| 摘要 |
PURPOSE:To suppress the simultaneous establishment of a retreat transmission system and the first speed transmission system by restraining a shift valve at the shift position for supplying oil into the second speed hydraulic clutch, during the time when a servovalve is at a retreat position, when a manual valve is switched from retreat to a low speed retention range. CONSTITUTION:In the selection operation of a manual valve 9 from retreat to a low speed retention range, a servovalve 11 sometimes remains at a retreat position because of biting a foreign material, even if a control valve 22 is switched to a nonrestrained position, and a line pressure is introduced into the oil chamber (h) of a shift valve 10 through the oil chamber 11c of the servovalve 11, oil passage L21 and L20 from an oil passage L19, and a shift valve 102 is restrained at the oil supply position to the second speed hydraulic clutch C2, and oil is not supplied into the first speed hold hydraulic clutch CH. When the servovalve 11 is switched to an advance position, the input of the line pressure into the shift valve 102 is cut off, and the switching to the oil supply position to the clutch CH is performed, and the traveling at the first speed stage in which engine brake is effective is carried out. Thus, the burn of the clutches C1 and CH and generation of abrasion can be prevented. |
