Hydraulic control system for automatic power transmission having transmission throttle valve with failsafe means

摘要

A hydraulic control system for an automatic power transmission for an automotive vehicle, comprising a pressure regulator valve for producing a line pressure, at least the shift valve predominant over shifts between predetermined gear ratios and operable to distribute the line pressure selectively to the frictional units, and a transmission throttle valve engaged by the accelerator pedal of the vehicle through a mechanical linkage and operative to supply the pressure regulator valve and the shift valve a throttle pressure variable with movement of the accelerator pedal in the absence of a failure in the mechanical linkage and to interrupt supply of the throttle pressure to the pressure regulator valve and the shift valve and pass the line pressure to the pressure regulator valve in response to a failure invited in the mechanical linkage.