Patent ID: 7713167

Claim:
An automatic transmission control system comprising: a shift determination section configured to determine an existence of a shift condition that requires a shift operation in an automatic transmission including at least first and second frictional elements that performs the shift operation by selective engagement of the first frictional element and selective disengagement of the second frictional element; a shift control section configured to selectively control a line pressure regulator valve that regulates line pressure by draining ejection pressure of an oil pump and first and second engagement-pressure pressure regulator valves that regulate line pressure to provide engagement pressure to the first and second frictional elements; an oil temperature detection section configured to detect oil temperature within the automatic transmission; and an engagement pressure at-low-temperature regulation section configured to selectively control at least one of the first and second engagement-pressure regulator valves, when the oil temperature detected by the oil temperature detection section is lower than a predetermined oil temperature and the shift determination section determines the existence of the shift condition for requiring the shift operation, either to issue an order of a maximum hydraulic pressure to the first engagement-pressure regulator valve to engage the first frictional element to start a shift with the order of the maximum hydraulic pressure being continuously maintained during the shift until the shift ends, or to issue an order of a minimum hydraulic pressure to the second engagement-pressure regulator valve to disengage the second frictional element to start a downshift as the shift operation, and to issue an order of a maximum hydraulic pressure to the first engagement-pressure regulator valve to engage the first frictional element upon elapse of a predetermined period from the start of the downshift with an order of a minimum hydraulic pressure to the first frictional element being continuously maintained during the predetermined period from the start of the down shift and then the order of the maximum hydraulic pressure to the first frictional element being continuously maintained until the downshift ends.