Power Transmission Device

A power transmission device comprising:

• a first rotating shaft;
• a piston that is disposed in the first rotating shaft in a state where an axial movement relative to the first rotating shaft is made possible and a circumferential movement relative to the first rotating shaft is blocked, and includes a first pawl portion;
• an oil chamber that is disposed between the first rotating shaft and the piston and to which hydraulic oil is delivered to cause the piston to move in the axial direction of the first rotating shaft;
• a first rotating shaft-side friction plate that is supported in the piston in a state of being coaxial with the piston and relative rotation to the piston being blocked;
• a second rotating shaft that is disposed to be coaxial with the first rotating shaft and to be capable of performing a relative rotation to the first rotating shaft, and includes a second pawl portion engageable to the first pawl portion;
• and
• a second rotating shaft-side friction plate that is supported in the second rotating shaft in a state of being coaxial with the second rotating shaft and relative rotation to the second rotating shaft being blocked, characterized in that:
• the first rotating shaft and the second rotating shaft are connected to be in a state where the transmission of the rotation is made possible by the first pawl portion of the piston and the second pawl portion of the second rotating shaft being engaged to each other based upon the delivery of the hydraulic oil into the oil chamber;,
• the first rotating shaft-side friction plate makes, when the first pawl portion of the piston is engaged with the second pawl portion of the second rotating shaft based upon the delivery of the hydraulic oil to the oil chamber, frictional contact with the second rotating shaft-side friction plate prior to the engagement of the first pawl portion and the second pawl portion;
• and
• engagement surfaces between the first pawl portion and the second pawl portion are formed as inclination surfaces so that a force is applied to the first pawl portion and the second pawl portion in a direction of axially moving away from each other when the rotation is transmitted between the first rotating shaft and the second rotating shaft.