Abstract:
A heat exchanger for conducting a fluid comprises a plurality of heat transfer tubes, a plurality of fins sandwiched by the heat transfer tubes, and first and second header pipes fixedly and hermetically mounted to the heat transfer tubes. A pair of union joint devices are disposed in the first and second header pipes respectively. Each of the union joint devices comprises a brazed area wherein one end of a fluid passage disposed therein is brazed to a hole formed on the header pipe. A space is created around the brazed area for observing a condition of brazing and insuring a flux therein. Thereby, the heat exchanger has completely hermetic connections between the union joint and header pipes and is easily examined by an operator to detect any improper brazing between the union joint and the header pipes.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a heat exchanger and more particularly, to a union joint mechanism for inlet and outlet ports suitable for use in automotive air conditioning systems. 
     BACKGROUND OF THE INVENTION 
     A heat exchanger may comprise one or more header pipes, an inlet port for introducing a fluid into the header pipes, and an outlet port for discharging the fluid from the header pipes. The inlet port and outlet port are fixedly and hermetically connected to the header pipes to circulate the fluid in the heat exchanger. In this arrangement, the inlet and outlet ports are generally connected to the header pipes by brazing. 
     With reference to FIG. 1, Japanese Utility Model publication No. H3-128275 discloses a pair of header pipes 13 each having a union joint mechanism thereon for joining an inlet pipe 15 and an outlet pipe 16, respectively. A union joint mechanism includes union element 14 which is directly connected to header pipe 13 by brazing. Thereby, inlet pipe 15 or outlet pipe 16 may be fixedly and hermetically joined with union element 14 for the purpose of freely selecting the position of inlet pipe 15 or outlet pipe 16 and increasing the strength of a union joint mechanism. 
     Further, in such union joint mechanisms, union element 14 includes a fluid passage 14a integrally formed therein. One end of fluid passage 14a protrudes into the interior of header pipe 13. That end of fluid passage 14a is connected to hole 13a of header pipe 13 by brazing. Union element 14 may be made of a high hardness aluminum alloy, such as A7000 series aluminum alloys, which provides a strong body although such material is generally difficult to braze properly. 
     One attempt to resolve these disadvantages may be shown with reference to Japanese Patent H6-31333. Referring to FIG. 2, union element 17 comprises an opening 17a formed therein. A sleeve member 18 may be inserted into opening 17a so that sleeve member 18 protrudes into the interior of header pipe 13. Fluid may flow through the inner surface of sleeve member 18. Sleeve member 18 may be made of a material which is easily brazed in character. Thereby, sleeve member 18, which functions as a fluid path, may be securely connected to header pipe 13 by brazing. 
     In this arrangement, however, a flux material must be coated on the areas at which sleeve member 18 is connected to hole 13a of header pipe 13 and union element 17 is connected to the peripheral surface of header pipe 13 before brazing. This coating work is difficult because the areas to be coated are hidden by union element 17 when union element 17 is set on header pipe 13. Without the coating, however, the areas are difficult to braze and as a result, the heat exchanger may leak heat exchanger fluid at the brazing area and may have weak connections between header pipe 13 and union element 17. On the other hand, if excess flux is coated on the connection areas to attempt to prevent leakage of the fluid and weakness of the connection, the flux flows into the interior of fluid passage 17a or sleeve member 18. Consequently, the heat exchanger does not seal properly when the heat exchanger is heated up in a furnace for brazing. 
     Furthermore, the connecting area may not receive a sufficient amount of the brazing material for proper brazing because the brazing material may be absorbed in the gap created between sleeve member 18 and union element 17 or between union element 17 and the outer peripheral of header pipe 13. The leakage of the brazing material in the connecting area may result in leakage of the fluid and a deterioration of pressure strength and may not insure the strength of union element 17. 
     Moreover, it is difficult to determine whether the flux or the brazing material has been properly coated or brazed to the connecting area because the area created between fluid passage 17a or sleeve member 18 and hole 13a of header pipe 13 is hidden between union element 14 and 17 and header pipe 13. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a heat exchanger which is easy to manufacture and has completely hermetic connections between a union joint and a header pipe. 
     It is another object of the present invention to provide a heat exchanger that may be readily examined to determine any possible failure of brazing between a union joint and a header pipe. 
     In order to achieve these and other objects, the present invention comprises a heat exchanger for conducting a fluid. The heat exchanger comprises a plurality of heat transfer tubes having opposite first and second ends respectively. A plurality of fins are sandwiched by the heat transfer tubes. First and second header pipes are fixedly and hermetically connected to one of the opposite ends of each of the heat transfer tubes. A pair of union joint devices are disposed in the first and second header pipes respectively for linking the heat exchanger to an external element of a fluid circuit. Each of the union joint devices includes a union member therein, a fluid passage disposed in the union member, and a brazed area wherein one end of the fluid passage is brazed to a hole formed on the header pipe. A space is created around the brazed area for enabling a person to examine the condition of brazing and insuring a flux therein. 
    
    
     Other objects, features and advantages will be apparent to persons of ordinary skill in the art in view of the following detailed description of the invention and the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an enlarged partial cross sectional view of a union joint mechanism of a heat exchanger according to an embodiment of the prior art. 
     FIG. 2 is an enlarged partial cross sectional view of a union joint mechanism of a heat exchanger according to another embodiment of the prior art. 
     FIG. 3 is an elevational view of a heat exchanger according to an embodiment of the present invention. 
     FIG. 4 is a top view of the heat exchanger shown in FIG. 3. 
     FIG. 5 is an enlarged fragmentary sectional view taken along line 5--5 of FIG. 3. 
     FIG. 6 is an overhead view of a union joint member according to an embodiment of the present invention. 
     FIG. 7 is a side view of the union joint member shown in FIG. 6. 
     FIG. 8 is schematic view of an external pipe joint member connected to a union joint mechanism according to another embodiment of the present invention. 
     FIG. 9 is a schematic view of a union joint mechanism according to another embodiment of the present invention. 
     FIG. 10 is an enlarged fragmentary sectional view taken along line 5--5 of FIG. 3 according to another embodiment of the present invention. 
     FIG. 11 is an overhead view of union joint member according to another embodiment of the present invention. 
     FIG. 12 is a side view of the union joint member shown in FIG. 11. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 3 and 4 depict a heat exchanger for an automotive air conditioning system according to an embodiment of the present invention. In this embodiment, a heat exchanger 20 includes a plurality of adjacent, essentially flat tubes 21 having an oval cross section and open ends which allow refrigerant fluid to flow therethrough. A plurality of corrugated fin units 22 may be disposed between adjacent tubes 21. Circular header pipes 23 and 24 may be disposed substantially perpendicularly to flat tubes 21 and may have, for example, a clad construction. Flat tubes 21 are fixedly connected to header pipes 23 and 24 and disposed in slots 27 such that the open end of flat tubes 21 communicate with the hollow interior of header pipes 23 and 24. 
     Header pipe 23 may have a closed top end and a bottom end. Inlet union joint mechanism 32 may be fixedly and hermetically connected to header pipe 23. Inlet union joint mechanism 32 may also be linked to the outlet of a compressor (not shown). Partition wall 23a may be fixedly disposed within header pipe 23 at a location about midway along its length and may divide header pipe 23 into an upper cavity 231 and a lower cavity 232, which is isolated from upper cavity 231. Second header pipe 24 may also have a closed top end and a bottom end. Outlet union joint mechanism 33 may be fixedly and hermetically connected to header pipe 24. Outlet union joint mechanism 33 may be linked to the inlet of a receiver (not shown). Partition wall 24a may be fixedly disposed within second header pipe 24 at a location approximately one third of the way along the length of second header pipe 24 and may divide second header pipe 24 into an upper cavity 241 and a lower cavity 242, which is isolated from upper cavity 241. The location of partition wall 24a may be lower than the location of partition wall 23a. 
     In operation, compressed refrigeration gas from a compressor flows into upper cavity 231 of first header pipe 23 through inlet union joint mechanism 32 and is distributed such that a portion of the gas flows through each of flat tubes 21 which is disposed above partition wall 23a and into an upper portion of upper cavity 241. Thereafter, the refrigerant in the upper portion of upper cavity 241 flows downward into the lower portion of upper cavity 241 and is distributed such that a portion flows through each of the plurality of flat tubes 21 disposed below partition wall 23a and partition wall 24a, and into an upper portion of lower cavity 232 of first header pipe 23. The refrigerant in an upper portion of lower cavity 232 flows downwardly into a lower portion of lower cavity 232 and is again distributed such that a portion flows through each of the plurality of flat tubes 21 disposed below partition wall 24a and into lower cavity 242 of second header pipe 24. As the refrigerant gas sequentially flows through flat tubes 21, heat from the refrigerant gas is exchanged with the atmospheric air flowing through corrugated fin unit 22 in the direction of arrow W as shown in FIG. 4. Since the refrigerant gas radiates heat to the outside air, it condenses to a liquid refrigerant in lower cavity 242 and flows from lower cavity 242 out through outlet union joint mechanism 33 and into the receiver and the further elements of the circuit as discussed above. 
     The details of the union joint mechanism are described below. Referring to FIG. 5, union joint mechanism 32 (33) includes a union element 34 and a sleeve member 37 inserted into an opening 36 integrally formed in union element 34. Union element 34 may comprise a rectangular-shaped body 34a, an opening 36 penetrating from a first end surface 34b to a second end surface 34c of union element 34, and an arm 35 extending from second end surface 34c. Arm 35 may comprise a wall portion 35a, an arc portion 35b extending from wall portion 35a, and an inner surface 35c of arm 35 formed on arc portion 35b. Inner surface 35c may be designed to closely contact the peripheral surface of header pipe 23. Opening 36 may comprise a first cylindrical hole 36a, a second cylindrical hole 36b, a shoulder portion 36c joining first cylindrical hole 36a to second cylindrical hole 36b, and a beveling surface 36d joining first end surface 34b to first cylindrical hole 36a. The inner diameter of first cylindrical hole 36a may be larger than that of second cylindrical hole 36b. 
     Sleeve member 37 may comprise a first cylindrical portion 37a, a second cylindrical portion 37b, a third cylindrical portion 37c, a first shoulder portion 37d joining first cylindrical portion 37a to second cylindrical portion 37b, a second shoulder portion 37e joining second cylindrical portion 37b to third cylindrical portion 37c, and a flange portion 37f extending from one end of first cylindrical portion 37a. The outer diameter of first cylindrical portion 37a may be larger than that of second cylindrical portion 37b. The outer diameter of second cylindrical portion 37b may be larger than that of third cylindrical portion 37c. Further, sleeve member 37 may be forcibly inserted into opening 36 of union element 34 such that third cylindrical portion 37c and a partial portion of second cylindrical portion 37b substantially protrude from second end surface 34c of union element 34. 
     Union element 34 may be made of a metal, for example, such as an aluminum alloy series 7000, which is difficult to braze but is very hard. Sleeve member 37 may be made of a metal, for example, such as an A3000 series aluminum alloy which is easily brazed. 
     Referring to FIGS. 6 and 7, union element 34 may comprise a threaded hole 46 straightly penetrating from first end surface 34b toward the inside of body 34a. Union element 34 may further comprise a cutaway portion 49 formed on a first side surface 34d. Cutaway portion 49 may completely join first side surface 34d to a second end surface 34c. 
     Referring to FIGS. 8 and 9, union element 34 may be securely connected to header pipe 23 at first joint area 38 such that inner surface 37c of arm 35 may be brazed to the peripheral surface of header pipe 23. Sleeve member 37 may also be fixedly and hermetically connected to header pipe 23 at second joint area 39 such that second shoulder portion 37e may be brazed to the circumference of hole 23b of header pipe 23. 
     Further, the external joint mechanism may comprise a joint block 43, a first pipe member 40 connected to one end surface therein, and a second pipe member 41, which is provided with an &#34;O&#34;-ring 42 thereon, connected to the other end surface therein. Joint block 43 includes hole 45 through which bolt 44 may be passed. After second pipe member 41 is inserted into opening 36 of union element 34, the external joint mechanism may be secured to union joint mechanism 32 such that bolt 44 penetrates hole 45 and is bound in threaded hole 46. 
     In this arrangement, wall portion 35a and second end surface 34c collectively form space 47 around the outer peripheral surface of second cylindrical portion 37b of sleeve member 37. Therefore, space 47 functions to maintain flux therein without permitting the flux to deviate into other gaps. Further, second joint area 39 may be securely brazed since space 47 also functions to insure a desirable amount of brazing material therein for brazing. Second joint area 39 thus provides superior sealing and strength in construction. 
     Furthermore, in the process of coating flux, an operator may be able to confirm whether the flux has properly coated second joint area 39 by observing the second joint area 39 through space 47. If it is not sufficiently coated, the flux may be supplemented at second joint area 39. In the process of brazing, the operator may confirm whether second joint area 39 is properly brazed by observing second joint area 39 from three direction as indicated by the arrows shown in FIG. 9. Therefore, if union element 34 includes either inclined portion 49 or space 47, the operator may confirm the coating condition of the flux and the resulting brazing condition as well. As a result, the improvement may decrease the leakage of the fluid from header pipe 23 (24) and may facilitate control of the production process in inspecting leakage of the fluid. 
     Referring to FIG. 10, another embodiment of the present invention is depicted. Elements similar to those of the other embodiments are designated with the same references numerals. 
     A union joint mechanism 132 (133) may comprise a union element 134 and a sleeve member 37 inserted into an opening 36 formed in union element 134. Union element 134 may comprise a rectangular shape body 134a, an opening 36 penetrating from a first end surface 134b to a second end surface 134c of union element 134, and an arm 135 extending from second end surface 134c. Union element 134 may comprise a thread hole 146 penetrating straight from first end surface 134b toward the inside of body 134a. Union element 134 may also comprise a notch portion 147 formed in body 134a so as to surround second cylindrical hole 36b and extend along the peripheral surface of sleeve member 37. Union element 134 may further comprise a cutaway portion 149 formed on one side surface 134d. Cutaway portion 149 inclines toward second end surface 134c and completely joins side surface 134d to second end surface 134c. Union element 134 may be securely connected to header pipe 23 at first joint area 138 such that arm 135 is brazed to the peripheral surface of header pipe 23. Sleeve member 37 may also be fixedly and hermetically connected to header pipe 23 at second joint area 139 such that second shoulder portion 37e is brazed to the circumference of hole 23b of header pipe 23. This structure also provides the advantages of the embodiments of FIGS. 3-9 as discussed above. 
     This invention has been described in connection with several embodiments, but these embodiments are merely presented for example only, and the invention should not be construed as limited thereto. It should be apparent to those skilled in the art that other variations or modifications can be made within the scope defined by the appended claims.