Sliding member and method for producing sliding member

Abstract

This sliding member comprises: a cylindrical metal base material; a porous layer formed on the inner circumferential surface of the metal base material; and a sliding layer covering the porous layer. The porous layer is formed of a metal element or an alloy composition. The sliding layer is formed of a resin composition. The sliding member has, on a portion of the inner circumferential surface thereof, a region in which the resin composition is not present and a non-porous layer formed of a metal element or an alloy composition is exposed.

Description

SLIDE MEMBER AND METHOD FOR MANUFACTURING SLIDE MEMBER

[0001] The present disclosure relates to a slide member and a method for manufacturing a slide member.

[0002] Currently, energy efficiency and CO ２ From the perspective of emissions, there has been a shift from conventional engine-powered vehicles to electric vehicles (EVs) powered by batteries and motors. The output of a motor depends on its rotation speed and torque, and increasing the rotation speed reduces torque and reduces volume. Therefore, high-speed motors are essential for reducing the size and weight of components and saving energy. Furthermore, there is an increasing need to reduce the size and weight of electric compressors built into drive motors for car air conditioners, which contribute to the comfort of automobiles.

[0003] The Automotive Power Transmission Technology Research Association (TRAMI), which brings together domestic automakers and other organizations, has announced that it will shift the focus of its research from internal combustion engines to electric vehicle (EV) motors and related technologies. While the rotation speed of current EV motors is typically around 13,000 rpm, it is predicted that this will rise to over 20,000 rpm in the near future, and research is being promoted with an eye toward ultra-high rotation speeds of 30,000 to 50,000 rpm. In particular, EV drive motors and electric compressors are required to be able to handle high rotation speeds in order to achieve both compactness and lightness while increasing output.

[0004] Rotating machinery, such as motors and compressors, relies on bearings, seals, and other components that support the rotating shaft. Over time, these components' sliding surfaces deteriorate, resulting in increased friction and wear. This heat generates temperatures, leading to deterioration in various parts of the rotating machinery, ultimately leading to the machinery no longer functioning properly and reaching the end of its service life. Furthermore, friction and heat generated by motors' high speeds can cause oil leakage or foreign matter to enter the bearing gaps supporting the rotating shaft, resulting in abnormally high temperatures and vibrations on the sliding surfaces, melting the surface of the sliding material and causing seizure. Thus, friction and wear are often the primary causes of performance degradation and failure of mechanical components. In particular, the sliding bearings used in compressors are lubricated with a sealed refrigerant and refrigerant oil. However, the lubrication conditions vary significantly depending on the compressor's operating conditions, including severe conditions such as when the compressor is operating in a liquid refrigerant-only or dry conditions.

[0005] Therefore, in boundary lubrication environments where oil film formation is difficult due to factors such as high rotation speeds in drive systems and eccentric shafts, plain bearings with excellent wear resistance and seizure resistance are required. Furthermore, because the dimensional accuracy of the bearing, such as the gap between the shaft and the bearing, the shape of the bearing's inner diameter surface that comes into contact with the shaft, and the presence or absence of protrusions due to joints, greatly affects the machine's lifespan, plain bearings also require high assembly accuracy.

[0006] Furthermore, the sliding bearings used in compressors are facing increasingly severe operating environments due to restrictions on fluorocarbons and the switch to new refrigerants in response to global warming countermeasures, so even higher performance bearings are required.

[0007] Japanese Patent Application Laid-Open Publication No. 2018-179049 proposes the use of rolling bearings in locations requiring high-speed rotation, such as automotive parts. However, rolling bearings have a shorter lifespan than plain bearings, so there is a demand for longer-life plain bearings that can be used even under high-speed rotation.

[0008] The applicant of the present application has already proposed a sliding member with a seamless sliding surface and a method for manufacturing the same, as a sliding member with excellent wear resistance and seizure resistance in the high-speed rotation range (Japanese Patent Application No. 2023-026107).

[0009] A slide member and a method for manufacturing a slide member in which temperature rise in the high-speed rotation region is suppressed more than in the slide member proposed in Japanese Patent Application No. 2023-026107 are desired.

[0010] A sliding member according to one embodiment includes a cylindrical metal substrate, a porous layer formed on an inner circumferential surface of the metal substrate, and a sliding layer covering the porous layer, wherein the porous layer is formed of a metal element or an alloy composition, and the sliding layer is formed of a resin composition, and the resin composition is absent from a portion of the inner circumferential surface, thereby providing an exposed region of the non-porous layer formed of the metal element or alloy composition.

[0011] A bearing according to one embodiment comprises a cylindrical metal substrate, a porous layer formed on the inner peripheral surface of the metal substrate, and a sliding layer covering the porous layer, wherein the porous layer is formed of a metal element or an alloy composition, and the sliding layer is formed of a resin composition, and the resin composition is absent from a portion of the inner peripheral surface, resulting in an area where the non-porous layer formed of the metal element or alloy composition is exposed.

[0012] A method for manufacturing a slide member according to one embodiment includes the steps of: forming a porous layer made of an elemental metal or an alloy composition on one surface of a metal substrate; rolling the metal substrate with the porous layer on the inside to form a cylindrical shape; welding a seam portion from the outer diameter side of the metal substrate, wherein the porous layer on the seam portion is melted to form a non-porous layer made of the elemental metal or the alloy composition; and impregnating a surface of the porous layer with a raw resin of a slide layer and baking the raw resin to form a slide layer made of a resin composition that covers the porous layer, wherein the surface of the non-porous layer is not impregnated with the raw resin, and therefore the resin composition is not present on a part of the inner circumferential surface of the slide member, and a region where the non-porous layer is exposed is formed.

[0013] A method for manufacturing a slide member according to one embodiment includes the steps of: forming a porous layer made of an elemental metal or an alloy composition on one surface of a metal substrate; impregnating a surface of the porous layer with a raw resin of the slide layer and baking the raw resin to form a slide layer made of a resin composition that covers the porous layer; rolling the metal substrate with the slide layer on the inside to form a cylindrical shape; and welding a seam from the outer diameter side of the metal substrate, in which the porous layer on the seam is melted to form a non-porous layer made of the elemental metal or the alloy composition and the slide layer on the seam is peeled off, thereby forming a region in which the resin composition is not present on a part of the inner circumferential surface of the slide member and the non-porous layer is exposed.

[0014] FIG. 1 is a perspective view showing a schematic configuration of a slide member according to an embodiment. FIG. 2 is a photographic image of a welded portion of a slide member according to an embodiment, taken from the outer periphery. FIG. 3 is a photographic image of a region corresponding to a welded portion of a slide member according to an embodiment, taken from the inner periphery. FIG. 4 is an optical microscope photograph of a cross-sectional structure of a region corresponding to a welded portion before forming a sliding layer (resin impregnation and sintering). FIG. 5 is a backscattered electron composition image of a cross-sectional structure of a region other than the welded portion of a slide member according to an embodiment. FIG. 6 is a flow chart showing an example of a method for manufacturing a slide member according to an embodiment. FIG. 7 is a flow chart showing another example of a method for manufacturing a slide member according to an embodiment. FIG. 8 is a diagram illustrating a raw material powder scattering step and a porous layer sintering step. FIG. 9 is a diagram illustrating a raw material resin impregnation step. FIG. 10 is a diagram illustrating a burnishing step. FIG. 11 is a diagram showing a schematic configuration of a high-speed rotational wear tester. FIG. 12 is a diagram illustrating the position of a load point (load category A) during measurement in a high-speed rotational wear test for a slide member according to an example. FIG. 13 is a table summarizing the compositions and the like of the slide members according to the Examples and Comparative Examples 1 to 3. FIG. 14 is a graph showing the time change in bearing temperature measured for the slide members according to the Examples and Comparative Examples 1 to 3 when the shaft rotation speed N is 15,000 rpm. FIG. 15 is a graph showing the time change in bearing temperature measured for the slide members according to the Examples and Comparative Examples 1 to 3 when the shaft rotation speed N is 20,000 rpm. FIG. 16 is a graph showing the time change in bearing temperature measured for the slide members according to the Examples and Comparative Examples 1 to 3 when the shaft rotation speed N is 25,000 rpm. FIG. 17 is a graph showing the time change in bearing temperature measured for the slide members according to the Examples and Comparative Examples 1 to 3 when the shaft rotation speed N is 30,000 rpm. FIG. 18 is a graph showing the time change in bearing temperature measured for the slide members according to the Example and Comparative Example 1 when the shaft rotation speed N is 35,000 rpm. FIG. 19 is a graph showing the change in the temperature rise rate with respect to the shaft rotation speed in the range of 10,000 to 50,000 rpm for the sliding members according to the example and comparative examples 1 to 3.FIG. 20 is a graph showing the change in power consumption with respect to shaft rotation speed in the range of 10,000 to 50,000 rpm for the sliding members according to the example and comparative examples 1 to 3. FIG. 21 is a graph showing the change in temperature rise rate with respect to shaft rotation speed in a range near the shaft rotation speed at which a sudden increase in the temperature rise rate and power consumption occurs for the sliding members according to the example and comparative examples 1 to 3. FIG. 22 is a graph showing the change in power consumption with respect to shaft rotation speed in a range near the shaft rotation speed at which a sudden increase in the temperature rise rate occurs for the sliding members according to the example and comparative examples 1 to 3. FIG. 23 is a diagram illustrating the position of the load point (load category B) during measurement in a high-speed rotational wear test for the sliding members according to the example. FIG. 24 is a graph showing the change in temperature rise rate with respect to shaft rotation speed measured at load categories A and B for the sliding members according to the example. FIG. 25 is a graph showing the change in power consumption with respect to shaft rotation speed measured at load categories A and B for the sliding members according to the example. FIG. 26 is a graph showing the inner diameter accuracy of the sliding members according to the example. FIG. 27 is a graph showing the inner diameter accuracy of the sliding member according to Comparative Example 1.

[0015] A sliding member according to a first aspect of the embodiment includes a cylindrical metal substrate, a porous layer formed on an inner circumferential surface of the metal substrate, and a sliding layer covering the porous layer, wherein the porous layer is formed of a metal element or an alloy composition, and the sliding layer is formed of a resin composition, and the resin composition is absent from a part of the inner circumferential surface, whereby the non-porous layer formed of the metal element or the alloy composition is exposed.

[0016] According to this embodiment, a portion of the inner circumferential surface of the sliding member is free of the resin composition and has an exposed non-porous layer formed of a metal element or an alloy composition. This region is recessed relative to the surrounding area because the surrounding resin composition is absent and the non-porous layer does not contain numerous voids like a porous layer. This allows the region to function like a groove. When the sliding member is in use, the inner surface of the groove does not come into contact with the shaft, which is the object being slid against, thereby contributing to reducing heat generation due to friction. This suppresses temperature rise in high-speed rotation regions and improves bearing performance. In particular, when lubricating oil or grease is present, the groove maintains the formation of an oil film on the sliding surface, which is expected to further reduce heat generation compared to use in a dry environment. Furthermore, a portion of the inner circumferential surface of the sliding member is free of the resin composition and has an exposed non-porous layer formed of a metal element or an alloy composition. Since no protrusions due to seams appear on the sliding surface, torque generated during friction at the seams is reduced. This contributes to reduced power consumption and energy loss. Therefore, it can contribute to carbon neutrality. Furthermore, for bearings used in high-speed environments such as EV motors and electric compressors, it becomes possible to replace conventional rolling bearings with the slide member according to this embodiment, leading to size and weight reduction. Furthermore, when conventional slide members with seams on the sliding surface are applied to motors or compressors, an inner diameter cutting step (i.e., surface alignment of the inner surface at the seam) is required, but with the slide member according to this embodiment, the resin composition is not present on part of the inner circumferential surface of the slide member, and an area is provided where a non-porous layer formed of a simple metal or an alloy composition is exposed, and no protrusions due to the seam appear on the sliding surface, so the inner diameter cutting step can be eliminated.

[0017] A sliding member according to a second aspect of the embodiment is the sliding member according to the first aspect, wherein the region is provided so as to extend from one end to the other end in the axial direction of the sliding member.

[0018] According to this aspect, the effect of reducing heat generation due to friction can be obtained continuously from one end to the other end in the axial direction, so that temperature rise in the high-speed rotation region can be further suppressed.

[0019] A slide member according to a third aspect of the embodiment is the slide member according to the first or second aspect, wherein a hard particle powder containing a Laves phase having a composition of Co, Mo, and Si is dispersed in the slide layer.

[0020] A slide member according to a fourth aspect of the embodiment is the slide member according to the third aspect, wherein the slide layer contains MoS ２ and at least one of a Laves phase-free bronze powder and a Laves phase-free bronze powder.

[0021] A slide member according to a fifth aspect of the embodiment is the slide member according to the first or second aspect, wherein the resin composition contains more than 3% by mass and less than 40% by mass of the copper sulfide, 0% by mass or more and less than 4% by mass of the thermoplastic resin, 0% by mass or more and 36% by mass or less of the molybdenum disulfide, 0% by mass or more and 10% by mass or less of the graphite, and 0% by mass or more and 10% by mass or less of the aramid fiber, and the remainder is the fluororesin.

[0022] A slide member according to a sixth aspect of the embodiment is the slide member according to any one of the first to fifth aspects, wherein the porous layer has: a matrix phase containing Cu and Sn; and hard particles dispersed in the matrix phase, the hard particles including a Laves phase having a composition of Co, Mo, and Si.

[0023] A slide member according to a seventh aspect of the embodiment is the slide member according to the sixth aspect, wherein the porous layer further has a compound phase dispersed in the matrix phase, the compound phase containing Co, Fe, Ni, Si, and Cr.

[0024] A sliding member according to an eighth aspect of the embodiment is the sliding member according to any one of the first to seventh aspects, wherein a ratio of a thickness of the porous layer to a thickness of the sliding layer is 6:4 to 8:2.

[0025] A bearing according to a ninth aspect of the embodiment comprises a cylindrical metal substrate, a porous layer formed on the inner circumferential surface of the metal substrate, and a sliding layer covering the porous layer, wherein the porous layer is formed of a metal element or an alloy composition, and the sliding layer is formed of a resin composition, and the resin composition is absent from a portion of the inner circumferential surface, resulting in an area where the non-porous layer formed of the metal element or alloy composition is exposed.

[0026] A method for producing a slide member according to a tenth aspect of the embodiment includes the steps of: forming a porous layer made of an elemental metal or an alloy composition on one surface of a metal substrate; rolling the metal substrate with the porous layer on the inside to form a cylindrical shape; welding a seam portion from the outer diameter side of the metal substrate, wherein the porous layer on the seam portion is melted to form a non-porous layer made of the elemental metal or the alloy composition; and impregnating a surface of the porous layer with a raw material resin of a slide layer and baking the raw material resin to form a slide layer made of a resin composition that covers the porous layer, wherein the surface of the non-porous layer is not impregnated with the raw material resin, and therefore the resin composition is not present on a part of the inner circumferential surface of the slide member, and a region where the non-porous layer is exposed is formed.

[0027] A method for producing a slide member according to an eleventh aspect of the embodiment includes the steps of: forming a porous layer made of an elemental metal or an alloy composition on one surface of a metal substrate; impregnating a surface of the porous layer with a raw resin of a slide layer and baking the raw resin to form a slide layer made of a resin composition that covers the porous layer; rolling the metal substrate with the slide layer on the inside to form a cylindrical shape; and welding a joint portion from the outer diameter side of the metal substrate, in which the porous layer on the joint portion is melted to form a non-porous layer made of the elemental metal or the alloy composition and the slide layer on the joint portion is peeled off, thereby forming a region in which the resin composition is not present on a part of the inner circumferential surface of the slide member and the non-porous layer is exposed.

[0028] A method according to a twelfth aspect of the embodiment is the method according to the tenth or eleventh aspect, further comprising the step of burnishing an inner circumferential surface of the sliding layer by pressing a cylindrical core metal into the inside of the sliding layer while restraining an outer circumferential surface of the metal base with a die.

[0029] Specific examples of the embodiments will be described in detail below with reference to the accompanying drawings. In this specification, "%" in a composition refers to "% by mass" unless otherwise specified. In this specification, "A to B" (where A and B are both numbers) means "A or more and B or less" unless otherwise specified. In this specification, "main component" refers to a component that accounts for 50% by mass or more of the total composition. In this specification, "hard particle powder" refers to the powder in the mixed powder before sintering or the powder dispersed in the resin composition of the sliding layer, and "hard particles" refers to the particles in the porous layer after sintering. As described below, because Cu and Sn contained in the hard particle powder migrate to a certain extent into the matrix phase during sintering, the content of the hard particles in the porous layer varies from the amount of the hard particle powder in the mixed powder, and the content of each constituent element in the hard particles differs from the content of each constituent element in the hard particle powder (hard particles are particles with a composition in which the Sn and Cu contents among the chemical components are somewhat lower than those of the hard particle powder). Furthermore, in this specification, the term "seam" refers to a portion that connects two objects (or two ends of one object) so that they are continuous, and is an expression that includes both welded and unwelded portions. When the portion is not welded, the term "seam" refers to both a portion where two objects (or two ends of one object) are in contact and a portion where they are separated by a small gap. Here, the "small gap" is not particularly limited in its specific width, as long as it can be regarded as a portion that is connected so that it is continuous when viewed as a whole, but it may be, for example, less than one-tenth, less than one-fiftieth, or less than one-hundredth of the overall length. Furthermore, in this specification, a "seam" that is not welded may also be referred to as a "seam."

[0030] <Configuration of Slide Member> Fig. 1 is a perspective view showing a schematic configuration of a slide member 10 according to one embodiment. Fig. 2 is a photographic image of a welded portion of the slide member 10 taken from the outer periphery side, Fig. 3 is a photographic image of a region of the slide member 10 corresponding to the welded portion taken from the inner periphery side, and Fig. 4 is an optical microscope photograph of the cross-sectional structure of the region corresponding to the welded portion before the formation of the sliding layer (resin impregnation and baking). Fig. 5 is a backscattered electron composition image of the cross-sectional structure of a region other than the welded portion of the slide member according to one embodiment. In Figs. 4 and 5, the upper side of the page corresponds to the inner periphery side of the slide member 10, and the lower side of the page corresponds to the outer periphery side of the slide member 10.

[0031] 1 to 5, the sliding member 10 is, for example, a sliding bearing, and includes a cylindrical metal substrate 11, a porous layer 12 formed on the inner peripheral surface of the metal substrate 11, and a sliding layer 13 covering the porous layer 12. Of these, the porous layer 12 is formed of a simple metal or an alloy composition, and the sliding layer 13 is formed of a resin composition.

[0032] As shown in Fig. 1, a sliding member 10 serving as a plain bearing supports a shaft 20, which is a sliding object, with a sliding layer 13 forming a cylindrical inner peripheral surface. The inner diameter roundness of the sliding layer 13 may be 50 µm or less, or may be 20 µm or less. In this case, friction on the inner peripheral surface of the sliding layer 13 is reduced, thereby achieving further reductions in wear and heat generation.

[0033] The sliding member 10 is applicable whether the shaft 20 moves in a rotational manner or in a linear manner. The sliding member 10 may be used in a sliding part where oil is used in a linear manner, such as a shock absorber for an automobile. The sliding member 10 may also be used in a sliding part where oil is used in a rotational manner, such as a gear pump that delivers oil by rotating a gear-shaped member. Each component of the sliding member 10 will be described in detail below.

[0034] 1 to 3, the metal substrate 11 has a cylindrical shape. The metal substrate 11 can be manufactured, for example, by rolling a metal plate material into a cylindrical shape and then welding a seam 11a (see FIG. 2). The material of the metal substrate 11 is not particularly limited as long as it has sufficient strength and shape stability to be usable as a backing metal base material for a bearing. For example, the metal substrate 11 may be low-carbon steel (SPCC, SS400, etc.) or a copper-plated steel sheet in which an Fe-based plate material is plated with Cu.

[0035] The porous layer 12 has a cylindrical shape and is formed by sintering metal powder (a mixed powder described below, or an alloy powder obtained by alloying the mixed powder during spraying) onto the surface of the metal substrate 11. The thickness of the porous layer 12 may be such that at least two or more particles of metal powder can be sintered together, and may be, for example, 0.5 mm or less.

[0036] The sliding layer 13 is formed by impregnating the porous layer 12 with a resin composition to a predetermined thickness and then baking the resin composition impregnated into the porous layer 12. The thickness of the sliding layer 13 (thickness from the surface of the metal substrate 11) may be set to be thicker on average than the thickness of the porous layer 12 so that the porous layer 12 is not exposed. The ratio of the thickness of the porous layer 12 to the thickness of the sliding layer 13 may be 6:4 to 8:2, and may be, for example, 7:3.

[0037] The resin composition of the sliding layer 13 contains a fluororesin as a main component. Examples of the fluororesin that can be used as the base resin of the resin composition include PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane), FEP (perfluoroethylene-propylene copolymer), and EFFE (ethylene-tetrafluoroethylene copolymer).

[0038] The resin composition contains PTFE as a main component of the fluororesin, and may contain other fluororesins other than PTFE, such as PFA, as optional additives. The content of the other fluororesins contained as optional components may be 0 vol% or more and 20 vol% or less in the resin composition.

[0039] Commercially available PTFE resins include Polyflon (registered trademark) D-210C and F-201 (manufactured by Daikin Industries, Ltd.), Fluon (registered trademark) AD911D (manufactured by Asahi Glass Co., Ltd.), and Teflon (registered trademark) 31JR and 6C-J (manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd.).

[0040] 5, hard particle powder 13a containing a Laves phase composed of Co, Mo, and Si may be dispersed in the resin composition of the sliding layer 13. Here, the Laves phase is an AB phase composed of elements A and B with an atomic radius ratio of approximately 1.2:1. ２ It is an intermetallic compound based on the MgZn type. ２ (C14) type, MgCu ２ (C15) type, MgNi ２ There are three types of structures of the (C36) type. ３ Mo ２ The Laves phase, which is composed of Mo and Co, is a Laves phase in which 25 at% of Co is replaced by Si, and MgZn with a hexagonal crystal structure ２ It is a type. ３ Mo ２ The Vickers hardness of the Laves phase composed of Si is Hv 1000 to 1200. It is considered that the hard particle powder 13a dispersed in the sliding layer 13 receives a higher load than the resin composition forming the sliding layer 13, but the hard Laves phase composed of Co, Mo, and Si precipitates on the friction surface and supports the load, which can act advantageously to reduce wear of the sliding layer 13.

[0041] In addition, Mo in the Laves phase and S in the lubricating oil form MoS on the friction surface. ２ A sulfide film of MoS can be formed. ２ is a material known as a sulfide that substitutes for the solid lubrication of lead and contributes to improving friction characteristics. Compared to the bonds between molybdenum and between molybdenum and sulfur, the bonds between sulfur are weaker, so when friction occurs, the bonds between sulfur are selectively broken, resulting in lubrication and effective wear suppression. In addition, Mo oxides, which are generated on the friction surface by oxidation of Mo in the Laves phase during sliding, also exhibit a lubricating effect and can be effective in suppressing wear.

[0042] The resin composition of the sliding layer 13 contains molybdenum disulfide (MoS ２ ) powder and Laves phase-free bronze powder may be further dispersed therein. ２ is a material known as a sulfide that replaces the solid lubricity of lead and contributes to improving friction characteristics. Compared to the bonds between molybdenum and between molybdenum and sulfur, the bonds between sulfur are weaker, so when friction occurs, the bonds between sulfur are selectively broken, resulting in lubrication and effective wear suppression.

[0043] In one variation, the resin composition of the sliding layer 13 is made of copper sulfide (CuS), a thermoplastic resin, molybdenum disulfide (MoS ２ The resin composition may be composed of more than 3% by mass and less than 40% by mass of copper sulfide, 0% by mass or more and less than 4% by mass of thermoplastic resin, 0% by mass or more and 36% by mass or less of molybdenum disulfide, 0% by mass or more and 10% by mass or less of graphite, 0% by mass or more and 10% by mass or less of aramid fiber, and the remainder being fluororesin (provided that the resin composition does not contain lithium phosphate). In this case, the resin composition may contain more than 3% by mass and less than 40% by mass of copper sulfide, 0% by mass or more and less than 4% by mass of thermoplastic resin, 0% by mass or more and 36% by mass or less of molybdenum disulfide, 0% by mass or more and 10% by mass or less of graphite, 0% by mass or more and 10% by mass or less of aramid fiber, and the remainder being fluororesin.

[0044] The resin composition forming the slide layer 13 contains copper sulfide as a metal sulfide, thereby improving the heat dissipation characteristics of the slide layer 13. This suppresses a temperature rise in the slide layer 13 due to the sliding of the sliding object, and suppresses deformation of the slide layer 13 due to the temperature rise.

[0045] Furthermore, by including copper sulfide in the resin composition that forms the sliding layer 13, the strength of the sliding layer 13 is improved. It is known that by including a carbon fiber filler in the resin composition that forms the sliding layer, the strength of the resin layer is improved. In contrast, by including copper sulfide in the resin composition, the strength is improved similarly to when a carbon fiber filler is included, even if the resin composition does not include a carbon fiber filler. The improvement in the strength of the sliding layer 13 also suppresses deformation of the sliding layer 5 due to sliding of the sliding object.

[0046] When the deformation amount of the slide layer 13 is large, the amount of wear increases compared to when the deformation amount is small. Therefore, by suppressing the deformation of the slide layer 13, the wear of the slide layer 13 is suppressed and the wear resistance characteristics are improved. Furthermore, by improving the strength of the slide layer 13, the wear is also suppressed. Furthermore, by suppressing the wear of the slide layer 13, the exposure of the porous layer 12 is suppressed, and it is possible to suppress dry touch, which is a cause of seizure and the like, caused by direct contact between the porous layer 12 and the sliding object, and improve the seizure resistance.

[0047] Copper sulfide is cuprous sulfide (Cu ２ S) and copper (II) sulfide (CuS). ２ S) is stable even at temperatures above 1000°C. In contrast, cupric sulfide (CuS) becomes copper sulfide (CuS) at around 200°C. ２ When polytetrafluoroethylene is used as the resin, the resin composition 4 is heated at a temperature exceeding 327°C in the step of baking the slide layer 13. Therefore, when the resin composition contains cupric sulfide (CuS), the cupric sulfide (CuS) is converted to cuprous sulfide (Cu ２ S).

[0048] As a result, the sliding layer 13 of the sliding member 10 manufactured as a result of this process contains copper(I) sulfide (Cu ２ However, the raw material for copper sulfide is copper(I) sulfide (Cu ２ Although copper sulfide (CuS) or copper sulfide (CuS) may be used, copper sulfide (CuS) is preferably used from the viewpoint of workability.

[0049] By further including molybdenum disulfide as a metal sulfide in the resin composition forming the slide layer 13, the sliding characteristics with respect to the sliding object that slides in contact with the slide layer 13 are improved. Furthermore, by including graphite in the resin composition forming the slide layer 13, the sliding characteristics are also improved. As a result, a lead (Pb)-free structure can achieve sliding characteristics comparable to those of a slide member that contains Pb. The resin composition of the slide layer 13 according to one modification will be described in detail below.

[0050] [Copper sulfide: more than 3% by mass and less than 40% by mass] The resin composition forming the sliding layer 13 preferably contains more than 8% by mass and less than 40% by mass of copper sulfide in order to improve heat dissipation characteristics and strength. If the amount of copper sulfide added is 3% by mass or less or 40% by mass or more, the heat dissipation characteristics deteriorate and the wear resistance characteristics are impaired. Commercially available copper sulfide includes cupric sulfide (CuS) manufactured by Terada Yakusen Kogyo Co., Ltd., cupric sulfide (CuS) manufactured by Kanto Chemical Co., Ltd., and cuprous sulfide (CuS) manufactured by Kojundo Chemical Laboratory Co., Ltd. ２ S) and the like.

[0051] [Plastic Resin: 0% by Mass or More and 4% by Mass or Less] In the resin composition of the sliding layer 13 according to one modification, a thermoplastic resin is not an essential additive. However, when added, it is preferable to add a thermoplastic resin because it can improve the wear resistance and creep resistance properties that are drawbacks of fluororesins.

[0052] If the thermoplastic resin is added in an amount exceeding 4 mass %, the low friction characteristics of the fluororesin will be impaired. Commercially available PPS resins as thermoplastic resins include PQ-208 manufactured by DIC Corporation and Fortron (registered trademark) KPS manufactured by Kureha Corporation.

[0053] [Graphite: 0% by mass or more and 10% by mass or less] In the resin composition of the sliding layer 13 according to one modification, graphite is not an essential additive, but it is expected to contribute to improving self-lubrication and heat resistance, as well as low friction and wear resistance. When graphite is added in an amount exceeding 10% by mass, the low friction characteristics are impaired. Commercially available graphite products include UCP and CPB manufactured by Nippon Graphite Industries Co., Ltd., and the AT series manufactured by Oriental Sangyo Co., Ltd.

[0054] [Molybdenum Sulfide: 0% by Mass or More and 36% by Mass or Less] In the resin composition of the slide layer 13 according to one modification, molybdenum disulfide (MoS ２ ) is not an essential additive, but adding it can reduce frictional resistance.

[0055] If the amount of molybdenum disulfide added exceeds 36 mass %, the impregnation into the porous layer becomes poor during the impregnation step. ２and the molybdenum disulfide powder series manufactured by Daizo Co., Ltd.

[0056] [Aramid Fiber: 0% by Mass or More and 10% by Mass or Less] In the resin composition of the sliding layer 13 according to one variation, aramid fiber is not an essential additive, but is added to improve mechanical strength. When aramid fiber is added in an amount of 10% by mass or more, uniform dispersion is hindered, resulting in a decrease in wear resistance. Examples of commercially available aramid fiber include Kevlar (registered trademark) manufactured by DuPont-Toray Co., Ltd. and Twaron (registered trademark) manufactured by Teijin.

[0057] In another modified example, the resin composition of the sliding layer 13 is a zinc compound (ZnS (zinc sulfide), ZnO (zinc oxide), ZnSO ４ (e.g., zinc sulfate), carbon fiber, iron oxide, barium sulfate, aramid fiber, graphite, calcium compounds (CaCO ３ (Calcium carbonate), CaSO ４ (Calcium sulfate), Ca(OH) ２ The resin composition may contain one or more of the following additives: calcium hydroxide (e.g., zinc), zinc alloy, or a combination thereof. The resin composition containing a zinc compound improves the modulus of elasticity, thereby suppressing deformation of the sliding layer 13 and preventing the sliding layer 13 from deforming due to external force, thereby preventing an increase or decrease in the contact area. Furthermore, the resin composition containing carbon fiber improves the value of dynamic friction force and the change between static friction force and dynamic friction force, thereby improving sliding characteristics. The resin composition containing iron oxide improves the modulus of elasticity in addition to improving wear resistance. The resin composition containing barium sulfate or aramid fiber improves wear resistance without interfering with the improvement in modulus of elasticity achieved by the addition of a zinc compound. The resin composition containing graphite reduces frictional resistance without interfering with the improvement in modulus of elasticity achieved by the addition of a zinc compound. The resin composition containing a calcium compound, zinc, or zinc alloy improves wear resistance without interfering with the improvement in modulus of elasticity achieved by the addition of a zinc compound.

[0058] As a modified example, the porous layer 12 may have a matrix phase containing Cu and Sn and hard particles dispersed in the matrix phase. The porous layer 12 may be formed by sintering an alloy powder obtained by alloying the mixed powder during atomization. By forming the alloy powder, sintering of the powder is promoted, forming necks, and the powder particles can be sufficiently bonded together. Furthermore, by forming the alloy powder, the hard particles are refined and uniformly dispersed in the matrix phase. Note that when the hard particle powder 13a is dispersed in the sliding layer 13 described above, the porous layer 13 does not need to contain hard particles.

[0059] The matrix phase is a bronze-based alloy containing Cu as a main component and further containing Sn, and may be composed of a solid solution of Cu, Sn, and Ni.

[0060] Bi particles may be distributed at the grain boundaries of the matrix phase. In this case, Bi exhibits a self-lubricating effect similar to that of Pb in conventional lead bronze at the friction surface where the sliding layer 4 wears and part of the porous layer 3 is exposed, and acts as a lubricant between the two rubbing surfaces, thereby reducing friction.

[0061] The hard particles may contain a Laves phase composed of Co, Mo, and Si. When the sliding layer 13 is worn and a part of the porous layer 12 is exposed, it is thought that the hard particles dispersed in the matrix phase will be subjected to a higher load than the soft bronze that forms the matrix phase. However, the hard Laves phase composed of Co, Mo, and Si precipitates on the friction surface and supports the load, which can advantageously act to reduce wear of the porous layer 12. In addition, Mo in the Laves phase and S in the lubricating oil form MoS on the friction surface. ２ A sulfide film of MoS can be formed. ２ is a material known as a sulfide that substitutes for the solid lubrication of lead and contributes to improving friction characteristics. Compared to the bonds between molybdenum and between molybdenum and sulfur, the bonds between sulfur are weaker, so when friction occurs, the bonds between sulfur are selectively broken, resulting in lubrication and effective wear suppression. In addition, Mo oxides, which are generated on the friction surface by oxidation of Mo in the Laves phase during sliding, also exhibit a lubricating effect and can be effective in suppressing wear.

[0062] When the porous layer 12 contains hard particles, the content of the hard particles may be, for example, 40% by mass or less when the entire porous layer 12 is taken as 100% by mass. When the entire porous layer 12 is taken as 100% by mass, the content of the hard particles may be, for example, 0.1% by mass or more. A hard particle content of 0.1% by mass or more achieves the wear reduction effect of the porous layer 12 described above. Furthermore, when the entire porous layer 12 is taken as 100% by mass, the content of the Laves phase composed of Co, Mo, and Si may be, for example, 0.1 to 20% by mass. When the hard particle powder 13a is dispersed in the sliding layer 13 and the porous layer 12 does not contain hard particles, the total content of Cu and Sn may be 99.9% or more when the entire porous layer 12 is taken as 100% by mass.

[0063] The porous layer 3 may further have a compound phase dispersed in the matrix phase. The compound phase may contain Co, Fe, Ni, Si, and Cr. The formation of the compound phase in the matrix phase can increase the hardness of the matrix phase, which can be advantageous in improving seizure resistance.

[0064] The slide member 10 according to the present embodiment includes four modes: (1) a mode in which the porous layer 12 contains hard particles but the slide layer 13 does not contain hard particle powder 13a; (2) a mode in which the porous layer 12 does not contain hard particles but the slide layer 13 contains hard particle powder 13a; (3) a mode in which the porous layer 12 contains hard particles and the slide layer 13 contains hard particle powder 13a; and (4) a mode in which the porous layer 12 does not contain hard particles and the slide layer 13 does not contain hard particle powder 13a. In any of modes (1) to (3), when the combined total of the porous layer 12 and the slide layer 13 (i.e., the entire slide member 10 excluding the metal substrate 11) is taken as 100% by mass, the total content of the hard particles and the hard particle powder 13a may be 1 to 20% by mass, for example, 15% by mass.

[0065] As shown in FIGS. 3 and 4 , the slide member 10 has a region 15 in which the resin composition is absent in a portion of the inner circumferential surface, exposing a non-porous layer 14 (see FIG. 4 ) formed of a metal element or an alloy composition. In the example shown in FIG. 3 , only one region 15 in which the resin composition is absent is provided on the inner circumferential surface of the slide member 10, but multiple regions 15 in which the resin composition is absent may be provided. As shown in FIG. 3 , the region 15 in which the resin composition is absent may be provided so as to extend from one end to the other end in the axial direction of the slide member 10. The region 15 in which the resin composition is absent may be provided on a seam portion 11 a (see FIG. 2 ) of the metal substrate 11. The non-porous layer 14 may be formed of the same metal element or alloy composition as the porous layer 12.

[0066] 4, the non-porous layer 14 has a recessed inner surface compared to the surrounding area due to the melting of the metal or alloy composition that constitutes the porous layer 12. The depth D of the recessed space in the non-porous layer 14 may be, for example, 0.2 to 0.3 mm. The width (length in the circumferential direction) W of the non-porous layer 14 may be 0.1 to 10% of the inner circumferential length of the slide member 10. For example, when the inner circumferential length of the slide member 10 is 60 to 70 mm, the width W of the non-porous layer 14 may be 1.0 mm to 3.0 mm.

[0067] <Method of manufacturing slide member> Next, an example of a method of manufacturing the slide member 10 having such a configuration will be described with reference to Fig. 6 and Figs. 8 to 10. Fig. 6 is a flow chart showing an example of a method of manufacturing the slide member 10. Fig. 8 is a diagram for explaining the raw material powder scattering step and the porous layer sintering step. Fig. 9 is a diagram for explaining the raw material resin impregnation step, and Fig. 10 is a diagram for explaining the burnishing step.

[0068] As shown in FIGS. 6 and 8, first, raw material powder for the porous layer 12 is spread on one surface of a plate-shaped metal substrate (step S10).

[0069] The raw material powder may be a first powder containing Cu and Sn, or a mixed powder obtained by mixing the first powder with a hard particle powder containing a Laves phase composed of Co, Mo, and Si, or a mixed powder obtained by mixing the first powder, the hard particle powder, and a second powder containing Cu, Co, Fe, Ni, Si, and Cr.

[0070] Here, the first powder is a bronze-based alloy powder containing Cu as a primary component and further containing Sn. The first powder may further contain Bi or P. If the first powder contains Bi, Bi particles precipitate in the matrix phase 10 during sintering of the raw material powder (i.e., step S20), as described below. Bi exhibits a self-lubricating effect similar to that of Pb in conventional lead bronze, thereby reducing friction. Furthermore, if the first powder contains P, oxygen mixed in the copper can be removed (deoxidized) to suppress hydrogen embrittlement. The contents of the constituent elements of the first powder may be 10 to 11% by mass of Sn and the remainder of Cu. If Bi is further contained, Bi is preferably 7 to 9% by mass, and if P is contained, P is preferably 0.02% by mass or less. The blending amount of the first powder in the raw material powder is the remainder obtained by subtracting the combined blending amount of all powders other than the first powder from the blending amount of the entire raw material powder.

[0071] The hard particle powder is an alloy powder containing Cu and a Laves phase composed of Co, Mo, and Si, and includes Cu, Si, Fe, Mo, Co, and Cr. The hard particle powder may further contain Sn, for example, 1 mass% or more of Sn. While the solidus temperature of hard particle powders without Sn reaches nearly 1450°C, the inclusion of Sn can lower the solidus temperature of the hard particle powder, enabling the hard particle powder to be solid-phase sintered to a backing metal base material at nearly 800°C. Furthermore, the Sn contained in the hard particle powder dissolves in the Cu-Sn matrix phase of the first powder during sintering and is diffusion-bonded. As sintering progresses due to powder shrinkage mediated by Sn, solid-solution strengthening can be achieved by the Sn in the matrix phase and the Sn contained in the hard particle powder. The contents of the respective constituent elements in the hard particle powder may be, when the entire hard particle powder is taken as 100% by mass, Co: 14 to 20% by mass, Mo: 24 to 28% by mass, Si: 3 to 7% by mass, Fe: 2 to 16% by mass, Cr: 1 to 10% by mass, and Cu: balance. When Sn is contained, the contents of the respective constituent elements in the hard particle powder may be, when the entire hard particle powder is taken as 100% by mass, Co: 14 to 20% by mass, Mo: 24 to 28% by mass, Si: 3 to 7% by mass, Fe: 2 to 16% by mass, Cr: 1 to 10% by mass, Sn: 1 to 15% by mass, and Cu: balance. When the entire raw material powder is taken as 100% by mass (i.e., when the entire sliding layer 12 is taken as 100% by mass), the blending amount of the hard particle powder may be 1 to 40% by mass, and preferably 1 to 3% by mass. Since Cu and Sn are dissolved from the hard particle powder during sintering, the content of hard particles in the sliding layer 12 varies depending on the blending amount of the hard particle powder in the raw material powder.

[0072] The second powder is an alloy powder containing Cu as a primary component and further containing Co, Fe, Ni, Si, and Cr. The second powder may further contain Sn, for example, 1% by mass or more of Sn. The solidus temperature of the second powder without Sn reaches nearly 1240°C, but by adding Sn, the solidus temperature of the second powder can be lowered, allowing the second powder to be solid-phase sintered into a backing metal base material at nearly 800°C. When Sn is included, the contents of each constituent element in the second powder may be, when the entire second powder is taken as 100% by mass, as follows: Co: 0.6 to 4.6% by mass, Fe: 1.6 to 5.6% by mass, Ni: 10 to 14% by mass, Si: 0.5 to 4.5% by mass, Cr: 0.5 to 1.5% by mass, Sn: 1 to 15% by mass, and Cu: the balance. When the raw material powder contains the second powder, the blending amount of the second powder may be 2 to 38 mass%, preferably 10 to 38 mass%, and more preferably 17 to 19 mass%, when the entire raw material powder is taken as 100 mass%.

[0073] When the total mass of the raw material powder is taken as 100 mass%, the blending amount of the hard particle powder may be 1 to 40 mass%, and the blending amount of the second powder may be 15 to 18 mass%, in which case excellent shear workability can be achieved.

[0074] The first powder, the hard particle powder, and the second powder can be produced by spraying, for example, by gas atomization. In gas atomization, the heat source for melting may be high frequency, and a zirconia crucible (with a nozzle at the bottom) may be used.

[0075] The particle size of the first powder may be, for example, 45 μm to 180 μm. The particle size of the hard particle powder may be a fine powder of 53 μm or less. The particle size of the second powder may be 53 μm to 150 μm. Here, "particle size" refers to the particle size distribution measured by a laser diffraction / scattering method using a particle size distribution measuring device MT3300EXII manufactured by Microtrac-Bell. This measurement method conforms to the test procedure from the step of extracting powder from the paste onwards in "4.2.3 Laser diffraction particle size distribution measurement test" of JIS Z3284-2.

[0076] Next, the raw material powder dispersed on the metal substrate 11 is sintered at 800 to 900°C to form the porous layer 12 (step S20). As described above, the solid-phase temperatures of the Sn-free hard particle powder and the second powder reach approximately 1450°C and 1240°C, respectively. However, by including Sn, the solid-phase temperatures of the hard particle powder and the second powder can be lowered, enabling the hard particle powder and the second powder to be solid-phase sintered to the metal substrate (backing metal base material) at approximately 800°C. Furthermore, the Sn contained in the hard particle powder dissolves in the Cu—Sn matrix phase 10 formed by the first powder during sintering, resulting in diffusion bonding. As sintering progresses due to powder shrinkage via Sn, solid-solution strengthening occurs between the Sn in the matrix phase 10 and the Sn contained in the hard particle powder, ultimately resulting in the formation of a high-strength alloy.

[0077] Next, the metal substrate 11 is wound with the porous layer 12 on the inside to form a cylindrical shape (step S30), and the seam portion 11a is welded from the outer diameter side of the metal substrate 11 (step S40). The welding method may be TIG welding (argon gas welding) or laser welding (pulse welding). During this process, the porous layer 12 above the seam portion 11a melts due to the heat generated during welding, thereby crushing the numerous voids contained in the porous layer 12 and forming a non-porous layer 14 formed of a simple metal or an alloy composition. No seam appears on the inner diameter surface. The non-porous layer 14 has an apparent volume reduced by the amount of the voids contained in the porous layer 12, resulting in a concave shape on the inner diameter surface compared to the surrounding porous layer 12.

[0078] Although not necessarily required, after the step of welding the seam portion 11 a (step S40), the inner surface of the porous layer 12 may be burnished by pressing a cylindrical core metal 42 into the inside of the porous layer 12 while restraining the outer surface of the metal substrate 11 with a die 41 (see FIG. 10 ).

[0079] Next, the surface of the porous layer 12 is impregnated with the raw material resin of the slide layer 13 (step S50). Specifically, for example, as shown in Fig. 9, a predetermined amount of resin composition may be supplied onto the porous layer 12 formed on the inner peripheral surface of the metal substrate 11, and the resin composition may be pressed against the porous layer 12 by the rotation pressure of an impregnation roll, thereby impregnating the porous layer 12 with the resin composition. The resin composition supplied onto the porous layer 12 may contain hard particle powder 13a containing a Laves phase composed of Co, Mo, and Si, and molybdenum disulfide (MoS ２ ) powder may be dispersed in the resin composition. In one variation, the resin composition may contain copper sulfide as an additive and may further contain molybdenum disulfide, or may contain graphite or aramid fiber as other additives. The amount of the resin composition supplied onto the porous layer 12 is an amount that covers the porous layer 12 to a thickness that prevents the porous layer 12 from being exposed from the surface of the sliding layer 13 after the resin composition is baked as described below.

[0080] At this time, since the metal or alloy composition constituting the porous layer 12 has melted, the surface of the non-porous layer 14 is not in a state where the raw material resin is impregnated between the porous portions, but rather the raw material resin is simply placed on the non-porous layer 14.

[0081] Next, the resin composition is heated at a temperature exceeding the melting point of the resin contained in the resin composition to melt the resin and volatilize the organic solvent, and then the resin is cured to form a sliding layer 13 made of the resin composition that covers the porous layer 12 (step S60). Heating the resin composition at a predetermined temperature to form the sliding layer 13 is called baking. The melting point of polytetrafluoroethylene used as the resin is 327°C. The sliding layer 13 may be baked by using a baking furnace to heat the resin composition at a temperature exceeding the melting point of polytetrafluoroethylene (for example, 400 to 500°C).

[0082] At this time, since the surface of the non-porous layer 14 is in a melted state due to welding, the resin composition easily peels off from the top of the non-porous layer 14. After the formation of the sliding layer 13, the resin composition may be peeled off from the top of the non-porous layer 14 in a non-contact manner by gravity or wind force, or may be peeled off by sweeping with a brush or the like. By peeling the resin composition off from the top of the non-porous layer 14, a region 15 is formed in which the resin composition is absent from part of the inner circumferential surface and the non-porous layer 14 is exposed.

[0083] 10, the outer peripheral surface of the metal substrate 11 is constrained by a die 41 while a cylindrical core metal 42 is pressed into the inside of the slide layer 13, thereby burnishing the inner peripheral surface of the slide layer 13 to reduce the inner diameter roundness to 50 μm or less (step S70). In this way, the slide member 10 (see FIGS. 1 to 5) having the above-described configuration is manufactured.

[0084] Next, another example of a method for manufacturing the slide member 10 will be described with reference to Fig. 7. Fig. 7 is a flow chart showing another example of a method for manufacturing the slide member 10.

[0085] As in the example of the manufacturing method described above, first, raw material powder for the porous layer 12 is scattered on one surface of the metal substrate (step S10), and then the raw material powder scattered on the metal substrate 11 is sintered to form the porous layer 12 (step S20).

[0086] 7 , a predetermined amount of resin composition is supplied onto the porous layer 12, and the resin composition is pressed against the porous layer 12 to impregnate the porous layer 12 with the resin composition (step S150). The amount of resin composition supplied onto the porous layer 12 is an amount that covers the porous layer 12 to a thickness that prevents the porous layer 12 from being exposed from the surface of the sliding layer 13 after the resin composition is baked, which will be described later.

[0087] Next, the resin composition is heated at a temperature exceeding the melting point of the resin contained in the resin composition to melt the resin and volatilize the organic solvent, and then the resin is cured to form the sliding layer 13 made of the resin composition that covers the porous layer 12 (step S160).

[0088] Next, the metal substrate 11 is rolled up with the sliding layer 13 on the inside to form a cylindrical shape (step S130), and then the seam 11a is welded from the outer diameter side of the metal substrate 11 (step S140). The welding method may be TIG welding (argon gas welding) or laser welding (pulse welding). At this time, the heat from the welding melts the porous layer 12 above the seam 11a, crushing the numerous voids contained in the porous layer 12 and forming a non-porous layer 14 made of a simple metal or an alloy composition. At the same time, the resin composition on the seam 11a peels off, leaving a region 15 where the resin composition is absent from a portion of the inner circumferential surface and the non-porous layer 14 is exposed.

[0089] 10, the outer peripheral surface of the metal substrate 11 is constrained by a die 41 while a cylindrical core metal 42 is pressed into the inside of the slide layer 13, thereby burnishing the inner peripheral surface of the slide layer 13 to reduce the inner diameter roundness to 50 μm or less (step S70). In this way, the slide member 10 (see FIGS. 1 to 5) having the above-described configuration is manufactured.

[0090] According to the embodiment described above, a portion of the inner circumferential surface of the slide member 10 is free of resin composition, providing a region 15 in which a non-porous layer 14 formed of a metal or alloy composition is exposed. Because the resin composition is absent from the surrounding area and the non-porous layer does not contain numerous voids like a porous layer, this region has a recessed shape compared to the surrounding area, acting as a groove. During use of the slide member 10, the inner surface of the groove does not come into contact with the shaft, which is the object being slid against, thereby contributing to reducing heat generation due to friction. This suppresses temperature rise in high-speed rotation regions and improves bearing performance. In particular, when lubricating oil or grease is present, the groove maintains the formation of an oil film on the sliding surface, which is expected to further reduce heat generation compared to use in a dry environment.

[0091] Furthermore, the resin composition is not present on a portion of the inner circumferential surface of the sliding member 10, and an area 15 is provided where the non-porous layer 14 formed of a simple metal or an alloy composition is exposed, and no protrusions due to seams appear on the sliding surface, reducing the torque generated by friction at the seams. This contributes to reducing power consumption and energy loss, and therefore contributes to carbon neutrality.

[0092] Furthermore, for bearings used in high-speed rotation environments such as EV motors and electric compressors, it will be possible to replace conventional rolling bearings with the sliding member 10 according to this embodiment, which will lead to smaller and lighter sizes.

[0093] Furthermore, when a conventional sliding member having a seam on the sliding surface is applied to a motor or a compressor, an inner diameter cutting step (i.e., surface alignment of the inner surface at the seam portion) is required. However, in the sliding member 10 according to the present embodiment, the resin composition is not present on a part of the inner peripheral surface of the sliding member 10, and an area 15 is provided where the non-porous layer 14 formed of a simple metal or an alloy composition is exposed. Therefore, no protrusions due to the seam appear on the sliding surface, and the inner diameter cutting step can be eliminated.

[0094] Furthermore, according to this embodiment, region 15 where no resin composition is present is provided so as to extend from one end to the other end in the axial direction of slide member 10, and therefore the effect of reducing heat generation due to friction can be obtained continuously from one end to the other end in the axial direction, thereby realizing further suppression of temperature rise in the high-speed rotation region.

[0095] Furthermore, according to the present embodiment, the region 15 where the resin composition is not present has a recessed shape compared to the surrounding area and serves as a groove. The region 15 is formed by heat generated during welding of the joint portion 11 a of the metal base material 11 at the same time. This allows the number of steps to be reduced compared to the case where the sliding layer is formed and then the sliding layer is processed into an uneven shape.

[0096] Next, a specific example according to the present embodiment will be described.

[0097] (Production of Sliding Member) First, a powder obtained by removing coarse powder having a particle size of 150 μm or more from bronze powder (irregular shape, brand: CP-301) manufactured by Fukuda Metal Foil and Powder Co., Ltd. was prepared as the raw material powder for the porous layer 12. The chemical composition of the bronze powder was Cu-10Sn.

[0098] Next, as an example, a raw material powder for the porous layer 12 was scattered on a copper-plated steel sheet and sintered at 880°C to form the porous layer 12. The steel sheet on which the porous layer 12 was formed was then slit to a width of 67.6 mm to obtain an inner diameter of 20 mm. The slit steel sheet was then shaped into a cylindrical shape from the width direction while applying pressure via side rolls, and the seam of the steel sheet was argon gas welded from the outer diameter side. After welding, the metal substrate 11 was water-cooled, deburred, and sized, and then cut to a total length of 10 mm to obtain a cylindrical metal substrate 11 with the porous layer 12 formed on its inner surface. Then, referring to FIG. 10 , an Amsler tester was used to apply a load to the inner surface of the porous layer 12 by pressing a core 42 into the inside of the porous layer 12 while restraining the outer surface of the metal substrate 11 with a die 41, thereby correcting the inner surface of the porous layer 12 (burnishing).

[0099] Next, the inner peripheral surface of the porous layer 12 was impregnated with a resin. The impregnated resin had a composition of 1.1 mass% graphite powder, 15 mass% hard particle powder containing a Laves phase composed of Co, Mo, and Si, and the remainder PTFE resin. MoS was added to improve self-lubrication. ２ Powder: 15% by mass was added. The chemical composition of the hard particle powder was Cu-4.5Sn-5Si-15Fe-16Co-4Cr-26Mo, and the particle size was under 53 μm. The graphite powder was manufactured by Nippon Graphite Co., Ltd. (brand: CPBW-5).

[0100] 9, the resin was applied to the inner peripheral surface of the porous layer 12 with a spatula, and while pressing with a rolling mandrel of Φ11.7, the resin was impregnated into the porous layer 12 by the rotation pressure of the rolling. Thereafter, the porous layer 12 was fired in a firing furnace at a firing temperature of 480°C and a conveyor speed of 1000 mm / min.

[0101] Next, referring to FIG. 10 , an Amsler testing machine was used to apply a load to the inner peripheral surface of the sliding layer 13, thereby correcting the inner peripheral surface of the sliding layer 13 (burnishing) while restraining the outer peripheral surface of the metal substrate 11 with a die 41.

[0102] The sliding member according to the example was obtained through the above manufacturing process. The sliding member according to the example had a weld mark on the outer peripheral surface of the metal substrate 11, extending from one end to the other end in the axial direction of the sliding member 10, and a region 15 in which the non-porous layer 14, where the resin composition is not present, was exposed on the inner peripheral surface behind the weld mark, extending from one end to the other end in the axial direction of the sliding member 10. Fig. 26 is a graph showing the inner diameters of the sliding member according to the example measured at angles of 90°, 180°, 270°, and 360° in the circumferential direction. As shown in Fig. 26, the inner diameter accuracy of the sliding member according to the example was 0.018 mm or less.

[0103] In addition, slide members according to Comparative Examples 1 and 2 were produced by the manufacturing process described in Japanese Patent Application No. 2023-026107. That is, in Comparative Example 1, a carbon steel round bar was machined on a lathe to an outer diameter of 22 mm, an inner diameter of 20.62 mm, and a total length of 10.35 mm, to obtain a seamless, thin-walled, cylindrical metal substrate. In Comparative Example 2, a carbon steel plate material measuring 67 mm in length, 11 mm in width, and 0.75 mm in thickness was machined into a wound bushing, to obtain a cylindrical metal substrate having a seam (seam type) with a width of 2 mm or less.

[0104] Next, for Comparative Example 1, referring to Figures 5 and 6A of Japanese Patent Application No. 2023-026107, a carbon steel jig with an outer diameter of 19.96 mm was inserted into a metal substrate with an inner diameter of 20.62 mm, and the same bronze powder as in the Examples was poured into the 0.3 mm gap between the inner surface of the metal substrate and the outer surface of the jig. The powder filling volume was 0.21 cm3, since the inner diameter of the metal substrate was 20.6 mm, the outer diameter of the jig was 19.96 mm, and the total length was 10.35 mm. For Comparative Example 2, referring to Figure 6B of Japanese Patent Application No. 2023-026107, the metal substrate was press-fitted into the inside of a housing to seal the seam, and then a carbon steel jig was coaxially placed inside the metal substrate pressed into the housing, and the same bronze powder as in the Examples was poured into the 0.3 mm annular gap between the inner surface of the metal substrate and the outer surface of the jig. In both Examples 1 and 2, in order to improve the fluidity of the powder poured into the gap, a rotating shaft was connected to the jig and the powder was filled while rotating the jig with a motor. In this state, sintering was carried out in a sintering furnace at a sintering temperature of 880°C and a conveyor speed of 230 mm / min.

[0105] Next, for Comparative Examples 1 and 2, resin was impregnated into the inside of a cylindrical metal substrate on which bronze powder had been sintered. The impregnated resin had a composition of 1.1 mass% graphite powder, 15 mass% hard particle powder containing a Laves phase composed of Co, Mo, and Si, and the remainder PTFE resin, with MoS added to improve self-lubrication. ２ Powder: 15 mass% was added. The chemical composition of the hard particle powder was Cu-4.5Sn-5Si-15Fe-16Co-4Cr-26Mo, and the particle size was fine powder under 53 μm. The graphite powder was manufactured by Nippon Graphite Co., Ltd. (brand: CPBW-5). The resin impregnation method was the same as in the above-mentioned examples, so a description thereof will be omitted.

[0106] Next, similarly to the above-described examples, an Amsler testing machine was used to apply a load to the inner peripheral surface of the sliding layer 13, thereby correcting the inner peripheral surface (burnishing) by pressing a core metal 42 into the inside of the sliding layer while restraining the outer peripheral surface of the metal substrate with a die 41.

[0107] The sliding members according to Comparative Examples 1 and 2 were obtained by the above manufacturing process. Fig. 27 is a graph showing the inner diameters of the sliding member according to Comparative Example 1 measured at angles of 90°, 180°, 270°, and 360° in the circumferential direction. As shown in Fig. 27, the inner diameter accuracy of the sliding members according to the Examples was 0.037 mm or less. It is presumed that the powder filling method in which bronze powder particles are filled one by one and sintered, as in Comparative Examples 1 and 2, results in greater variation in inner diameter than the method in which bronze powder is sintered and then shaped into a cylindrical shape, as in the Examples.

[0108] In Comparative Example 3, the same bronze powder as in Example and Comparative Examples 1 and 2 was scattered on a carbon steel plate (metal substrate) and sintered to form a porous layer. ２ The porous layer was impregnated with a resin composed of 7.25 mass % of powder and the remainder PTFE resin, and then the resin was baked to form a sliding layer covering the porous layer, followed by rolling. Next, the rolled metal substrate was processed into a wound bushing with the sliding layer on the inside, thereby producing a sliding member in which the metal substrate, the porous layer, and the sliding layer all had joints (seams).

[0109] FIG. 13 is a table showing the compositions and other information of the sliding members according to the example and comparative examples 1 to 3, which were produced by the above-described procedure.

[0110] (High-Speed ​​Rotational Wear Test) Next, the performance of the sliding members of the Example and Comparative Examples 1 to 3 was compared in a high-speed rotational wear test. Figure 11 shows a high-speed rotational wear tester. This tester measures the temperature at the back of the bearing when a load and speed are applied to the test material via a mating shaft, and is primarily suitable for evaluating wear and heat generation in the high-speed range. An oil bath was installed in the test section, enabling evaluation in both oil and dry environments. To enable high-speed evaluation, a Shino Electric Co., Ltd. spindle motor (model S262B-SJ03, rated output 1.2 kW, rated voltage 200 V, rated current 4.8 A) was directly connected to the tip of the mating shaft (Φ6h7) via a collect chuck. This resulted in a device capable of evaluation up to 60,000 rpm with an accuracy of 0.002 mm or less of shaft runout. The spindle motor was water-cooled via a chiller at a flow rate of 0.7 L / min.

[0111] The outer diameter of the mating shaft was Φ11.957mm to 11.975mm, and the inner diameter of the housing was Φ14.000mm to 14.018mm. Both were made of SKD-11 material, with a hardness of HRC58 after full quenching. The temperature on the back of the bearing was measured every second using a data logger at a position 1.5mm from the back of the bearing, using a thermocouple inserted into a Φ6mm hole.

[0112] Next, regarding the test environment, the presence or absence of lubrication for the bearings plays a major role in performance. For example, in air conditioning compressors, such as those used in car air conditioners, lubricating oil is difficult to infiltrate into the bearings when the orbiting scroll is tightly pressed against the fixed scroll during orbital motion. Furthermore, high-speed rotation is essential for EV drive motors to achieve both compactness and lightness while increasing power output. Oil-lubricated and grease-lubricated bearings are commonly used to support motors, but the simplification of the surrounding structure means that oil lubrication of the bearings is not readily apparent. Given these practical constraints, this test was conducted in an unlubricated environment, measuring frictional heat generation and wear volume relative to the shaft rotation speed. Frictional heat generation was evaluated using the bearing temperature rise rate as an evaluation index, and the temperature gradient versus time required for the bearing back surface temperature to reach 80°C was analyzed using regression analysis. Wear volume was determined by measuring the thickness of the sliding components before and after the test using a pipe micrometer and determining the change in thickness at the load point.

[0113] The rotation speed of a shaft is said to reach a maximum of 10,000 rpm for the main shaft of a compressor, and a maximum of around 30,000 rpm for an EV motor. Taking this into consideration, the range of 10,000 to 50,000 rpm was set. A radial load of 10 N was applied to the bearing in one direction, taking into account the usage limit of the spindle motor at high speeds and safety. The target clearance between the bearing and the shaft was set to 0.1 mm, and the shaft was polished to a surface roughness of Ra 0.17 μm before being used for the test.

[0114] The sliding member according to the example had a region 15 on the inner circumferential surface where the resin composition was not present, and as shown in FIG. 12 , a position 90° away from the region 15 in the circumferential direction was set as a load point (hereinafter, the position of this load point will be referred to as load category A).

[0115] Regarding friction torque caused by rotational motion, power can be converted into electric power, which can be expressed as in the following equation (1): E = P = 2π N T / 60 = 2π N F R / 60 ... equation (1) where R is the radius of rotation (m), F is the friction force (N), N is the shaft rotation speed (rpm), T is the torque (N m), E is the electric power (W), and P is the power (W).

[0116] (Results and Discussion) Fig. 14 is a graph showing the change over time in the bearing back surface temperature measured when the shaft rotation speed N was 15,000 rpm for the sliding members according to the example and comparative examples 1 to 3, Fig. 15 is a graph showing the change over time in the bearing back surface temperature measured when the shaft rotation speed N was 20,000 rpm, Fig. 16 is a graph showing the change over time in the bearing back surface temperature measured when the shaft rotation speed N was 25,000 rpm, Fig. 17 is a graph showing the change over time in the bearing back surface temperature measured when the shaft rotation speed N was 30,000 rpm, and Fig. 18 is a graph showing the change over time in the bearing back surface temperature measured when the shaft rotation speed N was 35,000 rpm.

[0117] 14 to 16, in the high-speed rotation region where the shaft rotation speed N is 15,000 to 30,000 rpm, the change in temperature with time of the slide member according to the example behaves similarly to the change in temperature with time of the slide members according to comparative examples 1 and 2. Therefore, it was confirmed that in the high-speed rotation region where the shaft rotation speed N is 15,000 to 30,000 rpm, the slide member according to the example maintains the same function as the slide members according to comparative examples 1 and 2 (i.e., the slide member proposed in Japanese Patent Application No. 2023-026107).

[0118] 17 and 18, in the high-speed rotation region where the shaft rotation speed N is 30,000 rpm or more, the temperature change of the slide member according to the example is slower than the temperature change of the slide members according to the comparative examples 1 and 2. Therefore, it was confirmed that, particularly in the high-speed rotation region where the shaft rotation speed N is 30,000 rpm or more, the slide member according to the example suppresses the temperature rise more than the sliding parts according to the comparative examples 1 and 2 (i.e., the slide member proposed in Japanese Patent Application No. 2023-026107).

[0119] FIG. 19 is a graph showing the change in temperature rise rate versus shaft rotation speed in the range of 10,000 to 50,000 rpm for the sliding members according to the example and comparative examples 1 to 3, and FIG. 20 is a graph showing the change in power consumption versus shaft rotation speed in the same range.

[0120] 19 and 20 , the shaft rotation speed at which a rapid increase in the temperature rise rate and power consumption occurs is 15,000 rpm for the sliding member of Comparative Example 3, 25,000 rpm for the sliding member of Comparative Example 2, and 30,000 rpm for the sliding member of Comparative Example 1, while it is 35,000 rpm for the sliding member of the Example. Therefore, it was confirmed that the sliding member of the Example has a higher allowable limit rotation speed than the sliding members of Comparative Examples 1 to 3.

[0121] Furthermore, an additional evaluation test was conducted in which the rotation speed was changed minutely in a range close to the shaft rotation speed at which a sudden increase in the temperature rise rate and power consumption occurs. Fig. 21 is a graph showing the change in the temperature rise rate with respect to the shaft rotation speed in a range close to the shaft rotation speed at which a sudden increase in the temperature rise rate and power consumption occurs for the sliding members according to the example and comparative examples 1 to 3, and Fig. 22 is a graph showing the change in power consumption with respect to the shaft rotation speed in the same range.

[0122] 21 and 22, the temperature rise rate and power consumption of the sliding member according to Comparative Example 3 are almost constant within the shaft rotation speed range of 7,000 to 8,000 rpm, but rise sharply above 8,000 rpm, so that the allowable limit rotation speed can be determined to be 8,000±1,000 rpm. Also, the temperature rise rate and power consumption of the sliding member according to Comparative Example 2 are almost constant within the shaft rotation speed range of 22,000 to 25,000 rpm, but rise sharply above 25,000 rpm, so that the allowable limit rotation speed can be determined to be 23,500±1,500 rpm. Furthermore, for the sliding member according to Comparative Example 1, the temperature rise rate and power consumption are almost constant within the shaft rotation speed range of 27,000 to 30,000 rpm, but rise sharply once the shaft rotation speed exceeds 30,000 rpm, so it can be determined that the allowable limit rotation speed is 28,500±1,500 rpm. In contrast, for the sliding member according to the example, the temperature rise rate and power consumption are almost constant within the shaft rotation speed range of 30,000 to 33,000 rpm, but rise sharply once the shaft rotation speed exceeds 33,000 rpm, so it can be determined that the allowable limit rotation speed is 31,500±1,500 rpm.

[0123] Next, in order to investigate the influence of a region 15 where the resin composition is not present on a part of the inner circumferential surface on the temperature rise suppression effect, an additional evaluation test was conducted on the sliding member according to the example, in which a position coincident with the region 15 in the circumferential direction was set as a load point, as shown in FIG. 23 (hereinafter, the position of this load point will be referred to as load category B).

[0124] FIG. 25 is a graph showing the change in temperature rise rate versus shaft rotation speed measured in load categories A and B for the sliding member according to the example, and FIG. 26 is a graph showing the change in power consumption versus shaft rotation speed.

[0125] 25 and 26, in the shaft rotation speed range of 30,000 to 33,000 rpm, load categories A and B have almost the same rate of temperature rise and changes in power consumption, but in the shaft rotation speed range of 33,000 rpm or higher, load category A has a higher rate of temperature rise and power consumption than load category B. In load category A, the temperature rises due to the accumulation of frictional heat at the contact points, whereas in load category B, it is presumed that the frictional heat at the contact points is mitigated by the grooves in region 15 where no resin composition is present, making it easier for the heat to be dissipated, thereby suppressing the temperature rise.

[0126] Although the embodiments and modifications have been described above by way of example, the scope of the present technology is not limited to these, and modifications and variations can be made according to the purpose within the scope of the claims. Furthermore, the embodiments and modifications can be combined as appropriate within the scope of not causing any contradiction in the processing content.

Claims

1. A sliding member comprising: a cylindrical metal substrate; a porous layer formed on an inner circumferential surface of the metal substrate; and a sliding layer covering the porous layer, wherein the porous layer is formed of a metal element or an alloy composition, and the sliding layer is formed of a resin composition, and the resin composition is absent in a portion of the inner circumferential surface, where a non-porous layer formed of the metal element or alloy composition is exposed.

2. The sliding member according to claim 1, characterized in that the region is provided so as to extend from one end to the other end in the axial direction of the sliding member.

3. The sliding member according to claim 1 or 2, characterized in that hard particle powder containing a Laves phase composed of Co, Mo and Si is dispersed in the sliding layer.

4. The sliding layer contains MoS ２ 4. The sliding member according to claim 3, further comprising at least one of a Laves phase-free bronze powder and a Laves phase-free bronze powder dispersed therein.

5. The sliding member according to claim 1 or 2, characterized in that the resin composition is made of copper sulfide, thermoplastic resin, molybdenum disulfide, graphite, aramid fibers, and the remainder is fluororesin, containing more than 3 mass% and less than 40 mass% of the copper sulfide, 0 mass% or more and less than 4 mass% of the thermoplastic resin, 0 mass% or more and 36 mass% or less of the molybdenum disulfide, 0 mass% or more and 10 mass% or less of the graphite, 0 mass% or more and 10 mass% or less of the aramid fibers, and the remainder is the fluororesin.

6. The sliding member according to claim 1 or 2, characterized in that the porous layer has: a matrix phase containing Cu and Sn; and hard particles dispersed in the matrix phase, the hard particles including a Laves phase composed of Co, Mo and Si.

7. The sliding member according to claim 6, characterized in that the porous layer further has a compound phase dispersed in the matrix phase, the compound phase including Co, Fe, Ni, Si and Cr.

8. The sliding member according to claim 1 or 2, characterized in that the ratio of the thickness of said porous layer to the thickness of said sliding layer is 6:4 to 8:

2.

9. A bearing comprising: a cylindrical metal substrate; a porous layer formed on an inner circumferential surface of the metal substrate; and a sliding layer covering the porous layer, wherein the porous layer is formed of a simple metal or an alloy composition, and the sliding layer is formed of a resin composition, the resin composition is absent in a portion of the inner circumferential surface, and the bearing has a region where the non-porous layer formed of the simple metal or alloy composition is exposed.

10. A method for producing a sliding member, comprising the steps of: forming a porous layer made of an elemental metal or an alloy composition on one surface of a metal substrate; rolling the metal substrate with the porous layer on the inside to form a cylindrical shape; welding a joint portion from the outer diameter side of the metal substrate, whereby the porous layer on the joint portion is melted to form a non-porous layer made of the elemental metal or the alloy composition; and impregnating a surface of the porous layer with a raw material resin of a sliding layer and baking the raw material resin to form a sliding layer made of a resin composition that covers the porous layer, whereby the surface of the non-porous layer is not impregnated with the raw material resin, so that a region where the resin composition is not present on a part of the inner peripheral surface of the sliding member and where the non-porous layer is exposed is formed.

11. A method for producing a sliding member, comprising the steps of: forming a porous layer made of an elemental metal or an alloy composition on one surface of a metal substrate; impregnating a surface of the porous layer with a raw resin of a sliding layer and baking the raw resin to form a sliding layer made of a resin composition that covers the porous layer; rolling the metal substrate with the sliding layer on the inside to form a cylindrical shape; and welding a seam from an outer diameter side of the metal substrate, in which the porous layer on the seam is melted to form a non-porous layer made of the elemental metal or an alloy composition and the sliding layer on the seam is peeled off, thereby forming an area in which the resin composition is not present on a part of the inner circumferential surface of the sliding member and the non-porous layer is exposed.

12. The method according to claim 10 or 11, further comprising a step of burnishing the inner circumferential surface of the sliding layer by pressing a cylindrical core metal into the inside of the sliding layer while restraining the outer circumferential surface of the metal substrate with a die.

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