Safety arrangement for protecting against the locking of wheels in motor vehicles

Claim 1

An anti-skid arrangement for a vehicle having a first wheel and additional wheels and brake means for said first wheel, comprising, in combination, brake-release means comprising an electrically actuated valve and amplifying means including a power-transistor stage having an output connected to said valve for controlling energization of the latter and having an input for receiving actuating signals; an OR-gate having an output connected to said input of said brake-release means and having a first input and a second input; triggerable memory means having a first state and a second state and having two inputs and having an output connected to said first input of said OR-gate and operative when triggered intO said first state for furnishing an actuating signal to said input of said brake-release means; signal generating means for generating a voltage proportional to the rotational speeds of said first, wheel, and including A.C. generator means synchronized with rotation of said first wheel and operative for generating an alternating current voltage having a frequency proportional to the speed of said first wheel, and low-pass filter means connected to the output of said signal generating means and operative for converting said alternating current voltage into a direct current speed signal having a magnitude varying in proportion to the speed of said first wheel; differentiating means operative for differentiating said speed signal to produce an acceleration voltage proportional to the acceleration of said first wheel; deceleration monitoring means comprising a first threshold switch having an output connected to said first input of said memory means and having an input connected to the output of said differentiating means and responsive to said acceleration voltage when the latter has a polarity corresponding to wheel deceleration and operative for triggering said memory means to said first state when the magnitude of the wheel deceleration exceeds a predetermined value; acceleration monitoring means comprising a second threshold switch having an output connected to said second input of said memory means and having an input connected to the output of said differentiating means and responsive to said acceleration voltage when the latter has a polarity corresponding to wheel acceleration and operative for triggering said memory means to said second state when the magnitude of the wheel acceleration exceeds a predetermined value; slip-detecting means having an output connected to said second input of said OR-gate and operative for furnishing an actuating signal to said brakerelease means when the slip of said first wheel exceeds a predetermined value, said slip-detecting means comprising a vehicle-velocity simulating stage operative for generating a vehicle-velocity signal simulating the speed of travel of the vehicle, comparator means for comparing the speed of travel of the vehicle with the speed of said first wheel to generate a signal representative of the slip of said first wheel and including summing means having a first input connected to the output of said low pass filter means and having a second input connected to the output of said simulating stage to receive said vehicle-velocity signal and having an output at which is furnished a voltage corresponding to the difference between the voltages at the first and second inputs thereof and a third threshold switch having an input connected to said output of said summing means and having an output connected to said input of said power-transistor stage for furnishing to the latter an actuating signal when the voltage at the output of said summing means exceeds a predetermined value; and means including a fourth threshold switch having an input connected to the output of said simulating stage for receipt of said vehicle-velocity signal and having an output connected to said input of said brake-release means and operative for preventing actuation of said brakerelease means when said vehicle-velocity signal has a value indicative of a vehicle speed below a predetermined speed.