In a hydraulic system with a dog clutch (23-25), a hydraulically operated dog clutch actuator is arranged to alternatively bring the dog clutch into a connect mode or a disconnect mode. The clutch actuator has a piston (27) reciprocally movable under hydraulic pressure between two end positions, corresponding to the two clutch modes. Pressurized hydraulic oil is supplied to the clutch actuator by a hydraulic power system comprising a pump (4) driven by an electric motor (3). Means are provided in the clutch actuator to decrease the hydraulic pressure acting on the piston (27) at the approaching by the piston of either of its end positions, so that a hydraulic signal is transmitted back to the hydraulic power system.

A nose landing gear system is disclosed. In various embodiments, the nose landing gear system includes an electric motor; a hydraulic pump connected to the electric motor; a gearbox connected to the electric motor; and a clutch configured to mechanically couple the gearbox to a steering collar.

A nose landing gear system is disclosed. In various embodiments, the nose landing gear system includes an electric motor; a hydraulic pump connected to the electric motor; a gearbox connected to the electric motor; and a clutch configured to mechanically couple the gearbox to a steering collar.

A frictional engagement element includes: a first piston, a second piston, a first urging member for urging the first piston in a direction of releasing a friction plate, and a second urging member for urging the second piston in the direction of releasing the friction plate with an urging force larger than the urging force of the first urging member. One of the first and second pistons has a communicating hole for connecting an engaging hydraulic chamber with an opposite hydraulic chamber and the other of the first and second pistons has a valve part for closing the communicating hole. The difference in travel distance between the first and second pistons in motion due to the different urging forces of the first and second urging members causes the valve part to open the communicating hole.

An automatic transmission includes a piston movable in an axial direction, a plurality of friction plates disposed on a side of a first surface of the piston, a fastening hydraulic chamber applying a hydraulic pressure to a second surface of the piston to move the piston to a fastening position where the friction plates are pressed to be fastened to each other, a release hydraulic chamber applying a hydraulic pressure to the first surface of the piston to move the piston to a release position where the friction plates are released, and a hydraulic pressure control valve that supplies and discharges the hydraulic pressure to and from each of the fastening hydraulic chamber and the release hydraulic chamber. An area of the second surface of the piston for receiving the hydraulic pressure is set to be larger than an area of the first surface for receiving the hydraulic pressure.

The disclosure relates to a method for actuating a decoupling unit in a powertrain which comprises at least one driven axle. The aim of the disclosure is to simplify the actuation of the decoupling unit. This is achieved in that the decoupling unit is passively actuated in an actuation direction using an actuation force, which is provided in a hydraulic system, via a first hydraulic functional surface, and the decoupling unit is passively actuated in a restoring direction using a restoring force via a second hydraulic functional surface.

A hydraulic system including a hydraulically actuated clutch, a hydraulically actuated shifting piston, and a pressure source for actuating the clutch as well as the shifting piston. The movement of the shifting piston also controls a valve function which serves to open a connection from the pressure source to the clutch only when the shifting piston has reached one of its end positions.

An assembly for driving a friction clutch, having a hydraulically driveable stepped piston, with: a pump driving the stepped piston, which has a working piston moveably arranged in a working chamber that divides it into first and auxiliary working chambers. The working piston is mechanically connected to an auxiliary working piston and hydraulically driveable via a second working chamber. A control valve is arranged between the stepped piston and pump. A first line path leads from the pump to the second working chamber, and a second line path leads from the pump to the first working chamber. The stepped piston has a working tappet which acts on the friction clutch. The first and second line paths are connected via a first line section of the supply line and a multi-port control valve, which has two valve positions, and the first line section is at least partially blocked in one valve position.

A frictional engagement element includes: a first piston, a second piston, a first urging member for urging the first piston in a direction of releasing a friction plate, and a second urging member for urging the second piston in the direction of releasing the friction plate with an urging force larger than the urging force of the first urging member. One of the first and second pistons has a communicating hole for connecting an engaging hydraulic chamber with an opposite hydraulic chamber and the other of the first and second pistons has a valve part for closing the communicating hole. The difference in travel distance between the first and second pistons in motion due to the different urging forces of the first and second urging members causes the valve part to open the communicating hole.

An automatic transmission includes a piston movable in an axial direction, a plurality of friction plates disposed on a side of a first surface of the piston, a fastening hydraulic chamber applying a hydraulic pressure to a second surface of the piston to move the piston to a fastening position where the friction plates are pressed to be fastened to each other, a release hydraulic chamber applying a hydraulic pressure to the first surface of the piston to move the piston to a release position where the friction plates are released, and a hydraulic pressure control valve that supplies and discharges the hydraulic pressure to and from each of the fastening hydraulic chamber and the release hydraulic chamber. An area of the second surface of the piston for receiving the hydraulic pressure is set to be larger than an area of the first surface for receiving the hydraulic pressure.