POWER TRANSMISSION DEVICE

To bring a dog clutch into a release state by a simple structure when excessive rotation torque is inputted from drive wheels.SOLUTION: A dog clutch 51 comprises a first member 52 having first dog teeth 53, and a second member 55 having second dog teeth 58, and energized to the first member 52 side by an elastic member 62. The elastic member 62 has a non-linear spring characteristic such as a tertiary curved line. When a deformation amount of the elastic member 62 is in a first intermediate value, a load becomes maximum in a value in a region between maximum rotation torque which is inputted to the first member 52 from an electric motor 11, and excessive rotation torque which is inputted to the first member 52 from drive wheels 15, and larger than the maximum rotation torque. When the deformation amount is in a second intermediate value which is larger than a value added with a tooth depth with respect to the first intermediate value, the load become minimum in the value which is smaller than the maximum rotation torque. In a region in which the deformation amount is smaller than the first intermediate value, the load is increased accompanied by an increase of the deformation amount, and in a region between the first intermediate value and the second intermediate value, the load is decreased accompanied by the increase of the deformation amount.SELECTED DRAWING: Figure 1 【課題】駆動輪から過大な回転トルクが入力された場合に、簡単な構造でドグクラッチを解放状態にする。【解決手段】ドグクラッチ５１は、第１ドグ歯５３を有する第１部材５２と、第２ドグ歯５８を有し、かつ弾性部材６２により第１部材５２側へ付勢される第２部材５５とを備える。弾性部材６２は三次曲線のような非線形のばね特性を有する。弾性部材６２の変形量が第１中間値のときには荷重は、電動モータ１１から第１部材５２に入力される最大回転トルクと、駆動輪１５から第１部材５２に入力され、かつ最大回転トルクよりも大きな過大回転トルクとの間の領域で極大値となる。変形量が第１中間値に対し、歯丈を加えた値よりも大きな第２中間値のときには、荷重は最大回転トルクよりも小さな極小値となる。変形量が第１中間値よりも少ない領域では変形量の増加に伴い荷重が増加し、第１中間値と第２中間値との間の領域では変形量の増加に伴い荷重が減少する。【選択図】図１