JP4451409B2 - Method for producing hydrodynamic sintered oil-impregnated bearing unit - Google Patents

Description

The present invention relates to a method for manufacturing a hydrodynamic sintered oil-impregnated bearing unit . This hydrodynamic sintered oil-impregnated bearing is used in the field of information equipment, in particular, optical disk devices such as DVD-ROM and DVD-RAM, magneto-optical disk devices such as MO, high capacity FDD such as HiFD and Zip [floppy disk drive ( Floppy is a registered trademark)], suitable for a disk drive bearing of a magnetic disk device such as an HDD, or a polygon scanner motor bearing such as an LBP, and particularly suitable as a bearing for a thin motor.

  The spindle motors of the above information devices are required to have higher rotational accuracy, higher speed, lower cost, lower noise, etc. The motor spindle is one of the components that determine these required performances. There are bearings to support. In recent years, as a bearing of this type, a sintered metal bearing body is impregnated with lubricating oil or lubricating grease, and a lubricating oil film is formed in the bearing gap by the dynamic pressure effect of the dynamic pressure groove provided on the bearing surface. The use of so-called hydrodynamic sintered oil-impregnated bearings that support non-contact is being studied. This hydrodynamic sintered oil-impregnated bearing has features such as high rotational accuracy and low noise at a low cost, and is considered to be able to sufficiently cope with the required performance.

  FIG. 12 is an example of a spindle motor of an optical disc apparatus using the dynamic pressure type sintered oil-impregnated bearing 1. As shown in the figure, this spindle motor includes a hydrodynamic sintered oil-impregnated bearing 1, a housing 2 for housing the bearing, a rotating shaft 3 supported by the bearing 1, a turntable 5 and a clamper 6 for supporting and fixing the optical disk 4, and a stator 7a. And a motor portion M including the rotor 7b, and the rotor case 8, the turntable 5, the optical disc 4, and the clamper 6 integrated with the rotor 7b are integrally rotated by energizing the stator 7a.

  As shown in FIG. 13, the hydrodynamic sintered oil-impregnated bearing 1 is held in the pores of the bearing body 1a by impregnation with a porous bearing body 1a formed in a thick cylindrical shape and lubricating oil or grease. It is composed of oil. A pair of bearing surfaces 1b facing the outer circumferential surface of the rotating shaft 3 via a bearing gap are formed on the inner circumferential surface of the bearing body 1a so as to be spaced apart from each other in the axial direction. A pressure groove 1c is formed.

As shown in FIGS. 12 and 14, the thrust load of the rotating shaft 3 is supported by a thrust bearing 9 provided at the bottom of the housing 2. The thrust bearing 9 generally has a structure (a so-called pivot bearing) in which a spherical shaft end is slid on a resin washer 9 a having a high lubricity provided on the bottom of the housing 2.
Japanese Patent Laid-Open No. 10-196644

  However, in the pivot bearing, the washer may be depressed due to elastic deformation, plastic deformation, deformation due to wear, or the like of the washer 9a, and the shaft position may change with time. The change in the axis position greatly affects the performance of the disk by causing a change in the disk position in the HDD device and a change in the mirror position in the polygon scanner motor of the LBP. As a countermeasure, the washer 9a may be formed of a metal material or a ceramic material. However, in this case, the shaft end is worn and the shaft end is changed from a spherical surface to a flat surface, thereby causing problems such as a change in shaft position, torque increase, and torque fluctuation. May be incurred.

  In recent years, it is often required to reduce the thickness of the spindle motor in consideration of mounting an optical disk device or an HDD device on a notebook computer or the like. However, as described above, the bearing surface 1b is provided at two locations in the axial direction. There is a limit to reducing the thickness of the arranged structure. For example, as shown in FIG. 15, the thinning can be realized by providing the bearing surface 1b only at one location, but this causes a problem of a decrease in rigidity against a moment load. That is, since an eccentric load such as the rotor case 8, the disk 4, the turntable 5, and the clamper 6 with the rotor magnet 7b fixed acts on the protruding portion of the rotary shaft 3 from the bearing 1, the shaft runout accuracy due to the moment load is improved. There is concern about the decline.

  Accordingly, an object of the present invention is to provide a hydrodynamic sintered oil-impregnated bearing that can maintain a desired bearing performance for a long period of time and can be thinned without causing a decrease in shaft runout accuracy. .

In order to achieve the above object, the present invention comprises a shaft and a bearing body which is formed of sintered metal and has a radial bearing surface opposed to the outer peripheral surface of the shaft via a bearing gap. A hydrodynamic sintered oil-impregnated bearing in which a plurality of hydrodynamic grooves inclined with respect to the axial direction are formed on the bearing surface, and the shaft is supported in a non-contact manner by the hydrodynamic action generated on the radial bearing surface during relative rotation between the shaft and the bearing body; A dynamic bearing having a thrust bearing composed of at least one end face of a hydrodynamic sintered oil-impregnated bearing and a flange provided on the shaft, wherein the perpendicularity between the flange and the outer peripheral surface of the shaft is set within 2 μm. A method for producing a pressure-type sintered oil-impregnated bearing unit , comprising:
Of the pair of punches, one of the punches presses the entire sintered metal into the die, and at the time of the press-fitting, the mold corresponding to the shape of the radial bearing surface is disposed on the inner periphery of the sintered metal. The mold is moved against the inner peripheral surface of the sintered metal, and the pair of punches are pressed against both end surfaces of the sintered metal, so that the inner peripheral surface of the hydrodynamic sintered oil-impregnated bearing is at least as described above. one of the end face sizing respectively, integrally raised while maintaining the mold positional relationship between sintered metal a pair of punch and mold, sintered metal to both end surfaces of the sintered metal to exit the die The sintered metal is spring-backed by being held by upper and lower punches, and the perpendicularity between the one bearing end surface of the sintered metal and the inner peripheral surface of the bearing is set within 3 μm .

  In the thrust bearing portion configured as described above, the contact between the rotating side and the fixed side is secured, so that the contact surface pressure can be reduced to prevent wear, and the shaft position fluctuates due to wear deformation of a washer such as a pivot bearing. Can be avoided. Further, since it is per surface, the rigidity against moment load is improved as compared with the per point of the pivot bearing.

  In the thrust bearing portion 14, if the accuracy of the bearing end surface 11f1 or the accuracy of the flange portion 13a is not sufficient, as shown in FIG. 16, the flange portion 13a may come into contact with the bearing end surface 11f1 without being in surface contact. . In the one-piece contact, the torque cross is large and the torque fluctuation causes a high rotational accuracy required for the information equipment. Even if a dynamic pressure groove is provided in the bearing end surface 11f1 to keep the thrust bearing portion in non-contact, the dynamic pressure effect is insufficient, causing contact and wear between the bearing end surface and the flange portion, resulting in rotation. Accuracy and durability cannot be improved.

  Therefore, in the present invention, the perpendicularity between at least one bearing end surface constituting the thrust bearing portion and the bearing inner peripheral surface, and the flange portion and the outer peripheral surface of the shaft (particularly, the outer peripheral surface of the shaft facing the radial bearing surface). The perpendicularity is managed to be a tolerance that the one bearing end face and the flange portion do not come into contact with each other at the time of relative rotation between the shaft and the bearing body.

  In this case, for example, if the perpendicularity between the bearing end surface 11f1 and the bearing inner peripheral surface is 4 μm or more and the perpendicularity between the flange portion 13a and the outer peripheral surface of the shaft is 3 μm or more, the flange portion 13a contacts the bearing end surface 11f1. There is a risk of hitting without touching. Accordingly, the perpendicularity between the bearing end surface 11f1 and the bearing inner peripheral surface is set within 3 μm, and the perpendicularity between the flange portion 13a and the outer peripheral surface of the shaft is set within 2 μm.

  The term “squareness” as used herein refers to the plane portion that should be perpendicular to the geometric plane perpendicular to the reference plane in the combination of the plane portion that should be perpendicular and the reference plane. This is the size of the madness.

  In conventional hydrodynamic sintered oil-impregnated bearings, the accuracy of the bearing end surface is not sufficient (the perpendicularity of the bearing end surface with respect to the inner peripheral surface of the bearing is about 10 μm), and it is difficult to mass-produce bearing bodies having accuracy within the above numerical range. . As a countermeasure, for example, after fixing the bearing to the housing, there is a method in which the bearing end surface is finished by machining on the basis of the bearing inner diameter surface or on the basis of the outer diameter surface in which the coaxiality is secured with respect to the bearing inner diameter surface. In that case, however, (1) since the shavings generated by the processing adhere to the inner peripheral surface of the bearing, cleaning is required after processing, and (2) additional steps such as post-processing and cleaning are required. For this reason, the cost is significantly increased, and problems such as a reduction in low cost, which is the greatest feature of the hydrodynamic sintered oil-impregnated bearing, occur.

  Therefore, in the present invention, a bearing body material is inserted in a state in which a molding die for forming a dynamic pressure groove on the radial bearing surface is inserted into the inner peripheral surface of the bearing body material and both end surfaces of the bearing body material are held by a pair of punch surfaces. A radial bearing surface having a dynamic pressure groove inclined with respect to the axial direction is formed on the inner peripheral surface of the bearing body material with a molding die by applying a pressing force to the bearing body material, and at least one punch surface of the bearing body material is When forming the thrust bearing surface constituting the thrust bearing portion between the end surface of the mold and the shaft, the perpendicularity between the at least one punch surface and the outer peripheral surface of the mold is within 2 μm (desirably Was set to within 1 μm.

  As a method for finishing the punch surface and the molding die with high accuracy in this way, it is conceivable to integrally form the one punch surface and the molding die. For example, the punch and the mold are integrally cut out from the same member, or are manufactured as separate bodies and fixed together by a method such as press fitting, and then the perpendicularity between the punch surface and the outer peripheral surface of the mold is set. Means such as finishing within 2 μm are possible. The shaft and the flange portion may be manufactured integrally with the same member, or after being manufactured separately, either one may be press-fitted into the other side and finished to a predetermined squareness.

  After the bearing body material is molded to the specified dimensions, the compression force is released and the bearing body material is spring-backed, and the inner diameter of the bearing body material and the outer diameter of the molding die are between the bearing body material and the mold. It is preferable to release the molding die from the inner peripheral surface of the bearing body material by causing a thermal expansion difference that increases the dimensional difference. Thereby, interference with a shaping | molding die and a bearing main body material is avoided, and it becomes possible to extract a shaping | molding die from the internal peripheral surface of a bearing main body raw material, without destroying the shape | molded dynamic pressure groove.

In order to cause the difference in thermal expansion, after the bearing surface is formed, for example, heating may be performed from the bearing body material side. As the material of the mold, a cemented carbide is usually used, and the linear expansion coefficient of this material is 5.1 × 10 ⁻⁶ [1 / ° C.]. On the other hand, the bearing body material is mainly composed of copper powder and iron powder, and an example of the linear expansion coefficient is 12.9 × 10 ⁻⁶ [1 / ° C.]. Therefore, when the bearing body material is heated to a high temperature, the difference in size between the inner diameter of the bearing body material and the outer diameter of the molding die increases due to the difference in thermal expansion between them, and the molding die can be easily removed from the bearing body material. .

  In the above configuration, it is preferable that the bearing inner diameter d and the bearing width L of the hydrodynamic sintered oil-impregnated bearing are set to L ≦ 1.2d, and the radial bearing surface is provided at one place on the inner peripheral surface of the bearing. As a result, the spindle motor can be made thinner.

  In addition, an oil supply dynamic pressure groove inclined with respect to the axial direction is provided on the inner peripheral surface of the hydrodynamic sintered oil-impregnated bearing, and oil is supplied to the thrust bearing portion by the dynamic pressure action generated in the dynamic pressure groove. It can also be. When the bearing end surface is a smooth surface without a dynamic pressure groove, the oil in the thrust bearing portion is discharged to the outer diameter side by centrifugal action, so that there is a concern that poor lubrication may occur, particularly in the case of high-speed rotation. On the other hand, if the dynamic pressure groove is provided, an oil film is easily formed on the thrust bearing portion, and lubricity is improved. Further, since wear at the thrust bearing portion is significantly reduced, the durability is greatly improved.

  The oil supplied to the thrust bearing portion is absorbed from the bearing end surface and the chamfer portion, collected inside the bearing, and supplied again to the bearing gap from the bearing inner peripheral surface.

  Moreover, in the said structure, it is good for a thrust bearing part to set it as the structure which supports a shaft non-contactingly by the dynamic pressure effect | action produced at the time of relative rotation of a shaft and a bearing main body. If it is non-contact support, the wear in the thrust bearing portion is eliminated, and the durability is further improved dramatically.

  Specifically, it is desirable to provide a plurality of concave portions (three or more locations) arranged in the circumferential direction on either one of the one bearing end surface and the flange portion facing the one bearing end surface constituting the thrust bearing portion. It is conceivable to provide a dynamic pressure generator having In this case, the concave portion becomes an oil reservoir, and pressure is generated when the oil in the concave portion is drawn to the adjacent convex portion with rotation, and the oil film pressure increases, so that the thrust bearing portion can be stably held in a non-contact state. . The concave portion of the dynamic pressure generating portion can be a dynamic pressure groove having a portion inclined with respect to a radial imaginary line drawn on the bearing end surface. In this case, the thrust bearing portion and the surrounding oil are rotated with rotation. Is collected on the inner peripheral side and the oil film pressure is increased, so that the thrust bearing portion can be more stably held in a non-contact state. As the dynamic pressure groove shape, a spiral type or a herringbone type can be applied.

  In the said structure, it is good to provide a thrust bearing part in two places spaced apart to the axial direction. In this case, the thrust load in both directions can be supported, and the shaft can be prevented from coming off.

  The surface area of the hydrodynamic sintered oil-impregnated bearing is 10% or less (preferably 5% or less) on the radial bearing surface, and 5% or less (preferably 2% or less) on the bearing end surface constituting the thrust bearing portion. It is good to set. If the surface opening ratio of the radial bearing surface is 10% or less, oil circulation can be secured while preventing a pressure drop, and if the surface opening ratio of the bearing end surface is 5% or less, the dynamic pressure Even when the groove is provided, oil escape from the opening due to pressure generation can be prevented. “Aperture” refers to the portion where the pores of the porous body structure are open on the outer surface, and “surface porosity” refers to the area ratio of the surface aperture that occupies the unit area of the outer surface. .

  According to the present invention, the bearing end face can be supported in the thrust direction, so that the shaft position does not change due to a depression due to deformation or wear of the thrust washer, such as a pivot bearing, and the bearing is made thinner. Even in this case, the moment rigidity can be kept high. Furthermore, when the shaft and the bearing body are rotated relative to each other, one bearing end face and the flange portion do not come into contact with each other, so that the torque cross is small and torque fluctuation is suppressed to achieve high rotational accuracy required for information equipment. Can do.

  When the thrust bearing portions are provided at two positions in the axial direction, the movement of the rotating shaft in the axial direction can be restricted, so that the impact load characteristics can be improved. In particular, when the reading head is arranged with a small gap from the disk as in the HDD device, it is possible to avoid a situation where the head collides with the disk even when an impact load is applied.

  Since the sintered oil-impregnated bearing is composed of a porous body such as a sintered alloy, high-precision name processing is possible at low cost. Moreover, since it is a porous body, the amount of oil retained is large, and since the oil circulates, the deterioration of the oil is delayed and the durability is improved.

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

  FIG. 1 is a cross-sectional view of a hydrodynamic sintered oil-impregnated bearing unit according to the present invention. The bearing unit includes a dynamic pressure type sintered oil-impregnated bearing 11, a cylindrical housing 12 in which the sintered oil-impregnated bearing 11 is fixed to the inner diameter portion, and a rotating shaft 13 inserted into the inner diameter portion of the sintered oil-impregnated bearing 11. To do.

The hydrodynamic sintered oil-impregnated bearing 11 is made by impregnating a cylindrical bearing body 11a made of sintered metal having a radial bearing surface 11b opposed to the outer peripheral surface of the rotating shaft 13 with a bearing gap impregnated with lubricating oil or lubricating grease. Configured. The bearing body 11a made of sintered metal is formed of a sintered metal mainly composed of copper, iron, or both, and preferably has a density of 6.4 to 7 using 20 to 95% by weight of copper. Molded to 2 g / cm ³ . As the material of the bearing body 11a, a porous body having many pores obtained by sintering or foaming cast iron, synthetic resin, ceramics, or the like can be used. The surface open area ratio of the bearing body 11a is preferably 10% or less for the radial bearing surface 11b and 5% or less for thrust bearing surfaces 11f1 and 11f2 described later.

  A radial bearing surface 11b provided on the inner peripheral surface 11h of the bearing body 11a is formed at only one location, and the bearing surface 11b has a plurality of dynamic pressure grooves 11c (herringbone type) inclined with respect to the axial direction. Are arranged in the circumferential direction. The dynamic pressure groove 11c only needs to be formed to be inclined with respect to the axial direction, and may have a shape other than the herringbone type, for example, a spiral type as long as this condition is satisfied. On the outer periphery of the sintered oil-impregnated bearing 11, one or a plurality of grooves 11 g are formed along the axial direction to serve as air vents when the shaft 13 is inserted into the inner diameter portion of the bearing 11. In order to reduce the thickness of the spindle motor, the bearing inner diameter d and the bearing width L are set so as to satisfy L ≦ 1.2d.

  In the sintered oil-impregnated bearing 11, the lubricant (lubricating oil or base oil of the lubricating grease) inside the bearing main body 11a is generated on the surface of the bearing main body 11a by the pressure generated by the rotation of the rotating shaft 13 and the thermal expansion of the oil due to the temperature rise. It oozes out and is drawn into the bearing gap by the action of the dynamic pressure groove 11c. The oil drawn into the bearing gap forms a lubricating oil film and supports the rotating shaft in a non-contact manner. That is, when the inclined dynamic pressure groove 11c is provided on the bearing surface 11b, the lubricant inside the bearing body 11a oozed out by the dynamic pressure action is drawn into the bearing gap and the lubricant is continuously pushed into the bearing surface 11b. Therefore, the oil film force is increased and the rigidity of the bearing can be improved. When assembling the bearing unit, when inserting the rotary shaft 13 into the bearing 11, it is desirable to lubricate the bearing gap and the periphery of the bearing with oil.

  When positive pressure is generated in the bearing gap, there is a hole in the surface of the bearing surface 11b, so that the lubricant returns to the inside of the bearing body. However, since new lubricant continues to be pushed into the bearing gap one after another, oil film strength and rigidity Is maintained high. In this case, since a continuous and stable oil film is formed, high rotational accuracy is obtained, and shaft runout, NRRO, jitter, and the like are reduced. Further, since the rotating shaft 13 and the bearing body 11a rotate without contact, the noise is low and the cost is low.

  The radial bearing surface 11b has a first groove region m1 in which a dynamic pressure groove 11c inclined on one side is arranged, and an axially separated dynamic pressure groove 11c which is spaced apart from the first groove region m1 and inclined in the other side. The second groove region m2 and the annular smooth portion n positioned between the two groove regions m1 and m2 are provided, and the dynamic pressure groove 11c of the two groove regions m1 and m2 is partitioned by the smooth portion n. Has been discontinuous. The back portion 11e between the smooth portion n and the dynamic pressure groove 11c is at the same level. This kind of non-continuous type dynamic pressure groove 11c is continuous type, that is, the smooth portion n is omitted, and the dynamic pressure groove 11c is formed in a V-shape that is continuous between both groove regions m1 and m2. Since oil is collected around the smooth portion n, the oil film pressure is high, and since the smooth portion n without a groove is provided, the bearing rigidity is high.

  A thrust bearing portion 14 is provided on one end side in the axial direction of the sintered oil-impregnated bearing 11. FIG. 1 shows an embodiment in which a thrust bearing portion 14 is provided on the upper end side of a sintered oil-impregnated bearing 11, and a disc-like shape fixed to the upper bearing end surface 11 f 1 (thrust bearing surface) of the sintered oil-impregnated bearing 11 and the rotary shaft 13. The flange portion 13a is configured to face each other. The rotary shaft 13 and the flange portion 13a are manufactured integrally with the same member, or are manufactured separately and then fitted and fixed to each other, and the outer peripheral surface of the rotary shaft 13, particularly when incorporated in the bearing 11, is a bearing surface. Finishing is performed so that the perpendicularity of the outer peripheral surface facing 11b is within 2 μm, preferably within 1 μm, with respect to the end surface 13a1 on the bearing 11 side of the flange portion 13a.

  With such a thrust bearing portion 14, the sliding contact portion comes into contact with the surface, so that the moment rigidity can be increased even with the single-row bearing surface 11 b while preventing the fluctuation of the shaft position which is a problem in the pivot bearing. The shaft can be supported with high accuracy.

  By the way, when the flange part 13a is provided in the rotating shaft 13 as mentioned above, since components, such as the rotor case 8 and a turntable (5: refer FIG. 13), are fixed to the upper end of the rotating shaft 13, the bearing 11 It becomes difficult to seal the upper end of the plate with a conventional seal washer 8 (see FIG. 15). Therefore, oil leakage from the upper end of the bearing 11 is performed by a capillary seal formed by a minute gap between the outer peripheral surface of the flange portion 13a and the inner peripheral surface of the housing 12. The seal gap c is 0.05 mm or less, preferably 0.02 mm or less, and the seal width a is 0.5 mm or more, preferably 1 mm or more. Applying a glaze agent to the outer peripheral surface of the flange portion 13a constituting the seal and the inner peripheral surface of the housing 12 is effective in preventing oil leakage.

  On the other hand, oil leakage from the lower end side of the bearing 11 can be prevented by, for example, pressing the bottom plate 15 into the bottom opening of the housing 12 and then caulking it. If the gap between the bottom plate 15 and the housing 12 is sealed with an adhesive, it is more effective in preventing oil leakage.

  FIG. 2A shows an embodiment in which an elastic material 15a such as resin or rubber is stacked on the bottom plate 15 and used as a packing in order to prevent oil leakage from the bottom plate 15 side. Also in this case, it is desirable that the bottom plate 15 is caulked if necessary after being press-fitted into the housing 12.

  FIG. 2B shows an embodiment in which an annular recess 12a is provided on the inner peripheral surface of the housing 12 facing the outer peripheral surface of the flange portion 13a. By rotating the flange portion 13a, oil accumulates in the concave portion 12a by centrifugal force, so that oil leakage from the upper end of the housing 12 can be reliably prevented (centrifugal seal). If only the centrifugal seal is used, oil leakage may occur when the shaft orientation is in the horizontal direction. Therefore, it is desirable to use in combination with a capillary seal.

  FIG. 3A shows an example in which an inclined groove 13a2 is provided on the outer peripheral surface of the flange portion 13a so as to generate an airflow toward the bearing 11 during rotation. Since the oil is pushed back to the bearing 11 side by the generated airflow, oil leakage from the upper end of the bearing can be prevented (oil leakage is prevented by a capillary seal during stoppage). Since the inclined groove 13a2 only needs to prevent oil leakage, it does not need to be processed with high accuracy like the dynamic pressure groove 11c of the radial bearing surface 11b. The groove depth is suitably about 5 to 30 μm and can be processed by a method such as rolling.

  If this inclined groove 13a2 is formed over the entire length of the width (axial dimension) of the flange portion 13a as shown in FIG. 3 (A), excess air may be sent to the bearing 11 side. As shown in FIG. In this case, it is desirable to provide an annular recess 12a on the inner peripheral surface of the housing 12 at a portion facing the non-formation region of the inclined groove 13a2.

  FIG. 4 shows an embodiment in which the thrust bearing portion 14 is configured by the lower bearing end surface 11f2 of the bearing 11 and the flange portion 13a provided at the shaft end. During the rotation, the rotary shaft 13 is lifted from the bottom plate 15 by receiving a floating force due to the exciting force between the rotor 7b and the stator 7a (see FIG. 13), and the lower bearing end surface 11f2 (thrust bearing surface) and the flange portion 13b Thrust force is supported by the upper surface 13b2. A thrust washer 15a made of a resin material having a high lubricity is disposed on the upper surface of the bottom plate 15 and directly below the rotary shaft 13, and friction between the shaft end immediately after the start of the motor and immediately before the stop is reduced. Yes. The upper end opening of the housing 12 is closed by a thrust washer 16 for preventing oil leakage, and the gap between the shaft and the shaft is 0.2 mm or less to prevent oil from leaking outside (capillary action). By applying a lubricant to the inner peripheral surface of the seal washer 16, the upper and lower surfaces of the inner peripheral portion, or the outer peripheral surface of the shaft 13 facing the inner peripheral surface of the seal washer 16, further effective oil leakage prevention is achieved.

  FIG. 5 shows that a dynamic pressure groove 11j for oil supply inclined with respect to the axial direction is provided on the bearing inner peripheral surface 11h of the dynamic pressure type sintered oil impregnated bearing 11, and the thrust bearing portion is generated by the dynamic pressure action generated in the dynamic pressure groove 11j. 14 is supplied with oil. The dynamic pressure groove 11j is formed in a V shape that is continuous with the dynamic pressure groove 11c in the groove forming region (on the thrust bearing portion 14 side) of the radial bearing surface 11b. By providing the dynamic pressure groove 11j for oil supply, an oil film is easily formed on the thrust bearing portion 14 and lubricity is improved. Also, wear at the thrust bearing portion 14 is remarkably reduced, so that durability is also greatly improved. Improve.

  6 and 7 show the thrust bearing portion 14 supported in a non-contact manner by the dynamic pressure generated when the rotating shaft 13 rotates. If it is non-contact support, the friction in the thrust bearing portion 14 is eliminated, and the durability is greatly improved. For the dynamic pressure action, a dynamic pressure generating portion 17 having a plurality of concave portions 11k arranged in the circumferential direction is provided on either one of the bearing end surface 11f1 constituting the thrust bearing portion 14 and the flange portion 13a opposed thereto. Can be obtained. As the recess 11k, for example, a dynamic pressure groove can be considered.

  FIG. 6 shows an example of the thrust bearing portion 14 having the dynamic pressure generating portion 17, and the thrust bearing surface 11f1 is provided with a dynamic pressure groove 11k having a portion inclined with respect to a radial imaginary line drawn on the bearing end surface. It is. The dynamic pressure groove 11k has a herringbone shape, that is, a V-shape having a bent portion at a substantially central portion in the radial direction, and the dynamic pressure grooves are formed at equal intervals in the circumferential direction. In this case, the thrust bearing portion 14 and the surrounding oil are collected at the bent portion of the dynamic pressure groove 11k as the rotation occurs, and the oil film pressure increases, so that the thrust bearing portion 14 can be stably held in a non-contact state. As a dynamic pressure groove shape, a spiral type can be applied in addition to the herringbone type. Further, the dynamic pressure groove 11k may be provided in the flange end surface 13a1, and the thrust bearing surface 11f1 may be a smooth surface without the dynamic pressure groove.

  FIG. 7 shows a structure in which a dynamic pressure groove 11k is provided on the thrust bearing surface 11f1 as in FIG. 6, and an oil supply dynamic pressure groove 11j is provided on the inner peripheral surface of the bearing as in FIG.

  8 and FIG. 9, thrust bearing portions 14a and 14b are provided at two locations separated in the axial direction so as to be able to support thrust loads in both directions. In FIG. 8, flanges 13a and 13b are arranged at both ends of the bearing, and two thrust bearing portions 14a and 14b formed between the flange portions 13a and 13b and both bearing end surfaces 11f1 and 11f2 are used in both directions. Can be supported. Any one of the thrust bearing surfaces 11f1 and 11f2 constituting the thrust bearing portion 14 and the end surfaces of the flange portions 13a and 13b opposed to the thrust bearing surfaces 11f1 and 11f2 (in the drawing, the thrust bearing surfaces 11f1 and 11f2) is shown in FIGS. As shown in FIG. 6, a dynamic pressure groove 11k similar to that shown in FIG. 6 is formed. With this structure, not only thrust support in both directions but also removal of the rotating shaft 13 from the bearing 11 can be prevented, so that even when an impact load is applied to the rotating shaft 13, damage to the motor can be avoided.

  In FIG. 9, a flange portion 13b is provided between the bearing 11 and the bottom plate 15, and thrust bearing portions 14a and 14b are formed on both sides of the flange portion 13b. That is, one of the upper end surface 13a1 and the lower bearing end surface 11f2 of the flange portion 13b, and one of the lower end surface 13b2 of the flange portion 13b and the upper surface of the bottom plate 15 (in the drawing, the lower bearing end surface 11f2 and the flange portion The lower end surface 13b2) is provided with a dynamic pressure groove 11k similar to that in FIG. 6, and the same effect as the structure in FIG.

  The bearing main body 11a of the hydrodynamic sintered oil-impregnated bearing 11 is formed by, for example, sizing → rotating a cylindrical sintered metal material (bearing body material) obtained by compression-molding the metal powder and firing the metal powder. Sizing → Bearing surface molding can be performed.

  The sizing process is a process of sizing the outer peripheral surface and the inner peripheral surface of the sintered metal material to correct bending in the sintering process, and press-fitting the outer peripheral surface of the sintered metal material into a cylindrical die, This is done by press-fitting sizing pins into the inner peripheral surface. In the rotational sizing process, a rotational sizing pin having a substantially polygonal cross section (a part of the outer peripheral surface of a circular cross section that has been partially flattened to leave an arc portion at the circumferentially equidistant position) This is a step of sizing the inner peripheral surface by rotating a sizing pin while pressing against the peripheral surface. By this rotational sizing, the roundness and cylindricity of the inner peripheral surface of the sintered metal material are corrected, and the surface area ratio is finished to 3 to 15%, for example. In the bearing surface forming step, the inner surface of the sintered metal material subjected to the sizing process as described above is pressed with a molding die having a shape corresponding to the bearing surface of the finished product, thereby forming the dynamic pressure grooves on the bearing surface. This is a step of simultaneously forming a formation region and other regions (back 11e and annular smooth region n).

  FIG. 11 illustrates a schematic structure of a molding apparatus used in the bearing surface molding process. This apparatus includes a cylindrical die 20 for press-fitting the outer peripheral surface of the sintered metal material 11 ′, a core rod 21 made of cemented carbide for forming the inner peripheral surface of the sintered metal material 11 ′, and both ends of the sintered metal material 11 ′. The upper and lower punches 22 and 23 that hold the surface in the vertical direction are configured as main elements. The core rod 21 and the upper punch 22 are integrated, and the perpendicularity between the outer peripheral surface of the core rod 21 and the punch surface 22a of the upper punch 22 is finished within 2 μm.

  As shown in FIG. 10, an uneven mold 21a corresponding to the shape of the finished bearing surface 11b is provided on the outer peripheral surface of the core rod 21. As shown in FIG. The convex portion 21a1 of the molding die 21a forms a region of the dynamic pressure groove 11c on the bearing surface 11b, and the concave portion 21a2 forms a region other than the dynamic pressure groove 11c (back 11e and annular smooth region n). The level difference between the convex portion 21a1 and the concave portion 21a2 in the mold 21a is as small as the depth of the dynamic pressure groove 11c in the bearing surface 11b (for example, about 2 to 5 μm), but is considerably exaggerated in the drawing. It is shown in the figure. When the dynamic pressure grooves 11k are provided on the upper and lower bearing end surfaces 11f1 and 11f2 (see FIGS. 6 to 9), the shape corresponding to the dynamic pressure grooves 11k is also transferred to the punch surfaces 22a and 23a of the upper and lower punches 22 and 23. A mold is provided.

  The molding by this molding apparatus is performed according to the procedures (1) to (4) shown in FIG.

  First, after placing the sintered metal material 11 ′ in alignment with the upper surface of the die 20, the upper punch 22 and the core rod 21 are lowered to press-fit the sintered metal material 11 ′ into the die 20, and further into the lower punch 23. Press and apply pressure from above and below (1).

  The sintered metal material 11 ′ is deformed by receiving a pressing force from the die 20 and the upper and lower punches 22 and 23, and the inner peripheral surface is pressed against the forming die 21 a of the core rod 21. Thereby, the shape of the forming die 21a is transferred to the inner peripheral surface of the sintered metal material 11 ′, and the bearing surface 11b is formed into a predetermined shape and dimensions (at the same time, the outer peripheral surface and both end surfaces of the sintered metal material 11 ′. Is also sized).

  After the formation of the bearing surface 11b is completed, the upper and lower punches 22 and 23 and the core rod 21 are integrally raised while maintaining the positional relationship between the sintered metal material 11 ′ and the core rod (2), and the sintered metal material 11 ′. Is removed from the die 20. Next, the sintered metal material 11 'is heated by blowing hot air to the outer peripheral surface of the sintered metal material 11' grasped by the clamper 24 with a heater 25 such as a hot air generator (3), and then the sintered metal material. 11 'is extracted from the core rod 21 (4). At this time, the sintered metal material 11 'is pulled out of the die 20 and at the same time, a springback is generated in the sintered metal material 11' and its inner diameter is increased. Moreover, since the temperature of the sintered metal material becomes higher than that of the core rod 21 by heating, and the thermal expansion coefficient of the sintered metal material 11 ′ (mainly made of copper) is larger than that of the core rod 21 (made of cemented carbide). Further, the inner diameter of the sintered metal material 11 ′ is further expanded. Therefore, interference between the core rod 21 and the sintered metal material 11 'is avoided, and the core rod 21 can be extracted from the inner peripheral surface of the sintered metal material 11' without breaking the dynamic pressure groove 11c. When the sintered metal material 11 ′ can be smoothly removed only by the spring back, the heating process by the heater 25 may be omitted.

  When the sintered metal material 11 ′ manufactured through the above steps is washed and impregnated with lubricating oil or lubricating grease to hold the oil, the dynamic pressure type sliding bearing (dynamic pressure type porous oil bearing) shown in FIG. Is completed. The bearing 11 is fixed to the inner peripheral surface of the housing 12 by, for example, adhesion. In addition, if the bearing gap and the space around the bearing are filled with oil by lubricating separately from the impregnation oil after the bearing 11 is incorporated into the housing 12, the lubricity is remarkably improved.

  As described above, if the perpendicularity between the outer peripheral surface of the core rod 21 and the punching surface 22a of the upper punch 22 is set within 2 μm, the sintered oil impregnation with the perpendicularity of the thrust bearing surface 11f1 with respect to the bearing inner peripheral surface 11h being within 3 μm. The bearing 11 can be provided. By combining this bearing 11, the flange portion 13a, and the rotating shaft 13 in which the perpendicularity of the outer peripheral surface is set within a predetermined range, it is possible to prevent one-side contact at the thrust bearing portion 14 and to realize the surface contact with certainty. it can.

It is sectional drawing of the hydrodynamic type sintered oil-impregnated bearing unit concerning this invention. It is sectional drawing which shows other embodiment of this invention. It is sectional drawing which shows other embodiment of this invention. It is sectional drawing which shows other embodiment of this invention. It is sectional drawing which shows other embodiment of this invention. It is a figure which shows other embodiment of this invention, A figure is sectional drawing, B figure is a top view. It is a figure which shows other embodiment of this invention, A figure is sectional drawing, B figure is a top view. It is a figure which shows other embodiment of this invention, A figure is sectional drawing, B figure is a top view, C figure is a bottom view. It is a figure which shows other embodiment of this invention, A figure is sectional drawing, B figure and C figure are bottom views. It is a side view of a core rod and an upper punch. It is sectional drawing which shows this invention method. It is sectional drawing of the optical disk apparatus incorporating the dynamic pressure type sintered oil-impregnated bearing unit. It is sectional drawing of the conventional dynamic pressure type sintered oil-impregnated bearing. It is sectional drawing of the conventional dynamic pressure type sintered oil-impregnated bearing unit. It is sectional drawing of a dynamic pressure type sintered oil-impregnated bearing unit. It is sectional drawing of a dynamic pressure type sintered oil-impregnated bearing unit.

Explanation of symbols

11 Hydrodynamic sintered oil-impregnated bearing
11a Bearing body
11b Radial bearing surface
11c Dynamic pressure groove on radial bearing surface
11f1 Bearing end face (Thrust bearing face)
11f2 Bearing end face (Thrust bearing face)
11h Bearing inner peripheral surface
11j Dynamic pressure groove for oil supply
11k Thrust bearing surface dynamic pressure groove (concave)
12 Housing 13 Rotating shaft (axis)
13a Flange part 14 Thrust bearing part 17 Dynamic pressure generating part

Claims (8)

A shaft and a plurality of bearings formed of sintered metal and impregnated with oil in a bearing body having a radial bearing surface opposed to the outer peripheral surface of the shaft via a bearing gap, and inclined to the axial direction on the radial bearing surface At least one of a hydrodynamic sintered oil-impregnated bearing and a hydrodynamic sintered oil-impregnated bearing that supports the shaft in a non-contact manner by the hydrodynamic action generated on the radial bearing surface when the shaft and the bearing body rotate relative to each other. This is a method for manufacturing a hydrodynamic sintered oil-impregnated bearing unit having a thrust bearing portion composed of an end face and a flange portion provided on a shaft, wherein the perpendicularity between the flange portion and the outer peripheral surface of the shaft is set within 2 μm. And
Of the pair of punches, one of the punches presses the entire sintered metal into the die, and at the time of the press-fitting, the mold corresponding to the shape of the radial bearing surface is disposed on the inner periphery of the sintered metal. The mold is moved against the inner peripheral surface of the sintered metal, and the pair of punches are pressed against both end surfaces of the sintered metal, so that the inner peripheral surface of the hydrodynamic sintered oil-impregnated bearing is at least as described above. one of the end face sizing respectively, integrally raised while maintaining the mold positional relationship between sintered metal a pair of punch and mold, sintered metal to both end surfaces of the sintered metal to exit the die A hydrodynamic sintered oil-impregnated bearing characterized in that the sintered metal is held back by a pair of punches and the sintered metal is spring-backed, and the perpendicularity between the one end face of the sintered metal and the inner peripheral surface of the bearing is set within 3 μm. method of manufacturing a unit Bearing inner diameter d and bearing width L of hydrodynamic sintered oil-impregnated bearing
L ≦ 1.2d
The method for manufacturing a hydrodynamic sintered oil-impregnated bearing unit according to claim 1, wherein a radial bearing surface is provided at one location on the inner peripheral surface of the bearing. An oil supply dynamic pressure groove inclined with respect to the axial direction is provided on the inner peripheral surface of the hydrodynamic sintered oil-impregnated bearing, and oil is supplied to the thrust bearing portion by the dynamic pressure action generated in the dynamic pressure groove. A method for producing a hydrodynamic sintered oil-impregnated bearing unit according to claim 1. The method of manufacturing a hydrodynamic sintered oil-impregnated bearing unit according to any one of claims 1 to 3, wherein the thrust bearing portion supports the shaft in a non-contact manner by a dynamic pressure action generated at the time of relative rotation between the shaft and the bearing body. The dynamic pressure generation part which has the some recessed part arrange | positioned in the circumferential direction was provided in either one of said one bearing end surface and the flange part which opposes this which comprises a thrust bearing part. Manufacturing method of hydrodynamic sintered oil-impregnated bearing unit. The method for producing a hydrodynamic sintered oil-impregnated bearing unit according to claim 5, wherein the concave portion of the dynamic pressure generating portion is a dynamic pressure groove having a portion inclined with respect to a radial imaginary line drawn on the bearing end surface. The method for manufacturing a hydrodynamic sintered oil-impregnated bearing unit according to any one of claims 1 to 6, wherein thrust bearing portions are arranged at two locations in the axial direction to support thrust loads in both directions. The hydrodynamic sintered oil-impregnated bearing according to any one of claims 1 to 7, wherein the surface porosity of the hydrodynamic sintered oil-impregnated bearing is set to 10% or less on the radial bearing surface and 5% or less on the bearing end surface constituting the thrust bearing portion. Manufacturing method of bearing unit.

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