GB988261A - Device for controlling the braking force of vehicle brakes - Google Patents

Abstract

988,261. Fluid-pressure brakes. H. TEVES, E. A. TEVES, and M. TAUSEND, (trading as ALFRED TEVES MASCHINENUND ARMATURENFABRIK KOMM.-GES.]. Jan. 25, 1962 [April 8, 1961], No. 2831/62. Heading F2F. A device for controlling braking force in dependence on deceleration of a supporting wheel of a vehicle is effective only when a change occurs in the ratio of such deceleration to braking force, measures of these being balanced either hydraulically or electrically whereby an out-of-balance resulting from a tendency to skid causes a reduction in braking force. In one embodiment, Figs. 1 and 2, hydraulic fluid is supplied to a wheel cylinder 3 by a pump 4 under control of a valve 6 which progressively restricts flow in a return line 7 to reservoir 8 so as to control pressure in a line 5. The device for controlling braking force is placed between line 5 and a line 5a leading to the cylinder 3, a line 11 leading from a chamber 14 of the device to reservoir 8. An inertia device within chamber 14 comprises a flywheel 30 driven via cam members 27, 28 and balls 29 from a shaft 26 coupled to the transmission 12 on which the braked wheel is mounted. The arrangement is such that on deceleration flywheel 30 moves axially inwards and so moves a valve member 25 which is rotatable and slidable within a sleeve 19 against the resistance of a spring 31. Sleeve 19 is in turn slidable within the casing of the device against the resistance of a spring 18. A ring 20 provided with seals 21, 22 is arranged between a reduced part of sleeve 19 and the casing to form a pressure space 71. The valve member and sleeve have co-operating control surfaces 56, 57 and 58, 59, respectively. A pressure limiting arrangement between line 5 and an annular space 55 bounded by the control surface comprises spring-urged pistons 36 and 37, the former acting through a rod 42 on a ball valve 40 within piston 37. When valve 6 is actuated, pressure builds up in chamber 71 via inlet port 66, Fig. 2, normally -open ball valve 40 in piston 37, piston chamber 65, passage 68, groove 53, passage 69 and passage 70, causing sleeve 19 to move to the left, compressing spring 18. The pressure at the same time is transmitted via groove 60, annular space 55, passage 61 and line 5a to wheel cylinder 3, causing the brake to be applied. The resulting deceleration of wheel 1 causes axial movement of valve member 25 to follow up the movement of sleeve 19, so that the relative positions of the control surfaces remain the same. Pressure also builds up in piston chamber 64 which is connected to the space 55 by passage 62, recess 54 and passage 63, but since the pressure is the same in chambers 64 and 65 piston 36 is not affected. Should deceleration be substantially greater than that normally obtained at a given brake pressure owing to wheel slip, valve member 25 moves ahead of sleeve 19, causing control surfaces 57, 59 to close up and cut off the supply of fluid to the wheel cylinder. Shortly afterwards, control surfaces 56, 58 move apart, opening a communication between the wheel cylinder and reservoir 8 via chamber 47, passages 50, 51, 52 within the valve member 25, chamber 14 and line 11. As a result brake pressure is reduced until the wheel deceleration decreases, resulting in lapping of the valve control surface 56, 58. Brake pressure in the cylinder 3 is subsequently less than the applied pressure in line 5 by an amount determined by the limiting arrangement, since reduced pressure in chamber 64 (connected with the brake cylinder) causes ball valve 40 to close, whereby the pressure in chamber 65, and hence in chamber 71 and recess 60, is determined by the relationship between the area of piston 37 and the resistance of a spring 38 acting on piston 37. In a second embodiment, Fig. 3, hydraulic fluid is supplied to wheel cylinders 72, 72<SP>1</SP>, 72<SP>11</SP>, 72<SP>111</SP> by lines 70 in each of which is disposed a solenoid-operated valve 73 adapted when energized sequentially to cut-off the supply of fluid and connect the wheel cylinder to a reservoir 82. The fluid is supplied by a pump 71 controlled by a driver's valve as in the previous embodiment. The solenoid 80 of each valve 73 is energized by unbalance current in a respective bridge circuit 75 comprising fixed resistors in two branches and variable resistors 74, 78 in the other two branches, the former of which is controlled by a brake pressure device and the latter by a deceleration-responsive device 77.