Abstract:
A secondary heat exchanger subassembly, such as a transmission oil cooler, is disposed in a metal tank of a radiator and has a pair of metal fluid fittings. Either a connector ring engages a fitting extending through the opening in the tank or a connector nut extends into the opening to threadedly engage the fitting whereby the metal fittings are held to the metal tank and inserted into a furnace for being brazed into sealed relationship with the metal tank.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     A heat exchanger assembly of the type including an auxiliary or secondary heat exchanger sub-assembly in one of the tanks and a method of fabricating such an assembly.  
         [0003]     2. Description of the Related Art  
         [0004]     The present heat exchangers, particularly automotive radiators, often consist of a composite structure including tanks of a reinforced plastic attached to an aluminum core by crimping with gasket seals between the components. One or both of the tanks, typically the outlet tank, contains auxiliary or secondary heat exchanger sub-assemblies known as transmission oil coolers (TOC) or engine oil coolers (EOC). These heat exchanger sub-assemblies are usually fastened to the inside of the tank by a threaded fitting extending through an opening in the tank with a nut threaded onto the fitting to sandwich a gasket seal and the tank between the nut and the fitting.  
         [0005]     Recently, more attention has been focused upon creating an all aluminum heat exchanger, e.g., an entire radiator including the tanks, to provide packaging advantages and recycling advantages with smaller tank width by eliminating the header crimp area between the core and the tanks. Whenever possible it is desirable to braze the components together rather than relying upon a mechanically held sealing connection between the components.  
       BRIEF SUMMARY OF THE INVENTION AND ADVANTAGES  
       [0006]     The subject invention provides a method of fabricating a heat exchanger assembly to replace mechanical sealing with brazing by disposing a metal fitting of a secondary heat exchanger subassembly into engagement with the interior of a metal tank about an opening therein, mechanically holding the fitting in engagement with the tank about the opening, and brazing the metal fitting to the metal tank to seal the fitting to the tank to prevent fluid communication between the tank and the subassembly.  
         [0007]     In accordance with the invention a heat exchanger assembly is produced comprising wherein the secondary heat exchanger subassembly has at least one fluid fitting comprising metal and the first tank comprises metal with the fitting is brazed into fluid tight sealing relationship with the first tank.  
         [0008]     As will be appreciated, the entire heat exchanger assembly may be held together and inserted into a furnace for brazing all of the components together at one time and to replace mechanically held seals with brazing. As an option, the TOC/EOC could also have been previously brazed in a separate operation. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0009]     Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:  
         [0010]      FIG. 1  is an elevational view of a heat exchanger fabricated in accordance with the subject invention;  
         [0011]      FIG. 2  is a cross sectional view of the lower fitting shown in  FIG. 1 ;  
         [0012]      FIG. 3  is an exploded view of the lower fitting shown in  FIG. 2 ;  
         [0013]      FIG. 4  is a view similar to  FIG. 3  but showing the connector crimped together;  
         [0014]      FIG. 5  is a cross sectional view of the upper fitting shown in  FIG. 1 ; and  
         [0015]      FIG. 6  is an exploded view of the elements shown in  FIG. 5 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a heat exchanger assembly constructed in accordance with the subject invention is generally shown at  10  in  FIG. 1 .  
         [0017]     The heat exchanger assembly  10  includes a heat exchanger core  12  extending between a first tank  18  and a second tank  22  for exchanging heat with a fluid flowing between the tanks  18  and  22 . The first tank  18  has a subassembly opening  20 . The core  12  includes tubes  24  with heat exchanger fins  26  extending between the tubes  24 , as is well known in the art. The ends of the tubes  24  are inserted into openings or slots  28  in the respective tanks  18  and  22  for fluid flow between the tanks  18  and  22 . In addition, as is customary in the art, reinforcing members  29  extend along the sides of the core  12 . A secondary heat exchanger subassembly  30 , such as a transmission oil cooler, is disposed in the first tank  18  and has a pair of fluid fittings  32  and  34  for fluid communication with the subassembly opening  20  in the first tank  18 . Preferably, all of the components are made of a metal, e.g., aluminum, and at least the first tank  18  and the fittings  32  and  34  comprise metal. Many of the components are assembled and coated with a braze clad at various interfaces for brazing the components in a sealing relationship with one another and particularly brazing the fittings  32  and  34  into fluid tight sealing relationship with the first tank  18 . The fittings  32  and  34  are held in the openings  20  by a connector mechanically connected to the fitting  32  and  34  to hold the fittings  32  and  34  in engagement with the interior of the first tank  18  about the openings  20 . The invention is illustrated by two different embodiments of the fitting and connector.  
         [0018]     In the first embodiment  32  of the fitting, the fitting  32  extends through the opening  20  in the first tank  18  and the connector  35  surrounds and mechanically connects to the fitting  32  on the exterior of the metal tank  18 . The fitting  32  includes an annular groove  36  and the connector  35  is disposed in the annular groove  36 . More specifically, the connector  35  comprises a pair of complimentary retention rings  38  disposed in the groove  36  and having ends abutting one another with mechanical connections  40 ,  42  connecting the abutting ends thereof. The connections  40 ,  42  comprise hooks  40  on one of the rings  38  that are crimped around radial tabs on the other of the rings  38 . The rings  38  may be identical with one of hooks  40  on one abutting end and one of the tabs  42  on the opposite abutting end. The braze clad is disposed on the interior surface of the connector  35  to engage the annular groove  36 . Once in the brazing oven, molten braze clad flows into the interface  44  between the fitting  32  and the interior of the tank  18 . However, the braze clad could be disposed on any or all of the surfaces for melting and flowing into the interfaces to braze the components into sealing relationship with one another.  
         [0019]     In the second embodiment  34  of the fitting, the fitting  34  does not extend thru the opening  20 , it is flush with the inside of the tank surface—this provides for the maximum size TOC/EOC to fit into a given size tank. The first tank  18  and the connector  46  is mechanically connected to the fitting  34  on the interior of the first tank  18 . More specifically, threads  48  are included for mechanically correcting the connector  46  to the fitting  34 .  
         [0020]     Although only illustrated in the second embodiment of  FIG. 5 , both embodiments may of the fitting  32 ,  34  may include an undercut defining a gap  50  between the interior of the first tank  18  and the fitting  32 ,  34  about the opening  20  in the first tank  18  whereby the braze clad is disposed in the gap  50  during the brazing in an oven. A braze foil washer  52  is optional and when used is disposed between the exterior of the tank  18  about the opening  20  and the connector  46  and flows into the gap  50  during the brazing step.  
         [0021]     The interior of either connector  32  or  46  may include threads  54  as shown in  FIG. 2  for connection to plumbing to the transmission or engine.  
         [0022]     Accordingly, the invention provides a method of fabricating a heat exchanger assembly  10  comprising the steps of disposing a metal fitting  32 ,  34  of a secondary heat exchanger subassembly  30  into engagement with the interior of a metal tank  18  about an opening  20  therein and mechanically holding the fitting  32 ,  34  in engagement with the tank  18  about the opening  20 . While so held in position and with all of the components assembled, the method continues by simultaneously brazing the entire assembly  10  whereby the metal fitting  32 ,  34  is brazed to the metal tank  18  to seal the fitting  32 ,  34  to the tank to prevent fluid communication between the tank  18  and the subassembly  30 . That is, the heat exchanger core  12  is moved into engagement with the metal tank  18  and into engagement with a second tank  22  before the entire assembly  10  is brazed together.  
         [0023]     The mechanical holding includes mechanically connecting a connector  38 ,  46  to the fitting  32 ,  34  to sandwich the metal tank  18  between the fitting  32 ,  34  and the connector  38 ,  46 . However, a braze clad is disposed on the tank about one of the fitting  32 ,  34 . More specifically, braze clad may be disposed between the fitting and the metal tank  18 , as on the radially facing interior of the retention rings  38 . An undercut is provided in the fitting  32 ,  34  to define a gap  50  between the interior of the metal tank  18  and the fitting  32 ,  34  about the opening  20  in the metal tank  18 . The braze clad may be conveniently brazed into the gap  50  from a braze washer  52 .  
         [0024]     The method may be further defined as extending the fitting  32  through the opening  20  in the metal tank  18  and surrounding the fitting  32  on the exterior of the metal tank  18  with the connector  35 . In this case, the braze clad is disposed radially on the flat surface of the connector  35  between the fitting  32  and the connector  35 . The fitting  32  is provided with an annular groove  36  and the method includes inserting the connector  35  radially into the groove  36 . More specifically, the insertion of the connector  35  comprises inserting complimentary retention rings  38  into the groove  36  with the ends of the rings  38  circumferentially abutting one another followed by mechanically connecting  40 ,  42  the abutting ends of the retention rings  38 . As explained above, the hooks at the abutting ends are crimped over the tabs  42  at the other abutting ends to mechanically connect the retention rings  38  together.  
         [0025]     Alternatively, the method includes extending the connector  46  through the opening  20  in the metal tank  18  and mechanically connecting the connector  46  to the fitting  34  on the interior of the metal tank  18 . This step may be further defined as mechanically connecting the connector  46  to the fitting  34  by threads  48 .  
         [0026]     As alluded to above, the method may include the step of providing an undercut in either fitting  32 ,  34  to define a gap  50  between the interior of the metal tank  18  and the fitting  32 ,  34  about the opening  20  in the metal tank  18  in order to facilitate brazing the braze clad of the washer  52  into the gap  50 . The washer braze clad may be conveniently disposed between or under the connector  46  and the exterior of the metal tank  18  about the opening  20  therein.  
         [0027]     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. The invention may be practiced otherwise than as specifically described within the scope of the appended claims, wherein that which is prior art is antecedent to the novelty set forth in the “characterized by” clause. The novelty is meant to be particularly and distinctly recited in the “characterized by” clause whereas the antecedent recitations merely set forth the old and well-known combination in which the invention resides. These antecedent recitations should be interpreted to cover any combination in which the incentive novelty exercises its utility. In addition, the reference numerals in the claims are merely for convenience and are not to be read in any way as limiting.