JP2002058231A - Three-phase hybrid type stepping motor - Google Patents

Abstract

[PROBLEMS] To reduce the cogging torque and current torque distortion of a conventional three-phase hybrid stepping motor, the pitches of stator small teeth and rotor small teeth are unequal. The vernier method was considered, but sufficient studies were not yet made and sufficient effects were not obtained. Therefore, in the present invention, it is an object of the present invention to elucidate the theory of the vernier system and obtain an effective vernier system having a higher degree of freedom. According to the present invention, the cause of the cogging torque of a three-phase hybrid type stepping motor is determined by the fact that permeance between small teeth provided on a stator magnetic pole and a rotor magnetic pole changes with rotation of a rotor. Considering that the change is due to a regularity, the six small teeth provided at the tip of the stator magnetic pole are composed of two groups of three small teeth, and the third permance of the three small teeth in each set is set. The sum of the permeance vectors in the second harmonic plane is made substantially zero, and the fifth permeance of the two small teeth corresponding to the two groups is set.
The arrangement is such that the sum of the permeance vectors in the second harmonic plane is substantially zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-phase hybrid stepping motor, and more particularly to a motor having six winding poles, capable of reducing cogging torque and improving a current waveform. And a three-phase hybrid type stepping motor.

[0002]

2. Description of the Related Art Conventionally, a three-phase hybrid type stepping motor has 12 winding poles as shown in FIGS. 1A to 1C, and 6 winding poles as shown in FIGS. 2A to 2C. There are things.

[0003] The basic structure is almost the same.
In FIG. 1B and FIG. 1C, twelve magnetic poles 2 are arranged at equal intervals on the inner periphery of the substantially annular yoke 1, and a winding 3 is wound around each of the magnetic poles 2 to form a three-phase winding. A stator 5 provided with a plurality of small teeth 4 at the tip of the magnetic pole 2, and two rotations opposed to the stator 5 via a gap and provided with a plurality of small teeth 6 at an equal pitch on the outer periphery thereof. The magnetic pole 7 is set at one of the arrangement pitches of the small teeth 6.
The rotor 9 is fixed to the end face of a permanent magnet 8 magnetized in the NS direction with two poles shifted by a half pitch, and the rotor 9 is rotatably supported. The number of small teeth provided on each rotor magnetic pole 7 is fifty.

On the other hand, the rotor shown in FIGS. 2A to 2C has six stator magnetic poles 7 and 40 small teeth provided on the rotor magnetic poles.

[0005]

Conventionally, in order to reduce the cogging torque and current torque distortion of a three-phase hybrid type stepping motor, a vernier system in which the pitch between the small teeth of the stator and the small teeth of the rotor is made unequal. However, sufficient studies have not yet been made and sufficient effects have not been obtained. Therefore, in the present invention, it is an object of the present invention to elucidate the theory of the vernier system and obtain an effective vernier system having a higher degree of freedom.

[0006] In the case of the twelve magnetic poles (hereinafter referred to as "winding poles") on which the windings shown in Figs. In contrast, FIGS.
In the case of the six-pole winding shown in FIG. 2C, the magnetic flux links to a plurality of phase windings. The 6-winding pole method is characterized in that not only is the structure simple and can be manufactured at low cost as shown in the figure, but also that the flux linkage of the winding is about twice that of the 12-winding pole, so a larger torque can be obtained. In addition, since there is mutual inductance between the phases as in an ordinary motor, there is a possibility that the electromagnetic energy of the coil can be easily absorbed and controlled.

In FIGS. 2A to 2C, each phase winding 3 is connected in series in the same direction with coils of opposite winding poles separated by 180 degrees. On the other hand, the small teeth 6 of the rotor 9 are twisted with a phase of 180 degrees so that peaks and valleys on the N pole side and the S pole side coincide with each other, and are attached to the side surfaces of the permanent magnet 8 magnetized in the axial direction. Have been.

FIG. 3 is an equivalent magnetic circuit of the six-pole type shown in FIGS. 2A to 2C.

In FIG. 3, F _u , F _v , F _w are U,
V, the magnetomotive force of the W-phase winding, (here i 1 to 6) P _i is the i-th winding pole permeance, F _m, the P _m is the magnetomotive force and the internal permeance of the magnet.

Since the winding poles at the axially symmetric positions have the same configuration, the same reference numerals are used.

P ₄ , P ₅ , and P ₆ are P ₁ ,
The permeance has an opposite phase (peak and valley) to P ₂ and P ₃ . On the S pole side, since the flow of the magnetic flux is opposite to that of the N pole, the polarity of the magnetomotive force is negative.

In the case of the twelve winding poles shown in FIGS. 1A to 1C, all four sub-circuits coincide with each other.
In the case of 6 winding poles shown in the figure, only two of them are matched on the N pole side and the S pole side, so it cannot be integrated into one sub circuit. Figure 4 Here, it is assumed that the magnet magnetomotive force is divided into the N pole side and the S pole side. Hereinafter, the distortion of the cogging torque and the current torque will be examined using the equivalent circuits shown in FIGS. 4A and 4B.

Since the generated torque is related to the total permeance of the winding poles, the torque is calculated assuming that the small teeth of the stator magnetic pole have a different pitch from the small teeth of the rotor.

For a three-phase hybrid type stepping motor having six winding poles, the general expression of the torque T is as shown in Equation 1 by analogy with the case of 12 winding poles. Here, N _R is the number of teeth of the rotor, F ₀ is the magnetomotive force drops voids containing excitation, 2S windings number (in this case S = 3), the閘_e is an electrical angle. Note that F ₀ is obtained as in Expression 2.

[0015]

(Equation 1)

[0016]

(Equation 2)

The permeances P ₁ , P ₂ , and P ₃ are:
Each of them has a phase difference of 120 degrees and is expressed as Equations 3, 4, and 5.

[0018]

(Equation 3)

[0019]

(Equation 4)

[0020]

(Equation 5)

The permeances P ₄ , P ₅ and P ₆ are
As shown in the equations (6) to (9), P ₁ , P ₂ , and P ₃ have opposite phases (180 ° phase difference).

[0022]

(Equation 6)

[0023]

(Equation 7)

[0024]

(Equation 8)

[0025]

(Equation 9)

[0026] From these equations, is shown in Table 1 when obtaining the respective orders of the component and contributes to the cogging torque sum component and the current torque contributing component of P _i (U-phase only).

[0027]

[Table 1]

According to Table 1, the cogging torque based on the fifth and lower harmonics becomes zero, but the sixth harmonic component remains in phase with each pole. Therefore, in order to reduce the cogging torque, it is necessary to remove the sixth harmonic component.

On the other hand, considering the U-phase winding, FIG.₁When
F_FourSince the magnetic flux flows in the opposite polarity, P ₁And P_FourThe effect of
Differential addition, P in V phase_TwoAnd P_Five, W phase, P_ThreeWhen
P₆Effect is added differentially to create linkage flux
Become.

From Table 1, it can be seen from the relationship between the Fourier coefficients of the respective harmonics that in the case of the differential, both the even-order harmonics are canceled out but the odd-order harmonics are slightly added. Therefore, the U-phase components P ₁ -P ₄ that contribute to the current torque become zero in the even order, and only the odd order remains. The V and W phases also have the same value except for the phase. Among these, the first-order component is a fundamental wave, but the third-order and fifth-order components are not preferable because they cause distortion of the fundamental sine wave. Therefore, in order to improve the waveform of the current torque, it is preferable to remove the third-order component and then the fifth-order component.

As a result, even in the 6-pole configuration, 12
It turns out that it is exactly the same as a winding pole. Therefore, the cogging torque and the current torque distortion can be reduced by exactly the same method as in the case of 12 winding poles.

First, a study will be made on an equal pitch vernier in which small teeth conventionally used are arranged at an equal pitch.

The sixth harmonic component of the permeance of one small tooth is as shown in Expression 10.

[0034]

(Equation 10)

Assuming that the small teeth of the winding pole are arranged as shown in FIG. 5, in order to make the fourth harmonic component zero, it is sufficient that the following equation 11 is satisfied.

[0036]

[Equation 11]

Here, Q is the number of small teeth of one winding pole, θ _k
Is the position (electrical angle) of each small tooth.

[0038] distributed at equal tooth width and equidistantly t _k at an equal pitch vernier prior art thinking, the sixth harmonic plane vector in this case is as shown in FIG.

In this case, each vector V _k has an electrical angle 36
The distribution should be made by dividing 0 degrees into six equal parts (360/6 = 60 degrees).

At this time, since any vector always has another vector at an axially symmetric position, they cancel each other as a pair. While maintaining this relationship, each vector rotates, so that it always balances to zero during rotation and becomes zero.
Is established.

This angular relationship is expressed by the following equation (12). In Expression 12, m is an integer including zero.

[0042]

(Equation 12)

In the configuration shown in FIGS. 2A to 2C, when the number of rotor teeth = the number of pole pairs p = 40, the electrical angle of 360 degrees in the first term corresponds to a mechanical angle of 9 degrees. The distribution may be performed while shifting the mechanical angle of the second term by 0.25 degrees. 0.
25 is an electrical angle of 0.25 × 40 × 6 = 60 degrees, and 60 × 3 = 180 degrees at the opposing position. In a uniform pitch vernier, the tooth width is usually the same, but in this theory, the widths of the opposing teeth are not necessarily all the same.

Next, the case of uneven pitch vernier when the pitch of the small teeth is different will be considered.

FIGS. 7A and 7B show examples of the vector relationship between the small teeth of the irregular pitch vernier.

In the case of FIG. 7A, even if the sizes are different from each other,
V ₁ and V _4, V ₂ and V _5, V ₃ corresponding that the V ₆ 2
If the vectors are balanced, Equation 13
As shown in FIG. 7, P ₁₆ = 0 holds, and the cogging torque is also minimized.

[0047]

(Equation 13)

Here, Q is the number of small teeth of one winding pole. As long as the vectors satisfy a canceling relationship (balance condition) within each pair, the arrangement of each pair may be arbitrary. This is the principle of cogging torque minimization.

There are various correspondences between vectors to be balanced, and the following three types can be considered.

(1) As shown in Expression 14, between adjacent small teeth

[0051]

[Equation 14]

(2) As shown in Expression 15, between diagonal small teeth

[0053]

(Equation 15)

(3) As shown in Expression 16, between the small teeth axially symmetric with respect to the central axis.

[0055]

(Equation 16)

In the above equation, 2mπ means that the pitch angle is the same as that of the rotor magnetic pole. Therefore, when rewritten using the deviation angle δθ from the reference position, the following equations are obtained.

[0057]

[Equation 17]

[0058]

(Equation 18)

[0059]

[Equation 19]

In the above equation, the right side is a mechanical angle of 0 when p = 40.
75 degrees, which is 180 degrees in electrical angle. When the cogging torque elimination method of the unequal pitch vernier according to this method is arranged, the following Expressions 20, 21, and 22 are obtained.

(1) When the number of small teeth of the rotor magnetic pole is p, the following equation is established.

(A) t ₁ and t ₂ , t ₃ and t ₄ , t ₅ and t
Number 20 relative angle difference ε of each adjacent pair of ₆ is obtained.

[0063]

(Equation 20)

(B) t ₁ and t ₄ , t ₂ and t ₅ , t ₃ and t
Equation 21 is obtained for the difference angle of each diagonal pair of ₆ .

[0065]

(Equation 21)

(C) t ₁ and t ₆ , t ₂ and t ₅ , t ₃ and t
Equation 22 is obtained for each axisymmetric pair of ₄ .

[0067]

(Equation 22)

(2) The widths of the corresponding small teeth are made equal to each other.

7A and 7B, as a practical matter, the small tooth width is determined in consideration of the symmetry of the iron core.

Table 2 shows a trial calculation example of the small tooth arrangement based on this concept.
Shown in

[0071]

[Table 2]

[0072] the sum of the reference angle and δθ in Table 2 is an angle theta _k from the winding pole center line of the teeth t _k. Further, the equal pitch corresponds to FIG. 6 and the trial calculation 1 corresponds to FIG. 7A. Trial calculation 2 is the case where the small tooth width is changed while being axially symmetric, and trial calculation 3 is the case where the difference is 0.75 degrees in all cases.

Another way of thinking when the number of small teeth is 6 is as follows.
This is a method of dividing the three into two and balancing the three. FIG. 7B shows an example of this case. Here, a set of V ₁ , V ₃ , and V ₅ and V ₂ , V ₄ , and V _{6 is formed} , and the _two are balanced by a vector relationship of 120 degrees from each other. Trial calculation 4 in Table 2 shows the small tooth arrangement at this time. Here, the three vectors are equally spaced at 120-degree intervals with the same tooth width, but one of them, for example, the tooth width of V ₁ or V ₆ is increased, and the other two V ₃ , V ₃ It is also possible to narrow the interval between ₅ or V ₄ and V ₆ to balance among the three vectors. FIG. 8 shows a small tooth configuration of the winding pole of FIG. 7B.

Next, a method for removing the third harmonic component of the current torque will be discussed. From Table 1, to the third-order harmonic component 2cos current torque (3閘_e) to zero, it is necessary to balance the third harmonic in each winding pole. In order to make the third harmonic component zero, Expression 23 may be satisfied.

[0075]

(Equation 23)

Here, θ _k is the position (electrical angle) of each small tooth.

[0077] or when the pitch vernier That is, when small teeth distribution equal pitch, the third harmonic angle 3q _k is 360 degrees and Q equal (in this case 360/6 = 60 degrees every ) Distribution is sufficient. FIG. 9A shows the vector arrangement of the third harmonic component at this time. This is a diagram of exactly the same shape as FIG. 6A. In the figure, V _k is a vector having an angle θ _k and a magnitude a ₃ . In the case of the equidistant distribution, each vector always has another vector at the axially symmetric position, so that the vectors cancel each other in pairs. Each vector rotates while maintaining this relationship, so that even if the rotation angle changes, the balance is always zero and the equation 23 holds.

This relationship is expressed by the following equation (24). Here, i is a winding pole number (1 to 6).

[0079]

(Equation 24)

The first term is a reference position of each winding pole obtained by dividing an electrical angle of 360 degrees (9 degrees in mechanical angle in the case of 40 pole pairs) into three phases corresponding to three phases. The small teeth may be distributed every 0.5 degrees, which is the second term, based on the small teeth. 0.5 in this case
× 40 × 3 = 60 degrees, and the opposing positions are balanced by 60 × 3 = 180 degrees.

Uneven pitch in case of uneven pitch vernier
Fig. 9B and Fig. 9B show examples of vector balance between each small tooth of vernier.
It is shown in 9C. FIG. 9B shows V in a diagonal relationship.₁And V_ThreeAnd V
_TwoAnd V _FourThis is an example of balancing
Relationship V₁And V_Four, V_TwoAnd V_ThreeOr V of the adjacency₁
And V_Two, V_ThreeAnd V_FourMay be balanced. these
In this case, Equation 25 holds for the third harmonic component, and
The sum of the third harmonic component of the mean is zero.

[0082]

(Equation 25)

This means that the following equation 26 is satisfied between the two small teeth i and j forming a pair. In this formula, m is an integer including 0.

[0084]

(Equation 26)

In Equation 26, 2mπ means the position of the tooth pitch of the rotor magnetic pole, which is not a vernier, which is a reference. Therefore, when rewriting using the deviation angle δθ from this reference position, Equation 2 is obtained.
It becomes 7.

[0086]

[Equation 27]

The right side of this equation is 1.5 degrees when p = 40, and is 180 degrees in electrical angle. The case of the equal pitch described above also corresponds to this special example.

The third harmonic torque elimination method according to this method is summarized as follows.

(1) The difference between the deviation angles δθ at the third harmonic of each pair of small teeth is set to 180 degrees in electrical angle.

(2) The width of the small teeth of each pair is made equal to each other.

However, as a practical matter, it is preferable that all the small teeth have the same width in order to maintain the symmetry of the iron core.

Table 3 shows an example of a trial calculation on the third harmonic plane corresponding to Table 2.

[0093]

[Table 3]

In Table 3, the sum of the reference angle and δθ is the small tooth t
_k is the angle θ _k from the winding pole center line. Further, the equal pitch corresponds to FIG. 7A, and the trial calculation 1 ′ corresponds to FIG. 7B. Trial calculation 2 'is the case where the small tooth width is changed while being axially symmetric, and trial calculation 3' is the case where the difference becomes 1.5 degrees in all cases.

FIG. 9C shows an example in which six small teeth are divided into two combinations of three and balanced among the three. Here, V ₁ , V ₃ , V ₅ and V ₂ , V ₄ , V _{6 form a} set, and are balanced with each other in a vector relationship of 120 degrees. Trial calculation 4 'in Table 3 shows the small tooth arrangement at this time. Here, the three vectors are equally spaced with the same tooth width of 120.
Although aligned in degrees intervals, one of the, for example, to increase the tooth width of the V ₁ or V _6, the other two V _3, V ₅ or V
_4, by narrowing the interval of V _6, it is possible to balance between the three vectors.

In any case, when the balance is made with the third harmonic, the deviation angle is twice the deviation angle of the sixth harmonic.

Up to now, the method of individually reducing the sixth harmonic related to the cogging torque or the third harmonic related to the current torque distortion has been considered, but it is also possible to reduce them at the same time. . As shown in Table 1, the third and fifth harmonics of the permeance that are problematic relate to the distortion of the current torque, and the sixth harmonic relates to the cogging torque. Normally, the lower the order, the higher the harmonic component is. Therefore, the third-order component is considered to have the greatest influence here.

Therefore, the tertiary and sixth erasures or the tertiary and fifth simultaneous erasures will be considered. First, it is considered that three sets of two vectors balanced on the third harmonic plane are balanced on the sixth harmonic plane. Two vectors 180 degrees apart (1.5 degrees mechanical angle) on the third harmonic plane
In the second harmonic plane, two vectors coincide in phase. Three vectors 120 degrees apart (0.5 degrees in mechanical angle) in the sixth harmonic plane become three vectors 60 degrees apart in the third harmonic plane. Become.

With this relationship in mind, look at Tables 2 and 3
Then, the equal pitch 2 'in Table 3 is V₁And V _Four, V_TwoAnd V_Five,
V_ThreeAnd V₆Are 180 degrees apart on the third harmonic plane
In the sixth harmonic plane, V₁, V_Two, V_ThreeAnd V_Four, V
_Five, V₆Are 120 degrees apart from each other
At the same time in the third and sixth harmonic planes
You can see that it is.

The vector relation of FIG. 9A is shown in FIG. 10 on the sixth harmonic plane, and it can be seen that two sets of three vectors overlap on the sixth harmonic plane.

FIG. 11 shows the arrangement of the small teeth at this time.

Another way is to balance two sets of three vectors balanced on the third harmonic plane on the sixth harmonic plane. However, two vectors separated by 120 degrees (1.0 mechanical angle) on the third harmonic plane are separated by 240 degrees on the sixth harmonic plane, and two vectors separated by -120 degrees on the third harmonic plane are defined by the second vector. Since −240 degrees = 120 degrees apart on the sixth harmonic plane, the three vectors balanced on the third harmonic plane are automatically balanced on the sixth harmonic plane. Therefore, the trial calculation example 4 'in Table 3 satisfies this condition. This is shown again in Table 4.

[0103]

[Table 4]

As a special case in this case, trial calculation 5 in Table 4 is an example in which three vectors overlap on the third and sixth harmonic planes. FIG. 12 shows the vector relation at this time.

Subsequently, the balance on the fifth harmonic plane will be examined. First, consider balancing the three vectors balanced on the third harmonic plane on the fifth harmonic plane. The vector relationship shown in FIG. 13 is obtained by considering that a vector 180 degrees apart on the fifth harmonic plane is 180 × 3/5 = 108 degrees on the third harmonic plane. In this case, it corresponds to the trial calculation 6 in Table 4, and the balance is automatically performed even at the sixth harmonic, so that the balance is performed at the third, fifth, and sixth harmonics for convenience.

FIG. 14 is a diagram showing the configuration of the small teeth in this case.

FIG. 15 shows an example in which three vectors are balanced on the fifth harmonic plane and two vectors are balanced on the third harmonic plane (trial calculation 7). While each of the three vectors of V _1, V _2, V ₃ and V _4, V _5, V ₆ are balanced within each fifth harmonic plane, the third harmonic plane V ₁ And V ₄ , V ₂ and V ₅ , and V ₃ and V ₆ , respectively. Table 4 summarizes these situations. Trial calculation 6 is the best in terms of balance in three types of harmonic planes of the third, fifth, and sixth orders, but the deviation angle is the largest, so the magnitude of the fundamental wave is slightly sacrificed. It seems to be.

If the number of small teeth is odd, balancing one pair of small teeth will result in one fraction, which is inconvenient. Therefore, one fraction is merged with any other pair of small teeth. Need to be balanced. In the case of seven small teeth as shown in FIG. 16, the vector relationship between them is as shown in FIG.
Here, the balance is made in three vectors V ₂ , V ₄ and V ₆ , and the balance is made between two pairs of vectors V ₁ and V ₅ and V ₃ and V ₇ respectively. The relationship shown in FIG. 17 is exactly the same as the sixth harmonic plane corresponding to the cogging torque, and the third harmonic plane relating to the torque waveform distortion. Table 5 shows the relationship between the mechanical angle and the number of teeth of the rotor magnetic pole when the number of teeth is 40. As before, the sum of the reference angle and δθ is the angle theta _k from the winding pole center line of the teeth t _k
become. The tooth width is shown as a percentage with respect to the rotor tooth pitch.

[0109]

[Table 5]

[0110] The balance angle between the two vectors indicates a mechanical angle to reach 180 degrees in each harmonic plane. 3
The balance angle between the vectors is a mechanical angle to reach 120 degrees. Note that the balance between the three vectors can be obtained when the tooth width is different. In this case, the angle between the vectors is also 120.
It will be different from the degree.

Although the details are omitted, in this case also, it is possible to balance simultaneously on a plurality of harmonic planes.

[0112]

A three-phase hybrid type stepping motor according to the present invention comprises a substantially annular yoke on the inner periphery thereof.
A stator in which three magnetic poles are arranged at equal intervals, a winding is wound around each of the magnetic poles to form a three-phase winding, and a plurality of at least six small teeth are provided at the tip of the magnetic pole. And two rotor magnetic poles having a plurality of small teeth provided at an equal pitch on the outer periphery thereof are shifted by half a pitch of the arrangement pitch of the small teeth, and are shifted in the axial direction by NS.
A three-phase hybrid type stepping motor comprising a rotor fixed to an end face of a permanent magnet magnetized into two poles, wherein the rotor is opposed to the stator via an air gap. The six small teeth are composed of at least three groups of sets of two small teeth, and the sum of the permeance vectors in the sixth harmonic plane of the permeance of the two small teeth of each set is substantially zero. In this case, the pitch of the small teeth between the sets is made different from each other.

In the three-phase hybrid type stepping motor of the present invention, six magnetic poles are arranged at equal intervals on the inner periphery of a substantially annular yoke, and a winding is wound around each of the magnetic poles to form a three-phase winding. A plurality of at least six lines at the tip of the pole.
A stator provided with a plurality of small teeth and two rotor magnetic poles provided with a plurality of small teeth on an outer periphery thereof at an equal pitch are shifted from each other by a half pitch of the arrangement pitch of the small teeth, and are shifted in the axial direction. A three-phase hybrid type stepping motor comprising a rotor fixed to an end face of a permanent magnet magnetized into two poles of NS, the rotor being provided at a tip of the stator magnetic pole in a three-phase hybrid type stepping motor opposed to the stator via a gap. The at least six small teeth are composed of at least two groups of sets of three small teeth, and the sum of the permeance vectors in the sixth harmonic plane of the permeance of the three small teeth of each set is substantially zero. The pitch of the small teeth in each set is different from each other so that

In the three-phase hybrid stepping motor of the present invention, six magnetic poles are arranged at equal intervals on the inner periphery of a substantially annular yoke, and a winding is wound around each of the magnetic poles to form a three-phase winding. A plurality of at least six lines at the tip of the pole.
A stator provided with a plurality of small teeth and two rotor magnetic poles provided with a plurality of small teeth on an outer periphery thereof at an equal pitch are shifted from each other by a half pitch of the arrangement pitch of the small teeth, to thereby provide A three-phase hybrid type stepping motor comprising a rotor fixed to an end face of a permanent magnet magnetized into two poles of NS, the rotor being provided at a tip of the stator magnetic pole in a three-phase hybrid type stepping motor opposed to the stator via a gap. The at least six teeth are composed of at least three groups of sets of two teeth, the sum of the permeance vectors in the third harmonic plane of the permeance of the two teeth of each set being substantially equal. The pitch of the small teeth between each pair is made different from each other so as to be zero.

Further, in the three-phase hybrid type stepping motor according to the present invention, six magnetic poles are arranged at equal intervals on the inner periphery of a substantially annular yoke, and windings are wound around each of the magnetic poles to form a three-phase winding. A plurality of at least six lines at the tip of the pole.
A stator provided with a plurality of small teeth and two rotor magnetic poles provided with a plurality of small teeth on an outer periphery thereof at an equal pitch are shifted from each other by a half pitch of the arrangement pitch of the small teeth, and are shifted in the axial direction. A three-phase hybrid type stepping motor comprising a rotor fixed to an end face of a permanent magnet magnetized into two poles of NS, the rotor being provided at a tip of the stator magnetic pole in a three-phase hybrid type stepping motor opposed to the stator via a gap. The at least six small teeth are composed of at least two groups of sets of three small teeth, and the sum of the permeance vectors in the third harmonic plane of the permeance of the three small teeth of each set is substantially. The pitch of the small teeth in each set is made different from each other so as to be zero.

In the three-phase hybrid type stepping motor of the present invention, six magnetic poles are arranged at equal intervals on the inner periphery of a substantially annular yoke, and a winding is wound around each of the magnetic poles to form a three-phase winding. A plurality of at least six lines at the tip of the pole.
A stator provided with a plurality of small teeth and two rotor magnetic poles provided with a plurality of small teeth on an outer periphery thereof at an equal pitch are shifted from each other by a half pitch of the arrangement pitch of the small teeth, and are shifted in the axial direction. A three-phase hybrid type stepping motor comprising a rotor fixed to an end face of a permanent magnet magnetized into two poles of NS, the rotor being provided at a tip of the stator magnetic pole in a three-phase hybrid type stepping motor opposed to the stator via a gap. The at least six small teeth are composed of at least two groups of three small tooth sets, and the sum of the permeance vectors in the third harmonic plane of the permeance of the three small teeth in each set is substantially zero. As well as
The pitch of the small teeth in each set is different from each other so that the sum of the permeance vectors of the small teeth in each set on the sixth harmonic plane is substantially zero.

In the three-phase hybrid stepping motor of the present invention, six magnetic poles are arranged at equal intervals on the inner periphery of a substantially annular yoke, and a winding is wound around each of the magnetic poles to form a three-phase winding. A plurality of at least six lines at the tip of the pole.
A stator provided with a plurality of small teeth and two rotor magnetic poles provided with a plurality of small teeth on an outer periphery thereof at an equal pitch are shifted from each other by a half pitch of the arrangement pitch of the small teeth, and are shifted in the axial direction. A three-phase hybrid type stepping motor comprising a rotor fixed to an end face of a permanent magnet magnetized into two poles of NS, the rotor being provided at a tip of the stator magnetic pole in a three-phase hybrid type stepping motor opposed to the stator via a gap. The at least six small teeth are composed of at least two groups of sets of three small teeth, and the sum of the permeance vectors in the sixth harmonic plane of the permeance of the three small teeth of each set is substantially zero. As well as
The pitch of the small teeth in each set is different from each other so that the sum of the permeance vectors in the third harmonic plane of the permeance of the small teeth of each set becomes substantially zero.

Further, in the three-phase hybrid type stepping motor according to the present invention, six magnetic poles are arranged at equal intervals on the inner periphery of the substantially annular yoke, and a winding is wound around each of the magnetic poles to form a three-phase winding. A plurality of at least six lines at the tip of the pole.
A stator provided with a plurality of small teeth and two rotor magnetic poles provided with a plurality of small teeth on an outer periphery thereof at an equal pitch are shifted from each other by a half pitch of the arrangement pitch of the small teeth, and are shifted in the axial direction. A three-phase hybrid type stepping motor comprising a rotor fixed to an end face of a permanent magnet magnetized into two poles of NS, the rotor being provided at a tip of the stator magnetic pole in a three-phase hybrid type stepping motor opposed to the stator via a gap. At least six small teeth are composed of two groups of three small teeth, and the sum of the permeance vectors in the third harmonic plane of the permeance of the three small teeth of each set is substantially zero. And if the pitches of the small teeth in each set are different from each other so that the sum of the permeance vectors of the two small teeth corresponding to the two groups in the fifth harmonic plane is substantially zero. It is characterized by being closed.

In the three-phase hybrid stepping motor of the present invention, six magnetic poles are arranged at equal intervals on the inner periphery of a substantially annular yoke, and a winding is wound around each of the magnetic poles. A plurality of at least six lines at the tip of the pole.
A stator provided with a plurality of small teeth and two rotor magnetic poles provided with a plurality of small teeth on an outer periphery thereof at an equal pitch are shifted from each other by a half pitch of the arrangement pitch of the small teeth, and are shifted in the axial direction. A three-phase hybrid type stepping motor comprising a rotor fixed to an end face of a permanent magnet magnetized into two poles of NS, the rotor being provided at a tip of the stator magnetic pole in a three-phase hybrid type stepping motor opposed to the stator via a gap. At least six small teeth are composed of two groups of three small teeth, and the sum of the permeance vectors in the fifth harmonic plane of the permeance of the three small teeth in each set is substantially zero. And if the pitches of the small teeth in each set are different from each other so that the sum of the permeance vectors of the two small teeth corresponding to the two groups in the third harmonic plane is substantially zero. It is characterized by being closed.

In the three-phase hybrid type stepping motor of the present invention, six magnetic poles are arranged at equal intervals on the inner periphery of a substantially annular yoke, and a winding is wound around each of the magnetic poles to form a three-phase winding. Lines and at the tip of the pole an odd number of at least 7
A stator provided with a plurality of small teeth and two rotor magnetic poles provided with a plurality of small teeth on an outer periphery thereof at an equal pitch are shifted from each other by a half pitch of the arrangement pitch of the small teeth, and are shifted in the axial direction. A three-phase hybrid type stepping motor comprising a rotor fixed to an end face of a permanent magnet magnetized into two poles of NS, the rotor being provided at a tip of the stator magnetic pole in a three-phase hybrid type stepping motor opposed to the stator via a gap. A permeance vector in the sixth harmonic plane of the permeance of each set of at least seven small teeth comprising at least three groups of three sets of small teeth and at least two sets of two small teeth; Are arranged to be substantially zero.

In the three-phase hybrid stepping motor of the present invention, six magnetic poles are arranged at equal intervals on the inner periphery of a substantially annular yoke, and a winding is wound around each of the magnetic poles. Lines and at the tip of the pole an odd number of at least 7
A stator provided with a plurality of small teeth and two rotor magnetic poles provided with a plurality of small teeth on an outer periphery thereof at an equal pitch are shifted from each other by a half pitch of the arrangement pitch of the small teeth, and are shifted in the axial direction. And a rotor fixed to the end face of a permanent magnet magnetized into two poles of NS. A permeance vector in the third harmonic plane of the permeance of each set of at least seven small teeth, comprising at least three groups of three sets of small teeth and at least two sets of two small teeth; Are arranged to be substantially zero.

[0122]

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

In the first embodiment of the present invention, the three-phase hybrid type stepping motor is connected to the substantially annular yoke 1.
Six magnetic poles 2 are arranged at equal intervals on the inner periphery of the magnetic pole, and a winding 3 is wound around each of the magnetic poles to form a three-phase winding, and a plurality of six small poles are formed at the tip of the magnetic pole. The stator 5 provided with the teeth 4 and the two rotor magnetic poles 7 provided with a plurality of small teeth 6 at an equal pitch on the outer periphery thereof are shifted by a half pitch of the arrangement pitch of the small teeth 6, A rotor 9 fixed to an end face of a permanent magnet 8 magnetized in the NS two poles in the axial direction, rotatably supporting the rotor 9 and facing the stator 5 via a gap; The six small teeth 4 provided at the tip of the magnetic pole 2 are constituted by three sets of two small teeth, and the sum of the permeance vectors in the sixth harmonic plane of the permeance of the two small teeth in each set. Are made different from each other so that is substantially zero.

In another embodiment of the present invention, the six small teeth are composed of two sets of three small teeth, and the sixth harmonic of the permeance of the three small teeth of each set is set. The pitches of the small teeth in each set are different from each other so that the sum of the permeance vectors in the plane is substantially zero.

In still another embodiment of the present invention, the six small teeth are constituted by two sets of three groups, and the third harmonic plane of the permeance of the two small teeth of each group is set. Are different from each other so that the sum of the permeance vectors at is substantially zero.

In still another embodiment of the present invention, the above-mentioned six small teeth are composed of three sets of two groups, and each group has three groups.
The pitches of the small teeth in each set are different from each other so that the sum of the permeance vectors in the third harmonic plane of the permeance of the small teeth is substantially zero.

In still another embodiment of the present invention, the above-mentioned six small teeth are composed of three sets of two groups,
The sum of the permeance vectors in the third harmonic plane of the permeance of the small teeth is substantially zero, and the sum of the vectors in the sixth harmonic plane of each set of small teeth is substantially equal to zero. The pitch of the small teeth in each set is made different from each other so as to be zero.

In still another embodiment of the present invention, the above-mentioned six small teeth are composed of three sets of two groups,
The sum of the permeance vectors in the sixth harmonic plane of the permeance of the small teeth is substantially zero, and the sum of the permeance vectors in the third harmonic plane of the permeance of each set of small teeth is The pitch of the small teeth in each set is made different from each other so as to be substantially zero.

In still another embodiment of the present invention, the above-mentioned six small teeth are composed of three sets of two groups,
The sum of the permeance vectors in the third harmonic plane of the permeance of the small teeth is made substantially zero, and the permeance of the small teeth included in the two corresponding small teeth between the two groups is set. The pitches of the small teeth in each set are different from each other so that the sum of the permeance vectors on the fifth harmonic plane is substantially zero.

In still another embodiment of the present invention, the above-mentioned six small teeth are composed of three sets of two groups,
The sum of the permeance vectors in the fifth harmonic plane of the permeance of the small teeth is made substantially zero, and the permeance of the small teeth included in the corresponding two small teeth between the two groups is set. The pitches of the small teeth in each set are made different from each other so that the sum of the permeance vectors on the third harmonic plane is substantially zero.

In another embodiment of the present invention, six magnetic poles 2 are arranged at equal intervals on the inner periphery of a substantially annular yoke 1, and a winding is wound around each of the magnetic poles to form a three-phase winding. And a stator 5 provided with an odd number of seven small teeth at the tip of the magnetic pole, and two rotor magnetic poles 4 provided with a plurality of small teeth 6 at an equal pitch on the outer periphery thereof. A rotor 9 fixed to an end face of a permanent magnet 8 magnetized in the axial direction by NS with a pitch shifted by 1/2 the arrangement pitch of the small teeth 6, and the rotor 9 is rotatably supported by the rotor 9; The stator 5 is opposed to the stator 5 via a gap, and the seven small teeth provided at the tip of the stator magnetic pole 2 are constituted by three groups of a set of three small teeth and two sets of two small teeth. Then, the three sets of small teeth are arranged such that the sum of the permeance vectors in the sixth harmonic plane of the permeance is substantially zero.

In another embodiment of the present invention, six magnetic poles 2 are arranged at equal intervals on the inner periphery of a substantially annular yoke 1, and a winding is wound around each of the magnetic poles to form a three-phase winding. And a stator 5 provided with an odd number of seven small teeth at the tip of the magnetic pole, and two rotor magnetic poles 4 provided with a plurality of small teeth 6 at an equal pitch on the outer periphery thereof. A rotor 9 fixed to an end face of a permanent magnet 8 magnetized in the axial direction by NS with a pitch shifted by 1/2 the arrangement pitch of the small teeth 6, and the rotor 9 is rotatably supported by the rotor 9; The stator 5 is opposed to the stator 5 via a gap, and the seven small teeth provided at the tip of the stator magnetic pole 2 are constituted by three groups of a set of three small teeth and two sets of two small teeth. The three sets of small teeth are arranged such that the sum of the permeance vectors on the third harmonic plane of the permeance is substantially zero.

[0133]

Since the three-phase hybrid type stepping motor according to the present invention has the above-described configuration, the arrangement of the small teeth provided at the tip of the winding pole is determined by the third harmonic plane vector and the fifth harmonic plane vector. 2 or 3 in both the single harmonic wave vector and the sixth harmonic wave flat vector alone or in combination
There is an effect that the third harmonic distortion of the cogging torque and the current torque can be reduced by balancing the pair of small teeth.

[Brief description of the drawings]

FIG. 1A is a vertical sectional front view of a conventional three-phase hybrid type stepping motor having 12 winding poles.

FIG. 1B is a left side view (N pole side) of the three-phase hybrid type stepping motor shown in FIG. 1A.

1C is a right side view (S pole side) of the three-phase hybrid type stepping motor shown in FIG. 1A.

FIG. 2A is a longitudinal sectional front view of a conventional three-phase hybrid type stepping motor having six winding poles.

FIG. 2B is a left side view (N-pole side) of the three-phase hybrid type stepping motor shown in FIG. 2A.

FIG. 2C is a right side view (S pole side) of the three-phase hybrid type stepping motor shown in FIG. 2A.

FIG. 3 is an equivalent magnetic circuit diagram of a three-phase six-winding-pole hybrid type stepping motor.

FIG. 4A is an N-pole integrated magnetic circuit diagram of a three-phase hybrid type stepping motor having six winding poles.

FIG. 4B is an S-pole side integrated equivalent magnetic circuit diagram of a three-phase hybrid type stepping motor having six winding poles.

FIG. 5 is an arrangement diagram of small teeth of winding poles.

FIG. 6 is a diagram showing a state of balance of sixth-harmonic plane vectors of an equal pitch vernier;

FIG. 7A is a diagram showing a balanced state between two vectors of a sixth-order harmonic plane vector of an irregular pitch vernier.

FIG. 7B is a diagram illustrating a state of balance between three vectors of sixth-order harmonic plane vectors of an irregular pitch vernier.

FIG. 8 is a diagram showing an arrangement of small teeth in FIG. 7B.

FIG. 9A is a diagram showing a state of balance of third harmonic plane vectors of an equal pitch vernier.

FIG. 9B is a diagram showing a state of magnetic balance between two vectors on a third harmonic electric angle plane.

FIG. 9C is a diagram showing a state of magnetic balance between three vectors on a third harmonic electric angle plane.

FIG. 10 is a diagram showing a state of balance of a sixth-order harmonic plane vector in an equal pitch vernier 2;

FIG. 11 is a diagram showing the arrangement of the small teeth in FIG. 10;

FIG. 12 is a diagram illustrating a state of balance of a third harmonic plane vector in trial calculation 5;

FIG. 13A is a diagram showing a state of balance of a third-order harmonic plane vector in trial calculation 6.

FIG. 13B is a diagram showing a state of balance of a fourth harmonic plane vector in trial calculation 6.

FIG. 14 is a diagram showing a configuration of a small tooth of trial calculation 6;

FIG. 15A is a diagram showing a state of balance in a third harmonic plane vector of trial calculation 7;

FIG. 15B is a diagram showing a balance state in a fifth harmonic plane vector of trial calculation 7.

FIG. 16 is a diagram showing a configuration of a magnetic pole having seven small teeth.

FIG. 17 is a diagram showing a state of vector balance when the number of small teeth is seven.

[Explanation of symbols]

Magnetomotive force F ₃ winding of F _u winding magnetomotive force F _v winding phases different magnetomotive force F _w of the winding phases different magnetomotive force F ₁ winding pole magnetomotive force F ₂ winding poles of different phases pole of magnetomotive force F of the _fourth winding pole force of force F ₅ winding pole magnetomotive force F ₆ winding pole magnetomotive force N ₁ N-pole side of the winding pole N ₂ N-pole winding pole N ₃ N pole N ₄ N pole N ₅ N pole N ₆ N pole S ₁ S pole S ₂ S pole S ₃ S pole side winding pole S ₄ S pole side winding pole S ₅ S pole side winding pole S ₆ S pole side winding pole P ₁ Permeance of winding pole P ₂ Permeance of winding pole internal permeance t ₁ each small tooth t ₂ each small tooth magnetomotive force P _m magnets permeance F _m magnets permeance P ₆ winding pole permeance P ₅ winding pole permeance P ₄ winding poles P ₃ winding poles t ₃ each small tooth t ₄ the teeth t ₅ respective small teeth t ₆ the teeth t ₇ respective small teeth theta _1-position of the teeth Position θ ₂ Position of each small tooth θ ₃ Position of each small tooth θ ₄ Position of each small tooth θ ₅ Position of each small tooth θ ₆ Position of each small tooth θ ₇ Position of each small tooth V ₁ Each vector V ₂ Each each vector 1 yen vector V ₃ each vector V ₄ each vector V ₅ each vector V ₆ each vector V ₇ annular yoke 2 pole 3 winding 4 small teeth 5 stator 6 teeth 7 rotor poles 8 permanent magnet 9 rotor

Claims (10)

[Claims] 1. A three-phase winding is formed by arranging six magnetic poles at equal intervals on the inner periphery of a substantially annular yoke, winding a winding around each of the magnetic poles, and forming a three-phase winding at the tip of the magnetic pole. A stator provided with a plurality of at least six small teeth and two rotor magnetic poles provided with a plurality of small teeth on the outer periphery thereof at an equal pitch are formed at a pitch of 1/2 of the arrangement pitch of the small teeth. A three-phase hybrid type stepping motor, comprising: a rotor fixed to an end face of a permanent magnet magnetized in the NS direction with two poles in an axial direction, wherein the rotor is opposed to the stator via a gap. At least six small teeth provided at the tip of the set are composed of at least three groups of two sets of small teeth, and the sum of the permeance vectors in the sixth harmonic plane of the permeance of the two small teeth of each set is set. The pitch of the small teeth between each pair is mutually 3-phase hybrid stepping motor, characterized in that it occupies not. 2. A three-phase winding is formed by arranging six magnetic poles at equal intervals on the inner periphery of a substantially annular yoke, winding a winding around each of the magnetic poles, and forming a three-phase winding at the tip of the magnetic pole. A stator provided with a plurality of at least six small teeth and two rotor magnetic poles provided with a plurality of small teeth on the outer periphery thereof at an equal pitch are formed at a pitch of 1/2 of the arrangement pitch of the small teeth. A three-phase hybrid type stepping motor, comprising: a rotor fixed to an end face of a permanent magnet magnetized to have two NS poles in the axial direction, wherein the rotor is opposed to the stator via a gap. , The at least six small teeth provided at the tip of the set are composed of at least two groups of sets of three small teeth, and the sum of permeance vectors in the sixth harmonic plane of the permeance of the three small teeth of each set is set. The pitch of the small teeth in each set is different from each other so that 3-phase hybrid stepping motor, characterized in that it occupies. 3. A three-phase winding is formed by arranging six magnetic poles at equal intervals on the inner periphery of a substantially annular yoke, winding windings on each of the magnetic poles, and forming a three-phase winding. A stator provided with a plurality of at least six small teeth and two rotor magnetic poles provided with a plurality of small teeth on the outer periphery thereof at an equal pitch are formed at a pitch of 1/2 of the arrangement pitch of the small teeth. A three-phase hybrid type stepping motor, comprising: a rotor fixed to an end face of a permanent magnet magnetized in the NS direction with two poles in an axial direction, wherein the rotor is opposed to the stator via a gap. At least six small teeth provided at the tip of the set of at least three groups of two sets of small teeth, the permeance vector of the permeance of the two small teeth of each set in the third harmonic plane The pitch of the small teeth between each pair is mutually shifted so that the sum is substantially zero. 3, characterized in that made different
Phase hybrid type stepping motor. 4. A three-phase winding is formed by arranging six magnetic poles at equal intervals on the inner periphery of a substantially annular yoke, winding a winding around each of the magnetic poles, and forming a three-phase winding at the tip of the magnetic pole. A stator provided with a plurality of at least six small teeth and two rotor magnetic poles provided with a plurality of small teeth on the outer periphery thereof at an equal pitch are formed at a pitch of 1/2 of the arrangement pitch of the small teeth. A three-phase hybrid type stepping motor, comprising: a rotor fixed to an end face of a permanent magnet magnetized to have two NS poles in the axial direction, wherein the rotor is opposed to the stator via a gap. At least six small teeth provided at the tip of the three small teeth are constituted by at least two groups, and the permeance vector of the permeance of the three small teeth in each set in the third harmonic plane is set. The pitches of the small teeth in each set differ from each other so that the sum is substantially zero. 3-phase hybrid stepping motor, characterized in that had RaShime. 5. A three-phase winding is formed by arranging six magnetic poles at equal intervals on the inner periphery of a substantially annular yoke, winding windings on each of the magnetic poles, and forming a three-phase winding. A stator provided with a plurality of at least six small teeth and two rotor magnetic poles provided with a plurality of small teeth on the outer periphery thereof at an equal pitch are formed at a pitch of 1/2 of the arrangement pitch of the small teeth. A three-phase hybrid type stepping motor, comprising: a rotor fixed to an end face of a permanent magnet magnetized to have two NS poles in the axial direction, wherein the rotor is opposed to the stator via a gap. At least six small teeth provided at the tip of the set are composed of at least two groups of sets of three small teeth, and the sum of the permeance vectors in the third harmonic plane of the permeance of the three small teeth of each set Is substantially zero, and the sixth height of each set of teeth is 3-phase hybrid stepping motor in which the sum of the permeance vectors are characterized in that occupies substantially different from each other pitch of small teeth in each set such that the zero in wasnt surface. 6. A three-phase winding is formed by arranging six magnetic poles at equal intervals on the inner periphery of a substantially annular yoke, winding a winding around each of the magnetic poles, and forming a three-phase winding at the tip of the magnetic pole. A stator provided with a plurality of at least six small teeth and two rotor magnetic poles provided with a plurality of small teeth on the outer periphery thereof at an equal pitch are formed at a pitch of 1/2 of the arrangement pitch of the small teeth. A three-phase hybrid type stepping motor, comprising: a rotor fixed to an end face of a permanent magnet magnetized to have two NS poles in the axial direction, wherein the rotor is opposed to the stator via a gap. , The at least six small teeth provided at the tip of the set are composed of at least two groups of sets of three small teeth, and the sum of permeance vectors in the sixth harmonic plane of the permeance of the three small teeth of each set is set. Is substantially zero and the permeation of each set of small teeth The third three-phase hybrid stepping motor, characterized in that it made different from each other the pitch of the small teeth of the harmonic wasnt surface in each set such that the sum of the permeance vector is substantially zero in the scan. 7. A three-phase winding is formed by arranging six magnetic poles at equal intervals on the inner circumference of a substantially annular yoke, winding windings on each of the magnetic poles, and forming a three-phase winding at the tip of the magnetic pole. A stator provided with a plurality of at least six small teeth and two rotor magnetic poles provided with a plurality of small teeth on the outer periphery thereof at an equal pitch are formed at a pitch of 1/2 of the arrangement pitch of the small teeth. A three-phase hybrid type stepping motor, comprising: a rotor fixed to an end face of a permanent magnet magnetized to have two NS poles in the axial direction, wherein the rotor is opposed to the stator via a gap. Set of at least six small teeth at the tip of the three small teeth 2
And the sum of the permeance vectors in the third harmonic plane of the permeance of the three small teeth in each set is substantially zero, and the two corresponding small A three-phase hybrid stepping motor, wherein the pitches of the small teeth in each set are different from each other so that the sum of the permeance vectors on the fifth harmonic plane of the tooth permeance is substantially zero. 8. Six magnetic poles are arranged at equal intervals on the inner periphery of a substantially annular yoke, and a winding is wound around each of the magnetic poles to form a three-phase winding. A stator provided with a plurality of at least six small teeth and two rotor magnetic poles provided with a plurality of small teeth on the outer periphery thereof at an equal pitch are formed at a pitch of 1/2 of the arrangement pitch of the small teeth. A three-phase hybrid type stepping motor, comprising: a rotor fixed to an end face of a permanent magnet magnetized to have two NS poles in the axial direction, wherein the rotor is opposed to the stator via a gap. Set of at least six small teeth at the tip of the three small teeth 2
And the sum of the permeance vectors in the fifth harmonic plane of the permeance of the three small teeth in each set is substantially zero, and the two corresponding small A three-phase hybrid stepping motor wherein the pitches of the small teeth in each set are different from each other so that the sum of the permeance vectors on the third harmonic plane of the permeance of the teeth is substantially zero. 9. A three-phase winding is formed by arranging six magnetic poles at equal intervals on the inner periphery of a substantially annular yoke, winding windings on each of the magnetic poles, and forming a three-phase winding. A stator having an odd number of at least seven small teeth, and two rotor magnetic poles having a plurality of small teeth provided at an equal pitch on an outer periphery thereof, are arranged at a pitch 1/2 of the arrangement pitch of the small teeth. A three-phase hybrid type stepping motor, comprising: a rotor fixed to an end face of a permanent magnet magnetized to have two NS poles in the axial direction, wherein the rotor is opposed to the stator via a gap. And at least three groups of at least three small teeth provided at the tip of each of the three small teeth and at least two sets of two small teeth, and the sixth harmonic of the permeance of each set of small teeth. The arrangement is such that the sum of the permeance vectors on the wave plane is substantially zero. 3-phase hybrid stepping motor according to claim. 10. Six magnetic poles are arranged at equal intervals on the inner periphery of a substantially annular yoke, and a winding is wound around each of the magnetic poles to form a three-phase winding. Odd number of at least 7
A stator provided with a plurality of small teeth and two rotor magnetic poles provided with a plurality of small teeth on an outer periphery thereof at an equal pitch are shifted from each other by a half pitch of the arrangement pitch of the small teeth, and are shifted in the axial direction. A three-phase hybrid type stepping motor comprising a rotor fixed to an end face of a permanent magnet magnetized into two poles of NS, the rotor being provided at a tip of the stator magnetic pole in a three-phase hybrid type stepping motor opposed to the stator via a gap. A permeance vector in the third harmonic plane of the permeance of each set of at least seven small teeth, comprising at least three groups of three sets of small teeth and at least two sets of two small teeth; Characterized in that the sum is substantially zero.