JP5196301B2 - Tribochemical reaction promoting surface structure - Google Patents

Description

  The present invention relates to a tribochemical reaction promoting surface structure.

  Sliding members such as automobile engines contain friction modifiers (additives) in addition to ordinary lubricating oil. This friction modifier has a function of generating a solid lubricating film on the surface, which is a reaction product having a very small frictional resistance, such as molybdenum disulfide, by rubbing the sliding member.

  By the way, it has been found in the conventional research that the generation of the reaction product is influenced by the surface state of the sliding surface (Non-Patent Document 1). That is, when sliding smooth surfaces covered with an oxide or the like, the chemical reaction hardly occurs because the surfaces are in a stable state. On the other hand, on the concavo-convex surface having the surface roughness, a new surface is likely to be formed due to stress concentration. The surface of the new surface where the bonds between atoms are broken is in an active state. In this case, the friction modifier itself is activated under the influence of heat and shearing force generated by friction caused by sliding, and the reaction with the metal surface is promoted to form a reaction product on the surface.

As described above, a chemical reaction is more likely to occur on the surface having a surface roughness than a smooth mirror surface, and a reaction product is likely to be generated. Therefore, conventionally, in order to impart surface roughness to the sliding surface, irregularities are intentionally formed by emery paper or machining.
Shingo Matsubo, Hideo Kubo, Hidetaka Nanao, Ichiro Minami, Masayuki Mori Controlling Tribochemical Reaction and Friction Properties by Surface Shape Tribology Conference Proceedings Saga 2007-9, (2007) 5

  As described above, when surface roughness is imparted by emery paper, machining, or the like, a processed surface composed of a plurality of convex portions 102 and concave portions 103 is formed on the sliding surface 101 as shown in FIG. The unevenness has a width (a dimension from the vertex 104 of the convex part 102 to the vertex 104 of the adjacent convex part 102), and an irregularity height (a dimension from the vertex 104 of the convex part 102 to the valley bottom 105 of the concave part 103). Becomes b. In this case, the width a is several tens μm to several hundreds μm, and the uneven height b is several μm. That is, the aspect ratio between the width a and the uneven height b was extremely small, and the sliding surface 101 was a gentle curve.

By sliding of the sliding member, the sliding surface 101 is shaved from the direction shown by the arrow in FIG. In this case, since the aspect ratio between the width a and the height dimension b is extremely small, the radius of curvature of the contact point with the other sliding surface (not shown) is large. For this reason, stress concentration is unlikely to occur, and a new surface is not efficiently generated. In addition, when the radius of curvature is large, the other sliding surface is also easily elastically deformed along the shape of the convex portion 102, and the range in which the sliding surface 101 abuts on the other sliding surface increases, resulting in a unit area. The hit force is reduced. For these reasons, it was necessary to give a large roughness to generate a new surface. When a large roughness is imparted, a large amount of wear is required until the area ratio of the new surface reaches a predetermined value, which causes problems such as a prolonged conforming process and a change in the dimensions of the sliding surface.

  Furthermore, since the width a is large, the width dimension of one convex part 102 is also large. For this reason, the area of the new surface formed by one convex part 102 becomes wide. As a result, the dimension from the central portion of the new surface (near the apex 104 of the convex portion 102) to the concave portion 103 becomes longer, and it is difficult for the friction modifier to be supplied to the central portion of the new surface. There was a problem that a chemical reaction hardly occurred without supplying the agent.

  In view of the above-described problems, the present invention provides a tribochemical reaction promoting structure that can be easily worn by providing a small roughness to generate a new surface, and that a friction modifier is finely supplied to the new surface.

In the tribochemical reaction promoting surface structure of the present invention, the sliding surface of the first member and the sliding surface of the second member slide relative to each other under lubricated additive oil containing a friction modifier. a tribochemical reaction promoting surface structure produced is obtained by forming a grating-like periodic structure having a spacing irregularities height of submicron order on at least one sliding surface.

In the present invention, the focus is not on the surface roughness of the sliding surface but on the radius of curvature of the contact point. According to the tribochemical reaction promoting surface structure of the present invention, a grating structure having a concavo-convex height and spacing of submicron order on at least one of the sliding surface of the first member and the sliding surface of the second member. Since it is formed, the aspect ratio between the height of the unevenness and the interval is larger than that of the conventional surface roughness imparting surface. Thereby, although the surface roughness is small, the radius of curvature of the tip of the convex portion becomes small (sharp), and the force applied per unit area of the convex portion becomes large. Moreover, since the space | interval from the front-end | tip part of a convex part to the front-end | tip part of an adjacent convex part is small, the area of the new surface produced | generated by one convex part becomes narrow, and the friction modifier of sufficient quantity for the whole new surface Finely and efficiently supplied. Furthermore, a sufficient area of the new surface is secured with a submicron wear amount. Here, the first member and the second member are mechanical parts having sliding portions such as a wet clutch, an engine piston, a gear, a spline, a plain bearing, and a valve train system part.

  The direction of the grating-like periodic structure can be orthogonal to the sliding direction. That is, after the other sliding surface comes into contact with the convex portion, it passes through the concave portion and comes into contact with the adjacent convex portion. As described above, the generation of the new surface and the supply of the friction modifier are repeated every other interval on the other sliding surfaces.

  One sliding surface hardness can be made different from the other sliding surface hardness. In this case, the grating-like periodic structure can be formed on the low hardness side sliding surface, or the grating-like periodic structure can be formed on the high hardness side sliding surface.

  Waviness having a height and interval larger than the grating-like periodic structure is formed on at least one sliding surface, and the grating-like periodic structure can be formed on this swell. The sliding surface becomes a smooth surface when the height of the unevenness is removed, and in this case, the life of the effect of the present invention is obtained. Therefore, by forming the undulation, the size from the apex of the convex portion at the highest position to the valley bottom of the concave portion at the lowest position can be increased by providing a difference in height over the entire sliding surface. Thereby, even if the periodic structure of a part of the sliding surface is worn out and smoothed, a reaction product is generated in the periodic structure of the other low part and can be spread over the entire sliding surface, The effect can be maintained until the entire sliding surface is smoothed.

  The grating structure can be formed in a self-organized manner by irradiating a linearly polarized femtosecond laser with an irradiation intensity in the vicinity of the processing threshold, and scanning while overlapping the irradiated portions. When this method is used, the grating structure can be formed on a cylindrical surface or a complicated shape.

  In the tribochemical reaction promoting surface structure of the present invention, since the force per unit area of the convex portion is large, it is easily worn out to generate a new surface, and the surface becomes active. In addition, a sufficient amount of friction modifier is finely and efficiently supplied to the new surface, the tribochemical reaction is promoted, and a reaction product with extremely low frictional resistance is formed on the surface to form a low friction sliding surface. Can do. Further, since it is in the form of a grating, there is an advantage that there is less leakage of the friction modifier than the columnar structure and there is also a small amount of wear due to the small interval. In addition, since the wear powder escapes (enters) into the recess during the conforming process, the wear powder can be prevented from being caught and a low friction surface can be secured stably.

  When the direction of the grating-like periodic structure is orthogonal to the sliding direction, generation of a new surface and supply of a friction modifier are repeated at each interval (period), and thus the tribochemical reaction is efficiently performed. Can be promoted.

  When the hardness of one sliding surface is different from the hardness of the other sliding surface, the new surface generated on the low hardness side is smoothed, so that a uniform sliding surface with less unevenness on which the reaction product is formed is formed. It can be formed and the frictional resistance can be reduced.

  When a waviness having a larger height and interval than the grating-like periodic structure is formed, even if some of the periodic structures are worn, reaction products with low friction are generated in other periodic structures, and the entire sliding surface It is possible to extend the service life.

  The grating structure is irradiated with linearly polarized laser light with an irradiation intensity near the processing threshold, and the irradiated part is scanned while overlapping, and the submicron period, which is difficult to machine by machining, is difficult to machine. A grating structure having a pitch can be formed on a flat surface, a cylindrical surface, or other complicated curved surfaces with almost no processing alteration. Further, when the grating structure is formed using a femtosecond laser, processing in the atmosphere is possible, and the processing apparatus can be simplified. On the other hand, in the case of electron beam machining, it is necessary to accommodate a workpiece, which is a workpiece, in a vacuum chamber or the like and process it in a vacuum atmosphere or a predetermined gas atmosphere, which increases the cost of the apparatus. In addition, this leads to an increase in size.

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

  The tribochemical reaction promoting surface structure of the present invention is such that the sliding surface 10 of the first member 1 and the sliding surface 4 of the second member 3 slide relative to each other. In the present embodiment, as shown in FIG. 1, the first member 1 is a flat plate, and the second member 3 is a pin having a spherical tip. The first member 1 and the second member 3 slide under lubrication with additive oil containing a friction modifier (additive) in the lubricant. As the lubricating oil, various oils such as turbine oil, engine oil, and gear oil can be used. Friction modifiers include oily improvers such as higher fatty acids, higher alcohols, aliphatic amines, amides and esters, extreme pressure additives containing compounds such as sulfur, phosphorus, chlorine and organometallics, molybdenum disulfide, graphite, ceramics A variety of solid lubricants including solid materials such as powder (including boron) and fine metal powder can be used.

  As the material of the first member 1, SUJ2 (high carbon chromium bearing steel JIS G4805) is used. The second member 3 uses a cemented carbide. Here, the cemented carbide (Cemented Carbide) is an alloy made by sintering a hard metal carbide powder, and is also simply called cemented carbide. Generally, tungsten carbide (WC, tungsten carbide) and cobalt (Co) as a binder (binder) are mixed and sintered. Further, in order to improve material properties, titanium carbide (TiC), tantalum carbide (TaC), or the like may be added. Thereby, the sliding surface hardness of the first member 1 is lower than the sliding surface hardness of the second member 3. That is, the grating structure 2 is formed on the low hardness side sliding surface. Thereby, the 1st member 1 which is a low hardness side will wear.

The sliding surface 10 of the first member 1 is provided with a grating structure 2 as shown in FIGS. The grating structure portion 2 has minute recesses (concave ridges) 5 and minute projections (projection ridges) 6 arranged alternately in parallel at a predetermined pitch, and has a cross-sectional shape close to a sine curve. In the unevenness, the interval (the dimension from the apex of the convex part 6 to the apex of the adjacent convex part 6) is A, and the concave / convex height (the dimension from the apex of the convex part 6 to the valley bottom of the concave part 5) is B. . In this case, the interval A is a dimension in the submicron order, and the uneven height B is also a dimension in the submicron order. In this embodiment, A is 0.7 μm, B is 0.2 μm, and the aspect ratio B / A between the interval A and the unevenness height B is 2/7. When the aspect ratio is less than 0.1, it is difficult to hold a sufficient friction modifier, and when it exceeds 0.5, the amount of wear and the familiar process increase. 0.5 is preferred. As a result, when the conventional grating structure portion and the grating structure portion 2 of the present embodiment are compared within a predetermined length, the arrangement pitch of the convex portions is sparse in the conventional grating structure portion. In the form of the grating structure portion 2, the pitch of the convex portions 6 can be made dense.

As a result, a fine periodic structure with a submicron-order concavo-convex height B and an interval A that have an aspect ratio higher than the normal surface roughness and a controlled direction can be formed on the sliding surface 10. That is, the radius of curvature of the tip of the convex portion 6 is reduced (sharpened), and the force applied per unit area of the convex portion 6 is increased. Moreover, since the space | interval A is small, the area of the new surface produced | generated by the one convex part 6 becomes narrow, and sufficient quantity of friction modifiers are efficiently supplied to the whole new surface. Thereby, tribochemical reaction is accelerated | stimulated and the reaction product with very small frictional resistance is formed in the surface.

  In sliding between the first member 1 and the second member 3, the second member 3 is fixed and the first member 1 is reciprocated in the direction indicated by the arrows in FIGS. 1 and 3. That is, the direction of the grating structure portion 2 is orthogonal to the sliding direction. Thereby, after the sliding surface 4 of the second member 3 abuts on the convex portion 6, it passes through the concave portion 5 and abuts on the adjacent convex portion 6. In this manner, the second member 3 sliding surface 4 repeats the generation of a new surface and the supply of the friction modifier at every interval.

  The grating structure portion 2 is formed in a self-organized manner by irradiating a linearly polarized laser beam with an irradiation intensity in the vicinity of the processing threshold and scanning the overlapped portion in an overlapping manner. Specifically, the femtosecond laser surface processing apparatus shown in FIG. 4 is used. A laser (eg, pulse width: 120 fs, center wavelength: 800 nm, repetition frequency: 1 kHz, pulse energy: 0.25 to 400 μJ / pulse) generated by a laser generator 11 (titanium sapphire femtosecond laser generator) is reflected by a mirror 12. It is folded back toward the work 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 half-wave plate 14 and the polarization beam splitter 16, the polarization direction is adjusted by the half-wave plate 15, and the condenser lens (focal length) : 150 mm) 17, the surface of the work material W on the XYθ stage 19 is condensed and irradiated.

  When a workpiece is irradiated with a linearly polarized laser beam at a fluence near the ablation threshold, a grating-like periodic structure with pitches and groove depths on the order of wavelengths due to interference between incident light and scattered light or plasma waves along the workpiece surface Are formed in a self-organized manner perpendicular to the polarization direction. At this time, the periodic structure can be expanded over a wide range by scanning the femtosecond lasers while overlapping them.

  Laser scanning may be performed by moving the XYθ stage 19 that supports the work material W while fixing the laser, or may move the laser while fixing the XYθ stage 19. Alternatively, the laser and the XYθ stage 19 may be moved simultaneously.

  As described above, the tribochemical reaction promoting surface structure of the present invention has a large force per unit area of the convex portion 6, so that it is easily worn immediately after the start of sliding to generate a new surface, and the surface is active. It becomes a state. In addition, a sufficient amount of friction modifier is finely and efficiently supplied to the new surface, the tribochemical reaction is promoted, and a reaction product with extremely low frictional resistance is formed on the surface to form a low friction sliding surface. Can do. When a low friction sliding surface is formed, the wear rate is greatly reduced. Further, since the periodic structure is a grating shape, there is an advantage that there is less leakage of the friction modifier than the columnar structure, and since the interval A is small, the wear amount is also small. In addition, since the wear powder escapes (enters) into the recess 5 during the conforming process, the wear powder can be prevented from being caught and a low friction surface can be secured stably.

  When the direction of the grating-like periodic structure is orthogonal to the sliding direction, generation of a new surface and supply of a friction modifier are repeated every interval (period), thereby efficiently promoting a tribochemical reaction. Can be made.

  Since the grating structure portion 2 is formed on the low hardness side sliding surface, the apex of the convex portion 6 of the grating structure portion 2 on the low hardness side is worn, resulting in a plateau-like uniform sliding surface. The frictional resistance can be reduced.

  The grating structure 2 is irradiated with a linearly polarized laser beam with an irradiation intensity in the vicinity of the processing threshold, scanned while overlapping the irradiation portion, and formed by self-organization. A grating structure having a periodic pitch can be formed on a flat surface, a cylindrical surface, or other complicated curved surfaces with almost no processing alteration. Further, when the grating structure is formed using a femtosecond laser, processing in the atmosphere is possible, and the processing apparatus can be simplified. On the other hand, in the case of electron beam machining, it is necessary to accommodate a workpiece, which is a workpiece, in a vacuum chamber or the like and process it in a vacuum atmosphere or a predetermined gas atmosphere, which increases the cost of the apparatus. In addition, this leads to an increase in size.

  FIG. 5 shows a tribochemical reaction promoting surface structure according to the second embodiment of the present invention. In this case, a swell having a gap C and a height D larger than the grating-like periodic structure 2 is formed on the sliding surface 10 of the first member 1 on the low hardness side, and the grating-like periodic structure 2 is formed on this swell. Forming. In the first embodiment, when the height of the unevenness is cut, the sliding surface 10 becomes a smooth surface, which is the life of the effect of the present invention. Therefore, by forming a undulation in the sliding surface 10, by making a height difference in the entire sliding surface, the dimension from the apex of the convex portion 6 at the highest position to the valley bottom of the concave portion 5 at the lowest position is increased. can do. Thereby, even if the periodic structure of a part of the sliding surface is worn out and smoothed, a reaction product is generated in the periodic structure of the other low part and can be spread over the entire sliding surface, The effect can be maintained until the entire sliding surface is smoothed.

  As described above, in the tribochemical reaction promoting surface structure according to the second embodiment of the present invention, when a swell having a larger interval C and height D than the grating-like periodic structure is formed, a part of the periodic structure is worn away. However, a reaction product with low friction can be generated in another periodic structure and can be spread over the entire sliding surface, thereby extending the life. In the tribochemical reaction promoting surface structure shown in FIG. 5, the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG.

  In each of the embodiments described above, the sliding surface hardness of the first member 1 is lower than the sliding surface hardness of the second member 3, but the sliding surface hardness of the first member 1 is that of the second member 3. It may be higher than the sliding surface hardness. The grating structure 2 may be formed on the high hardness side sliding surface. In addition to SUJ2 and cemented carbide, various materials such as SUS440C (martensitic stainless steel) can be used.

  As described above, the embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various modifications are possible. For example, as the interval A and the uneven height B of the grating structure portion 2, It does not have to be 0.7 μm or 0.2 μm, and is not limited to this as long as it is on a submicron order. The grating structure 2 may be formed on the sliding surface 4 of the second member 3.

  As sliding of the 1st member 1 and the 2nd member 3, the 1st member 1 may be fixed, the 2nd member 3 may be reciprocated, and both may be reciprocated. Further, it may be slid only in forward movement or backward movement without reciprocating during sliding. One member may rotate. The shape of the first member 1 and the second member 3 is not limited to that of the embodiment, and may be flat plates or disks, and the other member is slid on the cylindrical member. It may be a thing. As the 1st member 1 and the 2nd member 3, it can be used for a wet clutch, an engine piston, a gear, a spline, a slide bearing, valve system parts, etc., for example. The sliding stroke, the pressing load during sliding, and the like can be arbitrarily set according to the periodic pitch of the grating structure 2, the sliding speed, and the like.

  The sliding direction is preferably substantially perpendicular to the grating direction as in the embodiment, but even if it is substantially parallel to the grating direction, it is inclined at a predetermined angle (for example, 45 degrees) with respect to the grating direction. You may do.

  When forming the grating structure 2, other tools such as an electron beam processing machine may be used without using a femtosecond laser.

  As shown in FIG. 1, a pin (cylindrical body) 3 as a mating member was pressed against a plate 1 on which a periodic structure (grating structure portion 2) was formed, and slid back and forth. The plate 1 and the pin 3 were made of three types of materials: cemented carbide, SUJ2 and SUS440C, respectively. The plate 1 was finished to Ra 0.05 μm by buffing, and the grating structure 2 was formed only on the plate 1. The surface roughness after the formation of the periodic structure was Ra 0.13 μm. The direction of the grating structure part 2 was made into two types orthogonal and parallel to the sliding direction. The tip shape of the pin 3 was a hemisphere with a radius of 5 mm. Turbine oil (VG32) was supplied to the sliding surface, and molybdenum dialkyldithiocarbamate (Mo-DTC) was used as an additive. The additive concentration was 950 ppm. The sliding speed was 10 mm / s, the sliding stroke was 10 mm, the vertical load was 1000 reciprocates at 5 N, and the sliding resistance was measured with a load cell at a sampling frequency of 5 Hz. The coefficient of friction was calculated from the average measured value excluding the stroke end point.

  Slide the SUJ2 pin (cylindrical body formed of SUJ2) on a cemented carbide plate with a periodic structure (parallel periodic structure) in which the mirror surface and the grating direction are parallel (substantially parallel) to the sliding direction. FIG. 6 shows the change of the friction coefficient at the time. FIG. 6A shows a case where the friction modifier is not included, and FIG. 6B shows a case where the friction modifier is included. Under turbine oil lubrication that does not include a friction modifier, the friction coefficient was substantially constant regardless of the presence or absence of the periodic structure, as shown in FIG. On the other hand, it was found that under the turbine oil lubrication containing the friction modifier, the friction coefficient of the parallel periodic structure plate is greatly reduced as shown in FIG.

  FIG. 7 shows the friction coefficient when various pins are slid by 20 m on a cemented carbide plate having a mirror surface, a parallel periodic structure, and an orthogonal periodic structure in which the grating direction is orthogonal to the sliding direction. Hatching is a mirror surface plate, dots are parallel periodic structure plates, and white indicates orthogonal periodic structure plates. The friction coefficient of the SUJ2 pin was 0.07 to 0.08 with respect to the parallel periodic structure plate and the orthogonal periodic structure plate without depending on the direction of the periodic structure, and was greatly reduced as compared with the mirror plate. The friction coefficient of SUS440C pin (cylindrical body formed of SUS440C) showed a strong dependence on the direction of the periodic structure. The parallel periodic structure plate showed a higher friction coefficient than the mirror plate, whereas the orthogonal periodic structure plate reduced the friction coefficient to 0.08. The friction coefficient of the cemented carbide pin that slides between the same materials was higher than that of the mirror plate regardless of the direction of the periodic structure.

  Further, smoothing of the pins was observed with the cemented carbide plate. FIGS. 8 to 10 show photographs of the sliding surface and cross-sectional profile of the SUJ2 pin after sliding 20 m. FIG. 8A is a photograph of the sliding surface of the SUJ2 pin slid against the mirror plate, FIG. 8B is a cross-sectional profile view of FIG. 8A, FIG. 9A is a photograph of the sliding surface of the SUJ2 pin slid with respect to the parallel periodic structure plate, and FIG. 9B is FIG. 9A. FIG. 10A is a photograph of a sliding surface of the SUJ2 pin slid with respect to the orthogonal periodic structure plate, and FIG. 10B is a sectional profile view of FIG. The SUJ2 pin slid on the mirror plate shows a discolored area, but no noticeable wear. On the other hand, the sliding surface of the SUJ2 pin slid to the periodic structure is smoothed, and the pin slid on the parallel periodic structure plate is smoothed more widely than the pin slid on the orthogonal periodic structure plate It can be seen that the newly formed surface is generated. The main causes of reducing the friction of the pin with respect to the parallel periodic structure plate and the orthogonal periodic structure plate are promotion of tribochemical reaction with the friction modifier and smoothing of the pin.

  Further, a sliding surface photograph and a cross-sectional profile view of the SUS440C pin after sliding 20 m with respect to the cemented carbide plate are shown in FIGS. 11 to 13, and FIG. 11A shows the SUS440C pin slid with respect to the mirror plate. 11 (b) is a cross-sectional profile view of FIG. 11 (a), and FIG. 12 (a) is a photograph of the sliding surface of the SUS440C pin slid with respect to the parallel periodic structure plate, FIG. 12B is a cross-sectional profile view of FIG. 12A, FIG. 13A is a photograph of a sliding surface of a SUS440C pin slid with respect to the orthogonal periodic structure plate, and FIG. 13B is a view of FIG. FIG. The SUS440C pin slid on the mirror plate does not show any noticeable wear, but the sliding surface of the SUS440C pin slid on the periodic structure plate is smoothed and slid on the parallel periodic structure plate. The pin has a new surface smoothed more extensively than the pin slid on the orthogonal periodic structure plate. However, as shown in FIG. 7, the friction reduction is not caused in the parallel periodic structure plate, and the friction reduction is caused only in the orthogonal periodic structure plate. This is because the orthogonal periodic structure has a higher tribochemical reaction promoting function than the parallel periodic structure. That is, in the orthogonal periodic structure, the formation of the new surface and the supply of the additive are repeated every one interval (period), so that the tribochemical reaction can be efficiently promoted. This is because the opportunity for supplying the friction modifier to the new surface is reduced.

  Next, FIG. 14 shows a friction coefficient when various pins are slid by 20 m with respect to the SUJ2 plate having a mirror surface, a parallel periodic structure, and an orthogonal periodic structure. Hatching is a mirror surface plate, dots are parallel periodic structure plates, and white indicates orthogonal periodic structure plates. The friction coefficient of SUJ2 pin and SUS440C pin increased by forming a periodic structure on SUJ2 plate, whereas the friction coefficient of cemented carbide pin was greatly reduced.

  FIG. 15 shows the change in the coefficient of friction of the cemented carbide pin against the SUJ2 plate. The friction coefficient of the cemented carbide pin against the mirror plate was less than 0.1 immediately after sliding, but stabilized at about 0.11 after a sliding distance of 4 m. On the other hand, in the parallel periodic structure plate and the orthogonal periodic structure plate, the friction coefficient showed a tendency to decrease to near the sliding distance of 10 m, and then stabilized at about 0.07.

  A sliding surface photograph and a cross-sectional profile view of the SUJ2 plate with the cemented carbide pin are shown in FIGS. 16A is a sliding surface photograph of the mirror plate, FIG. 16B is a sectional profile view, FIG. 17A is a sliding surface photograph of the orthogonal periodic structure plate, and FIG. 17B is a sectional profile. FIG. FIG. 16 shows that in the case of a mirror plate, the surface roughness of the sliding trace is larger than that of the non-sliding portion. On the other hand, from FIG. 17, in the case of the orthogonal periodic structure plate, the surface roughness of the sliding trace is smaller than that of the mirror plate. FIG. 18A shows an SEM image of the periodic structure at I (high contact surface pressure portion) in FIG. 17A, and FIG. 18B shows an SEM image of the periodic structure at II (low contact surface pressure portion). Show. In I, wear of the periodic structure is observed, but the groove of the periodic structure still remains. In II, the periodic structure has a slight wear at the tip of the convex portion, but is almost in the form. FIG. 19 shows a cross-sectional profile of the periodic structure after a sliding test using a cemented carbide pin. The tip of the convex portion of the periodic structure is smoothed to form a plateau shape with extremely uniform height. When a cemented carbide pin with high hardness is slid, the protruding convex portion tip of the periodic structure is easily worn. At this time, since the wear powder is discharged to the groove portion, adhesion of the wear powder is suppressed. As a result, it becomes a plateau-like form in which the overall height is extremely uniform. A tribochemical reaction is actively generated by finely supplying the friction modifier from the periodic structure portion to the new surface generated at this time. Molybdenum disulfide, a tribochemical reaction product of Mo-DTC, was detected in cemented carbide pins with reduced friction. Therefore, the lowering of friction of cemented carbide pin against SUJ2 periodic structure plate is mainly due to acceleration of tribochemical reaction and plateau of plate. As plateau progresses, the contact surface pressure decreases, so the wear rate decreases and a stable low friction sliding surface is obtained. In the case of the SUJ2 pin and SUS440C pin, the hardness difference is small compared to the SUJ2 plate, and the same degree of wear occurs on both. Therefore, since a smooth surface based on pins or plates cannot be obtained, a reduction in friction did not occur.

  Next, FIG. 20 shows a friction coefficient when various pins are slid by 20 m on a SUS440C plate on which a mirror plate, a parallel periodic plate, and an orthogonal periodic plate are formed. Hatching is a mirror surface plate, dots are parallel periodic structure plates, and white indicates an orthogonal periodic structure. The friction coefficient of the SUJ2 pin and SUS440C pin hardly changed even when the periodic structure was formed on the SUS440C plate. The friction coefficient of cemented carbide pin was reduced only with the orthogonal periodic structure plate. The decreasing tendency of the coefficient of friction was the smallest among the three types of plates used in this example. This is because the activity of SUS440C is low and reaction with the friction modifier hardly occurs.

It is a simple perspective view of the tribochemical reaction promotion surface structure which shows 1st Embodiment of this invention. It is a principal part expansion simplified sectional view of the tribochemical reaction promotion surface structure which shows 1st Embodiment of this invention. FIG. 2 is an enlarged perspective view of the tribochemical reaction promoting surface structure of FIG. 1. It is a simplified diagram of a laser surface processing apparatus for forming a grating structure. It is a principal part expansion simplified sectional view of the tribochemical reaction promotion surface structure which shows 2nd Embodiment of this invention. The change of the friction coefficient when the SUJ2 pin is slid on the cemented carbide plate having a mirror surface and a parallel periodic structure is shown, (a) is a graph when no friction modifier is included, (b) It is a graph in the case of containing a friction modifier. It is a graph which shows the friction coefficient at the time of sliding the pin of cemented carbide, SUJ2, and SUS440C for 20 m with respect to the cemented carbide plate which formed the mirror surface, the parallel periodic structure, and the orthogonal periodic structure. The SUJ2 pin after sliding 20 m with respect to the mirror surface cemented carbide plate is shown, (a) is a photograph of the sliding surface of the SUJ2 pin, and (b) is a cross-sectional profile view thereof. The SUJ2 pin after sliding 20 m with respect to the cemented carbide plate having a parallel periodic structure is shown, (a) is a photograph of the sliding surface of the SUJ2 pin, and (b) is a cross-sectional profile view thereof. The SUJ2 pin after sliding 20 m with respect to the cemented carbide plate having an orthogonal periodic structure is shown, (a) is a photograph of the sliding surface of the SUJ2 pin, and (b) is a cross-sectional profile view thereof. The SUS440C pin after 20-m sliding with respect to the mirror surface cemented carbide plate is shown, (a) is a sliding surface photograph of the SUS440C pin, and (b) is a cross-sectional profile view thereof. The SUS440C pin after 20-m sliding is shown with respect to the cemented carbide plate which formed the parallel periodic structure, (a) is a sliding surface photograph of the SUS440C pin, (b) is the cross-sectional profile figure. The SUS440C pin after 20-m sliding is shown with respect to the cemented carbide plate which formed the orthogonal periodic structure, (a) is a sliding surface photograph of the SUS440C pin, (b) is the cross-sectional profile figure. It is a graph which shows the friction coefficient at the time of sliding the pin of cemented carbide, SUJ2, and SUS440C for 20 m with respect to the SUJ2 plate which formed the mirror surface, the parallel periodic structure, and the orthogonal periodic structure. It is a graph which shows the change of the friction coefficient of the cemented carbide pin with respect to SUJ2 plate. The sliding surface of SUJ2 plate by a cemented carbide pin is shown, (a) is a sliding surface photograph of a mirror surface plate, (b) is the cross-sectional profile figure. The sliding surface of SUJ2 plate by a cemented carbide pin is shown, (a) is the sliding surface of an orthogonal periodic structure plate, (b) is the cross-sectional profile figure. The details of FIG. 17A are shown, wherein FIG. 17A is an SEM image at a high contact surface pressure portion, and FIG. 17B is an SEM image at a low contact surface pressure portion. FIG. 6 is a cross-sectional profile diagram after a sliding test using a cemented carbide pin having a periodic structure formed on a SUJ2 plate. It is a graph which shows a friction coefficient at the time of sliding the pin of cemented carbide, SUJ2, and SUS440C for 20 m with respect to the SUS440C plate which formed the mirror surface, the parallel periodic structure, and the orthogonal periodic structure. It is a principal part expansion simplified sectional view of the conventional tribochemical reaction promotion surface structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st member 2 Periodic structure 3 2nd member 4, 10 Sliding surface 5 Concave part 6 Convex part A Space | interval B Concave height C Space | interval D Height

Claims (5)

A tribochemical reaction promoting surface structure in which a sliding surface of the first member and a sliding surface of the second member slide relative to each other under lubrication with an additive oil containing a friction modifier, thereby generating a new surface. ,
Forming a grating-like periodic structure having a concavo-convex height and spacing of the submicron order on at least one sliding surface,
While making the direction of the grating-like periodic structure perpendicular to the sliding direction,
A tribochemical reaction promoting structure characterized in that one sliding surface hardness is different from the other sliding surface hardness . 2. The tribochemical reaction promoting surface structure according to claim 1 , wherein the grating-like periodic structure is formed on a low hardness side sliding surface. 2. The tribochemical reaction promoting surface structure according to claim 1 , wherein the grating-like periodic structure is formed on a high hardness side sliding surface. Forming a waviness having a greater height and spacing from the grating-like periodic structure on at least one sliding surface, according to claim 1 to claim 3, characterized in that the formation of the grating-like periodic structure in this undulation The tribochemical reaction promoting surface structure according to any one of the above. The grating structure part is formed by self-organizing by irradiating linearly polarized femtosecond laser with an irradiation intensity in the vicinity of a processing threshold, and scanning while overlapping the irradiation part. The tribochemical reaction promoting surface structure according to claim 4 .