Patent ID: 7618344
Filing Date: 2009-11-17
Classification: F16H,Y10S,Y10T

Abstract:
1. A hydraulic control apparatus, for a multi-stage automatic transmission, having 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: an oil pump that generates an oil pressure in correspondence with the engine speed; a line pressure generating device that generates an oil pressure in the oil pump at a line pressure; a range pressure output device that can input the line pressure and output a forward range pressure based on a shift position; a first hydraulic servo among the respective hydraulic servos that engages and disengages a respective one of the friction engagement elements that engages at a relatively low speed; a second hydraulic servo among the respective hydraulic servos that engages and disengages a respective one of the friction engagement elements that engages at a relatively high speed; a plurality of engagement pressure control solenoid valves that include a first engagement pressure control solenoid valve that supplies an engagement pressure to the first hydraulic servo, and a second engagement pressure control solenoid valve that supplies the engagement pressure to the second hydraulic servo, wherein, when in a de-energized state, the plurality of engagement pressure control solenoid valves interrupt an input port that inputs oil pressure based on the line pressure and an output port and communicate the output port and a discharge port, and, when in an energized state, the plurality of engagement pressure control solenoid valves communicate the input port and the output port to thereby regulate the engagement pressure supplied to the respective hydraulic servos; a first switching valve that, during a failure in which all solenoid valves are de-energized, is switched to a reverse input pressure generating position that outputs the forward range pressure as a reverse input pressure; and a second switching valve that switches between a first position at which the reverse input pressure is input to the discharge port of the first engagement pressure control solenoid valve and a second position at which the reverse input pressure is input to the discharge port of the second engagement pressure control solenoid valve; wherein: the second switching valve is set at the second position during a normal engine startup and is locked at the second position based on a lock pressure by feeding the lock pressure, and during a failure in which all solenoid valves are de-energized, is set to a first position that interrupts the lock pressure after the engine is restarted.