WO2015081363A2

WO2015081363A2 - Sliding bearing

Info

Publication number: WO2015081363A2
Application number: PCT/AT2014/050293
Authority: WO
Inventors: Johannes WAMPL
Original assignee: Miba Gleitlager Gmbh
Priority date: 2013-12-05
Filing date: 2014-12-04
Publication date: 2015-06-11
Also published as: WO2015081363A3

Abstract

The invention relates to a sliding bearing (1) comprising a metallic support layer (2), a bearing metal layer (3) and an overlay (4) produced from a dry film lubricant. Said metallic bearing metal layer (3) is arranged between the support layer (2) and the overlay (4) from the dry film lubricant. Also, the overlay (4) comprises a matrix made from polyimide in which at least one platelet-shaped solid lubricant is contained. Fibres are also contained in the polyamideimide matrix.

Description

bearings

The invention relates to a sliding bearing comprising a metallic support layer, a Lagerme- tallschicht and a running layer of a bonded coating, wherein the metallic bearing metal layer between the support layer and the running layer of the lubricating varnish is arranged, and further wherein the running layer has a matrix of a polyimide the at least one platelet-shaped solid lubricant is contained. The use of bonded coatings in slide bearings for the engine industry instead of conventional metallic sliding layers is becoming increasingly important. There are therefore known in the relevant literature, a large number of compositions of various sliding coatings for this application. For example, EP 1 717 469 A2, which is based on the applicant, describes a bearing element with a metallic support body, a bearing metal layer arranged above it and a polymer layer arranged above it, the polymer layer comprising a polyimide resin, molybdenum disulfide and graphite, and optionally further layers between the layers are arranged, such as a binder film. The content of the polyimide resin is selected from a range having a lower limit of 60% by weight and an upper limit of 80% by weight, and the content of MoS ₂ is selected from a range having a lower limit of 15% by weight. and an upper limit of 25% by weight and the content of graphite is selected from a range having a lower limit of 5% by weight and an upper limit of 15% by weight, wherein the content of the polyimide resin is based on Polyimide resin with solvent to be removed.

Although this composition of the polymer layer has proved itself, it has been found that such polymer layers, especially in the high-speed range and in the truck sector, have an increased intake requirement so that the tribologically bearing plateaus can form from the MoS ₂ lamellae. The term "high-speed" is understood to mean high-performance diesel engines with a capacity of 15 liters to about 200 liters or a cylinder bore of 120 mm to 260 mm, the rated speed being about 1000 rpm If the "high-speed" and truck applications mentioned above do not adequately adapt the MoS ₂ lamellae, this leads to fatigue of the lamellae and consequently to breakage of the MoS ₂ lamellae. The consequence of this is an increased wear of the sliding layer. Especially dynamic loads on the slide bearing lead to fatigue and premature wear.

The object of the present invention is to provide a slide bearing for the "high-speed" range and for truck engines, which has an improved wear resistance. Matrix additionally contain fibers.

The advantage here is that reinforce by the fibers, as expected, the polymer matrix. As a result, the mechanical properties of the overlay, in particular their tensile strength and thus fatigue strength, are improved. As a result, as tensile forces are "dissipated" from the overlay over the fibers, the platelet-shaped solid lubricant is better retained in the polyamide-imide matrix and less flake outbreaks occur, allowing the tribologically active plateaus to form more rapidly and more effectively from the solid lubricant platelets. Surprisingly, however, it has also been found that especially in the applications mentioned high-speed "and for truck engine crumble the near-surface fibers by the load more or less. This should in itself lead to a deterioration of the performance of the plain bearing. However, the opposite could be stated. This is attributed to the fact that energy is taken out of the system "sliding bearing" by the crumbling of the fibers, whereby the thermal stability of the overlay is improved.

According to a preferred embodiment of the plain bearing is provided that the fibers are inorganic fibers. Although a thermal load of organic fibers would However, the inorganic fibers act not only in their comminution as energy-absorbing, but the resulting fragments of the fibers can still act matrix reinforcing hard particles as. Most preferably, the fibers are carbon fibers. Although these do not show the effect as hard particles, they can also act particulate as solid lubricant, so that any erupting lamellar solid lubricant particles are replaced by the comminuted carbon fibers. It can thus at least maintain the self-lubricating effect of the overlay.

It is also advantageous if the fibers have a fiber length which is selected from a range of 50 μιη to 400 μιη. With fibers which are shorter than 50 μm, it could be observed that the matrix reinforcement only occurs insufficiently, since broken fibers subsequently become too short too fast or can no longer absorb tensile forces. On the other hand, fibers hindering longer than 400 μm impede the formation of the desired, tribologically effective plateaus of solid lubricant lamellae.

It is furthermore advantageous if the fibers have a diameter which is selected from a range of 2 μm to 8 μm, since fibers having such a diameter value can be better embedded in the polyamide-imide matrix. In addition, the fibers are thus easier to process serially with methods known from the paint technology.

The proportion of the fibers in the overlay is preferably selected from a range of 1% by volume to 7% by volume. With a proportion of less than 1% by volume, the above-described, surprisingly observed effect occurs only insufficiently. Shares of more than 7

Vol .-% hinder, however, also the formation of the desired, tribologically effective plateaus of solid lubricant flakes because they lead to a strong crossover of the fibers. As a result, the fibers assume an unfavorable orientation in the overlay. According to another embodiment of the sliding bearing can be provided that at least a proportion of 80% of the fibers are oriented with their longitudinal extent in the circumferential direction of the overlay. The advantage here is that by the oriented storage tensile forces can be better absorbed because the fibers these tensile forces in the circumferential direction spread over a larger area of the bonded coating. In addition, thus, the above effect of plateau formation can be improved.

Preferably, the at least one platelet-shaped solid is selected from a group comprising MoS ₂ , graphite, hexagonal BN, WS ₂ , SnS, SnS ₂ and mixtures thereof. It was thus possible to achieve an improvement of the above effects.

For a better understanding of the invention, this will be explained in more detail with reference to the following figure.

It shows in a schematically simplified representation:

Fig. 1 is a plain bearing in the form of a plain bearing half-shell in an oblique view. By way of introduction, it should be noted that the location information chosen in the description, such as the top, bottom, side, etc. related to the immediately described and illustrated figure and are to be transferred to the new situation mutatis mutandis when a change in position.

Fig. 1 shows a sliding bearing 1 in the form of a Gleitlagerhalb shell. The sliding bearing 1 according to FIG. 1 consists of a metallic supporting layer 2, a bearing metal layer 3 and a running layer 4.

The backing layer 2 is usually made of steel, but may also be made of other materials, e.g. Brass, bronzes exist, with which the same or a similar function, namely the provision of mechanical strength and the dimensional stability of the sliding bearing 1, can be realized.

The bearing metal layer 3 is formed by a bearing metal alloy. This can consist of an aluminum matrix alloy in which at least one soft phase (eg Sn, In, Sb, Bi) and optionally hard particles (eg Cu, Mn, Co, Cr, Fe or intermetallic phases of these elements) are embedded. As bearing metal layer 3, in particular alloys based on tin, bismuth, indium, lead or aluminum as well as alloys based on, optionally highly lead, CuPb or AlSn or AlBi based. In particular, higher tin-containing tin-based alloys are advantageous. Lead-free copper-based alloys are also usable. To avoid repetition, reference is made in general to the aforementioned EP 1 717 469 A2 with regard to possible bearing metal alloys.

The plain bearing 1 may also comprise further layers, for example at least one bonding layer and / or diffusion barrier layer, an anti-scratch layer, etc., as known from the prior art.

The running layer 4 is that layer of the sliding bearing 1, on which the component to be stored, so for example a shaft, is supported. The running layer can be an inflow layer, which serves in particular for adapting the sliding bearing 1 to the surface of the component to be supported during the entry of a new sliding bearing, and / or a sliding layer which is operative in operation after running in of the sliding bearing 1.

The running layer 4 is made of a lubricating varnish. The bonded coating consists of a polyamido-based (PAI), which forms the matrix of the overlay 4, are embedded in the solid lubricant particles and optionally hard particles. In addition, the lubricating varnish may still contain various processing aids, such as e.g. Defoamer, etc., included. In addition, the lubricating varnish contains fibers.

In general, the bonded coating has a matrix of a polyimide. The polyimide is selected from a group including polyimide, polyamideimide, polybenzimidazole, and mixtures thereof.

In the following, for the sake of simplicity, only the polyamideimide will be referred to. However, the statements in the description also apply to the other polyimides mentioned above or mixtures thereof. However, preference is given to using a polyamideimide. The running layer 4 can be embodied in one or more layers, wherein in the multilayer embodiment only one of these layers contains the fibers, or different fractions of fibers are contained in the individual layers, wherein the fiber fraction increases in the direction of the radially inner sliding surface and the radially outermost one these layers of the running layer 4 has no fibers.

The proportion of the polyamideimide on the overlay 4 is between 25 wt .-% and 45 wt .-%, in particular between 34 wt .-% and 38 wt .-%. If necessary, this running layer 4 may contain hard particles to increase the mechanical strength and / or to adjust the coefficient of friction of the overlay 4, such as carbides, oxides, nitrides, for example CrO ₂ , Fe ₃ O ₄ , Fe ₂ O _3i PbO, ZnO, A1 ₂ 0 ₃ , Si0 ₂ , Sn0 ₂ , SiC, Si ₃ N ₄ . The proportion of hard particles on the overlay 4 may be between 1 wt .-% and 5 wt .-%.

Furthermore, the running layer contains 4 solid lubricant particles. These have a platelike, lamellar habit. It is also possible to use a particulate mixture of different solid lubricants, in which case at least one of the solid lubricants is platelet-shaped. If a mixture of solid lubricants is used, this preferably consists of MoS ₂ and graphite.

In general, the platelet-shaped solid lubricants may be selected from a group comprising MoS ₂ , graphite, hexagonal BN, WS ₂ , SnS, SnS ₂ and other solid lubricants known from the relevant literature, in particular MoS _{2 being} preferred.

The total proportion of solid lubricants on the overlay 4 is between 55% by weight and 75% by weight. If a mixture of MoS ₂ or WS ₂ and at least one further solid lubricant, in particular graphite, is used, the proportion of MoS ₂ or WS _{2 is} between 35% by weight and 55% by weight, and the proportion of the at least one other Solid lubricant between 15 wt .-% and 30 wt .-%, with the proviso that the total content of solid lubricants between 55 wt .-% and 75 wt .-% is. The platelet-shaped solid lubricant particles have, in particular, a length between 3 μm and 40 μm, a width between 3 μm and 40 μm and a thickness between 2 nm and 20 nm. Furthermore, the running layer 4 contains fibers, in particular inorganic fibers.

The fibers may be selected from a group comprising or consisting of carbon fibers, SiC fibers, aramid fibers and mixtures thereof. Particular preference is given to using carbon fibers (= carbon fibers).

The proportion of the fibers in the overlay 4 is preferably between 1% by volume and 7% by volume, in particular between 1.5% by volume and 4% by volume.

The fibers may have a fiber length selected from a range of 50 μηι to 400 μιη, in particular from a range of 100 μιη to 300 μιη. Preferably, ground fibers are used.

Further, the fibers may have a diameter which is selected from a range of 2 μιη to 8 μιη, in particular from a range of 5 μιη to 7 μιη.

For the production of the plain bearing 1, the metallic layers are produced or deposited in the usual way, for example by providing the metallic support layer 2 galvanically, by co-rolling, by PVD methods, in particular sputtering, by casting, by sintering, etc. Since these Manufacturing methods for sliding bearings 1 are known from the prior art, reference is made to avoid repetition to the relevant literature.

The running layer 4 is applied to the prepared layer composite, in particular by means of methods which are known from lacquer technology, for example by brushing, rolling, spraying, etc. For this purpose, the solids, ie a precursor PAI, or the solid lubricant substance (s), the fibers and optionally hard particles are stirred into a solvent and distributed as homogeneously as possible. If necessary, this suspension will be processed processing aids such as wetting agents, defoamers, etc. in a proportion of not more than 3 wt .-% added.

The finished suspension is subsequently applied to the prepared, cleaned metallic surface, the solvent is evaporated off and the precursor of the PAI is polymerized to form the running layer 4 at a temperature between 150 ° C. and 250 ° C.

As the solvent, for example, xylene can be used. Other usable solvents are n-methylpyrrolidone, n-ethylpyrrolidone, γ-butyrolactone, dimethylsulfoxide, dimethylacetamide, dimethylformamide. It is also possible to use mixtures of the solvents mentioned.

The proportion of the solvent or solvent mixture based on the amount of the precursor of the PAI can be between 40% by weight and 80% by weight.

According to an embodiment variant, it can be provided that the fibers are at least partially aligned. In particular, at least a proportion of 80%, preferably at least 90%, of the fibers with their longitudinal extent in a circumferential direction 5 of the overlay 4 is oriented. To achieve this, the fibers can be applied in a first step on the metallic surface to be coated and then coated with the above bonded coating, but without fiber content. The further procedure for forming the running layer 4 can be carried out as stated above. It can also be generated on the surface of the lubricating varnish with this procedure, a groove.

In addition to the application of the lubricating varnish on a separate sliding bearing 1, there is also the possibility of direct coating of the sliding stress subjected components, such as the application of the lubricating varnish on the surface of a connecting rod eye. The overlay 4 has a layer thickness which is selected from a range of 10 μπι to 50 μιη. Thus, by adding the fibers, significantly thicker running layers can be produced because the cohesion of the layer is strengthened by the incorporation of the fibers. The overlay 4 has good sliding and emergency running properties, which may even allow dry running. This is characterized in particular by low maintenance. It is a low-lubricant or lubrication-free operation possible.

In addition to training as Gleitlagerhalb shell, the sliding bearing 1 may be formed, for example, as a stop ring or slide bushing.

In the course of the development, the compositions of the overlay 4 given in Table 1 were tested. The data in Table 1 for quantitative proportions of the individual constituents of the overlay 4 are to be understood as wt .-%, with the exception of the proportions of the fibers. The proportions of the fibers are to be understood as% by volume, based on the total composition of the overlay 4. The composition details in% by weight relate to the compositions of the overlay 4 without fibers. These compositions together with the fibers then form the respective total mixture with 100% by volume.

Example No. 1 is a comparative example, wherein the running layer 4 according to EP 1 717 469 A2 consisted of PAI, MoS ₂ and graphite.

These slide bearings 1 each had a steel support layer 2 and a bearing metal layer 3 made of AlSn25Cu. The running layer 4 was applied directly to the bearing metal layer 3.

Table 1: Compositions of the overlay

No. PAI MoS ₂ WS ₂ Graphite Carbon fibers Length of excess wear

Carbon fibers [%] [%]

[Μηι]

1 30 45 25 0 42 100

2 34 35 31 1 50 16 89

3 25 50 25 5 100 62 78

4 37 35 28 3 200 20 69

5 20 45 25 3 50 14 85

6 40 38 22 3 200 49 72

These plain bearings 1 were tested for wear under high-speed applications or in truck engines under the following conditions: For each example, there are two test results.

The first value is the adaptability. On a ring o disc test stand, the load is increased in increments at constant speed (keep for 3 hours, increase the load in a ramp within 1 hour, repeat the whole thing more often). Meanwhile, the torque is recorded. It comes to an overshoot of the torque, which then stabilizes again. The lower the overshoot, the less adjustment the paint has. The value in the table is the percentage ratio of overshoot to true torque increase. The second value shows the normal wear on the bearing test stand. The wear value is normalized to the carbon fiber-free example 1, which has a wear of 100%.

The plain bearings according to Examples 2 to 6 show significantly better wear properties during operation than the comparative sliding bearing (Example 1). On the basis of microscopic investigations, the formation of the abovementioned, tribologically active plateaus 6 could be detected on the surface of the overlay 4. These plateaus 6 consisted of assembled MoS ₂ or WS ₂ lamellae, as revealed by electron microscopic examinations. The plateaus 6 formed during the (on) run of the sliding bearing 1, by removing the solid lubricant platelets from the surface of the running layer 4 through the shaft. The free solid lubricant platelets are not discharged in the sequence, however, with the lubricating oil but are deposited on the surface of the overlay 4 due to the fibers present in the overlay 4 again, but the homogeneous distribution by a heaped distribution, ie the plateau 6, is replaced , Comparable results were also achieved with the other compositions according to the invention and with the polyimides and fibers and solid lubricants mentioned further in the description, so that the results were not reproduced.

The embodiments show possible embodiments of the sliding bearing. 1

For the sake of order, it should finally be pointed out that, for a better understanding of the design of the slide bearing 1, this or its components have been shown partially unevenly and / or enlarged and / or reduced in size.

Reference signs slide bearing

backing

Bearing metal layer

Run shift

circumferentially

plateau

Claims

Patent claims

1. plain bearing (1) comprising a metallic support layer (2), a bearing metal layer (3) and a running layer (4) made of a bonded coating, wherein the metallic bearing metal layer (3) between the support layer (2) and the running layer (4) is arranged from the lubricating varnish, and further wherein the running layer (4) comprises a matrix of a polyimide, in which at least one platelet-shaped solid lubricant is contained, characterized in that in the polyamide-imide matrix additionally fibers are included.

2. plain bearing (1) according to claim 1, characterized in that the fibers are inorganic fibers.

3. plain bearing (1) according to claim 2, characterized in that the fibers are carbon fibers.

4. plain bearing (1) according to one of claims 1 to 3, characterized in that the fibers have a fiber length which is selected from a range of 50 μιη to 400 μπι.

5. plain bearing (1) according to one of claims 1 to 4, characterized in that the fibers have a diameter which is selected from a range of 2 μιη to 8 μηι.

6. plain bearing (1) according to one of claims 1 to 5, characterized in that the proportion of fibers on the running layer (4) is selected from a range of 1 vol .-% to 7 vol .-%.

7. plain bearing (1) according to one of claims 1 to 6, characterized in that at least a portion of 80% of the fibers with their longitudinal extent in a circumferential direction (5) of the overlay (4) are oriented.

8. plain bearing (1) according to one of claims 1 to 7, characterized in that the at least one platelet-shaped solid is selected from a group comprising MoS ₂ , graphite, hexagonal BN, WS ₂ , SnS, SnS ₂ and mixtures thereof.