Bearing device, method for manufacturing a bearing device, hard disk drive device, and motor

Abstract

To obtain technology that meets the requirements for bearing devices assembled using adhesives. [Solution] A bearing device 100 having a structure in which metal components are bonded using a delayed ultraviolet curing epoxy adhesive, wherein the components are either members with a dust-preventing coating formed on their surface or members that have undergone plastic deformation. The bearing device 100 holds the sleeve 110 in a rotatable state relative to the shaft 150 by ball bearings 120 and 130. Here, at least one of the shaft 150 and the sleeve 110 has a metallic nickel coating 153,118 formed on it, which is a dust-preventing coating made by electroless nickel plating. Alternatively, at least one of the shaft 150 and the sleeve 110 is made of a metal material suitable for plastic deformation.

Description

[Technical Field]

[0001] The present invention relates, for example, to a pivot bearing device for a hard disk drive, and more particularly to a technique for fixing components using an adhesive. [Background technology]

[0002] There is a technique for fixing the components of a pivot bearing device with an anaerobic adhesive (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-158038 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0004] There are various requirements for the pivot bearings of hard disk drive devices. These requirements include, for example, reducing the amount of fine particles that fall off the surface of the bearing device and reducing manufacturing costs. When using materials that meet these requirements, anaerobic adhesives may not exhibit effective adhesive strength, or the time it takes for the adhesive to become effective may be prolonged, resulting in poor productivity.

[0005] Against this backdrop, the present invention aims to provide a technology that satisfies the requirements for bearing devices assembled using adhesives. [Means for solving the problem]

[0006] The present invention relates to a bearing device having a structure in which metal components are bonded together using a delayed ultraviolet-curing epoxy adhesive, wherein the components are either members with a dust-preventing coating formed on their surface or members that have undergone plastic deformation.

[0007] The present invention relates to a method for manufacturing a bearing device, comprising the steps of forming a dust-preventing coating on the surface of a component made of a metal material, and bonding the component to other components with a delayed ultraviolet-curing epoxy adhesive. The present invention also relates to a method for manufacturing a bearing device, comprising the steps of obtaining a component made of a metal material by plastic deformation, and bonding the component to other components with a delayed ultraviolet-curing epoxy adhesive.

[0008] The present invention relates to a hard disk drive equipped with a bearing device, wherein the bearing device has a structure in which metal components are bonded using a delayed ultraviolet curing epoxy adhesive, and the components are members having a dust-preventing coating formed on their surface or members that have undergone plastic deformation.

[0009] The present invention relates to a motor equipped with a bearing device, wherein the bearing device has a structure in which metal components are bonded using a delayed ultraviolet curing epoxy adhesive, and the components are members having a dust-preventing coating formed on their surface or members that have undergone plastic deformation. [Effects of the Invention]

[0010] According to the present invention, a technology is obtained that satisfies the requirements for bearing devices assembled using adhesives. [Brief explanation of the drawing]

[0011] [Figure 1] This is a front view showing a bearing device according to an embodiment. [Figure 2] Figure 1 shows a cross-sectional view along line II-II (A), and enlarged views thereof (B) and (C). [Figure 3] This is an enlarged view of the area indicated by arrow III in Figure 2. [Figure 4] This is a schematic side view showing the assembly process of the embodiment. [Figure 5] This is a front view showing a bearing device according to an embodiment. [Figure 6] This is a cross-sectional view taken along the line VI-VI in Figure 5. [Figure 7] It is a schematic side view showing the assembly process of the embodiment. [Figure 8] It is a perspective view showing the hard disk drive of the embodiment. [Figure 9] It is a cross-sectional view showing the motor of the embodiment. [Figure 10] It is a cross-sectional view showing the bearing device of the embodiment. [Figure 11] It is a cross-sectional view showing the motor provided with the bearing device of the embodiment. [Figure 12] It is a cross-sectional view showing a modified example of the embodiment. [Figure 13] It is a schematic side view showing the assembly process of the embodiment. [Figure 14] It is a cross-sectional view showing the bearing device of the embodiment. [Figure 15] It is a schematic side view showing the assembly process of the embodiment.

Mode for Carrying Out the Invention

[0012] [1] First Embodiment 1. Configuration of Bearing Device The bearing device of the embodiment of the present invention will be described. FIGS. 1 to 4 show the bearing device 100 of the embodiment of the present invention. The bearing device 100 includes a sleeve (outer member) 110 made of metal and having a cylindrical shape. The metal constituting the sleeve 110 is, for example, stainless steel. If the sleeve 110 is formed by cutting, for example, SUS303 is used, and if the sleeve 110 is formed by plastic working, for example, SUS304 is used.

[0013] FIG. 2(B) is an enlarged view of a part of FIG. 2(A). As shown in FIG. 2(B), a metal nickel film 118 formed by electroless nickel plating is formed on the surface of the sleeve 110. In FIG. 2(A), the metal nickel film 118 is not shown.

[0014] The metallic nickel film 118 functions as a dust-preventing coating that suppresses the generation of particles (fine particles of the material constituting the substrate) on the surface of the sleeve 110, which is the substrate. The thickness of the metallic nickel film 118 is selected from the range of 1 μm to 30 μm, preferably from the range of 1 μm to 5 μm. This is the same for the metallic nickel film 153 described later and for the metallic nickel film in other embodiments. By providing the metallic nickel film 118, the generation of particles (fine particles) from the surface of the sleeve 110 is suppressed.

[0015] The bearing device 100 has a structure in which the shaft 150 and the sleeve 110 are connected in a manner that allows them to rotate relative to each other via ball bearings 120 and 130. The ball bearing 120 has an inner ring 121, an outer ring 122, and a ball 125 held between the inner ring 121 and the outer ring 122. The ball bearing 130 has an inner ring 131, an outer ring 132, and a ball 135 held between the inner ring 131 and the outer ring 132. The material of the inner rings 121, 131, the outer rings 122, 132, and the balls 125, 135 is known bearing steel.

[0016] An inner circumferential projection (spacer portion) 111 is formed in the axial center of the sleeve 110, projecting radially inward. A first ball bearing 120 and a second ball bearing 130 are fixed to both sides of the inner circumferential projection 111 with adhesive 140. The end faces of the outer rings 122 and 132 of the first and second ball bearings 120 and 130 are in contact with the end face of the inner circumferential projection 111.

[0017] The fit between the outer surfaces of the outer rings 122 and 132 and the inner surface of the sleeve 110 is a clearance fit as defined in JIS B 0401-1 and -2, and adhesive 140 is filled into the gap. The gap is preferably 2 to 15 μm. This structure provides adhesion between the sleeve 110 and the outer ring 122 of the ball bearing 120, and between the sleeve 110 and the outer ring 132 of the ball bearing 130.

[0018] The shaft 150 is made of stainless steel. If the shaft 150 is formed by machining, for example SUS303 can be used, and if the shaft 150 is formed by plastic deformation, for example SUS304 can be used.

[0019] Figure 2(C) is an enlarged view of a portion of Figure 2(A). As shown in Figure 2(C), a metallic nickel film 153 formed by electroless nickel plating is formed on the surface of the shaft 150. Note that the metallic nickel film 153 is omitted from the illustration in Figure 2(A). By providing the metallic nickel film 153, the generation of particles (fine particles) from the surface of the shaft 150 is suppressed.

[0020] The inner rings 121 and 131 are fixed to the shaft (shaft member) 150 with adhesive 140. A flange portion 151 is formed at the base end of the shaft 150, projecting radially outward. The end face of the inner ring 131 of the second ball bearing 130 is in contact with the flange portion 151. The fit between the inner circumferential surfaces of the inner rings 121 and 131 and the outer circumferential surface of the shaft 150 is a clearance fit as defined in JIS B 0401-1 and -2, and the adhesive 140 is filled into the gap. The gap is preferably 2 to 15 μm. This structure allows for bonding between the shaft 150 and the inner ring 121 of the ball bearing 120, and between the shaft 150 and the inner ring 131 of the ball bearing 130.

[0021] In Figure 2, reference numeral 125 denotes a ball, and multiple balls 125 are arranged at regular intervals in the circumferential direction between the raceway surface 121a of the inner ring 121 and the raceway surface 122a of the outer ring 122 by a cage 126. The second ball bearing 130 also has balls 135 arranged in a similar configuration using a cage 136.

[0022] As shown in Figure 3, annular grooves 123 are formed at both axial ends of the inner circumferential surface of the outer ring 122. A C-ring 124 is fitted into the annular groove 123, and the C-ring 124 presses the outer circumferential edge of the sealing member 127 against the outer ring 122. The inner circumferential edge of the sealing member 127 faces the outer circumferential surface of the inner ring 121 with a small gap between them. Such a sealing member 127 is also provided in the second ball bearing 130.

[0023] Meanwhile, a first hub cap 128 is fixed to the outer circumferential surface of the shaft 150, facing the first ball bearing 120. The outer edge of the first hub cap 128 faces the inner circumferential surface of the sleeve 110 with a small gap between them. A second hub cap 129, facing the first hub cap 128, is fixed to the opening of the sleeve 110 by press-fitting or adhesive. The second hub cap 129 is ring-shaped, and its inner circumferential edge faces the outer circumferential surface of the shaft 150 with a gap between them.

[0024] As a result, the gap between the sealing member 127 and the inner ring 121 and the first hub cap 128 overlap in the axial direction, and the gap between the first hub cap 128 and the sleeve 110 and the second hub cap 129 overlap in the axial direction. This effectively suppresses leakage of grease filled between the inner ring 121 and the outer ring 122, and prevents dust and other debris from entering the space between the inner ring 121 and the outer ring 122 from the outside.

[0025] On the other hand, the flange portion 151 formed at the base end of the shaft 150 overlaps the gap between the sealing member 127 and the inner ring 131 with the flange portion 151 in the axial direction, effectively suppressing leakage of grease filled between the inner ring 131 and the outer ring 132, and preventing dust and other debris from entering the space between the inner ring 131 and the outer ring 132 from the outside.

[0026] In this configuration, metallic nickel coatings 118 and 153 are formed on the surfaces of both the sleeve 110 and the shaft 150 by electroless nickel plating. It is also possible to form the metallic nickel coating on only one of the sleeve 110 or the shaft 150.

[0027] For example, when the bearing device 100 is used in the hard disk drive 300 shown in Figure 8 (described later), the end of the shaft 150 is exposed to the internal space of the hard disk drive 300. To suppress dust generation from this exposed portion, a metallic nickel coating is formed only on the surface of the shaft 150.

[0028] Here, an example of a metallic nickel coating formed by electroless nickel plating as a dust-preventing coating to suppress particle generation was described. Examples of dust-preventing coatings include coatings formed by chromium plating, coatings formed by electrodeposition coating, and epoxy resin coatings. This is also true for other embodiments.

[0029] 2. Composition of the adhesive The adhesive 140 will be described below. Note that the adhesive described below will also be used in other embodiments. Adhesive 140 is a delayed UV-curing epoxy adhesive. The reasons for using a delayed UV-curing epoxy adhesive are as follows.

[0030] For example, SUS303Cu has copper (Cu) added to improve its machinability. Cu is highly reactive and easily ionizes. When anaerobic adhesives are used to bond metals, the adhesive hardens by reacting with metal ions present on the surface of the metal that contribute to the hardening reaction. For this reason, SUS303Cu readily undergoes the hardening reaction of anaerobic adhesives and is compatible with anaerobic adhesives.

[0031] In contrast, the metallic nickel coating and SUS304 used in this embodiment do not contain Cu as additives, so compared to SUS303Cu, the efficiency of generating metal ions that contribute to the curing reaction is lower, resulting in a slower curing reaction of the anaerobic adhesive. Specifically, curing takes a long time.

[0032] The curing of delayed UV-curing epoxy adhesives is based on a chemical reaction caused by UV irradiation, and its curing mechanism does not depend on reactions with metal ions. Therefore, good adhesive effects can be obtained even with materials that do not have good compatibility with anaerobic adhesives, such as metallic nickel coatings and SUS304.

[0033] Materials that can be used for bonding with delayed UV-curing epoxy adhesives include metals in which the content of metals that generate metal ions contributing to the curing reaction (e.g., Cu) is smaller than that of SUS303Cu, specifically, metals in which the content of metals that generate metal ions contributing to the curing reaction (e.g., Cu) is 0.05% by weight or less, preferably 0.01% by weight or less. Of course, delayed UV-curing epoxy adhesives can also be used to bond metals that contain metal additives (in this case, Cu) that contribute to the generation of metal ions contributing to the curing reaction, such as SUS303Cu.

[0034] Delayed UV-curing epoxy adhesives should be those that begin to cure between 10 seconds and 30 minutes after UV irradiation. Ideally, the curing start time should be between 10 seconds and 5 minutes after UV irradiation. Note that the curing start time here is calculated using a 365nm wavelength UV-LED with 100mW / cm² of UV light. 2 This refers to the time it takes for the viscosity to increase tenfold after 20 seconds of UV irradiation, as monitored with a rheometer. Until the viscosity reaches tenfold compared to before UV irradiation, curing is considered not to have begun. Furthermore, the viscosity of the adhesive at 25°C before curing is preferably 100-1000 mPa·s, and particularly preferably 100-400 mPa·s. If the viscosity is less than 100 mPa·s, the applied adhesive may run off; if it exceeds 1000 mPa·s, springback may occur when preload is applied, preventing the preload from being applied. Here, the viscosity of the adhesive at 25°C before curing or after UV irradiation is measured using a cone-plate rheometer with a diameter of 75 mm and a cone angle of 1.0°, under a shear rate of 100 / s. This springback is more likely to occur with smaller applied preload loads.

[0035] In this embodiment, the preload applied to each bearing of the bearing device can be 5 to 30 N or 7 to 13 N in the axial direction. It is preferable that the adhesive 140 becomes 10,000 times more viscous than its viscosity before UV irradiation within 10 minutes, more preferably within 5 minutes, after the curing start time described above has elapsed. By using such an adhesive, the time of the preload application step described later can be appropriately shortened. It is preferable that the axial natural frequency of the bearing device 100 after the preload application step described later is 80% or more of the axial natural frequency of the bearing device 100 after the heating step described later. The preload application step can be, for example, 3 to 30 minutes.

[0036] The glass transition temperature of the cured adhesive is preferably 100°C or higher, and more preferably 120°C or higher. By setting the glass transition temperature in this way, changes in the natural frequency of the bearing device due to temperature changes can be suppressed. Furthermore, it is preferable that the adhesive composition before curing does not contain particles larger than the minimum value of the adhesive gap.

[0037] As a delayed UV-curing epoxy adhesive, an adhesive comprising a bisphenol F type liquid epoxy resin, a bisphenol A type liquid epoxy resin, a glycidyl compound, and a photopolymerization initiator can be used. Other additives such as modified acrylates may be added as needed.

[0038] In this case, when the total amount of adhesive components before curing is 100 parts by weight, it may contain 40 to 60 parts by weight of bisphenol A and bisphenol F, 40 to 60 parts by weight of glycidyl compounds, 0.1 to 10 parts by weight of photopolymerization initiators, and 0.1 to 5 parts by weight of other additives as needed.

[0039] Examples of glycidyl compounds include neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, phenyl glycidyl ether, 2-methylphenyl glycidyl ether, tert-butylphenyl glycidyl ether, 4-chlorophenyl glycidyl ether, 4-methoxyphenyl glycidyl ether, and 2-biphenyl glycidyl ether. One or more of the following can be used in combination: 1-naphthylglycidyl ether, methylglycidyl ether, isopropylglycidyl ether, butylglycidyl ether, tert-butylglycidyl ether, 2-ethylglycidyl ether, 2-ethylhexylglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol #200 diglycidyl ether, polyethylene glycol #400 diglycidyl ether, tripylene glycol diglycidyl ether, polypropylene glycol #400 diglycidyl ether, glycerin diglycidyl ether, etc. The glycidyl compound preferably has a viscosity of 30 mPa·s or less at 25°C, more preferably 20 mPa·s or less, and even more preferably 10 mPa·s or less.

[0040] Examples of photopolymerization initiators include salts in which the cationic species consists of iodonium-based or sulfonium-based cationic species, and the anionic species consists of phosphorus-based or boron-based anionic species. One or more of these can be used in combination. Specifically, the following are examples, but are not limited to these.

[0041] Examples of iodonium-based cation species include diphenyliodonium, di-p-tolyliodonium, bis(4-dodecylphenyl)iodonium, bis(4-methoxyphenyl)iodonium, (4-octyloxyphenyl)phenyliodonium, bis(4-decyloxyphenyl)iodonium, 4-(2-hydroxytetradecyloxy)phenylphenyliodonium, 4-isopropylphenyl(p-tolyl)iodonium, and isobutylphenyl(p-tolyl)iodonium.

[0042] Sulfonium-based cation species include triarylsulfonium such as triphenylsulfonium, tri-p-tolylsulfonium, tri-o-tolylsulfonium, 4-(phenylthio)phenyldiphenylsulfonium, bis[4-(diphenylsulfonio)phenyl]sulfide, 5-(4-methoxyphenyl)thiantherenium, 5-(4-ethoxyphenyl)thiantherenium, and 5-(4-(2-hydroxyethoxy)phenyl)thiantherenium; diarylsulfonium such as diphenylphenacylsulfonium, diphenyl(4-nitrophenacyl)sulfonium, diphenylbenzylsulfonium, and diphenylmethylsulfonium; and phenylmethylbenzylsulfonium and (4-hydroxyphenyl)methylbenzylsulfonium. Examples of monoarylsulfonium include methylsulfonium, (4-methoxyphenyl)methylbenzylsulfonium, (4-acetocarbonyloxyphenyl)methylbenzylsulfonium, (2-naphthyl)methylbenzylsulfonium, (2-naphthyl)methyl[(1-ethoxycarbonyl)ethyl]sulfonium, phenylmethylphenacylsulfonium, (4-hydroxyphenyl)methylphenacylsulfonium, (4-methoxyphenyl)methylphenacylsulfonium, (4-acetocarbonyloxyphenyl)methylphenacylsulfonium, (2-naphthyl)methylphenacylsulfonium, (2-naphthyl)octadecylphenacylsulfonium, and (9-anthracenyl)methylphenacylsulfonium.

[0043] Examples of phosphorus-based anion species include hexafluorophosphate, fluorinated alkyl fluorophosphate, etc. Specific examples of preferred fluorinated alkyl fluorophosphate anions include [(CF3CF2)2PF4] - , [(CF3CF2)3PF3] - , [((CF3)2CF)2PF4] - , [((CF3)2CF)3PF3] - , [(CF3CF2CF2)2PF4] - , [(CF3CF2CF2)3PF3] - , [((CF3)2CFCF2)2PF4] - , [((CF3)2CFCF2)3PF3] - , [(CF3CF2CF2CF2)2PF4] - and [(CF3CF2CF2CF2)3PF3] - are mentioned. Among these, [(CF3CF2)3PF3] - , [(CF3CF2CF2)3PF3] - , [((CF3)2CF)3PF3] - , [((CF3)2CF)2PF4] - , [((CF3)2CFCF2)3PF3] - and [((CF3)2CFCF2)2PF4] - are particularly preferred. Examples of boron-based anion species include tetrafluoroborate, tetrakis(pentafluorophenyl)borate, etc.

[0044] Specific examples of photopolymerization initiators include CPI-100P, CPI-101A, CPI-110B, CPI-200K, CPI-210S, IK-1, IK-2, CPI-410S, and HS-1A from Sunapro Co., Ltd., and WPI-113, WPI-116, WPI-169, WPI-170, WPAG-336, WPAG-367, WPAG-370, WPAG-469, and WPAG-638 from Wako Pure Chemical Industries, Ltd., as well as ADEKA products. Examples include, but are not limited to, Adeka Optomer SP-103, SP-150, SP-151, SP-170, SP-171, and SP-172 from Adeka Corporation; PC-2506, PC-2508, and PC-2520 from Polyset Corporation; San-Aid SI-60, SI-80, SI-100, SI-60L, SI-80L, SI-100L, SI-L145, SI-L150, SI-L160, SI-L110, and SI-L147 from Sanshin Chemical Industry Co., Ltd.; and BLUESIL PI2074 from Bluestar Silicones HK.

[0045] Other delayed UV-curing epoxy adhesives include those comprising alicyclic epoxy resin, oxetane compound, photopolymerization initiator, and photosensitizer. If necessary, other additives such as modified acrylate may be added.

[0046] In this case, when the total amount of adhesive components before curing is 100 parts by weight, it may contain 75 to 97 parts by weight of alicyclic epoxy resin, 1 to 15 parts by weight of oxetane compound, 0.1 to 10 parts by weight of photopolymerization initiator, 0.1 to 10 parts by weight of photosensitizer, and 0.1 to 5 parts by weight of other additives as needed.

[0047] Examples of alicyclic epoxy resins include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate compounds, such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate; 3,4-epoxy-1-methylcyclohexylmethyl-3,4-epoxy-1-methylcyclohexanecarboxylate; 6-methyl-3,4-epoxycyclohexylmethylmethyl-6-methyl-3,4-epoxycyclohexanecarboxylate; 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexanecarboxylate; 3,4-epoxy-3-methylcyclohexylmethyl-3,4-epoxy-3-methylcyclohexanecarboxylate; and 3,4-epoxy-5-methylcyclohexylmethyl-3,4-epoxy-5-methylcyclohexanecarboxylate. The alicyclic epoxy resin preferably has a viscosity of 400 mPa·s or less at 25°C.

[0048] Examples of oxetane compounds include 3-ethyl-3-hydroxymethyloxetane, 3-(meth)allyloxymethyl-3-ethyloxetane, (3-ethyl-3-oxetanylmethoxy)methylbenzene, 4-fluoro-[1-(3-ethyl-3-oxetanylmethoxy)methyl]benzene, [1-(3-ethyl-3-oxetanylmethoxy)ethyl]phenyl ether, isobutoxymethyl(3-ethyl-3-oxetanylmethyl) ether, 2-ethylhexyl(3-ethyl-3-oxetanylmethyl) ether, ethyldiethylene glycol(3-ethyl-3-oxetanylmethyl) ether, tetrahydrofurfuryl(3-ethyl-3-oxetanylmethyl) ether, tetrabromophenyl(3-ethyl-3-oxetanylmethyl) ether, 2-tetrabromophenoxyethyl(3-ethyl-3-oxetanylmethyl) ether, and tetrabromophenoxyethyl(3-ethyl-3-oxetanylmethyl) ether. Examples include chlorophenyl (3-ethyl-3-oxetanylmethyl) ether, pentabromophenyl (3-ethyl-3-oxetanylmethyl) ether, ethylene glycol bis(3-ethyl-3-oxetanylmethyl) ether, triethylene glycol bis(3-ethyl-3-oxetanylmethyl) ether, tetraethylene glycol bis(3-ethyl-3-oxetanylmethyl) ether, trimethylolpropane tris(3-ethyl-3-oxetanylmethyl) ether, pentaerythritol tris(3-ethyl-3-oxetanylmethyl) ether, pentaerythritol tetrakis(3-ethyl-3-oxetanylmethyl) ether, dipentaerythritol tetrakis(3-ethyl-3-oxetanylmethyl) ether, and ditrimethylolpropane tetrakis(3-ethyl-3-oxetanylmethyl) ether.

[0049] As a photopolymerization initiator, in addition to triarylsulfonium salts, other substances equivalent to those described above can be used. Among these, triarylsulfonium salts are preferred. Specific examples of such substances include CPI-100P manufactured by Sunapro Co., Ltd., which is equivalent to those described above.

[0050] Next, the photosensitizer can be any compound that, when combined with the photopolymerization initiator, increases the photoactivity of the composition, and the type of sensitization mechanism, such as energy transfer, electron transfer, or proton transfer, is not limited. From the viewpoint of good compatibility with the above photopolymerization initiator and excellent photocurability, radical polymerization initiators, aromatic hydrocarbons, nitro compounds, and the following dyes are preferred. For example, aromatic hydrocarbons selected from the group consisting of benzyl ketal-based photoradical polymerization initiators, α-hydroxyacetophenone-based photoradical polymerization initiators, benzoin-based photoradical polymerization initiators, aminoacetophenone-based photoinitiators, oxime ketone-based photoradical polymerization initiators, acylphosphine oxide-based photoradical polymerization initiators, naphthalene derivatives, and anthracene derivatives (e.g., 9,10-dibutoxyanthracene); nitro compounds selected from the group consisting of nitrobenzoic acid and nitroaniline; or dyes selected from the group consisting of riboflavin, rose bengal, eosin, erythrosine, methylene blue, and new methylene blue rose are preferred.

[0051] Furthermore, as photosensitizers, for example, 9-fluorenone, 2-hydroxy-9-fluorenone, 2-amino-9-fluorenone, fluorene, 2-bromofluorene, 9-bromofluorene, 9,9-dimethylfluorene, 2-fluorofluorene, 2-iodofluorene, 2-fluorenamine, 9-fluorenol, 2,7-dibromofluorene, 9-aminofluorene hydrochloride, 2,7-diaminofluorene, 9,9'-spirobi[9H-fluorene], 2-fluorenecarboxaldehyde, 9-fluorenylmethanol, 2 -Anthracenes such as acetylfluorene, fluorantene, anthracene, 9,10-dibutoxyanthracene, 9,10-dimethoxyanthracene, 9,10-diethoxyanthracene, 2-ethyl-9,10-dimethoxyanthracene, 9,10-dipropoxyanthracene; pyrene; 1,2-benzanthracene; perylene; tetracene; coronene; thioxanthone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, and 2,4-diethylthioxane Thioxanthones such as ton; phenothiazines such as phenothiazine, N-methylphenothiazine, N-ethylphenothiazine, N-phenylphenothiazine; xanthones; naphthalenes such as 1-naphthol, 2-naphthol, 1-methoxynaphthalene, 2-methoxynaphthalene, 1,4-dihydroxynaphthalene, and 4-methoxy-1-naphthol; dimethoxyacetophenone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 4'-isopropyl-2-hydroxy-2-methylpropan Examples include ketones such as ophenone and 4-benzoyl-4'-methyldiphenyl sulfide; carbazoles such as N-phenylcarbazole, N-ethylcarbazole, poly-N-vinylcarbazole, and N-glycidylcarbazole; chrycenes such as 1,4-dimethoxychrysene and 1,4-di-α-methylbenzyloxychrysene; and phenanthrenes such as 9-hydroxyphenanthrene, 9-methoxyphenanthrene, 9-hydroxy-10-methoxyphenanthrene, and 9-hydroxy-10-ethoxyphenanthrene.When using a triarylsulfonium salt as a photopolymerization initiator, it is preferable to use highly reducing agents such as anthracene, perylene, or phenothiazine as the photosensitizer.

[0052] In addition, examples of photosensitizers include intramolecular cleavage-type photoradical polymerization initiators and hydrogen abstraction-type photoradical polymerization initiators. Intramolecular cleavage-type photoradical polymerization initiators are radical initiators of the type in which the compound is cleaved and radicals are generated when irradiated with active energy rays. Specific examples include benzyl ketal-based photoradical polymerization initiators, α-hydroxyacetophenone-based photoradical polymerization initiators, benzoin-based photoradical polymerization initiators, aminoacetophenone-based photoinitiators, oxime ketone-based photoradical polymerization initiators, acylphosphine oxide-based photoradical polymerization initiators, titanocene-based photoradical polymerization initiators, thiobenzoic acid S-phenyl polymerization initiators, and derivatives of these with high molecular weight. Among these intramolecular cleavage-type radical initiators, benzyl ketal-based photoradical polymerization initiators, α-hydroxyacetophenone-based photoradical polymerization initiators, benzoin-based photoradical polymerization initiators, aminoacetophenone-based photoinitiators, oxime ketone-based photoradical polymerization initiators, and acylphosphine oxide-based photoradical polymerization initiators are preferred because they have good compatibility with the above-mentioned photopolymerization initiators and exhibit excellent photocurability. More preferably, α-hydroxyacetophenone-based photoradical polymerization initiators, benzoin-based photoradical polymerization initiators, aminoacetophenone-based photoinitiators, and oxime ketone-based photoradical polymerization initiators are used.

[0053] Examples of hydrogen abstraction type photoradical polymerization initiators include benzophenone-based photoradical initiators, thioxanthone-based photoradical polymerization initiators, and anthraquinone-based photoinitiators.

[0054] 3. Assembly method for bearing devices The assembly method of the bearing device 100 with the above configuration will be explained with reference to Figure 4. First, a sleeve 110 and a shaft 150 are obtained by an appropriate processing method. Next, a metallic nickel film 118 is formed on the surface of the sleeve 110 by electroless nickel plating, and a metallic nickel film 153 is formed on the surface of the shaft 150. The metallic nickel film is formed on the entire surface of the components (including the inner circumferential surface of the sleeve 110). Next, the bearing device 100 is assembled by performing the following steps (1) to (6).

[0055] (1) Apply adhesive 140 to the outer circumference of the end of the shaft 150 near the flange portion 151, and apply adhesive 140 to the inner circumference of one end of the sleeve 110. Then, irradiate the adhesive 140 with ultraviolet light L.

[0056] (2) Before the adhesive 140 begins to harden, the second ball bearing 130 is fitted onto the shaft 150 and pushed in until it reaches the adhesive 140, so that the end face of the inner ring 131 comes into contact with the flange portion 151. At the same time, the first ball bearing 120 is inserted into the sleeve 110 and pushed in until it reaches the adhesive 140, so that the end face of the outer ring 122 comes into contact with the end face of the inner circumferential projection 111.

[0057] (3) Apply adhesive 140 to the outer circumference of the end of the shaft 150 away from the flange portion 151, and apply adhesive 140 to the inner circumference of the other end of the sleeve 110 (the end opposite to the side into which the first ball bearing 120 is inserted). Then, irradiate the adhesive 140 with ultraviolet light L. Note that (3) shows the state in which the sleeve 110 has been inverted 180° vertically from the state shown in (2).

[0058] (4) Before the adhesive 140 begins to harden, the shaft 150 with the second ball bearing 130 mounted on it is inserted into the sleeve 110 with the first ball bearing 120 mounted on it, and the end face of the outer ring 132 of the second ball bearing 130 is brought into contact with the end face of the inner circumferential projection 111. As a result, the inner circumferential surface of the inner ring 121 of the first ball bearing 120 and the outer circumferential surface of the outer ring 132 of the second ball bearing 130 come into contact with the adhesive 140.

[0059] (5) Hold the sleeve 110 with a suitable jig and press the inner ring 121 of the first ball bearing 120 with the pre-pressure jig 160. Hold it in this state until the adhesive has hardened to a certain extent and the pre-pressure does not leak out. (6) Since the adhesive described above is not fully cured, the bearing device 100 is placed in an oven and heated to complete the curing process. Once curing is complete, the first hub cap 128 shown in Figure 3 is fixed to the outer circumference of the shaft 150, and then the second hub cap 129 shown in Figure 3 is fixed to the inner circumference of the sleeve 110.

[0060] 4. Effects The bearing device 100 is suitable for use as a pivot bearing device for a hard disk drive. Hard disk drives require a high degree of cleanliness inside. The bearing device 100 suppresses the generation of particles from its components by forming a metallic nickel film on the components using electroless nickel plating. Therefore, a hard disk drive with a high degree of internal cleanliness can be obtained.

[0061] Incidentally, the aforementioned metallic nickel film is incompatible with conventionally used anaerobic adhesives. Specifically, it tends to result in a slower curing speed and lower strength. In contrast, delayed UV-curing epoxy adhesives do not exhibit these problems even when bonding metallic nickel film. Therefore, good productivity and a strong bonded structure can be obtained.

[0062] Furthermore, since adhesive 140 is epoxy-based, it can suppress outgassing. Also, because adhesive 140 hardens upon irradiation with ultraviolet light, assembly can be carried out at room temperature from the start of assembly to the application of preload, resulting in excellent mass productivity. In addition, since adhesive 140 hardens with a delay after irradiation with ultraviolet light, its assembly properties are not compromised.

[0063] Furthermore, in the above embodiment, since ultraviolet light L can be irradiated onto the adhesive 140 before bringing the first and second ball bearings 120, 130 and other components into contact with the adhesive 140, it is possible to avoid the formation of uncured portions in the adhesive 140.

[0064] 5. Example of changes In the first embodiment, an inner circumferential projection 111 is formed on the sleeve 110, but the inner circumferential projection 111 may be integrated with the sleeve 110 or be a separate part. Alternatively, an outer circumferential projection may be formed on the shaft 150 instead of the inner circumferential projection 111. In this case, the end faces of the inner rings 121 and 131 of the first and second ball bearings 120 and 130 are brought into contact with the end face of the outer circumferential projection, and preloading is performed by pressing the outer ring 122 of the first ball bearing 120 with a preloading jig 160.

[0065] [2] Second embodiment The bearing device 100 is required to be low-cost as an industrial product and to be manufactured with minimal waste of resources. One way to meet these requirements is to minimize the use of cutting processes and maximize the use of plastic deformation processes in the processing of the component members. However, metal materials suitable for plastic deformation have low reactivity and are unsuitable for bonding with anaerobic adhesives. An example of how this problem has been solved is described below.

[0066] The basic structure of this embodiment is the same as that of the first embodiment, except that the metallic nickel coatings 118 and 153 are absent. In this example, the sleeve 110 and shaft 150 are made from SUS304 stainless steel and are processed by plastic deformation to the shape described in the first embodiment.

[0067] SUS304 is used as the material for the sleeve 110 and shaft 150 because it is suitable for plastic deformation. By employing plastic deformation, waste material can be reduced and raw material costs can be lowered. In addition, plastic deformation takes less time than machining, which can reduce manufacturing costs. It is also possible to perform some of the processing by machining.

[0068] While using SUS304 as the material for the sleeve 110 and shaft 150 facilitates plastic deformation, it creates difficulties in assembly using conventionally used anaerobic adhesives.

[0069] The following explains this point. SUS304 does not contain copper as an additive, and its curing reaction is reduced when anaerobic adhesives are used. As a result, the curing time increases, and the workability of the bonding process decreases.

[0070] Furthermore, SUS303Cu contains copper, an additive used to enhance machinability. As a result, it exhibits a high curing reaction rate for anaerobic adhesives, leading to excellent adhesion.

[0071] Delayed UV-curing epoxy adhesives do not suffer from the problem of poor curing reaction caused by a lack of metal ions contributing to the curing reaction, and good curing reactions can be obtained even when bonding SUS304. Substitutes for SUS304 include S10C and S20C. These materials have properties suitable for plastic deformation and are incompatible with anaerobic adhesives. The same applies to substitutes for SUS304 in other embodiments.

[0072] The manufacturing process for this modified example is described below. First, using SUS304 as the workpiece material, the sleeve 110 and shaft 150 are obtained by plastic deformation. Next, the bearing device 100 is assembled according to the procedure described in relation to Figure 4.

[0073] In the second embodiment, a metallic nickel coating 118 may be provided on the surface of the sleeve 110, and a metallic nickel coating 153 may be provided on the shaft 150. Alternatively, it is possible to provide only one of the metallic nickel coatings 118 or 153.

[0074] [3] Third embodiment 1. Bearing device configuration A third embodiment of the present invention will be described with reference to Figures 5 to 7. The bearing device 200 of the third embodiment differs from the first embodiment in that it does not have a sleeve 110 and does have a spacer 170. Therefore, components equivalent to those of the first embodiment are denoted by the same reference numerals and their descriptions are omitted. In this embodiment, both cases are possible, such as when a dust-preventing coating is present (see the first embodiment) and when there is no dust-preventing coating (see the second embodiment).

[0075] As shown in Figure 6, in the bearing device 200, a spacer 170 is interposed between the outer ring 122 of the first ball bearing 120 and the outer ring 132 of the second ball bearing 130. The spacer 170 is annular in shape, and a protrusion 171 is formed on its end face on the second ball bearing 130 side, which fits inside the outer ring 132. Due to this protrusion 171, the center of the spacer 170 coincides with the center of the outer ring 132.

[0076] 2. Assembly method of bearing device The assembly method of the bearing device 200 with the above configuration will be explained with reference to Figure 7. (1) Apply adhesive 140 to the outer circumference of the end of the shaft 150 near the flange portion 151 and irradiate with ultraviolet light L.

[0077] (2) Before the adhesive 140 begins to harden, the second ball bearing 130 is fitted onto the shaft 150 and pushed in until the adhesive 140 is in place, so that the end face of the inner ring 131 of the second ball bearing 130 comes into contact with the flange portion 151.

[0078] (3) The spacer 170 is passed through the shaft 150, and its protrusion 171 is fitted onto the outer ring 132 of the second ball bearing 130. (4) Apply adhesive 140 to the outer circumference of the end portion of the shaft 150 that is away from the flange portion 151, and irradiate the adhesive 140 with ultraviolet light L.

[0079] (5) Before the adhesive 140 begins to harden, the first ball bearing 120 is fitted onto the shaft 150 so that the end face of the outer ring 122 comes into contact with the end face of the spacer 170. This causes the inner surface of the inner ring 121 of the first ball bearing 120 to come into contact with the adhesive 140.

[0080] (6) The outer rings 122 and 132 of the first and second ball bearings 120 and 130 are held in place with a suitable jig, and the inner ring 121 of the first ball bearing 120 is pressed with the pre-pressure jig 160. This is maintained until the adhesive has hardened to a certain extent and the pre-pressure does not leak out.

[0081] (7) The first hub cap 128 (see Figure 6) is fixed to the outer circumference of the shaft 150. After that, since the adhesive has not fully cured, the bearing device 200 is placed in an oven and heated to complete the curing process.

[0082] In the second embodiment, the end face of the spacer 170 is in contact with the end faces of the outer rings 122 and 132 of the first and second ball bearings 120 and 130, but it may also be in contact with the end faces of the inner rings 121 and 131. In this case, preloading is performed by pressing the outer ring 122 of the first ball bearing 120 with a preloading jig 160.

[0083] [4] Fourth Embodiment This embodiment is an example of a hard disk drive using the bearing device 100 shown in Figure 2. Figure 8 is a perspective view showing the overall configuration of the hard disk drive 300 using the bearing device 100. The hard disk drive 300 includes a base portion 101 having a recess 117, in which a spindle motor 102 and a plurality of hard disks 113 attached to the spindle motor 102 and rotating are arranged. Also arranged in the recess 117 is a swing arm assembly 201 having a swing arm 210 that supports a plurality of magnetic heads 112 facing each of the hard disks 113, an actuator 114 that drives the swing arm 210, and a control unit 115 that controls these devices. A cover portion is attached to the upper surface of the base portion 101 to keep the recess 117 airtight, but the cover portion is omitted in Figure 1.

[0084] The swing arm assembly 201 has a structure that uses the bearing device 100 to hold the swing arm 210 of the hard disk drive unit 300 in a rotatable state. A through hole (not shown) is provided in the shaft portion of the swing arm 210. The bearing device 100 is fitted into this through hole. The bearing device 200 shown in Figure 6 can also be used in the hard disk drive unit 300.

[0085] [5] Fifth embodiment This embodiment is an example of a motor utilizing the bearing device 100 shown in Figure 2. Figure 9 is a cross-sectional view showing a motor 400 using the bearing device 100. In this embodiment, a third hub cap 190 is fixed to the outer rings 122 and 132 of the first and second ball bearings 120 and 130. The motor 400 uses the bearing device 100 described above. However, in the motor 400, instead of adhesive fixing with a gap between the shaft member and the inner ring of the bearing device 100, press-fit fixing may be used. That is, the outer surface of the shaft 152 and the inner surfaces of the inner rings 121 and 131 may be press-fitted, and a gap may be provided between the inner surface of the sleeve 110 and the outer surfaces of the outer rings 122 and 132, with a delayed ultraviolet curing epoxy adhesive provided in the gap for adhesive fixing.

[0086] In Figure 9, reference numeral 410 denotes the casing. The casing 410 is cylindrical in shape. The outer surface of the sleeve 110 of the bearing device 100 is fixed to the inner surface of the casing 410. The stator core 420 is also fixed to the inner surface of the casing 410. The stator core 420 is made of multiple thin, ring-shaped soft magnetic material (e.g., electrical steel sheet) stacked in the axial direction, and has multiple pole teeth that protrude radially inward. The multiple pole teeth are arranged at equal intervals along the circumferential direction, and a coil 421 is wound around each of them.

[0087] A spacer 180 is fixed to the shaft 152 adjacent to the inner ring 121 of the first ball bearing 120. A cylindrical rotor magnet 430 is also fixed to the shaft 152 adjacent to the spacer 180. The rotor magnet 430 is magnetized such that adjacent portions of SNSN·· along the circumferential direction have alternating opposite polarities. The outer circumference of the rotor magnet 430 faces the inner circumference of the pole teeth of the stator core 420 with a gap between them. When a drive current is supplied to the coil 421, a driving force is generated that attempts to rotate the rotor magnet 430, causing the rotor magnet 430 to rotate around the shaft 152 as its axis relative to the casing 410. The shaft 152 protrudes from an opening 190a formed in the third hub cap 190, and an impeller 450 is attached to its end. In this way, the motor 400 is configured as a blower.

[0088] The bearing device 200 in Figure 6 can also be used in the motor 400. In this case, the bearing device 200 is inserted inside the cylindrical casing 410, which is the cylindrical outer member. In this structure, a gap is provided between the outer circumference of the outer ring 122 of the first ball bearing 120 and the inner circumference of the casing 410, and adhesive 140 is provided (filled) in this gap, fixing the outer ring 122 of the first ball bearing 120 to the inner circumference of the casing 410. Also, a gap is provided between the outer circumference of the outer ring 132 of the second ball bearing 130 and the inner circumference of the casing 410, and adhesive 140 is provided (filled) in this gap, fixing the outer ring 132 of the second ball bearing 130 to the inner circumference of the casing 410.

[0089] The sleeve 110 may be fixed to the casing 410 using a delayed UV-curing epoxy adhesive. The stator core 420 may be fixed to the casing 410 using a delayed UV-curing epoxy adhesive. The spacer 180 may be fixed to the shaft 152 using a delayed UV-curing epoxy adhesive. The rotor magnet 430 may be fixed to the shaft 152 using a delayed UV-curing epoxy adhesive.

[0090] [6] Sixth Embodiment 1. Bearing device configuration A bearing device 500 according to the sixth embodiment of the present invention will be described with reference to Figures 10 to 13. In the bearing device 500, a spacer 141 is interposed between the inner ring 121 of the first ball bearing 120 and the inner ring 131 of the second ball bearing 130. The spacer 141 is press-fitted onto the shaft 152. In this embodiment, the inner rings 121 and 131 are press-fitted onto the shaft 152 on both sides of the spacer 141. On the other hand, the outer circumferential surfaces of the outer rings 122 and 132 are bonded to the inner circumferential surface of the sleeve 110 with adhesive 140 on both sides of the inner circumferential projection 111.

[0091] An O-ring (elastic member) 161 is interposed between the outer ring 122 of the first ball bearing 120 and the end face of the inner circumferential projection 111. In the state shown in Figure 10, the O-ring 161 is compressed, and the reaction force biases the outer ring 122 axially to the left (outward). In other words, the outer ring 122 is biased axially to the left (outward) than the inner ring 121, and as the adhesive 140 hardens in this biased state, a fixed position preload is applied to the first ball bearing 120. The outer ring 132 is also biased axially to the right (outward), and a fixed position preload is also applied to the second ball bearing 130.

[0092] The sleeve 110 is obtained by plastic deformation using SUS304 as the material. By using a delayed UV-curing epoxy adhesive as the adhesive 140, good workability and high adhesive strength can be obtained when bonding the outer rings 122 and 132 to the sleeve 110.

[0093] Figure 11 shows a motor 600 incorporating the bearing device 500 with the above configuration. Aside from the bearing device 500, the motor 600 has the same blower configuration as the motor 400 shown in Figure 9. The bearing device 500 can also be used in the structure that holds the swing arm 210 in a rotatable state in the hard disk drive unit 300 shown in Figure 8.

[0094] Figure 12 shows a modified example of the sixth embodiment described above. In this modified example, the thickness of the spacer 181 is made thicker than that of the sixth embodiment, and the outer diameter of the spacer 181 is made larger than the inner diameter of the seal member 127 (see Figure 3). As a result, the gap between the seal member 127 and the stepped portion 124a of the inner ring 121 and the spacer 181 overlap in the axial direction, suppressing grease leakage and the intrusion of water, dust, etc. from the outside. For this reason, in this modified example, the inner diameter of the fourth hub cap 191 is set to be larger.

[0095] 2. Assembly method of bearing device The assembly method of the bearing device 500 with the above configuration will be explained with reference to Figure 13. (1) The inner ring 121 of the first ball bearing 120 is press-fitted onto the shaft 152 up to one end of the shaft 152. (2) The spacer 141 is pressed onto the shaft 152 and brought into contact with the end face of the inner ring 121 of the first ball bearing 120. (3) Apply adhesive 140 to the inner circumference of the other end of sleeve 110, and irradiate the adhesive 140 with ultraviolet light L.

[0096] (4) Before the adhesive 140 begins to harden, the second ball bearing 130 is fitted onto the inner circumference of the sleeve 110, and the end face of the outer ring 132 of the second ball bearing 130 is brought into contact with the end face of the inner circumference projection 111. This causes the outer circumferential surface of the outer ring 132 to come into contact with the adhesive 140. (5) Insert the O-ring 161 into the inner circumference of one end of the sleeve 110 (in the axial direction, on the opposite side of the inner circumference projection 111 from the second ball bearing 130) and bring it into contact with the inner circumference projection 111 of the sleeve 110.

[0097] (6) Apply adhesive 140 to the inner circumference of one end of sleeve 110 and irradiate with ultraviolet light L. (7) Before the adhesive 140 begins to harden, the shaft 152, with the spacer 141 and the inner ring 121 of the first ball bearing 120 pressed into it, is inserted into the sleeve 110, and the shaft 152 is pressed into the inner ring 131 of the second ball bearing 130. At this time, the O-ring 161 is pressed against the end face of the outer ring 122 of the first ball bearing 120. This causes the outer circumferential surface of the outer ring 122 of the first ball bearing 120 to come into contact with the adhesive.

[0098] (8) By leaving the assembly at room temperature in the state shown in Figure 13(8), the outer ring 122 is biased axially to one side (outward) by the reaction force of the compressed O-ring 161, causing the outer ring 122 to be biased axially to one side (outward) compared to the inner ring 121, and as the adhesive 140 hardens, a fixed position preload is applied to the first ball bearing 120. Also, since the outer ring 132 of the second ball bearing 130 is biased axially to the other side (outward), a fixed position preload is also applied to the second ball bearing 130.

[0099] (9) Since the adhesive 140 described above is not fully cured, the bearing device 500 is placed in an oven and heated to complete the curing. In step (4), instead of applying the adhesive 140 to the inner circumference of the sleeve 110, the adhesive 140 may be applied to the outer circumference of the outer ring 132 of the second ball bearing 130. Similarly, in step (6), instead of applying the adhesive 140 to the inner circumference of the sleeve 110, the adhesive 140 may be applied to the outer circumference of the outer ring 122 of the first ball bearing 120. Also, instead of press-fitting the shaft 152 into the inner rings 121 and 131, it may be fixed with the adhesive 140.

[0100] [7] Seventh Embodiment 1. Bearing device configuration Figure 14 shows a bearing device 700 according to the seventh embodiment of the present invention. This bearing device 700 uses a sleeve 119 that lacks the inner circumferential protrusion 111 of the sleeve 110 shown in the modified example of the sixth embodiment in Figure 12, and places a coil spring (elastic member) 116 in the empty space, while omitting the O-ring 161 and the fourth hub cap 191.

[0101] The sleeve 119 is manufactured by plastic deformation using SUS304 as the material. The coil spring 116 is positioned between the outer ring 122 of the first ball bearing 120 and the outer ring 132 of the second ball bearing 130. The biasing force of the coil spring 116 biases the outer rings 122 and 132 outward in the axial direction, and in this state, the outer rings 122 and 132 are fixed to the inner circumferential surface of the sleeve 119 with adhesive 140, thereby applying a fixed position preload to the first and second ball bearings 120 and 130. In addition, the coil spring 116 may be fixed to the inner circumferential surface of the sleeve 119 with adhesive 140 after the fixed position preload has been applied. In this case, it is preferable that the outer diameter of the coil spring 116 is approximately equal to the outer diameter of the outer ring 122 of the first ball bearing 120 and the outer ring 132 of the second ball bearing 130, or that it is in a clearance fit relationship with the inner circumferential surface of the sleeve 119.

[0102] 2. Assembly method of bearing device The assembly method of the bearing device 700 with the above configuration will be explained with reference to Figure 15. (1) The inner ring 121 of the first ball bearing 120 is press-fitted onto the shaft 152 up to the other end of the shaft 152 (the axial lower end in Figure 15). (2) The spacer 141 is pressed onto the shaft 152 and brought into contact with the end face of the inner ring 121 of the first ball bearing 120. (3) The coil spring 116 is passed through the shaft 152, and the coil spring 116 is brought into contact with the outer ring 122 of the first ball bearing 120.

[0103] (4) The inner ring 131 of the second ball bearing is press-fitted onto one end of the shaft 152 (the upper axial end in Figure 15), and the outer ring 132 presses against the coil spring 116, thereby forming a bearing assembly on the shaft 152 with the first and second ball bearings 120 and 130 mounted. (5) Apply adhesive 140 to the inner circumference of both ends of the sleeve 119 in the axial direction, and irradiate the adhesive 140 with ultraviolet light L.

[0104] (6) Before the adhesive 140 begins to harden, the bearing assembly prepared in step (4) is fitted into the sleeve 119. This causes the outer surfaces of the outer rings 122 and 132 of the first and second ball bearings 120 and 130 to come into contact with the adhesive 140.

[0105] (7) By leaving the assembly at room temperature in the state shown in Figure 15(7), the reaction force of the compressed coil spring 116 biases the outer rings 122 and 132 axially (outward), causing the outer rings 122 and 132 to be more axially (outward) than the inner rings 121 and 131, and as the adhesive 140 hardens, a fixed position preload is applied to the first ball bearing 120 and the second ball bearing 130.

[0106] (8) Since the adhesive 140 described above is not fully cured, the bearing device 700 is placed in an oven and heated to complete the curing. In step (5), instead of applying the adhesive 140 to the inner circumference of the sleeve 110, the adhesive 140 may be applied to the outer circumference of the outer rings 122 and 132 of the first and second ball bearings 120 and 130. Alternatively, instead of press-fitting the inner rings 121 and 131 onto the shaft 152, they may be fixed with the adhesive 140.

[0107] 3. Others The bearing device 700 can also be used in the structure that holds the swing arm 210 in a rotatable state in the hard disk drive device 300 shown in Figure 8. The bearing device 700 can also be used in the motor 400 shown in Figure 9 and the motor 600 shown in Figure 11. [Industrial applicability]

[0108] This invention can be used in industrial fields such as pivot assembly bearing devices for hard disk drives, bearing devices for blowers used in home appliances such as hair dryers and cleaners, bearing devices for motors used in automobiles, and bearing devices for machine tools. [Explanation of Symbols]

[0109] 100, 200, 500, 700…Bearing device, 101…Base part, 102…Spindle motor, 110…Sleeve (outer member), 111…Inner circumference projection (spacer part), 112…Magnetic head, 113…Hard disk, 114…Actuator, 115…Control unit, 116…Coil spring (elastic member), 117…Recess, 118…Metallic nickel coating, 119…Sleeve, 120…First ball bearing, 121, 131…Inner ring, 122, 132…Outer ring, 121a, 122a…Raceway surface, 123…Annular groove, 124…C-ring, 124a…Step part, 125, 135…Ball, 126, 136…Cage, 127…Seal member, 128…First hub cap, 1 29...Second hub cap, 130...Second ball bearing, 140...Adhesive, 141...Spacer, 150,152...Shaft (axis member), 151...Flange part, 153...Metal nickel coating, 160...Preload jig, 161...O-ring (elastic member), 170...Spacer, 171...Protrusion, 180,181...Spacer, 190...Third hub cap, 190a...Opening, 191...Fourth hub cap, 201...Swing arm assembly, 210...Swing arm, 300...Hard disk drive unit, 400,600...Motor, 410...Casing, 420...Stator core, 421...Coil, 430...Rotor magnet, 450...Impeller, L...Ultraviolet light.

Claims

1. It has a structure in which metal components are bonded together using a delayed-UV-curing epoxy adhesive. The bearing device wherein the constituent members are members on which a dust-preventing coating is formed on the surface or members that have undergone plastic deformation.

2. The bearing device according to claim 1, wherein the dust-preventing coating is a metallic nickel film formed by electroless nickel plating.

3. The bearing device according to claim 1, wherein the dust-preventing coating or the plastically deformed member does not contain Cu as an additive.

4. The bearing device according to claim 1, wherein the dust-preventing coating or the plastically deformed member has a Cu content of 0.05% by weight or less.

5. The bearing device according to claim 1, wherein the dust-preventing coating or the plastically deformed member is made of a material that has a lower efficiency in generating metal ions that contribute to the curing reaction of the anaerobic adhesive than SUS303Cu.

6. The bearing device according to claim 1, wherein the dust-preventing coating or the plastically deformed member has a lower content of elements that contribute to the generation of metal ions that contribute to the curing reaction of the anaerobic adhesive than SUS303Cu.

7. The bearing device according to any one of claims 1 to 6, wherein the curing start time of the adhesive is 10 seconds or more and 30 minutes or less after ultraviolet irradiation.

8. The bearing device according to any one of claims 1 to 6, wherein the viscosity of the adhesive before curing is 100 mPa·s to 1000 mPa·s at 25°C.

9. The bearing device according to any one of claims 1 to 6, wherein the glass transition temperature of the adhesive after curing is 100°C or higher.

10. A process of forming a dust-preventing coating on the surface of a component made of a metal material, A step of bonding the aforementioned member to other members using a delayed ultraviolet curing epoxy adhesive. A method for manufacturing a bearing device having

11. The method for manufacturing a bearing device according to claim 10, wherein the dust-preventing coating is a metallic nickel coating.

12. The method for manufacturing a bearing device according to claim 10 or claim 11, wherein the curing start time of the adhesive is 10 seconds or more and 30 minutes or less after ultraviolet irradiation.

13. The method for manufacturing a bearing device according to claim 10 or claim 11, wherein the viscosity of the adhesive before curing is 100 mPa·s to 1000 mPa·s at 25°C.

14. The method for manufacturing a bearing device according to claim 10 or claim 11, wherein the glass transition temperature of the adhesive after curing is 100°C or higher.

15. A process for obtaining a component made of metal material by plastic deformation, A step of bonding the aforementioned member to other members using a delayed ultraviolet curing epoxy adhesive. A method for manufacturing a bearing device having

16. The method for manufacturing a bearing device according to claim 15, wherein the curing start time of the adhesive is 10 seconds or more and 30 minutes or less after ultraviolet irradiation.

17. The method for manufacturing a bearing device according to claim 15, wherein the viscosity of the adhesive before curing is 100 mPa·s to 1000 mPa·s at 25°C.

18. The method for manufacturing a bearing device according to claim 15, wherein the glass transition temperature of the adhesive after curing is 100°C or higher.

19. A hard disk drive device equipped with a bearing device, The bearing device is It has a structure in which metal components are bonded together using a delayed-UV-curing epoxy adhesive. The aforementioned component is a hard disk drive device in which a dust-preventing coating is formed on the surface of the component or a component that has undergone plastic deformation.

20. A motor equipped with a bearing device, The bearing device is It has a structure in which metal components are bonded together using a delayed-UV-curing epoxy adhesive. The motor is a component in which a dust-preventing coating is formed on the surface or a component that has undergone plastic deformation.

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