JPH0552221A - Sintered oil retaining bearing - Google Patents

Abstract

PURPOSE:To provide a sintered oil retaining bearing excellent in oil retaining performance and high in abrasion-resistance wherein a large sintering hole is secured without degrading mechanical strength. CONSTITUTION:A sintered oil retaining bearing has a composition containing 14 to 40wt.% of Sn, 0.5 to 4wt.% of C, remainder of Cu and inevitable impurity, and made of a sintered body wherein powder particulates 1 are fused to each other. An Sn diffusion layer 3 is formed on the surfaces of the powder particulates 1 opposed to a sintered hole 4 of the sintered body, while lubricating oil is impregnated into the sintered hole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered oil-impregnated bearing, and more particularly to a sintered oil-impregnated bearing which is excellent in lubricity and oil retention and is suitable as a bearing material for a portion which slides intermittently.

[0002]

2. Description of the Related Art Conventionally, bronze powder or copper (Cu) powder,
Sintered oil-impregnated bearing obtained by mixing graphite powder with metal powder such as tin (Sn) powder and lead (Pb) powder, compression-molding the mixture, and sintering the resulting porous body to impregnate lubricating oil. Are used as parts for automobiles and home appliances.

FIG. 5 and FIG. 6 are sectional views for explaining an example of use of a sintered oil-impregnated bearing arranged in a clutch of an automobile.
The clutch includes a flywheel 2 integrally formed with a crankshaft 1 on the engine side, a disc-shaped clutch disc 4 integrally formed with a clutch shaft 3 on the transmission side, and a driver 5 depresses a clutch pedal 6. Alternatively, the release operation causes the clutch disc 4 to pass through the hydraulic circuit 7 and the diaphragm spring 8.
Is released from the sliding surface of the flywheel 2 or is pressed against the sliding surface. Further, a pilot bush 10 as a sintered oil-impregnated bearing is press-fitted into the center of the flywheel 2 so as to receive and slidably support the end of the clutch shaft 3 that moves in the axial direction with gear shift.

By depressing the clutch pedal 6 as shown in FIG. 5, the clutch disc 4 pressed against the flywheel 2 by the clutch spring 8 is separated from the sliding surface, and the clutch shaft 3 is released from the rotational force of the engine. It At this time, the end portion of the clutch shaft 3 is in a state of being disengaged from the pilot bush 10.

On the other hand, when the clutch pedal 6 is released, the pressure plate 9 is urged toward the engine by the clutch spring 8, the clutch disc 4 is pressed against the flywheel 2, and the rotational force of the crankshaft 1 is transmitted to the clutch shaft 3. .. Thus, when the clutch is connected, the end portion of the clutch shaft 3 is fitted into the pilot bush 10. At this time crankshaft 1
And the relative rotational speed difference between the clutch shaft 3 (max. 7
(500-8000 rpm), the pilot bush 10 and the clutch shaft 3 are in sliding contact with each other at a high speed. Further, when the clutch disk 4 is completely pressed against the sliding surface of the flywheel 2 without slipping, the rotation speeds of the pilot bush 10 and the clutch shaft 3 become the same,
Both do not slide. In this way, the pilot bush 10
The clutch shaft 3 and the clutch shaft 3 intermittently slide each time the clutch switching operation is performed, but the lubricating oil impregnated inside the pilot bush 10 oozes out to the sliding surface, so that wear between both members is prevented. ..

Conventionally, as a sintered oil-impregnated bearing of this type, Sn has been used.
Is used, which is formed by shaving cutting powder prepared by shaving an ingot having a composition of 8 to 11 wt% and the balance substantially consisting of copper, and then impregnating it with lubricating oil.

[0007]

However, in the above-mentioned conventional pilot bush as a sintered oil-impregnated bearing, since the size of the sintered hole formed in the sintered body is small, the oil retaining property of the lubricating oil is poor, and particularly the pilot bush is used. When used for applications such as bushes that slide intermittently, oil may easily run out, and abnormal noise such as gear noise may occur when switching clutches, and the sliding parts may wear in a short period of time. was there.

According to the knowledge of the present inventors, in order to solve the above-mentioned problems, the size of the sintered hole is enlarged so that the lubricating oil is always floated on the sliding portion surface. It is necessary to form a sintered body that is a bearing base material.

However, simply using a coarse raw material powder to increase the size of the sintering pores leads to a decrease in the sintering density, and the strength as a bearing that is susceptible to mechanical impact force is insufficient. Such a cylindrical bearing has a problem that the radial crushing strength is significantly reduced.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to secure a large sintered hole without impairing the mechanical strength, which is excellent in oil retention and wear resistance. An object of the present invention is to provide a sintered oil-impregnated bearing having high properties.

[0011]

In order to achieve the above object, the present inventors manufactured sintered bodies made of various material compositions by various methods and compared and examined their characteristics.
As a result, a sintered oil-impregnated bearing having high strength and large sintering holes was obtained when the raw material powder to which a predetermined amount of coarse Sn raw material powder was added was fired, and the present invention was completed based on this finding.

That is, the sintered oil-impregnated bearing according to the present invention is
It has a composition of 15 to 40 wt% Sn, 0.5 to 4 wt% C, the balance Cu and unavoidable impurities, and is composed of a sintered body in which powder particles are fused to each other. The Sn diffusion layer is formed on the surface portion of the powder particles facing each other and the lubricating oil is impregnated in the sintering holes.

Further, a part of copper (Cu) forming the balance is
By substituting at least one of Pb, Ni and metal sulfide, the lubricity and strength of the bearing can be further improved. In this case, the Pb content (substitution amount) is 0.5
3 wt% is an appropriate amount, and Ni and metal sulfide contents are 1-10 wt% respectively.

Further, the lubricity can be improved by setting the ratio of the sintered holes having an inner diameter of 40 μm or more to 5% or more with respect to all the sintered holes of the sintered body.

The reasons for limiting the composition of the sintered oil-impregnated bearing according to the present invention will be described below.

Sn is an element that alloys with Cu to improve the sliding characteristics of the bearing, and in addition, Sn powder having an average particle size of 40 μm or more is added to the raw material powder in the state of the raw material powder, so that the pore size becomes smaller. It is an element necessary for forming a sintered hole of 40 μm or more. The content of Sn is appropriately 15 to 40 wt% with respect to the entire raw material powder, and the content of coarse Sn powder for forming sintered pores having a large pore diameter is 5 to 30 wt% particularly in the manufacturing method described later. It is set to the range of. If the content is less than 5 wt%, the formation ratio of the sintered pores having a large pore size is small, while if the content exceeds 30 wt%, the ratio of voids becomes large and the strength (crushing strength) of the sintered body decreases. Resulting in.

C enhances the strength of the sintered body base and is dispersed as a solid lubricant in the base to improve the lubricity of the sliding surface to prevent galling of the sliding material and improve the initial sliding characteristics. Therefore, 0.5 to 4 wt% is contained. C content is 0.5 wt%
If it is less than the above, the effect of improving the sliding property is not sufficient, while if the content exceeds 4 wt%, it becomes brittle and the formability is lowered, and it is difficult to obtain a high-density and high-strength sintered body. ..

Cu constitutes a sintered body base and is contained in an amount of 60 to 85 wt% in order to improve the strength of the sintered body. If the content is less than 60 wt%, sufficient strength cannot be obtained, while if the content exceeds 85 wt%, the sliding characteristics deteriorate.

Pb has the effect of improving the lubrication characteristics, and by adding a part of Cu in addition to Sn and C described above, the lubricity of the sintered body can be further improved.
When the content is less than 0.5 wt%, the effect of the addition is small, and when the content exceeds 3 wt%, the matrix strength is reduced.

Ni is an element effective for improving the strength of the sintered body matrix, and Ni may be added in the range of 1 to 10 wt%.
When the added amount is less than 1 wt%, the strength improving effect is small, while when the added amount exceeds 10 wt%, the expansion and coarsening of the sintered hole is hindered, and the lubricity as a bearing is deteriorated.

The metal sulfide is effective in improving the initial sliding characteristics and is added in the range of 1 to 10 wt%. As metal sulfides, there are molybdenum disulfide, iron sulfide, etc., and if the added amount is less than 1 wt%, the improvement effect is small, while if the added amount exceeds 10 wt%, the matrix strength decreases. I will invite you.

The sintered oil-impregnated bearing of the present invention exhibiting the above-mentioned characteristics is manufactured by the following steps. That is, first, with copper powder or bronze powder prepared by the atomizing method,
5 to 30 wt% of Sn powder having an average particle diameter of 40 μm or more, graphite powder, Sn powder, Pb powder, Ni powder, metal sulfide, and solid lubricant for molding are added in a predetermined amount and mixed to form a solid lubricant. 15-40 wt% Sn and C
A raw material mixture having a composition of 0.5 to 4 wt% and the balance being Cu and unavoidable impurities is prepared.

Next, this raw material mixture is molded at a molding pressure of 200-4.
Pressure molding at 00 MPa to form a molded body of a predetermined shape,
This molded body is heated at a temperature of 3 in a hydrogen or non-oxidizing atmosphere
Degreasing is performed at 00 to 600 ° C. for 30 to 120 minutes, and then firing is performed in hydrogen or a non-oxidizing atmosphere at a temperature of 700 to 800 ° C. for 40 to 120 minutes to form a sintered body having sintered pores having a large pore size. ..

The formation of sintered pores having a large pore size will be described with reference to FIGS. 1 and 2. That is, as shown in FIG. 2, when the temperature of the compact is increased so as to fire the compact body in which the coarse Sn powder 2 is mixed between the powder particles 1, the Sn having a relatively low melting point is heated in the heating process below the sintering temperature. While the powder melts and adheres to the surface of the adjacent powder particles 1, a part of Sn diffuses from the surface of the powder particles 1 to the inside, and as shown in FIG. More Sn-rich Sn diffusion layer 3 is formed. As a result, coarse Sn
A sintered hole 4 having a large pore size is formed in the tissue space filled with the powder 2. Then, as a final step, a sintered oil-impregnated bearing is manufactured by impregnating the obtained sintered body with lubricating oil under reduced pressure.

Here, in the case of a sintered body that constitutes a bearing that slides intermittently, such as a pilot bush of an automobile clutch, the diameter of the sintered hole 4 is such that the lubricating oil always floats on the sliding surface. In order to maintain the state, it is desirable that the thickness be 40 μm or more. Further, it is desirable that the ratio of the sintered pores having a diameter of 40 μm or more to all the sintered pores is 5% or more.

The pore diameter of the sintered pores 4 and the generation ratio thereof can be adjusted by appropriately changing the average particle diameter of the Sn powder added together with the powder particles and the addition amount of the Sn powder. Specifically, in order to generate the sintered pores 4 having a pore size of 40 μm or more at a rate of 5% or more, coarse Sn powder having an average particle size of 40 μm or more is added in an amount of 5 wt% or more, and the temperature rises below the sintering temperature. In the warming process, it is necessary to melt the Sn powder.

The density of the sintered body is 6.8 to 7.3 g / cm.
The range of ³ is preferable, and in this range, the pore size is 40μ.
The ratio of the sintered pores of m or more to all the sintered pores is 5% or more, and a sintered body having excellent lubricity can be obtained, and the radial crushing strength is 100 N / mm ^{2 in} spite of expanding the sintered pores.
The above bearing can be formed.

As described above, according to the sintered oil-impregnated bearing of the present invention, the Sn diffusion layer is formed on the surface portion of the powder particles facing the sintering holes of the sintered body constituting the bearing. Since a sintered hole having a large hole diameter can be formed in the portion surrounded by, it is possible to form a sintered oil-impregnated bearing having excellent lubricity and oil retention.

[0029]

EXAMPLE Next, an example of a sintered oil-impregnated bearing according to the present invention will be described in comparison with a conventional bearing, taking as an example the case where it is applied to a pilot bush 10 installed in a clutch of an automobile shown in FIG. To do.

As Example 1, 88.5% of bronze (Cu-10% Sn-1% Pb) powder having a particle size of 150 μm or less,
10% Sn powder with an average particle size of 40 μm, particle size 100 μm
1.5% of the following graphite powder and 1% of a solid lubricant for mold forming were added to prepare a mixed powder.

As Example 2, bronze (Cu-10% Sn) powder having a particle size of 150 μm or less was 88.5% and the average particle size was 4
A mixed powder was prepared by adding 10% of Sn powder of 0 μm, 1.5% of graphite powder having a particle size of 100 μm or less, and 1% of a solid lubricant for mold forming.

As Example 3, 83% of bronze (Cu-10% Sn) powder having a particle size of 150 μm or less and an average particle size of 40 μm were used.
10% Sn powder, 5% Ni powder, 100μ particle size
A mixed powder was prepared by adding 1.5% of graphite powder of m or less and 1% of a solid lubricant for mold forming.

As Example 4, bronze (Cu-10% Sn) powder having a particle size of 150 μm or less was 83.5% and the average particle size was 4
A mixed powder was prepared by adding 10% of Sn powder of 0 μm, 5% of metal sulfide powder, 1.5% of graphite powder having a particle size of 100 μm or less, and 1% of solid lubricant for molding.

As Example 5, bronze (Cu-10% Sn-1% Pb) powder having a particle size of 150 μm or less was 83.5%,
10% Sn powder and 5 Ni powder with an average particle size of 40 μm
%, 1.5% graphite powder having a particle size of 100 μm or less, and 1% solid lubricant for mold forming were added to prepare mixed powder.

As Example 6, bronze (Cu-10% Sn) powder having a particle size of 150 μm or less was 83.5% and the average particle size was 4
A mixed powder was prepared by adding 10% of Sn powder of 0 μm, 5% of metal sulfide powder, 1.5% of graphite powder having a particle size of 100 μm or less, and 1% of solid lubricant for molding.

On the other hand, as Comparative Example 1, 98.5% of bronze (Cu-10% Sn-1% Pb) powder and 1.5% of graphite powder having a particle size of 100 μm or less were added without adding coarse Sn powder.
%, And 1% of a solid lubricant for mold forming were added to prepare a conventional general-purpose mixed powder.

The mixed powders of Examples 1 to 6 and Comparative Example 1 thus prepared were pressed at a molding pressure of 200 to 400 MPa, and had dimensions of an outer diameter of 20 mm, an inner diameter of 16 mm and a height of 17 mm, and a molding density of 6 A molded product of 0.3 to 6.5 g / cm ³ was obtained. Then, each molded body is heated to a temperature of 30 in a hydrogen gas atmosphere.
Degreasing was performed by heating at 0 to 600 ° C. for 30 minutes to 2 hours.

Next, the degreased compacts were sintered in a depressurized hydrogen gas atmosphere at a temperature of 700 to 800 ° C. for 40 minutes to 2 hours and gradually cooled. Then, in the sizing step, as a result of adjusting the dimensional accuracy of the inner and outer diameters to a predetermined value, the density becomes 6.8.
A sintered body of ˜7.3 g / cm ³ was obtained. Then, the obtained sintered bodies were impregnated with lubricating oil under reduced pressure conditions to obtain sintered oil-impregnated bearings. The oil content of each bearing was 18 Vol%.

In order to evaluate the lubricity and oil retention characteristics of each of the sintered oil-impregnated bearings thus prepared, an oil removal test under high temperature conditions was carried out in the following manner. The test conditions are
The bearing of each sample was placed in a furnace whose environmental temperature was set to 200 ° C., and the residual ratio of the lubricating oil retained in each bearing was measured with time at a predetermined time interval from the start of the experiment. The test results are shown in FIG.

As is apparent from the results shown in FIG. 3, the bearings according to Examples 1 to 6 are excellent in lubricity and oil retention, and when used as a clutch pilot bush for automobiles, there is no squealing of gears. It was proved that the time required to reach the limit of the residual oil ratio (20 Vol%) for generating abnormal noise was about 20% longer than that of the bearing according to Comparative Example 1, and the lubricating performance was significantly improved. ..

Further, in order to evaluate the wear resistance characteristics of the bearings according to each of the examples and comparative examples, the Amsler type wear resistance tester shown in FIG. A wear resistance test was performed by pressing the rotary drum 6 to which a load of 250 N was applied at a speed of 23 m / min for 2 hours and measuring the maximum wear depth of each test piece 5 as the wear amount.

Further, the metallographic structure of each sintered body was examined under a microscope to measure the ratio of the sintered pores having a pore diameter of 40 μm or more, and the radial crushing strength of each bearing was measured to obtain the results shown in Table 1 below. It was

[0043]

[Table 1]

As can be seen from the results shown in Table 1, the bearings according to Examples 1 to 6 were superior to the conventional bearing shown in Comparative Example 1 in wear resistance without significantly impairing radial crushing strength. The property could be improved by about 20%. The bearings of Examples 3 and 5 in which Ni was contained in the sintered body composition were able to have a radial crushing strength of 150 N / mm ² as compared with the other Examples 1, 2, 4 and 6. It was found that both the wear resistance and the wear resistance can be improved.

[0045]

As described above, according to the sintered oil-impregnated bearing according to the present invention, the Sn diffusion layer is formed on the surface portion of the powder particles facing the sintering holes of the sintered body forming the bearing. Since a sintered hole having a large hole diameter can be formed in the portion surrounded by the diffusion layer, a sintered oil-impregnated bearing having excellent lubricity and oil retention can be formed.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a part of a matrix structure of a sintered oil-impregnated bearing according to the present invention.

FIG. 2 is a cross-sectional view schematically showing a part of the matrix structure before sintering.

FIG. 3 is a graph showing changes over time in the oil remaining rate of the bearing according to each example in comparison with the conventional example.

FIG. 4 is a diagram showing a wear resistance test procedure.

FIG. 5 is a cross-sectional view showing a state in which power is cut off in an automobile clutch using a sintered oil-impregnated bearing.

FIG. 6 is a cross-sectional view showing a state in which power is transmitted in an automobile clutch using a sintered oil-impregnated bearing.

[Explanation of symbols]

 1 powder particle 2 Sn powder 3 Sn diffusion layer 4 sintering hole 5 test piece 6 rotating drum

Claims (6)

[Claims] 1. Sn of 15 to 40 wt% and C of 0.5 to
4 wt%, the balance being Cu and the composition of unavoidable impurities, consisting of a sintered body in which powder particles are fused to each other, and an Sn diffusion layer is formed on the surface portion of the powder particles facing the sintering holes of the sintered body. A sintered oil-impregnated bearing, which is formed and impregnated with lubricating oil in the sintered hole. 2. Sn of 15 to 40 wt% and C of 0.5 to
4 wt%, Pb 0.5 to 3 wt%, the balance being Cu and an unavoidable impurity composition, and a powder composed of a sintered body in which powder particles are fused to each other and facing a sintering hole of the sintered body. A sintered oil-impregnated bearing, characterized in that a Sn diffusion layer is formed on the surface of the particles, and lubricating oil is impregnated in the sintered holes. 3. Sn of 15-40 wt% and C of 0.5-
4% by weight, 1 to 10% by weight of Ni, the balance being Cu and an unavoidable impurity, and composed of a sintered body in which powder particles are fused to each other. A sintered oil-impregnated bearing, characterized in that a Sn diffusion layer is formed on the surface portion, and lubricating oil is impregnated in the sintered holes. 4. Sn of 15-40 wt% and C of 0.5-
4% by weight, 1-10% by weight of metal sulfide, the balance being Cu and inevitable impurities, and a powder composed of a sintered body in which powder particles are fused to each other and facing a sintering hole of the sintered body. A sintered oil-impregnated bearing, characterized in that a Sn diffusion layer is formed on the surface of the particles, and lubricating oil is impregnated in the sintered holes. 5. The inner diameter is 40 with respect to all the sintered holes of the sintered body.
The ratio of sintered pores having a size of μm or more is 5% or more.
The sintered oil-impregnated bearing according to any one of to 4. 6. The sintered oil-impregnated bearing according to claim 1, wherein the radial crushing strength of the sintered body is set to 100 N / mm ² or more.