The invention relates to a method for producing a cooling duct piston for an internal combustion engine, which cooling duct piston has a cooling duct in its piston crown, wherein the piston crown is adjoined by a piston lower part with piston bosses, pin bores and piston skirts, wherein a piston main body is firstly produced with a collar which is circumferential and projects radially in the region of the piston crown, wherein the collar is formed in such a manner until its outer circumferential edge comes very closely or completely into contact with a bearing region of the piston lower part, in order to form the cooling duct, and subsequently at least one ring groove is introduced.
The present invention is based on a method for producing a cooling duct piston for an internal combustion engine and a cooling duct piston produced according to this which has a cooling duct in its piston crown, wherein the cooling duct base is adjoined by a piston lower part with piston bosses, pin bores and piston skirts, wherein a piston blank is initially produced with a collar which is circumferential and projects radially in the region of the piston crown and the collar is then formed, wherein in a transitional region between the piston crown and the piston lower part, a bearing region for the collar is formed and the collar is formed in such a manner until the outer radially circumferential edge thereof comes very closely or completely into contact with the bearing region, in order to form a closed cooling duct.
A method of this kind for producing a cooling duct piston and a cooling duct piston produced according to this is known from DE 10 2004 031 513 A1.
The cooling duct piston produced according to this has three grooves, wherein rings are inserted into these three ring grooves in a known manner so that the piston is ready for use.
With the method known in the art, the two regions adjacent to one another are welded about the dividing plane 7. Following this process, the cooling duct piston 1 is reworked, said cooling duct piston not having been ready for operation up to this point and therefore having to be brought up to the required standard, in particular through the removal of weld seams in the region of the dividing plane 7. Only once this has taken place is the cooling duct piston 1 ready for operation, so that it can be provided with further elements (in particular the insertion of rings into the ring grooves 4) and can then be fitted.
The problem addressed by the invention is that of developing the method known in the art and improving a cooling duct piston according to this method in terms of its functionality.
According to the invention, it is provided that below the at least one ring groove, in particular the lowest ring groove into which a ring is later inserted, a ring-free groove is formed, wherein a dividing plane between the outer circumferential edge of the formed collar and an upper edge of the piston lower part lies in the ring-free groove.
According to the invention, the dividing plane is therefore placed in a circumferential groove between the ring field (to be precise, the lower edge of the formed collar thereof) to the upwardly pointing end of the piston skirt, which circumferential groove is left free of a ring being inserted there. Therefore, in addition to the two, three or more ring grooves already present, into which rings are inserted, a further ring-free groove is created which is arranged below the oil ring groove which is known per se. The dividing plane (bearing region) is located with the aim that the joint can be made in the region of the additional ring-free groove and therefore a substance-bonded connection can be made between the ring field and the piston skirt, wherein the joining process advantageously takes place in a region which is free of a ring, so that after the join has been made there no machining or a small amount of machining can take place in order to remove beads from the join. Moreover, the joining plane or else the joining region lying around it is not located in a heavily loaded ring groove, which means that wear is thereby reduced and the strength of the cooling duct piston is increased. In a particularly advantageous manner, the invention is used with a piston with three grooves with rings inserted in each of them and the fourth circumferential groove in which the joining region is located is present below the lowermost ring groove (oil ring groove).
By locating the joining process in a further, in particular fourth, groove, negative effects which occur both during working (joining action during which steel fractures occur due to incompletely filled weld seams) and also in relation to the quality of the grooves (pores in the groove base, on the groove sides and the groove edge) are effectively avoided.
The invention therefore relates to a method for producing a cooling duct piston and a cooling duct piston produced according to this, in which a dividing plane is placed between the ring field and piston skirt in a circumferential groove without a ring additionally provided below the oil ring groove.
In a development of the invention, the collar is configured and formed in such a manner that in the region of the dividing plane between the outer circumferential edge of the formed collar and an upper side of the piston lower part a gap is created. Through a gap of this kind, the oil accumulating at the cylinder wall during the movement of the cooling duct piston can be removed in the direction of an inner region of the cooling duct. In addition or alternatively, cooling oil which is located in the inner region of the cooling duct piston and is injected into the cooling duct and moved out of it again can be conveyed via the gap in the direction of the cylinder wall, in order to improve friction. Via the further ring-free groove, oil can therefore be collected and removed or supplied oil conveyed in the direction of the cylinder wall. The gap may run continuously in only one plane or also in at least two or more than two different planes (preferably horizontally and vertically) from the outside of the cooling duct piston in the direction of its inner region.
In a development of the invention, the collar is configured and formed in such a manner that in the region of the dividing plane the outer circumferential edge of the formed collar comes into contact at the upper side of the piston lower part. In this way, a gap is avoided and the bearing region is therefore completely closed in the region of the dividing plane. In this way, insofar as it is necessary, oil is effectively prevented from being conveyed from the inner region of the cooling duct piston in the direction of the cylinder wall. Moreover, the accumulating effect of oil below the lowermost ring groove into which an oil ring, in particular, is inserted is thereby increased substantially through which the additional ring-free groove.
In a development of the invention, the ring-free groove is formed by a chip-removing machining process. After the initially radially projecting and circumferential collar has been formed and the cooling duct thereby created, the ring-free groove is produced below the lowermost (or single) ring groove by chip-removing machining, in particular by a puncturing process. This may take place irrespective of whether a gap is present in the region of the dividing plane or the circumferential lower edge of the collar has come into contact with the upper side of the piston lower part.
Alternatively or in addition to this, the ring-free groove is formed by non-cutting machining Through a non-cutting process of this kind (for example rolling, pressing or the like), material can be saved and the generation of chips avoided. Moreover, a non-cutting machining step of this kind has an advantageous effect on the structural conditions of the material about the gap.
Alternatively or in addition to the non-cutting or chip-removing production of the ring-free groove, said groove is created by forming the outer circumferential edge of the formed collar and an upper side of the piston lower part. On the one hand, it is conceivable for the circumferential lower edge of the collar and the corresponding region of the piston lower part to be configured in such a manner that following the forming process the ring-free groove (with or without gap in the region of the dividing plane) is created. In this way, this ring-free groove can be produced in a very simple manner If it should be necessary, particularly based on tolerances of the bearing regions involved or else based on the forming, it is on the other hand conceivable for the ring-free groove to be created not only by a corresponding shaping of the regions involved but also, in addition, through a further chip-removing machining process. The required tolerances are achieved through a chip-removing machining process of this kind, wherein at the same time due to the corresponding forming this machining process can be shortened, since less material has to be removed than if the complete ring-free groove had to be cut out.
It is therefore particularly advantageous for a development of the invention to involve the ring-free groove being created by a forming of the outer circumferential edge of the formed collar and an upper side of the piston lower part and a subsequent chip-removing machining process.
As a development of the invention, in the region of the dividing plane between the outer circumferential edge of the formed collar and an upper side of the piston lower part, a joining process is carried out. In this way, the adjacent regions can be supported against one another, which advantageously results in a uniform application of forces acting on the piston crown in the direction of the lower part of the piston.
Alternatively or in addition to a substance-bonded connection, form-fitting connections are also possible. These may, for example, be a tongue-and-groove connection, wherein a spring (projection) (for example projecting from the face of the outer circumferential edge of the circumferential collar) engages with a groove (for example present in the corresponding piston lower part) (or vice versa), when the collar has been formed. Geometries other than the tongue-and-groove geometry described are likewise conceivable.
As a development of the invention, the joining process is performed as a welding process, a soldering process, a bonding process, or the like. By means of a welding or soldering process of this kind, the adjacent regions can be permanently connected to one another quickly and in a substance-bonded and also process-reliable manner. The same applies to a bonding process by means of an adhesive which must be correspondingly temperature-resistant.
As a development of the invention, a welding bead created during the welding process is removed. This takes place either by reworking the outer surface of the blank of the cooling duct piston following the joining process and subsequent introduction of the ring-free groove (in particular through a chip-removing process) or without prior reworking of the surface of the blank of the cooling duct piston, so that a resulting welding bead is also removed at the same time by introducing the ring-free groove. The same applies to excesses that occur during the soldering process or the bonding process.
In terms of its production, a cooling duct piston 10 according to the exemplary embodiment is also based on the method described in DE 10 2004 031 513 A1.
The detail of the cooling duct piston 10, as shown in
The forming of the collar 30 leads to a drawing closer or contact between the circumferential lower edge of the collar 30 and the upper side of the piston lower part 50 in the region of a dividing plane 70. The regions corresponding to one another of the collar 30 and the piston lower part 50 either form a gap in the region of the dividing plane or, as shown in
Unlike in the case of the aforementioned exemplary embodiment according to
Consideration can also be given, however, to a further substance-bonding joining process in the region of the dividing plane 70, such as, for example, a welding process. In order to illustrate this further machining step, reference is made to
Finally,
“Ring groove” should be understood to mean a circumferential groove which is located in a ring field of the cooling duct piston and into which a piston ring (for example, an oil ring) is inserted.
The “outer circumferential edge” of the circumferential collar should, in particular, be understood to mean the face which points radially outwards before the forming of the collar projecting from the piston main body and which, following its forming, points downwards (in the direction of the piston skirt) when observing the piston stroke axis.
1. Cooling duct piston
2. Piston main body
3. Circumferential collar
4. Ring groove
5. Piston lower part
6. Cooling duct
7. Dividing plane
10. Cooling duct piston
20. Piston main body
30. Circumferential collar
40. Ring groove
50. Piston lower part
60. Cooling duct
70. Dividing plane
80. Ring-free groove
90. Piston crown
100. Piston boss
110. Pin bore
120. Piston skirt
130. Piston stroke axis
Number | Date | Country | Kind |
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10 2016 000 573.4 | Jan 2016 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2017/051241 | 1/20/2017 | WO | 00 |