GB1246053A - Improvements in or relating to anti wheel-spin devices - Google Patents

Abstract

1,246,053. Fluid-pressure brakes. MASCHINENFABRIK OERLIKON. 17 April, 1969 [17 April, 1968], No. 19726/69. Heading F2F. [Also in Divisions G3 and H2] An electrical device for limiting wheel slip in rail locomotives comprises means for producing a vehicle speed signal, means for producing a driving wheel speed signal, means for comparing the two signals to produce a wheel slip signal and slip control means to which are supplied both the slip signal and the vehicle speed signal. The vehicle speed is measured by a separate wheel 6 carried by a spring loaded and damped arm (Fig. 2, not shown) and having a heater for icy conditions. The output voltages of tachogenerators driven by the wheels 1 and 6 are compared at 19 and any difference is supplied as a signal S to a unit 24 and according to its polarity this reduces either the magnitude or frequency of the motor supply or the effect of a pneumatic brake 22 which is actuated by a cylinder 21 controlled by a valve 23. Regenerative or rheostatic braking may also be controlled. The unit 24 incorporates a "dead band" circuit whereby no correction is made until the slip exceeds a point at which maximum adhesion occurs (point A, Fig. 1, not shown) and this point is adjusted according to the vehicle speed signal VT and the motor count J, measured at 16, which is taken as a guide to the condition of the rail surface. An overriding limit is imposed beyond which the dead band is not extended. The dead band may also be controlled by the driver. The comparator 19 receives signals of motor count J and a brake pressure p, measured at 20 and when these, together with the vehicle speed, are of such values that it is evident that slip cannot occur any residual slip signal is switched to a servomotor which adjusts a potentiometer in circuit with the driving wheel tacho-generator so that the slip signal becomes truly zero. The driving motor 18 may be energized from an A.C. supply 13 by a transformer 15 and thyristor rectifiers 17 by which speed is controlled, and 17 may act as a converter for regenerative braking, controlled by the slip control signal. Alternatively rheostatic braking may be used the motor field being supplied by rectifiers controlled by the slip control signal. As other alternatives it is mentioned that the motors may be asynchronous A.C. machines controlled by frequency adjustment or the supply may be D.C with thyristors 17 acting as a "chopper". There may be several driving motors individually or group controlled. During normal running, control is by a signal S from the drivers controller 25. In Fig. 11 (not shown) the motor supply rectifier comprises a thyristor bridge controlled by the difference between the actual motor current J and a reference value Jc which is reduced by the slip controlled signal.