Automatic transmission control apparatus

An automatic transmission control apparatus, comprising:

• a clutch which, when a forward driving range is selected, is engaged to transmit rotation from an engine to a speed changing apparatus;
• a hydraulic servo for selectively engaging and releasing said clutch;
• fluid pressure control means for controlling fluid pressure supply to said hydraulic servo;
• range shift detecting means for detecting shift from a non-driving range to said forward driving range;
• and
• electronic control means for controlling said fluid pressure control means on the basis of a signal from said range shift detecting means,
• said fluid pressure control means comprising:
• a manual valve for outputting a forward driving range pressure when said forward driving range is selected;
• pressure regulating means for regulating said forward driving range pressure on the basis of a signal from said electronic control means to output a regulated fluid pressure;
• and
• changeover means able to be selectively changed over from a first position for supplying said forward driving range pressure to said hydraulic servo to a second position for supplying said regulated fluid pressure to said hydraulic servo, on the basis of a signal from said electronic control means,
• said electronic control means comprising:
• holding means for outputting a signal to said changeover means to hold said changeover means in said first position for an expected time period for starting clutch engagement after said range shift detecting means has detected shift to said forward driving range, and to shift said changeover means to said second position when said expected time period elapses;
• and
• fluid pressure raising means for outputting a signal to said pressure regulating means to cause said pressure regulating means to output an initial fluid pressure that is lower than said forward driving range pressure, before or when said holding means shifts said changeover means to said second position, and for outputting a signal to said pressure regulating means to cause said pressure regulating means to gradually raise fluid pressure from said initial fluid pressure, when or after said holding means shifts said changeover means to said second position.