GB617405A - Improvements in and relating to the control of electrically-actuated clutches adapted to couple a variable-speed motor to a driven element - Google Patents

Abstract

617,405. Transmitting mechanical power. SAMPIETRO, A. C., and ROBERTSON, D. R. Sept. 30, 1946, No. 29169. [Class 38 (iv)] A variable speed motor, such as an internalcombustion engine for driving a vehicle, is smoothly coupled to a transmission shaft by an eddy current clutch, or electrically-actuated friction clutch, having an excitation winding energized by a battery-charging generator which is driven by the motor and the output voltage of which rises with increasing motor speed. The connection between the generator and clutch excitation winding is independent of a cut-out in the charging circuit. Fig. 1 shows a system for use on a vehicle, comprising an engine-driven generator 9 for charging a battery 14 over a cut-out 13 and for energizing a dutch-actuating winding L1, the generator being provided with the usual voltage regulator 18 and including a main field winding L2 as well as a weak reverse field winding L3 which is for the purpose of reducing the residual magnetism of the machine to allow the clutch to disengage when the main field circuit is opened. A switch 15 in the main field circuit closes with the ignition switch of the vehicle, whilst a normally closed switch 16 in the same circuit may be opened to de-energize the machine and so de-clutch the transmission shaft when changing gears. With the engine running, engagement of the clutch is effected by accelerating the engine so that the voltage of the generator, which at this stage functions as a separately excited machine excited by the battery 14 over resistors R1, R2, rises to a value sufficient to actuate the clutch. When the generator voltage approaches that of the battery, a relay 7, 8 reduces or cuts out resistor R2, whereby the machine becomes shunt excited and builds up to normal voltage. A thermal switch 17 may reduce resistor R1 upon the machine attaining a prescribed temperature. Alternatively, a resistor with a large positive temperature coefficient may shunt the main field winding. Closure of the main field circuit, or of the clutch excitation circuit may be made dependent both on the engine speed and the setting of the fuel control member, the arrangement providing for a greater initial clutching torque as the setting of the fuel control member is advanced. In another arrangement, relays actuated by the generator's volts sequentially cut-out resistance from the clutch excitation circuit as the engine speed rises. Specifications 607,820 and 609,690 are referred to.