Method of manufacturing heat exchanger and heat exchanger

Abstract

A heat exchanger has a core including tubes and a core plate coupled to the core. The core plate has a coupling wall on which tube insertion holes are formed for receiving ends of the tubes. The coupling wall has an end portion and a clearance portion both coupled to the tubes. The clearance portion is integrally connected to the end portion and spaced from an imaginary plane, on which the end portion is located. A paste brazing material is applied to a joining portion between the core plate and each tube by a brazing material applying device through a space provided between the clearance portion and the imaginary plane.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2006-21666, filed on Jan. 31, 2006, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a method of manufacturing a heat exchanger and a heat exchanger manufactured by the method.

BACKGROUND OF THE INVENTION

In general, a heat exchanger has a core constructed of a stack of tubes and fins and a pair of header tanks at ends of the core. For example, in Japanese Unexamined Patent Publication No. 2005-118826 (US 2005/0082350), a header tank is constructed of a tank main body and a core plate. The core plate has a substantially box shape with a closed end on one side and an open end on the other side. The core plate is joined to the tank main body such that the open end engages with the tank main body. The core plate is formed with tube insertion holes on a plate portion of the closed end. Ends of the tubes are inserted in and brazed to the tube insertion holes.

In such a heat exchanger, a core plate and ends of tubes are for example brazed in the following manner. First, a paste brazing material is applied adjacent to the tube insertion holes of the core plate. Next, the tubes and the core plate are preliminarily fixed by inserting the ends of the tubes into the tube insertion holes of the core plate. Thereafter, the preliminarily fixed tubes and core plate is heated. Thus, the brazing material melts and flows into joining portions between the tubes and the core plate. Accordingly, the core plate and the tubes are brazed.

In the above brazing method, since the paste brazing material is applied beforehand, it will be displaced or drop when inserting the ends the tubes to the tubes insertion holes. Further, since the paste brazing material is applied adjacent to the tube insertion holes, it is concerned that the paste brazing material will not be distributed sufficiently and entirely in the joining portions during the heating. These issues result in decrease of brazability.

To solve the above issues, the paste brazing material may be directly applied to the joining portions after the core plate and the tubes are preliminarily fixed. In this case, however, it has been found difficult to apply the paste brazing material to the joining portions by using a brazing material applying device having a straight end, such as a general dispenser.

FIG. 11 shows an example when a paste brazing material is applied by a dispenser 200 having a straight end. In general, ends of fins 921 disposed between tubes 922 are located adjacent to a core plate 911 to provide sufficient heat exchanging performance. Therefore, the straight end of the dispenser 200 interferes with the ends of the fins 921, as shown by double dashed line in FIG. 11. It is difficult to enter the end of the dispenser 200 to a predetermined portion between the tubes 922. In a case that the end of the fin 921 is not formed at a position close to the core plate 911, it is easy to apply the brazing material. However, this causes a decrease of heat exchanging performance.

SUMMARY OF THE INVENTION

The present invention is made in view of the foregoing matter, and it is an object of the present invention to provide a method of manufacturing a heat exchanger with an enhanced brazability between a core plate and tubes, which does not cause a decrease in a heat exchanging capacity, and a heat exchanger manufactured by the method.

According to an aspect of the present invention, a heat exchanger has a core plate and tubes. The core plate has a coupling wall formed with tube insertion holes. The coupling wall includes an end portion and a clearance portion. The clearance portion is spaced from an imaginary plane on which the end portion is located. The tube insertion holes are formed across the clearance portion and the end portion. The core plate is preliminarily fixed to the tubes by inserting ends of the tubes into the tube insertion holes of the core plate. Then, a paste brazing material is applied to joining portions between the core plate and the tubes by a brazing material applying device. Thereafter, the preliminarily fixed core plate and tubes are heated, thereby brazing the joining portions.

In the core plate, since the clearance portion is spaced from an imaginary plane on which the end portion is located, a space is provided between the clearance portion and the imaginary plane. Therefore, the paste brazing material is applied to the joining portion by entering an end of the brazing material applying device in the space provided by the clearance portion. Thus, interference of the brazing material applying device with fins between the tubes reduces. Accordingly, brazability improves without reducing a heat exchanging capacity.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings, in which like parts are designated by like reference numbers and in which:

FIG. 1 is a schematic front view of an intercooler as a heat exchanger according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view of a part of the intercooler taken along a line II-II in FIG. 1;

FIG. 3 is a schematic cross-sectional view of a joining portion between a core plate and a tube of the intercooler when viewed along a longitudinal direction of the tube in FIG. 2;

FIGS. 4A to 4C are explanatory cross-sectional views for showing manufacturing steps of the intercooler according to the embodiment;

FIGS. 5A to 5C are explanatory cross-sectional views for showing manufacturing steps of the intercooler when taken along a line V-V in FIG. 3;

FIG. 6 is a schematic cross-sectional view for showing a portion to which a paste brazing material is applied according to the embodiment;

FIG. 7 is a schematic cross-sectional view of a part of an intercooler according to another embodiment of the present invention;

FIG. 8 is a schematic cross-sectional view of a part of an intercooler according to further another embodiment of the present invention;

FIG. 9 is a schematic cross-sectional view of a part of an intercooler according to still another embodiment of the present invention;

FIG. 10 is a schematic cross-sectional view of a part of an intercooler according to yet another embodiment of the present invention; and

FIG. 11 is a schematic cross-sectional view for showing an example of a paste brazing material applying step in a manufacturing process of a heat exchanger as a related art.

DETAILED DESCRIPTION OF EMBODIMENT

An embodiment of the present invention will now be described with reference to FIGS. 1 to 6. FIG. 1 shows an intercooler 100 that cools air having been pressurized in a supercharger before the air sucked into an engine, as a heat exchanger.

The intercooler 100 has a core 120 and a pair of header tanks 110. The core 120 has tubes 122, outer fins 121 for radiating heat and side plates 124 as core reinforcement members. The tubes 122 and the outer fins 121 are alternately stacked, and the side plates 124 are joined to outer fins 121 that are located at ends (upper and lower ends in FIG. 1). The tubes 122, the outer fins 121 and the side plates 124 are integrally brazed.

The header tanks 110 are arranged at ends 122a of the tubes 122 (left and right ends in FIG. 1). Each of the header tanks 110 extends in a direction perpendicular to a longitudinal direction of the tubes 122 and in communication with passages defined in the tubes 122. As shown in FIG. 2, the tube ends 122a are inserted in and brazed to tube insertion holes 111a formed on the header tanks 110 with a brazing material 220.

Each tube 122 has a substantially flat tubular shape, and an inner fin (not shown) is brazed inside of the tube 122. Also, the outer fins 121 are brazed to an outside of the tube 122. The inner fins and the outer fins 121 are for example made of copper in view of thermal conductivity and the like. The tubes 122 and the side plates 124 are for example made of copper alloy in view of strength, thermal conductivity and the like.

As shown in FIG. 2, each header tank 110 has a tank main body 112, a core plate 111 and a bottom wall member (not shown) that provides the bottom of the header tank 110. The tube insertion holes 111a are formed on the core plate 111. The respective components of the header tank 110 are for example formed of copper alloy plates. The core plate 111 and the tank main body 112 are joined to each other such as by brazing or welding to form a tank inside space 110a.

At least the surfaces of the respective components of the header tank 110 are made of copper, a copper alloy material, or a nickel material. For example, the core plate 111 can be formed of a stainless plate member having a copper coating on its surface, so as to have sufficient strength.

One of the header tanks 110 (e.g., a right header tank in FIG. 1) is provided with an inlet joint 113. The other header tank 110 (e.g., a left header tank in FIG. 1) is provided with an outlet joint 114. The inlet joint 113 is coupled to a discharge side of the supercharger (not shown), and the outlet joint 114 is coupled to a suction side of the engine (not shown).

The inlet joint 113 provides an inlet port for introducing air into the right header tank 110. The outlet joint 114 provides an outlet port for discharging air from the left header tank 110.

Each of the header tanks 110 narrows with a distance from the inlet or outlet joint 113, 114. Namely, a sectional area (tank inner space 110a) of each header tank 110 gradually reduces with the distance from the inlet or outlet joint 113, 114 so that the air is substantially uniformly introduced in the tubes 122. Further, stays 130 for fixing the intercooler 100 to a vehicle body, frame member or the like are joined to the outer surfaces of the header tanks 110.

To manufacture the intercooler 100, the respective components of the core 120 are preliminarily fixed with the core plate 111 such as by engaging or using jigs, and then integrally brazed. Then, the tank main bodies 112 and other necessary components are welded to the core plates 111. Here, the tank main bodies 112 and other components may be integrally brazed, instead of welding.

Hereafter, a joining structure and a joining method of the core plate 111 and the tubes 122 will be described in detail with reference to FIGS. 2 to 6. FIG. 3 shows a schematic cross-sectional view of a joining portion between the core plate 111 and the tube 112 when viewed from the right side in FIG. 2.

As shown in FIG. 2, the core plate 111 has a main wall (coupling wall) 110b coupled to the core 120 and a pair of side walls 110c on ends of the main wall 110b. The side walls 110c are joined to ends of the tank main body 112. The ends 111b of the main wall 110b are inclined relative to a direction perpendicular to the longitudinal direction of the tube 122 (up and down direction in FIG. 2). Thus, the ends 111b of the main wall 110b extend in directions separating from a center of the core 120.

Namely, the main wall 110b includes an end portion 111c and clearance portions (ends of the main wall 110b) 111b. The end portion 111c is located on an imaginary plane P1 and coupled to the core 120. The clearance portions 111b are inclined relative to the imaginary plane P1, i.e., spaced from the imaginary plane P1 for providing spaces P2 between the clearance portions 111b and the imaginary plane P1.

As shown in FIG. 3, each tube insertion hole 111a extends from one of the clearance portion 111b to the other clearance portion 111b through the end portion 111c. When the core plate 111 is coupled to the core 120, the boundary between the end portion 111c and the clearance portion 111b is located within the core 120. In other words, the space P2 is also provided within the core 120.

Next, a method of brazing of the core plates 111 and the tubes 122 will be described. First, the core plates 111 having the above described shape and the core 120 are coupled. Specifically, as shown in FIG. 4A, the tube ends 122a are inserted in the tube insertion holes 111a, thereby to preliminarily fix the core 120 and the core plates 111. As shown in FIG. 5A, a burring portion 111e having an inclined surface 111d is formed around each tube insertion hole 111a. The inclined surface 111d is inclined or curved along a tube insertion direction shown by an arrow in FIG. 5A.

Therefore, the tube end 122a is guided along the inclined surface 111d when being inserted into the tube insertion hole 111a. As such, the tube ends 122a are easily inserted in the tube insertion holes 111a. The step shown in FIGS. 4A and 5A corresponds to a preliminarily fixing step.

Next, as shown in FIGS. 4B and 5B, a paste brazing material 210 is applied to the joining portion 122b between the core plate 111 and the tube 122 by using a dispenser 200 as a brazing material applying device. In the example shown in FIG. 4B, the dispenser 200 is a generally used dispenser having a straight end (straight pipe shape).

Since the core plate 111 has the clearance portions 111b, the spaces P2 are provided, as shown in FIG. 2. Therefore, the straight end of the dispenser 200 can enter the spaces defined between the outer fins 121 and the core plate 111 and reach an inner position shown by a double dashed line in FIG. 4B.

In the example shown in FIG. 4B, the end of the dispenser 200 can reach at least the boundary between the clearance portions 111b and the end portion 111c. Thus, as shown by a dashed line in FIG. 6, the paste brazing material 210 can be applied along a part of the joining portion 122b, the part included in the clearance portion 111c.

Accordingly, the paste brazing material 210 can be applied over a relatively wide area of the joining portion 122b. The step shown in FIGS. 4B and 5B correspond to a brazing material applying step (hereafter, applying step).

In the applying step, as shown in FIG. 5B, the paste brazing material 210 is applied between the inclined surface 111d of the burring portion 111c and an outer surface of the tube 122. The brazing material 210 is formed of mixture of alloy powder and high polymeric organic substance binder. For example, the alloy powder contains 75 wt % copper (Cu), 15 wt % tin (Sn), 5 wt % nickel (Ni) and 5 wt % phosphorous (P). The brazing material 210 has a melting point of approximately 600° C.

After the applying step, a preliminarily fixed assembly of the core 120 and the core plates 111 is placed in a reducing atmosphere furnace (not shown) to perform a joining step. FIGS. 4C and 5C shows this joining step.

Specifically, the preliminarily fixed assembly is placed such that a core plane surface is substantially parallel to a horizontal direction. In other words, the preliminarily fixed assembly is placed such that the longitudinal directions of the core plate 111 and the tubes 122 are substantially parallel to the horizontal direction. Also in this case, the preliminarily fixed assembly is placed such that the part of the joining portion 122b to which the brazing material 210 is applied is higher than a middle portion of the joining portion 122b. That is, the preliminarily fixed assembly is placed such that each joining portion 122b is situated in the direction denoted by an up and down arrow in FIG. 6.

Further, reducing gas, e.g., hydrogen (H₂), is introduced into the furnace. The preliminarily fixed assembly is heated in a temperature condition between 600° C. and 800° C.

Thus, oxide films on the respective components of the preliminarily fixed assembly, such as the core plate 111 and the tubes 122, are removed by the phosphorous contained in the brazing material 210 and the reducing gas. Further, as the paste brazing material 210, which has been only applied to the upper portion of the joining portion 122b, melts, the melted brazing material flows into a lower portion of the joining portion 122b to which the paste brazing material 210 has not been applied. Namely, the brazing material can be filled into the brazing material non-applied portion in the joining portion 122b with capillarity.

In the applying step, the paste brazing material 210 is applied between the inclined surface 111d and the outer surface of the tube 122, as shown in FIG. 5B. Therefore, the joining portion 122b between the core plate 111 and the tube 120 is effectively filled with the brazing material 210 in the joining step.

In the embodiment, the core pate 111 has a coefficient of liner expansion smaller than that of the tubes 122. Therefore, the tube 122 relatively moves toward the core plate 111 due to the difference of liner expansion when heated in the joining step, so a clearance of the joining portion 122b reduces. Accordingly, brazability improves.

Further, since the core plate 111 has the clearance portions 111b, it is less likely that the dispenser 200 having the straight end will interfere with the outer fins 121 between the tubes 122. In a case shown in FIG. 11, it is difficult to apply the brazing material to a relatively wide area of the joining portion, because the dispenser 200 will interfere with the outer fin 921. Otherwise, it is necessary to reduce arrangement area of the outer fin 921 at a position adjacent to the core plate 911. However, this may result in a decrease of a heat radiation area.

In the embodiment, the paste brazing material 210 is applied to a relatively wide area in the joining portion 122b by using the space P2 defined by the clearance portions 111b of the core plate 111. It is not necessary to reduce the arrangement area of the outer fin 121. Also, the paste brazing material 210 is applied after the preliminarily fixing step. Therefore, it is not necessary to concern about dropping of the paste brazing material 210 in the preliminarily fixing step. Accordingly, brazability improves without reducing a heat exchanging capacity.

In the embodiment, since the intercooler 100 needs the thermal strength, compressive strength and the like, the components to be brazed have copper or copper alloy at least on those surfaces to improve brazability. Also, the surfaces of the core plate 111 and the tubes 122 can be made of nickel, instead of copper and copper alloy.

In general, members made of copper or copper alloy reduce strength with heat in the joining step. In the embodiment, therefore, the paste brazing material 210 having a relatively low melting point is used so as to set the temperature relatively lower in the joining step.

It is preferable to use a brazing material having the melting point between 550° C. to 700 C. as the paste brazing material 210. When a brazing material having the melting point lower than 550° C. is used, it is difficult to sufficiently maintain the brazing strength. On the other hand, when a brazing material having the melting point higher than 700° C. is used, it is necessary to increase the temperature in the joining step, resulting in the decrease of strength of the components to be brazed.

Further, a copper brazing material having the melting point between 550° C. to 700° C. is delicate and it is difficult to clad on the surface of the components to be brazed. Therefore, it is preferable to use the paste brazing material having the melting point between 550° C. to 700° C.

In the applying step, the paste brazing material 210 is only applied to the part of the joining portion 122b. In the joining step, the preliminarily fixed assembly is placed such that the part to which the paste brazing material 210 is applied is situated higher than the remaining part to which the brazing material 210 is not applied. Thus, the paste brazing material 210 flows downward as melted and the clearance of the joining portion 122b is entirely filled with the brazing material 220. Accordingly, even if the paste brazing material 210 is partly applied, brazability can be maintained.

In the example of FIG. 6, the paste brazing material 210 is applied to the joining portion defined between one clearance portion 111b and the tube 122, and the core plate 111 and the tubes 122 are placed such that the clearance portion 111b to which the brazing material 210 is applied is higher than the end portion Further, since the paste brazing material 210 is not applied to the lower portion of the joining potion 122b, it is less likely that the paste brazing material will overflow from the lower end of the joining portion 122b. Thus, the quality of brazing of the joining portion 122b improves and the amount of brazing material reduces. Also, as compared with a case that the paste brazing material 210 is entirely applied to the joining portion 122b, work-hour in the applying step reduces.

Other embodiments

In the above embodiments, the paste brazing material 210 is only applied to the upper portion of the joining portion 122b. However, the brazing material 210 can be also applied to the lower portion of the joining portion 122b.

The shape of the core plate 111 is not limited to the example shown in FIG. 2 as long as the main wall 110b separates from the center of the core 120 toward its end. In other words, the shape of the core plate 111 is not limited as long as a space for permitting the end of the dispenser 200 is provided. FIGS. 7 and 8 show examples of the shape of the core plate.

In FIG. 7, a core plate 311 has a main wall 310b coupled to the core 120. The main wall 310b is substantially curved or have a substantially arc-shaped cross-section. The main wall 310b has an end portion 311c on the imaginary plane P1 and clearance portions 311b spaced from the imaginary plane P1. The clearance portions 311b have the curved shape. In FIG. 8, a core plate 411 has a main wall 410b coupled to the core 120. The main wall 410b have a substantially V-shaped cross-section. For example, the main wall 410b have an end portion 410c on the imaginary plane P1 and inclined surfaces 411b converging at the end portion 410c. Also in these examples, spaces for entering the dispenser 200 are provided.

Further, in a case that the paste brazing material 210 is applied only to the upper portion of the joining portion 122b, the core plate may have only one clearance portion on the side that is arranged upper side in the joining step. For example, as shown in FIG. 9, a core plate 511 has an end portion 510c on the imaginary plane P1 and a clearance portion 511b inclined relative to the imaginary line P1 to provide a space.

Also, it is not always necessary that two clearance portions have the same inclination angle relative to the imaginary plane P1 as shown in FIG. 2. For example, as shown in FIG. 10, a core plate 611 have an end portion 610c on the imaginary plane P1 and two clearance portions 611b, 611c that are inclined relative to the imaginary plane P1 at different inclination angles. In the joining step, the core plate 611 is placed such that the clearance portion 611b that has a larger inclination angle is located higher than the clearance portion 611c. Further, the core plate may have any other shape.

In the above embodiment, the inclined surface 111d is formed around the perimeter of the tube insertion hole 111a by burring, as shown in FIG. 5B. However, the method of forming the inclined surface 111d is not limited to the burring. For example, the inclined surface 111d may be formed by chamfering.

In the above embodiment, the tubes 122 are flat tubes, and the joining portion 122b have a longitudinal axis in a direction perpendicular to the longitudinal direction of the core plate 111. This structure is effective in view of strength and the like. However, the shape of the tubes 122 is not limited to the flat shape. For example, the tubes 122 may have a substantially circular cross-sectional shape.

Further, it is not always necessary that the tubes 122 and the outer fins 121 are alternately stacked. The core 120 may have another structure. For example, the core 120 may be configured such that tubes intersect plate fins.

In the above embodiment, it is exemplary discussed about the intercooler 100. However, the present invention can be employed to other heat exchangers such as an oil cooler.

In the above embodiment, at least the surfaces of the core plate 111 and the tubes 122 are made of copper, copper alloy or nickel. However, the present invention can be applied to a heat exchanger in which components to be brazed such as core plates and tubes are made of materials other than copper or nickel.

The exemplary embodiments of the present invention are described above. However, the present invention is not limited to the above embodiments, but may be implemented in other ways without departing from the spirit of the invention.

Claims

1. A method of manufacturing a heat exchanger, comprising:

forming a core plate having a coupling wall for coupling to tubes, wherein the coupling wall includes an end portion and a clearance portion, the clearance portion is spaced from an imaginary plane on which the end portion is located, and tube insertion holes are formed across the end portion and the clearance portion;

preliminarily fixing the core plate and the tubes by inserting ends of the tubes into the tube insertion holes of the core plate;

applying a paste brazing material to joining portions between the core plate and the tubes by a brazing material applying device; and

heating the preliminarily fixed core plate and tubes for brazing the joining portions.

2. The method according to claim 1, wherein

the forming includes forming an inclined surface on a perimeter of each tube insertion hole, the inclined surface inclined relative to a direction perpendicular to the imaginary plane, and

in the applying, the paste brazing material is applied between the inclined surface and an outer wall of the tube.

3. The method according to claim 1, wherein the tubes have a substantially flat tubular shape.

4. The method according to claim 1, wherein each of the core plate and the tubes has an outer surface made of one of copper, copper alloy, and nickel.

5. The method according to claim 1, wherein the paste brazing material has a melting point between 550 and 700° C.

6. The method according to claim 1, wherein

in the applying, the paste brazing material is applied to a part of each joining portion, and

in the heating, the core plate is arranged such that the part to which the paste brazing material is applied is located higher than a remaining part of the respective joining portion.

7. The method according to claim 1, wherein the core plate has a coefficient of linear expansion smaller than that of the tubes.

8. The method according to claim 1, wherein

in the applying, the paste brazing material is applied to a part of the joining portion by entering an end of the brazing material applying device in a space defined between the clearance portion and the imaginary plane.

9. The method according to claim 1, wherein

in the applying, the paste brazing material is applied to a part of the joining portion, the part being formed on the clearance portion, and

in the heating, the core plate is arranged such that the clearance portion is located higher than the end portion.

10. The method according to claim 1, wherein the brazing material applying device has a straight end portion.

11. The method according to claim 1, wherein

the preliminarily fixing includes arranging fins between the tubes.

12. A heat exchanger comprising:

a core having tubes and fins; and

a header tank having a core plate, the core plate having a coupling wall formed with tube insertion holes, wherein ends of the tubes are received in and brazed with the tube insertion holes, wherein the coupling wall includes an end portion and a clearance portion, the end portion is located on an imaginary plane, and the clearance portion is spaced from the imaginary plane.

13. The heat exchanger according to claim 12, wherein

the tube insertion holes extend across the clearance portion and the end portion, and

the clearance portion is at least partly located within the core.

14. The heat exchanger according to claim 12, wherein

the imaginary plane is perpendicular to a longitudinal direction of the tubes, and

the clearance portion is inclined relative to the imaginary plane.

15. The heat exchanger according to claim 12, wherein the clearance portion has a curved wall.