A transmission system includes planetary gearing with a ring gear, a plurality of planet gears, a carrier, and a sun gear, a forward clutch operatively connected between the ring gear and carrier, a reverse brake operatively connected between the carrier and a rotationally fixed location, and a control subsystem to switch the transmission system between forward and reverse operational modes in the which the ring gear and the sun gear rotate in the same or opposite rotational directions, respectively. A control subsystem actuation stroke can actuate both the forward clutch and the reverse brake based on a common control signal.

A transmission system includes planetary gearing with a ring gear, a plurality of planet gears, a carrier, and a sun gear, a forward clutch operatively connected between the ring gear and carrier, a reverse brake operatively connected between the carrier and a rotationally fixed location, and a control subsystem to switch the transmission system between forward and reverse operational modes in the which the ring gear and the sun gear rotate in the same or opposite rotational directions, respectively. A control subsystem actuation stroke can actuate both the forward clutch and the reverse brake based on a common control signal.

A method is provided for controlling a friction clutch for connecting first and second rotatable axles in a vehicle, where the clutch includes a first friction part which is connected to the first axle, a second friction part which is connected to the second axle, a spring element which is adapted to bias the second friction part into engagement with the first friction part to connect the first and second axles, and an actuator including a movable actuator part which is engageable with the spring element, and adapted to move, upon being subjected to an actuation force from an actuator control system, towards a disengagement position, thereby deforming the spring element to disengage the second friction part from the first friction part to disconnect the first and second axles. The method includes subjecting the movable actuator part to a test force urging the movable actuator part towards the disengagement position, the test force being smaller than the actuation force, and subsequently or simultaneously to subjecting the movable actuator part to the test force, determining a position of the movable actuator part.

A method is provided for controlling a drivetrain of a vehicle, wherein the drive train includes a combustion engine in drive connection with a dual clutch transmission, wherein the dual clutch transmission is provided with a normally closed input clutch, a normally open input clutch, wherein the normally closed input clutch connecting the combustion engine with a first input shaft and the normally open input clutch connecting the combustion engine with a second input shaft and the first input shaft is in operative connection with a connection sleeve, wherein the connection sleeve can be arranged in an engaged and a disengaged position, whereby in the engaged position the connection sleeve enables an operative connection between the first input shaft to a gearwheel and in the disengaged position gearwheel is disconnected from the first input shaft and the connection sleeve is in a disengaged position when the drivetrain is turned off, wherein the method is automatically initiated at start of the drivetrain, and including the steps of; starting the combustion engine, controlling the normally open and the normally closed input clutch to an engaged or semi engaged state such that both the first and the second input shaft reaches a predetermined synchronized speed, and thereafter opening the normally closed input clutch, and when the countershaft sleeve reaches an essentially synchronous speed with the gearwheel engaging the connection sleeve.

When the control unit monitoring the dual clutch transmission detects input signals from the driver and/or the prime mover and transmission indicating that the free-wheeling mode should be exited, then the transmission is controlled to reconnect the prime mover and the driving wheels. According to the invention, a rapid reconnection of the prime mover to the driven wheels is achieved by engaging the second, normally open clutch unit. Prior to engagement, the control unit can select a suitable gear depending on the input signals from the driver and/or the prime mover. As none of the first set of gears connecting the first input shaft to the driving wheels in the first transmission mechanism is engaged, the first clutch unit can be disengaged during or after engagement of the second clutch unit.

A method is provided for controlling a friction clutch for connecting first and second rotatable axles in a vehicle, where the clutch includes a first friction part which is connected to the first axle, a second friction part which is connected to the second axle, a spring element which is adapted to bias the second friction part into engagement with the first friction part to connect the first and second axles, and an actuator including a movable actuator part which is engageable with the spring element, and adapted to move, upon being subjected to an actuation force from an actuator control system, towards a disengagement position, thereby deforming the spring element to disengage the second friction part from the first friction part to disconnect the first and second axles. The method includes subjecting the movable actuator part to a test force urging the movable actuator part towards the disengagement position, the test force being smaller than the actuation force, and subsequently or simultaneously to subjecting the movable actuator part to the test force, determining a position of the movable actuator part.

A transmission includes an input member, a hydraulic pump, a hydraulic circuit, a clutch assembly for transferring torque between the input member and an output member. A mechanically-driven hydraulic pump is rotatably coupled to the input member and is fluidly connected to the hydraulic circuit. The clutch assembly includes a friction clutch pack, a clutch-apply piston, a clutch-release piston and a coned-disc spring. The clutch-release piston is fluidly coupled to a first hydraulic chamber that is fluidly coupled to the hydraulic circuit. The clutch-apply piston is fluidly coupled to a second hydraulic chamber that is selectively fluidly coupled to the hydraulic circuit. A second spring urges the clutch-apply piston and the coned-disc spring urges the clutch-release piston. When the hydraulic pump is not rotating, the clutch assembly is activated by the coned-disc spring urging the clutch-release piston.

A method and an arrangement for controlling free-wheeling in a dual clutch transmission in a vehicle is provided, which transmission includes a first and a second transmission mechanism controllable by a first and a second clutch unit, each connected to a first and a second input shaft respectively. The method involves deactivating the first clutch unit, wherein the output shaft of the internal combustion engine and the first input shaft are engaged, and disengaging each of the first set of gears connecting the first input shaft to the driving wheels. Simultaneously, the second clutch unit is deactivated, wherein the output shaft of the internal combustion engine and the second input shaft are disengaged, and one of the second set of gears connecting the second input shaft to the driving wheels is engaged.

In friction engagement device having forward clutch 5 and clutch operation pack 6 controlling engagement/disengagement operation of the forward clutch 5, the clutch operation pack 6 has hydraulic piston 61, engagement pressure piston chamber 62, snap ring 64, diaphragm spring 65 and ball lock mechanism BL. The diaphragm spring 65 provides biasing engagement force to the forward clutch 5 at a clutch side of the hydraulic piston 61. The ball lock mechanism BL restrains movement, in a disengagement direction, of the hydraulic piston 61 at a position where the forward clutch 5 is in an engagement state by the biasing engagement force by exerting ON pressure on the engagement pressure piston chamber 62, and after restraining the movement of the hydraulic piston 61, maintains the restraint of the disengagement direction movement of the hydraulic piston 61 even when the ON pressure of the engagement pressure piston chamber 62 is drawn.

A method is provided for controlling a drivetrain of a vehicle, wherein the drive train includes a combustion engine in drive connection with a dual clutch transmission, wherein the dual clutch transmission is provided with a normally closed input clutch, a normally open input clutch. wherein the normally dosed input clutch connecting the combustion engine with a first input shaft and the normally open input clutch connecting the combustion engine with a second input shaft and the first input shaft is in operative connection with a connection sleeve, wherein the connection sleeve can be arranged in an engaged and a disengaged position, whereby in the engaged position the connection sleeve enables an operative connection between the first input shaft to a gearwheel and in the disengaged position gearwheel is disconnected from the first input shaft and the connection sleeve is in a disengaged position when the drivetrain is turned off, wherein the method is automatically initiated at start of the drivetrain, and including the steps of; starting the combustion engine, controlling the normally open and the normally closed input clutch to an engaged or semi engaged state such that both the first and the second input shaft reaches a predetermined synchronised speed, and thereafter opening the normally closed input clutch, and when the countershaft sleeve reaches an essentially synchronous speed with the gearwheel engaging the connection sleeve.