WO2003054371A1

WO2003054371A1 - Piston ring carrier with a cooling channel

Info

Publication number: WO2003054371A1
Application number: PCT/CH2002/000723
Authority: WO
Inventors: Karl Merz
Original assignee: Karl Merz
Priority date: 2001-12-21
Filing date: 2002-12-23
Publication date: 2003-07-03
Also published as: EP1456519A1; AU2002350364A1

Abstract

The invention relates to a piston ring carrier with a cooling channel used for casting a light metal piston for a combustion engine. Said piston ring carrier comprises a casting ring (1) supporting the cooling channel (4) which is limited by at least one first ring element (2) made of sheet metal. The outer radius of the first ring element (2) overlaps the inner radius of the casting ring (1) and is connected to the casting ring (1) in the overlapping area by means of resistance pressure welding. In a preferred embodiment of the invention, the cooling channel (4) is limited by two ring elements (2, 3) made of stainless steel sheet, said two ring elements (2, 3) overlapping and being connected to each other in an axial direction by means of laser welding. The cooling channel (4) can be directly adjacent to the casting ring (4) or be arranged at a distance therefrom.

Description

DESCRIPTION

TITLE

Piston ring carrier with cooling channel

TECHNICAL AREA

The present invention relates to a piston ring carrier with a cooling channel for casting into a light metal cast piston for an internal combustion engine, the piston ring carrier comprising a casting ring and the cooling channel being delimited by at least one first annular element made of sheet metal material and carried by the casting ring.

Pistons with cooled piston rings and corresponding piston ring carriers with a cooling channel through which a coolant circulates are increasingly required in the course of the striking increase in injection and compression pressure in modern internal combustion engines.

STATE OF THE ART

In a first known piston ring carrier of the type mentioned, two ring elements are formed as partial shells from a stainless steel sheet material, each with an inward into the cooling channel, i.e. thus provided in a ring plane bent collar and with this collar in abutment against each other, the welding is carried out by laser technology along the gap between the collars in the splitting plane. The connection of the partial shells with the cast ring is made along its inner edges by micro plasma welding with material application.

In another known piston ring carrier, the cooling channel is formed by the cast ring and a one-piece, in cross section approximately U-shaped or C-shaped ring element made of stainless steel sheet welded into the casting ring, the free edges of the ring element being sharp

BESTATIGUNGSKOPIE trained grooves are bent along the inner edges of the casting and are fixed therein by welding and / or soldering technology.

A piston ring carrier known from US-A-6, 105,540 is of similar design, but in which a one-piece, approximately u-shaped or c-shaped ring element made of stainless steel sheet is reduced in diameter under pressure and is thus pressed into the cast ring before it is welded to it.

The known piston ring carriers are alfinized before being poured into the pistons in order to produce an alfin layer on their surface, with which the cast material of the aluminum-based pistons can adequately bond. Alfining takes place at approx. 760 ° C in a liquid alfin bath. The parts are previously annealed at approx. 230 ° C and their oxide layer is removed by corundum blasting.

The problem with the known piston ring carriers is, above all, the connection between the cast ring and the stainless steel sheet part or parts, because the corresponding materials cannot be welded well to one another. On the other hand, the resilience and tightness of this connection are crucial because of the subsequent alfining, so that no air and thus oxygen can escape from the air-filled cooling channel during the alfining. Oxygen prevents the formation of an alfin layer and, under the high temperatures prevailing in the alfin bath, causes local oxidation, which in turn results in an intolerable, incomplete embedding of the piston ring carrier together with the cooling channel in the cast iron piston. Every leak, however small, leads to a committee part.

One means of limiting such rejects in the known piston ring carrier mentioned in the second place is to carry out the laser welding between the cast ring and the stainless steel ring element very slowly. Typically, around 20 sec are required per circumferential weld seam.

Another disadvantage of this known piston ring carrier is the unscrewing of the sharp grooves mentioned in the casting, which is associated with high tool wear. Furthermore, the metal forming production of one-piece stainless steel ring element at least complex and demanding, which also applies to the one-piece ring element according to US-A-6, 105,540.

Another disadvantage of the known piston ring carrier with the two partial shells is their comparatively complex manufacture by bending the mentioned collars inwards.

In all known piston ring carriers with a cooling channel, the cooling channel, which is initially self-contained, must also be drilled from the interior of the piston after it has been poured into the piston in order to establish a connection between the piston interior and the cooling channel for the flow of a coolant. It can happen that the connection between the casting material of the piston and the cooling channel is torn off around the borehole, which in turn is not tolerable and leads to rejects.

Finally, types of light metal cast pistons are known which are provided with a piston ring carrier, but which are not directly connected to a cooling channel. Rather, a cooling channel is arranged at a distance from the piston ring carrier in the casting piston, and in this respect is essentially completely embedded in the casting material. To produce this type of insulated cooling channel, it is common to insert salt rings into the mold when casting the pistons. The salt is released after pouring and drilling the cooling channel. At least the handling when inserting the salt rings into the mold is complex and therefore disadvantageous.

PRESENTATION OF THE INVENTION

In view of the above statements regarding the prior art and the disadvantages mentioned in relation to these, the present invention has in particular the object of specifying a piston ring carrier with a cooling channel of the type mentioned at the outset, which is simpler, more efficient, faster and with significantly less waste and thereby is generally less expensive to produce. This object is achieved according to the invention by a piston ring carrier with a cooling channel as defined in claim 1.

The piston ring carrier according to the invention is accordingly characterized in that the outer ring of the first ring element overlaps the inner radius of the cast ring and in this overlap area with the cast ring by resistance welding connected is. This welding process results in a good and possibly also tight weld connection between the parts which cannot be welded well to one another. The welding process is extremely fast and, for example, only takes about 40 milliseconds.

According to a first preferred embodiment, the cooling channel is delimited, apart from the first, at least also by a second ring element made of sheet metal material, the two ring elements, each with an inner collar oriented essentially in the axial direction, overlapping one another and essentially in the axial direction along one of these inner collars Laser welding are interconnected.

The welding in the axial direction is technically much easier to carry out than the welding mentioned perpendicular to it in a ring plane. If the same material is used for both ring elements, the laser welding can also be carried out very quickly in the course of only about one second, with a reproducibly tight weld seam being produced.

Furthermore, it is possible in this embodiment that the cooling channel is delimited not only by the two ring elements but also by the cast ring and that the two ring elements with their outer radius each overlap the inner radius of the cast ring and are connected to the cast ring in each of these overlap regions by resistance pressure welding.

In this embodiment, the cast ring is simply inserted between the two partial shells during manufacture before they are welded together in the axial direction by laser welding along the free edge of the inner collar.

The advantages of this design are, on the one hand, that the two partial shells are very easy to produce in terms of stamping and forming, and they only have to be machined from one direction, namely their axial direction. The inner collar formed on them does not have to be very high. On the other hand, their outside diameter and thus the mutual overlap with the cast ring can be chosen as large as desired The problematic connection between the stainless steel sheet metal parts and the cast ring in the prior art can also be produced easily and reproducibly by the resistance pressure welding, the mutual overlap of the stainless steel partial shells with the cast ring, which can be chosen as desired, being an additional advantage for the resistance welding. As already mentioned, the welding process is also extremely fast and, for example, only takes about 40 milliseconds.

According to another preferred embodiment of the invention, the cooling duct is arranged at a distance from the cast ring, which is not limited to the cooling duct itself, but is at least connected to the cooling duct via the first ring element. The casting ring and cooling channel thus form a unit which, as such, can be introduced into the casting mold during the production of the casting pistons. The use and complex additional placement of individual salt rings or the like is eliminated.

In this embodiment, it is further preferred that the cast ring is connected exclusively to the first ring element. The first ring element could in principle be designed such that it limits the cooling channel alone. However, it is also preferred here again to assemble the cooling duct from two ring elements, in such a way that they are laser-welded essentially in the axial direction along e.g. two welds can be connected.

In order to maintain the cast iron piston as a fixed unit in this embodiment as well, windows can be provided in the first ring element between the cast ring and the cooling channel. Finally, in this embodiment, the first ring element can be designed conically between the cast ring and the cooling channel.

According to a further preferred embodiment of the invention, at least one hollow nipple is formed on the first or a further ring element, which, after the piston ring carrier has been poured into the cast piston, facilitates the production of a connecting channel for the coolant between the cooling channel and the interior of the piston. Instead of drilling the cooling channel itself and, if necessary, loosening its connection to the surrounding casting material, it is sufficient to drill the hollow nipple, which is much less critical if the hollow nipple is placed alone because of the shallower drilling depth, especially if the hollow nipple is on it free end with a round cap is provided. With a suitable design of the casting tool for the piston with a recess, the hollow nipple can also be made so long that it protrudes into the interior of the piston. In this case, the hollow nipple only has to be shortened, for example in terms of cutting technology, and there is no need to drill out the connecting channel.

Finally, an opening can also be provided in the free end of the hollow nipple, which allows air to escape from the cooling channel during the finishing. The cross section of the opening may only be so large that, conversely, due to its surface tension, the liquid alfin cannot penetrate the cooling channel. The opening in the cooling channel provides the air in the cooling channel with a defined escape option, so that no excess pressure can occur in the cooling channel even under the high temperatures in the Alfin bath. As a result, the welded connections are not stressed and it can certainly be avoided that air escapes at another point. The local oxidation around the opening associated with the air outlet through the opening on the hollow nipple is harmless because the corresponding area of the hollow nipple is anyway removed again after being poured into the piston by drilling or shortening.

BRIEF EXPLANATION OF THE FIGURES

The invention will be explained in more detail below on the basis of exemplary embodiments in connection with the drawing. Show it:

Fig. 1 shows an embodiment of a piston ring carrier with a directly connected

Cooling channel according to the invention in section, wherein the individual elements are not yet fully welded together;

2 shows the piston ring carrier of FIG. 1 between two welding tongs of a resistance welding device;

3 shows a section of a finished piston ring carrier with a cooling channel according to the invention cast in a light metal cast piston, the right part of the figure additionally showing a connecting channel for the coolant flow between an interior of the piston and the cooling channel; Fig. 4 on a ring element of the cooling channel of the inventive

Piston ring carrier the formation of a mounting lug and the placement of a hollow nipple thereon;

FIG. 5 shows the use of such a hollow nipple for producing the connecting channel between the piston interior and the cooling channel in a representation according to the right part of FIG. 3;

6 shows a hollow nipple with a small opening;

Fig. 7 in a representation according to the right part of Fig. 3, the use of a long hollow nipple for producing the connecting channel between the piston interior and the cooling channel, the hollow nipple extending into the piston interior.

Fig. 8 shows an embodiment of a piston ring carrier with a spaced cooling channel according to the invention in section, and

Fig. 9 in section the piston ring carrier with a spaced cooling channel in one

Cast-in light alloy cast iron.

WAYS OF CARRYING OUT THE INVENTION

In FIG. 1, 1 denotes a cast ring of a piston ring carrier, a groove for the piston ring not being inserted here.

The cast ring 1 is inserted between two likewise ring-shaped elements 2 and 3 made of a thin stainless steel sheet, each of which is provided along its inner radius with an inner collar 2.1 or 3.1 formed in the axial direction, ie perpendicular to the ring plane. The inner radii of the two ring elements 2 and 3 are matched to one another so that the ring elements 2 and 3 with their inner collars 2.1 and 3.1 can be inserted into one another in close mutual contact. Fig. 1 shows the two ring elements inserted in such a way, with their inner collars 2.1 and 3.1 overlap each other to a certain extent. The cast ring 1 also overlaps the two Ring elements 2 and 3 in that its inner radius is smaller than the outer radii of the ring elements.

In the arrangement of Figure 1, the three parts described, i.e. the cast ring 1 and the ring elements 2 and 3 together form a circumferential cooling duct 4. Accordingly, the two ring elements 2 and 3 each form partial shells of the cooling duct 4.

In the left part of Fig. 1, the three parts 1-3 are only loosely assembled. To connect them, a circumferential weld seam 5 is produced between the two ring elements 2 and 3 along the free edge of the inner collar 2.1, which is smaller in diameter, by laser welding in the axial direction AR, which is shown in the right part of FIG. On the other hand, according to FIG. 2, the ring elements 2 and 3 are connected in their overlap area with the cast ring 1 by resistance pressure welding in a corresponding resistance pressure welding device with welding electrodes 6 and 7.

In order to achieve the resistance pressure welding between the two ring elements 2 and 3 and the cast ring 1, the latter is provided with circumferential welding bosses 8 and 9 on both sides.

Instead of exactly in the axial direction AR, the two inner collars could also be arranged at a certain angle with respect to the axial direction and the laser welding could also only be carried out essentially in the axial direction. The only decisive factor is that the weld seam can be carried out with a laser welding head arranged outside the ring plane and without deflecting the laser beam into the ring plane.

3 shows a finished piston ring carrier 1 with a cooling channel 4 according to the invention already cast into a light metal cast piston 10, wherein the groove 11 for the piston ring has already been inserted into the cast ring. The piston 10 is only partially shown. However, a depression 12 can be seen in its end face towards the combustion chamber and a hollow or interior space 13 which is open to the connecting rod and thus to the oil pan of the engine. In order to be able to supply the cooling channel 4 with oil as the coolant from the piston interior 13, a plurality of connecting channels between the cooling channel 4 and the piston interior 13 are provided over the circumference of the cooling channel 4. In the right part of FIG. 3, such a connecting channel 14 is shown, as can be produced from interior space 13, for example, by drilling after casting piston 10. Since there is a risk here of loosening the connection between the thin sheet material of the cooling channel and the surrounding cast material of the piston, for example in the area denoted by 15, an alternative for producing the connecting channels is explained below.

Fig. 4 shows in a detail e.g. the ring element or the cooling channel partial shell 2, on which a fastening lug 16 is formed. This can simply be produced by punching and / or drawing technology when punching out the ring element 2 and / or pulling out the inner collar 2.1. In a further operation, e.g. in terms of friction welding, a tubular hollow nipple 17 is welded on, this not necessarily vertically but also at an oblique angle. In Fig. 4, the hollow nipple 17 is closed at its free end and provided with a round cap.

5 now shows piston 10 with a piston ring carrier 1 according to the invention cast therein, with cooling channel 4, on which a hollow nipple 17 according to FIG. 4 is formed. The hollow nipple 17 serves here as a section of the connecting channel 14, for the production of which it is sufficient to drill and drill only the free end of the hollow nipple. The rounded end cap of the nipple makes drilling even easier.

Compared to the drilling of the cooling channel 4 itself, when drilling the hollow nipple 17 there is no risk of material tearing in the area 15 and there is also no need to drill so deep.

In an alternative embodiment, a small opening 18 could also be provided at the free end of the hollow nipple 17, through which air can escape from the cooling channel during the finishing, as shown in FIG. 6.

In a further alternative embodiment, the nipple 17 could also be made so long that it protrudes into the piston interior 13 and therefore not at all needs to be drilled, as shown in FIG. 7. In this case, to open the connecting channel 14, it is sufficient to remove the end projecting into the interior 13 by cutting.

The opening of the cooling channel from the piston interior 13 could also be carried out by eroding, with or without a hollow nipple.

8 shows an embodiment of a piston ring carrier according to the invention with a cast ring 21 and a cooling channel 24 spaced therefrom. The cooling channel 24 is delimited by a first ring element 22 and by a second ring element 23, both of which consist of a stainless steel sheet. However, only the first ring element 22 is here in connection with the cast ring 21 and overlaps this or its inner radius with a larger outer radius. In the corresponding overlap area, the parts, i.e. the cast ring and the first ring element are joined together by resistance pressure welding. The corresponding weld seam is preferably all-round.

The first ring element 22 initially has a conical section 22.1, in which a plurality of windows 22.2 are punched out over the circumference, in its overlap region with the cast ring 21. Further inward, the first ring element 22 is followed by a groove 22.3 which is approximately U-shaped in cross section and which in turn has an inner collar 22.4 oriented in the axial direction. The channel 22.3 is closed by forming the cooling channel 24 by the second ring element 23, which is also provided at least on the inside with an inner collar 23.1 oriented in the axial direction. As in the embodiment of FIG. 1, the two ring elements 22 and 23 are inserted into one another in such a way that their two inner collars are in close mutual contact and are connected to one another by means of a circumferential laser welding which is carried out in the axial direction or essentially in the axial direction.

A corresponding laser weld seam is present in a second overlap region of the two ring elements 22 and 23 which is further out. Here the second ring element 23 lies with an outer collar 23.2 on the conical section 22.2 of the first ring element 22 and is welded to the first ring element 22 along this outer collar 23.2. The outer collar 23.3 could also be oriented the other way round and point into the cooling channel 24. As in the embodiment of FIG. 1, in this embodiment the two ring elements can also be produced very easily by deformation in only one direction (axial direction). The joining and connecting of the individual parts only requires operations in this direction, which is a decisive advantage especially for large-scale production.

FIG. 9 shows the piston ring carrier of FIG. 8 cast in a light metal cast piston 30, it being particularly clear in this illustration how the cooling channel 24 is spaced from the cast ring 21 and, moreover, is not in the same plane as this.

A section A of FIG. 9 also shows how the cooling channel 24 could also be produced in one piece from a single ring element 22. This section A also shows that a hollow nipple 17 could also be formed on the cooling channel 24 spaced from the cast ring. A hollow nipple 17 could of course also be provided on a multi-part cooling duct 24 and be designed in accordance with each of the above-described configurations.

Claims

1. piston ring carrier with cooling channel (4; 24) for pouring into a light metal cast piston (10; 30) for an internal combustion engine, the piston ring carrier comprising a cast ring (1; 21) and the cooling channel (4; 24) through at least a first ring element (2; 22) limited from a sheet metal material and supported by the cast ring (1; 21), characterized in that the first ring element (2; 22) overlaps with the outer radius of the cast ring (1; 21) and in it Overlap area is connected to the cast ring (2; 21) by resistance pressure welding.

2. Piston ring carrier according to claim 1, characterized in that the cooling channel (4; 24) in addition to the first (2; 22) is at least also limited by a second ring element (3; 23) made of sheet metal material, the two ring elements (2, 3; 2, 23) with an inner collar (2.1, 3.1; 22.4, 23.1) oriented essentially in the axial direction (AR) overlap each other and in the axial direction (AR) along one of these inner collars (2.1; 22.4) Laser welding are interconnected.

3. Piston ring carrier according to claim 2, characterized in that the cooling channel (4) is limited by the two ring elements (2, 3) also by the cast ring (1) and that the two ring elements (2, 3) with their outer radius in each case overlap the inner radius of the cast ring (1) and are connected to the cast ring (1) in each of these overlap areas by resistance pressure welding.

4. Piston ring carrier according to claim 1 or 2, characterized in that the cooling channel (24) is arranged at a distance from the cast ring (21).

5. Piston ring carrier according to claims 2 and 4, characterized in that the cast ring (21) is connected exclusively to the first ring element (22).

6. piston ring carrier according to one of claims 4 or 5, characterized in that in the first ring element (22) between the cast ring (21) and the cooling channel (24) windows (22.2) are present.

7. Piston ring carrier according to one of claims 4-6, characterized in that the first ring element (22) between the cast ring (21) and the cooling channel (24) is conical.

8. Piston ring carrier according to one of claims 1, characterized in that at least one hollow nipple (17) is integrally formed on the first or a further ring element.

9. Piston ring carrier according to claim 8, characterized in that the hollow nipple comprises a tube piece which is placed on a mounting lug (16) provided on the respective ring element, in particular by friction welding.

10. Piston ring carrier according to one of claims 8 or 9, characterized in that the free end of the hollow nipple is provided with a round cap.

11. Piston ring carrier according to one of claims 8-10, characterized in that the free end of the hollow nipple is closed.

12. Piston ring carrier according to one of claims 8-10, characterized in that there is a small opening at the free end of the mock nipple.

13. Piston ring carrier according to one of claims 8 - 12, characterized in that the length of the hollow nipple is dimensioned such that the hollow nipple is also completely embedded in the casting compound when poured into the casting piston.

14. Piston ring carrier according to one of claims 8 - 12, characterized in that the length of the hollow nipple is dimensioned such that the hollow nipple protrudes into a cavity of the same when it is poured into the cast piston.

15. Piston ring carrier according to one of claims 1-14, characterized in that the sheet material is a stainless steel sheet.