JP2014156927A - Sliding surface structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sliding surface structure which has high load capacity and can alleviate aggressiveness of a periodic structure part.SOLUTION: A sliding surface of a first member and a sliding surface of a second member slide relatively under a lubricant, in a sliding surface structure. On at least one sliding surface of either of the first member and the second member, an uneven periodic structure part in a grating shape and a periodic structure unformed part are alternately formed along a sliding direction. A fluid introduction groove is formed on an upstream side in the sliding direction of the periodic structure part. The periodic structure part is communicated with a peripheral edge of the sliding surface. A projection height position of the periodic structure part is set lower than a height position of the unformed part.

Description

  The present invention relates to a sliding surface structure.

  Surface texturing is one of the methods for improving sliding characteristics, such as expanding the fluid lubrication area and reducing friction. Grating-like periodic structure with submicron periodic pitch and groove depth is known to have extremely high load capacity and rigidity at submicron oil film thickness, and is used for reciprocating sliding and rotational sliding. Has been.

  However, in situations where sufficient dynamic pressure cannot be obtained, such as immediately after starting or immediately before stopping, aggression by the periodic structure part becomes a problem. Here, the aggression property by the periodic structure portion is wear increase property or damage property to the counterpart member. In order to reduce the aggressiveness of the periodic structure portion, it is effective to make the height of the convex portion of the periodic structure portion lower than the height flush with the portion where the periodic structure is not formed.

  Therefore, conventionally, there is a thrust bearing in which a convex portion whose height is higher than the sliding surface is provided at the center of rotation (Patent Document 1). In this thrust bearing, when the rotation is stopped, the entire sliding surface (the surface facing the mating sliding surface) is in contact with the apex of the convex portion without contacting the mating sliding surface. For this reason, at the time of start-up, the contact between the apex of the convex portion and the other-side sliding surface is limited to the vicinity of the rotation center, and the influence on the start-up torque due to friction is made small.

JP 2001-12456 A

  In the thing of patent document 1, it is necessary to form a convex part on a sliding surface. As a forming method in this case, there is a method of forming the convex portion as a separate member and then joining the sliding surface, or a method of cutting or grinding so as to leave the convex portion. For this reason, any of the forming methods has many processing steps and is inferior in productivity.

  In addition, the oil film tends to be thicker by forming the convex portion. Thus, when the oil film becomes thick, low load capacity and low rigidity are caused.

  If the height of the convex portion of the periodic structure portion is made lower than the height flush with the portion where the periodic structure is not formed, the load capacity is adversely affected. Therefore, it is desired to develop a patterning that does not affect the load capacity and to set an appropriate height.

  In view of the above problems, the present invention provides a sliding surface structure that can reduce the aggressiveness of a periodic structure part while suppressing a reduction in load capacity.

  The sliding surface structure of the present invention is a sliding surface structure in which the sliding surface of the first member and the sliding surface of the second member slide relative to each other under a lubricant. At least one of the sliding surfaces of the member, the periodic structure portions of the grating-like irregularities communicating with the periphery of the sliding surface and the non-periodic structure forming portions are alternately formed along the sliding direction, and the period The convex portion height position of the structure portion is set lower than the height position of the non-formed portion, and the shape of the periodic structure non-formed portion is a saw blade shape.

  According to the sliding surface structure of the present invention, the periodic structure portion in the mixed lubrication with the contact between the two surfaces by setting the convex portion height position of the periodic structure portion lower than the height position of the non-formed portion. Wear and aggression are alleviated. Here, the aggression property by the periodic structure portion is wear increase property or damage property to the counterpart member. In addition, since the periodic structure portion communicates with the periphery of the sliding surface, the lubricant can be introduced into the sliding surface from the periphery of the sliding surface by the sliding operation of the first member and the second member ( This action is called a fluid introduction effect (pumping effect). The periodic structure portion and the periodic structure non-formed portion are alternately formed along the sliding direction, and the period height is set by setting the convex portion height position of the periodic structure portion lower than the height position of the non-formed portion. Pressure is generated at the boundary between the structure portion and the unformed portion, and a pressure gradient is generated in the sliding direction (this action is called a step effect). The load capacity due to the step effect is less affected by the step height (height difference between the convex part height position of the periodic structure part and the non-formed part height position) than the load capacity due to the pumping effect. The wear and aggressiveness of the periodic structure can be reduced while keeping the reduction low. Thus, by providing the periodic structure portion and the non-formed portion, the reduction in load capacity can be reduced even if the height difference between the height position of the convex portion of the periodic structure portion and the height position of the non-formed portion is increased. . In particular, by forming the periodic structure-unformed portion into a saw blade shape, the lubricant can be drawn from the entire periphery of the sliding surface.

  Therefore, the sliding surface structure of the present invention has both the fluid introduction effect and the step effect. The load capacity due to the step effect is less affected by the height position of the convex portion of the periodic structure portion being lower than the height position of the portion where the periodic structure is not formed, compared with the load capacity due to the fluid introduction effect.

  Moreover, it is preferable to form a fluid introduction groove having a pumping effect deeper than the depth of the concave portion of the periodic structure portion on the upstream side in the sliding direction of the periodic structure portion. With this configuration, the dynamic pressure by the fluid introduction groove is efficiently generated at high speed and low load. If there is no fluid introduction groove, a negative pressure region is generated upstream in the sliding direction of the periodic structure part. However, the provision of the fluid introduction groove eliminates the negative pressure region and can greatly increase the load capacity. it can.

  It is preferable that the height difference between the height position of the convex portion of the periodic structure portion and the height position of the non-formed portion is equal to or greater than the arithmetic average roughness of the sliding surface. Moreover, it is preferable that the height difference between the height position of the convex portion of the periodic structure portion and the height position of the non-formed portion is equal to or less than the maximum height roughness of the sliding surface.

  The periodic pitch of the periodic structure portion is preferably 10 μm or less, and the depth of the concave portion of the periodic structure portion is preferably 1 μm or less. Moreover, it is preferable that one end part of all the recessed parts of a periodic structure part opens outside, and becomes a fluid inlet.

  It is preferable that the depth of the fluid introduction groove is not less than 3 times and not more than 100 times the recess depth of the periodic structure portion. When the groove depth is about the same as the oil film thickness, the load capacity is maximized. Therefore, the load capacity due to the periodic structure portion rapidly decreases when the oil film thickness is on the order of microns. At this time, by setting the depth of the fluid introduction groove having the pumping effect in this way, a sufficient load capacity for holding the oil film can be obtained even when the oil film thickness is in the micron order. If the depth of the fluid introduction groove is less than three times the depth of the concave portion of the periodic structure portion, the effect of reducing the friction coefficient at high speed and low load becomes small, and the negative pressure region is also obstructed. If the depth of the fluid introduction groove exceeds 100 times the depth of the concave portion of the periodic structure portion, a load capacity can hardly be obtained with an oil film thickness on the order of microns.

  The periodic structure portion is preferably 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. Moreover, it is preferable that the periodic structure portion and the height difference are formed by simultaneous processing.

In the sliding surface structure of the present invention, the aggression by the periodic structure portion is alleviated, an increase in wear of the counterpart member can be prevented, and a stable function can be exhibited over a long period of time as the sliding surface structure. In addition, it has both fluid introduction effect (pumping effect) and step effect, which can effectively reduce the aggressiveness of the periodic structure part while keeping the load capacity reduction low, and can provide a high quality sliding surface structure It becomes. Lubricant can be drawn from the entire periphery of the sliding surface, and a load capacity can be obtained by the pumping effect and the step effect efficiently without generating negative pressure.

  In particular, by providing a fluid introduction groove having a pumping effect on the upstream side in the sliding direction of the periodic structure portion, excellent fluid / mixed lubrication characteristics are provided. In addition, the wear powder can be collected in the fluid introduction groove, and the deterioration of the lubricity sliding property due to the wear powder can be prevented.

  If the height difference between the height position of the convex portion of the periodic structure portion and the height position of the non-formed portion is equal to or greater than the arithmetic average roughness of the sliding surface, the periodic structure can be obtained in a mixed lubrication state involving contact between the two surfaces. It slides with almost no load support. For this reason, the aggressiveness of a periodic structure part can be reduced significantly.

  If the height difference between the height position of the convex portion of the periodic structure portion and the height position of the non-formed portion is set to be equal to or less than the maximum height roughness of the sliding surface, a significant reduction in load capacity can be prevented. .

  When the concavo-convex pitch of the periodic structure portion is 10 μm or less, it is possible to redundantly suppress the leakage of the lubricant (side leakage) due to the waviness of the sliding surface, and to efficiently obtain the dynamic pressure. . When the depth of the concave portion of the periodic structure portion is 1 μm or less, the oil film variation is small and high load capacity and rigidity can be obtained. Also, in mixed lubrication, there is an action of reducing the load of the solid contact portion, and the friction reducing effect is exhibited. In the case where one end portion of all the concave portions of the periodic structure portion is opened to the outside, the lubricant can be drawn from the entire periphery of the sliding surface.

  By setting the depth of the fluid introduction groove as described above, the friction coefficient at high speed and low load can be reduced, and the load capacity can be obtained with an oil film thickness on the order of microns.

  The periodic structure is irradiated with a linearly polarized laser beam with an irradiation intensity in the vicinity of the processing threshold, scanned while overlapping the irradiated part, and is formed in a self-organized manner. Those having a pitch and a depth of unevenness can be easily formed.

  In the case where the periodic structure portion and the height difference are formed by simultaneous processing, the processing time can be shortened, and the productivity can be improved and the cost can be reduced. Simultaneous machining is possible by adjusting the output of the laser, and the height difference between the convex part height position of the periodic structure part and the height position of the non-formed part can be adjusted simultaneously with the formation of the periodic structure. The sliding surface can be formed with a roughness order.

It is a principal part expanded sectional view of the sliding face structure which shows the 1st Embodiment of this invention. FIG. 2 is a simplified diagram of a sliding surface having a periodic structure portion of the sliding surface structure shown in FIG. 1. It is an enlarged view of the periodic structure part formed in the said sliding surface. It is a simplification figure of the laser surface processing apparatus for forming the said periodic structure part. It is a graph for demonstrating the definition of arithmetic mean roughness. It is a graph for demonstrating the definition of maximum height roughness. The modification of the periodic structure part and non-formation part which are formed in a sliding surface is shown, (a) is the simplified figure with which the corner part of a non-formation part corresponds to the outer periphery of the 1st member, (b ) Is a simplified diagram in which a corner portion is not formed in an unformed portion. It is a principal part expanded sectional view of the sliding surface structure which shows the 2nd Embodiment of this invention. FIG. 9 is a simplified view of a sliding surface having a periodic structure portion of the sliding surface structure shown in FIG. 8. It is a graph which shows the relationship between an oil film thickness and load capacity. A comparative example is shown, (a) is a schematic diagram of a sliding surface on which a periodic structure portion of a spiral pattern is formed, and (b) is a schematic diagram of a sliding surface on which a periodic structure portion of a step pattern is formed. . It is a graph which shows the relationship between level | step difference height and load capacity. It is a graph which shows the comparison of the average friction coefficient of a spiral pattern and a saw blade spiral pattern. It is a graph which shows the comparison of the average friction coefficient of a spiral pattern and a (groove + saw blade spiral) pattern. It is a graph which shows the comparison of the average friction coefficient of the test piece which formed only the fluid introduction groove | channel, a saw blade spiral pattern, and a (groove + saw blade spiral) pattern.

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

  As shown in FIG. 1, the sliding surface structure according to the present invention is such that the sliding surface 1a of the first member 1 and the sliding surface 2a of the second member 2 slide relative to each other under the lubricant L. It is. In this case, the first member 1 and the second member 2 may be carbon steel, copper, aluminum, platinum, cemented carbide, silicon ceramics such as silicon carbide or silicon nitride, engineer plastic, etc. It may be. Further, the lubricant L may be water or alcohol, or may be a lubricating oil such as engine oil. That is, various lubricants can be used depending on the material of the first and second members 1 and 2 and the environment in which they are used. Moreover, the 1st member 1 was made into the ring body as shown, for example in FIG. 2, and the 2nd member 2 was comprised by the disk shaped body, for example.

  The upper surface of the first member 1 becomes the sliding surface 1a, and the lower surface of the second member 2 becomes the sliding surface 2a. The sliding surface 1a of the first member 1 is provided with a periodic structure portion 3 having grating-like irregularities and a periodic structure non-formed portion 8 in which the periodic structure portion is not formed. That is, the ring-shaped periodic structure assembly portion 7 having the plurality of periodic structure portions 3 and the inner diameter side ring portion 9 are arranged on the sliding surface 1a of the first member 1 at a predetermined pitch along the circumferential direction. Thus, a periodic structure non-formed aggregate part 4 composed of a plurality of periodic structure non-formed parts 8 is formed. In this case, the periodic structure non-formation part 8 has a saw blade shape. In other words, the periodic structure non-formed portion 8 is composed of a plurality of fan-shaped bodies having a straight base 8a and an arcuate hypotenuse 8b.

  As shown in FIG. 3, the periodic structure portion 3 is formed by alternately arranging minute concave portions 5 and minute convex portions 6 at a predetermined pitch. It is preferable that the irregular pitch of the periodic structure portion 3 is 10 μm or less and the depth of the concave portion 5 is 1 μm or less. In this case, the concave portion 5 of the periodic structure portion 3 communicates (opens) with the outer peripheral edge (sliding surface peripheral edge) 1 b of the first member 1. There is no opening in the inner peripheral edge 1 c of the first member 1. Further, the central angle α of the periodic structure non-formed portion 8 is set to 19 deg, for example, and the central angle β of the interval between the adjacent periodic structure non-formed portions 8 is set to 26 deg, for example. Further, the corner portion 8 c between the bottom side 8 a and the oblique side 8 b of the periodic structure-unformed portion 8 is disposed closer to the inner diameter than the outer peripheral edge of the first member 1.

  The concave portion 5 of the periodic structure portion 3 is curved in a spiral shape, and the bending direction thereof is matched with the bending direction of the hypotenuse 8b of the non-formed portion 8. Then, when at least one of the first member 1 and the second member 2 rotates around its axis, the periodic structure portion 3 of the first member 1 is lubricated from the outer peripheral edge side of the sliding surface 1a. Is set to be introduced into the first member 1. In this case, since all the concave portions 5 of the periodic structure portion 3 are open to the outer peripheral edge 1b of the first member 1, the lubricant can be drawn from the entire peripheral edge of the sliding surface.

  The periodic structure portion 3 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 overlapping portions 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. A femtosecond laser is a light source that compresses energy in an extremely short time unit of the order of femtoseconds (one thousandth of a second).

  That is, when a workpiece (working material) W is irradiated with a linearly polarized laser beam at a fluence near the ablation threshold, the pitch and grooves on the order of wavelengths are caused by interference between incident light and scattered light or plasma waves along the surface of the processing material W. A grating-like periodic structure having a depth is formed in a self-organizing manner perpendicular to the polarization direction. At this time, the periodic structure part 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 processing 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. In addition, the said FIG. 3 is the figure which imaged the periodic structure part 3 formed with the said femtosecond laser surface processing apparatus with the electron microscope.

  And in the sliding surface structure of this invention, as shown in FIG. 1, the convex part height position of the periodic structure part 3 is set lower than the height position of the non-formation part 8. As shown in FIG. The height difference between the convex portion height position A of the periodic structure portion 3 and the height position B of the non-formed portion 8 is determined by the sliding surface 1a (the non-formed portion 8 on the upper surface of the first member 1 and the periodic structure portion 3 on the inner diameter side). Of the average surface roughness Ra). Further, this height difference is set to be equal to or less than the maximum height roughness Rz of the sliding surface 1a.

As shown in FIG. 5, the arithmetic average roughness Ra is obtained by extracting only the reference length from the roughness curve in the direction of the average line, the X axis in the direction of the average line m of the extracted portion, and the direction of the vertical magnification. When the Y-axis is taken and the roughness curve is represented by y = f (x), the value obtained by the following equation 1 is represented by micrometers (μm).

  Further, as shown in FIG. 6, the maximum height roughness Rz is obtained by extracting only the reference length from the roughness curve in the direction of the average line m, and roughening the distance between the peak line and the valley line of the extracted part. It is measured in the direction of the vertical magnification of the curve, and this value is expressed in micrometers (μm). That is, (Rz = Rp + Rv).

  In the present invention, as shown in FIG. 1, the height from the sliding surface 1 a to the convex portion height position A of the periodic structure portion 3 is referred to as a step height (height difference) T. The depth (depth of the concave portion 5 of the periodic structure portion 3) is called a periodic structure portion depth T1, and the gap between the sliding surfaces during the sliding motion is called a smooth portion clearance S.

  The periodic structure 3 and the height difference (step height) T can be formed by simultaneous processing. That is, in the femtosecond laser surface processing apparatus, when the periodic structure portion 3 is formed, the simultaneous processing can be performed by adjusting the output of the laser.

  In the sliding surface structure of the present invention, by setting the convex portion height position A of the periodic structure portion 3 to be lower than the height position B of the non-formed portion 8, in the mixed lubrication with contact between the two surfaces, Aggressiveness by the structure is reduced. Here, the aggression property by the periodic structure part 3 is wear increase property or damage property to the counterpart member. Further, since the periodic structure portion 3 communicates with the sliding surface peripheral edge 1b, the lubricant L is introduced from the sliding surface peripheral edge 1b into the sliding surface inward by the sliding operation of the first member and the second member. (This action is called fluid introduction effect (pumping effect)). The load capacity due to the step effect is less affected by the step height (height difference between the convex part height position of the periodic structure part and the non-formed part height position) than the load capacity due to the pumping effect. The wear and aggressiveness of the periodic structure can be reduced while keeping the reduction low. Thus, the periodic structure portions 3 and the non-formed portions 8 are alternately formed along the sliding direction, and the convex portion height position A of the periodic structure portion 3 is set higher than the height position B of the non-formed portion 8. If the pressure is set too low, pressure is generated at the boundary between the periodic structure portion 3 and the non-formed portion 8, and a pressure gradient is created in the sliding direction (this action is called a step effect). As described above, by providing the periodic structure portion 3 and the non-formed portion 8, even if the height difference between the convex portion height position A of the periodic structure portion 3 and the height position B of the non-formed portion 8 is increased, the load is increased. The decrease in capacity can be reduced. In particular, by forming the periodic structure-unformed portion into a saw blade shape, the lubricant can be drawn from the entire periphery of the sliding surface.

  Therefore, the sliding surface structure of the present invention has both the fluid introduction effect and the step effect. The load capacity due to the step effect is less affected by the fact that the convex height position A of the periodic structure portion 3 is lower than the height position B of the periodic structure-unformed portion 8 as compared with the load capacity due to the fluid introduction effect.

  That is, in the sliding surface structure of the present invention, the aggression by the periodic structure portion 3 is mitigated, and the wear of the counterpart member (in this case, the second member 2) can be prevented, and the sliding surface structure is stable for a long time. Function can be demonstrated. In addition, it has both a fluid introduction effect (pumping effect) and a step effect, effectively reducing the aggression of the periodic structure 3 while keeping the load capacity low, and providing a high quality sliding surface structure. It becomes possible. Lubricant can be drawn from the entire periphery of the sliding surface, and a load capacity can be obtained by the pumping effect and the step effect efficiently without generating negative pressure.

  If the height difference between the height position A of the convex portion of the periodic structure portion 3 and the height position B of the non-formed portion 8 is equal to or greater than the arithmetic average roughness of the sliding surface, a mixed lubrication state involving contact between the two surfaces The sliding structure slides with almost no load support. For this reason, the aggressiveness of the periodic structure part 3 can be reduced significantly.

  If the height difference between the convex part height position A of the periodic structure part 3 and the height position B of the non-formed part 8 is less than or equal to the maximum height roughness of the sliding surface 1a, a significant reduction in load capacity is prevented. can do.

  When the concavo-convex pitch of the periodic structure portion 3 is set to 10 μm or less, the leakage (side leakage) of the lubricant L due to the waviness of the sliding surface can be suppressed redundantly, and the dynamic pressure can be obtained efficiently. Can do. When the depth of the concave portion 5 of the periodic structure portion 3 is 1 μm or less, the oil film variation is small and high load capacity and rigidity can be obtained. Also, in mixed lubrication, there is an action of reducing the load of the solid contact portion, and the friction reducing effect is exhibited. In the case where one end portion of all the concave portions of the periodic structure portion is opened to the outside, the lubricant can be drawn from the entire periphery of the sliding surface.

  The periodic structure is irradiated with a linearly polarized laser beam with an irradiation intensity in the vicinity of the processing threshold, scanned while overlapping the irradiated part, and is formed in a self-organized manner. Those having a pitch and a depth of unevenness can be easily formed.

  If the periodic structure portion 3 and the height difference are formed by simultaneous machining, the machining time can be shortened, and the productivity can be improved and the cost can be reduced. Simultaneous machining is possible by adjusting the output of the laser, and the height difference between the convex part height position of the periodic structure part and the height position of the non-formed part can be adjusted simultaneously with the formation of the periodic structure. The sliding surface can be formed with a roughness order.

  Next, FIG. 7 shows a modified example, and FIG. 7A shows a case where the corner 8c of the base 8a and the hypotenuse 8b of the non-formed part 8 coincides with the outer periphery of the first member 1. . Moreover, in FIG.7 (b), the non-formation part 8 does not form the edge part 8c. That is, the outer peripheral edge 20 of the bottom 8a of the non-formed part 8 and the outer peripheral edge 21 of the hypotenuse 8b of the non-formed part 8 coincide with the outer peripheral edge 1b of the first member 1 in a state of being shifted in the circumferential direction. . Even if it is what is shown to this Fig.7 (a) (b), there exists an effect similar to what is shown in the said FIG.

  Next, FIG. 8 and FIG. 9 show a second embodiment of the sliding surface structure. In this sliding surface structure, the fluid introduction groove 30 is provided on the first member 1 in which the periodic structure portion 3 is formed on the upstream side in the sliding direction of the periodic structure portion 3. That is, the fluid introduction groove 30 is an arc-shaped concave groove formed along the arc-shaped oblique side 8 b of the non-formed portion 8, and opens to the outer peripheral edge 1 b of the first member 1. There is no opening in the inner peripheral edge 1c.

  The depth d of the fluid introduction groove 30 is not less than 3 times and not more than 100 times the recess depth T1 of the periodic structure portion 3. For example, the width dimension W1 of the fluid introduction groove 30 is about 0.6 mm, and the depth dimension d of the fluid introduction groove 30 is about 3 μm. Further, the depth d of the fluid introduction groove 30 is not less than 3 times and not more than 100 times the height difference T between the convex portion height position A of the periodic structure portion 3 and the height position B of the non-formed portion 8. Also good. In this case, the recess depth T1 and the height difference T may be the same, T1> T, or T1 <T.

  By providing the fluid introduction groove 30, the dynamic pressure by the fluid introduction groove 30 is efficiently generated at high speed and low load. If there is no fluid introduction groove 30, a negative pressure region may be generated upstream of the periodic structure in the sliding direction. However, the provision of the fluid introduction groove 30 eliminates the negative pressure region, greatly increasing the load capacity. Can be increased. For this reason, providing the fluid introduction groove 30 provides excellent fluid / mixed lubrication characteristics.

  Further, by providing the fluid introduction groove 30, wear powder that may be generated during sliding or the like can be collected in the fluid introduction groove 30, and the deterioration of the lubricity sliding property due to the wear powder can be prevented.

  As described above, the depth of the fluid introduction groove 30 is preferably 3 to 100 times the recess depth T1 of the periodic structure portion 3. When the groove depth is about the same as the oil film thickness, the load capacity is maximized. Therefore, the load capacity due to the periodic structure portion 3 rapidly decreases when the oil film thickness is on the order of microns. At this time, by setting the depth of the fluid introduction groove 30 having the pumping effect in this way, even when the oil film thickness is in the micron order, a sufficient load capacity for holding the oil film can be obtained. If the depth of the fluid introduction groove 30 is less than three times the depth of the concave portion of the periodic structure portion 3, the effect of reducing the friction coefficient at high speed and low load is reduced, and the negative pressure region can be eliminated. On the other hand, when the depth of the fluid introduction groove 30 exceeds 100 times the depth of the concave portion of the periodic structure portion 3, load capacity can hardly be obtained with an oil film thickness on the order of microns. For this reason, if the depth of the fluid introduction groove 30 is set to the above-described depth, the friction coefficient at high speed and low load can be reduced, and the load capacity can be obtained with the oil film thickness on the order of microns.

  As mentioned above, although it demonstrated per embodiment of this invention, this invention is not limited to the said embodiment, A various deformation | transformation is possible, for example, in the said embodiment, the periodic structure part 3 is the 1st member 1 side. However, the periodic structure portion 3 may be formed on the second member 2 side or 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 can be configured in other various shapes. The size and shape of the periodic structure portion 3 and the number, size, or shape of the unformed portions 8 are not limited to those shown in FIGS. 2 and 7, that is, the unformed portion 8 may be triangular or the like, Various changes can be made according to the size, material, type of lubricant, sliding speed, etc. of the first and second members used. Of course, it is preferable to provide the fluid introduction groove 30 as shown in FIG. 8 also in the sliding surface structure provided with the periodic structure portion 3 as shown in FIG.

  Even if the relative sliding movement 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 slid (rotated), the second member 2 side is reversed. May be fixed, and the first member side may be slid (rotated). That is, the direction in which the periodic structure portion 3 is formed may be slid, or the direction in which the periodic structure portion 3 is not formed may be slid (rotated). Further, both the first member 1 and the second member 2 may be slid (rotated).

  Moreover, in the said embodiment, in the periodic structure part 3 shown in FIG. 1 etc., the recessed part 5 is opened to the outer periphery 1b without opening to the inner periphery 1c of the 1st member 1, and it is made to open from an outer peripheral side to an inner peripheral side. The lubricant is drawn in, but conversely, the recess 5 may be opened in the inner peripheral edge 1c without opening in the outer peripheral edge 1b, and the lubricant may be drawn in from the inner peripheral side to the outer peripheral side.

  In the embodiment, the concave portion 5 of the periodic structure portion 3 is curved in a spiral shape, and the bending direction thereof is matched with the bending direction of the hypotenuse 8b of the non-formed portion 8, but it may be a case where they are not matched. That is, the bending direction of the periodic structure portion 3 may be twisted or struck along the circumferential direction with respect to the bending direction of the hypotenuse 8b of the non-formed portion 8.

  Furthermore, although the center angle α of the unformed portion 8 and the center angle β of the interval between the adjacent unformed portions 8 can be arbitrarily set, α: β = 1: 2-1 in order to effectively exhibit the step effect. : About 1 is preferable.

  By the way, in the said embodiment, when forming the periodic structure part 3, the femtosecond laser which is a pulse laser was used, However, Pulse lasers, such as picosecond lasers and nanosecond lasers other than a femtosecond laser, can also be used. .

  According to the sliding surface structure of the present invention, the fluid introduction effect and the step effect can be exhibited and low friction can be obtained. For this reason, the sliding surface structure of the present invention can be used for various devices such as various automobile parts, machine parts, and pumps.

  In the sliding surface structure shown in FIG. 8 and FIG. 9, the depth dimension and the width dimension of each fluid introduction groove 30 are set to be the same, but the fluid introduction groove 30 has a different depth dimension and width dimension. It may be. When the different fluid introduction grooves 30 are provided, it is preferable to arrange the different fluid introduction grooves 30 in a balanced manner so that the first member 1 and the second member 2 do not perform unbalanced rotational sliding. Thus, if the fluid introduction grooves 30 having different depth dimensions and the like are arranged, the pumping effect different for each different fluid introduction groove 30 can be exhibited, and the optimum function can be exhibited for the equipment to be used. . Further, in the sliding surface structure shown in FIGS. 8 and 9, the fluid introduction groove 30 is continuously provided for each periodic structure portion 3, but the desired periodic structure portion 3 is not provided for each periodic structure portion 3. Alternatively, the fluid introduction groove 30 may be provided continuously.

  A step height T (see FIG. 1) is provided to alleviate the wear of the periodic structure portion 3 and the opponent's aggression. It is effective to make it lower. However, when the step height T is increased, the load capacity is reduced and the load sharing ratio of the oil film is lowered, so that the mixed lubrication characteristics are also adversely affected. Therefore, it is desired to develop a patterning that hardly affects the load capacity due to the height of the step. At the same time, low friction during fluid lubrication is also strongly desired.

  As shown in FIG. 11A to be described later, in the spiral periodic structure, an oil film that is thinner and more rigid than a general spiral groove bearing having a groove depth of micron size is formed. FIG. 10 shows the result of calculating the relative load capacity when the groove depth of the spiral pattern is 200 nm and 6 μm. It can be seen that when the oil film thickness is reduced, the groove depth of 200 nm is overwhelmingly high in load capacity and rigidity. When the groove depth is 6 μm, there is little increase in load capacity as the oil film thickness decreases, so contact between the two surfaces easily occurs due to load fluctuations and vibration. On the other hand, when the groove depth is 200 nm, when the oil film thickness is reduced from 1 μm to 0.1 μm, the load capacity increases by three orders of magnitude, so that contact between the two surfaces can be substantially avoided on the sliding surface with high flatness. .

  The grating-like periodic structure with submicron periodic pitch and groove depth causes almost no load capacity when the oil film thickness increases to several microns, so the oil film thickness varies from low speed / high load to high speed / low load. Is suitable for a mechanical seal or a guide surface of a machine tool that requires a small oil film formation at all times. However, the friction coefficient at high speed and low load is a relatively high value for fluid lubrication. In view of this, a sliding surface structure capable of obtaining excellent lubrication characteristics under a wide range of sliding conditions ranging from fluid lubrication to mixed lubrication was studied.

  As a test piece (ring test piece), the periodic structure portion 3 has a spiral pattern as shown in FIG. 11 (a) and the periodic structure portion 3 has a step pattern as shown in FIG. 11 (b). used. That is, in FIG. 11B, there are six periodic structure portions 3 (3A) arranged concentrically at a predetermined pitch along the circumferential direction, and the non-periodic structure portion 4 is a test piece (ring test piece). Of the ring portion 4a disposed on the inner diameter side of the first and second non-formed portions 8 (8A) having a substantially rectangular shape disposed between the periodic structure portions 3A.

  The test piece of FIG. 11 (a) is a periodic structure part (pitch 0.7 μm, depth 0.2 μm) formed in a spiral shape, and the test piece of FIG. 11 (b) is a concentric periodic structure part. Is formed intermittently along the circumferential direction. FIG. 11 is a schematic diagram of each pattern, and the load capacity of each pattern (spiral pattern, step pattern) was calculated using the infinite groove number theory.

  FIG. 12 shows the relationship between the step height and the load capacity when the smooth portion clearance S (see FIG. 1) is 0.2 μm and the periodic structure forming region of the spiral pattern and step pattern is optimized. The spiral pattern can obtain a large load capacity at a step height of 0, but the load capacity decreases exponentially as the step height increases. In the step pattern, the load capacity once increases due to the increase in the step height, and then gradually decreases. The load capacity of the step pattern is less affected by the step height compared to the spiral pattern, and the load capacity of the step pattern is slightly larger than the spiral pattern at the step height of 0.1 μm. However, the step pattern has no pumping effect. The vertical axis in FIG. 12 is an arbitrary unit (au).

  Therefore, a sawtooth spiral pattern (pattern shown in FIG. 2) was created as a pattern in which a spiral periodic structure is connected to the entire periphery of the sliding edge and has a pumping effect and a step effect. By combining the pumping effect and the step effect, it is possible to provide a sliding surface structure that can reduce the aggressiveness of the periodic structure while keeping the load capacity from being reduced.

  Furthermore, a (groove + saw blade spiral) pattern (pattern shown in FIG. 9) was created by combining a spiral fluid introduction groove having both a pumping effect and a negative pressure elimination effect and a saw blade spiral. In the (Groove + Saw Blade Spiral) pattern, the spiral groove is expected to improve the lubrication characteristics at high speed and low load, as well as the effect of collecting wear powder and retaining the lubricant during mixed lubrication.

  Experiments were performed using a ring-on-disk test apparatus. The ring test piece was a rotating side test piece (SUS440C), and the disk test piece (alumina) was a fixed side test piece. The surface roughness of each test piece was set to Ra 0.02 μm or less. All disk test pieces are mirror surfaces, and ring test pieces (outer diameter 16 mm, inner diameter 10 mm) are spirals (pattern shown in FIG. 11A), saw blade spirals (pattern according to the present invention shown in FIG. 2), and (grooves). + Saw blade spiral) (pattern shown in FIG. 9). The inclination angle of the periodic structure with respect to the sliding direction was θ = 45 °. The pitch of the periodic structure was about 0.7 μm, the depth was about 0.2 μm, and the step height was about 0.1 μm. The width of the fluid introduction groove 30 was 0.6 mm, and the depth of the fluid introduction groove 30 was 3 μm. For comparison, a test piece in which only the fluid introduction groove 30 (width 0.6 mm, depth 3 μm) was formed was also prepared. In order to evaluate basic lubrication characteristics, PAO4 (18.82 cP @ 37 ° C.) having no polarity and being thermally and chemically stable was used as the lubricant. The load was 40 N (0.33 MPa), and the average friction coefficient of 5 min at each sliding speed was measured while the sliding speed was gradually reduced from 81.5 mm / s to 3.3 mm / s. In the sawtooth spiral pattern, the center angle α of the unformed portion 8 is 19 deg, and the center angle β of the interval between the adjacent unformed portions 8 is 26 deg.

  A comparison of the average friction coefficient between the spiral and the saw blade spiral is shown in FIG. The saw blade spiral can be said to be an effective pattern for increasing the load capacity because the friction coefficient in the fluid lubrication region is reduced despite the fact that the mirror surface portion with the minimum oil film thickness is wider than the spiral. In addition, the rising gradient of the coefficient of friction in the low-speed sliding region, which is mixed lubrication, is also reduced. In addition to the pumping effect due to the periodic structure and the step effect due to the step height, the load capacity due to the shape of the periodic structure forming region that tapers toward the inner circumference is generated as a factor of the load capacity increase. Possible possibility. FIG. 14 shows a comparison of the average friction coefficient between the spiral and the (groove + saw blade spiral). In the case of (groove + sawtooth spiral), the friction coefficient in the fluid lubrication zone decreases to about 1/3 of the spiral.

  Further, FIG. 15 shows a comparison of average friction coefficients of the test pieces in which only the saw blade spiral (groove + saw blade spiral) and the fluid introduction groove 30 are formed. The test piece in which only the fluid introduction groove 30 having a depth of 3 μm formed a lower friction than the saw blade spiral in a high speed region where a relatively thick oil film was formed. However, the load capacity was small in the low speed region where the oil film was thin, and seizure occurred. Combining the fluid introduction groove and the saw blade spiral (groove + saw blade spiral) was not an intermediate property between the two, and had the lowest friction in all speed ranges. In the high speed range, the characteristics of the fluid introduction groove 30 are asymptotic, and fluid lubrication becomes dominant up to the low speed range. The average equivalent clearance calculated from the average friction coefficient of 0.002 at (groove + sawtooth spiral) at 3.3 mm / s was 86 nm. Such a sliding state through an extremely thin oil film is considered to be realized by the high load capacity of the periodic structure 3 and the progress of ideal familiarity. As the average equivalent clearance becomes smaller, the pumping effect by the fluid introduction groove 30 becomes almost negligible, but the negative pressure elimination effect, foreign matter trapping effect, and lubricant retention effect by the fluid introduction groove 30 are ideally familiar. It is thought that it contributed.

DESCRIPTION OF SYMBOLS 1 1st member 1a Sliding surface 1b Sliding surface peripheral edge 1c Inner peripheral edge 2 Second member 2a Sliding surface 3 Periodic structure part 5 Recessed part 6 Convex part 8 Periodic structure non-formation part 30 Fluid introduction groove

The sliding surface structure of the present invention is a sliding surface structure in which the sliding surface of the first member and the sliding surface of the second member slide relative to each other under a lubricant. on one of the sliding surfaces at least one of the members, and the periodic structure of the grating-like unevenness that would allow for introduction into the sliding surface inwardly of the lubricant from the sliding surface peripheral edge and communicating with the sliding surface periphery, Periodic structure non-formed parts that generate a pressure gradient in the sliding direction at the boundary with the periodic structure part are alternately formed along the sliding direction, and the height of the convex part of the periodic structure part is not formed. And the shape of the periodic structure non-formed part is a saw blade shape.

The sliding surface structure of the present invention is a sliding surface structure in which the sliding surface of the first member and the sliding surface of the second member slide relative to each other under a lubricant. A periodic structure portion of grating-like irregularities that communicates with the periphery of the sliding surface and allows introduction of the lubricant from the periphery of the sliding surface to the inside of the sliding surface, on at least one of the sliding surfaces of the member; Periodic structure non-formed parts that generate a pressure gradient in the sliding direction at the boundary with the periodic structure part are alternately formed along the sliding direction, and the height of the convex part of the periodic structure part is not formed. In addition, the shape of the portion where the periodic structure is not formed is a saw blade shape that allows the lubricant to be drawn from the entire periphery of the sliding surface with which the periodic structure portion communicates .

Claims (10)

A sliding surface structure in which the sliding surface of the first member and the sliding surface of the second member slide relative to each other under a lubricant, the sliding surface of at least one of the first member and the second member. On the moving surface, the periodic structure portions of the grating-like irregularities communicating with the periphery of the sliding surface are alternately formed along the sliding direction, and the height of the convex portion of the periodic structure portion is determined. A sliding surface structure, wherein the sliding surface structure is set lower than the height position of the non-formed part and the shape of the non-formed periodic structure part is a saw blade shape.   The sliding surface structure according to claim 1, wherein a fluid introduction groove having a pumping effect deeper than a depth of the concave portion of the periodic structure portion is formed on the upstream side in the sliding direction of the periodic structure portion.   The height difference between the height position of the convex portion of the periodic structure portion and the height position of the non-formed portion is equal to or greater than the arithmetic average roughness of the sliding surface. Sliding surface structure.   The height difference between the height position of the convex portion of the periodic structure portion and the height position of the non-formed portion is equal to or less than the maximum height roughness of the sliding surface. The sliding surface structure according to claim 1.   The sliding surface structure according to any one of claims 1 to 4, wherein a periodic pitch of the periodic structure portion is 10 µm or less.   The sliding surface structure according to any one of claims 1 to 5, wherein a depth of the concave portion of the periodic structure portion is 1 µm or less.   The sliding surface structure according to any one of claims 1 to 6, wherein one end portion of all the concave portions of the periodic structure portion opens to the outside to become a fluid introduction port.   The sliding surface structure according to any one of claims 1 to 7, wherein a depth of the fluid introduction groove is set to be not less than 3 times and not more than 100 times a recess depth of the periodic structure portion. .   The periodic structure part is formed in a self-organized manner by irradiating a linearly polarized laser beam with an irradiation intensity in the vicinity of a processing threshold and scanning the overlapping part in an overlapping manner. The sliding surface structure according to claim 8.   The sliding surface structure according to claim 9, wherein the periodic structure portion and the height difference are formed by simultaneous processing.