GB1027782A - Brake control system - Google Patents

Abstract

1,027,782. Deceleration-responsive brake systems. GIRLING Ltd. May 22, 1964 [June 5, 1963], No. 8880/63. Heading F2F. In a vehicle braking system wherein pressure fluid is supplied to wheel brake cylinders through a control valve operated either manually or by fluid pressure generated in a master cylinder, means is provided which generates a force proportional to the deceleration of the vehicle wheels and applies this force in opposition to the application force on the control valve, such as to provide deceleration-responsive control over the full range of brake application. In one embodiment, Fig. 1, operation of pedal 16 causes spool 10 to uncover an inlet port 12 so that hydraulic fluid from a feed pipe 13 passes to pipe 15 connected to rear wheel brake cylinders of the vehicle. A branch pipe 18 from feed pipe 13 is connected to a deceleration responsive valve comprising a ball 19 normally seated by a spring and lifted off its seat when the rear wheels of the vehicle decelerate by a plunger 26 integral with a plate 35 which is splined to a spindle 30 rotated by the vehicle wheels and frictionally driving a flywheel 31. On deceleration, flywheel 31 tends to overrun plate 35 and causes balls 34 to ride up inclined recesses in the plate so that plunger 26 lifts the ball 19 off its seat, admitting fluid to a chamber 20. This fluid passes via pipes 22, 23 to a port 24 opposite the rear end of the spool 11 so that a force is applied to the latter opposing that applied by pedal 16. As pressure builds up in chamber 20 it acts on plunger 26 to oppose the camming action of balls 34 and lap the ball valve 19 when pressure in chamber 20 corresponds with the degree of deceleration of the rear wheels of the vehicle. To allow for the time lag before the deceleration valve operates an anticipator is provided comprising a piston 37 floating between two springs 38, 39 in a casing 40 connected at one end with the pipe 15 and at the other end by pipe 43 with the pipes 22, 23 so that sudden increases in pressure supplied to the brake cylinders are balanced by a rise in pressure in pipe 23 caused by movement of piston 37. Piston 37 does not affect pressure in pipe 23 once pressure in pipe 15 has become steady and ball valve 19 is operative to control pressure in chamber 20. Fig. 2 (not shown) is a simplified arrangement in which flywheel 61 is in threaded engagement with a boss 60 on spindle 59 driven by the rear wheels of the vehicle, and on deceleration of those wheels moves axially to cause a plunger 62 to act directly on valve spool 51 in opposition to pressure supplied to a port 56 by a pedal-operated master cylinder to control the supply of hydraulic fluid from a feed pipe 53 to pipe 55 leading to the brake cylinders. As in the Fig. 1 construction an anticipator 65 is fitted and causes sudden changes in the pressure supplied to the brake cylinders to effect corresponding changes at a port 66 opposing the applied pressure at port 56. Another embodiment, Fig. 4, employs a triple valve comprising a port 126 connected with a vacuum source, a a port 127 connected to one chamber of a vacuum-suspended brake cylinder, a diaphragm 125 separating chambers connected to the inlet and outlet, and a diaphragm 124 separating the former chamber from a control chamber which is supplied by an inlet valve 113 and bled by an orifice 128 to the interior of a valve operating cup 123 secured to the diaphragm 124 and having openings 130 normally interconnecting ports 126, 127. Valve 113 is operated by a lever system comprising lever 105 which is pivoted at 106 and connected to the valve by a pin 111, a lever 107 pivoted at 108 to lever, 105 and connected to lever 105 through a spring 110, a plunger 118 having a cup seal 117 acted on by hydraulic pressure from a pedal-operated master cylinder, and a plate 101 pivoted at 100 to a clamp 98 secured to spindle 90 driven by the vehicle rear wheels, a forked extension 109 of lever 107 abutting a collar 104 secured to the plate 101. A flywheel 95 frictionally driven by spindle 90 acts on the plate 101 via balls 103 and shaped recesses 102 when the spindle decelerates so as to oppose the force exerted by plunger 118 and modify the operation of valve 113. A screw stop 131 is adjustable to effect an overall modification. In operation, when pressure is fed to seal 117 by the pedal-operated master cylinder lever 107 pivots to compress spring 110 and thereby pivot lever 105 to open valve 113 to admit air to the control chamber of, the triple valve. This in turn causes cup 123 to act on plate valve 121 to admit air to the brake cylinder to apply the brake. The resulting deceleration causes plate 101 to pivot and act on the end 109 of lever 107 in opposition to the applying force to modify the control of valve 113 accordingly. In a modification (Fig. 6, not shown) of the Fig. 1 embodiment, pressure from a pedal-operated master cylinder acts on a piston 166 and then via a spring 158 on a valve plunger 152 to control the supply of fluid from a feed port 154 to a port 155 connected to the brakes, while pressure hydraulic fluid is fed at all times via port 199 to a chamber 197 to urge a plunger 192 against a plate 190 which is rotatable with but slidable relative to a spindle 169 driven from the vehicle rear wheels. When deceleration occurs a flywheel 171 acting through a friction disc 182 overruns the plate 190 causing threadedly connected members 188, 189 to unscrew and oppose the pressure in chambers 197 to modify the operation of the valve plunger 152. A bleed 201 from the pedal-operated master cylinder provides for emergency operation of the brake should the supply of pressure hydraulic fluid fail.