JP2012092928A - Piston-cylinder sliding structure and reciprocating internal combustion engine using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce relative friction between a cylinder and a piston by causing surface roughness of the cylinder to be proper and by improving wear resistance of a piston ring in a cylinder-piston sliding structure and a piston-cylinder sliding structure.SOLUTION: In the cylinder-piston sliding structure including a piston 3 having a skirt 3a, a cylinder 2 slidably and reciprocally receiving the piston 3 via lubrication oil, and piston rings 5, 6, 7 stretched on an outer circumferential surface of the piston 3 along a circumferential direction, the cylinder 2 is formed in a cylindrical shape, the piston rings 5, 6, 7 are formed in a ring shape capable of sliding relative to an inner surface 2a of the cylinder 2 via the lubrication oil, the sliding surface of the cylinder 2 with the piston rings 5, 6, 7 is formed as a mirror surface, and amorphous hard carbon coating 11 is formed on sliding surfaces of the piston rings 5, 6, 7.

Description

  The present invention relates to a piston / cylinder sliding structure that optimizes the surface roughness of a cylinder and improves the wear resistance of a piston ring, and more specifically, a cylinder / piston that can slide relative to each other via lubricating oil. The present invention relates to a sliding structure and a reciprocating internal combustion engine using the piston / cylinder sliding structure.

  In a piston / cylinder sliding structure and a reciprocating internal combustion engine using the piston / cylinder sliding structure, as shown in FIG. 5, a honing line 15 for retaining lubricating oil on the inner surface 2a of the cylinder 2 (the inner surface of the cylinder bore). Is formed by a honing process, and a lubricating oil film is formed on the inner surface of the cylinder 2 by the lubricating oil retained by the honing line 15. As is well known, a honing machine that performs a honing process is a device in which a grindstone is provided on the tip end side of a rotating shaft at intervals in the circumferential direction, and the central axis of the rotating shaft is set as the central axis of the cylinder 2. While rotating the rotating shaft in the combined state, the cylinder block is inserted from the crankshaft side into the cylinder head mounting side, and the grindstone is pressed against the inner surface 2a of the cylinder 2 with appropriate pressure at each insertion position. Is a device for grinding. In this honing machine, the surface roughness of the inner surface 2a of the cylinder 2 can be changed by changing the count of the grindstone, and the above-described cross hatched honing streak 15 can be formed by switching the rotation direction. . 5 is formed on the inner surface 2a of the cylinder 2 in this way.

In a piston / cylinder sliding structure in which a honing streak 15 is formed and a reciprocating internal combustion engine using the piston / cylinder sliding structure, a lubricating oil film is formed on the inner surface of the cylinder 2, and the inner surface of the cylinder 2 and the piston (the other member) 3) When the gap between the skirt 3 and the inner surface 2a of the cylinder 2 and the piston rings 5, 6, 7 are lubricated by the lubricating oil film, the skirt of the cylinder 2 and the skirt of the piston (the other member) 3, the cylinder 2 The friction coefficient between the inner surface 2a and the piston rings 5, 6, 7 is substantially reduced, and the reduction of the friction coefficient reduces the relative friction between the piston and the cylinder.
Moreover, the wear resistance of each part is substantially improved by lubricating the lubricating oil film. For this reason, in the piston / cylinder sliding structure and the piston / cylinder sliding structure, energy loss is reduced as the friction decreases, and fuel efficiency is improved in a reciprocating internal combustion engine using the piston / cylinder sliding structure.
As a prior art of this type, Patent Document 1 discloses that the inner surface of a cylinder is divided into a plurality of regions in the axial direction of the cylinder, and the angle of a cross hatched honing streak formed in each region is defined for each region It is stated that by optimizing, oil fluidity and oil retention are improved, oil cooling improves the sliding surface cooling effect, and oil retention reduces relative friction between the piston and cylinder liner. Has been.

JP 2004-176556 A

However, even if the cross hatched honing streaks 15 are formed on the inner surface 2a of the cylinder 2 and the lubricating oil film is formed by the lubricating oil, the convex portions (mountains) due to the surface roughness of the piston rings 5, 6, 7 are not formed. If a frictional force is generated between the adjacent honing streaks, the friction of the piston increases the friction of the piston, which may hinder the improvement of the fuel consumption of the internal combustion engine. is there.
For this reason, as shown in FIG. 6, the top of the honing streak 15 is removed by grinding, and the convex part due to the surface roughness of the piston rings 5, 6, 7 and the convex part between the honing streaks 15, 15 Although attempts have been made to suppress the generation of frictional force by preventing contact (interference), a certain effect cannot be obtained depending on the degree and variation of grinding.

  Accordingly, the present invention provides a piston / cylinder sliding structure and a reciprocating internal combustion engine using the piston / cylinder sliding structure by making the surface roughness of the cylinder appropriate and improving the wear resistance of the piston ring. The object is to reduce the relative friction between the cylinder and the piston.

  According to the first invention, a piston having a skirt, a cylinder that slidably and reciprocally moves the piston via lubricating oil, a connecting rod that connects the piston to a crankshaft, A cylinder having a piston ring stretched in the circumferential direction on the outer circumferential surface, and transmitting the reciprocating motion of the piston as a rotational driving force to the crankshaft via a connecting rod connecting the piston and the crankshaft. In the piston sliding structure, the cylinder is formed in a cylindrical shape, and the piston ring is formed in a ring shape that can slide relative to the inner surface of the cylinder via lubricating oil, and further, the piston of the cylinder A sliding surface with the ring is formed in a mirror surface, and an amorphous hard carbon film is formed on the sliding surface of the piston ring. A.

  According to the first invention, the friction coefficient of the lubrication surface of the cylinder is small because the lubrication surface of the cylinder is a mirror surface, and the friction coefficient of the lubrication surface of the piston ring is also an amorphous hard carbon film on the lubrication surface of the piston ring. It becomes small by forming. Furthermore, the lubrication surface of the cylinder is mirror-finished to improve the surface roughness, and the surface roughness of the piston ring lubrication surface is improved by the fact that the lubrication surface of the piston ring is composed of a dense amorphous hard carbon film. is doing. Further, since the cylinder and the piston ring are hardly affected by the surface roughness, the generation of frictional force due to the surface roughness is also suppressed.

  In other words, according to the first invention, the holding force of the lubricating oil in the cylinder is lower than the holding force of the conventional crosshatch streak, but the reduction in friction loss due to the reduction in the friction coefficient compensates for this, so that the lubricity is improved. Become good. Further, since the ratio of the lubricating oil in the frictional resistance is reduced by the reduction of the frictional resistance due to the mirror surface of the cylinder and the reduction of the friction coefficient by the amorphous hard carbon film, the consumption of the lubricating oil can be greatly reduced. Also, in terms of wear resistance, the amorphous hard carbon film has high wear resistance, and the lubricating surface of the cylinder has a small frictional force acting on it, and is hard to wear because it is lubricated by lubricating oil. Therefore, according to the first aspect of the present invention, it is possible to provide an energy-saving cylinder / piston sliding structure that has a smaller friction loss than that of the prior art and that consumes less lubricating oil.

  In this case, preferably, the surface roughness range of the mirror surface is set to 0.1 to 0.5 Rz in terms of 10-point average roughness. If the surface roughness of the mirror surface exceeds 0.5 Rz, a frictional force due to the surface roughness of the cylinder and the piston ring may be generated, resulting in an increase in friction loss, and a ten-point average roughness of less than 0.1 Rz. The holding power of the lubricating oil in the cylinder is reduced, which is not suitable for forming a lubricating oil film on the entire lubricating surface. When the range of the surface roughness of the mirror surface is set to 0.1 to 0.5 Rz in terms of 10-point average roughness (JIS), the lubricity of the lubricating surface is maintained and the friction loss is reduced.

  Preferably, with the piston stopped at the top dead center position with respect to the cylinder, the inner surface of the cylinder is divided into a region below the lower end surface of the skirt and a region above the skirt. It is preferable that a streak is provided so that the lubricating oil is held on the inner surface of the cylinder in a lower region formed on the mirror surface.

  When foreign matter adheres to the piston, the foreign matter comes into contact with the lubrication surface of the cylinder and causes scratches. Of the lubrication surface of the cylinder, a lubricating oil film is formed on at least the sliding surface of the cylinder lubrication surface with the foreign matter of the piston A streak that suppresses contact is provided, and the lubricant is held in the streak. This lubricating oil forms a lubrication film on at least the sliding surface of the lubricating surface of the cylinder with the foreign material of the piston, and prevents the occurrence of scratches due to the contact of the foreign material. In this case, the foreign matter concentrates in a region below the lower end surface of the piston skirt and causes scratches with the piston stopped at the top dead center position. For this reason, preferably, the piston is stopped at the top dead center position, and the inner surface of the cylinder is divided into a region below the lower end surface of the skirt and a region above the skirt, and a streak is provided on the entire lower region. Thereby, the contact of foreign matter is suppressed by the lubricating oil film, and the cylinder can be protected from damage such as abrasion and abnormal wear.

Preferably, the streak is formed in a cross hatch shape by honing. When honing marks are formed in a cross-hatch shape by honing, a lubricant film is formed by the lubricating oil retained by the honing process, preventing damage such as abrasion and abnormal wear, and cylinder reliability. Will improve.
In this case, preferably, the range of the surface roughness of the lubricating surface on which the cross-hatch-like streaks are formed is set to 2 to 3 μm.
If the surface roughness of the lubricated surface on which cross-hatched streaks are formed is less than 2 μm, the formation of the lubricating oil film is not stable, and if it exceeds 3 μm, frictional resistance is generated between one member and the other member. Absent. When the range of the surface roughness of the lubricating surface on which the cross-hatch-like streaks are formed is set to 2 to 3 μm, such a problem is solved.

  In the second invention, the piston / cylinder sliding structure of the first invention is used for a piston and a cylinder of a reciprocating internal combustion engine. According to the second invention, since the piston / cylinder sliding structure operates as in the first invention, the wear resistance of the piston ring and the cylinder can be ensured and the friction loss is small, so the fuel consumption is reduced. Will improve. Moreover, the consumption of lubricating oil can be reduced.

The present invention exhibits the following effects.
According to the first aspect of the present invention, the ratio of the lubricating oil to the frictional resistance is reduced by reducing the frictional resistance (friction coefficient) by mirroring the cylinder and by reducing the frictional resistance (friction coefficient) by the amorphous hard carbon film. Therefore, the friction loss can be greatly reduced as compared with the prior art. Further, since the ratio depending on the lubricating oil decreases due to the reduction of the frictional resistance, the consumption of the lubricating oil can be greatly reduced. Furthermore, the amorphous hard carbon film has high wear resistance, and the lubrication surface of the cylinder is lubricated with lubricating oil and the generation of frictional force is suppressed, so that the wear resistance can be improved. Therefore, it is possible to provide an energy saving cylinder / piston sliding structure that has a smaller friction loss and lower consumption of lubricating oil than conventional ones.

  According to the second aspect of the present invention, the lubricity of the lubricated surface can be maintained by setting the range of the surface roughness of the mirror surface to 0.1 to 0.5 Rz with a 10-point average roughness (JIS), so that the friction loss is reduced. Can be reduced.

  According to the third, fourth, and fifth aspects of the invention, the lubricant film prevents the foreign matter from contacting the inner surface of the cylinder, so that the cylinder can be protected from damage such as scratches and abnormal wear. In addition, since the lubricating oil film is formed by the lubricating oil held in the cross hatched honing streak, damage such as scratches and abnormal wear is prevented, and the reliability of the cylinder is improved.

  According to the invention described in claim 6, since the piston / cylinder sliding structure of the first invention is used for a reciprocating internal combustion engine, the friction loss is smaller than that of the prior art and the consumption of lubricating oil is low. In addition, fuel efficiency is improved, and wear resistance of the piston ring and cylinder can be improved.

It is explanatory drawing which shows the reciprocating internal combustion engine which concerns on Embodiment 1 of this invention, (a) shows a piston in a top dead center position, (b) shows the state of a piston in a bottom dead center position. It is explanatory drawing which shows the reciprocating internal combustion engine which concerns on Embodiment 2 of this invention, (a) shows a piston in a top dead center position, (b) shows the state of a piston in a bottom dead center position. It is explanatory drawing of the amorphous | non-crystalline hard carbon membrane | film | coat of Embodiment 1 of this invention. FIG. 3 is a diagram showing the relationship between the engine speed and the friction torque (friction force) of the reciprocating internal combustion engine according to the present invention. It is explanatory drawing which shows the conventional reciprocating internal combustion engine, (a) is a piston in a top dead center position, (b) shows the state of a piston in a bottom dead center position. It is principal part explanatory drawing of the XX cross section of FIG. It is explanatory drawing which shows the structure of a reciprocating internal combustion engine.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, as long as there is no specific description, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. Only.
In this embodiment, the piston / cylinder sliding structure according to the present invention is applied to a reciprocating internal combustion engine.

(Embodiment 1)
FIG. 7 shows the structure of a cylinder block of a reciprocating internal combustion engine (hereinafter simply referred to as an internal combustion engine). The reciprocating internal combustion engine includes a piston 3, a cylinder liner 1 that accommodates the piston 3 in a slidable and reciprocating manner via lubricating oil, and a piston pin on the crankshaft (not shown). A connecting rod 13 connected via a piston 17 and piston rings 5, 6, and 7 extending in the circumferential direction on the outer peripheral surface of the piston 3, and a rotational driving force is transmitted to the crankshaft via the connecting rod 13. To do. The crankshaft 12 is transmitted to an output shaft (not shown) connected to the crankshaft 12 to rotate the output shaft.

  1 is a cross-sectional view of a cylinder block of the reciprocating internal combustion engine shown in FIG. In the present embodiment, the cylinder 2 corresponds to the cylinder in the piston / cylinder sliding structure, and the piston rings 5, 6, and 7 correspond to the piston ring in the piston / cylinder sliding structure.

  The cylinder liner 1 is a cylindrical member having a cylinder 2 and guides the piston 3 so as to be slidable and reciprocally movable. The piston 3 is integrally provided with skirts 3a that slide on the inner surface 2a of the cylinder 2 through the lubricating oil, on both sides of the piston pin 17, and a plurality of top lands 4 that are upper peripheral portions of the piston 3 are arranged on the top land 4. Annular grooves 8, 9, 10 are formed. The plurality of grooves 8, 9, and 10 are provided at intervals in the axial direction, and the piston rings 5, 6, and 7 are respectively attached to the grooves. These piston rings 5, 6, and 7 can be expanded and contracted by elasticity, and are fitted into the ring grooves 8, 9, and 10 in an elastically expanded state. When the piston rings 5, 6, and 7 are incorporated in the inner surface 2 a of the cylinder 2, the piston rings 5, 6, and 7 come into contact with the inner surface 2 a of the cylinder 2 through lubricating oil at a pressure corresponding to the elasticity.

The piston rings 5 and 6 are compression rings that prevent gas leakage with the inner surface 2a of the cylinder 2, and the piston ring 7 is baked by scraping off excess lubricating oil held on the inner surface 2a of the cylinder 2. Oil ring to prevent
As shown in FIG. 3, an amorphous hard carbon film 11 is formed so as to cover at least the lubricating surface of the piston ring 5, 6, 7 with the inner surface 2a of the cylinder 2 of the piston ring 7. This amorphous hard carbon film (Diamond-Like Carbon, DLC) 11 is preferably formed by a negative pulse bias ion beam deposition apparatus at present, but is hard amorphous with low wear resistance and low friction coefficient. As long as it is a vapor deposition apparatus capable of forming the hard carbon film 11 by vapor deposition, it may be formed using a film deposition apparatus such as PVD or CVD (including plasma CVD).

  In this case, the range of the film thickness of the amorphous hard carbon film 11 is preferably set to 1 to 5 μm. When the film thickness of the amorphous hard carbon film 11 is less than the lower limit value, a defect in durability occurs. When the film thickness exceeds the upper limit value, the hard film has low toughness, so that defects such as cracking and chipping occur. Amorphous hard carbon film 11 is hard and excellent in wear resistance, and has a smaller friction coefficient than Cr plating, so the frictional resistance against the inner surface (sliding surface) 2a of cylinder 2 is reduced, reducing friction. As a result, it can contribute to fuel efficiency improvement.

  On the other hand, the inner surface 2a of the cylinder 2 is formed into a mirror surface by superfinishing. Here, the super finish processing means that after the inner surface 2a of the cylinder liner 1 is ground by a honing machine, a polishing machine such as a buff or a grinding machine in which the grindstone of the honing machine is changed to, for example, a buff, A process that finishes the surface roughness to a predetermined value. The range of the surface roughness of the mirror surface is set to 0.1 to 0.5 Rz in ten-point average roughness in this embodiment.

  If the surface roughness of the mirror surface exceeds 0.5 Rz, frictional resistance due to the surface roughness of the piston 3 may occur with respect to the inner surface 2a of the cylinder 2 and friction may increase, and the ten-point average roughness may be 0.1 Rz. If it is less than this, the holding force of the lubricating oil on the inner surface 2a of the cylinder liner 1 is lowered, and it is not suitable for forming a lubricating oil film on the entire lubricating surface. If the range of the surface roughness of the mirror surface is set to 0.1 to 0.5 Rz in terms of the 10-point average roughness, the frictional resistance against the cylinder liner 1 is reduced by the mirror surface, and the friction of the piston 3 is reduced by the decrease in the frictional resistance. When the friction decreases, the fuel consumption of the internal combustion engine improves. In addition, the thickness of the lubricating oil film formed on the entire lubricating surface of the inner surface 2a of the cylinder 2 can be reduced, and the amount of lubricating oil consumed can be reduced.

  Next, for the purpose of verifying that the cylinder 2 and the piston ring 7 shown in the above embodiment are excellent in wear resistance and exhibit the effect of reducing the friction coefficient on the sliding surface, the engine speed ( The engine speed) and the friction torque were measured. FIG. 4 shows this result.

  The conventional example (Line A) shows the relationship between the engine rotational speed of the piston 3 and the friction torque (frictional force) when the Cr-plated piston ring 7 is mounted. The first embodiment (Line B) is the cylinder 2 The relationship between the engine speed and the friction torque (frictional force) when the amorphous hard carbon film 11 is formed on the sliding surface of the piston ring 7 with the inner surface 2a as a mirror surface is shown.

  As shown in FIG. 4, when comparing the friction torque between the first embodiment and the conventional example, the friction torque of the first embodiment (Line B) is lower than the friction torque of the conventional example (Line A) at any engine speed. . That is, conventionally, in order to form a lubricating oil film on the lubricating surface, a streak for taking in and retaining the lubricating oil, for example, a cross hatched honing streak 15 is formed on the lubricating surface of the cylinder 2 or the lubricating surface of the piston 3. It is said that it is preferable to do this, and it largely depends on the holding power of the lubricating oil of the cross hatched honing streak 15.

However, the friction coefficient is reduced by using the lubrication surface of the cylinder 2 as a mirror surface, and the amorphous hard carbon film 11 is formed on the lubrication surface of the cylinder 2 of the piston ring 7, that is, the lubrication surface with the inner surface 2 a of the cylinder 2. When the coefficient is decreased, the ratio depending on the lubricating oil with respect to the reduction of the frictional resistance is reduced, so that the lubricity is improved.
Further, if the inner surface 2a of the cylinder 2 is formed as a mirror surface, the generation of frictional force due to the mutual surface roughness of the inner surface 2a of the cylinder 2 and the piston ring 7 can be suppressed, which also contributes to the reduction of the friction torque. is doing.
In addition, since the ratio depending on the lubricating oil is reduced with respect to the reduction of the frictional resistance, the consumption of the lubricating oil is also reduced.

On the other hand, since the amorphous hard carbon film 11 has high wear resistance and does not wear even when the lubricating oil film is thin, there is no problem with respect to the wear resistance of the amorphous hard carbon film 11.
Therefore, according to the cylinder 2 and the piston ring 7 of the first embodiment, the relative friction torque of the cylinder 2 and the piston ring 7 is reduced, and the fuel consumption of the reciprocating internal combustion engine can be improved by the reduction of the friction torque. , Can contribute to energy saving.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described with reference to FIG.
In this embodiment, the occurrence of vertical scratches in the cylinder 2 can be prevented by preventing mutual interference between the piston 3 and the cylinder 2 of the first embodiment.

That is, when the surface roughness of the inner surface 2a of the cylinder 2 is reduced to a mirror surface in the reciprocating internal combustion engine of the first embodiment, vertical scratches (scratches) S may occur on the inner surface 2a of the cylinder 2 as shown in FIG. . In the state where the piston 3 is stopped at the top dead center position, the occurrence location of the vertical scratch S of the cylinder 2 is examined. The lower end surface of the skirt 3a of the piston 3 is defined as the lower region E below the boundary, Is an upper region F, a plurality of vertical flaws S are concentrated in the lower region E.
As the cause, wear iron powder and steadite powder of the cylinder liner 1 buried in the surface of the skirt 3a of the piston 3 are mentioned, and the vertical scratch S on the inner surface 2a of the cylinder 2 is caused by these wear iron powder and steadite powder. It is thought that this is a grinding wear mark generated by the contact.

  Therefore, in order to specify the occurrence of the vertical scratch S, in the conventional reciprocating internal combustion engine in which the honing streak 15 is formed in the cylinder 2 by the conventional honing process, the occurrence state of the vertical scratch S is investigated. In the engine, it has not been reported that such a vertical scratch S has occurred in the cylinder 2. Therefore, it is considered that the vertical scratch S tends to occur more easily as the roughness of the inner surface 2a of the cylinder 2 is smaller, that is, as the mirror surface is made.

  Therefore, in the second embodiment, as shown in FIG. 2, in order to suppress the occurrence of the vertical scratches S, the foreign matter of the sliding surface (outer peripheral surface) of the piston 3 or the sliding surface of the inner surface 2 a of the cylinder 2 is reduced. For example, the cross hatched honing streaks 15 described in the prior art are provided at a position corresponding to the adhering portion, the lubricating oil is held, and the contact (interference) with the foreign matter is suppressed by the lubricating oil film.

  In the second embodiment, the honing streak 15 is located below the boundary with the position of the lower end surface of the skirt 3a of the piston 3 being the boundary of the region of the cylinder 2 with the piston 3 stopped at the top dead center position. The region E is defined as an upper region F above the boundary, and the lower region E is subjected to a honing process similar to the conventional one to form a cross hatched honing streak 15, while the upper region F is an embodiment. 1, the amorphous hard carbon film 11 is formed on the sliding surface of the piston ring 7.

  In this case, the range of the surface roughness of the lower region E where the cross hatched honing streaks 15 are formed is set to 2 to 3 μm. If the surface roughness of the lower region E is less than 2 μm, the formation of the lubricating oil film is not stable, and if it exceeds 3 μm, frictional resistance is generated between the cylinder 2 and the piston 3, which is not preferable. Therefore, the range of the surface roughness of the lubrication surface forming the cross hatched streak 15 is preferably set to 2 to 3 μm. The surface roughness of 2 to 3 μm indicates the depth of the streak.

  According to the lubricating structure of the internal combustion engine according to the second embodiment, the occurrence of the vertical scratches S can be prevented by the lubricating oil film formed by the lubricating oil held in the cross hatched honing streak 15. In the same manner as above, it is possible to prevent the generation of friction force between the lubrication surface of the cylinder 2 and the piston rings 5, 6 and 7 while keeping the lubrication between them favorable, the friction loss is small, the fuel consumption is good, A reciprocating internal combustion engine that consumes less lubricating oil can be obtained.

  In the second embodiment, the amorphous hard carbon film 11 is provided on at least the piston ring 7. However, the skirt 3a of the piston 3 may be covered with the amorphous hard carbon film 11 having a fine structure. . Further, the inner surface 2a of the cylinder 2 may be covered with the amorphous hard carbon film 11 having a fine structure. In this way, the wear resistance of the cylinder 2 and the piston 3 can be further improved, and the friction loss can be further reduced.

  According to the present invention, in the piston / cylinder sliding structure and the piston / cylinder sliding structure, the surface roughness of the cylinder is made appropriate, and the wear resistance of the piston ring is improved. Therefore, it is suitable for use in a reciprocating internal combustion engine.

DESCRIPTION OF SYMBOLS 1 Cylinder liner 2 Cylinder 2a Cylinder inner surface 3 Piston 3a Piston skirt 4 Top land 5, 6, 7 Piston rings 8, 9, 10 Ring groove 11 Amorphous hard carbon film (DLC)
12 Crankshaft 13 Connecting rod S Vertical scratch

Claims (6)

A piston having a skirt, a cylinder that slidably and reciprocally accommodates the piston via lubricating oil, a connecting rod that connects the piston to a crankshaft, and an outer peripheral surface of the piston in a circumferential direction A piston ring extending along the piston ring, and a piston / cylinder sliding structure that transmits the reciprocating motion of the piston as a rotational driving force to the crankshaft via a connecting rod that connects the piston and the crankshaft.
The cylinder is formed in a cylindrical shape, and the piston ring is formed in a ring shape that can slide relative to the inner surface of the cylinder via lubricating oil,
Furthermore, a sliding surface with the piston ring of the cylinder is formed in a mirror surface,
A piston / cylinder sliding structure characterized in that an amorphous hard carbon film is formed on the sliding surface of the piston ring.   2. The piston / cylinder sliding structure according to claim 1, wherein a range of the surface roughness of the mirror surface is set to 0.1 to 0.5 Rz in terms of ten-point average roughness.   With the piston stopped at the top dead center position with respect to the cylinder, the inner surface of the cylinder is divided into a region below and a region above the lower end surface of the skirt, and an upper region is formed on the mirror surface. 3. The piston / cylinder sliding structure according to claim 1, wherein a striation is provided so that the lubricating oil is held on the inner surface of the cylinder in a lower region.   4. The piston / cylinder sliding structure according to claim 3, wherein the striations are formed in a cross hatch shape by honing.   The piston / cylinder sliding structure according to claim 3 or 4, wherein a surface roughness range of the lubrication surface on which the streaks are formed is set to 2 to 3 µm.   A reciprocating internal combustion engine, wherein the piston / cylinder sliding structure according to claim 1 is used for a piston and a cylinder.

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