GB841706A - Means for automatically controlling a vehicle variable-speed power transmission mechanism - Google Patents

Abstract

841,706. Transistor relay circuits. LUCAS (INDUSTRIES) Ltd., J. Oct. 1, 1958 [July 8, 1957], No. 21503/57. Class 40(6). [Also in Group XXIV] The overdrive or other electrically controlled change-speed gear of a motor-car is controlled in dependence of engine speed by electrical impulses applied from the primary coil i of the usual ignition circuit, having a contact breaker b and spark reducing condenser c, through a smoothing inductance h to a clipping diode dl and a condenser cl. A pumping diode circuit, having diodes d2, d3 and a condenser c2, is fed with the impulses and is connected through a resistance rl and a potentiometer resistance r2 to the negative side of the circuit; the pumping diode circuit is also connected to the base terminal of a transistor t. A relay coil cr is fed by the transistor t and controls, either indirectly as shown, or directly, Fig. 1 (not shown), a switch sr1 in the circuit of a solenoid s energized to establish the overdrive or other ratio. The arrangement is such that, with the motor-car stationary and the engine switched off, the switch srl is closed by a spring. On starting the car engine, the relay coil cr is energized and opens the switch srl to deenergize the solenoid s and establish direct drive. As the speed of the engine increases, impulses fed through the pumping diode circuit d2, d3 change the base voltage of the transistor t, so that the relay cr becomes de-energized, and the switch srl closes to energize the solenoid s and establish overdrive. The relay cr acts upon a switch sr2 which, when the relay coil is energized, moves to the dotted position shown, and holds the relay coil cr1 de-energized. On increasing engine speed, the relay cr becomes de-energized and the switch sr2 is restored to the position shown, current then passing through a switch 3, a resistance r3 and the relay cr1 to a switch 5 and the switch sr2. The relay cr1 then closes the switch sr1, to establish the overdrive ratio.