DE102018207874B4 - Method for multidirectional forging of a piston - Google Patents

Abstract

Method for the multidirectional forging of a piston (10) for an internal combustion engine, in which a lifting groove (20) for a piston pin locking ring and a pocket (24) are forged below an annular field (12), which is deeper than a surrounding box wall (16) .

Description

Technical area

The invention relates to a method for multidirectional forging a piston for an internal combustion engine.

The general requirement for pistons in internal combustion engines is that they are designed to be as light as possible while at the same time being able to withstand the loads during operation.

State of the art

Pistons made of steel in particular are usually forged in one or two parts. In this regard it is from the EP 1 327 089 B1 known to forge such a piston multidirectionally and in particular in addition to the main forging direction, which runs essentially parallel to the piston axis, in a direction essentially perpendicular thereto and essentially parallel to the piston pin axis and in this case to forge the so-called box walls which contain the piston pin hub, to press in.

The DE 101 13 629 A1 relates to the production of pistons or piston components such as piston heads, in particular for internal combustion engines, comprising a first step (A), which consists in pre-forging a base body by deforming corresponding contours in a predetermined axial direction and at least one further step (B), consisting of forging of the preformed piston body in at least one further axial direction to form further contours.

In the CN 204 953 787 U Multidirectional hydraulic forging presses are disclosed.

• - Einbringen eines erhitzten Stauchlings, aus dem der Kolbenrohling geschmiedet werden soll, derart in eine im Wesentlichen zylinderförmige Ausnehmung einer Schmiedevorrichtung, dass er auf einem auf der einen Seite der Ausnehmung angeordneten Schmiedeboden zu liegen kommt,
• - Einführen eines Mittelstempels, der aus einem Dorn mit einem daran angebrachten, konisch zulaufenden Ansatz mit einer der Innenfläche des Kolbenrohlings entsprechenden Form besteht, mit dem Ansatz voran in die andere Seite der Ausnehmung, wobei der Ansatz auf den Stauchling einwirkt und sich dabei die Kastenwände und die damit verbundenen Schaftelemente ausbilden
• - Herausziehen des Mittelstempels aus der Ausnehmung der Schmiedevorrichtung,
• - Auswerfen des Kolbenrohlings.

The DE 10 2011 115 048 A1 relates to a method for forging a piston blank which has a piston crown and shaft elements attached to the piston crown, which are connected to one another via box walls, with the following method steps:

• - introducing a heated blank from which the piston blank is to be forged into a substantially cylindrical recess of a forging device in such a way that it comes to rest on a forging base arranged on one side of the recess,
• - Insertion of a center punch, which consists of a mandrel with an attached, conically tapered shoulder with a shape corresponding to the inner surface of the piston blank, with the shoulder first into the other side of the recess, the shoulder acting on the plunger and thereby the box walls and form the associated shaft elements
• - Pulling out the center punch from the recess in the forging device,
• - Ejecting the piston blank.

1. a) Schmieden eines Kolbenoberteils (2) aus Stahl, das einen Kolbenboden (3) mit einer radial außen an eine Unterseite (7a) des Kolbenbodens (3) angeformten, nach unten gerichteten Ringwand (5) und einer radial innerhalb der Ringwand (5) angeordneten, an die Unterseite (7a) des Kolbenbodens (3) angeformten ringförmigen Abstützung (6) aufweist, wobei zwischen der Ringwand (5) und der Abstützung (6) ein (oberer) Teil eines Kühlkanals (9) gebildet wird,
2. b) Plastisches Umformen von Ringwand (5) und/oder Abstützung (6) derart, dass ein Abstand (a) der beiden distalen, vom Kolbenboden (3) abgewandten Enden (28a, 28b) von Ringwand (5) und Abstützung (6) zueinander abnimmt.

The subsequently published one DE 10 2017 207 431 A1 relates to a method for producing a piston upper part (2) for a piston (1) of an internal combustion engine, comprising the following steps:

1. a) Forging a piston upper part (2) made of steel, which has a piston crown (3) with a downwardly directed annular wall (5) formed radially on the outside of an underside (7a) of the piston crown (3) and a radially inside the annular wall (5) arranged annular support (6) formed on the underside (7a) of the piston crown (3), an (upper) part of a cooling channel (9) being formed between the annular wall (5) and the support (6),
2. b) Plastic forming of the annular wall (5) and/or support (6) in such a way that a distance (a) of the two distal ends (28a, 28b) of the annular wall (5) and support (6) facing away from the piston crown (3) decreases relative to each other.

The WO 2015/ 016 122 A1 relates to a piston having a concave part (5) formed in a crown surface of the upper end of the piston (1) and which is made of an aluminum alloy.

The DE 38 11 200 A1 relates to a piston blank for a forged piston for an internal combustion engine with a piston crown with a heat throttling ring gap and pendulum shaft ears formed on the underside of the piston crown, which consist of a crown-side section and a pendulum shaft eye section and have pendulum shaft eyes in the pendulum shaft eye section for receiving a pendulum shaft bolt.

The JP S63 130 238 A relates to a method for improving yield and accuracy by forming a recessed part for a piston boss portion by a side punch on a piston skirt bounded by the upper and lower punches and at the same time an undercut recessed part on the inner wall of a stock at the upper and lower ones Stamp.

Presentation of the invention

Against this background, the invention is based on the object of further improving a piston for an internal combustion engine, particularly with regard to the manufacturing effort.

This problem is solved by the method according to claim 1.

Accordingly, as part of a multidirectional forging, a lifting groove for a piston pin retaining ring and a pocket are forged below the ring field, which is deeper than the surrounding box wall.

Regarding the lifting groove mentioned, it should be mentioned that it is usually produced by machining and essentially represents a recess by means of which a piston pin retaining ring can be removed. According to the invention, such a recess is produced by forging, so that the machining that was previously required can be reduced. Essentially, in addition to the main forging direction, which continues to run essentially parallel to the piston axis, forging is carried out essentially perpendicular thereto and essentially parallel to the piston pin axis in order to produce the depression described.

The direction mentioned also applies to the additional measure according to the invention, according to which a pocket, in other words a comparatively large depression, is formed below the ring field. This can advantageously save weight. At the same time, the solidification of the structure during forging ensures resilience. Typically, the method according to the invention processes a one- or two-part steel piston, which preferably has a cooling channel.

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

An effect that corresponds to that of the bag described above can be achieved by the preferred measure, according to which the wall thickness of at least one box wall is also reduced at least in areas as part of the method according to the invention. In this case, the thickness reduction can take place essentially uniformly, so that the surface of the box wall after forging is essentially parallel to the surface before forging.

In certain applications, however, it has proven to be advantageous to form at least one step during forging in order to adapt the remaining wall thickness particularly precisely to the requirements prevailing in certain areas. In this context, it should also be mentioned that the pocket according to the invention described above below the ring field is deeper than the surrounding surface of the box wall, even when the box wall is forged or “pressed in” as described above.

In particular, it is preferred that the pocket is made several times deeper than the surrounding box wall, based on the conditions before forging. In other words, the reduction in thickness in the area of the box wall is 10% - 60%. The remaining wall thickness in the area of the pocket as a result of forging is adjusted to the remaining thickness of the box wall as a result of forging. This reduces the wall thickness in the pocket area by up to 80% compared to the geometry before the pocket was forged.

In particular, in order to keep the manufacturing effort within limits and because a reduction in wall thickness in the area of the shaft surfaces, which represent parts of a cylinder surface, is to be avoided, it is preferred that the forging ends on the shaft walls or at a distance from them, in other words not in the shaft walls extends.

As already indicated, in the context of the method according to the invention, it is preferred to refrain from machining the excavation groove. If necessary, deburring can be carried out.

Although other directional relationships are possible, it is currently preferred to provide the described forging directions at an angle of substantially 90° to one another.

Furthermore, to save time, it is possible to carry out the two forging processes essentially at the same time, while in certain applications it offers advantages to carry out the forging of the excavation groove and/or the pocket after forging the contours in the main forging direction.

With regard to a good combination of weight reduction and load capacity, the formation of a minimum wall thickness in the area of the box wall of 2% - 4% of the piston diameter has proven to be advantageous.

Finally, within the scope of the method according to the invention, it offers further advantages if the later bolt drilling is also carried out using lubricant which is processed in order to facilitate their subsequent production.

Brief description of the drawings

• 1 einen erfindungsgemäß erzeugten Kolben in einer Seitenansicht; und
• 2 einen Teil des Kolbens von 1 in einer Schnittansicht.

The invention is explained in more detail below using a preferred training example with reference to the drawings. Show it:

• 1 a side view of a piston produced according to the invention; and
• 2 part of the piston from 1 in a sectional view.

Detailed description of a preferred embodiment of the invention

As in 1 can be seen, the piston 10 has, on the one hand, an annular field 12, and on the other hand, shaft 14 and box walls 16, in which a piston pin bore 18 is provided. The piston pin bore 18 was produced by machining, but is typically closed after forging on the corresponding blank and at best, as preferred according to the invention, circular, essentially concentric to the in 1 Piston pin bore 18 that can be seen is pressed in.

This can be done according to the invention by forging in a direction essentially perpendicular to the plane of the drawing 1 take place while the main forging direction is in accordance 1 runs from top to bottom. In the first-mentioned direction, the lifting groove 20 can be created, in particular before forging the piston pin bore, from which in 1 only half is left. The other half was removed during machining to form the piston pin bore 18. However, it can be seen that the lifting groove designed as a recess adjoins the piston pin bore, so that a locking ring, which is typically inserted into a groove a few mm inside the bore, can be removed by engaging the lifting groove 20 using a suitable tool. As mentioned, according to the invention, the excavation groove can be created in an efficient manner and in particular without the need for machining.

This also applies to recesses 22 in the box walls, the edges of which extend essentially parallel to the edges of the shaft walls 14, on the inside essentially parallel thereto and parallel to the lower piston edge. In particular, the box walls are essentially completely recessed, with the exception of an edge that is a few mm wide. In the example shown, the edges of the shaft walls 14 run essentially parallel to the piston pin axis.

According to the invention, the box walls are further recessed in an upper area, i.e. directly below the ring field 12, to form significantly deeper pockets 24, the side edges of which in the case shown run inclined in the direction of the piston pin bore 18. At their upper edge, the pockets 24 in the case shown are formed directly below the ring field, in other words below the third annular groove.

Like in particular 2 can be seen, considerable weight can be saved in this way, while at the same time the necessary wall thickness in the area of the box walls 16 remains. In the case shown, the step between the recess 22 and the pocket 24 runs slightly inwards, ie inclined to the piston pin axis.

Claims (10)

Method for the multidirectional forging of a piston (10) for an internal combustion engine, in which a lifting groove (20) for a piston pin locking ring and a pocket (24) are forged below an annular field (12), which is deeper than a surrounding box wall (16) . Procedure according to Claim 1 , characterized in that the thickness of at least one box wall (16) is reduced at least in some areas. Procedure according to Claim 1 or 2 , characterized in that at least one box wall (16) is designed to be stepped. Procedure according to one of the Claims 2 or 3 characterized in that at least one pocket (24) is designed to be several times deeper than a reduced box wall thickness. Method according to one of the preceding claims, characterized in that forging processing ends at or at a distance from at least one shaft wall (14). Method according to one of the preceding claims, characterized in that at least one excavation groove (20) is not machined. Method according to one of the preceding claims, characterized in that the forging directions run essentially at an angle of 90° to one another. Method according to one of the preceding claims, characterized in that the forging of the lifting groove (20) and/or at least one pocket (24) takes place at the same time or after forging as part of a main forging direction. Method according to one of the preceding claims, characterized in that a minimum wall thickness of at least one box wall (16) of 2% - 4% of the piston diameter is produced. Method according to one of the preceding claims, characterized in that the area of the later piston pin bore is also forged.

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