JP2003018816A - Stepping motor and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stepping motor which assures higher quality and realizes accurate drive with lower noise. SOLUTION: A spacer 13 is formed to be deformed elastically when it is placed in contact with and pushed toward the end face of a magnet 11, height in the axial direction when the magnets 11, 12 and spacer 13 are stacked is set so that the accumulated height before the insertion mold coupling of these members is higher than the height after the insertion mold coupling thereof, and the insertion mold coupling is realized while both end faces of two magnets are pushed and held with the mold metallic die.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor (hereinafter referred to as a motor) mainly used for information related equipment, and more particularly to a structure of a rotor assembly (hereinafter referred to as a rotor) thereof.

[0002]

2. Description of the Related Art In recent years, stepping motors with ever higher reliability have been demanded in information equipment.

Motors are required to have high speed, high torque, low vibration and low noise as characteristics, and at the same time, high quality and high reliability are required. The rotor to which the present invention is applied has a structure in which two magnets that are substantially cylindrical and are magnetized in multiple poles on the circumference, a shaft, and a spacer are connected by a molding member. In this case, a thermoplastic resin such as polyethylene terephthalate or polybutylene terephthalate to which various fillers have been added has been used as the molded member.

However, in the above-mentioned conventional ones, the magnets run out due to the molding contraction, and further, the molding pressure causes the cracks to chronically occur on the outer peripheral surface of the magnets, which causes the quality to be limited. Therefore, the present applicant has been working on solving these problems, and the results thereof have been disclosed in Japanese Patent Laid-Open No. 2000-3247.
69 publication. Although details are omitted, a thermosetting resin having high fluidity, low molding pressure, and low molding shrinkage was developed and applied.

However, a new problem that cannot be solved only by the above invention has occurred. There is a rotor of a type in which two cylindrical magnets are stacked in the axial direction and separated by a spacer, and integrally molded with a shaft. In manufacturing this rotor, these members are placed in a molding die and filled with resin for molding, but at that time, there is a problem that the magnet and the molding die interfere with each other and the magnet is damaged. It was This is because there is an excess or deficiency in the cumulative size of the magnets and spacers and the size of the molding die. When the mold size is small, the end surface of the magnet is pressed by excessive force and is damaged. On the other hand, when the size of the mold is large, the position of the magnet in the axial direction varies and the motor characteristics also vary.

A technique for preventing the occurrence of cracks and cracks on the outer peripheral edge of the magnet end surface is disclosed in Japanese Patent No. 294243.
No. 4 is disclosed. This is one in which the end surface of the magnet is completely covered so that damage due to contact does not occur. Therefore, in the molding die, the magnet support member of the die supports the end surface of the magnet before the resin is injected, and moves to another when the resin is injected so that the end surface of the magnet is completely covered with the resin. . However, this does not solve the problem caused by the excess and shortage of the cumulative size of the magnet spacer and the size of the molding die.

[0007]

That is, the object of the present invention is to provide a rotor of the type in which two cylindrical magnets are axially overlapped with each other and separated by a spacer, and integrally molded with a shaft. To reduce cracks and chips in the magnet due to interference with the
This is to prevent the accuracy of the rotor from deteriorating due to variations in the position of the magnet in the mold. It is therefore an object of the present invention to provide a stepping motor which is of high quality and operates quietly and accurately.

At the same time, it has been a problem to prevent the quality of the injected resin from being deteriorated due to breaking in an indefinite shape near the gate opening. It is an object of the present invention to solve this and provide a high quality stepping motor.

[0009]

In order to solve the above problems, a stepping motor according to claim 1 of the present invention comprises two magnets arranged coaxially with each other, a spacer for axially separating them, and a central shaft. The magnet has a substantially cylindrical shape and is magnetized in the circumferential direction with multiple poles.The spacer has a substantially cylindrical shape and its axial compression rigidity is smaller than that of the magnet. At least a part of the end surface on the opposite side is closely pressed to the spacer, and at least a part of the end surface on the non-opposing side is exposed to be pressed and clamped by the molding die, and is insert-molded and coupled by the resin member together with the shaft. Become.

As described above, the end faces of the magnet and the spacer having a small axial compression rigidity are pressed against each other while being insert-molded and joined by the resin member. According to this
The two magnets are insert-molded and bonded while being pressed against the mold surfaces at both ends by the spacers. Therefore, the axial position of the magnet is uniquely determined by the mold without being influenced by the cumulative dimensions of the related members. Therefore, a highly accurate rotor can be obtained, and a stepping motor that performs quiet and accurate driving can be provided. Further, according to this, the spacer is compressed and deformed in the axial direction in the insert molding step, and excessive stress is not applied to the end surface of the magnet that abuts against the mold. Therefore, cracking and chipping of the magnet are reduced, and a high-quality stepping motor can be provided.

A stepping motor according to a second aspect of the present invention comprises two magnets arranged coaxially with each other,
A spacer that separates it in the axial direction, and a rotor that has a shaft that forms a central axis, the magnet is substantially cylindrical and is magnetized in multiple poles in the circumferential direction, and the spacer is substantially cylindrical.
At least one of the end faces has an inclined portion that is elastically deformable to the inner diameter side when contacting and pressing the inner peripheral side corner portion of the end face of the adjacent magnet, and the magnet has an inner periphery of the end face on the side facing the spacer. At least a part of the side corner portion is in close contact with the spacer and pressed, and at least a part of the end surface on the non-opposing side is exposed to be pressed and sandwiched by the molding die, and is insert-molded and joined by the resin member together with the shaft.

As described above, the inner peripheral side corner of the end face of the magnet and the elastically deformable inclined portion of the spacer are pressed against each other while being insert-molded and joined by the resin member. According to this, the two magnets are insert-molded while being pressed against the mold surfaces at both ends by the axial component force generated in the inclined portion of the spacer. Therefore, the axial position of the magnet is uniquely determined by the mold. Therefore, a highly accurate rotor can be obtained, and a stepping motor that performs quiet and accurate driving can be provided. Further, according to this, the spacer is compressed and deformed in the axial direction in the insert molding step, and excessive stress is not applied to the end surface of the magnet that abuts against the mold. Therefore, cracking and chipping of the magnet are reduced, and a high-quality stepping motor can be provided. According to this, due to the existence of the inclined portion,
The axial displacement of the magnet per unit deformation of the spacer can be increased. Therefore, the axial dimension tolerance of the magnet can be expanded, and a low-cost stepping motor can be provided.

In a stepping motor according to a third aspect of the present invention, the spacer is provided with a compression-deformable projection on at least one end surface facing the magnet end surface. According to this, most of the space between the two magnets can be filled with the spacer, and the axial compression rigidity can be reduced. Therefore, while controlling the inertia of the rotor with the spacer, it is possible to obtain a rotor with few cracks and chips of the magnet and high positional accuracy.

In the stepping motor according to a fourth aspect of the present invention, the spacer has at least one end face facing the end face of the magnet formed in a wavy shape. This is to reduce the axial compression rigidity by forming the end face in a corrugated shape. Suitable for spacers made of relatively soft material.

In the stepping motor according to a fifth aspect of the present invention, the resin member is made of a thermosetting resin containing an unsaturated polyester resin in a weight ratio of 10% or more and 30% or less.

According to this, since the molding fluidity is good, the molding pressure can be lowered. Therefore, there is no fear that the magnet will be cracked by the molding pressure from the inner circumference side, and there may be a gap in the portion corresponding to the outer circumference of the magnet of the mold,
It may be a simple cylindrical cavity. Then, since the magnet can be moved in the axial direction within the mold, the resin molding can be performed while stably and reliably performing the operation of pressing and holding the magnet at both ends by the spacer. As a result, cracking and chipping of the magnet are reduced, and a high-quality stepping motor can be provided.

On the other hand, in the conventional thermoplastic resin, high molding pressure must be applied. Therefore, a slit is formed in a portion of the die corresponding to the outer circumference of the magnet so as to have a variable diameter, and the die is tightened to be in close contact with the outer circumferential surface of the magnet to prevent the magnet from cracking due to a high molding pressure. Then, the magnet cannot move in the axial direction inside the mold, and it may be damaged when the end face of the magnet is sandwiched by the mold,
The coating on the outer peripheral surface was sometimes peeled off. Therefore, a high quality stepping motor cannot be provided.

In order to prevent this, it is necessary to make the cumulative size of the magnet and the spacer smaller than the size of the mold, resulting in variation in the coupling position of the magnet. Therefore, a high-precision rotor cannot be obtained, and a stepping motor that performs quiet and accurate driving cannot be provided.

In the method for manufacturing a stepping motor according to claim 6 of the present invention, two substantially cylindrical magnets, a substantially cylindrical spacer that axially separates the magnets, and a shaft forming a central axis are provided in a molding die. A stepping motor manufacturing method comprising a rotor arranged and filled with resin and insert-molded and coupled, wherein the spacer is made elastically deformable when pressed against the end face side of the magnet, and the magnet and the spacer are overlapped. The height in the axial direction after the insert molding and joining is smaller than the cumulative height of these members before the insert molding and joining, and the insert molding is performed while pressing both end faces of the two magnets with the molding die. Combined.

In this manner, the insert molding is performed while pressing the two end surfaces of the two magnets with the molding die while sandwiching them. According to this, the magnet is resin-molded while its end face is pressed against the mold. Therefore, since the axial position of the magnet is uniquely determined by the mold, a highly accurate rotor can be obtained, and a stepping motor that performs quiet and accurate driving can be provided.

According to a seventh aspect of the present invention, in a stepping motor manufacturing method, a substantially cylindrical magnet and a shaft forming a central axis are arranged in a molding die, and a rotor is filled with resin and insert-molded and joined. A method of manufacturing a stepping motor, comprising: a molding die having a gate opening inside the outer diameter of the magnet on the end surface side of the magnet, wherein the gate opening has a substantially V-shaped tip that closely faces the end surface of the magnet. A mold movable pin is provided, and when the resin is filled in the cavity, the movable pin is retracted and separated, and the movable pin is moved forward and close until the resin is cured, and the gate port is formed thin in the axial direction.

According to this, the resin in a fluid state is reasonably separated into the inside and outside of the cavity by the V-shaped surface of the movable pin. At this time, the movable pin may be moved forward and close to a state where there is almost no gap. The V-shaped portion, which is the breaking portion, does not project outside the outer diameter of the magnet, and the quality of the rotor is kept good. Further, according to this, the resin in a semi-solid state having low fluidity is separated into the inside and outside of the cavity by the V-shaped surface of the movable pin, and at the same time, the resin near the thin gate port is broken by tensile stress. That is, the runner automatic separation method can be adopted. Then, since the fractured portion is not fractured by human power, the shape is stable and the quality of the rotor is kept good. Therefore, a high quality stepping motor can be provided.

If the invention is carried out with the invention in which both end faces of two magnets are pressed and sandwiched by a molding die and insert molding is carried out, the end faces of the magnets are always pressed against the die faces and are kept in good positional accuracy. The shape of the fractured part formed between the end face of the and the movable pin having a substantially V-shaped tip is always kept uniform. Therefore, a high quality stepping motor can be provided.

The inclined surface forming the V-shape at the tip of the movable pin may be provided on both inside and outside of the cavity, or only one of them may be provided. A side gate is suitable for the gate method. Also, the resin used should be a highly fluid resin,
A liquid crystal polymer or the like may be used as long as the magnet has sufficient strength.

In the stepping motor manufacturing method according to the eighth aspect of the present invention, the resin is a thermosetting resin containing an unsaturated polyester resin in a weight ratio of 10% or more and 30% or less. According to this, since the molding fluidity is good, the molding pressure can be lowered. Then, it is possible to select a side gate that is generally difficult to select. It is suitable for adopting the runner automatic separation method without the runner clogging occurring in the pin gate.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a sectional view of a rotor of a motor according to a first embodiment. FIG. 2 is a shape diagram of the spacer. In FIG. 1, the rotor has two magnets 11 and 12 that are arranged coaxially with each other, a spacer 13 that axially separates them, and a shaft 14 that forms a central axis. The magnets 11 and 12 have a substantially cylindrical shape and are magnetized in a circumferential direction with multiple poles. The spacer 13 has a substantially cylindrical shape, and as shown in FIG. 2, one end surface of the cylindrical portion 13a is provided with a small protrusion 13b which is pressed by the magnet 11 or 12 and can be compressed and deformed. And these are arrange | positioned in a metal mold | die, the resin member 15 is inject | poured, and insert molding is carried out, and the rotor is shape | molded.

This resin member has a weight ratio of 10% to 30%.
It is a thermosetting resin containing the following unsaturated polyester resin. This resin has a faster curing rate than general thermosetting resins, shortens the molding time, and improves the productivity. Further, in the above numerical range, a stable rotor can be constructed by obtaining good fluidity, mechanical properties, molding shrinkage and thermal expansion. Further, when the resin member contains an unsaturated polyester resin having a weight ratio of 10% or more and 30% or less and a thermoplastic resin having a weight ratio of 10% or more and 30% or less with respect to the unsaturated polyester resin, the thermoplastic resin becomes It plays a role of generating internal pressure to further reduce the shrinkage of the thermosetting resin.

Then, these are molded using a molding die. The two magnets 11 and 12, the spacer 13, and the shaft 14 are arranged in a molding die, and resin is filled to form a resin member 15 to form a rotor. At this time, the magnet 11
The axial height in which 12 and the spacer 13 are overlapped is set so that the height after insert molding connection is smaller than the cumulative height of these members before insert molding connection. Then, both ends of the two magnets 11 and 12 are pressed and sandwiched by a molding die, and insert molding is performed. At this time, the resin member covers the end faces of the magnets 11 and 12 over about half the width thereof and exposes over the remaining half width. This exposed portion is the portion that is pressed and sandwiched by the mold.

As described above, the spacer 13 in this embodiment is composed of the cylindrical portion 13a and the protruding portion 13b provided on the end surface thereof. And the magnet 1 1
2 and the spacer 13 are overlapped with each other, the axial height is
When there is b, it is set larger than the size of the molding die, and when there is no protrusion 13b, it is set smaller than the size of the molding die. Therefore, although a slight gap is opened between the magnet 12 and the cylindrical portion 13a of the spacer, the resin flows into the gap and is filled with the same outer diameter as the cylindrical magnet.

(Second Embodiment) FIG. 3 is a shape view of a spacer 23 of a motor according to another embodiment. As shown, the protrusions 23b are provided on both end surfaces of the cylindrical portion 23a. There is no direction when assembling the spacer,
In addition, the deformation rigidity can be reduced. Also, the rotor can be made axially symmetrical.

Two spacers having a protrusion on one side may be stacked in the axial direction. Providing protrusions on both end faces has the same effect.

(Third Embodiment) FIG. 4 is a shape view of a spacer 33 of a motor according to still another embodiment. In FIG. 4, the end surface 33b of the spacer 33 is formed in a wavy shape. By forming the end faces in a wavy shape, the axial compression rigidity is reduced. Suitable for spacers made of relatively soft material.

(Embodiment 4) FIG. 5 is a sectional view of a rotor of a motor according to still another embodiment. The spacer 43 has a substantially cylindrical shape, and one end surface of the spacer 43 is
An inclined portion 43b that is elastically deformable is provided on the inner diameter side when the inner peripheral side corner portion of the end surface of the adjacent magnet is pressed against. The inner peripheral side corner of the end surface of the magnet 11 facing the spacer 43 is pressed closely against the inclined portion 43b. On the other hand, the end faces on the side not facing each other are pressed and sandwiched by the molding die.
Then, it is insert-molded and coupled by a resin member 45 together with the shaft 14.

According to this, the spacer 43 is compressed and deformed in the axial direction in the insert molding step, and excessive stress is not applied to the end surface of the magnet that abuts against the mold. Therefore, cracking and chipping of the magnet are reduced, and a high-quality stepping motor can be provided. Further, according to this, the axial displacement of the magnet 11 per unit deformation of the spacer 43 can be increased due to the existence of the inclined portion 43b. Therefore, the axial dimensional tolerance of the magnets 11 and 12 can be increased, and a low-priced stepping motor can be provided.

(Embodiment 5) FIG. 6 is a partially enlarged sectional view of a rotor and a molding die of a motor of a motor according to still another embodiment. (A) shows the state at the time of resin injection, (b) shows the state after resin injection.

In the figure, the rotor is composed of a substantially cylindrical magnet 51, a spacer 53, and a resin 55 to be injected and filled. The shaft is not shown.

After arranging these in the lower mold 56, the upper mold 57 is overlapped to form a cavity. Then, as shown in the figure, the resin 55 is filled and insert molding is performed. This molding die is of a side gate type, and has a gate port 58 on the end face side of the magnet 51 inside the outer diameter of the magnet 51. A movable pin 59 having a substantially V-shaped tip is provided at the gate opening so as to closely face the end surface of the magnet. When the cavity is filled with resin, the movable pin 59 is retracted and separated as shown in FIG. 6A, and the movable pin 59 is advanced and approached as shown in FIG. It is formed thin in the axial direction. At this time, the runner 61 can be automatically separated by bringing the movable pin forward and close to a state where there is almost no gap.

The inclined surfaces forming the V-shape at the tip of the movable pin 59 may be provided on both inside and outside of the cavity as in the present embodiment, or only one of them may be provided.

Although several embodiments have been described above,
The present invention is not limited to the above-mentioned embodiment, and various application developments are possible within the scope of the gist of the present invention.

[0041]

As described above, according to the present invention, 2
In a rotor of the type in which two cylindrical magnets are stacked in the axial direction and separated by a spacer, and integrally molded with the shaft, it is possible to reduce cracking and chipping of the magnet due to interference between the magnet and the molding die. Thus, it is possible to prevent the accuracy of the rotor from being deteriorated due to the variation in the position of the magnet. As a result, it is possible to provide a stepping motor that is of high quality and operates quietly and accurately.

Further, it is possible to provide a high quality stepping motor by preventing the quality of the injected resin from being broken by an indefinite shape in the vicinity of the gate opening thereof and deteriorating the quality.

[Brief description of drawings]

FIG. 1 is a sectional view of a rotor of a motor according to a first embodiment.

2A is a motor spacer 1 according to the first embodiment; FIG.
3B is a side view of FIG.

FIG. 3A is a side view of a spacer 23 of a motor according to another embodiment, and FIG.

FIG. 4A is a side view of a spacer 33 of a motor according to still another embodiment, and FIG.

FIG. 5 is a sectional view of a rotor of a motor according to still another embodiment.

6A is a partially enlarged cross-sectional view of a rotor of a motor and a molding die thereof according to another embodiment. FIG. 6B is a partially enlarged cross-sectional view of a rotor of a motor and a molding die thereof according to another embodiment.

[Explanation of symbols]

11, 12, 51 magnets 13, 23, 33, 43, 53 Spacer 13a, 23a cylindrical part 13b, 23b Projection 33b wavy end face 43b inclined part 14 shaft 15, 45, 55 Resin, resin member 56 Lower mold 57 Upper mold 58 gate 59 Movable pin 61 runner

Claims (8)

[Claims] 1. A magnet having two magnets arranged coaxially with each other, a spacer for axially separating the magnets, and a rotor having a shaft serving as a central axis, wherein the magnets are substantially cylindrical and magnetized in a circumferential direction with multiple poles. The spacer is formed in a substantially cylindrical shape and has an axial compressive rigidity smaller than that of the magnet, and at least a part of the end surface of the magnet that faces the spacer is in close contact with the spacer and does not face the spacer. A stepping motor, which is insert-molded together with the shaft by a resin member in a state where at least a part of the end surface on the side is exposed so as to be pressed and sandwiched by a molding die. 2. A magnet having two magnets arranged coaxially with each other, a spacer for axially separating the magnets, and a rotor having a shaft serving as a central axis, wherein the magnets are substantially cylindrical and are magnetized in a circumferential direction with multiple poles. The spacer has a substantially cylindrical shape, and at least one end surface thereof has an inclined portion that is elastically deformable toward the inner diameter side when abutting and pressing the inner peripheral side corner portion of the end surface of the adjacent magnet, At least a part of the inner peripheral side corner portion of the end face of the magnet facing the spacer is in close contact with the spacer, and at least a part of the end face of the magnet not facing the spacer is exposed so as to be pressed and sandwiched by a molding die. In this state, the stepping motor is insert-molded together with the shaft by a resin member. 3. The stepping motor according to claim 1, wherein the spacer is provided with a protrusion capable of being compressed and deformed on at least one end surface facing the magnet end surface. 4. The stepping motor according to claim 1, wherein the spacer has at least one end face facing the end face of the magnet formed in a wave shape. 5. The stepping motor according to claim 1, wherein the resin member is a thermosetting resin containing an unsaturated polyester resin in a weight ratio of 10% or more and 30% or less. 6. A rotor in which two substantially cylindrical magnets, a substantially cylindrical spacer that axially separates the magnets, and a shaft that forms a central axis are arranged in a molding die, and a resin is filled and insert molding is performed. In the method of manufacturing a stepping motor, the spacer is made so as to elastically deform when abutting against the end face side of the magnet and being pressed, and the axial height of the magnet and the spacer overlapped is A stepping motor in which the height of the members after insert molding and coupling is made smaller than the cumulative height before insert molding and coupling, and insert molding and coupling is performed while pressing and sandwiching both end surfaces of the two magnets with the molding die. Manufacturing method. 7. A method of manufacturing a stepping motor, comprising a rotor having a substantially cylindrical magnet and a shaft forming a central axis arranged in a molding die, and resin-filled and insert-molded together. Is provided with a gate port on the end face side of the magnet inside the outer diameter of the magnet, the gate port is provided with a movable pin having a substantially V-shaped tip that closely faces the end face of the magnet, and the resin is provided in the cavity. The method of manufacturing a stepping motor is characterized in that the movable pin is retracted and separated when the resin is filled, and the movable pin is moved forward and close until the resin is hardened to form the gate port thinly in the axial direction. 8. The method of manufacturing a stepping motor according to claim 6, wherein the resin is a thermosetting resin containing an unsaturated polyester resin in a weight ratio of 10% or more and 30% or less.