SU68583A1 - The method of processing the inner surface of the cylinders of internal combustion engines - Google Patents

Description

In the practice of factory testing of aircraft air-cooled engines, as well as in their exploitation, engine smoke and stepped cylinder wear are observed. A particularly large defect of engines and cylinders for these defects occurs during factory acceptance and control tests.

Attempts to eliminate these defects have not yielded favorable results so far.

Studying the causes of these defects it has been established that they lie in the existing method of manufacturing cylinders.

The manufacturing process used in factories for manufacturing cylinders for air-cooled engines has the peculiarity that the final machining of the working surface (mirror) of the cylinder — grinding and honing — is done after a heated aluminum head is screwed onto the cylinder, which results in perfect integrity and reliability of the cylinder-head coupling.

With this method of manufacturing a cylinder, the following phenomena occur in it.

After screwing up the head due to the large tension in the thread and the thinness of the cylinder in its upper section over the thread, deformation occurs - the corset structure shown in FIG. one.

The subsequent processing — grinding and grinding the working surface (mirror) of the cylinder — gives it the required cylindrical surface, i.e., along the convexity A (Fig. 1) is removed. In this case, the nitrided layer is partially or completely removed. The working surface of the cylinder takes the form indicated in FIG. 2, and in this form the cylinder enters the engine assembly.

After the cylinder is warmed up on the working engine, the cylinder head expands and allows the cylinder to straighten, i.e., partially or completely get rid of the corset, causing at the same time a distortion of the working surface

lindra - barrel-shaped in the cross-thread (Fig. 3).

This barrel shape leads to disruption of the gaps between the cylinder and the piston, increases the pumping action of the piston rings, increasing the access of oil to the combustion chamber and causes smoking. And since the nitrided layer was partially or completely removed during grinding in the section of the barrel, localized wear of the cylinder occurs in this area. Due to the presence of barreling on the working surface of the cylinder, this wear will be stepwise.

It is proposed that the material bulge on the inner surface of the cylinder thread is not completely removed.

The essence of the method is as follows.

The final treatment of the working surface (mirror) by grinding is done before tightening the head onto the cylinder, after which it is given

FIG. one

easy lapping, not removing ca bulge B (Fig. 4).

After warming up on the engine and expanding the head, the cylinder manufactured by this method, due to the absence of residual deformation from tension on the thread, will get rid of the corset in the thread and will not have a barrel shape (Fig. 5), and therefore will not smoke and step wear.

Subject of the invention. A method for treating the inner surface of cylinders of an internal combustion engine with a screwed head, characterized in that the material bulge on the inner surface of the cylinder in the center of the thread caused by high tension in the threaded joint of the cylinder and the head is not completely removed. A barrel shaped in this area due to the expansion of the head from heating.

FIG. 2

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Head.