Power transmission device and joint device

A power transmission device comprising:

• a connection and disconnection mechanism;
• and
• a transmission, wherein
• the connection and disconnection mechanism includes:
• an engagement element disposed between a first rotation member and a second rotation member;
• and
• an operation unit configured to operate the engagement element to an engagement state where the first rotation member and the second rotation member are integrally rotatable and a non-engagement state where the first rotation member and the second rotation member are relatively rotatable,
• the operation unit includes an actuation element configured to move the engagement element, and an operation element provided to be capable of operating the engagement element via the actuation element or capable of operating the engagement element not via the actuation element,
• the first rotation member and the second rotation member are disposed such that respective rotation axes of the first rotation member and the second rotation member coincide with each other, and at least a part of the first rotation member and the second rotation member overlap each other as viewed in a radial direction with respect to the rotation axes,
• the operation element includes:
• an advance and retraction element provided to be capable of advancing and retracting along the radial direction;
• and
• an extending portion extending along the rotation axes and provided to be capable of advancing and retracting along the rotation axes,
• the transmission includes a planetary transmission unit including:
• a first rotation element;
• a third rotation element;
• a fourth rotation element disposed to be capable of transmitting power between the first rotation element and the third rotation element;
• and
• a second rotation element supporting the fourth rotation element in a rotatable and revolvable manner,
• the planetary transmission unit is configured such that rotation speeds of three rotation elements including the first rotation element, the third rotation element and the second rotation element satisfy a collinear relationship in which the rotation speeds are aligned on a single straight line in a collinear diagram, and
• in the planetary transmission unit, a rotation axis of the third rotation element corresponds to the rotation axes of the first rotation member and the second rotation member.

A joint device comprising:

• a first member;
• a second member;
• a coupling unit configured to couple the first member and the second member such that a formed angle formed between the first member and the second member is variable;
• and
• an enlarging and reducing device capable of enlarging and reducing the formed angle formed between the first member and the second member, wherein
• the enlarging and reducing device includes a power source, and a power transmission device configured to transmit power of the power source,
• the power transmission device has:
• a first power transmission path for transmitting the power at a first transmission ratio;
• and
• a second power transmission path for transmitting the power at a second transmission ratio different from the first transmission ratio,
• the enlarging and reducing device includes:
• a first connection and disconnection mechanism configured to switch between disconnection and connection of power in the first power transmission path;
• and
• a second connection and disconnection mechanism configured to switch between disconnection and connection of power in the second power transmission path,
• the first power transmission path includes a planetary transmission unit, and
• the second power transmission path includes the planetary transmission unit and another planetary transmission unit different from the planetary transmission unit.