Method for manufacturing rotor

Abstract

To provide a method for manufacturing a rotor capable of suppressing demagnetization of a magnet.SOLUTION: When Lm is defined as a length of a magnet 20 in an axial direction before a magnet housing hole 13 is filled with a resin material 30, Lr is defined as a length of a closing portion 31 in the axial direction when the length of the magnet 20 is shortened by being heated by the resin material 30 filled in the magnet housing hole 13, a negative linear expansion coefficient of the magnet 20 in the axial direction is defined as α, a contraction rate of the resin material 30 is defined as β, and a difference between temperature of the magnet 20 when being heated by the resin material 30 filled in the magnet housing hole 13 and the length of the magnet 20 is shortened and temperature of the magnet 20 when the resin material 30 is cooled and solidified is defined as ΔT, then, the length Lm of the magnet 20 and the length Lr of the closing portion 31 are set so as to satisfy a following expression: Lm α ΔT≥(Lr β) / 2.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a rotor. [Background technology]

[0002] The rotating electric machine includes a cylindrical stator and a rotor that rotates inside the stator. Patent Document 1 discloses a rotor used in a magnet-embedded rotating electric machine. This rotor includes a cylindrical rotor core with multiple magnet accommodating holes, magnets accommodated in the magnet accommodating holes, and a thermoplastic resin material that fills the magnet accommodating holes and fixes the magnets to the rotor core.

[0003] The length of the magnet in the axial direction (hereinafter simply referred to as the magnet length) is shorter than the length of the rotor core in the axial direction. The resin material covers one end face of the magnet in the longitudinal direction and has a closing portion that closes the opening of the magnet accommodating hole. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-119766 A Summary of the Invention [Problem to be solved by the invention]

[0005] Some rotors use neodymium magnets as magnets. Neodymium magnets have a positive linear expansion coefficient in the magnetization direction, but a negative linear expansion coefficient in the non-magnetization direction perpendicular to the magnetization direction. Therefore, when the length direction of the magnet becomes the non-magnetization direction, the temperature of the magnet increases due to the heat of the resin material filled in the magnet accommodating hole, shortening the length of the magnet. Then, as the resin material cools, the temperature of the magnet decreases, lengthening the magnet.

[0006] On the other hand, the resin material solidifies inside the magnet accommodating hole by cooling, and at this time, the resin material shrinks, shortening the length of the blocking portion in the axial direction (hereinafter simply referred to as the length of the blocking portion).

[0007] For these reasons, when the resin material cools, the length of the blocking portion shortens and the length of the magnet lengthens. Therefore, if the deformation amount of the blocking portion in the axial direction is greater than the deformation amount of the magnet, a gap may be generated between the magnet and the blocking portion. If heat is trapped in such a gap, the temperature of the magnet may become high when the rotor is in use. In this case, the magnet may be demagnetized, which may reduce the performance of the rotor. [Means for solving the problem]

[0008] A manufacturing method of a rotor for solving the above problems includes a cylindrical rotor core having magnet accommodating holes, magnets accommodated in the magnet accommodating holes, and a thermoplastic resin material filled in the magnet accommodating holes and fixing the magnets to the rotor core, the magnets having a negative linear expansion coefficient in a non-magnetization direction perpendicular to a magnetization direction, and being accommodated in the magnet accommodating holes in a position in which the non-magnetization direction coincides with the axial direction of the rotor core, the resin material covering one end face of the magnet in the axial direction inside the magnet accommodating holes and having a closing portion closing an opening of the magnet accommodating holes, the manufacturing method of a rotor including the steps of: a mold clamping process in which the rotor core is clamped from both sides in the axial direction by a mold that injects the resin material into the magnet accommodating holes while supporting another end face opposite to the one end face of the magnet accommodated in the magnet accommodating holes by the mold; and a magnet fixing process of filling the magnet accommodating holes in which the magnets are accommodated with the molten resin material and solidifying it, thereby fixing the magnets to the rotor core, wherein the length of the magnets in the axial direction before the resin material is filled into the magnet accommodating holes is Lm, the length of the blocking portion in the axial direction when the magnets are heated and shortened by the resin material filled into the magnet accommodating holes is Lr, the negative linear expansion coefficient of the magnets in the axial direction is α, the contraction rate of the resin material is β, and the difference between the temperature of the magnets when the magnets are heated and shortened by the resin material filled into the magnet accommodating holes and the temperature of the magnets when the resin material is cooled and solidified is ΔT. The length of the magnets Lm and the length of the blocking portion Lr are set so as to satisfy the following formula: Lm·α·ΔT≧(Lr·β) / 2.

[0009] According to the above method, the temperature of the magnet rises due to the heat of the resin material filled in the magnet accommodating hole, causing the length of the magnet to become shorter than Lm. The amount of deformation of the magnet in the axial direction at this time is Lm·α·ΔT. Then, as the resin material cools, the temperature of the magnet decreases, causing the length of the magnet to become longer. Since the amount of deformation of the magnet in the axial direction at this time is Lm·α·ΔT, the length of the magnet returns to its original length Lm.

[0010] On the other hand, when the resin cools, the resin contracts and the length of the blocked part becomes shorter than Lr. The amount of deformation of the blocked part in the axial direction at this time is Lr·β. Since the resin tries to contract uniformly on both sides in the axial direction, the blocked part tries to move away from the magnet by a distance of (Lr·β) / 2.

[0011] According to the above method, the length Lm of the magnet and the length Lr of the blocking portion are set so as to satisfy Lm·α·ΔT≧(Lr·β) / 2. As a result, when the resin material is cooled, the amount of deformation of the magnet when the length of the magnet increases is equal to or greater than the amount of deformation on one side of the axial direction when the length of the blocking portion decreases. As a result, it is possible to prevent a gap from occurring between the magnet and the blocking portion. Therefore, it is possible to prevent demagnetization of the magnet. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a plan view showing a rotor manufactured by a rotor manufacturing method according to one embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing the rotor of FIG. [Diagram 3] FIG. 3 is a cross-sectional view showing a molding apparatus for manufacturing the rotor of FIG. [Figure 4] FIG. 4 is a cross-sectional view showing the state immediately after the magnet accommodating holes of the rotor core are filled with resin material. [Diagram 5] FIG. 5 is a cross-sectional view showing a state in which the length of a magnet is shortened when the magnet is heated. [Figure 6] FIG. 6 is a cross-sectional view showing the state in which the length of the magnet increases when the magnet is cooled. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, one embodiment of a method for manufacturing a rotor will be described with reference to FIGS. (Rotor 10) 1, the rotor 10 includes a rotor core 11, a plurality of magnets 20, and a plurality of resin materials 30. The rotor 10 is a rotor used in, for example, an embedded magnet motor.

[0014] (Rotor core 11) The rotor core 11 has a substantially cylindrical shape. Hereinafter, the axial direction of rotor core 11 will be simply referred to as the axial direction, the radial direction of rotor core 11 will be simply referred to as the radial direction, and the circumferential direction of rotor core 11 will be simply referred to as the circumferential direction.

[0015] As shown in FIG. 2, rotor core 11 is formed, for example, by laminating a plurality of core pieces punched out from electromagnetic steel sheets. The rotor core 11 has a first end face 11a and a second end face 11b located opposite to each other in the axial direction.

[0016] The rotor core 11 has a central hole 12 into which a shaft (not shown) is inserted, and a plurality of magnet accommodating holes 13 in which magnets 20 are accommodated. The plurality of magnet accommodating holes 13 are formed at intervals from one another in the circumferential direction.

[0017] The center hole 12 and the magnet accommodating holes 13 penetrate the rotor core 11 in the axial direction. That is, the center hole 12 and the magnet accommodating holes 13 are both open to the first end face 11a and the second end face 11b.

[0018] 1, the cross-sectional shape of magnet accommodating hole 13 perpendicular to the axial direction is a substantially rectangular shape having long sides and short sides. The cross-sectional shape of magnet accommodating hole 13 is uniform throughout the axial direction.

[0019] (Magnet 20) The magnets 20 are housed one by one in each magnet accommodating hole 13. The magnets 20 are fixed to the rotor core 11 via the resin material 30 filled in the magnet accommodating hole 13.

[0020] 2, the magnet 20 has an elongated shape that is long in the axial direction. The length of the magnet 20 in the axial direction is shorter than the length of the rotor core 11 in the axial direction. One axial end face of the magnet 20 is located, for example, more inward in the axial direction than the first end face 11a. The other axial end face of the magnet 20 opposite to the one axial end face is, for example, flush with the second end face 11b.

[0021] The cross-sectional shape of magnet 20 perpendicular to the axial direction is a substantially rectangular shape having long and short sides. Note that the cross-sectional shape of magnet 20 in each drawing shows a cross section along the long side of magnet 20.

[0022] The magnet 20 is, for example, a neodymium magnet. The magnet 20 has a positive linear expansion coefficient in the magnetization direction, while it has a negative linear expansion coefficient in the non-magnetization direction perpendicular to the magnetization direction. The short side direction of the magnet 20 is the magnetization direction. The long side direction and length direction of the magnet 20 are the non-magnetization directions. Therefore, the magnet 20 is accommodated in the magnet accommodating hole 13 in a position where 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 accommodating hole 13.

[0023] (Resin material 30) The resin material 30 is filled, for example, between the inner surface of the magnet accommodating hole 13 and the outer surface of the magnet 20 around the entire periphery of the magnet 20 .

[0024] The resin material 30 has a closing portion 31 that covers one end face of the magnet 20 in the axial direction inside the magnet accommodating hole 13 and closes the opening of the magnet accommodating hole 13. The closing portion 31 is located inside the first end face 11a of the rotor core 11 in the axial direction.

[0025] The resin material 30 is, for example, a thermoplastic resin such as a liquid crystal polymer. (Molding device 40) Next, a description will be given of a molding device 40 that fills the magnet accommodating hole 13 with the resin material 30. The molding device 40 is an example of a "mold".

[0026] As shown in FIG. 3, the molding apparatus 40 includes a first mold 50 and a second mold 60 . (1st type 50) The first mold 50 includes a first mold body 51 and a pallet 52 .

[0027] The first mold body 51 has a support surface that supports the lower surface of the pallet 52 . The pallet 52 is transported between the first die body 51 and the second die 60 while supporting the rotor core 11 .

[0028] The pallet 52 includes a base plate 53, a post 54 protruding from the center of the base plate 53, and a spacer 56 disposed on the upper surface of the base plate 53. The post 54 penetrates the spacer 56.

[0029] The base plate 53 and the spacer 56 are each formed in a flat plate shape. The post 54 is formed in a cylindrical shape. A plurality of through holes 53a are provided at intervals in the circumferential direction in a portion of the base plate 53 on the outer circumferential side of the posts 54. The through holes 53a are covered with spacers 56.

[0030] The post 54 is inserted into the central hole 12 of the rotor core 11. A plurality of engagement pins 55 are provided at the tip of the post 54 at intervals in the circumferential direction. The spacer 56 supports the second end surface 11b of the rotor core 11 into which the post 54 is inserted.

[0031] (2nd type 60) The second die 60 includes a second die body 61 and a gate plate 63. The second die body 61 and the gate plate 63 are, for example, configured as separate bodies.

[0032] The second mold body 61 is, for example, a movable mold configured to be able to advance and retreat with respect to the first mold body 51. The second mold body 61 has a sprue 62 through which the resin material 30 injected from an injection device (not shown) flows.

[0033] The gate plate 63 is disposed between the second die body 61 and the rotor core 11. The gate plate 63 has a runner 64 that communicates with the sprue 62 and a plurality of gates 65 that extend from the runner 64.

[0034] The runners 64 open to an upper surface of the gate plate 63. The runners 64 extend radially in the radial direction from the center of the gate plate 63. The gate 65 opens to a lower surface of the gate plate 63. The gate 65 communicates between an end of the runner 64 and the magnet accommodating hole 13.

[0035] A plurality of engagement holes 66 into which the plurality of engagement pins 55 of the post 54 engage are provided on the lower surface of the gate plate 63. The engagement pins 55 engage with the engagement holes 66, whereby the gate plate 63 is positioned relative to the pallet 52.

[0036] (Method of manufacturing rotor 10) The manufacturing method of the rotor 10 includes a magnet accommodating step, a mold clamping step, and a magnet fixing step. The magnet accommodating step, the mold clamping step, and the magnet fixing step are performed in this order.

[0037] (Magnet storage process) 3, in the magnet accommodating step, magnets 20 are accommodated in magnet accommodating holes 13 of rotor core 11 supported by pallet 52. At this time, the lower surface of magnet 20 is in contact with the upper surface of spacer 56.

[0038] In the magnet housing step, the magnet 20 is housed in the magnet housing hole 13 at room temperature. In this specification, "room temperature" refers to 20°C±15°C. (Mold clamping process) In the mold clamping process, first, the pallet 52 supporting the rotor core 11 is placed on the support surface of the first mold body 51. Next, a gate plate 63 is placed on the first end face 11a of the rotor core 11. As a result, the entire first end face 11a of the rotor core 11 is covered by the gate plate 63. Thereafter, the first mold 50 and the second mold 60 are clamped together, and the rotor core 11 is sandwiched from both sides in the axial direction by the molding device 40. The first mold 50 and the second mold 60 are clamped together with the bottom surfaces of the magnets 20 accommodated in the magnet accommodating holes 13 supported by the spacers 56 constituting the first mold 50.

[0039] (Magnet fixing process) 4, in the magnet fixing process, first, an injection device (not shown) fills the magnet accommodating hole 13 in which the magnet 20 is accommodated with resin material 30. In the magnet fixing process, the resin material 30 that has been heated to a predetermined temperature and melted is filled into the magnet accommodating hole 13 through the gate 65. At this time, the resin material 30 is filled into the magnet accommodating hole 13 between the upper surface of the magnet 20 and the lower surface of the gate plate 63 without leaving any gaps.

[0040] As the magnet accommodating hole 13 is filled with the resin material 30, the magnet 20 is heated by the heat of the resin material 30. This shortens the length of the magnet 20 in the axial direction (hereinafter simply referred to as the length of the magnet 20) as shown in Fig. 5. At this time, the position of the bottom surface of the magnet 20 does not change because the bottom surface of the magnet 20 is in contact with the top surface of the spacer 56. Meanwhile, the position of the top surface of the magnet 20 moves downward as shown by the two-dot chain line in Fig. 5.

[0041] Here, the amount of deformation of magnet 20 in the axial direction when the length of magnet 20 shortens with an increase in temperature of magnet 20 can be expressed as Lm·α·ΔT. Lm is the length of magnet 20 in the axial direction before magnet accommodating hole 13 is filled with resin material 30. α is the negative linear expansion coefficient of magnet 20 in the axial direction. ΔT is the amount of temperature change of magnet 20. Note that the amount of temperature change ΔT at this time is the difference between the temperature of magnet 20 just before magnet accommodating hole 13 is filled with resin material 30 and the temperature of magnet 20 heated by resin material 30. Since the temperature of magnet 20 just before magnet accommodating hole 13 is filled with resin material 30 is room temperature, Lm can also be said to be the length of magnet 20 when the temperature of magnet 20 is room temperature.

[0042] As the length of magnet 20 shortens, the area of ​​magnet accommodating hole 13 above the top surface of magnet 20 increases. As the length of magnet 20 shortens, resin material 30 flows into magnet accommodating hole 13 to fill the area.

[0043] The resin material 30 filled in the magnet accommodating holes 13 is cooled and solidifies inside the magnet accommodating holes 13. The magnets 20 are fixed to the rotor core 11 as the resin material 30 is solidified.

[0044] As shown in Fig. 6, when the resin material 30 solidifies, the temperature of the resin material 30 drops, and the resin material 30 contracts. As a result, the length of the blocking portion 31 in the axial direction (hereinafter simply referred to as the length of the blocking portion 31) becomes shorter. The blocking portion 31 contracts on both sides in the axial direction. At this time, the upper surface of the blocking portion 31 moves downward and the lower surface of the blocking portion 31 moves upward. The deformation amounts on both sides of the blocking portion 31 in the axial direction are, for example, the same.

[0045] Here, the amount of deformation of the blocking portion 31 in the axial direction when the resin material 30 shrinks can be expressed as Lr·β. Therefore, the amount of deformation of one side of the blocking portion 31 in the axial direction can be expressed as (Lr·β) / 2. Lr is the length of the blocking portion 31 in the axial direction when the magnet 20 is shortened by heating with the resin material 30 filled in the magnet accommodating hole 13. β is the shrinkage rate of the resin material 30. Lr can also be said to be the length of the blocking portion 31 in the axial direction when the length of the magnet 20 is Lm-(Lm·α·ΔT).

[0046] In the magnet fixing process, the temperature of magnet 20 decreases as the temperature of resin material 30 decreases. This increases the length of magnet 20. At this time, the position of the bottom surface of magnet 20 does not change because the bottom surface of magnet 20 is in contact with the top surface of spacer 56. Meanwhile, as shown by the two-dot chain line in FIG. 6, the position of the top surface of magnet 20 moves upward. This returns the length of magnet 20 to the length Lm before magnet 20 was heated.

[0047] Here, the amount of deformation of magnet 20 in the axial direction when the length of magnet 20 increases as the temperature of magnet 20 decreases can be expressed as Lm·α·ΔT. The amount of temperature change ΔT at this time is the difference between the temperature of magnet 20 heated by resin material 30 and the temperature of magnet 20 when magnet 20 is cooled. Since the amount of temperature change ΔT when magnet 20 is heated by resin material 30 is the same as the amount of temperature change ΔT when magnet 20 is cooled, the length of magnet 20 returns to the length Lm before magnet 20 was heated.

[0048] Incidentally, when the length of magnet 20 changes with a change in temperature of magnet 20, the width of magnet 20 in the long side direction of magnet 20, which is the non-magnetized direction, changes. Then, resin material 30 tries to shrink between the outer surface constituting the short side of magnet 20 and the inner surface of magnet accommodating hole 13. However, since resin material 30 is firmly bonded to the outer surface of magnet 20 and the inner surface of magnet accommodating hole 13, a gap is unlikely to occur between resin material 30 and the outer surface of magnet 20 or the inner surface of magnet accommodating hole 13. Note that in each figure, the dimensional changes of magnet 20 and resin material 30 in the long side direction of magnet 20 are omitted from the illustration.

[0049] In this 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 with a decrease in temperature of the magnet 20 is equal to or greater than the amount of deformation of the blocking portion 31 on one side in the axial direction when the resin material 30 contracts. That is, in the rotor 10 of this embodiment, the length Lm of the magnet 20 and the length Lr of the blocking portion 31 are set so as to satisfy the formula Lm·α·ΔT≧(Lr·β) / 2. When the relationship between the length Lm of the magnet 20 and the length Lr of the blocking portion 31 satisfies the formula Lm·α·ΔT<(Lr·β) / 2, a gap will be generated between the magnet 20 and the blocking portion 31.

[0050] The length Lr of the blocking portion 31 can also be expressed as Lr = h - (Lm - Lm α ΔT) using the height h of the rotor core 11 in the axial direction. Therefore, in the rotor 10 of this 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 so as to satisfy Lm α ΔT ≧ {h - (Lm - Lm α ΔT)} β / 2.

[0051] The operation and effects of this embodiment will be described. The heat of the resin material 30 filled in the magnet accommodating hole 13 causes the temperature of magnet 20 to rise, causing the length of magnet 20 to become shorter than Lm. The amount of deformation of magnet 20 in the axial direction at this time is Lm·α·ΔT. Thereafter, the temperature of magnet 20 decreases as the resin material 30 cools, causing the length of magnet 20 to increase. Since the amount of deformation of magnet 20 in the axial direction at this time is Lm·α·ΔT, the length of magnet 20 returns to the original length Lm.

[0052] On the other hand, when the resin material 30 cools, the resin material 30 contracts, causing the length of the blocking portion 31 to become shorter than Lr. The amount of deformation of the blocking portion 31 in the axial direction at this time is Lr·β. Since the resin material 30 tries to contract uniformly on both sides in the axial direction, the blocking portion 31 tries to move away from the magnet 20 by a distance of (Lr·β) / 2.

[0053] According to the manufacturing method of the rotor 10 of this embodiment, the length Lm of the magnet 20 and the length Lr of the blocking portion 31 are set so as to satisfy Lm·α·ΔT≧(Lr·β) / 2. As a result, when the resin material 30 is cooled, the deformation amount of the magnet 20 when the length of the magnet 20 increases is equal to or greater than the deformation amount of the blocking portion 31 on one side in the axial direction when the length of the blocking portion 31 decreases. As a result, it is possible to suppress the occurrence of a gap between the magnet 20 and the blocking portion 31. Therefore, it is possible to suppress demagnetization of the magnet 20.

[0054] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

[0055] The magnet 20 may be a magnet other than a neodymium magnet as long as it has a negative linear expansion coefficient in the non-magnetized direction. The resin material 30 is not limited to a liquid crystal polymer, but may be, for example, PPS (polyphenylene sulfide), PEEK (polyether ether ketone), PA (polyamide), or the like.

[0056] In the magnet accommodating step, for example, the underside of the magnet 20 may be supported using a support pin provided on the spacer 56, thereby positioning the underside of the magnet 20 axially inward from the second end face 11b of the rotor core 11. In this case, in the magnet fixing step, the resin material 30 is solidified in a state in which the underside of the magnet 20 is positioned axially inward from the second end face 11b of the rotor core 11. Even with such a method, it is possible to achieve effects similar to those of the above embodiment. [Explanation of symbols]

[0057] α: Linear expansion coefficient β…shrinkage rate h: rotor core height ΔT: Temperature change of magnet Lm: Magnet length Lr: Length of the occlusion 10...Rotor 11...Rotor core 11a...first end surface 11b…Second end surface 12...Center hole 13...Magnet receiving hole 20…Magnet 30…Resin material 31...Occluded part 40…Molding device (mold) 50...Type 1 51…Type 1 main body 52...Palette 53…Base plate 53a...Through hole 54…Post 55...Engagement pin 56…Spacer 60…2nd type 61…Type 2 main body 62…Sprue 63…Gate plate 64…Runner 65…Gate 66…Engagement hole

Claims

[Claim 1] A manufacturing method of a rotor comprising: a cylindrical rotor core having magnet accommodating holes; magnets accommodated in the magnet accommodating holes; and a thermoplastic resin material filled in the magnet accommodating holes and fixing the magnets to the rotor core, wherein the magnets have a negative linear expansion coefficient in a non-magnetization direction perpendicular to a magnetization direction, and are accommodated in the magnet accommodating holes in a position where the non-magnetization direction coincides with an axial direction of the rotor core, the resin material has a closing portion that covers one end face of the magnet in the axial direction inside the magnet accommodating hole and closes an opening of the magnet accommodating hole, a mold clamping process in which the rotor core is sandwiched from both sides in the axial direction by a mold that injects the resin material into the magnet accommodating hole while supporting the other end face of the magnet accommodated in the magnet accommodating hole opposite to the one end face by the mold; a magnet fixing process of filling the molten resin material into the magnet accommodating hole in which the magnet is accommodated and solidifying the resin material to fix the magnet to the rotor core, The length of the magnet in the axial direction before the resin material is filled into the magnet accommodating hole is defined as Lm, The length of the blocking portion in the axial direction when the magnet is heated by the resin material filled in the magnet accommodating hole and the length of the magnet is shortened is defined as Lr, The negative linear expansion coefficient of the magnet in the axial direction is defined as α, The shrinkage rate of the resin material is β, When the difference between the temperature of the magnet when it is heated by the resin material filled in the magnet accommodating hole and the length of the magnet is shortened, and the temperature of the magnet when the resin material is cooled and solidified is ΔT, the following formula can be used Lm・α・ΔT≧(Lr・β) / 2 The length Lm of the magnet and the length Lr of the blocking portion are set so as to satisfy the above. A method for manufacturing a rotor.

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