JP4584093B2 - Plain bearing - Google Patents

Description

  The present invention relates to a sliding bearing which is an injection molded product of a resin with a metal part inserted.

  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 in various devices including industrial devices 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 is inserted into the axis of a resin molded part and is molded. Thus, by providing the electroformed part on the inner periphery of the resin molded part and forming the inner peripheral surface that becomes the bearing surface with metal, the wear resistance of the bearing surface is improved, and a highly durable bearing is obtained. .
JP 2003-56552 A

  In such a bearing, the coupling force between the inserted metal part and the resin part holding the metal part becomes a problem. If this bonding force is insufficient, the metal part and the resin part may be peeled off by an impact load or the like, which may adversely affect the bearing performance.

  An object of the present invention is to provide a bearing in which a metal part and a resin part are firmly bonded and have excellent durability.

In order to solve the above problems, the present invention comprises a metal part formed by electroforming, and a resin part molded by inserting the metal part into the inner periphery, and a bearing surface on the inner peripheral surface of the metal part A sliding bearing that supports relative rotation with a shaft member that is inserted into the inner periphery of the metal part, wherein a part of the outer peripheral surface of the metal part is removed, and the removal part includes When the resin part enters, the metal part and the resin part are engaged in the axial direction, and a dynamic pressure generating part is formed on the bearing surface by a mold formed on the outer peripheral surface of the master shaft. And

  As described above, the present invention is characterized in that a part of the outer peripheral surface of the metal portion is removed and the resin portion enters therein. Thereby, since an anchor effect is exhibited and a metal part and a resin part are combined firmly, peeling with a metal part and a resin part and various troubles resulting from this can be avoided.

  When the above metal part is formed by electroforming, the inner peripheral surface of the metal part that becomes the bearing surface can be finished with high surface accuracy, so the bearing gap can be set with high accuracy and the bearing performance can be improved. It is done.

  Further, the removal of the metal part can be performed until reaching the inner peripheral surface of the metal part, that is, until the metal part penetrates in the radial direction. In this case, the resin material that has entered the removal portion at the time of injection molding is molded in a state of being in close contact with the surface of the inner mold (core) inserted in the inner periphery of the metal portion. The surface molded into the inner mold undergoes molding shrinkage as it solidifies, but the molding shrinkage appears as a displacement toward the outer diameter side, and the resin material composition is selected so that this displacement amount is appropriate, or If the molding conditions are set, it is possible to form a groove with the resin portion as the bottom between the metal portions. This groove can be used, for example, as a dynamic pressure groove for generating a fluid dynamic pressure action in the bearing gap. In addition, the groove can be used as an oil retaining portion. As a representative example of a resin material that causes molding shrinkage toward the outer diameter side, a resin material having a liquid crystal polymer (LCP) as a base resin can be given.

  When the metal portion is removed by laser processing, the metal portion can be removed with high accuracy. Therefore, even when the dynamic pressure groove is formed by the removal portion, an accurate dynamic pressure groove can be obtained.

  A motor including a bearing device having the above-described bearing has excellent durability.

  As described above, according to the present invention, it is possible to provide a bearing in which the metal portion and the resin portion are firmly coupled and have excellent durability.

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

  FIG. 1 is a cross-sectional view of a bearing device 1 including a bearing 3 and a shaft member 2 inserted into the inner periphery of the bearing 3. Of these, the bearing 3 includes a metal part 4 and a resin part 5 that holds the metal part 4 on the inner periphery.

  The bearing surface 3 a provided on the inner peripheral surface of the bearing 3 is constituted by the inner peripheral surface 4 a of the metal portion 4. A plurality of removal portions 6 are formed on the outer peripheral surface of the metal portion 4. The resin portion 5 has a substantially cylindrical shape and is formed by molding a resin.

  Hereinafter, the manufacturing process of the bearing 3 will be described. The bearing 3 includes a step of depositing and forming a metal part 4 which is an electroformed shell on the outer surface of the master shaft 7 (electroforming process), a step of removing a part of the outer peripheral surface of the metal part 4 (removing step), a metal The resin part 5 is molded through the process of molding the resin part 5 using the part 4 and the master shaft 7 as insert parts (insert molding process) and the process of separating the metal part 4 and the master shaft 7 in order.

  The master shaft 7 used in the present embodiment is formed of, for example, a stainless steel that has been subjected to a quenching process so as to have a perfect cross-sectional outline and a uniform diameter in the axial direction. The material of the master shaft 7 can be arbitrarily selected from metals and non-metals as long as it has a masking property, conductivity, and chemical resistance, such as a chromium alloy or a nickel alloy, in addition to stainless steel. It is. When the master shaft 7 is used as the shaft member 2, it is desirable that the material satisfy the mechanical strength, rigidity, slidability, heat resistance, etc. required for the components of the bearing 3 in addition to the above characteristics. In this case, it is desirable to perform a surface treatment for reducing the frictional force with the metal part 4, for example, a fluorine-based resin coating, on at least a region where the metal part 4 is to be formed on the outer surface of the master shaft 7.

  The master shaft 7 may be a solid shaft in which a hollow shaft or a hollow portion is filled with another material (resin or the like), in addition to the peeled shaft (solid shaft). Further, the accuracy of the outer peripheral surface of the master shaft 7 directly affects the surface accuracy of the inner peripheral surface 4a of the metal part 4 that becomes the bearing surface 3a of the bearing 3, so that it is desirable to finish it as high as possible.

  Non-conductive masking is performed in advance on the outer surface of the master shaft 7 except for the region where the metal part 4 is to be formed (indicated by dotted points in FIG. 2). As the covering material for forming the masking portion 8, a material having non-conductive properties and corrosion resistance to the electrolyte solution is selectively used.

  The electroforming process is performed by immersing the master shaft 7 subjected to the above treatment in an electrolyte solution and energizing the electrolyte solution to deposit a target metal on the surface of the master shaft 2. As the electrolyte solution, a solution containing a metal (for example, Ni, Cu, or the like) that is a deposition material of the metal portion 4 is used. The kind of the deposited metal is appropriately selected according to required properties such as hardness required for the bearing surface 3a or resistance to lubricating oil (oil resistance). Further, the electrolyte solution can contain a sliding material such as carbon or a stress relaxation material such as saccharin, if necessary. Thus, as shown in FIG. 2, the metal portion 4 is deposited and formed at a predetermined location on the outer peripheral surface of the master shaft 7.

  Next, as shown in FIG. 3, a part of the outer peripheral surface 4b of the metal part 4 formed in the electroforming process is removed by an appropriate method such as laser machining or machining, and the removal part 6 shown by cross hatching is removed. Form (removal step). In the drawing, the case where the annular removal portions 6 are formed at three positions apart in the axial direction is illustrated, but the shape and number of the removal portions 6 are not limited to those in the illustrated example.

  A part (hereinafter, referred to as an electroformed shaft 9) made of the metal part 4 and the master shaft 7 manufactured through the above steps is supplied as an insert part into a molding die for insert molding the resin part 5.

  FIG. 4 conceptually shows an insert molding process of the resin portion 5, and a runner 12, a gate 13, and a cavity 14 are provided in a mold including the fixed mold 11 and the movable mold 10. In this embodiment, the gate 13 is a dotted gate, and is formed at a plurality of locations (for example, at equal intervals in the circumferential direction) at positions corresponding to one axial end surface of the resin portion 5 of the molding die (movable mold 10). Three places) formed. The gate area of each gate 13 is set to an appropriate value according to the viscosity of the molten resin to be filled and the shape of the molded product.

  In the mold configured as described above, the movable mold 10 is brought close to the fixed mold 11 and clamped while the electroformed shaft 9 is positioned at a predetermined position. Next, in a state where the mold is clamped, molten resin P is injected and filled into the cavity 14 through the spool (not shown), the runner 12, and the gate 13, and the resin portion 5 is molded integrally with the electroformed shaft 9. To do.

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

  After the mold opening, the molded product in which the master shaft 7, the metal part 4, and the resin part 5 are integrated is removed from the molds 10 and 11. This molded product is separated into a bearing 3 (see FIG. 1) composed of the metal part 4 and the resin part 5 and the master shaft 7 in a subsequent separation step.

  In this separation step, the internal stress accumulated in the metal part 4 is released, so that the inner peripheral surface of the metal 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 7 or the bearing 3 or by applying an axial pressure between the inner peripheral surface of the metal part 4 and the outer peripheral surface of the master shaft 7. . By releasing the internal stress, the inner peripheral surface of the metal portion 4 is radially expanded to form a gap having an appropriate size between the inner peripheral surface of the metal portion 4 and the outer peripheral surface of the master shaft 7. Thus, the master shaft 7 can be smoothly pulled out from the inner peripheral surface of the metal portion 4 in the axial direction. As a result, the molded product is separated into the bearing 3 including the metal portion 4 and the resin portion 5 and the master shaft 7. The diameter expansion amount of the metal part 4 can be controlled, for example, by changing the thickness of the metal part 4.

  When the inner circumference of the metal part 4 cannot be sufficiently expanded only by applying an impact, the metal part 4 and the master shaft 7 are heated or cooled to cause a difference in thermal expansion between them, thereby producing a master. The shaft 7 and the bearing 5 can also be separated.

  Thereby, the bearing 3 which uses the inner peripheral surface 4a of the metal part 4 as the bearing surface 3a is obtained. Thus, since the bearing surface 3a formed by electroforming has an accuracy that follows the outer peripheral surface accuracy of the master shaft 7, if the outer peripheral surface accuracy of the master shaft 7 is increased, a highly accurate bearing surface 3a. Can be obtained. Therefore, the bearing clearance (radial bearing clearance) between the bearing surface 3a and the outer peripheral surface of the shaft member 2 inserted into the inner periphery of the bearing 3 can be set with high accuracy, and the bearing performance can be improved. it can.

  In the bearing 3, the metal part 5 and the resin part 6 are fixed in a state where the resin part 5 enters the removal part 6. As a result, the anchoring effect is exerted between the metal part 4 and the resin part 5 to improve the coupling force, and the relative displacement of the metal part 4 with respect to the resin part 5, in this embodiment, the resistance to slipping in the axial direction. The power can be greatly increased.

  In order to further increase the bonding force between the metal part 4 and the resin part 5, it is preferable to increase the number of the removal parts 6 or to increase the depth of the removal parts 6 in the radial direction. The depth in the radial direction of the removal portion 6 can be set until the depth reaches the inner peripheral surface 4a of the metal portion 4 at the maximum, that is, until the removal portion 6 penetrates the metal portion 4 in the radial direction. Further, in order to obtain the effect of preventing the metal part 4 from rotating in the radial direction with respect to the resin part 5, a plurality of linear groove-like removal parts parallel to the axial direction are provided in the radial direction, or the removal part 6 is made of metal. It can also be provided spirally on the outer peripheral surface 4 b of the portion 4.

  By inserting the shaft member 2 into the bearing 3 thus obtained, the bearing device 1 that supports the shaft member 2 rotatably is completed. Lubricating between the bearing 3 and the shaft member 2 can be made smoother by filling the inside of the bearing device 1 with a lubricating fluid, for example, lubricating oil, and forming a fluid film in the bearing gap. As a lubricating fluid other than the lubricating oil, for example, a gas such as air, a fluid lubricant such as a magnetic fluid, or lubricating grease may be used.

  The bearing 3 described above can also be used as a hydrodynamic bearing device that generates pressure by a hydrodynamic action of fluid in a bearing gap between the shaft member 2 and the outer peripheral surface thereof. In this dynamic pressure bearing device, for example, a dynamic pressure generating portion such as a dynamic pressure groove, a multi-arc surface, or a step surface formed in a herringbone shape or the like is formed on the outer peripheral surface of the shaft member 2, and the dynamic pressure generating portion Can be configured to face the perfect circular inner peripheral surface 4a of the metal part 4. On the contrary, the dynamic pressure generating portion can be formed on the inner peripheral surface of the bearing 3 (the inner peripheral surface 4a of the metal portion 4). In this case, the dynamic pressure generating portion of the metal portion inner peripheral surface 4a is It can be formed by forming a mold corresponding to the shape of the dynamic pressure generating portion on the outer peripheral surface of the shaft 7 and performing electroforming using the master shaft 7. Thereafter, the bearing 3 and the master shaft 7 are separated by the same method as described above, and a shaft member having a perfectly circular outer peripheral surface is inserted into the inner peripheral surface of the bearing 3 to constitute a hydrodynamic bearing device. .

  The dynamic pressure generating portion on the inner peripheral surface of the bearing 3 can also be formed by the following procedure.

  First, as shown in FIG. 5, the masking part 28 is formed in the predetermined location of the outer peripheral surface of the master shaft 27, and the metal part 24 is deposited and formed in two places separated in the axial direction by electroforming. Thereafter, as shown in FIG. 6, a predetermined portion (removal portion 46) on the outer periphery of the metal portion 24 is removed until the inner peripheral surface is reached, and a herringbone-shaped metal portion 44 is formed, for example. In the removal processing in this case, high precision is required, the removal amount of the metal portion 24 is large, and the force acting on the interface between the metal portion 4 and the master shaft 27 is increased during the removal processing. Since it becomes easy to peel from the surface of the master shaft 27, it is desirable to perform removal processing by laser processing.

  Next, the resin portion 25 is injection-molded with a resin material using the master shaft 27 and the herringbone-shaped metal portion 44 as insert members. In general, when a substantially cylindrical member such as the resin portion 25 is injection-molded with a resin material, the inner peripheral surface of the member tends to shrink toward the inner diameter side due to molding shrinkage during solidification. However, among the resins exemplified above, for example, a resin material having a liquid crystal polymer as a base resin has a property that the inner peripheral surface of the member expands to the outer diameter side due to molding shrinkage. Therefore, when the resin portion 25 is injection-molded with a resin material having a liquid crystal polymer as a base resin, the resin material enters until it is flush with the inner peripheral surface 44a of the metal portion 44 at the time of injection (indicated by a dotted line in FIG. 7) Due to the above properties during solidification, the inner peripheral surface 25a1 of the resin portion 25 between the adjacent metal portions 44 expands due to molding shrinkage and becomes larger in diameter than the inner peripheral surface 44a of the metal portion 44. Thus, a dynamic pressure groove 47 having the resin portion inner peripheral surface 25a1 as the groove bottom is formed on the inner peripheral surface of the bearing 23. The depth of the dynamic pressure groove 47 is adjusted by, for example, changing the type and amount of filler in the resin material, adjusting the solidification speed of the resin material, and adjusting the amount of molding shrinkage at the resin portion 25. Thus, it is possible to set an arbitrary value.

  By inserting the shaft member into the inner periphery of the bearing 23 formed as described above, and filling the bearing gap between the inner peripheral surface 23a of the bearing 23 and the outer peripheral surface of the shaft member with a lubricating fluid, for example, lubricating oil. The bearing device (dynamic pressure bearing device) is completed (not shown). In this dynamic pressure bearing device, when the shaft member rotates, a dynamic pressure action is generated in the lubricating oil in the bearing gap by the dynamic pressure groove 47, and the shaft member is supported in a non-contact manner in the radial direction.

  5-7, an arbitrary shape can be selected as the dynamic pressure groove pattern. For example, a spiral dynamic pressure groove pattern can be formed in addition to the illustrated herringbone shape. Further, by forming the axial dynamic pressure grooves 47 at a plurality of locations in the circumferential direction in the same process, it is possible to form so-called step bearings.

  In the above embodiment, the master shaft 7 may be used as it is for the shaft member 2, or a shaft-like member manufactured separately from the master shaft 7 may be used as the shaft member 2. According to the latter, since the master shaft 7 once manufactured with high accuracy can be repeatedly used, the manufacturing cost of the master shaft 7 can be suppressed and the cost of the bearing device 1 can be further reduced. As described above, when a dynamic pressure generating portion such as a dynamic pressure groove is provided on the outer peripheral surface 2 a of the shaft member 2, the dynamic pressure is applied to the outer peripheral surface of the shaft-shaped member manufactured separately from the master shaft 7 having a perfect circular cross section. What provided the generating part is good to use as the shaft member 2.

  The bearing device described above can be used by being incorporated in a motor for information equipment, for example. Hereinafter, an example in which the bearing device 1 is used as a rotating shaft support device for the motor will be described with reference to FIG.

  As shown in FIG. 8, the motor 100 is used as a spindle motor for a disk drive device such as an HDD, and includes a bearing device 1 that rotatably supports a shaft member 102 in a non-contact manner, and a shaft member. A rotor (disk hub) 103 attached to 102, and a stator coil 104 and a rotor magnet 105 that face each other through a gap in the radial direction, for example. The stator coil 104 is attached to the outer periphery of the bracket 106, and the rotor magnet 105 is attached to the inner periphery of the disk hub 103. The disk hub 103 holds one or more disks D such as magnetic disks. When the stator coil 104 is energized, the rotor magnet 105 is rotated by the electromagnetic force between the stator coil 104 and the rotor magnet 105, whereby the disk hub 103 and the disk D held by the disk hub 103 are integrated with the shaft member 102. Rotate to.

  In this embodiment, the bearing device 1 includes a bearing 3, a shaft member 102 that is inserted into the inner periphery of the bearing 3, and a thrust plate 107 that is attached to one end of the bearing 3. Although FIG. 8 illustrates the bearing 3 shown in FIG. 1 as the bearing 3, the bearing 23 shown in FIG. 7 can also be used. On the upper end surface of the thrust plate 107, a region (thrust bearing surface) 107a in which a plurality of dynamic pressure grooves are arranged in a spiral shape is formed as a thrust dynamic pressure generating portion. When the shaft member 102 is rotated, an oil film is formed in a radial bearing gap between the outer peripheral surface 102a of the shaft member 102 and the bearing surface 3a of the bearing 3, whereby the shaft member 102 is supported in a non-contact manner so as to be rotatable in the radial direction. Part R is formed. At the same time, in the thrust bearing gap between the lower end surface 102b of the shaft member 102 and the upper end surface 107a of the thrust plate 107, the shaft member 102 is rotatably supported in the thrust direction by the dynamic pressure action of the lubricating oil by the dynamic pressure groove. A thrust bearing portion T is formed.

  The bearing device of the present invention is not limited to the above examples, and is used in a small motor for information equipment used under high-speed rotation, a polygon scanner motor of a laser beam printer, etc. It can also be suitably used for rotating shaft support.

  Although the case where the bearing 3 is used for supporting the rotating shaft is illustrated in the above description, the bearing 3 is used as a sliding bearing that supports linear relative sliding between the shaft and the relative sliding. It can also be used as a bearing for sliding rotation that supports both movement and relative rotation. In these applications, an oil groove for retaining oil is formed on the inner peripheral surface of the bearing 3 in the same manner as the method for forming the dynamic pressure groove 47 of the bearing 23 shown in FIG. be able to.

It is sectional drawing of the bearing apparatus 1 which concerns on 1st Embodiment of this invention. FIG. 3 is a perspective view showing a state where a metal part 4 is formed on a master shaft 2. It is a perspective view of the partial cross section which shows the state from which a part of outer peripheral surface of the metal part 4 was removed. It is sectional drawing which shows the state which attached the electroformed shaft 9 to the injection mold. 3 is a perspective view showing a state where a metal part 24 is formed on a master shaft 27. FIG. It is a perspective view which shows the state from which a part of metal part 24 was removed. It is sectional drawing which shows other embodiment of a slide bearing. It is sectional drawing which shows schematic structure of the motor 100 to which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bearing apparatus 2 Shaft member 3 Bearing 4 Metal part 5 Resin part 6 Removal part 7 Master shaft 8 Masking part 9 Electroformed shaft 47 Dynamic pressure groove 100 Motor 102 Shaft member R Radial bearing part T Thrust bearing part

Claims (4)

It has a metal part formed by electroforming, and a resin part that is molded by inserting the metal part into the inner periphery, has a bearing surface on the inner peripheral surface of the metal part, and is inserted into the inner periphery of the metal part A sliding bearing supporting relative rotation between the shaft member and
A part of the outer peripheral surface of the metal part is removed, and the resin part enters the removed part, whereby the metal part and the resin part are engaged in the axial direction, and the outer periphery of the master shaft is engaged with the bearing surface. A sliding bearing characterized in that a dynamic pressure generating portion is formed by a mold formed on a surface .   The sliding bearing according to claim 1, wherein the removal of the metal part is performed until the inner peripheral surface of the metal part is reached, and a hydrodynamic groove having the resin part as a groove bottom is formed at the removal part.   The plain bearing according to claim 1, wherein the outer peripheral surface of the metal part is removed by laser processing. The motor provided with the bearing apparatus which has a sliding bearing in any one of Claims 1-3 .

Images