Sliding member

Abstract

To provide a slide member capable of further reducing friction without impairing abrasion resistance on a slide surface, and capable of improving seizure resistance.SOLUTION: A slide member comprises a porous metal substrate, and a resin material impregnated in the porous metal substrate. The slide member has an exposed slide surface. The slide surface has a top surface made of the resin material, and a bottom surface made of the porous metal substrate. A height from the bottom surface to the top surface is 10 to 30 μm. The resin material contains fluororesin.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a slide member. [Background technology]

[0002] In conventional sliding bearings, it is known to use a resin material on the sliding surface that supports the mating member via a lubricant oil. Several proposals have been made to prevent seizure and wear and to reduce friction in such sliding bearings.

[0003] Patent Document 1 describes a sliding bearing in which multiple recesses are provided on the inner peripheral surface of a cylindrical base material that supports a shaft member, and the inner peripheral surface is further covered with a resin layer. Each recess has a first surface that is at an angle of approximately 90 degrees to the inner peripheral surface, and a second surface that intersects with the inner peripheral surface at an angle of less than 90 degrees, thereby providing an air layer in the area where the lubricating oil contacts the inner peripheral surface, thereby reducing friction of the oil film. However, the processing process of this sliding bearing is clearly complicated due to the provision of multiple recesses.

[0004] Patent Document 2 describes a bearing for a refrigerator compressor that uses a bronze alloy instead of aluminum, which is susceptible to corrosion by alternative refrigerants. In order to improve seizure resistance and reduce wear, this bearing is formed by impregnating a resin material into the pores of a porous bronze alloy provided on a backing metal, so that the bronze alloy and the resin material are exposed on the sliding surface. The resin material is a composite material made of a synthetic resin containing PTFE (polytetrafluoroethylene) and a lubricant that does not contain lead (claim 3), and it is also described that the ratio of the exposed area of ​​the bronze alloy is 5% or more and 60% or less.

[0005] Patent Document 3 describes that in a sliding member whose main component is a thermoplastic resin, instead of forming a low-friction coating such as a fluororesin on the surface, fine recesses are provided on the surface to reduce friction and improve slidability at a relatively low cost. The average maximum diameter of the opening of the fine recesses is 50 μm to 150 μm, and the arrangement density of the fine recesses per unit area is 3 pcs / mm 2 More than 30 pieces / mm2 The following is (paragraph 0006).

[0006] Patent Document 4 describes an oil-free bearing bush used in the hinge mechanism of an automobile door or the like. This bearing bush has a porous bronze sintered layer formed integrally on the surface of the back metal, and a sliding layer of a synthetic resin composition filled and coated in the pores and surface of the porous bronze sintered layer by a pressure roller, and the porous bronze sintered layer is exposed in a scattered manner on the surface of the sliding layer. During the manufacture of the bearing bush, the sliding layer expands due to stress relaxation after pressure is applied by the pressure roller, forming recesses with a depth of 1 to 2.5 μm (FIG. 7). In view of the problem that the electrical conductivity of the bearing bush required for electrostatic painting is reduced due to the recesses, Patent Document 4 proposes providing a metal plating layer in the recesses (FIG. 4). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2019-105334 A [Patent Document 2] JP 2006-132540 A [Patent Document 3] JP 2017-057862 A [Patent Document 4] JP 2008-164007 A Summary of the Invention [Problem to be solved by the invention]

[0008] In recent years, the viscosity of lubricating oil has been reduced from the viewpoint of resource saving, and the sliding surface of the sliding member is easily in a boundary lubrication state. Therefore, it is required to reduce the friction of the sliding surface of the sliding member when using a low-viscosity lubricating oil. On the other hand, in order to improve the seizure resistance and wear resistance, it is effective to expose the porous metal substrate on the sliding surface of the sliding member to increase heat dissipation, so it is necessary to reduce the friction when using the low-viscosity lubricating oil as described above while exposing the porous metal substrate.

[0009] The sliding bearing described in Patent Document 1 is complicated to manufacture, and when the entire inner peripheral surface is covered with a resin layer, heat dissipation is reduced and seizure is likely to occur. In addition, the sliding member described in Patent Document 3 is mainly composed of thermoplastic resin, so it is not easy to improve both heat dissipation and wear resistance. Furthermore, in the sliding members described in Patent Documents 2 and 4, the resin material and the metal material are uniformly arranged on the sliding surface, so that wear resistance can be improved, but it is difficult to further reduce friction.

[0010] Therefore, an object of the present invention is to provide a sliding member that supports a mating member via a lubricating oil, the sliding member including a porous metal substrate and a resin material impregnated into the porous metal substrate, which further reduces friction without impairing the wear resistance of the sliding surface, thereby improving seizure resistance. Another object of the present invention is to provide a sliding member that is easy to manufacture and economical. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention provides a sliding member comprising a porous metal substrate and a resin material impregnated into the porous metal substrate, the sliding member having an exposed sliding surface, the sliding surface being formed to have a top surface made of the resin material and a bottom surface made of the porous metal substrate, the height from the bottom surface to the top surface being 10 to 30 μm, and the resin material containing a fluororesin.

[0012] The ratio of the total area of ​​the bottom surface to the sliding surface is preferably 5 to 60%.

[0013] The sliding member may further include a back metal, and the porous metal substrate and the resin material are disposed on one surface of the back metal.

[0014] The porous metal substrate is preferably a metal or alloy having a spherical or irregular shape. Effect of the Invention

[0015] According to the present invention, the sliding surface of the sliding member has a top surface and a bottom surface (i.e., an uneven shape), so that the supported member such as the shaft member slides on the top surface made of a resin material and is prevented from contacting the porous metal substrate constituting the bottom surface. This reduces friction and, in turn, the amount of heat generated. In addition, the sliding surface has a recess having a depth of 10 to 30 μm formed by the top surface and the bottom surface, so that the oil retention can be improved.

[0016] In addition, according to the present invention, the bottom surface made of the porous metal substrate is exposed to the sliding surface, which enhances heat dissipation, thereby suppressing softening of the resin material and contributing to improving wear resistance.

[0017] According to the present invention, in order to achieve the above-mentioned effect, the distance from the bottom surface to the top surface measured perpendicularly to the sliding surface, i.e., the height, is 10 to 30 μm. If this height is 10 μm or less, the top surface will wear down by about 5 μm due to the break-in operation, so the transfer effect of the resin material to the supported member at the beginning of operation will be insufficient, and the supply of the resin material onto the porous metal substrate during operation will be insufficient. This will increase friction and may cause seizure. On the other hand, if the height from the bottom surface to the top surface is 30 μm or more, the heat dissipation effect of the sliding member due to the exposure of the porous metal substrate in the initial state will not be sufficiently obtained, and the resin material will soften and wear. As a result, the oil film will be easily broken, which will increase friction and also make seizure more likely to occur.

[0018] According to the present invention, the ratio of the total area of ​​the bottom surface in the sliding surface (i.e., the exposed ratio) is 5 to 60%. If this ratio is less than 5%, the above-mentioned effect of wear resistance due to the exposure of the porous metal substrate cannot be obtained, while if this ratio is more than 60%, the seizure resistance is reduced and the sliding member cannot fulfill its role.

[0019] The invention and its advantages will be explained in more detail below with reference to the accompanying drawings, in which it is understood that the drawings depict non-limiting embodiments for illustrative purposes only. [Brief description of the drawings]

[0020] [Figure 1] 1 is a schematic cross-sectional view of a sliding member according to the present invention, taken along a line perpendicular to a sliding surface. [Diagram 2] 2 is a schematic cross-sectional view of the sliding surface of the sliding member in FIG. 1 before being cut. FIG. [Diagram 3] FIG. 4 is a schematic cross-sectional view perpendicular to the sliding surface of another sliding member according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The structure and manufacturing method of a slide member 1 according to an embodiment of the present invention will be described in detail below.

[0022] (Structure of sliding members) 1 is a schematic cross-sectional view of a sliding member 1. The sliding member 1 has a backing metal 40, a porous metal substrate 20 formed on one surface 41 of the backing metal 40, and a resin material 30 impregnated into the voids of the porous metal substrate 20, and is formed in a plate shape.

[0023] The sliding member 1 also has a sliding surface 10 formed on the side opposite to the other surface (i.e., back surface) 42 of the back metal 40, and the porous metal substrate 20 and the resin material 30 are exposed in a mixed state on this sliding surface 10. Specifically, the sliding surface 10 has a flat top surface 31 made of the resin material 30 and a flat bottom surface 21 made of the porous metal substrate 20. The bottom surface 21 has a distance measured perpendicularly from one surface 41 of the back metal 40, i.e., a height Hp, and the top surface 31 is formed to be higher than this height Hp. As shown in FIG. 3, the top surface 31 does not have to be limited to a flat shape.

[0024] In this embodiment, the height Hp of the porous metal substrate 20 can be, for example, 0.3 mm. According to the present invention, the distance from the bottom surface 21 to the top surface 31 measured perpendicularly to the sliding surface 10 (or one surface 41 of the back metal 40), i.e., the height h, is 10 to 30 μm. In addition, when the top surface 31 is not flat as shown in FIG. 3, the height h is defined as the distance from the bottom surface 21 to the highest point of the top surface 31 measured perpendicularly to the sliding surface 10 (or one surface 41 of the back metal 40).

[0025] As shown in FIG. 1, it will be understood that the sliding surface 10 has a recess 11 formed due to the step between the top surface 31 and the bottom surface 21, and the depth of this recess is 10 to 30 μm.

[0026] According to the present invention, the ratio of the total area of ​​the bottom surface 21 on the sliding surface 10 (i.e., the exposure rate of the porous metal substrate 20) is preferably 5 to 60%, taking into consideration the lower limit of wear resistance and the upper limit of seizure resistance.

[0027] (Sliding material) The porous metal substrate 20 may be made of copper, copper alloys, bronze alloys, aluminum, aluminum alloys, iron, steel, etc. The porous metal substrate 20 may be made of spherical powder or powder having an irregular shape, but it is particularly preferable to use powder having an irregular shape.

[0028] The resin material impregnated in the porous metal substrate includes PTFE as a fluororesin, molten fluororesin as other resins, graphite or molybdenum disulfide as a solid lubricant, and may also include inorganic materials such as barium sulfate and hard particles such as alumina.

[0029] (Method of manufacturing slide member) The sliding member 10 is manufactured by the following steps. (1) After mixing the fluororesin with various fillers, a molding aid is added to the resulting mixture and stirred and mixed to obtain a resin raw material. (2) The resin raw material obtained in the above step (1) is spread on a porous metal substrate provided on a backing metal made of a steel plate. This is rolled with a roller to impregnate the resin raw material into the voids of the porous metal substrate provided by sintering, and a coating layer made of the resin raw material is uniformly formed on the surface of the porous metal substrate. (3) The part obtained in the above step (2) is kept in a drying furnace heated to 100 to 200° C. to remove the molding aid. (4) The component from which the molding aids have been removed is introduced into a heating furnace and heated to a temperature range of 380 to 420°C for sintering, after which it is cooled and rolled to the specified dimensions with rollers to form a component 1' of the specified thickness (Figure 2). (5) The coating layer 32 side of the member 1' obtained through the above steps (1) to (4) is cut so that the resin material and the porous metal substrate have a desired height (thickness) Hp (see the dashed line in FIG. 2), to form a sliding member of a desired thickness. This cutting step may be performed on a flat plate obtained by cutting the member 1' to a predetermined size, or may be performed after the member 1' is formed into a cylindrical wound bushing. When providing a cylindrical sliding member, it is preferable to perform the cutting step after forming it into a wound bushing, since this improves dimensional accuracy.

[0030] The sliding surface is initially formed uniformly (i.e., flat) by the above step (5), but after a certain time has passed, the top surface 31 made of the resin material 30 becomes higher (i.e., the distance measured vertically from the back metal is greater) than the bottom surface 21 made of the porous metal substrate 20. The principle is that the resin material that was impregnated and pressed into the voids of the porous metal substrate in the above step (4) is at least partially released from the constraint of the porous metal substrate by the cutting in the above step (5) (relief of internal pressure) and expands.

[0031] The inventors have found that the internal pressure is determined by the balance between the amount of molding aid mixed with the resin material, the porosity of the porous metal, the height Hp of the porous metal, and the rolling amount in the above step (4). In one embodiment of the present invention, the rolling amount in the above step (4) is set within a specific range to increase the internal pressure of the resin material in the voids of the porous metal substrate, and the cutting in the above step (5) relieves this internal pressure, thereby forming a predetermined height difference between the bottom surface made of the porous metal substrate and the top surface made of the resin material.

[0032] Specifically, the standard rolling amount L R (mm) using the following formula: L R = X / 100×Hp×V / 100 L R : Standard rolling amount (mm) X: Part by weight (%) of molding aid relative to the resin material made by mixing fluororesin and filler V: Porosity (%) of porous metal substrate Hp: Height of the porous metal substrate (mm) In order to obtain this embodiment, the rolling amount L (mm) is the standard rolling amount L R (mm) in the range of 100 to 200%, i.e., the formula: 100 ≦ L / L R ×100 ≦ 200 must be met.

[0033] Here, L / L R When L / L is less than 100%, the internal pressure of the resin material is insufficient, and the height from the bottom surface of the porous metal substrate to the top surface of the resin material is less than 10 μm. R When the rolling ratio was more than 200%, the internal pressure of the resin material was too high, and the height from the bottom surface to the top surface was more than 30 μm. Also, when the rolling amount was too large, the porous metal substrate was crushed, and the ratio (exposure rate) of the area of ​​the bottom surface (i.e., the porous metal substrate) to the sliding surface after cutting varied.

[0034] In order to form a height difference between the bottom surface 21 and the top surface 31, the resin material preferably contains 65% or more fluororesin. If the content is less than 65%, the resin material is less likely to expand due to the relaxation of internal pressure. Furthermore, the resin material more preferably contains PTFE and a solid lubricant. This is because a simpler composition is more suitable for utilizing the expansibility of the resin material, while a solid lubricant is more suitable for reducing friction. In addition, the porous metal substrate is preferably powder of an irregular shape. This is because if the powder is of an irregular shape, the resin material that expands due to the relaxation of internal stress will have difficulty returning to its original position. EXAMPLES

[0035] (Performance evaluation test) In order to evaluate the wear amount, friction coefficient, and seizure time of the sliding member according to the present invention, performance evaluation tests were carried out for Examples 1 to 7 and Comparative Examples 1 and 2.

[0036] (Test conditions) Testing machine: Thrust sliding test machine Load: (a: initial) 3MPa → (b: later) 6MPa Speed: 1.5m / s Time: (a) 10 minutes → (b) until baking Lubrication condition: (a) Oil bath → (b) Oil drain Mating shaft: S55C hardened

[0037] (Test piece) The sliding member obtained by the manufacturing method including the above-mentioned steps (1) to (5) was cut to prepare a sample having a side length of 30 mm. This sample was further cut to a desired thickness with a grinding wheel while using a water-soluble cutting fluid to obtain a test piece.

[0038] (Test Results) The test results of Examples 1 to 7 are shown in Table 1 below, and the test results of Comparative Examples 1 and 2 are shown in Table 2 below. In the table, "PTFE" is CD097 manufactured by AGC, "other resin" is a resin other than PTFE such as molten fluororesin, and "porous metal substrate" is a bronze-based alloy of Cu-10%Sn (irregular shape) or a Cu-3%Sn-8%Bi alloy (spherical shape). "Amount of molding aid X" means the weight part (%) of the molding aid relative to the resin material in which PTFE and filler are mixed, and "top surface height" means the height (μm) from the bottom surface to the top surface.

[0039] The molding aid X is mixed in an amount of 15 to 30 parts by weight with respect to the resin material, the porous metal substrate has a porosity in the range of 40% to 70%, and the height of the porous metal substrate is 0.2 to 0.4 mm. The resin material is adjusted to have a rolling amount L of 0.02 to 0.08 mm. Each item in the table was determined by the following method. Top surface height: The test piece was observed with a laser microscope and the height difference was measured. Exposure rate of porous alloy substrate: The brightness of the porous metal was detected using an optical microscope and binarized, and the proportion of the porous metal was taken as the exposure rate. Abrasion amount: The difference in thickness of the test piece before and after the test was measured. Friction coefficient: The friction coefficient was measured immediately after draining the oil. Burn time: The time from when the oil was removed to when the test was stopped (stopped at 190°C) was measured.

[0040] As shown in Table 1, by setting the ratio of the rolling amount to the standard rolling amount to 107 to 163%, the top surface height of the present invention of 15 to 30 μm can be obtained, and in this case, the wear amount is 10 μm or less, the friction coefficient is 0.04 or less, and the seizure time is 12 minutes or more. In contrast, as shown in Comparative Example 1 of Table 2, when the top surface height is 33 μm, the wear amount becomes too large at 18 μm, and the friction coefficient increases to 0.08. Also, as shown in Comparative Example 2, when the top surface height is small at 7 μm, the wear amount is small at 5 μm, but the friction coefficient increases to 0.12 and the seizure time also deteriorates significantly to 2 minutes.

[0041] The above describes in detail the embodiments and examples of the present invention with reference to the drawings and in relation to the performance evaluation tests. However, the specific configurations are not limited to these, and modifications that do not depart from the gist of the present invention described in the claims are included in the present invention.

[0042] [Table 1]

[0043] [Table 2] [Explanation of symbols]

[0044] 1 Sliding member 10 Sliding surface 11 Recess 20 Porous metal substrate 21 Bottom surface 30 Resin materials 31 Top surface 32 Covering layer 40. Secret funds 41 One side 42 Other surface, back

Claims

1. A sliding member comprising a porous metal substrate and a resin material impregnated into the porous metal substrate, The sliding member further has a back metal, the porous metal substrate and the resin material being disposed on one surface of the back metal, the sliding member has an exposed sliding surface, the sliding surface having a top surface made of the resin material and a bottom surface made of the porous metal substrate, the height from the bottom surface to the top surface being 10 to 30 μm; the bottom surface has a bottom surface height (Hp) measured perpendicularly from one surface of the backing metal, and a top surface height measured perpendicularly from one surface of the backing metal to the top surface is equal to or greater than the bottom surface height (Hp) at any location on the top surface; and The resin material of the sliding member includes a fluororesin.

2. 2. The sliding member according to claim 1, wherein the ratio of the total area of ​​the bottom surface to the sliding surface is 5 to 60%.

3. 3. The sliding member according to claim 1, wherein the porous metal substrate is made of a metal or alloy having a spherical or irregular shape.

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