Patent ID: 6220402
Filing Date: 2001-04-24
Classification: F16H

Abstract:
A hydraulic servo apparatus for engaging/disengaging a frictional engagement element in an automatic transmission including a case defining an interior space in which the hydraulic servo apparatus is mounted, said hydraulic servo apparatus comprising:a cylinder having an inner space which, at one end, is adapted for connected to the interior space of the case of the automatic transmission;a piston slidably mounted in the cylinder and dividing the inner space of the cylinder into a closed hydraulic chamber and a back chamber connected to the interior space of the case of the automatic transmission, said piston being moved in a first direction toward said back chamber by application of a hydraulic pressure to the hydraulic chamber;a rod slidably mounted in the piston for sliding movement relative to the piston over a predetermined distance, said rod being extended from the one end of the cylinder and adapted to press the frictional engagement element into engagement by the movement of said piston in said first direction;a passage formed between the piston and the rod and connecting the hydraulic chamber to the back chamber, said passage being opened/closed by the relative movement between the piston and the rod; anda closer which closes said passage at the completion of a return stroke of the piston in a second direction toward said hydraulic chamber.