EP2108055A2

EP2108055A2 - Sliding bearing

Info

Publication number: EP2108055A2
Application number: EP07817782A
Authority: EP
Inventors: Christiane Knoblauch; Ulrich Bischofberger
Original assignee: Mahle International GmbH
Current assignee: Mahle International GmbH
Priority date: 2006-12-19
Filing date: 2007-11-07
Publication date: 2009-10-14
Also published as: DE102006060474A1; WO2008074281A2; WO2008074281A3; CN201297342Y

Abstract

The present invention relates to a sliding bearing (10) having a carrier layer (12) made of a metallic material, a copper-based bearing metal layer (14) applied to the carrier layer (12), a diffusion barrier layer (16) applied to the bearing metal layer (14), and a sliding layer (18) made of tin that is applied to the diffusion barrier layer (16). The invention provides that the diffusion barrier layer (16) is made of pure iron.

Description

ZRI P / Po C56062WO

bearings

The present invention relates to a sliding bearing comprising a carrier layer made of a metallic material, a copper-based bearing metal layer applied to the carrier layer, a diffusion barrier layer applied to the bearing metal layer and a tin-based sliding layer applied to the diffusion barrier layer.

Plain bearings in the form of lead-free layer composites are needed worldwide for new engines, especially for transport and heavy duty vehicles, as more and more vehicles of different types are manufactured on the basis of common vehicle platforms.

Known in the prior art is a sliding bearing made of a layered composite material which comprises a steel support layer, a lead-free bearing metal layer, an intermediate layer or diffusion barrier layer and a tin-based lead-free sliding layer. Such a sliding bearing comes quite close to the known lead-containing plain bearings and represents an attempt to obtain the essential functional properties of these plain bearings, for example. Their good conformability and embedding ability, based on the soft, tin-based sliding layer, combined with a comparatively good load capacity and the good runflat in the event of complete wear of the sliding layer, which are based on the bearing metal layer. Such a plain bearing is described, for example, in the German patent application DE 103 37 030 A1.

In connection with such sliding bearings, however, it is a problem to limit the diffusion of tin from the sliding layer in the bearing layer, otherwise the brittle layer becomes brittle and the load capacity of the sliding bearing is significantly reduced. The German patent application DE 103 37 030 A1 proposes that a diffusion barrier layer between the sliding layer and the bearing metal layer should be provided, which consist of pure nickel and should be about 4 to 6 microns thick.

This measure has been found to be in need of improvement, since the nickel diffusion barrier layer must be comparatively thick. When tin migrates from the sliding layer into the diffusion barrier layer, a diffusion layer of tin and nickel forms there. Now, if the pure nickel diffusion barrier layer is too thin, it is completely converted to a tin / nickel layer. The tin present in this new diffusion layer migrates further into the bearing metal layer. When, as is usual, a copper-based bearing metal layer is used, the tin with the copper forms a new diffusion layer made of tin and copper. However, this diffusion layer is brittle, so it tends to flake off.

The object of the present invention is therefore to develop a sliding bearing of the above-mentioned type such that a better control of the diffusion of tin from the tin-based sliding layer into the bearing metal layer is possible.

The solution consists in a plain bearing with the features of claim 1. According to the invention it is provided that the diffusion barrier layer consists of pure iron.

It has surprisingly been found that a diffusion barrier layer made of pure iron effectively prevents the migration or diffusion of tin from the sliding layer into the bearing metal layer. Diffusion-related reactions do not occur even after long engine operating times. The inventive diffusion barrier layer of pure iron can also be applied to the bearing metal layer without any problems, for example by means of known galvanic methods.

Advantageous developments emerge from the subclaims. Due to the particularly effective diffusion barrier exerted by the diffusion barrier according to the invention, it is sufficient if the diffusion barrier layer is at most 4 μm is thick. Preferred embodiments provide a thickness of the diffusion barrier layer of at most 3 μm, more preferably of at most 2 μm. This saves material costs and shortens coating times,

The diffusion barrier layer of the sliding bearing according to the invention shows its good barrier effect, regardless of whether the sliding layer on a combination of tin and one or more elements selected from the group: silver, copper, nickel, cobalt, zinc, gold, indium, bismuth, lead or whether the overlay contains pure tin. Likewise, tin alloys with nickel and / or zinc and / or cobalt and / or gold and / or bismuth and / or lead can advantageously be used as a sliding layer, the tin content being at least 60% by weight.

In contrast to the sliding bearings with galvanically applied sliding layers known in the prior art, the sliding layer can also be applied by fusion metallurgy to the diffusion barrier layer. Not only can costs be saved and particularly fine structures can be achieved, but new material compositions for the sliding layer are also opened up. For example, it is possible to use alloy compositions which can not be prepared by galvanic methods, such as tin alloys with a particularly high proportion of silver or copper or tin-nickel alloys.

The bearing metal layer is a copper-based bearing metal layer, which in a preferred embodiment has a copper content of at least 85% by weight. For example, tin and / or nickel and / or bismuth can be contained as further alloy materials.

Between the diffusion barrier layer 16 and the sliding layer 18 may be provided an intermediate layer 16b, for example, a galvanically applied tin or silver or nickel layer or an alloy thereof. This serves as a corrosion protection layer and additionally increases the emergency running properties, in the event that after extended operation, the sliding layer is worn in the region of high load. In the case where the sliding layer is applied by fusion metallurgy, the intermediate layer 16b serves for bonding and is then preferably made of tin.

An embodiment of the present invention will be described below with reference to the accompanying drawings. 1 shows a schematic, not to scale representation of a cross section through an embodiment of a sliding bearing 10 according to the invention. This slide bearing 10 has a support layer 12, preferably made of steel, to which a bearing metal layer 14 is applied, which is based on copper, for example a copper-tin alloy or a copper-tin-nickel alloy or a copper-tin-bismuth alloy or a copper-tin-bismuth-nickel alloy, wherein the copper content is in each case at least 85 wt .-%. On the bearing metal layer 14, a diffusion barrier layer 16 and on this a sliding layer 18 is applied based on tin. The slip layer 18 contains tin and one or more elements selected from the group: silver, copper, nickel, indium, cobalt, zinc, gold, bismuth, lead. The sliding layer 18 may also consist of pure tin. In the exemplary embodiment, a eutectic tin-silver alloy with a tin content of 96% and a melting point of 221 ⁰ C was used. An electric tin-silver-copper alloy with a melting point of 217 ° C. would also be conceivable. In order to facilitate the molten deposition of the tin layer, it may be advantageous to add bismuth to the alloy. This further reduces the melting point.

The molten tin or alloy is deposited on the diffusion barrier layer 16 or on an additional layer 16b as shown in FIG. The removal of the excess tin or the excess alloy from the surface is carried out by a known brushing process or by centrifuging the excess still molten tin or the alloy. For this purpose, the sliding bearing is subjected to a corresponding centrifugal movement.

The pure iron diffusion barrier layer 16 is applied galvanically to the bearing metal layer 14 and effectively prevents the migration or diffusion of tin into the bearing metal layer 14. The diffusion barrier layer 16 can have a layer thickness of at most 4 microns, preferably at most 3 microns, more preferably at most 2 microns.

Exemplary embodiment 1 (compare FIG. 1):

Support layer of steel (12);

Bearing metal layer of a copper alloy 200 μm layer thickness (14);

Pure iron diffusion barrier, 2 μm layer thickness (16);

Galvanically applied sliding layer made of a tin-silver alloy with 8% by weight silver, 12 μm layer thickness (18).

Exemplary embodiment 2 (compare FIG. 2):

Support layer of steel (12);

Bearing metal layer of a copper alloy 190 μm layer thickness (14);

Pure iron diffusion barrier, 2 μm layer thickness (16);

Additional layer of galvanized tin, 2 μm layer thickness (16b);

Melt metallurgically applied sliding layer of a tin-nickel alloy with

3% by weight nickel, 20 μm layer thickness (18).

Claims

claims

A sliding bearing (10) having a carrier layer (12) made of a metallic material, a copper-based bearing metal layer (14) applied to the carrier layer (12), a diffusion barrier layer (16) applied to the bearing metal layer (14) and a diffusion barrier layer (16 ) applied sliding layer (18) based on tin, characterized in that the diffusion barrier layer (16) consists of pure iron.

2. plain bearing according to claim 1, characterized in that the diffusion barrier layer has a thickness of at most 4 microns, preferably at most 3 microns, more preferably at most 2 microns.

3. plain bearing according to one of claims 1 or 2, characterized in that between the diffusion barrier layer (16) and the sliding layer (18) an intermediate layer (16b) is provided to improve the emergency running properties and corrosion protection.

4. Plain bearing according to claim 3, characterized in that the intermediate layer (16b) is a preferably galvanically applied tin or silver or nickel layer.

5. Sliding bearing according to one of the preceding claims, characterized in that the sliding layer (18) based on tin either of pure tin or of tin and one or more elements selected from the group: silver, copper, nickel, indium, cobalt, Zinc, gold, bismuth, lead persists.

6. plain bearing according to one of the preceding claims, characterized in that the sliding layer (18) made of a tin alloy with nickel and / or zinc and / or cobalt and / or gold and / or bismuth and / or lead used as a sliding layer, wherein the tin content at least 60% by weight.

7. Sliding bearing according to one of the preceding claims, characterized in that the sliding layer (18) is applied on the basis of tin melt metallurgically on the diffusion barrier layer (16) or on the intermediate layer (16b).

8. Plain bearing according to one of the preceding claims, characterized in that the bearing metal layer (14) has a copper content of at least 85 wt .-%.

9. sliding bearing according to claim 8, characterized in that the bearing metal layer (14) further tin and / or nickel and / or bismuth.