Downshift control for automotive automatic transmission

An automatic transmission control apparatus for a vehicle comprising:

• a hydraulic control circuit working to control hydraulic pressures of working fluid loaded to a plurality of frictional elements of a transmission mechanism joined at an input shaft thereof to an engine mounted in a vehicle through a torque converter to selectively achieve engagement and disengagement of the frictional elements for establishing a required speed of the transmission mechanism;
• a downshift control circuit working to make a downshift of the transmission mechanism through said hydraulic control circuit to develop an engine braking speed which establishes engine braking in a sequence of a first, a second, and a third downshifting stage upon a deceleration downshift request that is a request to downshift the transmission mechanism to decelerate the vehicle, in the first downshifting stage, said downshift control circuit controlling a given parameter to perform quick loading control which loads the working fluid quickly to an on-coming frictional element that is one of the frictional elements which achieves the engine braking speed until just before the on-coming frictional element is engaged, in the second downshifting stage entered following the first downshifting stage, said downshift control circuit keeping the working fluid loaded to the on-coming frictional element at a given standby pressure to conduct the downshift, in the third downshifting stage entered when the downshift reaches a given degree in the second downshifting stage, said downshift control circuit increasing the hydraulic pressure applied to the on-coming clutch to complete the downshift;
• an engine output increasing circuit working to perform engine output increasing control to increase an output of the engine during the downshift of the transmission mechanism regardless of a request to accelerate the engine made by an operator;
• a fluid-lack decision circuit working to decide whether a quickly loaded fluid amount that is an amount of the working fluid loaded to the on-coming clutch during the quick loading control is lacking or not based on a determination of whether a return of one of a gear ratio of the transmission mechanism and a given downshift degree parameter representing a degree of the downshift of the transmission mechanism has occurred or not;
• and
• a fluid-loaded amount correcting circuit working to correct the parameter controlled by said downshift control circuit to increase an amount of the working fluid which is to be loaded to the on-coming clutch during the quick loading control upon a following input of the deceleration downshift request when it is decided that the quickly loaded fluid amount is lacking.