Control valve for reducing harshness of engagement of an automatic transmission clutch

Claim 1

In an automatic transmission mechanism having torque transmitting gear elements and clutch and brake means for controlling the relative motion of the gear elements to effect plural torque delivery paths from a driving member to a driven member; said clutch and brake means including multiple fluid pressure operated servos with a servo apply pressure chamber and a spring release means for opposing the fluid pressure servo apply force for each servo, a pressure source and a fluid circuit connecting said pressure source with said servos; the improvement comprising: a control valve in said circuit having a valve chamber between said pressure source and at least one of said servos, said control valve having a pressure inlet port, an exhaust flow path and a pressure outlet port in said valve chamber, a movable valve element in said valve chamber, said valve element comprising fluid pressure regulating lands registering with said valve ports whereby one of said lands progressively restricts communication between said ports when said valve element moves in one direction, and another of said lands progressively restricting said exhaust flow path when said valve element moves in the opposite direction, a regulated pressure feedback passage between said outlet port and one end of said valve element creating a pressure force urging said valve element in said one direction, said pressure inlet port being connected to said pressure source; a fluid connection between an additional one of said servos and said pressure inlet port, said additional servo communicating with the other end of said valve element whereby the pressure developed in said additional servo communicates with said control valve to establish a pressure force on said valve element urging it in the opposite direction thereby modifying the pressure regulating characteristic of said valve.