GB1234418A - - Google Patents

Abstract

1,234,418. Controlling clutches. C. CAPPA. 22 Aug., 1968, No. 40153/68. Heading F2L. A vehicle clutch is automatically disengaged by a vacuum-operated servomotor 17 on gear shift and, below a predetermined vehicle speed, an accelerator release and on application of the brakes. The clutch can also be disengaged manually by the usual clutch pedal 10. The servomotor 17 has a chamber 19 connected to a vacuum reservoir 25 on energization of a solenoid valve 24 to shift a piston 16 to the left and disengage the clutch by way of a flexible cable 14 or an hydraulic telemotor system. The control circuit of the valve 24 includes a centrifugal switch 29 which opens at a vehicle speed of 25 kilometres per hour, an accelerator controlled switch 26 opening on depression of the accelerator, an ignition switch 27 closed when the ignition is " on", a switch 74 closed on application of the brakes, a microswitch 68 which is opened on depression of the accelerator pedal, and a switch 72 closed on grasping the gear lever. Thus on starting, the ignition switch 27 is closed and the valve 24 energized so that the clutch is disengaged by vacuum in the chamber 19. On depression of the accelerator, the microswitch 68 is opened and the clutch engages under the action of the clutch engaging spring 69. Release of the accelerator below 25 kilometres per hour, i.e. when the centrifugal switch 29 is closed, energizes the valve 24 to disengage the clutch. Above this speed the switch 29 is open and the clutch remains engaged. Actuation of the brakes closes the switch 74 and if the switch 29 is also closed the clutch disengages. Operation of the gear shift lever closes switch 72 to disengage the clutch. The rate of clutch engagement is controlled by controlling venting of a servo chamber 18 behind the servo piston. Venting is controlled by three valves: a solenoid valve 21 which is closed when energized and is de-energized when the centrifugal switch 29 is open to give rapid re-engagement on completion of gear shift above 25 kilometres per hour, a valve 23 having a plurality of ports successively opened as the accelerator is depressed, and a valve 70 having a sleeve abutting the servo casing and co-operating with a vent port in the piston-rod. Thus assuming the valves 21, 23 to be closed, when the chamber 19 is connected to atmosphere the piston will move rightwardly until the valve 70 closes to give slipping clutch engagement, this position being set by adjusting the valve sleeve 70 by means of a screw-threaded collar thereon which abuts the casing. Air is admitted to the chamber 18 on clutch disengagement by a oneway valve 20.