JP2020125839A - Slide member - Google Patents

Abstract

To provide a slide member that improves fatigue strength.SOLUTION: A slide member according to one embodiment has a base material that has a shape of having a face for supporting an opposite material, with a metal sintering layer not exposed on the face, and a resin coating layer that is formed on the inner peripheral surface and has a fatigue strength of 50 MPa or more.SELECTED DRAWING: Figure 2

Description

The present invention relates to a sliding member.

A sliding member is known in which a resin coating layer is formed on the surface of the back metal in order to improve the characteristics of the sliding surface. For example, Patent Document 1 describes a sliding member using PAI resin as a binder resin and graphite as a solid lubricant.

Japanese Patent No. 5683571

In the sliding member of the cited document 1, a metal sintered layer is formed on the surface of the underlayer in order to improve the adhesion between the resin coating layer and the underlayer (back metal). However, in such a sliding member, there is a problem that stress concentrates on the upper end portion of the metal sintered layer, and as a result, the fatigue resistance strength of the resin coating layer decreases. There is also a method of making the resin coating layer thinner to improve the fatigue strength, but if the resin coating layer is too thin, there is a problem that the resin coating layer is worn and the underlying layer is exposed during use.

On the other hand, the present invention provides a technique for improving the fatigue strength of sliding members.

The present invention has a base material having a surface for supporting a mating material, and a metal sintered layer is not exposed on the surface, and a resin formed on the surface and having a fatigue strength of 50 MPa or more. A sliding member having a coating layer is provided.

The fatigue strength may be 80 MPa or more.

The surface roughness of the surface may be 60 μm Rz JIS or less.

The mating member may be a shaft, and the base material may have a cylindrical shape having an inner peripheral surface for supporting the shaft.

On the inner peripheral surface, the surface roughness in the axial direction of the shaft may be larger than the surface roughness in the circumferential direction of the shaft.

According to the present invention, the fatigue resistance of the sliding member can be improved.

The figure which illustrates the external appearance of the bush 1 which concerns on one Embodiment. The figure which illustrates the cross-section of the bush 1. The figure which illustrates the surface structure of the main body 11 and the resin layer 13. The figure which shows the result of an abrasion test.

1. Configuration FIG. 1 is a diagram illustrating an appearance of a bush 1 according to an embodiment. The bush 1 is an example of a sliding member according to the present embodiment. The bush 1 is used, for example, in a fuel injection pump. The bush 1 has a main body 11. The main body 11 has a cylindrical shape having an inner peripheral surface for supporting the mating shaft 9 (an example of a mating member). The main body 11 is formed of, for example, a metal (specifically, steel, cast iron, aluminum alloy, copper alloy, or the like) in order to secure strength and reliability required as parts. The body 11 may be formed of a single layer of metal or multiple layers of metal (eg, backing metal and lining layer).

FIG. 2 is a diagram illustrating a cross-sectional structure of the bush 1. FIG. 2 shows a cross section perpendicular to the sliding surface. The bush 1 has a main body 11 (an example of a base material or a back metal) and a resin layer 13 (an example of a resin coating layer). In some types of bushes, a sintered layer formed of powder of metal (for example, copper or copper alloy) is formed on the surface of a base material that is a base of a resin layer, but the bush 1 according to the present embodiment is burned. No tie layer (sintered metal layer is not exposed). By not having the sintered layer, it is possible to reduce the stress concentration at the upper end portion of the sintered layer in the resin layer, and consequently to improve the fatigue strength.

Instead of having the sintered layer, the surface of the main body 11 on which the resin layer 13 is formed is roughened. From the viewpoint of relaxing the stress concentration in the surface shape, the surface roughness of the surface on which the resin layer 13 is formed is, for example, 60 μmRzJIS or less, preferably 30 μmRzJIS or less, and more preferably 5 μmRzJIS or more and 10 μmRzJIS or less. preferable.

Suppressing peeling of the resin layer 13 from the main body 11 due to shear stress when the mating shaft 9 is unilaterally contacted (when the mating shaft 9 contacts the sliding surface in a state of being inclined with respect to the sliding surface). Therefore, the surface roughness of the mating shaft 9 in the axial direction is preferably larger than the surface roughness in the circumferential direction.

The resin layer 13 is formed of a resin material for sliding members. This resin material includes a binder resin 131 and an additive 132 dispersed in the binder resin 131. As the binder resin 131, for example, a thermosetting resin, more specifically, for example, at least one of a polyimide (PI) resin and a polyamideimide (PAI) resin is used. From the viewpoint of improving fatigue resistance, it is preferable to use a PI resin rather than a PAI resin, and a PI resin having a high strength (here, “high strength” means a tensile strength of 150 MPa or more). Is preferably used. From the viewpoint of improving fatigue resistance, the content of the binder resin in the resin layer 13 is preferably large, for example, preferably 80% by volume or more, more preferably 83% by volume or more, and 85% by volume. More preferably, it is more preferably 90% by volume or more.

The additive 132 is a substance for improving the characteristics of the resin layer 13, and includes, for example, at least one of a solid lubricant 1321, a hard material (hard particles) 1322, and a silane coupling agent (silane coupling). The agent is not shown). The solid lubricant 1321 is an additive for reducing the friction coefficient of the resin layer 13, and includes, for example, at least one of graphite and MoS2. Since MoS2 may easily aggregate in the resin layer, it is preferable to use graphite as the solid lubricant 1321 and not use MoS2. When graphite is used as the solid lubricant 1321, the degree of graphitization is preferably high from the viewpoint of reducing the friction coefficient, for example, 95% or more is preferable, and 99% or more is more preferable. The hard material 1322 is a substance for improving the seizure resistance and wear resistance of the resin layer 13, and includes, for example, at least one of clay, mullite, and talc. The silane coupling agent is a substance for strengthening the bond between the binder resin 131 and the solid lubricant 1321.

From the viewpoint of improving fatigue resistance, it is preferable that the content of the additive is small, for example, 20% by volume or less in total, preferably 17% by volume or less, more preferably 15% by volume or less. More preferably, it is more preferably 10% by volume or less. From the viewpoint of reducing the friction coefficient, it is preferable that the content of the solid lubricant is large, for example, 9% by volume or more. From the viewpoint of reducing the total amount of additives, it is preferable that the content of the solid lubricant is small, for example, 18% by volume or less. From the viewpoint of improving seizure resistance and wear resistance, it is preferable that the content of the hard material is large, for example, 0.5% by volume or more. From the viewpoint of reducing the total amount of additives, it is preferable that the content of the solid lubricant is small, for example, 3% by volume or less. In order to add both the solid lubricant and the hard material, the content of the solid lubricant is preferably 9% by volume or more and 17% by volume or less, and more preferably 14% by volume or less. The content of the hard material is preferably 0.5% by volume or more and 3% by volume or less. The content of the silane coupling agent is preferably 0.1% by weight or more, and more preferably 0.2% by weight or more, based on the binder resin. From the viewpoint of cost reduction, the content of the silane coupling agent is preferably, for example, 5% by weight or less, and more preferably 3% by weight or less, based on the binder resin.

From the viewpoint of reducing the surface roughness after cutting, the particle diameter of the additive 132 used as a material is preferably small. For example, the average particle diameter of the additive 132 is the average of the metal powders used in the sintered layer 12. It is preferably smaller than the particle size. Further, both the solid lubricant 1321 and the hard material 1322 preferably have an average particle size of 5 μm or less or less than 5 μm, and more preferably 3 μm or less or less than 3 μm.

Since the resin layer 13 is used for the sliding member, the fatigue strength, that is, the fatigue surface pressure is preferably 50 MPa or more, more preferably 80 MPa or more, and further preferably 90 MPa or more. The method of measuring the fatigue surface pressure will be described later. From the viewpoint of improving the fatigue resistance of the resin layer 13, the average particle size of the solid lubricant 1321 used as a material is preferably small, for example, it is preferably twice or less the average particle size of the hard material 1322. It is more preferable that the average particle size of the product 1322 is smaller.

It is considered that in the resin layer 13, the fatigue resistance of the resin layer 13 decreases as the content of the additive 132 increases. In this embodiment, the fatigue resistance is improved by suppressing the content of the additive.

FIG. 3 is a diagram illustrating the surface structure of the main body 11 and the resin layer 13. Similar to FIG. 2, FIG. 3 shows a cross section perpendicular to the sliding surface. The thickness of the resin layer 13 is preferably more than 20 μm, and more preferably more than 50 μm in order to prevent the underlying layer (main body 11) from being exposed by abrasion of the resin layer 13 due to the use of the bush 1. Preferably, it is more than 100 μm. From the viewpoint of improving fatigue strength and seizure resistance, the resin layer 13 preferably has a thickness of 300 μm or less. The film thickness T of the resin layer 13 refers to the length from the highest position of the unevenness on the surface of the main body 11 to the highest position of the surface of the resin layer 13, as shown in FIG.

2. Example The inventors of the present application produced test pieces of sliding members under various conditions, and evaluated the characteristics of the resin layer 13 for these test pieces.

2-1. Preparation of test piece As a base material, a steel plate (SPCC (JIS)) having a thickness of 1.5 mm was used. In Experimental Example 1, the surface of the base material was roughened by sanding. The surface roughness after roughening was 20 to 60 μm RzJIS. In Experimental Examples 2 and 3, copper alloy powder (average particle size 100 μm) was sprayed on the base material at a thickness of 100 μm, and then sintered at 930° C. in a reducing atmosphere without being pressed. For these samples, a precursor solution for forming a resin layer having the composition shown in Table 1 was prepared, and this precursor solution was applied onto the sintered layer by a knife coating method. After coating, it was dried at room temperature to about 200° C. for about 60 to 90 minutes. Then, it heated up to about 300 degreeC and baked for about 30 to 90 minutes.

In Experimental Examples 1 and 2, graphite having an average particle size (d50 based on volume) of 1.5 μm and a degree of graphitization of 99% was used. As the high-strength PI resin, one having a tensile strength of 195 MPa, an elongation of 90%, an elastic modulus of 3.8 GPa, and a glass transition temperature Tg of 285° C. was used. In Experimental Example 3, graphite having an average particle size of 12.5 μm and a degree of graphitization of 90% was used. MoS2 having an average particle size of 1.5 μm was used. Further, as the PI resin, one having a tensile strength of 119 MPa, an elongation of 47% and a glass transition temperature Tg of 360° C. is used as a PAI resin having a tensile strength of 112 MPa, an elongation of 17%, an elastic modulus of 2.7 GPa and a glass. A transition temperature Tg of 288° C. was used. In Experimental Examples 1 and 2, a silane coupling agent having a chemical formula of 3(H3CO)SiC3H6-NH-C3H6Si(OCH3)3 was used. In addition, in Table 1, the content of the silane coupling agent is shown as a weight ratio with respect to the high-strength PI resin. In Experimental Examples 1 to 5, clay having a structural formula of Al2O3·2SiO2 and an average particle diameter of 3 μm was used.

In Experimental Examples 1 and 2, only graphite was used as the solid lubricant (that is, other solid lubricants such as MoS2 were not included). Moreover, additives other than the solid lubricant, hard material, and silane coupling agent shown in Table 1 are not included. All the additives had an average particle size of 3 μm or less.

2-2. Abrasion test An abrasion test was performed on the test pieces of Experimental Examples 1 to 3. The wear test was performed under the following conditions, and the wear depth after the test was recorded.
・Testing machine: Box type bushing tester ・Surface pressure: 1.8 MPa
・Test pattern: Run & Stop (100,000 cycles)
・Lubricant: Kerosene (room temperature)

FIG. 4 is a diagram showing the results of the abrasion test. In comparison with Experimental Example 3, in Experimental Examples 1 and 2, the wear depth was reduced to less than half. That is, in comparison with Experimental Example 3, the abrasion resistance was improved in Experimental Examples 1 and 2.

2-3. Fatigue test A fatigue test was performed on the test pieces of Experimental Examples 1 to 3. The fatigue test was performed under the following conditions, and the maximum surface pressure at which no fatigue occurred in the resin layer (the maximum surface pressure of the tester was 100 MPa) was defined as the fatigue surface pressure.
・Test machine: Reciprocating load test machine ・Rotation speed: 3000 rpm
・Number of repetitions: 105 times ・Test temperature: 100°C (lubricating oil supply temperature)
・Mating material: S45C
・Lubricant: Engine oil

The fatigue resistance surface pressure of Experimental Example 3 was 20 MPa, whereas the fatigue resistance surface pressure of Experimental Example 1 was 110 MPa or more, and the fatigue resistance surface pressure of Experimental Example 2 was 80 MPa. In comparison with Experimental Example 3, in Experimental Examples 1 and 2, the fatigue surface pressure resistance was improved. Further, in comparison with Experimental Example 2, in Experimental Example 1, the fatigue resistance surface pressure was improved.

2-4. Seizure Test A seizure test was performed on the test pieces of Experimental Example 1 and Experimental Example 2. The seizure test was performed under the following conditions, and the surface pressure when seizure occurred was defined as the seizure surface pressure.
・Test machine: Static load seizure test machine ・Load: Step up 1kN/5 minutes ・Rotation speed: 6000rpm
・Lubricant: Paraffin oil

As a result of this test, the seizure surface pressure in Experimental Example 1 was 40 MPa, and the seizure surface pressure in Experimental Example 2 was 32 MPa. Thus, as compared with Experimental Example 2, in Experimental Example 1, the seizure resistance was improved. Regarding the state of the sliding surface after the test, the resin layer was broken in all cases, but the back metal was not exposed. That is, also in Experimental Example 1, the resin layer did not peel off and the backing metal was not exposed.

Further, the adhesion strength between the main body and the resin layer was tested with respect to Experimental Example 1 and Experimental Example 2, and both have an adhesion strength equal to or higher than the strength of the adhesive used in the test, and There was no difference in the adhesive strength within the range.

3. Modifications Note that the various materials and their compositions used in the above embodiments are merely examples, and the present invention is not limited to these. The resin material according to the present invention may contain inevitable impurities. The use of the bush 1 is not limited to that used as a bush in a fuel injection pump, and may be used in various bearings, a compressor, or the like. The sliding member according to the present invention is not limited to the bush 1, and the present invention may be applied to other sliding members such as a half bearing or a swash plate.

DESCRIPTION OF SYMBOLS 1... Bush 11... Main body 13... Resin layer 131... Binder resin 132... Additive

Claims (5)

A base material having a shape having a surface for supporting a mating material, and the metal sintered layer is not exposed on the surface,
A sliding member having a resin coating layer formed on the surface and having a fatigue strength of 50 MPa or more. The sliding member according to claim 1, which has a fatigue strength of 80 MPa or more. The sliding member according to claim 1, wherein the surface roughness of the surface is 60 μmRz JIS or less. The mating material is a shaft,
The sliding member according to any one of claims 1 to 3, wherein the base material has a cylindrical shape having an inner peripheral surface for supporting the shaft. The sliding member according to claim 4, wherein on the inner peripheral surface, a surface roughness of the shaft in the axial direction is larger than a surface roughness of the shaft in the circumferential direction.