JP2017193781A - Sintered bearing for fuel pump and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an aluminum bronze-based sintered bearing for a fuel pump, in which corrosion resistance and mechanical characteristics such as strength and abrasion resistance are enhanced, and compactness and reduction in cost are realized; and a method of manufacturing the aluminum bronze-based sintered bearing for a fuel pump, which has good productivity and low cost and is thus suitable for mass production.SOLUTION: A sintered bearing 1, 2 for a fuel pump comprises 8.5 to 10 wt.% of aluminum and 0.1 to 0.6 wt.% of phosphorus, with the balance including copper as a main component and inevitable impurities. The sintered bearing 1, 2 has a structure of a sintered aluminum-copper alloy, where a pore in a surface layer portion is smaller than an internal pore in the sintered bearing.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a sintered bearing for a fuel pump having excellent corrosion resistance and wear resistance and high strength, and a method for manufacturing the same.

  Conventionally, for example, an electric fuel pump is used for an engine using gasoline or light oil as fuel. In recent years, engines equipped with electric fuel pumps that use fuel such as gasoline and light oil have been widely used in various parts of the world, and the quality of gasoline and light oil used is different in each region of the world. There are many areas where is used. Gasoline and biofuel containing organic acids are known as a kind of bad gasoline, but when using a copper-based sintered bearing in the electric fuel pump, organic acids and biofuels contained in such bad gasoline As a result, the copper-based sintered bearing is corroded. This corrosion progresses to the periphery of the pore opening that opens on the bearing surface and the inner surface of the pore, and further to the inner surface of the pore that exists inside the bearing and communicates from the surface to the inner surface. The life of the copper-based sintered bearing is shortened.

  Furthermore, in recent years, engines such as automobiles have been remarkably reduced in size and weight, and accordingly, fuel pumps are also required to be reduced in size and weight, and sintered bearings incorporated therein are also required to be reduced in size. For example, in an electric fuel pump, it is necessary to increase the number of rotations in order to reduce the size while ensuring the discharge performance, and accordingly, the fuel such as gasoline taken into the fuel pump has a high pressure in the flow passage with a narrow gap. Under such conditions, the sintered bearing is required to be compact and have higher strength, wear resistance, friction characteristics, and corrosion resistance. For this reason, the conventional copper-based sintered bearings have high strength but are not particularly satisfactory in terms of corrosion resistance.

  As a sintered bearing used for such an application, for example, Patent Document 1 discloses a Cu—Ni—Sn—C—P based sintered bearing.

  On the other hand, an aluminum bronze sintered bearing is known as a sintered bearing having excellent mechanical properties and corrosion resistance. With this sintered bearing, an aluminum oxide film is formed on the surface in the process of raising the temperature during sintering, and a sintered body having sufficient corrosion resistance and strength to inhibit aluminum diffusion cannot be easily obtained. There's a problem. Patent Document 2 discloses a technique relating to a mixed powder for a sintered aluminum-containing copper alloy and a method for producing the same in order to improve the above problem.

Japanese Patent No. 45211871 JP 2009-7650 A

  The Cu—Ni—Sn—C—P based sintered bearing described in Patent Document 1 improves strength and wear resistance, but is not sufficient in terms of corrosion resistance. Further, since Ni which is a rare metal is contained, there is a problem in terms of cost.

  The aluminum-containing copper alloy powder described in Patent Document 2 is excellent in formability and sinterability, but as an aluminum bronze-based sintered bearing using the aluminum-containing copper alloy powder, stable corrosion resistance, Further studies are necessary to obtain a product suitable for mass production that satisfies the mechanical properties, compactness, and cost reduction.

In view of the conventional problems, the present invention provides an aluminum bronze sintered bearing for a fuel pump that is improved in mechanical properties such as corrosion resistance, strength, and wear resistance, and is compact and low in cost. It is another object of the present invention to provide a method for producing an aluminum bronze sintered bearing for a fuel pump that is good in productivity and low in cost and suitable for mass production.

In the aluminum bronze-based sintered bearing and the manufacturing method thereof, the present inventors have proposed a novel method in which expansion due to sintering is effectively used in order to improve the bearing function and to reduce the size, cost, and productivity. As a precondition, the sintered bearings for fuel pumps that are always in contact with gasoline as described above can suppress sulfidation corrosion due to poor gasoline, corrosion due to organic acids and biofuels, and the initial stage. In order to secure the familiarity, durability, and other performances, various investigations and test evaluations were performed, and the following knowledge was obtained, leading to the present invention.
(1) In the relationship between the amount of aluminum blended and sulfide corrosion resistance, the corrosion resistance improves as the amount of aluminum blended increases. This is considered that when the compounding amount of aluminum increases, diffusion into copper increases and corrosion resistance improves.
(2) In the relationship between the aluminum blending amount and the organic acid corrosion resistance, the corrosion resistance decreases as the aluminum blending amount increases. However, the rate of change in weight becomes moderate when the blending amount of aluminum is around 9.0% by mass.
(3) In the relationship between the blending amount of aluminum and the aluminum bronze structure, the proportion of β phase increases as the blending amount of aluminum increases. The β phase undergoes eutectoid transformation at 565 ° C., becomes an α phase and a γ phase, and the proportion of the γ phase increases as the aluminum content increases. Since the γ phase reduces the resistance to organic acid corrosion and the initial conformability, when the copper source is an aluminum-copper alloy powder and no copper is added, the ratio of the γ phase to the α phase is set to 0. <Γ phase / α phase ≦ 0.10.
(4) Regarding the relationship between the sintering temperature and the corrosion resistance, when the sintering temperature is increased, the diffusion of aluminum is enhanced and the corrosion resistance is improved.
(5) It is considered that phosphorus as an additive can promote the diffusion of aluminum during the sintering process, thereby reducing the amount of aluminum and reducing the precipitation of the γ phase of the aluminum structure that deteriorates the corrosion resistance and initial familiarity. It is done.
(6) Regarding the relationship between the blending amount of aluminum and the initial conforming time and friction coefficient, the blending amount of aluminum, the initial conforming time and the friction coefficient are in a proportional relationship. This is considered that the γ phase increases as the amount of aluminum added increases.

  As a technical means for achieving the above-mentioned object, the present invention contains 8.5 to 10% by weight of aluminum and 0.1 to 0.6% by weight of phosphorus, with the balance being copper as the main component, A sintered bearing for a fuel pump containing inevitable impurities, the sintered bearing having a structure in which an aluminum-copper alloy is sintered, and the pores of the surface layer portion of the sintered bearing are formed from the internal pores. Characterized by being made smaller. As a result, mechanical properties such as corrosion resistance, strength, and wear resistance, oil film formation, and oil retention can be improved, and compactness and cost reduction can be achieved.

  Further, the present invention as a method for producing a sintered bearing for a fuel pump contains 8.5 to 10% by weight of aluminum and 0.1 to 0.6% by weight of phosphorus, and the remaining main component is copper. A method for producing a sintered bearing for a fuel pump containing inevitable impurities, which uses aluminum-copper alloy powder, electrolytic copper powder, and phosphorous-copper alloy powder as raw material powder, and at least calcined the raw material powder. A forming step for forming a green compact to which a binder is added, a sintering step for obtaining a sintered body having an aluminum-copper alloy structure from the green compact, and a sizing step for dimensioning the sintered body, It is characterized by including. As a result, it is possible to realize a method for manufacturing an aluminum bronze sintered bearing for a fuel pump that is good in productivity, low in cost, and suitable for mass production. The sintered bearing for a fuel pump manufactured in this manner can improve mechanical properties such as corrosion resistance, strength, and wear resistance, oil film formation, and oil retention, and can be made compact.

  The structure of the aluminum-copper alloy preferably has an α phase. The α phase is effective for resistance to organic acid corrosion and initial conformability.

  The above-described aluminum-copper alloy structure (hereinafter also referred to as aluminum bronze structure) uses an aluminum-copper alloy powder as a copper source. The phase / α phase is preferably 0 <γ phase / α phase ≦ 0.10. In the range of 0 <γ phase / α phase ≦ 0.10, the organic acid corrosion resistance and initial conformability are excellent.

  As a blending amount of the above graphite, it is preferable that 3 to 10% by weight is added to 100% by weight of the total of aluminum, phosphorus, the raw material powder having copper as the main component and the inevitable impurities, for example, 3%. What is added to 5% by weight can be used. If it is less than 3% by weight, the effect of improving lubricity and wear resistance by adding graphite cannot be obtained as a sintered bearing for a fuel pump. On the other hand, when it exceeds 5% by weight, there is a concern that, for example, diffusion of aluminum into copper starts to be inhibited. If the added amount of graphite exceeds 10% by weight, diffusion of aluminum into copper is hindered, so it must be taken into consideration. As for the wear resistance, the wear resistance is improved when the amount of graphite added is increased, but the amount of wear is slightly increased from the amount of graphite added of 10% by weight, which is considered to be caused by a decrease in material strength.

  The graphite powder is preferably natural graphite or artificial graphite fine powder granulated with a resin binder and then pulverized into a graphite powder having a particle size of 145 mesh or less. In general, when 4% by weight or more of graphite is added, molding cannot be performed, but molding is enabled by using granulated graphite.

  It is preferable not to add tin as a sintering aid to the fuel pump sintered bearing. Tin is not preferred because it prevents the diffusion of aluminum.

  In the sintered bearing for a fuel pump, the aluminum content is more preferably 9 to 9.5% by weight. As a sintered bearing for a fuel pump, it can be used if the aluminum content is 8.5 to 10% by weight, and 9 to 9.5% by weight is the optimum range.

  As a sintering aid, a total of 0.05% of aluminum fluoride and calcium fluoride is used with respect to 100% by weight of the raw material powder made of the aluminum-copper alloy powder, electrolytic copper powder and phosphorous-copper alloy powder. It is preferable to add ~ 0.2% by weight. If it is less than 0.05% by weight, the effect as a sintering aid is insufficient, and a dense sintered body having an appropriate strength cannot be obtained. On the other hand, if it exceeds 0.2% by weight, the effect as a sintering aid will reach its peak even if it is added more, and it is preferable to keep it to 0.2% by weight or less from the viewpoint of cost.

  The ratio d2 / d1 between the average particle diameter d1 of the aluminum-copper alloy powder and the average particle diameter d2 of the electrolytic copper powder is preferably 2 to 3. When the ratio d2 / d1 is within this range, aluminum can be sufficiently diffused into copper, and the corrosion resistance is excellent.

  Said electrolytic copper powder is comprised by what a powder shape differs, and ratio W2 / W1 of the ratio W1 of the electrolytic copper powder whose aspect ratio is 2 or more and the ratio W2 of the electrolytic copper powder less than 2 shall be 3-9. It is preferable. Electrolytic copper powder having an aspect ratio of 2 or more is effective for diffusion of aluminum, but has poor formability. If the ratio W2 / W1 is less than 3, it is not preferable from the viewpoint of moldability, and if it exceeds 9, the aluminum diffusion becomes insufficient, which is not preferable. Here, the aspect ratio means a ratio obtained by dividing the major axis length of the powder by the thickness of the powder.

  2nd invention as a manufacturing method of the sintered bearing for fuel pumps contains 8.5 to 10 weight% of aluminum and 0.1 to 0.6 weight% of phosphorus, and the remainder is made into copper, A method for producing a sintered bearing for a fuel pump containing inevitable impurities, the production method using an aluminum-copper alloy powder and a phosphorus-copper alloy powder as a raw material powder without adding a powder of copper alone, At least a forming step of forming a green compact in which a sintering aid is added to the raw material powder, a sintering step of obtaining a sintered body having an aluminum-copper alloy structure from the green compact, and the sintered body And a sizing process for shaping the dimensions. Here, the phrase “without adding copper powder as a raw material powder” is used in the sense that the powder of copper unavoidably contained at the manufacturing site is allowed.

  The second invention as the above manufacturing method can also realize a manufacturing method of an aluminum bronze sintered bearing for a fuel pump that is good in productivity, low in cost, and suitable for mass production. Further, the sintered bearing for a fuel pump manufactured in this way can improve mechanical properties such as corrosion resistance, strength and wear resistance, oil film formation and oil retention, and can be made compact. Furthermore, since the powder of the copper simple substance is not added, the portion where the copper simple substance is biased is substantially eliminated, the occurrence of corrosion due to this part is avoided, and the corrosion resistance of each particle of the aluminum-copper alloy powder is reduced. By improving, corrosion resistance can be ensured even in a more severe use environment.

  The aluminum-copper alloy powder as the raw material powder is preferably 7-11 wt% aluminum-copper alloy powder, and more preferably 8-10 wt% aluminum-copper alloy powder. In these cases, the corrosion resistance of each aluminum-copper alloy powder is improved, and the corrosion resistance of the entire fuel pump sintered bearing is improved.

  The sintered bearing for a fuel pump according to the present invention can improve mechanical properties such as corrosion resistance, strength and wear resistance, oil film formation and oil retention, and can be made compact and cost-effective. In addition, the method for manufacturing a sintered bearing for a fuel pump according to the present invention can realize a method for manufacturing an aluminum bronze sintered bearing for a fuel pump that is good in productivity, low in cost, and suitable for mass production.

  Furthermore, according to the second invention as a manufacturing method using aluminum-copper alloy powder without adding the powder of copper alone, the portion where the copper simplex is biased is substantially eliminated, and the occurrence of corrosion due to this portion is avoided. In addition, the corrosion resistance of each aluminum-copper alloy powder is improved, so that the corrosion resistance can be ensured even in a more severe use environment.

It is a longitudinal section showing an outline of a fuel pump in which a sintered bearing for a fuel pump according to a first embodiment of the present invention is used. It is a longitudinal cross-sectional view of the sintered bearing for fuel pumps which concerns on the 1st Embodiment of this invention, and the sintered bearing for fuel pumps based on the manufacturing method which concerns on the 1st Embodiment of this invention. (A) is the schematic diagram which expanded the metal structure of the A section of FIG. 2, (b) is the schematic diagram which expanded the metal structure of the B section of FIG. 2, (c) is the metal structure of the C section of FIG. It is the schematic diagram which expanded. It is a graph which shows the test result about the relationship between the compounding quantity of aluminum, and sulfidation corrosion property. It is a graph which shows the test result about the relationship between the compounding quantity of aluminum, and organic acid corrosivity. It is a graph which shows the test result about the relationship between the compounding quantity of aluminum, and copper ion elution amount. It is a graph which shows the test result about the relationship between the compounding quantity of aluminum, and initial conforming time. It is a graph which shows the test result about the relationship between the compounding quantity of aluminum, and a friction coefficient. It is a figure explaining the manufacturing process of the sintered bearing for fuel pumps of FIG. It is a schematic diagram of the raw material powder mixer. It is a schematic diagram of a mesh belt type continuous furnace. It is a figure explaining a sizing process, (a) shows the state which set the sintered compact to the metal mold | die of sizing processing, (b) shows the state which the core fell, (c) completed sizing processing Indicates the state. It is a figure which shows the compression state of the product in a sizing process. It is a schematic diagram of an oil impregnation apparatus. It is a graph which shows the test result about the compounding quantity of aluminum about the sintered bearing for fuel pumps concerning the 2nd Embodiment of this invention, and organic acid corrosivity. It is a graph which shows the test result about the relationship between the compounding quantity of aluminum and the copper ion elution amount about the sintered bearing for fuel pumps concerning the 2nd Embodiment of this invention.

  Hereinafter, a first embodiment of a sintered bearing for a fuel pump of the present invention and a first embodiment of a manufacturing method thereof will be described with reference to the accompanying drawings. The 1st embodiment about a sintered bearing for fuel pumps is shown in Drawings 1-8, and the 1st embodiment about a manufacturing method is shown in Drawings 9-14.

  FIG. 1 is a longitudinal sectional view showing an outline of a fuel pump in which a sintered bearing according to this embodiment is used. In the electric fuel pump 40, a motor part 42 is incorporated in the upper part of a cylindrical metal housing 41, and a pump part 43 is incorporated in the lower part thereof. A synthetic resin motor cover 45 is fixed by crimping to the upper end of the housing 41. A metal pump cover 46 and a pump body 47 are attached to the lower end of the housing 41. A motor part chamber 48 is formed between the motor cover 45 and the pump cover 46 in the housing 41, and a pump part chamber 49 is formed between the pump cover 46 and the pump body 47. The pump cover 46 forms a partition wall that partitions the motor section chamber 48 and the pump section chamber 49.

  A motor armature 50 is disposed in the motor chamber 48. The upper and lower end portions of the shaft 52 of the armature 50 are rotatably supported by the motor cover 45 and the pump cover 46 via the slide bearings 1 and 2, respectively. These sliding bearings 1 and 2 are the sintered bearings for the fuel pump of this embodiment.

  A magnet 55 is fixed on the inner peripheral surface of the housing 41 at a predetermined interval with respect to the outer peripheral surface of the armature 50. A brush 56 slidably contacting the commutator 50 a of the armature 50 is incorporated in the motor cover 45 while being urged by a spring 57. The brush 56 is electrically connected to an external connection terminal (not shown) via the choke coil 58. The motor cover 45 is provided with a discharge port 70 for connecting a fuel supply pipe (not shown) leading to the fuel injection valve. A check valve 71 for preventing the back flow of fuel is incorporated in the discharge port 70 while being urged in the closing direction by a spring 72.

  A plate 74 is interposed between the pump cover 46 and the pump body 47 of the pump unit 43, and the pump unit chamber 49 is divided into two chambers. An impeller 75 is disposed in each chamber. Both impellers 75 are connected to the lower end of the shaft 52 and are driven to rotate by the motor unit 42. The pump body 47 is provided with a suction port 76, and the pump cover 46 is provided with a flow port 77.

  The fuel pump 40 rotates the impeller 75 of the pump unit 43 by the motor unit 42. As a result, the fuel in the fuel tank is pumped up from the suction port 76 to the pump unit chamber 49, and this fuel enters the motor unit chamber 48 through the flow port 77 of the pump cover 46 through the flow path of the pump unit 43 and from the discharge port 70. Discharged. Therefore, the sintered bearings 1 and 2 for the fuel pump of the present embodiment that rotatably support the shaft 52 of the armature 50 are in an environment in which they always come into contact with fuel (for example, gasoline). The fuel pump 40 shown in FIG. 1 is an in-tank type fuel pump 40 in which the fuel pump 40 is immersed in a liquid fuel such as gasoline.

  Here, the types of the fuel pump will be described. Examples of the fuel pump include two types of fuel pumps, an in-tank type fuel pump and an out-tank type fuel pump.

  The in-tank type fuel pump is, for example, a type in which the fuel pump itself is immersed in a liquid fuel such as gasoline. For this reason, for example, the sintered bearings 1 and 2 used in the in-tank type fuel pump do not necessarily need to be oil-impregnated. The sintered bearings 1 and 2 used are preferably oil-impregnated ones.

  On the other hand, the out-tank type fuel pump is a type that is used in the atmosphere without being immersed in a liquid fuel such as gasoline. For example, sintered bearings used for out-tank fuel pumps are not necessarily oil-impregnated, but in order to suppress initial wear even a little, sintered bearings used for out-tank fuel pumps It is preferable that oil is also impregnated.

  A longitudinal sectional view of the sintered bearing for the fuel pump of this embodiment is shown in FIG. A sintered bearing for a fuel pump (hereinafter also simply referred to as a sintered bearing) 1 is formed in a cylindrical shape having a bearing surface 1a on the inner periphery. When the shaft 52 of the armature 50 (see FIG. 1) is inserted into the inner periphery of the sintered bearing 1 and the shaft 52 is rotated in that state, the temperature of the lubricating oil held in the countless holes of the sintered bearing 1 increases. As a result, it oozes out to the bearing surface 1a. The oil that has oozed forms an oil film in the bearing gap between the outer peripheral surface of the shaft 52 and the bearing surface 1 a, and the shaft 52 is supported by the bearing 1 so as to be relatively rotatable. The sintered bearing 2 is different in shape and size from the sintered bearing 1 but is functionally the same. Therefore, the sintered bearing 1 will be described as an example, and the sintered bearing 2 is indicated by reference numeral 2 in FIG. Description of is omitted.

  The sintered bearing 1 for a fuel pump according to the present embodiment is formed by filling a raw material powder mixed with various powders into a mold, compressing this to form a green compact, and then sintering the green compact. Is done.

  The raw material powder is a mixed powder obtained by mixing aluminum-copper alloy powder, copper powder, phosphorus-copper alloy powder, graphite powder, aluminum fluoride and calcium fluoride as sintering aids. Details of each powder are described below.

[Aluminum-copper alloy powder]
40-60 wt% aluminum-copper alloy powder was pulverized to adjust the particle size. The particle size of the aluminum-copper alloy powder is 100 μm or less, and the average particle size is 35 μm. Here, in this specification, an average particle diameter means the average value of the particle diameter measured by laser diffraction. Specifically, it is set as the average value of the particle diameter when 5000 powder is measured by laser diffraction with SALD-3100 manufactured by Shimadzu Corporation.

  By using the aluminum-copper alloy powder, the effects of additives such as graphite and phosphorus are extracted, and the sintered bearing material is excellent in corrosion resistance, strength, sliding characteristics and the like. Moreover, since it is alloyed, there is no problem in handling due to the scattering of the single powder of aluminum having a small specific gravity.

  As for the aluminum bronze structure, the α phase is most excellent in corrosion resistance against sulfidation corrosion and organic acid corrosion and excellent in initial familiarity. By using 40-60 wt% aluminum-copper alloy powder, strength can be obtained even when graphite is added, and a sintered bearing can be manufactured. When the structure is in the γ phase, the wear resistance is excellent, but the organic acid corrosion resistance and initial familiarity are deteriorated. In the aluminum bronze structure, the ratio γ phase / α phase between the γ phase and the α phase is preferably 0.10 ≦ γ phase / α phase ≦ 0.25. If the ratio of γ phase / α phase is less than 0.10, the wear resistance decreases, which is not preferable. On the other hand, if it exceeds 0.25, the initial conformability and organic acid corrosion resistance decrease, which is not preferable.

[Copper powder]
Copper powder includes atomized powder, electrolytic powder, and pulverized powder. Dendritic electrolytic powder is effective for sufficiently diffusing aluminum in copper, and is excellent in moldability, sinterability, and sliding characteristics. Therefore, in this embodiment, electrolytic powder was used as copper powder. Further, in order to sufficiently diffuse aluminum into copper, two types of electrolytic copper powders having different powder shapes are used, and the ratio W1 of the electrolytic copper powder having an aspect ratio of 2 or more and the ratio W2 of the electrolytic copper powder of less than 2 The ratio W2 / W1 is preferably 3-9. Electrolytic copper powder having an aspect ratio of 2 or more is effective for diffusion of aluminum, but has poor formability. If the ratio W2 / W1 is less than 3, it is not preferable from the viewpoint of moldability, and if it exceeds 9, the aluminum diffusion becomes insufficient, which is not preferable.

  In this embodiment, the average particle diameter of the electrolytic copper powder is 85 μm. The ratio d2 / d1 between the average particle diameter d1 of the aluminum-copper alloy powder and the average particle diameter d2 of the electrolytic copper powder is preferably 2 to 3. When the ratio d2 / d1 is within this range, aluminum can be sufficiently diffused into copper, and the corrosion resistance is excellent. For this reason, in this embodiment, the average particle diameter d1 of aluminum-copper alloy powder was 35 micrometers, and the average particle diameter d2 of electrolytic copper powder was 85 micrometers. However, the present invention is not limited thereto, and an aluminum-copper alloy powder having an average particle size of about 20 to 65 μm can be used, and the electrolytic copper powder has a particle size of 200 μm or less and an average particle size of about 60 to 120 μm. Things can be used.

[Phosphor alloy powder]
As the phosphorus alloy powder, 7 to 10 wt% phosphorus-copper alloy powder was used. Phosphorus has the effect of increasing the wettability between the solid and liquid phases during sintering. The amount of phosphorus is preferably 0.1 to 0.6% by weight, specifically 0.1 to 0.4% by weight. If the amount is less than 0.1% by weight, the effect of promoting the sintering between the solid and liquid phases is poor. Phase precipitation increases and the sintered body becomes brittle.

[Graphite powder]
Graphite exists mainly as free graphite in pores dispersed and distributed in the base material, imparts excellent lubricity to the sintered bearing, and contributes to improvement of wear resistance. The blending amount of graphite is preferably 3 to 10% by weight, for example, 3 to 5% by weight, based on 100% by weight of the total of aluminum, phosphorus, the raw material powder having copper as the main component and the inevitable impurities. If it is less than 3% by weight, the effect of improving lubricity and wear resistance by adding graphite cannot be obtained as a sintered bearing for a fuel pump. On the other hand, when it exceeds 5% by weight, there is a concern that, for example, diffusion of aluminum into copper starts to be inhibited. When the added amount of graphite exceeds 10% by weight, the material strength is lowered and the diffusion of aluminum into copper is hindered. In general, when 4% by weight or more of graphite is added, molding cannot be performed, but molding is enabled by using granulated graphite. In the present embodiment, the graphite powder used is a graphite powder having a particle size of 145 mesh or less, which is obtained by granulating natural graphite or artificial graphite fine powder with a resin binder.

[Aluminum fluoride and calcium fluoride]
In the aluminum-copper alloy powder, the aluminum oxide film formed on the surface during sintering significantly inhibits the sintering. However, aluminum fluoride and calcium fluoride as sintering aids are produced by sintering the aluminum-copper alloy powder. By gradually evaporating while melting at a sintering temperature of 850 to 900 ° C., the surface of the aluminum-copper alloy powder is protected and the formation of aluminum oxide is suppressed, thereby promoting the sintering and promoting the diffusion of aluminum. Aluminum fluoride and calcium fluoride evaporate and volatilize during sintering, and therefore hardly remain in the finished product of the sintered bearing.

  Aluminum fluoride and calcium fluoride as sintering aids are 0.05 to 0.2 in total with respect to a total of 100% by weight of aluminum, phosphorus, raw material powder having copper as the main component and the inevitable impurities. It is preferable to add at about% by weight. If it is less than 0.05% by weight, the effect as a sintering aid is insufficient, and a dense sintered body having an appropriate strength cannot be obtained. On the other hand, if it exceeds 0.2% by weight, the effect as a sintering aid will reach its peak even if it is added more, and it is preferable to keep it to 0.2% by weight or less from the viewpoint of cost.

  In the sintered bearing for a fuel pump of this embodiment and the manufacturing method described later, the aluminum content is 8.5 to 10% by weight, phosphorus is 0.1 to 0.4% by weight, and the remaining main component is copper. Aluminum-copper alloy powder, electrolytic copper powder and phosphorus alloy powder are mixed in such a ratio, and graphite powder is mixed so that the compounding amount of graphite is 3 to 5% by weight with respect to the total 100% by weight. The raw material powder was used. As a sintering aid, 0.05 to 0.2% by weight of aluminum fluoride and calcium fluoride in total, and 0.1 to 1 lubricant such as zinc stearate and calcium stearate to facilitate moldability Weight percent was added.

  More specifically, for example, in the sintered bearing for a fuel pump of this embodiment and the manufacturing method described later, the aluminum content is 8.5 to 10 parts by weight, phosphorus is 0.1 to 0.4 parts by weight, and the balance Aluminum-copper alloy powder, electrolytic copper powder and phosphorus alloy powder are mixed in such a ratio that the main component is copper, and the compounding amount of graphite is 3 to 5 parts by weight with respect to 100 parts by weight in total. The graphite powder was mixed with the raw material powder. The blending amount of graphite is preferably 3 to 10 parts by weight, for example, 3 to 5 parts by weight, based on 100 parts by weight of the total of aluminum, phosphorus, raw material powder having copper as the main component and the inevitable impurities. If it is less than 3 parts by weight, the effect of improving lubricity and wear resistance by adding graphite as a sintered bearing for a fuel pump cannot be obtained. On the other hand, when the amount exceeds 5 parts by weight, there is a concern that, for example, diffusion of aluminum into copper starts to be inhibited. When the added amount of graphite exceeds 10 parts by weight, the material strength is lowered and the diffusion of aluminum into copper is hindered. In general, when 4 parts by weight or more of graphite is added, molding cannot be performed, but molding is made possible by using granulated graphite. In the present embodiment, the graphite powder used is a graphite powder having a particle size of 145 mesh or less, which is obtained by granulating natural graphite or artificial graphite fine powder with a resin binder. As a sintering aid, a total of 0.05 to 0.2 parts by weight of aluminum fluoride and calcium fluoride, and 0.1 to 1 lubricant such as zinc stearate and calcium stearate to facilitate moldability Part by weight was added.

  FIG. 3 shows a schematic diagram of a metal structure of a cross section of the sintered bearing according to the present embodiment. FIG. 3A is an enlarged view of part A in FIG. Similarly, FIG. 3B is an enlarged view of part B in FIG. 2, and FIG. 3C is an enlarged view of part C in FIG. 3A shows the metal structure of the surface layer portion of the bearing surface on the inner diameter side, FIG. 3B shows the metal structure of the inner surface, and FIG. 3C shows the metal structure of the surface layer portion of the outer diameter surface. Indicates. As shown in FIGS. 3A, 3B, and 3C, the hatched 3 is an aluminum-copper alloy structure, and an aluminum oxide film 4 exists around the surface and internal pores. For this reason, it is excellent in corrosion resistance and abrasion resistance. Although illustration is omitted, the grain boundary portion of the aluminum-copper alloy structure 3 has a lot of phosphorus. Since the free graphite 5 is distributed in the pores, it is excellent in lubricity and wear resistance.

  As shown in FIG. 3A, an open hole db1 formed on the bearing surface on the inner diameter side and an internal hole db2 on the surface layer of the bearing surface are formed. As shown in FIG. 3 (b), pores di are formed inside the bearing, and as shown in FIG. 3 (c), open pores do1 formed on the outer diameter surface and internal pores formed on the outer surface of the outer diameter surface. do2 is formed. The open pore db1 formed on the bearing surface, the internal pore db2 on the surface of the bearing surface, the pore di inside the bearing, the release pore do1 formed on the outer diameter surface, and the internal pore do2 formed on the outer surface of the outer diameter surface are , Each communicates.

  In the sintered bearing 1, both the outer diameter surface 1 b of the bearing and the bearing surface 1 a on the inner diameter side are sized after sintering in a manufacturing method (see FIG. 13) described later. Since the aluminum bronze-based sintered bearing expands by sintering, the outer diameter surface 1b of the bearing is sized in a larger amount than the bearing surface 1a on the inner diameter side. Therefore, the pores do (see FIG. 3C) in the surface layer portion on the outer diameter surface 1b side are crushed more than the pores db in the surface layer portion on the bearing surface 1a side (see FIG. 3A). Comparing the sizes of the pores do in the surface layer portion on the outer diameter surface 1b side, the pores db in the surface layer portion on the bearing surface 1a side, and the pores di (see FIG. 3B) inside the bearing that are not crushed, do <db <di It becomes a relationship. Because of this relationship, the bearing surface 1a side can improve the corrosion resistance and oil film formation, while the outer surface 1b side and the end surface 1c side close to the sealed state have corrosion resistance and oil retention. Can be improved.

  Lubricating oil is impregnated in the pores do, db, and di of the sintered bearing 1. Thereby, a better lubrication state can be obtained than at the start of operation. As the lubricating oil, mineral oil, polyalphaolefin (PAO), ester, liquid grease, and the like can be used. However, it is not always necessary to impregnate the lubricating oil for the intended use of the bearing.

  FIG. 2 shows the surface compression layer of the sintered bearing 1 by hatching. Hatching is given only to the upper half of the bearing 1 in the radial direction, and the lower half is not shown. The surface layer of the sintered bearing 1 has a compression layer. The density ratio αo of the outer compression surface Po on the outer diameter surface 1b side and the density ratio αb of the outer compression layer Pb on the bearing surface 1a side are both higher than the internal density ratio αi, and both density ratios αo and αb are present. Are set in the ranges of 80% ≦ αo and αb ≦ 95%. If the density ratios αo and αb are less than 80%, the bearing strength is insufficient. On the other hand, if it exceeds 95%, the oil content is insufficient, which is not preferable.

The average value of the depth of the compression layer Po of the surface layer on the outer diameter surface 1b side is To, the average value of the depth of the compression layer Pb of the surface layer on the bearing surface 1a side is Tb, and the inner diameter dimension D1 of the bearing surface When the ratios are To / D1 and Tb / D1, respectively, it is preferable to set 1/100 ≦ To / D1 and Tb / D1 ≦ 1/15. Here, the density ratio α is expressed by the following equation.
α (%) = (ρ1 / ρ0) × 100
However, ρ1: the density of the porous body, ρ0: the density To / D1 and Tb / D1 when the porous body is assumed to have no pores are less than 1/100, the collapse of the pores is insufficient, If it exceeds 1/15, the pores are too crushed, which is not preferable.

  Next, verification results up to this embodiment will be described with reference to FIGS. Dashed lines X1 to X4 in FIGS. 4, 5, 7 and 8 indicate the allowable levels of the respective test items.

FIG. 4 shows the results of testing the relationship between the amount of aluminum (Al) blended and sulfidation corrosion. It was confirmed that the corrosion resistance improved as the aluminum content increased. From this test result, it is understood that the compounding amount of aluminum is required to be 8.5% by weight or more with respect to the sulfide corrosion resistance of the sintered bearing for the fuel pump.
[Test conditions]
Solvent: 300 ppm sulfur was added to commercial gasoline.
・ Temperature: 80 ℃
・ Time: 300 hours ・ Test method: Immersion

FIG. 5 shows the results of testing the relationship between the amount of aluminum blended and organic acid corrosivity. It has been found that the corrosion resistance decreases as the aluminum content increases. However, the rate of change in weight becomes moderate from around 9.0% by mass of aluminum. The reason why the weight change rate increases as the amount of aluminum added increases is the elution of copper ions and aluminum ions. The reason for the increase in elution of copper ions and aluminum ions is that the precipitation of the γ phase of the aluminum structure increases. It is thought that it is. From this test result, it is understood that the amount of aluminum needs to be 10% by weight or less with respect to the organic acid corrosion resistance of the sintered bearing for the fuel pump.
[Test conditions]
Solvent: Organic acid with a concentration of 2%.
・ Temperature: 50 ℃
・ Time: 100 hours ・ Test method: Immersion

FIG. 6 shows the results of testing the relationship between the aluminum blending amount and the copper ion elution amount. It was confirmed that the copper ion elution amount decreased as the aluminum compounding amount increased, and the copper ion elution amount rapidly decreased from around 8.5% by mass of the aluminum compounding amount. The cause of the decrease in the copper ion elution amount may be that the diffusion proceeds sufficiently as the aluminum blending amount increases. From this test result, it can be seen that the compounding amount of aluminum needs to be 8.5% by weight or more.
[Test conditions]
Solvent: Organic acid with a concentration of 2%.
・ Temperature: 50 ℃
・ Time: 100 hours ・ Test method: Immersion

FIG. 7 shows the results of testing the relationship between the amount of aluminum blended and the initial fit-in time. It was confirmed that the amount of aluminum blended and the initial running-in time were proportional. This is presumably because the hard γ phase increases in the aluminum structure as the aluminum content increases. From this test result, it can be seen that the blending amount of aluminum needs to be 10% by weight or less with respect to the initial familiarity of the sintered bearing for the fuel pump.
[Test conditions]
・ PV value: 50 MPa · m / min
・ Sample size: inner diameter 5mm x outer diameter 10mm x width 7mm
・ Test time: 30 min

FIG. 8 shows the results of testing the relationship between the amount of aluminum blended and the friction coefficient. It was confirmed that the amount of aluminum blended and the coefficient of friction had a proportional relationship. This is presumably because the hard γ phase increases in the aluminum structure as the aluminum content increases. It can be seen that when the aluminum content is 10 wt% or less, there is a sufficient margin with respect to the allowable level X4.
[Test conditions]
・ PV value: 50 MPa · m / min
・ Sample size: inner diameter 5mm x outer diameter 10mm x width 7mm
・ Test time: 30 min

Table 1 shows the results of measuring the hardness of the sintered bearing for the fuel pump in the first embodiment. The hardness values shown in Table 1 are values evaluated based on Vickers hardness (Hv: Vickers hardness) at a test load of 25 g. Hereinafter, the hardness value will be described as a value based on the Vickers hardness (Hv). For comparison, the hardness of the copper-based sintered bearing is also shown as Comparative Example 1.

  As shown in Table 1, the hardness of the copper-based sintered bearing is 70 to 80, whereas the hardness of the sintered bearing for the fuel pump in the first embodiment is 120 to 220, for example. It can be determined that the sintered bearing for the fuel pump in the first embodiment is a sintered bearing having higher wear resistance than the copper-based sintered bearing. This is because the hardness of the α phase that is the soft phase is 120 to 140, the hardness of the γ phase that is the hard phase is 200 to 220, and any of the sintered bearings for the fuel pump in the first embodiment The hardness of the phase is also due to being harder than the hardness of the copper-based sintered bearing.

  From the test results shown in FIGS. 4 to 8 and Table 1, as a sintered bearing for a fuel pump, it can be used if the aluminum content is 8.5 to 10% by weight, and 9.0 to 9.5% by weight. It was confirmed that the amount of aluminum was optimal.

  Next, a first embodiment of a method for manufacturing a sintered bearing for a fuel pump will be described. It is manufactured through a raw material powder preparation step S1, a forming step S2, a sintering step S3, a sizing step S4, and an oil impregnation step S5 as shown in FIG.

[Raw material powder preparation step S1]
In the raw material powder preparation step S1, the raw material powder of the sintered bearing 1 is prepared and generated. The raw material powder is 40 to 60% by weight of aluminum-copper alloy powder of 17 to 20% by weight, 7 to 10% by weight of phosphorus-copper alloy powder of 2 to 4% by weight, and the electrolytic copper powder is 100% in total. % Of aluminum fluoride and calcium fluoride as a sintering aid in total, 0.05 to 0.2% by weight of graphite powder, and stearic acid to facilitate moldability. A lubricant such as zinc and calcium stearate was added in an amount of 0.1 to 1% by weight. By adding the lubricant, it is possible to smoothly release the green compact described later, and to avoid the collapse of the shape of the green compact accompanying the release. Specifically, for example, the raw material powder M is put into a can body 11 of a V-type mixer 10 shown in FIG. 10, and the can body 11 is rotated and mixed uniformly.

  For example, 40 to 60% by weight of aluminum-copper alloy powder is 17 to 20% by weight, 7 to 10% by weight of phosphorus-copper alloy powder is 2 to 4% by weight, and the electrolytic copper powder is 100% by weight. The aluminum content is, for example, 8.5 wt% or more and 10 wt% or less, specifically 9 wt% or more and 9.5 wt% or less. .

  For example, the raw material powder is a total of 17 to 20 parts by weight of 40 to 60% by weight aluminum-copper alloy powder, 2 to 4 parts by weight of 7 to 10% by weight phosphorus-copper alloy powder, and the remaining part by weight of electrolytic copper powder. For 100 parts by weight, a total of 0.05 to 0.2 parts by weight of aluminum fluoride and calcium fluoride as a sintering aid, 3 to 10 parts by weight of graphite powder, for example, 3 to 5 parts by weight, molding In order to facilitate the property, a lubricant added with 0.1 to 1 part by weight of a lubricant such as zinc stearate and calcium stearate can be used.

  For example, 17 to 20 parts by weight of 40 to 60% by weight aluminum-copper alloy powder, 2 to 4 parts by weight of 7 to 10% by weight phosphorous-copper alloy powder, and 100 parts by weight of electrolytic copper powder as the remaining part by weight ( The graphite content is not included) and the aluminum content is, for example, 8.5 parts by weight or more and 10 parts by weight or less, specifically 9 parts by weight or more and 9.5 parts by weight or less. .

[Molding step S2]
In the molding step S2, a green compact 1 ′ (see FIG. 13) having the shape of the sintered bearing 1 is formed by compacting the raw material powder. The green compact 1 ′ is compression-molded so that the density ratio α of the sintered body 1 ″ formed by heating at the sintering temperature or higher is 70% or more and 80% or less. In FIG. In particular, the green compact is labeled 1 'and the sintered body is labeled 1 ".

  Specifically, for example, a molding die that defines a cavity that follows the shape of a green compact is set in a CNC press machine that uses a servo motor as a drive source, and the above-described raw material powder filled in the cavity is 200 to The green compact 1 ′ is formed by compressing with a pressure of 700 MPa. When molding the green compact 1 ′, the molding die may be heated to 70 ° C. or higher.

  In the manufacturing method of the sintered bearing 1 for a fuel pump according to the present embodiment, the problem of insufficient strength of the green compact due to a decrease in formability due to fluidity is improved by using an aluminum-copper alloy powder as the aluminum source. In addition, there is no problem in handling associated with scattering of single particles of aluminum having a small specific gravity. In addition, it has good production efficiency and is suitable for mass production.

[Sintering step S3]
In the sintering step S3, the green compact 1 ′ is heated at a sintering temperature to sinter-bond adjacent raw material powders to form a sintered body 1 ″. A mesh belt type continuous furnace 15 shown in FIG. , And a large amount of the green compact 1 ′ is put into the mesh belt 16 to form a sintered body 1 ″. Thereby, stable quality and a manufacturing method are realizable.

  What is important in the sintering process is to improve corrosion resistance and bearing performance (initial familiarity) by sufficiently diffusing aluminum into copper to improve corrosion resistance and making the aluminum bronze structure an α phase. It is. When it becomes the γ phase, it becomes hard and has excellent wear resistance, but the organic acid corrosion resistance decreases. Therefore, it has been found that it is necessary to reduce the amount of aluminum so as to suppress the precipitation of the γ phase as much as possible.

  Further, in the aluminum structure, the ratio γ phase / α phase between the γ phase and the α phase is preferably 0.10 ≦ γ phase / α phase ≦ 0.25. If the ratio of γ phase / α phase is less than 0.10, the wear resistance decreases, which is not preferable. On the other hand, if it exceeds 0.25, the initial conformability and organic acid corrosion resistance decrease, which is not preferable.

  As a sintering condition that satisfies the above, the sintering temperature is preferably 900 to 950 ° C, and more preferably 900 to 920 ° C (for example, 920 ° C). The atmosphere gas may be hydrogen gas, nitrogen gas or a mixed gas thereof, and the sintering time may be longer for better corrosion resistance. For a sintered bearing for a fuel pump, 20 to 60 minutes (for example, 30 minutes) Is preferred.

  The aluminum-copper alloy powder generates various liquid phases when the eutectic temperature is 548 ° C. or higher. When the liquid phase is generated, the liquid phase expands, and a sintered neck is formed by the generated liquid phase, leading to densification and shrinking of dimensions. In the present embodiment, by sintering in the mesh belt type continuous furnace 15, the surface of the sintered body 1 "is oxidized, and the size is kept expanded without being densified by inhibiting the sintering. However, since the inside of the sintered body 1 "is sintered without being oxidized, the strength of the sintered body 1" can be sufficiently secured. Since the mesh belt type continuous furnace 15 is used, the green compact is used. Sintering time can be shortened and mass-produced from 1 'input to take-out, cost can be reduced, and sufficient strength can be secured in terms of the function of the sintered bearing.

  In the above-described sintering step, a high-quality sintered body can be formed by the effect of the added phosphorus alloy powder. Phosphorous improves the wettability between the solid and liquid phases during sintering, and a good sintered body can be obtained. As a compounding quantity of phosphorus, 0.1 to 0.6 weight%, specifically 0.1 to 0.4 weight% is preferable. If the amount is less than 0.1% by weight, the effect of promoting the sintering between the solid and liquid phases is poor. On the other hand, if the amount exceeds 0.6% by weight, preferably 0.4% by weight, the obtained sintered body segregates and becomes brittle. .

  Further, graphite is present as free graphite mainly in pores dispersed and distributed in the base material, imparts excellent lubricity to the sintered bearing, and contributes to improvement of wear resistance. The blending amount of graphite is preferably 3 to 10% by weight, for example, 3 to 5% by weight, based on 100% by weight of the total of aluminum, phosphorus, the raw material powder having copper as the main component and the inevitable impurities. If it is less than 3% by weight, the effect of improving lubricity and wear resistance by adding graphite cannot be obtained as a sintered bearing for a fuel pump. On the other hand, when it exceeds 5% by weight, there is a concern that, for example, diffusion of aluminum into copper starts to be inhibited. When the added amount of graphite exceeds 10% by weight, the material strength is lowered and the diffusion of aluminum into copper is hindered. In general, when 4% by weight or more of graphite is added, molding cannot be performed, but molding is enabled by using granulated graphite. In the present embodiment, the graphite powder used is a graphite powder having a particle size of 145 mesh or less, which is obtained by granulating natural graphite or artificial graphite fine powder with a resin binder.

[Sizing Step S4]
In the sizing step S4, the sintered body 1 "expanded as compared with the green compact 1 'by sintering is dimensionally shaped. The details of the sizing step S4 are shown in FIG. It consists of an upper punch 21, a lower punch 22, and a core 23. As shown in Fig. 12 (a), a sintered body 1 "is set on the lower punch 22 with the core 23 and the upper punch 21 retracted upward. To do. As shown in FIG. 12B, the core 23 first enters the inner diameter of the sintered body 1 ″, and then the sintered body 1 ″ is transferred to the die 20 by the upper punch 21 as shown in FIG. It is pushed in and compressed by the upper and lower punches 21 and 22. Thereby, the surface of the sintered body 1 ″ is dimensionally shaped. By the sizing process, pores in the surface layer of the expanded sintered body 1 ″ are crushed, and a density difference is generated between the inside of the product and the surface layer portion.

  FIG. 13 shows a state in which the sintered body 1 ″ is compressed by sizing. The sintered body 1 ″ before sizing is indicated by a two-dot chain line, and the product 1 after sizing is indicated by a solid line. As indicated by a two-dot chain line, the sintered body 1 ″ expands in the radial direction and the width direction. For this reason, the sintered body 1 ″ compresses the outer diameter surface 1b more than the bearing surface 1a on the inner diameter side. The As a result, the surface pores do [see FIG. 3C] on the outer diameter surface 1b side are crushed more than the surface pores db [see FIG. 3A] on the inner diameter side bearing surface 1b and are not crushed. The relationship of do <db <di is established with respect to the pores di (see FIG. 3B) inside the bearing. Because of this relationship, the bearing surface 1a on the inner diameter side can improve the corrosion resistance and oil film formation. On the other hand, the outer diameter surface 1b and the end surface 1c close to the sealed state can improve the corrosion resistance and oil retention.

  The die for the above sizing process is composed of a die 20, a pair of punches 21, 22 and a core 23. The punches 21, 22 and the die 20 are compressed from both sides in the axial direction and the outer diameter side of the sintered body 1 ″ and fired. By shaping the inner diameter side of the bonded body 1 ″ with the core 23, the expansion due to sintering of the aluminum bronze-based sintered bearing can be effectively used, and desired pores can be formed along with the shaping of the sintered bearing 1.

  Further, by adjusting the dimensional difference between the inner diameter dimension of the die 20 and the outer diameter dimension of the sintered body 1 ″ and the dimensional difference between the outer diameter dimension of the core 23 and the inner diameter dimension of the sintered body 1 ″, It is possible to set the size of the pores on the surface of the bonded body 1 ″. Thereby, the size of the pores on the surface of the sintered bearing 1 can be easily controlled. By rotating and sizing the surface 1a (see FIG. 13), the pores of the bearing surface 1a can be reduced.

[Oil impregnation step S5]
The oil impregnation step S5 is a step in which the product 1 (sintered bearing) is impregnated with lubricating oil. FIG. 14 shows an oil retaining device. The product 1 is put into the tank 26 of the oil impregnating device 25, and then the lubricating oil 27 is injected into the tank 26. Then, by depressurizing the inside of the tank 26, the lubricating oil 27 is impregnated in the pores do, db, di (see FIG. 3) of the product 1. Thereby, a better lubrication state can be obtained than at the start of operation. As the lubricating oil, mineral oil, polyalphaolefin (PAO), ester, liquid grease, and the like can be used. However, what is necessary is just to implement according to the use application of a bearing, and it does not necessarily need to implement.

  The sintered bearing 1 of the present embodiment manufactured by the process as described above improves mechanical properties such as corrosion resistance, strength, and wear resistance, oil film formation, and oil retention, as well as compactness and cost reduction. Can be planned. As a sintered bearing for a fuel pump, it suppresses sulfidation corrosion due to poor gasoline, corrosion against organic acids and biofuels, and is excellent in performance such as initial familiarity and durability.

  Next, a second embodiment of the sintered bearing for a fuel pump according to the present invention and a second embodiment of the manufacturing method will be described. In the sintered bearing and manufacturing method for the fuel pump of the first embodiment, the aluminum-copper alloy powder and the electrolytic copper powder are used as the raw material powder to be the aluminum source and the copper source. However, in the second embodiment, copper is used. The point which used aluminum-copper alloy powder, without adding a single electrolytic copper powder, differs from 1st Embodiment.

  For more severe use environments, we have found that adding powder of copper alone has a problem with corrosion resistance due to the occurrence of a portion of uneven copper. As a result of various investigations based on this knowledge, the present embodiment has been achieved based on the idea of using an aluminum-copper alloy powder as a raw material powder to be an aluminum source and a copper source, and not adding a powder of copper alone.

  The composition in which the aluminum content is 8.5 to 10% by weight, phosphorus is 0.1 to 0.4% by weight, and the remaining main component is copper in the sintered bearing and manufacturing method for the fuel pump of the present embodiment is The same as in the first embodiment. However, the raw material powders are different as follows. That is, without adding electrolytic copper powder of simple copper, aluminum-copper alloy powder and phosphorus alloy powder are mixed in such a proportion that the above composition is obtained, and the total amount of graphite is 100% by weight. Graphite powder was mixed so as to be 3 to 5% by weight to obtain a raw material powder. In addition, as a sintering aid, aluminum fluoride and calcium fluoride are added in a total of 0.05 to 0.2% by weight, and zinc stearate is added in an amount of 0.1 to 1% by weight to facilitate moldability. did.

  For example, in a sintered bearing for a fuel pump and a manufacturing method, the aluminum content is 8.5 to 10 parts by weight, phosphorus is 0.1 to 0.4 parts by weight, and if necessary, the compounding amount of graphite is 3 to 10 parts by weight. Part, for example, 3 to 5 parts by weight, with the remaining main component being copper. In this case, for example, the raw material powder is as follows. That is, without adding electrolytic copper powder of simple copper, aluminum-copper alloy powder and phosphorus alloy powder are mixed in such a ratio that the above composition is obtained, and the total amount of graphite is 100 parts by weight. The graphite powder was mixed so as to be 3 to 10 parts by weight, for example 3 to 5 parts by weight, to obtain a raw material powder. The blending amount of graphite is preferably 3 to 10 parts by weight, for example, 3 to 5 parts by weight, based on 100 parts by weight of the total of aluminum, phosphorus, raw material powder having copper as the main component and the inevitable impurities. If it is less than 3 parts by weight, the effect of improving lubricity and wear resistance by adding graphite as a sintered bearing for a fuel pump cannot be obtained. On the other hand, when the amount exceeds 5 parts by weight, there is a concern that, for example, diffusion of aluminum into copper starts to be inhibited. When the added amount of graphite exceeds 10 parts by weight, the material strength is lowered and the diffusion of aluminum into copper is hindered. In general, when 4 parts by weight or more of graphite is added, molding cannot be performed, but molding is made possible by using granulated graphite. In the present embodiment, the graphite powder used is a graphite powder having a particle size of 145 mesh or less, which is obtained by granulating natural graphite or artificial graphite fine powder with a resin binder. Moreover, 0.05 to 0.2 parts by weight of aluminum fluoride and calcium fluoride as a sintering aid in total, and 0.1 to 1 part by weight of zinc stearate is added to facilitate moldability. did.

  The aluminum bronze structure of the present embodiment using an aluminum-copper alloy powder as a copper source and not adding a powder of copper alone has a ratio γ phase / α phase ratio γ phase / α phase, where 0 <γ phase / α phase. It is preferable that ≦ 0.10. In the range of 0 <γ phase / α phase ≦ 0.10, the organic acid corrosion resistance and initial conformability are excellent.

  Since the metal structure of the cross section of the sintered bearing according to this embodiment is the same as that of the first embodiment shown in the schematic diagram of FIG. 3, the contents described above with reference to FIG.

  Moreover, since the state of the compression layer of the surface layer of the sintered bearing 1 of this embodiment is the same as that of the sintered bearing of the first embodiment shown in FIG. 2, the contents described above with reference to FIG. Is omitted.

  Next, verification results up to this embodiment will be described with reference to FIGS. 15 and 16. A broken line X2 in FIG. 15 indicates the allowable level of the test item. Although illustration is omitted, regarding the relationship between the aluminum blending amount and the sulfide corrosion resistance, a better result was confirmed in the sintered bearing in the second embodiment than in the sintered bearing in the first embodiment. In addition, regarding the relationship between the initial running-in time and the friction coefficient, the test result of the sintered bearing in the first embodiment and the test result of the sintered bearing in the second embodiment are substantially equivalent results. Therefore, detailed description thereof is omitted here.

  FIG. 15 shows the results of testing the relationship between the amount of aluminum blended and organic acid corrosivity. The test conditions are the same as in FIG. In FIG. 15, ♦ indicates the test result of the sintered bearing of the first embodiment shown in FIG. 5, but the sintered bearing of the present embodiment indicated by ◇ has an aluminum blending amount of 8.5 wt%. In addition, it was confirmed that the organic acid corrosion resistance was further improved as compared with the first embodiment. Since the aluminum-copper alloy powder was used as the raw material powder for the aluminum source and the copper source without adding the powder of the copper simple substance, the portion where the copper simple substance was biased was almost eliminated, and the occurrence of corrosion due to that part was avoided. It is considered that the corrosion resistance is improved. Combined with this, it is considered that the use of aluminum-copper alloy powder improved the corrosion resistance of each of the aluminum-copper alloy powder particles and improved the corrosion resistance of the entire sintered bearing. .

  FIG. 16 shows the results of testing the relationship between the aluminum blending amount and the copper ion elution amount. The test conditions are the same as in FIG. Also in FIG. 16, the ♦ marks indicate the test results of the sintered bearing of the first embodiment shown in FIG. 6, but the sintered bearing of the present embodiment indicated by ◇ has an aluminum blending amount of 8.5 weight. %, It was confirmed that the copper ion elution amount was reduced as compared with the first embodiment.

Table 2 shows the results of measuring the hardness of the sintered bearing for the fuel pump in the second embodiment. Since the hardness evaluation method shown in Table 2 is the same as the hardness evaluation method shown in Table 1, detailed description thereof is omitted here.

  As shown in Table 2, the hardness of the copper-based sintered bearing is 70 to 80, whereas the hardness of the sintered bearing for the fuel pump in the second embodiment is 100 to 240, for example. It can be determined that the sintered bearing for the fuel pump in the second embodiment is a sintered bearing having higher wear resistance than the copper-based sintered bearing. This is because the hardness of the α phase that is the soft phase is 100 to 140, the hardness of the γ phase that is the hard phase is 200 to 240, and any of the sintered bearings for the fuel pump in the second embodiment The hardness of the phase is also due to being harder than the hardness of the copper-based sintered bearing.

  From the test results shown in FIGS. 15 and 16 and Table 2, it was confirmed that the sintered bearing for a fuel pump of this embodiment can ensure corrosion resistance even in a more severe use environment.

  Next, a second embodiment of the manufacturing method will be described. Since the manufacturing method of the second embodiment is also the same as the manufacturing method of the sintered bearing of the first embodiment shown in FIG. 9, the above-described contents apply mutatis mutandis to the raw material powder preparation step S1 and the molding step S2. Only the differences will be described.

[Raw material powder preparation step S1]
In the raw material powder preparation step S1, the raw material powder of the sintered bearing 1 is prepared. The raw material powder is 7 to 11 wt% aluminum-copper alloy powder, preferably 8 to 10 wt% aluminum-copper alloy powder is 90 to 97 wt%, 7 to 10 wt% phosphorous-copper alloy powder is 1 to 6 wt% 3 to 5% by weight of graphite powder and 0.05 to 0.2% by weight of aluminum fluoride and calcium fluoride as a sintering aid in total, making the moldability easy As a lubricant, 0.1 to 1% by weight of zinc stearate was added. As the 7-11 wt% aluminum-copper alloy powder, a powder whose particle size was adjusted by pulverization was used. As in the first embodiment, the raw material powder is charged into, for example, the can body 11 of the V-type mixer 10 shown in FIG. 10, and the can body 11 is rotated and mixed uniformly.

  For example, a total of 100% by weight (not including the graphite portion) is 7 to 11% by weight of aluminum-copper alloy powder 90 to 97% by weight and 7 to 10% by weight phosphorus-copper alloy powder 1 to 6% by weight. The aluminum content is, for example, 8.5 wt% or more and 10 wt% or less, specifically 9 wt% or more and 9.5 wt% or less with respect to the alloy portion.

  For example, the raw material powder is 7 to 11 wt% aluminum-copper alloy powder, preferably 8 to 10 wt% aluminum-copper alloy powder is 90 to 97 parts by weight, and 7 to 10 wt% phosphorous-copper alloy powder is 1 to 6 3 to 10 parts by weight, for example 3 to 5 parts by weight of graphite powder, and 0.05 to 0.2 in total of aluminum fluoride and calcium fluoride as sintering aids, with respect to 100 parts by weight as a total. What added 0.1-1 weight part of zinc stearates as a weight part and the lubrication agent for making moldability easy can be used.

  For example, 7 to 11% by weight of aluminum-copper alloy powder is 90 to 97 parts by weight, and 7 to 10% by weight of phosphorus-copper alloy powder is 1 to 6 parts by weight. The aluminum content is, for example, not less than 8.5 parts by weight and not more than 10 parts by weight, specifically, not less than 9 parts by weight and not more than 9.5 parts by weight with respect to the alloy part.

[Molding step S2]
In the molding step S2, a green compact 1 ′ (see FIG. 13) having the shape of the sintered bearing 1 is formed by compacting the raw material powder. In this embodiment, since the aluminum-copper alloy powder was used as the raw material powder to be the aluminum source and the copper source without adding the powder of the copper simple substance, the portion where the copper simple substance was biased was substantially eliminated, and the corrosion caused by that part was eliminated. Is avoided. Thereby, corrosion resistance improves. Further, by using the aluminum-copper alloy powder, the corrosion resistance of each particle of the aluminum-copper alloy powder is improved, and the corrosion resistance of the entire sintered fuel pump bearing is improved.

  In the sintered bearing for a fuel pump based on the manufacturing method of the present embodiment, corrosion resistance can be ensured even in a particularly severe use environment. Further, as with the sintered bearing of the first embodiment, mechanical characteristics such as strength and wear resistance, oil film formation, and oil retention can be improved, and compactness and cost reduction can be achieved.

  In the description of each of the embodiments described above, the case where the present invention is applied to a perfect circle bearing having the perfect bearing surface 1a is illustrated, but the present invention is not limited to a perfect circle bearing, and the bearing surface 1a and the shaft 52 are 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, a spiral groove, or the like is provided on the outer peripheral surface.

  The sintered bearing of the present embodiment is, for example, a sintered bearing for a fuel pump that does not contain oils such as lubricating oil depending on the type of the fuel pump, and a sintered bearing for a fuel pump that contains a small amount of lubricating oil. Various types of sintered bearings for fuel pumps, such as sintered bearings for fuel pumps sufficiently containing lubricating oil, can be used.

  The present invention is not limited to the above-described embodiments, and can of course be implemented in various forms without departing from the scope of the present invention. The scope of the present invention is not limited to patents. It includes the equivalent meanings recited in the claims and the equivalents recited in the claims, and all modifications within the scope.

DESCRIPTION OF SYMBOLS 1 Sintered bearing for fuel pump 1 'Compact 1 "Sintered body 1a Bearing surface 1b Outer diameter surface 1c End surface 2 Sintered bearing for fuel pump 3 Aluminum copper alloy structure 4 Aluminum oxide film 5 Free graphite 15 Mesh belt type continuous Furnace 20 Die 21 Upper punch 22 Lower punch 23 Core 40 Fuel pump 52 Shaft D1 Inner diameter dimension of bearing surface db Pore di Pore do Pore Ti Compression layer To Compression layer

Claims (12)

  A sintered bearing for a motor type fuel pump containing 8.5 to 10% by weight of aluminum and 0.1 to 0.6% by weight of phosphorus, the remaining main component being copper and containing inevitable impurities, This sintered bearing has a structure in which an aluminum-copper alloy is sintered, and the pores in the surface layer portion of the sintered bearing are made smaller than the internal pores.   The sintered structure for a fuel pump according to claim 1, wherein the structure of the aluminum-copper alloy has an α phase.   The structure of the aluminum-copper alloy is characterized in that the ratio γ phase / α phase between the γ phase and the α phase is such that 0 <γ phase / α phase ≦ 0.10. The sintered bearing for fuel pumps as described.   The graphite of 3-10 weight% is added with respect to the total of 100 weight% of the raw material powder which uses copper as the main component of the said aluminum, phosphorus, and the remainder, and an unavoidable impurity, The sintered bearing for fuel pumps as described in any one of Claims.   The sintered bearing for a fuel pump according to any one of claims 1 to 4, wherein tin as a sintering aid is not added to the sintered bearing for a fuel pump.   The sintered bearing for a fuel pump according to any one of claims 1 to 5, wherein the aluminum content is 9 to 9.5 wt%.   A method for producing a sintered bearing for a fuel pump, which contains 8.5 to 10% by weight of aluminum and 0.1 to 0.6% by weight of phosphorus, the remaining main component being copper and containing inevitable impurities. The manufacturing method uses aluminum-copper alloy powder, electrolytic copper powder and phosphorous-copper alloy powder as raw material powder, and at least a forming step of forming a green compact obtained by adding a sintering aid to the raw material powder, Production of a sintered bearing for a fuel pump, comprising a sintering step for obtaining a sintered body having an aluminum-copper alloy structure from the green compact, and a sizing step for dimensioning the sintered body. Method.   As the sintering aid, aluminum fluoride and calcium fluoride total 0.05 to The method for producing a sintered bearing for a fuel pump according to claim 7, wherein 0.2% by weight is added.   9. The fuel pump according to claim 7, wherein a ratio d2 / d1 between the average particle diameter d1 of the aluminum-copper alloy powder and the average particle diameter d2 of the electrolytic copper powder is 2-3. Manufacturing method of sintered bearing.   The electrolytic copper powder is composed of powders having different shapes, and the ratio W2 / W1 between the ratio W1 of the electrolytic copper powder having an aspect ratio of 2 or more and the ratio W2 of the electrolytic copper powder of less than 2 is set to 3-9. A method for manufacturing a sintered bearing for a fuel pump according to any one of claims 7 to 9.   A method for producing a sintered bearing for a fuel pump, which contains 8.5 to 10% by weight of aluminum and 0.1 to 0.6% by weight of phosphorus, the remaining main component being copper and containing inevitable impurities. In this manufacturing method, as a raw material powder, an aluminum-copper alloy powder and a phosphorous-copper alloy powder are used, and at least a green compact in which a sintering aid is added to the raw material powder is used. A fuel pump comprising: a forming step for forming; a sintering step for obtaining a sintered body having an aluminum-copper alloy structure from the green compact; and a sizing step for dimensioning the sintered body. Method for manufacturing sintered bearings.   The method for producing a sintered bearing for a fuel pump according to claim 11, wherein the aluminum-copper alloy powder as the raw material powder is 7 to 11 wt% aluminum-copper alloy powder.

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