Method for finely processing a cylindrical inner surface

Abstract

The invention relates to a process for precision-machining a cylindrical inner surface, in particular a cylinder bearing surface, which has material of different hardnesses in the axial direction. The cylindrical inner surface is subjected to a precision-turning step, a preliminary honing step and a precision-honing step. The process is distinguished by the fact that the preliminary honing step produces a cone (11) in the cylindrical inner surface, in such a way that the cone (11) widens out from a harder region (4) toward a softer region (6). In the subsequent precision-honing step, the cone (11) is compensated for again in the harder region (4) to produce a cylindrical inner surface, whereas the cone (11) is retained in the softer region (6). This prevents the fine abrasive particles on the precision-honing stone from becoming clogged as a result of contact with the softer region.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The invention relates to a process for precision-machining a cylindrical inner surface in accordance with the preamble of claim 1. [0003] 2. Related Art of the Invention [0004] The precision-machining of cylindrical surfaces, in particular the precision-machining of cylinder bearing surfaces in cylinder crankcases, is generally realized by honing. There are a wide range of publications in this respect, such as for example DE 44 32 514 A1, which describes a process allowing a highly accurate final dimension of a honed surface to be achieved. [0005] DE 196 05 588 C2 describes a process in which a cylinder bearing surface is treated in such a way at a top dead center and bottom dead center of a piston that it is able to withstand higher wear conditions in these regions. [0006] However, the known prior art is restricted to the precision-machining of a surface which has the same surface material throughout. However, the ...

AI Technical Summary

Benefits of technology

[0008] The object of the invention is to precision-machine cylindrical inner surfaces which have different materials in such a way that the service lives of the machining tools are considerably improved.

[0013] The cone, which spans the boundary region between the softer and harder regions, prevents the extremely fine abrasive particles on a precision-honing stone from becoming clogged by the material of the softer region.

[0014] In one configuration of the invention, the cone is introduced by a conical honing stone or a honing stone which is oriented in the shape of a cone. The conical or conically oriented honing stone allows the cone to be predetermined by the tool so that it is accurately set.

[0019] To avoid a separate step in the softer region, the cone can open out into an opposite cone, which leads to a convex shape in the softer region. The convex shape can contribute to reducing noise when the engine is operating.

Problems solved by technology

However, the known prior art is restricted to the precision-machining of a surface which has the same surface material throughout.

In such cases, precision-machining, in particular honing, is particularly difficult, since the machining tools used, e.g. the honing stone, becomes clogged by the softer material, thereby losing its abrasive action.

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