CROSS REFERENCE TO RELATED APPLICATIONS This application is a U.S. National Stage Application of International Application No. PCT/JP2018/040493, filed on Oct. 31, 2018, which claims priority to Japanese Patent Application No. 2017-210289, filed on Oct. 31, 2017. The entire disclosures of the above applications are incorporated herein by reference.
BACKGROUND Technical Field The present invention relates to a swash plate for use in a swash plate type compressor.
Related Art In a swash plate in which a resin coating layer is formed on a base material, a technique of forming a groove on a surface of the resin coating layer is known (for example, JP-A-2006-266139; JP-A-2014-151499; and WO 2002/075172).
The inventors of the present application have found a problem in that formation of grooves on the substrate in the swash plate can cause uneven abrasion in the resin coating layer formed on the base material.
The present invention provides a technique for suppressing uneven abrasion in such a resin coating layer.
SUMMARY The present invention provides a swash plate including: an annular-shaped substrate that includes a surface facing a mating member; a plurality of grooves extending in a direction intersecting the sliding direction of the mating member along the entire circumference of the annular shape on the surface; and a resin coating layer formed on the surface and forming a sliding surface with the mating material.
The plurality of grooves may extend radially from the center of the annular shape.
In the plurality of grooves, the distance between adjacent grooves may be 20 to 240 μm.
The surface may have a roughness of 5 to 15 μm RzJIS.
Advantageous Effect According to the present invention, uneven abrasion in a resin coating layer can be suppressed.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view showing a structure of a compressor 1 according to an embodiment of the invention;
FIG. 2 shows an exemplary shape of a swash plate 3.
FIG. 3 shows an exemplary cross-sectional structure of a swash plate 3.
FIG. 4 shows an exemplary surface shape of the substrate 31.
FIG. 5 shows an exemplary shape of the groove 312.
FIG. 6 shows an exemplary surface shape of the coating layer 32.
FIGS. 7A and 7B show abnormal abrasions.
FIG. 8 is an exemplary flow chart for a method of manufacturing the swash plate 3.
FIGS. 9A and 9B show the surface shapes of the substrate 31 in the Working Examples and Comparative Examples.
FIGS. 10A and 10B are schematic representations of a surface state of the resin coating layer after an abrasion test.
DETAILED DESCRIPTION 1. Configuration FIG. 1 is a schematic cross-sectional view showing a structure of a compressor 1 according to an embodiment of the invention. The compressor 1 is a so-called swash-plate-type compressor. The compressor 1 includes 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 in the figures). The swash plate 3 is fixed at an oblique angle to the rotation axis of the shaft 2. The swash plate 3 is an example of a sliding member according to the present invention. The piston 4 reciprocates in a cylinder bore (not shown in the figures) provided in the housing. The shoe 5 is provided between the swash plate 3 and the piston 4, and slides with each of the swash plate 3 and the piston 4. The surface of the shoe 5 on which the swash plate 3 slides is substantially flat; while the surface on which the piston 4 slides is dome-shaped (has a hemispherical shape). According to the present invention, the shoe 5 is an example of a mating member that slides with the sliding member. The swash plate 3 converts he rotation of the shaft 2 into a reciprocating motion of the piston 4.
FIG. 2 shows an exemplary shape of the swash plate 3. FIG. 2 is a view from a direction perpendicular to the axial sliding surface. The swash plate 3 is disk-shaped (doughnut-shaped, or annular-shaped) and is provided with a hole 39 at an overall center. Viewed from the swash plate 3, the shoe 5 rotates on the sliding surface. Here, rotation refers to a motion by which the shoe 5 draws a circular arc or a circular trajectory relative to the swash plate 3. For example, with respect to the sliding surface of the compression chamber side, a force is applied toward the compression chamber at a position where the piston 4 is fully withdrawn (at which a compression rate is lowest) to a position where the piston is fully inserted (at which a compression rate is highest), the shoe 5 is caused to slide with the swash plate 3. However, when the piston 4 moves from the fully inserted position toward the fully withdrawn position, a force is applied to the opposite side of the compression chamber, as a result of which the shoe 5 may be caused to float away from the sliding surface of the swash plate 3. This is why the locus is in the shape of a circular arc. The hole 39 is a hole for receiving the shaft 2.
FIG. 3 shows an exemplary cross-sectional structure of the swash plate 3. FIG. 3 is a schematic view showing a structure in a cross section perpendicular to a sliding surface with respect to 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 on the shoe 5. Each of the coating layer 32 and the coating layer 33 is an example of the resin coating layer according to the present invention. The base material 31 has a disk shape having a hole in the center, and is formed of a metal that satisfies required characteristics; for example, an iron-based alloy, a copper-based alloy, or an aluminum-based alloy. For the purpose of preventing adhesion to the shoe 5, the base material 31 is preferably formed of a material different from that of the shoe 5.
The coating layer 32 is provided to improve the characteristics of the sliding surface of the swash plate 3. The coating layer 32 includes at least a binder resin. In this respect, the coating layer 32 is an example of a resin coating layer. The binder resin is formed of, for example, a thermosetting resin. As the thermosetting resin, for example, at least one of polyamide imide (PAI), polyamide (PA), and polyimide (PI), epoxies, polyether ether ketones (PEEK), and phenolic resins is used. The coating layer 32 may include a solid lubricant as an additive. Solid lubricants are added to improve the lubricating properties; i.e. to reduce the coefficient of friction. The coating layer 32 includes, for example, 20 to 70 vol % of a solid lubricant. As the solid lubricant, for example, at least one of MoS2, graphite (Gr), carbon, fluorine-based resins (polytetrafluoroethylene (PTFE), etc.), soft metals (Sn, Bi, etc.), WS2, and h-BN is used. The coating layer 32 may include hard particles as additives. As the hard particles, for example, at least one of oxides, nitrides, carbides, and sulfides is used.
For the purpose of preventing abrasion 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 still more 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 to expose the base material 31. When the substrate 31 is exposed, problems occur in which the coefficient of friction increases or the substrate 31 adheres to the shoe 5. Further, since there is a possibility that if the film of the coating layer 32 is too thick seizure resistance may be lowered, it is preferable that thickness is 50 μm or less. The material and thickness of the coating layer 33 are the same as those of the coating layer 32.
FIG. 4 shows an exemplary surface shape of the base material 31. A plurality of grooves 312 are formed on the surface 311 of the base material 31. The surface 311 is a surface facing the shoe 5, which is an example of a mating member. The groove 312 is formed along the sliding direction with respect to the shoe 5. In this example, the groove 312 has a shape that extends radially from the center of the hole 39, as viewed from a position moved from the center of the hole 39 in a direction perpendicular to the surface 311. The groove 312 is an example of a groove extending in a direction crossing the sliding direction with the mating member in the entire circumference of the ring shape of the base material 31.
FIG. 5 shows an exemplary shape of the groove 312. FIG. 5 is a schematic view of the groove 312 as viewed from a direction perpendicular to the surface 311. In this example, the groove 312 is formed by laser machining. Laser machining refers to machining technology that utilizes the energy of laser light. Specifically, the groove 312 is formed by moving the irradiation position while pulsing the base material 31 with the laser beam. Part of the base material 31 is melted and scattered by one pulse of laser light irradiation, whereby a substantially circular recess (or hole) is formed. By moving the irradiation position concentrically, concentric grooves 312 are formed. In a cross section perpendicular to the sliding direction, the plurality of grooves 312 have a substantially arc shape. The interval p1 between the bottoms of the adjacent grooves 312 is, for example, 10 to 100 μm, and the width w1 of the opening of the groove 312 is, for example, 10 to 100 μm. In this example, the spacing p1 and the width w1 are approximately equal. In one example, the spacing p1 is between 40 and 80 μm. The interval p1 may be larger than the width w1. In the cross section parallel to the sliding direction, the groove 312 is not flat, but has minute irregularities caused by the spot of the laser beam. In one example, the interval p2 between the concavities and convexities is 10 to 30 μm.
FIG. 6 shows an exemplary surface shape of the coating layer 32. The surface 321 of the coating layer 32 becomes a sliding surface that slides with the shoe 5. A plurality of grooves 322 are formed in the surface 321. In this example, the grooves 322 have the shape of concentric circles having a common center with the hole 39 when viewed from a position moved from the center Cs of the hole 39 in a direction perpendicular to the surface 321. In the plurality of grooves 322, each distance p2 between the bottoms of adjacent grooves 322 and each width w2 of the grooves 322 are substantially the same as the distance p1 and the width w1, respectively. The interval p2 and the width w2 may be different from the interval p1 and the width w1.
Here, the problem to be solved by the present invention will be described in detail. The inventors of the present application have been working to replace the roughening treatment of the surface 311 of the base material 31, which has been conventionally performed by shot blasting, by laser processing. First, a base material 31 having concentric grooves whose centers are common to the centers of the holes 39 on the surface 311 was prototyped. When the swash plate having the resin coating layer formed on the base material 31 was subjected to an abrasion test, the inventors discovered that abnormal abrasion occurs.
FIGS. 7A and B illustrate abrasion. FIG. 7A shows normal abrasion and tear and FIG. 7B shows abnormal abrasion. In normal abrasion, the sliding surface after use is substantially flat. On the other hand, in the abnormal abrasion, the surface of the coating layer 32 is abraded following the groove formed in the surface 311 of the base material 31. That is, in the coating layer 32, the portion corresponding to the groove is worn more deeply than the other portions. Due to such uneven abrasion, convexity (or a groove) following the groove formed in the surface 311 of the base material 31 is formed on the sliding surface after use.
To avoid unexpected failures, it is desirable to reduce such uneven abrasion. The inventors of the present application have made the following hypothesis as to the cause of the occurrence of uneven abrasion. In the example using the base material 31 having the concentric grooves, since the coating layer 32 has few irregularities in the sliding direction, a force that opposes a shearing force generated in the sliding direction has little effect. Therefore, abrasion tends to progress in the direction along the groove, that is, in the sliding direction. Based on this hypothesis, the inventors of the present application have conceived a surface structure in which a force that opposes a shearing force generated in the sliding direction works easily.
2. Manufacturing Method FIG. 8 shows an exemplary flowchart illustrating a method of manufacturing the swash plate 3. In step S1, the base material 31 is prepared. The preparation of the base material 31 includes, for example, grinding of the surface and cleaning using a cleaning liquid. In step S2, a groove 312 is formed in the surface 311 of the base material 31. The groove 312 is formed by, for example, laser processing. In step S3, the surface 311 is cleaned. This washing is performed by air blowing without using a washing liquid such as alcohol, for example. In step S4, a precursor material of the coating layer 32 is applied onto the substrate 31. The application of the precursor material is carried out, for example, by roll coating or pad printing. In step S5, the coating layer 32 is dried and fired. In step S6, a groove 322 is formed in the surface 321 of the coating layer 32. The groove 322 is formed by cutting, for example.
3. Examples (1) Sample Preparation FIGS. 9A and B show the surface shapes of the base material 31 in working examples and comparative examples. In the comparative example (FIG. 9A), concentric grooves 312 were formed by laser machining. The distance between the concave portions formed by the pulse irradiation of the laser beam in the traveling direction of the machining process (in this case, the traveling direction is substantially equal to the sliding direction) was 10 to 30 μm, and the distance between the concave portions formed in the direction perpendicular to the traveling direction was 40 to 80 μm. The surface roughness after processing was about 8 RzJIS in the direction of progress of the processing. In the example (FIG. 9B), radial grooves 312 were formed by laser machining. The surface roughness after processing was about 6 RzJIS.
A resin coating layer was formed on the substrate 31 subjected to the above surface treatment. PAIs were used as binder resins, and MoS2 and graphite were used as solid lubricants.
(2) Abrasion Test The abrasion test was carried out under the following conditions, known as poor lubrication conditions.
Lubrication method: oil mist spraying
Lubrication: 0.22 mg/min
Peripheral speed: 4.2 m/s
Surface pressure: 3.2 MPa
Test time: 20 min.
Atmosphere: Atmosphere
(3) Test Results FIGS. 10A and B show the surface state of the resin coating layer after the abrasion test. FIG. 10A shows the results of the example, and FIG. 10B) shows the results of the comparative example. In the comparative example, in the direction perpendicular to the sliding direction, grooves having a depth of about 2 to 3 μm were present on the surface (sliding surface) of the sample at the same interval as the grooves 312 on the base material 31. That is, uneven abrasion occurred. On the other hand, in the example, the surface of the sample was almost flat (about 0.3 μmRa) without any groove. Thus, according to the embodiment, uneven abrasion can be suppressed.
In addition to suppressing uneven abrasion of the resin coating layer, the swash plate according to the example can simplify the roughening step and the subsequent cleaning step as compared with the example in which shot blasting is used for roughening the surface 311 of the base material 31.
4. Modification The present invention is not limited to the embodiments described above, and various modifications can be applied. Several variations are described below. Two or more of the items in the following modifications may be combined.
The shape of the groove 322 is not limited to the example shown in the embodiment. For example, the grooves 322 may have other shapes, such as concentric circles, spirals, or grids.
Substrate 31 is not limited to being formed of a single material. For example, a two-layer structure in which a copper alloy lining layer is formed on a steel backing metal, or a structure having three or more layers may be used.
