The present invention relates to a parallel flow type of heat exchanger which is arranged at the front in an engine room of a vehicle and which is provided with porous tubes constituted by inner fin tubes.
In a heat exchanger which is applied to a refrigerant condenser of an air-conditioning system for automobile use, a structure which is comprised of a plurality of porous tubes which are fabricated by extrusion and are inserted at their two sides into header plates of header tanks at predetermined intervals and which is provided with outer fins for heat dissipation use between the porous tubes and other porous tubes has been employed. However, in recent years, due to the demand for reducing costs of heat exchangers, the most costly parts, the porous tubes, are being fabricated by, instead of extrusion, sheet forming for bending belt-shaped sheet members to form tubes and providing inner fins at the insides so as to simplify the method of production, lighten the weight, and reduce the costs.
Porous tubes which are obtained by sheet forming for bending belt-shaped sheet members to form tubes and providing inner fins at the insides are called “inner fin tubes”. A heat exchanger which employs such inner fin tubes is disclosed in PLT 1. The biggest advantages of production of inner fin tubes by sheet forming of belt-shaped sheet members are the ease of reducing weight by suitably setting the sheet thickness and the greater degree of freedom of shaping than the extrusion method and therefore the enlarged heat conduction area etc. and consequent ability to improve the heat exchange performance of the heat exchanger.
A heat exchanger which uses the inner fin tubes which are shown in PLT 1 etc. is for use for air-conditioning systems for vehicular use. Its configuration is shown simplified in
At the insides of the entry side header tank 3 and exit side header tank 4, in this example, separators 26 are provided. At the two end parts, caps 23 and 24 which close the opening parts of the header tanks are brazed. The insides of the entry side header tank 3 and exit side header tank 4 are separated by the separators 26 into a plurality of spaces. Further, the entry side header tank 3 has an inflow port 21 for the refrigerant, while the exit side header tank 4 has an outflow port 22 for the refrigerant. Further, the refrigerant which flows from the inflow port 21 to the inside of the heat exchanger 1 flows through the insides of the entry side header tank 3 and exit side header tank 4 which are separated by the separators 26 and the insides of the inner fin tubes 10 as shown by the broken lines and discharged from the outflow part 22. Note that, the number of the inner fin tubes 10 and the number of the separators 26 which are shown in
Specifically, the tube 11 is comprised of a belt-shaped sheet member with a center part which is bent into an arc to form a curved end part 11a and with parallel parts 11p which extend from this curved end part 11a to form a swaged part 11b at the end part at the opposite side from the curved end part 11a of the parallel parts 11p. At this time, the two end parts of the belt-shaped sheet member are made different in lengths from the curved end part 11a for swaging at the swaged part 11b. The inner fin 12, like the tube 11, is formed in a wave shape by rolling a thin (for example thickness 0.1 mm) aluminum belt-shaped sheet and providing flat plate parts 15 and 16 at the two end parts. The bent parts 14 of the wave parts of the inner fin 12 are brazed at the inside wall surface 13 of the tube 11, while the end part of the flat plate part 16 is brazed to the inside wall surface 14 of the curved end part 11a. On the other hand, the end part of the flat plate part 15 of the inner fin 12 is joined with the tube 11 by swaging at the swaged part 11b.
PLT 1: Japanese Patent Publication No. 2007-125590A
However, if brazing the front end parts of the inner fin tubes 10 to the header plates 41 by brazing material which is arranged between the header plates 41 and the tank plates 42, there was the problem that the brazing material of the header plates 41 flows into the inner fin tubes 10 and melts the tubes. Further, as shown in
Here, tube melting will be explained in detail.
Further, the long end part 11e and one slanted part 11c of the belt-shaped sheet member are brazed together by a brazing material 51, while the flat plate part 15 of the inner fin 12 and the inside surfaces of the slanted parts 11c are brazed together by the brazing material 52. Further, the bent parts 14 of the inner fin 12 and the inner wall surface 13 of the tube 11 are brazed by the brazing material 53.
Inflow of brazing material to the inner fin tube occurs due to the step difference at the swaged part of the tube which is formed by the bent sheet, so up to now measures have been taken such as welding together the swaged part or reducing the step difference at the swaged part. However, each of these measures leads to increased cost. Further, special steps are required where the brazing temperature has to be strictly managed. Insufficient measures have been taken against the flow of brazing material to the inside of the inner fin tube.
The present invention, in consideration of the above problem, provides a heat exchanger which is brazed after tubes are assembled into the header tanks wherein tube melting at the time of attachment of the tubes to the header tanks can be prevented and productivity can be improved.
To solve the above problem, the present invention provides a heat exchanger (1) which has a plurality of tubes (11) which are provided with refrigerant passages inside them and a pair of header tanks (3, 4) to which end parts of the tubes (11) are brazed, wherein brazing materials (8) which are used for brazing to the header tanks (3, 4) are arranged at the outer circumferential surfaces of the tubes (11), and the base materials of the metal sheet members which form the header tanks (3, 4) are exposed at the inner circumferential surfaces and outer circumferential surfaces of the header tanks (3, 4).
According to the heat exchanger of the present invention, the brazing material which is necessary for brazing a tube and a header tank is supplied from the outer circumferential surface of the tube, so tube melting at the time of brazing is prevented, and the heat exchanger is improved in productivity.
Further, reference notations attached above are examples which show the correspondence with specific examples of the later explained embodiments.
Below, referring to the drawings, embodiments of the present invention will be explained. In the embodiments, parts which are configured the same are assigned the same reference notations and explanations will be omitted. Parts of the embodiments of the present invention which are the same in configuration as the comparative art forming the basis of the present invention are assigned the same reference notations and explanations are omitted.
The belt-shaped sheet member is folded back as explained above to form the flat tube 11. At the inside, an inner fin 12 is housed whereby a flat shaped flow path of the medium is formed. The inner fin 12 is formed into a wave shape by rolling a thin (for example thickness 0.1 mm) aluminum belt-shaped sheet member in the same way as the tube 11. At the two end parts, flat plate parts 15 and 16 are provided. The bent parts 14 of the wave shaped parts of the inner fin 12 are brazed to the inside wall surface 13 of the tube 11. The end part of the flat plate part 16 is also brazed to the inside wall surface 13 of the curved end part 11a. On the other hand, the end part of the other flat plate part 15 of the inner fin 12 is sandwiched between the two end parts bent to become parallel.
The two end parts 11e and 11f of the belt-shaped sheet member which sandwich the flat plate part 15 of the inner fin 12 in the first embodiment become longer at the end part 11e than the end part 11f. Accordingly, the end part 11e is folded back to the end part 11f side in a state sandwiching the flat plate part 15 and the end part 11f and is swaged to join them whereby the swaged part 11b is formed. In the first embodiment, a brazing material 8 is arranged (clad) at the outer surface as a whole at the thus formed inner fin tube 10. The amount of this brazing material 8 becomes an amount which is required for brazing the inner fin tube 10 to the entry side and exit side header tanks 3 and 4 when inserting and brazing the two end parts of the inner fin tube 10, as shown in
In this case, the inner circumferential surfaces N and outer circumferential surfaces S of the header plates 31 and 41 which form the entry side header tank 3 and the exit side header tank 4, as shown in
As explained above, the brazing material which flows to the inside of the inner fin tube 10 is a sufficient amount of brazing material 8 which is clad over the entire outer surface of the inner fin tube 10. For this reason, the amount of the brazing material which is supplied to the brazing part of the inner fin tube 10 becomes sufficient, and the brazing fillet of the inner fin tube 10 can be made larger. Further, a fillet commensurate with the amount of brazing material of the part itself is formed and the brazeability of parts other than the inner fin tube 10 is also improved.
Here, consider the case of the comparative art where the brazing material which is at the entry side and exit side header tanks 3 and 4 flows into the inner fin tube 10 and where the brazing material which is at the entry side and exit side header tanks 3 and 4 and the brazing material of the inner fin tube 10 are connected. In this case, the size of the fillet radius of the fillet which is formed at the inner fin 12 and the size of the fillet radius which is formed at the tank plate 32 and header plate 31 become substantially equal. However, in this case, the amounts of brazing material at the entry side and exit side header tanks 3 and 4 are small, so the size of the fillet radius of the tank plate 32 and header plate 31 ends up becoming the same 0.1 mm or so as the fillet radius of the fillet which is formed at the inner fin 12. That is, sometimes the size of the fillet radius which is formed at the tank plate 32 and the header plate 31 is extremely small and the gap at the part requiring brazing cannot be filled resulting in leakage.
As opposed to this, if making the inner circumferential surfaces N and outer circumferential surfaces S of the header plates 31 and 41 brazing material-free, the connection of the brazing material of the fillet which is formed between the tank plate 32 and header plate 31 and the brazing material of the fillet 52 or 53 which is formed at the inner fin 12 can be broken. As a result, it is possible to form a large fillet at the joint of the tank plate 32 and header plate 31 or the joint of the tank plate 32 and a cap 24. That is, it is possible to form a large fillet of the fillet radius 0.3 mm to 0.6 mm or so which can inherently be obtained at the joint of the tank plate 32 and header plate 31 or the joint of the tank plate 32 and a cap 24, the gap can be easily filled, and the brazeability can be improved. Note that, the “size of the fillet radius” which is referred to here envisions the case of using the generally widely used brazing material with 10 wt % of amount of Si.
Further, the surface of the inner fin tube 10 sometimes has an anticorrosion layer or sacrificial brazing material on which the brazing material layer is superposed arranged on it, but by making the header plates 31 and 41 brazing material-free, it is possible to prevent the inflow of brazing material from the entry side and the exit side header tanks 3 and 4, so the flow of brazing material to the surface of the inner fin tube 10 is also prevented. The brazing material ends up obstructing the action of the anticorrosion layer, so by preventing the flow of brazing material to the surface of the inner fin tube 10, it is possible to improve the corrosion resistance of the inner fin tube 10.
Further, it is possible to use as the material of the header plates 31 and 41 a metal material which does not contain a brazing material and provide the inner circumferential surfaces N or outer circumferential surfaces S of the header plates 31 and 41 with a low potential anticorrosion layer constituted by a sacrificial material.
Still further, the inner circumferential surfaces N and outer circumferential surfaces S of the entry side and exit side header tanks 3 and 4 may be made brazing material-free even in the case where the entry side and exit side header tanks 3 and 4 are single-piece pipes 30 not split into header plates 31 and 41 and tank plates 32 and 42. Further, the single-piece pipes 30 which are used for the entry side and exit side header tanks 3 and 4 are effective regardless of their cross-sectional shapes such as the circular shape which is shown in
Note that, in the entry side and exit side header tanks 3 and 4 which are shown from
In the case of this arrangement, the header plates 31 and 41 and the separator 26 are brazing material-free, but brazing material which is arranged at the tank plates 32 and 42 is supplied, whereby the header plates 31 and 41 and the separator 26 can be brazed. Tank brazing material flows through the fine clearances between the separator 26 and header plates 31 and 41 whereby these are brazed together. In this case, as the brazing material of the tank plates 32 and 42, a brazing material with an amount of Si of 6 wt % or more is suitable.
If, in this way, making the metal sheet member which forms the separator 26 a sheet member with the base material exposed and not providing a brazing material, that is, making it brazing material-free, it is possible to cut the flow paths of brazing material to the header plates 31 and 41 resulting in a further reduction in the occurrence of tube melting.
If in this way providing the two surfaces of the separator 26 with grooves or holes, even if the two surfaces of the entry side header tank 3 and the exit side header tank 4 are provided with brazing material, the excess brazing material can be held at the grooves or holes and flow of excess brazing material to the header plate side can be prevented. As a result, excess brazing material no longer flows into the inner fin tubes and tube melting can be prevented.
The brazing material which causes tube melting flows to an inner fin tube through a brazing part of a separator 26 and an inside of a tank. Therefore, as shown in the first to the sixth specific examples, by providing the two surfaces of the separator 26 with grooves 36 or ribs 37, it is possible to reduce or delay the amount of brazing material which flows from the inside of the tank through the separator 26 to the inner fin tube. That is, the grooves 36 or ribs 37 which are provided at the two surfaces of the separator 26 can extend the flow paths from the inside of the tank to the inner fin tube and can increase the time it takes for the brazing material to reach the inner fin tube due to the large flow resistance of the brazing material. As a result, it is possible to reduce the temperature difference from the core part before the brazing material reaches the inner fin tube, so tube melting is reduced.
In the embodiments which were explained above, the type and thickness of the brazing material which was actually used was a brazing material with a 4 wt % to 5 wt % amount of Si and with a clad rate of 20% (since the sheet thickness t was 0.2 mm, the film thickness was 40 μm). However, in the present invention, as the brazing material which is clad at the tube surface, a usually used 10 wt % brazing material is also possible. The invention is effective even for a tube provided with a clad rate 10% (film thickness 20 μm) or so brazing material. That is, the invention is effective even for a tube with an amount of Si of the brazing material 8 at the tube surface of 3.5 wt % to 10 wt %. However, the amount of the brazing material at the tube surface is preferably 3.5 wt % to 7.5 wt %.
As explained above, in the present invention, there is provided a heat exchanger which employs tubes which were produced by sheet bending wherein the brazing materials which are required at the time of brazing the tubes are supplied from the outer circumferential surfaces of the tubes, so tube melting at the time of brazing the tubes to the header tanks is prevented and the productivity of the heat exchanger is improved. Further, by making the separators which are provided at the inside of the header tanks brazing material-free or by providing the separators with structures for holding the brazing materials, tube melting at the time of brazing the tubes to the header tanks is prevented. Further, by combining the above-mentioned first to third embodiments, it is possible to further reduce the tube melting at the time of brazing the tubes to the header tanks.
Note that, in the above-mentioned embodiments, examples of using tubes with inner fins at their insides as the tubes which were brazed to the header plates were explained, but it is also possible to use tubes in which no inner fins are arranged. In particular, if the tubes which are brazed to the header plates are tubes of structures comprised of sheet members which are folded back and are superposed at their two end parts, the brazing materials are sucked in at the superposed parts due to the capillary phenomenon, so the brazing materials easily pool near the superposed parts, but it is possible to prevent tube melting by application of the present invention.
Further, in the above-mentioned embodiments, the example of use of aluminum as the material of the inner fin tubes and inner fins was explained, but in all of the above embodiments, it is possible to use aluminum alloy as the material of the inner fin tubes and inner fins.
Number | Date | Country | Kind |
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2012-085849 | Apr 2012 | JP | national |
2013-077780 | Apr 2013 | JP | national |
This application is a divisional of U.S. patent application Ser. No. 14/390,003, filed Oct. 1, 2014, which is a U.S. National Phase Application under 35 U.S.C. 371 of International Application No. PCT/JP2013/060354 filed on Apr. 4, 2013 and published in Japanese as WO 2013/151138 A1 on Oct. 10, 2013. This application is based on and claims the benefit of priority from Japanese Patent Application Nos. 2013-077780 filed on Apr. 3, 2013 and 2012-085849 filed on Apr. 4, 2012. The entire disclosures of all of the above applications are incorporated herein by reference.
Number | Date | Country | |
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Parent | 14390003 | Oct 2014 | US |
Child | 16285981 | US |