GB1519853A - Electric vehicle speed control systems - Google Patents

Abstract

1519853 Control of D.C. motors LINDE AG 16 July 1975 [16 July 1974] 29734/75 Heading H2J In a speed control for an electrically propelled vehicle, a diaphragm arranged in the light path to a photo-transducer is arranged to be moved from a central rest position in opposite directions for forward and reverse motion, means also being provided to inhibit drive current when the diaphragm is passing through its central rest position. In Fig. 2, a luminescence diode 13 and a photo-resistor 14 are mounted in a block 10 having a slot 12 in which is movable a diaphragm 6 secured to a shaft 5, the latter being rotatable by the speed control pedal (2) of an electric vehicle coupled to shaft 5 by a lever (3) and pivot member (4), Fig. 1 (not shown). The resistor 14 forms part of an impedance transformer including resistors r4, r5 and transistor T2 and controlling a transistor T1, whose output voltage at 17, 18 is used to vary the speed of the vehicle driving motor (preferably D.C.) through a conventional pulse control unit for a semiconductor switch controlling the supply (preferably from a battery) to the motor. The portion of the diaphragm 6 in the slot 12 includes an aperture (7), Fig. 1 (not shown), whereby movement of the control pedal varies the amount of light reaching photoresistor 14 and hence the speed of the motor. Shaft 5 also carries cam members 8, 9 actuating a reversing switch for the motor, the diaphragm 6 being movable from a central rest position to provide speed control in either direction of rotation. To prevent current surges when the motor is reversed, caused by the change in photo-resistor 14 lagging the change in diaphragm movement to produce an incorrect transformer output voltage at the central position of the pedal, the reversing switch includes contacts 19, 20 which open at the central position to switch off transistor T2, the output voltage controlling T1 then being determined by resistors r4, r6 chosen to ensure that the motor current is zero at the central position. The diaphragm may be designed to vary the change of light over its path of movement, so that the corresponding speed change is non- uniform to provide greater control sensitivity at low speeds. Similarly light changes for the same movement may be different for opposite directions of diaphragm movement to provide a lower speed range for reverse movement of the vehicle. Alternatively, the light changes may be chosen to provide the same speed ranges. The resistor 14 may be replaced by a photocell, the diaphragm may be completely black or expose the light in its central position and the various electrical components may be constructed as a printed circuit. The motor current may be controlled by contactors instead of a semiconductor switch.