WO2015050200A1 - Palier fritté et son procédé de fabrication - Google Patents

Palier fritté et son procédé de fabrication Download PDF

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Publication number
WO2015050200A1
WO2015050200A1 PCT/JP2014/076399 JP2014076399W WO2015050200A1 WO 2015050200 A1 WO2015050200 A1 WO 2015050200A1 JP 2014076399 W JP2014076399 W JP 2014076399W WO 2015050200 A1 WO2015050200 A1 WO 2015050200A1
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Prior art keywords
powder
copper
iron
bearing
sintered
Prior art date
Application number
PCT/JP2014/076399
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English (en)
Japanese (ja)
Inventor
容敬 伊藤
山下　智典
Original Assignee
Ntn株式会社
容敬 伊藤
山下　智典
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP2014007911A external-priority patent/JP6302259B2/ja
Priority claimed from JP2014008892A external-priority patent/JP6389038B2/ja
Application filed by Ntn株式会社, 容敬 伊藤, 山下　智典 filed Critical Ntn株式会社
Priority to CN201480053495.2A priority Critical patent/CN105593543B/zh
Priority to US15/026,134 priority patent/US20160223016A1/en
Priority to EP14850756.9A priority patent/EP3054185B1/fr
Publication of WO2015050200A1 publication Critical patent/WO2015050200A1/fr
Priority to US16/402,698 priority patent/US10907685B2/en

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/02—Parts of sliding-contact bearings
    • F16C33/04—Brasses; Bushes; Linings
    • F16C33/06—Sliding surface mainly made of metal
    • F16C33/14—Special methods of manufacture; Running-in
    • F16C33/145—Special methods of manufacture; Running-in of sintered porous bearings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/02—Parts of sliding-contact bearings
    • F16C33/04—Brasses; Bushes; Linings
    • F16C33/06—Sliding surface mainly made of metal
    • F16C33/10—Construction relative to lubrication
    • F16C33/1095—Construction relative to lubrication with solids as lubricant, e.g. dry coatings, powder
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/02—Parts of sliding-contact bearings
    • F16C33/04—Brasses; Bushes; Linings
    • F16C33/06—Sliding surface mainly made of metal
    • F16C33/12—Structural composition; Use of special materials or surface treatments, e.g. for rust-proofing
    • F16C33/122—Multilayer structures of sleeves, washers or liners
    • F16C33/124—Details of overlays
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/02—Parts of sliding-contact bearings
    • F16C33/04—Brasses; Bushes; Linings
    • F16C33/06—Sliding surface mainly made of metal
    • F16C33/12—Structural composition; Use of special materials or surface treatments, e.g. for rust-proofing
    • F16C33/122—Multilayer structures of sleeves, washers or liners
    • F16C33/125—Details of bearing layers, i.e. the lining
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/02—Parts of sliding-contact bearings
    • F16C33/04—Brasses; Bushes; Linings
    • F16C33/06—Sliding surface mainly made of metal
    • F16C33/12—Structural composition; Use of special materials or surface treatments, e.g. for rust-proofing
    • F16C33/128—Porous bearings, e.g. bushes of sintered alloy
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2202/00—Solid materials defined by their properties
    • F16C2202/50—Lubricating properties
    • F16C2202/52—Graphite
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2204/00—Metallic materials; Alloys
    • F16C2204/10—Alloys based on copper
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2204/00—Metallic materials; Alloys
    • F16C2204/60—Ferrous alloys, e.g. steel alloys
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2220/00—Shaping
    • F16C2220/20—Shaping by sintering pulverised material, e.g. powder metallurgy
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2223/00—Surface treatments; Hardening; Coating
    • F16C2223/30—Coating surfaces
    • F16C2223/42—Coating surfaces by spraying the coating material, e.g. plasma spraying

Definitions

  • the present invention relates to a sintered bearing made of sintered metal and a method for manufacturing the same.
  • Sintered bearings are porous bodies having innumerable internal pores, and are usually used in a state in which internal pores are impregnated with a lubricating fluid (for example, lubricating oil).
  • a lubricating fluid for example, lubricating oil
  • the lubricating oil retained in the internal pores of the sintered bearing oozes into the inner peripheral surface (bearing surface) of the sintered bearing as the temperature rises. put out.
  • the oozed lubricating oil forms an oil film in the bearing gap between the bearing surface of the sintered bearing and the outer peripheral surface of the shaft, and the shaft is supported so as to be relatively rotatable.
  • Patent Document 1 copper and iron-based sintered bearings mainly composed of iron and copper are coated with 10% by mass or more and less than 30% by mass of copper, and the particle size is 80%.
  • a powdered and sintered copper-coated iron powder having a mesh or less is described.
  • Patent Document 2 it is known to use a slide bearing as a bearing that rotatably supports a motor shaft in an automobile starter.
  • an automobile starter in order to obtain a large torque necessary for starting an engine, it is usual to reduce the motor output via a reduction gear having a large reduction ratio, for example, a planetary gear mechanism.
  • a reduction gear having a large reduction ratio for example, a planetary gear mechanism.
  • a copper-based sintered bearing If a copper-based sintered bearing is used, oxidation is less likely to occur, so fretting wear can be prevented.
  • copper-based sintered bearings tend to have insufficient bearing strength because copper itself is soft. Therefore, when the shaft contacts the bearing surface due to engine vibration, the bearing surface is deformed, or when the sintered bearing is press-fitted into the inner periphery of the housing, the effect of the reduced diameter deformation of the sintered bearing due to the press-fitting is Also, the accuracy of the bearing surface may be reduced.
  • copper-based sintered bearings are advantageous in terms of sliding characteristics such as initial conformability and quietness, but are difficult in terms of bearing strength.
  • sintered iron bearings with high iron content and copper-iron alloys are advantageous in terms of bearing strength, but have difficulty in terms of sliding characteristics (as described above, depending on the operating conditions Ting wear is also a concern).
  • An object of the present invention is to provide a sintered bearing that has good sliding characteristics, can achieve both wear resistance and bearing strength of the bearing surface, and can reduce costs, and a method for manufacturing the same. To do.
  • a sintered bearing according to the present invention is a sintered bearing mainly composed of iron, copper, a metal having a lower melting point than copper, and a solid lubricant, and has an iron structure and a copper structure.
  • ⁇ Flat copper powder has the property of adhering to the mold molding surface during molding of the raw powder, so that the compact after molding contains a large amount of copper in the surface layer. Therefore, a surface layer having a high copper content is formed in the sintered body after sintering (preferably a copper structure having an area ratio of 60% or more is formed on the surface of the surface layer). In this way, by increasing the copper content in the surface layer, it is possible to improve initial conformability and quietness, and in combination with the action of a solid lubricant such as graphite, the sliding characteristics are good. It will be something. In addition, since the aggression against the shaft is reduced, the durability life is improved. In addition, since a copper-rich bearing surface that is not easily oxidized is formed, fretting wear of the bearing surface can be prevented.
  • the copper structure in contact with the iron structure of the base layer is basically a low melting point metal diffused into the copper powder.
  • the low melting point metal wets the surface of copper and advances liquid phase sintering, so that the bonding force between the metal particles can be strengthened particularly in the base portion.
  • the base part is basically formed of partially diffused alloy powder in which part of copper powder is diffused into iron powder, the sintered copper structure (structure containing copper as a main component) and iron structure (iron) High neck strength can be obtained between the main components). From the above, it is possible to prevent the copper structure and the iron structure from falling off the bearing surface and to improve the wear resistance of the bearing surface.
  • the bearing strength can be increased. Therefore, even when a sintered bearing is press-fitted and fixed to the inner periphery of the housing, the bearing surface is not deformed following the shape of the inner peripheral surface of the housing. Can be achieved. Further, since the foundation of the bearing surface is reinforced, deformation of the bearing surface when the shaft contacts the bearing surface due to vibration or the like can be suppressed. Accordingly, it is possible to provide a sintered bearing suitable for use in a starter for starting an engine (including a speed reducer incorporated in the starter) and a vibration motor used in a portable terminal or the like. .
  • the proportion of copper in the partial diffusion alloy powder is preferably 10 wt% or more and 30 wt% or less.
  • the flat copper powder may be spheroidized.
  • the partial diffusion alloy powder which diffused a part of copper powder to iron powder since the partial diffusion alloy powder which diffused a part of copper powder to iron powder is used, many copper powder exists around a low melting-point metal at the time of sintering. In this case, the low melting point metal melted as the temperature of sintering diffuses into the copper powder of the partial diffusion alloy powder prior to the flat copper powder, so the influence of the low melting point metal powder on the flat copper powder of the surface layer is affected. Can be suppressed. Therefore, spheroidization of the flat copper powder in the surface layer can be prevented, and the copper concentration on the surface of the surface layer can be increased.
  • the iron structure and copper structure of the base layer are either partially diffused alloy powder, simple iron powder and simple copper powder or It can be formed with both.
  • the content of the low melting point metal relative to the flat copper powder should be less than 10 wt% in order to minimize the effect of spheroidization. Is the common technical knowledge so far.
  • the content of the low melting point metal in the bearing can be increased. As the content of the low melting point metal increases in this way, the bonding force between the metal particles is further strengthened, which is effective in improving the bearing strength.
  • the low melting point metal can be contained in a weight ratio of 10 wt% to 30 wt% with respect to the flat copper powder.
  • the iron structure can be formed of a ferrite phase (only), or can be formed of a ferrite phase and a pearlite phase present at the grain boundary of the ferrite phase.
  • the iron structure is mainly composed of a ferrite phase, so that the aggression against the shaft is weakened even if the copper content is small. Increase durability.
  • the hard pearlite phase supplements the wear resistance of the ferrite phase, the wear on the bearing surface can be suppressed.
  • the pearlite content is excessive, the aggression against the shaft increases and the shaft tends to wear.
  • the sintered bearing is preferably impregnated with a lubricating oil having a kinematic viscosity of 30 mm 2 / sec or more and 200 mm 2 / sec or less.
  • the sintered bearing described above is a mixture of partially diffused alloy powder obtained by partially diffusing copper powder in iron powder, flat copper powder, metal powder having a melting point lower than that of copper, and solid lubricant powder. After the green compact is formed with the mixed powder, it can be manufactured by sintering the green compact at a temperature lower than the melting point of copper.
  • FIG. 7 is an enlarged cross-sectional view of a region Q in FIG. 6. It is an enlarged view in the radial cross section of a sintered bearing (area
  • tissue It is an enlarged view explaining spheroidization of flat copper powder, and shows before sintering. It is an enlarged view explaining spheroidization of flat copper powder, and shows after sintering. It is an enlarged view which shows notionally the compact structure before sintering of this invention. It is sectional drawing which shows other embodiment of the sintered bearing concerning this invention. It is sectional drawing which shows other embodiment of the sintered bearing concerning this invention. It is a principal part schematic sectional drawing of a vibration motor. It is sectional drawing in the AA line shown in FIG. It is a microscope picture of the cross section containing a bearing surface. It is a figure which shows a part of powder compact notionally. It is a microscope picture of the cross section containing the bearing surface of the sintered bearing concerning a prior art.
  • the sintered bearing 1 is formed in a cylindrical shape having a bearing surface 1a on the inner periphery.
  • the sintered bearing 1 of this embodiment is used by impregnating lubricating oil in the internal pores of a porous sintered body (also called a sintered oil-impregnated bearing).
  • a porous sintered body also called a sintered oil-impregnated bearing.
  • FIG. 2 shows a simplified representative configuration of a starter ST used for starting an automobile engine.
  • the starter ST includes a housing 3, a motor unit 4 having a motor shaft 2a, a reduction gear 5 having an output shaft 2b, an overrunning clutch 6 having an output shaft 2c, a pinion gear 7, a shift lever. 8 and the electromagnetic switch 9 are main components.
  • the shift lever 8 is rotatable around a fulcrum O, and the tip thereof is disposed behind the overrunning clutch 6 (input side).
  • the overrunning clutch 6 is a one-way clutch, and an output shaft 2b of the reduction gear 5 is connected to an input side of the overrunning clutch 6 via a spline or the like so as to be slidable in the axial direction.
  • a pinion gear 7 is attached to the output shaft 2 c of the overrunning clutch 6, and the overrunning clutch 6 can move in the axial direction integrally with the output shaft 2 c and the pinion gear 7.
  • the motor unit 4 When the ignition is turned on, the motor unit 4 is driven, and the torque of the motor shaft 2a is transmitted to the pinion gear 7 via the speed reduction device 5 and the overrunning clutch 6. Further, the electromagnetic switch 9 is turned on and a rotational force in the direction of the arrow in the figure is applied to the shift lever 8, so that the overrunning clutch 6 and the pinion gear 7 move forward together. As a result, the pinion gear 7 meshes with the ring gear 10 coupled to the crankshaft, the torque of the motor unit 4 is transmitted to the crankshaft, and the engine is started. After the engine is started, the electromagnetic switch 9 is turned off, the overrunning clutch 6 and the pinion gear 7 are retracted, and the pinion gear 7 is separated from the ring gear 10. Since the engine torque immediately after engine startup is interrupted by the overrunning clutch 8, it is not transmitted to the motor unit 4.
  • the sintered bearing 1 of the present invention is press-fitted and fixed to the inner periphery of the housing 3 or the like of the starter ST described above and supports the various shafts 2 (2a to 2c) in the starter ST (in FIG. 2, the motor shaft 2a and The case where the output shaft 2c of the overrunning clutch 6 is supported by the sintered bearing 1 is illustrated).
  • the sintered bearing 1 can also be used for supporting the gear of the reduction gear 5.
  • the speed reducer 5 is constituted by a planetary gear mechanism
  • the planetary gear is rotatably supported with respect to the shaft by press-fitting the sintered bearing 1 of the present invention into the inner periphery of the planetary gear rotating with respect to the shaft. can do.
  • the sintered bearing 1 described above is formed by filling raw material powder mixed with various powders into a mold, compressing this to form a green compact, and then sintering the green compact.
  • the raw material powder is a mixed powder mainly composed of partially diffused alloy powder, flat copper powder, low melting point metal powder, and solid lubricant powder.
  • various molding aids for example, a lubricant (metal soap or the like) for improving releasability are added as necessary.
  • a lubricant metal soap or the like
  • Part diffusion alloy powder As the partial diffusion alloy powder, as shown in FIG. 3, Fe—Cu partial diffusion alloy powder 11 in which a large number of copper powders 13 are partially diffused on the surface of iron powder 12 is used.
  • the diffusion part of the partial diffusion alloy powder 11 forms an Fe—Cu alloy, and as shown in the enlarged partial view in FIG. 3, the alloy part is formed by bonding iron atoms 12a and copper atoms 13a to each other. It has a crystal structure.
  • the partial diffusion alloy powder 11 one having an average particle diameter of 75 ⁇ m to 212 ⁇ m is preferably used.
  • the iron powder 12 constituting the partial diffusion alloy powder 11 known iron powders such as reduced iron powder and atomized iron powder can be used, but reduced iron powder is used in this embodiment.
  • the reduced iron powder has an irregular shape that approximates a spherical shape and has a sponge shape (porous shape) having internal pores, and is also referred to as sponge iron powder.
  • the iron powder 12 used preferably has an average particle size of 45 ⁇ m to 150 ⁇ m, and more preferably an average particle size of 63 ⁇ m to 106 ⁇ m.
  • the average particle size is determined by irradiating a particle group with laser light and calculating the particle size distribution by calculating from the intensity distribution pattern of diffraction / scattered light emitted from the particle group. (The average particle size of each powder described below can also be measured by the same method).
  • the copper powder 13 constituting the partial diffusion alloy powder 11 a widely used irregular shape or dendritic copper powder can be widely used.
  • electrolytic copper powder, atomized copper powder, or the like is used.
  • an atomized copper powder having a large number of irregularities on the surface, an irregular shape that approximates a spherical shape as a whole particle, and excellent in formability is used.
  • the copper powder 13 to be used has a smaller particle diameter than the iron powder 12, and specifically, one having an average particle diameter of 5 ⁇ m to 45 ⁇ m is used.
  • the proportion of Cu in the partial diffusion alloy powder 11 is 10 to 30 wt% (preferably 22 to 26 wt%).
  • the flat copper powder is flattened by stamping raw material copper powder made of water atomized powder or the like.
  • “length” and “thickness” refer to the geometric maximum dimension of each flat copper powder 3 as shown in FIG.
  • the apparent density of the flat copper powder is 1.0 g / cm 3 or less. If the flat copper powder has the above size and apparent density, the adhesion of the flat copper powder to the mold forming surface is increased, so that a large amount of flat copper powder can be attached to the mold forming surface.
  • Fluid lubricant In order to attach the flat copper powder to the molding surface, a fluid lubricant is previously attached to the flat copper powder. This fluid lubricant only needs to be attached to the flat copper powder before filling the raw material powder into the mold, preferably before mixing the raw material powder, more preferably to the raw material copper powder at the stage of crushing the raw material copper powder. Let The fluid lubricant may be attached to the flat copper powder by means such as supplying the fluid lubricant to the flat copper powder and stirring it after mixing and before mixing with other raw material powders.
  • the blending ratio of the fluid lubricant to the flat copper powder should be 0.1% by weight or more, and aggregation due to the adhesion of the flat copper powders In order to prevent this, the blending ratio is 0.8% by weight or less. Desirably, the lower limit of the blending ratio is 0.2% by weight or more, and the upper limit is 0.7% by weight.
  • the fluid lubricant fatty acids, particularly linear saturated fatty acids are preferred. This type of fatty acid is represented by the general formula C n-1 H 2n-1 COOH. This fatty acid has a Cn in the range of 12 to 22, and for example, stearic acid can be used as a specific example.
  • the low melting point metal powder is a metal powder having a melting point lower than that of copper.
  • a metal powder having a melting point of 700 ° C. or lower for example, a powder of tin, zinc, phosphorus or the like is used. Of these, tin is preferred because it causes less transpiration during sintering.
  • the average particle diameter of the low-melting metal powder is preferably 5 ⁇ m to 45 ⁇ m, and is preferably smaller than the average particle diameter of the partial diffusion alloy powder 11.
  • the low melting point metal powder By blending the low melting point metal powder with the raw material powder, the low melting point metal powder is first melted at the time of sintering to wet the surface of the copper powder and diffused into the copper to melt the copper. Liquid phase sintering proceeds by the molten alloy of copper and low melting point metal, and the bond strength between iron particles, between iron particles and copper particles, and between copper particles is strengthened.
  • Solid lubricant powder The solid lubricant powder is added to reduce friction at the time of metal contact due to sliding with the shaft 2, and for example, graphite is used. At this time, as the graphite powder, it is desirable to use scaly graphite powder so that adhesion to the flat copper powder can be obtained.
  • molybdenum disulfide powder can be used in addition to graphite powder. Molybdenum disulfide powder has a layered crystal structure and peels into layers, and thus adheres to flat copper powder in the same manner as scale graphite.
  • flat copper powder is adhered to the mold in layers when the raw powder is filled into the mold. If the blending ratio of flat copper in the raw material powder is less than 8% by weight, the amount of flat copper adhering to the mold becomes insufficient, and the effect of the present invention cannot be expected. Moreover, the adhesion amount of the flat copper powder to the mold is saturated at about 20 wt%, and even if the blending amount is further increased, the cost increase due to the use of the high-cost flat copper powder becomes a problem.
  • the ratio of the low melting point metal powder is less than 0.8 wt%, the strength of the bearing cannot be ensured, and if it exceeds 6.0 wt%, the influence of spheroidizing the flat copper powder cannot be ignored. Further, if the ratio of the solid lubricant powder is less than 0.5% by weight, the effect of reducing friction on the bearing surface cannot be obtained, and if it exceeds 2.0% by weight, the strength is reduced.
  • the flat copper powder 15 and the graphite powder 14 adhere to each other and overlap each other due to the fluid lubricant or the like attached to the flat copper powder, and the apparent density of the flat copper powder increases. Therefore, it becomes possible to uniformly disperse the flat copper powder in the raw material powder during the secondary mixing. If a lubricant is added separately during the primary mixing, the adhesion between the flat copper powder and the graphite powder is further promoted, so that the flat copper powder can be more uniformly dispersed during the secondary mixing.
  • a powdery lubricant can be used in addition to the same or different fluid lubricant as the fluid lubricant.
  • the above-mentioned forming aid such as metal soap is generally powdery and has a certain degree of adhesion, which can be promoted by adhesion of flat copper powder and graphite powder.
  • the mold 20 includes a core 21, a die 22, an upper punch 23, and a lower punch 24, and a raw material powder is filled in a cavity partitioned by these.
  • the raw material powder is formed by the molding surface formed by the outer peripheral surface of the core 21, the inner peripheral surface of the die 22, the end surface of the upper punch 23, and the end surface of the lower punch 24.
  • a cylindrical green compact 25 is obtained by molding.
  • the flat copper powder has the smallest apparent density. Further, the flat copper powder is a foil having the length L and the thickness t, and the area of the wide surface per unit weight is large. Therefore, the flat copper powder 15 is easily affected by the adhesion force of the fluid lubricant adhered to the surface thereof, and further by the Coulomb force, etc.
  • FIG. 7 (in FIG. 6) As shown in an enlarged view of the region Q), the flat copper powder 15 has a layer state in which a wide surface is directed to the molding surface 20a of the mold 20 and a plurality of layers (about 1 to 3 layers) overlap. And adheres to the entire area of the molding surface 20a.
  • the green compact 25 is sintered in a sintering furnace.
  • the sintering conditions are determined so that the iron structure becomes a two-phase structure of a ferrite phase and a pearlite phase.
  • the hard pearlite phase contributes to the improvement of wear resistance and suppresses the wear of the bearing surface under high surface pressure, thereby improving the bearing life. Can be made.
  • the abundance of pearlite ( ⁇ Fe) becomes excessive, and when the proportion is equal to or higher than that of ferrite ( ⁇ Fe), the aggression of the pearlite against the shaft is remarkably increased and the shaft is easily worn.
  • the pearlite phase ( ⁇ Fe) is suppressed to the extent that it exists (is scattered) at the grain boundary of the ferrite phase ( ⁇ Fe) (see FIG. 9).
  • the “grain boundary” here means both the grain boundary formed between the powder particles and the crystal grain boundary 18 formed in the powder particle.
  • the iron structure is formed of a two-phase structure of a ferrite phase ( ⁇ Fe) and a pearlite phase ( ⁇ Fe)
  • the growth rate of pearlite mainly depends on the sintering temperature. Therefore, in order to allow the pearlite phase to exist at the grain boundary of the ferrite phase in the above-described manner, the sintering temperature (furnace atmosphere temperature) is about 820 ° C. to 900 ° C., and the gas containing carbon as the furnace atmosphere, for example, Sintering using natural gas or endothermic gas (RX gas). Thereby, carbon contained in the gas diffuses into iron during sintering, and a pearlite phase ( ⁇ Fe) can be formed. Sintering at a temperature exceeding 900 ° C. is not preferable because carbon in the graphite powder reacts with iron and the pearlite phase increases more than necessary. With the sintering, the fluid lubricant, other lubricants, and various molding aids burn inside the sintered body or vaporize from inside the sintered body.
  • the sintered body 1 sintered oil-impregnated bearing shown in FIG. 1 is completed by sizing the sintered body and further impregnating it with lubricating oil or liquid grease by a method such as vacuum impregnation.
  • the lubricating oil impregnated in the sintered body is held not only in the pores formed between the particles of the sintered structure, but also in the pores of the reduced iron powder of the partial diffusion alloy powder.
  • the lubricating oil impregnated into the sintered body one having a kinematic viscosity of 30 mm 2 / sec or more and 200 mm 2 / sec or less is preferable.
  • the impregnation process of lubricating oil can be abbreviate
  • FIG. 8 schematically shows the microstructure near the surface of the sintered bearing 1 (region P in FIG. 1) that has undergone the above manufacturing steps.
  • the green compact 25 is formed in a state where the flat copper powder 15 is adhered in a layered manner to the mold forming surface 20a (see FIG. 7). Since the powder 15 is sintered, a surface layer S1 having a higher copper concentration than the others is formed on the entire surface including the bearing surface 1a of the bearing 1. In addition, the wide surface of the flat copper powder 15 may have adhered to the molding surface 20a, so that most of the copper structure 31a of the surface layer S1 has a flat shape in which the thickness direction of the surface layer S1 is thinned.
  • the thickness of the surface layer S1 corresponds to the thickness of the flat copper powder layer adhering to the mold forming surface 20a in layers, and is about 1 ⁇ m to 6 ⁇ m.
  • the surface of the surface layer S1 is mainly composed of free graphite 32 (shown in black) in addition to the copper structure 31a, and the remainder is a pore opening or an iron structure described later.
  • the area of the copper structure 31a is the largest, specifically, 60% or more of the surface becomes the copper structure 31a.
  • One copper structure 31b (first copper structure) is formed from the flat copper powder 15 contained in the green compact 25, and has a flat shape corresponding to the flat copper powder.
  • the other copper structure 31 c (second copper structure) is formed by diffusing a low-melting-point metal into the copper powder 13 constituting the partial diffusion alloy powder 11, and is formed in contact with the iron structure 33. .
  • the second copper structure 31c plays a role of increasing the bonding force between the particles.
  • FIG. 9 shows an enlarged view of the sintered iron structure 33 and its surrounding structure shown in FIG.
  • tin as a low melting point metal is first melted during sintering and diffused into copper powder 13 constituting partial diffusion alloy powder 11 (see FIG. 3), and bronze phase 16 (Cu—Sn). ).
  • Liquid phase sintering proceeds by this bronze layer 16, and iron particles, iron particles and copper particles, or copper particles are firmly bonded.
  • the molten tin is diffused into the part where the part of the copper powder 13 is diffused to form the Fe—Cu alloy, and the Fe—Cu—Sn alloy (alloy phase 17 ) Is formed.
  • a combination of the bronze layer 16 and the alloy phase 17 becomes the second copper structure 31c.
  • the ferrite phase ( ⁇ Fe), the pearlite phase ( ⁇ Fe), and the like are represented by shades of color. Specifically, the colors are darkened in the order of ferrite phase ( ⁇ Fe) ⁇ bronze phase 16 ⁇ alloy phase 17 (Fe—Cu—Sn alloy) ⁇ pearlite phase ( ⁇ Fe).
  • the partial diffusion alloy powder 11 in which substantially the entire circumference of the iron powder 12 is covered with the copper powder 13 is used as the raw material powder.
  • a large number of copper powders 13 are present in the vicinity of.
  • the low melting point metal powder 16 melted with the sintering diffuses into the copper powder 13 of the partial diffusion alloy powder 11 before the flat copper powder 15.
  • the fluid lubricant remains on the surface of the flat copper powder 15, and this phenomenon is promoted.
  • the influence which the low melting metal powder 16 has on the flat copper powder 15 of the surface layer S1 can be suppressed (even if the low melting metal powder 16 exists directly under the flat copper powder 15, the flat copper powder The surface tension acting on 15 is reduced). Therefore, the spheroidization of the flat copper powder 15 in the surface layer can be suppressed, the ratio of the copper structure on the bearing surface including the bearing surface 1a can be increased, and good sliding characteristics can be obtained.
  • the blending ratio of the low melting point metal powder 16 in the bearing can be increased. That is, in the conventional technical common sense, in order to suppress the influence of the spheroidization of the flat copper powder 15, the blending ratio (weight ratio) of the low melting point metal to the flat copper powder 15 should be suppressed to less than 10 wt%. According to the present invention, this ratio can be increased to 10 wt% to 30 wt%.
  • the area ratio of the copper structure to the iron structure can be 60% or more over the entire surface of the surface layer S1 including the bearing surface 1a, and the copper-rich bearing surface 1a that is not easily oxidized is stably obtained. be able to. Even if the surface layer S1 is worn, the copper structure 31c derived from the copper powder 13 adhered to the partial diffusion alloy powder 11 appears on the bearing surface 1a. Therefore, even when the sintered bearing 1 is used for the starter ST, it is possible to prevent fretting wear of the bearing surface 1a. In addition, the sliding characteristics of the bearing surface 1a including initial conformability and quietness can be improved.
  • the base portion S2 inside the surface layer S1 has a hard structure with a small amount of copper and a large amount of iron compared to the surface phase S1.
  • the content of Fe is the maximum in the base portion S2, and the content of Cu is 20 to 40 wt%.
  • the iron content increases in the base portion S2 that occupies most of the bearing 1, the amount of copper used in the entire bearing 1 can be reduced, and cost reduction can be achieved. Further, since the iron content is large, the strength of the entire bearing can be increased.
  • a predetermined amount of a metal having a melting point lower than that of copper is blended, and the bonding force between metal particles (between iron particles, between iron particles and copper particles, or between copper particles) is improved by liquid phase sintering.
  • high neck strength can be obtained between the copper structure 31c and the iron structure 33 derived from the partial diffusion alloy powder 11. From the above, it is possible to prevent the copper structure and the iron structure from falling off the bearing surface 1a, and to improve the wear resistance of the bearing surface.
  • the bearing strength can be increased, and specifically, it is possible to achieve a crushing strength (300 MPa or more) that is twice or more that of an existing copper-iron-based sintered body.
  • the bearing surface 1a is not deformed following the shape of the inner peripheral surface of the housing 3, and the bearing surface even after the mounting.
  • the roundness and cylindricity of 1a can be stably maintained. Therefore, after press-fitting and fixing the sintered bearing 1 to the inner periphery of the housing 3, a desired roundness (for example, sizing) is additionally performed without finishing processing (for example, sizing) for finishing the bearing surface 1a to an appropriate shape and accuracy. For example, a roundness of 3 ⁇ m or less can be ensured. Further, deformation of the bearing surface 1a can be prevented even when the shaft 2 contacts the bearing surface 1a due to engine vibration.
  • the iron structure is a two-layer structure of a ferrite phase and a pearlite phase, but the pearlite phase ( ⁇ Fe) is a hard structure (HV300 or higher) and has a strong attacking property against the counterpart material. For this reason, depending on the use conditions of the bearing, there is a possibility that the wear of the shaft 2 may proceed. In order to prevent this, the entire iron structure 33 can be formed of a ferrite phase ( ⁇ Fe).
  • the sintering atmosphere is a gas atmosphere (hydrogen gas, nitrogen gas, argon gas, etc.) not containing carbon or a vacuum.
  • the raw material powder does not react with carbon and iron, and therefore the iron structure after sintering is all soft (HV200 or less) and a ferrite phase ( ⁇ Fe).
  • HV200 or less a gas atmosphere
  • ⁇ Fe ferrite phase
  • tapered surfaces 1b1 and 1b2 whose opening side has a large diameter may be formed on both axial sides of the cylindrical bearing surface 1a of the sintered bearing 1 having the surface layer S1 and the base portion S2. it can.
  • the tapered surfaces 1b1 and 1b2 at both ends in the axial direction of the sintered bearing 1 in this way, even when the shaft 2 is bent, the outer peripheral surface of the shaft 2 is locally applied to the end of the sintered bearing 1. It is possible to prevent contact, and it is possible to prevent local wear of the bearing surface 1a due to stress concentration, a decrease in bearing strength, and the generation of abnormal noise.
  • the ratio X (X X) of the maximum value ⁇ of the radial drop amount with respect to the axial lengths b1 and b2 (both not including the chamfers at the axial ends) of the tapered surfaces 1b1 and 1b2.
  • the ratio of the sum of the axial lengths of the two tapered surfaces 1b1 and 1b2 to the total axial length a of the sintered bearing 1 is set in a range of 0.2 ⁇ (b1 + b2) /a ⁇ 0.8. Is preferred.
  • the sintered bearing 1 shown in FIG. 12 can be used, for example, for a power window drive mechanism or a power seat drive mechanism of an automobile.
  • a tapered surface 1b1 having a large diameter on the opening side can be formed only on one side in the axial direction of the cylindrical bearing surface 1a of the sintered bearing 1, and this is also shown in FIG. The same effect as the embodiment can be obtained.
  • the ratio of the axial length of the tapered surface 1b1 to the total axial length a of the sintered bearing 1 is preferably set in the range of 0.2 ⁇ b / a ⁇ 0.8.
  • the sintered bearing 1 shown in FIG. 13 can be used, for example, for a power window drive mechanism or a power seat drive mechanism of an automobile.
  • the sintered bearing 1 shown in FIG. 1 can be used in a vibration motor that functions as a vibrator for notifying incoming calls or emails in mobile terminals such as mobile phones and smartphones.
  • the vibration motor is configured by rotating a weight (eccentric weight) W attached to one end of the shaft 3 as shown in FIG. It is the structure which generates a vibration in the whole portable terminal.
  • FIG. 1 conceptually shows a main part of a vibration motor 1 when two sintered bearings 1 (101, 102) are used.
  • a shaft 2 protruded on both sides in the axial direction of the motor unit 4. Both sides are supported by the sintered bearing 1 (101, 102) so as to be rotatable.
  • the sintered bearing 101 on the weight W side is disposed between the weight W and the motor unit 4.
  • the sintered bearing 101 on the weight W side is thicker than the sintered bearing 102 on the opposite side of the weight W. And it is formed in a large diameter.
  • Each of the two sintered bearings 1 has a bearing surface 1a on the inner periphery, and is fixed to the inner periphery of the housing 3 made of, for example, a metal material by means such as press fitting.
  • the shaft 2 is driven at a rotational speed of 10,000 rpm or more.
  • the shaft 2 rotates under the influence of the weight W while swinging along the entire surface of the bearing surface 1a.
  • the shaft 2 rotates while maintaining an eccentric state in the direction of gravity.
  • the sintered bearing 1 for a vibration motor as shown in FIG. The shaft 2 rotates in a state where the center Oa is decentered not only in the direction of gravity but also in all directions.
  • the shaft 2 swings around the entire bearing surface, and the bearing surface is frequently hit by the shaft due to an unbalanced load (the shaft frequently comes into sliding contact with the bearing surface).
  • the bearing surface is more easily worn than a sintered bearing for normal use.
  • the sintered bearing is press-fitted into the inner periphery of the housing 3, if the bearing surface is slightly deformed following the shape of the inner peripheral surface of the housing, the rotational accuracy of the shaft 2 is greatly affected.
  • the sintered bearing 1 for a vibration motor it is preferable to use a powder having an average particle size of 145 mesh or less (average particle size of 106 ⁇ m or less) as the partial diffusion alloy powder.
  • the porous structure of the bearing can be made uniform to prevent the formation of rough air holes, so that the bearing 1 can be densified to obtain the crushing strength and wear resistance that can withstand use as a vibration motor bearing. It becomes possible.
  • the proportion of the partial diffusion alloy powder having an average particle size of 350 mesh (average particle size 45 ⁇ m) or less is preferably less than 25% by mass.
  • the sintered bearing 1 for the vibration motor the sintered bearing 1 described in any one of FIG. 12 and FIG. 13 may be used.
  • the ratio X of the maximum value ⁇ of the radial drop amount to the axial length of the tapered surface in both figures can be set in the same range as described above.
  • the proportion of the partial diffusion alloy powder in the raw material powder is preferably 50% by mass or more.
  • the raw material powder includes 8 to 20 wt% of flat copper powder, 0.8 to 6.0 wt% of low melting point metal powder (eg, tin powder), and 0.5 to 6.0 wt.
  • solid lubricant powder eg, graphite powder
  • 2.0 wt% is blended, and the balance is made into simple iron powder or simple copper powder (or both simple powders).
  • the bearing amount is maintained while maintaining the wear resistance, high strength, and good sliding characteristics obtained by using the partial diffusion alloy powder by changing the blending amount of the single iron powder and the single copper powder.
  • the characteristics can be adjusted. For example, by adding simple iron powder, it is possible to increase the wear resistance and strength of the bearing while reducing the cost by reducing the amount of partially diffused alloy powder, and by adding simple copper powder, the sliding characteristics are further improved. can do. As a result, the development cost of sintered bearings suitable for various applications can be reduced, and it is possible to cope with the production of various types of sintered bearings in small quantities.
  • the copper structure of the bearing surface 1a is formed of flat copper powder, but the copper structure of the bearing surface 1a is copper powder contained in the partial diffusion alloy powder. It can also be formed.
  • the details of the sintered bearing 1 will be described as a second embodiment, taking as an example the case of use in a vibration motor (FIG. 14).
  • the raw material powder in the second embodiment is a mixture in which a partial diffusion alloy powder, a low melting point metal powder, a solid lubricant powder, and an additive powder composed of either one or both of a simple iron powder and a simple copper powder are mixed. It becomes powder.
  • the mass ratio of each powder in the raw material powder is the largest for the partially diffused alloy powder.
  • Various molding lubricants for example, a lubricant for improving releasability may be added to the raw material powder as necessary.
  • the proportion of particles having an average particle size of 145 mesh or less (average particle size of 106 ⁇ m or less) and an average particle size of 350 mesh (average particle size of 45 ⁇ m) or less is less than 25 mass as described above. It is preferable to use the above.
  • iron powder 12 constituting the partially diffused alloy powder 11 known iron powder such as reduced iron powder and atomized iron powder can be used. In this embodiment, reduced iron powder is used.
  • the iron powder 12 used preferably has an average particle size of 20 ⁇ m to 106 ⁇ m, and more preferably an average particle size of 38 ⁇ m to 75 ⁇ m.
  • the irregular shape and dendritic copper powder which are generally used can be widely used, for example, electrolytic copper powder, atomized copper powder, etc. are used.
  • an atomized copper powder having a large number of irregularities on the surface, an irregular shape that approximates a spherical shape as a whole particle, and excellent in formability is used.
  • the copper powder 13 to be used has a smaller particle diameter than the iron powder 12, and specifically, an average particle diameter of 5 ⁇ m to 20 ⁇ m (preferably less than 20 ⁇ m) is used.
  • the proportion of Cu in the partial diffusion alloy powder 11 is 10 to 30% by mass (preferably 22 to 26% by mass).
  • the low melting point metal powder a metal powder having a melting point of 700 ° C. or less, for example, a powder of tin, zinc, phosphorus or the like is used.
  • tin powder that can easily diffuse into copper and iron and can be used as a single powder, particularly atomized tin powder, is used.
  • tin powder those having an average particle diameter of 5 to 63 ⁇ m are preferably used, and those having an average particle diameter of 20 to 45 ⁇ m are more preferably used.
  • one or more powders such as graphite and molybdenum disulfide can be used.
  • graphite powder particularly scaly graphite powder is used in consideration of cost.
  • the soot-added powder is composed of one or both of simple iron powder and simple copper powder.
  • simple iron powder either reduced iron powder or atomized iron powder can be used, and the iron powder to be used is selected according to the application of the bearing.
  • the mixture of reduced iron powder and atomized iron powder can also be used as a single-piece iron powder.
  • both the electrolytic copper powder and the atomized copper powder can be used as the single copper powder, and the copper powder to be used is selected according to the application of the bearing.
  • the mixture of electrolytic copper powder and atomized copper powder can also be used as a simple substance copper powder.
  • the average particle size of the simple iron powder and the simple copper powder can be widely selected according to the application of the bearing.
  • the average particle size is in the range of 45 to 200 ⁇ m (preferably 100 to 150 ⁇ m)
  • a single copper powder having an average particle diameter of 45 to 150 ⁇ m preferably 80 to 125 ⁇ m
  • the raw material powder is compression-molded using a molding die set in a die set of a cam-type molding press, for example, to form a compact.
  • the partial diffusion alloy powder 11, the tin powder 16, the graphite powder (not shown) and the additive powder are uniformly dispersed. Since the partial diffusion alloy powder 11 used in the present embodiment uses reduced iron powder as the iron powder 12, the powder is softer than the partial diffusion alloy powder using atomized iron powder, and the compression moldability is improved. Excellent. Therefore, the strength of the green compact 25 can be increased even at a low density, and chipping or cracking of the green compact 25 can be prevented.
  • the green compact 25 is sintered to obtain a sintered body.
  • the sintering conditions are such that graphite (graphite powder) does not react with iron (no carbon diffusion occurs).
  • iron-carbon equilibrium state there is a transformation point at 723 ° C., and beyond this, the reaction between iron and carbon is initiated and a pearlite phase ( ⁇ Fe) is generated in the iron structure.
  • ⁇ Fe pearlite phase
  • the pearlite phase ( ⁇ Fe) has high hardness (HV300 or higher) and is highly aggressive against the mating material, if the pearlite phase ( ⁇ Fe) is excessively present in the iron structure of the sintered bearing 4, the wear of the shaft 3 may be advanced.
  • endothermic gas RX gas
  • endothermic gas carbon may diffuse and the surface of the green compact may be cured, and the same problem as described above is likely to occur.
  • the green compact 25 is heated at 900 ° C. or lower, specifically 800 ° C. (preferably 820 ° C.) or higher and 880 ° C. or lower (low temperature sintering).
  • the sintering atmosphere is a gas atmosphere containing no carbon (hydrogen gas, nitrogen gas, argon gas, etc.) or a vacuum. Under such sintering conditions, the reaction between carbon and iron does not occur in the raw material powder, and therefore the iron structure after sintering becomes a soft ferrite phase (HV200 or less).
  • various molding lubricants such as a fluid lubricant are included in the raw material powder, the molding lubricant volatilizes with sintering.
  • the pig iron structure can be a two-phase structure of ferrite phase ⁇ Fe and pearlite phase ⁇ Fe.
  • the pearlite phase ⁇ Fe harder than the ferrite phase ⁇ Fe contributes to the improvement of the wear resistance of the bearing surface, and the wear of the bearing surface under high surface pressure can be suppressed to improve the bearing life.
  • the pearlite phase ⁇ Fe is present in an excessive proportion and becomes equal to the ferrite phase ⁇ Fe, the aggressiveness of the pearlite against the shaft 3 increases and the shaft 3 is likely to wear. In order to prevent this, as shown in FIG.
  • the pearlite phase ⁇ Fe is suppressed to the extent that it exists (is scattered) at the grain boundary of the ferrite phase ⁇ Fe.
  • the term “grain boundary” as used herein means both a grain boundary formed between powder particles and a crystal grain boundary formed in the powder particle.
  • the amount of precipitation of the pearlite phase ⁇ Fe mainly depends on the sintering temperature and the atmospheric gas. Therefore, in order to allow the pearlite phase ⁇ Fe to be present at the grain boundary of the ferrite phase ⁇ Fe in the above-described manner, the sintering temperature is raised to about 820 ° C. to 900 ° C., and the gas containing carbon as the furnace atmosphere, such as natural gas, Sintering is performed using an endothermic gas (RX gas). As a result, carbon contained in the gas diffuses into iron during sintering, and pearlite phase ⁇ Fe can be formed. As described above, when the green compact 25 is sintered at a temperature exceeding 900 ° C., the carbon in the graphite powder reacts with iron to form a pearlite phase ⁇ Fe. Sintering is preferred.
  • Lubricating oil impregnated in the internal pores of the sintered body is low viscosity, specifically, kinematic viscosity at 40 ° C. is 10 to 50 mm 2 / s (for example, synthetic hydrocarbon lubricating oil). This is to suppress the increase in rotational torque while ensuring the rigidity of the oil film formed in the bearing gap.
  • the internal pores of the sintered body may be impregnated with grease based on a lubricating oil having a kinematic viscosity at 40 ° C. of 10 to 50 mm 2 / s. Further, sizing is sufficient if necessary, and it is not always necessary. In addition, depending on the application, the step of impregnating the lubricating oil can be omitted, and a sintered bearing used without oil supply can be obtained.
  • the sintering temperature of the green compact 25 is 900 ° C. or lower, which is much lower than the melting point of copper (1083 ° C.)
  • the partial diffusion alloy powder 11 contained in the green compact 25 is obtained.
  • the constituent copper powder 13 does not melt, and therefore copper does not diffuse into iron (iron structure) with sintering. Therefore, an appropriate amount of copper structure is formed on the surface (bearing surface 1a) of the sintered body. Moreover, free graphite is also exposed on the surface of the sintered body. Therefore, it is possible to obtain a sintered bearing 1 having good initial conformability with the shaft 2 and a small friction coefficient of the bearing surface 1a.
  • an iron structure mainly composed of iron and a copper structure mainly composed of copper are formed. Although most of the iron structure and copper structure of the sintered body are formed of the partial diffusion alloy powder 11, in the partial diffusion alloy powder, a part of the copper powder is diffused into the iron powder. High neck strength can be obtained between the copper structure and the copper structure. Further, at the time of sintering, the tin powder 16 in the green compact 25 melts and wets the surface of the copper powder 13 constituting the partial diffusion alloy powder 11. Along with this, liquid phase sintering proceeds between tin (Sn) and copper (Cu), and as shown in FIG.
  • the iron structure and copper structure of adjacent partial diffusion alloy powders 11, or between copper structures A bronze phase (Cu-Sn) 16 is formed.
  • molten Sn is diffused and Fe—Cu is diffused in a part where a part of the copper powder 13 is diffused on the surface of the iron powder 12 to form an Fe—Cu alloy.
  • the Sn alloy (alloy phase) 17 is formed, the neck strength between the iron structure and the copper structure is further increased. Therefore, a high crushing strength, specifically, a crushing strength of 300 MPa or more can be obtained even at the low temperature sintering as described above.
  • the bearing surface 1a can be hardened to improve the wear resistance of the bearing surface 1a.
  • the additive powder which consists of a single-piece
  • the diffusion amount of the copper powder in the partial diffusion alloy powder is limited to about 30% by mass. Therefore, when the copper structure is formed only with the partial diffusion alloy powder, it becomes difficult to increase the ratio of copper in the bearing further. .
  • the ratio of the copper in a bearing can be made larger than 30 mass% by mix
  • the blending ratio of the partial diffusion alloy powder in the raw material powder is preferably 50% by mass or more (desirably 75% by mass or more). Further, if the amount of the solid lubricant powder is too small, the sliding characteristics will be impaired, and if it is too large, the crushing strength will be lowered. Therefore, the blending ratio in the raw material powder is set to 0.3 to 1.5 mass%. If the amount of the low melting point metal powder is small, the progress of liquid phase sintering becomes insufficient and the strength is lowered.
  • the blending ratio of the low melting point metal powder should be about 10% by mass of the total mass of the copper powder in the raw material powder (the sum of the copper powder in the partial diffusion alloy powder and the single copper powder added as the additive powder). preferable. Specifically, the blending ratio of the low melting point metal in the raw material powder is set to 0.5 to 5.0 mass%. The balance of the raw material powder consists of additive powder and inevitable impurities. The blending ratio of the additive powder is preferably at least 1.0% by mass or more of the raw material powder, considering the merit of blending it.
  • the ratio of copper in the sintered bearing 1 is at least 10% by mass (preferably 15% by mass or more).
  • the porous structure of the sintered body can be made uniform to prevent the formation of rough atmospheric pores. . Therefore, the density of the sintered body can be increased to further improve the crushing strength and the wear resistance of the bearing surface 1a.
  • the sintered body of the present embodiment has a crushing strength of 300 MPa or more, and the value of this crushing strength is more than twice that of an existing copper-iron-based sintered body. is there.
  • the density of the sintered body of the present embodiment is 6.8 ⁇ 0.3 g / cm 3 , which is higher than the density of the existing iron-copper-based sintered body (about 6.6 g / cm 3 ).
  • Even existing iron-copper-based sintered bodies can be densified by high compression in the green compact molding process, but this will prevent the internal fluid lubricant from burning during sintering. Because of gasification, the pores in the surface layer portion become coarse. In the present invention, it is not necessary to perform high compression at the time of forming the green compact, and such a problem can be prevented.
  • the oil content can be increased to 15 vol% or more, and the oil content comparable to that of existing iron-copper sintered bearings can be ensured.
  • This is mainly due to the use of reduced iron powder having a spongy shape and excellent oil retention as the iron powder 12 constituting the partial diffusion alloy powder 11.
  • the lubricating oil impregnated in the sintered body is reduced not only in the pores formed between the particles of the sintered structure, but also reduced iron powder (in addition to the reduced iron powder constituting the partial diffusion alloy powder, as additive powder) When iron powder is used, the reduced iron powder is also contained).
  • the surface layer portion of the sintered body region from the sintered body surface to a depth of 100 ⁇ m.
  • the surface layer is formed as described above. It is possible to increase the density of the surface layer portion by preventing the generation of rough atmospheric holes in the portion.
  • the porosity of the surface layer portion can be 5 to 20%. This porosity can be obtained, for example, by image analysis of the area ratio of the pores in an arbitrary cross section of the sintered body.
  • the surface area ratio of the bearing surface 1a is also reduced. Specifically, the surface area ratio of the bearing surface 1a is set within a range of 5% to 20%. can do. When the surface area ratio is less than 5%, it becomes difficult to exude a necessary and sufficient amount of lubricating oil into the bearing gap (insufficient oil film forming ability), and a merit as a sintered bearing can be obtained. Can not.
  • the raw material powder for obtaining this sintered body since the main raw material is partially diffused alloy powder 11 in which copper powder 13 is partially diffused on the surface of iron powder 12, existing iron copper is used. It is possible to prevent the segregation of copper, which is a problem in the sintered sintered bearing. Further, with this sintered body, the mechanical strength can be improved without using expensive metal powder such as Ni or Mo, so that the cost of the sintered bearing 4 can be reduced.
  • the sintered bearing 1 according to the second embodiment has high crushing strength (crushing strength of 300 MPa or more), even when press-fitted and fixed to the inner periphery of the housing 3 as shown in FIG.
  • the bearing surface 1a is not deformed following the shape of the inner peripheral surface of the housing 3, and the roundness, cylindricity, and the like of the bearing surface 1a can be stably maintained even after the mounting. Therefore, after press-fitting and fixing the sintered bearing 1 to the inner periphery of the housing 3, a desired roundness (for example, sizing) is additionally performed without finishing processing (for example, sizing) for finishing the bearing surface 1a to an appropriate shape and accuracy. For example, a roundness of 3 ⁇ m or less can be ensured.
  • the sintered bearing 1 has a crushing strength of 300 MPa or more, a vibration motor incorporating this sintered bearing 4 (and thus a portable terminal equipped with this vibration motor) will drop, etc., thereby causing a bearing surface 1a. Even when a large impact load is applied, the deformation of the bearing surface 1a is prevented as much as possible. Further, since the bearing surface 1a is hardened and has high wear resistance, even if the shaft 2 swings around the entire surface of the bearing surface 1a or the shaft 2 frequently collides with the bearing surface 1a, the bearing surface 1a. Wear and damage can be suppressed. Therefore, according to the present invention, the sintered bearing 1 suitable for supporting the vibration motor can be provided at low cost.
  • FIG. 14 a micrograph of a surface layer portion of a sintered bearing (hereinafter referred to as “copper-coated iron powder bearing”) according to the technical means described in Patent Document 1 is shown in FIG. Comparing FIG. 18 with a micrograph (see FIG. 16) of the surface layer portion of the sintered bearing 1 according to the second embodiment, the sintered bearing 1 according to the second embodiment is a copper-coated iron powder bearing.
  • the porous structure of the surface layer is uniform and dense.
  • the porosity of the surface layer portion of the sintered bearing 1 according to the second embodiment was 13.6%, whereas the porosity of the surface layer portion of the copper-coated iron powder bearing was about 25.5%. there were.
  • the copper-coated iron powder only the copper film is in close contact with the iron powder, and the neck strength between the iron phase and the copper phase is insufficient.
  • a sintered bearing having a bearing surface on the inner periphery that forms a bearing gap between the shaft to be supported, a partial diffusion alloy powder obtained by partially diffusing copper powder into iron powder, a low melting point metal powder, It is characterized by comprising a sintered body obtained by molding and sintering a raw material powder containing a solid lubricant powder and an additive powder composed of one or both of simple iron powder and simple copper powder.
  • the partially diffused alloy powder since a part of the copper powder is diffused into the iron powder, a higher neck strength is obtained between the sintered iron structure and the copper structure than when the copper-coated iron powder is used. Moreover, the low melting point metal powder contained in the green compact is melted by sintering after the raw material powder is molded (compressed). Since the low melting point metal has high wettability with respect to copper, the iron structure and the copper structure of adjacent partial diffusion alloy powders, or the copper structures can be firmly bonded by liquid phase sintering. Furthermore, among the individual partial diffusion alloy powders, the molten low melting point metal diffuses into the part where a part of the copper powder is diffused on the surface of the iron powder and the Fe—Cu alloy is formed.
  • the neck strength between the structure and the copper structure can be further increased. From these facts, it becomes possible to obtain a high-strength sintered bearing having excellent bearing surface wear resistance even at low-temperature sintering. In addition, since the partial diffusion alloy powder contains a considerable amount of copper powder, a large amount of copper structure can be formed on the bearing surface, and therefore good sliding characteristics (low torque, initial conformability, quietness, etc.) ) Can be obtained.
  • the additive powder consisting of one or both of single iron powder and single copper powder is blended into the raw material powder, high wear resistance can be achieved by changing the blending amount of single iron powder and single copper powder. It is possible to adjust the bearing characteristics according to the application while satisfying the properties and strength and the good sliding characteristics. For example, if single iron powder is added, wear resistance and bearing strength can be further increased, and if single copper powder is added, sliding characteristics can be improved. In order to ensure the minimum wear resistance, strength, and sliding characteristics, the proportion of the partial diffusion alloy powder in the raw material powder is preferably 50 wt% or more.
  • This sintered bearing preferably has a crushing strength of 300 MPa or more.
  • the partial diffusion alloy powder As a main raw material, it is easy to ensure the crushing strength.
  • the partial diffusion alloy powder included in the raw material powder copper powder having an average particle size of 5 ⁇ m or more and less than 20 ⁇ m partially diffuses on the surface of the iron powder, and in the alloy powder It is preferable to use a material containing 10 to 30% by mass of Cu.
  • the raw material powder contains a partially diffused alloy powder having a large particle size exceeding the average particle size of 106 ⁇ m, rough air holes are likely to be formed inside the sintered body, and as a result, the required bearing surface wear resistance is required. It has been found that there are cases where it is not possible to ensure properties and crushing strength. Accordingly, it is preferable to use a partially diffused alloy powder having an average particle size of 145 mesh or less (average particle size of 106 ⁇ m or less). By using such an alloy powder, it is possible to stably obtain a sintered body in which the sintered metal structure (porous structure) is made uniform and the generation of rough atmospheric pores in the metal structure is suppressed. it can. Thereby, it becomes possible to stably obtain a sintered bearing in which the wear resistance of the bearing surface and the crushing strength of the bearing are further improved.
  • tin powder can be used as the low melting point metal powder
  • graphite powder can be used as the solid lubricant powder
  • the iron structure of the sintered body mainly composed of a soft ferrite phase By making the iron structure of the sintered body mainly composed of a soft ferrite phase, the aggressiveness of the bearing surface against the shaft can be weakened, and the shaft wear can be suppressed.
  • An iron structure mainly composed of a ferrite phase can be obtained, for example, by sintering a green compact at a temperature of 900 ° C. or less at which iron and graphite do not react.
  • the iron structure mainly composed of a ferrite phase includes an iron structure in which a pearlite phase harder than a ferrite phase is present at the grain boundary of the ferrite phase in addition to a structure in which all of the ferrite phase is a ferrite phase.
  • a pearlite phase at the grain boundary of the ferrite phase, it is possible to improve the wear resistance of the bearing surface as compared with the case where the iron structure is composed only of the ferrite phase.
  • the proportions of ferrite phase ( ⁇ Fe) and pearlite phase ( ⁇ Fe) in the iron structure are 80 to 95% and 5 to 20%, respectively.
  • Reduced iron powder can be used as the iron powder constituting the partially diffused alloy powder (Fe—Cu partially diffused alloy powder).
  • the iron powder for example, atomized iron powder can be used in addition to the reduced iron powder.
  • the reduced iron powder has a spongy shape (porous shape) having internal pores, it is compared with the atomized iron powder.
  • the powder is soft and excellent in compression moldability. Therefore, the green compact strength can be increased even at low density, and chipping and cracking of the green compact can be prevented.
  • reduced iron powder makes a spongy shape as described above, it also has an advantage of superior oil retention as compared with atomized iron powder.
  • the porosity of the surface layer portion is preferably 5 to 20%.
  • the surface layer portion is a region from the surface to a depth of 100 ⁇ m.
  • the sintered body (internal pores) can be impregnated with a lubricating oil, and a lubricating oil having a kinematic viscosity at 40 ° C. in the range of 10 to 50 mm 2 / s is preferably used. This is to suppress the increase in rotational torque while ensuring the rigidity of the oil film formed in the bearing gap.
  • the oil impregnated in the sintered body may be a liquid grease based on an oil (lubricating oil) having a kinematic viscosity at 40 ° C. in the range of 10 to 50 mm 2 / s.
  • the present invention is not limited to a perfect circle bearing, and the outer circumference of the bearing surface 1a and the shaft 2 is exemplified.
  • the present invention can be similarly applied to a fluid dynamic pressure bearing in which a dynamic pressure generating portion such as a herringbone groove or a spiral groove is provided on the surface.
  • a dynamic pressure generating portion such as a herringbone groove or a spiral groove is provided on the surface.
  • the vibration motor etc. which are used for the starter for vehicles, a portable terminal, etc. were illustrated as a use, the use of the sintered bearing 1 concerning this invention is not limited to these, It applies widely also to other uses other than illustrated Is possible.
  • the green compact 25 When the green compact 25 is compression-molded, a so-called warm molding method in which the green compact 25 is compression-molded in a state where at least one of the molding die 20 and the raw material powder is heated, A die lubrication molding method may be employed in which the green compact 25 is compression molded in a state where a lubricant is applied to the molding surface. By adopting such a method, the green compact 25 can be molded with higher accuracy.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Sliding-Contact Bearings (AREA)

Abstract

L'invention concerne un palier fritté (1) comprenant du fer, du cuivre, un métal ayant une température de fusion inférieure à celle du cuivre et un lubrifiant solide en tant que composants principaux. Ce palier fritté (1) est composé d'une couche de surface (S1) et d'une partie de base (S2). La couche de surface (S1) est formée principalement de particules de poudre de cuivre plates qui sont agencées dans un état tel que les particules de poudre de cuivre plates sont plus minces dans la direction de l'épaisseur de la couche de surface (S1). Dans la couche de base (S2), les structures de fer (33) et les structures de cuivre (31c) présentes en contact avec les structures de fer (33) sont formées d'une poudre d'alliage de diffusion partielle dans laquelle la poudre de cuivre est partiellement diffusée dans la poudre de fer. Ainsi, il est possible de fabriquer un palier fritté économique qui combine une grande résistance à l'usure d'une surface de palier et une résistance élevée du palier.
PCT/JP2014/076399 2013-10-03 2014-10-02 Palier fritté et son procédé de fabrication WO2015050200A1 (fr)

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CN201480053495.2A CN105593543B (zh) 2013-10-03 2014-10-02 烧结轴承及其制造方法
US15/026,134 US20160223016A1 (en) 2013-10-03 2014-10-02 Sintered bearing and manufacturing process therefor
EP14850756.9A EP3054185B1 (fr) 2013-10-03 2014-10-02 Procédé de fabrication d'un palier fritté
US16/402,698 US10907685B2 (en) 2013-10-03 2019-05-03 Sintered bearing and manufacturing process therefor

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JP2013-208277 2013-10-03
JP2014007911A JP6302259B2 (ja) 2014-01-20 2014-01-20 焼結軸受の製造方法
JP2014-007911 2014-01-20
JP2014-008892 2014-01-21
JP2014008892A JP6389038B2 (ja) 2013-10-03 2014-01-21 焼結軸受およびその製造方法

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WO2017110778A1 (fr) * 2015-12-25 2017-06-29 三菱マテリアル株式会社 Palier fritté de retenue d'huile et son processus de production
WO2018047923A1 (fr) * 2016-09-08 2018-03-15 Ntn株式会社 Palier fritté et procédé de production dudit palier fritté
EP3530384A4 (fr) * 2016-10-18 2020-04-08 Diamet Corporation Roulement fritté imprégné d'huile et procédé de production associé

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WO2017110778A1 (fr) * 2015-12-25 2017-06-29 三菱マテリアル株式会社 Palier fritté de retenue d'huile et son processus de production
US10570959B2 (en) 2015-12-25 2020-02-25 Mitsubishi Materials Corporation Oil-retaining sintered bearing and method of producing the same
WO2018047923A1 (fr) * 2016-09-08 2018-03-15 Ntn株式会社 Palier fritté et procédé de production dudit palier fritté
EP3530384A4 (fr) * 2016-10-18 2020-04-08 Diamet Corporation Roulement fritté imprégné d'huile et procédé de production associé
US10731704B2 (en) 2016-10-18 2020-08-04 Diamet Corporation Oil-impregnated sintered bearing and production method therefor

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