JP7398898B2 - Motor core structure and its formation method - Google Patents

Description

The present invention relates to a motor core structure and a method for forming the same.

Iron core members such as motor cores are formed by punching electromagnetic steel plates into a predetermined shape, stacking them, and fixing them with clamps or the like.
After the iron core member is subjected to a wire winding process, a motor frame (housing) is attached to the core member by shrink fitting (see, for example, Patent Document 1).

International Publication No. 2018/167853

Figure 8 is a diagram showing the relationship between magnetic flux density and iron loss when multiple different stresses are applied to the iron core material, and Figure 9 is a diagram showing the relationship between magnetic flux density and magnetic permeability when multiple different stresses are applied to the iron core material. FIG. In FIGS. 8 and 9, 0 to 100 [MPa] indicates the case where tensile stress is applied, and -20 to -90 [MPa] indicates the case where compressive stress is applied.
When the motor frame is attached to the core member by shrink fitting, compressive stress is generated in the circumferential direction of the core member. As shown in FIGS. 8 and 9, as compressive stress increases, iron loss increases and magnetic permeability decreases. Thus, compressive stress deteriorates the magnetic properties of the iron core member and reduces the efficiency of the motor.
In order to suppress this decrease in motor efficiency, it is possible to reduce the interference between the motor frame and the core member during shrink fitting, but in that case, the restraining force of the motor frame on the core member decreases. Therefore, there was a risk that the iron core member would rotate when the motor was driven.

An object of the present invention is to properly fix a motor frame core member.

The motor core structure according to the present invention includes:
a cylindrical iron core member,
a cylindrical motor frame provided on the outer periphery of the iron core member;
a bonding layer provided at the boundary between the iron core member and the motor frame to fix them over the entire circumference ;
The bonding layer includes a metal material of the iron core member and a metal material of the motor frame that undergo plastic flow.

A method for forming a motor core structure according to the present invention includes:
A cylindrical motor frame is provided around the outer periphery of a cylindrical iron core member,
The metal material of the iron core member and the metal material of the motor frame are configured to form a bonding layer over the entire circumference at the boundary between the metal material and the metal material of the motor frame, thereby bonding the iron core member and the motor frame. There is.

According to the present invention, the motor frame and the core member can be properly fixed while reducing the compressive stress applied from the motor frame to the core member.

FIG. 1 is a perspective view of an iron core structure according to the present embodiment. It is a top view showing a part of iron core structure. It is a top view of the iron core structure at the time of performing friction stir welding. FIG. 2 is a perspective view of a tool used during friction stir welding. FIG. 3 is a plan view showing a state in which the protrusion of the tool is offset toward the motor frame with respect to the boundary line between the iron core member and the motor frame. FIG. 6(A) is a partial axial cross-sectional view of the core structure before ultrasonic bonding, and FIG. 6(B) is a partial axial cross-sectional view of the core structure after ultrasonic bonding. It is a perspective view showing a perspective view showing a joining position of ultrasonic joining. FIG. 2 is a diagram showing the relationship between magnetic flux density and iron loss when a plurality of different compressive stresses are applied to the iron core material. FIG. 3 is a diagram showing the relationship between magnetic flux density and magnetic permeability when a plurality of different compressive stresses are applied to the iron core material.

Embodiments of the present invention will be described in detail below with reference to the drawings.

[Iron core structure]
First, the core structure 10 according to this embodiment will be explained.
FIG. 1 is a perspective view of a core structure 10 according to this embodiment, and FIG. 2 is a plan view showing a part of the core structure 10. The core structure 10 includes a cylindrical core member 20, a motor frame 30 provided on the outer periphery of the core member 20, and a bonding layer 40 that joins the core member 20 and the motor frame 30.

The motor frame 30 is a substantially cylindrical member made of metal, for example, aluminum or an alloy thereof. On the outer periphery of both end portions in the axial direction, four rectangular extending portions 31 extending outward in the radial direction are formed at uniform intervals in the circumferential direction. These extensions 31 are formed with through holes 32 extending in the axial direction for fixing the core structure 10 to the outside or for attaching other members such as flanges to the core structure 10. .
Further, a heat radiation structure such as a heat radiation fin may be provided on the outer peripheral surface of the motor frame 30.

The iron core member 20 is a stator core for a motor, and includes a yoke 21, a plurality of teeth 22, and a plurality of slots 23 formed between the plurality of teeth 22. The yoke 21 is formed into a substantially cylindrical shape. The plurality of teeth 22 are formed at uniform intervals in the circumferential direction on the inner circumference of the yoke 21, and protrude (extend) from the inner circumference of the yoke 21 toward the inside in the radial direction. The slots 23 between adjacent teeth 22 are open slots with the inner diameter side open. The iron core member 20 is formed to have a substantially uniform cross-sectional shape in the direction along the central axis of the yoke 21.
In the following description, the direction along the central axis of the core structure 10 (the central axis of the cylinder) is referred to as the "axial direction", the direction perpendicular to the central axis is referred to as the "radial direction", and the direction centered on the central axis is referred to as the "radial direction". The direction of rotation is called the "circumferential direction."

This iron core member 20 is made by laminating thin electromagnetic steel plates (non-oriented electromagnetic steel plates in this embodiment) punched into a planar shape having a yoke 21 and a plurality of teeth 22 to a predetermined axial thickness. It is fixed by clamping, welding, caulking, etc. However, the manufacturing process of this iron core member 20 is not particularly limited, and for example, wire cutting may be used instead of punching.
Note that each tooth 22 is subjected to a winding process to form a coil, but illustration of the coil is omitted here.

The bonding layer 40 is formed of an iron alloy, which is the metal material of the iron core member 20, and an aluminum alloy, which is the metal material of the motor frame 30, which have undergone plastic flow due to friction stir welding at the boundary between the iron core member 20 and the motor frame 30. ing. Note that friction stir welding will be described later.

[Method for forming iron core structure (1)]
Next, a method for forming the core structure 10 will be explained.
When forming the core structure 10, first, the core member 20 is fitted inside the motor frame 30 by an intermediate fit or an interference fit. Specifically, the motor frame 30 is heated and attached to the iron core member 20 by shrink fitting. When performing an interference fit, the interference should be as strong and small as possible. Thereby, the compressive stress of the iron core member 20 is reduced by the motor frame 30.

Then, plastic flow is caused in the metal material of the core member 20 and the metal material of the motor frame 30 to join the core member 20 and the motor frame 30 together. Plastic flow between the metal material of the iron core member 20 and the metal material of the motor frame 30 is caused by friction stir welding.

FIG. 3 is a plan view of the core structure 10 when performing friction stir welding, and FIG. 4 is a perspective view of a tool 100 used during friction stir welding.
Friction stir welding refers to friction stir welding in which the metal material of the core member 20 and the metal material of the motor frame 30 are bonded by generating frictional heat at the boundary between the core member 20 and the motor frame 30 by the rotation of the tool 100 and the pressing force in the direction of the rotation axis. This is a joining method in which the iron core member 20 and the motor frame 30 are integrated by softening the iron core member 20 and the motor frame 30 by causing plastic flow around the joint part by the rotational force of the tool 100 and mixing.
Due to the friction stir welding described above, the bonding layer 40 is mainly composed of only the metal material of the iron core member 20 and the metal material of the motor frame 30, unlike in the case of brazing, adhesion, etc.

The tool 100 has a substantially cylindrical shape, and a protrusion 102 is provided at the center of a circular tip surface 101. At the time of joining, the protrusion 102 is inserted into the softened boundary between the core member 20 and the motor frame 30, and the core member 20 and the motor frame 30 are subjected to plastic flow while pressing the tip surface 101 around the protrusion 102. The bonding layer 40 is formed by kneading and mixing.

One end surface of the iron core member 20 and the motor frame 30 in the axial direction is flush with each other, and as shown in FIG. 3, the bonding layer 40 is formed on the one end surface that is flush with each other.
During friction stir welding, the through hole 32 formed in the extending portion 31 of the motor frame 30 is used as a start point and an end point. That is, at the start of friction stir welding, the protrusion 102 of the tool 100 is loosely inserted into one of the through holes 32, and welding is started while pressing one end surface of the motor frame 30 against the tip surface 101 of the rotating tool 100. do. Then, the tool 100 moves relatively from the through hole 32 toward the boundary between the core member 20 and the motor frame 30, goes around the boundary, and returns to the starting point of the through hole 32 again, and friction stir welding is performed. .

Further, as shown in FIG. 5, when the tool 100 moves around relatively along the boundary between the iron core member 20 and the motor frame 30, the tool 100 Friction stir welding is performed with the protrusion 102 offset toward the motor frame 30, where the forming material has a low melting point.
Thereby, temperature rise in the iron core member 20 and the motor frame 30 is suppressed, melting of the respective metal materials is avoided as much as possible, and joining is performed in a state where plastic flow occurs.

[Method for forming iron core structure (2)]
Furthermore, ultrasonic welding may be selected for joining the iron core member 20 and the motor frame 30 instead of friction stir welding.
When forming the core structure 10, the core member 20 is fitted inside the motor frame 30 by an intermediate fit or an interference fit, as in the case of friction stir welding described above.

FIG. 6 is a partial sectional view in the axial direction of the core structure 10 when performing ultrasonic bonding, and FIG. 7 is a perspective view showing the joining position of ultrasonic bonding.
Ultrasonic bonding refers to applying ultrasonic vibration to the core member 20 and the motor frame 30 using an ultrasonic vibrator (FIG. 6(A)), so that the interface between the core member 20 and the motor frame 30 rubs against each other and is exposed. This is a joining method in which clean metal surfaces are joined in a solid state by plastic flow under pressure (Figure 6(B)). The symbol S in FIG. 6(B) indicates a joint location.
Also in the case of the ultrasonic bonding described above, the bonding layer 40 is mainly composed of only the metal material of the iron core member 20 and the metal material of the motor frame 30, unlike in the case of brazing, adhesion, etc.

In the above ultrasonic bonding, the tip of the horn 110 that amplifies the ultrasonic vibrations of the ultrasonic vibrator is pressed against the outer peripheral surface of the motor frame 30, and ultrasonic waves are applied to the interface between the iron core member 20 and the motor frame 30. Bonding is performed by applying vibration.
As shown in FIG. 7, the joint is made around the outer peripheral surface of the motor frame 30 at least around an intermediate position in the axial direction.

[Technical effects of this embodiment]
As described above, according to the present embodiment, the core member 20 and the motor frame 30 are joined by the bonding layer 40 having the metal material of the core member 20 and the metal material of the motor frame 30 that have undergone plastic flow. Therefore, even if the interference of the motor frame 30 with respect to the iron core member 20 is made small, it is possible to ensure sufficient joint strength between them. Therefore, when the core structure 10 is incorporated into a motor, it is possible to effectively reduce the occurrence of rotation of the core member 20 with respect to the motor frame 30.
Since the interference by the motor frame 30 can be reduced, it is possible to reduce the compressive stress generated in the core member 20, thereby reducing core loss, increasing magnetic permeability, and improving the magnetic properties of the core member 20. becomes possible. Thereby, it becomes possible to improve the efficiency of the motor using the iron core structure 10.
Note that when forming the bonding layer 40, it is sufficient that the core member 20 and the motor frame 30 can be temporarily held together, so other methods that can temporarily fasten them may be used, such as interference fit or intermediate It is not necessary to use a fixing method that causes tightening, such as fitting. In that case, the compressive stress generated in the iron core member 20 can be further reduced.

Furthermore, since the joining layer 40 joins the metal material of the iron core member 20 and the metal material of the motor frame 30 by plastic flow, these do not melt, resulting in metamorphosis of the material due to welding and intervention of different materials due to adhesion. Therefore, the conductivity of the iron core member 20 and the motor frame 30 can be maintained high, and the magnetic properties of the iron core member 20 can be maintained high. Further, for the same reason, it is possible to maintain high heat conductivity between the iron core member 20 and the motor frame 30, and it is possible to improve heat dissipation.

In particular, when the bonding layer 40 is formed by friction stir welding, the bonding layer 40 undergoes plastic flow at least to the depth of the protrusion 102 of the tool 100, so that highly reliable bonding can be performed. It is possible.
Further, since the bonding layer 40 is located at the end of the core member 20 and the motor frame 30 in the axial direction, it is possible to shorten the time required for forming the bonding layer and to facilitate the work.

In addition, when the bonding layer 40 is formed by ultrasonic bonding, the bonding layer 40 can be easily formed over a wide range of the circumferential surface that forms the boundary between the iron core member 20 and the motor frame 30, resulting in high bonding strength. can be easily obtained. Furthermore, by forming the bonding layer 40 over a wide area, it is possible to reduce deviations in magnetic properties and heat dissipation properties depending on the location of the member.
Furthermore, if the bonding layer 40 is provided at least in the intermediate portion of the core member 20 and the motor frame 30 in the axial direction, torque will be generated between the motor frame 30 and the core member 20 when the core structure 10 is incorporated into a motor. Since the axially intermediate portion, which is easy to maintain, can be held, rotation of the iron core member 20 with respect to the motor frame 30 can be effectively suppressed.

[others]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.
For example, in the embodiment described above, the bonding layer 40 by friction stir welding is formed on one end surface side in the axial direction of the iron core member 20 and the motor frame 30, but it may be formed on both end surfaces.
Further, in the above embodiment, the bonding layer 40 by ultrasonic bonding is formed by bringing the horn 110 into contact with the axially intermediate portion of the outer circumferential surface of the motor frame 30; The bonding layer 40 may be formed by pressing the horn 110.
Further, the bonding layer 40 formed by ultrasonic bonding is formed at the axially intermediate portion of the iron core member 20 and the motor frame 30, but other than the axially intermediate portion or including the intermediate portion, the bonding layer 40 is The bonding layer 40 may be formed in the entire position or in the axial direction.

Further, in the above embodiment, the iron core member 20 is an integrated stator core, but the iron core member according to the present invention may be a split core in which the yoke, teeth, and other parts are divided. In the case of using this split core, for example, a grain-oriented electrical steel sheet may be used instead of a non-oriented electrical steel sheet as the electrical steel sheet constituting the core member.

Further, in the above embodiment, the motor frame 30 is made of aluminum or an aluminum alloy and is joined to the iron core member 20 by dissimilar metals, but the motor frame 30 may also be made of steel and joined by a joining layer 40 using plastic flow.

10 Core structure 20 Core member 21 Yoke 22 Teeth 23 Slot 30 Motor frame 31 Extension portion 32 Through hole 40 Bonding layer 100 Tool 101 Tip surface 102 Projection 110 Horn S Joint location

Claims (7)

a cylindrical iron core member,
a cylindrical motor frame provided on the outer periphery of the iron core member;
a bonding layer provided at the boundary between the iron core member and the motor frame to fix them over the entire circumference;
The bonding layer is an iron core structure of a motor, which is a metal material of the iron core member and a metal material of the motor frame that have undergone plastic flow. The bonding layer is located on one end surface in the axial direction where the core member and the motor frame are flush with each other, and the metal material of the core member and the metal of the motor frame are in a state where plastic flow has occurred due to friction stir welding. The iron core structure of a motor according to claim 1, which is made of a material. 2. The motor core structure according to claim 1, wherein the bonding layer is a metal material of the core member and a metal material of the motor frame that have undergone plastic flow due to ultrasonic bonding. The motor core structure according to claim 3, wherein the bonding layer is located at least in an axially intermediate portion of the core member and the motor frame. A cylindrical motor frame is provided around the outer periphery of a cylindrical iron core member,
An iron core structure of a motor in which a bonding layer is formed by plastic flow at the boundary between the metal material of the iron core member and the metal material of the motor frame over the entire circumference to bond the iron core member and the motor frame. How the body is formed. The motor according to claim 5, wherein a bonding layer is formed by causing plastic flow between the iron core member and the motor frame by friction stir welding at one end surface in the axial direction where the iron core member and the motor frame are flush with each other. How to form an iron core structure. 6. The method of forming a motor core structure according to claim 5, wherein a bonding layer is formed by causing plastic flow between the core member and the motor frame by ultrasonic bonding.

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