JPH06209554A - Stepping motor - Google Patents

Abstract

PURPOSE:To sharply improve the T/N property value of a brushless motor, with simple structure. CONSTITUTION:This is one which has enabled both the number of magnetic poles and the effective magnetic flux phi to be increased at the same time, making use of the magnetic flux of a field magnet 27 at all times to the utmost without magnetizing the field magnet into-multipole as before and besides while maintaining the structure on the side of an armature easily by performing the multipolarization by the structure of concentrating all the magnetic fluxes of the field magnet 27 without dispersing them while inverting them on the side of the iron core 23 of an armature by the shapes of the yoke plates 26 and 28 attached to the field magnet 27.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor including an armature and a field magnet provided so as to move relatively.

[0002]

2. Description of the Related Art In recent years, various stepping motors have been developed, and as an example of a conventional stepping motor, there is a motor having a structure shown in FIGS. This is a so-called 2-3 (number of magnetic poles-number of core poles) structure, in which a hollow cylindrical field magnet 2 is fixed to the inner peripheral wall of a casing 1 forming a rotor. The armature 3 is arranged on the inner peripheral side of the field magnet 2 so as to form a stator. The field magnet 2 is magnetized so as to form two different magnetic poles N and S in the circumferential direction, and the armature 3 approaches the inner peripheral wall of the field magnet 2 to generate a magnetic flux. Salient poles 3a, 3
a, 3a, and the coils 3b, 3b, 3b are wound around the salient poles 3a, respectively.

As a multi-pole type stepping motor,
For example, there is a motor having a structure as shown in FIG. In this configuration, a large number of different magnetic poles N and S are magnetized at a predetermined pitch along the circumferential direction in a hollow cylindrical field magnet 12 fixed to the inner peripheral wall of the rotor casing 11, and this field is also magnetized. A large number of salient poles 13 are provided on the armature 13 arranged so as to form a stator on the inner peripheral side of the magnet 12.
, a, 13a, ... Are provided. A coil 13b is wound around each of these salient poles 13a.

[0004]

However, in such conventional stepping motors, there is a problem that the so-called T / N characteristic value is still insufficient. That T / N characteristic value is the quotient of the rotational speed N and the torque T in the T-N characteristic of the stepping motor, specifically, T / N characteristic value _{= T S / N O = ΔT} / ΔN = K It is represented by _E・ K _T / R. Here, T _S ; starting torque N _O ; no-load rotation speed K _E ; back electromotive force constant K _T ; torque constant R; internal resistance.

This T / N characteristic value represents the size of the T-N characteristic which is the basis of the motor, and the sizes of the stepping motors can be compared. For example, a T / N = 3 stepping motor can produce the same T-N characteristics as when three T / N = 1 stepping motors are simultaneously rotated. More specifically, the T / N characteristic value is in proportion to about the square of the volume of the motor (more precisely, to the 5/3 power), and has a relation substantially proportional to BH _MAX in the field magnet. ing. Therefore, conventionally, when a larger motor or a stronger magnet is used, the T / N characteristic value is consequently increased.

When the T / N characteristic value is increased, the following is possible. 1) Increase in generated torque. 2) Reduction of rise time. 3) Increasing torque constant and back electromotive force constant. 4) Reduction of rated current. 5) Reduction of loss (copper loss). 6) Higher efficiency. 7) Reduction of heat generation. 8) Increased output. 9) Reduction of the influence on the rotation speed fluctuation due to load fluctuation.

If the T / N characteristic value has a margin,
Depending on how you use it, you can do the following. 1) Smaller, thinner and lighter motor. 2) Lower costs by reviewing materials. 3) Greater freedom of design.

[0008] As described above, various proposals regarding the stepping motors that have been proposed in the related art often result in higher T / N characteristic values. In other words, the requirements for making the stepping motor lighter, thinner and shorter, saving power, saving resources, and lowering prices are based on (T / N characteristic value) / (physique) and (T / N characteristic value). / (Cost), and how to efficiently obtain the T / N characteristic value has been a conventional problem. For example: 1) Miniaturization, thinning, and weight reduction. 2) Extension of starting torque. 3) Shorter rise time. 4) Reduction of current value. 5) Reduction of loss (copper loss). 6) Streamline. Therefore, many proposals related to the conventional stepping motor technology can be said to be studies for eventually improving the T / N characteristic value. Practically, the T / N characteristic value is 5
% To 10% of the difference is competing.

Next, as factors for determining such T / N characteristic values, P (number of magnetic poles), Φ (effective magnetic flux), H (number of parallel coils), A (coil cross-sectional area), L (per 1T). Coil length), which can be expressed by an equation: T / N characteristic value = P ² · Φ ² · H · A / L ... Therefore, the T / N characteristic value becomes maximum when these elements are combined so as to maximize the total.
In particular, the point is how to increase P ² × Φ ² .

From this point of view, in the case of the so-called 2-3 (number of magnetic poles-number of core poles) structure shown in FIGS. 10 and 11, the number of magnetic poles in a three-phase motor is considered. And the number of salient poles are the minimum combination. For example, in the illustrated positional relationship, N
The total magnetic flux of the poles is concentrated on one salient pole 3a. Therefore, the effective magnetic flux Φ is large. However, since the number of magnetic poles P is 2, there is a limit to the improvement of the T / N characteristic value.

On the other hand, in the multipolar type shown in FIG.
The T / N characteristic value is improved by increasing the number of magnetic poles P and the number of parallel coils H and simultaneously reducing the coil length L. However, the salient pole 13a of the armature 13 and the field The facing area per salient pole with the magnet 12 is small, and the magnetic flux is dispersed and used. That is, since the same total magnetic flux is used by dividing it into multiple poles, the number of magnetic poles P is increasing, but the effective magnetic flux Φ is decreasing.
The value of ² × Φ ² has not changed. Further, although the number H of parallel coils can be increased, the reduction in the coil cross-sectional area A cancels out and the structure becomes complicated, but the T / N characteristic value cannot be significantly improved. Therefore, in the case of this multi-pole type, in the present situation, a magnet having a large BH _MAX is adopted to obtain an effective magnetic flux Φ to improve the T / N characteristic value.

As described above, the conventional stepping motor has a problem that the T / N characteristic value can be improved only by a method of using a strong magnet, which leads to a significant cost increase.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a stepping motor capable of significantly improving the T / N characteristic value with a simple structure.

[0014]

In order to achieve the above object, the present invention provides an armature having a plurality of coils wound around an iron core, and a field magnet arranged so as to be movable relative to the armature. In the stepping motor having, the field magnet is extended in a relative movement direction with respect to the armature, and is magnetized in a direction orthogonal to the extension direction,
A yoke plate is attached to each of the magnetized end faces of the field magnet along the extending direction of the field magnet,
The two yoke plates are provided with a plurality of magnetic path forming convex portions arranged at a predetermined pitch in the extending direction of the yoke plates, and the iron core and the magnetic path forming convex portions are The directions of the magnetic fluxes that are close to and away from each other so as to focus the magnetic flux of the magnetic magnet on the iron core and that pass through the iron core are It is provided in a positional relationship of reversing for each arrangement pitch.

[0015]

In the means having such a structure, the shape of the yoke plate attached to the field magnet allows the magnet to have a large number of poles due to the structure in which the total magnetic flux of the magnet is concentrated without being dispersed. Both the number of magnetic poles and the effective magnetic flux are increased at the same time without performing the pole magnetization and easily maintaining the structure on the armature side.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings. First, the first embodiment shown in FIGS. 1 and 2 is one in which the present invention is applied to a three-phase stepping motor, and a hollow cylindrical bearing holder erected at the center of a substrate 20. A rotary shaft 22 is rotatably supported in the shaft 21, and an iron core 23 of an armature is fixed to the outer periphery of the bearing holder 21 so as to form a stator. The iron core 23 is formed by laminating silicon steel plates or the like to a predetermined thickness, and three radially extending salient poles 23a, 23b, and 23c are formed in a circumferential direction 120 around the rotation axis. The coils 24, 24, 24 for three-phase excitation are respectively wound around the salient poles 23a, 23b, 23c at pitch intervals of °.

On the other hand, in the bearing protruding portion of the rotary shaft 22,
A cylindrical rotating body 25 constituting the rotor is fixed so as to rotate integrally, and a case 25a made of a dish-shaped non-magnetic member is provided on the lower surface portion of the rotating body 25 in the drawing.
Are concentrically attached. Further case 25
A field magnet 27 is annularly fixed to the inner peripheral wall portion of the flange-shaped portion provided on the outer peripheral portion of a. The field magnet 27 includes the salient poles 23a, 23b, 23c of the armature.
It is composed of a hollow cylindrical body that surrounds the outer periphery of the armature in a ring shape with a predetermined gap, and is arranged so as to rotate around the fixed armature to form the rotor. A ferrite or rare earth magnet is used as the field magnet 27, and is magnetized in a direction (axial direction) orthogonal to the circumferential direction, which is the extending direction of the magnet. In the present embodiment, the illustrated upper end surface of the field magnet 27 is magnetized to the N pole, and the illustrated lower end surface is magnetized to the S pole.

Further, a yoke plate 26 and a yoke plate 28 are attached to the magnetized end faces of the field magnet 27 on the upper side and the lower side in the drawing, respectively. Each of these yoke plates 26 and 28 is made of a ring-shaped ferromagnetic material extending along each magnetized end face of the field magnet 27.
The yoke plate 26 attached to the N pole side on the upper side of the figure is N
In addition to being magnetized to the pole, the yoke plate 28 attached to the S pole side below the field magnet 27 in the figure is magnetized to the S pole.

On the inner peripheral edge of the one yoke plate 26,
Four magnetic path forming protrusions 26 protruding toward the axial center
a, 26b, 26c, 26d are provided, and four magnetic path forming protrusions 28a, 28b, 2 protruding toward the axial center are provided on the inner peripheral edge of the other yoke plate 28.
8c and 28d are provided. Each of these yoke plates 26
The magnetic path forming projections 26a, ... And the magnetic path forming projections 28a, ... Of the yoke plate 28 are configured to rotate while sandwiching the iron core 23 of the armature from the axial direction. That is, the iron core 23 of the armature and the magnetic path forming projections 26a, ... And 28a, ... When approaching each other so as to face each other, the magnetic flux from the field magnet 27 is focused on the iron core 23 side through the magnetic path forming projections 26a, ... And 28a ,. Has been done. At this time, the plate thickness of the magnetic path forming convex portions 26a, ... And 28a, ... And the facing length with the iron core 23 are set to be substantially the same as the thickness of the iron core 23.

.. and 28a, ... on the two yoke plates 26 and 28 are arranged side by side at a pitch of 90.degree. In the circumferential direction, and the magnetic path forming protrusions on one side are formed. , And the magnetic path forming protrusions 28a on the other side,
Are arranged so as to be offset from each other by 45 ° in the circumferential direction. That is, in plan view, the magnetic path forming convex portions 26a, ... Which are magnetized to the N pole and the magnetic path forming convex portions 28a, ... That are magnetized to the S pole are alternately arranged at a pitch interval of 45 ° in the circumferential direction. Are arranged in a ring shape, and the magnetic path forming convex portion 26 on one side is formed.
a, the magnetic path forming convex portion 28a on the other side, the magnetic path forming convex portion 26b on the one side, and the magnetic path forming convex portion 28b on the other side are alternately arranged in this order. As a result, a total of 8 magnetic poles are formed without performing multipolar magnetization. Therefore, the direction of the magnetic flux passing through the portion of the iron core 23 where the coil 24 is mounted is such that the magnetic path forming protrusions 26a and 28 on both sides are formed.
The arrangement relationship is such that it is inverted at every arrangement pitch (45 °) of a.

The lead wire extending from the substrate 20 is connected to the drive control circuit 29 provided outside the motor.

In the stepping motor in such an embodiment, when the armature side and the field magnet side are in the illustrated positional relationship, that is, the magnetic path forming convex portion 26a (N pole) of one yoke plate 26 is formed. Are adjacent to one salient pole 23a, and the pair of magnetic path forming projections 28 on the other yoke plate 28
When the b and 28c (S pole) are close to the other salient poles 23b and 23c, the total magnetic flux from the field magnet 27 is changed to the magnetic path forming convex portions 26a, 28b and 28 as shown by arrows in the figure.
It is focused on the iron core 23 through c.

Next, when the field magnet side is rotated by 45 ° from this state, for example, the magnetic path forming convex portion 28a (S pole) of the yoke plate 28 is brought close to the salient pole 23a and the pair of yoke plates 26 is Magnetic path forming protrusions 26c, 26d
(N pole) approaches the salient poles 23b and 23c. Therefore, the total magnetic flux from the field magnet 27 is inverted to the side opposite to the direction of the arrow and focused on the iron core 23.

As described above, in this embodiment, due to the shape of the pair of yoke plates 26 and 28 attached to the field magnet 27, the total magnetic flux of the field magnet 27 is concentrated without being dispersed to achieve multi-pole. As a result, the magnetic flux from the field magnet 27 is always utilized to the maximum extent, and both the magnetic pole number P and the effective magnetic flux Φ are simultaneously increased. In order to make the poles multi-pole, the field magnet is not multi-pole magnetized as in the prior art, and the structure on the armature side is simply maintained.

In this state, the total magnetic flux concentration state is the same as in the stepping motor having the so-called 2-3 structure shown in FIGS. 10 and 11, and the number P of magnetic poles is increased. Then, as shown in the above equation, T / N
Since the number P of magnetic poles contributes to the characteristic value as a square, if the number P of magnetic poles is tripled, the T / N characteristic value becomes 9 times, and as in the present embodiment, the number P of magnetic poles becomes four times. If T / N characteristic value is 1
If the magnetic pole number P is 6 times and the magnetic pole number P is 5, the T / N characteristic value is set to 25 times, and the T / N characteristic value is greatly improved.

Here, the torque generated by the motor is the change in the magnetic flux Φ passing through the coil per unit angle θ (dΦ / dθ;
The T / N characteristic value is proportional to the square of the gradient of the magnetic flux density). Therefore, the change of the magnetic flux Φ during one rotation of the stepping motor is changed by the conventional two-pole motor (P = 2), the conventional multi-pole motor (P = 10) and the motor according to the present invention (P = 10). Let's compare about.

As is apparent from FIG. 3, the large magnetic flux changes slowly in the conventional two-pole motor () indicated by the broken line, and the magnetic flux Φ in the conventional multi-pole motor () indicated by the thick line. Is 5 times as many. However, since the magnetic flux Φ itself is ⅕, the change dΦ / dθ (magnitude of inclination) of the magnetic flux Φ is the same in both cases. On the other hand, in the case of the structure () of the present invention shown by the thin line, the same total magnetic flux as that of the conventional two-pole motor () is concentrated and the same interval as that of the conventional multi-pole motor (). Is being switched in. Therefore, the change dΦ / dθ (magnitude of inclination) of the magnetic flux Φ is extremely large. In this case, assuming that the conditions of the armatures of the respective motors are the same, the motor of the present invention has a generated torque (torque constant) of 5 times and T / N as compared with the conventional motor.
The characteristic value becomes 25 times.

In the embodiment shown in FIG. 4, the components corresponding to the embodiments of FIGS. 1 and 2 described above are
The tens code "2" is replaced with "4". In this embodiment, a large number of magnetic path forming projections 46a to 46h and 48a to 48h are provided on each of the yoke plates 46 and 48 so as to have more poles than in the above embodiment, and the iron core 43 Each salient pole 43a, 43b, 43c
Is divided into two forks. If the tip of the salient pole is bifurcated in this manner, the load on the yoke plate can be reduced.

Further, in the embodiment shown in FIG. 5, the components corresponding to the embodiments of FIGS. 1 and 2 are represented by replacing the tens sign "2" with "5". In this embodiment, the magnetic path forming projections of the yoke plates 56 and 58 are increased in number as shown by reference numerals 56a to 56h and 58a to 58h to make them multi-pole, and the number of salient poles of the iron core 53 is set to 53.
It is increased like a to 53f.

Furthermore, in the embodiment shown in FIG. 6, the structure corresponding to the above-mentioned first embodiment is
The tens place "2" in the reference numeral is shown in place of the reference numeral "6". In the present embodiment, the magnetic path forming projections 66a and 68a provided on the two yoke plates 66 and 68 face the circumferential end surface of the iron core 63 on the armature side and are substantially L-shaped in the axial direction.
It is bent in a letter shape.

Next, the embodiment shown in FIG. 7 is one in which the present invention is applied to a two-phase motor, and regarding the structure corresponding to the first embodiment, the tenth digit "" in the reference numeral. 2 "is replaced with the reference numeral" 7 ". The armature in this embodiment has a pair of iron cores 73, 73, and salient poles 73a, 73b provided at both ends of one iron core 73 and salient poles provided at both ends of the other iron core 73. 73c, 73d
Are the magnetic path forming projections 76a to 7 of the yoke plates 76 and 78.
6h and 78a to 78h are arranged so as to approach and separate from each other.

Further, in the embodiment shown in FIGS. 8 and 9, the constituent corresponding to the above-mentioned first embodiment is represented by replacing the tens place "2" with the reference "8". ing. In the present embodiment, the armature and the field magnet in each of the above-described embodiments are arranged with the inside and the outside being in an inverse relationship, and the cylindrical field magnet 87 constituting the rotor is An armature iron core 83 and a coil 84 are arranged on the outer peripheral side so as to form a stator. The iron core 83 is 3
It is provided with salient poles 83a, 83b, 83c of the body, and is arranged only in a part in the circumferential direction.

As described above, in the present invention, armatures and field magnets having various shapes can be adopted, and similar actions and effects can be obtained.

[0034]

As described above, in the stepping motor according to the present invention, the total magnetic flux of the field magnet is concentrated so as to be repeatedly inverted on the iron core side of the armature by the shape of the yoke plate attached to the field magnet. Since the multi-pole is performed by the structure in which the total magnetic flux of the field magnet is concentrated without being dispersed, the multi-pole magnetization is not performed on the field magnet as in the conventional case.
Moreover, while simply maintaining the structure on the armature side, it is possible to increase the number of magnetic poles and the effective magnetic flux at the same time by making maximum use of the magnetic flux from the field magnet at all times.
The / N characteristic value can be significantly improved.

[Brief description of drawings]

FIG. 1 is an explanatory plan view showing a stepping motor according to a first embodiment of the invention.

2 is a cross-sectional explanatory view showing the structure of the stepping motor shown in FIG.

[Fig. 3] Magnetic flux Φ during one rotation of the stepping motor
It is the diagram which compared the change of.

FIG. 4 is a plan view showing a stepping motor according to a second embodiment of the invention.

FIG. 5 is a plan view showing a stepping motor according to a third embodiment of the invention.

FIG. 6 is a half cross-sectional explanatory view showing a stepping motor according to a fourth embodiment of the present invention.

FIG. 7 is an explanatory plan view showing a stepping motor according to a fifth embodiment of the present invention.

FIG. 8 is an explanatory plan view showing a stepping motor according to a sixth embodiment of the present invention.

9 is a cross-sectional explanatory diagram showing the structure of the stepping motor shown in FIG.

FIG. 10 is a plan view showing an example of a conventional stepping motor.

11 is a cross-sectional explanatory diagram showing the structure of the stepping motor shown in FIG.

FIG. 12 is an explanatory plan view showing another example of a conventional stepping motor.

[Explanation of symbols]

23,43,53,63,73,83 Iron core 24,44,54,64,74,84 Coil 26,46,56,66,76,86 Yoke plate 28,48,58,68,78,88 Yoke plate 27, 47, 57, 67, 77, 87 Field magnets 26a, 26b, 26c, 28a, 28b, 28c Magnetic path forming projections 46a to 46h, 48a to 48h Magnetic path forming projections 56a to 56h, 58a ... 58h Magnetic path forming projections 66a to 66h, 68a to 68h Magnetic path forming projections 76a to 76h, 78a to 78h Magnetic path forming projections 86a to 86i, 88a to 88i Magnetic path forming projections

Claims (2)

[Claims] 1. A stepping motor having an armature, in which coils of a plurality of phases are wound around an iron core, and a field magnet arranged so as to be movable relative to the armature, wherein the field magnet is Extends in the direction of relative movement with the armature,
In addition, the yoke plate is magnetized in a direction orthogonal to the extending direction, and a yoke plate is attached to each of the magnetized end faces of the field magnet along the extending direction of the field magnet. Each of the yoke plates is provided with a plurality of magnetic path forming protrusions arranged at a predetermined pitch in the extending direction of the yoke plates, and the iron core and the magnetic path forming protrusions are field magnets. The magnetic fluxes of the magnetic fluxes of the magnetic field forming convex portions are arranged close to and away from each other so as to be focused on the iron core, and the direction of the magnetic flux passing through the iron core is determined by the relative pitch between the armature and the field magnet. A stepping motor, which is provided in a positional relationship of reversing for each. 2. The stepping motor according to claim 1, wherein the field magnet and the yoke plate forming the rotor are arranged on the outer peripheral side of the armature forming the stator.