Abstract:
A housingless plate heat exchanger including a plate stack defining fluid passages, at least one collecting tank with a peripheral edge enclosing one end of the plate stack, and a valve receivable in the collecting tank through an assembly opening of the soldered collecting tank and plate stack. The collecting tank and plate stack are soldered together and have a fluid opening. A method of manufacturing the heat exchanger includes the steps of assembling plates of the plate heat exchanger in a plate stack, placing a collecting tank on one end of the plate stack, soldering the plate stack and collecting tank together, and after the soldering step mounting a valve in the collecting tank.

Description:
CROSS REFERENCE TO RELATED APPLICATION(S)  
         [0001]    Not applicable.  
         STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not applicable.  
         REFERENCE TO A MICROFICHE APPENDIX  
         [0003]    Not applicable.  
         TECHNICAL FIELD  
         [0004]    The present invention is directed toward heat exchangers, and particularly toward housingless heat exchangers having a valve therein.  
         BACKGROUND OF THE INVENTION AND TECHNICAL PROBLEMS POSED BY THE PRIOR ART  
         [0005]    Housingless plate heat exchangers are known in the art having plates secured in a plate stack with a collecting tank or header on one or more ends. In some heat exchangers of this type, a valve is used to allow regulation of the fluid flow(e.g., an exhaust stream) through the collecting tank. Unfortunately, heretofore manufacturing costs for heat exchangers have been relatively high, especially because of the not insignificant assembly costs for the valve.  
           [0006]    This is the case with, as an example, the exhaust heat exchanger known from DE 101 42 539 A1 (which, however, is not a housingless plate heat exchanger). De 101 42 539 A1 teaches manufacturing the exhaust heat exchanger by welding connections, which is fairly costly. Welding methods also appear to be the preferred connection technique in the exhaust heat exchanger taught in DE 199 62 863 A1 (also not a housingless plate heat exchanger). In EP 916 837 A2, a valve is screwed onto the end of the heat exchanger in a housing, which will also cause significant manufacturing costs. The exhaust line is detachably fastened to the housing.  
           [0007]    Valve components that are guided with their stem through two openings of a jacket tube, through which an exhaust stream can be guided, which is controllable by means of a flap fastened to the stem, are known from German applications DE 101 42 411 A1 and DE 101 44 293 A1. However, such arrangements also appear to cause enormous manufacturing expense, since numerous assembly operations must be conducted to manufacture the entire heat exchanger.  
           [0008]    The present invention is directed toward overcoming one or more of the problems set forth above.  
         SUMMARY OF THE INVENTION  
         [0009]    The invention concerns a housingless plate heat exchanger with at least one collecting tank and with inlet or outlet openings for fluid, which encloses one end of the plate stack with the peripheral wall edge of its wall, so that the plate heat exchanger can be manufactured with its at least one collecting tank in one process step, for example in a soldering operation. The invention also concerns a manufacturing method for such a plate heat exchanger, and an advantageously mounted valve for controlling flow in the heat exchanger.  
           [0010]    According to one aspect of the present invention, a housingless plate heat exchanger is provided, including a plate stack defining fluid passages, at least one collecting tank with a peripheral edge enclosing one end of the plate stack, and a valve receivable in the collecting tank through an assembly opening of the soldered collecting tank and plate stack. The collecting tank and plate stack are soldered together and have a fluid opening.  
           [0011]    In one form of this aspect of the present invention, the valve has a flap inside the collecting tank and a stem extending outside the collecting tank. In a further form, a bearing bushing is in the at least one assembly opening supporting the valve stem.  
           [0012]    In another form of this aspect of the present invention, a second assembly opening is provided in the one collecting tank. In a further form, the first and second assembly openings are in opposite walls of the one collecting tank.  
           [0013]    In still another form of this aspect of the present invention, cover plates are on the plate stack, protrusions are on the cover plates, and a valve retaining device is secured to the protrusions.  
           [0014]    In another aspect of the present invention, a method of manufacturing a housingless plate heat exchanger is provided, including the steps of assembling plates of the plate heat exchanger in a plate stack, placing a collecting tank on one end of the plate stack, soldering the plate stack and collecting tank together, and after the soldering step mounting a valve in the collecting tank.  
           [0015]    In one form of this aspect of the present invention, the valve is inserted through an assembly opening in the collecting tank to mount the valve in the collecting tank. In a further form, the assembly opening is formed in the collecting tank prior to the placing step.  
           [0016]    In another form of this aspect of the present invention, the collecting tank includes a fluid opening, the opening being at least one of a heat exchanger inlet and outlet, and the valve is inserted through the opening during the mounting step.  
           [0017]    In still another form of this aspect of the present invention, the valve includes a flap inside the collecting tank and a stem extending outside the collecting tank after the mounting step, and the flap and the stem are assembled together prior to the mounting step. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 is an exploded view of a plate heat exchanger;  
         [0019]    [0019]FIG. 2 is section through the collecting tank of the plate heat exchanger; and  
         [0020]    [0020]FIG. 3 is a top view of the plate heat exchanger; 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    A housingless heat exchanger  10  in accordance with the present invention is shown in exploded view in FIG. 1. In the practical example described herein, the heat exchanger  10  is an exhaust heat exchanger cooled with a fluid, the heat exchanger  10  being is a component of an exhaust gas recirculation unit of a vehicle operating with an internal combustion engine.  
         [0022]    In the exemplary heat exchanger  10  shown, plates  14 ,  16  are suitably shaped or profiled such as is known to those skilled in the art so that they may be secured to one another along their lateral edges to form flat tubes  18 . The flat tubes  18  define a longitudinal channel for exhaust gas the direction of arrow  20 . It should be understood that flow in either direction, as indicated by arrow  20 , would be within the scope of the present invention.  
         [0023]    Separate flow channels  24  for a coolant are defined between adjacent flat tubes  18 , with the plates  14 ,  16  of the flat tubes  18  being suitably shaped or profiled such as is known to those skilled in the art so that the coolant flow channels  24  are enclosed about the perimeter so that coolant will flow generally in the direction of arrows  28  between aligned inlet openings  30  and aligned outlet openings  32 . It should be understood that flow in either direction would be within the scope of the present invention. Coolant inlet connectors  36  and coolant outlet connectors  38  are suitably secured to the openings  30 ,  32 , and are suitably connected to the system (not shown) with which the heat exchanger  10  is used and through which the coolant circulates.  
         [0024]    A heat exchanger/plate arrangement such as illustrated in FIG. 1 is generally described in various detail in EP 992 756 A2, German Application DE 102 29 083.0, and EP Application EP 03 007 724.2, the disclosures of which are hereby fully incorporated by reference. It should be understood, however, that housingless heat exchangers of different configurations than the one shown in the Figures may be advantageously used in connection with the present invention.  
         [0025]    One collecting tank  40  is illustrated in FIG. 1, and has an inlet or outlet opening  42  (depending on the direction of flow according to arrow  20 ) for the exhaust gas flowing through the flat tubes  18 . As illustrated, however, the opening  42  may advantageously be an outlet for exhaust gas which has already passed through the flat tubes  18 , and been cooled by the coolant in the flow channels  24 .  
         [0026]    It should be understood that a second collecting tank generally of the type illustrated could also be provided at the other end of the heat exchanger  10 , though only the one tank  40  is illustrated. The second collecting tank may be generally identical to the illustrated tank  40  except that the openings for the valve (described below) may be omitted.  
         [0027]    The collecting tanks  40  may advantageously have the shape of a diffuser, for which reason they exhibit significant tapering or conicity, which extends from the connection side on the plate stack to the connection side on the exhaust connection line (not shown) so that a relatively small cross-section of the inlet or outlet opening  42  is present.  
         [0028]    As described in EP Application 03 007 724.2, the plates  14 ,  16  are assembled into a plate stack and collecting tanks  40  are pushed onto both ends of the plate stack (though only one such tank  40  is illustrated in FIG. 1), with the peripheral edge  46  of its wall  48  over the end of the plate stack. Where the plate stack includes protrusions  50  on the connected edges of the plates  14 ,  16 , for example, the edge  46  of collecting tank  40  may be advantageously provided with folds  54  which are intended to accommodate one protrusion  50  each on the periphery of the plate stack, such as described in detail in EP Application 03 007 724.2, the full disclosure of which is hereby incorporated by reference.  
         [0029]    The clamping effect of the collecting tank  40  on the plate stack is facilitated by this assembly manner. The individual plates  14 ,  16  and, if necessary, the collecting tank  40  may advantageously include an appropriate solder coating, so that the plate heat exchanger  10  prepared in this way can be joined into a compact plate heat exchanger  10  in a single soldering operation. Further, the connectors  36 ,  38  for the coolant (see FIG. 1) may also be introduced to the openings  30 ,  32  of the cover plate  60  and connected by soldered in the same manner. A second cover plate  62  is provided on the opposite side of the heat exchanger  10 , whereby coolant flow channels  24  may be defined adjacent the outermost heat exchanging surface of the top and bottom flat tubes  18  carrying exhaust gas.  
         [0030]    The collecting tank  40  in the illustrated example has two assembly openings  70 , which are arranged in opposite walls  48  of the collecting tank  40 . It should be understood, however, that a single assembly opening may also be advantageously used in accordance with the present invention, with the number of assembly openings  70  chosen based, for example, on the type of valve (described below) being incorporated, and/or the configuration of the collecting tank  40  itself.  
         [0031]    A valve  80  may be advantageously provided in accordance with the present invention, with the valve  80  having a stem  84  consisting of two stem parts which are suitably fastened at opposite axial ends to a flap  88 . The flap  88  may be suitably secured in the collecting tank  40  as described herein so that it may be selectively rotated to expose or block a larger or smaller cross-section of the collecting tank  40  based on rotation of the stem  84 . The stem  84  is effectively connected to a control element  90  which may be suitably used to position the flap  88  as desired (e.g., according to the prevailing temperature).  
         [0032]    In both assembly openings  70 , a bearing bushing  94  may be advantageously inserted with the stem  84  rotatably supported in the bearing bushes  94 . At the same time, the assembly openings  70  are sealed outward by the bearing bushes  94 , with one stem part effectively connected to the control element  90  and passing through the corresponding bearing bushing  94  and expediently sealed therein. The other bearing bushing  94  may be advantageously designed to be cup-like. However, it should be recognized that it would be within the scope of the present invention to omit this second bearing bushing  94  and the corresponding second assembly opening  70 . For example, an embossed or shaped recess of the wall  48  could instead be provided to rotatably mount the portion of the stem  84  at that end. Also, a one-sided support of stem  84  could also be provided for only the stem portion that is effectively connected to the control element  90 .  
         [0033]    If collecting tanks  40  which do not have a conical wall in the fashion of a diffuser are used, incorporation of the valve  7  can also be carried out through the inlet or outlet opening  42  in the collecting tank  40  facing the connection line, since this has a correspondingly larger cross-section without tapering or conicity.  
         [0034]    A suitable retaining bracket  100  facilitates fastening of individual elements of valve  80  and the control element  90  to the heat exchanger  10  as a pre-assembled valve unit. The depicted retaining bracket  100 , which may be produced by machining from sheet metal having several cut-outs, may be suitably adjusted to the height of the plate stack. Two angled legs  102  are provided on the retaining bracket  100 , and have holes therein which cooperate with ears or protrusions  106  on the cover plates  60 ,  62  of the plate heat exchanger  10  for the purpose of fastening, as by screwing together (see screws  110 ).  
         [0035]    In further accordance with the present invention, the housingless plate heat exchanger  10  may be advantageously assembled by stacking the plates  14 ,  16 ,  60 ,  62  into a plate stack, with the plate stack then held together and fixed by sliding a collecting tank  40  onto the two opposite ends. The plate heat exchanger  10  may then be completely soldered in a soldering furnace, after which the valve  80  (which may be advantageously used to enhance operation of the heat exchanger  10 ) is incorporated in one of the collecting tanks  40 . Of course, additional parts (e.g., the connectors  36 ,  38 ) which can also be fastened by soldering may also be advantageously introduced to the plate stack and attached, either during an initial soldering step, or during the soldering step involving the stacked plates  14 ,  16 ,  60 ,  62  and collecting tanks  40 .  
         [0036]    It should therefore be appreciated that advantageous housingless plate heat exchangers  10  with a valve  80  integrated in the collecting tank  40  such as described may be advantageously manufactured in accordance with the above described process. That is, by assembling the plate stack and collecting tank  40  and then securing the assembly together by using a single initial soldering process with at least one assembly opening  70  in the wall  48  of the collecting tank  40  during assembly, the assembly opening  70  can be readily provided during manufacture of the collecting tank  40 . Providing the assembly opening  70  at that stage of manufacturing eliminates undesirable residues which can remain in the plate heat exchanger  10  if the opening were created later in the process, and therefore the more or less demanding and therefore costly processes potentially required to remove such residues may be eliminates. (It should be understood, however, that it would be possible to use some aspects of the present invention by manufacturing the assembly openings  70  after the soldering step). Moreover, after soldering of the plate heat exchanger  10  with the collecting tank  40 , the valve  80  can be incorporated by means of the assembly opening as a preinstalled valve unit. By providing the assembly opening, it is therefore possible to retain a very favorable manufacturing method of the plate heat exchanger.  
         [0037]    Still other aspects, objects, and advantages of the present invention can be obtained from a study of the specification, the drawings, and the appended claims. It should be understood, however, that the present invention could be used in alternate forms where less than all of the objects and advantages of the present invention and preferred embodiment as described above would be obtained.