valves (44,45,46, 47) are integrated in the valve block.

11. An automotive vehicle brake system as claimed in claim 2, characterised in that the hydraulic arrangement (15) is integrated in the master brake cylinder (2).

12. An automotive vehicle brake system as claimed in any one of the preceding claims, characterised in that a second hydraulic arrangement (19) is connected to the first pressure chamber (7), which affords a limited movement of the first piston (9), respectively of the input member (4) in the direction of actuation when the first 212-way valve (44) is being closed.

13. An automotive vehicle brake system as claimed in claim 12, characterised in that the second hydraulic arrangement is formed by a hydraulic cylinder (19) within the housing (49) of which a piston (51) is slidingly positioned and elastically pre-stressed.

14. An automotive vehicle brake system substantially as hereinbefore described with reference to Figure 1 or Figure 2 of the accompanying drawings.

Published 3991 at The Patent Office. Conrept House. Cardiff Road. Newporl. Gwent NP9 I RH. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Point. Cwmfelinfarh. Cross Keys. Nmpori. NPI 7HZ. Printed by Multiplex tech"ues Iltd. St Mary Cray. Kent.