JPH0638417A - Permanent magnet field rotor - Google Patents

Abstract

PURPOSE:To prevent the decentering and cracking of the permanent magnet field of a rotary field brushless motor using a permanent magnet. CONSTITUTION:Peripheral projections 4 having small widths are provided on the outer periphery of a yoke 3 made of a soft magnetic material. A cylindrical permanent magnet 1 is put on the yoke 3 with small gaps between the magnet 1 and projections 4 and the magnet 1 is stuck and fixed to the yoke 3 with a bonding agent 6 having a large degree of shrinkage after hardening. The projections 4 can be split in the peripheral direction when the projections 4 are formed on the outer peripheral surface in an arc-like state. Therefore, the sticking position of the magnet 1 can be accurately maintained by means of the projections 4 and the stress of the projections 4 caused by thermal expansion can be reduced. When the gap between the magnet 1 and part of the yoke 3 except the projections 4 is made larger, the stress can be absorbed and cracking of the magnet 1 can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a permanent magnet field rotor in a rotating field type brushless motor.

[0002]

2. Description of the Related Art Conventionally, small-sized brushless motors of the rotary field type have come to use high-performance permanent magnets made of a base material of a rare earth iron system, as the characteristics of the permanent magnets have improved. As described above, when the permanent magnet is used as the rotor of the magnetic flux generator of the rotating field type brushless motor, the winding 1 is provided inside the frame 11 as shown in FIG.
Cylindrical permanent magnet 1 in which a stator core 13 wound with 2 is fixed and is opposed to the inside of the stator core 13 with a gap.
4 is fitted to the outer periphery of a soft magnetic material yoke 16 which is integral with or separate from the shaft 15 with an appropriate gap, and a resin adhesive 17 is poured into this gap and fixed. 1
Reference numeral 8 is a bracket, and 19 is a bearing.

Further, as shown in FIG. 5, a step 22 is provided on a shaft 21 to integrally form a collar 23 which plays a role of a bearing, and a recess is provided at a central portion of the step between the collars so that the collar 23 can be radially extended. The one in which the thick resin permanent magnet 24 is integrally formed or the recess is filled with an adhesive to adhere the thick cylindrical permanent magnet is a permanent magnet for a rotor.
No. 248.

[0004]

However, when a cylindrical permanent magnet is fitted to the outer periphery of the yoke as shown in FIG. 4, a rare earth iron-based magnet is used to improve the performance of the permanent magnet, and the permanent magnet of the radial direction is used. The thickness of the magnet is small, and the thermal expansion coefficient of this magnet is usually −3 × 10 ⁻⁶ / ° C. to 3 × 10 ⁻⁶ / ° C., whereas the thermal expansion coefficient of the soft magnetic material yoke is 11 ×. 1
At 0 ^-6 / ° C, there is a large difference between the two, so if the fitting gap is small, the thermal expansion of the yoke due to heat generation during operation will apply a large thermal stress to the permanent magnet from the inside, and the permanent magnet base material Since the strength is weak, the magnet may be cracked or cracked. Therefore, if the gap between the permanent magnet and the yoke is increased within the range allowed by the magnetic characteristics, cracking of the permanent magnet due to the effect of thermal stress can be prevented. However, as shown in FIG. There is a defect that the layer of the resin adhesive 17 between 16 is offset and the rotor outer periphery is eccentric.

Further, in the case where a permanent magnet having a large thickness is attached to the outer periphery of the collar having a small diameter as shown in FIG. 5, since the strength of the permanent magnet is large, it is not necessary to consider the influence of thermal expansion, but the characteristics are improved. However, when a rare earth iron-based magnet having a reduced thickness is used, the effect of the difference in the coefficient of thermal expansion is large, and thus it was not possible to form the magnet directly on the outer circumference of the shaft.

[0006]

SUMMARY OF THE INVENTION The present invention has solved the above-mentioned problems and has a permanent magnet in which a rare earth iron-based magnet having a small thickness is fixed to the outer circumference of a yoke made of a soft magnetic material through an adhesive. A field rotor is provided, in which a circumferential circumferential protrusion having a small width is provided at least in the vicinity of both ends of a portion of the outer periphery of the yoke where the permanent magnet is fitted, and a fitting gap between the tubular permanent magnet and the yoke is provided. The protrusions are small, and the other parts are large within the range allowed by the characteristics, and an adhesive having a large expansion and contraction after adhesive curing is filled in the gaps and fixed by adhesion.

[0007]

Therefore, the fitting between the yoke and the permanent magnet is held with a small gap due to the circumferential projection, and the fitting and holding is performed without causing eccentricity between the permanent magnet and the yoke. Since the opposing surfaces of are small, the influence of stress due to the difference in thermal expansion is small, and most of the other fitting parts have large gaps, the thermal stress can be absorbed by the adhesive layer and the permanent magnet Prevents cracks and cracks.

[0008]

1 is a side sectional view showing an embodiment of the present invention.
Is a cylindrical permanent magnet made of rare earth iron, 2 is a shaft made of a soft magnetic material, 3 is a yoke, and is generally formed integrally with the shaft. Reference numeral 4 denotes a small-width circumferential protrusion provided near both ends of the yoke 3, and 5 is a gap between the inner surface of the permanent magnet and the yoke. The circumferential protrusion portion is made as small as possible and other portions do not affect the characteristics. It's big.
Reference numeral 6 denotes an adhesive filled in the gap 5, which has a large expansion / contraction rate due to heat after being hardened and adhered.

The permanent magnet 1 fitted to the yoke 3 is held concentrically with the yoke 3 with both ends facing the circumferential projection 4 with a slight gap, and the circumferential projection 4 has a small width. The expansion of the yoke 3 has little influence of thermal stress on the permanent magnet 1, and the other portions have large gaps. Therefore, the difference in thermal expansion is absorbed by the adhesive layer to eliminate the stress applied to the permanent magnet 1, and the cracking is prevented. To prevent cracks.

In the illustrated embodiment, the circumferential protrusions 4 are continuous in the circumferential direction. However, as shown in FIG. 2, the circumferential protrusions are provided with notches 7 or a plurality of them are provided in the circumferential direction. As the small protrusions provided, they are made to face the inner surface of the permanent magnet, and as shown in FIG. 3, they are divided in the circumferential direction and the axial positions are mutually changed so that the radial stress due to the protrusions is reduced. By dispersing in the axial direction and the axial direction, the stress due to thermal expansion can be reduced while effectively maintaining the concentricity of the permanent magnet and the yoke.

If the outer peripheral surface of the projection is curved so as to form an arcuate shape in the axial direction as shown in FIG. 3, the influence of stress on the permanent magnet can be further reduced, and there is substantially no gap. Even when is contacted with the inner surface of the permanent magnet, the stress other than the vertex is released from the arc surface to the adhesive layer, and the influence of the radial stress can be further reduced.

[0012]

As described above, on the outer peripheral surface of the yoke made of a soft magnetic material, a small width circumferential projection is provided at least near both ends of the portion where the permanent magnet is fitted, and the permanent magnet is fitted on the outer circumference of the projection. As a result, the protrusion can hold the permanent magnet concentrically with the shaft, the gap other than the protrusion can be enlarged to eliminate the influence of stress due to thermal expansion, and the permanent magnet can be prevented from cracking or cracking. In addition, by dividing the circumferential protrusion and providing a gap between the portions facing the inner surface of the permanent magnet, the influence of stress is reduced, and the adhesive layers on both sides of the protrusion are connected to improve the adhesive strength, There is an effect that the inflow of the adhesive can be facilitated.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention.

FIG. 2 is a front sectional view of another embodiment.

FIG. 3 is a side sectional view showing still another embodiment.

FIG. 4 is a cross-sectional view of an upper half portion showing an example of a conventional rotary field type brushless motor.

FIG. 5 is a side view showing another example of a conventional rotor with its upper half section taken as a cross section.

FIG. 6 is a sectional view of a rotor in a conventional example.

[Explanation of symbols]

 1 Permanent Magnet 2 Shaft 3 Yoke 4 Circumferential Protrusion 5 Gap 6 Adhesive 11 Frame 12 Winding 13 Stator Core 14 Permanent Magnet 15 Shaft 16 Yoke 17 Resin Adhesive 21 Shaft 22 Step 23 Color 24 Resin Permanent Magnet

Claims (4)

[Claims] 1. A permanent magnet field rotor in which a cylindrical rare earth iron-based permanent magnet is fitted and fixed to the outer circumference of a yoke made of a soft magnetic material with an adhesive, and a yoke outer peripheral portion to which the permanent magnet is fitted. A circumferential protrusion having a small width is provided at least near both ends of the, the permanent magnet is fitted to face the circumferential protrusion, and the gap between the yoke and the permanent magnet is filled with an adhesive having a large expansion / contraction ratio after curing. A permanent magnet field rotor characterized in that 2. The permanent magnet field rotor according to claim 1, wherein the circumferential projections form a plurality of circumferentially divided projections. 3. The permanent magnet field rotor according to claim 2, wherein the circumferential projections axially shift the circumferentially divided projections from each other. 4. The permanent magnet field rotor according to claim 1, wherein an outer peripheral surface of the circumferential projection is formed in an arcuate shape in the axial direction.