Valve timing adjustment device

A valve timing adjustment device comprising:

• a first rotating body that rotates synchronously with a crankshaft;
• and a second rotating body that rotates synchronously with a camshaft,
• wherein the first rotating body includes a plate having an opening portion around a rotation axis,
• the second rotating body includes:
• a main body portion that is disposed to pass through the opening portion of the plate and is disposed around the rotation axis;
• and a holder having a first arm and a second arm that each extends to an outer peripheral side from an end portion of a part of the main body portion projecting from a front surface of the plate,
• a spiral spring is installed between the front surface of the plate and the first and the second arms, in which the spiral spring is wound around the main body portion, an inner peripheral side end portion of the spiral spring is held by the plate, and a terminal hook portion of the spiral spring is formed by bending an outer peripheral side end portion toward an outer peripheral side,
• a first arm projection portion is caught by the terminal hook portion of the spiral spring, is urged toward a lock phase side by the spiral spring and is installed on a face opposite to the front surface of the plate in the first arm in a case where a rotational phase of the second rotating body with respect to the first rotating body is on a first rotational phase side, and
• a second arm projection portion abuts on an outermost peripheral portion of the spiral spring and is installed on a face opposite to the front surface of the plate in the second arm in a case where the rotational phase is on the first rotational phase side.