Patent ID: 7128676

Claim:
A failsafe hydraulic circuit for avoiding simultaneous engagement of a first friction engagement element that is engaged or disengaged by a first hydraulic servo and a second friction engagement element that is engaged or disengaged by a second hydraulic servo, the failsafe hydraulic circuit comprising: an oil pressure generator device that generates an oil pressure to be supplied to the first hydraulic servo or the second hydraulic servo; a first valve that has one of an open position that allows a supply of a first engaging pressure to the first hydraulic servo, and a closed position where the supply of the first engaging pressure to the first hydraulic servo is stopped and the first engaging pressure is discharged from the first hydraulic servo; a first oil pressure detector device that detects an oil pressure output from the first valve; a second valve that has one of an open position that allows a supply of a second engaging pressure to the second hydraulic servo, and a closed position where the supply of the second engaging pressure to the second hydraulic servo is stopped and the second engaging pressure is discharged from the second hydraulic servo; and a second oil pressure detector device that detects an oil pressure output from the second valve, wherein when one of the first valve and the second valve is set to an open position state, another one of the first valve and the second valve is set to a closed position state by inputting the oil pressure generated by the oil pressure generator device to the first valve and the second valve, and the first engaging pressure is input to the first oil pressure detector device via the second valve, and wherein the second engaging pressure is input to the second oil pressure detector device via the first valve.