JP2005273583A - Piston ring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow a piston ring to attain well balanced characteristics of high hardness, high wear resistance and a highly maintaining function of sealing performance irrespective of changes of operation condition and the like. <P>SOLUTION: A soft coating (91) is provided on a first portion lying on a combustion chamber side (the upper side in the figure) of a sliding surface (91) and a hard coating (912) harder than the soft coating is provided on a second portion of the sliding surface continuous with the first portion. In the figure, a soft coating (913) is further provided on a third portion lying on a crank case side (the lower side in the figure). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to the technical field of piston rings.

  This type of piston ring is provided in a piston, which is a component constituting an engine used in various vehicles, and includes a compression ring and an oil ring. The former further includes a top ring (or first pressure ring) and a second ring (or Second pressure ring). The top ring, second ring, and oil ring are arranged in this order from the combustion chamber side of the engine. These are responsible for releasing the heat of the piston to the cylinder, and the oil ring is mainly responsible for scraping off the lubricant on the cylinder wall to maintain the proper amount of oil consumption, and the compression ring is mainly used for the combustion chamber. It plays a role of maintaining the gas tightness of the combustion gas.

  The role of such a piston ring is extremely important for realizing smooth operation of the engine. However, in recent years, there has been a demand for the piston ring to fulfill its role sufficiently for reasons such as higher engine output, higher rotation, longer service life, etc., and compliance with exhaust gas regulations. Satisfaction is becoming more difficult.

  Therefore, various techniques have been proposed in the past, including techniques for increasing the hardness of the sliding surface or the outer peripheral surface and increasing the wear resistance in order to improve the quality of the piston ring. For example, Patent Document 1 proposes a piston ring having a lubricant film formed by injecting lubricant particles on its sliding surface, thereby preventing Al adhesion from a ring groove of an aluminum alloy piston. It is said that the effect that it can prevent effectively is acquired. Patent Document 2 also proposes a technique for preventing cracks and peeling of the surface treatment layer by devising the shape of the piston ring.

JP 2003-148242 A JP 2002-39384 A

  However, there are the following problems in improving the quality of conventional piston rings. In other words, in order to achieve high hardness or high wear resistance of the piston ring, simply forming a hard coating on the sliding surface deteriorates the so-called initial familiarity in the initial state of engine operation. In order to make the seal between the sliding surface and the inner circumference of the cylinder bore incomplete, seizure may occur due to local high surface pressure generation, or combustion gas leakage (so-called blow-by) or lubricating oil leakage may occur. The fear increases.

  In this respect, the above Patent Document 1 and Patent Document 2 do not always provide sufficient effects. That is, in Patent Document 1, it is considered that at least the lower surface of the piston ring, or the upper surface including the piston ring (see FIG. 1 (b) or (c) in Patent Document 1) corresponds to the soft coating referred to in this specification. “Lubricant coating” is formed, but according to such a configuration, the wear of the lubricant coating increases the clearance between the lower surface or the upper surface and the side surface of the ring groove (side clearance), There is a possibility that problems such as combustion gas leakage may occur due to this gap.

  Moreover, in patent document 2, while making the shape of a piston ring into what is called a barrel shape, a corner part is provided between the sliding surface, a lower surface, and an upper surface, and the curvature radius of this corner part is made into a sliding surface (following). In this paragraph, a configuration in which the term “barrel surface” in Patent Document 2 is used is made smaller than that of Patent Document 2. However, with this configuration alone, initial familiarity at the upper and lower ends of the piston ring is disclosed. It is difficult to cope with the fact that the amount of wear until completion is different depending on the type of engine or operating conditions. In other words, the upper end of the piston ring usually wears faster than the lower end of the piston ring.However, in this document, this problem is not dealt with explicitly, and there is a risk of malfunction. is there. In addition, this document discloses that a nitride film that is a hard film is formed without distinguishing between the barrel surface and the corner portion. However, in this case, the amount of wear (amount of wear) is larger than the barrel surface shape that is initially set. ) May delay the progress of familiarity. Furthermore, although the structure which makes the thickness of the hard film in a corner part 1/2 or less of the thickness of the hard film of a barrel surface is disclosed, only a thinner film exists in the corner part which is easy to wear. This has a disadvantage in terms of durability.

  The present invention has been made in view of the above problems, and for example, a piston capable of realizing, in a balanced manner, characteristics such as high hardness, high wear resistance, and high airtightness maintaining function regardless of changes in operating conditions and the like. The problem is to provide a ring.

  In order to solve the above-mentioned problem, the first piston ring of the present invention has a sliding surface, a first portion located on the combustion chamber side of the sliding surface is provided with a soft coating, and the sliding surface The second part connected to the first part is provided with a hard film harder than the soft film.

  In the first piston ring of the present invention, first, the “combustion chamber” means a chamber in which an explosion is caused in a cylinder in which a piston provided with the piston ring is arranged. There is a crankcase on the opposite side of the combustion chamber across the piston. The “sliding surface” refers to a surface of the piston ring that faces the wall surface of the cylinder and is in contact with the wall surface. As is widely known, the piston reciprocates inside the cylinder triggered by an explosion in the combustion chamber in the cylinder (that is, the piston ring slides against the cylinder wall surface). Is converted into rotational power by a crankshaft in the crankcase.

  Incidentally, in this case, since the reciprocating motion usually corresponds to “vertical motion”, in this sense, the concept of “upper” and “lower” means that the combustion chamber side is viewed from the piston or piston ring. Usually, the “upper side” and the crankcase correspond to “lower side”. Hereinafter, for convenience of explanation, the terms “upper” and “lower” may be used in such a relative relationship.

  Under such a premise, in the present invention, in particular, the first portion located on the combustion chamber side of the sliding surface is provided with a soft coating, and the second portion connected to the first portion is provided with a hard coating. ing. That is, typically, the sliding surface is divided into two parts, and it is assumed that a soft film is provided in a part near the combustion chamber, and a hard film is provided in the remaining part. With such a configuration, the following operation can be obtained.

  That is, the portion of the sliding surface of the piston ring located on the combustion chamber side is under extremely severe lubrication conditions such that it receives a high pressure at a higher temperature than the other portions. In this regard, among the piston rings, the top ring is exposed directly to the combustion gas and directly receives the combustion pressure, so that it is subjected to more severe lubrication conditions even under severe conditions. Therefore, it is conceivable that, among the sliding surfaces of the piston ring, the portion on the combustion chamber side wears faster, and the other portion wears more slowly.

  In this regard, in the present invention, as described above, the soft coating is provided on the combustion chamber side portion and the hard coating is provided on the other portion, so that the above situation can be coped with well. That is, since the soft coating progresses faster than the hard coating, the piston ring of the present invention can acquire a stable shape earlier.

  Further, in the present invention, since the second portion is provided with the hard coating, the second portion is less likely to wear. Therefore, the progress of wear at the initial stage of operation can be suppressed, and the occurrence of combustion gas leakage, lubricating oil leakage, and the like due to an increase in the clearance gap can be effectively prevented.

  Furthermore, as described above, the soft coating wears quickly and the hard coating remains, so that the piston ring can reach a stable shape at an early stage. Because it means that it can be realized at an early stage, it is possible to improve the scraping performance of the lubricating oil, lower the tension of the piston ring, reduce friction, etc., and also the catalyst by sulfur and phosphorus contained in the lubricating oil Poisoning is suppressed and emissions can be improved.

In the above description, it has been described that the top ring of the piston ring is subjected to particularly severe lubrication conditions. This means that a greater effect can be obtained by applying the present invention to the top ring. Therefore, the intention to exclude the application of the present invention to other second rings or oil rings is not expressed. In these rings, it is needless to say that corresponding effects can be obtained by applying the present invention.
In one aspect of the first piston ring of the present invention, the sliding surface is curved with a predetermined curvature, and the curvature in the second portion is smaller than the curvature in the first portion.

According to this aspect, since the sliding surface is curved, the shape of the sliding surface typically takes a so-called barrel shape. In addition, the curvature of the second portion of the sliding surface is smaller, and the curvature of the first portion is larger. In other words, the radius of curvature of the former is larger and that of the latter is smaller. According to this, since the piston ring of this aspect has a shape close to the shape after familiarization in advance (that is, the shape after completion of so-called initial familiarization) from the start of actual use, it is stable. It becomes possible to acquire a typical shape remarkably fast.
In the aspect in which the sliding surface is curved, the distance from the projecting end portion of the second portion to the boundary line of the first portion and the second portion as viewed along the radial direction of the piston ring is 0. You may comprise so that it may be 5 [micrometers] or more and 3.0 [micrometers] or less.

According to such a configuration, the distance from the projecting end portion to the boundary line between the first portion and the second portion as viewed along the radial direction of the piston ring, in other words, the soft film on the upper side after the hard film formation region ends. Since the distance to the part where the film formation region starts is specifically and suitably determined from the viewpoint of initial familiarity, the above-described effects can be more effectively enjoyed.
In another aspect of the first piston ring of the present invention, a hard coating as the same film as the hard coating in the second portion is further provided below the soft coating in the first portion.

According to this aspect, in the piston ring before the formation of the soft coating and the hard coating, first, the hard coating is formed on the entire sliding surface, and then the soft coating is formed as the upper layer of the hard coating, The piston ring according to this aspect can be manufactured by a process such as removing only the soft film corresponding to the above. That is, in general, it is difficult to remove the hard coating, but according to the piston ring according to this aspect, it is not necessary to carry out such a hard coating removal step, and therefore, the manufacture can be performed easily and at low cost. It can be done.
In order to solve the above problems, the second piston ring of the present invention has a sliding surface, and the first portion located on the combustion chamber side and the third portion located on the crankcase side of the sliding surface are soft. A hard coating harder than the soft coating is provided in a second portion connected to the first portion and the third portion of the sliding surface.

According to the second piston ring of the present invention, in addition to the configuration of the first piston ring of the present invention described above, the hard coating is applied to the third portion located on the crankcase side, that is, the lower side of the sliding surface. A soft coating is provided instead. Therefore, in the second piston ring of the present invention, typically, it is assumed that a soft coating is present on the upper and lower portions of the sliding surface, and a hard coating is present so as to be sandwiched between them. According to such a form, substantially the same effect as described above can be obtained also at the lower end portion, which is generally considered to have a fast progress of wear, after the upper end portion including the first portion of the piston ring. That is, the second piston ring of the present invention can obtain a stable shape even earlier than the above.
In one aspect of the second piston ring of the present invention, the sliding surface is curved with a predetermined curvature, and the curvature in the second portion is smaller than the curvature in the first portion or the third portion. .

According to this aspect, since the sliding surface is curved, the shape of the sliding surface typically takes a so-called barrel shape. Further, the curvature of the second portion of the sliding surface is smaller, and the curvature of the first portion or the third portion is larger. According to this, since the piston ring of this aspect has taken a shape close to the shape after familiarization from before the start of actual use, it is possible to acquire a stable shape remarkably quickly. Become.
In the aspect in which the sliding surface is curved, the distance from the projecting end of the second part to the boundary line of the first part and the second part as seen along the radial direction of the piston ring, or You may comprise so that the distance to the boundary line of a 3rd part and the said 2nd part may be 0.5 [micrometers] or more and 3.0 [micrometers] or less.

According to such a configuration, the distance from the projecting end portion to the boundary line between the first portion and the second portion as viewed along the radial direction of the piston ring is specifically preferably determined from the viewpoint of initial familiarity. Therefore, the above-described effects can be more effectively enjoyed. This is the distance to the boundary line between the first part and the third part seen from the protruding part, in other words, the part where the hard film formation region ends and the lower soft film formation region begins The same can be said about the distance.
In another aspect of the second piston ring of the present invention, the same film as the hard coating in the second portion is formed on at least one of the lower layer of the soft coating in the first portion and the lower layer of the soft coating in the third portion. As a hard coating.

According to this aspect, in the piston ring before the formation of the soft coating and the hard coating, first, the hard coating is formed on the entire sliding surface, and then the soft coating is formed as the upper layer of the hard coating, The piston ring according to this aspect can be manufactured by a process such as removing only the soft film corresponding to the above.
In another aspect of the first or second piston ring of the present invention, the distance from the projecting end of the second part to the end of the sliding surface on the combustion chamber side is the combustion chamber viewed from the projecting end. You may comprise so that it may be larger than the distance to the edge part of the said sliding surface on the opposite side.

  According to this aspect, when the sliding surface has a typical barrel shape, the protruding end coincides with the apex of the barrel shape. The “protruding end portion” according to the present invention means a portion having a maximum diameter when the piston ring is viewed in plan. In this configuration, the distance from the protruding end to the end of the sliding surface on the combustion chamber side is larger than the distance to the crankcase side. In other words, when viewed from the projecting end portion, the upper end portion of the piston ring is more “retracted” toward the radial direction of the piston ring than the lower end portion. According to this, since the piston ring of this aspect is taking a shape closer to the shape after the initial familiarization, compared to the above-described aspect, from the start of actual use, it is stable. It becomes possible to acquire the shape very remarkably fast.

The piston ring according to this aspect can be manufactured, for example, by appropriately adjusting the shape of the sliding surface itself. Besides this, after forming a uniform soft film, the piston ring is formed on the upper side of the soft film. About the part located, it can also manufacture by increasing the grinding | polishing amount of this name chamber film rather than the part located in the lower side.
In another aspect of the first or second piston ring of the present invention, the soft coating is not provided on the groove facing surface connected to the sliding surface.

  In this embodiment, the “groove facing surface” has the following significance. That is, the piston ring is mounted so as to fit in a groove provided in the piston. When the piston ring is fitted in the groove, a part of the inner surface of the groove and the surface connected to the sliding surface of the piston ring face each other. The “groove facing surface” refers to the latter of these. In other words, using the above-described concepts of “upper” and “lower”, the groove facing surface can be rephrased as “upper surface” or “lower surface” of the piston ring.

  In this aspect, the groove facing surface is not provided with a soft coating. Therefore, according to this aspect, it is difficult to generate a gap between the upper surface or lower surface of the piston ring and the side surface of the groove, so that the possibility of occurrence of blow-by due to the gap can be significantly reduced.

  In addition, the piston ring according to this aspect is, for example, a state in which the lower surface of another piston ring is superimposed on the upper surface of one piston ring among the plurality of piston rings (hereinafter referred to as another piston ring) before the formation of the soft coating. It can be manufactured by performing a soft film formation process after the same as in the state where the lower surface of another piston ring is further overlapped with the upper surface of the above. Moreover, it can also manufacture by performing a soft film removal process from the upper surface and lower surface of the piston ring after a soft film formation process.

  As described above, according to the present invention, for example, characteristics such as high hardness, high wear resistance, and high airtightness maintaining function can be realized in a balanced manner regardless of changes in operating conditions.

  Such operations, effects and other advantages of the present invention will become apparent from the embodiments described below.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS.

  First, with reference to FIG. 1, the structure around the engine 150, especially the piston 18 will be described. FIG. 1 is a schematic configuration diagram of the engine according to the first embodiment.

  As shown in FIG. 1, the engine 150 includes a cylinder block 14. The cylinder block 14 is formed with a cylinder 16 that forms the inner periphery thereof. The engine 150 includes a plurality of cylinders. For convenience of explanation, FIG. 1 shows one cylinder among the plurality of cylinders. A piston 18 is disposed inside the cylinder 16. A crankshaft (not shown) housed in the crankcase CC is connected to the piston 18 via a connecting rod 189, and a flywheel FW is connected to the crankshaft. A ring gear FW1 is provided on the outer periphery of the flywheel FW. The ring gear FW1 meshes with a pinion gear SM1 attached to a starter motor (electric motor) SM. At the normal start or cold start of the engine 150, the power generated by the rotation of the starter motor SM is transmitted to the flywheel FW and the crankshaft via the pinion gear SM1 and the ring gear FW1. Thus, the engine 150 is cranked.

  Inside the cylinder 16, a combustion chamber 20 is formed above the piston 18 in FIG. The tip of the spark plug 26 is exposed in the combustion chamber 20. The spark plug 26 ignites the fuel in the combustion chamber 20 by receiving an ignition signal from an ECU (Engine Control Unit) (not shown) or the like. An intake manifold 34 communicates with the combustion chamber 20 via an intake valve 32, and an exhaust manifold 30 communicates with an exhaust valve 28. The piston 18 reciprocates in the vertical direction in FIG. 1 with the explosion in the combustion chamber 20 as an opportunity, and this reciprocating motion is rotated by the crankshaft in the crankcase CC via the connecting rod 189. Is converted to

  The engine 150 having such a configuration is particularly characterized in the configuration of the piston ring in the first embodiment. Below, the structure of this piston ring is demonstrated, referring FIG.2 and FIG.3. FIG. 2 is an enlarged cross-sectional view of a part of the piston to which the piston ring is mounted, and FIG. 3 is an enlarged cross-sectional view of only the top ring part from FIG. .

  In FIG. 2, the piston 18 is formed with ring grooves 18a, 18b and 18c. In these ring grooves 18 a, a top compression ring 81 (hereinafter simply referred to as “top ring 81”), a second compression ring 82 (hereinafter simply referred to as “second ring 82”) and an oil ring are arranged in order from the top in FIG. 1. 83 is installed. In addition to the role of releasing the heat of the piston 18 to the cylinder 16, the oil ring 83 mainly plays a role of scraping off the lubricant on the wall surface of the cylinder 16 and maintaining the amount of lubricant consumption properly. And mainly play the role of maintaining the gas tightness of the combustion gas in the combustion chamber 20.

  In FIG. 3, the top ring 81 has a sliding surface 91, an upper surface 92, and a lower surface 93. Of these, the sliding surface 91 is provided with soft coatings 911 and 913 and a hard coating 912 that is superior in hardness. Of these, the soft coatings 911 and 913 are the portions of the sliding surface 91 located on the combustion chamber 20 side, that is, the upper portion in FIGS. 1 and 2, and the portion located on the crankcase CC side, ie, FIG. And it is formed in the lower part in FIG. The hard coating 912 is formed so as to be sandwiched between the soft coatings 911 and 913.

  The soft coatings 911 and 913 and the hard coating 912 can be manufactured by various methods. Specifically, for example, a nitriding treatment method, an electroplating method, an electrocomposite plating method, a vapor deposition method, a thermal spraying method, a spray coating, and the like. Method, chemical conversion treatment method can be used. Preferably, the soft coatings 911 and 913 are preferably manufactured to have a Hv of less than 1000 using Cr plating, Sn plating, Ni composite plating, resin coating, etc., and the hard coating 912 is PVD (Physical Vapor Deposition). ), DLC, nitriding treatment, thermal spraying or the like is preferably used for manufacturing at Hv 1000 or higher.

  On the other hand, the upper surface 92 and the lower surface 93 correspond to an example of the “groove facing surface” in the present invention, and are surfaces facing the lower surface and the upper surface in FIG. 1 inside the ring groove 18a, respectively. In the first embodiment, the upper surfaces 92 and 93 are not provided with a soft coating continuous to the soft coatings 911 and 913.

  The sliding surface 91 has a so-called barrel shape as shown in FIG. More details are as follows. That is, first, the sliding surface 91 has a protruding end T. Therefore, the top ring 81 has the maximum diameter in the protruding portion 91 along the horizontal direction in FIG. 3, that is, along the radial direction of the top ring 81. The sliding surface 91 is curved with a predetermined curvature so that the protruding end T is the apex. More specifically, for the region where the hard coating 912 is formed, the curvature derived from the curvature radius R, that is, 1 / R, and for the region where the soft coatings 911 and 913 are formed, the curvature radius r ( However, it is curved with a curvature derived from r <R), that is, 1 / r. Here, from r <R, 1 / r> 1 / R.

  Further, on such a curved sliding surface 91, the hard coating 912 viewed along the radial direction of the top ring 81 from the protrusion T included in the formation region of the hard coating 912 and the soft coating on the upper side in FIG. The distance to the boundary line 911 is h1. The same applies to the distance between the protrusion T, the hard coating 912, and the boundary of the lower soft coating 913 in FIG. 3 (see FIG. 3). Further, in the first embodiment, the distance from the projecting end T to the end of the upper sliding surface 91 in FIG. 3 and the end of the lower sliding surface 91 in FIG. The distance to is the same. Although this distance may be measured along the sliding surface 91, in FIG. 3, distances h2 and h3 measured along the radial direction of the top ring 81 are shown. From the above description, in the first embodiment, h2 = h3 (hereinafter, h2 and h3 and the amount represented by h1 described above may be referred to as “barrel height”).

  According to the piston ring of the first embodiment having such a configuration, the following operational effects can be obtained. This will be described below with reference to the drawings referred to above and FIGS. 4 and 5. Here, FIG. 4 is a diagram having the same concept as in FIG. 3, and is a cross-sectional view illustrating an enlarged behavior of the top ring while the piston is descending. FIG. 5 is a so-called sliding surface of the top ring. It is sectional drawing which shows an example when initial familiarity is completed (however, illustration of the hard film 912, the soft films 911, and 913 etc. which were demonstrated in FIG.2 and FIG.3 is abbreviate | omitted in these figures).

  First, in the engine 150 shown in FIG. 1, as is well known, four cycles of an intake process, a compression process, an explosion / expansion process, and an exhaust process are repeated. Of these, in the explosion / expansion stroke, the mixture 18 introduced into the combustion chamber 20 via the intake valve 32 is ignited by the ignition plug 26, and an explosion occurs. 16 rapidly descends downward in FIG. At this time, the piston rings 81 to 83 generally behave as shown in FIG. That is, in FIG. 4, since the piston 18 'is rapidly descending downward in the figure, the top ring 81' is also rapidly descending downward in the figure, but at the same time, the top ring 81 ' Since the explosive force in the combustion chamber (not shown) in the upper part of the figure is directly received, the tip is inclined. The degree of this inclination varies depending on the type of engine, the operating conditions, and various conditions such as the clearance between the ring groove 18'a and the top ring 81 '. In any case, the top ring 81' After taking a proper posture, it is subjected to extremely severe lubrication conditions of being subjected to high pressure and high pressure. Then, even in the sliding surface of the top ring 81 ′, the portion located on the combustion chamber side wears faster than the other portions. As a result, after the operation for a certain period, the top ring 81 'has a shape as shown in FIG. That is, the portion located on the combustion chamber side of the sliding surface 811 ′ when new is retracted along the radial direction of the top ring 81 ′ (see the sliding surface 812 ′). Such a phenomenon is noticeable in the early stage of engine operation. In this case, the process of change from the sliding surface 811 ′ to the sliding surface 812 ′ that is stable to a certain degree is generally called “initial familiarity”. .

  The shorter the period until such initial familiarization is completed, the better. This is because the piston rings 81 to 83 maintain a stable shape after the initial familiarization, and the engine 150 can be stably operated.

  From such a viewpoint, in the first embodiment, an extremely good effect can be obtained. That is, first, in the top ring 81 in the first embodiment, the soft coating 911 is provided on the sliding surface 91 on the combustion chamber 20 side, and the hard coating 912 is provided on the other portion. It becomes possible to acquire a typical shape earlier. This is because the soft coating 911 progresses faster than the hard coating 912. Second, the sliding surface 91 has a barrel shape, and the region 1 / r where the soft coating 911 is formed is made larger than the curvature 1 / R of the region where the hard coating 912 is formed. Therefore, it can be said that the top ring 81 of the first embodiment has a shape close to the shape after the initial familiarization has been completed in advance (see FIG. 3 and FIG. 5 comparison), and thus the above-described effect is obtained. Further promoted.

  Moreover, in 1st Embodiment, in addition to the above-mentioned effect, the effect described below is show | played. That is, first, in the first embodiment, in addition to the soft film 911 on the upper side in FIG. 3, the soft film 913 is also provided on the lower side in FIG. 3, and the soft film 913 is formed. The curvature r / 1 of the area where the film is formed is larger than the curvature 1 / R of the area where the hard film 912 is formed. Thereby, the effect of the above-mentioned acquisition of the stable shape at an early stage becomes more remarkable. This is because it is generally considered that the lower end portion of the top ring 81 has the fastest wear after the tip portion. This is because the influence of the frictional force acting between the tip of the cylinder 16 'and the top ring 81' stands out after the influence of the explosive force is hidden in FIG. This is because it may be inclined upward as opposed to FIG.

  Second, in the first embodiment, as described with reference to FIG. 3, the upper surface 92 and the lower surface 93 of the top ring 81 are not provided with a soft coating. Therefore, according to the first embodiment, the gap between the upper surface 92 or the lower surface 93 of the piston ring 81 and the side surface of the ring groove 18a is less likely to occur, so the possibility of occurrence of blow-by due to the gap is remarkable. Can be reduced.

  Third, in the first embodiment, the hard coating 912 is provided on the sliding surface 81 so as to be sandwiched between the upper soft coating 911 and the lower soft coating 913 in FIG. In the region where the coating 912 is formed, the wear hardly progresses. Therefore, the progress of wear at the initial stage of operation can be suppressed, and the occurrence of combustion gas leakage, lubricating oil leakage, and the like due to an increase in the clearance gap can be effectively prevented.

  In addition, fourth, as described above, the soft coatings 911 and 913 are worn quickly and the hard coating 912 remains, so that the top ring 81 can reach a stable shape at an early stage. Means that a shape in which the barrel heights h2 and h3 are larger can be realized at an early stage. Therefore, improvement of the lubricating oil scraping performance, lower tension of the top ring 81, reduction of friction, etc. Further, the catalyst poisoning by sulfur / phosphorus contained in the lubricating oil is suppressed, and the emission can be improved.

  Incidentally, in this regard, FIG. 6 and FIG. 7 are graphs showing the qualitative relationship between the barrel height h2 (= h3), the lubricant consumption amount / blow-by occurrence rate, and the friction magnitude, respectively. Let me show you. According to the former, it can be seen that as the barrel height h2 increases, the lubricant consumption decreases and the blow-by rate decreases. According to the latter, the friction increases as the barrel height h2 increases. It turns out that it becomes small. The horizontal axis in FIG. 7 can be read as the formation region length L of the hard coating 912 shown in FIG. 3 instead of the barrel height h2 (in this case, the horizontal axis is on the right side in the figure). The length L is read as it decreases as it progresses.) Further, although related to these figures, in order to more effectively obtain the various actions and effects, mainly the action and effect of early acquisition of the stable shape described above, the barrel described with reference to FIG. The value of the height h1 is preferably 0.5 [μm] or more and 3.0 [μm] or less. If the barrel height h1 is less than 0.5 [μm], the formation region length L of the hard coating 912 is too short, and if it exceeds 3.0 [μm], L becomes too long, and after initial familiarity This is because the deviation from the obtained shape becomes large.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to FIG. Here, FIG. 8 is a view having the same concept as FIG. 3 and is a cross-sectional view in which the soft film and the hard film are formed differently on the sliding surface. In the following description, since the configuration and operation related to the engine described in the first embodiment are the same, the description thereof will be simplified or omitted, and only the characteristic configuration in the second embodiment will be described. An explanation will be added. In addition, regarding the reference numerals used in the drawings referred to in the first embodiment, the same reference numerals are used in the drawings referred to in the second embodiment when the same objects are indicated. The same applies to the third and subsequent embodiments described below.

  In the second embodiment, as shown in FIG. 8, a hard coating 914 is provided on the entire sliding surface 91. Of the hard coating 914, a soft coating 915 is provided for a portion located on the combustion chamber 20 side, and a soft coating 916 is provided for a portion located on the crankcase CC side. In other words, it can be said that a hard coating 914 as the same film as the hard coating 914 exposed to the outside is further provided below the soft coatings 915 and 916.

  Also according to the second embodiment as described above, it is apparent that substantially the same operational effects as those of the first embodiment can be obtained.

  Moreover, according to 2nd Embodiment, the following effects are obtained especially. That is, the top ring 81 having the form as shown in FIG. 8 is a top ring before the formation of the soft coatings 915 and 916 and the hard coating 914. First, after forming the hard coating 914 on the sliding surface 91 over the entire surface, A soft film is formed on one surface as the upper layer of the hard film 914, and then only the soft film located on the portion of the hard film 914 to be exposed to the outside is removed (thereby, the soft films 915 and 916 remain). It can be manufactured by a process such as. That is, in general, it is difficult to remove the hard film. However, according to the top ring 81 according to the second embodiment, it is not necessary to perform such a hard film removal step, so that the manufacture thereof is easy and low cost. It can be done.

(Third embodiment)
Below, the 3rd Embodiment of this invention is described, referring FIG.9 and FIG.10. 9 is a cross-sectional view having the same concept as in FIG. 3 and having a different sliding surface shape, and FIG. 10 is a cross-sectional view having the same purpose as in FIG. 8 and having a different sliding surface shape. FIG.

  In 3rd Embodiment, as shown in FIG. 9, the barrel shape of the sliding surface 95 differs from FIG. That is, h2 = h3 in FIG. 3 of the first embodiment, but h2> h3 in FIG. In order to correspond to this, the position of the protruding end T in FIG. 9 is shifted to the lower side in the drawing from that in FIG. Further, in FIG. 9, the curvature 1 / R of the region where the hard coating 952 is formed and the curvatures 1 / r1 and 1 / r2 of the regions where the soft coatings 951 and 953 are respectively formed are 1 in FIG. The relations 1 / R <1 / r1 and 1 / R <1 / r2 corresponding to the relation / R <1 / r are satisfied. Incidentally, in FIG. 9, r1> r2.

  According to such 3rd Embodiment, the effect described in the said 1st Embodiment can be enjoyed more effectively. Because, as already described in the description of the first embodiment, if the sliding surface 95 is divided into an upper part, a central part, and a lower part, these are arranged in descending order of wear progressing speed, the upper part, This is because the lower part and the central part are obtained. The shape in FIG. 9 better reflects such circumstances, and therefore the top ring 84 can be said to have a shape that is closer to the shape after the initial familiarization is completed. It is possible to acquire extremely remarkably fast.

  Incidentally, FIG. 10 shows another form related to the third embodiment. FIG. 10 is based on the same idea as FIG. 9 and is a modification of FIG. 8 of the second embodiment. That is, in FIG. 10, as in FIG. 9, h2> h3, and at the same time as in FIG. 8, the upper and lower portions of the hard coating 954 formed on the entire sliding surface 95 in the figure. Only soft coatings 955 and 956 are formed. Therefore, according to FIG. 10, the operational effects according to the third embodiment can be obtained, and at the same time, the operational effects described in the second embodiment can also be obtained.

(Other embodiments)
Hereinafter, other embodiments of the present invention will be described with reference to FIGS. 11 to 13. FIGS. 11 to 13 are diagrams having the same purpose as FIG. 3 or FIGS. 8 to 10, but show various modifications of the present invention that could not be touched on above.

  First, in the first to third embodiments, the description is made mainly for the top ring, but the present invention is not limited to such a form. In the description of the first embodiment, what has been described with reference to FIGS. 4 and 5 applies to the second ring 82 and the oil ring 83 to some extent. That is, the structure and concept described in the first to third embodiments can be applied to the second ring 82 and the oil ring 83 in the same manner, and as a result, substantially the same functions and effects as described above can be obtained. Can be obtained. In FIG. 11, the example which applied the structure of 1st Embodiment to the oil ring 83 is shown as the example. In FIG. 11, the oil ring 83 has a so-called three-piece structure, and includes an upper rail 831, an expander 832, and a lower rail 833. Of these, the tip of the upper rail 831 and the lower rail 833 are in contact with the wall surface of the cylinder 16, and therefore, this portion can have the same structure as FIG. 3 as shown in FIG. 11.

  Next, in the first to third embodiments, the mode in which the soft coating is provided on both the combustion chamber 20 side and the crankcase CC side of the sliding surface 91 or 95 has been described. The form is not limited. For example, as shown in FIG. 12, a portion of the sliding surface 91 located on the combustion chamber 20 side is provided with a soft coating 911, but a portion located on the crankcase CC side is not provided with a soft coating, but a soft coating is provided. The piston ring may be a hard coating 917 except for the portion provided with 911.

  Furthermore, in the said 1st thru | or 3rd embodiment, although the sliding surface 91 or 95 becomes a barrel shape, this invention is not limited to this form. For example, as shown in FIG. 13, a piston ring in which the sliding surface 96 is a flat surface may be used. Incidentally, in FIG. 13, a soft coating 961 and 963 are provided on the combustion chamber 20 side and the crankcase CC side of the sliding surface 96 which is a flat surface, and a hard coating 962 is provided so as to be sandwiched between them. 3 is shown, but it goes without saying that the configuration shown in FIG. 12 may be provided instead.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification, and a piston ring with such a change is also applicable. Moreover, it is included in the technical scope of the present invention.

1 is a schematic configuration diagram of an engine according to a first embodiment of the present invention. It is sectional drawing which expanded and depicted a part of piston with which the piston ring was mounted | worn. FIG. 3 is a cross-sectional view in which only the top ring portion is further enlarged from FIG. 2. FIG. 4 is a view having a similar concept to that of FIG. 3, and is a cross-sectional view illustrating an enlarged behavior of the top ring during lowering of the piston. It is sectional drawing which shows an example when what is called initial familiarity is completed in the sliding surface of a top ring. It is a graph which shows the qualitative relationship between barrel height (h2 thru | or h3 in FIG. 3), lubricating oil consumption, and blow-by generation rate. 4 is a graph showing a qualitative relationship between a barrel height (h2 or h3 in FIG. 3) and the magnitude of friction. FIG. 4 is a view having the same concept as in FIG. 3 according to the second embodiment of the present invention, and is a cross-sectional view in which a soft film and a hard film are formed on a sliding surface. FIG. 4 is a cross-sectional view of the third embodiment of the present invention, the same meaning as in FIG. 3, and the shape of the sliding surface is different. FIG. 10 is a cross-sectional view of the third embodiment of the present invention having the same concept as in FIG. FIG. 11 is a diagram having the same purpose as in FIG. 3 or FIG. 8 to FIG. 10, and shows various modifications (No. 1) of the present invention. FIG. 11 is a diagram having the same purpose as FIG. 3 or FIG. 8 to FIG. 10, and shows various modifications (No. 2) of the present invention. FIG. 11 is a diagram having the same purpose as in FIG. 3 or FIG. 8 to FIG. 10, and shows various modified embodiments (part 3) of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 150 ... Engine 20 ... Combustion chamber CC ... Crankcase 18 ... Piston 18a ... Ring groove 81, 84 ... Top ring 82 ... Second ring 83 ... Oil ring 91, 95, 96 ... Sliding surface 911, 913, 915, 916, 951 , 953, 955, 956, 961, 963 ... Soft coating 912, 914, 952, 954, 917, 962 ... Hard coating T ... Projection end 92 ... Upper surface 93 ... Lower surface

Claims (10)

  A sliding surface has a soft coating on a first portion located on the combustion chamber side of the sliding surface, and the soft coating on a second portion of the sliding surface connected to the first portion Piston ring characterized by having a hard coating that is harder. The sliding surface is curved with a predetermined curvature,
2. The piston ring according to claim 1, wherein the curvature of the second portion is smaller than the curvature of the first portion.   The distance from the projecting end of the second part to the boundary line of the first part and the second part as viewed along the radial direction of the piston ring is 0.5 [μm] or more and 3.0 [μm]. The piston ring according to claim 2, wherein:   The piston according to any one of claims 1 to 3, further comprising a hard coating as the same film as the hard coating in the second portion, below the soft coating in the first portion. ring.   A first portion located on the combustion chamber side and a third portion located on the crankcase side of the sliding surface, the first portion of the sliding surface being provided with a soft coating; A piston ring comprising a hard coating harder than the soft coating on the second portion connected to the third portion. The sliding surface is curved with a predetermined curvature,
The piston ring according to claim 5, wherein the curvature of the second portion is smaller than the curvature of the first portion or the third portion.   The distance from the projecting end of the second part to the boundary line of the first part and the second part, or the boundary line of the third part and the second part, viewed along the radial direction of the piston ring The piston ring according to claim 6, wherein the distance to the piston ring is 0.5 [μm] or more and 3.0 [μm] or less.   At least one of the lower layer of the soft coating in the first portion and the lower layer of the soft coating in the third portion is further provided with a hard coating as the same film as the hard coating in the second portion. The piston ring according to any one of claims 5 to 7.   The distance from the projecting end of the second portion to the end of the sliding surface on the combustion chamber side is the distance from the projecting end to the end of the sliding surface opposite to the combustion chamber side. The piston ring according to claim 1, wherein the piston ring is larger than the piston ring. The piston ring according to any one of claims 1 to 9, wherein the soft coating is not provided on a groove facing surface connected to the sliding surface.

Images