EP2841223B1 - Casting process and mould - Google Patents

Description

FIELD OF THE INVENTION

The invention relates to a method for casting a piston for an internal combustion engine, as well as an associated use of a casting tool.

In rotationally symmetrical components, such as pistons for internal combustion engines, lying and stationary casting methods are known. In the horizontal casting process, the axis of rotation of the component to be cast is oriented substantially horizontally. This process is currently used mainly in the production of diesel pistons, which are mainly cast with inserts, such as ring carriers and salt cores for the subsequent cooling channel. For casting pistons for gasoline engines, which for the most part have no casting parts, the standing casting method is predominantly used.

STATE OF THE ART

For the standing casting are known as Vorbenutzungsgegenstände machines, which make it possible to pour in a tilted up to 30 degrees from the vertical state.

From the DE 10 2006 058 145 A1 is a casting process, in which the introduction of the material according to the principle of the bottom casting and the solidification takes place according to the principle of the head casting. The CH 135526 A relates to a method and a mold for casting composite blocks, in which during casting the angular position of the mold is changed.

PRESENTATION OF THE INVENTION

It is an object of the present invention to provide a casting method and related use which is improved over the known approaches and to combine at least some of the advantages of both the horizontal and standing casting methods.

The solution of this object is achieved on the one hand by the method described in claim 1.

Accordingly, after filling the casting cavity or at least towards the end of this process and before solidification, the tool cavity defining tooling sections are rotated or tilted at least 45 degrees about a horizontal axis so that the axis of rotation of the piston to be cast moves in the vertical direction this preferably at least approximates. The basic idea of the invention thus consists essentially in filling the casting cavity in a largely "lying" position of the casting cavity. This offers particularly favorable filling conditions, since comparatively thin regions, such as, for example, the remaining wall thickness between a later cooling channel of a piston and a ring carrier can be filled better than in the standing casting method. Furthermore, foreign substances that are defects in the cast component, such as oxides or almin residues, when filling in the lying state, are advantageously conducted into regions of the workpiece which can later be removed with little effort or have to be processed anyway and thus removed.

The invention makes use of the advantages of the upright casting method insofar as the feeding behavior is better here. This is essentially due to the fact that a largely rotationally symmetrical component is cast, whose Gießhohlraum is filled in the horizontal casting with a single-sided feeder. In the tilting according to the invention in the direction of the stationary casting method, the cheaper, largely symmetrical feeding behavior of a central feeder is used. In particular, the improved feed is expected to reduce the porosity in the molded component.

According to the invention it is important that the casting cavity is tilted as a whole, so that the axis of rotation of the component to be cast, as described, changes its orientation. The known in the prior art devices and methods in which individual tool sections adjacent to the casting cavity, but not define this total, are pivotable, are so far not comparable with the inventive approach.

The tool can be referred to as a mold.

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

In order to be able to influence the behavior of the material to be filled or filled into the casting cavity in an advantageous manner, it is preferred that the tilting movement, in other words, the position of the axis of rotation of the component during filling, and / or the tilt angle and / or the Location of the axis of rotation of the component during solidification are adjustable. By a flexible adjustment of the tilt angle, the filling behavior and / or the solidification behavior can be influenced in an advantageous manner.

In order to be able to make extensive use of the advantages and the existing experience with lying casting methods, it is presently preferred that the axis of rotation of the piston to be cast be largely aligned horizontally during filling.

For the same reasons, it offers advantages when the axis of rotation of the piston to be cast is largely vertically aligned during solidification.

For the filling of the casting cavity, it is preferred for the advantages of a horizontal casting method to be used that the liquid material is filled at a lateral region of the piston to be cast. In other words, there is a sprue in a lateral region and preferably in the lower third of the pouring cavity to be filled with a horizontal casting method.

With regard to the use of a casting tool according to the invention, it offers advantages if the mold cavity has at least one recess which is located in an upright casting manner in an upper, preferably at the highest region of the mold cavity. This forms in this area after the complete filling a kind of dirt bag, in which any impurities were flushed.

The advantages of the upright casting method can be used particularly extensively by arranging a feeder after tilting the casting cavity in an upper region, in particular at a location other than the sprue.

As indicated at the outset, the method according to the invention unfolds its advantages in a particular way when the component to be cast is cast with at least one insert, such as a ring carrier and / or a core for a cooling channel of a piston for an internal combustion engine. Although it is easier, and therefore represents a preferred way to insert Eingießteile in a horizontal orientation of the component to be cast, it is preferred for certain applications to insert castings in standing casting, then the tool too tilt, and fill the mold cavity with lying casting.

The solution of the above object is further achieved by the use of a casting tool described in claim 8, with which the method described above, including its advantages is implemented device technology. The preferred embodiments of the casting tool used according to the invention essentially correspond to those of the preferred methods described above. It should also be noted that the individual features of all the methods described herein are applicable to the device, and vice versa.

BRIEF DESCRIPTION OF THE DRAWING

The figure shows schematically the procedure according to the invention in the casting of a piston for an internal combustion engine.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

As can be seen in the figure, the procedure according to the invention is explained on the basis of the positive piston 10 to be cast for an internal combustion engine, however, it is understood that the casting cavity occupied by the later piston is initially empty and of suitable, not shown , Tool sections is defined and bounded. As shown in the figure, the axis of rotation A of the piston to be produced in the initial state, that is, for filling the mold cavity, largely aligned horizontally. Approximately in the middle of the piston whose piston pin bore 12 can be seen. Further, for the example shown, one feeder 16 is present in the one end region that is up after tipping (compare the right part of the figure). During filling, the feeder is located on one side of the workpiece, after filling, and for solidifying the workpiece but at the highest point of the workpiece. The reference numeral 14 denotes a sprue which is located laterally in the filling of the casting cavity, as shown in the figure "in front of" the mold cavity. The gate 14 is preferably provided at a location other than the feeder 16, and preferably separately therefrom. At the highest point of the molding cavity during pouring, a recess 18 is preferably provided in the mold cavity which forms a kind of dirt pocket to which impurities are flushed. Here they can be easily removed during subsequent processing. The recess 18 may be provided at an arbitrary position along the axis of rotation A of the piston 10.

The symmetry of the piston 10 to be generated in the course of the solidification process is utilized in that the mold cavity defining the later piston, as shown in the right-hand area of the figure, is tilted after filling of the molten material in such a way that the axis of rotation of the component to be produced is substantially perpendicular is aligned. In the embodiment shown, the feeder 16 is in an upper region in this state. In this orientation, it is to be expected for the solidification conditions that they lead to advantageous properties on the component produced. For example, foreign matters such as oxides and almin residues due to filling in the recumbent state are located in an edge portion of the piston where they can be easily removed and not in a bottom portion of the piston as expected in a standing state filling , Accordingly, this floor area can be provided by the procedure according to the invention as a finished cast floor area with corresponding contours that can no longer be reworked.

Claims (12)

1. A method for casting a piston (10) for an internal combustion engine wherein the tool sections defining the casting cavity are tilted about a horizontal axis by at least 45 degrees after filling and before solidification such that the axis of rotation (A) of the component (10) moves in the direction of the vertical.
2. The method according to Claim 1, characterised in that a tilt angle can be set.
3. The method according to Claim 1 or 2, characterised in that the axis of rotation (A) of the piston (10) is aligned largely horizontally during filling.
4. The method according to any of the preceding claims, characterised in that the axis of rotation (A) of the piston (10) is aligned largely vertically during solidification.
5. The method according to any of the preceding claims, characterised in that the casting material is poured into a side region of the piston (10).
6. The method according to any of the preceding claims, characterised in that after the tilting of the tool sections a feeder (16) is disposed in an upper region of the piston (10).
7. The method according to any of the preceding claims, characterised in that at least one insert, such as e.g. a core for a cooling channel and/or a ring carrier, is cast into the piston (10).
8. The use of a casting tool for casting a piston (10) for an internal combustion engine, wherein the tool sections defining the casting cavity can be tilted by at least 45 degrees about a horizontal axis after the filling and before the solidification such that the axis of rotation (A) of the piston (10) moves in the direction of the vertical, in a method according to any of Claims 1 to 7.
9. The use according to Claim 8, characterised in that a tilt angle can be set.
10. The use according to Claim 8 or 9, characterised in that a feeder is disposed in a region lying along the axis of rotation (A) of the piston (10) at the end of the piston (10).
11. The use according to any of Claims 8 to 10, characterised in that the tool sections defining the casting cavity can be tilted such that a feeder (16) is disposed in an upper region after the tilting.
12. The use according to any of Claims 8 to 11, characterised in that the mould cavity has at least one recess (18) which, when the axis of rotation of the piston (10) to be cast is aligned so as to be horizontal, is located in an upper region, preferably at a highest point.

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