Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-12-03
2004-03-16
Ponomarenko, Nicholas (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S156380, C310S156430, C310S156450
Reexamination Certificate
active
06707178
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improvement of a permanent magnet type three-phase twelve-pole stepping motor that is employed in OA equipment such as a copier, a scanner g or the like.
2. Description of Prior Arts
A pitch of stator teeth of a conventional three-phase twelve-pole permanent magnet type stepping motor is equal to a pitch of rotor teeth, and three phases, which are U-phase, V-phase and W-phase, are spatially distributed at 120 degrees intervals. Further, since a hybrid type rotor has 180 degrees of phase difference among the magnet poles, a N-pole and a S-pole, the fourth harmonic component is erased in a space of a field magnet of an air gap among the phases.
In this case, although the fourth harmonic component forms a cogging torque in the space of the field magnet of the air gap, the cogging torque of the conventional three-phase hybrid type stepping motor becomes minimum according to the above-described effect.
Incidentally, in the above-described conventional construction, the fourth harmonic component included in the magnetic flux in the field magnet formed in the air gap takes small value when the pole pair number Nr of the rotor becomes large, because the phase between the N-pole and the S-pole formed on the rotor equals to (180/Nr) degrees in a mechanical angle. Accordingly, since a slight error of the mechanical angle results in a large error of the electrical angle, the fourth harmonic component of the field magnet formed among the phases cannot be erased.
Therefore, the values of the cogging torque vary and there may be a product having a part of large cogging torque, which results the variation in an oscillation noise. Further, the effect of the harmonic components is the same when the second harmonic component, the third harmonic component and the fifth harmonic component exist, and therefore, these harmonic components are required to be removed.
An object of the present invention is to provide a permanent magnet type twelve-pole stepping motor that eliminates the defects mentioned above.
SUMMARY OF THE INVENTION
A permanent magnet type twelve-pole stepping motor of an inner rotor type described in claim 1 comprises,
a stator comprising a yoke portion having approximately annular shape, a stator iron-core made from magnetic material having twelve stator main poles that are directed from the inner circumferential surface of the yoke portion toward the center and each having a plurality of small teeth on the tip end thereof, and stator coils wound in the stator iron-core;
a so-called hybrid type rotor, which is rotatably supported by the stator through a predetermined air gap, having a cylindrical permanent magnet magnetized in a rotation axis direction that is sandwiched between a pair of rotors made from magnetic material each having Nr pieces of pole teeth around the outer circumferential surface thereof at equal pitch and the rotors being arranged such that the pole teeth are deviated with each other, or a permanent magnet type rotor whose cylindrical outer circumferential surface is magnetized in a direction parallel to the rotation axis to form Nr pairs of N-pole and S-pole alternately;
wherein said stator is formed as three-phase winding and second harmonic component, third harmonic component, fourth harmonic component and fifth harmonic component are removed by composing cogging torque of the respective phases by means of the three-phase twelve-pole construction, further any one harmonic component of the cogging torque among the second harmonic component, the third harmonic component, the fourth harmonic component and the fifth harmonic component is independently erased by making a difference between the small teeth pitch of said stator main pole and the rotor teeth pitch or the pole pair number pitch, thereby any one harmonic component among the second harmonic component, the third harmonic component, the fourth harmonic component and the fifth harmonic component is doubly erased.
Further, a permanent magnet type twelve-pole stepping motor of an outer rotor type described in claim 2 comprises,
a stator comprising a yoke portion having approximately annular shape, a stator iron-core made from magnetic material having twelve stator main poles that are formed on the outer circumferential surface of the yoke portion aligned radially and each having a plurality of small teeth on the tip end thereof, and stator coils wound in the stator iron-core;
a so-called hybrid type rotor, which is rotatably supported by the stator through a predetermined air gap, having a cylindrical permanent magnet magnetized in a rotation axis direction that is sandwiched between a pair of rotors made from magnetic material each having Nr pieces of pole teeth around the inner circumferential surface thereof at equal pitch and the rotors being arranged such that the pole teeth are deviated with each other, or a permanent magnet type rotor whose cylindrical inner circumferential surface is magnetized in a direction parallel to the rotation axis to form Nr pairs of N-pole and S-pole alternately;
wherein said stator is formed as three-phase winding and second harmonic component, third harmonic component, fourth harmonic component and fifth harmonic component are removed by composing cogging torque of the respective phases by means of the three-phase twelve-pole construction, further any one harmonic component of the cogging torque among the second harmonic component, the third harmonic component, the fourth harmonic component and the fifth harmonic component is independently erased by making a difference between the small teeth pitch of said stator main pole and the rotor teeth pitch or the pole pair number pitch, thereby any one harmonic component among the second harmonic component, the third harmonic component, the fourth harmonic component and the fifth harmonic component is doubly erased.
Further, a permanent magnet type twelve-pole stepping motor of an inner rotor type described in claim 3 comprises,
a stator comprising a yoke portion having approximately annular shape, a stator iron-core made from magnetic material having twelve stator main poles that are directed from the inner circumferential surface of the yoke portion toward the center and each having a plurality of small teeth on the tip end thereof, and stator coils wound in the stator iron-core;
a so-called hybrid type rotor, which is rotatably supported by the stator through a predetermined air gap, having a cylindrical permanent magnet magnetized in a rotation axis direction that is sandwiched between a pair of rotors made from magnetic material each having Nr pieces of pole teeth around the outer circumferential surface thereof at equal pitch and the rotors being arranged such that the pole teeth are deviated with each other, or a permanent magnet type rotor whose cylindrical outer circumferential surface is magnetized in a direction parallel to the rotation axis to form Nr pairs of N-pole and S-pole alternately;
wherein said stator is formed as three-phase winding and second harmonic component, third harmonic component, fourth harmonic component and fifth harmonic component are removed by composing cogging torque of the respective phases by means of the three-phase twelve-pole construction, further any one harmonic component of the cogging torque among the component from the second harmonic to the third harmonic, the component from the third harmonic to the fourth harmonic and the component from the fourth harmonic to the fifth harmonic is independently erased by making a difference between the small teeth pitch of said stator main pole and the rotor teeth pitch or the pole pair number pitch.
Further, a permanent magnet type twelve-pole stepping motor of an outer rotor type described in claim 4 comprises,
a stator comprising a yoke portion having approximately annular shape, a stator iron-core made from magnetic material having twelve stator main poles that are formed on the outer circumferential surface of the yoke portion aligned radially and each h
Kikuchi Noriyoshi
Kobayashi Toru
Sakamoto Masafumi
Aguirrechea J.
Japan Servo Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ponomarenko Nicholas
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