JPH0951640A - Yoke structure for motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the structure of magnetic yoke in a motor wherein the rotary torque is enhanced without subjecting a magnetic plate to squeezing. SOLUTION: The base part 21a of pole tooth 21 is squeezed inward into neck-shape and an intermediate part 21b having a substantially linear edge is formed ahead thereof. A squeezed part 21c having steep edge part is formed ahead of the intermediate part 21b and followed by a head part 21d having small radius of curvature. Since the width is reduced significantly in the vicinity of head part of pole tooth, the effective width of pole tooth is increased thus increasing the effective cross-sectional area of magnetic path. This structure increases the number of effective flux and the rotary torque of motor while reducing the hysteresis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a yoke structure of a motor, and more particularly to a shape of a magnetic pole tooth of a yoke formed by press molding to project a central portion of a magnetic plate to form a plurality of magnetic pole teeth.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, as a structure of a magnetic yoke 10 used for a stepping motor or the like, a plurality of magnetic pole teeth 11 are formed by punching a central portion of a magnetic plate by a press, and the magnetic pole teeth 11 are formed. There is one formed by standing up in the axial direction by press molding. Pole teeth 11
The state before standing is shown by the dotted line in the figure, and the formation width is gradually narrowed from the base portion provided at the peripheral edge of the center hole 10a, and the tip end portion is formed in a curved end shape. . The motor has this magnetic yoke 10
, A stator or a rotor is used, in which an electromagnetic coil is housed between the magnetic yoke and another magnetic yoke, and the magnetic pole teeth 11 of the two magnetic yokes mesh with each other.

In order to increase the rotational torque of the motor, it is generally necessary to increase the diameter or the axial length of the rotor. However, if the diameter of the rotor is increased, the outer diameter is increased and the self-starting frequency of the motor is reduced. Therefore, by increasing the axial length of the rotor without increasing the diameter of the rotor, it is possible to increase the rotational torque without increasing the motor outer diameter and lowering the self-starting frequency.

However, the magnetic yoke 10 has good productivity because the center hole 10a and the magnetic pole teeth 11 can be formed simultaneously by press molding, but due to its structure, the magnetic pole teeth 1 are formed.
The length d of 1 can be formed only to a length shorter than the inner diameter R of the central hole 10a. Therefore, in the case of the inner rotor type, the inner diameter R of the central hole 10a is determined in accordance with the diameter of the rotor. Therefore, when the diameter of the rotor is determined, the maximum value of the length d of the magnetic pole teeth 11 is also determined due to the above-mentioned restriction. The axial length of the rotor is limited by the length d of the magnetic pole teeth 11.

As described above, in the conventional motor structure of this type, there is a predetermined limitation between the diameter and the length of the rotor, and it is not possible to freely set the dimensions to increase the rotational torque or the self-starting frequency. It was To solve this point, for example, as described in Japanese Patent Publication No. 1-32747,
The central portion of the magnetic plate is previously drawn into a trapezoidal shape or a bowl shape, and the shape portion is punched to make the length d of the magnetic pole tooth 11 larger than that shown in FIG.
Need to be formed long.

[0006]

In the method of forming a magnetic yoke by the above drawing process, the number of pressing steps is increased by one or more as compared with the usual press forming of a magnetic yoke.
The structure of the die used for punching the drawn portion becomes complicated and polishing is difficult. Moreover, since the magnetic pole teeth are formed to be long by the drawing process, it is necessary to increase the thickness of the original magnetic plate, and it is necessary to process with a larger press machine, resulting in an increase in processing cost. . In addition to this, it is difficult to maintain the die corresponding to the above drawing shape, and it is difficult to maintain the shape accuracy of the product.

Therefore, the present invention is to solve the above-mentioned problems, and an object thereof is to realize a structure of a magnetic yoke of a motor having a high rotational torque without performing a drawing process on a magnetic plate.

[0008]

Means for Solving the Problems In order to solve the above-mentioned problems, the means of the present invention is a motor provided with a plurality of magnetic pole teeth formed by projecting a central portion of a magnetic plate around a central hole by press molding. In the yoke structure of, the plane shape of the magnetic pole teeth formed by punching in the press molding is
On the base side of the magnetic pole teeth, the change rate of the formation width of the magnetic pole teeth seen in the protruding direction is formed small, and on the tip side of the magnetic pole teeth, the reduction rate of the formed width seen in the protruding direction is formed large. Characterize.

By forming the shape of the magnetic pole teeth with a small change in the forming width from the base portion and greatly reducing the forming width in the vicinity of the tips of the magnetic pole teeth, the effective width of the magnetic pole teeth is increased and the effective cross-sectional area of the magnetic path is increased. And the number of effective magnetic fluxes are increased, the rotational torque of the motor is also increased and the hysteresis is reduced. Further, by forming a large reduction rate of the forming width at the tip portion, it is possible to make the interval between the plurality of magnetic pole tooth tip portions larger than before, so that the punching width of the press can be sufficiently secured. The length of the magnetic pole teeth can be made relatively long.

[0010]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing the shape of an outer yoke 20 having five magnetic pole teeth 21. FIG.
3A is a diagram showing the overall shape of the outer yoke 20, FIG. 6B is a diagram showing a central portion for showing a punched shape by a press, and FIG. 4C is a diagram showing a state in which magnetic pole teeth are raised. It is a figure which shows a central part.

The method of manufacturing the outer yoke 20 is as follows. First, the central portion of the metal plate of the magnetic material is punched by a press as shown in (b) to form the shape of five mutually inward facing magnetic pole teeth as shown by the dotted line in (a). Next, as shown in (c), the metal plate is moved onto a die having a hole having the shape of the center hole 20a to form the center hole 2
The pole teeth 21 are erected in the axial direction of the center hole 20a by a punch having a shape of 0a. Center hole 2 if needed
The inner surface of the magnetic pole tooth 21 is subjected to a scoring process to improve the shape accuracy of the inner surface of the magnetic pole tooth 21.

As shown by the dotted line in FIG. 1 and FIG. 2, the base portion 21a of the magnetic pole tooth 21 is formed in the shape of a neck slightly hollowed inward,
An intermediate portion 21b having an edge formed in a substantially linear shape is formed at the tip thereof. At the tip of the intermediate portion 21b, a width reducing portion 21c having a sharp edge is formed, and a tip portion 21d having a small radius of curvature is formed following the width reducing portion 21c.

In the intermediate portion 21b, the formation width of the magnetic pole teeth 21 is slightly reduced toward the tip portion 21d, but in the width reduction portion 21c, the formation width is formed in the tip portion 21d.
Has been greatly reduced towards. In this way, by providing the portion of the magnetic pole tooth 21 whose width is greatly reduced, the effective width of the magnetic pole tooth 21 as a whole can be increased and the length of the magnetic pole tooth 21 can be increased. Even in this case, it is possible to secure a space between the tips of the adjacent magnetic pole teeth.

In order to perform stable punching during press working or to suppress the degree of wear of the die, the width of the punched portion is generally about 0.8 times the thickness of the metal plate, depending on the material. It is necessary to be above. In the punching process for forming the magnetic pole teeth, the gap between the adjacent magnetic pole teeth becomes small near the tip of the magnetic pole teeth as described above, so the length of the magnetic pole teeth should be centered in order to secure the width of the punched part. Hole 20a
Smaller than the inner diameter of. In the present invention, since the formation width is sharply reduced near the tips of the magnetic pole teeth, it is possible to reduce the degree to which the length of the magnetic pole teeth is made shorter than the inner diameter of the center hole in order to maintain the spacing near the tips.

In FIG. 2, the magnetic pole teeth 15 of which the length is increased by the conventional prior drawing process are shown by dotted lines. Magnetic pole tooth 1
In the reference numeral 5, the punched surface is expanded into a trapezoidal shape or a bowl shape by drawing, and the pole teeth are formed from the expanded punched surface to increase the length. On the other hand, the magnetic pole tooth 21 has substantially the same shape as the magnetic pole tooth 15, the base portion 21a and the intermediate portion 21b, but the width reducing portion 21c is formed on the tip side. The magnetic pole tooth 21 has a shorter protruding length than the magnetic pole tooth 15, but as described below, there is almost no difference in motor performance, and it is more effective in the manufacturing process.

FIG. 3 shows the outer yoke 20 shown in FIG.
An inner yoke 30 formed so as to fit to this
FIG. 3 is an exploded vertical sectional view showing a stator structure of a stepping motor including and. The inner yoke 30 is the outer yoke 20.
Magnetic pole teeth 31 similar to the magnetic pole teeth 21 of
The magnetic pole teeth 21 and the magnetic pole teeth 31 are arranged so as to be meshed with each other with a predetermined gap by being fitted so as to face 0.

Here, two outer yokes and two inner yokes are prepared, and the outer yoke 20 and the inner yoke 3 are provided.
The outer yoke 20 'and the inner yoke 30' face each other and are assembled. An electromagnetic coil 40 formed by winding a coil around a coil spool having an inner diameter corresponding to the center holes 20a and 20a 'is housed between each outer yoke and inner yoke.

The stator assembled from the outer yoke, the inner yoke, and the electromagnetic coil in this manner is mounted in a casing (not shown) with the rotor housed in the center hole thereof to form a stepping motor.

The power performance of a stepping motor having magnetic pole teeth 15 (hereinafter referred to as a conventional product) shown in FIG. 2 and a stepping motor having magnetic pole teeth 21 (hereinafter referred to as an improved product) were compared. Table 1 shows the results.

[0020]

[Table 1]

As shown in Table 1, the improved product is superior to the conventional product in the average value of the pull-in torque, although there is some variation, while the continuous response frequency and the self-starting frequency are slightly lowered. As a whole, the improved product has almost the same performance as the conventional product, and is greatly superior to the conventional product in manufacturing cost and processing accuracy.

In the above-described yoke structure according to the present invention, since the shape of the magnetic pole teeth is sharply reduced in the width in the vicinity of the tip, the effective cross-sectional area of the magnetic pole teeth is made larger than in the conventional case. In addition, since the length can be increased even if the effective area is increased, the number of effective magnetic flux of the magnetic circuit can be increased as a whole, and the motor performance can be improved. Therefore, according to the present invention, it is possible to obtain substantially the same motor performance as in the case where the length of the magnetic pole teeth is lengthened by the manufacturing method such as drawing by the orthodox manufacturing method. It has a great effect.

In the above-described embodiment, the magnetic pole teeth 21 and 31 are formed so that the middle portion and the width reduction portion are clearly defined, but the width reduction rate gradually increases toward the tip side. It may have a curvilinear shape so as to increase.

[Brief description of drawings]

FIG. 1 is a plan view showing a structure of an outer yoke according to the present invention (a), a plan view of a central portion showing a punched shape (b), and a plan view of a central portion showing a state in which magnetic pole teeth are raised (c). Is.

FIG. 2 is an explanatory diagram comparing the shapes of the magnetic pole teeth according to the present invention and the conventional magnetic pole teeth.

FIG. 3 is an exploded vertical sectional view showing a structure of a stator of a motor using an outer yoke and an inner yoke according to the present invention.

FIG. 4 is a plan view showing the structure of a conventional magnetic yoke.

[Explanation of symbols]

 20, 20 'Outer yoke 20a Center hole 21, 31 Magnetic pole teeth 21a Base 21b Intermediate part 21c Width reduction part 21d Tip part 30,30' Inner yoke 40 Electromagnetic coil

Claims (1)

[Claims] 1. A yoke structure of a motor having a plurality of magnetic pole teeth formed by projecting a central portion of a magnetic plate by press molding around a center hole, wherein a plane of the magnetic pole teeth formed by punching the press molding. The shape is formed so that the change rate of the forming width of the magnetic pole tooth viewed in the protruding direction is small on the base side of the magnetic pole tooth, and the decrease rate of the forming width viewed in the protruding direction is large on the tip side of the magnetic pole tooth. A motor yoke structure characterized by being formed.