JP2020056438A - Contact area structure product and method for forming contact area structure product - Google Patents

Abstract

To provide a contact area structure product capable of improving oil release degree without depending on base oil kinetic viscosity and worked penetration, to improve oil film formation capability and protective film formation capability, and reduce fretting wear, and a method for forming the contact area structure product.SOLUTION: A contact surface structure product relatively vibrates or minutely moves under grease lubrication. On at least one of a contact surfaces, a periodic structure of grating-shaped irregularities whose height continuously changes is formed, where convex vertices become non-flat surfaces. Moreover, a ratio (A/D) of an amplitude A of the vibration or minute movement to a contact width D in a minute movement direction is more than or equal to 1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a contact surface structure product and a method for forming the contact surface structure product.

  When vibrations or minute oscillating movements act on the rolling bearings or the mating surfaces of the shafts, the lubricant does not spread to the contact surfaces, and fretting wear may occur. Fretting wear has an adverse effect on accuracy, bearing torque, and the like, and therefore, improvement of fretting resistance has been an issue.

  Patent Literature 1 proposes a rolling bearing that prevents abrasion (fretting wear) of contact surfaces between a pair of track members and a rolling element during a minute swing. In the rolling bearing described in Patent Document 1, the amplitude at the time of the minute swing of the pair of track members is A, the radius of the contact circle generated on the track surfaces of the pair of track members in contact with the rolling elements is B, and the amplitude A is Assuming that the ratio (A / B) to the radius B of the osculating circle is the amplitude ratio R, the amplitude ratio R at the time of minute swing exceeds 1.5.

JP 2008-95868 A

  Grease is a semi-solid lubricant in which a fine solid called a thickener is dispersed in a liquid lubricant (base oil or base oil). When tangential vibration or micro-oscillating motion acts under grease lubrication, the fretting resistance improves as the kinematic viscosity of the base oil of the grease decreases and the penetration becomes higher (the degree of oil release increases). This is thought to be due to the fact that grease with a low base oil kinematic viscosity and a large degree of penetration has a high degree of oil release, and the high-concentration thickener remaining in the contact area forms a protective film to improve fretting resistance. Because.

  In the case of Patent Document 1, the grease has a low degree of oil separation, and a thickening agent that becomes a material of the protective film together with the base oil is also removed from the contact area, so that the protective film forming ability is poor and fretting wear is reduced. May occur.

  In addition, as a grease for fretting resistance of rocking motion, when a grease having a low base oil kinematic viscosity and a high penetration consistency is used, when the base oil kinematic viscosity is reduced, an oil film forming ability is reduced and an oil film breakage easily occurs. When the mixing penetration becomes large, the thickener for forming the protective film becomes insufficient, so that the ability to form the protective film derived from the thickener decreases. For this reason, it is desirable to improve the degree of oil separation without depending on the kinematic viscosity of the base oil or the penetration consistency.

  In view of the above problems, the present invention improves oil separation without depending on base oil kinematic viscosity and mixing consistency, improves oil film forming ability and protective film forming ability, and reduces fretting wear. And a method for forming the contact surface structure.

  The contact surface structure product of the present invention is a contact surface structure product that relatively vibrates or moves slightly under grease lubrication. A periodic structure of changing grating-like irregularities is formed, and the ratio (A / D) of the amplitude A of the vibration or minute movement to the contact width D in the minute movement direction is 1 or more.

  According to the contact surface structure product of the present invention, at least one of the contact surfaces is formed with a periodic structure of grating-like irregularities in which the height of the convex portion is a non-flat surface and the height is continuously changed. On the other hand, it exhibits high wettability, increases the degree of oil release of the grease, and promotes the formation of a transfer film derived from the thickener. Since the transfer film acts as a protective film, fretting wear can be prevented. Further, by setting the ratio (A / D) of the amplitude A of the vibration or the minute movement to the contact width D in the direction of the vibration or the minute movement to be 1 or more, it is possible to eliminate the constant contact portion where the contact portions overlap. As a result, the re-inflow property of grease and the discharge property of wear powder are improved, and fretting wear can be further prevented.

  In the above-described configuration, the periodic structure of the grating-shaped irregularities may communicate with the outside of the contact surface and abut against the grease attached to the outside of the contact surface. As a result, the oil is separated from the grease outside the contact surface, and the oil is moved into the contact surface, so that fretting wear can be prevented.

  In the above-described configuration, the unevenness of the periodic structure of the grating-shaped unevenness can be 50 nm or more and 10 μm or less, and the periodic pitch can be 10 μm or less. Thereby, the oil retention and mobility can be improved. If the unevenness of the periodic structure is less than 50 nm, a sufficient amount of the thickener cannot be carried, and if the unevenness and the periodic pitch exceed 10 μm, the thickener and oil will almost flow out.

  In the above-mentioned configuration, the periodic structure of the grating-shaped irregularities may be oriented along the direction of vibration or minute movement. As a result, the oil component quickly moves to the contact surface, and the lubrication characteristics can be improved. In addition, the thickener having a high concentration due to the oil releasing action is hardly removed to the side, and is held along the periodic structure, so that the carrying property of the thickener is improved. Further, the discharging property of the wear powder is also improved.

  In the above configuration, grooves in a direction intersecting with the vibration or minute movement direction may be formed on at least one contact surface at an interval smaller than the amplitude A of the vibration or minute movement. Thereby, the contact width in the minute movement direction can be divided. As a result, even when the contact width in the minute movement direction is wide, the ratio (A / D) between the amplitude A of the minute movement and the contact width D in the minute movement direction can be made 1 or more, and fretting wear can be prevented. it can.

  A shaft member and a part having a fitting surface for the shaft member are provided, and the one contact surface is preferably an outer peripheral surface of the shaft member or the fitting surface, and is particularly used for a rolling bearing. Is preferred.

  According to the method for forming a contact surface structure product of the present invention, in the method for forming a contact surface structure product that relatively vibrates or moves slightly under grease lubrication, at least one of the contact surfaces has a convex apex that is a non-flat surface. A periodic structure of grating-like irregularities whose height continuously changes is formed, and the ratio (A / D) between the amplitude A of the vibration or minute movement and the contact width D in the minute movement direction is 1 or more.

  The contact surface structure product and the method for forming the contact surface structure product of the present invention improve the oil separation without depending on the base oil kinematic viscosity and the mixing consistency, and improve the oil film forming ability and the protective film forming ability. And fretting wear can be reduced.

It is a figure which shows the contact part with the 2nd member of the 1st member of the contact surface structure product which shows embodiment of this invention, (a) is A / D <1, (b) is A / D = 1, ( c) shows A / D> 1. FIG. 4 is a simplified perspective view of a state where a first member is slid with respect to a second member. It is an enlarged plan view of a periodic structure. It is a simplified diagram of a laser surface processing device used for forming the periodic structure. It is a simplified plan view of the first member and the second member of the contact surface structure product showing the second embodiment of the present invention. A graph showing the relationship between the amplitude ratio and the length of the ball-side wear mark in the vibration direction when the number of reciprocating movements is 10000, and the relationship between the amplitude ratio and the vibration direction length of the ball-side wear mark when reciprocating 5000 times with a sliding stroke of 4 mm. FIG. FIG. 7 is a photograph of a ball-side wear mark in FIG. 6. It is a graph which shows the result of the ball side wear mark length in 50,000 reciprocations. FIG. 9 is a photograph of the ball-side wear mark in FIG. 8. It is a graph which shows the result of the plate side wear mark depth in 50,000 reciprocating motion times. It is a photograph figure of the plate side wear trace in the said FIG.

  An embodiment of the present invention will be described below with reference to FIGS.

  In the contact surface structure product according to the present invention, as shown in FIG. 2, the first member 1 and the second member 2 relatively perform tangential vibrations and minute movements under grease lubrication. In the present embodiment, “vibration or minute motion” means all motions with small amplitudes such as tangential swings and reciprocating motions with relatively small amplitudes. In the present invention, it is not necessary to distinguish between vibration and minute movement, and "vibration or minute movement" may be simply referred to as minute movement.

  In the illustrated example, the first member 1 is formed of a metal sphere such as SUJ2 (high carbon chromium bearing steel), and the second member 2 is formed of a metal plate such as SUJ2 (high carbon chromium bearing steel). ing. The grease uses alicyclic urea grease in the present embodiment, and is attached to the contact surface of the first member 1 (sphere) with the second member 2.

  As shown in FIG. 3, in the second member 2, a contact surface 2 a with the first member 1 has a grating-like unevenness in which minute concave portions 4 and minute convex portions 5 are alternately arranged at a predetermined pitch. The periodic structure 3 is formed in a band shape with a predetermined width. The height of the periodic structure 3 having the grating-like unevenness changes continuously. It is preferable that the height difference of this unevenness (the height from the bottom of the concave portion 4 to the apex of the convex portion 5) is 50 nm or more and 10 μm or less, and the periodic pitch is 10 μm or less. In the present embodiment, the periodic structure 3 having grating-like irregularities is oriented along the direction of minute movement (the direction of the arrow in FIG. 2). Further, the periodic structure 3 having the grating-like irregularities communicates with the outside of the contact surface 2a, and is in contact with grease adhering to the outside of the contact surface 2a.

The oil contact angle can be expressed by Wenzel's equation as shown in Equation 1. In Equation 1, r is a surface area magnification, and r> 1. θ _e is the contact angle of the smooth surface, and θ _w is the contact angle of apparent. The number 1, a theta _e> In 90 ° become _{θ w> θ e, θ e} <90 ° in θ _w <θ _e. That is, the larger the surface area ratio r, the smaller the oil contact angle, and the better the surface roughness, the better the wettability of the lubricating oil. That is, in this embodiment, when the periodic structure 3 of the grating-like irregularities in which the minute concave portions 4 and the minute convex portions 5 are alternately arranged at a predetermined pitch is formed, a high wettability to oil is exhibited, and The degree of oil separation is increased, and the formation of a transfer film derived from the thickener is promoted. Since the transfer film acts as a protective film, fretting wear can be prevented.

  When the first member 1 and the second member 2 vibrate or move minutely at the amplitude A, the ratio (A / D) between the amplitude A (see FIG. 1) and the contact width D (see FIG. 1) in the minute movement direction is determined. 1 or more. FIG. 1 shows a contact portion 6 of the first member 1 with the second member 2 (an outer edge of a portion where the first member 1 is in contact with the second member 2, and a circular inner portion denoted by reference numeral 6). In contact with the second member 2), and the contact portion 6 reciprocates from the position of the solid line indicated by 6a to the position of the virtual line indicated by 6b. 1A shows a case where A / D <1, FIG. 1B shows a case where A / D = 1, and FIG. 1C shows a case where A / D> 1. That is, in the present embodiment, the first member 1 makes a small movement as shown in FIG. 1B or FIG. 1C.

  When the minute movement between the first member 1 and the second member 2 is A / D <1, as shown in FIG. 1A, a constant contact portion where the contact portions 6 overlap is generated. As shown by hatching in FIG. 1A, the constant contact portion is a portion (region) where the first member 1 is always in contact with the second member 2, and the first member that does not appear outside during exercise. This is an area where the member 1 and the second member 2 are in continuous contact with each other. On the other hand, when the minute movement between the first member 1 and the second member 2 is A / D = 1 as shown in FIG. 1B, or when A / D> 1 as shown in FIG. There is no contact at all times. As a result, the re-inflow property of grease and the discharge property of wear powder are improved, and fretting wear can be further prevented.

  In the method for forming the contact surface structure, first, the periodic structure 3 is formed on the contact surface of the first member 1 or the second member 2. The periodic structure 3 is formed by using a laser surface processing device having a laser generator 11 and an optical system 10, as shown in FIG.

In the laser surface processing apparatus shown in FIG. 4, the laser generator 11 is turned toward the processing material W by the mirror 12 and is guided to the mechanical shutter 13. At the time of laser irradiation, the mechanical shutter 13 is opened, and the laser irradiation intensity is reduced to a half-wave plate 14 and a polarization beam splitter 16.
The polarization direction is adjusted by the half-wave plate 15, and the condensing lens 17 condenses and irradiates the surface of the processing material W on the XYθ stage 19.

  The periodic structure 3 is formed in a self-organizing manner by irradiating a linearly polarized laser with an irradiation intensity near the processing threshold value and scanning while overlapping the irradiated portions. That is, when a work (working material) W is irradiated with a linearly polarized laser beam at a fluence near the ablation threshold, the interference between incident light and scattered light or plasma waves along the surface of the working material W causes the laser light to be substantially equal to the laser wavelength. At periodic intervals, there is a slight densification of the energy distribution. Although the entire laser irradiation surface is processed by a general processing method, high-energy portions can be selectively processed by laser irradiation at an energy density near a processing threshold. As a result, a grating-shaped periodic structure 3 is formed while laser irradiation is performed on one optical axis. At this time, as the pulse width of the laser used for processing becomes longer, the periodic structure is more disturbed due to the influence of heat and the scattering of the laser due to the interaction with the evaporated material.

  Then, as described above, when the first member 1 and the second member 2 vibrate or move minutely with the amplitude A, the ratio (A / D) between the amplitude A and the contact width D in the direction of the minute movement is 1 or more. To be.

  In the present invention, the periodic structure 3 of the grating-like irregularities in which the peaks of the convex portions are non-flat surfaces and whose height continuously changes is formed on at least one of the contact surfaces. As a result, the degree of oil release of the grease increases, and the formation of a transfer film derived from the thickener is promoted. Since the transfer film acts as a protective film, fretting wear can be prevented. In addition, by setting the ratio (A / D) of the amplitude A of the vibration or minute movement to the contact width D in the minute movement direction to be 1 or more, it is possible to eliminate the constant contact portion where the contact portions overlap. As a result, the re-inflow property of grease and the discharge property of wear powder are improved, and fretting wear can be further prevented. As described above, in the present embodiment, it is possible to improve the oil separation degree without depending on the base oil kinematic viscosity and the mixing consistency, improve the oil film forming ability and the protective film forming ability, and reduce the fretting wear. it can.

  In addition, since the periodic structure 3 of the grating-like irregularities communicates with the outside of the contact surface and is in contact with the grease adhering to the outside of the contact surface, the oil separates from the grease outside the contact surface and moves the oil to the inside of the contact surface. By doing so, fretting wear can be prevented.

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

  Since the periodic structure 3 of the grating-shaped irregularities is oriented along the direction of vibration or micro-motion, the oil can quickly move to the contact surface, and the lubrication characteristics can be improved. In addition, the thickener having a high concentration due to the oil releasing action is hardly removed to the side, and is held along the periodic structure, so that the carrying property of the thickener is improved. Further, the discharging property of the wear powder is also improved.

  FIG. 5 shows a second embodiment. A groove 7 is formed on at least one contact surface (the second member 2 in the present embodiment) in a direction intersecting the direction of vibration or minute movement. The number and width of the grooves 7 may be arbitrary, and in the present embodiment, two grooves (7a, 7b) are provided. The grooves 7 are formed at intervals smaller than the amplitude A of the minute movement.

  Thereby, when the first member 1 comes into contact with the second member 2, it does not come into contact with the groove 7, so that the contact portion 6 is divided into regions d 1, d 2 and d 3. That is, the contact width D in the minute movement direction can be divided, and in the present embodiment, the contact width D is divided into three (d1, d2, d3) in the movement direction. As a result, even when the contact width D in the small movement direction is large and (A / D) <1 as shown in FIG. 5, the amplitude A of the small movement and the contact width D in the small movement direction are different from each other. (A / D) can be set to 1 or more, and fretting wear can be prevented.

  The present invention can be variously modified without being limited to the above-described embodiment. For example, the contact surface between the first member 1 and the second member 2 may have a flat surface shape or a convex curved surface shape. The first member 1 and the second member 2 may have a columnar shape, a conical shape or a truncated conical shape. The sliding direction may be circular or elliptical, instead of linear. For this reason, the first member 1 and the second member 2 may not rotate, or may rotate around their axes. In particular, it is preferable that the first member 1 (or the second member 2) is a shaft and the second member 2 (or the first member 1) is a member having a fitting surface with the shaft, and is applied to, for example, a rolling bearing. Is preferred.

  As a laser used in the periodic structure forming step, a pulse laser such as a femtosecond laser, a picosecond laser, and a nanosecond laser can be used. Further, even if the first member 1 is fixed and the second member 2 is slid with respect to the first member 1, on the contrary, the second member 2 is fixed and the first member 1 is , Or the first member 1 and the second member 2 may be slid. The periodic structure 3 may be provided on the first member 1. The type of grease can be arbitrarily selected to be suitable for use as the contact surface structure product of the present invention.

  Using a reciprocating ball-on-plate tester as shown in FIG. 2, a fretting test was performed during a minute reciprocating motion under grease lubrication. The plate test piece was an optically polished SUJ substrate (Ra 2 nm). The ball test piece was a SUJ2 ball (Ra8 nm) having a diameter of 6.35 mm. A grating-shaped periodic structure (pitch: about 900 nm, depth: about 250 nm) was formed on a plate test piece in a band-like region having a width of 1 mm. The orientation direction of the periodic structure was two directions perpendicular to the vibration direction (hereinafter, referred to as a periodic orthogonal plate) and parallel (hereinafter, referred to as a periodic parallel plate). For comparison, an unprocessed plate test piece (hereinafter referred to as a mirror surface plate) was also used.

  The test conditions were as follows: load 5N (Hertz contact circle diameter D = 95 μm), reciprocating speed 4 mm / s, reciprocating amplitude A = 40, 60, 90, 140, 190 μm (amplitude ratio A / D = 0.42, 0. 63, 0.95, 1.47, 2.00), and the number of reciprocating movements was 10,000 (some 50,000). The grease was an alicyclic urea grease (16% thickener, base oil PAO6, consistency 250), and about 0.1 mg was attached to the contact portion on the ball side before the test. For the evaluation of fretting wear, the length of the ball-side wear mark in the vibration direction was used. Those having a reciprocating frequency of 50,000 were also evaluated on the plate side wear scar depth.

  FIG. 6 shows the relationship between the amplitude ratio and the length of the ball-side wear mark in the vibration direction at 10,000 reciprocations. For reference, FIG. 6 also shows wear marks when the reciprocating motion was performed 5000 times with a sliding stroke of 4 mm. FIG. 7 shows a photograph of a ball-side wear mark.

  When the amplitude ratio of the mirror surface plate was 1 or more, the wear scar length increased as the amplitude increased. In addition, as shown in FIG. 7 (Polished), it was considered that the amount of wear increased as the amplitude increased, because the formation of the protective film on the ball-side wear scar was poor regardless of the amplitude ratio in the mirror surface plate.

  The periodic parallel plate had a stable wear scar length equivalent to the Hertzian contact circle diameter at all amplitude ratios. In the periodic structure parallel to the vibration direction, the thickener having a high concentration due to the oil releasing action is hardly removed to the side, and is held along the periodic structure. As a result, as shown in FIG. 7 (Textured (//)), it is considered that the formation of the protective film derived from the thickener (black portion in the photograph) was promoted, and the abrasion amount was reduced. In addition, the effect of suppressing the growth of wear powder by the periodic structure is also considered to be one of the causes of the reduction in the wear amount.

 In the periodic plate, the wear scar length increased rapidly in the low amplitude ratio region (A / D <1) where the contact circles overlap. In the periodic structure perpendicular to the vibration direction, the fluidity of the wear powder is poor, and in the low amplitude ratio region (A / D <1) where continuous contact occurs, the wear powder replaces the grease in the periodic structure in the periodic structure. It is considered that they accumulated and abrasion increased. However, as shown in FIG. 7 (Textured (⊥)), the formation of the protective film derived from the thickener was promoted with the increase in the amplitude ratio, and the wear scar length was equivalent to that of the periodic parallel plate.

  FIG. 8 shows the result of the length of the ball-side wear mark at 50,000 reciprocations, and FIG. 9 shows a photograph of the ball-side wear mark. In FIG. 8, dots are mirror plates, and hatchings are periodic parallel plates. There was almost no difference in the length of the wear trace on the ball side between the mirror surface plate and the periodic parallel plate when A / D = 0.63 where the contact circles overlap. When A / D = 1.47 where the amplitude was larger than the diameter of the contact circle, almost no wear occurred on the periodic parallel plate, and the wear scar length was equivalent to the Hertzian contact circle diameter. With respect to the length of the wear scar on the ball side, the result was almost the same as when the number of reciprocations was 10,000.

  FIG. 10 shows the results of the plate-side wear scar depth when the number of reciprocations was 50000, and FIG. 11 shows a photograph of the plate-side wear scar. In FIG. 10, dots are mirror-surface plates, and hatchings are periodic parallel plates. At A / D = 0.63, the depth of wear mark of the periodic parallel plate was larger than that of the mirror plate. The lubrication was insufficient at the constant contact portions where the contact circles overlap, and the periodic structure was worn. However, when A / D = 1.47, the wear scar depth of the periodic parallel plate was 9 nm, and hardly any wear occurred. Further, at A / D = 2.0, the wear scar depth of the periodic parallel plate was below the detection limit. At this time, formation of a thickening agent-derived protective film (black portion in the photograph) was also observed on the plate side.

  From the above results, it was found that in the present embodiment, under the condition of A / D ≧ 1.47, the periodic structure parallel to the vibration direction is extremely effective in preventing fretting wear on both the ball side and the plate side.

REFERENCE SIGNS LIST 1 first member 2 second member 3 periodic structure 4 convex portion 5 concave portion

Claims (8)

For contact surface structure products that relatively vibrate or move slightly under grease lubrication,
On at least one contact surface, a periodic structure of grating-like irregularities whose height is continuously changed by forming a convex apex as a non-flat surface is formed. A contact surface structure product having a ratio (A / D) to a width D of 1 or more.   2. The contact surface structural product according to claim 1, wherein the grating-like concave-convex periodic structure communicates outside the contact surface and is in contact with grease adhering outside the contact surface. 3.   The contact surface structure product according to claim 1, wherein the unevenness of the periodic structure of the grating-like unevenness is 50 nm or more and 10 μm or less, and the periodic pitch is 10 μm or less.   The contact surface structure product according to any one of claims 1 to 3, wherein the periodic structure of the grating-shaped irregularities is oriented along the direction of vibration or minute movement.   The groove in a direction intersecting the vibration or minute movement direction is formed on at least one contact surface at an interval smaller than the amplitude A of the vibration or minute movement. The contact surface structure product described in the item.   A shaft member and a component having a fitting surface with the shaft member, wherein the one contact surface is an outer peripheral surface of the shaft member or the fitting surface. Item 6. The contact surface structure product according to any one of items 5.   The contact surface structure product according to claim 6, which is used for a rolling bearing. In the method of forming a contact surface structure product that relatively vibrates or moves slightly under grease lubrication,
On at least one contact surface, a peak structure is formed as a non-flat surface to form a periodic structure of grating-like irregularities whose height changes continuously,
A method for forming a contact surface structure, wherein a ratio (A / D) of an amplitude A of vibration or micro motion to a contact width D in the micro motion direction is 1 or more.