JP2012189223A - Low friction slide member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low friction slide member capable of reducing friction and wear which are caused between sliding surfaces, the sliding member being used in an internal combustion engine for a piston, a cylinder and the like sliding relatively under the presence of lubricant.SOLUTION: The low friction slide member is formed with a number of fine recesses on a sliding surface of at least one slide member of slide members for the internal combustion engine which relatively slide under the presence of lubricant, the fine recesses form second fine recesses whose widths and depths in the slide direction have smaller values than those of first fine recesses, on the sliding surface of the plurality of first fine recesses, and the second fine recesses are formed in a groove shape extended continuously on the sliding surface between the first fine recesses, characteristically.

Description

  The present invention relates to a low friction sliding member that slides relatively in the presence of lubricating oil.

  For example, since pistons and cylinders are generally made of metal, there is a problem of wear and seizure of the sliding surface due to sliding at high speed. In order to prevent such wear and the like, there is a method of interposing a viscous fluid between the sliding surfaces, but reduction of friction or the like is not sufficient.

  In order to further reduce friction and the like, conventionally, a method of forming an uneven surface on a sliding surface has been performed. For example, in the following Patent Document 1, in the sliding members that slide with each other through the lubricating oil, the inflow amount of the lubricating oil with respect to the gap between the sliding surfaces of the sliding member to maintain the oil film thickness of the lubricating oil Means is disclosed in which the closest distance between the sliding surfaces when the amount of outflow is balanced is made larger than the maximum height of the concavo-convex portion formed on the sliding surface. Thereby, the oil film thickness of lubricating oil is ensured and friction reduces.

  However, even in the conventional sliding member as described above, although it is possible to reduce friction, further reduction of friction is desired.

Japanese Patent Laid-Open No. 2002-213612 (Summary, see FIG. 1)

  The present invention provides a low friction sliding member that can reduce friction and wear generated between sliding surfaces in a low friction sliding member for an internal combustion engine that slides relatively in the presence of lubricating oil. Objective.

  The present invention is a low friction sliding member in which a plurality of fine concave portions are formed on a sliding surface of at least one sliding member of a sliding member that slides relatively in the presence of lubricating oil, the fine concave portion Forming a second fine recess having a width and depth in the sliding direction smaller than those of the first fine recess between the first fine recesses, and the second fine recess is between the first fine recesses. The low friction sliding member is characterized in that the sliding surface is formed into a groove shape extending continuously.

  Further, the present invention is a low friction sliding member in which a number of fine recesses are formed on a sliding surface of at least one sliding member of a sliding member that slides relatively in the presence of lubricating oil, The fine concave portion forms a second fine concave portion whose width and depth in the sliding direction are smaller than those of the first fine concave portion between the multiple first fine concave portions, and the second fine concave portion has the first fine concave portion. The surface roughness (Rz) between the concave portions is 0.03 μm ≦ Rz ≦ 0.25 μm, and the surface roughness distortion (Rsk; described in JIS B 0601) is a random groove having a negative value. It is a low friction sliding member.

  According to the low friction sliding member of the present invention, a large number of first fine recesses are formed on the sliding surface of the sliding member that slides relatively in the presence of lubricating oil, and the first fine recesses are formed between the first fine recesses. Since the two minute recesses are formed, the oil retaining property on the sliding surface is improved, and the friction generated between the sliding surfaces can be reduced. Further, by making the width and depth of the second fine recess in the sliding direction smaller than those of the first fine recess, it becomes possible to reduce friction without causing direct contact due to a decrease in load capacity. . In the present specification, the “fine concave portion” means an extremely small concave portion on the order of microns.

It is a schematic sectional drawing which shows the principal part of the engine in which the low friction sliding member which concerns on embodiment of this invention is used. It is a schematic perspective view which shows the principal part of the same low friction sliding member. It is a top view which shows the recessed part of the same low friction sliding member. FIG. 4 is an end view taken along line 4-4 of FIG. 3. It is the schematic which shows the example of various shapes of a 2nd fine recessed part. It is a schematic perspective view which shows the principal part of a reciprocating test machine. A is a plan view of a pin test piece, and B is a side view of the pin test piece. A is a plan view showing the size of a flat test piece, and B is a side view of the flat test piece. 6 is a graph showing a cross-sectional curve of Comparative Example 1. 10 is a graph showing a cross-sectional curve of Comparative Example 2. 3 is a graph showing a cross-sectional curve of Example 1.

  Hereinafter, the low friction sliding face material according to the present invention will be described in detail.

  1 is a schematic cross-sectional view showing a main part of an engine in which a low friction sliding member according to an embodiment of the present invention is used, FIG. 2 is a schematic perspective view showing the main part of the low friction sliding member, and FIG. FIG. 4 is a plan view showing a concave portion of the low friction sliding member, and FIG. 4 is an end view taken along line 4-4 of FIG.

  The low-friction sliding member according to the present embodiment is a portion that slides in the presence of lubricating oil, such as an engine piston 1 and cylinder 2, a crankshaft 3 and a metal bearing 4 as shown in FIG. Used to greatly reduce friction.

  In a pair of sliding members that slide in contact with each other in the presence of lubricating oil, the length of the convex portion formed in one sliding member in a direction parallel to the sliding direction is the other sliding member. If it is longer than the length of the recess in the direction parallel to the sliding direction formed on the member, the lubricating oil can be trapped in the recess during sliding, and a constant oil film thickness can be maintained between the sliding members. Low friction can be realized. However, if the recess is too large or too deep, the load capacity decreases and direct contact tends to occur. The present inventors have completed the present invention based on such findings. That is, in the present invention, in order to improve the oil retaining property of the lubricating oil in a state where the influence on the load capacity is small, a concave portion having a small depth and a shallow depth is formed in the sliding direction or the lubricating oil flow direction. Thus, the present invention is suitable for application to a component side having an arcuate inner surface such as the bore of the cylinder 2 or the inner peripheral surface of the metal bearing 4.

  Further details will be described. The low-friction sliding member of the present embodiment includes a first sliding member 10 and a second sliding member 11 that slide relatively in the direction of the arrow shown in FIG. 2 in the presence of lubricating oil. The sliding surfaces 10 a, 11 a of both sliding members 10, 11 are formed with a large number of first fine recesses 12 and a plurality of second fine recesses 12 formed between these first fine recesses 12 and smaller than the first fine recesses 12. A fine recess 13 is formed.

  2-4, the 1st fine recessed part 12 is a flat part flat in the direction orthogonal to a sliding direction, has the value of width X1 and depth h1, and the 2nd fine recessed part 13 is 1st. It is formed on the sliding surfaces 10a and 11a between the fine concave portions 12, and has a width X2 and a depth h2 which are smaller than the width X1 and the depth h1 of the first fine concave portion 12 in the sliding direction. Thus, when the 2nd fine recessed part 13 used as an oil reservoir exists in the flat part between the 1st fine recessed parts 12, oil retention property can improve, a friction can be reduced, and seizure resistance can be improved.

  However, in order to improve oil retention and reduce friction, the size of the first fine concave portion 12 and the second fine concave portion 13 is a problem, and this size depends on the sliding direction or the oil flow direction. It should be small and shallow. In the present embodiment, the ratio (X2 / X1) of the width X2 in the sliding direction of the second fine recess 13 to the width X1 in the sliding direction of the first fine recess 12 is 1/15 to 2/3, The ratio (h2 / h1) between the depth h2 of the second fine recess 13 and the depth h1 of the first fine recess 12 is set to 1/10 to 1/2.

  If the second fine recess 13 is too large, the area ratio becomes too large, so that the load capacity decreases and direct contact is likely to occur, and the same is true when the depth is too deep. Therefore, it has been confirmed by experiments that the ratios X2 / X1 and h2 / h1 are preferably set to the above values in order to improve the oil retaining property of the surface oil in a state where the influence on the load capacity is small. .

  The influence on the load capacity and the oil retaining property of the surface are not only such a ratio but also the ratio of the sliding members of the first fine recess 12 and the second fine recess 13 to the entire sliding surfaces 10a, 11a, that is, the area ratio. (%), Depth, and individual size are also important factors.

  The area ratio (%) of the first fine recess 12 is preferably 0.3% to 10%. If it is 0.3% or less, the effect of thickening the oil film cannot be obtained sufficiently, and if it is 10% or more, the load capacity decreases and direct contact tends to occur, and the friction reduction effect cannot be sufficiently obtained. Such an area ratio can be calculated, for example, by subjecting a surface observation photograph to image processing.

  With respect to the depth of the first fine recess 12, the maximum depth is preferably 0.5 μm to 20 μm. If it is 0.5 μm or less, the dynamic pressure effect is not exhibited, and the oil confinement effect is not sufficient, so that the friction reduction effect is not sufficiently exhibited. If it exceeds 20 μm, the load capacity is reduced, metal contact is likely to occur, and sufficient friction reduction cannot be realized. The depth of the concave portion is measured by a non-contact three-dimensional white light phase modulation interference method using a three-dimensional surface structure analysis microscope NewView 5032 (manufactured by Zygo Corporation).

  Regarding the size of the first fine recess 12, the length of the short side is preferably 50 μm to 150 μm, and the length of the long side is preferably not less than 2 times and not more than 10 times the short side. If the short side of the fine recess is 50 μm or less, the oil does not sufficiently flow into the fine recess and the effect of dynamic pressure is not sufficiently obtained, and if it is 150 μm or more, the load capacity may decrease and metal contact may occur easily. is there. Therefore, if it is this range, the 1st fine recessed part 12 will fully exhibit a dynamic pressure effect, and can express the friction reduction effect by thickening an oil film.

  On the other hand, it is preferable that the area ratio (%) of the 2nd fine recessed part 13 is 0.5%-20%. In the case of 0.5% or less, the effect of the oil reservoir by the second fine concave portion 13 is not sufficient, and the friction reducing effect is not sufficiently expressed, and in the case of 20% or more, the load capacity is reduced and the friction characteristics are deteriorated.

  The depth of the second fine recess 13 is shallower than that of the first fine recess 12, and the maximum depth is preferably 1/2 to 1/10 of the maximum depth of the first fine recess 12. When the depth of the 2nd fine recessed part 13 is too deep, the fall of a load capacity will be caused and it will become easy to generate | occur | produce a metal contact. Moreover, even if it is too shallow, the ability to retain oil is lost, and metal contact is likely to occur.

  The size of the second fine recess 13 is such that the width in the sliding direction is smaller than the width of the first fine recess 12 and the width in the sliding direction is 1/15 to 2/3 of the width of the first fine recess 12. Is preferred. If the second fine recess 13 is too small, the oil retaining effect is lost and metal contact is likely to occur. Moreover, when too large, load capacity will fall and it will become easy to generate | occur | produce a metal contact.

  The sum of the area ratio (%) × depth (μm) values of the first fine recess 12 and the second fine recess 13 is preferably 30 or less. If the value of area ratio (%) x depth (μm) of each of these recesses 12 and 13 exceeds 30, the amount of oil that enters the recesses increases as the load capacity decreases, and the oil film becomes thinner and direct contact is reduced. This is because they tend to occur and sufficient friction reduction cannot be realized.

  The shape of the first fine concave portion 12 and the second fine concave portion 13 is a rectangular shape in FIG. 3, but is not limited to this, and any shape such as a rectangle, an ellipse, and an indefinite shape can be adopted. .

  In particular, since the shape of the second fine recess 13 is formed as a role of an oil reservoir for improving oil retention, each may be formed independently, but may be a continuous groove shape. . 5A to 5E are schematic views illustrating various shape examples of the second fine recess.

  Regarding the shape of the second fine recess 13, for example, as shown in FIG. 5A, a larger number than that shown in FIG. 3 may be formed on the sliding surface 11 a between the first fine recesses 12. As shown in FIG. 5B, a groove shape that continuously extends on the sliding surface 11 a between the first fine recesses 12 may be used. In the case of the groove-shaped second fine recess 13, it may be formed in parallel with the first fine recess 12 as shown in FIG. 5C. Depending on the case, the 2nd fine recessed part 13 may be formed in dot shape, as shown to FIG. 5D. However, even the second fine concave portion 13 having such a shape should have the above-described area ratio and depth.

  Furthermore, as shown in FIG. 5E, the second fine recess 13 can exhibit a function of holding the oil film even if it is randomly formed in a streak shape (hereinafter referred to as a random groove).

  When the second fine recess 13 is a random groove 15, the surface roughness Rz between the first fine recesses 12 is preferably 0.03 μm ≦ Rz ≦ 0.25 μm.

  When the surface roughness Rz is 0.03 μm or less, the oil is not sufficiently retained because the surface is smooth. When the surface roughness Rz is 0.25 μm or more, the roughness is too large and The direct contact resulting from the increase in the height of the protrusion occurs, and the friction is not sufficiently reduced. The surface roughness Rz is measured by, for example, a stylus type surface shape measuring device FormTalysurf-120L (manufactured by Taylor-Hobson).

  Further, the random groove 15 preferably has a negative surface roughness distortion (Rsk; described in JIS B 0601). If the Rsk value of the distortion of the surface roughness is negative, the distribution of the recessed portion from the surface of the roughness component is increased, and the oil retaining property is excellent, which is preferable.

Example 1
6 is a schematic perspective view showing a main part of a test machine for reciprocating the test piece, FIG. 7A is a plan view of the pin test piece, FIG. 7B is a side view of the pin test piece, and FIG. 8A shows the size of the flat plate test piece. FIG. 8B is a side view of a flat plate test piece.

  In the experiment, as shown in FIG. 6, on a flat plate test piece 20 having various concave shapes formed on a flat surface, the pin test piece 21 is slid back and forth in the direction of a double arrow with a vertical load W applied. Was done. The flat test piece 20 has a thickness of 7 mm, a length of 60 mm, and a width of 40 mm. On the sliding surface, the first fine concave portion 12 and the second fine concave portion 13 were formed on the surface. The pin test piece 21 has a thickness of 8 mm, a length of 40 mm, and a height of 11.5 mm. The tip surface has a radius of curvature R, but is a DLC that is a hard carbon thin film using a CVD method. (Diamond like carbon) was coated.

  The vertical load W with respect to the pin test piece 21 is 25 kgf, the speed is 600 rpm, and the lubricating oil is 5W30 oil (oil temperature 80 ° C.) dropped at 0.8 cc / min, and the friction coefficient is measured. The friction coefficient in the case of 1 was set to “1” and compared with this.

  Here, in Comparative Example 1, after making a smooth mirror surface by polishing, only the first fine concave portion 12 is formed on the surface, and the surface roughness of the flat portion is Rz = 0.3 μm, the first fine surface. The recess 12 was rectangular and had a size of 80 μm × 320 μm, a depth of 3 μm, and an area ratio of 1%.

  In Comparative Example 2, the first fine concave portion 12 is not formed in the flat portion, and the surface roughness of the flat portion is processed with a cross hatch of Rz = 3 μm.

  In Example 1, the surface roughness of the flat portion is Rz = 0.3 μm, the first fine recess 12 is rectangular, has a size of 80 μm × 320 μm, a depth of 3 μm, an area ratio of 1%, The second fine recess 13 is a cross-hatched groove having a length X2 in the sliding direction of 20 μm, a depth of 1 μm, and an area ratio of 10%.

  9, 10, and 11 are graphs showing the cross-sectional curves of Comparative Examples 1 and 2 and Example 1, in which the vertical axis indicates the surface roughness and the horizontal axis indicates the position. FIGS. 9 and 11 also show enlarged views of the main part. This enlarged view of the main part shows the surface roughness of the vertical axis in units of 1 μm and the position of the horizontal axis in units of 200 μm. ing. As is apparent from FIGS. 9 to 11, the surface of Comparative Example 1 is a very smooth surface, the surface of Comparative Example 2 is rough, and the surface of Example 1 has both a very smooth surface and a rough portion. .

  Examples include Examples 2 to 7 in addition to Example 1. In Examples 2 to 7, Example 1 and second fine recess 13 are different as described below. That is, in Examples 2 to 7, as in Example 1, the surface roughness of the flat portion was processed to Rz = 0.3 μm, the first fine recess 12 was rectangular, the size was 80 μm × 320 μm, and the depth Is formed with a thickness of 3 μm and an area ratio of 1%, and the second fine concave portion 13 is a cross-hatched groove. In Examples 2 to 7, the second fine concave portion 13 is shown in Table 1. This also shows differences in the following points.

  In Example 2, the second fine recess 13 has a sliding direction length X2 of 20 μm, a depth of 1 μm, and an area ratio of 25%.

  In Example 3, the second fine recess 13 has a length X2 in the sliding direction of 20 μm, a depth of 1 μm, and an area ratio of 0.5%.

  In Example 4, the second fine recess 13 has a sliding direction length X2 of 20 μm, a depth of 0.2 μm, and an area ratio of 10%.

  In Example 5, the second fine recess 13 has a sliding direction length X2 of 20 μm, a depth of 2 μm, and an area ratio of 20%.

  In Example 6, the second fine recess 13 has a sliding direction length X2 of 60 μm, a depth of 1 μm, and an area ratio of 10%.

  In Example 7, the second fine recess 13 has a sliding direction length X2 of 10 μm, a depth of 1 μm, and an area ratio of 10%.

  In Examples 8 and 9, the surface roughness of the flat portion of the first fine recess 12 is processed to Rz = 0.3 μm, and the first fine recess 12 has a rectangular shape with a size of 80 μm × 320 μm and a depth of 8 μm. However, the area ratio of the first fine recesses 12 is set to 5%, and the second fine recesses 13 are formed as cross-hatched grooves. However, in Example 8, the area ratio of the second fine concave portion 13 is set to 20%, and in Example 9, the area ratio of the second fine concave portion 13 is set to 10%.

  In these examples and comparative examples, the size, depth, area ratio, product of depth and area ratio of the first fine recess 12 and the second fine recess 13 are summarized, and the experimental results are shown in Table 1. Become.

  As is apparent from Table 1, the present invention is more effective than Comparative Example 1 in which a relatively large first fine recess 12 is formed on a mirror-finished surface and Comparative Example 2 having only fine cross-hatch eyes. It can be seen that in the applied embodiment, the frictional resistance is reduced in most cases. In the embodiment to which the present invention is applied, a relatively large first fine concave portion 12 and a second fine concave portion 13 made of a cross-hatched groove or the like are formed on a smooth surface. The function of the recess 12 itself as an oil reservoir is added to the function of an oil reservoir by the small second micro recess 13 formed in the flat portion between the first micro recesses 12, thereby greatly improving the oil retaining property of the entire micro recess. In addition, the friction reducing effect is exhibited. In particular, the presence or absence of a large number or a plurality of second fine recesses 13 supplements the oil retaining property of the first fine recesses 12 over the entire sliding surface, and contributes greatly to the reduction of frictional resistance. It has become.

  When the low friction sliding member of the present invention is applied to a sliding member for an internal combustion engine that slides in the presence of lubricating oil, for example, a cylinder, a metal bearing, or the like that forms an arc-shaped inner surface, The 1st fine recessed part 12 and the 2nd fine recessed part 13 exhibit the role of the oil sump which improves oil retention, and the amount of the oil which penetrates into these recessed parts increases, and the situation where the load capacity falls and the oil film becomes thin is prevented. In addition, it is a preferable internal combustion engine in which direct contact between metals does not occur and frictional resistance is reduced.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. For example, in the above-described embodiment, the first micro concave portion 12 and the second micro concave portion 13 are formed on a flat low friction sliding member. However, not only this but also other various shapes, for example, Also, the present invention can be applied to one that is curved to some extent, one that has an arcuate surface, or one that is spherical.

  INDUSTRIAL APPLICABILITY The present invention can be used for an internal combustion engine component that reduces sliding friction of a sliding member that slides in the presence of lubricating oil, particularly a piston, cylinder, or bearing member.

10, 11 ... sliding member,
10a, 11a ... sliding surface,
12 ... 1st minute recessed part,
13 ... 2nd fine recessed part.

Claims (2)

A low-friction sliding member in which a large number of fine recesses are formed on the sliding surface of at least one sliding member of a sliding member that relatively slides in the presence of lubricating oil,
The fine concave portion forms a second fine concave portion having a smaller width and depth in the sliding direction between the first fine concave portions than the first fine concave portion,
The low-friction sliding member, wherein the second fine recess is formed in a groove shape that continuously extends the sliding surface between the first fine recesses. A low-friction sliding member in which a large number of fine recesses are formed on the sliding surface of at least one sliding member of a sliding member that relatively slides in the presence of lubricating oil,
The fine concave portion forms a second fine concave portion having a smaller width and depth in the sliding direction between the first fine concave portions than the first fine concave portion,
The second fine recess has a surface roughness (Rz) between the first fine recesses,
0.03 μm ≦ Rz ≦ 0.25 μm
A low-friction sliding member, characterized in that a random groove having a negative surface roughness distortion (Rsk; described in JIS B 0601) is negative.