JP2002285266A - Bearing made of copper based sintered alloy of motor type fuel pump and motor type fuel pump incorporated with the bearing - 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 and high speed circulation of a liquid fuel. SOLUTION: The bearing of a motor type fuel pump consists of a Cu based sintered alloy having a composition containing, by mass, 10 to 25% Ni, 10 to 25% Zn, 0.1 to 0.9% P and 0.5 to 5% MoS2 , and the balance Cu with inevitable impurities, 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-Zn 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, in a casing 1, rotating shafts 2 fixed to both ends of a motor 5 are supported by bearings 3a and 3b, and one end of the rotating shaft 2 is provided with an impeller. 4 is inserted, and a gasoline flow passage having a narrow gap is formed along an outer peripheral surface of the impeller 4, an outer peripheral surface of the motor (armature) 5, and a gap (not shown) between the bearings 3a, 3b and the rotary shaft 2. The impeller 4 rotates by the rotation of the motor 5, and gasoline is taken into the casing 1 by the rotation of the impeller 4, and the taken gasoline is applied to the outer peripheral surface of the impeller 4 and the outer peripheral surface of the motor 5. It is sent out through the gasoline flow path formed along the way and operates so as to be sent into a separate gasoline engine. In FIG. 1, a small amount of fuel passes between the inner surfaces of the bearings 3a and 3b and the outer peripheral surface of the rotary shaft 2, and plays a role of lubricating oil for sliding the rotary shaft. 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, the weight and performance of engines such as automobiles have been remarkably reduced in recent years, and accordingly, motor-type fuel pumps used in these engines have been strongly required to be reduced in size. However, in the case of the above-mentioned motor-type fuel pump, high drive, that is, a high rotation speed is required to reduce the size while ensuring the discharge performance. The bearing which is a structural member of the above is required to have higher strength and wear resistance, but in the conventional Cu-based sintered alloy bearing used in the motor type fuel pump described above, Since it does not have sufficient strength and wear resistance, the wear progresses rapidly, and the wear progress is further accelerated when the liquid fuel contains sulfur or its compound as impurities. Becomes way, the reach this result relatively short time service life 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: 10 to 25%, Zn: 10 to 25%, P: 0.1 to 0.9%, molybdenum disulfide (hereinafter, referred to as MoS ₂ ) in mass% (hereinafter,% indicates mass%) : 0.5 ~
5%, with the balance consisting of Cu and unavoidable impurities, and a base made of a solid solution phase of a Cu-Ni-Zn-based alloy, a hard Cu-P compound and MoS having high lubricity.
₂ is composed of a Cu-based sintered alloy having a dispersed and distributed structure and having a porosity of 5 to 25%. It is alleviated by the action of the fluid lubricating film 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, while the wear resistance is reduced by the amount of the pores. However, this decrease in wear resistance is compensated for by the highly lubricating MoS ₂ dispersed and distributed in the matrix similarly to the hard Cu-P compound dispersed and distributed in the matrix composed of the solid solution phase of the Cu-Ni-Zn alloy. Therefore, the resulting Cu-based sintered alloy bearing is exposed to a high-pressure and high-speed flow of liquid fuel, in combination with the excellent strength and corrosion resistance of the Cu-Ni-Zn-based alloy forming the base. Environment Research has shown that the bearings made of loose abrasion resistance exhibited excellent resistance to liquid fuel containing sulfur and its compounds as impurities. It was.

The present invention has been made on the basis of the above research results, wherein Ni: 10 to 25%, Zn: 10 to 25%, P: 0.1 to 0.9%, and MoS ₂ : 0 And a base composed of a solid solution phase of a Cu-Ni-Zn-based alloy, a hard Cu-P compound and MoS having high lubricity.
₂ is a motor-type fuel having a structure in which the particles are dispersed and distributed, and further comprising a Cu-based sintered alloy having a porosity of 5 to 25%. The present invention has a feature in a Cu-based sintered alloy bearing of a pump.

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 and Zn These components are dissolved in Cu together with
It has the effect of forming a base consisting of a solid solution phase of a u-Ni-Zn-based alloy and improving the strength and corrosion resistance of the bearing.
If the content exceeds 5%, the strength decreases, and if the content of Zn is less than 10%, the corrosion resistance decreases, while if the content exceeds 25%, the strength sharply decreases. Therefore, the content of each of Ni: 10 to 25%, desirably 15 to 20%, Z
n: 10 to 25%, preferably 15 to 20%.

(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 base material, imparts excellent lubricity to the bearing, and thus contributes to the improvement of the wear resistance of the bearing. If the content is less than 0.5%, the desired excellent lubricity cannot be ensured. On the other hand, if the content exceeds 5%, the strength rapidly decreases. %, Desirably 1 to 3%, respectively.

(2) Porosity The porosity dispersed in the Cu-Ni-Zn alloy base material reduces the strong friction and high surface pressure applied to the bearing under the high-pressure and high-speed flow of the liquid fuel as described above. Has the effect of significantly suppressing the wear of the steel, but if the porosity is less than 5%,
When the porosity exceeds 25%, the strength of the bearing rapidly decreases because the ratio of the pores distributed in the base material is too small to sufficiently exert the above-mentioned effect. The porosity is determined to be 5 to 25%, preferably 10 to 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 raw material powders, various Cu-Ni-Zn alloy powders formed by a water atomization method and each having an average particle diameter of 45 µm, but having different contents of Ni and Zn, water having an average particle diameter of 45 µm Atomized Cu-P alloy (P: 33%
Containing) powder, MoS with an average particle size of 75 μm
₂ powders are prepared, and these raw material powders are blended in a predetermined composition and mixed for 40 minutes by a ball mill.
A green compact is press-molded at a predetermined pressure in the range of 0 MPa, and this green compact is placed in an ammonia decomposition gas atmosphere at 750
By sintering at a predetermined temperature in the range of up to 900 ° C. for 40 minutes, each is made 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 21 of the present invention having dimensions of × inner diameter: 5 mm × height: 6 mm were manufactured. When an arbitrary cross section of the resulting sintered bearings 1 to 21 of the present invention obtained as described above was observed using an optical microscope (200 ×),
Both Cu-Ni-Zn-based green body to a fine Cu-P alloy and MoS ₂ consisting of a solid solution phase of the alloy are dispersed distribution, and showed pores also present tissue. For the purpose of comparison, Cu was used under the same conditions except that the composition was as shown in Table 1.
Bearings 1 to 10 made of a base sintered alloy (hereinafter referred to as comparative sintered bearings) were prepared. Each of the comparative sintered bearings 1 to 10 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-described sintered bearings 1 to 21 of the present invention and comparative sintered bearings 1 to 10 have the outer dimensions of 110 m in length.
m × Diameter: incorporated in a 40 mm fuel pump, this fuel pump was installed in a gasoline tank, and the rotation speed of the impeller: 3000 (minimum rotation speed) to 1200
0 (maximum rotational speed) r. p. m. Gasoline flow rate: 45 liters / hour (minimum flow rate) ~ 17
0 liters / hour (maximum flow rate), the pressure that the bearing receives from the high-speed rotating shaft: maximum 300 KPa, test time: 150 hours, that is, gasoline flows through a narrow gap at high speed,
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 21 of the present invention, the Cu-based sintered alloy constituting the sintered bearings 1 to 21 has a high strength and the Cu-Ni-Zn-based alloy Due to the excellent corrosion resistance of the solid solution phase, the effect of pores and a hard Cu-P alloy dispersed and distributed on the base material thereof, and the effect of MoS ₂ having high lubricity, the high pressure and high speed While exhibiting even better wear resistance under distribution, comparative sintered bearings 1-1
As can be seen from FIG. 0, if any one of the component content and the porosity of the Cu-based sintered alloy constituting the same deviates from the scope of the present invention, a decrease in at least one of the strength and the wear resistance is avoided. It is clear that this is not possible. 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. Excellent abrasion resistance even when used in an environment subject to high surface pressure from the rotating shaft and exposed to a high-speed flow of liquid fuel, and even when liquid fuel contains sulfur or its compounds as impurities. Therefore, it is possible to satisfactorily cope with a reduction in the weight of an engine using a liquid fuel and an improvement in its performance.

[Brief description of the drawings]

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

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 1/10 C22C 1/10 J 9/04 9/04 32/00 32/00 DE F02M 37/08 F02M 37/08 E (72) Inventor Tsuneo Maruyama 3-1 Koganemachi, Niigata City, Niigata Prefecture Mitsubishi Materials Corporation Niigata Works (72) Inventor Yoshio Ebihara 1-1-1 Showa-cho, Kariya City, Aichi Prefecture DENSO Corporation F term (reference) 4K018 AA04 AB05 AC01 BA20 DA11 KA03 KA22 4K020 AA22 AA23 AA27 AC04 BB29

Claims (2)

[Claims] 1. The composition contains Ni: 10 to 25%, Zn: 10 to 25%, P: 0.1 to 0.9%, and molybdenum disulfide: 0.5 to 5% by mass%. Is C
u and unavoidable impurities, and Cu-Ni-Z
C, which 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 an n-based alloy, and further has a porosity of 5 to 25%
A bearing made of a Cu-based sintered alloy for a motor-type fuel pump that exhibits excellent abrasion resistance under high-pressure and high-speed flow of liquid fuel, comprising a u-based sintered alloy. 2. A motor type fuel pump incorporating the Cu-based sintered alloy bearing according to claim 1.