TW202045740A - Sintered bearing and method for manufacturing sintered bearing - Google Patents

Abstract

In the sintered bearing, mechanical strength and vibration resistance are improved, and damage to the rotating shaft is prevented.

The sintered bearing 20 according to the present invention is formed of a sintered body based on nickel white (Cu-Ni-Zn). Herein, in the sintered bearing 20, P is not added to the sintered body. Alternatively, the content of P in the sintered body is less than 0.05% by mass in the mass ratio to the total mass. By this, the crystal grain which comprises a sintered compact can be refined. In particular, in the sintered bearing 20, the average grain size of the crystal grains constituting the sintered body is 20 μm or less. This makes it possible to improve mechanical strength and vibration resistance, and to prevent damage to the rotating shaft.

Description

Sintered bearing and manufacturing method of sintered bearing

The present invention relates to a sintered bearing and a method of manufacturing a sintered bearing, and particularly relates to a sintered bearing suitable for use in a motor of a liquid pump, and a method of manufacturing the sintered bearing.

Conventionally, various pumps have been known for pumps for liquid transportation (hereinafter referred to as "liquid pumps").

For example, liquid pumps installed in automobiles are known to be useful for circulating cooling water for engine cooling, washing liquid pumps for discharging windshield washer liquid, oil pumps for generating oil pressure in hydraulic mechanisms, and Fuel pumps for pumping engine oil, fuel pumps for supplying fuel (gasoline, light oil, alcohol, etc.), etc.

In recent years, in liquid pumps, from the viewpoint of stabilization of the discharge volume (pumping volume), electrification that obtains power from an electric motor is being developed.

For example, the conventional water pump obtains power from the engine, so changes in the number of revolutions of the engine will affect the amount of cooling water discharged, and there is a problem that the cooling efficiency becomes unstable. Therefore, in recent years, the water pump obtains power from an electric motor to stabilize the discharge volume, and even the cooling efficiency. In particular, the water pumps on hybrid vehicles, electric vehicles, and fuel cell vehicles cannot The engine gains power, or the stable power cannot be obtained from the engine. Therefore, in order to obtain a stable discharge volume, electric motors are being developed to obtain power from an electric motor.

In particular, in recent years, in order to achieve the miniaturization and higher output of liquid pumps, the miniaturization and higher output of electric motors are being developed. With this situation, the load on the bearings of the electric motors will increase. Therefore, the bearings (hereinafter referred to as "bearings for liquid pumps") provided in the electric motors arranged in the liquid pumps are required to be improved in load resistance. Furthermore, the bearings for liquid pumps will be used in liquids, so it is required to improve the load resistance as well as the water resistance/corrosion resistance.

In the past, bearings made of ceramic, carbon, or resin have been known for bearings with excellent water resistance and corrosion resistance. However, although bearings made of ceramic or carbon are excellent in water resistance and corrosion resistance, they have the problem of high processing costs. In addition, the bearing system made of resin has a problem that it is difficult to ensure dimensional accuracy and insufficient load resistance.

On the other hand, for bearings having excellent load resistance, sintered bearings made by sintering metal powder are known. However, sintered bearings have low water resistance/corrosion resistance and are not suitable for use in liquids. In particular, when sintered bearings are used in water, there is a problem of insufficient sliding properties.

Therefore, in recent years, in terms of bearings for liquid pumps, an embryo made of nickel silver (Cu-Ni-Zn alloy), a material with excellent water resistance/corrosion resistance, added with P (phosphorus) and solid lubricants has been developed. A sintered bearing composed of a body (base material) (see Patent Document 1).

The sintered bearing system described in Patent Document 1 uses nickel silver as the base of the green body to improve water resistance and corrosion resistance, and also improves the sliding properties by adding graphite (solid lubricant) to the green body.

In particular, the sintered bearing system described in Patent Document 1 promotes the diffusion of other added constituent elements (Ni, Zn, etc.) during sintering by adding P to the green body, thereby suppressing water resistance/corrosion resistance in the sintered bearing The part with low sex.

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] JP 2015-187307 A

However, the conventional sintered bearings may have reduced mechanical strength and vibration resistance.

That is, in the conventional sintered bearing system, since P is added to the green body, the crystal grains constituting the green body tend to become coarse during sintering. Then, if the crystal grains constituting the embryonic body become coarse, the mechanical strength and vibration resistance may decrease.

In addition, the conventional sintered bearing may damage the rotating shaft.

That is, in the conventional sintered bearing system, since P is added to the green body, the Ni-Sn-P alloy layer is easily precipitated in the green body. Here, the Ni-Sn-P alloy layer has a very high hardness compared with other parts of the body. Therefore, in the embryo body, if the Ni-Sn-P alloy is chromatographed, when the shaft rotates, since the rotating shaft contacts the Ni-Sn-P alloy layer, the rotating shaft may be damaged.

The subject of the present invention is to improve the mechanical strength and vibration resistance of a sintered bearing and prevent damage to the rotating shaft.

In order to solve the above-mentioned problems, the sintered bearing system of the first invention is composed of a sintered body with an average crystal grain size of 20 μm or less. The sintered system has a mass ratio of more than 10 mass% to less than 20 μm. Mass% Ni, more than 13 mass% and less than 20 Mass% of Zn, more than 0.5% by mass and less than 3% by mass of Sn, and more than 0.5% by mass and less than 4% by mass of solid lubricant, and the remainder is composed of Cu and unavoidable impurities.

In addition, the sintered bearing of the second invention is composed of a sintered body having an average crystal grain size of 20 μm or less, and the sintered system has a mass ratio of more than 10 mass% to less than 20 mass%. Ni, Zn exceeding 13% by mass and less than 20% by mass, Sn exceeding 0.5% by mass and less than 3% by mass, solid lubricant exceeding 0.5% by mass and less than 4% by mass, and less than 0.05% by mass P, and the rest is composed of Cu and unavoidable impurities.

In the sintered bearing of the first or second invention, the sintered system is formed based on nickel silver (Cu-Ni-Zn). This can improve water resistance and corrosion resistance.

Furthermore, in the sintered bearing of the first or second invention, the sintered body contains a solid lubricant. This can improve sliding properties.

Furthermore, in the sintered bearing of the first or second invention, Sn is contained in the sintered body (powder compact). Thereby, the sinterability is improved, and the sintering strength can be improved. As a result, it is possible to compensate for the reduced sintering strength due to the solid lubricant. In addition, by containing Sn in the sintered body, the resistance to dezincification corrosion in water can be improved.

In particular, in the sintered bearing of the first invention, P is not contained in the sintered body. Furthermore, in the sintered bearing of the second invention, the content of P in the sintered body is less than 0.05% by mass in terms of mass ratio to the total mass.

Thereby, the crystal grains constituting the sintered body can be made finer, and as a result, the mechanical strength and vibration resistance can be improved. In addition, in the sintered body, precipitation of the Ni-Sn-P alloy layer can be suppressed, and damage to the rotating shaft during shaft rotation can be prevented.

Furthermore, in the sintered bearing of the first or second invention, the average crystal grain size of the crystal grains constituting the sintered body of the crystal structure is 20 μm or less.

Here, if the average crystal grain size of the crystal grains constituting the sintered body exceeds 20 μm, the mechanical strength and resistance required for the sintered bearing of the motor installed in the liquid pump (especially, the liquid pump installed in the automobile) cannot be satisfied. The fear of vibration.

Therefore, by setting the average crystal grain size of the crystal grains constituting the sintered body to 20 μm or less, it is possible to satisfy the mechanical strength and mechanical strength required for the sintered bearing of the motor installed in the liquid pump (especially, the liquid pump installed in the automobile). Vibration resistance.

According to the above, the sintered bearing according to the first or second invention can improve the mechanical strength and vibration resistance and prevent damage to the rotating shaft.

Here, the sintered bearing of the first or second invention is preferably a sintered body formed by using Cu-Ni-Zn-Sn alloy powder. Specifically, it is preferable that the sintered body is formed using a raw material powder obtained by mixing raw material powder containing Cu-Ni-Zn-Sn alloy powder and solid lubricant powder.

That is, in the Cu-Ni-Zn-Sn alloy powder, the constituent elements (constitutive elements) such as Ni and Zn are uniformly dispersed in the particles constituting the powder. Therefore, by using Cu-Ni-Zn-Sn alloy powder to form a sintered body, the concentration of each component such as Ni and Zn in the sintered body can be prevented from becoming uneven. As a result, Ni and Zn in the sintered body can be prevented The low-concentration part is selectively etched.

Hereinafter, the function/effect of each element constituting the sintered body (green body) will be explained in detail.

Furthermore, in the present invention, the content of each element is defined according to the mass ratio (mass %) of the entire sintered body.

〔About Ni (Nickel)〕

By containing Ni in the sintered body, water resistance and corrosion resistance can be improved.

At this time, if the Ni content in the sintered body is 10% by mass or less, the water resistance/corrosion resistance becomes insufficient. On the other hand, if the Ni content in the sintered body becomes 20% by mass or more, the material cost will increase.

Therefore, by making the content of Ni in the sintered body more than 10% by mass and less than 20% by mass, the increase in material cost can be suppressed and the water resistance/corrosion resistance can be improved.

〔About Zn (Zn)〕

By containing Zn in the sintered body, water resistance and corrosion resistance can be improved.

At this time, if the content of Zn in the sintered body is 13% by mass or less, the water resistance/corrosion resistance becomes insufficient. On the other hand, if the content of Zn in the sintered body is 20% by mass or more, the productivity will decrease and the risk of dezincification corrosion will increase due to the evaporation of zinc during sintering.

Therefore, by making the content of Zn in the sintered body more than 13% by mass and less than 20% by mass, the decrease in productivity can be suppressed and the water resistance/corrosion resistance can be improved.

In particular, Zn is an inexpensive material compared to Ni. Therefore, when the water resistance/corrosion resistance is to be improved, the increase in the material cost can be suppressed by increasing the content of Zn while suppressing the increase in the Ni content.

〔About Sn (tin)〕

By containing Sn in the sintered body (powder compact), the sinterability can be improved and the sintering strength can be improved. Moreover, even if it is contained in a small amount, dezincification corrosion can be suppressed.

At this time, if the Sn content in the sintered body is 0.5% by mass or less, the above-mentioned effect becomes insufficient. On the other hand, if the content of Sn in the sintered body is 3% by mass or more, deformation due to dimensional changes during sintering is likely to occur.

Therefore, by setting the Sn content in the sintered body to exceed 0.5% by mass and less than 3% by mass, the occurrence of deformation can be suppressed and the sintered strength can be improved.

〔About solid lubricants〕

By containing a solid lubricant in the sintered body, the lubricity will be improved, the friction coefficient can be reduced, and the burning property and abrasion resistance can be improved.

At this time, if the content of the solid lubricant in the sintered body is 0.5% by mass or less, the above-mentioned effect becomes insufficient. On the other hand, if the content of the solid lubricant in the sintered body becomes 4% by mass or more, the sintered strength is significantly reduced.

Therefore, by making the content of the solid lubricant in the sintered body exceed 0.5% by mass and less than 4% by mass, it is possible to suppress the decrease in sintered strength and improve the wear resistance.

〔About P (phosphorus)〕

By containing P in the sintered body, oxidation of the metal constituting the sintered body can be prevented.

That is, as described later, when the raw material powder forming a sintered body is produced, the raw material powder is preferably an alloy powder such as Cu-Ni-Zn-Sn alloy powder.

Here, alloy powders such as Cu-Ni-Zn-Sn alloy powder are produced by an atomization method or the like. Specifically, the molten metal is produced by melting various raw metals constituting the target alloy powder at a high temperature, and the produced molten metal is sprayed/quickly solidified and powdered to produce the alloy powder.

At this time, in the raw metal, a small amount of P can be added as an oxygen scavenger to prevent the oxidation of the molten metal.

Here, if the P content in the raw material metal is 0.05% by mass or more, the crystal grains constituting the sintered body are likely to be coarsened during sintering, and the Ni-Sn-P alloy layer is likely to precipitate in the sintered body.

Therefore, by setting the P content in the raw metal (sintered body) to less than 0.05% by mass, it is possible to suppress the coarsening of the crystal grains constituting the sintered body and the precipitation of the Ni-Sn-P alloy layer in the sintered body. And to prevent the oxidation of molten metal.

[About the average crystal grain size]

If the average crystal grain size of the crystal grains of the sintered body constituting the crystal structure (fine structure) exceeds 20 μm, it may not meet the requirements for the sintered bearing of the motor installed in the liquid pump (especially, the liquid pump installed in the automobile) Concerns about mechanical strength and vibration resistance.

Therefore, by setting the average crystal grain size of the crystal grains constituting the sintered body of the crystal structure to 20 μm or less, it is possible to satisfy the requirements for the sintered bearing of the motor arranged in the liquid pump (especially, the liquid pump mounted on the automobile) Mechanical strength and vibration resistance.

〔About effective porosity〕

Here, in the sintered bearing of the first or second invention, the effective porosity in the sintered body is preferably 8 vol% or more and 18 vol% or less.

That is, if the effective porosity is less than 8% by volume, the density becomes very high, and the pressure required for powder compaction becomes large, and the productivity decreases. On the other hand, if the effective porosity exceeds 18% by volume, the strength of the compact is reduced, and the handling until sintering becomes difficult. In addition, since the sintered strength is reduced, the minimum strength required as a bearing cannot be obtained.

Therefore, by setting the effective porosity to 8% by volume or more and 18% by volume or less, it is possible to suppress a decrease in productivity and improve sintering strength.

In the sintered bearing of the third invention, in the sintered bearing of the first or second invention, the solid lubricant contains at least one of graphite, molybdenum disulfide, and boron nitride.

According to the sintered bearing of the second invention, the lubricity can be improved.

The sintered bearing of the fourth invention is the sintered bearing of any one of the first to third inventions, wherein the sintered body is impregnated with lubricating oil.

According to the sintered bearing of the fourth invention, during the period from the manufacture of the bearing to the assembly of the motor, and even the period until the motor is used, rust of the bearing can be prevented by the impregnated lubricant. In addition, when the bearing is sealed and isolated from the flow path of the conveying liquid, an oil film can be formed between the rotating shaft in accordance with the rotation of the rotating shaft, and the frictional resistance generated between the rotating shaft can be reduced. Furthermore, even when the bearing is not sealed and used in the conveying liquid, as a result, the lubricant impregnated in the bearing body will be replaced by the conveying liquid. However, it is possible to use a higher viscosity lubricant than the conveying liquid. To help lubrication at the beginning of operation.

The sintered bearing of the fifth invention is used in the motor of a liquid pump in the sintered bearing of any one of the first to fourth inventions.

According to the sintered bearing of the fifth invention, the durability of the liquid pump can be improved.

The manufacturing method of the sintered bearing of the sixth invention includes the steps of mixing a plurality of powders to produce raw powders; compressing and forming the raw powders to form a compact; sintering the compact to form a sintered body; and A step of sizing the aforementioned sintered body; wherein the aforementioned plural kinds of powders include Cu-Ni-Zn-Sn alloy powder and a solid lubricant; the aforementioned raw material powders have a mass ratio relative to the total mass , Containing more than 10% by mass And less than 20% by mass of Ni, more than 13% by mass and less than 20% by mass of Zn, more than 0.5% by mass and less than 3% by mass of Sn, and more than 0.5% by mass and less than 4% by mass of solid lubricants , And the rest is composed of Cu and inevitable impurities; the average crystal grain size of the aforementioned sintered body is 20μm or less.

In addition, the manufacturing method of the sintered bearing of the seventh invention includes the steps of mixing a plurality of powders to produce raw powders; compressing and forming the raw powders to form a compact; and sintering the compacts to form a sintered body And the step of applying dimension correction to the sintered body; wherein the plurality of powders include Cu-Ni-Zn-Sn alloy powder, solid lubricant and P powder; the raw material powder has a mass relative to the total mass In terms of ratio, Ni containing more than 10% by mass and less than 20% by mass, Zn more than 13% by mass and less than 20% by mass, Sn more than 0.5% by mass and less than 3% by mass, and more than 0.5% by mass and less than 4% by mass solid lubricant, less than 0.05% by mass P, and the rest is composed of Cu and inevitable impurities; the average crystal grain size of the aforementioned sintered body is 20μm or less.

In the manufacturing method of the sintered bearing of the sixth or seventh invention, the sintered bearing is formed by using nickel silver (Cu-Ni-Zn) as a base raw material powder. Thereby, the water resistance/corrosion resistance of the sintered bearing can be improved.

Furthermore, in the method of manufacturing a sintered bearing of the sixth or seventh invention, a solid lubricant is added to the raw material powder. Thereby, the sliding properties of the sintered bearing can be improved.

Furthermore, in the method of manufacturing a sintered bearing of the sixth or seventh invention, Sn is added to the raw material powder. As a result, the sinterability during sintering is improved, and the sintering strength of the sintered bearing can be improved. As a result, the sintering strength reduced by the addition of the solid lubricant can be compensated. In addition, by adding Sn to the raw material powder, the resistance to dezincification corrosion in water can be improved.

In particular, in the method of manufacturing a sintered bearing of the sixth invention, P is not added to the raw material powder. Furthermore, in the manufacturing method of the sintered bearing of the seventh invention, the addition amount of P in the raw material powder is less than 0.05% by mass in terms of the mass ratio to the total mass.

Thereby, the crystal grains constituting the sintered body can be made finer, and as a result, the mechanical strength and vibration resistance can be improved. In addition, in the sintered body, the precipitation of the Ni-Sn-P alloy layer can be suppressed, and damage to the rotating shaft can be prevented when the shaft rotates.

Furthermore, in the method of manufacturing a sintered bearing of the sixth or seventh invention, the average crystal grain size of the crystal grains constituting the sintered body of the crystal structure is 20 μm or less.

Thereby, the mechanical strength and vibration resistance required for the sintered bearing of the motor arranged in the liquid pump (especially, the liquid pump mounted on the automobile) can be satisfied.

Furthermore, in the method of manufacturing a sintered bearing of the sixth or seventh invention, the Cu-Ni-Zn-Sn alloy powder is contained in the plurality of powders.

Here, in the Cu-Ni-Zn-Sn alloy powder, the constituent elements (constituent elements) such as Ni and Zn are uniformly dispersed in the particles constituting the powder.

Thereby, by using Cu-Ni-Zn-Sn alloy powder to form a sintered body, in the sintered body, the concentration of each component such as Ni and Zn can be prevented from becoming non-uniform. As a result, the sintered body can be prevented The part where the concentration of Ni and Zn is low is selectively etched.

According to the above, if the sintered bearing manufacturing method according to the sixth or seventh invention is used, the mechanical strength and vibration resistance can be improved, and damage to the rotating shaft can be prevented.

Here, the function/effect of each element constituting the raw material powder is the same as the function/effect of each element constituting the sintered body of the first or second invention.

With the sintered bearing or the method of manufacturing the sintered bearing of the present invention, the mechanical strength and vibration resistance can be improved, and damage to the rotating shaft can be prevented.

1‧‧‧Water pump

10‧‧‧Shell

11‧‧‧Suction port

12‧‧‧Exit

20‧‧‧Sintered Bearing

21‧‧‧Bearing hole

21a‧‧‧Bearing surface

30‧‧‧Motor

31‧‧‧Fixer

32‧‧‧Rotator

32a‧‧‧Rotation axis

40‧‧‧Impeller

A‧‧‧Ni-Sn-P alloy layer

Fig. 1 is a cross-sectional view showing a schematic configuration of the water pump 1.

Figure 2 is a cross-sectional view of the sintered bearing 20.

Figure 3 is a diagram showing the blending content of the raw material powder of the sintered bearings of Comparative Examples 1 to 4 and the blending content of the raw material powder of the sintered bearings of Comparative Examples 1 to 4.

Figure 4 is a diagram comparing the composition of the raw material powder (sintered body) of the sintered bearings of Examples 1 to 4 and the composition of the raw material powder (sintered body) of the sintered bearings of Comparative Examples 1 to 4.

Figure 5 is a diagram showing an example of the metal structure of the sintered bearing of the embodiment.

Figure 6 is a diagram showing an example of the metal structure of the sintered bearing of the comparative example.

Figure 7 is a diagram showing the metal structure of the sintered bearing of Example 4.

Figure 8 shows the results of Example 1 as an example of the cross-section of the sintered bearing analyzed by EDX.

Figure 9 is a graph comparing the characteristics of the sintered bearings of Examples 1 to 4 and the characteristics of the sintered bearings of Comparative Examples 1 to 4.

Hereinafter, the sintered bearing 20 according to the embodiment of the present invention will be described with reference to the drawings.

The sintered bearing 20 can be applied to electric motors of various liquid pumps.

Various liquid pumps include: a water pump to circulate the cooling water used for engine cooling, a washer fluid pump to spit out windshield washer fluid, an oil pump to generate oil pressure in a hydraulic mechanism, and to press and deliver engine oil The fuel pump used to supply fuel (gasoline, light oil, alcohol, etc.), etc.

In this embodiment, the sintered bearing 20 is applied to the electric motor of the water pump 1.

(Composition of water pump 1)

First, the schematic configuration of the water pump 1 will be described.

Fig. 1 is a cross-sectional view showing a schematic configuration of the water pump 1. Figure 2 is a cross-sectional view of the sintered bearing 20.

The water pump 1 is a pump for supplying cooling water (Coolant) cooled by a radiator to a water jacket (water path) provided in the engine.

The water pump 1 shown in FIG. 1 includes a housing 10, a pair of sintered bearings 20, a motor (electric motor) 30, and an impeller 40.

The casing 10 has a suction port 11 for sucking in cooling water and a discharge port 12 for discharging cooling water. The suction port 11 is connected to the radiator via a hose (not shown). The discharge port 12 is connected to a water jacket via a hose (not shown).

Each sintered bearing 20 is fixed to the inside of the housing 10. As shown in FIG. 2, each sintered bearing 20 is formed in a substantially cylindrical shape. Each sintered bearing 20 has a bearing hole 21 through which a rotating shaft 32a of a motor 30 described later is inserted. Each sintered bearing 20 is provided with a bearing hole 21 so as to penetrate along its central axis. Then, each sintered bearing 20 supports the rotating shaft 32a by the inner peripheral surface of the bearing hole 21 (hereinafter referred to as "bearing surface 21a").

The motor 30 has a stator 31 and a rotor 32. In addition, the rotor 32 has a rotating shaft 32a. The rotating shaft 32 a is inserted through the bearing hole 21 of each sintered bearing 20. That is, the end on one side of the rotating shaft 32 a is supported by a sintered bearing 20, and the end on the other side is supported by the other sintered bearing 20. Thereby, the rotating shaft 32a is rotatably supported by the pair of sintered bearings 20.

The impeller 40 is fixed to the end on one side of the rotating shaft 32a.

In the water pump 1, when the impeller 40 is rotated by the driving of the motor 30, cooling water is sucked in from the suction port 11 and the sucked cooling water is discharged from the discharge port 12. Thereby, the water pump 1 circulates cooling water between the radiator and the water jacket.

(Composition of sintered bearing 20)

Next, the structure of each sintered bearing 20 will be described in detail.

The sintered bearing 20 is composed of a porous sintered body (green body) and lubricating oil impregnated in the sintered body.

The sintered body is a sintered metal. Thereby, the sintered system has a porous structure (porous structure) and is constituted (see Fig. 5). In addition, the sintered system has a crystal structure (fine structure). In particular, a solid lubricant is dispersed in the sintered body.

Specifically, the sintering system is composed of Cu-Ni-Zn-Sn alloy.

In the present embodiment, the sintered system has a mass ratio with respect to the total mass of the sintered body, containing more than 10% by mass and less than 20% by mass of Ni, more than 13% by mass and less than 20% by mass of Zn, and more than 0.5% by mass and less than 3% by mass of Sn, and more than 0.5% by mass and less than 4% by mass of solid lubricant, and the rest is composed of Cu and inevitable impurities.

Here, in the sintered body, a structure containing a trace amount of P may also be adopted. That is, the sintered body may also be a structure containing a Cu-Ni-Zn-Sn-P alloy.

In such a configuration, the content of P in the sintered body is set to be less than 0.05% by mass, preferably less than 0.04% by mass in terms of mass ratio to the total mass.

That is, regarding the sintered body, it is assumed that the sintered body contains more than 10% by mass and less than 20% by mass, and more than 13% by mass and less than 20% by mass, based on the mass ratio to the total mass of the sintered body. , Sn exceeding 0.5% by mass and less than 3% by mass, solid lubricant exceeding 0.5% by mass and less than 4% by mass, and P less than 0.05% by mass (preferably less than 0.04% by mass), and the rest Partly composed of Cu and unavoidable impurities.

The solid lubricant may use one of graphite, molybdenum disulfide, and boron nitride. Alternatively, the solid lubricant can be used by mixing two or more of graphite, molybdenum disulfide, and boron nitride.

In particular, in the sintered body, the average crystal grain size of the crystal grains is 20 μm or less. Here, the "average crystal grain size" refers to the average value of the grain size of the crystal grains appearing in the arbitrarily set observation area of the sintered body.

In this embodiment, the average crystal grain size is calculated as follows. That is, first, after embedding the sintered body in resin, the cross section of the sintered body is ground with an automatic grinder. Then, the cross section of the ground sintered body was etched with an etching solution, and 10 line segments with a length of 200 μm were drawn on the image obtained by using a microscope at a predetermined magnification. Here, among the lengths of 200 μm, the value minus the length of the pores is used as the reference length. Secondly, by dividing each reference length by the number of crystal grains existing on the line segment, the average value of the particle diameters of the crystal grains present on the line segment is calculated (hereinafter referred to as "individual average value"). Furthermore, the individual average values calculated for each line segment are averaged for 10 line segments to calculate the average crystal grain size.

In addition, in the sintered body, the effective porosity is 8 to 18% by volume. Here, "effective porosity" refers to the ratio of the volume of pores connected to the surface of the sintered body to the total volume of the sintered body.

As the lubricating oil, flowing paraffin, mineral-based lubricating oil, synthetic hydrocarbon-based lubricating oil, silicone-based lubricating oil, fluorine-based lubricating oil, etc. can be used. In addition, the sintered bearing 20 may have a structure that does not contain lubricating oil.

(Function/Effect of Sintered Bearing 20)

Next, the function/effect of the sintered bearing 20 will be explained.

The sintered bearing 20 is formed by a sintered body (green body) based on nickel silver (Cu-Ni-Zn). This can improve water resistance and corrosion resistance.

In addition, the sintered bearing 20 contains a solid lubricant in the sintered body. This can improve sliding properties.

In addition, in the sintered bearing 20, Sn is contained in a sintered body (powder compact). As a result, the sinterability is improved, and the sintering strength can be improved. As a result, the sintering strength decreased by the addition of the solid lubricant can be compensated.

In addition, by containing Sn in the sintered body, the resistance to dezincification corrosion in water can be improved.

In addition, in the sintered bearing 20, the porous structure is impregnated with lubricating oil. As a result, during the period from the manufacture of the bearing to the assembly of the motor, and even the period until the motor is used, the bearing can be prevented from rusting due to the impregnated lubricant. In addition, when the bearing is sealed and isolated from the flow path of the conveying liquid, an oil film can be formed between the rotating shaft 32a and the rotating shaft 32a according to the rotation of the rotating shaft 32a, and the generation between the rotating shaft 32a and the bearing surface 21a can be reduced. Frictional resistance. Furthermore, even when the bearing is not sealed and used in the conveying liquid, as a result, the lubricating oil impregnated in the bearing body will be replaced by the conveying liquid. However, by using a higher viscosity lubricant than the conveying liquid, Can help lubrication at the beginning of operation.

In particular, in the sintered bearing 20, P is not contained in the sintered body. Alternatively, the content of P in the sintered body is less than 0.05% by mass in terms of mass ratio to the total mass. Thereby, the crystal grains constituting the sintered body can be refined, and as a result, the mechanical strength and vibration resistance can be improved. In addition, in the sintered body, precipitation of the Ni-Sn-P alloy layer can be suppressed, and damage to the rotating shaft 32a during shaft rotation can be prevented.

Furthermore, in the sintered bearing 20, the average crystal grain size of the crystal grains constituting the sintered body is 20 μm or less. Thereby, the mechanical strength and vibration resistance can be improved, and the mechanical strength and vibration resistance required for the sintered bearing of the motor arranged in the liquid pump (especially, the liquid pump mounted on the automobile) can be met.

As described above, according to the sintered bearing 20, mechanical strength and vibration resistance can be improved, and damage to the rotating shaft can be prevented.

Hereinafter, the function/effect of each element constituting the sintered body of the sintered bearing 20 will be described in detail.

〔About Ni (Nickel)〕

By containing Ni in the sintered body, water resistance and corrosion resistance can be improved.

At this time, if the Ni content in the sintered body is 10% by mass or less, the water resistance/corrosion resistance becomes insufficient. On the other hand, if the Ni content in the sintered body becomes 20% by mass or more, the material cost will increase.

Therefore, by making the content of Ni in the sintered body more than 10% by mass and less than 20% by mass, the increase in material cost can be suppressed and the water resistance/corrosion resistance can be improved.

〔About Zn (Zn)〕

By containing Zn in the sintered body, water resistance and corrosion resistance can be improved.

At this time, if the content of Zn in the sintered body is 13% by mass or less, the water resistance/corrosion resistance becomes insufficient. On the other hand, if the content of Zn in the sintered body is 20% by mass or more, due to the evaporation of zinc during sintering, productivity will decrease and the risk of dezincification corrosion will increase.

Therefore, by making the content of Zn in the sintered body more than 13% by mass and less than 20% by mass, the decrease in productivity can be suppressed and the water resistance/corrosion resistance can be improved.

In particular, Zn is an inexpensive material compared to Ni. Therefore, when the water resistance/corrosion resistance is to be improved, the increase in the material cost can be suppressed by increasing the content of Zn while suppressing the increase in the Ni content.

〔About Sn (tin)〕

By containing Sn in the sintered body (powder compact), the sinterability can be improved and the sintering strength can be improved. Moreover, even if it contains a small amount, dezincification corrosion can still be suppressed.

At this time, if the Sn content in the sintered body is 0.5% by mass or less, the above-mentioned effect becomes insufficient. On the other hand, if the Sn content in the sintered body is 3% by mass or more, deformation due to dimensional changes during sintering is likely to occur.

Therefore, by setting the Sn content in the sintered body to exceed 0.5% by mass and less than 3% by mass, the occurrence of deformation can be suppressed and the sintered strength can be improved.

〔About solid lubricants〕

By containing a solid lubricant in the sintered body, the lubricity is improved, the friction coefficient can be reduced, and the burning property and abrasion resistance can be improved.

At this time, if the content of the solid lubricant in the sintered body is 0.5% by mass or less, the above-mentioned effect becomes insufficient. On the other hand, if the content of the solid lubricant in the sintered body becomes 4% by mass or more, the sintered strength is significantly reduced.

Therefore, by making the content of the solid lubricant in the sintered body exceed 0.5% by mass and less than 4% by mass, it is possible to suppress the decrease in sintered strength and improve the wear resistance.

〔About P (phosphorus)〕

By including P in the sintered body, oxidation of the metal constituting the sintered body can be prevented.

That is, as described later, when the raw material powder forming a sintered body is produced, the raw material powder is preferably an alloy powder such as Cu-Ni-Zn-Sn alloy powder.

Here, alloy powders such as Cu-Ni-Zn-Sn alloy powder are produced by an atomization method or the like. Specifically, a molten metal is produced by melting various raw metals constituting the target alloy powder at a high temperature, and the produced molten metal is sprayed/quickly solidified and powdered to produce alloy powder.

At this time, in the raw metal, a small amount of P can be added as an oxygen scavenger to prevent the oxidation of the molten metal.

Here, if the P content in the raw material metal is 0.05% by mass or more, the crystal grains constituting the sintered body are likely to be coarsened during sintering, and the Ni-Sn-P alloy layer is likely to precipitate in the sintered body.

Therefore, by setting the P content in the raw metal (sintered body) to less than 0.05% by mass, it is possible to suppress the coarsening of the crystal grains constituting the sintered body and the precipitation of the Ni-Sn-P alloy layer in the sintered body. And to prevent the oxidation of molten metal.

[About the average crystal grain size]

If the average crystal grain size of the crystal grains constituting the sintered body exceeds 20 μm, the mechanical strength and vibration resistance required for the sintered bearing of the motor installed in the liquid pump (especially, the liquid pump installed in a car) cannot be satisfied. Yu.

Therefore, by setting the average crystal grain size of the crystal grains constituting the sintered body to 20 μm or less, it is possible to satisfy the mechanical strength and mechanical strength required for the sintered bearing of the motor installed in the liquid pump (especially, the liquid pump installed in the automobile). Vibration resistance.

〔About effective porosity〕

If the effective porosity is less than 8% by volume, the density becomes very high, and the pressure required for powder compacting becomes large, and productivity decreases. On the other hand, if the effective porosity exceeds 18% by volume, the strength of the compact will be reduced, making it difficult to handle sintering. In addition, since the sintered strength is reduced, the minimum strength required as a bearing cannot be obtained.

Therefore, by setting the effective porosity to 8% by volume or more and 18% by volume or less, it is possible to suppress a decrease in productivity and improve sintering strength.

(Method of manufacturing sintered bearing 20)

Next, the manufacturing method of the sintered bearing 20 will be described.

To manufacture the sintered bearing 20, raw material powder is first produced.

The raw material powder is produced by stirring and mixing a plurality of powders (metal powder, solid lubricant, etc.). At this time, a mold lubricant may be added to the raw material powder.

The raw material powder has a mass ratio relative to the total mass of the raw material powder, containing more than 10 mass% and less than 20 mass% Ni, more than 13 mass% and less than 20 mass% Zn, more than 0.5 mass% and not It is composed of 3% by mass of Sn and more than 0.5% by mass but less than 4% by mass of solid lubricant, and the remainder is composed of Cu and inevitable impurities.

Alternatively, the raw material powder may contain a small amount of P as an oxygen scavenger. At this time, the content of P in the raw material powder is set to be less than 0.05% by mass, preferably less than 0.04% by mass in terms of mass ratio relative to the total mass.

That is, the raw material powder is set to contain Ni in excess of 10% by mass and less than 20% by mass, and Zn in excess of 13% by mass and less than 20% by mass based on the mass ratio relative to the total mass of the raw material powder. , Sn exceeding 0.5% by mass and less than 3% by mass, solid lubricant exceeding 0.5% by mass and less than 4% by mass, and P less than 0.05% by mass (preferably less than 0.04% by mass), and the rest Partly composed of Cu and unavoidable impurities.

The raw material powder can be produced using Cu powder (pure metal powder), Ni powder (pure metal powder), Zn powder (pure metal powder), Sn powder (pure metal powder), Cu-Ni alloy powder, Cu-Zn alloy powder, One or a combination of Cu-Sn alloy powder, Cu-Ni-Zn alloy powder, Cu-Ni-Sn alloy powder, Cu-Ni-Zn-Sn alloy powder, and Cu-Ni-Zn-Sn-P alloy powder Use multiple powders.

For example, the raw material powder can be produced by using Cu powder, Ni powder, Cu-Zn alloy powder, and Sn powder to satisfy the above composition.

Here, if the diffusion of Ni and Zn in the raw material powder is insufficient, the concentration of Ni and Zn in the sintered body becomes uneven. As a result, corrosion is likely to occur in the portion where the concentration of Ni and Zn in the sintered body is low.

Therefore, in the state of the metal powder (each particle constituting the powder), it is preferable that more of the metals contained in the above-mentioned composition be uniformly alloyed.

Therefore, when generating raw material powder, it is better to reduce the type of metal powder used by using alloy powders in which a plurality of metals are alloyed. This can prevent the diffusion of Ni and Zn in the raw material powder from becoming insufficient.

Therefore, the powder used for the production of the raw material powder preferably contains at least one alloy powder. Or, the powder used in the production of the raw material powder contains two or more alloy powders It is better at the end. In particular, the powder used for the production of the raw material powder preferably does not contain pure metal powder but only alloy powder.

For example, the raw material powder can be generated by using Cu-Ni-Zn alloy powder and Cu-Sn alloy powder, and the combination of alloy powder can satisfy the above composition.

In this embodiment, one type of alloy powder, namely, Cu-Ni-Zn-Sn alloy powder, is used as the alloy powder used for the production of the raw material powder. Specifically, Cu-Ni-Zn-Sn alloy powder and solid lubricant are used to generate raw material powder. Alternatively, Cu-Ni-Zn-Sn-P alloy powder and solid lubricant are used to generate raw material powder. Thereby, it is possible to more reliably prevent the diffusion of Ni and Zn in the raw material powder from becoming insufficient.

As the solid lubricant, one or a combination of graphite (Graphite) powder, molybdenum disulfide powder, and boron nitride powder can be used.

Mold lubricants can use metal soap powders represented by zinc stearate, lithium stearate, etc., or fatty amide powders such as ethylene bis-stearamide, or wax-based lubricant powders such as polyethylene. In addition, the mold lubricant system is not limited to these.

Then, the raw material powder is compression-molded to form a compact.

Specifically, the produced raw material powder is contained in a mold. Then, the raw material powder contained in the mold is press-formed under a pressure of 100 to 500 MPa to form a pressed powder body.

Next, the compact is sintered to form a sintered body.

Specifically, the formed compact is sintered at a predetermined sintering temperature in a predetermined environment, and then cooled at a predetermined cooling rate to form a sintered body. By sintering the compact, the adjacent metal particles are diffusely joined, and the metal particles are combined to form a porous structure sintered body (sintered metal).

The predetermined environment is in vacuum, reducing gas (ammonia decomposition gas, hydrogen, endothermic gas, etc.), inert gas (nitrogen, argon, etc.), mixed gas of these reducing gas and inert gas, etc., Choose appropriately according to the composition of the raw material powder.

The sintering temperature is in the range of 700 to 1050°C, and is appropriately selected according to the composition of the raw material powder.

The predetermined cooling rate is set to 15°C/min or higher, and is appropriately selected according to the composition of the raw material powder. In this embodiment, the cooling rate is set to 30°C/min. Thereby, the average crystal grain size of the sintered body can be set to 20 μm or less.

Secondly, dimension correction is applied to the sintered body.

Specifically, the formed sintered body is contained in a mold. Furthermore, dimension correction (recompression) is applied to the sintered body contained in the mold to form a recompressed body. By applying dimension correction to the sintered body, the dimensional accuracy is improved and the surface roughness is improved.

Then, the body is cleaned and recompressed to remove dirt such as metal chips generated by processing and lubricating oil for dimension correction.

Then, the washed recompressed body is impregnated with lubricating oil. In this way, the sintered bearing 20 is completed. In addition, the sintered bearing 20 may have a structure not impregnated with lubricating oil.

(Function/effect of manufacturing method of sintered bearing 20)

In the manufacturing method of the sintered bearing 20, a sintered bearing is formed by using nickel silver (Cu-Ni-Zn) as a base raw material powder. Thereby, the water resistance/corrosion resistance of the sintered bearing 20 can be improved.

Moreover, in the manufacturing method of the sintered bearing 20, a solid lubricant is added to the raw material powder. Thereby, the sliding properties of the sintered bearing 20 can be improved.

Moreover, in the manufacturing method of the sintered bearing 20, Sn is added to the raw material powder. As a result, the sinterability during sintering is improved, and the sintering strength of the sintered bearing 20 can be improved. As a result, the sintering strength decreased by the addition of the solid lubricant can be compensated.

In addition, by adding Sn to the raw material powder, the resistance to dezincification corrosion in water can be improved.

In particular, in the manufacturing method of the sintered bearing 20, P is not added to the raw material powder. Alternatively, the addition amount of P in the raw material powder is based on the mass ratio relative to the total mass, which is less than 0.05% by mass.

Thereby, the crystal grains constituting the sintered body can be made finer, and as a result, the mechanical strength and vibration resistance can be improved. In addition, in the sintered body, precipitation of the Ni-Sn-P alloy layer can be suppressed, and damage to the rotating shaft during shaft rotation can be prevented.

Furthermore, in the manufacturing method of the sintered bearing 20, the average crystal grain size of the crystal grains constituting the sintered body is 20 μm or less. Thereby, the mechanical strength and vibration resistance can be improved, and the mechanical strength and vibration resistance required for the sintered bearing of the motor arranged in the liquid pump (especially, the liquid pump mounted on the automobile) can be satisfied.

Furthermore, in the method of manufacturing the sintered bearing 20, Cu-Ni-Zn-Sn alloy powder and solid lubricant powder are mixed to form raw material powder. Alternatively, Cu-Ni-Zn-Sn-P alloy powder and solid lubricant powder are mixed to form raw material powder. Thereby, in the sintered body, the concentration of each component such as Ni and Zn can be prevented from becoming non-uniform, and as a result, it is possible to prevent a situation in which the portions of the sintered body with low concentrations of Ni and Zn from being selectively corroded.

As described above, according to the manufacturing method of the sintered bearing 20, the mechanical strength and vibration resistance can be improved, and damage to the rotating shaft can be prevented.

Here, the action/effect of each element (each element) constituting the raw material powder is as described above.

(Example)

Next, embodiments of the present invention will be explained.

The example of the present invention is to manufacture 4 types of sintered bearings (Examples 1 to 4). In addition, the comparative example produced four types of sintered bearings (Comparative Examples 1 to 4).

The sintered bearings of Examples 1 to 4 were manufactured using the raw material powder of the composition of the present invention. Thereby, the sintered systems of the sintered bearings of Examples 1 to 4 have the composition of the present invention.

That is, the sintering system of the sintered bearings of Examples 1 to 3 has a mass ratio with respect to the total mass of the raw material powder (sintered body), containing more than 10% by mass and less than 20% by mass of Ni, and exceeding 13% by mass And less than 20% by mass of Zn, more than 0.5% by mass and less than 3% by mass of Sn, and more than 0.5% by mass and less than 4% by mass of solid lubricants, and the remainder is composed of Cu and inevitable impurities The composition.

On the other hand, the sintered system of the sintered bearing of Example 4 has a mass ratio relative to the total mass of the raw material powder (sintered body), containing more than 10 mass% and less than 20 mass% of Ni, more than 13 mass% and Less than 20% by mass of Zn, more than 0.5% by mass and less than 3% by mass of Sn, more than 0.5% by mass and less than 4% by mass of solid lubricant, and less than 0.05% by mass of P, and the remainder is made of Cu And unavoidable impurities.

In addition, in the sintered bearings of Examples 1 to 4, the combinations of powders used for the production of the raw powders are different.

On the other hand, the sintered bearings of Comparative Examples 1 to 4 were manufactured using raw material powders having a composition different from that of the present invention. Thereby, the sintered system of the sintered bearings of Comparative Examples 1 to 4 has a composition different from that of the present invention. Specifically, the burning of the sintered bearings of Comparative Examples 1 to 4 The sintered body (raw material powder) is composed of P in an amount of 0.05% by mass or more in terms of mass ratio to the total mass of the sintered body (raw material powder).

In addition, in the sintered bearings of Comparative Examples 1 to 4, the combinations of powders used for the production of the raw powders are different.

Here, the sintered bearings of Examples 1 to 4 and the sintered bearings of Comparative Examples 1 to 4 are manufactured under the same manufacturing conditions (manufacturing steps, pressure when forming a compact, environment when forming a sintered body/sintering temperature/ Cooling rate, etc.).

Specifically, the raw material powder contained in the mold is press-formed under a pressure of 100 to 500 MPa to form a compact. In addition, the compact is sintered at a sintering temperature of 800 to 950°C in an ammonia decomposition gas, and then cooled at a cooling rate of 30°C/min to form a sintered body.

Hereinafter, the comparison results of the sintered bearings of Examples 1 to 4 and the sintered bearings of Comparative Examples 1 to 4 will be described in detail.

(Composition of each sintered bearing)

Figure 3 is a diagram comparing the blending content of the raw material powders of the sintered bearings of Examples 1 to 4 and the blending content of the raw material powders of the sintered bearings of Comparative Examples 1 to 4.

In addition, the numbers shown in Fig. 3 indicate the ratio (unit: mass %) of the mass of each powder (alloy powder or solid lubricant) to the total mass of the raw material powder.

In addition, the composition of each raw material powder is also expressed in mass %. For example, Cu-14Ni-14Zn-2Sn alloy powder means an alloy powder containing 14% by mass of Ni, 14% by mass of Zn, and 2% by mass of Sn, with the remainder being Cu. The same is true for other alloy powders.

The raw material powders of the sintered bearings of Examples 1 to 3 are produced from Cu-14Ni-14Zn-2Sn alloy powder and graphite powder (solid lubricant).

The raw material powder of the sintered bearing of Example 4 is produced from Cu-14Ni-14Zn-2Sn-0.03P alloy powder and graphite powder (solid lubricant).

On the other hand, the raw material powders of the sintered bearings of Comparative Examples 1 to 3 were produced from Cu-18Ni-18Zn alloy powder, Cu-11Sn alloy powder, Cu-8P alloy powder, and graphite powder (solid lubricant).

In addition, the raw material powder of the sintered bearing of Comparative Example 4 was produced from Cu-18Ni-18Zn alloy powder, Cu-8P alloy powder, and graphite powder (solid lubricant).

Specifically, as shown in Fig. 3, the raw material powder of the sintered bearing of Example 1 is obtained by stirring and mixing 97.5% by mass of Cu-14Ni- in a mass ratio relative to the total mass of the raw material powder (sintered body). 14Zn-2Sn alloy powder and 2.5% by mass graphite powder are produced.

The raw material powder of the sintered bearing of Example 2 is calculated by stirring and mixing 96.5% by mass of Cu-14Ni-14Zn-2Sn alloy powder and 3.5% by mass of graphite in a mass ratio relative to the total mass of the raw material powder (sintered body) Powder is generated.

The raw material powder of the sintered bearing of Example 3 is calculated by stirring and mixing 99.4% by mass of Cu-14Ni-14Zn-2Sn alloy powder and 0.6% by mass of graphite in a mass ratio relative to the total mass of the raw material powder (sintered body) Powder is generated.

The raw material powder of the sintered bearing of Example 4 is calculated by stirring and mixing 97.5 mass% of Cu-14Ni-14Zn-2Sn-0.03P alloy powder and 2.5 mass by the mass ratio relative to the total mass of the raw powder (sintered body) % Of graphite powder.

The raw material powder of the sintered bearing of Comparative Example 1 is calculated by stirring and mixing 75.5 mass% of Cu-18Ni-18Zn alloy powder and 20.0% of the total mass of the raw material powder (sintered body). It is produced by mass% Cu-11Sn alloy powder, 2.0 mass% Cu-8P alloy powder, and 2.5 mass% graphite powder.

The raw material powder of the sintered bearing of Comparative Example 2 is calculated by mixing 73.5 mass% Cu-18Ni-18Zn alloy powder and 20.0 mass% Cu-11Sn in a mass ratio relative to the total mass of the raw powder (sintered body). Alloy powder, 2.0% by mass Cu-8P alloy powder, and 4.5% by mass graphite powder are produced.

The raw material powder of the sintered bearing of Comparative Example 3 is calculated by mixing 50.0 mass% Cu-18Ni-18Zn alloy powder and 45.5 mass% Cu-11Sn in a mass ratio relative to the total mass of the raw material powder (sintered body). Alloy powder, 2.0% by mass Cu-8P alloy powder and 2.5% by mass graphite powder are produced.

The raw material powder of the sintered bearing of Comparative Example 4 is calculated by stirring and mixing 93.5% by mass of Cu-18Ni-18Zn alloy powder and 4.0% by mass of Cu-8P in a mass ratio relative to the total mass of the raw material powder (sintered body) Alloy powder and 2.5% by mass graphite powder are produced.

Figure 4 is a diagram comparing the composition of the raw material powder (sintered body) of the sintered bearings of Examples 1 to 4 and the composition of the raw material powder (sintered body) of the sintered bearings of Comparative Examples 1 to 4.

In addition, the numbers shown in Fig. 4 indicate the ratio (unit: mass %) of the mass of each element (alloy powder or solid lubricant) to the total mass of the raw material powder (sintered body).

As shown in Figure 4, the composition of the raw material powder of the sintered bearing of Example 1 is based on the mass ratio relative to the total mass of the raw material powder, consisting of 68.3% by mass of Cu, 13.7% by mass of Ni, and 13.7% by mass of Zn , 2.0% by mass of Sn, and 2.5% by mass of C.

The composition of the raw material powder of the sintered bearing of Example 2 is based on the mass ratio relative to the total mass of the raw material powder, consisting of 67.6 mass% Cu, 13.5% by mass Ni, 13.5% by mass Zn, 1.9% by mass Sn, And 3.5% by mass of C.

The composition of the raw material powder of the sintered bearing of Example 3 is based on the mass ratio relative to the total mass of the raw material powder, consisting of 69.6 mass% Cu, 13.9 mass% Ni, 13.9 mass% Zn, 2.0 mass% Sn, And 0.6% by mass of C.

The composition of the raw material powder of the sintered bearing of Example 4 is based on the mass ratio relative to the total mass of the raw material powder, consisting of 68.3% by mass Cu, 13.7% by mass Ni, 13.7% by mass Zn, 2.0% by mass Sn, It is composed of 0.03% by mass of P and 2.5% by mass of C.

The composition of the raw material powder of the sintered bearing of Comparative Example 1 is based on the mass ratio relative to the total mass of the raw material powder, consisting of 68.0 mass% Cu, 13.6 mass% Ni, 13.6 mass% Zn, 2.2 mass% Sn, It is composed of 0.2% by mass of P and 2.5% by mass of C.

The composition of the raw material powder of the sintered bearing of Comparative Example 2 is based on the mass ratio relative to the total mass of the raw powder, consisting of 66.7% by mass of Cu, 13.2% by mass of Ni, 13.2% by mass of Zn, 2.2% by mass of Sn, It is composed of 0.2% by mass of P and 4.5% by mass of C.

The composition of the raw material powder of the sintered bearing of Comparative Example 3 is based on the mass ratio relative to the total mass of the raw powder, consisting of 74.3% by mass of Cu, 9.0% by mass of Ni, 9.0% by mass of Zn, 5.0% by mass of Sn, It is composed of 0.2% by mass of P and 2.5% by mass of C.

The composition of the raw material powder of the sintered bearing of Comparative Example 4 is based on the mass ratio relative to the total mass of the raw material powder, consisting of 63.5 mass% Cu, 16.8 mass% Ni, 16.8 mass% Zn, 0.3 mass% P, And 2.5% by mass of C.

(Metal structure of each sintered bearing)

Figure 5 is a diagram showing an example of the metal structure of the sintered bearing of the embodiment. Figure 6 is a diagram showing an example of the metal structure of the sintered bearing of the comparative example.

The sintered bearings of Examples 1 to 4 and Comparative Examples 1 to 4 were immersed in an etching solution, and the metal structure after etching was observed with a microscope. As an example of an example, the metal structure of the sintered bearing of Example 1 is shown in Fig. 5, and as an example of a comparative example, the metal structure of the sintered bearing of Comparative Example 1 is shown in Fig. 6.

Fig. 5 is a photograph obtained by observing the metal structure of the sintered bearing of Example 1 after etching with a microscope.

Figure 6 is a photograph obtained by observing the metal structure of the sintered bearing of Comparative Example 1 after etching with a microscope.

In addition, in Fig. 6, the Ni-Sn-P alloy layer is indicated by the symbol "A". As shown in Fig. 6, it can be seen that in the metal structure of the sintered bearing of Comparative Example 1, a Ni-Sn-P alloy layer is precipitated. Therefore, the sintered bearing of Comparative Example 1 may damage the rotating shaft when the shaft rotates.

On the other hand, as shown in Fig. 5, it can be seen that in the metal structure of the sintered bearing of Example 1, the Ni-Sn-P alloy layer is not precipitated. Therefore, according to the sintered bearing of Example 1, it is possible to prevent damage to the rotating shaft when the shaft rotates.

In addition, Fig. 7 is a photograph obtained by observing the metal structure of the sintered bearing of Example 4 after etching with a microscope. As shown in Fig. 4, the composition of the raw material powder of the sintered bearing of Example 4 is based on the mass ratio relative to the total mass of the raw material powder, and contains 0.03% by mass of P. However, as shown in Figure 7, it can be seen that in the metal structure of the sintered bearing of Example 4, the Ni-Sn-P alloy layer is not precipitated. Therefore, according to the sintered bearing of Example 4, it is possible to prevent damage to the rotating shaft when the shaft rotates.

Moreover, as shown in Figs. 5 to 7, it can be seen that the average crystal grain size of the sintered bearings of Examples 1 and 4 is smaller than that of the sintered bearing of Comparative Example 1.

Specifically, it was confirmed that the average crystal grain size of the sintered bearing of Example 1 was 8.1 μm, and it was confirmed that the average crystal grain size of the sintered bearing of Example 2 was 8.7 μm. It was confirmed that the average crystal grain size of the sintered bearing of Example 3 was 8.5 μm, and it was confirmed that the average crystal grain size of the sintered bearing of Example 4 was 8.3 μm.

On the other hand, it was confirmed that the average crystal grain size of the sintered bearing of Comparative Example 1 was 28.4 μm, and it was confirmed that the average crystal grain size of the sintered bearing of Comparative Example 2 was 27.8 μm. It was confirmed that the average crystal grain size of the sintered bearing of Comparative Example 3 was 28.6 μm, and it was confirmed that the average crystal grain size of the sintered bearing of Comparative Example 4 was 33.4 μm.

Thus, it can be seen that in the sintered bearings of Examples 1 to 4, the average crystal grain size is 20 μm or less. On the other hand, it can be seen that in the sintered bearings of Comparative Examples 1 to 4, the average crystal grain size exceeds 20 μm.

Therefore, the sintered bearings according to Examples 1 to 4 have higher mechanical strength and vibration resistance than the sintered bearings of Comparative Examples 1 to 4.

(Result of concentration analysis of each element)

Figure 8 shows the result of analyzing the cross section of the sintered bearing of Example 1 by EDX (Energy Dispersive X-ray spectrometry).

Figure 8 shows the distribution of the constituent elements (Cu, Ni, Zn, Sn) in the cross section of the sintered bearing of Example 1. In particular, Figure 8 shows the concentration (mass concentration %) of each constituent element (Cu, Ni, Zn, Sn) in the cross section of the sintered bearing of Example 1 by the difference in color (difference in shade of color). Also, in Figure 8, the lighter the color, the stronger the density.

Figure 8(b) shows the distribution of Cu in the cross section shown in Figure 8(a). Figure 8(c) shows the distribution of Ni in the cross section shown in Figure 8(a). Figure 8(d) shows the distribution of Zn in the section shown in Figure 8(a). Figure 8(e) shows the distribution of Sn in the section shown in Figure 8(a).

As shown in Fig. 8 (b), (c), (d), and (e), it can be seen that in the sintered bearing of Example 1, the constituent elements (Cu, Ni, Zn, Sn) are uniformly dispersed.

Therefore, in the sintered bearing of Example 1, in the sintered body, the production of the low-concentration parts of Ni and Zn is suppressed, and as a result, it is possible to prevent the occurrence of selective corrosion of the parts with low Ni and Zn concentrations.

(The characteristics of sintered bearings)

Figure 9 is a graph comparing the characteristics of the sintered bearings of Examples 1 to 4 and the characteristics of the sintered bearings of Comparative Examples 1 to 4.

In addition, Figure 9 uses symbols ("◎", "○", "△", "×") to show the pros and cons of each characteristic (corrosion resistance, compression ring strength, vibration resistance, friction coefficient). At this time, each symbol indicates the degree of excellent characteristics in the order of "◎", "○", "△", and "×". In particular, the characteristics with the “×” mark indicate that it does not meet the standards required for bearings for liquid pumps.

As shown in Fig. 9, it can be seen that the sintered bearings of Examples 1 to 4 meet the standards required for bearings for liquid pumps in terms of corrosion resistance, compression ring strength, vibration resistance, and friction coefficient.

On the other hand, as shown in Figure 4, in the raw material powder of the sintered bearing of Comparative Example 1, the average crystal grain size of the sintered body is large due to the addition of 0.2% by mass of P in terms of mass ratio to the total mass. To 28.4 μm, and as shown in Figure 9, it can be seen that the vibration resistance is insufficient. Also, the corrosion resistance due to use As for Cu-18Ni-18Zn alloy powder and Cu-11Sn alloy powder, it was confirmed that the parts with low Ni and Zn concentrations were selectively corroded.

In addition, as shown in Figure 4, the content of C (solid lubricant) in the raw material powder of the sintered bearing of Comparative Example 2 is 4% by mass or more in terms of mass ratio to the total mass. Therefore, in the sintered bearing of Comparative Example 2, the sintered strength is reduced. As a result, as shown in Fig. 9, it can be seen that in the sintered bearing of Comparative Example 2, the compression ring strength is insufficient.

On the other hand, as shown in Fig. 4, it can be seen that in the raw material powder of the sintered bearing of Comparative Example 3, the content of Ni is less than 10% by mass relative to the total mass, and the content of Zn is relative to The mass ratio of the total mass is calculated to be less than 13 mass%. Therefore, as shown in Fig. 9, it can be seen that the sintered bearing of Comparative Example 3 has insufficient corrosion resistance.

Moreover, as shown in Fig. 4, in the raw material powder of the sintered bearing of Comparative Example 3, the content of Sn is 3% by mass or more in terms of the mass ratio to the total mass. Therefore, in the sintered bearing of Comparative Example 3, deformation due to dimensional changes during sintering is likely to occur, and the precipitation of the alloy layer that becomes hard Ni-Sn-P is promoted. As a result, as shown in Fig. 9, it can be seen that in the sintered bearing of Comparative Example 3, the friction coefficient becomes larger.

On the other hand, as shown in Fig. 4, compared with the sintered bearings of Comparative Examples 1 to 3, the sintered bearing of Comparative Example 4 has a higher content of P in the raw material powder. That is, in the raw material powder of the sintered bearing of Comparative Example 4, the content of P was 0.3% by mass in terms of the mass ratio to the total mass. Therefore, it can be seen that the average crystal grain size of the sintered body is as large as 33.4 μm, and the vibration resistance is insufficient. In addition, as shown in Fig. 4, the raw material powder of the sintered bearing of Comparative Example 4 does not contain Sn. Therefore, it can be seen that in the sintered bearing of Comparative Example 4, the sintered strength is reduced. As a result, as shown in Fig. 9, it can be seen that in the sintered bearing of Comparative Example 4, the strength of the pressure ring is reduced.

In particular, as shown in Fig. 4, compared with the sintered bearing of Example 1, the raw material powder of the sintered bearing of Example 2 contains more C (solid lubricant). Therefore, as shown in Fig. 9, it can be seen that the friction coefficient of the sintered bearing of Example 2 is lower than that of the sintered bearing of Example 1. Therefore, when it is desired to give priority to the reduction of the friction coefficient, it is preferable to set the content of C (solid lubricant) to 3% by mass or more in the composition of the present invention, especially 3.5% by mass or more.

In addition, as shown in Fig. 4, compared with the sintered bearing of Example 1, the content of C (solid lubricant) in the raw material powder of the sintered bearing of Example 3 is less. Therefore, as shown in Fig. 9, it can be seen that the pressure ring strength of the sintered bearing of Example 3 is improved compared to the sintered bearing of Example 1. Therefore, when it is desired to give priority to the improvement of the compression ring strength, it is preferable to set the content of C (solid lubricant) to 1% by mass or less in the composition of the present invention.

Claims (7)

A sintered bearing composed of a sintered body with an average crystal grain size of 20 μm or less. The sintered system has a mass ratio of more than 10 mass% and less than 20 mass% of Ni and more than 13 Mass% and less than 20% by mass of Zn, more than 0.5% by mass and less than 3% by mass of Sn, and more than 0.5% by mass and less than 4% by mass of solid lubricants, and the remainder is made of Cu and unavoidable impurities Constitute the composition. A sintered bearing composed of a sintered body with an average crystal grain size of 20 μm or less. The sintered system has a mass ratio of more than 10 mass% and less than 20 mass% of Ni and more than 13 Mass% and less than 20% by mass of Zn, more than 0.5% by mass and less than 3% by mass of Sn, more than 0.5% by mass and less than 4% by mass solid lubricant, and less than 0.05% by mass of P, and the rest Partly composed of Cu and unavoidable impurities. The sintered bearing described in item 1 or 2 of the scope of patent application, wherein the solid lubricant contains at least one of graphite, molybdenum disulfide and boron nitride. The sintered bearing described in any one of items 1 to 3 in the scope of the patent application is made by impregnating the aforementioned sintered body with lubricating oil. The sintered bearing described in any one of items 1 to 4 in the scope of the patent application is used in the motor of a liquid pump. A method for manufacturing a sintered bearing includes the steps of mixing a plurality of powders to produce raw powders; compressing and forming the raw powders to form a compact; sintering the compact to form a sintered body; and The step of applying dimension correction to the aforementioned sintered body; wherein, the aforementioned plural kinds of powders include Cu-Ni-Zn-Sn alloy powder and a solid lubricant, and the aforementioned raw material powders have a mass ratio relative to the total mass, and contain more than 10% by mass and less than 20% by mass Ni, more than 13% by mass and less than 20% by mass Zn, more than 0.5% by mass and less than 3% by mass Sn, and more than 0.5% by mass and less than 4% by mass Solid lubricant, and the remainder is composed of Cu and unavoidable impurities. The average crystal grain size of the aforementioned sintered body is 20 μm or less. A method for manufacturing a sintered bearing includes the steps of mixing a plurality of powders to produce raw material powder; compressing and forming the raw material powder to form a compact; sintering the aforementioned compact to form a sintered body; and The step of applying dimension correction to the sintered body; wherein the aforementioned plural kinds of powders include Cu-Ni-Zn-Sn alloy powder, solid lubricant and P powder, and the aforementioned raw material powder has a mass ratio relative to the total mass, containing Ni in excess of 10% by mass and less than 20% by mass, Zn in excess of 13% by mass and less than 20% by mass, Sn in excess of 0.5% by mass and less than 3% by mass, and Sn in excess of 0.5% by mass and less than 4% by mass A solid lubricant and P less than 0.05% by mass, and the remainder is composed of Cu and inevitable impurities. The average crystal grain size of the sintered body is 20 μm or less.

Images