JP2007077988A - Piston ring set - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piston ring set to be used for a piston in a large two-stroke diesel engine. <P>SOLUTION: The piston 2 in a mounted condition is arranged reciprocatingly along a cylinder working surface 7 of a cylinder wall 3 of a cylinder 4 in the large two-stroke diesel engine. The piston ring set comprises a first piston ring K1 arranged nearest the combustion chamber of the cylinder and having a first supporting surface L1, and a second piston ring K2 having a second supporting surface L2. The first piston ring is arranged in a first piston ring groove N1 of the piston and the second piston ring is arranged in a piston ring groove N2 of the piston so that the first supporting surface of the first piston ring including a wear protecting portion and the second supporting surface of the second piston ring are put in sliding contact with the cylinder wall during operation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The invention relates to a set of piston rings for a piston of a large two-stroke diesel engine, and further to a piston with a set of piston rings according to the invention as described in the preceding paragraphs of the independent claims 1 and 11.

  A piston for a large diesel engine known as the prior art includes a set of a plurality of piston rings arranged in each piston groove side by side in principle. A known set of piston rings usually has at least two piston rings (often 3 or 4 depending on the size and / or power of the large diesel engine and / or depending on the operating requirements or special operating conditions of the engine. Or optionally five piston rings).

  Piston rings that fulfill various functions, such as guiding the piston in the cylinder, dispensing lubricant on the cylinder working surface, and / or scraping and sealing the combustion chamber against the crank housing, are subject to severe loads during operation. Exposed to. Therefore, the piston ring is in direct sliding contact with the cylinder working surface and must be subjected to combustion pressure at the piston ring, which is ultimately exposed to significant thermal, mechanical and chemical loads. The

  In such a configuration, the piston ring that is subjected to the most severe loads, particularly with respect to receiving combustion pressure, is usually called the “top ring” and is the piston ring that is located closest to the combustion chamber of the cylinder. In this regard, in the case of piston rings known from the prior art, only the top ring has a wear protection coating on the working surface, the so-called low wear coating, which is formed, for example, from a suitable chrome ceramic. it can. In contrast, the other piston rings of the piston assembly do not have a wear protection layer, but these piston rings can have a removable embedded layer, the so-called familiar running layer, as a running surface, The corresponding piston ring moves ideally along the cylinder liner, the cylinder liner, after completion of the implant phase, since it wears off relatively quickly in a manner well known to the average person skilled in the art.

  With such a configuration, it has been found that the solution poses a problem. After the familiar operation phase, that is, when the familiar operation layer is somewhat worn, for example, the base material of the piston ring, which is cast iron material, is exposed to the running surface of the piston ring that is in sliding contact with the working surface of the cylinder wall. . That is, in operation, sliding contact occurs between the two cast materials of the piston ring and the cylinder wall, which can cause significant wear and cause so-called “fretting”, also called “scuffing” in bad scenarios. there is a possibility.

  With such a configuration, in the prior art, only the top ring, in other words, only the piston ring disposed closest to the cylinder combustion chamber in the set of piston rings was covered with the wear protection layer. There were several reasons. On the other hand, the top ring is the ring that receives the most severe loads. According to established opinions, the wear protection coating on the top ring is sufficient because each other piston ring in the set of piston rings underneath is considered to be subjected to a fairly low load, and therefore This is because coating was considered unnecessary. On the other hand, the application of wear protection coatings is relatively complex, especially time consuming and costly, which inter alia in order to ensure optimal fitting and ideal travel of the piston ring in the cylinder, This is due to the fact that the wear protection coating must be applied very precisely.

  Furthermore, it was an established opinion that a piston ring with a wear protection layer under the top ring adversely affects the lubricant film on the cylinder wall. As is well known, the top ring also serves as an oil scraping ring, i.e., it applies lubricant applied to the working surface of the cylinder wall away from the combustion chamber, away from the crank housing, or vice versa. Transfer (pumping) in the direction. In this way, on the one hand, a large amount of lubricating oil can be prevented from entering the combustion process. On the other hand, the lubricating oil passes through the top ring which acts as an oil scraping ring and is transferred to the underlying piston ring, thus improving their lubrication.

  With such a configuration, the oiling effect of the top ring is not only through a special design of the shape of the running surface of the top ring, but also by special hydrodynamic conditions and thus in connection with special tribological conditions. These conditions are obtained by the interaction between the coated surface and the working surface of the cylinder wall made of cast iron material.

  Therefore, the piston ring under the top ring and having a wear protection layer also acts as an oil scraping ring, thus not only greatly impairing the lubrication for the remaining piston rings in the set of piston rings, but especially the top ring. Since the ring lubrication was also impaired, a considerably increased risk was expected.

  Thus, it was obvious to the average person skilled in the art that the piston ring under the top ring should not have a wear protection coating.

  For example, for a four-stroke internal combustion engine such as that described in German Patent DE-19540803-A1, a piston ring coating disposed under the top ring is well known. This is the reason why 4-stroke engines have a completely different lubrication system than that known from the lubrication system of large two-stroke diesel engines, for example when used in automobiles. For known four-stroke engines, not only is sufficient lubricant provided on the cylinder's operating surface, but generally there is excess lubricant on the cylinder's operating surface, which causes a large amount of lubricant to be drawn. It must be returned to the crankcase sump from the working surface.

  However, it turns out that the piston ring located below the top ring is always exposed to higher loads, especially in modern large two-stroke diesel engines, which always tend to higher power and / or power density ing. It is also known that the problem of friction loss occurring in the operating state after the run-in phase between the piston ring made of cast iron material and the cylinder wall made of cast iron material as well as the cast iron material has been considerably underestimated. .

  The object of the invention therefore guarantees an improved set of piston rings and a much improved running behavior of the pistons, a higher wear resistance and thus a more economical operation of a large two-stroke diesel engine. It is to propose a piston having this kind of piston ring.

  The subject matter of the present invention that fulfills these objectives is defined by the features described in the independent claims 1 and 11.

  The dependent claims relate to particularly advantageous embodiments of the invention.

Accordingly, the present invention relates to a set of piston rings for a piston of a large two-stroke diesel engine. In this configuration, the piston is arranged so that it can reciprocate along the cylinder wall of the cylinder of a large two-stroke diesel engine when mounted, and the piston ring set is located closest to the combustion chamber of the cylinder. And a first piston ring having a first running surface and a second piston ring having a second running surface.
The first piston ring is disposed in the first piston ring groove so that the first traveling surface of the first piston ring and the second traveling surface of the second piston ring are in frictional contact with the cylinder wall in the operating state. A second piston ring is disposed in the second piston ring groove. With this configuration, according to the present invention, the first traveling surface of the first piston ring and the second traveling surface of the second piston ring both include the wear protection portion.

  Thus, in addition to the top ring, at least one further piston ring of the set of piston rings, preferably the piston ring closest to the top ring, includes a wear protection on the running surface of the piston ring. Is important to.

  Surprisingly, it has been found that this means does not degrade the tribological conditions and running characteristics of the remaining piston rings in the set. In stark contrast, by appropriately designing a piston ring with wear protection as well, in particular by designing the running surface shape of this piston ring and / or the remaining piston ring and / or piston By appropriately selecting the piston ring arrangement in the ring set, the running characteristics of the piston ring set can be significantly improved by providing a wear protection on the piston ring arranged below the top ring.

  In a particular embodiment, the set of piston rings includes a third piston ring having a third running surface provided in a third piston ring groove, the third running surface being in cylinder running on the cylinder wall in the operating state. In frictional contact with the surface.

  In this arrangement, the second running surface and / or the third running surface includes a wear protection part and / or a familiar running layer. Thus, for example, the second piston ring, for example located closest to the first piston ring, also referred to as the top ring, includes a wear protection, while the third piston ring and possibly another piston ring in the set of piston rings is familiar. Has a layer. It goes without saying that in addition to the second piston ring, a third piston ring and / or yet another piston ring of the set of piston rings can likewise include a wear protection.

  In another embodiment, the piston ring disposed closest to the first piston ring includes a familiar operating layer, while the third piston ring and / or further piston ring disposed below the wear ring Can also be included. This can be advantageous especially when the load acting on the piston ring located closest to the first piston ring in operating conditions does not exceed the maximum load that can be scheduled. No wear protection is required. However, this lower piston ring has a wear protection. This is because, through this wear protection, the oil film in the region of the piston ring set is improved, for example, by this means so that the tribological and other travel characteristics of the piston ring set are optimized as a whole. is there.

  In a particular embodiment of the set of piston rings according to the invention, the first piston ring and / or the second piston ring and / or the third piston ring and / or the further piston ring are formed of a wear-resistant material. Yes. That is, the casting material normally used as a material for the piston ring can be made wear resistant by adding appropriate components or suitable alloy elements. This can be done, for example, by alloying or adding this material to a material which is said to be suitable for this, for example chromium, chrome, well known to the average person skilled in the art, for example as a wear protection material, in particular for piston rings. This can occur by adding ceramics or oxides such as ceramics, aluminum oxide, silicates, diamond particles, especially Tritor, CKS-36, CKS-37, carbides, especially chromium carbide. It goes without saying that in certain cases the piston ring can be made entirely of wear-resistant material, so that the casting material known in the art and normally used for piston rings can be omitted completely or partially. .

  In one particularly important embodiment for practical use, the wear protection is a wear protection coating. In this arrangement, the thickness of the wear protection coating of the second piston ring, and / or the thickness of the wear protection coating of the third piston ring, and / or the thickness of the wear protection coating of yet another piston ring, 100% of the thickness of the wear protection coating on the piston ring, in particular only ¾ of the thickness, preferably only ½ of the thickness, in particular １ ／ of the thickness, especially ¼ of the thickness Or at most 10% of the thickness.

  In this configuration, the thickness of the wear protection coating of the first piston ring and / or the second piston ring and / or the third piston ring and / or the further piston ring is equal to the thickness of the wear protection coating of the first piston ring. It can be particularly advantageous if it is smaller than the thickness. Since the load on the second piston ring and each other piston ring is generally much smaller than the load to which the first piston ring is exposed in operating conditions, the second piston ring, the third piston ring, and possibly yet another piston ring. In many cases, the thickness of the wear protection layer can be selected to be smaller than the thickness of the wear protection coating of the first piston ring. Typical values for the thickness of the wear protection layer of the first piston ring are 200 μm to 660 μm, in particular 330 μm to 400 μm. Furthermore, the thickness of the wear protection layer of another piston ring, for example the second piston ring, can be made smaller, for example 10 μm to 200 μm, in particular 50 μm to 100 μm.

  Selecting a smaller thickness for the wear protection layer of the second piston ring and / or each other piston ring is of interest in this arrangement for economic considerations only. That is, the wear protection layer is preferably sacrificial or is added by laser cladding, so the time consumption required for layer formation increases with increasing layer thickness.

  In this regard, of course, the wear protection layer can of course be used by any other suitable coating method, in other words well-known thermal spraying such as HVOF, plasma spraying, flame spraying, powder spraying, and other such as welding. It will be appreciated that any suitable coating method can be used to produce.

  In this regard, for example, the second piston ring of the set of piston rings according to the invention and / or all other piston rings can be made from the same piston ring semi-finished product as that making the first piston ring. Since the piston ring semi-finished product generally has a ring width of 5 mm to 50 mm, preferably 15 mm to 30 mm, the total width of the piston ring is not affected by itself / substantially by the coating, and thus wear protection of several tens of micrometers or several hundreds of micrometers The difference in coating thickness does not actually affect the correct fitting of the piston ring in the cylinder.

  In this regard, the running surfaces of the first piston ring and / or the second piston ring and / or the third piston ring and / or other piston rings are convex in the direction toward the cylinder running surface of the cylinder wall. Preferably it is formed.

  In this configuration, the travel surfaces of the first piston ring and / or the second piston ring and / or the third piston ring and / or other piston rings are directed toward the cylinder travel surface with respect to the central plane of the respective piston ring. It can be designed symmetrically or asymmetrically in the direction.

  In one embodiment, which is particularly important as an implementation problem for the set of piston rings according to the invention, the first piston ring, for example the top ring, is designed asymmetrically and assumes the function of an oil scraping ring, The two piston rings or the other piston ring running surface or wear protection coating of the piston ring set is designed symmetrically with respect to the central plane of the respective piston ring, and the second piston ring or other piston ring running surface cylinder The outer boundary surface as viewed in the direction towards the running surface is made in a convex shape, for example in the shape of a symmetrical circular cross section, in particular of a circle.

  In another embodiment, the running surfaces of the first piston ring and / or the second piston ring and / or the third piston ring and / or other piston rings are asymmetric, in particular in the direction towards the combustion chamber. Convex shape can be designed asymmetrically.

  In yet another embodiment, the travel surface of the first piston ring, and / or the second piston ring, and / or the third piston ring, and / or the other piston ring is on the cylinder travel surface with respect to the central plane of the piston ring. It should be understood that the design can be asymmetrical in the direction of the direction, in particular asymmetrically convex in the direction away from the combustion chamber.

  It is particularly preferred that the first piston ring is designed asymmetrically in the direction toward the combustion chamber or asymmetrically convex in the direction away from the combustion chamber to perform the function of the oil scraping ring.

  For example, the wear protection on the piston ring made of cast material, i.e. the piston ring itself or the wear protection coating, is, among others, chromium and / or aluminum oxide and / or silicate and / or diamond particles and / or chromium ceramic. , In particular Tritor, and / or CKS-36, and / or CKS-37, and / or carbides, in particular chromium carbide. In the end, all known wear protection materials which are advantageous for the formation of wear protection layers or for the production of piston rings made of wear-resistant materials are suitable.

  The above-described embodiments of the set of piston rings according to the invention are to be understood as examples only, in particular pistons with more than three, in other words four, five, six or more piston rings. It goes without saying that a ring set is also included, and all suitable combinations of the specifically described embodiments are also included by the present invention.

  Furthermore, the present invention relates to a piston ring having a set of piston rings as will be described in further detail above.

  Next, the present invention will be described with reference to the accompanying drawings showing schematic views.

  FIG. 1 is a schematic view partially showing in cross section a cylinder of a two-stroke large diesel engine equipped with a set of piston rings according to the present invention, generally designated 1 below.

  A piston 2 is arranged in the cylinder 4 in a well-known manner, and can be reciprocated along the cylinder running surface 7 of the cylinder wall 3. The piston 2, the cylinder wall 3 and the cylinder cover 8 define a combustion chamber 5 of the cylinder 4. An exhaust valve 9 for exhausting exhaust gas and an injection valve 10 for injecting fuel are provided in the cylinder cover 8. For the sake of clarity, FIG. 1 shows only two piston rings, ie only the first piston ring K1 and the second piston ring K2, for the sake of clarity. Has been. The piston ring K1 located closest to the combustion chamber is often referred to as the top ring and is provided in the piston ring groove N1, whereas the second piston ring K2 according to the drawing is the first piston ring K1. Is disposed in the piston ring groove N2 below.

  When describing the second piston ring K2 in the context of this application, it goes without saying that the piston ring K2 is not automatically located closest to the first piston ring K1. Rather, one or more piston rings are arranged between the first piston ring K1 and the second piston ring K2, so that in certain cases the second piston ring K2 is the lowest piston ring of the set of piston rings, In other words, it is completely possible in certain cases to be able to be a piston ring which is arranged farthest from the first piston ring K1.

  In the particular embodiment illustrated in FIG. 1, the first piston ring K1 and the second piston ring K2 are formed from a casting material in a manner known per se, not only the first piston ring K1 but also the second piston ring K2. A wear protection coating 6 is provided, which is designed in a convex form and thus extends in a convex direction in the direction towards the cylinder running surface 7. In the operating state of the two-stroke large diesel engine, the wear protection coating 6 of the piston rings K1, K2 is in frictional contact with the cylinder running surface 7 of the cylinder 4.

  FIG. 2 shows a specific embodiment of the piston ring set 1 in which the illustration of the piston 2 and the cylinder 4 has been omitted for the sake of clarity.

  A first piston ring K1 located closest to the combustion chamber 5 is shown, and the position of the combustion chamber 5 relative to the piston rings K1, K2, K3 is indicated by an arrow with reference numeral 5. The first piston ring K1 and the second piston ring K2 are made from two substantially identical piston ring semi-finished products 11 or piston ring bodies 11 of height H and width B made of a casting material known per se. Both the first piston ring K1 and the second piston ring K2 are each provided with a wear protection coating 6 on the first running surface L1 and the second running surface L2, respectively, and the wear protection coating 6 of the first piston ring K1. Has a thickness S1, and the wear protection coating 6 of the second piston ring K2 has a thickness S2. In this arrangement, the width B of the piston ring body 11 of the piston rings K1, K2 is larger than the thicknesses S1, S2 of the wear protection coating 6. The width B of the piston ring body 11 can be, for example, 25 mm, but the thickness S1 of the wear protection layer 6 of the first piston ring K1 is 350 μm, and the thickness S2 of the wear protection layer 6 of the second piston ring K2 Can be as small as 75 μm. In the embodiment shown in FIG. 2, the first travel surface L1 of the first piston ring K1 and the second travel surface L2 of the second piston ring K2 are in a direction toward the cylinder travel surface 7 not shown in FIG. It is designed to be asymmetric with respect to the center plane of the piston ring in the direction away from the combustion chamber 5.

  Three specific examples of a wear protection coating 6 designed in the convex form of piston rings K1, K2, K3 having a width B are shown in FIGS. 3a, 3b, 3c. It will be understood that the piston ring itself, which is not entirely equipped with a wear-resistant coating and is made of a wear-resistant material, can of course be designed on its running surface according to the illustrated example.

  A convex asymmetric embodiment of the piston travel surfaces L1, L2, L3 is shown in FIGS. 3a and 3b, respectively. The embodiment according to FIG. 3 a shows an embodiment of the running surfaces L 1, L 2, L 3, which is in the direction of the cylinder running surface 7 not shown with respect to the central plane II and against the combustion chamber 5. Convex shape asymmetric in direction. In contrast, in FIG. 3b, of the running surfaces L1, L2, L3 which are convexly asymmetric in the direction towards the cylinder running surface 7 not shown relative to the central plane II and in the direction towards the combustion space 5. Examples are shown.

  Finally, FIG. 3c is particularly important as a practical matter, in which a symmetrical embodiment of the running surfaces L1, L2, L3 is shown relative to the central plane II in the direction towards the cylinder running surface 7 not shown. Examples are shown. This embodiment is preferably suitable for the running surfaces L2, L3 of the second piston ring K2 and / or the third piston ring K2 and / or further piston rings.

  Finally, FIG. 4 schematically shows in partial section a further embodiment of a complete set of piston rings according to the invention, which is of particular importance in practice.

  The piston 2 shown in FIG. 4 has at least three piston ring grooves N1, N2, N3, which receive a first piston ring K1, a second piston ring K2, and a third piston ring K3, respectively. Incidentally, during operation, the running surfaces L1, L2, L3 of the piston rings K1, K2, K3 are in frictional contact with the cylinder running surface 7 of the cylinder wall 3 of the cylinder 4 which is simply shown in FIG.

  The first piston ring K1, in other words, the piston ring arranged closest to the combustion chamber 5 is exactly the same as the piston ring K2 directly adjacent to the piston ring K1 in the present embodiment and below the K1 in the drawing. In this manner, a wear protection layer 6 is provided. The third piston ring K3, which receives a considerably smaller load than the first piston ring K1 and the second piston ring K2, is in the piston ring groove N3 by its arrangement and has a familiar operating layer known per se. The layer forms a running surface L3 of the third piston ring K3.

  In this arrangement, the first piston ring K1 is formed in a convex asymmetric shape on the running surface L1, and in particular functions as an oil scraping ring in a manner known per se. In contrast, the second piston ring K2 is formed in a convex symmetrical shape with respect to the central plane I-I, and the running surface L2 of the piston ring K2 is formed symmetrically, by this means the piston ring complete set 1 A particularly advantageous and uniform distribution of the oil film in the region can be achieved, thus ensuring an ideal lubrication of the piston ring K1 in particular.

It is a figure which shows the cylinder of the 2-stroke large diesel engine provided with the piston ring set by this invention. It is a figure which shows one Example of a set of piston rings by this invention. It is a figure which shows the piston ring which has a convex-shaped asymmetrical running surface. Fig. 3a shows a further embodiment according to Fig. 3a. It is a figure which shows the piston ring which has a convex-shaped symmetrical running surface. It is a figure which shows another Example of a set of piston rings by this invention.

Claims (14)

A set of piston rings used in the piston (2) of a large two-stroke diesel engine,
The piston (2) is disposed so as to be capable of reciprocating along a cylinder wall (3) of a cylinder (4) of a large two-stroke diesel engine in a mounted state,
The set of piston rings is:
A first piston ring (K1) disposed closest to the combustion chamber (5) of the cylinder (4) and having a first running surface (L1);
A second piston ring (K2) having a second running surface (L2),
In the operating state, the first travel surface (L1) of the first piston ring (K1) and the second travel surface (L2) of the second piston ring (K2) act as cylinder actuation of the cylinder wall (3). The first piston ring (K1) is disposed in the first piston ring groove (N1) of the piston (2) so as to be in sliding contact with the surface (7), and the second piston ring (K2). ) Is disposed in the second piston ring groove (N2) of the piston (2),
A set of piston rings, wherein the first travel surface (L1) of the first piston ring (K1) and the second travel surface (L2) of the second piston ring (K2) include a wear protection portion.   At least one third piston ring (K3) having a third running surface (L3) is disposed in the third piston ring groove (N3), and the third running surface (L3) A set of piston rings as claimed in claim 1, wherein the piston ring is in frictional contact with the cylinder running surface (7) of the cylinder wall (3).   The piston ring according to claim 1 or 2, wherein the second running surface (L2) and / or the third running surface (L3) includes a wear protection portion and / or a familiar running layer (12). Complete set.   The set of piston rings according to any one of claims 1 to 3, wherein the first piston ring (K1) is formed of a wear-resistant material.   The set of piston rings according to any one of claims 1 to 4, wherein the second piston ring (K2) is formed of a wear-resistant material.   6. A set of piston rings according to any one of claims 1 to 5, wherein the third piston ring (K3) and / or the further piston ring is made of a wear-resistant material.   The set of piston rings according to any one of claims 1 to 6, wherein the wear protection portion is a wear protection coating (6).   The thickness (S2) of the wear protection coating (6) of the second piston ring (K2) and / or the thickness (S3) of the wear protection coating (6) of the third piston ring (K3), and / or Alternatively, the thickness of the wear protection coating of the further piston ring is 100% of the thickness (S1) of the wear protection coating (6) of the first piston ring (K1) or the thickness (S1). 3/4, or preferably 1/2 of thickness (S1), or 1/3 of thickness (S1), or 1/4 of thickness (S1), or thickness (S1) The piston ring set according to any one of claims 1 to 7, wherein the piston ring is 10% at the maximum.   The running surface (L1, L2, L3) of the first piston ring (K1) and / or the second piston ring (K2) and / or the third piston ring (K3) and / or the further piston ring The piston ring set according to any one of claims 1 to 8, wherein the piston ring is designed in a convex shape toward the cylinder operation surface of the cylinder wall (3).   The running surface (L1, L2, L3) of the first piston ring (K1) and / or the second piston ring (K2) and / or the third piston ring (K3) and / or the further piston ring Is designed symmetrically and / or asymmetrically in the direction of the cylinder working surface (7) with respect to the central plane (II) of each piston ring (K1, K2, K3) A set of piston rings described in any one of the above.   The running surface of the first piston ring (K1) and / or the second piston ring (K2) and / or the third piston ring (K3) and / or the further piston ring is the combustion chamber (5 The piston ring set according to any one of claims 1 to 10, wherein the piston ring is designed asymmetrically in a direction toward ().   The traveling surface of the first piston ring (K1) and / or the second piston ring (K2) and / or the third piston ring (K3) and / or the further piston ring is the cylinder traveling surface ( 7) in a direction towards the piston plane (K1, K2, K3) asymmetrically convex with respect to the central plane (II) of the piston ring (K1, K2, K3), in particular asymmetrically convex, especially in a direction away from the combustion chamber (5) The set of piston rings according to any one of claims 1 to 11, which is designed as follows.   Said wear protection is made of chromium and / or aluminum oxide and / or silicate and / or diamond particles and / or chromium ceramic, in particular Tritor, and / or CKS-36 and / or CKS-37 and / or carbide, in particular The set of piston rings according to any one of claims 1 to 12, comprising chromium carbide.   A piston comprising the set of piston rings according to any one of claims 1 to 13.

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