Abstract: Shift valves 141, 142, 143 are provided to switch oil passage connections to a state in which an oil pressure in one hydraulic clutch of an arbitrary speed transmission train and an oil pressure in a hydraulic clutch of a transmission train which is adjacent thereto as seen in the order of speed are controllable by a pair of linear solenoid valves 201, 202. Skipped speed change from a predetermined first speed transmission train to a second speed transmission train which is not adjacent to the first speed transmission train is made possible. In concrete, a large-capacity accumulator A5 is connected to an oil passage L19 which is in communication with 5th-speed hydraulic clutch C5. At the time of skipped speed changing from 5th speed to 3rd speed, shift valves 141, 142, 143 are switched to a state of 3rd-4th speed change. The oil pressures in the hydraulic clutches C3, C4 for 3rd and 4th speed transmission trains, respectively, are made controllable by the linear solenoid valves 201, 202.

Abstract: Upshifting is performed in a short time without giving rise to shocks. For that purpose, at the time of upshifting, a hydraulic pressure (QUPOFF) of a hydraulic engaging element on disengaging side is controlled such that the input and output speed ratio ("Gratio") of a transmission is decreased to, and held at, a predetermined slipping region (YG(N)S) that is lower than an engaging region (YG(N)L)-YG(N)H) to be set based on a gear ratio which is established by the engagement of the hydraulic engaging element on the disengaging side. The hydraulic pressure (QUPON) of a hydraulic engaging element on engaging side is gradually increased. When "Gratio" once falls below YG(N)L and then increases up again to YGCONOK, QUPOFF is lowered to a predetermined low pressure (QUPOFFB) at a lapse of a predetermined time (YTMUP8). Once "Gratio">YGCONOK, QUPON is increased to a predetermined high pressure QUPONB at a lapse of a second predetermined time YTMUP3.

Abstract: Even if a rotational speed of an engine has already increased due to slipping of a fluid torque converter at the time of start of downshifting, a smooth downshifting is performed. For that purpose, there is obtained a speed change developing degree function K(etrm) of the rotational speed of the engine at the time of start of downshifting, the developing degree being dependent on an increase in the rotational speed of the engine due to slipping in the fluid torque converter. The function K(etrm) is obtained with a speed ratio "etrm" of the fluid torque converter at the time of starting of downshifting as a parameter. A boosting correction value QDNOFFZ is computed by multiplying a reference correction value QDNOFFZO by K(etrm) (step S108-5). The hydraulic pressure of the hydraulic engaging element on the disengaging side during downshifting is boosted by the amount of QDNOFFZ (step S108-6).