Patent ID: 8744706

Claim:
A line pressure control device for an automatic transmission, the line pressure control device controlling a line pressure by regulating an oil pressure from an oil pressure source in the automatic transmission for a vehicle that sets up a predetermined gear by selecting and causing any of a plurality of frictional engagement elements to engage, the line pressure becoming a base pressure of hydraulic oil for controlling operations of the frictional engagement elements, the line pressure control device comprising: a storage section for storing hydraulic pressure control characteristics for setting the line pressure to any of a high pressure region and a low pressure region on the basis of an engine load, wherein the high pressure region and low pressure region are separated by a boundary line, and the oil pressure from the oil pressure source is regulated to a given high line pressure when the line pressure is set to the high pressure region on the basis of the engine load, while the oil pressure from the oil pressure source is regulated to a given low line pressure when the line pressure is set to the low pressure region on the basis of the engine load; a hydraulic oil temperature sensor for detecting a temperature of the hydraulic oil; and a region changing section for changing the hydraulic pressure control characteristics of the line pressure stored in the storage section on the basis of the temperature of the hydraulic oil detected by the hydraulic oil temperature sensor; wherein the region changing section is configured to adjust the boundary line and change the hydraulic pressure control characteristics so that the low pressure region is enlarged in the changed hydraulic pressure control characteristics upon determining that the temperature of the hydraulic oil has been shifted from a predetermined high temperature range to a predetermined low temperature range, and further upon detecting that a throttle valve opening degree is totally closed or the line pressure is currently set at the given low pressure.