Patent ID: 6486576
Filing Date: 2002-11-26
Classification: H02K

Abstract:
A permanent magnet type stepping motor comprising:a rotor having a permanent magnet element fixed on a revolving shaft; said permanent magnet element being constructed into a cylindrical configuration so as to permit n N magnetic poles and n S magnetic poles to alternately appear at equal pitches thereon in a circumferential direction thereof, wherein n is a positive integer of 4 or more; and a stator including two or more claw pole type yoke units juxtaposed to each other in an axial direction of said revolving shaft; said claw pole type yoke units each including first and second yokes and an exciting winding; said first and second yokes each including n pole teeth arranged opposite to said permanent magnet element at a predetermined interval in a radial direction of said revolving shaft and positioned at predetermined pitches in said circumferential direction; said exciting winding being constructed so as to permit said n pole teeth of said first yoke and said n pole teeth of said second yoke to be excited at polarities different from each other; said first and second yokes being combined with each other so that said n pole teeth of said first yoke and said n pole teeth of said second yoke are engaged with each other while being kept from being contacted with each other; said claw pole type yoke unit being so constructed that a pitch between each adjacent two of said pole teeth is constant; said n N magnetic poles of said rotor being so arranged that magnetic pole center-magnetic pole center pitches between said magnetic poles are not defined to be constant at 360Â°/n but defined to be two or more pitches different from each other between more than 270Â°/n and less than 450Â°/n; said n S magnetic poles of said rotor being so arranged that magnetic pole center-magnetic pole center pitches between said magnetic poles are not defined to be constant at 360Â°/n but defined to be two or more pitches different from each other between more than 270Â°/n and less than 450Â°/n; said two or more pitches different from each other being arranged so as to approach composite static torque to a sinusoidal wave.