Abstract:
A vehicle header tank of the type in which most or all of the header tank is metal and brazed concurrently with the rest of the core includes a simplified oil cooler structure integrated with the tank and brazed concurrently with the rest of the core. A section of tubing similar to the radiator coolant flow tubes passes into and out of the header tank through a pair of slots with a geometry similar to that in the regular slotted tank header plate that accommodates the coolant flow tubes. Consequently, the oil cooler tube can be installed in leak proof fashion inside the header tank concurrently with the main core braze operation.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to vehicle engine and oil cooling systems in general, and specifically to a radiator with a metal header tank and flat extruded tube oil cooler incorporated in the metal header tank.  
         BACKGROUND OF THE INVENTION  
         [0002]    Vehicles with often incorporate a transmission fluid or engine oil cooler mounted in the liquid coolant outlet tank of the engine cooling radiator as a convenient means to cool those fluids. Typically, the radiator consists of a basic core with header tanks on each side, and flattened metal coolant flow tubes, generally aluminum, extending between the tanks. Each tank is a plastic box open on one side, the open side being clinched to a metal header plate that receives the ends of the radiator flow tubes. As shown in co assigned U.S. Pat. No. 5,645,125, a conventional oil cooler consists of a series of plates stacked into a general box shape, which is installed inside the radiator outlet tank, with sealed inlet and outlet pipes running through the radiator tank wall. This requires very careful sealing not only of the many joints between the oil cooler plates, but also of the metal to plastic interface between the cooler pipes and radiator tank wall. That interface requires mechanical sealing, such as threaded fittings and compressible O rings, which is not as robust as a brazed joint of the type found between the ends of the radiator flow tubes and the radiator tank header plate. Such an oil cooler is also quite massive and heavy, and blocks a good deal of flow area within the radiator tank.  
           [0003]    A relatively newer proposed oil cooler construction is incorporated within all metal (aluminum) header tanks of an all metal core. In effect, the tank and the header plate are one and the same part, or at least formed of the same material. An example may be seen in co assigned U.S. Pat. No. 5,823,250. There, the header tank itself has an extruded body, with integral slotted header plate and integral internal oil cooler passage. End caps are brazed on the seal the ends of the header tanks and the internal oil cooler passage simultaneously. This type of integral oil cooler construction depends on the header tank being made as an extrusion, which is not always practical, because of weight and cost considerations.  
           [0004]    In tank oil coolers of differing construction are known, at least in the published patent art. Co assigned U.S. Pat. No. 5,645,125 discloses a radiator with header tanks of unspecified material, within one of which a helical round oil cooler tube is arrayed. The ends of the helical tube are sealed through the radiator tank wall in an unspecified fashion. The helical tube is of a round construction not typically used in radiators per se, so it is not clear how such a design would actually be manufactured.  
           [0005]    The manufacture of the radiator itself, or of similar headered heat exchangers, is a well understood and well controlled process, whether the tank is all metal or of plastic with a metal header plate only. The flattened metal flow tubes, typically extruded or fabricated aluminum, with our without internal strengthening webs, are inserted through closely matching slots formed through the header plates. Braze material provided on the surface of either the flat metal tube or the header plate is melted when the core itself is brazed, and drawn into the tube end-slot interface to form a simple, consistent and leak proof joint. If similar materials and techniques could be used to form the oil cooler, as well, maximum design flexibility and minimum cost would be achieved.  
         SUMMARY OF THE INVENTION  
         [0006]    The invention provides a radiator header tank and oil cooler incorporated within the tank in which the oil cooler itself and its sealed interface with the radiator header tank do incorporate the same material and manufacturing technique as are typically used to make the radiator core.  
           [0007]    In the preferred embodiment disclosed, the radiator core uses typical flattened metal tubes and a metal header tank that can be formed by any desired technique, not just extrusion. The in tank oil cooler consists of a length of the same kind of tubing used in the radiator flow tubes itself, which enters and exits at some point on the tank wall through slots in the tank wall formed with the same geometry as the slots in the header plate. The entire core, with oil cooler, can be brazed in one step, and the sealed interface between oil cooler tube and tank wall is formed in the same way, and is just as robust as, the sealed interface between the ends of the radiator flow tubes and the header plate slots of the basic core. Since it is formed of a single length (or lengths) of seamless tubing, the integral, in tank oil cooler so formed is small in volume, lightweight, low cost, and has no potential oil leak points within the radiator tank. It can be formed with a wide variety of shapes, by simple tube bending, and can enter and exit the radiator tank wall at any desired point, to give maximum design flexibility. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    These and other features of the invention will appear from the following written description, and from the drawings, in which:  
         [0009]    [0009]FIG. 1 is a perspective view of a radiator having all metal header tanks;  
         [0010]    [0010]FIG. 2 is a perspective view of a radiator tank like that shown in FIG. 1, modified so as to incorporate an oil cooler made according to the invention;  
         [0011]    [0011]FIG. 3 is an end view of the type of tube used to form the oil cooler;  
         [0012]    [0012]FIG. 4 is a close up of the interface between the ends of the oil cooler tube and the header tank;  
         [0013]    [0013]FIG. 5 shows the oil cooler inserted into the header tank, ready for brazing;  
         [0014]    [0014]FIG. 6 shows a inlet outlet fitting that may be attached to the exposed ends of the oil cooler tube, during or after the basic brazing process. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]    Referring first to FIG. 1, an all metal radiator  1  consists of a basic core of flow tubes  12  and interposed corrugated oil cooling fins  14 . Bordering each side of the basic core are a pair of all metal header tanks, indicated generally at  16 . Tanks  16  are generally box shaped structures, with an inner side  18  that is regularly slotted at  20 , so as to form a header plate to receive the ends of the flow tubes  12 . The ends of the header tanks  16  are closed by upper and lower end caps  22 . Coolant inlets and outlets  24  admit engine coolant to, and drain engine coolant from, each of the tanks  16 . Significantly, the basic construction of the tanks  16  is not limited to any particular material (although it is generally aluminum) or technique. That is, the basic tank shell could be formed as an extrusion, so that the inner side header plate  18  would be integral. Or, the tank shell could be a fabricated series of pieces, with an integral end cap  22  and a separate slotted header plate  18  that was clinched to the tank shell to be brazed later. Each possible construction has its own well known advantages and drawbacks. An extruded shell has an integral header plate  18 , but is heavy, and difficult to clad with brazing material. A fabricated shell consists of separated stamped aluminum pieces, which requires more fabrication, but is light and can be easily pre clad with brazing material. Any brazed radiator construction in which the header tank (or some significant portion of it) is brazed along with the rest of the core will have some header tank wall portion, such as the end cap  22 , that is suitable to be slotted similarly to the slotted header plate. Accumulated years of brazing process development has assured that the interface between the ends of the flow tubes  12  and the slots  20  in header plate  18 , each of which is a potential coolant leak point, has a consistent geometric interface, and a consistent, robust braze joint that is solid and leak proof. Also, years of development in tube fabrication has assured that the tubes  12  themselves are consistent, leak proof, lightweight and cost effective. The invention disclosed takes maximum advantage of these features.  
         [0016]    Referring next to FIG. 2, the invention uses the same basic known, all metal radiator construction shown above, with one simple modification. Some point on the body of the header tank  16 , here, the end cap  22 , has a pair of side by side oil cooler slots  26  cut through it, similar to the regular tube slots  20  in header plate  18 . The oil cooler slots  26  would be formed by the same tooling and technique as the header plate slots  20  and, again, the end cap  22  consists of the same material as the header plate  18 . As such, the tank wall slots  26  represent a very minor and simple change in the basic construction of tank  16 .  
         [0017]    Referring next to FIGS. 2 and 3, the other addition, besides the slots  26 , consists of a length of oil cooler tube  28 , which has two free ends  30 . As best seen in FIG. 3, oil cooler tube  28  is a typical “flat oval” aluminum extrusion, with internal webs  32  and, as shown, is bent into a generally sinuous shape. Tube  28  is either identical to, or at least has a similar outer geometry to, the radiator flow tubes  12 . Radiator flow tubes  12  do not generally require the internal strengthening webs typical in an extrusion, and are most often formed of fabricated sheet metal stock, which is easier to clad on the outside with brazing material. But, again, the outer tube geometry can be consistently held, just as with the oil cooler tube  28 . Likewise, oil cooler tube  28  need not absolutely be formed as an integral extrusion, though it would be most practical to do so. In that case, it would be difficult to clad it with brazing material, but it would be relatively simple to clad the end caps  22  in that fashion on their outer surface, even if the body of tank  16  were itself an integral extrusion. So, there is a great deal of flexibility in how the various parts may be formed. However formed, tube  28  will be effectively seamless and sealed, with the same high degree of structural integrity as the flow tubes  12  themselves. It is much easier to assure a leak proof condition for tube  
         [0018]    Referring next to FIG. 4, before the end caps  22  are installed to the body of the tanks  16 , the oil cooler tube ends  30  are inserted through the end cap slots  26 . Their mutual interface would have the same configuration as that between the ends of the radiator flow tubes  12  and header plate slots  20 , even if not exactly the same size, although they could be exactly the same size, as well. Both for the flow tubes  12  and the oil cooler tube ends  30 , there is a ready supply of braze material, whether clad onto the part surfaces surrounding the tube to slot interface, or clad onto the tube surfaces themselves.  
         [0019]    Referring next to FIG. 5, the end cap  22  has been inserted into tank  16 , closing the end thereof, and serving to insert the body of the bent oil cooler tube  28  down into the interior of the tank  16 . The tube ends  30  remain accessible outside the tank  16 . At the same time, the rest of the radiator core would be assembled and stacked, and the ends of the flow tubes  12  inserted into the header plate slots  20  and the entire unit would be ready for the brazing operation. Inside the tank  16 , there are no possible leak points out of the unitary tube  28 . The only possible leak point out of the tank  16 , the interface between tube ends  30  and the end cap slots  26 , becomes sealed during the braze process identically to the interface between the ends of the flow tubes  12  and the header plate slots  20 . That is, braze material, whether located on the surface of the tube ends  30 , or on the surface of the end cap  22  surrounding the slots  26 , or both, is melted, drawn into the carefully sized and controlled tube end  30 -slot  26  interface, after which it hardens into a leak proof joint. No other seals or mechanical structures are needed to create the oil cooler to header tank seal. The use of the flat tube  28 , which is relatively light, and yet relatively stiff (and which is effectively stiffened by virtue of being bent into a U or sinuous shape), in conjunction with the straight slots  26 , serves to keep the tube  28  oriented within the header tanks  16 , spaced from the interior walls thereof. Concurrently, the fins  14  braze to the tubes  12 , and the end caps  22  braze to the tanks  16 , leaving a solid, effectively unitized core structure. The oil cooler can thus take advantage of the one shot braze process and technology in a very efficient manner.  
         [0020]    Referring finally to FIG. 6, since the oil cooler slots  26  are proximate, a single inlet-outlet block fitting  32  can be attached to the oil cooler tube ends  30 , either after the basic braze operation, or during. This allows oil lines to be easily attached, leak free, and any potential leak points, again, would be external to the tank 16 . In operation, coolant entering the tank  16  that contains the oil cooler tube  28  (generally the cooler return tank) flows around the tube  28 , cooling the oil flowing through it. In the completed unit, there is not only less cost, less weight, and less potential internal tank leakage there is also less volume occupied inside tank  16 , and less potential flow blockage and pressure drop in the coolant flow. If desired, corrugated fins could be brazed between the parallel bends in the oil cooler tube  28 , similar to the fins  14  brazed between the radiator coolant tubes  12 .  
         [0021]    Other configurations for the oil cooler tube  28  could be used, of differing construction, and incorporating more or fewer bends, or even multiple tubes (which would necessitate multiple slots  26 ). For example, tubes could be fabricated or folded of clad stock, with an internal configuration similar to the integral, extruded tube  28 . Extruded and fabricated tubes of essentially identical configuration have been known alternative constructions in myriad applications for decades. Either construction would work to have its tube ends brazed into the slots  26  during the single braze process and, in the case of fabricated oil cooler tubes, the tubes themselves would be formed as part of the same braze process. The slots  26  could be formed through any suitable wall surface of the tank  16 , not just the end caps  22  and need not be proximate to one another. Or, the slots  26  could be proximate to one another and actually joined by a thinner slot, so as to allow an integral, U shaped tube with two enlarged “ends” joined by a central web to be used. The central web would pass through the thinner central slot, and would be brazed thereto. The tank  16  need not be entirely metal, so long as it has some suitable surface, such as the end cap  22 , through which the ends of the oil cooler tube or tubes could be passed and brazed. Therefore, it will be understood that it is not intended to limit the invention to just the embodiment disclosed.