JP2023026722A - oil ring - Google Patents

Abstract

To provide a technology capable of easily identifying each of a pair of segments, in an oil ring comprising the pair of segments.SOLUTION: An oil ring comprises a pair of segments that are annularly formed along the circumferential direction of the oil ring and arranged independently of each other in the axial direction of the oil ring, and a spacer expander positioned between the pair of segments. A surface treatment film is formed on at least a part of at least one of at least one axial end surface of at least one of the pair of segments so that the surface colors of the pair of segments are different from each other.SELECTED DRAWING: Figure 1

Description

The present invention relates to an oil ring with a pair of segments.

2. Description of the Related Art An internal combustion engine mounted on a general automobile employs a configuration in which a combination of a piston ring (an example of a ring-shaped member) including a compression ring (pressure ring) and an oil ring is mounted in a ring groove of a piston. The compression ring has a gas seal function that suppresses the outflow (blow-by) of combustion gas from the combustion chamber side to the crank chamber side by maintaining airtightness, and scrapes off excess oil that the oil ring could not scrape off. It has an oil seal function that suppresses oil rise. The oil ring has an oil seal function that suppresses the outflow of oil to the combustion chamber side by scraping off excess engine oil (lubricating oil) adhering to the inner wall surface of the cylinder toward the crank. By adjusting the amount of oil so that it is properly retained on the inner wall surface, it has the function of preventing seizure of the compression rings and pistons that accompany the operation of the internal combustion engine.

Here, the oil ring includes a pair of segments (also called side rails) arranged independently of each other in the axial direction of the oil ring and sliding on the inner wall surface of the cylinder, and a segment provided between the pair of segments. A three-piece combination oil ring is widely used, which is combined with a spacer expander that urges a pair of segments against the inner wall surface of the cylinder. In relation to this, Patent Document 1 discloses that in a pair of segments, the upper segment provided on the combustion chamber side and the lower segment provided on the crank chamber side have different outer peripheral surface shapes to reduce oil consumption and friction. An oil ring is disclosed that reduces the

As described above, when an oil ring having a pair of segments with different shapes for the upper segment and the lower segment is assembled to the piston, in order for the oil ring to fully exhibit its function in the internal combustion engine, the upper segment and the lower segment must be assembled in the correct arrangement.

WO2019/008780 JP 2019-124288 A

In order to prevent erroneous assembly of the upper segment and the lower segment, it is necessary to identify whether each pair of segments is an upper segment or a lower segment. However, conventionally, it has been difficult to identify each of a pair of segments. For example, it was possible to distinguish between the upper and lower segments by coloring the outer peripheral surface of the segment with paint. It was difficult to identify the segments, and there was a risk that the upper and lower segments would be mistakenly assembled to the piston in the opposite arrangement.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique that enables easy identification of each of a pair of segments in an oil ring that includes a pair of segments.

In order to solve the above problems, the present invention employs the following configurations. That is, the present invention provides an oil ring to be assembled to a piston in an internal combustion engine, which is annularly formed along the circumferential direction of the oil ring and arranged independently of each other in the axial direction of the oil ring. A pair of segments, and a spacer expander disposed between the pair of segments, wherein at least one axial end face of the pair of segments is arranged such that the surface colors of the pair of segments are different from each other. A surface treatment film is formed on at least a part of at least one of the oil rings.

According to the present invention, a user (mainly an operator who assembles a piston ring to a piston) can easily distinguish between the upper segment and the lower segment by visually recognizing the surface color of the segment. That is, according to the present invention, it is possible to improve the distinguishability between the upper segment and the lower segment, and reduce the risk of erroneous assembly. In addition, since the surface treatment film formed on the axial end face, which has a larger area than the outer peripheral surface and the inner peripheral surface, is used for identification, it is possible to easily distinguish between the upper segment and the lower segment. In making the surface colors different, any of the hue, lightness, saturation, or color tone, which are color attributes, may be made different.

Further, in the present invention, the surface treatment film may be formed on at least one of axial end faces of an upper segment of the pair of segments located on the combustion chamber side in the internal combustion engine. According to this, it is possible to reduce the wear of the upper segment, which slides under more severe conditions than the lower segment.

Furthermore, in the present invention, the surface treatment film may be formed on an axial end face facing the combustion chamber side in the internal combustion engine, among the axial end faces of the upper segment. According to this, it is possible to reduce wear of the upper surface of the upper segment and prevent deterioration of the oil seal function.

Furthermore, the surface treatment film may have oil retention properties. According to this, since the lubricity of the segment upper surface of the upper segment on which the surface treatment film is formed is improved, the wear resistance of the segment upper surface can be enhanced.

Furthermore, in the present invention, the surface treatment coating may include a phosphate coating layer. This makes it possible to impart oil retention to the surface treatment film.

Further, in the present invention, the surface treatment film includes a coating film, a resin film, a chemical conversion treatment film, an oxidation treatment film, a nitriding treatment film, a Ni-P plating treatment film, a chromium plating treatment film, a PVD treatment film, and a DLC treatment film. It may be configured to include at least any one layer of. Thereby, the wear resistance of the surface on which the surface treatment film is formed can be improved.

Moreover, in the present invention, the surface treatment film may be formed such that the pair of segments have different brightnesses.

Further, in the present invention, when an image of the axial end face of each of the pair of segments is acquired and the image is expressed in a gray scale of 256 gradations, the axial end face of one of the pair of segments is and the brightness of the axial end face of the other segment may be 10 or more. By doing so, it is possible to enhance the distinguishability between the upper segment and the lower segment.

According to the present invention, in an oil ring having a pair of segments, each of the pair of segments can be easily identified.

1 is a partial cross-sectional view of an internal combustion engine provided with an oil ring according to an embodiment; FIG. FIG. 5 is a partial cross-sectional view of an internal combustion engine provided with an oil ring according to a modified example of the embodiment;

Preferred embodiments of the present invention will be described below with reference to the drawings. It should be noted that the configurations described in the following embodiments are not meant to limit the technical scope of the invention only to them unless otherwise specified.

[overall structure]
FIG. 1 is a partial cross-sectional view of an internal combustion engine 100 provided with an oil ring 40 according to an embodiment. FIG. 1 shows a cross section perpendicular to the circumferential direction of the oil ring 40 . As shown in FIG. 1, in the internal combustion engine 100, a predetermined separation distance is secured between the inner wall surface 101 of the cylinder 10 and the outer peripheral surface 201 of the piston 20 mounted on the cylinder 10, so that the piston clearance PC1 is formed. formed. A ring groove 30 having a substantially rectangular cross section is formed in the outer peripheral surface 201 of the piston 20 . The ring groove 30 connects an upper wall 301 formed on the combustion chamber side, a lower wall 302 formed on the crank chamber side and facing the upper wall 301, and inner peripheral edges of the upper wall 301 and the lower wall 302. wall 303; An oil ring 40 according to this embodiment is mounted in the ring groove 30 .

The oil ring 40 is a sliding member that is attached to the piston 20 by being fitted in the ring groove 30 and that slides on the inner wall surface 101 of the cylinder 10 as the piston 20 reciprocates. The oil ring 40 is a so-called three-piece combination oil ring, and includes a pair of segments 1 and 2 and a spacer expander 3 as shown in FIG.

Hereinafter, as shown in FIG. 1, the direction (axial direction) along the central axis of the oil ring 40 is defined as the "vertical direction". Further, in the axial direction of the oil ring 40, the combustion chamber side (upper side in FIG. 1) of the internal combustion engine 100 is defined as "upper side", and the opposite side, that is, the crank chamber side (lower side in FIG. 1) is defined as "upper side". defined as 'lower side'. In the following description of the oil ring 40, unless otherwise specified, the term "peripheral direction" refers to the circumferential direction of the oil ring 40, and the term "radial direction" refers to the radial direction of the oil ring 40. , and the “axial direction” refers to the axial direction of the oil ring 40 . Further, in this specification, the state in which the oil ring is attached to the piston attached to the cylinder of the internal combustion engine as shown in FIG. 1 is referred to as the "used state". Further, in this specification, the term “barrel shape” refers to a surface shape that is curved so as to be convex radially outward including the apex, which is the maximum diameter of the piston ring, and the apex is in the axial direction of the ring It includes a "symmetrical barrel shape" located in the center of the width and an "eccentric barrel shape" in which the apex is located closer to the crankcase than the center of the axial width of the ring. Further, in this specification, the term “tapered shape” refers to a surface shape that is inclined so as to increase in diameter toward the crank chamber.

The pair of segments 1 and 2 are annularly formed along the circumferential direction of the oil ring 40 and are provided independently of each other and separated from each other in the axial direction. As shown in FIG. 1, the upper segment 1, which is one of the pair of segments 1 and 2, is provided on the upper side (combustion chamber side) of the internal combustion engine 100, and the other, the lower segment 2, is provided on the lower side of the internal combustion engine 100. side (crank chamber side). As shown in FIG. 1, the pair of segments 1 and 2 have different shapes of outer peripheral surfaces.

As shown in FIG. 1, the upper segment 1 includes a base material 1a formed in a ring shape from a segment wire, an outer peripheral coating 1b formed on the outer peripheral surface of the base material 1a, and an upper surface of the base material 1a. It includes a surface treatment film 1c formed thereon and a surface treatment film 1d formed on the lower surface of the substrate 1a. The upper segment 1 has an outer peripheral surface 11 , an inner peripheral surface 12 , an upper surface 13 and a lower surface 14 . An outer peripheral coating 1b is formed on the outer peripheral surface 11, a surface treatment coating 1c is formed on the upper surface 13, and a surface treatment coating 1d is formed on the lower surface . The upper surface 13 and the lower surface 14 are axial end surfaces of the upper segment 1. In use, the upper surface 13 faces the combustion chamber side and the lower surface 14 faces the crank chamber side. The upper surface 13 and the lower surface 14 define the axial width of the upper segment 1 . The upper segment 1 is provided so that the upper surface 13 faces the upper wall 301 of the ring groove 30 in use, and slides on the inner wall surface 101 of the cylinder 10 using the outer peripheral surface 11 as a sliding surface. As shown in FIG. 1, the outer peripheral surface 11 of the upper segment 1 is formed in an eccentric barrel shape with its apex positioned closer to the crank chamber than the center of the upper segment 1 in the axial direction.

As shown in FIG. 1, the lower segment 2 includes a base material 2a formed in an annular shape from a segment wire and an outer coating 2b formed on the outer peripheral surface of the base material 2a. there is The lower segment 2 has an outer peripheral surface 21 , an inner peripheral surface 22 , an upper surface 23 and a lower surface 24 . An outer coating 2 b is formed on the outer peripheral surface 21 . The upper surface 23 and the lower surface 24 are axial end surfaces of the lower segment 2. In use, the upper surface 23 faces the combustion chamber side and the lower surface 24 faces the crank chamber side. The upper surface 23 and the lower surface 24 define the width of the lower segment 2 in the axial direction. The lower segment 2 is provided so that the lower surface 24 faces the lower wall 302 of the ring groove 30 when in use, and slides on the inner wall surface 101 of the cylinder 10 using the outer peripheral surface 21 as a sliding surface. As shown in FIG. 1 , the outer peripheral surface 21 of the lower segment 2 is formed in a symmetrical barrel shape with its apex located at the axial center of the lower segment 2 .

As shown in FIG. 1, a spacer expander 3 is provided between a pair of segments 1, 2 and is self-tensioning so that it expands in use. Therefore, the upper segment 1 and the lower segment 2 are urged radially outward by the spacer expander 3, and the outer peripheral surface 11 of the upper segment 1 and the outer peripheral surface 21 of the lower segment 2 press the inner wall surface 101 of the cylinder 10. do. As a result, an oil sealing function is obtained, and an oil film is formed so that the engine oil present on the inner wall surface 101 of the cylinder 10 has an appropriate thickness. The shape of the spacer expander according to the present invention is not particularly limited.

In the oil ring 40 according to the present embodiment, the outer peripheral surface 11 of the upper segment 1 located on the upper side of the pair of segments 1 and 2 has an eccentric barrel shape with excellent oil scraping performance, and the lower segment located on the lower side. 2 has a symmetrical barrel shape with low friction. As a result, it is possible to reduce the oil consumption of the internal combustion engine 100 while suppressing an increase in friction. However, in the present invention, the shape of the pair of segments is not limited to that shown in FIG. For example, both outer peripheral surfaces of a pair of segments may have a symmetrical barrel shape or an eccentric barrel shape. Alternatively, the outer peripheral surface of the upper segment may have a symmetrical barrel shape, and the outer peripheral surface of the lower segment may have an eccentric barrel shape. Further, the outer peripheral surface of the upper segment may have a tapered shape with excellent oil scraping performance, or both outer peripheral surfaces may have a tapered shape. Alternatively, the outer peripheral surface of the upper segment may be formed into a symmetrical barrel shape, and the outer peripheral surface of the lower segment may be formed into a tapered shape.

Although the material of the base material 1a of the upper segment 1 and the material of the base material 2a of the lower segment 2 are not particularly limited, examples thereof include SUS and SWRH. Also, martensitic stainless steel, silicon chromium steel, aluminum alloy, or the like may be used as the base material. The material of the base material 1a and the material of the base material 2a may be the same or different.

The surface treatment coatings 1c and 1d are formed on the upper surface 13 and the lower surface 14 of the upper segment 1 so that the surface colors of the upper surface 13 and the lower surface 14 of the upper segment 1 are the same as those of the upper surface 23 and the lower surface 24 of the lower segment 2. A coating is selected such that it differs from the surface color. In this example, the surface treatment coatings 1c and 1d are selected so that their surface color is different from the surface color of the base material 2a of the lower segment 2. FIG. The surface treatment coatings 1c and 1d of this example are coating films, resin coatings, chemical conversion coatings, oxidation coatings, nitriding coatings, Ni-P plating coatings, chromium plating coatings, PVD coatings, and DLC coatings. It is formed as a coating including at least one of the layers. However, the surface treatment coating according to the present invention is not limited to these. The term "coating film" refers to a film formed by applying paint. A "resin coating" refers to a coating formed of a resin material. Examples of the "coating film" and "resin coating" include a resin coating film made of water-based or oil-based resin paint. "Chemical conversion coating" refers to a coating formed by chemical conversion treatment. Examples of chemical conversion treatments include triiron tetraoxide treatment (blackening), phosphate treatment, and chromate treatment. Examples of phosphate treatment include manganese phosphate treatment, zinc phosphate treatment, and iron phosphate treatment. A "nitriding coating" refers to a coating formed by infiltrating nitrogen into a metal surface by nitriding. “Oxidation treatment film” refers to a film formed by oxidizing a metal surface by oxidation treatment. Examples of oxidation treatment include alumite treatment. “Ni—P plating film” refers to a film formed by electroless Ni—P plating. In addition, the term "chromium-plated film" refers to a film formed by chromium plating. Chrome plating is also called industrial chrome plating. Also, “PVD (physical vapor deposition
) “treated film” refers to a film formed by the PVD method. A "DLC (Diamond Like Carbon) treated coating" refers to an amorphous hard carbon coating mainly composed of hydrocarbons and allotropes of carbon. By forming such a hard coating, the wear resistance of the upper and lower surfaces of the segment can be enhanced.

The outer coating 1b and the outer coating 2b according to this example are formed as DLC coatings with high abrasion resistance. In addition, the outer coating is not limited to the DLC coating, but the nitriding coating, Ni-P
It may be formed as a hard coating including at least one layer of a plating coating, a chromium plating coating, a PVD coating, and a DLC coating. The outer coating 1b of the upper segment 1 and the outer coating 2b of the lower segment 2 may have different configurations. In addition, the outer coating is not an essential configuration in the present invention, and either or both of the upper segment and the lower segment may not have the outer coating.

[Action/effect]
When an oil ring having different outer peripheral surface shapes between the upper segment and the lower segment, such as the oil ring 40 according to the present embodiment, is assembled to the piston, or when the coating on the outer peripheral surface is different between the upper segment and the lower segment. In order for the oil ring to fully exhibit its function, it is necessary to assemble the upper segment and the lower segment in a correct arrangement. If the arrangement of the upper segment and the lower segment is reversed and they are assembled in reverse, there is a risk that the function as an oil ring will not be exhibited sufficiently. Therefore, in order to prevent erroneous assembly, it is necessary to accurately identify whether each pair of segments is an upper segment or a lower segment.

To address such a problem, the oil ring 40 according to the present embodiment has the surface treatment coatings 1c and 1d only on the upper and lower surfaces of the upper segment 1 out of the upper and lower surfaces of the upper segment 1 and the upper and lower surfaces of the lower segment 2. By forming, the surface colors of the upper segment 1 and the lower segment 2 are made different from each other. In this example, the surface colors of the upper and lower surfaces of the upper segment 1 and the upper and lower surfaces of the lower segment 2 are made different. As a result, a user (mainly a worker who assembles the piston ring to the piston) can distinguish between the upper segment 1 and the lower segment 2 by visually recognizing the surface colors of the upper and lower surfaces of the pair of segments 1 and 2. can be easily identified, and the risk of incorrect assembly can be reduced.

As described above, the oil ring 40 according to the present embodiment is formed by forming the surface treatment coatings 1c and 1d on the upper and lower surfaces of the upper segment 1 so that the surface colors of the pair of segments 1 and 2 are different from each other. 1 and the lower segment 2 can be enhanced to reduce the risk of erroneous assembly. In addition, since the surface treatment coatings formed on the axial end faces (upper and lower surfaces), which have a larger area than the outer and inner peripheral surfaces, are used for identification, it is possible to easily identify the upper and lower segments. In making the surface colors different, any of the hue, lightness, saturation, or color tone, which are color attributes, may be made different. Note that color tone refers to a combination of lightness and saturation.

Moreover, in this example, the surface treatment coating is formed on the upper surface 13 and the lower surface 14 of the upper segment 1, but the present invention is not limited to this. In the present invention, it is sufficient that a surface treatment film is formed on at least one of the axial end surfaces (upper and lower surfaces) of at least one of the pair of segments so that the surface colors of the pair of segments are different from each other. In making the surface color different, for example, a surface treatment film having a surface color different from that of the base material of the lower segment may be formed only on the upper surface or only on the lower surface of the upper segment. Further, a surface treatment film having a surface color different from that of the base material of the upper segment may be formed on at least one of the axial end faces of the lower segment. Moreover, surface treatment films having different surface colors may be formed on the axial end faces of the pair of segments. These can also enhance the distinguishability between the upper segment and the lower segment. Moreover, the surface treatment film may be formed on at least a part of the axial end face. That is, the surface treatment film may be formed on a portion of the upper or lower surface of the segment, or may be formed on the entire upper or lower surface of the segment. For example, a coating film for identification may be formed by painting on a part of the upper surface or the lower surface. However, rather than forming the surface treatment film on a part of the axial end face, forming the surface treatment film on the entire surface as in the present embodiment can further improve the identifiability. Moreover, from the viewpoint of improving the distinguishability, it is preferable that the surface color of the surface treatment film on the upper surface or the lower surface of the segment is different from the surface color of the outer peripheral surface or the inner peripheral surface of the segment. Thereby, the surface treatment coating on the upper surface or the lower surface can be conspicuous as an identification coating. However, the present invention is not limited to this.

From the standpoint of improving identifiability, when an image of the axial end face of each of the pair of segments is acquired and the image is expressed in a gray scale of 256 gradations, the axial end face of one of the pair of segments It is more preferable that the difference between the brightness of the segment and the brightness of the axial end face of the other segment is 10 or more. This makes it easier to identify the upper and lower segments. However, the present invention is not limited to this.

Here, in general, in the case of an oil ring having a pair of upper and lower segments, the upper segment arranged on the side of the combustion chamber slides under more severe conditions than the lower segment arranged on the side of the crank chamber. The upper segment tends to wear more than the lower segment. On the other hand, in the oil ring 40 according to this embodiment, the upper segment 1 is improved in wear resistance by forming the surface treatment coatings 1c and 1d on the upper segment 1 . Thereby, wear of the upper segment 1 can be reduced. In particular, in the oil ring 40, the wear resistance of the upper surface 13 is improved by forming the surface treatment film 1c on the upper surface 13 of the upper segment 1. FIG. If the upper surface of the upper segment wears significantly due to long-term use, the gap (side clearance) between the upper groove wall of the ring groove and the upper segment may expand, which may reduce the oil seal function of the oil ring. In the embodiment, by forming the surface treatment film 1c on the upper surface 13 of the upper segment 1, wear of the upper surface 13 of the upper segment 1 can be reduced and deterioration of the oil seal function can be prevented. Due to such characteristics, the oil ring 40 according to the present embodiment can be suitably used for gasoline engines and engines using low-viscosity oil, in which there are many opportunities for direct contact between the segments and the inner wall of the ring groove. . However, the internal combustion engine to which the oil ring according to the present invention is applied is not limited to these.

In addition, the surface treatment films 1c and 1d of the oil ring 40 according to the present embodiment are a coating film, a resin film, a chemical conversion treatment film, an oxidation treatment film, a nitriding treatment film, a Ni-P plating treatment film, a chromium plating treatment film, and a PVD treatment film. It is configured to include at least one layer of a treated coating and a DLC treated coating. As a result, the wear resistance of the upper surface 13 and the lower surface 14 on which the surface treatment films 1c and 1d are formed becomes more excellent.

Here, the surface treatment coating 1c formed on the upper surface 13 of the upper segment 1 may be a coating having an oil-retaining structure. Since the lubricity of the upper surface 13 of the upper segment 1 is improved by imparting oil retention to the surface treatment film 1c, the wear resistance of the upper surface 13 can be further improved. At this time, the surface treatment coating 1c may be a coating containing a layer of a phosphate coating, which is an example of a chemical conversion coating. "Phosphate coating" refers to a coating formed by phosphate coating treatment, which is a type of chemical conversion treatment. Examples of the phosphate coating treatment include manganese-based phosphate coating treatment and zinc-based phosphate coating treatment. The phosphate coating is formed of a chemically formed layer, a phosphate crystal layer is formed on the surface, and etching pockets are formed under the crystal layer by local elution of the base material. there is An amorphous layer having high oil retention is formed in the etching pocket. By forming the surface treatment film 1c into a structure including a phosphate film layer, the surface treatment film 1c can be imparted with oil retention properties. In addition, the surface treatment film may have oil retention properties by other configurations.

[Modification]
FIG. 2 is a partial cross-sectional view of an internal combustion engine 100A including an oil ring 40A according to a modification of the embodiment. FIG. 2 shows a cross section orthogonal to the circumferential direction of the oil ring 40A. In the description of the oil ring 40A according to the modified example, differences from the oil ring 40 shown in FIG. 1 will be mainly described, and the same reference numerals will be given to the same configurations, and detailed description will be omitted.

As shown in FIG. 2, the oil ring 40A differs from the oil ring 40 in that a surface treatment film 2c is formed on the upper surface 23 of the lower segment 2A and a surface treatment film 2d is formed on the lower surface 24 of the lower segment 2A. Specifically, the lower segment 2A according to the modification includes a base material 2a, an outer coating 2b, a surface treatment coating 2c formed on the upper surface of the base material 2a, and a lower surface of the base material 2a. and a surface treatment film 2d.

For the surface treatment films 2c and 2d, those having surface colors different from those of the surface treatment films 1c and 1d of the upper segment 1 are selected. As a result, according to the oil ring 40A according to the modification, by making the surface colors of the pair of segments 1 and 2A different from each other, the distinguishability between the upper segment 1 and the lower segment 2A is enhanced, and the risk of assembly error is reduced. be able to. Here, the surface treatment coatings 2c and 2d are coating films, resin coatings, chemical conversion coatings, oxidation coatings, nitriding coatings, Ni-P plating coatings, chromium plating coatings, PVD coatings,
and a DLC-treated coating. Moreover, the surface treatment coatings 2c and 2d may be coatings having an oil-retaining structure, and may include a phosphate coating layer.

各セグメントの軸方向一端面を市販のカラーＣＣＤカメラで撮像し、得られた画像を市販の画像処理ソフトにより解析することで、セグメントの軸方向端面の明度を取得した。表１に示すＲ，Ｇ，Ｂの明度は、カメラで取得したカラー画像に基づいて２５６階調のＲＧＢそれぞれの色相毎の明度を取得したものである。また、表１に示すグレースケールの明度は、カメラで取得したカラー画像に基づいて２５６階調の明度のグレースケール画像を生成し、明度を取得したものである。つまり、グレースケールの明度は、各セグメントの軸方向端面の画像を２５６階調のグレースケールで表したときの、軸方向端面の明度である。Ｒ，Ｇ，Ｂの明度及びグレースケールの明度は、画像内の軸方向端面上における３点で取得された明度の平均値とした。 [Identification evaluation test]
A test was conducted to evaluate the identifiability of the segments of the oil ring according to the present invention. Segments numbered 1 to 3 shown in Table 1 were used in the test. Table 1 shows the brightness of the base material, the surface treatment coatings on both axial end faces (upper and lower faces), and the axial end faces of segments Nos. 1 to 3. The segments numbered 1 to 3 had the same shape and the outer peripheral surface used had a symmetrical barrel shape. Segment No. 1 used a base material of SUS and had no surface treatment film formed on the axial end faces. For the segment No. 2, SWRH was used as the base material, and trimiron tetroxide coating was formed as a surface treatment coating on both axial end faces. Segment No. 3 used SWRH as the base material and had a manganese-based phosphate film formed as a surface treatment film on both axial end faces.

One axial end face of each segment was imaged with a commercially available color CCD camera, and the resulting image was analyzed by commercially available image processing software to obtain the brightness of the axial end face of the segment. The lightnesses of R, G, and B shown in Table 1 are the lightnesses obtained for each hue of RGB in 256 gradations based on the color image obtained by the camera. The brightness of the grayscale shown in Table 1 was obtained by generating a grayscale image with brightness of 256 gradations based on the color image acquired by the camera. That is, the brightness of the grayscale is the brightness of the axial end face when the image of the axial end face of each segment is represented by a grayscale of 256 gradations. The lightness of R, G, and B and the lightness of gray scale were the average values of the lightness obtained at three points on the end surface in the axial direction in the image.

実施例１は、番号２のセグメントを上側セグメントとし、番号１のセグメントを下側セグメントとしたオイルリングである。実施例２は、番号３のセグメントを上側セグメントとし、番号１のセグメントを下側セグメントとしたオイルリングである。実施例３は、番号２のセグメントを上側セグメントとし、番号３のセグメントを下側セグメントとしたオイルリングである。比較例は、上下のセグメントを両方とも番号１のセグメントとしたオイルリングである。表２に示す上下の明度差は、表１に示した番号１～３のセグメントにおけるグレースケールの明度に基づいて算出した。また、識別性は、目視による軸方向端面の観察で表面色の違いにより上下のセグメントを識別できた場合に「〇」とし、識別でき
なかった場合には「×」とした。 Regarding the oil rings according to Examples 1 to 3 of the present invention and the oil rings according to the comparative example, the upper segment and the lower segment are visually observed, and the upper and lower segments can be identified by the difference in surface color of the axial end face. It was determined whether Table 2 shows the number of segments used for combinations of upper and lower segments, the difference in brightness between upper and lower segments, and the distinguishability of upper and lower segments in Examples 1 to 3 and Comparative Example.

Example 1 is an oil ring in which the segment of number 2 is the upper segment and the segment of number 1 is the lower segment. Example 2 is an oil ring in which the segment of number 3 is the upper segment and the segment of number 1 is the lower segment. Example 3 is an oil ring in which the segment of number 2 is the upper segment and the segment of number 3 is the lower segment. A comparative example is an oil ring in which both upper and lower segments are numbered 1 segments. The upper and lower lightness differences shown in Table 2 were calculated based on the grayscale lightness in the segments numbered 1 to 3 shown in Table 1. The identifiability was evaluated as "O" when the upper and lower segments could be identified due to the difference in surface color in visual observation of the axial end face, and as "X" when they could not be identified.

As shown in Table 2, the brightness difference in gray scale between the upper and lower segments was 68.9 in Example 1, 58.3 in Example 2, 10.6 in Example 3, and 0.0 in Comparative Example. . In Examples 1 to 3, the upper and lower segments could be distinguished by the difference in surface color, whereas in the comparative example, the upper and lower segments could not be distinguished by the difference in surface color. From the above test results, it was confirmed that the examples of the present invention are excellent in distinguishability between the upper and lower segments.

<Others>
Although the preferred embodiments of the present invention have been described above, the various forms described above can be combined as much as possible. Further, in the present invention, the surface colors of a pair of segments may be made different from each other by differentiating the so-called temper color due to discoloration due to oxidation between the base material of the upper segment and the base material of the lower segment.

100: Internal combustion engine 10: Cylinder 20: Piston 30: Ring groove 40: Oil ring 1: Upper segment 2: Lower segment 3: Spacer expander 1c, 1d, 2c, 2d: Surface treatment coating

Claims (8)

An oil ring assembled to a piston in an internal combustion engine,
A pair of segments that are annularly formed along the circumferential direction of the oil ring and arranged independently of each other in the axial direction of the oil ring; and a spacer expander that is arranged between the pair of segments. and
A surface treatment film is formed on at least a portion of at least one of at least one axial end face of at least one of the pair of segments so that the surface colors of the pair of segments are different from each other.
oil ring. The surface treatment film is formed on at least one of both axial end faces of an upper segment of the pair of segments located on the combustion chamber side in the internal combustion engine.
The oil ring according to claim 1. The surface treatment film is formed on an axial end face of the upper segment facing the combustion chamber side in the internal combustion engine, among the axial end faces of the upper segment.
The oil ring according to claim 2. The surface treatment film has oil retention,
The oil ring according to claim 3. The surface treatment coating comprises a layer of phosphate coating,
The oil ring according to claim 4. The surface treatment film is at least one of a coating film, a resin film, a chemical conversion treatment film, an oxidation treatment film, a nitriding treatment film, a Ni-P plating treatment film, a chromium plating treatment film, a PVD treatment film, and a DLC treatment film. containing one layer,
The oil ring according to any one of claims 1 to 5. The surface treatment film is formed such that the pair of segments have different brightnesses.
The oil ring according to any one of claims 1 to 6. When an image of the axial end face of each of the pair of segments is obtained and the image is expressed in a gray scale of 256 gradations, the brightness of the axial end face of one of the pair of segments and the brightness of the other segment The difference in brightness of the axial end faces in is 10 or more,
The oil ring according to claim 7.

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