JP7549997B2 - Sliding member - Google Patents

Description

This disclosure relates to a sliding member.

Oil-free sliding members with excellent performance such as wear resistance have been known for some time. For example, Patent Document 1 discloses a sliding member for high temperature use that exhibits good sliding performance even when a high load acts under high temperature conditions. This sliding member includes an expanded graphite layer, and a first metal plate and a second metal plate sandwiching the expanded graphite layer. A plurality of holes are formed in the first metal plate. Each of these holes is filled with the surface portion of the expanded graphite layer. This provides an anchor effect for the bond between the first metal plate and the expanded graphite layer.

JP 2018-173169 A

In a sliding member such as that disclosed in Patent Document 1, a rotating body such as an operating shaft slides on the surface of the first metal plate as it rotates, and the rotational force of the rotating body acts on the first metal plate. For this reason, in the initial stage of use of the sliding member, a shear force is applied from the first metal plate to the protrusions consisting of the portions of the expanded graphite layer that fill the holes in the first metal plate, and stress concentration is likely to occur at the base of the protrusions. If the protrusions break due to stress concentration at the base of the protrusions, the first metal plate becomes more likely to peel off from the expanded graphite layer, reducing the durability of the sliding member.

The purpose of the technology disclosed herein is to improve the durability of sliding members.

The technology disclosed herein is directed to a sliding member that includes a first metal plate having a plurality of holes formed therein and an expanded graphite layer to which the first metal plate is pressure-bonded, and in which the surface portion of the expanded graphite layer penetrates into the holes of the first metal plate to form first protrusions. In the sliding member according to the technology disclosed herein, a first resin film made of a fluororesin is provided on the surface of the expanded graphite layer facing the first metal plate so as to cover the first protrusions.

According to this configuration, the first projections are covered with a first resin film made of a fluororesin, which reinforces the rigidity of the first projections. This reduces the shear force applied to the first projections from the first metal plate, and relieves the stress generated at the base of the first projections. This makes it possible to prevent the first projections provided on the expanded graphite layer from breaking during the initial use of the sliding member.

The technology disclosed herein can improve the durability of sliding members.

FIG. 1 is a perspective view illustrating a sliding member. FIG. 2 is a cross-sectional view illustrating an example of a sliding member. FIG. 3 is a diagram illustrating an example of the inner circumferential surface of the sliding member. FIG. 4 is a cross-sectional view of the sliding member taken along line IV-IV in FIG. FIG. 5 is a diagram illustrating a coating and baking system used in the manufacture of a sliding member. FIG. 6 is a cross-sectional view illustrating a state of a main part of the sliding member at the beginning of use. FIG. 7 is a cross-sectional view illustrating a state in which the inner resin film constituting the sliding surface of the sliding member is broken. FIG. 8 is a cross-sectional view illustrating a state in which a thin film of expanded graphite is formed on the inner circumferential surface of a sliding member. FIG. 9 is a cross-sectional view showing a main part of a sliding member of a comparative example. FIG. 10 is a diagram showing a schematic configuration of a test device used in the durability evaluation test. FIG. 11 is an enlarged view of the area surrounded by XI in FIG. FIG. 12 is a graph showing the results of the durability evaluation test. FIG. 13 is a cross-sectional view showing a main part of a sliding member of a modified example. FIG. 14 is a diagram showing an inner circumferential surface of a sliding member according to a modified example.

An exemplary embodiment is described in detail below with reference to the drawings.

- Configuration of sliding member -
The sliding member 1 shown in Fig. 1 is used as a radial bearing that supports an operating shaft 81 such as a stem on its outer periphery (outer side in the radial direction) in, for example, a ball valve, a butterfly valve, a gate valve, or a globe valve. The sliding member 1 is held in a predetermined position by a metallic holding member 83, and is disposed between the holding member 83 and the operating shaft 81 (see Fig. 2). The sliding member 1 is configured to exhibit good sliding performance even under high temperature conditions of 350°C or higher.

As shown in Figures 2 and 4, the sliding member 1 comprises an expanded graphite layer 3, an inner metal plate 5, and an outer metal plate 7. The sliding member 1 is a molded product that is formed by bending the expanded graphite layer 3, the inner metal plate 5, and the outer metal plate 7 in a stacked state so that both end edges face each other and pressurizing the stack into a substantially cylindrical shape, and both end edges of the stack of the expanded graphite layer 3, the inner metal plate 5, and the outer metal plate 7 form a slit 9. The sliding member 1 is flexible, and is attached to the operating shaft 81 by deforming it so as to open the slit 9.

The expanded graphite layer 3 is a sliding material that constitutes the sliding surface 15 of the sliding member 1. The expanded graphite layer 3 is, for example, composed of one expanded graphite sheet 3s. The expanded graphite sheet 3s is made of expanded graphite and has flexibility as well as heat resistance and chemical resistance. The thickness t1 of the expanded graphite layer 3 is appropriately set according to the depth of both holes 5h, 7h, that is, the total dimension of the thickness t2 of the inner metal plate 5 and the thickness t3 of the outer metal plate 7, so that the surface portion of the expanded graphite sheet enters each of the holes 5h, 7h of the inner metal plate 5 and the outer metal plate 7 by pressure molding. In this example, the thickness t1 of the expanded graphite layer 3 before pressure molding is, for example, 0.7 mm or more and 0.8 mm or less, and the thickness t1 of the expanded graphite layer 3 after pressure molding is, for example, 0.3 mm or more and 0.5 mm or less.

The inner metal plate 5 is made of expanded metal such as stainless steel as shown in FIG. 3. The expanded metal is a mesh-like metal plate with diamond-shaped or other meshes arranged in a staggered pattern. The outer metal plate 7 is also made of expanded metal similar to the inner metal plate 5. The inner metal plate 5 is an example of a first metal plate. The outer metal plate 7 is an example of a second metal plate.

The inner metal plate 5 and the outer metal plate 7 each have a plurality of holes 5h, 7h formed of an expanded metal mesh (see Figures 1 and 2). In this example, the inner metal plate 5 and the outer metal plate 7 are arranged in the thickness direction (radial direction) of the sliding member 1 such that the intersections of the linear portions and the holes 5h, 7h correspond to each other. The inner metal plate 5 and the outer metal plate 7 may also be arranged in the thickness direction of the sliding member 1 such that the holes 5h, 7h correspond to each other.

The inner metal plate 5 is pressure-bonded to the inner periphery of the expanded graphite layer 3 without the use of adhesive. The outer metal plate 7 is pressure-bonded to the outer periphery of the expanded graphite layer 3 without the use of adhesive. The inner metal plate 5 and the outer metal plate 7 are each embedded in the surface portion of the expanded graphite layer 3. The thicknesses t2 and t3 of the inner metal plate 5 and the outer metal plate 7 are preferably as thin as possible, provided that the strength of the sliding member 1 can be ensured, and are, for example, 0.2 mm or more and 0.4 mm or less.

As shown in FIG. 4, the surface portion on the inner periphery of the expanded graphite layer 3 penetrates into each hole 5h of the inner metal plate 5. This provides an anchor effect for the joint between the expanded graphite layer 3 and the inner metal plate 5. The portions of the expanded graphite layer 3 that penetrate into each hole 5h of the inner metal plate 5 form inner protrusions 11. That is, multiple inner protrusions 11 are provided on the inner periphery of the expanded graphite layer 3. The multiple inner protrusions 11 are arranged in a staggered pattern around the entire inner periphery of the expanded graphite layer 3. The inner protrusions 11 are an example of first protrusions.

An inner resin film 13 is provided on the surface (inner peripheral surface) of the expanded graphite layer 3 facing the inner metal plate 5 so as to cover each inner protrusion 11. The inner resin film 13 is a film common to the multiple inner protrusions 11, and covers the entire inner peripheral surface of the expanded graphite layer 3. The inner resin film 13 is an example of a first resin film. The inner resin film 13 functions as a reinforcing material that reinforces the rigidity of the inner protrusions 11.

The inner resin film 13 is interposed between the expanded graphite layer 3 and the inner metal plate 5. The inner resin film 13 is also interposed between the inner peripheral surface of each hole 5h of the inner metal plate 5 and the outer peripheral surface of the inner protrusion 11. The portion of the inner resin film 13 covering the end face of each inner protrusion 11 is exposed to the inner peripheral side of the sliding member 1 from the hole 5h of the inner metal plate 5. The surface of the inner resin film 13 exposed from the hole 5h of the inner metal plate 5 constitutes the sliding surface 15 on which the operating shaft 81 slides.

The sliding surface 15 of the inner resin film 13 fits within the hole 5h of the inner metal plate 5 in the thickness direction of the sliding member 1 and is approximately flush with the surface on the inner circumference side of the inner metal plate 5. The sliding surface 15 of the inner resin film 13 may protrude from the hole 5h of the inner metal plate 5 to the inner circumference side of the resin part 1. The inner resin film 13 is made of a fluororesin. Specifically, the inner resin film 13 is a fired film made of polytetrafluoroethylene (PTFE). The fired film has heat resistance, chemical resistance and slipperiness (low friction, self-lubrication).

The inner resin film 13 may contain a filler such as glass fiber, graphite, or molybdenum disulfide. The thickness t4 of the inner resin film 13 is preferably as thin as possible, provided that the inner resin film 13 and the inner protrusion 11 can withstand the shear force applied from the inner metal plate 5 at the beginning of use of the sliding member 1. The thickness t4 of the inner resin film 13 is, for example, 8 μm or more and 13 μm or less.

Fine irregularities 17 are formed on the inner surface of the expanded graphite layer 3. In this example, the irregularities 17 are formed over the entire inner surface of the expanded graphite layer 3. The surface roughness (arithmetic mean roughness) Ra of the inner surface of the expanded graphite layer 3 is, for example, 6.0 or more and 7.5 or less. The inner resin film 13 adheres closely to the fine irregularities 17. The inner resin film 13 is bonded to the inner surface of the expanded graphite layer 3 by the anchor effect of the irregularities 17.

The outer peripheral surface portion of the expanded graphite layer 3 penetrates into each hole 7h of the outer metal plate 7. The portions of the expanded graphite layer 3 that penetrate into each hole 7h of the outer metal plate 7 form outer protrusions 19. That is, multiple outer protrusions 19 are provided on the outer peripheral surface of the expanded graphite layer 3. The multiple outer protrusions 19 are arranged in a staggered pattern around the entire outer periphery of the expanded graphite layer 3. The outer protrusions 19 are an example of second protrusions.

An outer resin film 21 is provided on the surface (outer peripheral surface) of the expanded graphite layer 3 facing the outer metal plate 7 so as to cover each outer protrusion 19. The outer resin film 21 is a film common to the multiple outer protrusions 19, and covers the entire outer peripheral surface of the expanded graphite layer 3. The outer resin film 21 is an example of a second resin film. The outer resin film 21 functions as a reinforcing material that reinforces the rigidity of the outer protrusions 19.

The outer resin film 21 is interposed between the expanded graphite layer 3 and the outer metal plate 7. The outer resin film 21 is also interposed between the inner peripheral surface of each hole 5h of the outer metal plate 7 and the outer peripheral surface of the outer protrusion 19. The portions of the outer resin film 21 that cover the end faces of each outer protrusion 19 are exposed from the holes 7h of the outer metal plate 7 to the outer peripheral side of the sliding member 1. The surface of the outer resin film 21 exposed from the holes 7h of the outer metal plate 7 constitutes the contact surface 23 that comes into contact with the retaining member 83.

The contact surface 23 of the outer resin film 21 fits within the hole 7h of the outer metal plate 7 in the thickness direction of the sliding member 1 and is approximately flush with the outer peripheral surface of the outer metal plate 7. The contact surface 23 of the outer resin film 21 may protrude from the hole 7h of the outer metal plate 7 to the outer peripheral side of the resin part 1. The outer resin film 21 is made of a fluororesin. Specifically, the outer resin film 21 is a sintered film made of polytetrafluoroethylene (PTFE). The outer resin film 21 may contain a filler such as glass fiber, graphite, or molybdenum disulfide.

The thickness t5 of the outer resin film 21 is preferably as thin as possible, provided that it can withstand the shear force applied from the outer metal plate 7 together with the outer protrusion 19 when the sliding member 1 slides against the retaining member 83 on the outer peripheral surface in a corotation phenomenon in which the sliding member 1 rotates together with the operating shaft 81 due to the loosening of the holding force of the retaining member 83 against the sliding member 1 caused by use under high temperature conditions. The thickness t5 of the outer resin film 21 is, for example, 8 μm or more and 13 μm or less.

The outer peripheral surface of the expanded graphite layer 3 is formed with fine irregularities 25. In this example, the irregularities 25 are formed over the entire outer peripheral surface of the expanded graphite layer 3. The surface roughness (arithmetic mean roughness Ra) of the outer peripheral surface of the expanded graphite layer 3 is, for example, 6.0 or more and 7.5 or less. The outer resin film 21 is in close contact with the fine irregularities 25. The outer resin film 21 is bonded to the outer peripheral surface of the expanded graphite layer 3 by the anchor effect of the irregularities 25.

- Manufacturing method of slide member -
The slide member 1 having the above-mentioned configuration is manufactured by forming the resin films 31 that become the inner resin film 13 and the outer resin film 21 on the expanded graphite sheet 3s that constitutes the expanded graphite layer 3, and then pressing the expanded graphite layer 3 made of the expanded graphite sheet 3s while it is sandwiched between the inner metal plate 5 and the outer metal plate 7, so that the surface portions on both sides of the expanded graphite sheet 3s together with the resin films 31 enter each of the holes 5h of the inner metal plate 5 and each of the holes 7h of the outer metal plate 7.

In the process of forming the resin film 31 on both sides of the expanded graphite sheet 3s, for example, a coating and baking system 51 as shown in FIG. 5 is used. The coating and baking system 51 is a system that continuously performs a series of processes, in which a long expanded graphite sheet 3s is transported by a roll-to-roll method, and dispersion D is applied to both sides of the expanded graphite sheet 3s during transportation by a dip coating method, followed by drying and baking.

The coating and baking system 51 includes an unwinding device 53, a winding device 55, multiple guide rollers 57, a surface treatment device 59, a liquid tank 61, a drying and baking machine 63, and a controller 65. The operations of the unwinding device 53, the winding device 55, the multiple guide rollers 57, the surface treatment device 59, and the drying and baking machine 63 are controlled by the controller 65.

In the coating and baking system 51, the expanded graphite sheet 3s is set in a rolled state wound around a core material. The unwinding device 53 supports the rolled expanded graphite sheet 3s and delivers the expanded graphite sheet 3s at a constant speed. The expanded graphite sheet 3s delivered from the unwinding device 53 is transported while supported by multiple guide rollers 57, and passes through the surface treatment zone Z1, coating zone Z2, and drying and baking zone Z3 in that order before being wound up by the winding device 55.

In the surface treatment zone Z1, a surface treatment device 59 is arranged. The surface treatment device 59 has a pair of press rollers 69 that sandwich the expanded graphite sheet 3s transported to the surface treatment zone Z1. The outer peripheral surface of each press roller 69 is provided with a large number of convex portions 71 of a grain size equivalent to coarse or medium-grain abrasive paper, which are provided all around the circumference. The pair of press rollers 69 rotate in opposite directions to each other, sandwiching and sending out the expanded graphite sheet 3s. At this time, the expanded graphite sheet 3s is pressed by the pair of press rollers 69, so that the surface shape of the press rollers 69 is transferred to both sides of the expanded graphite sheet 3s, forming fine irregularities 17, 25.

A liquid tank 61 is disposed in the coating zone Z2. The liquid tank 61 stores a dispersion D in which polytetrafluoroethylene resin (PTFE) particles are dispersed in water. The guide roller 57 is disposed in the liquid tank 61 so as to be immersed in the dispersion D. In the coating zone Z2, the expanded graphite sheet 3s enters the liquid tank 61, passes under the guide roller 57 in the liquid tank 61, and is transported to the outside of the liquid tank 61. At this time, the expanded graphite sheet 3s is immersed in the dispersion D, and the dispersion D is coated on both sides of the expanded graphite sheet 3s. Although not shown, a scraping device such as a blade or an air knife is disposed at the location where the expanded graphite sheet 3s after coating is transported. The excess dispersion D coated on the expanded graphite sheet 3s is scraped off by the scraping device.

A dryer/sintering machine 63 is disposed in the dryer/sintering zone Z3. The expanded graphite sheet 3s transported to the dryer/sintering zone Z3 is carried into the dryer/sintering machine 63 and transported vertically inside the dryer/sintering machine 63. Inside the dryer/sintering machine 63, a heater 73 is provided for heating the expanded graphite sheet 3s from both sides. The dryer/sintering machine 63 dries the expanded graphite sheet 3s coated with the dispersion D by heating with the heater 73 and then sinters it. The sintering temperature at this time is, for example, 350°C or higher and 400°C or lower. Thus, a resin film 31 is formed on both sides of the expanded graphite sheet 3s.

The expanded graphite sheet 3s discharged from the drying and baking machine 63 is guided to the winding device 55 by the guide roller 57. The long expanded graphite sheet 3s thus obtained is cut to a predetermined length and used as the expanded graphite layer 3 for the sliding member 1.

- Behavior of sliding components during use -
When the sliding member 1 having the above configuration is used, in the early stages of use, as shown in Fig. 6, the operating shaft 81 slides on the inner metal plate 5, and the rotational force of the operating shaft 81 acts on the inner metal plate 5. Therefore, a shear force is applied from the inner metal plate 3 to the inner protrusions 11 provided on the inner circumferential surface of the expanded graphite layer 3. At this time, the inner protrusions 11 are reinforced by being covered with the inner resin film 13 made of a sintered film of polytetrafluoroethylene resin. Therefore, the inner protrusions 11 covered with the inner resin film 13 can withstand the shear force applied from the inner metal plate 5.

When the sliding member 1 is in use, a radial load is applied, and the expanded graphite layer 3 is pressed against the inner metal plate 5 and the outer metal plate 7. As a result, the inner protrusion 11 deforms so as to bulge out from the hole 5h of the inner metal plate 5 toward the inner circumference of the sliding member 1. This causes the inner resin film 13 covering the inner protrusion 11 to be pressed against the operating shaft 81, which slides on the inner resin film 13. As the sliding member 1 continues to be used, the inner resin film 13 is worn and stretched by the sliding of the operating shaft 81, and is torn, as shown in FIG. 7, and the end face of the inner protrusion 11 is exposed from the hole 5h of the inner metal plate 5.

The end face of the inner protrusion 11 exposed from the hole 5h of the inner metal plate 5 is pressed against the operating shaft 81 instead of the inner resin film 13. When the operating shaft 81 slides against the end face of the inner protrusion 11, the expanded graphite forming the inner protrusion 11 advances to the inner periphery of the sliding member 1 and is stretched and spread between the inner metal plate 5 and the operating shaft 81 as the operating shaft 81 rotates. As a result, as shown in FIG. 8, a thin film 4 of expanded graphite is formed so as to cover the inner metal plate 5. When the thin film 4 of expanded graphite is formed, the rotational force of the operating shaft 81 is less likely to act on the inner metal plate 5, and the shear force applied from the inner metal plate 3 to the inner protrusion 11 is reduced. This allows the sliding member 1 to exhibit stable sliding characteristics.

-Features of the embodiment-
In the slide member 1 of this embodiment, the inner projections 11 are covered with the inner resin film 13 made of a fluororesin, thereby reinforcing the rigidity of the inner projections 11. This reduces the shear force applied to the inner projections 11 from the inner metal plate 5, and relieves the stress generated at the base of the inner projections 11. This makes it possible to suppress breakage of the inner projections 11 provided on the expanded graphite layer 3 in the initial period of use of the slide member 1. As a result, the inner metal plate 5 becomes less likely to peel off from the expanded graphite layer 3, and the durability of the slide member 1 is improved.

In the sliding member 1 of this embodiment, the inner resin film 13 is provided in a state of being in close contact with the fine irregularities 17 formed on the inner peripheral surface of the expanded graphite layer 3. This increases the bonding strength of the inner resin film 13 to the expanded graphite layer 3 due to the anchor effect of the irregularities 17. This makes it possible to prevent the inner resin film 13 from peeling off from the expanded graphite layer 3. This is advantageous for improving the durability of the sliding member 1.

In the sliding member 1 of this embodiment, the outer protrusions 19 are covered with an outer resin film 21 made of fluororesin. This reinforces the rigidity of the outer protrusions 19. When the sliding member 1 slides against the retaining member 83 on the outer peripheral surface due to the occurrence of a corotation phenomenon, a shear force is applied to the outer protrusions 19 from the outer metal plate 7. In this case, the shear force applied to the outer protrusions 19 from the outer metal plate 7 is reduced, and the stress generated at the base of the outer protrusions 19 is alleviated. This makes it possible to prevent the outer protrusions 19 provided on the expanded graphite layer 3 from breaking. As a result, the outer metal plate 7 is less likely to peel off from the expanded graphite layer 3, and the durability of the sliding member 1 is improved.

In the sliding member 1 of this embodiment, the outer resin film 21 is provided in a state of being in close contact with the fine irregularities 25 formed on the outer peripheral surface of the expanded graphite layer 3. This increases the bonding strength of the outer resin film 21 to the expanded graphite layer 3 by the anchor effect of the irregularities 25. This makes it possible to suppress peeling of the outer resin film 21 from the expanded graphite layer 3 when a co-rotation phenomenon occurs and the sliding member 1 slides on the outer peripheral surface against the retaining member 83. This is advantageous for improving the durability of the sliding member 1.

In the sliding member 1 of this embodiment, the inner resin film 13 and the outer resin film 21 are each a fired film made of tetrafluoroethylene resin. This provides good heat resistance and slipperiness in the inner resin film 13 and the outer resin film 21. This is advantageous in ensuring reliability when the sliding member 1 is used under high temperature conditions. Since tetrafluoroethylene resin can be used in the form of dispersion D dispersed in water, it is easy to form the inner resin film 13 on the surface of the expanded graphite layer 3 using wet coating technology, and is suitable for mass production.

-Durability evaluation test-
The slide members 1 of the examples and the slide members of the comparative examples shown below were manufactured, and tests were carried out to evaluate the durability of the slide members 1 of the examples and the slide members of the comparative examples. For convenience, the slide members of the comparative examples will be described below by using the same reference numerals to designate the same components as those in the above embodiment.

Both the sliding member 1 of the example and the sliding member of the comparative example were manufactured by sandwiching an expanded graphite layer 3 between an inner metal plate 5 and an outer metal plate 7, each made of expanded metal, and then pressure-molding the expanded graphite layer 3, the inner metal plate 5, and the outer metal plate 7. The dimensions of the sliding member 1 of the example are an inner diameter of 35 mm, an outer diameter of 37 mm, and a length of 16 mm. The dimensions of the sliding member of the comparative example are the same as those of the sliding member 1 of the example.

As shown in FIG. 4, in the sliding member 1 of the embodiment, fine irregularities 17 are formed on the inner peripheral surface of the expanded graphite layer 3, and the inner resin film 13 is provided so as to cover each inner protrusion 11 while being in close contact with the irregularities 17. In addition, fine irregularities 25 are formed on the outer peripheral surface of the expanded graphite layer 3, and the outer resin film 21 is provided so as to cover each outer protrusion 19 while being in close contact with the irregularities 25. The inner resin film 13 and the outer resin film 21 are each a sintered film made of polytetrafluoroethylene resin.

In contrast, as shown in FIG. 9, in the sliding member of the comparative example, no fine irregularities are formed on either the inner or outer peripheral surface of the expanded graphite layer 3, and no resin film is provided. In other respects, the sliding member of the comparative example is the same as the sliding member 1 of the example.

A test device 101 shown in Figs. 10 and 11 was used to evaluate the durability of the sliding member 1 of the embodiment and the sliding member of the comparative example. The test device 101 includes a bearing box 103, a stem 105, a torque converter 107, an electric motor 109, an upper stage 111, a lower stage 113, a cylinder 115, and a surface pressure measuring device 117.

The bearing box 103 is a retaining member that simulates the sliding part of a bearing. The bearing box 103 has an insertion hole 119 through which the stem 105 is inserted, and a housing part 121 in which the sliding member is assembled. The housing part 121 is provided on the outer periphery of the insertion hole 119. The stem 105 is made of SUS403. The surface roughness (maximum height) Rz of the outer periphery of the stem 105 is 1.6 μm. The stem 105 is connected to the torque converter 107 via a gear coupling 123.

The torque converter 107 is connected to the electric motor 109 via a gear coupling 125. The torque converter 107 is a converter that measures the torque transmitted from the electric motor 109 to the stem 105. The electric motor 109 transmits torque to the stem 105 via the torque converter 107, causing the stem 105 to rotate. The direction of rotation of the stem 105 is switched to the opposite direction every time the electric motor 109 rotates the stem 105 by 90°.

The upper stage 111 is a stage that supports the bearing box 103. A through hole 127 is formed in the upper stage 111 to expose the lower surface of the bearing box 103 downward. A press rod 129 is inserted into the through hole 127 from below. The press rod 129 is supported by the lower stage 113. The lower stage 113 is fixed to the upper end of the cylinder 115.

The cylinder 115 is provided so as to be extendable and contractible in the vertical direction. As the cylinder 115 extends upward, the lower stage 113 pushes up the press rod 129, applying pressure in a direction that presses the sliding member assembled in the housing portion 121 of the bearing box 103 against the stem 105 (see the white arrow in FIG. 11). The surface pressure gauge 117 measures the surface pressure applied to the sliding member by pushing up the press rod 129.

In the durability evaluation test, first, the sliding member is assembled in the housing portion 121 of the bearing box 103, and the bearing box 103 is placed on the upper stage 111. Next, the stem 105 is inserted into the insertion hole 119 of the bearing box 103 and connected to the torque converter 107 via the gear coupling 123. Next, the cylinder 115 is operated to raise the lower stage 113, thereby applying a predetermined surface pressure to the contact portion between the sliding member and the stem 105. The surface pressure in this test was set to 10 N/ ^mm2 . Then, the electric motor 109 was driven to rotate the stem 105. The number of rotations of the stem 105 in this test was set to 30 times/second. The rotation speed of the stem 105 was 0.05 m/second. Here, the number of rotations of the stem 105 was counted as one count when the stem 105 rotated 90° in one direction from a predetermined position, then rotated 90° in the other direction and returned to the predetermined position (a reciprocating motion of 90°). This test was carried out at room temperature (about 25° C.).

As shown in FIG. 12, in this test, the sliding member of the comparative example (see FIG. 9) was broken when the stem 105 was rotated (reciprocated) 275 times, with the inner metal plate 5 and the outer metal plate 7 peeling off from the expanded graphite layer 3. In contrast, the sliding member 1 of the example maintained a state in which the inner metal plate 5 and the outer metal plate 7 were bonded to the expanded graphite layer 3, even after the stem 105 was rotated 15,000 times, and was not broken. From this, it was confirmed that the durability of the sliding member 1 was improved by providing the inner resin film 13 on the inner peripheral surface of the expanded graphite layer 3 so as to cover each inner protrusion 11, and providing the outer resin film 21 on the outer peripheral surface of the expanded graphite layer 3 so as to cover each outer protrusion 19.

--Modifications--
13 , in the slide member 1, the inner resin film 13 is provided on the inner circumferential surface of the expanded graphite layer 3, but the outer resin film 21 may not be provided on the outer circumferential surface of the expanded graphite layer 3. In the slide member 1 of this example, the outer circumferential surface of the expanded graphite layer 3 is not formed with fine irregularities 25. That is, the surface roughness of the outer circumferential surface of the expanded graphite layer 3 is smoother than the surface roughness of the inner circumferential surface of the expanded graphite layer 3. The expanded graphite sheet 3s forming such an expanded graphite layer 3 can be produced by using a roller without protrusions 71 as one press roller 69 of the surface treatment device 59 in the above-mentioned coating and baking system 51.

As shown in FIG. 14, in the sliding member 1, the inner metal plate 5 may be made of a punched metal made of stainless steel or the like. The punched metal is a porous plate having a large number of holes 5h, such as circular holes, arranged in a staggered pattern. Furthermore, the outer metal plate 7 may also be made of a punched metal similar to the inner metal plate 5. Alternatively, the inner metal plate 5 may be made of expanded metal, and the outer metal plate 7 may be made of punched metal.

As described above, a preferred embodiment has been described as an example of the technology of the present disclosure. However, the technology of the present disclosure is not limited to this, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. Furthermore, some of the components described in the attached drawings and detailed description may not be essential for solving the problem. Therefore, just because these non-essential components are described in the attached drawings or detailed description, it should not be immediately assumed that these non-essential components are essential.

For example, the above embodiment may be configured as follows:

The expanded graphite layer 3 may be formed of a sheet stack in which multiple expanded graphite sheets 3s are stacked on top of each other. The number of expanded graphite sheets 3s that make up the sheet stack may be two or three or more.

The inner metal plate 5 may be a metal plate other than expanded metal or punched metal, so long as it has a plurality of holes 5h. The same applies to the outer metal plate 7. The outer metal plate 7 may not be necessary as long as the strength of the sliding member 1 can be ensured. In this case, the sliding member 1 may be provided with another reinforcing material in place of the outer metal plate 7.

The fine irregularities 17, 25 on the inner and outer peripheral surfaces of the expanded graphite layer 3 may be formed by a physical surface processing technique other than the transfer of the surface shape by the press roller 69, such as a blasting process in which particulate abrasive is projected onto the surface of the expanded graphite sheet 3s to roughen it.

When forming the resin film 31 on the expanded graphite sheet 3s, the dispersion D may be applied to the surface of the expanded graphite sheet 3s using a coating method other than the dip coating method, such as a reverse method in which a roll scoops up the dispersion D in the liquid tank 61 by rotating and transfers it to the expanded graphite sheet 3s, or a slot die method in which a die head applies the dispersion D to the expanded graphite sheet 3s while pushing it out.

The fired film constituting the inner resin film 13 may contain fluororesins other than tetrafluoroethylene resin, such as tetrafluoroethylene perfluoroalkoxyethylene copolymer resin (PFA), tetrafluoroethylene hexafluoropropylene copolymer resin (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), etc. The inner resin film 13 may be formed of fluororesins (PFA, FEP, ETFE, PVDF, etc.) other than tetrafluoroethylene resin (PTFE) as long as it can reinforce the rigidity of the inner protrusion 11. It is preferable that the inner resin film 13 is a fired film from the viewpoint of the reinforcing function and heat resistance of the inner protrusion 13. The same applies to the outer resin film 21.

The sliding member 1 may be used as a thrust bearing that axially supports an operating shaft such as a stem in, for example, a ball valve, a butterfly valve, a gate valve, or a globe valve. The sliding member 1 is manufactured by sandwiching an expanded graphite layer 3 provided with a resin film 31 between an inner metal plate 5 and an outer metal plate 7, pressure-molding the laminate, and punching the laminate into a circular plate shape.

The sliding member 1 can be used as a component of bearings other than radial bearings and thrust bearings, and various sliding parts, and the thicknesses t1, t2, t3, t4, t5 and shapes of the expanded graphite layer 3, inner metal plate 5, outer metal plate 7, inner resin film 13 and outer resin film 21 can be changed as desired depending on the mode of use.

As explained above, the present invention is useful for sliding members.

1 Sliding member 3 Expanded graphite layer 5 Inner metal plate (first metal plate)
5h Hole 7 Outer metal plate (second metal plate)
7h hole 11 inner protrusion (first protrusion)
13 Inner resin film (first resin film)
17 Unevenness 19 Outer protrusion (second protrusion)
21 Outer resin film (second resin film)
25 Unevenness

Claims (7)

a first metal plate having a plurality of holes formed therein;
an expanded graphite layer to which the first metal plate is pressed;
a surface portion of the expanded graphite layer enters the hole of the first metal plate to form a first protrusion,
The expanded graphite layer is a layer in which no pores are formed penetrating in the thickness direction,
a first resin film made of a fluororesin is provided on a surface of the expanded graphite layer facing the first metal plate so as to cover the first projections while being in close contact with the first resin film ,
A sliding member in which the entire surface of one side of the first metal plate constitutes a sliding surface together with the first resin film . 2. The sliding member according to claim 1,
The first metal plate is a sliding member made of expanded metal. The sliding member according to claim 1 or 2,
The first resin film is a sintered film containing polytetrafluoroethylene resin. The sliding member according to any one of claims 1 to 3,
A second metal plate facing the first metal plate via the expanded graphite layer is further provided.
The second metal plate has a plurality of holes formed therein,
A sliding member, wherein a surface portion of the expanded graphite layer penetrates into the hole of the second metal plate to form a second projection. 5. The sliding member according to claim 4,
The second metal plate is a sliding member that is a separate member from the first metal plate. The sliding member according to claim 4 or 5,
The second metal plate is a sliding member made of expanded metal. The sliding member according to any one of claims 4 to 6,
A sliding member, wherein fine irregularities are formed on a surface of the expanded graphite layer facing the second metal plate, and a second resin film made of a fluororesin is provided to cover the second protrusions while being in close contact with the irregularities.