Patent ID: 7575079

Claim:
A power output device comprising: a prime mover that outputs power; a speed change mechanism that is capable of switching between a plurality of speed change ratios and that gives an output of the prime mover to a drive shaft after changing the output in speed at a predetermined speed change ratio; a first rotation speed detector that detects rotation speed of the prime mover; a second rotation speed detector that detects rotation speed of the prime mover; and a controller that adopts information about prime mover rotation speed detected by the first rotation speed detector as present prime mover rotation speed information when the rotation speed of the prime mover is in a predetermined low rotation speed region, and that adopts information about the prime mover rotation speed detected by the second rotation speed detector as the present prime mover rotation speed information when the rotation speed of the prime mover is in a predetermined high rotation speed region, and that switches the prime mover rotation speed information adopted from the information about the prime mover rotation speed detected by the first rotation speed detector to the information about the prime mover rotation speed detected by the second rotation speed detector if the rotation speed of the prime mover changes from the low rotation speed region to the high rotation speed region, and that switches the prime mover rotation speed information adopted from the information about the prime mover rotation speed detected by the second rotation speed detector to the information about the prime mover rotation speed detected by the first rotation speed detector if the rotation speed of the prime mover changes from the high rotation speed region to the low rotation speed region, wherein if a gradient of change in the prime mover rotation speed is greater than or equal to a predetermined value while the information about the prime mover rotation speed detected by one rotation speed detector of the first rotation speed detector and the second rotation speed detector is adopted as the present prime mover rotation speed information, the controller prohibits a switching operation for adopting the information about the prime mover rotation speed detected by the other rotation speed detector as the present prime mover rotation speed information, and continues to adopt the information about the prime mover rotation speed detected by the one rotation speed detector as the present prime mover rotation speed information.