JP3292804B2 - Rotor and method of manufacturing rotor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rotor having a rotor magnet formed by injection molding using an iron-based rare earth magnet material, and a method of manufacturing the rotor .

[0002]

2. Description of the Related Art Conventionally, when an iron-based rare earth magnet, for example, a neodymium-iron-boron alloy (Nd-Fe-B) is used as a rotor material of a stepping motor, a rare-earth bonded magnet material is compression-molded (98% by weight of magnetic powder). %).
Then, after being formed into a rotor shape, a rust prevention treatment is performed.
As the rust-prevention treatment, a multi-step treatment step of washing → sealing treatment (a treatment for closing a hole formed in a magnet) → cleaning → painting is required.

On the other hand, a medium-diameter stepping motor using an iron-based rare earth magnet is, for example, a pellet (magnetic powder 9) obtained by kneading powder of an Nd—Fe—B magnet with a polyamide resin.
3% by weight) by injection molding.
This is because the injection molding method is preferable when the diameter is small in terms of inertia determined by the magnetic powder content. Note that a small-diameter stepping motor, for example, a motor having a rotor magnet having a diameter of 2 to 5 mm is difficult to perform injection molding, and therefore, compression molding is performed.

[0004] In the case of an iron-based rare earth magnet formed by injection molding, a skin layer of polyamide resin is provided on the magnet surface.
Usually, no surface treatment for rust prevention is performed. That is, because the polyamide resin covers the magnetic powder, it has an antirust effect.

[0005]

As described above, the rotor magnet formed by compression molding, which is conventionally performed, requires many steps for rust prevention, resulting in poor production efficiency and an increase in cost. On the other hand, in the rotor magnet formed by injection molding, rust prevention treatment is usually unnecessary, but since the gate portion is torn off from the sprue runner, rust prevention treatment is required for the gate mark portion.

However, injection molding is preferable in view of the easiness of the rust prevention treatment and the inertia, so that an attempt has been made to adopt the injection molding method even for small-diameter rotor magnets, for example, those having a diameter of 2 to 5 mm. Was. However, when such a small-diameter rotor magnet having a diameter of 2 to 5 mm is to be formed by injection molding, the gap width of the gate hole is reduced by μm.
I have to order. When injection molding is performed using magnetic powder having a maximum particle size of 220 μm for such a gate hole having a width of 300 μm, for example, a gate hole having a width of 300 μm, the magnetic powder is clogged by the gate and does not flow into the mold. Was found to occur. In order to solve this phenomenon, the molding conditions such as the heating cylinder temperature, the injection pressure and the injection speed were changed. However, the phenomenon that the magnetic particles were clogged at the gate was not improved.

Further, when a small-diameter rotor magnet is formed by injection molding, if a conventional side gate is used, that is, if the gate is provided on the outer peripheral surface of the cylinder of the rotor magnet, the gate is small because the rotor magnet is small. The influence of the trace has a great effect on the characteristics of the motor.

SUMMARY OF THE INVENTION An object of the present invention is to provide a rotor, particularly a small-diameter rotor, which can reduce the influence of gate marks during injection molding on motor characteristics. Another object of the present invention is to provide a rotor capable of preventing rust at a gate mark portion of injection molding caused by using an iron-based rare earth magnet material.

[0009]

Means for Solving the Problems To achieve the above object, a rotor according to the first aspect of the present invention includes a rotor magnet formed by injection molding using an iron-based rare earth magnet material, and a rotor magnet formed on the rotor magnet. And a rotor shaft fixed to the shaft hole.
In the formed concave portion, a gate mark where an iron-based rare earth magnet material is injected is provided , and the gate mark is sealed with an adhesive .

Further, the rotor according to the second aspect of the present invention
2. The rotor according to claim 1, wherein the gate mark is adjacent to the shaft hole.
And a rotor shaft inserted into the shaft hole.
Fixing material used to integrate the rotor magnet
The gate traces are sealed with an adhesive material.

Further, a method of manufacturing the rotor according to claim 3.
The method uses the tip provided on the tip side of the center of the center pin.
Protrude conical part into sprue to form sprue with central part
A concentric gate hole is formed between the
Inject iron-based rare earth magnet material around the pin from the gate hole
To form a donut-shaped rotor magnet,
After that, pull out the rotor magnet from the center pin and
In the shaft hole after removing the center pin provided in the center,
Insert the rotor shaft and the rotor shaft and rotor magnet with adhesive.
Fix and fix the gate mark by the gate hole with the adhesive
It is sealed.

In the rotor of the present invention, a rotor magnet is formed by injection molding using an iron-based rare earth magnet material, for example, an Nd—Fe—B-based magnet material. The gap width of the gate hole for injection is set to, for example, 500 μm or less, so that the gate mark remains in the concave portion on the axial end surface of the rotor magnet. For this reason, even with a rotor magnet for a stepping motor having a small diameter, for example, a diameter of 2 to 5 mm, the influence of the gate mark hardly appears on the motor characteristics. In particular, the gate mark should be placed on the axial end of the rotor magnet.
Since it is provided in the recess formed on the surface, it is sealed with adhesive
Gate marks remain on the outer peripheral surface of the rotor magnet cylinder
Also, it does not protrude on the end face in the axial direction. Therefore, the motor
To the part facing the stator part of
Gate marks are not left in the parts that have a great effect
The characteristics are stable and the rotor magnet axis
It does not affect the direction accuracy. And touch the trace of the gate
Sealing with an adhesive material prevents rust generated at the gate cut
Prevention can also be achieved.

In the method for manufacturing a rotor according to the present invention,
Efficient production of rotors with the above characteristics
Can be. Particularly, it is preferable when the rotor becomes small.
It will be.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

First, the rotor 1 of the present invention and the rotor 1
The configuration of the stepping motor 10 using the motor will be described with reference to FIGS.

The rotor 1 has a rotor magnet 2 and
And a rotor shaft 3. A shaft hole 4 is formed in the center of the rotor magnet 2, and the rotor shaft 3 is inserted through the shaft hole 4. Concave portions 5, 6 are formed on both end surfaces of the rotor magnet 2, and an adhesive 7 as a fixing material is put in the concave portions 5, 6, and the rotor magnet 2 and the rotor shaft 3 are integrated.

As shown in FIG. 1 (B), the rotor 1 is of a 10-pole alternating NS type. And the total flux is 77 to 83 μwb. Also,
The adhesive 7 may be a combination in which an adhesive is applied on a primer as an undercoat in addition to a case where only an adhesive is used. Further, when the rotor magnet 2 and the rotor shaft 3 are integrated by an insert method, a resin at the time of insert fulfills its function as a fixing material.

The detailed shape of the rotor magnet 2 is as follows.
It is as shown in FIG. That is, its diameter Φ
1 is 4 mm, and the diameter Φ2 of the shaft hole 4 is 2 mm.
The diameter Φ3 of the bottom 8 of the recess 6 is 3 mm.
That is, the width of the bottom 8 is 0.5 mm.
Then, a gate hole 39 described later abuts on the bottom portion 8, and a gate mark remains. A slope 9 is provided around the bottom 8. On the other hand, the concave portion 5 is also provided with a similar slope portion 9.

The configuration of the stepping motor 10 using the rotor 1 will be described with reference to FIG. A lead screw 11 is formed on the rotor shaft 3, and its tip is supported by a pivot bearing 13 held on a frame 12. A portion of the rotor shaft 3 between the rotor magnet 2 and the lead screw 11 is
Support. The bearing 14 is attached to the frame 12.

The frame 12 has a mounting plate 15 to which the stator of the stepping motor 10 is fixed.
Installed by. The stator portion was wound around a case 17 having one pole tooth of the stator, a core 18 having the other pole tooth of the stator, a cylindrical bobbin 19 arranged on the outer periphery of the pole tooth, and a bobbin 19. And a winding 20.

The tip of the rotor shaft 3 on the rotor magnet 2 side is in contact with a leaf spring 22 held by a stopper 21. Further, a winding 2 is provided on the outer peripheral side surface of the stator portion.
A pin 23 for supplying power to the zero is attached.

A method for manufacturing the rotor magnet 2 used in the stepping motor 10 having the above-described structure is as follows.

First, commercially available Nd—Fe—B magnetic powder (hereinafter referred to as “Nd magnetic powder”) having a composition ratio as shown in FIG. 4A is ground in a nitrogen purge. The Nd magnetic powder has a particle diameter of 425 μm or less and an average particle diameter of about 154 μm. Then, this Nd magnetic powder is sieved with a 100 mesh to obtain a Nd magnetic powder having a composition ratio as shown in FIG.
As described below, Nd magnetic powder having an average particle diameter of about 64 μm is obtained.

Then, using nylon 12 as a powder,
A pellet of 93% by weight of magnetic powder is prepared. The rotor magnet 2 is manufactured by injection molding using the pellets.

In order to form the rotor magnet 2,
A molding die 31 shown in FIG. 5 is used. This mold 31
Is composed of an upper mold 33, a central mold 34, a lower mold 35, a center pin 36, and a sleeve ejector 37. The upper mold 33 is provided with the sprue 32 for introducing the magnet material made from the above-mentioned pellets, and the cavity 38 surrounded by the molds 34, 35, 36, and 37 is provided.

The tip of the upper mold 33 projecting into the cavity 38 is provided with an inclined portion 33a and a flat portion 33b. Further, the tip of the center pin 36 has a tip conical portion 36a, a columnar central portion 36b, and a central portion 3b.
A cylindrical root 36c having a diameter larger than the diameter of 6b
, A flat shoulder portion 36d between the tip conical portion 36a and the central portion 36, and a conical connecting portion 36 between the central portion 36b.
e is provided. Then, the tip conical portion 36a protrudes into the sprue 32, and a ring-shaped gate hole 39 is formed between the center portion 36b of the center pin 36 and the surface of the upper die 33 on which the sprue 32 is formed. The gap width of the gate hole 39 is 300 μm.

The molding of the rotor magnet 2 using the molding die 31 is performed as follows. That is, sprue 32
In addition, the liquid Nd-Fe-
A B-based magnet material is injected and injected into the cavity 38 through the ring-shaped gate hole 39. After the entire cavity 38 is filled with the magnet material, the cavity 38 is cooled for a predetermined time. Thereafter, the mold is opened. First, the sprue 32 is cut off at the gate hole 39 and extracted. Next, the upper mold 33 and the center mold 34 are opened. Then, the sleeve ejector 37 is protruded, and the formed rotor magnet 2 is inserted into the center pin 3.
6 and the rotor magnet 2 shown in FIG. 2 is obtained.

Next, the rotor shaft 3 is inserted into the shaft hole 4 of the rotor magnet 2, and the recesses 5, 6 on both end surfaces of the rotor magnet 2 are filled with an adhesive 7 serving as a fixing material. The shaft 3 is integrated. And FIG.
Is obtained. At this time, the gate mark of the gate hole 39 remains in the plane portion 8 of the recess 6 of the rotor magnet 2 facing the gate hole 39, but the adhesive mark seals the gate mark. It will be. For this reason, the gate trace is prevented from rusting and does not rust. In addition, although the ultraviolet curing anaerobic adhesive is used as the adhesive 7, another adhesive may be used.

It is to be noted that a mold 31 having the same structure is used, and the gap width of the gate hole 39 is set to 300 μm, and the maximum particle diameter (212 μm) of ／ or more of the gap width is set.
When the Nd magnetic powder having m) was used (see FIG. 6), the magnet material did not flow into the cavity 38, and a molded product could not be obtained. This seems to be because the shape of the Nd magnetic powder is pointy or square, and they are caught depending on the direction, so that even if the particle diameter is smaller than the gap width, it does not flow. When the maximum particle diameter was set to 2/3 or less of the gap width, the finished product of the rotor magnet 2 was obtained due to the fluidity of the polyamide resin and the like as described above.

On the other hand, when the maximum particle diameter of the magnetic powder is 10 μm or more, the increase in the slicing cost is not so large, and the magnetic properties are not deteriorated, which is preferable.

In the embodiment described above, the magnetic powder has a particle diameter of 150 μm or less and an average particle diameter of about 64 μm, and is easy to mold in view of the shape of the magnetic powder, the fluidity of the polyamide resin, and the like. Advantages such as not deteriorating the characteristics are produced, which is preferable. Further, since the gate hole 39 is a ring-shaped disk gate using the center pin 36, the dimensional accuracy in injection molding is improved, and the outer periphery of the rotor magnet 2 and the shaft hole 4 are formed.
The concentric accuracy is very good.

In addition, since the gate mark is sealed with the adhesive 7, the gate mark does not rust. Further, since the concave portions 5 and 6 are present, it is convenient to store the adhesive 7 serving as a fixing material, and the rotor magnet 2 and the rotor shaft 3 can be firmly fixed. Further, since the inclined portions 9 are formed in the concave portions 5 and 6, the rotor shaft 3 is easily inserted and the adhesive 7 is easily injected.

Each of the above embodiments is an example of a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the spirit of the present invention. It is. For example, instead of forming the gate hole 39 in a circular shape, the gate hole 39 may be formed in an arc shape that becomes a part of a circle,
One spot-shaped gate may be provided, or a plurality of spot-shaped gate holes may be provided. When the rotor 1 is formed, the rotor magnet 2 and the rotor shaft 3 are bonded with the adhesive 7.
Instead of bonding them, they may be integrated by insert molding. In this case, the material used as the fixing material is a plastic resin used for insert molding. Further, the rotor shaft 3 may be integrally provided by insert molding using a resin material. In the case of the two insert moldings described above, in any case, if the gate mark formed on the rotor magnet 2 is sealed with a resin used for insert molding, the gate mark is prevented from being rusted, which is preferable. Becomes

In the above-described embodiment, the diameter Φ1 of the rotor magnet 2 is 4 mm, and the gap width of the gate hole is 3 mm.
The diameter Φ1 may be set to about 2 to 5 mm, or may be further reduced or increased. The gap width of the gate hole may be made larger or smaller in accordance with the diameter Φ1. However, when the gap width of the gate hole is set to 500 μm or less, it is preferable to set the diameter Φ1 of the rotor magnet to about 5 mm or less from the viewpoint of production efficiency. Also, if the diameter Φ1 of the rotor magnet is made too small,
The gap width of the gate hole needs to be further reduced, and the diameter of the magnetic powder needs to be extremely small. Therefore, in consideration of production efficiency such as cost and ease of injection molding, the diameter Φ1 of the rotor magnet is preferably about 2 mm or more.

In the above-described embodiment, the concave portion 6 is provided on the axial end surface of the rotor magnet 2 and the gate mark is provided in the concave portion 6. However, the concave portion 6 is not provided, and the gate end is provided on the planar end surface. A trace may be left.

As described above, in the rotor of the present invention , the concave portion formed on the axial end surface of the rotor magnet.
Since the gate traces appear inside, the gate traces do not affect the motor characteristics. For this reason, a rotor having stable operation can be provided.

In particular, the gate mark is sealed with an adhesive.
So it is advantageous in terms of rust prevention and the adhesive enters the recess
As a result, it is difficult to affect the axial length of the rotor.
Therefore, it becomes more suitable for a small rotor.

Further, in another invention, in addition to the effects described above,
In addition, since the gate trace is provided at a position adjacent to the shaft hole, the influence of the gate trace on the inertia is small. Ma
Also, the adhesive for fixing the rotor shaft and the sealing of the gate mark
For the rotor shaft
Fixing and sealing of the gate trace can be performed efficiently.

In the method for manufacturing a rotor according to the present invention,
A rotor capable of efficiently manufacturing a rotor having the above-described characteristics.
Becomes

[Brief description of the drawings]

FIG. 1 is a view showing a configuration of a rotor according to the present invention.
(B) is a BB sectional view of (A) in a partial sectional side view.

FIG. 2 is a sectional view of a rotor magnet used in the rotor of the present invention.

FIG. 3 is a partially sectional side view showing a stepping motor using the rotor of FIG. 1;

FIG. 4 is a graph showing the particle distribution of Nd magnetic powder used in the rotor of the present invention, (A) is a graph showing the particle size distribution of the purchased Nd magnetic powder in an unpulverized state, and (B) is ( A)
3 is a graph showing the particle size distribution of the Nd magnetic powder after being sieved and sieved with 100 mesh.

FIG. 5 is a diagram showing a mold used when manufacturing a rotor magnet of the rotor of the present invention.

FIG. 6 is a graph showing a particle size distribution of Nd magnetic powder used when injection molding was not successful.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotor 2 Rotor magnet 3 Rotor shaft 4 Shaft hole 5, 6 Recess 7 Adhesive (fixing material) 39 Gate hole

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02K 15/03 H02K 1/02 H02K 1/27 501

Claims (3)

(57) [Claims] 1. A rotor magnet formed by injection molding using an iron-based rare earth magnet material, and a rotor shaft fixed to a shaft hole formed in the rotor magnet, and an axial end face of the rotor magnet. In the recess formed in
Only set the gate mark injected with the iron-based rare earth magnet material, this
Wherein the gate mark is sealed with an adhesive . 2. The method according to claim 1, wherein the gate mark is positioned adjacent to the shaft hole.
And the rotor shaft inserted into the shaft hole.
Used to integrate the rotor magnet with the rotor magnet
The rotor according to claim 1, wherein the gate mark is sealed with an adhesive serving as a fixing material . 3. A center pin is provided at the front end of the center of the center pin.
The tip conical part projected into the sprue
A concentric gate hole is formed between the sprue forming surface and the sprue forming surface.
Form the iron-based rare earth magnet material around the center pin
Is injected from the gate hole, and the donut-shaped rotor mug
A net is formed and then the center pin is
Data magnet and pull out the center magnet
Insert the rotor shaft into the shaft hole after removing the
When fixing the rotor shaft and the above rotor magnet with adhesive
In both cases, seal the gate trace from the gate hole with the adhesive.
A method for manufacturing a rotor.