Patent Publication Number: US-2007095514-A1

Title: Tube for heat exchanger and method of manufacturing the same

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 A 1  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  11   b  and a bent portion  11   a  at ends of the flat plate portions  11   b.  The bent portion  11   a  has an arc shape, for example. Also, the bent portion  11   a  has a shape corresponding to a part of a circle that has a diameter equivalent to a distance between the flat plate portions  11   b  of the tube member  11 . Alternatively, the bent portion  11   a  has another shape such as a V-shape or a bracket-shape.  
      The flat plate portions  11   b  extend from the bent potion  11   a.  As shown in  FIG. 2 , the flat plate portions  11   b  have inclined wall portions  11   c   3 ,  11   c   4  at ends opposite to the bent portion  11   a.  The inclined wall portions  11   c   3 ,  11   c   4  are inclined toward a centerline between the flat plate portions  11   b  to form a V-shape. Further, the flat plate portions  11   b  have a first end portion  11   c  and a second end portion  11   c   2  at the ends of the inclined wall portions  11   c   3 ,  11   c   4 , respectively. The first end portion  11   c   1  and the second end  11   c   2  are crimped.  
      For example, the second end portion  11   c   2  overlaps and is folded over the first end portion  11   c   1 . Specifically, the second end portion  11   c   2  has a length equal to or larger than twice of the first end portion  11   c   1 . The second end portion  11   c   2  has a first portion extending from the end of the inclined wall portion  11   c   4  parallel to and opposed to an inner surface of the first end portion  11   c   1 , a second portion extending from the first portion and wrapped over the end of the first end portion  11   c   1 , and a third portion extending from the second portion along an outer wall of the first end portion  11   c   1 . The third portion ends at a position adjacent to a boundary between the first end portion  11   c   1  and the inclined wall portion  11   c   3 .  
      As such, a crimped portion  11   c  is formed at an end opposite to the bent portion  11   a  by crimping the ends of the flat plate portions  11   b,  i.e., by folding the second end portion  11   c   2  over the first end portion  11   c.  Here, crimping means a structure that the first end portion  11   c   1  and the second end portion  11   c   2  are closed by folding the second end portion  11   c   2  over the first end portion  11   c   1 .  
      As shown in  FIGS. 1 and 2 , the second end portion  11   c   2  is folded and wrapped over the first end portion  11   c   1  such that both surfaces of the first end portion  11   c   1  are generally included in the folded second end portion  11   c   2 . In this embodiment, the crimped portion  11   c  has a generally flat shape. The crimped portion  11   c  extends from the inclined wall portions  11   c   3 ,  11   c   4  in a length substantially equal to the distance between the flat plate portions  11   b.    
      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  12   a  having a wave form.  
      Further, the inner fin  12  has a first flat plate portion  12   b  and a second flat plate portion  12   c  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  12   b  is in contact with an inner wall of the bent portion  11   a  of the tube member  11 . Further, the first end portion  11   c   1  and the second end portion  11   c   2  of the tube member  11  are crimped in a condition that the second flat portion  12   c  is interposed between the first end portion  11   c   1  and the second end portion  11   c   2 .  
      Further, the second flat portion  12   c  is formed with a bent portion  12   c   1 . The bent portion  12   c   1  is formed by bending an end of the second flat portion  12   c  into a substantially L-shape. The bent portion  12   c   1  contacts and partly covers the end of the first end portion  11   c   1  of the tube member  11 . The bent portion  12   c   1  extends parallel to an end surface of the first end portion  11   c   1 . As such, the bent portion  12   c   1  provides a hook portion to be engaged with or held on the end of the first end portion  11   c   1 .  
      The bent portion  12   c   1  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  12   c   1  serves as a positioning member to position the inner fin  12  with respect to the tube member  11 .  
      The bent portion  12   c   1  has the length in a direction perpendicular to the first end portion  11   c   1  equal to or less than the thickness of the first end portion  11   c   1 . Preferably, the bent portion  12   c   1  has the length as long as possible within the thickness of the first end portion  11   c   1 . The bent portion  12   c   1  can be formed throughout the end of the second flat plate portion  12   c  in a longitudinal direction of the inner fin  12 . Alternatively, the bent portion  12   c   1  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  23   a  (double-dashed chain line in  FIG. 2 ). The longitudinal ends of the inner fin tubes  10  are inserted in the tube holes  23   a  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  110 A, an inserting and crimping section  110 B and a cutting section  110 C. The sections  110 A to  110 C 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  110 A to  110 C for carrying the material, for example. Thus, operations in the respective sections  110 A to  110 C can be performed continuously.  
      The tube outer wall forming section  110 A has multiple rollers for mainly forming the bent portion  11   a  and the flat plate portions  11   b  from the coiled band plate material, thereby to form a tube outer wall as the tube member  11 . The inserting and crimping section  110 B has multiple rollers R 0  through Rn for forming the crimped portion  11   c  on the tube outer wall  11  after inserting the inner fin  12  in the tube outer wall  11 . In the cutting section  110 C, the continuous formed member carried from the inserting and crimping section  110 B 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  110 B. In the inserting and crimping section  110 B, the rollers R 0  to Rn are arranged in a processing direction, i.e., a feeding direction. Further, each of the rollers R 0  to Rn rotates while contacting the second end portion  11   c  of the tube outer wall  11 .  
      Moreover, the rollers R 0  to Rn are arranged such that directions of rotation axes of the rollers R 0  to Rn varies from a position A 0  to a position An, as shown in  FIG. 5 . That is, a rotation axis A 0  of the roller R 0  is parallel to an original extending direction of the second end portion  11   c   2 . A rotation axis An of the roller Rn is parallel to the rotation axis A 0  of the roller R 0 . Rollers between the roller R 0  and the roller Rn are arranged such that the rotation axes thereof are gradually angled from the rotation axis A 0  to the rotation axis An.  
      Thus, the rotation axes are varied 180 degrees from the rotation axis A 0  to the rotation axis An. As such, the second end portion  11   c   2 , which is straight before the folding, is folded over the first end portion  11   c   1  through the rollers R 0  to Rn. Accordingly, the crimped portion  11   c  is formed.  
      The inner fin forming unit  120  is arranged parallel to the tube outer wall forming section  110 A such that the formed inner fin  12  is located separate from the tube outer wall  11  formed in the tube outer wall forming section  110 A 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  12   a,  the first and second flat portions  12   b,    12   c  and the L-shaped bent portion  12   c   1  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  110 B.  
      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  110 A (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  110 B by the inner fin carrying unit  130 .  
      Next, in the inserting and crimping section  110 B, the continuous inner fin  12  is inserted in the continuous tube outer wall  11  (inserting step). Then, the second end portion  11   c   2  of the tube outer wall  11  is continuously folded over the first end portion  11   c   1  (crimping sep). Thus, a continuous inner fin tube is formed.  
      In the inserting step, the bent portion  12   c   1  of the inner fin  12  engages with the end of the first end portion  11   c   1  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  12   c   1 . Then, in the crimping step, the second end portion  11   c   2  of the tube outer wall  11  is sequentially folded over the first end portion  11   c   1  by the rollers R 0  to Rn in a condition that the second flat portion  12   c  of the continuous inner fin  12  is sandwiched between the first end portion  11   c   1  and the second end portion  11   c   2  and the bent portion  12   c   1  is engaged with the first end portion  11   c   1 . Accordingly, even after the crimping step, the bent portion  12   c   1  maintains the condition engaged with the first end portion  11   c   1 .  
      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 ( 110 D). 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  12   c   1  is held in contact with the end of the first end portion  11   c   1 . Namely, the inner fin  12  is positioned with respect to the tube outer wall  11  by the bent portion  12   c   1 . 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  11   c   2  is stabled or uniformed. Namely, the second end portion  11   c   2  is uniformly folded over the first end portion  11   c   1 . Accordingly, the inner fin tubes  10 , the ends of which are uniformly crimped, are manufactured.  
      Further, in the crimping step, the second end portion  11   c   2  is bend over a corner of the bent portion  12   c   1  of the inner fin  12 . Thus, the second end potion  11   c   2  is turned substantially 180 degrees over the bent portion  12   c   1  while maintaining a bent shape (R-shape). Moreover, the second end portion  11   c   2  can uniformly maintain a predetermined length L at a folded end, as shown in  FIG. 2 .  
      Since the crimped portion  11   c  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  23   a  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  11   c   2  in the substantially equal length L, the clearance S defined between each tube hole  23   a  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  23   a  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  11   b  are continuous through the bent portion (connecting portion)  11   a  on a side opposite to the crimped end  11   c.  Therefore, durability of the inner fin tube  10  against a pressure of the inner fluid improves.  
      Also, the length of the bent portion  12   c   1  of the inner fin  12  is shorter than the thickness of the end of the first end portion  11   c   1 . Therefore, it is less likely that the bent portion  12   c   1  will interfere with the folded second end portion  11   c   2 .  
     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  11   c  and the second end portion  11   c   2 .  FIG. 7  shows an intermediate stage of the crimping step.  
      In the second embodiment, the bent portion  12   c   1  of the inner fin  12  is formed at the same time as folding the second end portion  12   c   1  in the crimping step. In other words, the bent portion  12   c   1  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  12   c  is held between the first end portion  11   c   1  and the second end portion  11   c   2 , and the end of the second flat plate portion  12   c  extends longer than the first end portion  11   c   1 , as shown in  FIG. 6 . It is preferable that the end of the second flat plate portion  12   c  protrudes from the end of the first end portion  11   c   1  as long as possible in a range shorter than the thickness of the first end portion  11   c   1 .  
      When the second end portion  11   c   2  is bent in the crimping step, the end of the second flat plate portion  12   c  of the inner fin  12  is bent with the second end portion  11   c   2  at a position corresponding to the end of the first end portion  11   c   1  as a bending base point, as shown in  FIG. 7 . As such, the bent portion  12   c   1  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  12   c   1 , 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  11   c  is stably and uniformly formed.  
      Also in this embodiment, the flat plate portions  11   b  are continuous through the bent portion (connecting portion)  11   a  on a side opposite to the crimped end  11   c.  Therefore, durability of the inner fin tube  10  against a pressure of the inner fluid improves. Also, the length of the bent portion  12   c   1  of the inner fin  12  is shorter than the thickness of the end of the first end portion  11   c   1 . Therefore, it is less likely that the bent portion  12   c   1  will interfere with the folded second end portion  11   c   2 .  
      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  12   a.  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  11   b  of the tube member  11  are continuous through the bent portion  11   a.  However, the shape of the tube member  11  is not limited to the above. For example, the flat plate portions  11   b  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.