Patent GB-1437656-A (GB)
Title: Brake control device
IPC: B60T8/1761
Filed: 1974-07-29
Abstract: 1437656 Hydraulic boosters; antiskid control AISIN SEIKI KK 29 July 1974 [28 July 1973] 33372/74 Heading F2F A brake control device adapted for location between a brake pedal 43 and a single master cylinder, a tandem master cylinder or twin master cylinders of a vehicle hydraulic braking system comprises a power piston 20 for actuating (one of) the master cylinder(s) in response to the hydraulic pressure in a working chamber 21 adapted to receive hydraulic fluid under pressure from a pump 14, a flow control valve 56 for varying the pressure in the working chamber 21, which flow control valve 56 is co-operable with a hole 63 to define a variable area restricted passage for discharging hydraulic fluid from the chamber 21 to drain and which valve 56 also includes a constant area restricted orifice 56a for bleeding hydraulic fluid from chamber 21 to a flow control hydraulic chamber 60, and a pressure control valve 64, 57a comprising a seat 57a of a hollow seat member 57 and a movable member 64 which valve 64, 57a operates to vary the discharging resistance of fluid from the chamber 60 through a passage 61 to drain in response to operation of pedal 43 and also in response to antiskid energization of a solenoid 69 by a logic circuit 70. In the illustrated embodiment there are provided two similar devices to form an assembly 10 and the devices respectively control master cylinders 12, 12<SP>1</SP> for front and rear wheel cylinders 11, 11<SP>1</SP> respectively. The pump 14 supplies hydraulic fluid from a reservoir 15 to a flow divider 17 which supplies the working chambers 21, 21<SP>1</SP> of the two devices with hvdraulic fluid via conduits 18, 18<SP>1</SP>-the flow divider 17 may give the same or different pressures in the conduits 18, 18<SP>1</SP>. A port 24 of the assembly 10 is also supplied with fluid from pump 14 via a conduit 25. An outlet port 22 connects the assembly 10 with the reservoir 15 via a conduit 23. In its inactivated condition and taking the front brake system device as exemplary the hydraulic fluid supplied to the working chamber 21 via conduit 18 passes into an hydraulic chamber 58 defined by the body 26 of the assembly and the valve 56. The fluid passes via the orifice 56a into the flow control chamber 60 and via the passage 61 in the seat member 57 into an hydraulic chamber 48. As the fluid passes through orifice 56a a pressure drop occurs and the resulting difference between the pressures in chambers 58, 60 moves valve 56 rightwardly against a spring 62 until there is limited communication between chamber 58 and hole 63 whereafter the pressure difference between chambers 58, 60 remains constant-the hole 63 communicates via a chamber 75 and holes 79, 80 with a chamber 51 on the opposite side of piston 20 to working chamber 21, which chamber 51 is connected to outlet port 22. Hydraulic fluid in chamber 48 supplied via the passage 61 is also communicated with chamber 51 via a hole 47 in an operating member 37, a chamber 38 and hole.80. When the brake pedal 43 is depressed the operating member 37 is moved leftwardly to compress a spring 41 to give a reaction force. A plate member 44 is also moved leftwardly by means of a spring 45 to thereby increase the biasing force of a spring 46 acting between the plate member 44 and a projecting portion 64a of the movable member 64 and the spring 46 moves member 64 leftwardly against a spring 67 to close passage 61. The pressure within chamber 60 is thus increased to move valve 56 leftwardly to close the variable orifice between valve 56 and hole 63 until equilibrium is again attained with an increased pressure in chamber 21 so that piston 20 is moved and actuates a piston 12a of master cylinder 12 via a rod 53. Should pressure in chamber 60 reach a predetermined upper level, a relief valve 76 is opened. During braking a piston 31 receives the progressively increased force of spring 41 but the piston 31 maintains its illustrated rest position by the action of increased discharge pressure of pump 14 which is transmitted to a chamber 35 leftwardly of piston 31 via the conduit 35 and port 24. When the operating pedal 43 is released the valve 57a, 64 opens to allow decrease of pressure in chamber 58 and the return of piston 20 to its release position. If during braking actual or incipient skidding of one or both front wheels is detected by the logic circuit 70 the circuit 70 supplies a current to the solenoid 69 which causes member 64 to be urged rightwardly against spring 46 by a force dependent on the size of the current to reopen passage 61 and relieve pressure in chamber 58 and in chamber 21. Antiskid operation of the rear brake can operate simultaneously with or independently from the antiskid operation of the front brakes. Should the pump 14 fail then movement of the operating member 37 leftwardly will move piston 31 leftwardly when the force of the operating member 37 transmitted through spring 41 exceeds the combined force of springs 32, 54. A lever 34 connected via a rod 31a with piston 31 is thereby actuated to move rods 53 to operate the master cylinders 12, 12<SP>1</SP>.