| 摘要 |
PURPOSE:To improve durability of cylinders and a belt, and traveling performance by making an arrangement so that the secondary pressure necessary for the secondary control system may be set to the minimum speed change ratio side when the primary control valve fails and the speed change ratio can not be calculated due to stop of a vehicle. CONSTITUTION:When a primary control valve 60 falls in an unenergized condition due to power failure or the like, the primary control valve 60 is actuated at higher pressure by the initial setting condition, increasing the primary pressure in a forcible manner. In such cases, shifting up is made to the minimum speed change ratio side to make a smooth stop, preventing the braking phenomenon. On the other hand, a control unit 70 makes a judgement of any failures, and in the condition where the speed change ratio by the primary and the secondary number of rotation can not be calculated due to stop of a vehicle, the minimum speed change ratio is determined by means of an hydraulic pressure suppressing part, (not shown in figure) setting the required secondary pressure. This allows the secondary control valve 50 to control the secondary pressure to the minimum level, to suppress the rise in the primary pressure and to reduce the belt clamping force of a secondary pulley 25. |
