Rotor of an electric motor and method of manufacturing the same, and method of manufacturing a sheet

Abstract

The present invention provides a technology capable of improving both adhesion and swelling of a sheet. The technology disclosed in the present specification is embodied in a rotor of an electric motor. The rotor has a rotor core having a hole, a magnet inserted into the hole, and a sheet between an inner face of the hole and a side face of the magnet, the side face facing the inner face. The sheet has a first contact layer in contact with the inner face of the hole, a second contact layer in contact with the side face of the magnet, and a main body layer between the first contact layer and the second contact layer, the main body layer having a porous structure. The main body layer has a higher porosity than at least one of the first contact layer and the second contact layer. Here, each of the first contact layer and the second contact layer can or can not have a porous structure. That is, at least one of the first contact layer and the second contact layer can have a porosity of zero.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a rotor for an electric motor and a method for manufacturing the same, as well as a method for manufacturing the sheet material used in the manufacturing method. Background Technology

[0002] Patent Document 1 discloses a rotor for an electric motor. The rotor comprises: a rotor core having a hole (referred to as a magnet insertion slot in Patent Document 1); a magnet inserted into the hole; and a sheet (referred to as an insulating sheet in Patent Document 1) wound around the magnet. The sheet is made of a foamable material and, after being inserted into the hole in the rotor core along with the magnet, is heated to expand its volume. The expanded sheet fills the gap between the inner surface of the hole and the side surface of the magnet, thus fixing the magnet relative to the hole. Prior art literature Patent documents Patent document 1: Japanese Patent Application Publication No. 2020-115712. Summary of the Invention The problem the invention aims to solve

[0003] In the rotor of Patent Document 1, the greater the expansion of the sheet, the more reliably the expanded sheet can fill the gap between the inner surface of the hole and the side surface of the magnet. On the other hand, the greater the expansion of the sheet, the higher the porosity of the expanded sheet, resulting in a decrease in the adhesion of the sheet relative to the inner surface of the hole and the side surface of the magnet. Therefore, in conventional structures, it is difficult to improve both the expansion capacity and adhesion of the sheet. This specification provides a technique that improves both the adhesion and expansion capacity of the sheet. Methods for solving problems

[0004] The technology disclosed in this specification is embodied in the rotor of an electric motor. The rotor has: a rotor core having a hole; a magnet inserted into the hole; and a sheet located between the inner surface of the hole and the side surface of the magnet, the side surface facing the inner surface. The sheet has: a first contact layer contacting the inner surface of the hole; a second contact layer contacting the side surface of the magnet; and a main body layer located between the first and second contact layers and having a porous structure. The main body layer has a higher porosity than at least one of the first and second contact layers. Here, the first and second contact layers may each have a porous structure or not. That is, at least one of the first and second contact layers may also have a porosity of zero.

[0005] In the aforementioned rotor, the sheet has a first contact layer that contacts the inner surface of the hole, a second contact layer that contacts the side surface of the magnet, and a main body layer located between the first and second contact layers. Furthermore, the main body layer has a higher porosity compared to at least one of the first and second contact layers. With this structure, by primarily expanding the main body layer, the sheet's expandability can be improved, while simultaneously, by maintaining a low porosity in the first and / or second contact layers, the sheet's adhesion can be improved.

[0006] Furthermore, this specification also discloses a method for manufacturing a rotor of an electric motor. This manufacturing method includes: a step of inserting a sheet and a magnet into a hole in the rotor; and an expansion step of expanding the sheet disposed in the hole. The sheet has: a first contact layer in contact with the inner surface of the hole; a second contact layer in contact with the side surface of the magnet facing the inner surface; and a main body layer located between the first and second contact layers and having a porous structure. In the expansion step, the main body layer expands more significantly than at least one of the first and second contact layers and has a higher porosity than at least one of the first and second contact layers.

[0007] According to the manufacturing method described above, in the expansion process, the main body layer expands more significantly than at least one of the first contact layer and the second contact layer, and has a higher porosity compared to that layer. A rotor that can be manufactured according to this method improves the expandability of the sheet by primarily expanding the main body layer, while simultaneously improving the adhesion of the sheet through the first and / or second contact layers with low porosity.

[0008] The details of the technology disclosed in this specification and further improvements will be described in the following "Detailed Description". Attached Figure Description

[0009] Figure 1 A perspective view of rotor 2 in an embodiment. Figure 2 This is a top view of rotor core 2c. Figure 3 Indicates being Figure 2 A magnified view of the area enclosed by the double-dotted line III. Figure 4 It is along Figure 3 Sectional view of IV-IV. Figure 5 This represents a sectional view during the lamination process. Figure 6 This is a cross-sectional view showing the heating and compression process. Figure 7 This is a cross-sectional view showing the sheet bonding process. Figure 8 This is a cross-sectional view showing the magnet insertion process. Figure 9 This is a cross-sectional view representing the expansion process. Detailed Implementation

[0010] In one embodiment of the invention, the main body layer may also have a higher porosity than either the first contact layer or the second contact layer. With this structure, the sheet exerts a large adhesive force relative to both the inner surface of the hole and the side surface of the magnet, thus securing the magnet more firmly.

[0011] In one embodiment of the invention, the hole may also extend through the rotor core in the axial direction of the rotor. A magnet fixed in a through hole is more likely to detach from the hole compared to a magnet fixed in a closed hole. Therefore, the above-described technique is advantageous for rotors with through holes.

[0012] In one embodiment of the invention, the sheet may also comprise glass fibers and resin. In this case, the main body layer may contain more glass fibers than at least one of the first contact layer and the second contact layer, and at least one of the first contact layer and the second contact layer may contain more resin than the main body layer. However, in another embodiment, the main body layer may replace the glass fibers and contain more material that expands through chemical reactions such as neutralization compared to at least one of the first contact layer and the second contact layer.

[0013] In one embodiment of the invention, the rotor core may also be formed by stacking multiple steel plates. However, in another embodiment, the rotor core may also be made by cutting steel.

[0014] In one embodiment of the invention, the sheet can be expanded by heating during the expansion process. However, in another embodiment, the sheet can also be expanded by a chemical reaction such as neutralization.

[0015] In one embodiment of the present invention, the method for manufacturing the sheet may also include: a lamination step of laminating a first material layer and a second material layer, wherein the first material layer constitutes the main body layer and the second material layer constitutes at least one of the first contact layer and the second contact layer; and a heat compression step of heating and simultaneously compressing the laminated first material layer and the second material layer. The first material layer and the second material layer are made of thermoplastic material, and at least the first material layer contains fibrous material. The first material layer has a higher content of fibrous material compared to the second material layer. According to this manufacturing method, the sheet's expandability is improved through a relatively easy process using the first material layer with a high fibrous material content, and the porosity of the first contact layer and / or the second contact layer can be maintained at a low level using the second material layer.

[0016] (Example) Reference Figure 1 The rotor 2 of the embodiment is illustrated. The Z-axis shown in the figure is an axis parallel to the axis 100 of the rotor 2. The XY plane is a plane orthogonal to the Z-axis. In this specification, the direction parallel to the Z-axis is sometimes simply referred to as the "axial direction." Furthermore, the direction of a straight line parallel to the XY plane and passing through the intersection of the XY plane and the axis 100 is sometimes simply referred to as the "radial direction."

[0017] Rotor 2 constitutes an electric motor (illustration omitted). Although the illustration is omitted, the stator is arranged radially outside rotor 2. When current flows through the coils of the stator, a magnetic force is generated between rotor 2 and the stator, causing rotor 2 to rotate around axis 100. Rotor 2 constitutes a radially gapped type electric motor.

[0018] like Figure 1 As shown, the rotor 2 includes a rotor core 2c, a shaft 4, and a magnet 6. The rotor core 2c is formed by stacking multiple steel plates axially. The individual steel plates constituting the rotor core 2c are insulated from each other. By stacking multiple insulated steel plates to form the rotor core 2c, overcurrent in the rotor core 2c can be suppressed. Furthermore, this reduces iron losses generated on the rotor 2.

[0019] The rotor core 2c has multiple holes 2h. Holes are pre-formed in multiple steel plates constituting the rotor core 2c, and by overlapping the holes in the stacked steel plates, holes 2h are formed that axially penetrate the rotor core 2c. Magnets 6 are inserted into the multiple holes 2h. The shaft 4 has an axially extending cylindrical shape. The shaft 4 axially penetrates the center of the rotor core 2c.

[0020] like Figure 2 As shown, the rotor core 2c has 16 holes 2h. These 16 holes 2h are arranged in 8 pairs. The paired holes 2h correspond to the rotor 2 (see reference). Figure 1One pole of the rotor core 2c. That is, the rotor core 2c has holes 2h corresponding to a total of 8 poles. The pairs of holes 2h are arranged symmetrically to each other. The pairs of holes 2h are arranged along the outer periphery of the rotor core 2c with their orientation toward the center of the rotor core 2c. Furthermore, the number of holes 2h in the rotor core 2c is adjusted according to the number of poles of the rotor 2.

[0021] A shaft hole 4h is formed in the center of the rotor core 2c. The shaft hole 4h axially penetrates the rotor core 2c. Two protrusions 4p are formed on the inner circumferential surface of the shaft hole 4h. One protrusion 4p is positioned facing the other protrusion 4p. Grooves are formed on both sides of each protrusion 4p. Shaft 4 (refer to...) Figure 1 It is fixed to the rotor core 2c by engaging with the protrusion 4p and groove of the shaft hole 4h.

[0022] Reference Figure 3 The detailed shape of hole 2h is described. Figure 3 Is it by Figure 2 The enlarged view of the area enclosed by the double-dotted line III is a magnified view of the perimeter of one hole 2h. Furthermore, the other holes 2h have roughly the same shape. Hole 2h has a roughly rectangular shape. At one end of the length direction of hole 2h ( Figure 3 At the upper middle end, its width gradually narrows. At the other end along the length of the hole 2h (in... Figure 3 The lower end of the hole 2h has a plane extending toward the center (i.e., axis 100) of the rotor core 2c. The hole 2h is a shape formed by combining multiple shapes into a generally rectangular shape. The hole 2h has inner surfaces 2i facing each other along its short side. One inner surface 2i extends approximately parallel to the other inner surface 2i. That is, the distance between the inner surfaces 2i is fixed.

[0023] like Figure 3 As shown, a rectangular magnet 6 is inserted into the hole 2h of the rotor core 2c along the axis 100 (i.e., axial direction). As described above, the rotor core 2c is formed by stacking multiple steel plates. By inserting the magnet 6 into the hole 2h of the rotor core 2c with stacked steel plates, magnetic flux is generated in the rotor core 2c. Sheets 10 are respectively arranged between the inner surface 2i of the hole 2h of the rotor core 2c and the side surface 6s of the magnet 6 facing the inner surface 2i. For details, refer to... Figure 4 To illustrate, the magnet 6 is fixed in the hole 2h by the sheet 10.

[0024] The sheet 10 contains resin. Therefore, the sheet 10 also functions as an insulating material to prevent conductivity between the magnet 6 and the rotor core 2c. By positioning the sheet 10 between the inner surface 2i and the side surface 6s, direct contact between the side surface 6s of the magnet 6 and the inner surface 2i of the rotor core 2c can be prevented. When the side surface 6s and the inner surface 2i are in direct contact and conduction occurs between them, in the rotor 2 (refer to...) Figure 1 Iron loss is generated in the rotor 2. Iron loss is reduced by placing a resin-containing sheet 10 between the side surface 6s and the inner surface 2i.

[0025] Furthermore, a space S1 is provided between one end of the magnet 6 along its length and one end of the hole 2h along its length, and a space S2 is provided between the other end of the magnet 6 along its length and the other end of the hole 2h along its length. Spaces S1 and S2 axially penetrate the rotor core 2c. When the rotor 2c is assembled in the motor (not shown), Figure 1 When the rotor 2 rotates, the magnet 6 heats up. The longitudinal end of the magnet 6 is exposed in spaces S1 and S2. When the rotor 2 rotates, the longitudinal end of the heated magnet 6 can be directly cooled by circulating the oil that cools the magnet 6 in spaces S1 and S2.

[0026] Reference Figure 4 The detailed structure of sheet 10 is described below. Sheet 10 has a main body layer 11, a first contact layer 12, and a second contact layer 13. The first contact layer 12 contacts the inner surface 2i of the rotor core 2c. The second contact layer 13 contacts the side surface 6s of the magnet 6. The main body layer 11 is located between each of the contact layers 12 and 13.

[0027] Figure 4 Below is an enlarged view of the cross-sectional view of sheet 10. The main body layer 11 is composed of three fiber layers 21. Each fiber layer 21 contains a plurality of glass fibers 31 and resin 32. The plurality of glass fibers 31 are fibrous materials that meander in the axial direction. The plurality of glass fibers 31 are at least partially covered by resin 32. A gap is provided between each of the plurality of glass fibers 31. That is, the main body layer 11 composed of the plurality of glass fibers 31 has a porous structure. As described above, oil for cooling magnet 6 circulates in the holes 2h of rotor core 2c. The main body layer 11 has a porous structure, so that the oil passes through the spaces between the plurality of glass fibers 31 of the main body layer 11. Thus, sheet 10 can cool magnet 6 from the side 6s by the oil passing through the main body layer 11. As a result, the cooling efficiency of magnet 6 can be improved compared to a structure in which the main body layer 11 does not have a porous structure. Similarly, sheet 10 can cool rotor core 2c from the inner surface 2i by the oil passing through the main body layer 11.

[0028] Each contact layer 12 and 13, like the main body layer 11, comprises glass fiber 31 and resin 32. That is, each contact layer 12 and 13, like the main body layer 11, has a porous structure. Figure 4 As shown in the enlarged view, the amount of glass fiber 31 contained in each contact layer 12, 13 is less than the amount of glass fiber 31 contained in the main layer 11. As a result, each contact layer 12, 13 has a lower porosity than the main layer 11. Each contact layer 12, 13 contains more resin 32 than glass fiber 31. Although the main layer 11 also contains resin, the amount of resin 32 contained in the main layer 11 is less than the amount of resin 32 contained in each contact layer 12, 13. The resin 32 is thermoplastic, for example, polyetherimide (PEI).

[0029] Details will be provided later. Figure 9 To explain, the resin 32 of the first contact layer 12 is melted by heating and then cooled, thereby bonding the first contact layer 12 to the inner surface 2i of the hole 2h of the rotor core 2c. Similarly, the resin 32 of the second contact layer 13 is melted by heating and then cooled, thereby bonding the second contact layer 13 to the side surface 6s of the magnet 6. Therefore, the more resin 32 contained in each contact layer 12 and 13, the greater the adhesive force of each contact layer 12 and 13.

[0030] As described above, each contact layer 12, 13 contains more resin 32 compared to the main body layer 11. Therefore, the adhesive strength of each contact layer 12, 13 is greater than that of the main body layer 11. Figure 4 As shown, in sheet 10, the first contact layer 12 contacts the inner surface 2i of the hole 2h of the rotor core 2c, and the second contact layer 13 contacts the side surface 6s of the magnet 6. Therefore, sheet 10 can firmly fix the magnet 6 in the hole 2h of the rotor core 2c through the contact layers 12 and 13, which have strong adhesive force.

[0031] Furthermore, the sheet 10 expands to fill the gap between the inner surface 2i of the hole 2h in the rotor core 2c and the side surface 6s of the magnet 6. As a result, the first contact layer 12 is pressed against the inner surface 2i of the hole 2h in the rotor core 2c, making contact with the inner surface 2i. The stronger the first contact layer 12 is pressed against the inner surface 2i, the stronger its adhesive force becomes. Similarly, the second contact layer 13 is pressed against the side surface 6s of the magnet 6, making contact with the side surface 6s. The stronger the second contact layer 13 is pressed against the side surface 6s, the stronger its adhesive force becomes.

[0032] By heating, the sheet 10 expands, and the first contact layer 12 is pressed against the inner surface 2i, while the second contact layer 13 is pressed against the side surface 6s. Therefore, the greater the expansion of the sheet 10, the greater the adhesive force of each contact layer 12 and 13 becomes.

[0033] As described above, the main body layer 11 contains more glass fibers 31 compared to the contact layers 12 and 13. See details below. Figure 6 As described later, the stress generated in the glass fibers 31 by heating and compression is released by heating, and the glass fibers 31 regain their shape, thereby causing the sheet 10 to expand. Therefore, the more glass fibers 31 there are, the greater the expansion of the sheet 10. The main layer 11, which contains more glass fibers 31 than the contact layers 12 and 13, expands more than the contact layers 12 and 13. As a result, the main layer 11 has a higher porosity than the contact layers 12 and 13.

[0034] As described above, sheet 10 aims to contain a large amount of resin 32 and a large amount of glass fiber 31. However, the more the amount of resin 32 contained in sheet 10 increases, the less the amount of glass fiber 31 contained in sheet 10 decreases. Similarly, the more the amount of glass fiber 31 contained in sheet 10 increases, the less the amount of resin 32 contained in sheet 10 decreases.

[0035] In sheet 10, contact layers 12 and 13 containing a greater amount of resin are disposed on both radial sides of sheet 10, and a main body layer 11 containing a greater amount of glass fiber 31 is disposed between contact layers 12 and 13. Thus, the first contact layer 12 contacts the inner surface 2i of the hole 2h of the rotor core 2c, and the second contact layer 13 contacts the side surface 6s of the magnet 6. Therefore, its porosity is low, and the contact layers 12 and 13 containing a greater amount of resin 32 can be firmly bonded to the contact surfaces 2i and 6s. Furthermore, a greater amount of glass fiber 31 is disposed on the main body layer 11 disposed between contact layers 12 and 13, and the sheet 10 can improve its expansion properties by using the main body layer 11 which does not contact the surfaces 2i and 6s. Thus, sheet 10 can forcefully press the contact layers 12 and 13 onto the surfaces 2i and 6s. In this manner, the rotor 2 disclosed in this specification (see reference...) Figure 1 This can improve both the expansion and adhesion of the sheet 10.

[0036] The following is for reference Figure 5 , Figure 6 This describes the manufacturing method of sheet 10. First, refer to... Figure 5 The following describes the lamination process. In the lamination process, after the second contact layer 13 is placed on top of the fixture 40, three fiber layers 21 and the first contact layer 12 are sequentially laminated on top of it. Thus, the three fiber layers 21 are located between the second contact layer 13 and the first contact layer 12.

[0037] Next, the explanation Figure 6The heating and compression process is described below. In the heating and compression process, with the second contact layer 13, the three fiber layers 21, and the first contact layer 12 stacked, the compression jig 42 moves from above along arrow F1. The compression jig 42 compresses the second contact layer 13, the three fiber layers 21, and the first contact layer 12 in the direction of arrow F1. At this time, the compression jig 42 and jig 40 heat the second contact layer 13, the three fiber layers 21, and the first contact layer 12. As described above, each contact layer 12, 13, and fiber layer 21 contains glass fiber 31 and resin 32. Resin 32 is thermoplastic and therefore softens upon heating. Furthermore, in the heating and compression process, the compression jig 42 and jig 40 compress the second contact layer 13, the three fiber layers 21, and the first contact layer 12 while heating them at a temperature exceeding the glass transition temperature of the resin 32. Therefore, the shape of the glass fiber 31 is easily deformed in the heating and compression process. As a result, as Figure 6 As shown, during the heating and compression process, the thickness of each contact layer 12, 13 and fiber layer 21 is reduced.

[0038] When the heating and compression process ends, heating of the compression fixtures 42 and 40 stops, and the contact layers 12, 13 and fiber layer 21 are cooled. As a result, resin 32 cures. In this manner, sheet 10 is manufactured. At this moment, through the cured resin 32, the shape of the glass fiber 31 is maintained in a deformed state. That is, the thickness of sheet 10 is maintained in a reduced state.

[0039] Next, refer to Figures 7-9 This indicates that rotor 2 (refer to) Figure 1 The manufacturing method of ). First, refer to Figure 7 The sheet pressing process is described below. In the sheet pressing process, sheet 10 is placed on a heated pressing jig 44, and magnet 6 is placed on top of sheet 10 in sequence. As a result, the side 6s of magnet 6 contacts the second contact layer 13 of sheet 10. Further, sheet 10 and magnet 6 are compressed in the direction of arrow F2 by heated pressing jig 46. At this time, heated pressing jigs 44 and 46 heat sheet 10 and magnet 6 to the melting temperature of resin 32, and then cool them. Thus, contact layer 13 and side 6s of magnet 6 are bonded together by resin 32.

[0040] Next, refer to Figure 8 The magnet insertion process is described below. In the magnet insertion process, the magnet 6 and the sheet 10, which is bonded to its two sides 6s, are inserted into the hole 2h of the rotor core 2c in the direction of arrow F3. At this time, as mentioned above, in the heating and compression process and the sheet pressing process, the sheet 10 is compressed while being heated, so the thickness of the sheet 10 is reduced. Therefore, as... Figure 8As shown, during the magnet insertion process, a gap d1 is created between the first contact layer 12 of the sheet 10 and the inner surface 2i of the hole 2h. Therefore, during the magnet insertion process, the sheet 10 is less likely to interfere with the inner surface 2i. In the magnet insertion process, by inserting the magnet 6, with the sheet 10 bonded to it in a reduced-thickness state, into the hole 2h, the insertability of the magnet 6 can be improved. During the magnet insertion process, the magnet 6 and the sheet 10 are inserted until they abut against the underside of the magnet 6 on the upper surface of the support clamp 48 supporting the rotor core 2c from below.

[0041] Next, refer to Figure 9 The expansion process is described below. In the expansion process, with the magnet 6 and sheet 10 inserted into the hole for 2 hours, the rotor core 2c, magnet 6, and sheet 10 are heated. At this time, the rotor core 2c, magnet 6, and sheet 10 are heated to a temperature exceeding the glass transition temperature of resin 32. As a result, resin 32 softens. Consequently, in the heating compression process (refer to...), Figure 6 The deformed glass fiber 31 in the sheet 10 is restored to its original shape. As a result, the thickness of the sheet 10 increases. That is, the sheet 10 expands. As a result, the sheet 10 fills the gap between the side surface 6s of the magnet 6 and the inner surface 2i of the hole 2h. As a result, the first contact layer 12 is pressed against the inner surface 2i of the hole 2h. Further, the resin 32 is pressed against the inner surface 2i in a molten state by heating. After the sheet 10 expands, the rotor core 2c, the magnet 6, and the sheet 10 are cooled. As a result, the resin 32 is cured again, and the first contact layer 12 is bonded to the inner surface 2i. After the magnet 6 is fixed in the hole 2h by the sheet 10, the shaft 4 (refer to Figure 1 Insert the rotor core 2c, thereby completing rotor 2.

[0042] The following are variations of the above embodiments.

[0043] (Modification 1) In the rotor 2 described above, the sheet 10 has a first contact layer 12 and a second contact layer 13. In this modification, the sheet 10 may also have only the first contact layer 12. In this case, during the sheet pressing process, the sheet 10 may also be bonded to the magnet 6 with an adhesive.

[0044] (Modification 2) In the rotor 2 described above, two sheets 10 are used to fix the magnet 6 in the hole 2h. In this modification, instead, a single sheet 10 can be used to fix the magnet 6 in the hole 2h.

[0045] (Modification 3) In the rotor 2 described above, the hole 2h penetrates the rotor core 2c axially. In this modification, the hole 2h may also be a recess provided on the rotor core 2c.

[0046] (Modification 4) In the rotor 2 described above, a rotor core 2c consisting of multiple stacked steel plates is used to manufacture the rotor 2. In this modification, instead, a rotor core 2c formed integrally may also be used.

[0047] (Modification 5) In the above-described method for manufacturing rotor 2, in the sheet pressing process, after pressing magnet 6 and sheet 10 together, in the magnet insertion process, magnet 6 and sheet 10 are inserted into hole 2h in rotor core 2c. In this modification, instead, magnet 6 can be inserted into hole 2h first, and then sheet 10 can be inserted between side surface 6s of magnet 6 and inner surface 2i of hole 2h. Furthermore, in other modifications, a pair of sheets 10 can be inserted into hole 2h first, and then magnet 6 can be inserted between the pair of sheets 10.

[0048] (Modification 6) In the rotor 2 described above, the sheet 10 comprises resin 32 and glass fiber 31. In this modification, the sheet 10 may also comprise a material that expands through a chemical reaction such as neutralization instead of glass fiber 31. In this case, the main body layer 11 may also contain more of this material compared to the contact layers 12 and 13. Furthermore, in this case, during the expansion process, a substance that causes the material to expand may be added instead of heating, thereby causing the sheet 10 to expand. In addition, the main body layer 11 may also comprise a material that expands through heating instead of glass fiber 31.

[0049] (Modification 7) In the rotor 2 described above, the main body layer 11 of the sheet 10 is composed of three fiber layers 21. In this modification, the main body layer 11 may be composed of one fiber layer 21, or it may be composed of two or more fiber layers 21.

[0050] (Modification 8) In the rotor 2 described above, each contact layer 12, 13 of the sheet 10 contains glass fiber 31. In this modification, each contact layer 12, 13 may also not contain glass fiber 31. In this case, each contact layer 12, 13 may also be formed by coating the surface of the laminated fiber layer 21 with resin 32.

[0051] (Modification 9) In the rotor 2 described above, the same three fiber layers 21 are stacked between each contact layer 12, 13. In this modification, the central fiber layer of the three fiber layers 21 may contain more glass fibers 31 compared to the other fiber layers 21. As a result, the amount of glass fibers 31 is greatest in the center of the sheet 10 in the thickness direction, and the amount of resin 32 is greatest on the surface side of the sheet 10 in the thickness direction. In this way, the amount of glass fibers 31 (i.e., porosity) and resin 32 in the sheet 10 can also vary in the thickness direction of the sheet 10.

[0052] The specific examples of the present invention have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations to the specific examples described above. The technical elements illustrated in this specification or drawings are elements that exert their technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of application. Furthermore, the technology illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful. Explanation of reference numerals in the attached figures

[0053] 2: Rotor; 2c: Rotor core; 2h: Hole; 2i: inner surface; 4: Axis; 4h: Shaft hole; 4p: protrusion; 6: Magnet; 6s: Side view; 10: Sheets; 11: Main body layer; 12: First contact layer; 13: Second contact layer; 21: Fiber layer; 31: Fiberglass; 40: Fixture; 42: Compression clamp; 44, 46: Heated pressing fixtures; 48: Support clamp.

Claims

1. A rotor, specifically the rotor of an electric motor, having: Rotor core, which has holes; A magnet, which is inserted into the hole; A sheet material is positioned between the inner surface of the hole and the side surface of the magnet, the side surface facing the inner surface. The sheet material has the following characteristics: A first contact layer that contacts the inner surface of the hole; A second contact layer that contacts the side surface of the magnet; A main body layer with a porous structure is located between the first contact layer and the second contact layer. The main body layer has a higher porosity compared to at least one of the first contact layer and the second contact layer. The sheet material comprises glass fiber and resin. The main body layer contains more glass fibers than at least one of the first contact layer and the second contact layer. At least one of the first contact layer and the second contact layer contains more of the resin compared to the main body layer. The main body layer comprises a plurality of glass fibers and resin, with each of the glass fibers being at least partially covered by resin. A gap is provided between each of the plurality of glass fibers, allowing oil for cooling the magnet to pass through the gaps between the plurality of glass fibers in the main body layer.

2. The rotor according to claim 1, wherein, The main body layer has a higher porosity than either the first contact layer or the second contact layer.

3. The rotor according to claim 1 or 2, wherein, The hole penetrates the rotor core in the axial direction of the rotor.

4. The rotor according to claim 1 or 2, wherein, The rotor core is composed of multiple steel plates stacked together.

5. A manufacturing method for a rotor of an electric motor, comprising: The process of inserting the sheet and magnet into the hole of the rotor; An expansion process that causes the sheet disposed in the hole to expand. The sheet material has the following characteristics: A first contact layer that contacts the inner surface of the hole; A second contact layer that contacts the side surface of the magnet facing the inner surface; A main body layer with a porous structure is located between the first contact layer and the second contact layer. During the expansion process, the main body layer expands significantly compared to at least one of the first contact layer and the second contact layer, and has a higher porosity compared to at least one of the first contact layer and the second contact layer. The sheet material comprises glass fiber and resin. The main body layer contains more glass fibers than at least one of the first contact layer and the second contact layer. At least one of the first contact layer and the second contact layer contains more of the resin compared to the main body layer. The main body layer comprises a plurality of glass fibers and resin, with each of the glass fibers being at least partially covered by resin. A gap is provided between each of the plurality of glass fibers, allowing oil for cooling the magnet to pass through the gaps between the plurality of glass fibers in the main body layer.

6. The manufacturing method according to claim 5, wherein, In the expansion process, the sheet is expanded by heating.

7. A manufacturing method for the sheet used in the manufacturing method according to claim 6, comprising: The lamination process involves laminating a first material layer and a second material layer, wherein the first material layer constitutes the main body layer and the second material layer constitutes at least one of the first contact layer and the second contact layer. The heating and compression process involves heating and simultaneously compressing the stacked first and second material layers. The first material layer and the second material layer are made of thermoplastic material. At least the first material layer and the second material layer comprise a fibrous material. The first material layer has a higher content of fiber material compared to the second material layer.

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