Abstract:
A heat exchanger manifold comprising tank and header members secured together, each of the tank and header members having an interior surface facing the interior of the manifold. The header member comprises at least one raised surface feature on its interior surface so as to define longitudinal channels in the interior surface of the header member, and longitudinal passages within the manifold. One or more openings extend through the header plate and the raised surface feature. The width of at least one of the openings through the surface feature is less than the remainder of the opening, so that a portion of the surface feature defines a tube stop that limits the extent to which a tube received in the opening can extend into the interior of the manifold.

Description:
BACKGROUND OF INVENTION 
     1. Field of the Invention 
     The present invention generally relates to heat exchangers comprising tubes that carry a coolant or other heat transfer medium to and from a pair of manifolds, such as those of the type used as evaporators in automobile air-conditioning systems. More particularly, this invention relates a heat exchanger manifold comprising a tank plate and a header plate in which tube ports are formed, and in which ribs are present on the interior of the header plate to define tube stops that positively locate the ends of the tubes within the manifold. 
     2. Description of the Related Art 
     Heat exchangers are employed within the automotive industry as condensers and evaporators for use in air conditioning systems, radiators for cooling engine coolant, and heater cores for internal climate control. In order to efficiently maximize the amount of surface area available for transferring heat between the environment and a fluid flowing through the heat exchanger, heat exchanger designs are typically of a tube-and-fin type in which numerous tubes thermally communicate with high surface area fins. The fins enhance the ability of the heat exchanger to transfer heat from the fluid to the environment, or vice versa. For example, heat exchangers used the automotive industry as air conditioner evaporators serve to vaporize a refrigerant by transferring heat from air forced over the external surfaces of the evaporator to the refrigerant flowing through the evaporator. 
     One type of heat exchanger used in the automotive industry is constructed of a number of parallel tubes that are joined to and between a pair of manifolds, creating a parallel flow arrangement. An internal passage within each manifold defines a reservoir that is in fluidic communication with tubes through tube ports, e.g., holes or slots, formed in the manifold. One or both manifolds include one or more inlet and outlet ports through which a heat transfer fluid enters and exits the heat exchanger. To promote thermal efficiency, such heat exchangers have been constructed by soldering or brazing the tubes to their respective ports. Finally, fins are provided in the form of panels having apertures through which the tubes are inserted, or in the form of sinusoidal centers that can be positioned between adjacent pairs oblong or “flat” tubes. A notable flat tube design is known as a microtube, whose oval shape accommodates a row of small parallel passages separated walls (webs) formed integrally with the microtube, such that heat transfer is enhanced by increasing the surface area in contact with the heat transfer fluid. 
     Various manifold constructions have been suggested. Tubular manifolds with a circular cross-section have typically been preferred for use in high pressure applications, such as evaporators and condensers. However, tubular manifolds are relatively difficult to punch or pierce in order form tube ports. Two-piece manifolds that comprise a tank plate and header plate overcome this problem by locating the tube ports in the header which can be relatively flat to facilitate piercing or punching. The header plate is then mechanically or metallurgically secured to the tank plate to define a passage that fluidically communicates with the tube ports. To increase heat transfer (by improving refrigerant distribution) and the high strength of the manifold, either or both of the tank and header plates can be formed to have multiple channels such that the resulting two-piece manifold has multiple parallel internal passages extending the length of the manifold. 
     The end of a tube can restrict flow through a manifold if the tube is installed too far into its tube port, and may block flow entirely if the end contacts the tank plate. For this reason, either the tank plate or the tubes are typically formed to define tube stops that positively locate the ends the tubes within the manifold. An example is disclosed in commonly-assigned U.S. Pat. No. 6,155,340 to Folkedal et al., which makes use of a one-piece extruded manifold in which multiple parallel passages are defined. Each passage has a substantially circular shape and is separated from adjacent passages by walls, which also extend along the length of the manifold. Tube ports are formed by machining holes through one surface of the manifold and partially through the walls that separate the passages. The portions of the walls that remain serve as integral tube stops, limiting the extent to which the tubes can be inserted into the manifold so as to prevent the tube ends from excessively restricting the flow of heat transfer fluid through the passages. Other types of tube stops formed by raised surface features on the tank plate of a two-piece manifold are also known, as shown U.S. Pat. Nos. 4,971,145 and 5,172,761. 
     A difficulty encountered with manifolds having integral tube stops is the cost and practicality of production in very large quantities. A heat exchanger, manifold that makes possible a simplified process of forming tube ports and tube stops would be desirable. 
     SUMMARY OF INVENTION 
     The present invention provides a heat exchanger manifold comprising tank and header members secured together to define an interior of the manifold, with openings formed in the header member to receive heat exchanger tubes, and with tube stops for the tubes defined by raised surface features on the interior surface of the header member, as opposed to the tank member. 
     The tank and header members of this invention have interior surfaces that face each other and the interior of the manifold. The header member comprises a base portion and at least one raised surface feature rising therefrom that define the interior surface of the header member. The feature is oriented parallel to the longitudinal length of the manifold so as to define at least two longitudinal channels in the interior surface of the member. When the tank and header members are assembled, the surface feature of the header member preferably contacts the interior surface the tank member, so that the channels in the header member define longitudinal passages within the interior of the manifold. One or more openings extend through the base portion of the header member and through at least a portion of the surface feature. The openings are sized to receive tubes with ends having complementary shapes to that of the openings. 
     According to the invention, the extent to which a tube received in one of the openings can extend into the interior of the manifold is determined at least in part by the width of the opening through the surface feature. This portion of the opening defines what is termed herein a transverse gap that separates opposing portions of the surface feature defined by the opening. If the transverse gap in the surface feature has a width that is less than the width of the remainder of the opening through the base portion, at least one of the opposing portions of the surface feature will be present in the opening, creating a step in the size of the opening. A tube fully inserted into such an opening will abut the portion (step) and thus be prevented from contacting the interior surface of the tank member. As a result, there exists a standoff gap between the end of the tube and the interior surface of the tank member through which a heat transfer fluid is able flow between the end of the tube and the passages within the manifold. Furthermore, the transverse gap formed by the opening through the surface feature allows the heat transfer fluid to flow between the end of the tube and each of the manifold passages. On the other hand, if the opening has a uniform width through the header member and its surface feature, i.e., the width of the transverse gap is the same as the width of the opening, a tube can be inserted into the opening without encountering a tube stop. In this case, the tube can be inserted until it abuts the interior surface of the tank member, with the result that the end of the tube defines a baffle that may restrict or divert flow through the manifold. 
     From the above, it can be appreciated that as long as a portion of the raised surface feature remains in the opening in the header member, a step is present that provides a tube stop for a tube inserted into the opening. The width of the opening through the raised surface feature and the distance of the step from the interior surface of the tank member determine the widths of the transverse and standoff gaps, respectively. Flow distribution of the heat transfer fluid within the manifold can be altered by varying the widths of these gaps to promote flow through any one of the passages. For example, the width of the transverse gap through the surface feature can be tailored to promote flow toward either of the manifold passages. In this manner, flow can be promoted to the front and then the back of the heat exchanger in alternate tubes, thereby optimizing flow through the heat exchanger. If the tubes are microtubes that are brazed in the openings, the stops can also have the beneficial effect of inhibiting the flow of brazing material into the small parallel passages of the microtubes, thereby reducing the risk that the microtube passages will become plugged by the brazing material. 
     From the above, it can also be seen that the manifold of this invention can make use of an uncomplicated die and punching operation to simultaneously produce the openings in the header member and tube stops for tubes inserted in the openings. A significant aspect of the invention is the ability to produce the header member by extrusion, taking advantage of the two-dimensional aspects of extrusion technology to mass produce a header member that largely defines the manifold passages and provides the structural integrity of the manifold. As a result, the tank member can have an uncomplicated plate-shaped configuration that can be formed by stamping or any other suitable process. Optionally, the tank member can be fabricated to have one or more raised surface features located and sized to block one or more of the channels in the header member, thereby defining baffles within the longitudinal passages of the manifold. The raised surface features can formed in the tank member to provide any number of baffles that can be to alter the refrigerant flow and distribution within the manifold. 
     Other objects and advantages of this invention will be better appreciated from the following detailed description. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a partial perspective view of a heat exchanger assembly utilizing a manifold comprising a tank plate and header plate in accordance with a preferred embodiment of the present invention. 
     FIG. 2 is a perspective view of the manifold of FIG.  1 . 
     FIG. 3 is a plan view of the manifold of FIGS. 1 and 2. 
     FIGS. 4,  5 ,  6  and  7  are cross-sectional views of the manifold in FIG.  3 . 
     FIG. 8 is an end view of the header plate of the manifold. 
     FIG. 9 is a perspective view of the tank plate of the manifold shown in FIGS. 1 and 2 in accordance with an embodiment of the invention. 
     FIG. 10 is an end view of the header plate of FIG. 8 incorporating a baffle in accordance with another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION 
     A manifold  10  configured in accordance with this invention is represented in FIG. 2, and shown in FIG. 1 assembled in a heat exchanger  50 . The heat exchanger  50  is of a tube-and-center type used as evaporators for automotive air-conditioning systems, though other applications are within the scope of the invention. The heat exchanger  50  is shown with tubes  52  geometrically and hydraulically in parallel with each other though a serpentine tube configuration could also be used. The tubes  52  are represented as being flat, such as a microtube that can be extruded to have multiple internal passages. A suitable fluid, such as for example a refrigerant, flows through the tubes  52  between the manifold  10  and a second manifold (not shown), which may have the same configuration as the manifold  10 . 
     The heat exchanger  50  is represented in FIG. 1 as having a monolithic construction, in which the entire heat exchanger  50  is preferably brazed or soldered together in a single operation. For this purpose, the components of the heat exchanger  50  are preferably formed from a suitable aluminum alloy, such as aluminum alloy AA 3003 or 6005, as designated by the Aluminum Association (AA), though other aluminum alloys could be used. To further facilitate assembly and joining, some or all of the components of the heat exchanger  50  may be formed from a clad aluminum alloy. For example, the components can be formed to have a core formed of AA 3003 which is clad with a suitable braze alloy, such as aluminum-silicon eutectic brazing alloys AA 4045, AA 4047 and AA 4343, or a zinc-aluminum alloy for soldering operations. As a result, the cladding temperature has a lower melting temperature than the AA 3003 core material, and can therefore flow to form brazements or solder joints at temperatures that will not damage the heat exchanger  50 . 
     The manifold  10  is shown in FIG. 2 as a subassembly comprising a tank plate  12  and a header plate  14 . Each of the manifold  10 , tank plate  12  and header plate  14  generally has a longitudinal length in the direction of the row of tubes  52  shown in FIG. 1, and a lateral width transverse to its longitudinal length. The tank plate  12  is shown as having a generally planar shape and the header plate  14  is shown as having a generally U-shaped cross-section, though other configurations are possible. In the configurations shown, the tank plate  12  can be formed by stamping, while the header plate  14  can be formed by extrusion, though other fabrication methods could be used. Slots  16  are formed in the header plate  14  to serve as tube ports for the tubes  52  shown in FIG. 1, with each slot  16  sized to receive one end of a tube  52 . Each slot  16  extends through a base wall  26  of the header plate  14  (FIGS. 4 through 7) to fluidically connect one or more cooling passages within the tube  52  to an interior region of the manifold  10  defined between the tank and header plates  12  and  14 . 
     The interior region of the manifold  10  is interrupted by four longitudinally-extending raised portions or ribs  20  defined by the interior surface of the header plate  14 . Each adjacent pair of ribs  20  defines a channel  22  in the interior surface of the header plate  14 . In FIG. 2, the interior surface of the header plate  14  is represented as having a sinusoidal shape with the ribs  20  and channels  22  being defined by peaks and valleys the of sinusoidal surface form. The crests of the ribs  20  are shown as contacting the tank plate  12  so as to divide the interior region of the manifold  10  into five separate and parallel internal chambers or passages  18 , with each channel  22  and the opposing interior surface of the tank plate  12  defining one of the passages  18 . Alternatively, the tubs  20  could be formed so as not to contact the tank plate  12 , such that the passages  18  fluidically communicate with each other through gaps between the ribs  20  and the tank plate  12 . The ribs  20  preferably extend the entire length of the manifold  10 , such that the channels  22  (and therefore the passages  18 ) also extend the entire length of the manifold  10  unless interrupted by a baffle, as will be discussed below. The passages  18  can be seen to have a semicircular cross-section in FIG. 2 as a result of the planar interior surface of the tank member  12  and the arcuate shape of the channels  22 , though other cross-sectional shapes are foreseeable for the passages  18 . When used in combination with the multiport tubes  52  of FIG. 1, individual passages within the tubes  52  can be fluidically connected to one or more of the passages  18  of the manifold  10 . The header plate  14  can be configured so that the manifold  10  has any desired number of passages  18 , which may or may not correspond to the number of passages in the tubes  52 . 
     The header plate  14  is shown as being mechanically secured to the tank plate  12  as a result of the lateral edges  25  of the tank plate  12  being engaged by ears  24  defined by the lateral edges of the header plate  14 . In the preferred embodiment of the invention, the operation of brazing or soldering the tank and header plates  12  and  14  together also serves to braze or solder each rib  20  to the tank plate  12 , forming a fluid-tight joint with the interior surface of the tank plate  12 . For this purpose, the interior surface of the tank plate  12  is preferably clad with a braze or solder material, though suitable solder or braze materials could be provided in other forms. 
     FIG. 3 is a view of the manifold  10  looking toward the slots with FIGS. 4 through 7 being different sectional views of the manifold  10 . As seen in FIGS. 3 and 4, the slots  16  in the header plate  14  are formed entirely through the base wall  26  of the header plate  14 , and also through the ribs  20  extending inward from the base wall  26 . However, FIGS. 4,  5  and  6  show the width of the slot  16  through the base wall  26  as being greater than the width of the slot  16  through the ribs  20 . As a result, opposing portions  34  of the ribs  20 , separated by a transverse gap  38 , are visible in FIG. 3, and project laterally inward beneath the lateral edges of slot  16  through the base wall  26 , thereby defining steps in the opening of slot  16 . These opposing portions  34  serve as tube stops for the tubes  52  in phantom in FIGS. 5 and 6. The transverse gaps  38  allow heat fluid to flow between a tube  52  and each of the manifold passages  18 . The distance that the end  32  of a tube  52  is spaced from the interior wall the tank plate  12 , referred herein as a standoff gap, can be tailored by controlling the distance from the crest of the rib  20  of the step defined by the opposing portions  34  of the rib  20  remaining in the slot  16 . In practice, half of the height of each rib  20  can be removed to provide an adequate cross-sectional flow area through the passages  18  of the manifold 
     FIG. 7 is a sectional view through a slot  16  formed in the header plate  14  that differs from the other slots  16  as a result of the width of the slot  16  being constant through the base wall  26  and the ribs  20 . In other words, the width of the transverse gap  38  is essentially equal to the width of the slot  16  through the base wall  26 . As a result, portions of the ribs  20  are not visible in FIG.  3  through the slot  16  depicted in FIG.  7 . Without portions of the ribs  20  to serve as tube stops for a tube  52  (indicated in phantom in FIG.  7 ), the end  32  of the tube  52  abuts the interior wall of the tank plate  12 , such that the tube end  32  functions as a baffle for altering the flow through the heat exchanger  50 . 
     FIGS. 8,  9  and  10  represent two techniques by which baffles can be provided within the passages  18 , in lieu of or in addition to the technique represented in FIGS. 3 and 7. In FIG. 9, the tank plate  12  is shown as having been stamped to define integral raised baffles  28  on its interior surface. When the tank plate  12  is assembled with the header plate  14  shown in FIG. 8, the baffles  28  are received in the channels  22  of the header plate  14  and block the passages  18 . Brazing the tank and header plates  12  and  14  as discussed above results in the baffles  28  forming a fluid-tight joint with the channels  22 . In FIG. 10, a discrete baffle member  30  is formed separately of the tank and head plates  12  and  14 , such as by stamping. The baffle member  30  is shown as having been pressed or otherwise retained in one of the channels  22  of the header plate  14 . Again, brazing the tank and header plates  12  and  14  as discussed above preferably results in the baffle  30  forming fluid-tight metallurgical joints with the interior surfaces of the tank and header plates  12  and  14 . For this purpose, the baffle member  30  can be clad with a suitable braze or solder material. End plugs  36  shown in FIG. 1 as closing the ends of the passages  18  can be produced and installed in the manifold  10  in a manner similar to the baffle member  30 . 
     The slots  16  can be formed in the header plate  12  by various known methods. In a preferred embodiment, a punching operation is performed from the exterior surface of the header plate  14  with a punch appropriately shaped to form the portion of the slot  16  through the base wall  26  and the transverse gap  38  defined by the slot  16  through the ribs  20 . As a result a single punching operation serves to simultaneously form tube ports (slots  16 ) and tube stops (rib portions  34 ) in the header plate  14 . The pressure applied to the interior surface of the header plate  14  during the punching operation can have the additional benefit of truing up the interior dimensions of the header plate  14 , thereby facilitating the installation of the baffles  28  and  30  and plugs  36  in the passages  18 , and facilitating the clinching of the lateral edges  25  of the tank plate  12  with the ears  24  of the header plate  14 . 
     While the invention has been described in terms of a preferred embodiment, it is apparent that other forms could be adopted by one skilled in the art. For example, materials and processes other than those noted above could be adopted, and the manifold and heat exchanger could be modified from that shown in the Figures in order to be suitable for a variety of applications. Accordingly, the scope of the invention is to be limited only by following claims.