JP3178616B2 - Outer rotor type 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 an outer rotor type stepping motor in which a stator is provided with a permanent magnet and an exciting winding and a rotor is of a variable reluctance type.

[0002]

2. Description of the Related Art An annular permanent magnet is fixed to a stator iron core which is disposed so as to sandwich the permanent magnet, has a plurality of magnetic poles formed radially, and an excitation winding is wound around each magnetic pole. 2. Description of the Related Art An outer rotor type stepping motor in which a stator is formed and a variable reluctance rotor is disposed on an inner peripheral surface of the stator exists as a conventional technique. 5 and 6 are a front view and a side sectional view showing an example of an inner rotor type stepping motor according to the prior art.

As shown in FIG. 5, the stator core 21 has an even number (eight in this figure) of stator magnetic poles projecting radially inward, and windings 22, 28 are wound around the respective magnetic poles. .
The rotor cores 23, 24 are disposed so as to sandwich the permanent magnet 25, and in the present figure, the permanent magnet 25 magnetized in the axial direction is magnetized to an N pole and 24 to an S pole, and is fixed respectively. It is rotatably supported so as to face the inner peripheral surface of the daughter magnetic pole via air gaps 26 and 27.

The magnetic flux emitted from the permanent magnet 25 passes through the rotor core 23 and the air gap 26 and passes through the stator core 21.
To form a magnetic path returning to the other rotor core 24 through the air gap 27 at another position. In this figure, when an alternating current is applied to the winding 22 and the stator magnetic pole is magnetized to the S pole, the stator magnetic pole opposed to one rotor iron core 23 by the winding 22 has a winding. Since the magnetic flux intersecting with the magnetic flux 22 overlaps and strengthens the magnetic flux of the rotor iron core 23, the pole teeth of the rotor iron core 23 and the pole teeth of the stator side excited by the winding 22 attract each other. On the other hand, the pole teeth on the stator side, which are magnetized by the windings 22 facing the rotor core 24,
2, the magnetic flux weakens (subtracts) each other because the rotor iron core 24 is also an S pole.

The positioning of the rotor with respect to the stator is made up of the pole teeth of the stator magnetic pole facing the air gap 26 and the pole teeth of the rotor iron core 23, and the stator magnetic pole facing the air gap 27. And the pole teeth of the rotor iron core 24 tend to have a minimum permeance positional relationship. That is, in the air gap 26, the magnetic flux generated by the winding and the magnetic flux of the permanent magnet are in an additive state in which the magnetic flux is strengthened, and in the air gap 27, the magnetic flux is in a subtractive state in which the magnetic flux is weakened. By passing the alternating current through the winding 22 in this way, the addition and subtraction states of the air gaps 26 and 27 are alternately changed. By passing the alternating currents having a 90 ° electrical angle and different phases through the windings 22 and 28, the rotor Rotate step by step. This is the principle of rotation of a so-called inner rotor / HB (hybrid) type stepping motor.

FIGS. 7 and 8 show examples of the prior art of an outer rotor type stepping motor which rotates on the same principle as that of FIGS. 5 and 6 described above. FIG. 7 is a front view, FIG.
Shows a side sectional view of the stator iron cores 31 and 3.
1 ′ oppose each other with the permanent magnet 33 interposed therebetween, and the respective stator magnetic poles 31-1 to 31-8 and 31-1 ′ to 31-8 ′
Are provided with a plurality of pole teeth at the ends thereof, and windings 32-1 to 32-32 are provided so as to straddle both of the stator magnetic poles forming a pair.
8 is wound. The stator iron cores 31 and 31 'forming the above-mentioned pair are respectively provided with the stator magnetic poles 31-1 to 31-31.
-8 and 31-1 'to 31-8' are arranged so as to be shifted from each other by a half of the rotor tooth pitch. One of the stator magnetic poles 31-1 to 31-8 has an air gap 34,
The other stator magnetic poles 31-1 ′ to 31-8 ′ face the rotor 36 via the air gap 35, and the inner circumference of the rotor 36 has outer circumferential tips of the stator magnetic poles 31-1 to 31-8. The pole teeth of the same pitch as the pole teeth provided in are provided at an equal pitch.
In the air gaps 34 and 35, as in the case of the inner rotor type stepping motor shown in FIGS. -1, 32-3, 32-5, and 32-7 as one phase, and an alternating current is applied.
2,32-4, 32-6, 32-8 as the second phase 90
回 転 The rotor rotates stepwise by passing currents with different phases.

The structure shown in FIGS. 7 and 8 has a merit that a large torque can be obtained since the rotor diameter can be made larger than those shown in FIGS. However, the prior art of this structure requires that the number of stator magnetic poles be an even number of 4 or more, as described in, for example, Japanese Patent Publication No. 3-4153. For example, in FIGS. Stator magnetic pole 3
1-1 and 31-1 'had to be provided with a phase shift of 1/2 of the rotor tooth pitch.

In this case, the radial attractive force between the stator and the rotor is, for example, the stator magnetic poles 31-1 and 31-.
In FIG. 5, the force acting on the axis of the rotating shaft should theoretically be canceled and become zero because the magnetic force is drawn at a point shifted by 180 ° in mechanical angle. However, in this configuration, the stator is disposed inside. Since the bearing structure for supporting the rotor 36 is a cantilever structure, it is actually difficult to keep the air gaps 34 and 35 uniform over the entire 360 ° in view of the rigidity and accuracy of the shaft support.
Further, the stator magnetic poles 31-1 and 31-1 'forming a pair are reduced by half.
When the pitch is shifted, when a stator core having the same size and shape is used together, the slot for winding the winding is shifted by ピ ッ チ pitch, which makes the winding difficult. On the other hand, using the pair of stator magnetic poles 31-1 and 31-1 'as separate members having different shapes shifted in advance by ピ ッ チ pitch inevitably involves an economic problem.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide an outer rotor type stepping motor which solves the above-mentioned problems in the conventional structure and realizes the following objects. (1) While maintaining a high torque with the outer-rotor type, low vibration and positioning accuracy are improved while maintaining the cantilever structure. (2) A structure in which a small step angle can be obtained at low cost.

[0010]

In the outer rotor type stepping motor according to the present invention, Q magnetic poles are implanted at equal pitches radially outward in an annular yoke, and the outer periphery of each of the Q magnetic poles is provided. Two or more stator cores having the same number of pole teeth are arranged concentrically, and the two stator iron cores are arranged so that an annular permanent magnet is coaxially sandwiched therebetween and fixed. When the child winding is a P-phase, Q = mP (where m is an odd number of 1 or more, P is 3 or 5, and Q is an odd number of 15 or less), and oppose each other across the permanent magnet. A pair of poles is arranged at the same position in the direction of the rotation axis, and a winding is wound over the pair of poles to form a stator, which is made of a magnetic material having high magnetic permeability.
Zr pole teeth are provided at an equal pitch over the entire circumference of the inner peripheral surface, and are magnetically coupled to each other in a state where the teeth are shifted at a half pitch so as to be approximately divided in the axial direction to form a rotor, and It is configured to have the relationship shown in Equation 1 and / or to make the number of power supply terminals equal to the number of phases of the stator winding.

(Equation 1)

[0011]

According to the above-described structure, an operation effect can be provided such that an inexpensive high-precision stepping motor capable of performing a minute angle operation can be realized without impairing the advantage of the outer rotor structure for realizing high torque.

[0012]

1 and 2 are a front view and a side sectional view, respectively, of an embodiment of the present invention. The present invention is characterized in that the number of magnetic poles implanted in the stator core 1 is an odd number. In this embodiment, the magnetic pole group is indicated by Q _{1 to} Q ₉ in FIG. 1 with 9 parts, but a plurality of pole teeth formed at each magnetic pole tip are actually omitted for simplification of description. ing. A winding 6 is wound around each of the _nine stator magnetic poles Q _{1 to} Q _9.
Is the mechanical angle of the _nine stator poles Q _{1 to} Q ₉ of 120 °.
The windings 6 belonging to the first phase are connected and wound around magnetic poles Q ₁ , Q ₄ , Q ₇ as shown in FIG. The windings 6 belonging to the second phase, which are omitted in FIG. 1, have magnetic poles Q ₂ , Q ₅ , Q
₈ , the winding 6 also belonging to the third phase has magnetic poles Q ₃ , Q ₆ , Q
₉ , each is wound. Therefore, for example, when the first phase winding 6 is energized, the magnetic poles Q ₁ , Q ₄ , Q ₇ are magnetized to the same polarity, but the stator iron core 1 and the stator iron The core 1 ′ is axially opposed with the same magnetic pole position, and each is magnetized by the same winding 6.

On the other hand, the rotor has nine stator magnetic poles Q _{1 to} Q _1.
9 is disposed so as to face an air gap on the outer peripheral surface of 24 on the inner peripheral surface opposite to the stator poles Q ₁ to Q ₉
The rotor-side pole teeth are formed. The rotor has a structure that is substantially bisected in the axial direction, and has a predetermined pitch and a predetermined number of pole teeth on an inner peripheral surface of one side 3 which faces the stator core 1 via an air gap 4. Is formed on the inner peripheral surface of the air gap 5 side 3 'facing the other stator iron core 1', which is circumferentially shifted by an equal pitch and the same number, but by an angle of 1/2 of the pole tooth pitch. The two are integrally fixed so that the pole teeth are positioned, and are rotatably supported.

With the above configuration, as shown in FIGS.
When the rotor is energized, the rotor is driven by the magnetic poles Q ₁ ,
In the air gap 4 opposed to Q ₄ , Q ₇ , the magnetic flux is strengthened, and the magnetic poles Q ₁ ′, Q ₄ ′,
Q ₇ 'will be destructive in the air gap 5 of the side. That is,
By applying an alternating current to the winding 6, the air gap 4,
The magnetic flux at step 5 alternates between strengthening and weakening, and the second and third phase windings are stepped and rotated by supplying an alternating current having a phase difference of 60 ° in electrical angle to each of the second and third phase windings.

In this configuration, in the case of three-phase two-excitation, the magnetization of the magnetic pole of the second phase is opposite in polarity to the first phase. For example, when the magnetic poles Q ₁ , Q ₄ , Q ₇ belonging to the first phase are strengthened by the north pole, the magnetic poles Q ₂ ′, Q ₅ ′, Q ₈ ′ belonging to the second phase are strengthened by the south pole,
The magnetic flux exiting the magnetic poles Q ₁ , Q ₄ and Q ₇ passes through the air gap 4, one rotor pole tooth 3 and the other rotor pole tooth 3 ′, and
The process proceeds to the poles Q ₂ ′, Q ₅ ′, and Q ₈ ′. The purpose of arranging the rotor iron core in approximately two parts and displacing the two at a pole tooth pitch of 1/2 is to form the above-described magnetic path.

FIG. 3 shows a second embodiment according to the present invention, in which the stator has 15 magnetic poles and the rotor has 21 teeth, and a five-phase winding is provided. The first phase winding has magnetic poles Q _{1 to} Q
_{Of the 15} , Q ₁ , Q ₆ and Q ₁₁ mechanically separated by 120 °
The second phase component is magnetic poles Q ₂ , Q ₇ , Q ₁₂ , the third phase component is magnetic poles Q ₃ , Q ₈ and Q ₁₃ , the fourth phase component is Q ₄ , Q ₉ , Q ₁₄ ,
The fifth phase is wound around Q ₅ , Q ₁₀ , and Q ₁₅ , respectively.
To simplify the description in the example of the second stator magnetic poles Q ₁ ~
A plurality of pole teeth of the distal end of the Q ₁₅ has been omitted, as well stator with the aforementioned first embodiment, constructive flux in the structure and the air gap of the rotor, since the state of destructive are the same Description is omitted.

FIG. 4 shows still another embodiment in which the number of stator magnetic poles is three, and in this example, three pole teeth are formed at the tip of each magnetic pole.
The number of rotor pole teeth is 16, and the magnetic poles Q ₁ , Q ₂ , Q ₃
Are wound with windings C ₁ , C ₂ and C ₃ respectively. The purpose of this example is slightly different from the first example shown in FIGS. 1 and 2 and the second example shown in FIG. 3, and the stator poles Q ₁ , Q ₂ ,
Q ₃ and the other stator magnetic poles Q ₁ ′, Q ₂ ′, Q ₃ ′ (not shown) opposed to the permanent magnet across the permanent magnet are arranged at the same position.

The combination of the number of magnetic poles on the stator side and the number of pole teeth on the rotor side is the same, but the winding C _{1 for} the first phase has the magnetic pole Q _1.
Only, the second phase winding C ₂ is wound only on the magnetic pole Q ₂ , and the third phase winding C ₃ is wound only on the magnetic pole Q ₃ , so that the radial force is canceled in the above two embodiments. Although there is no effect, the number of magnetic poles is 3 and the structure is simple, which is advantageous in terms of cost. In addition, the effect of the three-phase structure is that the step angle can be reduced with the same size as that of the two-phase structure. effective.

According to the present invention, as described above, by setting the number of stator magnetic poles Q to an odd number, by setting Q = mP and m = 3, as shown in FIGS. Since the attractive force between the teeth and the rotor-side pole teeth is applied to the rotating shaft at a point separated by 120 °, it is canceled by the vector synthesis of three points. (4) The degree of cancellation is further improved with respect to cancellation at two separated points. Also, in the outer-rotor structure, since the bearing that supports the rotor is a cantilever structure, it is difficult to keep the air gap uniform, and there are two points where suction force acts from this surface. The cancellation degree is further improved by increasing the number of points to three points and increasing the number of points to five points to cancel the radial force of the suction force. If this vector sum is not zero, it tends to cause vibration and noise during rotation, and the step angle accuracy and the positioning accuracy of the rotor tend to deteriorate.

However, dispersing the radial force at multiple points means increasing the number of stator magnetic poles Q, and increasing the number of magnetic poles complicates the winding, so there is an economic limit. The outer rotor type stepping motor according to the present invention is mainly used for constant speed rotation control of OA equipment such as a drum drive of a laser beam printer. It was as follows.

Assuming that Q = mP and m = 1, in the case of P = 3, the result is as shown in FIG. 4 of the embodiment, and the above-mentioned effects of low vibration and low noise are lost, but the number of magnetic poles is small and economically advantageous. Therefore, m = 1 for applications where vibration / noise is not a major problem.
Is also available. Since the step angle θs of the stepping motor is determined by Equation 2, even if the number of stator magnetic poles Q is small, the number of phases P is 3 or 5, and the number of rotor-side pole teeth Zr is 2
Θs can be reduced as long as it has the same phase structure.

(Equation 2)

As is well known, the positioning accuracy of the stepping motor generally improves as the step angle θs decreases. This is because if the positioning amount θ is θ = Nθs, N increases when θs is small, and the error of the stepping motor is almost constant at a level of about 3 to 6% of θs, so that the accuracy is relatively improved. You do it. Therefore, even if the number of magnetic poles Q is smaller than that of the two-phase motor, the positioning accuracy may be improved by the effect of the number of phases P, which is why m = 1.

Table 1 shows the range of Q = mP in the present invention.

[Table 1] When P = 5 and m = 5, Q = 25. However, for economic reasons, Q is practically limited to 15 or less.

The above-described equation (1) limiting Zr is obtained by adding Q =
It is obtained by substituting mP and solving for Zr.

(Equation 3) The left side and the right side of Equation 3 each represent the step angle of the P-phase stepping motor with the number of rotor-side pole teeth being Zr. Table 2 shows the relationship between the number of pole teeth Zr on the rotor side and the step angle θs when n = parameter when P = 3 and m = 3 in Equation 1.

[Table 2]

As shown in Table 1, when m = 5, P = 3 and Q
= 15, but in this case, one phase is composed of five magnetic poles, and the above-described radial suction force is dispersed and canceled at five points separated by a mechanical angle of 72 °, resulting in lower vibration and lower noise. It can be said that it is suitable for conversion. Table 3 shows the relationship between the number of pole teeth Zr on the rotor side and the step angle θs when n is a parameter when P = 5 and m = 3 as another example of the configuration.

[Table 3] As shown in Table 1, when m = 5, P = 3 and Q = 15. In this case, one phase is composed of five magnetic poles, and the above-mentioned radial attractive force is separated from the above-mentioned radial angle by a mechanical angle of 72 °. The five points are dispersed and canceled, and it can be said that this is suitable for lowering vibration and noise.

In a three-phase motor and a five-phase motor, the total cost can be reduced by selecting the driving means. 3
Both phase stepping motor and 5-phase stepping motor
There is a method of shorting the winding start and winding end of each phase winding. FIG. 9 shows a three-phase motor having a six-terminal structure indicated by a, a ', b, b', c, and c '. The magnetic poles A, B, and C have N, S, and S, respectively.
FIG. 10 shows an example in which the winding ends of each winding are short-circuited and the input terminals are a, b, and c.
By connecting a to the (+) power supply and connecting b and c to the (-) power supply by switching elements, the polarities of the magnetic poles A, B, and C can be set to N, S, and S, respectively. Each input terminal a, b,
Since the polarity of c can be freely selected, the polarities of the magnetic poles A, B, and C also have a degree of freedom within the range, a rotating magnetic field can be created, and the stepping motor of the present invention can be driven.

FIG. 11 is a simplified diagram of a five-phase stepping motor having ten terminals, in which the magnetic poles A, B, C, D, and E are N, N, S, S, O (non-polarity, E is no polarity). FIG. 12 shows the state of the five-phase stepping mode.
In this configuration, the number of input terminals is five, terminals a and b are (+) power supply, terminals c and d are (−) power supply, and terminal e is Are not connected to the power supply, the magnetic poles A, B, C, D, and E have the same polarity as in FIG. 11, which is the same as the three-phase case shown in FIG. Terminals a, b, c, d, e
Since the polarity of the power supply can be freely selected, the polarity of each of the magnetic poles A to E can be arbitrarily selected within the range, so that the terminals a, b, c, d, and e can generate a rotating magnetic field. If the power supply polarity is selected by a switching element, the five-phase stepping motor of the present invention can be driven.

The three-phase and five-phase stepping motors are
The number of power supply terminals can also be reduced by sequentially connecting the winding end and winding start of each phase winding in a ring shape. FIG.
In FIG. 9 described above, terminals a and b, b and c, and c and a are respectively connected, and the connection points are a, b, and c, and three terminals are used, a is (+), and b is (-). , C are (+), and the polarities of the magnetic poles A, B, C are N, S,
O (no polarity). Terminal a and terminal c are connected to the winding of the magnetic pole C.
Becomes the same potential as (+), and no current flows.

Similarly, FIG. 14 shows that the winding end and winding start of each winding of FIG.
In this case, a and e are set to (+), c is set to (-), and b and d are not connected to the power supply, so that each magnetic pole A,
B, C, D, and E indicate that the same polarity as in FIGS. 11 and 12 can be obtained. 13 and 14 can also generate a rotating magnetic field, and can drive the stepping motor of the present invention.

The reason why the phase number P is set to an odd number of 3 or 5 in the present invention is that if the phase number P is an even number, the rotating magnetic field cannot be made well when a ring connection is made as shown in FIGS.
This is to realize an input terminal and five input terminals. For example, FIG.
At 3, the magnetic pole A needs to start from the N pole and then to the S pole. However, even numbers such as a four-phase motor do not change to the S pole and also become the N pole. To do so requires special ingenuity.

[0031]

(1) When m = 3 or m = 5 in Q = mP, low vibration and low noise can be obtained even in a cantilever bearing structure.
In addition, it is possible to provide an outer rotor type stepping motor with high torque and high accuracy. (2) When m = 1 when Q = mP, three phases or five
Inexpensive and high torque outer while retaining the effect of phase motor
A rotor type stepping motor can be provided. (3) Since the permanent magnets are provided on the stator side, the area is larger than that provided on the rotor side, and the efficiency is good. (4) Since the slots of the two stators sandwiching the permanent magnet are not displaced, winding is easy. (5) The number of phases can be set to an odd number, and driving can be performed even with a three-terminal or five-terminal input, and high torque can be output by inexpensive driving means.

[Brief description of the drawings]

FIG. 1 is a front view of one embodiment of the present invention.

FIG. 2 is a side sectional view of the example shown in FIG.

FIG. 3 is a front view of another embodiment of the present invention.

FIG. 4 is a front view of still another embodiment of the present invention.

FIG. 5 is a front view showing an example of a conventional inner rotor.

FIG. 6 is a side sectional view of the example shown in FIG. 5;

FIG. 7 is a front view showing an example of a conventional outer rotor.

FIG. 8 is a side sectional view of the example shown in FIG. 7;

FIG. 9 is a simplified diagram of six input terminals with three phases.

FIG. 10 is a simplified diagram of three input terminals with three phases.

FIG. 11 is a simplified diagram of five phase and ten input terminals.

FIG. 12 is a simplified diagram of five input terminals with five phases.

FIG. 13 is another simplified diagram of three input terminals with three phases.

FIG. 14 is another simplified diagram of five input terminals with five phases.

[Explanation of symbols]

1,1 ', 21,31,31'
: Stator iron core 2, 25, 33
: Permanent magnet 3,3 ', 23,14
: Rotor iron core 36
: Rotor 4,5,26,27,34,35
: Air gap _{6, C 1 ~C 3, 22,28,32-1~32-8} :
Winding 31-1~31-8,31-1'~31-8 ', Q ₁ ~Q
_{15, Q 1 '~Q 15'} : stator magnetic pole

Claims (2)

(57) [Claims] 1. A stator in which Q magnetic poles are implanted at equal pitches radially outward in an annular yoke, and one or more equal number of pole teeth are provided on the outer periphery of each of the Q magnetic poles. In an outer rotor type stepping motor having a structure in which two cores are arranged concentrically and an annular permanent magnet is coaxially sandwiched between the two stator iron cores, the stator windings are set to P. When it is a phase, Q = mP (where m is an odd number of 3 or more , P is 3 or 5, and Q is an odd number of 15 or less). A pair of coils are arranged at the same position in the direction of the rotation axis, and a winding is wound over the pair of poles to form a stator. The stator is made of a magnetic material having high magnetic permeability. Zr pole teeth are provided at an equal pitch over the rotor, and magnetically coupled with the teeth shifted by a half pitch so as to be approximately bisected in the axial direction. And an outer having a permanent magnet in the stator, characterized by having the relationship shown in Equation 1.
Rotor type stepping motor. ## EQU1 ## Zr = m (Pn + (1-P) / 2) (where n is a natural number of 2 or more) 2. The outer rotor type stepping motor according to claim 1, wherein the number of power supply terminals is equal to the number of phases of the stator winding.