Patent Application
20090032231
This application is based on Japanese Patent Application No. 2007-202024 filed on Aug. 2, 2007, the contents of which are incorporated herein by reference in its entirety.
The present invention relates to a stacked plate heat exchanger, and is preferably applied to an oil cooler for an internal combustion engine used for an automobile.
Conventionally, the stacked plate heat exchanger such as an oil cooler is known in this field, also called as a housingless oil cooler. This type of oil cooler has a plurality of plates, typically made of metal such as aluminum or aluminum alloy. The plates include a first plate and a second plate formed in different shapes. The first and second plates are alternately stacked to define a plurality of passages therebetween. The passages include a first passage for coolant, such as cooling water and a second passage for hot medium, such as oil to be cooled. The first and second passages are alternately arranged. In one of conventional structures, each plate has a core layer and brazing material layers formed on both sides of the core layer. However, this oil cooler may have a leak hole on the plate due to corrosion by moisture or chlorine. Also, it is known that each plate may have a core layer, a brazing material layer on one side, and a corrosion resistant layer on the other side. The corrosion resistant layer may be a sacrificial layer. However, this oil cooler may also have a leak hole on the plate due to corrosion, since the brazing material layer on one of the first and second plates directly faces to the passage for coolant and causes corrosion.
In order to address such a corrosion problem, JP H05-1890A discloses an improved oil cooler having a first plate with cylindrical portion and a second plate with protruding portion. In this structure, the first plate is formed to have a cylindrical portion integrally on an outer rim of the first plate and to locate the sacrificial layer inside. The second plate is formed to have a protruding portion integrally along an outer rim of the second plate, protruding toward a main part of the first plate. Then, a brazing material layer on the outside of the protruding portion is brazed on the sacrificial layer on the inside the cylindrical portion. This improved structure may prevent corrosion from a coolant side, since the sacrificial layers on the first and second plates face to the passage for coolant, and the brazing material layers on the first and second plates face to the passage for oil.
In order to improve a brazing quality, it is required to make tightly contact the surfaces to be brazed. For this purpose, the above mentioned stacked plate oil coolers are usually employ a jig to hold and press the plates for brazing process.
However, the stacked plate oil cooler has brazing surfaces on a direction to which a pressing force can not apply. To overcome this problem, it is required to improve accuracy in size to reduce distance of gaps between the brazing surfaces, or to add a precise shaping process such as a sizing process to make contact the brazing surfaces.
Further, in case of attaching a support plate on a core formed by the stacked plates, it is difficult to braze such a support plate on the core, since the sacrificial layer exposed to the outside of the core hinders a brazing. To avoid this problem, it is required to form a brazing material layer on the support plate, or to add a further brazing member between the core and the support plate.
Considering the above mentioned problems, JP H10-185462A discloses a stacked plate oil cooler made of four-layered plates having a core layer, a first sacrificial layer being formed on one side of the core layer, a second sacrificial layer being formed on the other side of the core layer, and a brazing material layer being formed on the second sacrificial layer. The plate in this document is formed in a disc shape having a tapered outer rim. Therefore, it is possible to make the plate contact firmly by applying pressing force, since the tapered outer rims receive the pressing force.
However, it is not avoidable to increase material costs, and increase cost for the product, since the four-layered plates are required.
In view of the foregoing problems, it is an object of the present invention to provide a stacked plate oil cooler having sufficient resistance to corrosion and reliable joint of brazing.
It is a further object of the present invention to provide a stacked plate oil cooler having sufficient resistance to corrosion and reliable joint of brazing by using three-layered plates.
An embodiment of the invention provides a stacked plate heat exchanger for a first medium and a second medium. The oil cooler has a core section including alternately stacked first plates and second plates, each of the first and second plates being made of a three-layered plate having a core layer, a sacrificial layer formed on one side of the core layer, and a brazing material layer formed on the other side of the core layer. The oil cooler comprises a first tapered portion formed on an outer rim of each of the first plates. The first tapered portion is enlarged toward an opening. The first tapered portion includes a first folded portion formed by bending an outer rim of the first plate to place the sacrificial layer on the first plate outside the first tapered portion. The oil cooler further has a second tapered portion formed on an outer rim of each of the second plates. The first plates and the second plates are stacked alternately to define first passages for the first medium between the sacrificial layers on the first plate and the second plate, and to define second passages for the second medium between the brazing material layers on the first plate and the second plate. The first tapered portion and the brazing material layer on the second tapered portion are placed next to each other.
According to the invention, it is possible to prevent corrosion on a surface defining the first passages, since the first passages are completely surrounded by the sacrificial layers on the first plate and the second plate. Additionally, the first tapered portion and the second tapered portion enables to apply pressing force onto a brazing interface. Therefore, it is possible to improve brazing quality. Further, it is possible to achieve sufficient resistance to corrosion and reliable joint of brazing by using relatively low cost three-layered plates.
In a preferred embodiment, the second tapered portion may be enlarged toward an opening. The first plate may have a corner portion on the outer rim, and the corner portion may have a recess extending at least along the first folded portion. The recess ease to form the tapered portion without wrinkle even it has a folded portion.
Further, the second tapered portion may include a second folded portion formed by bending an outer rim of the second plate to place the brazing material layer on the second plate outside the second tapered portion.
The second tapered portion may have a brazing passage corresponding to the second folded portion to introduce brazing material to an interface between the sacrificial layers on the second plate. The second plate may have a corner portion on the outer rim, and the corner portion has a recess extending at least along the second folded portion. Further, at least one of the first and second tapered portions may be formed into a U-turn shape that is easy to manufacture.
The first fluid may be cooling water. The second fluid may be oil. The core layer of the first and second plates may be made of aluminum alloy.
Additional objects and advantages of the present invention will be more readily apparent from the following detailed description of preferred embodiments when taken together with the accompanying drawings. In which:
A first embodiment of the invention is described below with the drawings. The first embodiment is an oil cooler also called as a housingless oil cooler for cooling oil lubricating an internal combustion engine mounted on a vehicle. The oil cooler is attached on a side wall of an engine cylinder block and performs heat exchange between oil and engine cooling water.
Referring to
The cover plate 2 is made of a double-layered plate having a core layer made of aluminum alloy and a sacrificial layer having galvanic potential lower than that of the core layer. The sacrificial layer is a clad layer covering the side of the core layer opposite from the core 10.
The support plate 4 has a water inlet 4a for introducing the cooling water into the core 10, a water outlet 4b for flowing out the cooling water from the core 10, an oil inlet 4c for introducing the oil into the core 10, and an oil outlet 4d for flowing out the oil from the core 10. The support plate 4 further has through holes 4e or recesses formed on corners for accepting attaching member such as bolts for attaching the support plate 4 on the cylinder block.
The core 10 has a plurality of disc shaped plates. The plates include the first plates 1 and the second plates 2 alternately stacked along thickness directions to define water passages 21 and oil passages 22 alternately therebetween. The water passage 21 provides a first passage, and is a flat and thin passage for cooling water. The water passage 21 is surrounded by sacrificial layers formed on the first and second plates 1 and 2. The oil passage 22 provides a second passage, and is a flat and thin passage for oil. The oil passage 22 is surrounded by brazing material layers formed on the first and second plates 1 and 2. Therefore, a pair of the second plate 2 and the first plate 1 defines a fluid passage for cooling water. Similarly, a pair of the first plate 1 and the second plate 2 defines a fluid passage for oil.
The water passages 21 and the oil passages 22 respectively have first inner fins 23 and second inner fins 24 therein. The inner fins 23 and 24 are offset fins to facilitate heat transfer. The first inner fins 23 located inside the water passages 21 are made of a clad plate having brazing material layers on both sides of a core layer. The second inner fins 24 located inside the oil passages 22 are made of a bare plate without brazing material layer.
The oil cooler has four connecting passages penetrating the core 10 in a stacking direction for connecting the passages 21 and 22, since the water passages 21 and the oil passages 22 are arranged in parallel with respect to the stacking direction. The connecting passages include a water inlet passage connecting the water passages 21 at inlet portions thereof, and include a water outlet passage connecting the water passages 21 at outlet portions thereof. In FIG. 2, the water inlet passage 25 is illustrated. Similarly, the connecting passages include an oil inlet passage connecting the oil passages 22 at inlet portions thereof, and include an oil outlet passage connecting the oil passages 22 at outlet portions thereof. In
Referring to
The second plate 2 is made of a second three-layered aluminum alloy clad sheet. The second plate 2 has a second core layer 34 made of aluminum alloy, a second brazing material layer 35 having a lower melting point than the second core layer 34, and a second sacrificial layer 36 having lower galvanic potential than that of the second core layer 34. The second sacrificial layer 36 is formed on one side surface of the second core layer 34 which faces to the water passage 21. The second brazing material layer 35 is formed on the other side surface of the second core layer 34 which faces to the oil passage 22. The second sacrificial layer 36 has a higher melting point than the second brazing material layer 35, and poorer resistance to corrosion than the second core layer 34. The second sacrificial layer 36 provides anti-corrosion protection for the second core layer 34 by its sacrificial corrosion.
Back to
The second plate 2 has a partitioning portion 51 formed in flat and having four through holes, ring shaped first protrusions 52 joining portions) formed on the partitioning portion 51 around the through holes for the connecting passages 25, and ring shaped second protrusions 53 Coining portions) formed around the through holes for the connecting passages 25. The first protrusions 52 and the second protrusions 53 have ring shaped frat tops respectively, and protrude toward opposite direction to each other. The flat tops of the first protrusions 52 are brazed with the joining margins 42. Inside surfaces of the flat tops of the second protrusions 53 are brazed with insides of the burring portions 43 and are mechanically clamped by the burring portions 43. The flat tops of the second protrusions 53 may be brazed with the base region of the burring portions 43 by the brazing material supplied from the first and second brazing material layers 35.
Referring to
Similarly, the second plate 2 has a second tapered portion 54 on an outer rim surrounding the partitioning portion 51. The second tapered portion 54 provides enlarged rim from the partitioning portion 51 toward the outer end. The second tapered portion is formed to enlarge a span of its opening toward its opening side. The second tapered portion 54 is formed by stacking a sloping rim and a second folded portion 55. The second folded portion 55 is formed to fold the outer rim of the second plate 2 to make the second brazing material layer 35 exposed to the outside at the second tapered portion 54. The second folded portion 55 is formed to cover entire area of the second tapered portion 54. Therefore, the distal end of the second folded portion 55 reaches to a boundary between the partitioning portion 51 and the second tapered portion 54. As a result, the lateral outside surface of the second plate 2 is fully covered with the second brazing material layer 35.
In an assembled form, the first plates 1 and the second plates 2 are alternately stacked to place the first plate 1 on one end and the second plate 2 on the other end. The first plate 1 and the second plate 2 are placed and stacked so that the first tapered portion 44 comes into contact with the second brazing material layer 35. In detail, the first sacrificial layer 32 on the first folded portion 45 comes into contact with the second brazing material layer 35 on the second folded portion 55. The first plate 1 is folded at an outer rim to place the first sacrificial layer 32 on a lateral outside of a core assembly to decrease exposure of the brazing material layer to the lateral outside.
The core assembly has at least one combination of one of the first plate 1 and two of the second plates 2 stacked on both sides of the first plate 1. In this combination, the sacrificial layer 32 placed on both sides of the first tapered portion 44 of the first plate 1 are brazed with the brazing material layer 35 on the second tapered portion 54 of one of the second plates 2 and brazed with the brazing material layer 35 on the second tapered portion 54 of the other one of the second plates 2. This combination enables brazing between the first and second plates, and improves resistance to corrosion.
The stacked plate oil cooler can be manufactured by the following process. First, the first three-layered aluminum alloy clad sheet is prepared by forming the first brazing material layer 33 on one side of the first core layer 31 and forming the first sacrificial layer 32 on the other side of the first core layer 31. Similarly, the second three-layered aluminum alloy clad sheet is prepared by forming the second brazing material layer 35 on one side of the second core layer 34 and forming the second sacrificial layer 36 on the other side of the second core layer 34. The first and second three-layered aluminum alloy clad sheets can be the same and used in reversed fashion.
The first and second core layers 31 and 34 are made of Al—Mn alloy for decreasing weight and improving heat conductivity. The first and second brazing material layers 33 and 35 are made of Al—Si alloy. The first and second sacrificial layers 32 and 36 are made of Al—Zn alloy. The layers 32, 33, 35, 36 can be formed by a clad process in which a film shaped brazing material and a film shaped sacrificial material are firmly fixed onto the core material by pressing them below the melting temperature of the materials.
In a cutting process, the first and second three-layered aluminum alloy clad sheets are cut into a predetermined shape, a rectangular shape, by pressing machines. Simultaneously, the through holes and recesses are formed on predetermined locations. As a result, predetermined shaped plates are prepared.
In a bending and folding process, the plates are processed into a predetermined shape as illustrated in
In an assembling process, the first plates 1 and the second plates 2 are stacked alternately along their thickness direction. The inner fins 23, 24 are also alternately placed between the first plates 1 and the second plates 2. The first plate 1 and the second plate 2 are placed as illustrated in
Then, the cover plate 3 is assembled onto the second plate 2 placed on one end of the core assembly. The support plate 4 is assembled onto the first plate 1 placed on the other end of the core assembly. As a result, an oil cooler assembly is assembled. In order to keep the assembled condition to the end of the following brazing process, the oil cooler assembly is preferably tightened along its stacking direction by an appropriate tightening jig. The jig also applies pressing force to the oil cooler assembly to make the plates 1 and 2 come in contact firmly in order to improve brazing quality.
In a brazing process, the oil cooler assembly is brought into a brazing furnace such a vacuum furnace. In the brazing process, the oil cooler assembly is integrally brazed into a single unit by heating to a temperature equal to or higher than a melting point of the first and second brazing material layers 33 and 35, and lower than a melting point of the first and second sacrificial layers 32 and 36. As a result, the first brazing material layer 33 is brazed with the second sacrificial layer 36. The first brazing material layer 33 is brazed with the second brazing material layer 35. The first sacrificial layer 32 is brazed with the second brazing material layer 35. It is possible to prevent an excessive sacrificial corrosion on the brazed portion on the tapered portions 44 and 54, since the sacrificial material in the first sacrificial layer 32 and the brazing material in the second brazing material layer 35 are mixed and diffused to each other, and form an alloy having a higher galvanic potential than that of the original first sacrificial material.
Referring to
The recess 46 is formed on each corner of the plates in the cutting process. The corner has a recess extending at least along the first folded portion 45. The recess 46 is formed in a triangular shape to enable the corner deformed upwardly without wrinkle. The recess 46 is formed to cross the mountain fold line. The plates are pressed to have generally a disc like shape. An outer rim of the plate is bent and folded into the tapered portions 44. The recess 46 is closed during the pressing process as shown in
Referring to
The first inner fins 23 located inside the water passages 21 are made of a clad plate having brazing material layers on both sides of a core layer, since the water passages 21 are completely covered with the sacrificial materials. The second inner fins 24 located inside the oil passages 22 can be made of a bare plate without brazing material layer, since the oil passages 22 are completely covered with the brazing material.
As described above, the first plate 1 and the second plate 2 are stacked to define the water passages 21 between the first sacrificial layer 32 and the second sacrificial layer 36. Therefore, it is possible to decrease corrosion of the first plates 1 and the second plates 2 from the water passages 21. In addition, it is possible to improve brazing quality between the first and second tapered portions 44 and 54, since the first and second tapered portions 44 and 54 enables to apply pressing force on brazing interfaces and make the first and second plates 1 and 2 come into contact firmly. Further, it is possible to decrease cost of the oil cooler, since the oil cooler can be assembled by using relatively cheaper three-layered sheet.
It is possible to improve resistance to corrosion against moisture or chlorine on a lateral outside of the oil cooler, since the first sacrificial layer 32 is exposed to the lateral outside of the first plate 1 by forming the folded portion 45.
It is possible to attach the cover plate 3 and the support plate 4 in a single brazing process, since the first brazing material layer 33 and the second brazing material layer 35 are placed on the ends of the core assembly. It is also possible to improve resistance to corrosion against moisture or chlorine on the cover plate 3 by forming a sacrificial layer on a side opposite to the core 10.
A second embodiment of the invention is described below with the drawings. Referring to
A third embodiment of the invention is described below with the drawings. Referring to
A fourth embodiment of the invention is described below with the drawings. Referring to
In the above described embodiments, the oil coolers are mounted on the cylinder block, alternately, the oil coolers may be mounted on an outside surface of a crank case of an engine or a body of a transmission for vehicles. Further, the invention may be applied to an oil cooler integrally formed with an oil filter.
Further, the invention may be applied to a heat exchanger other than the oil cooler, for example, a heat exchanger for automatic transmission fluid (ATF), a heat exchanger for pneumatic oil for a power steering mechanism, and a heat exchanger for other fluid.
Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-202024 | Aug 2007 | JP | national |
