| 摘要 |
PURPOSE:To always maintain the clutch pressure or the like suitably by controlling a solenoid valve for a line pressure control valve or the like in accordance with the operating condition, and by controlling the drive frequency of a signal applied to the solenoid valve in accordance with the temperature of hydraulic oil. CONSTITUTION:A belt drive type continuously variable transmission 2 is composed of a primary pressure control valve 44 as a speed change control valve, a constant pressure control valve 48, a line pressure control valve 54 and a clutch pressure control valve 62 in an oil pressures circuit, and the valves 44, 54, 62 are controlled by a control section 70 through solenoid valves 42, 50, 58, respectively. The clutch pressure control valve 62 is provided so as to control the clutch pressure of an oil pressure clutch 74. In this arrangement, the control section 90 controls so that the drive frequency of a signal applied to the solenoid valves 52, 60, 68 is changed over in accordance with the temperature of hydraulic oil detected by an oil temperature sensor 92 provided in an oil pan 32, enabling decuring of appropriate oil pressure at all times, regardless of the viscosity of the oil.
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