Method for producing rotor

Abstract

In a method for manufacturing a rotor, when "Lm" represents a length of a magnet in an axial direction before a resin material is injected into a magnet accommodating hole, "Lr" represents a length of a closed portion in the axial direction when the magnet is heated and shortened by the resin material in the magnet accommodating hole, "alpha" represents a negative linear expansion coefficient of the magnet in the axial direction, and "Lm" represents a length of the closed portion in the axial direction before the resin material is injected into the magnet accommodating hole. When [beta] represents a shrinkage rate of the resin material, and [delta] T represents a difference between a temperature at which the magnet is heated and shortened by the resin material in the magnet accommodating hole and a temperature of the magnet when the resin material is cooled and cured, a length Lm of the magnet and a length Lr of the closed portion are set to satisfy an inequality Lm * [alpha] * [delta] T > = (Lr * [beta]) / 2.

Description

Technical Field

[0001] The following description relates to a method for producing a rotor. Background Art

[0002] The rotating electric machine includes a cylindrical stator and a rotor that rotates inside the stator.

[0003] Japanese Patent Laid-Open No. 2016-119766 discloses a rotor for a magnet-embedded rotating electric machine, wherein the rotor includes a cylindrical rotor core, the rotor core including a magnet receiving hole, a magnet received in the magnet receiving hole, and a thermoplastic resin material filling the magnet receiving hole and fixing the magnet to the rotor core.

[0004] The length of each magnet in the axial direction (hereinafter referred to as the magnet length) is smaller than the length of the rotor core in the axial direction. The resin material has a closing portion that covers one end surface of the magnet in its length direction and closes the opening of the magnet receiving hole. Summary of the invention

[0005] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0006] Some rotors use neodymium magnets as magnets. Neodymium magnets have a positive linear expansion coefficient in the magnetizing direction and a negative linear expansion coefficient in the non-magnetizing direction orthogonal to the magnetizing direction. Therefore, when the length direction of the magnet coincides with the non-magnetizing direction, the heat of the resin material disposed in the magnet receiving hole causes the temperature of the magnet to increase and the length of the magnet to decrease. In addition, the decrease in the temperature of the resin material causes the temperature of the magnet to decrease and the length of the magnet to increase.

[0007] When the resin material is cooled, the resin material solidifies in the magnet receiving hole. In this case, the resin material shrinks, so that the length of the closing portion in the axial direction (hereinafter simply referred to as the length of the closing portion) decreases.

[0008] Therefore, when the resin material is cooled, the length of the enclosed portion decreases and the length of the magnet increases. Accordingly, if the amount of deformation of the enclosed portion in the axial direction is greater than that of the magnet, a gap may be formed between the magnet and the enclosed portion. When the rotor is in use, such a gap may trap heat and increase the temperature of the magnet. This may cause the magnetic strength of the magnet to decrease and adversely affect the performance of the rotor.

[0009] In one general aspect, a method for manufacturing a rotor is provided. The rotor includes a cylindrical rotor core, which includes a magnet receiving hole, a magnet received in the magnet receiving hole, and a thermoplastic resin material that fills the magnet receiving hole and fixes the magnet to the rotor core. The magnet has a negative linear expansion coefficient in a non-magnetization direction orthogonal to the magnetization direction. The magnet is oriented and received in the magnet receiving hole in such a way that the non-magnetization direction coincides with the axial direction of the rotor core. The resin material includes a closure portion that covers an end face of the magnet in the axial direction inside the magnet receiving hole and closes the opening of the magnet receiving hole. The method includes a die clamping step, which uses a die to hold the rotor core from opposite sides in the axial direction while the die supports another end face of the magnet received in the magnet receiving hole. The other end face is opposite to the one end face. The die is configured to inject the resin material into the magnet receiving hole. The method also includes a magnet fixing step, which fixes the magnet to the rotor core by filling the magnet receiving hole containing the magnet with a molten resin material and solidifying the molten resin material. The axial length of the magnet before the resin material is injected into the magnet receiving hole is represented by Lm, the axial length of the closed portion when the magnet is heated by the resin material configured in the magnet receiving hole and the length of the magnet is reduced is represented by Lr, the negative linear expansion coefficient of the magnet in the axial direction is represented by α, the shrinkage rate of the resin material is represented by β, and when the difference between the temperature of the magnet when the magnet is heated by the resin material configured in the magnet receiving hole and the length of the magnet is reduced and the temperature of the magnet when the resin material is cooled and solidified is represented by ΔT, the length Lm of the magnet and the length Lr of the closed portion are set to satisfy the inequality Lm·α·ΔT≥(Lr·β) / 2.

[0010] Other features and aspects will be apparent from the following detailed description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a plan view of a rotor manufactured by the manufacturing method according to the embodiment.

[0012] Figure 2 yes Figure 1 A cross-sectional view of the rotor shown.

[0013] Figure 3 It is used to manufacture Figure 1 A cross-sectional view of the mold assembly of the rotor is shown.

[0014] Figure 4 is a cross-sectional view showing a state immediately after the magnet accommodating holes of the rotor core are filled with a resin material.

[0015] Figure 5 is a cross-sectional view showing a state in which the length of the magnet is reduced when the magnet is heated.

[0016] Figure 6 is a cross-sectional view showing a state in which the length of the magnet increases when the magnet is cooled.

[0017] Like reference numerals refer to like elements throughout the drawings and detailed description. The drawings may not be drawn to scale, and the relative sizes, proportions, and depictions of elements in the drawings may be exaggerated for clarity, illustration, and convenience. DETAILED DESCRIPTION

[0018] This detailed description provides a comprehensive understanding of the described methods, devices and / or systems. Modifications and equivalents of the described methods, devices and / or systems will be apparent to those skilled in the art. Except for operations that must occur in a particular order, the order of operations is exemplary and may be changed as apparent to those skilled in the art. Descriptions of functions and configurations known to those skilled in the art may be omitted.

[0019] Example embodiments may have different forms and are not limited to the described examples. However, the described examples are thorough and complete, and convey the full scope of the present disclosure to those skilled in the art.

[0020] Herein, “at least one of A and B” should be understood to mean “only A, only B, or both A and B”.

[0021] Now refer to Figures 1 to 6 Embodiments of a method for manufacturing a rotor are described.

[0022] Rotor 10

[0023] like Figure 1 As shown, the rotor 10 includes a rotor core 11, a magnet 20, and a resin material 30. For example, the rotor 10 is used for a magnet embedded motor.

[0024] Rotor core 11

[0025] The rotor core 11 is substantially cylindrical.

[0026] Hereinafter, the axial direction of the rotor core 11 will be simply referred to as the axial direction. The radial direction of the rotor core 11 will be simply referred to as the radial direction. The circumferential direction of the rotor core 11 will be simply referred to as the circumferential direction.

[0027] like Figure 2 As shown, the rotor core 11 is formed by stacking core pieces punched out of electromagnetic steel sheets, for example.

[0028] The rotor core 11 includes a first end surface 11 a and a second end surface 11 b located on opposite sides in the axial direction.

[0029] The rotor core 11 includes a central hole 12 and magnet receiving holes 13. A shaft (not shown) is inserted into the central hole 12. The magnets 20 are received in the magnet receiving holes 13. The magnet receiving holes 13 are arranged at intervals in the circumferential direction.

[0030] The center hole 12 and the magnet receiving hole 13 extend in the axial direction through the rotor core 11. In other words, the center hole 12 and the magnet receiving hole 13 open in the first end surface 11a and the second end surface 11b.

[0031] like Figure 1 As shown, each magnet receiving hole 13 has a substantially rectangular cross-sectional shape orthogonal to the axial direction. The rectangular cross-sectional shape has a long side and a short side. The cross-sectional shape of the magnet receiving hole 13 is the same in the entire axial direction.

[0032] Magnet 20

[0033] Each magnet 20 is received in the corresponding magnet receiving hole 13. The magnet 20 is fixed to the rotor core 11 by the resin material 30 disposed in the magnet receiving hole 13.

[0034] like Figure 2 As shown, each magnet 20 is long in the axial direction. The magnet 20 is shorter than the rotor core 11 in the axial direction.

[0035] The magnet 20 includes one end face in the axial direction. For example, the one end face is located at the inner side of the first end face 11a in the axial direction. The magnet 20 includes another end face in the axial direction opposite to the one end face. For example, the other end face is flush with the second end face 11b.

[0036] Each magnet 20 has a substantially rectangular cross section orthogonal to the axial direction. The rectangular cross-sectional shape has a long side and a short side. The drawings show the cross-sectional shape of the magnet 20 taken along the long side of the magnet 20.

[0037] The magnet 20 is, for example, a neodymium magnet. The magnet 20 has a positive linear expansion coefficient in the magnetization direction and a negative linear expansion coefficient in the non-magnetization direction orthogonal to the magnetization direction. The short side direction of the magnet 20 is the magnetization direction. The long side direction and the length direction of the magnet 20 are the non-magnetization directions. Therefore, each magnet 20 is oriented and received in the corresponding magnet receiving hole 13 in the following manner: the non-magnetization direction coincides with the axial direction of the rotor core 11, and the magnetization direction coincides with the short side direction of the magnet receiving hole 13.

[0038] Resin material 30

[0039] The resin material 30 is disposed, for example, along the entire circumference of the magnet 20 between the inner wall of the magnet accommodation hole 13 and the outer surface of the magnet 20 .

[0040] The resin material 30 includes a closing portion 31 that covers one axial end surface of the magnet 20 inside the magnet accommodation hole 13 and closes the opening of the magnet accommodation hole 13. The closing portion 31 is located at the inner side of the first end surface 11a of the rotor core 11 in the axial direction.

[0041] The resin material 30 is, for example, a thermoplastic resin such as a liquid crystal polymer.

[0042] Mold device 40

[0043] A description will now be given of the mold device 40 configured to fill the magnet receiving hole 13 with the resin material 30. The mold device 40 is an example of a mold.

[0044] like Figure 3 As shown, the mold assembly 40 includes a first die 50 and a second die 60 .

[0045] The first die 50

[0046] The first die 50 includes a first die body 51 and a support plate 52 .

[0047] The first die body 51 includes a supporting surface that supports a lower surface of the support plate 52 .

[0048] The pallet 52 is conveyed between the first die main body 51 and the second die 60 in a state where the pallet 52 supports the rotor core 11 .

[0049] The support plate 52 includes a base plate 53, a column 54, and a spacer 56. The column 54 protrudes from a central portion of the base plate 53. The spacer 56 is disposed on an upper surface of the base plate 53. The column 54 extends through the spacer 56.

[0050] The base plate 53 and the spacer 56 each have a flat plate form. The column 54 is cylindrical.

[0051] The base plate 53 includes through holes 53a arranged in the radially outer side of the pillars 54. The through holes 53a are spaced apart from each other in the circumferential direction. The through holes 53a are covered by the spacers 56.

[0052] The post 54 is inserted into the central hole 12 of the rotor core 11. Engagement pins 55 are arranged on the protruding ends of the posts 54. The engagement pins 55 are spaced apart from each other in the circumferential direction.

[0053] The spacer 56 supports the second end surface 11 b of the rotor core 11 into which the pillar 54 is inserted.

[0054] Second die head 60

[0055] The second die 60 includes a second die body 61 and a gate plate 63. For example, the second die body 61 and the gate plate 63 are formed separately.

[0056] The second die body 61 can, for example, move toward and away from the first die body 51. The second die body 61 includes a sprue 62 through which the resin material 30 injected from an injection device (not shown) flows.

[0057] The gate plate 63 is disposed between the second die body 61 and the rotor core 11. The gate plate 63 includes a runner 64 and a gate 65. The runner 64 is connected to the injection port 62. The gate 65 extends from the runner 64.

[0058] The runner 64 opens in the upper surface of the gate plate 63. The runner 64 extends radially from the central portion of the gate plate 63 in the radial direction. The gate 65 opens in the lower surface of the gate plate 63. The gate 65 connects the end of the runner 64 and the magnet accommodating hole 13.

[0059] An engagement hole 66 is provided in the lower surface of the gate plate 63. The engagement hole 66 is engaged with the engagement pin 55 of the column 54. The engagement of the engagement pin 55 and the engagement hole 66 positions the gate plate 63 relative to the support plate 52.

[0060] Method for manufacturing a rotor 10

[0061] The method for manufacturing the rotor 10 includes a magnet housing step, a die clamping step, and a magnet fixing step. The magnet housing step, the die clamping step, and the magnet fixing step are performed in this order.

[0062] Magnet Storage Steps

[0063] like Figure 3 As shown, in the magnet receiving step, the magnets 20 are received in the magnet receiving holes 13 of the rotor core 11 supported by the support plate 52. In this case, the lower surface of each magnet 20 is in contact with the upper surface of the spacer 56.

[0064] In the magnet receiving step, the magnet 20 at normal temperature is received in the magnet receiving hole 13. Herein, normal temperature refers to 20°C ± 15°C.

[0065] Die clamping steps

[0066] In the die clamping step, the support plate 52 supporting the rotor core 11 is first set on the supporting surface of the first die body 51. Then the gate plate 63 is installed on the first end face 11a of the rotor core 11. Accordingly, the first end face 11a of the rotor core 11 is completely covered by the gate plate 63. Subsequently, the first die 50 and the second die 60 are clamped so that the rotor core 11 is held from opposite sides in the axial direction by the mold device 40. The first die 50 and the second die 60 are clamped in a state where the lower surface of the magnet 20 received in the magnet receiving hole 13 is supported by the spacer 56 of the first die 50.

[0067] Magnet Fixing Steps

[0068] like Figure 4 As shown, in the magnet fixing step, first, an injection device (not shown) fills the magnet receiving hole 13 containing the magnet 20 with the resin material 30. The magnet fixing step fills the magnet receiving hole 13 with the resin material 30 that has been heated to a predetermined temperature and melted through the gate 65. In this case, the resin material 30 is injected into the magnet receiving hole 13 without any gap between the upper surface of each magnet 20 and the lower surface of the gate plate 63.

[0069] When the magnet receiving hole 13 is filled with the resin material 30, the heat of the resin material 30 heats the magnet 20. Figure 5 As shown in FIG. 1 , the length of the magnet 20 in the axial direction (hereinafter referred to as the length of the magnet 20) is reduced. In this case, since the lower surface of each magnet 20 is in contact with the upper surface of the spacer 56, the position of the lower surface of the magnet 20 does not change. On the other hand, as shown in FIG. Figure 5 As indicated by the double-dashed line, the position of the upper surface of the magnet 20 is moved downward.

[0070] When the length of the magnet 20 decreases according to the increase in the temperature of the magnet 20, the amount of deformation of the magnet 20 in the axial direction can be expressed as "Lm·α·ΔT". "Lm" represents the axial length of each magnet 20 before the magnet accommodating hole 13 is filled with the resin material 30. "α" represents the negative linear expansion coefficient of the magnet 20 in the axial direction. "ΔT" represents the temperature change in the magnet 20. In this case, the temperature change ΔT corresponds to the difference between the temperature of each magnet 20 before the magnet accommodating hole 13 is about to be filled with the resin material 30 and the temperature of the magnet 20 heated by the resin material 30. Since the magnet 20 is at room temperature before the magnet accommodating hole 13 is about to be filled with the resin material 30, "Lm" can also be referred to as the length of the magnet 20 when the magnet 20 is at room temperature.

[0071] As the length of the magnet 20 decreases, the area of ​​the magnet receiving hole 13 above the upper surface of the magnet 20 increases. As the magnet 20 becomes shorter, more resin material 30 flows into the magnet receiving hole 13 to fill the above area.

[0072] When the resin material 30 disposed in the magnet receiving hole 13 is cooled, the resin material 30 is solidified inside the magnet receiving hole 13. The solidification of the resin material 30 fixes the magnet 20 to the rotor core 11.

[0073] like Figure 6As shown, when the resin material 30 is cured, the temperature of the resin material 30 decreases, causing the resin material 30 to shrink. This reduces the length of the closing portion 31 in the axial direction (hereinafter, simply referred to as the length of the closing portion 31). The closing portion 31 shrinks at opposite sides in the axial direction. In this case, the upper surface of the closing portion 31 moves downward, while the lower surface of the closing portion 31 moves upward. For example, the amount of deformation of the closing portion 31 in the axial direction is the same on both sides.

[0074] The amount of deformation of the closing portion 31 in the axial direction when the resin material 30 shrinks can be expressed as "Lr·β". Correspondingly, the amount of deformation of the closing portion 31 in the axial direction on one side can be expressed as "(Lr·β) / 2". "Lr" represents the axial length of the closing portion 31 when the resin material 30 configured in the magnet accommodating hole 13 of the magnet 20 is heated and the length of the magnet 20 is reduced. "β" represents the shrinkage rate of the resin material 30. "Lr" can also be referred to as the axial length of the closing portion 31 when the length of the magnet 20 is "Lm-(Lm·α·ΔT)".

[0075] In the magnet fixing step, the temperature of the magnet 20 decreases according to the decrease in the temperature of the resin material 30. Therefore, the length of the magnet 20 increases. In this case, since the lower surface of each magnet 20 is in contact with the upper surface of the spacer 56, the position of the lower surface of the magnet 20 does not change. On the other hand, as Figure 6 As indicated by the double-dashed line, the position of the upper surface of the magnet 20 moves upward. As a result, the length of the magnet 20 returns to the length Lm before the magnet 20 is heated.

[0076] When the length of the magnet 20 increases according to the decrease in the temperature of the magnet 20, the deformation amount of the magnet 20 in the axial direction can be expressed as "Lm·α·ΔT". In this case, the temperature change amount ΔT corresponds to the difference between the temperature of the magnet 20 heated by the resin material 30 and the temperature of the magnet 20 when the magnet 20 is cooled. The temperature change amount ΔT when the magnet 20 is heated by the resin material 30 is equal to the temperature change amount ΔT when the magnet 20 is cooled. Therefore, the length of the magnet 20 returns to the length Lm before the magnet 20 is heated.

[0077] When the length of the magnet 20 changes according to the change in the temperature of the magnet 20, the length of the magnet 20 in the long side direction of the magnet 20 (which is the non-magnetized direction) also changes. In addition, the resin material 30 shrinks between the inner wall of the magnet accommodating hole 13 and the outer surface of the magnet 20 forming the short side. However, the resin material 30 is firmly bonded to the outer surface of the magnet 20 and the inner wall of the magnet accommodating hole 13. Therefore, it is unlikely that a gap is formed between the resin material 30 and the outer surface of the magnet 20 and between the resin material 30 and the inner wall of the magnet accommodating hole 13. The accompanying drawings do not show such changes in the size of the magnet 20 and the size of the resin material 30 in the long side direction of the magnet 20.

[0078] In the present embodiment, the rotor 10 is manufactured so that the amount of deformation of the magnet 20 in the axial direction when the length of the magnet 20 increases according to the increase in the temperature of the magnet 20 is greater than or equal to the amount of deformation of the closure portion 31 on one side in the axial direction when the resin material 30 shrinks. Specifically, in the rotor 10 of the present embodiment, the length Lm of the magnet 20 and the length Lr of the closure portion 31 are set to satisfy the inequality "Lm·α·ΔT≥(Lr·β) / 2". If the relationship between the length Lm of the magnet 20 and the length Lr of the closure portion 31 satisfies the inequality "Lm·α·ΔT<(Lr·β) / 2", a gap will be formed between the magnet 20 and the closure portion 31.

[0079] The length Lr of the closing portion 31 can be expressed as "Lr = h-(Lm-Lm·α·ΔT)", where "h" represents the height h of the rotor core 11 in the axial direction. Therefore, in the rotor 10 of the present embodiment, it can also be said that the length Lm of the magnet 20 and the height h of the rotor core 11 are set to satisfy the inequality "Lm·α·ΔT≥{h-(Lm-Lm·α·ΔT)}·β / 2".

[0080] The operation and advantages of the present embodiment will now be described.

[0081] When the heat of the resin material 30 disposed in the magnet receiving hole 13 increases the temperature of the magnet 20, the length of the magnet 20 becomes smaller than the length Lm. In this case, the amount of deformation of the magnet 20 in the axial direction is "Lm·α·ΔT". Subsequently, the temperature of the magnet 20 decreases as the resin material 30 cools, so that the length of the magnet 20 increases. In this case, the amount of deformation of the magnet 20 in the axial direction is "Lm·α·ΔT". Therefore, the length of the magnet 20 returns to the initial length Lm.

[0082] When the resin material 30 is cooled, the resin material 30 shrinks and the length of the closing portion 31 becomes smaller than the length Lr. In this case, the amount of deformation of the closing portion 31 in the axial direction is "Lr·β". The resin material 30 shrinks uniformly on both sides of the axial direction. Therefore, the closing portion 31 moves away from the magnet 20 by a distance of "(Lr·β) / 2".

[0083] In the method for manufacturing the rotor 10 of the present embodiment, the length Lm of the magnet 20 and the length Lr of the closing portion 31 are set to satisfy "Lm·α·ΔT≥(Lr·β) / 2". Therefore, when the resin material 30 is cooled, the deformation amount of the magnet 20 when the length of the magnet 20 increases becomes greater than or equal to the deformation amount of the closing portion 31 on one side in the axial direction when the length of the closing portion 31 decreases. As a result, a gap is not formed between the magnet 20 and the closing portion 31. This avoids a decrease in the magnetic strength of the magnet 20.

[0084] Variations

[0085] The present embodiment can be modified as described below. The present embodiment and the following modifications can be combined as long as the combined modifications remain technically consistent with each other.

[0086] The magnet 20 may be a magnet other than a neodymium magnet as long as the magnet 20 has a negative linear expansion coefficient in the non-magnetized direction.

[0087] The resin material 30 is not limited to liquid crystal polymer, but may be, for example, polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyamide (PA), or the like.

[0088] In the magnet receiving step, for example, a support pin may be arranged on the spacer 56 to support the lower surface of each magnet 20 so that the lower surface of the magnet 20 is located axially inside the second end surface 11b of the rotor core 11. In this case, in the magnet fixing step, the resin material 30 is cured in a state where the lower surface of the magnet 20 is located axially inside the second end surface 11b of the rotor core 11. This method also has the same advantages as the above-described embodiment.

[0089] Various changes in form and detail may be made to the above examples without departing from the spirit and scope of the claims and their equivalents. These examples are for descriptive purposes only and not for limiting purposes. The description of the features in each example should be considered applicable to similar features or aspects in other examples. Appropriate results may also be achieved if the sequence is performed in a different order, and / or if the components in the described system, architecture, device or circuit are combined in a different manner, and / or replaced or supplemented by other components or their equivalents. The scope of the present disclosure is not limited by the specific embodiments, but by the claims and their equivalents. All variations within the scope of the claims and their equivalents are included in the present disclosure.

Claims

1. A method for manufacturing a rotor, The rotor includes a cylindrical rotor core, the rotor core including a magnet receiving hole, a magnet received in the magnet receiving hole, and a thermoplastic resin material filling the magnet receiving hole and fixing the magnet to the rotor core; The magnet has a negative linear expansion coefficient in a non-magnetization direction orthogonal to the magnetization direction, and the magnet is oriented and received in the magnet receiving hole in such a manner that the non-magnetization direction coincides with the axial direction of the rotor core; as well as The resin material includes a sealing portion, the sealing portion covers one end surface of the magnet in the axial direction inside the magnet accommodating hole and seals the opening of the magnet accommodating hole, and the method includes: a die clamping step of holding the rotor core from opposite sides in the axial direction using the die in a state where the die supports the other end face of the magnet received in the magnet receiving hole, the other end face being opposite to the one end face, the die being configured to inject the resin material into the magnet receiving hole; and a magnet fixing step of fixing the magnet to the rotor core by filling the magnet receiving hole accommodating the magnet with the molten resin material and solidifying the molten resin material, Wherein, the length of the magnet in the axial direction before the resin material is injected into the magnet accommodating hole is represented by Lm, the length of the closing portion in the axial direction when the magnet is heated by the resin material arranged in the magnet accommodating hole and the length of the magnet is reduced is represented by Lr, the negative linear expansion coefficient of the magnet in the axial direction is represented by α, the shrinkage rate of the resin material is represented by β, and the difference between the temperature of the magnet when the magnet is heated by the resin material arranged in the magnet accommodating hole and the length of the magnet is reduced and the temperature of the magnet when the resin material is cooled and solidified is represented by ΔT, The length Lm of the magnet and the length Lr of the closing portion are set to satisfy the inequality Lm·α·ΔT≥(Lr·β) / 2.

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