Heat transfer device and heat transfer precursor assembly and method for producing such a heat transfer device

Abstract

Heat transfer device for an internal combustion engine consisting of an inner housing (2) which has a first housing part (12) and a second housing part (14), the base surfaces (16, 18) of which are arranged opposite one another and spaced apart from one another and which are firmly connected to one another, so that a channel (6) through which a first medium can flow is formed in the interior of the inner housing (2), a partition wall (22) which extends from the base surface (16) of the first housing part (12) to the base surface (18) of the second housing part (14), and an outer housing (4) which is arranged surrounding the inner housing (2) in such a way that a second channel (10) through which a second medium can flow is formed between the outer housing (4) and the inner housing (2), characterized in that a weld seam (44) is formed on the base surface (18) of the second housing part (14), which weld seam extends through the base surface (18) of the second housing part (14) to an end (26) of the partition wall (22) remote from the base surface (16) of the first housing part (12), so that the partition wall (22) is fastened to the second housing part (14) via the weld seam (44).

Description

The invention relates to a heat transfer device for an internal combustion engine, comprising an inner housing which has a first housing part and a second housing part, the base surfaces of which are arranged opposite one another and spaced apart from one another and which are firmly connected to one another, so that a channel through which a first medium can flow is formed in the interior of the inner housing, a separating wall which extends from the base surface of the first housing part to the base surface of the second housing part, and an outer housing which is arranged surrounding the inner housing in such a way that a second channel through which a second medium can flow is formed between the outer housing and the inner housing, a heat transfer precursor arrangement for producing such a heat transfer device, wherein the base surface of the second housing part has a groove into which a tapered section of the separating wall corresponding to the groove projects, which tapered section is arranged at the end remote from the base surface of the first housing part, and wherein a step is formed on the end of the partition wall remote from the base surface of the first housing part, and a method for producing such a heat transfer device having such a heat transfer precursor arrangement.Heat transfer devices are well known using various manufacturing techniques. In the automotive and engine fields in particular, heat transfer devices are becoming increasingly important. They are used both for cooling recirculated exhaust gas and for charge air cooling or oil cooling. By using such heat transfer devices, for example, the temperature of the gas supplied to the cylinder can be reduced and thus the filling of the cylinders and the efficiency of the internal combustion engines can be improved.Among other methods for producing heat transfer devices, it is known to assemble die cast shells with ribs extending from the bases of the shells to form heat transfer devices. The medium to be cooled usually flows through the inner housing of the heat transfer device, while a channel for a cooling medium is formed between the inner housing and an outer housing surrounding the inner housing on at least four sides.For example, DE 10 2005 058 204 A1 discloses a heat transfer device which has a housing through which a U-shape flows, such that the gas to be cooled enters and exits are arranged next to one another on the head side of the heat transfer device. This heat transfer device is constructed from an inner housing and an outer housing, which are pushed into one another. Both the outer housing and the inner housing consist of an upper part and a lower part which are joined together by welding before the inner housing is assembled with the outer housing. The inner housing disclosed here has ribs on its upper part and on its lower part which project in each case into the channel through which the gas to be cooled flows, said ribs extending in the cross section of the inner housing alternately from the upper part or from the lower part into the channel. The upper part is designed in the form of a lid, while the lower part has a pot shape. The cover part is fastened to the lower part via a weld seam which extends over the entire circumference of the cover part.A similar heat transfer device is known from DE 10 2008 012 930 B3. The inner housing has a cover with two inwardly pointing protuberances, between which a groove is formed, into which a partition wall of the other housing part protrudes. The partition wall is not fastened to the cover.In order to produce such parts by die casting, it is necessary to design the lower part with an upper housing part wall in the region of the head side, since otherwise no circumferential welded seam could be achieved. However, this means at the same time that an additional lateral slide, which is removed to the head side, is required in order to produce such a lower part. A further slide is led out of the lower part in the direction of extension of the ribs upwards.However, such a heat transfer device has the disadvantage that the existing pressure-loaded explosion surface, which is formed by the cover part, is relatively large. The load on the inner housing and the existing welded seams can lead to leaks at the heat exchanger or even to the cover part breaking loose when such a construction is used in the truck region and thus at higher occurring heat exchanger inner pressures.It is therefore an object of the invention to provide a heat transfer device which can be used even at high internal pressures, such as occur in the truck sector, and which accordingly has a high strength. For this purpose, the necessary arrangements of the precursors with respect to one another and a method for producing such a heat transfer device should also be provided.This object is achieved by a heat transfer device in which a weld seam is formed on the base surface of the second housing part, which weld seam extends through the base surface of the second housing part to an end of the partition wall remote from the base surface of the first housing part, so that the partition wall is fastened to the second housing part via the weld seam. The explosive surface of the inner housing is thus significantly reduced and the strength is thus increased.Preferably, the partition divides the channel in the inner housing into two parts of substantially equal size in cross section to the direction of flow. In this way, a sufficiently large cross section is furthermore available for exchange flows due to eddy formation at existing ribs in the channel, so that a good efficiency is furthermore achieved.In an advantageous embodiment of the invention, the partition wall extends substantially over the length of the inner housing in the direction of flow. This increases strength compared to versions with interrupted partitions.In a special embodiment, a weld seam extends along the circumference of the second housing part, via which the first housing part is fastened to the second housing part. Such a fastening is to be carried out in one production step with the fastening of the partition wall, in particular in the case of cover-shaped second housing parts. This reduces the manufacturing costs with complete tightness of the housing.Preferably, the partition wall has steps running substantially perpendicular to the flow direction. These steps serve to reduce the sottling when using such a heat transfer device, for example as an exhaust gas cooler. At the stages, the boundary layer of the flow is broken up, so that vortices are produced which counteract a sottling.The object set is achieved according to the invention by means of a heat transfer precursor arrangement for producing a heat transfer device, in which a section surrounding the groove of the base surface of the second housing part rests on the shoulder of the partition wall. The base surface of the second housing part thus has a groove into which a tapered section of the partition wall corresponding to the groove projects, which is arranged at the end remote from the base surface of the first housing part. This embodiment allows both the centering of the first housing part relative to the second housing part prior to the final fastening to be fixed by a type of positive connection and also significantly facilitates the fastening itself by welding, since during the friction stir welding process it is ensured that a cohesive connection to the partition wall is produced. Since a shoulder is formed on the end of the partition wall remote from the base surface of the first housing part, on which shoulder the surrounding section of the second housing part rests, no stresses arise in the housing part due to the compressive forces to be applied during friction stir welding, since the second housing part, which is pressure-loaded by the tool, can be supported on the shoulder.Advantageously, the depth of the groove corresponds to the thickness of the base surface of the second housing part, so that the groove forms a continuous opening into which the friction stir welding tool can be directly inserted. Although this makes the production of the second housing part more difficult, it reduces the welding forces to be applied.In a particularly preferred embodiment, the second housing part is designed as a cover which rests with its circumference on a shoulder which is formed at one end of side walls which extend from the circumference of the base surface of the first housing part in the direction of the cover. In this way, a support is ensured over the entire circumference of the cover, so that the shoulder can again be used as a support during welding in order to absorb the compressive forces.The object is accordingly achieved by a method for producing such a heat transfer device with such a heat transfer precursor arrangement, in which a friction stir welding tool is introduced at one end of the groove from the side of the base surface of the second housing part opposite the groove as far as into the groove and is subsequently guided along the groove on the partition wall. This ensures reliable fastening of the second housing part to the first housing part, reduces the explosive surface, and so a heat exchanger of this type can also be used in the region of a truck with higher compressive loads.The heat transfer device according to the invention, the heat transfer precursor arrangement according to the invention and the corresponding method ensure a cost-effective production of a heat exchanger with high load capacity, which can also be used in the exhaust gas region of a truck and has a good efficiency with low consumption of soot.An embodiment is shown in the drawings and will be described below: FIG. 1 shows a cross-section of a heat transfer device according to the invention in a sectional view. FIG. 2 shows a sectional view of a first and a second housing part of the heat transfer device according to the invention from FIG. 1 in a cross section to the flow direction before assembly. FIG. 3 shows a plan view of the first housing part.The heat transfer device according to the invention consists of an inner housing 2, which is surrounded by an outer housing 4 at least in cross section. Both housing parts are of multipart design and produced by die casting.A first channel 6, through which a medium can flow, is formed in the interior of the inner housing 2, which channel is, for example, through which exhaust gas flows and which project in the ribs 8 to improve the heat transfer. The outer housing 4 is fastened at a distance from the inner housing 2, so that a jacket-shaped channel 10 through which a second medium, for example a coolant, can flow is produced between the inner housing 2 and the outer housing 4. In this channel 10, webs can be arranged in order to avoid regions without flow.The inner housing 2 has a first housing part 12 which is closed on three sides in cross section and a second housing part 14 which is designed as a cover part for closing the open side of the first housing part 12. Both from a base surface 16 of the first housing part 12 and from a base surface 18 of the second housing part 14, the ribs 8 project in cross section alternately in each case in the direction of the opposite base surface 18, 16 into the channel 6.In FIG. 2, the first housing part 12 is shown. In addition to the ribs 8 extending into the channel 6, a partition wall 22 is formed approximately in the middle of the channel 6, which extends over the length of the channel 6 to both ends as far as just before the respective end of the channel 6 and divides the channel 6 in cross section into two approximately equally sized parts, as can also be seen in FIG. 3. This partition wall 22, like the ribs 8 and the side walls 24 laterally delimiting the inner housing 2, extends substantially perpendicularly to the base surface 16 of the first housing part 12 in the direction of the opposite second base surface 18 of the housing part 14.The partition wall 22 has, at its end 26 remote from the base surface 16 and pointing toward the second housing part 14, a shoulder 28, from which an upper section 30 of the partition wall 22 extends further in a clearly tapering manner. Also formed on the side walls 24 at the same height as on the partition wall 22 is a shoulder 32 extending over the circumference. From this shoulder 32, the side walls 24 extend further upwards only in their outer region.FIG. 2 also shows the corresponding second housing part 14, which in the assembled state rests with its outer periphery 34 on the circumferential shoulder 32 of the first housing part 12. Furthermore, a groove 36 extending in the flow direction is formed in the base surface 18 of the second housing part 14, the length and width of which groove corresponds substantially to the extent of the tapered section 30 of the partition wall 22 above the shoulder 28, so that this tapered section 30 projects into the groove 36, while a section 38 of the cover part 14 delimiting the groove rests on the shoulder 28.It can additionally be seen in FIG. 3 that steps 40 running perpendicular to the flow direction 20 are formed on the partition wall 22, on which steps a formation of vortices occurs, which prevents a squamation. These steps 40 alternate with continuous extensions so that essentially half ribs 8 are formed on the partition wall 22. It can additionally be seen from FIGS. 1 and 2 that the base surfaces 16, 18 of the housing parts 12, 14 have indentations 42 on the side facing the outer housing 4 in each case at the height of the ribs 8, through which indentations the coolant can be guided closer to the ribs 8 and thus to the medium to be cooled. Furthermore, such a mold has flow advantages during die casting.If the second housing part 14 is now placed on the first housing part 12, a heat transfer precursor arrangement according to the invention is thereby produced. To produce a heat transfer device according to the invention, a friction stir welding tool is now introduced into the groove 36 both along the outer circumference 34 of the second housing part 14 and from the opposite side of the groove 36 and is then guided along the length of the groove 36, so that a cohesive connection of the two housing parts 12, 14 is produced both along the circumference 34 and along the partition wall 22 or the groove 36 corresponding to the partition wall 22. The necessary pressure of the friction stir welding tool to be applied to the second housing part 14 can still be absorbed by the first housing part 12 by the second housing part 14 resting on the shoulders 28, 32 of the first housing part 12 even if the groove 36 is formed as a continuous opening of the second housing part 14. Depending on the desired width, the friction stir welding tool can be guided along the groove 36 either once or twice over or through the groove 36. As a result of the weld seam 44 which is produced in this case and which can be seen in FIG. 1, a cohesive connection is produced in the central region of the two housing parts 12, 14, and as a result of the encircling weld seam 46, a cohesive connection is produced over the circumference 34 of the second housing part 14.This halves the available explosive surface at an increased internal pressure, so that a clearly increased strength of the inner housing 2 is achieved. Such a heat transfer device can also be used in the exhaust system of a truck at the higher pressures present there. In this case, the production remains cost-effective and the efficiency good.It should be obvious that structural changes with respect to the design of such a heat exchanger are possible within the scope of the claims. In particular, the parting planes of the individual shells or the design of the ribs can be chosen differently. It is also possible, of course, in the case of a cooler through which a U-shape flows, to design the partition wall which separates the supply and return flow from one another in the form according to the invention. The groove can be formed at a depth corresponding to the thickness of the base surface of the second housing part, so that the partition wall protrudes through the base surface.

Claims

Heat transfer device for an internal combustion engine, comprising an inner housing (2) which has a first housing part (12) and a second housing part (14), the base surfaces (16, 18) of which are arranged opposite one another and spaced apart from one another and which are firmly connected to one another, such that a channel (6) through which a first medium can flow is formed in the interior of the inner housing (2), a dividing wall (22) which extends from the base surface (16) of the first housing part (12) to the base surface (18) of the second housing part (14), and an outer housing (4) which is arranged so as to surround the inner housing (2) such that a second channel (10) through which a second medium can flow is formed between the outer housing (4) and the inner housing (2), characterized in that a welded seam (44) is formed on the base surface (18) of the second housing part (14), which extends through the base surface (18) of the second housing part (14) to an end (26) of the partition wall (22) remote from the base surface (16) of the first housing part (12), so that the partition wall (22) is fastened to the second housing part (14) via the weld seam (44).Heat transfer device for an internal combustion engine according to Claim 1, characterized in that the partition wall (22) divides the duct (6) in the inner housing (2) into two parts of substantially equal size in cross section with respect to the direction of flow (20).Heat transfer device for an internal combustion engine according to either of Claims 1 and 2, characterized in that the separating wall (22) extends substantially over the length of the inner housing (2) in the flow direction (20).Heat transfer device for an internal combustion engine according to one of the preceding claims, characterized in that a weld seam (46) extends along the circumference (34) of the second housing part (14), via which weld seam the first housing part (12) is fastened to the second housing part (14).Heat transfer device for an internal combustion engine according to one of the preceding claims, characterized in that the separating wall (22) has steps (40) running substantially perpendicularly to the flow direction (20).Heat transfer precursor arrangement for producing a heat transfer device according to one of the preceding claims, wherein the base surface (18) of the second housing part (14) has a groove (36) into which a tapered section (30) of the dividing wall (22) corresponding to the groove (36) projects, which tapered section is arranged at the end (26) remote from the base surface (16) of the first housing part (12), and wherein a shoulder (28) is formed at the end (26) of the dividing wall (22) remote from the base surface (16) of the first housing part (12), characterized in that a section (38) surrounding the groove (36) of the base surface (18) of the second housing part (14) rests on the shoulder (28).Heat transfer precursor arrangement according to claim 6, characterised in that the depth of the groove (36) corresponds to the thickness of the base surface (18) of the second housing part (14), so that the groove (36) forms a continuous opening.Heat transfer precursor arrangement according to either of Claims 6 and 7, characterized in that the second housing part (14) is designed as a cover which rests with its periphery (34) on a shoulder (32) which is formed at one end of side walls (24) which extend from the periphery of the base surface (16) of the first housing part (12) in the direction of the cover (14).Method for producing a heat transfer device according to one of Claims 1 to 5 with a heat transfer precursor arrangement according to one of Claims 6 to 8, in which a friction stir welding tool is introduced at one end of the groove (36) from the side of the base surface (18) of the second housing part (14) opposite the groove (36) as far as into the groove (36) and is subsequently guided along the groove (36) on the dividing wall (22).

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