Heat exchanger

Abstract: A heat exchanger includes a tank (1) and a base plate (2), and each of the tank and the base plate is formed in a box shape having a U-shaped cross-section. The tank is connected to the base plate to close an end portion of an opening side of the tank using the base plate. Protrusion portions (15) are provided inside a folded portion of the base plate in a lateral direction to be opposite to connection portions of first and second folded portions of the tank. Further, ribs (16) are provided in the folded portion of the base plate in the lateral direction to increase stiffness of the base plate in a longitudinal direction thereof. Thus, connection portions of the tank and the base plate can be securely brazed.

Description: 1. Field of the Invention: The present invention relates to a heat exchanger according to the preamble of claim 1. 2. Description of Related Art: Such a heat exchanger is disclosed in EP-A-0 718 580. Conventionally, inventors of the present invention have proposed, as disclosed in JP-A-8-226786 (EP 0718580 A1), to manufacture the heat exchanger in a low cost and to reduce the number of assembling steps. The heat exchanger includes a tank 1 and base plate 2 as shown in FIG. 10. In the heat exchanger, unfolded metal plates are respectively folded and the folded portions are connected to each other to form the tank 1 and the base plate 2. However, in the heat exchanger, connection surfaces are formed at folded portions of the tank 1 to ensure a connection area to be brazed. When the base plate 2 is connected to an opened end portion of the tank 1, a clearance 51 is formed in an connection portion A as shown in FIG. 11. Further, a claw portion 3 for receiving an insert plate for holding a core portion of the heat exchanger is provided on a folded portion of the base plate 2 in lateral direction (i.e., a short side portion) as shown in FIG. 10. Since a brazing material is clad on the core portion before brazing, the insert plate may extend outwardly in a longitudinal direction of the base plate so that the claw portion 3 may extend outwardly in the longitudinal direction of the base plate. Therefore, the folded portion of the base plate in the lateral direction also extends outwardly in the longitudinal direction of the base plate 2 so that the clearance 51 shown in FIG. 11 is further enlarged. Thus, the tank 1 and the base plate 2 cannot be securely connected and brazed to each other. SUMMARY OF THE INVENTION In view of the foregoing problems, it is an object of the present invention to provide a heat exchanger in which a tank and a base plate are securely connected and brazed to each other sufficiently. This problem is solved by the features cited in the characterising part of claim 1 and in claim 10. According to the present invention, a protrusion protrudes from an inner wall of the base plate to be opposite to a connection portion between folded portions of the tank. Therefore, a clearance formed between an outside of the connection portion of the folded portions of the tank and an inside of the base plate is greatly decreased to securely braze a joined portion between the tank and the base plate. Preferably, a rib for increasing stiffness of the base plate in a longitudinal direction is provided in a claw portion formed on a folded portion of the base plate in the lateral direction. Therefore, even if a force extending outwardly in a longitudinal direction of the base plate is applied to the base plate before brazing, the folded portion of the base plate is not bent outwardly by forming the rib. Thus, the clearance between the tube and the base plate is not enlarged in assembling process of the heat exchanger, and a brazing between the tube and the base plate can be securely performed. BRIEF DESCRIPTION OF THE DRAWINGS Additional objects and advantages of the present invention will be more readily apparent from the following detailed description of preferred embodiments when taken together with the accompanying drawings, in which: FIG. 1 is a perspective view showing a heat exchanger according to a preferred embodiment of the present invention; FIG. 2 is a plan view showing a metal plate forming a tank of the heat exchanger shown in FIG. 1; FIG. 3 is an exploded view showing an assembly of the tank and a base plate in FIG. 1; FIG. 4 is a plan view showing a metal plate forming the base plate in FIG. 1; FIG. 5 is a perspective view showing a connection state of the tank and the base plate according to the first embodiment; FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5; FIG. 7 is a perspective view showing the tank when viewed from an inside of the tank in FIG. 1; FIG. 8 is a bottom view showing the base plate in FIG. 5; FIG. 9 is a side view showing the base plate in FIG. 5; FIG. 10 a perspective view showing a conventional connection state of a tank and a base plate; and FIG. 11 is a cross-sectional view taken along line XI-XI in FIG. 10. DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS A preferred embodiment of the present invention will described hereinafter with reference to the accompanying drawings. As shown in FIG. 1, a heat exchanger includes a tank 1 formed in a U-shape in a cross-section thereof and a base plate 2 connected to an opening end portion of the tank 1. The base plate 2 is also formed in a U-shape in a cross-section thereof. A plurality of tube receiving holes 4 are provided on the base plate 2 in such a manner that a longitudinal direction of the flat holes 4 for receiving the tubes is parallel to a lateral direction of the base plate 2. A cross-section of a flat tube 5 is formed in a flat shape, and each end portion of the flat tube 5 is inserted into and joined with the tube receiving holes 4 of the base plate 2. A plurality of corrugated fins 6 are formed in a wavy shape and are disposed between the flat tubes 5 to be joined with the flat tubes 5. Both insert plates 7 are respectively disposed at both side portions of a core portion (i.e., heat exchanging portion) having the flat tubes 5 and the corrugated fins 6 and are connected to the base plates 2 and the corrugated fins 7. An inlet pipe 8 for warm water (e.g., engine cooling water) is inserted into and connected to a hole (not shown) provided at the tank 1. An outlet pipe 9 for cooled water (e.g., engine cooling water) is inserted into and connected to a hole (not shown) provided at the tank 1. Since a structure of the heat exchanger in FIG. 1 is a symmetrical structure with respective to the left and right direction, the positions of inlet pipe 8 and the outlet pipe 9 may be changed. In this embodiment, the heater core shown in FIG.1 is structured by an aluminum heat exchanger integrally connected by brazing. Although the corrugated fins 6, the inlet pipe 8 and the outlet pipe 9 are made of aluminum bare material in which a brazing material is not clad, other materials (1, 2, 5 and 7) are made of an aluminum clad material in which a brazing material is clad at both sides of the aluminum core material. FIG. 2 shows an unfolded state of a metal plate forming the tank 1. An unfolded metal plate 13 has a rectangular body portion 13a, and first folded portions 13f are formed in the body portion 13 along a long side portion thereof. Further, second folded portions 13b protruding from short side portions of the body portion 13a are formed. A plurality of semicircular protrusions 13c are formed proximate to long ends of body portion 13a. Connection surfaces 13d for ensuring brazing by increasing a connection area to be brazed are formed at both outer edge portions formed in a vertical direction of the second folded portions 13b. After a flat metal plate is cut into an unfolded shape shown in FIG. 2 by a pressing process, the unfolded metal plate 13 for the tank 1 is formed in a tank shape shown FIG. 3, that is, a tank shape (i.e., box shape) having a U-shaped cross section. As shown in FIGS. 2 and 3, by folding the first and second folded portions 13f and 13b and the connection surface 13d at a ridgeline 13e shown with dotted lines in FIG. 2, the tank where one end side is opened and another end side is closed is formed. The connection surfaces 13d of the second folded portions 13b contact inner surfaces of the first folded portions 13f to increase the brazing area therebetween. Therefore, the ridgeline 13e of the first folded portion 13f is offset outwardly from the ridgeline 13e of the connection surface 13d by a plate thickness d1 of the unfolded metal plate 13. As shown in FIG. 4, an unfolded metal plate 14 for the base plate has the same shape as the unfolded metal plate 13 for the tank. The unfolded metal plate 14 includes a rectangular body portion 14a, first folded portions 14b and second folded portions. The first folded portions 14b are formed along a long side portion of the body portion 14a, and the second folded portions 14c are formed to protrude from short side portions of the body portion 14a. A plurality of semicircular concave portions are formed on the first folded portions 14b of the body portion 14a to correspond to the semicircular protrusions 13c of the unfolded metal plate 13. In FIG. 4, a dotted line 14e illustrates a ridgeline as a folding position of the first and second folded portions 14b and 14c. End portions in the longitudinal direction of the second folded portion 14c are offset outwardly from the dotted line 14e of the first folded portions 14b by a plate thickness d2 of the unfolded metal plate 14. Therefore, after folding the first and the second folded portions 14b and 14c, the second folded portions 14c can be folded on end surfaces of the first folded portions (see FIG. 3). Thus, the second folded portions 14c can be securely brazed on the end surfaces of the first folded portions 14b. After cutting the metal plate 14 into the unfolded shape in FIG. 4 by a pressing process, the first and second folded portions 14b and 14c are folded along the dotted line 14c so that the metal plate 14 is formed in a shape shown in FIG. 3, i.e., a box shape in which one end side is closed and another end side is opened. Since the second folded portions 14c are folded on the end surfaces of the first folded portions 14b, a brazing area between the first and second folded portions 14b and 14c is increased to sufficiently braze therebetween. As shown in FIG. 3, the tank 1 and the base plate 2 are assembled in such a manner that the first and second folded portions 13f and 13b of the tank are inserted into inner peripheral sides of the first and second folded portions 14b and 14c of the base plate 2. At this time, by fitting the semicircular protrusions 13c of the tank 1 into the semicircular concave portions 14c of the base plate 2, an assembled state of the tank 1 and the base plate 2 can be maintained to prevent the tank 1 and the base plate 2 from being separated after being assembled together. Next, a main portion of the heat exchanger of the present invention will be described with reference to FIGS. 5 through 9. As shown in FIGS. 5 and 6, protrusion portions 15 are formed inside the second folded portions 14c of the base plate 2, and the protrusion portions 15 protrude from the second folded portions 14c of the base plate 2 to be opposite to a position where the first and second folded portions 13f and 13b are connected to each other. The protrusion portions 15 are formed by an ironing process at the same time as the folding step of the base plate 2. By the protrusion portions 15, clearances (51) formed at connection portions between the first and second folded portions 13f and 13b of the tank 1 are filled. Therefore, a brazing between the tank 1 and the base metal 2 can be securely performed. Further, four concave portions are formed in the second folded portion 14 of the base plate 2 to form four ribs 16. By the ribs 16, a rigidity of the base plate 2 in the longitudinal direction thereof can be improved. Even if the insert plate 7 is inserted into the claw portions 3 so that the insert plate 7 extends outwardly in the longitudinal direction of the tube 1 before brazing, the second folded portion 14c of the base plate 2 is not bent outwardly by forming the ribs 16 due to the concave portions. Thus, in this embodiment, the clearances 51 (see FIG. 11) formed at a connection portion between the first and second folded portions 13f and 13b of the tank 1 is not further enlarged. Therefore, a brazing between the tank 1 and the base metal 2 can be securely performed. The ribs 16 due to the concave portions are formed by a coining process or a press process in an unfolded metal plate before folding the base plate 2. Further, as shown in FIG. 9, the claw portions 3 for receiving the insert plate 7 are formed on the second folded portion 14 of the base plate 2, and a concave portion 18 is formed in each claw portion 3. By the concave portions 18, the rigidity of the claw portion 3 is increased, and the insert plate 7 is accurately set to prevent the insert plate 7 from being shifted in the lateral direction of the tank 1 when the insert plate 7 is inserted into the claw portions 3. In this case, small holes are formed at an end portion of the insert plate 7 to engage with the convex portions 18. Although the present invention has been fully described in connection with preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. For example, in the first embodiment, on the connection surface of the tank 1 and base plate 2, the connection surface is provided in the second folded portion 13b of the tank 1 and the protrusion portion 15 is provided inside the second folded portion 14b of the base plate 2. However, a connection surface may be provided in the first folded portion 13a of the tank 1 and the protrusion portion 15 may be provided at a position of the first folded portion 14a of the base plate 2 to be opposite to the connection surface. In this case, the ribs 16 formed in the second folded portion 14b of the base plate 2 may be formed in the first folded portion 14a of the base plate 2. The present invention is not limited to a heater core for a heater and can be used widely in a heat exchanger for an automotive radiator or the like. Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims.

Claims: A heat exchanger comprising: a tank (1) having a box shape which is U-shaped in cross section and in which one end side is closed and another end side is opened, said tank including first and second folded portions (13f, 13b) connected to each other to form a connection portion, having a clearance (51) formed between said connecting portion of said first and second folded portions (13f, 13b) of said tank (1); a base plate (2) having a box shape which is U-shaped in cross section and in which one end side is closed and another end side is opened, said base plate is connected to said tank to cover said opened side of said tank, said base plate including first and second folded portions (14b, 14c) fixed to said first and second folded portions (13f, 13b) of said tank and a bottom portion having a hole (4) therein; wherein said folded portions (13f, 13b) of said tank (1) are inserted into inner peripheral surfaces of said folded portions (14b, 14c) of said base plate (2); a tube (5) inserted into said hole of said base plate and fixed to said base plate to communicate with said tank; characterized by a protrusion (15) protruding from an inner surface of the second folded portion (14c) of said base plate (2) to be opposite to said connection portion between said folded portions (13f, 13b) of said tank, wherein the protrusion (15) fills the clearance (51) in order to improve a brazing joint between the tank and the base plate. A heat exchanger according to claim 1, wherein each of said tank and said base plate is made from an unfolded metal plate (13 and 14) by folding. A heat exchanger according to claim 2, wherein said unfolded metal plate includes: a rectangular body portion (13a and 14a) having a pair of first sides and a pair of second sides, a length of each first side being larger than that of each second side; a pair of first folded portions (13f and 14b) formed along said first sides of said body portion; a pair of second folded portions (13b and 14c) formed along said second sides of said body portion, wherein said first and second folded portions are folded and connected to each other to form a box shape. A heat exchanger according to claim 3, wherein said folded portion of said unfolded metal plate (13, 14) has a connection surface connecting between said tank (1) and said base plate (2). A heat exchanger according to claim 4, wherein said connection surface is provided at said second folded portion (13b) of said unfolded metal plate (13) for said tank (1). A heat exchanger according to claim 3, wherein said protrusion (15) is provided at said second folded portion (14c) of said unfolded metal plate (14) for said base plate (2). A heat exchanger according to claim 3, further comprising: an insert plate (7) for holding said tube; and a claw portion (3) for receiving said insert plate therein, wherein said claw portion is provided on said second folded portion of said unfolded metal plate for said base plate. A heat exchanger according to claim 3, wherein said second folded portion (14c) of said unfolded metal plate (14) for said base plate (2) has a rib (16) for increasing rigidity of said base plate in a longitudinal direction thereof. A heat exchanger according to claim 7, wherein said claw portion has a concave portion (18). A method for manufacturing a heat exchanger including a box-shaped tank (1) having first and second folded portions (13f, 13b) connected to each other to form a connection portion having a clearance (51) between connection portions of said folded portions (13f, 13b), a box-shaped base plate (2), and a tube (5), said method comprising: cutting a first metal plate (13) for forming said box-shaped tank; cutting a second metal plate (14) for forming said base plate and making a hole (4) through which said tube is inserted to communicate with said tank; folding said first metal plate (13) along a predetermined folding line to form said tank (1) into a box shape which is U-shaped in cross section and in which one end side is closed and another end side is opened; folding said second metal plate (14) along a predetermined folding line to form said base plate (2) into a box shape which is U-shaped in cross section, and in which one end side is closed and another end side is opened, and forming a protrusion (15) on said second metal plate to be opposite to said connection portion between said folded portions (13f, 13b) of said tank; inserting an end portion of said tube (5) into said hole of said base plate (2) and assembling said tank (1) with said base plate to cover said opening of said tank, wherein said folded portions (13f, 13b) of said tank are inserted to inner peripheral surfaces of said folded portions (14b, 14c) of said base plate, and wherein the protrusion (15) fills the clearance (51); and brazing said tank and said base plate and said tube integrally to make an assembled body. A method for manufacturing a heat exchanger according to claim 10, wherein said folding of said second metal plate and said forming of said protrusion are performed simultaneously.

Inventors: AKI YOSHIFUMI, FUKUOKA MIKIO, SUGIMOTO NAOKI, AKI, YOSHIFUMI, FUKUOKA, MIKIO, SUGIMOTO, NAOKI
Applicants: DENSO CORP, DENSO CORPORATION
Application year: 1997
Main classification: F28F9
IPC codes: F28F9