Volkswagen Ag

Reinhard Vogelsang

Udo Schlegel

In the particular embodiments described in the specification, bearing material is applied to the bearing surface of a connecting rod eye by thermal spraying of the bearing material such as by plasma coating. In a particular embodiment the large connecting rod eye is plasma-coated with an aluminum bronze. After the plasma coating, the connecting rod eye is opened by removing the bearing cover from the rest of the connecting rod, thereby breaking the plasma layer. Subsequently, the cover is screwed on again, and the surface of the bearing layer is finished by fine spindling. The method results in reduced assembly costs.

Method for producing a connecting rod eye

When bearing layers are producing by thermal coating the coating flame causes oxidation of a part of the coating material. To reduce this oxide formation and especially to lower the formation of oxide clusters in the layer a gas stream is projected next to the burner flame with an oxygen content lower than that of air. Preferably a gas with nitrogen &gE;99% is used for the gas stream and as cooling gas for the burner. The method disclosed provides a bearing layer for a connecting rod eye. The large connecting rod eye is subjected to pre-spindle trimming, cracking and further spindle trimming to the coating tolerance, sandblasted and plasma coated with an aluminum bronze to produce a microporous layer. At the start of plasma spraying the plasma layer is deposited at a high temperature, which results in good adhesion of the plasma layer to the material of the connecting rod eye and low porosity of the plasma layer. To prevent annealing of the material of the connecting rod eye, the deposit temperature of the plasma layer is reduced during deposition of material which is removed by subsequent machining of the bearing layer. After plasma coating the connecting rod eye is opened by removing the bearing cap, which ruptures the bearing layer. The cap is then remounted and the final bearing surface is formed by fine spindle trimming. To improve the oil retention volume the bearing layer has an annular groove.

Method for thermal coating of bearing layers

In the method described in the specification, the large eye of a connecting rod is microporously plasma-coated with an aluminum bronze. After plasma coating the connecting-rod eye is opened by breaking or cutting to remove the bearing cap, which breaks the plasma layer. The cap is then remounted the bearing surface is produced by fine spindle trimming. To improve the oil retention volume the bearing layer has an annular groove. The aluminum bronze bearing layer is especially firmly bonded to the connecting rod material by multiple sandblasting treatment of the surface to be coated, using sand particles of successively increasing particle size.

Connecting rod with thermally sprayed bearing layer

In order to produce connecting rod bearings which are easier to mount and which are the larger strongly bonded, the large connecting rod eye is plasma-coated with an aluminum-bronze. At the start of the plasma-spraying process, the plasma layer is deposited at a high temperature in order to ensure that the plasma layer bonds well to the connecting rod eye material and has a low level of porosity. In order to prevent the connecting rod eye material from annealing, the depositing temperature of the plasma layer is reduced so that the material to be removed during subsequent finishing is deposited at a lower temperature. After the plasma-coating process is complete, the connecting rod eye is opened by taking off the bearing cover, thus breaking the plasma layer. The cover is then remounted and the bearing surface is finished by fine spindling. The bearing layer has an annular groove in order to improve the oil holding volume. A particularly strong bond between the aluminum-bronze and the connecting rod material can be achieved by multiple sand-blasting of the surface to be coasted with sand particles of increasing grain size.

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Salzgitter, Germany

Reinhard Vogelsang