| 摘要 |
PURPOSE:To make discharge of a hydraulic fluid out of a second actuator ever so easy, by varying rate of the hydraulic fluid to be fed to a first actuator operating a first gear step on the basis of hydraulic fluid temperature in an automatic transmission at the time of selection from a second gear step to the first gear step. CONSTITUTION:An automatic transmission transmits power of an engine 8 to a drive shaft via a continuously variable transmission 12, a transfer 14 or the like to be automatically selected to a high speed gear step and a low speed gear step. In this case, when selecting a gear step of the transfer 14 from the high speed step to the low speed gear step, an optimum duty ratio is determined on the basis of hydraulic fluid temperature inside the transfer 14 from the preset constant relation at an electronic controller 330. And, in accordance with this duty ratio, a shifting solenoid valve 314 is driven to its on-off operations. With this constitution, a hydraulic fluid supply to a hydraulic actuator for a low speed step brake is varied in relation to the hydraulic fluid temperature, whereby outflow of the hydraulic fluid out of the hydraulic actuator of a high speed step clutch is made so easy.
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