Patent ID: 8246514

Claim:
A transmission device that is built into a power output device outputting power to a drive shaft in combination with a power source and that includes an automatic transmission that changes a shift speed by switching an engagement state of at least one friction engagement element and transmits power from the power source to the drive shaft, the transmission device comprising: an engagement pressure regulating device that regulates an engagement pressure of the friction engagement element; and a control unit that controls the power source and the engagement pressure regulating device when a change of the shift speed is performed by engaging the friction engagement element in the state in which a torque is acting on an input shaft of the automatic transmission, so that the change of the shift speed is performed through two phases of a torque phase in which transmission of torque is changed to be made at the shift speed after shifting and an inertia phase in which a rotation speed of the input shaft is changed to a rotation speed corresponding to the shift speed after shifting, and controlling the power source and the engagement pressure regulating device so that the torque phase is executed by standing by with the friction engagement element engaged with a slip at a predetermined engagement pressure and the inertia phase is executed by reducing the torque acting on the input shaft from the power source in the state of standing by at the predetermined engagement pressure.