JP3004580B2 - Stepping motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to OA equipment, for example,
The present invention relates to an improvement of a stepping motor used for driving a scanner of a copying machine.

[0002]

2. Description of the Related Art As a first conventional example, there are provided two sets of rotors 15a and 15b shown in FIG. 8A, and the pole teeth of these rotors are only θ0 as shown in FIG. There is known a technique in which the third harmonic is eliminated by disposing the angle so as to satisfy θ0 = π / 3 so as to satisfy θ0 = π / 3. A second conventional example is disclosed in Japanese Patent Laid-Open No. 3-212149. As shown in FIG. 9, for example, eight stator magnetic poles 17-1 to 17-8 are provided on a stator 16 on which windings are wound.
And n pole teeth at equal pitches on the circumference of a rotor 18 spaced apart from the stator magnetic poles 17-1 to 17-8 by a gap.
When the number of pole teeth of the (i = 1, 2,..., K) -th stator magnetic pole is m1, the magnetic pole pitch of the first stator magnetic pole is (360 ° / n). (1 ± 1 / qm). Here, q is an integer of 2 or more. In this configuration, the harmonic torque is reduced by configuring the stator as described above.

[0003]

By the way, each of the above-mentioned conventional structures has the following problems. The first conventional example requires two sets of rotors, which is inconvenient when the motor is made thin. The second conventional example is limited to reducing the vibration torque of the fourth harmonic with respect to the fundamental wave. Therefore, in a two-phase machine,
There is no problem with this means because the vibration torque of the harmonics is a large part, but the three-phase machine generates the vibration torque of the sixth harmonic with the field magnetic flux density of the fifth harmonic and the seventh harmonic. It is not suitable for a machine. SUMMARY OF THE INVENTION An object of the present invention is to provide a stepping motor that solves the above-mentioned problems of the conventional one.

[0004]

In order to solve the above-mentioned problems, a stepping motor according to the present invention has n stator magnetic poles on which windings are wound, and is arranged with a gap between the stator magnetic poles. In a stepping motor having a plurality of rotor pole teeth at equal pitches on the circumference of the rotor, when n is an integer of 3 or more and m is an even number of 4 or more, each of the n stator magnetic poles is m stator pole teeth, and the (m)
The (/ 2) -th and [(m / 2) +1] -th pole teeth pitches are (τ ± θ ₀ ), and the other pole tooth pitches are τ. However, π / 5 ≦ θ ₀ <π / 2, and τ and θ ₀
Are electrical angles. Alternatively, when n is an integer of 3 or more and m is an odd number of 5 or more, each of the n stator magnetic poles has m stator pole teeth, and The pole teeth pitch on both sides at the center may be set to (τ ± θ ₀ ), and the other pole teeth pitch may be set to τ. Instead of these, a plurality of 3L stator poles on which a three-phase winding is wound and a plurality of rotor poles are arranged at equal pitches on the circumference of a rotor arranged with a gap from the stator poles. In the stepping motor having teeth, when the 3L stator magnetic poles are provided with m stator pole teeth, respectively, and the rotor pole tooth pitch is 2π in electrical angle, the stator pole tooth pitch is (2π ± α). ), When L is an integer of 2 or more and m is an even number of 4 or more, α ₁ and α ₂ are obtained by the following equations (1) and (2), and α ₂ ≦ α ≦ α ₁
May be configured as follows. Here, α, α ₁ and α ₂ are each an electrical angle. Further, instead of this, each of the 3L stator magnetic poles
Stator pole teeth, and the rotor pole tooth pitch is 2 electrical degrees.
When L is an integer of 2 or more and m is an odd number of 3 or more, where π is the stator pole tooth pitch and (2π ± α), α _{1 is obtained} by the following equations (3) and (4). , Α ₂ and α ₂
≦ α ≦ α it may be as _one. In each of these cases, the rotor of the stepping motor is made of a cylindrical permanent magnet, and is magnetized alternately with N and S poles with the same number of pole pairs as the number of rotor pole teeth. good.

In the first aspect of the present invention, the stator pole teeth group is divided into two groups on the left and right sides from the center of each of the stator magnetic poles. The harmonic torque can be reduced by selecting θ0 as described later by the phase difference of θ0 (electrical angle) provided therebetween. According to the second aspect of the invention, in the three-phase machine, the third harmonic of permeance does not generate an oscillating torque, and the provision of the vernier slot eliminates the fifth harmonic and higher components.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First and second embodiments shown in FIGS.
The present invention will be specifically described by the embodiments. 1 and 2 show the configuration of each stator pole according to the first embodiment to which the present invention is applied, and FIGS. 3 and 4 show the configuration of each stator pole according to the second embodiment, respectively.

First Embodiment First, the basic structure of a hybrid stepping motor to which the present invention is applied is as shown in FIGS. 5A and 5B. FIG. 1A is a vertical sectional front view, and FIG. 1B is a cross-sectional view taken along the line XX 'of FIG. 1A. In the drawing, reference numeral 1 denotes a housing, 2 denotes a stator, and the number of magnetic poles of the stator is 12 as shown in FIG. 9B, which is 8 as shown in FIG. It may be a pole.
3 is a coil, 4 and 4 'are front and rear covers, respectively, which support bearings 5 and 5'. Reference numeral 6 denotes a rotating shaft, which fixes a permanent magnet 7 and two rotor magnetic poles 8 and 9 sandwiching the permanent magnet 7, and is rotatably supported by bearings 5 and 5 'via a gap with the stator 2 with an air gap. . The rotor magnetic poles 8, 9
Has pole teeth formed on the outer periphery.

By the way, in the first embodiment,
The configuration shown in FIGS. 5A and 5B is characterized in that the configuration of the pole teeth of the stator 2 is formed as shown in FIGS. 1 and 2. FIG. 1 shows the case where the number of pole teeth of the stator is even, specifically, the case of six, and FIG. 2 shows the case where the number of pole teeth is odd, specifically, the case of five. With one for each
FIG. 9 shows a relative relationship between the stator magnetic poles 2-1 and a rotor.

In the configuration of FIG. 1 where the number of stator pole teeth is even, the stator pole teeth are shifted only by θ0 with respect to 2π, which is the pitch angle of the other part, so that (2π + θ0). I have. Note that θ0 is represented by an electrical angle. The pitch other than the central portion of the stator pole teeth may not be 2π, but they are all equal pitches. The corresponding rotor pole tooth pitch is 2π (electrical angle).

FIG. 2 is a diagram in which the pitch on both sides of the central stator pole tooth of the stator magnetic pole 2-1 is made different from the pitch of the other stator pole teeth. As in FIG. 1, the same value as 2π of the rotor pole tooth pitch is displayed.

The operation of these configurations will be described with reference to the following equations (5), (6) and (7). εpq = cos ｛(q · θ0) / 2} (6) P (θ) = P0 (εP1cosθ + εP3k3cos3θ + εp5k5cos5θ + ..) (7) In each of these equations, θ is the rotor rotation angle (electrical Corner),
P indicates the permeance of the gap, and k3 and k5 indicate the maximum amplitude ratios of the third and fifth harmonics to the fundamental wave. The first of equation (5)
The term indicates the permeance of the stator pole teeth on the left side from the center in FIG. 1, and the second term indicates the permeance of the stator pole teeth on the right side from the center. Here, for the q-th harmonic,
By transforming equation (5) by the coefficient shown in equation (6), P
(Θ) can be expressed as shown in equation (7).

From equations (6) and (7), if θ0 = π / 3 in FIG. 1, εP3 = 0, and the third harmonic component of equation (7) can be eliminated. Similarly, θ0 =
If π / 5, the fifth harmonic component can be eliminated from equation (7). P0 represents the maximum value of the fundamental component of P (θ) in permeance.

The principle of harmonic torque elimination will be further explained with reference to the drawings. The fundamental wave torque indicated by a solid line in FIG. 6 corresponds to the center left side in FIG. 1, and the broken line corresponds to the center right side in FIG. Then, the harmonic torque is eliminated by the sum.

FIG. 7 shows how each harmonic of P (θ) is reduced by θ0. In each figure, θ0 = π
Assuming / 3, the third harmonic component is zero, but the fundamental wave torque at this time is 86.6%. On the other hand, in the vernier method of the prior art in which the stator pole teeth have the same pitch, the third
Assuming that the harmonic component is zero, in the example where the number of stator pole teeth is 5, the rotor pole tooth pitch is P3 = 0 at 24 ° (electrical angle), and the fundamental wave torque at this time is 83.3%. Therefore, according to the configuration of the present invention described above, it can be seen that the torque increases by 3.3%. Since the operation is exactly the same when the number of pole teeth shown in FIG. 2 is an odd number, the description thereof is omitted.

Second Embodiment FIGS. 3 and 4 show a configuration of a second embodiment of the present invention, respectively, and show a configuration of a vernier slot when applied as a three-phase stepping motor. is there.

As described above, the second conventional example shown in FIG. 9 is a means for eliminating the fourth harmonic component of the air gap, and eliminating the fourth harmonic component by a two-phase stepping motor. However, the three-phase stepping motor was not effective. The reason is given by the following equations (8) to (1).
The basic principle of the present embodiment will be described with reference to 2). P (θ) = P0 (k1sinθ + k3sin3θ + k5sin5θ + sin7θ) (8) T = K′IP (θ) (9) T2 = K'IP0 {k1cos (θ−ωt) −k3cos (3θ + ωt) + k5cos (5θ−ωt) + k7cos (7θ + ωt)} (11) ωt = θ−δ (12) )

Equations (8) and (9) show the gap permeance of a general stepping motor, and it is well known that only the odd-order harmonics are present. In equation (9), I is a current, and K 'is a proportional constant. When the three-phase machine is microstepped, the current can be approximated to a sine wave, and the torque at that time is represented by T3 in equation (10). Here, ω is the angular velocity of the current. Here, the currents Ia, Ib, Ic supplied to the respective phases a, b, c of the three-phase machine
Is calculated as Ia = Isinωt, Ib = Isin (ωt−2π / 3), and Ic = Isin (ωt−4π / 3), and the generated torque T3 of Expression (10) is obtained.

The relationship between θ and ωt (t: time) is given by equation (12) according to the load angle δ. If this ωt is substituted into equation (10), the second term of T3 becomes the fifth term of P (θ). The sixth harmonic is represented by (5θ + ωt = 6θ−δ) by the harmonic component and the current, and the third term is represented by (7θ−ωt = 6θ + δ) by the seventh harmonic component of P (θ) and the current. It can be seen that the sixth harmonic is included and the vibration torque of the sixth harmonic is included.

On the other hand, in the case of the two-phase machine, considering the micro step, the currents of the a-phase and the b-phase supplied to the two-phase machine are Ia = Isinωt and Ib = Isin (ωt−π / 2). The generated torque T2 is as shown in Expression (11), and the third, fifth, and seventh terms thereof are (3θ + ωt = 4
θ-δ), (5θ-ωt = 4θ + δ), (7θ + ωt = 8θ-
δ) to include the vibration torque of the fourth harmonic and the eighth harmonic. The reason why the second conventional example eliminates the fourth harmonic is due to this phenomenon peculiar to the two-phase machine, and it can be seen from T3 in the equation (10) that the elimination of the fourth harmonic is not effective in the three-phase machine. .

Comparing Equation (8) and Equation (10),
The former third harmonic component is eliminated in the latter. That is, in the three-phase machine, the third harmonic component of P (θ) does not become the vibration torque, and the fifth harmonic component and the seventh harmonic component are converted to the sixth harmonic component.
This means that harmonic vibration torque is generated. Therefore, it can be analyzed that eliminating the fifth harmonic component and the seventh harmonic component of P (θ) is an effective means for eliminating the vibration torque in the three-phase machine.

The second embodiment of the present invention focuses on such a phenomenon and shows a configuration of a vernier slot for removing a vibration torque in a three-phase machine, and has an even number of stator pole teeth. An example is shown in FIG. 3 and an odd number is shown in FIG.
In both cases, the stator pole tooth pitch is α for the rotor pole tooth pitch.
(Electrical angle). The number of stator poles is an integral multiple of three.

In FIG. 3, the magnitude of the permeance of the fundamental wave component, the third harmonic component and the fifth harmonic component per stator pole is represented by the following equation (13) as P1, P3 and P5. Expressions (14) and (15) respectively show the expressions. FIG. 3 shows an example in which the number of pole teeth of the stator is 6. P5 and P7 in the case where the number of pole teeth is generally m are shown in the following equations (16) and (17), respectively.

Similarly, in FIG. 4 showing a case where the number of pole teeth is an odd number (for example, 7), P1, P3 and P5 are expressed by the following equations (18), (19) and (20). P5 and P7 in the case where the number of stator pole teeth is m are respectively shown in Equation (2).
1) and Equation (22).

To make the fifth harmonic component zero, P5 =
0, to make the seventh harmonic component zero, set P7 = 0 and α
Will be required. In the three-phase machine, since the third harmonic component is eliminated, α may be selected so that each of the fifth harmonic component and the seventh harmonic component is zero.

The value of α does not necessarily need to be strictly selected so that the fifth harmonic component and the seventh harmonic component are zero. However, a small value is effective for a three-phase machine. In addition, the effectiveness of setting the fifth harmonic component to zero is that the higher the order of the harmonics including the respective coefficients, the smaller the amplitude. Therefore, eliminating harmonics having a large amplitude is effective in reducing vibration. That is easy to understand.

[0026]

As described above, the stepping motor of the present invention has the following excellent effects.
By configuring as in the first embodiment and setting the configuration of the stator pole teeth to a specific configuration, the vibration torque can be significantly reduced as compared with the conventional technology. In addition, the third harmonic component can be reduced by selecting the vernier angle at which the fifth and seventh harmonic components of permeation are eliminated by using a three-phase stepping motor, as in the second embodiment. Can be eliminated, and the vibration torque can be further greatly reduced.

[Brief description of the drawings]

FIG. 1 is a developed view showing a relative relationship between a stator magnetic pole and a rotor according to a first embodiment of the present invention, showing a case where the number of pole teeth is even.

FIG. 2 is a developed view showing a relative relationship between a stator magnetic pole and a rotor according to the first embodiment of the present invention, showing an odd number of pole teeth.

FIG. 3 is a developed view showing a relative relationship between a stator magnetic pole and a rotor according to a second embodiment of the present invention, showing a case where the number of pole teeth is an even number.

FIG. 4 is a developed view showing a relative relationship between a stator magnetic pole and a rotor according to a second embodiment of the present invention, showing an odd number of pole teeth.

5A and 5B show a basic configuration of a stepping motor according to the present invention, wherein FIG. 5A is a vertical sectional front view, and FIG. 5B is a sectional view taken along line XX ′ of FIG.

FIG. 6 is a magnetic flux density-angle characteristic diagram for explaining the principle of harmonic reduction according to the present invention.

FIG. 7 is a diagram illustrating a change in harmonics due to a tooth shift angle for explaining the principle of harmonics reduction according to the present invention.

FIG. 8 shows a configuration of a first conventional example, and FIG.
FIG. 2 is a schematic longitudinal sectional front view of the rotor, and FIG. 2B is an enlarged development view of a main part of the rotor magnetic pole.

FIG. 9 is a cross-sectional front view showing the configuration of a second conventional example.

[Explanation of symbols]

 2: Stator 2-1 to 2-12: Stator magnetic pole 8, 9: Rotor magnetic pole

Claims (5)

(57) [Claims] 1. A rotor having n stator poles on which windings are wound, and a plurality of rotor pole teeth at equal pitches on a circumference of a rotor arranged with a gap from the stator poles. In the stepping motor, when n is an integer of 3 or more and m is an even number of 4 or more, each of the n stator magnetic poles has m stator pole teeth, and A stepping motor characterized in that the (m / 2) th and [(m / 2) +1] th pole tooth pitches are (τ ± θ ₀ ), and the other pole tooth pitches are τ. Here, π / 5 ≦ θ ₀ <π / 2, and τ and θ ₀ are each an electrical angle. 2. A motor having n stator magnetic poles on which windings are wound and a plurality of rotor pole teeth at equal pitches on a circumference of a rotor arranged with a gap from the stator magnetic poles. In the stepping motor, when n is an integer of 3 or more and m is an odd number of 5 or more, each of the n stator magnetic poles has m stator pole teeth, and the center of the stator pole teeth has A stepping motor characterized in that the pole tooth pitch on both sides is (τ ± θ ₀ ) and the other pole tooth pitch is τ. Here, π / 5 ≦ θ ₀ <π / 2, and τ and θ ₀ are each an electrical angle. 3. A plurality of rotor pole teeth at equal pitches on a circumference of 3L stator magnetic poles on which a three-phase winding is wound and a rotor arranged with a gap from the stator magnetic poles. When the 3L stator poles are provided with m stator pole teeth and the rotor pole tooth pitch is 2π in electrical angle, the stator pole tooth pitch is (2π ± α). When L is an integer of 2 or more and m is an even number of 4 or more, α1 and α2 are obtained by the following equations (1) and (2), and α
A stepping motor characterized in that 2 ≦ α ≦ α1. Here, α, α1, and α2 are each an electrical angle. 4. A plurality of 3L stator poles on which a three-phase winding is wound, and a plurality of rotor pole teeth at equal pitches on a circumference of a rotor arranged with a gap from the stator poles. When the 3L stator poles are provided with m stator pole teeth and the rotor pole tooth pitch is 2π in electrical angle, the stator pole tooth pitch is (2π ± α). When L is an integer of 2 or more and m is an odd number of 3 or more, α1 and α2 are obtained by the following equations (3) and (4), and α
A stepping motor characterized in that 2 ≦ α ≦ α1. Here, α, α1, and α2 are each an electrical angle. 5. The stepping motor according to claim 3, wherein the rotor is formed of a cylindrical permanent magnet and is alternately magnetized to N and S poles with the same number of pole pairs as the number of rotor pole teeth. A stepping motor.