JPH11356031A - Rotor of stepping motor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a number of machining man-hours, by placing first and second iron cores in positions shifted from each other by 1/2 teeth in a mold by means of a positioning portion, and integrally molding a portion equivalent to a magnet between them using magnet material. SOLUTION: The rotor 3 of the stepping motor comprises a core portion 4 and a shaft 5, and iron cores 41, 42 are in cylindrical shape of the same diameter. Teeth 45... extending in the axial direction are formed on the circumference of the iron cores in a gear-like pattern, and the teeth 45, 45 are shifted from each other by 1/2 teeth. A portion 43 equivalent to a magnet coupling the iron cores 41, 42 together and a shaft receiving portion 44 in which the shaft 5 is inserted and supported form the core portion 4. The core portion 4 can be completed in one process by molding it by such a means as an injection molding machine or the like using a plastic magnet. As a result, when the molding process is completed, a rotor with the relative positions of the teeth of the first and second iron cores fixed is obtained. Therefore, a positioning jig which is required for conventional assembling processes is obviated, and a number of machining man-hours can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor for a stepping motor and a method of manufacturing the same, and more particularly, to shortening a machining time, eliminating the need for alignment and positioning work required for a positioning jig, and using an expensive stainless steel for a shaft. The present invention relates to a rotor and a manufacturing method that do not require the use of steel.

[0002]

2. Description of the Related Art In a rotor of a stepping motor, an iron core is manufactured by laminating a plurality of thin steel plates having teeth on the outer periphery.
In a state in which the teeth of two iron cores are shifted from each other by １ ／ in the circumferential direction, a permanent magnet is sandwiched between the two, and a shaft is inserted through these and supported.

[0003]

However, due to the structure of the conventional rotor, in order to support the two iron cores in a state where the shafts are shifted by half by press-fitting the shaft, the two iron cores are mutually moved. Jigs and tools to fix in place were required.

When a magnet sandwiched between both iron cores is magnetized in the axial direction, if the shaft is made of a magnetic material, a closed magnetic path is formed between the shaft and the iron core, and the magnetic force of the outer teeth is extremely reduced. There was a problem, and to prevent this, it was necessary to use expensive stainless steel, which was a non-magnetic material.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks. A first object is to reduce the number of processing steps, and a second object is to improve a magnetic circuit to reduce expensive stainless steel. The goal is to avoid having to use it.

[0006]

SUMMARY OF THE INVENTION Accordingly, a rotor of a stepping motor according to the present invention is sandwiched between first and second iron cores having a plurality of teeth formed on an outer peripheral surface thereof and gears. In the rotor of the stepping motor composed of a core portion made of a magnet and a shaft that inserts and supports the core portion, the first and second iron cores are formed with positioning portions for performing mutual positioning. The first and second iron cores mutually move their teeth in the circumferential direction by the positioning portion.
While the two cores are opposed to each other in a shifted state, a portion corresponding to the magnet of the core portion is integrally formed of a magnet material between the first and second cores.

One of the features of the present invention is that a positioning portion is formed on the first and second cores, and the first and second cores are shifted from each other by a half tooth in the molding die by the positioning portion. And a portion corresponding to the magnet is integrally formed with a magnet material between the two. This eliminates the need for a positioning jig required for shifting the tooth portions of the first and second iron cores by half, thereby achieving the first object.

The positioning portion may be any type,
Holes and notches should be used. The first and second cores are positioned relative to each other by using a positioning portion. In the case of the above-mentioned hole or notch, for example, the positioning can be performed by setting the pin or the like on a molding die. Thus, when the forming step is completed, the first and second iron cores automatically have a relationship shifted from each other by １ ／ in the circumferential direction.

The first and second iron cores may be formed by laminating a plurality of thin steel sheets punched in the same manner as in the prior art. However, it is considered that a portion corresponding to a magnet is integrally formed between the first and second iron cores. Then, the first and second cores are formed into a bowl shape having a predetermined height formed on the outer peripheral edge of the circular bottom wall, and a plurality of teeth are formed on the outer peripheral surface of the side wall. It may be formed in a gear shape while extending in the vertical direction, and a hole may be formed in the center of the bottom wall portion, and a shaft receiving portion constituting a shaft or a core portion may be inserted into the hole.

As the magnet material, for example, a plastic magnet or a rubber magnet can be used, but of course, other magnet materials may be used.

Further, according to the present invention, a core portion comprising a first and a second iron core having a plurality of teeth formed on the outer peripheral surface thereof in a gear shape and a magnet sandwiched between the two iron cores, When manufacturing a rotor of a stepping motor composed of a shaft for inserting and supporting the first and second cores, a positioning portion for performing mutual positioning is formed on the first and second iron cores.
The second core is set in the forming die so as to face the same, and the tooth portions of the first and second cores are set to 1/2 in the circumferential direction by the positioning portion.
In this state, a magnet material is injected into the mold so that a portion corresponding to the magnet of the core is integrally formed between the first and second iron cores. The manufacturing method of the rotor of the stepping motor which can be provided.

More specifically, the method of positioning the iron core is a quarter of a straight line passing through the center line of the shaft and perpendicular to the center line on the side surfaces of the first and second iron cores in the circumferential direction opposite to each other.
At least one hole or notch is formed as a positioning portion at a position shifted from the tooth, and the first and second iron cores are opposed to each other on their side surfaces, and the holes or notches are overlapped on the same axis, whereby the first, A method of arranging the tooth portions of the second iron cores so as to be shifted by １ ／ from each other can be adopted.

Although the shaft may be press-fitted into the shaft receiving portion, the shaft receiving portion is formed by using a magnetic material. Therefore, the shaft is set as an insert part in a molding die and subjected to insert molding. Well,
In that case, there is no need to separately provide a shaft press-fitting step.

Further, a part of the shaft receiving portion can be used as a shaft. That is, the shaft receiving portion can be integrally formed with a shaft functional portion which has a shape of a shaft and is supported by the bearing.

In the present invention, it is important to improve the magnetic circuit in order to achieve the second object. Therefore,
When the gap is provided by making the center hole diameter of the first and second cores larger than the outer diameter of the shaft, the magnetic flux leaking to the shaft side can be greatly reduced. That is, the hole diameter at the center of the bottom wall of the first and second iron cores is preferably set to a size having a predetermined gap between the hole diameter and the outer diameter of the shaft.

[0016]

According to the present invention, the first and second cores are provided with positioning portions to position the teeth in a predetermined relationship with each other, and the core is located between the first and second cores. Since the portion corresponding to the magnet of the portion is integrally molded, when the molding process is completed, a rotor in which the relative positions of the teeth of the first and second iron cores are fixed is obtained, which is required in the conventional assembly process. No positioning jig is required, and the number of processing steps can be reduced.

Further, since the gaps are provided by making the diameters of the center holes of the first and second cores larger than the outer diameter of the shaft, magnetic leakage to the shaft side is greatly reduced, and a short circuit of the magnetic circuit is substantially prevented. Therefore, there is no need to use expensive non-magnetic stainless steel for the shaft, and it is possible to use an inexpensive magnetic material.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to specific examples shown in the drawings. FIG. 1 is a cross-sectional view showing an example of the overall configuration of a stepping motor having a rotor that is an object of the present invention.
FIG. 2 is a diagram showing a cross-sectional side surface (a), a main part front surface (b), and a main part rear surface (c) of a preferred embodiment of the rotor according to the present invention.
Is a sectional side view (a) of the second embodiment of the rotor according to the present invention.
FIG. 4 is a view showing a front part (b) and a rear part (c) of a main part, and FIG. 4 is a front view showing an example of a rotor (a) having a positioning hole and a rotor (b) having a notch for positioning. FIGS. 5, 5 and 6 are diagrams for explaining a magnetic circuit in the rotor according to the present invention, and FIG. 7 shows another embodiment (a) and (b) of a rotor in which a shaft is integrally formed by insert molding. FIG. 8 is a view showing another embodiment (a) and (b) of a rotor in which a shaft is made of a magnetic material, and FIG. 9 is a view showing an example of a conventional rotor.

First, the configuration of the stepping motor will be described. As shown in FIG. 1, the stator 1 is fixedly held on the inner surface of the housing 2, and brackets 61 and 62 are fitted and fixed to both ends of the housing 2. On the other hand,
The rotor 3 comprises a core portion 4 and a shaft 5. The shaft 5 is rotatably supported by bearings 71 and 72. The bearings 71 and 72 are held by the brackets 61 and 62. Pulley 8 as a driving means
Is attached.

Next, a conventional rotor will be described to facilitate understanding of the present invention. For example, in FIG.
1 is the first core, 42 is the second core, 49 is the first and second cores.
The core portion 4 is constituted by the magnets sandwiched between the iron cores 41 and 42. Reference numeral 5 denotes a shaft for inserting and supporting the core portion 4.

The first and second cores 41 and 42 are manufactured by laminating a plurality of punched thin steel plates, and have, for example, 50 teeth on the outer periphery thereof. Since the iron core 41 and the second iron core 42 have their teeth shifted from each other by ず, the shaft 5 is inserted (or press-fitted).
In this case, a jig or the like for accurately positioning both iron cores 41 and 42 with each other is required.

The shaft 5 is connected to the first and second iron cores 41 and 42.
In order to apply the Hameai theory between the hole diameters of the iron cores 41 and 42 and the shaft diameter of the shaft 5, it is necessary to accurately and precisely control the dimensions of both the cores 41 and 42 in order to press-fit them properly.

In the conventional rotor 3 configured as described above, the magnet 49 is magnetized in the direction indicated by the arrow a, and the rotor 3 and the stator 1 are indicated by solid lines b and c in FIG. A magnetic circuit is configured. Although the magnetic circuit indicated by the solid line b is necessary for the motor function, it is preferable that the magnetic circuit indicated by the solid line c is not provided.

However, since the magnet 49 is actually magnetized in the axial direction, a magnetic circuit indicated by a solid line c is generated. Therefore, when the shaft 5 is made of a magnetic material, a magnetic short circuit is substantially formed, and the magnetic force of the magnetic circuit indicated by the solid line b is greatly reduced. Therefore, in order to prevent this, generally expensive stainless steel has to be used for the shaft 5.

FIGS. 2 to 8 solve the drawbacks of the conventional rotor described above, which eliminates the necessity of aligning and positioning operations requiring jigs and tools, and eliminates the use of expensive stainless steel for the shaft. A preferred embodiment of the rotor of the stepping motor according to the present invention will be described.

FIG. 2 shows a first embodiment. In the drawing, reference numerals 41 and 42 denote cylindrical cores having the same diameter, and have, for example, 50 tooth portions 45... Extending in the axial direction on the outer peripheral surface thereof formed in a gear shape. (B) and
As shown in (c), the teeth 45, 45
/ 2 teeth are set.

Reference numeral 43 denotes a portion corresponding to a magnet connecting the iron cores 41 and 42, and reference numeral 44 denotes a shaft receiving portion through which the shaft 5 is inserted and supported.

The core portion 4 configured as described above can be molded in a general manner. That is, the core portion 4 can be completed in one step by molding using a plastic magnet by means such as an injection molding machine. This eliminates the need for the conventional mutual alignment of the iron cores 41 and 42. The shaft 5 is pressed into the shaft receiving portion 44 to complete the rotor 3.

FIG. 3 shows a second embodiment. In the figure, 41 and 42 are iron cores. The iron cores 41 and 42 are manufactured in a bowl shape having a side wall portion having a predetermined height around a circular bottom wall portion by, for example, adding drawing and forging to the forging process. Are formed in a gear shape, and a shaft receiving portion 44 is provided at the center of the bottom wall portion.
A hole 46 is formed in which is fitted. There is an advantage that the number of parts is reduced as compared with the method of laminating a plurality of thin plates.

FIG. 4 shows an example of the positioning method in the embodiment shown in FIGS. (A) of FIG.
2 is an example in which two holes 47 are provided, and FIG. 2B is an example in which two notches 48 are provided. The two holes 47 or the notches 48 are provided on a straight line that is shifted by 1/4 tooth from the center of the tooth portion 45. The same surfaces of both iron cores 41, 42 are opposed to each other, and holes 47, 47 or
When the positions 8 and 48 are located, the required half-tooth deviation between the iron core 41 and the iron core 42 is obtained.

In order to obtain this relationship, the tooth portions 45, 4
Hole 47 on a straight line shifted 1/4 tooth from the center of the groove between 5
Alternatively, a notch 48 may be provided.

For example, this hole 47 is formed in a molding die (not shown).
Alternatively, if positioning means (positioning portions) such as pins that can cooperate with each other by engaging with the notch 48 are provided, the iron cores 41 and 4 can be provided.
By setting 2 in the mold, both cores 4
The relationship of 1/2 tooth shift is obtained for the tooth portions 45, 45 of 1, 42. The number and positions of the holes 47 can be appropriately determined in consideration of the purpose of facilitating cooling by passing air in the axial direction.

FIGS. 5 and 6 show a magnetic circuit constituted by the rotor 3 and the stator 1 according to the present invention.
As shown by an arrow a in FIG. 6, the magnet-equivalent portion 43 is magnetized in the axial direction. A magnetic circuit b on the stator 1 side and a magnetic circuit c on the shaft 5 are configured. However, since the iron cores 41 and 42 are separated from the shaft 5 in the magnetic circuit c, the distributed magnetic force is the magnetic force of the stator 1. It is smaller than circuit b and can be substantially ignored. Therefore, there is an excellent effect that it is not necessary to use a non-magnetic material for the material of the shaft 5. As a result, there is no need to use expensive stainless steel, and inexpensive carbon steel can be used.

FIGS. 7A and 7B show an embodiment in which the shaft 5 is set as an insert part in a molding machine or the like and integrally molded. In the figure, reference numerals 51, 51 denote protrusions for preventing rotation and retaining. Generally, the press-fitting requires thorough dimensional control in order to apply the hammer-eye theory of the hole and the shaft. However, if the shaft 5 and the rotor 3 are integrally formed as in this example, such control becomes unnecessary. Further, it goes without saying that the degree of freedom in the shape of the ridges 51 for preventing rotation and retaining can be increased as compared with the conventional press-fitting method.

FIG. 8 shows an embodiment in which the shaft corresponding portion 52 is integrally formed with the shaft receiving portion 44. In this example, there is an effect that the shaft 5 does not need to be separately prepared.
In addition, the shaft equivalent portion 52 can be reinforced by the mandrel 53 if necessary.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an overall configuration example of a stepping motor having a rotor that is an object of the present invention.

FIG. 2 is a diagram showing a cross-sectional configuration (a), a main part front (b), and a main part back (c) of a preferred embodiment of a rotor according to the present invention.

FIG. 3 is a diagram showing a cross-sectional configuration (a), a main part front (b), and a main part back (c) of a rotor according to a second embodiment of the present invention.

4 is a diagram showing a side surface (a) of the iron core in the embodiment of FIG. 2 and a side surface (b) of the iron core in the embodiment of FIG.

FIG. 5 is a diagram for explaining a magnetic circuit formed in the embodiment of FIG. 2;

FIG. 6 is a diagram for explaining a magnetic circuit formed in the embodiment of FIG. 3;

FIG. 7 is a view showing another embodiment (a) or (b) in which a shaft is integrally insert-molded.

FIG. 8 shows another embodiment in which the shaft is made of a magnetic material.
It is a figure showing (a) and (b).

FIG. 9 is a cross-sectional view showing a configuration of a conventional rotor.

[Explanation of symbols]

 Reference Signs List 3 rotor 4 core part 41, 42 first and second iron cores 43 magnet equivalent part 44 shaft receiving part 45 tooth part 46 center hole 47 positioning hole 48 positioning notch 5 shaft 52 shaft equivalent part

Claims (9)

[Claims] A first core having a plurality of teeth formed in a gear shape on an outer peripheral surface thereof, a core comprising magnets sandwiched between the two cores, and a shaft for inserting and supporting the core. In the rotor of the stepping motor, the first and second iron cores are formed with positioning portions for performing mutual positioning, and the first and second iron cores are toothed by the positioning portions. The cores are opposed to each other in a state in which the cores are shifted from each other in a circumferential direction by ２, and a portion corresponding to the magnet of the core is integrally formed of a magnet material between the first and second cores. A rotor for a stepping motor. 2. The method according to claim 1, wherein the first and second cores are formed in a bowl shape with a side wall having a predetermined height formed on an outer peripheral edge of a circular bottom wall, and a plurality of teeth are formed on an outer peripheral surface of the side wall. Is formed in a gear shape by extending in the height direction of the side wall portion, while a hole is formed in the center of the bottom wall portion, and the shaft receiving portion constituting the shaft or the core portion is inserted into the hole. The rotor of the stepping motor according to claim 1, wherein 3. The rotor for a stepping motor according to claim 1, wherein a hole diameter at a center portion of each of the first and second cores is a size having a predetermined gap with an outer diameter of the shaft. 4. The stepping motor rotor according to claim 1, wherein the magnet material corresponding to the magnet is a plastic magnet or a rubber magnet. 5. The rotor of a stepping motor according to claim 1, wherein the whole or a part of the shaft is formed integrally with the core by a magnetic material corresponding to the iron core. 6. The rotor for a stepping motor according to claim 1, wherein the portion corresponding to the magnet is magnetized in the axial direction. 7. A core comprising a first and second iron core having a plurality of teeth formed on an outer peripheral surface thereof in a gear shape and a magnet sandwiched between the two iron cores, and a shaft for inserting and supporting the core. In manufacturing the rotor of the stepping motor composed of: the first and second iron cores are formed with positioning portions for determining mutual measures, and the first and second iron cores are placed in a molding die. And the teeth of the first and second iron cores are shifted by 1/2 in the circumferential direction by the positioning portion. In this state, a magnet material is injected into the molding die, and A method for manufacturing a rotor of a stepping motor, wherein a portion corresponding to the magnet of the core is integrally formed between the first and second iron cores. 8. A side surface of each of the first and second cores is shifted from a straight line passing through a center line of the shaft and perpendicular to the center line by 1/4 tooth in a circumferential direction opposite to each other. By forming at least one hole or notch as the positioning portion, by opposing the first and second cores on their side surfaces and overlapping the hole or notch coaxially, the first and second holes are formed. 8. The method for manufacturing a rotor of a stepping motor according to claim 7, wherein the tooth portions of the two iron cores are shifted by 1/2 from each other. 9. The method for manufacturing a rotor of a stepping motor according to claim 7, wherein said shaft is insert-molded in said core portion.