Abstract:
The present invention relates to heat exchangers and heat exchanger assemblies, and, in particular, leak tight heat exchanger assemblies with coined or extruded corners. The present invention further provides for heat exchanger assemblies that improves leak tight features while maintaining or providing increased heat exchanger assembly structural integrity and durability. The present invention also provides for a method for making leak tight heat exchangers using various bonding processes.

Description:
[0001]     This application claims priority of provisional application 60/539,368 filed Jan. 26, 2004 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to a heat exchanger and heat exchanger assembly, and, particularly, leak tight heat exchanger assemblies with coined or extruded corners.  
       BACKGROUND OF THE INVENTION  
       [0003]     Heat exchangers are used in the automotive industry as essential parts of a vehicle cooling system. Modern heat exchangers usually consist of a fin and tube assembly called a core, with variations to the basic design including tube attachments to manifold components on opposite ends of the core. As part of a normal production process, the heat exchanger can be placed in an oven along with other attachments and components to ‘bake’ or braze individual them together, yielding a resultant product that combines fins, tubes, and manifolds bonded together to form a single integrated heat exchanger assembly.  
         [0004]     Physical parameters determine the required characteristics of heat exchanger assemblies. For example, heat exchangers assemblies are subject to pressure variations and act as pressure vessels. Such so-called vessels can take many shapes and require specific contours in order to deal with the constraints of limited space packaging, etc. of the motor vehicle. They must, however, at the same time, be able to maintain their structural integrity (remain ‘leak tight’) in often extremely high and/or low pressure environments.  
         [0005]     In the past many designs have compromised more efficient practices in order to obtain functional units for use in automotive applications. However, these designs have often been made at the expense of process consistency and have led to less than reliable braze joints or junctions between individual or multiple components in heat exchanger assemblies, due, in large part, to the variability of the contact surfaces or areas of mating (mating fits) between parts. In addition to the resultant leaks at the braze junctions and the like, many prior art solutions have led to designs where leaks are difficult to locate and expensive to repair, while at the same time producing heat exchanger assembly products not capable of reaching their full design potential.  
         [0006]     Assemblies requiring sheet metal formed channels to seal off multiple brazing planes within the manifold are subjected to the variability in sheet stock such as gauge and temper, along with tool wear resulting in poor dimensional control. At corner braze junctions where a first intersecting set of surfaces must braze to seal against a second set of braze surfaces it is difficult to match the radial bends of set surfaces due to tolerances on materials and variability of processes. To accommodate this design shortfall a variety of ‘repair’ methods are used including rebonding, welding, epoxy fill, additional components, and additional applications of a bonding alloy.  
         [0007]     One of the common problems found in the prior art relates to bonding joints, and, in particular, compound bonding joints. Compound bonding joints are joints commonly made up of at least two flat intersecting planes forming a sharp corner, mated with two flat intersecting planes connected by a radius. The fit yields a form of bonding joint, and, particularly, a joint that may be bonded or brazed in an oven or the like. Compound bonding joints often have the disadvantage of developing leaks at points where the greatest gap occurs between the radius and sharp corner in the bonding joint. The same problem exists in the prior art in similar designs involving at least three intersecting planes. Also, bonding joints are often comprised of various bonding materials of somewhat differing natures, including added bonding materials to increase material mass, addition of other components parts near or around the joint area, or otherwise compensate for structural weakness. These manufacturing variations may comprise good joint fitup, or joint integrity and the like. Addition of increased mass or volume of materials near or around the joint area may be a way of providing thicker gage base material to get better bonding results, but is not an ideal way to compensate for poor bonding joint design, as it does not assure the joint will be leak free, and usually results in resultant higher manufacturing costs.  
         [0008]     In addition to bonding material problems, the need for durability or increased lifetimes under high pressure environments means that joints in heat exchanger assemblies must maximize fit between elements in order to retain both durability and to remain basically leak tight. The prior art solution of flat planes with a curve or radius connecting them, though providing some structural stability, led to joint ‘mismatches’ or related fit problems has often led to leaks through the mismatched area after brazing or oven bonding.  
         [0009]     Other solutions to prior art problems have involved the use of resins, such as epoxy, to seal small leaks from poorly bonded joints. These solutions, however, also ultimately increase manufacturing costs and provide a “soft” seal with shorter longevity that can reduce the ultimate effective life of the heat exchanger. Testing and then welding or re-bonding in areas of small leaks after brazing is also found in the prior art. These solutions, however, have the disadvantages of not only distorting the physical parameters of the heat exchanger, but also may weaken adjacent braze joints and/or increase assembly costs.  
       SUMMARY OF THE INVENTION  
       [0010]     An object of the present invention is to provide an improved joint, and, in particularly, a “bonded” or bonding joint that would be used in a ‘leak tight’ heat exchanger assembly. It is further an object of the present invention to provide for a improved heat exchanger assembly that retains its leak tight features while additionally maintaining heat exchanger assembly structural integrity and durability. The present invention, in its preferred embodiments, eliminates the radius found in the prior art, while maintaining structural integrity and providing for leak tight bonds in the bonding joint area, particularly for heat exchanger assemblies that have brazed bonding joints.  
         [0011]     In preferred aspects of the present invention, the heat exchanger assembly is designed to provide for a leak tight seal or connection between heat exchanger assembly components, without the need for a radius for increased structural integrity. Preferred aspects of the present invention provide for a leak tight joint or joints at areas of contact between elements of the manifold assembly. Particularly preferred aspects of the present invention provide for a leak tight joint at the point of contact or ‘intersection’ of plane surfaces in a manifold assembly. Preferred aspects of the present invention also provide for a method of making a heat exchanger assembly providing leak tight features while maintaining heat exchanger structural integrity and durability by ‘coining’ or extruding matching component intersecting surfaces in a local area to preferably create shaped contour areas that match or mate with each other at the binding joints. More preferred aspects provide for a method a making and a heat exchanger assembly wherein the local area comprises a localized brazing zone at the point or points of contact or mating fits found at or near the intersection of the manifold assembly intersecting planes, creating a so-called ‘mating’ or ‘pairing’ surface or surfaces where consistent bonding may occur. Even more preferred aspects of the present invention provide for a heat exchanger assembly, with manifold, having corner bonding joint between the header or manifold, formed from a channel, a tube, or a cap, or any combination of the above. Also more preferred aspects provide for at least one corner bonding joint that is sharp or angled, and, preferably straight angled corner; in most preferred aspects, the corner comprising the bonding joint is a coined corner.  
         [0012]     In preferred embodiments of the present invention, heat exchanger assemblies are found with localized transition zone bonds provide for optimized seal formation without compromising structural or braze seal integrity. The advantage of this strengthened bond design is components designed for strength also have a properly designed bond joint which provides superior quality bond joints for leak free service, improved fitup of components, no impact to durability of the assembly, and reduced cost to manufacture.  
         [0013]     A coined corner is a corner formed by at two or more straight planes at some angle of intersection. In preferred aspects of the present invention, three or more straight planes meet at straight (uncurved) angles at a zone of intersection.  
         [0014]     By corner bonding joint is meant a joint capable of being bonded, formed at a corner, the corner formed with straight angles, and not utilizing a radius between connecting planes of the bonding joint area.  
         [0015]     By coined corner is mean a corner formed by extrusion or press fit, or, preferably, by extrusion and press fitting. In preferred embodiments, the coined corner is formed at a localized zone of junction of the tube and header and more preferred, formed at a localized zone between the tube and header. More preferably, it is formed at the transition wherein the tube, or tube and header, all have mating surfaces where a bond joint can be formed. More preferably, the tube at the area of the bond joint has approximately the same or similar dimension (is equal to or less then twice the size of the tube at the corner area), or is unsplit.  
         [0016]     In another preferred aspect of the invention, a method of producing an heat exchanger assembly that is designed for strength and durability, with components that have a strength/bond transition zone for providing proper joint clearances to oven bond leak tight heat exchangers, is provided. The heat exchanger assembly is subsequently tested prior to other procedures or immediately leak tested and shipped to the customer thereby shortening the manufacturing process and reducing overall cost.  
         [0017]     Also, the present invention provides for preferred embodiments whose design promotes the use of a single material or materials that have approximately the same metallurgical composition as the bonding material to make the complete heat exchanger thereby supporting recycling mandates. In summary, this invention reduces cost, and rework, while shortening manufacturing time. This invention provides a manifold designed for durability, where needed, and designing proper bond joints, where needed, without compromising either durability or bond joint design.  
         [0018]     The present invention, therefore, provides a method of making a heat exchanger assembly wherein maximum durability of the heat exchanger co-exists with best practices, i.e. efficient and leak tight assemblies utilizing bond joint designs. In preferred embodiments of the present invention, various materials may be used in the manufacture of the heat exchanger assembly. In more preferred embodiments, the present invention provides for use of clad or unclad materials. These materials may be metallic or non-metallic materials. Preferred is when the materials used in the heat exchanger are either metallic or non-metallic. Preferred is when at least one of the materials used in the heat exchanger assembly is metallic at a point of surface contact or bonding, or at a joint. Also preferred is when at least one of the materials used in the heat exchanger assembly is non-metallic. Even more preferred is a heat exchanger assembly using combination of metallic and non-metallic materials. Even more preferred is a heat exchanger assembly wherein the joints and/or surface areas or zones where bonding occur are comprised of metallic or non-metallic materials. Most preferred is wherein the joints and/or surface areas or zones where bonding occur are of essentially the same material. Also preferred is wherein the joints and/or surface areas or zones where bonding occur are more than 90% metallic and are essentially the same material.  
         [0019]     In preferred embodiments of the present invention, the bond joint uses standard materials (i.e. materials used in normal quantity and of normal quality during assembly and brazing, and not including additional material or products such as glues or resins or other such additional materials) in the construction of heat exchangers comprising the embodiments of the present invention, resulting in reduced overall production costs per unit of the heat exchanger.  
         [0020]     In more preferred embodiments of the present invention, the adjacent surface area is maximized for bonding. The present invention uses ‘simplified’ bond joint designs to provide adjacent surface areas or a zone of a relatively greater nature than those in the prior art designs described hereinabove.  
         [0021]     In a preferred method of the present invention, a standardized method of producing a bond joint is provided. The heat exchangers produced thereby provide a substantially or essentially leak tight heat exchanger assembly joint or bond. In more preferred methods of the present invention, the surfaces that form the joint or bond are ‘coined’ or extruded contiguous with a transition surface to provide for a long durability bonding between components of the heat exchanger assembly, and, particularly, brazed components. Also, in more preferred methods of the present invention, additional process steps of component manufacturing found in the prior art are eliminated via the integrality of form tooling, thereby reducing assembly complexity. In the more preferred methods of the present invention, additional formed features such as ‘fillers’ or other ‘gap closers’ that have been used to close gaps of normal bend radii at the joint area, are eliminated.  
         [0022]     The present invention provides for a heat exchanger and heat exchanger assembly, particularly a ‘one shot’ or similar material brazed heat exchanger assembly wherein braze closure is uniform or practically achieved over the entire surface of the joint areas or zone, to form essentially leak proof joints. The present invention further provides a multiple component interface braze closure uniform or practically achieved over the entire surfaces of the joint areas or zone at multiple component interfaces. The present invention further provides a sealed multiple component assembly useful in a variety of bonding process. The present invention preferably provides a braze sealed with a bend radius.  
         [0023]     Preferred embodiments of the present invention provide a light weight heat exchanger, essentially without additional material to ensure braze leak tight joints or correct for joint deficiencies.  
         [0024]     By all metal heat exchanger or manifold assembly it is meant a heat exchanger or assembly where all or most parts or components capable of being brazed or joined together in a device such as an oven, are based on metallic materials. Preferred are so called ‘one shot braze’ all metal heat exchanger with manifold assemblies wherein the part or components, as well as any brazing or joining materials, are of a similar or like substance, so as to be capable of being brazed or joined together in an oven while providing for leak tight seals amongst the components at the joints. More preferred are all metal heat exchanger or manifold assemblies wherein coining or extrusion features appear at the areas of contact or zones of the joint. Also, more preferred are heat exchanger or manifold assemblies where the edges or surfaces of joints that occur at the junctures of planes in the assembly are coined or extruded.  
         [0025]     In preferred embodiments of the present invention, the coining or extrusion feature is only done at the naturally reinforced juncture of multiple planes so as it does not impact the durability of the heat exchanger. By naturally reinforced it is meant that multiple thicknesses of the mating surfaces in the area of the coined corner are bonded together to form a single zone or area, a so called ‘single assembly’. The heat exchanger assembly and, subsequently the heat exchanger ‘single assembly’ so produced, maximizes durability and design for the bond joint in the area of the coined corner. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]      FIG. 1  is an elevation view of heat exchanger joint section using forms in the header pan to fill gaps in braze joint in the prior art;  
         [0027]      FIG. 2  is an elevation view of an heat exchanger using nothing to fill gaps left by header pan radius, the cap butts against end header well radius in the prior art;  
         [0028]      FIG. 3  is an elevation view of a heat exchanger header and tank assembly used for the example of coined edge for square corner in accordance with an aspect of the present invention.  
         [0029]      FIG. 4  is a perspective view of  FIG. 3  Section A ( 47 ) from inside manifold tank in accordance with an aspect of the present invention.  
         [0030]      FIG. 5  is a perspective view of  FIG. 4  sealing cap rotated 90 degrees in accordance with an aspect of the present invention.  
         [0031]      FIGS. 6   a  and  b  show corners, as typically found in the prior art;  
         [0032]      FIGS. 7   a  and  b  show localized bond transition areas at corners, as they appear in accordance with an aspect of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]     As described above, the present invention provides for structual sections designed for strength and durability with formed sections having two or more planes unconnected by a radius, that increase or enhance the leak proof or leak tight nature of the assembly at the area of the angle and joint formed at the intersection of the two or more planes.  
         [0034]     In a preferred embodiment of a heat exchanger assembly in accordance with the present invention, the heat exchanger comprises a core composed of tubes and fins, with manifolds preferably formed of flat sheet stock, the manifold having a header portion with at least one opening or openings connecting to the at least one tube end or ends; a first and second component portion comprising or consisting of an header or tubes or tanks or channels within or near a corner area with each portion having an extended planer bonding surface that are closely aligned to each other; and, a more preferably third component portion. Preferrably the third component portion has an extended planar bonding surface being adjoined or affixed to the first bonding surface forming intersecting bonding surfaces located near the terminal end of the first and second portion surfaces bonding surfaces. Preferable, the second component portion has matching intersecting surfaces such that the transition contour of the second portion is locally deformed to create a shaped contour that matches the transition area of the first component portion intersecting surface transition area forming bonding joints. More preferably, the bonding joints are bonded with a bonding material.  
         [0035]     In more preferred embodiments of the present invention, a first part of the bonding joint is formed into one section where two or more planes are at an angle with each other (a structural part or section), while a second part is formed out of the structural section and is coined to form a small section where the planes are at an angle with each other and mate with the first part of the bonding joint to form an improved complete bonding joint.  
         [0036]     The preferred bonding joints of the present invention can be formed with intersection planar surfaces from various components of the heat exchanger assembly. For example, the bonding joint preferably occurs at an area where a heat exchanger core tube and header meet at the header ferrule, where a heat exchanger core tube and tank meet, where a tank and a header meet, where a tube and a header meet, or where a bonding joint is itself included as part of a mounting structure to a tank. Caps, walls, pans, channels and other such components where flat planes are capable of intersection in a corner transition area, are intended as unlimiting examples useful in embodiments of the present invention.  
         [0037]     In more preferred embodiments, the first and second component portion within or near a corner area are found, with each portion having an extended planer bonding surface that closely follows or runs in parallel to each other. In preferred embodiments having three or more component portions, one of the component portions forms a single plane in the area of the bonding joint, and the two other component portions (two structural members) abutt and are parallel to the bonding joint adjacent to the single plane; even more preferred are two component portions parallel to one another and a third forming an angle relative to the two at the intersection area of the joint.  
         [0038]     Also, preferably, embodiments of the present invention further have a third component portion having an extended planar bonding surface adjoined or affixed to the first component portion bonding surface, the bonding surfaces intersecting near terminal ends of the first and second component portions planar bonding surfaces, the terminal ends of the bonding surfaces being within or near a corner area.  
         [0039]     In other preferred embodiments of the present invention, the first and second component portion are formed in a “U” channel shape such that the second portion is more narrow and sits or rests within and between the first portion. Also preferred are embodiments wherein the heat exchanger first and second component portion has symmetrically opposed formed transition corners. Even more preferred is wherein the transition area approximately forms a sharp corner.  
         [0040]     Preferably, in one aspect of the present invention, a heat exchanger assembly comprising a manifold assembly having at least one tube and a header and, a heat exchanger core, wherein the manifold assembly has at least one coined corner and wherein the assembly is essentially leak tight at the area of the corner.  
         [0041]     Referring to  FIG. 1 ,  FIG. 1  shows a design wherein tank  12  forms a braze joint between tank  12  and header wall  11  to form the manifold assembly. Header wall  11  has an additional form  13  to fill a gap caused by fitting the flat side of tank  12  against a formed radius on tank end  14 .  
         [0042]      FIG. 2  refers to an all-metal heat exchanger assembly, for example, wherein a plurality of components is assembled together to create the manifold assembly. In  FIG. 2 , Sealing Cap  23 , Header Wall  22 , Header Pan  21 , and Cap Crimp Tab  25  are ‘baked’ of oven ‘brazed’ to form an integral manifold  26  for an heat exchanger assembly.  
         [0043]      FIG. 2  is a prior art design where header wall  22  butts against header pan  21  and against sealing cap  23  forming the manifold assembly. Header wall  22 , sealing cap  23 , and header pan  21  form a joint where the radius of the header pan  21  fits against the square edges of header wall  22  and sealing cap  23  at location  24 .  
         [0044]      FIG. 3  is an embodiment of the present invention wherein combined header and channel  32  is assembled to a cap  32  to form a manifold assembly with the coined area  33  providing a proper braze joint between header and channel  32  and cap  31  at the junction shown at section A ( 35 ).  
         [0045]     Referring to  FIGS. 3, 4  and  5 ,  FIG. 3  shows a preferred embodiment of the present invention wherein header and channel  32  are combined and assembled to a cap  31  to form a manifold assembly. Coined area  33  provides a proper braze joint between header and channel  32  and cap  31  at the junction shown at section A  35 .  
         [0046]     Referring to  FIG. 4 , in a preferred embodiment of the present invention a transition or transition zones  42  is created in a component between the area  43  designed for durability and the somewhat small area  44  wherein bonding occurs at the intersection of intersecting planes  47 . Typically in a sheet metal manifold one half of the bond joint will consist of one or more components.  FIG. 4  further illustrates intersecting on different planes with a sharp corner  47  at the intersection of said planes. Planar component portion P 1  and planar component portion P 2  has a radius that connects the plane for strength. Area  47  of intersecting planes is coined to improve the braze joint by having a sharp or straight angled corner fit into another sharp or straight angled corner.  
         [0047]     Referring to  FIGS. 4 and 5 ,  FIG. 5  shows a preferred embodiment of the present invention wherein formed components with intersecting planes  65  are connected with a radius  62 , which provides a transition zone for stresses between planes.  FIG. 5  further illustrates an embodiment wherein the design is particularly suitable for bond joint fitup. Intersecting planes  65  include a sharp corner at intersection localized section or zone  64 , to assure appropriate levels of material adjacent to the mating portion or zone of the bond joint over the maximum surface.  FIG. 5  shows  FIG. 3  Section A  35  with the details of the header pan  46  with a reverse bend  48  and header wall  41  as an integral component, cap  45  has bend radius  43  for strength with connecting transition  42  to coined area  44  which enable proper design for durability and proper design for bonding at the intersection of the intersecting planes  47 .  FIG. 5  is  FIG. 4  cap  45  rotated 90 degrees, cap  63  is comprised of features of intersecting planes  65 , radius  62  for durability, coined corner  64  for bonding, and transition  61  connecting radius  62  to coined corner  64 . Plane demarcations A 1  and B 1  show a structural strengthening joint area. Plane demarcations A 1  and B 2  show a joint area that allows for improved brazing while surprisingly maintaining structural integrity and providing for reduced possibility for leakage (leak tight joint).  
         [0048]     The mating component  FIG. 5  will have matching planes  65  formed into said component with a radius  62  connecting said planes. This invention utilizes a coining or extrusion process to reform and remold a localized portion  64  of a component from intersecting planes connected by a radius  62  to intersection planes with a sharp corner at the localized portion  64  at the intersection of the intersecting plane with transition  61  as a key feature. The reformed section  44  of the component  FIG. 4  will then fit adjacent to the mating portion of the bond joint  46 ,  41 ,  48 , maximizing the surface area of the bond joint and minimizing the gaps between components. This enables the bond joint  47  to be fused in an oven for leak tight service. The coining or extrusion process would typically be part of the component form tooling, thereby providing this feature with minimal cost.  
         [0049]     As shown in  FIG. 5 , part of the transition area between the two planar component portions forms a radius  62  and part of the transition area forms a sharp or coined corner  64 . In such embodiments, the total bonding joint is improved by the structural strength sections as well as the leak tight coined corner sections.  
         [0050]     Referring to  FIGS. 6   a  and  6   b  is shown typical prior art corner  600 ,  601  showing un-sharp  603  and non-coined  604  corner in area  602 . First plane component  605  and second plane component  606  meet at intervening radius  607  to form structural feature. Gap  608  partially filled by feature  609 . Gap  610  for potential leak path not filled during bonding.  
         [0051]     Referring to  FIGS. 7   a  and  7   b  is shown sharp  701  and coined  702  corners, with improved leak tight areas  703 ,  704 , illustrated. Coined corner  705 , has, preferably, all bonding surfaces at a constant distance apart  707 .  
         [0052]     In more preferred embodiments of the present invention, components of the heat exchanger manifold, after assembly, are bonded together using a heating means such as a ‘furnace’ or ‘oven’. The ability of the manifold assembly to bond together without detectable leaks, as in the present invention, has been found to be related directly to the design constraints related to durability and bond joint fitup. The present invention, therefore, provides for durability and bond joint fitup in a non-compromising manner.  
         [0053]     In preferred embodiments of the present invention, it is especially preferred where the first or second component is made of material that has essentially the same metallurgical composition as the bonding material. It is possible, however, that depending on materials, component material can differ in metallurgical composition from the bonding material.  
         [0054]     In preferred embodiments of the present invention, a method of providing for a heat exchanger assembly with manifold and first and second component portions at the area of at least one corner by: coining the manifold and portions in the area of the corner by press filting or extrusion; forming a bond joint at the area of the corner between surfaces at their mating areas; brazing the heat exchanger assembly; so that the heat exchanger assembly two component portions meet at a sharp angle to one another in at least one coined corner that is essentially leak tight after brazing.  
         [0055]     As described herein, heat exchangers in accordance with the present invention preferably have a joint or joints bonded by an oven baking or brazing process. In particularly preferred embodiments in accordance with the present invention, the joints are bonded by a flame braze process.  
         [0056]     In addition, while a feature of the present invention may have been described in the context of only one of the illustrated embodiments, such feature may be combined with one or more other features of other embodiments, for any given application. It will also be appreciated from the above that the fabrication of the unique structures herein and the operation thereof also constitute methods in accordance with the present invention.  
         [0057]     The preferred embodiment of the present invention has been disclosed. A person of ordinary skill in the art would realize however, that certain modifications would come within the teachings of this invention. Therefore, the following claims should be studied to determine the true scope and content of the invention.