EP3396296B1

EP3396296B1 - Heat exchanger assembly

Info

Publication number: EP3396296B1
Application number: EP17461529.4A
Authority: EP
Inventors: Radoslaw Jonczyk; Dariusz Potok; Maciej KLUSEK; Rafa PAC
Original assignee: Valeo Autosystemy Sp zoo
Current assignee: Valeo Autosystemy Sp zoo
Priority date: 2017-04-28
Filing date: 2017-04-28
Publication date: 2020-09-09
Anticipated expiration: 2037-04-28
Also published as: EP3396296A1

Description

Technical Field

The present invention relates to a heat exchanger assembly, according to claim 1, especially a water charge air cooler for a motor vehicle.

Prior Art

A general structure of heat exchanger assemblies is known from the prior art. The prior art heat exchanger assembly comprises: a housing; a core situated in the housing and comprising a plurality of spaced-apart flow tubes; two headers placed on the core; and inlet and outlet conduits covering the headers and closing the housing. The headers comprise at their perimeters a plurality of teeth. The inlet and outlet conduits are received in the headers so that the teeth are bent over protruding portions of the inlet and outlet conduits. In order to make the bending of the teeth easier, each tooth is provided on its inner surface with an undercut. The undercut can be circular or elliptic in cross-section. The radius of the prior art undercuts was 0,5 mm, a general thickness of the tooth was 2 mm and a limited thickness of the tooth at the undercut was 1,5 mm.
In the prior art solution described above, when the tooth is bent over the inlet or outlet conduits, a sharp edge is formed inside the undercut. When the heat exchanger assembly undergoes pressure tests or is used in a motor vehicle, high stresses concentrate at the sharp edge formed inside the undercut and this can lead to cracking of the teeth and in turn can damage the headers themselves. FR 2 968 753 A1 describes a heat exchanger assembly according to the preamble of claim 1.
The aim of the present invention is to eliminate the drawbacks of the prior art mentioned above. Especially, the aim of the present invention is to provide a heat exchanger assembly having a new undercut configuration, by which stresses in the undercut itself are significantly reduced.

Summary of the Invention

The above aim is achieved by a heat exchanger assembly according to the independent claim. In particular, the heat exchanger assembly comprises: a housing; a core situated inside the housing; two headers placed on the core; and inlet and outlet conduits covering the headers and closing the housing. The headers comprise at their perimeters a plurality of teeth, which are bent over the inlet and outlet conduits. Each of the teeth is provided on its inner surface with an undercut, which has an undercut axis. The undercut axis divides each of the teeth into a base portion and a bendable portion. The bendable portion has a height measured from the undercut axis to an end of each of the teeth. Each of the teeth has a general thickness as well as a reduced thickness at the undercut. Prior to bending of the teeth over the inlet and outlet conduits: the undercut has a substantially elliptic cross-section; a semi-minor axis of an ellipse of the undercut cross-section coincides with the undercut axis; the semi-minor axis has a length, which is at least half of the general thickness; and the reduced thickness of each of the teeth is at most two times smaller than the height of the bendable portion.
Further advantageous embodiments of the present invention are presented in the dependent claims.
The configuration of the undercuts described above allows for the stresses at the undercuts, once the teeth have been bent over the inlet and outlet conduits, to be significantly reduced due to the fact that there are no sharp edges inside the undercuts following the bending. In other words, the undercuts, after bending, still include only smooth surfaces, which are free from any sharp edges, violent bends, etc., where stresses could cumulate. Moreover, the undercuts used in the heat exchanger assembly of the present invention help to define a precise bending line for each tooth. Also, the repeatability of the bending process in mass production is increased.

Brief description of the drawings

The present invention will be described in more detail below, by non-limiting embodiments thereof, with reference to the accompanied drawings, wherein:

Fig. 1 shows a perspective exploded view of a heat exchanger assembly of the present invention;
Fig. 2 shows a partial cross-section view of the heat exchanger assembly of the present invention;
Fig. 3 shows a perspective view of a header used in the heat exchanger assembly of the present invention, prior to bending;
Fig. 4 shows a cross-section view of the header prior to bending;
Fig. 4a shows a detail of fig. 4;
Fig. 5 shows a view similar to that of fig. 4a, but illustrating an another embodiment of the present invention;
Fig. 6 shows an another example of an undercut prior to bending; and
Fig. 7 shows and enlarged detailed view of an another example of the undercut.

Embodiments of the invention

A heat exchanger assembly according to the present invention is indicated as a whole by numeral reference 1. The heat exchanger assembly 1 comprises a housing 2, which in the embodiment shown in the figures is made of two separate half-shells, i.e. a first half-shell 21 and a second half-shell 22. Of course, the housing 2 can consist of any appropriate number of shells and/or plates, e.g. three, four, etc. The housing 2 includes inlet and outlet ports 23, 24 for a coolant, in particular a cooling liquid, as well as a degassing port 25, which serves to remove the air that may be trapped in the coolant.
A core 3 is placed tightly inside the housing 2. The core 3 includes a plurality of spaced-apart flat hollow flow tubes 31, i.e. there is some free space between two adjacent flow tubes 31 and the coolant flows through these free spaces. In a preferred embodiment of the invention, shown in the figures, especially in figures 1 and 2, the core 3 further includes a plurality of coolant turbulators 32 arranged between the flow tubes 31. Namely, one coolant turbulator 32 is situated between two adjacent flow tubes 31. The coolant turbulators 32 function to turn a laminar flow of the coolant into a turbulent one and, in turn, to increase the heat exchange efficiency. Of course, in another embodiments of the invention, the coolant turbulators 32 can be omitted.
The flow tubes 31 are hollow and a medium to be cooled down, for example a fluid, such as a gas, flows therethrough. The flow tubes 31 have two wide sides, two narrow sides and two open ends. The flow tubes 31 are arranged with their wide sides parallel to each other. The flow tubes 31 can be provided internally with a series of fluid fins.
The heat exchanger assembly 1 further comprises two headers 4. Each header 4 is located on and connected to one end of the core 3, i.e. that presenting the open ends of the flow tubes 31. Moreover, each of the headers 4 is, preferably at its entire outer perimeter, see in particular fig. 2, in contact with an inner wall of the housing 2. The header 4 comprises a plurality of through slots 42 so that the open ends of the flow tubes 31 fit into the slots 42. The number of the through slots 42 is equal to the number of the flow tubes 31 and the shape of the slots 42 corresponds to the shape of the cross-section of the open ends of the flow tubes 31.
Moreover, the heat exchanger assembly 1 comprises inlet and outlet conduits 51, 52 for the medium to be cooled down. The inlet conduit 51 receives a hot medium from a motor vehicle and transfers it to the core 3 where it can be cooled down, whereas the outlet conduit 52 delivers a medium of a lower temperature back to the motor vehicle. The inlet and outlet conduits 51, 52 cover the headers 4 and close the housing 2. In other words, the inlet and outlet conduits 51, 52 close two openings in the housing 2, which are intended for the flow of the medium to be cooled down, and make the housing 2 complete. A seal 6 may be placed between each of the headers 4 and each of the inlet and outlet conduits 51, 52.
All components of the heat exchanger assembly 1, except for the seal 6, can be made of materials suitable for brazing, for example aluminum, steel and their alloys. In order to obtain the proper fluid-tightness of the assembly all components thereof are connected to each other by brazing.
The headers 4 comprise at their perimeters a plurality of teeth 41. As seen in figure 2, when the heat exchanger assembly 1 is assembled, the inlet and outlet conduits 51, 52 cover the headers 4. Moreover, the teeth 41 of the headers 4 are bent over protruding portions of the inlet and outlet conduits 51, 52. In fact, it can be said that the inlet and outlet conduits 51, 52 are received in a space defined between the teeth 41 of the headers 4. The teeth 41 and the headers 4 include an inner surface 44 and an outer surface 45. Additionally, the teeth 41 are provided on their inner surfaces 44 with undercuts 43. The function of the undercuts 43 is to facilitate bending of the teeth 41 over the inlet and outlet conduits 51, 52, namely the inlet and outlet conduits 51, 52 are introduced between the teeth 41 of the headers 4 and the teeth 41 are subsequently bent over the inlet and outlet conduits 51, 52, more precisely over their protruding end portions, as seen in figure 2.
Reference is now made, particularly, to fig. 4a, which shows in more detail the structure of the teeth 41 before they are bent over the inlet and outlet conduits 51, 52. Each of the undercuts 43 has an undercut axis A. The undercut axis A extend through the deepest point of the undercut 43 and, if the teeth 41 are straight, is perpendicular to the inner surface 44 of the tooth 41. Moreover, in case of the undercuts 43 with a circular or elliptic cross-section, the undercut axis A divides the undercut 43 into two identical halves. The undercuts 43, more precisely their undercut axes A, divide each tooth 41 into a base portion 41a and a bendable portion 41b. When the teeth 41 are straight their undercut axes A are perpendicular to the base portion 41a and the bendable portion 41b. The bendable portion 41b has a height H measured from the undercut axis A to an end of the tooth 41.
In this embodiment, the headers 4 and the teeth 41 have a general thickness GT. The general thickness GT of the header 4 and/or teeth 41 should be understood as a thickness of a material used for headers 4 and teeth 41 because both the headers 4 and the teeth 41 are preferably made of a single sheet of material having a uniform thickness. Of course, if necessary, the headers 4 and the teeth 41 can be made of a material with a varying thickness. Moreover, the teeth 41 have at their undercuts 43 a reduced thickness RT. Namely, the reduced thickness RT corresponds to the amount of header/tooth material left once the undercuts 43 have been made and prior to bending. The reduced thickness RT can also be defined as a distance between the deepest point of the undercut 43 and the nearest point on the outer surface 45 of the tooth 41.
In a preferred embodiment of the present invention, the general thickness GT of the header 4 and, especially, the teeth 41 is 2mm. In such case, prior to bending, each undercut 41 has a circular cross-section and has a radius R of 1mm, while the reduced thickness RT is 1,5 mm and the height H is 3mm. This in turn means that the undercut 43 has a surface, which is in fact a sector of a cylindrical surface. The position of the undercut 43 on the inner surface 44 of the tooth 41 is such that the undercut axis A, when the inlet and outlet conduits 51, 52 are received between the teeth 41 prior to bending, is located above a surface over which the teeth 41 are to be bent, in this case a surface 51a of the inlet and outlet conduits 51, 52. In this way, once the teeth 41 have been bent over the protruding portions of the inlet and outlet conduits 51, 52, namely the surface 51a, sharp edges inside the undercuts 43 of the already bent teeth 41 are avoided. In particular, following bending, in the undercuts 43 there always remains a smooth surface with a radius, what in turn means that stresses caused by bending do not concentrate critically in the undercuts 43, as it is the case with solutions known from the prior art.
It is also important to note that the undercuts 43 should be originally free from any sharp edges, i.e. they should include only smooth surfaces.
Of course, the present invention is not limited to the dimensions mentioned above, which represent only one embodiment of the heat exchanger assembly 1. In more general terms, it is important to note that, before bending the teeth 41 over the inlet and outlet conduits 51, 52, the reduced thickness RT should be at most two times smaller than the height H of the bendable portion 41b of the tooth 41, while the radius R of the undercut 43 should be at least half of the general thickness GT of the material used for the headers 4 and, especially, the teeth 41.
Additionally, the undercuts 43 may have other shapes of cross-section than those shown in figures 1-5 and described above. In an another embodiment of the invention, the undercuts 43 may have an elliptic cross-section before bending the teeth 41 over the inlet and outlet conduits 51, 52. In this case, as shown in figure 6, a semi-minor axis A1 of an ellipse of the undercut cross section coincides with the undercut axis A, whereas a semi-major axis A2 of the ellipse of the undercut 43 is perpendicular to the undercut axis A. Similarly to the embodiment with the circular cross-section of the undercuts 43, especially as regards the radius R of the undercut 43, the semi-minor axis A1 of the ellipse has a length, which is at least half of the general thickness GT of the material used for the headers 4 and, especially, the teeth 41. Preferably, the semi-minor axis A1 is 1 mm long and the general thickness GT is 2mm. The length of the semi-major axis A2 is in general greater than the length of the semi-minor axis A1. However, in a particular case, the semi-major axis A2 and the semi-minor axis A1 of the undercut 43 can be of equal lengths. It means that the undercuts 43 have once again the circular cross-section, as discussed above. In other words a circle is the special case of an ellipse, and the semi-minor axis A1 and the semi-major axis A2 of the ellipse simply become the radius R of the circle, which is constant throughout the undercut 43.
As shown in figure 3, the undercuts 43 extend through the entire width of the teeth 41, i.e. they open to edges of the teeth 41. However, in another embodiments of the present invention the undercuts 43 can be interrupted in a distance from the edges of the teeth 41 (Figure 7), i.e. the undercuts 43 end before reaching the edges.
In yet another embodiment of the present invention, to allow for easier introduction of the inlet and outlet conduits 51, 52 between the teeth 41 of the headers 4, before assembling the heat exchanger assembly 1, the bendable portions 41b of the teeth 41 are slightly pre-bent at the undercuts 43 towards the outside of the headers 4. Preferably, an angle of the pre-bend is 20° with respect to the extension of the base portion 41a. As the teeth 41 are pre-bent at their undercuts 43, the undercut axes A are no longer perpendicular to the base portion 41a of each tooth 41 but are slightly rotated, depending on the angle at which the bendable portion 41b is pre-bent. Of course, all relevant relationships between the reduced thickness RT, the general thickness GT, the height H and the radius R, as well as the semi-minor axis A1 and the semi-major axis A2, defined for the embodiments described above, apply to this embodiment as well. One must only take into account the pre-bend of the teeth 41 as well as the resultant rotation of the undercut axes A.
Of course, the present invention is not limited to the literal meaning of the features described above and presented in the claims but also includes other equivalent features, which are obvious for a skilled person.

Claims

A heat exchanger assembly (1) comprising:
a housing (2);

a core (3) situated inside said housing (2);

two headers (4) placed on said core (3); and

inlet and outlet conduits (51, 52) covering said headers (4) and closing said housing (2);

wherein said headers (4) comprise at their perimeters a plurality of teeth (41), which are bent over said inlet and outlet conduits (51, 52);

characterised in that each of said teeth (41) is provided on its inner surface (44) with an undercut (43) having an undercut axis (A); said undercut axis (A) dividing each of said teeth (41) into a base portion (41a) and a bendable portion (41b), said bendable portion (41b) having a height (H) measured from said undercut axis (A) to an end of each of said teeth (41);

wherein each of said teeth (41) has a general thickness (GT) as well as a reduced thickness (RT) at said undercut (43); and

wherein prior to bending of said teeth (41) over said inlet and outlet conduits (51, 52) said undercut (43) has a substantially elliptic cross-section and a semi-minor axis (A1) of an ellipse of said undercut cross-section coincides with said undercut axis (A);

wherein said semi-minor axis (A1) has a length, which is at least half of said general thickness (GT); and said reduced thickness (RT) of each of said teeth (41) is at most two times smaller than said height (H) of said bendable portion (41b).
The heat exchanger assembly (1) according to claim 1, characterized in that said length of said semi-minor axis (A1) is equal to a length of a semi-major axis (A2), whereby said undercuts (43) have in fact a circular cross-section so that said undercuts (43) have only one constant radius (R).
The heat exchanger assembly (1) according to any one of the preceding claims, characterized in that said semi-minor axis (A1) and/or said radius (R) is/are 1mm long, said general thickness (GT) is 2mm, said reduced thickness (RT) is 1,5 mm and said height (H) is 3 mm.
The heat exchanger assembly (1) according to any one of the preceding claims, characterized in that said undercuts (43) are positioned on said teeth (41) so that said undercut axes (A), prior to bending of said teeth (41) over said inlet and outlet conduits (51, 52), are situated above a surface (51a) over which said teeth (41) are to be bent.
The heat exchanger assembly (1) according to any one of the preceding claims, characterized in that said undercuts (43) end in a distance from edges of said teeth (41).
The heat exchanger assembly (1) according to any one of claims 1 to 4, characterized in that said undercuts (43) extend through an entire width of each of said teeth (41).
The heat exchanger assembly (1) according to any one of the preceding claims, characterized in that said heat exchanger assembly (1) is a water charge air cooler.