| 摘要 |
PURPOSE:To obtain expected locking timing by providing a buffer means for suppressing the rise of oil pressure caused by the compression of oil in a release chamber at the time of a piston performing its stroke, in a release pressure passage communicated with the release chamber of servo mechanism. CONSTITUTION:There is provided a buffer means 66 formed into such structure as to open an pressure discharge passage 63 to discharge residual oil in a release chamber 40b at the time of 1-2 speed change, that is, when a piston 40a performs its upward (in the drawing) stroke to lock a 2-4 brake by the locking pressure acting upon the lock chamber 40c of a servo mechanism 40, so as to suppress the rise of oil pressure caused by the compression of the residual oil. At the speed change time, the locking pressure is promptly supplied into the lock chamber 40c of the servo mechanism 40 and the residual oil in the release chamber 40b is going to be compressed with large force, but at this time, a pressure discharge control valve 64 is already open, so that the residual oil is discharged from a pressure discharge passage 63. With the compression of the residual oil thus dissolved, the 2-4 brake is locked immediately by the action of the locking pressure upon the lock chamber 40c, and the rising responsiveness of locking can be secured desirably. |
