DE4038139A1 - Composite plain bearing used in Diesel engines - comprises aluminium@ alloy coating on steel support layer having aluminium oxide-contg. coating having pores filled with solid lubricant - Google Patents

Abstract

Composite plain bearing (I) consisting of a Al alloy coating esp. of the type AlSi12CuMgNi, AlSi4Cd, AlZn5SiCuPbMg or AlNi2Mn1 on a steel support layer (8) which has an Al oxide-contg. coating (5) with open pores (6) of which the majority are filled with a solid lubricant (7). Also claimed are: (i) prepn. of (I) by converting Al in a surface coating of the alloy into a porous oxide layer anodic oxidation; (ii) galvanisation appts. for processing bearing shells comprising electrolytes suitable for anodic oxidn. of Al, at least one plastic container (9) with a semicylindrical cross-section in which the bearing shell (I) is fixed to immersing in the electrolytes and also an impregnating apparatus (24) with an evacuatable, solid lubricant-contg. impregnating container. USE/ADVANTAGE - (I) is used in highly-loaded mechanisms of combustion engines, esp. loaded diesel engines. It has a thermally and mechanically highly loadable lubricant coating. (Dwg.1/6)

Description

The invention relates to composite plain bearings according to the Preamble of claim 1. The invention relates also a process for producing such Composite sliding bearing and a device for Machining composite plain bearings.

For heavy-duty connecting rod and main bearings from Internal combustion engines are still three-component stores today used. The steel support shell carries a about 4 mm thick bearing metal layer, the predominant from cast lead bronze and one on it galvanically deposited sliding layer of about 20 µm Thickness exists. This is a ternary lead alloy with about 10% tin and 3% copper.

To diffusion processes between the tin of this Sliding layer and the copper of the Lead bronze intermediate layer to prevent that due to the formation of brittle intermetallic Phases would lead to sliding layer detachments known from DE-PS 8 44 664, a thin Nickel dam of 1 to 2 µm between the Sliding layer and the lead bronze intermediate layer to apply. The sliding layer has very good ones Sliding properties, such as low tendency to eat, good Embedding ability of dirt particles as well as good Adaptability to the shaft or journal, however, it has been recognized that with these Three-component bearings with very high loads and high Oil temperatures the galvanically applied Sliding layer wears out and then the underlying nickel dam is released. In addition comes that at elevated temperatures  the layer consisting of PbSnCu at 183 ° C PbSn eutectic forms so that this sliding layer Shows melting. Because the temperatures today already considerably above 180 ° C, sometimes up to These three-component bearings cannot be at 190 ° C be used more safely. From EP 03 04 109 are plain bearings based on steel / Aluminum alloys known, the Aluminum alloy z. B. from AlZn₅SiCuPbMg or AlNi₂Mn₁ exists. Such plain bearings can, however without a galvanic sliding layer not perfect be operated as it is without the galvanic Adjustment layers for uncontrolled failures is coming.

According to EP 03 04 108 is on the aluminum bearing alloy layer a zinc phosphate overlay from 2 to 8 µm thick applied. For this layer the same applies as for the classic ones Three-component bearings, namely: insufficient thermal Resilience and insufficient wear resistance. The zinc phosphate running layer conveys the plain bearing has good adaptability, is however not sufficiently wear-resistant, so that due to the relatively short lifespan Aluminum alloy layer with the shaft in Comes into contact and eating occurs.

From E. Hornung "Ways to reduce wear with oil-lubricated bearings " Lubrication Technology, Berlin 18 (1987) 7, page 199 to 204, it is known to be self-lubricating layers made of solid lubricants, especially MoS₂ and Apply PTFE to sliding elements. It has however, shown that the bond strength and thus the wear resistance of z. B. resin bound PTFE on the support element is unsatisfactory. In addition  comes that the technique of applying such Sliding layers by spraying, dipping or Deletion with regard to an industrial Large-scale production of plain bearings is not can be designed inexpensively.

It is therefore an object of the present invention Composite plain bearing with a thermal and mechanical to create highly resilient sliding layer that also is inexpensive to manufacture. Object of the invention is also a method of making such Composite plain bearing and a suitable one To provide device.

This task is carried out according to the characteristic Features of claim 1 solved. The The inventive method is the subject of Claim 11 and the device according to the invention is claimed in claim 21. Beneficial Embodiments of the invention are the subject of Subclaims.

The invention is based on the knowledge that Composite sliding bearing especially for the Can be used at high temperatures are when in the bearing alloy layer Solid lubricant is stored. The wear of the Bearing alloy layer is reduced in that the stored solid lubricant during the Operation is released and thus to protect the Aluminum bearing alloy layer contributes.

It has been shown that such composite plain bearings with this superior to the state of the art Properties manufactured particularly inexpensively can be if the bearing alloy layer has open pores with a  Solid lubricant can be filled. Since the Contribution of the solid lubricant to the Sliding properties of the composite plain bearing as possible should be constant over the entire operating time, a procedure had to be found which Formation of channel-like pores in the Allows aluminum bearing alloy layer, where these channel-like pores are as constant as possible Have cross section and perpendicular to Extend sliding surface. As particularly suitable for the formation of such pores has anodic oxidation, in which the Bearing alloy layer in a surface layer converted into a pore oxide layer becomes.

Preferably, the thickness D₁ is the pores having top layer to about 10 to 30 microns preferably limited to 16 to 20 microns because larger Layer thicknesses, especially those with <50 µm tend to "chalk". With these big ones Layer thicknesses take place in the operation of a depository a transformation of the oxide layer into a powdery one Modification instead, which leads to high wear. This chalking occurs at layer thicknesses below 30 µm not on. Because of the stored Solid lubricants are also thicker layers not necessary because of the solid lubricant the wear of the bearing alloy layer opposite the state of the art.

The bearing alloy layer underneath the pores having top layer is preferably as Barrier layer formed. This barrier layer is non-porous, with the aluminum largely increasing Al₂O₃ has been reduced. Preferably the barrier layer formed as thin as possible, so  a good bond of the top layer on the Alumina-free bearing alloy layer is guaranteed.

The diameter of the pores in the top layer is preferably 120 to 330 A. This diameter of Pores have proven to be particularly advantageous in terms of the introduction of the solid lubricant exposed. The capillary traction is at these pore diameters for the used Solid lubricant particularly cheap.

The density of the pores is preferably between 0.4 × 10 ¹⁰ to 7.7 × 10 ¹⁰ cm ^-2 .

The solid lubricant can be in the form of a Solid lubricant dispersion or a paste are present, which may be diluted with water. A dispersion is preferably formed Polytetrafluoroethylene used. The Solid lubricant can also be other active ones Friction reducing additives such as boron nitrite, Have molybdenum 4-sulfide, graphite or polymers. Polyethylene (PE), Perfluoroalkoxy polymers (PFA), polyvinylidene fluoride (PVDF), tetrafluoroethylene copolymer / ethylene (PETFE), polytrifluorochloroethylene (PCTFE), Tetrafluoroethylene / hexafluoropropylene copolymer (PFEP). A copolymer has also proven itself Hexafluoroisobutylene (HFIB) and vinylidene fluoride (VF₂). This copolymer has been successfully used in Form of an aqueous dispersion with 25% Solids content used.

Regarding the paste to be used, too PTFE pastes preferred, which are additionally active Fillers such as MoS₂ or boron nitride or graphite can be moved. The one used  PTFE paste can be made from a PTFE dispersion with a Solids content of 33% can be produced. In the Dispersion is added 2% emulsifier and the Dispersion stirred for 10 minutes. Subsequently add about 40% by weight based on PTFE MoS₂ added and homogenized by 10minutes Stir. The dispersion is then by adding Aluminum nitrate (10% solution) precipitated by a Filter the perlon filter and then stick out left so that the residual moisture less than 25% H₂O has. This paste is then ready to use for impregnation.

To a at higher sliding speeds improved dissipation of the frictional heat from the It has to get sliding surface to the bearing housing proven itself, the paste fine metal powder, e.g. B. Add copper powder.

The manufacturing method according to the invention this composite plain bearing uses the anodic one Oxidation, with the help of which the aluminum in one Surface layer of the storage layer in a pore oxide layer is converted. For this, the bearing shells are placed in a suitable one Electrolytes dipped and with the positive pole connected to a DC voltage source. As a cathode can serve, for example, stainless steel. By the continuity becomes the Aluminum bearing alloy layer anodized. So that this layer can build up regularly, the surface of the bearing shells is Free of impurities. Under the influence of high electric field strength - it is preferably 10⁷ V / cm - occurs in the Aluminum layer ion line. It finds one Cargo and mass transportation through the primary  formed, very thin oxide layer and thus a Layer growth instead. The resulting, non-porous Layer is called a barrier layer. The The barrier layer is underneath the surface Exposure to the electrolyte converts and grows further in the form of a porous layer. After graduation the anodic oxidation are on the Steel beams a total of three layers, namely first the one not converted to aluminum oxide Aluminum bearing alloy layer, on top of that pore-free barrier layer and then the pores showing top layer.

As particularly suitable for the training of porous cover layers have become electrolytes Proven sulfuric acid and oxalic acid.

Preferably the anodic oxidation is 15% Sulfuric acid and with current densities of 1 to 2 A / dm² carried out. To achieve this Current densities are voltages from 15 to 18 V. required. In this way, 40 Minutes layer thicknesses of about 15 to 20 µm achieve.

Will the anodic oxidation in oxalic acid carried out, either direct current or AC are applied.

Depending on the method used, how can the following tables 1 and 2 show different pore diameters and pore densities be set so that it is possible to set the anodic oxide layer on the solid lubricant to coordinate and overall the purpose adapt.  

Table 1

Pore structure data of differently produced oxide layers

Table 2

Pore density of differently produced oxide layers

It has also been found that the Bath temperature of the electrolyte special Attention needs to be paid. So at a bath temperature of 10 ° C and one Sulfuric acid concentration of 15% a Vickers hardness reached 250 in the resulting oxide layer. This is hardness for certain applications especially with regard to the embedding of Dirt particles not suitable. However, it has shown that by controlling bath temperatures, the so-called redissolving power, the hardness so controlled can be that a hardness range between 70 and 150 Hv is achievable, which is also a good one Embedding ability allowed. For this range of hardness have been using the sulfuric acid process Bath temperatures up to max. 50 ° C, preferably 25 to Well proven at 50 ° C.

After the oxidation process, the bearing shells are in given an impregnation container that with the in the Solid lubricant to be introduced into the pores is filled.

If a solid lubricant in the form of a dispersion is used by means of anodic Oxidation treated bearing shells in this Dispersion dipped. This process takes place in the Impregnation container, which after evacuation a pressure of about 1 to 2 bar with the respective Dispersion is flooded. During the watering the dispersion solution kept moving so the solid lubricant dispersion is better distributed.

If a paste is used as the solid lubricant the immersion process takes place at negative pressure. This has the advantage that the capillary traction is increased, thereby causing the penetration of the paste into the  open pores is facilitated. Then will with a gas, preferably nitrogen or oil-free Air replenished to absorb the porous Support structure for the solid lubricant.

After the impregnation treatment, the Plain bearing cups in alcohol or White spirit washed.

Below is a procedure for the anodic oxidation of Steel / AlNi₂Mn₁ bearings described.

Below is an overview of the physicochemical properties of Pure PTFE dispersion, which has proven to be suitable for the Appropriate application proven:

Table 3

The manufactured by the method described Bearing cups have the advantage that already at the first attempt at a bearing Effect of e.g. B. polytetrafluoroethylene is given. It has been shown that after a short time Times a transfer of the solid lubricant to the Counter-rotating or rubbing on the pin takes place causing a significant drop in the coefficient of friction is brought about.  

The device for performing this method has a known galvanizing device on, the electrolyte used for anodic Oxidation of the aluminum is suitable. The Bearing shells are placed in a plastic container semi-cylindrical cross section used and with this plastic container in the electrolyte immersed. The plastic container can be one or several stacks, preferably two stacks of Pick up bearing shells. The container is preferably made of plastic, in particular made of foamed polypropylene and exhibits the Form a semi-cylindrical column. The container is completely electric from the electrolyte completed and he only owns his Front wall has a slot opening that is almost over stretches the entire length. Through this slit the electrolyte can get inside the container penetrate so that the one to be treated Aluminum bearing alloy layer with the electrolyte comes into contact.

The electroplating device is one Impregnation device downstream, the one has evacuable impregnation container. In this The impregnation container is located there Solid lubricant either in the form of a dispersion or a paste. The impregnation container is on one Pressurized gas device connected. So that Dispersion in the container during the Dipping process of the bearing shells evenly distributed, the impregnation container is with a Provide facility that the container in Vibrations, in a circular motion or in a shaking motion.  

The one in the electroplating device Electrolyte is preferably H₂SO₄ or Oxalic acid. The electroplating device can with AC or operated with direct current.

Below are exemplary embodiments the invention with reference to the drawings. It shows

Fig. 1 is a plain bearing shell according to the invention in perspective view;

Fig. 2 shows a section through the bearing shell along the line II-II in Fig. 1,

Fig. 3, the drawn in FIG. 1 detail III in an enlarged scale;

Fig. 4 is a schematic representation of the Galvani kVideo,

Fig. 5 shows a section through the electroplating shown in Fig. 4 along the line VV and

Fig. 6 is a schematic representation of the impregnation device.

In Fig. 1, a bearing shell ( 1 ) is shown in perspective. An aluminum bearing alloy layer ( 8 ) is located on a steel bearing back ( 2 ), the surface layer of which is formed by a porous cover layer ( 5 ).

A detailed representation of the layer structure can be seen in FIG. 2, which represents a section through the bearing shell shown in FIG. 1. The bearing alloy layer ( 8 ) of the bearing shell ( 1 ) was converted in the upper region by the anodic oxidation, with the formation of the barrier layer ( 4 ) and the cover layer ( 5 ). The area of the bearing alloy layer ( 8 ) that has not been converted is designated by ( 3 ). In this layer ( 3 ) the bearing alloy layer ( 8 ) applied to the steel bearing back ( 2 ) is present in an unchanged form. The barrier layer and the porous cover layer have aluminum oxide, which is to be indicated by the points drawn.

In addition to the aluminum oxide, the cover layer ( 5 ) also has channel-like pores ( 6 ) which are filled with a solid lubricant ( 7 ). The length of the pores ( 6 ) corresponds to the thickness D₁ of the porous cover layer ( 5 ). The pores ( 6 ) run essentially perpendicular to the sliding surface ( 25 ). This offers the advantage that with decreasing thickness D 1 of the porous cover layer ( 5 ) the proportion of solid lubricant available for lubrication remains essentially constant.

The thickness D₂ of the barrier layer ( 4 ) is about 20 microns.

In Fig. 3, the area of the cover layer ( 5 ) designated III is shown enlarged. This is an electron micrograph of the surface of the porous cover layer. The points shown in black represent the pores ( 6 ) which are completely filled with the solid lubricant ( 7 ). The pores ( 6 ) are distributed substantially uniformly over the entire surface.

In FIG. 4, the Galvani kVideo (9) is shown. On a bottom part ( 13 ) are the

In FIG. 4, the plastic container (9) is shown. The bearing shells ( 1 ) are arranged in two stacks ( 10 ) and ( 11 ) one above the other on a base part ( 13 ). In the upper area of the container there is a terminal strip ( 15 ) which presses on the bearing shells ( 1 ) and is provided with an electrical connection via a spring clip ( 16 ) so that the positive voltage pole is applied to the bearing shells. The entire container ( 9 ) is suspended in the electroplating device with the holding pin ( 17 ).

A slot ( 12 ) is made in the front wall ( 19 ) of the container ( 9 ) (see FIG. 5), through which the electrolyte can penetrate into the interior ( 26 ) of the container ( 9 ). At least one outlet opening ( 14 ) is located in the bottom part ( 13 ) of the container ( 9 ). The rear wall ( 18 ) of the container ( 9 ) is round, so that the entire container has a semicircular cross section.

In FIG. 6, the impregnating device (24) is shown schematically. The centerpiece of the impregnation device ( 24 ) is the impregnation tank ( 21 ), which is connected to a swivel or vibrating device ( 27 ) that moves the impregnation tank ( 21 ) during the impregnation process, so that the dispersion of the solid lubricant in the impregnation tank ( 21 ) is always on is kept in motion. The impregnation container ( 21 ) is connected to a solid lubricant reservoir ( 20 ) via a connecting line ( 28 ). Air / argon or nitrogen can be supplied under pressure to the impregnation container ( 21 ) via a supply line ( 22 ). The desired vacuum can be set in the impregnation tank ( 21 ) via the evacuation line ( 23 ), which is connected to a vacuum pump (not shown).

Reference symbol list

1 bearing shell
2 steel backs
3 remaining aluminum bearing alloy layer
4 barrier layer
5 top layer
6 pores
7 solid lubricant
8 bearing alloy layer
9 electroplating
10 stacks of bearings
11 bearing shell stacks
12 slot
13 bottom part
14 outlet opening
15 terminal block
16 spring element
17 holding pins
18 rear wall
19 wall
20 storage containers for solid lubricants
21 impregnation container
22 supply line
23 Evacuation line
24 impregnation device
25 sliding surface
26 free space
27 Swiveling or vibrating device
28 connecting line
29 rubber cover
30 robber cathode
D₁ layer thickness
D₂ layer thickness

Claims (27)

1. Composite plain bearing for highly loaded engines of internal combustion engines, especially for supercharged diesel engines, consisting of a steel support layer and an aluminum bearing alloy layer applied thereon, in particular of the type AlSi₁₂CuMgNi, AlSi₄Cd, AlZn₅SiCuPbMg or AlNi₂Mn₁, characterized in that
that the bearing alloy layer ( 8 ) has an aluminum oxide-containing cover layer ( 5 ) with open pores ( 6 ), the majority of the open pores ( 6 ) being filled with a solid lubricant ( 7 ). 2. composite sliding bearing according to claim 1, characterized in that the cover layer ( 5 ) has a thickness (D₁) of 10 to 30 microns. 3. composite sliding bearing according to claim 1 or 2, characterized in that the bearing alloy layer ( 8 ) below the cover layer ( 5 ) is designed as a barrier layer ( 4 ). 4. composite sliding bearing according to one of claims 1 to 3, characterized in that the diameter of the pores ( 6 ) is 120 Å to 330 Å. 5. composite sliding bearing according to one of claims 1 to 4, characterized in that the density of the pores ( 6 ) is between 0.4 × 10¹⁰ to 7.7 × 10¹⁰ cm ^-2 . 6. Composite sliding bearing according to one of claims 1 to 5, characterized in that the solid lubricant ( 7 ) contains boron nitride, graphite, molybdenum sulfide or a polymer. 7. composite sliding bearing according to claim 6, characterized characterized in that the polymer PTFE, PE, PFA, PVDF, PETFE, PCTFE, PFEP or a copolymer Is hexafluoroisobutylene and vinylidene fluoride. 8. composite sliding bearing according to one of claims 1 to 7, characterized in that the solid lubricant ( 7 ) is a paste. 9. composite sliding bearing according to claim 8, characterized characterized that the paste is fine Contains metal powder. 10. composite sliding bearing according to claim 9, characterized characterized in that the metal powder Copper powder is. 11. Method for producing a composite plain bearing, in which a steel back
Aluminum bearing alloy layer, in particular of the AlSi₁₂CuMgNi, AlSi₄Cd, AlZn₅SiCuPbMg or AlNi₂Mn₁ type is applied, characterized in that
that the aluminum in a surface layer of the bearing alloy layer is converted into an oxide layer having pores by means of anodic oxidation, and
that the pores resulting from this conversion are then largely filled with a solid lubricant. 12. The method according to claim 11, characterized characterized in that the anodic oxidation in 15% H₂SO₄ and with current densities of 1 to 2 A / dm² is carried out. 13. The method according to claim 12, characterized characterized in that the anodic oxidation in H₂SO₄ at a temperature between 15 and 50 ° C is carried out. 14. The method according to claim 11, characterized characterized in that the anodic oxidation in Oxalic acid with the application of direct current is carried out. 15. The method according to claim 11, characterized characterized in that the anodic oxidation in Oxalic acid with the application of alternating current is carried out. 16. The method according to any one of claims 11 to 15, characterized in that after the anodic Oxidation to fill the pores of the bearing shells be soaked in solid lubricant. 17. The method according to claim 16, characterized characterized that soaking in one Dispersion solution made of PTFE. 18. The method according to claim 17, characterized characterized in that while soaking the Dispersion solution is kept in motion. 19. The method according to claim 11-15, characterized characterized in that the pores by means of a paste containing solid lubricants Apply a vacuum to be filled out.   20. The method according to any one of claims 16 to 19, characterized in that after filling the Pore nitrogen or oil-free air becomes. 21. Device for processing bearing shells, which have a bearing alloy layer on a steel back, in particular of the type AlSi₁₂CuMgNi, AlSi₄Cd, AlZn₅SiCuPbMg or AlNi₂Mn₁, characterized by
a galvanizing device with an electrolyte suitable for anodic oxidation of the aluminum,
at least one plastic container ( 9 ) with a semi-cylindrical cross section, in which the bearing shells ( 1 ) to be machined are stacked, for immersion in the electrolyte, and
an impregnation device ( 24 ) with an evacuable impregnation container ( 21 ) containing solid lubricant. 22. The apparatus according to claim 21, characterized characterized in that the electrolyte H₂SO₄ or is oxalic acid. 23. The device according to one of claims 21 or 22, characterized in that the Electroplating device for operation with AC or DC is formed. 24. Device according to one of claims 21-23, characterized in that the plastic container ( 9 ) is a semi-cylindrical. 25. Device according to one of claims 21-24, characterized in that the electroplating holder ( 9 ) receives at least two stacks ( 10, 11 ) bearing shells ( 1 ). 26. Device according to one of claims 21-25, characterized in that the impregnation container ( 21 ) is connected to a compressed gas device ( 22 ). 27. The device according to any one of claims 21-26, characterized in that the impregnation container ( 21 ) is designed to carry out oscillating or vibrating movements.