Method for manufacturing a rotor

Abstract

The present disclosure relates to a manufacturing method of a rotor for fixing a magnet to a rotor core with high strength. The manufacturing method of the rotor has a step of arranging a magnet and a thermoplastic resin in a rotor core composed of a laminate in which a plurality of metal plates are laminated. The rotor core is provided with a magnet fixing portion composed of a hole or a groove extending along a lamination direction of the laminate. In this step, the magnet and the thermoplastic resin are arranged in the magnet fixing portion. The manufacturing method has a step of heating the rotor core while rotating the rotor core around a central axis of the rotor core in a state where the central axis intersects with a vertical direction, and a step of fixing the magnet to the rotor core via the thermoplastic resin by cooling the rotor core while rotating the rotor core around the central axis in a state where the central axis intersects with the vertical direction.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a method for manufacturing rotors. Background Technology

[0002] In the rotor manufacturing method disclosed in Patent Document 1, a step of fixing a magnet to a rotor core is included. The rotor core has a laminate formed by stacking multiple metal plates. A magnet fixing part is provided in the laminate, which is composed of holes extending along the stacking direction. In this manufacturing method, a magnet and an adhesive sheet are placed in the magnet fixing part. Then, the adhesive sheet is cured by heating the rotor core. As a result, the magnet is fixed in the magnet fixing part. Furthermore, in Patent Document 1, the magnet fixing part is composed of holes provided in the laminate, but there are also rotors where the magnet fixing part is composed of slots provided in the laminate.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2006-311782 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] To achieve high-speed rotation of the rotor, it is desirable to increase the fixing strength of the magnet to the rotor core. Therefore, this specification proposes a technique for fixing the magnet to the rotor core with high strength.

[0008] Methods for solving problems

[0009] The rotor manufacturing method disclosed in this specification includes a step of placing a magnet and thermoplastic resin in a rotor core composed of a laminate of multiple metal plates. A magnet fixing portion is provided in the rotor core, consisting of holes or slots extending along the lamination direction of the laminate. In this step, the magnet and the thermoplastic resin are disposed within the magnet fixing portion. The manufacturing method includes a step of heating the rotor core while rotating it around the central axis with the central axis intersecting the vertical direction; and a step of cooling the rotor core while rotating it around the central axis with the central axis intersecting the vertical direction, thereby fixing the magnet to the rotor core via the thermoplastic resin.

[0010] In this manufacturing method, after a magnet and thermoplastic resin are placed in the magnet fixing part, a step of heating the rotor core is performed. The thermoplastic resin softens as the rotor core is heated. Therefore, during the rotor core heating step, the softened thermoplastic resin flows within the magnet fixing part. Since the rotor core heating step is performed while the rotor core is rotated around its central axis with its central axis intersecting the vertical direction, the direction of gravity applied to the thermoplastic resin changes during this step. Therefore, the thermoplastic resin flows in a complex manner in the region between the magnet and the rotor core. This improves the adhesion of the thermoplastic resin to both the magnet and the rotor core. Next, a step of cooling the rotor core while rotating it around its central axis with its central axis intersecting the vertical direction is performed. Therefore, the thermoplastic resin cures while adhering tightly to both the magnet and the rotor core with high adhesion. Thus, the magnet can be fixed to the rotor core with high strength. Attached Figure Description

[0011] Figure 1 This is a 3D view of rotor 10.

[0012] Figure 2 It is a cross-sectional view of the rotor 10 in a plane including the central axis AX.

[0013] Figure 3 It is a cross-sectional view of the rotor 10 in a plane orthogonal to the central axis AX.

[0014] Figure 4 It is an enlarged sectional view of the through hole 70 and the groove 72 in a plane orthogonal to the central axis AX.

[0015] Figure 5 It is an enlarged cross-sectional view of the boundary between magnet 40 and rotor core 30.

[0016] Figure 6 This is a perspective view showing the rotor core 30 in the heating and cooling processes. Detailed Implementation

[0017] In one example of the manufacturing method disclosed in this specification, during the step of heating the rotor core, the temperature of the rotor core can be controlled to be higher than the softening temperature of the thermoplastic resin.

[0018] Furthermore, in this specification, softening temperature means the temperature at which the thermoplastic resin softens and becomes deformable. Softening temperature can be the glass transition point.

[0019] In one example of the manufacturing method disclosed in this specification, during the step of heating the rotor core, the temperature of the rotor core can be controlled to be lower than a temperature that is 50°C higher than the softening temperature of the thermoplastic resin.

[0020] This configuration can suppress extreme drops in the viscosity of the thermoplastic resin. Therefore, it can prevent the thermoplastic resin from leaking out of the magnet fixing part.

[0021] In one manufacturing method disclosed in this specification, a recess extending along the boundary of the plurality of metal plates may be provided on the inner surface of the magnet fixing part.

[0022] According to this configuration, since the thermoplastic resin enters the recess, the magnet can be fixed to the rotor core with higher strength through the anchoring effect.

[0023] Figure 1 The rotor 10 shown is used, for example, in a motor (not shown) mounted in a vehicle such as an electric vehicle or a hybrid vehicle. When electricity is supplied to the motor, the rotor 10 rotates. The rotor 10 has a cylindrical rotor core 30. Figure 1 The central axis AX represents the central axis of rotor core 30. The central axis AX of rotor core 30 coincides with the rotation axis of rotor 10. That is, rotor 10 rotates around the central axis AX. Figure 1 As shown, the rotor 10 includes a shaft 20, a first end plate 50, and a second end plate 52.

[0024] The shaft 20 is made of a metallic material (e.g., carbon steel, special steel, non-magnetic aluminum, or stainless steel). The shaft 20 has a cylindrical shape. Figure 1 , 2 As shown, flange 24 protrudes from the outer peripheral surface of shaft 20. A rotary transformer 26 is mounted on the outer peripheral surface of shaft 20. The rotary transformer 26 is positioned adjacent to flange 24. The rotary transformer 26 detects the rotation angle of rotor 10.

[0025] like Figure 1 , 2 As shown, the rotor core 30 is a laminated body composed of multiple electromagnetic steel plates 34. Figure 3 As shown, each electromagnetic steel plate 34 has a ring shape. A cylindrical rotor core 30 is formed by stacking multiple electromagnetic steel plates 34 with ring shapes. Figure 1 , 2 As shown, the rotor core 30 has end faces 30a and 30b on both sides of its axial direction.

[0026] The first end plate 50 is made of a metallic material (e.g., non-magnetic aluminum or stainless steel). Figure 1 , 2 As shown, the first end plate 50 has an annular shape. The first end plate 50 covers the end face 30a of the rotor core 30. The first end plate 50 and the rotor core 30 are arranged concentrically. The first end plate 50 is fixed to the end face 30a of the rotor core 30 by welding.

[0027] The second end plate 52 is made of a metallic material (e.g., non-magnetic aluminum or stainless steel). The second end plate 52 is fixed to the end face 30b of the rotor core 30 by welding. The second end plate 52 has an annular shape. The second end plate 52 covers the end face 30b of the rotor core 30. The second end plate 52 and the rotor core 30 are arranged concentrically.

[0028] like Figures 1-3 As shown, a shaft 20 is inserted through the central hole 32 of the first end plate 50, the rotor core 30, and the second end plate 52. The central axis of the shaft 20 coincides with the central axis AX of the rotor core 30. The first end plate 50 abuts against the flange 24. A washer 27 and a nut 28 are disposed on the opposite side of the flange 24. The washer 27 abuts against the second end plate 52. The first end plate 50, the rotor core 30, and the second end plate 52 are sandwiched between the flange 24 and the nut 28. Thus, the first end plate 50, the rotor core 30, and the second end plate 52 are fixed to the shaft 20.

[0029] like Figure 3 As shown, two fixing grooves 22 are provided on the outer peripheral surface of the portion of the shaft 20 that is inserted into the rotor core 30. The two fixing grooves 22 extend along the length direction of the shaft 20. Two protrusions 32a are formed on the inner surface of the central hole 32 of the rotor core 30. The shaft 20 is inserted into the central hole 32 of the rotor core 30 by engaging the protrusions 32a with the fixing grooves 22. This prevents the shaft 20 from rotating relative to the rotor core 30.

[0030] like Figure 2 , 3 As shown, a plurality of through holes 70 are provided in the rotor core 30. Each through hole 70 extends in a direction parallel to the central axis AX of the rotor core 30. That is, each through hole 70 extends along the stacking direction of the electromagnetic steel plates 34. The through holes 70 are interconnected by the through holes provided in each electromagnetic steel plate 34. Figure 2 As shown, each through hole 70 penetrates the rotor core 30. That is, each through hole 70 extends from end face 30a to end face 30b. Both ends of the through hole 70 are blocked by the first end plate 50 and the second end plate 52. Figure 3 As shown, in a section perpendicular to the central axis AX, each through hole 70 has a flat cross-sectional shape. Figure 4 As shown, the two wide surfaces (surfaces facing each other) of the inner surface of each through hole 70 are referred to as inner surfaces 70a and 70b.

[0031] like Figure 1 , 3As shown, a plurality of slots 72 are provided on the outer peripheral surface of the rotor core 30. Each slot 72 extends in a direction parallel to the central axis AX of the rotor core 30. That is, each slot 72 extends along the stacking direction of the electromagnetic steel plates 34. The slots 72 are interconnected by cutouts provided in each electromagnetic steel plate 34. Figure 1 As shown, each groove 72 extends from end face 30a to end face 30b. Both ends of each groove 72 are covered by a first end plate 50 and a second end plate 52. Figure 4 As shown, the two opposing surfaces on the inner surface of each groove 72 will be referred to as inner surfaces 72a and 72b.

[0032] like Figures 2-4 As shown, magnets 40 and resin sheets 48 are disposed in each through hole 70 and each groove 72.

[0033] Magnet 40 is a permanent magnet. For example, neodymium magnets, AlNiCo magnets, ferrite magnets, samarium cobalt magnets, praseodymium magnets, samarium iron nitride magnets, platinum magnets, or cerium cobalt magnets can be used as magnet 40. Figure 2 As shown, each magnet 40 has a shape that is elongated in a direction parallel to the central axis AX of the rotor core 30. Additionally, as... Figure 3 , 4 As shown, each magnet 40 has a flat cross-sectional shape in a section perpendicular to the central axis AX. Figure 4 As shown, each magnet 40 has wide surfaces 40a and 40b. Wide surface 40a is located on the opposite side of wide surface 40b. Within the through hole 70, the wide surface 40a of the magnet 40 faces the inner surface 70a of the through hole 70, and the wide surface 40b of the magnet 40 faces the inner surface 70b of the through hole 70. Within the slot 72, the wide surface 40a of the magnet 40 faces the inner surface 72a of the slot 72, and the wide surface 40b of the magnet 40 faces the inner surface 72b of the slot 72.

[0034] Resin sheet 48 is composed of a material containing a thermoplastic resin. As the thermoplastic resin of resin sheet 48, a material with a high glass transition temperature (Tg) can be used. Furthermore, as the thermoplastic resin of resin sheet 48, a material with excellent insulation, water resistance, oil resistance, creep resistance, and thermal shock resistance can be used. Additionally, the thermoplastic resin of resin sheet 48 can be crystalline or amorphous. For example, polyetherimide (Tg = 217°C), polyethersulfone (Tg = 230°C), and polysulfone (Tg = 190°C) can be used as the thermoplastic resin of resin sheet 48. Figure 4As shown, within the through hole 70, a resin sheet 48 is disposed between the wide surface 40a of the magnet 40 and the inner surface 70a of the through hole 70, and between the wide surface 40b of the magnet 40 and the inner surface 70b of the through hole 70. The resin sheet 48 bonds the magnet 40 to the inner surfaces 70a and 70b. Within the groove 72, a resin sheet 48 is disposed between the wide surface 40a of the magnet 40 and the inner surface 72a of the groove 72, and between the wide surface 40b of the magnet 40 and the inner surface 72b of the groove 72. The resin sheet 48 bonds the magnet 40 to the inner surfaces 72a and 72b. In this way, the magnet 40 is fixed within the through hole 70 and the groove 72 by the resin sheet 48.

[0035] Figure 5 An enlarged view of the bonding area between the magnet 40 and the rotor core 30 is shown. Furthermore, Figure 5 In the text, surface 30c of rotor core 30 represents the inner surfaces 70a and 70b of through hole 70 and the inner surfaces 72a and 72b of slot 72. For example... Figure 5 As shown, a recess 30d extending along the boundary of the stacked electromagnetic steel plates 34 is provided on the surface 30c of the rotor core 30. Each electromagnetic steel plate 34 is formed by stamping and shearing, thus forming a slight inclined portion on the end face of each electromagnetic steel plate 34. Therefore, a recess 30d extending along the boundary of the electromagnetic steel plates 34 exists on the surface 30c of the stack of multiple electromagnetic steel plates 34, i.e., the rotor core 30. Thermoplastic resin constituting the resin sheet 48 is filled seamlessly into each recess 30d.

[0036] Next, the manufacturing method of the rotor 10 will be described. First, a rotor core 30 is formed by stacking multiple electromagnetic steel plates 34 and fixing the stacked electromagnetic steel plates 34 together. Next, magnets 40 and resin sheets 48 are inserted into each through hole 70 and each slot 72 of the rotor core 30. The resin sheet 48 before use is a sheet-like component made primarily of thermoplastic resin, which has the property of expanding upon heating. As the resin sheet 48, a resin sheet obtained by sealing compressed glass fibers (so-called fillers) with thermoplastic resin can be used. When this resin sheet is heated, the stress of the compressed glass fibers is released when the thermoplastic resin softens, and the glass fibers expand. Therefore, the resin sheet expands. Alternatively, as the resin sheet 48, a component in which a foaming agent (e.g., a foam capsule) is dispersed in thermoplastic resin can also be used. When this resin sheet is heated, the thermoplastic resin softens and the foaming agent vaporizes. As a result, the resin sheet foams and expands. Here, as Figure 4 As shown, the magnet 40 and the resin sheet 48 are inserted into the through hole 70 such that the resin sheet 48 is positioned between the wide surface 40a of the magnet 40 and the inner surface 70a of the through hole 70, and between the wide surface 40b of the magnet 40 and the inner surface 70b of the through hole 70. Additionally, as... Figure 4As shown, the magnet 40 and the resin sheet 48 are inserted into the groove 72 in such a way that the resin sheet 48 is disposed between the wide surface 40a of the magnet 40 and the inner surface 72a of the groove 72, and between the wide surface 40b of the magnet 40 and the inner surface 72b of the groove 72.

[0037] Next, as Figure 6 As shown, the rotor core 30, which is equipped with the magnet 40 and the resin sheet 48, is fixed to the shaft 20x. Furthermore, the shaft 20x can be... Figure 1 The shaft 20 shown (i.e., the shaft that is a component of the rotor 10) can also be a shaft provided in a fixture used in the manufacturing process. Next, as... Figure 6 As shown, the shaft 20x is rotated while the shaft 20x is positioned so that it intersects the vertical direction. Furthermore, in... Figure 6 In the diagram, the arrow UP indicates the vertical direction. If the shaft 20x is rotated in this manner, the rotor core 30 rotates around the central axis AX with its central axis AX intersecting the vertical direction. In this embodiment, the rotor core 30 is rotated around the central axis AX with its central axis AX horizontally positioned. Here, the rotor core 30 is rotated at a relatively low speed of approximately 1 to 5 rpm. At this speed, the centrifugal force applied to each resin sheet 48 is less than the force of gravity. The rotor core 30 remains in a state where its central axis AX intersects the vertical direction until the heating and cooling processes described below are completed.

[0038] Next, a heating process is performed on the rotor core 30. During this heating process, one side... Figure 6The rotor core 30 is rotated as shown, while the resin sheet 48 is heated together with the rotor core 30. As a result, the thermoplastic resin in the resin sheet 48 softens, and the resin sheet 48 expands. That is, the thickness of the resin sheet 48 increases. Therefore, the thermoplastic resin in the resin sheet 48 is pressurized towards the magnet 40 and the rotor core 30. During the heating process, the rotor core 30 and the resin sheet 48 are held at a temperature higher than the softening temperature of the thermoplastic resin contained in the resin sheet 48 for a predetermined time. Since the rotor core 30 is rotating about a central axis AX that intersects with respect to the vertical direction, the direction of gravity applied to the thermoplastic resin softened during the heating process changes. For example, for the resin sheet 48 at position A1, which is located above the central axis AX, gravity acts towards the central axis AX side. Furthermore, for the resin sheet 48 at position A3, which is located below the central axis AX, gravity acts towards the outer periphery of the rotor core 30. Additionally, for the resin sheet 48 at position A2, which is located horizontally with respect to the central axis AX, gravity acts in the circumferential direction (rotation direction). Furthermore, for the resin sheet 48 located at position A4 in the horizontal direction relative to the central axis AX, gravity acts in the circumferential direction (opposite to rotation). Thus, due to the change in the direction of gravity applied to the thermoplastic resin, the thermoplastic resin flows in a complex manner in the region between the magnet 40 and the rotor core 30. Therefore, the thermoplastic resin can adhere to the surfaces of both the magnet 40 and the rotor core 30. This improves the adhesion of the thermoplastic resin to the magnet 40 and the rotor core 30. In particular, by changing the direction of gravity applied to the softened thermoplastic resin, it is possible to achieve… Figure 5 As shown, the thermoplastic resin is spread throughout each recess 30d on the surface 30c of the rotor core 30. Therefore, the thermoplastic resin can be tightly adhered to the inner surface of each recess 30d.

[0039] Furthermore, during the heating process, the rotor core 30 and resin sheet 48 can be maintained at a temperature lower than 50°C above the softening temperature of the thermoplastic resin. By controlling the heating temperature in this way, excessive decrease in the viscosity of the thermoplastic resin can be prevented. This, in turn, prevents softened thermoplastic resin from dripping from the rotor core 30.

[0040] Next, a cooling process is performed on the rotor core 30. During this cooling process, one side... Figure 6 The rotor core 30 is rotated as shown, while the resin sheet 48 and rotor core 30 are cooled to room temperature together. The thermoplastic resin then solidifies. Consequently, the magnet 40 is bonded to the rotor core 30 via the resin sheet 48. Because the cooling process is performed while the rotor core 30 is rotated, the thermoplastic resin solidifies in a state of close adhesion to the magnet 40 and rotor core 30. Therefore, the magnet 40 can be firmly bonded to the rotor core 30 using thermoplastic resin. Furthermore, as shown... Figure 5As shown, the thermoplastic resin solidifies in a state that fills the recess 30d on the surface of the rotor core 30. Therefore, through the anchoring effect, the thermoplastic resin is more firmly bonded to the rotor core 30.

[0041] Next, as Figure 1 As shown, the rotor core 30, after the cooling process, is installed together with the first end plate 50 and the second end plate 52 onto the shaft 20. Thus, Figure 1 The rotor 10 shown is now complete.

[0042] As explained above, according to the manufacturing method of this embodiment, the magnet 40 can be firmly connected to the rotor core 30 using the thermoplastic resin of the resin sheet 48. Therefore, it is possible to manufacture a rotor 10 that can withstand high-speed rotation.

[0043] Furthermore, in the above embodiment, the magnet 40 is bonded to the rotor core 30 using a resin sheet 48, but the bonding member with thermoplastic resin may also have other configurations.

[0044] While the embodiments have been described in detail above, they 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 illustrated above. The technical elements described in this specification or drawings 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 even one of these objectives is itself technically useful.

Claims

1. A manufacturing method of a rotor, comprising: a step of arranging a magnet and a thermoplastic resin in a rotor core configured of a laminate of a plurality of metal sheets, wherein a magnet fixing portion configured of a hole or a groove extending along a laminating direction of the laminate is provided in the rotor core, and in the step, the magnet and the thermoplastic resin are arranged in the magnet fixing portion, and a recess extending along boundaries of the plurality of metal sheets is provided on an inner surface of the magnet fixing portion, the recess being configured of a slight inclined portion formed at an end surface of the plurality of metal sheets; a step of rotating the rotor core around a central axis of the rotor core at a speed of 1 to 5 rpm while the central axis is crossed with respect to a vertical direction, and heating the rotor core; and a step of rotating the rotor core around the central axis at a speed of 1 to 5 rpm while the central axis is crossed with respect to the vertical direction, and cooling the rotor core, thereby fixing the magnet to the rotor core via the thermoplastic resin.

2. The manufacturing method of a rotor according to claim 1, in the step of heating the rotor core, the temperature of the rotor core is controlled to be higher than a softening temperature of the thermoplastic resin.

3. The manufacturing method of a rotor according to claim 2, in the step of heating the rotor core, the temperature of the rotor core is controlled to be lower than a temperature 50°C higher than the softening temperature with respect to the thermoplastic resin.

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