US20070039717A1

US20070039717A1 - Heat exchanger unit and method of manufacturing the same

Info

Publication number: US20070039717A1
Application number: US11/502,497
Authority: US
Inventors: Mitsuharu Inagaki; Jun Abei; Kenta Gocho; Takao Ikeda; Toshiyuki Shoji; Shizuo Maruo
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2005-08-19
Filing date: 2006-08-10
Publication date: 2007-02-22
Also published as: DE102006038463A1; JP4552805B2; JP2007053307A

Abstract

A heat exchanger unit has tubes each having a body section and at least one of an inner pipe section and an outer pipe section extending from the body section and defining an opening at an end. Each of the inner pipe section and the outer pipe section has a first portion and a second portion adjacent to the first portion. The tubes are stacked such that the body sections are spaced from each other. Further, the inner pipe section is received in the outer pipe section such that the first portion of the inner pipe section overlaps the first portion of the outer pipe section, and the second portions of the inner and outer pipe sections are located on opposite sides of the overlapped first portions. The first and second portions of the inner pipe section have an outer diameter smaller than an inner diameter of the first and second portions of the outer pipe section.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2005-238869 filed on Aug. 19, 2005, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a heat exchanger unit and a method of manufacturing the same.

BACKGROUND OF THE INVENTION

For example, a stacked-type heat exchanger unit 9 shown in FIG. 20 is known. In the heat exchanger unit 9, electronic components 4 are arranged between the tubes 92 to be cooled by a heat medium flowing in the tubes 92 through side surfaces thereof. This kind of heat exchanger unit is for example disclosed in Japanese Patent Publication No. 2001-320005.
In the heat exchanger unit 9, ends of the tubes 92 are connected to a first header 94 and a second header 95. Because the first header 94 and the second header 95 are provided as individual parts, the number of parts increases. As such, manufacturing costs are likely to increase.
Further, the tubes 92 are fixed to the first header 94 and the second header 95. Therefore, it is difficult to change spaces between adjacent tubes 92. With this, it is difficult to insert the electronic components 4 between the tubes 92 so that both of the side surfaces of the electronic components 4 properly contact the tubes 92.
Another stacked-type heat exchanger unit is known, as shown in FIG. 21. In the heat exchanger unit 90 shown in FIG. 21, tubes 92 are arranged such that electronic components 4 are interposed between the adjacent tubes 92. Further, communication members 93 are disposed between the tubes 92 so that the tubes 92 communicate with each other through the communication members 93. This kind of heat exchanger unit is for example disclosed in Japanese Patent Publication No. 2002-26215.
Also in this heat exchanger 90, the tubes 92 and the communication members 93 are provided as individual parts. It is necessary to connect the communication members 93 to the tubes 92. As such, manufacturing costs are likely to increase. Further, it is difficult to improve productivity.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, a heat exchanger unit has a plurality of tubes each having a flat body section and at least one of an inner pipe section and an outer pipe section extending from the body section in a direction perpendicular to an axis of the body section and defining an opening at an end. The body section defines a passage through which a heat medium flows. Each of the inner pipe section and the outer pipe section has a first portion and a second portion adjacent to the first portion. The first portion and the second portion of the inner pipe section have an outer diameter smaller than an inner diameter of the first portion and the second portion of the outer pipe section.
The tubes are stacked such that the body sections are spaced from each other for performing heat exchange between the heat medium and an object existing between the adjacent body sections, and the inner pipe section is received in the outer pipe section, to thereby form a header part for permitting communication between the adjacent body sections. Also, the inner pipe section is received in the outer pipe section such that the first portion of the inner pipe section overlaps the first portion of the outer pipe section, and the second portions of the inner pipe section and the outer pipe section are located on opposite sides of the overlapped first portions in an axial direction of the inner pipe section and the outer pipe section.
Accordingly, the passages of the adjacent tubes are communicated with each other through the inner pipe sections and the outer pipe sections, which are coupled to each other. As such, it is not necessary to use an additional member for coupling the adjacent tubes. Thus, the number of parts reduces and manufacturability improves.
Also, the inner pipe section and the outer pipe section are coupled by joining side walls thereof. As such, the header part has an inner diameter substantially equal to the inner diameter of the inner and outer pipe sections. Therefore, flow resistance in the header part is reduced, and pressure loss in the header part is suppressed. Accordingly, the heat medium can be distributed substantially equally into the plural tubes. As a result, heat exchange is properly performed.
Further, the inner pipe section has the second portion that has the outer diameter smaller than the inner diameter of the first portion of the outer pipe section. Similarly, the outer pipe section has the second portion that has the inner diameter larger than the outer diameter of the first portion of the inner pipe section. Therefore, the inner pipe section and the outer pipe section do not have portions that contact and push each other in the axial direction of the inner pipe section and the outer pipe section while the inner pipe section is inserted in the outer pipe section.
Accordingly, it is less likely that the inner pipe section and the outer pipe section will receive loads in the axial direction. Even if the lengths of the inner pipe sections and the outer pipe sections are slightly uneven, loads in the axial direction are reduced. Further, it is less likely that the inner pipe section, the outer pipe section and portions on the periphery of the inner pipe section and the outer pipe section will receive stress and be deformed unnecessarily while the tubes are stacked.
According to a second aspect of the present invention, a heat exchanger unit has a plurality of tubes each having a flat body section and at least one of an inner pipe section and an outer pipe section extending from the body section in a direction perpendicular to an axis of the body section and defining an opening at an end. The body section defines a passage through which a heat medium flows. The outer pipe section has a flange portion at the end. An end of the flange has a diameter larger than an inner diameter of a remaining portion of the outer pipe section.
The tubes are stacked such that the inner pipe section is inserted in the outer pipe section in a condition that a brazing material is disposed between the flange of the outer pipe section and the inner pipe section. When the brazing material is melted and then hardened, an outer side wall of the inner pipe section and an inner side wall of the outer pipe section are brazed to each other.
Since the outer pipe section has the flange, the brazing material is easily held by the flange while the inner pipe section is inserted in the outer pipe section. Furthermore, the brazing material can easily flow between the outer side wall of the inner pipe section and the inner side wall of the outer pipe section. Accordingly, the adjacent tubes are easily and properly joined to each other.
For example, electronic components can be arranged between the body section of the tubes, as the object for heat exchange. As such, the heat exchanger unit according to the first aspect and the second aspect can provide an electronic component cooling unit, manufactured with a reduced cost.

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 plan view of a heat exchanger unit having a heat exchanger and electronic components according to a first example embodiment of the present invention;
FIG. 2 is a cross-sectional view of a header part of the heat exchanger according to the first example embodiment;
FIG. 3 is a schematic cross-sectional view of a joint portion between an inner pipe section and an outer pipe section, which construct the header part, according to the first example embodiment;
FIG. 4 is a schematic cross-sectional view of a flange of an outer pipe section having a taper shape according to a modification of the first example embodiment;
FIG. 5 is a schematic cross-sectional view of a flange of an outer pipe section including a perpendicular flat wall according to another modification of the first example embodiment;
FIG. 6 is a schematic cross-sectional view of a flange of an outer pipe section including a bent portion according to further another modification of the first example embodiment;
FIG. 7 is a perspective view of a tube of the heat exchanger, partly including a cross-section, according to the first example embodiment;
FIG. 8 is an explanatory side view of tubes before the tubes are coupled together according to the first example embodiment;
FIG. 9 is an explanatory side view of the tubes when the tubes are coupled together according to the first example embodiment;
FIG. 10A to 10D are schematic cross-sectional views of a part of the heat exchanger for showing manufacturing steps, in which FIG. 10A shows a condition that the tubes are coupled through a spacing jig between them; FIG. 10B shows a condition that the tubes have been brazed; FIG. 10C shows a condition that an electronic component is placed between the tubes; and FIG. 10D shows a condition that the electronic component is held between the tubes;
FIG. 11 shows a schematic cross-sectional view of an introduction pipe and an inlet port of the heat exchanger according to the first example embodiment;
FIG. 12 is a schematic view of a part of a heat exchanger adjacent to a header part according to a second example embodiment of the present invention;
FIG. 13 is a schematic view of a part of a heat exchanger adjacent to a header part according to a third example embodiment of the present invention;
FIG. 14 is a schematic view of a part of a heat exchanger adjacent to a header part according to a fourth example embodiment of the present invention;
FIG. 15 is a plan view of a plate including a pair of outer plates for a tube of a heat exchanger according to a fifth example embodiment of the present invention;
FIG. 16 is a cross-sectional view of the plate taken along line XVI-XVI in FIG. 15;
FIG. 17 is a schematic view of a part of a heat exchanger adjacent to a header part according to the fifth example embodiment of the present invention;
FIG. 18 is a schematic view of a part of a heat exchanger adjacent to a header part according to a sixth example embodiment of the present invention;
FIG. 19 is a schematic cross-sectional view of a part of a heat exchanger adjacent to a header part as a comparative example;
FIG. 20 is a side view of a stacked-type heat exchanger unit of a prior art; and
FIG. 21 is a cross-sectional view of a stacked-type heat exchanger unit of another prior art.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT

First Example Embodiment

A first example embodiment of a heat exchanger unit 10 will be described with reference to FIGS. 1 through 11. The heat exchanger unit 10 of the first example embodiment has a heat exchanger 1 through which a heat medium 5 flows. The heat exchanger unit 10 performs heat exchange between the heat medium 5 and a heat exchanging object existing between tubes 2 of the heat exchanger 1. For example, electronic components 4 are disposed between the tubes 2 as the heat exchanging object. This heat exchanger unit 10 for example constructs a part of a power conversion apparatus.
As shown in FIG. 1, the heat exchanger 1 is formed of a stack of tubes 2. The electronic components 4 are arranged between the adjacent tubes 2. Each of the electronic components 4 has a flat rectangular parallelepiped shape. The electronic component 4 for example includes a power element therein for controlling high power. Although not illustrated, an electrode for power supply extends from one of longitudinal side walls of the electronic component 4 and an electrode for controlling the power extends from the opposite longitudinal side wall of the electronic component 4.
Further, the electronic components 4 are interposed between the tubes 2 such that a first main surface and a second main surface of each electronic component 4 are in contact with outer surfaces of the tubes 2. As such, the electronic components 4 are cooled by the heat medium 5 flowing in the tubes 2 through the first and second main surfaces. Namely, the electronic components 4 and the tubes 2 are alternately arranged. Further, end tubes 2 are disposed at both ends of the stack of tubes 2 and electronic components 4.
Also, the heat exchanger 1 forms a supply header part (hereafter, a first header part) 11 and a discharge header part (hereafter, a second header part) 12 at ends of the tubes 2. The adjacent tubes 2 communicate with each other through the first header part 11 and the second header part 12.
In the heat exchanger 1, the tubes 2 are stacked such that the electronic components 4 are sandwiched from both sides. Each of the tubes 2 has a body section and projecting pipe sections 22 at ends of the body section. The body section has generally a flat tubular shape and defines a passage 21 therein through which the heat medium flows 5.
The projecting pipe sections 22 project from the body section in a direction generally perpendicular to a longitudinal axis of the body section. In other words, the projecting pipe sections 22 project in a direction parallel to a stacking direction (up and down direction in FIG. 1) of the tubes 2. Each of the projecting pipe section 22 forms an opening that opens in the stacking direction at an end. The first header part 11 and the second header part 12 are formed by coupling the projecting pipe sections 22 of the adjacent tubes 2 and joining side walls of the projecting pipe sections 22. FIG. 2 shows a manufacturing step of the heat exchanger 1. In the illustrated step, spacing jigs 6 are placed between the adjacent tubes 2.
The passages 21 of the adjacent body sections communicate with each other through the first header part 11 and the second header part 12. For example, the heat medium 5 is distributed into the passages 21 from the first header part 11. The heat medium 5 having passed through the passages 21 flows into the second header part 12 and is discharged from the heat exchanger 1.
As shown in FIGS. 2 and 3, each tube 2, except the end tubes 2, has an inner pipe section 222 on one side (lower side in FIG. 2) and an outer pipe section 223 on the opposite side (upper side in FIG. 2) as the projecting pipe sections 22. The inner pipe section 222 defines a passage therein and forms an opening at an end. Likewise, the outer pipe section 223 defines a passage therein and forms an opening at an end. The tubes 2 are stacked such that the inner pipe sections 222 are received in the outer pipe sections 223 of the adjacent tubes 2. Thus, the first header part 11 and the second header part 12 are constructed by inner pipe sections 222 and the outer pipe sections 223.
Each of the inner pipe sections 222 has an extending wall portion 227 a, an adjacent wall portion 225 a, and an overlapping wall portion 224 a. The extending wall portion 227 a extends from the body section of the tube 2 in the direction perpendicular to the axis of the passage 21. That is, the extending wall portion 227 a generally forms a base portion of the inner pipe section 222. The adjacent wall portion 225 a extends from the extending wall portion 227 a and connects to the overlapping wall portion 224 a.
Likewise, the outer pipe section 223 has an extending wall portion 227 b, an adjacent wall portion 225 b, an overlapping wall portion 224 b. Further, the outer pipe section 223 has a flange portion 226. The extending wall portion 227 b extends from the body section of the tube 2 in the direction perpendicular to the axis of the passage 21. That is, the extending wall portion 227 b generally forms a base portion of the outer pipe section 223. The adjacent wall portion 225 b extends from the extending wall portion 227 b and connects to the overlapping wall portion 224 b.
The flange portion 226 radially expands from an end of the overlapping wall portion 224 b and defines the end of the outer pipe section 223. In a cross-sectional plane defined parallel to an axis of the outer pipe section 223, the flange 226 has a curled-shape outwardly curling toward the end of the outer pipe section 223, as shown in FIG. 3. However, the shape of the flange 226 is not limited to the illustrated example of FIG. 3.
For example, the flange 226 can have a taper shape linearly expanding toward the end of the outer pipe section 223, as shown in FIG. 4. Alternatively, the flange 226 forms a wall extends from an end of the overlapping wall portion 224 b in a direction substantially perpendicular to the overlapping wall portion 224 b, as shown in FIG. 5. Further, the flange 226 radially expands from the end of the overlapping wall portion 224 b, bends and further extends in a direction parallel to the overlapping wall portion 224 b, as shown in FIG. 6.
As shown in FIG. 2, the inner pipe section 222 and the outer pipe section 223 of the adjacent tubes 2 are coupled such that the overlapping wall portion 224 a of the inner pipe section 222 overlaps the overlapping wall portion 224 b of the outer pipe section 223. Also, the adjacent wall portions 225 a, 225 b are located on opposite sides of the overlapping wall portions 224 a, 224 b in the axial direction of the inner and outer pipe sections 222, 223. Namely, each of the adjacent wall portions 225 a, 225 b is located downstream or upstream of the overlapping wall portions 224 a, 224 b.
Further, an outer diameter D1 of the inner pipe section 222 is smaller than an inner diameter D2 of the outer pipe section 223 at least at the overlapping wall portions 224 a, 224 b and the adjacent wall portions 225 a, 225 b. Namely, the outer diameter D1 of the overlapping wall portion 224 a and the adjacent wall portion 225 a of the inner pipe section 222 is smaller than the inner diameter D2 of the overlapping wall portion 224 b and the adjacent wall portion 225 b of the outer pipe section 223, as shown in FIG. 2.
As shown in FIG. 3, the extending wall portion 227 a of the inner pipe section 222 has an outer diameter Dt larger than an outer diameter Dk of the overlapping wall portion 224 a. Further, the extending wall portion 227 a of the inner pipe section 222 and the extending wall portion 227 b of the outer pipe section 223, which are opposed to each other, have a generally equal inner diameter.
As shown in FIG. 7, each of the tubes 2 is constructed of a stack of metal plates having high heat conductivity such as aluminum plates or copper plates. The metal plates are joined by a jointing method such as by brazing. For example, the tube 2 has a pair of outer plates 27, a middle plate 28 interposed between the outer plates 27, and inner fins 29 interposed between the outer plates 27 and the middle plate 28. The inner fins 29 have a corrugated shape, for example. The passage 21 is defined by spaces formed between the middle plate 28 and the outer plates 27.
Further, the outer plates 27, the middle plate 28 and the inner fins 29 are brazed to each other. The middle plate 28 has a rectangular shape. As shown in FIG. 2, the middle plate 28 is formed with circular holes (openings) 284 at longitudinal ends, i.e., at positions corresponding to the first header part 11 and the second header part 12. The ends of the middle plate 28 can be held between the ends of the outer plates 27. Alternatively, the ends of the middle plate 28 can be bent to hold the ends of the outer plate 27, as shown in FIG. 7.
As shown in FIG. 1, the heat exchanger 1 has an introduction pipe 31 for introducing the heat medium 5 into the heat exchanger 1 and a discharge pipe 32 for discharging the heat medium 5 from the heat exchanger 1. The introduction pipe 31 and the discharge pipe 32 are respectively coupled to an inlet port 13 and an outlet port 14 of the end tube 2 x that is located at an outermost layer of the stack of tubes 2 (the bottom end tube in FIG. 1). The heat medium 5 is introduced in the first header 11 through the introduction pipe 31 and the inlet port 13 and discharged from the second header 12 through the outlet port 14 and the discharge pipe 32.
As shown in FIG. 11, the end tube 2 x has projecting portions 24 at longitudinal ends of the tube 2 x. The projecting portions 24 projects from the body section of the end tube 2 x in the direction perpendicular to the longitudinal axis of the body section. The projecting portions 24 form openings at ends. The inlet port 13 and the outlet port 14 are defined by the openings of the projecting portions 24. The introduction pipe 31 and the discharge pipe 32 are engaged with the projecting portions 24 of the end tube 2 x.
The projecting portions 24 are for example formed by burring. Each of the projecting portions 24 extends approximately 2 mm from the main wall of the body section of the tube 2 in the direction substantially perpendicular to the main wall. Each of the introduction pipe 31 and the discharge pipe 32 has a flange 34 at a position approximately 2 mm from an end 33 that forms an opening.
The ends 33 of the introduction pipe 31 and the discharge pipe 32 are engaged with inner walls of the projecting portions 24 of the end tube 2 x. For example, the flanges 34 contact the ends of the projecting portions 24. As such, the ends 33 of the introduction pipe 31 and the discharge pipe 32 do not enter the inside of the outer plate 27 of the tube 2 x. Accordingly, it is less likely that the passage 21 of the end tube 2 x will be closed by the ends 33.
Each of the outer plates 27 includes a portion for forming the body section and portions for forming the first header part 11 and the second header part 12. The portion for forming the body section includes a flat wall for making contact with the electronic components 4 so as to receive heat from the electronic components 4. The portions for forming the first header part 11 and the second header part 12 are formed at longitudinal ends of the outer plate 27.
The portions for forming the first header part 11 and the second header part 12 are characterized by the projecting pipe sections 22 and diaphragm portions 23. The projecting pipe sections 22 project from the flat wall portion of the outer plate 27 in the direction perpendicular to the flat wall portion. Each of the diaphragm portions 23 is defined by the peripheral portion of the base of the projecting pipe section 22. Namely, the diaphragm portions 23 is defined by an annular portion with a predetermined width (diameter) on the periphery of the base of the projecting pipe section 22. The projecting pipe sections 22 are coupled such that portions between the adjacent tubes 2 are connected in the stacking direction, thereby to form the first header part 11 and the second header part 12. The projecting pipe sections 22 provide strength such that the header pipe 11 and the second header 12 are not buckled with respect to the stacking direction.
Namely, each of the tubes 2 constructed of the above outer plates 27 has the flat body section 20, the diaphragm portions 23 and the projecting pipe sections 22, as shown in FIG. 8. The projecting pipe sections 22 of the adjacent tubes 2 are coupled in a socket and spigot manner. That is, the projecting pipe sections 22 includes the inner pipe section 222 and the outer pipe section 223. The inner pipe section 222 is inserted in the outer pipe section 223.
Each tube 2 is constructed of two types of outer plates 27. A first type outer plate 27 has the inner pipe sections 222 at the longitudinal ends as the projecting pipe sections 22. A second type outer plate 27 has the outer pipe sections 223 at the longitudinal ends as the projecting pipe sections 22. In one tube 2, the first type outer plate 27 and the second type outer plate 27 are joined such that the inner pipe sections 222 and the outer pipe sections 223 project outwardly and in opposite direction to each other. Further, in the heat exchanger 1, the first type outer plates and the second type outer plates are stacked alternately and in opposite directions.
The end tubes located at the outermost layers of the heat exchanger 1 have different outer plates. An outer plate located at the outermost end (uppermost end in FIG. 1) of the heat exchanger 1, which is on a side opposite to the introduction pipe 31 and the discharge pipe 32, does not have the projecting pipe sections 22. This outer plate forms the ends of the first header 11 and the second header 12. Also, the outer plate located at the outermost end (lowermost end in FIG. 1) of the heat exchanger 1 has the projecting portions 24 to which the introduction pipe 31 and the discharge pipe 32 are connected.
As described above, the inner pipe section 222 is received in the outer pipe section 223. A predetermined clearance is defined between the inner side wall of the outer pipe section 223 and the outer side wall of the inner pipe section 222 such that the inner pipe section 222 can be inserted in the outer pipe section 223 during the coupling. The inner side wall of the outer pipe section 223 and the outer side wall of the inner pipe section 222 are joined by brazing. Thus, the clearance is sealed by brazing.
The heat exchanger 1 is produced in the following manner. First, the flat tubes 2 having the inner pipe sections 222 and the outer pipe sections 223 are formed. As shown in FIG. 2, the overlapping wall portion 224 a and the adjacent wall portion 225 a of the inner pipe section 222 have the outer diameter D1 smaller than the inner diameter D2 of the overlapping wall portion 224 b and the adjacent wall portion 225 b of the outer pipe section 223. Also, the flange 226 is formed at the end of the outer pipe section 223. As shown in FIG. 3, the outer diameter Dt of the extending wall portion 227 a is larger than the outer diameter Dk of the overlapping wall portion 224 a of the inner pipe section 222.
Next, the tubes 2 are stacked in a condition that the spacing jigs 6 are placed between the adjacent tubes 2, as shown in FIGS. 8 and 9. Specifically, the inner pipe section 222 and the outer pipe section 223 of the adjacent tubes 2 are engaged by inserting the inner pipe section 222 into the outer pipe section 223 in a condition that a wire brazing material 15 having a ring-shape is arranged between the flange 226 of the outer pipe section 223 and the inner pipe section 222. Here, an outer diameter Dp of the flange 226 is larger than an outer diameter Dr of the wire brazing material 15, as shown in FIG. 3.
At this time, the inner pipe section 222 is inserted into the outer pipe section 223 until the flat body section 20 of the tube 2 contacts the spacing jig 6, as shown in FIGS. 9 and 10A. Next, the wire brazing material 15 is melted. Thereafter, the brazing material 15 is hardened, so the outer side wall of the inner pipe section 222 and the inner side wall of the outer pipe section 223 are brazed to each other. In this way, the plural tubes 2 are stacked.
Here, the brazed projecting pipe sections 22 have rigidity in the axial direction, that is, in the stacking direction so that the pipe sections 22 are not buckled even if pressure having the magnitude that can deform the diaphragm portions 23 is applied.
The spacing jig 6 is interposed between the tubes 2 until the wire brazing material 15 is hardened, as shown in FIG. 10A. After the brazing material 15 is hardened and the brazed portions are fixed, the spacing jig 6 is removed, as shown in FIG. 10B. Then, the electronic component 4 is placed between the adjacent tubes 2, as shown in FIG. 10C.
The spacing jig 6 has a thickness slightly larger than a thickness of the electronic component 4. Therefore, there are clearances between the tubes 2 and the electronic component 4 at the stage shown in FIG. 10C. After the plural electronic components 4 are placed between the stacked tubes 2, the heat exchanger 1 is pressed in the stacking direction. At this time, the diaphragm portions 23 receive pressure through the projecting pipe sections 22. Therefore, the diaphragm portions 23 are deformed inside of the tubes 2, that is, in a direction parallel to the axis of the header parts 11, 12, as shown in FIG. 10D.
Namely, in the condition shown in FIG. 10C, that is, before applying the pressure, the tubes 2 are in condition stacked with spaces slightly larger than the thickness of the electronic components 4. Also in this condition, the tubes 2 are connected through the projecting pipe sections 22. Then, when pressure is applied to the stacked tubes 2, the spaces between the adjacent tubes 2 are reduced so that the tubes 2 becomes in contact with the electronic components 4. Accordingly, the electronic components 4 are held between the tubes 2, as shown in FIG. 10D.
For example, the electronic components 4 are constructed as semiconductor modules having semiconductor elements such as IGBT (Insulated Gate Bipolar Transistor) and diodes. The semiconductor modules construct part of an inverter for an automobile. As the heat medium 5, water containing ethylene glycol antifreeze liquid is used, for example.
The electronic components 4 can be held in directly contact with the tubes 2. Alternatively, insulation plates such as ceramic plates or heat conductive grease can be interposed between the electronic components 4 and the tubes 2.
Next, advantageous effects of the first example embodiment will be described. As shown in FIGS. 1 and 2, the passages 21 of the adjacent tubes 2 are communicated with each other through the projecting pipe sections 22, which are coupled to each other. The projecting pipe sections 22 are integrally formed into the tube 2. Therefore, it is not necessary to couple the tubes 2 by using separate members. As such, the number of components reduces. Also, the heat exchanger 1 is easily manufactured.
The projecting pipe sections 22 are coupled by joining the side walls, as shown in FIG. 2. Therefore, the passage areas of the first header part 11 and the second header part 12 are ensured by the inner diameter of the projecting pipe sections 22. Namely, the passage diameter of the first header part 11 and the second header part 12 is substantially equal to the inner diameter of the projecting pipe sections 22. As such, a flow resistance in the first header 11 and the second header 12 is reduced, and therefore pressure loss in the first header 11 and the second header 12 is reduced. With this, the heat medium 5 is substantially equally distributed into the plural tubes 2. As a result, the plural electronic components 4 are equally cooled.
Also, the outer diameter D1 of the overlapping wall portion 224 a and the adjacent wall portion 225 b of the inner pipe section 222 is smaller than the inner diameter D2 of the overlapping wall portion 224 b and the adjacent wall portion 225 b of the outer pipe section 223. Therefore, it is less likely that the inner pipe section 222 and the outer pipe section 223 will push each other. As such, the inner pipe section 222 and the outer pipe section 223 do not receive load in the axial direction of the inner pipe section 222 and the outer pipe section 223.
Namely, even if the inner pipe section 222 and the outer pipe section 223 have small dimensional errors in the axial direction, it is less likely that the inner pipe section 222 and the outer pipe section 223 receive loads in the axial direction. Therefore, it is less likely that the projecting pipe sections 22 and the peripheral portions of the projecting pipe sections 22 such as the diaphragm portions 23 will receive stress and be deformed while the tubes 2 are stacked.
After the tubes 2 are stacked, the electronic components 4 are placed in the tubes 2, as shown in FIG. 10C. Then, the stack of tubes 2 are compressed in the stacking direction. As such, the tubes 2 contact the electronic components 4, as shown in FIG. 10D. If the tubes 2 are partly deformed before the electronic components 4 are placed, it is difficult to place the electronic components 4 between the tubes 2. Therefore, it is significant to reduce the deformation of the tubes 2 during the stacking.
Further, the outer pipe section 223 has the flange 226 at the end. Therefore, it is easy to arrange the wire brazing material 15 between the flange 226 and the inner pipe section 222, which is opposed to the flange 226. Further, the melted brazing material 15 easily flows in the space defined between the inner pipe section 222 and the outer pipe section 223 along the flange 226. Accordingly, the adjacent tubes 2 are easily and properly joined. Thus, the heat exchanger 1 is easily manufactured.
As shown in FIG. 3, the outer diameter Dt of the extending wall portion 227 a is larger than the outer diameter Dk of the overlapping wall portion 224 a. When the tubes 2 are stacked, the wire brazing material 15 can be pressed against the flange 226 by the extending wall portion 227 a of the inner pipe section 222. Therefore, it is less likely that the wire brazing material 15 will be displaced. As such, the inner pipe section 222 and the outer pipe section 223 are properly brazed.
The tubes 2 have the diaphragm portions 23 on the peripheries of the projecting pipe sections 22. Therefore, the spaces between the adjacent tubes 2 are easily adjusted with deformation of the diaphragm portions 23, as shown in FIGS. 10C and 10D. Accordingly, the electronic components 4 are easily and securely held between the adjacent tube 2. Further, the electronic components 4 can be in close contact with the tubes 2.
As shown in FIG. 7, at least each of intermediate tubes 2 is constructed of the pair of outer plates 27, the middle plate 28 and the inner fins 29. Here, the intermediate tubes 2 are the tubes 2 that are located in a middle section of the stack of the tubes 2. That is, the intermediate tubes 2 are the tubes 2 other than the end tubes 2. The outer plates 27, the middle plate 28 and the inner fins 29 are separately formed into the predetermined shapes such as by pressing. Then, the outer plates 27, the middle plate 28 and the inner fins 29 are joined to each other. By this, the tubes 2 having drawn cup structure can be produced. Accordingly, the tubes 2 are easily manufactured. Also, the end tubes 2 can be formed of the outer plates 27, the middle plate 28 and the inner fins 29.
In addition, it is easy to form the inner fins 29 at desired positions. Because the inner fins 29 are not arranged at positions corresponding to the first header 11 and the second header 12, it is easy to process the first header 11 and the second header 12.
As shown in FIG. 7, each of the tubes 2 has double layered passages 21 in the stacking direction. Therefore, it is less likely that heat will be transferred between the adjacent electronic components 4 arranged on opposite sides of the tube 2. As such, even if the temperature of the electronic component 4 arranged on one side of the tube 2 is rapidly increased, the electronic component 4 arranged on the opposite side of the tube 2 will not be affected.
In the tube 2, the inner diameter of the extending wall portion 227 a and the inner diameter of the extending wall portion 227 b that is opposite to the extending wall portion 227 a in the same tube 2 have the equal inner diameter. Therefore, the diaphragm portion 23 on one side of the tube 2 and the diaphragm portion 23 on the opposite side of the same tube 2 have the same diameter. Accordingly, the amount of deformation is equal in the pair of diaphragm portions 23 in the same tube 2.
Further, the projecting pipe sections 22 are easily shaped. First, the extending wall portions 227 a, 227 b are formed. Then, other portions such as the adjacent wall portions 225 a, 225 b and the overlapping portions 224 a, 224 b are formed such as by drawing and bending. Since the extending wall portion 227 a of the inner pipe section 222 and the extending wall portion 227 b of the outer pipe section 223 have the equal diameter, the pair of projecting pipe sections 22, that is, the inner pipe section 222 and the outer pipe section 223, are formed by using the same die at the first stage of the shaping. Accordingly, productivity improves.
Further, the outer diameter Dp of the flange 226 is larger than the outer diameter Dr of the wire brazing material 15, as shown in FIG. 3. Therefore, the wire brazing material 15 is easily and properly held between the inner pipe section 222 and the outer pipe section 223, at the flange 226. Also, when the brazing material 15 melts, the melted brazing material 15 easily flows between the inner pipe section 222 and the outer pipe section 223 without overflowing from the flange 226.
Accordingly, the heat exchanger unit 10 can be easily manufactured in the above manner. Further, it is less likely that the tubes 2 will be deformed during the stacking. Also, the manufacturing cost reduces.

Second Example Embodiment

Next, a second example embodiment of the heat exchanger unit 10 will be described with reference to FIG. 12. The outer plates 27, the middle plate 28 and the inner fins 29 of the tube 2 are made of the following metal plates.
The outer plate 27 has a core 271 made of aluminum. The outer surface of the outer plate 27 is defined by a bare surface 274 of the core 271. That is, the aluminum of the core 271 is bared to the outside of the tube 2.
As the material for the core 271, another material such as copper (including copper alloy) may be used, in place of aluminum (including aluminum alloy) However, aluminum is preferably used in view of efficiency, corrosion resistance, weight, and the like.
The outer plates 27 are joined to the middle plate 28 such that inner surfaces of the ends of the outer plates 27 contact the surfaces of the ends of the middle plate 28. Namely, the ends of the middle plate 28 are held between the ends of the outer plates 27. The middle plate 28 is made of a brazing sheet having a core 281 made of aluminum and a brazing material 282 disposed on both surfaces of the core 281.
Although not illustrated in FIG. 12, the inner fin 29 is made of a brazing sheet having a core and a brazing material disposed on both surfaces of the core. The core of the inner fin 29 is made of aluminum containing zinc.
In the second example embodiment, structural parts other than the outer plates 27, the middle plate 28 and the inner fins 29 are similar to those of the first example embodiment. As such, the description of like parts will not be repeated, hereafter.
In the second example embodiment, the electronic components 4 directly contact the tubes 2 through the bare surfaces 274 of the outer plates 27. Because the bare surfaces 274 are not coated with the brazing material and the like, the outer surface of the tube 2 is smooth. Therefore, thermal contact resistance between the electronic components 4 and the outer plates 27 reduces. As such, cooling efficiency improves.
Further, the core of each inner fin 29 is made of aluminum containing zinc. Therefore, the core of the inner fins 29 has an electrical potential (corrosion potential) lower than that of the core 271 of the outer plate 27. Because the inner fin 29 is more likely to be corroded than the outer plate 27, the corrosion of the outer plate 27 is reduced.
The heat exchanger unit 10 of the second example embodiment have the structure similar to that of the first example embodiment other than the outer plates 27, the middle plate 28 and the inner fins 29. In addition to the above advantageous effects, advantageous effects similar to those of the first example embodiment are also provided in the second example embodiment.

Third Example Embodiment

Next, a third example embodiment of the heat exchanger unit 10 will be described with reference to FIG. 13. As shown in FIG. 13, the outer plate 27 is made of a brazing sheet having the core 271 and a sacrificial anode material 273 on an inner surface.
As the sacrificial anode material 273, a metal material in which zinc is added to aluminum is used, for example. In this case, because the corrosion of the core 271 of the outer plate 27 is restricted by selectively corroding the sacrificial anode material 273, the material of the core of the inner fin 29 is not always necessary to contain zinc.
The outer surface of the outer plate 27, which makes contact with the electronic components 4, is the bare surface 274, similar to the second example embodiment. Further, the core of the inner fin 29 is made of a material having a potential (corrosion potential) higher than that of the sacrificial anode material 273. For example, the core of the inner fin 29 has a potential difference with respect to the sacrificial anode material 273 in a range between 0 and +50 mV.
Other structural parts are similar to those of the heat exchanger unit 10 of the second example embodiment.
In the heat exchanger unit 10 of the third example embodiment, it is less likely that the tubes 2 will corrode and the heat medium 5 will leak from the tubes due to the corrosion. In other words, since the inner surface of the core 271 of the outer plate 27 is covered with the sacrificial anode material 273, the sacrificial anode material 273 is selectively corroded. Therefore, it is less likely that the core 271 will corrode. Because the corrosion of the outer plate 27 in its thickness direction is restricted, it is less likely that the tubes 2 will have holes due to corrosion.
The core of the inner fin 29 has the potential higher than that of the sacrificial anode material 273 of the outer fin 27, and has the potential difference in the range between 0 and +50 mV. Because the potential of the inner fin 29 is close to the potential of the sacrificial anode material 273 of the outer fin 27, corrosion speed of the sacrificial anode material 273, which is selectively corroded, is reduced. If the potential difference is large the corrosion of the sacrificial anode material 273 enhances.
In addition to the above effects, the heat exchanger unit 10 of the third example embodiment provides advantageous effect similar to those of the first and second example embodiments.

Fourth Example Embodiment

Next, a fourth example embodiment of the heat exchanger unit 10 will be described with reference to FIG. 14. As shown in FIG. 14, a brazing material 272 is disposed on the inner surface of the core 271 of the outer plate 27. Further, sides of the pair of outer plates 27 are directly joined. In the core 281 of the middle plate 28, zinc is added. Other structural parts are similar to those of the third example embodiment.
In this case, the tubes 2 are easily assembled. Since the brazing material 272 is disposed on the inner surfaces of the outer plates 27, it is easy to join the outer plates 27 each other and with the inner fins 29. Further, the brazing material 272 is also disposed on the inner surface of the projecting pipe section 22, it is not necessary to use the wire brazing material 15 as the first to third example embodiments. As such, the inner pipe section 222 and the outer pipe section 223 are easily and properly brazed through the brazing material 272.
Since the core 281 of the middle plate 28 is made of aluminum containing zinc, the core 281 has a potential (corrosion potential) lower than that of the core 271 of the outer plate 27. Therefore, the middle plate 28 is more likely to be corroded than the outer plate 27. As such, corrosion of the outer plate 27 is reduced.
In addition to the above advantageous effects, the heat exchanger unit 10 of the fourth example embodiment provides advantageous effects similar to those of the third example embodiment.

Fifth Example Embodiment

A fifth example embodiment of the heat exchanger unit 10 will be described with reference to FIGS. 15 to 17. As shown in FIGS. 15 to 17, the pair of outer plates 27 that makes a first side and a second side of one tube 2 is formed from a single plate.
Namely, as shown in FIGS. 15 and 16, the pair of outer plates 27 for one tube 2 is formed of a single aluminum plate 270 in which sections corresponding to the outer plates 27 are continuous through a connecting portion 276. The plate 270 is formed by such as pressing. The aluminum plate 270 is folded at the connecting portion 276, so the tube 2 shown in FIG. 17 is formed. While folding the plate 270, the middle plate 28 and the inner fins 29 are placed so that the middle plate 28 and the inner fins 29 are sandwiched between the folded plate 270. Structural parts other than the outer plates 27 are similar to those of the fourth example embodiment.
In the fifth example embodiment, productivity of the outer plates 27 improves. Further, productivity of the heat exchanger 1 improves. In addition to the above advantageous effects, the heat exchanger unit 10 of the fifth example embodiment provides advantageous effects similar to those of the fourth example embodiment.
In the illustration of FIGS. 16 and 17, the aluminum plate 270 has the brazing material 272 on a surface corresponding to the inner surface of the tube 20. Alternatively, the outer plates 27 of the first to third example embodiments can be formed of the method of the fifth example embodiment.

Sixth Example Embodiment

A sixth example embodiment will be described with reference to FIG. 18. The outer plate 27 is formed of a brazing sheet shown in FIG. 18. In the brazing sheet, the sacrificial anode material 273 is disposed on the inner surface of the core 271. Further, the brazing material 272 is disposed on the inner surface of the sacrificial anode material 273. As the sacrificial anode material 273, a metal material in which zinc is added to aluminum can be used.
In this case, the sacrificial anode material 273 is selectively corroded so as to reduce the corrosion of the core 271. Therefore, it is not always necessary that the materials of the cores of the middle plate 28 and the inner fin 29 contain zinc. Structural parts other than the outer plate 27 are similar to those of the fourth example embodiment.
Since the sacrificial anode material 273 will be corroded prior to the core 271, the corrosion of the core 271 is reduced. Therefore, corrosion of the outer plate 27 in its thickness direction is restricted. As such, it is less likely that the tubes 2 will form holes due to corrosion.
In addition to the above effects, the heat exchanger 1 and the electronic components cooling unit 10 of the sixth example embodiment provide advantageous effects similar to those of the fourth example embodiment. Further, the outer plates 27 of the sixth embodiment can be formed in a manner similar to the fifth example embodiment.

Comparative Example

FIG. 19 shows a comparative example of a heat exchanger. In the heat exchanger of FIG. 19, the outer pipe section 223 has a step 229 for limiting the amount of insertion of the inner pipe section 222 in the outer pipe section 223. In this case, the insertion length or depth of the inner pipe section 222 in the outer pipe section 223 is limited when the end of the inner pipe section 222 contacts the step 229.
A portion of the outer pipe section 223 that is adjacent to the body section of the outer pipe section 223, i.e. a portion lower than the step 229 in FIG. 19 has an inner diameter smaller than an outer diameter of the inner pipe section 222. A portion of the outer pipe section 223 that is adjacent to the end of the outer pipe section 223, i.e., a portion above the step 229 in FIG. 19 has an inner diameter larger than the outer diameter of the inner pipe section 222.
When the tubes 2 are stacked, the inner pipe sections 222 are inserted in the outer pipe sections 223 so that the ends of the inner pipe sections 222 contact the steps 229 of the outer pipe sections 223. The heat exchanger shown in FIG. 19 has a structure similar to that of the heat exchanger 1 shown in FIG. 1, other than the structure of the inner pipe section 222 and the outer pipe section 223.
In the heat exchanger shown in FIG. 19, however, the diaphragm portions 23 are likely to be deformed when the tubes 2 are coupled through the engagement of the inner pipe sections 222 and the outer pipe sections 223. Namely, the ends of the inner pipe sections 222 contact the steps 229 during the stacking. Therefore, if the dimensions (e.g., length) of the projecting pipe sections 22 and the pressure applied during the stacking are uneven, the projecting pipe sections 22 receive loads in the stacking direction. As a result, the diaphragm portions 23 formed on the peripheries of the bases of the projecting pipe sections 22 are likely to be deformed.
In other words, the diaphragm portions 23 are likely to be deformed before the electronic components 4 are arranged in the heat exchanger. In this case, the spaces between the tubes 2 have been narrowed due to the deformation of the diaphragm portions 23 before the arrangement of the electronic components 4. Therefore, it is difficult to arrange the electronic components 4 between the tubes 2. Also, the heat exchanger is compressed in the stacking direction after the arrangement of the electronic components 4 so that the tubes 2 closely contact the electronic components 4. However, if the diaphragm portions 23 are already deformed before the compression of the heat exchanger, it is likely to be difficult to properly bring the tubes 2 in close contact with the electronic components 4.
On the contrary, in the heat exchanger 1 of the first example embodiment, the outer diameter D1 of the overlapping wall portion 224 a and the adjacent wall portion 225 a of the inner pipe section 222 is smaller than the inner diameter D2 of the overlapping wall portion 224 b and the adjacent wall portion 225 b of the outer pipe section 223. Namely, the inner pipe section 222 and the outer pipe section 223 have the adjacent wall portions 225 a, 225 b in addition to the overlapping wall portions 224 a, 224 b, respectively.
The outer diameter of the adjacent wall portion 225 a of the inner pipe section 222 is smaller than the inner diameter of the overlapping wall portion 224 b and the adjacent wall portion 225 b of the outer pipe section 223. Also, the inner diameter of the adjacent wall portion 225 b of the outer pipe section 223 is larger than the outer diameter of the overlapping wall portion 224 a of the inner pipe section 222. Therefore, the inner pipe section 222 and the outer pipe section 223 do not push each other when engaging each other in the axial direction during the stacking. Therefore, it is less likely that the inner pipe section 222 and the outer pipe section 223 will receive loads in the axial direction, that is, in the insertion direction.
Namely, even if the dimensions (e.g., length) of the inner pipe sections 222 and the outer pipe sections 223 are slightly different, it is less likely that the inner pipe sections 222 and the outer pipe sections 223 will receive loads in the axial direction. Therefore, it is less likely that the projecting pipe sections 22 and the peripheral portions of the projecting pipe sections 22 will receive stress and deform. Also in the second to sixth example embodiments, similar advantageous effects can be provided.
In the first to sixth example embodiments, a limiting portion such as the step 229 shown in FIG. 19 can be additionally employed. In such a case, however, it is preferable that the limiting portion is formed at a position (depth) such that it does not contact the end of the inner pipe section 222 at least in a proper manufacturing step in which the spacing jig 6 is used between the tubes 2. Namely, in this case, the limiting portion can be employed to provide supplemental effects such as reinforcement of the outer pipe section 223, stopper for restricting excess insertion of the inner pipe section 222, and positioning means at a position where the spacing jig 6 is not used.
In the above first to sixth embodiments, the electronic components 4 are placed between the tubes 2 so that heat exchange is performed between the heat medium 5 flowing in the tubes 2 and the electronic components 4. However, the heat exchanging object is not limited to the electronic components 4. For example, the object can be air passing between the adjacent tubes 2. As such, heat exchange is performed between the heat medium 5 flowing in the tubes 2 and the air passing between the adjacent tubes 2. Alternatively, tubes of another device can be arranged between the tubes 2 so that heat exchange is performed between the heat medium 5 flowing in the tubes 2 and a fluid flowing in the tubes of the another device. Further, devices other than the electronic components 4 can be arranged as the heat exchanging object.
Also, the heat medium 5 is not limited to water containing ethylene glycol antifreeze liquid. For example, hot fluid or any other fluid can be used as the heat medium 5. For example, natural refrigerant such as water or ammonia, carbon fluoride refrigerant such as Fluorinate (3M), fleon refrigerant such as HCFC123 or HFC134a, alcohol refrigerant such as alcohol or methanol, ketone refrigerant such as acetone can be used as the heat medium 5.
The electronic components 4 arranged between the tubes 2 are not limited to the semiconductor module used for the automobile inverter. The electronic components 4 can be a semiconductor module used for another device such as motor-driven inverters of industrial devices and inverters of air conditioner systems for buildings. Further, the electronic components 4 are not limited to the above semiconductor modules. For example, the electronic components 4 can include power transistors, power-FET, IGBT, and the like.
In the above example embodiments, the outer diameter of the inner pipe section 222 is larger than the inner diameter of the outer pipe section 223 at the expanding wall portion 227 a. Instead, the outer diameter of the inner pipe section 222 can be smaller than the inner diameter of the outer pipe section 223 thoroughly from its base portion to its end.
Also, the adjacent wall portions 225 a, 225 b are the portions adjacent to the overlapping wall portions 224 a, 224 b when the inner pipe section 222 is inserted in the outer pipe section 223. That is, the adjacent wall portions 225 a, 225 b are located upstream or downstream of the overlapping wall portions 224 a, 224 b with respect to the flow direction of the heat medium 5 in the first header part 11 and the second header part 12.
In the above example embodiments, the diaphragm portions 23 are deformed into the inside of the tubes 2 so that the spaces between the adjacent tubes 2 are narrowed so as to hold the electronic components 4. The electronic components 4 can be held in another way. For example, the spaces between the adjacent tubes 2 can be widened by deforming the diaphragm portions 23 toward the outside of the tubes 2 once, before the electronic components 4 are placed between the tubes 2. Then, after the electronic components 4 are placed in the spaces between the tubes 2, the spaces are narrowed, thereby holding the electronic components 4.
In the above example embodiments, the surfaces of the middle plate 28 are coated with the brazing material. Thus, the ends of the outer plates 27 can be easily brazed to the ends of the middle plate 28.
Further, as the brazing materials disposed on the outer plates 27, the middle plate 28 and the inner fins 29, a metallic material having a fusing point lower than that of the material of the core of the respective plates 27 to 29 can be used. For example, when the core is made of aluminum, the brazing material is made of aluminum having a fusing point lower than that of the aluminum of the core.
In the above example embodiments, the tubes 2 are brazed in the condition that the spacing jigs 6 are arranged between the tubes 2. Therefore, the adjacent tubes 2 can be easily and properly held with desired spaces. As such, the electronic components 4 can be easily arranged between the tubes 2.
In the above embodiments, the sectional shape of the first and second header parts 11, 12 are not limited to a circle, but may include other circular or generally round shapes such as an ellipse or any other shapes. Here, the term “diameter” is not limited to a dimension of the circle, but includes a dimension of another circular or generally round shape.
Further, the heat exchanger unit 10 can be implemented by variable combinations of the above example embodiments.
The example embodiments of the present invention are described above. However, the present invention is not limited to the above example embodiments, but may be implemented in other ways without departing from the spirit of the invention.

Claims

1. A heat exchanger unit comprising a plurality of tubes, each tube having a flat body section and at least one of an inner pipe section and an outer pipe section extending from the body section in a direction perpendicular to an axis of the body section and defining an opening at an end, the body section defining a passage through which a heat medium flows, wherein

each of the inner pipe section and the outer pipe section includes a first portion and a second portion adjacent to the first portion,

the tubes are stacked such that the body sections are spaced from each other for performing heat exchange between the heat medium and an object existing between the adjacent body sections and the inner pipe section and the outer pipe section are coupled to each other and joined through side walls thereof, thereby to construct a header part that allows communication between adjacent body sections, wherein

the inner pipe section is disposed in the outer pipe section such that the first portion of the inner pipe section overlaps the first portion of the outer pipe section, and the second portions of the inner pipe section and the outer pipe section are located on opposite sides of the overlapped first portions in an axial direction of the inner pipe section and the outer pipe section, and

the first portion and the second portion of the inner pipe section have an outer diameter smaller than an inner diameter of the first portion and the second portion of the outer pipe section.

2. The heat exchanger unit according to claim 1, wherein

the inner pipe section and the outer pipe section are brazed to each other,

the outer pipe section has a flange at an end, and an end of the flange has a diameter larger than the inner diameter of the first portion of the outer pipe section.

3. The heat exchanger unit according to claim 1, wherein

the inner pipe section further includes a third portion that extends between the body section and the second portion and defines a base portion of the inner pipe section, and

the third portion has an outer diameter larger than the outer diameter of the first portion of the inner pipe section.

4. A heat exchanger unit comprising a plurality of tubes, each tube having a flat body section and at least one of an inner pipe section and an outer pipe section extending from the body section in a direction perpendicular to an axis of the body section and defining an opening at an end, the body section defining a passage through which a heat medium flows, wherein

the tubes are stacked such that the body sections are spaced from each other for performing heat exchange between the heat medium and an object existing between the adjacent body sections, and the inner pipe section and the outer pipe section are coupled such that an outer side wall of the inner pipe section is brazed to an inner side wall of the outer pipe section, thereby to construct a header part that allows communication between adjacent body sections,

the outer pipe section has a flange at an end, and

the flange has a diameter larger than an inner diameter of a remaining portion of the outer pipe section.

5. The heat exchanger unit according to claim 1, wherein the object is an electronic component.

6. The heat exchanger unit according to claim 1, wherein

the body section of each tube has a diaphragm portion on a periphery of each of the inner pipe section and the outer pipe section, and

the diaphragm portion is deformed in a direction substantially parallel to an axis of the header part.

7. The heat exchanger unit according to claim 6, wherein

each of the inner pipe section and the outer pipe section includes a third portion adjacent to the body section, and

the third portion of the inner pipe section has an inner diameter substantially equal to an inner diameter of the third portion of the outer pipe section.

8. The heat exchanger unit according to claim 1, wherein

each of the tubes that are located at other than ends of a stack of tubes has a pair of outer plates, a middle plate and corrugated inner fins,

the middle plate is disposed between the outer plates,

the inner fins are disposed between the outer plates and the middle plate, and

the passages are defined by spaces between the outer plates and the middle plate.

9. The heat exchanger unit according to claim 8, wherein each of the outer plates includes a core made of a metallic material, and an outer surface of the tube is defined by a bare surface of the core.

10. The heat exchanger unit according to claim 8, wherein each of the outer plates is formed of a brazing sheet that has a core and a sacrificial anode material disposed on a surface of the core, and an inner surface of the tube is defined by the sacrificial anode material.

11. The heat exchanger unit according to claim 8, wherein the pair of outer plates is directly brazed at ends thereof.

12. The heat exchanger unit according to claim 11, wherein each of the outer plates has a brazing material on a surface that defines an inner surface of the tube.

13. The heat exchanger unit according to claim 11, wherein

each of the outer plates is formed of a brazing sheet having a core, a sacrificial anode material disposed on a surface of the core, and a brazing material disposed on the sacrificial anode material, and

an inner surface of the tube is defined by the brazing material.

14. The heat exchanger unit according to claim 8, wherein the pair of outer plates is formed of a single plate member.

15. The heat exchanger unit according to claim 8, wherein each of the outer plates has a core, and each of the inner fins is made of a material having an electric potential lower than that of the core of the outer plate.

16. The heat exchanger unit according to claim 10, wherein each of the inner fins has a core made of a material having an electric potential higher than that of the sacrificial anode material of the outer plate.

17. The heat exchanger unit according to claim 16, wherein the core of the inner fin has a potential difference with respect to the sacrificial anode material in a range between 0 and +50 mV.

18. The heat exchanger unit according to claim 8, wherein each of the outer plates has a core, and the middle plate is made of a material having an electric potential lower than that of the core of the outer plate.

19. The heat exchanger unit according to claim 1, further comprising:

an electronic component arranged between the tubes such that the electronic component is cooled by the heat medium flowing in the tubes.

20. The heat exchanger unit according to claim 1, wherein the outer pipe section has no portion that contacts the end of the inner pipe section in the axial direction of the outer pipe section.

21. A method of manufacturing a heat exchanger unit, the method comprising:

forming tubes, wherein each tube has a body section having a flat tubular shape and at least one of an inner pipe section and an outer pipe section that extend from the body section in a direction perpendicular to an axis of the body section, each of the inner pipe section and the outer pipe section has a first portion and a second portion adjacent to the first portion, the first portion and the second portion of the inner pipe section have an outer diameter smaller than an inner diameter of the first portion and the second portion of the outer pipe section; and

stacking the tubes such that the inner pipe section is inserted in the outer pipe section of the adjacent tube, wherein the first portion of the inner pipe section overlaps the first portion of the outer pipe section, and the second portions of the inner and outer pipe sections are disposed on opposite sides of the overlapped first portions in an axial direction of the inner and outer pipe sections.

22. The method according to claim 21, further comprising:

joining an outer side wall of the inner pipe section and an inner side wall of the outer pipe section in a condition that a spacing jig is placed between the adjacent tubes.

23. The method according to claim 21, wherein the inner side wall of the outer pipe section has no portion that contacts an end of the inner pipe section when the inner pipe section is inserted in the outer pipe section.

24. A method of manufacturing a heat exchanger unit, the method comprising:

forming tubes, wherein each tube has a body section having a flat tubular shape and at least one of an inner pipe section and an outer pipe section that extend from the body section in a direction perpendicular to an axis of the body section and define an opening at an end, and the outer pipe section has a flange at an end;

stacking the tubes such that the inner pipe section is inserted in the outer pipe section of the adjacent tube in a condition that a brazing material is placed between the flange of the outer pipe section and the inner pipe section; and

brazing an outer side wall of the inner pipe section and an inner side wall of the outer pipe section.

25. The method according to claim 24, wherein

the brazing material is a ring-shaped wire brazing material, and

the flange has an outer diameter larger than an outer diameter of the wire brazing material.

26. The method according to claim 24, wherein the inner pipe section and the outer pipe section are brazed in a condition that a spacing jig is placed between the adjacent tubes.