JP4901171B2 - Bearing device and motor equipped with the same - Google Patents

Description

The present invention relates to a bearing device and a motor including the same.

  Sliding bearings (hereinafter simply referred to as “bearings”) are widely used in applications that support relative rotation, sliding, or sliding rotation with a shaft member. In particular, resin-made bearings are widely used because they are lightweight and have a small inertial force and can be mass-produced.

As such a bearing, for example, Patent Document 1 proposes a bearing component in which an electroformed part by electroforming is inserted into the shaft center of a resin molded part and molded. Thus, by providing the electroformed part on the inner periphery of the resin molded part and forming the inner peripheral surface serving as the bearing surface with metal, high wear resistance can be obtained.
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, the bearing gap between the inner circumferential surface of the bearing and the outer circumferential surface of the shaft member is set to a gap width as small as possible in order to suppress the shakiness of the shaft member. The amount of is very small. For this reason, if the lubricating oil is reduced due to scattering, evaporation, etc., it causes a lubrication failure due to insufficient lubricating oil, and causes problems such as generation of abnormal noise and wear of the member due to contact sliding between the bearing and the shaft member.

  An object of the present invention is to provide a bearing that has good lubrication with a shaft member, prevents abnormal noise and wear of the member, and has a long product life.

In order to solve the above-mentioned problems, the bearing of the present invention is formed by deposition on the outer peripheral surface of the master shaft, the electroformed part having the bearing surface on the inner periphery, and the electroformed part inserted in the inner periphery. A sliding bearing having a resin portion ; a shaft member inserted in an inner periphery of the sliding bearing ; and a bearing gap formed between the bearing surface and the outer peripheral surface of the shaft member and filled with lubricating oil. A bearing device comprising a surface where the bearing surface starts to precipitate on the surface of the master shaft, wherein the resin portion is formed of an oil-containing resin, and oil oozed from the resin portion is supplied to the bearing gap. And

  Thus, in this invention, the resin part of the bearing was shape | molded with the oil-containing resin. As a result, the lubricating oil is retained not only in the bearing gap but also in the resin portion, so that the amount of lubricating oil retained increases. Therefore, even if the lubricating oil is reduced due to scattering and evaporation, the oil that oozes from the resin part is supplied to the bearing gap, so the bearing device operates smoothly due to the oil film formed in the bearing gap, and abnormal noise due to poor lubrication And wear due to sliding contact with the shaft member can be avoided.

  The bearing surface formed by electroforming has a surface accuracy that follows the surface accuracy of the master shaft by accurately transferring the surface of the master shaft due to the characteristics of electroforming. Therefore, if the surface accuracy of the master shaft is increased, high bearing surface accuracy can be obtained, and the rotation accuracy and sliding accuracy of the bearing can be increased.

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, since the bearing of the present invention is well lubricated with the shaft member, it is possible to prevent the generation of abnormal noise and the wear of the member. Therefore, the product life can be extended as compared with conventional products that are prone to lubrication failure due to lack of lubricating oil.

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

A bearing 5 (see FIG. 3) showing an embodiment of the present invention is a process of masking a required portion of the master shaft 2, and a process of forming an electroformed shaft 1 by electroforming a non-mask portion (see FIG. 1). The electroformed shaft 1 is inserted and the resin portion 5 is injection molded with resin (see FIG. 2), and the electroformed portion 4 and the master shaft 2 are separated from each other.

  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” has both functions of the two bearings, and means a bearing that supports both rotational motion and linear motion between the shafts. Further, the “oscillating bearing” means a bearing that allows movement in the three-dimensional direction of the shaft, such as a ball joint.

The master shaft 2 is made of a conductive material, for example, hardened stainless steel, and is manufactured as a straight shaft having a circular cross section. 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 4, and so on. 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 master shaft 2 is preferably subjected to a surface treatment for reducing the frictional force with the electroformed part 4, for example, a fluorine-based resin coating.

  In addition to the solid shaft, the master shaft 2 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 master shaft is basically formed in a circular shape, but in the case of a sliding bearing, the cross section can be made into an arbitrary shape. It can also be a perfect circle shape. In a sliding bearing, the cross-sectional shape of the master shaft 2 is basically constant in the axial direction. However, a rotating bearing or a rotating / sliding bearing does not have a constant cross-sectional shape over the entire length of the shaft. May take the form.

  Since the accuracy of the outer peripheral surface of the master shaft 2 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 bearing for rotation, roundness is important from the viewpoint of avoiding contact with the bearing surface, and therefore the outer peripheral surface of the master shaft 2 needs to have as high a roundness 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 master shaft is finished to a roundness of 1.6 μm or less.

Masking is applied to the outer peripheral surface of the master shaft 2 except for the portion where the electroformed portion 4 is to be formed, as indicated by the dotted points in FIG. As the masking covering material 3, an existing product having non-conductivity and corrosion resistance against the electrolyte solution is selectively used.

The electroforming process is performed by immersing the master shaft 2 in an electrolyte solution containing metal ions such as Ni and Cu, and energizing the electrolyte solution to deposit a target metal on the surface of the master shaft 2. 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 4 is too thick, the peelability from the master shaft 2 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.

By passing through the above process, as shown in FIG. 1, the electroformed shaft 1 which manufactured the cylindrical electroformed part 4 on the outer periphery of the master shaft 2 is manufactured. When the masking covering material 3 is thin, both ends of the electroformed portion 4 may protrude toward the covering material 3 and a tapered chamfered portion may be formed on the inner peripheral surface. Using this chamfered portion, a flange portion that prevents the electroformed portion from falling off from the resin portion can be formed. In this embodiment, the case where a chamfer part is not formed is illustrated.

The electroformed shaft 1 is transferred to the injection molding process shown in FIG. 2, and insert molding is performed using the electroformed portion 4 and the master shaft 2 as insert parts.

  In this injection molding process, the electroformed shaft 1 is supplied into the mold composed of the upper mold 6 and the lower mold 7 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 7 is formed with a positioning hole 9 adapted to the outer diameter of the master shaft 2, and the lower end of the electroformed shaft 1 transferred from the previous process is inserted into the positioning hole 9 to position the electroformed shaft 1. Made. A guide hole 10 is formed coaxially with the positioning hole 9 in the upper die 6, and the movable die (upper die 6 in this embodiment) is changed to a fixed die (lower die 7 in this embodiment) at the time of clamping. When the mold is close and clamped, the upper end of the electroformed shaft 1 is first inserted into the guide hole 10 and the electroformed shaft 1 is centered. Further, the upper mold 6 and the lower mold 7 come into contact with each other, and the mold clamping is completed.

In the present embodiment, at the time of mold clamping completion shown in FIG. 2, the lower end of the electroformed shaft 1 abuts the lower end of the positioning holes 9, the upper end of the electroformed part 4 is located below the upper end surface of the molding surface, electroforming The lower end of the part 4 is located above the lower end surface of the molding surface. That is, the axial dimension of the electroformed part 4 is set smaller than the axial dimension of the molding surface. In this state, a resin material is injected into the cavity 8 through the spool 12, the runner 13, and the gate 14, and insert molding is performed.

  An oil-containing resin is used as the resin material used in the injection molding process. As the oil-impregnated resin, for example, a solidified (cured) lubricant component (lubricating oil or lubricating grease) dispersed and held in the resin can be used. The types of resin, lubricating oil, and lubricating grease used as the component are as follows. It can employ without limitation. Specific examples of the resin component of such an oil-containing resin include thermoplastic resins such as ultrahigh molecular weight polyolefin, polyphenylene sulfide, and liquid crystal polymer, and specific examples of the lubricating component include mineral oil, synthetic hydrocarbon oil, ester oil. And the like. Further, when a thermoplastic resin is used as the resin and a lubricating grease is used as the lubricating component, it is preferable to employ a lubricating grease having a dropping point higher than the melting point of the thermoplastic resin. Various fillers such as a reinforcing material (regardless of the form of fiber, powder, etc.) and a stress relaxation material may be added to these resin materials as necessary.

  The oil-containing resin that can be used in the present invention is not limited to the above. For example, a porous material obtained by blending a resin material with a water-soluble additive such as sodium chloride or sodium sulfate and immersing in water after molding to melt the additive It is also possible to use a quality resin impregnated with a lubricating oil. In this case, in order to prevent the lubricating oil impregnated inside from leaking out to the surroundings, it is desirable that the surface excluding the portion supplying the lubricating oil to the bearing gap is subjected to a sealing treatment. As a means for the sealing treatment, impregnation with resin or the like in the voids exposed on the surface, surface coating by forming a metal plating film such as nickel, etc. can be considered. In addition, resins containing oil-containing porous particles can also be used.

After the mold opening, the molded product removed from the mold has a structure in which the master shaft 2, the electroformed part 4, and the resin part 15 are integrated as shown in FIG. This molded product is then transferred to a separation step and separated into a bearing 5 composed of an electroformed part 4 and a resin part 15 and a master shaft 2.

In this separation step, the internal stress accumulated in the electroformed part 4 is released, so that the inner peripheral surface of the electroformed part 4 is expanded and peeled off from the outer peripheral surface of the master shaft 2. The internal stress is released by applying an impact to the master shaft 2 or the bearing 5 or by applying axial pressure between the inner peripheral surface of the electroformed part 4 and the outer peripheral surface of the master shaft 2. Is called. By releasing the internal stress, the inner peripheral surface of the electroformed part 4 is radially expanded to form an appropriate gap between the inner peripheral surface of the electroformed part 4 and the outer peripheral surface of the master shaft 2. By doing so, the master shaft 2 can be smoothly pulled out in the axial direction from the inner peripheral surface of the electroformed part 4, whereby the molded product can be obtained as a bearing 5 composed of the electroformed part 4 and the resin part 15, and the master shaft 2. And separated. Incidentally, the enlarged diameter of the electroformed part 4 can be controlled by varying e.g. the thickness of the electroformed part 4.

If only grant impact can not be feel more alert sufficiently enlarged to the inner periphery of the electroformed part 4, heat or cool the electroformed portion 4 and the master shaft 2, by causing the thermal expansion amount difference therebetween The master shaft 2 and the bearing 5 can also be separated.

  A bearing member is completed by inserting a separately manufactured shaft member into the inner periphery of the bearing 5 formed in this way, and filling the bearing gap between the inner peripheral surface of the bearing 5 and the outer peripheral surface of the shaft member with lubricating oil. (Not shown).

  In the present embodiment, as shown in FIG. 3, the inner peripheral surface of the bearing 5 is formed by the inner peripheral surface 4 a of the electroformed part 4 and the small diameter inner peripheral surface 15 a of the resin part 15. The surface 4 a acts as the bearing surface 11. Considering the composition of the resin material and molding conditions so that the small-diameter inner peripheral surface 15a of the resin portion 15 expands due to molding shrinkage when solidified after injection molding, a minute gap is formed between the outer peripheral surface of the master shaft 2 and the like. Can be formed. Thereby, the resin part 15 and the master shaft 2 can be easily separated. If the width of the minute gap is appropriate, in the bearing device in which the shaft member is inserted into the inner periphery of the bearing, the minute gap between the small-diameter inner peripheral surface 15a of the resin portion 15 and the outer peripheral surface of the shaft member is used as a capillary seal. It can function, and is effective in preventing the lubricating oil from flowing out from the bearing gap. In addition, after the master shaft 2 is separated, the small-diameter inner peripheral surface 15a may be formed by machining or the like.

  In this way, the capillary seal is configured by expanding the small-diameter inner peripheral surface 15a of the resin portion 15 and forming a small-diameter outer peripheral surface (not shown) on the outer peripheral surface of the shaft member that opposes the small-diameter inner peripheral surface 15a. You can also. Further, if the capillary seal is a taper seal in which the gap width is gradually reduced toward the bearing gap side, it is possible to prevent the lubricating oil from flowing out more effectively.

The master shaft 2 can also be used as the shaft member. In this case, the minute gap between the inner peripheral surface of the electroformed part 4 and the master shaft 2, which is formed in the separation process of the electroformed part 4 and the master shaft 2, functions as a bearing gap. Since this bearing gap has the characteristics that the clearance is extremely small and has high accuracy due to the characteristics of electroforming, it is possible to provide a bearing having high rotational accuracy or slidability. As described above, when a bearing is configured by replacing a separately manufactured shaft member, once the master shaft 2 is manufactured, it can be reused repeatedly. 5 can be further reduced in cost.

  Since the resin portion 15 made of oil-impregnated resin impregnated with oil partially faces the bearing gap, the resin portion 15 oozes out from the resin portion 15 when the bearing 5 is operated (rotation, sliding, rotational sliding, or swinging). The oil forms an oil film between the bearing surface 11 and the outer peripheral surface of the shaft member. Accordingly, since abundant lubricating oil is always present in the bearing gap, generation of noise due to poor lubrication due to lack of oil and wear due to contact sliding between the shaft member and the bearing 5 are avoided, and the product life is extended.

Further, the step portion 16 formed between the small-diameter inner peripheral surface 15a and the large-diameter inner peripheral surface 15b of the resin portion 15 is engaged with the upper end and the lower end of the electroformed portion 4, so that the shaft of the electroformed portion is formed. An anchor effect that prevents the direction from falling off is also obtained.

The present invention is not limited to the above embodiment. For example, by adjusting the axial dimension of the electroformed part 4 formed on the master shaft 2 by electroforming and the shapes of the molds 6 and 7, the entire inner peripheral surface of the bearing 5 is formed by the electroformed part 4. (See FIG. 4). In this case, the resin portion 15 made of oil-impregnated resin does not reach the bearing gap, but since the oil that has oozed out wraps around the upper end or the lower end of the electroformed portion 4 and reaches the bearing gap, the same lubricating effect as described above can be obtained.

  Further, as another embodiment, electroforming can be performed by masking a plurality of locations separated in the axial direction, and a plurality of electroformed surfaces spaced in the axial direction can be provided on the inner peripheral surface of the bearing 5 (FIG. 5). reference). According to this method, since only a necessary portion (for example, a dynamic pressure groove forming portion) can be used as an electroformed surface, the cost can be reduced. Further, if the area where the resin portion made of the oil-containing resin faces the bearing gap, the oil is easily supplied, and a smoother lubricating effect can be obtained. Furthermore, since the bearing surface 11 is formed at a plurality of locations separated in the axial direction, the bearing rigidity against moment load is also increased.

The bearing shown above can also be used as a hydrodynamic bearing that generates pressure by the hydrodynamic action of fluid in the bearing gap between the inner peripheral surface 4a of the electroformed part 4 and the outer peripheral surface of the shaft member. is there. In this dynamic pressure bearing, for example, a dynamic pressure generating portion such as a herringbone shape, a multi-arc surface, or a step surface is formed on the outer peripheral surface of a shaft member, and this dynamic pressure generating portion is electroformed. It can be configured by facing the perfect circular inner peripheral surface 4a of the portion 4. On the contrary, a dynamic pressure generating part can be formed on the inner peripheral surface 4 a of the electroformed part 4. In this case, the dynamic pressure generating part of the inner peripheral surface 4 a of the electroformed part is the outer periphery of the master shaft 2. It can be formed by forming a die corresponding to the shape of the dynamic pressure generating portion on the surface and performing electroforming. Thereafter, the bearing 5 and the master shaft 2 are separated by the same procedure, and a shaft member having a perfectly circular outer peripheral surface is inserted into the inner periphery of the bearing 5 to constitute a hydrodynamic bearing.

  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 includes a radial bearing portion R that supports the shaft member 22 rotatably in the radial direction, and a thrust bearing portion T that supports the shaft member 22 rotatably in the thrust direction. The radial bearing portion R is configured by inserting the shaft member 22 into the inner periphery of the bearing 5, and the thrust bearing portion T is a thrust plate in which the convex spherical shaft end of the shaft member 22 faces the end surface of the bearing 5. It is comprised by carrying out contact support by 23. The bearing 5 is formed by injection molding with 4 inserted as described in the above description. 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 22 are rotated together.

  As the shaft member 22 of the motor 21, not only the master shaft 2 but also another member replaced with the master shaft 2 can be used. Further, FIG. 6 illustrates the case where the thrust bearing portion T is constituted by a pivot bearing, but in addition, the shaft member 22 is supported in a non-contact manner in the thrust direction by a dynamic pressure generating means such as a dynamic pressure groove. A hydrodynamic bearing can also be used.

  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 be any one of a sliding bearing, a rotating / sliding bearing, and a swinging bearing. It can also be applied to.

1 is a perspective view of an electroformed shaft 1 of the present invention. It is a schematic diagram which shows the state (at the time of mold clamping) which attached the electroformed shaft 1 to the injection mold. It is sectional drawing of the oil-containing resin bearing 5 in the state provided with the master shaft 2 of this invention. It is sectional drawing which shows another embodiment of the oil-impregnated resin bearing. It is sectional drawing which shows another embodiment of the oil-impregnated resin bearing. It is a schematic diagram which shows the motor 21 to which this invention is applied.

DESCRIPTION OF SYMBOLS 1 Electroformed shaft 2 Master shaft 3 Coating material 4 Electroformed part 5 Bearing 6 Upper mold | type 7 Lower mold | type 11 Bearing surface 15 Resin part 16 Step part 21 Motor 22 Shaft member 23 Thrust plate 24 Rotor (disc hub)
25 Stator coil 26 Rotor magnet 27 Bracket R Radial bearing part T Thrust bearing part

Claims (3)

Is deposited formed on the outer peripheral surface of the master axis, electroformed portion having a bearing surface on the inner periphery, and a sliding bearing having a resin portion molded by insert to the inner peripheral of electric cast part, among the sliding bearing A shaft member inserted in the periphery, and a bearing gap formed between the bearing surface and the outer peripheral surface of the shaft member and filled with lubricating oil, and the bearing surface begins to precipitate on the surface of the master shaft. A bearing device comprising a flat surface,
A bearing device, wherein the resin portion is formed of an oil-containing resin, and oil that oozes from the resin portion is supplied to the bearing gap.   The bearing according to claim 1, wherein the resin portion is provided with a portion extending in an axial direction beyond an end portion of the electroformed portion, and an inner peripheral surface of the portion is opposed to an outer peripheral surface of the shaft member in a radial direction. apparatus.   A motor comprising the bearing device according to claim 1, a stator coil, and a rotor magnet.

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