Patent Publication Number: US-6904677-B2

Title: Method of manufacturing tube and apparatus for manufacturing the same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is based on Japanese Patent Application No. 2001-254498 filed on Aug. 24, 2001, the disclosure of which is incorporated herein by reference. 
   FIELD OF THE INVENTION 
   The present invention relates to a method of manufacturing a tube used for a heat exchanger such as a radiator and a water heater and an apparatus for manufacturing the tube. 
   BACKGROUND OF THE INVENTION 
   According to a radiator for a vehicle disclosed in JP-A-6-159986, dents or projections (dimples) are formed on inside walls of tubes at least at portions other than longitudinal ends (header insertion portions) of the tubes. This improves a coefficient of heat transfer between fluid flowing through the tubes (e.g. cooling water and hot water) and the tubes. Further, this restricts gaps between the header insertion portions of the tube ends and insertion holes formed on header tanks from excessively increasing, thereby preventing defective brazing between the tubes and the header tanks. 
   With respect to a method of manufacturing the tube, a work in a form of band plate is pressed so that dimples are formed. Further, to deal with variation of length of the tubes, it is proposed to control the timing of feeding the work into a pressing device and the timing of operation of the pressing device so that portions where the dimples are formed can be changed. After the dimples are formed, the work is shaped into a tube by a shaping roller and thereafter cut into a predetermined length. In this method, however, the work is fed intermittently. Therefore, it is difficult to continuously form the dimples, resulting in low productivity and production rate. 
   On the other hand, it is proposed to use a roller shaping machine having a roller formed with dents or projections on its outer peripheral surfaces in order to continuously form dimples. The roller has a portion having the dents or projections for forming the dimples and a portion without having the dents or projections. By this, portions where the dimples are formed and portions where the dimples are not formed, which corresponds the header insertion portions, are formed at predetermined intervals. In this method, however, the roller needs to be exchanged with another roller whenever the length of the tubes is changed. Therefore, it is difficult to deal speedily with variations in the length of the tubes. 
   SUMMARY OF THE INVENTION 
   The present invention is made in view of the forgoing matters and it is an object of the present invention to provide a method of manufacturing tubes, which have a plurality of projections (dimples) projecting inwardly at portions other than predetermined portions, capable of dealing speedily with variations of length of the tubes and improving productivity. 
   It is another object of the present invention to provide an apparatus for manufacturing tubes, which have projections (dimples) projecting inwardly at portions other than predetermined portions, capable of improving productivity by dealing with variations of length of the tubes. 
   According to the present invention, a method of manufacturing tubes, each of which has a plurality of projections projecting inwardly at a portion other than a predetermined portion. includes pressing a work having a shape of band plate to form projections while the work is fed in its longitudinal direction, crushing a projection formed at a predetermined portion of the work to flatten the predetermined portion, and shaping the work into a tubular shape and cutting the work into predetermined lengths to form the tubes. 
   According to the method, the projections are formed continuously while the work is continuously fed. To contrast with a method of feeding the work intermittently, the projections can be formed continuously. Therefore, productivity and production rate of the tubes improve. In addition, by changing the portion to be crushed, the portions without having the projections, such as portions corresponding to ends of the tubes, can be changed easily. Therefore, the method can deal with variations of length of the tubes without exchanging a roller. Accordingly, the method of manufacturing the tubes of the present invention deals with tube length variations and improves productivity and production rate. 
   Alternatively, the method of manufacturing the tubes of the present invention includes a first step of pressing only a predetermined portion of the work to form a projection at the predetermined portion and a second step of shaping the work into a tube and cutting the work into a predetermined length. By this, it is possible to deal speedily with variations of length of the tubes without exchanging the roller. Accordingly, productivity and production rate improve, as compared with a method of feeding the work intermittently. 
   According to the present invention, an apparatus for manufacturing the tubes includes a first shaping device that forms projections on the work having a shape of band plate by pressing while the work is continuously fed in Its longitudinal direction, a second shaping device that flattens a predetermined portion of the work by crushing a projection formed at the predetermined portion, and a third shaping device that shapes the work into a tubular shape and cuts the work into hail predetermined lengths to form the tubes. The third shaping device is placed forward of the second shaping device In a feed direction of the work. 
   The apparatus can form the projections continuously while the work is continuously fed. In contrast with the method of feeding the work intermittently, productivity of tubes and production rate improve because the projections can be formed continuously. Further, portions without having the projections, such as portions corresponding to ends of tubes, can be easily changed by changing portions that are crushed by the second shaping device. Therefore, it is possible to deal with variations of length of tubes without exchanging a roller. 
   Alternatively, the apparatus for manufacturing the tubes of the present invention includes a first shaping device that forms projections at a predetermined portion of the work by pressing only the predetermined portion while the work is continuously fed in its longitudinal direction, and a second shaping device that shapes the work into a tube and cutting the work into a predetermined length. The second shaping device is placed forward of the first shaping device in the feed direction of the work. By this, it is not required to exchange a roller. Accordingly, productivity of the tubes and production rate improve. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a plan view of a radiator according to the first embodiment of the present invention; 
       FIG. 2  is an enlarged perspective view of a core portion of the radiator according to the first embodiment of the present invention; 
       FIG. 3  is a perspective view of a tube according to the first embodiment of the present invention; 
       FIG. 4  is a perspective view of an apparatus for manufacturing the tube according to the first embodiment of the present invention; 
       FIGS. 5A  to  5 D are explanatory views for illustrating operations of the apparatus for manufacturing the tube according to the first embodiment of the present invention; 
       FIGS. 6A  to  6 D are explanatory views for illustrating a process of bending the tube according to the first embodiment of the present invention; 
       FIGS. 7A  to  7 D are explanatory views for illustrating the process of further bending the tube according to the first embodiment of the present invention; 
       FIGS. 8A  to  8 C are explanatory views for illustrating a process of manufacturing the core portion shown in  FIG. 2 ; 
       FIG. 9  is a perspective view of an apparatus for manufacturing a tube according to the second embodiment of the present invention; 
       FIGS. 10A  to  10 D are explanatory views for illustrating operation of the apparatus for manufacturing the tube according to the second embodiment of the present invention; and 
       FIGS. 11A and 11B  are explanatory views for illustrating modifications of the apparatus for manufacturing the tube according to the second embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF EMBODIMENTS 
   Embodiments of the present invention will be described hereinafter with reference to the drawings. 
   [First Embodiment] 
   Tubes of the present invention are for example used for a radiator that is a kind of a heat exchanger performing heat exchange between a vehicular engine coolant and air.  FIG. 1  is a plan view of the radiator according to the embodiment. 
   Referring to  FIG. 1 , radiator tubes (hereinafter, tubes)  110  are made of aluminum. The engine coolant (fluid) flows through the insides of the tubes  110 . Radiator fins (hereinafter, fins)  120  are made of aluminum. The fins  120  are attached to the outside surfaces of the tubes  110  to increase heat-radiating areas. The tubes  110  and the fins  120  construct a heat-exchanging core portion for performing heat exchange between the engine coolant and the air. The tubes  110  will be described later in detail. 
   Header tanks (hereinafter, tanks)  130  are made of aluminum. The tanks  130  are located at the longitudinal ends of the tubes  110  to communicate with the tubes  110 . One of the tank  130  (for example, left tank in  FIG. 1 ) is to distributes the engine coolant into the tubes  110  and the remaining tank  130  (right tank) is to collect the engine coolant that has been exchanged heat between itself and air. The tubes  110 , the fins  120  and the tanks  130  are brazed together by a brazing material. The brazing material contains a metal having a melting point lower than that of the aluminum forming the tubes  110 , the fins  120  and the tanks  130 . 
   Next, the tubes (tube bodies)  110  will be described. 
     FIG. 2  is a perspective view of the heat-exchanging core portion and partly includes a cross-section. The tube  110  is produced by shaping an aluminum band plate into a flat tube. The tubes  110  are arranged such that a flow direction of air passing between the tubes  110  is substantially parallel to a major axis of a tube cross-section. Also, a passage (inside space) through which the engine coolant flows of the tube  110  is divided into two spaces in substantially a middle portion with respect to the major axis direction of the tube cross-section. As shown in  FIG. 3 , the tubes  110  are formed with a plurality of projections (dimples)  110   b  projecting inside of the tubes  110 . The projections are formed over the tubes  110  other than the longitudinal ends (insertion portions)  110   a  that are inserted into the tanks  130 . 
   As shown in  FIG. 2 , in the tube  110 , a groove portion (wrapping groove)  111  is formed at a side of a work (a plate material) having a shape of band plate by bending the side, and an insert portion (wrapped end portion)  112  is formed at a remaining side of the work. The groove portion  111  and the insert portion  112  are brazed in a condition that the insert portion  112  is interposed in the groove portion  111 . The groove portion  111  includes a first side wall (wrapping end portion)  111   a , a second side wall (wrapping base portion)  111   b  opposing to the first side wall  111   a , and an arc-shaped connecting portion  111   c  connecting the first side wall  111   a  and the second side wall  111   b . The groove portion  111  has substantially a U-shaped cross-section. The groove portion  111  is located in the inside of the tube  110 . 
   The second side wall  111   b  is integrally formed and connected from the inside wall of the tube body  110 . On the other hand, the first side wall  111   a  is not integrally connected from the inside wall of the tube wall  110  before the brazing because it is formed at the side of the plate member. After the brazing, the first side wall  111   a  is integrated with the inside wall of the tube body  110  by the brazing material. 
   The first side wall  111   a  is formed with first projections (contact claws)  113   a . The first projections  113   a  project from a portion between the first side wall  111   a  and the connecting portion  111   c  to a side opposite to the connecting portion  111   c  with respect to the first side wall  111   a  (toward left bottom in FIG.  2 ). Similar to this, the second side wall  111   b  is formed with second projections (receiving claws)  113   b . The second projections  113   b  project from a portion between the second side wall  111   b  and the connecting portion  111   c  to a side opposite to the connecting portion  111   c  with respect to the second side wall  111   b  (to right bottom in FIG.  2 ). The ends of the first projections  113   a  and the second projections  113   b  are in contact with the inside wall  110   d  opposing to the connecting portion  111   c  (the inside wall  110   d  is an inside wall located under the connecting portion  111   c  in FIG.  2 ). The connecting portion  111   c  is also in contact with the inside wall  110   d.    
   Next, the method of manufacturing the tubes  110  and the radiator will be described. 
     FIG. 4  is a schematic view of a tube manufacturing apparatus  200  employing the method of manufacturing the tubes of the embodiment. Numeral  10 W denotes the work, which is a material of the tubes  110 , in a form of band plate. A base material of the work  10 W is aluminum and at least one of surfaces of the work  10 W is coated (clad) with a brazing material. The work  10 W is fed continuously at a predetermined speed in a direction denoted by an arrow A 1  of  FIG. 4  by a pair of cylindrical (tubular) rollers of a feeding device (not shown). 
   A projection-forming device (first shaping device)  210  is a roller shaping device that shapes the work  10 W while rotating. That is, the work  10 W is pressed while continuously fed in its longitudinal direction (A 1 ) so that the projections  110   b  are formed. The projection-forming device  210  includes a pair of projection-forming rollers  211 ,  212  that are arranged to sandwich the work  10 W from both the surfaces. 
   As shown in  FIGS. 5A  to  5 D, the projection-forming roller  212  that is placed under the work  10 W in  FIGS. 5A  to  5 D is formed with projections  212   a  for pressing and developing the work  10 W partly. On the other hand, the projection-forming roller  211  that is placed above the work  10 W is formed with dents  211   a  corresponding to the projections  212   a.    
   A projection-crushing device (second shaping device)  220  shown in  FIG. 4  is a roller shaping device that shapes the work  10 W while rotating. The projection-crushing device  220  crushes the projections  110   b  that are formed at predetermined portions in the work low (portions corresponding to the tank insertion portions  110   a ) so that the predetermined portion of the work  10 W is flattened. As shown in  FIGS. 5A  to  5 D, the projection-crushing device  220  includes a pair of projection-crushing rollers  221 ,  222  that are arranged to sandwich the work  10 W from both the surfaces of the work  10 W. The projection-crushing roller  222  that is placed under the work  10 W in  FIGS. 5A  to  5 D has a simple cylindrical (tubular) shape. The projection-crushing roller  222  rotates with the projection-forming rollers  211 ,  212  at the same speed. Here, as shown in  FIG. 4 , the projection-crushing roller  222  is mechanically linked with the projection-forming rollers  211 ,  212  through gears G 1 , G 2 . 
   The projection-crushing roller  221  that is placed above the work  10 W is formed with a pressing projection  221   a  for crushing the projections  110   b . The pressing projection  221   a  is formed only at a predetermined area in the cylindrical surface of the projection-crushing roller  221 . The projection-crushing roller  221  is electrically connected with a cutting device  230  (described later). The projection-crushing roller  221  rotates at a rate in accordance with length of the tubes  110  to be manufactured and crushes the projections formed at the predetermined portion by the pressing projection  221   a.    
   Therefore, the projection-forming device  210  (projection-forming rollers  211 ,  212 ) and the projection-crushing roller  222  are operated by the same servomotor (driving device). Also, the projection-crushing device  221  is operated by another servomotor  223 . 
   The tube  110  (work  10 W) Is shaped Into a flat tube by a bending device (described later)  234  and cut into a predetermined length by the cutting device  230 . A cutter  231  of the cutting device  230  is driven by a servomotor (driving device)  232  that Is electrically connected to the servomotor  223  of the projection-crushing roller  221 , to rotate with the projection-crushing roller  221 . 
   The projection-crushing device  220  (specially, the projection-crushing roller  221 ) and the cutting device  230  are controlled by a control unit  240 . 
   As shown by a general box in  FIG. 4 , the bending device, which functions to bend the band plate work  10 W into a flat tube shown in  FIG. 2 , is provided between the projection-crushing device  220  and the cutting device  230 .  FIGS. 6A  to  6 D and  7 A to  7 D illustrate the works l 0 W in time sequence while the work  10 W Is bent by the bending device  234 . 
   In the order from  FIG. 6A  to  FIG. 6D , sides of the work  10 W is bent to form the groove portion  111  and the insertion portion  112 . (Side forming step) The work  10 W is further bend in the order shown from  FIGS. 7A  to  7 D. Thus, the insertion portion  112  is interposed in the groove portion  111 . 
   (Inserting Step) 
   Next, operation of the tube manufacturing apparatus  200  and the method of manufacturing the tube of the embodiment will be described. 
   First, the projection-forming device  210  presses the work low while the work low continuously feeds in the longitudinal direction (A 1 ), thereby forming the projections  110   b . (First step) Next, the projection-crushing device  220  crushes the projections  110   b  formed at the predetermined portion, such as at the portion corresponding to the tank insertion portion  110   a , thereby flattening the predetermined portion of the work  10 W. 
   (Second Step) 
   Thereafter, the work  10 W is shaped into a flat tube by the bending device  234  provided forward of the projection-crushing device  220  in the feed direction (A 1 ) of the work l 0 W and cut into the predetermined length by the cutting device  230 . 
   (Third Step) 
   After the tubes  110  are produced in this way, the tubes  110  and the fins  120  are alternately laminated, so the heat-exchanging core portion is assembled. Then, the tubes  110  and the fins  120  are compressed by using a tool such as a wire so that the tubes  110  and the fins  120  are press-contact to each other. (Temporary assembling step) After, the heat-exchanging core portion is joined with the tanks  130  by integrally brazing. 
   (Brazing Step) 
   Here, after the completion of the inserting step, the work  10 W changes its shape from a state shown in  FIG. 7D  to a state shown in  FIG. 7B  by a spring back force. In the temporary assembling step, the tubes  110  and the fins  120  are compressed in a direction parallel to the first side wall  111   a  and the second side wall  111   b,  that is, parallel to minor axes of the tube cross-sections. Therefore, the tubes  110  are bent in the order shown from  FIG. 8A  to  FIG. 8C  during the temporary assembling step. Then, the tubes  110  are brazed in the conditions shown in FIG.  8 C. Hereinafter, the force compressing the tubes  110  and the fins  120  is referred to as a compress force of the temporary assembling step. 
   Next, features of the embodiment will be described. 
   After the projections  110   b  are formed, the projections  110   b  formed at the predetermined portion of the work  10 W is crushed and the predetermined portion of the work  10 W is flattened. Therefore, the projections  110   b  are continuously formed while the work  10 W is continuously fed. In contrast with a case of feeding the work  10 W intermittently, the projections  110   b  are formed continuously. Accordingly, productivity of the tubes  110  improves. 
   Also, because operation timing of the projection-crushing roller  221  is controlled, portions where the projections  110   b  are crushed can be changed. Therefore, the portions without having the projections  110   b , for example, the portions corresponding to the tank insertion portions  110   a , can be changed easily. Accordingly, it is possible to deal with variations of length of the tubes  110  without exchanging the rollers  211 ,  212 . 
   In this way, the method of manufacturing the tubes and the tube manufacturing apparatus of the embodiment can deal with variations in tube length smoothly and improve productivity and production rate. 
   Also, the tube  110  of the embodiment is formed with the first projections  113   a  that project from the portion between the first side wall  111   a  and the connecting portion  111   c  to a side opposite to the connecting portion  111   c  with respect to the first side wall  111   a . The groove portion  111  easily opens by the spring back force such that a width of the groove, that is, a distance between the first side wall  111   a  and the second side wall  111   b  (see FIG.  8 A), increases. When the tubes  110  are compressed, the ends of the first projections  113   a  are brought into contact with the inside wall  110   d  first, as shown in FIG.  8 B. 
   With this, reaction force against the compress force of the temporary assembling step exerts to the ends of the first projections  113   a . Further, the ends of the first projections  113   a  are in contact with the inside wall  110   d  and fixed thereon. Therefore, a bending moment to reduce the width of the groove is exerted to the first side wall  111   a  and the connecting portion  111   c . Accordingly, as the compression continues from the state shown in  FIG. 8B  to the state shown in  FIG. 8C , the first side wall  111   a  approaches the insertion portion  112 . Further, the first side wall  111   a  comes in contact with the insertion portion  112  and presses the insertion portion  112  toward the second side wall  111   b.    
   That is, as the compression increases, the insertion portion  112  is automatically wrapped by the first side wall  111   a  and the second side wall  111   b  that construct the groove portion  111 , so the insertion portion  112  is interposed in the groove portion  111 . Further, the insertion portion  112  is securely interposed in the groove portion  111  such that the gap between the inside wall of the groove portion  111  and the insertion portion  112 , especially, the gap δ (see  FIG. 2 ) between the second side wall  111   b  and the insertion portion  112 , is uniformed. Therefore, the groove portion  111  and the insertion portion  112  are securely brazed. This improves yields of the tubes (brazing). Further, this reduces a manufacturing cost of the radiator  100 . 
   Further, the second side wall  111   b  is formed with the second projections  113   b  that project from the portion between the second side wall  111   b  and the connecting portion  111   c  to a side opposite to the connecting portion  111   c  with respect to the second side wall  111   b . The ends of the second projections  113   b  are in contact with the inside wall  110   d.  Therefore, when the first side wall  111   a  approaches the insertion portion  112  and presses the insertion portion  112  toward the second side wall  111   b , that is, when the compression increases from the state shown in  FIG. 8B  to the state shown in  FIG. 8C , the second side wall  111   b  is less likely to move and separate from the insertion portion  112 . 
   Therefore, the gap between the insertion portion  112  and the inside wall of the groove portion  111 , especially the second side wall  111   b , can be uniformed and the insertion portion  112  can be interposed in the groove portion  111 . 
   [Second Embodiment] 
   In the first embodiment, the projection-forming device  210  is continuously driven with the feeding of the work  10 W so that the projections  110   b  are continuously formed. Also, the projections formed at the predetermined portion of the work low are crushed to flatten the predetermined portion. In the second embodiment, only a predetermined of the work  10 W other than a portion corresponding to the tank insertion portion  110   a  is pressed to form the projections  110   b  while the work  10 W is continuously feed in its longitudinal direction. (First step) Then, the work  10 W is shaped into a flat tube. Further, the work  10 W (tube  110 ) is cut into a predetermined length. 
   (Second Step) 
     FIG. 9  is a schematic view of a projection-forming device  210  that is an essential part of the tube-manufacturing device  200  of the embodiment. The projection-forming roller  212  has the projections  212   a  for forming the projections  110   b . The projection-forming roller  212  moves in a direction (arrow A 2 ) that the thickness of the work  10 W is measured. The movement of the projection-forming roller  212  is switched between a time when the projections  110   b  are formed and a time when the projections  110   b  are not formed. 
   Specifically, when the portion of the work  10 W that corresponds to the tank insertion portion  110   a  passes between the projection-forming rollers  211 ,  212  of the projection-forming device  210 , the projection-forming roller  212  moves downwardly (in a direction denoted by an arrow A 2 ′) and separates from the work  110 W, as shown in FIG.  10 B. Thus, the work low maintains the portion  110   a ′ corresponding to the tank insertion portion  110   a  flat. 
   Here, the projection-forming roller  212  is moved by a link mechanism  250  shown in FIG.  9 . In  FIG. 9 , numeral  251  denotes a link lever for driving the link mechanism  250 . Numeral  252  denotes an off-centered table (off-centered cam) for sliding the link lever  251 . Numeral  253  denotes a servomotor (driving device) for rotating the off-centered table  252 . The control unit  240  controls the servomotor  253 . 
   Numeral  224  denotes a driving-gear box for transmitting the rotation of a servomotor (not shown) to the projection-forming roller  211 ,  212  to rotate the rollers  211 ,  212 . In the embodiment, the projection-forming rollers  211 ,  212  are linked to the driving-gear box  224  through joints  225  for allowing output shaft to off-center. The joints  225  offsets gaps between output shafts  225  of the driving-gear box  224  and the projection-forming rollers  211 ,  212  when the projection-forming roller  212  is moved. 
   Next, effects and advantages of the embodiment will be described. 
   The projections  110   b  are formed by pressing only the predetermined portion of the longitudinal work  10 W, the predetermined portion corresponding to the portion other than the tank insertion portion  110   a . Therefore, it is not required to exchange the roller  211 ,  212  when the length of the tubes  110  is changed. As compared with the method of feeding the work  10 W intermittently, the productivity of the tubes  110  and the production rate improve. 
   According to the method and the apparatus for manufacturing the tubes  110  of the embodiment, it is possible to deal with variations of length of the tubes and improve the productivity and the production rate. 
   Here, only the projection-forming roller  212  is moved. It is also possible to move the projection-forming roller  211  with the projection-forming roller  212 . The projection-forming roller  212  is moved downwardly (in the direction of A 2 ′) and separated from the work  10 W. Therefore, in a case that heights of the projections  110   b  are large, the work  10 W may warp toward the projection-forming roller  212  (downwardly) when the projection-forming roller  212  separates from the work  10 W. In such a case, a guide  226  can be provided for restricting the work  10 W from warping toward the projection-forming roller  212  (downwardly), as shown in FIG.  11 A. 
   Here, the guide  226 , shown in  FIG. 11A , is in a form of block that guides the work  10 W with a relatively large surface. The guide  226 , shown in  FIG. 11B , is in a form of cylindrical roller that rotates to guide the work  10 W. 
   [Other Modified Embodiments] 
   In the first and the second embodiments, the first projections  113   a  and the second projections  113   b  are formed on the first side wall  111   a  and the second side wall  111   b , respectively. At least the first side wall  111   a  requires the projections. Thus, it is possible to eliminate the second projections  113   b.    
   In the first and the second embodiments, the present invention is employed to the tubes  110  of the radiator  100 . However, the present invention is not limited to this, but can be employed to tubes (pipes) for other purposes. In addition, the cross-section of the tube  110  is not limited to the shape described in the above embodiments, but can be a simple elliptic shape or circular shape. 
   The tubes  110  can be joined by methods other than brazing. For example, the tubes  110  can be joined by electric welding, as an electro-resistance-welded tube. Further, in the above embodiments, the projections  110   b  are formed in a step shown in FIG.  6 A. The present invention is not limited to this. For example, the projections  110   b  can be formed in a step shown in FIG.  6 C.