FR3056726A1 - UNITARY TUBULAR MODULE FOR MOTOR VEHICLE WITH THERMAL MOTOR, AND THERMOELECTRIC GENERATOR INCORPORATING SEVERAL OF THESE MODULES - Google Patents

Abstract

The invention relates to a unitary tubular module for a motor vehicle with an internal combustion engine, and a thermoelectric generator comprising at least one sheet of said modules. This unitary tubular module (1 ') comprises: an inner monoblock tube, called a hot tube (2), adapted to convey vehicle exhaust gases and with an external surface intended to be surrounded by external tubes arranged in a screw-in position; -vis, said cold tubes, adapted to convey a coolant of the vehicle, - two transverse fastening flanges (6 '), each flange enclosing one end of the hot tube, the flanges being intended to be assembled by means of assembly (9) two gas manifold plates (7), and - thermoelectric elements (4a and 4b) integral with said outer surface and coated with electrical conduction tracks to be in contact with the cold tubes. According to the invention, the assembly means are external to each flange, which is devoid of threaded hole for its assembly to the collector plate.

Description

® FRENCH REPUBLIC

NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY © Publication number: 3,056,726 (to be used only for reproduction orders) (© National registration number: 16 59262

COURBEVOIE © IntCI ⁸ : F 28 F 9/007 (2017.01), H 01 L 35/30, F 02 N 5/02

A1 PATENT APPLICATION

©) Date of filing: 28.09.16. © Applicant (s): VALEO THERMAL SYSTEMS (© Priority: Simplified joint stock company - FR. @ Inventor (s): MONNET VERONIQUE, DE VAULX CEDRIC, AZZOUZ KAMEL, AMBROISE SERVANTIE (43) Date of public availability of the and BOISSELLE PATRICK. request: 30.03.18 Bulletin 18/13. (© List of documents cited in the report of preliminary research: Refer to end of present booklet (© References to other national documents © Holder (s): VALEO THERMAL SYSTEMS related: Joint stock company. ©) Extension request (s): © Agent (s): VALEO THERMAL SYSTEMS.

THERMAL, AND

VX) UNIT TUBULAR MODULE FOR MOTOR VEHICLE WITH THERMOELECTRIC GENERATOR MOTOR INCORPORATING SEVERAL OF THESE MODULES.

FR 3 056 726 - A1

The invention relates to a unitary tubular module for a motor vehicle with an internal combustion engine, and a thermoelectric generator comprising at least one layer of said modules.

This unitary tubular module (1 day includes:

- a one-piece inner tube, called a hot tube (2), adapted to transport vehicle exhaust gases and with an external surface intended to be surrounded by external tubes arranged opposite, said cold tubes, suitable for conveying vehicle coolant,

- two transverse fixing flanges (6d, each flange enclosing one end of the hot tube, the flanges being intended to be assembled by means of assembly (9) to two collecting plates (7) of the gases, and

- thermoelectric elements (4a and 4b) integral with said external surface and coated with electrical conduction tracks to be mounted in contact with the cold tubes.

According to the invention, the assembly means are external to each flange, which is devoid of a tapped hole for its assembly with the manifold plate.

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UNIT TUBULAR MODULE FOR MOTOR VEHICLE WITH HEAT ENGINE, AND GENERATOR

THERMOELECTRIC INCORPORATING SEVERAL OF THESE MODULES.

The present invention relates to a unitary tubular module intended to equip a motor vehicle with an internal combustion thermal engine, and a thermoelectric generator comprising at least one layer or bundle of said modules. The invention applies to the recovery of thermal energy from the operation of the vehicle to generate electrical energy in the vehicle.

Thermoelectric generators are known in motor vehicles using rows of thermoelectric elements to generate an electric current in the presence of a temperature gradient between two of their opposite faces, by the Seebeck effect. These generators usually comprise a stack of plies of hot tubes carrying vehicle exhaust gases and cold tubes carrying a coolant, between and in contact with which the thermoelectric elements are sandwiched typically by brazing in contact with the hot tubes. These elements are subjected to a temperature gradient generated by the temperature difference between these gases and this liquid, so that these generators make it possible to produce electricity from a conversion of this thermal gradient resulting from the recycling of the gases. .

Documents US 2015/0333244 A1 and KR 101327735 B1 present such thermoelectric generators, the hot tubes of which are each provided at each of their ends with a connection flange to a member for fixing the fluidic distribution circuit. In US 2015/0333244 A1, each hot tube is produced in several blocks and has a rectangular section for example with a double envelope defining two large opposite faces surmounted by thermoelectric elements, while in KR 101327735 B1 each hot tube has a polygonal section surrounded over its entire perimeter by thermoelectric elements.

These generators have the major drawbacks of having a high weight and size with, for each hot tube / thermoelectric elements module, mass and volume ratios [thermoelectric elements / module] which are relatively high.

Figures 1 and 2 schematically illustrate in longitudinal section and in perspective a unitary tubular module 1 according to another example of the prior art, with a 2-piece hot tube of rectangular section (conveying the exhaust gases in the direction of arrow A ) which is surrounded on its large opposite faces 2a and 2b by at least two upper and lower series of cold tubes 3 (conveying the coolant in the direction of arrow B) with interposition, by brazed interfaces with the hot tube 2 and not brazed with the cold tubes 3, of thermoelectric elements 4 coated with flat electrical conduction tracks 5a, 5b in contact with the cold tubes 3. More specifically, the elements 4 are brazed on the faces 2a, 2b of the hot tube 2 and are coated by brazing tracks 5a, 5b which are in "dry" contact with the cold tubes 3 (ie without brazing, usually with the interposition of an interface material th ermique between tracks 5a, 5b and tubes 3). The hot tube 2 is equipped at each of its ends with a transverse fixing flange 6 incorporating each of the threaded holes 6a receiving assembly screws (not visible) to a transverse plate 7 collecting the exhaust gases (illustrated in the Figure 4) outside the flange 6.

As visible in Figure 1, which shows in addition to Figure 2 the two upper and lower pairs of coolant collectors 8 (these collectors 8 form tubes inserted in the coolant distribution boxes, called water boxes ), these collectors 8 are mounted clearly outside the flanges 6, which has the drawbacks that they are located too close to the hot source which can affect their proper functioning, and that these collectors 8 thus offset relative to the hot tube 2 give the cold tubes 3 a high overall length which would benefit from being reduced, since it generates an additional pressure drop and goes against the efficiency and compactness desired for the generator.

Another major drawback of the tubular module 1 of FIGS. 1 and 2 resides in the fixing of the flanges 6 to the manifold plates 7 by these assembly screws which pass through the flanges 6 while passing axially inwardly, so that, from on the one hand, each screw occupies in particular by its head a non-negligible axial space between the flange 6 which it passes through and the thermoelectric elements 4 which forms a non-functional dead volume which could be used otherwise and that, on the other hand, each flange 6 must be thick enough (usual thickness of at least 3 mm) to be able to be tapped and receive these screws. However, these very thick flanges 6 represent in known manner about 50% of the total mass of each hot tube 2, which penalizes the overall mass of the thermoelectric generator.

Yet another drawback of the module of FIGS. 1 and 2 resides in the axial size of the electrical conduction tracks of the ends 5a which extend axially beyond the row of proximal thermoelectric elements 4a with respect to the flanges 6 (ie the closest to these), these end tracks 5a which line each proximal row 4a being mounted in contact with the cold tubes 3 above or below, extending axially opposite the space separating this row 4a of the adjacent flange 6.

It therefore follows in particular from this arrangement known from FIGS. 1 and 2 that the aforementioned mass and volume ratios remain relatively high for a thermoelectric generator incorporating these hot tubes 2.

An object of the present invention is to propose a unitary tubular module intended to equip a motor vehicle with an internal combustion thermal engine, which overcomes all of the aforementioned drawbacks, the module comprising:

a one-piece inner tube, called a hot tube, which is suitable for conveying exhaust gases at high temperature from the vehicle and which has an external surface extending around a longitudinal axis of symmetry for the hot tube, said external surface being intended to be surrounded by at least two series of external tubes arranged opposite, called cold tubes, adapted to convey a coolant of said vehicle on either side of the hot tube,

- Two transverse fixing flanges, each of the flanges respectively enclosing one end of the hot tube, the flanges being respectively intended to be assembled by means of assembly to two transverse plates collecting said exhaust gases, said collecting plates extending at beyond the flanges relative to said axis, and

- thermoelectric elements which are integral with said external surface and which are coated with electrical conduction tracks intended to be mounted in contact with cold tubes.

To this end, a unitary tubular module according to the invention is such that said assembly means are external to each of the flanges.

According to another characteristic of the invention, each of the flanges is advantageously devoid of a tapped hole passing through it to receive a connecting screw to a said manifold plate.

It will be noted that this assembly of the flanges according to the invention which is not traversing with respect to these makes it possible to dispense with the aforementioned assembly screws of the prior art between flanges and manifold plates, which has the double advantage of being able to minimize the thickness of the flanges (and therefore their mass and size) and to otherwise use the vacant space between each flange and the proximal thermoelectric elements on the hot tube resulting from the absence of any screw head in this space. As will be detailed below, this vacant space can advantageously be occupied by each collector of the upper and lower pairs of collectors.

It will also be noted that this assembly of each flange to the manifold plate from the outside of this flange allows not only to position the collectors in this vacant space between flanges and thermoelectric elements, but also to use this same vacant space to implant therein. other electrical conduction tracks, as explained below.

It will also be noted that these non-tapped flanges according to the invention make it possible to obtain a denser beam for the thermoelectric effect than in this prior art of FIGS. 1 and 2.

Advantageously, each of the flanges may have a thickness of less than 3 mm which may be equal to 1 mm in an axial direction parallel to said axis, so that the module is lightened in comparison with a reference module with flanges with tapped holes for screws. assembly.

It will be noted that the flanges of the invention provide a substantial reduction in mass for a given hot tube (ie of the same geometry and material) both along said axis and in a transverse plane, in comparison with the hot tube with tapped flanges of FIGS. 1- 2.

According to another characteristic of the invention, each flange without assembly screws is advantageously distant from a row of said thermoelectric elements proximal to the flange by a reduced distance in said axial direction, so that the module be more compact in comparison with a reference module with flanges with tapped holes receiving assembly screws and therefore imposing a greater distance with said proximal row.

Note that the removal of the space required for the flange assembly screws of Figures 1-2 makes it possible to halve the transverse dead volume required around each hot tube. As a result, an assembly of several unitary tubular modules according to the invention (i.e. to several hot tubes fitted with these flanges) is significantly more dense than in this prior art.

According to another aspect of the invention, for which the hot tube has in cross section a substantially rectangular shape with two large upper and lower sides receiving two upper and lower series of thermoelectric elements, said electrical conduction tracks of said upper series (respectively lower) can advantageously extend along several distinct planes and include:

said main tracks which electrically connect the thermoelectric elements parallel and adjacent to said large upper side (respectively lower) of said external surface of the hot tube along a first upper longitudinal plane (respectively lower), and

- Other said external tracks with respect to said axis which extend said main end tracks and which are adapted to electrically connect two respective rows, proximal to the flanges, thermoelectric elements of two consecutive hot tubes overflowing of said large upper side (respectively lower), said external tracks extending along a second plane intersecting said first plane and transverse to said hot tube.

Advantageously, said external tracks can be formed by end portions of said main end tracks coating the proximal thermoelectric elements, portions which are folded from said first plane towards said second plane in close proximity to said proximal rows of the thermoelectric elements of consecutive hot tubes, alternating at said two ends of the latter.

It will be noted that these folded external tracks provide the electrical connection between the respective proximal rows of hot tubes two to two consecutive as close as possible to these hot tubes, because these external tracks project laterally from these rows in the transverse direction of the hot tubes.

It will also be noted that these two planes for said main and external tracks make it possible to use less space in the longitudinal direction of said axis than in the prior art of FIG. 1, and thus to compact the unitary tubular module even further according to the 'invention. In fact, said first longitudinal plane (eg horizontal) for said main connection tracks between the thermoelectric elements is advantageously chosen perpendicular to said second transverse plane (eg vertical) of connection between consecutive hot tubes, or of connection to the electrical inputs and outputs of the generator. thermoelectric.

Preferably, the thermoelectric elements consist of prismatic studs (i.e. defined broadly by a directorate in the form of a broken closed line extending along a generator) for example parallelepipedic or cubic. As a variant, one could use studs in the shape of a pyramid or trunk of a pyramid, cylindrical studs (ie defined in the broad sense by a director in the shape of a closed closed line extending along a generator) or even studs shaped like a cone or truncated cone.

A thermoelectric generator intended to equip a motor vehicle with an internal combustion engine according to the invention is such that it comprises:

- at least one ply of said unitary tubular modules as defined above in relation to the invention,

- said two transverse plates collecting the exhaust gases to which said flanges are assembled by said assembly means, and

- Said at least two series of cold tubes which are respectively provided with two upper and lower pairs of coolant collectors, each said upper pair (respectively lower) comprising two said upper collectors (respectively lower) each positioned axially with respect to said axis, between the flanges and rows of said proximal thermoelectric elements with respect to the flanges.

It will be noted that this mounting of each of the two upper and lower manifolds axially between the adjacent flange and the proximal row of thermoelectric elements, instead of the mounting of the prior art (see FIG. 1) of such a manifold axially at - beyond the adjacent flange - this assembly according to the invention being made possible by the substantial reduction in the volume of each flange in particular along said longitudinal axis - therefore makes it possible to minimize the length of each hot tube and the length of the bundle of cold tubes and bringing the collectors closer to the thermoelectric elements, thereby giving the thermoelectric generator increased density both for its geometry and for its efficiency.

According to another characteristic of the invention, said assembly means may comprise clamping jaws which at least partially enclose the flanges and which are fixed to the collector plate opposite by assembly screws passing through said jaws and the collector plate , with the interposition of a seal axially between the flanges and the collector plate, each of said clamping jaws being mounted in a transverse plane parallel to said flanges, being able to hold in position at least one said hot tube and to densify said at least one ply in two perpendicular transverse and vertical directions defining said transverse plane.

It will be noted that it is the reduction in volume of each flange according to the invention in particular along said longitudinal axis which makes it possible to use these clamping jaws which grip the flange by pressing it axially against the adjacent collector plate. These jaws form mechanical clamping jaws allowing each hot tube to be held in position and sealing the exhaust gas side with this plate.

Advantageously, said clamping jaws may each have a length, measured in said transverse or vertical direction, at least equal to half the length of each flange in the same transverse or vertical direction, and even more advantageously at most equal to the length of each flange in the transverse or vertical direction multiplied by N + 1, where N is the number of consecutive hot tubes of the generator in the transverse or vertical direction.

In general, a thermoelectric generator according to the invention makes it possible to double the aforementioned mass ratio (mass of the thermoelectric elements / mass of the generator) compared to the generator of the prior art illustrated in FIGS. 1-2.

According to another aspect of the invention, said generator further comprises boxes for distributing the cooling liquid, called water boxes, which are capable of receiving and distributing the liquid between different layers of the cold tubes, at least one said water boxes which can advantageously support temperature sensors and / or electrical connectors.

It will be noted that these water boxes according to the invention make it possible, for this desired purpose of increased density of the thermoelectric generator, to combine the functions of distribution of the cooling circuit and collection of electrical connectors.

Advantageously, said at least one water box can be provided with an electrically insulating closure plate forming an electrical panel, which is adapted to modify electrical parameters of the generator as a function of the desired current / voltage variables at the output and / or to isolate any electrical faults detected.

Other characteristics, advantages and details of the present invention will emerge on reading the following description of an exemplary embodiment of the invention, given by way of illustration and not limitation, the description being made with reference to the accompanying drawings, among which :

FIG. 1 is a schematic view in longitudinal section in plane II of FIG. 2 of a unitary tubular module according to the prior art with a hot tube provided with flanges, equipped with cold tubes and corresponding collectors, FIG. 2 is a top view and perspective view of the unitary tubular module of FIG. 1, without these cold tubes or their manifolds, FIG. 3 is a top view and perspective view of a unitary tubular module according to the invention, with a hot tube provided with flanges of the invention, thermoelectric elements and their conductive tracks according to the invention but without the cold tubes and their collectors, FIG. 4 is a schematic view in longitudinal section in the plane IV-IV of FIG. 3 of this module according to the invention, illustrated without ίο these tracks but with the assembly means according to the invention of the flanges to the manifolds of the exhaust gases, Figure 5 is a top view and in pers pective of a module according to the invention, schematically showing the two intersecting planes containing the two types of tracks according to the invention visible in FIG. 3, FIG. 6 is a schematic view in longitudinal section of this module of the invention at hot tube provided with flanges, cold tubes and corresponding collectors, for comparison with that of FIG. 1, FIG. 7 is a partial view from above and in perspective of a thermoelectric generator according to the invention incorporating a stack of plies of modules according to FIG. 6, collectors included, and further showing the assembly means of FIG. 4, FIG. 8 is a partial front and perspective view of this thermoelectric generator according to the invention showing the stack of layers according to FIG. 7 but without the collectors, and the arrangement of the external tracks, and FIG. 9 is a partial view in semi-exploded perspective of this thermoelectric generator. e according to the invention, further showing the assembly of two water boxes laterally in relation to the collectors of the cold tubes.

The unitary tubular module 1 ’according to the exemplary embodiment of the invention illustrated in FIGS. 3 to 6, which forms the thermoelectric generator 10 of FIGS. 7-9 by stacking several layers of these modules 1’, comprises:

a hot tube 2 (eg made of stainless steel), which carries exhaust gases at high temperature of the vehicle and which has an external surface of generally rectangular section extending around the longitudinal axis of symmetry Y ′ of the tube, whose long horizontal sides 2a and 2b are intended to be surrounded by at least two upper and lower series of cold tubes 3 (eg made of aluminum, see FIG. 6) vis-à-vis conveying a vehicle coolant,

- two transverse fixing flanges 6 'extending in the transverse plane XZ of FIG. 3, each flange 6' front or rear respectively enclosing a front end 2c or rear 2d of the tube 2 (immediately below or flush with the ends 2c , 2d) with which they are formed in one piece (ie the flanges 6 'can also be made of stainless steel), the flanges 6' being respectively intended to be assembled by assembly means 9 (see FIG. 4) with two transverse plates collecting the exhaust gases 7 extending axially outside the flanges 6 ′ with respect to the axis Y ′, and

- two upper and lower series of n rows each (n = 9 in this illustrated example, with two rows proximal to the two flanges connected to each other by seven central rows) of thermoelectric elements 4a, 4b formed in this example of parallelepipedic studs (eg cubic) which are respectively secured to the upper upper sides 2a and lower 2b by two brazed internal interfaces and which are coated with main electrical conduction tracks 5b intended to be in contact with the cold tubes 3 by two external interfaces not brazed.

As in particular visible in FIGS. 3 and 5, each flange 6 ′ is devoid of any tapped hole passing through it to receive a connecting screw to a manifold plate 7, unlike the prior art of FIGS. 1-2, which makes it possible to minimize its axial thickness (which can advantageously be only 1 mm) and therefore its mass and size (thanks to these thinned 6 'flanges, it is possible to reduce the total mass by up to 60% of each hot tube 2).

The elimination of the space required for the flange assembly screws 6 ′ thus makes it possible to halve the dead volume required around each hot tube 2 in the transverse plane XZ and along the axial direction Y, and therefore to densify in the three directions X, Y, Z the assembly of several unitary tubular modules 1 ′ according to the invention (see FIGS. 7 and 8).

As illustrated in FIG. 4, the assembly means 9 between each flange 6 ′ and the adjacent collector plate 7 comprise, in place of the assembly screws used in the past, two transverse clamping jaws 9a (extending in the XZ plane and for example made of stainless steel) which each enclose at least one flange 6 'at the axially internal face 6a' of the flange (s) 6 '(face located towards the inside of the tube 2 with respect to the 'axis Y') and its peripheral edge 6b 'by pressing it against the collector plate 7 opposite by assembly screws 9b passing through each jaw 9a and the plate 7 around each flange 6'. In addition, a gasket 9c is interposed axially (e.g. in compressed graphite) between each flange 6 ’and the plate 7 to seal the exhaust gas side.

Each of the two jaws 9a thus makes it possible to maintain in position several hot tubes 2 of two horizontal plies stacked one on the other (see FIGS. 8-9) and to densify each ply in the transverse X and vertical Z directions. We see in fact in FIG. 8 that each jaw 9a has a length, measured in the transverse direction X, substantially equal to three times the length of each flange 6 'in the direction X.

This absence of through fixing between each flange 6 ’and the adjacent collector plate 7 also allows:

- as illustrated in Figure 6, fill the vacant space between each flange 6 'and the adjacent proximal row 4a with one of the two coolant collectors 8' of an upper pair and a lower pair of collectors 8 ', each manifold 8' being mounted relative to the axis Y 'between a flange 6' and the proximal row 4a and no longer beyond the adjacent flange 6 (cf. FIG. 1), which makes it possible to minimize the length L2 of each hot tube 2 and the length L3 of the bundle of cold tubes 3 and bring the collectors 8 'closer to the thermoelectric elements 4a, 4b (thus avoiding that the collectors 8' are located too close to the hot source as in FIG. 1), finally conferring an increased density on the generator 10; and

- As illustrated in Figures 3 and 5-8, use the space left vacant axially inside each flange 6 'to implant axially external tracks 5a' upper and lower electrical conduction which extend by bending at an angle straight along a vertical plane XZ of the terminal portions of main tracks 5b of upper and lower ends extending along a horizontal longitudinal plane XY to connect the upper and lower thermoelectric elements 4b in series.

As can be seen in FIGS. 5-6, the external tracks 5a ′ are folded vertically as close as possible to proximal rows 4a two to two consecutive equipping a horizontal sheet of hot tubes 2 neighbors, consecutive proximal rows 4a that these tracks 5a ′ connect electrically to each other by projecting laterally from these consecutive rows 4a in the transverse direction X to join between two consecutive hot tubes 2. FIG. 8 shows that these external tracks 5a ′ can be folded alternately in front of and as close as possible to the two proximal rows 4a situated at the opposite ends 2c, 2d of the hot tubes 2 (ie in the transverse direction X, below the end before 2c of the first hot tube 2 of the tablecloth then of the rear end 2d of the second hot tube 2 of the tablecloth, etc.).

These two planes XY and XZ perpendicular to the main tracks 5b and external 5a 'provide an increased compactness in the direction Y, compared to the known arrangement of the tracks 5a, 5b of FIG. 1 in which the end tracks 5a ( contained like the other tracks in the only horizontal plane XY) extended axially to the flanges 6.

A thermoelectric generator 10 according to the invention as illustrated in FIGS. 7-9 makes it possible to double by two the ratio (mass of the thermoelectric elements 4a, 4b / mass of the generator 10) relative to the generator with tubular modules 1 of the art Figure 1-2, this mass ratio can for example reach a value as high as 0.15.

As specifically illustrated in FIG. 9 and in order to have a “densified” thermoelectric generator 10 (ie of increased compactness and efficiency), it is advantageous to combine the functions of fluid distribution of the cooling and assembly circuit electrical connectors, via water boxes 11 according to the invention, the design of which has been optimized as explained below.

Are particularly visible in Figure 9:

the stacks of layers of hot tubes 2 / thermoelectric elements 4a, 4b / cold tubes 3 (four layers each comprising six hot tubes 2 arranged in parallel in this example) with in particular, on each front and rear side of the generator 10, the coolant collectors 8 '(transverse pipes), the flanges 6' provided with clamping jaws 9a, the exhaust gas collector plate 7 to which the flanges 6 'are fixed by these jaws 9a and the screws 9b, and the seal 9c interposed between the plate 7 and each flange 6 '; and

- two water boxes 11 forming two opposite side walls in fluid communication with the collectors 8 ′, each comprising an inlet / outlet 11a for the coolant and provided with a closure plate 12 fixed to the water box 11 (l one of the water boxes 11 is shown assembled, the other in exploded view).

Each water box 11 according to the invention, which can be made of an electrically insulating material (preferably plastic) or aluminum for example, is suitable not only for distributing the coolant between each layer of cold tubes 3, but also :

- To serve as a support for temperature sensors comprising for example thermocouples 11b for measuring the temperature of the exhaust gases, and / or

- To collect the electrical connections of the circuit integrating the thermoelectric generator 10 via the closure plate 12 (preferably made of an electrical insulating material) which is provided with each water box 11, which closure plate 12 advantageously comprises a table electrical connectors, in order to be able to modify, as necessary, the electrical circuit of the generator 10 as a function of the magnitudes of current / voltage desired at the output and to isolate potential electrical faults which could appear during operation.

Claims (13)

1) Unit tubular module (T) intended to equip a motor vehicle with internal combustion engine, the module comprising: - an inner one-piece tube, called a hot tube (2), which is adapted to convey exhaust gases at high temperature of the vehicle and which has an external surface (2a, 2b) extending around a longitudinal axis of symmetry (Y ′) for the hot tube, said external surface being intended to be surrounded by at least two series of external tubes arranged opposite, said cold tubes (3), adapted to convey a coolant from said vehicle on the one hand and on the other side of the hot tube, - two transverse fixing flanges (6 '), each of the flanges respectively enclosing one end (2c and 2d) of the hot tube, the flanges being respectively intended to be assembled by means of assembly (9) to two transverse collecting plates ( 7) of said exhaust gases, said manifold plates extending beyond the flanges relative to said axis, and - thermoelectric elements (4a and 4b) which are integral with said external surface and which are coated with electrical conduction tracks (5a 'and 5b) intended to be mounted in contact with cold tubes, characterized in that said assembly means are external to each of the flanges. 2) Unit tubular module (T) according to claim 1, characterized in that each of the flanges (6 ’) has no tapped hole passing through it to receive a connecting screw to a said manifold plate (7). 3) unitary tubular module (T) according to claim 2, characterized in that each of the flanges (6 ') has a thickness less than 3 mm which may be equal to 1 mm in an axial direction (Y) parallel to said axis (Y' ), so that the module is lightened compared to a reference module (1) with flanges (6) with threaded holes (6a) for assembly screws. 4) unitary tubular module (1 ') according to claim 3, characterized in that each of the flanges (6') devoid of assembly screws is distant from a row of said thermoelectric elements (4a), which is proximal vis- opposite the flange, by a reduced distance in said axial direction (Y), so that the module is more compact compared to a reference module (1) with flanges (6) with tapped holes (6a ) receiving assembly screws imposing a greater distance with said proximal row (4a). 5) unitary tubular module (1 ') according to one of the preceding claims, the hot tube (2) having in cross section a substantially rectangular shape with two large upper (2a) and lower (2b) sides receiving two upper and lower series of elements thermoelectric (4a and 4b), characterized in that said electrical conduction tracks (5a 'and 5b) of said upper series (respectively lower) extend along several distinct planes (XY and XZ) and include: - said main tracks (5b) which electrically connect the thermoelectric elements (4a and 4b) parallel and adjacent to said large upper side (respectively lower) of said external surface of the hot tube along a first longitudinal (XY) upper plane (respectively lower), and - other said external tracks (5a ') with respect to said axis (Y') which extend said main end tracks and which are adapted to electrically connect two respective rows, proximal to the flanges (6 ' ), thermoelectric elements (4a) of two consecutive hot tubes projecting from said large upper side (respectively lower), said external tracks extending along a second plane (XZ) intersecting said first plane and transverse to said hot tube. 6) unitary tubular module (1 ') according to claim 5, characterized in that said external tracks (5a') are formed by end portions of said main tracks (5b) of ends coating the proximal thermoelectric elements (4a), portions which are folded from said first plane (XY) to said second plane (XZ) in the immediate vicinity of said proximal rows (4a) of the thermoelectric elements of the hot tubes (2) consecutive, alternately at said two ends (2c and 2d) of the latter. 7) Unit tubular module (1 ’) according to one of the preceding claims, characterized in that the thermoelectric elements (4a and 4b) consist of prismatic studs, for example parallelepipedic or cubic. 8) Thermoelectric generator (10) intended to equip a motor vehicle with internal combustion thermal engine, characterized in that the generator comprises: - at least one ply of said unitary tubular modules (1 ’) according to one of the preceding claims, - said two transverse collector plates (7) of the exhaust gases to which said flanges (6 ’) are assembled by said assembly means (9), and - Said at least two series of cold tubes (3) which are respectively provided with two upper and lower pairs of coolant collectors (8 '), each said upper pair (respectively lower) comprising two said upper collectors (respectively lower) each positioned axially with respect to said axis (Y '), between the flanges and rows of said thermoelectric elements (4a) proximal to the flanges. 9) Thermoelectric generator (10) according to claim 8, characterized in that said assembly means (9) comprise clamping jaws (9a) which at least partially enclose the flanges (6j and which are fixed to said manifold plate ( 7) opposite by assembly screws (9b) passing through said jaws and said manifold plate, with the interposition of a seal (9c) axially between the flanges and said manifold plate, each of said clamping jaws being mounted in a transverse plane (XZ) parallel to said flanges being able to hold in position at least one said hot tube (2) and to densify said at least one ply in two perpendicular transverse (X) and vertical (Z) directions defining said transverse plane (XZ). 10) thermoelectric generator (10) according to claim 9, characterized in that said clamping jaws (9a) each have a length (L1), measured in said transverse (X) or vertical (Z) direction, which is at least equal to half the length of each of the flanges (6d in said same transverse or vertical direction. 11) Thermoelectric generator (10) according to claim 10, characterized in that said clamping jaws (9a) each have said length (L1) which is at most equal to the length of each of the flanges (6j in said transverse direction (X ) or vertical (Z) multiplied by N + 1, where N is the number of consecutive hot tubes 2 of the generator in said transverse or vertical direction. 12) Thermoelectric generator (10) according to one of the preceding claims, characterized in that the generator further comprises boxes for distributing the coolant, called water boxes (11), which are capable of receiving and distributing the liquid between different layers of cold tubes (3), at least one of said water boxes supporting temperature sensors (11 b) and / or electrical connectors. 13) Thermoelectric generator (10) according to claim 12, characterized in that said at least one water box (11) is provided with an electrically insulating closure plate (12) forming an electrical panel, which is adapted to modify electrical parameters of the generator as a function of the current / voltage variables desired at the output and / or to isolate any detected electrical faults. 1/4 x 2c oa