TWI777046B - 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 for producing the sintered bearing, particularly a sintered bearing suitable for use in a motor of a liquid pump, and a method for producing the sintered bearing.

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

For example, the liquid pumps installed in automobiles are known to include a water pump for circulating cooling water for engine cooling, a washer liquid pump for discharging windshield washer fluid, an oil pump for generating oil pressure in an oil hydraulic mechanism, and a Oil pump for pumping engine oil, fuel pump for supplying fuel (gasoline, light oil, alcohol, etc.), etc.

In recent years, in the liquid pump, from the viewpoint of stabilizing the discharge amount (pumped water amount), electrification has been developed in which power is obtained from an electric motor.

For example, a conventional water pump obtains power from an engine, so a change in the number of revolutions of the engine affects the discharge amount of cooling water, 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 to stabilize the cooling efficiency. In particular, water pumps mounted on hybrid vehicles, electric vehicles, fuel cell vehicles, etc. cannot be Power is obtained from the engine, or stable power cannot be obtained from the engine. Therefore, in order to obtain a stable output, electrification is being developed to obtain power from an electric motor.

In particular, in recent years, in order to reduce the size and increase the output of the liquid pump, the electric motor has been reduced in size and the output has been increased, and the load on the bearing of the electric motor has increased accordingly. Therefore, the bearing provided in the electric motor of the liquid pump (hereinafter, referred to as "the bearing for the liquid pump") is required to be improved in load resistance. Furthermore, since the bearing for the liquid pump is used in the liquid, the improvement of the load resistance and the improvement of the water resistance and the corrosion resistance are also required.

Conventionally, as bearings excellent in water resistance and corrosion resistance, bearings made of ceramics, carbon, or resins have been known. However, a bearing made of ceramic or carbon has a problem of high processing cost, although it is excellent in water resistance and corrosion resistance. In addition, the bearing system made of resin has problems in that it is difficult to ensure dimensional accuracy and the load resistance is insufficient.

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

Therefore, in recent years, as a bearing for a liquid pump, an embryo made of nickel silver (Cu-Ni-Zn alloy), which is a material excellent in water resistance and corrosion resistance, added with P (phosphorus) and a solid lubricant has been developed. A sintered bearing composed of a body (base material) (refer to Patent Document 1).

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

In particular, in the sintered bearing described in Patent Document 1, by adding P to the green body, during sintering, the diffusion of other added constituent elements (Ni, Zn, etc.) is promoted, and the occurrence of water resistance/corrosion resistance in the sintered bearing is suppressed. low sex part.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2015-187307

However, in the conventional sintered bearing, there is a possibility that the mechanical strength and the vibration resistance are lowered.

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 be coarsened during sintering. Then, if the crystal grains constituting the embryo body are coarsened, there is a possibility that the mechanical strength and vibration resistance may be lowered.

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 alloy layer of Ni-Sn-P is easily precipitated in the green body. Here, the alloy layer of Ni-Sn-P has a very high hardness compared with other parts of the green body. Therefore, if the Ni-Sn-P alloy layer is precipitated in the green body, when the shaft rotates, the rotating shaft may be damaged because the rotating shaft contacts the Ni-Sn-P alloy layer.

An object of the present invention is to improve mechanical strength and vibration resistance in a sintered bearing, and to prevent damage to the rotating shaft.

In order to solve the above-mentioned problems, the sintered bearing of the first 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 relative to the total mass of more than 10 mass % and less than 20 mass %. Mass % Ni, more than 13 mass % and less than 20 Zn in mass %, Sn in excess of 0.5 mass % but not up to 3 mass %, solid lubricant in excess of 0.5 mass % but not up to 4 mass %, and the rest is composed of Cu and unavoidable impurities.

Furthermore, 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 more than 10 mass % and less than 20 mass % in terms of mass ratio with respect to the total mass. Ni, more than 13 mass % and less than 20 mass % of Zn, more than 0.5 mass % and less than 3 mass % of Sn, more than 0.5 mass % and less than 4 mass % of solid lubricants, and less than 0.05 mass % P, and the rest is composed of Cu and inevitable impurities.

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

Furthermore, in the sintered bearing of the first or second invention, the sintered body contains a solid lubricant. Thereby, slidability can be improved.

Further, 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, the reduced sintering strength due to the inclusion 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 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 mass % in terms of mass ratio with respect 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 the rotating shaft can be prevented from being damaged when the shaft rotates.

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, there is a possibility that the mechanical strength and resistance required for the sintered bearing to be installed in a motor of a liquid pump (in particular, a liquid pump mounted in an automobile) cannot be satisfied. Vibration hazard.

Therefore, by setting the average crystal grain size of the crystal grains constituting the sintered body to be 20 μm or less, the mechanical strength and Vibration resistance.

According to the above, according to the sintered bearing of the first or second invention, the mechanical strength and vibration resistance can be improved, and damage to the rotating shaft can be prevented.

Here, in the sintered bearing of the first or second invention, it is preferable that the sintered body is formed 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 powders containing Cu-Ni-Zn-Sn alloy powder and solid lubricant powder.

That is, in the Cu-Ni-Zn-Sn alloy powder, each constituent element (constituent element) such as Ni and Zn is uniformly dispersed in each particle constituting the powder. Therefore, by using Cu-Ni-Zn-Sn alloy powder to form a sintered body, it is possible to prevent the sintered body from becoming non-uniform in the concentrations of various constituent elements such as Ni and Zn, and as a result, to prevent Ni and Zn in the sintered body from becoming non-uniform. A state of selective corrosion occurs in a portion with a low concentration.

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

Moreover, in this invention, content of each element is defined according to the mass ratio (mass %) in the whole sintered body.

[About Ni (nickel)]

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

At this time, when the content of Ni in the sintered body is 10 mass % or less, water resistance and corrosion resistance become insufficient. On the other hand, when the content of Ni in the sintered body is 20 mass % or more, the material cost increases.

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

[About Zn (zinc)]

Water resistance and corrosion resistance can be improved by containing Zn in the sintered body.

At this time, when the content of Zn in the sintered body is 13 mass % or less, water resistance and corrosion resistance become insufficient. On the other hand, when the content of Zn in the sintered body is 20 mass % or more, the productivity is lowered due to the evaporation of zinc during sintering, and the risk of dezincification corrosion is increased.

Therefore, by making the content of Zn in the sintered body more than 13% by mass and less than 20% by mass, the reduction 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 content of Ni.

[About Sn (tin)]

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

At this time, when the Sn content in the sintered body is 0.5 mass % or less, the above-mentioned effects become insufficient. On the other hand, when the content of Sn in the sintered body is 3 mass % or more, deformation due to dimensional changes during sintering tends to occur.

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

[About solid lubricants]

By including the solid lubricant in the sintered body, the lubricity can be improved, the friction coefficient can be reduced, and the burnout property and the wear resistance can be improved.

At this time, when the content of the solid lubricant in the sintered body is 0.5 mass % or less, the above-mentioned effects become insufficient. On the other hand, when the content of the solid lubricant in the sintered body is 4 mass % or more, the sintered strength is significantly lowered.

Therefore, by making the content of the solid lubricant in the sintered body more than 0.5 mass % and less than 4 mass %, the decrease in sintering strength can be suppressed and the wear resistance can be improved.

[About P (phosphorus)]

Oxidation of the metal constituting the sintered body can be prevented by containing P in the sintered body.

That is, it is preferable to use alloy powder, such as Cu-Ni-Zn-Sn alloy powder, as a raw material powder when generating the raw material powder which will form a sintered body as mentioned later.

Here, alloy powders such as Cu-Ni-Zn-Sn alloy powders are produced by an atomization method or the like. Specifically, alloy powder is produced by generating molten metal obtained by melting various raw materials constituting the target alloy powder at high temperature, spraying/quick solidifying the generated molten metal, and pulverizing.

At this time, in the raw metal, the oxidation of the molten metal can be prevented by adding a trace amount of P as a deoxidizer.

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

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

[About average crystal grain size]

If the average crystal grain size of the crystal grains constituting the sintered body of the crystal structure (fine structure) exceeds 20 μm, the requirements for sintered bearings installed in a motor of a liquid pump (in particular, a liquid pump mounted in an automobile) may not be satisfied. Risk of 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 be 20 μm or less, it is possible to satisfy the requirements for sintered bearings installed in the motors of liquid pumps (in particular, liquid pumps installed in automobiles). Mechanical strength and vibration resistance.

[About effective porosity]

Here, in the sintered bearing of the first or second invention, it is preferable that the effective porosity of the sintered body is 8 volume % or more and 18 volume % or less.

That is, if the effective porosity is less than 8% by volume, the density becomes very high, the pressure required for powder compaction increases, and the productivity decreases. On the other hand, when the effective porosity exceeds 18 vol %, the strength of the green compact is lowered, so that the workability until sintering becomes difficult. In addition, since the sintering strength is lowered, the minimum strength required as a bearing cannot be obtained.

Therefore, by setting the effective porosity to 8 vol % or more and 18 vol % or less, the reduction in productivity can be suppressed and the sintering strength can be improved.

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, 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, rusting of the bearing can be prevented by the lubricating oil impregnated during the period from the manufacture of the bearing to the assembly of the motor, and even during the period until the motor is used. In addition, when the bearing portion is sealed and isolated from the flow path for conveying the liquid, an oil film can be formed between the rotating shaft and the rotating shaft according to the rotation of the rotating shaft, and the frictional resistance between the rotating shaft and the rotating shaft can be reduced. Furthermore, even when the bearing portion is not sealed and used in the conveying liquid, the lubricating oil impregnated in the bearing body will be replaced by the conveying liquid as a result, but by using the lubricating oil with a higher viscosity than the conveying liquid, To help lubricate at the beginning of operation.

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

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 comprises: mixing a plurality of powders to form raw material powder; compressing the raw material powder to form a compact; sintering the compact to form a sintered compact; and The step of applying sizing to the sintered body; wherein, the plurality of powders include Cu-Ni-Zn-Sn alloy powder and solid lubricant; the 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 lubricant , and the rest is composed of Cu and unavoidable impurities; the average crystal grain size of the aforementioned sintered body is 20 μm or less.

In addition, the method for manufacturing a sintered bearing of the seventh invention comprises the steps of: mixing a plurality of powders to form raw material powders; compressing the raw material powders to form a powder compact; sintering the compacted powder to form a sintered compact ; 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 full mass In terms of ratio, it contains more than 10 mass % and less than 20 mass % of Ni, more than 13 mass % and less than 20 mass % of Zn, more than 0.5 mass % and less than 3 mass % of Sn, more than 0.5 mass % and less than 0.5 mass % 4 mass % of the solid lubricant and less than 0.05 mass % of P, and the rest is composed of Cu and inevitable impurities; the average crystal grain size of the sintered body is 20 μm or less.

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

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

Moreover, in the manufacturing method of the sintered bearing of the sixth or seventh invention, Sn is added to the raw material powder. Thereby, the sinterability at the time of sintering can be improved, and the sintering strength of the sintered bearing can be improved, and 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 manufacturing method of the sintered bearing of the sixth invention, P is not added to the raw material powder. Moreover, in the manufacturing method of the sintered bearing of 7th invention, the addition amount of P in a raw material powder is less than 0.05 mass % as a mass ratio with respect to the whole 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 alloy layer of Ni-Sn-P can be suppressed, and the rotating shaft can be prevented from being damaged when the shaft rotates.

Furthermore, in the method for producing 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 installed in the motor of the liquid pump (especially, the liquid pump mounted in an automobile) can be satisfied.

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

Here, in the Cu-Ni-Zn-Sn alloy powder, each constituent element (constituent element) such as Ni and Zn is uniformly dispersed in each particle constituting the powder.

In this way, by using the Cu-Ni-Zn-Sn alloy powder to form a sintered body, the sintered body can be prevented from becoming non-uniform in the concentrations of components such as Ni and Zn, and as a result, the sintered body can be prevented from becoming non-uniform. The occurrence of a state of selective corrosion of parts with low concentrations of Ni and Zn.

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

Here, the functions and effects of the elements constituting the raw material powder are the same as those of the elements constituting the sintered body of the first or second invention described above.

According to the sintered bearing or the manufacturing method of the sintered bearing of the present invention, 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‧‧‧Spit

20‧‧‧Sintered bearings

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 a water pump 1 .

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

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

FIG. 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 bearing of Comparative Examples 1 to 4.

Fig. 5 is a view showing an example of the metal structure of the sintered bearing of the embodiment.

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

FIG. 7 is a view showing the metal structure of the sintered bearing of Example 4. FIG.

FIG. 8 shows the result of Example 1 as an example of analyzing the cross section of the sintered bearing by EDX.

FIG. 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, a sintered bearing 20 according to an 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 used to circulate cooling water for engine cooling, a washer fluid pump used to spit out windshield washer fluid, an oil pump used to generate oil pressure in the hydraulic mechanism, and used to pressurize engine oil fuel pump, fuel pump for supplying fuel (gasoline, light oil, alcohol, etc.).

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

(Constitution 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 a water pump 1 . FIG. 2 is a cross-sectional view of the sintered bearing 20 .

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

The water pump 1 shown in FIG. 1 includes a casing 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 the cooling water and a discharge port 12 for discharging the cooling water. The suction port 11 is connected to the radiator via a hose (not shown). The discharge port 12 is connected to the water jacket via a hose (not shown).

Each sintered bearing 20 is fixed to the inner side 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 therethrough 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 . Moreover, 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, one end of the rotating shaft 32 a is supported by one sintered bearing 20 , and the other end of the rotating shaft 32 a is supported by another sintered bearing 20 . Thereby, the rotating shaft 32a is rotatably supported by the pair of sintered bearings 20. As shown in FIG.

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

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

(Constitution 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 sintering system is constituted to have a porous structure (porous structure) (see FIG. 5 ). In addition, the sintered system is configured to have a crystal structure (fine structure). In particular, the solid lubricant is dispersed in the sintered body.

Specifically, the sintering system consists of a Cu-Ni-Zn-Sn alloy.

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

Here, the sintered body may have a structure containing a trace amount of P. That is, the sintered body may be constituted by 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 mass %, preferably less than 0.04 mass %, in terms of mass ratio with respect to the total mass.

That is, regarding the sintered body, it is assumed that the sintered body contains more than 10 mass % and less than 20 mass % of Ni, and more than 13 mass % and less than 20 mass % of Zn in terms of mass ratio with respect to the total mass of the sintered body. , more than 0.5 mass % and less than 3 mass % of Sn, more than 0.5 mass % and less than 4 mass % of solid lubricants, and less than 0.05 mass % (preferably less than 0.04 mass %) of P, and the rest Part of it is composed of Cu and inevitable impurities.

As the solid lubricant, one of graphite, molybdenum disulfide and boron nitride can be used. Alternatively, the solid lubricant may 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 sizes of crystal grains appearing in an observation region arbitrarily set in the sintered body.

In the present 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 for an image obtained by photographing at a predetermined magnification using a microscope. Here, in the length of 200 μm, the value obtained by subtracting the length of the pores was used as the reference length. Next, by dividing each reference length by the number of crystal grains present on the line segment, the average value of the particle diameters of the crystal grains present on the line segment (hereinafter, referred to as "each average value") is calculated. In addition, each average value calculated for each line segment was averaged with respect to 10 line segments, and the average crystal grain size was calculated.

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

As the lubricating oil, fluid paraffin, mineral-based lubricating oil, synthetic hydrocarbon-based lubricating oil, polysiloxane-based lubricating oil, and fluorine-based lubricating oil can be used. In addition, the sintered bearing 20 may not be impregnated with lubricating oil.

(Function/effect of sintered bearing 20)

Next, the action/effect of the sintered bearing 20 will be described.

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

Moreover, in the sintered bearing 20, the solid lubricant is contained in the sintered body. Thereby, slidability can be improved.

In addition, in the sintered bearing 20, Sn is contained in the sintered body (powder compact). As a result, the sinterability can be improved, and the sintering strength can be increased, and as a result, the sintering strength reduced 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. Thereby, rust of the bearing can be prevented by the lubricating oil impregnated during the period from the manufacture of the bearing to the assembly of the motor, and even until the period when the motor is used. In addition, when the bearing portion is sealed and isolated from the flow path for conveying the 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 of oil between the rotating shaft 32a and the bearing surface 21a can be reduced. frictional resistance. Furthermore, even when the bearing portion is not sealed and used in the transport liquid, the lubricating oil impregnated in the bearing body will be replaced by the transport liquid as a result, but by using the lubricating oil with a higher viscosity than the transport liquid, It can help with lubrication in the early stage 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 mass % in terms of mass ratio with respect 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 alloy layer of Ni—Sn—P can be suppressed, and the rotating shaft 32a can be prevented from being damaged when the shaft rotates.

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 the vibration resistance can be improved, and the mechanical strength and the vibration resistance required for the sintered bearing installed in the motor of the liquid pump (in particular, the liquid pump mounted in the automobile) can be satisfied.

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

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

[About Ni (nickel)]

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

At this time, when the content of Ni in the sintered body is 10 mass % or less, water resistance and corrosion resistance become insufficient. On the other hand, when the content of Ni in the sintered body is 20 mass % or more, the material cost increases.

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

[About Zn (zinc)]

Water resistance and corrosion resistance can be improved by containing Zn in the sintered body.

At this time, when the content of Zn in the sintered body is 13 mass % or less, water resistance and corrosion resistance become insufficient. On the other hand, if the content of Zn in the sintered body is 20 mass % or more, the productivity will decrease due to the evaporation of zinc during sintering, 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 reduction 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 content of Ni.

[About Sn (tin)]

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

At this time, when the Sn content in the sintered body is 0.5 mass % or less, the above-mentioned effects become insufficient. On the other hand, when the Sn content in the sintered body is 3 mass % or more, deformation due to dimensional changes during sintering tends to occur.

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

[About solid lubricants]

By including the solid lubricant in the sintered body, the lubricity can be improved, the friction coefficient can be reduced, and the burnout property and the wear resistance can be improved.

At this time, when the content of the solid lubricant in the sintered body is 0.5 mass % or less, the above-mentioned effects become insufficient. On the other hand, when the content of the solid lubricant in the sintered body is 4 mass % or more, the sintered strength is significantly lowered.

Therefore, by making the content of the solid lubricant in the sintered body more than 0.5% by mass and less than 4% by mass, the decrease in sintering strength can be suppressed and the wear resistance can be improved.

[About P (phosphorus)]

Oxidation of the metal constituting the sintered body can be prevented by containing P in the sintered body.

That is, it is preferable to use alloy powder, such as Cu-Ni-Zn-Sn alloy powder, as a raw material powder when generating the raw material powder which will form a sintered body as mentioned later.

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

At this time, in the raw metal, the oxidation of the molten metal can be prevented by adding a trace amount of P as a deoxidizer.

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

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

[About average crystal grain size]

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

Therefore, by setting the average grain size of the crystal grains constituting the sintered body to 20 μm or less, the mechanical strength and 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 molding increases, thereby reducing the productivity. On the other hand, when the effective porosity exceeds 18% by volume, the strength of the green compact is lowered, so that handling until sintering becomes difficult. In addition, since the sintering strength is lowered, the minimum strength required as a bearing cannot be obtained.

Therefore, by setting the effective porosity to 8 vol % or more and 18 vol % or less, the reduction in productivity can be suppressed and the sintering strength can be improved.

(Manufacturing method of sintered bearing 20 )

Next, the manufacturing method of the sintered bearing 20 is demonstrated.

In order 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 with respect to the total mass of the raw material powder, which contains more than 10 mass % and less than 20 mass % of Ni, more than 13 mass % and less than 20 mass % of Zn, and more than 0.5 mass % and not more than 0.5 mass %. It is composed of Sn in an amount of 3 mass %, a solid lubricant in an amount exceeding 0.5 mass % and less than 4 mass %, and the rest is composed of Cu and unavoidable impurities.

Alternatively, the raw material powder may contain a trace 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 mass %, preferably less than 0.04 mass %, in terms of mass ratio with respect to the total mass.

That is, regarding the raw material powder, it is assumed that it contains more than 10 mass % and less than 20 mass % of Ni and more than 13 mass % and less than 20 mass % of Zn in terms of mass ratio with respect to the total mass of the raw material powder. , more than 0.5 mass % and less than 3 mass % of Sn, more than 0.5 mass % and less than 4 mass % of solid lubricants, and less than 0.05 mass % (preferably less than 0.04 mass %) of P, and the rest Part of it is composed of Cu and inevitable impurities.

The raw material powder can be produced by 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 Multiple powders are used.

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

Here, if the diffusion of Ni and Zn in the raw material powder is insufficient, the concentrations of Ni and Zn in the sintered body become non-uniform. As a result, corrosion is likely to occur in the portion where the concentrations of Ni and Zn in the sintered body are low.

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

Therefore, when generating the raw material powder, it is preferable to reduce the type of metal powder used by using an alloy powder in which a plurality of metals are alloyed. Thereby, the diffusion of Ni and Zn in the raw material powder can be suppressed from becoming insufficient.

Therefore, it is preferable that the powder used for the generation of the raw material powder contains at least one kind of alloy powder. Alternatively, the powder used for the generation of the raw material powder may contain two or more kinds of alloy powders The end is better. In particular, it is preferable that the powder used for the generation of the raw material powder 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 above-mentioned composition can be satisfied by the combination of the alloy powder.

In the present embodiment, a Cu-Ni-Zn-Sn alloy powder, which is one kind of alloy powder, is used as the alloy powder used for the generation of the raw material powder. Specifically, a raw material powder is produced using Cu-Ni-Zn-Sn alloy powder and a solid lubricant. Alternatively, a raw material powder is produced using Cu-Ni-Zn-Sn-P alloy powder and a solid lubricant. Thereby, the diffusion of Ni and Zn in the raw material powder can be more reliably suppressed from becoming insufficient.

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

As the mold lubricant, powders of metal soaps represented by zinc stearate, lithium stearate, etc., powders of fatty amides such as ethylenedistearylamine, or powders of wax-based lubricants such as polyethylene can be used. In addition, the mold lubricant system is not limited to these.

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

Specifically, the generated raw material powder is accommodated in a mold. Then, the raw material powder accommodated in the mold is press-molded at a pressure of 100 to 500 MPa to form a powder compact.

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 powder compact, adjacent metal particles are diffusely bonded, and the metal particles are bonded to form a sintered body (sintered metal) with a porous structure.

The predetermined environment is in vacuum, in reducing gas (ammonia decomposition gas, hydrogen, endothermic gas, etc.), in inert gas (nitrogen, argon, etc.), in the mixed gas of these reducing gas and inert gas, etc., It is appropriately selected 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 more, and is appropriately selected according to the composition of the raw material powder. In the present embodiment, the cooling rate is set to 30°C/min. Thereby, the average crystal grain size of the sintered body can be made 20 μm or less.

Next, scale correction is applied to the sintered body.

Specifically, the formed sintered body is housed in a mold. Further, the sintered body accommodated in the mold is subjected to dimension correction (recompression) to form a recompressed body. By applying dimensional correction to the sintered body, dimensional accuracy is improved and surface roughness is improved.

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

Next, the cleaned recompressed body is impregnated with lubricating oil. Thereby, the sintered bearing 20 is completed. In addition, the sintered bearing 20 may be a structure not impregnated with lubricating oil.

(Action/effect of the manufacturing method of the sintered bearing 20)

In the method of manufacturing the sintered bearing 20 , the sintered bearing is formed from raw material powder based on nickel silver (Cu-Ni-Zn). 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 raw material powder. Thereby, the sliding property 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. Thereby, the sinterability at the time of sintering can be improved, and the sintering strength of the sintered bearing 20 can be improved, and 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 manufacturing method of the sintered bearing 20, P is not added to the raw material powder. Alternatively, the amount of P added in the raw material powder is less than 0.05% by mass in terms of the mass ratio with respect 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 the rotating shaft can be prevented from being damaged when the shaft rotates.

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 the vibration resistance can be improved, and the mechanical strength and the vibration resistance required for the sintered bearing installed in the motor of the liquid pump (in particular, the liquid pump mounted in the automobile) can be satisfied.

Moreover, in the manufacturing method of the sintered bearing 20, the Cu—Ni—Zn—Sn alloy powder and the solid lubricant powder are mixed to form the raw material powder. Alternatively, the Cu-Ni-Zn-Sn-P alloy powder and the solid lubricant powder are mixed to form the raw material powder. Thereby, in the sintered body, the concentration of each of the constituent elements such as Ni and Zn can be prevented from becoming non-uniform, and as a result, the occurrence of selective corrosion of the portion where the concentrations of Ni and Zn are low in the sintered body can be prevented.

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 described.

In the embodiment of the present invention, four kinds of sintered bearings (Examples 1 to 4) were manufactured. In addition, the comparative example produced four kinds of sintered bearings (Comparative Examples 1 to 4).

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

That is, the sintered systems of the sintered bearings of Examples 1 to 3 contained more than 10% by mass and less than 20% by mass of Ni, and more than 13% by mass in terms of the mass ratio relative to the total mass of the raw material powder (sintered body). 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 lubricant, and the rest is composed of Cu and inevitable impurities composition.

On the other hand, in the sintered system of the sintered bearing of Example 4, in terms of the mass ratio with respect to the total mass of the raw material powder (sintered body), it contained more than 10 mass % and less than 20 mass % of Ni, more than 13 mass % and Zn less than 20% by mass, Sn more than 0.5% by mass and less than 3% by mass, solid lubricant more than 0.5% by mass and less than 4% by mass, and P less than 0.05% by mass, and the rest is composed of Cu and unavoidable impurities.

In addition, in the sintered bearings of Examples 1 to 4, the combinations of the powders used for the generation of the raw material powders were different from each other.

On the other hand, the sintered bearings of Comparative Examples 1 to 4 were produced using raw material powders having compositions different from those of the present invention. Accordingly, the sintered systems of the sintered bearings of Comparative Examples 1 to 4 had compositions different from those of the present invention. Specifically, the firing of the sintered bearings of Comparative Examples 1 to 4 The compact (raw material powder) is constituted by containing 0.05 mass % or more of P in a mass ratio with respect 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 the powders used for the generation of the raw material powders were different from each other.

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

Specifically, the raw material powder accommodated in the mold is press-molded at a pressure of 100 to 500 MPa to form a powder compact. Then, after sintering the powder compact at a sintering temperature of 800 to 950° C. in an ammonia decomposition gas, it is 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.

(The composition of each sintered bearing)

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

In addition, each number shown in FIG. 3 represents the ratio (unit: mass %) of the mass of each powder (alloy powder or solid lubricant) to the whole mass of a raw material powder.

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

The raw material powders of the sintered bearings of Examples 1 to 3 were 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 was mixed by stirring and mixing 97.5 mass % Cu-14Ni- 14Zn-2Sn alloy powder and 2.5 mass % graphite powder are produced.

The raw material powder of the sintered bearing of Example 2 was obtained by stirring and mixing 96.5% by mass of Cu-14Ni-14Zn-2Sn alloy powder and 3.5% by mass of graphite based on the mass ratio relative to the total mass of the raw material powder (sintered body). generated from powder.

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

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

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

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

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

The raw material powder of the sintered bearing of Comparative Example 4 was obtained 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 mass % graphite powder are produced.

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

In addition, each number shown in FIG. 4 represents the ratio (unit: mass %) of the mass of each element (alloy powder or solid lubricant) to the whole mass of the raw material powder (sintered body).

As shown in Fig. 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, which consists of 68.3 mass % of Cu, 13.7 mass % of Ni, and 13.7 mass % of Zn , 2.0 mass % of Sn, and 2.5 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, which consists of 67.6 mass % of Cu, 13.5 mass % of Ni, 13.5 mass % of Zn, 1.9 mass % of 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, which consists of 69.6 mass % of Cu, 13.9 mass % of Ni, 13.9 mass % of Zn, 2.0 mass % of Sn, and 0.6 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, which consists of 68.3 mass % of Cu, 13.7 mass % of Ni, 13.7 mass % of Zn, 2.0 mass % of Sn, It consists of 0.03 mass % of P and 2.5 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, which consists of 68.0 mass % of Cu, 13.6 mass % of Ni, 13.6 mass % of Zn, 2.2 mass % of Sn, It consists of 0.2 mass % of P and 2.5 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 material powder, which consists of 66.7 mass % of Cu, 13.2 mass % of Ni, 13.2 mass % of Zn, 2.2 mass % of Sn, It consists of 0.2 mass % of P and 4.5 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 material powder, consisting of 74.3 mass % of Cu, 9.0 mass % of Ni, 9.0 mass % of Zn, 5.0 mass % of Sn, It consists of 0.2 mass % of P and 2.5 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, which consists of 63.5 mass % of Cu, 16.8 mass % of Ni, 16.8 mass % of Zn, 0.3 mass % of P, and 2.5% by mass of C.

(Metallic structure of each sintered bearing)

Fig. 5 is a view showing an example of the metal structure of the sintered bearing of the embodiment. FIG. 6 is a diagram showing an example of the metallographic structure of the sintered bearing of the comparative example.

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

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

FIG. 6 is a photograph showing 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 represented by the symbol "A". As shown in FIG. 6 , in the metal structure of the sintered bearing of Comparative Example 1, it can be seen that the alloy layer of Ni—Sn—P 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, in the metal structure of the sintered bearing of Example 1, it turns out that the alloy layer of Ni-Sn-P does not precipitate. Therefore, according to the sintered bearing of Embodiment 1, the rotating shaft can be prevented from being damaged 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 contains 0.03% by mass of P in terms of the mass ratio with respect to the total mass of the raw material powder. However, as shown in FIG. 7, in the metallographic structure of the sintered bearing of Example 4, the alloy layer of Ni-Sn-P was not precipitated. Therefore, according to the sintered bearing of the fourth embodiment, the rotating shaft can be prevented from being damaged when the shaft rotates.

Further, 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, the average crystal grain size of the sintered bearing of Example 1 was confirmed to be 8.1 μm, and the average crystal grain size of the sintered bearing of Example 2 was confirmed to be 8.7 μm. The average crystal grain size of the sintered bearing of Example 3 was confirmed to be 8.5 μm, and the average crystal grain size of the sintered bearing of Example 4 was confirmed to be 8.3 μm.

On the other hand, the average grain size of the sintered bearing of Comparative Example 1 was confirmed to be 28.4 μm, and the average grain size of the sintered bearing of Comparative Example 2 was confirmed to be 27.8 μm. The average grain size of the sintered bearing of Comparative Example 3 was confirmed to be 28.6 μm, and the average grain size of the sintered bearing of Comparative Example 4 was confirmed to be 33.4 μm.

As described above, it was found that in the sintered bearings of Examples 1 to 4, the average crystal grain size was 20 μm or less. On the other hand, in the sintered bearings of Comparative Examples 1 to 4, it was found that the average crystal grain size exceeded 20 μm.

Therefore, according to the sintered bearings of Examples 1 to 4, as compared with the sintered bearings of Comparative Examples 1 to 4, the mechanical strength and the vibration resistance are improved.

(Result of concentration analysis of each element)

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

In Fig. 8, the distribution of each constituent element (Cu, Ni, Zn, Sn) in the cross section of the sintered bearing of Example 1 is plotted. In particular, Fig. 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). In addition, in Fig. 8, the lighter the color, the higher the density.

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

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

Therefore, in the sintered bearing of Example 1, in the sintered body, the occurrence of portions with low concentrations of Ni and Zn is suppressed, and as a result, the occurrence of selective corrosion of portions with low concentrations of Ni and Zn can be prevented.

(Characteristics of sintered bearings)

FIG. 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, Fig. 9 shows the advantages and disadvantages of each characteristic (corrosion resistance, pressure ring strength, vibration resistance, friction coefficient) with symbols (“◎”, “○”, “△”, and “×”). At this time, each symbol indicates the degree of excellent characteristics in the order of "◎", "○", "△", and "×". In particular, the characteristic with the appendix "x" indicates that it does not satisfy the standard required as a bearing for a liquid pump.

As shown in Fig. 9, it can be seen that the sintered bearings of Examples 1 to 4 satisfy the standards required as bearings for liquid pumps with respect to the properties of corrosion resistance, pressure ring strength, vibration resistance, and friction coefficient.

On the other hand, as shown in Fig. 4, in the raw material powder of the sintered bearing of Comparative Example 1, the average crystal grain size of the sintered body was large because 0.2 mass % of P was added in terms of mass ratio to the total mass. It was found that the vibration resistance was insufficient as shown in FIG. 9 . In addition, the corrosion resistance depends on the use of The Cu-18Ni-18Zn alloy powder and the Cu-11Sn alloy powder were confirmed to be selectively corroded at the portion where the concentrations of Ni and Zn are low.

Moreover, as shown in FIG. 4, in the raw material powder of the sintered bearing of Comparative Example 2, the content of C (solid lubricant) was 4 mass % or more in terms of mass ratio with respect to the total mass. Therefore, in the sintered bearing of Comparative Example 2, the sintered strength decreased. As a result, as shown in FIG. 9, it can be seen that in the sintered bearing of Comparative Example 2, the strength of the pressure ring 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 in terms of mass ratio relative to the total mass, and the content of Zn is in terms of mass ratio relative to the total mass. The mass ratio of the whole mass was considered 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 the comparative example 3, the content of Sn was 3 mass % or more by mass ratio with respect to the whole mass. Therefore, in the sintered bearing of Comparative Example 3, deformation due to dimensional changes during sintering is likely to occur, and precipitation of the hard Ni-Sn-P alloy layer is promoted. As a result, as shown in FIG. 9, it can be seen that in the sintered bearing of Comparative Example 3, the coefficient of friction is increased.

On the other hand, as shown in FIG. 4, the content of P in the raw material powder of the sintered bearing of Comparative Example 4 is higher than that of the sintered bearings of Comparative Examples 1 to 3. 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 with respect to the total mass. Therefore, it was found that the average crystal grain size of the sintered body was as large as 33.4 μm, and the vibration resistance was insufficient. In addition, as shown in FIG. 4, the raw material powder of the sintered bearing of Comparative Example 4 did not contain Sn. Therefore, in the sintered bearing of Comparative Example 4, it was found that the sintered strength was lowered. 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 lowered.

In particular, as shown in FIG. 4, the content of C (solid lubricant) in the raw material powder of the sintered bearing of Example 2 is higher than that of the sintered bearing of Example 1. 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, in order to prioritize the reduction of the friction coefficient, in the composition of the present invention, the content of C (solid lubricant) is preferably 3 mass % or more, particularly 3.5 mass % or more.

Moreover, 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 small. Therefore, as shown in FIG. 9, it can be seen that the strength of the pressure ring of the sintered bearing of Example 3 is improved compared with that of the sintered bearing of Example 1. Therefore, in the composition of the present invention, it is preferable to set the content of C (solid lubricant) to 1 mass % or less in order to give priority to the improvement of the strength of the pressing ring.

Claims (7)

A sintered bearing composed of a sintered body with an average crystal grain size of 20 μm or less, the sintered system having more than 10 mass % and less than 20 mass % of Ni, more than 13 Mass % and less than 20 mass % of Zn, more than 0.5 mass % and less than 3 mass % of Sn, and more than 0.5 mass % and less than 4 mass % of solid lubricants, effective porosity of 8 volume % or more and 18 Volume % or less, and the rest is composed of Cu and inevitable impurities. A sintered bearing composed of a sintered body with an average crystal grain size of 20 μm or less, the sintered system having more than 10 mass % and less than 20 mass % of Ni, more than 13 Zn in 20 mass % or less, Sn in excess of 0.5 mass % and 3 mass %, solid lubricant in excess of 0.5 mass % and 4 mass %, and P in 0.05 mass % or less, effectively porous The ratio is 8 vol % or more and 18 vol % or less, and the rest is composed of Cu and unavoidable impurities. The sintered bearing according to claim 1 or 2, wherein the solid lubricant contains at least one of graphite, molybdenum disulfide and boron nitride. The sintered bearing as described in claim 1 or 2 of the claimed scope is obtained by impregnating the sintered body with lubricating oil. The sintered bearing described in claim 1 or 2 of the scope of the application is used in a motor of a liquid pump. A method for manufacturing a sintered bearing, comprising: mixing a plurality of powders to generate raw material powder; compressing the raw material powder to form a powder compact; The step of sintering the powder compact 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 and solid lubricant, and the raw material powder is It contains more than 10 mass % and less than 20 mass % of Ni, more than 13 mass % and less than 20 mass % of Zn, and more than 0.5 mass % and less than 3 mass % of Sn in terms of mass ratio with respect to the total mass , and more than 0.5 mass % and less than 4 mass % of the solid lubricant, and the rest is composed of Cu and unavoidable impurities, and the effective porosity of the aforementioned sintered body is 8 volume % or more and 18 volume % or less, The average crystal grain size is 20 μm or less. A method for manufacturing a sintered bearing, comprising: mixing a plurality of powders to generate raw material powder; compressing the raw material powder to form a compact; sintering the compact to form a sintered compact; 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, and the raw material powder has a mass ratio relative to the total mass, containing More than 10 mass % and less than 20 mass % of Ni, more than 13 mass % and less than 20 mass % of Zn, more than 0.5 mass % and less than 3 mass % of Sn, more than 0.5 mass % and less than 4 mass % Solid lubricant, and P less than 0.05% by mass, and the rest is composed of Cu and unavoidable impurities, the effective porosity of the sintered body is 8% by volume or more and 18% by volume or less, and the average crystal grain size is 20 μm or less.

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