JP2002180163A - BEARING MADE OF Cu BASED SINTERED ALLOY FOR MOTOR TYPE FUEL PUMP - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing of a motor type fuel pump which exhibits excellent wear resistance under the high pressure-high speed passage of a liquid fuel. SOLUTION: The bearing of a motor type fuel pump is consisting of a Cu based sintered alloy having a composition containing, by mass, 20 to 40 Ni, 0.1 to 0.9% P and 0.5 to 5% MoS2, and the balance Cu with inevitable impurities, and having a structure in which a hard Cu-P compound and MoS2 having high lubricity are dispersedly distributed into a base consisting of a solid solution phase of a Cu-Ni based alloy, and having a porosity of 5 to 25% as well.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Cu-based sintered alloy bearing which exhibits excellent wear resistance particularly when applied to a motor type fuel pump which is miniaturized and operated at a high speed. .

[0002]

2. Description of the Related Art Conventionally, an engine using a liquid fuel such as gasoline or light oil as a fuel is generally provided with a motor-type fuel pump. For example, FIG. 1 is a schematic cross-sectional view of a motor-type fuel pump for a gasoline engine. Is known. That is, as shown in the figure, in the motor-type fuel pump, a rotating shaft fixed to both ends of a motor is supported by bearings in a casing, an impeller is inserted into one end of the rotating shaft, and the impeller is A gasoline flow passage with a narrow gap formed along an outer peripheral surface of a motor (armature) and a gap (not shown) between the bearing and the rotating shaft, and the rotation of the motor causes the impeller to rotate. Gasoline is taken into the casing by the rotation of the impeller, and the taken-in gasoline is sent out through the gasoline flow passage formed along the impeller, the outer peripheral surface of the motor, and a gap (not shown) between the bearing and the rotating shaft. It operates so that it is fed into a separate gasoline engine. In FIG. 1, a small amount of fuel passes through the outer peripheral portions of the two bearings, and gasoline pressurized by the impeller reaches the outer peripheral surface of the armature through a fuel passage of a casing (not shown). Also, various Cu-based sintered alloys are used as the bearings, which are structural members of the motor-type fuel pump.

[0003]

On the other hand, in recent years, for example, engines such as automobiles have been remarkably reduced in weight and improved in performance, and accordingly, motor-type fuel pumps used in the engines have been strongly required to be reduced in size. However, in the case of the motor-type fuel pump described above, in order to reduce the size while securing the discharge performance, it is necessary to increase the driving speed, that is, to increase the rotation speed. Liquid fuel, such as gasoline, passes through the narrower flow passage at high pressure and at a high flow rate, and under such conditions, the bearing, which is a structural member of the fuel pump, has a higher strength and higher durability. Although wear resistance is required, conventional Cu-based sintered alloy bearings used in the above-described motor-type fuel pump all have sufficient strength and wear resistance. Therefore, when the liquid fuel contains sulfur and its compounds as impurities, the wear progresses more rapidly, and as a result, the service life is relatively short. At present.

[0004]

Means for Solving the Problems Accordingly, the present inventors have:
From the above viewpoints, as a result of conducting research to develop bearings suitable for use in motorized fuel pumps that are miniaturized and operated at high drive, the bearings of motorized fuel pumps were
Ni: 20 to 4% by mass (hereinafter,% indicates mass%)
0%, P: 0.1~0.9%, molybdenum disulfide (hereinafter, indicated by MoS _2): 0.5~5%, containing, composition balance being Cu and inevitable impurities, and Cu- Ni
In a base material composed of a solid solution phase of a base alloy, a Cu-based sintered alloy having a structure in which a hard Cu-P compound and MoS ₂ having high lubricity are dispersed and distributed, and further having a porosity of 5 to 25%. With this configuration, the frictional resistance of the bearing caused by the high-speed rotation of the motor that generates the high-pressure high-speed flow of the liquid fuel is formed by the liquid fuel supplied from the outer peripheral surface of the bearing to the inner peripheral surface of the bearing through the pores present in the bearing. Is reduced by the action of the fluid lubricating film, while the wear resistance is reduced by the amount of the pores.
From being supplemented by Ni-based high lubricity MoS ₂ similarly dispersed distribution matrix and Cu-P compounds of the hard dispersed distribution matrix consisting of a solid solution phase of the alloy, Cu-based sintered alloy bearing made of the results of this Combined with the excellent strength and corrosion resistance of the Cu-Ni-based alloy forming the base material, the alloy exhibits excellent wear resistance in an environment exposed to a high-pressure and high-speed flow of a liquid fuel. Research results have shown that this Cu-based sintered alloy bearing exhibits excellent corrosion resistance even to liquid fuels containing sulfur and its compounds as impurities.

The present invention has been made based on the results of the above-mentioned research, wherein Ni: 20 to 40% and P: 0.
_{1~0.9%, MoS 2: 0.5~5%} , containing, composition balance being Cu and inevitable impurities, as well as Cu-N
A Cu-based sintered alloy having a structure in which a hard Cu-P compound and MoS ₂ having high lubricity are dispersed and distributed on a base made of a solid solution phase of an i-based alloy, and further having a porosity of 5 to 25%. The present invention is characterized in that the bearing is made of a Cu-based sintered alloy of a motor-type fuel pump which exhibits excellent wear resistance under high-pressure and high-speed flow of liquid fuel.

Next, the reason why the component composition and the porosity of the Cu-based sintered alloy constituting the bearing of the present invention are limited as described above will be described. (1) Component composition (a) Ni The Ni component forms a solid solution in Cu as described above,
Has the effect of forming a base consisting of a solid solution phase of the base alloy and improving the strength and corrosion resistance of the bearing, but its content is 2%.
If it is less than 0%, the desired high strength and high corrosion resistance cannot be ensured, and if one of the contents exceeds 40%, the strength is reduced.
It was determined to be 20 to 40%, preferably 21 to 30%.

(B) The PP component contributes to improving the bearing strength by improving the sinterability, and also forms a hard Cu-P alloy dispersed and distributed on the base material to improve the wear resistance. However, if the content is less than 0.1%, a desired improvement effect cannot be obtained in the above-mentioned action, while if the content exceeds 0.9%, the strength tends to decrease, and Since it is difficult to stably secure high strength, the content is 0.1 to
0.9%, desirably 0.3 to 0.6%.

(C) MoS _{2 The} MoS ₂ component is dispersed and distributed in the matrix as the MoS ₂ phase, imparts excellent lubricity to the bearing, and thus has the effect of contributing to the improvement of the wear resistance of the bearing. If the amount is less than 0.5%, the desired excellent lubricating property cannot be secured, while if the content exceeds 5%, the strength rapidly decreases. 5-5%, desirably 1-3%, respectively.

(2) Porosity Pores dispersed in the Cu-Ni-based alloy base material reduce strong friction and high surface pressure applied to the bearing under high-pressure and high-speed flow of liquid fuel, as described above, and thus wear of the bearing. However, if the porosity is less than 5%, the proportion of porosity distributed in the base material becomes too small and the above effect cannot be sufficiently exerted, while the porosity is 25%.
%, The strength of the bearing rapidly decreases, so that the porosity is 5 to 25%, preferably 10 to 25%.
It was set at 20%.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A bearing made of a Cu-based sintered alloy according to the present invention will be specifically described with reference to examples. As a raw material powder, various Cu— formed by a water atomization method and having an average particle diameter of 45 μm but different in Ni content.
Ni alloy powder, water atomized Cu-P alloy (containing 33% P) powder also having an average particle diameter of 45 μm, and MoS ₂ powder having an average particle diameter of 75 μm were prepared. And mixed with a ball mill for 40 minutes, and then pressed into a green compact at a predetermined pressure in the range of 150 to 300 MPa, and the green compact is heated in an ammonia decomposition gas atmosphere at a temperature of 750 to 900 ° C. By sintering at a predetermined temperature for 40 minutes under the conditions of holding, each is composed of a Cu-based sintered alloy having the composition and porosity shown in Table 1, and each has an outer shape of 9 mm
× Sintered bearings 1 to 20 of the present invention having dimensions of × inner diameter: 5 mm × height: 6 mm were produced. An arbitrary cross section of the sintered bearings 1 to 20 of the present invention obtained as a result is taken with an optical microscope (20
0 ×), it was found that a fine Cu-P alloy and M
It showed a structure in which oS ₂ was dispersed and had pores. Further, for the purpose of comparison, bearings (hereinafter referred to as comparative sintered bearings) 1 to 8 each made of a Cu-based sintered alloy were prepared under the same conditions except that the compositions were as shown in Table 1. Each of the comparative sintered bearings 1 to 8 is made of a Cu-based sintered alloy in which one of the alloy component content and the porosity is out of the range of the present invention.

Next, the above-mentioned sintered bearings 1 to 20 of the present invention and comparative sintered bearings 1 to 8 have an outer dimension of 110 mm in length.
X Incorporated in a 40 mm diameter fuel pump, this fuel pump was installed in a gasoline tank, and the impeller rotation speed: 3000 (minimum rotation speed)-8000
(Maximum number of rotations) r. p. m. Gasoline flow rate: 45 liters / hour (minimum flow rate) ~ 12
0 liters / hour (maximum flow rate), the pressure that the bearing receives from the high-speed rotating shaft: maximum 300 KPa, test time: 250 hours
An actual machine test was performed under the condition that the bearing was subjected to high pressure by the high-speed rotating shaft of the motor and exposed to gasoline at a high flow rate, and the maximum wear depth on the bearing surface after the test was measured. The measurement results are also shown in Table 1. Table 1 shows the crushing strength of each sintered bearing for the purpose of evaluating the strength.

[0012]

[Table 1]

[0013]

According to the results shown in Table 1, in the sintered bearings 1 to 20 of the present invention, the Cu-based sintered alloy constituting each of the sintered bearings has high strength, and the solid solution phase of the Cu-Ni alloy is obtained. The excellent corrosion resistance of MoS2, which has excellent corrosion resistance, and pores and hard Cu-P alloy dispersed and distributed over the base material, and MoS ₂ having high lubricity, especially as a bearing for motor type fuel pumps, under high pressure and high speed flow of gasoline Thus, while exhibiting even better wear resistance, as seen in the comparative sintered bearings 1 to 8, any one of the component content and the porosity of the Cu-based sintered alloy constituting the same is It is evident that departures from the scope of the invention inevitably result in a reduction in strength and / or wear resistance. As described above, the Cu-based sintered alloy bearing of the present invention is used not only for motor-driven fuel pumps of engines using ordinary liquid fuels, but also in particular with the miniaturization and high drive of motor-driven fuel pumps. The liquid fuel contains sulfur and its compounds as impurities even when used in an environment where it is exposed to a high surface pressure from the rotating shaft and exposed to a high-speed flow of liquid fuel. In this case, since it exhibits excellent abrasion resistance, it can sufficiently cope with the reduction in weight and performance of an engine using liquid fuel.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a motor fuel pump for a gasoline engine.

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Claims (1)

[Claims] 1. The composition contains, by mass%, Ni: 20 to 40%, P: 0.1 to 0.9%, and molybdenum disulfide: 0.5 to 5%, with the balance being Cu and unavoidable impurities. The composition has a structure in which a hard Cu-P compound and molybdenum disulfide having high lubricity are dispersed and distributed on a base made of a solid solution phase of a Cu-Ni alloy, and further has a porosity of 5 to 25%. A motor-driven fuel pump bearing made of a Cu-based sintered alloy, which exhibits excellent wear resistance under high-pressure and high-speed flow of liquid fuel.