Patent Application
20110024081
The present invention relates to an end plate for a heat exchanger, particularly a heat exchanger intended to be fitted to a motor vehicle.
Conventional heat exchangers comprise a core of tubes delimited by two end tubes. In addition, there may be inserts between the tubes of the core in order to improve the exchange of heat. An insert may be positioned on the external face of each of the end tubes.
The exchanger further comprises two header plates through which the ends of the core of tubes pass. Furthermore, an end plate is conventionally positioned directly on the end insert of each of the end tubes.
The end plates of a heat exchanger thus form a brace between the header plates in order to maintain a constant separation between these header plates and make the exchanger easier to manufacture. Furthermore, they may be used to support and hold accessories associated with the heat exchanger, such as an engine fan.
In general, each end plate comprises a central web flanked by two longitudinal flanges which run along the end plate. The central web is generally of rectangular and flat shape. Each longitudinal flange projects with respect to the plane defined by the central web. The end plate thus in cross section is substantially U-shaped. The longitudinal flanges are conventionally designed to stiffen and strengthen the associated end plate.
When the exchanger is in operation, variations in the flow of coolant inside the tubes may give rise to temperature differences which cause these tubes to undergo thermal expansion. This results in mechanical stresses in the tubes. Such stresses may cause the tubes to break.
Furthermore, conventional heat exchanger tubes have a tendency to have a relatively small thickness, in order to limit the cost of manufacture of the exchanger. As a result, the tubes are increasingly less able to withstand thermal shock and the aforementioned risks of breakage increase accordingly.
To limit these risks of breakage, it is appropriate for the ends of each end plate to be mechanically dissociated from the central part of the end plate, so as to prevent the transfer of stresses associated with the thermal expansion of the tubes. To do that, it is known practice to make a transverse cut in the end plate in the region of its central part, once the exchanger has been brazed. For example, a cut such as this can be made with a saw. This solution improves the ability of the tubes to withstand thermal shock, but has the disadvantage of generating swarf which detracts from the cleanness of the exchangers and of the machines, and of reducing the ability of the exchanger to withstand vibration and/or reverse-cycle pressures.
In other existing embodiments, it is known practice to create weaknesses in the end plate in order to allow it to expand locally, and thereby limit the transfer of stress to the tubes.
For example, patent FR 2 183 375 proposes a transverse bend, in the form of a loop, on the attaching lug that connects the end plate to the header plate or on the end plate directly.
Patents EP 1 195 573 and U.S. Pat. No. 6,328,098 propose an opening in each end plate so that part of the edge of the opening is situated near an edge of the U-shaped end plate. Furthermore, a bend (rupture zone) is provided and this runs transversely from the aforesaid part of the edge of the opening to the edge of the end plate located near to it. The V-shaped rupture zones locally reduce the thickness in the central web and/or in the flanges of the U. Also, each opening between the bends is directed, in its elongate part, such that it makes an acute angle with the lengthwise direction of the end plate.
At the present time, these solutions do not propose end plates which have both small thicknesses and which are able to provide all the elements of the exchanger with the required rigidity, particularly while the components are being handled or when the temperature of the fluid entering the exchanger is very high, and this therefore leads to severe thermal shocks particularly between the end plate and the adjacent inserted tubes.
The present invention intends to overcome the disadvantages of the existing end plates and existing heat exchangers.
Thus, the invention relates to an end plate for a heat exchanger, running longitudinally, comprising at least one opening, said opening forming a cut in the end plate, and at least two areas of weakness, characterized in that the two areas of weakness are situated in distinct parallel planes.
What is meant by the expression “area of weakness” is an area that has a frangible function and/or a longitudinal expansion function, that is to say, by virtue of the invention, that the end plate is able to break at the area of weakness if necessary and is possibly able to expand longitudinally (in the longitudinal direction of the end plate).
Furthermore, by virtue of the fact that at least two areas of weakness have been positioned in two distinct parallel planes, the phenomenon of bending of the end plate while it is being handled, and during its expansion due to thermal differences, is avoided. Specifically, by positioning its areas of weakness, which incidentally retain two sides or parts of the end plate, in two parallel planes, one below the other, the end plate is stiffened a great deal thereby avoiding the phenomena of bending.
Other particulars or features are listed below:
The present invention also relates to a heat exchanger, not depicted in the attached figures, particularly for a motor vehicle, comprising two headers connected by a core of tubes and of inserts, characterized in that it comprises at least one end plate as defined hereinabove.
Advantageously, the end plate is fixed to one of the ends or sides of the aforesaid core.
One embodiment of the invention will be described hereinafter, by way of nonlimiting example, with reference to the attached drawings in which:
Viewed from above, there are, in this embodiment, three openings 5, 5′, 5″, two openings 5′, 5″ extending from the opposite lateral edges and a central opening 5 positioned between the two areas of weakness 6, 6′. The openings 5′, 5″ extending from a lateral edge are directed obliquely, that is to say that they make an acute angle β (with 0°<β<90°) with the longitudinal axis XX′ of the end plate 1. The central opening 5 is V-shaped with its two segments also extending at an acute angle with respect to the longitudinal axis XX′.
The areas of weakness 6, 6′ here are present in each of the two projections 2, 3 and are respectively incorporated into a sinusoidal or wave-shaped portion 7, 7′ of these projections 2, 3. The areas of weakness 6, 6′ extend from the parts located near the vertex, including the vertex, of each of these sinusoidal portions 7, 7′. In this example, the areas of weakness 6, 6′ consist of the two elements shown enlarged in
Because one, 7, of these sinusoidal portions is directed upward while the other portion 7′ is directed downward, the respective vertices of each of these sinusoidal portions 7, 7′ are opposed, one of the vertices being situated in the flat flanks 4 while the other vertex is situated in the upper face of the projections 2, 3.
Furthermore, the areas of weakness 6, 6′ comprise a narrowing or decrease in material 8, 8′ located at the respective vertices of each of the areas of weakness 6, 6′; this narrowing or decrease in material 8, 8′ extending over the entire width of the area of weakness 6 or 6′. Thus, aside from the possibility that the areas of weakness 6, 6′ have of extending, in this instance longitudinally along the axis XX′, particularly under the effects of thermal expansion phenomena, these areas of weakness 6, 6′ are also capable of breaking; this breakage being facilitated by these narrowings or decreases in material 8, 8′ of the areas of weakness 6, 6′.
As can be seen in
The third embodiment, illustrated in
In this example, two openings 12, 12′ extend from the respective two opposite lateral edges, while two other central openings 13, 13′, that is to say openings distant from the lateral edges, have an L-shape or L-shaped cross section. In this embodiment as in all the embodiments, the areas of weakness 14, 14′, 14″ extend between the openings 12, 12′, 13, 13′. Once again, one area of weakness 14 is situated in the bottom plane, that is to say the plane formed by the flat parts, or the plane of the web 4, of the end plate 1, while two other areas of weakness 14′, 14″, are situated in the plane formed by, or containing, the upper faces or sides 2′, 3′ of the projections 2, 3, these two planes indeed being parallel planes.
In this embodiment, the areas of weakness 14, 14′, 14″ do not extend along the same axis, for example along the axis AA of the second embodiment, but each of the two groups of areas of weakness 14 and 14′, 14″, which run respectively in the aforesaid two parallel planes, are aligned along distinct axes.
The fourth embodiment, depicted in
As illustrated in
The fifth embodiment, shown in
Finally, the last embodiment chosen for illustrating the invention, depicted in
All the embodiments depicted here have features that can be combined, while still remaining within the scope defined by the invention in the attached claims.
The present invention applies to any kind of exchanger that requires end plates designed to counter the phenomena of expansion and torsion due to thermal differences.
