JP6745760B2 - Sintered bearing for fuel pump and manufacturing method thereof - Google Patents

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 has been used for an engine that uses gasoline, light oil, or the like as fuel. In recent years, engines equipped with electric fuel pumps that use fuels such as gasoline and light oil have been widely used all over the world, and the quality of gasoline and light oil used differs in each region of the world. Is used in many areas. Gasoline and biofuel containing organic acids are known as a kind of poor gasoline, but when a copper-based sintered bearing is used in an electric fuel pump, the organic acid and biofuel contained in such bad gasoline are used. As a result, the copper-based sintered bearing is corroded. This corrosion progresses around the openings of the pores that open to the bearing surface and the inner surfaces of these pores, and further to the inner surfaces of the pores that are internal to the bearing and communicate with the interior, increasing the strength of the bearing. And shorten the life of the copper-based sintered bearing.

Further, 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 rotational speed in order to reduce the size while ensuring the discharge performance. As a result, fuel such as gasoline taken into the fuel pump has a high pressure in the flow passage with a narrow gap. In addition, the sintered bearing is required to be compact and to have higher strength, wear resistance, friction characteristics and corrosion resistance under such conditions. Therefore, the conventional copper-based sintered bearing has high strength, but is not particularly satisfactory in corrosion resistance.

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

On the other hand, as a sintered bearing having excellent mechanical properties and corrosion resistance, an aluminum bronze-based sintered bearing is known. With this sintered bearing, an aluminum oxide film is formed on the surface during the temperature rise during sintering, and it is difficult to obtain a sintered body having sufficient corrosion resistance and strength because it inhibits the diffusion of aluminum. 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 problems.

Japanese Patent No. 4521871 JP, 2009-7650, A

The Cu-Ni-Sn-C-P type sintered bearing described in Patent Document 1 has improved 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 has excellent formability and sinterability, but as an aluminum bronze-based sintered bearing using the aluminum-containing copper alloy powder, stable corrosion resistance, Further studies are needed to obtain products suitable for mass production that meet mechanical characteristics, compactness, and cost reduction.

In view of the conventional problems, the present invention provides a sintered aluminum bronze-based bearing for a fuel pump, which has improved mechanical properties such as corrosion resistance, strength, and wear resistance, and is compact and low in cost. And a method of manufacturing an aluminum bronze-based sintered bearing for a fuel pump, which has good productivity, low cost, and is suitable for mass production.

In the aluminum bronze-based sintered bearing and the method for manufacturing the same, the inventors of the present invention have proposed that the expansion by sintering is effectively used in order to improve the bearing function and to achieve compactness, cost reduction, and productivity improvement. As a prerequisite, the sintered bearings for fuel pumps, which are always in contact with gasoline as described above, suppress sulfide corrosion due to poor gasoline, corrosion due to organic acid and biofuel, and The present invention has been accomplished by conducting various studies and test evaluations and obtaining the following findings in order to secure familiarity, durability and other performances.
(1) Regarding the relationship between the aluminum content and the sulfidation corrosion resistance, the corrosion resistance is improved as the aluminum content is increased. It is considered that when the compounding amount of aluminum is increased, the diffusion into copper is enhanced and the corrosion resistance is improved.
(2) Regarding the relationship between the amount of aluminum compounded and the organic acid corrosiveness, the corrosion resistance decreases as the amount of aluminum compounded increases. However, the weight change rate becomes mild when the amount of aluminum compounded 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. to become an α phase and a γ phase, and the proportion of the γ phase increases as the aluminum content increases. Since the γ phase lowers the organic acid corrosion resistance and the initial running-in property, when the aluminum-copper alloy powder is used as the copper source and the powder of copper alone is not added, the ratio between the γ phase and the α phase is 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 promoted and the corrosion resistance is improved.
(5) Phosphorus, which is an additive, is thought to promote the diffusion of aluminum during the sintering process, thereby reducing the amount of aluminum and reducing the precipitation of γ phase in the aluminum structure that deteriorates the corrosion resistance and the initial familiarity. To be
(6) Regarding the relationship between the blending amount of aluminum and the initial running-in time and the friction coefficient, the blending amount of aluminum and the initial running-in time and the frictional coefficient are in a proportional relationship. It is considered that the γ phase increases as the aluminum content 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, and the remaining main component is copper, A sintered bearing for a fuel pump containing unavoidable 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 from the internal pores. It is characterized by being made smaller. As a result, it is possible to improve mechanical properties such as corrosion resistance, strength, and wear resistance, as well as oil film forming properties and oil retaining properties, and to achieve compactness and cost reduction.

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 manufacturing a sintered bearing for a fuel pump containing unavoidable impurities, which comprises using aluminum-copper alloy powder, electrolytic copper powder and phosphorous-copper alloy powder as raw material powder, and burning at least raw material powder. A forming step of forming a green compact to which a binder is added, a sintering step of obtaining a sintered body having an aluminum-copper alloy structure from the green compact, and a sizing step of dimensioning the sintered body. It is characterized by including. As a result, it is possible to realize a method for manufacturing an aluminum bronze-based sintered bearing for a fuel pump, which has good productivity, low cost, and which is suitable for mass production. The sintered bearing for a fuel pump thus manufactured can be made compact while improving mechanical properties such as corrosion resistance, strength, and wear resistance, oil film forming property, and oil retaining property.

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

The structure of the above-mentioned aluminum-copper alloy (hereinafter, also referred to as an aluminum bronze structure) uses an aluminum-copper alloy powder as a copper source, and when a powder of copper alone is not added, the ratio γ to α phase is γ. The phase/α phase is preferably 0<γ phase/α phase≦0.10. Within the range of 0<γ phase/α phase≦0.10, the organic acid corrosion resistance and the initial running-in property are excellent.

It is preferable that the graphite is added in an amount of 3 to 10% by weight based on 100% by weight of the total amount of aluminum, phosphorus, raw material powder containing copper as the main component of the balance, and unavoidable impurities. It is possible to use the one added at up to 5% by weight. 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, if it exceeds 5% by weight, it is feared that diffusion of aluminum into copper starts to be hindered. If the amount of graphite added exceeds 10% by weight, the diffusion of aluminum into copper is hindered, so consideration is necessary. Regarding the wear resistance, the wear resistance is improved by increasing the addition amount of graphite, but it is considered that the wear amount is slightly increased from the addition amount of graphite of 10% by weight and the material strength is lowered.

It is preferable that the above graphite powder is obtained by granulating fine powder of natural graphite or artificial graphite with a resin binder and then pulverizing it to obtain graphite powder having a particle size of 145 mesh or less. Generally, when graphite is added in an amount of 4% by weight or more, it cannot be molded, but the use of granulated graphite enables molding.

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

In the above sintered bearing for a fuel pump, it is more preferable that the content of aluminum is 9 to 9.5% by weight. The sintered bearing for a fuel pump 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 the above sintering aid, aluminum fluoride and calcium fluoride are added in a total amount of 0.05% with respect to a total of 100% by weight of the raw material powder consisting of the aluminum-copper alloy powder, electrolytic copper powder and phosphorus-copper alloy powder. It is preferable to add ~0.2 wt%. If it is less than 0.05% by weight, the effect as a sintering aid becomes 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 the ceiling even if it is added in excess, and it is preferable to keep it to 0.2% by weight or less from the viewpoint of cost.

It is preferable that 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 2 to 3. When the ratio d2/d1 is in this range, aluminum can be sufficiently diffused in copper, and the corrosion resistance is excellent.

The above-mentioned electrolytic copper powder is composed of different powder shapes, and the ratio W2/W1 of 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 having an aspect ratio of less than 2 is set to 3 to 9. It is preferable. Electrolytic copper powder having an aspect ratio of 2 or more is effective for diffusing aluminum, but has poor formability. If the ratio W2/W1 is less than 3, it is not preferable from the viewpoint of moldability, while if it exceeds 9, the diffusion of aluminum 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.

A second invention as a method for manufacturing 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 balance of the main component is copper, A method for manufacturing a sintered bearing for a fuel pump containing unavoidable impurities, wherein this manufacturing method does not add powder of copper alone as raw material powder, and uses aluminum-copper alloy powder and phosphorus-copper alloy powder, 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 step for shaping. Here, without adding the powder of the copper simple substance as the raw material powder, the powder of the copper simple substance inevitably contained at the manufacturing site is used in the meaning of allowing.

The second invention as the above manufacturing method can also realize a manufacturing method of an aluminum bronze-based sintered bearing for a fuel pump, which has high productivity, low cost, and suitable for mass production. Further, the sintered bearing for a fuel pump manufactured in this manner can be improved in mechanical characteristics such as corrosion resistance, strength, and wear resistance, oil film forming property, and oil retaining property, 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, and the occurrence of corrosion due to this portion is avoided, and the corrosion resistance of each aluminum-copper alloy powder grain is improved. By improving, the corrosion resistance can be secured even in a more severe use environment.

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

The sintered bearing for a fuel pump according to the present invention can improve mechanical characteristics such as corrosion resistance, strength, and wear resistance, oil film forming property, and oil retaining property, and can be made compact and low in cost. Further, the method for producing a sintered bearing for a fuel pump according to the present invention has high productivity, is low in cost, and can realize a method for producing an aluminum bronze-based sintered bearing for a fuel pump, which is suitable for mass production.

Further, according to the second invention as the manufacturing method using the aluminum-copper alloy powder without adding the powder of the simple substance of copper, the uneven portion of the simple substance of copper is substantially eliminated, and the occurrence of corrosion due to this part is avoided. In addition, since the corrosion resistance of each aluminum-copper alloy powder is improved, the corrosion resistance can be ensured even in a more severe use environment.

It is a longitudinal cross-sectional view showing an outline of a fuel pump in which the sintered bearing for a fuel pump according to the first embodiment of the present invention is used. FIG. 1 is a vertical sectional view of a sintered bearing for a fuel pump according to a first embodiment of the present invention and a sintered bearing for a fuel pump based on a manufacturing method according to the first embodiment of the present invention. 2A is an enlarged schematic view of the metal structure of the A portion of FIG. 2, FIG. 2B is an enlarged schematic view of the metal structure of the B portion of FIG. 2, and FIG. 2C is a metal structure of the C portion of FIG. It is the schematic diagram which expanded. It is a graph which shows the test result about the compounding quantity of aluminum and a sulfidation corrosivity. It is a graph which shows the test result about the compounding quantity of aluminum and organic acid corrosiveness. It is a graph which shows the test result about the compounding amount of aluminum and the elution amount of copper ion. It is a graph which shows the test result about the relationship of the compounding quantity of aluminum and initial familiarization time. It is a graph which shows the test result about the relationship of 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 a mixer of raw material powder. 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 in the metal mold of sizing processing, (b) shows the state which the core descended, (c) shows the sizing processing completed. Indicates the state. It is a figure which shows the compressed state of the product in a sizing process. It is a schematic diagram of an oil impregnation device. It is a graph which shows the test result about the relationship of the compounding quantity of aluminum and organic acid corrosiveness about the sintered bearing for fuel pumps which concerns on the 2nd Embodiment of this invention. It is a graph which shows the test result about the relationship of the compounding quantity of aluminum and the elution amount of copper ion about the sintered bearing for fuel pumps which concerns on the 2nd Embodiment of this invention.

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

FIG. 1 is a vertical cross-sectional view showing the 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 an upper part of a cylindrical metal housing 41, and a pump part 43 is incorporated under the motor part 42. A synthetic resin motor cover 45 is swaged and fixed 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 chamber 48 is formed between the motor cover 45 and the pump cover 46 in the housing 41, and a pump 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 chamber 48 and the pump chamber 49.

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

A magnet 55 is fixed to the inner peripheral surface of the housing 41 at a predetermined distance from the outer peripheral surface of the armature 50. A brush 56, which is in sliding contact with the commutator 50a of the armature 50, is incorporated in the motor cover 45 in a state of being biased by a spring 57. The brush 56 is electrically connected to an external connection terminal (not shown) via a choke coil 58. The motor cover 45 is provided with a discharge port 70 for connecting a fuel supply pipe (not shown) communicating with the fuel injection valve. A check valve 71 for preventing a backflow of fuel is incorporated in the discharge port 70 in a state of being biased in a closing direction by a spring 72.

A plate 74 is interposed between the pump cover 46 and the pump body 47 of the pump part 43, and the pump part chamber 49 is divided into two chambers. An impeller 75 is arranged in each chamber. Both impellers 75 are connected to the lower end of the shaft 52, and are rotationally driven 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 chamber 49, and this fuel enters the motor chamber 48 from the flow port 77 of the pump cover 46 through the flow path of the pump unit 43 and from the discharge port 70. Is ejected. Therefore, the fuel pump sintered bearings 1 and 2 of this embodiment, which rotatably support the shaft 52 of the armature 50, are in an environment where they are always in contact with fuel (for example, gasoline). The fuel pump 40 shown in FIG. 1 is, for example, an in-tank type fuel pump 40 in which the fuel pump 40 is immersed in a liquid fuel such as gasoline.

Explaining the types of fuel pumps, there are two types of fuel pumps, for example, 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 used while being immersed in a liquid fuel such as gasoline. Therefore, for example, the sintered bearings 1 and 2 used in an in-tank type fuel pump do not necessarily need to be impregnated with oil, but in order to suppress initial wear as much as possible, an in-tank type fuel pump is used. The sintered bearings 1 and 2 used are preferably oil-impregnated.

On the other hand, the out-tank type fuel pump is a type that is used in the atmosphere without the fuel pump itself being immersed in the liquid fuel such as gasoline. For example, a sintered bearing used in an out-tank type fuel pump does not necessarily need to be impregnated with oil, but in order to suppress initial wear as much as possible Is also preferably oiled.

FIG. 2 shows a vertical cross-sectional view of the sintered bearing for a fuel pump of this embodiment. 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 circumference. When the shaft 52 of the armature 50 (see FIG. 1) is inserted into the inner circumference of the sintered bearing 1 and the shaft 52 is rotated in that state, the temperature of the lubricating oil held in the numerous holes of the sintered bearing 1 rises. Along with this, it oozes out to the bearing surface 1a. The lubricating oil thus exuded forms an oil film in the bearing gap between the outer peripheral surface of the shaft 52 and the bearing surface 1a, 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 reference numeral 2 is also shown in FIG. The 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 the powder to form a green compact, and then sintering the green compact. To be done.

The raw material powder is a mixed powder in which aluminum-copper alloy powder, copper powder, phosphorus-copper alloy powder, graphite powder and aluminum fluoride and calcium fluoride as a sintering aid are mixed. The details of each powder are described below.

[Aluminum-copper alloy powder]
The 40-60 wt% aluminum-copper alloy powder was crushed and the particle size was adjusted. The particle size of the aluminum-copper alloy powder is 100 μm or less, and the average particle size is 35 μm. Here, in the present specification, the average particle diameter means an average value of particle diameters measured by laser diffraction. Specifically, it is the average value of the particle size when 5000 powders are measured by laser diffraction using SALD-3100 manufactured by Shimadzu Corporation.

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

In the aluminum bronze structure, the α phase is the most excellent in corrosion resistance to sulfidation corrosion and organic acid corrosion and is initially familiar. By using 40 to 60 wt% aluminum-copper alloy powder, strength can be obtained even if 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 the initial running-in deteriorate. The aluminum bronze structure preferably has a ratio of γ phase to α phase of γ phase/α phase of 0.10≦γ phase/α phase≦0.25. If the ratio of γ phase/α phase is less than 0.10, wear resistance is undesirably lowered, while if it exceeds 0.25, initial running-in property and organic acid corrosion resistance are unfavorably lowered.

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

In this embodiment, an electrolytic copper powder having an average particle diameter of 85 μm was used. It is preferable that 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 2 to 3. When the ratio d2/d1 is in this range, aluminum can be sufficiently diffused in copper, and the corrosion resistance is excellent. Therefore, in the present embodiment, the average particle size d1 of the aluminum-copper alloy powder is 35 μm, and the average particle size d2 of the electrolytic copper powder is 85 μm. However, without being limited to this, an aluminum-copper alloy powder having an average particle size of about 20 to 65 μm can be used, and an 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.

[Phosphorus 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 phosphorus content is preferably 0.1 to 0.6% by weight, specifically 0.1 to 0.4% by weight. If it is less than 0.1% by weight, the effect of accelerating the sintering between the solid and liquid phases is poor. On the other hand, if it exceeds 0.6% by weight, and preferably more than 0.4% by weight, the sintering proceeds excessively and aluminum segregates to produce γ. Phase precipitation increases and the sintered body becomes brittle.

[Graphite powder]
Graphite mainly exists as free graphite in the pores dispersedly distributed in the matrix, 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, and may be, for example, 3 to 5% by weight, based on 100% by weight of the total of the raw material powder containing aluminum, phosphorus, the balance of the main component being copper, and 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, if it exceeds 5% by weight, it is feared that diffusion of aluminum into copper starts to be hindered. If the amount of graphite added exceeds 10% by weight, the material strength is lowered and the diffusion of aluminum into copper is hindered, which is not preferable. Generally, when graphite is added in an amount of 4% by weight or more, it cannot be molded, but the use of granulated graphite enables molding. In this embodiment, as the graphite powder, a fine powder of natural graphite or artificial graphite is granulated with a resin binder and then pulverized to use graphite powder having a particle size of 145 mesh or less.

[Aluminum fluoride and calcium fluoride]
In the aluminum-copper alloy powder, the film of aluminum oxide formed on the surface during sintering remarkably inhibits the sintering, but aluminum fluoride and calcium fluoride as sintering aids are used as the sintering agent for the aluminum-copper alloy powder. It gradually evaporates while melting at a binding temperature of 850 to 900° C., protects the surface of the aluminum-copper alloy powder and suppresses the formation of aluminum oxide, thereby promoting sintering and promoting diffusion of aluminum. Aluminum fluoride and calcium fluoride evaporate and volatilize during sintering, so that they hardly remain in the finished product of the sintered bearing.

Aluminum fluoride and calcium fluoride as sintering aids are added in a total amount of 0.05 to 0.2 with respect to a total of 100% by weight of raw material powder containing aluminum, phosphorus, and the remaining main component being copper, and inevitable impurities. It is preferable to add it in an amount of about wt %. If it is less than 0.05% by weight, the effect as a sintering aid becomes 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 the ceiling even if it is added in excess, 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 and the manufacturing method described later of the present embodiment, the aluminum content is 8.5 to 10% by weight, the 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 the graphite powder is mixed so that the blending amount of graphite is 3 to 5% by weight with respect to the total 100% by weight. As raw material powder. Aluminum fluoride and calcium fluoride are added in a total amount of 0.05 to 0.2 wt% as a sintering aid, and a lubricant such as zinc stearate or calcium stearate is added in an amount of 0.1 to 1 to facilitate moldability. Wt% was added.

More specifically, for example, in the fuel pump sintered bearing of the present embodiment and the manufacturing method described later, the aluminum content is 8.5 to 10 parts by weight, the phosphorus is 0.1 to 0.4 parts by weight, and the balance of Aluminum-copper alloy powder, electrolytic copper powder and phosphorus alloy powder are mixed in a ratio such that the main component is copper, and the blending amount of graphite is 3 to 5 parts by weight based on 100 parts by weight of the total. Graphite powder was mixed with to obtain a raw material powder. The blending amount of graphite is preferably 3 to 10 parts by weight, and may be, for example, 3 to 5 parts by weight, based on 100 parts by weight of the total of the raw material powder containing aluminum, phosphorus, the balance of copper as the main component, and unavoidable impurities. If it is less than 3 parts 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, if it exceeds 5 parts by weight, for example, there is a concern that diffusion of aluminum into copper may start to be hindered. When the amount of graphite added exceeds 10 parts by weight, the material strength is lowered and the diffusion of aluminum into copper is unfavorable. Generally, when graphite is added in an amount of 4 parts by weight or more, it cannot be molded, but the use of granulated graphite enables molding. In this embodiment, as the graphite powder, a fine powder of natural graphite or artificial graphite is granulated with a resin binder and then pulverized to use graphite powder having a particle size of 145 mesh or less. As a sintering aid, 0.05 to 0.2 parts by weight of aluminum fluoride and calcium fluoride in total, and 0.1 to 1 of a lubricant such as zinc stearate or calcium stearate to facilitate moldability. Parts by weight was added.

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

As shown in FIG. 3A, an open pore db1 formed in the bearing surface on the inner diameter side and an internal pore db2 in the surface layer of the bearing surface are formed. As shown in FIG. 3B, pores di are formed inside the bearing, and as shown in FIG. 3C, open pores do1 formed on the outer diameter surface and inner pores formed on the outer surface of the outer diameter surface. do2 is formed. The open pores db1 formed on the bearing surface, the internal pores db2 on the surface of the bearing surface, the pores di inside the bearing, the open pores do1 formed on the outer diameter surface and the internal pores do2 formed on the outer surface of the outer diameter surface are , They are in communication with each other.

In the sintered bearing 1, in the manufacturing method described later (see FIG. 13), both the outer diameter surface 1b and the inner diameter side bearing surface 1a of the bearing are sized after sintering. 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. 3(c)] in the surface layer portion on the outer diameter surface 1b side are crushed more than the pores db [see FIG. 3(a)] in the surface layer portion on the bearing surface 1a side. 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 inside the uncrushed bearing [see FIG. 3(b)], do<db<di It becomes a relationship. Because of such a relationship, the bearing surface 1a side can improve the corrosion resistance and the oil film forming property, while the outer diameter surface 1b side and the end surface 1c side which are close to the sealed state have the corrosion resistance and the oil retaining property. Can be improved.

Lubricating oil is impregnated into the pores do, db, and di of the sintered bearing 1. As a result, it is possible to obtain a better lubrication state than at the start of operation. As the lubricating oil, mineral oil, poly α-olefin (PAO), ester, liquid grease or 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 compression layer on the surface of the sintered bearing 1 by hatching. The hatching is attached 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 surface compression layer Po on the outer diameter surface 1b side and the density ratio αb of the surface compression layer Pb on the bearing surface 1a side are both higher than the internal density ratio αi, and both the density ratios αo and αb are Is set in the range of 80%≦αo and αb≦95%. If the density ratios αo and αb are less than 80%, the bearing strength will be insufficient, while if it exceeds 95%, the oil content will be insufficient, which is not preferable.

Then, 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 is the density of the porous body, ρ0 is the density To/D1 and Tb/D1 under the assumption that the porous body has no pores, and if the density is less than 1/100, collapse of the pores becomes insufficient, while If it exceeds 1/15, the pores are excessively collapsed, which is not preferable.

Next, the verification results up to the present embodiment will be described based on 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) compounded and sulfide corrosion resistance. It was confirmed that the corrosion resistance was improved as the amount of aluminum compounded increased. From these test results, it can be seen that the amount of aluminum blended must be 8.5% by weight or more with respect to the sulfidation corrosion resistance of the sintered bearing for a 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 aluminum content and the organic acid corrosiveness. It has been found that the corrosion resistance decreases as the aluminum content increases. However, the rate of weight change becomes mild from about 9.0% by mass of aluminum. The factor that the weight change rate increases as the amount of aluminum compounded increases is the elution of copper ions and aluminum ions.The reason that the elution of copper ions and aluminum ions increases is that the precipitation of the γ phase in the aluminum structure increases. It is possible that From these test results, it is understood that the amount of aluminum blended should be 10% by weight or less with respect to the organic acid corrosion resistance of the sintered bearing for a 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 compounding amount and the copper ion elution amount. It was confirmed that the amount of copper ions eluted decreased as the amount of aluminum compounded increased, and the amount of copper ions eluted decreased sharply from the amount of aluminum compounded around 8.5% by mass. It is conceivable that the factor that reduces the amount of copper ion elution is that diffusion proceeds sufficiently as the amount of aluminum compounded increases. From this test result, it can be seen that the amount of aluminum blended must 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 compounded and the initial running-in time. It was confirmed that the aluminum blending amount and the initial familiarization time have a proportional relationship. It is considered that this is because the hard γ phase increases in the aluminum structure as the aluminum content increases. From these test results, it can be seen that the amount of aluminum blended should be 10% by weight or less with respect to the initial familiarity of the sintered bearing for a fuel pump.
[Test conditions]
・PV value: 50 MPa・m/min
・Sample size: Inner diameter 5 mm × Outer diameter 10 mm × Width 7 mm
・Test time: 30 min

FIG. 8 shows the results of testing the relationship between the aluminum compounding amount and the friction coefficient. It was confirmed that the amount of aluminum compounded and the friction coefficient have a proportional relationship. It is considered that this is 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% by weight 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 5 mm × Outer diameter 10 mm × Width 7 mm
・Test time: 30 min

Table 1 shows the results of measuring the hardness of the sintered bearing for a fuel pump according to the first embodiment. The hardness values shown in Table 1 are values evaluated based on the Vickers hardness (Hv: Vickers hardness) at a test load of 25 g. Hereinafter, the hardness value will be described as a value based on 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 fuel pump sintered bearing in the first embodiment is 120 to 220, for example. The sintered bearing for a fuel pump according to the first embodiment can be determined to be a sintered bearing having higher wear resistance than the copper-based sintered bearing. This is because the hardness of the α phase, which is a soft phase, is 120 to 140, the hardness of the γ phase, which is a hard phase, is 200 to 220, and the hardness of any of the sintered bearings for a fuel pump in the first embodiment. The hardness of the phases is also higher than the hardness of the copper-based sintered bearing.

From the test results shown in FIGS. 4 to 8 and Table 1, it is possible to use as a sintered bearing for a fuel pump if the amount of aluminum compounded is 8.5 to 10% by weight, and 9.0 to 9.5% by weight. It was confirmed that the optimum aluminum compounding amount was obtained.

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 molding 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, raw material powder for the sintered bearing 1 is prepared and generated. The raw material powder is 40 to 60% by weight of aluminum-copper alloy powder 17 to 20% by weight, 7 to 10% by weight of phosphorus-copper alloy powder of 2 to 4% by weight, and electrolytic copper powder of the remaining weight% is 100% in total. %, aluminum fluoride and calcium fluoride as a sintering aid in a total amount of 0.05 to 0.2% by weight, graphite powder 3 to 5% by weight, and stearic acid to facilitate moldability. Lubricants such as zinc and calcium stearate were added in an amount of 0.1 to 1% by weight. By adding the lubricant, the powder compact described later can be smoothly released from the mold, and the shape collapse of the powder compact due to the mold release can be avoided. Specifically, the above-mentioned raw material powder M is put 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 uniformly mixed.

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 electrolytic copper powder is the remaining weight%. The aluminum content is, for example, 8.5% by weight or more and 10% by weight or less, specifically 9% by weight or more and 9.5% by weight or less with respect to the alloy portion (not including the graphite portion). ..

For example, the raw material powder is a total of 40 to 60% by weight of aluminum-copper alloy powder 17 to 20 parts by weight, 7 to 10% by weight of phosphorus-copper alloy powder of 2 to 4 parts by weight, and electrolytic copper powder as the remaining part by weight. With respect to 100 parts by weight, as a sintering aid, 0.05 to 0.2 parts by weight of aluminum fluoride and calcium fluoride in total, 3 to 10 parts by weight of graphite powder, for example 3 to 5 parts by weight, and molding It is possible to use a lubricant to which 0.1 to 1 part by weight of a lubricant such as zinc stearate or calcium stearate is added in order to improve the properties.

For example, 17 to 20 parts by weight of 40 to 60% by weight of aluminum-copper alloy powder, 2 to 4 parts by weight of 7 to 10% by weight of phosphorus-copper alloy powder, and 100 parts by weight of electrolytic copper powder as the remaining part ( 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 with respect to the alloy part (excluding the graphite part). ..

[Molding step S2]
In the molding step S2, the above-mentioned raw material powder is pressed to form a green compact 1′ (see FIG. 13) having the shape of the sintered bearing 1. 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. Therefore, the reference numeral 1'is given to the green compact and the reference numeral 1" is given to the sintered body.

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 servomotor as a drive source, and the raw material powder filled in the cavity is set to 200- The green compact 1'is molded by compressing with a pressure of 700 MPa. At the time of molding the green compact 1', the molding die may be heated to 70°C or higher.

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

[Sintering process S3]
In the sintering step S3, the green compact 1'is heated at a sintering temperature to sinter and bond the raw material powders adjacent to each other to form a sintered body 1". The mesh belt type continuous furnace 15 shown in FIG. A large amount of the green compact 1'is charged into the mesh belt 16 to form a sintered body 1". Thereby, stable quality and a manufacturing method can be realized.

What is important in the sintering process is to improve the corrosion resistance by sufficiently diffusing aluminum into copper and to improve the corrosion resistance and the bearing performance (initial familiarity) by making the aluminum bronze structure into α phase. 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.

Furthermore, the aluminum structure preferably has a ratio of γ phase to α phase of γ phase/α phase of 0.10≦γ phase/α phase≦0.25. If the ratio of γ phase/α phase is less than 0.10, wear resistance is undesirably lowered, while if it exceeds 0.25, initial running-in property and organic acid corrosion resistance are unfavorably lowered.

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). Further, the atmosphere gas is hydrogen gas, nitrogen gas or a mixed gas thereof, and the longer the sintering time is, the better the corrosion resistance is. The sintered bearing for a fuel pump has 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 a liquid phase is generated, the liquid phase expands, a sintering neck is formed by the generated liquid phase, densification occurs, and the dimensions shrink. 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 sintering is hindered so that densification does not occur and the dimension remains expanded. 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 was used, It is possible to reduce the cost by shortening the sintering time from the input of 1'to the removal, mass production, and to secure the sufficient strength in terms of the function of the sintered bearing.

In the above-mentioned sintering step, the added phosphorus alloy powder exerts its effect, so that a good quality sintered body can be formed. Phosphorus enhances the wettability between the solid and liquid phases during sintering, and a good sintered body can be obtained. The content of phosphorus is preferably 0.1 to 0.6% by weight, specifically 0.1 to 0.4% by weight. If it is less than 0.1% by weight, the effect of promoting sintering between the solid and liquid phases is poor, while if it exceeds 0.6% by weight, preferably 0.4% by weight, the obtained sintered body is segregated and becomes brittle. ..

Further, graphite is present as free graphite mainly in the pores dispersedly distributed in the matrix, imparts excellent lubricity to the sintered bearing, and contributes to improvement in wear resistance. The blending amount of graphite is preferably 3 to 10% by weight, and may be, for example, 3 to 5% by weight, based on 100% by weight of the total of the raw material powder containing aluminum, phosphorus, the balance of the main component being copper, and 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, if it exceeds 5% by weight, it is feared that diffusion of aluminum into copper starts to be hindered. If the amount of graphite added exceeds 10% by weight, the material strength is lowered and the diffusion of aluminum into copper is hindered, which is not preferable. Generally, when graphite is added in an amount of 4% by weight or more, it cannot be molded, but the use of granulated graphite enables molding. In this embodiment, as the graphite powder, a fine powder of natural graphite or artificial graphite is granulated with a resin binder and then pulverized to use graphite powder having a particle size of 145 mesh or less.

[Sizing step S4]
In the sizing step S4, the sintered body 1″ that has been expanded in comparison with the green compact 1′ by sintering is dimensioned. FIG. 12 shows the details of the sizing step S4. The sizing die is a die 20, The upper punch 21, the lower punch 22, and the core 23. As shown in Fig. 12(a), the 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. 12( b ), the core 23 first enters the inside diameter of the sintered body 1 ″, and then the upper punch 21 moves the sintered body 1 ″ into the die 20 as shown in FIG. 12( c ). It is pushed in and compressed by the upper and lower punches 21, 22. As a result, the surface of the sintered body 1″ is dimensioned. By the sizing process, the expanded pores of the surface layer of the sintered body 1″ are crushed, and a density difference occurs between the inside of the product and the surface layer portion.

13 shows a state in which the sintered body 1″ is compressed by the sizing process. The sintered body 1″ before the sizing process is shown by a two-dot chain line, and the product 1 after the sizing process is shown by a solid line. As indicated by the chain double-dashed line, the sintered body 1″ has expanded in the radial direction and the width direction. Therefore, in the sintered body 1″, the outer diameter surface 1b is compressed more than the bearing surface 1a on the inner diameter side. It As a result, the surface pores do [see FIG. 3(c)] on the outer diameter surface 1b side are crushed more than the surface layer pores db [see FIG. 3(a)] on the inner diameter side bearing surface 1b, and are not crushed. The relationship of do<db<di is satisfied with respect to the pores di inside the bearing (see FIG. 3B). Because of such a relationship, the bearing surface 1a on the inner diameter side can improve the corrosion resistance and the oil film forming property. On the other hand, in the outer diameter surface 1b and the end surface 1c which are close to the sealed state, the corrosion resistance and the oil retaining property can be improved.

The die for the sizing step is composed of a die 20, a pair of punches 21 and 22, and a core 23. The punches 21 and 22 and the die 20 compress the sintered body 1″ from both axial sides and the outer diameter side, and burn it. By shaping the inner diameter side of the united body 1″ by the core 23, the expansion due to the sintering of the aluminum bronze-based sintered bearing can be effectively utilized, and the desired pores can be formed together with the dimension shaping of the sintered bearing 1.

Further, by adjusting the dimensional difference between the inner diameter of the die 20 and the outer diameter of the sintered body 1″ and the dimensional difference between the outer diameter of the core 23 and the inner diameter of the sintered body 1″, the firing is performed. It is possible to set the size of the pores on the surface of the bonded body 1″. This makes it possible to easily control the size of the pores on the surface of the sintered bearing 1. Further, although not shown, the bearing By rotationally sizing the surface 1a (see FIG. 13), the pores on the bearing surface 1a can be reduced.

[Oil impregnation step S5]
The oil impregnation step S5 is a step of impregnating the product 1 (sintered bearing) with lubricating oil. FIG. 14 shows an oil impregnating device. The product 1 is put into the tank 26 of the oil impregnation device 25, and then the lubricating oil 27 is poured into the tank 26. Then, by depressurizing the inside of the tank 26, the lubricating oil 27 is impregnated into the pores do, db, di (see FIG. 3) of the product 1. As a result, it is possible to obtain a better lubrication state than at the start of operation. As the lubricating oil, mineral oil, poly α-olefin (PAO), ester, liquid grease or the like can be used. However, it may be carried out according to the intended use of the bearing, and it is not always necessary.

The sintered bearing 1 of the present embodiment manufactured by the above-described steps improves mechanical characteristics such as corrosion resistance, strength, and wear resistance, oil film forming property, and oil retaining property, and at the same time, is compact and cost-effective. Can be planned. As a sintered bearing for a fuel pump, it suppresses sulfide corrosion due to poor gasoline, corrosion against organic acids and biofuels, and has excellent performance such as initial running-in and durability.

Next, a second embodiment of a sintered bearing for a fuel pump and a second embodiment of a manufacturing method according to the present invention will be described. In the sintered bearing for a fuel pump and the manufacturing method according to the first embodiment, the aluminum-copper alloy powder and the electrolytic copper powder are used as the raw material powders serving as the aluminum source and the copper source, but in the second embodiment, copper is used. It differs from the first embodiment in that an aluminum-copper alloy powder is used without adding a single electrolytic copper powder.

It has been found that when a powder of a simple substance of copper is added to a more severe use environment, a portion of the simple substance of copper is biased to cause a problem in corrosion resistance. As a result of various investigations based on this finding, the present embodiment has been achieved based on the idea that an aluminum-copper alloy powder is used as a raw material powder serving as an aluminum source and a copper source and a powder of copper alone is not added.

In the sintered bearing for a fuel pump and the manufacturing method of the present embodiment, the composition in which the aluminum content is 8.5 to 10% by weight, the phosphorus is 0.1 to 0.4% by weight, and the remaining main component is copper is The same as in the first embodiment. However, the raw material powder is different as follows. That is, the aluminum-copper alloy powder and the phosphorus alloy powder were mixed in such a ratio that the above composition was obtained without adding the electrolytic copper powder of simple copper, and the total amount of graphite was 100% by weight. Graphite powder was mixed so as to be 3 to 5% by weight to obtain a raw material powder. Further, as a sintering aid, aluminum fluoride and calcium fluoride are added in a total amount of 0.05 to 0.2% by weight, and further, 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, the phosphorus is 0.1 to 0.4 parts by weight, and the compounding amount of graphite is 3 to 10 parts by weight if necessary. Parts, for example, 3 to 5 parts by weight, and the composition whose main component is copper can be used. In this case, for example, the raw material powder is as follows. That is, the aluminum-copper alloy powder and the phosphorus alloy powder were mixed in a ratio such that the above composition was obtained without adding electrolytic copper powder of simple substance of copper, and the blending amount of graphite was 100 parts by weight in total. 3 to 10 parts by weight, for example, 3 to 5 parts by weight of graphite powder was mixed to obtain a raw material powder. The blending amount of graphite is preferably 3 to 10 parts by weight, and may be, for example, 3 to 5 parts by weight, based on 100 parts by weight of the total of the raw material powder containing aluminum, phosphorus, the balance of copper as the main component, and unavoidable impurities. If it is less than 3 parts 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, if it exceeds 5 parts by weight, for example, there is a concern that diffusion of aluminum into copper may start to be hindered. When the amount of graphite added exceeds 10 parts by weight, the material strength is lowered and the diffusion of aluminum into copper is unfavorable. Generally, when graphite is added in an amount of 4 parts by weight or more, it cannot be molded, but the use of granulated graphite enables molding. In this embodiment, as the graphite powder, a fine powder of natural graphite or artificial graphite is granulated with a resin binder and then pulverized to use graphite powder having a particle size of 145 mesh or less. Also, as a sintering aid, 0.05 to 0.2 parts by weight of aluminum fluoride and calcium fluoride in total, and 0.1 to 1 parts by weight of zinc stearate to facilitate moldability are added. did.

The aluminum bronze structure of the present embodiment, which uses aluminum-copper alloy powder as a copper source and does not add powder of copper alone, has a ratio of γ phase to α phase of γ phase/α phase, 0<γ phase/α phase. It is preferable that ≦0.10. Within the range of 0<γ phase/α phase≦0.10, the organic acid corrosion resistance and the initial running-in property are excellent.

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

Further, the state of the compression layer on the surface layer of the sintered bearing 1 of the present embodiment is also the same as that of the sintered bearing of the first embodiment shown in FIG. 2, so the content described above with reference to FIG. Is omitted.

Next, the verification result up to the present embodiment will be described with reference to FIGS. 15 and 16. The broken line X2 in FIG. 15 indicates the allowable level of the test item. Although illustration is omitted, regarding the relationship between the aluminum compounding 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. Regarding the relationship between the initial running-in time and the coefficient of friction, the test results of the sintered bearing in the first embodiment and the test results of the sintered bearing in the second embodiment are substantially the same. Therefore, detailed description thereof is omitted here.

FIG. 15 shows the results of testing the relationship between the amount of aluminum compounded and the organic acid corrosiveness. The test conditions are the same as in FIG. In FIG. 15, the ♦ mark is the test result of the sintered bearing of the first embodiment shown in FIG. 5, but the sintered bearing of the present embodiment shown by the ◇ mark has an aluminum compounding amount of 8.5% by weight. In, it was confirmed that the organic acid corrosion resistance is further improved as compared with the first embodiment. As the raw material powder to be the aluminum source and the copper source, without using the powder of copper simple substance, since the aluminum-copper alloy powder was used, the portion where the copper simple substance is biased is almost eliminated, and the occurrence of corrosion due to that portion is avoided. It is considered that the corrosion resistance is improved. In combination with this, it is considered that by using the aluminum-copper alloy powder, the corrosion resistance of each grain of the aluminum-copper alloy powder is improved, and the corrosion resistance of the entire sintered bearing is improved. ..

FIG. 16 shows the results of testing the relationship between the aluminum compounding amount and the copper ion elution amount output. The test conditions are the same as in FIG. 16 also shows the test results of the sintered bearing of the first embodiment shown in FIG. 6, the sintered bearing of the present embodiment shown by the symbol ◇ has an aluminum compounding amount of 8.5 weight. %, it was confirmed that the elution amount of copper ions was smaller than that in the first embodiment.

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

As shown in Table 2, the hardness of the copper-based sintered bearing is 70 to 80, whereas the hardness of the fuel pump sintered bearing in the second embodiment is, for example, 100 to 240. It can be determined that the sintered bearing for a 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, which is a soft phase, is 100 to 140, the hardness of the γ phase, which is a hard phase, is 200 to 240, and the hardness of any of the sintered bearings for a fuel pump according to the second embodiment. The hardness of the phases is also higher than the hardness of the copper-based sintered bearing.

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

Next, a second embodiment of the manufacturing method will be described. Since the manufacturing method of the second embodiment is also similar to the manufacturing method of the sintered bearing of the first embodiment shown in FIG. 9, the above-described contents are applied correspondingly, and the raw material powder preparing step S1 and the molding step S2 are performed. Only the differences will be described.

[Raw material powder preparation step S1]
In the raw material powder preparation step S1, raw material powder for 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 90 to 97 wt%, and 7 to 10 wt% phosphorus-copper alloy powder 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, to facilitate 100% by weight. As a lubricant for this purpose, zinc stearate was added in an amount of 0.1 to 1% by weight. The 7-11 wt% aluminum-copper alloy powder was used after being crushed and adjusted in particle size. Similar to the first embodiment, the above-mentioned raw material powder is put into, for example, the can body 11 of the V-type mixer 10 shown in FIG. 10, and the can body 11 is rotated to be uniformly mixed.

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

For example, the raw material powder is 7 to 11 wt% aluminum-copper alloy powder, preferably 8 to 10 wt% aluminum-copper alloy powder 90 to 97 parts by weight, and 7 to 10 wt% phosphorus-copper alloy powder 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 a sintering aid with respect to a total of 100 parts by weight. It is possible to use those containing 0.1 to 1 part by weight of zinc stearate as a lubricant for facilitating moldability.

For example, 90 to 97 parts by weight of 7 to 11% by weight aluminum-copper alloy powder and 1 to 6 parts by weight of 7 to 10% by weight phosphorus-copper alloy powder, for a total of 100 parts by weight (graphite part is not included). The content of aluminum with respect to the alloy portion 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, the above-mentioned raw material powder is pressed to form a green compact 1′ (see FIG. 13) having the shape of the sintered bearing 1. In the present embodiment, as the raw material powder to be the aluminum source and the copper source, since the aluminum-copper alloy powder is used without adding the powder of the copper simple substance, the portion where the copper simple substance is biased almost disappears, and the corrosion by the portion is caused. The occurrence of is avoided. This improves the corrosion resistance. Further, by using the aluminum-copper alloy powder, the corrosion resistance of each grain of the aluminum-copper alloy powder is improved, and the corrosion resistance of the entire sintered bearing for a fuel pump 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 operating environment. Further, similar to the sintered bearing of the first embodiment, mechanical characteristics such as strength and wear resistance, oil film forming property, and oil retaining property can be improved, and at the same time, compactness and cost reduction can be achieved.

In the above description of each embodiment, the case where the present invention is applied to a perfect circular bearing in which the bearing surface 1a has a perfect circular shape has been illustrated, but the present invention is not limited to the perfect circular bearing, and the bearing surface 1a and the shaft 52 are not limited thereto. The present invention can be similarly applied to a fluid dynamic pressure bearing having a dynamic pressure generating portion such as a herringbone groove or a spiral groove on the outer peripheral surface thereof.

The sintered bearing of the present embodiment is, for example, a fuel pump sintered bearing that does not contain oils such as lubricating oil, or a fuel pump sintered bearing that contains a small amount of lubricating oil, depending on the type of fuel pump. It is possible to use various types of sintered bearings for fuel pumps, such as sintered bearings for fuel pumps containing sufficient lubricating oil.

The present invention is not limited to the embodiments described above, and it is needless to say that the present invention can be implemented in various forms without departing from the gist of the present invention. It is indicated by the scope of the claims and further includes equivalent meanings to the claims and all modifications within the scope.

1 Sintered Bearing for Fuel Pump 1'Green Powder 1" Sintered Body 1a Bearing Surface 1b Outer Diameter Surface 1c End Face 2 Sintered Bearing for Fuel Pump 3 Aluminum Copper Alloy Structure 4 Aluminum Oxide Film 5 Free Graphite 15 Continuous Mesh Belt Type Furnace 20 Die 21 Upper punch 22 Lower punch 23 Core 40 Fuel pump 52 Shaft D1 Inner diameter of bearing surface db Pore di Pore do Po Pore Ti Compression layer To Compression layer To

Claims (7)

For motor type fuel pump containing graphite, alloy part containing 8.5-10% by weight aluminum and 0.1-0.6% by weight phosphorus, balance copper as the main component and unavoidable impurities A sintered bearing,
This sintered bearing has an aluminum-copper alloy structure in which an aluminum-copper alloy is sintered, and the pores of the surface layer of the sintered bearing are made smaller than the internal pores, so that the sintered bearing has a bias of copper alone. no portion, and the aluminum - fuel pump sintered bearing and having a copper alloy structure α-phase and γ-phase. The graphite is added in an amount of 3 to 10% by weight with respect to a total of 100% by weight of the raw material powder containing aluminum, phosphorus, the remaining main component being copper, and inevitable impurities. Sintered bearings for fuel pumps. The sintered bearing for a fuel pump according to claim 1 or 2, 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 3, wherein an aluminum content is 9 to 9.5% by weight. Sintering for fuel pump containing graphite, alloy part containing 8.5-10% by weight aluminum and 0.1-0.6% by weight phosphorus, balance copper as the main component and inevitable impurities A method of manufacturing a bearing, comprising:
The above-mentioned manufacturing method uses aluminum-copper alloy powder and phosphorus-copper alloy powder as the raw material powder without using copper simple powder ,
At least, a shaping step of shaping the green compact graphite powder and sintering aid in the raw material powder is added,
From the green compact, aluminum - a sintering step to obtain a sintered body α phase in the copper alloy structure and γ phase is included, - have a copper alloy structure, the aluminum
A method of manufacturing a sintered bearing for a fuel pump, comprising a sizing step of dimensioning the sintered body. 6. The fuel according to claim 5 , wherein 3 to 10% by weight of graphite powder is added to 100% by weight of the total of the aluminum-copper alloy powder , the phosphorus -copper alloy powder , and the unavoidable impurities. Manufacturing method of sintered bearing for pump. As the sintering aid, 0.05 to 0.2% by weight of aluminum fluoride and calcium fluoride in total is added to 100% by weight of the total of the aluminum-copper alloy powder and the phosphorus-copper alloy powder. The method for manufacturing a sintered bearing for a fuel pump according to claim 5 or 6 , characterized in that.

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