Abstract: An automatically operated clutch (3) between a motor vehicles engine (2) and gearbox (4) is moved by a hydraulic actuator (8), which acts on the clutch release, from a fully disengaged position through positions in which clutch slip occurs into a fully engaged position. A point of contact on the clutch at which transmission of engine torque begins is determined and the corresponding position of the actuator (8) stored. In the region above the contact point within which no torque is transmitted, the position of the actuator is adjusted by a position control circuit (70), while in the region below the contact point in which torque is transmitted, an engine speed control circuit (78) is superimposed on the actuator position control circuit. The engine speed at the point of contact is adjusted to a figure somewhat (approx. 50 rpm) above the speed of the clutch (output) shaft.

Abstract: A vehicle fluid pressure supply system in which a fluid pressure supply pump (10) is connected via solenoid-operated flow control valve (15) with a plurality of separate fluid pressure operated circuits(A, B, C) each operating separate functions of the vehicle. Detectors (25, 26, 27, 30 to 35) are provided for detecting the current operative state and the fluid pressure supply status of each circuit, and an electrical control unit (28) means which receives signals from the detectors operates the control valve to direct available pump flow to the appropriate circuit to maintain each circuit at least at a minimum pressure level required to operate the associated function.

Abstract: A ratio selector mechanism for the selection of the operative ratio in an associated synchromesh vehicle transmission in which a fluid pressure operated actuator operates synchromesh units. The operating pressure of the actuator is varied either mechanically or electronically during selection of a given ratio in the associated transmission or dependent on the ratio being selected. A first actuator selects a shift rail, and a second actuator engages a gear. A valve member acts against a bias force which is varied based on the position of the first actuator to control the pressure in the second actuator.

Abstract: A vehicle transmission having a main drive clutch (14), a multi-ratio gearbox (12), a gear engaging mechanism (25) for engaging the operative ratio of the gearbox, and a manually operable gear selector (24) allowing the operator to manually select the operative ratio of the gearbox when the transmission is acting in a manual mode. An electronic control unit (36) is also included which controls the disengagement and engagement of the drive clutch at start-up and halting of the associated vehicle and during gear changes and which controls the operation of the gear engaging mechanism (25) in response to movements of the gear selector (24). The electronic control unit (36) is also arranged to override the gear ratio currently selected by the operator to select a more appropriate gear ratio for the current conditions if a predetermined operating condition occurs when in its manual mode.

Abstract: An actuation system particularly for a vehicle clutch, in which a source of pressurized fluid is interconnected with a slave cylinder (11) via a displacement means (12). The displacement means (12) includes a component which is displaced by the pressurized fluid from the source to provide a displacement proportional to the actuating movement of the slave cylinder (11) caused by the pressurized fluid, and a sensing means is provided which is operable to measure the displacement to indicate the actuating movement of the slave cylinder. Various displacement means in the form of valves are disclosed together with a mechanism for interconnecting the operation of a vehicle clutch and throttle.