JP6964392B2 - Sliding surface structure and manufacturing method of sliding surface structure - Google Patents

Description

The present invention relates to a sliding surface structure and a method for manufacturing a sliding surface structure.

With increasing interest in environmental issues, not only reducing friction on sliding parts, but also reducing the amount of lubricating oil used has become an important issue. Therefore, expansion of application of grease lubrication is being studied, and a sliding surface structure having an enhanced grease holding effect has been proposed (Patent Document 1 and Patent Document 2).

In Patent Document 1 and Patent Document 2, a recess is formed on the inner surface of the pocket of the bearing cage, and the recess is used as a grease reservoir. As a result, when the rolling element arranged in the pocket rolls (rotates), the rolling element and the inner surface of the pocket of the cage are in sliding contact with each other, and the grease is held in the recess and the grease held in the recess. Is resupplied to the sliding contact part of the rolling element.

JP-A-2015-31344 Japanese Unexamined Patent Publication No. 2015-148241

The recesses described in Patent Document 1 and Patent Document 2 are for storing grease on the inner surface of the pocket, and do not have an action of promoting oil separation and oil mobility of grease. That is, in the above-mentioned Patent Document 1 and Patent Document 2, the grease accumulated in the concave portion moves between the rolling element and the concave portion to prolong the life of the sliding surface structure. However, since grease has low fluidity, once it is discharged to the outside of the sliding surface due to relative movement, there is a problem that friction increases or seizure occurs on the sliding surface due to insufficient lubrication.

Therefore, the present invention provides a sliding surface structure and a method for manufacturing a sliding surface structure capable of maintaining low friction for a long period of time under grease lubrication by improving the holding property and reinflow property of grease.

The sliding surface structure of the present invention is a sliding surface structure in which the sliding surface structure slides relatively under grease lubrication containing a thickener and oil, and the convex apex becomes a non-flat surface on at least one sliding surface. A periodic structure of grease-like unevenness whose height changes continuously is formed, and the unevenness of the periodic structure of the grease-like unevenness is 50 nm or more and 10 μm or less and the periodic pitch is 10 μm or less. This periodic structure supports the thickener, promotes oil separation and oil transfer of the grease, and the supported thickener is derived from the thickener on the other side. and also for the forming the boundary layer, the boundary layer to be formed is to reduce friction and wear.

According to the sliding surface structure of the present invention, the oil content is formed on at least one of the sliding surfaces by forming a periodic structure of grating-like unevenness in which the apex of the convex portion becomes a non-flat surface and the height changes continuously. On the other hand, the wettability is improved, the oil separation of the grease and the oil transferability are promoted, and the reinflow property of the grease discharged to the outside of the sliding surface is improved. Further, since the periodic structure of the grating-like unevenness supports the thickener, the oil content can be propagated to the supported thickener, and the oil content retention and mobility are improved. Further, the supported thickener can form a boundary film on the mating material.

In the above configuration, it is preferable that the periodic structure of the grating-like unevenness communicates with the outside of the sliding surface and is in contact with the grease adhering to the outside of the sliding surface.

In the above configuration, it is preferable that the periodic structure of the grating-like unevenness is oriented along the sliding direction.

In the above configuration, it is preferable that the unevenness of the periodic structure of the grating-like unevenness is 50 nm or more and 10 μm or less and the periodic pitch is 10 μm or less.

The method for manufacturing a sliding surface structure of the present invention is a method for manufacturing a sliding surface structure that slides relatively under grease lubrication containing a thickener and oil, in which at least one of the sliding surfaces has a convex apex. A periodic structure of grease-like unevenness that becomes a non-flat surface and continuously changes in height is formed, and the unevenness of the periodic structure of the grating-like unevenness is 50 nm or more and 10 μm or less and the periodic pitch is 10 μm or less. Only the thickener is supplied to the uneven periodic structure, and this periodic structure supports the thickener to promote oil separation and oil transfer of the grease, and the supported thickener increases to the other side. It forms a boundary film derived from a filler , and the formed boundary film reduces friction and wear .

In the above configuration, the periodic structure of the grating-like unevenness can be self-organized by irradiating a linearly polarized laser with an irradiation intensity near the processing threshold value and scanning the irradiated portions while overlapping them.

In the sliding surface structure of the present invention, the periodic structure of the grating-like unevenness promotes oil separation and oil mobility of grease, and improves the reinflow property of grease discharged to the outside of the sliding surface, resulting in insufficient lubrication. It is possible to prevent an increase in friction and seizure. Further, by supporting the thickener in the periodic structure of the grating-like unevenness, the oil content can be improved in retention and mobility, and the lubrication characteristics can be improved. Further, since the supported thickener can form a boundary film on the mating material, friction and wear can be reduced.

The periodic structure of the grating-like unevenness communicates with the outside of the sliding surface and comes into contact with the grease adhering to the outside of the sliding surface to separate the oil from the grease outside the sliding surface and move the oil into the sliding surface. be able to. As a result, it is possible to prevent an increase in friction and seizure due to insufficient lubrication.

By orienting the periodic structure of the grating-like unevenness along the sliding direction, the oil component quickly moves to the sliding surface, and the lubrication characteristics can be improved. In addition, the supportability of the thickener oriented in the sliding direction is improved.

By setting the unevenness of the periodic structure of the grating-like unevenness to 50 nm or more and 10 μm or less and the periodic pitch to 10 μm or less, the oil content retention and mobility can be improved. If the unevenness of the periodic structure is less than 50 nm, a sufficient amount of thickener cannot be supported, and if the unevenness and the periodic pitch exceed 10 μm, the thickener and oil almost flow out.

According to the method for manufacturing a sliding surface structure of the present invention, the periodic structure of grating-like irregularities promotes oil separation and oil mobility of grease, and improves reinflow of grease discharged to the outside of the sliding surface. Therefore, it is possible to prevent an increase in friction and seizure due to insufficient lubrication. Further, since the periodic structure of the grating-like unevenness supports the thickener, the supported thickener further improves the oil content retention and mobility, so that the lubrication characteristics can be improved. Further, since the supported thickener can form a boundary film on the mating material, friction and wear can be reduced.

By irradiating a linearly polarized laser with an irradiation intensity near the processing threshold and scanning while overlapping the irradiated parts to form it in a self-organizing manner, the submicron periodic pitch and unevenness depth are difficult to machine. A periodic structure having the above can be easily obtained.

It is an enlarged sectional view of the main part of the sliding surface structure which shows the embodiment of this invention. It is an enlarged plan view of the periodic structure formed on the sliding surface. It is a cross-sectional profile diagram of a periodic structure. It is an enlarged sectional view of the sliding surface. It is a figure which shows the state which the oil content propagates the thickener, (a) shows the state which carried the thickener in a periodic structure, and (b) shows the state which carried a thickener in a periodic structure. .. It is a simplified drawing of the laser surface processing apparatus for forming the periodic structure. It is a perspective view of the manufacturing method of the sliding surface structure which shows the embodiment of this invention. It is a graph which shows the friction coefficient of various SUJ2 plates. It is a figure which shows the sliding mark and the cross-sectional profile of the SUJ2 ball which slid on various SUJ2 plates, (a) is an optical mirror surface SUJ2, (b) is a periodic parallel SUJ2, and (c) is a periodic orthogonal SUJ2. It is a top view which shows the oil diffusion state from the grease mass formed at the end of a stroke after a sliding test to the outside of a sliding mark, (a) is an optical mirror surface SUJ2, (b) is a periodic parallel SUJ2, (c). Is a periodic orthogonal SUJ2. It is a figure which shows the sliding mark, (a) is an optical mirror surface SUJ2, (b) is a periodic parallel SUJ2.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 11.

In the sliding surface structure according to the present invention, as shown in FIG. 1, the sliding surface 1a of the first member 1 and the sliding surface 2a of the second member 2 slide relatively under the grease L. be. In this case, the first member 1 and the second member 2 may be carbon steel, copper, aluminum, platinum, cemented carbide or the like, silicon-based ceramics such as silicon carbide or silicon nitride, engineer plastic or the like. It may be. The grease L may contain a thickener and an oil, and the thickener may be, for example, alicyclic urea, an aliphatic urea, a Teflon (registered trademark) type, or the like. May be. That is, various greases can be used depending on the materials of the first and second members 1 and 2, the environment in which they are used, and the like. In the present embodiment, the first member 1 is a sphere as shown in FIG. 7, and the second member 2 is a flat plate.

As shown in FIG. 7, a strip-shaped portion 20 is provided on the upper surface of the second member 2 along one direction, and the upper surface of the strip-shaped portion 20 is a sliding surface 2a. As shown in FIG. 1, a periodic structure 3 having grating-like irregularities is formed on the sliding surface 2a of the second member 2. Further, as shown in FIG. 1, the lower surface of the first member 1 is the sliding surface 1a.

As shown in FIGS. 1 and 2, the periodic structure 3 is formed by alternately arranging minute concave portions 5 and minute convex portions 6 at a predetermined pitch. It is preferable that the height difference of the unevenness of the periodic structure 3 (height from the bottom of the concave portion 5 to the apex of the convex portion 6) is 50 nm or more and 10 μm or less. Further, it is preferable that the periodic pitch of the periodic structure 3 is 10 μm or less. FIG. 3 shows a cross-sectional profile of the periodic structure 3. As described above, the periodic structure 3 is the periodic structure 3 of the grating-like unevenness in which the apex of the convex portion becomes a non-flat surface and the height changes continuously. By forming such a periodic structure, the wettability with respect to the oil is improved, and the oil separation and the oil mobility of the grease are promoted, and as shown by the arrow in FIG. 4, the sliding surface is out of the sliding surface. The re-inflow property of the grease L0 discharged into the water is improved.

In the present embodiment, since the second member 2 reciprocates in the direction of the arrow in FIG. 7 and the first member 1 is on the fixed side, the periodic structure 3 of the grating-like unevenness is oriented along the sliding direction. It has become. Further, as shown in FIG. 4, the periodic structure 3 of the grating-like unevenness communicates with the outside of the sliding surface and is in contact with the grease L0 adhering to the outside of the sliding surface.

The periodic structure 3 of the grating-like unevenness carries the thickener 7 as shown in FIG. The thickener 7 has a network structure as shown in FIG. 5, and oil propagates through the thickener 7. As shown in FIG. 5B, if the thickener 7 is not supported on the periodic structure 3, oil cannot propagate and the sliding surface 2a has poor oil retention and mobility. It becomes. Therefore, if the thickener 7 is supported on the periodic structure 3 as shown in FIG. 5 (a), the oil can be propagated to the thickener 7 as shown by the arrow in FIG. 5 (a). Oil retention and mobility can be improved. Further, the supported thickener 7 can form a boundary film on the mating material (first member 1).

Next, a method of manufacturing the sliding surface structure will be described. The periodic structure 3 is formed in a self-organized manner by irradiating a linearly polarized laser with an irradiation intensity near the processing threshold value and scanning while overlapping the irradiated portions. Specifically, the femtosecond laser surface processing apparatus shown in FIG. 6 is used. The laser (for example, pulse width: 120 fs, center wavelength 800 nm, repetition frequency: 1 kHz, pulse energy: 0.25 to 400 μJ / pulse) generated by the laser generator 11 (titanium sapphire femtosecond laser generator) is driven by the mirror 12. It is folded back toward the processing material W and guided to the mechanical shutter 13. At the time of laser irradiation, the mechanical shutter 13 is opened, the laser irradiation intensity can be adjusted by the 1/2 wavelength plate 14 and the polarizing beam splitter 16, the polarization direction is adjusted by the 1/2 wavelength plate 15, and the condenser lens (focal distance). : 150 mm) 17 condenses and irradiates the surface of the processed material W on the XYθ stage 19. The femtosecond laser is a light source in which energy is compressed in an extremely short time unit of femtosecond (1/1000 trillion second) order.

When the work (processed material) W is irradiated with a linearly polarized laser with fluence near the ablation threshold, the pitch and groove depth of the wavelength order are caused by the interference between the incident light and the scattered light or plasma wave along the surface of the processed material W. A grating-like periodic structure with is formed in a self-organizing manner perpendicular to the polarization direction. At this time, the periodic structure can be expanded over a wide range by scanning while overlapping the femtosecond lasers.

The laser scan may be performed by fixing the laser and moving the XYθ stage 19 that supports the processing material W, or by fixing the XYθ stage 19 and moving the laser. Alternatively, the laser and the XYθ stage 19 may be moved at the same time. Note that FIG. 2 is a diagram in which the periodic structure 3 formed by the femtosecond laser surface processing apparatus is imaged with an electron microscope.

The thickener 7 is supported on the periodic structure 3 thus formed. The method can be carried out by various methods such as a method of sliding the first member 1 and the second member 2 under grease lubrication, a method of supplying only the thickener 7 to the periodic structure 3, and the like.

As described above, in the sliding surface structure of the present invention, the oil separation and oil mobility of the grease are promoted by the periodic structure 3 of the grating-like unevenness, and the re-inflow property of the grease L0 discharged to the outside of the sliding surface is improved. Therefore, it is possible to prevent an increase in friction and seizure due to insufficient lubrication. Further, since the periodic structure 3 of the grating-like unevenness supports the thickener 7, the supported thickener 7 further improves the oil retention and mobility, thereby improving the lubrication characteristics. can. Further, since the supported thickener 7 can form a boundary film on the mating material, friction and wear can be reduced.

The periodic structure 3 of the grating-like unevenness communicates with the outside of the sliding surface and comes into contact with the grease L0 adhering to the outside of the sliding surface to separate the oil from the grease L0 outside the sliding surface and separate the oil from the inside of the sliding surface. Can be moved to. As a result, it is possible to prevent an increase in friction and seizure due to insufficient lubrication.

By orienting the periodic structure 3 of the grating-like unevenness along the sliding direction, the oil component quickly moves to the sliding surface 2a, and the lubrication characteristics can be improved. In addition, the supportability of the thickener 7 oriented in the sliding direction is improved.

By setting the unevenness of the periodic structure 3 of the grating-like unevenness to 50 nm or more and 10 μm or less and the periodic pitch to 10 μm or less, the oil content retention and mobility can be improved. If the unevenness of the periodic structure 3 is less than 50 nm, a sufficient amount of the thickener 7 cannot be supported, and if the unevenness and the periodic pitch exceed 10 μm, the thickener 7 and the oil component will almost flow out.

The periodic structure 3 is irradiated with a linearly polarized laser at an irradiation intensity near the processing threshold, and the irradiated portions are scanned while overlapping to form a self-organized structure, which has a submicron period that is difficult to machine. A periodic structure having a pitch and an uneven depth can be easily obtained.

Although the embodiment of the present invention has been described above, the present invention is not limited to the embodiment, and various modifications can be made. For example, in the embodiment, the periodic structure 3 is placed on the first member 1 side. It may be formed, or may be provided on both sides of the first member 1 and the second member 2. Further, the shapes of the first member 1 and the second member 2 are not limited to those in the illustrated example, and may be formed in various other shapes. That is, the first member 1 may be a cylindrical roller, a tapered roller, or the like, and if the first member 1 is such a roller, the second member 2 becomes an inner ring or an outer ring of the roller bearing. That is, the sliding surface structure of the present invention can be used for various devices such as various automobile parts and mechanical parts.

The size of the periodic structure 3 can be variously changed according to the sizes, materials, types of grease, sliding speed, etc. of the first and second members 1 and 2 to be used. The relative sliding motion of the first member 1 and the second member 2 is such that the first member 1 is fixed and the second member 2 is reciprocated, but on the contrary, the second member 2 side is fixed. , The first member 1 side may be slid. That is, the side on which the periodic structure 3 is formed may be slid, or the side on which the periodic structure 3 is not formed may be slid. Further, both the first member 1 and the second member 2 may be slid.

By the way, in the above-described embodiment, the femtosecond laser which is a pulse laser is used when forming the periodic structure 3, but a pulse laser such as a picosecond laser or a nanosecond laser other than the femtosecond laser can also be used.

A test was conducted using a reciprocating ball-on-plate tester. As shown in FIG. 7, the reciprocating ball-on-plate testing machine includes a second member 2 which is a reciprocating test piece and a first member 1 which is a fixed side test piece. The first member 1 is a ball test piece made of SUJ2 balls (Ra8 nm) having a diameter of 6.35 mm, and the second member 2 is a plate test piece made of an optically polished SUS440C substrate (Ra2 nm).

The plate test piece, which is the second member 2, was irradiated with a femtosecond laser at an energy density near the processing threshold to form a grating-like periodic structure (pitch of about 700 nm, depth of about 200 nm) in a strip-shaped region having a width of 1 mm. The orientation direction of the periodic structure was two directions, orthogonal to the sliding direction (referred to as periodic orthogonal SUJ2) and parallel (referred to as periodic parallel SUJ2). For comparison, an unprocessed plate test piece (called an optical mirror surface SUJ2) was also used.

The sliding conditions were a load of 5 N, a stroke of 4 mm, and a reciprocating frequency of 0.5 Hz, and the sliding resistance was measured by a load cell. As the lubricant, alicyclic urea grease (thickness thickener amount 16%, base oil PAO6, consistency 250) was used.

The coefficient of friction of various SUJ2 plates under alicyclic urea grease lubrication is shown in FIG. The friction coefficient of the periodic parallel SUJ2 at 3000 round trips was reduced by 28% with respect to the optical mirror surface SUJ2, and a remarkable friction reducing effect was observed. Further, the friction coefficient of the periodic orthogonal SUJ2 was also found to have a friction reduction effect of 17% with respect to the optical mirror surface SUJ2.

FIG. 9 shows a photograph of sliding marks and a cross-sectional profile of SUJ2 balls slid on various SUJ2 plates. The sliding marks of the SUJ2 ball slid on the optical mirror surface SUJ2 had a large amount of wear, and the surface roughness and the contact area became the maximum. In addition, it had a metallic luster, and no thickener adhesion or deposition was observed. On the other hand, a boundary film derived from a thickener was formed on the sliding marks of the SUJ2 balls slid between the periodic parallel SUJ2 and the periodic orthogonal SUJ2, and the wear was suppressed. In particular, in the SUJ2 ball slid on the periodic parallel SUJ2, a boundary film was formed on the entire surface of the sliding marks, and almost no wear occurred.

FIG. 10 shows the state of oil diffusion from the grease lump formed at the end of the stroke after the sliding test to the outside of the sliding mark. In FIGS. 10 (b) and 10 (c), the white portion is an optical mirror surface portion (width 340 μm) that does not form a periodic structure. On the optical mirror surface SUJ2 shown in FIG. 10A, no oil diffusion was observed on the plate. On the other hand, in the periodic parallel SUJ2 and the periodic orthogonal SUJ2 shown in FIGS. 10B and 10C, oil diffuses along the band-shaped region forming the periodic structure, and the color of the periodic structure forming region changes from brown to black under a microscope. bottom. The oil diffused to the end face of the periodic parallel SUJ2 plate in which the periodic structure was oriented in the long axis direction of the band-shaped region, whereas the oil movement was limited in the periodic orthogonal SUJ2 in which the periodic structure was oriented in the short axis direction of the band-shaped region. .. Further, since the oil content does not diffuse in the optical mirror surface portion (width 340 μm), the periodic structure in which the grease lumps are not in contact in FIG. 10B did not change to black and was maintained in brown. From this result, it can be confirmed that the periodic structure promotes oil separation of grease and promotes oil movement along the orientation direction of the periodic structure.

FIG. 11 shows the sliding marks of the optical mirror surface SUJ2 and the periodic parallel SUJ2. The optical mirror surface SUJ2 has a large number of scratches, but the periodic parallel SUJ2 has a large amount of oil and the image is unclear, but no scratches are observed. Since the thickener is retained in the periodic structure in the sliding portion of the periodic parallel SUJ2, the oil content is improved in retention and mobility, and the oil content is abundantly present from the outside of the sliding marks shown in FIG. 11 (b). It is considered to be.

The factors that reduced the friction and wear of the periodic parallel SUJ2 are that the periodic structure promotes oil separation and oil movement, and the thickener held in the periodic structure further improves the oil retention and mobility. At the same time, a boundary film derived from a thickener may be formed on the SUJ2 ball side as well.

1a Sliding surface 2a Sliding surface 3 Periodic structure 5 Recessed part 6 Convex part 7 Thickener L Grease L0 Grease adhering to the outside of the sliding surface

Claims (5)

In a sliding surface structure that slides relatively under grease lubrication containing a thickener and oil, the apex of the convex portion on at least one sliding surface becomes a non-flat surface and the height changes continuously. periodic structure of Jo irregularities are formed, and unevenness of the periodic structure of the grating-like unevenness is not more 10μm or less and the period pitch than 50nm is 10μm or less, by supplying only the thickener to the periodic structure of the grating-like unevenness the periodic structure carries the thickener, is promoted oil separation and oil mobility of the grease, it supported thickener is than also forms a boundary layer from the thickener to the other party, The boundary film formed is a sliding surface structure characterized by reducing friction and wear. The sliding surface structure according to claim 1, wherein the periodic structure of the grating-like unevenness communicates with the outside of the sliding surface and is in contact with grease adhering to the outside of the sliding surface. The sliding surface structure according to claim 1 or 2, wherein the periodic structure of the grating-like unevenness is oriented along the sliding direction. In a method for manufacturing a sliding surface structure that slides relatively under grease lubrication containing a thickener and oil, the apex of a convex portion is a non-flat surface on at least one sliding surface, and the height is continuously increased. forming a periodic structure of varying the grating-like unevenness, the unevenness of the periodic structure of the grating-like unevenness is not more 10μm or less and the period pitch than 50nm is 10μm or less, by supplying only the thickener to the periodic structure of the grating-like unevenness Therefore, this periodic structure supports the thickener, promotes oil separation and oil transfer of the grease, and the supported thickener forms a thickener-derived boundary film on the mating side . A method for manufacturing a sliding surface structure, wherein the boundary film formed is characterized by reducing friction and wear. 4. The periodic structure of the grating-like unevenness is characterized in that it irradiates a linearly polarized laser with an irradiation intensity near the processing threshold, scans the irradiated portions while overlapping, and forms the grating in a self-organized manner. The method for manufacturing a sliding surface structure according to.

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