MANUFACTURING SAID HEAT EXCHANGER

The present invention concerns, in general and according to a first aspect, a heat exchanger for gases, in particular for exhaust gases from an engine, that includes a plurality of gas circulation pipes and a housing for exchanging heat between said gases and a coolant fluid that surrounds the gas circulation pipes contained in the housing. A second aspect of the present invention concerns a gas circulation pipe for said heat exchanger, and a third aspect concerns a method for manufacturing said heat exchanger according to the first aspect. The invention is used especially in exhaust gas recirculation coolers (EGRC) of an engine.

Background to the invention The main function of EGRC exchangers is to exchange heat between the exhaust gases and the coolant fluid, in order to cool said gases. Nowadays, EGRC heat exchangers are widely used in diesel applications in order to reduce emissions, as well as in petrol applications to reduce fuel consumption.

The current layout of the EGRC exchangers on the market includes a metal heat exchanger usually made of stainless steel or aluminium. There are essentially two types of EGR heat exchangers: a first type has a housing containing a bundle of parallel pipes for carrying the gases, in which the coolant flows through the housing outside the pipes, and the second type has a series of parallel plates that form the heat exchange surfaces, such that the exhaust gases and the coolant flow between the two plates, in alternating layers. In pipe-bundle heat exchangers, the join between the pipes and the housing can be of different types. Generally, the ends of the pipes are attached between two support parts that are coupled to each end of the housing, both support parts having a plurality of orifices designed to receive the ends of the respective tubes .

Heat exchangers for gases that include gas circulation pipes formed from two open half-pipes that are designed to be mounted opposite one another such that the sides of a half-pipe overlap portions of the respective sides of the other half -pipe are known in the prior art.

Patent EP2096294 describes a heat exchanger provided with this type of gas pipe made of two open half-pipes, which have the advantage over pipes made from a single part of facilitating assembly with no risk of breaking the disturbance elements, which are arranged inside the gas pipes to improve the transfer of heat from the gas flow. These disturbance elements are usually narrow fins that are easily damaged by pressure when inserted laterally into pipes made from a single part. Conversely, exchangers that include gas circulation pipes made from two open half -pipes, such as those described in the aforementioned patent, facilitate assembly of the disturbance elements, which makes it possible to reduce the thickness of said elements, thereby reducing the overall cost of the exchanger. However, gas circulation pipes made from two open half- pipes have the drawback of not ensuring optimum contact between components (disturbance elements and half- pipes) . Furthermore, the shape of the cross section of these pipes leaves a join space (e) in the orifices of the support parts that receive the ends of said gas circulation pipes. The seal between the support parts and the ends of the gas pipes is made by brazing using a brazing filler material that is inserted into said join space (e) in order to ensure an optimum seal between components. However, the join space (e) in the orifices of the support parts is too large, and as a result a lot of brazing filler material is required and, even then, optimum seal quality cannot be assured.

Description of the invention

In order to overcome the aforementioned drawbacks, according to a first aspect, the present invention concerns a heat exchanger for gases, in particular for exhaust gases from an engine, that includes:

- a heat-exchange housing that delimits a circuit for the circulation of a coolant fluid, a plurality of gas circulation pipes that are arranged inside the housing to exchange heat with said coolant fluid, and at least two structural parts provided with a plurality of orifices for receiving the ends of the gas circulation pipes in the respective ends of the heat exchanger housing, in which each pipe includes two open half -pipes, preferably two U-shaped half-pipes, that are designed to be mounted opposite one another such that the sides of one half-pipe overlap a portion of the respective sides of the other half-pipe, the shape of the cross section of the gas pipe leaving a join space (e) in the orifices of the structural parts that receive the ends of said gas circulation pipes, and characterized in that:

- the ends of each of the gas circulation pipes have at least two locking tabs arranged to overlap the same number of portions of the sides of one of the half- pipes to at least partially block the join space (e) in the orifices of the structural parts of the exchanger. According to a second aspect, the present invention provides a gas circulation pipe for a heat exchanger such as the one claimed, including:

- two open half -pipes, preferably two U-shaped half- pipes, that are designed to be mounted opposite one another such that the sides of one half -pipe overlap a portion of the respective sides of the other half-pipe, the shape of the cross section of the gas circulation pipe leaving a join space (e) in the orifices of the structural parts that receive the ends of said gas circulation pipe, and characterized in that: - the ends of said gas circulation pipe have at least two locking tabs arranged to overlap the same number of portions of the sides of one of the half-pipes to at least partially block the join space (e) in the orifices of the structural parts of the heat exchanger.

Since the gas circulation pipes of the exchanger are made from two open half -pipes, the disturbance elements of the exchanger (for example, the heat- transfer fins) can be easily mounted inside the gas circulation pipes without risk of being damaged. Consequently, the thickness of these disturbance elements can be significantly reduced, thereby also reducing the total manufacturing cost of the exchanger. Furthermore, the locking tabs make it possible to block the join space (e) in the orifices of the structural parts that receive the ends of the gas circulation pipes, acting as a barrier for the brazing filler material. These locking tabs can be designed to also act as stops and to delimit the position of the aforementioned structural parts of the exchanger. This makes the sealing of the two elements more efficient, guaranteeing a complete seal with no risk of leaks.

Preferably, said exchanger includes a plurality of tabs in the form of projections that extend separately along each of the sides of one of the half-pipes, in which at least two of said projections act as locking tabs at the ends of each gas circulation pipe.

According to another embodiment, said at least two locking tabs are formed from a single projection extending continuously along each of the sides of one of the half-pipes.

These projections can be folded and made to overlap the portions of the sides of one of the half-pipes to ensure contact between these half-pipes and the disturbance elements during the assembly and brazing phase of the two components. This provides an exchanger that is more robust and compact, and that has a lower risk of leaks.

Advantageously, said locking tabs take the form of lengthwise projections on at least one of the sides of one of said half-pipes, said projections being foldable to overlap side portions of another half-pipe, once said half-pipes have been assembled.

According to one embodiment, a portion (D) of the ends of the gas circulation pipes has no locking tabs, and the ends of each pipe can be inserted into the same number of orifices of the structural parts of the exchanger until stopped against one of the locking tabs, such that said locking tabs delimit the position of said structural parts.

Preferably, the length (L) of the projections or locking tabs is between 0.5 mm and 15 mm. Advantageously, the half-pipes that form the gas circulation pipe are U-shaped plates, and said locking tabs are formed, preferably as projections, on the sides of one of said U-shaped plates. Also advantageously, the structural parts that receive the ends of the gas circulation pipes of the exchanger include a plurality of rectangular orifices that are arranged to receive the ends of each of the gas circulation pipes on both ends of the heat-exchange housing.

According to a third aspect, the present invention provides a method for manufacturing the exchanger and the claimed gas circulation pipe, including the following steps: a. stacking two open half -pipes, preferably two U- shaped half-pipes, to form each of the gas circulation pipes , b. folding the locking tabs of the ends of the sides of a half -pipe over the same number of portions of the sides of another half-pipe, c. inserting the ends of each gas circulation pipe into the orifices of the structural parts of the exchanger that receive the ends of each pipe to at least partially block the respective join spaces (e) with the locking tabs, d. filling the join spaces (e) with brazing filler material, and e. brazing the ends of the gas circulation pipes with the structural parts using said brazing filler material .

Preferably, in step c) , a portion of the end of each gas circulation pipe is inserted into an orifice of the structural parts until stopped against one of the locking tabs, such that said locking tab delimits the position of said structural part.

According to a preferred embodiment, in step a) , a gas disturbance element is arranged between the two open half-pipes .

The claimed manufacturing method ensures and improves the contact between components, in particular the contact between the half-pipes and the disturbance elements, and between the gas circulation pipe formed by said open half-pipes and the structural parts that receive the ends of the gas circulation pipes. This ensures the good quality of the braze or weld, and therefore an exchanger that is more robust and has a longer service life.

Short description of figures

The attached schematic drawings show a practical embodiment and are provided by way of non- limiting example to aid comprehension of the foregoing.

Figure 1 is an exploded view of a gas heat exchanger that includes a heat-exchange housing, a plurality of gas circulation pipes made from open half-pipes containing disturbance elements, and structural parts that receive the ends of the gas pipes seated inside the housing.

Figure 2a is a perspective view of an end of an open half-pipe that includes two locking tabs in the form of projections on the sides thereof. Figure 2b is a perspective view of an end of a gas circulation pipe made from two open half-pipes assembled after folding and overlapping the locking tabs over the same number of side portions of the gas circulation pipe.

Figure 2c is an exploded perspective view of an end of a gas circulation pipe that contains a disturbance element and the same number of locking tabs. Figure 3 is a cross section of the gas circulation pipe in Figure 2b, showing the locking tabs. The disturbance element is not shown in this figure, for the sake of clarity. Figure 4 is a schematic perspective view of a structural part provided with orifices and of one end of a gas circulation pipe inserted into one of said orifices until stopped by the same number of locking tabs .

Figure 5 is a detail of the front view in Figure 4 showing a locking tab blocking the join space (e) formed in the orifice in the structural part. Figure 6 shows an exchanger from the prior art that is similar to Figure 5. This figure shows the join space (e) formed by the shape of the cross section of a gas circulation pipe made from two U-shaped open half- pipes .

Description of a preferred embodiment

A preferred embodiment of a heat exchanger for gases and of a gas circulation pipe according to the present invention is described below with reference to Figures 1 to 6.

The gas exchanger according to the present invention includes :

- a heat-exchange housing 1 that delimits a circuit for the circulation of a coolant fluid,

- a plurality of gas circulation pipes 2 that are arranged inside the housing 1 to exchange heat with the coolant fluid, and

- two structural parts 3 provided with a plurality of orifices 4 for receiving the ends of the gas pipes 2 in the respective ends of the heat exchanger housing 1. Figure 1 is an exploded schematic view of the gas exchanger claimed showing, by way of example, a gas circulation pipe 2 made of two open half-pipes 2a, 2b that are formed by two U-shaped plates, that contain a disturbance element 5 to improve the transfer of heat from the gases. Each of the gas circulation pipes 2 is assembled by mounting the two half -pipes 2a, 2b opposite one another such that the sides of one half- pipe 2b overlap a portion 7 of the respective sides of the other half-pipe 2a, the shape of the cross section of the ends of the gas pipes 2 leaving a join space (e) in the orifices 4 of the structural parts 3 that receive the ends of said gas circulation pipes 2. Figure 6 shows the cross section of an end of a gas circulation pipe 2 according to the prior art, made from two U-shaped open half -pipes 2a, 2b and mounted in an orifice 4 in the structural part 3 that receives the ends of the gas circulation pipes 2. This figure shows the join space (e) left by the particular shape of the cross section of the gas pipe 2.

The claimed exchanger has the advantage that the surface of the ends of the gas circulation pipes 2 has at least two locking tabs 6a arranged to block said joint space (e) and to act as a barrier for the brazing filler material (see Figure 5) . In the embodiment described and shown in the figures, there is a plurality of tabs 6 that extend separately along the sides of an open half -pipe 2b in the form of a U-shaped plate, with the exception of a portion (D) of the end of the half -pipe 2b. These tabs 6 take the form of projections that can be folded and made to overlap portions 7 of the sides of another plate or open half -pipe 2a to form the gas circulation pipe 2. In the embodiment described, the length (L) of the projections is approximately 15 mm. However, this length (L) can be varied as a function of the design of the exchanger.

At least one pair of the aforementioned projections is positioned at the end of the gas circulation pipe 2 to act as locking tabs 6a. For example, both locking tabs

6a can be positioned at a distance (D) of 0.5 mm from the end of the plate or half-pipe 2b and act as a stop to delimit the position of each structural part 3. The width (A) of these projections that act as locking tabs 6a can for example be approximately 0.5 mm to at least partially block the join space (e) of the orifices 4 of the structural parts 3 and act as a barrier for the brazing filler material. The remaining projections that

SUBSTITUTE SHEET RULE 26 extend along the sides of the plate or half-pipe 2b are designed to ensure contact between the components during the sealing operation. Figure 2a shows the width (A) and length (L) values respectively of the projections or tabs 6 provided on one of the plates or half-pipes 2a, 2b, which can be adjusted as a function of the design of the exchanger. The steps of the method for manufacturing the heat exchanger and gas circulation pipe claimed are described below with reference to the figures.

In a first step, the two open half-pipes 2a, 2b are stacked to form each one of the gas circulation pipes 2. Optionally, the interior cavity of the gas pipe 2 can contain a gas disturbance element 5 that is inserted between the open half-pipes 2a, 2b with no risk of being damaged. As a result, the thickness of this component can be reduced, which helps to reduce the final cost of the exchanger.

In a second step, the projections or locking tabs 6 of the ends of each gas pipe 2 are folded to overlap the same number of portions 7 of the sides of one of the half-pipes 2a, thereby ensuring contact with the disturbance element 5 during the sealing step. In a subsequent third step, the ends of each gas circulation pipe 2 are inserted into the orifices 4 in the respective structural parts 3 that receive the ends of said gas pipes 2 until stopped against the projections acting as locking tabs 6a (see Figure 4) .

In a fourth step, a sealing operation is carried out by filling the join space (e) of the orifices 4 in the structural parts 3 that receive the ends of the gas pipes 2 with brazing filler material. All of the components are then brazed. As mentioned in the description of the invention, the claimed manufacturing method ensures a good quality braze or weld, and therefore an exchanger that is more robust and has a longer service life.

Although reference has been made to a specific embodiment of the invention, it is obvious for a person skilled in the art that numerous variations and modifications may be made to the heat exchanger, the gas circulation pipe and the method described, and that all of the details mentioned may be replaced by other technically equivalent details without thereby moving outside the scope of protection defined by the attached claims.

For example, although the description of the examples refers to tabs 6, 6a formed by a plurality of projections, said tabs may be formed from a single projection extending continuously along the sides of one of the plates or half-pipes 2a, 2b, also overlapping the same number of side portions of the ends of another half -pipe 2a, 2b to block the join space (e) of the orifices 4 of the structural parts 3.