JPH1023733A - Stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attenuate the higher harmonic components generated between the pole teeth of a stepping motor so as to reduce the vibration and noise of the motor, by establishing a paired relation between the poles of the same polarity in one phase of a stator and unevenly arranging the pole teeth pairs at a specific angle. SOLUTION: The pole teeth 211 and 221 of a stator 2 are not arranged on the internal surface of the stator at regular angular pitches, but at irregular pitches of (360 deg./n) (p±1/8) (where, the p is the pitch between paired pole teeth 211 and 221 and the number of pitches of pole teeth of the same polarity in one phase is set at a positive integer) by establishing a paired relation between the pole teeth 211 and 221. Therefore, the vibration and noise of a stepping motor can be reduced, because the T-θ characteristic curve of the stepping motor can be brought nearer to an extremely proper sine wave by removing the fourth harmonics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in vibration and noise reduction characteristics of a stepping motor during rotation.

[0002]

2. Description of the Related Art A stepping motor according to the present invention comprises:
A so-called sheet metal structure type multi-pole PM stepping motor, the structure of which is shown in FIG. 1 of FIG.
Is a flange for mounting the motor, 21 is A phase, 22 is B
Of the two sets of stators in phase, both 21 and 22 are combined together as a step angle shift to form stator 2. 212 is an A-phase stator winding, and 222 is a B-phase stator winding. Numerals 211 and 221 denote stator pole teeth of each phase. For one phase, n pole teeth of the same polarity are alternately arranged at a uniform pitch of a total of 2n. Reference numeral 3 denotes a rotor of a permanent magnet magnetized on the outer periphery at a uniform pitch, and reference numeral 4 denotes a shaft.

[0003] In order to show the relationship between the A-phase and B-phase pole teeth in this state, the stator inner diameter 360 ° was linearly developed.
FIG. FIG. 2 shows the most common 7.5 ° / step,
That is, a 24-pole (n = 12) stepping motor is illustrated as an example.

[0004]

Recently, stepping motors include FDD, HDD, printer, facsimile,
At the same time as the application fields of computer equipment such as copiers and office equipment have become widespread, the noise and vibration inherent in stepping motors have become a problem. Where the emergence of a stepper motor with lower vibration and noise is strongly expected, the present invention
The solution is provided.

[0005]

In order to investigate the torque waveform, the magnetic flux distribution between the pole teeth, etc. of the conventional pole tooth uniform arrangement type stepping motor using the latest advanced measuring equipment, the conventional pole He concluded that even tooth distribution was not always a sensible approach.

[0006] Vibration and noise of the stepping motor are represented by a torque / shaft angle waveform (usually called T-θ characteristic) or
It has been known for a long time that the harmonics of the air gap magnetic flux distribution are the cause. Therefore, based on the premise that the pole teeth are arranged at a uniform pitch, only research was conducted on what pole tooth shape could minimize the harmonics, and the idea of offsetting by changing the pole tooth arrangement was not reached. .

According to the present invention, in order to cancel harmonic components between pole teeth, a cylindrical permanent magnet in which magnetic poles N and S are alternately and uniformly pitched on the outer periphery is used as a rotor, The stator pole teeth are made equal to the inner diameter of the stator for a so-called sheet-metal structure two-phase multi-pole stepping motor, which is composed of two sets of stators each having a wire and 2n pole teeth assembled with a step angle shift with respect to each other. A pair relationship is created between the poles of the same polarity of the stator for each phase without disposing them at an appropriate angular pitch, and (360 ° / n) (p ± 1/8)
.. (Where p is the pitch between the pole teeth forming a pair and a positive integer of the number of pitches counted by pole teeth of the same polarity), the pole teeth are arranged unequally.

[0008]

The main reason why the present invention is constructed as described above is that the distortion of the T-.theta. Curve shown in FIG. 3 is corrected. When analyzing FIG. 3 in detail, it was confirmed that most of the torque curve distortion generated by the strong influence of the fourth harmonic of the air gap magnetic flux distribution between pole teeth was caused by the fourth harmonic (FIG. 4). In other words, if the fourth harmonic can be removed, the T-θ curve can be approximated to a very correct sine wave.

The fourth harmonic torque means that one cycle of the fundamental wave torque of this stepping motor is 360 ° / n.
On the other hand, it is not necessary to say that a quarter cycle is a fine cycle. Therefore, a further half cycle of 1/4, 1 /
The fourth harmonic can be canceled by shifting by eight cycles.

FIG. 2 shows the most popular 24-pole (n = 12), 7.5 ° / step pole tooth positional relationship among the multi-pole two-phase PM stepping motors. FIG. All 24 pole teeth per phase represent the conventional type arranged at a uniform pitch. A1, A
2... An have the same polarity, and A1 ′, A2 ′,. . A
n ′ is the same polarity pole tooth of the opposite polarity as described above.

By the way, the basis of the present invention will be described with reference to FIG. 2. If the combination of A1 ′ opposing the pole tooth A1 is different from the combination of Ap and Ap ′ separated by p pitches by (3)
When the angle is 60 ° / n) (p ± １ ／), the torque curves generated by both combinations have a phase difference of ８ cycle, and the fourth harmonic is canceled out. is there.

FIG. 5 shows the relationship between the fourth harmonic and the fundamental sine wave of the distorted waveform having the fourth harmonic, and the fourth harmonic generated by a pair of pole teeth having a phase difference of 1/8 cycle is shown in FIG. It shows the situation of canceling each other.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 2 shows a conventional 24-pole 2-phase PM stepping motor of 7.5 ° / step as described above. The pole teeth are all arranged at an equal pitch on the inner diameter of the stator.

FIG. 6 shows a first embodiment in which the arrangement of the pole teeth according to the present invention is effective for low vibration and low noise. In FIG. 6, the pole teeth ○ and ●, □ and △, △ and ▲
They are in a pairing relationship with each other, and between the pole teeth of the pair, (360 ° / n) (p ± 1 /
8) The pitch angle has been applied.

FIG. 7 shows a second embodiment in which pairs of pole teeth of the same stepping motor are selected in different combinations. As in the first embodiment, the pole teeth ○ and ●, □ and △, and △ and ▲ have a paired relationship with each other.
A (360 ° / n) (p ± １ ／) pitch angle is applied.

Although it has been understood from the first and second embodiments how to select a pair for setting the fourth harmonic so as to be canceled out, another embodiment will be described as a unique case.

FIG. 8 is a developed view of a conventional pole tooth of an 18 ° / step two-phase PM stepping motor having the same structure as described above. That is, the stator pole teeth are all arranged uniformly with respect to the rotor 10 poles.

On the other hand, FIG. 9 shows a third embodiment according to the present invention to which a pair of pole tooth pitches (360 ° / n) (p ± １ ／) is applied. In this case, since the number of pole teeth of the same polarity is odd, one pole tooth that cannot be paired is generated. This is indicated by the ☆ mark electrode tooth in FIG. All four sets of the fourth harmonic generated in the five sets of N and S poles are canceled out, and the remaining 1/5 is
Only the remaining will remain, so its offsetting effect is deemed sufficient.

FIG. 10 shows a fourth embodiment of the present invention. In this embodiment, a pair of pairs is formed in order to further reduce the fourth harmonic remaining in the third embodiment. Not ☆
It has a pole tooth structure that lacks the pole teeth.

The lack of the positive pole teeth makes it possible to reduce the torque somewhat as compared with the third embodiment having the positive pole teeth, but it is unavoidable that the fourth harmonic is further increased. It is possible to reduce the number of motors, and to exhibit a higher level of low vibration and low noise characteristics without losing the function of the step motor.

In the present invention, the rotor is constituted by cylindrical permanent magnets on the outer periphery of which magnetic poles N and magnetic poles S are alternately magnetized at an equal pitch, but the number of poles of NS is the number of pole teeth. May be different or the same.

[0023]

According to the present invention, most of the generated torque curve distortion is due to the fourth harmonic of the air gap magnetic flux distribution between the pole teeth. However, according to the present invention, the T-θ characteristic curve is eliminated by removing the fourth harmonic. It becomes possible to approach a very correct sine wave,
It has become possible to provide a stepping motor with lower vibration and noise.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a two-phase multi-pole PM stepping motor, usually a sheet metal structure PM stepping motor.

FIG. 2 shows the structure of FIG. 1 with the most common 7.5 ° / step, 24-pole PM stepping motor, conventional pole tooth position,
FIG. 7 is a diagram in which a magnetic gap 360 ° is linearly developed to explain an angular relationship.

FIG. 3 is an explanatory diagram of a curve of a generated torque with respect to a shaft angle of the stepping motor, which is generally called a T-θ curve.

FIG. 4 is a diagram illustrating that a generated torque curve (T-θ curve) includes a fourth harmonic, and explains the fourth harmonic.

FIG. 5 is a diagram illustrating that a fourth harmonic is canceled by a ８ cycle phase shift, and a combined torque of a fundamental wave in that case.

FIG. 6 is a diagram of a first embodiment in which the present invention is applied to the most common stepping motor shown in FIG.

FIG. 7 is a diagram of a second embodiment in which the present invention is applied to the most common stepping motor shown in FIG.

FIG. 8 is a developed view of a conventional pole tooth in a 18-pole / step, sheet metal structure, 10-pole stepping motor.

FIG. 9 shows a third example in which the present invention is applied to the developed view of FIG.
It is an Example figure.

FIG. 10 is a diagram of a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flange 2 Stator 21 A-phase stator 22 B-phase stator 211 A-phase stator pole teeth 212 A-phase stator winding 221 B-phase stator pole teeth 222 B-phase stator winding 3 Rotor 4 Shaft An pole Teeth An 'pole teeth

Claims (1)

[Claims] A cylindrical permanent magnet having magnetic poles N and magnetic poles S alternately and uniformly pitched on its outer periphery is used as a rotor,
In a PM stepping motor having a so-called sheet metal structure in which two sets of stators each having a winding and having 2n pole teeth on the inside diameter are assembled by being shifted by a step angle with respect to each other, the stator pole teeth are equal to the stator inside diameter. Without arranging at an angular pitch, create a paired relationship between poles of the same pole of the one-phase stator,
(360 ° / n) (p ± 1/8) ...
(However, p is a pitch between pole teeth forming a pair and has a positive integer which is a pitch number for counting pole teeth of the same polarity of one phase)
Multi-pole PM stepping motor characterized by non-uniform arrangement of pole teeth.