| 摘要 |
PURPOSE:To aim at improvement in the reliability of a hydraulic circuit by feeding a clutch with hydraulic pressure via a control valve at time of a changeover from the neutral position of a manual valve to the running position, but at time of reversal, discharging it in bypassing the control valve. CONSTITUTION:When a manual valve 31 is selected from the neutral position to the running position, a spool 34a of a control valve 34 is gradually moved to the right by hydraulic pressure out of a pressure regulating valve 36, clamping a forward clutch 10 by the gradually increased hydraulic, and when the spool 34a is reached to the right moving end, hydraulic pressure of a pressure regulating valve 30 is fed, thereby keeping the clamp. Next, when it is selected from the forward position to the neutral position, the hydraulic pressure of the forward clutch 10 bypasses the control valve 34 and then it is discharged to an oil tank 41 via a bypass passage 42, a one-way valve 43 and the manual valve 31. Thus, no shift shock occurs there, and responsiveness in clutch opening action is improved and, what is more, ever in case the control valve fails, clutch opening can be surely done.
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