JP2021050768A - Sliding structure - Google Patents

Abstract

To more improve sliding characteristics than before, in a sliding structure having a plurality of dimples on a sliding surface.SOLUTION: In a sliding structure, a first sliding surface (20a) of a first member (20) and a second sliding surface (30a) of a second member (30) slide against each other in a predetermined sliding direction (SD). The first sliding surface (20a) has a plurality of dimples (21) and satisfies the following condition A. Condition A: a distance Px in an x direction between at least one dimple (21) and a first adjacent dimple (21x) closest to the x direction among the other dimples (21) adjacent to the x direction in the sliding direction (SD) is larger than a distance Py in a y direction between at least one dimple and a second adjacent dimple 21y closest to the y direction among the other dimples (21) adjacent in the y direction.SELECTED DRAWING: Figure 3

Description

The present invention relates to a sliding structure.

Conventionally, as one of the surface modification techniques, surface texturing that improves sliding characteristics such as friction coefficient by finely processing the sliding surface is known.
For example, Patent Document 1 describes that by providing a large number of fine dimple-shaped recesses on a sliding surface, lubricating oil held in the recesses is exuded to a flat portion to suppress friction loss and wear. ing.

Japanese Patent No. 5636748

However, although Patent Document 1 mentions the opening area ratio (ratio of the opening area to the whole), the depth, the cross-sectional shape, etc. of the recesses (dimples), the shape and arrangement of the recesses and the sliding direction There is no mention of the relationship between. In particular, in this respect, it cannot be said that the technique described in Patent Document 1 can sufficiently improve / improve the sliding characteristics.

The present invention has been made in view of the above circumstances, and an object of the present invention is to improve sliding characteristics in a sliding structure having a plurality of dimples on a sliding surface as compared with the conventional case.

The present invention has a sliding structure in which the first sliding surface of the first member and the second sliding surface of the second member slide with each other in a predetermined sliding direction.
The first sliding surface has a plurality of dimples and has a plurality of dimples.
It was configured to satisfy the following condition A.
Condition A: At least one of the plurality of dimples has a distance in the sliding direction between the other dimples adjacent to the sliding direction and the first adjacent dimple closest to the sliding direction. It is larger than the distance in the orthogonal direction between the other dimples adjacent in the orthogonal direction orthogonal to the sliding direction and the second adjacent dimple closest to the orthogonal direction.

According to the present invention, in a sliding structure having a plurality of dimples on the sliding surface, the sliding characteristics can be improved as compared with the conventional case.

It is a figure which shows the sliding structure which has the sliding structure which concerns on embodiment of this invention, (a) is the perspective view of the sliding structure, (b) is the sectional view in line AA of (a). Is. It is a top view which shows the 1st sliding surface of 1st member. It is a figure for demonstrating the arrangement of a plurality of dimples. It is a figure for demonstrating the shape of each dimple. It is a figure which shows the analysis model of the analysis example. Among the analysis results, it is a contour diagram of the pressure distribution on the first sliding surface having dimples.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1A and 1B are views showing a sliding structure 10 having a sliding structure according to the present embodiment, in which FIG. 1A is a perspective view of the sliding structure 10 and FIG. 1B is a line AA of FIG. It is a cross-sectional view in.
As shown in FIGS. 1A and 1B, the sliding structure 10 includes a flat plate-shaped first member 20 and a second member 30, respectively. The first member 20 and the second member 30 slide against each other in a predetermined sliding direction SD with their sliding surfaces (first sliding surface 20a, second sliding surface 30a) facing each other. .. In this sliding, both the first member 20 and the second member 30 may move, or only one of them may move. A lubricating oil (lubricant) L atmosphere is formed between the first sliding surface 20a and the second sliding surface 30a.

The second sliding surface 30a of the second member 30 is formed in a flat surface shape.
On the other hand, the first sliding surface 20a of the first member 20 is based on a flat surface parallel to the second sliding surface 30a, and has a plurality of dimples (recesses) 21 on the flat surface.

FIG. 2 is a plan view showing a first sliding surface 20a of the first member 20, FIG. 3 is a view for explaining an arrangement of a plurality of dimples 21, and FIG. 4 is a view showing the shape of each dimple 21. It is a figure for demonstrating. In the following description, among the in-plane directions of the first sliding surface 20a, the direction along the sliding direction SD is referred to as the x direction, and the direction orthogonal to the sliding direction SD is referred to as the y direction.
As shown in FIG. 2, the plurality of dimples 21 in the present embodiment are arranged in a matrix along the x-direction and the y-direction at a uniform pitch in each direction. Further, the pitch (x pitch) between the two dimples 21 adjacent to each other in the x direction (sliding direction SD) is larger than the pitch (y pitch) between the two dimples 21 adjacent to each other in the y direction.

The arrangement of the plurality of dimples 21 is not limited to the matrix-like arrangement as shown in FIG. As shown in FIG. 3A, the dimple 21 has a distance Px in the x direction between the other dimples 21 adjacent in the x direction and the first adjacent dimple 21x closest to the x direction, which is adjacent in the y direction. It suffices that the dimples 21 are formed so as to be larger than the distance Py in the y direction between the other dimples 21 and the second adjacent dimple closest to the y direction (condition A). Here, the other dimples 21 "adjacent" in a certain direction are a predetermined angular range (for example, ± 45 °, or ± 30 ° in the x direction, y direction) centered on the reference dimple 21. Then, it means the other most recent dimple 21 at ± 60 °, etc.). In this case, it is preferable that Px / Py> 2.
Furthermore, it is not necessary for all the dimples 21 of the first sliding surface 20a to satisfy the above condition A. It is sufficient that at least one dimple 21 satisfies the above condition A, and it is more preferable that more than half of all the dimples 21 satisfy the above condition A. Therefore, each dimple 21 may be displaced in the x-direction or the y-direction from other adjacent dimples 21.

However, as shown in FIG. 3B, the dimple 21 overlaps at least a part with the first adjacent dimple 21x when viewed from the x direction, and at least a part overlaps with the second adjacent dimple 21y when viewed from the y direction. (Condition B). However, the dimples 21 are arranged in a matrix along the x-direction and the y-direction as in the present embodiment, that is, they overlap with the first adjacent dimples 21x when viewed from the x-direction, and are viewed from the y-direction. It is more preferable that the whole overlaps with the second adjacent dimple 21y.
Furthermore, it is not necessary for all the dimples 21 of the first sliding surface 20a to satisfy the above condition B. It is sufficient that at least one dimple 21 satisfying the above condition A satisfies the above condition B, and it is more preferable that more than half of all the dimples 21 including the dimple 21 satisfy the above condition B. ..

The plan view shape of each dimple 21 is formed into an elliptical shape having a long axis in the x direction.
However, each dimple 21 may be formed to be elongated in the x direction, that is, the maximum width a in the x direction is larger than the maximum width b in the y direction (condition C). Therefore, each dimple 21 may be an oval shape (rounded rectangle) or a plan view shape whose width changes in the x direction (and / or the y direction), as shown in FIG. 4A, for example.
Furthermore, it is not necessary for all the dimples 21 of the first sliding surface 20a to satisfy the above condition C. It is sufficient that at least one dimple 21 satisfying the above condition A satisfies the above condition C, and it is more preferable that more than half of all the dimples 21 including the dimple 21 satisfy the above condition C. ..
The width of each dimple 21 (maximum width a in the x direction and maximum width b in the y direction) is preferably in the range of 5 to 500 μm.

The cross-sectional shape of each dimple 21 in the depth direction is not particularly limited. Therefore, as shown in FIG. 4B, for example, the cross-sectional shape may be a partial spherical shape, an arc shape, a rectangular shape, or the like.
The depth d of each dimple 21 is preferably in the range of 0.5 to 20 μm.

As described above, according to the present embodiment, the dimple 21 is located in the x direction between the first adjacent dimple 21x closest to the x direction among the other dimples 21 adjacent in the x direction (sliding direction SD). The distance Px is formed to be larger than the distance Py in the y direction between the other dimples 21 adjacent in the y direction and the second adjacent dimple 21y closest to the y direction.
Thereby, the load capacity can be improved. That is, when sliding, a positive dynamic pressure is generated on one side of the sliding direction SD and a negative dynamic pressure is generated on the other side around the dimples 21, and the distance between two dimples 21 adjacent to each other in the x direction is If they are close to each other, the positive dynamic pressure will be offset by the negative dynamic pressure. On the other hand, in the y direction orthogonal to the sliding direction SD, dynamic pressure is similarly generated in the two adjacent dimples 21, so that this phenomenon does not occur. Therefore, by making the distance Px between the first adjacent dimples 21x adjacent in the x direction larger than the distance Py between the second adjacent dimples 21y adjacent in the y direction, the dimples 21 in the sliding direction SD It is possible to suppress the cancellation of dynamic pressure between them and improve the load capacity. As a result, the coefficient of friction can be reduced.
Therefore, in the sliding structure having a plurality of dimples 21 on the first sliding surface 20a, the sliding characteristics such as the load capacity and the friction coefficient are compared with the conventional case in which the influence of the sliding direction on the dimple configuration is not considered. Can be improved. As a result, direct contact with the sliding surface and breakage of the oil film can be prevented, and adhesion and absorptive wear can be suppressed.

Further, according to the present embodiment, the dimple 21 is formed so that the maximum width a in the x direction is larger than the maximum width b in the y direction, that is, the dimple 21 is elongated in the sliding direction SD.
As a result, the fine wedge effect of the dimples 21 and the lubricating oil can be effectively generated, the fluid pressure can be improved, and the load capacity can be further improved.

[Analysis example]
Next, an analysis example in which the effect of the sliding structure according to the present embodiment has been confirmed will be described.
In this analysis, for multiple analytical models with different dimple arrangements and shapes, the load capacity of each was calculated using the Reynolds equation and cavitation model that describe the motion of the lubricating oil with reference to the following papers.
・ Elrod, H, G., "A Cavitation Algorithm," Trans. ASME, J.Lub. Tech., 103, 1981, 350-354.
・ Vijayaraghavan, D. and Keith Jr., TG, "Development and Evaluation of a Cavita-tion Algorithm," Tribol. Trans., 32, 1989, 225-233.

<Analysis model>
The analysis model is shown in FIG. Table 1 below shows the x-direction pitch (x-pitch), y-direction pitch (y-pitch), and area ratio of the dimples in each analysis model. The "area ratio" of the dimples (hereinafter, simply referred to as "area ratio") refers to the ratio of the total opening area of the dimples to the total area area (5 mm square) of the first sliding surface.

As shown in FIGS. 5 and 1, in this analysis, there is an example corresponding to the sliding structure of the above embodiment, and a comparative example 1 having the same area ratio as that of the embodiment and having circular dimples arranged at an equal pitch. , Four analysis models of Comparative Example 2 in which the x-pitch of Comparative Example 1 was multiplied by 1.26 and Comparative Example 3 in which the x-pitch of Comparative Example 1 was doubled were analyzed. All circular dimples had a diameter of 200 μm. The elliptical dimples had a major axis of 400 μm and a minor axis of 200 μm. The cross-sectional shape of the dimples in the depth direction was a rectangular cross section (see the right side view of FIG. 4B).

<Analysis conditions>
The first member provided with dimples was fixed, and the other second member was moved in the sliding direction. Both sides of the sliding direction (horizontal direction in FIG. 5) of both members were set to periodic boundary conditions (infinity boundary), and both sides in the direction orthogonal to the sliding direction (vertical direction in FIG. 5) were set to atmospheric pressure conditions.
Other analysis conditions are shown in Table 1 below. In the table, "clearance" indicates the gap between the sliding surfaces, and "depth" indicates the depth of the dimples. In Table 1, the power of 10 is represented by using "E".

<Analysis result>
FIG. 6 shows a contour diagram of the pressure distribution of the first sliding surface having dimples. Table 3 below summarizes the analysis results. The "average pressure" in Table 3 was calculated from the pressure distribution, and the "load capacity" was calculated by subtracting the atmospheric pressure (1 atm) as the reference pressure from the average pressure. In this analysis, the area ratio that affects the load capacity is not matched between the analysis models, so the load capacity of each analysis model is simply eliminated by the parameter obtained by dividing the load capacity by the area ratio. Evaluated ability.

From Table 3, it can be seen that the values obtained by dividing the load capacity by the area ratio are larger in Comparative Examples 2 and 3 in which the x-pitch in the sliding direction is longer than in Comparative Example 1. Therefore, it is considered that the load capacity is improved and the friction coefficient is reduced by making the x-pitch in the sliding direction larger than the y-pitch. From the pressure distribution diagram of FIG. 6, it is considered that this effect is due to the fact that by widening the x-pitch, the positive dynamic pressure of each dimple is less likely to be offset by the negative pressure of other dimples adjacent in the x-direction.
Further, from Table 3, it can be seen that the value obtained by dividing the load capacity by the area ratio is larger in the examples than in any of the comparative examples. Therefore, it is considered that the load capacity is further improved and the friction coefficient is reduced by making the circular dimples into elliptical dimples that are long in the sliding direction.

[Other]
Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.
For example, in the above embodiment, the case where the sliding surfaces (first sliding surface 20a and second sliding surface 30a) are flat surfaces has been described, but the sliding surfaces may be curved surfaces. Therefore, the sliding structure according to the present invention is widely applied not only to linear guides in which sliding surfaces are flat surfaces, but also to pin-bush and pin-pin grooves in which sliding surfaces are curved surfaces. Can be done.

Further, the plurality of dimples 21 need only be formed on at least one of the two sliding surfaces (first sliding surface 20a and second sliding surface 30a), and are formed on both of the two sliding surfaces. It may have been.
Further, the method for forming the plurality of dimples is not particularly limited, and laser processing, shot peening, cutting processing and other processing methods can be used.
In addition, the details shown in the above-described embodiment can be appropriately changed without departing from the spirit of the invention.

10 Sliding structure 20 1st member 20a 1st sliding surface 21 Multiple dimples 21 x 1st adjacent dimple 21y 2nd adjacent dimple 30 2nd member 30a 2nd sliding surface ax direction maximum width by direction maximum Significantly L Lubricating oil Px Distance in x direction from the first adjacent dimple Py Distance in the y direction from the second adjacent dimple SD Sliding direction

Claims (7)

A sliding structure in which the first sliding surface of the first member and the second sliding surface of the second member slide with each other in a predetermined sliding direction.
The first sliding surface has a plurality of dimples and has a plurality of dimples.
A sliding structure that satisfies the following condition A.
Condition A: At least one of the plurality of dimples has a distance in the sliding direction between the other dimples adjacent to the sliding direction and the first adjacent dimple closest to the sliding direction. It is larger than the distance in the orthogonal direction between the other dimples adjacent in the orthogonal direction orthogonal to the sliding direction and the second adjacent dimple closest to the orthogonal direction. More than half of the plurality of dimples satisfy the condition A.
The sliding structure according to claim 1. Satisfy the following condition B,
The sliding structure according to claim 1 or 2.
Condition B: The at least one dimple overlaps at least a part with the first adjacent dimple when viewed from the sliding direction, and at least a part overlaps with the second adjacent dimple when viewed from the orthogonal direction. The at least one dimple overlaps the first adjacent dimple when viewed from the sliding direction, and overlaps the entire second adjacent dimple when viewed from the orthogonal direction.
The sliding structure according to claim 3. More than half of the plurality of dimples satisfy the condition B.
The sliding structure according to claim 3 or 4. Satisfy the following condition C,
The sliding structure according to any one of claims 1 to 5.
Condition C: The maximum width of the at least one dimple in the sliding direction is larger than the maximum width in the orthogonal direction. More than half of the plurality of dimples satisfy the condition C.
The sliding structure according to claim 6.

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