Hydraulic servo apparatus for automatic transmission

摘要

A hydraulic servo includes a cylinder, a piston and a rod. The piston divides the interior space of the cylinder between a closed hydraulic chamber and a back chamber which has an opening to the interior space of an automatic transmission. The rod is slidably mounted in the piston for relative movement through a predetermined distance. A frictional engagement element is engaged by the rod which is extended from one end of the cylinder by applying a hydraulic pressure to the hydraulic chamber. A passage is provided between the piston and the rod which is opened or closed by the relative movement between the piston and rod so that the hydraulic chamber and the back chamber are connected or disconnected. A valving arrangement ("closer") closes the passage at the end of the return stroke of the piston toward the hydraulic chamber.