JP2001045718A - Permanent magnet type motor and other permanent magnet application equipment - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To achieve further miniaturization, higher performance, and lower cost by using inexpensive permanent magnets that have strong magnetic force, have little variation in magnetic flux even when multipolarized, and are inexpensive. Provided are a permanent magnet type motor that can be used, an actuator using the same, and a magnetic encoder. SOLUTION: Rare earth-iron particles having a particle size of 10 μm or less are used as a movable portion or a fixed portion having a permanent magnet of a permanent magnet type motor and an actuator, and as a magnetic scale of a magnetic encoder having a magnetic scale and a magnetic detecting element.
Nitrogen magnet powder and ferrite magnet powder are resin-bonded,
A multi-pole magnetized bond magnet is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet for controlling and driving used in various devices including a computer peripheral device such as a fixed disk or floppy (registered trademark) disk drive of a computer and a printer. Related to application equipment.

[0002]

2. Description of the Related Art Permanent magnet motors having a permanent magnet in a movable or fixed part and actuators using the same are widely used for controlling and driving computer-related equipment, printers, cameras, clocks, and the like. I have. In addition, a magnetic encoder including a magnetic scale made of a permanent magnet and a magnetic detection element such as a Hall element or a magnetoresistive element is known as one type of a sensor that measures displacement such as length and angle.

[0003] Conventionally, neodymium (Nd) -iron (F) has been used as a permanent magnet used for a movable portion or a fixed portion of a permanent magnet type motor and a magnetic scale of a magnetic encoder.
e) A sintered magnet such as -boron (B) -based or samarium (Sm) -cobalt (Co) -based, or a bonded magnet obtained by bonding a Nd-Fe-B-based quenched magnet powder with a resin binder is mainly used. Have been.

However, Nd-Fe-B and Sm-
Co-based sintered magnets are manufactured by mixing these magnet powders with a binder, molding and sintering.
Necessary dimensional accuracy cannot be obtained in the as-sintered state.
Therefore, in order to use it for small precision equipment such as a permanent magnet type motor, it is necessary to perform machining such as grinding until sufficient dimensional accuracy is obtained after sintering.

[0005] On the other hand, Nd-Fe-B-based bond magnets and rare-earth-iron-nitrogen-based bond magnets are manufactured by compression molding or injection molding, and thus have the advantage that they can be mass-produced with sufficient dimensional accuracy. Ferrite-based sintered magnets and bonded magnets have inferior characteristics to Nd-Fe-B-based and rare-earth-iron-nitrogen-based bonded magnets, but have the advantage of being very inexpensive. .

[0006]

In recent years, with the miniaturization of various devices, there has been a growing demand for permanent magnet type motors, magnetic encoders and the like to be further miniaturized, improved in characteristics and reduced in price. Therefore, there is a demand for a permanent magnet that is small, has high characteristics, is easy to process, has high productivity, and is inexpensive for permanent magnets used in permanent magnet motors and magnetic encoders. However, due to such a demand for miniaturization, it becomes more and more difficult to process the sintered magnet, and it becomes more difficult to maintain high characteristics as the size of the bonded magnet decreases.

In addition, recent miniaturization of magnets has progressed to such a point that variations in the particle size of the Nd-Fe-B-based quenched magnet powder in the bonded magnet become a problem. That is, when multi-pole magnetization is performed, the size of the magnet powder particles with respect to the size of one magnetic pole becomes a problem, and the strength of each magnetic pole is not uniform. As a result, permanent magnet type motors and actuators using such bonded magnets do not operate smoothly, and magnetic encoders have the disadvantage that errors are likely to occur in output signals.

Further, in the case of the conventional bonded magnet using the Nd-Fe-B-based quenched magnet powder, a considerably large magnetic field is required in the magnetizing step when performing multi-polar magnetization. However, when the size of the magnet is reduced, a small magnetized yoke is used to perform multipolar magnetization, and the size of one magnetic pole is reduced to several millimeters or less. Therefore, the characteristics have to be lowered as compared with the case where the magnetic field is magnetized with a sufficiently large magnetic field.

The present invention has been made in view of such conventional circumstances,
Use permanent magnet type motors with good productivity that can respond to further miniaturization, higher performance, and lower cost by using bonded magnets that have less variation in magnetic flux even when magnetized with multiple poles. And a magnetic encoder.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a permanent magnet type motor having a permanent magnet on a movable or fixed portion, and an actuator using the permanent magnet type motor. Further, the permanent magnet is characterized in that it is made of a multi-polar magnetized bond magnet obtained by resin-bonding a rare earth-iron-nitrogen magnet powder having a particle size of 10 μm or less and a ferrite magnet powder.

Further, the present invention provides a magnetic encoder having a magnetic scale and a magnetic detecting element.
The magnetic scale is characterized in that it is made of a multi-polar magnetized bond magnet in which a rare earth-iron-nitrogen magnet powder having a particle diameter of 10 μm or less and a ferrite magnet powder are resin-bonded.

The bonded magnet used in the above-described permanent magnet type motor, actuator, and magnetic encoder has a variation in the absolute value of the magnetic flux density from each of the multi-polarized magnetic poles of less than 10%, or The distance between the multi-pole magnetized magnetic poles is 10 mm or less.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The permanent magnet used in the present invention is a bonded magnet in which a rare earth-iron-nitrogen based magnet powder having a particle size of 10 μm or less and a ferrite based magnet powder are bonded with a resin binder. It was done. Bonded magnets using rare earth-iron-nitrogen based magnet powders have the characteristic that the variation in magnetic flux density of each magnetic pole is small even when multi-polarized, and among them, samarium (Sm) is the most preferable as a rare earth element. The composition of the magnetic powder is 24-25% by weight Sm-
There is 3-4 wt% N- balance Fe. Further, part of iron may be replaced with cobalt (Co).

The above rare earth-iron-nitrogen based magnet powder can be prepared by, for example, a melting casting method described in JP-A-2-57663.
Alternatively, Japanese Patent No. 1702544 and Japanese Patent Laid-Open No. 9-15
It can be obtained by producing a rare earth-iron alloy powder by the reduction diffusion method described in Japanese Patent No. 7803 and nitriding it. The rare earth-iron-nitrogen magnet powder is finely pulverized to have a particle diameter of 10 μm or less or an average particle diameter of 4 μm or less. The reason why the particle size of the magnet powder is 10 μm or less or the average particle size is 4 μm or less is that the particle size is sufficiently small with respect to the size of each magnetic pole when multipolar magnetization is performed, thereby suppressing variations in magnetic flux density. That's why.

The rare earth-iron-nitrogen magnet powder having a particle diameter of 10 μm or less means that the maximum diameter of 100 observed particles is measured by observing the magnet powder with a scanning electron microscope (SEM). 9 particles having a maximum diameter of 10 μm or less
Occupies 5 or more. The average particle diameter is a volume-based average particle diameter obtained by converting the maximum diameter measured as described above to a volume.

By adding and mixing the ferrite-based magnet powder with the rare-earth-iron-nitrogen-based magnet powder, even if the rare-earth-iron-nitrogen-based magnet powder is multipolar magnetized, the variation of the magnetic flux density of each magnetic pole is small. A more inexpensive bonded magnet can be obtained without impairing the characteristics of (1). The mixing ratio of ferrite magnet powder to the entire magnet powder is 10% by weight.
If it is less than 99% by weight, the cost will not be sufficiently reduced, and if it exceeds 99% by weight, the above-mentioned properties of the rare earth-iron-nitrogen based magnet powder will be almost lost.
The range of 0 to 97% by weight is more preferable. The type of the ferrite magnet powder is not specified, and ordinary Ba ferrite magnet powder, Sr ferrite magnet powder, and the like can be used. For example, NF-110 Sr ferrite manufactured by Nippon Benzo Kogyo is available. The particle size of the Sr ferrite magnet powder is 10 μm or less, and the average particle size is 1.4 μm.

The resin binder used for bonding the rare earth-iron-nitrogen magnet powder and the ferrite magnet powder may be any of those conventionally used in the production of bonded magnets, such as epoxy resins, phenol resins and melamine resins. And a thermosetting resin such as a silicone resin, or a thermoplastic resin such as a polyamide resin, a polyethylene resin, a polystyrene resin, and a polyolefin resin. Generally, epoxy resin is preferred for compression molding, nylon 12 resin is used for injection molding, and polyolefin resin is used for extrusion molding, but is not limited to these. .

The bonded magnet used in the present invention is obtained by mixing the above-mentioned rare earth-iron-nitrogen based magnet powder and ferrite based magnet powder with a resin binder and compressing, injection molding or extruding the same as ordinary bond magnets. It can be manufactured by molding. At that time, an electromagnet or a permanent magnet for generating an orientation magnetic field is incorporated in the molding die, and a magnetic field is applied to the magnet powder to perform magnetic orientation. The resulting bonded magnet is magnetized in multiple poles using a magnetized yoke.

The shape of the bonded magnet and the state of multipolar magnetization are as follows.
It is selected appropriately according to the device using it. For example, a permanent magnet type motor generally has a rotor type in which a magnet rotor serving as a movable portion is arranged inside or outside a drive coil. Therefore, as shown in FIG. Multipole magnetization is performed on the outer peripheral surface or inner peripheral surface of the bonded magnet in the shape of a circle. In a linear permanent magnet type motor, for example, as shown in FIG. 2, NS poles are multipolarly magnetized in a striped pattern on a plane of a flat bonded magnet which is a movable portion.

The same applies to a magnetic encoder.
The permanent magnet used as the magnetic scale is multipolar magnetized on the outer peripheral surface of a ring-shaped or disc-shaped bonded magnet in a rotary encoder, and multi-polarized on a plane of a flat bonded magnet in a linear encoder. .

Incidentally, a permanent magnet type motor, an actuator,
The configuration of the magnetic encoder is determined based on the design concept thereof, and any structure may be used. For example, in a typical inner rotor type permanent magnet type motor, a stator yoke having a plurality of drive coils is arranged outside a ring-shaped magnet rotor made of the multi-polar magnetized bond magnet of the present invention. . Further, in the magnetic encoder, a Hall element or a magnetoresistive element is arranged so as to face the magnetic scale formed of the multipolar magnetized bond magnet of the present invention.

In general, the shorter the distance between the multipole-magnetized magnetic poles is, the more difficult it is to multipole magnetize and the greater the variation in the magnetic flux density of each magnetic pole is.
In a bonded magnet containing iron-nitrogen based magnet powder, even if the size of one magnetic pole is reduced due to the downsizing of the magnet, a sufficiently large magnetic field is generated in each of the multi-polarized magnetic poles, and the magnetic flux of each magnetic pole is generated. Can be kept small.

More specifically, the variation in the absolute value of the magnetic flux density from each of the multi-pole magnetized magnetic poles can be suppressed to less than 10%. Therefore, the operation of the permanent magnet type motor or actuator of the present invention is smooth. In the magnetic encoder, a stable output signal without error can be obtained. This effect is particularly remarkable when the distance between the multi-pole magnetized magnetic poles of the bonded magnet is 10 mm or less, as compared with the conventional one.

[0024]

【Example】Example 1  Composition: Sm: 24% by weight, Fe: 72.5% by weight, N:
3.5% by weight, particle size 10 μm, average particle size 4 μm
m Sm-Fe-N based magnet powder and Sr ferrite
And magnet powder at a weight ratio of 1: 1.
After adding and mixing 5% by weight of resin, the cavity of the molding die
And then compression-molded, 4.3 mm outside diameter, 2 mm inside diameter,
A ring-shaped bonded magnet having a height of 5 mm was manufactured. That
At the time, a magnet for generating an orientation magnetic field
The magnet powder is magnetically oriented by applying an orientation magnetic field from outside the
It was configured so that:

The ring-shaped bonded magnet was magnetized to eight poles in the circumferential direction along the outer peripheral surface using a magnetized yoke as shown in FIG. The distance between the magnetic poles of the obtained multipolar magnetized bond magnet was 1.7 mm, the magnetic flux density at the center of each magnetic pole was 1.5 kG at the maximum, and the variation of the magnetic flux density (the magnetic flux density of each pole) The difference between the maximum value and the minimum value of the absolute value divided by the maximum value) was 6.8%.

Next, a permanent magnet type motor was manufactured by using the multi-polarized ring-shaped bonded magnet as a magnet rotor and arranging a stator yoke provided with a plurality of drive coils on the outside thereof. When the torque of this motor was measured, the torque variation (a value obtained by dividing the difference between the maximum value and the minimum value of the torque during one rotation by the maximum value) was 3%.

[0027]Comparative Example 1  Composition: Nd: 13% by weight, Fe: 81% by weight, B: 6 layers
% And the particle size is not more than 200 μm and not less than 30 μm.
Nd-Fe-B magnet powder (Magnequench Internal
SHP, MQP-B) and Sr ferrite magnet powder
And the same as in Example 1 except that
The outer diameter is 4.3 mm, the inner diameter is 2 mm, and the height is 5 mm.
A bonded magnet having a ring shape was manufactured.

A permanent magnet obtained by magnetizing this bond magnet into eight poles using a magnetized yoke in the same manner as in Embodiment 1 has a maximum magnetic flux density of 1.2 kG and a variation in magnetic flux density of 15%.
Met. Further, when a permanent magnet type motor was manufactured using this permanent magnet in the same manner as in Example 1, the torque fluctuation was as large as 6%.

[0029]Example 2  The same Sm-Fe-N-based magnet powder and Sr
Light magnet powder and a 1: 1 weight ratio are mixed.
After adding and mixing 8% by weight of Iron 12 resin, an alignment magnetic field is generated.
Injection molding using a molding die incorporating a raw magnet
Outer diameter 2.0mm, inner diameter 1mm, height 3mm
Was manufactured.

The ring-shaped bonded magnet was magnetized to four poles in the radial direction on the outer peripheral surface using a magnetized yoke in the same manner as in Example 1. The distance between the magnetic poles of the multi-pole magnetized bond magnet was 1.6 mm, the maximum magnetic flux density at the center of each magnetic pole was 0.8 kG, and the variation in the magnetic flux density was 8.4%.

Next, a permanent magnet type motor was manufactured by using the ring-shaped bonded magnet magnetized as a multipolar magnet as a magnet rotor and arranging a stator yoke provided with a drive coil on the outside thereof. When the torque of this motor was measured, the torque fluctuation was 4%.

[0032]Comparative Example 2  The same Nd-Fe-B-based magnet powder and Sr
Using a light magnet powder, the outer diameter was determined in the same manner as in Example 2.
2.0mm, 1mm inner diameter, 3mm height ring-shaped bon
Manufactured magnets. Using this bonded magnet with magnetized yoke
Thus, the permanent magnet magnetized into four poles as in Example 2
The flux density is 0.75kG at maximum and the variation of magnetic flux density
Was 17%. In addition, the embodiment using this permanent magnet
When a permanent magnet type motor was manufactured as in
The fluctuation of Luku was as large as 7%.

[0033]Example 3  The same Sm-Fe-N-based magnet powder and Sr
Light powder and 65:35 by weight.
Mix with 9.5% by weight of olefin resin to generate alignment magnetic field
Extrusion using a molding die incorporating a magnet
100mm, 2mm thick, 500mm long belt
Obtained the form. This molded body is cut into 88 mm x 5 mm,
By rolling it into a ring shape in the longitudinal direction of 88 mm
Ring, outer diameter 28 mm, inner diameter 24 mm, height 5 mm
A bonded magnet was manufactured.

This ring-shaped bonded magnet was magnetized to eight poles in the circumferential direction using a magnetized yoke in the same manner as in Example 1. The distance between each magnetic pole of the multi-pole magnetized bond magnet is 1
The magnetic flux density at the center of each magnetic pole was 1.4 kG at the maximum, and the variation of the magnetic flux density was 2.5%.

[0035]Comparative Example 3  The same Nd-Fe-B-based magnet powder and Sr
Using a light magnet powder, the outer diameter was determined in the same manner as in Example 3.
28mm, 24mm inner diameter, 5mm height ring-shaped bon
Manufactured magnets. Using this bonded magnet with magnetized yoke
In the same manner as in Example 3, the multipole magnetized to 8 poles
Permanent magnets have a maximum magnetic flux density of 1.2 kG and a high magnetic flux density.
The degree of variation was 8.5%.

[0036]Example 4  The same Sm-Fe-N-based magnet powder and Sr
Light magnet powder is mixed in a weight ratio of 35:65,
After mixing 8% by weight of nylon 12 resin,
Injection molding using a molding die incorporating a magnet for generation
A 10 mm long, 3 mm wide, 1 mm thick flat plate
Manufactured magnets.

The plate-like bonded magnet was multipolar magnetized to 10 poles in the length direction using a magnetized yoke. The distance between the magnetic poles of the multi-pole magnetized permanent magnet was 1 mm, the magnetic flux density at the center of each magnetic pole was 440 G at the maximum, and the variation of the magnetic flux density was 6.5%.

Next, a magnetic encoder using a Hall element to detect signals was manufactured using the multipolar-magnetized flat permanent magnet as a magnetic scale. The variation of the signal output of the magnetic encoder (the value obtained by dividing the difference between the maximum value and the minimum value of the peak voltage at the position corresponding to each magnetic pole by the maximum value) was 4.9%.

[0039]Comparative Example 4  The same Nd-Fe-B-based magnet powder and Sr
Same as Example 4 except that light magnet powder was used.
A 10 mm long, 3 mm wide, 1 mm thick flat plate
Manufactured magnets. Use this bond magnet with magnetized yoke
Then, when the multi-pole magnetized to 10 poles as in Example 4,
Permanent magnet has a maximum magnetic flux density of 340G and a magnetic flux
The variation in density was 14.0%.

A magnetic encoder was manufactured in the same manner as in Example 4 using the multipolar-magnetized flat permanent magnet. When the variation of the signal output of the magnetic encoder was measured, it was as large as 10.9%.

[0041]

According to the present invention, by using a rare earth-iron-nitrogen magnet powder and a ferrite magnet powder in combination, the productivity is excellent, the magnetic force is strong, and the magnetic flux is obtained even when magnetized with multiple poles. Bond magnets with little variation can be obtained at low cost,
By using a permanent magnet composed of this bonded magnet, it is possible to provide a permanent magnet type motor capable of responding to further downsizing, higher performance and lower cost, an actuator using the same, and a magnetic encoder. it can.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing NS poles of a multi-polarized ring-shaped bonded magnet.

FIG. 2 is a perspective view schematically showing NS poles of a multi-pole magnetized plate-like bonded magnet.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02K 21/14 H01F 1/08 A 21/22 1/113 F term (Reference) 5E040 AA03 AA19 AB03 AC05 BB03 CA01 NN06 5H621 AA03 GA02 GA04 GA14 GB01 JK02 JK05 JK15 5H622 AA03 CA01 CA05 CB06 DD01 DD02 DD04 DD05 PP03 PP18 PP19 QA02 QA03 QA04

Claims (7)

[Claims] 1. A permanent magnet motor having a permanent magnet on a movable or fixed part, wherein the permanent magnet has a particle size of 10 μm.
A permanent magnet type motor comprising a multi-polarized bonded magnet obtained by resin bonding rare earth-iron-nitrogen based magnet powder and ferrite based magnet powder of m or less. 2. The permanent magnet motor according to claim 1, wherein a variation in an absolute value of a magnetic flux density from each of the multi-pole magnetized magnetic poles of the bond magnet is less than 10%. 3. The permanent magnet type motor according to claim 1, wherein a distance between the multi-pole magnetized magnetic poles of the bond magnet is 10 mm or less. 4. An actuator using the permanent magnet type motor according to claim 1. 5. A magnetic encoder comprising a magnetic scale and a magnetic detecting element, wherein the magnetic scale has a particle size of 10%.
A magnetic encoder comprising a multi-polar magnetized bond magnet obtained by resin-bonding a rare-earth-iron-nitrogen-based magnet powder and a ferrite-based magnet powder of μm or less. 6. The magnetic encoder according to claim 5, wherein a variation in an absolute value of a magnetic flux density from each of the multi-pole magnetized magnetic poles of the bond magnet is less than 10%. 7. The magnetic encoder according to claim 5, wherein a distance between the multi-pole magnetized magnetic poles of the bond magnet is 10 mm or less.