Oil pressure control method a case pole low temperature

摘要

A method for controlling hydraulic pressure at low temperature is provided to prevent a gear shift drooping and impact by filling hydraulic oil in advance when an automatic transmission is shifted from a neutral range to a rear range. It is determined whether or not temperature of a hydraulic oil for operating an automatic transmission is at extreme low temperature(S1). In case the detected temperature of the hydraulic pressure is below the extreme low temperature, a control hydraulic pressure for a rear range is filled with 100 % to enter a low temperature region when the automatic transmission is switched to a parking range or a neutral range(S2). In case the automatic transmission is switched to the rear range, a filling time is delayed and a filling amount of the hydraulic oil is compensated in order to completely fill the hydraulic oil at the low temperature region so that the automatic transmission is switched from the neutral range to the rear range(S3). In case the detected temperature of the hydraulic oil is over the extreme low temperature, the control hydraulic pressure for the rear range is not filled when the automatic transmission is switched to the parking range and the neutral range(S4). In case the automatic transmission is switched to the rear range, the filling time and the filling amount are controlled in a room temperature region(S5).