| 摘要 |
PURPOSE:To reduce discontinuity of speed change and shock due to a shift of NULL value by driving a control valve of hydraulic pressure at the frequency corresponding to hydraulic temperature, and also by controlling the frequency so as to change from a high side to a low side when a speed change ratio is lowered below a trigger value at an ordinary temperature. CONSTITUTION:A transmission 2 changes the speed change ratio continuously by changing a turning radius of a belt 2A wound on a driving pulley 4 and a driven pulley 10 through changing the intervals between the respective fixed pieces 6, 12 and the respective movable pieces 8, 14. In this case, a primary pressure control valve 34, a constant pressure control valve 38, a line pressure control valve 44 and a clutch pressure control valve 52 are arranged in a hydraulic passage respectively, and also these valves are controlled by means of a control part 82 through three-way electromagnetic valves 42, 50 and 58 respectively. The respective control valves 34, 38, 44 and 52 are operated at the frequency corresponding to the state of oil temperature, and also the frequency is controlled so as to be switched from a high side to a low side when the speed change ratio becomes lower than a trigger value in the case where the frequency is switched from the high side to the low side at ordinary temperature. |
