A clutch apparatus includes a clutch hub, a clutch drum, a multi-plate clutch having inner clutch plates and outer clutch plates, a piston for pressing the multi-plate clutch, an electric motor, a moving mechanism for moving the piston in an axial direction in accordance with the amount of rotation of the electric motor, and a control unit for controlling the electric motor. When increasing a rotational force that is transmitted between the clutch hub and the clutch drum by increasing electric current that is supplied to the electric motor, the control unit moves the piston in the axial direction by temporarily supplying the electric motor with the electric current having a first current value that is greater than a second current value corresponding to a target rotational force that needs to be transmitted between the clutch hub and the clutch drum.

A drive force transmission apparatus is mountable on a four-wheel drive vehicle switchable between a four-wheel drive mode that transmits a drive force of an engine to front wheels and rear wheels, and a two-wheel drive mode that transmits the drive force to only the front wheels. The drive force transmission apparatus allows adjustment of the drive force to the rear wheels, and includes a multi-plate clutch, a piston for axially pressing the multi-plate clutch, an actuator for axially moving the piston, and a control unit for controlling the actuator. Upon satisfaction of a predetermined condition that indicates a high probability of the vehicle needing to be switched from the two-wheel drive mode to the four-wheel drive mode, the control unit causes the actuator to displace the piston by a predetermined amount with respect to an initial position of the piston toward the multi-plate clutch.

A clutch apparatus includes a clutch hub, a clutch drum, a multi-plate clutch having inner clutch plates and outer clutch plates, a piston for pressing the multi-plate clutch, an electric motor, a moving mechanism for moving the piston in an axial direction in accordance with the amount of rotation of the electric motor, and a control unit for controlling the electric motor. When increasing a rotational force that is transmitted between the clutch hub and the clutch drum by increasing electric current that is supplied to the electric motor, the control unit moves the piston in the axial direction by temporarily supplying the electric motor with the electric current having a first current value that is greater than a second current value corresponding to a target rotational force that needs to be transmitted between the clutch hub and the clutch drum.

A method for controlling an engine clutch includes steps of controlling the hydraulic pressure transmitted from a master cylinder, driven by a motor, to a concentric slave cylinder using a controller outputting a motor control command for controlling an engine clutch so as to switch the engine clutch to a target state, driving the engine clutch using the concentric slave cylinder, after the step of controlling hydraulic pressure, detecting a position of a piston of the master cylinder using a first travel sensor and detecting a position of a piston of the concentric slave cylinder using a second travel sensor, and performing compensation control with respect to the motor based on the positions of the pistons detected by the first travel sensor and the second travel sensor using the controller so that the engine clutch is switched to the target state.

The invention relates to an actuating device for actuating a clutch and/or a transmission of a motor vehicle, including a pump having two fluid connections and including a movable actuating element fluidically connected to a first fluid connection of the pump, wherein the pump is designed such that in a first pump position, in which the pump is driven in a first direction of rotation, for extending the actuating element the pump conveys a pressure fluid in a first conveying direction from a second fluid connection to the first fluid connection, wherein the pump is configured as a variable displacement pump which is reversible with regard to the conveying direction of the pump, wherein the pump is designed such that after it has been moved into a second pump position, in which the pump is driven in the first direction of rotation, for retracting the actuating element the pump conveys a pressure fluid in a second conveying direction, opposite the first conveying direction, from the first fluid connection to the second fluid connection. The invention further relates to a clutch and to a transmission system having such an actuating device.