EP1348924B1 - Exhaust gas heat exchanger for vehicle - Google Patents

Description

The invention relates to an exhaust gas heat exchanger for motor vehicles, which consists of a stack of heat exchanger plates and which has the further features of the preamble of claim 1.

An exhaust gas heat exchanger is out of the DE 101 24 383 known. The known exhaust gas heat exchanger has single-flow exhaust paths. For example, if the exhaust gas of an internal combustion engine with multiple cylinders, for example with six cylinders to recool, under certain circumstances, two exhaust lines for each three cylinders must be present, in each strand such a known exhaust gas heat exchanger would have to be arranged. Since such a structure of the exhaust gas recirculation system is visibly complex, the Applicant suspects that double-flow exhaust gas heat exchangers could belong to the prior art, ie where the exhaust gas from both strands separated by a double-flow, possibly also of several strands passed through a multi-flow exhaust heat exchanger is, so that the exhaust gas recirculation can be done by means of a single exhaust gas heat exchanger.

The matching with the preamble exhaust gas heat exchanger is off EP 974 804A2 known. Even with this exhaust gas heat exchanger a dual-flow exhaust system in the aforementioned sense is not possible.

This statement also applies to the exhaust gas heat exchanger, with the older but not vorverlaglichtem EP 1 411 315 A1 was made known.

The object of the invention is to design an exhaust gas heat exchanger so that it can be constructed inexpensively as a single-flow or optionally also as a multi-flow exhaust heat exchanger.

This object is achieved by the features of claim 1. Thereafter, it is envisaged that identical flat tube halves will be used with folded longitudinal edges. The flat tube halves differ from the heat exchanger plates of the former publication, inter alia, in that they are "open" at the front ends, whereas heat exchanger plates are "closed" around their entire circumference by an edge. Each two such flat tube halves are mirror-inverted assembled with their longitudinal edges and include in an exhaust path. The transverse edges of the flat tube halves are free from bends or other deformations, so that the exhaust gas can enter and leave the exhaust gas paths with the least possible pressure loss. In other words, that means the Flat tube halves are designed approximately U-shaped in their cross section. The cooling water paths are designed as "open" paths, so that the cooling water has contact with the housing. This has the advantage that the housing is not heated as much as in the exhaust gas heat exchanger from the DE 101 24 383 A1 where the hot exhaust gas is in contact with the housing. Furthermore, the flat tube halves are provided at their broad sides with transverse ribs to force the cooling water to the snake-like flow through the cooling water paths. Depending on how large the distance of the transverse ribs from each other - seen in the longitudinal direction of the flat tube halves - is, between the transverse ribs and support studs may be arranged to raise the turbulence of the cooling water. At a relatively small distance can possibly be dispensed with support knobs. As the distance increases, the effectiveness (strength and efficiency of the heat exchange) of the support nubs increases. In the longitudinal direction of the flat tube halves is in each case a separating element in the exhaust paths, whereby each exhaust path is divided into two separate paths in which the exhaust gas can flow in the same direction. Obviously, therefore, the number of floods can be determined by the corresponding number of separating elements. In particular, no changes to the flat tube halves themselves are required.

The housing is preferably formed in two parts, which is also advantageous in terms of manufacturability, because the pairs of flat tube halves can be easily inserted into the housing. Both housing parts are connected to each other at about half the height of the stack of flat tube halves or half the width of the flat tube halves. The housing parts are approximately U - shaped in cross section - simply folded on both sides. The transverse ends are undeformed.

Furthermore, reference is made to the other dependent claims. For example, with the features of claim 2, an exhaust gas heat exchanger is provided, whose entire length is available for heat exchange.

Claim 3 ensures in a cost effective manner, the fluidic separation of the two exhaust paths. This advantage can also affect the features

Claim 7 to be said. The amazing simplicity of the terminals, the features of which are listed in claim 9, also have a cost-cutting effect.

The invention will now be described in an embodiment with reference to the accompanying drawings.

• Fig. 1 Explosionsdarstellung des Abgaswärmetauschers;
• Fig. 2 Querschnitt durch den Abgaswärmetauscher;
• Fig. 3 Vergrößerter Teil - Längsschnitt durch den Abgaswärmetauscher;
• Fig. 4 Draufsicht auf den Abgaswärmetauscher;
• Fig. 5 Längsschnitt durch die Mitte des Abgaswärmetauschers;
• Fig. 6 Perspektivische Ansicht auf den Abgaswärmetauscher;
• Fig. 7 Vergrößerte Ansicht auf einen Teil eines Abgasweges;

The figures show:

• Fig. 1 Exploded view of the exhaust gas heat exchanger;
• Fig. 2 Cross section through the exhaust gas heat exchanger;
• Fig. 3 Enlarged part - longitudinal section through the exhaust gas heat exchanger;
• Fig. 4 Top view of the exhaust gas heat exchanger;
• Fig. 5 Longitudinal section through the center of the exhaust gas heat exchanger;
• Fig. 6 Perspective view of the exhaust gas heat exchanger;
• Fig. 7 Enlarged view of part of an exhaust path;

The exhaust gas heat exchanger of the embodiment is constructed of formed stainless steel sheets. The items of the exhaust gas heat exchanger are, as described below, assembled and connected in a brazing furnace. Since the coating of the stainless steel sheets with a solder material is still problematic, solder foils / pastes are preferably applied or provided at the connecting seams between the individual parts in a manner known per se and therefore not to be described in detail.

The essential individual parts of the exhaust gas heat exchanger in the embodiment shown are the flat tube halves 1 , the separating elements 15 , the tube plates 19 , the connecting flanges 12 and the housing. 2 The flat tube halves 1 are produced from strip to forming machines. All flat tube halves 1 are identical, which means that they can be produced with the same tool. The flat tube halves 1 have beveled longitudinal edges 14 . ( Figure 7 The longitudinal edges 14 are bent in an L shape, wherein the short leg of the arm in the exemplary embodiment is provided in each case for the connection of two flat tube halves 1 , since with these short legs there are respectively two Flat tube halves 1 to each other and form a connecting surface 21st At this connection surface 21 are spaced-apart projections, tabs 22 or the like, are provided, which serve the mechanical connection of two flat tube halves 1 to a pair. For this purpose, a flat tube half 1 is rotated by 180 ° in order to be able to be attached with its longitudinal edges 14 to the longitudinal edges 14 of the other flat tube half 1 . Before joining two flat tube halves 1 to a pair or to a flat tube, a Trennelemet 15 , which is a prefabricated rod of the same material in the embodiment, inserted in the longitudinal direction of the flat tube. As a result of this separating element 15 , two separate exhaust gas passages 4.1 and 4.2 result later within a flat tube . ( Fig. 2 ) In addition, in order to increase the heat exchange surface, as far as possible smooth-walled inner inserts 33 (FIG. Fig. 7 ) is inserted in the exhaust gas paths 4.1 and 4.2 . In other embodiments, not shown, the function of the separating element 15 has been formed by a partition wall within a one-piece inner insert 33 . However, if, as in the embodiment shown, the total length (see 4 and 5 ) of the exhaust gas heat exchanger is so large that the usual bandwidth for producing such inner inserts 33 is exceeded, the shown embodiment of the separating element 15 is more useful, because by the juxtaposition of several inner inserts 33 in the longitudinal direction of the exhaust gas heat exchanger each set at the joints of adjacent inner inserts 33 sealing problems , Thereafter, the already mentioned tabs 22 are bent over - and seen - in the longitudinal direction - alternately upwards and downwards - to reach over the connecting edge 21 and thus to fix the pair of flat tube halves 1 to a flat tube. The broad sides 23 of the flat tubes thus formed have embossed transverse ribs 31 and in this embodiment also supporting nubs 30 . The transverse ribs 31 and the Abstütznoppen 30 have on all flat tube halves 1, the same position. The transverse ribs 31 do not extend over the entire width of the flat tube halves 1 but advantageously (see below) only over about half the width. They are arranged in alternating positions to the two longitudinal edges 14 of the flat tube halves 1 , ie, on a transverse rib 31 , which ends approximately at a longitudinal edge 14 follows the next transverse rib 31 , which ends at the opposite other longitudinal edge 14 , etc. As seen Fig. 1 can be seen better, the pairs of flat tube halves 1 on top of each other stacked. In this case, the support nubs 30 and the transverse ribs 31 of adjacent pairs of flat tube halves 1 come to rest against each other, to be connected later. When the stack 3 of pairs of flat tube halves 1 is completed with the provided number of pairs, the tube plates 19 are attached to both open ends 40 and 50 of the flat tubes and mounted. The ends are inserted into the corresponding openings 18 of the tubesheets 19 , so that there later a quality soldering connection is possible. Thereafter, the prefabricated unit described so far is inserted into a housing half 2a and enclosed by means of the other housing half 2b . The exhaust gas heat exchanger is completed by the attachment of the connecting flanges 12 at the opposite ends 40 and 50 and at the end faces 11 and by the connections 13 for the cooling water, which are arranged on a longitudinal wall 10 of the housing 2 .

The terminals 13 are noteworthy, since they are quite simply formed by means of one approximately over the entire height of the stack 13 reaching slot 32 in the longitudinal wall 10 of the housing 2 , via the (slot 32 ) to the longitudinal wall 10 open towards ports 13 are attached , As a result, in addition to the very production-friendly design, a relatively uniform and low pressure loss-causing division of the cooling liquid to the "open" cooling water paths 5 is achieved. (see also Fig. 1 . 4 and 6 The slots 32 are, as shown in the cited figures, arranged in the longitudinal sides of the housing 2 in which the two housing halves 2a , 2b are joined together. It is understood that in this case one slot 32 (connection 13 ) in one longitudinal wall 10 and the other slot 32 (connection 13 ) could be arranged in the opposite longitudinal wall 10 . You could also be in the other opposite and continuous longitudinal sides of the housing 2 , then of course the continuous longitudinal sides should be arranged in the stacking direction of the flat tube halves 1 , so that the cooling water can easily enter and exit the cooling water 5 . In the figures shown, the continuous longitudinal sides of the housing 2 are arranged above and below or parallel to the flat tube halves 1 .

Another essential feature of the exhaust gas heat exchanger is seen in the formation of the strut 17 on the flanges 12 . ( Fig. 1 . 3 . 5 and 6 The strut 17 is located exactly on the line passing through the dividers 15 ( Fig. 2 ) is described in each flat tube. (In the case of several lines of separating elements 15 or more than two exhaust gas paths in each flat tube, corresponding to a plurality of struts 17 ). The strut 17 has projections 60 on its side facing the open flat tube ends 40 , 50 . The projections 60 coincide in their thickness with the height of the cooling water paths 5 and with the distance between the pairs of flat tube halves 1 . As a result, two important purposes are met, namely, first, ensures that no flow connection between the exhaust paths 4.1 and 4.2 is possible, which would occur in certain operating points of the drive motor problems in the exhaust gas recirculation system, and secondly, a very production-friendly way of prefixing the parts of the exhaust gas heat exchanger before created the soldering.

At this point, again the formation of the transverse ribs 31 in the flat tube halves 1 will be discussed, because even by the transverse ribs 31 may, due to their interaction with the separating elements 15 (FIG. Fig. 7 ), no flow connection between the exhaust paths 4.1 and 4.2 caused or allowed. Therefore, the transverse ribs 31 in their length I do not extend beyond the position of the separating elements 15 . Since in the exemplary embodiment only a number of separating elements 15 is provided and the row is arranged approximately in the middle of the exhaust path 4 , the length I of the transverse ribs 31 should be shorter than the dimension L, measured from the edge 14 to the separator 15. If this condition is respected, it is certainly not necessary, other u. U. consuming measures for sealing in the area of the separating elements 15 and the transverse ribs 31 make. In addition, the snake-like flow through the cooling water paths 5 is ensured by such somewhat shorter transverse ribs 31 , whereby an excellent heat exchange is achieved. How the serpentine flow is possible, or how it is meant, is by looking at the Fig. 1 and 7 comprehensibly. In Fig. 7 For indicating a dashed serpentine line has been drawn.

The inventors also consider it worth mentioning that the upper and lower flat tube half 1 of the stack 3 rests with its transverse ribs 31 and Abstütznoppen 30 on the wall of the housing 2 and is also connected thereto, because this creates a stable unit. This shows in particular the Fig. 2 ,

The Fig. 2 , but also the Fig. 1 and 6 FIGS. 12 also show how the housing halves 2 a , 2 b are interconnected. Namely, each of the legs of the U-shaped housing halves 2a, 2b at its longitudinal edge by about the thickness of material deposited to the outside, so that in each case the other undeformed leg can be attached and connected with its longitudinal edge from the inside to the remote longitudinal edge of the other housing half , Since the overlap of the longitudinal edges and thus the size of the connecting surface is a pure dimensioning, it can be expected that the tight connection of the housing halves 2a , 2b meets high quality standards. In addition, remain by this simple connection of the housing halves 2a , 2b with each other are not protruding from the housing wall 10 edges that could be regarded as disturbing. From the above description, in conjunction with the figures, it can be seen that both housing halves 2a and 2b are identical except for the arrangement of the slots 32 for the terminals 13 (see above), which is undoubtedly a manufacturing advantage. If the housing 2 is rotated by 90 ° about the longitudinal axis and the slots 32 are provided in the other (continuous) longitudinal walls of the housing 2 (see above), then the housing halves 2a , 2b are completely identical.

The Fig. 6 shows that it is possible, two exhaust strands of the engine (although not shown) to lead together on the connecting flange 12 and the exhaust, fluidly separated from each other, to cool in the exhaust paths 4.1 and 4.2 , to then pass it separately separately, because in the picture rear flange 12 is also identical to the front flange 12th

Claims (9)

1. Exhaust-gas heat exchanger for motor vehicles, which exhaust-gas heat exchanger is composed of a stack of heat-exchanger plates (1); the stack (3) of heat exchanger plates (1) comprises exhaust-gas paths (4) which have inner inserts (33) and cooling water paths (5); the exhaust-gas paths (4) and the cooling water paths (5) alternate in the stack direction, with the one set of paths being enclosed in each case within a pair of heat-exchanger plates (1) and the other set of paths being arranged in each case between the pairs; exhaust-gas connecting flanges (12) are arranged at opposite end sides (11), such that the exhaust gas can flow on a straight path through the exhaust-gas heat exchanger, with in each case two heat exchanger plates being designed as identical flat-tube halves (1) and being joined together in a mirror-symmetrical fashion at their bent-up longitudinal edges (14) and enclosing within them the exhaust-gas path (4), with the ends (40, 50) of the flat-tube halves (1) opening out in openings (18) of tube plates (19), and having connections (13) for the cooling water,
   characterized in that
   the stack of heat-exchanger plates (1) is surrounded by a housing (2), with the connections (13) for the cooling water being arranged on the wall (10) of the housing (2),
   in that each exhaust-gas path (4) is divided by one or more separating elements (15), which are provided in the exhaust-gas path (4), into two or more exhaust-gas paths (4.1, 4.2) which are separated from one another,
   in that the cooling water paths (5) are open in the direction of the housing (2) and are provided with transverse ribs (31) which are arranged on the flat-tube halves (1) and which force the cooling water to flow in a serpentine fashion through the cooling water paths (5),
   in that the exhaust-gas connecting flanges (12) have struts (17) which are arranged corresponding to the number of separating elements (15) and which are arranged precisely on the lines which are described by the separating elements (15) in each flat tube,
   and in that the struts (17) have, at their sides which point towards the open flat tube ends (40, 50), projections (60) which fit into the spacing between the pairs of flat-tube halves (1) and which seal off the exhaust-gas paths (4.1, 4.2) with respect to one another.
2. Exhaust-gas heat exchanger according to Claim 1, characterized in that the tube plates (19) and the connecting flanges (12) are either flat plates which are joined together in flat form at the edge (20), or
   in that the tube plates (19) and the connecting flanges (12) are combined to form a single component.
3. Exhaust-gas heat exchanger according to the preceding claims, characterized in that the separating elements (15) are rods or longitudinal walls which are integrated in the inner insert (33) and which separate the exhaust-gas paths (4.1 and 4.2) from one another.
4. Exhaust-gas heat exchanger according to the preceding claims, characterized in that the exhaust gas in the exhaust-gas paths (4.1 and 4.2) flows in the same direction.
5. Exhaust-gas heat exchanger according to one of the preceding claims, characterized in that the separating elements (15) extend over the entire length of the flat-tube halves (1).
6. Exhaust-gas heat exchanger according to Claim 1, characterized in that the length (1) of the transverse ribs (31) is shorter than the dimension (L) measured from the edge (14) of the flat-tube halves (1) to the position of the separating element(s) (15).
7. Exhaust-gas heat exchanger according to Claims 1 and 6, characterized in that, between the transverse ribs (31), support knobs (30) are embossed into the wide sides (23) of the flat-tube halves (1), wherein the support knobs (30) of adjacent pairs of flat-tube halves (1) - in the same way as the transverse ribs (31) - bear against one another and are intended to be connected to one another.
8. Exhaust-gas heat exchanger according to Claim 1, characterized in that the connections (13) are designed as connecting boxes which are open at one side and which, with their open side, are placed over a slot (32) in the longitudinal wall (10) of the housing (2), with the slot (32) and the connecting boxes extending virtually over the entire height of the stack (3) of the flat-tube halves (1).
9. Exhaust-gas heat exchanger according to Claim 1, characterized in that the longitudinal edges (14) of the flat-tube halves (1) are bent approximately in an L-shape and connecting surfaces (21) are formed by in each case one limb of the L, and in that lugs (22) which are spaced apart in the longitudinal direction of the flat-tube halves (1) project from the limbs, which lugs (22) are bent upwards and downwards in an alternating sequence in order to connect in each case two flat-tube halves (1) to form a pair.

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