JP4655609B2 - Sliding member - Google Patents

Description

  The present invention relates to a sliding member that is slid through a viscous fluid.

  Conventionally, in order to reduce friction in a sliding member that is slid through a viscous fluid such as oil, it has been practiced to form fine depressions, recesses, grooves, or the like on the sliding surface of the sliding member. It has been broken.

  The technology for forming such depressions, recesses, grooves, and the like in the sliding member is aimed at reducing the friction of the piston / bore used in, for example, an internal combustion engine that performs reciprocal sliding.

As an example of such a conventional technique, there is a sliding member for reducing friction, in which a sliding surface is formed with a minute recess whose depth is changed with respect to the sliding direction ( Patent Document 1).
JP 2003-235852 A

  However, in the conventional sliding member, there is no mention about the cross-sectional shape of the fine recessed part currently formed in the sliding surface.

  For example, the cross-sectional shape of the fine recess formed by projecting hard particles at a right angle to the sliding portion using a mask blasting process or the like is a U-shape with the center of the recess as the deepest portion. In the case of such a fine recess shape, although a certain degree of friction reduction effect is obtained, the effect is limited, and further reduction of the friction coefficient is desired.

  Accordingly, an object of the present invention is to provide a sliding member having a high effect of reducing the friction coefficient.

In order to solve the above problems, the present invention provides a sliding member that is slid by interposing a viscous fluid, and is provided on a sliding surface having a higher hardness between two sliding objects of the sliding member. S / L is a length from the one end of the recess in the opening sliding direction to the lowest position of the recess. 0-0.3 der is, occupying area ratio of the recesses in the sliding surface, characterized in that 0.5 to 10%.

According to the present invention, the shape of the fine recess formed on the sliding surface having the higher hardness between the two objects sliding on the sliding member is L, and the length of the recess in the opening sliding direction is L, By setting the length from one end of the concave portion in the sliding direction of the concave portion to the lowest position of the concave portion as S, so that S / L is 0 to 0.3, the friction coefficient of the sliding member is reduced. Thus, wear resistance and seizure resistance can be improved. Furthermore, since the occupied area ratio of the recesses on the sliding surface is 0.5% or more, the function of the recesses can be sufficiently expressed, and the reduction of the friction coefficient is sufficiently expressed. Also, the occupied area ratio of the recesses on the sliding surface Therefore, the ratio of solid contact does not increase, friction does not increase, and deterioration of seizure property can be suppressed.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  1 and 2 are drawings showing the structure of a sliding member to which the present invention is applied. FIG. 1 (a) is a plan view, and FIG. 1 (b) is a cross section taken along the line AA in FIG. 1 (a). FIG. 1C is an enlarged view of the sliding surface. FIG. 2 is a cross-sectional view showing an example of the cross-sectional shape of the recess formed on the sliding surface.

  The sliding member 1 includes a first member 11 and a second member 12. The first member 11 is illustrated in the U1 direction with respect to the second member 12, and the second member 12 is illustrated U2 with respect to the first member 11. Rotates relative to the direction.

  As shown in FIG. 1C, a plurality of fine concave portions 21 are provided on the sliding surface 23 of the second member 12. FIG. 1C conceptually shows fine concave portions on the sliding surface, and is not formed with a size or arrangement as shown in the drawings.

  As shown in FIG. 2, the shape of such a fine recess is such that the length of the cross section of the recess 21 in the opening sliding direction (arrow direction in the drawing) is L, and the recess 21 has an opening sliding direction. When the length from one end to the lowest position of the recess 21 is S, S / L is 0 to 0.3 or less, preferably 0.2 or less, more preferably 0.1 or less. The lower limit is 0 in all cases.

  Further, the shape of the fine concave portion 21 is such that the cross section thereof is 0 degree (that is, perpendicular to the sliding surface 23) to 30 degrees with respect to a line C in which at least a part of the wall surface 22 in the concave portion is perpendicular to the sliding surface 23. Degree, preferably 0 to 10 degrees. More preferably, the inclination of the wall surface 22 is as close to a right angle as possible with respect to the sliding surface 23.

  This is because the S / L is 0.3 or less, or the shear rate due to the increase in the geometric average oil film thickness due to the fine recesses 21 by bringing the inclination of the wall surface 22 close to the sliding surface 23 at a right angle. In addition to the reduction of the above, the micro dynamic pressure effect is increased, the oil film is increased, and the excellent effect that the friction coefficient can be reduced is brought about.

  When the S / L value and the angle of the wall surface 23 exceed 0.3 or exceed 30 degrees, the micro-dynamic thickness effect is not sufficiently exhibited, and the oil film increasing effect is reduced. However, it is not preferable because the effect of reducing the friction coefficient is lowered.

  The cross-sectional shape of the concave portion is, for example, a right triangle shape, a W shape, a rectangular shape, or the like, as in the embodiments described later, preferably a shape in which the wall surface at the front end in the sliding direction is substantially perpendicular to the sliding surface 23. And

  The depth of the concave portion 21 is such that the ratio h / t is 0, where t is the depth to the lowest position of the concave portion 21 and h is the thickness of the viscous fluid film (normal oil film) during sliding. .04-5. This demonstrates an excellent friction reducing effect. When the ratio h / t is smaller than 0.04, the solid contact ratio increases and the seizure resistance may be deteriorated, which is not preferable. On the other hand, when h / t is larger than 5, the coefficient of friction is not preferable. Since the reduction effect is not sufficiently expressed, it is not preferable.

  Furthermore, it is preferable that the occupation area ratio of the concave portion 21 formed on the sliding surface 23 (the total opening area of the concave portion / the total area of the sliding surface) is 0.5 to 10%. This is not preferable when the occupied area ratio is less than 0.5% because the function of the recess cannot be sufficiently expressed and the reduction of the friction coefficient is not sufficiently expressed. On the other hand, the occupied area ratio is less than 10%. Exceeding this is not preferable because the solid contact ratio increases and friction not only increases but also seizure tends to deteriorate.

  Furthermore, the shape seen from the sliding surface 23 of the fine recess 21 is a flat shape that is longer in the direction perpendicular to the sliding direction than in the sliding direction. And the length of the short side (length in the sliding direction) is 50 to 150 μm, and the length of the long side (length in the direction perpendicular to the sliding direction) is 2 to 10 times the short side. It is preferable.

  The reason why the size of the opening of the concave portion is flattened and the length of the short side is 50 to 150 μm is that when the actual contact area is a rigid body because the sliding parts of many internal combustion engines are accompanied by elastic deformation. Therefore, when the length is longer than 150 μm, the ratio of the concave portion to the contact area increases, and the friction reducing function is not sufficiently exhibited. On the other hand, when the length is shorter than 50 μm, From the relationship between the depth of the recess and the size of the recess, the dynamic pressure effect cannot be sufficiently obtained, and the friction reducing effect cannot be sufficiently obtained, which is not preferable.

  In addition, when the length of the long side (the length in the direction orthogonal to the sliding direction) is 2 to 10 times the short side, if it is less than 2 times, the oil pool in the concave portion with respect to the sliding direction. The effect is not sufficiently exhibited, which is not preferable.

  On the other hand, in an actual engine sliding part, when a crankshaft is taken as an example, there is actually a thin portion of the oil film at the end of the shaft due to the deflection of the shaft relative to the projected area of the shaft and metal. In such a contact state, if the size of the concave portion exceeds 10 times, the concave portion protrudes from the thin contact area of the oil film at the end portion, so that the oil film becomes thin, which is not preferable.

  In addition, such a recess is only required to be formed in at least one of the sliding members. For example, in the sliding surface 23 of the sliding member composed of the first member 11 and the second member 12. When the hardness is different between the two members, it is preferable to form fine concave portions 21 on the sliding surface having the higher hardness. This is because the concave portion 21 is formed on the harder side so that the change in the depth of the concave portion 21 is small, and the sliding member is excellent in durability.

  Such a recess 21 can be formed by, for example, excimer laser, plastic working, mask blasting, MRF (micro roll forming, fine plastic working). In addition, the viscous fluid interposed between sliding members is not specifically limited, For example, it is lubricating oil etc. which are normally used for a sliding member.

  Next, based on the embodiment configured as described above, an experiment was performed in which sliding members actually having various concave shapes were manufactured to obtain a friction coefficient.

  As shown in FIG. 1, the sliding member used in the experiment includes an outer cylinder that is the first member 11 and an inner cylinder that is the second member 12. As a test for such a member, an inscribed two-cylinder testing machine shown in FIG. 4 was used.

  The cylindrical testing machine used is an outer cylinder 101 in which an aluminum metal with an inner diameter of 45 mm is press-fitted into a steel cylinder with an outer diameter of φ60, while the inner cylinder 102 has a steel with an outer diameter of φ43 and an axial curvature radius of R700 mm ( SCM420H steel) carburizing and tempering material was used. The inner cylinder is pivotally supported by the shaft 103 and is brought into contact with the outer cylinder 101 in the arrow W direction with a predetermined radial load. The widths of the inner cylinder 102 and the outer cylinder 101 are both 20 mm. An AC servomotor (not shown) is attached to each of the outer cylinder 101 and the inner cylinder 102 so that the rotation can be controlled independently.

  Then, the outer cylinder 102 and the inner cylinder 102 were immersed in an oil bath 105 containing 5 W 30 of oil to form an oil film between the outer cylinder 102 and the inner cylinder 102.

  In the experiment, when the radial load is 20 kg, the oil temperature is 80 ° C., the relative sliding speed is 0.3 to 12 m / s, the average speed is changed from 0 to 2 m / s, and the rotational torque is measured by the torque sensor attached to the inner cylindrical shaft 103. Then, the tangential force was calculated, and the coefficient of friction was obtained by dividing by the radial load. The average speed is (u1 + u2) / 2 when the inner cylinder speed is u1 and the outer cylinder speed u2. Similarly, the relative slip speed is (u1-u2).

(Examples and Comparative Examples)
In each of Examples 1 to 6, fine concave portions to which the present invention was applied were formed on the inner cylindrical surface of φ43 mm. On the other hand, in Comparative Examples 1 and 2, a concave portion to which the present invention was not applied was formed. These recesses were formed by excimer laser, plastic processing, MRF processing, mask blasting, or the like. The cross-sectional shapes are a right triangle shape, a rectangular shape, and an isosceles triangle shape, which were produced by an indenter using plastic working, an W shape by excimer laser processing, and a U shape by mask blasting. .

  In each of the examples and comparative examples, after the formation of the recesses, the bulge of the edge portion formed around the recess shape was removed with a tape wrap film having a particle size of 9 μm and subjected to the test.

  FIG. 3 is a drawing showing the shape of a recess in each example and comparative example. In addition, the arrow in a figure shows a relative sliding direction.

  In the first embodiment, as shown in FIG. 3A, the cross section is a right triangle, and the wall surface at the front end in the sliding direction is perpendicular to the line perpendicular to the sliding surface.

  In the second embodiment, as shown in FIG. 2B, the cross section is W-shaped, and the wall surfaces at the front end and the rear end in the sliding direction are perpendicular to the line perpendicular to the sliding surface.

  In the third embodiment, as shown in FIG. 3C, the cross section is rectangular, and the wall surfaces at the front and rear ends in the sliding direction are perpendicular to the line perpendicular to the sliding surface.

  In Example 4, as shown in FIG. 3A, the cross section has a right triangle shape, and the wall surfaces at the front end and the rear end in the sliding direction are perpendicular to the line perpendicular to the sliding surface. (The size is different from Example 1.)

  In Example 5, as shown in FIG. 3B, the cross section is W-shaped, and the wall surfaces at the front and rear ends in the sliding direction are perpendicular to the line perpendicular to the sliding surface ( The size is different from Example 2.)

  In Example 6, as shown in FIG. 3C, the cross section is rectangular, and the wall surfaces at the front and rear ends in the sliding direction are perpendicular to the line perpendicular to the sliding surface ( The size is different from Example 3.)

  As shown in FIG. 3 (d), Comparative Example 1 has a U-shaped cross section, and its wall surface has a shape that gently curves over 30 degrees with respect to a line perpendicular to the sliding surface.

  As shown in FIG. 3E, the comparative example 2 has a substantially isosceles triangular cross section, and all the wall surfaces exceed 45 degrees with respect to a line perpendicular to the sliding surface.

  Table 1 shows the size of the recess, the occupied area ratio (area ratio in the table), the depth, the cross-sectional shape in FIG. 3, and the experimental results in each example and comparative example.

  Next, the results of experiments on the relationship between S / L and the friction coefficient in the concave shape are shown. FIG. 5 shows the measurement shape of the cross-sectional shape of the actually produced recess, and FIG. 6 shows the recess 21 formation pattern of the sliding surface 23 in which the recess 21 is formed (of (a) to (c) shown in FIG. 5). All the recesses have the same pattern).

  FIG. 7 shows the relationship between the S / L and the reduction rate (%) of the friction coefficient in each concave shape shown in FIG. Note that the recess cross-sectional shape shown in FIG. 5 is a recess (produced by blasting) with S / L = 0.5 in FIG. 5A, and S / L = 0.2 in FIG. 5B. As shown in FIG. 5C, the front end wall in the sliding direction has an angle from a perpendicular perpendicular to the sliding surface (produced by MRF processing), so that S / L = about 0.1 or less. The front wall in the sliding direction is a recess (produced by indenting with an indenter) substantially perpendicular to the sliding surface. Further, the reduction rate of the friction coefficient shown in FIG. 7 is a reduction rate based on the case where S / L = 0.5.

  First, it can be seen from Table 1 that each of the examples to which the present invention is applied has a lower coefficient of friction than the comparative example. Further, from each of the examples, it is understood that an isosceles triangle shape having a wall surface perpendicular to only the front end in the sliding direction is particularly preferable. Further, from the shape of the comparative example and the shape of the example, the friction coefficient is smaller when the wall surface in the recess has a steeper angle (Comparative Example 2 and Example) than the gentle shape (Comparative Example 1). It can be seen that this tendency is shown.

  Next, FIG. 7 shows that the friction coefficient decreases as the value of S / L decreases. In particular, the reduction rate is about 10% near S / L = 0.3, and it can be seen that there is an effective friction coefficient reduction effect at S / L = 0.3. In addition, at S / L = 0.2 or less, it is understood that the slope of the reduction rate is larger than that between S / L = 0.5 to 0.3, and the effect of reducing the friction coefficient is greater. . Therefore, the value of S / L is more preferably 0.2 or less, and further more preferably S / L = 0.1 or less.

  The mechanism for reducing the friction coefficient in such a sliding member is not clear at present, but is inferred as follows. That is, by forming fine recesses in the sliding direction, in addition to the effect that the average oil film thickness is increased by the amount of the recesses and the average shear rate is reduced relative to the smooth surface where there are no recesses, By making the wall surface of the recess in the direction perpendicular to the sliding direction steep and as close to a right angle as possible, it becomes possible to allow more oil to flow into the contact portion, and to reduce the microscopic dynamic pressure effect due to the recess. It is considered that the friction reduction effect is expressed under a wider operating condition.

  As described above, by applying the present invention, a fine recess is formed on at least one sliding surface of at least two sliding members with a viscous fluid such as oil interposed therebetween, and at least one in the recess is formed. By making two wall surfaces steep and as close to a right angle as possible, the friction coefficient is reduced and the sliding characteristics are improved. This also keeps the oil film thickness thick, reducing friction and improving wear resistance and seizure resistance.

  The present invention is suitable for a sliding portion of an internal combustion engine, for example, a piston / bore of an internal combustion engine (engine).

It is drawing which shows a sliding member, (a) is a top view, (b) is sectional drawing which follows the AA line in Fig.1 (a), (c) is an enlarged view of the surface of a sliding surface. It is sectional drawing which shows an example of the cross-sectional shape of the recessed part currently formed in the sliding surface of the said sliding member. It is drawing for demonstrating the recessed part cross-sectional shape in an Example and a comparative example. It is a schematic diagram of an inscribed 2 cylinder testing machine. It is drawing which shows the recessed part shape which experimented the relationship between S / L and a friction coefficient. It is drawing which shows the recessed part formation pattern of a sliding surface. It is a graph which shows the decreasing rate of S / L and a friction coefficient.

Explanation of symbols

1 ... sliding member,
11 ... 1st member,
12 ... 2nd member,
22 ... wall surface,
23: Sliding surface.

Claims (9)

In a sliding member that slides with a viscous fluid interposed,
Having a fine recess provided on the sliding surface of the higher hardness between the two sliding objects of the sliding member;
The length of the recess in the opening sliding direction is L, the length from one end of the recess in the opening sliding direction to the lowest position of the recess is S, and S / L is 0 to 0.3. Oh it is,
The sliding member, wherein an area ratio occupied by the recesses on the sliding surface is 0.5 to 10% .   The shape of the opening of the recess is a flat shape that is longer in the direction orthogonal to the sliding direction than the sliding direction, and the length in the direction orthogonal to the sliding direction is the length of the sliding direction. The sliding member according to claim 1, wherein the sliding member is 2 to 10 times.   The shape of the opening of the recess is a flat shape that is longer in the direction perpendicular to the sliding direction than the sliding direction, and the length of the opening in the sliding direction is 50 to 150 μm. The sliding member according to claim 1 or 2, characterized by the above.   The sliding member according to any one of claims 1 to 3, wherein the S / L is 0 to 0.2.   The sliding member according to any one of claims 1 to 4, wherein at least a part of the wall surface in the recess has an inclination of 0 to 30 degrees with respect to a line perpendicular to the sliding surface.   The sliding member according to any one of claims 1 to 5, wherein one end of the concave portion in the sliding direction of the opening is a front end of the concave portion in the sliding direction.   The sliding member according to claim 5 or 6, wherein the wall surface having the angle is a wall surface positioned at least in a front end direction of the sliding direction.   8. The sliding member according to claim 1, wherein a cross-sectional shape of the concave portion is any one of a right triangle shape, a rectangular shape, and a W shape.   The recess has a ratio h / t of 0.04 to 5 when the depth to the lowest position is t and the viscous fluid film thickness when sliding on the sliding surface is h. It is formed so that it may become. The sliding member as described in any one of Claims 1-8 characterized by the above-mentioned.

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