Stator and electric motor

Abstract

This stator (2) is disposed inside a housing (3) of an electric motor (1), the stator (2) comprising: a stator core (20); a coil (21) formed by winding a winding around the stator core (20), the coil (21) having a coil end (21a) that protrudes in the axial direction from each of the two axial-direction end surfaces of the stator core (20); and two thermoconductive resin parts (22) provided to the two axial-direction end surfaces of the stator core (20), the two thermoconductive resin parts (22) covering the coil end (21a). The outer peripheral surface (22g) of at least one of the two thermoconductive resin parts (22) has formed therein a notch (22h) that is notched from the radial-direction outer side to the radial-direction inner side. The notch (22h) is formed in a portion of the outer peripheral surface (22g) of the thermoconductive resin part (22) in the axial direction and the circumferential direction, and is open to the stator-core (20) side among the two axial-direction end surfaces of the thermoconductive resin part (22).

Description

Stator and motor

[0001] The present disclosure relates to a stator and an electric motor including a stator core and a coil.

[0002] Conventionally, a stator has been known that includes a cylindrical stator core and a coil. The coil is formed by winding a wire around the stator core. The coil has coil ends. The coil ends are portions of the coil that protrude in the axial direction from the axial end face of the stator core. The coil ends are covered with a resin portion.

[0003] The stator is disposed inside a cylindrical housing. The housing has an insertion hole for disposing the stator. When disposing the stator inside the housing during manufacturing of the electric motor, it is necessary to determine the axial position of the housing relative to the stator.

[0004] Patent Document 1 describes a technology for axially positioning the housing relative to the stator by providing an exposed surface that is exposed from the resin portion on the outer peripheral edge of the axial end face of the stator core and bringing this exposed surface into contact with a stepped surface provided on the inner peripheral surface of the insertion hole of the housing. The exposed surface is formed by making the outer diameter of the entire resin portion smaller than the outer diameter of the stator core, or by providing a notch that penetrates the outer peripheral surface of the resin portion in the axial direction.

[0005] International Publication No. 2022 / 045166

[0006] However, with the technology disclosed in Patent Document 1, if the exposed surface is formed by making the outer diameter of the entire resin portion smaller than the outer diameter of the stator core, the outer surface of the resin portion does not come into contact with the housing. Also, with the technology disclosed in Patent Document 1, if the exposed surface is formed by providing a notch penetrating the outer surface of the resin portion in the axial direction, the size of the notch becomes too large to ensure a sufficient contact area between the outer surface of the resin portion and the housing. Therefore, in either case, heat generated from the coil is less likely to be transferred to the housing through the resin portion, resulting in a problem of reduced cooling performance for the coil.

[0007] The present disclosure has been made in consideration of the above, and aims to provide a stator that can position the housing axially relative to the stator and can suppress a decrease in cooling performance for the coil.

[0008] In order to solve the above-mentioned problems and achieve the object, the stator according to the present disclosure is a stator disposed inside the housing of an electric motor, and includes a stator core, a coil formed by winding a winding around the stator core and having coil ends protruding in the axial direction from both axial end faces of the stator core, and two thermally conductive resin portions provided on both axial end faces of the stator core and covering the coil ends. A notch cut from the outer periphery of at least one of the two thermally conductive resin portions is formed in the outer periphery from the outer side toward the inner side in the radial direction. The notch is formed in a part of the outer periphery of the thermally conductive resin portion in the axial and circumferential directions, and opens to the stator core side of both axial end faces of the thermally conductive resin portion.

[0009] The stator according to the present disclosure has the advantage that it is possible to determine the axial position of the housing relative to the stator and to suppress a decrease in cooling performance for the coil.

[0010] FIG. 1 is a cross-sectional view showing an electric motor including a stator according to a first embodiment, the cross-sectional view being taken along the axial direction; FIG. 2 is a side view showing a stator according to the first embodiment, the cross-sectional view showing an example of a notch in the first embodiment; FIG. 3 is a side view showing a stator according to the first embodiment, the cross-sectional view showing another example of a notch in the first embodiment; FIG. 4 is a side view showing a stator according to a second embodiment, the cross-sectional view showing an example of a notch in the second embodiment;

[0011] A stator and an electric motor according to an embodiment will be described in detail below with reference to the drawings.

[0012] First Embodiment Fig. 1 is a cross-sectional view showing an electric motor 1 including a stator 2 according to a first embodiment, taken along the axial direction. The electric motor 1 includes a stator 2, a housing 3, a rotor 4, and two brackets 5. A stator core 20 (described later) of the stator 2 is formed in a cylindrical shape having a central axis C. Hereinafter, when describing the directions of each component of the electric motor 1, the direction parallel to the central axis C will be referred to as the axial direction, the direction perpendicular to the central axis C as the radial direction, and the direction of rotation about the central axis C as the circumferential direction.

[0013] The housing 3 is formed in a cylindrical shape with both axial ends open. An insertion hole 30 for disposing the stator 2 is formed in the housing 3. A hole 31 for inserting a positioning pin 7 is formed in the housing 3. The hole 31 penetrates the side wall of the housing 3 in the radial direction. The hole 31 is disposed at a position that coincides with one of the notches 22h described below in the axial direction. In other words, the hole 31 is disposed at a position that faces one of the notches 22h in the radial direction. The pin 7 is a member used to axially position the housing 3 relative to the stator 2 when disposing the stator 2 inside the housing 3. Although it is not a component of the electric motor 1, the pin 7 is also shown in FIG. 1 for ease of explanation.

[0014] The rotor 4 is disposed on the inner periphery of the stator 2. The rotor 4 is provided with a shaft portion 6 extending along the central axis C of the stator 2. One bracket 5 is disposed at one end and the other end in the axial direction of the housing 3. Each bracket 5 has a bearing 60 that rotatably supports the shaft portion 6 of the rotor 4. The shaft portion 6 of the rotor 4 is rotatably supported by the two bearings 60.

[0015] The stator 2 is disposed inside the housing 3 of the electric motor 1. The stator 2 includes a stator core 20, a plurality of coils 21, two thermally conductive resin portions 22, and a plurality of lead wires 23.

[0016] The stator core 20 is formed in a cylindrical shape. The stator core 20 is configured to include, for example, a laminate of rolled steel sheets or electromagnetic steel sheets stacked in the axial direction. A through hole 20a extending in the axial direction is formed in the stator core 20. The rotor 4 is disposed in the through hole 20a. The stator core 20 has a plurality of teeth 20b. The plurality of teeth 20b are arranged radially around the central axis C.

[0017] Each of the multiple coils 21 is formed by winding a wire around the stator core 20. A coil 21 is formed by winding a wire around each tooth portion 20b. Each coil 21 has two coil ends 21a that protrude in the axial direction from both axial end faces of the stator core 20. The coil ends 21a protrude in the axial direction away from the axial center of the stator core 20 along the axial direction.

[0018] Hereinafter, when distinguishing between the coil end 21a that protrudes in the axial direction from one axial end face 20c of the stator core 20 and the coil end 21a that protrudes in the axial direction from the other axial end face 20d of the stator core 20, they will be referred to as the first coil end 21b and the second coil end 21c. Note that in Figure 1, the portion of each coil 21 located between the two coil ends 21a is omitted from illustration.

[0019] The lead wires 23 electrically connect a power supply unit (not shown) to the coils 21. One end of the lead wires 23 in the length direction is connected to the power supply unit, and the other end of the lead wires 23 in the length direction is connected to a terminal portion (not shown) of the coils 21. Power is supplied to each coil 21 from the power supply unit via the lead wires 23. The length of the lead wires 23 is not limited to the example shown in the figure and may be changed as appropriate.

[0020] The thermally conductive resin portion 22 is provided on each of both axial end surfaces (one end surface 20c and the other end surface 20d) of the stator core 20. The thermally conductive resin portion 22 is formed in a cylindrical shape. The thermally conductive resin portion 22 is formed by molding. The material of the thermally conductive resin portion 22 is a resin having thermal conductivity. Examples of such resins include thermosetting resins such as epoxy resin. The thermally conductive resin portion 22 may contain a filler or the like.

[0021] The thermally conductive resin portion 22 covers the coil end 21a. The thermally conductive resin portion 22 covers the entire coil end 21a. The thermally conductive resin portion 22 serves to transfer heat generated from the coil 21 to the housing 3. The heat generated from the coil 21 is transferred to the thermally conductive resin portion 22. The heat transferred to the thermally conductive resin portion 22 is transferred to the housing 3. A cooling medium such as cooling oil (not shown) flowing around the outer periphery of the housing 3 absorbs the heat transferred to the housing 3. As a result, the coil 21 is cooled by the cooling medium via the thermally conductive resin portion 22 and the housing 3.

[0022] An outer peripheral surface 22g of the thermally conductive resin portion 22 is a surface that faces the housing 3 in the radial direction. The thermally conductive resin portion 22 has a first thermally conductive resin portion 22a and a second thermally conductive resin portion 22b. The first thermally conductive resin portion 22a is provided on one axial end surface 20c of the stator core 20. The first thermally conductive resin portion 22a covers first coil ends 21b of the multiple coils 21. The second thermally conductive resin portion 22b is provided on the other axial end surface 20d of the stator core 20. The second thermally conductive resin portion 22b covers second coil ends 21c of the multiple coils 21. The first thermally conductive resin portion 22a and the second thermally conductive resin portion 22b may be formed of the same resin or different resins.

[0023] Lead wires 23 are arranged in the first thermally conductive resin portion 22a to electrically connect the coil 21 to a power supply portion (not shown). The first thermally conductive resin portion 22a has a first outer axial end face 22c facing away from the stator core 20 and a first inner axial end face 22d facing toward the stator core 20. The first outer axial end face 22c and the first inner axial end face 22d are flat surfaces extending in the radial direction. The first inner axial end face 22d is a surface that contacts the stator core 20. The first inner axial end face 22d contacts one axial end face 20c of the stator core 20. The first inner axial end face 22d is located at the boundary of the first thermally conductive resin portion 22a with the stator core 20.

[0024] The second thermally conductive resin portion 22b has a second outer axial end face 22e facing away from the stator core 20, and a second inner axial end face 22f facing toward the stator core 20. The second outer axial end face 22e and the second inner axial end face 22f are flat surfaces extending in the radial direction. The second inner axial end face 22f is a surface that contacts the stator core 20. The second inner axial end face 22f contacts the other axial end face 20d of the stator core 20. The second inner axial end face 22f is located at the boundary between the second thermally conductive resin portion 22b and the stator core 20.

[0025] FIG. 2 is a side view of the stator 2 according to the first embodiment. FIG. 3 is a side view of the stator 2 according to the first embodiment, illustrating an example of the notch 22h according to the first embodiment. FIG. 4 is a side view of the stator 2 according to the first embodiment, illustrating another example of the notch 22h according to the first embodiment. FIGS. 3 and 4 are views of the stator 2 viewed from an angle different from that of FIG. 2. As shown in FIG. 2, a notch 22h is formed in an outer peripheral surface 22g of a first thermally conductive resin portion 22a of the two thermally conductive resin portions 22, the outer peripheral surface 22g being cut radially inward. The notch 22h is formed in a part of the outer peripheral surface 22g of the first thermally conductive resin portion 22a in the axial and circumferential directions, and opens to the stator core 20 side of both axial end faces of the first thermally conductive resin portion 22a. In other words, the notch 22h does not penetrate the outer peripheral surface 22g of the first thermally conductive resin portion 22a in the axial and circumferential directions. In this embodiment, the number of notches 22h is two, but may be changed as appropriate. The two notches 22h are arranged at equal angles (at 180-degree intervals in this embodiment). Hereinafter, a portion of the outer peripheral surface 22g of the first thermally conductive resin portion 22a where no notches 22h are formed in the circumferential direction and where the outer diameter of the outer peripheral surface 22g is constant over the entire circumferential length will be referred to as a "reference portion 22i."

[0026] The shape of the notch 22h when viewed in the radial direction is not particularly limited, and may be a rectangle as shown in Fig. 3 or a circle (perfect circle) as shown in Fig. 4. In this embodiment, the outer diameter D2 of the reference portion 22i shown in Fig. 2 is the same as the outer diameter D1 of the stator core 20, but is preferably smaller than the outer diameter D1 of the stator core 20. The outer diameter D3 of the portion of the outer surface 22g of the first thermally conductive resin portion 22a that includes the notch 22h is smaller than the outer diameter D1 of the stator core 20 and the outer diameter D2 of the reference portion 22i.

[0027] Next, the effects of the stator 2 and the electric motor 1 according to this embodiment will be described.

[0028] 2, in the present embodiment, a notch 22h is formed in the outer peripheral surface 22g of the first thermally conductive resin portion 22a of the two thermally conductive resin portions 22, cutting the outer peripheral surface 22g radially inward. Furthermore, in the present embodiment, the notch 22h is formed in a portion of the outer peripheral surface 22g of the first thermally conductive resin portion 22a in the axial and circumferential directions, and is open on the stator core 20 side of both axial end faces of the first thermally conductive resin portion 22a. With this configuration, a portion of one axial end face 20c of the stator core 20 is exposed from the first thermally conductive resin portion 22a through the notch 22h. Therefore, when the stator 2 is disposed inside the housing 3 shown in FIG. 1, the pin 7 inserted through the hole 31 of the housing 3 can be placed against this exposed portion to axially position the housing 3 relative to the stator 2. That is, when the stator 2 is disposed inside the housing 3, the portion of the axial end face 20c of the stator core 20 that is exposed from the first thermally conductive resin portion 22a can be used as a positioning surface.

[0029] Furthermore, in this embodiment, because the notches 22h do not penetrate the outer peripheral surface 22g of the first thermally conductive resin portion 22a in the axial and circumferential directions, the size of the notches 22h can be reduced to ensure a sufficient contact area between the outer peripheral surface 22g of the first thermally conductive resin portion 22a and the housing 3. As a result, even when the first thermally conductive resin portion 22a has the notches 22h, heat generated from the coil 21 is more easily transferred to the housing 3 through the first thermally conductive resin portion 22a, thereby suppressing a decrease in cooling performance for the coil 21. Therefore, in this embodiment, the axial positioning of the housing 3 with respect to the stator 2 can be performed and a decrease in cooling performance for the coil 21 can be suppressed.

[0030] A conventional technique for axially positioning a housing relative to a stator, as disclosed in Japanese Patent Publication No. 7333887, involves providing recesses on the axial top and bottom surfaces of a resin portion and contacting a stepped surface on the inner circumferential surface of the housing insertion hole to axially position the housing relative to the stator. The bottom surface of the recess serves as a positioning surface that contacts the stepped surface. However, this conventional technique involves contacting the entire axial end surface of the stator core with the resin portion, which poses a problem in that it is not possible to support the stator core by contacting a jig or the like with the axial end surface of the stator core during molding resin encapsulation. In this regard, in the present embodiment, a portion of a molding jig (not shown) can be positioned at the position where the notch 22h shown in FIG. 2 is formed, and a portion of the molding jig can be brought into contact with one axial end surface 20c of the stator core 20 to support the stator core 20 during molding resin encapsulation. In the above-described conventional technology, recesses are provided on the axial top and bottom surfaces of the resin portion, and the axial end face of the stator core is not exposed. This makes it impossible to measure the dimension between the axial end face of the stator core and the positioning surface of the resin portion. Furthermore, in the above-described conventional technology, the positioning surface is made of resin, and dimensional variation due to resin shrinkage after molding is large. This makes it difficult to accurately determine the dimension between the axial end face of the stator core and the positioning surface of the resin portion, resulting in large variations in the positional relationship between the stator core and the rotor. Due to these factors, the above-described conventional technology has a problem in that it is difficult to align the stator and rotor. In this regard, in the present embodiment, as shown in FIG. 1 , a portion of the axial end face 20c of the stator core 20 is exposed from the first thermally conductive resin portion 22a through the cutout 22h, forming a positioning surface. This allows the position of the axial end face 20c of the stator core 20 and the housing 3 to be accurately determined. This facilitates alignment of the stator 2 with the rotor 4, which is held in the housing 3 via a bearing 60.

[0031] Next, a modification of this embodiment will be described.

[0032] In this embodiment, as shown in Figure 2, the notch 22h is formed on the outer peripheral surface 22g of only the first thermally conductive resin part 22a, but it is sufficient if it is formed on the outer peripheral surface 22g of at least one of the two thermally conductive resin parts 22.

[0033] Second Embodiment Next, a stator 2A according to a second embodiment will be described with reference to Figures 5 and 6. Figure 5 is a side view of a stator 2A according to the second embodiment, showing an example of a notch 22h in the second embodiment. Figure 6 is a side view of a stator 2A according to the second embodiment, showing another example of a notch 22h in the second embodiment. In this embodiment, the shape of the notch 22h differs from that of the first embodiment. In the second embodiment, parts that overlap with those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0034] In this embodiment, the shape of the notch 22h when viewed in the radial direction is semicircular as shown in Fig. 5 or trapezoidal as shown in Fig. 6. The notch 22h shown in Fig. 5 is formed in a semicircular shape that is convex in the direction away from the stator core 20. The notch 22h shown in Fig. 6 is formed in a trapezoidal shape that is convex in the direction away from the stator core 20.

[0035] Next, the effects of the stator 2A according to this embodiment will be described.

[0036] In this embodiment, the shape of the notch 22h when viewed radially is semicircular or trapezoidal, which does not hinder the flow of the molded resin when it is sealed, and can suppress the occurrence of voids and cracks in the thermally conductive resin part 22.

[0037] Third Embodiment Next, a stator 2B according to a third embodiment will be described with reference to Fig. 7. Fig. 7 is a side view showing a stator 2B according to the third embodiment. This embodiment differs from the first embodiment in that a notch 22h is formed in each of the two thermally conductive resin portions 22. In the third embodiment, parts that overlap with those in the first embodiment are denoted by the same reference numerals and will not be described again.

[0038] The configuration (the configuration of the coil 21, the lead wire 23, etc.) is the same as that of the first embodiment described above (see FIG. 1 ), except that the notch 22h is formed in each of the two thermally conductive resin portions 22. When one axial side of the stator 2 on which the lead wire 23 for electrically connecting the coil 21 to a power supply unit (not shown) is disposed is defined as the wire connection side, and the axial side opposite the wire connection side is defined as the anti-wire connection side, the notch 22h is formed in the first thermally conductive resin portion 22a provided on the wire connection side and the second thermally conductive resin portion 22b provided on the anti-wire connection side. In other words, the notch 22h is provided on both axial sides of the stator 2.

[0039] Next, the effects of the stator 2B according to this embodiment will be described.

[0040] In this embodiment, the notches 22h are formed in the first thermally conductive resin portion 22a provided on the wire connection side and the second thermally conductive resin portion 22b provided on the non-wire connection side, so that when the molding resin is filled, the molding resin can be poured from either end face in the axial direction of the stator core 20, and therefore the filling direction of the molding resin can be freely selected. This improves the workability when filling the molding resin.

[0041] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0042] 1 electric motor, 2, 2A, 2B stator, 3 housing, 4 rotor, 5 bracket, 6 shaft portion, 7 pin, 20 stator core, 20a through hole, 20b teeth portion, 20c one end face, 20d other end face, 21 coil, 21a coil end, 21b first coil end, 21c second coil end, 22 thermally conductive resin portion, 22a first thermally conductive resin portion, 22b second thermally conductive resin portion, 22c first outer shaft end face, 22d first inner shaft end face, 22e second outer shaft end face, 22f second inner shaft end face, 22g outer peripheral surface, 22h notch, 22i reference portion, 23 lead wire, 30 insertion hole, 31 hole, 60 bearing, C central axis, D1, D2, D3 outer diameter.

Claims

1. A stator placed inside the housing of an electric motor, comprising: a stator core; a coil formed by winding wire around the stator core, the coil having coil ends protruding in the axial direction from both axial end faces of the stator core; and two thermally conductive resin sections provided on both axial end faces of the stator core and covering the coil ends, wherein the outer peripheral surface of at least one of the two thermally conductive resin sections has a notch cut out from the outside radially toward the inside, the notch being formed in part of the outer peripheral surface of the thermally conductive resin section in the axial and circumferential directions, and opening on the stator core side of both axial end faces of the thermally conductive resin section.

2. The stator according to claim 1, wherein the shape of said notch when viewed along the radial direction is semicircular or trapezoidal.

3. A stator as described in claim 1, characterized in that when one side of the axial direction of the stator where lead wires for electrically connecting the power supply unit and the coil are arranged is defined as the connection side and the side opposite the connection side in the axial direction is defined as the anti-connection side, the notches are formed in the thermally conductive resin part provided on the connection side and the thermally conductive resin part provided on the anti-connection side.

4. An electric motor comprising: a housing; a stator according to any one of claims 1 to 3 that is placed inside the housing; a rotor that is placed on the inner periphery of the stator; and brackets that are placed at one end and the other end of the housing in the axial direction and have bearings that rotatably support the rotor.

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