JP2023042220A - Permanent magnet type stator - Google Patents

Abstract

To disclose a permanent magnet type stator in which the size and weight of an electric motor can be suppressed from increasing and the occurrence of magnetic saturation can be suppressed.SOLUTION: A yoke 22 includes a ferromagnetic material-made projection 23 (yoke piece 22B) in a portion corresponding to a magnetic pole boundary. In the yoke 22, the radial dimension of the portion where the projection 23 is disposed is larger than the radial dimension of any other portion. Accordingly, with a stator 20, the cross section of the portion of the yoke 22 corresponding to the magnetic pole boundary is large. Thus, near the magnetic pole boundary, the magnetic flux density is relaxed, and occurrence of magnetic saturation is suppressed. Further, a portion that corresponds to the projection 23 is not disposed in any portion of the yoke 22 other than the portion corresponding to magnetic pole boundary. Thus, the total size and weight of the yoke 22 are suppressed from increasing.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to permanent magnet stators used in electric motors.

A permanent magnet stator includes at least a yoke or the like made up of a permanent magnet and a ferromagnetic material, as disclosed in Patent Document 1, for example.

Japanese Utility Model Laid-Open No. 7-27261

A yoke is a yoke forming a path of magnetic flux generated in a permanent magnet. Therefore, if the cross-sectional area of the yoke is small, the yoke is magnetically saturated, and a large magnetic flux cannot be generated.

Therefore, it is desirable that the cross-sectional area of the yoke is large enough to prevent magnetic saturation. However, when the cross-sectional area of the yoke increases, the size and mass of the electric motor increase.

In view of the above points, the present disclosure discloses an example of a permanent magnet stator capable of suppressing the occurrence of magnetic saturation while suppressing an increase in size and mass of an electric motor.

The inventors discovered that "magnetic saturation is likely to occur near the magnetic pole boundary (Mb) because the magnetic flux density is particularly large near the magnetic pole boundary (Mb)". And this case is made by paying attention to the said discovery.

That is, the permanent magnet type stator used in the electric motor is, for example, a cylindrical yoke (22) surrounding the outer periphery of the permanent magnet, and the yoke (22) is made of a ferromagnetic material and the yoke (22) The yoke (22 ), the radial dimension (T1) of the portion where the convex portion (23) is provided is preferably larger than the radial dimension (T2) of the other portion.

As a result, according to the permanent magnet stator, the cross-sectional area of the portion of the yoke (22) corresponding to the magnetic pole boundary (Mb) is increased, thereby suppressing the occurrence of magnetic saturation near the magnetic pole boundary (Mb). can be

Furthermore, since there is no portion corresponding to the convex portion (23) other than the portion corresponding to the magnetic pole boundary (Mb), an increase in size and mass of the entire yoke (22) is suppressed. Furthermore, with the permanent magnet stator, it may be possible to suppress the occurrence of magnetic saturation while suppressing an increase in the size and mass of the electric motor.

Incidentally, the symbols in each parenthesis above are examples showing the correspondence with the specific configurations and the like described in the embodiments described later, and the present disclosure is not limited to the specific configurations and the like indicated by the symbols in the parentheses. .

It is a figure which shows the electric motor which concerns on 1st Embodiment. It is a figure which shows the stator etc. which concern on 1st Embodiment. It is a figure which shows the stator which concerns on 1st Embodiment. FIG. 3 is a diagram showing the distribution of magnetic flux density in a conventional stator; FIG. 4 is a diagram showing distribution of magnetic flux density in the stator according to the first embodiment;

The following "embodiment of the invention" shows an example of an embodiment belonging to the technical scope of the present disclosure. In other words, the matters specifying the invention described in the claims are not limited to the specific configurations, structures, etc. shown in the following embodiments.

It should be noted that arrows and oblique lines indicating directions in each drawing are provided to facilitate understanding of the relationship between the drawings and the shape of each member or portion. Accordingly, the inventions shown in this disclosure are not limited to the orientations attached to each figure. Figures with hatching are not necessarily cross-sectional views.

At least one member or portion described with at least a reference numeral is provided unless otherwise specified as "one" or the like. In other words, two or more members may be provided unless there is a notice such as "one". The electric motors shown in this disclosure comprise at least the components labeled and described, as well as the structural parts shown.

(First embodiment)
<1. Outline of electric motor>
In this embodiment, an example of an electric motor according to the present disclosure is applied to an electric motor applied to a vehicle actuator such as a wiper drive device or a power window device. The electric motor 10, as shown in FIG. 1, includes a permanent magnet type stator (hereinafter referred to as stator) 20, a rotor 30, a housing 40, and the like.

The housing 40 is a casing made of resin that covers at least the outer peripheral side of the stator 20 (see FIG. 2) that is configured in a substantially cylindrical shape. The housing 40 is provided with a flange portion 41 . The flange portion 41 is a fixing portion for fixing the electric motor 10 to a reduction gear housing (not shown).

For this reason, the flange portion 41 is provided with at least one (in this embodiment, a plurality of) insertion holes 42 into which fixing bolts (not shown) are inserted. The flange portion 41 is an integrally molded portion integrally molded with the cylindrical housing 40 from resin.

Rotor 30 is a rotor that rotates within stator 20 . The rotor 30 has a core portion 31, a rotor shaft 32, a coil portion (not shown), and the like. The core portion 31 is composed of a large number of electromagnetic steel plates laminated in a direction parallel to the axial direction of the rotor shaft 32 .

<2. Configuration of Stator>
The stator 20 includes at least a magnet portion 21, a yoke 22, and the like, as shown in FIG. The magnet part 21 is composed of a permanent magnet formed in a cylindrical shape or a ring shape.

A plurality of magnetic pole boundaries Mb are present in the magnet portion 21 along the circumferential direction. The two-dot chain line in FIG. 3 is the magnetic pole boundary Mb. In other words, if the space between the magnetic pole boundaries Mb that are adjacent in the circumferential direction is assumed to be one permanent magnet, the magnet unit 21 includes a plurality of virtual permanent magnets (hereinafter referred to as virtual magnets) along the circumferential direction. (four in FIG. 3) equal to the side-by-side structure.

Incidentally, the N pole or S pole of the virtual magnet exists on the inner peripheral surface or the outer peripheral surface of the magnet portion 21, and the N pole and S pole of each virtual magnet alternate along the circumferential direction. . That is, when the outer peripheral surface of a specific virtual magnet is the N pole, the inner peripheral surface of the specific virtual magnet and the outer peripheral surfaces of the two adjacent virtual magnets are S poles.

The yoke 22 is a member made of a ferromagnetic material and formed in a substantially cylindrical shape so as to surround the outer circumference of the magnet portion 21 . The yoke 22 constitutes a yoke that guides the magnetic flux generated by the magnet portion 21 .

A convex portion 23 made of a ferromagnetic material is provided at a portion of the yoke 22 corresponding to the magnetic pole boundary Mb. Therefore, the radial dimension T1 of the portion of the yoke 22 where the protrusion 23 is provided is larger than the radial dimension T2 of the portion other than the portion.

In other words, the yoke 22 according to this embodiment includes a cylindrical yoke body 22A and a yoke piece 22B that forms the projection 23 . The yoke piece 22B, that is, the convex portion 23 is arranged on the outer peripheral side of the yoke main body 22A.

The yoke piece 22B according to this embodiment is a separate member from the yoke main body 22A, and is made of a material having a higher magnetic permeability than the yoke main body 22A. The yoke main body 22A and the yoke piece 22B are integrated together with the housing 40 by insert molding when the housing 40 is molded.

That is, the yoke main body 22A and the yoke piece 22B are arranged in the mold cavity for molding the housing 40 when the housing 40 is molded. Then, the yoke main body 22A and the yoke piece 22B are fixed with the resin by injecting molten resin into the cavity in this state.

<3. Features of the electric motor (particularly the stator) according to the present embodiment>
In a conventional stator, that is, a stator without protrusions 23, the magnetic flux density increases near the magnetic pole boundary Mb, as shown in FIG. That is, the lines of flux exit the north pole and enter the south pole, ie divB=0. Therefore, in the conventional stator, magnetic saturation is likely to occur near the magnetic pole boundary Mb.

On the other hand, in the yoke 22 according to the present embodiment, a convex portion 23 made of a ferromagnetic material, that is, a yoke piece 22B is provided at a portion corresponding to the magnetic pole boundary Mb, and the convex portion 23 is provided in the yoke 22. The radial dimension T1 of the part is larger than the radial dimension T2 of the other parts.

As a result, according to the stator 20, the cross-sectional area of the portion of the yoke 22 corresponding to the magnetic pole boundary Mb is increased, so that the magnetic flux density is relaxed near the magnetic pole boundary Mb as shown in FIG. Saturation is suppressed.

Furthermore, since no portion corresponding to the convex portion 23 is provided in the yoke 22 other than the portion corresponding to the magnetic pole boundary Mb, an increase in size and mass of the yoke 22 as a whole is suppressed. Further, with the stator 20 , it is possible to suppress the occurrence of magnetic saturation and improve the output of the electric motor 10 while suppressing an increase in the size and mass of the electric motor 10 .

(Other embodiments)
In the above-described embodiment, the yoke piece 22B is a separate member from the yoke main body 22A. However, the present disclosure is not so limited. That is, the disclosure does not apply to, for example, a configuration in which the yoke piece 22B is integrally molded with the same material as the yoke body 22A, or a configuration in which the yoke piece 22B is made of the same material as the yoke body 22A and is a separate member. good.

In the above-described embodiment, the radial dimension T1 of the portion of the yoke 22 where the convex portion 23 is provided is constant. However, the present disclosure is not so limited. That is, according to the disclosure, for example, the portion of the yoke 22 provided with the convex portion 23 may have a smooth mountain-like convex shape whose radial dimension gradually changes. In this configuration, it is desirable that the shape be such that the vicinity of the magnetic pole boundary Mb has the maximum radial dimension.

In the above-described embodiment, the yoke piece 22B is provided on the outer peripheral side of the yoke main body 22A. However, the present disclosure is not so limited. That is, the disclosure may be, for example, a configuration in which the yoke piece 22B is provided on the inner peripheral side of the yoke main body 22A.

The electric motor according to the embodiment described above is an electric motor applied to a vehicle actuator. However, the present disclosure is not so limited. That is, the disclosure is applicable to other electric motors, for example.

In the magnet portion 21 according to the above-described embodiment, a plurality of magnetic pole boundaries Mb exist in one permanent magnet configured in an annular or cylindrical shape. However, the present disclosure is not so limited.

That is, according to the disclosure, for example, a plurality of permanent magnets may be circumferentially arranged to form a magnet portion. In this configuration, the boundary between the adjacent permanent magnets is the magnetic pole boundary Mb.

Furthermore, the present disclosure is not limited to the above-described embodiments as long as it conforms to the gist of the disclosure described in the above-described embodiments. Therefore, in the configuration in which at least two of the above-described embodiments are combined, or in the above-described embodiments, any one of the illustrated constituent elements or the constituent elements described with reference numerals is abolished. It may be a configuration that is

DESCRIPTION OF SYMBOLS 10... Electric motor 20... Stator 21... Magnet part 22... Yoke 22A... Yoke body 22B... Yoke piece 23... Convex part 30... Rotor

Claims (7)

In a permanent magnet type stator used in an electric motor,
a cylindrical yoke surrounding the outer periphery of the permanent magnet, the yoke being made of a ferromagnetic material;
a convex portion provided at a portion of the yoke corresponding to a magnetic pole boundary of the permanent magnet, the convex portion being made of a ferromagnetic material;
A permanent magnet stator in which a radial dimension of a portion of the yoke provided with the convex portion is larger than a radial dimension of the portion other than the yoke. 2. The permanent magnet stator according to claim 1, wherein the yoke has a cylindrical yoke body and a yoke piece forming the protrusion. 3. The permanent magnet stator according to claim 2, wherein the yoke piece is made of a material having a higher magnetic permeability than the yoke body. 3. The permanent magnet stator according to claim 2, wherein said yoke piece is made of the same material as said yoke body. 5. The permanent magnet stator according to claim 2, wherein the yoke piece is arranged on the outer peripheral side of the yoke body. a resin housing that covers the yoke from the outer peripheral side and is integrated with the yoke;
The permanent magnet stator according to any one of claims 1 to 5, further comprising: a fixing flange portion integrally molded with the housing. a permanent magnet stator according to any one of claims 1 to 6;
and a rotor that rotates within the permanent magnet stator.

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