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.

A regulator for clutch actuator includes a housing having a cylindrical damping space inside, a first fluid path interconnecting the damping space and a master cylinder, and a second fluid path interconnecting the damping space and a an operating cylinder. The regulator further includes a flexible valve member contained in the damping space for reducing vibrations. The flexible valve member comprises a first inflow guiding portion configured to receive and guide fluid from the first fluid path. The first inflow guiding portion has a plurality of through holes such that elastic deformation of the first inflow guiding portion reduces vibration when fluid flow into the cylindrical damping space from the master cylinder.

Disclosed a regulator for clutch actuator. The regulator for clutch actuator includes a housing having a cylindrical damping space inside, a first fluid path interconnecting the damping space and a master cylinder, and a second fluid path interconnecting the damping space and a an operating cylinder. The regulator further includes a flexible valve member contained in the damping space for reducing vibrations. The flexible valve member comprises a first inflow guiding portion configured to receive and guide fluid from the first fluid path. The first inflow guiding portion has a plurality of through holes such that elastic deformation of the first inflow guiding portion reduces vibration when fluid flow into the cylindrical damping space from the master cylinder.

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.