EP1565646A1

EP1565646A1 - Valve seat and method for producing a valve seat

Info

Publication number: EP1565646A1
Application number: EP03811739A
Authority: EP
Inventors: Reiner Heigl
Original assignee: DaimlerChrysler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2002-11-28
Filing date: 2003-10-21
Publication date: 2005-08-24
Also published as: WO2004048756A1; JP2006516313A; DE10255447A1; US20060162686A1

Abstract

The invention relates to a valve seat (5) for a cylinder head (1) of an internal combustion engine, comprising an additional material that is fused with the base material of the cylinder head. The additional material comprises at least two layers lying one on top of the other, the inner layer (6) facing the cylinder head having excellent bonding characteristics with the base material of the cylinder head and the outer layer (7) facing away from the cylinder head having excellent strength and wear characteristics.

Description

Valve seat and method for manufacturing a valve seat

The invention relates to a valve seat for a cylinder head of an internal combustion engine as defined in the preamble of claim 1. The invention further relates to a method for producing a valve seat for a cylinder head of an internal combustion engine as defined in the preamble of claim 10.

DE 199 12 889 AI describes a generic valve seat and a generic method for producing the same. An additional material, namely an alloy or a mixture of an aluminum-silicon alloy and nickel, is fused to the base material of the cylinder head by a laser beam.

From DE 35 17 077 Cl a method for armoring the valve seat surface of a gas exchange valve is known, in which armor material consisting of a nickel or cobalt-based superalloy is preferably introduced into a circumferential recess on the valve plate.

DE 199 12 894 A1 describes a method for coating the surface of metal workpieces with a filler material in powder or wire form. Another such method is known from EP 00 92 683 B1. The base material of the cylinder head consists essentially of aluminum and as an additional material for forming the valve seat either iron or nickel or an alloy with one of these two metals is used as the main component.

The disadvantage here is that iron and nickel have a much higher melting point than the cylinder head made of aluminum. This can lead to the fact that when a laser beam is applied, the cylinder head may already have melted when the additional material only begins to melt. It can also happen that the previously liquid iron has already solidified while the aluminum is still in the form of a melt. This leads to the formation of intermetallic phases in the border area between iron and aluminum material, which can result in a very brittle structure. It is therefore difficult to achieve a homogeneous connection between the valve seat to be created and the base material of the cylinder head, the different surface tensions of the materials also playing an important role here.

EP 02 28 282 B1 describes a cylinder head consisting of an aluminum alloy. The valve seats of this cylinder head are made of a plated copper alloy layer.

If copper is used as the material for valve seats, however, the disadvantage arises in particular in diesel internal combustion engines that the sulfur contained in the diesel fuel attacks the copper, which causes problems with regard to exhaust gas development and corrosion. The use of copper for valve seats is therefore only for Internal combustion engines make sense and can therefore not be used in an economical manner.

DE 196 39 480 AI describes a method for the inner coating of cylinder surfaces by means of powdery additives which are alloyed by laser radiation.

A method for surface coating of light metal components, in particular light metal pistons of internal combustion engines, with a strength-increasing and / or wear-resistant filler material is apparent from DE 22 00 003 AI.

For further prior art relating to valve seats for internal combustion engines and methods for their production, reference is also made to the following documents: US 4,059,876, JP 05256190 A, JP 07284970 A, JP 08047787 A, JP 08224680 A, JP 08224681 A, JP 08224682 A, JP 08224683 A, JP 10141132 A, JP 10176511 A, JP 11002154 A, EP 02 09 366 AI, US 4,723,518, JP 02196117 A, JP 04123885 A, JP 06042320 A and JP 08174245 A.

If the valve seat is to be fused with the base material of the cylinder head as an additional material, there is regularly the problem that this additional material has both the adhesion to the base material of the cylinder head and the strength properties for absorbing the forces introduced by the gas exchange valve and the tribological properties for minimizing wear must ensure on the surface of the valve seat. This defines very complex boundary conditions for the selection of the materials, which is reflected in the state of the art through the most varied of proposals for the use of certain materials. So far, however, no solution has been so convincing that it has been a long press in the valve seat rings used in practice.

It is therefore an object of the present invention to provide a valve seat for a cylinder head of an internal combustion engine and a method for its production which have both good adhesion to the base material of the cylinder head and good strength and wear properties.

According to the invention, this object is achieved by the features mentioned in claim 1.

By means of the two layers lying one above the other, the very different tasks that the valve seat has to fulfill can advantageously be divided. According to the invention, the inner layer facing the cylinder head can take over the task of connecting the valve seat to the base material of the cylinder head, and the outer layer facing away from the cylinder head can be designed so that it has good strength and wear properties for the valve seat.

This advantageously improves the adhesion of the valve seat to the cylinder head, which prevents the entire valve seat from detaching from the cylinder head. Nevertheless, due to the design of the outer layer, higher loads with lower wear rates on the valve seat according to the invention are possible. Overall, this results in a considerably expanded range of materials, especially with regard to the different requirements of gasoline and diesel engines.

If, in an advantageous embodiment of the invention, the inner layer has good heat conduction properties points, the heat dissipation from the valve seat surface into the cylinder head is advantageously improved in that the air gap between the valve seat and the cylinder head is avoided by the melt-metallurgical connection.

In the case of aluminum cylinder heads in particular, it has proven to be advantageous if the inner layer has copper or a copper alloy, since just such a material combines with the aluminum material of the cylinder head. In this context, the outer layer prevents the copper material of the inner layer from coming into contact with sulfur-containing fuel or exhaust gas constituents and can thus worsen the emission values.

Furthermore, it can be provided that the outer layer has nickel, iron and / or cobalt or an alloy with at least one of these materials. These materials have proven to be particularly hard and wear-resistant and have a very high strength. Another advantage of these materials is the good connectivity with the copper material of the inner layer that may be used.

A procedural solution results from the features of claim 10.

By means of this sequential method, the at least two layers according to the invention can be connected to the base material of the cylinder head in a particularly simple and process-reliable manner, the advantageous properties of the valve seat explained above being retained.

A process that is particularly efficient in terms of production technology results if the inner layer is placed on the cylinder head in the form of a fixed ring and the outer right layer in powder form is applied to the inner layer.

Further advantageous refinements and developments of the invention result from the remaining subclaims and from the exemplary embodiments shown in principle below with reference to the drawing.

Show:

1 shows a section through an inventive valve seat for a cylinder head of an internal combustion engine.

2 shows an embodiment for carrying out the method according to the invention;

3 shows a further embodiment for carrying out the method according to the invention; and

Fig. 4 shows a further embodiment of the method according to the invention.

Fig. 1 shows part of a cylinder head 1 of an internal combustion engine, not shown in its entirety. The cylinder head 1 has, in a manner known per se, an inlet duct 2 which can be closed or opened by a gas exchange valve 3. When the gas exchange valve 3 is open, a fuel / air mixture can enter the combustion chamber 4 in a manner known per se and is located below the cylinder head 1. The cylinder head 1 also has a valve seat 5, against which the gas exchange valve 3 rests in its closed state and in this way separates the inlet duct 2 from the combustion chamber 4. As can be seen also from FIG. 1, the valve seat 5 has two formed of respective additional material layers 6 and 7, namely a lower or inner, the Zy ^¬ linder head 1 facing layer 6 and an upper or outer, the cylinder head 1 facing away from and Layer 7 facing gas exchange valve 3. Inner layer 6 serves to connect valve seat 5 to cylinder head 1 and therefore has good connection properties to the base material of cylinder head 1. The outer layer 7, on the other hand, has good strength and wear properties in order to be able to absorb the forces acting on the valve seat 5 through the gas exchange valve 3.

Since the cylinder head 1 in the present case consists of a light metal, in particular aluminum, copper or a copper alloy is used for the inner layer 6, since this material has a particularly good affinity for aluminum. When using the alloy CuAlio, ie a copper alloy with 10 percent by weight aluminum, the inner layer 6 is well bonded to the material of the cylinder head 1. Iron has also proven to be a suitable alloy component for the inner layer. However, pure copper can also be used for the inner layer 6.

In addition to the good connection properties to the base material of the cylinder head 1, the inner layer 6 also has good heat conduction properties in order to achieve an improvement in heat dissipation from the surface of the valve seat 5 into the cylinder head 1. The air-gap between the valve seat 5 and the cylinder head 1 is avoided by the melting metallurgical application. In this context, the thermal conductivity of copper at 20 ° C is approx. 350 - 400 W / mK, that of aluminum at 20 ° C is approx. 200 - 250 W / mK and that of the alloy used for the inner layer 6 at 20 ° C. approx. 200-400 W / mK.

In order to achieve the necessary strength and wear or hardness properties of the outer layer 7, nickel, iron and / or cobalt or an alloy with at least one of these materials is preferably used for the same. Although such a material may have a tendency to form intermetallic phases when it is connected to the aluminum of the cylinder head 1, which could lead to cracking, the outer layer 7 is not connected to the cylinder head 1 due to the presence of the inner layer 6, so that such intermetallic phases do not occur.

Chromium, silicon and molybdenum have proven to be particularly suitable as further alloy constituents for the material of the outer layer 7. Some alloys that can be used for the outer layer 7 are given below by way of example, wherein in addition to the three elements mentioned above, other elements are also used as further alloy components: Co25Crl0Ni7W0.5C, Co28Mo8Cr2Si, Co28Mol7Cr3Si, Nil7Cr6A10.5Y, Ni22CrlOAll .0Y, Ni25Cr6A10.4Y, Ni31CrllA10.6Y, Ni23Co20Cr8.5A14Ta0.6Y, Nil5Cr4Si3Fe3B0.75C, Ni21.5Cr8.5Mo3Fe0.5Co, Nil9Crl8Fe3MolColTi or Ni8.5Cr3T2A15M2C2Ti. Of course, this list makes no claim to completeness and materials used in commercially available valve seat rings can be used. The choice of material also depends, among other things, on whether the cylinder head 1 is used in an Otto or a diesel internal combustion engine.

If other materials are used for the cylinder head 1, the two can of course also be used Layers 6 and 7 are made of other materials which ensure that the inner layer 6 has good bonding properties to the base material of the cylinder head 1 and the outer layer 7 has good strength and wear properties.

FIGS. 2 and 3 show two different methods for producing the valve seat 5 by fusing the additional materials specified above with the cylinder head 1, only the attachment of the inner layer 6 on the cylinder head 1 being shown in each case.

2, a nozzle 8 is arranged in the region of the valve seat 5 to be formed, which nozzle 8 outputs the additional material for forming the inner layer 6 in the direction of the cylinder head 1. As soon as the additional material hits the cylinder head 1 or in a groove formed in the same, it is melted simultaneously by the process of a laser beam 9 together with the outer layer of the base material of the cylinder head 1 in order to produce a melt 10 on the cylinder head 1. During the production of the groove, the machining pre-processing is coordinated with the coating process. Instead of the described laser beam 9, the use of an electron beam (not shown) or a suitable device is also possible as an energy source in order to generate the melt 10 from the additional material 7 by applying or introducing energy. The additional material 7 is applied in powder form, application as a tape also being possible.

In order to achieve a progressing process, the nozzle 8 and the laser beam 9 are continuously moved in a circular movement corresponding to the contour of the valve seat 5. When the laser beam 9 moves away from the melt 10 in the feed direction according to arrow A. has solidified to the inner layer 6. This is a so-called one-step process.

Fig. 3 shows an alternative method for producing the valve seat 5, in which the additional material, for example in the form of a paste, a wire, a sintered body or a powder preform, preferably placed in a ring shape in a groove of the cylinder head 1 or applied to it and then with the same Laser beam 9 or an electron beam is melted into the melt 10. In this case too, the inner layer 6 of the valve seat 5 arises from the melt 10 after the removal of the laser beam 9 in the direction of arrow A. This method is referred to as a two-stage process.

The outer layer 7 can be applied in a very similar manner in both methods, which of course is not fused to the cylinder head 1 but to the inner layer 6. A combination of these two methods is also possible, in which, for example, the inner layer 6 is placed on the cylinder head 1 in the form of a ring and the outer layer 7 can then be connected in powder form to the inner layer 6.

Fig. 4 shows in a very schematic representation another way to carry out the method for manufacturing the valve seat 5. Here are two laser or. Electron beams 9 and 9 'are provided, of which the first laser beam 9 ensures the connection of the inner layer 6 to the cylinder head 1 and the second laser beam 9 ^{1 is} responsible for the connection of the outer layer 7 to the inner layer 6. Since the melt 10 of the inner layer 6 has solidified in the direction of arrow A after only a few millimeters of the distance from the laser beam 9, the second laser beam 9 ′ can be the first -Il¬

Follow the laser beam 9 at a relatively short distance, so that the entire method for producing the valve seat 5 takes only slightly more time than if the valve seat 5 consisted of only one layer. This method can be carried out advantageously if the outer layer 7 is applied in powder form, the material for the inner layer 6 being able to be applied in a manner as described above.

Claims

Patent claims

1. Valve seat for a cylinder head of an internal combustion engine, which has an additional material fused to the base material of the cylinder head, characterized in that the additional material has at least two layers (6, 7) lying one above the other, the inner layer (1) facing the cylinder head (1). 6) has good connection properties to the base material of the cylinder head (1), and the outer layer (7) facing away from the cylinder head (1) has good strength and wear properties.

2. Valve seat according to claim 1, so that the inner layer (6) has good heat conduction properties.

3. Valve seat according to claim 1 or 2, so that the inner layer (6) has copper or a copper alloy.

4. Valve seat according to claim 3, characterized in that the copper alloy has aluminum as an alloy component.

5. Valve seat according to claim 3 or 4, so that the copper alloy has iron as an alloy component.

6. Valve seat according to one of claims 1 to 5, so that the outer layer (7) has nickel, iron and / or cobalt or an alloy with at least one of these materials.

7. Valve seat according to claim 6, d a d u r c h g e k e n n z e i c h n e t that the nickel, iron and / or cobalt alloy has chromium as an alloy component.

8. Valve seat according to claim 6 or 7, which also means that the nickel, iron and / or cobalt alloy has silicon as the alloy component.

9. Valve seat according to claim 6, 7 or 8, d a d u r c h g e k e n n z e i c h n e t that the nickel, iron and / or cobalt alloy has molybdenum as an alloy component.

10. A method for producing a valve seat for a cylinder head of an internal combustion engine according to one of claims 1 to 9, in which the additional material is fused to the cylinder head at the point at which the valve seat is to be formed by the introduction of energy, characterized in that according to the Fusion of the inner layer (6) with the base material of the cylinder head (1), the outer layer (7) with the inner layer (6) is fused by the introduction of energy.

11. The method according to claim 10, so that the additional material is fused to the cylinder head (1) by means of a laser beam (9,9 ').

12. The method according to claim 10, so that the additional material is fused to the cylinder head (1) by means of an electron beam.

13. The method according to claim 10, 11 or 12, characterized in that the inner layer (6) in the form of a fixed ring is placed on the cylinder head (1), and that the outer layer (7) in powder form on the inner layer (6 ) is applied.

14. The method according to claim 10, 11 or 12, so that the inner layer (6) and the outer layer (7) are applied in powder form.

15. The method according to claim 10, 11 or 12, so that the inner layer (6) and the outer layer (7) are applied in the form of a solid ring.