JP2010091001A - Sintered bearing and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a sintered bearing supplying oil from a bearing surface while reducing the quantity of internally impregnated oil. <P>SOLUTION: A resin 21 is impregnated in internal pores 20 of a sintered body, whereby the quantity of oil impregnated in the internal pores 20 can be reduced. Sizing is performed after impregnating the sintered body with the resin 21, whereby the resin 21 cured within the pores 20 is deformed by sizing, and the volume of the pores 20 communicating with the surface of the sintered body can be increased. Accordingly, since the internal pores 20 of the sintered bearing are not perfectly sealed by the resin, but the internal pores 20 to which oil can penetrate are appropriately formed, the oil retained in the pores 20 can be supplied from the bearing surface. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sintered bearing and a manufacturing method thereof.

  Sintered bearings are formed by compacting metal powder and then sintering, and have countless pores on the surface and inside. For example, Patent Document 1 includes a sintered bearing (bearing sleeve) in which internal pores are impregnated with oil, and a shaft member inserted into the inner periphery of the sintered bearing, There is shown a bearing device that rotatably supports a shaft member with an oil film generated in a radial bearing gap between the shaft member and the outer peripheral surface thereof. When the shaft member rotates, the oil impregnated in the sintered bearing is supplied to the radial bearing gap from the pores opened in the bearing surface, thereby improving the lubricity. This bearing device is provided with a seal space, and this seal space functions as a buffer that absorbs the volume expansion accompanying the temperature rise of the lubricant filled in the bearing device, thereby leaking the lubricant to the outside. Prevents sticking out.

JP 2007-250095 A JP 2005-337274 A

  However, in the bearing device as described in Patent Document 1, the amount of oil filled in the bearing is increased by impregnating the surface and internal pores of the sintered bearing with the lubricating oil, and accompanying this, the temperature changes. Oil volume changes also increase. Therefore, it is necessary to expand the volume of the seal space that absorbs the volume change of the oil, and there is a risk that the axial dimension of the bearing device is increased or the bearing rigidity is reduced due to the reduction of the bearing span.

  For example, as in Patent Document 2, if the internal pores of the sintered bearing are impregnated with resin, the internal pores of the sintered bearing are not impregnated with oil, and the amount of oil filled in the bearing can be reduced. The above problems can be avoided. However, if the entire sintered bearing is impregnated with resin, the oil cannot be held in the pores opened on the bearing surface of the sintered bearing, which may result in poor lubrication due to insufficient oil.

  An object of the present invention is to provide a sintered bearing capable of reducing the amount of oil impregnated inside and retaining an appropriate amount of oil, and a method for manufacturing the same.

  In order to solve the above-mentioned problems, the present invention is a method for producing a sintered bearing comprising a sintered body obtained by sintering a compacted body of metal powder and having a bearing surface. After impregnating the pores of the bonded body with resin, the sintered body is sized to increase the gap volume in the pores communicating with the surface of the sintered body.

  Thus, the amount of oil impregnated in the pores can be reduced by impregnating the pores of the sintered body with the resin. In addition, by impregnating the pores of the sintered body with resin and then sizing, the resin impregnated in the pores is deformed (including cracking, peeling from the sintered matrix, volume compression) and communicating with the surface. It is possible to enlarge the gap volume inside the pores. In the sintered bearing thus formed, the pores communicating with the surface are impregnated with a resin deformed by sizing. As a result, the pores of the sintered bearing are not completely sealed with resin, and a gap that allows oil to enter is moderately formed in the pores, so that an appropriate amount of oil is retained inside the bearing to improve lubricity. Can do. Further, if the surface having pores holding oil is used as the bearing surface, the lubricity can be further improved by supplying the oil held in the pores from the bearing surface.

  In the above manufacturing method, if the region excluding the bearing surface is impregnated with resin in the sintered body, pores not impregnated with resin can be opened on the bearing surface. While being able to supply from the surface, the pores of the bearing surface can be made to function as a filter that captures contamination such as wear powder inside the bearing. Also, since the pores of the sintered body are impregnated with resin, the resin may be elastically repelled during subsequent sizing and the molding accuracy may be reduced. However, as described above, do not impregnate the bearing surface with resin. Thus, it is possible to avoid the above-mentioned problems in the bearing surface and increase the molding accuracy of the bearing surface.

  On the other hand, when the resin is impregnated in the region including the bearing surface of the sintered body, the bearing surface is formed of the metal material of the base material of the sintered body if the resin of the bearing surface is removed by sizing after impregnating the resin. Thus, the wear resistance of the bearing surface can be improved.

  As described above, according to the present invention, it is possible to obtain a sintered bearing capable of reducing the amount of oil impregnated inside and retaining an appropriate amount of oil.

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

  FIG. 1 is an example of a spindle motor for information equipment having a sintered bearing (bearing sleeve 8) according to an embodiment of the present invention. The spindle motor is used in a disk drive device such as an HDD, and includes a fluid dynamic bearing device 1 that rotatably supports the shaft member 2 in a non-contact manner, a disk hub 3 mounted on the shaft member 2, and a radius, for example. A stator coil 4 and a rotor magnet 5 are provided to face each other with a gap in the direction. The stator coil 4 is attached to the outer periphery of the motor bracket 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The disk hub 3 holds one or a plurality of magnetic disks D (two in FIG. 1) on its outer periphery. In the spindle motor configured as described above, when the stator coil 4 is energized, the rotor magnet 5 rotates, and accordingly, the disk hub 3 and the disk D held by the disk hub 3 rotate integrally with the shaft member 2.

  FIG. 2 shows an example of a fluid dynamic bearing device. The fluid dynamic pressure bearing device 1 includes a shaft member 2, a bottomed cylindrical housing 7, a bearing sleeve 8 as a sintered bearing, and a seal member 9 as main components. In the following, for convenience of explanation, the following description will be made with the closed side of the housing 7 as the lower side and the opening side as the upper side in the axial direction.

  The shaft member 2 is formed of a metal material such as stainless steel, for example, and includes a shaft portion 2a and a flange portion 2b provided at the lower end of the shaft portion 2a. The shaft portion 2a has a cylindrical outer peripheral surface 2a1 and a tapered surface 2a2 that is gradually reduced in diameter upward. The outer peripheral surface 2 a 1 of the shaft portion 2 a is disposed on the inner periphery of the bearing sleeve 8, and the tapered surface 2 a 2 is disposed on the inner periphery of the seal member 9. In addition to integrally forming the shaft portion 2a and the flange portion 2b, the shaft member 2 can also be partially formed of resin (for example, both end faces 2b1 and 2b2 of the flange portion 2b). The flange portion 2b is not necessarily provided. For example, a pivot bearing may be configured by forming a spherical portion at the end of the shaft portion and sliding the spherical portion and the bottom portion 7b of the housing 7 in contact with each other. it can.

  The bearing sleeve 8 is formed in a substantially cylindrical shape by a sintered metal obtained by sintering a compacted body of metal powder. The inner peripheral surface 8a of the bearing sleeve 8 functions as a radial bearing surface, and the lower end surface 8c functions as a thrust bearing surface. The pores of the bearing sleeve 8 are impregnated with a resin deformed by sizing, and a gap in the internal pores generated by the deformation is impregnated with lubricating oil. In the present embodiment, the region excluding the bearing surface of the bearing sleeve 8 is impregnated with resin (the cross-sectional views of FIGS. 3A and 3B indicate the region impregnated with the resin by hatching). Specifically, of the surface of the bearing sleeve 8, the inner peripheral surface 8a (radial bearing surface), the lower end surface 8c (thrust bearing surface), and the upper end surface 8b are not impregnated with resin, and are opened in the outer peripheral surface 8d. The resin is impregnated with the pores inside and the pores connected to the pores. Thus, the inner peripheral surface 8a and the lower end surface 8c serving as bearing surfaces are formed of the metal material of the sintered metal base material, and innumerable recesses are formed on these surfaces. Specifically, as conceptually shown in FIG. 3B, the pore 80 communicating with the bearing surface 8a (8c) is provided with a region not impregnated with resin up to a predetermined depth, and lubricating oil is held in this region. Can do.

  On the inner peripheral surface 8a of the bearing sleeve 8, a radial dynamic pressure generating portion for generating a dynamic pressure action on the fluid film (oil film) in the radial bearing gap is formed. In this embodiment, as shown in FIG. In addition, two dynamic pressure groove regions in which herringbone-shaped dynamic pressure grooves 8a1 and 8a2 are arranged are formed apart from each other in the axial direction. Of the two dynamic pressure groove regions, portions with cross hatching except for the dynamic pressure grooves 8a1 and 8a2 are hill portions. In the upper dynamic pressure groove region, the dynamic pressure groove 8a1 is formed in an axially asymmetric shape, specifically, the axial direction of the upper groove with respect to the belt-like portion formed in the substantially central portion in the axial direction of the hill. The dimension X1 is larger than the axial dimension X2 of the lower groove (X1> X2). In the lower dynamic pressure groove region, the dynamic pressure groove 8a2 is formed in an axially symmetrical shape. Due to the unbalance of the pumping ability in the vertical dynamic pressure groove region described above, the oil filled between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface of the shaft portion 2a is rotated during the rotation of the shaft member 2. It will be pushed downward.

  A thrust dynamic pressure generating portion for generating a dynamic pressure action on the oil film in the thrust bearing gap is formed on the lower end surface 8 c of the bearing sleeve 8. In the present embodiment, the thrust dynamic pressure generating portion has a spiral shape as shown in FIG. On the outer peripheral surface 8d of the bearing sleeve 8, axial grooves 8d1 are formed at a plurality of locations (for example, three locations) at equal intervals in the circumferential direction. In a state where the outer peripheral surface 8d of the bearing sleeve 8 and the inner peripheral surface 7c of the housing 7 are fixed, the axial groove 8d1 functions as an oil communication path, and the pressure balance inside the bearing is maintained within an appropriate range by this communication path. be able to.

  The housing 7 has a cup shape opened in one axial direction, and integrally includes a cylindrical side portion 7a in which a bearing sleeve 8 is held on the inner periphery and a bottom portion 7b that closes the lower end of the side portion 7a. The material of the housing 7 is not particularly limited, and a metal such as brass or an aluminum alloy, an inorganic material such as resin, glass, or the like can be used. As the resin material, either a thermoplastic resin or a thermosetting resin can be used. Further, if necessary, a resin composition in which various additives such as carbon nanomaterials such as glass fiber, carbon fiber, and carbon black, and graphite are blended can be used. On the upper end surface 7b1 of the bottom 7b of the housing 7, for example, a spiral dynamic pressure groove is formed as a thrust dynamic pressure generating portion for generating a dynamic pressure action on the oil film in the thrust bearing gap (not shown).

  The seal member 9 is formed in an annular shape with, for example, a resin material or a metal material, and is disposed on the inner periphery of the upper end portion of the side portion 7 a of the housing 7. The inner peripheral surface 9a of the seal member 9 is opposed to the tapered surface 2a2 provided on the outer periphery of the shaft portion 2a in the radial direction, and a seal space S in which the radial dimension is gradually reduced downward is formed therebetween. The Due to the capillary force of the seal space S, the lubricating oil is drawn into the inside of the bearing, and oil leakage is prevented. In this embodiment, since the taper surface 2a2 is formed on the shaft portion 2a side, the seal space S also functions as a centrifugal force seal.

  The oil level of the lubricating oil filled in the internal space of the housing 7 sealed with the seal member 9 is maintained within the range of the seal space S. That is, the seal space S has a volume that can absorb the volume change of the lubricating oil. In the present embodiment, as described above, the internal pores of the bearing sleeve 8 are impregnated with the resin, so that the amount of oil entering the internal pores is reduced, thereby reducing the total amount of oil filled in the bearing. Therefore, compared with the case where the resin is not impregnated in the internal pores of the bearing sleeve 8, the volume change of the oil with the temperature is reduced, so that the volume of the seal space S can be reduced. Thereby, since the axial direction dimension of the sealing member 9 can be reduced, size reduction of the fluid dynamic pressure bearing apparatus 1 is achieved. Alternatively, the axial rigidity (bearing span) of the first and second radial bearing portions R1 and R2 can be expanded without changing the size of the device, thereby improving the bearing rigidity (especially moment rigidity).

  In the fluid dynamic bearing device 1 having the above configuration, when the shaft member 2 rotates, a radial bearing gap is formed between the inner peripheral surface 8a (radial bearing surface) of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a. . The oil film pressure generated in the radial bearing gap is increased by the dynamic pressure grooves 8a1 and 8a2 formed on the inner peripheral surface 8a of the bearing sleeve 8, and the dynamic pressure action allows the shaft portion 2a to be rotatably supported in a non-contact manner. A first radial bearing portion R1 and a second radial bearing portion R2 are configured.

  At the same time, a thrust bearing gap between the upper end surface 2b1 of the flange portion 2b and the lower end surface 8c (thrust bearing surface) of the bearing sleeve 8, and the lower end surface 2b2 of the flange portion 2b and the upper portion of the bottom portion 7b of the housing 7 An oil film is formed in the thrust bearing gap with the end surface 7b1, and the pressure of the oil film is increased by the dynamic pressure action of the dynamic pressure groove. By this dynamic pressure action, the first thrust bearing portion T1 and the second thrust bearing portion T2 are configured to support the flange portion 2b in a non-contact manner so as to be rotatable in both thrust directions.

  At this time, as described above, since the bearing surface (inner peripheral surface 8a, lower end surface 8c) of the bearing sleeve 8 is not impregnated with resin, the pores opened in the bearing surface can function as an oil reservoir. . Lubricity is improved by supplying the oil retained in the pores to the radial bearing gap or the thrust bearing gap. Further, since the pores opened in the bearing surface function as a filter that captures wear powder generated by contact between the bearing sleeve 8 and the shaft member 2, contamination can be prevented from entering the oil film in the bearing gap.

  Hereinafter, an example of the manufacturing method of the sintered bearing (bearing sleeve 8) which concerns on embodiment of this invention is demonstrated based on drawing. The bearing sleeve 8 is manufactured through a compacting process (see FIG. 4), a sintering process (not shown), a resin impregnation process (see FIG. 5), and a sizing process (see FIG. 6).

  In the compacting process, first, as shown in FIG. 4A, the metal powder M is filled into a cylindrical cavity surrounded by the die 11, the core rod 12, and the lower punch 13. As the metal powder M to be filled, for example, copper powder, copper alloy powder, or those in which iron powder is blended are used, and an appropriate amount of graphite or the like is added to and mixed with the metal powder as necessary. The upper punch 14 is lowered from this state, and the metal powder M is compressed from the upper side in the axial direction (see FIG. 4B), whereby the green compact Ma is obtained. Thereafter, the compression molded body Ma is released from the mold (see FIG. 4C).

  In the sintering step, the compression molded body Ma is sintered at a predetermined sintering temperature, whereby a cylindrical sintered body 15 is obtained. The sintering step is performed, for example, in a vacuum or in an inert gas atmosphere, and is sintered at the sintering temperature (about 700 to 1100 ° C.) of the metal powder.

  In the resin impregnation step, resin is impregnated in the sintered body 15 except for the radial bearing surface (inner peripheral surface 15a) and the thrust bearing surface (end surface 15c). As the resin used at this time, a resin having a low viscosity is suitable so that the internal pores of the sintered body 15 are easily impregnated. For example, an acrylic resin (viscosity: about 20 mPa · s) or an epoxy resin (viscosity: about 40 to 50 mPa · s) can be preferably used. Moreover, you may mix | blend additives, such as a hardening | curing agent, in the resin solution.

  Specifically, as shown in FIG. 5, the sintered body 15 is arranged so that the axial direction is horizontal, and a shaft 41 is inserted into the inner periphery of the sintered body 15, and the sintered body 15 and the shaft 41 are inserted. The resin is dropped from the nozzle 40 onto the outer peripheral surface 15d of the sintered body 15 while rotating the nozzle integrally. The resin dropped on the outer peripheral surface 15d penetrates into the inner diameter side of the sintered body 15 (see the arrow in FIG. 5A) and spreads on both sides in the axial direction (see the arrow in FIG. 5B). At this time, the dripping amount and dropping speed of the resin, the viscosity of the resin, and the resin soaked into the sintered body 15 do not reach the inner peripheral surface 15a serving as the radial bearing surface and the end surface 15c serving as the thrust bearing surface. The rotational speed of the sintered body 15 or the porosity (density) of the sintered body 15 is adjusted. Further, as shown in the figure, if the nozzle 40 is arranged offset from the axially central portion of the sintered body 15 to the side away from the end surface 15c serving as the thrust bearing surface, the resin is disposed on the end surface 15c serving as the thrust bearing surface. Can be prevented. Thereafter, the resin is cured to complete the resin impregnation step.

  In the sizing process, the inner peripheral surface, outer peripheral surface, and axial dimension of the sintered body 15 impregnated with resin are corrected to appropriate dimensions, and dynamic pressure generating portions are formed on the inner peripheral surface and the lower end surface. Specifically, as shown in FIG. 6 (a), first, as shown in FIG. 6 (b), the sintered body 15 is supported (restrained) from both sides in the axial direction by the upper and lower punches 18 and 19. The sintered body 15 is press-fitted into the inner periphery of the die 16. As a result, the sintered body 15 is deformed by receiving a pressing force from the die 16 and the upper and lower punches 18 and 19, and is sized in the radial direction. Along with this, the inner peripheral surface 15a of the sintered body 15 is pressed against the molding die 17a of the core rod 17, and the irregular shape of the molding die 17a is transferred to the inner peripheral surface 15a of the sintered body 15, and moves on this surface. A pressure groove is formed. At the same time, the lower end surface 15c of the sintered body 15 is pressed against a forming die (not shown) of the upper end surface 19a of the lower punch 19, and a dynamic pressure groove is formed on this surface. Then, as shown in FIG.6 (c), the die | dye 16 is lowered | hung and the sintered compact 15 is extracted from the die | dye 16, and the radial direction compression force is cancelled | released. At this time, with release from the die 16, a radial spring back is generated in the sintered body 15, a minute gap is formed between the sintered body 15 and the core rod 17, and both are separable. Become. Then, by pulling the sintered body 15 out of the core rod 17, the sintered body 15 is released. In FIG. 6, the depths of the dynamic pressure grooves and the molding die 17a are exaggerated for easy understanding.

  By pressing the sintered body 15 in this sizing process, the resin impregnated in the internal pores of the sintered body 15 and cured is deformed (destructed / compressed). That is, the diameter difference (indicated by P in FIG. 6A) between the sintered body 15 and the die 16 in the sizing process is set so that the resin in the internal pores of the sintered body 15 is deformed. In this way, the resin in the internal pores of the sintered body 15 is deformed, so that the gap volume in the internal pores (pores communicating with the surface of the sintered body) of the sintered body 15 increases. That is, in the bearing sleeve 8 after sizing, not all the internal pores are completely filled with the resin, but gaps are left in some of the pores, so that an appropriate oil replenishment capability can be maintained.

  The reason why the gap volume in the pores communicating with the surface is increased by sizing is as follows.

(1) Expansion of pore volume by communication of bubbles in resin (see Fig. 7)
The resin 21 impregnated in the internal pores 20 of the sintered body 15 may be cured in a state including the bubbles 22 (see FIG. 7A). When the sintered body 15 is sized, a crack 23 is generated in the resin 21 due to compression by sizing, and the bubbles 22 communicate with the bearing surface 8a (8c) (see FIG. 7B). Alternatively, after the resin 21 is compressed and deformed by the amount of the bubbles 22 by sizing, the sintered body 15 is spring-backed, whereby a gap (step) 24 between the bearing surface 8a (8c) and the surface of the resin 21 is obtained. Is formed (see FIG. 7C). As a result, a new gap communicating with the bearing surface 8a (8c) is formed in the pore 20, and the volume of the gap that can be impregnated with oil is increased by the volume of the bubble 22.

(2) Expansion of pore volume by communication of independent pores of sintered body (see FIG. 8)
When the sintered body 15 is impregnated with the resin 21, not all the pores 20 inside are impregnated with the resin 21, but the independent pores 30 sealed with the resin 21 (not communicating with the surface of the sintered body 15). Pore) may be formed (see FIG. 8A). Due to the sizing pressure, a crack 23 is formed in the resin 21 sealing the independent pores 30 (see FIG. 8B), or the resin 21 is peeled off from the sintered body 15 and a minute gap 24 is formed between them. By forming (see FIG. 8C), the independent pores 30 communicate with the bearing surface 8a (8c), and the volume of the gap that can be impregnated with oil is increased by the volume of the independent pores 30.

  Further, in the above manufacturing method, the inner peripheral surface 15a and the lower end surface 15c serving as the bearing surface of the sintered body 15 are not impregnated with resin, and therefore these surfaces are not impregnated with resin. Is left. Thereby, it becomes easy to plastically deform the bearing surface of the sintered body 15 in the sizing process, and the bearing surface can be accurately molded. In particular, as described above, when a dynamic pressure generating portion (dynamic pressure groove) having a fine shape is formed on the bearing surface, it is effective to improve moldability by leaving pores that are not impregnated with resin on the bearing surface. Become.

  The present invention is not limited to the above embodiment. Hereinafter, other embodiments of the present invention will be described, but the same reference numerals are given to portions having the same configurations and functions as those of the above-described embodiments, and description thereof will be omitted.

  In the above embodiment, in the resin impregnation step, the resin is dropped from the nozzle 40 onto the outer peripheral surface of the sintered body 15. However, the present invention is not limited to this, and as shown in FIG. It is also possible to impregnate the sintered body 15 with resin using the application member 42. Specifically, the resin impregnated in the application member 42 is made to contact the outer peripheral surface 15d of the sintered body 15 and the sintered body 15 is rotated with respect to the application member 42 so that the resin impregnated in the application member 42 is sintered. Pulled into the side. As in the example shown in FIG. 5, the resin drawn into the sintered body 15 permeates both the inner diameter side and the axial direction, thereby impregnating the resin in the pores in a predetermined region of the sintered body 15. As described above, since the application member 42 and the sintered body 15 are brought into contact with each other in a predetermined axial region, the resin is supplied from the entire contact region to the sintered body 15, so that the inside of the sintered body 15 is uniform. Can be impregnated with resin. Further, as shown in the drawing, if the sintered body 15 is rotated while dripping the resin from the nozzle 40 to the application member 42, the application member 42 can be always impregnated with abundant resin. A sufficient amount of resin can be supplied to 15. Further, in order to prevent the resin from reaching the thrust bearing surface, the application member 42 is separated from the end surface 15c serving as the thrust bearing surface with respect to the central portion in the axial direction of the sintered body 15 in the same manner as the nozzle 40 shown in FIG. It is preferable to arrange it in an offset direction.

  Further, in the resin impregnation step shown in FIG. 5, the resin is dropped from the single nozzle 40, but not limited to this, for example, the resin may be dropped from a plurality of nozzles 40 as shown in FIG. 10. Simultaneously with the dropping of the resin, if a high-speed air flow 50 is passed through the inner periphery of the sintered body 15 by an air blower or the like as shown in the figure, the pressure at the inner peripheral portion of the sintered body 15 is reduced, and the outer peripheral surface 15d It becomes easy to impregnate the resin dripped in the inner diameter side.

  In the above embodiment, in the resin impregnation step, the resin is dropped onto the outer peripheral surface 15d from the nozzle 40 above the sintered body 15. However, the present invention is not limited to this. For example, as shown in FIG. The resin may be impregnated by rolling the sintered body 15 in the container 61 having a shallow bottom. Alternatively, instead of rolling the sintered body 15, as shown in FIG. 12, the sintered body 15 may be rotated on the spot in a state where the sintered body 15 is in contact with the resin 60.

  Alternatively, as shown in FIG. 13, the inner peripheral surface 15 a serving as the radial bearing surface and the lower end surface 15 c serving as the thrust bearing surface of the sintered body 15 are covered with the covering materials 71 and 72 and sintered in this state. It is possible to impregnate the resin by completely immersing the body 15 in the resin solution. As a result, the resin is impregnated from the pores opened in the regions of the sintered body 15 that are not covered with the covering materials 71 and 72 (the outer peripheral surface 15d and the upper end surface 15b in the illustrated example). When the impregnation is completed, the sintered body 15 is taken out from the resin solution, and the covering materials 71 and 72 are removed. As described above, the resin can be impregnated in the sintered body 15 except for the radial bearing surface (inner peripheral surface 15a) and the thrust bearing surface (lower end surface 15c). The covering material is preferably formed of a material that can prevent the invasion of the resin by physical or chemical action. For example, a film containing polyethylene or a substance containing water such as gel-like polyvinyl alcohol may be used. it can.

  In the above-described embodiment, the sintered body is impregnated with resin in a region excluding the bearing surface, thereby providing pores that are opened in the bearing surface, and the pores function as a filter that collects oil or captures contamination. However, the present invention is not limited to this, and in the case where problems such as oil shortage and contamination are unlikely to occur, for example, the entire region of the sintered body may be impregnated with resin. At this time, the surface of the sintered body is covered with the resin including the bearing surface. For example, if the resin covering the bearing surface is removed by sizing after the resin impregnation step, the metal material of the base material of the sintered body can be exposed on the bearing surface, and the wear resistance of the bearing surface can be improved.

  In the above embodiment, the inner peripheral surface 8a and the lower end surface 8c of the bearing sleeve 8 function as a bearing surface. However, the present invention is not limited to this. For example, only the inner peripheral surface is a bearing surface. The manufacturing method of the present invention can also be applied to a solid bearing.

  In order to confirm the usefulness of the present invention, the following tests were conducted. First, as a test piece, a sintered body (NTN Co., Ltd .: EZ06) formed using a metal powder containing copper and iron, a comparison product in which pores of this sintered body are impregnated with resin, and impregnation of resin A product that was later sized was prepared, each test piece was impregnated with oil, and the amount of impregnation was compared. Each test piece was formed in a cylindrical shape having an outer diameter of 7.4 mm, an inner diameter of 4 mm, and an axial length of 7 mm. As the oil, Shell Terrace 46 manufactured by Showa Shell Sekiyu KK was used. As a result, as shown in Table 1 below, the impregnated amount of the resin obtained by sizing after impregnating the resin increased as compared with the comparative product not subjected to sizing. From this, it became clear that by applying sizing to the sintered body after the resin impregnation, the volume of the gaps in the pores communicating with the surface (gaps that can be impregnated with oil) is increased.

It is sectional drawing of a spindle motor. It is sectional drawing of a fluid dynamic pressure bearing apparatus. (A) is sectional drawing of a bearing sleeve, (b) is the elements on larger scale of the sectional drawing, (c) is a bottom view of a bearing sleeve. (A)-(c) is sectional drawing which shows the compacting process of a bearing sleeve. (A) is a cross-sectional view showing the resin impregnation step of the bearing sleeve, (b) is a longitudinal cross-sectional view thereof. (A)-(c) is sectional drawing which shows the sizing process of a bearing sleeve. It is sectional drawing which shows the inside of the pore of the sintered compact impregnated with resin. It is sectional drawing which shows the mode inside the pore after giving sizing. It is sectional drawing which shows the mode inside the pore after giving sizing. It is sectional drawing which shows the inside of the pore of the sintered compact impregnated with resin. It is sectional drawing which shows the mode inside the pore after giving sizing. It is sectional drawing which shows the mode inside the pore after giving sizing. It is sectional drawing which shows the other example of the resin impregnation process of a bearing sleeve. It is sectional drawing which shows the other example of the resin impregnation process of a bearing sleeve. It is sectional drawing which shows the other example of the resin impregnation process of a bearing sleeve. It is sectional drawing which shows the other example of the resin impregnation process of a bearing sleeve. It is sectional drawing which shows the other example of the resin impregnation process of a bearing sleeve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid dynamic pressure bearing apparatus 2 Shaft member 7 Housing 8 Bearing sleeve 9 Seal member 15 Sintered body 20 Pore 21 Resin 22 Bubble 23 Crack 24 Micro gap 30 Independent pore R1, R2 Radial bearing part T1, T2 Thrust bearing part S Seal space

Claims (5)

A sintered bearing comprising a sintered body obtained by sintering a compacted body of metal powder, and having a bearing surface,
A sintered bearing in which pores communicating with the surface of the sintered body are impregnated with a resin deformed by sizing, and a gap in the pores is impregnated with lubricating oil.   The sintered bearing according to claim 1, wherein a surface having pores impregnated with a lubricating oil is used as a bearing surface. A method for producing a sintered bearing having a bearing surface, comprising a sintered body obtained by sintering a compacted body of metal powder,
A method for manufacturing a sintered bearing in which pores of a sintered body are impregnated with a resin, and then the sintered body is subjected to sizing, thereby expanding a gap volume in the pores communicating with the surface of the sintered body.   The method for manufacturing a sintered bearing according to claim 3, wherein the region excluding the bearing surface is impregnated with resin.   4. The method for manufacturing a sintered bearing according to claim 3, wherein after impregnating the resin, the resin on the bearing surface is removed by sizing.

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