Heat exchanger and method for manufacturing the same

Abstract: A heat exchanger (1) includes a tank (2,3) having a pipe insertion hole (14,15) disposed in a tank wall (16) and a fluid pipe (4,5) connected to the tank wall (16) for introducing a fluid into the tank or discharging the fluid from the tank. The tank wall (16) has a burr (17) formed around the pipe insertion hole (14,15) extending toward an interior of the tank. The fluid pipe (4,5) has a flange (4b) formed on its periphery by bending the fluid pipe onto itself. An end portion (4c) of the fluid pipe is inserted into the pipe insertion hole (14,15) so that the flange (4b) contacts an outer surface of the tank wall (16), and the inserted end portion (4c) is expanded and caulked together with the burr (17). A brazing material (18) may be fixed between the flange and the tank wall during brazing even during vibration. The length of the pipe inserted into the tank may be minimized. The contact area between the fluid pipe and the tank is thereby enlarged.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger and a method for manufacturing the same comprising the features of the preamble of claim 1. 2. Description of the Related Art In a conventional heat exchanger having a tank and a fluid pipe connected to the tank, for example, a fluid inlet pipe or outlet pipe, brazing between the tank and the fluid pipe may be performed as follows. For example, Fig. 9 depicts a heat exchanger tank 104 having a pipe insertion hole 102 disposed in tank wall 103 of tank 104. A burr 101 may be formed around pipe insertion hole 102 to increase the surface area of tank 104 contacting fluid pipe 105, i.e., to enlarge the brazing area between tank 104 and fluid pipe 105. An end portion of fluid pipe 105 may be inserted into pipe insertion hole 102 so that a tip 110 of fluid pipe 105 may be positioned over a tip 111 of burr 101. The inserted fluid pipe 105 may be temporarily fixed to tank 104 by spot welding 106. Annular brazing material 107 may be placed around the periphery of fluid pipe 105 and brought into contact with an outer surface 108 of tank wall 103. Then, the assembly may be is heated in a furnace, whereby fluid pipe 105 is brazed to tank 104. In such a conventional connecting and brazing structure, when the assembly is heated in a furnace, if any vibration occurs, annular brazing material 107 may shift away from outer surface 108 of tank wall 103. If shifting occurs, an insufficient amount of molten brazing material may remain in contact with burr 101 and fluid pipe 105 to form a good brazed and connected state between fluid pipe 105 and tank 104. Further, the portion of fluid pipe 105 inserted into the interior of tank 104 is often relatively long. Consequently, the portion disrupts fluid flow in tank 104 resulting in significant pressure loss of fluid flow in the tank 104. Furthermore, the contact area, i.e., brazing area, between tank 104 and fluid pipe 105 is relatively small. Hence, the connection strength between fluid pipe 105 and tank 104 may be insufficient. From JP 03-199 897 a heat exchanger according to the preamble of claim 1 is known. The burr extends nearly perpendicularly from the tank wall into the interior of the tank. The fluid pipe has an end portion which is bent U-shaped. The burr extends into the U-shaped end portion of the fluid pipe. From DE 93 05 497 U a heat exchanger is known comprising a tank including a tank wall having a pipe insertion hole disposed in the tank wall, a burr being formed around the pipe insertion hole extending toward an interior of the tank, and a fluid pipe is connected to the tank wall for introducing a fluid into the tank or discharging a fluid from the tank. The heat exchanger is made of plastic. It is an object of the present invention to minimize the length of the fluid pipe which is inserted into an interior of the tank, thereby minimizing the pressure loss in the tank. This object is solved by a heat exchanger having the features of claim 1. The object is also solved by a method for manufacturing a heat exchanger with the features of claim 6. Preferred developments of the invention can be taken from the respective subclaims. In such a heat exchanger and a method for manufacturing the same according to the present invention, because the flange is formed on the periphery of the fluid pipe, an annular brazing material may be placed on the periphery of the fluid pipe before insertion of the fluid pipe into the pipe insertion hole so that the annular brazing material engages the flange. Thereby, when the end portion of the fluid pipe is inserted into the pipe insertion hole and the flange is brought into contact with the outer surface of the tank wall, the annular brazing material may be securely fixed between the flange and the tank wall. Moreover, because the fluid pipe and the tank are heated and brazed in a furnace in the described assembly, the position of the annular brazing material may always be maintained at a desired position during heating, even if vibrations occur on the assembly. As a result, a sufficient amount of molten brazing material may be supplied to the connection portion between the fluid pipe and the tank wall, thereby ensuring a good brazed state. Moreover, because the inserted end portion of the fluid pipe is expanded and caulked together with the burr, the length of the fluid pipe inserted into the interior of the tank may be minimized. Therefore, the pressure loss in the tank originating from the inserted portion of the fluid pipe into the tank may be minimized as compared with the conventional structure. Further, because the flange contacts the outer surface of the tank wall and the inserted end portion of the fluid pipe contacts the burr formed on the tank wall, the contact area between the fluid pipe and the tank may be increased. Therefore, the connection strength therebetween and the brazing strength therebetween may also be increased. Furthermore, because the inserted end portion of the fluid pipe is caulked together with the burr such that the inserted end portion of the fluid pipe extends over and is caulked together with the burr, the fluid pipe may be securely fixed to the tank. Also, the end opposite from the inserted end of the fluid pipe (a fluid introducing port or a fluid discharging port) may be precisely positioned before brazing. Therefore, a temporary fixing between the fluid pipe and the tank before brazing is not necessary, and a fixing during brazing such as one using a fixing jig is also unnecessary. As a result, the manufacturing process may be simplified, and the cost for the manufacture may be reduced. Further objects and advantages of the present invention will be understood from the detailed description of the preferred embodiments of the present invention with reference to the appropriate figures. BRIEF DESCRIPTION OF THE DRAWINGS Some preferred exemplary embodiments of the present invention will now be described with reference to the appropriate figures, which are given by way of example only, and are not intended to limit the present invention. Fig. 1 is a perspective view of a heat exchanger according to an embodiment of the present invention. Fig. 2 is an exploded perspective view of the heat exchanger depicted in Fig. 1. Fig. 3 is an enlarged elevational view of part of the heat exchanger depicted in Fig. 1. Fig. 4 is an enlarged vertical sectional view of a connection portion between a fluid pipe and a tank wall of the heat exchanger depicted in Fig. 1. Fig. 5 is an enlarged vertical sectional view of the connection portion between the fluid pipe and the tank wall of the heat exchanger depicted in Fig. 1 and depicts a method for expanding and caulking an end portion of the fluid pipe together with a burr of the tank wall according to another embodiment of the present invention. Fig. 6 is an enlarged vertical sectional view of the connection portion between the fluid pipe and the tank wall of the heat exchanger depicted in Fig. 1 prior to brazing. Fig. 7 is a vertical sectional view of part of a connection portion between a fluid pipe and a tank wall of a heat exchanger according to another embodiment of the present invention. Fig. 8 is a vertical sectional view of part of a connection portion between a fluid pipe and a tank wall of a heat exchanger according to another embodiment of the present invention. Fig. 9 is a vertical sectional view of part of a connection portion between a fluid pipe and a tank wall of a conventional heat exchanger. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Figs. 1 and 2, a heat exchanger 1 is provided according to an embodiment of the present invention. Heat exchanger 1 includes a pair of tanks 2 and 3. Each of tanks 2 and 3 may be constructed from tank member 2a or 3a and seat member 2b or 3b to form barrel 2c or 3c. Inlet pipe 4 and outlet pipe 5 may be provided as fluid pipes for introducing a fluid (for example, refrigerant) into tank 2 and discharging the fluid from tank 2, respectively. Inlet pipe 4 and outlet pipe 5 may be connected to tank 2 by brazing. A plurality of flat heat transfer tubes 6 (for example, refrigerant tubes) may be fluidly interconnected between tanks 2 and 3. Corrugated fins 7 may be disposed on either or both surfaces of each heat transfer tube 6. Side members 8 and 9 may be provided on the upper surface of the uppermost fin 7a and on the lower surface of the lowermost fin 7b, respectively. Each of tanks 2 and 3 may be closed at both longitudinal ends by caps 10 and 11, respectively. The interior of tank 2 may be divided into two sections 12a and 12b by partition 13 provided in tank 2. One end of inlet pipe 4 and outlet pipe 5 may be connected to pipe insertion holes 14 and 15, respectively defined on tank member 2a of tank 2. The other ends of inlet pipe 4 and outlet pipe 5 form open ends 4a or 5a and function as a fluid introducing port or a fluid discharging port, as shown in Figs. 2 and 3. Inlet pipe 4 and outlet pipe 5 may be connected to tank 2 as follows. For purposes of explanation, connection of inlet pipe 4 will be described. Outlet pipe 5 may also be connected in the following manner. The term fluid pipe may refer to either inlet pipe 4 or outlet pipe 5. Tank member 2a has a tank wall on which pipe insertion holes 14 and 15 are defined. As depicted in Figs. 4-6, a burr 17 is be formed around pipe insertion hole 14 to extend toward the interior of tank 2. A flange 4b may be formed on the periphery of fluid pipe 4 near end portion 4c of fluid pipe 4. Flange 4b may be formed by bending fluid pipe 4 onto itself so a flange formation portion protrudes outwardly in the axial direction. Other methods of forming flange 4b may also be used. End portion 4c of fluid pipe 4 is be inserted through pipe insertion hole 14 extending toward the interior of tank 2. Before end portion 4c of fluid pipe 4 is inserted into pipe insertion hole 14, annular brazing material 18 is placed around the periphery of end portion 4c of fluid pipe 4 so that annular brazing material 18 is brought into contact with flange 4b. Annular brazing material 18 may have an inner diameter smaller than an outer diameter of flange 4b. In this embodiment, annular brazing material 18 may have a trapezoidal cross section. In such a condition, end portion 4c of fluid pipe 4 may be inserted into pipe insertion hole 14 until flange 4b is brought into contact with the outer surface of tank wall 16, as depicted in Fig. 5. The inserted end portion 4c of fluid pipe 4 extends over tip 30 of burr 17. The assembly of tank member 2a (tank wall 16), fluid pipe 4 and annular brazing material 18 may be supported from the underside by lower jig 19. Punch 20 may be pressed from the upper side onto the inserted end portion 4c of fluid pipe 4. Punch 20 may have an annular caulking portion 20a formed as a curved recessed portion. End portion 4c of fluid pipe 4 is be caulked together with burr 17 by the dowmward pressing of punch 20. When punch 20 presses down on end portion 4c of fluid pipe 4 and burr 17, end portion 4c and burr 17 expand to open outwardly and become caulked to the surface of tank wall 16. End portion 4c is caulked so that the upper surface of end portion 4c is curved along caulking portion 20a of punch 20. In other words, the surface of the caulked end portion 4c facing the interior of tank 2 is formed as a curved surface convex toward the interior of tank 2. Such punching and caulking may be possible during manufacture because tank member 2a and seat member 2b of tank 2 are separate structures. By the above-described caulking, as depicted in Fig. 6, fluid pipe 4 is fixed to tank wall 16 by caulked end portion 4c and to flange 4b by caulked burr 17. Also a tapered portion 25 of annular brazing material 18 may be provided. The taperd portion 25 may have a trapezoidal cross section and may be fixed between the outer surface of tank wall 16 and flange 4b. After caulking, the assembly is placed in a furnace, heated and brazed therein. Annular brazing material 18 is molten during the heating, and the molten brazing material 18 is supplied to the contact portion of fluid pipe 4 and tank wall 16 for brazing. The brazed state is shown in Fig. 4. In this embodiment, because annular brazing material 18 is securely fixed between flange 4b and tank wall 16 before brazing, when the assembly is heated and brazed, the fixed annular brazing material 18 does not shift from the desired position during heating in a furnace, even if vibration occurs. Therefore, a sufficient amount of molten brazing material is always supplied to the connection portion between fluid pipe 4 and tank wall 16, and a good brazing state is achieved therebetween. A strong connection between fluid pipe 4 and tank wall 16 is thereby ensured. Further, because inserted end portion 4c of fluid pipe 4 is outwardly expanded and caulked together with burr 17, the insertion length of end portion 4c of fluid pipe 4 in a direction toward the interior of tank 2 may be minimized. Therefore, any pressure loss in tank 2 caused by the inserted end portion 4c may be minimized as compared with the conventional structure. Further, flange 4b of fluid pipe 4 comes into contact with the outer surface of tank wall 16 and caulked end portion 4c of fluid pipe 4 comes into contact with the surface of caulked burr 17 formed on tank wall. Therefore, fluid pipe 4 comes into contact with tank wall 16 over a sufficiently broad contact area, thereby further increasing the connection strength between fluid pipe 4 and tank wall 16. Further, end portion 4c of fluid pipe 4 is caulked together with burr 17 so that the caulked surface is formed as a curved surface convex toward the interior of tank 2. Therefore, the pressure loss in tank 2 may be minimized as compared with, for example, a concave curved surface. Furthermore, end portion 4c of fluid pipe 4 may be inserted into pipe connection hole 14 so as to extend over tip 30 of burr 17. Also, the inserted end portion 4c is caulked together with burr 17. Therefore, fluid pipe 4 may be extremely securely fixed to tank wall 16. As a result, when heated and brazed, the fluid pipe 4, particularly, fluid introducing port 4a, may be positioned and maintained at a desired position relative to tank member 2a without fixing fluid pipe 4 to tank member 2a using a specified jig. As a result, the manufacturing process may be simplified and the cost for manufacturing heat exchanger 1 may be reduced. Although annular brazing material may have a trapezoidal cross section in the above-described embodiment, the cross-sectional shape is not particularly restricted. For example, an annular brazing material 21 having a triangular cross section before caulking may be employed according to another embodiment depicted in Fig. 7. Also, as a structure before caulking, an annular brazing material 22 having a rectangular cross section before caulking may be employed according to yet another embodiment depicted in Fig. 8. Although several embodiments of the present invention have been described in detail herein, the invention is not limited thereto. Accordingly, the embodiments disclosed herein are by way of example only.

Claims: A heat exchanger (1) comprising: a tank (2,3) including a tank wall (16) having a pipe insertion hole (14, 15) disposed in said tank wall (16), a burr (17) being formed around said pipe insertion hole (14, 15) extending toward an interior of said tank (2, 3); and a fluid pipe (4, 5) brazed to said tank wall (16) for introducing a fluid into said tank (2, 3) or discharging a fluid from said tank (2, 3), characterized in that an inserted end portion (4c) of said fluid pipe (4,5) is caulked together with said burr (17) to the surface of said tank wall (16). The heat exchanger of claim 1, wherein said fluid pipe has a flange (4b) formed on a periphery of said fluid pipe (4, 5), the end portion (4c) of said fluid pipe (4, 5) inserted into said pipe insertion hole (14, 15) so that said flange (4b) contacts an outer surface of said tank wall (16). The heat exchanger of claim 2, wherein said flange (4b) is formed by bending said fluid pipe (4, 5) onto itself, preferably said flange (4b) being formed near a tip of said fluid pipe, said end portion (4c) of said fluid pipe extending over said burr (17). The heat exchanger of one of claims 1 to 3, wherein said end portion (4c) of said fluid pipe (4, 5) is caulked so that a surface of said end portion (4c) facing the interior of said tank (2, 3) forms as a curved surface convex toward the interior of said tank (2, 3). The heat exchanger of one of claims 1 to 4, wherein said tank (2, 3) comprises a first member (2a, 3a) having said tank wall and a second member (2b, 3b) connected to said first member for forming a barrel (2c, 3c) of said tank. A method for manufacturing a heat exchanger (1) having at least a tank (2, 3) and a fluid pipe (4, 5) connected to said tank (2, 3) for introducing a fluid into said tank (2, 3) or discharging said fluid from said tank (2, 3), the method comprising the steps of: forming a burr (17) extending toward an interior of said tank (2, 3) around a pipe insertion hole (14, 15) disposed in a tank wall (16) of said tank (2, 3); forming a flange (4b) on a periphery of said fluid pipe (4, 5); inserting an end portion (4c) of said fluid pipe (4, 5) into said pipe insertion hole (14, 15) so that said flange (4b) contacts an outer surface of said tank wall (16); and caulking said inserted end portion (4c) of said fluid pipe (4, 5) together with said burr (17) to the surface of said tank wall (16), and brazing the fluid pipe (4, 5) to the tank wall (16) after said caulking step. The method of claim 6, wherein the annular brazing material (18) has a trapezoidal cross section, or a triangular cross section, or a rectangular cross section. The method of claims 6 or 7, wherein said inserting step comprises inserting the end portion (4c) of the fluid pipe (4, 5) into the pipe insertion hole (14, 15) to extend over the burr (17). The method of claim 6, wherein said caulking step comprises caulking inserted end portion (4c) of the fluid pipe (4, 5) so that a surface of the caulked end portion facing the interior of the tank (2, 3) forms a curved surface convex toward said interior of the tank (2, 3) and/or said forming step of the flange (4b) comprises a step of bending the fluid pipe (4, 5) onto itself.

Inventors: KADO HIROTAKA, WATANABE AKIMICHI, KADO, HIROTAKA, WATANABE, AKIMICHI
Applicants: SANDEN CORP, SANDEN CORPORATION
Application year: 1996
Main classification: F28F9
IPC codes: F28F9, B21D53