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Plain bearings are an important component of internal combustion engines.
The development of plain bearings is therefore closely linked with engine development. Today, the complex requirements and increased stresses imposed on the bearings of the moving engine parts, such as crankshafts, conrods, tappets and camshaft generally call for the use of materials that are carefully tuned to the respective application. The large number of proven material combinations available meanwhile enables the design engineer to select the optimally suited bearing system. |
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Bearing types and names |
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Plain bearing shells
Plain bearing shells are used for both conrod bearings and main bearings. They are mostly designed as thinwalled composite bearing shells. Bearings made of two materials have a steel back onto which the bearing metal, typically aluminium with tin and copper additives, is plated. In the case of bearings made of three materials, the bearing metal is copper with additives of lead and tin cast onto the steel back or applied by the sinter-rolling-sinter method. A nickel dam (diffusion seal) separates the bearing metal and the galvanic sliding layer. |
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Free spread: locates the bearing
Measured across the end faces, the bearing shells are larger than the diameter of the housing support. During assembly, this provides a good contact with the bore and prevents drop-out or twist.
Press fit by crush height
The circumferential length of the bearing shells is larger than that of the bore. On assembly, this bearing length is reduced by elastic deformation. The resulting stress gives the press fit which ensures correct location
of the bearing. |
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Bushes
With few exceptions, thin-walled steel composite bushes are used as conrod, camshaft or rocker arm bushes. Blanks are punched out from coated band steel, which are already provided with oil holes, oil grooves, oil distribution pockets or location grooves. These blanks are then rolled
to form bushes. Grooves and holes may become deformed in the process. Both butted and locked joints are possible. |
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