| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydraulic circuit to perform hydraulic control by generating a signal pressure corresponding to the number of revolutions of a prime mover during the occurrence of a trouble and prevent an influence from being exercised on regulation of the line pressure of a regulator valve. SOLUTION: A hydraulic circuit for a transmission comprises a throttle 41 arranged in the discharge oil passage 61 of a regulator valve; an S/C backup valve 48 driven by a differential pressure between oil pressures (oil pressures in an oil passage 61a and an oil pressure in an oil passage 61b) on the sides situated upper stream and downstream from the throttle 41; a bypass oil passage 62 bypassing the throttle 41; and a bypass opening closing valve 42 to open and close the bypass oil passage 62. When an electric control valve is failed in operation, by receiving an oil pressure generated thereby, the bypass opening closing valve 42 closes the bypass oil passage 62. The spool of the S/C backup valve 48 is driven according to a differential pressure between oil pressures in places preceded and followed by the spoolthrottle 41. This constitution regulates an oil pressure in an oil passage 71b and outputs it as an oil passage signal pressure PS to an oil passage 72a. |
