JP4804894B2 - Bearing device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a bearing device that fits a shaft member into a shaft hole of a bearing and supports the shaft member so that both of them can rotate, slide, or slide and rotate relative to each other. The present invention relates to a bearing device that requires precise rotation, sliding, or sliding rotation, and a manufacturing method thereof.

As a bearing of such a bearing device, for example, Patent Document 1 proposes a bearing component in which an electroformed part by electroforming is inserted into a shaft and molded. According to this bearing part, since the inner peripheral surface of the electroformed part, which is an electroformed shell, forms the shaft hole of the bearing part, the roundness and the inner diameter dimensional accuracy are high, and the slidability is also good. The clearance with respect to the shaft member to be used by being mounted on the inner peripheral surface is minimized, and high-precision rotation, sliding, or sliding rotation is possible.
JP 2003-56552 A

  In a bearing device having the above-described bearing and a shaft member inserted in the inner periphery of the bearing, in order to maintain lubricity between the bearing and the shaft member, the inner peripheral surface of the bearing and the outer peripheral surface of the shaft member are A lubricating fluid (for example, lubricating oil) may be interposed therebetween. However, as described above, since the clearance between the electroformed part that becomes the bearing gap and the shaft member is set to a minimum, the amount of lubricating oil held in the bearing gap is extremely small. For this reason, if the lubricating oil decreases due to scattering to the outside due to the operation (for example, rotation) of the shaft member, evaporation, etc., it results in poor lubrication due to lack of lubricating oil, generation of abnormal noise, contact between the bearing and the shaft member Problems such as wear of members due to sliding occur. In addition, when the bearing device is used in a high temperature environment, the volume of the lubricating oil expands, and the lubricating oil that cannot be held in the minute bearing gaps leaks out, which may lead to contamination of the surrounding environment and a shortage of lubricating oil. .

  In order to avoid such a problem, it is conceivable to form a seal space at the end of the bearing. However, in order to form the seal space, a seal member manufactured separately, or the inner peripheral surface of the bearing or It is necessary to remove a part of the outer peripheral surface of the shaft member by machining or the like. As the number of members and the number of processes increase in this way, the manufacturing cost of the bearing device increases.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a bearing device having a long product life at low cost, which can avoid generation of abnormal noise, wear of members, and contamination of the surrounding environment.

  In order to solve the above-mentioned problems, the present invention has a bearing comprising an electroformed part and a holding part for holding the electroformed part, and a shaft member inserted in the inner periphery of the bearing, and the electroformed part has a shaft member. In a bearing device provided with a bearing surface opposed to the outer peripheral surface, the shaft member is provided with a small diameter portion and a large diameter portion, and the holding portion is provided with a molding surface formed with the large diameter portion of the shaft member, thereby bearing the electroformed portion. The surface and the molding surface of the holding portion are respectively opposed to the outer peripheral surface of the small diameter portion of the shaft member.

  In addition, the manufacturing method of the bearing device of the present invention includes a bearing including an electroformed portion and a holding portion that holds the electroformed portion, and a shaft member inserted in the inner periphery of the bearing, and the shaft member is disposed in the electroformed portion. In manufacturing a bearing device provided with a bearing surface facing the outer peripheral surface of the shaft member, after forming an electroformed portion using at least the small diameter portion as a master among shaft members having a small diameter portion and a large diameter portion, at least the shaft member is large. A holding part for holding the electroformed part is formed by injection molding with the diameter part as an inner mold, and then the shaft member is separated from the electroformed part and the holding part, and the outer peripheral surface of the small diameter part of the separated shaft member is pivoted. It is made to oppose the molding surface of the holding part shape | molded by the large diameter part of the member.

  As described above, in the present invention, the molding surface of the holding portion formed by the large diameter portion of the shaft member is opposed to the outer peripheral surface of the small diameter portion of the shaft member. The minute gap between the molding surface and the outer peripheral surface of the small-diameter portion of the shaft member has a larger gap width than the bearing gap between the bearing surface and the shaft member, so that more lubricating oil can be retained. Therefore, the minute gap functions as an oil reservoir for supplying oil to the bearing gap, and a problem due to lack of lubricating oil can be avoided. Also, by fulfilling the buffer function that absorbs the volume change accompanying the temperature change of the lubricating oil filled in the bearing gap with the minute gap, the lubricating oil expanded due to the high temperature of the bearing device's operating environment leaks to the outside of the bearing. Can be prevented.

  Further, the minute gap is formed by making a molding surface formed by using the large diameter surface of the shaft member as an inner mold in the injection molding process of the holding portion and the outer peripheral surface of the small diameter portion of the shaft member. That is, since the shaft member is separated from the electroformed part integrally formed by injection molding, the holding part, and the shaft member, the minute gap can be formed only by moving the shaft member in the axial direction. An oil sump can be formed at low cost without requiring a separate member or a separate process.

  Further, when such a minute gap is provided at the end portion of the inner peripheral surface of the bearing, the minute gap functions as a seal space, and leakage of the lubricating oil to the outside can be prevented.

  Since the motor including the bearing device, the stator coil, and the rotor magnet operates smoothly, no abnormal noise is generated and the product life is long.

  As described above, according to the present invention, it is possible to avoid generation of abnormal noise, wear of members, and contamination of the surrounding environment, and a bearing device having a long product life can be obtained at low cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The bearing 5 (see FIG. 4) constituting the bearing device showing the first embodiment of the present invention uses the shaft member 1 as a master and performs electroforming to form the electroformed shaft 4 (FIG. 1). And the process of separating the electroformed part 3 and the shaft member 1 from each other (see FIG. 3), and a process of separating the electroformed part 3 and the shaft member 1 from each other. Produced.

  In the following description, the “rotating bearing” means a bearing that supports relative rotation with the shaft member, and it does not matter whether the bearing is on the rotating side or the fixed side. “Sliding bearing” means a bearing that supports relative linear motion with respect to the shaft, and it does not matter whether the bearing is on the moving side or the stationary side. The “rotating and sliding bearing” refers to a bearing that has both functions of the two bearings and supports both rotational movement and linear movement with respect to the shaft.

  The shaft member 1 is made of a conductive material, for example, hardened stainless steel, and is manufactured as a shaft having a circular cross section having a large diameter portion and a small diameter portion as shown in FIG. Of course, the material is not limited to stainless steel, but it has a mechanical function such as rigidity, slidability, heat resistance, chemical resistance, workability and separability of the electroformed part 3, and the convenience of the bearing or the manufacture of the bearing. A material and a heat treatment method suitable for the characteristics required above are selected. Even non-metallic materials such as ceramics can be used by conducting a conductive treatment (for example, by forming a conductive metal film on the surface). The surface of the shaft member 1 is preferably coated with, for example, a fluorine-based resin coating in order to reduce friction with the bearing member when used as a bearing device.

  In addition to the solid shaft, the shaft member 1 may be a solid shaft in which a hollow shaft or a hollow portion is filled with resin. In addition, in the bearing for rotation, the cross section of the shaft member is basically formed in a circular shape, but in the case of the bearing for sliding, the cross section can be an arbitrary shape. It can also be a perfect circle shape. Further, in the sliding bearing, the cross-sectional shape of the sliding portion of the shaft member 1 is formed constant in the axial direction, but in the rotating bearing, the cross-sectional shape of the shaft member may take a form that is not constant in the axial direction. is there.

  Since the accuracy of the outer peripheral surface of the shaft member 1 directly affects the accuracy of the bearing gap described later, surface accuracy that is important for bearing functions such as roundness, cylindricity, and surface roughness is finished in advance with high accuracy. There is a need. For example, in a rotation bearing, since roundness is important from the viewpoint of avoiding contact with the bearing surface, it is necessary to increase the roundness of the outer peripheral surface of the shaft member 1 as much as possible. For example, it is desirable to finish to 80% or less of an average width (radial dimension) of a bearing gap described later. Therefore, for example, when the average width of the bearing gap is set to 2 μm, it is desirable that the outer peripheral surface of the shaft member is finished to a roundness of 1.6 μm or less.

  Masking is performed on the outer peripheral surface of the shaft member 1 except for the portion where the electroformed portion 3 is to be formed, as indicated by the dotted points in FIG. As the masking covering material 2, an existing product having non-conductivity and corrosion resistance against the electrolyte solution is selectively used.

  Electroforming is performed by immersing the shaft member 1 in an electrolyte solution containing metal ions such as Ni and Cu, and energizing the electrolyte solution to deposit the target metal on the surface of the shaft member 1. If necessary, the electrolyte solution may contain a sliding material such as carbon or a stress relaxation material such as saccharin. The type of electrodeposited metal is appropriately selected according to physical properties and chemical properties such as hardness and fatigue strength required for the bearing surface of the bearing. If the thickness of the electroformed part 3 is too thick, the peelability from the shaft member 1 is reduced, and if it is too thin, the durability of the bearing surface is reduced. The optimum thickness is set accordingly. For example, in a rotating bearing having a shaft diameter of 1 mm to 6 mm, the thickness is preferably 10 μm to 200 μm.

  The electroformed shaft 4 is transferred to the injection molding step shown in FIG. 3, and insert molding is performed using the electroformed portion 3 and the shaft member 1 as insert parts.

  In this injection molding process, the electroformed shaft 4 is supplied into the mold composed of the upper mold 7 and the lower mold 8 with its axial direction parallel to the mold clamping direction (the vertical direction in the drawing) as shown in FIG. Is done. The lower die 8 is formed with a positioning hole 10 adapted to the outer diameter of the outer peripheral surface 1b of the small diameter portion of the shaft member 1, and the lower end of the electroformed shaft 4 transferred from the previous process is inserted into the positioning hole 10 to The cast shaft 4 is positioned. The upper mold 7 is formed with a guide hole 11 having an inner diameter that matches the outer dimension of the outer peripheral surface 1a of the large-diameter portion of the shaft member 1 coaxially with the positioning hole 10, and is movable when the mold is clamped (in this embodiment, For example, when the upper die 7) is brought close to the fixed die (lower die 8 in this embodiment) and clamped, first, the upper end of the electroformed shaft 4 is inserted into the guide hole 11 and the electroformed shaft 4 is centered. Is called. Further, the upper mold 7 and the lower mold 8 come into contact with each other, and the mold clamping is completed.

  When the clamping shown in FIG. 3 is completed, the lower end of the electroformed shaft 4 hits the lower end of the positioning hole 10 and is formed between the large diameter outer peripheral surface 1a and the small diameter outer peripheral surface 1b of the shaft member 1. 1c is located below the upper end surface of the molding surface. In this embodiment, the electroformed part 3 is provided from the step part 1c until it contacts the lower end surface of the molding surface. In this state, a resin material is injected into the cavity 9 through the sprue 12, the runner 13, and the gate 14, and insert molding is performed.

  The resin material to be injected is a thermoplastic resin, and amorphous resins such as polysulfone (PSF), polyethersulfone (PES), polyphenylsulfone (PPSU), and polyetherimide (PEI) are crystalline resins. As the liquid crystal polymer (LCP), polyether ether ketone (PEEK), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), or the like can be used. Further, the type of filler to be filled in the above resin is not particularly limited, for example, fibrous filler such as glass fiber, whisker-like filler such as potassium titanate, scaly filler such as mica, carbon fiber, Fibrous or powdery conductive fillers such as carbon black, graphite, carbon nanomaterial, and metal powder can be used. These fillers may be used alone or in combination of two or more.

  A metal material can also be used as the injected material. For example, a low melting point metal material such as a magnesium alloy or an aluminum alloy can be used. In this case, strength, heat resistance, conductivity, etc. can be further improved as compared with the case of using a resin material. In addition, so-called MIM molding may be employed in which after injection molding with a mixture of metal powder and binder, degreasing and sintering.

  As shown in FIG. 4, the molded product removed from the mold after opening the mold has a structure in which the shaft member 1, the electroformed part 3, and the holding part 6 are integrated. The molded product is then transferred to a separation step and separated into a bearing 5 including the electroformed portion 3 and the holding portion 6 and the shaft member 1.

  In this separation step, the internal stress accumulated in the electroformed part 3 is released, so that the inner peripheral surface of the electroformed part 3 is expanded and separated from the outer peripheral surface of the shaft member 1. The internal stress is released by applying an impact to the shaft member 1 or the bearing 5 or by applying an axial pressure between the inner peripheral surface of the electroformed part 3 and the outer peripheral surface of the shaft member 1. Is called. By releasing the internal stress, the inner peripheral surface of the electroformed part 3 is radially expanded, and an appropriate size is provided between the inner peripheral surface 3a of the electroformed part 3 and the small diameter outer peripheral surface 1b of the shaft member 1. By forming the gap, the shaft member 1 can be moved in the axial direction with respect to the inner peripheral surface of the electroformed part 3, whereby the molded product has a bearing 5 including the electroformed part 3 and the holding part 6, It is separated into the shaft member 1. The diameter expansion amount of the electroformed part 3 can be controlled by changing the thickness of the electroformed part 3, the composition of the electrolyte solution, and the electroforming conditions, for example.

  When the diameter of the inner periphery of the electroformed part 3 cannot be sufficiently expanded only by applying an impact, the electroformed part 3 and the shaft member 1 are heated or cooled, thereby causing a difference in thermal expansion between them. The shaft member 1 and the bearing 5 can also be separated.

  Further, by considering the composition of the resin material and molding conditions so that the surface of the holding portion 6 in contact with the shaft member 1 is expanded by molding shrinkage when solidified after injection molding, the holding portion 6 and the shaft member 1 Can be easily separated.

  After separating the bearing 5 and the shaft member 1 in this way, by moving the shaft member 1 upward, the outer peripheral surface 1b of the small diameter portion of the shaft member 1 and the holding portion 6 formed by the large diameter portion of the shaft member 1 The molding surface 6a is opposed (see FIG. 5). At this time, the inner peripheral surface 3a of the electroformed portion 3 facing the small diameter outer peripheral surface 1b of the shaft member 1 functions as a bearing surface. Since the bearing gap between the bearing surface and the outer peripheral surface 1b of the small diameter portion of the shaft member 1 has the characteristics that the clearance is extremely small and highly accurate from the characteristics of electroforming, high rotational accuracy or sliding It is possible to provide a bearing having a property. Further, since it is only necessary to move the shaft member 1 while it is inserted into the inner periphery of the bearing 5, for example, foreign matter is mixed in compared to the case where a shaft member manufactured separately after the shaft member 1 is removed from the bearing 5 is inserted. Therefore, there is little risk of abnormal noise due to foreign matter or wear of members.

  Further, a minute gap 15 is formed between the outer peripheral surface 1 b of the small diameter portion of the shaft member 1 and the molding surface 6 a of the holding portion 6. As is apparent from the manufacturing processes so far, the minute gap 15 is set to a gap width larger than the bearing gap. By filling the bearing gap and the minute gap 15 with lubricating oil, the bearing device is completed.

  When the bearing 5 operates (rotates, slides, or rotates and slides), the lubricating oil retained in the minute gap 15 is supplied to the bearing gap. Generation of noise due to poor lubrication and wear due to contact sliding between the shaft member and the bearing 5 are avoided, and the product life is extended. In addition, since the minute gap 15 performs a buffer function, even if the volume of the lubricating oil expands as the operating environment of the bearing device increases, leakage of the lubricating oil to the outside of the bearing can be prevented. Etc. can be avoided.

  Further, since the minute gap 15 also functions as a seal space, it is possible to prevent the lubricating oil from leaking out or splashing with the operation of the bearing 5, reducing the lubricating oil, contaminating the surrounding environment, etc. Can be prevented more reliably. The gap width of the minute gap 15 is set in a range where a capillary force can be obtained so that the lubricating oil does not leak out, for example, 0.5 mm or less, preferably 0.3 mm or less.

  The present invention is not limited to the above embodiment. In the bearing device according to the second embodiment of the present invention shown in FIG. 6, the axial dimension of the electroformed part 3 is shorter than that of the first embodiment, and the minute gap 15 and the electroformed part 3 are separated in the axial direction. is doing. Thus, since the electroformed part 3 is formed only in the minimum necessary part, cost reduction can be aimed at.

  In the bearing device according to the third embodiment of the present invention shown in FIG. 7, electroformed portions 31 and 32 are formed on the large-diameter inner peripheral surface 5a and the small-diameter inner peripheral surface 5b of the bearing 5, respectively. According to this, even when using a bearing device without lubricating oil, for example, the molding surface (large-diameter inner peripheral surface) of the holding portion 6 formed by the large-diameter portion of the shaft member 1 and the small-diameter outer peripheral surface of the shaft member 1 Since the minute gap 15 formed between 1b acts as a relief portion, a plurality of bearing surfaces separated in the axial direction can be provided, and the bearing rigidity against moment load can be increased. When the bearing device is used by filling the bearing with lubricating oil, the molding surface (large-diameter inner peripheral surface) of the holding portion 6 molded with the large-diameter portion of the shaft member 1 and the small-diameter portion of the shaft member 1 are used. The minute gap 15 formed between the outer peripheral surface 1b serves as an oil sump, thereby preventing oil shortage.

  The fourth embodiment of the present invention shown in FIG. 8 is different from the other embodiments in that the lower end side opening of the bearing 5 is closed with a thrust plate 23. In this case, similarly to the other embodiments, the shaft member is shifted upward, and the outer peripheral surface 1b of the small diameter portion of the shaft member 1 and the molding surface 6a of the holding portion 6 molded by the large diameter portion of the shaft member 1 are formed. A minute gap 15 is formed therebetween, and then the thrust plate 23 is fixed to the lower end opening of the bearing 5. In this embodiment, the lower end portion 1d of the shaft member is formed in a convex spherical shape, and a thrust bearing portion T that supports the shaft member 1 in the thrust direction is formed between the lower end portion 1d and the upper end surface 23a of the thrust plate 23. It is formed.

  Next, the bearing device provided with the bearing described above is applied to support the rotating shaft of the motor 21, and one embodiment thereof will be described with reference to FIG.

  The motor 21 in the illustrated example is a spindle motor used in a disk drive device such as an HDD. The bearing device of the motor 21 has a radial bearing portion R that supports the shaft member 1 rotatably in the radial direction, and a thrust bearing portion T that supports the shaft member 1 rotatably in the thrust direction. The radial bearing portion R is constituted by the outer peripheral surface of the shaft member 1 and the inner peripheral surface of the electroformed portion 3, and the thrust bearing portion T is opposed to the end surface of the bearing 5 with the convex spherical shaft end of the shaft member 1. It is configured by contacting and supporting with the thrust plate 23 made to be. As described in the above description, the bearing 5 is formed by injection molding in which the electroformed part 3 is inserted. In addition to the bearing device, the motor 21 includes a rotor (disk hub) 24 on which a shaft member is mounted, and a stator coil 25 and a rotor magnet 26 that are opposed to each other with a gap in the radial direction, for example. The stator coil 25 is attached to the outer periphery of the bracket 27, and the rotor magnet 26 is attached to the inner periphery of the disk hub 24. The disk hub 24 holds one or more magnetic disks D.

  When the stator coil 25 is energized, the rotor magnet 26 is rotated by the electromagnetic force between the stator coil 25 and the rotor magnet 26, whereby the disk hub 24 and the shaft member 1 are rotated together. At this time, the oil retained in the minute gap 15 is supplied to the radial bearing portion R and the thrust bearing portion T.

  FIG. 9 illustrates the case where the thrust bearing portion T is configured by a pivot bearing, but in addition to this, the dynamic pressure in which the shaft member 1 is supported in a non-contact manner in the thrust direction by dynamic pressure generating means such as a dynamic pressure groove. A bearing can also be used. Or a flange part can be provided in the lower end part of the shaft member 1, and it can also be made to act as a retaining from the bearing 5. FIG.

  The bearing device of the present invention is not limited to the above examples, and can be widely applied to support a rotating shaft of a motor. Since this bearing device has a high-precision bearing gap (radial bearing gap) in the radial bearing portion R as described above, information that requires high rotational accuracy, such as a spindle motor for driving a magnetic disk such as the HDD described above. It is particularly suitable for supporting a rotating shaft in a small motor for equipment, for example, a spindle motor for driving a magneto-optical disk of an optical disk or a polygon scanner motor of a laser beam printer. It can also be applied to fan motors that require a long service life.

  Although the case where the bearing 5 is used as a bearing for rotation is illustrated in the above description, the bearing 5 can also be applied to a sliding bearing and a bearing for rotation and sliding. When the present invention is applied to a sliding or rotary sliding bearing, it is necessary to set the sliding range of the bearing so that the bearing does not interfere with the step portion between the large diameter portion and the small diameter portion of the shaft member. .

1 is a perspective view of a shaft member 1. FIG. 3 is a perspective view of an electroformed shaft 4. FIG. It is sectional drawing which shows the state (at the time of mold clamping) which attached the electroformed shaft 4 to the injection mold. It is sectional drawing which shows the state by which the bearing 5 and the shaft member 1 were integrally molded. It is sectional drawing of the bearing apparatus which shows the 1st Embodiment of this invention. It is sectional drawing of the bearing apparatus which shows the 2nd Embodiment of this invention. It is sectional drawing of the bearing apparatus which shows the 3rd Embodiment of this invention. It is sectional drawing of the bearing apparatus which shows the 4th Embodiment of this invention. It is sectional drawing which shows the motor 21 to which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shaft member 1a Large-diameter part outer peripheral surface 1b Small-diameter part outer peripheral surface 2 Coating | covering material 3 Electroformed part 4 Electroformed shaft 5 Bearing 6 Holding | maintenance part 6a Forming surface 15 Minute clearance 21 Motor 25 Stator coil 26 Rotor magnet

Claims (4)

A bearing having an electroformed part and a holding part that holds the electroformed part, and a shaft member inserted in the inner periphery of the bearing, and the electroformed part provided with a bearing surface facing the outer peripheral surface of the shaft member In the device
The shaft member is provided with a small-diameter portion and a large-diameter portion, and the holding portion is provided with a molding surface formed by the large-diameter portion of the shaft member, and the bearing surface of the electroformed portion and the molding surface of the holding portion are respectively provided with a small diameter of the shaft member. Bearing device characterized by facing the outer peripheral surface of the part. The bearing device according to claim 1, wherein a minute gap between the molding surface of the holding portion formed by the large diameter portion of the shaft member and the outer peripheral surface of the small diameter portion of the shaft member is formed at an end portion of the inner peripheral surface of the bearing.   A motor comprising the bearing device according to claim 1, a rotor magnet, and a stator coil. A bearing having an electroformed part and a holding part that holds the electroformed part, and a shaft member inserted in the inner periphery of the bearing, and the electroformed part provided with a bearing surface facing the outer peripheral surface of the shaft member When manufacturing the device,
Among shaft members having a small diameter portion and a large diameter portion, after forming an electroformed portion using at least the small diameter portion as a master, the electroformed portion is held by injection molding using at least the large diameter portion of the shaft member as an inner mold. After forming the holding portion, the shaft member is separated from the electroformed portion and the holding portion, and the outer peripheral surface of the small-diameter portion of the separated shaft member is opposed to the molding surface of the holding portion formed by the large-diameter portion of the shaft member. A method for manufacturing a bearing device.

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