JP2019168080A - Sliding bearing and spherical surface sliding bearing - Google Patents

Abstract

To provide a sliding bearing capable of improving hardness of a sliding surface while maintaining toughness of the sliding surface.SOLUTION: A sliding bearing is made of pure titanium or a titanium alloy. The sliding bearing includes: a diffusion layer in which oxygen is in a solid solution state; and a scale of titanium oxide coming into contact with the diffusion layer and constituting the sliding surface. The thickness of the scale is equal to or less than 0.015 mm. The oxygen concentration in the diffusion layer is equal to or greater than 0.99 mass% at a position where a distance from the sliding surface is 0.1 mm.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a plain bearing and a spherical plain bearing. More specifically, the present invention relates to a plain bearing and a spherical plain bearing made of pure titanium or a titanium alloy.

  Pure titanium or a titanium alloy has a lower hardness than steel. For this reason, when a mechanical component composed of pure titanium or a titanium alloy is used for an application requiring wear resistance, it is necessary to perform a surface treatment.

  Conventionally, a surface treatment method described in International Publication No. 97/36018 (Patent Document 1) is known. In the surface treatment method described in Patent Document 1, a titanium alloy member is held at a heating temperature for a predetermined time in a nitrogen-based mixed atmosphere gas containing a small amount of oxygen. According to the surface treatment method described in Patent Document 1, nitrogen and oxygen are dissolved in the surface of the titanium alloy member.

International Publication No. 97/36018

  A titanium alloy in which nitrogen is solid solution has improved toughness but low toughness. For this reason, the wear resistance of the titanium alloy member subjected to the surface treatment according to the surface treatment method described in Patent Document 1 is not sufficient.

  Titanium alloys can also be improved in hardness by dissolving oxygen. A titanium alloy in which oxygen is dissolved has higher toughness than a titanium alloy in which nitrogen is dissolved. However, since the surface treatment for dissolving oxygen on the surface of the titanium alloy member is performed in an atmosphere containing oxygen, a scale (a film composed of titanium oxide) is formed on the surface of the member.

  The present invention has been made in view of the above-mentioned problems of the prior art. More specifically, the present invention provides a plain bearing and a spherical plain bearing that can improve the hardness of the sliding surface while maintaining the toughness of the sliding surface.

  The plain bearing according to one embodiment of the present invention is made of pure titanium or a titanium alloy. A plain bearing according to one embodiment of the present invention includes a diffusion layer in which oxygen is dissolved, and a titanium oxide scale that is in contact with the diffusion layer and forms a sliding surface. The thickness of the scale is 0.015 mm or less. The concentration of oxygen in the diffusion layer is 0.99 mass percent or more at a position where the distance from the sliding surface is 0.1 mm.

  According to the slide bearing according to one aspect of the present invention, the thickness of the fragile scale is thin, and the diffusion layer is cured while maintaining toughness by solid solution of oxygen. Therefore, according to the sliding bearing which concerns on 1 aspect of this invention, the hardness of a sliding surface can be improved, maintaining the toughness of a sliding surface.

  In the slide bearing described above, the hardness of the diffusion layer may be 500 Hv or more at a position of 0.1 mm from the sliding surface. The sliding bearing may be an aerospace sliding bearing.

  A spherical plain bearing according to an aspect of the present invention includes an inner ring and an outer ring. The outer ring and the inner ring are made of pure titanium or a titanium alloy. At least one of the outer ring and the inner ring includes a diffusion layer in which oxygen is dissolved, and a titanium oxide scale that is in contact with the diffusion layer and forms a sliding surface. The thickness of the scale is 0.015 mm or less. The concentration of oxygen in the diffusion layer is 0.99 mass percent or more at a position where the distance from the sliding surface is 0.1 mm.

  According to the spherical plain bearing according to one aspect of the present invention, the thickness of the fragile scale is thin, and the diffusion layer is cured while maintaining toughness by solid solution of oxygen. Therefore, according to the spherical plain bearing which concerns on 1 aspect of this invention, the hardness of a sliding surface can be improved, maintaining the toughness of a sliding surface.

  The spherical plain bearing may further include a liner made of a self-lubricating material disposed between the inner ring and the outer ring. In this case, friction between the inner ring and the outer ring can be reduced.

  In the above spherical plain bearing, the liner may be a woven fabric including at least one fiber selected from the group consisting of polytetrafluoroethylene fiber, aramid fiber, glass fiber, and polyester fiber. In this case, the friction between the inner ring and the outer ring can be further reduced.

  In the above spherical plain bearing, the liner may be a molded body including at least one material selected from the group consisting of polytetrafluoroethylene, polyamide, polyimide, and polyphenylene sulfide. In this case, the friction between the inner ring and the outer ring can be further reduced.

  The spherical plain bearing may be an aerospace plain bearing.

  According to the sliding bearing which concerns on 1 aspect of this invention, the hardness of a sliding surface can be improved, maintaining the toughness of a sliding surface. According to the spherical plain bearing according to one aspect of the present invention, the hardness of the sliding surface can be improved while maintaining the toughness of the sliding surface.

It is a top view of the machine part concerning an embodiment. It is sectional drawing in II-II of FIG. It is an enlarged view in the area | region III of FIG. It is process drawing which shows the surface treatment method of the machine component which concerns on embodiment. It is a typical graph which shows the relationship between the hardness of the test piece 1, and the distance from the surface. It is a typical graph which shows the relationship between the hardness of the test piece 2, and the distance from the surface. 3 is a schematic graph showing the relationship between the oxygen concentration in the test piece 1 and the distance from the surface. 3 is a schematic graph showing a relationship between an oxygen concentration in a test piece 2 and a distance from a surface. It is sectional drawing of the spherical plain bearing 20 which concerns on embodiment. It is process drawing which shows the manufacturing method of the spherical plain bearing 20 which concerns on embodiment.

  Embodiments will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

(Configuration of mechanical parts according to the embodiment)
Below, the structure of the machine component which concerns on embodiment is demonstrated with reference to FIGS. 1-3. FIG. 1 is a top view of a mechanical component according to the embodiment. 2 is a cross-sectional view taken along the line II-II in FIG. As shown in FIGS. 1 and 2, the mechanical component according to the embodiment is, for example, a plain bearing 10. However, the machine component according to the embodiment is not limited to this.

  The plain bearing 10 is made of pure titanium (Ti) or a titanium alloy. Pure titanium is a metal material composed of titanium and inevitable impurities. The titanium alloy constituting the slide bearing 10 is ASTM standard B348-13GR. 5 is preferably a Ti-6Al (aluminum) -4V (vanadium) alloy. In the following, this Ti-6Al-V alloy is referred to as a 64 titanium alloy.

  The slide bearing 10 is composed of a ring-shaped member. The plain bearing 10 has an upper surface 10a, a bottom surface 10b, an inner peripheral surface 10c, and an outer peripheral surface 10d. The bottom surface 10b is a surface opposite to the top surface 10a. The outer peripheral surface 10d is a surface opposite to the inner peripheral surface 10c. The top surface 10 a and the bottom surface 10 b are surfaces of the slide bearing 10 that are orthogonal to the central axis of the slide bearing 10. The inner peripheral surface 10c and the outer peripheral surface 10d are connected to the upper surface 10a and the bottom surface 10b. The distance between the inner peripheral surface 10c and the central axis is smaller than the distance between the outer peripheral surface 10d and the central axis. The inner peripheral surface 10 c constitutes a sliding surface of the slide bearing 10.

  FIG. 3 is an enlarged view of region III in FIG. The plain bearing 10 has a diffusion layer 10f. The slide bearing 10 may further include a scale 10e. The scale 10e may be removed as described later. The scale 10 e and the diffusion layer 10 f are on the inner peripheral surface 10 c of the slide bearing 10. The diffusion layer 10f is on the inner side of the slide bearing 10 than the scale 10e. That is, the scale 10e is in contact with the diffusion layer 10f and constitutes a sliding surface.

  The scale 10e has a thickness T1. The diffusion layer 10f has a thickness T2. The thickness T1 and the thickness T2 are the thicknesses of the scale 10e and the diffusion layer 10f in the direction orthogonal to the inner peripheral surface 10c. Preferably, the thickness T1 is 0.015 mm or less. Particularly preferably, the thickness T1 is 0.005 mm or less. The thickness T2 is preferably 0.15 mm or more.

The scale 10e is made of a titanium oxide. The titanium oxide constituting the scale 10e is, for example, TiO or TiO ₂ . Oxygen is dissolved in the diffusion layer 10f. Preferably, diffusion layer 10f includes crystal grains formed of an α phase of titanium. Preferably, the α-phase crystal grains included in the diffusion layer 10f are arranged in an equiaxed manner.

  The concentration of oxygen in the diffusion layer 10f is 0.99 mass percent or more at a position where the distance from the inner peripheral surface 10c is 0.1 mm. The oxygen concentration in the diffusion layer 10f is more preferably 1.46% by mass or more at a position where the distance from the inner peripheral surface 10c is 0.1 mm. The oxygen concentration in the diffusion layer 10f is preferably 2.2 mass percent or more at a position where the distance from the inner peripheral surface 10c is 0.05 mm. More preferably, the concentration of oxygen in the diffusion layer 10f is 3.47 mass percent or more at a position of 0.05 mm from the inner peripheral surface 10c. If the machining allowance when removing the scale 10e is 0.10 mm, the position where the distance from the inner peripheral surface 10c is 0.1 mm corresponds to the position of the sliding surface after the scale 10e is removed. If the allowance for removing the scale 10e is 0.05 mm, the position where the distance from the inner peripheral surface 10c is 0.05 mm corresponds to the position of the sliding surface after the scale 10e is removed. To do.

  The nitrogen concentration and the oxygen concentration in the diffusion layer 10f are measured by, for example, EPMA (electron beam microanalyzer).

  The hardness of the diffusion layer 10f decreases as the distance from the inner peripheral surface 10c increases. The hardness of the diffusion layer 10f is preferably 630 Hv or more at a position where the distance from the inner peripheral surface 10 c is 0.05 mm and 500 Hv or more at a position where the distance from the inner peripheral surface 10 c is 0.1 mm. . The hardness of the diffusion layer 10f is more preferably 690 Hv or more at a position where the distance from the inner peripheral surface 10 c is 0.05 mm, and 520 Hv or more at a position where the distance from the inner peripheral surface 10 c is 0.1 mm. is there.

  The hardness of the diffusion layer 10f is measured according to the Vickers hardness test method defined in JIS Z 2244: 2009.

(Surface treatment method for machine parts according to an embodiment)
Below, the surface treatment method of the machine component which concerns on embodiment is demonstrated, referring FIG. FIG. 4 is a process diagram illustrating a surface treatment method for a machine part according to the embodiment. As shown in FIG. 4, the method for manufacturing a machine part according to the embodiment includes a preparation step S1, an acid immersion step S2, a cooling step S3, and a post-processing step S4.

  In the preparation step S1, a member to be processed is prepared. This member to be processed is a ring-shaped member made of pure titanium or a titanium alloy when the mechanical component according to the embodiment is the slide bearing 10. The member to be processed has an inner peripheral surface. The inner peripheral surface of the member to be processed is a surface that eventually becomes the inner peripheral surface 10c of the slide bearing 10.

  In the soaking step S2, soaking treatment is performed on the surface of the workpiece. More specifically, the dipping treatment is performed on the inner peripheral surface of the workpiece. In the immersion treatment, heat treatment is performed using a heat treatment furnace in an atmosphere gas containing an inert gas and oxygen. The pressure of the atmospheric gas is, for example, normal pressure (atmospheric pressure). This heat treatment furnace may have an atmospheric gas recovery facility.

  The inert gas contained in the atmospheric gas is, for example, argon (Ar). The heating temperature in the heat treatment is preferably 900 ° C. or higher. The heating temperature in the heat treatment is preferably equal to or lower than β transus of pure titanium or titanium alloy constituting the workpiece. Here, β transus is a temperature at which the α phase in pure titanium or a titanium alloy is transformed into a β phase. For example, the β transus of 64 titanium alloy is 995 ° C. The holding time in the heat treatment is preferably 4 hours or longer. The holding time in the heat treatment is more preferably 8 hours or longer.

  The partial pressure of oxygen in the atmospheric gas is set so that the growth of the oxide of the member to be processed (that is, the oxide of titanium) is suppressed at the heating temperature. More specifically, the concentration of oxygen in the atmospheric gas is 100 ppm or more and 500 ppm or less.

  In the soaking step S2, oxygen in the atmospheric gas enters and diffuses from the surface of the workpiece to be processed into the workpiece to form the diffusion layer 10f. Further, in the immersion step S2, the scale 10e is formed on the surface of the workpiece. The scale 10e may be removed, for example, in the post-processing step S4.

  As shown in FIG. 4, the surface treatment method for mechanical parts according to the embodiment may further include an atmospheric gas recovery step S5. The atmospheric gas recovery step S5 is performed using an atmospheric gas recovery facility provided in the heat treatment furnace. In the atmospheric gas recovery step S5, the atmospheric gas used in the immersion acid step S2 is recovered and impurities are removed from the atmospheric gas. The atmospheric gas that has been recovered and removed impurities in the atmospheric gas recovery step S5 is used again in the immersion acid step S2.

  In the cooling step S3, the workpiece is removed from the heat treatment furnace and cooled. The processing target member is cooled by water-cooling the processing target member taken out from the heat treatment furnace with, for example, a saline solution.

  In post-processing process S4, the post-processing with respect to a process target member is performed. In the post-processing step S4, for example, cleaning of the processing target member, machining such as grinding and polishing of the processing target member, and the like are performed. Thereby, the slide bearing 10 is manufactured from the member to be processed. In addition, the machining allowance when the scale 10e is removed from the inner peripheral surface side of the processing target member in the post-processing step S4 is, for example, 0.10 mm. The removal allowance when the scale 10e is removed from the inner peripheral surface side of the processing target member in the post-processing step S4 may be 0.05 mm.

(Relationship between scale thickness and diffusion layer hardness and oxygen concentration in diffusion layer)
Below, the evaluation test about the relationship between the thickness of the scale 10e, the hardness of the diffusion layer 10f, and the oxygen concentration in the diffusion layer 10f and the results thereof will be described.

<Specimen>
First, the test piece used for said test is demonstrated. Table 1 shows the composition of the titanium alloy used for each test piece. As shown in Table 1, the titanium alloy used for each test piece is a 64 titanium alloy. In addition, the dimension of a test piece is 20 mm x 10 mm x 10 mm.

<Heat treatment conditions>
The above-mentioned immersion step S2 and cooling step S3 were performed on each test piece. Table 2 shows the heating temperature, holding time, and atmospheric gas in the soaking step S2. As shown in Table 2, in both the test piece 1 and the test piece 2, the heating temperature was 920 ° C. and the holding time was 8 hours. In both the test piece 1 and the test piece 2, the heat treatment was performed in an atmospheric gas containing oxygen and argon. However, the oxygen concentration in the atmospheric gas used for the test piece 1 was 100 ppm, and the oxygen concentration in the atmospheric gas used for the test piece 2 was 500 ppm. The cooling step S3 was performed by water cooling with 5% saline.

<Scale thickness>
When the cross section of the test piece 1 and the test piece 2 was polished and observed with a microscope, the thickness of the scale 10e formed on the surface of the test piece 1 was 0.005 mm and was formed on the surface of the test piece 2. The thickness of the scale 10e was 0.015 mm. The thickness of the scale 10e was 0.35 mm when the same member as that of the test piece 1 and the test piece 2 was subjected to an acid treatment in the atmosphere with a heating time of 850 ° C. and a holding time of 24 hours. .

<Hardness evaluation test>
FIG. 5 is a schematic graph showing the relationship between the hardness of the test piece 1 and the distance from the surface. FIG. 6 is a schematic graph showing the relationship between the hardness of the test piece 2 and the distance from the surface. As shown in FIGS. 5 and 6, the hardness of the test piece 1 and the test piece 2 decreased as the distance from the surface increased.

  As shown in FIG. 5, the hardness of the test piece 1 was 630 Hv at a position at a distance of 0.05 mm from the surface, and 520 Hv at a position at a distance of 0.1 mm from the surface. The hardness of the test piece 1 was almost constant at a position where the distance from the surface was 0.15 mm or more. Therefore, in the test piece 1, it became clear that the diffusion layer 10f of about 0.15 mm was formed.

  As shown in FIG. 6, the hardness of the test piece 2 was 690 Hv at a position at a distance of 0.05 mm from the surface, and 500 Hv at a position at a distance of 0.1 mm from the surface. The hardness of the test piece 2 was almost constant at a position where the distance from the surface was 0.15 mm or more. Therefore, in the test piece 2, it became clear that the diffusion layer 10f of about 0.15 mm was formed.

  FIG. 7 is a schematic graph showing the relationship between the oxygen concentration in the test piece 1 and the distance from the surface. FIG. 8 is a schematic graph showing the relationship between the oxygen concentration in the test piece 2 and the distance from the surface. As shown in FIG.7 and FIG.8, the oxygen concentration in the test piece 1 and the test piece 2 became small as the distance from the surface became large.

  As shown in FIG. 7, the oxygen concentration in the test piece 1 is 2.2 mass percent at a position at a distance of 0.05 mm from the surface, and 0.99 mass at a position at a distance of 0.1 mm from the surface. It was a percentage. The oxygen concentration in the test piece 1 was substantially constant at a position where the distance from the surface was 0.15 mm or more. Therefore, in the test piece 1, it was also clarified from this test result that the diffusion layer 10f of about 0.15 mm was formed.

  As shown in FIG. 8, the oxygen concentration in the test piece 2 is 3.47 mass percent at a position at a distance of 0.05 mm from the surface, and 1.46 mass at a position at a distance of 0.1 mm from the surface. It was a percentage. The oxygen concentration in the test piece 2 was substantially constant at a position where the distance from the surface was 0.15 mm or more. Therefore, it was also clarified from this test result that the diffusion layer 10f of about 0.15 mm was formed in the test piece 2.

(Effects of machine parts and surface treatment method according to embodiment)
The effects of the surface treatment method for machine parts according to the embodiment will be described below. In the surface treatment method for mechanical parts according to the embodiment, the immersion step S2 is performed using an atmospheric gas having a small amount of oxygen, and thus the thickness of the scale 10e formed on the surface of the member to be processed. The surface of the member to be processed can be hardened by solid solution strengthening of oxygen while suppressing the above.

  In the mechanical component surface treatment method according to the embodiment, when the holding time is 4 hours or more, more oxygen diffuses on the surface of the workpiece. Therefore, in this case, the hardness of the diffusion layer 10f can be improved by increasing the amount of dissolved oxygen in the diffusion layer 10f.

  In the mechanical component surface treatment method according to the embodiment, when the oxygen concentration in the atmospheric gas is 100 ppm or less and 500 ppm or more, the thickness of the scale 10e formed on the surface of the workpiece is suppressed and the workpiece is processed. Can be hardened by solid solution strengthening of oxygen.

  In the heat treatment of pure titanium and titanium alloy, the crystal grains tend to be coarsened by the transformation of the α phase into the β phase during the heat treatment. Therefore, in the surface treatment method for mechanical parts according to the embodiment, when the heating temperature is 900 ° C. or higher and β transus or lower, the crystal grains constituting the workpiece to be processed are coarsened during the acid treatment. Can be suppressed.

  In the surface treatment method for a machine part according to the embodiment, when the workpiece is a 64 titanium alloy, the surface of the workpiece is oxygen-suppressed while suppressing the thickness of the scale 10e formed on the surface of the workpiece. It can be cured by solid solution strengthening.

  When the surface treatment method for mechanical parts according to the embodiment includes the atmospheric gas recovery step S5, the processing cost can be reduced by reusing the atmospheric gas.

  In the slide bearing 10 as the mechanical component according to the embodiment, the thickness of the fragile scale 10e formed on the sliding surface is suppressed. Further, since the diffusion layer 10f is strengthened by solid solution of oxygen, it is cured while maintaining toughness. Therefore, according to the slide bearing 10 as the mechanical component according to the embodiment, the hardness of the sliding surface can be improved while maintaining the toughness of the sliding surface.

(Configuration of spherical plain bearing according to the embodiment)
Below, the structure of the spherical plain bearing 20 which concerns on embodiment is demonstrated.

  FIG. 9 is a cross-sectional view of the spherical plain bearing 20 according to the embodiment. As shown in FIG. 9, the spherical plain bearing 20 has an inner ring 21 and an outer ring 22. The spherical plain bearing 20 may further include a liner 23.

  The inner ring 21 is a ring-shaped member. The inner ring 21 has an upper surface 21a, a bottom surface 21b, an inner peripheral surface 21c, and an outer peripheral surface 21d. The top surface 21a and the bottom surface 21b are orthogonal to the central axis 21e. The bottom surface 21b is a surface opposite to the top surface 21a. The inner peripheral surface 21c and the outer peripheral surface 21d are connected to the upper surface 21a and the bottom surface 21b. The inner peripheral surface 21c is linear in a cross-sectional view (in a cross section passing through the central axis 21e). The outer peripheral surface 21d has an arc shape in cross-sectional view. The distance between the inner peripheral surface 21c and the outer peripheral surface 21d once increases from the upper surface 21a toward the bottom surface 21b, and then decreases again toward the bottom surface 21b. The outer peripheral surface 21d constitutes a sliding surface. The inner ring 21 is made of a titanium alloy. The titanium alloy constituting the inner ring 21 is, for example, a 64 titanium alloy.

  The outer ring 22 is a ring-shaped member. The outer ring 22 has an upper surface 22a, a bottom surface 22b, an inner peripheral surface 22c, and an outer peripheral surface 22d. The top surface 22a and the bottom surface 22b are orthogonal to the central axis 22e. The bottom surface 22b is a surface opposite to the top surface 22a. The inner peripheral surface 22c and the outer peripheral surface 22d are connected to the upper surface 22a and the bottom surface 22b. The outer peripheral surface 22d is linear in a cross-sectional view (in a cross section passing through the central axis 22e). The inner peripheral surface 22c has an arc shape in a sectional view. The distance between the inner peripheral surface 22c and the outer peripheral surface 22d once decreases from the upper surface 22a toward the bottom surface 22b, and then increases again toward the bottom surface 22b. The inner peripheral surface 22c constitutes a sliding surface. The outer ring 22 is made of a titanium alloy. The titanium alloy constituting the outer ring 22 is, for example, a 64 titanium alloy. The outer ring 22 is disposed so that the inner peripheral surface 22c faces the outer peripheral surface 21d.

  The inner ring 21 has a diffusion layer 21f and a scale 21g. The scale 21g is in contact with the diffusion layer 21f. The scale 21g constitutes an outer peripheral surface 21d (sliding surface). The outer ring 22 has a diffusion layer 22f and a scale 22g. The scale 21g is in contact with the diffusion layer 22f. The scale 22g constitutes an inner peripheral surface 22c (sliding surface). The inner ring 21 may not have the diffusion layer 21f and the scale 21g, and the outer ring 22 may have the diffusion layer 22f and the scale 22g. The outer ring 22 may not have the diffusion layer 22f and the scale 22g, and the inner ring 21 may have the diffusion layer 21f and the scale 21g. That is, any one of the inner ring 21 and the outer ring 22 may have the diffusion layer 21f (diffusion layer 22f) and the scale 21g (scale 22g).

  The diffusion layer 21f and the diffusion layer 22f have the same configuration as the diffusion layer 10f. The scale 21g and the scale 22g have the same configuration as the scale 10e. More specifically, the thickness of the scale 21g (scale 22g) is 0.015 mm or less. The thickness of the scale 21g (scale 22g) is preferably 0.005 mm or less.

  In the diffusion layer 21f (diffusion layer 22f) at a position where the distance from the outer peripheral surface 21d (inner peripheral surface 22c) is 0.1 mm, the oxygen concentration is 0.99 mass percent or more. In the diffusion layer 21f (diffusion layer 22f) at a position where the distance from the outer peripheral surface 21d (inner peripheral surface 22c) is 0.1 mm, the oxygen concentration is preferably 1.46 mass percent or more.

  In the diffusion layer 21f (diffusion layer 22f) at a position where the distance from the outer peripheral surface 21d (inner peripheral surface 22c) is 0.05 mm, the oxygen concentration is 2.2 mass percent or more. In the diffusion layer 21f (diffusion layer 22f) at a position where the distance from the outer peripheral surface 21d (inner peripheral surface 22c) is 0.1 mm, the oxygen concentration is preferably 3.47 mass percent or more.

  The hardness of the diffusion layer 21f (diffusion layer 22f) at a position where the distance from the outer peripheral surface 21d (inner peripheral surface 22c) is 0.1 mm may be 500 Hv or more. The hardness of the diffusion layer 21f (diffusion layer 22f) at a position where the distance from the outer peripheral surface 21d (inner peripheral surface 22c) is 0.1 mm may be 520 Hv or more. The hardness of the diffusion layer 21f (diffusion layer 22f) at a position where the distance from the outer peripheral surface 21d (inner peripheral surface 22c) is 0.05 mm may be 630 Hv or more. The hardness of the diffusion layer 21f (diffusion layer 22f) at a position where the distance from the outer peripheral surface 21d (inner peripheral surface 22c) is 0.1 mm may be 690 Hv or more.

  The liner 23 is disposed between the inner ring 21 and the outer ring 22. More specifically, the liner 23 is attached to the inner peripheral surface 22c. The liner 23 is made of a self-lubricating material. A self-lubricating material refers to a material having a lower coefficient of friction than the counterpart material. For the liner 23, for example, a woven fabric including at least one fiber selected from the group consisting of polytetrafluoroethylene fiber, aramid fiber, glass fiber, and polyester fiber is used. For the liner 23, a molded body containing at least one material selected from the group consisting of polytetrafluoroethylene, polyamide, polyimide, and polyphenylene sulfide may be used. In addition, when the spherical plain bearing 20 does not have the liner 23, the oil supply hole may be provided in the inner ring 21, for example.

(Method for Manufacturing Spherical Plain Bearing According to Embodiment)
Below, the manufacturing method of the spherical plain bearing 20 which concerns on embodiment is demonstrated.

  FIG. 10 is a process diagram illustrating a method for manufacturing the spherical plain bearing 20 according to the embodiment. As shown in FIG. 10, the method for manufacturing the spherical plain bearing 20 includes an inner ring manufacturing step S6, an outer ring manufacturing step S7, a liner mounting step S8, and an assembly step S9.

  In the inner ring manufacturing step S6, the inner ring 21 is manufactured. In the outer ring manufacturing step S7, the outer ring 22 is manufactured. The inner ring manufacturing step S6 and the outer ring manufacturing step S7 are performed according to the method for manufacturing a mechanical component according to the above embodiment. In the liner attachment step S8, the liner 23 is attached to the inner peripheral surface 22c. When the liner 23 is composed of a woven fabric, the liner 23 is attached by sticking the woven fabric to the inner peripheral surface 22c. When the liner 23 is formed of a resin molded body, the liner 23 is attached by injection molding a resin material that forms the liner 23 on the inner peripheral surface 22c.

  In the assembly step S9, the inner ring 21 and the outer ring 22 are assembled. The assembly step S9 is performed by plastic working, for example. As one of more specific methods, in the assembly step S9, firstly, a diameter expanding step for expanding the inner diameter of the outer ring 22 is performed. Second, the inner ring 21 is inserted into the outer ring 22 having an enlarged inner diameter. Thirdly, a diameter reducing process for reducing the diameter of the outer ring 22 in a state where the inner ring 21 is inserted is performed. Thus, the manufacture of the spherical plain bearing 20 is completed.

(Effect of the spherical plain bearing according to the embodiment)
Below, the effect of the spherical plain bearing 20 which concerns on embodiment is demonstrated.

  As described above, in the spherical plain bearing 20, at least one of the inner ring 21 and the outer ring 22 has the diffusion layer 21f (diffusion layer 22f) and the scale 21g (scale 22g) having the same configuration as the diffusion layer 10f and the scale 10e. ing. Therefore, according to the spherical plain bearing 20, the hardness in a sliding surface can be improved, maintaining the toughness in a sliding surface.

  When the spherical plain bearing 20 has the liner 23, the liner 23 is made of a self-lubricating material, so that friction between the inner ring 21 and the outer ring 22 can be reduced. When the liner 23 is a woven fabric including at least one fiber selected from the group consisting of polytetrafluoroethylene fiber, aramid fiber, glass fiber, and polyester fiber, or made of polytetrafluoroethylene, polyamide, polyimide, polyphenylene sulfide When the molded body includes at least one material selected from the group, the friction between the inner ring 21 and the outer ring 22 can be further reduced.

  Although the embodiment of the present invention has been described above, the above-described embodiment can be variously modified. Further, the scope of the present invention is not limited to the above-described embodiment. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The above embodiment is advantageously applied to a mechanical component made of pure titanium or a titanium alloy and a surface treatment method thereof.

  S1 preparation step, S2 soaking step, S3 cooling step, S4 post-treatment step, S5 atmosphere gas recovery step, S6 inner ring manufacturing step, S7 outer ring manufacturing step, S8 liner mounting step, S9 assembly step, 10 inner ring, 10a upper surface, 10b Bottom surface, 10c inner peripheral surface, 10d outer peripheral surface, 10e scale, 10f diffusion layer, 20 spherical plain bearing, 21 inner ring, 21a upper surface, 21b bottom surface, 21c inner peripheral surface, 21d outer peripheral surface, 21e central axis, 21f diffusion layer, 22 Outer ring, 22a upper surface, 22b bottom surface, 22c inner peripheral surface, 22d outer peripheral surface, 22e central axis, 22f diffusion layer, T1 thickness, T2 thickness.

Claims (8)

A plain bearing made of pure titanium or titanium alloy,
The sliding bearing has a diffusion layer in which oxygen is dissolved, and a scale of titanium oxide that is in contact with the diffusion layer and constitutes a sliding surface,
The thickness of the scale is 0.015 mm or less,
The slide bearing, wherein the concentration of oxygen in the diffusion layer is 0.99 mass percent or more at a position where the distance from the sliding surface is 0.1 mm.   The slide bearing according to claim 1, wherein the hardness of the diffusion layer is 500 Hv or more at a position of 0.1 mm from the sliding surface.   The sliding bearing according to claim 1, which is an aerospace sliding bearing. Inner ring,
With an outer ring,
The outer ring and the inner ring are made of pure titanium or a titanium alloy,
At least one of the outer ring and the inner ring has a diffusion layer in which oxygen is dissolved, and a titanium oxide scale that is in contact with the diffusion layer and forms a sliding surface,
The thickness of the scale is 0.015 mm or less,
A spherical plain bearing in which the concentration of oxygen in the diffusion layer is 0.99 mass percent or more at a position where the distance from the sliding surface is 0.1 mm.   The spherical plain bearing according to claim 4, further comprising a liner made of a self-lubricating material disposed between the inner ring and the outer ring.   The spherical plain bearing according to claim 5, wherein the liner is a woven fabric including at least one fiber selected from the group consisting of polytetrafluoroethylene fiber, aramid fiber, glass fiber, and polyester fiber.   The spherical plain bearing according to claim 6, wherein the liner is a molded body including at least one material selected from the group consisting of polytetrafluoroethylene, polyamide, polyimide, and polyphenylene sulfide.   The spherical plain bearing according to any one of claims 4 to 7, which is an aerospace plain bearing.

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