JP2006283970A - Piston ring and piston provided with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piston ring having low attack property for an aluminum alloy member and having excellent resistance to aluminum coagulation and wear and to provide a piston provided with the piston ring. <P>SOLUTION: This piston ring 5 is composed of a piston ring main body 50 and an amorphous hard carbon membrane 51 covering at least a part of a surface of the piston ring main body 50. Si content of the amorphous hard carbon membrane 51 is 1 at% or more and 10 at% or less, and H content is 20 at% or more and 40 at% or less. Hardness of the amorphous hard carbon membrane 51 is 7 GPa or more and 20 GPa or less and its modulus of elasticity is 70 GPa or more and 160 GPa or less to realize excellent sliding property even in lubricating oil containing soot. This piston is provided with a piston main body provided with a piston ring groove around it and the piston ring 5 arranged in the piston ring groove. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a piston ring that is low in aggressiveness to an aluminum alloy member and excellent in aluminum adhesion resistance and wear resistance, and a piston including the same. Furthermore, the present invention relates to a piston ring that has a low opponent attack and excellent wear resistance even when foreign matter such as soot is mixed in the lubricating oil, and a piston including the same.

  With the recent reduction in weight and output of engines, piston rings constituting the engine are also required to be improved in characteristics such as weight reduction and wear resistance. For this reason, surface treatment such as film formation such as CrN film by PVD method, Cr plating, nitriding treatment is applied to the outer peripheral surface that is in sliding contact with the cylinder and the opposing surface that is in sliding contact with the piston ring groove and is opposed to the reciprocating direction of the piston. To improve wear resistance. Various attempts have also been made to reduce the piston ring width and improve the shape.

  However, in a piston ring having a CrN film or a nitride layer on the surface, the aggressiveness of the aluminum alloy piston against the piston ring groove becomes a problem. That is, when the CrN film on the piston ring surface and the piston ring groove are in sliding contact, aluminum adheres to the surface of the CrN film or the like, and the piston ring groove is worn.

  For this reason, conventionally, measures have been taken to reinforce the piston ring groove by subjecting the piston ring groove to a surface treatment such as cast-off of a wear resistant ring-resisting cast iron and an alumite treatment. On the other hand, from the viewpoint of suppressing the adhesion of aluminum, Patent Document 1 discloses that a diamond-like carbon (DLC) film containing 5 to 40 at% of elements such as Si, Ti, W, and Cr is formed on the upper and lower surfaces (opposing surfaces). A formed piston ring is disclosed. Patent Document 2 discloses a piston ring formed by laminating a first hard carbon film containing W and Ni and a second hard carbon film containing 50 to 70 wt% of Si on upper and lower surfaces (opposing surfaces). Is disclosed.

  However, the reinforcement of the piston ring groove and the methods described in Patent Documents 1 and 2 do not sufficiently suppress the adhesion of aluminum and the wear of the piston ring and the piston ring groove. For example, when the piston ring has an internal bevel shape in order to improve the sealing performance, the piston ring is torsionally deformed during actual operation, so that the edge portion of the piston ring and the piston ring groove are in sliding contact locally. Further, even when the piston ring is thinned to reduce the weight, the piston ring is easily twisted and deformed. In Patent Documents 1 and 2, it is assumed that the piston ring slides between the opposed surface of the piston ring and the piston ring groove. For this reason, the methods described in both documents cannot suppress such adhesion of aluminum due to local contact and wear of the piston ring and the piston ring groove.

  Moreover, the 2nd hard carbon membrane | film | coat containing 50 to 70 wt% of Si is formed in the piston ring disclosed by patent document 2. FIG. Since the Si content is large, the wear resistance of the second hard carbon film is low. In addition, aluminum easily adheres to the second hard carbon film, and wear of the piston ring and the piston ring groove easily proceeds.

  By the way, in diesel engines and the like, it is known that foreign matters such as soot mixed in engine oil affect engine performance. Specifically, when soot is mixed into the engine oil, the viscosity of the oil increases and fuel consumption deteriorates, and the amount of soot increases and wear of the sliding part increases. Cause problems. Particularly in the piston ring, not only the piston ring itself but also the wear of the piston ring groove and the cylinder in sliding contact with the piston ring becomes a problem. In general, “soot” is an incomplete combustion product of fuel or engine oil.

A piston ring having a hard surface, such as a CrN film in which carbon and oxygen are solid-dissolved disclosed in Patent Document 3, and a nitrided layer formed by nitriding treatment of a high chromium martensitic steel disclosed in Patent Document 4. If it exists, the abrasion resistance of a piston ring will improve. However, even when the piston rings described in Patent Documents 3 and 4 are used, for example, when using a piston ring groove subjected to surface treatment such as cast-off of a wear resistant ring-resisting cast iron or anodized as a counterpart material, The presence of hard wrinkles causes abrasive wear and the ring groove wears. That is, in the case where a conventional piston ring groove or cylinder is used, it is difficult to reduce the wear of the mating member due to wrinkles only by forming a CrN film or the like on the surface of the piston ring.
JP 11-166625 A Japanese Patent Laid-Open No. 2003-14122 Japanese Patent Laid-Open No. 10-306386 JP 2002-30394 A

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a piston ring and a piston that are low in aggressiveness against aluminum alloy members and excellent in aluminum adhesion resistance and wear resistance. And

  Another object of the present invention is to provide a piston ring that is low in attacking opponent and excellent in wear resistance even if foreign matter such as soot is mixed in the lubricating oil, and a piston including the same.

  (1) The piston ring of the present invention comprises a piston ring main body and an amorphous hard carbon film covering at least a part of the surface of the piston ring main body, and the Si content of the amorphous hard carbon film is 1 at% or more and 10 at% or less, and H content is 20 at% or more and 40 at% or less.

  The piston ring of the present invention includes an amorphous hard carbon film having an Si content of 1 at% or more and 10 at% or less and an H content of 20 at% or more and 40 at% or less. This amorphous hard carbon film has an amorphous structure, has a smooth surface, and has a lower surface energy than other metals and nitrides. For this reason, even if the amorphous hard carbon film and the aluminum alloy member slide, aluminum hardly adheres. In addition, since the present amorphous hard carbon film contains the predetermined amount of Si, it has excellent wear resistance and exhibits a low coefficient of friction. Therefore, when sliding the piston ring of the present invention and an aluminum alloy member, if the amorphous hard carbon film is used as a sliding surface, adhesion of aluminum is suppressed, and the piston ring itself and the counterpart material Wear of certain aluminum alloy members is reduced.

  Therefore, for example, when the piston ring of the present invention is assembled to an aluminum alloy piston, if the sliding surface with the piston ring groove is composed of the amorphous hard carbon film, the piston ring groove is cast or anodized. The need to apply is reduced. Therefore, the manufacturing cost of the piston can be reduced.

  Further, since the present amorphous hard carbon film contains Si, silanol (SiOH) is generated on the surface of the amorphous hard carbon film during sliding. The generated silanol is considered to contribute to the reduction of boundary friction. In other words, the piston ring of the present invention exhibits a low coefficient of friction in addition to low opponent attack and wear resistance. For this reason, if the piston ring of this invention is employ | adopted, the energy loss by friction will reduce and it will lead to the improvement of a fuel consumption.

  (2) The piston of the present invention includes a piston main body in which a piston ring groove is provided, and the piston ring of the present invention disposed in the piston ring groove. For example, when the piston ring of the present invention adopts a mode in which a pair of opposed surfaces facing the reciprocating direction of the piston of the piston ring main body are covered with an amorphous hard carbon film, the piston ring groove and the amorphous are used in actual operation. The hard carbon film is in sliding contact. In this case, the wear of the piston ring and the piston ring groove is small, and the friction coefficient is also small. In particular, when the piston ring groove (piston main body) is made of an aluminum alloy, adhesion of aluminum is suppressed, so that the effect of providing the piston ring of the present invention is great. In addition, when the cast-in or alumite treatment conventionally applied to the piston ring groove is not required, the manufacturing cost of the piston can be reduced.

  Moreover, the piston of this invention is arrange | positioned so that a reciprocation is possible in a cylinder. Here, when the cylinder is made of an aluminum alloy, the same effect as described above can be obtained. That is, by adopting an aspect in which the outer peripheral surface of the piston ring body is coated with an amorphous hard carbon film as the piston ring of the present invention, aluminum adhesion is suppressed, and wear of the piston ring and cylinder is reduced. be able to. Also, the friction coefficient can be reduced.

  (3) The piston ring of the present invention is used in the presence of lubricating oil containing 0.5% by weight or more and 10% by weight or less of soot and covers the piston ring body and at least a part of the surface of the piston ring body. The amorphous hard carbon film has an Si content of 1 at% to 10 at%, an H content of 20 at% to 40 at%, a hardness of 7 GPa to 20 GPa, and an elastic property. The rate is 70 GPa or more and 160 GPa or less.

  The piston ring of the present invention includes an amorphous hard carbon film having an Si content of 1 at% or more and 10 at% or less and an H content of 20 at% or more and 40 at% or less. This amorphous hard carbon film has an amorphous structure, has a smooth surface, and has a lower surface energy than other metals and nitrides. For this reason, even if the amorphous hard carbon film and the counterpart material slide, the counterpart material hardly adheres. In addition, since the present amorphous hard carbon film contains the predetermined amount of Si, it has excellent wear resistance and exhibits a low coefficient of friction. Therefore, when the piston ring of the present invention and the counterpart material are slid, if the amorphous hard carbon film is used as a sliding surface, the adhesion of the counterpart material is suppressed, and the piston ring itself and the counterpart material wear. Is reduced.

  In addition, in the piston ring of the present invention, the hardness of the amorphous hard carbon film is 7 GPa or more and 20 GPa or less, and the elastic modulus is 70 GPa or more and 160 GPa or less. When the sliding of the piston ring is performed in the presence of lubricating oil containing foreign matter such as wrinkles and wear powder, these foreign matter acts as an abrasive material, increasing the wear of the piston ring itself and the counterpart material. The amorphous hard carbon film having the above-mentioned predetermined physical property values and low elastic properties is deformed under such conditions, and a part of the foreign matter is buried and held in the film. The resulting unevenness of the sliding surface is substantially reduced, and the abrasive action on the counterpart material is reduced. For example, a piston ring (left side in FIG. 23) in which an amorphous hard carbon film (DLC-Si film) having a low elastic characteristic is formed on the surface of a steel base material, and a piston in which a CrN film having a high elastic characteristic is formed. Each of the rings (on the right side of FIG. 23) is slid with a mating material made of Niresist cast iron under the same conditions. In the CrN film having high elastic properties, deformation due to foreign matter does not occur, and the abrasive wear of the counterpart material is promoted by the unevenness of the foreign matter. On the other hand, in the DLC-Si film having low elastic properties, the film itself is deformed to hold foreign matter, so that unevenness due to the foreign matter is reduced and wear of the counterpart material is suppressed.

  Therefore, for example, when the piston ring of the present invention is assembled to a piston, if the sliding surface with the piston ring groove is composed of this amorphous hard carbon film, the piston ring groove is subjected to cast or alumite treatment. Even with conventional pistons, wear is reduced.

  Further, since the present amorphous hard carbon film contains Si, silanol (SiOH) is generated on the surface of the amorphous hard carbon film during sliding. The generated silanol is considered to contribute to the reduction of boundary friction. In other words, the piston ring of the present invention exhibits a low coefficient of friction in addition to low opponent attack and wear resistance. For this reason, if the piston ring of this invention is employ | adopted, the energy loss by friction will reduce and it will lead to the improvement of a fuel consumption.

  (4) The piston of the present invention includes a piston main body in which a piston ring groove is provided, and the piston ring of the present invention disposed in the piston ring groove. For example, when the piston ring of the present invention adopts a mode in which a pair of facing surfaces facing the reciprocating direction of the piston of the piston ring main body are covered with an amorphous hard carbon film, the piston ring groove and the amorphous are used in actual operation. The hard carbon film is in sliding contact. In this case, the wear of the piston ring and the piston ring groove is small, and the friction coefficient is also small. That is, even in a conventional piston in which the piston ring groove (piston main body) is casted with cast iron wear-resistant ring or anodized, adhesion is suppressed and wear due to foreign matters is reduced.

  Moreover, the piston of this invention is arrange | positioned so that a reciprocation is possible in a cylinder. Here, even if the cylinder is a conventional cylinder that has been cast or anodized, the same effect as described above can be obtained. That is, as the piston ring of the present invention, by adopting an aspect in which the outer peripheral surface of the piston ring main body is covered with an amorphous hard carbon film, the inner surface of the cylinder that is in sliding contact with the outer peripheral surface is subjected to cast or alumite treatment. Even in the conventional cylinder, adhesion is suppressed and wear due to foreign matters is reduced. Also, the friction coefficient can be reduced.

  Hereinafter, the piston ring and the piston of the present invention will be described in detail.

<piston ring>
The piston ring of the present invention comprises a piston ring body and an amorphous hard carbon film that covers at least part of the surface of the piston ring body. The material of the piston ring body is preferably an iron-based material such as carbon steel, alloy steel, or cast iron.

  The amorphous hard carbon film contains carbon (C), hydrogen (H), and silicon (Si). Si content is 1 at% or more and 10 at% or less. When the Si content is less than 1 at%, the effect of improving wear resistance and the effect of reducing the friction coefficient are small. On the other hand, if the Si content exceeds 10 at%, the wear resistance is lowered and the elastic modulus is increased. It is preferable that the Si content is 8 at% or less, and further less than 5 at%.

  Further, the H content is 20 at% or more and 40 at% or less. When the H content is less than 20 at%, the hardness of the amorphous hard carbon film is increased, but the adhesion and toughness are reduced. A preferable H content is 25 at% or more. On the other hand, if the H content exceeds 40 at%, the hardness of the amorphous hard carbon film is reduced, and the wear resistance is lowered. It is preferable that the H content is 35 at% or less, and further 30 at% or less.

  The hardness of the amorphous hard carbon film is not particularly limited, but is preferably 7 GPa or more in consideration of wear resistance and the like. 10 GPa or more is more preferable. Moreover, it is good to set it as 20 GPa or less in consideration of the followability to a deformation | transformation of a piston ring main body, and the aggression property to an other party material.

  The elastic modulus of the amorphous hard carbon film is not particularly limited, but is preferably 70 GPa or more in consideration of sealing properties. 100 GPa or more is preferable. The elastic modulus of steel is about 200 GPa. Therefore, if the elastic modulus of the amorphous hard carbon film is 200 GPa or less, when the steel piston ring main body is elastically deformed, the amorphous hard carbon film coating is also easily deformed following the deformation. As a result, peeling of the amorphous hard carbon film is suppressed. In particular, the elastic modulus is preferably 160 GPa or less. In this specification, the value measured by a nanoindenter tester (MTS manufactured by Toyo Corporation) is adopted as the hardness and elastic modulus values of the amorphous hard carbon film.

  The surface roughness of the amorphous hard carbon film is desirably Rzjis 3 μm or less. When the surface roughness exceeds Rzjis 3 μm, the aggressiveness to the mating material increases, and the effect of reducing the friction coefficient decreases. The surface roughness is more preferably Rzjis 1 μm or less. In particular, the surface roughness of the outer peripheral surface that slides with the cylinder is preferably smaller than the other surfaces, and the fuel efficiency is improved. The amorphous hard carbon film covers at least a part of the surface of the piston ring body, and the same applies to the surface roughness of the part not covered with the amorphous hard carbon film. The method for calculating the surface roughness follows the method defined in JIS B 0601 (1994).

  Note that the lubricating oil used for sliding the piston ring of the present invention is preferably a lubricating oil containing almost no foreign matter. The foreign matter mixed in the engine oil varies depending on the use conditions, but examples include wear powder and soot containing metal and metal oxides. Among them, since soot is hard, the sliding characteristics, particularly the wear of the sliding member Greatly affects. For this reason, the content of soot as a component of the lubricating oil is preferably less than 0.5% by weight. If the soot content is less than 0.5% by weight, there is almost no influence of the abrasive wear caused by the presence of soot.

  On the other hand, the piston ring of the present invention used in the presence of lubricating oil containing 0.5% by weight or more and 10% by weight or less of soot is a piston ring body and a non-ring that covers at least a part of the surface of the piston ring body. The amorphous hard carbon film has an Si content of 1 at% to 10 at%, an H content of 20 at% to 40 at%, a hardness of 7 GPa to 20 GPa, and an elastic modulus of 70 GPa or more and 160 GPa or less.

  In general, lubricating oil can be regarded as equivalent to engine oil for gasoline engines if the soot content is less than 0.5% by weight. There is almost no. If the soot content is 0.5% by weight or more, and further 3.0% by weight or more, the sliding part is easily worn. The present invention can reduce wear even under such conditions. Further, it is known that the viscosity of the engine oil increases as the content of soot in the engine oil increases after the period of use. Engine oil containing soot in excess of a predetermined amount has a high viscosity and is difficult to use, so it is usually replaced with fresh oil. The present invention exhibits an excellent effect even when 10% by weight or less of an engine oil that can be used as an engine oil of a diesel engine is used as a lubricating oil.

  The amorphous hard carbon film contains carbon (C), hydrogen (H), and silicon (Si). Si content is 1 at% or more and 10 at% or less. When the Si content is less than 1 at%, the effect of improving wear resistance and the effect of reducing the friction coefficient are small. On the other hand, if the Si content exceeds 10 at%, the wear resistance is lowered and the elastic modulus is increased. It is preferable that the Si content is 8 at% or less, and further less than 5 at%.

  Further, the H content is 20 at% or more and 40 at% or less. When the H content is less than 20 at%, the hardness of the amorphous hard carbon film is increased, but the adhesion and toughness are reduced. A preferable H content is 25 at% or more. On the other hand, if the H content exceeds 40 at%, the hardness of the amorphous hard carbon film is reduced, and the wear resistance is lowered. It is preferable that the H content is 35 at% or less, and further 30 at% or less.

  The hardness of the amorphous hard carbon film is 7 GPa or more and 20 GPa or less. If it is 7 GPa or more, sufficient wear resistance can be obtained. 10 GPa or more is more preferable. Moreover, it is set to 20 GPa or less from the followability to a deformation | transformation of a piston ring main body, and the aggression property to a counterpart material. More preferably, it is 15 GPa or less.

  The elastic modulus of the amorphous hard carbon film is 70 GPa or more and 160 GPa or less. 70 GPa or more from the viewpoint of sealing properties. 100 GPa or more is preferable. The amorphous hard carbon film is preferably lower than the elastic modulus of the counterpart material, and the amorphous hard carbon film having an elastic modulus of 160 GPa or less is deformed so that a part of the ridge is buried in the film. Therefore, the abrasive action on the counterpart material is reduced.

  The elastic modulus of steel is about 200 GPa. Since the elastic modulus of the amorphous hard carbon film is 160 GPa or less, when the steel piston ring main body is elastically deformed, the amorphous hard carbon film coating is easily deformed following the deformation. As a result, peeling of the amorphous hard carbon film is suppressed. In particular, the elastic modulus is preferably 130 GPa or less. In this specification, the value measured by a nanoindenter tester (MTS manufactured by Toyo Corporation) is adopted as the hardness and elastic modulus values of the amorphous hard carbon film.

  The surface roughness of the amorphous hard carbon film is desirably Rzjis 3 μm or less. When the surface roughness exceeds Rzjis 3 μm, the aggressiveness to the mating material increases, and the effect of reducing the friction coefficient decreases. The surface roughness is more preferably Rzjis 1 μm or less. In particular, the surface roughness of the outer peripheral surface that slides with the cylinder is preferably smaller than the other surfaces, and the fuel efficiency is improved. The amorphous hard carbon film covers at least a part of the surface of the piston ring body, and the same applies to the surface roughness of the part not covered with the amorphous hard carbon film. The method for calculating the surface roughness follows the method defined in JIS B 0601 (1994).

  The amorphous hard carbon film can be formed by a known CVD method or PVD method such as a plasma CVD method, an ion plating method, or a sputtering method. However, as represented by the sputtering method, the PVD method is a directional film forming method. Therefore, in order to form a film uniformly by the PVD method, it is necessary to arrange a plurality of targets in the apparatus and to rotate the base material (piston ring body) on which the film is formed. As a result, the structure of the film forming apparatus becomes complicated and expensive. Further, in the PVD method, film formation on the inner peripheral surface of the piston ring body is not easy.

  On the other hand, since the plasma CVD method forms a film with a reactive gas, it can be easily formed even in a complicated shape. Further, the structure of the film forming apparatus is simple and inexpensive. Examples of the plasma CVD method include a high frequency plasma CVD method using high frequency discharge and a direct current plasma CVD method using direct current discharge. In particular, the direct-current plasma CVD method is preferable because it can be performed by a film forming apparatus having a simple configuration including a vacuum furnace and a direct-current power source and is the cheapest among the plasma CVD methods. Further, the direct-current plasma CVD method can be formed on the surface including the inner peripheral surface of the piston ring body at the same time, and thus is particularly suitable for forming a film on the piston ring.

For example, when an amorphous hard carbon film is formed by a direct current plasma CVD method, first, a piston ring body is arranged in a vacuum vessel, and a reaction gas and a carrier gas are introduced. Then, plasma ions in the reaction gas may be attached to the substrate by discharge. The reaction gas includes hydrocarbon gas such as methane (CH ₄ ) and acetylene (C ₂ H ₂ ), and silicon compound gas such as Si (CH ₃ ) ₄ [TMS], SiH ₄ , SiCl ₄ , and SiH ₂ F _4. And hydrogen gas, argon gas, or the like may be used as the carrier gas.

  The piston ring is used in a sliding environment with a high sliding surface pressure. For this reason, considering the durability, the amorphous hard carbon film should be thick. For example, the film thickness may be 2 μm or more, preferably 5 μm or more. Further, it is more preferable that the thickness is 10 μm or more. In addition, when the hardness of the amorphous hard carbon film is small and the elastic modulus is low, even if the film is formed thicker than 10 μm, the amorphous hard carbon film is hardly peeled or damaged, and the surface is smooth. . In particular, when used in the presence of a lubricating oil containing 0.5% by weight or more and 10% by weight or less of soot, the thickness may be 3 μm or more, preferably 5 μm or more.

  Further, in order to suppress the peeling of the amorphous hard carbon film from the piston ring body, it is desirable that the adhesion between the piston ring body and the amorphous hard carbon film be 10 N or more. More preferably, it is 20N or more. In particular, when used in the presence of lubricating oil containing 0.5% by weight or more and 10% by weight or less of soot, it may be 15N or more, preferably 25N or more. For the adhesion between the piston ring body and the amorphous hard carbon film, a film peeling load by a normal scratch test is employed. That is, a load is applied to a diamond cone having an apex angle of 120 degrees and a tip radius of 0.2 mm to scratch the film, and the load when the film is peeled is defined as adhesion.

  From the viewpoint of improving the adhesion between the piston ring main body and the amorphous hard carbon film, the surface of the piston ring main body on which the amorphous hard carbon film is formed is previously subjected to an unevenness forming process by an ion bombardment method. It is desirable that

  Specifically, first, the piston ring body is installed in the container, and the gas in the container is exhausted to a predetermined gas pressure. Next, a noble gas for forming irregularities is introduced into the container. Next, ion bombardment is performed by glow discharge or an ion beam to form unevenness of several tens of nm on the surface of the piston ring body. Further, in order to form uniform and fine irregularities on the surface of the piston ring body, it is preferable to perform a nitriding treatment before the irregularity forming process. Examples of the nitriding method include a gas nitriding method, a salt bath nitriding method, and an ion nitriding method.

  The piston ring of the present invention can adopt various shapes in order to obtain desired characteristics. Here, the amorphous hard carbon film may be appropriately formed on the surface of the piston ring body in consideration of the shape of the piston ring body, the material of the counterpart material, and the like. For example, when the surface of the piston ring main body has an outer peripheral surface, an inner peripheral surface, and a pair of opposing surfaces that oppose the reciprocating direction of the piston, the following modes are exemplified. In the aspect in which the amorphous hard carbon film is formed on the outer peripheral surface disposed on the cylinder side during actual operation, the friction coefficient with the cylinder is reduced, and the wear of the cylinder is suppressed. Further, in the aspect in which the amorphous hard carbon film is formed on the inner peripheral surface or the pair of opposing surfaces opposed to the outer peripheral surface in the diameter reducing direction, the friction coefficient with the piston ring groove is lowered, and the mating of the counterpart material is reduced. And the wear of the piston ring groove is suppressed.

  In addition to the outer peripheral surface, the inner peripheral surface, and the pair of opposing surfaces facing the reciprocating direction of the piston, the surface of the piston ring body is further between at least one of the inner peripheral surface and the pair of opposing surfaces. In addition, it is possible to adopt a mode having an inner peripheral side corner portion having a chamfered portion. In this aspect, since the edge portion between the inner peripheral surface and the opposing surface is chamfered, the aggressiveness to the piston ring groove is reduced. In addition, by covering the inner peripheral corner portion including the chamfered portion with an amorphous hard carbon film, the piston ring is twisted and deformed, and even if the inner peripheral corner portion slidably contacts the piston ring groove locally, It is possible to suppress material adhesion and wear of the piston ring and the piston ring groove. Furthermore, in order to improve the wear resistance of the piston ring and the piston ring groove and reduce the friction coefficient, an amorphous hard carbon film is formed on the pair of opposed surfaces of the piston ring body in addition to the inner peripheral corner portion. It is desirable to coat with.

  In order to reduce the weight of the piston ring and reduce the friction with the mating member, it is desirable that the piston ring width is thin. Conventionally, when the piston ring width is reduced, the piston ring is easily twisted and deformed, and wear of the piston ring groove due to local contact has occurred. However, according to the piston ring of the present invention in which at least the inner peripheral corner portion is covered with the amorphous hard carbon film, the wear of the piston ring groove hardly progresses even if the piston ring width is reduced. For example, in the piston ring of the present invention, it is desirable that the width between the pair of opposed surfaces of the piston ring body is 0.6 mm or more and 1.5 mm or less. In particular, in the case of 1.2 mm or less, the effect of reducing weight and reducing friction is large. In particular, when used in the presence of lubricating oil containing 0.5% by weight or more and 10% by weight or less of soot, it is desirable that the thickness be 0.6 mm or more and 3.5 mm or less, and further 0.6 mm It may be 1.7 mm or less, 0.8 mm or more and 1.7 mm or less, or 0.8 mm or more and 1.3 mm or less.

  Hereinafter, embodiments of the piston ring of the present invention having an inner peripheral corner portion will be described. FIG. 1 shows a partial cross-sectional view of the piston ring of the first embodiment of the present invention. As shown in FIG. 1, the piston ring 5 includes a piston ring body 50 and an amorphous hard carbon film 51.

  The piston ring body 50 has an outer peripheral surface 52, an inner peripheral surface 53, an upper surface 54, and a lower surface 55. The upper surface 54 and the lower surface 55 correspond to a pair of opposed surfaces that face each other in the reciprocating direction of the piston. A first chamfered portion 56 is disposed between the inner peripheral surface 53 and the upper surface 54. A second chamfer 57 is disposed between the inner peripheral surface 53 and the lower surface 55. Both the first chamfered portion 56 and the second chamfered portion 57 are curved. In this embodiment, the surface of the piston ring main body 50 has two inner peripheral side corners. The inner peripheral corner portion includes a first chamfered portion 56 and a second chamfered portion 57, respectively.

  A third chamfered portion 58 is disposed between the outer peripheral surface 52 and the upper surface 54. A fourth chamfered portion 59 is disposed between the outer peripheral surface 52 and the lower surface 55. The third chamfered portion 58 and the fourth chamfered portion 59 have the same curved shape as the first chamfered portion 56 and the second chamfered portion 57.

  The amorphous hard carbon film 51 covers the entire surface of the piston ring body 50 including the first chamfered portion 56 and the second chamfered portion 57.

  In the present embodiment, a curved first chamfered portion 56 and a second chamfered portion 57 are provided between the inner peripheral surface 53 and the upper surface 54 and the lower surface 55, respectively. The double-sided chamfers 56 and 57 are covered with the amorphous hard carbon film 51. For this reason, the piston ring 5 is twisted and deformed during actual operation, and adhesion does not occur even if the first chamfered portion 56 and the second chamfered portion 57 are in sliding contact with the piston ring groove locally. It is suppressed. Further, since the entire surface of the piston ring body 50 is covered with the amorphous hard carbon film 51, wear of the cylinder and the piston ring groove is suppressed, and the friction coefficient is small.

  FIG. 2 shows a partial cross-sectional view of the piston ring according to the second embodiment of the present invention. Members corresponding to those in FIG. 1 are denoted by the same reference numerals. The difference between the second embodiment and the first embodiment is that the shape of each chamfered portion is changed from a curved surface shape to a planar shape. Since the other configuration is the same as that of the first embodiment, only the differences will be described here.

  As shown in FIG. 2, a first chamfered portion 60 is disposed between the inner peripheral surface 53 and the upper surface 54. A second chamfer 61 is disposed between the inner peripheral surface 53 and the lower surface 55. Both the first chamfered portion 60 and the second chamfered portion 61 are planar. In this embodiment, the surface of the piston ring main body 50 has two inner peripheral side corners. The inner peripheral corner portion includes a first chamfered portion 60 and a second chamfered portion 61, respectively.

  A third chamfered portion 62 is disposed between the outer peripheral surface 52 and the upper surface 54. A fourth chamfered portion 63 is disposed between the outer peripheral surface 52 and the lower surface 55. The third chamfered portion 62 and the fourth chamfered portion 63 have the same planar shape as the first chamfered portion 60 and the second chamfered portion 61.

  In the present embodiment, the first chamfered portion 60 and the second chamfered portion 61 both have a planar shape and are covered with the amorphous hard carbon film 51. For this reason, the effect similar to said 1st embodiment is acquired.

  FIG. 3 shows a partial cross-sectional view of the piston ring of the third embodiment of the present invention. Members corresponding to those in FIG. 1 are denoted by the same reference numerals. The main difference between the third embodiment and the first embodiment is that the piston ring body has an internal bevel shape.

  As shown in FIG. 3, the piston ring 5 includes a piston ring body 50 and an amorphous hard carbon film 51. The piston ring body 50 has an outer peripheral surface 52, an inner peripheral surface 53, an upper surface 54, and a lower surface 55. The upper part of the inner peripheral surface 53 has a tapered shape with a diameter decreasing downward. A first chamfered portion 64 is disposed between the inner peripheral surface 53 and the lower surface 55. The first chamfered portion 64 has a curved surface shape. In the present embodiment, the surface of the piston ring body 50 has one inner peripheral corner portion. The inner peripheral corner portion includes a first chamfered portion 64.

  A third chamfered portion 65 is disposed between the outer peripheral surface 52 and the upper surface 54. A fourth chamfered portion 66 is disposed between the outer peripheral surface 52 and the lower surface 55. The third chamfered portion 65 and the fourth chamfered portion 66 have a planar shape.

  The amorphous hard carbon film 51 covers the entire surface of the piston ring body 50 including the first chamfered portion 64.

  In the present embodiment, a curved first chamfered portion 64 is provided between the inner peripheral surface 53 and the lower surface 55. The first chamfered portion 64 is covered with the amorphous hard carbon film 51. For this reason, the aggressiveness to the piston ring groove of the first chamfered portion 64 is low. Therefore, even if the piston ring body has an internal bevel shape, adhesion of the mating member and wear of the piston ring 5 and the piston ring groove due to the first chamfered portion 64 slidingly contacting the piston ring groove are suppressed. Moreover, according to this embodiment, effects peculiar to the internal bevel shape such as improvement in sealing performance can be obtained.

  As mentioned above, although embodiment of the piston ring of this invention which has an inner peripheral side corner part was described, the same piston ring is not limited to the said embodiment. For example, in the above embodiment, the entire surface of the piston ring body is covered with the amorphous hard carbon film. However, the amorphous hard carbon film only needs to cover at least one of the inner peripheral corners, and the other surfaces may be appropriately coated as necessary. Also, the piston ring main body can adopt various shapes.

  In the said embodiment, the chamfering part was arrange | positioned also between the outer peripheral surface and a pair of opposing surface, respectively. However, these chamfered portions may be only one or may not be present. In the said embodiment, the chamfered part of the inner peripheral side corner part was made into planar shape or curved surface shape. For example, in the case of a curved surface, it is preferable to use an R shape with a constant curvature radius. In addition, the suitable dimension of a chamfer part is mentioned later.

  In the said embodiment, the inner peripheral side corner part was comprised only from the chamfering part. However, it is desirable that the inner peripheral side corner portion includes a chamfered portion and a boundary portion extending from the chamfered portion to the opposing surface, and the boundary portion has a curved surface shape. When a curved boundary portion is provided between the chamfered portion and the opposed surface, the edge portion is eliminated, and therefore, the peeling or chipping of the amorphous hard carbon film formed at the inner peripheral corner portion can be suppressed.

  Below, the suitable aspect of an inner peripheral side corner part is mentioned. In FIG. 4, the partial cross-section enlarged view of the piston ring of 4th embodiment of this invention is shown. As shown in FIG. 4, the inner peripheral corner portion is disposed between the inner peripheral surface 71 and the lower surface 72 of the piston ring main body 70. The lower surface 72 corresponds to one of a pair of opposed surfaces. The inner peripheral corner portion includes a chamfered portion 73 and a boundary portion 74. The chamfered portion 73 has a planar shape following the inner peripheral surface 71. The boundary portion 74 connects the chamfered portion 73 and the lower surface 72 and exhibits a curved surface shape.

  FIG. 5 shows an enlarged partial cross-sectional view of the piston ring of the fifth embodiment of the present invention. Components corresponding to those in FIG. 4 are denoted by the same reference numerals. As shown in FIG. 5, the inner peripheral corner portion includes a chamfered portion 75 and a boundary portion 76. The chamfered portion 75 has a curved surface shape following the inner peripheral surface 71. The boundary portion 76 connects the chamfered portion 75 and the lower surface 72 and has a curved surface shape.

  Here, it is desirable that the boundary portion has an R shape with a constant curvature radius. In this case, it is preferable that the radius of curvature is R10 to 1000 mm. When R is less than 10 mm, R processing is difficult, and the effect of suppressing the peeling or chipping of the amorphous hard carbon film is not sufficient. On the other hand, if it exceeds R1000 mm, the sealing performance is lowered, and the piston ring performance such as oil consumption becomes a problem. In addition, even if it is a case where it is a case where it is used in presence of the lubricating oil containing 0.5 weight% or more and 10 weight% or less of soot, what is necessary is just to be R10-1000mm. Moreover, it is preferable that the drop of the boundary portion, that is, the height h from the continuous facing surface is 0.0005 mm or more and 0.015 mm or less. If the drop at the boundary is less than 0.0005 mm, the effect of providing the boundary is not exhibited, and peeling or chipping of the amorphous hard carbon film cannot be sufficiently suppressed. On the other hand, if it exceeds 0.015 mm, the area of the gas passage is increased, which may cause a problem. Even when used in the presence of lubricating oil containing 0.5% by weight or more and 10% by weight or less of soot, the height h may be 0.0005 mm or more and 0.015 mm or less.

  Dimensions of chamfered portion, that is, chamfered length a in the piston ring radial direction and chamfered length b in the piston reciprocating direction with respect to a virtual outer edge (indicated by a one-dot chain line in FIGS. 4 and 5) when no chamfered portion is provided. Is preferably, for example, 0.05 mm or more and 0.5 mm or less. If it is less than 0.05 mm, chamfering is difficult, and the effect of suppressing the peeling or chipping of the amorphous hard carbon film is not sufficient. On the other hand, if it exceeds 0.5 mm, the sealing performance is lowered, and the performance of the piston ring such as oil consumption becomes a problem. In addition, even if it is a case where it is a case where it uses in presence of the lubricating oil containing 0.5 weight% or more and 10 weight% or less of soot, what is necessary is just 0.05 mm or more and 0.5 mm or less.

<piston>
The piston of the present invention includes a piston main body in which a piston ring groove is provided and the piston ring of the present invention disposed in the piston ring groove. The material of the piston body is preferably an aluminum alloy (AC8A or the like), cast iron or the like. When used in the presence of lubricating oil containing 0.5% by weight or more and 10% by weight or less of soot, at least the groove surface of the piston ring groove that is in sliding contact with the opposed surface of the piston ring and the peripheral portion thereof, It is preferable that the wear-resistant ring-resist cast iron used for the piston body as a material having high wear resistance, or an aluminum alloy in which the groove surface is anodized. The surface of the anodized surface is Hv300-400 in terms of Vickers hardness, the hardness of Niresist cast iron is HRB75-92 in terms of Rockwell hardness, and wear resistance makes ring ring wear due to wrinkles reduced. The

  Below, one embodiment of the piston of the present invention is shown. In FIG. 6, the permeation | transmission perspective view of the cylinder by which the piston of this embodiment is arrange | positioned is shown. FIG. 7 shows a perspective view of the top ring assembled to the piston.

  As shown in FIG. 6, the piston 2 is disposed in the cylinder 1 so as to be able to reciprocate in the vertical direction. The cylinder 1 is made of cast iron. The piston 2 is made of an aluminum alloy. Three piston ring grooves 21 are provided around the piston body 20 constituting the piston 2. None of the piston ring grooves 21 are subjected to surface treatment such as cast-in or alumite treatment. That is, the piston body 20 and the piston ring groove 21 are the same material. A top ring 30, a second ring 31, and an oil ring 32 are assembled in the piston ring groove 21 in order from the top. The top ring 30, the second ring 31, and the oil ring 32 are each included in the piston ring of the present invention.

  As shown in FIG. 7, the top ring body 300 constituting the top ring 30 has an outer peripheral surface 301, an inner peripheral surface 304, an upper surface 302, and a lower surface 303. The top ring body 300 is made of Cr steel and corresponds to the piston ring body in the present invention. Further, the upper surface 302 and the lower surface 303 correspond to a pair of opposing surfaces that oppose the reciprocating direction of the piston 2. The outer peripheral surface 301, the inner peripheral surface 304, the upper surface 302, and the lower surface 303 are amorphous hard carbon films (not shown) having an Si content of 1 at% to 10 at% and an H content of 20 at% to 40 at%. Covered with. Similarly to the top ring 30, each surface of the second ring 31 and the oil ring 32 is covered with the same amorphous hard carbon film (not shown).

  The piston 2 reciprocates up and down in the cylinder 1 in the presence of lubricating oil. At this time, the amorphous hard carbon film covering the outer peripheral surfaces of the piston rings 30, 31, and 32 and the inner peripheral surface 11 of the cylinder body 10 constituting the cylinder 1 are in sliding contact with each other. Further, the amorphous hard carbon film covering the upper and lower surfaces of the piston rings 30, 31, 32 and the piston ring groove 21 are in sliding contact with each other. Thus, in the piston rings 30, 31, 32, the sliding surface with the cylinder 1 and the sliding surface with the piston ring groove 21 are covered with the amorphous hard carbon film. Therefore, there is little adhesion of the counterpart material due to sliding contact with the piston ring groove 21, and wear of the piston ring groove 21 is suppressed. In addition, since the amorphous hard carbon film is not easily worn, the piston rings 30, 31, and 32 are excellent in wear resistance. Further, the friction coefficient between the piston rings 30, 31, 32 and the cylinder 1 and the piston ring groove 21 is small.

  When used in the presence of a lubricating oil containing 0.5% by weight or more and 10% by weight or less of soot, the piston has at least an inner surface that is in sliding contact with the outer peripheral surface of the piston ring and a peripheral portion thereof with a high-strength aluminum alloy or It is good to arrange | position at the cylinder which consists of cast iron so that a reciprocation is possible. Examples of the high-strength aluminum alloy include a powder extruded material made of a hypereutectic aluminum-silicon alloy. Moreover, as a cast iron, Niresist cast iron is mentioned. Further, it may be a cylinder made of cast iron or aluminum alloy and having a sprayed coating made of metal and / or ceramics on the inner surface. As a metal-based spray coating, a thermal spray coating containing iron or aluminum as a main component, and as a ceramic-based spray coating, an oxide such as alumina or chromia, a carbide such as silicon carbide, or a nitride such as silicon nitride is used as a main component. A thermal spray coating is mentioned. Moreover, a cermet may be sufficient. The thermal spray coating may be formed on at least the inner surface that is in sliding contact with the outer peripheral surface of the piston ring.

  As mentioned above, although embodiment of the piston of this invention was described, the piston of this invention is not limited to the said embodiment. For example, in the above embodiment, the top ring, the second ring, and the oil ring are all configured by the piston ring of the present invention. However, any of these may be replaced with a conventional piston ring. Moreover, about the aspect of the amorphous hard carbon film | membrane in a piston ring, a coating location, the shape of a piston ring, etc., the suitable aspect of the piston ring of this invention mentioned above can be employ | adopted suitably.

  Next, the present invention will be described more specifically with reference to examples.

<Amorphous hard carbon film>
(1) Formation of Si-containing amorphous hard carbon film (hereinafter referred to as “DLC-Si film” as appropriate) Using the DC plasma CVD film forming apparatus shown in FIG. A Si film was formed. As shown in FIG. 8, the direct-current plasma CVD film forming apparatus 4 includes a stainless steel container 40, a base 41, a gas introduction pipe 42, and a gas outlet pipe 43. The gas introduction pipe 42 is connected to various gas cylinders (not shown) through valves (not shown). The gas outlet pipe 43 is connected to a rotary pump (not shown) and a diffusion pump (not shown) via a valve (not shown).

  First, the base material 45 was arranged on the base 41 installed in the container 40. The base material 45 is made of 13Cr steel (Hv380), and the surface thereof is nitrided. Next, the container 40 was sealed, and the gas in the container 40 was exhausted by a rotary pump and a diffusion pump connected to the gas outlet pipe 43. Hydrogen gas was introduced into the container 40 through the gas introduction pipe 42 at 15 sccm, and the gas pressure was set to about 133 Pa. Thereafter, a DC voltage of 200 V was applied between the stainless steel anode plate 44 and the base 41 provided inside the container 40 to start discharging. And it heated up by the ion bombardment using hydrogen gas until the temperature of the base material 45 became 500 degreeC.

  Next, 30 sccm of hydrogen gas and argon gas are introduced from the gas introduction pipe 42 at a time, and sputtering is performed at a pressure of about 533 Pa, a voltage of 300 V (current of 1.6 A), and a temperature of 500 ° C., and fine irregularities are formed on the surface of the substrate 45. Formed (unevenness forming treatment). The width of the convex portion was 60 nm and the height was 30 nm. Next, TMS and methane gas are introduced from the gas introduction pipe 42 as reaction gases, and hydrogen gas and argon gas are introduced as carrier gases, and the pressure is about 533 Pa, voltage 320 V (current 1.8 A), and temperature 500 ° C. Filmed. The film formation time was controlled to set the film thickness to 2.7 μm.

  Separately, a DLC-Si film was formed on the surface of the 13Cr steel substrate by the cathode arc method. Further, a CrN film is formed by arc ion plating, a W-containing amorphous hard carbon film (hereinafter referred to as “DLC-W film”) and a H-containing amorphous hard carbon film (hereinafter “DLC”) are formed by magnetron sputtering. -H film "), respectively.

  Table 1 shows the deposition method, composition, hardness, elastic modulus, and adhesion of each formed film. In Table 1, the hardness and elastic modulus of the base material without nitriding treatment (indicated as “13Cr steel” in the table, the same applies hereinafter), and the hardness and elasticity of the base material (nitriding treatment on the surface). The rate is also shown. In Table 1, # 1 and # 2 DLC-Si films are included in the amorphous hard carbon film constituting the present invention.

  The Si content in the DLC-Si film was quantified by electron probe microanalysis (EPMA), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and Rutherford backscattering method (RBS). Moreover, H content in a film | membrane was quantified by the elastic recoil particle detection method (ERDA). ERDA is a method of measuring the hydrogen concentration in the film by irradiating the surface of the film with a 2 MeV helium ion beam, detecting hydrogen ejected from the film with a semiconductor detector.

(2) Friction and wear test A friction and wear test was performed using a reciprocating friction tester (made by Teikoku Piston Ring Co., Ltd.) to evaluate the friction and wear characteristics of the films # 1, # 6 and # 8 shown in Table 1. did. FIG. 9 shows the configuration of a reciprocating friction tester. As shown in FIG. 9, the reciprocating friction tester 8 is composed of a pin-type test piece 80 and a plate material 81 as a counterpart material. The pin-type test piece 80 is made of 13Cr steel and has a cylindrical shape with a diameter of 8 mm. One end of the pin-type test piece 80 has a spherical portion 800 having a mirror-finished surface. The plate material 81 is made of an aluminum alloy (AC8A). The size of the plate material 81 is 17 mm × 7 mm × 70 mm, and the surface roughness is Rzjis 1.0 μm. The pin-type test piece 80 is installed in a state where the top of the spherical surface portion 800 is in contact with the plate material 81.

  The frictional wear test was performed by reciprocating the plate material 81 in the left-right direction in FIG. 9 with the pin-type test piece 80 pressed against the plate material 81 with a load of 29.4 N. The reciprocating distance was 50 mm, and the reciprocating cycle was 300 cpm (cycles per minute). 10 W-30 engine oil as a lubricating oil was supplied at 1.0 ml / h from the oil supply pipe 82 to the sliding portion between the pin-type test piece 80 and the plate material 81. Thus, after sliding the pin type test piece 80 and the plate material 81 for 1 minute, the friction coefficient was measured. Moreover, after sliding for 30 minutes, each wear depth of the pin-type test piece 80 and the plate material 81 was measured.

  The frictional wear test was performed without any surface treatment on the spherical surface portion 800 of the pin-type test piece 80 (# 10), and the spherical surface portion 800 was subjected to the above # 1 (DLC-Si film) and # 6 (DLC-). W film) and # 8 (CrN film) were respectively coated, and the nitriding treatment of # 9 was performed. 10 and 11 show the results of each friction and wear test. In addition, each wear amount ratio shown in FIG. 10 was calculated on the basis of the nitriding treatment.

  As shown in FIG. 10, when the surface treatment was not performed (13Cr steel), the wear amount of the pin-type test piece was very large. However, it can be seen that the wear of the pin-type test piece can be suppressed by applying some surface treatment. On the other hand, from the viewpoint of aggressiveness against the counterpart material, when the amount of wear of the plate material was compared in the case where the surface treatment was performed, the amount decreased in the order of CrN film> nitriding treatment> DLC-W film> DLC-Si film. From this, it can be seen that the amorphous hard carbon film constituting the present invention has the least aggressiveness to the counterpart material.

  As shown in FIG. 11, the friction coefficient decreased in the order of 13Cr steel> nitriding treatment> CrN film> DLC-W film> DLC-Si film. From this, it can be seen that according to the amorphous hard carbon film constituting the present invention, the friction coefficient can be reduced. From the above, it was confirmed that the amorphous hard carbon film constituting the present invention is excellent in wear resistance, exhibits low opponent attack and low friction coefficient.

(3) Seizure test A seizure test was performed using the reciprocating friction tester shown in FIG. 9, and the seizure resistance of each of the films # 1, # 6, and # 8 shown in Table 1 was evaluated. The seizure test was performed by reciprocating the plate material 81 in the left-right direction in FIG. 9 in a state where the pin-type test piece 80 was pressed against the plate material 81 with a load of 19.6 N. The reciprocating distance was 50 mm, and the reciprocating cycle was 200 cpm (cycles per minute). In addition, about the spherical surface part 800 of the pin type test piece 80, and the surface of the plate material 81 slidably contacting therewith, 10W-30 engine oil was applied in advance and then wiped off. Thus, the pin type test piece 80 and the plate material 81 were slid to measure the friction coefficient, and the time when the friction coefficient rapidly increased was defined as the baking time. Similar to the friction and wear test, the seizure test was performed without performing any surface treatment on the spherical surface portion 800 of the pin-type test piece 80, and the above-mentioned # 1 (DLC-Si film) and # 6 (DLC) were applied to the spherical surface portion 800. -W film) and # 8 (CrN film) were coated, and the nitriding treatment of # 9 was performed. FIG. 12 shows the baking time ratio in each baking test. The baking time ratio was calculated based on the nitriding treatment.

  As shown in FIG. 12, even when the nitriding treatment was performed or the CrN film was formed, the baking time was shorter than when the surface treatment was not performed (13Cr steel). That is, it can be seen that these surface treatments are inferior in aluminum adhesion resistance. On the other hand, no seizure occurred when the DLC-Si film was coated. This means that aluminum adhesion was suppressed. From this, it was confirmed that the amorphous hard carbon film constituting the present invention is excellent in aluminum adhesion resistance.

(4) Comprehensive evaluation The sliding characteristics in each surface treatment were evaluated based on both the results of the frictional wear test and the seizure test described above. Table 2 summarizes the evaluation results.

  As shown in Table 2, the DLC-Si film, that is, the amorphous hard carbon film constituting the present invention is excellent in wear resistance and seizure resistance, and exhibits a low friction coefficient. Aggressiveness against is very low. Therefore, according to the piston ring of the present invention provided with such an amorphous hard carbon film, adhesion of aluminum can be suppressed and wear of the piston ring groove can be reduced.

  Next, assuming the use of engine oil containing soot as a lubricating oil, the friction and wear characteristics of each film and the like were evaluated. Hereinafter, examples will be described.

(5) Formation of Si-Containing Amorphous Hard Carbon Film Using the DC plasma CVD film forming apparatus shown in FIG. 8 described above, the surface of a base material made of 10Cr steel (Hv1000) subjected to nitriding treatment is A DLC-Si film was formed in the same procedure as in 1). Separately, a W-containing amorphous hard carbon film (DLC-W film) was formed on the surface of the same base material by a magnetron sputtering method, and a CrN film was formed by an arc ion plating method.

  Table 3 shows the deposition method, composition, hardness, elastic modulus, and adhesion of each formed film. In Table 3, the hardness and elastic modulus of the base material (nitriding treatment on the surface) are also shown as # 12. In Table 3, # 11 DLC-Si film is included in the amorphous hard carbon film constituting the present invention.

  The Si content in the DLC-Si film was quantified by electron probe microanalysis (EPMA), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and Rutherford backscattering method (RBS). Moreover, H content in a film | membrane was quantified by the elastic recoil particle detection method (ERDA) already demonstrated.

(6) Friction and wear test A friction and wear test was performed using a block-on-ring type friction tester (FFWEX LFW-1 type tester), and each of the films # 11 to # 14 shown in Table 3 was tested. The friction and wear characteristics were evaluated. FIG. 13 shows the configuration of a block-on-ring friction tester. As shown in FIG. 13, the block-on-ring friction tester 8 ′ is composed of a ring test piece 85 and a block test piece 86 as a counterpart material. The ring test piece 85 is made of nitrided 10Cr steel and has a ring shape with an outer diameter of 35 mm and a width of 7 mm. The block test piece 86 is made of Ni-resist cast iron. The size of the block test piece 86 is 6.3 mm × 15.7 mm × 10.1 mm, and the surface roughness is Rzjis 0.08 μm. The ring test piece 85 is installed with its outer peripheral surface 850 in contact with the surface 860 of the block test piece 86.

  The frictional wear test was performed by rotating the ring test piece 85 in the direction of the arrow in FIG. 13 while pressing the block test piece 86 against the ring test piece 85 with a load of 600 N (maximum Hertz surface pressure of 310 MPa). The rotation speed was 160 rpm (0.3 m / sec). About half of the ring specimen 85 is contained in engine oil (150 ° C.) filled in an oil tank 89. When the ring test piece 85 rotates, engine oil is supplied as a lubricating oil to the sliding portion with the block test piece 86. Thus, after the ring test piece 85 and the block test piece 86 were slid for 60 minutes, the weight change of the ring test piece 85 and the wear depth of the block test piece 86 were measured. The wear depth was measured with a non-contact type surface roughness measuring machine (NewView 5022 manufactured by Zygo). In addition, the coefficient of friction immediately before the end of the test was measured.

  In the friction test, each film of # 11 (DLC-Si film), # 13 (DLC-W film), and # 14 (CrN film) is coated on the outer peripheral surface 850 of the ring test piece 85 with a thickness of 3 μm or more. The nitriding treatment of # 12 was performed. The surface roughness of the outer peripheral surface 850 of each ring test piece 85 was Rzjis 1.6 μm. The engine oil used was a carbon-dispersed engine oil in which 6% by weight of carbon black was dispersed in a diesel engine oil having a viscosity grade OW-20 and containing Mo-DTC. With respect to the ring test pieces 85 subjected to the surface treatments of # 11 and # 12, tests were also conducted on engine oil in which carbon was not dispersed (simply described as “engine oil”). 14 to 20 show the results of each friction test. In addition, a test is implemented twice about each sample and FIGS. 14-16 shows the average value.

  The wear weight of each ring test piece is shown in FIG. As shown in FIG. 14, wear of the ring specimen in the engine oil could be greatly suppressed by forming a DLC-Si film or performing a general nitriding treatment as a piston ring. However, in carbon dispersed engine oil, the amount of wear increased regardless of whether a DLC-Si film was formed or a nitriding treatment was performed. In particular, when the nitriding treatment was performed, the amount of wear increased significantly.

  When the DLC-Si film was formed, the increase in the amount of wear due to the carbon mixing into the engine oil was less than that of the nitriding treatment. That is, it was found that the DLC-Si film has excellent wear resistance. On the other hand, the DLC-W film was greatly worn by a friction test using carbon dispersed engine oil. Although the DLC-Si film and the DLC-W film are the same amorphous carbon film, the DLC-Si film having a covalent bond with Si atoms is considered to have high wear resistance.

  From FIG. 14, it was determined that a DLC-Si film or a CrN film is effective for ensuring the wear resistance of the sliding member during sliding in engine oil mixed with foreign matters such as soot. . However, as shown in FIG. 15, it was found that when the CrN film was formed, the amount of wear of the block test piece (the counterpart material) was remarkably large. In other words, in engine oil mixed with foreign matter such as soot, the use of a DLC-Si film on the surface of the piston ring reduces the wear resistance of the piston ring itself and reduces the wear of the mating material such as the piston ring groove. It can be compatible.

  Moreover, as shown in FIG. 15, wear of the block test piece (counter member) in engine oil can be suppressed by forming a DLC-Si film or performing a general nitriding treatment as a piston ring. It was. Compared with the amount of wear in the engine oil, the increase in the amount of wear was small in the carbon-dispersed engine oil when the DLC-Si film was formed. However, when the nitriding treatment was performed, the amount of wear was remarkably increased and the opponent attack was high. This is because the elastic wear after nitriding is as high as 200 GPa, so that the abrasive wear of the counterpart material caused by the presence of carbon particles is not reduced. Also, the CrN film having an elastic modulus of 350 GPa has high opponent attack for the same reason. On the other hand, the DLC-Si film was able to reduce the wear of the counterpart material to half or less compared to other films and the like. Since the elastic modulus of the DLC-Si film is as low as 128 GPa, the carbon particles can be embedded and held in the film by deformation of the DLC-Si film, so that the abrasive action of the carbon particles is suppressed.

  Accordingly, it has been found that the elastic modulus of the formed film greatly affects the wear reduction of the counterpart material, and the formed film is required to have an elastic modulus of at least less than 200 GPa. Although the elastic modulus of the DLC-W film is as low as 130 GPa, as already described, since the film itself is severely worn, the surface roughness of the film itself increases and the opponent attacking property becomes high.

  FIG. 16 shows the friction coefficient in each friction test. The friction coefficient of the DLC-Si film was the lowest. 17 to 20 show the surface roughness of each test piece after the friction test. The arrow in the figure is the sliding direction. 17 to 20, the surfaces of both the DLC-Si film (FIG. 17A) and the block test piece (FIG. 17B) of the ring test piece were smoothed. This smoothing of the sliding surface is presumed to have promoted the formation of an oil film and contributed to friction reduction.

  Therefore, if the piston ring of the present invention having such an amorphous hard carbon film is used, even if it is in the presence of lubricating oil containing soot, the opponent attack is low and the wear resistance is excellent.

<Piston ring shape>
(1) Tapping friction test A tapping friction test was conducted to examine the difference in adhesion of the DLC-Si film depending on the shape of the piston ring. FIG. 21 shows the configuration of the tapping friction tester. An enlarged view of portion A in FIG. 21 is shown in FIG. As shown in FIG. 21, the tapping friction tester 9 includes a piston material 90, a ring holding member 91, and a spring 92.

  The piston material 90 is made of an aluminum alloy and has a cylindrical shape with a diameter of 86 mm and a thickness of 10 mm. A piston material heater 900 is disposed in the piston material 90 in the axial direction.

  The ring holding member 91 is disposed to face the piston member 90 and is supported by a spring 92. A ring holding member heater 910 is arranged at the bottom of the ring holding member 91 in the direction perpendicular to the axis. An annular ring groove 911 is formed on the upper surface of the ring holding member 91 facing the piston member 90. The bottom of the ring groove 911 is inclined downward in the diameter increasing direction. A piston ring 93 to be tested is disposed in the ring groove 911. The piston ring 93 is arranged in a state of slightly protruding from the upper surface of the ring holding member 91.

  As shown in FIG. 22, the piston ring 93 includes a piston ring body 930 and a DLC-Si film 931 that covers the entire surface of the piston ring body 930. The piston ring main body 930 has an internal bevel shape. The surface of the piston ring main body 930 has an inner peripheral corner portion 932. The piston ring 93 is disposed with the inner peripheral side corner portion 932 facing upward.

  The hit test was performed by reciprocating the piston member 90 in the vertical direction and rotating and reversing the ring holding member 91 by 180 ° in the axially horizontal plane. Thereby, the inner peripheral side corner portion 932 of the piston ring 93 is hit by the piston material 90. The conditions of the tapping test are two kinds of tapping loads of 29.4N and 58.8N, the tapping speed of the piston material 90 is 700 rpm, the rotating speed of the ring holding member 91 is 10 cpm, the test temperature is 200 ° C., the test time is 3 hours, and there is no lubrication. It was.

(2) Test results Table 4 shows the results of a hit test performed by changing the aspect of the inner peripheral corner and the composition of the DLC-Si film. In Table 4, the numerical value in the parenthesis of the boundary shape indicates the radius of curvature. Table 4 also shows the results when the DLC-H film was coated instead of the DLC-Si film (# 33) and when the film was not formed (# 34).

  As shown in Table 4, when a DLC-Si film having a Si content of less than 1 at% or more than 10 at% is coated, the film is formed regardless of the mode of the inner peripheral corner portion even if the load is low (29.4 N). Peeling occurred. For example, when # 22, # 28, # 29, and # 33 having the same aspect of the inner peripheral side corner portion are compared, the presence or absence of delamination, that is, the state of the film, depends on the type of film covering the inner peripheral side corner portion and Si content. It can be seen that the adhesion is different. In # 22 coated with a DLC-Si film having a Si content of 1 at%, no peeling of the film occurred even when the load was high (58.8 N).

  Note that in the # 30 piston ring, both the chamfered portion and the boundary portion were in an edge state, that is, the inner peripheral side corner portion in the present invention was not disposed, so that the film peeled even when the Si amount was 4 at%. . On the other hand, in the piston rings of # 21 to # 24, in which the DLC-Si film having a Si amount of 1 at% to 10 at% is coated and the boundary portion has an R shape with a curvature radius of 10 to 1000 mm, No peeling occurred. From this, it can be seen that the shape of the inner peripheral corner, particularly the boundary, is important in order to suppress the peeling of the film.

It is a partial sectional view of the piston ring of the first embodiment of the present invention. It is a partial sectional view of the piston ring of the second embodiment of the present invention. It is a partial cross section figure of the piston ring of 3rd embodiment of this invention. It is a partial cross section enlarged view of the piston ring of 4th embodiment of this invention. It is a partial cross section enlarged view of the piston ring of 5th embodiment of this invention. It is a permeation | transmission perspective view of the cylinder by which the piston is arrange | positioned. It is a perspective view of the top ring assembled | attached to the piston. It is the schematic of a direct-current plasma CVD film-forming apparatus. It is the schematic of a reciprocating friction tester. It is a graph which shows the abrasion loss ratio of the pin type test piece and plate material in a friction wear test. It is a graph which shows the measurement result of the friction coefficient in a friction abrasion test. It is a graph which shows the baking time ratio in a baking test. It is a schematic diagram of a block on ring type friction tester. It is a graph which shows the abrasion weight of the ring test piece in a block on ring type friction test. It is a graph which shows the wear depth of the block test piece in a block on ring type friction test. It is a graph which shows the measurement result of the friction coefficient in a block on ring type friction test. The surface roughness (FIG. 17A) of the DLC-Si film (# 11) of the ring test piece after the block-on-ring friction test (FIG. 17A) and the surface roughness of the block test piece (FIG. 17B) are shown. FIG. 18 shows the surface roughness (FIG. 18A) of the nitrided ring specimen (# 12) and the block specimen (FIG. 18B) after the block-on-ring friction test. The surface roughness (FIG. 19A) of the DLC-W film | membrane (# 13) of the ring test piece after a block on ring type friction test (FIG. 19A) and the surface roughness (FIG. 19B) of a block test piece are shown. The surface roughness (FIG. 20A) of the CrN film (# 14) of the ring test piece after the block-on-ring friction test (FIG. 20A) and the surface roughness of the block test piece (FIG. 20B) are shown. It is the schematic of a tapping friction tester. It is an enlarged view of the A section in FIG. It is explanatory drawing which shows the generation | occurrence | production mechanism of the abrasive wear by a foreign material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Cylinder 10: Cylinder main body 11: Inner peripheral surface 2: Piston 20: Piston main body 21: Piston ring groove 30: Top ring 31: Second ring 32: Oil ring 300: Top ring main body 301: Outer peripheral surface 302: Upper surface 303: Lower surface 304: Inner peripheral surface 4: DC plasma CVD film forming apparatus 40: Container 41: Base 42: Gas inlet tube 43: Gas outlet tube 44: Stainless steel anode plate 45: Base material 5: Piston ring 50: Piston ring body 51: Amorphous hard carbon film 52: Outer peripheral surface 53: Inner peripheral surface 54: Upper surface 55: Lower surface 56, 60, 64: First chamfered portion 57, 61: Second chamfered portion 58, 62, 65: Third chamfered Portions 59, 63, 66: Fourth chamfered portion 70: Piston ring main body 71: Inner peripheral surface 72: Lower surface 73, 75: Chamfered portions 74, 76: Boundary part 8: Reciprocating friction tester 80: Pin type test piece 800: Spherical part 81: Plate material 82: Oil supply pipe 8 ': Block-on-ring type friction tester 85: Ring test piece 850: Outer peripheral surface 86: Block specimen
860: Surface (sliding surface)
9: Tapping friction tester 90: Piston material 900: Piston material heater 91: Ring holding member 910: Ring holding member heater 911: Ring groove 92: Spring 93: Piston ring 930: Piston ring body 931: DLC-Si film 932: Inner peripheral corner

Claims (26)

A piston ring main body, and an amorphous hard carbon film covering at least a part of the surface of the piston ring main body,
The piston ring, wherein the amorphous hard carbon film has an Si content of 1 at% to 10 at% and an H content of 20 at% to 40 at%.   2. The piston ring according to claim 1, which is used in the presence of a lubricating oil containing less than 0.5% by weight of soot.   The piston ring according to claim 1 or 2, wherein the amorphous hard carbon film has a hardness of 7 GPa to 20 GPa and an elastic modulus of 70 GPa to 200 GPa.   The piston ring according to claim 1 or 2, wherein the surface roughness of the amorphous hard carbon film is Rzjis 3 µm or less.   The piston ring according to claim 1, wherein the amorphous hard carbon film is formed by a direct current plasma CVD method. The surface of the piston ring body has an outer peripheral surface, an inner peripheral surface, and a pair of opposing surfaces facing the reciprocating direction of the piston,
The surface further has an inner peripheral corner portion having a chamfered portion between the inner peripheral surface and at least one of the pair of opposing surfaces,
The piston ring according to claim 1 or 2, wherein the amorphous hard carbon film covers at least one of the inner peripheral corner portions.   The piston ring according to claim 6, wherein the amorphous hard carbon film further covers the pair of opposed surfaces.   The piston ring according to claim 6, wherein the chamfered portion has a planar shape or a curved surface shape. The inner peripheral side corner portion includes the chamfered portion and a boundary portion extending from the chamfered portion to the opposing surface,
The piston ring according to claim 6, wherein the boundary portion has a curved surface shape.   The piston ring according to claim 9, wherein a radius of curvature of the boundary portion is R10 to 1000 mm.   The piston ring according to claim 6, wherein the piston ring body has an internal bevel shape.   The piston ring according to claim 6, wherein a width between the pair of opposed surfaces is 0.6 mm or more and 1.5 mm or less. A piston body around which a piston ring groove is provided;
The piston ring according to claim 1 or 2 disposed in the piston ring groove;
Piston with   The piston according to claim 13, wherein the amorphous hard carbon film covers a sliding surface of the piston ring with the piston ring groove. A piston ring body used in the presence of a lubricant containing 0.5% by weight or more and 10% by weight or less of soot, and an amorphous hard carbon film covering at least a part of the surface of the piston ring body. Become
The amorphous hard carbon film has a Si content of 1 at% to 10 at%, an H content of 20 at% to 40 at%, a hardness of 7 GPa to 20 GPa, and an elastic modulus of 70 GPa to 160 GPa. Piston ring to do.   The piston ring according to claim 15, wherein the surface roughness of the amorphous hard carbon film is Rzjis 3 µm or less.   The piston ring according to claim 15, wherein the amorphous hard carbon film is formed by a direct current plasma CVD method. The surface of the piston ring body has an outer peripheral surface, an inner peripheral surface, and a pair of opposing surfaces facing the reciprocating direction of the piston,
The surface further has an inner peripheral corner portion having a chamfered portion between the inner peripheral surface and at least one of the pair of opposing surfaces,
The piston ring according to claim 15, wherein the amorphous hard carbon film covers at least one of the inner peripheral corner portions.   The piston ring according to claim 18, wherein the amorphous hard carbon film further covers the pair of opposed surfaces.   The piston ring according to claim 18, wherein the chamfered portion has a planar shape or a curved shape. The inner peripheral side corner portion includes the chamfered portion and a boundary portion extending from the chamfered portion to the opposing surface,
The piston ring according to claim 18, wherein the boundary portion has a curved surface shape.   The piston ring according to claim 21, wherein a radius of curvature of the boundary portion is R10 to 1000 mm.   The piston ring according to claim 18, wherein the piston ring body has an internal bevel shape.   The piston ring according to claim 18, wherein a width between the pair of opposed surfaces is 0.6 mm or more and 3.5 mm or less. A piston body around which a piston ring groove is provided;
The piston ring according to claim 15 disposed in the piston ring groove;
Piston with   The piston according to claim 25, wherein the amorphous hard carbon film covers a sliding surface of the piston ring with the piston ring groove.

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