Coating for a metal seal, metal seal and use thereof

Abstract

The present invention relates to a coating for a metal seal, comprising an elastomer and particles of an electrically conductive material, wherein the coating has a specific resistance of less than approximately 20∙10-3 Ω∙m. The invention further relates to a metal seal, comprising a metal substrate and a coating of this kind which is applied to at least one side, preferably to both sides, of the metal substrate.

Description

[0001] Coating for a metal seal, metal seal and its use

[0002] The present invention relates to a coating for a metal seal.

[0003] The invention further relates to a metal seal comprising a metallic substrate and such a coating.

[0004] Furthermore, the invention relates to the use of such a metal seal for sealing machine, device or housing parts.

[0005] Metal gaskets have long been known as a form of flat gaskets and are used in various technical fields for sealing between individual parts of machines, devices, or housings. Such metal gaskets comprise a single- or multi-layer metallic substrate, often coated with an elastomer on at least one side, but preferably on both sides of the substrate. Due to its high conformability, this coating improves the sealing properties of the metal gasket and also serves to protect the metallic substrate, particularly against corrosion.

[0006] Due to the electrically insulating properties of elastomers, coated metal seals electrically decouple the sealed parts. This is disadvantageous in certain applications, particularly when electromagnetic compatibility (EMC) must be ensured, such as in the housings of electric motors or power electronics. To establish electrical contact between the sealed parts in such applications, special screws, washers, or clamps are used, or metal seals with only a partially coated surface are employed. These measures all involve increased design and manufacturing effort. The object of the invention is to propose a coating for a metal seal with which the disadvantages of the prior art can be completely or partially avoided.

[0007] This object is achieved according to the invention by a coating for a metal seal, which comprises an elastomer and particles of an electrically conductive material, wherein the coating has a specific resistance of less than approximately 20-10' 3 sqm.

[0008] The coating according to the invention can be used to provide a metal seal that, on the one hand, offers all the known advantages of an elastomer coating, while, on the other hand, exhibiting sufficiently high electrical conductivity to ensure electrical contact between the sealed parts in EMC-critical applications. This eliminates the need for additional design measures, simplifying assembly and disassembly of the parts. Furthermore, the coating according to the invention can be applied over the entire surface of the metallic substrate of a metal seal, reducing the manufacturing effort for the seal compared to a partial coating.

[0009] The coating according to the invention has a specific resistance of less than approximately 2CL10' 3 Qm, which corresponds to a specific conductivity of more than approximately 50 S / m. Preferably, the coating has a specific resistance of less than approximately 15-10' 3 sqm, more preferably less than 10-10' 3 sqm, even more preferably less than approx. 5-10' 3 sqm.

[0010] The electrically conductive material is preferably selected from the group comprising carbon black, graphite, graphite compounds, graphene, borides, especially chromium boride and titanium boride, carbides, especially chromium carbide and titanium carbide, and metals, especially aluminum, copper, silver, and zinc. In general, any electrically conductive materials can be used that are sufficiently stable under the operating conditions of the metal seal and with which a correspondingly low specific resistance of the coating can be achieved.

[0011] In a particularly preferred embodiment of the invention, the electrically conductive material comprises titanium carbide. Unlike carbon black or graphite, titanium carbide particles do not tend to agglomerate, thus ensuring a very uniform distribution of the particles in the elastomer.

[0012] Depending on the type of electrically conductive material, as well as depending on the desired specific resistance of the coating, the particles of the electrically conductive material are advantageously contained in the coating in a proportion of approximately 15 to approximately 85 wt.%, preferably in a proportion of approximately 25 to approximately 75 wt.%, more preferably of approximately 35 to approximately 65 wt.%.

[0013] The particles of the electrically conductive material preferably have an average particle size of approximately 2 pm to approximately 70 pm, more preferably approximately 2 pm to approximately 20 pm.

[0014] In principle, the elastomer materials known from the prior art can be used as the elastomer for the coating according to the invention. The elastomer is preferably selected from the group comprising acrylonitrile butadiene rubber (NBR), fluororubber (FKM), ethylene acrylate rubber (AEM), silicone rubber, and silicone elastomers.

[0015] Depending on the type of elastomer used, the coating may also include a crosslinking agent for the elastomer.

[0016] In addition to the elastomer, the particles of the electrically conductive material, and optionally a crosslinker, the coating may further comprise one or more additives. The particles of the electrically conductive material are advantageously dispersed in a matrix of the elastomer. The elastomer also acts as a binder for the particles of the electrically conductive material. The particles are preferably distributed or dispersed as evenly as possible in the elastomer.

[0017] The coating according to the invention advantageously has a thickness of approximately 10 pm to approximately 100 pm, preferably approximately 20 pm to approximately 30 pm. The optimal thickness of the coating depends in particular on the type of elastomer and the intended application of the metal seal and can be adjusted accordingly by a person skilled in the art.

[0018] The coating according to the invention is preferably applied to at least one side, particularly preferably to both sides, of a metallic substrate of the metal seal. In particular, the invention provides for a full-surface coating of the metallic substrate on one or both sides.

[0019] Suitable application methods for the coating are known in the art and include, in particular, spraying, rolling, dipping, and coil coating. Depending on the type of elastomer, the coating is applied to the metallic substrate using a suitable solvent and then dried. When a crosslinker is used, the elastomer is typically crosslinked in situ after the coating is applied.

[0020] The object underlying the invention is further achieved by a metal seal which comprises a metallic substrate and a coating according to the invention which is applied to at least one side, preferably to both sides of the metallic substrate.

[0021] The metallic substrate can be single-layer or multi-layer, in particular two-layer or three-layer. The metallic substrate is preferably made of steel, aluminum, or copper.

[0022] Typically, the metallic substrate has a thickness of approximately 0.1 to approximately 0.5 mm, preferably approximately 0.2 to approximately 0.3 mm.

[0023] The metallic substrate may have one or more beads. Alternatively, the metallic substrate may be unbeaded.

[0024] Further advantages and preferred embodiments of the metal seal according to the invention have already been explained in connection with the coating according to the invention.

[0025] The invention further relates to the use of a metal seal according to the invention for sealing machine, device, or housing parts. The metal seal according to the invention can be used particularly advantageously in EMC-critical applications, in particular for sealing housing parts of electric motors, electric drive units, power electronics, and inverters.

[0026] The embodiment described below serves to explain the invention in more detail without limiting it in any way.

[0027] The drawings show:

[0028] Figure 1: a schematic cross-sectional view of an embodiment of a metal seal according to the invention; and

[0029] Figure 2: A schematic perspective view of an embodiment of a metal seal according to the invention. An embodiment of a metal seal 10 according to the invention is shown in cross section in Figure 1 and in perspective view in Figure 2, wherein the representations are each schematic and in particular not to scale.

[0030] The metal seal 10 according to the invention comprises a metallic substrate 12, wherein the metallic substrate 12 in this case is formed in a single layer and is, for example, a steel sheet with a thickness of approximately 0.2 mm. A coating 14 according to the invention is applied to both sides of the metallic substrate 12, said coating comprising an elastomer 16 and particles 18 of an electrically conductive material. The thickness of the coatings 14 is, for example, approximately 25 μm, and the average particle size of the particles 18 is, for example, approximately 10 μm.

[0031] The coating 14 is preferably applied over the entire surface of both sides of the metallic substrate 12. The depiction of a portion of the metallic substrate 12 without the coating 14 in Figure 2 is for illustrative purposes only.

[0032] The current conduction through the coating 14 by means of the particles 18 of the electrically conductive material is symbolically indicated by the arrows 20.

[0033] Examples:

[0034] For a first concrete embodiment of a coating according to the invention, NBR was used as the elastomer, and titanium boride particles with a particle size in the range of approximately 10 μm were used in a weight proportion of approximately 40% of the coating. A specific resistance of approximately 1.2-10' was achieved for this coating. 3 -m measured.

[0035] For a second specific embodiment of a coating according to the invention, NBR was also used as the elastomer, and titanium carbide particles with a particle size in the range of approximately 3 μm were used in a weight proportion of approximately 58% of the coating. A specific resistance of less than 1-10' was achieved for this coating. 3 Measured in square meters.

[0036] For a third specific embodiment of a coating according to the invention, NBR was also used as the elastomer, and particles of a copper / silver alloy with a particle size in the range of approx.

[0037] 15 pm in a weight fraction of approximately 10 wt.% of the coating. For this coating, a specific resistance of less than 2-10' 3 Measured in square meters.

[0038] List of reference symbols Metal seal Metallic substrate Coating Elastomer Particle Power line

Claims

Patent claims 1. A coating for a metal seal comprising an elastomer and particles of an electrically conductive material, the coating having a resistivity of less than about 20-10' 3 sqm.

2. Coating according to claim 1, wherein the coating has a resistivity of less than about 15-10' 3 Qm, preferably less than about 10- 10' 3 sqm, more preferably less than approx. 5-10' 3 sqm.

3. Coating according to claim 1 or 2, wherein the electrically conductive material is selected from the group comprising carbon black, graphite, graphite compounds, graphene, borides, in particular chromium boride and titanium boride, carbides, in particular chromium carbide and titanium carbide, and metals, in particular aluminum, copper, silver and zinc.

4. The coating of claim 3, wherein the electrically conductive material comprises titanium carbide.

5. Coating according to one of the preceding claims, wherein the particles of the electrically conductive material are contained in the coating in a proportion of approximately 15 to approximately 85% by weight, preferably in a proportion of approximately 25 to approximately 75% by weight, more preferably of approximately 35 to approximately 65% ​​by weight.

6. Coating according to one of the preceding claims, wherein the particles of the electrically conductive material have an average particle size of approximately 2 pm to approximately 70 pm, preferably approximately 2 pm to approximately 7. Coating according to one of the preceding claims, wherein the elastomer is selected from the group comprising acrylonitrile butadiene rubber (NBR), fluororubber (FKM), ethylene acrylate rubber (AEM), silicone rubber and silicone elastomers.

8. A coating according to any one of the preceding claims, wherein the coating further comprises a crosslinking agent for the elastomer.

9. A coating according to any one of the preceding claims, wherein the coating further comprises one or more additives.

10. Coating according to one of the preceding claims, wherein the particles of the electrically conductive material are dispersed in a matrix of the elastomer.

11. Coating according to one of the preceding claims, wherein the coating has a thickness of approximately 10 pm to approximately 100 pm, preferably approximately 20 pm to approximately 30 pm.

12. Coating according to one of the preceding claims, wherein the coating is applied to at least one side, preferably to both sides of a metallic substrate of the metal seal.

13. A metal seal comprising a metallic substrate and a coating according to claim 12.

14. Metal seal according to claim 13, wherein the metallic substrate is single-layered or multi-layered, in particular two-layered or three-layered.

15. A metal gasket according to claim 13 or 12, wherein the metallic substrate is formed of steel, aluminum or copper.

16. Metal seal according to one of claims 13 to 15, wherein the metallic substrate has a thickness of about 0.1 to about 0.5 mm, preferably about 0.2 to about 0.3 mm.

17. A metal gasket according to any one of claims 13 to 16, wherein the metallic substrate has one or more beads or is unbeaded.

18. Use of a metal seal according to one of claims 13 to 17 for sealing machine, device or housing parts, in particular housing parts of electric motors, electric drive units, power electronics and inverters. * * *

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