Patent ID: 8798883

Claim:
An automatic transmission apparatus to be mounted to a straddle-type vehicle, the automatic transmission apparatus comprising: a multi-speed transmission mechanism that includes a plurality of transmission gears arranged to engage with each other via a dog clutch and changes a combination of the engaging transmission gears in association with rotation of a shift drum; an actuator arranged to rotate the shift drum; and a control device arranged and programmed to control the actuator, the control device including: a determining unit arranged to detect a state of the straddle-type vehicle and to determine whether the straddle-type vehicle is in a first state in which an engaging force between the transmission gears having engaged with each other before gear shifting is estimated to be equal to or greater than a predetermined value or in a second state in which the engaging force is estimated to be less than the predetermined value; a first gear shifting control unit arranged and programmed to control the actuator so that, if the determining unit determines that the straddle-type vehicle is in the first state, a rotational speed of the shift drum becomes a first rotational speed when the transmission gears come into engagement with each other; and a second gear shifting control unit arranged and programmed to control the actuator so that, if the determining unit determines that the straddle-type vehicle is in the second state, the rotational speed of the shift drum becomes a second rotational speed that is lower than the first rotational speed when the transmission gears come into engagement with each other.