JP7184009B2 - Heat transfer tube and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat transfer tube and a manufacturing method thereof.

Japanese Patent Application Laid-Open No. 2011-47542 (Patent Document 1) is a prior document that discloses the configuration of a heat transfer tube used in an EGR (Exhaust Gas Recirculation) cooler. The heat transfer tube described in Patent Literature 1 includes a flat tube having a flat cross-sectional shape and a corrugated fin structure embedded in the flat tube.

JP 2011-47542 A

Heat transfer tubes used in EGR coolers are required to have improved heat exchange efficiency per volume in order to comply with strict exhaust gas regulations.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat transfer tube and a method of manufacturing the same that can improve the heat exchange efficiency per unit volume.

A heat transfer tube according to the present invention comprises a flattened tube and inner fins. A flattened tube has a flattened shape along the length direction orthogonal to the thickness direction. The inner fins are arranged inside the flattened tube so as to define a plurality of channels extending in an axial direction orthogonal to both the thickness direction and the length direction. The inner fin consists of one metal plate. The inner fins are provided with a plurality of thin-walled portions in which the thickness of the metal plate is thin when viewed in the axial direction. The plurality of thin portions extend in the length direction while being alternately positioned on one side and the other side in the thickness direction when viewed from the axial direction. The inner fin contacts the flattened tube at each of the thinned portions.

In one form of the present invention, the inner fin does not have a folded portion where the metal plates are folded back so as to overlap each other.

In one form of the present invention, the inner fin includes a protrusion that is separated from the flat tube by cutting and raising a part of the metal plate. The thickness of the metal plate at the protrusion is greater than the thickness of each of the plurality of thin portions.

A method for manufacturing a heat transfer tube according to the present invention includes a step of pressing a metal plate to form a plurality of thin portions having a small thickness of the metal plate at intervals; a step of bending a metal plate to form inner fins so as to extend in a direction orthogonal to the thickness direction while being alternately positioned on one side and the other side in the thickness direction; placing inner fins inside the flattened tube in contact with the flattened tube at.

In one aspect of the present invention, the metal plate is coined in the step of forming the plurality of thin portions at intervals.

ADVANTAGE OF THE INVENTION This invention can improve the heat exchange efficiency per volume of a heat exchanger tube.

1 is a cross-sectional view showing the configuration of a heat exchanger having heat transfer tubes according to Embodiment 1 of the present invention. FIG. It is a figure which expands and shows the II section of the heat exchanger tube of FIG. FIG. 4 is a cross-sectional view showing a state in which a metal plate is pressed in the heat transfer tube manufacturing method according to Embodiment 1 of the present invention. FIG. 4 is a cross-sectional view showing a state in which a plurality of thin-walled portions are formed on a metal plate in the method for manufacturing a heat transfer tube according to Embodiment 1 of the present invention; FIG. 4 is a cross-sectional view showing a state in which a metal plate is bent in the heat transfer tube manufacturing method according to Embodiment 1 of the present invention. FIG. 4 is a cross-sectional view showing a state in which inner fins are formed by bending a metal plate in the heat transfer tube manufacturing method according to Embodiment 1 of the present invention. FIG. 4 is a cross-sectional view showing a state in which inner fins are arranged inside flat tubes in the method for manufacturing a heat transfer tube according to Embodiment 1 of the present invention. FIG. 5 is a cross-sectional view showing the shape of inner fins included in the heat transfer tube according to the first modified example of the first embodiment of the present invention; FIG. 7 is a cross-sectional view showing the shape of inner fins provided in a heat transfer tube according to a second modification of Embodiment 1 of the present invention; FIG. 6 is a partial perspective view showing the appearance of inner fins provided in a heat transfer tube according to Embodiment 2 of the present invention.

A heat transfer tube and a method for manufacturing the same according to each embodiment of the present invention will be described below with reference to the drawings. In the following description, the same reference numerals are given to the same or corresponding parts in the drawings, and the description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing the configuration of a heat exchanger having heat transfer tubes according to Embodiment 1 of the present invention. FIG. 2 is an enlarged view of part II of the heat transfer tube of FIG.

As shown in FIGS. 1 and 2 , a heat exchanger 1 having heat transfer tubes 100 according to Embodiment 1 of the present invention includes a housing 10 and a plurality of heat transfer tubes 100 housed within the housing 10 . In the heat exchanger 1 , the exhaust gas G flows inside each of the plurality of heat transfer tubes 100 , and the refrigerant W flows outside each of the plurality of heat transfer tubes 100 inside the housing 10 .

The plurality of heat transfer tubes 100 are arranged so as to face each other at intervals and extend in parallel. Each of the plurality of heat transfer tubes 100 includes flat tubes 110 and inner fins 120 .

The flat tube 110 has a flat shape along the length direction L perpendicular to the thickness direction T. As shown in FIG. The plate thickness of the material forming flat tube 110 is, for example, 0.3 mm. The flattened tube 110 is constructed of a corrosion-resistant and highly thermally conductive material such as stainless steel.

The inner fins 120 are arranged inside the flat tube 110 so as to define a plurality of flow paths extending in an axial direction A orthogonal to both the thickness direction T and the length direction L. Exhaust gas G flows through each of the plurality of flow paths. The inner fin 120 is made of one metal plate.

As shown in FIG. 2, the inner fin 120 is provided with a plurality of thin portions 121 in which the thickness of the metal plate is thin when viewed from the axial direction A. As shown in FIG. Thick portions 122 are provided between the thin portions 121 in the inner fin 120 . The thickness T1 of the thin portion 121 is thinner than the thickness T2 of the thick portion 122 . For example, T1=0.3 mm and T2=0.5 mm.

The plurality of thin portions 121 extend in the length direction L while being alternately positioned on one side and the other side in the thickness direction T when viewed from the axial direction A. As shown in FIG. The thin portions 121 adjacent to each other in the length direction L when viewed from the axial direction A are connected to each other by thick portions 122 extending in the thickness direction T. As shown in FIG. In this embodiment, the thin portion 121 and the thick portion 122 are substantially perpendicular to each other.

The inner fin 120 does not have a folded portion where the metal plates are folded so as to overlap each other. The folded portion is a portion where the metal plate is folded by approximately 180° and overlapped with each other.

Inner fin 120 is in contact with flat tube 110 at each of a plurality of thinned portions 121 . Each of the thick portions 122 is not in contact with the flat tube 110 .

A distance D1 between the thick portions 122 facing each other with a space therebetween in the length direction L is, for example, 4.8 mm. A distance D2 between the thin portion 121 and the flat tube 110 facing each other with a distance in the thickness direction T is, for example, 3.0 mm. The metal plate forming the inner fins 120 is made of a material such as stainless steel that has corrosion resistance and high thermal conductivity.

Here, a method for manufacturing the heat transfer tube 100 according to Embodiment 1 of the present invention will be described.
FIG. 3 is a cross-sectional view showing a state in which a metal plate is pressed in the heat transfer tube manufacturing method according to Embodiment 1 of the present invention. As shown in FIG. 3, one metal plate 20 is placed on one side in the thickness direction T of the metal plate 20 with a mold 30 and a metal plate 30 on the other side in the thickness direction T of the metal plate 20. Press with a mold 40 .

The mold 30 is provided with a plurality of protrusions 31 that are spaced apart from each other in the length direction L and protrude to the other side in the thickness direction T. As shown in FIG. The mold 40 is provided with a plurality of protrusions 41 that are spaced apart from each other in the length direction L and protrude to one side in the thickness direction T. As shown in FIG. The plurality of protrusions 41 are arranged so as to be positioned between the protrusions 31 in the length direction L one by one.

FIG. 4 is a cross-sectional view showing a state in which a plurality of thin-walled portions are formed on a metal plate in the heat transfer tube manufacturing method according to Embodiment 1 of the present invention. As shown in FIG. 4, by pressing the metal plate 20 between the metal mold 30 and the metal mold 40, the plurality of thin portions 21 of the metal plate 20 are spaced apart from each other in the length direction L. to form.

Specifically, the plurality of protrusions 31 press the metal plate 20 to form the plurality of recesses 23 , and the plurality of protrusions 41 press the metal plate 20 to form the plurality of recesses 24 . The recesses 23 and the recesses 24 are alternately formed on one side and the other side in the thickness direction T of the metal plate 20 .

In the metal plate 20 , the portions thinned by forming the recesses 23 and the portions thinned by forming the recesses 24 each become the thin portion 21 . A portion of the metal plate 20 located between the recess 23 and the recess 24 adjacent to each other becomes the thick portion 22 .

In this embodiment, a plurality of thin portions 21 are formed by so-called coining processing of the metal plate 20 . However, the method of forming the plurality of thin portions 21 is not limited to coining, and may be forging, cutting, casting, or the like.

FIG. 5 is a cross-sectional view showing a state in which a metal plate is bent in the heat transfer tube manufacturing method according to Embodiment 1 of the present invention. As shown in FIG. 5 , the metal plate 20 having the plurality of thin portions 121 formed thereon is separated into a mold 50 arranged on one side in the thickness direction T of the metal plate 20 and the other side in the thickness direction T of the metal plate 20 . It is pressed by a mold 60 arranged on the side.

The mold 50 is provided with a convex portion 51 projecting to the other side in the thickness direction T at a position corresponding to the concave portion 23 . The mold 60 is provided with a convex portion 61 projecting to one side in the thickness direction T at a position corresponding to the concave portion 24 .

FIG. 6 is a cross-sectional view showing a state in which inner fins are formed by bending a metal plate in the heat transfer tube manufacturing method according to Embodiment 1 of the present invention. As shown in FIG. 6 , the metal plate 20 is sandwiched between a mold 50 and a mold 60 and pressed to bend the metal plate 20 to form the inner fins 120 .

Specifically, the convex portion 51 presses a position corresponding to the concave portion 23 of the metal plate 20 to form the thin portion 121 located on the other side of the metal plate 20 in the thickness direction T, and the convex portion 61 presses a position corresponding to the concave portion 24 of the metal plate 20 to form a thin portion 121 positioned on one side in the thickness direction T of the metal plate 20 . At this time, the thick portion 122 is formed by changing the extending direction of the thick portion 22 from the length direction L to the thickness direction T so as to be positioned in the gap between the convex portion 51 and the convex portion 61. do.

In this manner, the metal plate 20 is formed so that the plurality of thin portions 121 are alternately positioned on one side and the other side of the thickness direction T of the metal plate 20 and extend in the length direction L orthogonal to the thickness direction T. The plate 20 is bent to form inner fins 120 .

FIG. 7 is a cross-sectional view showing a state in which inner fins are arranged inside flat tubes in the method for manufacturing a heat transfer tube according to Embodiment 1 of the present invention. As shown in FIG. 7 , the inner fins 120 are arranged inside the flat tube 110 so as to contact the flat tube 110 at each of the plurality of thin portions 121 .

Here, a modification that differs from the heat transfer tube 100 according to the first embodiment only in the extending direction of the thick portion will be described. FIG. 8 is a cross-sectional view showing the shape of inner fins included in the heat transfer tube according to the first modified example of the first embodiment of the present invention. As shown in FIG. 8, the angle between the thick portion 122a of the inner fin 120a of the heat transfer tube according to the first modification of the first embodiment of the present invention and the thin portion 121 when viewed from the axial direction A is It extends along the thickness direction T so as to form an acute angle. FIG. 9 is a cross-sectional view showing the shape of inner fins included in the heat transfer tube according to the second modification of the first embodiment of the present invention. As shown in FIG. 9, the thick portion 122b of the inner fin 120b included in the heat transfer tube according to the second modification of the first embodiment of the present invention has an angle of It extends along the thickness direction T so as to form an obtuse angle.

The inner fin 120 of the heat transfer tube 100 according to Embodiment 1 of the present invention is provided with a plurality of thin portions 121 in which the thickness of the metal plate 20 is thin when viewed from the axial direction A. The plurality of thin portions 121 are It extends in the length direction L while being alternately positioned on one side and the other side of the thickness direction T. As shown in FIG. Inner fin 120 is in contact with flat tube 110 at each of a plurality of thinned portions 121 .

This shortens the length of the heat transfer path when the heat transferred from the exhaust gas G to the inner fins 120 is transferred to the refrigerant W through the thin portion 121 and the flat tube 110, thereby improving the heat exchange efficiency of the heat transfer tube 100. can do.

In addition, since the thin portions 121 adjacent to each other in the length direction L are connected to each other by the thick portion 122 extending in the thickness direction T, the heat transferred from the exhaust gas G to the thick portion 122 is reduced. It is possible to secure a large cross-sectional area of the heat transfer path when the heat is transmitted to the thin portion 121 , and improve the heat transfer efficiency from the thick portion 122 to the thin portion 121 . As a result, the heat exchange efficiency of the heat transfer tubes 100 can be improved.

Since the volume occupied by the heat transfer tube 100 hardly changes when the inner fins 120 are provided with the thin portion 121 and the thick portion 122, the heat transfer tube 100 according to the first embodiment of the present invention has a volume It is possible to improve the heat exchange efficiency per unit. By providing the thin portion 121 and the thick portion 122 in the inner fin 120, the flow path area of the exhaust gas G hardly changes, so that the influence of the exhaust gas G on the pressure loss can be suppressed.

By using the heat transfer tube 100 for the EGR cooler, the exhaust gas G can be effectively cooled and recirculated in a reduced volume. As a result, it is possible to effectively reduce the generation of nitrogen oxides in the internal combustion engine and improve the fuel efficiency. Note that the heat transfer tube 100 is not limited to being used for an EGR cooler, and may be used for other purposes.

The inner fin 120 of the heat transfer tube 100 according to Embodiment 1 of the present invention does not have a folded portion where the metal plates 20 are folded back so as to overlap each other. As a result, there is no portion where the metal plate 20 is largely plastically deformed, and the folded portion is not opened due to thermal expansion, so the reliability of the inner fin 120 can be ensured.

The method for manufacturing the heat transfer tube 100 according to the first embodiment of the present invention includes a step of pressing one metal plate 20 to form a plurality of thin portions 21 with a small thickness of the metal plate 20 at intervals; The metal plate 20 is bent so that the plurality of thin portions 121 are alternately positioned on one side and the other side in the thickness direction T of the metal plate 20 and extend in the length direction L orthogonal to the thickness direction T. and forming the inner fins 120 inside the flattened tube 110 so as to contact the flattened tube 110 at each of the plurality of thin-walled portions 121 .

As a result, the plate thickness of one metal plate 20 can be easily partially changed by press forming or the like, and the heat exchange efficiency can be improved without substantially changing the volume occupied by the heat transfer tubes 100 . Moreover, since it is not necessary to increase the weight of the metal plate 20 in order to form the plurality of thin portions 121, an increase in material cost can be suppressed.

The step of forming the plurality of thin portions 21 on the metal plate 20 and the step of bending the metal plate 20 to form the inner fins 120 may be performed in the same step. That is, by press-molding a flat metal plate 20 without a plurality of thin-walled portions 21 only once, the inner fins 120 are formed by bending the metal plate 20 while forming a plurality of thin-walled portions 21 . good too.

In the method for manufacturing the heat transfer tube 100 according to the first embodiment of the present invention, the metal plate 20 is coined in the step of forming the plurality of thin portions 121, so that the plurality of thin portions 121 are formed in the metal plate 20. It can be formed easily and with high accuracy.

(Embodiment 2)
A heat transfer tube according to Embodiment 2 of the present invention will be described below with reference to the drawings. The heat transfer tube according to the second embodiment of the present invention differs from the inner fins 120 according to the first embodiment only in the shape of the inner fins. do not have.

FIG. 10 is a partial perspective view showing the appearance of inner fins included in a heat transfer tube according to Embodiment 2 of the present invention. As shown in FIG. 10, the inner fin 220 provided in the heat transfer tube according to the second embodiment of the present invention includes a protrusion 221 that is separated from the flat tube by cutting and raising a part of the metal plate. The thickness of the metal plate in the protruding portion 221 is thicker than the thickness of each of the plurality of thin portions 121 .

Specifically, when viewed from the axial direction A, a portion of the metal plate 20 positioned on one side in the thickness direction T and extending in the length direction extends toward the other side in the thickness direction T. The protrusion 221 is cut and raised. Similarly, a portion of the metal plate 20 located on the other side in the thickness direction T and extending in the length direction is cut and raised toward one side in the thickness direction T to form the protrusion 221. ing. The protrusion 221 is thicker than the surrounding thin portion 121 .

In the heat transfer tube according to the second embodiment of the present invention, since a part of the metal plate 20 is cut and raised to form an opening, heat can be transferred from the exhaust gas G in the opening to the refrigerant W through the flat tube 110. Therefore, the heat exchange efficiency can be further improved.

In addition, since the projecting portion 221 is thicker than the thin portion 121, the contact area between the exhaust gas G and the inner fin 220 is increased, and a large cross-sectional area of the electric heating path from the projecting portion 221 to the thin portion 121 is ensured. As a result, the efficiency of heat conduction from the projecting portion 221 to the thin portion 121 can be improved. Since the volume occupied by the heat transfer tubes hardly changes due to the provision of the protrusions 221 on the inner fins 220, the heat exchange efficiency per volume of the heat transfer tubes according to the second embodiment of the present invention can be improved.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the meaning and range of equivalents of the scope of the claims.

1 heat exchanger 10 housing 20 metal plate 21, 121 thin portion 22, 122, 122a, 122b thick portion 23, 24 recess 30, 40, 50, 60 mold 31, 41, 51, 61 Projection 100 Heat transfer tube 110 Flat tube 120, 120a, 120b, 220 Inner fin 221 Projection A Axial direction D1, D2 Spacing G Exhaust gas L Length direction T Thickness direction T1 , T2 thickness, W refrigerant.

Claims (5)

A flat tube having a flat shape along the length direction orthogonal to the thickness direction;
an inner fin made of a single metal plate disposed inside the flat tube so as to define a plurality of flow paths extending in an axial direction orthogonal to both the thickness direction and the length direction; prepared,
The inner fin is provided with a plurality of thin-walled portions in which the thickness of the metal plate is thin when viewed from the axial direction,
When viewed from the axial direction, the plurality of thin portions extend in the length direction while being alternately positioned on one side and the other side in the thickness direction,
The heat transfer tube, wherein the inner fin is in contact with the flat tube at each of the plurality of thin-walled portions. 2. The heat transfer tube according to claim 1, wherein said inner fin does not have a folded portion in which said metal plates are folded so as to overlap each other. The inner fin includes a protrusion that is separated from the flat tube by cutting and raising a part of the metal plate,
3. The heat transfer tube according to claim 1, wherein the thickness of the metal plate at the protrusion is greater than the thickness of each of the plurality of thin portions. a step of pressing a single metal plate to form a plurality of thin-walled portions of the metal plate at intervals;
The inner fins are formed by bending the metal plate so that the plurality of thin portions are alternately positioned on one side and the other side in the thickness direction of the metal plate and extend in a direction orthogonal to the thickness direction. forming;
and disposing the inner fin inside the flat tube so as to contact the flat tube at each of the plurality of thin-walled portions. 5. The method of manufacturing a heat transfer tube according to claim 4, wherein the metal plate is coined in the step of forming the plurality of thin portions at intervals.

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