| 摘要 |
PURPOSE:To permit the smooth speed change and prevent the excessive blowing up of an engine by installing shift suppressing apparatuses for cutting off the switching signals of shift valves until the oil pressure of the hydraulic engagement element of a transmission system becomes a prescribed value. CONSTITUTION:When the oil pressure of a second-speed hydraulic clutch C2 is over a prescribed value, the first shift suppressing apparatus 16 is installed so that the governor pressure supplied from a governor valve 12 is not introduced into the third shift valve 103, even if the throttle pressure of the first throttle valve 131 lowers. Further, the second shift suppressing apparatus is installed so that the throttle pressure supplied from the first throttle valve 131 is not introduced into the second shift valve 102 when the oil pressure of the fourth-speed hydraulic clutch C4 is over a prescribed value. Since the shift valves 101, 102, and 103 are not switching-operated until each hydraulic pressure of the hydraulic clutches C1, C2, C3, and C4 becomes each prescribed value, even if the opening degree of the throttle is sharply varied, smooth speed change is permitted, and the excessive blowing up of the engine can be prevented. |
