Rotor structure of embedded magnet motor, manufacturing method thereof, and manufacturing device for rotor structure of embedded magnet motor

Abstract

To provide a rotor structure of a magnet embedded motor with simple structure, whose weight can be reduced, and materials of a bond magnet can be reduced, a manufacturing method thereof, and a manufacturing device of the rotor structure of the magnet embedded motor.SOLUTION: A rotor structure of a magnet embedded motor of an embodiment comprises a rotor having a shaft and a rotor core attached to the shaft. The rotor core is an electromagnetic steel plate laminate with a cylindrical outer peripheral surface and has a through hole penetrating in an axial direction of the shaft. In the through hole, a resin iron core and a bond magnet are arranged in order from a shaft side toward the outside in a radial direction. The resin iron core is a resin molding containing a soft magnetic material. The bond magnet has a gate mark formed on a surface side facing the resin iron core in the radial direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a rotor structure of an embedded magnet motor, a manufacturing method thereof, and a manufacturing apparatus for the rotor structure of an embedded magnet motor. [Background technology]

[0002] Interior permanent magnet motors (IPM motors), in which permanent magnets are embedded in the rotor core, can use both the magnetic torque generated by the magnetic flux of the permanent magnet and the reluctance torque generated by changes in the magnetic resistance (reluctance) of the rotor core as torque, and are used in a variety of fields. In some cases, bonded magnets, which are a mixture of magnetic powder and resin, are used as permanent magnets.

[0003] 2. Description of the Related Art Conventionally, embedded magnet motors have been disclosed that aim to reduce the weight of the rotor, improve the degree of orientation of the bonded magnets, and suppress rotor deformation (see, for example, Patent Documents 1 to 3, etc.). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-100634 A [Patent Document 2] JP 2001-16810 A [Patent Document 3] JP 2017-34765 A Summary of the Invention [Problem to be solved by the invention]

[0005] This type of embedded magnet motor is generally required to be simple in structure and lightweight, but with conventional embedded magnet motors, problems have arisen such as reduced rotor strength in an effort to reduce weight, insufficient weight reduction, and waste of material when filling with bonded magnets.

[0006] The present invention has been made in consideration of the above, and aims to provide a rotor structure for an embedded magnet motor that is simple in structure, lightweight, and capable of reducing the amount of bonded magnet material, a manufacturing method thereof, and a manufacturing apparatus for the rotor structure for an embedded magnet motor. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, a rotor structure of an embedded magnet motor according to one aspect of the present invention includes a rotor having a shaft and a rotor core attached to the shaft. The rotor core is an electromagnetic steel sheet laminate having a cylindrical outer circumferential surface and has a through hole penetrating in the axial direction of the shaft. A resin core and a bonded magnet are sequentially arranged in the through hole from the shaft side toward the radially outward side. The resin core is a resin molded body containing a soft magnetic material. The bonded magnet has a gate mark formed on the surface side radially facing the resin core.

[0008] The rotor structure of an embedded magnet motor according to one aspect of the present invention has a simple structure, can be made lighter, and can reduce the amount of bonded magnet material used. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a completed rotor according to one embodiment. [Diagram 2] FIG. 2 is a plan view of the rotor of FIG. [Diagram 3] FIG. 3 is a perspective view of a rotor core which is a part of the rotor. [Figure 4] FIG. 4 is a plan view of the rotor core of FIG. [Diagram 5] FIG. 5 is a perspective view of a die core used in manufacturing the rotor. [Figure 6] FIG. 6 is a plan view of the die core of FIG. [Figure 7]FIG. 7 is a perspective view showing a state in which the mold core is inserted into the rotor core and injection for the bond magnet is performed, leaving the sprue and runner. [Figure 8] FIG. 8 is a plan view of FIG. [Figure 9] FIG. 9 is a flow chart showing an example of steps of a manufacturing method for a rotor structure of an embedded magnet motor. [Figure 10] FIG. 10 is a cross-sectional view of a state in which the rotor core and the die core are set in the die for primary molding, and the fixed die and the movable die are closed. [Figure 11] FIG. 11 is a cross-sectional view of the bonded magnet after filling has been completed. [Figure 12] FIG. 12 is a cross-sectional view of the movable die when it is opened from the fixed die. [Figure 13] FIG. 13 is an enlarged view of the area surrounded by a dashed line in FIG. 12 around the rotor core. [Figure 14] FIG. 14 is a cross-sectional view showing a state in which the runner is separated by the rise of the first-stage ejector pin. [Figure 15] FIG. 15 is a cross-sectional view showing the rotor core, the bond magnet, and the mold core being pushed out of the movable die by the rise of the first-stage ejector pins and the second-stage ejector pins. [Figure 16] FIG. 16 is a cross-sectional view of the state in which the die core has been separated from the rotor core and the bond magnet by the descent of the first-stage ejector pins and the second-stage ejector pins. [Figure 17] FIG. 17 is a cross-sectional view of the rotor core, bonded magnets, and shaft set in a metal mold for secondary molding, with resin injection having been performed. [Figure 18] FIG. 18 is a diagram showing a structure of a first comparative example (Patent Document 1). [Figure 19] FIG. 19 is a diagram showing a structure of a second comparative example (Patent Document 2). [Figure 20] FIG. 20 is a diagram showing a structure of a third comparative example (Patent Document 3). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the rotor structure of an embedded magnet motor, its manufacturing method, and manufacturing device of the rotor structure of an embedded magnet motor according to the embodiment will be described with reference to the drawings. Note that the present invention is not limited to the embodiment. In addition, the dimensional relationship of each element in the drawings, the ratio of each element, etc. may differ from the reality. There may be parts in which the dimensional relationship and ratio differ between the drawings. In addition, the contents described in one embodiment or modified example are, in principle, similarly applied to other embodiments and modified examples.

[0011] (Structure of rotor 20) FIG. 1 is a perspective view of a rotor 20 in a completed state according to one embodiment. FIG. 2 is a plan view of the rotor 20 in FIG. 1. FIG. 3 is a perspective view of a rotor core 21 that is a part of the rotor 20. FIG. 4 is a plan view of the rotor core 21 in FIG. 3. FIG. 5 is a perspective view of a mold core 4 used in manufacturing the rotor 20. FIG. 6 is a plan view of the mold core 4 in FIG. 5. FIG. 7 is a perspective view showing a state in which the mold core 4 is inserted into the rotor core 21 and the bond magnet 22 is injected, leaving the sprue 50 and the runner 51. FIG. 8 is a plan view of FIG. 7. For convenience, the axial direction of the shaft 10 is the Z-axis direction, and the two axial directions on the end face of the rotor core 21 perpendicular to the shaft 10 are the X-axis direction and the Y-axis direction, but the posture during use is not limited.

[0012] 1 to 4, a predetermined number of cores made of electromagnetic steel sheets pressed into a predetermined shape are stacked in the axial direction (Z-axis direction) and the cores are fixed together by crimping to form rotor core 21 made of an electromagnetic steel sheet laminate. Through holes 211 (FIGS. 3 and 4) formed in each core and rotor core 21 communicate (penetrate) over the entire axial length of rotor core 21.

[0013] Shaft 10 is disposed in the center of through hole 211, resin core 23 is formed around it, and bonded magnet 22 is formed on the periphery of resin core 23. Rotor core 21 is also provided with outer core portions 212 that are evenly arranged in the circumferential direction centered on the rotation axis of rotor core 21. These outer core portions 212 have a shape that bulges radially inward and curves. Adjacent outer core portions 212 are connected to each other by connecting portions 213.

[0014] Rotor core 21 is made into one component connected at its outer periphery by connecting portion 213, and through hole 211 is provided inside thereof, and by filling through hole 211 with bonded magnet 22 and resin core 23, the ratio of the electromagnetic steel sheet laminate occupied by the resin core and bonded magnet is reduced, and the weight of rotor core 21 is reduced, thereby achieving a reduction in weight of rotor 20. Furthermore, since no hollow holes are provided in rotor core 21 to reduce weight, there is no reduction in strength due to hollow holes.

[0015] Between each outer core portion 212 of rotor core 21, i.e., at connecting portion 213, boundary portion 214 is formed extending circumferentially inward. Boundary portion 214 separates adjacent bonded magnets 22 and becomes a portion in contact with resin core 23.

[0016] On the other hand, mold core 4 used in manufacturing rotor 20 has a generally cylindrical shape as shown in Figures 5 and 6, and its outer circumferential edge has a shape in which convex portions 40 and concave portions 41 are arranged alternately in the circumferential direction. Then, by inserting mold core 4 into through hole 211 of rotor core 21, the radially outward facing surfaces of convex portions 40 of mold core 4 come into contact with the radially inward facing surfaces of boundary portions 214 (Figures 3 and 4) of rotor core 21, and a generally U-shaped magnet filling hole (604) for bonded magnet 22 is formed in through hole 211 of rotor core 21 by boundary portions 214, convex portions 40, and concave portions 41.

[0017] 5 and 6, a slug well 44 recessed in the axial direction is formed in the center of the top surface 42 of the mold core 4, and a runner groove 43 is provided extending radially outward from the slug well 44. The slug well 44 is located at a position where it overlaps with a nozzle (E1) of an injection molding machine provided in the fixed mold (60) in a plan view when the mold (A) described below is closed, and the magnet molding resin material (bonded magnet in a fluid state) injected from the nozzle (E1) of the injection molding machine passes through the slug well 44 and the runner groove 43 to fill the magnet filling hole (604).

[0018] 7 and 8 show the state in which the bond magnet 22 is formed by injecting magnet molding resin material into the rotor core 21, and the runner 51 and sprue 50 that serve as a flow path for the magnet molding resin material still remain. As shown in the plan view of FIG. 8, the gate G1 has a tapered structure. As shown in the perspective view of FIG. 7, the top surface 42 of the mold core 4, which corresponds to the bottom surface of the fixed mold (60) of the mold (A), is one step lower than the top surface of the rotor core 21, so that the gate G1 can be arranged on the side (inner diameter side) of the bond magnet 22. In the subsequent process, the sprue 50 and runner 51 are removed, and the gate G1 portion is hidden by the filling of the resin core 23, so that there is no need to remove the gate mark remaining in the portion where the gate G1 was, and work efficiency is improved.

[0019] (Materials of bonded magnet 22 and resin core 23) The area radially outside of the bond magnet 22 is composed of a laminated body of laminated electromagnetic steel sheets. This outside area is an area through which magnetic flux that contributes to torque passes, such as magnetic flux that contributes to reluctance torque generated by magnetic flux generated by current supplied to coils wound around the teeth of the stator arranged opposite the outer circumferential surface of the rotor 20 through a predetermined gap, which flows from the teeth of the stator through the laminated body to the adjacent teeth, and magnetic flux that flows from the bond magnet 22 to the teeth of the stator, and is an area where the magnetic flux changes drastically, so it needs to be made of a material with high magnetic permeability and low loss in the high frequency range. For this reason, the bond magnet 22 is made of a magnet molding resin material mixed with rare earth magnet powder. As the rare earth magnet, SmCo5 magnet, Sm2Co17 magnet, rare earth iron magnet (NdFeB magnet or SmFeN magnet), etc. can be used.

[0020] In contrast, the region radially inward of bonded magnet 22 is composed of resin core 23 made of a resin molded body containing a soft magnetic material. This inner region has less magnetic flux fluctuation than a laminated core in which electromagnetic steel sheets are laminated, and this region functions mainly as a back yoke for bonded magnet 22. For this reason, resin core 23 is mixed with powder of a soft magnetic material with high magnetic permeability, allowing it to function as a magnetic path. Also, because resin core 23 is formed by mixing powder of a soft magnetic material with a resin material, it can be significantly lighter than a configuration formed from laminated electromagnetic steel sheets.

[0021] In this way, since rotor 20 is configured with a laminate in which electromagnetic steel sheets are laminated only in the region radially outward of bond magnet 22, the weight of rotor 20 as a whole can be reduced.

[0022] (Method of manufacturing rotor 20) Fig. 9 is a flow chart showing an example of steps in a manufacturing method for a rotor structure of an embedded magnet motor. The following manufacturing steps are performed manually by an operator, by a robot mechanism operated under the control of a control device (computer device), or by a combination of both. Figs. 10 to 16 are cross-sectional views showing the state of a mold A used in the primary molding step. Fig. 17 is a cross-sectional view showing the state of a mold B used in the secondary molding step.

[0023] (Configuration of mold A used for primary molding) As shown in Figs. 10 to 16, the mold A used for the primary molding is composed of a fixed mold 60 and a movable mold 61. The fixed mold 60 is composed of a plate-shaped member 601, a member 602 that fits into a hole in the center of the member 601 and has a step on the outer periphery, and a member 603 that is placed on the underside of the members 601 and 602 in the figure and has a convex part below the center. A bond magnet flow path 605 is provided from the center of the member 602 through the center of the member 603, and the nozzle E1 of the injection molding machine is adapted to abut on the opposite side of the bond magnet flow path 605 of the member 602 with the center aligned. The bottom surface 609 (Fig. 12) of the member 603 has the same shape as the top surface 42 (Figs. 5 and 6) of the mold core 4 when viewed from the bottom, and when the mold A is closed, the outer periphery of the bottom surface 609 and the outer periphery of the top surface 42 of the mold core 4 are perfectly aligned.

[0024] The movable die 61 is composed of a plate-like member 6101, a cylindrical member 6102 arranged above the member 6101 in the figure, a plate-like member 6103 arranged above the member 6102, a roughly cylindrical member 6104 arranged above the member 6103, a roughly cylindrical member 6105 arranged inside the member 6104, and a plate-like member 6106 arranged inside the member 6105. A cylindrical field magnetic body S1 is arranged above the member 6106, and a space in which the rotor core 21 and the die core 4 are set is provided inside the field magnetic body S1.

[0025] The movable mold 61 is also provided with first-stage ejector pins 6110 and second-stage ejector pins 6111 for displacing the positions of the mold core 4 and the rotor core 21, and eject operation plates 6107-6109 for moving the first-stage ejector pins 6110 and second-stage ejector pins 6111. The eject operation plates 6107-6109 are divided into three, with the top first-stage ejector operation plate 6107 having a space for accommodating the lower end of the first-stage ejector pin 6110, and the second-stage ejector operation plate 6108 and third-stage ejector operation plate 6109 being connected to the second-stage ejector pin 6111, respectively.

[0026] The first stage ejector pin 6110 has an ejector rod (not shown) disposed at its lower end, and moves axially following the movement of the ejector rod, independently of the second stage ejector pin 6111. The second stage ejector pin 6111 has its bottom fixed to a third stage eject operation plate 6109, and moves up and down following the axial movement of the third stage eject operation plate 6109.

[0027] As shown in Fig. 10, the top surface of the rotor core 21 and the top surface 42 of the mold core 4 (Figs. 5 and 6) are offset so that the top surface 42 of the mold core 4 is positioned lower than the top surface of the rotor core 21. This offset allows the magnet molding resin material to be injected from the side (side gate method) instead of from the top surface, using the bond magnet flow path 605 (a flow path that descends vertically from the nozzle E1 in the figure and continues horizontally along the runner groove 43) formed by the runner groove 43 of the mold core 4 and the fixed mold 60. Injection from the side allows the gate to be easily cut (separated) by the rise of the mold core 4, and allows the gate marks of the bond magnet 22 to be buried by the filling of the resin core 23 in the subsequent secondary molding.

[0028] (Primary molding process) In Fig. 9, as a step of primary molding, an operator or a control device sets the rotor core 21 and the mold core 4 in the movable die 61 of the mold A (step ST11) and closes the movable die 61 (step ST12). Fig. 10 is a cross-sectional view of the state in which the rotor core 21 and the mold core 4 are set in the mold A for primary molding, and the fixed die 60 and the movable die 61 are closed. That is, the operator or the control device prepares the mold A in a state in which the magnet molding resin material can be filled. When closing the movable die 61, the movable die 61 and the fixed die 60 are aligned by a positioning pin C connected to the movable die 61.

[0029] Next, an operator or a control device fills in bond magnet 22 (forms bond magnet 22 by filling magnet molding resin material) (step ST13). Fig. 11 is a cross-sectional view of the state after filling for bond magnet 22 has been completed. That is, magnet molding resin material is filled into rotor core 21 from nozzle E1 of an injection molding machine set on the top surface of fixed mold 60 through bond magnet flow path 605 opened in the center of fixed mold 60.

[0030] When forming bond magnet 22 in the space of rotor core 21, mold core 4 is set so that the space required for forming resin core 23 is secured and the magnet molding resin material forming bond magnet 22 does not flow into this location. Rotor core 21 and mold core 4 form a space that is approximately U-shaped in plan view, and magnet molding resin material made of thermoplastic resin (e.g. PA resin, PPS resin, etc.) mixed with anisotropic rare earth magnet powder having a predetermined particle size distribution is injected and filled into this approximately U-shaped space to form bond magnet 22 that is approximately U-shaped in plan view. During filling, bond magnet 22 is oriented as desired by field magnetic body S1 using an orienting permanent magnet arranged to surround bond magnet 22 in movable mold 61.

[0031] Next, the operator or the control device opens the movable die 61, cuts the gate G1 with the first-stage ejector pin 6110, and removes the sprue 50 and the runner 51 from the mold A (step ST14). Fig. 12 is a cross-sectional view showing a state in which the movable die 61 is opened from the fixed die 60. Fig. 13 is an enlarged view of the dashed-dotted line portion around the rotor core 21 in Fig. 12. Fig. 14 is a cross-sectional view showing a state in which the runner 51 is separated by the rise of the first-stage ejector pin 6110.

[0032] 12 and 13 show a state in which movable die 61 is opened. The surface where movable die 61 and fixed die 60 face each other becomes parting line P, and this parting line P forms the top surface of bond magnet 22. In the state shown in Figs. 12 and 13, sprue 50 and runner 51 still remain. Also, first-stage ejector pin 6110 built into movable die 61 is already located at the lower end side of mold core 4.

[0033] As shown in Fig. 13, the gate G1 is inclined on one side (the lower side in the figure) and is formed in a tapered shape. This increases the force of filling the magnet molding resin material and also makes it possible to reduce the cross-sectional area of ​​the gate G1, making it easier to cut the gate G1.

[0034] In Fig. 14, the first-stage ejector pin 6110 moves upward, pushing the die core 4 upward. This cuts the gate G1, leaving a gate mark at the cut location. When the gate G1 is cut, the sprue 50 and the runner 51 may fall off naturally due to the momentum of the first-stage ejector pin 6110 as it rises, or they may be removed manually or by a pickup robot. Normally, such a die A is often placed horizontally with the Z-axis direction in the figure horizontal, so the sprue 50 and the runner 51 often fall off naturally.

[0035] Next, the operator or the control device uses the second-stage ejector pins 6111 to push out and remove the rotor core 21 from the mold A (step ST15). Fig. 15 is a cross-sectional view of the state in which the rotor core 21, the bond magnet 22, and the mold core 4 are pushed out of the movable mold 61 by the rise of the first-stage ejector pins 6110 and the second-stage ejector pins 6111. Fig. 16 is a cross-sectional view of the state in which the mold core 4 is separated from the rotor core 21 and the bond magnet 22 by the descent of the first-stage ejector pins 6110 and the second-stage ejector pins 6111.

[0036] The top of the second-stage ejector pin 6111 provided adjacent to the first-stage ejector pin 6110 is disposed at a position overlapping with the portion filled with the bond magnet 22 in a plan view. Therefore, when the first-stage ejector pin 6110 and the second-stage ejector pin 6111 are moved upward at the same time, the rotor core 21 filled with the bond magnet 22 is displaced upward together with the mold core 4 as shown in FIG. 15. Thereafter, by displacing the first-stage ejector pin 6110 and the second-stage ejector pin 6111 downward, the mold core 4 descends and is separated from the rotor core 21 as shown in FIG. 16, and the rotor core 21 can be removed from the mold A. The downward displacement of the first-stage ejector pin 6110 and the second-stage ejector pin 6111 is performed by a general mechanism using a spring or the like (not shown) that elastically returns to the original position.

[0037] (Configuration of mold B used for secondary molding) As shown in FIG. 17, the mold B used for the secondary molding is a so-called three-plate type mold. That is, the mold B has a first fixed mold 62, a second fixed mold 63, and a movable mold 64. The first fixed mold 62 is composed of a plate-shaped member 621, a member 622 that fits into a hole with a step on the outer periphery in the center of the member 621 and has a step on the outer periphery, and a plate-shaped member 623 that is placed on the lower surface of the members 621 and 622 in the figure. A first resin core flow path 606 is provided from the center of the member 622 through the center of the member 623, and the nozzle E2 of the injection molding machine is adapted to abut on the opposite side of the member 622 from the first resin core flow path 606 with the center aligned. The molten resin for the resin core 23 injected from the nozzle E2 of the injection molding machine passes through the first resin core flow path 606. The bottom surface of the first fixed die 62 is different from that of the die A in that it does not have a step or the like and has a flat surface.

[0038] The second fixed die 63 is sandwiched between the movable die 64 and the first fixed die 62, and is composed of a substantially cylindrical member 631 having a step on the inner circumferential surface, a substantially plate-shaped member 632 arranged inside the member 631 and having a hole in the center of the lower side in the figure, a substantially plate-shaped member 633 arranged below the member 632, and a substantially plate-shaped member 634 arranged in the recess in the center of the upper side of the member 632. In addition, a resin core flow groove 607 is formed in the top surface of the member 634 in a direction perpendicular to the axial direction, and a second resin core flow path 608 is formed further along the axial direction from the resin core flow groove 607. The second resin core flow path 608 is formed with a tapered lower end, which has the effect of increasing the force of filling the resin core 23 and the effect of making the gate cutting work easier by reducing the cross-sectional area of ​​the gate G2 at the tip.

[0039] The movable die 64 is composed of a plate-shaped member 641, a cylindrical member 642 arranged above the member 641 in the figure, a plate-shaped member 643 arranged above the member 642, a substantially cylindrical member 644 arranged above the member 643, a substantially plate-shaped member 645 arranged inside the member 644, and a cylindrical member 646 arranged above the member 645. A space is provided inside the member 646 in which the rotor core 21 and the shaft 10 are set.

[0040] The movable die 64 is provided with an ejector pin 649 for displacing the axial position of the shaft 10, and a first eject operation plate 647 and a second eject operation plate 648 for moving the ejector pin 649. The ejector pin 649 abuts against the bottom surface of the shaft 10 inserted into the rotor core 21. The lower end of the ejector pin 649 is connected to the first eject operation plate 647 and the second eject operation plate 648.

[0041] (Secondary molding process) In Fig. 9, as a secondary molding step, an operator or a control device inserts shaft 10 into through hole 211 (Figs. 3 and 4) of rotor core 21, fits rotor core 21 and shaft 10 into mold B, and closes movable die 64 (step ST21). Next, an operator or a control device fills resin core 23 (forming resin core 23 by filling) (step ST22). Fig. 17 is a cross-sectional view showing a state in which rotor core 21, bond magnet 22, and shaft 10 are set in mold B for secondary molding, and injection for resin core 23 has been performed.

[0042] That is, shaft 10 is set in through hole 211 of rotor core 21 removed at the end of primary molding, and rotor core 21 with shaft 10 inserted therein is set in mold B, after which mold B is closed.

[0043] After rotor core 21 is fitted into mold B, a resin material made of thermoplastic resin (such as PA resin, PPS resin, etc.) mixed with iron powder (powder whose main component is iron) having a predetermined particle size is injected and filled into through holes 211 of rotor core 21 by a pin gate method using primary sprue 52, runner 53 and secondary sprue 54 to form resin core 23. The outer circumferential surface of shaft 10, which serves as the bonding surface with resin core 23, is knurled (iris patterned) to improve bonding strength and prevent rotation.

[0044] By filling resin core 23 in the secondary molding, gate G1 that occurs when filling bond magnet 22 in the primary molding is provided on the side, that is, the surface that faces radially from resin core 23, so it looks good because it is not visible from the outside due to the filling of resin core 23. Furthermore, it also contributes to reducing the number of processes because it is no longer necessary to remove the gate marks after filling in order to ensure clearance with other parts, etc.

[0045] The resin core 23 is a resin molded body containing a soft magnetic material. As the soft magnetic material, powders such as silicon steel (Fe-Si alloy), sendust (Fe-Si-Al alloy), and permalloy (Fe-Ni alloy) may be used in addition to powders mainly composed of iron (iron powder, pure iron powder). The soft magnetic material has a predetermined particle size. As the resin contained in the resin molded body together with the soft magnetic material, a thermoplastic resin (for example, polyamide (PA) resin such as PA12, PA6, and PA66, polyphenylene sulfide (PPS) resin, etc.) is preferably used. When the resin core 23 requires further heat resistance, heat-resistant nylon (PA6, PA66) or PPS resin can be used instead of PA12. In 100% by volume of the resin molded body, it is preferable that the soft magnetic material is contained in an amount of 40% by volume to 60% by volume, and the resin is contained in an amount of 40% by volume to 60% by volume. If the volume of the soft magnetic material exceeds 60%, the fluidity of the resin material decreases when molding the resin core 23, and the resin core may not be molded well. On the other hand, if it is less than 40%, the ratio of the soft magnetic material decreases, so the saturation magnetic flux density of the resin core may not be sufficient, and the back yoke may not function properly. More specifically, the volume of the pure iron powder and the volume of the polyamide 12 (PA12) resin can each be 50%. The bond magnet 22 and the resin core 23 can be formed by using a so-called two-color molding technique.

[0046] Next, the operator or the control device opens the movable mold 64 and removes the molded body (rotor 20) (step ST23). That is, in Fig. 17, when the first ejection operation plate 647 and the second ejection operation plate 648 are displaced in the axial direction, the ejector pin 649 also displaces in the axial direction following therewith, so that the completed rotor core 21 filled with the resin core 23 is pushed out from the mold B and can be removed. When the mold B is opened, the primary sprue 52, the runner 53, and the secondary sprue 54 are discarded. This completes the molding of the rotor core 21.

[0047] The compact removed from the mold B is demagnetized to remove irregular magnetization. Next, the demagnetized compact is set in a magnetizing yoke (not shown) around which a magnetizing coil is wound, and a pulse current is applied to the magnetizing coil to magnetize the rotor core 21 from its outer periphery in a predetermined direction.

[0048] (First Comparative Example) Fig. 18 is a diagram showing the structure of a first comparative example (Patent Document 1). In Fig. 18, a rotor 10' is composed of a rotor core 14' and a shaft 12'. The rotor core 14' is composed of magnetic steel plates 22' stacked in the axial direction. In the rotor core 14', magnet storage holes 18' are formed at predetermined intervals in the circumferential direction, and hollow holes 20' for reducing the weight of the rotor 10' are formed at predetermined intervals in the circumferential direction radially inward from the magnet storage holes 18'. The hollow holes 20' formed in the rotor core 14' reduce the weight of the rotor 10'.

[0049] (Second Comparative Example) Fig. 19 is a diagram showing the structure of a second comparative example (Patent Document 2). In Fig. 19, a rotor 15' is composed of a laminated core 31' and an output shaft 30'. The laminated core 31' is composed of magnetic core plates 37' laminated in the axial direction. Outer edge through-holes 39' provided near the outer periphery of the laminated core 31' are filled with resin magnets 40'. Through-holes 42' are formed in the laminated core 31' to reduce weight.

[0050] (Third Comparative Example) Fig. 20 is a diagram showing the structure of a third comparative example (Patent Document 3). In Fig. 20, one end of a rotor core 1' is provided with runner portions 221'-226' extending laterally from a sprue portion 21' toward the center of the opening of each of the slots 121'-126', and short secondary sprue portions 231'-236' extending axially from the downstream side of each of the runner portions 221'-226' to the opening of each of the slots 121'-126', and a gate is formed at the tip of the secondary sprue portion 231'-236'. The gate is located at the center of the approximately U-shaped slots 121'-126'. Reference numeral 11' denotes a shaft hole.

[0051] (Comparison between Comparative Example and Embodiment) In the first comparative example of Fig. 18, the weight of the rotor 10' is reduced by the hollow holes 20' formed in the rotor core 14', and the weight reduction is promoted by making the hollow holes 20' larger. However, if the hollow holes 20' are too large, there is a risk that the strength of the rotor 10' will be reduced.

[0052] 19, similarly to the first comparative example, the weight of the rotor 15' is reduced by the through holes 42' formed in the laminated core 31', and the weight reduction is promoted by making the through holes 42' larger. However, if the through holes 42' are too large, there is a risk that the strength of the rotor 15' will be reduced.

[0053] In this regard, in the embodiment of Figures 1 and 2, there are no hollow holes, and the space within rotor core 21 is filled with bonded magnets 22, resin core 23, and shaft 10, so there is no reduction in strength due to hollow holes.

[0054] In addition, in the embodiment of Figures 1 and 2, bond magnet 22 is approximately U-shaped and convex radially inward, so that the area of ​​outer core portion 212 of rotor core 21 can be secured, and the strength of rotor 20 can be maintained while reducing its weight.

[0055] Furthermore, in the third comparative example of Figure 20, in addition to the sprue portion 21' and the runner portions 221'-226', secondary sprue portions 231'-236' are formed, which are then discarded, resulting in a large waste of magnet molding resin material for the bonded magnet.

[0056] In this regard, in the embodiment, by using the side gate method, as shown in Figures 7 and 13, what is discarded is the sprue 50 and the runner 51, and there is no equivalent to the secondary sprue portion, so there is a cost reduction effect due to the reduction in residual bonded magnets. In particular, the reduction effect is large for bonded magnets 22 mixed with rare earth magnet powder.

[0057] Furthermore, because filling is possible from the side of bottom 223 (FIGS. 1 and 2) of bonded magnet 22 with a roughly U-shaped cross section, bonded magnet 22 can be filled evenly up to tip 222. This allows the orientation of the bonded magnet to be uniform.

[0058] In addition, the gate mark created at the position of gate G1 is formed on the side of bonded magnet 22, i.e., the surface facing resin core 23, so it is buried when resin core 23 is filled and becomes invisible from the outside, which gives it a good appearance, and eliminates the need to remove the gate mark after filling, which also contributes to a reduction in the number of processes.

[0059] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0060] As described above, the rotor structure of the embedded magnet motor according to the embodiment includes a rotor having a shaft and a rotor core attached to the shaft, the rotor core is an electromagnetic steel sheet laminate with a cylindrical outer circumferential surface and has a through hole penetrating in the axial direction of the shaft, in which a resin core and a bonded magnet are sequentially arranged from the shaft side toward the outside in the radial direction, the resin core is a resin molded body containing a soft magnetic material, and the bonded magnet has a gate mark formed on the surface side facing the resin core in the radial direction. This makes it possible to provide a rotor structure for an embedded magnet motor that is simple in structure, lightweight, and allows for a reduction in the material of the bonded magnet.

[0061] That is, the rotor is composed of a shaft, a resin core, a bonded magnet, and a rotor core, resulting in a simple structure. Also, the ratio of the electromagnetic steel sheet laminations is reduced by the resin core and the bonded magnet, and the weight of the rotor core is reduced, resulting in a lighter rotor. Also, the bonded magnet is filled using the so-called side gate method, which makes a secondary sprue as shown in Patent Document 3 unnecessary, reduces residual bonded magnets, and reduces the material for the bonded magnets.

[0062] The rotor core also has multiple boundaries that extend radially inward from the outer edge of the rotor core and are lined up in the circumferential direction, and the radially inward surfaces of the boundaries abut against the radially outward surfaces of the convex portions of the convex portions and concave portions that are lined up alternately in the circumferential direction on the outer periphery of a cylindrical mold core that is inserted into the through hole of the rotor core when manufacturing the rotor, and the mold core, the boundaries, the convex portions, and the concave portions form a substantially U-shaped hole for filling the bonded magnet in the through hole of the rotor core. This makes it easy for the rotor core and the mold core to form the hole for filling the bonded magnet.

[0063] In addition, a slug well is provided in the center of one end face in the axial direction of the mold core, and runner grooves extend radially from the slug well to the outer edge of the mold core, making it possible to fill the magnet molding resin material from the nozzle of the injection molding machine through the slug well and the runner groove.

[0064] Also, a manufacturing method for a rotor structure of an embedded magnet motor includes a rotor having a shaft and a rotor core attached to the shaft, the rotor core being a laminate of electromagnetic steel sheets with a cylindrical outer circumferential surface, having a through hole penetrating in the axial direction of the shaft, and a resin core and a bonded magnet being disposed in that order in the through hole from the shaft side toward the outside in the radial direction, the manufacturing method including a first filling step of filling the bonded magnet from the surface side facing the resin core in the radial direction, and a second filling step of filling the through hole with the resin core, which is a resin molded body containing a soft magnetic material and a resin, and is made of a resin material containing a soft magnetic material and a resin. This provides a manufacturing method for a rotor structure of an embedded magnet motor.

[0065] The first filling step includes inserting a mold core into the through hole of the rotor core, and the rotor core and the mold core form a filling hole into which the bonded magnet is filled. This makes it easy to form the filling hole for the bonded magnet.

[0066] The second filling process also includes a process of filling the resin core to bury the gate marks that are created when filling the bonded magnet, which improves the appearance and reduces the number of steps required to remove the gate marks after filling.

[0067] The method also includes a process for demagnetizing the rotor after the resin core and the bonded magnet are filled to obtain the rotor, and then magnetizing the rotor core from the outer periphery in a predetermined direction to obtain the completed rotor.

[0068] Also, a manufacturing device for a rotor structure of an embedded magnet motor includes a rotor having a shaft and a rotor core attached to the shaft, the rotor core being a laminate of electromagnetic steel sheets with a cylindrical outer circumferential surface and having a through hole penetrating in the axial direction of the shaft, in which a resin core and a bonded magnet are arranged in order from the shaft side toward the outside in the radial direction, the manufacturing device including a first mold for filling the bonded magnet from the surface side facing the resin core in the radial direction, and a second mold for filling the through hole with the resin core, which is made of a resin material containing a soft magnetic material and resin and is a resin molded body containing the soft magnetic material. This provides a manufacturing device for a rotor structure of an embedded magnet motor.

[0069] Furthermore, the present invention is not limited to the above-mentioned embodiment. The present invention also includes a configuration in which the above-mentioned components are appropriately combined. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the above-mentioned embodiment, and various modifications are possible. [Explanation of symbols]

[0070] 10 shaft, 20 rotor, 21 rotor core, 211 through hole, 212 outer core portion, 213 connecting portion, 22 bonded magnet, 222 tip portion, 223 bottom portion, 23 resin core

Claims

1. A rotor having a shaft and a rotor core attached to the shaft, the rotor core is an electromagnetic steel sheet laminate having a cylindrical outer circumferential surface and has a through hole penetrating in the axial direction of the shaft, A resin core and a bonded magnet are disposed in the through hole in this order from the shaft side toward the outside in the radial direction, The resin core is a resin molded body containing a soft magnetic material, The bonded magnet has a gate mark formed on a surface side facing the resin core in the radial direction. Rotor structure of an embedded magnet motor.

2. The rotor core includes a plurality of boundaries extending radially inward from an outer edge of the rotor core and aligned in a circumferential direction, The radially inward surface of the boundary portion abuts against the radially outward surface of the convex portion of the convex portions and concave portions that are alternately arranged in the circumferential direction on the outer periphery of a cylindrical mold core that is inserted into the through hole of the rotor core during the manufacture of the rotor, and the mold core, the boundary portion, the convex portion, and the concave portion form a substantially U-shaped filling hole for the bonded magnet within the through hole of the rotor core.

2. The rotor structure of the embedded magnet motor according to claim 1.

3. One end face of the die core in the axial direction is provided with a slug well at its center, A runner groove extends radially from the slug well to the outer edge of the die core. The rotor structure of a magnet embedded motor according to claim 2.

4. A rotor having a shaft and a rotor core attached to the shaft, the rotor core is an electromagnetic steel sheet laminate having a cylindrical outer circumferential surface and has a through hole penetrating in the axial direction of the shaft, a resin core and a bonded magnet are disposed in the through hole in this order from the shaft side toward a radially outward side, a first filling step of filling the bonded magnet from a surface side that faces the resin core in a radial direction; and a second filling step of filling the through hole with the resin core, which is made of a resin material containing a soft magnetic material and a resin and is a resin molded body containing the soft magnetic material. A manufacturing method for the rotor structure of an embedded magnet motor.

5. The first filling step includes a step of inserting a mold core into the through hole of the rotor core, The rotor core and the mold core form a filling hole into which the bonded magnet is filled. A method for manufacturing the rotor structure of the embedded magnet motor according to claim 4.

6. The second filling step includes a step of filling the resin core to bury gate marks that are created when filling the bonded magnet, A method for manufacturing the rotor structure of the magnet embedded motor according to claim 4 or 5.

7. After the rotor is obtained by filling the resin core and the bonded magnet, The rotor is demagnetized, and then magnetized from an outer circumferential side of the rotor core so as to be magnetized in a predetermined direction. A method for manufacturing the rotor structure of the embedded magnet motor according to any one of claims 4 to 6.

8. A rotor having a shaft and a rotor core attached to the shaft, the rotor core is an electromagnetic steel sheet laminate having a cylindrical outer circumferential surface and has a through hole penetrating in the axial direction of the shaft, a resin core and a bonded magnet are disposed in the through hole in this order from the shaft side toward a radially outward direction, a first mold for filling the bonded magnet from a surface side that faces the resin core in a radial direction; and a second mold for filling the resin core, which is made of a resin material containing a soft magnetic material and a resin and is a resin molded body containing the soft magnetic material, into the through hole. Manufacturing equipment for the rotor structure of embedded magnet motors.

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