Patent ID: 8413782

Claim:
A multiple disc clutch apparatus comprising: a plurality of driving clutch plates spline-fitted and axially slidable on an input member rotated by a driving source; a plurality of driven clutch plates arranged alternately with the driving clutch plates and spline-fitted and axially slidable on an output member; a clutch piston having a first surface facing axially toward an oil pressure chamber and a second surface facing toward the driving clutch plates or driven clutch plates, the clutch piston being configured to be displaced toward a clutch-on side when oil is supplied to the oil pressure chamber and thereby pressure-contact the driving clutch plates and driven clutch plates to each other so as to transmit a driving force of the input member to the output member, the clutch piston also being configured to be returned toward a clutch-off side when oil is discharged from the oil pressure chamber and thereby allowing the driving and driven clutch plates to separate from each other so as to cut off the transmission of driving force from the input member to the output member; a valve disposed at least partially in a valve recess in the first surface of the clutch piston and formed so as to pass through the first surface and the second surface of the clutch piston and configured to occupy a closed condition preventing the oil from flowing from the oil pressure chamber to the side of second surface of the clutch piston when the clutch apparatus is clutched-on, the valve also being configured to occupy an opened condition allowing flow of air from the side of second surface to the oil pressure chamber when the clutch apparatus is clutched-off; and a suppressing plate configured to limit movement of one or more portions of the valve in at least one direction; wherein at least one weight reducing recess providing weight reduction is formed on the first surface of the clutch piston at a position near the outer circumference of the clutch piston and circumferentially spaced from the valve recess.