JP2007321861A - Low-friction sliding member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide low-friction sliding members for an internal combustion engine, which relatively slide under the existence of viscous fluid while less producing friction and wear between the sliding faces, wherein fine recessed portions are easily formed in the sliding faces in the way of easily managing dispersion regarding their depths and sizes to actualize high friction reducing performance. <P>SOLUTION: The low-friction sliding members 10, 11 which relatively slide under the existence of viscous fluid have continuous-waveform finely recessed grooves 12 in the sliding faces 10a, 11a on at least one side. The fine recessed grooves 12 are formed so that the extending direction of the waveform corresponds to the sliding direction of the sliding members 10, 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  For example, since pistons and cylinders are generally made of metal, there is a problem of friction, wear or seizure of the sliding surface due to sliding at a 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.

  Furthermore, in order to reduce friction and the like, conventionally, a method of forming an uneven surface on the sliding surface has been performed. For example, in Patent Document 1 below, a large number of lubricating oil pockets having a predetermined depth are formed in a bearing that slides on each other via a viscous fluid by embossing or the like, so that concave portions that exist independently of each other are formed, and friction is generated. A bearing element for reducing the above is disclosed.

However, as in the conventional bearing element as described above, forming the recesses independent of each other makes the molding operation itself troublesome, and in order to guarantee the quality of the bearing element, In order to manage the variation in size, a great amount of man-hours are required.
JP 2000-504089 (summary, see Fig. 1)

  The present invention relates to a minute recess formed on a sliding surface in order to reduce friction and wear generated between the sliding surfaces in a sliding member for an internal combustion engine that slides relatively in the presence of a viscous fluid. It is an object of the present invention to provide a low-friction sliding member having a high friction-reducing performance that can be easily formed and that can easily manage variations in depth and size.

  The present invention is a low friction sliding member in which a continuous wave-shaped fine concave groove is formed on a sliding surface of at least one sliding member of a sliding member that slides relatively in the presence of a viscous fluid, The fine groove is a low-friction sliding member characterized in that the extending direction of the corrugation coincides with the sliding direction of the sliding member.

  In the low-friction sliding member of the present invention, a continuous wave-shaped fine concave groove is formed on the sliding surface of at least one sliding member that slides relatively in the presence of a viscous fluid. Since the extending direction of the wave shape of the groove is aligned with the sliding direction of the sliding member, fine grooves can be formed very easily by machining etc., and variation in depth and size can be easily managed. . In particular, when the extending direction of the waveform coincides with the sliding direction, the flow of viscous fluid in the sliding direction, for example, the lubricating oil is promoted and the leakage of the lubricating oil to the side is suppressed. Can be increased. Increasing the thickness of the lubricant film results in a decrease in the coefficient of friction.

  Further, by forming the continuous concave groove in which the extending direction of the corrugation coincides with the sliding direction, it becomes possible to make the lubricant stay in the contact portion for a long time, and as a result, the effect of developing low friction is brought about. .

  In the present specification, the “fine groove” refers to a very small recess on the order of microns, but its shape is like a sine wave or a triangular wave continuously formed on the surface of the sliding member. As long as the waveform changes periodically, the shape is not particularly limited, and includes various shapes.

  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 an explanatory view of a mechanism for reducing friction, and FIG. 3 is a low friction sliding of FIG. FIG. 4 is a schematic perspective view showing a main part of the member, FIG. 4 is a plan view showing a fine recess of the low friction sliding member, and FIG. 5 is a cross-sectional view taken along line 5-5 of FIG.

  The low-friction sliding member according to the present embodiment is a portion that slides in the presence of a viscous fluid, 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 and wear.

  First, the mechanism for reducing friction will be described with reference to the drawings. As shown in FIG. 2, when sliding a pair of sliding members in the sliding direction (indicated by double arrows in the figure) in the presence of lubricating oil, the sliding surface of at least one sliding member is uneven. The length X of the convex portion in the direction parallel to the sliding direction of one sliding member is greater than the length Y of the concave portion in the direction parallel to the sliding direction of the other sliding member. In some cases, the lubricating oil can be confined in the recess during sliding. Thereby, a fixed oil film thickness can be maintained between the sliding portions, and 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.

  As the shape of the concave portion and the convex portion, all shapes of a rectangular shape, an elliptical shape, and an indefinite shape can be adopted in a plan view. In particular, the shape of the concave portion is continuously formed parallel to the sliding direction. Then, the flow of oil in the sliding direction is promoted and leakage to the side is suppressed, so that the oil film can be increased, thereby reducing the friction coefficient.

  The present inventors have completed the present invention based on such findings. That is, the present invention forms a continuous wave-shaped fine groove so as to extend in a direction that is coincident with or parallel to the sliding direction, and improves the oil retention of the viscous fluid in a state where the influence on the load capacity is small, The friction coefficient is reduced.

  Further details will be described. As shown in FIG. 3, the low-friction sliding member includes a first sliding member 10 and a second sliding member that slide relative to each other in the direction of a double-headed arrow in the state of being in close contact with each other in the presence of a viscous fluid. 11, and a plurality of fine grooves 12 are formed on the sliding surfaces 10 a and 11 a of both sliding members 10 and 11. The fine groove 12 may be either one of the sliding surfaces 10a and 11a.

  As shown in FIGS. 2 and 3, the fine groove 12 of the present embodiment is formed so that the sliding direction of the sliding members 10 and 11 and the extending direction of the waveform are parallel or coincide with each other. If the continuous concave grooves 12 are formed in parallel with or coincident with the sliding direction of the sliding members 10 and 11, the oil flow in the sliding direction is promoted along with the sliding, and side leakage is caused. Therefore, the oil film can be increased, thereby reducing the friction coefficient.

  In order to further reduce the friction between the sliding members 10 and 11 each having a cylindrical shape, one is a flat cylinder in the axial direction, but the other is a so-called drum-shaped one that bulges in the axial direction. However, when the molding is performed in this way, the contact area generated between the sliding members 10 and 11 is an elliptical contact area C as shown in FIG. In the present embodiment, the state of the fine groove 12 in such an elliptical contact region C was verified.

  The contact area C where the sliding members 10 and 11 are in contact with each other has a major axis of 2a and a minor axis of 2b. However, there are at least two micro-concave grooves 12 of this embodiment in the contact area C. It is preferable to form.

  When at least two or more fine grooves 12 are formed in the contact region C, not only can the oil flow in the sliding direction be effectively promoted, but also the function of increasing the oil film while suppressing leakage to the side. Can be promoted more. However, in the case of one, sufficient effect cannot be obtained.

  In the contact region C, it is preferable that a waveform that periodically changes such as a sine waveform or a triangular wave exists for at least two cycles. In this way, it becomes possible to make the lubricating oil stay in the contact region C for a longer time, and the effect of further reducing friction can be obtained, and the seizure prevention property is improved even when the lubricating oil is not sufficiently present. .

  The friction of the sliding members 10 and 11 is reduced by the groove width W, the groove depth D, the surface roughness Ra of the flat portion 13 where the fine concave grooves 12 of the sliding members 10 and 11 are not formed, or the fine concaves. It is also affected by the area ratio that the groove 12 occupies in the contact region C.

  As shown in FIG. 5, the fine groove 12 is formed as a groove having a rectangular cross section cut from the flat sliding surfaces 10 a, 11 a of the sliding members 10, 11, or a groove having a triangular cross section. However, the groove depth D is preferably 0.5 μm or more and 20 μm or less regardless of the groove having any cross-sectional shape. Experiments have shown that when the groove depth D is within this range, the friction coefficient can be stably reduced, and the anti-seizure property can be improved. The depth D of the fine groove 12 can be 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).

  The groove width W is preferably 200 μm or less. If the groove width W is 200 μm or less, the friction reducing effect is sufficiently exhibited. If the groove width W is 200 μm or more, the oil flows into the fine groove 12 and the load capacity is reduced. This is particularly problematic when the contact area C is small.

  Even in such a fine groove 12, the occupation ratio of the sliding members 10, 11 in the contact area C {(number of grooves in the contact area C × groove width W × groove length / πab) × 100% )}, That is, it is a problem if the area ratio is too large or too small. If the area ratio of the fine grooves 12 is 1% or more and 15% or less, the friction coefficient can be stably reduced, and the seizure prevention property can be improved. When the area ratio is smaller than 1%, the effect of forming the fine concave grooves 12 cannot be sufficiently exhibited. When the area ratio is 15% or more, the load capacity decreases and the metal contact increases. Friction increases and seizure decreases. The area ratio can be calculated from, for example, a resin mask having a fine concave shape used in the mask blasting method.

  It is preferable that the surface roughness Ra of the flat sliding surfaces 10a and 11a in which the fine concave grooves 12 of the sliding members 10 and 11 are not formed is 0.05 μm or less. If the surface roughness Ra is 0.05 μm or more, there is a problem that metal contact increases and seizure prevention property decreases when the oil film thickness of the lubricating oil is small, but if it is 0.05 μm or less. Thus, there is no such a thing and a stable burn-in preventing property can be obtained. The surface roughness Ra can be measured by, for example, a stylus type surface shape measuring device FormTalysurf-120L (Taylor-Hobson).

  The friction coefficient of the sliding members 10 and 11 described above was measured by experiment, and verification was made on those having various groove shape patterns.

  FIG. 6 is a schematic perspective view showing an inscribed two cylinder used in the experiment, and FIG. 7 is a plan view exemplarily showing the groove shape of the fine groove.

  As the sliding members 10 and 11 used in the experiment, those having an inscribed two cylinder as shown in FIG. 6 were used.

  The outer cylinder 15 is a steel cylinder with an outer diameter of φ60 that is press-fitted with an aluminum metal with an inner diameter of φ45 mm. The inner cylinder 16 is a quenching and tempering material of steel with an outer diameter of φ43 mm (SCM435H steel). did.

  The inner cylinder 16 was formed to have an arcuate outer peripheral surface with an axial curvature radius r of 700 mm, and an elliptical contact region C was formed between the inner cylinder 16 and the outer cylinder 15. The major axis (2a) of the contact area C is 2.5 mm, and the minor axis (2b) is 1.9 mm.

  Each test piece uses a tape film having an average particle diameter of 9 μm for the purpose of removing bulges and burrs formed by plastic deformation at the end, and the surface roughness Ra of the sliding surfaces 10a and 11a is Finishing was performed so as to be 0.02 μm or less.

  In the experiment, in order to form an oil film between the outer cylinder 15 and the inner cylinder 16, a part of the oil was immersed in a bath of engine oil, and the oil temperature of the engine oil was 80 ° C.

  Then, 20 kg is added as the radial load F (open arrow), the relative sliding speed U is 6 m / s, the rotational torque is measured by the torque sensor 17 attached to the shaft 16a of the inner cylinder 16, and the tangential force is calculated. The coefficient of friction was determined by dividing by the radial load F.

  As a shape pattern of the fine groove 12 of the present embodiment, there are various shape patterns such as those shown in FIGS. 7A, 7B, and 7F as specific examples. 7A, B, C, D, and E having the shape pattern were used.

Example 1
The pattern of the fine groove 12 of Example 1 is shown in FIG. 7A. Using a c-BN cutting tool having a different tool edge curvature radius, the tool is swung while the inner cylinder is rotated, and the inner cylinder 16 is rotated. A sinusoidal continuous groove 12 was formed on the outer peripheral surface. The groove width W was 50 μm, the amplitude T was 500 μm, the groove depth D was 3 μm, the number of peaks in the contact area C was 3, and the number of grooves in the elliptical contact area C was 3. The area ratio of the grooves in the elliptical contact region C was 11.1%.

(Example 2)
In Example 2, the pattern shown in FIG. The same groove processing as in Example 1 was performed, and the groove width W, amplitude T, groove depth D, number of peaks in the contact area C, number of grooves in the elliptical contact area C, and groove area ratio were also the same. It was.

(Example 3)
The fine groove 12 of Example 3 has the same pattern and groove processing as Example 1, but the groove width W was 100 μm and the amplitude T was 250 μm. The area ratio of the grooves was 15.6%.

Example 4
The fine concave groove 12 of Example 4 has the same pattern and groove processing as Example 1, but the groove width W is 190 μm, the amplitude T is 250 μm, the groove depth D is 1 μm, and the number of peaks in the contact region C. 2 and the number of grooves in the contact area C was 2. The area ratio of the grooves was 18.0%.

(Example 5)
The fine concave groove 12 of Example 5 has the same pattern and groove processing as Example 1, but the groove width W is 30 μm, the amplitude T is 500 μm, the groove depth D is 18 μm, and the number of peaks in the contact region C. 2 and the number of grooves in the contact area C was 2. The area ratio of the grooves was 3.6%.

(Example 6)
The fine groove 12 of Example 5 has the same pattern and groove processing as Example 1, but the groove width W is 50 μm, the amplitude T is 250 μm, the groove depth D is 10 μm, and the number of peaks in the contact region C. 2 and the number of grooves in the contact area C was 2. The area ratio of the grooves was 5.9%.

(Example 7)
The fine groove 12 of Example 5 has the same pattern and groove processing as Example 1, but the groove width W is 50 μm, the amplitude T is 500 μm, the groove depth D is 6 μm, and the number of peaks in the contact region C. 3 and the number of grooves in the contact area C was 3. The area ratio of the grooves was 11.1%.

(Comparative Example 1)
In Comparative Example 1, continuous grooves were not formed. Similar to Example 1, the surface roughness Ra of the sliding surfaces 10a and 11a was set to 0.02 μm or less. All other conditions were the same as in Example 1.

(Comparative Example 2)
In Comparative Example 2, the continuous groove pattern is shown in FIG. 7A. The groove width W was 250 μm, the amplitude T was 250 μm, the groove depth D was 25 μm, the number of peaks in the contact area C was 2, and the number of grooves in the contact area C was 2. The area ratio of the grooves was 23.7%.

(Comparative Example 3)
The fine groove 12 of Comparative Example 3 has a pattern shown in FIG. 7A. The groove width W was 30 μm, the amplitude T was 500 μm, the groove depth D was 0.3 μm, the number of ridges in the contact area C was 1, and the number of grooves in the contact area C was 1. The area ratio of the grooves was 1.6%.

(Comparative Example 4)
The fine groove 12 of Comparative Example 4 was shown in FIG. 7C formed so that the waveform extending direction was a direction orthogonal to the sliding direction. This groove was formed by mask blast processing. That is, using a photolithographic technique, a fine shape is formed on a resin mask, the resin mask is affixed to the cylindrical surface and the metal inner surface, and then ceramic particles having an average particle size of 25 um are desired at a projection pressure of 5 kg / cm 2. Projection was performed until a depth of 1 mm was formed, and fine concave grooves were formed. Thereafter, the bulge of the edge portion formed around the fine groove was removed with a tape film having a particle size of 9 μm. This test piece also uses a tape film having an average particle diameter of 9 μm for the purpose of removing bulges and burrs formed by plastic deformation at the end, and the surface roughness Ra of the sliding surfaces 10a and 11a is Finishing was performed to 0.02 μm or less. The contact width between the inner cylinder and the outer cylinder is 20 mm.

  In Comparative Example 4, the groove width W is 50 μm, the amplitude T is 500 μm, the groove depth D is 3 μm, the number of peaks in the contact area C is 3, the number of grooves in the contact area C is 3, and the groove area ratio is 11.1%.

(Comparative Example 5)
Comparative Example 5 is a sine wave-like continuous groove of pattern D, and, as in Comparative Example 4, is formed by mask blasting in a direction in which the waveform extending direction is orthogonal to the sliding direction, and has a mean particle size of 9 μm. The bulge and burrs were removed using a flap film, and finishing was performed so that the surface roughness Ra was 0.02 μm or less.

  In Comparative Example 5, the groove width W is 50 μm, the amplitude T is 500 μm, the groove depth D is 3 μm, the number of peaks in the contact region C is 3, the number of grooves in the contact region C is 3, and the groove area ratio is 11.1%.

(Comparative Example 6)
Comparative Example 6 is a mesh-like groove of pattern E, and the groove width W is 50 μm, the amplitude T is 500 μm, the groove depth D is 3 μm, and the number of peaks in the contact region C is the same as in Comparative Examples 4 and 5. 3. The number of grooves in the contact area C was 3. The area ratio of the grooves was 22.2%.

  As a result of comparing the friction coefficient of each experimental example with this, the friction coefficient in the case of Comparative Example 1 was “1”, and the results shown in Table 1 below were obtained. For convenience, the patterns A to E of the fine grooves 12 in each experimental example are also shown.

  As is clear from Table 1, in this example, the friction coefficient coefficient ratio in each case is lower than that in Comparative Example 1, but in the comparative example, the friction resistance coefficient ratio is close to 1 or 1 or more. This shows that the oil retaining property of the fine groove 12 itself greatly contributes to the friction reduction effect.

  When such a 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 a viscous fluid, such as a cylinder, a metal bearing, or the like that forms an arcuate inner surface, The fine grooves 12 serve as an oil reservoir that improves oil retention, the amount of oil that enters these recesses increases, prevents a decrease in load capacity and a thin oil film, and there is no direct contact between metals. Therefore, it becomes a preferable internal combustion engine with reduced frictional resistance.

  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 fine concave groove 12 is formed on the flat low friction sliding member. However, not only this but also other various shapes such as a curved portion or a circle The present invention can also be applied to an arcuate surface or a spherical surface. Further, the fine groove 12 may be not only a sine wave and a triangular wave with the same period and the same wave height but also a deformed waveform or a waveform having various shapes.

  The present invention can reduce sliding friction of a sliding member for an internal combustion engine that slides in the presence of a viscous fluid.

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 explanatory drawing of the mechanism which reduces friction. It is a schematic perspective view which shows the principal part of the low friction sliding member of FIG. It is a top view which shows the fine recessed part of the same low friction sliding member. It is sectional drawing which follows the 5-5 line of FIG. It is a schematic perspective view which shows the inscribed 2 cylinder used in experiment. It is a top view which shows the groove shape of a fine ditch | groove illustratively.

Explanation of symbols

10, 11 ... sliding member,
10a, 11a ... sliding surface,
12 ... fine groove,
C ... contact area,
D ... groove depth,
T ... cycle,
W: Groove width.

Claims (7)

  A low friction sliding member in which a continuous wave-shaped fine groove is formed on a sliding surface of at least one of the sliding members that slide relatively in the presence of a viscous fluid, the fine groove Is a low-friction sliding member formed so that the extending direction of the corrugation coincides with the sliding direction of the sliding member.   The low-friction sliding member according to claim 1, wherein at least two of the fine concave grooves are present in a contact region where the sliding members are in contact with each other.   The low-friction sliding member according to claim 1, wherein the fine groove has at least two cycles of the corrugation in a contact region where the sliding members contact each other.   4. The low friction according to claim 1, wherein the fine groove has an area ratio occupied by a contact region where the sliding members come into contact with each other between 1% and 15%. Sliding member.   The low-friction sliding member according to claim 1, wherein the fine groove has a groove width of 200 μm or less.   The low-friction sliding member according to claim 1, wherein the fine groove has a groove depth of 0.5 μm or more and 20 μm or less.   The low friction sliding according to any one of claims 1 to 6, wherein a surface roughness (Ra) of a flat portion in which the fine groove is not formed of the sliding member is 0.05 µm or less. Moving member.