Method for manufacturing rotors for rotating electric machines

Abstract

To reduce or eliminate wraparound of a material for a bond magnet to a flux barrier part while preferably improving workability according to an insertion of a non-magnetic body into a magnet hole.SOLUTION: The present invention discloses a rotor manufacturing method for a rotary electric machine, including: a step of preparing a workpiece of a rotor core for a rotary electric machine having a magnet hole; an insertion step of inserting a non-magnetic body into one part of magnet hole; a heating step of heating the workpiece before the insertion step or after the insertion step; and a filling step of filling a material for a bond magnet of which a magnet powder and a binding material are mixed into a part adjacent to the non-magnetic body in the magnet hole after a cooling after the heating step or subsequent to the heating step.SELECTED DRAWING: Figure 5

Description

[[TECHNICAL FIELD]]

[0001] The present disclosure relates to a method for manufacturing a rotor for a rotating electrical machine. [[BACKGROUND ART]]

[0002] A technique is known in which, in a state where the inside of a magnet insertion hole of a rotor core is divided into two spaces by a spacer made of a non-magnetic material (such as resin), a material for a bonded magnet is filled (injected) into one of the spaces (the space that becomes the bonded magnet), thereby preventing the material for the bonded magnet from filling the other space (the space that becomes the flux barrier portion). [[PRIOR ART DOCUMENTS]] [[PATENT DOCUMENTS]]

[0003] [[Patent Document 1]] Japanese Patent Laid-Open No. 2013-143791 [[SUMMARY OF THE INVENTION]] [[Problem to be Solved by the Invention]]

[0004] However, when inserting the non-magnetic body (spacer) into the magnet insertion hole, a clearance is generated between the rotor core and the non-magnetic body. When such a clearance is generated, the material for the bonded magnet injected into one space (the space that becomes the bonded magnet) flows into the other space (the space that becomes the flux barrier portion) through the clearance, which may deteriorate the magnetic properties of the finally obtained rotor for a rotating electrical machine.

[0005] Therefore, in one aspect, an object of the present disclosure is to reduce or eliminate the flowing of the bonded magnet material into the flux barrier portion while improving workability related to the insertion of the non-magnetic body into the magnet insertion hole. [[Means for Solving the Problem]]

[0006] In one aspect, the method includes: a step of preparing a workpiece of a rotor core for a rotating electrical machine having a magnet insertion hole; An insertion step of inserting a non-magnetic material into a portion of the aforementioned magnet hole, A heating step is performed to heat the workpiece before or after the insertion step, A method for manufacturing a rotor for a rotating electric machine is provided, which includes a filling step of filling the portion of the magnet hole adjacent to the non-magnetic material with a bonded magnet material, which is a mixture of magnetic powder and a binder, after cooling following the heating step or following the heating step. [Effects of the Invention]

[0007] In one aspect, this disclosure makes it possible to improve the workability of inserting non-magnetic material into the magnet hole while reducing or eliminating the leakage of bond magnet material into the flux barrier portion. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view showing the cross-sectional structure of a motor according to one embodiment. [Figure 2] This is a cross-sectional view of the rotor (a cross-sectional view taken from a plane perpendicular to the axial direction). [Figure 3] This is an enlarged view of the portion related to one of the magnetic poles shown in Figure 2. [Figure 4] This is an enlarged view of the portion related to one of the magnetic poles, based on a modified example. [Figure 5] This flowchart schematically shows the manufacturing process of the rotor in this embodiment. [Figure 6] This is a plan view showing the initial workpieces prepared during the preparation process. [Figure 6A] This is an enlarged view of section Q1 in Figure 6. [Figure 7] This diagram schematically shows the relationship between the rotor core and the non-magnetic material immediately after the insertion process, viewed in the axial direction. [Figure 8] This diagram schematically shows the relationship between the rotor core and the non-magnetic material after the cooling process, viewed in the axial direction. [Figure 9] This diagram schematically shows the state during the filling process in an axial view. [Figure 10] This is an explanatory diagram of the manufacturing method using comparative examples. [Figure 11] FIG. 1 is a diagram illustrating an example of a temperature change mode of a workpiece accompanying a heating step or the like according to the present manufacturing method. [Figure 12] FIG. 2 is a diagram illustrating another example of a temperature change mode of a workpiece accompanying a heating step or the like according to the present manufacturing method. [Figure 13] FIG. 3 is a diagram illustrating another example of a temperature change mode of a workpiece accompanying a heating step or the like in the manufacturing method according to the present modified example. MODE FOR CARRYING OUT THE INVENTION

[0009] Hereinafter, each embodiment will be described in detail with reference to the accompanying drawings. It should be noted that the dimensional ratios in the drawings are merely examples and are not limited thereto, and shapes and the like in the drawings may be partially exaggerated for convenience of explanation.

[0010] FIG. 1 is a cross-sectional view schematically showing a cross-sectional structure of a motor according to one embodiment. FIG. 2 is a cross-sectional view of a rotor (a cross-sectional view taken along a plane perpendicular to the axial direction). Note that in FIG. 2 and other drawings, for ease of viewing, reference numerals may be only partially given to a plurality of portions having the same attribute.

[0011] In FIG. 1, a rotating shaft 12 of the motor 1 is illustrated. In the following description, the axial direction refers to a direction in which the rotating shaft (rotation center) 12 of the motor 1 extends, and the radial direction refers to a radial direction centered on the rotating shaft 12. Accordingly, radially outer side refers to a side away from the rotating shaft 12, and radially inner side refers to a side toward the rotating shaft 12. The circumferential direction corresponds to a rotation direction around the rotating shaft 12.

[0012] The motor 1 may be, for example, a vehicle driving motor used in hybrid vehicles or electric vehicles. However, the motor 1 may be used for any other applications.

[0013] The motor 1 is an inner rotor type, and is provided such that a stator 21 surrounds a radially outer side of a rotor 30. A radially outer side of the stator 21 is fixed to a motor housing 10. The stator 21 includes a stator core 211 made of, for example, annular magnetic laminated steel sheets, and a plurality of slots (not shown) around which a coil 22 is wound are formed on a radially inner side of the stator core 211.

[0014] The rotor 30 is disposed radially inward of the stator 21.

[0015] The rotor 30 includes a rotor core 32, a rotor shaft 34, end plates 35A and 35B, and bonded magnets 61 and 62.

[0016] The rotor core 32 is fixed to a radially outer surface of the rotor shaft 34, and rotates integrally with the rotor shaft 34. The rotor core 32 has a shaft hole 320 (see FIG. 2), and the rotor shaft 34 is fitted into the shaft hole 320. The rotor shaft 34 is rotatably supported by the motor housing 10 via bearings 14a and 14b. Note that the rotor shaft 34 defines the rotating shaft 12 of the motor 1.

[0017] The rotor core 32 is formed of, for example, annular magnetic laminated steel sheets. In a modified example, the rotor core 32 may be formed of a compact obtained by compressing and solidifying magnetic powder. Bonded magnets 61 and 62 (see FIG. 2) are disposed inside the rotor core 32. That is, the rotor core 32 has magnet holes 321 and 322 (see FIG. 2) penetrating in the axial direction, and the bonded magnets 61 and 62 are formed in the magnet holes 321 and 322. Each of the plurality of bonded magnets 61 and 62 is formed by injection molding a bonded magnet material obtained by mixing magnetic powder and a binder (hereinafter, also simply referred to as "bonded magnet material"). The injection molding method is arbitrary, and may include, for example, transfer molding, resin injection by compression molding using a cylinder, and the like. Details of the method for forming the bonded magnet will be described in connection with the manufacturing method described later.

[0018] As shown in Figure 2, the rotor core 32 has a rotationally symmetrical configuration with respect to the rotation axis 12 when viewed in the axial direction. In the example shown in Figure 2, the rotor core 32 is configured such that each pair of bonded magnets 61 and 62 overlaps every 45 degrees of rotation around the rotation axis 12.

[0019] In the example shown in Figure 2, the multiple bond magnets 61 and 62 are arranged in a roughly V-shape (a roughly V-shape with the radially outward side opening) with pairs of two types of bond magnets 61 and 62 when viewed in the axial direction. In this case, a common magnetic pole is formed between the pairs of bond magnets 61 and between the pairs of bond magnets 62. The multiple bond magnets 61 and 62 are arranged in a manner in which the south poles and north poles appear alternately in the circumferential direction. In this embodiment, there are eight magnetic poles, but the number of magnetic poles is arbitrary.

[0020] Although Figure 1 shows a motor 1 with a specific structure, the structure of the motor 1 is not limited to this specific structure. For example, in Figure 1, the rotor shaft 34 is hollow, but it may be solid.

[0021] Next, the rotor core 32 and bonded magnets 61 and 62 will be further described with reference to Figure 3 and subsequent figures. The following description will focus on the configuration for one magnetic pole, but the configurations for other magnetic poles may be similar.

[0022] Figure 3 is an enlarged view of the portion related to one of the magnetic poles shown in Figure 2. The configuration related to one of the magnetic poles is basically symmetrical with respect to the d-axis. In the following, "outer circumferentially" refers to the side away from the d-axis.

[0023] The rotor core 32 has a radially outer magnet hole 321 (hereinafter also referred to as the "first magnet hole 321") and a radially inner magnet hole 322 (hereinafter also referred to as the "second magnet hole 322").

[0024] The first magnet holes 321 are formed in pairs in a substantially V-shape (a substantially V-shape with the radially outward side opening). However, in modified examples, the first magnet holes 321 may be formed in pairs in a straight line, or only one may be formed in a straight line (a straight line perpendicular to the d-axis). A bonded magnet 61 is provided in each of the first magnet holes 321. Gaps (cavities) are formed in the first magnet holes 321 at both longitudinal ends of the bonded magnet 61. These gaps function as flux barriers. In this embodiment, a non-magnetic material 71 is placed in the gap related to the flux barrier. The non-magnetic material 71 is provided adjacent to the bonded magnet 61. For example, of the non-magnetic materials 71 on both sides of the bonded magnet 61, the radially outward non-magnetic material 71 abuts (in this case, surface contact) against the radially outward end face of the bonded magnet 61. The non-magnetic material 71 may be provided in such a manner that it fills the entire flux barrier portion, or it may be provided in such a manner that a cavity remains in a part of the flux barrier portion. Further details of the non-magnetic material 71 will be described in relation to the manufacturing method described later. In the modified example, the non-magnetic material 71 may be removed before reaching the final product (at an appropriate stage in the manufacturing process), as described in the manufacturing method described later.

[0025] The second magnet holes 322 are provided radially inward from the first magnet holes 321. The two second magnet holes 322 are paired and formed in a substantially V-shape (a substantially V-shape with the radially outward side opening). The pair of second magnet holes 322 have a wider circumferential extension than the pair of first magnet holes 321. Bonded magnets 62 are provided in each of the second magnet holes 322. Gaps (cavities) are formed in the second magnet holes 322 at both longitudinal ends of the bonded magnets 62. These gaps function as flux barriers. In this embodiment, a non-magnetic material 72 is placed in the gaps related to the flux barrier. The non-magnetic material 72 is provided adjacent to the bonded magnets 62. The configuration of the non-magnetic material 72 itself may be the same as that of the non-magnetic material 71 described above. In a modified example, the non-magnetic material 72 may be removed before reaching the final product (at an appropriate stage in the manufacturing process).

[0026] The rotor core 32 has such a first magnet hole 321 and a second magnet hole 322, and has three parts 3211, 3212, and 3213 (hereinafter also referred to as the first part 3211, the second part 3212, and the third part 3213) that are connected only radially via a bridge portion.

[0027] Specifically, the first portion 3211 extends radially outward from the first magnet hole 321. The first portion 3211 forms part of the outer circumferential surface 328 of the rotor core 32.

[0028] The second portion 3212 extends circumferentially from the second magnet hole 322 to the outer circumferential surface 328 of the rotor core 32, passing between the second magnet hole 322 and the first magnet hole 321. On both circumferential sides of the first portion 3212, the second portion 3212 forms a part of the outer circumferential surface 328 of the rotor core 32. The second portion 3212 forms a magnetic path for the q-axis magnetic flux. Specifically, the q-axis magnetic flux flows from one end of the second portion 3212 to the other, passing between the second magnet hole 322 and the first magnet hole 321.

[0029] The third portion 3213 extends radially inward from the second magnet hole 322, with both sides extending circumferentially to the outer circumferential surface 328 of the rotor core 32. On both sides circumferentially of the second portion 3212, the third portion 3213 forms a part of the outer circumferential surface 328 of the rotor core 32.

[0030] Furthermore, the rotor core 32, having these three parts 3211, 3212, and 3213, has multiple bridge sections 41, 42, 43, and 44 connecting the three parts 3211, 3212, and 3213.

[0031] The bridge portion 41 (hereinafter also referred to as the "first bridge portion 41") supports the first portion 3211 radially outward relative to the second portion 3212. The first bridge portions 41 are provided in pairs on both sides (outward in the circumferential direction) of the first portion 3211. The first bridge portions 41 extend between the outer circumferential surface 328 of the rotor core 32 and the first magnet hole 321.

[0032] The bridge portion 42 (hereinafter also referred to as the "second bridge portion 42") supports the second portion 3212 radially outward from the third portion 3213. The second bridge portions 42 are provided in pairs on both sides (outward in the circumferential direction) of the second portion 3212. The second bridge portions 42 extend between the outer peripheral surface 328 of the rotor core 32 and the second magnet hole 322.

[0033] The bridge portion 43 supports the first portion 3211 on the d-axis relative to the second portion 3212.

[0034] The bridge portion 44 supports the second portion 3212 on the d-axis relative to the third portion 3213.

[0035] The configuration of the bonded magnets 61 and 62 in the rotor core 32 is arbitrary and not limited to the configurations shown in Figures 2 and 3. For example, in the examples shown in Figures 2 and 3, a bonded magnet 61 is provided, but as in the modified rotor 30A (rotor core 32A) shown in Figure 4, the bonded magnet 61 may be omitted. In this case, the first part 3211 and the second part 3212 are integrated, and the first bridge part 41 is substantially eliminated. Alternatively, a further bonded magnet may be arranged radially inward from the bonded magnet 62 in a manner in which the third part 3213 becomes the magnetic path for the q-axis magnetic flux.

[0036] Next, we will explain in detail the manufacturing method of the rotor core 32 (and the rotor core 32A) as described above.

[0037] Figure 5 is a flowchart illustrating the general flow of the manufacturing method for the rotor 30 in this embodiment. Figures 6 to 9 are explanatory diagrams of specific steps in the manufacturing method shown in Figure 5.

[0038] This manufacturing method first includes a preparation step (step S500) to prepare the workpiece W of the rotor core 32. As described above, the rotor core 32 has magnet holes 321 and 322. Figure 6A is an enlarged view of part Q1 in Figure 6. Figure 6 is a plan view showing the initial workpiece (rotor core 32) prepared in the preparation step. At the preparation stage, as shown in Figure 6, nothing is placed in the magnet holes 321 and 322.

[0039] Next, this manufacturing method includes a preparation step (step S502) for preparing non-magnetic materials 71 and 72. The non-magnetic materials 71 and 72 are sized to be inserted into the flux barrier portion of the magnet holes 321 and 322 to be inserted. In this manufacturing method, as an example, the non-magnetic materials 71 and 72 are sized to be the same as or slightly larger than the flux barrier portion of the magnet holes 321 and 322 to be inserted. Figure 6A shows the space SC0 that will become the bonded magnet 62 described above, and the other spaces SC1 and SC2 on either side of it (spaces that will become the flux barrier portion). Note that in Figure 6A, for illustrative purposes, the spaces SC0, SC1 and SC2 are shown slightly inside the hole edge 3221 of the magnet hole 322, but the hole edge 3221 borders the spaces SC0, SC1 and SC2. The position (boundary, etc.) of the space SC0 is determined by design. In this case, for example, the non-magnetic material 72 placed in the flux barrier portion related to space SC1 has a cross-sectional shape that is the same size as or slightly larger than the cross-sectional shape of space SC1 in an environment at a specific temperature (e.g., 20°C) within the room temperature range (e.g., 20°C ± 15°C). Note that the cross-sectional shape refers to the cross-sectional shape when cut by a plane perpendicular to the axial direction (the same applies hereinafter). In this case, the non-magnetic material 72 placed in the flux barrier portion related to space SC1 may have a cross-sectional shape that is substantially similar to the cross-sectional shape of space SC1 when viewed in the axial direction. The same applies to each of the non-magnetic materials 71 and 72 placed in the other flux barrier portions.

[0040] Furthermore, the non-magnetic materials 71 and 72 have a significantly larger coefficient of thermal expansion than the rotor core 32. The non-magnetic materials 71 and 72 may be formed from, for example, thermosetting resin materials or rubber materials (e.g., silicone rubber or fluororubber). The non-magnetic materials 71 and 72 may or may not have significant elasticity. For example, the non-magnetic materials 71 and 72 may include stainless steel or manganese steel.

[0041] The following description will mainly focus on the non-magnetic material 72 inserted into the space SC1, but the same applies to the non-magnetic material 72 inserted into the space SC2 and the non-magnetic material 71 inserted into the similar space of the magnet hole 321.

[0042] Next, this manufacturing method includes a heating step (step S504) for heating the rotor core 32 workpiece. The heating step is a step to cause thermal expansion of the rotor core 32. When the rotor core 32 expands due to heat, the cross-sectional shape of the magnet hole 322 also expands accordingly. The heating step is performed under heating conditions such that the cross-sectional shape of the space SC1 in the magnet hole 322 is the same as or larger than the cross-sectional shape of the non-magnetic material 72. In this manufacturing method, as an example, the heating step is performed under heating conditions such that the cross-sectional shape of the space SC1 in the magnet hole 322 is significantly larger than the cross-sectional shape of the non-magnetic material 72.

[0043] Note that the heating process (step S504) is applied to the workpiece of the rotor core 32, but not to the non-magnetic materials 71 and 72. Therefore, the size of the non-magnetic materials 71 and 72 immediately before the next insertion process (step S506) remains substantially unchanged from the time of the preparation process (step S502) (i.e., the time under normal temperature conditions).

[0044] Next, this manufacturing method includes an insertion step (step S506) in which non-magnetic materials 71 and 72 are inserted into the spaces SC1 and SC2, which are flux barrier portions that are part of the magnetic holes 321 and 322, respectively, of the rotor core 32 workpiece that has been heated to a high temperature by the heating step (step S504).

[0045] In this manufacturing method, as described above, by performing the heating step, the cross-sectional shape of the space SC1 in the magnet hole 322 becomes significantly larger than the cross-sectional shape of the non-magnetic material 72, thus improving the workability of the insertion step (insertion of the non-magnetic material 72 into the space SC1 in the magnet hole 322). Figure 7 is a schematic diagram showing the state immediately after the completion of the insertion step (step S506). Similar to Figure 6A, Figure 7 shows the spaces SC0 and SC1 in the magnet hole 322 that will become the bonded magnet 62 described above. Immediately after the completion of the insertion step (step S506), as schematically shown in Figure 7, the cross-sectional shape of the space SC1 in the magnet hole 322 is significantly larger than the cross-sectional shape of the non-magnetic material 72, so a clearance Δ is formed between the non-magnetic material 72 and the rotor core 32.

[0046] Next, this manufacturing method includes a cooling step (step S508) for cooling the workpiece rotor core 32 into which the non-magnetic materials 71 and 72 are inserted. The cooling step (step S508) may include lowering the temperature of the rotor core 32, which rose in the heating step (step S506), to, for example, room temperature. The method of performing the cooling step (step S508) is arbitrary and may be natural cooling or forced cooling using a cooling device (e.g., a blower). Figure 8 is a schematic diagram showing the state immediately after the completion of the cooling step (step S508). When the temperature of the rotor core 32 drops to room temperature, the rotor core 32 thermally shrinks, and the clearance Δ that existed immediately after the completion of the insertion step (step S506), as described above, becomes substantially zero. That is, the clearance Δ is substantially eliminated.

[0047] Next, this manufacturing method includes a step (step S510) of setting a rotor core 32 (workpiece) that has been cooled after inserting non-magnetic materials 71 and 72 into a magnet molding jig (not shown). The magnet molding jig may include a mold device having an upper mold and a lower mold that sandwich the workpiece from above and below, and an injection device.

[0048] Next, this manufacturing method includes a filling step (step S512) in which bonded magnet material is filled into the portions of the magnet holes 321 and 322 adjacent to the non-magnetic materials 71 and 72 using an injection molding machine (not shown). The filling step (step S512) may be performed with an oriented magnetic field applied. The filling step may also be performed following a step of heating the workpiece to a starting temperature suitable for injection molding (hereinafter also referred to as the "preheating step"). Figure 9 is a schematic diagram showing, in an axial view, the state of the force (reaction force, etc.) generated by the non-magnetic material 72 when bonded magnet material 90 is filled into the portion of the space SC1 adjacent to one of the non-magnetic materials 72. When the bonded magnet material 90 is injection molded, the bonded magnet material 90 is filled into the space SC0 with a fluid pressure corresponding to the injection pressure.

[0049] Figure 9 is a schematic diagram, viewed in the axial direction, showing the state of the force (reaction force, etc.) generated by the non-magnetic material 72 when the bonded magnet material 90 is being filled into the space SC1 adjacent to one of the non-magnetic materials 72. When the bonded magnet material 90 is injection molded, the bonded magnet material 90 is filled into the space SC0 with a fluid pressure corresponding to the injection pressure. In this manufacturing method, the filling process (step S512) is performed with virtually no clearance Δ between the rotor core 32 and the non-magnetic materials 71 and 72, as described above, so the possibility of the bonded magnet material flowing into the space SC1 and space SC2 can be reduced.

[0050] Here, we will further explain the effects of the filling process (step S512) in the present manufacturing method described above, in comparison with the manufacturing method of the comparative example.

[0051] Figure 10 is an explanatory diagram of the manufacturing method according to the comparative example, showing the state of the non-magnetic material 72' and bonded magnet material 90' in one magnet hole, from a view similar to Figure 9 relating to the present manufacturing method. In the comparative example, the non-magnetic material 72' inserted into the space SC1 differs from the non-magnetic material 72 in this embodiment (whose cross-sectional shape is larger than that of the space SC1, as described above) in that its cross-sectional shape is the same as that of the space SC1.

[0052] In the comparative example, the bonded magnet material 90 is injection molded with a small clearance Δ between the rotor core 32 and the non-magnetic materials 71 and 72. In this case, as described above in the "Problems to be Solved by the Invention" section, there is a risk that the bonded magnet material 90' may leak into the spaces SC1 and SC2 through the small clearance Δ. Such leakage of the bonded magnet material 90' can cause deterioration of the magnetic properties of the rotor for the rotating electric machine that is ultimately obtained.

[0053] In this regard, according to this manufacturing method, as described above, the filling step (step S512) is performed with virtually no clearance Δ between the rotor core 32 and the non-magnetic materials 71 and 72, due to the inclusion of a heating step (step S504). This reduces the possibility of the bonded magnet material 90 flowing into the spaces SC1 and SC2.

[0054] If the non-magnetic materials 71 and 72 are elastic, the non-magnetic materials 72 may generate elastic force when pressure is applied to them from the bonded magnet material 90 during the filling process (step S512). This elastic force functions as a reaction force in the direction that eliminates the clearance Δ (see pressure p91 in Figure 9). That is, the non-magnetic material 72 can generate a reaction force corresponding to the injection pressure of the bonded magnet material 90 (see pressure p91 in Figure 9), and the bonded magnet material does not spread into the space SC1. Since the non-magnetic material 72 is housed in the spaces SC1 and SC2 in a slightly elastically deformed state, the adhesion between the non-magnetic material 72 and the hole edge 3221 of the magnet hole 322 becomes very high. This prevents the problems that occur in the comparative example described above (the leakage of the bonded magnet material 90' and the resulting deterioration of the magnetic properties of the motor 1).

[0055] In this embodiment, the clearance Δ between the rotor core 32 and the non-magnetic material 72 (and the non-magnetic material 71) is set to 0 over the entire circumference of the non-magnetic material 72, excluding the area facing the space SC0, when viewed in the axial direction. However, this is not limited to this. For example, the non-magnetic material 72 may be configured such that the clearance Δ with respect to the rotor core 32 is 0 only in a portion of the circumference of the non-magnetic material 72, including both ends of the area facing the space SC0, when viewed in the axial direction.

[0056] Once the filling process (step S512) is completed, the manufacturing method includes other subsequent processes (step S520). These subsequent processes include, for example, a process of forming bonded magnets 61 and 62 by curing the bonded magnet material 90 filled in step S512, and a process of assembling the rotor shaft 34, etc.

[0057] In this way, according to this manufacturing method, by utilizing pre-prepared non-magnetic materials 71 and 72, the number and types of injection molding machines can be reduced compared to the case where similar non-magnetic materials are formed in the spaces SC1 and SC2 by injection molding. In other words, unlike the case where two types of injection molding are performed, one for non-magnetic materials and one for bonded magnet materials, the structure of the manufacturing equipment can be simplified (and costs reduced).

[0058] In this manufacturing method, the insertion step (step S506) and the cooling step (step S508) are performed before the setting step (step S510), but they may also be performed after the setting step (step S510). That is, the insertion step (step S506) and the cooling step (step S508) may be performed on the rotor core 32 (workpiece) while it is set in a magnet molding jig (not shown). In this case, the heating step (step S504) may also be performed after the setting step (step S510).

[0059] Next, with reference to Figures 11 and 12, some examples of how the temperature of the workpiece changes during the heating process and other steps in the manufacturing method described above will be explained.

[0060] Figure 11 is a diagram illustrating an example of how the temperature of a workpiece changes during the heating process and other steps in the manufacturing method described above. In Figure 11, time is plotted on the horizontal axis and temperature on the vertical axis, and the time series of the temperature of the rotor core 32 (labeled "core temperature" in Figure 11) and the time series of the non-magnetic materials 71 and 72 (labeled "non-magnetic material temperature" in Figure 11) are schematically shown. In Figure 11, under conditions of a specific temperature (e.g., 20°C) within the room temperature range (e.g., 20°C ± 15°C), the non-magnetic material 72 is assumed to have the same cross-sectional shape as the space SC1.

[0061] In Figure 11, the heating process begins from the point corresponding to the origin, and the temperature of the rotor core 32 rises. When the temperature of the rotor core 32 rises to a predetermined temperature (for example, around 200 degrees), the heating process ends. Then, at time t1, the insertion process is performed. Note that the non-magnetic materials 71 and 72 are not subjected to the heating process, so at time t1 they remain at their initial temperature. Next, at time t2, the cooling process is completed when the temperature of the rotor core 32 (≈ the temperature of the non-magnetic materials 71 and 72) returns to room temperature, and the clearance Δ (see Figure 7) between the rotor core 32 and the non-magnetic materials 71 and 72 becomes 0. Then, from time t3, the workpiece (rotor core 32 with the non-magnetic materials 71 and 72 assembled) is heated to a starting temperature suitable for injection molding, and at time t4, after reaching the starting temperature, the filling process (injection molding) is performed. The starting temperature suitable for injection molding may be, for example, 60°C to 90°C. As mentioned above, the coefficients of thermal expansion of the non-magnetic materials 71 and 72 are greater than those of the rotor core 32. Therefore, a clearance significantly greater than 0 will not occur due to temperature during the preheating process or the filling process (during injection molding).

[0062] Figure 12 shows another example of how the temperature of the workpiece changes during the heating process and other steps in the manufacturing method described above. In Figure 12, time is plotted on the horizontal axis and temperature on the vertical axis, and the time series of the temperature of the rotor core 32 (labeled "core temperature" in Figure 12) and the time series of the temperatures of the non-magnetic materials 71 and 72 (labeled "non-magnetic material temperature" in Figure 12) are schematically shown.

[0063] In the example shown in Figure 12, the temperature of the non-magnetic materials 71 and 72 increases during the cooling process due to heat absorption from the rotor core 32, which is different from the example shown in Figure 11. In this case, the cooling process is completed when the clearance Δ (see Figure 7) between the rotor core 32 and the non-magnetic materials 71 and 72 becomes 0 at time t12, before the temperature of the rotor core 32 (≈ temperature of the non-magnetic materials 71 and 72) reaches room temperature. Therefore, the cooling process can be shortened, and the start time t14 of injection molding can be advanced. In other words, the preheating process performed in the example shown in Figure 11 is unnecessary, so compared to the example shown in Figure 11, the process time can be shortened and energy efficiency can be improved.

[0064] In the example shown in Figure 12, since the filling process (injection molding) is performed following the cooling process, the heating process (step S504), insertion process (step S506), and cooling process (step S508) may be performed after the setting process (step S510) described above.

[0065] Next, with reference to Figure 13, a modified example of the above-described embodiment will be explained.

[0066] In the embodiments described above, it is assumed that, under the environment of a specific temperature (e.g., 20°C) within the room temperature range (e.g., 20°C ± 15°C), the non-magnetic material 72 (and the non-magnetic material 71) has a cross-sectional shape that is the same as or slightly larger than the cross-sectional shape of the space SC1, but is not limited to this.

[0067] In this modified example, under conditions of a specific temperature (e.g., 20°C) within the room temperature range (e.g., 20°C ± 15°C), the non-magnetic material 72 (and similarly the non-magnetic material 71) has a cross-sectional shape that is the same as or slightly smaller than the cross-sectional shape of the space SC1.

[0068] Figure 13 shows another example of how the temperature of the workpiece changes during the heating process and other steps in the manufacturing method according to this modified example. In Figure 13, time is plotted on the horizontal axis and temperature on the vertical axis, and the time series of the temperature of the rotor core 32 (labeled "core temperature" in Figure 13) and the time series of the temperatures of the non-magnetic materials 71 and 72 (labeled "non-magnetic material temperature" in Figure 13) are schematically shown.

[0069] In the example shown in Figure 13, the insertion of the non-magnetic materials 71 and 72 into the rotor core 32 is performed before the heating process of the rotor core 32. In this modified example, even before the heating process of the rotor core 32, the insertion process is easy because the non-magnetic material 72 (and similarly the non-magnetic material 71) has a cross-sectional shape that is the same as or slightly smaller than the cross-sectional shape of the space SC1. Specifically, after the insertion of the non-magnetic materials 71 and 72 into the rotor core 32 is performed at time t31, the heating process of the workpiece is started at time t32. In this case, the heating process may be performed in the same manner as the preheating process. Since the heating process is performed on the workpiece, the temperature of the non-magnetic materials 71 and 72 rises along with the temperature of the rotor core 32. Since the coefficient of linear expansion of the non-magnetic materials 71 and 72 is greater than that of the rotor core 32, the clearance Δ (see Figure 7) between the rotor core 32 and the non-magnetic materials 71 and 72 becomes 0 at time t33. Therefore, the filling process (injection molding) is performed at time t34, after the clearance Δ becomes 0.

[0070] Even with such modifications, the clearance Δ can be maintained at 0 within the temperature range during injection molding, thus achieving the same effects as in the above-described embodiment. Thus, the non-magnetic material 72 should have a cross-sectional shape that is the same as or slightly smaller than the cross-sectional shape of the space SC1 in the state before it is inserted into the magnet hole 322 of the rotor core 32 (during the placement process), and in the state after it is inserted into the magnet hole 322 of the rotor core 32, it should have a cross-sectional shape that is slightly larger than the cross-sectional shape of the space SC1 within the temperature range during injection molding. The same applies to the non-magnetic material 71.

[0071] In the example shown in Figure 13, if the temperature of the workpiece drops to room temperature after the filling process, the clearance Δ (see Figure 7) between the rotor core 32 and the non-magnetic materials 71 and 72 may become 0 or slightly greater than 0. Therefore, in this case, the non-magnetic materials 71 and 72 may be removed from the magnet holes 321 and 322 after the filling process.

[0072] Although each embodiment has been described in detail above, the invention is not limited to any particular embodiment, and various modifications and changes are possible within the scope described in the claims. Furthermore, it is possible to combine all or more of the components of the embodiments described above.

[0073] For example, in the above-described embodiment, the non-magnetic material 72 (and the non-magnetic material 71) has a form that fills the entire space SC1, but is not limited to this. The non-magnetic material 72 may have a form that fills only the portion of the space SC1 adjacent to the space SC0 (the portion that can define the boundary of the space SC0). In this case, the "relationship between the cross-sectional shape of the non-magnetic material 72 and the cross-sectional shape of the space SC1" in the above-described embodiment can be similarly applied by reinterpreting it as "the relationship between the cross-sectional shape of the non-magnetic material 72 and the cross-sectional shape of the portion of the space SC1 adjacent to the space SC0". [Explanation of symbols]

[0074] 1...Motor (rotating electric machine), 30...Rotor (rotor for rotating electric machine), 32, 32A...Rotor core (rotor core for rotating electric machine), 321, 322...Magnet hole, 71, 72...Non-magnetic material, 61, 62...Bonded magnet

Claims

1. A process for preparing a rotor core for a rotating electric machine having magnetic holes, A step of preparing a non-magnetic material having a cross-sectional shape similar to the cross-sectional shape of a part of the magnetic hole, An insertion step of inserting the non-magnetic material into a part of the magnetic hole, A heating step is performed to heat the workpiece either before or after the insertion step. A method for manufacturing a rotor for a rotating electric machine, comprising a filling step of filling the portion of the magnet hole adjacent to the non-magnetic material with a bonded magnet material, which is a mixture of magnetic powder and a binder, after cooling following the heating step or following the heating step.

2. The method for manufacturing a rotor for a rotating electric machine according to claim 1, wherein the non-magnetic material has a higher coefficient of thermal expansion than the material used to form the rotor core for the rotating electric machine, and is sized to be inserted into the magnet holes in the rotor core for the rotating electric machine during the insertion step.

3. The heating step is performed before the insertion step and includes increasing the size of the magnet hole so that a gap is formed in the magnet hole that allows the non-magnetic material to be inserted during the insertion step. The method for manufacturing a rotor for a rotating electric machine according to claim 1 or 2, wherein the filling step is performed after the gap has been eliminated due to cooling following the heating step.

4. The heating step is performed after the insertion step and includes eliminating the gap that allowed the non-magnetic material to be inserted into the magnet hole during the insertion step. The method for manufacturing a rotor for a rotating electric machine according to claim 2, wherein the filling step is performed following the heating step, after the gap has been eliminated as a result of the heating step.

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