Patent GB-1282310-A (GB)
Title: An anti-skid apparatus for use in a braking system for a motor vehicle
IPC: B60T8/64
Filed: 1969-08-08
Abstract: 1282310 Antiskid braking systems NISSAN MOTOR CO Ltd 8 Aug 1969 [22 Aug 1968 30 Nov 1968] 39812/69 Headings F2E and F2F In an antiskid device 14 for a vehicle hydraulic braking systems two different annular deceleration rates of at least one wheel are detected whereby two antiskid signals are generated, the first of which controls a first pressure differential control unit 12 to a diaphragm causing 70 to move operating a valve 37 connected between a master cylinder and wheel cylinders 22 thereby lowering the pressure supplied to wheel cylinders 23 and the second of which causes a second differential control unit 13 to operate the diaphragm 70 and valves 37 to further lower the brake fluid pressure. Valve 37 has a ball 41 connected by a plunger 35 to the diaphragm 70, which diaphragm separates an air chamber 57 from a vacuum chamber 63. Air chamber 57 is connected to atmosphere past an air filter 60 through a conduit 69 and solenoid valve 65 of the second unit 13, conduit 58 solenoid valve 43 of the first unit 12 and relief valve 43 and vacuum chamber 63 is connected with the engine intake manifold 62 through a conduit 64, relief valve 45 and check valve 104. At a predetermined angular deceleration rate of 20 rad./sec. a signal from the antiskid device 14 energizes solenoid 43 thereby moving valve member 47 to communicate air chamber 57 with atmosphere. The differential pressure across diaphragm 70 causes it to move downwardly causing ball 41 so seat at 42 to cut off pressure supply to wheel cylinders 23. At a further predetermined deceleration rate less than 20 rad./sec. solenoid valve 43 is deenergized and valve 47 closes, the differential pressure across a valve member 52 causing it to unseat to exhaust air in chamber 57 through manifold 62. Device 14 comprises electromagnetic pickups 83, 84 feeding pulses to shapers 85, 86 so as to form square waves which are passed to speed detectors 87, 88 which intergrates the waves to produce voltages proportional to the respective wheel speeds. The voltages are differentiated at 89, 90 to produce voltages proportional to angular deceleration and which are fed to Schmitt circuits 91, 92 and 93, 94 for the right and left rear wheels respectively. Circuits 91, 93 generate predetermined voltages when they receive voltages corresponding to 20 rad./sec. and 92, 94 generate predetermined voltages when they receive voltages corresponding 30 rad/seo<SP>2</SP>. When the output from at least one of circuits 91, 93 reaches a valve corresponding to the deceleration 20 rad./sec.<SP>2</SP> OR circuit 95 passes an output to a power amplifier 97 to cause solenoid coil 46 to be energized while when the output from at least one of circuits 92, 94 reaches a predetermined value corresponding to a deceleration rate of 30 rad./sec.<SP>2</SP> an output from a further OR circuit 96 is fed to a power amplifier 98 causing solenoid coil 65 to be energized. If amplifiers 97, 98 fail to operates switches 102, 103 cut off current through coils 46, 65. A safety device 106, Fig. 6 (not shown), may be provided which, upon detection of malfunction of the antiskid device over a specified period, generates a by pass signal which opens a by-pass fluid passage (118) so that braking fluid is still supplied to be rear wheel cylinders, and a warning lamp (118) is also operated.