Patent ID: 8522946

Claim:
A hydraulic control device that controls a hydraulic pressure to be supplied to a hydraulic servo for a hydraulically driven friction engagement element in an automatic transmission that changes between shift speeds by switching an engagement state of the friction engagement element, comprising: a pump that generates a hydraulic pressure; a first pressure regulation mechanism that includes a normally-open solenoid and that regulates the hydraulic pressure from the pump to generate a line pressure; a second pressure regulation mechanism that includes a normally-closed solenoid and that receives and regulates the line pressure to output the regulated pressure; a signal pressure output mechanism that includes a normally-closed solenoid to output a signal pressure; and a switching mechanism that is connected to oil passages for the respective mechanisms and an oil passage for the hydraulic servo and that includes a signal pressure input oil passage to which at least the signal pressure from the signal pressure output mechanism can be input, the switching mechanism allowing communication between the oil passage for the first pressure regulation mechanism and the oil passage for the hydraulic servo and blocking communication between the oil passage for the second pressure regulation mechanism and the oil passage for the hydraulic servo when the signal pressure is not input to the signal pressure input oil passage, and blocking communication between the oil passage for the first pressure regulation mechanism and the oil passage for the hydraulic servo and allowing communication between the oil passage for the second pressure regulation mechanism and the oil passage for the hydraulic servo when the signal pressure is input to the signal pressure input oil passage.