Patent Publication Number: US-9903253-B2

Title: Heat exchanger having a stress absorption zone with a convex surface

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage of International Patent Application No. PCT/EP2012/069503, filed Oct. 2, 2012, which claims priority to and all the advantages of French Patent Application No. FR 11/58953, filed Oct. 4,2011, the content of which is incorporated herein by reference. 
     The invention relates to a heat exchanger, notably for a motor vehicle. 
     More particularly, the invention relates to a heat exchanger for a motor vehicle engine air supply circuit. 
     The invention relates to the general field of the supply of air to motor vehicle engines, more particularly to engines the charge air of which comes from a compressor or a turbocharger, so that it is then referred to as supercharged charge air. 
     It is known practice to cool the supercharged charge air leaving the compressor using a heat exchanger which is also referred to as a charge air cooler (or CAC for short). 
     In this case, the CAC heat exchanger allows the supercharged engine charge air to be cooled by exchange of heat with another fluid such as external air or a liquid such as the water from the engine cooling circuit, thus forming an exchanger of the air/air or liquid/air type. 
     Such exchangers generally comprise a heat exchange core bundle comprising a stack of tubes or plates defining respective circulation canals for the fluids, so as to allow an exchange of heat between the two fluids circulating within the core bundle. 
     The core bundle is, in the known way, housed in a casing. Such a casing may comprise end plates on each side of the stack of plates or of the tubes of the core bundle defining the fluid circulation canals, and generally one or more side walls connecting these end plates. 
     To allow the fluid to be admitted to and then removed from the core bundle, fluid inlet and outlet header tanks are, according to a known solution, attached to the casing that houses the heat exchange core bundle. 
     The casing that houses the core bundle has a structural role by contributing to the rigidity of the exchanger. 
     However, in operation, the boost pressure may deform the casing, particularly the side walls of the casing. 
     This pressure leads to a level of mechanical stress which may exceed the limit of the material used. 
     It is known practice to increase the thickness of the material or even to provide additional components in order to withstand such mechanical stresses. 
     Moreover, in order notably to limit the cost of manufacture of an exchanger there is an increasing tendency toward a reduced thickness of materials. However, that leads to reduced ability to withstand the mechanical stresses. 
     It is an objective of the invention to propose a heat exchanger that does not have the disadvantages of the prior art. 
     To this end, one subject of the invention is a heat exchanger, notably for a motor vehicle, said exchanger comprising:
         a core bundle for exchanging heat between fluids,   a casing for housing said core bundle,   a fluid inlet header tank, and   a fluid outlet header tank,       

     characterized in that said casing has at least one stress absorption zone adjacent to said at least one inlet header tank so as to withstand the mechanical stresses applied to said casing as said fluid flows through said core bundle from said fluid inlet tank toward said fluid outlet tank. 
     Said exchanger may further comprise one or more of the following features, considered separately or in combination:
         said casing comprises at least two end plates one on each side of said core bundle in the direction of stacking of fluid circulation canals, and at least one side wall connecting said at least two end plates, and said at least one side wall has at least one stress absorption zone;   said at least one absorption zone has at least one convex surface, the convex face facing in the general direction of stress;   said at least one convex surface is formed substantially at the center of said at least one side wall;   said at least one convex surface extends substantially over the whole of said at least one side wall;   said casing comprises stiffening means formed as one with said casing;   said stiffening means are produced by deforming said casing;   at least one stress absorption zone comprises stiffening means;   said at least one side wall has at least one border bent over along a bent edge for connection to an end plate, and said at least one side wall has stiffening means arranged substantially at the bent edge;   said at least one side wall comprises stress limiting means on at least one zone of connection to an end plate;   said at least one side wall has at least one stress limiting groove on at least one peripheral contour of said at least one side wall;   said exchanger is configured to cool the supercharged charge air of a motor vehicle engine and in that said fluid outlet header tank is configured to admit the supercharged charge air to said engine.       

    
    
     
       Other features and advantages of the invention will become more clearly apparent from reading the following description, given by way of nonlimiting illustration, and from studying the attached drawings in which: 
         FIG. 1  depicts a heat exchanger, 
         FIG. 2  is a schematic and simplified view of a convex surface of a side wall of the casing of the exchanger of  FIG. 1 , and 
         FIG. 3  depicts an alternative form of heat exchanger with a side wall that has two convex surfaces. 
     
    
    
     In these figures, elements that are substantially identical bear the same references. 
       FIG. 1  depicts a heat exchanger  1  notably for a motor vehicle. 
     This exchanger is intended to be placed in an engine air supply circuit. 
     Such an exchanger  1  is notably configured to cool the supercharged charge air for a combustion engine of the motor vehicle. 
     This exchanger  1  comprises a core bundle of tubes or plates for exchange of heat between a first fluid such as the supercharged charge air and a second fluid such as a liquid coolant. 
     This core bundle of tubes or plates is housed in a casing  3 . 
     The exchanger  1  further comprises a first header tank  5  for the inlet of the first fluid, and a second header tank  7  for the outlet of the fluid. 
     According to the embodiment described, the outlet tank  7  is fixed to the cylinder head of the engine (the engine is not depicted) to allow cooled air to be admitted, and therefore forms an admission tank for the first fluid. 
     According to the example illustrated, the casing  3  comprises for example:
         two end plates  9  one on each side of the core bundle in the direction of stacking of the plates or of the tubes defining the fluid circulation canals, and   at least one side wall  11 ,  12  connecting the two end plates  9 .       

     According to the embodiment illustrated, the exchanger  1  comprises a first side wall  11  adjacent to the inlet tank  5 , and a second side wall  12 . 
     The first side wall  11  is arranged near the inlet tank  5  and is therefore situated substantially level with the arrival of the supercharged charge air relative to the direction in which the air flows. 
     It is therefore referred to as a frontal wall  11  relative to the direction in which the fluid flows. The rear part of the exchanger  1  is defined by the outlet tank  7  mounted on the cylinder head of the engine (the engine is not depicted). 
     The side wall or walls  11 ,  12  have zones of connection to the end plates  9 . 
     In the example illustrated, the side walls  11 ,  12  respectively have peripheral borders  15 ,  17  which are bent over for connection to the end plates. 
     These borders  15 ,  17  are bent over along a bent edge  19 . 
     These borders  15 ,  17  are held on the end plates  9  for example by crimping. 
     The assembly is then for example brazed thereafter. 
     The casing  3  further comprises at least one stress absorption zone for withstanding the stresses applied to the casing  3  as the supercharged charge air flows. 
     The absorption zone or zones are arranged adjacent to the inlet tank  5 . 
     According to the embodiment illustrated in  FIG. 1 , it is the first side wall  11  that has such an absorption zone. 
     This for example involves providing a substantially convex surface  13  on the side wall  11 , as indicated schematically in  FIG. 2 . 
     The convex face is oriented in the general direction of stresses applied to the casing  3  as the supercharged charge air flows, as schematically indicated by the arrow F. 
     This convex surface  13  is in this instance arranged substantially at the center of the side wall  11 . 
     In addition, this convex surface  13  extends substantially over the whole of the side wall  11 . 
     This surface  13  therefore extends substantially over the whole height and over the whole width of the side wall  11 . 
     Such a convex surface  13  makes it possible to limit the movements of the surface of the side wall  11  as the supercharged charge air flows from the inlet tank  5  toward the outlet tank  7 . 
     Specifically, a side wall  11  is obtained that is more rigid and therefore better able to withstand the mechanical stresses applied to the side wall  11  as the supercharged charge air flows toward the engine (not depicted). 
     It is therefore possible, for the same order of ability to withstand the mechanical stresses, to provide a side wall  11  that is thinner than in the prior art. By way of example, for the same order of strength, it is possible to come down from a wall 3 mm thick to a wall 1.5 mm thick having such a convex surface  13 . 
     According to an alternative form of the embodiment, provision may be made for the side wall  11  to have two convex surfaces  13  rather than just one, as illustrated in  FIG. 3 . 
     With these two convex surfaces  13 , the side wall  11  is even stronger, making it possible to reduce the thickness of the wall  11  still further. 
     The casing  3  may also have stiffening means (not depicted in the figures). 
     These stiffening means are formed as one with the casing  3 . For example, the stiffening means are produced by deforming the casing  3 . 
     The stiffening means are, for example, formed at the stress absorption zone or zones of the casing  3 . 
     As an alternative or in addition to the convex surface  13 , the side wall  11  may have such stiffening means. 
     By way of example of stiffening means, mention may be made of substantially cross-shaped deformations. Such a cross-shaped deformation may be provided substantially in the center of the side wall  11  or in the center of the convex surface or surfaces  13  of the wall  11 . 
     As an alternative, deformations produced substantially in the form of domes may be provided. 
     According to an alternative form of the embodiment, the first side wall  11  may have stiffening means at the bent edge  19  of the peripheral borders  15  which are bent over for connection to the end plates  9 . 
     Such stiffening means may for example be produced by deforming the material of the wall  11 , for example by forming a boss, at the bent edge  19 . These stiffening means have, for example, a substantially triangular shape with its vertex level with the bent edge  19  and its base connecting the bent-over peripheral border  15  and the side wall  11 . Such stiffening means are generally referred to as “bulldozers”. 
     Furthermore, the casing  3  may comprise stress limitation means  21  in one or more zones of connection of the side wall or walls  11 ,  12  to the end plates  9 . 
     According to the embodiment illustrated, the first side wall  11  comprises such limitation means  21  on its peripheral contours. 
     By way of example, the limitation means may comprise limitation grooves  21  (cf.  FIG. 2 ). 
     According to the embodiment illustrated, the first side wall  11  therefore comprises limitation grooves  21  on its peripheral contours forming zones of connection to the end plates  9 . 
     Moreover, the casing  3  may also comprise inlet and outlet nozzles  23  for the second fluid (cf.  FIG. 3 ). 
     Referring once again to  FIG. 1 , the header tanks  5 ,  7  for their part are for example produced by molding. 
     The header tanks  5  and  7  are arranged in such a way that having passed through the core bundle, the cooled air leaves the exchanger  1  to be supplied to the engine. 
     For that, the inlet tank  5  communicates with an air inlet duct  25 . 
     To allow cooled air to be admitted to each of the cylinders of the engine (not depicted), the outlet tank  7  is open to allow the cooled air to pass toward the engine. 
     The positioning of the inlet tank  5  and outlet tank  7  is given by way of illustration. 
     Thus, the supercharged charge air enters the exchanger  1  via the inlet tank  5  for the first fluid, circulates through the heat-exchange core bundle  3  then leaves the exchanger  1  via the outlet tank  7  for the first fluid so as to be fed to the engine (not depicted). 
     As for the second fluid, that enters the heat-exchange core bundle via an inlet nozzle  23  for the second fluid, circulates through the heat-exchange core bundle to exchange heat with the supercharged charge air that is to be cooled and then leaves the heat-exchange core bundle via an outlet nozzle  23  for the second fluid. 
     It will therefore be appreciated that such a heat exchanger casing  3  for admitting supercharged charge air to the combustion engine is better able to withstand the stresses applied as the air flows through the exchanger  1  because of the absorption zone provided for example by one or more convex surfaces of the side wall  11  adjacent to the inlet tank  5  and/or because of the variable-geometry deformations of this side wall  11 .