JP7068885B2 - Sintered bearings and their manufacturing methods - Google Patents

Description

The present invention relates to a sintered bearing and a method for manufacturing the same.

As a bearing for a small motor, for example, a bearing for a fan motor installed in a notebook computer or the like, a plurality of dynamic pressure generating grooves arranged in a herringbone shape or the like are formed on the inner peripheral surface of a sintered metal bearing member. In many cases, a hydrodynamic bearing is used (Patent Document 1). By forming the dynamic pressure generating groove in this way, during the rotation of the shaft, the lubricating oil is collected in a part of the axial direction of the bearing surface by the dynamic pressure generating groove to generate a dynamic pressure effect, and the dynamic pressure effect causes the dynamic pressure effect. The rotating shaft is non-contactly supported with respect to the bearing member.

Japanese Unexamined Patent Publication No. 2016-50648

For example, when sizing a sintered body, the dynamic pressure generating groove on the inner peripheral surface of the bearing member forms a plurality of convex portions corresponding to the shape of the dynamic pressure generating groove on the outer peripheral surface of the core pin, and the pressure is applied due to the sizing. Therefore, it can be formed by feeding the inner peripheral surface of the sintered body to the convex portion of the outer peripheral surface of the core pin. However, in this step, since the dynamic pressure generating groove is formed by the plastic deformation of the sintered material, there is a limit in ensuring the accuracy due to the variation in the amount of plastic deformation.

On the other hand, if the number of coarse air holes in the bearing surface is reduced, the oil film formation rate is improved, and it is considered that sufficient oil film rigidity can be obtained even if the dynamic pressure generation groove is omitted. Therefore, it is possible to replace the fluid dynamic pressure bearing having the dynamic pressure generating groove with a so-called perfect circular bearing having no such dynamic pressure generating groove, and it is considered that the cost of the bearing device can be reduced.

Therefore, an object of the present invention is to provide a sintered bearing in which the number of coarse air holes in the bearing surface is reduced and the surface openings and internal pores are made finer and more homogenized.

In order to achieve the above object, the present invention is an alloyed copper in which copper and a low melting point element having a lower melting point than copper are alloyed in a sintered bearing having a bearing surface and containing copper and iron as main components. The alloyed copper powder has a structure formed by sintering the partially diffused alloy powder obtained by adhering the powder to the surface of the iron powder by partial diffusion, and the maximum particle size of the partially diffused alloy powder is 106 μm. The maximum particle size of the copper is 45 μm or less.

In the present invention, the maximum particle size of the partially diffused alloy powder and the alloyed copper powder is limited, and the maximum particle size of the alloyed copper powder is set to 45 μm or less to reduce the particle size of the alloyed copper powder. Therefore, the partial diffusion alloy powder does not contain particles in which the coarse iron powder and the coarse alloyed copper powder are integrated, and the particle size of the partial diffusion alloy powder can be made uniform. As a result, it is possible to prevent the formation of coarse air pores after sintering. On the other hand, the particle size of the raw material powder does not become too small, and the fluidity of the raw material powder when forming the powdered compact is also good.

By using alloyed copper powder (for example, bronze powder) in which a low melting point element having a lower melting point than copper is alloyed with copper as the copper component of the partially diffused alloy powder, the generation of crude air pores is more effectively generated. It can be suppressed. That is, when the low melting point element is used as a simple substance powder, the entire low melting point element powder is melted into a liquid phase at the time of sintering, and this moves to form pores in the original place. On the other hand, by using the alloyed copper powder, since only the surface of the alloyed copper powder is melted at the time of sintering, it is possible to prevent the generation of such vacancies. Further, by using the alloyed copper powder, it is possible to avoid segregation, which is a problem when a simple substance powder of a low melting point element is used.

On the other hand, powder (Cu—Sn alloy powder) in which a low melting point element is alloyed with copper is generally hard and difficult to deform. Therefore, if such alloyed copper powder is added to the raw material powder as it is, it becomes compressible. Since the formability is poor, gaps are likely to be formed between the particles during the molding of the powder powder, which causes coarse air pores to be formed after sintering. On the other hand, if the alloyed copper powder is made porous, the entire powder is softened, so that the compressibility of the raw material powder is improved and gaps are less likely to occur between the particles. Therefore, it is possible to suppress the generation of crude air pores after sintering. The porosity of the alloyed copper powder is achieved, for example, by heating (low temperature heating) a mixed powder of the iron powder and the alloyed copper powder during the production of the partially diffused alloy powder to heat the alloyed copper powder.

With the configuration described above, it is possible to secure sufficient oil film rigidity and obtain a high oil film formation rate. Therefore, it is possible to form the bearing surface in a cylindrical shape and omit the dynamic pressure generating groove, and the cost of the bearing device is lower than that in the case of using a fluid dynamic pressure bearing having such a dynamic pressure generating groove. Can be achieved.

Further, the present invention is a method for manufacturing a sintered bearing having a bearing surface and containing copper and iron as main components, and is an alloyed copper powder obtained by alloying copper and a low melting point element having a melting point lower than that of copper. Is formed into a green compact using the partial diffusion alloy powder adhered to the surface of the iron powder by partial diffusion, so that the maximum particle size of the partial diffusion alloy powder is 106 μm and the maximum particle size of the alloyed copper powder is 106 μm. Is 45 μm or less, and the green compact is sintered.

As described above, according to the present invention, it is possible to reduce the number of coarse air holes on the bearing surface and to make the surface openings finer and more homogenized. As a result, pressure relief on the bearing surface is less likely to occur, so that a high oil film formation rate can be obtained.

It is sectional drawing of a fan motor. It is sectional drawing of the bearing device for a fan motor. Both the figure (a) and the figure (b) are views schematically showing the morphology of the partially diffused alloy powder. It is a graph which shows the particle size distribution of a partial diffusion alloy powder. It is a figure which shows the other example of a partial diffusion alloy powder schematically. It is a figure which shows the comparative test result of the oil film formation rate. It is a circuit diagram which shows the measuring apparatus of the oil film formation rate.

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

FIG. 1 shows a cooling fan motor incorporated in an information device, particularly a mobile device such as a mobile phone or a tablet terminal. This fan motor has a stator that faces the bearing device 1, the rotor 3 mounted on the shaft member 2 of the bearing device 1, and the blade 4 attached to the outer diameter end of the rotor 3 via a radial gap. A coil 6a, a rotor magnet 6b, and a casing 5 for accommodating these are provided. The stator coil 6a is attached to the outer periphery of the bearing device 1, and the rotor magnet 6b is attached to the inner circumference of the rotor 3. By energizing the stator coil 6a, the rotor 3, the blade 4, and the shaft member 2 rotate integrally, which generates an air flow in the axial direction or the outer diameter direction.

As shown in FIG. 2, the bearing device 1 includes a shaft member 2, a housing 7, a sintered bearing 8, a seal member 9, and a thrust receiver 10.

The shaft member 2 is made of a metal material such as stainless steel in a cylindrical shape, and is inserted into the inner peripheral surface of the cylindrical sintered bearing 8. The shaft member 2 is rotatably supported in the radial direction on the inner peripheral surface 8a of the sintered bearing 8 which is the bearing surface. The lower end of the shaft member 2 is in contact with the thrust receiver 10 arranged on the bottom portion 7b of the housing 7, and when the shaft member rotates, the shaft member 2 is supported in the thrust direction by the thrust receiver 10. The housing 7 has a substantially cylindrical side portion 7a and a bottom portion 7b that closes the opening below the side portion 7a. The casing 5 and the stator coil 6a are fixed to the outer peripheral surface of the side portion 7a, and the bearing member 8 is fixed to the inner peripheral surface of the side portion 7a. The sealing member 9 is formed of a resin or metal in an annular shape, and is fixed to the upper end of the inner peripheral surface of the side portion of the housing. The lower end surface of the seal member 9 is in axial contact with the upper end surface of the bearing member 8. The inner peripheral surface of the seal member 9 faces the outer peripheral surface of the shaft member 2 in the radial direction, and a seal space S is formed between the two. In such a bearing device 1, at least the radial gap formed between the inner peripheral surface of the bearing member 8 and the outer peripheral surface of the shaft member 2 is filled with the lubricating oil. In addition, the entire internal space of the housing 7 may be filled with lubricating oil (in this case, an oil level is formed in the seal space S).

The bearing member 8 is formed of an iron-copper-based sintered body containing iron and copper as main components. This sintered body is manufactured by supplying a raw material powder, which is a mixture of various powders, to a mold, compressing the raw powder to form a pressure powder, and then sintering the pressure powder. Hereinafter, this manufacturing process will be described in detail.

As shown in FIG. 3A, the partially diffused alloy powder 11 is obtained by partially diffusing alloyed copper powder 13 having a particle size smaller than that of the iron powder on the surface of the core iron powder 12. .. For details, as shown in the partially enlarged view in FIG. 3 (b), a part of the copper structure (copper atom 13a) diffuses into the iron structure at the boundary between the iron powder and the copper powder, and also into the copper structure. It has a crystal structure in which the iron atom 12a and the copper atom 13a are partially replaced by the diffusion of a part of the iron structure (iron atom 12a).

As the iron powder 12 of the partial diffusion alloy powder 11, reduced iron powder, atomized iron powder, or the like can be used, but in the present embodiment, the reduced iron powder is used. The reduced iron powder has an irregular shape and is spongy (porous) with internal pores. By using the reduced iron powder, the compressibility can be improved and the moldability can be improved as compared with the case where the atomized iron powder is used. Further, since the iron structure after sintering becomes porous, the lubricating oil can be retained in the iron structure, and there is an advantage that the oil retention property of the sintered body can be improved. Further, since the adhesion of the alloyed copper powder 13 to the iron powder is improved, a partially diffused alloy powder having a uniform copper concentration can be obtained.

Further, as the iron powder 12 which is the core of the partial diffusion alloy powder 11, a powder having a particle size of 145 mesh or less is used. Here, the "particle size 145 mesh" means a powder of an under material having a mesh size of 145 mesh (about 106 μm) passed through a sieve (that is, a powder containing no over material that cannot pass through a sieve having a mesh size of 145 mesh). .. Therefore, the maximum particle size of the iron powder in this case is 106 μm. "Particle size of 145 mesh or less" means that the particle size of the powder is 145 mesh or less, that is, the maximum particle size of the powder is 106 μm or less. The particle size of the iron powder is preferably 20 μm or more, and even more preferably 38 μm or more. The maximum particle size of the iron powder is preferably 75 μm or less. In terms of particle size, it is preferable to use iron powder having a particle size of 230 mesh (opening 63 μm, maximum particle size 63 μm) or less. Iron powder having a particle size of 325 mesh or less (opening 45 μm, maximum particle size 45 μm) can also be used. The average particle size of the iron powder is 106 μm or less, specifically 45 μm or more and 75 μm or less (preferably 45 μm or more and 63 μm or less). The particle size (including the average particle size) of the powder can be measured by, for example, a laser diffraction / scattering method (hereinafter, the same).

The alloyed copper powder 13 is a powder (complete alloy powder) obtained by alloying copper and a low melting point element having a melting point lower than that of copper. The low melting point element functions as a binder at the time of sintering, and an element having a melting point lower than that of copper, particularly an element having a melting point of 700 ° C. or lower (for example, tin, zinc, phosphorus, etc.) is used as the low melting point element. In particular, it is preferable to use a low melting point metal such as tin or zinc. Among the low melting point metals, tin has a characteristic that it easily diffuses into copper and iron. Therefore, it is preferable to use bronze powder (Cu—Sn alloy powder) using tin as a low melting point element as the alloyed copper powder 13. .. The maximum particle size of the alloyed copper powder 13 is 45 μm or less, preferably 20 μm or less. The average particle size of the alloyed copper powder 13 is preferably about 1/10 or less (specifically, 1/100 or more and 1/10 or less) of the average particle size of the iron powder 12.

When the mixture of the iron powder and the alloyed copper powder described above is carried into a belt-type heating furnace and heated for a predetermined time, a part of the alloyed copper powder is diffused into the iron powder, and the partially diffused alloy powder is formed. can get. It is appropriate that the temperature inside the furnace is several hundred degrees Celsius and the heating time is several tens of minutes. The partial diffusion alloy powder used in the present embodiment is obtained by diffusion-bonding iron powder and alloyed copper powder and then pulverizing the powder. Since the Cu-Sn mixed powder is generally hard and hard to be deformed, if the mixed powder containing the iron powder and the Cu-Sn mixed powder is used as the raw material powder, there is a problem that the compressibility and moldability at the time of compaction forming are lowered. .. On the other hand, if the Fe—Cu—Sn partially diffused alloy powder is used as described above, each powder (particularly the alloyed copper powder 13) is heat-treated by heating during the production of the powder to make it porous. As a result, the individual particles of the partial diffusion alloy powder are softened, so that the compressibility and moldability at the time of compaction molding are improved.

As shown in the enlarged schematic diagram on the right side of FIG. 3, a Fe—Cu—Sn alloy is formed in the diffusion portion (scattering point pattern portion) of the partial diffusion alloy powder 11. This alloy portion has a crystal structure in which iron atoms, copper atoms, and tin atoms are bonded to each other and arranged. Of the alloyed copper powder 13, the structure of the original Cu—Sn alloy is maintained as it is except for the diffusion portion.

As the partial diffusion alloy powder 11 described above, those having a particle size of 145 mesh or less (maximum particle size of 106 μm or less) are used. The particle size of the partially diffused alloy powder after pulverization shows a normal distribution as shown in FIG. 4, but after pulverization, for example, by sieving with a sieve having a mesh size of 145 mesh, the particle size represented by the scattered spot pattern in the figure. A partially diffused alloy powder having a distribution is obtained. In the present embodiment, the partially diffused alloy powder of the under material after sieving as described above is used.

In the present embodiment, the composition of the raw material powder is 100% of the partial diffusion alloy powder. The ratio of each element in the raw material powder is 15% by mass to 40% by mass (preferably 20% by mass to 30% by mass) for copper, 1% to 4% by mass for low melting point elements such as low melting point metal, and iron for the balance. And it is preferable to use unavoidable impurities.

When using only partial diffusion alloy powder, there is a limit to the upper limit of the copper content, so if you want to increase the copper content above the upper limit, use copper powder (pure copper powder) as the raw material powder. May be added alone. Further, in the present embodiment, no solid lubricant is blended in the raw material powder. This is because, for example, when graphite powder, which is generally used as a solid lubricant, is mixed with the raw material powder, when the shaft is rotated at high speed (for example, peripheral speed of 600 m / min or more), the graphite structure exposed on the bearing surface contains wear powder and the like. This is because there is a risk that foreign matter may get entangled and worsen the slidability. Of course, if it is a sintered bearing that is not used for high-speed rotation, graphite powder may be mixed with the raw material powder at a ratio of, for example, about 0.1 to 1.5% by mass. Molybdenum disulfide or the like can also be used as the solid lubricant.

The molding lubricant is blended in an amount of 0.1 to 1.0% by mass with respect to 100% of the raw material powder described above. As the molding lubricant, for example, metal soap (zinc stearate, calcium stearate, etc.) or wax can be used. However, since these molding lubricants are decomposed and disappeared by sintering and cause coarse air pores, it is preferable to reduce the amount of molding lubricant used as much as possible.

The powder is formed by filling the inside of the mold with the above raw material powder and compressing it. Then, by sintering the powdered body, a sintered body is obtained. The sintering temperature is a temperature equal to or higher than the melting point of the low melting point element (low melting point metal) and lower than the melting point of copper, specifically, about 760 ° C. to 900 ° C. By sintering the compactor, the surface of the alloyed copper powder contained in the partially diffused alloy powder becomes a liquid phase and wets the surface of other alloyed copper powder, so that copper-based particles or copper-based particles and iron Suction between particles is promoted.

This sintered body has, for example, a density of 6.0 to 7.4 g / cm ³ (preferably 6.9 to 7.3 g / cm ³ ) and an internal porosity of 4 to 20%, preferably 4 to 12% (preferably 4 to 12%). More preferably, it is 5 to 11%). Further, since the raw material powder and the atmosphere of the sintering furnace do not contain carbon and the sintering temperature is 900 ° C. or lower, the iron structure of the sintered body is all a ferrite phase. Incidentally, the content of each element in the sintered body is the same as the content ratio of each element in the raw material powder.

By shaping this sintered body by sizing, the roundness of the bearing surface can be increased to 1 μm or less. After that, the sintered bearing 8 (sintered oil-impregnated bearing) shown in FIG. 2 is completed by impregnating the internal pores of the sintered body with lubricating oil by a method such as vacuum impregnation. As the lubricating oil, for example, one having a kinematic viscosity at 40 ° C. of 10 to 200 mm ² / sec, preferably 20 to 80 mm ² / sec and a viscosity index of 100 to 250 is used.

The sintered structure of this sintered body has a form in which the Cu-based structure derived from the alloyed copper powder 13 of the partial diffusion alloy powder 11 is dispersed around the Fe structure derived from the iron powder 12 of the partial diffusion alloy powder 11. Nasu. As a result, the iron structure is in the form of being covered with a copper-based structure, so that the amount of exposure of the iron structure on the bearing surface can be reduced, and thereby the initial familiarity of the sintered bearing 8 can be improved. .. The sintered structure in which the circumference of the iron structure is covered with a copper-based structure can also be obtained by using copper-coated iron powder obtained by copper-plating iron powder, but when copper-coated iron powder is used, it can be obtained. As compared with the partially diffused alloy powder used in the present embodiment, the neck strength between the copper-based structure and the iron structure after sintering is lowered, so that the annular strength of the sintered bearing is significantly lowered.

If the maximum particle size of the iron powder 12 and the alloyed copper powder 13 is not limited as described above in the process of producing the Fe—Cu—Sn partially diffused alloy powder, even if the iron powder 12 and the alloyed copper powder 13 are produced. Even if the average particle size is close to the maximum particle size, the partially diffused alloy powder is produced in a state where iron powder and alloyed copper powder having a large particle size are also mixed. Therefore, as schematically shown in FIG. 5, a considerable amount of particles (coarse particles) in which iron powder having a large particle size and alloyed copper powder are integrated are formed. If such coarse particles are sintered in an aggregated state, the gaps between the particles become large, so that coarse air pores are generated after sintering.

On the other hand, in the present invention, the maximum particle size of the alloyed copper powder 13 and the partially diffused alloy powder is limited, and the maximum particle size of the alloyed copper powder 13 is larger than the maximum particle size of the partially diffused alloy powder. It's pretty small. Therefore, the particle size distribution of the partially diffused alloy powder becomes sharp (the particle size of the partially diffused alloy becomes uniform). On the other hand, the particle size of the raw material powder does not become too small, and the fluidity in the powder state is also good. Therefore, it becomes difficult to generate coarse air pores after sintering, and the pores in the sintered structure can be made finer and more homogenized.

Further, in the present invention, as the copper-based powder, the alloyed copper powder 13 in which a low melting point element having a lower melting point than copper is alloyed with copper is used, so that the generation of coarse air pores is suppressed more effectively. can do. That is, when the elemental powder as a low melting point element is blended with the raw material powder, the entire low melting point element powder melts into a liquid phase at the time of sintering, and this moves to form pores in the original place. However, by using the alloyed copper powder, only the surface of the alloyed copper powder is melted at the time of sintering, so that it is possible to prevent the generation of such vacancies. Further, by using the alloyed copper powder, it is possible to avoid segregation, which is a problem when a simple substance powder of a low melting point element is used.

Powder, which is simply an alloy of a low melting point element with copper, is generally solid, hard, and difficult to deform. .. On the other hand, in the Fe-Cu-Sn partial diffusion alloy powder, the Cu-Sn alloy powder is heat-treated to become porous by low-temperature heating at the time of its production, so that the raw material powder is softened to improve compressibility and moldability. Can be made to. Therefore, it becomes difficult to generate gaps between the particles, and from this point as well, it is possible to suppress the generation of coarse air pores after sintering. In order to promote the porosity of the Cu—Sn alloy powder, the partial diffusion alloy powder may be reheated under the same heating conditions as described above after the partial diffusion alloy powder 11 is produced.

In addition, the verification by the present inventors has revealed that if a porous copper alloy powder is used as the copper-based powder, the sintered body after sintering shrinks more than the compaction body. Specifically, the dimensional change rate of the sintered body with respect to the powdered body was about 0.995 to 0.999 for both the inner diameter dimension and the outer diameter dimension. It is considered that this is because the porous copper alloy powder acts to attract the surrounding copper-based particles at the time of sintering. On the other hand, in the existing copper-iron-based sintered body using non-porous copper alloy powder, it is customary to expand more than the state of the compaction body at the time of sintering. By shrinking the sintered body during sintering in this way, the sintered structure is densified, so that it is possible to more reliably suppress the generation of coarse air pores.

Through these actions, it is possible to obtain a sintered body having an area of each surface pore of 0.01 mm ² (0.1 mm × 0.1 mm) or less, and it is possible to prevent the generation of coarse air pores. Incidentally, the surface opening ratio of the bearing surface is 4% or more and 20% or less (preferably 12% or less and the variation is 5% or less) in terms of area ratio. The oil permeability of the sintered body is 0.010 to 0.025 g / 10 minutes. The "oil permeability" here is a parameter [unit: g / 10 min] for quantitatively indicating how much lubricating oil can be circulated through the porous structure of the porous work. be. The degree of oil permeability is such that the inner peripheral hole of the cylindrical test piece is filled with lubricating oil while applying a pressure of 0.4 MPa in an environment of room temperature (26 to 27 ° C.), and the surface opened on the outer diameter surface of the test piece. It can be obtained by collecting the oil that has exuded from the holes and dropped.

As described above, according to the present invention, it is possible to eliminate the coarse air pores generated on the bearing surface (the maximum area of the surface pores is 0.01 mm ² ) and to make the size of the surface pores uniform. As a result, pressure relief on the bearing surface 8a can be suppressed and the oil film formation rate can be increased, so that high oil film rigidity can be ensured and the shaft can be stably supported regardless of low-speed rotation or high-speed rotation. Become. Therefore, even in the form of a perfect circular bearing that does not have a dynamic pressure generating groove, it is possible to obtain bearing performance equivalent to that of a sintered bearing with a dynamic pressure generating groove, and it is a substitute for a sintered bearing with a dynamic pressure generating groove. Can be used as. In particular, a sintered bearing with a dynamic pressure groove is difficult to use in a region where the peripheral speed is 5 m / min or less because the dynamic pressure effect cannot be sufficiently obtained. However, the sintered bearing of the present invention has a peripheral speed. The merit that the shaft can be stably supported even in a low speed region of 5 m / min or less can be obtained. Further, since an oil film can be continuously formed over the entire circumference of the bearing gap between the bearing surface 8a and the outer peripheral surface of the shaft 2 even at a high speed rotation exceeding 600 m / min, the shaft 2 should be stably supported. Can be done. Incidentally, in the existing sintered bearing, the peripheral speed is about 10 m / min to 300 m / min.

Further, in the coarse particles shown in FIG. 5, since the area of the diffusion bonding portion is smaller than the volume of the alloyed copper powder 13, the bonding strength between the two is lowered. Therefore, when the partially diffused alloy powder is sieved, the copper-based particles (Cu—Sn alloy particles) are likely to fall off from the iron particles due to the impact. In this case, since a large amount of Cu—Sn alloy powder having a small particle size is mixed in the raw material powder, the fluidity of the raw material powder is lowered, which causes segregation of copper and the like. On the other hand, in the present invention, since the maximum particle size of the alloyed copper powder 13 used for producing the partially diffused alloy powder is limited, the partially diffused alloy powder generally has a form as shown in FIG. In this case, since the area of the diffusion bonding portion is relatively large compared to the volume of the alloyed copper powder 13, the bonding strength between the iron powder 12 and the alloyed copper powder 13 is increased. Therefore, even when sieving is performed, the alloyed copper powder is less likely to fall off, and the above-mentioned adverse effects can be prevented.

FIG. 6 shows the measurement results of the oil film formation rate between the product of the present invention and the comparative product. The comparative product is a sintered bearing using copper-coated iron powder having an iron powder of 80 mesh under as a core, and the product of the present invention uses a partial diffusion alloy powder having an iron powder of 145 mesh under as a core. It is a sintered bearing that was used.

The oil film formation rate is determined by using the circuit shown in FIG. 7, setting a combination of a shaft and a sintered bearing as a sample, and measuring the voltage. If the detected voltage is 0 [V], the oil film formation rate is 0%, and if the detected voltage is equal to the power supply voltage, the oil film formation rate is 100%. An oil film formation rate of 100% means that the shaft and the sintered bearing are in a non-contact state, and an oil film formation rate of 0% means that the shaft and the sintered bearing are in contact with each other. The horizontal axis of FIG. 6 represents time. As the measurement conditions, the rotation speed of the shaft is set to 2000 min ^-1 , and the thrust load of the shaft is set to 0.2N.

As is clear from FIG. 6, the comparative product has almost no period in which the oil film formation rate is 100%, and the shaft and the sintered bearing are in frequent contact with each other, whereas the product of the present invention has an oil film formation rate. Since it is almost 100%, the non-contact state is maintained. Therefore, it was confirmed that the product of the present invention can obtain a better oil film formation rate than the comparative product.

As described above, the fan motor has been exemplified as an example of the use of the sintered bearing according to the present invention, but the application target of the sintered bearing according to the present invention is not limited to this, and it can be used for various purposes.

Further, although the case where the dynamic pressure generating groove is not formed on the inner peripheral surface of the bearing surface 8a of the sintered bearing 8, a plurality of dynamic pressure generating grooves can be formed on the bearing surface 8a as needed. The dynamic pressure generation groove can also be formed on the outer peripheral surface of the shaft 2. Further, the sintered bearing 8 can be used not only to support rotational motion but also to support linear motion.

1 Bearing device 2 Shaft member 8 Sintered bearing 8a Inner peripheral surface (bearing surface)
11 Partial diffusion alloy powder 12 Iron powder 13 Alloyed copper powder

Claims (3)

In a sintered bearing that has a bearing surface and is mainly composed of copper and iron.
It has a structure formed by sintering a partially diffused alloy powder obtained by alloying copper and a low melting point element having a lower melting point than copper and adhering it to the surface of the iron powder by partial diffusion. death,
The alloyed copper powder of the partial diffusion alloy powder is porous.
A sintered bearing characterized in that the maximum particle size of the partially diffused alloy powder is 106 μm and the maximum particle size of the alloyed copper powder is 45 μm or less. The sintered bearing according to claim 1, wherein the bearing surface is formed into a cylindrical surface having no dynamic pressure generating groove. It is a method of manufacturing a sintered bearing that has a bearing surface and is mainly composed of copper and iron.
A green compact is formed by forming an alloyed copper powder, which is an alloy of copper and a low melting point element having a melting point lower than that of copper, on the surface of the iron powder by partial diffusion to form a green compact. The alloyed copper powder of the diffusion alloy powder is made porous by heat treatment.
The maximum particle size of the partially diffused alloy powder is 106 μm, and the maximum particle size of the alloyed copper powder is 45 μm or less.
A method for manufacturing a sintered bearing, which comprises sintering the green compact.

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