Magnetic disc apparatus having uniform torque imparting means for imparting uniform torque irrespective of rotational position of a head arm

Claim 1

A swing arm type magnetic disc apparatus comprising: a housing; a magnetic disc having a data read and write zone and a contact start stop zone, and being accommodated in said housing and rotating at a high speed; a spindle rotatably supported on said housing; a head arm provided with a floating-type magnetic head and secured to said spindle; said spindle having an operational torque thereon, which varies in direction depending upon angular position of said head arm and which causes said magnetic head to move toward or away from said contact start stop zone, caused by a moment of forces acting upon said head arm, said operational torque varying in magnitude depending upon the angular position of said head arm; complementary torque generation means for generating an imparting torque to said spindle in a manner that said imparting torque is applied in a direction toward said contact start stop zone such that, during a seek operation, said operational torque and said imparting torque together comprising a combined torque which is applied on said spindle, said combined torque being substantially constant regardless of angular position of said head arm; and said combined torque, which is substantially constant, acts in a direction which causes said magnetic head to move toward said contact start stop zone; and a motor for driving said spindle when a seek operation is performed for moving said head arm out of said start stop zone and for overcoming said combined torque by means of a generated force produced by said motor.