Sliding material and fluid machine

Abstract

The present invention addresses the problem of providing a sliding material capable of preventing a fiber material from falling off during sliding. In order to solve this problem, a sliding material (12) is composed of a composite material (12c) and has a sliding surface (12d) on a surface of the composite material (12c), the composite material (12c) including a resin material (12a) as a base material and a fiber material (12b1) disposed inside the resin material (12a). The number of pieces of the fiber material (12b) oriented in a direction within ± 45° with respect to an axis (L1) extending in a direction perpendicular to the sliding surface (12d) is 50% or more of the total number of pieces of the fiber material (12b) included in the composite material (12c).

Description

Sliding materials and fluid machinery

[0001] The present disclosure relates to a sliding member and a fluid machine.

[0002] Gas compressors that compress gases such as air generally include reciprocating gas compressors and scroll gas compressors. For example, in a reciprocating gas compressor, a piston that reciprocates within a metal cylinder is fitted with a piston ring as a sliding member that slides against the inner surface of the cylinder. In a scroll gas compressor, for example, a metal fixed scroll and a rotating scroll that orbits relative to the fixed scroll are fitted with chip seals as the sliding members at each end thereof.

[0003] The abstract of Patent Document 1 states that "a rotating cylinder member 2 and a piston holding member 5 are rotatably supported by a casing and a case top lid, respectively, and pistons 3 and 4 are held at a rotation center position eccentric from the rotation center position of the piston holding member 5 so as to be rotatable around that position, and the relative rotation between the rotating cylinder member 2 and the piston holding member 5 causes the pistons 3 and 4 themselves to rotate around the rotation center position and also around the rotation center position, thereby moving in and out of cylinder chambers 23a to 23d, and the casing is provided with suction ports and discharge ports connected to the cylinder chambers 23a to 23d, and the pistons 3 and 4 are formed of a resin material containing carbon nanofibers."

[0004] Japanese Patent Application Laid-Open No. 2004-270506

[0005] In the pistons 3 and 4 described in Patent Document 1, the orientation of the carbon nanofibers is not controlled. Therefore, when the pistons 3 and 4 slide, the carbon nanofibers may easily fall off from the pistons 3 and 4. The problem to be solved by the present disclosure is to provide a sliding material and a gas compressor that can prevent the fiber material from falling off during sliding.

[0006] The sliding material of the present disclosure is constituted by a composite material including a resin material as a base material and a fiber material disposed inside the resin material, the composite material has a sliding surface on its surface, and the number of fiber materials oriented in a direction within ±45° with respect to an axis extending in a direction perpendicular to the sliding surface is 50% or more of the total number of fiber materials contained in the composite material. Other solutions will be described later in the description of the preferred embodiment of the invention.

[0007] According to the present disclosure, it is possible to provide a sliding material and a gas compressor that can suppress the fibrous material from falling off during sliding.

[0008] 3A is a cross-sectional view showing a sliding part in a fluid machine of one embodiment; FIG. 3B is a view showing ideal fiber material orientation; FIG. 3C is a view showing a state in which a molten composite material flows inside a mold; FIG. 3D is a cross-sectional view of a composite material obtained by cutting at the portion indicated by the thin solid arrow in FIG. 3A; FIG. 3E is a cross-sectional view showing the configuration of a scroll-type gas compressor as an example of a fluid machine; FIG. 3F is an enlarged view of a portion of the fixed scroll and the orbiting scroll of the gas compressor shown in FIG. 4; FIG. 3G is a view showing a gas compression unit constituting a reciprocating gas compressor as another embodiment of the fluid machine; FIG. 3H is a view explaining a method of a friction test; FIG. 3I is a view showing the results of wear volume obtained in a friction test; and FIG. 3J is a view showing the results of friction coefficient obtained in a friction test.

[0009] Hereinafter, modes for carrying out the present disclosure (hereinafter referred to as "embodiments") will be described with reference to the drawings. In the following description of one embodiment, other embodiments applicable to the one embodiment will also be described as appropriate. The present disclosure is not limited to the one embodiment described below, and different embodiments can be combined with each other or modified as desired without significantly impairing the effects of the present disclosure. Furthermore, the same components will be given the same reference numerals, and duplicate descriptions will be omitted. Furthermore, components having the same functions will be given the same names. The contents shown are merely schematic, and for convenience of illustration, changes may be made from the actual configuration within the scope of not significantly impairing the effects of the present disclosure, and some components may be omitted or modified between drawings. Furthermore, the same embodiment does not necessarily have to include all of the configurations.

[0010] FIG. 1 is a cross-sectional view showing a sliding portion 10 of a fluid machine 100 according to one embodiment. The fluid machine 100 is, for example, a gas compressor that compresses gas. The gas compressor may be, for example, a scroll type or a reciprocating type. The specific structure of the gas compressor will be described later with reference to FIG. 4 and the like.

[0011] The sliding unit 10 includes a metal member 11 such as a metal cylinder, and a sliding material 12 such as a piston ring. The sliding material 12 is fitted onto the outer periphery of a piston, for example. In the sliding unit 10, the sliding material 12 comes into contact with and slides on the member 11 at a sliding surface 11c. The sliding surface 11c is formed on the surface of the member 11. The sliding form between the sliding material 12 and the member 11 may be a reciprocating motion, a circular motion, or an approximately circular motion that is not strictly circular but is similar to a circular motion.

[0012] The sliding material 12 is made of a composite material 12c. The composite material 12c includes a resin material 12a as a base material and a fiber material 12b disposed inside the resin material 12a. The fiber material 12b is dispersed, preferably uniformly, inside the resin material 12a, for example. The sliding material 12 includes a sliding surface 12d on the surface of the composite material 12c. The sliding surface 12d faces the sliding surface 11c and slides against the sliding surface 11c.

[0013] The resin material 12a can be composed of any resin. For example, the resin material 12a can be a fluororesin. Examples of the fluororesin include at least one of polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-ethylene copolymer (ETFE), and polyvinylidene fluoride (PVDF). For example, two or more types of PTFE and other fluororesins can be used in combination. The resin material 12a can also be a resin other than fluororesin, such as polyether ether ketone (PEEK), polyimide (PI), polyphenylene sulfide (PPS), or modified versions of these. The resin material 12a can also be a combination of two or more resins, such as a mixture of PTFE and a fluororesin other than PTFE. The resin material 12a does not have to be a fluororesin, and can be any other resin.

[0014] Among these, the resin material 12a preferably contains at least one of polyphenylene sulfide, polytetrafluoroethylene, and polyether ether ketone. By including these, the durability of the sliding material 12 can be particularly improved. Among these, PTFE has high crystallinity and low shear strength. Therefore, when subjected to shear, PTFE easily peels off at the microscopic level and transfers to the mating surface (sliding surface), such as the inner surface of a cylinder, thereby improving sliding properties.

[0015] The fiber material 12b can be made of any material as long as it has a fibrous structure. Examples of the fiber material 12b include carbon fiber, glass fiber, metal fiber, and ceramic fiber. Examples of the carbon fiber that can be used include pitch-based carbon fiber and PAN-based carbon fiber. The fiber material 12b may be made of one type only, or two or more types may be used in combination.

[0016] Among these, it is preferable that the fiber material 12b contains carbon fiber. Because carbon fiber is relatively soft, it is less aggressive to the sliding surface 11c and causes less damage to the sliding surface 11c during sliding. This improves the durability of the sliding surface 11c. Furthermore, when the carbon fiber wears due to sliding, a carbon film is formed on the sliding surface 11c. This improves the lubricity of the sliding surface 11c. Therefore, by including carbon fiber, excellent effects can be obtained in terms of wear durability. Furthermore, the high affinity between the carbon fiber and the resin material 12a makes it difficult for the carbon fiber to fall off during sliding.

[0017] The type of the fiber material 12b can be easily confirmed by performing morphological observation and chemical analysis using a scanning electron microscope, energy dispersive X-ray analysis, infrared spectroscopy, X-ray diffraction, or the like on a sample such as the surface of the sliding material 12 or crushed pieces of the sliding material 12.

[0018] The fibrous material 12b preferably has a solid rod shape with a fiber length longer than its diameter. By having such a shape, the fibrous material 12b embedded in the resin material 12a can support the load received from the sliding surface 11c when the sliding material 12 slides.

[0019] The diameter (fiber diameter) of the fiber material 12b is, for example, preferably 2 μm or more and 30 μm or less, more preferably 5 μm or more and 20 μm or less. As will be described in detail later, in the present disclosure, the fiber material 12b is disposed inside the resin material 12a along the wear direction. Therefore, by setting the fiber diameter within this range, the fiber material 12b can bear the load received from the sliding surface 12d through a relatively wide surface area. This makes it easier to support the load applied to the fiber material 12b, and prevents the fiber material 12b from falling off the resin material 12a. This effect is particularly noticeable in harsh environments such as high pressure and high temperature.

[0020] The length of the fibrous material 12b (fiber length) is, for example, preferably 1 μm to 1000 μm, more preferably 50 μm to 1000 μm, and even more preferably 100 μm to 250 μm. By setting the fiber length within this range, the length of the fibrous material 12b is sufficiently maintained even when the sliding material 12 is worn due to sliding, making it difficult for the fibrous material 12b to fall off from the resin material 12a.

[0021] The diameter and length of the fibrous material 12b can be measured, for example, based on image analysis. Specifically, the diameter and length of the fibrous material 12b are preferably determined by, for example, selecting a plurality of (e.g., five) fibrous materials 12b in a cross-sectional micrograph and using the average values ​​of the diameter and length of each selected fibrous material 12b. Note that, because cross-sectional micrographs are typically two-dimensional images, it may be impossible to measure the diameter and length of the fibrous material 12b for the same fibrous material 12b. For this reason, the diameter and length do not need to be measured for the same fibrous material 12b, and may be measured for different fibrous materials 12b.

[0022] In the sliding material 12 of the present disclosure, the number of fibers 12b oriented in a direction within ±45° of the axis L1 extending perpendicular to the sliding surface 12d (hereinafter referred to as the number in the present disclosure) is 50% or more of the total number of fibers 12b contained in the composite material 12c. That is, if the axis extending in the extension direction of the fibers 12b is defined as axis L2, the number of fibers 12b (the number in the present disclosure) for which the angle θ between axis L1 and axis L2 is within 45° is 50% or more of the total number of fibers 12b contained in the composite material 12c. Hereinafter, the ratio of the number (quantity, number) of fibers 12b oriented in a direction within ±45° of the axis L1 to the total number (total quantity, total number) of fibers 12b contained in the composite material 12c will be referred to as the "orientation of the fibers 12b," "orientation in the present disclosure," etc., as appropriate. Therefore, in the present disclosure, the orientation of the fibers 12b is 50% or more.

[0023] The direction perpendicular to the sliding surface 12d is the thickness direction of the sliding material 12 and also the wear direction of the sliding material 12. The orientation direction of the fibrous material 12b is also the longitudinal direction of the fibrous material 12b.

[0024] By controlling the orientation of the fiber material 12b in this manner, the fiber material 12b can be arranged along the wear direction (extension direction of the axis L1) of the composite material 12c (sliding material 12). This reduces the effect of the load on the side surface of the fiber material 12b during sliding. In other words, the load can be mainly borne by the end surface (e.g., the circular upper surface) of the fiber material 12b during sliding, and falling off of the fiber material 12b can be suppressed. As a result, the wear resistance of the sliding material 12 can be improved, and friction during sliding (e.g., the friction coefficient described below) can be reduced.

[0025] The orientation of the fiber material 12b in the sliding material 12 can be confirmed by observing the morphology of a cross section in the thickness direction of the sliding material 12 using a scanning electron microscope or the like, and calculating the directionality of each fiber material 12b in the observed cross section by image analysis. In this case, the orientation of the fiber material 12b may be confirmed for the entire cross section of the sliding material 12, but for simplicity, the orientation of the fiber material 12b may be confirmed based on only a portion (for example, one arbitrary) of a cross-sectional micrograph, and the result may be used to consider the orientation of the fiber material 12b in the entire cross section of the sliding material 12.

[0026] The angle θ can be determined as follows: For example, in a cross-sectional photograph taken using a scanning electron microscope, an axis L2 indicating the extension direction of the fiber material 12b is determined by an appropriate approximation method or the like, and the angle θ can be measured as the angle between the axis L2 and the axis L1.

[0027] 2 is a diagram showing an ideal orientation of the fiber material 12b. Ideally, it is preferable that all of the fiber material 12b be oriented in the same direction as the axis L1. That is, it is preferable that the axis L1 and the axis L2 are parallel, and the angle θ (FIG. 1) is 0°. By doing so, when the sliding material 12 wears, the load received from the sliding surface 11c can be received by the end face of the fiber material 12b (the face on the sliding surface 12d side), making it particularly difficult for the fiber material 12b to fall off.

[0028] However, in reality, such orientation control is often difficult (however, the present disclosure does not exclude the configuration shown in FIG. 2). Therefore, taking into consideration the effort and ease of orientation control, the number of fiber materials 12b oriented in a direction preferably within ±30°, more preferably within ±15°, with respect to axis L1 is 50% or more of the total number of fiber materials 12b contained in composite material 12c. In other words, it is preferable that the number of fiber materials 12b having axes L2 whose angle θ is preferably within 30°, more preferably within 15°, is 50% or more of the total number of fiber materials 12b contained in composite material 12c.

[0029] 1 , the number of the above-described fibers according to the present disclosure is preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more of the total number of fiber materials 12b contained in the composite material 12c (based on the total number of fiber materials 12b contained in the composite material 12c). By doing so, as many fiber materials 12b as possible can be arranged along the axis L1, making it more difficult for the fiber materials 12b to fall off.

[0030] The reason for controlling the orientation of the fibrous material 12b will be explained. The inventors conducted numerous friction tests and found a correlation between the wear of the sliding material 12, which is a composite resin, and the orientation of the fibrous material 12b. Specifically, they determined that when the number of fibers of the present disclosure described above is less than 50% of the total number of fibers 12b contained in the composite material 12c, the shear strength of the sliding material 12 is significantly reduced. Furthermore, they confirmed that in this case, the fibrous material 12b falls off from the sliding material 12, and the effect of the fibrous material 12b in supporting the shear stress is lost. As a result, they found that the abrasive action of the fallen fibrous material 12b increases wear. They also confirmed that the abrasive action tends to increase friction by impairing the surface smoothness of the sliding material 12.

[0031] On the other hand, when the number of the above-described fibers according to the present disclosure is 50% or more of the total number of fiber materials 12b contained in the composite material 12c, the decrease in shear strength of the sliding material 12 is suppressed, thereby maintaining the durability of the composite material 12c itself. Furthermore, the fiber materials 12b are oriented such that they are embedded in the sliding material 12 (ideally, in a direction perpendicular to the sliding surface 12d, as shown in FIG. 2, for example) in response to shear stress. This increases the contact area between the fiber materials 12b and the sliding material 12 at the sliding surface 12d. This suppresses the fiber materials 12b from falling off. As a result, the fiber materials 12b maintain their effect of supporting shear stress and also reduce abrasive action, thereby reducing wear and friction.

[0032] As described above, by appropriately controlling the orientation of the fiber material 12b in the sliding material 12, it is possible to maintain the shear strength of the composite material 12c and reduce the abrasive action of the fallen fiber material 12b, thereby contributing to improving the wear resistance of the sliding material 12 and reducing friction.

[0033] For example, the "pistons 3 and 4" described in Patent Document 1 may be made of various resins as a base material and contain carbon nanotubes (hereinafter referred to as CNTs). CNTs have a smaller diameter than fiber materials such as carbon fiber. Therefore, they cannot effectively support shear stress in harsh environments such as high pressure and high temperature. Furthermore, because CNTs have a small diameter and a short length, their contact area with the base material is small. Therefore, they are prone to falling off from the base material and being worn away by abrasive action, especially in harsh environments.

[0034] As described above, by controlling the orientation of the fiber material 12b in the sliding material 12, it is possible to improve the wear resistance of the sliding material in a harsh environment while reducing friction.

[0035] The orientation control of the fiber material 12b can be performed, for example, as follows, but the method of orientation control is not limited to the following example.

[0036] Fig. 3A is a diagram showing the flow of molten composite material 12c inside mold 70. Fig. 3B is a cross-sectional view of composite material 12c obtained by cutting at the portion indicated by the thin solid arrow in Fig. 3A. In Fig. 3A, the outline arrow indicates the flow direction of molten composite material 12c.

[0037] When a composite material 12c containing a resin material 12a and a fiber material 12b is injection molded in a mold 70, the composite material 12c flows from one direction to another within the mold 70, away from the injection port (inlet) of the composite material 12c, as indicated by the white arrows. Due to this flow, the fiber material 12b in the composite material 12c is generally aligned along the flow direction of the composite material 12c (i.e., the longitudinal direction of the fiber material 12b faces the flow direction). Therefore, in the solidified composite material 12c, the orientation of the fiber material 12b is generally unidirectional. Therefore, the orientation of the fiber material 12b in the composite material 12c molded in this manner can be confirmed by a cross-sectional micrograph. The orientation of the fiber material 12b in the sliding material 12 can be controlled by, for example, cutting the composite material 12c along the thin solid arrows so that the orientation of the fiber material 12b is in the desired direction.

[0038] Returning to FIG. 1 , the content of the fiber material 12b relative to the composite material 12c (the content of the fiber material 12b in the composite material 12c) is preferably 5% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 30% by mass or less. By setting the content of the fiber material 12b within this range, aggregation of the fiber material 12b within the composite material 12cb can be suppressed, and the fiber material 12b can be dispersed to easily apply a load to the fiber material 12b. Furthermore, excessively high rigidity of the molten composite material 12c during the injection molding can be suppressed, and injection molding can be easily performed, making it easy to control the orientation of the fiber material 12b. The content of the fiber material 12b can be measured, for example, based on thermal analysis using a simultaneous thermal mass and differential heat measurement device, mass change evaluation, or the like.

[0039] The composite material 12c may contain any additives other than the resin material 12a and the fiber material 12b. For example, the composite material 12c may contain a solid lubricant (not shown) disposed in the resin material 12a. The solid lubricant is preferably in particulate form and is disposed, preferably dispersed, in the resin material 12a.

[0040] Examples of solid lubricants include at least one of polytetrafluoroethylene (PTFE), molybdenum disulfide, graphite, and boron nitride. The inclusion of a solid lubricant can improve sliding properties. It is preferable that PTFE be included as a solid lubricant when the resin material 12a is a resin material other than PTFE. Even when the resin material 12a is PTFE, it is preferable that the PTFE constituting the resin material 12a and the PTFE constituting the solid lubricant have different physical properties, such as number average molecular weight and degree of polymerization.

[0041] Among these, the solid lubricant preferably contains at least one of polytetrafluoroethylene, molybdenum disulfide, and graphite, which can particularly improve the lubricity of the sliding material 12.

[0042] The solid lubricant may have a particle shape with an average particle size of 10 μm or more and 500 μm or less as measured by a laser diffraction particle size distribution analyzer, for example.

[0043] The composite material 12c may include a metal material (not shown, e.g., a filler) disposed in the resin material 12a. The metal material is preferably in the form of particles and is disposed, preferably dispersed, in the resin material 12a. Examples of the metal material include at least one of copper, copper alloy, aluminum, and aluminum alloy. In particular, the metal material preferably includes at least one of copper and copper alloy. By including these, the wear resistance of the sliding material 12 can be particularly improved.

[0044] The metal material may have a particle shape with an average particle size of 10 μm or more and 500 μm or less as measured by a laser diffraction particle size distribution analyzer, for example.

[0045] The composite material 12c may contain at least one of ceramics, carbon, etc. By including these, it is possible to obtain the same effects as a metal material. These materials may have a particle shape with an average particle size of 10 μm or more and 500 μm or less as measured by a laser diffraction particle size distribution analyzer, for example.

[0046] The sliding surfaces (sliding interfaces) 11 c, 12 d may contain lubricants such as lubricating oil, grease, etc. However, it is preferable that the fluid machine 100 is a fluid machine that is particularly effective when used in an oil-less state without sufficient lubricating oil, or when used in an oil-free state without any lubricating oil, etc.

[0047] The member 11 preferably has a surface treatment layer 11b on the surface of a metal material 11a serving as a base material. That is, a sliding surface 11c, which is the surface of the surface treatment layer 11b, comes into contact with a sliding surface 12d, and the sliding material 12 slides on the sliding surface 11c. However, the member 11 does not necessarily have to have the surface treatment layer 11b, and the metal material 11a may be exposed without having the surface treatment layer 11b. Therefore, the sliding surface 11c, which is the surface of the member 11, may be formed of the metal constituting the metal material 11a, or may be formed of the surface treatment layer 11b.

[0048] Examples of the metal material 11a include at least one of light metals such as aluminum, magnesium, and silicon, and transition metals such as iron, chromium, nickel, molybdenum, titanium, and copper. Specific examples of the metal material 11a that can be used include at least one of the following: aluminum-based materials such as aluminum and aluminum alloys; iron-based materials such as iron and iron-nickel alloys; titanium-based materials such as titanium and titanium alloys; and copper-based materials such as copper and copper alloys. Among these, the use of aluminum-based materials provides excellent wear resistance. The aluminum-based materials may contain, for example, small amounts of magnesium, silicon, etc. The iron-based materials may also contain, for example, chromium, nickel, molybdenum, etc.

[0049] The surface treatment layer 11b may be, for example, a natural oxide film formed naturally on the metal material 11a, an artificially applied surface coating, etc. That is, the surface treatment layer 11b may be a layer formed naturally in the natural environment, or may be a layer formed artificially by any surface treatment (e.g., sulfuric acid anodizing treatment). In the case of a natural oxide film, for example, if the metal material 11a is aluminum, the surface treatment layer 11b may be made of aluminum oxide; if the metal material 11a is iron, the surface treatment layer 11b may be made of iron oxide; and if the metal material 11a is copper, the surface treatment layer 11b may be made of copper oxide.

[0050] When the surface treatment layer 11b is a surface coating layer, the surface coating layer can be formed by, for example, plating, physical vapor deposition (PVD), chemical vapor deposition (CVD), carburizing, etc. The surface coating layer is made of a material containing at least one of aluminum, phosphorus, chromium, iron, nickel, and zinc. Examples of surface coatings containing such elements include anodizing, aluminum plating, nickel plating, chromium plating, iron plating, and zinc plating.

[0051] 4 is a cross-sectional view showing the configuration of a scroll-type gas compressor 20 as an example of fluid machinery 100. Gas compressor 20 includes a casing 23 forming the outer shell of gas compressor 20, a drive shaft 24 rotatably provided in casing 23, a fixed scroll 21 attached to casing 23, and an orbiting scroll 22 rotatably provided on a crankshaft 24A of drive shaft 24.

[0052] The fixed scroll 21 includes a fixed end plate 21 a and a fixed scroll wrap 21 b formed in a spiral shape on one main surface side of the fixed end plate 21 a. The orbiting scroll 22 includes a orbiting end plate 22 a and a orbiting scroll wrap 22 b formed in a spiral shape on one main surface side of the orbiting end plate 22 a. The orbiting scroll 22 includes a boss portion 22 f protruding from the center of the back side of the orbiting end plate 22 a.

[0053] The orbiting scrolls 22 are arranged opposite each other so that the orbiting scroll wrap 22b and the fixed scroll wrap 21b are meshed with each other, thereby forming a compression / expansion chamber 25 as a working space for compressing or expanding gas between the fixed scroll wrap 21b and the orbiting scroll wrap 22b.

[0054] The compression / expansion chamber 25 is provided in the gas compressor 20 (an example of a fluid machine 100) and is an example of a chamber that performs at least one of compression and expansion. However, the compression / expansion chamber 25 may be a chamber that performs both compression and expansion. The sliding portion 30 is provided in the gas compressor 20 and includes a sliding member 12 that slides on a sliding surface 12d that defines the compression / expansion chamber 25. The sliding member 12 is a chip seal 291, 292 described below. The sliding surface 12d is a wrap bottom surface 21e, 22e (FIG. 5) described below.

[0055] An intake port 26 is formed on the outer periphery of the fixed head 21a. The intake port 26 communicates with the compression / expansion chamber 25 on the outermost periphery. A discharge port 27 is formed in the center of the fixed head 21a. The discharge port 27 opens to the compression / expansion chamber 25 on the innermost periphery.

[0056] The drive shaft 24 is rotatably supported by the casing 23 via ball bearings 28. One end of the drive shaft 24 is connected to an electric motor (not shown) or the like outside the casing 23, and the other end of the drive shaft 24 extends into the casing 23 to form a crankshaft 24A. The axis of the crankshaft 24A is eccentric with respect to the axis of the drive shaft 24 by a predetermined distance.

[0057] An annular thrust bearing portion 31 is provided on the inner periphery on the orbiting scroll 22 side. A thrust plate 32 is provided between the thrust bearing portion 31 and the orbiting end plate 22a. The thrust plate 32 is formed as an annular plate made of a metal material such as iron. When the orbiting scroll 22 orbits, the surface of the orbiting scroll 22 slides against the orbiting end plate 22a. At this time, the thrust plate 32, together with the thrust bearing portion 31, bears the load acting on the orbiting scroll 22 in the thrust direction (the direction that moves the orbiting scroll 22 away from the fixed scroll 21) mainly during compression operation. This suppresses galling, abnormal wear, and the like between the casing 23 and the orbiting end plate 22a.

[0058] An Oldham ring 33 is provided between the thrust bearing portion 31 and the orbiting end plate 22a at a position closer to the center than the thrust plate 32. When the orbiting scroll 22 is rotationally driven by the drive shaft 24, the Oldham ring 33 suppresses the rotation of the orbiting scroll 22 and imparts circular motion with a predetermined orbital radius to the crankshaft 24A.

[0059] When the drive shaft 24 is driven to rotate by an electric motor (not shown) or the like, the orbiting scroll 22 orbits with a predetermined orbital radius. As a result, external air drawn in through the suction port 26 is sequentially compressed in a compression / expansion chamber 25 defined between the fixed scroll wrap 21 b and the orbiting scroll wrap 22 b. The compressed air thus generated is discharged from the discharge port 27 of the fixed scroll 21 to an external air tank (not shown) or the like.

[0060] Fig. 5 is an enlarged view of a portion of the fixed scroll 21 and the orbiting scroll 22 of the gas compressor 20 shown in Fig. 4. A groove 21d is formed in an end face 21c of the fixed scroll wrap 21b facing the orbiting end plate 22a, and a tip seal 291 (sliding member) is fitted into the groove 21d. A groove 22d is also formed in an end face 22c of the orbiting scroll wrap 22b facing the fixed end plate 21a, and a tip seal 292 (sliding member) is also fitted into the groove 22d.

[0061] As the orbiting scroll 22 orbits, the tip seal 291 slides against the wrap bottom surface 21 e (sliding surface) of the orbiting end plate 22 a, and the tip seal 292 slides against the wrap bottom surface 22 e (sliding surface) of the fixed end plate 21 a. This makes it possible to suppress contact between the fixed scroll wrap 21 b and the wrap bottom surface 21 e, and between the orbiting scroll wrap 22 b and the wrap bottom surface 22 e, thereby achieving a smooth sliding state.

[0062] In Figure 5, the fixed scroll 21 and the orbiting scroll 22 correspond to the member 11 in Figure 1. The fixed scroll 21 and the orbiting scroll 22 (particularly the wrap bottom surfaces 21e, 22e) are made of an aluminum-based material such as aluminum or an aluminum alloy. The wrap bottom surfaces 21e, 22e, together with the fixed scroll wrap 21b and the orbiting scroll wrap 22b, define a compression / expansion chamber 25. An anodized aluminum layer (not shown) is formed on the surface of each of the fixed scroll 21 and the orbiting scroll 22, as an example of the surface treatment layer 11b (Figure 1). Therefore, in the gas compressor 20, the sliding surface 11c is formed on the surface of an aluminum member containing aluminum and is also the surface of the anodized aluminum layer.

[0063] In the sliding portion 30 between the thrust plate 32 and the rotating head plate 22a, the surface of the thrust plate 32 or the surface of the rotating head plate 22a that form the sliding surface may be coated with the composite resin material described above. Also, in the above explanation, an example was shown in which the thrust plate 32 is made of a metal material such as iron, but the thrust plate 32 itself may be made of the sliding material 12 (composite resin material).

[0064] In the above description, gas compressor 20 is provided with a mechanism (rotation suppression mechanism) that suppresses rotation of orbiting scroll 22 by means of thrust plate 32 and Oldham ring 33 provided at a position closer to the center than thrust plate 32. However, gas compressor 20 is not limited to the above description, and may be a scroll-type gas compressor that is provided with a rotation suppression mechanism such as an auxiliary crank or an Oldham coupling (not shown).

[0065] FIG. 6 is a diagram showing a gas compression section 40 constituting a reciprocating gas compressor 400 as another embodiment of the fluid machine 100. There are two types of gas compressors 400. The first type is a normal piston type in which a bearing is provided at the compression / expansion chamber side end of the connecting rod and the piston is oscillatably supported by the bearing. A normal piston type gas compressor compresses gas by the reciprocating motion of the piston oscillatably supported by the bearing. The second type is a swing piston type in which there is no bearing on the compression / expansion chamber side of the connecting rod and the piston is integrated with the connecting rod. FIG. 6 shows a gas compression section 40 of the second type, the swing piston type, as an example.

[0066] The gas compression section 40 includes a cylinder 41 and a piston 42 that reciprocates while oscillating within the cylinder 41. The cylinder 41 (an example of a member 11) is made of an aluminum-based material, such as aluminum or an aluminum alloy. An anodized aluminum layer (not shown) is formed on an inner surface 48 of the cylinder 41 as an example of a surface treatment layer 11b (FIG. 1). However, the anodized aluminum layer or other surface treatment layer 11b does not necessarily have to be formed. The anodized aluminum layer may be formed by natural oxidation or by anodizing. The inner surface 48 is an example of a sliding surface 11c, and is formed on the surface of an aluminum member containing aluminum and is the surface of an anodized aluminum layer. The inner surface 48, together with a partition plate 45 and the piston 42, defines a compression / expansion chamber 44.

[0067] A piston ring 43 (an example of a sliding member 12) is fitted around the piston 42. A compression / expansion chamber 44, which is a working space for compressing or expanding gas, is formed in the space above the piston 42 within the cylinder 41. The compression / expansion chamber 44 is provided in the gas compressor 400 (an example of a fluid machine 100), and is an example of a chamber that performs at least one of compression and expansion. However, the compression / expansion chamber 44 may be a chamber that performs both compression and expansion.

[0068] The upper end of the cylinder 41 is closed by a partition plate 45, which has an inlet port 45a and an outlet port 45b. The inlet port 45a and the outlet port 45b are provided with an inlet valve 45c and an outlet valve 45d. The inlet port 45a and the outlet port 45b are connected to pipes (not shown), respectively.

[0069] The operating principle of gas compression will be explained below. The piston 42 is integrally formed with the connecting rod 46. As the crankshaft 47 rotates, the piston 42 moves up and down. As a result, gas is drawn into the compression / expansion chamber 44 through the intake port 45a and compressed within the compression / expansion chamber 44. The compressed gas is discharged to the outside through the discharge port 45b and collected by piping (not shown).

[0070] The sliding portion 50 in the gas compressor 400 will be described below. The sliding portion 50 is provided in the gas compressor 400 (an example of a fluid machine 100), and includes a piston ring 43 (an example of a sliding member 12) that slides on an inner surface 48 that defines the compression / expansion chamber 44. As described above, the piston ring 43 is fitted onto the outer periphery of the piston 42. The piston 42 is a separate part from the connecting rod 46 that supports the piston 42. The connecting rod 46 may be made of metal or resin. As the piston 42 reciprocates up and down, the piston 42 and the piston ring 43 slide on the inner circumferential surface of the cylinder 41.

[0071] In the above description, the reciprocating gas compressor 400 is of a swing piston type, but is not limited to this and may be of the normal piston type, for example. In the normal piston type, the sliding member 12 can be applied to a piston ring, a rider ring, or the like (neither of which are shown).

[0072] The gas supplied by the gas compressors 20 and 400 is not limited to air, but may be atmospheric air or a dry gas with an extremely low water vapor content. Examples of dry gases include gases with a dew point of −30° C. or lower. Examples of dry gases include synthetic air, high-purity nitrogen gas, oxygen gas, helium gas, argon gas, and hydrogen gas.

[0073] The sliding material 12 can exhibit sufficient wear resistance and low friction regardless of the type of gas being compressed. Therefore, a gas compressor using the sliding material 12 can also be used to compress, for example, dry gas.

[0074] The present disclosure will be explained in more detail below with reference to examples.

[0075] The effects of improving the wear resistance and reducing friction of the sliding material 12 were confirmed through experiments using a friction test method.

[0076] <Materials Used> In the studies of Examples 1 to 3 and Comparative Examples 1 and 2, polyphenylene sulfide (PPS) was used as the resin material 12a (FIG. 1), and carbon fiber was used as the fiber material 12b (FIG. 1). The content of fiber material 12b in the composite material 12c (FIG. 1) was 10% by mass. The length and diameter of the carbon fiber were 130 μm and 12 μm, respectively, as the average length and average diameter based on the above measurement methods.

[0077] In Examples 1 to 3, the orientation of the fiber material 12b (orientation according to the present disclosure) was set to 50% or more. Specifically, it was 75% in Example 1, 60% in Example 2, and 50% in Example 3. On the other hand, in Comparative Examples 1 and 2, the orientation of the fiber material 12b (orientation according to the present disclosure) was set to less than 50%. Specifically, it was 35% in Comparative Example 1 and 20% in Comparative Example 2. The materials used and the orientation of the fiber material 12b are summarized in Table 1 below.

[0078]

[0079] <Method of Friction Test> Figure 7 is a diagram illustrating the method of the friction test. Each of the composite materials 12c of Examples 1 to 3 and Comparative Examples 1 and 2 was molded into a block-shaped test piece 61. The test piece 61 imitated the sliding material 12 (Figure 1). The test piece 61 was a rectangular parallelepiped with a width of 6 mm, a length of 20 mm, and a height of 5 mm, and was produced by C-chamfering two opposing longitudinal sides of the top surface. The C-chamfering was 0.5 mm each.

[0080] The test piece 62 used in the friction test was prepared by the following method. The test piece 62 is a replica of the member 11 (FIG. 1), for example. The test piece 62 was prepared by molding an aluminum alloy into a ring shape (annular, cylindrical) with an outer diameter of 13 mm and an inner diameter of 9 mm. An anodized aluminum layer was formed on the surface (particularly the lower surface) of the test piece 62 by sulfuric acid anodizing treatment.

[0081] The friction test was carried out by contacting and rotating (i.e., sliding) the lower surface of the ring-shaped test piece 62 with the upper surface of the test piece 61. The test conditions were controlled as follows: contact pressure: 0.9 MPa, rotation speed: 1.9 m / s, temperature: 90° C., and rotation for 15 hours.

[0082] FIG. 8 is a diagram showing the results of the wear amount obtained in the friction test. The wear amount was the difference in mass of the test piece 61 before and after the wear test. In both FIG. 8 and FIG. 9 described below, the wear amount is expressed as a relative value when Comparative Example 2 is set to 1. In Examples 1 to 3, the wear amount was reduced to about 0.3 (30%) compared to Comparative Example 2. On the other hand, in Comparative Example 1, the wear amount was about 0.9 (90%) compared to Comparative Example 2, and it was found that there was no significant difference in the wear amount between Comparative Examples 1 and 2.

[0083] FIG. 9 is a diagram showing the results of the friction coefficient obtained in the friction test. The friction coefficient was calculated by dividing the mass loss (amount of wear) before and after the friction test by the density of the test piece 61. The smaller the friction coefficient, the less likely it is to wear, and the higher the durability, such as wear resistance, is. In Examples 1 to 3, the friction coefficient was reduced to about 0.6 (60%) compared to Comparative Example 2. On the other hand, Comparative Example 1 was almost the same as Comparative Example 2, and it was found that there was no significant difference in the friction coefficient.

[0084] These results demonstrate that controlling the orientation of the fiber material 12b (the orientation of the present disclosure) to 50% or more reduces the amount of wear and the coefficient of friction. As shown in FIG. 9 , Examples 1-3 and Comparative Examples 1-2 show completely different results at the 50% boundary. This demonstrates the superiority of increasing the orientation of the fiber material 12b to 50% or more. These results are likely due to the fact that most of the fiber material 12b is oriented along the wear direction of the sliding material 12, making it difficult for the fiber material 12b to come out of the resin material 12a during sliding. Furthermore, because the fiber material 12b is difficult to come out, it is believed that the fiber material 12b can support the load from the sliding surface 12d over a long period of time, thereby suppressing abrasive action. Therefore, it was confirmed that increasing the orientation of the fiber material 12b to 50% or more can simultaneously improve the wear resistance of the sliding material 12 and reduce the coefficient of friction.

[0085] Therefore, by applying the sliding material 12 to, for example, tip seals of scroll gas compressors or pistons of reciprocating gas compressors, the wear resistance of the tip seals, pistons, etc. can be improved, thereby extending their replacement lifespan. Also, loss due to friction can be reduced. As a result, the maintenance cycle and lifespan of fluid machinery such as scroll gas compressors and reciprocating gas compressors can be extended, and their efficiency can be improved.

[0086] On the other hand, Comparative Example 1 was almost the same as Comparative Example 2, and it was found that there was no significant difference in the amount of wear and the coefficient of friction. This result is thought to be due to a decrease in the shear strength of the composite material 12c and a decrease in the contact area with the resin material 12a on the sliding surface 12d, which resulted in an increase in the amount of fiber material 12b falling off. As a result, it is thought that the amount of wear increased and the coefficient of friction increased due to the abrasive action.

[0087] DESCRIPTION OF SYMBOLS 10 Sliding part 100 Fluid machine 11 Member 11a Metal material 11b Surface treatment layer 11c Sliding surface 12 Sliding material 12a Resin material 12b Fiber material 12c Composite material 12c Composite material 12d Sliding surface 20 Gas compressor 21 Fixed scroll 21a Fixed head plate 21b Fixed scroll wrap 21c End face 21d Groove 21e Wrap bottom surface (sliding surface) 22 Orbiting scroll 22a Orbiting head plate 22b Orbiting scroll wrap 22c End face 22e Wrap bottom surface (sliding surface) 25 Compression / expansion chamber (chamber) 291 Tip seal (sliding material) 292 Tip seal (sliding material) 30 Sliding part 40 Gas compression part 400 Gas compressor 41 Cylinder 42 Piston 43 Piston ring (sliding material) 44 Compression / expansion chamber (chamber) 45 Partition plate 48 Inner surface (sliding surface) 50 Sliding portion 61, 62 Test piece L1, L2 Shaft

Claims

1. A sliding material comprising a composite material containing a resin base material and a fiber material disposed inside the resin material, the composite material having a sliding surface on its surface, the number of fiber materials oriented in a direction within ±45° of an axis extending in a direction perpendicular to the sliding surface being 50% or more of the total number of fiber materials contained in the composite material.

2. The sliding material according to claim 1, characterized in that the fiber material has a solid rod shape with a fiber length longer than its diameter.

3. The sliding material according to claim 2, characterized in that the fiber length is 1 μm or more and 1000 μm or less.

4. The sliding material according to claim 1, characterized in that the fiber material contains carbon fiber.

5. The sliding material according to claim 1, characterized in that the resin material contains at least one of polyphenylene sulfide, polytetrafluoroethylene, and polyether ether ketone.

6. The sliding material according to claim 1, characterized in that the composite material contains a solid lubricant disposed in the resin material.

7. The sliding material according to claim 6, characterized in that the solid lubricant contains at least one of polytetrafluoroethylene, molybdenum disulfide, and graphite.

8. The sliding material according to claim 1, characterized in that the composite material includes a metal material disposed in the resin material.

9. The sliding material according to claim 8, characterized in that the metal material contains at least one of copper and a copper alloy.

10. The sliding material according to claim 1, characterized in that the content of said fiber material in said composite material is 5 mass % or more and 30 mass % or less.

11. A fluid machine comprising: a chamber for performing at least one of compression and expansion of a gas; and a sliding part having a sliding material that slides on a sliding surface that defines the chamber, wherein the sliding material is made of a composite material including a resin material as a base material and a fiber material disposed inside the resin material, the composite material has a sliding surface, and the number of fiber materials oriented in a direction within ±45° of an axis extending in a direction perpendicular to the sliding surface is 50% or more of the total number of fiber materials contained in the composite material.

12. The fluid machinery according to claim 11, characterized in that the sliding surface is formed on the surface of an aluminum member containing aluminum and is the surface of an anodized aluminum layer.

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