Vehicle automatic transmission with valve duty factor control

A controller device for vehicle automatic transmission including oil-pressure driven type friction elements controls the duty factors of the solenoid valves for the respective friction elements involved in the gear shift. In the first control interval A, the duty factors are controlled in accordance with predetermined patterns, such that the friction elements engage with predetermined amounts of slip at the actual beginning of the gear shift. The first interval A is terminated either when a change in the rotational speed of the input shaft of the automatic transmission is detected or when a predetermined length of upper limit for the first interval A expires. When the first interval A terminates, the second control interval B begins, and the duty factors are controlled by a feedback control method. The second interval B is terminated either when the rotational speed of the input shaft of the automatic transmission reaches a predetermined level corresponding to the completion of the gear shift or when a predetermined length of the upper limit for the second interval B expires. The upper limits for the first and the second intervals may be measured by respective timers.