JPH089573A - Magneto rotor and its manufacture - Google Patents

Abstract

PURPOSE:To provide a technique which can prevent the idling of a magnet and a collar made of a synthetic resin and the fall of the magnet from the collar made of the synthetic resin while following the insert molding technique high in productivity. CONSTITUTION:This is a magnet rotor which has a ring-shaped magnet 1, where one or more open grooves open from the end face or faces to the inside periphery are made at one or both end faces, and a collar 2 made of synthetic resin, which is molded, being inserted into the hole of the ring-shaped magnet 1, and gets in the condition that a projection to fit in the open groove 3 of the ring-shaped magnet 1 is made after molding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnet rotor which is a built-in component such as a stepping motor.

[0002]

2. Description of the Related Art A rotor used for a PM type stepping motor or the like used for driving a head of a floppy disk drive uses two ring-shaped magnets A, A as shown in FIG. As a material for the ring-shaped magnet A, a resin-bonded magnet composed of NdFeB-based magnetic powder capable of exerting a high magnetic force and a synthetic resin is often used, and about 10 poles are equally spaced around the outer circumference of the ring-shaped magnet A. Most are magnetized.

The assembly of this magnet rotor is shown in FIG.
As shown in Fig. 5, ring magnets A, A are fitted from both ends and bonded simultaneously to an aluminum collar B having a spacing portion B1 in the middle, and then a lead screw is inserted into the shaft hole of the aluminum collar B. Through the process of fixing.

In such a conventional magnet rotor, there is a problem that productivity is low because the work of adhering the ring-shaped magnet A and the aluminum collar B is required. Therefore, recently, the ring-shaped magnet is used for the injection molding die. A method of inserting a magnet and molding a synthetic resin is being adopted.

[0005]

This method eliminates the need for bonding the ring-shaped magnet and the collar to improve the productivity, but it also causes a new problem. In the magnet rotor, rotational torque is generated between the magnet and the synthetic resin collar as the motor rotates. In addition, since the temperature environment in which the motor is used covers a wide range from -10 to 80 ° C, a gap is created on the joint surface due to the difference in the thermal expansion coefficient between the magnet and the synthetic resin collar, and the magnet will move against the collar during rotation. It has been pointed out that a situation where the magnet slips out of the collar and eventually falls out of the collar.

The present invention has been made in view of the above circumstances, and can prevent the idle rotation of the magnet and the synthetic resin collar and the dropping of the magnet from the synthetic resin collar while following the insert molding technique with high productivity. It is intended to provide technology.

[0007]

[Means for Solving the Problems] The applicant of the present invention has studied the means for solving the above problems, and has obtained the following idea. In order to prevent the magnet from falling out of the collar, it is necessary to securely fix the magnet against the stress in the circumferential direction and the axial direction due to the rotating operation. If a discontinuous opening groove is formed on the inner peripheral side of the end surface of the ring-shaped magnet, the opening groove exerts an anchoring effect between the magnet and the collar, and is resistant to stress in the circumferential direction and the axial direction. It has been found that it exerts an effective restraining effect.

A magnet rotor according to the present invention made on the basis of the above idea has a ring-shaped magnet having at least one end surface formed with one or a plurality of opening grooves opened from the end surface to the inner peripheral surface, and the ring-shaped magnet. It is characterized in that it has a collar made of synthetic resin, which is insert-molded in the inner diameter portion and has a projection formed to be engaged with the opening groove of the ring-shaped magnet after the molding.

The width, depth and depth of the opening groove are preferably set in the range of 0.2 mm to 1.0 mm, respectively.

The magnetic powder contained in the ring magnet is
R-T-B (where R is Nd and / or Pr, or a part of these is substituted with one or more other rare earth elements: T is a 3d group transition metal element mainly composed of Fe It is desired that the magnetic powder is an intermetallic compound mainly composed of a rare earth metal represented by: B) and a transition metal.

The procedure for producing the magnet rotor is as follows: A synthetic resin having an engaging protrusion that engages with the opening groove of the ring-shaped magnet by filling the inside diameter of the ring-shaped magnet with the opening groove with synthetic resin. The manufacturing collar is insert-molded on the inner diameter portion of the ring-shaped magnet.

[0012]

In such a magnet rotor, a part of the collar is engaged with the circumferentially discontinuous opening groove formed in the end surface of the ring-shaped magnet, that is, the opening groove that does not extend over the entire circumference. By doing so, the ring-shaped magnet and the synthetic resin collar are firmly connected and integrated by the anchor effect, and the floating of the ring-shaped magnet in both the axial direction and the axial direction is restricted, and the idling and movement of the magnet during motor rotation and It is prevented from falling off.

If the width, depth and depth of the opening groove are in the range of 0.2 mm to 1.0 mm, the mold resin can flow into the opening groove sufficiently and a sufficient anchor effect can be expected. If the size of the opening groove is within this range, the influence on the magnetic characteristics of the magnet can be substantially ignored.

As magnetic powder contained in the ring-shaped magnet, R
A magnet rotor capable of exhibiting a high magnetic force is provided when an intermetallic compound magnetic powder containing a rare earth metal represented by -TB and a transition metal as main components is used.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to illustrated embodiments. FIG. 1 is an external perspective view of a magnet rotor of the present invention, and FIG. 2 is an axial sectional view. This magnet rotor is composed of two ring-shaped magnets 1 and 1 and a synthetic resin collar 2 like the conventional magnet rotor.

According to the present invention, in the magnet rotor having such a structure, at least one end face of the ring-shaped magnet 1 is formed with one or a plurality of opening grooves 3 opened from the end face to the inner peripheral face, and the inner diameter of the ring-shaped magnet 1 is formed. It is characterized in that the portion is filled with synthetic resin, and a synthetic resin collar having a portion that engages with the opening groove 3 of the ring-shaped magnet 1 is insert-molded in the inner diameter portion of the ring-shaped magnet.

For example, a plurality of opening grooves 3 are formed at equal intervals as shown in FIG. The opening grooves are not formed as stepped annular grooves over the entire circumference in the circumferential direction, but a plurality of circumferentially discontinuous opening grooves 3 as shown in the figure are used. On the other hand, the binding force can be exerted, but the binding force cannot be exerted against the stress in the circumferential direction. By providing the plurality of opening grooves 3 in the circumferential direction discontinuously as shown in the figure, it is possible to exert a restraining force in both the circumferential direction and the axial direction, and the ring-shaped magnet is rotated when the motor rotates. It is possible to reliably prevent 1 from slipping or falling off from the synthetic resin collar 2.

The shape of the opening groove 3 can form an opening volume between the die surface and the mold surface so that the resin molded inside the ring-shaped magnet 1 can surely flow in, and the circumferential direction and the axial direction due to the rotation operation. If an anchor effect that can reliably fix the ring-shaped magnet 1 against both stresses of
The shape is not particularly limited. For example, the rectangular groove 3a (FIG. 4), the semicircular end face shape chamfered groove 3b (FIG. 5), and the hemispherical groove 3c (FIG. 6) can be appropriately adopted.

In the case of the rectangular groove 3a, for example, the size of the opening groove 3 is preferably such that the width a, the depth b, and the depth c are in the range of approximately 0.2 mm to 1.0 mm. The range is approximately in the case of the chamfered groove 3b and the hemispherical groove 3c or the opening groove of any other shape. If less than 0.2 mm,
The mold resin does not sufficiently flow into the groove, and a sufficient anchor effect cannot be expected. Further, if it exceeds 1.0 mm, the influence on the magnetic characteristics of the magnet cannot be ignored, which is not preferable.

It is preferable to provide a plurality of opening grooves 3 at equal intervals so that stress in the circumferential direction can be evenly distributed and received, but as shown in FIG. 7, only one opening groove 3 is provided. The case is not excluded. Further, in the above embodiment, the opening groove 3 is provided only on one end surface of the ring-shaped magnet 1, but the opening grooves 3 and 3 may be provided on both end surfaces of the ring-shaped magnet 1 as shown in FIG.

In such a magnet rotor, after the ring-shaped magnet 1 is molded, the ring-shaped magnet 1 is set in an injection molding die, and the inner diameter of the ring-shaped magnet 1 is filled with a thermoplastic resin. The synthetic resin collar 2 is insert-molded on the inner diameter of the ring-shaped magnet 1.

Both compression molding and injection molding can be used to mold the ring-shaped magnet 1. From the viewpoint of obtaining high magnetic force, the compression molding method, which has a high magnetic powder content and enables high-density molding, is more advantageous.

Ferrite magnetic powder, alnico magnetic powder, samarium cobalt magnetic powder, or the like can be used as the magnetic powder contained in the molding material for the ring-shaped magnet 1, but from the viewpoint of achieving both high magnetic characteristics and low cost. , RT
B (provided that R is Nd and / or Pr, or a part of these is substituted with one or more other rare earth elements: T is a 3d group transition metal element mainly composed of Fe: B is boron It is preferable to use an intermetallic compound magnetic powder containing (4) as a main component.

The rare earth element (R) is at least one kind of rare earth element containing yttrium (Y), such as neodymium (Nd), praseodymium (Pr) and lanthanum (L).
a), cerium (Ce), samarium (Sm), gadolinium (Gd), promesium (Pm), europium (Eu), lutetium (Lu), dysprosium (D)
y), terbium (Tb), holmium (Ho), etc. can be illustrated. Yttrium (Y) is not a rare earth element, but can be treated in the same manner as other rare earth elements in the present invention. In the present invention, the preferred rare earth element (R) is mainly composed of Nd or Pr, but it may contain misch metal, didymium or other rare earth element which is a composite rare earth element.

The intermetallic compound magnetic powder preferably has a particle size of 1 to 1000 μm or less from the viewpoint of moldability, and more preferably 700 μm or less.

For the purpose of increasing the surface magnetic flux density, RT
Substitution of part of T of the intermetallic compound magnetic powder containing -B as a main component with cobalt is also appropriately adopted.

As the thermosetting resin, epoxy resin, phenol resin, urea resin, melamine resin, furan resin,
An unsaturated polyester resin, a polyimide resin, etc. can be illustrated, but an epoxy resin and a phenol resin are preferable.

A thermoplastic resin is used as a material for the synthetic resin binder and the synthetic resin collar when the ring-shaped magnet is molded by injection molding. As the thermoplastic resin, polybutylene terephthalate (PBT), vinyl chloride resin, polyamide resin, polyethylene resin, polypropylene resin, polyphenylene sulfide resin, polyether resin or the like can be used.

Nickel plating on the surface of the ring-shaped magnet,
It is preferable to take rust preventive measures such as epoxy electrodeposition coating, epoxy spray coating or various resin impregnation treatments.

Next, examples and comparative examples conducted to confirm the effects of the present invention will be described. (Example) An epoxy binder was added to the NdFeB alloy magnetic powder in the following compounding ratio, mixed in a MEK solvent, dried, and then classified to obtain a granulated product of 200 μm or less. This is pressurized at 8 ton / cm ² and outer diameter φ8 mm, inner diameter φ
A ring-shaped magnet molded body having a height of 6 mm and a height of 4 mm was obtained.
Protrusions for forming grooves were provided on the pressing punch, and four opening grooves each having a width, length, and depth of 0.8 mm were formed on one end surface of the molded body at equal intervals with the inner peripheral surface opened. . This was heat-cured at 150 ° C, 2Hr, Air, and
The surface of the magnet was plated with Ni. The ring-shaped magnet thus obtained was inserted into an injection molding machine and molded with PBT resin to obtain a magnet rotor. NdFe
The rotational torque strength and the axial pull-out strength were measured in order to confirm the binding force of the B magnet with respect to the stress in the circumferential direction and the axial direction with respect to the PBT resin collar. The results are shown in Table 1. <NdFeB Bonded Magnet Composition> NdFeB Alloy Magnetic Powder 96.0% Epoxy Resin 3.5 st-Mg 0.5 (Magnesium Stearate: Lubricant) (Comparative Example) Except that no opening groove is formed on the end face of the magnet, the above implementation is carried out. Make a magnet rotor under exactly the same conditions as the example,
The rotation torque strength and pull-out strength of this magnet rotor were also measured. The results are shown in Table 1.

[0031]

[Table 1] As is clear from Table 1, the magnet rotor of the embodiment of the present invention has an extremely superior binding force in both the axial direction and the circumferential direction as compared with the conventional magnet rotor having no groove. I understand.

[0032]

In the magnet rotor of the present invention, since a part of the collar is engaged with the circumferentially discontinuous opening groove formed in the end face portion of the ring-shaped magnet, it is combined with the ring-shaped magnet. The resin collar and the resin collar are firmly coupled and integrated by the anchor effect, and the ring magnet is prevented from moving in both the axial direction and the axial direction with respect to the collar, and the magnet is prevented from idling and falling off when the motor rotates.

When each of the width, depth and depth of the opening groove is set in the range of 0.2 mm to 1.0 mm, the mold resin can sufficiently flow into the opening groove and a sufficient anchor effect can be expected. If the size of the opening groove is within this range, the influence on the magnetic characteristics of the magnet can be substantially ignored.

As magnetic powder contained in the ring-shaped magnet, R
When the intermetallic compound magnetic powder containing a rare earth metal and a transition metal represented by -TB is used, the magnetic force of the magnet rotor becomes extremely high.

[Brief description of drawings]

FIG. 1 is an external perspective view of an embodiment of a magnet rotor of the present invention.

FIG. 2 is an axial sectional view of the same embodiment.

FIG. 3 is a perspective view of a ring-shaped magnet having an opening groove formed on one end surface.

FIG. 4 is an enlarged perspective view of a main part when a square groove is formed.

FIG. 5 is an enlarged perspective view of an essential part in the case where a semi-circular groove is formed.

FIG. 6 is an enlarged perspective view of a main part when a hemispherical groove is formed.

FIG. 7 is a plan view of a ring-shaped magnet when only one opening groove is formed.

FIG. 8 is an axial cross-sectional view when opening grooves are formed on both end faces of a ring-shaped magnet.

FIG. 9 is a perspective view of a conventional magnet rotor.

FIG. 10 is an exploded perspective view of the magnet rotor.

[Explanation of symbols]

1 ring-shaped magnet 2 synthetic resin collar 3 opening groove 3a square groove 3b chamfered groove 3c hemispherical groove A ring magnet B aluminum collar

Claims (4)

[Claims] 1. A ring-shaped magnet having at least one end face formed with one or a plurality of opening grooves opened from the end face to the inner peripheral surface, and insert-molded into the inner diameter portion of the ring-shaped magnet, and the ring after the molding. A rotor made of a synthetic resin, in which a protrusion that engages with the opening groove of the magnet is formed. 2. The magnet rotor according to claim 1, wherein the width, the depth and the depth of the opening groove are set in a range of 0.2 mm to 1.0 mm, respectively. 3. The magnetic powder contained in the ring-shaped magnet is R-
TB (where R is Nd and / or Pr, or a part of these is replaced by one or more other rare earth elements: T is a 3d group transition metal element containing Fe as a main component: B
The magnet rotor according to claim 1 or 2, wherein the magnet rotor is an intermetallic compound magnetic powder mainly composed of a rare earth metal represented by boron and a transition metal. 4. A synthetic resin is filled into the inner diameter of a ring-shaped magnet in which at least one end surface is formed with one or more opening grooves opened from the end surface to the inner peripheral surface, and the opening groove of the ring-shaped magnet is filled with the synthetic resin. A method for manufacturing a magnet rotor, comprising insert-molding a synthetic resin collar having engaging projections to engage with an inner diameter portion of a ring-shaped magnet.