| 摘要 |
PURPOSE:To reduce the speed-change shock on shift-down by permitting the shift to a low-speed shift when it is detected that an operating brake is in operation and the number of engine revolution is below a prescribed number of revolution when the speed change ratio is within a high-speed ratio. CONSTITUTION:In an automatic speed change gear in which a manual speed change gear 3 provided with 4-stages for advance and one-stage for retreat and a sub speed change gear 4 equipped with hydraulically driven high-speed and low-speed clutches 27 and 28 are integrally installed into a common case 5, and the high-speed clutch 27 is connected by the electric conduction to a solenoid valve 33 through a control circuit, and the low-speed clutch 28 is connected by deenergizing a solenoid valve 34, input and output revolution-angle sensors 37 and 38, a brake switch, etc. are connected to the control circuit. When the control circuit detects that the speed change ratio is within a high-speed ratio and a brake is in operation, the solenoid valves 33 and 34 are controlled so that the shift-down to a low-speed ratio is performed when the number of engine revolution lowers below a prescribed number of revolution. |
