JP2014114817A - Gas exchange valve and method for manufacturing the gas exchange valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas exchange valve that is used for a reciprocating piston internal combustion engine, and to provide its manufacturing method.SOLUTION: A gas exchange valve 1 comprises a valve shaft 2 extending along an axial valve shaft axis A, and a valve body having a valve disc 3 connected to the valve shaft 2. This valve disc 3 extends apart from the valve shaft 2 in an axial direction, and extends spreading outside in the radial direction to the valve shaft axis A. A valve mating surface 32 is formed in the valve disc 3 between a lower surface 31 of the valve disc 3 formed substantially perpendicular to the valve shaft axis A and the valve shaft 2. According to the present invention, a recess 4 in the form of a first coating recess 41 is provided at a lower surface 31 of the valve disc, and a corrosion protection coating 5 in the form of a first etching protective layer 51 is provided in this coating recess 41.

Description

  The present invention relates to a gas exchange valve for a reciprocating internal combustion engine, in particular a discharge valve for a longitudinal scavenging large two-stroke diesel engine, and a method for producing the gas exchange valve according to the preceding stage of the independent claims of each category.

  Protective coatings against hot corrosion, often referred to simply as hot corrosion or hot gas corrosion, are well known in the prior art. These are understood to be surface layer protective coatings which have a high resistance to, for example, corrosion, especially oxidation or sulfidation in high temperatures and chemically harsh environments. They are produced, for example, by thermal spraying, and MCrAlY layers are widely used as hot corrosion protection. In this context, the metal M can be, for example, iron, cobalt or nickel or an alloy of these or other metals. Also, for example, an aluminum chrome layer formed by chromizing exhibits generally good resistance to high temperature corrosion, especially to oxide-containing media, in many applications.

  The phenomenon of hot corrosion generally appears in this respect where there are relatively high process temperatures that are well above several hundred to 1000 ° C., and often such high temperatures are only responsible for the appearance of the corrosion effect. But also found in chemically harsh environmental conditions that can be tied back to combustion products or other chemical reaction products or brought about by mixtures in fuels, lubricants, etc. it can.

  Thus, in particular, workpieces, components and machine parts that are more or less in direct contact with the combustion process are at risk of hot corrosion. Examples of this include piston surfaces of internal combustion engines pistons, cylinder walls, cylinder covers, injection nozzles, gas exchange valves, as well as, for example, turbochargers, in particular turbine components and / or exhaust supply or exhaust extraction and turbocharger systems Etc., which are components of an exhaust gas system of an internal combustion engine

  In this connection, large diesel combustion motors are often composed of a nickel-based alloy (superalloy), such as Nimonic 80A. This nickel-based alloy has adequate corrosion resistance against aggressive media generated by heavy oil combustion. A cost-effective deformation compared to nickel-based alloys is the use of corrosion-resistant chromium nickel steel for the manufacture of valve bodies. However, this corrosion-related property does not reach that of nickel-base alloys. In order to adapt the corresponding properties of these steels to the corresponding requirements, the areas at risk of corrosion of these gas exchange valves can be deposited in multiple layers by means of welding, for example approximately 6 to 9 layers. Are known. The heat introduced by welding in this connection leads to strong intrinsic stresses in the valve body and deformation of the parts, thus increasing the risk of crack formation in the valve body.

  This well-known problem situation is described below with reference to FIG.

  In this regard, at this stage, the reference signs provided for example features relating to the state of the art include inverse commas, whereas features relating to embodiments according to the invention do not have inverse commas. It should be noted that.

  FIG. 1 schematically shows an exhaust valve, which is well known from the state of the art of a large longitudinal scavenging two-stroke diesel engine.

  1 includes a valve body having a valve shaft 2 ′ extending along an axial valve shaft axis A ′ and a valve disk 3 ′ joined to the valve shaft 2 ′. It extends away from the shaft 2 'in the axial direction and extends radially outward with respect to the valve shaft axis A'. In this connection, the valve disc 3 between the lower surface 31 'of the valve disc 3' and the valve shaft 2 ', in which the valve mating surface 32' is formed substantially perpendicular to the valve shaft axis A '. 'Made to.

  In the installed state, the bottom surface 31 ′ of the valve disc 3 ′ facing the surface of the piston moving in the cylinder of the large diesel engine, is deposited continuously on top of each other. Provided for protection of the lower surface 31 'against aggressive, thermal, chemical and physical loads due to combustion processes in the cylinder in the operating state in the form of protective layers 51', 52 ' There is a corrosion protection coating 5 '. In this regard, the corrosion protection coating 5 'of the discharge valve 1' of FIG. 1 is spread over the entire radius R1 'of the lower surface 31'.

  Corrosion protection coatings 5 'deposited in multiple layers on the lower surface 31' in this connection often have roughly 6 to 9 layers deposited in succession, although only two layers are That is, two corrosion protection coatings 51 ', 52' are shown in FIG. 1 for clarity. The heat introduced by welding in this connection results in a strong intrinsic stress Z 'in the valve body, but not only in the region of the valve disk 3', in particular indicated by Z 'in FIG. During weld welding, these result in a component deformation W 'indicated by the arrow W' in FIG. 1, which in particular greatly increases the risk of crack formation in the valve body. In addition, the risk of hot cracking and the formation of repeated melt cracks in the weld weld increases with the heat introduced.

  As a result of the component deformation W ′, the valve disc 3 ′ swells very strongly in the direction away from the valve shaft 2 ′ as a result of multilayer welding, so that an additional corrosion protection layer 52 ′ in the center of the valve disc 3 ′ is added. The welding of the layers requires a machining allowance to offset the component deformation W ′ again so that a flat surface is again secured at the lower surface 31 ′.

  In this context, it should be noted that the welding of each further layer can increase the risk of hot crack formation and repeated weld cracking and lead to further component deformation W ′. . Furthermore, as already mentioned, the intrinsic stress Z 'arises due to the welding heat introduced, in particular in an important area of the transition from the valve shaft 2' to the valve disc 3 '. In this regard, the mechanical load on the discharge valve 1 'is significant and the intrinsic stress Z' promotes crack formation.

  For this purpose, the object of the present invention is to avoid component deformation during weld welding and / or to bring about a large reduction in component deformation during weld welding, and thus in the valve body, in particular valve To avoid the accompanying inherent stress reduction and critical crack formation in the welded corrosion protection layer in the critical region where the shaft transitions to the valve disc.

  The means of the invention that fulfill this purpose are characterized by the features of the independent claims.

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

  Accordingly, the present invention relates to a gas exchange valve for a reciprocating piston internal combustion engine, and more particularly to a longitudinal scavenging large two-stroke diesel engine exhaust valve, the gas exchange valve extending along an axial valve shaft axis and the valve A valve body having a valve disk joined to the shaft, the valve disk extending axially away from the valve shaft and extending radially outward relative to the valve shaft axis. In this connection, a valve mating surface is formed in the valve disc between the lower surface of the valve disc and the valve shaft, which is formed substantially perpendicular to the valve shaft axis. According to the invention, a recess in the form of a first coating recess is provided in the lower surface of the valve disk, and this coating recess is provided with a corrosion protection coating in the form of a first corrosion protection layer.

  In accordance with the present invention, the construction is due to the fact that the corrosion protection coating is not welded directly to the flat outer surface of the lower surface of the valve disk, but rather is welded into a coating recess machined into the lower surface of the valve disk. Element deformation can be substantially prevented during weld welding and can generally be completely prevented with respect to technically relevant dimensions.

  The important reason for this is that the introduction of heat into the valve disc no longer occurs over the entire lower surface and essentially only parallel to the valve shaft axis, rather, the valve shaft axis of the valve according to the invention. The introduction of heat should also include an essential component that is perpendicular to the valve shaft axis.

  Furthermore, if at least only a first recess in the form of a first coating recess is provided on the lower surface of the valve disk and / or if the outer boundary area of the lower surface is not provided with a corrosion protection layer, Since the outer boundary region is not strongly applied with heat introduced during the weld welding, component deformation can therefore also be significantly reduced and / or completely prevented.

  Particularly preferably, the corrosion protection coating comprises at least a second corrosion protection layer, which can be provided in particular in the second coating recess. In this connection, the first corrosion protection layer is particularly preferably provided in the region between the valve shaft and the second corrosion protection layer, in practice the second corrosion protection layer is the first corrosion protection layer. Welded directly on the protective layer.

  Due to the fact that at least the first and second corrosion protection layers are preferably welded directly onto each other in the first coating recess and / or the second coating recess, respectively, the welding heat introduced corresponds. Can be reduced for each welding process. Each of these welding processes further reduces and / or substantially completely prevents harmful component deformations known from the state of the art. A reduction in the total introduction of heat into the valve disk can thus be achieved advantageously by reducing the number of weld layers and the weld area.

  In this connection, in a preferred embodiment, first through the use of a coating recess according to the invention, only a single corrosion protection layer arranged on the lower surface, preferably in the central region around the valve axis, It should be noted that sufficient corrosion protection can be achieved. In this way, the overall heat introduction to the valve disc can naturally be greatly reduced, so the risk of component deformation as a result of weld welding can actually be completely eliminated. .

  In this connection, the corrosion of the lower surface of the valve disc is, for example, very strong in the region about 2/3 of the diameter of the lower surface of the valve disc, and at most less than the aforementioned inner region. It is shown to be up to about 3/4 of the diameter. Furthermore, depending on the field of application and the operating conditions of the motor (internal combustion engine), for example, the corrosion load is greatest in a ring-shaped region radially spaced from the central welding shaft axis and the corrosion load is It may be possible to decrease within the region radially in and radially outward. It should be understood that the foregoing description may have values or geometries that are actually offset and will depend on the motor, its load, etc.

  For this reason, the outer boundary of the first corrosion protection layer is formed in a circle with an outer boundary radius around the valve shaft axis for certain embodiments of the present invention, for example, the corrosion load is often under the valve. When prevailing in a circular area of the lower surface, also referred to as the side, the first corrosion protection layer can also be formed in an annulus with a predetermined inner boundary radius around the valve shaft axis or in principle also different Appropriate geometry can be taken.

  In practice, the corrosion protection coating can of course also include at least a second corrosion protection layer or even an additional protection layer, which is preferably but not necessarily the second protection layer. And, in some cases, an additional corrosion protection layer can likewise be provided in the corresponding coating recess.

  In this connection, the first corrosion protection layer is, although not necessarily, particularly preferably provided in the region between the valve shaft and the second corrosion protection layer, outside the second corrosion protection layer. The boundary line can be configured, for example, in a circle with an outer boundary radius around the valve shaft, but of course can take any other suitable geometry.

  For example, a first corrosion protection layer and / or a second corrosion protection layer may be provided on the valve disk to better handle the gas exchange valve during installation or removal or for all other surfacing operations. It can be provided in a manner known per se around the service hole. In practice, the service hole can have an internal thread to which, for example, a handling device for a more comfortable handling of the gas exchange valve can be screwed. It should be understood that the service hole is preferably introduced first when the corrosion protection coating is already welded.

  In this connection, the corrosion coating itself is composed of any suitable material, and the material to be used can be selected according to the requirements of the person skilled in the art. In this context, in practice it can be known to use nickel-based corrosion protection coatings, in particular corrosion protection coatings made from nickel-based alloys containing at least nickel and chromium, the chromium content preferably being Between 10% and 60% chromium, more particularly between 15% and 50% chromium, particularly preferably between 20% and 45% chromium. For example, 43% by weight.

  In this connection, the first corrosion protection layer can be manufactured from the same material as the second corrosion protection layer, but in particular two or more corrosion protection layers of different materials can also be used. Is possible.

  The valve body of the gas exchange valve can of course also be produced in this connection from any suitable material, but is particularly preferably made from chromium nickel steel, in particular iron-containing corrosion coating. The amount is less than 5% by weight, preferably between 0.5% and 4% by weight, more specifically less than 3% by weight.

  The invention further relates to a method for manufacturing a gas exchange valve as described in detail above, in which a valve body is provided and a recess in the form of a first coating recess and / or a second coating recess. Is provided on the lower surface of the valve disc of the valve body of the gas exchange valve. In this connection, a corrosion protection coating in the form of a first corrosion protection layer and / or a second corrosion protection layer is provided in the first coating recess and / or the second coating recess.

  In this connection, the first corrosion protection layer and / or the second corrosion protection layer can be applied by welding, in particular by metal protective gas welding, the corrosion protection coating comprising at least nickel and chromium. Made from containing nickel base alloy. The chromium content is particularly preferably between 10% and 60% by weight of chromium, more specifically between 15% and 50% by weight of chromium, particularly preferably 20% by weight. Between 45% chromium by weight.

  In this connection, metal protective gas welding is a welding method known from the technical field, the principle of which is briefly described below for the sake of clarity. Metal protective gas welding, often abbreviated as MSG, is known for its different variants, for example as metal welding with inert gas, as MIG welding or as MAG welding. , Meaning that it is a light arc welding method in terms of the basic principle that it can react and the melt welding wire is often automatically and continuously supplied by a variable speed motor. Commonly used welding wire diameters are, for example, between 0.6 mm and 2 mm, or even up to 3 mm. At the time of wire feeding, protection or gas mixture is supplied to the welding point by a nozzle in a predefinable amount that is naturally determined by the particular application. The supplied gas in particular protects the liquid metal under the light arc from chemical changes, in particular from oxidation which weakens the weld bead. In this connection, in so-called MAG welding (MAG), people often work with pure CO2 or argon and a small amount of CO2 and O2 mixed gas, and in MIG welding (MIG) the inert gas argon is Often used, and in rare cases, the expensive inert gas helium is also used. In this connection, the MAG method is mainly used in practice mainly for steel, and the MIG method is preferably used for NE metal.

  Filling wires can of course also optionally be used for metal protective gas welding. These can be provided with slag forming materials and optionally alloy additives inside. They are used for the same purpose as the encapsulation of the wire electrode. On the one hand, the components contribute to the weld volume, on the other hand they form slag and protect the weld location from oxidation.

  In this context, the valve body of the gas exchange valve according to the invention can be produced, for example, from chromium-nickel steel or from different materials, particularly preferably the metal protective gas welding described above is a metal protective In gas welding, in order to achieve an iron content of the corrosion protection coating of less than 5% by weight, preferably between 0.5% and 4% by weight, in particular less than 3% by weight, is achieved. Used as a welding process.

  In the following, the present invention will be described in detail with reference to the schematic drawings.

FIG. 1 is a discharge valve of a large two-stroke diesel engine known from the state of the art. FIG. 2a is a first embodiment of a gas exchange valve according to the present invention. FIG. 2b is a second embodiment of a gas exchange valve according to the present invention having two coating recesses. FIG. 2c is a different embodiment according to FIG. 2b. FIG. 2d is a different embodiment according to FIG. 2b with a service hole and a coating valve seat. FIG. 2e is an embodiment of a gas exchange valve according to the present invention having a ring-shaped coating recess.

  The exhaust valve of the large two-stroke diesel engine according to FIG. 1, which is known from the state of the art, has already been discussed in detail in the introduction and therefore does not need to be discussed further at this stage.

  FIG. 2a shows a first simplified embodiment of a gas exchange valve according to the invention, which is indicated in the following using the reference numeral 1 as a whole.

  The specific embodiment of the gas exchange valve 1 according to the invention for the reciprocating piston internal combustion engine of FIG. 2a is in this example an exhaust valve for a longitudinal scavenging large two-stroke diesel engine. The gas exchange valve 1 includes a valve body 2 having a valve shaft 2 extending along an axial valve shaft axis A and a valve disk 3 joined to the valve shaft 2, and the valve disk 3 is axially extended from the valve shaft 2. It extends away from the valve shaft axis A and extends radially outward. In this connection, a valve mating surface 32 is created in the valve disc 3 between the lower surface 31 of the valve disc 3 and the valve shaft 2, which is formed substantially perpendicular to the valve shaft axis A. This lower surface is often also referred to by those skilled in the art as simply the bottom side of the valve disc. According to the invention, a recess 4 in the form of a first coating recess 41 is provided in the lower surface 31 of the valve disc 3, in which the corrosion protection in the form of a first corrosion protection layer 51 is provided. A coating 5 is provided. In this connection, the coating recess 41 can be machined using known methods before applying the corrosion protection layer 51. The outer boundary line of the first corrosion protection layer 51 is formed in a circle having an outer boundary radius R1 around the valve shaft axis A for this example.

  The corrosion protection layer 51 is applied in this example using weld welding, preferably using metal protective gas welding as described in more detail above with different variations.

  Referring to FIG. 2b, a second embodiment of the gas exchange valve 1 according to the invention with two coating recesses 41, 42 is schematically shown, which is very important especially in practice. The embodiment of FIG. 2b differs from that of FIG. 2a in that, in this example, the corrosion protection coating 5 includes at least a Dow 2 corrosion protection layer 52, the corrosion protection layer 52 being a second coating recess 42. The first corrosion protection layer 51 is welded immediately below the second corrosion protection layer 52 in a region between the valve shaft 2 and the second corrosion protection layer 52.

  In this connection, the outer boundary line of the second corrosion protection layer 52 is formed around the valve shaft axis A with an outer boundary radius R 2, which is smaller than the radius of the lower surface 31.

  In this context, however, the outer boundary radius R2 can also be substantially the same as the radius of the lower surface 31, as schematically illustrated by FIG. 2c. This is because, for the embodiment of FIG. 2 c, the second coating recess 42 is actually the same as the surface of the first corrosion protection layer 51 and the remaining surface of the lower surface 31 is defined by the first corrosion protection layer 51. It means not covered.

  In this connection, service holes 6 are often provided in the lower surface 31 in a well-known manner, as schematically shown in FIG. 2d. This service hole preferably includes an internal thread so that the handling tool can be screwed into the service hole 6 for installation and service work.

  FIG. 2 e finally shows a different specific embodiment of the gas exchange valve 1 according to the invention with a ring-shaped coating recess 41. This means that the first corrosion protection layer 51 is arranged annularly around the valve shaft axis A, for example, with an inner boundary radius R12 and an outer boundary radius R1.

  The embodiment according to FIG. 2e also provides that when the corrosion load occurs particularly strongly in the region of the ring-shaped corrosion protection layer 51 and is not very intense inside and outside the ring-shaped corrosion protection layer 51 so that the corrosion protection layer can be omitted. It can be used particularly advantageously.

  The specific embodiments of the present invention described in the context of the present application are to be understood merely as examples, and the present invention will of course also be apparent to all suitable combinations of the described embodiments, as well as to those skilled in the art. It is of course understood that further developments of the invention relating to the scope of protection described in the claims are also included.

  Therefore, according to the present invention, the application of a highly corrosive protective layer according to requirements has been proposed for gas exchange valves for internal combustion engines using for the first time a greatly reduced heat introduction. For example, in areas with strong corrosion, the corrosion protection layer has a large layer thickness, preferably corresponding to the previously provided coating recess in the lower upper surface of the valve disk, and in areas with low corrosion. Can be attached with a small layer thickness. Depending on the corrosion load, in this regard, for example, an outer region that is spaced a predetermined distance from the lower surface of the valve shaft, for example, more than 3/4 of the diameter, can also be configured without plating. This also means that there is no weld-deposited corrosion protection layer. The shape of the plating carried out in accordance with the present invention is such that deformation is minimized or complete so that multiple weld layer weld welds for compensation of component deformation at the lower surface known from the state of the art are no longer required. Even decrease. This means that the final machining of the plating can very often be omitted when preparing the weld bead through deformations that are greatly minimized and / or substantially no longer present. However, this means that the coating recess according to the invention is machined into the valve disc base prior to the welding process, and the thickness of the weld weld corresponds to the depth of the coating recess.

Claims (15)

A valve body extending along an axial valve shaft axis, and a valve body having a valve disk joined to the valve shaft, the valve disk extending away from the valve shaft in the axial direction and extending to the valve shaft axis In contrast, extending radially outward,
A valve mating surface is formed on the valve disk between the valve shaft and the lower surface of the valve disk formed substantially orthogonal to the valve shaft axis;
A gas exchange valve for a reciprocating piston internal combustion engine, in particular a discharge valve for a longitudinal scavenging large two-stroke diesel engine,
A recess in the form of a first coating recess is provided in the lower surface of the valve disk, and the coating recess is provided with a corrosion protection coating in the form of a first corrosion protection layer;
Gas exchange valve. An outer boundary line of the first corrosion protection layer is formed in a circle having an outer boundary radius around the valve shaft axis;
The gas exchange valve according to claim 1. The first corrosion protection layer is formed in an annular shape around the valve shaft axis and having an inner boundary radius.
The gas exchange valve according to claim 1 or 2. The corrosion protection coating includes at least a second corrosion protection layer;
The gas exchange valve according to any one of claims 1 to 3. The second corrosion protection layer is provided in a second coating recess;
The gas exchange valve according to claim 4. The first corrosion protection layer is provided in a region between the valve shaft and the second corrosion protection layer;
The gas exchange valve according to claim 4 or 5. An outer boundary line of the second corrosion protection layer is configured in a circle around the valve shaft and having an outer boundary radius;
The gas exchange valve according to any one of claims 4 to 6. The first corrosion protection layer and / or the second corrosion protection layer is provided around a service hole provided in the valve disk.
The gas exchange valve according to any one of claims 1 to 7. The corrosion coating is a nickel-based corrosion protection coating;
The gas exchange valve according to any one of claims 1 to 8. The corrosion coating is made from a nickel-based alloy comprising at least nickel and chromium;
The chromium content is preferably between 10% and 60% by weight of chromium, more specifically between 15% and 50% by weight of chromium, particularly preferably 20% by weight. And 45% by weight chromium,
The gas exchange valve according to any one of claims 1 to 9. The first corrosion protection layer is made of the same material as the second corrosion protection layer;
The gas exchange valve according to any one of claims 1 to 10. The valve body of the gas exchange valve is manufactured from chrome nickel steel and / or the iron content of the corrosion coating is less than 5% by weight, preferably between 0.5% and 4% by weight. In between, more specifically less than 3% by weight,
The gas exchange valve according to any one of claims 1 to 11. A method for manufacturing a gas exchange valve according to any one of claims 1 to 12,
A valve body is provided,
A recess in the form of a first coating recess and / or a second coating recess is provided in the lower surface of the valve disc of the valve body of the gas exchange valve;
A corrosion protection coating in the form of a first corrosion protection layer and / or a second corrosion protection layer is provided in the first coating recess and / or the second coating recess;
Method. The first corrosion protection layer and / or the second corrosion protection layer is applied by welding, in particular by metal protective gas welding;
The method of claim 13. The corrosion protection coating is made from a nickel base alloy comprising at least nickel and chromium;
The chromium content is preferably between 10 wt% and 60 wt% chromium, more specifically between 15 wt% and 50 wt% chromium, particularly preferably 20 wt% and 45 wt%. Selected between weight percent chromium and
The valve body of the gas exchange valve is preferably manufactured from chromium nickel steel so that the metal protective gas welding achieves an iron content of the corrosion protective coating of less than 5% by weight in the metal protective gas welding. Used as a welding process to be achieved between 0.5% and 4% by weight, more specifically less than 3% by weight,
15. A method according to claim 13 or 14.

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