Abstract: A dynamic pressure type fluid bearing device includes a rotary shaft, a hollow sleeve in which the rotary shaft is rotatably mounted, and at least two sets of dynamic pressure generating grooves formed in either an outer surface of the rotary shaft or an inner surface of the sleeve. In this construction, a value obtained from k.times.sin .beta. is made equal to about 0.1 or ranges from 0.09 to 0.12, where k=d/e, d is a width of the dynamic pressure generating grooves, e is an interval between neighboring dynamic pressure generating grooves, and .beta. is an angle of the dynamic pressure generating grooves relative to a direction of rotation of the rotary shaft.

Abstract: A rotating polygon mirror driving apparatus has a rotor having a rotating polygon mirror fixed thereto, a rotational shaft and a rotor magnet; a bracket having a base plate provided opposite to the rotor magnet and a collar forming a bearing holding portion of a resin outserted to the base plate and made; and a bearing fitted to the bracket so as to support the rotational shaft. The driving apparatus can be decreased in cost and thickness while maintaining excellent rotational precision and mechanical precision.

Abstract: A rotating polygon mirror driving apparatus has a rotor having a rotating polygon mirror fixed thereto, a rotational shaft and a rotor magnet; a bracket having a base plate provided opposite to the rotor magnet and a collar forming a bearing holding portion of a resin outserted to the base plate and made; and a bearing fitted to the bracket so as to support the rotational shaft. The driving apparatus can be decreased in cost and thickness while maintaining excellent rotational precision and mechanical precision.