WET MULTI-PLATE CLUTCH

A disk spring 46 is, at its outer peripheral part, is supported by a clutch drum 10 and contacts, at its inner peripheral part, with a spring presser part 12-1 of the piston 12. The disk spring 46 faces, at the side opposite the piston 12, with clutch pack 20. A forward movement of the piston 12 by operating pressure in a hydraulic chamber is transmitted to the clutch pack 20 via the disk spring 46, resulting in an engaged condition of the clutch pack 20. A driving force of the piston 12 by the hydraulic oil pressure is boosted under a lever ratio a/b of the disk spring 46 and is transmitted to the clutch pack 20. The disk spring 46 to the spring presser part 12-1 without obstructing the slide movement of the piston 12 of obtaining an increased radial length of the spring, resulting in an increased return force of the spring 46 for a positive reverse movement of the piston 12 for obtaining a disengaged condition of the clutch.