Outer Rotor Type Hybrid Stepping Motor

Abstract

An outer rotor type hybrid stepping motor includes a stator, a rotor, a magnet disposed axially in the stator or the rotor, a stator core disposed inwardly from a gap between the stator and rotor, and a stator winding on the stator core. The rotor is disposed outside the gap. The magnet has an axial cross sectional area A. The residual magnetic flux density of the magnet is Br, and a total of magnetic fluxes exiting axially from the surface is A×Br. A gap average magnetic flux density, determined by dividing A×Br by the top cross sectional area small teeth poles on the rotor is Bg; pitch of the teeth is τ; and tooth width is Tw. Average magnetic flux density Bg, tooth pitch τ, and tooth width Tw are determined by the equation K=1/(π×Bg×Tw/τ), with the coefficient k in a range of 0.56-0.66 (1/T).

1 . An outer rotor type hybrid stepping motor including a stator, a rotor, a magnet disposed in an axial space in either of the stator or the rotor, a stator core disposed inner side portion from a gap formed between the stator and the rotor and a stator winding wound around the stator core and the rotor is disposed outside the gap, wherein when assuming that a cross sectional area in the axial direction of the magnet is A, a residual magnetic flux density of the magnet is Br, a total sum of magnetic fluxes coming out from the surface in the axial direction is A×Br, a gap average magnetic flux density determined by dividing A×Br with cross sectional area of top ends of small teeth poles on the rotor is Bg, a pitch of the teeth is τ and a tooth width is Tw, the average magnetic flux density Bg, the teeth pitch τ and tooth width Tw is determined according to the following equation under a condition that a coefficient k in the following equation is kept in a range of 0.56-0.66(1/T);
     K= 1/(π× Bg× Tw/τ).   
   
   
       2 . An outer rotor type hybrid stepping motor including a stator, a rotor, a magnet disposed in an axial space in either of the stator or the rotor, a stator core disposed inner side portion from a gap formed between the stator and the rotor and a stator winding wound around the stator core and the rotor is disposed outside the gap, wherein when assuming that a plate thickness of electromagnetic steel plates used for the core is t, a gap portion diameter is D and number of small teeth poles on the rotor is Nr, the following equation stands under a condition that a coefficient α in the following equation is kept in a range of 0.3-0.56;
     Nr=α×π×D/t