Abstract: A hydraulic clutch actuation system having a hydraulic clutch control device which includes at least one clutch master cylinder that communicates via a pressure-medium line with a clutch slave cylinder used for actuating a clutch device, the pressure prevailing in the pressure-medium line being relievable via at least one emergency release valve device to permit disengagement of the clutch device in an emergency situation. The hydraulic clutch actuation system is distinguished in that the emergency release valve device has a seal-carrier device for a sealing element which is movable in response to an electromagnet out of an open position, in which a pressure-medium inlet is open, into a closed position in which the sealing element seals the pressure-medium inlet.

Abstract: Axially-movable first and second shift rails (70, 72) control engagement of one of a pair of gears (37, 32, 33, 34) coupled thereto. A first shift finger (102) rotates with a drive shaft (110) and is also pivotable thereto. A second shift finger (104) is mounted on the drive shaft so as to be selectively rotatable therewith, and is formed as a bell crank lever (154) having a first limb, which non-removably engages the second shift rail, and a second limb. The first shift finger is pivoted by a solenoid actuator (134) between a disengaged position, in which the first shift finger is clear of the first shift rail and the second limb of the bell crank lever, and an engaged position in which the first shift finger engages the first shift rail or the second limb depending upon the angular orientation, or rotational position, of the first shift finger.

Abstract: Axially-movable first and second shift rails (70, 72) control engagement of one of a pair of gears (37, 32, 33, 34) coupled thereto. A first shift finger (102) rotates with a drive shaft (110) and is also pivotable thereto. A second shift finger (104) is mounted on the drive shaft so as to be selectively rotatable therewith, and is formed as a bell crank lever (154) having a first limb, which non-removably engages the second shift rail, and a second limb. The first shift finger is pivoted by a solenoid actuator (134) between a disengaged position, in which the first shift finger is clear of the first shift rail and the second limb of the bell crank lever, and an engaged position in which the first shift finger engages the first shift rail or the second limb depending upon the angular orientation, or rotational position, of the first shift finger.

Abstract: A hydraulic actuation system for an automated transmission system including an active clutch includes; a hydraulic clutch actuator controlling engagement of the clutch, the hydraulic control actuator being preloaded towards a disengaged position of the clutch, whereby pressure above a first predetermined value is required in order to move the clutch to a predetermined position; first and second gear engagement actuators for controlling the selection and engagement of a selected gear ratio; a source of hydraulic fluid under pressure, a hydraulic fluid reservoir; a clutch control valve for selectively connecting the clutch actuator to the source of hydraulic fluid under pressure or to the reservoir; a gear engagement control valve for selectively connecting each gear engagement actuator to the source of hydraulic fluid under pressure or to the reservoir; and a changeover valve situated between the gear engagement control valve and the first and second gear engagement actuators, said changeover valve in a first

Abstract: A hydraulic actuation system for an automated transmission system includes; a hydraulic fluid accumulator (275), a hydraulic fluid reservoir (278), a clutch slave cylinder 22 and gear engagement select and shift actuators (114, 115); the clutch slave cylinder (22) and select and shift actuators (114, 115) are selectively connected to the accumulator (275) or to the reservoir (278) via a main control solenoid valve (120); a further clutch control solenoid valve (122) being connected between the main control valve (120) and the clutch slave cylinder (22), the clutch control valve (122) being switchable between a open position in which slave cylinder (22) is connected to the main control valve (120) and a closed position in which the clutch slave cylinder (22) is isolated from the main control valve (120); the working chambers (118, 119) of the select and shift actuators (114, 115) being selectively connected to the main control valve (120) or to the reservoir (278) via gear control solenoid valves (144, 145, 14

Abstract: A hydraulic actuation system for an automated transmission system including, a hydraulic clutch actuator (22) for controlling engagement of a clutch (14), a gear engagement actuator (114,115) for controlling engagement of a gear, said gear engagement actuator (114,115) being in the form of a double acting ram having first and second working chambers (118,119) acting on opposite sides of a piston (116,117), a main control valve (120), the main control valve (120) selectively connecting the clutch actuator (22) and/or the gear engagement actuator (114,115) to an accumulator (275) or to a reservoir (278); a gear engagement control valve (144,146) selectively connecting the first and second working chambers (118,119) of the gear engagement actuator (114,115) to the main control valve (120) or to the reservoir (278); an electrically driven pump (223) being provided to charge the accumulator, the pressure of fluid supplied by the pump being controlled by variation of the current driving the pump (223).

Abstract: A hydraulic actuation system for an automated transmission system including an active clutch includes, a hydraulic clutch actuator for controlling engagement of the active clutch, a gear engagement actuator for controlling engagement of a gear, a hydraulic accumulator, a hydraulic fluid reservoir, a main control valve for selectively connecting the hydraulic clutch actuator and the gear engagement actuator to the accumulator or to the reservoir and an isolation valve for isolating the gear engagement actuator from the main control valve, when the clutch actuator is connected to the accumulator, the clutch actuator causing the clutch to engage when connected to the accumulator and causing the clutch to disengage when connected to the reservoir. Two such hydraulic actuation systems may be connected in parallel to control the clutches of a twin clutch transmission system, allowing the twin clutch transmission system to be driven in a restricted emergency mode, using only one clutch.

Abstract: A hydraulic actuation system for an automated transmission system including an active clutch includes; a hydraulic clutch actuator controlling engagement of the clutch, the hydraulic control actuator being preloaded towards a disengaged position of the clutch, whereby pressure above a first predetermined value is required in order to move the clutch to a predetermined position; first and second gear engagement actuators for controlling the selection and engagement of a selected gear ratio; a source of hydraulic fluid under pressure, a hydraulic fluid reservoir; a clutch control valve for selectively connecting the clutch actuator to the source of hydraulic fluid under pressure or to the reservoir; a gear engagement control valve for selectively connecting each gear engagement actuator to the source of hydraulic fluid under pressure or to the reservoir; and a changeover valve situated between the gear engagement control valve and the first and second gear engagement actuators, said changeover valve in a first

Abstract: A hydraulic actuation system for an automated transmission system includes; a hydraulic fluid accumulator (275), a hydraulic fluid reservoir (278), a clutch slave cylinder 22 and gear engagement select and shift actuators (114, 115); the clutch slave cylinder (22) and select and shift actuators (114, 115) are selectively connected to the accumulator (275) or to the reservoir (278) via a main control solenoid valve (120); a further clutch control solenoid valve (122) being connected between the main control valve (120) and the clutch slave cylinder (22), the clutch control valve (122) being switchable between a open position in which slave cylinder (22) is connected to the main control valve (120) and a closed position in which the clutch slave cylinder (22) is isolated from the main control valve (120); the working chambers (118, 119) of the select and shift actuators (114, 115) being selectively connected to the main control valve (120) or to the reservoir (278) via gear control solenoid valves (144, 145, 14

Abstract: A hydraulic actuation system for an automated transmission system including an active clutch includes, a hydraulic clutch actuator for controlling engagement of the active clutch, a gear engagement actuator for controlling engagement of a gear, a hydraulic accumulator, a hydraulic fluid reservoir, a main control valve for selectively connecting the hydraulic clutch actuator and the gear engagement actuator to the accumulator or to the reservoir and an isolation valve for isolating the gear engagement actuator from the main control valve, when the clutch actuator is connected to the accumulator, the clutch actuator causing the clutch to engage when connected to the accumulator and causing the clutch to disengage when connected to the reservoir. Two such hydraulic actuation systems may be connected in parallel to control the clutches of a twin clutch transmission system, allowing the twin clutch transmission system to be driven in a restricted emergency mode, using only one clutch.

Abstract: A hydraulic actuation system for an automated transmission system including, a hydraulic clutch actuator (22) for controlling engagement of a clutch (14), a gear engagement actuator (114,115) for controlling engagement of a gear, said gear engagement actuator (114,115) being in the form of a double acting ram having first and second working chambers (118,119) acting on opposite sides of a piston (116,117), a main control valve (120), the main control valve (120) selectively connecting the clutch actuator (22) and/or the gear engagement actuator (114,115) to an accumulator (275) or to a reservoir (278); a gear engagement control valve (144,146) selectively connecting the first and second working chambers (118,119) of the gear engagement actuator (114,115) to the main control valve (120) or to the reservoir (278); an electrically driven pump (223) being provided to charge the accumulator, the pressure of fluid supplied by the pump being controlled by variation of-the current driving the pump (223).

Abstract: A variable pressure hydraulic system includes a hydraulic pressure source which is selectively connected to a hydraulic system or to drain, via a control valve and a pressure transducer; the control valve in a first position isolating the pressure source from the hydraulic system and connecting it to the pressure transducer and in a second position connecting the pressure source to the pressure transducer and the hydraulic system.

Abstract: An actuation system particularly for the operation of a vehicle clutch and/or gearbox ratio selector members in which a pump charges an accumulator via a non-return valve. A slave cylinder receives pressurised fluid from the accumulator via a solenoid-operated control valve. The control valve also controls the exhaust of fluid from the slave cylinder. The control valve has a rest position in which pressurised fluid from the pump is returned to sump and the slave cylinder is vented to sump, a first energised position in which the return of pressured fluid to sump is cut-off and the slave cylinder remains vented to sump, and a further energised position in which venting of the slave cylinder is cut-off and the slave cylinder is supplied with pressurised fluid from the accumulator. The pump may be electrically driven and stopped when the accumulator pressure is above a pre-determined level.

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 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: 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.

Abstract: An actuation system for a vehicle in which a pump (10b) draws fluid from a reservoir (10a) to supply one or more first consumers, such as steering valve (50). One of more second consumers, such as a clutch actuator (12), are actuated via a solenoid valve (12a) from an accumulator (10c) charged by the pump. The solenoid valve connects each second actuator (12) to the accumulator or to the reservoir. When the pressure in the accumulator is below a predetermined charge pressure, flow to the first consumer is restricted to a level sufficient to ensure effective operation of the first consumer, while generating a back pressure sufficient to ensure charging of the accumulator. The flow restriction to the first consumer may be achieved by the solenoid valve (12a) or by a separate charging valve (20).

Abstract: A booster operated master cylinder piston for use in an anti-skid braking system includes a modulator piston located between the master cylinder piston and the booster valve assembly. In the event of a skid the pressure of booster fluid acting on the modulator piston is equalized across the modulator piston.

Abstract: In a power control valve assembly in which the position of an inlet valve member relative to its seat is controlled by a control rod extending through a passage terminating in the seat, an end portion of the control rod has a profile which gives a variable throttling of flow through the passage in dependence upon the axial position of the control rod. In the valve described the end portion of the rod has an end part of constant diameter connected to a further part of reduced diameter by a sloping shoulder. Two such valve assemblies are shown arranged in parallel and operated through a single resilient block and a balance beam.

Abstract: In a modulator assembly for a vehicle anti-skid braking system comprising a housing having a chamber of which the effective volume is variable by an expander piston to modulate the pressure supplied to a wheel brake in accordance with skid conditions, the chamber comprises first and second compartments, and a valve assembly is located in the housing to control communication between the compartments. The valve assembly is closed when the expander piston is in an advanced position in which the effective volume of the chamber is substantially at a minimum so that a first area of the piston is exposed only to pressure in one of the compartments, and the valve assembly is open when the expander piston is retracted away from the advanced position so that a second area of the piston which is greater than the first is exposed to pressure in both compartments.