Patent GB-1409288-A (GB)
Title: Valve unit for anti-locking brake systems
IPC: B60T8/94
Filed: 1972-12-20
Abstract: 1409288 Anti-locking brake systems; valves; warning devices ROBERT BOSCH GmbH 20 Dec 1972 [23 Dec 1971 31 Aug 1972] 58716/72 Headings F2F F2V and F2E A pneumatic or hydraulic anti-locking brake system has a valve unit 1 interposed between a brake valve 2 (or an hydraulic master cylinder) and a wheel cylinder 3, the unit 1 having two main valves 18, 19 responsive to the operation of respective solenoid pilot control valves 6, 7 to control the communication between valve 1 and cylinder 3 in response to wheel lock; operation of valves 6, 7 is controlled by an electronic device 3<SP>1</SP> connected to a wheel speed sensor 2<SP>1</SP> but at least one of the main valves (e.g. valve 19) is associated with a respective safety valve 51 which provides an override control, should one or more of the valves stick in a brake pressure relieving condition, to thereby allow a braking operation to be resumed.  In the embodiment of Fig. 1, the valve 18 has a closure member 26 co-operable with a valve seat 34, and the valve 19 has a closure member 27 co-operable with valve seats 36, 37. The valves 6, 7 have electromagnets 6<SP>1</SP>, 7<SP>1</SP> and armatures 8, 9 with closure members 10, 11 controlling communication between respective main valve working chambers 12, 13 and a compressed air connection 14 or respective atmospheric air connections 16, 17. The safety valve 51 has a piston 54 secured to a closure element 52 which is co-operable with a valve seat 53 located in an atmospheric air connection 39 to a chamber 41 of valve 19. Chamber 41 is connected to a working chamber 43 of an inductive pressure receiver 44 having a sensing diaphragm 43<SP>1</SP>. When the vehicle is travelling the parts of the valve unit 1 assume the illustrated position and when the valve 2 is operated, pressure is communicated to cylinder 3 via open valve 18. Should the wheel lock the valves 6, 7 are energized, the brake pressure causing the lock having entered chamber 43 via a passage 38 to be stored in the electronic control device 3<SP>1</SP>. Operation of valves 6, 7 causes compressed air to enter chambers 12, 13 whereby valves 26/34, 27/36 are closed and valve 27/37 is opened: cylinder 3 is thereby cut off from valve 2 and is connected to atmosphere via passage 38, opened valve 27/37 and connection 39 to reduce braking pressure: the wheel reaccelerates to cause device 3<SP>1</SP> to switch off valves 6, 7 and allow valves 18, 19 to assume their original condition and a braking pressure is then established at a value almost equal to the locking pressure as stored by device 3<SP>1</SP>. Valve 6 is then operated again and a braking pressure increase can now be effected only by way of throttle 33 and open valve 27/36. However if the locking pressure is not attained within a period of time predetermined by the control device 3<SP>1</SP> by means of a timing device 60 the magnet 6<SP>1</SP> is switched off to allow rapid pressure increase if the locking pressure is reached before the period of time has expired the valves 6, 7 are operated again and the brake is released. Should armature 9 stick after the first release of brake pressure compressed air acting upon the top of piston 54 via a passage 55 closes valve 51 to shut off the connection 39 to allow braking pressure to build up again. valve 6 is operated again when the pressure reaches a certain value and compressed air acting on the underside of piston 54 to open valve 51. This operating sequence continues and can be used in the device 3<SP>1</SP> to operate a sensor 61 and pilot lamp 62.  In the embodiment of Fig. 2, valves 18, 19 are connected sequentially between valve 2 and brake cylinder 3. A throttle 67 in the form of a throttling check valve is connected to an operating chamber 66 above a piston 68 of a safety valve 65. If wheel lock occurs during a braking operation only valve 7 is operated initially whereby valve 19 is actuated to connect cylinder 3 to atmosphere. Subsequently valve 6 is operated to acutate valve 18, whereby the drop in braking pressure takes place less steeply by way of a throttle 72. Chamber 66 is pressurized after operation of valve 6 by way of throttle 67 and should valve 19 not change back again after about 1 second as a result of sticking of the armature of valve 7 piston 68 is moved to close vavle 69/71 and open valve 69/70 to allow pressure to enter cylinder 3 by way of a line 77. Main valve 19 has a rod 75 and valve 65 has a rod 73, which rods 75, 73 are operable on respective switches 76, 74 to monitor operation of the valve unit. In the embodiment of Fig. 3, a safety valve 51 operates in conjunction with main valve 19<SP>1</SP> as in the Fig. 1 embodiment and a safety valve 80 responds to sticking of valve 18 to open a valve 83, 84 to connect valve 2 to brake cylinder 3 via a passage 86. Valves 51, 80 are associated with limit switches 74, 74<SP>1</SP>. Fig. 4 is similar to Fig. 2 except that an auxiliary valve 89 is coupled to the main valve 19 by a rod 94 which valve 89 controls the pressure in chamber 66 of a safety valve 95.