DE102009025035A1 - Large piston processing method for internal combustion engine of passenger car, involves forming reservoir for lubricant by set of recesses, and supporting piston shaft at inner wall of cylinder chamber with areas around recesses - Google Patents

Abstract

The method involves producing an oscillating movement of a shaft of a large piston in a cylinder chamber of an internal combustion engine, and forming a set of recesses in a surface of the piston shaft. A reservoir is formed for lubricant e.g. engine oil, by the set of recesses, and the piston shaft is supported at an inner wall of the cylinder chamber with areas around the recesses. A manganese phosphate coating is applied on the piston shaft, where the piston has an external diameter of 160 mm.

Description

The The invention relates to a method for processing a piston of a Internal combustion engine according to the features of claim 1.

It is known to be useful in the operation of pistons in cylinder chambers of Internal combustion engines due to the oscillating motion and downward movement) to a contact between a piston skirt of the piston and the Inner wall of the cylinder chamber (cylinder tube) comes. This creates high contact pressures between these two partners. Since it does not come to a food should, the pistons, at least in the area of the piston skirt, coated to a galling, at least during the break-in period, however even while of the entire operation of the piston, to prevent.

These Coating has basically defended itself in practice, but it does an additional step using additional Materials (chemicals), their handling and disposal, especially under economic Point of view, is critical.

Of the The invention is therefore based on the object, a method for processing a piston of an internal combustion engine, a corresponding application of the method and a piston produced by the method to make ready, being ensured after the manufacture of the piston is that eating in a cylinder chamber of the internal combustion engine effectively avoided.

These Task is inventively achieved in that in the surface the piston shaft a plurality of recesses are introduced, wherein these depressions form a reservoir for a lubricant and the piston skirt with the areas around the recesses is supported on an inner wall of the cylinder chamber. The process step the coating is thus replaced by the process step, that the surface the piston shaft provided with a plurality of wells becomes. This process step is in a particularly advantageous manner designed as spherical radiation, at the a beam with balls of the desired diameter and predeterminable Impact speed from which results in the plurality of wells on the piston shaft, at least partially, in particular completely, directed becomes. When hitting the balls on the piston stem produce this a well with desired Diameter and desired Depth to the reservoir for to form the lubricant, in particular engine oil. It is still here beneficial that the balls after hitting the piston shaft collected and for Further process steps can be used again.

On The bottom of the recesses in the piston skirt are formed during the Operation of the piston in the engine oil reservoir, that is, that These depressions fill up with the engine oil, which through an oil ring of the Piston has been stripped in advance. This creates a variety from small oil posters, as a sliding film between the piston skirt and the inner wall of the Serving cylinder space. These oil reservoirs thus provide between the piston skirt and the inner wall of the cylinder chamber for the necessary friction-free Up and down movement, so that a seizure of the piston is effectively avoided, because that in the oil reservoirs collected engine oil can not escape, since the individual oil reservoirs with each other Have connection.

Farther it is envisaged that after machining the piston skirt, with which the plurality of wells have been introduced, one Coating, preferably a manganese phosphate coating, on the piston shaft is applied. In this variant will indeed the step of applying a coating, which basically avoided should be, executed again, after the recesses have been introduced into the piston skirt are. However, this variant has the advantage that the effects the pits and the effect of the coating in the areas complement the piston skirt around the wells around each other, since the oil reservoir in the wells the one and the coating in the areas around the wells, create another slip film, so that the seizure of the piston is particularly effectively prevented.

Farther a piston is provided, which according to the inventive method has been produced. For this purpose, in a conventional manner, a piston, in which it is a one- or multi-part (pendulum shaft) piston act in a corresponding process (casting and / or Forging process), wherein such a piston, the usual Design features, such as piston crown, ring field, pin boss with pin bore and piston skirt and optionally other features (such as a combustion bowl). After such a piston finished has been made, the process step for introduction the depressions in the piston skirt, in particular the shot peening, executed. Thereafter, the piston is ready for use, if not the additional Process step of the coating of the piston skirt is performed.

One Particularly important and important aspect of the invention is the Application of the method in a large-displacement piston.

For small pistons, in particular such pistons, in internal combustion engines for passenger power be used, it is already known that the piston skirt is coated for the reasons mentioned above. This coating is carried out by applying a corresponding liquid or paste in a screen printing process. This method can be readily applied to the so-called small pistons, which have a maximum diameter of 160 mm (millimeters). In large-diameter pistons with a diameter greater than 160 mm and more, however, there is the disadvantage that plastic piston stem coatings applied by screen-printing coating can not be used because the liquids or pastes used dry out before or while they can be applied to the large-bore pistons Drying of large piston due to the compared to small pistons much larger surface when spraying the coating faster.

Consequently is at the big piston only applied a manganese phosphating, but during the Production process of the large piston requires a lot of effort, so they are not too safety and health critical situations. Therefore, the introduction is of recesses in the piston skirt in large pistons particularly advantageous, because this process step of manganese phosphating (actually the corrosion protection of the existing of a Shahlwerkstoff large piston serves) can be omitted (but not compulsorily eliminated) and eating of the big piston in the cylinder chamber of the internal combustion engine due to steadily increasing contact pressures due to higher Loads of the internal combustion engine is avoided. Since it is usual with large bulbs, that these consist of two parts (upper part and lower part) and the two parts are bolted together, it is special advantageous, the manufactured lower part, which also the piston shaft includes, to provide with the wells, in particular ball to radiate, so that the inventive method also in large piston rationally performed can be because for the purpose of introducing the wells not the entire Piston, but only the lower part, must be handled.

Claims (6)

Method for machining a piston of an internal combustion engine, wherein the piston has a piston shaft, with which the piston performs an oscillating movement in a cylinder chamber of the internal combustion engine, characterized in that in the surface of the piston shaft a plurality of recesses are introduced, said recesses being a reservoir form a lubricant and the piston skirt with the areas around the wells is supported on an inner wall of the cylinder chamber. Method according to claim 1, characterized in that that the piston shaft shot peened to achieve the wells becomes. Method according to claim 1 or 2, characterized that a coating is applied to the piston skirt after the depressions have been introduced. Method according to claim 3, characterized that as a coating, a manganese phosphate coating on the piston skirt is applied. Piston machined according to the method of one of the preceding claims. Application of the method according to at least one of previous claims at a large piston with an outer diameter greater than 160 mm.