To provide a piston chamber oil feeding passage hole structure for reliably giving sliding motion to a piston provided at a pump cover toward a friction element.
In the piston chamber oil feeding passage hole structure, openings of a first oil hole 33 and a second oil hole 43 on sides of piston chambers 32, 42 are set as long holes so that the kinetic energy of oil fed to the piston chambers 32, 42 does not exceed the elastic energy of return springs 36, 46 for energizing pistons 31, 41. Thus, the shape deformation of the return springs 36, 46 is prevented and the inclination of the first piston 31 and the second piston 41 is prevented while avoiding the collective blow of strong hydraulic pressure at one point on the pressure receiving face 31c of the first piston 31 or on the pressure receiving face 41c of the second piston 41. As a result, no trouble such as a stick slip occurs in the first piston 31 or the second piston 41 and sliding motion is reliably given thereto toward a first brake 35 or a second brake 45.
TSUCHIYA KOHEI
Tetsuro Maki
Maki Reiko
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