Patent Application
20150369545
The present invention relates to a heat exchanger that performs heat exchange through a heat medium and to a method for manufacturing the heat exchanger. More specifically, the present invention relates to a heat exchanger implementing cooling by performing heat exchange with, for example, an electronic component of an electronic control circuit and to a method for manufacturing the same.
Heat exchangers of various structures in which heat is efficiently moved from one physical body to another have been suggested for heating and cooling and used in a variety of field. In particular, in the field of cooling devices for electronic components, since semiconductor elements, such as CPU which are installed on a substrate of a control circuit, generate a large amount of heat, such semiconductor elements need to be cooled, and cooling units are provided therefor. For example, electronic components in the automotive filed in which coolers of air cooling system or water cooling system are used are often placed under a harsh environment when an automobile is driven in a high temperature desert area or in a cold region.
In the related automotive filed, functions of electronic components installed in the automobiles need to be maintained in a normal state at all times even under such adverse environment. Since failure to maintain the normal state of electronic components constituting control circuits can result in major accidents, an abnormal state should be avoided by all means. In particular, since electronic components and electronic circuits in the automotive field relate to human life, they need to operate reliably and safely. Weight reduction is another problem associated with the automobile-related parts and devices.
This is because when the weight of a cooling device that cools electronic components is heavy, for example, fuel consumption is affected and fuel efficiency is decreased. For this reason, all of the components for use in automobiles have recently become the objects of weight reduction. The weight reduction also contributes to cost reduction. Therefore, weight reduction is also required for automotive cooling devices, and the increase in cooling efficiency is also needed. For those reasons, aluminum alloys have recently been used for base members of cooling devices.
For example, it is well known that aluminum alloys which are used for cooling engine systems of automobiles have already been used for a long time as materials therefor. However, joining between the aluminum alloy components is performed by brazing using Al—Si system brazing alloys. Cooling devices made from aluminum alloys joined by brazing have also recently been put to use as the main constituent members for cooling in cooling of electronic components on control circuit boards. A cooling device in which a base plate integrated with the cooling device is configured by a molded member has been disclosed as an example of the abovementioned cooling device for use, for example, in a switching power supply apparatus (see, for example, Patent Documents 1 and 2).
The base plate constituting the frame body of the cooling device is brought into contact with electronic components mounted on an electronic circuit board and performs cooling by heat conduction. For this reason, the base plate has a flat rectangular shape matching the shape of the electronic circuit board. The specific feature of the disclosed example is that the cooling device does not have an independent structure. Instead, the base plate is brought into direct contact with the electronic component to increase heat exchange efficiency and miniaturize the base plate. The integrated structure is obtained by providing the cooling device in a recess in the base plate. In this structure, the height of pedestals is changed according to the difference in height between the electronic components in order to enable the area of contact therewith.
An example of using a thin metal body for a cooling is also known (see, for example, Patent Document 3). In this example, a cooling device is disclosed in which two press-molded plates are joined to obtain a tubular shape and fins are arranged inside the tube. A structure including a plurality of such tubes is disclosed in which the tubes are stacked at a predetermined interval in a direction perpendicular to the flow direction of a cooling fluid. The tube thickness is indicated to be 0.4 mm and the tube can be deformed to a certain extent. However, although an aluminum alloy is also used as a material in all of the above-described examples to reduce weight, brazing, which is the conventional method for adherence, has been mainly used for joining the aluminum alloy components to each other.
Since brazing in the automotive field lacks reliability, various measures have been implemented and certain suggestions have been made to improve resistance to a harsh environment, but none of them seems to be perfect. Techniques, members, and devices that have been established in other industrial fields can be also effectively considered when examining weight and cost reduction. In particular, a can body which has been used as a thin-wall metal body for typical canned beer uses a thin-sheet aluminum alloy coil body with a thickness equal to or less than 0.1 mm (see, for example, Patent Documents 4 and 5). Such a thin aluminum alloy coil body which is used as a material for can body has a laminated structure in which the alloy surface is coated with a resin film, and pressing and drawing can be performed even in such resin-coated state.
The aluminum alloy coil body is disclosed to be suitable for molding DI cans or bottle cans. The aluminum alloy coil body is a very thin material and, therefore, can be easily bent and deformed. Further, the resin coating film prevents the metal from contacting with water and also has gas-barrier ability such that prevents beer from oxidation. Furthermore, joining techniques that excel in weight reduction and bonding strength have been established for joining aluminum alloys and resins (see, for example, Patent Documents 6 and 7). Thus, with one technique, an aluminum alloy surface is performed to chemical etching to form an ultrafine uneven surface, and a thermoplastic resin composition is bonded to the ultrafine uneven surface by injection molding. As a result, the metal surface and the resin are strongly adhered to each other. A method is also known for obtaining a box-shaped metal structure by bringing the edge portions of two aluminum alloy sheets, which have been treated by the aforementioned technique and have a bent shape, into intimate contact with each other and adhering the edge portions to each other by injection molding by the same method as described hereinabove (see, for example, Patent Document 8).
Patent Document 1: Japanese Patent Application Publication No. 2012-210002.
Patent Document 2: Japanese Patent Application Publication No. 2004-297887.
Patent Document 3: Japanese Patent Application Publication No. 2005-203732.
Patent Document 4: Japanese Patent Application Publication No. H09-277434.
Patent Document 5: Japanese Patent Application Publication No. 2011-208258.
Patent Document 6: Japanese Patent Application Publication No. 2009-101563.
Patent Document 7: WO 2009/031632.
Patent Document 8: Japanese Patent Application Publication No. 2010-30298.
However, although the weight of the above-described conventional heat exchangers has been reduced by using aluminum alloys, structures thereof still leave room for improvement in terms of weight and cost reduction. Thus, the base body serving as a base is a member obtained by molding an aluminum alloy and therefore is an aluminum alloy body having a certain thickness. Since the base body is an aluminum alloy molded member, the structure obviously has a certain thickness.
Since there is a limit to reduction of a molded member in thickness, possible weight reduction thereof is also limited. Further, as mentioned hereinabove, a cooling device with a tubular configuration has also been suggested as a structure enabling weight reduction. This structure is obtained by press-molding an aluminum alloy in the form of a thin sheet material and arranging fins inside the molded body. However, although the thickness is rather thin, there is still room for thickness reduction. In addition, such a structure is complex and costly as a cooling device structure. A thin metal sheet using as a material for the tube has a thickness of 0.4 mm, but although it can be deformed to a certain degree, it is not a material of a thickness such that part of the material is locally bent in response to an internal pressure from a liquid heat medium, such as water, located inside thereof.
Thus, although the conventional structures enable certain weight reduction, further reduction in weight and cost poses difficulties. Yet another problem is that brazing is used for joining the aluminum alloys. The aforementioned tube has a structure in which two plates are overlapped, and the overlapping portions are brazed. With the braze joining method, the joined state can become imperfect, for example, corrosion or joining defects can occur, due to vibrations, or the like, under a harsh usage environment. In particular, in the case of cooling devices for automobiles, since vibrations are an ever-present factor, water serving as a heat medium can leak in the case of fracture, and the devices are not necessarily reliable. Further, salt damage caused by freezing-preventing agents sprayed on the road in cold climates and salt damage in seaside or coastal areas are also a problem.
Structures in which cooling is performed by contact with semiconductor elements in an automobile, which are heat-generating bodies, need to be fully resistance to vibrations and thermal fluctuation in the automobile which can occur, as mentioned hereinabove, under a severe environment. Thus, a structure is required in which joints do not separate due to corrosion, or the like. Further, cooling performed by direct contact with semiconductor elements, as mentioned hereinabove, is effective because the structure ensures direct cooling. However, the cooling space is narrowed, and it is presently difficult to introduce changes aimed to expand the cooling space in order to further increase the cooling effect. Thus, at present, the cooling style is structurally limited and the cooling efficiency remains decreased.
In particular, in a stacked arrangement of a plurality of semiconductor elements and cooling devices, a large amount of heat is generated, and therefore further increase in cooling efficiency is required. As mentioned hereinabove, where the temperature of electronic components of semiconductor elements, rises, functions of the elements are disrupted. In the cooling systems for such applications, water cooling, which produces a better cooling effect than air cooling, has been used. Furthermore, with consideration for cold climates, it is preferred that cooling be performed with cooling water such as a non-freezing solution. It is considered to be ideal that the temperature of semiconductor elements be kept equal to or less than 70° C. by implementing such cooling measures.
The present invention has been created in view of the above-described technical background and attains the below-described objective.
The objective of the present invention is to provide a safe and reliable heat exchanger which has a simple structure and enables weight and cost reduction and also provide a method for manufacturing the heat exchanger.
The present invention employs the following means to attain the aforementioned objective.
A heat exchanger according to the present invention 1 is
a heat exchanger for exchanging heat with a heat exchange object (3) through a heat medium (8), the heat exchanger comprising:
a first molded body (4) which comprises a thin metal sheet that can be bent by an internal pressure of the heat medium (8), and which comprises an outer surface (4a) that can contact with the heat exchange object and an inner surface (4b) coated with a resin, and an edge portion formed on a periphery and a recess formed in a concave cross-sectional shape between the edge portions;
a second molded body (5) which is a member facing the first molded body (4) and combined therewith, comprises a thin metal sheet that can be bent by an internal pressure of the heat medium (8), and which comprises an outer surface (5a) that can contact with the heat exchange object and an inner surface (5b) coated with a resin, and an edge portion formed on a periphery and a recess formed in a concave cross-sectional shape between the edge portions;
a joining member (6) which is provided to straddle the edge portion (4c) of the first molded body (4) and the edge portion (5c) of the second molded body (5), which are abutted against each other, the joining member integrally joining the edge portion of the first molded body and the edge portion of the second molded body by performing injection molding using a thermoplastic resin composition on the outer surface (4a) of the edge portion of the first molded body and on the outer surface (5a) of the edge portion of the second molded body; and
a space (7) as a fluid passage for the heat medium (8) which is surrounded and formed by the first molded body and the second molded body which are integrally joined by the joining member, and has a supply port (10) and a discharge port (11), wherein
the inner surface (4b) of the edge portion (4c) of the first molded body and the inner surface (5b) of the edge portion (5c) of the second molded body are brought into intimate contact with each other by thermally fusing the resins coated thereupon, thereby sealing the space.
A heat exchanger according to the present invention 2 is the heat exchanger according to the present invention 1, wherein the thin metal sheet is an aluminum alloy sheet of a predetermined thickness that is coated with the resin.
A heat exchanger according to the present invention 3 is the heat exchanger according to the present invention 1 or 2, wherein the heat exchange object is an electronic component installed on an electronic control circuit board of an automobile, and a main component of the heat medium is cooling water.
A heat exchanger according to the present invention 4 is the heat exchanger according to the present invention 1 or 2, wherein the outer surface (4a) of the first molded body and the outer surface (5a) of the second molded body, to which the thermoplastic resin composition is adhered by the injection molding, is performed to ultrafine processing to strengthen the adherence of the thermoplastic resin composition, and the thermoplastic resin composition comprises one selected from a polybutylene terephthalate resin, a polyphenylene sulfide resin, and a polyamide resin as a main component.
A heat exchanger according to the present invention 5 is the heat exchanger according to the present invention 1 or 2, wherein projecting portions (14, 15) of protruding shapes that project to the space (7) side are provided at parts of the shape of the recess in the first molded body (4) and/or the second molded body (5) to cause the heat medium to meander.
A heat exchanger according to the present invention 6 is the heat exchanger according to the present invention 1 or 2, wherein projecting portions of protruding shapes that project to the electronic component side are provided at parts of the shape of the recess in the first molded body and/or the second molded body.
A heat exchanger according to the present invention 7 is the heat exchanger according to the present invention 1 or 2, wherein parts of the shape of the recess are protruded and depressed and steps matching the height of the electronic components are provided in the first molded body and/or the second molded body.
A heat exchanger according to the present invention 8 is the heat exchanger according to the present invention 1 or 2, wherein the bendable thin metal sheet is a metal sheet of an aluminum alloy with a thickness of 0.1 mm to 0.8 mm.
A heat exchanger according to the present invention 9 is the heat exchanger according to the present invention 1 or 2, wherein heat exchange enhancing bodies that are in surface contact with the first molded body and the second molded body and enhance heat exchange are contained in the space.
A method for manufacturing a heat exchanger according to the present invention 10 is
a method for manufacturing a heat exchanger for exchanging heat with a heat exchange object (3) through a heat medium (8), the method comprising:
a process for press-molding two thin bendable metal sheets coated with a resin on surfaces on one side thereof into a first molded body (4) and a second molded body (5), which have, respectively, outer surfaces (4a, 5a) that are to be in contact with the heat exchange objects (3) and inner surfaces (4b, 5b) that are resin-coated surfaces which are coated with the resin, an edge portion formed on a periphery and a recess formed in a concave cross-sectional shape between the edge portions;
a process for combining the first molded body (4) and the second molded body (5) such that the inner surface (4b) of the former and the inner surface (5b) of the latter face each other, thereby forming a space (7) that serves as a flow channel for the heat medium (8), and thermally fusing the resin-coated surface of the edge portion (4c) of the first molded body and the resin-coated surface of the edge portion (5c) of the second molded body by hot press working;
an injection molding process for inserting the first molded body (4) and the second molded body (5), which are thermally fused, into a die (12), injecting a thermoplastic resin composition into cavities (12d) formed in regions of the edge portions (4c, 5c), and forming a joining member (6) that joins integrally the first molded body and the second molded body; and
a process for providing the first molded body and the second molded body, which are joined by the joining member, with a supply port (10) and a discharge port (11) communicating with the space (7).
A method for manufacturing a heat exchanger according to the present invention 11 is the method for manufacturing a heat exchanger according to the present invention 10, wherein the thin metal sheet is an aluminum alloy sheet of a predetermined thickness that is coated with the resin; the thermoplastic resin composition comprises one selected from a polybutylene terephthalate resin, a polyphenylene sulfide resin, and a polyamide resin as a main component; and the method comprises a process for performing the outer surface (4a) of the first molded body (4) and the outer surface (5a) of the second molded body (5) to ultrafine processing to strengthen the adherence of the thermoplastic resin composition before the injection molding.
A method for manufacturing a heat exchanger according to the present invention 12 is the method for manufacturing a heat exchanger according to the present invention 10 or 11, wherein the process for press-molding comprises a process for molding projecting portions that project in a protruding shape in parts of the shape of the recess of the first molded body (4) and/or the second molded body (5) in order to cause the heat medium to meander.
The method for manufacturing a heat exchanger according to the present invention 13 is the method for manufacturing a heat exchanger according to the present invention 10 or 11, wherein the process for press-molding comprises a process for molding step shapes in parts of the shape of the recess of the first molded body (4) and/or the second molded body (5).
In the heat exchanger in accordance with the present invention, the base body of the heat exchanger is a molded body of a thin metal sheet. Therefore, the heat exchanger in which two molded bodies are combined has a structure that can be easily bendable and partially deformable. The outer surfaces of the edge portions of the two molded bodies are performed to ultrafine surface processing providing a fine uneven surface thereon, a thermoplastic resin composition is injected onto those regions, and a joining member is molded that joins the periphery of the edge portions of the two molded bodies in a sandwiched state. The resultant strong joining makes it possible to obtain a highly reliable high-quality heat exchanger in which the heat medium does not leak to the outside from the space serving as the flow channel for the heat medium, even under the effect of vibrations of an automobile.
Further, the resins coated on the inner surface of the edge portions of the two molded bodies are thermally fused by hot press working and the inner surfaces of the edge portions are sealed. The double-seal structure obtained by sealing with the joining member and sealing by thermal fusion of the resins on the inner surfaces makes it possible to obtain a highly reliable high-quality heat exchanger in which the heat medium does not leak to the outside from the space. Further, since such heat exchanger does not use brazing performed with a braze, product reliability is improved.
The method for manufacturing a heat exchanger in accordance with the present invention is a high-productivity manufacturing method that comprises a press-molding process, a hot pressing process, and an injection molding process as the main processes and makes it possible to manufacture a highly reliable high-quality heat exchanger at a low cost and with good productivity.
a) to 2(e) are explanatory process diagrams illustrating the process for manufacturing a heat exchanger.
Embodiments of the present invention will be described hereinbelow with reference to the drawings. The structure depicted in
The electronic components 3 are heat-generating sources and need to be cooled, since where a critical temperature is exceeded, the function thereof as electronic components is lost. In the heat exchanger 1 of the present embodiment, a first molded body 4 which is obtained by press-molding a thin aluminum alloy coil sheet and a second molded body 5 of the same structure are combined, and a joining member 6 which is a thermoplastic synthetic resin is formed by injection molding in the combination portions of the molded bodies. A heat medium 8 is circulated in an internal space 7 which is formed by combining the molded bodies, and heat exchange is performed. The heat medium in the present embodiment is cooling water.
The electronic components 3 are mainly cooled as a result of contact with an outer surface 4a of the first molded body 4, or an outer surface 5a of the second molded body 5, or both outer surfaces 4a, 5a. The thin aluminum alloy coil sheet which is used in the present embodiment is the same kind of thin aluminum alloy sheets used for beer cans or the like. This aluminum alloy coil sheet is a very thin sheet of a predetermined thickness (for example, 0.1 mm to 0.4 mm), and a very thin resin is covered on at least one surface thereof at a stage of coil-shaped material. On the inner and outer surface of a beer can, a coating is provided which has a thickness, for example, of about 4 μm on the inner surface and 4 μm to 10 μm (including the thickness of a paint) on the outer surface.
The resin coating film is typically a monolayer or multilayer laminated film. As for the resin type, for example, polypropylene (PP) is used. PP has a high melting point, a high thermal deformation temperature, high resistance to water boiling temperature, and a certain luster, and is suitable for forming transparent films. Furthermore, it is harder than polyethylene terephthalate (PET). However, the type of the coated resin is not limited to polypropylene (PP), and other resins, such as polyethylene terephthalate (PET), may be also used. The first molded body 4 and the second molded body 5 are obtained by press-molding a flat material for molded bodies (thin metal sheets) obtained by cutting the aluminum alloy coil sheet to predetermined shape and dimensions.
The thickness of the aluminum alloy coil sheet should be determined with consideration for the internal pressure, durability, and bendability, and it may be 0.1 mm to 0.8 mm, preferably 0.3 to 0.8, and more preferably 0.3 mm to 0.5 mm. For example, when the internal pressure is 0.6 Mpa to 1 Mpa, the thickness may be 0.3 mm to 0.5 mm. The first molded body 4 is constituted by edge portions 4c formed at the periphery, and a recess, in the cross-sectional view (a protrusion when viewed from the other side), which is molded by press-molding between the edge portion 4c and the edge portion 4c. Likewise, the second molded body 5 is constituted by edge portions 5c formed at the periphery, and a recess, in the cross-sectional view (a protrusion when viewed from the other side), between the edge portion 5c and the edge portion 5c.
The recesses are molded by press-molding. The base body of the heat exchanger 1 constituted by the molded body 4 and the second molded body 5 is constructed by abutting the edge portions 4c and the edge portions 5c in a state in which the first molded body 4 and the second molded body 5 are combined such that the recess molded in the first molded body 4 and the recess molded in the second molded body 5 face each other. Alternatively, the base body of the heat exchanger 1 is obtained by combining the first molded body 4 and the second molded body 5 such that the inner surface 4b and the inner surface 5b face each other. The inner surfaces 4b, 5b are resin-coated surfaces, and those resin-coated surfaces are obtained by coating the surface of the aluminum alloy with the resin. The resin-coated surfaces prevent the material (aluminum alloy) of the first molded body 4 and the second molded body 5 from aging corrosion caused by the heat medium 8 flowing into the heat exchanger and also prevent the heat medium 8 from degradation during the use.
Therefore, the resin-coated surface prevents the material from erosion even when a heat medium such a non-freezing liquid is used, and demonstrates excellent gas barrier effect. The material of the first molded body 4 and the second molded body 5 which is coated with the resin can be performed to press working which is plastic processing. The resin-coated surface of the edge portion 4c of the first molded body 4 and the resin-coated surface of the edge portion 5c of the second molded body 5 are performed to hot press working after the inner surface 4b of the edge portion 4c and the inner surface 5b of the edge portion 5c have been abutted against each other. As a consequence, the resins forming the resin-coated surfaces are thermally fused. As a result of the resin-coated surface of the inner surface 4b of the edge portion 4c and the resin-coated surface of the inner surface 5b of the edge portion 5c being thermally fused, the resin-coated surfaces are brought into intimate contact with each other, and the heat medium 8 contained inside the space 7 is prevented from leaking to the outside of the heat exchanger 1 from the portions of such intimate contact. From the standpoint of the manufacturing process, this thermal fusion can be also considered as provisional joining.
In an example of processing a beer can, the coil sheet therefor is processed into a can shape by DI molding (drawing and ironing) and a beer can is manufactured. Thus, the material is very thin, has properties suitable for DI molding, and can be press-molded while maintaining the thickness. For example, Patent Document 4 discloses an example of an aluminum alloy suitable for a DI can or bottle can which ensures moldability and suppresses strength reduction after coating with a resin to a minimum.
It is preferred that a metal with such capabilities be used. For example, a H19-tempered 3004-H19 alloy (see “JIS H 4000” stipulated by Japanese Industrial Standard) which is used as a beer can body material and processed to a predetermined thickness (for example, 0.3 mm) is preferred. The embodiment of the heat exchanger 1 which uses the above-described material is further described hereinbelow. In addition to the heat exchanger 1, a heat exchange apparatus is also provided with, for example, a heat medium circulation pump, a circulation circuit piping, and a control device, which are not depicted in the drawings. As mentioned hereinabove, the heat exchanger 1 is basically constituted by the first molded body 4 and the second molded body 5, which are two molded bodies. The space 7 is created inside the heat exchanger by combining the two molded bodies 4, 5, in which the recesses have been molded, such that the inner surfaces 4b, 5b face each other.
The internal space 7 is a flow channel for the heat medium 8, and the inner surfaces 4b, 5b are resin-coated surfaces which are coated with the resin. Therefore, when the two molded bodies 4, 5 are combined, the edge portion 4c of the first molded body 4 and the edge portion 5c of the second molded body 5 abut against each other. Since the abutting edge portions 4c, 5c are coated with the resin on the inner surfaces 4b, 5b, the coated resins are fused together when hot press working is performed, and the inner surface 4b of the edge portion 4c and the inner surface 5b of the edge portion 5c can be brought into perfect intimate contact with each other.
Thus, the thermally fused portion serves as a first seal that prevents the heat medium 8 from leaking from the space 7 to the outside of the heat exchanger 1 between the edge portion 4c and the edge portion 5c, thereby making it possible to seal the space 7. The outer surfaces 4a, 5a of the recesses are in contact with the electronic components 3, and the thickness of the two molded bodies 4, 5 is so thin that the bodies can be bent easily by the inner pressure of the heat medium 8. As a result, a structure is obtained which can be easily flexurally deformed.
Peripheral shapes of the edge portions 4c, 5c of the two molded bodies 4, 5, which have been combined together are rectangular shape to match the shape of the board 2 where the electronic component 3 are arranged. The outer surface 4a of the edge portion 4c and the outer surface 5a of the edge portion 5c are not coated with the resin. Further, the outer surface 4a of the edge portion 4c and the outer surface 5a of the edge portion 5c are performed to ultrafine surface treatment to form a fine uneven surface. This treatment is performed in order to increase the adhesion strength of the outer surface 4a of the edge section 4c and the outer surface 5a of the edge portion 5c to the joining member 6.
The ultrafine treatment is performed by a well-known method, but the essence thereof is described hereinbelow to facilitate the understanding of the present invention. Three conditions are associated with the treatment of the metal alloy surface in the present context. The first condition is that a rough surface is obtained by a chemical etching method such that a relief height difference measured for depressions and protrusions with a peak-valley average spacing (RSm) having a period of 1 μm to 10 μm is less than about half of the period, that is, the maximum roughness height (Rz) is 0.2 μm to 5 μm. Rephrasing, a surface with a micron-order roughness is obtained.
The second condition is that an ultrafine uneven surface with a period equal to or greater than 10 nm, preferably about 50 nm, is present on the inner wall surface of the depressions forming the aforementioned rough surface. The third condition is that the surface of such a complex configuration is a ceramic material, more specifically, a metal oxide layer which is thicker than the natural oxidation layer on the metal alloy species that inherently have poor corrosion resistance, and, a thin layer of a metal oxide or metal phosphorus oxide produced by chemical conversion treatment on the metal alloy species that inherently have poor corrosion resistance.
Thus, (1) a surface with large depressions and protrusions of a micron order is obtained by certain chemical processing for a metal alloy. Then, in greater detail, (2) ultrafine depressions and protrusions with a period equal to or greater than 10 nm are provided on the inner wall surface of at least the large depressions of a micron order, and then (3) the metal alloy surface having such ultrafine depressions and protrusions and also depressions and protrusions of a micron-order which are larger than the ultrafine depressions and protrusions are themselves coated with a thin ceramic material.
In a specific example of such surface treatment, for example, the surface is chemically etched to a roughness of 0.5 μm to 10 μm, this surface is covered with a ultrafine uneven surface with an irregular period of 5 nm to 500 nm, and the resultant surface is covered with a thin layer of a metal oxide or metal phosphorus oxide. Such a treatment enables strong integration of the metal with the resin. Since such surface treatment is described in detail in the aforementioned Patent Documents 6 and 7, detailed explanation thereof is herein omitted.
The edge portions 4c, 5c which have been treated to obtain the fine uneven surface are abutted against each other, inserted in a die in a state in which the resin-coated surface of the inner surface 4b and the resin-coated surface of the inner surface 5b are thermally fused, the resin joining member 6 is formed by injection molding at the edge portions 4c, 5c, and the base body shape of the unitary heat exchanger 1 is obtained. As depicted in the figure, the joining member 6 is configured such that the regions (regions separated by 1a from the end surfaces of the recesses of the molded bodies 4, 5) located outside of a portion 12e (see FIG. 2(2)) representing the control portion of the die, that is, the edge portions 4c, 5c on the perimeter of the two molded bodies 4, 5, are surrounded by the joining member in an endless manner. The joining member 6 covers and surrounds the edge portions 4c, 5c of the two molded bodies 4, 5 in a straddling manner.
As a result, a second seal is produced in which the periphery of the edge portions 4c, 5c of the two molded bodies 4, 5 is in a completely sealed state, and this seal in combination with the first seal configured by thermally fusing the resin-coated surfaces of the inner surfaces 4b, 5b makes it possible to ensure double sealing of the space 7. Further, since the periphery of the two molded bodies 4, 5 is completely sealed, the heat medium 8 can be prevented from leaking from the joining member 6 to the outside of the heat exchanger 1 regardless of the adverse environment in which the heat medium 8 of the heat exchanger 1 may be present. The joining member 6 combines together and joins the two molded bodies 4, 5 in the above-described manner, and it is preferred that the resin body thereof be obtained by injection molding of a crystalline thermoplastic resin composition (referred to hereinbelow as “resin composition”) preferably comprising a polybutylene terephthalate resin (PBT), a polyphenylene sulfide resin (PPS), or a polyamide resin (Nylon 6, Nylon 66, etc.) as a main component.
As a result, the outer surface 4a of the edge portion 4c and the outer surface 5a of the edge portion 5c of the two molded bodies 4, 5 made from an aluminum alloy, and the joining member 6, which is a resin body, are strongly integrated and joined together. Further, where the joining member 6 is molded, even when burrs, or the like, are formed during molding at the edge portions 4c, 5c of the two molded bodies 4, 5, which are made from a metal, it is not necessary to remove the burrs, and the joining member 6 can be molded while the burrs are present. The possibility to omit the deburring makes a significant contribution to the reduction in the number of processing steps, in particular, in the case of mass production.
The structure in
Therefore, no spread in the contact state is caused by the electronic components 3, and the efficiency of heat exchange does not change depending on a region. Further, a structure is obtained in which rod-shaped support bodies 9 that support the edge portions 4c, 5c of the heat exchanger 1 are provided between the board 2 and the heat exchanger 1. The rod-shaped support bodies 9 are fixing means for positioning and fixing such as to prevent displacement even in the case of vibrations. The heat exchanger 1 can be integrally attached through the rod-shaped support bodies 9 to the board 2 where the electronic components 3 are arranged.
With fixing means such as the rod-shaped support bodies, a cooling space is ensured between the electronic components 3 and the heat exchanger 1. The heat medium 8 is supplied from a supply port 10 of the two molded bodies 4, 5, flows as depicted by an arrow (see
The cooling temperature of the electronic components 3 is a predetermined set temperature, and temperature control of the heat medium 8 is performed according thereto. In the present embodiment, the set temperature is equal to or less than 70° C. The heat medium 8 is cooling water, but when the heat exchanger is to be used in cold climates, the cooling water is a non-freezing liquid. The cooling water in this case is preferably, for example, water including an ethylene-glycol-type additive. The ethylene glycol is one of the main starting materials for polyethylene terephthalate (PET resin), but since it is easily soluble in water and has a low melting point, it is advantageous for a non-freezing liquid for automobiles.
The plurality of electronic components 3 is not necessarily of the same height. In the conventional configurations, although tubular shapes of a certain thickness can be deformed, they are not deformed according to the height of each electronic component 3. In the present embodiment, the thickness of the two molded bodies 4, 5 is set to a predetermined thickness (for example, 0.1 mm or less). Therefore, even when there is an error in height or attachment, provided that it is in a predetermined range, the outer surface 4a is easily flexurally deformed, as mentioned hereinabove, due to the pressure, which is applied by the flowing heat medium 8, according to the individual electronic component 3. Furthermore, since the internal pressure of the heat medium 8 is the same in all locations according to the Pascal's principle, a constant contact pressure can be maintained for each electronic component, and therefore constant cooling capacity can be maintained. Thus, an intimate contact state can be realized for each electronic component 3 at all times.
A method for manufacturing a heat exchanger will be described hereinbelow in detail.
Then, as depicted in
Then, as depicted in
The die 12 is constituted by an upper die 12a and a lower die 12b, and the two molded bodies 4, 5, are inserted across the two dies 12a, 12b. When the die 12 is closed, a cavity 12d for forming the joining member 6 is formed around the edge portions 4c, 5c. In the structure obtained, portions 12e of the control portions of the die 12a and the die 12b sandwich parts of the edge portions 4c, 5c on the recess side thereof. The structure is thus obtained in which the edge portions 4c, 5c, in the irregular state thereof, of the two molded bodies 4, 5 protrude into the cavity 12d. The two thermally-fused molded bodies 4, 5 are aligned, the die 12 is closed, and a resin composition is then injected into the cavity 12d through a gate 12c.
As mentioned hereinabove, in the present example, the resin composition is a resin comprising PBT or PPS as the main component. The resin composition injected into the cavity 12d sandwiches the periphery of the edge portions 4c, 5c and seals the space 7. Then, after the resin composition has solidified, the die 12 is opened and the two integrated molded bodies 4, 5 including the solidified joining member 6 are removed from the die. As depicted in
The supply port 10 and the discharge port 11 which are essential to the functions of the heat exchanger 1 are attached to the base body so as to communicate with the space 7, and the manufacture of the heat exchanger 1 in the basic form thereof is thus completed. The forms of the supply port 10 and the discharge port 11 are not limited. In a simple example, a method can be used by which holes are drilled at appropriate locations, but the present embodiment is explained by providing a pipe.
The supply port 10 and the discharge port 11 may be provided at a stage of the process before or after the stage at which the two molded bodies 4, 5 are combined together. In this case, the die structure to be used at the injection molding stage, which is the subsequent process, needs to be such as to avoid the interference with the supply port 10 and the discharge port 11. Further, where the supply port 10 and the discharge port 11 can be provided on the flat portions on the two molded bodies 4, 5 on the outer surface 5a side, the supply port 10 and the discharge port 11 can be produced by only molding the respective regions at the press-molding stage by a method of partially projecting the regions in a pipe-like shape and forming holes in the end portions thereof.
The heat exchanger in accordance with the present invention is basically manufactured according to the method of the present embodiment, and other embodiment of the heat exchanger are explained hereinbelow as the cases of cooling in which electronic components are the heat exchange object. In the explanation of the other embodiments, the parts same as those of the above-described embodiment are assigned with the same reference numerals and the detailed explanation thereof is herein omitted.
Another Embodiment 1 will be explained hereinbelow with reference to
Another Embodiment 2 will be explained hereinbelow with reference to
Another Embodiment 3 will be explained hereinbelow with reference to
The shape of the external surface of the first molded body 4 is determined by the die at the press working stage, and the uneven surface is formed in the press working according to the height and arrangement of the electronic components 3. As a result, even when the electronic components 3 differ from each other, that is, when the electronic components 3 differ in shape and height, both the outer surface 4a and the stepped surfaces 14 can be brought into intimate contact and cooling efficiency can be increased. In this case, even when it is necessary to cool the electronic components 3 with the second molded body 5, as depicted in
Another Embodiment 4 will be explained hereinbelow with reference to
Another Embodiment 5 will be explained hereinbelow with reference to
In the structural example depicted in
Another Embodiment 6 will be explained hereinbelow with reference to
Another Embodiment 7 will be explained hereinbelow with reference to
The examples illustrating the cooling effect of the heat exchanger 1 and the joining state thereof, which are explained hereinabove, are focused on the examples of shape deformation of the heat exchanger 1 which is brought into contact with and caused to cool the electronic components 3. Structural examples in which the cooling efficiency of the heat exchanger 1 is further increased are explained hereinbelow. In the structural examples of the following embodiments, heat exchange enhancing bodies produced from materials, such as metals, that enhance heat exchange are inserted into the space 7 of the heat exchanger 1. The structural examples explained hereinbelow represent techniques that can be also applied to the above-described other embodiments.
The honeycomb structure is obtained by superimposing two configurations obtained by bending thin sheets of an aluminum alloy, or the like, and has the so-called beehive shape with a hexagonal cross section. Where such a structure is inserted into the heat exchanger 1, the section modulus of the heat exchanger 1 is improved and a strong configuration capable of withstanding stresses such as bending stresses is obtained. At the same time, the heat medium 8 is caused to pass in spaces 20a having a hexagonal shape, and the heat exchange efficiency is increased. Since the honeycomb structure has a large area of contact with the heat medium 8, heat conduction from the heat medium 8 is increased and heat exchange is further enhanced as compared with the above-described examples configured only of the space.
The heat exchange enhancing body 21 in the form of a metal block is molded by extrusion molding an aluminum alloy, and the molding can be performed to obtain the desired wall thickness between the through holes 21a. The metal block is provided with a wall surface 21b which is a wall surface in a wall region between the metal block and the main body of the heat exchanger 1. As a result, deformation in the production process can be prevented, the area of contact with the heat medium 8 can be ensured, and smooth heat exchange can be performed. The through holes 21a depicted in the figure have a rectangular cross-sectional shape, but they obviously may have another cross-sectional shape, such as round or elliptical shape.
Such a structure can be manufactured at a low cost. In addition, where the meandering spacing is narrowed, the area of contact with the heat medium 8 is increased, the heat exchange is enhanced, and the heat exchange effect can be improved. Such a structure presumes that the heat exchanger 1 is a thin metal sheet and that the joint is the resin joint 6. The figure illustrates a simple structure, but the shape of the heat exchange enhancing body 23 may be different. For example, as depicted partially in
a) and 17(b) illustrate the flow of the heat medium 8 in the heat exchanger 1 in the other embodiments depicted in abovementioned
b) illustrates an example in which the directions of the inflow port 10 and the outflow port 11 of the heat medium 8 are changed. In this example, the heat medium flows in from the same direction as the flow direction of the heat medium 8 in the heat exchanger 1. In the same manner as described hereinabove, the heat medium 8 that has flown in from the inflow port 10 flows into the abovementioned heat exchange enhancing bodies 20, 21, 22, 23 in the directions shown by the arrows through the reservoir space 7a, the heat is absorbed, the flows of the heat medium 8, which is in the heated state, merge in the reservoir space 7b on the outflow side, as shown by the arrows in the figure, and the heat medium is discharged to the outside through the outflow port 11 in the same direction as the flow direction thereof.
Thus, for example, the height, diameter, and shape of the heat exchange enhancing bodies are changed and controlled to obtain the uniform flow of the heat medium 8, or according to heat generation by individual electronic components, and the efficiency of heat exchange is increased.
The embodiments of the present invention are explained hereinabove, but the present invention is not limited to those embodiments. It goes without saying that changes can be made without departing from the objective and essence of the present invention. For example, metals other than aluminum alloys, for example, copper, can be also used as the main constituent material of the heat exchanger, provided that they are metals in the form of thin sheets, have high corrosion resistance, can be press worked, and have adhesion to resins.
Further, only the cooling application of the heat exchanger is explained hereinabove in detail, but the heat exchanger can be also used when the heat medium is heating water and, for example, heating with a heating device is required. Furthermore, a structure is explained above in which heat exchange is performed by bringing the heat exchanger into direct contact with electronic components, but a structure in which a member with good thermal conductivity (for example, an insulating material, such as a ceramic, with good thermal conductivity) is interposed therebetween may be also used. The material of the heat exchange enhancing bodies 20, 21, 22, 23 is not limited to metals and may be a synthetic resin with high thermal conductivity which has a low material cost and ensures high productivity may be also used.
1 heat exchanger
2 electronic control circuit board
3 electronic component (heat exchange object)
4 first molded body
5 second molded body
6 joining member
7 space
8 heat medium (cooling water)
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-007892 | Jan 2013 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2014/050845 | 1/17/2014 | WO | 00 |
