Abstract:
A heat exchanger has a rectangular-shaped core having a plurality of fluid passages extending in a width direction and air fins interleaved between said fluid passages. The heat exchanger has tanks that define fluid manifolds located at opposite ends of the core and fluidly connected by the plurality of fluid passages between the tanks. The tanks each include a tank section with open ends and end caps that enclose the ends of the tank section. The tanks are assembled and attached to the core such that each of the end caps is located at each of four corners of the rectangular-shaped core.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Continuation-in-Part of PCT Patent Application No. PCT/US2016/033440, which was filed on May 20, 2016 and which claims priority to U.S. Provisional Patent Application No. 62/165,596, filed on May 22, 2015, the entire contents of both of which are hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    Heat exchangers are used to transfer thermal energy from one stream of fluid at a first, higher temperature to another stream of fluid at a second, lower temperature. Oftentimes such heat exchangers are used to remove waste heat from a process fluid such as oil, coolant, or the like by transferring that heat to a flow of cooler air directed to pass through the heat exchanger. 
         [0003]    In certain applications, the process fluid to be cooled is also at an operating pressure that is substantially greater than the ambient atmospheric pressure of the heat exchanger&#39;s surroundings. As a result, it becomes necessary for the heat exchanger to be designed to withstand the pressure forces that result from the process fluid passing through the heat exchanger. This can become challenging, especially in cases where the heat exchanger is to be used in large systems and machinery such as, for example, construction equipment, agricultural machines, and the like. As the size of the machine or system increases, the flow rate of the process fluid also increases, necessitating larger heat exchangers to accommodate both the heat transfer requirements and the fluid flow rates. Such larger heat exchangers can have substantially large surface areas exposed to the pressure of the process fluid, especially in tank areas, and the force of the fluid pressure acting on these large surfaces can lead to destructive mechanical stresses in the heat exchanger structure. 
         [0004]    An example of such a heat exchanger as known in the art is depicted in  FIG. 1 . The heat exchanger  101  is of a bar and plate construction, and can be used as, for example, an oil cooler for an off-highway vehicle such as an excavator, wheel loader, combine, etc. Oil to be cooled by the heat exchanger  101  travels through a plurality of channels provided within a heat exchanger core  102 , those channels alternating with channels for cooling air that is directed in a cross-flow orientation to the oil through the core  102 . Tanks  103  are provided at either end of the core  102  to direct the oil to and from the core  102 , and inlet/outlet ports  106  are provided at each of the tanks  103  to fluidly couple the heat exchanger  101  to the oil circuit. 
         [0005]    The tanks  103  must be sized to be large enough to evenly distribute the flow of oil to the individual channels. As a result, substantially large surface areas within the tank are exposed to the typically high pressure of the oil, and must be designed to be capable of withstanding such forces. A typical tank construction for such high-pressure applications includes an extruded tank section  104  with an arcuate (e.g. cylindrical) internal profile in order to evenly distribute the forces resulting from the pressure loading. Flat end caps  105  are welded to the ends of the extruded tank section  104  in order to close off the ends of the tank  103 . Those flat end caps  105  must again be designed with a thickness that is suitable for withstanding the pressure forces imposed on them by the fluid in the tank  103 . Such a tank construction can be more economical than a tooled cast tank for low-volume manufacturing. 
         [0006]    Even when such heat exchangers have been designed with wall sections suitable for withstanding the elevated operating pressure of the intended application, the forces acting on the end caps can result in undesirable and damaging stresses in the remainder of the heat exchanger. Thus, there is still room for improvement. 
       SUMMARY 
       [0007]    According to an embodiment of the invention, a heat exchanger includes a rectangular shaped core having fluid passages extending therethrough in a width direction, and air fins interleaved between the fluid passages. Tank end caps are arranged at each of four corners of the core. First and second tank sections are arranged at ends of the core in the width direction, with the first tank section extending between and joined to a first and second one of the tank end caps and the second tank section extending between and joined to a third and fourth one of the tank end caps. The first tank section and first and second tank end caps together define a first fluid manifold and the second tank section and third and fourth tank end caps together define a second fluid manifold. The fluid passages provide fluid communication between the first and second fluid manifolds. 
         [0008]    In some embodiments, at least one of the fluid passages extends between a portion of the first fluid manifold defined by one of the first and second end caps and a portion of the second fluid manifold defined by one of the third and fourth end caps. 
         [0009]    In some embodiments the first, second, third and fourth tank end caps are all identical and interchangeable parts. 
         [0010]    In some embodiments each one of the tank end caps provides a corner mounting feature of the heat exchanger. 
         [0011]    According to another embodiment of the invention, a tank end cap for a heat exchanger includes a first open planar face having a generally rectangular shape, and a second open planar face oriented perpendicular to the first open planar face, with the first and second faces sharing a common edge. The second open planar face has a generally semicircular shape. An internal volume is bounded by the first and second open planar faces. 
         [0012]    In some embodiments the tank end cap is cast from an aluminum alloy. In some other embodiments the tank end cap includes a mounting aperture that extends through the tank end cap. 
         [0013]    In some embodiments, at least one of the first and second tank sections is formed by an extrusion process. In some embodiments, at least one of the first and second tank section is first produced at a first length, and is subsequently reduced in length to a second length shorten than the first length before being joined to the end caps. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view of a prior art heat exchanger. 
           [0015]      FIG. 2  is a perspective view of a heat exchanger according to an embodiment of the invention. 
           [0016]      FIG. 3  is a partial perspective view of a core of the heat exchanger of  FIG. 2 . 
           [0017]      FIG. 4  is a perspective view of a tank to be used in the heat exchanger of  FIG. 2  according to some embodiments of the invention. 
           [0018]      FIG. 5  is an exploded perspective view of the tank of  FIG. 4 . 
           [0019]      FIGS. 6A and 6B  are perspective views of an end cap portion of the tank of  FIG. 4 . 
           [0020]      FIG. 7  is a plan view showing an extrusion profile used in the tank of  FIG. 4 . 
           [0021]      FIG. 8  is a partial perspective view of a tank to be used in the heat exchanger of  FIG. 2  according to some embodiments of the invention. 
           [0022]      FIGS. 9A and 9B  are plan views showing various production stages of a tank to be used in the heat exchanger of  FIG. 2  according to some embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
         [0024]    A heat exchanger  1  embodying the present invention is shown in  FIG. 2 , and can provide durability advantages over other known heat exchangers when used in high-pressure applications such as oil cooling, engine coolant cooling, charge-air cooling, and the like. For purposes of description, reference will be made to the heat exchanger  1  as being an air-cooled oil cooler to be used for the cooling of engine oil, but it should be understood that the invention can find applicability in other heat exchanger applications as well. 
         [0025]    The heat exchanger  1  is of a bar-plate construction, and includes a brazed heat exchanger core  2  defining alternating passages for the flow of oil and cooling air. As best seen in  FIG. 3 , the core  2  is formed by stacking flat separator plates  11  spaced apart alternatingly by long bars  9  and short bars  10  to define alternating oil passages  8  and air passages  7 . The oil passages  8 , bounded by long bars  9  arranged at opposing air inlet and outlet faces of the heat exchanger  1 , extend in the heat exchanger width direction. The air passages  7 , bounded by short bars  10  arranged at opposing tank ends of the heat exchanger  1 , extend in the heat exchanger depth direction, so that the oil passages  8  and air passages  7  are arranged to be perpendicular to one another, resulting in a cross-flow heat exchange orientation. Oil inserts  20  are arranged between the separator plates  11  in the oil passages  8 , and air fins  21  are arranged between the separator plates  11  in the air passages  7 . The oil inserts  20  and air fins  21  provide heat transfer enhancement through additional heat exchange surface area and flow turbulation for their respective fluids, as well as provide structural support to the separator plates in order to withstand the pressurization forces imposed by the fluids. The core  2  is bounded by side plates  26  at both the top and bottom ends of the stack. 
         [0026]    Flat sides of the short bars  10 , ends of the long bars  9 , and edges of the separator plates  11  and side plates  12  together form a generally planar wall  13  at each tank end of the core  2 . Inlet and outlet tanks  3  are welded or otherwise joined to the walls  13  to provide inlet and outlet manifolding for the oil flowing through the oil passages  8 . A representative tank  3  is shown in  FIGS. 4-5 , and will be described in greater detail with reference to those figures and  FIGS. 6-8 . 
         [0027]    In order to withstand the elevated pressure forces imposed by the oil or other pressurized fluid traveling through the heat exchanger  1 , the tank  3  is formed as a welded assembly, preferably of an aluminum alloy, although other metals could be substituted as required for the application. The tank  3  is of a generally box-like construction, with three of the sides provided by an extruded tank section  4 , the profile of which is shown in  FIG. 7 . The extruded tank section  4  extends in a longitudinal direction (indicated by the double-ended arrow labeled “L” in  FIG. 5 ) and includes a pair of opposing sides  18  spaced apart to define a tank width approximately equal to the depth of the heat exchanger core  2 , joined by a third side  19  to form the outer perimeter of the box-like tank. A fluid inlet or outlet port  6  extends through one of the side walls  18 , although such a port  6  could alternatively extend through the side wall  19 . A cylindrical surface  16  is provided in the interior of the tank section  4  and extends along the length direction L so that internal pressure forces are resolved primarily as membrane stresses in the tank section  4 , rather than as bending stresses. Such a configuration can provide enhanced durability to the tank  3  when the fluid passing through the channels  8  of the heat exchanger  1  is at a pressure that is substantially elevated over the ambient pressure. 
         [0028]    The ends  24  of the extruded tank section  4  are capped by a pair of end caps  5 . The end caps  5  are preferably cast components of a similar alloy as the extruded tank section  4 , so that the completed tank  3  can be manufactured by metallurgically joining the tank section  4  and the end caps  5  (by welding, for example). Such joining of the end caps  5  to the section  4  results in a tank  3  having an internal volume  14  to provide for the requisite manifolding of the oil or other fluid. 
         [0029]    The end cap  5  has a first open face  22  (illustrated in cross-hatched fashion in  FIG. 6A ) which generally complements the extrusion profile of the tank  4 . As such, the face  22  is defined by a semi-circular arcuate edge, so that the cylindrical surface  16  continues for some length into the end cap  5 . The face  22  is bounded by an edge  25  which can be disposed directly abutting an end face  24  of the extruded tank section  4 , and a weld joint can be created along the edge  25  in order to join the end cap  5  to that end face  24 . 
         [0030]    The tank  3  has a generally rectangular peripheral edge  15  that bounds the open end of the tank and that is joined (by welding, for example) to a face  13  of the heat exchanger core  2  in order to provide a fluid-tight seal between the tank and the face  13 . The rectangular peripheral edge  15  includes two long edges spaced apart by a distance corresponding to the heat exchanger depth, and two relatively short edges spaced apart by a distance corresponding to the total heat exchanger height (i.e. the distance between the opposing side plates  26 ). Each of the end caps  5  defines one of the short edges of the peripheral edge  15  and end portions of each of the two long edges of the peripheral edge  15 . As a result, the end cap  5  has a second open face  23  (illustrated in cross-hatched fashion in  FIG. 6B ) defined by those portions of the peripheral edge  15 . 
         [0031]    The first open face  22  and the second open face  23  are oriented perpendicular to one another and share a common edge  29 . It should be understood that the open faces  22  and  23  are not physical faces of the end cap  5 , but rather represent fluid boundaries of the end cap  5 . Furthermore, the common edge  29  of the faces  22  and  23  is not a physical edge, but is rather the intersection line of the two fluid boundaries represented by the open faces  22  and  23 . A portion of the tank internal volume  14  is thus contained within each of the end caps  5 , and is bounded by those open faces  22  and  23 . 
         [0032]    By extending the cylindrical surface  16  of the tank  3  into the end caps  5  at either end of the tank  3 , the extruded tank section  4  has a length in the extrusion direction (indicated as “L” in  FIG. 5 ) that is somewhat less than the total height of the heat exchanger  1 . The amount by which the length of the tank section  4  is less than that total heat exchanger height is defined by the extents of those portions of the long edges of the peripheral edge  15  provided by the end caps  5 . It is preferable that at least the outermost ones of the oil passages  8  open into a portion of the tank  3  that is defined by the end caps  5 . In other words, the dimension of the end cap  5  in the heat exchanger height direction is preferably at least equal to the combined height of a short bar  10  and a long bar  9 . Even more preferably, the end cap  5  has a dimension in that direction which is at least three times that amount, so that at least the outermost three or more oil passages  8  at each end of the heat exchanger open into a portion of the tank  3  that is defined by the end caps  5 . 
         [0033]    Oil coolers, radiators, charge-air coolers, and other heat exchangers similar in construction to the heat exchanger  101  of  FIG. 1  are known to be prone to failure resulting from elevated fluid pressure within the tanks  103 . Such failures are typically manifested at the ends of the tanks, where the planar caps  105  are subjected to deformation caused by the elevated pressures. In contrast, the cast end cap  5  of the present invention is believed to provide improved structural reinforcement at the ends of the tank  3  in order to ameliorate this pressure sensitivity. 
         [0034]    Mounting features  12  can be advantageously incorporated into the tank ends  5  in order to provide the heat exchanger  1  with structural mounting locations at each of the four corners. In the exemplary embodiment depicted in the figures, the mounting features  12  include a cylindrical aperture that extends through the end cap  5  in the depth direction of the heat exchanger. Mounting isolators  31  can be inserted into the aperture from both ends, as shown in  FIG. 8 . Such mounting isolators  31  allow for secure structural attachment of the heat exchanger  1  using bolts or the like (not shown) while simultaneously preventing or dampening the transmission of undesirable shocks and/or vibrations to the heat exchanger  1 . 
         [0035]    The isolator  31  can be constructed of a rigid core  32  fabricated of steel or other metal alloy, surrounded over a portion of its length by an over-molded elastomeric sleeve  33 . The rigid core  32  has a hollow cylindrical shape, and is sized to permit the passage therethrough of a threaded bolt or similar fastener. The elastomeric sleeve  33  is of a shape and size that closely corresponds to the geometry of the aperture  12 , so that the isolator  31  can be securely received therein. An anti-rotational protrusion  35  can be provided on the elastomeric sleeve  33  and be received within a corresponding slot feature  30  of the end cap  5 , so that rotation of the isolator  31  within the end cap  5  is prevented. The isolator  31  terminates in a cap portion  34  of the elastomeric sleeve  33 , which is disposed against a seating surface  36  of the end cap  5  upon insertion of the isolator  31 . 
         [0036]    The rigid core  32  of the isolator  31  allows for a secure fastening of the heat exchanger  1  into a vehicular frame or other system. Such secure mounting is especially necessary when the heat exchanger  1  is of a relatively large size and, therefore, has substantial weight due to the large volume of liquid that can be contained within the tank  3  and the fluid passages  8 . Vibrations (such as may be generated by an engine that is present within the vehicle or system) are damped by the elastomeric sleeves  33 , so that the transmission of those undesirable vibrations to the heat exchanger  1  is reduced. This reduction in transmission of vibrations can lead to an enhanced durability life of the heat exchanger  1 . 
         [0037]    Preferably, the end cap  5  is a bilaterally symmetrical part, so that a common part can be used at each of the four corners of the heat exchanger  1 . Accommodating such use of a single part provides economies of scale and reduces the overall cost of the heat exchanger  1 . Furthermore, a common end cap  5  can be used for heat exchangers of varying heights, as the length of the tank  3  can be easily modified by adjusting the length to which the extruded tank section  4  is cut. This allows for great flexibility in heat exchanger sizing, as the overall height of the heat exchanger  1  is otherwise easily varied by increasing or decreasing the number of layers of fluid passages  7 ,  8 . 
         [0038]    The central tank section  4  can be readily produced through an extrusion process, wherein material is forced through a die in order to produce long bars having a constant cross-section along the length of the bar, with that cross-section corresponding to the end face  24  of the tank section  4 . A tank section  4  having a desired length L 2  can subsequently be cut from the extruded bars in order to form a tank  3  that corresponds to the desired height of the heat exchanger. In such a construction, the inlet or outlet port  6  is provided as a separate component that is joined (for example, by welding) to the tank section  4  at an orifice that is machined into the extruded section. The orifice can be machined into the tank section after the section is cut to the desired length. In this way, the positioning of the port  6  along the length of the tank  3  can be placed in order to, for example, optimize fluid flow through the tank, achieve required packaging constraints, or meet other requirements. 
         [0039]    In some embodiments, the tank section  4  is produced by a process wherein the inlet or outlet port  6  is integrally formed into the section  4 . By way of example, the tank section  4  can be produced by a casting process such as die casting, sand casting, permanent molding, or the like. This eliminates the need to machine the orifice and attach a separate component to provide the fluid port  6 , thereby simplifying the manufacturing of the tank  3 . In such an embodiment, it may still be preferable to allow for variation of the location of the port  6  along the length of the tank  3 .  FIGS. 9A-9B  partially depict a method by which such a tank can be produced. 
         [0040]    As illustrated in  FIG. 9A , an initial master tank component  44  having a length L 1 , with the desired cross-sectional shape of the ends  24  along at least a substantial portion of each end of the master tank component  44 , is produced. The port  6  is preferably provided at or near a midpoint location along the length L 1 . The tank section  4  of a desired length L 2  is produced by removing a first portion of material (represented by the hatched area  40 ) having a length L 3  from an end  40  of the master tank component  44  and by removing a second portion of material (represented by the hatched area  41 ) having a length L 4  from an opposite end  41  of the tank component  44 . This removal of material can be readily accomplished by, for example, a sawing operation, a milling operation, or other such machining operations. The lengths L 3  and L 4  are selected in order to achieve both the desired final length L 2  of the tank section  4 , as well as to place the port  6  at a desired location along the length L 2 . As shown in  FIGS. 9A and 9B , the lengths L 3  and L 4  can be selected to be unequal, so that the port  6 , can be located closer to one end of the tank section  4  than to the other end of the tank section  4 . In this way, the final location of the port  6  can be other than at the center of the tank section  4 . It should be understood that, in some embodiments, the tank section  4  can be produce by removing material from only one end of the master tank component  44 . In other words, one of the lengths L 3 , L 4  can be set equal to zero. Once the tank section  4  having the desired length L 2  has been produced from the master tank component  44 , the end caps  5  can be joined to the cut ends of the tank section  4  as previously described in order to produce the tank  3 , as depicted in  FIG. 9B . 
         [0041]    Various alternatives to the certain features and elements of the present invention are described with reference to specific embodiments of the present invention. With the exception of features, elements, and manners of operation that are mutually exclusive of or are inconsistent with each embodiment described above, it should be noted that the alternative features, elements, and manners of operation described with reference to one particular embodiment are applicable to the other embodiments. 
         [0042]    The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention.