JP7053531B2 - Surface treatment method - Google Patents

Description

The present invention relates to a surface treatment method.

In recent years, in order to reduce the environmental load, it has been raised as issues to reduce fuel consumption and oil consumption of internal combustion engines. Reducing the friction loss of the piston system is effective as a means of reducing fuel consumption of an internal combustion engine. Further, with the increase in output of internal combustion engines in recent years, a piston ring having excellent wear resistance is required. The internal combustion engine installed in a general automobile is equipped with three piston rings, which are a combination of two compression rings (pressure rings) including a top ring and a second ring, and one oil ring. The configuration provided on the piston is adopted. In connection with this, a technique has been proposed in which a Cr nitride film is applied to the outer peripheral surface of the piston ring by PVD treatment to reduce the frictional force and improve the wear resistance (for example, Patent Document 1). In addition to reducing fuel consumption of internal combustion engines, it is also important to reduce oil consumption. From the viewpoint of reducing oil consumption, it is known that the oil scraping performance is improved by forming an undercut in the lower part of the outer peripheral surface of the piston ring. For example, in Patent Document 2, an undercut is formed in the lower part of the compression ring.

Japanese Unexamined Patent Publication No. 2013-61072 Japanese Unexamined Patent Publication No. 10-252891

However, for example, when a thin-film deposition film is formed on the outer peripheral surface of a piston ring having an undercut by a thin-film deposition method using a target such as the PVD method, the material of the thin-film deposition film is formed on the lower surface (the surface on the crank chamber side) of the undercut. The particles may not easily collide with each other, and the thin-film deposition film on the lower surface of the undercut may not be formed with a uniform film thickness. In that case, the treatment liquid may permeate between the surface of the base material and the vapor-deposited film from the thin portion of the vapor-film-deposited film during the chemical conversion treatment in the subsequent step, and the vapor-filmed film may be peeled off in the engine assembly work of the piston ring. The peeled vapor-film film becomes a foreign substance, which causes scratches on the inner wall of the cylinder during operation of the internal combustion engine.

The present invention has been made in view of the above-mentioned problems, and in a surface treatment method for forming a film by a vapor deposition method using a target on the outer peripheral surface of a piston ring, the adhesion of the vapor deposition film is to be good. The purpose is to provide possible technologies.

In order to solve the above problems, the present invention has adopted the following means. The present invention is a surface treatment method for forming a vapor deposition film on the outer peripheral surface of a compression ring as an example of a piston ring mounted in a ring groove of a piston for an internal combustion engine, and is a base material of the compression ring. A base material facing the upper wall of the ring groove when the compression ring is mounted in the ring groove, and a group facing the lower wall of the ring groove when the compression ring is mounted in the ring groove. By a base material preparation step of preparing a base material having a lower surface of the material and a base material outer peripheral surface connecting the outer peripheral edge of the upper surface of the base material and the outer peripheral edge of the lower surface of the base material, and a vapor deposition method using a target. A vapor deposition step of forming the vapor deposition film on the outer peripheral surface of the substrate by adhering particles emitted from the target to the substrate is included, and the outer peripheral surface of the substrate has a maximum diameter in the substrate. An outer peripheral end face having an edge on the lower surface side of the base material formed radially outside the outer peripheral edge of the lower surface of the base material, and an edge on the lower surface side of the base material and the lower surface of the base material on the outer peripheral end surface. It has a cut surface connecting to the outer peripheral edge, and the cut surface is connected to the edge of the outer peripheral end surface on the lower surface side of the base material and is inclined so as to shrink in diameter toward the lower surface side of the base material. A surface treatment method including an inclined surface and facing the outer side in the radial direction over the entire region of the cut surface, and the vapor deposition step is performed in a state where the target and the outer peripheral end surface face each other. Is.

According to the present invention, by arranging the outer peripheral end face and the target so as to face each other in the vapor deposition process, the vapor-deposited film is formed with a highly uniform film thickness on the outer peripheral end face, and the cut surface S2 is radially over the entire region. By forming the shape facing the outside, particles of the material easily adhere to the entire area of the cut surface, and a PVD film having a high uniform film thickness can be formed on the cut surface as well. As a result, the adhesion of the thin-film vapor film becomes good, and the floating and peeling of the thin-film film can be suppressed. Here, "the surface faces the outer side in the radial direction" means that the surface faces the outer side in the radial direction, and the diameter while the surface is orthogonal to the radial direction (that is, parallel to the axial direction). It is not limited to the case where the surface is facing outward in the direction, but also includes the case where the surface is inclined outward in the radial direction while being inclined with respect to the axial direction. Further, the inclination angle of the inclined surface does not have to be uniform.

The surface treatment method according to the present invention can be applied as a piston ring to, for example, a compression ring including a top ring and a second ring. The "perimeter direction" refers to the perimeter direction of the piston ring or the base material. "Diameter" refers to the radial direction of the piston ring or substrate. "Diameter inside" refers to the inner peripheral surface side of the piston ring or the base material, and "diameter outside" refers to the opposite side (that is, the outer peripheral surface side of the base material). "Axial direction" refers to the direction along the central axis of the piston ring or substrate. The "upper wall" of the ring groove of the piston refers to the inner wall of the inner wall of the ring groove on the combustion chamber side, and the "lower wall" refers to the inner wall of the crank chamber side. Further, the vapor deposition method according to the present invention may be any vapor deposition method in which particles emitted from the target are attached to a substrate to form a film on the surface of the substance. PVD (physical vapor deposition) can be exemplified as such a vapor deposition method. The PVD method can also be called physical vapor deposition. The PVD method can include an ion plating method, an ion beam vapor deposition method, a vacuum vapor deposition method, a sputtering method, an FCVA (Filtered Cathodic Vacuum Arc) method and the like.

Further, in the present invention, the cut surface may include a connecting surface connecting the outer peripheral edge of the lower surface of the base material and the edge of the inclined surface on the lower surface side of the base material. According to this, an inclined surface whose cut surface is inclined so as to decrease in diameter toward the lower surface 12 of the base material, and a connecting surface connecting the outer peripheral edge of the lower surface of the base material and the edge on the lower surface side of the base material on the inclined surface are provided. By including it, the outer peripheral surface of the base material is formed in an undercut shape. By applying a surface treatment to such a substrate, a compression ring having an undercut is formed, and this compression ring has good oil scraping performance.

Further, in the present invention, the vapor deposition step is performed in a state where a plurality of the base materials are stacked in the axial direction so that their respective central axes coincide with each other, and the base materials are formed from the central axis in the radial direction. The distance to the outer peripheral edge of the upper surface of the base material and the distance from the central axis to the outer peripheral edge of the lower surface of the base material may be formed to be equal to each other. According to this, in the thin-film deposition step, the upper surface of the substrate and the lower surface of the substrate facing each other in the two axially adjacent substrates overlap each other without causing a step in the radial direction (without shifting). Therefore, it is possible to suppress the formation of a thin-film deposition film on the upper surface of the base material and the lower surface of the base material, and it is possible to omit the polishing process for removing the vapor-film deposition film from the upper surface of the base material and the lower surface of the base material. Such a surface treatment method is suitable for forming a PVD film on a plurality of substrates.

Further, in the present invention, it is preferable that the inclination angle of the inclined surface with respect to the radial direction of the base material is 5 ° or more in the cross section orthogonal to the circumferential length direction of the base material. By doing so, the particles of the material are more likely to adhere to the entire area of the inclined surface, and the uniformity of the film thickness on the inclined surface can be further improved. As a result, the adhesion of the thin-film deposition film can be further improved.

Further, in the present invention, it is more preferable that the inclination angle of the inclined surface with respect to the radial direction of the base material is 5 ° or more and 25 ° or less in the cross section orthogonal to the circumferential length direction of the base material. By setting the inclination angle to 25 ° or less, it is possible to secure a larger axial dimension of the outer peripheral end face. As a result, for example, when the outer peripheral end face is formed in a tapered shape inclined so as to increase in diameter toward the crank chamber side, the tapered outer peripheral end face can be left for a long time, and the outer peripheral end face disappears at an early stage. It is possible to suppress the deterioration of the oil scraping function due to this. As a result, the oil scraping performance of the compression ring can be improved.

Further, in the present invention, the vapor deposition step includes a base film forming step of forming a base film made of Cr or Ti on the outer peripheral surface of the base material, and a hard film forming step of forming a hard film on the base film. May include. According to this, by forming a hard film on the outer peripheral surface of the base material via the base film made of Cr or Ti, the adhesion of the hard film to the outer peripheral surface of the base material can be improved. As a result, floating and peeling of the hard coating can be suitably suppressed.

Further, in the present invention, it is more preferable that the film thickness of the undercoat film is 50% or less of the film thickness of the entire vapor-filmed film including the hard film and the undercoat film from the viewpoint of improving the adhesion. ..

The present invention can also be applied to the case where a vapor-deposited film is formed on the outer peripheral surface of a segment in a three-piece oil ring as a piston ring. That is, the present invention has a pair of segments provided on both sides in the axial direction and an expander for urging the pair of segments outward in the radial direction, and the oil is mounted in the ring groove of the piston for an internal combustion engine. A surface treatment method may be used in which a vapor-deposited film is formed on the outer peripheral surface of the segment in the ring. In this case, the present invention is the base material of the segment, and is located on the upper wall side of the ring groove when the oil ring is mounted on the ring groove among the surfaces on both sides in the axial direction of the segment. The upper surface of the base material, the lower surface of the base material located on the lower wall side of the ring groove when the oil ring is mounted in the ring groove, the outer peripheral edge of the upper surface of the base material, and the outer peripheral edge of the lower surface of the base material. By adhering particles emitted from the target to the base material by a base material preparation step of preparing a base material having a base material outer peripheral surface to be connected and a vapor deposition method using a target, the base material outer peripheral surface is formed. The outer peripheral surface of the base material includes a top having the maximum diameter in the base material, and the edge on the lower surface side of the base material is from the outer peripheral edge of the lower surface of the base material. Also has an outer peripheral end surface formed on the outer side in the radial direction, and a cut surface connecting the edge of the outer peripheral end surface on the lower surface side of the base material and the outer peripheral edge of the lower surface of the base material, and the cut surface is the outer periphery. Includes an inclined surface that is connected to the lower surface side edge of the substrate and is inclined so as to shrink in diameter toward the lower surface side of the substrate, and is radially outward over the entire region of the cut surface. The vapor deposition step is a surface treatment method performed in a state where the target and the outer peripheral end face face each other.

The present invention can also be applied to the case where a vapor-deposited film is formed on the outer peripheral surface of the ring body in a two-piece oil ring as a piston ring. That is, the present invention has a ring body in which a pair of rails projecting outward in the radial direction are provided on both sides in the axial direction, and an expander for urging the ring body outward in the radial direction, and is a piston for an internal combustion engine. A surface treatment method may be used in which a vapor-deposited film is formed on the outer peripheral surface of the ring body of the oil ring mounted in the ring groove of the above. In this case, the present invention is the base material of the ring body, and the upper surface of the base material facing the upper wall of the ring groove when the oil ring is mounted in the ring groove, and the oil ring is the ring. A base material having a lower surface of the base material facing the lower wall of the ring groove when mounted in the groove, and an outer peripheral surface of the base material connecting the outer peripheral edge of the upper surface of the base material and the outer peripheral edge of the lower surface of the base material. A base material preparation step for preparing the substrate, and a vapor deposition step for forming the vapor deposition film on the outer peripheral surface of the substrate by adhering particles emitted from the target to the substrate by a vapor deposition method using the target. The outer peripheral surface of the base material includes an upper rail surface included in the outer peripheral surface of the rail on the upper wall side of the ring groove and a lower surface included in the rail on the lower wall side of the ring groove among the pair of rails. The upper rail surface has a side rail surface, and the upper rail surface includes a top having the maximum diameter in the upper rail surface, and an edge on the upper surface side of the base material is formed radially outside the outer peripheral edge of the upper surface of the base material. An upper cut surface connecting the upper outer peripheral end surface, the edge on the upper surface side of the base material on the upper outer peripheral end surface, and the outer peripheral edge of the upper surface of the base material, and the base material on the upper outer peripheral end surface. The upper side, which is connected to the edge on the upper surface side and includes the first inclined surface on the upper side which is inclined so as to reduce the diameter toward the upper surface side of the base material, and which faces the outer side in the radial direction over the entire region. The cut surface, the edge on the lower surface side of the base material on the upper outer peripheral end surface, and the edge on the upper surface side of the base material on the upper and lower rail connection surfaces are connected and inclined so as to reduce the diameter toward the lower surface side of the base material. The lower rail surface includes a top having the maximum diameter in the lower rail surface, and the edge on the lower surface side of the base material is the outer peripheral edge of the lower surface of the base material. It is a lower cut surface that connects the lower outer peripheral end surface formed on the outer side in the radial direction, the edge on the lower surface side of the base material on the lower outer peripheral end surface, and the outer peripheral edge of the lower surface of the base material. Includes a lower first inclined surface that is connected to the lower surface side edge of the lower outer peripheral end surface and is inclined so as to shrink in diameter toward the lower surface side of the base material, and includes the entire area. The lower cut surface facing the outer side in the radial direction, the edge on the upper surface side of the base material on the lower outer peripheral end surface, and the edge on the lower surface side of the base material on the upper and lower rail connecting surfaces are connected. It has a lower second inclined surface that is inclined so as to reduce its diameter toward the upper surface side of the base material, and the vapor deposition step is performed in a state where the target and the outer peripheral end surface face each other. It is a surface treatment method to be performed.

Further, when a vapor-deposited film is formed on the outer peripheral surface of the ring body in the two-piece oil ring, in the present invention, the upper cut surface is the outer peripheral edge of the upper surface of the base material and the upper surface side of the base material on the upper inclined surface. The lower cut surface comprises the upper connecting surface connecting to the edge of the substrate, and the lower cut surface is a lower surface connecting the outer peripheral edge of the lower surface of the substrate and the lower edge of the substrate on the lower inclined surface. It may include a connecting surface.

According to the present invention, in a surface treatment method for forming a film on the outer peripheral surface of a piston ring by a vapor deposition method using a target, it is possible to improve the adhesion of the vapor deposition film.

FIG. 1 is a cross-sectional view showing a state in which a second ring having been surface-treated according to the first embodiment is provided in an internal combustion engine. FIG. 2 is a partially enlarged view of FIG. FIG. 3 is a diagram showing a process of the surface treatment method according to the first embodiment. FIG. 4 is a schematic view showing a film forming apparatus that performs a vapor deposition step of the surface treatment method according to the first embodiment. FIG. 5 is a schematic diagram for explaining the vapor deposition process. FIG. 6 is a diagram showing details of the vapor deposition process. FIG. 7 is a schematic diagram for explaining the vapor deposition process of the surface treatment method according to the comparative example. FIG. 8 is a diagram for explaining a twist test. FIG. 9 is a diagram showing a cross section of the base material used in the surface treatment method according to the first modification of the first embodiment, which is orthogonal to the circumferential direction. FIG. 10 is a cross-sectional view showing a state in which the surface-treated second ring according to the second modification of the first embodiment is provided in the internal combustion engine. FIG. 11 is a diagram showing a cross section of the base material used in the surface treatment method according to the second modification of the first embodiment, which is orthogonal to the circumferential direction. FIG. 12 is a diagram showing a cross section of the base material used in the surface treatment method according to the third modification of the first embodiment, which is orthogonal to the circumferential direction. FIG. 13 is a diagram showing a cross section of the base material used in the surface treatment method according to the modified example 4 of the first embodiment, which is orthogonal to the peripheral length direction. FIG. 14 is a cross-sectional view showing a state in which the surface-treated oil ring according to the second embodiment is provided in the internal combustion engine. FIG. 15 is a diagram showing a cross section of the base material used for the surface treatment according to the second embodiment, which is orthogonal to the peripheral length direction. FIG. 16 is a cross-sectional view showing a state in which the surface-treated oil ring according to the third embodiment is provided in the internal combustion engine. FIG. 17 is a diagram showing a cross section of the base material used for the surface treatment according to the third embodiment, which is orthogonal to the peripheral length direction.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the configurations described in the following embodiments are not intended to limit the technical scope of the invention to those alone unless otherwise specified.

In the following description, the "perimeter direction" refers to the perimeter direction of the piston ring or the base material unless otherwise specified. The "radial direction" refers to the radial direction of the piston ring or substrate unless otherwise specified. "Diameter inside" refers to the inner peripheral surface side of the piston ring or the base material, and "diameter outside" refers to the opposite side (that is, the outer peripheral surface side of the base material). "Axial direction" refers to the direction along the central axis of the piston ring or substrate unless otherwise specified. The "upper wall" of the ring groove of the piston refers to the inner wall of the inner wall of the ring groove on the combustion chamber side, and the "lower wall" refers to the inner wall of the crank chamber side. The "upper side" of the base material refers to the upper wall side of the ring groove when the piston ring is provided in the ring groove in the axial direction of the base material, and the "lower side" means that the piston ring is provided in the ring groove. Refers to the lower wall side of the ring groove in the case. Further, PVD (physical vapor deposition) is a kind of vapor deposition method for forming a film on the surface of a substance by adhering particles emitted from a target to a substrate, and can also be called physical vapor deposition. The PVD method can include an ion plating method, a vacuum vapor deposition method, an ion beam vapor deposition method, a sputtering method, an FCVA (Filtered Cathodic Vacuum Arc) method and the like.

<Embodiment 1>
In the first embodiment, the surface treatment method according to the present invention is applied to a second ring which is an example of a compression ring as a piston ring. However, the surface treatment method according to the present invention may be applied to the top ring. FIG. 1 is a cross-sectional view showing a state in which a second ring having been surface-treated according to the first embodiment is provided in an internal combustion engine. FIG. 1 shows a cross section orthogonal to the peripheral direction of the second ring. FIG. 2 is a partially enlarged view of FIG. The internal combustion engine 100 shown in FIG. 1 has a cylinder 20, an internal combustion engine piston 30 (hereinafter, piston 30) mounted on the cylinder 20, and a combustion chamber and a crank chamber (not shown). When FIG. 1 is viewed in a plan view, the upper side is the combustion chamber side, and the lower side is the crank chamber side. As shown in FIG. 1, in the internal combustion engine 100, a predetermined separation distance is secured between the cylinder inner wall 20a which is the inner peripheral surface of the cylinder 20 and the piston outer peripheral surface 30a which is the outer peripheral surface of the piston 30. PC1 is formed. A ring groove 40, which is a groove having a substantially rectangular cross-sectional shape, is formed on the outer peripheral surface 30a of the piston. The ring groove 40 connects the upper wall 401 formed on the combustion chamber side, the lower wall 402 formed on the crank chamber side and facing the upper wall 401, and the inner peripheral edges of the upper wall 401 and the lower wall 402. It has a wall 403 and. A second ring 10 is mounted on the ring groove 40.

[Second ring]
The second ring 10 is a sliding member that slides on the inner wall 20a of the cylinder with the reciprocating motion of the piston 30. As shown in FIG. 1, the surface of the second ring 10 has a ring upper surface 101, a ring lower surface 102, a ring outer peripheral surface 103, and a ring inner peripheral surface 104. When the second ring 10 is mounted in the ring groove 40, the upper surface 101 of the ring faces the upper wall 401, the lower surface 102 of the ring faces the lower wall 402, the outer peripheral surface 103 of the ring slides into the inner wall 20a of the cylinder, and the inside of the ring. The peripheral surface 104 faces the connection wall 403. The second ring 10 has an annular shape in which a joint (not shown) is formed. Further, the second ring 10 has a self-tension so that the outer peripheral surface 103 presses the cylinder inner wall 20a when mounted in the ring groove 40. As shown in FIG. 2, the second ring 10 has a base material 1, a PVD film 2, and an oxide film 3. The second ring 10 is formed by forming a PVD film 2 and an oxide film 3 on the surface of the base material 1 by using the surface treatment method according to the first embodiment. Hereinafter, the base material 1, the PVD coating 2, and the oxide coating 3 will be described in detail.

[Base material]
The base material 1 is to be subjected to the surface treatment according to the first embodiment. The base material 1 has an intermittent annular shape as a whole. The base material 1 is mainly formed of a steel material (steel). Examples of the steel material used as the material of the base material 1 include carbon steel material, stainless steel material, alloy steel, cast iron material, and cast steel material. However, the material of the base material 1 is not limited to this, and titanium-based materials and aluminum-based materials can also be used.

As shown in FIG. 1, the surface of the base material 1 has a base material upper surface 11, a base material lower surface 12, a base material outer peripheral surface 13, and a base material inner peripheral surface 14. The upper surface 11 of the base material is a surface facing the upper wall 401 when the second ring 10 is mounted in the ring groove 40. The lower surface 12 of the base material is a surface facing the lower wall 402 when the second ring 10 is mounted in the ring groove 40. The upper surface of the base material 11 and the lower surface of the base material 12 are orthogonal to each other in the axial direction and are formed on flat surfaces parallel to each other. As shown in FIG. 2, the base material outer peripheral surface 13 is a surface connecting the outer peripheral edge E1 of the base material upper surface 11 and the outer peripheral edge E2 of the base material lower surface 12, and the second ring 10 is mounted in the ring groove 40. In this case, it faces the cylinder inner wall 20a. The inner peripheral surface 14 of the base material is a surface that connects the inner peripheral edge of the upper surface surface 11 of the base material and the inner peripheral edge of the lower surface 12 of the base material, and faces the connection wall 403 when the second ring 10 is mounted in the ring groove 40. ..

As shown in FIG. 2, the base material outer peripheral surface 13 has an outer peripheral end surface S1, a cut surface S2, and a second inclined surface S3. The outer peripheral end surface S1 has a tapered shape that is inclined so as to increase in diameter toward the crank chamber side. The outer peripheral end surface S1 is a surface constituting the outermost outer peripheral portion of the base material 1. More specifically, the outer peripheral end surface S1 includes a top portion P1 having the maximum diameter in the base material 1. As shown in FIG. 2, the top P1 is formed by the edge E3 on the lower surface 12 side of the base material on the outer peripheral end surface S1. Further, the outer peripheral end surface S1 is formed on the outer side in the radial direction with respect to the outer peripheral edge E2 of the lower surface surface 12 of the base material. That is, the edge E3 is located radially outside the outer peripheral edge E2 of the lower surface surface 12 of the base material. When the second ring 10 is mounted in the ring groove 40, the outer peripheral end surface S1 is in sliding contact with the cylinder inner wall 20a via the PVD coating 2 to scrape off the oil in the gap PC1. The shape of the outer peripheral end surface S1 is not limited to the tapered shape. The outer peripheral end surface S1 may have a straight shape extending along the axial direction.

As shown in FIG. 2, the cut surface S2 is a surface connecting the edge E3 of the outer peripheral end surface S1 and the outer peripheral edge E2 of the lower surface surface 12 of the base material. The cut surface S2 includes a first inclined surface S21 and a connecting surface S22. The first inclined surface S21 is connected to the edge E3 of the outer peripheral end surface S1 and is inclined so as to reduce its diameter toward the lower surface 12 side of the base material. The connection surface S22 connects the edge E4 on the lower surface 12 side of the base material on the first inclined surface S21 and the outer peripheral edge E2 of the lower surface 12 of the base material, and extends along the axial direction of the base material 1. However, the connection surface S22 may be inclined with respect to the axial direction of the base material 1. As shown in FIG. 2, the cut surface S2 faces the outer side in the radial direction in the entire region (entire range) of the cut surface S2. Here, in the present specification, "the surface faces radially outward" means that the surface faces radially outward, and the surface is orthogonal to the radial direction (that is, in the axial direction). (Parallel to) Not only when facing outward in the radial direction, but also when the surface is inclined outward in the axial direction while facing outward in the axial direction. The outer peripheral surface 13 of the base material is formed in an undercut shape in which a portion on the crank chamber side is cut out by the first inclined surface S21 and the connecting surface S22. By subjecting such a base material 1 to a surface treatment described later, a second ring 10 having an undercut is formed on the outer peripheral surface 103. Therefore, as shown in FIG. 1, in the internal combustion engine 100, a space 50 is formed between the lower portion of the ring outer peripheral surface 103 and the cylinder 20. This space 50 becomes an oil pool, and when the second ring 10 scrapes off the oil in the gap PC1 when the piston 30 is lowered, the oil is buffered in the space 50, so that the increase in hydraulic pressure is suppressed. As a result, good oil scraping performance can be obtained. The first inclined surface S21 corresponds to an example of the "inclined surface" in the present invention.

As shown in FIG. 2, the second inclined surface S3 is a surface connecting the outer peripheral edge E1 of the upper surface surface 11 of the base material and the edge E5 of the outer peripheral end surface S1 on the upper surface 11 side of the base material. The second inclined surface S3 is inclined so as to reduce its diameter toward the upper surface 11 side of the base material.

The upper surface of the base material 11, the lower surface of the base material 12, the outer peripheral end surface S1, the first inclined surface S21, the connecting surface S22, the second inclined surface S3, and the inner peripheral surface of the base material 14 have an arcuate cross section formed by R processing or the like. It may be smoothly connected via the curved surface of.

[PVD coating]
The PVD film 2 is a film formed on substantially the entire area of the outer peripheral surface 13 of the base material by the vapor deposition process described later. The PVD coating film 2 includes an undercoat film 21 formed directly on the outer peripheral surface 13 of the base material and a hard coating film 22 formed on the undercoat film 21. The undercoat film 21 is a Cr film or a Ti film, and is provided to enhance the adhesion of the hard film 22 to the outer peripheral surface 13 of the base material. The undercoat film 21 is formed on the outer peripheral surface 13 of the base material in the undercoat film forming step in the vapor deposition step described later. The hard film 22 is a film provided to improve the wear resistance of the second ring 10. Examples of the hard coating film 22 include a Cr—N film, a Cr—BN film, and an amorphous carbon film (also referred to as diamond-like carbon). The hard film 22 is formed on the base film 21 in the hard film forming step in the vapor deposition process described later. The PVD film is an example of the "deposited film" in the present invention.

[Oxide film]
The oxide film 3 is a film provided for the purpose of preventing rust on the surface of the base material 1 and for good initial familiarization between the second ring 10 and the ring groove 40. The oxide film 3 is formed on the upper surface of the base material 11, the lower surface of the base material 12, and the inner peripheral surface of the base material 14 by the oxide film forming step described later. For example, when the base material 1 is formed of a steel material, a triiron tetraoxide film is formed as the oxide film 3, and when the base material 1 is formed of an aluminum-based material, an aluminum oxide film is formed as the oxide film 3. ..

[Surface treatment method]
Next, a method of forming the PVD coating 2 and the oxide coating 3 on the substrate 1 will be described using the surface treatment method according to the first embodiment. In the example shown below, a case where a film is formed on the base material 1 formed of a steel material will be described. FIG. 3 is a diagram showing a process of the surface treatment method according to the first embodiment. As shown in FIG. 3, the surface treatment method according to the first embodiment includes a substrate preparation step, a vapor deposition step, and an oxide film forming step. Hereinafter, each step will be described.

First, in the base material preparation step of S110, the base material 1 shown in FIGS. 1 and 2 is prepared. In S110, for example, the base material 1 is formed by blasting or buffing the raw material of the base material 1 obtained by processing the above-mentioned steel material. However, in the base material preparation step, a preformed base material 1 may be prepared. Further, in the base material preparation step, the surface of the base material 1 may be cleaned by performing an ion bombardment treatment as a pre-step of the vapor deposition step of S120.

Next, in the vapor deposition step of S120, the PVD coating film 2 is formed on the outer peripheral surface 13 of the base material by the PVD method. However, the vapor deposition method used in the vapor deposition step is not limited to the PVD method. The vapor deposition method used in the vapor deposition step may be any vapor deposition method in which particles emitted from the target are attached to a substrate to form a film on the surface of the substance. Hereinafter, a case where a PVD film is formed on the outer peripheral surface 13 of a plurality of base materials 1 by the arc ion plating method, which is an example of the PVD method, will be described.

FIG. 4 is a schematic view showing a film forming apparatus that performs a vapor deposition step of the surface treatment method according to the first embodiment. FIG. 4 shows a part of the plurality of base materials 1. The film forming apparatus 200 shown in FIG. 4 is an apparatus for performing a film forming process on the outer peripheral surface 13 of the base material by arc ion plating. The arc ion plating method is one of the ion plating methods, which uses vacuum arc discharge to vaporize and ionize the cathode material to form a film on the surface of the object to be coated. The film forming apparatus 200 includes a chamber 210, a target 220, an arc supply source 230, a work rotation apparatus 240, and a bias voltage supply source 250. The chamber 210 is a space for accommodating the base material 1 and the target 220. The target 220 is formed to include a material for forming the PVD coating film 2, and has an exit surface 220S from which particles (metal ions) of the material are ejected. The arc supply source 230 supplies the target 220 with an arc current to emit particles of the material. The arc source 230 has a cathode connected to the target 220 and an anode connected to the chamber 210. The work rotating device 240 rotates the base material 1 around the rotation axis A1 during the film forming process. The bias voltage supply source 250 applies a bias voltage to the base material 1 via the work rotation device 240.

FIG. 5 is a schematic diagram for explaining the vapor deposition process. In FIG. 5, for convenience, only two base materials 1 adjacent to each other in the axial direction are shown among the plurality of base materials 1. As shown in FIG. 5, the vapor deposition step is performed in a state where the target 220 is arranged on the radial outer side of the base material 1 and the exit surface 220S of the target 220 and the outer peripheral end surface S1 face each other. Further, in the example shown in FIG. 5, the vapor deposition step is performed in a state where a plurality of base materials 1 are stacked in the axial direction. More specifically, the plurality of base materials 1 are installed so that their central axes coincide with the rotation axis A1. That is, the plurality of base materials 1 are installed so as to be coaxial.

A bias potential is applied to the base material 1 in the chamber 210 from the bias voltage supply source 250 via the work rotation device 240. In this state, an arc current is supplied from the arc supply source 230 to the target 220. As a result, an arc discharge is generated between the target 220 (cathode) and the inner surface (anode) of the chamber 210, the material contained in the target 220 evaporates, and high-energy particles are ejected from the exit surface 220S. At this time, when the bias voltage is applied to the base material 1, the particles are accelerated toward the base material 1 and collide with the base material outer peripheral surface 13 to adhere to the base material 1. As a result, the PVD coating 2 is formed on the outer peripheral surface 13 of the base material. At this time, the work rotating device 240 rotates the base material 1 around the rotation axis A1 (that is, around the central axis of the base material 1), so that the PVD coating 2 is formed over the entire circumference of the outer peripheral surface 13 of the base material. To.

Here, most of the particles of the material emitted from the emission surface 220S are incident on the base material 1. The arrows shown by the chain lines in FIGS. 4 and 5 schematically represent the trajectories of the particles incident on the outer peripheral surface 13 of the base material 1 from the exit surface 220S. As shown in FIG. 5, since the outer peripheral end surface S1 and the emission surface 220S are arranged to face each other, particles incident on the base material 1 from the emission surface 220S are likely to adhere to the entire area of the outer peripheral end surface S1 and the outer peripheral end surface S1. It is possible to form a PVD film 2 having a high uniformity of film thickness. Further, with respect to the cut surface S2, since the cut surface S2 faces the outer side in the radial direction in the entire region, the particles incident from the exit surface 220S are likely to adhere to the entire area of the cut surface S2. As a result, the PVD film 2 having a high film thickness uniformity can be formed even on the cut surface S2. Similarly, since the second inclined surface S3 is formed to be inclined, particles incident from the exit surface 220S can adhere to the entire area of the second inclined surface S3, and the film thickness is also formed on the second inclined surface S3. It is possible to form a PVD film 2 having a high degree of uniformity.

FIG. 6 is a diagram showing details of the vapor deposition process. As shown in FIG. 6, the vapor deposition step includes a base film forming step and a hard film forming step. In the undercoat film forming step of S121, a Cr film or a Ti film is formed as the undercoat film 21. In the base film forming step, Cr or Ti is used as the material of the target 220. Next, in the hard film forming step of S122, a Cr—N film, a Cr—BN film, or an amorphous carbon film is formed as the hard film 22 on the undercoat film 21. When forming a Cr—N film or a Cr—B—N film, Cr or CrB ₂ is used as the material of the target 220, and nitrogen as a reaction gas is introduced into the chamber 210. When forming an amorphous carbon film, graphite is used as the material of the target 220. As described above, the undercoat film 21 and the hard film 22 are formed.

Next, in the oxide film forming step of S130, the oxide film 3 is formed on the upper surface 11 of the base material, the lower surface 12 of the base material, and the inner peripheral surface 14 of the base material by performing a chemical conversion treatment. In S130, an alkaline coloring treatment is used. In the alkaline coloring treatment, the treatment liquid acts on the surface of the steel material by immersing the steel material in a treatment liquid in which an oxidizing agent, a reaction accelerator, etc. are added to an alkaline solution and boiling the steel material. Is formed. In the oxide film forming step, the oxide film 3 is formed on the surface of the base material 1 that is not covered by the PVD film 2, that is, the upper surface 11 of the base material, the lower surface 12 of the base material, and the inner peripheral surface 14 of the base material by the alkali coloring treatment. Is formed.

By going through the above steps, the surface treatment according to the first embodiment is completed. As a result, the PVD film 2 and the oxide film 3 are formed on the surface of the base material 1. After the above surface treatment is completed, the second ring 10 shown in FIG. 1 is completed by performing blasting, buffing, lapping and the like.

[Action / Effect]
As described above, the surface treatment method for the compression ring according to the first embodiment is a substrate preparation step for preparing the substrate 1 and a PVD method which is a vapor deposition method using a target to coat the outer peripheral surface 13 of the substrate with a PVD. Includes a vapor deposition step of forming 2. The outer peripheral surface 13 of the base material includes the top portion P1 having the maximum diameter in the base material 1, and is formed on the outer peripheral end surface S1 radially outside the outer peripheral edge E2 of the lower surface surface 12 of the base material, and the base material on the outer peripheral end surface S1. It has a cut surface S2 that connects the edge E3 on the lower surface side and the outer peripheral edge E2 of the lower surface 12 of the base material. The cut surface S2 includes a first inclined surface S21 that is connected to the edge E3 on the lower surface 12 side of the base material on the outer peripheral end surface S1 and is inclined so as to reduce the diameter toward the lower surface 12 side of the base material, and is cut. It faces the outer side in the radial direction over the entire region of the surface S2. Then, the thin-film deposition step is performed in a state where the target 220 that emits particles that are the material of the PVD coating 2 and the outer peripheral end surface S1 face each other.

According to such a surface treatment method, by arranging the outer peripheral end surface S1 and the target 220 so as to face each other in the vapor deposition step, the PVD coating film 2 is formed on the outer peripheral end surface S1 with a highly uniform film thickness, and the cut surface S2 is formed. By forming the shape facing outward in the radial direction over the entire region, the particles of the material easily adhere to the entire area of the cut surface S2, and the PVD film 2 having a high uniform film thickness is formed on the cut surface S2 as well. Can be filmed.

Further, the first inclined surface S21 whose cut surface S2 is inclined so as to decrease in diameter toward the lower surface 12 of the base material, and the outer peripheral edge E2 of the lower surface 12 of the base material and the edge of the first inclined surface S21 on the lower surface 12 side of the base material. By including the connection surface S22 connecting the E4, the outer peripheral surface 13 of the base material is formed in an undercut shape. By applying surface treatment to the outer peripheral surface 13 of the base material, a second ring 10 having an undercut is formed on the outer peripheral surface 103. Thereby, good oil scraping performance can be obtained.

Here, if the film thickness of the PVD film formed is not uniform, the treatment liquid is transferred from the thin portion of the PVD film between the outer peripheral surface of the substrate and the PVD film when the chemical conversion treatment is performed in the oxide film forming step. It may penetrate and the PVD film may float from the outer peripheral surface of the substrate. As a result, there is a risk that the PVD coating will peel off when stress acts on the second ring in the engine assembly work of the second ring. The peeled film becomes a foreign substance, which causes scratches on the inner wall of the cylinder during operation of the internal combustion engine. That is, if the film thickness of the PVD film is not uniform, the adhesion of the PVD film may be deteriorated.

FIG. 7 is a schematic diagram for explaining the vapor deposition process of the surface treatment method according to the comparative example. FIG. 7 shows a single substrate for convenience. The surface treatment method according to the comparative example is different from the surface treatment method described with reference to FIG. 3 in that the base material 1X is used instead of the base material 1, and is the same in other respects. The base material 1X is different from the base material 1 in that the outer peripheral surface 13X is formed in an undercut shape, but the cut surface S2X has an inclined surface S23 and a straight surface S24 instead of the first inclined surface S21. The inclined surface S23 is connected to the edge E3 of the outer peripheral end surface S1 and is inclined so as to reduce its diameter toward the lower surface 12 of the base material. The straight surface S24 is connected to the edge E6 on the lower surface 12 side of the base material on the inclined surface S23, and extends in parallel with the radial direction in a cross section orthogonal to the circumferential length direction of the base material 1. That is, the straight surface S24 faces downward in the axial direction. As a result, the cut surface S2X has a shape that does not face the outer side in the radial direction on the straight surface S24. A connecting surface S22 is connected to the radial inner edge E4 of the straight surface S24. As shown in FIG. 7, in the case of the comparative example, since the straight surface S24 does not face the outer side in the radial direction, it is difficult for particles incident from the exit surface 220S of the target 220 to adhere to the straight surface S24. As a result, the PVD coating film 2 having a high film thickness uniformity is not formed on the straight surface S24, and the PVD coating film 2 on the straight surface S24 may be peeled off.

On the other hand, in the surface treatment method according to the first embodiment, since the PVD coating film 2 having a high film thickness uniformity can be formed even on the first inclined surface S21, the adhesion of the PVD coating film on the undercoat film 21 can be formed. Can be improved as compared with the comparative example. As a result, it is possible to improve the adhesion of the PVD film 2 while imparting good oil scraping performance to the second ring 10, and it is possible to suppress the floating and peeling of the PVD film 2.

Further, the thin-film deposition step includes a base film forming step of forming a base film 21 made of Cr or Ti on the outer peripheral surface 13 of the base material, and a hard film forming step of forming a hard film 22 on the base film 21. There is. According to this, by forming the hard coating film 22 on the outer peripheral surface 13 of the base material via the base film 21 made of Cr or Ti, the adhesion of the hard coating 22 to the outer peripheral surface 13 of the base material can be improved. As a result, floating and peeling of the hard coating 22 can be suitably suppressed. Further, since the adhesion is improved by the base film 21, even when the hard film 22 is thinly formed, floating and peeling are less likely to occur. As a result, the thickness of the PVD coating 2 can be made thinner. Here, the film thickness of the undercoat film 21 is not particularly limited, but it is better to make it 50% or less of the film thickness of the entire vapor-filmed film 2 including the hard film 22 and the undercoat film 21 from the viewpoint of improving the adhesion. preferable.

Here, the distance from the top P1 in the radial direction to the outer peripheral edge E1 of the upper surface 11 of the base material is defined as d1. Further, the distance d2 from the top P1 in the radial direction to the outer peripheral edge E2 of the lower surface 12 of the base material is set. FIG. 2 shows d1 and d2. At this time, in the first embodiment, d1 and d2 are made to each other by forming a second inclined surface S3 inclined so as to reduce the diameter toward the upper surface 11 of the base material on the outer peripheral surface 13 of the base material of the base material 1. Equal. As a result, in the base material 1, the distance from the central axis in the radial direction to the outer peripheral edge E1 of the upper surface surface 11 of the base material and the distance from the central axis to the outer peripheral edge E2 of the lower surface surface 12 of the base material are equal to each other. Then, the thin-film deposition step is performed in a state where a plurality of base materials 1 are stacked in the axial direction so that their respective central axes coincide with each other. According to this, as shown in FIG. 5, in the vapor deposition process, the outer peripheral edge E1 of the upper surface surface 11 of the base material and the outer peripheral edge E2 of the lower surface 12 of the base material facing each other in the two axially adjacent base materials 1 are in the radial direction. The positions in match. That is, the upper surface 11 of the base material and the lower surface 12 of the base material facing each other overlap each other without forming a step in the radial direction (without shifting). Here, if a step is generated between the upper surface 11 of the base material and the lower surface 12 of the base material facing each other, the PVD coating film 2 may be formed on the upper surface 11 of the base material or the lower surface 12 of the base material at the step portion. In that case, polishing processing is required to remove the PVD coating 2 from the base material upper surface 11 and the base material lower surface 12 to make the ring upper surface 101 and the ring lower surface 102 a flat surface. On the other hand, in the surface treatment method according to the first embodiment, the upper surface surface 11 of the base material and the lower surface 12 of the base material that face each other overlap each other without causing a step in the radial direction, so that the upper surface surface 11 of the base material and the lower surface 12 of the base material are overlapped with each other. It is possible to suppress the formation of the PVD film 2 on the surface, and the above-mentioned polishing process can be omitted. Such a surface treatment method is suitable for forming a PVD coating film 2 on a plurality of substrate 1s.

Here, the reference numeral θ shown in FIG. 2 indicates the inclination angle of the first inclined surface S21 with respect to the radial direction (that is, the direction orthogonal to the axial direction) of the base material 1 in the cross section orthogonal to the peripheral direction of the base material 1. show. At this time, by setting the inclination angle θ to 5 ° or more, the particles of the material of the target 220 are more likely to adhere to the entire area of the first inclined surface S21, and the uniformity of the film thickness on the first inclined surface S21 is further improved. be able to. As a result, the adhesion of the PVD coating 2 to the first inclined surface S21 can be further improved. However, the present invention is not limited to this.

When the inclination angle θ is 5 ° or more, the larger the inclination angle θ is within the range not exceeding 90 °, the better the adhesion of the PVD coating 2 is. Here, the ring width (axial dimension) of the second ring depends on the vertical width of the ring groove accommodating the second ring, and the range of the designable ring width is, for example, 1.0 to 1.5 mm. Limited. Therefore, in order to increase the inclination angle θ, it is necessary to form the edge E3 closer to the combustion chamber side, and as a result, the axial dimension of the outer peripheral end surface S1 is reduced. Here, when the outer peripheral end surface S1 has a tapered shape as in the present embodiment, the outer peripheral end surface S1 gradually wears with the reciprocating motion of the piston 30. At this time, the larger the axial dimension of the outer peripheral end surface S1, the longer the outer peripheral end surface S1 can remain. Considering this, the inclination angle θ is preferably 5 ° or more and 25 ° or less. By setting the inclination angle θ to 25 ° or less, it is possible to secure a larger axial dimension of the outer peripheral end surface S1. As a result, the tapered outer peripheral end surface S1 can be left for a long time, and the deterioration of the oil scraping function due to the early disappearance of the outer peripheral end surface S1 can be suppressed. As a result, the oil scraping performance of the second ring 10 can be improved. However, the present invention is not limited to this.

Although the case where the PVD coating is formed on the outer peripheral surface 13 of the substrate 1 of the plurality of substrates 1 by the arc ion plating method has been described above, the surface treatment method according to the present invention is not limited to this. Examples of the PVD method used in the vapor deposition step include an ion plating method, an ion beam vapor deposition method, a vacuum vapor deposition method, a sputtering method, and an FCVA (Filtered Cathodic Vacuum Arc) method. Further, the vapor deposition method used in the present invention is not limited to the PVD method, and may be any vapor deposition method using a target. Further, in the vapor deposition step, a PVD film may be formed on one substrate 1.

Further, the vapor deposition film formed in the vapor deposition process of the present invention is not limited to the undercoat film and the hard film, and the material of the PVD film is not limited to the above-mentioned materials. For example, the PVD coating may have only a hard coating without an undercoat. Further, the surface treatment method according to the present invention does not have to include an oxide film forming step. For example, in the surface treatment method according to the present invention, a phosphate film may be formed instead of the oxide film.

[Adhesion evaluation]
The adhesion of the PVD film formed by the surface treatment method according to the first embodiment was evaluated. In the evaluation of adhesion, a twist test was carried out on the second ring after the oxide film was formed by chemical conversion treatment, and it was visually observed whether or not the PVD film was peeled off on the cut surface. FIG. 8 is a diagram for explaining a twist test. In the twist test, as shown in FIG. 8, the pair of abutment ends 110, 120 forming the abutment of the second ring 10 is grasped, and the second ring is set with the portion 130 opposite to the abutment as a fulcrum with respect to the central axis. The second ring was twisted at a predetermined twist angle in the direction shown by the solid line in FIG. The twist angles at this time were 45 ° and 90 °.

[Example]
As Examples 1 to 5, the adhesion when a PVD film was formed on the outer peripheral surface of the base material by using the surface treatment method shown in FIG. 3 was evaluated. In Examples 1 to 5, the base material having the shape shown in FIG. 1 was used, and the inclination angle of the first inclined surface was made different. More specifically, in Example 1, the inclination angle of the first inclined surface was set to 2 °, and a PVD film was obtained. In Example 2, a PVD film was obtained in the same manner as in Example 1 except that the inclination angle of the first inclined surface was set to 5 °. In Example 3, a PVD film was obtained in the same manner as in Example 1 except that the inclination angle of the first inclined surface was set to 10 °. In Example 4, a PVD film was obtained in the same manner as in Example 1 except that the inclination angle of the first inclined surface was set to 15 °. In Example 5, a PVD film was obtained in the same manner as in Example 1 except that the inclination angle of the first inclined surface was set to 25 °.

[Comparison example]
As Comparative Example 1, the adhesion when a PVD film was formed on the outer peripheral surface of a base material whose cut surface did not have an inclined surface was evaluated. In Comparative Example 1, a PVD film was obtained in the same manner as in Example 1 except that the inclination angle of the first inclined surface was set to 0 °.

[Experimental result]
The evaluation results shown in Table 1 represent the results of the adhesion evaluation according to the following evaluation criteria. At each twist angle, the one in which the PVD coating did not peel off was marked with “◯”, and the one in which the peeling occurred was marked with “x”. The adhesion shown in Table 1 is set to "A" for those in which peeling did not occur at both the twist angle of 45 ° and the twist angle of 90 °, and the twist angle of 45 was found in the case where peeling occurred at the twist angle of 90 °. Those in which peeling did not occur at ° were given "B", and those in which peeling occurred at both a twist angle of 45 ° and a twist angle of 90 ° were given "C". As shown in Table 1, the results of Examples 1 to 5 were superior to those of Comparative Example 1. As a result, it was confirmed that the adhesion of the PVD coating was improved by the surface treatment method according to the first embodiment. Further, when the examples were compared with each other, the results of Examples 2 to 5 were superior to those of Example 1. As a result, it was confirmed that the adhesion of the PVD coating was further improved by setting the inclination angle of the first inclined surface to 5 ° or more.

［実施形態１の変形例１］
図９は、実施形態１の変形例１に係る表面処理方法に用いる基材１Ａの、周長方向に直交する断面を示す図である。実施形態１の変形例１に係る表面処理方法は、基材１に代えて基材１Ａを用いる点で、図３で説明した表面処理方法と相違し、その他の点は同じである。また、基材１Ａは、基材外周面１３Ａが第２傾斜面Ｓ３を有さない点で基材１と相違し、その他の点は同じである。図９に示すように、本発明に係る表面処理方法では、第２傾斜面Ｓ３を有さない基材を用いてもよい。

[Modification 1 of Embodiment 1]
FIG. 9 is a diagram showing a cross section of the base material 1A used in the surface treatment method according to the first modification of the first embodiment, which is orthogonal to the circumferential direction. The surface treatment method according to the first modification of the first embodiment is different from the surface treatment method described with reference to FIG. 3 in that the base material 1A is used instead of the base material 1, and is the same in other respects. Further, the base material 1A is different from the base material 1 in that the base material outer peripheral surface 13A does not have the second inclined surface S3, and is the same in other respects. As shown in FIG. 9, in the surface treatment method according to the present invention, a substrate having no second inclined surface S3 may be used.

[Modification 2 of Embodiment 1]
FIG. 10 is a cross-sectional view showing a state in which the surface-treated second ring according to the second modification of the first embodiment is provided in the internal combustion engine. FIG. 11 is a diagram showing a cross section of the base material 1B used in the surface treatment method according to the second modification of the first embodiment, which is orthogonal to the peripheral length direction. The surface treatment method according to the second modification of the first embodiment is different from the surface treatment method described with reference to FIG. 3 in that the base material 1B is used instead of the base material 1, and is the same in other respects.

As shown in FIG. 11, the base material outer peripheral surface 13B of the base material 1B according to the modified example 2 of the first embodiment includes the top portion P1 having the maximum diameter in the base material 1B, and is larger than the outer peripheral edge E2 of the base material lower surface 12. It includes an outer peripheral end surface S1 formed on the outer side in the radial direction, and a cut surface S2 connecting the edge E3 of the outer peripheral end surface S1 and the outer peripheral edge E2 of the lower surface surface 12 of the base material. Further, the cut surface S2 connects the edge E3 on the lower surface 12 side of the base material on the outer peripheral end surface S1 and the outer peripheral edge E2 of the lower surface 12 of the base material, and is inclined so as to reduce the diameter toward the lower surface 12 side of the base material. It is formed by an inclined surface S21. That is, the base material 1B is different from the base material 1 in that the cut surface S2 of the base material outer peripheral surface 13B does not have the connection surface S22, and is the same in other respects. As shown in FIG. 11, since the cut surface S2 is formed by the first inclined surface S21, the cut surface S2 has a shape facing outward in the radial direction in the entire region.

The outer peripheral surface 13B of the base material is formed in a bevel shape in which the portion on the crank chamber side is cut diagonally because the cut surface S2 is formed by the first inclined surface S21. As shown in FIG. 10, the ring outer peripheral surface 103B of the second ring 10B whose surface treatment is applied to the base material 1B forms a space 50 which becomes an oil pool in the internal combustion engine 100. Therefore, good oil scraping performance can be obtained. Further, in the surface treatment method according to the second modification of the first embodiment, the cut surface S2 is formed to face the outer side in the radial direction in the entire region, so that the particles of the material adhere to the entire area of the cut surface S2 in the vapor deposition step. It becomes easy to form a PVD film 2 having a high uniformity of film thickness on the cut surface S2. As a result, it is possible to improve the adhesion of the PVD coating 2 to the outer peripheral surface 13B of the base material while imparting good oil scraping performance to the second ring, and suppress the floating and peeling of the PVD coating 2. Can be done.

[Modification 3 of Embodiment 1]
FIG. 12 is a diagram showing a cross section of the base material 1C used in the surface treatment method according to the third modification of the first embodiment, which is orthogonal to the circumferential direction. The surface treatment method according to the third modification of the first embodiment is different from the surface treatment method described with reference to FIG. 3 in that the base material 1C is used instead of the base material 1, and is the same in other respects. Further, the base material 1C is different from the base material 1B in that the base material outer peripheral surface 13C does not have the second inclined surface S3, and is the same in other respects.

[Modification 4 of Embodiment 1]
The inclination angle θ of the first inclined surface S21 does not have to be uniform. FIG. 13 is a diagram showing a cross section of the base material 1D used in the surface treatment method according to the third modification of the first embodiment, which is orthogonal to the circumferential direction. The surface treatment method according to the modified example 4 of the first embodiment is different from the surface treatment method described with reference to FIG. 3 in that the base material 1D is used instead of the base material 1, and is the same in other respects. As shown in FIG. 13, the first inclined surface S21D of the base material outer peripheral surface 13D according to the modified example 4 is formed by connecting a plurality of surfaces having different inclination angles, and the base material outer peripheral surface shown in FIG. 2 is formed. It is different from the first inclined surface S21 of 13. More specifically, the first inclined surface S21D is connected to the outer surface S211 connected to the edge E3 of the outer peripheral end surface S1 and the outer surface S211 and connected to the edge E4 on the lower surface 12 side of the base material in the first inclined surface S21D. It has an inner side surface S212 to be formed. The outer side surface S211 is inclined at an inclination angle θ1 so as to decrease in diameter toward the lower surface 12 side of the base material, and the inner side surface S212 is inclined at an inclination angle θ2 so as to decrease in diameter toward the lower surface 12 side of the base material. are doing. As shown in FIG. 13, although the first inclined surface S21D faces the outer side in the radial direction in the entire region, θ1> θ2, and the inclination angle of the first inclined surface S21D is not uniform.

<Embodiment 2>
FIG. 14 is a cross-sectional view showing a state in which the surface-treated oil ring according to the second embodiment is provided in the internal combustion engine. FIG. 15 is a diagram showing a cross section of the base material 4 used in the surface treatment method according to the second embodiment, which is orthogonal to the peripheral direction. In the second embodiment, the surface treatment method according to the present invention is applied to a three-piece oil ring as a piston ring. It is applied to the second ring, which is an example of the compression ring. The surface treatment method according to the second embodiment uses the surface treatment according to the first embodiment described with reference to FIG. 3 in that the base material 4 of the segment in the three-piece oil ring is used instead of the base material 1 of the second ring (compression ring). It differs from the method and is the same in other respects.

[Oil ring]
The oil ring 300 shown in FIG. 14 is formed by combining a pair of segments 60, 60 provided on both sides in the axial direction and an expander 70 for urging the pair of segments 60, 60 outward in the radial direction. There is. The pair of segments 60, 60 slide on the inner wall 20a of the cylinder with the reciprocating motion of the piston 30. As shown in FIG. 14, the surface of the segment 60 has a segment upper surface 601, a segment lower surface 602, a segment outer peripheral surface 603, and a segment inner peripheral surface 604. When the oil ring 300 is mounted in the ring groove 40, the upper segment upper surface 601 is located on the upper wall 401 side, the lower segment lower surface 602 is located on the lower wall 402 side, and the segment outer peripheral surface 603 is the cylinder inner wall. It is in sliding contact with 20a, and the inner peripheral surface of the segment 604 comes into contact with the expander 70. The segment 60 has an annular shape in which a joint (not shown) is formed. The segment 60 is formed by forming a PVD film 2 and an oxide film 3 on the surface of the base material 4 by using a surface treatment method. Hereinafter, the base material 4 will be described in detail, and the detailed description of the PVD film 2 and the oxide film 3 will be omitted.

As shown in FIG. 14, the surface of the base material 4 has a base material upper surface 41, a base material lower surface 42, a base material outer peripheral surface 43, and a base material inner peripheral surface 44. The upper surface 41 of the base material is a surface located on the upper wall 401 side when the oil ring 300 is mounted in the ring groove 40. The lower surface 42 of the base material is the oil ring 300.
Is a surface located on the lower wall 402 side when mounted in the ring groove 40. The base material upper surface 41 and the base material lower surface 42 are orthogonal to each other in the axial direction and are formed on flat surfaces parallel to each other. As shown in FIG. 15, the base material outer peripheral surface 43 is a surface connecting the outer peripheral edge E1 of the base material upper surface 41 and the outer peripheral edge E2 of the base material lower surface 42, and the oil ring 300 is mounted on the ring groove 40. In this case, it faces the cylinder inner wall 20a. The base material inner peripheral surface 44 is a surface connecting the inner peripheral edge of the base material upper surface 41 and the inner peripheral edge of the base material lower surface 42, and faces the expander 70 when the oil ring 300 is mounted in the ring groove 40. ..

As shown in FIG. 15, the base material outer peripheral surface 43 has an outer peripheral end surface S1 and a cut surface S2. The outer peripheral end surface S1 has an arc shape curved outward in the radial direction in a cross section orthogonal to the circumferential length direction. The outer peripheral end face S1 includes a top portion P1 having the maximum diameter in the base material 4. As shown in FIG. 15, the top portion P1 is formed at the apex of the arc on the outer peripheral end surface S1. Further, the outer peripheral end surface S1 is formed on the outer side in the radial direction with respect to the outer peripheral edge E2 of the lower surface surface 42 of the base material. That is, the top portion P1 is located radially outside the outer peripheral edge E2 of the lower surface surface 42 of the base material. When the oil ring 300 is attached to the ring groove 40, the outer peripheral end surface S1 is in sliding contact with the cylinder inner wall 20a via the PVD coating 2 to scrape off the oil in the gap PC1. The shape of the outer peripheral end surface S1 is not limited to the arc shape.

As shown in FIG. 15, the cut surface S2 is a surface connecting the edge E3 of the outer peripheral end surface S1 on the lower surface 42 side of the base material and the outer peripheral edge E2 of the lower surface 42 of the base material. The cut surface S2 includes a first inclined surface S21 and a connecting surface S22. The first inclined surface S21 is connected to the edge E3 of the outer peripheral end surface S1 and is inclined so as to reduce its diameter toward the lower surface 42 side of the base material. The connection surface S22 connects the edge E4 on the lower surface 42 side of the base material on the first inclined surface S21 and the outer peripheral edge E2 of the lower surface 42 of the base material. The connection surface S22 may extend along the axial direction of the base material 1 or may be inclined with respect to the axial direction of the base material 1. As shown in FIG. 15, the cut surface S2 faces radially outward in the entire region. The outer peripheral surface 43 of the base material is formed in an undercut shape in which a portion on the crank chamber side is cut out by the first inclined surface S21 and the connecting surface S22. By applying a surface treatment to such a base material 4, an undercut is formed on the outer peripheral surface 603 of the segment 60. As a result, good oil scraping performance can be obtained. The upper surface of the base material 41, the lower surface of the base material 42, the outer peripheral end surface S1, the first inclined surface S21, the connection surface S22, and the inner peripheral surface of the base material 44 are connected via a curved surface having an arcuate cross section formed by R processing or the like. May be done.

In the surface treatment method according to the second embodiment, as in the first embodiment, the target 220 is arranged on the radial outer side of the base material 4, and the emission surface 220S of the target 220 and the outer peripheral end surface S1 face each other in the vapor deposition step. Is done. By forming the cut surface S2 so as to face the outer side in the radial direction in the entire region, the particles of the material easily adhere to the entire area of the cut surface S2 in the vapor deposition process, and the PVD having high film thickness uniformity on the cut surface S2. The film 2 can be formed. As a result, it is possible to improve the adhesion of the PVD coating 2 to the outer peripheral surface 43 of the base material while imparting good oil scraping performance to the oil ring 300, and suppress the floating and peeling of the PVD coating 2. be able to.

Further, also in the second embodiment, the distance from the central axis in the radial direction to the outer peripheral edge E1 of the upper surface 41 of the base material and the distance from the central axis to the outer peripheral edge E2 of the lower surface 42 of the base material are made equal to each other, and a plurality of groups are used. By performing the vapor deposition step in a state where the materials 4 are stacked in the axial direction so that their central axes coincide with each other, it is possible to prevent the PVD coating film 2 from being formed on the upper surface 41 of the base material and the lower surface 42 of the base material.

Further, also in the second embodiment, by forming the hard coating film 22 on the outer peripheral surface 43 of the base material via the base film 21 made of Cr or Ti, the adhesion of the hard coating 22 to the outer peripheral surface 43 of the base material is further enhanced. be able to. As a result, floating and peeling of the hard coating 22 can be more preferably suppressed. The film thickness of the undercoat film 21 is not particularly limited, but it is more preferable to make it 50% or less of the film thickness of the entire vapor-filmed film 2 including the hard film 22 and the undercoat film 21 from the viewpoint of improving adhesion. ..

Further, also in the second embodiment, by setting the inclination angle θ to 5 ° or more, the adhesion of the PVD coating 2 to the first inclined surface S21 can be further improved. Further, it is preferable that the inclination angle θ is 5 ° or more and 25 ° or less from the viewpoint of oil scraping performance. However, the present invention is not limited to these.

<Embodiment 3>
FIG. 16 is a cross-sectional view showing a state in which the surface-treated oil ring according to the third embodiment is provided in the internal combustion engine. FIG. 17 is a diagram showing a cross section of the base material 5 used in the surface treatment method according to the third embodiment, which is orthogonal to the peripheral direction. In the third embodiment, the surface treatment method according to the present invention is applied to a two-piece oil ring as a piston ring. The surface treatment method according to the third embodiment uses the base material 5 of the ring body in the two-piece oil ring instead of the base material 1 of the second ring (compression ring), and the surface according to the first embodiment described with reference to FIG. It differs from the processing method and is the same in other respects.

[Oil ring]
The oil ring 400 shown in FIG. 16 includes a ring body 80 in which a pair of rails 810 and 810 projecting outward in the radial direction are provided on both sides in the axial direction, and an expander 90 for urging the ring body 80 outward in the radial direction. Are combined and formed. The pair of rails 810 and 810 slide on the inner wall 20a of the cylinder as the piston 30 reciprocates. As shown in FIG. 16, the surface of the ring body 80 has an upper surface 801 and a lower surface 802, an outer peripheral surface 803, and an inner peripheral surface 804. When the oil ring 400 is mounted in the ring groove 40, the upper surface 801 faces the upper wall 401, the lower surface 802 faces the lower wall 402, the outer peripheral surface 803 slides into contact with the cylinder inner wall 20a, and the inner peripheral surface 804 Contact the expander 90. The ring body 80 has an annular shape in which a joint (not shown) is formed. The ring body 80 is formed by forming a PVD film 2 and an oxide film 3 on the surface of the base material 5 by using a surface treatment method. Hereinafter, the base material 5 will be described in detail, and the detailed description of the PVD film 2 and the oxide film 3 will be omitted.

As shown in FIG. 16, the surface of the base material 5 has a base material upper surface 51, a base material lower surface 52, a base material outer peripheral surface 53, and a base material inner peripheral surface 54. The upper surface 51 of the base material is a surface facing the upper wall 401 when the oil ring 400 is mounted in the ring groove 40. The lower surface 52 of the base material is a surface facing the lower wall 402 when the oil ring 400 is mounted in the ring groove 40. The base material upper surface 51 and the base material lower surface 52 are orthogonal to each other in the axial direction and are formed on flat surfaces parallel to each other. As shown in FIG. 17, the base material outer peripheral surface 53 is a surface connecting the outer peripheral edge E1 of the base material upper surface 51 and the outer peripheral edge E2 of the base material lower surface 52, and the oil ring 400 is mounted in the ring groove 40. In this case, it faces the cylinder inner wall 20a. The inner peripheral surface 54 of the base material is a surface connecting the inner peripheral edge of the upper surface surface 51 of the base material and the inner peripheral edge of the lower surface 52 of the base material, and faces the expander 90 when the oil ring 400 is mounted in the ring groove 40. ..

As shown in FIG. 17, the base material outer peripheral surface 53 has a vertically symmetrical shape. More specifically, the base material outer peripheral surface 53 includes the upper rail surface 531 included in the outer peripheral surface of the rail 810 on the upper wall 401 side of the ring groove 40 among the pair of rails 810 and 810 in the ring body 80, and the ring. It has a lower rail surface 532 included in the rail 810 on the lower wall 402 side of the groove 40, and an upper and lower rail connecting surface 533 connecting the upper rail surface 531 and the lower rail surface 532.

The upper rail surface 531 further has an upper outer peripheral end surface S1, an upper cut surface S2, and an upper second inclined surface S3. The upper outer peripheral end surface S1 has an arc shape curved outward in the radial direction in a cross section orthogonal to the circumferential length direction. The upper outer peripheral end surface S1 includes the upper top portion P1 having the maximum diameter on the upper rail surface 531 and is formed on the outer side in the radial direction with respect to the outer peripheral edge E1 of the upper surface surface 51 of the base material.

As shown in FIG. 17, the upper cut surface S2 is a surface connecting the edge E3 of the upper outer peripheral end surface S1 on the upper surface 51 side of the base material and the outer peripheral edge E1 of the upper surface 51 of the base material. The upper cut surface S2 includes an upper first inclined surface S21 and an upper connecting surface S22. The upper first inclined surface S21 is connected to the edge E3 of the upper outer peripheral end surface S1 and is inclined so as to shrink in diameter toward the upper surface 51 side of the base material. The upper connecting surface S22 connects the edge E4 on the upper surface 51 side of the base material on the upper first inclined surface S21 and the outer peripheral edge E1 of the upper surface 51 of the base material, and extends along the axial direction of the base material 5. There is. However, the upper connecting surface S22 may be inclined with respect to the axial direction of the base material 5. As shown in FIG. 17, the upper cut surface S2 faces radially outward in the entire region. The upper second inclined surface S3 connects the edge E5 on the lower surface 52 side of the base material on the upper outer peripheral end surface S1 and the edge E7 on the upper surface side 51 of the base material on the upper and lower rail connecting surfaces 533, and faces the lower surface 52 side of the base material. It is inclined so as to reduce the diameter according to.

The lower rail surface 532 further has a lower outer peripheral end surface S1, a lower cut surface S2, and a lower second inclined surface S3. The lower outer peripheral end surface S1 has an arc shape curved outward in the radial direction in a cross section orthogonal to the circumferential length direction. The lower outer peripheral end surface S1 includes the lower top portion P1 having the maximum diameter on the lower rail surface 532, and is formed radially outside the outer peripheral edge E2 of the lower surface 52 of the base material.

As shown in FIG. 17, the lower cut surface S2 is a surface connecting the edge E3 on the lower surface 52 side of the lower outer peripheral end surface S1 and the outer peripheral edge E2 of the lower surface 52 of the base material. The lower cut surface S2 includes a lower first inclined surface S21 and a lower connecting surface S22. The lower first inclined surface S21 is connected to the edge E3 of the lower outer peripheral end surface S1 and is inclined so as to shrink in diameter toward the lower surface 52 side of the base material. The lower connecting surface S22 connects the edge E4 on the lower surface 52 side of the base material on the lower first inclined surface S21 and the outer peripheral edge E2 of the lower surface 52 of the base material, and extends along the axial direction of the base material 5. are doing. However, the lower connection surface S22 may be inclined with respect to the axial direction of the base material 5. As shown in FIG. 17, the lower cut surface S2 faces radially outward in the entire region. The lower second inclined surface S3 connects the edge E5 on the upper surface 51 side of the base material on the lower outer peripheral end surface S1 and the edge E8 on the lower surface side 52 of the base material on the upper and lower rail connecting surfaces 533, and is on the upper surface 51 side of the base material. It is inclined so that the diameter is reduced toward.

The upper surface of the base material 51, the lower surface of the base material 52, the outer peripheral end surface S1, the first inclined surface S21, the connecting surface S22, and the inner peripheral surface of the base material 54 are connected via a curved surface having an arcuate cross section formed by R processing or the like. May be done.

When the oil ring 400 is attached to the ring groove 40, the upper and lower outer peripheral end faces S1 are slidably contacted with the cylinder inner wall 20a via the PVD coating 2 to scrape off the oil in the gap PC1. The shape of the outer peripheral end surface S1 is not limited to the arc shape.

In the surface treatment method according to the third embodiment, as in the first embodiment, the target 220 is arranged on the radial outer side of the base material 5, and the vapor deposition step is carried out in a state where the exit surface 220S of the target 220 and the outer peripheral end surface S1 face each other. Is done. By forming the upper and lower cut surfaces S2 to face radially outward in the entire region, it becomes easy for material particles to adhere to the entire area of the cut surface S2 in the vapor deposition process, and the film thickness is increased on the cut surface S2. A PVD film 2 having high uniformity can be formed. Further, the second inclined surface S3 of the upper rail surface 531 is inclined so as to shrink in diameter toward the lower surface 52 side of the base material, and the second inclined surface S3 of the lower rail surface 532 shrinks toward the upper surface 51 side of the base material. By inclining so as to have a diameter, the particles of the material are likely to adhere to the entire area of the upper and lower second inclined surfaces S3, and the PVD coating 2 having high film thickness is also applied to each of the second inclined surfaces S3. Can be formed. As a result, it is possible to improve the adhesion of the PVD coating 2 to the outer peripheral surface 53 of the base material while imparting good oil scraping performance to the oil ring, and suppress the floating and peeling of the PVD coating 2. Can be done.

Further, also in the third embodiment, the distance from the central axis in the radial direction to the outer peripheral edge E1 of the upper surface surface 51 of the base material and the distance from the central axis to the outer peripheral edge E2 of the lower surface 52 of the base material are made equal to each other, and a plurality of groups are used. By performing the vapor deposition step in a state where the materials 5 are stacked in the axial direction so that their central axes coincide with each other, it is possible to prevent the PVD coating film 2 from being formed on the upper surface surface 51 of the base material and the lower surface 52 of the base material.

Further, also in the third embodiment, by forming the hard coating film 22 on the outer peripheral surface 53 of the base material via the base film 21 made of Cr or Ti, the adhesion of the hard coating 22 to the outer peripheral surface 53 of the base material is further enhanced. be able to. As a result, floating and peeling of the hard coating 22 can be more preferably suppressed. The film thickness of the undercoat film 21 is not particularly limited, but it is more preferable to make it 50% or less of the film thickness of the entire vapor-filmed film 2 including the hard film 22 and the undercoat film 21 from the viewpoint of improving adhesion. ..

Further, also in the third embodiment, by setting the inclination angles φ1 to φ4 of each inclined surface to 5 ° or more, the adhesion of the PVD coating 2 to the first inclined surface S21 and the second inclined surface S3 can be further improved. can. Further, it is preferable that the inclination angles φ1 to φ4 of each inclined surface are 5 ° or more and 25 ° or less from the viewpoint of oil scraping performance. However, the present invention is not limited to these.

Although the preferred embodiments of the present invention have been described above, the various embodiments described above can be combined as much as possible.

1: Substrate 11: Substrate upper surface 12: Substrate lower surface 13: Substrate outer peripheral surface 2: PVD coating film (example of vapor deposition film)
21: Undercoat 22: Hard coating 3: Oxide coating 10: Second ring (example of compression ring)
20: Cylinder 30: Piston for internal combustion engine 40: Ring groove 401: Upper wall 402: Lower wall 100: Internal combustion engine S1: Outer peripheral end surface S2: Cut surface S21: First inclined surface (example of inclined surface)
S22: Connection surface S3: Second inclined surface (an example of an inclined surface)

Claims (7)

A surface treatment method for forming a thin-film deposition film on the outer peripheral surface of a compression ring mounted in the ring groove of a piston for an internal combustion engine.
When the upper surface of the base material of the compression ring facing the upper wall of the ring groove when the compression ring is mounted in the ring groove and the compression ring are mounted in the ring groove. A base material preparation step for preparing a base material having a lower surface of the base material facing the lower wall of the ring groove, and an outer peripheral surface of the base material connecting the outer peripheral edge of the upper surface of the base material and the outer peripheral edge of the lower surface of the base material. When,
A vapor deposition step of forming the vapor deposition film on the outer peripheral surface of the substrate by adhering particles emitted from the target to the substrate by a vapor deposition method using a target other than a thermal spraying method is included.
The outer peripheral surface of the base material includes an upper portion having the maximum diameter in the base material, and an outer peripheral end surface having an edge on the lower surface side of the base material formed radially outside the outer peripheral edge of the lower surface of the base material, and the outer peripheral end surface. Has a cut surface connecting the edge on the lower surface side of the base material and the outer peripheral edge of the lower surface of the base material.
The cut surface includes an inclined surface that is connected to the edge of the outer peripheral end surface on the lower surface side of the base material and is inclined so as to reduce the diameter toward the lower surface side of the base material, and covers the entire region of the cut surface. Facing the outside in the radial direction over
The cut surface further includes a connecting surface connecting the outer peripheral edge of the lower surface of the base material and the edge of the inclined surface on the lower surface side of the base material.
The vapor deposition step is performed in a state where the target and the outer peripheral end face face each other.
Surface treatment method. It has a pair of segments provided on both sides in the axial direction and an expander that urges the pair of segments outward in the radial direction, and has an outer periphery of the segment in an oil ring mounted in a ring groove of a piston for an internal combustion engine. A surface treatment method for forming a vapor-filmed film on a surface.
Of the surfaces of the segment on both sides in the axial direction, the upper surface of the substrate located on the upper wall side of the ring groove when the oil ring is mounted in the ring groove, and the oil. When the ring is mounted in the ring groove, the lower surface of the base material located on the lower wall side of the ring groove, and the outer peripheral surface of the base material connecting the outer peripheral edge of the upper surface of the base material and the outer peripheral edge of the lower surface of the base material. A base material preparation process for preparing a base material having, and
A vapor deposition step of forming the vapor deposition film on the outer peripheral surface of the substrate by adhering particles emitted from the target to the substrate by a vapor deposition method using a target other than a thermal spraying method is included.
The outer peripheral surface of the base material includes an upper portion having the maximum diameter in the base material, and an outer peripheral end surface having an edge on the lower surface side of the base material formed radially outside the outer peripheral edge of the lower surface of the base material, and the outer peripheral end surface. Has a cut surface connecting the edge on the lower surface side of the base material and the outer peripheral edge of the lower surface of the base material.
The cut surface includes an inclined surface that is connected to the edge of the outer peripheral end surface on the lower surface side of the base material and is inclined so as to reduce the diameter toward the lower surface side of the base material, and covers the entire region of the cut surface. Facing the outside in the radial direction over
The cut surface further includes a connecting surface connecting the outer peripheral edge of the lower surface of the base material and the edge of the inclined surface on the lower surface side of the base material.
The vapor deposition step is performed in a state where the target and the outer peripheral end face face each other.
Surface treatment method. The thin-film deposition step is performed in a state where a plurality of the substrates are stacked in the axial direction so that their respective central axes coincide with each other.
The base material is formed so that the distance from the central axis to the outer peripheral edge of the upper surface of the base material in the radial direction and the distance from the central axis to the outer peripheral edge of the lower surface of the base material are equal to each other.
The surface treatment method according to claim 1 or 2 . In the cross section orthogonal to the circumferential length direction of the base material, the inclination angle of the inclined surface with respect to the radial direction of the base material is 5 ° or more.
The surface treatment method according to any one of claims 1 to 3 . In the cross section orthogonal to the circumferential length direction of the base material, the inclination angle of the inclined surface with respect to the radial direction of the base material is 5 ° or more and 25 ° or less.
The surface treatment method according to claim 4 . The vapor deposition step includes a base film forming step of forming a base film made of Cr or Ti on the outer peripheral surface of the base material, and a hard film forming step of forming a hard film on the base film.
The surface treatment method according to any one of claims 1 to 5 . The film thickness of the undercoat film is 50% or less of the film thickness of the entire vapor-filmed film including the hard film and the undercoat film.
The surface treatment method according to claim 6 .

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