Molded article and method for producing molded article

Abstract

In this molded article in which a bonded magnet is bonded to a surface of a shaft, a bonding surface to which the bonded magnet of the shaft is bonded has a roughened region that has been roughened. This method for producing a molded article in which a bonded magnet is bonded to a surface of a shaft includes: a roughening step of roughening a bonding surface to which the bonded magnet of the shaft is bonded; and a bonding step of bonding the bonded magnet to the bonding surface having been roughened in the roughening step.

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] In the molded product described in Patent Document 1, knurling is formed on the circumferential surface of the shaft, but because the surface is smooth, the bonding strength between the shaft and the bonded magnet is not necessarily sufficient.

[0005] Therefore, an object of the present disclosure is to provide a molded product and a method for manufacturing the molded product that can increase the bonding strength between a shaft and a bonded magnet.

[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 surface of the shaft to which the bonded magnet is bonded has a roughened region.

[0007] In this molded product, the joining surface of the shaft has a roughened area, so the bonded magnet fits into the minute irregularities of the roughened area. This increases the contact area between the shaft and the bonded magnet, and also increases the anchor effect between the minute irregularities of the roughened area and the bonded magnet, thereby increasing the bond strength between the shaft and the bonded magnet.

[0008] [2] In the molded article according to [1], the arithmetic mean roughness of the roughened region may be 2 μm or more. In this molded article, the arithmetic mean roughness of the roughened region is 2 μm or more, which further increases the contact area between the shaft and the bonded magnet, and further increases the anchoring force (anchor effect) between the fine irregularities in the roughened region and the bonded magnet.

[0009] [3] In the molded article according to [1] or [2], the roughened region may have an arithmetic mean roughness of 300 μm or less. In this molded article, the arithmetic mean roughness of the roughened region is 300 μm or less, which further increases the contact area between the shaft and the bonded magnet and makes it easier to form the roughened region.

[0010] [4] In the molded product according to any one of [1] to [3], 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 a roughened area. In this molded product, since the non-bonded surface of the shaft does not have a roughened area, it is possible to prevent other components from coming into contact with the roughened area and being damaged. In addition, it is possible to prevent deterioration of the appearance of the molded product due to the exposed roughened area, and to prevent contamination of the molded product due to dust entering the roughened area.

[0011] [5] In the molded product according to any one of [1] to [4], the joining surface has a plurality of grooves, and the grooves may have roughened areas. In this molded product, the joining surface has a plurality of grooves, and the bonded magnet fits into these grooves, increasing the bond strength between the shaft and the bonded magnet. Moreover, because these grooves have roughened areas, the bond strength between the shaft and the bonded magnet is further increased in these grooves.

[0012] [6] In the molded product described in [5], the multiple grooves may extend spirally along the central axis of the shaft. In this molded product, the multiple grooves extend spirally along the central axis of the shaft, allowing each groove to be longer. In other words, a single groove can increase the contact area between the shaft and the bonded magnet. This allows for high bonding strength to be obtained even with a small number of grooves. Furthermore, by reducing the number of grooves, it is possible to suppress the decrease in shaft strength that occurs with an increase in the number of grooves.

[0013] [7] In the molded product according to [6], the number of the plurality of grooves may be 2 or more and 5 or less. In this molded product, the number of the plurality of spirally extending grooves is 2 or more and 5 or less, so that high bonding strength can be obtained and a decrease in the strength of the shaft can be suppressed.

[0014] [8] In the molded product according to any one of [5] to [7], the grooves may intersect with each other. In this molded product, the grooves intersect with each other, which makes it possible to prevent the bonded magnet from slipping relative to the shaft in any direction.

[0015] [9] In the molded article according to any one of [5] to [7], the plurality of grooves may not intersect with each other. In this molded article, the plurality of grooves do not intersect with each other, making it easy to form the plurality of grooves.

[0016]

[10] In the molded product described in [9], the grooves may be arranged at equal intervals. In this molded product, the grooves are arranged at equal intervals, making it easy to form the grooves. In addition, it is possible to suppress variations in the bonding strength between the shaft and the bonded magnet depending on the position.

[0017]

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

[10] , the bonding surface has a plurality of recesses that are independent of each other, and the plurality of recesses may have roughened areas. In this molded product, because the bonding surface has a plurality of recesses that are independent of each other, the bond magnet enters these recesses, increasing the bonding strength between the shaft and the bond magnet. Moreover, because these recesses have roughened areas, the bonding strength between the shaft and the bond magnet is further increased in these recesses.

[0018]

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

[11] , the bonded magnet has a magnet powder and a resin portion, and the resin portion contains a cured product of a thermosetting resin, and the thermosetting resin contains an epoxy resin and a phenolic resin. In this molded product, the resin portion of the bonded magnet contains an 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 and the shaft. This further increases the bond strength between the shaft and the bonded magnet.

[0019]

[13] A method for manufacturing a molded product according to the present disclosure is a method for manufacturing a molded product in which a bonded magnet is bonded to the surface of a shaft, and includes a roughening step of roughening the joining surface of the shaft to which the bonded magnet is bonded, and a joining step of joining the bonded magnet to the joining surface roughened in the roughening step. In this manufacturing method for a molded product, the above-mentioned molded product can be easily manufactured by roughening the joining surface of the shaft and joining the bonded magnet to the roughened joining surface.

[0020]

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

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

[0021]

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

[13] , 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.

[0022]

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

[15] , 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 fine irregularities in the roughened area. Then, by drying the resin solution, a resin film can be easily formed on the joining surface with high joining strength.

[0023]

[17] The method for manufacturing a molded product according to any one of

[13] to

[16] may further include a shaft processing step of forming a plurality of grooves or a plurality of independent depressions on the joining surface of the shaft to which the bonded magnet is joined before the surface roughening step. In this method for manufacturing a molded product, since a plurality of grooves or a plurality of independent depressions are formed on the joining surface of the shaft to which the bonded magnet is joined before the surface roughening step, the plurality of grooves or a plurality of independent depressions can also be roughened regions.

[0024]

[18] The method for manufacturing a molded product according to any one of

[13] to

[16] may further include a shaft processing step of forming a plurality of grooves or a plurality of independent depressions on the joining surface of the shaft to which the bonded magnet is joined after the surface roughening step. In this method for manufacturing a molded product, since a plurality of grooves or a plurality of independent depressions are formed on the joining surface of the shaft to which the bonded magnet is joined after the surface roughening step, the roughening step can be carried out efficiently.

[0025] The bond strength between the shaft and the bonded magnet can be increased.

[0026] FIG. 1 is a perspective view showing a molded product according to a first embodiment. FIG. 2 is a cross-sectional view showing a molded product according to the first embodiment. FIG. 3 is a front view showing a shaft of the molded product according to the first embodiment. FIG. 4 is a cross-sectional view showing an enlarged portion of the shaft of the molded product according to the first embodiment. FIG. 5 is a cross-sectional view showing an enlarged portion of the molded product according to the first embodiment. FIG. 6 is a front view for explaining a method for manufacturing a molded product according to the first embodiment. FIG. 7 is a cross-sectional view for explaining a method for manufacturing a molded product according to the first embodiment. FIG. 8 is a cross-sectional view for explaining a method for manufacturing a molded product according to the second embodiment. FIG. 9 is a front view showing a shaft of a molded product according to a third embodiment. FIG. 10 is a cross-sectional view showing an enlarged portion of the shaft of the molded product according to the third embodiment. FIG. 11 is a cross-sectional view showing an enlarged portion of the shaft of the molded product according to the third embodiment. FIG. 12 is a cross-sectional view for explaining a method for manufacturing a molded product according to the third embodiment. FIG. 13 is a cross-sectional view for explaining a method for manufacturing a molded product according to the fourth embodiment. FIG. 14 is a front view showing a shaft of a molded product according to a fifth embodiment. FIG. 15 is a cross-sectional view showing an enlarged portion of the shaft of the molded product according to the fifth embodiment. FIG. 16 is a front view showing a shaft of a molded product according to a sixth embodiment. FIG. 17 is a cross-sectional view showing an enlarged portion of the shaft of the molded product according to the sixth embodiment. Fig. 18 is an enlarged cross-sectional view of a part of the shaft of the molded product according to the sixth embodiment. Fig. 19 is a cross-sectional view for explaining the method for manufacturing the molded product according to the sixth embodiment.

[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] [First embodiment] Fig. 1 is a perspective view showing a molded product according to a first embodiment. Fig. 2 is a cross-sectional view showing a molded product according to the first embodiment. As shown in Figs. 1 and 2, a 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 the first embodiment. As shown in FIGS. 1 to 3, the shaft 2 is a cylindrical metal member. Metallic materials for the shaft 2 include, for example, alloy steel, carbon steel, stainless steel, and bearing steel. Major product names include the SCR / SCM / SNC / SNCM / SACM series, SC series, SUS series, and SUJ series. The shaft 2 has a bonded surface 2a to which the bonded magnet 3 is bonded and a non-bonded surface 2b to which the bonded magnet 3 is not bonded. The bonded surface 2a and the non-bonded surface 2b are surfaces of the shaft 2 that form the circumferential surface of the shaft 2. The bonded surface 2a is located, for example, in the center in the axial direction AD of the shaft 2. The axial direction AD of the shaft 2 is a direction along the central axis A of the shaft 2. The non-bonded surfaces 2b are located, for example, on both sides of the non-bonded surface 2b in the axial direction AD of the shaft 2.

[0030] Fig. 4 is an enlarged cross-sectional view of a portion of the shaft of the molded product according to the first embodiment. Fig. 5 is an enlarged cross-sectional view of a portion of the molded product according to the first embodiment. As shown in Figs. 1 to 5, the joining surface 2a has a roughened region 4. The roughened region 4 may be located over the entire joining surface 2a or only over a portion of the joining surface 2a. In this embodiment, as an example, the roughened region 4 is located over the entire joining surface 2a. The non-joining surface 2b does not have a roughened region 4.

[0031] Roughened region 4 has minute irregularities formed by roughening. Bond magnet 3 is embedded in the minute irregularities formed in roughened region 4.

[0032] The arithmetic mean roughness Ra of the roughened region 4 is, for example, 2 μm or more, preferably 50 μm or more, and more preferably 75 μm or more. The arithmetic mean roughness Ra of the roughened region 4 is, for example, 300 μm or less, preferably 200 μm or less, and more preferably 100 μm or less. The arithmetic mean roughness Ra of the roughened region 4 can be measured, for example, using a stylus surface roughness measuring instrument (Kosaka Laboratory Co., Ltd., Surface Roughness and Contour Measuring Instrument SEF-680). The surface roughness can also be measured using a non-contact confocal laser microscope. For example, a non-contact confocal laser microscope (Olympus Corporation, OLS-5100) or a contact Surftest (Mitutoyo Corporation) can be used. Measurements are performed on any portion of the shaft at a measurement length of 1 to 5 mm in the longitudinal direction.

[0033] Bond magnet 3 is bonded to bonding surface 2a of shaft 2. In other words, bond magnet 3 is bonded to roughened region 4 of shaft 2. Bond magnet 3 has magnetic powder 3a and a resin portion 3b. Magnetic powder 3a is dispersed in resin portion 3b.

[0034] The magnet powder 3a may be any magnetic powder, and rare earth magnetic powder is preferable.

[0035] 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.

[0036] The rare earth magnetic powder is preferably a powder containing an Nd--Fe--B permanent magnet (NdFeB powder).

[0037] The rare earth magnetic powder may also be a powder containing an Sm--Fe--N permanent magnet (SmFeN powder).

[0038] 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.

[0039] The resin portion 3b includes a cured product of a thermosetting resin. The thermosetting resin includes an epoxy resin and a phenol resin. The thermosetting resin preferably includes a naphthalene-type epoxy resin and a phenol resin.

[0040] 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.

[0041] 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 Showa Denko Materials Co., Ltd. ＴＭ These may be used alone or in combination of two or more.

[0042] Next, a method for manufacturing a molded article according to the first embodiment will be described. The method for manufacturing a molded article according to the first embodiment is a method for manufacturing the molded article 1 described above. Fig. 6 is a front view for explaining the method for manufacturing a molded article according to the first embodiment. Fig. 7 is a cross-sectional view for explaining the method for manufacturing a molded article according to the first embodiment.

[0043] First, a cylindrical shaft 102 is prepared as shown in Fig. 6. The shaft 102 is similar to the shaft 2 except that the roughened region 4 is not formed.

[0044] Next, as shown in FIGS. 6 and 3 , a roughening process is performed to roughen the joining surface 2 a of the shaft 102. The roughening process can be performed by, for example, sandblasting, shot blasting, shot peening, barrel processing, lathe processing, or sandpaper processing. Sandblasting is a process of roughening the surface of the shaft 102 by spraying an abrasive such as sand onto the surface of the shaft 102 to create fine irregularities (scratches). Shot blasting and shot peening are processes of roughening the surface of the shaft 102 by colliding with small steel balls (shot). Barrel processing is a process of roughening the surface of the shaft 102 by mixing it with an abrasive or the like in a drum (barrel). Lathe processing is a process of roughening the surface of the shaft 102 by bringing it into contact with a rotating lathe. Sandpaper processing is a process of roughening the surface of the shaft 102 by creating fine irregularities (scratches) on the surface of the shaft 102 with sandpaper. This provides the shaft 2 with the roughened region 4 formed on the joining surface 2a. The roughening can also be performed by electrochemical treatment or chemical treatment.

[0045] Next, a bonding process is carried out in which bond magnet 3 is bonded to bonding surface 2a that has been roughened in the roughening process. As shown in Figure 7, in the bonding process, a molding process is carried out in which bond magnet compound 103 is compression molded while in contact with bonding surface 2a. Bond magnet compound 103 is a compound that becomes bond magnet 3 when compacted. Bond magnet compound 103 has, for example, the above-mentioned magnet powder 3a and a resin composition.

[0046] 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.

[0047] 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, metal soap, 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.

[0048] 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.

[0049] In the forming process using manufacturing apparatus 5, first, the non-bonding surface 2b of shaft 2 is inserted into upper punch 51 or lower punch 52. Next, bond magnet compound 103 is filled into the space surrounded by die 53 and lower punch 52, or the space surrounded by die 53, lower punch 52, and shaft 2. Next, upper punch 51 is forced into hole 53a to press bond magnet compound 103. Then, bond magnet compound 103 is compression molded while in contact with bonding surface 2a, and bond magnet 3 is bonded to bonding surface 2a. This results in molded product 1 in which bond magnet 3 is bonded to bonding surface 2a of shaft 2. After that, molded product 1 is removed from die 53, and molded product 1 is obtained.

[0050] As explained above, in molded product 1 according to this embodiment, bonding surface 2 a of shaft 2 has roughened region 4, and therefore bond magnet 3 enters into the fine irregularities of roughened region 4. This increases the contact area between shaft 2 and bond magnet 3, and also increases the engagement force (anchor effect) between the fine irregularities of roughened region 4 and bond magnet 3, thereby increasing the bonding strength between shaft 2 and bond magnet 3.

[0051] Furthermore, in this molded product 1, the arithmetic mean roughness Ra of the roughened region 4 is 2 μm or more, preferably 50 μm or more, and more preferably 75 μm or more, so the contact area between the shaft 2 and the bonded magnet 3 is further increased, and the engagement force (anchor effect) between the fine irregularities in the roughened region 4 and the bonded magnet 3 is further increased.

[0052] Furthermore, in this molded article 1, the arithmetic mean roughness Ra of the roughened region 4 is 300 μm or less, preferably 200 μm or less, and more preferably 100 μm or less, so that the roughened region 4 can be easily formed.

[0053] Furthermore, in this molded article 1, the non-bonding surface 2b of the shaft 2 does not have the roughened region 4, which prevents other members from coming into contact with and being damaged by the roughened region 4. Furthermore, it is possible to prevent the appearance of the molded article 1 from being deteriorated due to the exposure of the roughened region 4, and it is also possible to prevent contamination of the molded article 1 due to dust entering the roughened region 4.

[0054] Furthermore, in this molded product 1, resin portion 3b of bonded magnet 3 contains a cured product of a 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 resin portion 3b and shaft 2 and improves the adhesion between resin portion 3b and shaft 2. This further increases the bond strength between shaft 2 and bonded magnet 3.

[0055] In the manufacturing method of the molded product according to this embodiment, the surface of the shaft 2 is roughened and a bonded magnet 3 is joined to the roughened joining surface 2a, so that the above-mentioned molded product 1 can be easily manufactured.

[0056] Furthermore, in this manufacturing method of the molded product, the bond magnet compound 103 is compression molded while being in contact with the joining surface 2a, so that the bond magnet 3 can be easily joined to the joining surface 2a.

[0057] [Second Embodiment] Next, a second embodiment will be described. The second embodiment is basically the same as the first embodiment, and differs from the first embodiment only in that the manufacturing process of the method for manufacturing a molded product is different. Therefore, only the differences from the first embodiment will be described below, and a description of the same points as the first embodiment will be omitted.

[0058] Fig. 8 is a cross-sectional view illustrating the manufacturing method of a molded product according to the second embodiment. As shown in Fig. 8, the manufacturing process of the manufacturing method of a molded product according to the second embodiment begins with a coating step in which a resin film 103b containing the same resin as the resin contained in bond magnet 3 is formed on joining surface 2a. The resin contained in bond magnet 3 is the resin contained in resin portion 3b, and is, for example, the 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 the resin 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.

[0059] 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 first 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 first embodiment.

[0060] 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.

[0061] 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 allowed to penetrate into the minute irregularities of roughened region 4. Then, by drying this resin solution, resin film 103b can be easily formed on joining surface 2a with high joining strength.

[0062] [Third Embodiment] Next, a third embodiment will be described. The third embodiment is basically the same as the first embodiment, and differs from the first embodiment only in that a groove is formed in the shaft 2. Therefore, only the differences from the first embodiment will be described below, and a description of the similarities between the first embodiment and the third embodiment will be omitted.

[0063] Fig. 9 is a front view showing a shaft of a molded product according to the third embodiment. Fig. 10 is a cross-sectional view showing an enlarged portion of the shaft of the molded product according to the third embodiment. Fig. 11 is a cross-sectional view showing an enlarged portion of the molded product according to the third embodiment. As shown in Figs. 9 to 11, shaft 2A of molded product 1A according to this embodiment has, like shaft 2 of the first embodiment, a bonding surface 2a to which bonded magnet 3 is bonded and a non-bonding surface 2b to which bonded magnet 3 is not bonded. Bonding surface 2a of shaft 2A has a plurality of grooves 6.

[0064] The multiple grooves 6 extend in a direction inclined relative to the central axis A of the shaft 2A and are regularly arranged so as to intersect with one another. The multiple grooves 6 include multiple first grooves 6a that are inclined in a first direction relative to the central axis A of the shaft 2A and multiple second grooves 6b that are inclined in a second direction opposite to the first direction relative to the central axis A of the shaft 2A. The multiple first grooves 6a are arranged at equal intervals without intersecting with one another. The multiple second grooves 6b are arranged at equal intervals without intersecting with one another. The multiple first grooves 6a and the multiple second grooves 6b intersect with one another.

[0065] The grooves 6 may extend over the entire region of the joining surface 2 a in the axial direction AD, or may extend over only a portion of the region of the joining surface 2 a in the axial direction AD, but in this embodiment, as an example, they extend over the entire region of the joining surface 2 a in the axial direction AD. Also, the grooves 6 may or may not extend to the non-joint surface 2 b, but in this embodiment, as an example, they do not extend to the non-joint surface 2 b.

[0066] The plurality of grooves 6 have roughened regions 4. That is, in this embodiment, not only the surface of the joining surface 2 a where the plurality of grooves 6 are not formed, but also the surfaces of the plurality of grooves 6 are roughened. The surface of the joining surface 2 a where the plurality of grooves 6 are not formed is the circumferential surface of the shaft 2, and the surfaces of the plurality of grooves 6 are surfaces recessed from the circumferential surface of the shaft 2. The roughened regions 4 may be located on all surfaces of the plurality of grooves 6 or may be located on only a portion of the surfaces of the plurality of grooves 6, but in this embodiment, as an example, the roughened regions 4 are located on all surfaces of the plurality of grooves 6.

[0067] Next, a method for manufacturing a molded product according to a third embodiment will be described. The method for manufacturing a molded product according to the third embodiment is a method for manufacturing the molded product 1A described above. The method for manufacturing a molded product according to the third embodiment is basically the same as that according to the first embodiment, and differs from the first embodiment only in that a groove is formed in the shaft. Therefore, only the differences from the first embodiment will be described below, and a description of the similarities with the first embodiment will be omitted.

[0068] Fig. 12 is a cross-sectional view illustrating a method for manufacturing a molded product according to the third embodiment. First, a shaft 102 is prepared as shown in Fig. 6. Next, as shown in Fig. 12, a shaft machining step is performed to form a plurality of grooves 6 on the joining surface 2a of the shaft 102. The grooves 6 are formed, for example, by pressing a mold corresponding to the plurality of grooves 6 against the joining surface 2a of the shaft 102. This results in a shaft 102Aa having a plurality of grooves 6 formed on the joining surface 2a.

[0069] 12 and 9, a roughening step is performed to roughen the joining surface 2a of the shaft 102Aa, thereby obtaining a shaft 2A in which the roughened region 4 is formed on the surface of the joining surface 2a where the plurality of grooves 6 is not formed and on the surfaces of the plurality of grooves 6.

[0070] Next, a bonding step is performed in which bond magnet 3 is bonded to bonding surface 2a that has been roughened in the roughening step. This bonding step is the same as the bonding step of the first embodiment, except that shaft 2A is used instead of shaft 2. This results in molded product 1A.

[0071] As explained above, in molded product 1A according to this embodiment, multiple grooves 6 are formed on bonding surface 2a, and bond magnet 3 fits into these grooves 6, thereby increasing the bond strength between shaft 2A and bond magnet 3. Furthermore, because these grooves 6 have roughened regions 4, the bond strength between shaft 2A and bond magnet 3 is further increased in these grooves 6 as well.

[0072] Furthermore, in this molded product 1A, multiple grooves 6 intersect with each other, making it possible to prevent bonded magnet 3 from slipping relative to shaft 2A in any direction.

[0073] Furthermore, in this molded product 1A, multiple first grooves 6a are arranged at equal intervals, and multiple second grooves 6b are also arranged at equal intervals, making it easy to form multiple grooves 6. Also, it is possible to suppress variation in the bonding strength between shaft 2A and bonded magnet 3 depending on the position.

[0074] In the manufacturing method of this molded product according to this embodiment, multiple grooves 6 are formed on the joining surface 2a of the shaft 2 before the roughening process, and therefore the multiple grooves 6 can also be made into a roughened area.

[0075] [Fourth Embodiment] Next, a fourth embodiment will be described. The fourth embodiment is basically the same as the third embodiment, and differs from the third embodiment only in that the same manufacturing steps as in the second embodiment are performed in the manufacturing method of the molded product. Therefore, only the differences from the third embodiment will be described below, and a description of the same points as in the third embodiment will be omitted.

[0076] Fig. 13 is a cross-sectional view illustrating the manufacturing method for a molded product according to the fourth embodiment. As shown in Fig. 13, the manufacturing process of the manufacturing method for a molded product according to the fourth embodiment begins with a coating step in which a resin film 103b containing the same resin as that contained in bond magnet 3 is formed on joining surface 2a. 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. Joining surface 2a on which resin film 103b is formed includes not only the surface of joining surface 2a on which multiple grooves 6 are not formed, but also the surfaces of multiple grooves 6.

[0077] 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 third embodiment, except that shaft 2A having resin film 103b formed on roughened region 4 is used. This results in a molded product 1A similar to that of the third embodiment.

[0078] As described above, in the manufacturing method of the molded product according to this embodiment, the resin film 103b is formed not only on the surface of the joining surface 2a where the multiple grooves 6 are not formed, but also on the surface of the multiple grooves 6, so that the resin film 103b can be formed on the joining surface 2a with high joining strength.

[0079] [Fifth Embodiment] Next, a fifth embodiment will be described. The fifth embodiment is basically the same as the third embodiment, and differs from the third embodiment only in that the groove extends in a spiral shape. Therefore, hereinafter, only the differences from the third embodiment will be described, and a description of the similarities with the third embodiment will be omitted.

[0080] Fig. 14 is a front view showing a shaft of a molded product according to the fifth embodiment. Fig. 15 is a cross-sectional view showing an enlarged portion of the shaft of the molded product according to the fifth embodiment. As shown in Fig. 14 and 15, shaft 2B of molded product 1B according to this embodiment has, like shaft 2A of the third embodiment, a bonding surface 2a to which bonded magnet 3 is bonded and a non-bonding surface 2b to which bonded magnet 3 is not bonded. Bonding surface 2a of shaft 2B has a plurality of grooves 7.

[0081] The multiple grooves 7 extend spirally along the central axis A of the shaft 2A and are arranged at equal intervals so as not to intersect with one another. The number of grooves 7 is, for example, 2 to 5, and in this embodiment, as an example, 4. The number of turns of the grooves 7 around the central axis A of the shaft 2A is not particularly limited, but in this embodiment, as an example, it is one turn. Note that one turn of the grooves 7 means one turn around the central axis A of the shaft 2A.

[0082] The grooves 7 may extend over the entire region of the joint surface 2 a in the axial direction AD, or may extend over only a portion of the region of the joint surface 2 a in the axial direction AD, but in this embodiment, as an example, they extend over the entire region of the joint surface 2 a in the axial direction AD. Also, the grooves 7 may or may not extend to the non-joint surface 2 b, but in this embodiment, as an example, they extend from one end of the shaft 2B to the other end in the axial direction AD.

[0083] The plurality of grooves 7 have roughened regions 4. That is, in this embodiment, not only the surfaces of the joining surface 2a where the plurality of grooves 7 are not formed, but also the surfaces of the plurality of grooves 7 are roughened. The roughened regions 4 may be located on all surfaces of the plurality of grooves 7 or only on some surfaces of the plurality of grooves 7, but in this embodiment, as an example, they are located on all surfaces of the plurality of grooves 7.

[0084] The manufacturing method of the molded product according to the fifth embodiment differs from the manufacturing method of the molded product according to the third embodiment only in that, instead of the multiple grooves 6, multiple grooves 7 extending spirally are formed on the shaft 102.

[0085] As explained above, in molded product 1B according to this embodiment, multiple grooves 7 extend spirally along central axis A of shaft 2B, allowing each groove 7 to be long. In other words, each groove 7 can increase the contact area between shaft 2B and bonded magnet 3. This makes it possible to obtain high bonding strength even with a small number of grooves 7. Furthermore, by reducing the number of grooves 7, it is possible to suppress a decrease in the strength of shaft 2B that would otherwise occur with an increase in the number of grooves 7.

[0086] Furthermore, in this molded product 1B, the number of spirally extending grooves 7 is 2 or more and 5 or less, so that high bonding strength can be obtained and a decrease in the strength of the shaft 2B can be suppressed.

[0087] Furthermore, in this molded product 1B, the plurality of grooves 7 do not intersect with each other, so that the plurality of grooves 7 can be easily formed.

[0088] Furthermore, in this molded product 1B, multiple grooves 7 are arranged at equal intervals, making it easy to form multiple grooves 7. Furthermore, it is possible to suppress variations in the bonding strength between shaft 2B and bonded magnet 3 depending on the position.

[0089] [Sixth Embodiment] Next, a sixth embodiment will be described. The sixth embodiment is basically the same as the first embodiment, and differs from the first embodiment only in that a recess is formed in the shaft 2. Therefore, only the differences from the first embodiment will be described below, and a description of the similarities between the first embodiment and the sixth embodiment will be omitted.

[0090] Fig. 16 is a front view showing a shaft of a molded product according to the sixth embodiment. Fig. 17 is a cross-sectional view showing an enlarged portion of the shaft of a molded product according to the sixth embodiment. Fig. 18 is a cross-sectional view showing an enlarged portion of the shaft of a molded product according to the sixth embodiment. As shown in Figs. 16 to 18, shaft 2C of molded product 1C according to this embodiment has, like shaft 2 of the first embodiment, a bonding surface 2a to which bonded magnet 3 is bonded and a non-bonding surface 2b to which bonded magnet 3 is not bonded. Bonding surface 2a of shaft 2A has a plurality of recesses 8 that are independent of each other.

[0091] The plurality of recesses 8 may be formed in the entire region of the bonding surface 2 a or in only a part of the region of the bonding surface 2 a, but in this embodiment, as an example, they are formed in the entire region of the bonding surface 2 a. Also, the plurality of recesses 8 may be formed in the non-bonding surface 2 b or may not be formed in the non-bonding surface 2 b, but in this embodiment, as an example, they are not formed in the non-bonding surface 2 b.

[0092] The plurality of recesses 8 have roughened regions 4. That is, in this embodiment, not only the surface of the joining surface 2a where the plurality of recesses 8 is not formed, but also the surfaces of the plurality of recesses 8 are roughened. The roughened regions 4 may be located on all surfaces of the plurality of recesses 8 or only on some surfaces of the plurality of recesses 8, but in this embodiment, as an example, the roughened regions 4 are located on all surfaces of the plurality of recesses 8.

[0093] Next, a method for manufacturing a molded product according to a sixth embodiment will be described. The method for manufacturing a molded product according to the sixth embodiment is a method for manufacturing the molded product 1C described above. The method for manufacturing a molded product according to the sixth embodiment is basically the same as that according to the first embodiment, and differs from the first embodiment only in that a recess is formed in the shaft. Therefore, only the differences from the first embodiment will be described below, and a description of the similarities with the first embodiment will be omitted.

[0094] Fig. 19 is a cross-sectional view illustrating a method for manufacturing a molded product according to the sixth embodiment. First, a shaft 102 is prepared as shown in Fig. 6. Next, as shown in Fig. 19, a shaft processing step is performed in which a plurality of depressions 8 are formed on the joining surface 2a of the shaft 102. The plurality of depressions 8 are formed, for example, by pressing a mold corresponding to the plurality of depressions 8 against the joining surface 2a of the shaft 102. This results in a shaft 102Ca having a plurality of depressions 8 formed on the joining surface 2a.

[0095] 19 and 17, a roughening step is performed to roughen the joining surface 2a of the shaft 102Ca, thereby obtaining a shaft 2C in which the joining surface 2a is free of the plurality of recesses 8 and in which the roughened regions 4 are formed on the surfaces of the plurality of recesses 8.

[0096] Next, a bonding process is performed in which bond magnet 3 is bonded to bonding surface 2a that has been roughened in the roughening process. This bonding process is the same as the bonding process of the first embodiment, except that shaft 2C is used instead of shaft 2. This results in molded product 1C.

[0097] As explained above, in molded product 1C according to this embodiment, multiple recesses 8 that are independent of each other are formed on bonding surface 2a, and bond magnet 3 enters these recesses 8, thereby increasing the bond strength between shaft 2C and bond magnet 3. Furthermore, because these recesses 8 have roughened regions 4, the bond strength between shaft 2C and bond magnet 3 is further increased in these recesses 8 as well.

[0098] In the manufacturing method of the molded product according to this embodiment, before the roughening process, a plurality of independent depressions 8 are formed on the joining surface 2a of the shaft 2C, and therefore the plurality of independent depressions 8 can also be made into the roughened area 4.

[0099] 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.

[0100] For example, in the above embodiment, the non-bonding surface has been described as not having a roughened region, but the non-bonding surface may also have a roughened region.

[0101] Furthermore, in the third to fifth embodiments, specific shapes of the grooves etc. are mentioned, but the shapes of the grooves etc. can be changed as appropriate.

[0102] Furthermore, in the third to sixth embodiments, the joining surface is described as being roughened after forming the multiple grooves or multiple independent depressions, but the joining surface may be roughened before forming the multiple grooves or multiple independent depressions. If the joining surface is roughened before forming the multiple grooves or multiple independent depressions, the multiple grooves or multiple independent depressions will not have roughened areas, but the surface of the joining surface where the multiple grooves or multiple independent depressions are not formed will have roughened areas, thereby achieving the same effect as the above embodiments. Furthermore, by forming the multiple grooves or multiple independent depressions on the joining surface of the shaft after the roughening process, the roughening process can be performed efficiently.

[0103] 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.

[0104] 1...molded product, 1A...molded product, 1B...molded product, 1C...molded product, 2...shaft, 2A...shaft, 2B...shaft, 2C...shaft, 2a...bonding surface, 2b...non-bonding surface, 3...bonded magnet, 3a...magnet powder, 3b...resin part, 4...roughened area, 5...manufacturing apparatus, 6...groove, 6a...first groove, 6b...second groove, 7...groove, 8...depression, 51...upper punch, 52...lower punch, 53...die, 53a...hole, 102...shaft, 102Aa...shaft, 102Ca...shaft, 103...bonded magnet compound, 103b...resin film, A...central axis, AD...axial direction.

Claims

1. A molded product having a bonded magnet bonded to the surface of a shaft, wherein the surface of the shaft to which the bonded magnet is bonded has a roughened area.

2. The molded product according to claim 1, wherein the roughened area has an arithmetic mean roughness of 2 μm or more.

3. The molded product according to claim 1 or 2, wherein the roughened region has an arithmetic mean roughness of 300 μm or less.

4. A molded product according to any one of claims 1 to 3, 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 roughened region.

5. A molded product according to any one of claims 1 to 4, wherein the joining surface has a plurality of grooves, and the grooves have the roughened area.

6. The molded product according to claim 5, wherein the plurality of grooves extend spirally along the central axis of the shaft.

7. The molded product according to claim 6, wherein the number of said plurality of grooves is 2 or more and 5 or less.

8. A molded product according to any one of claims 5 to 7, wherein the plurality of grooves intersect with each other.

9. A molded product according to any one of claims 5 to 7, wherein the plurality of grooves do not intersect with each other.

10. The molded product according to claim 9, wherein the plurality of grooves are arranged at equal intervals.

11. A molded product according to any one of claims 1 to 10, wherein the joining surface has a plurality of recesses that are independent of each other, and the plurality of recesses have the roughened area.

12. A molded product according to any one of claims 1 to 11, wherein the bonded magnet has a magnetic powder and a resin portion, the resin portion includes a cured thermosetting resin, and the thermosetting resin includes an epoxy resin and a phenolic resin.

13. A method for manufacturing a molded product in which a bonded magnet is bonded to the surface of a shaft, comprising: a roughening step of roughening the joining surface of the shaft to which the bonded magnet will be joined; and a joining step of joining the bonded magnet to the joining surface roughened in the roughening step.

14. A method for manufacturing a molded product as set forth in claim 13, wherein the joining step includes a molding step of compression molding a bond magnet compound while the bond magnet compound is in contact with the joining surface.

15. A method for manufacturing a molded product as described in claim 13, 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.

16. The method for manufacturing a molded product according to claim 15, 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 then dried.

17. The method for producing a molded product according to any one of claims 13 to 16, further comprising a shaft processing step of forming a plurality of grooves or a plurality of recesses independent of one another on the joining surface before the surface roughening step.

18. The method for producing a molded product according to any one of claims 13 to 16, further comprising a shaft processing step of forming a plurality of grooves or a plurality of recesses independent of one another on the joining surface after the surface roughening step.

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