Patent ID: 8475332

Claim:
A rotary meshing engagement apparatus comprising: an engaging device having a first engaging element, a second engaging element, and a driving force applying device, the first engaging element capable of rotating around a shaft line, the first engaging element comprising, on a surface, a first tooth-shaped member in which a plurality of convex portions and a plurality of concave portions are alternately arranged in a rotational direction, the second engaging element being opposed to the first engaging element and capable of engaging with the first engaging element in a direction of the shaft line, the second engaging element comprising, on a surface, a second tooth-shaped member having a plurality of convex portions and a plurality of concave portions which mesh with the convex portions and the concave portions of the first tooth-shaped member in a lock state in which the second engaging element engages with the first engaging element, the driving force applying device capable of applying a driving force to the first or second engaging element in order to displace the first or second engaging element along the shaft line from a position corresponding to a release state in which the first engaging element does not engage with the second engaging element to a position corresponding to the lock state, engagement surfaces of the first and second tooth-shaped members being inclined at a predetermined angle with respect to the shaft line such that the first engaging element and the second engaging element perform relative rotation in a process in which the first or second engaging element is displaced along the shaft line; a specifying device for specifying a relative rotation amount between the first engaging element and the second engaging element; an estimating device for estimating a displacement amount in the shaft line direction of the first or second engaging element on the basis of the specified relative rotation amount and the predetermined angle in engaging the first engaging element and the second engaging element; a release force applying device for always applying a release force to the first or second engaging element in order to maintain the first or second engaging element at the position corresponding to the release state; a judging device for judging whether or not the release force applying device is in a normal state on the basis of the estimated displacement amount; and a controlling device for controlling the driving force applying device to apply the driving force corresponding to the release force, to the first or second engaging element, if it is judged that the release force applying device is not in the normal state, wherein the driving force applying device applies the driving force which is greater than the release force, to the first or second engaging element, in engaging the first engaging element and the second engaging element.