Shift control device for vehicle transmission

A shift control device for a vehicle transmission having a plurality of gear ranges grouped into first and second gear groups, the shift control device comprising:

• rotational speed detecting means for detecting a current rotational speed of a drive source of a vehicle;
• deceleration detecting means for detecting a deceleration rate of the vehicle;
• rotational speed estimating means for determining an estimated rotational speed of the drive source after downshifting;
• gear determining means for determining a next gear range to be used from one of the first and second gear groups that does not include a current gear range;
• and
• pre-shifting means for controlling the transmission to achieve a waiting state for the next gear range before switching from the current gear range to the next gear range when the next gear range is on a downshift side of the current gear range and the estimated rotational speed determined is lower than a first prescribed rotational speed.

A shift control method for a vehicle transmission having at least first and second gear ranges, the shift control method comprising:

• determining whether a downshifting operation from the first gear range to the second gear range is required based on a vehicle speed and an accelerator position;
• determining an estimated rotational speed of a drive source of a vehicle after the downshifting operation based on a current rotational speed of the drive source and a deceleration rate of the vehicle;
• and
• controlling the vehicle transmission to achieve a waiting state for the second gear range before the downshifting operation when the downshifting operation is required and the estimated rotational speed is lower than a prescribed rotational speed.