Stacking-type, multi-flow, heat exchangers and methods for manufacturing such heat exchangers

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.

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 inFIGS. 10–12. In a heat exchanger, thus constructed, a heat transfer tube is formed as in a known heat exchanger, as depicted inFIGS. 10 and 11. Namely, a pair of tube plates101, each formed as depicted inFIG. 10, are disposed so as to compare each other, as depicted inFIG. 11, and the circumferential edges thereof are connected to each other to form fluid passages102therein. An inner fin103is inserted into each fluid passage102in order to increase the efficiency of heat exchange. Flanges104are formed on tube plates101at the end portions of each tube plate101in its width direction. Flanges104are disposed at the front and rear positions in the direction of air flow40, as depicted inFIG. 12, which is viewed along Line A—A ofFIG. 8. Thus, a known heat transfer tube105is constructed, for example, as disclosed in Japanese Patent Application No. JP-A-2002-267383.

Such a known heat transfer tube105is manufactured, for example, as depicted inFIG. 13. The manufacturing method shown inFIG. 13has the following steps:

Step11(S11): Tube plates101and101′ and inner fins103are made as complete parts, separately, and plates101and fin103are provided in a tube assembling process.

Step13(S13): Inner fins103, conveyed by insertion arm106, are disposed on a first or lower-side tube plate101within predetermined cavities so as not to be shifted from the predetermined positions.

Step14(S14): Insertion arm106is returned to its initial position.

Step15(S15): After insertion arm106is withdrawn from between tube plates101, a second or upper-side tube plate101′ disposed onto the lower-side tube plate101.

Step16(S16): The pair of tube plates101and101′ are secured temporarily to each other, so that the configuration of the heat transfer tube formed by the pair of tube plates101and101′ 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 S13.

(3) A positional shift of an inner fin may occur during the covering of first-tube plate101with second tube plate101′ at above-described S15.

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 claim1.

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.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

BecauseFIGS. 8 and 9are 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 exchanger31, as depicted inFIG. 8, a plurality of heat transfer tubes32and a plurality of outer fins33are stacked alternately to form a heat exchanger core34. An end plate35and side tank36are connected to the outer sides of heat exchanger core34. An inlet port38for introducing fluid (for example, refrigerant) into heat exchanger31and an outlet port39for discharging the fluid from heat exchanger31are provided on side tank36, and a flange37for connecting an expansion valve (not shown) is mounted onto side tank36. As depicted inFIG. 9, air flows in the direction shown by arrow40, from the front side of heat exchanger core34of heat exchanger31towards the rear side of heat exchanger core34, thereby carrying out the heat exchange between the air flowing through and the fluid flowing in heat exchanger core34. 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 inFIGS. 8 and 9.

Referring toFIGS. 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. 1depicts steps of a process for manufacturing a heat transfer tube,FIG. 2depicts a relationship between a tube plate and an inner fin used in the method, as depicted inFIG. 1, andFIG. 3depicts a heat transfer tube manufactured by the method.

The manufacturing method, as depicted inFIG. 1, comprises the following steps:

Step1(S1): An inner fin formed as a wave shape is not cut beforehand, and it is formed as a continuous, inner-fin forming material3. Inner-fin forming material3is formed as a continuous material extending in a width direction W of a heat transfer tube to be formed, and wavy or undulating portions1and linear portions2are arranged alternately in continuous material3in width direction W of the heat transfer tube. A pair of tube plates4aand4b, 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 inFIG. 1) of tube plates4aand4bin width direction W of the heat transfer tube are formed as linear end portions6extending linearly in an outward or lateral direction, without forming flanges. Inner-fin forming material3is fed continuously toward tube plates4aand4bin a direction shown by arrow28.

Step2(S2): Inner-fin forming material3is inserted between the pair of tube plates4aand4bdisposed to oppose each other, for forming inner fins5. At that time, because inner-fin forming material3is fed to a predetermined extent, the positioning of material3between plates4aand4bmay be carried out readily.

Step3(S3): Upper-side tube plate4bis placed in contact with and over lower-side tube plate4a, and linear portion2of inner-fin forming material3is nipped or seized by linear end portions6of tube plates4aand4b. At that time, because inner-fin forming material3remains as a continuous material, in which a portion forming inner fins5still is connected to a following inner-fin forming portion, the portion forming inner fins5does not shift in position.

Step4(S4): Stacked tube plates4aand4band inner-fin forming material3then are cut simultaneously by a cutter7at a predetermined position. In this embodiment, tube plates4aand4bare temporarily secured to each other, simultaneously with this cutting.

Step5(S5): Cutter7is withdrawn or retracted, and a series of steps for manufacturing a heat transfer tube8with 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 S1–S5are repeated.

In heat transfer tube8manufactured by this method, as depicted inFIG. 2, tube plates4aand4band inner fin5are temporarily secured and integrated with each other. Inner fin5is fixed precisely at a predetermined position, relative to tube plates4aand4b.

Further, the cross-sectional shape of heat transfer tube8is formed, as depicted inFIG. 3. Although flange portions10are formed in a first end portion9of heat transfer tube8in its width direction:, in a second end portion11of heat transfer tube8, linear portion2positioned at the end portion of inner fin5is nipped or seized between linear end portions6of tube plates4aand4band temporarily secured and integrated with tube plates4aand4b. Therefore, inner fin5is fixed and desired at a predetermined position in a fluid passage12formed within heat transfer tube8. A plurality of heat transfer tubes8thus manufactured may be assembled to form a stacking-type, multi-flow, heat exchanger, as depicted inFIG. 8, and assembled heat transfer tubes8may be integrated or fused by brazing in a furnace to complete a desired heat exchanger31, as depicted inFIG. 8.

In the above-described first embodiment because the step for returning an inner fin insertion arm (shown as insertion arm106inFIG. 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 tubes8may 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 plates4aand4bas a continuous inner-fin forming material3, 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 material3, tube plates4aand4bmay 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 inFIGS. 4–6.

The manufacturing method depicted inFIG. 4comprises the following steps:

Step6(S6): A pair of tube plates21aand21b, which are formed by pressing, are disposed so as to oppose each other. In this embodiment, both end portions of tube plates21aand21bin a width direction W of a heat transfer tube are formed as linear end portions6and22extending linearly in outward or lateral directions, without forming flanges. Inner-fin forming material3, formed as a continuous material having alternately arranged wavy or undulating portions1and linear portions2, is fed between tube plates21aand21bin a direction shown by arrow28.

Step7(S7): Inner-fin forming material3is inserted between the pair of tube plates21aand21b, which are vertically disposed to oppose each other in order to form inner fins24. At that time, because inner-fin forming material3is fed to a predetermined extent, the positioning may be carried out readily.

Step8(S8): Second or upper-side tube plate21bis positioned over first or lower-side tube plate21a, and linear portions2of inner-fin forming material3are nipped or seized by linear end portions6and22of tube plates21aand21b. At that time, because inner-fin forming material3remains as a continuous material and because a portion forming inner fins24still is connected to a following inner-fin forming portion, the portion forming inner fins24does not shift in position.

Step9(S9): Stacked tube plates21aand21band inner-fin forming material3are cut simultaneously by cutters7and23at respective, predetermined positions. In this embodiment, tube plates21aand21bare secured to each other temporarily and simultaneously by this cutting.

Step10(S10): Cutters7and23are withdrawn or retracted, and a series of steps for manufacturing a heat transfer tube25with a predetermined width W are completed. If a plurality of heat transfer tubes are manufactured sequentially, the method returns to S6, and the series of S6–S10are repeated.

In heat transfer tube25manufactured by this method, as depicted inFIG. 5, tube plates21aand21band inner fin24are temporarily secured and integrated with each other. Inner fin24is fixed precisely at a predetermined position, relative to tube plates21aand21b.

The cross-sectional shape of heat transfer tube25also is formed, as depicted inFIG. 6. Linear portions2positioned at the end portions of inner fin24are nipped or seized between linear end portions22and6of tube plates21aand21bat respective end positions26and27of heat transfer tube25in its width direction W. Inner fin24is temporarily secured and integrated within tube plates21aand21b. Therefore, inner fin24is fixed at a predetermined and desired position in fluid passage12formed in heat transfer tube25. A plurality of heat transfer tubes25thus manufactured are assembled as a stacking-type, multi-flow, heat exchanger, as depicted inFIG. 8, and assembled heat transfer tubes25may be integrated or fused by brazing in a furnace to complete a desired heat exchanger31, as depicted inFIG. 8.

In the above-described second embodiment, the time required for manufacturing heat transfer tubes25may 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 plates21aand21bas a continuous inner-fin forming material3, 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 material3are nipped or seized at both sides in the width direction W of heat transfer tubes25, the positioning of inner fin24may be achieved with more certainty. Moreover, tube plates21aand21bmay 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 tubes8or25, such as those manufactured in the above-described first or second embodiment of the invention, the orientation of heat transfer tubes8or25may be employed variously. If heat transfer tubes8, each having a linear end portion at one end in its width direction, are used, for example, as depicted inFIG. 7Aor7B; the linear end portions are disposed at either an upstream-side position (FIG. 7A) relative to air flow direction shown by arrow29or at a downstream-side position (FIG. 7B). If, however, heat transfer tubes25, each having linear end portions at both ends in its width direction, are used, for example, as depicted inFIG. 7C; the linear end portions are present at both the upstream-side and downstream-side positions relative to air flow direction shown by arrow29.

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.