sliding mechanism

Abstract

The present invention provides a sliding mechanism that reduces friction. The sliding mechanism includes a ring (20) and a disk (10) that slide against each other, configured such that lubricating oil can pass between a first sliding surface (20A) of the ring (20) opposite to the disk (10) and a second sliding surface (10A) of the disk (10) opposite to the ring (20). The first sliding surface (20A) has corrugations (21). The corrugations (21) include an inclination (21A) in which the distance between the first sliding surface (20A) and the second sliding surface (10A) shortens toward the sliding direction (D) of the ring (20) relative to the disk (10).

Description

Technical Field

[0001] The present invention relates to a sliding mechanism having a first component and a second component that slide against each other. Background Technology

[0002] The sliding mechanism described in Patent Document 1 has a plurality of recesses on the sliding surface of at least one of a pair of sliding members. These recesses have an opening diameter of 5 μm to 50 μm and a depth of 0.5 μm to 10.0 μm. The area of ​​the plurality of recesses is 10% to 30% of the total area of ​​the sliding surface. The lubricating oil between the pair of sliding members contains an organic molybdenum compound.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2021-38840 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] On the other hand, the requirements for extending the lifespan of sliding mechanisms are constantly increasing, so the aforementioned sliding mechanisms still require reduced friction.

[0008] Solution for solving the problem

[0009] The sliding mechanism for solving the above-mentioned problem includes a first component and a second component that slide against each other, configured such that lubricating oil can pass between the sliding surfaces of the first component and the second component, i.e., the first sliding surface, and the sliding surfaces of the second component and the first component, i.e., the second sliding surface. If the length of the sliding direction in which the distance between the first sliding surface and the second sliding surface, which slides along the sliding direction with the lubricating oil, is less than 10 μm is defined as the sliding length, then the first sliding surface includes at least one convex peak and one concave peak of a ripple that have a wavelength component shorter than the sliding length along the sliding direction of the first component relative to the second component. If the surface roughness of the first sliding surface in the sliding direction is defined as σ, and the distance between the convex peak and the concave peak is defined as the height of the ripple, then the ripple is configured such that the value obtained by adding 3σ to the height of the ripple is more than 3.3σ and less than 30σ.

[0010] According to the structure described, when the first member slides relative to the second member, an oil film reaction force accompanied by a wedge effect is generated between the first and second members using the lubricating oil between the two members. Regarding this wedge effect, when the ripples are configured such that the value is 3.3σ or higher and 30σ or lower (the height of the ripples plus 3σ), the oil film reaction force becomes higher. As a result, the friction between the first and second members is reduced.

[0011] In the sliding mechanism, the corrugations may also be configured such that the height of the corrugations plus 3σ results in a value of 3.9σ or more and 15σ or less.

[0012] In the sliding mechanism, the corrugations may also be configured such that the height of the corrugations plus 3σ results in a value of 6.6σ or higher.

[0013] In the sliding mechanism, the sliding length can also be 0.1mm to 50mm. Alternatively, the sliding mechanism can also include two corrugations within the sliding length.

[0014] In the sliding mechanism, the corrugation may also include: a first convex peak, which is the convex peak adjacent to the concave peak in the sliding direction; a second convex peak, which is located in the sliding direction in the opposite direction to the first convex peak and adjacent to the concave peak with reference to the concave peak; a first inclination, in which the distance between the first sliding surface and the second sliding surface decreases as it moves from the concave peak toward the first convex peak; and a second inclination, in which the distance between the first sliding surface and the second sliding surface decreases as it moves from the concave peak toward the second convex peak; and a recess for accumulating the lubricating oil is provided in at least one of the first inclination and the second inclination.

[0015] In the sliding mechanism, there may be multiple recesses, and the total area of ​​the openings of the multiple recesses is 5% to 15% of the area of ​​the first sliding surface.

[0016] The effects of the invention

[0017] According to the present invention, the friction of the sliding surface can be reduced by utilizing the reaction force of the oil film. Attached Figure Description

[0018] Figure 1 This is a perspective view showing the structure of one embodiment of the sliding mechanism.

[0019] Figure 2 This is a top view showing the sliding surface of the ring.

[0020] Figure 3 It is a graph representing the corrugation curve of the sliding surface.

[0021] Figure 4 This is a table showing the relationship between surface roughness and cutoff value.

[0022] Figure 5 This is a schematic diagram illustrating the reaction force of the oil film in the sliding mechanism.

[0023] Figure 6 This is a schematic diagram showing a sliding mechanism with a corrugated surface on the sliding mask.

[0024] Figure 7 This is a schematic diagram showing a sliding mechanism with two corrugations on the sliding mask.

[0025] Figure 8 It is a graph showing the dependence of Cp on the gap ratio m.

[0026] Figure 9 It is a chart representing circular curves and disc curves.

[0027] Figure 10 It is a graph representing the composite curve.

[0028] Figure 11 This is a table representing the oil film reaction force in the sliding mechanism of each calculation example.

[0029] Figure 12 This is a diagram illustrating the function of a sliding mechanism with two corrugations on a sliding mask.

[0030] Figure 13 This is a diagram illustrating the function of a sliding surface with corrugations and a storage tank.

[0031] Figure 14 This is a diagram illustrating the function of a sliding surface with ripples and pits.

[0032] Figure 15 This is a table representing the surface properties of the sliding surface in each test case.

[0033] Figure 16 It is a graph representing the coefficient of friction relative to the rotational speed of the sliding mechanism.

[0034] Figure 17 This diagram illustrates an example of applying a sliding mechanism to a bearing mechanism.

[0035] Figure 18 This diagram illustrates an example of applying a sliding mechanism to a speed reduction mechanism.

[0036] Figure 19 yes Figure 18 A magnified view of a portion of it.

[0037] Figure 20This diagram illustrates an example of applying a sliding mechanism to a hydraulic pump.

[0038] Figure 21 It is a graph representing the curves used in the analysis of the sliding surface.

[0039] Figure 22 It is a graph that divides the analysis of the sliding surface into multiple motifs using curves.

[0040] Figure 23 It is a diagram representing the envelope.

[0041] Figure 24 This is a graph representing the analysis results of the Fourier transform.

[0042] Explanation of reference numerals in the attached figures

[0043] 10. Disc; 10A. Second sliding surface; 20. Ring; 20A. First sliding surface; 21. First ripple; 21A. First inclination; 21B. Second inclination; 21m. Concave peak; 21p. First convex peak; 21q. Second convex peak; 22. Second ripple; 22A. First inclination; 22B. Second inclination; 22m. Concave peak; 22p. First convex peak; 22q. Second convex peak; 23. Storage tank; 24. Pits. Detailed Implementation

[0044] The following is for reference Figures 1-16 One embodiment of the sliding mechanism will be described. The sliding mechanism includes a first member and a second member that slide against each other. The corrugation of the first sliding surface of the first member includes an inclination such that the distance between the first sliding surface and the second sliding surface of the second member decreases with increasing sliding direction. In order to help understand the friction suppression effect of the corrugation of the sliding surface, this embodiment will first show an example where the second sliding surface is a mirror with extremely low flatness and planarity. Next, the case where both the first and second sliding surfaces have corrugations will be described.

[0045] (Sliding mechanism)

[0046] like Figure 1 As shown, the sliding mechanism is suitable for ring-disc testing. The sliding mechanism has a disk 10 as an example of a second component and a ring 20 as an example of a first component. The disk 10 and ring 20 are, for example, made of metal. Hereinafter, the direction along the rotation axis of the ring 20 will be simply referred to as the axial direction. The circumferential direction centered on the rotation axis of the ring 20 will be simply referred to as the circumferential direction. The radial direction centered on the rotation axis of the ring 20 will be simply referred to as the radial direction.

[0047] The disc 10 is fixed to a device equipped with a sliding mechanism. A first sliding surface 20A, which is the lower surface of the ring 20, rests on a second sliding surface 10A, which is the upper surface of the disc 10. A predetermined amount of lubricating oil is placed between the first sliding surface 20A and the second sliding surface 10A. In the ring-disc test, a load F is applied to the ring 20 along its axial direction while the ring 20 is rotated about its central axis. As the ring 20 rotates, the first sliding surface 20A slides relative to the second sliding surface 10A. Hereinafter, the sliding direction of the first sliding surface 20A relative to the second sliding surface 10A will be simply referred to as the sliding direction D.

[0048] The two sliding surfaces 10A and 20A intersect the rotation axis of the ring 20. Specifically, the two sliding surfaces 10A and 20A are approximately orthogonal to the rotation axis of the ring 20. The two sliding surfaces 10A and 20A are opposite each other in the axial direction. Here, the distance between the first sliding surface 20A and the second sliding surface 10A in the axial direction is less than 10 μm at any point in the radial and circumferential directions of the first sliding surface 20A. That is, the two sliding surfaces 10A and 20A are configured such that the distance between them is less than 10 μm regardless of their position. Furthermore, the two sliding surfaces 10A and 20A slide with a distance between them of less than 10 μm regardless of their position. Additionally, the distance between the first sliding surface 20A and the second sliding surface 10A is related to the direction of the axial direction, and thus the direction orthogonal to the second sliding surface 10A. Hereinafter, the distance between the first sliding surface 20A and the second sliding surface 10A will sometimes be simply referred to as the distance between the two sliding surfaces 10A and 20A.

[0049] like Figure 2 As indicated by the varying density of the dots, the first sliding surface 20A is formed with irregularities through processing. That is, in Figure 2 The portion marked with darker dots is located closer to the front of the paper than the portion marked with lighter dots. In other words, the portion with darker dots bulges towards the second sliding surface 10A relative to the portion with lighter dots. Figure 2 In the process, portions with the densest point and portions with lighter points alternate along the sliding direction D. The portion with the densest point and the adjacent portion with lighter points form a ripple. That is, in... Figure 2 In the example shown, the first sliding surface 20A has a first corrugation 21 and a second corrugation 22. For example, the first corrugation 21 and the second corrugation 22 are arranged at equal intervals along the sliding direction D. Furthermore, details such as the dimensions of the unevenness treated as "corrugation" in this embodiment will be described later. For example, the corrugation is obtained by polishing and grinding the first sliding surface 20A while rotating the ring 20. For example, the corrugation can also be obtained by laser processing using an atomic second laser or by etching utilizing an etching effect. For example, the corrugation can also be obtained by surface processing combining etching and photolithography with partial exposure using a mask.

[0050] (Evaluation Path)

[0051] The surface characteristics of the first sliding surface 20A are described below. When describing these surface characteristics, as follows... Figure 2 As shown, consider a specific path along the first sliding surface 20A, namely the evaluation path PA. The evaluation path PA is an imaginary circle drawn along the sliding direction D. In this embodiment, corresponding to the sliding of the first sliding surface 20A in the rotational direction, the evaluation path PA is a circle centered on the rotation center of the ring 20.

[0052] The first sliding surface 20A has a first corrugation 21 and a second corrugation 22 in the evaluation path PA. In other words, the evaluation path PA can also be described as a path extending through the two corrugations 21 and 22 along the sliding direction D (circumferential in this embodiment). In this embodiment, the two corrugations 21 and 22 are arranged approximately at the radial center of the first sliding surface 20A. Moreover, the evaluation path PA has a diameter approximately half the outer diameter of the first sliding surface 20A. The first corrugation 21 and the second corrugation 22 are arranged at equal intervals along the sliding direction D.

[0053] Furthermore, multiple evaluation paths PA can be set. For example, the first corrugation 21 and the second corrugation 22 can also be formed at different positions in the radial direction. Multiple evaluation paths PA with different diameters can also be set according to the different positions of such corrugations. In short, it is sufficient to set the evaluation path PA in a manner that involves at least one corrugation.

[0054] (Wave curve)

[0055] Figure 3 The cross-sectional curve represents the evaluation path PA. The cross-sectional curve represents the height of the first sliding surface 20A at each position of the evaluation path PA, with the phase angle representing the central angle of each ring 20. That is, Figure 3 The horizontal axis represents the phase angle. The phase angle is set to advance along the sliding direction D. Figure 3 The vertical axis represents the depth of the recess in the first sliding surface 20A from the reference position. That is, in Figure 3 In this context, the larger the positive value of the vertical axis, the greater the distance between the first sliding surface 20A and the second sliding surface 10A. In other words, in... Figure 3 In the middle, the further down you go, the shorter the distance between the two sliding surfaces 10A and 20A becomes. The height of "0," representing the reference position, is determined taking into account the observation position of the measuring equipment and may not necessarily coincide with the lowest point of the first sliding surface 20A, i.e., the position of the flat portion of the first sliding surface 20A that does not form a depression. Furthermore, Figure 3 Strictly speaking, it is the ripple curve obtained by filtering the cross-sectional curve, which will be described later.

[0056] The cross-sectional profile is obtained by setting the sliding direction D in the measurement direction and following the methods of Japanese Industrial Standards JIS B 0601:2013 and JIS B 0633:2001. That is, the cross-sectional profile is the contour of the first sliding surface 20A when the ring 20 is cut along the evaluation path PA in the axial direction. For example, the cross-sectional profile can be obtained from the measurement results of a white light interferometer, NewView8300 (manufactured by Zygo Corporation). White light interferometers can rapidly observe a large area, making them suitable for obtaining the overall surface characteristics of the first sliding surface 20A.

[0057] The cross-sectional curve of the evaluation path PA contains roughness and ripple components formed in the unevenness of the first sliding surface 20A. The ripple component is the unevenness with a wavelength component longer than the roughness component. The roughness and ripple components can be separated by filtering the cross-sectional curve to extract specific wavelength regions. By applying a first cutoff value λc as a high-pass filter to the cross-sectional curve, the roughness component is separated from the cross-sectional curve as a roughness curve. By applying the first cutoff value λc as a low-pass filter to the cross-sectional curve and applying a second cutoff value λf, which is larger than the first cutoff value λc, as a high-pass filter to the cross-sectional curve, the ripple component is separated from the cross-sectional curve. That is, "ripple" refers to the unevenness in the cross-sectional curve obtained by an evaluation device capable of evaluating minute surface unevenness with a wavelength component longer than the first cutoff value λc and shorter than the second cutoff value λf. In the following description, the curve separated using the two cutoff values ​​λc and λf will be referred to as the ripple curve.

[0058] Furthermore, in this embodiment, for ease of understanding, an example is taken where the undulations representing "ripples" clearly appear in the ripple curve. For example, in Figure 3 In the wavy curve shown, the valleys that appear around 120 degrees and 300 degrees in the circumferential direction are used as boundaries, and the existence of two wavy lines can be visually confirmed.

[0059] (First cutoff value)

[0060] The first cutoff value λc is the boundary value between the roughness component and the waviness component. The first cutoff value λc is obtained according to the method of Japanese Industrial Standard JIS B 0633:2001. Figure 4 This represents a reference value for the first cutoff value λc. The first cutoff value λc is predetermined and corresponds to the arithmetic mean roughness Ra. The first cutoff value λc is determined based on the range of each arithmetic mean roughness Ra.

[0061] The arithmetic mean roughness Ra is obtained from the roughness curve according to the method of Japanese Industrial Standard JIS B 0601:2013. That is, when the first cutoff value λc is set as the reference length, the arithmetic mean roughness Ra is obtained by averaging the heights of the roughness curves along the reference length. The arithmetic mean roughness Ra represents the surface roughness within the range of the first cutoff value λc in the sliding direction D of the first sliding surface 20A.

[0062] When separating the corrugated curve from the cross-sectional curve, from Figure 4 Among the multiple first cutoff values ​​λc shown, an appropriate value is selected corresponding to the roughness of the first sliding surface 20A. For example, depending on the specifications of the applicable object, if there is a desired arithmetic mean roughness Ra of the first sliding surface 20A, the first cutoff value λc is set corresponding to the desired arithmetic mean roughness Ra. For example, if the desired arithmetic mean roughness Ra is 0.01 μm, according to... Figure 4 The reference value, the first cutoff value λc is set to 0.08 mm. For example, if the desired arithmetic mean roughness Ra is other values, it is also from... Figure 4 Select the corresponding first cutoff value λc. For example, the desired arithmetic mean roughness Ra can be obtained using a stylus-type roughness shape measuring machine SEF800-N (manufactured by Kosaka Research Institute). Although the stylus-type roughness shape measuring machine has a local measurement range, it can obtain precise information about the roughness.

[0063] Alternatively, when selecting the first cutoff value λc, the maximum height roughness Rz can be used instead of the arithmetic mean roughness Ra. The maximum height roughness Rz is obtained from the roughness curve according to the method in Japanese Industrial Standard JIS B 0601:2013. That is, it is obtained as the average height of the roughness curve over the reference length. When the first cutoff value λc is set as the reference length, the maximum height roughness Rz is obtained as the sum of the maximum peak height and the maximum valley depth in the roughness curve over the reference length.

[0064] (Second cutoff value)

[0065] The second cutoff value λf is the boundary value between the ripple component and the wavelength component longer than the ripple component. Specifically, the second cutoff value λf is the sliding length R, which will be explained later. Furthermore, as shown in Japanese Industrial Standard JIS B 0633:2001, even when the sliding length R is set to the second cutoff value λf, the filtered ripple curve does not contain components of the sliding length R, but rather extracts wavelength components shorter than that sliding length R. This is because the amplitude-frequency response of the filter attenuates near the second cutoff value λf. Alternatively, wavelength components shorter than the sliding length R can be separated from the cross-sectional curve by setting the second cutoff value λf to a value slightly smaller than the sliding length R. In short, it is acceptable to separate wavelength components shorter than the sliding length R from the cross-sectional curve.

[0066] The sliding length R is the length of the sliding direction D in which the distance between the first sliding surface 20A and the second sliding surface 10A, which slides along the sliding direction D through the lubricating oil, is less than 10 μm. As described above, in this embodiment, the distance between the first sliding surface 20A and the second sliding surface 10A is less than 10 μm regardless of their positions. Relatedly, in this embodiment, the length of the evaluation path PA is the sliding length R. The sliding length R can also be described as the length of the sliding between the first sliding surface 20A and the second sliding surface 10A during one rotation of the ring 20. When the rotation of the ring 20 is taken as a unit action, the sliding length R can also be described as the length of the sliding between the two sliding surfaces 10A and 20A in one cycle of the unit action. Furthermore, the length of the evaluation path PA varies depending on the radial position of the first sliding surface 20A. Therefore, the sliding length R varies depending on the evaluation position. The sliding length R is, for example, about 10 mm to 50 mm.

[0067] Based on the first cutoff value λc and the second cutoff value λf described above, when the arithmetic mean roughness Ra of the first sliding surface 20A is greater than 0.006 μm and less than 0.02 μm, the "ripple" is an uneven surface with a wavelength component longer than 0.08 mm and shorter than the sliding length R.

[0068] Similarly, when the arithmetic mean roughness Ra of the first sliding surface 20A is greater than 0.02 μm and less than 0.1 μm, the "ripple" is an unevenness having a wavelength component longer than 0.25 mm and shorter than the sliding length R. When the arithmetic mean roughness Ra of the first sliding surface 20A is greater than 0.1 μm and less than 2 μm, the "ripple" is an unevenness having a wavelength component longer than 0.8 mm and shorter than the sliding length R. When the arithmetic mean roughness Ra of the first sliding surface 20A is greater than 2 μm and less than 10 μm, the "ripple" is an unevenness having a wavelength component longer than 2.5 mm and shorter than the sliding length R. When the arithmetic mean roughness Ra of the first sliding surface 20A is greater than 10 μm and less than 80 μm, the "ripple" is an unevenness having a wavelength component longer than 8 mm and shorter than the sliding length R.

[0069] like Figure 3 As shown, two "ripples" satisfying any one of these conditions are formed on the first sliding surface 20A. Furthermore, it is permissible for more than one "ripple" to be formed on the first sliding surface 20A; the number of "ripples" is not limited to two.

[0070] (Details of the ripples)

[0071] like Figure 3 As shown, the first ripple 21 has concave peaks 21m, convex peaks 21p and 21q, a first tilt 21A, and a second tilt 21B.

[0072] The concave peak 21m is the most concave part of the portion of the first corrugation 21 located on the evaluation path PA. In other words, the concave peak 21m is the part of the first corrugation 21 located on the evaluation path PA that is farthest from the second sliding surface 10A. The distance between the concave peak 21m and the second sliding surface 10A is less than 10 μm. That is, the corrugation of the first sliding surface 20A is configured such that the maximum distance between the two sliding surfaces 10A and 20A is less than 10 μm.

[0073] The convex peaks 21p and 21q are the portions corresponding to the two ends of the first corrugation 21 in the circumferential direction. The convex peaks 21p and 21q are portions of the first corrugation 21 located near the second sliding surface 10A. Specifically, at least one of the convex peaks 21p and 21q is the portion of the first corrugation 21 closest to the second sliding surface 10A. For ease of explanation, the convex peak 21p located in the sliding direction D relative to the concave peak 21m is designated as the first convex peak 21p, and the convex peak located in the opposite direction to the concave peak 21m relative to the concave peak 21m is designated as the second convex peak 21q. That is, the first convex peak 21p is the convex peak adjacent to the concave peak 21m in the sliding direction D. The second convex peak 21q is the convex peak located in the sliding direction D, in the opposite direction to the first convex peak 21p and adjacent to the concave peak 21m, with the concave peak 21m as a reference. Furthermore, the height positions of the two convex peaks 21p and 21q can be the same or different.

[0074] Two inclinations 21A and 21B are positioned on either side of the concave peak 21m. The first inclination 21A connects the concave peak 21m and the first convex peak 21p. In this case, it can also be said that the first circumferential end of the first inclination 21A is the concave peak 21m, and the second circumferential end of the first inclination 21A is the first convex peak 21p. The first end of the first inclination 21A is the part of the first inclination 21A farthest from the second sliding surface 10A, and the second end of the first inclination 21A is the part of the first inclination 21A closest to the second sliding surface 10A.

[0075] The first inclination 21A tilts such that the distance between the first sliding surface 20A and the second sliding surface 10A decreases as it moves from the concave peak 21m toward the first convex peak 21p. Alternatively, the first inclination 21A can tilt as a whole, or it can include portions with locally constant distances. The first inclination 21A is located in the sliding direction D relative to the concave peak 21m. The first inclination 21A is located in the opposite direction to the sliding direction D relative to the first convex peak 21p.

[0076] The second inclination 21B connects the concave peak 21m and the second convex peak 21q. The second inclination 21B is inclined such that the distance between the first sliding surface 20A and the second sliding surface 10A decreases as it moves from the concave peak 21m toward the second convex peak 21q. Furthermore, the second inclination 21B can be an integral inclination, or it can include portions with locally constant distances. The second inclination 21B is located in the opposite direction to the sliding direction D relative to the concave peak 21m. The second inclination 21B is located in the sliding direction D relative to the second convex peak 21q.

[0077] In this embodiment, the circumferential lengths of the two inclinations 21A and 21B, in other words, the phase angles occupied by the two inclinations 21A and 21B, are set to be the same. However, this is not a limitation, and the circumferential lengths of the two inclinations 21A and 21B may also be different.

[0078] like Figure 3 As shown, the second ripple 22 has concave peaks 22m, convex peaks 22p and 22q, a first tilt 22A, and a second tilt 22B.

[0079] The concave peak 22m is the most concave part of the portion of the second corrugation 22 located on the evaluation path PA. In other words, the concave peak 22m is the part of the second corrugation 22 located on the evaluation path PA that is furthest from the second sliding surface 10A. The distance between the concave peak 22m and the second sliding surface 10A is also less than 10 μm, similar to the case of the concave peak 21m in the first corrugation 21.

[0080] The convex peaks 22p and 22q are the portions corresponding to the two ends of the second corrugation 22 in the circumferential direction. The convex peaks 22p and 22q are portions of the second corrugation 22 located near the second sliding surface 10A. Specifically, at least one of the convex peaks 22p and 22q is the portion of the second corrugation 22 closest to the second sliding surface 10A. For ease of explanation, the convex peak 22p located in the sliding direction D relative to the concave peak 22m is designated as the first convex peak 22p, and the convex peak located in the opposite direction to the concave peak 22m relative to the concave peak 22m is designated as the second convex peak 22q. That is, the first convex peak 22p is the convex peak adjacent to the concave peak 22m in the sliding direction D. The second convex peak 22q is the convex peak located in the opposite direction to the first convex peak 22p and adjacent to the concave peak 22m, with the concave peak 22m as a reference. Furthermore, the height positions of the two convex peaks 22p and 22q can be the same or different.

[0081] In this embodiment, the two corrugations 21 and 22 are arranged continuously in the circumferential direction. Therefore, the first peak 21p of the first corrugation 21 and the second peak 22q of the second corrugation 22 are at the same position, and the first peak 22p of the second corrugation 22 and the second peak 21q of the first corrugation 21 are at the same position.

[0082] The two inclinations 22A and 22B of the second wave 22 are arranged on both sides of the concave peak 22m. The first inclination 22A connects the concave peak 22m and the first convex peak 22p. In this case, it can also be said that the first circumferential end of the first inclination 22A is the concave peak 22m, and the second circumferential end of the first inclination 22A is the first convex peak 22p. The first end of the first inclination 22A is the part of the first inclination 22A farthest from the second sliding surface 10A, and the second end of the first inclination 22A is the part of the first inclination 22A closest to the second sliding surface 10A.

[0083] The first inclination 22A tilts such that the distance between the first sliding surface 20A and the second sliding surface 10A decreases as it moves from the concave peak 22m toward the first convex peak 22p. Alternatively, the first inclination 22A can tilt as a whole, or it can include portions with locally constant distances. The first inclination 22A is located in the sliding direction D relative to the concave peak 22m. The first inclination 22A is located in the opposite direction to the sliding direction D relative to the first convex peak 22p.

[0084] The second inclination 22B connects the concave peak 22m and the second convex peak 22q. The second inclination 22B is inclined such that the distance between the two sliding surfaces 10A and 20A decreases as it moves from the concave peak 22m toward the second convex peak 22q. Furthermore, the second inclination 22B can be inclination as a whole, or it can include portions with locally constant distances. The second inclination 22B is located in the opposite direction to the sliding direction D relative to the concave peak 22m. The second inclination 22B is located in the sliding direction D relative to the second convex peak 22q.

[0085] In this embodiment, the circumferential lengths of the two inclinations 22A and 22B, in other words, the phase angles occupied by the two inclinations 22A and 22B, are set to be the same. However, this is not a limitation, and the circumferential lengths of the two inclinations 22A and 22B may also be different.

[0086] In the corrugated curve obtained from the cross-sectional curve of the evaluation path PA, the phase angle corresponding to the portion of the first corrugation 21 is the first phase angle θ1. In the corrugated curve obtained from the cross-sectional curve of the evaluation path PA, the phase angle corresponding to the portion of the second corrugation 22 is the second phase angle θ2 (=360°-first phase angle θ1). In this embodiment, the two phase angles θ1 and θ2 are the same. If we focus on this point, the two corrugations 21 and 22 in this embodiment can also be said to have a periodic concavity and convexity with phase angles obtained by dividing 360° by the number of corrugations.

[0087] (Oil film reaction force)

[0088] The two corrugations 21 and 22 serve to reduce the friction between the two sliding surfaces 10A and 20A. This function will be explained using the first corrugation 21 as an example. As described above, in the first corrugation 21, the first inclination 21A is inclined relative to the second sliding surface 10A in the sliding direction D. As a result, as... Figure 5As shown, the first inclination 21A forms a wedge shape such that the distance between the second sliding surface 10A and the first sliding surface 20A decreases as it moves toward the sliding direction D. With this wedge shape, lubricating oil between the second sliding surface 10A and the first sliding surface 20A is introduced into the minimum gap between these surfaces as the ring 20 rotates, exhibiting a so-called wedge effect. Accompanying this wedge effect, an oil film reaction force P is generated, causing the first sliding surface 20A to move away from the second sliding surface 10A. The minimum gap between the first sliding surface 20A and the second sliding surface 10A is located at the position in the first inclination 21A where the distance to the second sliding surface 10A is shortest, i.e., the first peak 21p. Figure 5 In the figure, the flow of lubricating oil is indicated by the symbol K.

[0089] As shown in equation (1) below, the oil film reaction force P acting on the first sliding surface 20A is derived from the clearance ratio m, the outlet distance h2, the wedge distance L, the viscosity μ of the lubricating oil, the sliding speed U, and the distribution constant Cp. As shown in equation (2), the clearance ratio m is the ratio of the inlet distance h1 to the outlet distance h2. The distribution constant Cp is derived by applying the clearance ratio m to equation (3) below. The oil film reaction force P derived from equation (1) is preferably larger from the viewpoint of suppressing friction, and more preferably exceeds the magnitude of the load F. When the oil film reaction force P exceeds the load F, the fluid lubrication of the disc 10 and the ring 20 significantly reduces friction.

[0090] [Mathematical Expression 1]

[0091]

[0092] The above-mentioned parameters involved in deriving the oil film reaction force P are described in detail. For example... Figure 5 As shown, the inlet distance h1 is the distance between the first sliding surface 20A and the second sliding surface 10A at the position of the concave peak 21m of the first corrugation 21. The outlet distance h2 is the distance between the first sliding surface 20A and the second sliding surface 10A at the position of the first convex peak 21p. If the arithmetic mean roughness Ra of the first sliding surface 20A is set as σ, then the outlet distance h2 is usually considered to be 3σ. The sliding speed U is the speed along the sliding direction D of the ring 20 relative to the disk 10. Furthermore, the inlet distance h1 is the length of the axial direction, which is orthogonal to the second sliding surface 10A. The outlet distance h2 is similarly long.

[0093] The wedge distance L is the length along the sliding direction D from the concave peak 21m to the first convex peak 21p. That is, the wedge distance L is the circumferential length of the first inclination 21A. When the first convex peak 21p is the part of the first corrugation 21 closest to the second sliding surface 10A, the wedge distance L can also be described as the length along the sliding direction D between the part of the first corrugation 21 with the longest distance from the second sliding surface 10A and the part with the shortest distance from the second sliding surface 10A.

[0094] Furthermore, strictly speaking, Equation (1) is a formula for calculating the oil film reaction force P when the two sliding surfaces 10A and 20A are rectangular. In this embodiment, a portion of the circumferential direction of the annular first sliding surface 20A, namely the first inclined surface 21A, is approximately considered as a rectangle, and the oil film reaction force P is calculated according to Equation (1). In addition, Equation (1) is a formula for calculating the oil film reaction force P for a single wedge. When there are multiple wedges on the evaluation path PA, the oil film reaction force P of each wedge is derived according to Equation (1) and they are added together, thereby obtaining the total oil film reaction force P.

[0095] (Oil film reaction force and ripple distance)

[0096] As can be seen from equation (1), the oil film reaction force P becomes a value that reflects the magnitude of the corrugation distance L. Moreover, the corrugation distance L is related to the number of corrugations provided on the first sliding surface 20A. Hereinafter, the preferred number of corrugations for obtaining a higher oil film reaction force P will be explained.

[0097] like Figure 6 As shown, when only the first corrugation 21 exists in the evaluation path PA, only the first inclination 21A produces a wedge effect in the first sliding surface 20A. The wedge distance L of the first inclination 21A is the circumferential length of the first inclination 21A. Assuming that the circumferential lengths of the two inclinations 21A and 21B of the first corrugation 21 are the same, the wedge distance L is equivalent to 1 / 2 of the sliding length R. That is, when the length of the sliding length R is set to R, the wedge distance L is R / 2.

[0098] like Figure 7 As shown, when a first corrugation 21 and a second corrugation 22 exist in the evaluation path PA, the first inclination 21A of the first corrugation 21 and the first inclination 22A of the second corrugation 22 produce a wedge effect in the first sliding surface 20A. Assuming that the circumferential length of all inclinations is the same, the wedge distance L is equivalent to 1 / 4 of the sliding length R. That is, when the length of the sliding length R is set to R, the wedge distance L is R / 4.

[0099] As shown in equation (1), the oil film reaction force P is proportional to the square of the wedge distance L. Therefore, if the oil film reaction force P in the case where there is only one corrugation in the evaluation path PA is defined as reaction force P1, then the oil film reaction force P of each corrugation in the case where there are two corrugations in the evaluation path PA becomes reaction force P2 (=P1×1 / 4). That is, the more the number of corrugations increases, the lower the oil film reaction force P of each corrugation decreases. As mentioned above, when there are multiple wedges in the evaluation path PA, the overall oil film reaction force P of the evaluation path PA becomes the value obtained by adding the oil film reaction forces P of each corrugation. Therefore, the total oil film reaction force P in the case where there are two corrugations in the evaluation path PA is P1×1 / 2. That is, the more the number of corrugations increases, the lower the oil film reaction force P is when viewed from the perspective of the overall evaluation path PA. Therefore, from the viewpoint of increasing the oil film reaction force P, it is preferable to have fewer corrugations. As an example, there are two ripples in each sliding length R.

[0100] In addition, when there are multiple corrugations in the evaluation path PA and the wedge distances L of each corrugation are different from each other, at least one corrugation distance L can be greater than or equal to the sliding length R / 6, and further greater than or equal to the sliding length R / 4.

[0101] (Oil film reaction force and inlet distance)

[0102] The conditions for obtaining a higher oil film reaction force P, including the required inlet distance h1, are explained. As a prerequisite, the relationship between the distribution constant Cp and the clearance ratio m is also explained. Figure 8 This represents the theoretical relationship between the distribution constant Cp and the clearance ratio m obtained from equation (3). As shown in equation (1), the larger the distribution constant Cp is, the larger the oil film reaction force P is. Therefore, from the perspective of suppressing friction, the distribution constant Cp is preferably larger.

[0103] like Figure 8 As shown, the distribution constant Cp exhibits a unimodal distribution relative to the gap ratio m, with a maximum value near the gap ratio m of 2. If the combination of the gap ratio m and the distribution constant Cp derived from it is expressed as [m, Cp], then the distribution constant Cp increases sharply with increasing gap ratio m via [1.1, 0.049] and [1.3, 0.10]. The distribution constant Cp has a maximum value at [2.19, 0.16] and decreases exponentially with increasing gap ratio m via [5.0, 0.11] and [10, 0.049].

[0104] From the viewpoint of obtaining a distribution constant Cp of 0.049 or higher, the clearance ratio m is preferably 1.1 or higher and 10 or lower, more preferably 1.3 or higher and 5 or lower, and even more preferably 2.2 or higher. Furthermore, as mentioned above, the exit distance h2 is generally considered to be 3σ, therefore the clearance ratio m derived by equation (2) is considered to be the inlet distance h1 / 3σ. Therefore, the inlet distance h1 is preferably 3.3 times (=1.1×3σ) or higher and 30 times (=10×3σ) or lower of the arithmetic mean roughness Ra in the evaluation path PA. More preferably, the inlet distance h1 is 3.9 times (=1.3×3σ) or higher and 15 times (=5×3σ) or lower of the arithmetic mean roughness Ra in the evaluation path PA, and even more preferably 6.6 times (=2.2×3σ) or higher.

[0105] The first ripple 21 is configured to satisfy the condition of such an inlet distance h1. That is, as... Figure 5 As shown, the height of the first convex peak 21p relative to the concave peak 21m is defined as the corrugation height h3. The corrugation height h3 is the distance between the first convex peak 21p and the concave peak 21m in the direction of the axis, which is orthogonal to the second sliding surface 10A. The corrugation height h3 can also be described as the height difference between the two ends of the first inclined surface 21A. Figure 5 As shown, the inlet distance h1 depends on the corrugation height h3, and more specifically, it is the value obtained by adding the outlet distance h2 to the corrugation height h3.

[0106] In this structure, the first corrugation 21 is configured to satisfy the following height condition. That is, when the arithmetic mean roughness Ra is set to σ, regarding the height condition, considering that the outlet distance h2 is typically 3σ, the sum of the corrugation height h3 and 3σ can be more than 3.3 times and less than 30 times the arithmetic mean roughness Ra. A more preferred embodiment of the height condition is that the above-mentioned sum is more than 3.9 times and less than 15 times the arithmetic mean roughness Ra, and further, the sum is more than 6.6 times.

[0107] Furthermore, similarly to the first corrugation 21, the second corrugation 22 can also be configured to satisfy the aforementioned height condition. However, it is not limited to this; instead of each corrugation 21 and 22 satisfying the height condition separately, a corrugation height h3 representing the two corrugations 21 and 22 can be determined, and the first sliding surface 20A can be constructed in such a way that this representative height satisfies the height condition. An example of the representative height can be the average value of each corrugation height h3, or it can be the higher value among the various corrugation heights h3. The representative height can also be defined in the same way when there are more than three corrugations on the evaluation path PA.

[0108] As described above, multiple evaluation paths PA with different diameters can be set on the first sliding surface 20A. Furthermore, the first sliding surface 20A can be configured such that the average value of the corrugation height h3 of each evaluation path PA satisfies the height condition. When setting multiple evaluation paths PA, consider setting three evaluation paths PA as follows: Here, 10% of the value obtained by subtracting the inner diameter from the outer diameter of the first sliding surface 20A is called the first value. The first evaluation path PA is a path near the inner periphery of the annular first sliding surface 20A. Specifically, the first evaluation path PA is an imaginary circle with the sum of the inner diameter of the first sliding surface 20A and the first value as its diameter. The second evaluation path PA is a path at the center between the inner and outer peripheries of the first sliding surface 20A. Specifically, the second evaluation path PA is an imaginary circle with the sum of the inner diameter of the first sliding surface 20A and five times the first value as its diameter. The third evaluation path PA is a path near the outer periphery of the first sliding surface 20A. Specifically, the third evaluation path PA is an imaginary circle with the value obtained by subtracting the first value from the outer diameter of the first sliding surface 20A as its diameter.

[0109] The above, with Figures 5-7 Taking the case where the sliding direction D is to the right of each figure as an example, but when the sliding direction D is in the opposite direction, the wedge effect is manifested not through the first inclination 21A, but through the second inclination 21B. In this case, the wedge distance L becomes the circumferential length of the second inclination 21B. The ripple height h3 is the height difference of the second inclination 21B, that is, the height from the concave peak 21m to the second convex peak 21q.

[0110] Here, in the corrugated curve, there are sometimes multiple concave and convex sections with different heights. In this case, the corrugation with the maximum height Wz1 in the evaluation path PA can also be used, and the concave and convex sections with a corrugation height h3 that satisfies the following equation (4) can be taken as corrugations.

[0111] Wz1 / 2≤corrugation height h3≤Wz1 (4)

[0112] That is, the oil film reaction force P generated by a convex portion where the corrugation height h3 is less than 50% of the maximum corrugation height Wz1, compared to a corrugation exceeding 50% of the maximum corrugation height Wz1, is negligible. Therefore, such unevenness can also be disregarded as corrugation. Furthermore, unevenness refers to a surface with both concave and convex peaks.

[0113] The maximum height corrugation Wz1 is obtained from the corrugation curve according to the method of Japanese Industrial Standard JIS B 0601:2013. That is, the maximum height corrugation Wz1 is obtained as the sum of the maximum value of the peak height and the maximum value of the trough depth in the corrugation curve.

[0114] (Synthetic ripples)

[0115] For the case where the first sliding surface 20A and the second sliding surface 10A are each corrugated, the corrugation structure required to obtain a higher oil film reaction force P will be explained. First, the definitions of the parameters required to explain this structure will be explained, followed by the conditions required by these parameters. When the first sliding surface 20A and the second sliding surface 10A are each corrugated, it is necessary to correlate the corrugations of the two sliding surfaces 10A and 20A to understand their respective surface properties. Therefore, in addition to the first sliding surface 20A, an evaluation path PA is also set on the second sliding surface 10A. The evaluation path PA of the second sliding surface 10A is set at a position opposite to the evaluation path PA of the first sliding surface 20A. The length of this evaluation path PA is defined as the sliding length R of the corrugation. Furthermore, as a premise for the following explanation, the corrugations of the two sliding surfaces 10A and 20A are configured such that the maximum distance between the two sliding surfaces 10A and 20A during one rotation of the ring 20 is less than 10 μm. For example, when the concave peaks of the ripples on the first sliding surface 20A and the second sliding surface 10A are opposite each other, the distance between the two concave peaks is less than 10 μm. Here, it is assumed that no ripples are formed on the first sliding surface 20A and the second sliding surface 10A, and that the two sliding surfaces 10A and 20A are flat. Moreover, the two sliding surfaces 10A and 20A are in surface contact. The two sliding surfaces 10A and 20A at this time are referred to as imaginary reference surfaces. In the description of the composite ripples, the distance between the two sliding surfaces 10A and 20A is the length in a direction orthogonal to the imaginary reference surface. In this embodiment, the direction orthogonal to the imaginary reference surface is the axial direction.

[0116] The corrugated curve of the evaluation path PA of the first sliding surface 20A is set as a loop curve. Additionally, the corrugated curve of the evaluation path PA of the second sliding surface 10A is set as a disk curve. Now, the ring 20 is in a specific rotational position. Figure 9 This is a simplified representation of an example of the loop curve 101 and the disk curve 102 at this time. Figure 9 The annular curve 101 and disk curve 102 shown are only for easy understanding of the surface properties and may not be consistent with the actual situation. Figure 9 The vertical axis is set such that its value increases in the direction of the ring 20 relative to the disk 10. That is, the greater the depth of the recess from the first sliding surface 20A, the greater the absolute value of the ring curve 101. Similarly, the greater the depth of the recess from the second sliding surface 10A, the greater the absolute value of the disk curve 102.

[0117] exist Figure 9 In the example shown, loop curve 101 has two ripples. Each ripple contains a convex peak and a concave peak, respectively. Similarly, disk curve 102 has two ripples. Each ripple contains a convex peak and a concave peak, respectively. Furthermore, loop curve 101 only needs to contain one or more ripples, and disk curve 102 also only needs to contain one or more ripples.

[0118] like Figure 10 As shown, the composite curve 103 is formed by combining the loop curve 101 and the curve that reverses the positive and negative values ​​of the disk curve 102. The composite curve 103 represents the distance between the first sliding surface 20A and the second sliding surface 10A at each phase angle. Hereinafter, the height shown by the composite curve 103 will be referred to as the composite height.

[0119] The following explanation uses composite curve 103 as an example to illustrate the content of each parameter. For example... Figure 10 As shown, the composite curve 103 has two composite ripples 110 and 120. The composite ripples 110 and 120 are arranged in the circumferential direction.

[0120] The first synthetic ripple 110 includes a synthetic concave peak 110m, synthetic convex peaks 110p and 110q, and a first synthetic tilt 110A and a second synthetic tilt 110B.

[0121] The synthetic concave peak 110m is the portion of the first synthetic corrugation 110 located on the evaluation path PA where the distance between the two sliding surfaces 10A and 20A is the longest. The synthetic convex peaks 110p and 110q are portions corresponding to the two ends of the first synthetic corrugation 110 in the circumferential direction. The synthetic convex peaks 110p and 110q are portions of the first synthetic corrugation 110 where the distance between the two sliding surfaces 10A and 20A is shortest. Specifically, at least one of the synthetic convex peaks 110p and 110q is the portion of the first synthetic corrugation 110 where the distance between the two sliding surfaces 10A and 20A is shortest. For ease of explanation, among the two synthetic convex peaks 110p and 110q, the synthetic convex peak located in the sliding direction D relative to the synthetic concave peak 110m is designated as the first synthetic convex peak 110p, and the synthetic convex peak located in the opposite direction to the sliding direction D relative to the synthetic concave peak 110m is designated as the second synthetic convex peak 110q. That is, the first synthetic peak 110p is a synthetic peak adjacent to the synthetic concave peak 110m in the sliding direction D. The second synthetic peak 110q is a synthetic peak located in the sliding direction D, in the opposite direction to the first synthetic peak 110p and adjacent to the synthetic concave peak 110m, with the synthetic concave peak 110m as a reference. Furthermore, the height positions of the two synthetic peaks 110p and 110q can be the same or different.

[0122] Two composite tilting surfaces 110A and 110B are positioned on either side of the composite concave peak 110m. The first composite tilting surface 110A connects the composite concave peak 110m and the first composite convex peak 110p. In this case, the first circumferential end of the first composite tilting surface 110A is the composite concave peak 110m, and the second circumferential end of the first composite tilting surface 110A can also be referred to as the first composite convex peak 110p. The first end of the first composite tilting surface 110A is the part with the longest distance between the two sliding surfaces 10A and 20A, and the second end of the first composite tilting surface 110A is the part with the shortest distance between the two sliding surfaces 10A and 20A.

[0123] The first composite tilt 110A tilts in such a way that the distance between the two sliding surfaces 10A and 20A decreases as it moves from the composite concave peak 110m toward the first composite convex peak 110p. Furthermore, the first composite tilt 110A can tilt as a whole, or it can include portions with locally constant distances. The first composite tilt 110A is located in the sliding direction D relative to the composite concave peak 110m. The first composite tilt 110A is located in the opposite direction to the sliding direction D relative to the first composite convex peak 110p.

[0124] The second composite tilt 110B tilts in such a way that the distance between the two sliding surfaces 10A and 20A decreases as it moves from the composite concave peak 110m toward the second composite convex peak 110q. Alternatively, the second composite tilt 110B can be tilted as a whole, or it can include portions with locally constant distances. The second composite tilt 110B is located in the opposite direction to the sliding direction D relative to the composite concave peak 110m. The second composite tilt 110B is located in the sliding direction D relative to the second composite convex peak 110q.

[0125] Thus, the first composite ripple 110 is derived from the change in distance between the two sliding surfaces 10A and 20A in the sliding direction D. Furthermore, in this embodiment, the circumferential lengths of the two composite tilts 110A and 110B, in other words, the phase angles occupied by the two composite tilts 110A and 110B, are set to be the same. However, this is not a limitation; the circumferential lengths of the two composite tilts 110A and 110B may also be different.

[0126] The second composite corrugation 120 includes a composite concave peak 120m, composite convex peaks 120p and 120q, and a first composite tilt 120A and a second composite tilt 120B. Since these have the same structure as the corresponding first composite corrugation 110, detailed descriptions are omitted.

[0127] In this structure, the oil film reaction force P generated by the first composite corrugation 110 is determined based on equation (1). In this case, the inlet distance h1 is the distance between the first sliding surface 20A and the second sliding surface 10A at the position of the composite concave peak 110m of the first composite corrugation 110. The outlet distance h2 is the distance between the first sliding surface 20A and the second sliding surface 10A at the position of the first composite convex peak 110p. The inlet distance h1 is the value obtained by adding the corrugation height h3 of the first composite corrugation 110 to the outlet distance h2. If the arithmetic mean roughness Ra of the first sliding surface 20A is set as σ, the outlet distance h2 is usually considered as 3σ. Therefore, the inlet distance h1 is the value obtained by adding 3σ to the corrugation height h3 of the first composite corrugation 110. In addition, the inlet distance h1, outlet distance h2 and corrugation height h3 of the first composite corrugation 110 are lengths in the axial direction, which are lengths in the direction orthogonal to the above-mentioned hypothetical reference plane.

[0128] The ripple height h3 of the first synthetic ripple 110 is the height of the first synthetic convex peak 110p relative to the synthetic concave peak 110m, or the height of the first synthetic tilt 110A. Furthermore, in the first synthetic ripple 110, the wedge distance L, which contributes to the wedge effect, is the circumferential length of the first synthetic tilt 110A.

[0129] Furthermore, if the sliding direction D is opposite, the oil film reaction force P depends on the corrugation height h3 of the second composite tilt 110B. The corrugation height h3 of the second composite tilt 110B is the height of the second composite convex peak 110q relative to the composite concave peak 110m, and the wedge distance L is the circumferential length of the second composite tilt 110B.

[0130] Here, the relative positions of the corrugated portions of the first sliding surface 20A and the second sliding surface 10A in the sliding direction D change according to the rotation of the ring 20. Furthermore, the shapes of the combined corrugations 110 and 120 formed by the corrugations of the first sliding surface 20A and the second sliding surface 10A also change. That is, the shapes of the combined corrugations 110 and 120 and their height h3 change as the two sliding surfaces 10A and 20A slide.

[0131] To account for such shape variations, the composite curve 103 is generated for various rotational positions during one revolution of the ring 20. For example, composite curve 103 is generated for each change in the rotational position of the ring 20 by a specified angle. An example of a specified angle is 10 degrees. In this case, 36 composite curves 103 are generated. For each of these composite curves 103, the values ​​of the parameters characterizing the ripples are determined.

[0132] In detail, for each of the multiple composite curves 103, in other words, for each rotational position, the corrugation height h3 (inlet distance h1), outlet distance h2, and wedge distance L of the first composite corrugation 110 are derived. Therefore, multiple corrugation heights h3, multiple inlet distances h1, multiple outlet distances h2, and multiple wedge distances L are derived. These average values ​​are respectively called the average corrugation height h3a, average inlet distance h1a, average outlet distance h2a, and average wedge distance La. The average corrugation height h3a is the average of the corrugation heights h3 when the ring 20 rotates one revolution. The average inlet distance h1a is the average of the inlet distances h1 when the ring 20 rotates one revolution. The average outlet distance h2a is the average of the outlet distances h2 when the ring 20 rotates one revolution. The average wedge distance La is the average of the wedge distances L when the ring 20 rotates one revolution.

[0133] In the same viewpoint as the previously explained exit distance h2, the average exit distance h2a is generally considered to be 3σ. σ is the arithmetic mean roughness Ra of the first composite corrugation 110. Here, the arithmetic mean roughness Ra of the first composite corrugation 110 is the combined value of the surface roughness of the first sliding surface 20A and the surface roughness of the second sliding surface 10A. In detail, the arithmetic mean roughness Ra is the square root of the sum of the squares of the arithmetic mean roughness Ra of the first sliding surface 20A and the squares of the arithmetic mean roughness Ra of the second sliding surface 10A.

[0134] Furthermore, similar to the viewpoint regarding the inlet distance h1, the average inlet distance h1a in the first composite corrugation 110 is preferably 3.3 times or more and 30 times or less of the arithmetic mean roughness Ra in the evaluation path PA. More preferably, the average inlet distance h1a is 3.9 times or more and 15 times or less of the arithmetic mean roughness Ra in the evaluation path PA, and even more preferably 6.6 times or more. The corrugations of the two sliding surfaces 10A and 20A are constructed in a manner that satisfies such an average inlet distance h1a. That is, the corrugations of the two sliding surfaces 10A and 20A can be constructed such that the value obtained by adding 3σ to the average corrugation height h3a is 3.3 times or more and 30 times or less of the arithmetic mean roughness Ra in the evaluation path PA.

[0135] The average wedge distance La is also similar to the wedge distance L, and is preferably longer. When the length of the sliding length R is set to R, the average wedge distance La can be, for example, greater than R / 6 or greater than R / 4.

[0136] Incidentally, such as Figure 10As shown, when multiple composite corrugations 110 and 120 exist in a composite curve 103, necessary parameters (corrugation height h3, wedge distance L, etc.) can be derived for each composite corrugation 110 and 120. Based on this, representative values ​​can also be determined. For example, the representative value of corrugation height h3 can be either the average value of the corrugation height h3 of the two composite corrugations 110 and 120, or the maximum value.

[0137] When determining the values ​​of the parameters characterizing the synthetic ripples, multiple evaluation paths PA with different diameters can be set. For example, three evaluation paths PA—a first evaluation path PA, a second evaluation path PA, and a third evaluation path PA—can be set in connection with the case where only the first sliding surface 20A of the two sliding surfaces 10A and 20A has ripples. When setting these three evaluation paths PA, for example, with respect to a certain parameter, a representative value such as an average or maximum value is calculated for each evaluation path PA. Then, the average of the representative values ​​of the three evaluation paths PA is taken as the final value. For example, if it is the ripple height h3, the average ripple height h3a is calculated for each of the three evaluation paths PA using the calculation method already described. Then, the average of the average ripple height h3a of the three evaluation paths PA is determined as the final value.

[0138] (Theoretical calculation example)

[0139] like Figure 11 As shown, a theoretical calculation example illustrates the oil film reaction force P when the second sliding surface 10A is set to a mirror with extremely small flatness and planarity, and the number of corrugations or corrugation height h3 of the first sliding surface 20A is changed. In addition, the arithmetic mean roughness Ra of the second sliding surface 10A is set to 0.01 [μm].

[0140] The oil film reaction force P in Calculation Example 1 is obtained by setting various parameters as follows. The oil film reaction force P in Calculation Example 1 is 4360 [N].

[0141] • Diameter of ring 20: 16 mm

[0142] • Inner diameter of ring 20: 5 mm

[0143] • Diameter of evaluation path PA: 10.5 mm

[0144] • Evaluation path PA length (= sliding length R): 33.0 [mm]

[0145] • Lubricating oil viscosity μ: 7.17 × 10 -8 [N / mm 2 ·s]

[0146] • Sliding speed U: 1 [mm / s]

[0147] • Number of ripples: two relative to the sliding length R

[0148] • Corrugation distance L: R / 4

[0149] • Ripple height h3: 130 [nm] (<15σ)

[0150] • The arithmetic mean roughness Ra of the first sliding surface 20A is 0.01 [μm]

[0151] Next, the number of corrugations was changed to eight evenly spaced along the sliding direction D, and the corrugation distance L was changed to R / 16. Otherwise, it remained the same as in Calculation Example 1, yielding the oil film reaction force P for Calculation Example 2. The oil film reaction force P in Calculation Example 2 was 1090 [N], which is 1 / 4 of the oil film reaction force P in Calculation Example 1. Based on the comparison between Calculation Example 1 and Calculation Example 2, when a higher oil film reaction force P is required, it is preferable to have fewer corrugations than one.

[0152] Next, the peak height h3 of the ripples was changed to 1 [μm] (>30σ), and the oil film reaction force P of Calculation Example 3 was obtained in the same manner as in Calculation Example 1. The oil film reaction force P of Calculation Example 3 was 460 [N], which was less than 1 / 6 of the oil film reaction force P of Calculation Example 1. Based on the comparison between Calculation Example 1 and Calculation Example 3, when a higher oil film reaction force P is required, the peak height h3 of the ripples is preferably 30 times or less than the arithmetic mean roughness Ra, and more preferably 15 times or less.

[0153] (Supply of lubricating oil)

[0154] The first sliding surface 20A described above may also have a recess for storing lubricating oil. The recess for storing lubricating oil will be described below.

[0155] To generate the wedge-effect-based oil film reaction force P, a sufficient amount of lubricating oil is required in the wedge-shaped space between the first inclined plane 21A and the second sliding surface 10A. Therefore, as Figure 13 As shown, the second corrugation 22 may also have a storage groove 23 as a recess for storing lubricating oil.

[0156] In detail, as already explained, the second inclination 22B of the second corrugation 22 is connected to the first inclination 21A of the first corrugation 21. In detail, as... Figure 12 As shown, the second inclination 22B of the second corrugation 22 is an inclination surface with the first convex peak 21p of the first corrugation 21 and the concave peak 22m of the second corrugation 22 as its two ends, and the distance between the first sliding surface 20A and the second sliding surface 10A increases as it moves from the first convex peak 21p of the first corrugation 21 toward the sliding direction D.

[0157] Furthermore, as the two sliding surfaces 10A and 20A slide, the lubricating oil flows in the circumferential direction at the following positions. That is, the lubricating oil flows in the following sequence: concave peak 21m of the first corrugation 21 → first inclination 21A of the first corrugation 21 → first convex peak 21p of the first corrugation 21 → second inclination 22B of the second corrugation 22 → concave peak 22m of the second corrugation 22 → first inclination 22A of the second corrugation 22 → first convex peak 22p of the second corrugation 22.

[0158] In this structure, such as Figure 13 As shown, the reservoir 23 is recessed near the boundary between the second inclination 22B and the first inclination 22A. The reservoir 23 spans both the second inclination 22B and the first inclination 22A. The reservoir 23 has approximately the same cross-sectional area at various locations in the direction in which the recess deepens. The reservoir 23 supplies lubricating oil to the region between the first inclination 22A and the second sliding surface 10A. Therefore, in this region, insufficient lubricating oil is suppressed, and the oil film reaction force P is increased. As a result, the frictional resistance is reduced. Furthermore, in Figure 13 In the text, the size of the storage tank 23 is exaggeratedly enlarged compared to its actual size.

[0159] In addition, such as Figure 14 As shown, the second corrugation 22 may also include a recess 24 as a reservoir for storing lubricating oil. The recess 24 is recessed at the first inclination 22A and the second inclination 22B, respectively. The cross-sectional area of ​​the recess 24 decreases as it deepens. The recess 24 supplies lubricating oil to the region between the second corrugation 22 and the second sliding surface 10A. This suppresses insufficient lubricating oil in this region and increases the oil film reaction force P. Figure 14 In the example, the state of the recess 24 of the second inclination 22B after being supplied with lubricating oil is shown. Afterwards, the recess 24 stores lubricating oil again. The recess 24 repeatedly performs this supply and storage of lubricating oil. Alternatively, the recess 24 of either the first inclination 22A or the second inclination 22B can be discarded.

[0160] exist Figure 14 In the example, in the first inclination 21A and the second inclination 21B of the first corrugation 21, the pits 24 are also recessed respectively. These pits 24 also function in the same way as the pits 24 of the second corrugation 22. Therefore, insufficient lubricating oil in the area between the first corrugation 21 and the second sliding surface 10A is suppressed. In addition, in Figure 14 In the text, the size of the pit 24 is exaggeratedly enlarged compared to its actual size.

[0161] Thus, multiple recesses 24 can be provided on the first sliding surface 20A. When multiple recesses 24 are provided on the first sliding surface 20A, the total opening area of ​​the multiple recesses 24 relative to the area of ​​the first sliding surface 20A can be 5% to 15%. However, this is not limited to this example; as long as multiple recesses 24 are provided, it is suitable for suppressing insufficient lubricating oil.

[0162] Here, Figure 13 The illustrated storage tank 23 and Figure 14 The illustrated pit 24 is an irregularity in the cross-sectional curve of the evaluation path PA, having a wavelength component longer than the first cutoff value λc and shorter than the third cutoff value λd. The third cutoff value λd is greater than the first cutoff value λc and less than the second cutoff value λf. For example, the third cutoff value λd is half of the second cutoff value λf. The two ripples 21 and 22 can also be determined based on the ripple curve after filtering with such a third cutoff value λd. That is, if the cross-sectional curve is filtered using the third cutoff value λd, the wavelength component of the irregularity of the storage groove 23 or the pit 24 can be obtained. The depth of the pit 24, which is a recess, is greater than the arithmetic mean roughness Ra of the first sliding surface 20A and smaller than the ripple height h3 of the second ripple 22.

[0163] (Effects of this implementation method)

[0164] Next, the effects of this embodiment will be explained.

[0165] (1) If one or more corrugations are formed on the first sliding surface 20A, when the first sliding surface 20A slides relative to the second sliding surface 10A, an oil film reaction force P, which is associated with a wedge effect, is generated between the two sliding surfaces 10A and 20A. In the structure of this embodiment, the corrugations are configured such that the value obtained by adding 3σ to the height h3 of the corrugations is 3.3σ or more and 30σ or less. In this case, the oil film reaction force P associated with the wedge effect is particularly high. Therefore, the friction between the two sliding surfaces 10A and 20A can be reduced.

[0166] (2) When the value obtained by adding 3σ to the corrugation height h3 is greater than 3.9σ and less than 15σ, the first sliding surface 20A and the second sliding surface 10A slide against each other within the range where the oil film reaction force P increases sharply in the relationship between the corrugation height h3 and the oil film reaction force P. Therefore, the friction can be significantly reduced by utilizing the oil film reaction force P.

[0167] (3) When the value obtained by adding 3σ to the corrugation height h3 is 6.6σ or higher, the effectiveness of the effect corresponding to (2) is improved.

[0168] (4) When the first inclination 22A and the second inclination 22B of the second corrugation 22 are provided with recesses, a necessary oil film can be formed between the two sliding surfaces 10A and 20A by supplying lubricating oil accumulated in the recesses. Specifically, by supplying lubricating oil from the recesses, the two sliding surfaces 10A and 20A become fluid lubricated. As a result, the desired oil film reaction force P can be obtained between the two sliding surfaces 10A and 20A. The recesses of the first corrugation 21 also have the same effect.

[0169] (5) When the total area of ​​the openings of the multiple recesses storing lubricating oil is 5% to 15% of the area of ​​the first sliding surface 20A, a sufficient amount of lubricating oil can be stored in the multiple recesses while obtaining a high oil film reaction force P. By supplying the lubricating oil to the wedge-shaped portion, a significant reduction in friction can be achieved by utilizing the oil film reaction force P.

[0170] (Experimental example)

[0171] Reference Figure 15 and Figure 16 The test examples of the sliding mechanism are explained.

[0172] [Experimental Example 1]

[0173] In Test Example 1, the corrugation height h3 and corrugation distance L of the ring 20 are 0.109 μm and 1 / 4 (=R / 4) of the sliding length R, respectively. In Test Example 1, the corrugation height h3 and corrugation distance L of the disk 10 are 0.105 μm and half (=R / 2) of the sliding length R, respectively. In the sliding mechanism of Test Example 1, the average corrugation height h3a and average corrugation distance La are 0.2 μm and 1 / 4 (=R / 4) of the sliding length R, respectively. The ring 20 of Test Example 1 includes a storage tank 23 for storing lubricating oil. Furthermore, the surface roughness Ra of the ring 20 and disk 10 of Test Example 1 is 0.01 μm.

[0174] [Experimental Example 2]

[0175] In Test Example 2, the corrugation height h3 and corrugation distance L of the ring 20 are 0.057 μm and half the sliding length R (=R / 2), respectively. In Test Example 2, the corrugation height h3 and corrugation distance L of the disk 10 are 0.076 μm and half the sliding length R (=R / 2), respectively. The average corrugation height h3a and average corrugation distance La in the sliding mechanism of Test Example 2 are 0.122 μm and 1 / 8 of the sliding length R (=R / 8). The surface roughness of the ring 20 and disk 10 in Test Example 2 is the same as in Test Example 1. The ring 20 of Test Example 2 has a recess 24 for storing lubricating oil. The volume of the recess 24 is 2617 μm. 3 Furthermore, the theoretically required pit volume is 1648 μm.3 The theoretically required pit volume is calculated as follows. Hereinafter, the ring 20 is viewed from above along the axial direction. Furthermore, as a premise, a plurality of pits 24 are arranged at approximately equal intervals between each other in the ring 20. Here, the sliding surface is imaginarily divided into multiple regions. A pit 24 is located at the center of one region. Moreover, each region is assigned as the area where a pit 24 should supply lubricating oil. If each pit 24 can supply a sufficient amount of lubricating oil to its assigned region, it is expected that an oil film reaction force P sufficient to reduce friction will be generated at each position on the sliding surface. The area of ​​the aforementioned region assigned to a pit 24 is called the coverage area. That is, for a specific pit 24, the coverage area is the area of ​​the region surrounding that pit 24 in the sliding surface, which is the area of ​​the sliding surface where that pit 24 should supply lubricating oil. In the ring 20 of this embodiment, the interval between adjacent pits 24 is determined such that the coverage area is, for example, 10 times the opening area of ​​the pit 24. The theoretically required pit volume can be calculated as the product of the coverage area and 6σ. That is, the theoretically required pit volume is the volume of pit 24 when a lubricant of an amount equivalent to a height of 6σ (=2×exit distance h2(3σ)) is supplied to the entire coverage area.

[0176] [evaluate]

[0177] For each of the above test examples, evaluate the dependence of the friction coefficient on the rotational speed of ring 20. For example... Figure 16 As shown, the coefficients of friction in Test Examples 1 and 2 continuously decrease from 300 rpm to 10 rpm. This tendency in the coefficient of friction reflects the state of fluid lubrication where the two sliding surfaces 10A and 20A are completely separated by an oil film due to the supply of lubricating oil from the recess. The coefficient of friction in Test Example 1 shows a sharp increase below 10 rpm, while the coefficient of friction in Test Example 2 does not show a sharp increase below 10 rpm, but continuously decreases from 300 rpm towards the minimum speed. That is, when the recess has a volume with a height of 6σ as assumed above, the two sliding surfaces 10A and 20A can significantly suppress friction even in the low-speed range below 10 rpm.

[0178] The sliding mechanism may also include a drive unit that allows the first member to slide relative to the second member. The drive unit may also allow the first member to slide stably relative to the second member at a predetermined speed of 250 rpm or less relative to the second sliding surface 10A. Furthermore, the drive unit may also allow the first member to slide stably relative to the second member at a predetermined speed U of 0.17 m / sec or less (= diameter of evaluation path PA (0.013 m) × 3.14 × 250 rpm / 60).

[0179] (Other implementation methods)

[0180] The above embodiments can be implemented by modification as follows. The above embodiments and the following modifications can be combined with each other to implement them within the scope of technical inconsistency.

[0181] • At least one of the first sliding surface 20A and the second sliding surface 10A may have at least one of the storage groove 23 and the recess 24. At least one of the first inclinations 21A, 22A and the second inclinations 21B, 22B may also have at least one of the storage groove 23 and the recess 24.

[0182] • At least one of the first sliding surface 20A and the second sliding surface 10A may also have a groove such as a herringbone that communicates with the part where lubricating oil is to be introduced, so as to supply lubricating oil from its surroundings. According to this modified example, when the oil film reaction force P is increased, the sliding speed U is increased accordingly with the supply of lubricating oil from the groove.

[0183] • If a high sliding speed U is not required, the recesses for storing lubricating oil, such as storage grooves 23 and pits 24, can be omitted from the first sliding surface 20A and the second sliding surface 10A.

[0184] • When the two sliding surfaces 10A and 20A slide in only one direction, the circumferential length of the inclination that exhibits a wedge effect relative to the sliding direction D among the first inclinations 21A and 22A and the second inclinations 21B and 22B can be longer than the circumferential length of the inclination that does not exhibit such a wedge effect. Therefore, a larger oil film reaction force P can be obtained relative to the sliding direction D.

[0185] The length of the sliding length R is not limited to the example of the above embodiment. The sliding length R can vary depending on the product being addressed. For example, the length of the sliding length R is about 0.1 mm to 50 mm. However, the length of the sliding length R is not limited to this example.

[0186] • The sliding mechanism can also be applied beyond ring disk tests. For example… Figure 17 As shown, a sliding mechanism can also be applied to the bearing mechanism 200, for example. In this case, the bearing mechanism 200 includes a rotating shaft 220 as a first component and a bearing 210 as a second component.

[0187] Bearing 210 is annular. Bearing 210 is fixed in position in a non-movable manner. Rotating shaft 220 is cylindrical. Rotating shaft 220 passes through bearing 210. Rotating shaft 220 is supported by the inner circumferential surface of bearing 210 and is able to rotate. Rotating shaft 220 rotates relative to bearing 210 about its own central axis.

[0188] The portion of the side surface of the rotating shaft 220 opposite to the inner circumferential surface of the bearing 210 constitutes a first sliding surface 220A. That is, the first sliding surface 220A is the portion of the side surface of the rotating shaft 220 located inside the bearing 210. On the other hand, the inner circumferential surface of the bearing 210 constitutes a second sliding surface 210A. The diameter of the rotating shaft 220 is slightly smaller than the diameter of the bearing 210. The distance between the two sliding surfaces 210A and 220A is 10 μm at any position circumferentially and radially centered on the central axis of the rotating shaft 220. Furthermore, in Figure 17 In the diagram, the distance between the two sliding surfaces 210A and 220A is exaggeratedly magnified. Lubricating oil is present in the entire area between the two sliding surfaces 210A and 220A. The two sliding surfaces 210A and 220A slide as the rotating shaft 220 rotates. The direction of rotation of the rotating shaft 220 corresponds to the sliding direction D of the first sliding surface 220A relative to the second sliding surface 210A.

[0189] For example, a plurality of corrugations 222 are formed on the first sliding surface 220A. The plurality of corrugations 222 are arranged circumferentially. Furthermore, in... Figure 17 For convenience, six dashed lines are used to represent multiple corrugations 222, but this does not represent the number of corrugations 222; rather, it schematically indicates the presence of corrugations. Similarly to the first sliding surface 220A, multiple corrugations 212 are formed on the second sliding surface 210A, for example. The multiple corrugations 212 are arranged circumferentially. Similar to the first sliding surface 220A, in... Figure 17 For convenience, the corrugations 212 of the second sliding surface 210A are represented by six dashed lines. The corrugations 212 and 222 of the two sliding surfaces 210A and 220A are formed at positions opposite each other in the radial direction. The corrugations 212 and 222 of the two sliding surfaces 210A and 220A are configured to satisfy the conditions for the composite corrugations described in the above embodiment. Furthermore, the evaluation path PA for extracting the corrugations 222 of the first sliding surface 220A is set as a path that connects one circumferential turn of the side surface of the rotating shaft 220. The evaluation path PA of the second sliding surface 210A is set as a path that connects one circumferential turn of the inner circumferential surface of the bearing 210. Moreover, the sliding length R of the corrugations is defined by the bearing mechanism 200 as the inner circumferential dimension of the inner circumferential surface of the bearing 210. For example, the sliding length R is approximately 50 mm. In addition, depending on the size of the gap between the outer circumferential surface of the rotating shaft 220 and the inner circumferential surface of the bearing 210, the following situations may exist. That is, due to the weight of the rotating shaft 220, the rotating shaft 220 sometimes moves closer to the lower side relative to the central axis of the bearing 210. Furthermore, sometimes only the portion of the outer circumferential surface of the rotating shaft 220 that is lower relative to the central axis contacts the inner circumferential surface of the bearing 210. In this case, the sliding length R is shorter than the inner circumferential dimension of the bearing 210.

[0190] Similar to the embodiments described above, at least one of the first sliding surface 220A and the second sliding surface 210A may be corrugated to form a recess for storing lubricating oil. Alternatively, corrugations may be formed only on one of the first sliding surface 220A and the second sliding surface 210A. In this case, the corrugation configuration only needs to satisfy the height requirements of the embodiments described above.

[0191] ·like Figure 18 As shown, a sliding mechanism can also be applied to the reduction mechanism 250, for example. The reduction mechanism 250 includes an output wheel 260, a oscillating gear 270, and multiple rotating shafts 280. The output wheel 260 is annular. The output wheel 260 has multiple arcuate grooves 262. The arcuate grooves 262 are recessed on the inner circumferential surface of the output wheel 260. The multiple arcuate grooves 262 are arranged at equal intervals in the circumferential direction centered on the central axis of the output wheel 260. The arcuate grooves 262 are semi-circular when viewed from above in the direction along the central axis of the output wheel 260. That is, the arcuate grooves 262 are curved.

[0192] A rotating shaft 280 is disposed in each arcuate groove 262. The rotating shaft 280 is cylindrical. The diameter of the rotating shaft 280 is slightly smaller than the diameter of the arcuate groove 262. The rotating shaft 280 is located within the arcuate groove 262. The central axis of the rotating shaft 280 passes through a position approximately coinciding with the center of the arcuate groove 262. Approximately half of the circumferential portion of the rotating shaft 280 is opposite the arcuate groove 262. The remaining portion of the rotating shaft 280 is exposed from the arcuate groove 262. The rotating shaft 280 is supported by the arcuate groove 262 to be rotatable. The rotating shaft 280 rotates relative to the arcuate groove 262 about its own central axis. The distance between the side of the rotating shaft 280 and the surface dividing the arcuate groove 262 is less than 10 μm at any position in the circumferential and radial directions of the rotating shaft 280. Lubricating oil is disposed between the rotating shaft 280 and the arcuate groove 262.

[0193] The oscillating gear 270 is located inside the output wheel 260. The outer circumferential surface of the oscillating gear 270 is wavy. That is, the outer circumferential surface of the oscillating gear 270 has a smooth, repeating pattern of bumps and grooves. The number of recesses on the outer circumferential surface of the oscillating gear 270 is one less than the number of recesses on the rotating shaft 280. A portion of these recesses, within a certain circumferential range of the oscillating gear 270, meshes with the rotating shaft 280. The rotation of the oscillating gear 270 with an input shaft (not shown) corresponds to the oscillation of the circumferential range meshing with the rotating shaft 280. The oscillation of the oscillating gear 270 is transmitted to the output wheel 260 via the rotating shaft 280. The output wheel 260 rotates at a lower speed than the input shaft.

[0194] Figure 19The magnified view shows the periphery of one of the plurality of rotating shafts 280. In the reduction mechanism 250, the rotating shaft 280 constitutes the first component of the sliding mechanism. The output wheel 260 constitutes the second component of the sliding mechanism. The side surface of the rotating shaft 280 constitutes the first sliding surface. The surface of the output wheel 260 with the dividing arcuate groove 262 constitutes the second sliding surface. Here, the rotating shaft 280 rotates due to contact with the oscillating gear 270. As the rotating shaft 280 rotates, the first sliding surface and the second sliding surface slide relative to each other. The direction of rotation of the rotating shaft 280 corresponds to the direction of sliding of the first sliding surface relative to the second sliding surface.

[0195] Multiple corrugations may also be formed on at least one of the first and second sliding surfaces of the reduction mechanism 250. Figure 19 The image shows an example where ripples are formed on both the first and second sliding surfaces. Figure 19 For convenience, three dashed lines are used to represent the multiple corrugations 285 formed on the side of the rotation shaft 280. The multiple corrugations 285 are arranged circumferentially. Additionally, in... Figure 19 For convenience, two dashed lines represent the multiple corrugations 265 formed in the arc groove 262. The multiple corrugations 265 are arranged circumferentially. The corrugations 265 and 285 on the two sliding surfaces are formed at radially opposite positions. The corrugations 265 and 285 on the two sliding surfaces are configured to satisfy the conditions for the composite corrugation described in the above embodiment. The evaluation path PA of the first sliding surface is set as a path connecting one circumference of the side of the rotating shaft 280. The evaluation path PA of the second sliding surface is set as connecting the two ends of the arc groove 262 circumferentially around the center of the circle. In these evaluation paths PA, the sliding length R of the corrugation is defined as the circumferential length of the arc groove 262 circumferentially around the center of the circle. For example, the sliding length R is approximately 20 mm. Furthermore, similar to the above embodiment, a recess for storing lubricating oil can be provided in the corrugation of at least one of the two sliding surfaces. Additionally, if corrugations are formed only on one of the two sliding surfaces, the corrugation only needs to satisfy the height condition.

[0196] • The application of sliding mechanisms is not limited to rotational movements; it can also be used for linear movements. For example, ... Figure 20 As shown, in the hydraulic pump 300, the piston 310 reciprocates linearly within a cylindrical recess 322 defined by the cylinder body 320. During this reciprocating motion, the outer circumferential surface of the piston ring 340, mounted on the side of the piston 310, slides against the circumferential surface 322A of the recess 322. Furthermore, the gap between the outer circumferential surface of the piston ring 340 and the circumferential surface 322A of the recess 322 is less than 10 μm, and lubricating oil is present between them. It is also possible to form more than one corrugation on at least one of the outer circumferential surface of the piston ring 340 and the circumferential surface 322A of the recess 322. That is, as... Figure 20As illustrated, consider forming multiple corrugations 323 on the circumferential surface 322A of the recess 322, or multiple corrugations 343 on the outer circumferential surface of the piston ring 340. The sliding length R of these corrugations is defined as the length of the piston ring 340 along its central axis. The direction along the central axis of the piston ring 340 corresponds to the sliding direction D of the piston ring 340 relative to the circumferential surface 322A of the recess 322. Figure 20 For convenience, four dashed lines are used to represent the multiple ripples 323 formed on the peripheral surface 322A of the recess 322. Additionally, in Figure 20 For convenience, a dashed line is used to represent the multiple corrugations 343 formed on the piston ring 340.

[0197] The definition of "ripple" and the calculation methods for the parameters characterizing "ripple" are not limited to the examples of the above embodiments. In addition to the examples of the above embodiments, a large uneven patch appearing in the cross-sectional curve of a specific evaluation path PA can also be treated as a "ripple".

[0198] For example, the "ripples" can be determined and the parameters involved in the ripples can be calculated using an envelope method as described below. In explaining this envelope method, the sliding mechanism consisting of a ring 20 and a disk 10, as described in the above embodiment, will be used as an example. Furthermore, the case where ripples exist only on the first sliding surface 20A in both the first sliding surface 20A and the second sliding surface 10A will be used as an example. Additionally, the case where three evaluation paths PA are set will be used as an example.

[0199] In the envelope method, a first step is performed. In this first step, the cross-sectional curves of the first evaluation path PA, the second evaluation path PA, and the third evaluation path PA are obtained. The definitions of these three evaluation paths PA are as described in the above embodiment. That is, the first evaluation path PA is the path near the inner periphery of the first sliding surface 20A. The second evaluation path PA is the path at the center between the inner and outer peripheries of the first sliding surface 20A. The third evaluation path PA is the path near the outer periphery of the first sliding surface 20A. The cross-sectional curves of each evaluation path PA can be obtained through observation using a white light interferometer. After obtaining the cross-sectional curves of each evaluation path PA in the first step, the following second to fifth steps are performed on these cross-sectional curves. The second to fifth steps will be explained below using a specific evaluation path PA as an example.

[0200] In the second step, the first cutoff value λc is applied as a low-pass filter to the cross-sectional curve. Therefore, in the second step, we obtain... Figure 21 The analysis is shown using curve ZL. Figure 21 The horizontal axis and Figure 3 Similarly, the phase angle is represented. Figure 21 The vertical axis and Figure 3 Similarly, this represents the depth of the recess in the first sliding surface 20A from the reference position. That is, the larger the positive value of the vertical axis, the greater the distance between the first sliding surface 20A and the second sliding surface 10A. Figure 3 Similarly, the reference position is determined by considering the observation position of the measuring equipment. For example, the first cutoff value λc used to obtain the analytical curve ZL is 0.08 mm. (In conjunction with...) Figure 4 In the corresponding calculation, other values ​​can also be used as the first cutoff value λc. The analysis curve ZL can also be a ripple curve. That is, the analysis curve ZL can also be obtained by applying the first cutoff value λc as a low-pass filter to the cross-sectional curve and applying the second cutoff value λf as a high-pass filter to the cross-sectional curve. The second cutoff value λf is the sliding length R. For example... Figure 21 As shown, the analysis curve ZL contains many small bumps and depressions corresponding to the accumulation grooves 23 or pits 24.

[0201] In the third process, such as Figure 22 As shown, by applying the so-called pattern method to the analytical curve ZL, the numerous convex and concave sections appearing in the analytical curve ZL are divided into multiple patterns ZM. A pattern ZM is a larger convex section obtained by ignoring smaller convex sections below a certain level in the convex sections shown in the analytical curve ZL. The pattern method is based on Japanese Industrial Standard JIS B0631:2000. Furthermore, an example of the maximum circumferential width of a pattern ZM is 1 / 20th of the sliding length R. In the third process, after dividing the analytical curve ZL into multiple patterns ZM, an envelope ZQ is generated by sequentially connecting the two ends of each pattern ZM in the circumferential direction. Figure 22 In the diagram, the envelope ZQ is represented by a thick solid line. Figure 23 The envelope ZQ is represented by a magnified image. Furthermore, Figure 23 The envelope ZQ shown is obtained by dividing the value of the envelope ZQ at each position in the circumference by the average value of the entire circumference region.

[0202] In the fourth step, the envelope ZQ obtained in the third step is subjected to Fourier transform. Figure 24 This represents the amplitude of each order obtained through the Fourier transform. The order is the wave number.

[0203] In the fifth step, the provisional index value ZUA is calculated. The provisional index value ZUA is the value obtained by dividing the cumulative value of the amplitude from order 1 to a specific order by the cumulative value of the amplitude from order 1 to order 20 for each order obtained through Fourier transform. An example of a specific order is order 4. The analysis of steps two through five above is performed on the three evaluation paths PA respectively. Thus, the provisional index value ZUA for each evaluation path PA is calculated. Then, the sixth step is performed.

[0204] In the sixth step, the average of the provisional index values ​​ZUA for each of the three evaluation paths PA is calculated as the final index value ZU. If the final index value ZU is above a threshold, it is treated as a "ripple" representing the unevenness or undulation in the cross-sectional curve. An example of the threshold is 0.4. The threshold is set to a value considered to represent a relatively large wave in the envelope ZQ, in conjunction with the specific number described above. Here, each index value, referred to as the provisional index value ZUA or the final index value ZU, represents the contribution rate of the amplitude of the wave components with wave numbers 1 to 4 among the various wave components contained in the envelope ZQ. In other words, a large index value indicates a large contribution rate of the wave components with small wave numbers in the envelope ZQ. Moreover, a large index value can be said to mean that the envelope ZQ as a whole constitutes a wave representing unevenness or undulation. When this unevenness or undulation is understood as a "ripple," it can be said that the larger the index value, the longer the wavelength of the ripple, and consequently, the longer the "wedge distance L" described in the above embodiment. That is, the index value can be considered an indicator of the size of the "wedge distance L."

[0205] If the presence of corrugations is known from the sixth process, proceed to the seventh process. In the seventh process, calculate the corrugation height h3. Specifically, as follows... Figure 23 As shown, for a given evaluation path PA, the width of the envelope ZQ, from its minimum to its maximum height, is calculated as a provisional ripple height Zh3. When determining the maximum and minimum heights of the envelope ZQ, a moving average or similar method can be applied to smooth out minor bumps and depressions. Based on this, a provisional ripple height Zh3 can also be calculated. In the seventh step, this provisional ripple height Zh3 is calculated for each of the three evaluation paths PA. Then, the average of the provisional ripple heights Zh3 for the three evaluation paths PA is calculated as the final ripple height h3. If the value obtained by adding the arithmetic mean roughness Ra to this ripple height h3 is more than 3.3 times but less than 30 times the arithmetic mean roughness Ra in the evaluation path PA, a higher oil film reaction force P can be obtained. Furthermore, the location where the height of the envelope ZQ reaches its maximum value can be understood as a "concave peak" of the ripple. In the envelope ZQ, the part where the height of the envelope ZQ becomes the minimum can be understood as the "peak" of the ripple.

[0206] Furthermore, when calculating the provisional corrugation height h3 in the seventh step, the following method can also be used. That is, by applying Fourier transform and inverse Fourier transform to the envelope ZQ generated in the third step, a specific envelope is generated that extracts only a specific wavenumber component from the various variable components contained in the envelope ZQ. Specifically, the specific envelope is a curve obtained by extracting, for example, waves with wavenumbers of 1 to 4 from the original envelope ZQ. The width from the minimum to the maximum height in such a specific envelope can also be used as the provisional corrugation height h3. At the same time, the width of the sliding direction D in the specific envelope, that is, the width of the range from the minimum to the maximum height, can also be treated as the corrugation distance L.

[0207] When the above-described envelope method is applied to a sliding mechanism where the first sliding surface 20A and the second sliding surface 10A each have corrugations, the following analysis is performed. For ease of understanding, an example is taken where a specific evaluation path PA is defined. In this embodiment, when both sliding surfaces 10A and 20A have corrugations, a composite corrugation curve representing the distance between the two sliding surfaces 10A and 20A is generated and analyzed, taking each rotational position during one revolution of the ring 20 as the object. When using the envelope method, a composite envelope line is generated instead of the composite corrugation curve. The composite envelope line is obtained by combining the envelope line ZQ of the first sliding surface 20A with a curve obtained by reversing the envelope line ZQ of the second sliding surface 10A. The envelope lines ZQ of each of the two sliding surfaces 10A and 20A can be generated using the method described in the third step. Such composite envelope lines are generated taking each rotational position during one revolution of the ring 20 as the object. Then, the fourth and fifth steps described above are performed on each composite envelope line. That is, for a given composite envelope, a Fourier transform is applied to the composite envelope, and a provisional index value ZUA is calculated based on the analysis results of the Fourier transform. Following this approach, the provisional index value ZUA is calculated for each rotational position during one revolution of ring 20. Then, after obtaining the provisional index values ​​ZUA for each rotational position, their average value is calculated as the composite index value. Furthermore, if the composite index value is, for example, above the aforementioned threshold of 0.4, it can be treated as the presence of "ripples". Then, in the case of "ripples", the provisional ripple height Zh3 at each rotational position is calculated based on the composite envelope of each rotational position. Then, the average of these multiple provisional ripple heights Zh3 is calculated as the average ripple height h3a. If the value obtained by adding the arithmetic mean roughness Ra to the average ripple height h3a is more than 3.3 times and less than 30 times the arithmetic mean roughness Ra, a higher oil film reaction force P can be obtained. The arithmetic mean roughness Ra mentioned here is the same as the description of the composite ripple in the above embodiment, and is the composite value of the arithmetic mean roughness Ra of the two sliding surfaces 10A and 20A.

[0208] Alternatively, multiple evaluation paths PA can be set when both the first sliding surface 20A and the second sliding surface 10A have corrugations. In this case, after calculating the composite index value in each evaluation path PA, their average value can be used as the final composite index value. Furthermore, the average corrugation height h3a can be calculated in each evaluation path PA, and their average value can be used as the final average corrugation height h3a.

[0209] In the above embodiments, a component composed of multiple objects can also be integrated into one object; conversely, a component composed of one object can be divided into multiple objects. Whether or not they are integrated, as long as the configuration achieves the purpose of the invention.

Claims

1. A sliding mechanism comprising a first member and a second member that slide against each other, and configured such that lubricating oil can pass between a first sliding surface of the first member opposite to the second member (i.e., a first sliding surface) and a second sliding surface of the second member opposite to the first member (i.e., a second sliding surface), wherein, If the length in the sliding direction of the portion where the distance between the first sliding surface and the second sliding surface, which slides along the sliding direction through the lubricating oil, is less than 10 μm, is defined as the sliding length. The first sliding surface then contains at least one convex peak and one concave peak, which are ripples with wavelength components shorter than the sliding length, along the sliding direction of the first member relative to the second member. If the surface roughness of the first sliding surface in the sliding direction is set as σ, and the distance between the convex peak and the concave peak is set as the height of the ripple, then... The ripple is configured such that the height of the ripple plus 3σ results in a value of 3.3σ or more and 30σ or less.

2. The sliding mechanism according to claim 1, wherein, The ripples are configured such that the height of the ripples plus 3σ results in a value of 3.9σ or more and 15σ or less.

3. The sliding mechanism according to claim 2, wherein, The ripples are configured such that the height of the ripples plus 3σ results in a value of 6.6σ or higher.

4. The sliding mechanism according to claim 1, wherein, The sliding length is 0.1mm to 50mm.

5. The sliding mechanism according to claim 1, wherein, The sliding length contains two of the ripples.

6. The sliding mechanism according to claim 1, wherein, The ripples include: The first convex peak is the convex peak that is adjacent to the concave peak in the sliding direction; The second convex peak is located in the sliding direction in the opposite direction to the first convex peak and is adjacent to the concave peak, with the concave peak as a reference. In the first inclination, the distance between the first sliding surface and the second sliding surface decreases as the distance moves from the concave peak toward the first convex peak; as well as In the second inclination, the distance between the first sliding surface and the second sliding surface decreases as the distance moves from the concave peak toward the second convex peak. At least one of the first inclination and the second inclination is provided with a recess for accumulating the lubricating oil.

7. The sliding mechanism according to claim 6, wherein, The recess is provided in multiple ways, and the total area of ​​the openings of the multiple recesses is 5% to 15% of the area of ​​the first sliding surface.

Images