Electromagnetic clutch and water pump

An electromagnetic clutch for a water pump of a vehicle engine comprising:

• a base portion;
• a driving member rotatably driven at a rotational axis by receiving an external driving force;
• a driven unit including an output shaft that rotates at the rotational axis by receiving a rotation of the driving member;
• and
• an electromagnetic solenoid generating a magnetic force while being supplied with electric power,
• the driving member, the driven unit, and the electromagnetic solenoid being assembled on the base portion,
• the driven unit including an intermediate member that engages with the output shaft in a thrust manner to transmit a torque to the output shaft while being relatively moved along the rotational axis, the intermediate member being magnetically attracted to the base portion by the magnetic force of the electromagnetic solenoid, the driven unit including a rotation member that is biased towards the driving member to make contact with the driving member when electric power is not supplied to the electromagnetic solenoid and that is pivotally supported to transmit the rotation of the driving member to the output shaft by making contact with the driving member, the driven unit including a guide mechanism that causes the rotation member to be displaced and separated from the driving member when electric power is supplied to the electromagnetic solenoid while the intermediate member is restrained from moving by being magnetically attracted by the magnetic force of the electromagnetic solenoid, the driven unit including a holding mechanism holding a position of the rotation member that is displaced and separated from the driving member.