JP2017101602A - Slide member and swash plate-type compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slide member having improved oil retention properties.SOLUTION: A swash plate 3 as a slide member comprises a base material 31, and a coating layer 32 formed on the base material 31. The coating layer 32 comprises a binder resin 321, and a solid lubricant 322 dispersed in the binder resin 321. An exposure rate of the solid lubricant 322 on a slide surface of the coating layer 32 is 7% or more.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a sliding member having a resin coating layer in which a solid lubricant is dispersed.

  A sliding member having a resin coating layer in which a solid lubricant is dispersed is known. Patent Document 1 describes a sliding member provided with a plurality of recesses at the end of a sliding surface in order to prevent oil film destruction and seizure. The opening area of the recess increases as it goes to the end of the sliding surface.

JP 2004-340248 A

  In Patent Document 1, the amount of solid lubricant on the sliding surface is not controlled, and there is room for improvement in oil retention.

  In contrast, the present invention provides a sliding member and a swash plate compressor with improved oil retention.

  The present invention has a base material and a coating layer formed on the base material, and the coating layer has a binder resin and a solid lubricant dispersed in the binder resin, and the coating Provided is a sliding member having an exposure rate of 7% or more of the solid lubricant on the sliding surface of the layer.

  The exposure rate of the solid lubricant on the sliding surface of the coating layer may be 10% or more.

  The solid lubricant may have c-axis orientation, and a relative c-axis strength ratio of the solid lubricant in the coating layer may be 80% or more.

  In the load curve, the occupation ratio of 50% of the depth from the surface roughness with respect to the maximum surface roughness may be 50% or less.

  The occupation ratio may be 70% or less.

  The surface roughness on the sliding surface of the coating layer may be 1 to 20 μm.

  The surface roughness may be 8 to 15 μm.

  The present invention also provides a swash plate compressor using any one of the above sliding members as a swash plate.

  According to the present invention, oil retention and initial conformability can be improved in a sliding member and a swash plate compressor.

The cross-sectional schematic diagram which shows the structure of the compressor 1 which concerns on one Embodiment. The figure which illustrates the structure of the swash plate. 3 is a schematic view illustrating the structure of a coating layer 32. FIG. FIG. 3 is a schematic diagram showing an orientation state of a solid lubricant 322 in a coating layer 32. FIG. 5 is a schematic diagram showing an outline of a load curve of the coating layer 32. 6 is a flowchart illustrating a method for manufacturing the swash plate 3. The figure which shows the solid lubricant exposure rate in Experimental example 1-3. It shows a MoS ₂ additive amount dependency of the coefficient of friction. The schematic diagram which shows the load curve of Experimental example 1 and Experimental example 2. FIG. The figure which shows the load length rate Rmr (50) dependence of the contact angle of lubricating oil.

1. Structure FIG. 1 is a schematic cross-sectional view showing the structure of a compressor 1 according to an embodiment. The compressor 1 is a so-called swash plate compressor. The compressor 1 has a shaft 2, a swash plate 3, a piston 4, and a shoe 5. The shaft 2 is rotatably supported with respect to a housing (not shown). The swash plate 3 is fixed obliquely with respect to the rotation axis of the shaft 2. The swash plate 3 is an example of the sliding member of the present invention. The piston 4 reciprocates in a cylinder bore (not shown) provided in the housing. The shoe 5 is provided between the swash plate 3 and the piston 4, and slides with the swash plate 3 and the piston 4, respectively. In the shoe 5, the surface that slides with the swash plate 3 is substantially flat, and the surface that slides with the piston 4 has a dome-like (hemispherical) shape. The rotation of the shaft 2 is converted into a reciprocating motion of the piston 4 by the swash plate 3.

  FIG. 2 is a diagram illustrating the structure of the swash plate 3. FIG. 2 is a schematic diagram showing a structure in a cross section perpendicular to the sliding surface with the shoe 5. The swash plate 3 has a base material 31, a coating layer 32, and a coating layer 33. Both the coating layer 32 and the coating layer 33 slide with the shoe 5. The base material 31 has a disk shape, and is formed of a metal that satisfies required characteristics, for example, an iron-based, copper-based, or aluminum-based alloy. From the viewpoint of preventing adhesion with the shoe 5, the swash plate 3 is preferably formed of a material different from that of the shoe 5.

FIG. 3 is a schematic view illustrating the structure of the coating layer 32. The coating layer 32 is provided to improve the characteristics of the sliding surface of the swash plate 3. The coating layer 32 has a binder resin 321 and a solid lubricant 322. The coating layer 32 includes, for example, 20 to 70 vol% solid lubricant. The balance is a binder resin. The binder resin 321 is formed of, for example, a thermosetting resin. As the thermosetting resin, for example, at least one of polyamideimide (PAI), polyamide (PA), polyimide (PI), epoxy, polyetheretherketone, phenol, and elastomer is used. Solid lubricant 322 is added to improve lubrication characteristics. The solid lubricant 322, crystalline material having a c-axis orientation, for example, MoS _2, graphite (Gr), carbon, fluorine resin, soft metal (Sn, Bi, etc.), of WS _2, and h-BN At least one is used. A crystalline substance having c-axis orientation refers to a substance having a layered crystal structure, such as a hexagonal system. The coating layer 32 may include other additives such as hard particles in addition to the solid lubricant 322. As the hard particles, for example, at least one of oxide, nitride, carbide, and sulfide is used.

  From the viewpoint of preventing wear of the coating layer 32, the thickness of the coating layer 32 is preferably 10 μm or more, more preferably 15 μm or more, and further preferably 20 μm or more. For example, if the thickness of the coating layer 32 is less than 5 μm, the coating layer 32 may be worn and the substrate 31 may be exposed. When the base material 31 is exposed, there arises a problem that the coefficient of friction increases or adheres to the shoe 5. Further, if the coating layer 32 is too thick, the seizure resistance may be lowered. Therefore, the thickness is preferably 50 μm or less.

  From the viewpoint of improving seizure resistance, the relative c-axis strength ratio of the solid lubricant 322 in the coating layer 32 is preferably 80% or more, and more preferably 85% or more. Here, the relative c-axis intensity ratio refers to the ratio of the diffraction peak intensity from the cleavage plane to the total diffraction peak intensity in X-ray diffraction. More specifically, the relative c-axis intensity ratio is determined from the (002), (004), (100), (101), (102), (103), (105), (110), and (008) planes. Is defined as the ratio of the integrated value of diffraction peak intensities from the (002), (004), and (008) planes to the integrated value of diffraction peak intensities. Although diffraction peaks from other than the above nine crystal planes may appear, they are ignored in calculating the relative c-axis intensity ratio because the peak intensity is weak.

  The state in which the relative c-axis intensity ratio is 80% or more, that is, the state in which the relative c-axis intensity ratio is high means that the solid lubricant 322 has a uniform crystal orientation in the coating layer 32. The relative c-axis intensity ratio is hereinafter referred to as “orientation ratio” in the sense that it indicates the degree of alignment of crystal orientations. In general, solid lubricants exhibit a low coefficient of friction due to interlayer slip in crystals having a layer structure. The fact that the crystal orientations are aligned means that the directions in which interlayer slip occurs are aligned.

  FIG. 4 is a schematic diagram showing the orientation state of the solid lubricant 322 in the coating layer 32. FIG. 4A shows a state where the orientation rate is low, and FIG. 4B shows a state where the orientation rate is high. In these figures, the solid lubricant 322 is represented as hexagonal flakes. In the example of FIG. 4B, the solid lubricant 322 has a cleaved surface aligned in a direction substantially parallel to the sliding surface. When the orientation ratio of the solid lubricant 322 is high in the coating layer 32 as shown in FIG. 4B, the friction coefficient is reduced and the seizure resistance is improved.

  The average particle diameter of the solid lubricant 322 is, for example, 1 to 10 μm. The average particle diameter is measured by, for example, a laser diffraction method.

FIG. 5 is a schematic diagram showing an outline of the load curve of the coating layer 32. The load curve represents the load length ratio of the contour curve element expressed as a function of the cutting level. The load curve is defined in JIS B0601: 2013. The cutting level refers to the depth from the maximum peak height of the contour curve for obtaining a cutting surface parallel to the surface of the base material of the sliding surface. The maximum peak height is the cutting level 0%, and the maximum valley depth is the cutting level 100%. The load length ratio Rmr (c) represents a ratio of the load length Ml (c) of the contour curve element at the cutting level c to the evaluation length (the following formula (1)). Note that ln represents the evaluation length, and m represents the number of peaks at the cutting level c.

  In this example, in the coating layer 32, the load length ratio Rmr at the position where the cutting level c is 50% is preferably 70% or less, and more preferably 50% or less. The relatively low load length ratio means that even if the surface of the coating layer is worn by several μm due to initial conformance, the recess still remains, and the lubricating oil can be retained in this recess, so that the lubrication characteristics are excellent. .

  Moreover, this recessed part is not discontinuous like the recessed part of patent document 1, but is mutually continuous. Therefore, a flow is generated in the lubricating oil. As a result, cooling of the sliding heat generation proceeds and the sliding characteristics are not impaired.

  The coating layer 33 is formed in the same manner as the coating layer 32.

2. Manufacturing Method FIG. 6 is a flowchart illustrating a method for manufacturing the swash plate 3. In step S1, a substrate is prepared. In step S2, the base material is molded into a predetermined shape. In this example, the base material is molded into a disk shape. In order to improve the adhesion between the substrate and the coating layer, the surface of the substrate may be roughened.

  In step S3, a paint for forming the coating layer is prepared. First, the binder resin and the solid lubricant are mixed by a known method. These mixtures are diluted with a diluent. Any diluent may be used. For example, N-methylpyrrolidone (NMP) is used. The blending ratio of the diluent is, for example, 30 to 70% by volume with respect to the solid content.

  In step S4, a paint is applied to the surface of the substrate. The paint is applied, for example, by pad printing, roll coating, or spray coating. When the thickness of the paint that can be applied at one time is limited, two or more overcoats may be performed. In step S5, the coating layer is dried and baked. The surface roughness (Rzjis in JIS B 0601: 2001) of the coating layer is preferably, for example, 1 to 20 μm, and more preferably 8 to 15 μm. After application of the paint, drying and baking are performed (step S5).

3. Experimental Example Test pieces of sliding members were prepared under various conditions, and their characteristics were evaluated. More specifically, a plurality of test pieces were produced in each of the four sections of Experimental Examples 1 to 4. In Experimental Examples 1 to 4, the material and composition of the coating layer 32 are common. PAI was used as the binder resin, and MoS ₂ and graphite were used as the solid lubricant. In Experimental Examples 1-4, 40 vol% of the solid lubricant was added to 60 vol% of the binder resin. In Experimental Examples 1 to 3, graphite was 10 vol% and MoS ₂ was 30 vol%. In Experimental Example 4, only MoS ₂ was added as a solid lubricant without using graphite. In Experimental Examples 1 to 4, the average particle size of MoS ₂ was about 2 μm, and the average particle size of graphite was 5 to 10 μm. As the substrate, cast iron (FCD700) was used.

  In Experimental Examples 1 to 4, the coating method for forming the coating layer and the film thickness of the coating layer are different. More specifically, in Experimental Examples 1 and 4, the coating layer was formed by pad printing, whereas in Experimental Example 2, the coating layer was formed by roll coating, and in Experimental Example 3, the coating layer was formed by spray coating. For these experimental examples 1 to 4, the orientation ratio and the surface roughness were measured. For Experimental Examples 1 and 2, the solid lubricant exposure rate on the outermost surface, the load length rate (when c = 50%), the friction coefficient, and the contact angle of the lubricating oil were measured.

Table 1 shows the measurement results of the orientation ratio and the surface roughness in Experimental Examples 1 to 4.

  Samples coated with pad printing (Experimental Examples 1 and 4) and other methods (Experimental Example 2: roll coating, Experimental Example 3: spray coating) are compared, and the sample coated with pad printing is oriented. A high tendency was seen. In the pad coat, a thin film is laminated to obtain a desired film thickness. The film thickness per layer is about the same as the size of the additive, and the effect of pressing the additive is obtained, so that a high orientation ratio is obtained. On the other hand, in roll coating and spray coating, a film having a desired thickness is applied once. Therefore, when the additive size is used as a reference, the film thickness becomes thicker (than the pad coat), the effect of pressing the additive becomes weak, and a relatively low orientation rate can be obtained.

  Regarding the surface roughness, since the surface roughness is different between Experimental Example 1 and Experimental Example 4 in which the coating method is the same, the solid lubricant is not simply dependent on the coating method. It is considered that this also depends on the particle size of the particles.

FIG. 7 is a diagram showing the solid lubricant exposure rate in Experimental Examples 1 to 3. The solid lubricant exposure rate was calculated by the following procedure. First, a photomicrograph of the coating layer surface is taken. An area of MoS ₂ is specified by using image processing software from the color shading in the photographed micrograph. The area ratio of the MoS ₂ region with respect to the observation region is calculated and used as the solid lubricant exposure rate. As is clear from this measurement procedure, the solid lubricant exposure rate here is the exposure rate of MoS ₂ .

  In the three pieces of samples of Experimental Example 1, the solid lubricant exposure rates were 7.9%, 12.3%, and 7.7%. In the three pieces of samples of Experimental Example 2, the solid lubricant exposure rates were 1.3%, 0.8%, and 0.5%. In the three samples of Experimental Example 3, the solid lubricant exposure rates were 8.1%, 9.2%, and 13.0%. In Experimental Example 2, since the surface is finished (polished, etc.) after applying the paint by roll coating, the solid lubricant is detached from the surface at that time, and the solid lubricant exposure rate is low. Conceivable. In the sample prepared by the same method as in Experimental Example 1, a solid lubricant exposure rate of 15% was obtained.

FIG. 8 is a diagram showing the dependency of the coefficient of friction on the amount of MoS ₂ added. This figure shows how the friction coefficient changes when the amount of MoS ₂ added to the coating layer is changed in the case where the coating layer is formed by roll coating as in Experimental Example 2. From this figure, it can be seen that the friction coefficient tends to decrease as the amount of MoS ₂ added to the entire coating layer increases. From this result, it is predicted that the friction coefficient decreases as the exposure amount of MoS _{2 on} the sliding surface increases.

  When the contact angles of the lubricating oil were measured for Experimental Example 1 and Experimental Example 2, they were about 2 ° and about 4 °, respectively. Thus, the reason why the contact angle of the lubricating oil, that is, the oil retaining property is different in Experimental Example 1 will be examined.

  FIG. 9 is a schematic diagram showing load curves of Experimental Example 1 and Experimental Example 2. 8A shows the load curve of Experimental Example 1, and FIG. 8B shows the load curve of Experimental Example 2, respectively. Comparing Experimental Example 1 and Experimental Example 2, in Experimental Example 1, the load length ratio increases relatively uniformly, whereas in Experimental Example 2, the load length ratio increases abruptly at a relatively shallow depth. It shows a two-stage change in which the load length ratio gradually increases deeper. Specifically, at c = 50%, the load length ratio was 40% in Experimental Example 1 and about 90% in Experimental Example 2.

  FIG. 10 is a diagram showing the dependency of the contact angle of the lubricating oil on the load length ratio Rmr (50). Rmr (50) represents the load length ratio at c = 50%. The smaller the load length ratio Rmr (50), the smaller the contact angle, that is, the higher the lipophilicity. From this result, it is considered that the contact angles in Experimental Example 1 and Experimental Example 2 are due to the difference in the load curve.

  The sliding member according to the present invention is not limited to that used as the swash plate 3 of the compressor 1. The sliding member according to the present invention may be used as a sliding member other than a swash plate compressor, such as a half bearing or a bush. The material, composition, film thickness, etc. of the coating layer in the experimental example are merely examples. The present invention is not limited to this.

DESCRIPTION OF SYMBOLS 1 ... Compressor 2 ... Shaft 3 ... Swash plate 31 ... Base material 32 ... Coating layer 321 ... Binder resin 322 ... Solid lubricant 33 ... Coating layer 4 ... Piston 5 ... Shoe

Claims (8)

A substrate;
A coating layer formed on the substrate,
The coating layer is
A binder resin,
A solid lubricant dispersed in the binder resin,
A sliding member having an exposure rate of 7% or more of the solid lubricant on the sliding surface of the coating layer. The sliding member according to claim 1, wherein an exposure rate of the solid lubricant on the sliding surface of the coating layer is 10% or more. The solid lubricant has c-axis orientation;
The sliding member according to claim 1, wherein a relative c-axis strength ratio of the solid lubricant in the coating layer is 80% or more. The sliding member according to any one of claims 1 to 3, wherein an occupancy ratio of 50% of the depth from the surface roughness is 70% or less with respect to the maximum surface roughness in the load curve. The sliding member according to claim 4, wherein the occupation ratio is 50% or less. 6. The sliding member according to claim 1, wherein a surface roughness of the coating layer on the sliding surface is 1 to 20 μm. The sliding member according to claim 6, wherein the surface roughness is 8 to 15 μm.   A swash plate compressor using the sliding member according to any one of claims 1 to 7 as a swash plate.

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