Sliding member combining a photocurable resin composition and surface treatment of the mating material

Abstract

To provide a sliding member that achieves low frictional coefficients not only in a room temperature environment but also in a low temperature environment.SOLUTION: A sliding member includes a self-lubricating liner and a bearing element member to be in surface contact with it. The bearing element member includes a coating on the surface of a metal member. The surface of the coating includes a sliding contact opposing surface to be in slide contact with the self-lubricating liner. The surface roughness Ra on the sliding contact opposing surface, as expressed by arithmetic mean roughness, is 0.3 μm or more and 1.8 μm or less, and the coating has an indentation hardness of 400 mgf / μm2 or more and 1200 mgf / μm2 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sliding member that combines a sliding surface having a self-lubricating liner made of a photocurable resin composition with a surface treatment of the mating material, and more particularly to a sliding member that achieves a low coefficient of friction not only at room temperature but also at low temperatures. [Background technology]

[0002] Sliding bearings, which support the shaft through a sliding surface, are used in a wide range of applications, including aircraft, railways, automobiles, and general industrial machinery. In particular, lubrication-free sliding bearings, which have a self-lubricating liner on the sliding surface and do not use lubricating oil, are used in applications such as ships and aircraft where low friction coefficient, high durability, high load capacity, high heat resistance, and high oil resistance are required.

[0003] One embodiment of such a lubrication-free sliding bearing is disclosed, in which a self-lubricating liner layer is provided on the sliding surface. For example, Patent Document 1 discloses an ultraviolet-curable resin composition containing an isocyanuric acid ring (meth)acrylate compound and a polytetrafluoroethylene resin as a solid lubricant, and discloses an embodiment in which this is used as a self-lubricating liner. Furthermore, embodiments are disclosed in which a coating is provided on the opposing surface in contact with the self-lubricating liner layer. For example, Patent Document 2 discloses a self-lubricating sliding bearing comprising a bearing element member having a sliding contact opposing surface that slides in contact with a self-lubricating liner, wherein the bearing element member is made of a titanium alloy having a nitride diffusion layer on the sliding contact opposing surface, and the sliding contact opposing surface has a surface roughness of less than 18 nanometers CLA. Patent Document 3 also discloses a self-lubricating sliding bearing in which the sliding contact opposing surface has a surface finish of less than 20 nm and a hardness of less than approximately 1000 VPN, wherein the sliding contact opposing surface has a coating such as a physically vapor-deposited film on a convex curved surface. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 5882451 [Patent Document 2] Japanese Patent Publication No. 2006-162068 [Patent Document 3] Special Publication No. 2007-507674 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] For unlubricated sliding bearings used in aircraft and other applications, a low coefficient of friction and minimal change in that coefficient are required over a wide temperature range from low to high temperatures (for example, -55°C to 163°C in aircraft applications). However, it has been confirmed that the coefficient of friction increases significantly below 0°C in sliding bearings proposed to date, so the ability to achieve a low coefficient of friction in low-temperature environments is required.

[0006] The present invention has been made in view of these circumstances, and aims to provide a sliding member that can achieve a low coefficient of friction not only in a normal temperature environment but especially in a low temperature environment. [Means for solving the problem]

[0007] One aspect of the present invention comprises a self-lubricating liner and a bearing element member that is in surface contact with the same, The bearing element member has a coating on the surface of a metal member, and the surface of the coating has a sliding contact opposing surface that slides into contact with the self-lubricating liner. The surface roughness Ra, expressed as an arithmetic mean roughness, of the sliding contact opposing surfaces is 0.3 μm or greater. The thickness is 0.8 μm or less, and the coating has an indentation hardness of 400 mg f / μm 2 More than 1200mgf / μm 2 This invention relates to a sliding member characterized by having the following hardness. [Brief explanation of the drawing]

[0008] [Figure 1]It is a schematic diagram for explaining the structure of a self-lubricating sliding bearing (spherical sliding bearing), which is an example of the sliding member of the present invention. [Figure 2] It is a cross-sectional view showing an enlarged part of the self-lubricating sliding bearing in FIG. 1. [Figure 3] It is a schematic diagram for explaining the structure of a cylindrical journal bearing, which is an example of the sliding member of the present invention, and is a longitudinal sectional view (FIG. 3(a)) cut along the axial direction of the journal bearing and a cross-sectional view (FIG. 3(b)) cut in a direction perpendicular to the axis. [Figure 4] It is a diagram showing the external appearance (FIG. 4(a)) and cross-sectional view (FIG. 4(b)) of the pinion disk wear tester used in the rocking test of the embodiment. [Figure 5] In the embodiment, it is a diagram showing the result of the value of the coefficient of friction (vertical axis) with respect to the hardness (horizontal axis) at normal temperature (25°C). [Figure 6] In the embodiment, it is a diagram showing the result of the value of the coefficient of friction (vertical axis) with respect to the surface roughness (horizontal axis) at normal temperature (25°C). [Figure 7] In the embodiment, it is a diagram showing the result of the value of the coefficient of friction (vertical axis) with respect to the hardness (horizontal axis) at -55°C. [Figure 8] In the embodiment, it is a diagram showing the result of the value of the coefficient of friction (vertical axis) with respect to the surface roughness (horizontal axis) at -55°C. [Figure 9] In the embodiment, it is a diagram showing the result of the value of the coefficient of friction (vertical axis) with respect to the surface roughness (horizontal axis) at normal temperature (25°C) [vertical axis: □ without coating (SUS304), ● with coating (same composition)]. [Figure 10] In the embodiment, it is a diagram showing the result of the value of the coefficient of friction (vertical axis) with respect to the surface roughness (horizontal axis) at -55°C [vertical axis: □ without coating (SUS304), ● with coating (same composition)].

Mode for Carrying Out the Invention

[0009] As described above, in light of the challenge of achieving a low coefficient of friction for sliding members in low-temperature environments, the inventors focused on the surface roughness and hardness of the opposing surface that slides in contact with the self-lubricating liner in a sliding member having a self-lubricating liner. They discovered for the first time that when the sliding contact opposing surface has a specific range of surface roughness and hardness, it is possible to suppress the increase in the coefficient of friction not only in normal temperature environments but also in low-temperature environments, thereby achieving a low coefficient of friction. The present invention will be described in detail below.

[0010] The sliding member according to the present invention comprises a self-lubricating liner and a bearing element member that is in surface contact with the self-lubricating liner, as described later, wherein the bearing element member has a coating on the surface of a metal member, and the surface of the coating has a sliding contact opposing surface that is in sliding contact with the self-lubricating liner. Furthermore, the surface roughness Ra, expressed as an arithmetic mean roughness, of the sliding contact opposing surface is 0.3 μm or more and 1.8 μm or less, and the indentation hardness of the coating is 400 mgf / μm 2 More than 1200mgf / μm 2 It is characterized by having the following hardness levels. This sliding contact surface and the coating configuration have the characteristic of achieving a low coefficient of friction not only at room temperature but also in low-temperature environments. The details will be explained below.

[0011] [Sliding member] The present invention relates to a sliding member comprising a self-lubricating liner and a bearing element member. The sliding member described above may include, for example, a first member and a second member that slide relative to each other, and a liner provided on the sliding surface of the first member or the sliding surface of the second member. It is possible. Preferred embodiments of the sliding member according to the present invention will be described in detail below with reference to the attached drawings, but the present invention is not limited to the embodiments described below.

[0012] Figure 1 is a cross-sectional view showing a self-lubricating sliding bearing 1, which is an example of a preferred sliding member of the present invention. The self-lubricating sliding bearing 1 comprises a housing 2 having a sliding contact bearing surface 3, a self-lubricating liner 4 fixed to the sliding contact bearing surface 3, and a bearing element member 6 (coating not shown) held within the housing 2 and having a sliding contact opposing surface 10 that precisely slides into contact with the self-lubricating liner 4.

[0013] In the embodiment shown in Figure 1, the self-lubricating sliding bearing 1 is a spherical sliding bearing in which the sliding contact bearing surface 3 is concave spherical and the sliding contact opposing surface 10 is convex spherical. In other words, Figure 1 can be said to show a radial cross-sectional view of the spherical sliding bearing. In this embodiment, a spherical self-lubricating plain bearing 1 is consistently used as a reference, but the present invention is not limited to spherical plain bearings, and includes cylindrical journal bearings and planar contact type bearings, and is not limited to them, and can be similarly applied to other types of self-lubricating plain bearings.

[0014] Figure 2 is a cross-sectional view showing an enlarged view of portion A of the self-lubricating sliding bearing 1 in Figure 1. In Figure 2, the bearing element member 6 has a coating 9 on the sliding contact opposing bearing surface 8, which is the surface of the metal member 7, and the coating 9 constitutes a sliding contact opposing surface 10 that slides in contact with the sliding contact surface 5 of the self-lubricating liner 4 fixed to the sliding contact bearing surface 3 of the housing 2.

[0015] In the coating 9, the surface roughness of the sliding contact opposing surface 10, which is its surface, is arithmetic mean roughness of 0.3 μm or more and 1.8 μm or less, preferably 0.5 μm or more and 1.2 μm or less. Furthermore, the indentation hardness of the coating 9 is 400 mgf / μm 2 More than 1200mgf / μm 2 The following, preferably 400 mgf / μm 2 More than 900mgf / μm 2 The following applies. Note that in this book, indentation hardness is measured using the nanoindentation method. Generally, the surface roughness of a coating is related to the occurrence of abrasive wear and the size of the true contact area, and the hardness of the coating is related to the occurrence of wear on the opposing surface (e.g., the liner) and wear on the coating itself; both can be factors that increase the coefficient of friction. In this invention, by achieving the above surface roughness, the potential wear and damage to the self-lubricating liner 4 caused by the sliding contact opposing surface 10 can be significantly reduced, and by achieving the above hardness, scratches on the sliding contact opposing surface 10 during subsequent use of the self-lubricating sliding bearing 1 can be kept to a minimum. As a result, a low coefficient of friction can be achieved, and consequently, the lifespan of the self-lubricating sliding bearing 1 can be increased.

[0016] The metal member 7 of the bearing element member 6 is formed from a metal such as bearing steel, stainless steel, die steel, duralumin, or titanium alloy. In a preferred embodiment, the metal member 7 of the bearing element member 6 may be made of stainless steel or die steel.

[0017] The coating 9 formed on the metal member 7 (sliding contact opposing bearing surface 8) of the bearing element member 6, and constituting the sliding contact opposing surface 10, can be, but is not limited to, a composite coating in which a resin material is dispersed in a metal matrix or ceramic matrix. Any material having the aforementioned hardness and surface roughness is acceptable, such as a chromium carbide alloy, for example, hard chromium carbide. A rom alloy or similar material can be used as the coating 9. In a preferred embodiment, the coating 9 may be a composite coating in which a fluororesin material is dispersed in a nickel-containing matrix, and in a more preferred embodiment, it may be a composite coating in which a fluororesin material is dispersed in a nickel and phosphorus-containing matrix.

[0018] The coating 9 can be formed, for example, by using a coating-forming material comprising a dispersion of a metal matrix and a resin material, and bringing it into contact (coating, dipping, etc.) with the sliding contact opposing bearing surface 8, but is not limited to this. Examples of preferred film-forming materials include electroless plating solutions. Alternatively, for example, a coating material consisting of a ceramic raw material matrix and a resin material dispersed in it can be used to form a coating 9 on the sliding contact opposing bearing surface 8, in which the resin material is dispersed in the ceramic matrix, using a sol-gel method or the like. A preferred ceramic matrix is, for example, Al2O3. Furthermore, a coating 9 made of a hard chromium carbide alloy can be formed using hard chromium plating technology.

[0019] The thickness of the coating 9 is not particularly limited, but can be, for example, between 1 μm and 50 μm, or between 5 μm and 30 μm, or between 10 μm and 15 μm.

[0020] The housing 2 can be formed from a metal such as bearing steel, stainless steel, die steel, duralumin, or titanium alloy.

[0021] Furthermore, the self-lubricating liner 4 fixed to the sliding contact bearing surface 3 of the housing 2 is made of a cured product of a photocurable resin composition, which will be described later.

[0022] The self-lubricating plain bearing 1 (spherical plain bearing) shown in Figure 1 can be manufactured, for example, by the following process. First, a coating 9 is formed on the sliding contact opposing bearing surface 8 (outer surface) of the metal member 7 of the bearing element member 6, for example, by applying a coating-forming material or by using a sol-gel method or plating technology. On the other hand, a photocurable resin composition, described later, is applied to the sliding contact bearing surface 3 (inner circumferential surface) of the housing 2, and then the applied photocurable resin composition is cured by irradiating it with ultraviolet light. Next, the cured product is finished by machining to form a self-lubricating liner 4 of a predetermined thickness. At this time, the thickness of the liner is not particularly limited, but it can be, for example, about 0.25 mm. All self-lubricating liners 4 can be easily dimensionally adjusted by cutting and / or grinding, and in this sense they are sometimes appropriately called "machinable liners". Subsequently, the bearing element member 6 is inserted into the housing 2, and the housing 2 is pressed to perform swaging, which involves plastically deforming the bearing element member 6 so that it conforms to the convex spherical surface of the sliding contact opposing surface 10 of the coating 9. Finally, the outside of the housing 2 is finished by machining to complete the self-lubricating sliding bearing 1 (spherical sliding bearing).

[0023] Figure 3 also shows a longitudinal section (Figure 3(a)) cut along the axial direction and a cross section (Figure 3(b)) cut perpendicular to the axis of a cylindrical journal bearing 20, which is another embodiment of a self-lubricating sliding bearing, an example of a preferred sliding member of the present invention.

[0024] As shown in Figure 3(a), the cylindrical journal bearing 20 has a cylindrical outer ring 21 and a self-lubricating liner 23 formed on the sliding contact bearing surface 22, which is the inner circumferential surface of the outer ring 21. The sliding contact surface 2 of the self-lubricating liner 23, which is the sliding surface of the cylindrical journal bearing 20 In step 4, the bearing element member 28 (the so-called shaft, shown as a dashed line in Figure 3(a)), which is the object being slid, is supported. The outer ring 21 is formed from the same metal as the housing in the self-lubricating sliding bearing 1 described above.

[0025] As shown in Figure 3(b), the bearing element member 28 has a coating 27 on the sliding contact opposing bearing surface 26, which is the surface of the shaft 25, which is a form of a metal member, and the coating 27 constitutes a sliding contact opposing surface 29 that slides in contact with the sliding contact surface 24 of the self-lubricating liner 23 fixed to the sliding contact bearing surface (inner circumferential surface) 22 of the outer ring 21. In the aforementioned coating 27, the surface roughness and indentation hardness of the sliding contact opposing surface 29 are the same as those of the sliding contact opposing surface 10 of the coating 9 in the self-lubricating sliding bearing 1 described above. Furthermore, the type of coating 27 (composite coating, chromium carbide alloy, etc.), the material and method of forming the coating 27, and the thickness of the coating 27 are the same as those of the coating 9 in the self-lubricating sliding bearing 1 described above. Furthermore, the shaft 25, which is one embodiment of the metal member of the bearing element member 28, is formed from the same metal as the metal member 7 in the self-lubricating sliding bearing 1 described above.

[0026] The cylindrical journal bearing 20 shown in Figure 3 can be manufactured, for example, by the following process, similar to the self-lubricating sliding bearing 1 described above. A photocurable resin composition, described later, is applied to the sliding contact bearing surface 22, which is the inner circumferential surface of the outer ring 21 member. Then, the applied photocurable resin composition is irradiated with ultraviolet light to cure the composition. Next, the cured product is finished by machining to form a self-lubricating liner 24 of a predetermined thickness (for example, about 0.25 mm). On the other hand, a coating 27 is formed on the sliding contact opposing bearing surface 26 (surface of the shaft 25), which is a metal member of the bearing element member 28, by, for example, applying a coating-forming material or by using a sol-gel method or plating technology.

[0027] [Self-lubricating liner: Photocurable resin composition] In the sliding member according to the present invention, the self-lubricating liner that slides into contact with the aforementioned sliding contact opposing surface may be made of a photocurable resin composition containing a (meth)acrylate compound having an isocyanuric acid ring and a polytetrafluoroethylene resin.

[0028] [(meth)acrylate compounds having an isocyanuric acid ring] The photocurable resin composition may contain a (meth)acrylate compound having an isocyanuric acid ring [also known as an isocyanurate having a (meth)acryloyl group] as a component that hardens upon light irradiation. The (meth)acrylate compound having an isocyanuric acid ring has the function of imparting heat resistance to the photocurable resin composition. The (meth)acrylate compound having an isocyanuric acid ring is preferably having two or more (meth)acryloyl groups, for example, two or three. In this document, for example, "(meth)acryloyl group" refers to both acryloyl group and methacryloyl group. The (meth)acryloyl group is also called a (meth)acrylic group, and the (meth)acryloyloxy group is also called a (meth)acryloxy group.

[0029] The (meth)acrylate compound having an isocyanuric acid ring is preferably a compound represented by the following formula (1). [ka] In formula (1), X is a group that includes a (meth)acryloyl group and consists only of C, H, and O, and Y and Z are groups that consist only of C, H, and O. The above Y and Z may or may not contain a (meth)acryloyl group. The above X is preferably a (meth)acryloylethyl group or a (meth)acryloxyethyl group modified with ε-caprolactone, and Y and Z are preferably the same group as X.

[0030] Examples of the (meth)acrylate compound having an isocyanuric acid ring include bis(2-(meth)acryloyloxyethyl)hydroxyethyl isocyanurate, di-(2-(meth)acryloxyethyl) isocyanurate, tris-(2-(meth)acryloxyethyl) isocyanurate, ε-caprolactone-modified tris-(2-(meth)acryloxyethyl) isocyanurate, and the like. These can be used alone or in combination of two or more. Among them, preferred compounds include di-(2-acryloxyethyl) isocyanurate (DAEIC), tris-(2-acryloxyethyl) isocyanurate (TAEIC), ε-caprolactone-modified tris-(2-acryloxyethyl) isocyanurate (CTAI), and mixtures thereof.

[0031] The (meth)acrylate compound having an isocyanuric acid ring can be used at a ratio of 20% to 89.75% by mass, for example, 20% to 50% by mass, or for example, 20% to 40% by mass, based on the total mass of the photocurable resin composition. If it is less than 20% by mass, the fluidity of the resin is insufficient, making it difficult to apply, and the liner strength also tends to be insufficient. Also, when the content exceeds 89.75% by mass, the content of polytetrafluoroethylene resin, which is a solid lubricant described later, decreases, and the lubricity tends to deteriorate.

[0032] [Polytetrafluoroethylene resin] The above photocurable resin composition can contain a component having a function of imparting lubricity, that is, polytetrafluoroethylene resin (hereinafter also referred to as PTFE) as a solid lubricant. PTFE is a polymer of tetrafluoroethylene and is represented by the general formula: [C2F4] n (n: degree of polymerization). The shape of the PTFE described above is not particularly limited, and any form such as powder, particulate (spherical, polyhedral, needle-shaped), or fibrous may be used alone or in combination. For example, if the PTFE is in particulate form, the size of the particles is not particularly limited, but polytetrafluoroethylene with an average particle size of 0.5 to 200 μm can be used.

[0033] The above PTFE may be subjected to a surface treatment in which its surface is etched with sodium naphthalene and then coated with epoxy-modified acrylate. By applying such a surface treatment, the affinity with the acrylic resin produced from the (meth)acrylate compound having an isocyanuric acid ring is increased, and the bond with the acrylic resin becomes stronger. As a result, when the cured product of the above photocurable resin composition is used as a self-lubricating liner, the PTFE powder, particles, Alternatively, it can prevent the fibers from falling off the self-lubricating liner, and the PTFE solid lubricant in contact with the sliding surface reduces the coefficient of friction of the self-lubricating liner. Consequently, the amount of wear on the self-lubricating liner can be reduced.

[0034] The above polytetrafluoroethylene resin can be used in a proportion of 10% to 50% by mass relative to the total mass of the photocurable resin composition, for example, in a proportion of 20% to 40% by mass. If the proportion is less than 10% by mass, the amount of PTFE in contact with the sliding surface will be small, and the effect of reducing the coefficient of friction will be small, which may result in not satisfying the desired lubrication performance. If the proportion exceeds 50% by mass, the wear of PTFE will be significant, which may increase the amount of wear on the self-lubricating liner and increase the coefficient of friction of the self-lubricating liner.

[0035] [Other (meth)acrylate compounds] The above photocurable resin composition may contain other (meth)acrylate compounds other than the (meth)acrylate compound having an isocyanuric acid ring. Other (meth)acrylate compounds that do not have an isocyanuric acid ring may have functions such as imparting chemical resistance, accelerating curing reactions, improving adhesion to metals, accelerating crosslinking reactions, and imparting toughness, but are not limited to these functions. Other (meth)acrylate compounds can be set in various ways, depending on the types and amounts of other components. For example, the total amount of other (meth)acrylate compounds can be in the range of approximately 0.1 to 30% by mass relative to the total mass of the photocurable resin composition.

[0036] Other (meth)acrylate compounds may include epoxy (meth)acrylate alone or in combination of two or more. Epoxy (meth)acrylate can function as a chemical resistance modifier, that is, it imparts chemical resistance without impairing the strength after curing. The epoxy (meth)acrylate is not particularly limited, but examples include modified bisphenol A type epoxy acrylate or bisphenol A type epoxy-modified acrylate. When using epoxy (meth)acrylate, the amount used can be 20% by mass or less of the total mass of the photocurable resin composition, for example, 1% to 10% by mass. If the amount exceeds 20% by mass, cracking may occur in the cured product when the photocurable resin composition is cured, due to the epoxy's own rigid structure.

[0037] Other (meth)acrylate compounds may include polyfunctional (meth)acrylates without isocyanuric acid rings, such as those with three or more functions (i.e., having three or more (meth)acrylic groups), either alone or in combination of two or more. Since polyfunctional (meth)acrylates contain multiple functional groups that serve as starting points for polymerization reactions, they can accelerate the polymerization reaction (curing reaction) without impairing the strength or heat resistance after curing, and can thus act as curing reaction accelerators. Examples of polyfunctional (meth)acrylates include pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol polyacrylate, and trimethylolpropane tri(meth)acrylate. When using polyfunctional (meth)acrylates that do not have an isocyanuric acid ring in combination, the amount of these acrylates can be 15% by mass or less, for example, 1% to 15% by mass, relative to the total mass of the photocurable resin composition. If the amount exceeds 15% by mass, it may lead to a rapid curing reaction, making handling during the production of the cured product difficult.

[0038] Other (meth)acrylate compounds may include (meth)acrylates having a hydroxyl group or isobornyl (meth)acrylates, either alone or in combination of two or more. Hydroxyl (meth)acrylates and isobornyl (meth)acrylates may function as adhesion enhancers to metals (i.e., sliding surfaces), and hydroxyl (meth)acrylates may function as viscosity modifiers (reactive diluents). Examples of (meth)acrylates having a hydroxyl group include hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate. When using (meth)acrylates or isobornyl (meth)acrylates having a hydroxyl group, the amount used can be 1% to 30% by mass, for example, 2% to 20% by mass, relative to the total mass of the photocurable resin composition.

[0039] Other (meth)acrylate compounds may include crosslinkable (meth)acrylates, such as those having multiple unsaturated bonds of equal reactivity and lacking an isocyanuric acid ring, either alone or in combination of two or more. The above crosslinkable (meth)acrylates can function as auxiliary agents for crosslinking reactions. Examples of (meth)acrylates that have multiple unsaturated bonds of equal reactivity and do not have an isocyanuric acid ring include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate. When a bifunctional (meth)acrylate that does not have an isocyanuric acid ring is used in combination, the amount of the acrylate added can be 5% by mass or less, for example, 0.1% to 5% by mass, relative to the total mass of the photocurable resin composition.

[0040] Other (meth)acrylate compounds may include urethane (meth)acrylate alone or in combination of two or more. Urethane (meth)acrylate can function as a toughness-imparting agent. When using urethane (meth)acrylate, the amount added can be 10% by mass or less, for example, 1% to 5% by mass, relative to the total mass of the photocurable resin composition.

[0041] [Filler] The above photocurable resin composition may contain fillers such as glass fibers, fumed silica, melamine cyanurate, and phosphates.

[0042] <Glass fiber> Glass fibers may be added to the above-mentioned photocurable resin composition for the purpose of improving the strength of the self-lubricating liner. As the glass fibers, circular cross-section glass fibers may be used, or irregular cross-section glass fibers with a non-circular cross-section may be used. In addition to glass fibers, the above-mentioned photocurable resin composition may also contain inorganic fibers such as carbon fibers, aramid fibers, and potassium titanate whiskers as reinforcing fibers. Glass fibers can be included in the photocurable resin composition in an amount of 30% by mass or less, for example, 1% to 30% by mass, relative to the total mass. If the glass fiber content exceeds 30% by mass, when the self-lubricating liner is cut or ground, the cut glass fibers may scratch the surface of the mating material, increasing the surface roughness and accelerating wear, which may impair the advantages of the machinable liner. Glass fibers are preferable because they do not reduce the transmittance of ultraviolet light.

[0043] <Hummed Silica> Fumed silica is used to impart thixotropy to photocurable resin compositions. If the liner forming material lacks sufficient thixotropy, dripping may occur when applying it to the application area (sliding surface), making liner formation difficult. In such cases, adding fumed silica can adjust the thixotropy of the material and improve handling during liner formation. Fumed silica can be included in the photocurable resin composition in an amount of 5% by mass or less, for example, 0.1% to 3% by mass, relative to the total mass. If the fumed silica content exceeds 5% by mass, it will cause sliding scratches on the surface of the mating material, resulting in uneven surface roughness, which leads to increased wear of the liner and is therefore undesirable.

[0044] <Melamine cyanurate> Melamine cyanurate, like PTFE, functions as a solid lubricant. By using melamine cyanurate together with PTFE, the coefficient of friction of the cured product of the photocurable resin composition can be reduced compared to when PTFE is used alone. Melamine cyanurate has a structure in which melamine molecules with a six-membered ring structure and cyanuric acid molecules are bonded by hydrogen bonds and arranged in a planar manner, and these planes overlap each other in layers by weak bonds, giving it cleavage properties. This structure is thought to contribute to its solid lubricity. Melamine cyanurate can be included in the photocurable resin composition at a concentration of 30% by mass or less, for example, 1% to 20% by mass, relative to the total mass. If the concentration exceeds 30% by mass, the friction coefficient of the self-lubricating liner decreases, but the amount of wear tends to increase, which is undesirable.

[0045] <Phosphate> By using phosphates as a component of self-lubricating liners, initial break-in is improved, and the coefficient of friction can be stabilized earlier than in the case without phosphates. Examples of phosphates include tertiary phosphates, disative phosphates, pyrophosphates, phosphates, or metaphosphates of alkali metals or alkaline earth metals. Specifically, these include trilithium phosphate, dilithium hydrogen phosphate, sodium hydrogen phosphate, lithium pyrophosphate, tricalcium phosphate, monocalcium hydrogen phosphate, calcium pyrophosphate, lithium metaphosphate, magnesium metaphosphate, and calcium metaphosphate. The phosphate can be included in the photocurable resin composition in an amount of, for example, 1% to 5% by mass relative to the total mass.

[0046] [Additives] The above photocurable resin composition may also contain various additives as desired, such as antioxidants, light stabilizers, preservatives, polymerization initiators (photoinitiators, thermal initiators), polymerization inhibitors, and dyes. When using the above additives, they can be used in a total proportion of 0.2% to 10% by mass relative to the total mass of the photocurable resin composition.

[0047] <Polymerization initiator: Photopolymerization initiator> Photoinitiators have the function of promoting the polymerization reaction of photocurable resin compositions by light irradiation (ultraviolet irradiation). Photoinitiators can be added to the photocurable resin composition in an amount of, for example, 0.1% to 5% by mass relative to the total mass. Photoinitiators can be used, for example, individually or in combination with the following, but are not limited to these: benzophenone, 4,4-bis(diethylamino)benzophenone, 2,4,6-trimethylbenzophenone, methyl orthobenzoylbenzoate, 4-phenylbenzophenone, 2-t-butylanthraquinone, 2-ethylanthraquinone, 2,2-diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 1-hydroxycyclohexyl-phenyl ketone, benzoin methyl ether, benzyl benzoin methyl ether, benzoin methyl ether, benzoin methyl ether, benzoin methyl ether, benzoin methyl ether, benzoin Zoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide Ido, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one, methylbenzoyl formate, 1,2-octanedione, 1-[4-(phenylthio)phenyl]-,2-(O-benzoyl oxime), ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-,1-(O-acetyl oxime), etc.

[0048] <Polymerization initiator: Thermal initiator> The thermal initiator has the function of promoting polymerization reactions by heat and can be incorporated into the photocurable resin composition in an amount of, for example, 0.1% to 5% by mass relative to the total mass. Examples of thermal initiators include azo polymerization initiators and organic peroxides that generate radicals when heated. When these are incorporated into a photocurable resin composition, the heat of reaction from the polymerization reaction caused by ultraviolet irradiation generates radicals in the azo polymerization initiator or organic peroxide, which in turn triggers the polymerization reaction of (meth)acrylate. As a result, the polymerization reaction proceeds even in areas not exposed to ultraviolet light, such as the inside of the photocurable resin composition, allowing the entire resin composition to be cured. Azo polymerization initiators may be used individually or in combination with the following, but are not limited to these: 2,2'-azobis(2-methylpropionic acid)dimethyl, 1,1'-azobis(1-cyclohexanecarboxylate methyl), 2,2'-azobis(2-methyl-N-2-propenylpropanamide), 2,2'-azobis(N-butyl-2-methylpropionamide), 1,1'-azobis(1-acetoxy-1-phenylethane), 2,2'-azobis(isobutyric acid)dimethyl, etc. Organic peroxides may also be used, but are not limited to, the following, either alone or in combination: methyl ethyl ketone peroxide, cyclohexanone peroxide, t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, p-menthane hydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, 2,5-dimethyl- 2,5-di(benzoylperoxy)hexane, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(t-butylperoxy)valerate, t-butylperoxylaurate, t-butylperoxypivalate, t-butylperoxybenzoate, t-butylperoxyisopropyl monocarbonate, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, t-amylperoxy-2-ethylhexanoate, t-butylperoxyneodikenate, etc.

[0049] Furthermore, considering that the above-mentioned photocurable resin composition will be used by coating, as will be described later, it is preferable that it be liquid at room temperature and have a viscosity that is easy to handle (a viscosity that allows for coating without dripping during coating). The viscosity of the photocurable resin composition can be, for example, about 20 Pa·s to 100 Pa·s at room temperature. [Examples]

[0050] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited thereto. It's not something that can be done.

[0051] [Photocurable resin composition] The photocurable resin compositions used in the examples were prepared using the components and content (mass%) listed in Table 1 below.

[0052] [Table 1]

[0053] [Oscillation test] The cured product of the above photocurable resin composition and the coating described later were agitated at room temperature (25°C) and in a low-temperature environment (in a chamber maintaining a low temperature of -54°C or lower), and the coefficient of friction was measured according to the following procedure. The test was conducted using the pin-on-disk wear tester shown in Figure 4, following the procedure below.

[0054] As shown in Figure 4, the pin-on-disk wear tester 30 has a pin 31 and a disc-shaped disk 32. The pin 31 has a diameter of φ5.85 mm, and the disk 32 has a diameter of φ30 mm. After applying the photocurable resin composition shown in Table 1 to the tip of pin 31, the integrated light intensity was 3000 mJ / cm². 2 The composition was then cured by irradiation with ultraviolet light to form a cured product, which was then machined to a thickness of 0.25 mm to form a layer (Prc layer) consisting of the cured photocurable resin composition. Disc 32 was made of SUS304 (stainless steel) or SKD (die steel), and coating C of the examples and comparative examples, having the composition and film thickness shown in Table 2 or Table 3, was formed on the surface of Disc 32. Discs without coating C (made of SUS304) were also used in the oscillation test as reference examples. In the following explanation, the example numbers for coatings, etc., shown in Table 2 or Table 3 will also be treated as example numbers for the evaluation of the coefficient of friction. The pin 31 was positioned so that the Prc layer at the tip of the pin was in perpendicular contact with the disk 32 (coating C), and the pin 31 was pressed against the disk 32 with a surface pressure of 5 MPa. In this state, it was moved back and forth with a rotation radius of 15 mm, an oscillation angle of 90 degrees, and a frequency of 0.1 Hz when one reciprocating motion constituted one cycle. The coefficient of friction was measured continuously during a 3-hour back-and-forth motion, and the measurement data after 3 hours was used as the test data. This test was conducted twice, and the coefficient of friction was calculated as the average value.

[0055] Prior to the oscillation test, the surface roughness Ra and surface indentation hardness of coating C (and SUS304 in the reference example) of the examples and comparative examples were evaluated according to the following procedure. [Surface roughness Ra (arithmetic mean roughness)] The surface roughness Ra was measured using a non-contact surface shape measuring instrument. A Zygo NewView200, utilizing scanning white light interferometry, was used. Five points were measured at arbitrary locations using the 50x objective lens mode, and the average value of the obtained measurements was defined as Ra. The measurement range was 0.257 mm × 0.192 mm, and the light source was a white LED. [Indentation hardness (hardness)] Hardness was measured using an ultra-micro indentation hardness tester. The ultra-micro indentation hardness tester used was the ENT-1100a, manufactured by Elionix Co., Ltd., which utilizes the nanoindentation method. Under conditions of a triangular pyramidal indenter (Berkovich indenter) and a load of 1000 mgf, 30 points on the coating cross-section were measured. The indentation hardness was defined as the average value obtained by subtracting 5 points each from the maximum and minimum values ​​when the samples were arranged in ascending order. The coating cross-sections used were buffed and polished before the indentation hardness measurement.

[0056] The results obtained are shown in Tables 2 and 3. Furthermore, regarding the results in Table 2, Figure 5 shows the coefficient of friction (vertical axis) against hardness (horizontal axis) at room temperature (25°C), Figure 6 shows the coefficient of friction (vertical axis) against surface roughness (horizontal axis) at room temperature (25°C), Figure 7 shows the coefficient of friction (vertical axis) against hardness (horizontal axis) at -55°C, and Figure 8 shows the coefficient of friction (vertical axis) against surface roughness (horizontal axis) at -55°C. Furthermore, regarding the results in Table 3, Figure 9 shows the coefficient of friction (vertical axis) against surface roughness (horizontal axis) at room temperature (25°C) when the coating components are the same [□ No coating (SUS304), ● With coating (indicated as NYF-11S in the figure)], and Figure 10 shows the coefficient of friction (vertical axis) against surface roughness (horizontal axis) at -55°C [□ No coating (SUS304), ● With coating (indicated as NYF-11S in the figure)].

[0057] [Table 2]

[0058] [Table 3]

[0059] As shown in Table 2, in Reference Examples 1 and 2, where the disc material was SUS304 (stainless steel) and no coating was applied, the coefficient of friction at -55°C was approximately 0.23, and at room temperature (25°C) it was approximately 0.14 to 0.15, regardless of surface roughness. These values ​​for the coefficient of friction without coating are intended as reference values, as shown in Figures 5, 6, and 9 (room temperature). In Figures 7, 8, and 10 (-55℃), dashed lines are shown at a friction coefficient (vertical axis) of 0.14, while in Figures 7, 8, and 10, dashed lines are shown at a friction coefficient (vertical axis) of 0.23.

[0060] As shown in Table 2 and Figures 5 to 8, the above disc (made of SUS304 (stainless steel)) has an indentation hardness of 400 mgf / μm 2 More than 1200mgf / μm 2 Examples 1 to 7, which were provided with a coating having the following characteristics and a surface roughness Ra of 0.3 μm to 1.8 μm, showed a friction coefficient of less than 0.14 at room temperature (25°C) and less than 0.23 at -55°C. It was confirmed that a lower friction coefficient was achieved compared to Reference Examples 1 and 2 at both low temperatures and room temperatures. On the other hand, the indentation hardness is 1200 mgf / μm 2 Comparative Example 1, which formed a coating with a hardness exceeding [a certain value], showed a high coefficient of friction value at room temperature (25°C) compared to Examples 1 to 7 and Reference Examples 1 and 2, even when it had a smooth surface with low surface roughness.

[0061] Similarly, when the disc material is made of SKD (die steel), the indentation hardness is 400 mgf / μm. 2 More than 1200mgf / μm 2Examples 8 to 10, which consist of a coating having the following characteristics and a surface roughness Ra of 0.3 μm to 1.8 μm, achieved a friction coefficient of less than 0.14 at room temperature (25°C) and a low friction coefficient of less than 0.23 even at -55°C. On the other hand, Comparative Examples 2 to 4, in which at least one of the indentation hardness and surface roughness Ra fell outside the above range, showed a higher coefficient of friction at room temperature (25°C) compared to Examples 8 to 10 and Reference Examples 1 and 2.

[0062] As shown in Table 2 and Figures 5-8 above, the indentation hardness is 400 mgf / μm 2 More than 1200mgf / μm 2 It was confirmed that, when the following conditions are met and the surface roughness Ra is between 0.3 μm and 1.8 μm, the coefficient of friction at room temperature (25°C) is below the guideline value of 0.14, and the coefficient of friction at -55°C is below the guideline value of 0.23.

[0063] Furthermore, as shown in Table 3 and Figures 9 and 10, when the disc material and coating composition are kept the same, and the surface roughness is changed, the indentation hardness is 400 mgf / μm 2 More than 1200mgf / μm 2 Examples 11, 2 (reiterated), 12, and 13, which have a surface roughness Ra of 0.3 μm or more and 1.8 μm or less, exhibited a low coefficient of friction of less than 0.23 at -55°C and also exhibited a low coefficient of friction of less than 0.14 at room temperature (25°C). On the other hand, the indentation hardness is 400 mgf / μm 2 More than 1200mgf / μm 2 Even with the following conditions, Comparative Example 5, which had a surface roughness Ra greater than 1.8 μm, showed a higher coefficient of friction compared to the above examples at both room temperature (25°C) and -55°C. Furthermore, Comparative Example 6, which had a surface roughness Ra of less than 0.3 μm, showed a higher coefficient of friction compared to the above examples at -55°C, and also showed a higher coefficient of friction compared to Examples 2, 12, and 13 at room temperature (25°C). Thus, it was confirmed that the coefficient of friction increases not only when the surface roughness is large, but also when the surface roughness is small (smooth). In Reference Examples 1 to 3, where no coating was applied, the coefficient of friction at -55°C was approximately 0.23, and at room temperature (25°C) it was approximately 0.14 to 0.15, regardless of the change in surface roughness, similar to the results shown in Table 2.

[0064] As shown in Table 3 and Figures 9-10 above, the indentation hardness is 400 mgf / μm 2 More than 1200mgf / μm 2 It was confirmed that when the following conditions are met, and the surface roughness Ra is between 0.3 μm and 1.8 μm, the coefficient of friction at room temperature (25°C) is below the guideline value of 0.14, and the coefficient of friction at -55°C is below 0.23.

[0065] As described above, a coating having a predetermined hardness and surface roughness is brought into sliding contact with a self-lubricating liner. By providing it on the sliding surface, a low coefficient of friction can be achieved at room temperature and low temperature environments. At first glance, it might seem that a hard and smooth surface would be advantageous for achieving a low coefficient of friction, but contrary to these expectations, the results of the above-described examples show that it is difficult to achieve a low coefficient of friction at room temperature and low temperature if the hardness is too high or the surface is too smooth. The present invention is the first to provide such advantageous effects.

[0066] The present invention can be applied to any sliding member having a sliding contact opposing surface that slides in contact with a self-lubricating liner, and encompasses sliding members used for sliding motion in any direction, such as rotational motion, translational (linear) motion of members or parts, oscillating motion, and combinations thereof.

[0067] Although the best embodiment has been described in detail above, the present invention is not limited to the above embodiment, and any modifications, improvements, etc. that can achieve the objectives of the present invention are included in the present invention. [Explanation of Symbols]

[0068] 1... Self-lubricating sliding bearing, 2... Housing, 3... Sliding contact bearing surface, 4... Self-lubricating liner, 5... Sliding contact surface, 6... Bearing element member, 7... Metal member, 8... Sliding contact opposing bearing surface, 9... Coating, 10... Sliding contact opposing surface 20...Journal bearing, 21...Outer ring, 22...Sliding contact bearing surface, 23...Self-lubricating liner, 24...Sliding contact surface, 25...Shaft (metal component), 26...Sliding contact opposing bearing surface, 27...Coating, 28...Bearing element component, 29...Sliding contact opposing surface 30...Pin-on-disk wear tester, 31...Pin, 32...Disk

Claims

1. It comprises a self-lubricating liner and a bearing element member that is in surface contact with it, The bearing element member has a coating on the surface of a metal member, and the surface of the coating has a sliding contact opposing surface that slides into contact with the self-lubricating liner. The aforementioned coating is a composite coating in which a resin material is dispersed in a metal matrix or a ceramic matrix, or a coating made of one selected from the group consisting of chromium carbide alloy, Ni-P, and Ni-P-B. The self-lubricating liner is made of a cured product of a photocurable resin composition containing an isocyanuric acid ring (meth)acrylate compound and a polytetrafluoroethylene resin. The surface roughness Ra of the sliding contact opposing surface is 0.3 μm or more and 1.8 μm or less, and the indentation hardness of the coating, as measured by the nanoindentation method, is 3923 MPa (400 mg f / μm), which is the average of 20 measurements obtained by subtracting 5 points each from the maximum and minimum values ​​when 30 measurements are arranged in ascending order. ２ ) or more 11768MPa (1200mgf / μm ２ A sliding member characterized by having a hardness of the following degree.

2. The surface roughness Ra, expressed as an arithmetic mean roughness, of the sliding contact opposing surfaces is 0.5 μm or more and 1.2 μm or less, and the coating has an indentation hardness of 3923 MPa (400 mg f / μm). ２ ) or more 8826MPa (900mgf / μm ２ The sliding member according to claim 1, characterized in that it has a hardness of the following degree.

3. The sliding member according to claim 1, characterized in that the metal member of the bearing element member is made of stainless steel.

4. The sliding member according to claim 1, characterized in that the metal member of the bearing element member is made of die steel.

5. The aforementioned coating is a composite coating in which a fluororesin material is dispersed in a nickel-containing matrix. The sliding member according to claim 1, characterized by the following:

6. The sliding member according to claim 5, characterized in that the coating is a composite coating in which a fluororesin material is dispersed in a matrix containing nickel and phosphorus.

7. The sliding member according to claim 1, characterized in that the sliding member is a cylindrical journal bearing or a spherical plain bearing.

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