GB860545A - Improvements in vehicle transmission systems - Google Patents

Abstract

860,545. Clutch control. SMITH & SONS (ENGLAND) Ltd., S. July 15, 1957 [July 13, 1956], No. 21730/56. Class 80 (2). To prevent jerks on a vehicle due to sudden engagement of an electromagnetic clutch, particularly of the powder type as in Specification 649,553, when the clutch is engaged whilst the vehicle is overrunning the engine (e.g. on downshift), the clutch winding 28 is energized under control of means responsive to drive torque, e.g. a torque-meter on the propeller shaft or, as shown, an acceleration responsive mercury switch 39, 40 which permits only partial energization of the clutch through a resistor 38 to about onethird maximum drive torque capacity, unless drive torque exceeds a predetermined value, whereupon the acceleration switch shorts the resistor 38 and fully energizes the clutch. Function summary.-For starting the clutch is energized by the usual engine-driven generator 1 which has supplementary battery excitatation together with choke control for fast idle. At above 10 m.p.h. an output driven governor switch 16 opens to change to battery energization of the clutch through the acceleration responsive switches 39, 40. In high gear with open throttle the acceleration switches 39, 40 are cut-out and the clutch fully energized. During gear shift a touch-sensitive switch 17 on the shift lever breaks the clutch circuit and substitutes a reverse demagnetizing circuit. A similar action occurs on engaging neutral below 10 m.p.h. Closure of the engine throttle at speeds below 10 m.p.h. breaks the clutch-energizing circuit but does not supply the reverse demagnetizing current. On an upgrade the mercury switches 39, 40 are gravitationally closed for full clutch energization. Operation.-Initially the circuit is in the condition shown. Closure of the engine ignition switch 12 energizes three relay coils T, G, C. Starting.-To start the vehicle a gear is established, opening a neutral switch 15; and the throttle is opened, opening a throttle switch 14; de-energizing the relay coils C, T. The remaining energized relay coil G changes over contacts G1, G2, the latter completing an energizing circuit from the generator 1 to the clutch winding 28, the former ensuring that the generator field 3, in addition to excitation from the usual voltage regulator 4 through a resistor 10, is also excited from the battery 9 through a resistor 37, thus causing gradual clutch energization at very low speeds. If the choke is operating, a switch 33 is opened thereby, to insert an additional resistor 11 in the field circuit of the generator to compensate for increased idle speed. Normal running.-When the vehicle speed exceeds 10 m.p.h. the output driven governor switch 16 opens to de-energize the relay G which changes contacts G1, G2 to the position shown, in which the generator field 3 is fed directly and only from the regulator 4 and the clutch winding 28 is energized from the battery 9 at reduced value through the resistor 38, unless vehicle acceleration is sufficient to close one or other of the mercury switches 39, 40 to short the resistor 38 for full energization of the clutch. Two switches 39, 40, inclined to the forward direction 41, are used to cancel effect of transverse acceleration. Gear shift.-Operation of the gear-shift lever closes the touch-sensitive switch 17 which energizes the relay C operating change-over contacts C1, C2 to break the clutch energizing circuit and substitute a reduced reverse demagnetizing circuit through a resistor 32. Movement into neutral below 10 m.p.h. (governor switch 16 closed) has an identical effect by closing a neutral switch 15 to energize the relay C. Supplementary functions.-Movement into high gear closes a switch 23 which shorts the resistor 38 producing full energization of the clutch with open throttle above 10 m.p.h. (switches 14, 16 open). Closing the throttle closes the switch 14, energizing the relay T to operate switches TI, T2 which, below 10 m.p.h. (switch 16 closed), de-energizes the clutch. To avoid freezing of the mercury the resistor 38 is wound round the gloss tubes of switches 39, 40.