Method for controlling line pressure of automatic transmission

A method for controlling a line pressure of an automatic transmission, which has a regulator valve, a torque converter control valve, an oil pan, and an oil pump, for a vehicle, the method comprising:

• a line pressure setting operation of setting the line pressure of the automatic transmission to be equal to or lower than a set pressure when the vehicle starts;
• and
• a line pressure converting operation of converting the line pressure into a pressure higher than the set pressure when the automatic transmission is operated for shifting or when a set time has lapsed since the vehicle starting,
• wherein, in the line pressure setting operation, the set pressure is a pressure at which oil is introduced to re-circulation passages that have not been filled with oil before the vehicle starting,
• wherein the re-circulation passages comprise:
• a first re-circulation passage extending from the regulator valve to the oil pan;
• and
• a second re-circulation passage extending from the torque converter control valve to the oil pan, and
• wherein the first re-circulation passage and the second re-circulation passage adjoin at one point and then extend to the oil pan.