| 摘要 |
A gear unit provides a number of operative ratios engaged by fluid pressure operated ratio engaging clutches (C1, C2) operated by clutch actuators (26, 29 : 33, 36). These actuators are controlled by two-position flow reversing valves (50, 51), one valve for each fluid pressure operated actuator. These valves are hydraulically connected in series with at least one actuator (33, 36) connected downstream of the last valve (51) in the series connection and at least one actuator (26, 29) connected between each valve of the series. A valve control means (50a - 54) is provided for controlling the operating sequence of the valves so that by changing the operative condition of one valve at a time the operative ratio of the gear unit can be changed to the next adjacent ratio provided by the unit in a progressive manner throughout the entire ratio range of the unit. In one four ratio unit disclosed a first fluid pressure operated clutch (C1) is paired with a first spring-engaged clutch (C4) and the second fluid pressure operated clutch (C2) is paired with a second spring-engaged clutch (C3), so that when the pressure operated clutch of each pair is engaged, the spring-engaged clutch of the respective pair is automatically disengaged and vice versa providing four ratio engaging clutch conditions. |
