Abstract:
In a method for manufacturing a stacking-type, multi-flow, heat exchanger, heat transfer tubes and outer fins are stacked alternately, each heat transfer tube being formed by connecting a pair of tube plates and including an inner fin therebetween. The manufacturing method includes the steps of disposing the tube plates so as to oppose each other, inserting an inner-fin forming material between the tube plates, stacking the tube plates with respect to each other so as to nip or seize the inner-fin forming material between the tube plates, and cutting the inner-fin forming material and end portions of the tube plates simultaneously. By this method, the time for required manufacturing heat transfer tubes may be reduced significantly, and the productivity of the heat exchanger may be increased significantly. The positioning of inner fins may be achieved with a high degree of accuracy. Therefore, a stacking-type, multi-flow, heat exchanger having superior performance qualities and manufactured with a high degree of reliability may be manufactured at a reduced cost.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a stacking-type, multi-flow, heat exchangers, each heat exchanger comprising a plurality of heat transfer tubes, each tube having an inner fin therein and outer fins which are stacked alternately between the tubes, and methods for manufacturing such heat exchangers. Specifically, the present invention relates to a process for manufacturing the heat transfer tubes, each tube having an inner fin therein, and a stacking-type, multi-flow, heat exchanger manufactured by using the methods, suitable as a heat exchanger for use in an air conditioning system, in particular, for vehicles. 
   2. Description of Related Art 
   Stacking-type, multi-flow, heat exchangers having alternately stacked heat transfer tubes, each tube having an inner fin therein and outer fins therebetween, are known, for example, as depicted in  FIGS. 10–12 . In a heat exchanger, thus constructed, a heat transfer tube is formed as in a known heat exchanger, as depicted in  FIGS. 10 and 11 . Namely, a pair of tube plates  101 , each formed as depicted in  FIG. 10 , are disposed so as to compare each other, as depicted in  FIG. 11 , and the circumferential edges thereof are connected to each other to form fluid passages  102  therein. An inner fin  103  is inserted into each fluid passage  102  in order to increase the efficiency of heat exchange. Flanges  104  are formed on tube plates  101  at the end portions of each tube plate  101  in its width direction. Flanges  104  are disposed at the front and rear positions in the direction of air flow  40 , as depicted in  FIG. 12 , which is viewed along Line A—A of  FIG. 8 . Thus, a known heat transfer tube  105  is constructed, for example, as disclosed in Japanese Patent Application No. JP-A-2002-267383. 
   Such a known heat transfer tube  105  is manufactured, for example, as depicted in  FIG. 13 . The manufacturing method shown in  FIG. 13  has the following steps: 
   Step  11  (S 11 ): Tube plates  101  and  101 ′ and inner fins  103  are made as complete parts, separately, and plates  101  and fin  103  are provided in a tube assembling process. 
   Step  12  (S 12 ): Inner fins  103  are grasped by insertion arm  106  and conveyed toward tube plates  101  and  101 ′. 
   Step  13  (S 13 ): Inner fins  103 , conveyed by insertion arm  106 , are disposed on a first or lower-side tube plate  101  within predetermined cavities so as not to be shifted from the predetermined positions. 
   Step  14  (S 14 ): Insertion arm  106  is returned to its initial position. 
   Step  15  (S 15 ): After insertion arm  106  is withdrawn from between tube plates  101 , a second or upper-side tube plate  101 ′ disposed onto the lower-side tube plate  101 . 
   Step  16  (S 16 ): The pair of tube plates  101  and  101 ′ are secured temporarily to each other, so that the configuration of the heat transfer tube formed by the pair of tube plates  101  and  101 ′ is not disturbed during the stacking of a plurality of heat transfer tubes and a plurality of outer fins alternately, for example, temporarily secured by caulking to each other by crimping. 
   In such a method for manufacturing a heat transfer tube, however, at least the following problems remain: 
   (1) As the number of heat transfer tubes used per heat exchanger increases, the time for assemble increases, and the productivity declines. 
   (2) It is difficult to accurately position inner fins within the predetermined cavities of the fluid passage forming portions of a tube plate during of the above-described S 13 . 
   (3) A positional shift of an inner fin may occur during the covering of first-tube plate  101  with second tube plate  101 ′ at above-described S 15 . 
   SUMMARY OF THE INVENTION 
   Accordingly, a need has arisen to provide a method for manufacturing stacking-type, multi-flow, heat exchangers, which reduces the manufacturing time for a heat transfer tube, thereby increasing the productivity of the heat exchanger manufacturing method, which facilitates the positioning of inner fins being disposed at predetermined positions in each tube plate, and which prevents a positional shift of the inner fins after the inner fins are so positioned, and to provide stacking-type, multi-flow, heat exchangers, which are manufactured by using this manufacturing method. 
   To satisfy the foregoing need and to achieve other objects, a method for manufacturing a stacking-type, multi-flow, heat exchanger, according to the present invention, is provided. The stacking-type, multi-flow, heat exchanger comprises a plurality of heat transfer tubes and a plurality of outer fins, which are stacked alternately. Each heat transfer tube is formed by connecting a pair of tube plates to form a fluid passage in each heat transfer tube, and each heat transfer tube has an inner fin, which extends in a longitudinal direction of the pair of tube plates, in the fluid passage. The manufacturing method comprises the steps of disposing the pair of tube plates so as to oppose each other; inserting an inner-fin forming material between the pair of opposing tube plates; stacking the pair of tube plates with respect to each other so as to nip or seize the inner-fin forming material between the pair of tube plates; and cutting the inner-fin forming material and end portions of the pair of tube plates substantially simultaneously. 
   In this method, it is preferred that the stacked pair of tube plates are temporarily secured simultaneously with the cutting at the above-described cutting step. As a result, the manufacturing method may be further simplified. 
   Further, it is preferred that at least one end portion of each heat transfer tube in a width direction of the heat transfer tube is formed as a shape linearly extending in an outward or lateral direction. In such a structure, the nipping or seizing of the inner-fin forming material between the pair of tube plates may be facilitated, and the cutting of the inner-fin forming material and the end portions of the pair of tube plates simultaneously also may be facilitated. 
   Moreover, it is preferred that the inner-fin forming material is formed as a portion of a continuous material extending in a width direction of each heat transfer tube, and after the continuous material is inserted between the pair of opposing tube plates, the continuous material and the end portions of the pair of tube plates are cut simultaneously. In this case, it is more preferable that wavy or undulating portions and linear portions are arranged alternately in each portion of the continuous material in a width direction of each heat transfer tube. After the continuous material is inserted between the pair of opposing tube plates, the continuous material and the end portions of the pair of tube plates are cut simultaneously at a position of a linear portion of the continuous material. 
   In the method according to the present invention, a plurality of heat transfer tubes are formed by continuously feeding the continuous material in a width direction of each of the heat transfer tube plates and repeating the steps of claim  1 . 
   A stacking-type, multi-flow, heat exchanger, according to the present invention, is manufactured by using such a method. 
   In the method for manufacturing a stacking-type, multi-flow, heat exchanger, according to the present invention, the time required for manufacturing heat transfer tubes may be reduced significantly, and by reducing the manufacturing time, the productivity of the method for manufacturing the heat exchanger may be increased significantly. Moreover, the positioning of inner fins at the predetermined positions on a tube plate may be facilitated and may be carried out with a high degree of accuracy. Further, a positional shift of an inner fin at the time of manufacturing a heat transfer tube may be prevented readily. 
   Therefore, a stacking-type, multi-flow, heat exchanger, manufactured by using this method, may be produced at a high productivity and at a low cost. In addition, a heat exchanger, having a high degree of reliability in the positional accuracy of inner fins and other components and having a high quality, may be provided. 
   Further objects, features, and advantages of the present invention will be understood from the following detailed description of preferred embodiments of the present invention with reference to the accompanying figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention now are described with reference to the accompanying figures, which are given by way of example only and are not intended to limit the present invention. 
       FIG. 1  is a schematic diagram, showing steps for manufacturing a heat transfer tube in a method for manufacturing a stacking-type, multi-flow, heat exchanger, according to a first embodiment of the present invention. 
       FIG. 2  is a plan view of a tube plate and an inner fin for use in the method depicted in  FIG. 1 . 
       FIG. 3  is a cross-sectional view of a heat transfer tube manufactured by the process depicted in  FIG. 1 . 
       FIG. 4  is a schematic diagram, showing steps for manufacturing a heat transfer tube in a method for manufacturing a stacking-type, multi-flow, heat exchanger, according to a second embodiment of the present invention. 
       FIG. 5  is a plan view of a tube plate and an inner fin for use in the method depicted in  FIG. 4 . 
       FIG. 6  is a cross-sectional view of a heat transfer tube manufactured by the method depicted in  FIG. 4 . 
       FIGS. 7A–7C  are partial, cross-sectional views of heat exchangers manufactured using heat transfer tubes depicted in  FIGS. 3 and 6 , showing examples of the disposition of the heat transfer tubes. 
       FIG. 8  is a plan view of a stacking-type, multi-flow, heat exchanger, showing elements of the structure of such a heat exchanger common to a known heat exchanger and the present invention. 
       FIG. 9  is a side view of the heat exchanger depicted in  FIG. 8 . 
       FIG. 10  is a plan view of a tube plate and an inner fin for use in a known heat exchanger. 
       FIG. 11  is a cross-sectional view of a known heat transfer tube. 
       FIG. 12  is a partial, cross-sectional view of a heat exchanger manufactured using the heat transfer tubes depicted in  FIG. 11 , as viewed along Line A—A of  FIG. 8 , showing an example of the disposition of the heat transfer tubes. 
       FIG. 13  is a schematic diagram, showing steps for manufacturing a heat transfer tube in a known method for manufacturing a stacking-type, multi-flow, heat exchanger. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Because  FIGS. 8 and 9  are figures common to the related art and the present invention, the structure depicted in these figures is described below. In a stacking-type, multi-flow, heat exchanger  31 , as depicted in  FIG. 8 , a plurality of heat transfer tubes  32  and a plurality of outer fins  33  are stacked alternately to form a heat exchanger core  34 . An end plate  35  and side tank  36  are connected to the outer sides of heat exchanger core  34 . An inlet port  38  for introducing fluid (for example, refrigerant) into heat exchanger  31  and an outlet port  39  for discharging the fluid from heat exchanger  31  are provided on side tank  36 , and a flange  37  for connecting an expansion valve (not shown) is mounted onto side tank  36 . As depicted in  FIG. 9 , air flows in the direction shown by arrow  40 , from the front side of heat exchanger core  34  of heat exchanger  31  towards the rear side of heat exchanger core  34 , thereby carrying out the heat exchange between the air flowing through and the fluid flowing in heat exchanger core  34 . As afore-mentioned, a structure of a stacking-type, multi-flow, heat exchanger, which is achieved with a method according to the present invention, is substantially similar to that depicted in  FIGS. 8 and 9 . 
   Referring to  FIGS. 1–3 , a method for manufacturing a stacking-type, multi-flow, heat exchanger is depicted according to a first embodiment of the present invention.  FIG. 1  depicts steps of a process for manufacturing a heat transfer tube,  FIG. 2  depicts a relationship between a tube plate and an inner fin used in the method, as depicted in  FIG. 1 , and  FIG. 3  depicts a heat transfer tube manufactured by the method. 
   The manufacturing method, as depicted in  FIG. 1 , comprises the following steps: 
   Step  1  (S 1 ): An inner fin formed as a wave shape is not cut beforehand, and it is formed as a continuous, inner-fin forming material  3 . Inner-fin forming material  3  is formed as a continuous material extending in a width direction W of a heat transfer tube to be formed, and wavy or undulating portions  1  and linear portions  2  are arranged alternately in continuous material  3  in width direction W of the heat transfer tube. A pair of tube plates  4   a  and  4   b , which may be formed by pressing, are disposed so as to oppose each other. In this embodiment, a first end portions (i.e., right-side end portions in  FIG. 1 ) of tube plates  4   a  and  4   b  in width direction W of the heat transfer tube are formed as linear end portions  6  extending linearly in an outward or lateral direction, without forming flanges. Inner-fin forming material  3  is fed continuously toward tube plates  4   a  and  4   b  in a direction shown by arrow  28 . 
   Step  2  (S 2 ): Inner-fin forming material  3  is inserted between the pair of tube plates  4   a  and  4   b  disposed to oppose each other, for forming inner fins  5 . At that time, because inner-fin forming material  3  is fed to a predetermined extent, the positioning of material  3  between plates  4   a  and  4   b  may be carried out readily. 
   Step  3  (S 3 ): Upper-side tube plate  4   b  is placed in contact with and over lower-side tube plate  4   a , and linear portion  2  of inner-fin forming material  3  is nipped or seized by linear end portions  6  of tube plates  4   a  and  4   b . At that time, because inner-fin forming material  3  remains as a continuous material, in which a portion forming inner fins  5  still is connected to a following inner-fin forming portion, the portion forming inner fins  5  does not shift in position. 
   Step  4  (S 4 ): Stacked tube plates  4   a  and  4   b  and inner-fin forming material  3  then are cut simultaneously by a cutter  7  at a predetermined position. In this embodiment, tube plates  4   a  and  4   b  are temporarily secured to each other, simultaneously with this cutting. 
   Step  5  (S 5 ): Cutter  7  is withdrawn or retracted, and a series of steps for manufacturing a heat transfer tube  8  with a predetermined width W are completed. If a plurality of heat transfer tubes are to be manufactured sequentially, the method returns to SI, and the series of S 1 –S 5  are repeated. 
   In heat transfer tube  8  manufactured by this method, as depicted in  FIG. 2 , tube plates  4   a  and  4   b  and inner fin  5  are temporarily secured and integrated with each other. Inner fin  5  is fixed precisely at a predetermined position, relative to tube plates  4   a  and  4 b. 
   Further, the cross-sectional shape of heat transfer tube  8  is formed, as depicted in  FIG. 3 . Although flange portions  10  are formed in a first end portion  9  of heat transfer tube  8  in its width direction:, in a second end portion  11  of heat transfer tube  8 , linear portion  2  positioned at the end portion of inner fin  5  is nipped or seized between linear end portions  6  of tube plates  4   a  and  4   b  and temporarily secured and integrated with tube plates  4   a  and  4   b . Therefore, inner fin  5  is fixed and desired at a predetermined position in a fluid passage  12  formed within heat transfer tube  8 . A plurality of heat transfer tubes  8  thus manufactured may be assembled to form a stacking-type, multi-flow, heat exchanger, as depicted in  FIG. 8 , and assembled heat transfer tubes  8  may be integrated or fused by brazing in a furnace to complete a desired heat exchanger  31 , as depicted in  FIG. 8 . 
   In the above-described first embodiment because the step for returning an inner fin insertion arm (shown as insertion arm  106  in  FIG. 13 ), which is described in the known method, may be omitted, and, therefore, the time required to employ this insertion arm may be saved, the time required for manufacturing heat transfer tubes  8  may be reduced significantly. As a result, the productivity of methods for manufacturing stacking-type, multi-flow, heat exchangers may be increased. 
   Moreover, because an inner fin is inserted between tube plates  4   a  and  4   b  as a continuous inner-fin forming material  3 , the positioning may be facilitated significantly, and the positioning accuracy may be increased significantly. 
   In addition, by stacking and covering one tube plate over the other tube plate before cutting inner-fin forming material  3 , tube plates  4   a  and  4   b  may be temporarily and simultaneously secured by cutting the end portions of the tube plates and the inner-fin forming material. Consequently, a positional shift of an inner fin, which may occur in known processes, may be prevented. 
   Although a step for cutting only one end portion of the tube plates is employed in the above-described first embodiment, steps for cutting both end portions of the tube plates may be employed, as shown in a second embodiment of the present invention, depicted in  FIGS. 4–6 . 
   The manufacturing method depicted in  FIG. 4  comprises the following steps: 
   Step  6  (S 6 ): A pair of tube plates  21   a  and  21   b , which are formed by pressing, are disposed so as to oppose each other. In this embodiment, both end portions of tube plates  21   a  and  21   b  in a width direction W of a heat transfer tube are formed as linear end portions  6  and  22  extending linearly in outward or lateral directions, without forming flanges. Inner-fin forming material  3 , formed as a continuous material having alternately arranged wavy or undulating portions  1  and linear portions  2 , is fed between tube plates  21   a  and  21   b  in a direction shown by arrow  28 . 
   Step  7  (S 7 ): Inner-fin forming material  3  is inserted between the pair of tube plates  21   a  and  21   b , which are vertically disposed to oppose each other in order to form inner fins  24 . At that time, because inner-fin forming material  3  is fed to a predetermined extent, the positioning may be carried out readily. 
   Step  8  (S 8 ): Second or upper-side tube plate  21   b  is positioned over first or lower-side tube plate  21   a , and linear portions  2  of inner-fin forming material  3  are nipped or seized by linear end portions  6  and  22  of tube plates  21   a  and  21   b . At that time, because inner-fin forming material  3  remains as a continuous material and because a portion forming inner fins  24  still is connected to a following inner-fin forming portion, the portion forming inner fins  24  does not shift in position. 
   Step  9  (S 9 ): Stacked tube plates  21   a  and  21   b  and inner-fin forming material  3  are cut simultaneously by cutters  7  and  23  at respective, predetermined positions. In this embodiment, tube plates  21   a  and  21   b  are secured to each other temporarily and simultaneously by this cutting. 
   Step  10  (S 10 ): Cutters  7  and  23  are withdrawn or retracted, and a series of steps for manufacturing a heat transfer tube  25  with a predetermined width W are completed. If a plurality of heat transfer tubes are manufactured sequentially, the method returns to S 6 , and the series of S 6 –S 10  are repeated. 
   In heat transfer tube  25  manufactured by this method, as depicted in  FIG. 5 , tube plates  21   a  and  21   b  and inner fin  24  are temporarily secured and integrated with each other. Inner fin  24  is fixed precisely at a predetermined position, relative to tube plates  21   a  and  21   b.    
   The cross-sectional shape of heat transfer tube  25  also is formed, as depicted in  FIG. 6 . Linear portions  2  positioned at the end portions of inner fin  24  are nipped or seized between linear end portions  22  and  6  of tube plates  21   a  and  21   b  at respective end positions  26  and  27  of heat transfer tube  25  in its width direction W. Inner fin  24  is temporarily secured and integrated within tube plates  21   a  and  21   b . Therefore, inner fin  24  is fixed at a predetermined and desired position in fluid passage  12  formed in heat transfer tube  25 . A plurality of heat transfer tubes  25  thus manufactured are assembled as a stacking-type, multi-flow, heat exchanger, as depicted in  FIG. 8 , and assembled heat transfer tubes  25  may be integrated or fused by brazing in a furnace to complete a desired heat exchanger  31 , as depicted in  FIG. 8 . 
   In the above-described second embodiment, the time required for manufacturing heat transfer tubes  25  may be reduced significantly, and the productivity of methods for manufacturing a stacking-type, multi-flow, heat exchanger may be increased significantly. Further, because an inner fin is inserted between tube plates  21   a  and  21   b  as a continuous inner-fin forming material  3 , the positioning of the inner fin may be facilitated significantly, and the positioning accuracy may be increased significantly. In particular, because the linear portions of inner-fin forming material  3  are nipped or seized at both sides in the width direction W of heat transfer tubes  25 , the positioning of inner fin  24  may be achieved with more certainty. Moreover, tube plates  21   a  and  21   b  may be temporarily and simultaneously secured by cutting the end portions of the tube plates and the inner-fin forming material. Consequently, a positional shift of an inner fin, which may occur in known processes, may be prevented. 
   When a stacking-type, multi-flow, heat exchanger is manufactured using heat transfer tubes  8  or  25 , such as those manufactured in the above-described first or second embodiment of the invention, the orientation of heat transfer tubes  8  or  25  may be employed variously. If heat transfer tubes  8 , each having a linear end portion at one end in its width direction, are used, for example, as depicted in  FIG. 7A  or  7 B; the linear end portions are disposed at either an upstream-side position ( FIG. 7A ) relative to air flow direction shown by arrow  29  or at a downstream-side position ( FIG. 7B ). If, however, heat transfer tubes  25 , each having linear end portions at both ends in its width direction, are used, for example, as depicted in  FIG. 7C ; the linear end portions are present at both the upstream-side and downstream-side positions relative to air flow direction shown by arrow  29 . 
   The present invention may be applied to any stacking-type, multi-flow, heat exchanger, which is formed with alternatively stacked heat transfer tubes and outer fins. The heat transfer fluid used in such heat exchangers, however, is not limited to refrigerant. 
   Although embodiments of the present invention have been described in detail herein, the scope of the invention is not limited thereto. It will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the invention. Accordingly, the embodiments disclosed herein are only exemplary. It is to be understood that the scope of the invention is not to be limited thereby, but is to be determined by the claims which follow.