Spindle motor

A spindle motor, comprising:

• a motor stator;
• a motor rotor;
• a driving motor having a stator secured to said motor stator and a rotor secured to said motor rotor;
• a thrust bearing and a radial bearing rotatably supporting said motor rotor on said motor stator, at least said thrust bearing being a hydrodynamic bearing;
• and
• a thrust load adjusting means for adjusting the thrust load applied to said thrust bearing by applying forces on said motor in directions both toward and away from said thrust bearing to increase and decrease the amount of force applied to said thrust bearing under varying conditions of operation of said motor such that the thrust load applied to said thrust bearing is reduced during starting of said driving motor and such that the thrust load applied to said thrust bearing is increased when the rotational speed of said driving motor undergoes a predetermined increase, said thrust load adjusting means comprising an electromagnet on said motor stator and a permanent magnet disposed on said motor rotor.