Patent ID: 7621837
Filing Date: 2009-11-24
Classification: F16H,Y10S,Y10T

Abstract:
1. A hydraulic control apparatus, for an automatic transmission, in which the automatic transmission establishes a plurality of shift speeds according to an engagement state of a plurality of friction engagement elements that are engaged and disengaged by respective hydraulic servos, the hydraulic control apparatus comprising: a fail solenoid valve that switches between outputting and not outputting a signal pressure during normal operation and during a failure; a first switching valve that switches to at least one of a normal position and a fail position based on the signal pressure, and during a failure, carries out fail-safe control by the first switching valve switching to the fail position; a first engagement pressure output device that can output an engagement pressure to a first hydraulic servo among the respective hydraulic servos that engages and disengages a first friction engagement element among the plurality of friction engagement elements that engages at a prescribed shift speed; and a second switching valve that switches based on the signal pressure of the fail solenoid valve, wherein the first switching valve inputs an engagement pressure of the first hydraulic servo that is output from the first engagement pressure output device when in the normal position, and locks in the normal position.