Method for manufacturing magnetic modulator, magnetic modulator, and magnetic modulation gear

Abstract

A method for manufacturing a magnetic modulator 50 comprises: a punching step for punching an electromagnetic steel sheet S into the planar shape of a magnetic pole piece 54 to produce a plurality of steel sheet pieces 54a; a stacking step for stacking the plurality of steel sheet pieces 54a to produce a plurality of magnetic pole pieces 54; a disposing step for disposing the plurality of magnetic pole pieces 54 on a peripheral surface of a cylindrical jig 70; and a molding step for performing resin molding so that the plurality of magnetic pole pieces 54 supported on the jig 70 are connected in a circumferential direction with resin. The peripheral surface of the jig 70 is formed with a plurality of recessed parts 70a into which the plurality of magnetic pole pieces 54 individually fit.

Description

Manufacturing method of magnetic modulation body, magnetic modulation body and magnetic modulation gear

[0001] The present invention relates to a method for manufacturing a magnetic modulation body, a magnetic modulation body, and a magnetic modulation gear.

[0002] Conventionally, a magnetic modulation gear is known in which a plurality of magnetic pole pieces are arranged between two magnet rotors arranged on the inner and outer peripheries, and the magnetic flux distribution between the two magnet rotors is modulated.

[0003] The multiple magnetic pole pieces are arranged at equal intervals in the circumferential direction. For example, the magnetic modulation gears described in Patent Documents 1 and 2 employ a structure in which magnetic pole pieces (magnetic material) and non-magnetic material are alternately arranged in the circumferential direction. However, such a structure results in an increase in the number of parts and a complicated manufacturing process. For this reason, a structure in which the multiple magnetic pole pieces and the connecting portions (bridge portions) between them are made of a single magnetic material is sometimes employed.

[0004] Patent No. 5350438 Patent No. 5408355

[0005] However, when a magnetic material integral with the pole piece is used as the connecting portion, magnetic flux leaks through the connecting portion, resulting in a decrease in output performance such as torque and efficiency.

[0006] The present invention has been made in view of the above circumstances, and has as its object to obtain suitable output performance.

[0007] The present invention is a method for manufacturing a magnetic modulator, comprising: a punching process in which an electromagnetic steel sheet is punched into the planar shape of a magnetic pole piece to produce a plurality of steel plate pieces; a stacking process in which the plurality of steel plate pieces are stacked to produce a plurality of magnetic pole pieces; an arrangement process in which the plurality of magnetic pole pieces are arranged on the circumferential surface of a cylindrical jig; and a molding process in which the plurality of magnetic pole pieces supported by the jig are resin-molded so that they are circumferentially connected with resin, and the circumferential surface of the jig is formed with a plurality of recesses into which the plurality of magnetic pole pieces individually fit.

[0008] According to the present invention, it is possible to obtain favorable output performance.

[0009] 1. A cross-sectional view of a magnetic modulation gear according to an embodiment. A cross-sectional view of a magnetic modulation body according to an embodiment. A cross-sectional view taken along line III-III in FIG. 1. A flowchart showing an outline of the manufacturing process of a magnetic modulation body. A diagram for explaining the manufacturing process of a magnetic modulation body. A diagram for explaining the manufacturing process of a magnetic modulation body. A diagram for explaining the manufacturing process of a magnetic modulation body. A diagram for explaining the manufacturing process of a magnetic modulation body. A diagram for explaining the manufacturing process of a magnetic modulation body. A diagram for explaining the manufacturing process of a magnetic modulation body. A diagram for explaining the manufacturing process of a magnetic modulation body. A diagram for explaining a modified example of a pole piece according to an embodiment. A diagram for explaining a modified example of a pole piece according to an embodiment. A diagram showing punching out of a conventional pole piece.

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] [Overall Configuration of Magnetic Modulation Gear] Fig. 1 is a cross-sectional view of a magnetic modulation gear 1 according to this embodiment. In the following description, the direction along the central axis Ax of the magnetic modulation gear 1 is referred to as the "axial direction," the direction perpendicular to the central axis Ax as the "radial direction," and the direction of rotation around the central axis Ax as the "circumferential direction." In addition, in the axial direction, the side that is connected to an external driven member (the left side in the drawing) is referred to as the "output side," and the opposite side (the right side in the drawing) is referred to as the "input side."

[0012] As shown in FIG. 1, the magnetic modulation gear 1 according to this embodiment includes a casing (frame) 10, an input cover 20 and an output cover 30 that cover both axial sides of the casing 10, and an input shaft 40 and a magnetic modulation body 50 whose main part is housed inside the covers 20 and 30.

[0013] The casing 10 is formed in a substantially cylindrical shape centered on the central axis Ax, and has a stator yoke 11 and an external magnet 12 on its inner periphery. The stator yoke 11 is also formed in a cylindrical shape and fitted inside the casing 10. The external magnet 12 has a greater number of poles than the internal magnet 41a of the input shaft 40 (described later), and is affixed to the inner periphery of the stator yoke 11 so that multiple magnets with different polarities are arranged alternately in the circumferential direction. However, the external magnet 12 may be an integral ring-shaped magnet, or may be divided and arranged in the circumferential direction. In addition, a bearing 61 (e.g., a ball bearing) that rotatably supports the magnetic modulator 50 is arranged on the input side of the stator yoke 11 on the inner periphery of the casing 10.

[0014] The input-side cover 20 is disposed on the input side of the casing 10 and covers the inner opening of the casing 10 from the input side. The outer periphery of the input-side cover 20 is fitted with the casing 10 via a spigot. A bearing 62 (e.g., a ball bearing) that rotatably supports the input shaft 40 is disposed on the inner periphery of the input-side cover 20.

[0015] The output-side cover 30 is disposed on the output side of the casing 10 and covers the inner opening of the casing 10 from the output side. The outer periphery of the output-side cover 30 is fitted with the casing 10 via a spigot. A bearing 63 (e.g., a ball bearing) that rotatably supports the magnetic modulation body 50 is disposed on the inner periphery of the output-side cover 30.

[0016] The input shaft 40 rotates around the central axis Ax and includes a disk portion 41 and a motor coupling portion 42. The input shaft 40 is rotatably supported by a bearing 62 disposed between the input side cover 20 and the disk portion 41 and a bearing 64 disposed between the input shaft 40 and the magnetic modulator 50. The disk portion 41 has an internal pole magnet 41a disposed on the inner diameter side of the external pole magnet 12 on its outer periphery. The internal pole magnet 41a is a permanent magnet, such as a neodymium magnet, and is attached to the outer periphery of the disk portion 41 so that multiple magnets with different polarities are arranged alternately in the circumferential direction. However, the internal pole magnet 41a may be an integral ring-shaped magnet or may be a group of segments arranged in the circumferential direction. The motor coupling portion 42 extends from the disk portion 41 toward the input side in the axial direction. The tip of the motor coupling portion 42 protrudes from the input side cover 20 and is coupled to a motor (not shown).

[0017] [Configuration of Magnetic Modulation Body] Fig. 2 is a cross-sectional view of the magnetic modulation body 50, and Fig. 3 is a cross-sectional view taken along line III-III in Fig. 1. As shown in Figs. 1 and 2, the magnetic modulation body 50 has an output shaft portion 51 and a cylindrical portion 52.

[0018] The output shaft portion 51 is a metal shaft that rotates around the central axis Ax. Approximately half of the output side of the output shaft portion 51 protrudes outward from the output-side cover 30, and this protruding portion is connected to a driven member (not shown). Approximately the central portion of the output shaft portion 51 in the axial direction is rotatably supported by a bearing 63 arranged between the output-side cover 30 and the output shaft portion 51. Furthermore, a bearing 64 (e.g., a ball bearing) that rotatably supports the input shaft 40 is arranged at the input-side end of the output shaft portion 51. The output-side end of the cylindrical portion 52 is connected to the outer periphery of the output shaft portion 51 at a position axially between the bearings 63 and 64.

[0019] The cylindrical portion 52 is formed in a substantially cylindrical shape centered on the central axis Ax and has multiple magnetic pole pieces 54 arranged axially corresponding to the external magnet 12 and the internal magnet 41a. As shown in FIG. 3 , the multiple magnetic pole pieces 54 are arranged at predetermined intervals in the circumferential direction and form an overall annular shape. The multiple magnetic pole pieces 54 are arranged concentrically on the inner diameter side of the external magnet 12 and the outer diameter side of the internal magnet 41a, with a predetermined gap between them. Each magnetic pole piece 54 is formed by laminating thin electromagnetic steel sheets (laminated steel sheets) in the axial direction. The number of magnetic pole pieces 54 is (number of external pole pairs ± number of internal pole pairs), typically (number of external pole pairs + number of internal pole pairs). The number of external pole pairs is the number of pole pairs of the external magnet 12, and the number of internal pole pairs is the number of pole pairs of the internal magnet 41a.

[0020] Circumferentially adjacent pole pieces 54 are connected to each other by a connecting portion 54b between them. The connecting portion 54b is made of resin and constitutes a part of a resin portion 56 described later. The outer peripheral surface of the connecting portion 54b is recessed radially inward relative to the outer peripheral surface of the pole piece 54. However, it is sufficient that at least one of the inner and outer peripheral surfaces of the connecting portion 54b is recessed relative to the pole piece 54. In this case, the other surface may be flush with the corresponding surface of the pole piece 54.

[0021] The pole pieces 54 modulate the spatial magnetic flux waveform formed by the internal magnets 41 a when the input shaft 40 rotates around the central axis Ax to the same frequency as the external magnets 12. Then, rotational torque is transmitted to the magnetic modulation body 50 using the magnetic force between the pole pieces 54 and the external magnets 12. In this case, the reduction ratio is (number of pole pieces 54 / number of internal magnet pole pairs). At this time, forces acting on the pole pieces 54 are mainly radial, due to the internal magnets 41 a and the external magnets 12. In this way, the rotational motion input to the input shaft 40 is decelerated and output to a driven member (not shown) connected to the output shaft portion 51 of the magnetic modulation body 50.

[0022] As shown in FIG. 2 , a metal (e.g., stainless steel) bearing support ring 55 is disposed at the input end of the cylindrical portion 52. The bearing support ring 55 is fixed to the outer periphery of the cylindrical portion 52, and the inner ring of a bearing 61 disposed between the cylindrical portion 52 and the casing 10 is fitted onto the outer periphery (see FIG. 1 ). The remaining portion of the cylindrical portion 52, excluding the pole pieces 54 and the bearing support ring 55, is a resin portion 56 made of resin (e.g., super engineering plastic). Resin is also filled between the multiple pole pieces 54, and this portion constitutes the connecting portion 54b described above. The output end of the resin portion 56 extends radially inward and is connected to the output shaft portion 51. A plurality of protrusions 57 protruding toward the inner diameter are circumferentially arranged on the inner periphery of this end. These multiple convex portions 57 are molded to correspond to the multiple concave portions 51a on the outer surface of the output shaft portion 51, and the engagement between these convex portions 57 and concave portions 51a firmly fixes the output shaft portion 51 and the cylindrical portion 52 (resin portion 56), suppressing relative movement in the radial and axial directions.

[0023] [Manufacturing Process of Magnetic Modulation Body] Fig. 4 is a flowchart showing an outline of the manufacturing process (manufacturing method) of the magnetic modulation body 50, and Figs. 5A to 7C are diagrams for explaining the manufacturing process of the magnetic modulation body 50. Figs. 8A to 8C are diagrams for explaining modified examples of the pole piece 54. Note that in Figs. 5A and 5B, the shape of the pole piece 54 (steel plate piece) is simplified to a rectangular shape rather than a sector shape.

[0024] 4, in the manufacturing process of the magnetic modulator 50, first, the magnetic pole pieces 54 are punched one by one from an electromagnetic steel sheet (step S1). Specifically, a sheet-like electromagnetic steel sheet S is punched in the planar shape (shape as viewed from the axial direction) of the magnetic pole pieces 54 to produce the required number of steel plate pieces 54a (FIG. 5A). The punched steel plate pieces 54a are arranged so as to minimize wasted space on the electromagnetic steel sheet S.

[0025] In this case, the orientation of the steel plate pieces 54a is such that the radial direction of the magnetic modulation gear 1 is approximately aligned with the rolling direction RD of the electromagnetic steel sheet S. This improves the performance of the magnetic modulation gear 1. Specifically, the magnetic steel sheet S has different magnetic properties in the rolling direction RD of its main surface and the orthogonal direction WD, which is perpendicular to the rolling direction RD. The rolling direction RD has a higher magnetic permeability (magnetic flux passes more easily) than the orthogonal direction WD. Therefore, by approximately aligning the orientation of the steel plate pieces 54a corresponding to the radial direction of the magnetic modulation gear 1 with the rolling direction RD of the electromagnetic steel sheet S, the magnetic flux passing through the pole pieces 54 can be suitably uniformed. This in turn suppresses torque degradation and reduces torque ripple and iron loss. More precisely, the orientation of the steel plate pieces 54a corresponding to the radial direction of the magnetic modulation gear 1 (magnetic modulation body 50) should be approximately aligned with (corresponds to) the rolling direction of the (isotropic) electromagnetic steel sheet. The same effect can be obtained by aligning the orientation of the steel plate pieces 54a corresponding to the radial direction of the magnetic modulation gear 1 with the easy direction of magnetization of the grain-oriented electromagnetic steel sheet. Also, by aligning the orientation relationship with the rolling direction RD among the multiple pole pieces 54 (or each pole piece 54), variation in magnetic properties can be reduced compared to when the orientations are not aligned.

[0026] Next, the pole pieces 54 (steel sheet pieces 54a) punched out from the electromagnetic steel sheet S in step S1 are stacked in a predetermined axial length (step S2; FIG. 5B). In this way, the required number of pole pieces 54 are produced.

[0027] Next, the multiple pole pieces 54 are placed on a molding jig 70 (step S3; FIG. 6A ). The jig 70 of this embodiment supports the outer diameter portions of the pole pieces 54 in the magnetic modulator 50 and is cylindrical. The inner circumferential surface of the jig 70 is formed with multiple recesses 70a that support the outer diameter portions of the multiple pole pieces 54. In this step, the multiple pole pieces 54 are fitted into the recesses 70a of the jig 70. As a result, the multiple pole pieces 54 are properly positioned and arranged in an annular shape as a whole.

[0028] Next, the multiple magnetic pole pieces 54 are connected by resin molding (step S4; FIG. 6B ). In this step, the previously fabricated output shaft portion 51 and bearing support ring 55 are placed in a molding die for resin molding together with the multiple magnetic pole pieces 54, and then positioned. In this case, the molding die may be a jig 70 or may be a separate entity. The molding die including the jig 70 is then filled with resin, and the resin portion 56 is molded (by resin casting, injection molding, or the like). The jig 70 is then removed, yielding the magnetic modulation body 50 in which the multiple magnetic pole pieces 54, output shaft portion 51, and bearing support ring 55 are fixed (integrated) with the resin portion 56 with the required positional accuracy ( FIG. 6C ). The outer peripheral surface of the magnetic modulation body 50 has resin connecting portions 54 b recessed relative to the magnetic pole pieces 54, corresponding to the inner peripheral surface shape of the jig 70.

[0029] Next, finishing is performed (step S5). In this step, the output shaft portion 51 and the bearing support ring 55 are machined. Both the output shaft portion 51 and the bearing support ring 55 are machined to a predetermined finished shape. If necessary, the inner and outer peripheral surfaces of the pole pieces 54 may also be finished. The outer peripheral surface may be machined to make the pole pieces 54 and the connecting portions 54b flush. This finishing is not limited to machining using a lathe or grinding machine, but may also include heat treatment, surface treatment, manual grinding, and the like. In this way, the magnetic modulation body 50 is completed, in which the multiple pole pieces 54, the output shaft portion 51, and the bearing support ring 55 are integrally connected by the resin portion 56.

[0030] The molding jig used in step S3 may be any jig capable of positioning the multiple pole pieces 54 and is not limited to one that supports the outer diameter portions of the pole pieces 54. For example, as shown in FIG. 7A , a jig 71 that supports the inner diameter sides of the pole pieces 54 may be used. The outer peripheral surface of the jig 71 is formed with multiple recesses 71a that support the inner diameter portions of the multiple pole pieces 54, and the pole pieces 54 are molded with the resin fitted into the recesses 71a. In this case, as shown in FIG. 7B , the inner peripheral surface of the resulting magnetic modulation body 50 has resin connecting portions 54b recessed relative to the pole pieces 54, corresponding to the shape of the outer peripheral surface of the jig 71. The jig 71 may be configured to be removed axially after molding, or may have a half-split shape or a three-piece wedge shape. Alternatively, as shown in FIG. 7C , jigs 70 and 71 may be used together. In this case, the resulting magnetic modulation body 50 has resin connecting portions 54b recessed relative to the pole pieces 54 on both the inner and outer peripheral surfaces. The jig 70 supporting the outer diameter portion of the pole piece 54 can hold the pole piece 54 more firmly than the jig 71 supporting the inner diameter portion. Therefore, the jig 70 supporting the outer diameter portion allows for more accurate circumferential pitch setting (positioning) and also makes it easier to prevent the pole piece 54 from moving due to resin contraction during resin cooling. Furthermore, when only one of the inner and outer diameter portions of the pole piece 54 is supported by the jig 70 or 71, the peripheral surface of the other side not supported by the jig may be supported by the cylindrical surface of another positioning jig. In this case, the connecting portion 54b and the pole piece 54 on the peripheral surface of the other side are formed flush with each other. Furthermore, the recess of the jig used to support (hold) the pole piece 54 during molding need not extend over the entire axial length of the pole piece 54, but may extend only partially. In this case, the final shape will have the connecting portion 54b recessed below the pole piece 54 in that portion of the axial direction.

[0031] Furthermore, the planar shape of the pole pieces 54 (as viewed from the axial direction) is not limited to a sector shape or a square shape. For example, the pole pieces 54 may have irregularities on at least one of their circumferential surfaces (surfaces substantially perpendicular to the circumferential direction). In this case, the shape and position of the irregularities are not particularly limited. For example, as shown in FIG. 8A , the circumferential surface may have a gently concave recess 54d as a whole, or may have a tangential recess 54e as shown in FIG. 8B . Alternatively, as shown in FIG. 8C , the pole pieces 54 may have a circumferential protrusion 54f. Providing irregularities on the circumferential surface of the pole pieces 54 in this manner strengthens the connection between the pole pieces 54 and the connecting portion 54b. As described above, radial force from the magnet acts on the pole pieces 54. Therefore, providing irregularities (recesses 54d, 54e, and 54f) on the circumferential surface can prevent the pole pieces 54 from detaching from the connecting portion 54b due to the radial force. From the viewpoint of suppressing magnetic flux leakage, the recessed portion is more preferable than the protruding portion.

[0032] [Technical Effects of the Present Embodiment] As described above, according to the present embodiment, the plurality of pole pieces 54 are circumferentially connected by the connecting portions 54b made of resin. This reduces leakage magnetic flux through the connecting portions compared to when the connecting portions are made of magnetic material integral with the pole pieces 54. Therefore, favorable output performance can be obtained. Furthermore, when forming the connecting portions 54b, the plurality of pole pieces 54 are individually fitted into the plurality of recesses 70a formed on the circumferential surface of the jig 70 for resin molding. This allows the plurality of pole pieces 54 to be favorably positioned when forming the connecting portions 54b. Furthermore, because the plurality of pole pieces 54 are punched out of the electromagnetic steel sheet S in an unconnected state, the pole pieces 54 (steel sheet pieces 54a) can be arranged on the electromagnetic steel sheet S without waste (see FIG. 5A ). Therefore, as shown in FIG. 9 , the amount of scrap of electromagnetic steel sheet can be reduced compared to when the plurality of pole pieces connected by connecting portions are punched out of the electromagnetic steel sheet.

[0033] Furthermore, according to this embodiment, in the punching process of step S1 in which the electromagnetic steel sheet S is punched into the planar shape of the pole pieces 54 to produce the plurality of steel sheet pieces 54a, the orientation of the steel sheet pieces 54a corresponding to the radial direction of the magnetic modulation body 50 corresponds to the rolling direction of the electromagnetic steel sheet S. Since the electromagnetic steel sheet S has a higher magnetic permeability in the rolling direction RD than in the orthogonal direction WD (magnetic flux passes more easily), by orienting the radial direction of the steel sheet pieces 54a to correspond to the rolling direction of the electromagnetic steel sheet S, the magnetic flux passing through the pole pieces 54 can be suitably uniformed. This makes it possible to suppress torque reduction and reduce torque ripple and iron loss, thereby improving the performance of the magnetic modulation gear 1.

[0034] Furthermore, according to this embodiment, the pole pieces 54 have irregularities on at least one of their circumferential surfaces. This strengthens the connection between the pole pieces 54 and the connecting portions 54b on the circumferential surface. Therefore, even if a radial force is applied to the pole pieces 54 by the magnet, it is possible to prevent the pole pieces 54 from detaching from the connecting portions 54b.

[0035] [Others] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, in the above embodiments, the external magnet 12 is used as a stator, and output is extracted from the magnetic modulator 50 having the pole pieces 54. However, the pole pieces 54 may be fixed, and the external magnet 12 may be provided on a rotatable low-speed rotor, and output may be extracted from the low-speed rotor.

[0036] In the above embodiment, it is preferable to prepare multiple types of jigs for holding the magnetic pole pieces in an annular shape during molding, each type having a different number of magnetic pole pieces. In this case, the shape of each magnetic pole piece, i.e., the shape of the recess of the jig, may be the same. This makes it possible to easily produce magnetic modulation bodies with different numbers of magnetic pole pieces by simply using different jigs.

[0037] In addition, the details shown in the above embodiment can be modified as appropriate without departing from the spirit of the invention.

[0038] As described above, the present invention is useful for obtaining favorable output performance in a magnetic modulation gear.

[0039] REFERENCE SIGNS LIST 1 magnetic modulation gear 12 outer pole magnet 41a inner pole magnet 50 magnetic modulation body 51 output shaft portion 52 cylindrical portion 54 magnetic pole piece 54a steel sheet piece 54b connecting portion 54d, 54e recessed portion 54f protruding portion 55 bearing support ring 56 resin portion 70, 71 jig 70a, 71a recessed portion Ax central axis S electromagnetic steel sheet RD rolling direction WD orthogonal direction

Claims

1. A method for manufacturing a magnetic modulator, comprising: a punching process for punching an electromagnetic steel sheet into the planar shape of a pole piece to produce a plurality of steel plate pieces; a lamination process for stacking the plurality of steel plate pieces to produce a plurality of pole pieces; an arrangement process for arranging the plurality of pole pieces on the circumferential surface of a cylindrical jig; and a molding process for resin molding the plurality of pole pieces supported by the jig so that they are circumferentially connected with resin, wherein the circumferential surface of the jig has a plurality of recesses formed therein into which the plurality of pole pieces individually fit.

2. The method for producing a magnetic modulation body according to claim 1, wherein in the punching step, the orientation of the steel plate pieces corresponding to the radial direction of the magnetic modulation body is made to correspond to the rolling direction of the electromagnetic steel plate.

3. The method for manufacturing a magnetic modulator according to claim 1, wherein the pole piece has irregularities on at least one of its circumferential faces.

4. A method for producing a magnetic modulation body as set forth in claim 1, further comprising, after said molding step, a machining step of machining connecting portions that connect adjacent magnetic pole pieces in the circumferential direction and the peripheral surfaces of the magnetic pole pieces to be flush.

5. A magnetic modulator comprising a plurality of magnetic pole pieces arranged in the circumferential direction and a resin connecting portion that connects adjacent magnetic pole pieces in the circumferential direction, wherein the connecting portion is recessed further than the magnetic pole pieces on at least one of the inner and outer circumferential surfaces.

6. A magnetic modulation body as set forth in claim 5, wherein on the inner circumferential surface, the magnetic pole pieces and the connecting portions are flush with each other, and on the outer circumferential surface, the connecting portions are recessed more than the magnetic pole pieces.

7. The magnetic modulator according to claim 5, wherein the pole pieces have irregularities on at least one of their circumferential faces.

8. A magnetic modulation gear comprising: a magnetic modulation body manufactured by the method for manufacturing a magnetic modulation body according to any one of claims 1 to 4; an input shaft having a plurality of inner pole magnets arranged on the inner diameter side of the plurality of magnetic pole pieces and aligned in the circumferential direction; and a plurality of outer pole magnets arranged on the outer diameter side of the plurality of magnetic pole pieces and aligned in the circumferential direction.

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