Patent ID: 8864626
Filing Date: 2014-10-21
Classification: F16H,Y10T

Abstract:
1. A hydraulic control device of an automatic transmission including a hydraulic control circuit provided with a plurality of friction elements to be coupled by being supplied with a line pressure and a plurality of hydraulic control valves, the hydraulic control circuit achieving a gear position corresponding to an operating state of an engine by selectively supplying the line pressure to one or more of the friction elements, and the device comprising: a pressure reducing valve; a first friction element for achieving a first gear position and a second friction element for achieving a second gear position that produces a lower speed than the first gear position, the pressure reducing valve serving as one of the plurality of hydraulic control valves to reduce the line pressure; and a switch valve formed with an input port to be inputted with the line pressure in a forward gear position range, and for switching its state between a first state where the input port is communicated with a first oil path communicating with the first friction element in a state of failure of power distribution to the plurality of hydraulic control valves and a second state where the input port is communicated with the second friction element in the same power distribution failure state, wherein the switch valve is formed with, as ports for switch control, a first control port to which a first control pressure is inputted so that the switch valve is biased toward the first state, a second control port to which a second control pressure outputted from the pressure reducing valve is inputted so that the switch valve is biased toward the second state, and a third control port to which the line pressure is inputted only when the line pressure is inputted to the input port in the first state and for fixing the switch valve in the first state regardless of the control pressures at the first and second control ports, and wherein in a state where the line pressure is not inputted to the third control port and the control pressure is inputted to the first control port, the switch valve transitions to the first state when the control pressure inputted to the second control port is reduced by the pressure reducing valve, and the switch valve transitions to the second state when the control pressure inputted to the second control port is not reduced by the pressure reducing valve.