Direct-coupling control system for torque converter in automatic transmission for vehicles

Claim 1

In an automatic transmission for a vehicle, comprising a fluid torque converter having an input member and an output member; and an auxiliary transmission having a plurality of stages of gear trains selectively connected to the output member of said torque converter and having frictionally engaging elements engageable upon receipt of hydraulic pressure fed through hydraulic fluid passages; a direct-coupling clutch and control system for the torque converter, which comprises: a direct-coupling clutch interposed between the input and output members for mechanically coupling said members together; and a hydraulic pressure source and said direct-coupling clutch for controlling engagement of said clutch; wherein said control means comprises an oil line, a valve in said oil line having first and second switching positions on opposite ends of the valve for opening said oil line and for temporarily releasing the pressure fed to the direct-coupling clutch at the time of shifting of the valve between the first and second switching positions, said valve being normally urged by a resilient means toward the first position and being urged toward the second position against a force of the resilient means when said valve receives, on a pressure receiving portion of the valve, a part of the hydraulic pressure being fed to said auxiliary transmission for engagement of the gear trains from one gear train stage of said gear train stages to another gear train stage of said gear train stages of said plurality of gear train stages, which part of pressure is fed through oil lines branched off the oil lines feeding hydraulic fluid for engagment of said another gear train stage.