JPH09191627A - Stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress oscillation torque by providing a stator having a three- phase winding applied to a plurality of cores each provided, at the forward end, with a stator pole tooth directing toward the center from the inner circumferential surface of an annular yoke, and a corresponding rotor having rotor poles provided with specified number of rotor pole teeth. SOLUTION: A plurality of stators 2 are fixed, while directing inward, to the inner circumferential surface of a housing 1 forming an annular yoke. It is fixed, on the opposite sides with front and rear covers 4, 4' and the shaft 6 of a rotor 7 is held ratatably by means of bearings 5, 5'. Twelve stator poles 10-1,..., 10-12 are applied with stator coils 11-1,..., 11-12. Every third coils 11-1, 11-4, 11-7, 11-10 constitute a single phase. When the stator pole teeth of stator pole 10-1 face Nr pole teeth of rotor, the angle with respect to a rotor pole tooth closest to a stator pole tooth 10-2 becomes the step angle and a formula is satisfied. From the formula, Nr=12n±4 (n is an integer of 1 or above) is obtained. This structure realizes a microangle, low vibration three-phase motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a stepping motor used in OA equipment such as a scanner of a copying machine and a paper feed of a facsimile.

[0002]

2. Description of the Related Art Conventionally, a stepping motor used in an OA device such as a scanner of a copying machine or a paper feed of a facsimile is formed as shown in FIG. 11 in view of the required level of performance and the balance of cost. Stator K and rotor R
In general, the stator K has six magnetic poles, and pole teeth are formed at the tips of the respective stators.

[0003]

By the way, in the prior art, if the air gap between the stator and the rotor is uniform, the unbalanced electromagnetic force is large, and the stator core is rotated and laminated due to the configuration of the pole teeth. Therefore, there is a magnetic and mechanical problem caused by the deviation of the magnetic orientation and thickness of the magnetic steel sheet. It is an object of the present invention to provide a stepping motor that solves the problems (problems) of the conventional ones.

[0004]

Among the stepping motors of the present invention, first, an inner rotor type three-phase VR type stepping motor has an annular yoke portion and an inner peripheral surface of the annular yoke portion, which extends from the inner peripheral surface toward the center and has respective tips. A stator including a stator core made of a magnetic material having 12 stator magnetic poles formed with a plurality of stator pole teeth, and a stator coil concentratedly wound around the stator core in a three-phase configuration. And a three-phase VR type stepping motor including a rotor made of a magnetic material that is rotatably supported by the stator via a gap and has Nr rotor pole teeth formed at equal pitches on the outer peripheral surface thereof. Nr
= 12n ± 4 (n is an integer of 1 or more). Further, also in the case of the outer rotor type three-phase VR type stepping motor, it was configured such that Nr = 12n ± 4 (n is an integer of 1 or more). Further, in the case of the inner rotor type hybrid stepping motor, there are 12 stator magnetic poles, each having an annular yoke portion and a plurality of stator pole teeth formed at respective tips from the inner peripheral surface of the annular yoke portion toward the center. And a stator provided with a stator core made of a magnetic material having a stator coil and a stator coil wound around the stator core, and the stator and the stator are rotatably supported through a gap, and the like on the outer peripheral surface thereof. Two rotor cores made of a magnetic material in which Nr rotor pole teeth are formed at pitches are arranged such that the rotor pole tooth pitches are offset from each other by 1/2, and a disk-shaped permanent magnet magnetized in the axial direction is sandwiched. In the hybrid type stepping motor including the rotor, the plurality of stator pole teeth at the tips of the twelve stator magnetic poles have a pitch angle between the same positions of the respective stator magnetic poles, and α is a deviation angle larger than zero. As 30 ° , 30 °,
(30-α) °, 30 °, 30 °, (30 + α) °, 3
0 °, 30 °, (30-α) °, 30 °, 30 °, (3
0 + α) °, or 30 °, 30 °, 30 °, 30
°, 30 °, (30-α) °, 30 °, 30 °, 30
It was configured to be arranged at an angle of 30 °, 30 ° (30 + α) °. Alternatively, instead of these, an annular yoke portion having an outer peripheral shape of a substantially square shape and twelve stator magnetic poles each having a plurality of stator pole teeth formed at respective tips from the inner peripheral surface of the annular yoke portion toward the center. A stator including a stator iron core made of a magnetic material, a stator coil wound around the stator magnetic pole, a rotor rotatably supported by the stator and a gap, and front and rear covers. In the stepping motor, the stator core has two holes formed on each side of a square of an outer peripheral edge thereof at positions symmetrical with respect to a perpendicular bisector, and the stator core can be laminated by rotating 90 °. An inner rotor type stepping motor configured to form a stator may be used. Further, instead of these, an annular yoke portion having an outer peripheral shape of a substantially square shape, and twelve stator magnetic poles each having a plurality of stator pole teeth formed at respective tips from the inner peripheral surface of the annular yoke portion toward the center. A stator including a stator iron core made of a magnetic material, a stator coil wound around the stator magnetic pole, a rotor rotatably supported by the stator and a gap, and front and rear covers. In the stepping motor, the two stator cores U are provided at positions symmetrical to the bisector perpendicular to each side of the outer peripheral square.
It is also possible to use an inner rotor type stepping motor in which a groove is formed and rotated by 90 ° so as to form a stackable perfectly symmetrical stator.

With the above construction, it is possible to stack 12 stator magnetic poles in a symmetrical shape by rotating them at a pitch of 90 °, and in comparison with the number of stator magnetic poles of 6 in the prior art, The unbalanced electromagnetic force due to the eccentricity of the air gap can be suppressed to about 36%, and the vibration and noise during rotation can be significantly reduced.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. First Embodiment: FIG. 1 shows a first embodiment of the present invention. FIG. 1 is a vertical sectional front view of a three-phase VR stepping motor having 12 stator magnetic poles, and FIG. X-of 1
It is X 'sectional drawing. In each figure, 1 is a housing, 2
Is a stator, and 4 and 4'are front and rear covers, respectively.
Bearings 5 and 5'are held respectively. 6 is a rotor shaft, 7 is a rotor, 10-1 to 10-12 are 12 stator magnetic poles directed from the annular portion of the stator core toward the center, 11
-1 to 11-12 are stator coils wound around the stator magnetic poles, and these stator coils 11-1 to 11-12
Is, for example, 11-1, 11-4, 11-7, 11-10.
As shown in the figure, two pieces and four pieces constitute one phase.

In FIG. 2, for example, when the stator pole teeth of the stator magnetic pole 10-1 and the rotor pole teeth face each other, the rotor pole tooth closest to the stator magnetic pole 10-2 is Is the step angle

[Equation 1] The relationship of the formula (1) shown in is established. The left side of the equation (1) is the step angle indicated by the number of rotor pole teeth, and the right side is the angle formed by the first term between the stator pole 10-1 and the stator pole 10-2 adjacent thereto, and the second term is It is an angle formed by the stator pole 10-1 and the rotor pole tooth closest to the stator pole 10-2 adjacent thereto, and this also indicates a step angle. From the formula (1), Nr = 12n ± 4 is obtained.

The unbalanced electromagnetic force F ₁₂ is g with respect to the average air gap length g when four coils 11-1, 11-4, 11-7 and 11-10 for one phase are excited by direct current, for example. _{This is} an approximate calculation assuming that the eccentricity is one. This relationship

(Equation 3) Is shown in equation (3). Similarly, unbalanced electromagnetic force F ₆ in the case of the stator magnetic poles 6 of the prior art example shown in FIG. 11, since one phase is formed by two stator poles apart 180 °, only g ₁ Assuming eccentricity, F ₆ is expressed as the difference

[Equation 2] From the relations of the formulas (2) and (3), the relation between F ₆ and F ₁₂ is

(Equation 4) As shown in equation (4), F ₁₂ is about 36% of F ₆ .

FIG. 3 is a development view for explaining the operation of the stator pole teeth and the rotor pole teeth of FIGS. 1 and 2, and shows 6 of 12 stator poles (180 °). , VR type suction force operates in three steps by the rotor pole tooth pitch, so that one step angle becomes an electrical angle of 2π / 3. In FIG. 3, (1) shows that the rotor is attracted in the 11th phase, and then the excitation phase is sequentially changed to (2), (3), and (4), and the rotor is attracted, and the rotor advances. Has been done. In addition,
(4) is a diagram meaning returning to (1).

FIG. 9 shows the voltage sequence corresponding to FIG. 3 described above by one-phase excitation for only six of the 12 stator poles. In FIG. 3, the four stator magnetic poles for one phase are shown as N, S, N, and S,
In the case of two-phase excitation, all four may have the same polarity, for example, N for the first phase and S for the second phase.

FIG. 4 shows the number Nr of rotor pole teeth and the step angle θs according to the present invention. According to the table,
For example, when Nr = 100, θs = 1.2 ° is obtained.

When operating at the same step angle, low vibration and low noise can be realized by configuring with 12 stator magnetic poles in comparison with 6 stator magnetic poles in the prior art.

Second Embodiment: FIGS. 5 and 6 show a second embodiment of the present invention. A hybrid type stepping motor (hereinafter abbreviated as HB type) in which the stator 2 has 12 magnetic poles. Can be a three-phase type or a six-phase type. Further, FIG. 7 shows another configuration having a magnetic pole pitch different from that of FIG. Those shown in FIGS. 5 to 7 are H
Since it is a B type stepping motor, the rotor R is provided by the rotor magnetic poles 8A and 8B and the permanent magnet 9 different from those of the first embodiment shown in FIGS. 1 and 2, and two rotor magnetic poles are provided. 8A and 8B are arranged such that the rotor pole tooth pitches are offset by 1/2.

Since the step angle is inversely proportional to the number of phases, the step angle θs can be halved for the same number of rotor pole teeth Nr in 6 phases as in 3 phases. For example, Nr = 100
At this time, θs = 0.6 ° for the three-phase HB type and θs = 0.3 ° for the six-phase HB type, which doubles the resolution.

First, the 6-phase stepping motor of the present embodiment will be described with reference to FIG. As shown in the figure, the coil for one phase is composed of two stator magnetic poles separated by 180 °, and the coils for one phase to six phases are respectively (11-1, 1).
1-7), (11-4, 11-10), (11-2, 1)
1-8), (11-5, 11-11), (11-3, 1
1-9), (11-6, 11-12), and the pitch between the stator magnetic poles is set to the magnetic poles (10-3, 10-3) so as to operate by exciting in this order. −
4), magnetic poles (10-6, 10-7), magnetic poles (10-9,
10-10) and magnetic poles (10-12, 10-1) are arranged so that four positions between the magnetic poles of each combination are shifted by α °, and the other portions are arranged at the standard 30 °. In this example, 1
Stator magnetic poles for phases, for example, magnetic pole 10-1 and magnetic pole 10-7
Are excited to the same polarity and current is applied so that the next phase is opposite to the polarity of the previous phase, so the winding end of each phase is short-circuited, or the first, third and fifth phases are The second, fourth and sixth phases are short-circuited. Further, the deviation angle α is (30 ° / N
r) or an integer multiple thereof, but the smaller α is, the closer it is to the symmetric type, so it is better to choose smaller α in view of workability such as coil winding.

When Nr = 100, which is the number of rotor pole teeth,
α = 0.3 °, which is the step angle θs = 0.3 °
It becomes a 6-phase HB type stepping motor.

As described above, since the winding ends of the coils for each of the six phases are short-circuited, only 12 switching transistors are required. If the end of winding is not shorted, then 24 transistors are required.

There are the following two means for driving the one shown in FIG. 6 in three phases. One is the same coil as in the above-mentioned 6-phase type, and α is selected to have the same value, and coils for one phase are coils 11-1, 11-7, 11-4, and 11-10.
The coils for the phases are coil 11-2, 11-8, 11-5,
11-11, coils for three phases are coils 11-3, 1
As 1-9, 11-6, 11-12, a voltage may be applied to the three-terminal coil as shown in FIG. 10. Another method is that in FIG. 6, the coil for one phase is the same as the first method described above. In the same way, the polarities are, for example, coil 11-1 and coil 11-
7, the coil 11-4 and the coil 11-11 are wound so as to be reversed, and the other phases are also wound in the same manner.
In this case, α becomes 1.8 ° at Nr = 100, which is larger than that in the first method, but since there are two polarities in one phase, the magnetic circuit is independent in one phase. On the other hand, in the first method, four stator magnetic poles in one phase, for example, the magnetic pole 10 are used.
Since -1, 10-4, 10-7, and 10-10 have the same polarity, the magnetic circuit will span other phases,
There is a problem that it is easily affected by switching of other phases. FIG. 10 shows a drive voltage sequence of a three-phase HB type stepping motor when two-phase excitation is performed.

What is shown in FIG. 7 is the same as the example of FIG.
Phases and 6 phases are possible. Among the stator pole tooth pitches of the 12 stator magnetic poles, one position is 30-α, its diagonal portion is 30 + α, and all other angles are 30 °, and the principle is the same as the example of FIG. 6 described above. The description is omitted.

Third Embodiment: FIG. 8 shows a stator core for making the three-phase VR type stepping motor shown in FIGS. 1 and 2 completely symmetrical. In FIG. 1, the front and rear covers 4, 4'constitute a casing 2 so as to sandwich the stator 2, and are usually fixed by four bolts although not shown. The four bolts penetrate the stator core, but in the case of the square shape as shown in FIG. 8, it is better to provide these four through holes in the wide portions of the yoke parts at the four corners as shown in the figure. This is preferable because it can suppress an increase in resistance. 4 in the case of FIG.
In contrast to the use of a single bolt, in the configuration of FIG. 8, eight holes 20 to 27 are provided as shown in the figure. The holes provided at the four corners are laminated on the stator core by rotating as described above. This is because the magnetic resistance increases at the four corners of the square fixed iron core, and the magnetic resistance is made uniform in the entire magnetic pole. The bolt through hole shown in FIG. 8 is not limited to the hole and may be a U groove, for example.

[0021]

Since the stepping motor of the present invention is constructed as described above, it has the following excellent effects. By setting the stator magnetic poles to 12 and specific Nr, it is possible to manufacture a three-phase VR type stepping motor with a minute angle and low vibration. When a rectangular iron core is used for the outer shape and the stator magnetic poles are 12 poles, by providing 8 holes or U grooves at the positions of line symmetry of the bisector perpendicular to each side of the outer peripheral square, 90 °
It becomes possible to rotate and stack, and a structure that is advantageous for reducing vibration can be obtained. By providing a tooth pitch of 12 arms that is deviated from 30 ° evenly by α °, a 3-phase or 6-phase HB type stepping motor can be obtained, and the degree of freedom in selection is increased with high resolution. The application can be expanded. When the stator magnetic poles have 12 poles, the coil end can be made smaller than that of the conventional 6 poles, and a thin stepping motor can be configured.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional front view of a VR type stepping motor according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX ′ of FIG.

FIG. 3 is a development view for explaining the operation of the stator pole teeth and the rotor pole teeth of the stepping motor according to the first embodiment.

FIG. 4 is a chart showing a relationship between rotor pole teeth and step angles of the stepping motor according to the first embodiment.

FIG. 5 is a vertical sectional front view of an HB type stepping motor according to a second embodiment of the present invention.

6 is a sectional view taken along line XX ′ of FIG.

7 is an HB type stepping motor according to a second embodiment of the present invention, which is a configuration example different from that shown in FIG. 6, and is a cross-sectional view of a portion corresponding to XX ′ in FIG. 5. FIG. .

FIG. 8 is a plan view showing a stator core including a 12-pole polygonal core according to a third embodiment of the present invention.

FIG. 9 is a waveform diagram of a command pulse and a drive voltage of the VR type stepping motor according to the first embodiment.

FIG. 10 is a waveform diagram of command pulses and drive voltage of the three-phase HB type stepping motor according to the second embodiment.

FIG. 11 is a plan view showing iron cores of a stator and a rotor of a conventional 6-pole 3-phase stepping motor.

[Explanation of symbols]

2: Stator 7: Rotor R: Rotor 8A, 8B: Rotor magnetic pole 10-1, 10-2, 10-3, ...: Stator magnetic pole 11-1, 11-2, 11- 3, ...: Stator winding Nr: Number of rotor pole teeth

Claims (5)

[Claims] 1. A fixed member made of a magnetic material having an annular yoke portion and twelve stator magnetic poles, each of which has a plurality of stator pole teeth formed at a tip thereof from the inner peripheral surface of the annular yoke portion toward the center. A stator provided with a child core and a stator coil concentratedly wound around the stator core in a three-phase configuration, rotatably supported by the stator and an air gap with the stator, and Nr pieces on the outer peripheral surface at equal pitches. In a three-phase VR type stepping motor including a rotor made of a magnetic material having rotor rotor teeth,
= 12n ± 4 (n is an integer of 1 or more), an inner rotor type three-phase variable reluctance type (hereinafter referred to as VR type) stepping motor. 2. A magnetic body having an annular yoke portion and twelve stator magnetic poles radially provided from the outer peripheral surface of the annular yoke portion and having a plurality of stator pole teeth formed at respective tips thereof. A stator including a stator core and a stator coil concentratedly wound around the stator core in a three-phase configuration, and a stator and a stator that are rotatably supported through a gap and have an equal pitch on the inner peripheral surface thereof. In a three-phase VR type stepping motor including a rotor made of a magnetic material with Nr rotor pole teeth formed,
An outer rotor type three-phase VR type stepping motor, characterized in that Nr = 12n ± 4 (n is an integer of 1 or more). 3. A fixed member made of a magnetic material having an annular yoke portion and twelve stator magnetic poles, each of which has a plurality of stator pole teeth formed at its tip and extends from the inner peripheral surface of the annular yoke portion toward the center. A stator provided with a child core and a stator coil wound around the stator core, rotatably supported by the stator and a gap through a gap, and Nr rotor poles at an equal pitch on the outer peripheral surface thereof. A hybrid type stepping device having a rotor in which two rotor cores each having teeth and made of a magnetic material are sandwiched by a disk-shaped permanent magnet magnetized in the axial direction with rotor pole tooth pitches shifted by ½ from each other. In the motor, the pitch angles between the same positions of the stator poles of the plurality of 12 stator pole teeth are 30 °, 30 °, where α is a deviation angle larger than zero. 30-α)
°, 30 °, 30 °, (30 + α) °, 30 °, 30
°, (30-α) °, 30 °, 30 °, (30 + α)
Or 30 °, 30 °, 30 °, 30 °, 30
°, (30-α) °, 30 °, 30 °, 30 °, 30
An inner rotor type hybrid stepping motor, which is arranged so as to be at 30 ° (30 + α) °. 4. An annular yoke portion having an outer peripheral edge of a substantially square shape and twelve stator magnetic poles, each of which has a plurality of stator pole teeth formed at its tip and extends toward the center from the inner peripheral surface of the annular yoke portion. A stator having a stator core made of a magnetic material, a stator coil wound around the stator magnetic pole, a rotor rotatably supported by the stator and a gap, and front and rear covers. In the stepping motor, the stator core has two holes formed on each side of a square of an outer peripheral edge thereof at positions symmetrical with respect to a perpendicular bisector, and the stator core can be laminated by rotating 90 °. An inner rotor type stepping motor characterized in that it constitutes a stator. 5. An annular yoke portion having an outer peripheral edge of a substantially square shape, and twelve stator magnetic poles each having a plurality of stator pole teeth formed at respective tips from the inner peripheral surface of the annular yoke portion toward the center. A stator having a stator core made of a magnetic material, a stator coil wound around the stator magnetic pole, a rotor rotatably supported by the stator and a gap, and front and rear covers. In the stepping motor, the stator core has two U-grooves formed on each side of the outer peripheral square at positions symmetrical to each other by a perpendicular bisector, and the stator core can be rotated by 90 ° to be stacked completely symmetrically. An inner rotor type stepping motor characterized by being configured as a shape stator.