Molded article and method for producing molded article

Abstract

In this molded article, in which a bond magnet is bonded to a surface of a shaft, a bonding surface to which the bond magnet of the shaft is bonded has a plurality of spiral grooves that are separated from each other and extend spirally along the center axis of the shaft. This method for manufacturing a molded article, in which a bond magnet is bonded to a surface of a shaft, comprises: a groove formation step for forming a plurality of spiral grooves that are separated from each other and extend spirally along the center axis of the shaft on a bonding surface to which the bond magnet of the shaft is bonded; and a bonding step for bonding the bond magnet to the bonding surface of the shaft on which the plurality of spiral grooves have been formed.

Description

Molded product and manufacturing method of molded product

[0001] The present disclosure relates to a molded article in which a bonded magnet is joined to a shaft, and a method for manufacturing the molded article.

[0002] Patent Document 1 describes a molded product (shaft-integrated bonded magnet) in which a cylindrical bonded magnet is integrally provided on the circumferential surface of a cylindrical shaft. In this molded product, knurling is formed on the circumferential surface of the central portion in the axial direction of the shaft, thereby improving the bonding strength between the shaft and the bonded magnet.

[0003] Japanese Patent Application Laid-Open No. 2020-141134

[0004] However, in the molded product described in Patent Document 1, the grooves constituting the knurling are a large number of linear grooves extending in the axial direction of the shaft or a large number of diamond-shaped grooves intersecting each other, which poses a problem of a large number of grooves. If a large number of grooves are formed in a shaft, this may result in, for example, a decrease in the strength of the shaft or a decrease in the ease of processing the shaft.

[0005] Therefore, an object of the present disclosure is to provide a molded product and a method for manufacturing a molded product that can reduce the number of grooves formed in a shaft.

[0006] [1] The molded product according to the present disclosure is a molded product in which a bonded magnet is bonded to the surface of a shaft, and the bonding surface of the shaft to which the bonded magnet is bonded has a plurality of spiral grooves that extend spirally along the central axis of the shaft without intersecting each other.

[0007] In this molded product, multiple spiral grooves extend spirally along the central axis of the shaft, making it possible to increase the length of each groove and increase the specific surface area of ​​each groove. Moreover, because the multiple spiral grooves do not intersect with each other, even with a small number of spiral grooves, it is possible to suppress variations in the bond strength between the shaft and the bonded magnet. This makes it possible to reduce the number of grooves formed on the shaft while ensuring the bond strength between the shaft and the bonded magnet.

[0008] [2] In the molded product according to [1], the number of the spiral grooves may be 2 or more and 5 or less. In this molded product, since the number of the spiral grooves is 2 or more and 5 or less, high bonding strength can be obtained and a decrease in the strength of the shaft can be suppressed.

[0009] [3] In the molded product according to [1] or [2], the plurality of spiral grooves may be arranged at equal intervals. In this molded product, the plurality of spiral grooves are arranged at equal intervals, which makes it easy to form the plurality of spiral grooves. In addition, it is possible to further suppress variations in the bonding strength between the shaft and the bonded magnet.

[0010] [4] In the molded product according to any one of [1] to [3], the inclination angle of the multiple spiral grooves relative to a cross section perpendicular to the central axis of the shaft may be 60 degrees or more and less than 90 degrees. In this molded product, the inclination angle of the multiple spiral grooves relative to a cross section perpendicular to the central axis of the shaft is 60 degrees or more and less than 90 degrees. Therefore, when inserting the shaft into the bond magnet compound during the manufacturing of the molded product, the bond magnet compound will easily enter the multiple spiral grooves. This can increase the bond strength between the shaft and the bond magnet.

[0011] [5] In the molded product according to any one of [1] to [4], the surface of the shaft may have a non-bonded surface to which the bonded magnet is not bonded, and the non-bonded surface may have multiple spiral grooves. In this molded product, since the non-bonded surface of the shaft has multiple spiral grooves, multiple spiral grooves can be easily formed.

[0012] [6] In the molded product according to any one of [1] to [4], the surface of the shaft has a non-bonded surface to which the bonded magnet is not bonded, and the non-bonded surface may not have multiple spiral grooves. In this molded product, since the non-bonded surface of the shaft does not have multiple spiral grooves, it is possible to prevent other components from coming into contact with the multiple spiral grooves and being damaged. In addition, it is possible to prevent the appearance of the molded product from being deteriorated due to the multiple spiral grooves being exposed, and it is also possible to prevent contamination of the molded product due to dust getting into the multiple spiral grooves.

[0013] [7] In the molded product according to any one of [1] to [5], the plurality of spiral grooves may extend to both ends of the shaft. In this molded product, the plurality of spiral grooves extend to both ends of the shaft, making it easy to form the plurality of spiral grooves.

[0014] [8] In the molded product described in [7], the inclination angle of the multiple spiral grooves relative to the end face of the shaft may be 60 degrees or more and less than 90 degrees. In this molded product, the inclination angle of the multiple spiral grooves relative to the end face of the shaft is 60 degrees or more and less than 90 degrees. Therefore, when performing the step of inserting the shaft into the bond magnet compound during production of the molded product, the bond magnet compound can easily enter the multiple spiral grooves. This can increase the bond strength between the shaft and the bond magnet.

[0015] [9] In the molded product according to any one of [1] to [8], the number of turns of the plurality of spiral grooves relative to the central axis of the shaft may be 0.1 to 1.5. In this molded product, the number of turns of the plurality of spiral grooves relative to the central axis of the shaft is 0.1 to 1.5, which prevents the inclination angle of the plurality of spiral grooves relative to a plane perpendicular to the central axis of the shaft from becoming too small.

[0016]

[10] In the molded product according to any one of [1] to [9], the maximum depth of the plurality of spiral grooves may be 0.1 mm or more and 4.0 mm or less. In this molded product, since the maximum depth of the plurality of spiral grooves is 0.1 mm or more and 4.0 mm or less, the plurality of spiral grooves can be easily formed while ensuring the bonding strength between the shaft and the bonded magnet.

[0017]

[11] In the molded product according to any one of [1] to

[10] , the maximum width of the plurality of spiral grooves may be 0.5 mm or more and 16 mm or less. In this molded product, the plurality of spiral grooves can be easily formed while ensuring the bonding strength between the shaft and the bonded magnet.

[0018]

[12] In the molded product according to any one of [1] to

[11] , the groove shape of the plurality of spiral grooves in a cross section perpendicular to the central axis of the shaft may be a trapezoidal shape that widens outward from the shaft. In this molded product, the groove shape of the plurality of spiral grooves in a cross section perpendicular to the central axis of the shaft is a trapezoidal shape that widens outward from the shaft, making it possible to easily form the plurality of spiral grooves while ensuring the bonding strength between the shaft and the bonded magnet.

[0019]

[13] In the molded product according to any one of [1] to

[12] , the bonded magnet has a magnet powder and a resin portion, and the resin portion may include a cured thermosetting resin, and the thermosetting resin may include an epoxy resin and a phenolic resin. In this molded product, the resin portion of the bonded magnet includes a cured thermosetting resin, and the thermosetting resin includes an epoxy resin and a phenolic resin, so that the affinity between the resin portion and the shaft is increased, and the adhesion between the resin portion and the shaft is improved. This further increases the bond strength between the shaft and the bonded magnet.

[0020]

[14] A manufacturing method of a molded product according to the present disclosure is a manufacturing method of a molded product in which a bonded magnet is bonded to the surface of a shaft, and includes a groove forming step of forming a plurality of spiral grooves that extend spirally along the central axis of the shaft without intersecting each other on the joining surface of the shaft to which the bonded magnet is joined, and a joining step of joining the bonded magnet to the joining surface of the shaft on which the plurality of spiral grooves have been formed.

[0021] In this method of manufacturing a molded product, multiple spiral grooves are formed on the joint surface of the shaft, extending spirally along the central axis of the shaft without intersecting each other, and a bonded magnet is bonded to the joint surface of the shaft on which the multiple spiral grooves are formed, making it easy to manufacture the above-mentioned molded product.

[0022]

[15] In the manufacturing method of a molded product described in

[14] , the joining step may include a molding step in which a bond magnet compound is compression molded while in contact with the joining surfaces. In this manufacturing method of a molded product, by compression molding the bond magnet compound while in contact with the joining surfaces, the bond magnet can be easily joined to the joining surfaces.

[0023]

[16] In the manufacturing method of a molded product described in

[14] , the joining step may include a coating step of forming a resin film containing the same resin as that contained in the bond magnet on the joining surface, and a molding step of compression molding the bond magnet compound with the bond magnet compound in contact with the resin film. In this manufacturing method of a molded product, by forming a resin film containing the same resin as that contained in the bond magnet on the joining surface and compression molding the bond magnet compound with the bond magnet compound in contact with the resin film, the bond magnet can be joined to the joining surface with high joining strength.

[0024]

[17] In the method for manufacturing a molded product described in

[16] , the coating step may involve applying a resin solution containing the same resin as that contained in the bonded magnet to the joining surface, and then drying the resin solution. In this method for manufacturing a molded product, applying a resin solution containing the same resin as that contained in the bonded magnet to the joining surface allows the resin solution to penetrate into the multiple spiral grooves. Then, by drying the resin solution, a resin film can be easily formed on the joining surface with high joining strength.

[0025] The number of grooves formed in the shaft can be reduced.

[0026] FIG. 1 is a perspective view showing a molded product according to an embodiment. FIG. 2 is a cross-sectional view showing a molded product according to an embodiment. FIG. 3 is a front view showing a shaft of the molded product according to the embodiment. FIG. 4 is a plan view showing a shaft of the molded product according to the embodiment. FIG. 5 is a cross-sectional view taken along line V-V shown in FIG. 3. FIG. 6 is a cross-sectional view showing a shaft of a modified example. FIG. 7 is a cross-sectional view showing a shaft of a modified example. FIG. 8 is a cross-sectional view showing a shaft of a modified example. FIG. 9 is a front view showing a shaft of a modified example. FIG. 10 is a developed view showing the circumferential surface of the shaft. FIG. 11 is a perspective view showing the end of the shaft. FIG. 12 is a cross-sectional view showing an enlarged portion of the molded product according to the embodiment. FIG. 13 is a front view for explaining a method for manufacturing a molded product according to the embodiment. FIG. 14 is a cross-sectional view for explaining a method for manufacturing a molded product according to the embodiment. FIG. 15 is a cross-sectional view for explaining a method for manufacturing a molded product according to the modified example.

[0027] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. In the drawings, identical or corresponding parts are designated by the same reference numerals, and duplicate explanations will be omitted. Also, in the drawings, dimensional proportions and the like have been appropriately changed to make the explanation easier to understand.

[0028] Fig. 1 is a perspective view showing a molded product according to an embodiment. Fig. 2 is a cross-sectional view showing a molded product according to an embodiment. As shown in Figs. 1 and 2, the molded product 1 according to this embodiment includes a shaft 2 and a bonded magnet 3 bonded to the surface of the shaft 2. The molded product 1 is also called a shaft-integrated molded product, etc. Examples of such molded products 1 include a shaft-integrated rotor for a motor, a sensor component, etc.

[0029] FIG. 3 is a front view showing a shaft of a molded product according to an embodiment. FIG. 4 is a plan view showing a shaft of a molded product according to an embodiment. FIG. 5 is a cross-sectional view taken along line V-V in FIG. 3. As shown in FIGS. 1 to 5, the shaft 2 is a cylindrical metal member. Examples of metal materials for the shaft 2 include alloy steel, carbon steel, stainless steel, and bearing steel, and main product names include the SCR / SCM / SNC / SNCM / SACM series, SC series, SUS series, and SUJ series. The shaft 2 has a circumferential surface 21, an end face 22 on one side of the shaft 2, and an end face 23 opposite the end face 22 of the shaft 2. The circumferential surface 21, the end face 22, and the end face 23 form the surface of the shaft 2. The end face 22 is an end face on one side of the shaft 2 in the axial direction AD and is perpendicular to the central axis A of the shaft 2. The end face 23 is the other end face in the axial direction AD of the shaft 2 and is an end face perpendicular to the central axis A. The axial direction AD of the shaft 2 is a direction along the central axis A.

[0030] Additionally, circumferential surface 21 of shaft 2 has bonding surface 2a to which bonded magnet 3 is bonded, and non-bonding surfaces 2b to which bonded magnet 3 is not bonded. Bonding surface 2a is located, for example, in the center in axial direction AD of shaft 2. Non-bonding surfaces 2b are located, for example, on both sides of non-bonding surface 2b in axial direction AD of shaft 2.

[0031] The joint surface 2a has a plurality of spiral grooves 4. The plurality of spiral grooves 4 are grooves that extend spirally along the central axis A without intersecting each other. Extending spirally along the central axis A means extending along the central axis A so as to circle the central axis A. The plurality of spiral grooves 4 are also spaced apart from each other and are not connected to each other. Each of the plurality of spiral grooves 4 (hereinafter simply referred to as a "spiral groove 4") forms a groove recessed from the circumferential surface 21 and, together with the circumferential surface 21, forms the joint surface 2a of the shaft 2.

[0032] The multiple spiral grooves 4 may extend over the entire area of ​​the joining surface 2a in the axial direction AD, or may extend over only a portion of the area of ​​the joining surface 2a in the axial direction AD. In this embodiment, as an example, the multiple spiral grooves 4 extend over the entire area of ​​the joining surface 2a in the axial direction AD.

[0033] The non-bonding surface 2b may or may not have multiple spiral grooves 4, but in this embodiment, as an example, it has multiple spiral grooves 4. The multiple spiral grooves 4 may extend over the entire region of the non-bonding surface 2b in the axial direction AD, or may extend over only a portion of the region of the non-bonding surface 2b in the axial direction AD, but in this embodiment, as an example, it extends over the entire region of the non-bonding surface 2b in the axial direction AD. Therefore, the multiple spiral grooves 4 extend to both ends of the shaft 2. In other words, the multiple spiral grooves 4 extend from the tip on the end face 22 side to the tip on the end face 23 side.

[0034] The multiple spiral grooves 4 may or may not be arranged at equal intervals in the circumferential direction CD of the shaft 2, but in the present embodiment, as an example, they are arranged at equal intervals in the circumferential direction CD of the shaft 2. The circumferential direction CD of the shaft 2 is the direction around the central axis A.

[0035] The number of the plurality of spiral grooves 4 is, for example, 2 to 5, preferably 3 to 5, more preferably 4 to 5, and in the present embodiment, as an example, it is 4. Fig. 6 shows a modified shaft 2A in which the number of the plurality of spiral grooves 4 is 2, Fig. 7 shows a modified shaft 2B in which the number of the plurality of spiral grooves 4 is 3, and Fig. 8 shows a modified shaft 2C in which the number of the plurality of spiral grooves 4 is 5. Figs. 6 to 8 are cross-sectional views corresponding to Fig. 5.

[0036] The number of turns of the spiral groove 4 around the central axis A is, for example, 0.1 to 1.5, preferably 0.2 to 1.2, more preferably 0.5 to 1.1, and in the present embodiment, for example, is 1. In a shaft 2D of a modified example shown in Fig. 9, the number of turns of the spiral groove 4 around the central axis A is 0.5. The number of turns of the spiral groove 4 being 1 means that the spiral groove 4 makes one turn around the central axis A, and the number of turns of the spiral groove 4 being 0.5 means that the spiral groove 4 makes 0.5 turns around the central axis A.

[0037] Fig. 10 is a development view of the circumferential surface of the shaft. Note that Fig. 10 shows only one of the multiple spiral grooves 4 for convenience. In Fig. 10, the tip position of the spiral groove 4 on the end face 23 side is set as the development start position of the circumferential surface 21. As shown in Fig. 10, in the shaft 2 (see Fig. 3) in which the spiral groove 4 has one turn around the central axis A, the spiral groove 4 extends over the entire area in the circumferential direction CD. On the other hand, in the shaft 2D (see Fig. 9) in which the spiral groove 4 has 0.5 turns around the central axis A, the spiral groove 4 extends over half the area in the circumferential direction CD.

[0038] Fig. 11 is a perspective view showing the end of the shaft. For convenience, Fig. 11 shows only one of the multiple spiral grooves 4. As shown in Figs. 11 and 10, the inclination angle θ1 of the spiral groove 4 with respect to a cross section C perpendicular to the central axis A is, for example, 60 degrees or more and less than 90 degrees, preferably 70 degrees or more and 85 degrees or less, and more preferably 75 degrees or more and 80 degrees or less. The inclination angle θ1 is the inclination angle of the spiral groove 4 with respect to the side 21a of the circumferential surface 21 on the end face 23 side in the developed view shown in Fig. 10.

[0039] 11 and 10, the inclination angle θ2 of the spiral groove 4 with respect to the end face 23 of the shaft 2 is equal to or greater than 60 degrees and less than 90 degrees, preferably equal to or greater than 70 degrees and less than 85 degrees, and more preferably equal to or greater than 75 degrees and less than 80 degrees. The inclination angle θ2 is the inclination angle of the spiral groove 4 with respect to the imaginary line 21b on the circumferential surface 21 where the cross section C is located in the developed view shown in FIG.

[0040] 5, the maximum depth D of the spiral groove 4 is, for example, 0.1 mm to 4.0 mm, preferably 0.2 mm to 3.0 mm, and more preferably 0.3 mm to 2.0 mm. The maximum depth D of the spiral groove 4 is the maximum depth of the spiral groove 4 with respect to an imaginary circumferential surface obtained by extending the circumferential surface 21 onto the spiral groove 4.

[0041] The maximum width W of the spiral groove 4 is 0.5 mm to 16 mm, preferably 0.8 mm to 10 mm, and more preferably 1 mm to 5 mm. The maximum width W of the spiral groove 4 is the maximum linear distance between both ends of the spiral groove 4 connected to the peripheral surface 21 in a cross section perpendicular to the central axis A.

[0042] The groove shape of the spiral groove 4 in a cross section perpendicular to the central axis A can be, for example, trapezoidal, rectangular, or semicircular, and in the present embodiment, as an example, is a trapezoidal shape that widens toward the outside of the shaft 2. The outside of the shaft 2 refers to the outside in the radial direction of the shaft 2 (the direction perpendicular to the central axis A).

[0043] Figure 12 is an enlarged cross-sectional view of a portion of a molded product according to an embodiment. As shown in Figures 1 to 5 and 12, bond magnet 3 is bonded to joining surface 2a of shaft 2. In other words, bond magnet 3 is bonded to circumferential surface 21 that forms joining surface 2a of shaft 2 and to helical groove 4. Note that "bond magnet 3 is bonded to helical groove 4" means that bond magnet 3 enters helical groove 4 and is bonded to the surface of helical groove 4. Bond magnet 3 has magnetic powder 3a and a resin portion 3b. Magnetic powder 3a is dispersed in resin portion 3b.

[0044] The magnet powder 3a may be any magnetic powder, and rare earth magnetic powder is preferable.

[0045] Examples of rare earth magnetic powders include samarium-cobalt magnetic powder (SmCo), neodymium-iron-boron magnetic powder (NdFeB), and samarium-iron-nitride compound magnetic powder (SmFeN). Rare earth magnetic powders are manufactured, for example, by a rapid solidification method. In the rapid solidification method, a molten magnet alloy is released onto the surface of a rotating water-cooled roll, whereby the molten magnet alloy is rapidly cooled and solidified to produce a quenched alloy. The quenched alloy is then pulverized to produce the rare earth magnetic powder. Rare earth magnetic powder manufactured by the HDDR (Hydrogenation Disproportion Desorption Recombination) method may also be used.

[0046] The rare earth magnetic powder is preferably a powder containing an Nd--Fe--B permanent magnet (NdFeB powder).

[0047] The rare earth magnetic powder may also be a powder containing an Sm--Fe--N permanent magnet (SmFeN powder).

[0048] The magnet powder 3a is, for example, a powder containing an Sm—Fe—N permanent magnet (SmFeN powder). The average particle size of the SmFeN powder may be preferably 0.5 μm or more and 100 μm or less, more preferably 1 μm or more and 10 μm or less, and even more preferably 2 μm or more and 3 μm or less. The average particle size of the SmFeN powder can be measured using a laser diffraction particle size distribution analyzer. For example, the SmFeN powder may be a non-pulverized powder (spherical magnet powder) obtained by the build-up method of Nichia Corporation. The surface of each magnet particle constituting the SmFeN powder may be coated with an inorganic film by surface treatment. For example, the inorganic film may contain a phosphate or a silica-based compound.

[0049] The resin portion 3b includes a cured product of a thermosetting resin. The thermosetting resin includes an epoxy resin and a phenol resin. Preferably, the thermosetting resin includes a naphthalene-type epoxy resin and a phenol resin.

[0050] The naphthalene-type epoxy resin is preferably a tetrafunctional naphthalene-based epoxy resin, and also preferably a trifunctional naphthalene-based epoxy resin or a β-naphthol-type epoxy resin. Commercially available naphthalene-type epoxy resins include, for example, HP-4700 manufactured by DIC Corporation. ＴＭ , EXA-5740 ＴＭ , or EXA-7311-G4 ＴＭ These may be used alone or in combination of two or more.

[0051] Examples of phenolic resins include compounds having two phenolic hydroxyl groups per molecule, such as aralkyl phenolic resins, dicyclopentadiene phenolic resins, salicylaldehyde phenolic resins, novolac phenolic resins, copolymerized phenolic resins of benzaldehyde phenols and aralkyl phenols, paraxylylene and / or metaxylylene-modified phenolic resins, melamine-modified phenolic resins, terpene-modified phenolic resins, dicyclopentadiene naphthol resins, cyclopentadiene-modified phenolic resins, polycyclic aromatic ring-modified phenolic resins, biphenyl phenolic resins, triphenylmethane phenolic resins, and phenolic resins obtained by copolymerizing two or more of these. These may be used alone or in combination. Examples include resorcinol, catechol, bisphenol A, bisphenol F, and substituted or unsubstituted biphenols. Commercially available phenolic resins include, for example, Tamanol 758 and 73.0 manufactured by Arakawa Chemical Industries, Ltd., and HP-850N manufactured by Resonac Corporation. ＴＭ These may be used alone or in combination of two or more.

[0052] Next, a method for manufacturing a molded article according to the embodiment will be described. The method for manufacturing a molded article according to the embodiment is a method for manufacturing the molded article 1 described above. Fig. 13 is a front view for explaining the method for manufacturing a molded article according to the embodiment. Fig. 14 is a cross-sectional view for explaining the method for manufacturing a molded article according to the embodiment.

[0053] First, a cylindrical shaft 102 is prepared as shown in Fig. 13. The shaft 102 is similar to the shaft 2 except that the plurality of spiral grooves 4 is not formed.

[0054] 13 and 3, a groove forming step is performed in which a plurality of helical grooves 4 extending helically along the central axis A of the shaft 102 without intersecting each other are formed on the circumferential surface 21 of the shaft 102, including the joining surface 2a. The plurality of helical grooves 4 are formed, for example, by pressing a mold corresponding to the plurality of helical grooves 4 against the circumferential surface 21 of the shaft 102. This results in a shaft 2 having a plurality of helical grooves 4 formed on the circumferential surface 21.

[0055] Next, a joining process is carried out in which a bond magnet 3 is joined to the joining surface 2a of the shaft 2 on which multiple spiral grooves 4 were formed in the groove forming process. As shown in Figure 14, in the joining process, a molding process is carried out in which bond magnet compound 103 is compression molded while in contact with joining surface 2a. Bond magnet compound 103 is a compound that becomes bond magnet 3 when compacted. Bond magnet compound 103 includes, for example, the above-mentioned magnet powder 3a and a resin composition.

[0056] The resin composition contains at least the thermosetting resin described above. The resin composition may further contain at least one component selected from the group consisting of a curing agent, a curing accelerator, a coupling agent, a flame retardant, and a flow aid. The bonded magnet compound 103 itself may contain an organic solvent.

[0057] The bonded magnet compound 103 may contain wax. The wax may be at least one composition selected from the group consisting of synthetic wax, saturated fatty acid, saturated fatty acid salt, and saturated fatty acid ester. For example, the wax may be at least one wax selected from the group consisting of polyethylene wax, amide wax, and montan wax.

[0058] In the molding process, for example, a manufacturing device 5 is used that includes cylindrical upper punch 51 and lower punch 52 facing each other, and a die 53 formed with holes 53a into which the upper punch 51 and the lower punch 52 can be inserted. In this manufacturing device 5, the inner diameters of the upper punch 51 and the lower punch 52 and the outer diameter of the shaft 2 are approximately the same, and the outer diameters of the upper punch 51 and the lower punch 52 and the inner diameter of the hole 53a of the die 53 are approximately the same.

[0059] In the forming process using the manufacturing apparatus 5, first, the non-bonding surface 2b of the shaft 2 is inserted into the upper punch 51 or the lower punch 52. Next, the space surrounded by the die 53 and the lower punch 52, or the space surrounded by the die 53, the lower punch 52, and the shaft 2, is filled with the bond magnet compound 103. Next, the upper punch 51 is forced into the hole 53a to press the bond magnet compound 103. The bond magnet compound 103 is then compression molded while in contact with the bonding surface 2a, and the bond magnet 3 is bonded to the bonding surface 2a. This results in the molded product 1 in which the bond magnet 3 is bonded to the bonding surface 2a of the shaft 2. The molded product 1 is then removed from the die 53, and the molded product 1 is obtained.

[0060] As explained above, in the molded product 1 according to this embodiment, the multiple spiral grooves 4 extend spirally along the central axis A, so the length of each groove can be increased, thereby increasing the specific surface area of ​​each groove. Moreover, because the multiple spiral grooves 4 do not intersect with each other, even if the number of spiral grooves 4 is small, it is possible to suppress variations in the bonding strength between the shaft 2 and the bonded magnet 3. This makes it possible to reduce the number of grooves formed in the shaft 2 while ensuring the bonding strength between the shaft 2 and the bonded magnet 3.

[0061] Furthermore, in this molded product 1, the number of multiple spiral grooves 4 is 2 or more and 5 or less, preferably 3 or more and 5 or less, and more preferably 4 or more and 5 or less, so that high bonding strength can be obtained and a decrease in the strength of the shaft 2 can be suppressed.

[0062] Furthermore, in this molded product 1, multiple spiral grooves 4 are arranged at equal intervals, making it easy to form multiple spiral grooves 4. In addition, it is possible to further suppress variations in the bonding strength between shaft 2 and bonded magnet 3 depending on the position.

[0063] Furthermore, in this molded product, the inclination angle θ1 of the multiple spiral grooves 4 with respect to the cross section C perpendicular to the central axis A is 60 degrees or more and less than 90 degrees, preferably 70 degrees or more and 85 degrees or less, and more preferably 75 degrees or more and 80 degrees or less. Therefore, when performing the step of inserting the shaft 2 into the bond magnet compound 103 during the production of the molded product 1, the bond magnet compound 103 easily enters the multiple spiral grooves 4. This makes it possible to increase the bonding strength between the shaft 2 and the bond magnet 3.

[0064] Furthermore, in this molded product 1, the non-joint surface 2b of the shaft 2 has a plurality of spiral grooves 4, so that the plurality of spiral grooves 4 can be easily formed.

[0065] Furthermore, in this molded product 1, the multiple spiral grooves 4 extend to both ends of the shaft 2, so that the multiple spiral grooves 4 can be easily formed.

[0066] Furthermore, in this molded article 1, the inclination angle θ2 of the multiple spiral grooves 4 relative to the end face 23 of the shaft 2 is equal to or greater than 60 degrees and less than 90 degrees, preferably equal to or greater than 70 degrees and less than 85 degrees, and more preferably equal to or greater than 75 degrees and less than 85 degrees. Therefore, when performing the step of inserting the shaft 2 into the bond magnet compound 103 during the manufacture of the molded article 1, the bond magnet compound 103 can easily enter the multiple spiral grooves 4. This makes it possible to increase the bonding strength between the shaft 2 and the bond magnet 3.

[0067] If the non-joint surface of the shaft does not have multiple spiral grooves, it is possible to prevent other members from coming into contact with the multiple spiral grooves and being damaged, and it is also possible to prevent the appearance of the molded product from being deteriorated due to the multiple spiral grooves being exposed, and to prevent the molded product from being contaminated by dust entering the multiple spiral grooves.

[0068] Furthermore, in this molded product 1, the number of turns of the multiple spiral grooves 4 relative to the central axis A is 0.1 or more and 1.5 or less, preferably 0.2 or more and 1.2 or less, and more preferably 0.5 or more and 1.1 or less, so that the inclination angle θ1 of the multiple spiral grooves 4 relative to a plane perpendicular to the central axis A can be prevented from becoming too small.

[0069] Furthermore, in this molded product 1, the maximum depth D of the multiple spiral grooves 4 is 0.1 mm or more and 4.0 mm or less, preferably 0.2 mm or more and 3.0 mm or less, and more preferably 0.3 mm or more and 2.0 mm or less, so that the multiple spiral grooves 4 can be easily formed while ensuring the bonding strength between the shaft 2 and the bonded magnet 3.

[0070] Furthermore, in this molded product, the maximum width W of the multiple spiral grooves 4 is 0.5 mm or more and 16 mm or less, preferably 0.8 mm or more and 10 mm or less, and more preferably 1 mm or more and 5 mm or less, so that the multiple spiral grooves 4 can be easily formed while ensuring the bonding strength between the shaft 2 and the bonded magnet 3.

[0071] Furthermore, in this molded product 1, the groove shape of the multiple spiral grooves 4 in the cross section perpendicular to the central axis A is a trapezoid that widens toward the outside of the shaft 2, so that the multiple spiral grooves 4 can be easily formed while ensuring the bonding strength between the shaft 2 and the bonded magnet 3.

[0072] Furthermore, in this molded product 1, the resin portion 3b of the bonded magnet 3 contains a cured thermosetting resin, and the thermosetting resin contains an epoxy resin (preferably a naphthalene-type epoxy resin) and a phenolic resin, which increases the affinity between the resin portion and the shaft, thereby increasing the adhesion between the resin portion 3b and the shaft. This further increases the bond strength between the shaft 2 and the bonded magnet 3.

[0073] In the manufacturing method of the molded product according to this embodiment, a plurality of spiral grooves 4 that extend spirally along the central axis A without intersecting each other are formed on the joining surface 2a of the shaft 2, and a bonded magnet 3 is joined to the joining surface 2a of the shaft 2 on which the plurality of spiral grooves 4 are formed, so that the above-mentioned molded product 1 can be easily manufactured.

[0074] Furthermore, in this manufacturing method for a molded product, the bond magnet compound 103 is compression molded while in contact with the joining surface 2a, thereby easily joining the bond magnet 3 to the joining surface 2a.

[0075] The present disclosure is not limited to the above-described embodiments, and modifications can be made as appropriate without departing from the spirit of the present disclosure.

[0076] For example, in the method for producing a molded article, a molded article may be obtained by carrying out the coating step and molding step described below.

[0077] Figure 15 is a cross-sectional view illustrating a manufacturing method for a molded product of a modified example. As shown in Figure 15, first, a coating step is performed to form a resin film 103b containing the same resin as that contained in bond magnet 3 on joining surface 2a. The resin contained in bond magnet 3 is the resin contained in resin portion 3b, and is, for example, a thermosetting resin containing the above-mentioned naphthalene-type epoxy resin and phenol resin. In the coating step, for example, a resin solution containing the same resin as that contained in bond magnet 3 is applied to joining surface 2a, and the resin solution is dried to form resin film 103b on joining surface 2a.

[0078] Next, a molding process is performed in which bond magnet compound 103 is compression molded while in contact with resin film 103b. This molding process is basically the same as the molding process of the above embodiment, except that shaft 2 having resin film 103b formed on joining surface 2a is used. This results in a molded product 1 similar to that of the above embodiment.

[0079] As explained above, in the manufacturing method of the molded product according to this embodiment, a resin film 103b containing the same resin as that contained in the bond magnet 3 is formed on the joining surface 2a, and the bond magnet compound 103 is compression molded while being in contact with the resin film 103b, thereby making it possible to join the bond magnet 3 to the joining surface 2a with high joining strength.

[0080] Furthermore, in this manufacturing method for a molded product, by applying a resin solution containing the same resin as that contained in bond magnet 3 to joining surface 2a, the resin solution can be made to penetrate into multiple spiral grooves 4. Then, by drying this resin solution, resin film 103b can be easily formed on joining surface 2a with high joining strength.

[0081] The present disclosure can be used as a molded article in which a bonded magnet is bonded to a shaft, and a method for manufacturing the molded article.

[0082] 1...molded product, 2...shaft, 2A...shaft, 2B...shaft, 2C...shaft, 2D...shaft, 2a...bonding surface, 2b...non-bonding surface, 3...bonded magnet, 3a...magnetic powder, 3b...resin portion, 4...spiral groove, 5...manufacturing apparatus, 21...circumferential surface, 21a...edge, 21b...imaginary line, 22...end face, 23...end face, 51...upper punch, 52...lower punch, 53...die, 53a...hole, 102...shaft, 103...bonded magnet compound, A...central axis, AD...axial direction, C...cross section, CD...circumferential direction, D...maximum depth, W...maximum width, θ1...tilt angle, θ2...tilt angle.

Claims

1. A molded product in which a bonded magnet is bonded to the surface of a shaft, wherein the surface of the shaft to which the bonded magnet is bonded has a plurality of spiral grooves that extend spirally along the central axis of the shaft without intersecting each other.

2. The molded product according to claim 1, wherein the number of said spiral grooves is 2 or more and 5 or less.

3. The molded product according to claim 1 or 2, wherein the plurality of spiral grooves are arranged at equal intervals.

4. A molded product according to any one of claims 1 to 3, wherein the inclination angle of the plurality of spiral grooves with respect to a cross section perpendicular to the central axis of the shaft is equal to or greater than 60 degrees and less than 90 degrees.

5. A molded product according to any one of claims 1 to 4, wherein the surface of the shaft has a non-bonded surface to which the bonded magnet is not bonded, and the non-bonded surface has the plurality of spiral grooves.

6. A molded product according to any one of claims 1 to 4, wherein the surface of the shaft has a non-bonded surface to which the bonded magnet is not bonded, and the non-bonded surface does not have the plurality of spiral grooves.

7. A molded product according to any one of claims 1 to 5, wherein the plurality of spiral grooves extend to both ends of the shaft.

8. The molded product according to claim 7, wherein the inclination angle of the plurality of spiral grooves relative to the end face of the shaft is equal to or greater than 60 degrees and less than 90 degrees.

9. A molded product according to any one of claims 1 to 8, wherein the number of turns of the plurality of spiral grooves around the central axis of the shaft is 0.1 to 1.

5.

10. A molded product according to any one of claims 1 to 9, wherein the maximum depth of the plurality of spiral grooves is 0.1 mm or more and 4.0 mm or less.

11. A molded product according to any one of claims 1 to 10, wherein the maximum width of the plurality of spiral grooves is 0.5 mm or more and 16 mm or less.

12. A molded product according to any one of claims 1 to 11, wherein the groove shape of the plurality of spiral grooves in a cross section perpendicular to the central axis of the shaft is a trapezoidal shape that widens outward from the shaft.

13. A molded product according to any one of claims 1 to 12, wherein the bonded magnet has a magnetic powder and a resin portion, the resin portion includes a cured product of a thermosetting resin, and the thermosetting resin includes an epoxy resin and a phenolic resin.

14. A method for manufacturing a molded product in which a bonded magnet is bonded to the surface of a shaft, comprising: a groove forming step of forming a plurality of spiral grooves that extend spirally along the central axis of the shaft without intersecting each other on the joining surface of the shaft to which the bonded magnet is joined; and a joining step of joining the bonded magnet to the joining surface of the shaft on which the plurality of spiral grooves have been formed.

15. A method for manufacturing a molded product as set forth in claim 14, wherein the joining step includes a molding step of compression molding a bond magnet compound in a state where the bond magnet compound is in contact with the joining surface.

16. A method for manufacturing a molded product as described in claim 14, wherein the joining process comprises: a coating process for forming a resin film containing the same resin as that contained in the bonded magnet on the joining surface; and a molding process for compression molding the bonded magnet compound while the bonded magnet compound is in contact with the resin film.

17. The method for manufacturing a molded product according to claim 16, wherein in the coating step, a resin solution containing the same resin as that contained in the bonded magnet is applied to the joining surface, and the resin solution is dried.

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