Tube for heat exchanger and method of manufacturing the same

Abstract

A tube for a heat exchanger has a tube member and a fin inserted in the tube member. The tube member has a first wall having a first end portion and a second wall having a second end portion. The second end portion of the second wall is folded over the first end portion of the first wall. Also, an end of the fin is held between the first end portion and the second end portion of the tube member. Further, the end of the fin has a bent portion at an end of the first end portion within the folded second end portion. The bent portion of the fin is engaged with the first end portion of the tube member for positioning the fin with respect to the tube member.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2005-315213 filed on Oct. 28, 2005, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to tubes for a heat exchanger such as an evaporator and a method of manufacturing the same.

BACKGROUND OF THE INVENTION

In a heat exchanger, tubes have inner fins therein. The tubes having the inner fins are for example manufactured in a method described in Japanese Patent Publication No. 2003-336989. Hereafter, the tubes having the inner fins are referred to as inner fin tubes. In each of the inner fin tubes, a corrugated inner fin is disposed in a tube wall having a flat tubular shape.

The tube wall is for example formed by folding a band plate at a middle portion and crimping ends of the folded band plate. The tube wall has a bent portion at a first end and a crimped portion at a second end in a cross-section defined in a direction perpendicular to a longitudinal axis of the tube. The inner fin is formed by shaping a band plate into a wave form.

The inner fin is arranged in the tube such that its first end is in contact with an inside of the bent portion of the tube wall and its second end is interposed between the crimped ends of the tube wall. Namely, the ends of the tube wall are crimped in a condition interposing the second end of the inner fin between them so as to restrict displacement of the inner fin in the tube wall.

Since the displacement of the inner fin is reduced, the above inner fin tube can be manufactured continuously at high speeds. Namely, as disclosed in Japanese Patent Publication No. 2003-336989, the tube wall and the inner fin are continuously formed and the inner fin is inserted in the tube wall in the same roll forming apparatus.

In the above inner fin tubes, however, when the ends of the folded tube wall are crimped even in a condition interposing the second end of the inner fin between them, the inner fin is likely to be displaced due to shrinkage of a corrugated portion of the inner fin. If the inner fin is displaced, it is difficult to stably or uniformly form a crimped end on the tube wall. Moreover, joining portions between an inner surface of the tube wall and the inner fin are likely to be displaced.

SUMMARY OF THE INVENTION

The present invention is made in view of the foregoing matter, and it is an object of the present invention to provide a tube for a heat exchanger, capable of positioning a fin with respect to a tube member.

It is another object of the present invention to provide a method of manufacturing a tube for a heat exchanger, capable of positioning a fin with respect to a tube member.

It is further another object of the present invention to provide a tube for a heat exchanger and a method of manufacturing the tube, capable of crimping ends of a tube member stably.

According to a first aspect of the present invention, a heat exchanger includes a tube member and a fin inserted in the tube member. The tube member has a first wall and a second wall that are opposed to each other. The first wall has a first end portion and the second wall has a second end portion. The second end portion is folded over the first end portion. The fin has an end held between the first end portion and the second end portion of the tube member. Further, the end of the fin has a fin bent portion over an end of the first end portion of the tube member. The fin bent portion contacts the end of the first end portion for positioning the fin with respect to the tube.

In manufacturing the tube, the tube member is formed to have the first wall and the second wall. The second end portion of the second wall is folded after the fin is inserted in the tube member. Also, the second end portion is folded in a condition that the end of the fin is held between the first end portion and the second end portion and the fin bent portion is engaged with the first end portion. For example, the fin bent portion can be formed before the second end portion of the tube member is folded. Alternatively, the fin bent portion can be formed when the second end portion of the tube member is folded.

Since the fin is positioned with respect to the tube member by the fin bent portion, the second end portion of the tube member is stably or uniformly folded over the first end portion and the end of the fin. As such, the first end portion and the second end portion of the tube member are stably or uniformly crimped.

Accordingly, a plurality of tubes can be uniformly formed. In a heat exchanger having the tubes, a clearance is uniformly defined between an end of each tube and a tube hole of a header tank. Therefore, the quality of joining between the tubes and the header tank improves.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings, in which like parts are designated by like reference numbers and in which:

FIG. 1 is a cross-sectional view of an inner fin tube taken in a direction perpendicular to a longitudinal axis of the inner fin tube according to a first embodiment of the present invention;

FIG. 2 is an enlarged view of the inner fin tube at a part denoted by a circle II in FIG. 1;

FIG. 3 is a schematic side view of a heat exchanger having the inner fin tubes according to the first embodiment of the present invention;

FIG. 4 is a schematic diagram of an apparatus of manufacturing the inner fin tubes according to the first embodiment of the present invention;

FIG. 5 is an explanatory view for showing a crimping step performed by the apparatus according to the first embodiment of the present invention;

FIG. 6 is a schematic sectional view of an inner fin tube in a crimping step of an inner fin tube manufacturing method according to a second embodiment of the present invention; and

FIG. 7 is a schematic sectional view of the inner fin tube in another stage of the crimping step according to the second embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT

First Embodiment

A first embodiment of the present invention will be described with reference to FIGS. 1 through 5. As shown in FIG. 1, an inner fin tube 10 of the first embodiment has a tube member 11 and an inner fin 12 inserted in the tube member 11. As shown in FIG. 3, the inner fin tube 10 is for example used as a tube of a heat exchanger 20 such as an evaporator of a refrigerating cycle.

The tube member 11 has a flat tubular shape. The tube member 11 is formed by folding a thin aluminum band plate. As shown in FIG. 1, in a cross-section defined in a direction perpendicular to a longitudinal direction of the tube member 11, the tube member 11 has a substantially elliptical shape. In FIG. 1, an arrow A1 denotes a direction parallel to a major axis of the elliptical shape.

The band plate is folded at a substantially middle portion thereof so that the tube member 11 has flat plate portions 11b and a bent portion 11a at ends of the flat plate portions 11b. The bent portion 11a has an arc shape, for example. Also, the bent portion 11a has a shape corresponding to a part of a circle that has a diameter equivalent to a distance between the flat plate portions 11b of the tube member 11. Alternatively, the bent portion 11a has another shape such as a V-shape or a bracket-shape.

The flat plate portions 11b extend from the bent potion 11a. As shown in FIG. 2, the flat plate portions 11b have inclined wall portions 11c3, 11c4 at ends opposite to the bent portion 11a. The inclined wall portions 11c3, 11c4 are inclined toward a centerline between the flat plate portions 11b to form a V-shape. Further, the flat plate portions 11b have a first end portion 11c and a second end portion 11c2 at the ends of the inclined wall portions 11c3, 11c4, respectively. The first end portion 11c1 and the second end 11c2 are crimped.

For example, the second end portion 11c2 overlaps and is folded over the first end portion 11c1. Specifically, the second end portion 11c2 has a length equal to or larger than twice of the first end portion 11c1. The second end portion 11c2 has a first portion extending from the end of the inclined wall portion 11c4 parallel to and opposed to an inner surface of the first end portion 11c1, a second portion extending from the first portion and wrapped over the end of the first end portion 11c1, and a third portion extending from the second portion along an outer wall of the first end portion 11c1. The third portion ends at a position adjacent to a boundary between the first end portion 11c1 and the inclined wall portion 11c3.

As such, a crimped portion 11c is formed at an end opposite to the bent portion 11a by crimping the ends of the flat plate portions 11b, i.e., by folding the second end portion 11c2 over the first end portion 11c. Here, crimping means a structure that the first end portion 11c1 and the second end portion 11c2 are closed by folding the second end portion 11c2 over the first end portion 11c1.

As shown in FIGS. 1 and 2, the second end portion 11c2 is folded and wrapped over the first end portion 11c1 such that both surfaces of the first end portion 11c1 are generally included in the folded second end portion 11c2. In this embodiment, the crimped portion 11c has a generally flat shape. The crimped portion 11c extends from the inclined wall portions 11c3, 11c4 in a length substantially equal to the distance between the flat plate portions 11b.

The inner fin 12 is used for providing a turbulence effect of a fluid flowing in the tube member 11 and increasing a heat transfer area. The inner fin 12 is formed of a thin aluminum band plate that is thinner than the band plate of the tube member 11 by roll forming. Also, the inner fin 12 is formed with corrugated portion 12a having a wave form.

Further, the inner fin 12 has a first flat plate portion 12b and a second flat plate portion 12c at ends with respect to a width of the band plate. The inner fin 12 is inserted in the tube member 11 such that the first flat portion 12b is in contact with an inner wall of the bent portion 11a of the tube member 11. Further, the first end portion 11c1 and the second end portion 11c2 of the tube member 11 are crimped in a condition that the second flat portion 12c is interposed between the first end portion 11c1 and the second end portion 11c2.

Further, the second flat portion 12c is formed with a bent portion 12c1. The bent portion 12c1 is formed by bending an end of the second flat portion 12c into a substantially L-shape. The bent portion 12c1 contacts and partly covers the end of the first end portion 11c1 of the tube member 11. The bent portion 12c1 extends parallel to an end surface of the first end portion 11c1. As such, the bent portion 12c1 provides a hook portion to be engaged with or held on the end of the first end portion 11c1.

The bent portion 12c1 determines a position of the inner fin 12 with respect to the tube member 11 against a force generated in the inner fin 12 to move into the inside of the tube member 11 before a brazing step. Namely, the bent portion 12c1 serves as a positioning member to position the inner fin 12 with respect to the tube member 11.

The bent portion 12c1 has the length in a direction perpendicular to the first end portion 11c1 equal to or less than the thickness of the first end portion 11c1. Preferably, the bent portion 12c1 has the length as long as possible within the thickness of the first end portion 11c1. The bent portion 12c1 can be formed throughout the end of the second flat plate portion 12c in a longitudinal direction of the inner fin 12. Alternatively, the bent portion 12c1 can be formed partly or at intervals in the longitudinal direction of the inner fin 12.

The inner fin tubes 10 having the above configuration are stacked at predetermined intervals, as shown in FIG. 3. Further, outer fins 21 are interposed between the inner fin tubes 10. Each of the outer fins 21 have a corrugated shape, similar to the inner fins 12. Thus, the stack of the inner fin tubes 10 and the outer fins 21 forms a core portion 22 for performing heat exchange between an inner fluid and an outer fluid. Further, longitudinal ends of the inner fin tubes 10 are coupled to a first header tank 23 and a second header tank 24. As such, the heat exchanger 20 is constructed.

Each of the first header tank 23 and the second header tank 24 is formed with tube holes 23a (double-dashed chain line in FIG. 2). The longitudinal ends of the inner fin tubes 10 are inserted in the tube holes 23a and joined to the first header tank 23 and the second header tank 24 by brazing.

The first header tank 23 and the second header tank 24 are provided with a fluid inlet member 25 and a fluid outlet member 26, respectively. When the heat exchanger 20 shown in FIG. 3 is used as the evaporator, a refrigerant as an inner fluid circulating in the refrigerating cycle flows into the first header tank 23 through the fluid inlet member 25. Further, the refrigerant flows through the inner fin tubes 10 toward the second header tank 24. Then, the refrigerant flows out from the fluid outlet port 26. Heat exchange is performed between the refrigerant flowing in the inner fin tubes 10 and air flowing outside of the core portion 22. As such, while the refrigerant evaporates, the air is cooled. The air is for example used for air conditioning.

Next, a method of manufacturing the above inner fin tubes 10 will be described with reference to FIGS. 4 and 5. FIG. 4 shows a manufacturing apparatus 100 for manufacturing the inner fin tubes 10.

The manufacturing apparatus 100 has a tube forming unit 110 for forming the tube member 11 and inserting the inner fin 12 in the tube member 11, an inner fin forming unit 120 for forming the inner fin 12, an inner fin carrying unit 130 for carrying the inner fin 12 to the tube forming unit 110, and the like.

Further, the tube forming unit 110 has a tube outer wall forming section 110A, an inserting and crimping section 110B and a cutting section 110C. The sections 110A to 110C are arranged in series. The tube outer wall 11 is formed by using a coiled band plate material. Although not illustrated, rollers are arranged between the respective sections 110A to 110C for carrying the material, for example. Thus, operations in the respective sections 110A to 110C can be performed continuously.

The tube outer wall forming section 110A has multiple rollers for mainly forming the bent portion 11a and the flat plate portions 11b from the coiled band plate material, thereby to form a tube outer wall as the tube member 11. The inserting and crimping section 110B has multiple rollers R0 through Rn for forming the crimped portion 11c on the tube outer wall 11 after inserting the inner fin 12 in the tube outer wall 11. In the cutting section 110C, the continuous formed member carried from the inserting and crimping section 110B is cut into a predetermined length, thereby producing the individual inner fin tubes 10.

FIG. 5 shows a crimping step performed in the inserting and crimping section 110B. In the inserting and crimping section 110B, the rollers R0 to Rn are arranged in a processing direction, i.e., a feeding direction. Further, each of the rollers R0 to Rn rotates while contacting the second end portion 11c of the tube outer wall 11.

Moreover, the rollers R0 to Rn are arranged such that directions of rotation axes of the rollers R0 to Rn varies from a position A0 to a position An, as shown in FIG. 5. That is, a rotation axis A0 of the roller R0 is parallel to an original extending direction of the second end portion 11c2. A rotation axis An of the roller Rn is parallel to the rotation axis A0 of the roller R0. Rollers between the roller R0 and the roller Rn are arranged such that the rotation axes thereof are gradually angled from the rotation axis A0 to the rotation axis An.

Thus, the rotation axes are varied 180 degrees from the rotation axis A0 to the rotation axis An. As such, the second end portion 11c2, which is straight before the folding, is folded over the first end portion 11c1 through the rollers R0 to Rn. Accordingly, the crimped portion 11c is formed.

The inner fin forming unit 120 is arranged parallel to the tube outer wall forming section 110A such that the formed inner fin 12 is located separate from the tube outer wall 11 formed in the tube outer wall forming section 110A by a predetermined distance in a horizontal direction and under the tube outer wall 11. The inner fin 12 is formed by using a coiled band plate material. In the inner fin forming unit 120, the corrugated portion 12a, the first and second flat portions 12b, 12c and the L-shaped bent portion 12c1 are formed on the band plate material buying rollers. As such, a continuous inner fin 12 in a form of longitudinal band is formed.

The inner fin carrying unit 130 feeds the continuous inner fin 12 from the inner fin forming unit 120 to the inserting and crimping section 110B.

In the above manufacturing apparatus 100, first, the tube outer wall 11 is formed from the band plate material in the tube outer wall forming section 110A (tube outer wall forming step). Also, in the inner fin forming unit 120, the continuous inner fin 12 is formed. The continuous inner fin 12 is carried to the inserting and crimping section 110B by the inner fin carrying unit 130.

Next, in the inserting and crimping section 110B, the continuous inner fin 12 is inserted in the continuous tube outer wall 11 (inserting step). Then, the second end portion 11c2 of the tube outer wall 11 is continuously folded over the first end portion 11c1 (crimping sep). Thus, a continuous inner fin tube is formed.

In the inserting step, the bent portion 12c1 of the inner fin 12 engages with the end of the first end portion 11c1 of the tube outer wall 11. Namely, the inner fin 12 is positioned with respect to the tube outer wall 11 by the bent portion 12c1. Then, in the crimping step, the second end portion 11c2 of the tube outer wall 11 is sequentially folded over the first end portion 11c1 by the rollers R0 to Rn in a condition that the second flat portion 12c of the continuous inner fin 12 is sandwiched between the first end portion 11c1 and the second end portion 11c2 and the bent portion 12c1 is engaged with the first end portion 11c1. Accordingly, even after the crimping step, the bent portion 12c1 maintains the condition engaged with the first end portion 11c1.

Thereafter, the continuous inner fin tube 10 is cut into a predetermined length. The cut inner fin tubes 10 are arranged regularly and in a predetermined area (110D). Accordingly, the individual inner fin tubes 10 for the heat exchanger 20 are produced.

In the inserting step and the crimping step, the bent portion 12c1 is held in contact with the end of the first end portion 11c1. Namely, the inner fin 12 is positioned with respect to the tube outer wall 11 by the bent portion 12c1. As such, it is less likely that the inner fin 12 will be displaced with respect to the tube outer wall 11. Therefore, in the crimping step, the bending position of the second end portion 11c2 is stabled or uniformed. Namely, the second end portion 11c2 is uniformly folded over the first end portion 11c1. Accordingly, the inner fin tubes 10, the ends of which are uniformly crimped, are manufactured.

Further, in the crimping step, the second end portion 11c2 is bend over a corner of the bent portion 12c1 of the inner fin 12. Thus, the second end potion 11c2 is turned substantially 180 degrees over the bent portion 12c1 while maintaining a bent shape (R-shape). Moreover, the second end portion 11c2 can uniformly maintain a predetermined length L at a folded end, as shown in FIG. 2.

Since the crimped portion 11c is uniformly formed, the inner fin tubes 10 have uniformed outlines. Thus, in constructing the heat exchanger 20 using the above inner fin tubes 10, clearances are substantially equally defined between the tube holes 23a of the first and second header tanks 23, 24 and the ends of the plural inner fin tubes 10. Therefore, the inner fin tubes 10 and the first and second header tanks 23, 24 are securely jointed to each other.

Specifically, since the inner fin tubes 10 have the folded ends of the second end portions 11c2 in the substantially equal length L, the clearance S defined between each tube hole 23a and each inner fin tube 10 can be reduced. Namely, unevenness of the clearances among the inner fin tubes 10 is reduced. Therefore, a quality of brazing improves.

Accordingly, the inner fin tubes 10 are securely brazed to the first and second header tanks 23, 24. It is less likely that the inner fluid such as the refrigerant will leak through the joining portions between the inner fin tubes 10 and the tube holes 23a of the first and second header tanks 23, 24. As such, reliability of the heat exchanger 20 improves.

In the above tube member 11, the flat plate portions 11b are continuous through the bent portion (connecting portion) 11a on a side opposite to the crimped end 11c. Therefore, durability of the inner fin tube 10 against a pressure of the inner fluid improves.

Also, the length of the bent portion 12c1 of the inner fin 12 is shorter than the thickness of the end of the first end portion 11c1. Therefore, it is less likely that the bent portion 12c1 will interfere with the folded second end portion 11c2.

Second Embodiment

Next, a second embodiment of the present invention will be described with reference to FIGS. 6 and 7. In the second embodiment, inner fin tubes 10 have the same shape as the inner-fin tubes 10 of the first embodiment shown in FIG. 1. However, a method of manufacturing the inner fin tubes 10 is different from that of the first embodiment. FIG. 6 shows an early stage of the crimping step for crimping the first end portion 11c and the second end portion 11c2. FIG. 7 shows an intermediate stage of the crimping step.

In the second embodiment, the bent portion 12c1 of the inner fin 12 is formed at the same time as folding the second end portion 12c1 in the crimping step. In other words, the bent portion 12c1 is not formed in the inner fin forming unit 120.

In a condition that the inner fin 12 is inserted in the tube outer wall 11 in the inserting step, the second flat plate portion 12c is held between the first end portion 11c1 and the second end portion 11c2, and the end of the second flat plate portion 12c extends longer than the first end portion 11c1, as shown in FIG. 6. It is preferable that the end of the second flat plate portion 12c protrudes from the end of the first end portion 11c1 as long as possible in a range shorter than the thickness of the first end portion 11c1.

When the second end portion 11c2 is bent in the crimping step, the end of the second flat plate portion 12c of the inner fin 12 is bent with the second end portion 11c2 at a position corresponding to the end of the first end portion 11c1 as a bending base point, as shown in FIG. 7. As such, the bent portion 12c1 is formed in the crimping step. Also in this case, because the inner fin 12 is positioned with respect to the tube outer wall 11 by the bent portion 12c1, it is less likely that the inner fin 12 will be displaced with respect to the tube outer wall 11 in the crimping step. Accordingly, the crimped portion 11c is stably and uniformly formed.

Also in this embodiment, the flat plate portions 11b are continuous through the bent portion (connecting portion) 11a on a side opposite to the crimped end 11c. Therefore, durability of the inner fin tube 10 against a pressure of the inner fluid improves. Also, the length of the bent portion 12c1 of the inner fin 12 is shorter than the thickness of the end of the first end portion 11c1. Therefore, it is less likely that the bent portion 12c1 will interfere with the folded second end portion 11c2.

The use of the inner fin tubes 10 of the first and second embodiment will not be limited to the evaporator. For example, the inner fin tubes 10 can be used in other heat exchangers such as a radiator, a condenser and a heater core.

Also, the shape of the inner fin 12 is not limited to the corrugated shape having the corrugated portion 12a. For example, the inner fin 12 have projections and grooves discontinuously or irregularly. Alternatively, the inner fin 12 is formed with openings and the like.

In the above embodiments, the flat plate portions 11b of the tube member 11 are continuous through the bent portion 11a. However, the shape of the tube member 11 is not limited to the above. For example, the flat plate portions 11b can be crimped at both ends.

The example embodiments of the present invention are described above. However, the present invention is not limited to the above example embodiments, but may be implemented in other ways without departing from the spirit of the invention.

Claims

1. A tube for a heat exchanger, comprising: a tube member having a first wall and a second wall that are opposed to each other, the first wall having a first end portion, the second wall having a second end portion, the second end portion folded over the first end portion; and a fin disposed in the tube member, the fin having an end held between the first end portion and the second end portion of the tube member, wherein the end of the fin has a fin bent portion over an end of the first end portion of the tube member for positioning the fin with respect to the tube member.

2. The tube according to claim 1, wherein the first wall connects to the second wall through a tube bent portion on a side opposite to the first end portion and the second end portion.

3. The tube according to claim 1, wherein the fin bent portion has a dimension with respect to a direction perpendicular to the first end portion of the tube member equal to or smaller than a thickness of the first end portion.

4. The tube according to claim 1, wherein the fin bent portion has a substantially L-shape.

5. A heat exchanger comprising a tube according to claim 1.

6. The heat exchanger according to claim 5, further comprising: a header tank formed with a plurality of tube holes, wherein the tube is one of a plurality of tubes and ends of the tubes are received in the tube holes of the header tank.

7. A method of manufacturing a tube for a heat exchanger, comprising: forming a tube member to have a first wall having a first end portion and a second wall having a second end portion; inserting a fin between the first wall and the second wall of the tube member; folding the second end portion of the second wall over the first end portion of the first wall in a condition that an end of the fin is interposed between the first end portion and the second end portion and the end of the fin is engaged with the first end portion of the first wall by a fin bent portion.

8. The method according to claim 7, further comprising: forming the fin bent portion on the end of the fin before the inserting.

9. The method according to claim 7, wherein the folding includes bending the end of the fin over an end of the first end portion of the tube member to form the fin bent portion.

10. The method according to claim 9, wherein the inserting includes placing the fin such that the end of the fin protrudes from the first end portion of the tube member.

11. The method according to claim 7, further comprising: cutting the tube member into a predetermined length after the folding.

12. The method according to claim 7, wherein the forming of the tube member includes folding a plate member to have the first wall, the second wall and a tube bent portion between the first wall and the second wall.