| 摘要 |
PROBLEM TO BE SOLVED: To prevent that a friction fastening element becomes non-releasable due to an open failure of a hydraulic control valve which controls hydraulic pressure supplied to a pressing chamber, in an automatic transmission having the friction fastening element which has a clearance adjusting chamber for adjusting a clutch clearance and the pressing chamber for pressing a friction plate, and is fastened by being supplied with the hydraulic pressure to both the chambers.SOLUTION: In a hydraulic control circuit 100 having a shift valve 111 for switching the feed and discharge of hydraulic pressure to/from a clearance adjusting chamber 61 of an LR brake 60, and a linear SV 113 for controlling the hydraulic pressure supplied to a pressing chamber 62 of the brake 60, the hydraulic control circuit comprises a source pressure oil passage 124 for supplying the hydraulic pressure supplied to the clearance adjusting chamber 61 from the shift valve 111 to a source pressure port a of the linear SV 113. At an open failure of the linear SV 113, the pressing chamber 62 is discharged in pressure by a drain port g of the shift valve 111 by pressure-discharging the clearance adjusting chamber 61. |
