sliding member

Abstract

The present invention provides a sliding member which has wear resistance without damaging a sliding surface, and which can further reduce friction and improve sintering resistance. The present invention provides a sliding member including a porous metal base material, and a resin material impregnated in the porous metal base material, the sliding member having an exposed sliding surface, the sliding surface having a top surface composed of the resin material, and a bottom surface composed of the porous metal base material, a height from the bottom surface to the top surface being 10 to 30 μm, and the resin material including a fluororesin.

Description

TECHNICAL FIELD

[0001] The present application relates to a sliding member. BACKGROUND

[0002] It is known that in the conventional sliding bearing, a resin material is used on a sliding surface that supports a corresponding member by lubricating oil. In such a sliding bearing, in order to prevent seizure or abrasion and reduce friction, some proposals have been made.

[0003] In Patent Literature 1, a sliding bearing is described in which a plurality of recesses are provided in the inner peripheral surface of a cylindrical base material that supports a shaft member, and a resin layer further covers the inner peripheral surface. Each recess has a first surface that is approximately 90 degrees with respect to the inner peripheral surface, and a second surface that intersects the inner peripheral surface at an angle of less than 90 degrees, whereby an air layer is present in a region where the lubricating oil contacts the inner peripheral surface, and the friction of the oil film is reduced. However, this sliding bearing is significantly complicated in terms of the number of processing steps because of the plurality of recesses.

[0004] In Patent Literature 2, a bearing for a compressor of a refrigerator is described in which a bronze alloy is used instead of aluminum that is easily corroded by a replacement refrigerant. In order to improve seizure resistance and reduce the amount of abrasion, a resin material is formed in the pores of a porous bronze alloy provided on a backing, in such a manner that the bronze alloy and the resin material are exposed on the sliding surface. The resin material is a composite material composed of a synthetic resin containing PTFE (polytetrafluoroethylene) and a lubricant that does not contain lead (claim 3), and the proportion of the exposed area of the bronze alloy is 5% or more and 60% or less.

[0005] In Patent Literature 3, a sliding member in which a thermoplastic resin is the main component is described in which fine recesses are provided on the surface instead of forming a low-friction coating film such as a fluororesin on the surface, in order to reduce friction and improve sliding properties at a low cost. The average maximum diameter of the openings of the fine recesses is 50 μm to 150 μm, and the arrangement density per unit area of the fine recesses is 3 / mm 2 30 / mm 2 Hereinafter (paragraph 0006).

[0006] Patent Literature 4 describes an oilless bearing bush for a hinge mechanism of a door or the like of an automobile. The bearing bush has a porous bronze sintered layer that is integrally formed on the surface of a backing, and a sliding layer that is filled by a pressurizing roll and covers the pores and surface of the porous bronze sintered layer, and the porous bronze sintered layer is scattered and exposed on the surface of the sliding layer. When the bearing bush is manufactured, the sliding layer expands due to stress relaxation after pressurization by the pressurizing roll, and recesses having a depth of 1 to 2.5 μm are formed (Fig. 7). In Patent Literature 4, in view of the problem that the electrical conductivity of the bearing bush, which is necessary in electrostatic painting, is reduced due to the recesses, a metal plating layer is provided in the recesses (Fig. 4).

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Patent Laid-Open No. 2019-105334

[0010] Patent Document 2: Japanese Patent Laid-Open No. 2006-132540

[0011] Patent Document 3: Japanese Patent Laid-Open No. 2017-057862

[0012] Patent Document 4: Japanese Patent Laid-Open No. 2008-164007 SUMMARY

[0013] PROBLEMS TO BE SOLVED BY THE INVENTION

[0014] In recent years, from the viewpoint of saving resources, the viscosity of lubricant is becoming lower and lower, and the sliding surface of the sliding member is more likely to form a boundary lubrication state. Therefore, in the sliding member, in the case of using a low-viscosity lubricant, it is required to reduce the friction of the sliding surface. On the other hand, in order to improve the sintering resistance and the wear resistance, it is effective to expose the porous metal substrate to the sliding surface of the sliding member and to improve the heat dissipation, and therefore it is necessary to reduce the friction in the case of using a low-viscosity lubricant while exposing the porous metal substrate as described above.

[0015] The sliding bearing described in Patent Document 1 is complicated to manufacture, and if the entire inner circumferential surface is covered with a resin layer, the heat dissipation decreases and sintering is likely to occur. In addition, the sliding member described in Patent Document 3 has a thermoplastic resin as a main component, and therefore it is difficult to improve both the heat dissipation and the 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, and therefore it is possible to improve the wear resistance but it is difficult to further reduce the friction.

[0016] Therefore, an object of the present application is to provide a sliding member that supports a corresponding member by a lubricant, including a porous metal substrate and a resin material impregnated in the porous metal substrate, and to further reduce the friction without impairing the wear resistance of the sliding surface, thereby improving the sintering resistance. Another object of the present application is to provide a sliding member that is easy to manufacture and economical.

[0017] Technical Solution

[0018] To achieve the above object, the present application provides a sliding member including a porous metal base material, and a resin material impregnated in the porous metal base material, the sliding member having an exposed sliding surface formed in a manner that a top surface composed of the resin material and a bottom surface composed of the porous metal base material are provided, a height from the bottom surface to the top surface is 10 to 30 μm, and the resin material includes a fluororesin.

[0019] The proportion of the total area of the bottom surface in the sliding surface is preferably 5 to 60%.

[0020] The sliding member can further have a backing on one surface of which the porous metal base material and the resin material are disposed.

[0021] The porous metal base material is preferably a metal or an alloy in a spherical or irregular shape.

[0022] Effects of the Invention

[0023] If the present application is employed, since the sliding surface of the sliding member has the top surface and the bottom surface (i.e., a concavo-convex shape), the shaft member or the like supported by the member slides on the top surface composed of the resin material, avoiding contact with the porous metal base material constituting the bottom surface. Thus, the friction can be reduced, thereby suppressing the amount of heat generation. Further, in the sliding surface, the recess having a depth of 10 to 30 μm is formed by the top surface and the bottom surface, so that the oil retention property can be improved.

[0024] Further, if the present application is employed, the bottom surface composed of the porous metal base material is exposed on the sliding surface, so that the heat dissipation property becomes high. This contributes to suppression of softening of the resin material and improvement of the wear resistance.

[0025] If the present application is employed, in order to achieve the above effects, the distance vertically measured on the sliding surface from the bottom surface to the top surface, i.e., the height is 10 to 30 μm. If the height is below 10 μm, due to the running-in, the top surface is worn by about 5 μm or so, so that the transfer effect of the resin material to the supported member in the initial stage of the running is insufficient, and the supply of the resin material to the porous metal base material during the running is insufficient. This increases the friction, thereby causing seizure. On the other hand, if the height from the bottom surface to the top surface is above 30 μm, in the initial state, the heat dissipation effect of the sliding member due to the exposure of the porous metal base material is not sufficiently obtained, the resin material is softened, and wear occurs. Thus, the oil film is more easily broken, which leads to an increase in the friction, and seizure is easily caused.

[0026] And if the present application is employed, the proportion of the total area of the bottom surface in the sliding surface (i.e. the exposure rate) is 5 to 60%. If this proportion is below 5%, the above-mentioned effect of wear resistance due to the exposure of the porous metal substrate cannot be obtained, on the other hand, if this proportion is above 60%, the sintering resistance is lowered and the function as a sliding member cannot be achieved.

[0027] For the present application and its advantages, the following detailed description is made with reference to the drawings. It is to be understood that the drawings are for illustration only and that the present application is not limited to the embodiments shown therein. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a cross-sectional view of the sliding member of the present application perpendicular to the sliding surface.

[0029] Figure 2 is a cross-sectional view of the sliding surface of Figure 1 before cutting processing.

[0030] Figure 3 is a cross-sectional view of another sliding member of the present application perpendicular to the sliding surface. DETAILED DESCRIPTION

[0031] The structure of the sliding member 1 of an embodiment of the present application and the manufacturing method thereof are described in detail below.

[0032] (Structure of the sliding member)

[0033] Figure 1 is a cross-sectional view of the sliding member 1. The sliding member 1 has a backing 40, and a porous metal substrate 20 formed on one surface 41 of the backing 40, and a resin material 30 impregnated in the voids of the porous metal substrate 20, formed in a plate shape.

[0034] The sliding member 1 also has a sliding surface 10 formed on the side opposite to the other surface (i.e. the back surface) 42 of the backing 40, in which the porous metal substrate 20 and the resin material 30 are mixed and exposed. Specifically, the sliding surface 10 has a flat top surface 31 composed of the resin material 30, and a flat bottom surface 21 composed of the porous metal substrate 20. The bottom surface 21 has a distance, i.e. a height Hp, measured perpendicularly from the one surface 41 of the backing 40, and the top surface 31 is formed in a manner higher than this height Hp. In addition, as shown in Figure 3 , the top surface 31 is not limited to a flat shape.

[0035] In this embodiment, the height Hp of the porous metal base material 20 is set to 0.3 mm, for example. If the present application is employed, the distance from the bottom surface 21 measured perpendicularly to the sliding surface 10 (or one surface 41 of the backing 40) to the top surface 31, i.e., the height h, is 10 to 30 μm. In addition, as shown in FIG. 3, in the case where the top surface 31 is not flat, the height h is defined as the distance from the bottom surface 21 measured perpendicularly to the sliding surface 10 (or one surface 41 of the backing 40) to the highest point of the top surface 31. Figure 3

[0036] As shown in FIG. 3, it is to be understood that the sliding surface 10 has a recess 11 formed by the step difference of these top surfaces 31 and bottom surfaces 21, and the depth of the recess is 10 to 30 μm. Figure 1

[0037] In addition, if the present application is employed, the proportion of the total area of the bottom surface 21 in the sliding surface 10 (i.e., the exposure rate of the porous metal base material 20) is preferably 5 to 60% in consideration of the lower limit value of the wear resistance and the upper limit value of the sintering resistance.

[0038] (Material of the sliding member)

[0039] The porous metal base material 20 can use copper, copper alloy, bronze alloy, aluminum, aluminum alloy, iron, steel, etc. Also, the porous metal base material 20 can use spherical powder or irregularly shaped powder, but it is particularly preferable to use irregularly shaped powder.

[0040] The resin material impregnated in the porous metal base material includes PTFE as a fluororesin, a melt fluororesin as another resin, and graphite and molybdenum disulfide as solid lubricants. The resin material can also include other inorganic materials such as barium sulfate, or hard particles such as alumina.

[0041] (Method of manufacturing the sliding member)

[0042] The sliding member 10 is manufactured by the following procedures.

[0043] (1) After mixing a fluororesin and various fillers, a molding aid is added to the obtained mixture, and the resin raw material is obtained by mixing by stirring.

[0044] (2) The resin raw material obtained in the above procedure (1) is supplied and scattered on the porous metal base material provided on a backing made of a steel plate. This is calendered with a roll to impregnate the resin raw material in the voids of the porous metal base material while setting by sintering, and to uniformly form a coating layer made of the resin raw material on the surface of the porous metal base material.

[0045] ​​(3) The member obtained in the above process (2) is kept in a drying oven heated to 100 to 200°C, and the forming aid is removed.

[0046] (4) The member from which the forming aid is removed is introduced into a heating oven, heated and fired at a temperature in the range of 380 to 420°C, and then cooled, and rolled to a predetermined size to form a member 1' having a predetermined thickness. Figure 2 ).

[0047] (5) The coated layer 32 on one side of the member 1' obtained in the above processes (1) to (4) is cut so that the resin material and the porous metal base material reach a desired height (thickness) Hp (see the dotted line in FIG. 1) to form a sliding member having a desired thickness. In addition, this cutting process can be performed on a flat plate obtained by cutting the member 1' to a predetermined size, or after the member 1' is formed into a cylindrical convolute bush. In the case where a cylindrical sliding member is provided, since the dimensional accuracy is good, it is preferable to perform the cutting process after the member 1' is formed into a convolute bush. Figure 2

[0048] By the above process (5), the sliding surface is once uniformly (i.e., flatly) formed, but after a certain period of time, the top surface 31 formed of the resin material 30 becomes higher (i.e., the distance measured vertically from the backing is larger) than the bottom surface 21 formed of the porous metal base material 20. The principle is that the resin material impregnated and pressed into the voids of the porous metal base material in the above process (4) is at least partially released (relaxation of internal pressure) from the restraint of the porous metal base material and expanded by the cutting of the above process (5).

[0049] The present inventors found that the above internal pressure is determined in accordance with a balance of the amount of the forming aid mixed in the resin material, the porosity of the porous metal, the height Hp of the porous metal, and the amount of rolling in the above process (4). In an embodiment of the present application, in particular, by setting the amount of rolling in the above process (4) to a specific range, the internal pressure of the resin material in the voids of the porous metal base material is increased, and this internal pressure is relaxed by the cutting of the above process (5), so that a predetermined amount of difference in height is formed between the bottom surface formed of the porous metal base material and the top surface formed of the resin material.

[0050] Specifically, the reference amount of rolling L R (mm) is found by the following equation:

[0051] L R = X / 100 x Hp x V / 100

[0052] L R : reference amount of rolling (mm)

[0053] ​X: weight parts (%) of the forming aid with respect to the resin material mixed with the fluororesin and the filler

[0054] V: porosity (%) of the porous metal base material

[0055] Hp: height (mm) of the porous metal base material

[0056] In order to obtain the present embodiment, the calendering amount L (mm) with respect to the reference calendering amount L R (mm) is in the range of 100 to 200%, that is, the following expression must be satisfied:

[0057] 100 < L / L R < 200.

[0058] Here, if L / L R < 100%, the internal pressure of the resin material is insufficient, the height from the bottom surface constituted by the porous metal base material to the top surface constituted by the resin material becomes less than 10 μm, on the other hand, if L / L R > 200%, the internal pressure of the resin material is too high, the height from the bottom surface to the top surface exceeds 30 μm. Further, if the calendering amount is too large, the porous metal base material is broken, the proportion (exposure rate) of the bottom surface (i.e., the porous metal base material) after cutting with respect to the area of the sliding surface is deviated.

[0059] In order to form the difference in level between the bottom surface 21 and the top surface 31, the resin material preferably contains the fluororesin by 65% or more. If the content is less than 65%, the resin material becomes difficult to expand due to relaxation of the internal pressure. Further, the resin material more preferably contains the PTFE and the solid lubricant. This is because the simple composition is suitable for taking advantage of the expandability of the resin material, and on the other hand, the solid lubricant is suitable for reduction of the friction. Further, the porous metal base material is preferably the irregularly shaped powder. If it is the irregularly shaped powder, the expanded resin material is not easily returned to the original position due to relaxation of the internal stress.

[0060] Example

[0061] (Performance evaluation test)

[0062] In order to evaluate the wear amount, the friction coefficient, and the sintering time of the sliding member of the present application, performance evaluation tests were performed on Examples 1 to 7 and Comparative Examples 1 and 2.

[0063] (Test conditions)

[0064] Test machine: thrust sliding tester

[0065] Load: (a: initial) 3 MPa → (b: thereafter) 6 MPa

[0066] Speed: 1.5 m / s

[0067] Time: (a) 10 minutes → (b) until sintering

[0068] Lubrication: (a) oil bath → (b) no oil

[0069] Counter shaft: S55C quenched

[0070] (Test piece)

[0071] The sliding member obtained by the production method comprising the above-mentioned steps (1) to (5) was cut to prepare a test piece having one side of 30 mm. The test piece was cut to an arbitrary thickness using an aqueous cutting fluid, and a grinding stone to obtain a test piece.

[0072] (Test results)

[0073] 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. "PTFE" in the table is CD097 manufactured by AGC, "other resin" means a non-PTFE melt fluororesin or the like, and "porous metal base material" is a bronze-based alloy (irregular shape) of Cu-10% Sn or a Cu-3% Sn-8% Bi alloy (spherical shape). Further, "amount X of forming aid" means the weight parts (%) of the forming aid with respect to the resin material mixed with PTFE and a filler, and "height of top surface" means the height (μm) from the bottom surface to the top surface.

[0074] The forming aid X was mixed in an amount of 15 to 30 parts by weight with respect to the resin material, the porous metal base material was used in a range of 40 to 70% in porosity, the porous metal base material was used in a height of 0.2 to 0.4 mm, and the resin material was adjusted in a calendering amount L of 0.02 to 0.08 mm.

[0075] Further, each item in the table was determined by the following method.

[0076] Height of top surface: The test piece was observed with a laser microscope, and the difference in height was measured

[0077] Exposure rate of porous alloy base material: The luminance of the porous metal was detected by an optical microscope, binarization processing was performed, and the proportion of the porous metal was taken as the exposure rate

[0078] Wear amount: The difference in thickness of the test piece before and after the test was measured

[0079] Friction coefficient: The friction coefficient immediately after the oil was removed was measured

[0080] Sintering time: time from the start of the test to the stop of the test (stop at 190°C)

[0081] As shown in Table 1, by setting the ratio of the calendering amount to the reference calendering amount to 107 to 163%, the top surface height of 15 to 30 μm of the present application was obtained, and in this case, the abrasion amount was all 10 μm or less, the friction coefficient was 0.04 or less, and the sintering time was 12 minutes or more. In contrast, as shown in Comparative Example 1 of Table 2, if the top surface height was 33 μm, the abrasion amount was 18 μm, which was too large, and the friction coefficient increased to 0.08. Also, as shown in Comparative Example 2, if the top surface height was as small as 7 μm, the abrasion amount was as small as 5 μm, but the friction coefficient increased to 0.12, and the sintering time deteriorated to 2 minutes.

[0082] The embodiments and examples of the present application are described above in detail with reference to the drawings and in conjunction with the performance evaluation test, but the specific configuration is not limited thereto, and some changes not departing from the technical idea of the present application described in the scope of the claims are also included in the present application.

[0083] [Table 1]

[0084]

[0085] [Table 2]

[0086]

[0087] Explanation of symbols

[0088] 1 sliding member

[0089] 10 sliding surface

[0090] 11 recess

[0091] 20 porous metal base material

[0092] 21 bottom surface

[0093] 30 resin material

[0094] 31 top surface

[0095] 32 coating layer

[0096] 40 backing

[0097] 41 one surface

[0098] 42 other surface, back surface

Claims

1. A sliding member comprising a porous metal substrate and a resin material impregnated in the porous metal substrate. The sliding member further has a backing, on which the porous metal substrate and the resin material are disposed on one surface of the backing. The sliding member has an exposed sliding surface, which has a top surface made of the resin material and a bottom surface made of the porous metal substrate, whereby the porous metal substrate of the bottom surface is exposed on the sliding surface, and the height from the bottom surface to the top surface is 10 to 30 μm. The bottom surface has a bottom surface height (Hp) measured perpendicularly from one surface of the backing, and the height measured perpendicularly from one surface of the backing to the top surface is higher than the bottom surface height (Hp) at any point on the top surface. The resin material includes fluororesin.

2. The sliding member as described in claim 1, characterized in that, The proportion of the total area of ​​the bottom surface in the sliding surface is 5% to 60%.

3. The sliding member as described in claim 1 or 2, characterized in that, The porous metal substrate is formed of spherical or irregularly shaped metals or alloys.

4. The sliding member as described in claim 1, characterized in that, The porous metal substrate is formed of spherical or irregularly shaped metals or alloys.

Images