Magnet structure, rotation angle detector, and electric power steering device

Abstract

A magnet structure 10 comprises: a resin tubular member 2; and a bonded magnet molded body 4 that is packed into the tubular member 2.

Description

[Technical Field]

[0001] The present invention relates to a magnet structure, a rotation angle detector, and an electric power steering device. [Background technology]

[0002] In recent years, magnetic rotation angle detectors have been widely used for various purposes, such as detecting the rotation position of a steering wheel in an automobile. A known example of a magnetic rotation angle detector is the rotation angle detector described in Patent Document 1. The rotation angle detector includes a magnetic structure and a magnetic sensor, and the magnetic structure includes a cylindrical member and a bonded magnet molding attached to the cylindrical member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2017-173035 Summary of the Invention [Problem to be solved by the invention]

[0004] The end of a rotating shaft is inserted into and fixed to the cylindrical member of the magnetic structure. From the viewpoints of ease of attachment between the shaft and the cylindrical member, prevention of detachment of the cylindrical member from the shaft due to vibrations, etc., and improvement of sensor accuracy, further improvement in the dimensional accuracy of the cylindrical member is required.

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a magnet structure with excellent dimensional accuracy, and a rotation angle detector and an electric power steering device using the same. [Means for solving the problem]

[0006] The magnetic structure according to the present invention comprises a cylindrical member made of resin, and a bonded magnet molded body filled in the cylindrical member.

[0007] Here, the cylindrical member may have a recess or a protrusion in the portion that comes into contact with the bonded magnet compact.

[0008] The recessed or protruding portion may extend in the axial direction of the cylindrical member.

[0009] The magnetic structure may also have multiple recesses or protrusions.

[0010] The plurality of recesses or protrusions may be spaced apart in the circumferential direction of the cylindrical member.

[0011] The cylindrical member may further have a space that communicates with the outside of the cylindrical member and that is not filled with the bonded magnet molded body.

[0012] The magnetic structure may have a protrusion or a recess on the inner surface of the space.

[0013] The inner surface of the space may have an uneven surface.

[0014] The inner surface of the space may have one or more protrusions extending in the axial direction of the cylindrical member.

[0015] The inner surface of the space may have a protrusion that can be fitted into a recess that is inserted into the inner surface of the space.

[0016] the cylindrical member has a first cylindrical portion and a second cylindrical portion having an inner diameter smaller than that of the first cylindrical portion, The bonded magnet molded body may be provided within the first cylindrical portion or the second cylindrical portion.

[0017] the cylindrical member has a first cylindrical portion and a second cylindrical portion having an inner diameter smaller than that of the first cylindrical portion, The bonded magnet molded body is provided in either the first cylindrical portion or the second cylindrical portion, The cross section perpendicular to the axis of the inner surface of the other of the first cylindrical portion and the second cylindrical portion may have a non-circular contour.

[0018] Furthermore, the cylindrical member has a large diameter cylindrical portion, a small diameter cylindrical portion with an inner diameter smaller than that of the large diameter cylindrical portion, and a connecting cylindrical portion connecting the large diameter cylindrical portion and the small diameter cylindrical portion, and the bonded magnet molded body is provided within the large diameter cylindrical portion, and the outline shape of a cross section perpendicular to the axis of the inner surface of the small diameter cylindrical portion can be non-circular.

[0019] The cylindrical member has a large-diameter cylindrical portion, a small-diameter cylindrical portion having an inner diameter smaller than that of the large-diameter cylindrical portion, and a connecting cylindrical portion connecting the large-diameter cylindrical portion and the small-diameter cylindrical portion, The bonded magnet molded body may be provided inside the large diameter cylindrical portion.

[0020] The cylindrical member may have a large diameter cylindrical portion, a small diameter cylindrical portion having an inner diameter smaller than that of the large diameter cylindrical portion, and a connecting cylindrical portion connecting the large diameter cylindrical portion and the small diameter cylindrical portion, and the thickness of the connecting cylindrical portion may be greater than the thicknesses of the large diameter cylindrical portion and the small diameter cylindrical portion.

[0021] A rotation angle detector according to the present invention includes the above-described magnet structure and a magnetic sensor.

[0022] An electric power steering device according to the present invention includes the above rotation angle detector. [Effects of the Invention]

[0023] According to the present invention, there are provided a magnet structure having excellent dimensional accuracy, and a rotation angle detector and an electric power steering device obtained using the same. can be done. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a perspective transparent view of a cylindrical member 2 included in a magnetic structure according to a first embodiment of the present invention. [Figure 2]Figure 2(a) is a cross-sectional view including the central axis C of the cylindrical member 2 provided in the magnetic structure according to the first embodiment of the present invention, and Figure 2(b) is an enlarged view of the vicinity of the recess 6c in Figure 2(a). [Figure 3] FIG. 3(a) is a cross-sectional view including the central axis C of the magnetic structure 10 according to the first embodiment of the present invention, and FIG. 3(b) is an enlarged view of the vicinity of the recess 6c in FIG. 3(a). [Figure 4] 4(a) and 4(b) are enlarged cross-sectional views including the central axis C near the recess of a magnetic structure according to another embodiment of the present invention. [Figure 5] 10 is a cross-sectional view including the central axis C of a magnetic structure 10 according to still another embodiment of the present invention. [Figure 6] 6(a) and 6(b) are perspective views of a cylindrical member 2 included in a magnetic structure according to another embodiment of the present invention. [Figure 7] 7(a) and 7(b) are perspective views of a cylindrical member 2 included in a magnetic structure according to another embodiment of the present invention. [Figure 8] 8(a) and 8(b) are perspective views of a cylindrical member 2 included in a magnetic structure according to another embodiment of the present invention. [Figure 9] FIG. 10 is a perspective view of a cylindrical member 2 included in a magnetic structure according to another embodiment of the present invention. [Figure 10] FIG. 10(a) is a cross-sectional view including the central axis C of a magnetic structure 10 according to another embodiment of the present invention, and FIG. 10(b) is a top view of the cylindrical member 2 of FIG. 10(a). [Figure 11] 10 is a cross-sectional view including the central axis C of a magnetic structure 10 according to another embodiment of the present invention. [Figure 12] 12(a) and 12(b) are perspective views of the bottom side of a cylindrical member 2 included in a magnetic structure according to another embodiment of the present invention. [Figure 13] FIG. 13 is a partially cutaway exploded perspective view of a magnetic structure 10 according to another embodiment of the present invention. [Figure 14] FIG. 14 is a partially cutaway exploded perspective view of a magnetic structure 10 according to another embodiment of the present invention. [Figure 15] FIG. 15 is a partially cutaway exploded perspective view of a magnetic structure 10 according to another embodiment of the present invention. [Figure 16] FIG. 16 is an exploded cross-sectional view taken along the axis of a magnetic structure 10 according to another embodiment of the present invention. [Figure 17] 17(a) is a top view of the cylindrical member 2 in FIG. 16, and FIG. 17(b) is a top view of the shaft 122 in FIG. [Figure 18] FIG. 18 is a cross-sectional view including the central axis of a magnetic structure according to another embodiment of the present invention. [Figure 19] FIG. 19 is a cross-sectional view including the central axis of a magnetic structure according to another embodiment of the present invention. [Figure 20] 1 is a perspective view showing a rotation angle detector 20 according to an embodiment of the present invention. [Figure 21] 1 is a schematic cross-sectional view showing a motor assembly 110 including a rotation angle detector 20 according to an embodiment. [Figure 22] FIG. 22 is a block diagram showing an electric power steering device 150 in which the motor assembly 110 of FIG. 21 is used. DETAILED DESCRIPTION OF THE INVENTION

[0025] Preferred embodiments of the present invention will be described below with reference to the drawings, although the present invention is not limited to the following embodiments.

[0026] [Magnet structure] (First embodiment) 1 and 2 are a perspective view and a cross-sectional view, respectively, of a cylindrical member 2 provided in a magnetic structure 10 according to a first embodiment of the present invention.

[0027] 1 and 2(a), the cylindrical member 2 has a cylindrical shape with a hollow portion that penetrates in the axial direction. The cylindrical member 2 has a large-diameter cylindrical portion (first cylindrical portion) 2a on the upper end 2V side, a small-diameter cylindrical portion (second cylindrical portion) 2c on the lower end (end portion) 2L side, and an annular plate (connecting cylindrical portion) 2b between the large-diameter cylindrical portion 2a and the small-diameter cylindrical portion 2c that connects them. The outer diameter d1 and inner diameter d2 of the large-diameter cylindrical portion 2a are larger than the outer diameter d3 and inner diameter d4 of the small-diameter cylindrical portion 2c, respectively.

[0028] The outer diameter d1 of the large diameter cylindrical portion 2a can be, for example, 2 to 30 mm. The outer diameter d3 of the small diameter cylindrical portion 2c can be, for example, 2 to 30 mm. The inner diameter d2 of the large diameter cylindrical portion 2a can be, for example, 1 to 29 mm. The inner diameter d4 of the small diameter cylindrical portion 2c can be, for example, 1 to 29 mm.

[0029] The thickness t of the cylindrical member 2 can be, for example, 0.3 to 3 mm, and is preferably 0.5 to 2 mm.

[0030] 2(a) can be, for example, 3 to 25 mm, and preferably 5 to 20 mm, inclusive. The proportions of the height H1 of the cylindrical member 2 that are accounted for by the height H2 of the large-diameter cylindrical portion 2a and the height H3 of the small-diameter cylindrical portion 2c can be 30 to 70%.

[0031] The cylindrical member 2 has a recess 6 on the inner circumferential surface 2as of the large-diameter cylindrical portion 2a. The recess 6 refers to an internal space that extends radially outward from the inner circumferential surface of the large-diameter cylindrical portion 2a, which serves as a reference surface. Figure 2(b) is an enlarged view of a cross section including the central axis C of the recess 6 in Figure 2(a). The shape of the recess 6 in the cross section including the central axis C is triangular.

[0032] The magnetic structure 10 has a plurality of recesses 6. In Fig. 1(a), eight recesses 6 are arranged at equal intervals in the circumferential direction on the inner peripheral surface 2as of the large-diameter cylindrical portion 2a. The distance Lc between the recesses 6 and the upper end 2V of the cylindrical member 2 shown in Figs. 1 and 2(a) is, for example, 0.3 to 5.0 mm, and may be 0.5 to 3.0 mm.

[0033] As shown in Figure 2(b), the inner surface of the recess 6 has an inclined surface 6a that is inclined relative to the inner surface 2as of the large-diameter cylindrical portion 2a so that the recess is deeper at the lower end 2L of the cylindrical member 2 than at the upper end 2V, an inclined surface 6b that is inclined relative to the inner surface 2as of the large-diameter cylindrical portion 2a so that the recess is shallower at the lower end 2L of the cylindrical member 2 than at the upper end 2V, and a pair of side surfaces 6c that face each other in the circumferential direction of the large-diameter cylindrical portion 2a, as shown in Figure 2(a).

[0034] As shown in Figure 2(b), in a cross section including the central axis C, the angle θ formed between the inclined surfaces 6a and 6b and the inner peripheral surface 2as of the large-diameter cylindrical portion 2a can be, for example, 1 to 90°. The lengths of the inclined surfaces 6a and 6b in the cross section of Figure 2(b) may be the same and the cross-sectional shape may be an isosceles triangle, or they may be different and the cross-sectional shape may be a scalene triangle, or a right-angled triangle (for example, one inclined surface and the inner peripheral surface form a right angle).

[0035] Height of the recess 6 in the direction of the central axis C (length in the direction of the central axis C) L HH For example, the thickness can be 0.1 to 2.0 mm, and is preferably 0.2 to 1.0 mm.

[0036] Radial depth L of recess 6 HD For example, the thickness can be 0.1 to 2.0 mm, and is preferably 0.2 to 1.0 mm.

[0037] The width L of the recess 6 along the circumferential direction shown in FIG. HW The thickness can be, for example, 0.3 to 3.0 mm, and is preferably 0.5 to 2.0 mm.

[0038] The cylindrical member 2 is made of resin. The resin may be a thermoplastic resin or a cured thermosetting resin. Examples of thermoplastic resins include so-called general-purpose plastics such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), acrylonitrile butadiene styrene (ABS), acrylonitrile styrene (AS), polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), polyvinylidene chloride (PVDC), and polyethylene terephthalate (PET); so-called engineering plastics such as polycarbonate (PC), polyphenylene ether (PPE), polyamide (PA), polyacetal (POM), and polybutylene terephthalate; and so-called super-engineering plastics such as polyphthalamide (PPA), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polysulfone (PSU), polyethersulfone (PES), polyetherimide (PEI), polyamideimide (PAI), polyetheretherketone (PEEK), and polytetrafluoroethylene (PTFE).

[0039] Examples of thermosetting resins are phenolic resin (PF), urea resin (UF), melamine resin (MF), unsaturated polyester resin (UP), epoxy resin (EP), silicone resin (SI), and polyurethane resin (PUR).

[0040] The resin constituting the cylindrical member 2 may contain one type of resin, or may contain two or more types of resin.

[0041] 3(a), the magnetic structure 10 has a cylindrical member 2 and a bonded magnet molded body 4. The bonded magnet molded body 4 has a substantially cylindrical shape, and has an end face (exposed upper surface) 4t perpendicular to the central axis C of the cylindrical member 2 on the side of the upper end 2V of the cylindrical member 2, and a lower surface 4s perpendicular to the central axis C on the opposite side to the end face 4t.

[0042] The bonded magnet molded body 4 fills the large-diameter cylindrical portion 2a so as to come into contact with the inner peripheral surface 2as of the large-diameter cylindrical portion 2a and the inner surface 2bs of the annular plate 2b, and also fills the recessed portion 6. In other words, the bonded magnet molded body 4 has a protruding portion 4c that protrudes into the recessed portion 6 and comes into contact with the inner surface of the recessed portion 6.

[0043] The recess 6 and protrusion 4c make it difficult for the bond magnet molded body 4 to fall off in the direction of the upper end 2V from the cylindrical member 2. Furthermore, as shown in Figure 3(a), a pair of side surfaces 6c of the recess 6 contact the protrusion 4c of the bond magnet molded body 4 from both sides in the circumferential direction of the large diameter cylindrical portion 2a. This makes it possible to prevent the bond magnet molded body 4 from shifting in the circumferential direction of the large diameter cylindrical portion 2a.

[0044] The inside of the small diameter cylindrical portion 2c of the cylindrical member 2 of the magnetic structure 10 is not filled with the bonded magnet molding 4, and as will be described later, a shaft such as an automobile steering wheel shaft can be inserted and fixed from the lower end 2L side of the cylindrical member 2.

[0045] As shown in Figures 3(a) and 3(b), the end face 4t of the bonded magnetic molded body 4 is located further inward in the axial direction of the cylindrical member 2 than the upper end 2V of the cylindrical member 2. The distance E between the end face 4t of the bonded magnetic molded body 4 and the upper end 2V of the cylindrical member 2 can be, for example, 0.02 to 0.25 mm, and preferably 0.02 to 0.20 mm. If the distance E between the end face 4t of the bonded magnetic molded body 4 and the upper end 2V of the cylindrical member 2 is 0.02 mm or more, the bonded magnetic molded body 4 is less likely to protrude from the end face of the cylindrical member 2 even if it expands in a severe temperature change environment, making it easier to prevent damage or detachment due to external forces. If the distance E between the end face 4t of the bonded magnetic molded body 4 and the upper end 2V of the cylindrical member 2 is 0.25 mm or less, the distance between the bonded magnetic molded body 4 and the magnetic sensor is not too large, making it easier for the magnetic sensor to receive a magnetic field sufficient for detection.

[0046] The north and south poles of the bonded magnet molded body 4 can be spaced apart in a direction perpendicular to the central axis C, as will be described later (see FIG. 20).

[0047] The bonded magnet molded body 4 contains a resin and a magnetic powder. Examples of the resin are a cured thermosetting resin or a thermoplastic resin, examples of which are as described above in the section on the cylindrical member 2. The bonded magnet molded body 4 may contain one type of resin alone, or may contain two or more types of resins.

[0048] Examples of magnetic powder include rare earth magnetic powder and ferrite magnetic powder. From the viewpoint of obtaining high magnetic properties, the magnetic powder is preferably rare earth magnetic powder. The average particle size of the magnetic powder is, for example, 30 to 250 μm. The bonded magnet molded body 4 may contain one type of magnetic powder alone, or may contain two or more types of magnetic powder.

[0049] (Action and effect) According to the magnetic structure of this embodiment, the cylindrical member 2 is made of resin. Therefore, it is possible to easily mass-produce a precise shape using a mold. In contrast, when the cylindrical member 2 is made of metal as in the conventional case, it is manufactured by press working or the like, making it difficult to improve the dimensional accuracy.

[0050] Improving dimensional accuracy brings about the following effects. For example, improving the circularity of the cylindrical member 2 also makes it possible to improve the circularity of the bonded magnetic molded body 4 formed inside, improving the accuracy of angle detection using the magnetic field generated by the bonded magnetic molded body 4. Furthermore, reducing the deviation between the center of gravity at the lower end 2L of the cylindrical member 2 and the center of gravity at the upper end 2V of the cylindrical member 2 and the designed central axis of the cylindrical member reduces eccentricity of the bonded magnetic molded body 4 during rotation, improving the accuracy of angle detection using the magnetic field. Furthermore, improving the dimensional accuracy of the large-diameter cylindrical portion 2a also reduces variation in the volume of the bonded magnetic molded body 4, reducing individual differences in the magnetic properties of the magnetic structure 10 and contributing to improved detection accuracy.

[0051] (Magnetic structure manufacturing method) First, the cylindrical member 2 having the recess 6 is manufactured. There are no particular limitations on the method for manufacturing the cylindrical member 2, and for example, injection molding, compression molding, cast molding, etc. can be used.

[0052] Next, a bonded magnet molded body 4 is formed inside the large-diameter cylindrical portion 2a of the cylindrical member 2. Here, it is preferable to form the bonded magnet molded body 4 by injection molding. First, the cylindrical member 2 provided with the recess 6 as described above is fixed, for example, in a first mold with the large-diameter cylindrical portion 2a facing the first mold. Next, a second mold having columnar protrusions that fill the small-diameter cylindrical portion 2c is attached to the first mold, and the mold is closed. Next, a raw material composition containing resin and magnet powder is fluidized by heating or the like, injected into the mold, and solidified by cooling or the like, to form the bonded magnet molded body 4 inside the large-diameter cylindrical portion 2a.

[0053] If the bonded magnetic molded body 4 is an isotropic bonded magnetic molded body, the injection molding in the above-mentioned filling step is carried out in a magnetic field. On the other hand, if the bonded magnetic molded body 4 is an anisotropic bonded magnetic molded body, the injection molding in the above-mentioned filling step is carried out in a magnetic field. Another method for forming the bonded magnetic molded body 4 inside the cylindrical member 2 is to fit a bonded magnetic molded body 4 produced by compression molding, extrusion molding, or the like into the cylindrical member 2. The bonded magnetic molded body 4 may also be fixed to the cylindrical member 2 using an adhesive.

[0054] If the resin of the cylindrical member 2 and the resin of the bonded magnet molded body 4 are the same, the adhesion between the cylindrical member 2 and the bonded magnet molded body 4 tends to be strong.

[0055] If the resin of cylindrical member 2 and the resin of bonded magnet molded body 4 have the same melting point, the adhesion between cylindrical member 2 and bonded magnet molded body 4 tends to be strong.

[0056] (Other embodiments) Next, a magnetic structure according to another embodiment of the present invention will be described. In the following description, descriptions that overlap with the first embodiment will be omitted, and only the differences will be described.

[0057] 4(a) and 4(b) are enlarged cross-sectional views including the central axis C of a cylindrical member 2 according to another embodiment. In the embodiment of FIG. 4(a), convex portions 6' each have a triangular cross-section instead of the concave portions 6 having a triangular cross-section. The radial height LHD' and circumferential width of the convex portions 6' can be set to the same values ​​as the radial depth LHD and width LHW of the concave portions 6 in the first embodiment. The height LHH of the convex portions 6' in the direction of the central axis C can be set to the same value as in the first embodiment. The bonded magnet molded body 4 is provided so as to cover the surface of the convex portions 6', and has concave portions corresponding to the convex portions 6'.

[0058] The embodiment in Figure 4(b) has a recess 6 with a rectangular cross section instead of the recess 6 with a triangular cross section. The radial depth LHD, height LHH in the direction of the central axis C, and circumferential width of the recess 6 can be set in the same manner as in the first embodiment. The bond magnet molded body 4 is provided to fill the recess 6, and has a protrusion that corresponds to the recess 6.

[0059] FIG. 5 is a cross-sectional view including the central axis C of a magnetic structure 10 according to still another embodiment of the present invention. In magnetic structure 10 of this embodiment, cylindrical member 2 further has, at the upper end of large-diameter cylindrical portion 2a, an annular plate 2d that contacts the peripheral edge of end face 4t of bonded magnetic molded body 4. In this embodiment, annular plate 2d further prevents bonded magnetic molded body 4 from coming off in the upward direction. The radial distance 2da over which annular plate 2d covers end face 4t of bonded magnetic molded body 4 can be 1 to 3 mm.

[0060] 6(a), (b), and 7(a) are perspective views of a cylindrical member 2 used in a magnetic structure 10 according to still another embodiment of the present invention. These embodiments differ from the first embodiment in the shape of the recesses 6. In these embodiments, the recesses 6 extend axially and reach the upper end 2V of the large-diameter cylindrical portion 2a. The cross-sectional shape of the recesses 6 perpendicular to the central axis C is rectangular in FIG. 6(a) and triangular in FIGS. 6(b) and 7(a). In FIGS. 6(a) and 6(b), a predetermined gap is provided between the recesses 6 in the circumferential direction, but in FIG. 7(a), the recesses 6 are provided adjacent to each other in the circumferential direction. Therefore, it can also be seen that convex portions, rather than recesses, are provided adjacent to each other. The radial depth and circumferential width of the recesses 6 can be set in the same manner as in the first embodiment.

[0061] 6(a), 6(b) and 7(a), the recess 6 extends to the upper end 2V of the cylindrical member 2 and is open, but it may be configured so as not to reach the upper end 2V to provide a retaining function. Also, a ring plate 2d as shown in FIG. 5 may be provided to provide a retaining function.

[0062] FIG. 7(b) is a perspective view of a cylindrical member 2 used in a magnetic structure 10 according to yet another embodiment of the present invention. This embodiment differs from FIG. 6(b) in that, instead of the recessed portion 6 having a triangular cross section perpendicular to the central axis C, a protruding portion 6' having a triangular cross section perpendicular to the central axis C is provided. The radial height of the protruding portion 6' can be set in the same manner as in the embodiment of FIG. 4(a). The circumferential width of the protruding portion 6' can be set in the same manner as in the first embodiment. Note that the protruding portion 6' extends open to the upper end 2V of the cylindrical member 2, but may be made shorter than the upper end 2V to provide a retaining function. Alternatively, a circular plate 2d as shown in FIG. 5 may be provided to provide a retaining function.

[0063] Figures 8(a) and (b) are oblique views of a cylindrical member 2 used in a magnetic structure 10 according to yet another embodiment of the present invention, where the large-diameter cylindrical portion 2a in Figure 8(a) has a recess 6 extending in the axial direction, and the large-diameter cylindrical portion 2a in Figure 8(b) has a protrusion 6' extending in the axial direction.

[0064] The recesses 6 and the protrusions 6' each extend in the axial direction and are open at the upper end 2V. The cross-sectional shape of the recesses 6 perpendicular to the C-axis is a concave arc. The cross-sectional shape of the protrusions 6' perpendicular to the C-axis is a convex arc. In this embodiment, there are three recesses 6 and three protrusions 6', which are arranged at equal intervals in the circumferential direction. The radial depth / height and circumferential width of the recesses 6 and the protrusions 6' can be set in the same way as the depths LHD and LHW in the first embodiment.

[0065] 8(a) and 8(b), the recessed portion 6 and the protruding portion 6' extend open to the upper end 2V of the cylindrical member 2, but they may be made not to reach the upper end 2V to provide a retaining function. Also, a circular plate 2d as shown in FIG. 5 may be provided to provide a retaining function.

[0066] FIG. 9 is a perspective view of a cylindrical member 2 used in a magnetic structure 10 according to still another embodiment of the present invention. This embodiment differs from the first embodiment in the extension direction of the recesses 6 formed on the inner peripheral surface 2as of the large-diameter cylindrical portion 2a. In this embodiment, some of the recesses 6 are parallel to one another and extend in a direction oblique to the central axis C when viewed from a direction perpendicular to the central axis C. The remaining recesses 6 are parallel to one another and extend in a direction oblique to the central axis C when viewed from a direction perpendicular to the central axis C, and intersect with the remaining recesses 6, forming a diagonal lattice shape as a whole. The width, depth, etc. of the recessed portions 6 can be appropriately set in the same manner as in the first embodiment. Note that protrusions may be used instead of recessed portions. Furthermore, the inner circumferential surface 2as may have an uneven surface (textured surface) region 8', which will be described later. The size, etc. of the uneven surface region can be as described later.

[0067] Figure 10(a) is a cross-sectional view of a magnetic structure 10 according to yet another embodiment of the present invention, taken along line M including the central axis C, and Figure 10(b) is a top view of the cylindrical member of Figure 10(a).

[0068] This embodiment differs from the first embodiment in that the recesses 6 are provided on the inner surface 2bs of the annular plate 2b, rather than on the inner circumferential surface 2as of the large-diameter cylindrical portion 2a. In this embodiment, the recesses 6 are provided at equal intervals in the circumferential direction.

[0069] In this embodiment, the shape of the recess 6 is a cylinder, but the shape is not particularly limited and may be a prism, etc. The depth of the recess 6 may be 0.1 to 2.0 mm, and the diameter of the recess 6 may be 0.1 to 5.0 mm.

[0070] FIG. 11 is a cross-sectional view including the central axis C of a magnetic structure 10 according to still another embodiment of the present invention.

[0071] This embodiment differs from the first embodiment in that the thickness 2bt of the annular plate 2b is thicker than the thicknesses of the large-diameter cylindrical portion 2a and the small-diameter cylindrical portion 2c. The ratio of the thickness 2bt of the annular plate 2b to the thicknesses of the large-diameter cylindrical portion 2a and the small-diameter cylindrical portion 2c can be 1.2 to 5 times. Increasing the thickness 2bt of the annular plate 2b can suppress thermal deformation of the annular plate 2b. Deformation of the annular plate 2b tilts the end face 4t of the bonded magnet molded body 4. This changes the direction of the magnetic flux passing through the magnetic sensor, increasing the angle error. Increasing the thickness 2bt of the annular plate 2b can prevent such angle error from occurring. Since the cylindrical member 2 according to this embodiment is made of resin, it is easy to partially change the wall thickness in this way by injection molding or the like, allowing for a high degree of design freedom. This structure of the annular plate 2b can be combined with not only the first embodiment but also the various cylindrical members described above.

[0072] 12(a) and 12(b) are perspective views including the bottom surface of a magnetic structure 10 according to still another embodiment of the present invention.

[0073] The magnetic structure 10 of FIG. 12(a) differs from the first embodiment in that the contour shape of the inner surface of the small-diameter cylindrical portion 2c perpendicular to the central axis C is not circular but rectangular with a straight portion L. The magnetic structure 10 of FIG. 12(b) differs from the first embodiment in that the contour shape of the inner surface of the small-diameter cylindrical portion 2c perpendicular to the central axis C is not circular but barrel-shaped with straight portions L at both opposing ends of the circle. The non-circular inner contour shape of the small-diameter cylindrical portion 2c makes it easier to prevent the shaft inserted into the small-diameter cylindrical portion 2c from spinning freely. Since the cylindrical member of this embodiment is made of resin, it is easy to form the inner contour shape of the small-diameter cylindrical portion 2c into a non-circular shape by injection molding or the like, allowing for greater design flexibility. This structure of the small-diameter cylindrical portion 2c can be combined with not only the first embodiment but also the various cylindrical members described above. Furthermore, examples of cases where the inner contour shape of the small diameter cylindrical portion 2c is non-circular are not limited to the above; for example, if part of the contour shape has a straight line portion L, the shape of the other part may be an arc, or it may be an ellipse without having a straight line portion.

[0074] Next, other embodiments of the magnetic structure will be described with reference to FIGS. FIG. 13 is a perspective view of a magnetic structure 10 according to still another embodiment of the present invention.

[0075] The magnetic structure 10 according to this embodiment differs from the magnetic structure of Figure 8(a) in that (1) the outer diameters of the large diameter cylindrical portion (first cylindrical portion) 2a and the small diameter cylindrical portion (second cylindrical portion) 2c are the same, and (2) an uneven surface (textured surface) region 8' is formed on the inner surface of the small diameter cylindrical portion 2c.

[0076] Within the small-diameter cylindrical portion 2c, there is provided a space V that is connected to the outside of the cylindrical member 2 and is not filled with the bonded magnet molded body 4, and a textured surface region 8' is provided on the inner surface of the space V. Examples of patterns of the textured surface region 8' include a group of recesses or protrusions such as wrinkles, matte finish, hairlines, and disk-shaped protrusions. This pattern can be a repeating pattern. Such textured surface region 8' can be formed by roughening the surface of the molding die and machining the inner surface of the small-diameter cylindrical portion after molding. The area ratio of the uneven surface region 8' is not particularly limited, but is preferably 50% or more of the total area of ​​the inner circumferential surface of the small-diameter cylindrical portion 2c. The maximum height difference (surface roughness) in the uneven surface region 8' can be 0.01 to 0.2 mm.

[0077] The inner and outer diameters and height H2 of the large diameter cylindrical portion 2a, the inner and outer diameters and height H3 of the small diameter cylindrical portion 2c, and the height H1 of the cylindrical member 2 can be set in the same manner as described in the first embodiment above.

[0078] The wall thickness of the large diameter cylindrical portion 2a can be set to 0.3 to 3 mm, and the wall thickness of the small diameter cylindrical portion can be set to 0.5 to 14.5 mm.

[0079] According to this embodiment, as will be described later, when using the magnetic structure 10, the shaft 122 is inserted into the small diameter cylindrical portion 2c, and the shaft 122 and the small diameter cylindrical portion 2c are fitted together. However, the uneven surface region 8' increases the frictional force between the shaft 122 and the small diameter cylindrical portion 2c, enabling more secure fixation by fitting.

[0080] In addition, since the thickness of the small diameter cylindrical portion 2c can be made thicker than the thickness of the large diameter cylindrical portion 2a, it is possible to prevent cracks in the small diameter cylindrical portion 2c due to insertion of the shaft 122. Furthermore, no special processing is required for the shaft 122, making it highly versatile.

[0081] FIG. 14 is a perspective view of a magnetic structure 10 according to still another embodiment of the present invention. This embodiment differs from the magnetic structure of FIG. 13 in that a plurality of protrusions 8 extending in the axial direction are provided on the inner surface of the space V of the small diameter cylindrical portion 2c instead of the uneven surface area 8'.

[0082] Each of the protrusions 8 extends in the axial direction, reaching from one end (bottom) of the space V of the small-diameter cylindrical portion 2c to the other end (opening). The protrusions 8 may be formed only in a portion of the space V from one end to the other in the axial direction. In this embodiment, the cross-sectional shape of the protrusions 8 perpendicular to the axis is a convex arc. In this embodiment, three of the protrusions 8 are provided, arranged at equal intervals in the circumferential direction. The height of the protrusions 8 can be 0.1 to 1.0 mm, and the width of the protrusions 8 in the circumferential direction can be 0.1 to 5.0 mm.

[0083] In this embodiment as well, when using the magnetic structure 10, the shaft 122 is inserted into the small diameter cylindrical portion 2c and the shaft 122 and the small diameter cylindrical portion 2c are fitted together, but the frictional force between the shaft 122 and the small diameter cylindrical portion 2c is increased by the protrusion 8, enabling more secure fixation by fitting. Furthermore, no special processing is required for the shaft 122, making it highly versatile.

[0084] FIG. 15 is a perspective view of a magnetic structure 10 according to still another embodiment of the present invention. This embodiment differs from the magnetic structure of Fig. 13 in that, instead of the uneven surface region 8' on the inner surface of the space portion V of the small diameter cylindrical portion 2c, the outline of the cross section perpendicular to the axis of the space portion V of the small diameter cylindrical portion 2c has a part of a straight line portion L. In Fig. 15, the outline of the cross section of the space portion V is a D-shape that combines the straight line portion L and a circular arc portion.

[0085] The cross-sectional outline may be non-circular, and may be rectangular as in Figure 12(a), barrel-shaped as in Figure 12(b), or elliptical without straight lines. Furthermore, the non-circular cross-sectional shape does not need to continue throughout the entire space V from the back to the opening outlet; a portion of the back side, i.e., the cross section of the opening is circular, but the cross section of the back side may be non-circular.

[0086] In this case, a notch 122D is also provided at the tip of the shaft 122, and the cross-sectional outline of the tip of the shaft 122 is D-shaped.

[0087] According to this embodiment, it is possible to achieve the effect of preventing the shaft 122 from rotating and coming off while maintaining the strength of the small diameter cylindrical portion 2c.

[0088] 16 and 17 are an exploded cross-sectional view and a top view of a cylindrical member and a shaft of a magnetic structure 10 according to still another embodiment of the present invention.

[0089] This embodiment differs from the magnetic structure of Fig. 13 in that, instead of the uneven surface region 8' on the inner surface of the space V of the small diameter cylindrical portion 2c, a plurality of protrusions 8 protruding toward the axis of the cylindrical member are formed on the inner surface of the space V of the small diameter cylindrical portion 2c. The height of the protrusions 8 can be 0.05 to 0.5 mm. The plurality of protrusions 8 are provided spaced apart in the circumferential direction.

[0090] The tip of the shaft 122 is also provided with a plurality of recesses 122G capable of accommodating the protrusions 8. The protrusions 8 are each capable of fitting into the recesses 122G. In the fitted state, the protrusions 8 have a surface 8R that contacts the inner surface of the recesses 122G of the shaft 122 when viewed from the axial direction as shown in (a) of Figure 17, and have a surface 8S that contacts the recesses 122G of the shaft 122 when viewed from a direction perpendicular to the axis as shown in Figure 16.

[0091] In this embodiment, when using the magnetic structure 10, the shaft 122 is inserted into the small diameter cylindrical portion 2c, and the recess 122G of the shaft 122 engages with the protrusion 8, thereby providing anti-rotation and anti-slip functions and enabling more secure fixation through engagement.

[0092] (Deformation of the magnetic structure) The number of recesses 6 and protrusions 6' each need only be one or more, and may be 1 to 10, or may be 3 to 8, from the viewpoint of more stably fixing the bonded magnet molded body 4. In the above embodiment, multiple recesses 6 or protrusions 6' are arranged at equal intervals in the circumferential direction on the inner surface of the cylindrical member 2, but they may also be arranged at different intervals. Multiple recesses 6 or protrusions 6' may also be arranged spaced apart from each other in the axial direction. The cylindrical member 2 may have both recesses 6 and protrusions 6'.

[0093] In the above embodiment, the cross-sectional shape including the central axis C of the recessed portions 6 and the protruding portions 6' or the cross-sectional shape perpendicular to the central axis C of the recessed portions 6 and the protruding portions 6' is a rectangle, a triangle, or a circular arc, but it may also be an elliptical arc, another polygon, etc. Furthermore, when the shape of the recessed portions or the protruding portions in the cross section is a rectangle, a triangle, another polygon, etc., the corners of each shape may be rounded.

[0094] Furthermore, the recesses or protrusions do not have to be spaced apart in the circumferential direction as in the first embodiment, and for example, the recesses or protrusions may extend in the circumferential direction to form a ring.

[0095] Furthermore, although in the above embodiment, the cylindrical member 2 always includes a convex portion 6' or a concave portion 6, it is not necessary for it to have a concave portion or a convex portion. If the cylindrical member 2 is made of resin, the contact surfaces of the cylindrical member 2 and the bonded magnet molded body 4 melt when heated and solidify and become one body when cooled, improving the adhesion between the bonded magnet molded body 4 and the cylindrical member 2. This makes it easier to prevent misalignment between the cylindrical member 2 and the bonded magnet molded body 4.

[0096] When the bonded magnetic molded body 4 is integrally molded into the cylindrical member 2 by injection molding, the volume of the bonded magnetic molded body is reduced because injection pressure is applied to the bonded magnetic molded body 4 during molding. After molding, when the injection pressure is released, the volume of the bonded magnetic molded body expands. As a result, the bonded magnetic molded body 4 applies pressure to the inner surface of the large-diameter cylindrical portion 2a of the cylindrical member 2, making it difficult for the bonded magnetic molded body 4 to fall off or shift from the cylindrical member 2, and it can function as a stopper and a rotation stopper even though the inner surface of the large-diameter cylindrical portion 2a does not have any protrusions or recesses.

[0097] The number of protrusions 8 on the inner surface of the space V of the cylindrical member 2, i.e., the inner surface of the small-diameter cylindrical portion 2c, may be one or more, and may be 1 to 10, or may be 3 to 8, from the viewpoint of more stably fixing the shaft 122. In some embodiments, the multiple protrusions 8 are arranged at equal intervals in the circumferential direction on the inner surface of the cylindrical member 2, but they may also be arranged at different intervals. The multiple protrusions 8 may also be arranged spaced apart from each other in the axial direction. The space V of the cylindrical member 2 may have recesses instead of protrusions 8, or may have both recesses and protrusions. When the space V of the cylindrical member 2 has recesses, the shaft 122 may have protrusions instead of recesses and fit into the recesses of the space V.

[0098] In the above embodiment, the cross-sectional shape of the convex portion 8 of the space portion V may be other than a circular arc, such as a square, a triangle, an elliptical arc, or another polygon. Furthermore, when the cross-sectional shape of the convex portion is a square, a triangle, or another polygon, the corners of each shape may be rounded.

[0099] Furthermore, the protrusions 8 of the space V do not have to be spaced apart in the circumferential direction, and may, for example, extend in the circumferential direction to form a ring.

[0100] In the above embodiment, the cylindrical member 2 has a large-diameter cylindrical portion 2a, an annular plate 2b, and a small-diameter cylindrical portion 2c, but the annular plate 2b may be a connecting cylindrical portion that can connect the large-diameter cylindrical portion 2a and the small-diameter cylindrical portion 2c, and may be, for example, a tapered tube instead of a flat-shaped annular plate. Furthermore, from the perspective of making the outer diameter of bonded magnet molded body 4 larger than the outer diameter of the shaft, it is sufficient that at least the inner diameter of large-diameter cylindrical portion 2a is larger than the inner diameter of small-diameter cylindrical portion 2c. In other words, in this specification, the term "large-diameter cylindrical portion" means having an inner diameter larger than the "small-diameter cylindrical portion," and does not necessarily mean having an outer diameter larger than the "small-diameter cylindrical portion."

[0101] Alternatively, the entire cylindrical member may be a tapered tube whose outer and inner diameters decrease from one end to the other in the axial direction, with the bonded magnet molded body filled at either end.

[0102] In addition, the cylindrical member may have a straight pipe section and a tapered pipe section connected to the straight pipe section, the inner diameter and outer diameter of which increase as the section moves away from the straight pipe section, and the bond magnet molding may be filled in the straight pipe section or the tapered pipe section.

[0103] Alternatively, the cylindrical member may comprise a straight pipe section and a barrel-shaped section connected to the straight pipe section, with the bonded magnet molded body filled in the straight pipe section or the barrel-shaped section. The barrel-shaped section has an outer and inner diameter that increases with increasing distance from the straight pipe section, but once the distance from the straight pipe section exceeds a certain value, the inner and outer diameters decrease with increasing distance from the straight pipe section. When the bonded magnet molded body is placed inside the barrel-shaped section, it acts to prevent the bonded magnet molded body from slipping out.

[0104] In the above embodiment, only the large diameter cylindrical portion 2a of the cylindrical member 2 is filled with the bonded magnet molded body 4, but the bonded magnet molded body 4 may also be filled in part of the small diameter cylindrical portion 2c.

[0105] Furthermore, the bonded magnet molded body 4 may be filled in the small diameter cylindrical portion 2c rather than in the large diameter cylindrical portion 2a. In this case, the recessed portion 6 and the protruding portion 6' can be provided on the inner surface of the small diameter cylindrical portion 2c rather than the large diameter cylindrical portion 2a of the cylindrical member 2. In this case, a shaft is inserted into the large diameter cylindrical portion 2a, and the lower end (end face) 2L of the small diameter cylindrical portion 2c faces the magnetic sensor.

[0106] For example, the cylindrical member 2 of the magnetic structure 10 shown in Figure 18 has a large-diameter cylindrical portion 2a and a small-diameter cylindrical portion 2c whose inner and outer diameters are smaller than those of the large-diameter cylindrical portion 2a, similar to Figures 2 and 3. Recesses 6 (or protrusions 6') are provided within the small-diameter cylindrical portion 2c, and an uneven surface region 8' (or protrusions 8) is provided within the large-diameter cylindrical portion 2a. A bonded magnet molded body 4 is provided within the small-diameter cylindrical portion 2c, and the bonded magnet molded body 4 has unevenness corresponding to the recesses 6 (or protrusions 6'). A space V not filled with the bonded magnet molded body is provided within the large-diameter cylindrical portion 2a, and a shaft is inserted into the large-diameter cylindrical portion 2a.

[0107] Similar to FIGS. 13 to 16, the cylindrical member 2 of the magnetic structure 10 shown in FIG. 19 has a large-diameter cylindrical portion 2a and a small-diameter cylindrical portion 2c that has an inner diameter smaller than that of the large-diameter cylindrical portion 2a but an outer diameter the same. Recesses 6 (or protrusions 6') are provided within the small-diameter cylindrical portion 2c, and an uneven surface region 8' (or protrusions 8) is provided within the large-diameter cylindrical portion 2a. A bonded magnet molded body 4 is provided within the small-diameter cylindrical portion 2c, and the bonded magnet molded body 4 has unevenness corresponding to the recesses 6 (or protrusions 6'). A space V that is not filled with the bonded magnet molded body is provided within the large-diameter cylindrical portion 2a, and a shaft is inserted into the large-diameter cylindrical portion 2a.

[0108] 18 and 19, the height H1 of the cylindrical member 2, the height H2 of the large-diameter cylindrical portion 2a (the length of the portion with a relatively large inner diameter), the height H3 of the small-diameter cylindrical portion 2c (the length of the portion with a relatively small inner diameter), and the distance E between the end face 4t of the bonded magnet molded body 4 and the end 2L of the cylindrical member 2 can be the same as those of the above-mentioned embodiment. Also, in the embodiment shown in FIGS. 18 and 19, the outer diameter d1 of the large-diameter cylindrical portion 2a can be 3 to 101 mm, the inner diameter d2 of the large-diameter cylindrical portion 2a can be 2 to 100 mm, and the inner diameter d4 of the small-diameter cylindrical portion 3d can be 1 to 29 mm. In the embodiment shown in FIG. 18, the outer diameter d3 of the small-diameter cylindrical portion 2c can be 2 to 30 mm. In the above-described embodiment, the outer diameter of the shaft is larger than the outer diameter of the bonded magnet molded body. In this case, if the magnetization direction of the bonded magnet molded body is set to the axial direction and the shaft is made of a magnetic material such as iron, leakage of magnetic flux from the bottom surface of the magnet is eliminated, making it possible to increase the magnetic flux emitted from the top surface (sensor side).

[0109] Furthermore, the cylindrical member 2 may further have a cylindrical portion having a diameter different from that of the large diameter cylindrical portion 2a and the small diameter cylindrical portion 2c as described above.

[0110] Furthermore, the cylindrical member 2 may be a straight tube with constant inner and outer diameters along the direction of the central axis C, or may have a constant outer diameter and only the inner diameter differs from one another in the axial direction, or may have a constant inner diameter and only the outer diameter differs from one another in the axial direction.

[0111] 13 to 17 and 19, if the outer diameter of the large-diameter cylindrical portion 2a and the outer diameter of the small-diameter cylindrical portion 2c are the same, or if the cylindrical member 2 is a tapered tube or the like whose outer shape changes integrally from the large-diameter cylindrical portion 2a to the small-diameter cylindrical portion 2c (not shown), the large-diameter cylindrical portion 2a and the small-diameter cylindrical portion 2c can be directly connected (joined), so no annular plate (connecting cylindrical portion) is required. Therefore, in this embodiment, the annular plate 2b does not necessarily need to be provided separately from the small-diameter cylindrical portion 2c and the large-diameter cylindrical portion 2a.

[0112] Considering that the magnetic structure 10 rotates around an axis during operation, it is preferable that any cross-sectional shape including the central axis C of the cylindrical member 2 be symmetrical about the central axis C.

[0113] In the above embodiment, the outer shape of the cylindrical member 2 in a cross section perpendicular to the central axis C is circular, but it may be polygonal, such as octagonal or dodecagonal. Even in this case, it is preferable that the outline of the inner surface of the cylindrical member 2 in a cross section perpendicular to the central axis C is circular.

[0114] In the above embodiment, the upper end 2V and the lower end 2L of the cylindrical member 2 are in communication with each other, but the cylindrical member 2 may have a partition wall that blocks this communication. For example, the annular plate 2b may be a circular plate without a hole in the center.

[0115] Furthermore, the upper end 2V of the cylindrical member 2 may be provided with a flange portion extending radially outward.

[0116] Furthermore, in the above embodiment, the north and south poles of the bonded magnet molded body 4 are spaced apart in a direction perpendicular to the central axis C, but depending on the usage conditions of the magnetic structure 10, the north and south poles of the bonded magnet molded body 4 may be spaced apart in other directions, such as in the direction of the central axis C.

[0117] Furthermore, in the above embodiment, the end face 4t of the bonded magnet molded body 4 is positioned a distance E inside the cylinder from the upper end 2V of the tubular member 2, but it is also possible to implement the invention even if the distance E is 0 or negative, i.e., the end face 4t of the bonded magnet molded body 4 protrudes outward from the upper end 2V of the tubular member 2.

[0118] [Rotation angle detector] 20 is a perspective view showing a rotation angle detector 20 according to one embodiment of the present invention. The rotation angle detector 20 according to this embodiment comprises the above-described magnetic structure 10 and a magnetic sensor 12. The magnetic sensor 12 is disposed above the end face (exposed surface) 4t of the bonded magnet molded body 4 of the magnetic structure 10, with a certain gap between it and the magnetic structure 10. The gap between the magnetic structure 10 and the magnetic sensor 12 can be selected as appropriate depending on the magnetic characteristics of the magnetic structure 10, the detection performance of the magnetic sensor 12, etc.

[0119] The magnetic sensor 12 detects the magnetic field generated by the magnet structure 10. The magnetic sensor 12 has a detection circuit configured, for example, by a Wheatstone bridge circuit or the like, and has a magnetoresistive element (MR element) as the magnetic detection element of the Wheatstone bridge circuit. Examples of the MR element include a tunnel magnetoresistive element (TMR element), an anisotropic magnetoresistive element (AMR element), and a giant magnetoresistive element (GMR element). A TMR element is preferably used for the magnetic sensor 12. The magnetic sensor 12 may be a biaxial type having two MR elements, and detects the direction of the magnetic field in a plane perpendicular to the central axis C of the magnet structure 10.

[0120] As described above, in the magnetic structure 10, the north and south poles of the bonded magnet molded body 4 are arranged at a distance from each other in a direction perpendicular to the central axis C. This generates a static magnetic field as shown in the figure, and a magnetic field perpendicular to the central axis C is generated on the central axis C of the cylindrical member 2. The direction of the magnetic field on the central axis changes depending on the rotational position of the magnetic structure 10 in the rotational direction R, so the rotation angle of the magnetic structure 10 can be detected by detecting the direction of the magnetic field with the magnetic sensor 12.

[0121] In rotation angle detector 20, shaft 122, such as a steering wheel shaft of an automobile, is inserted from the small diameter cylindrical portion 2c side of cylindrical member 2 into a space in cylindrical member 2 that is not filled with bonded magnet molded body 4, and is fixed to magnetic structure 10. Then, magnetic structure 10 rotates in direction R about the central axis of cylindrical member 2 in conjunction with the rotation of shaft 122. Therefore, by detecting the rotation angle of magnetic structure 10, the rotation angle of shaft 122 can be detected.

[0122] [Motor assembly] A motor assembly 110 including a rotation angle detector 20 according to this embodiment will be described with reference to Fig. 21. As shown in Fig. 21, the motor assembly 110 includes the rotation angle detector 20, an electric motor 120, and a housing 112 that houses these components.

[0123] The electric motor 120 includes a shaft 122 having a torque-side end 122a and a sensor-side end 122b. The torque-side end 122a of the shaft 122 is rotatably held by a ball bearing 114A provided in the housing 112. The sensor-side end 122b is rotatably held by a ball bearing 114B provided in the housing 112.

[0124] The rotation angle detector 20, i.e., the magnet structure 10 and the magnetic sensor 12, are disposed at the sensor-side end 122b. The magnet structure 10 is attached to the sensor-side end 122b of the shaft 122 of the electric motor 120. As a result, the magnet structure 10 rotates together with the shaft 122, and the direction of the magnetic field generated by the magnet structure 10 changes in accordance with the rotation of the electric motor 120. The magnetic sensor 12 is disposed inside the housing 112 at a position facing the magnet structure 10. The rotation angle detector 20 detects the rotation angle of the electric motor 120 by utilizing the fact that the resistance value of the magnetic sensor 12 continuously changes in accordance with the direction of the magnetic field generated by the magnet structure 10. The change in the resistance value of the magnetic sensor 12 is measured by a detection circuit configured, for example, by a Wheatstone bridge circuit.

[0125] Next, an electric power steering device 150 having the motor assembly 110 will be described with reference to FIG.

[0126] In addition to the motor assembly 110, the electric power steering device 150 includes a control unit 152, generally referred to as an Electronic Control Unit (ECU), and a steering wheel 154. The control unit 152 is configured to receive a vehicle speed signal from the vehicle, information related to the rotation angle of the shaft 122 detected by the rotation angle detector 20 of the motor assembly 110, and a torque signal from a torque sensor 156 related to the steering force of the steering wheel 154. The control unit 152 is also configured to adjust the current driving the electric motor 120. Upon receiving the vehicle speed signal and torque signal, the control unit 152 sends a current corresponding to the vehicle speed signal and torque signal to the power assist electric motor 120 to drive the electric motor 120, and assists the steering force with the torque of the shaft 122. At this time, the control unit 152 feedback-controls the current of the electric motor 120 in accordance with the rotation angle of the shaft 122 received from the rotation angle detector 20, thereby adjusting the amount of power assist. [Explanation of symbols]

[0127] 2...cylindrical member, 2a...large diameter cylindrical portion (first cylindrical portion), 2b...annular plate (connecting cylindrical portion), 2c...small diameter cylindrical portion (second cylindrical portion), 4...bonded magnet molded body, 6...recess, 6'...protrusion, 10...magnetic structure, 12...magnetic sensor, 20...rotation angle detector, 150...electric power steering device.

Claims

1. a cylindrical member made of resin; a bonded magnet molded body filled in the cylindrical member, The bonded magnet molded body contains resin and magnet powder, The resin of the cylindrical member is the same as the resin of the bonded magnet molded body, The magnetic structure has a recess or a protrusion in the cylindrical member at a portion where the cylindrical member comes into contact with the bonded magnet molded body.

2. The magnetic structure according to claim 1 , wherein the recessed or protruding portion extends in the axial direction of the cylindrical member.

3. The magnetic structure according to claim 1 or 2, having a plurality of said recesses or protrusions.

4. The magnetic structure according to claim 3 , wherein the plurality of recesses or protrusions are arranged at intervals in the circumferential direction of the cylindrical member.

5. The magnetic structure according to any one of claims 1 to 4, wherein the cylindrical member further has a space portion that communicates with the outside of the cylindrical member and that is not filled with the bonded magnet molded body.

6. The magnetic structure according to claim 5 , wherein the inner surface of the space has a protrusion or a recess.

7. 6. The magnetic structure according to claim 5, wherein the inner surface of said cavity has an uneven surface area.

8. The magnetic structure according to claim 5 , wherein the inner surface of the space has one or more protrusions extending in the axial direction of the cylindrical member.

9. The magnetic structure according to claim 5 , wherein the inner surface of the space has a protrusion that can be fitted into a recess that is inserted into the inner surface of the space.

10. the cylindrical member has a first cylindrical portion and a second cylindrical portion having an inner diameter smaller than that of the first cylindrical portion, The bonded magnet molded body is provided in the first cylindrical portion or the second cylindrical portion. The magnetic structure according to any one of claims 1 to 9.

11. the cylindrical member has a first cylindrical portion and a second cylindrical portion having an inner diameter smaller than that of the first cylindrical portion, the bonded magnet molded body is provided in one of the first cylindrical portion and the second cylindrical portion, 10. The magnetic structure according to claim 1, wherein the cross section of the inner surface of the other of the first cylindrical portion and the second cylindrical portion perpendicular to the axis has a non-circular outline shape.

12. A rotation angle detector comprising the magnet structure according to any one of claims 1 to 11 and a magnetic sensor.

13. An electric power steering device comprising the rotation angle detector according to claim 12.

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