| 摘要 |
PURPOSE:To eliminate the shifting of the neutral point of a spool valve chip by controlling a pair of hydraulic cylinders for modifying the effective diameters of a pair of variable pulleys and controlling the speed ratio of a continuously variable transmission by means of a speed control valve unit of specific structure having four spool valve chips. CONSTITUTION:A hydraulic control circuit for a continuously variable transmission 14 where a transmission belt 24 is entrained about the primary and secondary variable pulleys 20, 22 the effective diameters of which being modified by means of the hydraulic cylinders 26, 28 is provided with a speed change control valve unit 44 for feeding the working oil of relatively high pressure being fed from an oil pump 42 to one of said cylinders 26, 28 while simultaneously flowing out the working oil from the other cylinder and regulating the speed ratio of the continuously variable transmission 14. Here, the speed change control valve 44 is constructed with spool valve chips 88, 90, 92, 94 fitted slidably in four cylinder bores formed in the valve body 78, springs 96, 98, 100, 102 for energizing respective valve chips to the right and a valve chip driving means containing solenoid valves 74, 76. |
