GB968939A - A device for automatically avoiding locking of motor vehicle wheels - Google Patents

Abstract

968,939. Fluid-pressure brakes. EDITORIALE DOMUS S.p.A. July 19, 1962 [July 26, 1961], No. 27749/62. Heading F2F. A device responsive to deceleration of a vehicle wheel for controlling hydraulic pressure supplied to a wheel brake cylinder to prevent wheel locking comprises two hydraulic cylinders the pistons of which are connected respectively to opposite ends of a rocker arm having a movable fulcrum, one cylinder being pressurized by a pedal-operated master cylinder and the other cylinder being connected with the wheel cylinder, and means responsive to deceleration of the wheel to vary the position of the fulcrum. As shown, an hydraulic master cylinder 1 operated by pedal 2 pressurizes a cylinder 3 whose piston is connected at 25 to one end of a rocker arm 4 fulcrumed on a roller 5 carried by a lever 6. The other end of the arm 4 is connected at 26 to the piston of a cylinder 7 constructed as a master cylinder to supply hydraulic fluid to wheel cylinder 8 at a pressure dependent upon the pressure in master cylinder 1 and the ratio between the lengths of arm 4 on opposite sides of the roller 5. The latter is varied by a diaphram-type actuator 13 controlled by a solenoid-operated valve 15 in turn controlled electrically by a deceleration responsive unit 19 associated with the wheel. The actuator 13 comprises a diaphragm 41 acted on by a spring 45 and secured to a membrane 42 dividing the actuator housing into chambers 43, 44, the former being open to atmosphere and the latter connectible by the valve 15 either to atmosphere or (when the va've is energized) to a vacuum reservoir 17 evacuated by the inlet manifold 18 of the vehicle engine. The diaphragm is connected by a link 12 to the lever 6 which is slidable in a sleeve 35 pivoted at 36 and also carried by a pin 38 engaging a slot 37 in the lever, the arrangement being such that on movement of the diaphragm from its rest position shown the roller 5 moves linearly towards the connection 25 with the piston 21 of cylinder 3 to reduce the pressure in cylinder 7 relatively to that in cylinder 3 and hence prevent wheel locking. Piston 21 is sealed by a resilient ring 22 acted on by spring 23, and piston 28 in the cylinder 7 is a compound piston, seals 30 being provided between the piston parts and at the inner face of the inner part and compressed axially by spring 31. Inlet 29 is connected to an hydraulic reservoir. The circuit for energizing the solenoid-operated valve 15 is housed in the unit 19 and comprises a relay 58, Fig. 4, connected across a rectifier 57 which is interposed between large condenser 55, 59. Current is supplied from a generator 65, 66 driven by the vehicle wheel via a rectifier 54 and the rectifier 57 to charge the condensers to a voltage dependent upon the speed as the wheel accelerates, the current by-passing relay 58, but during decleration condenser 59 discharges through the relay 58 at a rate dependent on the rate at which the voltage on condenser 55, also discharging through resistance 56, drops. By a suitable choice of time constant for condenser 55 and resistance 56 relay 58 is arranged to operate on a predetermined rate of deceleration being exceeded. The condenser 67 and resistance 61 are provided to ensure that the voltage across the network, i.e. across resistance 61 is proportional to the frequency where the generator is an A.C. type. As an alternative to a generator a battery may supply a contact breaker device driven by the wheel (Fig. 3, not shown), the intermittent current resulting from this being passed through the primary of transformer designed to produce a secondary voltage proportional to the frequency. In this embodiment condenser 67 and resistance 61 are omitted.