GB989119A - Improvements relating to slip control apparatus - Google Patents

Abstract

989,119. Vehicle brakes. WESTING- HOUSE BRAKE & SIGNAL CO. Ltd. May 6, 1963 [May 11, 1962], No. 18161/62. Heading F2F. [Also in Divisions B7, G1 and H3] Apparatus for preventing excessive slipping between one or more members of a first body engaging a second body on a surface on which forces are exerted via the members to tend to produce a change of speed of the first body comprises means for deriving respective signals representative of the peripheral velocities of the members, selective means for selecting in accordance with the relative magnitudes thereof that one of the signals which corresponds to the member which slips least and respective comparison means for comparing each signal with the signal thus selected to give indication of slip between a member or members and the surface being excessive with means responsive to such indication for adjusting the force applied via the member or members in such a sense as to tend to reduce the slip. As shown compressed air from a compressor is applied to a storage reservoir 2 the output pipe 3 of which is connected through a driver's valve 5 and pipes 6, 7 to electro pneumatic valves 17, 18. The latter are connected respectively to the front and rear brake cylinders 8, 10 and 9, 11. Associated with each wheel is a generator 12, 13, 14, 15, e.g. a variable reluctance toothed wheel generator which induces a voltage in a coil of a permanent magnet the frequency of which is proportional to the angular velocity of the wheel. A diode pump circuit, Fig. 3, produces at the point A a voltage proportional to the angular velocity of the wheel. The respective voltages produced by the generators 14, 15 are then compared by a comparison amplifier circuit comprising transistors T2, T3 and diode D3 which along with the corresponding transistors and diode in the other half of the circuit makes available at the point B whichever of the signals derived from the two diode pumps is the greater. The signal at B is fed to the transistor T2 and also to the corresponding transistor to produce at C a signal which represents any difference that exists between the angular velocity of the wheel associated with that circuit and the greater value of angular velocity represented by the signal at B. This difference signal is then fed to the transistor T4 which is so biased as to permit energization thereof by signals above a predetermined value which corresponds to the amount of slip which can occur before the slip is regarded as excessive. The transistor T4 when energized operates a relay RL1 which is connected via a diode D5 to the transistor in the circuit corresponding to the other front wheel. Energization of relay RL1 or RL2 causes the valve 17 or 18, as the case may be, to reduce the pressure in the corresponding front or rear brake cylinders. A network R4, R5, D4, C3 is effective as a delay storage network to permit a fixed rate of delay of the last received signal in the event of all wheels locking at once so as to ensure that a reference signal is always available for the comparison amplifiers. If the nearside and offside wheels are to be compared provision may be made to compensate for unequal angular velocities arising from cornering. Such compensation may be a signal applied to the apparatus indicative of the linear velocity of the vehicle and the radius of the turning circle or alternatively means may be provided to render the apparatus inoperative in the event of the vehicle traversing a turning circle of less than a predetermined radius, such an amount being indicated by the steering wheel. The invention may be applied to a wheeled road vehicle for the purpose of preventing wheel spin during acceleration. If the angular velocity of the two compared wheels differs by more than a predetermined amount the driving force may be relieved on all driven wheels, e.g. by throttling back the engine, easing the clutch or braking the driving wheels or at least the wheel whose angular velocity is excessive. If only the driving wheel on one side of the vehicle is unable to grip means may be effective to lock the differential. The invention may also be employed for detecting a difference in angular velocity of wheels arising from a difference in radius caused by the tyre on one becoming defective due to a puncture or leaking air valve. This indication may energize a light or other warning means. The invention may also be applied to metal rolling mills, the second body being a sheet of metal and the members being the rollers of the mill.