| 摘要 |
PURPOSE:To effectively suppress a fluctuation of speed change ratio by inputting to a speed change controlling solenoid valve a duty signal, and setting its frequency in accordance with the speed change ratio, that is, so as to be increased in a low speed shift side. CONSTITUTION:A continuously variable transmission introduces to its speed change solenoid valve 62 a line pressure in an oil line 33 as the original pressure, when a duty signal of frequency in accordance with each speed change ratio is input from a control unit 70, a duty pressure is generated in an accurate pulse state of low frequency with a small differential pressure in a high speed shift and of high frequency with a large differential pressure in a low speed shift. This duty pressure acts on a speed change control valve 50 supplying a corresponding pressure of oil to a primary cylinder 9 performing an up or down shift while changing a speed change speed. Here in the low speed shift, a primary pulley 7 fine changes its volume by the duty pressure of high frequency even with speed change ratio fine controlled. Thus, a fluctuation of the speed change ratio can be suppressed. |
