EP1466683A1 - Process for making a piston for an internal combustion engine and piston for an internal combustion engine - Google Patents

Abstract

An insert (12) is prepared and set into a piston main body (PMB) made from an aluminum cast alloy. The insert is then partly recast with piston material and its immediate surroundings (14) are recast in the PMB. The material of the insert has a higher proportion of alloy elements than the PMB that increase resistance to high temperatures, e.g. silicon, copper, nickel, magnesium and iron. An independent claim is also included for an internal combustion engine's piston with a piston main body and an insert firmly bonded to the piston main body.

Description

Technical field

The invention relates to a method for producing a Pistons for an internal combustion engine and a piston for an internal combustion engine.

Pistons from internal combustion engines are common during the Operation high loads, especially thermal Exposed to stress. Here are different Areas of the piston vary considerably Exposed to stresses and temperatures. For example vary on a piston, especially one Diesel engine, temperatures occurring in one extensive area. There are also different types mechanical stress at different points of the piston occur and overlap the temperature field. On Area of a piston, in particular a diesel piston, the is known to be claimed in a special way, is the Edge of the combustion chamber trough.

State of the art

To strengthen the particularly stressed areas of a Kolbens is known to strengthen these areas locally. For example, missions have been common in the past made of materials with particularly cheap High temperature properties on the particularly stressed Areas provided. These inserts can be used with the piston be connected by welding. The structure remains of the reinforcement insert in the particularly stressed Areas. The requirements are accordingly the properties and structure of the inserts used very high. In particular, the required Properties often only through particularly complex processes can be achieved, making such operations only with considerable costs are to be produced.

Furthermore, it is known to weld the structure in to change the particularly stressed areas of the piston, and, if necessary, by adding an additional material change local material composition. Such a thing The method is for example in DE 102 34 669 and EP 03 003 199 described by the applicant. A restriction However, there is the fact that as a filler in Essentially the piston material as the base material must be introduced, and other elements only in can be added to a limited extent.

Presentation of the invention

The invention has for its object a method for Creating a piston that is designed with regard to the high temperature resistance and resilience in particular critical areas is improved. Furthermore, a piston should with these characteristics.

This task is solved on the one hand by the Claim 1 described method.

Accordingly, the manufacturing process a piston for an internal combustion engine prepared. This is suitably converted into one Piston base body used and preferably with this connected. In conclusion, the stake is at least partially remelted. Furthermore, at least the melting takes place immediate environment of use in the Piston base body.

The invention is based on the basic idea that Properties of the particularly stressed areas To improve piston on the one hand by using it with particularly favorable properties is introduced. This However, deployment can be extremely simple and provides essentially just a stock of certain Elements representing an improvement in properties to care. These have the effect that the Use in the process according to the invention is remelted. This poses a special fine structure of the insert. Such a structure shows significantly improved high temperature properties on and increases, as tests show, the resilience of the particularly critical areas of a piston. In a particularly advantageous way Way also takes place in the context of remelting the insert a fusion with the piston body. Here is a particularly intimate connection with the piston body reached. This takes place in the transition area between Insert and piston body a flowing and gradual and never abrupt changes in properties. Therefore, problems that have occurred so far, for example Cracks in the connection between a high-strength insert and the piston body are avoided. It is beyond that to emphasize that in an economically advantageous manner and Way through a single process step, namely Melting of the insert, both the structural change of the Use as well as its firm connection and that Fusion with the piston body can be effected.

The advantages of the method according to the invention thus exist on the one hand in the fact that the insert can be manufactured inexpensively is. In particular, there are no complex procedures here to achieve favorable high-temperature properties required. Rather, its use is intended for certain the high temperature properties favorable elements contribute. The desired properties are about it in particular by remelting the insert and the particularly fine structure achieved thereby ensures. On the other hand, the initial insertion can also be done if necessary, the connection of the insert with the Piston base body are comparatively loose. It does not necessarily have sufficient strength for this first connection can be achieved because the required firm connection when remelting the insert to a certain extent automatically due to the merger with the surrounding piston material takes place.

Because the insert with the piston material on its edge melts, but still one of the piston body represents delimited object, there are none significant restrictions with regard to the material of the Insert. While the previously known introduction of Additional materials only to a limited extent Alloy elements could be added, the Use a favorable, for the improvement of the properties, basically contain any amount of other elements, and in the piston ultimately produced, these can Elements fully unfold their advantages. By selection suitable parameters when remelting the insert the transition between the insert and the piston material in be designed appropriately. For example, show attempts to mix in the area of this transition the actual piston material with the material of the Be approved for use. This will make this transition designed particularly soft, and the risk of cracks and The like due to an abrupt transition can be extensive be narrowed down.

Finally, the material of the insert can differ from that differentiate other piston material. This is one particularly good adaptation of the material used in each case possible to meet the requirements of certain areas of the Be piston. In particular, the material of the Use for the occurring loads in the particular critical areas, such as the trough edge, be adjusted. At the same time, the piston material in the Incidentally, so far for the requirements in the particularly stressed areas had to be designed, largely exclusively according to the requirements in others, areas that may be critical in other respects be interpreted. This is, for example those areas where a cooling duct or the Piston pin bore is to be formed. Having something here other needs than in the area of Trough edge, the piston material can be used especially for those areas are designed where the Piston material remains on the finished piston and not is replaced by the insert. Furthermore, the use especially targeted for the requirements with regard to the High temperature resistance can be designed. Hence can the properties of the piston in all critical Areas to be improved.

Preferred developments of the method according to the invention are described in the further claims.

For the material of the piston body, a Aluminum alloy, especially a cast aluminum alloy prefers. This unfolds with these materials The inventive method in a special way Benefits. However, it should be noted that this is basically also applicable to a piston made of steel.

With regard to the material of the insert, as above executed, a special flexibility, since only a little Scope on a compatibility with the material of the Piston base body must be observed. Nevertheless, for the material of the insert is also an aluminum alloy prefers.

The properties of a can be particularly extensive the piston produced by the method according to the invention be improved when the material of the insert, especially the aluminum alloy, a higher proportion of Contains alloying elements, which the Increase high temperature strength than the material of the Piston base body, especially the one used Aluminum alloy. For example, it can be used alloy used a higher proportion of one or more of the following alloy elements: silicon, copper, Nickel, magnesium, iron.

For the first connection of the insert with Pouring is currently preferred for the piston base body. In other words, use in a mold arranged and is in the course of the casting process by the Surround piston material. Nevertheless, the use can also be on otherwise connected to the piston body first or only used in this. For example is pressing, shrinking and welding of use with the piston base body possible.

The remelt of the insert where the insert preferably completely liquid at least in some areas is preferably carried out by a deep welding process. Here, for example, electron beam welding, an arc welding, a plasma welding, a TIG welding or laser welding. in the Essentially any method is suitable in which the Use at least in those zones after a possible post-processing in particularly stressed areas remain, as well as at the interfaces to the Piston material can be remelted.

As mentioned, the insert can initially be used as a mere "package" or "stock" of elements provided for the Areas particularly exposed to high temperature resistance increase. Therefore, the use can initially be one if possible have simple shape. In the context of the Invention Method, however, it is preferred that the piston, in particular in the area of use. For example, a combustion chamber trough can be used here be worked out.

In this case, an optimization of the invention Procedure take place in that at least those parts the use that remains after the post-processing, be remelted. In contrast, the melting in those areas that are involved in post-processing, for example, to form a combustion chamber trough be omitted.

The above object is also achieved by a piston according to claim 9. This has one Piston base and at least one insert that is fixed is connected to the piston body, the insert and at least the areas of the piston body that are are in the immediate vicinity of the mission, at least are partially remelted. The fact that here Remelting was made, is recognizable by the extreme fine structure of the remelted areas. The Piston according to the invention is thus characterized in that in the field of use, which particularly temperature-stressed areas is provided, on the one hand advantageous, finer structure is present, and secondly the material used by suitable, already above Alloying elements mentioned to those in these areas occurring requirements is adjusted. The transition between the insert and the piston material is through the Remelt especially at this interface fluently. In other words, this can happen in this zone Material of the insert with that of the piston material mix. Because of the remelting occurs in this area here, too, a very fine structure. After all, that is The insert is fused to a certain extent with the piston material and thereby particularly well connected to it. By the steady and non-discrete transition between use and the piston material can increase the risk of cracking this area can be significantly reduced.

In particular, the piston according to the invention can therefore also be described by making a bet from a material other than the piston material that with the piston material is fused. Preferably changes the material composition between the insert and the Piston material gradually, and preferably point at least Parts of the insert and areas of the piston body a finer structure at least in the area of use on as remaining areas of the piston material.

The preferred embodiments of the invention Pistons essentially correspond to those pistons that through the preferred embodiments of the invention Process can be produced. This can be the case Pistons according to the invention in particular around a diesel piston, which is preferably attributed to the highly loaded diesel piston is act. Furthermore, the piston preferably has one Combustion chamber trough that is trained in the area of use is.

Brief description of the drawings

Fig. 1

schematisch einen in eine Gießform eingesetzten Einsatz;

Fig. 2

schematisch den in den Kolbenwerkstoff eingegossenen Einsatz;

Fig. 3

schematisch den mit dem Kolbenwerkstoff verschmolzenen Einsatz; und

Fig. 4

den fertiggestellten Kolben mit einem nachbearbeiteten Einsatz.

The invention is explained in more detail below on the basis of an embodiment shown as an example in the figures. Show it:

Fig. 1

schematically an insert inserted into a mold;

Fig. 2

schematically the insert cast into the piston material;

Fig. 3

schematically the insert fused with the piston material; and

Fig. 4

the finished piston with a reworked insert.

Detailed description of a preferred embodiment the invention

In Fig. 1 is schematically a mold 10 and one therein insert 12 shown. Here, the use in particular provided adjacent to an edge of the mold because the use is typically in the final state of the Piston forms an edge region of the piston. As already in 1 can be seen, for example, in Form a thick disc or large tablet in which Be provided area that later forms the piston crown. This area is located in Fig. 1 at the bottom. The Use in this area, especially the interior Form the area of the piston crown, as it were ring-shaped on the finished piston in the area 14 of the Piston material used is provided.

Pouring the insert 12 with the piston material 16 is shown in FIG Fig. 2 shown. The one provided with the insert 12 Casting mold 10 is filled with piston material 16, so that the Insert 12 subsequently poured into piston material 16 is. 3 schematically shows the remelting of the insert 12 and the resulting fusion with the surrounding Piston material 16 shown. By remelting the Insert 12 solve the previously fixed and defined Limits between insert 12 and piston material 16 to a certain extent. The material of the insert 12 can change at least in the marginal areas of use with the Mix piston material 16. Thus, based on that Area inside the insert where the insert continue entirely from the original material of the There is a transition area at the former boundary between the insert 12 and the Piston material 16 to those zones in which the Piston material 16 is present in its pure form, a flowing Transition before. As mentioned, this makes a very fine structure and secondly an intimate and at the same time harmonious connection of the insert with the piston material 16 reached.

Finally, as shown in Fig. 4, another Machining the finished piston, especially in the area of Insert 12 take place, for example, in the area of Insert 12 to form a combustion chamber trough 18. The edge of the The combustion chamber trough is thus formed by the use of the Material composition and structure after remelting in special requirements in this area, especially with regard to high temperature resistance, Takes into account. Here, the edge of the trough, which is through the Material of the insert 12 is formed as armored be designated.

Claims (13)

Method for producing a piston for an internal combustion engine, comprising the following steps: Preparing at least one insert (12), Inserting, in particular connecting the insert (12) into or with a piston base body, and at least partially remelting the insert (12) and at least the immediate vicinity of the insert (12) in the piston body. Method according to claim 1,
characterized in that
the material of the piston base body is an aluminum alloy, in particular a cast aluminum alloy. Method according to claim 1 or 2,
characterized in that
the material of the insert (12) is an aluminum alloy. Method according to one of the preceding claims,
characterized in that
the material of the insert has a higher proportion of alloy elements which increase the high temperature strength, such as silicon, copper, nickel, magnesium, iron, than the material of the piston base body. Method according to one of the preceding claims,
characterized in that
the insert is poured into the piston body. Method according to one of the preceding claims,
characterized in that
the remelting is carried out by a deep welding process. Method according to one of the preceding claims,
characterized in that
the piston is reworked, particularly in the area of the insert, in particular a combustion chamber trough is worked out. Method according to claim 7,
characterized in that
at least the part of the insert remaining after the post-processing is remelted. Piston for an internal combustion engine with a Piston base body and at least one insert (12), the is firmly connected to the piston body, the Use (12) and at least the immediate area of use in the piston body at least are partially remelted. Piston according to claim 9,
characterized in that
the piston base body consists of an aluminum alloy, in particular an aluminum casting alloy. Piston according to claim 9 or 10,
characterized in that
the insert (12) consists of an aluminum alloy. Piston according to one of claims 9 to 11,
characterized in that
the material of the insert (12) has a higher proportion of alloy elements, which increase the high temperature strength, such as silicon, copper, nickel, magnesium, iron, than the material of the piston body. Piston according to one of claims 9 to 12,
characterized in that
this has a combustion chamber trough (18).

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