Abstract:
Provided are a pipe bender which is capable of spiral pipe bending and a method for spiral pipe bending with radii of bend using the pipe bender. The pipe bender includes an XY sliding mechanism), which has a Y-axis movement means travelling back and forth and an X-axis movement means travelling from side to side; a turning table device for rotating a turning table provided on top thereof, the turning table device being placed on the XY sliding mechanism; a bender with a cylindrical shaft rotatably supported, the cylindrical shaft placed on the turning table and secured to a worm wheel; a center shaft passing through the hole of the cylindrical shaft and having a lower end secured to a bottom; and a bending roller provided on top of the cylindrical shaft rotatable about the center of a support roller and which is disposed adjacent to the support roller.

Description:
This application is a National Stage Application of PCT/JP2011/062562, filed 1 Jun. 2011, which claims benefit of Serial No. 2010-128522, filed 4 Jun. 2010 in Japan and which applications are incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications. 
     TECHNICAL FIELD 
     The present invention relates to a pipe bending machine and a bending method for producing a spiral pipe by using the pipe bending machine. 
     BACKGROUND ART 
     In recent years, use of combustionless, heat-pump type water heaters (e.g., EcoCute (registered trademark)) has been widely spread in industry and ordinary household as measures for reduction of CO 2 , which is assumed to be a ringleader of the global warming. In addition, fuel cells (e.g., ENE FARM (registered trademark)) by Tokyo Gas Co., Ltd.), which are new energy systems extracting hydrogen from gas and generating electricity. In the above new water heaters, heat exchange from cold water to warm water is necessary, and the heat exchanger using the meandering type copper pipe illustrated in  FIG. 8(   a ) is generally known. 
     As illustrated in  FIG. 10 , the conventional pipe bending machine  90  includes a support roller  92 , a bending roller  93 , and a chuck  94 . A groove having the shape of a semicircle is formed on the outer circumferential surface of the support roller  92  in such a manner that a pipe can be inserted through the groove. Another groove having the shape of a semicircle is formed on the outer circumferential surface of the bending roller  93 , and the bending roller  93  is supported in such a manner that the bending roller  93  can be turned around a center of rotation, which is the center O of the support roller  92 . The chuck  94  holds the pipe. When a pipe is inserted through the gap formed between the two grooves in the support roller  92  and the bending roller  93 , and the bending roller  93  is turned around the center O of the support roller  92 , the pipe can be bent so as to have a bend diameter identical to the diameter of the support roller  92 . (See, for example, Patent Literature 1.) 
     As illustrated in  FIG. 8(   a ), the characteristic of the conventional meandering type heat exchanger pipe is that the bend diameter of the pipe is uniformized to a single value φD. Since the conventional pipe bending machine  90  can perform only one type of pipe bending realizing the single bend diameter of φD, the meandering type pipes have been used as heat exchanger pipes until now. 
     However, the meandering type heat exchanger pipes as above need installation space with some extent, and it is impossible to avoid increase in the installation space in order to secure certain heat exchanger effectiveness. In addition, the future direction of the products such as water heaters is weight reduction and downsizing. Therefore, the use of the meandering type heat exchanger pipes goes against the future direction. 
       FIG. 8  ( b ) is a front view illustrating a shape of a spiral type heat exchanger pipe. The space needed for accommodation of the spiral type heat exchanger pipe having a length is approximately one-third of the installation space needed for accommodation of the meandering type heat exchanger pipe having the same length. In other words, the heat exchanging capacity which the spiral type heat exchanger pipe can achieve in a space is three times the heat exchanging capacity which the meandering type heat exchanger pipe can achieve in the same space, and therefore the spiral type heat exchanger pipe is suitable for the downsizing in EcoCute in the future. 
     Nevertheless, in the case where a spiral pipe is produced by bending a pipe in a conventional pipe bending machine as illustrated in  FIG. 8  ( b ), the bend diameter is increased after every bend as D 1 &lt;D 2 &lt;D 3  . . . &lt;Dn. Therefore, the support roller  92  is required to be replaced after every bend is made in the pipe, so that the pipe bending operations cannot be successively performed. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Patent Laid-Open No. 2003-53432 (FIG. 1) 
       
    
     SUMMARY OF THE INVENTION 
     Technical Problem 
     The present invention is made in view of the above problems. An object according to the present invention is to provide a pipe bending machine which can cope with increase in the bend diameter and can successively perform bending operations for producing a spiral pipe in which the bend diameter is increased after every bending operation, and another object according to the present invention is to provide a pipe bending method using the above pipe bending machine. 
     Solution to Problem 
     The pipe bending machine ( 100 ) described in claim  1  is a pipe bending machine which feeds a pipe (W) to the gap between a support roller ( 42 ) and a bending roller ( 43 ), and successively performs bending operations with bend diameters (D 2 , D 3 , . . . , Dn) greater than the diameter (D 1 ) of the support roller ( 42 ) while changing the position of the center (O) of the support roller ( 42 ) in synchronization with the turning angle of the bending roller ( 43 ). The pipe bending machine ( 100 ) described in claim  1  is characterized in including: an XY slide mechanism (G) being placed on a frame ( 1 ) and including, a Y-axis movement means (E) which moves in the Y-axis (back-and-forth) direction by rotation of a Y-axis servomotor ( 10   m ), and an X-axis movement means (F) which moves in the X-axis (lateral) direction by rotation of an X-axis servomotor ( 20   m ); a turntable device ( 30 ) being placed on the XY slide mechanism (G), having a turntable ( 31 ) on an upper side, and causing the turntable ( 31 ) to be rotated by rotation of a C2-axis servomotor ( 30   m ); a central shaft ( 42   a ) fixed to the turntable ( 31 ); the support roller ( 42 ) supported by an upper end portion of the central shaft ( 42   a ); a cylindrical shaft ( 47 ) placed on the turntable ( 31 ) and rotatably supported by the central shaft ( 42   a ); the bending roller ( 43 ) arranged on an upper end face of the cylindrical shaft ( 47 ); and a bending device ( 40 ) causing the cylindrical shaft ( 47 ) to be rotated around the central shaft ( 42   a ) by rotation of a C1-axis servomotor ( 40   m ). In the above construction, the pipe is bent by causing, by the XY slide mechanism (G), movement of the center (O) of the support roller ( 42 ) by a first predetermined angle along a semicircular arc having a diameter equal to the difference (Dn−D 1 ) between each of the bend diameters (Dn) of the pipe W and the diameter (D 1 ) of the support roller ( 42 ), rotating the support roller ( 42 ) by the first predetermined angle, turning the bending roller ( 43 ) by the first predetermined angle around the support roller ( 42 ), and further turning the bending roller ( 43 ) by a second predetermined angle around the support roller ( 42 ) by rotating the cylindrical shaft ( 47 ) by rotation of the C1-axis servomotor ( 40   m ), the rotating of the support roller ( 42 ) by the first predetermined angle and the turning of the bending roller ( 43 ) by the first predetermined angle are realized by rotating the turntable ( 31 ) by rotation of the C2-axis servomotor ( 30   m ) in synchronization with the movement of the center (O), and the turning of the bending roller ( 43 ) by the second predetermined angle is realized by rotating the cylindrical shaft ( 47 ) by rotation of the C1-axis servomotor ( 40   m ). 
     The bending method described in claim  2  uses the pipe bending machine ( 100 ) described in claim  1 , and successively performs the bending operations with the bend diameters (D 2 , D 3 , . . . , Dn) greater than the diameter (D 1 ) of the support roller ( 42 ) by use of the support roller ( 42 ). The bending method described in claim  2  includes: a step of causing, in response to a command to move (along an X-axis and a Y-axis) the XY slide mechanism (G), the movement of the center (O) of the support roller ( 42 ) by the first predetermined angle along the semicircular arc having the diameter equal to the difference (Dn−D 1 ) between each of the bend diameters (Dn) of the pipe W and the diameter (D 1 ) of the support roller ( 42 ); a step of rotating the support roller ( 42 ) by the first predetermined angle and turning the bending roller ( 43 ) by the first predetermined angle around the support roller ( 42 ), by rotating, in response to a command to rotate the C2-axis servomotor ( 30   m ), the turntable ( 31 ) in synchronization with the movement of the center (O); and a step of turning the bending roller ( 43 ) by a second predetermined angle around the support roller ( 42 ) by rotating the cylindrical shaft ( 47 ) in response to a command to rotate the C1-axis servomotor ( 40   m ). 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration of the entire system including a pipe bending machine according to the present invention. 
         FIG. 2  is a magnified perspective view of the pipe bending machine according to the present invention. 
         FIG. 3  illustrates the pipe bending machine according to the present invention, where the part (a) is a plan view of the pipe bending machine with an upper cover removed, and the part (b) is a cross-sectional view at a cross section indicated by the A-A line in the part (a). 
         FIG. 4  illustrates the bending machine, where the part (a) is a plan view, and the part (b) is a cross-sectional view. 
         FIG. 5  illustrates a bending method for producing a spiral pipe with a large bend diameter, where the parts (a) to (d) illustrate the first to fourth steps. 
         FIG. 6  is a diagram illustrating the principle of the bending by the pipe bending machine according to the present invention. 
         FIG. 7  is a diagram illustrating a method of bending with a large bend diameter according to a conventional technique. 
         FIG. 8(   a ) is a plan view illustrating the shape of a conventional meandering type heat exchanger pipe, and  FIG. 8(   b ) is a plan view illustrating the shape of a spiral heat exchanger pipe. 
         FIG. 9  illustrates a pipe bending machine as a variation of the present invention, where the part (a) is a plan view with an upper cover removed, and the part (b) is a cross-sectional view at a cross section indicated by the B-B line in the part (a). 
         FIG. 10  is a plan view a conventional pipe bending machine. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A pipe bending machine according to the present invention and a bending method for producing a spiral pipe by using the pipe bending machine are explained in detail below with reference to the drawings. 
     As for the coordinate system and the motion nomenclature for the NC machine, Industrial automation system in JIS B6310 (ISO/DIS 841: 1994 Industrial automations-Physical device control-Coordinate system and motion nomenclature) provides stipulations. 
     According to the stipulations in the above standard, when the cylindrical shaft of the support roller on the turntable corresponds to the Z-axis, the lateral axis perpendicular to the Z-axis is the X-axis, the longitudinal axis perpendicular to the Z-axis is the Y-axis, the turn in the bending device is made around the C1-axis, and the turn in the turntable device is made around the C2-axis. 
     As illustrated in  FIG. 1 , a coil  81 , a straightener  70 , and a pipe bending machine  100  are arranged in this order from the right to the left. The coil  81  is a metal pipe attached to a coil stand  80 . The straightener  70  straightens the pipe. The pipe bending machine  100  successively bends the pipe for realizing the bend diameters of a spiral pipe. 
     As illustrated in  FIG. 2 , the pipe bending machine  100  according to the present invention has a total length of 4 m, a width of 1.2 m, and a height of 0.9 m. The main body of the pipe bending machine  100  according to the present invention is arranged inside the tip end portion. Therefore, the following explanations are focused on the mechanism of the main body of the pipe bending machine  100  according to the present invention. 
     A pipe W, for example, a copper pipe, which is straightened by the straightener  70 , is inserted into collet chuck  61  in a chuck device  60 , and is then fed to the pipe bending machine  100 . 
     The collet chuck  61  or a three jaw chuck is attached to a tip end portion of the chuck device  60 , and the chuck is brought into a clamped state or an unclamped state by a push or a pull realized by an air cylinder (not shown). Arrangements for linear motion guides (not shown) are provided at the bottom end portion of the chuck device  60  so that the chuck device  60  can be moved (forward and backward) over the full movable length by a driving system using a servomotor and a ball screw. However, the chuck device  60  may be moved in other driving techniques. The chuck device  60  feeds the pipe W when the chuck is in the clamped state and the chuck device  60  moves forward. The chuck device  60  moves backward when the chuck is in the unclamped state. 
     &lt;Construction of Pipe Bending Machine&gt; 
     As illustrated in  FIG. 3 , ( a ) and ( b ), the pipe bending machine  100  is constituted by a base frame  1 , an XY slide mechanism G, a turntable device  30 , and a bending device  40 . The XY slide mechanism G includes a Y-axis movement means E, an X-axis movement means F. The Y-axis movement means E moves along the Y-axis (forward and backward) and the X-axis movement means F moves along the X-axis (leftward and rightward). The turntable device  30  is placed on the XY slide mechanism G, has a turntable  31  on the upper side, and rotates the turntable  31 . The bending device  40  is placed on the turntable  31 . In the bending device  40 , a cylindrical shaft  47 , oriented in the vertical direction, (illustrated in  FIG. 4  ( b )) is rotatably supported. As illustrated in  FIG. 4  ( b ), a support roller  42  for pipe bending is arranged at the center of the bending device  40 . In addition, a bending roller  43  is arranged in such a manner that the bending roller  43  can turn around the center O of the support roller  42 . 
     &lt;Constitution of Base Frame&gt; 
     As illustrated in  FIG. 3 , ( a ) and ( b ), the base frame  1  has a framed structure which is mainly formed of square pipes. The members of the framed structure are joined by welding, so that the framed structure of the base frame  1  has high rigidity. However, the base frame  1  needs not be limited to the square-pipe structure, and may use other materials. For example, the base frame  1  may use other steel materials such as H-beams, I-beams, steel channels, and steel angles, and may be realized by a casted head structure. 
     &lt;Construction of the XY Slide Mechanism&gt; 
     As illustrated in  FIG. 3 , ( a ) and ( b ), the XY slide mechanism G is constituted by the Y-axis movement means and the X-axis movement means F. The Y-axis movement means E moves along the Y-axis (forward and backward) and the X-axis movement means F moves along the X-axis (leftward and rightward). 
     Although, in the illustrated construction, the X-axis movement means F is arranged above the Y-axis movement means E, alternatively, the X-axis movement means F may be arranged under the Y-axis movement means E. In the following explanations, the Y-axis movement means E and the X-axis movement means F are respectively referred to as the Y-axis slide device  10  and the X-axis slide device  20 . That is, the XY slide mechanism G is the set of the Y-axis slide device  10  and the X-axis slide device  20 . 
     &lt;Construction of Y-axis Slide Device&gt; 
     The Y-axis slide device  10  is a slide device for Y-axis control which moves a Y-axis slide  11  forward or backward. The Y-axis slide  11  has a planar shape and is placed on upper surfaces of linear motion nuts  10   e.    
     The Y-axis slide device  10  is placed in the back-and-forth direction on the frame  1  and fixed to the frame  1 . 
     As illustrated in  FIG. 3 , ( a ) and ( b ), in the Y-axis slide device  10 , a base  10   a , a Y-axis ball screw  10   b , a nut  10   n , and a Y-axis servomotor  10   m  constitute the Y-axis movement means E. The base  10   a  has a rectangular shape in a plan view, the Y-axis ball screw  10   b  is arranged at the center of the base  10   a , the nut  10   n  is screwed into the Y-axis ball screw  10   b , and a shaft end of the Y-axis ball screw  10   b  is coupled to the Y-axis servomotor  10   m  through a coupling  10   c.    
     In addition, linear motion guides  10   d  are arranged on the left and right sides of the Y-axis slide device  10  for guiding in the Y-axis direction, and two linear motion nuts  10   e  are engaged with each of the linear motion guides  10   d.    
     The planar Y-axis slide  11  is placed on the upper surfaces of the four linear motion nuts  10   e . The nut  10   n  is connected to the lower surface of the Y-axis slide  11 , and converts the rotation of the Y-axis servomotor  10   m  into a linear motion, so that the Y-axis slide  11  is moved in the Y-axis direction. 
     &lt;Construction of X-axis Slide Device&gt; 
     The X-axis slide device  20  is a slide device for X-axis control which moves an X-axis slide  21  leftward or rightward. The X-axis slide  21  has a planar shape and is placed on upper surfaces of linear motion nuts  20   e.    
     As illustrated in  FIG. 3 , ( a ) and ( b ), the X-axis slide device  20  is placed on the Y-axis slide  11  in the Y-axis slide device  10 . 
     In the X-axis slide device  20 , a base  20   a , an X-axis ball screw  20   b , a nut  20   n , and an X-axis servomotor  20   m  constitute the X-axis movement means F. The base  20   a  has a rectangular shape in a plan view, the X-axis ball screw  20   b  is arranged at the center of the base  20   a , the nut  20   n  is screwed into the X-axis ball screw  20   b , and a shaft end of the X-axis ball screw  20   b  is coupled to the X-axis servomotor  20   m  through a coupling  20   c.    
     In addition, linear motion guides  20   d  are arranged on the front and rear sides of the X-axis slide device  20  for guiding in the X-axis direction, and two linear motion nuts  20   e  are engaged with each of the linear motion guides  20   d . The planar X-axis slide  21  is placed on the upper surfaces of the four linear motion nuts  20   e . The nut  20   n  is connected to the lower surface of the X-axis slide  21 , and converts the rotation of the X-axis servomotor  20   m  into a linear motion, so that the X-axis slide  21  is moved in the X-axis direction. 
     &lt;Construction of Turntable Device&gt; 
     The turntable device  30  is a turntable for C2-axis control, placed on the X-axis slide  21  in the X-axis slide device  20 , and rotates a turntable  31  (not shown). 
     As illustrated in  FIG. 4  ( b ), a gear-reduction device, which is a combination of a worm and a worm wheel, is built in the turntable device  30 . The arrangement of the gear-reduction device in the turntable device  30  is similar to the arrangement of a gear-reduction device in the bending device  40 , which is explained later. 
     The rotation of the servomotor  30   m  is converted by the worm wheel into rotation of the cylindrical shaft (which stands upright), so that the turntable  31  (fixed to the upper end of the cylindrical shaft) is turned. Alternatively, the rotary driving may be realized by using a combination of large and small spur gears or a pulley, instead of the worm gear. 
     &lt;Construction of Bending Device&gt; 
     As illustrated in  FIG. 4  ( b ), the bending device  40  is placed, concentrically with the turntable  31 , on the turntable  31  of the turntable device  30  by using a positioning pin  48   a , and fixed to the turntable  31  by using a position locator  48 . 
     The bending device  40  is arranged in the uppermost position, and turns the bending roller  43  around the center O of the support roller  42  (having the diameter D 1 ) under C1-axis control. 
     The gear-reduction device, in which the worm  45  and the worm gear  46  are engaged, is built in the bending device  40 . The upright cylindrical shaft  47 , which is fixed to the worm wheel  46 , is rotatably supported by a bearing  44 . The use of the above worm gear enables thinning. 
     In addition, a central shaft  42   a  is inserted through a through-bore  47   a  in the cylindrical shaft  47 , and a flange portion  42   b  in the lower part of the central shaft  42   a  is engaged with a depression arranged in the bottom of the body  41 . In addition, the support roller  42  is attached via needle rollers  42   d  to a diameter-reduced, upper portion of the central shaft  42   a  (as a diameter-reduced shaft  42   c ), so that the support roller  42  is rotatably supported. A groove having the shape of a semicircle is formed on the outer circumferential surface of the support roller  42  in such a manner that the pipe W can be inserted through and engaged with the groove. 
     The bending roller  43  is fixed to the cylindrical shaft  47  by being screwed into a threaded hole formed at the upper end surface of the cylindrical shaft  47 . The upper part of the bending roller  43  is also rotatable as the support roller  42 . 
     A groove having the shape of a semicircle is also formed on the outer circumferential surface of the bending roller  43  in such a manner that the pipe W can be inserted through and engaged with the groove. 
     A preferable diameter D 1  of the support roller  42  is, for example, 20 mm, and a preferable diameter of the bending roller  43  is, for example, 14 mm. 
     The rotation of the cylindrical shaft  47  and the resultant turning of the bending roller  43  are caused by rotation of the servomotor  40   m  (cf.  FIG. 3  ( a )). In response to an NC command for the C1-axis, the bending roller  43  can be turned by an arbitrary angle. 
     In addition, the pipe retainer  49  illustrated in  FIG. 4 , ( a ) and ( b ) is provided for suppressing deflection of the pipe W. In this example, the pipe retainer  49  is put in and out by a pneumatic actuator  51 . 
     A bending method for producing a spiral pipe W with the bend diameters Dn is explained below. 
     The first one of the bend diameters Dn is the bend diameter D 1 , and the second one of the bend diameters Dn is the bend diameter D 2 . Therefore, the bending with the bend diameter D 2  is explained in detail. 
     Hereinbelow, the procedure and the principle of a bending method of bending with the bend diameter D 2  (which is greater than the diameter of the support roller  42 ) by using the support roller  42  having the small diameter D 1  is explained with reference to  FIG. 5  (( a ) to ( d )) and  FIG. 6  (the magnified diagram). 
     As illustrated in  FIG. 5  ( a ), in the first step, the pipe W is fed forward by moving the chuck device  60  forward, although the chuck device  60  is not shown in  FIG. 5 . 
     As illustrated in  FIG. 5  ( b ), in the second step, the bending roller  43  is turned around the support roller  42  (having the diameter D 1 ) by 180 degrees by the rotary driving (around the C1-axis) in the bending device  40 , so that the pipe W is bent to have the bend diameter D 1 . 
     As illustrated in  FIG. 5  ( c ), in the third step, the pipe W is fed forward by moving the chuck device  60  forward. 
     As illustrated in  FIG. 5  ( d ), in the fourth step, the center O of the support roller  42  moves along the X- and Y-axis directions in cooperation with the bending roller  43  so that the diameter of the support roller  42  is virtually increased to the bend diameter D 2  and the pipe W is bent to have an inner curvature corresponding to the target bend diameter D 2  of the spiral pipe. 
     The above operations are performed at successive positions of the pipe W from a position near the center of the spiral to a position near the end of the spiral. 
       FIG. 6  is a magnified developed view of the portion “a” illustrated in  FIG. 5  ( d ), and  FIG. 7  is a diagram illustrating a conventional bending method. 
     As illustrated in  FIG. 7 , according to the conventional bending method, the support roller  42  with the diameter D 1  is replaced with the support roller  42  having the larger bend diameter D 2 , and thereafter the bending roller  43  is turned by 180 degrees in a similar manner to the second step. However, according to the conventional bending method, the number of different types of support rollers increases, and work for the replacement is needed. Therefore, it is difficult for the conventional bending method to successively bend a pipe for producing a spiral pipe W. 
     On the other hand, according to the present invention, the bending for producing a spiral pipe W with large bend diameters Dn is performed by using only the single support roller  42  having the small diameter D 1  as illustrated in  FIG. 6 . 
     According to the principle of the present invention, in order to virtually increase the diameter of the support roller  42  (having the diameter D 1 ) to the diameter Dn, the Y-axis slide device  10  being freely movable along the Y-axis and the X-axis slide device  20  being freely movable along the X-axis are arranged, and the center O of the support roller  42  is moved by a predetermined amount along a 180-degree arc which has a diameter corresponding to the diameter difference Dn−D 1  and is convex upward in the first quadrant of the XY coordinate system. 
     For example, assume that the diameter D 1  of the support roller  42  is 20 mm, and the first one D 2  of the bend diameters Dn of the spiral pipe W is 36 mm. 
     In this case, the diameter difference D 2 −D 1  is 36 mm−20 mm=16 mm, and the Y-axis slide device  10  and the X-axis slide device  20  are moved so that the center O of the support roller  42  is moved along the 180-degree arc which has a diameter corresponding to the above diameter difference and is convex upward. Therefore, the support roller  42  can be moved so that the outer circumference of the support roller  42  draws a contour with the bend diameter Dn. That is, the diameter of the support roller  42  can be virtually increased to the bend diameter Dn. 
     Table 1 indicates the amounts of movement (along the X-axis and the Y-axis) in the above movement along the 180-degree arc. In the column “Division”, predetermined angles in increments of 10 degrees are indicated. Although the angle is divided in increments of 10 degrees for the bending with the bend diameter D 2  in this example, the increments may be reduced to, for example, 5 degrees, 4 degrees, 3 degrees, . . . for the bending with greater bend diameters Dn. Further, the movement may be divided on the basis of the length along the arc instead of the angle. 
     The amounts of movement indicated in Table 1 are values for the case where D 1  is 20 mm and D 2  is 36 mm. 
     In the column “C2-axis”, the turning angles in the turning of the entire bending device  40  are indicated. 
     In the column “C1-axis”, the turning angles by which the turning of the bending roller  43  is advanced relative to the turning around the C2-axis are indicated. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Division 
                 X-axis (mm) 
                 Y-axis (mm) 
                 C2-axis (deg) 
                 C1-axis (deg) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 0° 
                 0.00 
                 0.00 
                 0° 
                 10° 
               
               
                 10° 
                 0.13 
                 1.39 
                 10° 
                 10° 
               
               
                 20° 
                 0.48 
                 2.74 
                 20° 
                 10° 
               
               
                 30° 
                 1.07 
                 4.00 
                 30° 
                 10° 
               
               
                 40° 
                 1.87 
                 5.14 
                 40° 
                 10° 
               
               
                 50° 
                 2.86 
                 6.13 
                 50° 
                 10° 
               
               
                 60° 
                 4.00 
                 6.93 
                 60° 
                 10° 
               
               
                 70° 
                 5.26 
                 7.52 
                 70° 
                 10° 
               
               
                 80° 
                 6.61 
                 7.87 
                 80° 
                 10° 
               
               
                 90° 
                 8.00 
                 8.00 
                 90° 
                 10° 
               
               
                 100° 
                 9.39 
                 7.87 
                 100° 
                 10° 
               
               
                 110° 
                 10.74 
                 7.52 
                 110° 
                 10° 
               
               
                 120° 
                 12.00 
                 6.93 
                 120° 
                 10° 
               
               
                 130° 
                 13.14 
                 6.13 
                 130° 
                 10° 
               
               
                 140° 
                 14.13 
                 5.14 
                 140° 
                 10° 
               
               
                 150° 
                 14.93 
                 4.00 
                 150° 
                 10° 
               
               
                 160° 
                 15.52 
                 2.74 
                 160° 
                 10° 
               
               
                 170° 
                 15.88 
                 1.39 
                 170° 
                 10° 
               
               
                 180° 
                 16.00 
                 0.00 
                 180° 
                 10° 
               
               
                   
               
             
          
         
       
     
     That is, according to the turning angles indicated in the column “C2-axis” in Table 1, the turntable device  30  smoothly turns under C2-axis control in synchronization with the movement along the X-axis and Y-axis corresponding to the 10-degree increments of the predetermined angle (cf.  FIG. 6 ). 
     Further, according to the turning angles indicated in the column “C1-axis” in Table 1, the bending device  40  advances the turning of the bending roller  43  by 10 degrees, relative to the turning around the C2-axis, under the C1-axis control in synchronization with the turning in the turntable device  30 . Then, operation for bending the pipe W to the predetermined bend diameter D 2  is performed by repeating a turn and a return while maintaining the difference of 10 degrees between the turning angles. 
     In other words, the operations for bending the pipe W to the predetermined bend diameter D 2  are performed by the turn of the bending roller  43  by 10 degrees, which is the difference between the turning angle of the bending roller  43  caused by (the C2-axis control in) the turntable device  30  (e.g., 10 degrees) and the turning angle of the bending roller  43  caused by the bending device  40  (e.g., 20 degrees) 
     However, the turning angle by which the bending roller  43  is turned is not limited to 10 degrees, may be varied according to the bend diameter Dn, and is preferably 2 to 20 degrees. 
     Alternatively, the arc length by which the bending roller  43  is turned is preferably 5 to 20 mm. The arc length by which the bending roller  43  is turned may be changed according to the bend diameter Dn as needed. 
     Thereafter, the pipe W is further fed forward by forward movement of the chuck device  60  (not shown) in a similar manner to the third step. As illustrated in  FIG. 8  ( b ), the bending with the bend diameter D 3  is to be performed subsequent to the bending with the bend diameter D 2 . The bending with the bend diameter D 3  is performed in a similar manner to the fourth step. 
     In the bending with each of the larger bend diameters D 3 , D 4 , D 5 , . . . , Dn, the operations in the third and fourth steps are performed. Therefore, it is possible to easily perform, in succession, the bending with each of the larger bend diameters D 3 , D 4 , D 5 , . . . , Dn for the spiral pipe W. 
     Since the explanations on the bending with the bend diameter D 3  are similar to the explanations on the bending with the bend diameter D 2 , the explanations on the bending with the bend diameter D 3  are not presented here. 
     In the above explanations on the present embodiment, the coil  81  of the continuous metal pipe attached to the coil stand  80  is indicated as an example. Alternatively, a straight pipe which is cut to have a predetermined length may be directly subjected to the bending by the pipe bending machine  100 . 
     The diameter of the support roller  42  is virtually increased to the bend diameters (D 2 , D 3 , . . . , Dn), which are greater than the actual diameter of the support roller  42 , by using the XY slide mechanism G (which changes the position of the center O of the support roller  42 ). Therefore, the diameter to be increased can be arbitrary set even when the bend diameter is increased as D 2 , D 3 , . . . , Dn. Thus, the bending can be performed in succession. 
     The bending with the large bend diameters (Dn) is performed by using the support roller  42  and the turning angle of the bending device  40  caused by the turntable device  30 . 
     Further, in order to improve the precision in the bend diameter (Dn) for finishing, the bending is performed by use of the difference in the turning angle of the bending roller  43  arranged in the bending device  40 . 
     The present invention is not limited to the embodiment explained above, and may be modified as appropriate. For example, it is possible to reconfigure the pipe bending machine by changing the order of stacking of the devices as illustrated in FIG.  9 . The differences of the construction of  FIG. 9  from the construction of  FIG. 3  are explained below. 
     In the construction of  FIG. 3 , the X-axis slide device  20  is arranged in the second layer, and the turntable device  30  is arranged in the third layer. It is possible to reconfigure the X-axis slide device  20  and the turntable device  30  in such a manner that the turntable device  30  is arranged in the second layer, and the X-axis slide device  20  is arranged in the third layer, as illustrated in  FIG. 9 . 
     In addition, it is possible to separately arrange the chuck device  60 , and replace the chuck device  60  with the X-axis slide device  20 , as illustrated in  FIG. 2 . 
     Further, the movement (forward and backward) of the chuck device  60  may be realized by use of, for example, a system constituted by a servomotor and a timing belt, instead of the explained driving system constituted by the servomotor and the ball screw. In this case, a timing belt is arranged instead of the ball screw in such a manner that the timing belt is engaged with a pulley attached to a motor shaft of the servomotor, and the chuck device  60  is moved forward and backward through the timing belt. Furthermore, other systems may be used instead of the above system using the belt. 
     The pipe W is preferably formed of a metal exhibiting high conductivity such as copper or aluminum. However, the pipe W may be other pipe materials. 
     INDUSTRIAL APPLICABILITY 
     The pipe bending machine according to the present invention includes: the XY slide mechanism having the Y-axis movement means which moves in the back-and-forth direction and the X-axis movement means which moves in the lateral direction; the turntable device which rotates the turntable on the upper side; the bending device which is placed on the turntable and rotates the cylindrical shaft; the support roller which is supported by an upper end portion of the central shaft inserted through the hole in the cylindrical shaft and the bottom surface of which is fixed to a lower end portion of the central shaft; and the bending roller arranged adjacent to the support roller on the upper end face of the cylindrical shaft, where the cylindrical shaft can freely turn around the center of the support roller. 
     In the bending with a bend diameter greater than the diameter of the support roller, the XY slide mechanism which changes the position of the support roller is used. Since the bending with the greater bend diameter using the support roller can be realized by the difference between the turning angle of the bending device caused by the turntable device and the turning angle of the bending roller arranged in the bending device, the bending operations for making respective bends in a spiral pipe in which the bend diameter is increased after every bend can be performed in succession, while such bending operations cannot be performed in succession by the conventional pipe bending machine. 
     In addition, the present invention can provide a pipe bending machine which can cope with downsizing of water heaters. 
     In the bending method according to the present invention (using a pipe bending machine), the pipe bending machine described in claim  1  is used. In order to enable successive execution of the bending operations with the bend diameters greater than the diameter of the support roller, the bending device is turned by the first predetermined angle (determined by division) in response to a command to rotate the turntable device in synchronization with the movement of the center of the support roller along the arc (convex upward) having the diameter equal to the difference between the two diameters, and the bending roller is turned forward and backward by the second predetermined angle or the predetermined arc length (determined by division) in response to a command to rotate the bending device, so that the pipe can be bent with each of the predetermined bend diameters by use of the difference between the turning angle of the bending roller caused by the turntable device and the turning angle of the bending roller caused by the bending device. 
     Therefore, it is possible to provide a bending method which can produce a spiral pipe in which the bend diameter increases after every bend, although the spiral pipe cannot be conventionally produced as above. 
     As illustrated in  FIG. 8  ( a ), meandering types pipes have been used as the conventional heat exchanger pipes. However, the meandering type pipes need large installation space. Further, the future direction of the products such as water heaters or EcoCute is weight reduction and downsizing. In order to achieve downsizing, heat exchanger pipes are spiral types as illustrated in  FIG. 8  ( b ), which can be installed in narrow space. The pipe bending machine according to the present invention is suitable for pipe bending for spiral heat exchanger pipes, which can be installed in narrow space. 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 List of the Reference Numbers 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                  1 
                 Frame 
               
               
                   
                 10: 
                 Y-axis slide device (Y) 
               
               
                   
                 20: 
                 X-axis slide device (X) 
               
               
                   
                 30: 
                 turntable device (C2) 
               
               
                   
                 31: 
                 turntable 
               
               
                   
                 40: 
                 bending device (C1) 
               
               
                   
                 42: 
                 support roller 
               
               
                   
                 42a: 
                 central shaft 
               
               
                   
                 43: 
                 bending roller 
               
               
                   
                 51: 
                 pneumatic actuator 
               
               
                   
                 60: 
                 chuck device 
               
               
                   
                 100: 
                 pipe bending machine 
               
               
                   
                 D1: 
                 diameter (support roller) 
               
               
                   
                 D2, D3, D4 . . . Dn: 
                 bend diameter 
               
               
                   
                 E: 
                 Y-axis movement means 
               
               
                   
                 F: 
                 X-axis movement means 
               
               
                   
                 G: 
                 XY slide mechanism