EP3463722A1

EP3463722A1 - Valve seat ring

Info

Publication number: EP3463722A1
Application number: EP17731073.7A
Authority: EP
Inventors: Ekkehard KÖHLER; Dirk EMDE; Ingwar Hünsche; Robert HAMMELMANN; Christian Blecking; Anna SEYFARTH
Original assignee: Bleistahl-Produktions & Co Kg GmbH
Current assignee: Bleistahl-Produktions & Co Kg GmbH
Priority date: 2016-05-24
Filing date: 2017-05-24
Publication date: 2019-04-10
Also published as: CN109195734A; JP2019520475A; CN109195734B; US20190143415A1; US11311936B2; KR102288185B1; KR20190013753A; DE102016109539A1; WO2017202998A1; JP7071931B2

Abstract

The invention relates to a highly heat-conductive valve seat ring (1) having a carrier layer (2) and a functional layer (3), the carrier layer (2) has a solidified copper matrix having 0.10 - 20 wt.% of a solidified component, and the functional layer (3) has a solidified copper matrix which also contains 5 - 35 wt.% of more or more hard phases with respect to the copper matrix.

Description

Valve seat ring The invention relates to a valve seat ring with a carrier layer and a functional layer, each with a very high thermal conductivity. Carrier layer and functional layer each have a copper base. The invention relates in particular to a valve seat ring produced by powder metallurgy.

Valve seat rings of the type mentioned are known for example from Japanese Patent Application JP 6145720 A. This document describes a copper-infiltrated multilayer valve seat ring with Co and Mo contents for internal combustion engines.

In principle, the previously known valve seat rings have the advantage that they have excellent strength. This can be explained in particular with the use of two different material layers. In this case, the carrier material has sufficient strength values while the functional material has the properties essential for the sealing function, such as wear resistance.

However, the prior art valve seat rings of the type mentioned have the disadvantage that they are no longer meet the increasing demands of internal combustion engines due to their poor thermal conductivity. The thermal conductivity of conventional carrier materials is usually below 45 W / mK. High thermal conductivity helps to lower the valve temperature and contributes to an environmentally friendly run. To improve the thermal conductivity of valve seat rings, it is known to infiltrate the rings produced by powder metallurgy with copper. The copper content increases the thermal conductivity, but the absorption capacity of the pores of the material for copper is limited. From DE 10 2012 013 226 A1 valve seat rings are known, which are significantly improved in terms of their thermal conductivity. The rings have an increased copper content in the carrier material, which is introduced via copper alloyed into the carrier matrix, sintered-in copper powder and infiltrated copper. The copper content can be up to 40% by weight of the carrier matrix. With this material a thermal conductivity of up to 80 W / mK can be achieved. In the functional layer can be achieved by the increased copper content, a thermal conductivity of about 50 W / mK maximum.

A further increase in thermal conductivity can no longer be achieved with conventional materials and methods. In particular for the carrier material must be transferred to higher heat conductive materials.

Another problem of conventional valve seat inserts is the dissipation of heat into the cylinder head. For this purpose, an optimization of the heat flow is required, which depends on the one hand by the contact surface of the valve seat ring with the cylinder head, in particular of the carrier material with the cylinder head, on the other hand, but also by the structure of the material. A high porosity as well as disturbances in the material structure counteract a good heat flow.

Basically, however, the two-layer construction of valve seat rings with a carrier matrix and a functional layer has proven itself. In particular, this allows a good dissipation of heat through a carrier matrix with high thermal conductivity. However, with the conventional materials, as used for functional layers, the possibilities for improvement are exhausted.

The problem that occurs is the removal of heat from the functional layer into the cylinder head. The functional layer itself has only one limited contact surface with the cylinder head, so that a heat accumulation can arise here. For this reason, it is necessary to dissipate the heat through the carrier layer into the cylinder head, ie to exploit the contact surface between functional layer and carrier layer on the one hand and between carrier layer and cylinder head on the other hand for heat transfer. Here it makes sense to match the materials with regard to their thermal conductivity.

The functional layer usually contains a hard phase, which significantly reduces the thermal conductivity. As a rule, thermal conductivities are achieved which do not exceed 50 W / mK.

For the individual layers of such a valve seat ring is basically copper as a material with high thermal conductivity. However, pure copper is not suitable because of its low strength and ductility. A copper alloy that has the requisite hardness and strength contains larger amounts of beryllium, a highly toxic metal that should not be used by special applications, such as racing, if possible. Furthermore, alumina is known as a solidifying supplement.

It is an object of the invention to provide a valve seat ring of the aforementioned type, which provides a higher thermal conductivity over the materials. At the same time, this material should have a high heat flux. Incidentally, the valve seat ring should meet the usual requirements for tightness, dimensional stability and strength.

This object is achieved with a powder-metallurgically produced valve seat ring of the type mentioned above, in which the carrier layer consists of a solidified copper matrix containing 0.10 to 20 wt .-% of a solidifying component, and the functional layer also consists of a solidified copper matrix, which further 5 to 35 wt .-%, preferably 5 to 25 wt .-% of a hard phase. In principle, the carrier layer has a thermal conductivity which exceeds the thermal conductivity of the material used for the cylinder head, in particular more than 120 W / mK at 500 ° C. The functional layer should have a thermal conductivity which comes as close as possible to the thermal conductivity of the cylinder head material, that is above 50 W / mK preferably above 70 W / mK at 500 ° C. This can be achieved according to the invention but also with other materials.

The solidifying components of the carrier layer and the functional layer may be the same or different. The valve seat rings according to the invention are so-called double-layer valve seat rings, in which a carrier layer is superimposed as a base with a functional layer. The support layer according to the invention consists of a solidified copper matrix with 0.10 to 20 wt .-%, preferably 0.25 to 15% by weight of one or more solidifying components. Particularly suitable solidifying components are oxides and intermetallic phases.

Suitable solidifying oxides are, for example, alumina, silica and yttrium oxide. Furthermore, the oxides of rare earth metals and titanium dioxide may be mentioned. Preferred solidifying components are alumina, Al 2 O 3, yttria, Y 2 O 3 and titanium oxide Tio 2, which may be added to the copper in an amount of preferably 0.1 to 2.5% by weight. Such a small addition is already sufficient to increase the heat resistance of the copper. At the same time the thermal conductivity is only slightly reduced. Intermetallic phases are in particular those based on Cu, Cr, Nb, Ni, Zr and Si. By way of example, mention may be made of Cr2Nb, CusZr, Cr2Zr, Ni2Si, NisSi, Ni3iSii2 and CuZr. Such intermetallic phases form during the cooling by precipitation from the supersaturated matrix in finely dispersed form. Preference is given to intermetallic phases of chromium and niobium, for example Cr 2 Nb, which can be used, for example, in an amount of from 2 to 15% by weight. Chromium and zirconium with 0.5 to 5 wt .-% go in the same direction.

Another suitable component is nickel-silicon phases, such as Ni2Si, NisSi or Ni3iSii2, for example in an amount of 0.5 to 5 wt .-%.

Finally, the use of copper-zirconium phases, such as CusZr or CuZr in amounts up to 5 wt .-% is also suitable to bring about the solidification. In any case, silver can be mixed, which has the advantage of contributing positively to the thermal conductivity. The silver additive can be up to 10% by weight.

For the functional layer, a solidified copper matrix is used as described above, but with 5 to 35 wt .-%, preferably 5 to 25 wt .-% additionally equipped a hard phase. Such a hard phase is added as alloy powder to the copper powder, wherein the alloy powder can form intermetallic phases. The percentage of hard phase refers to the weight of the solidified copper matrix of the functional layer.

The hard phase may in particular be based on iron, nickel or cobalt. Also in question are carbides, oxide ceramics or nitridic ceramics. It is essential that the hard phase is incorporated in the solidified copper matrix and provides the necessary wear resistance.

As the hard phase, for example, a known iron-based hard phase can be used with cobalt, carbon, molybdenum, vanadium and tungsten. Alternatively, a cobalt hard phase with molybdenum, silicon and chromium, optionally also nickel can be used.

As carbide materials are in particular tungsten carbide, silicon carbide, titanium carbide and chromium carbide in question. Come as oxidic ceramic For example, alumina and as nitridic ceramic titanium nitride, chromium nitride and cubic boron nitride in question.

The functional layer may contain the usual solid lubricants, for example MnS, M0S2, WS2 CaF2 or hexagonal boron nitride, usually in amounts of 0.1 to 5 wt .-%, based on the solidified copper matrix.

An overview of the materials used can be found in Table 1 (carrier materials) and Table 2 (hard phases for the functional material).

The preferred material for solidifying the copper matrix is Al 2 O 3, which already leads in small amounts to the desired solidification. As the hard phase, those based on iron, nickel or cobalt are preferred, in particular of the tribaloy type, such as T400 and T800.

The valve seat ring according to the invention is constructed in two layers in each case. In this case, the dividing line between the layers can run more or less horizontally, ie the two layers rest on one another and combine in the contact zone under pressure and temperature. However, an oblique course of the separating layer is preferred with an angle of up to 65 °, in particular from 35 ° to 65 °, wherein the carrier layer widens outwards and creates a large contact surface to the cylinder head as well as to the functional layer. Particularly preferred are angles of 40 ° to 55 °. The carrier layer of the valve seat rings according to the invention has a thermal conductivity of> 120 W / mK at 500 ° C and preferably of> 220 W / mK at 500 ° C. It is possible to achieve thermal conductivities of more than 300 W / mK at 500 ° C, which corresponds to three to four times the thermal conductivity achievable so far. In the functional layer, thermal conductivities of more than 70 to 250 W / mK at 500 ° C can be achieved, which is also far above the previously achievable values. The valve seat rings according to the invention may be infiltrated both in the carrier layer and in the functional layer in order to increase the thermal conductivity. The functional layer can also contain other additives that support the function, such as lubricants such as molybdenum sulfide or metallic additives such as molybdenum or niobium. Such additives may be present in the order of up to 15% by weight, based on the weight of the functional layer. Molybdenum and niobium, which are added in the form of powder to the green compact to be sintered, oxidize superficially and are suitable for reducing the friction. For example, copper alloys are suitable for infiltration, but also silver and silver alloys.

The valve seat rings according to the invention are produced in particular by powder metallurgy. The valve seat rings according to the invention can be produced by a process which comprises the compression and sintering of the corresponding powders in several steps:

Mixing the powders,

Introducing the powder of the carrier layer into a die,

optionally precompressing the powder of the carrier layer,

Introducing the powder of the functional layer into the matrix,

Compacting the powders in the matrix,

Sintering the powder and

Thermal and / or mechanical aftertreatment of the sintered

Rings.

For compaction of the powder uniaxial pressing can be used, but alternatively, for example, cold isostatic pressing (CIP) is possible.

The sintering can also be followed by a hot isostatic process (HIP) or replace this step. The sintering steps take place at a temperature of for example> 850 ° C. It may be expedient to recompress the powders after the first sintering and optionally to sinter them again.

Unless otherwise indicated, all weights are based on the weight of the particular layer. The invention is explained in more detail by the accompanying drawings.

1 shows a valve seat ring 1 according to the invention in cross-section with a lower carrier layer 2 and a functional layer 3 arranged thereon. The dividing line between the two layers runs essentially horizontally.

2 shows a cross section through a valve seat ring 1 according to the invention with an oblique dividing line between the carrier layer 2 and the functional layer 3. In so doing, the carrier layer 2 expands towards the outer edge and thus increases the contact area with the surrounding cylinder head. In this way, an improved heat flow is achieved in the cooled cylinder head. Between the layers there is a transition region 4, in which the dividing line runs between the carrier layer 2 and the functional layer 3.

3 shows the thermal conductivities of various materials according to the invention at different temperatures. The materials are 1. a carrier material of an oxide-reinforced copper;

2. a functional material with 20% hard phase;

3. a functional material with 30% hard phase and

4. a functional material with 40% hard phase. For all functional materials, the carrier matrix is the same as in the carrier material.

Claims

claims

1 . Valve seat ring (1) with a carrier layer (2) and a functional layer (3),

characterized in that the carrier layer (2) consists of a solidified copper matrix containing 0.10 to 20 wt .-% of a solidifying component, and the functional layer (3) consists of a solidified copper matrix, which further 5 to 35 wt .-% , based on the copper matrix, one or more hard phases.

2. valve seat ring according to claim 1, characterized in that the solidifying component of the copper matrix is an oxide, in particular Al2O3

3. Valve seat ring according to claim 1, characterized in that the solidifying component of the copper matrix is an intermetallic phase, in particular containing Cu, Cr, Zr, Nb, Ni and / or Si.

4. valve seat ring according to claim 1, characterized in that the solidifying component Al2O3 0der Cr2Nb.

5. valve seat ring according to one of the preceding claims, characterized in that the hard phase of the functional layer is an iron-based, cobalt-based, nickel-based hard phase, a carbide, oxide and / or nitride.

6. valve seat ring according to claim 5, characterized in that the

Hard phase is a hard phase based on iron, nickel or cobalt.

7. Valve seat ring according to one of the preceding claims, characterized in that the functional layer contains 0.1 to 5 wt .-% of a solid lubricant.

8. valve seat ring according to claim 7, characterized in that the

Solid lubricant is MnS, M0S2, WS2, CaF2 or hexagonal BN.

9. Valve seat ring according to one of the preceding claims, characterized in that the dividing line between carrier layer (2) and functional layer (3) extends at an angle of 0 ° to 65 °, wherein the carrier layer (2) widens outwardly.

10. valve seat ring according to claim 9, characterized in that the

Dividing line at an angle of 35 ° to 65 °.

1 1. Valve seat ring according to one of the preceding claims with a thermal conductivity of the carrier layer (2) of> 120 W / mK at 500 ° C.

12. valve seat ring according to claim 1 1, characterized in that the thermal conductivity of the carrier layer (2)> 220 W / mK at 500 ° C.

13. Valve seat ring according to one of the preceding claims, characterized in that the thermal conductivity of the functional layer (3)> 70 W / mK at 500 ° C.

14. Valve seat ring according to one of the preceding claims manufactured in powder metallurgy manner.

15. A method for producing a valve seat ring according to one of the preceding claims 1 to 14, characterized by the steps:

Mixing the powders,

Filling the powder of the carrier layer (2) into a die, optionally pre-compacting the powder of the carrier layer (2),

Filling the powder of the functional layer (3) into the matrix, compacting the powders in the matrix,

Sintering or HIPpen the powder and

Thermal or mechanical aftertreatment of the sintered ring.

16. The method according to claim 1 6, characterized in that the powders are post-densified after the first sintering and / or resintered.

17. The method according to claim 15 or 16, characterized in that the sintering steps take place at a temperature> 850 ° C.

18. The method according to any one of claims 14 to 17, characterized in that the compression takes place by means of CIP.

19. Valve seat ring according to one of claims 1 to 14 with a coating.