Dog clutch and transmission

A dog clutch, comprising:

• a gear rotatably mounted on a power transmission shaft;
• a first dog ring configured to be engaged with the power transmission shaft in a rotating direction, the first dog ring being configured to move axially for engagement with the gear in the rotating direction, the first dog ring being capable of transmitting torque in a positive rotation direction between the gear and the power transmission shaft;
• a second dog ring disposed adjacent to the first dog ring on a side of the first dog ring axially farther from the gear, the second dog ring being configured to be engaged with the power transmission shaft in the rotating direction, the second dog ring being configured to move axially for engagement with the gear in the rotating direction, the second dog ring being capable of transmitting torque in a negative rotation direction between the gear and the power transmission shaft;
• a fork configured to move the first dog ring or the second dog ring axially;
• springs configured to pull the first dog ring and the second dog ring to bring the first dog ring and the second dog ring into pressure contact with each other axially;
• and
• cam grooves axially extending on the power transmission shaft,
• the cam grooves each including, on a surface in the positive rotation direction, a first parallel surface parallel to an axial direction and a first slope surface inclined from the first parallel surface toward the positive rotation direction as the first slope surface approaches the gear, the cam grooves each including, on a surface in the negative rotation direction, a second parallel surface parallel to the axial direction,
• the first dog ring including first cam protrusions each configured to be engaged with the first slope surface of the corresponding cam groove to transmit the torque in the positive rotation between the first dog ring and the power transmission shaft and to receive axial thrust from the first slope surface toward the gear,
• the second dog ring including second cam protrusions each configured to be engaged with the second parallel surface of the corresponding cam groove to transmit the torque in the negative rotation direction between the second dog ring and the power transmission shaft.