To prevent generation of following rotation phenomenon to reduce generation of fan noise and improve fuel consumption by providing a liquid clutch at a position facing a movable disc, supporting an electromagnet attracting the disc to a rotational shaft, and variably providing a gap between a drive disc and the movable disc by the electromagnet.

A torque transmission 5 incoporates a movable disc 6 facing a drive disc 4 and there is a function capable of controlling a gap between the discs 4, 6 by moving the disc 6 by an electromagnet 8. Even if a great deal of oil exists in the chamber 5, a so-called following rotation phenomenon generating at the time of re-start or abrupt acceleration can be prevented effectively. Since the rotational frequency of a cooling fan 19 can be controlled corresponding to various drive conditions, reduction of fan noise and improvement in fuel consumption are attained, and also improvement of acceleration performance can be expected.