Patent Publication Number: US-2013248636-A1

Title: Winding device and winding method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-066275, filed Mar. 22, 2012, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a winding device and a winding method for winding a windable material, such as an electrode of a battery, around a winding core. 
     BACKGROUND 
     Conventionally, a lithium-ion battery comprises a coiled electrode assembly. There is a method in which a coiled electrode assembly is formed by winding positive and negative electrodes, with a separator therebetween, around a flat winding core. An integral structure comprising these electrodes and separator is wound around the winding core by rotating the winding core. 
     The winding core is designed to have a hexagonal cross-section, which keeps the integral structure comprising the positive and negative electrodes and separator from flapping as it is wound around the winding core. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view showing a winding device according to a first embodiment; 
         FIG. 2  is a side view showing a holding device of the winding device; 
         FIG. 3  is an enlarged view of first and second rollers of the holding device; 
         FIG. 4  is a schematic view of the winding device in which first and second sections of a winding core are spaced apart from each other; 
         FIG. 5  is an enlarged view showing the first and second rollers and their surroundings in one state where the winding core does not overlap an imaginary line, out of states where the winding core is rotating so that an electrode plate is wound around it; 
         FIG. 6  is an enlarged view showing the first and second rollers and their surroundings in one state where the winding core overlaps the imaginary line, out of the states where the winding core is rotating so that the electrode plate is wound around it; 
         FIG. 7  is a schematic view of the winding device showing a state before the electrode plate is secured to the winding core; 
         FIG. 8  is a schematic view of the winding device showing a state where the electrode plate is secured between the first and second sections of the winding core and the first and second sections are connected to each other so that an end face is elliptical; 
         FIG. 9  is an enlarged view showing first and second pressing sections of a winding device according to a second embodiment; 
         FIG. 10  is a schematic view showing a winding device according to a third embodiment; 
         FIG. 11  is a schematic view showing a winding device according to a fourth embodiment; and 
         FIG. 12  is a schematic view showing a winding device according to a fifth embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a winding device includes a winding core, configured to rotate so that a windable material is wound therearound and having a non precise circle cross-section perpendicular to a direction in which a center of rotation extends, and a holding device located upstream relative to the winding core in a moving direction of the windable material and configured to hold the windable material therein, the holding device comprising a first holding section and a second holding section configured to hold the windable material therebetween such that an imaginary line which passes between the first and second holding sections and extends perpendicular to a direction in which the windable material is introduced between the first and second holding sections and the extending direction of the center of rotation passes through a position off the center of rotation and that at least part of the winding core overlaps the imaginary line while the winding core is rotating. 
     In general, according to one embodiment, a winding method includes locating relative positions of a winding core and a holding device, which is located upstream relative to the winding core in a moving direction of a windable material and comprising first and second holding sections, such that an imaginary line which passes between the first and second holding sections and extends perpendicular to a direction in which the windable material is introduced between the first and second holding sections and the extending direction of a center of rotation of the winding core passes through a fixing device disposed in the winding core and configured to secure the windable material to the winding core, passing the windable material between the first and second holding sections, securing the windable material passed between the first and second holding sections to the fixing device of the winding core, locating the relative positions of the winding core and the holding device so that the imaginary line passes through a position off the center of rotation of the winding core and that at least part of the winding core overlaps the imaginary line while the winding core is rotating, and winding the windable material around the winding core by rotating the winding core. 
     A winding device and a winding method according to a first embodiment will be described with reference to  FIGS. 1 to 8 .  FIG. 1  is a schematic view showing a winding device  10 . As shown in  FIG. 1 , the winding device  10  comprises a winding core  20 , core drive device  30 , holding device  40 , holding-device position adjustment device  50 , feeding device  65 , control device  70 , and feeding-device position adjustment device  80 . The winding device  10  winds an electrode plate  5 , as an example of a windable material, around the winding core  20 . The electrode plate  5  comprises a positive-electrode sheet, negative-electrode sheet, and separator sandwiched between the positive- and negative-electrode sheets. 
     The winding core  20  is rotatably supported on the core drive device  30  (described later) by a rotating shaft  27 . An end face  21  of the winding core  20  is shown in  FIG. 1 . Rotating shaft  27 , which is located on the opposite side to the end face  21 , is indicated by a dotted line in  FIG. 1 . The end face  21  has an elliptical shape. The elliptical shape is an example of a non precise circle shape. The non precise circle shape is assumed to be different from the shape of a perfect circle. The perfect circle is a circle having a constant radius. A cross-sectional shape of the winding core  20  perpendicular to a direction D in which an axis X of rotating shaft  27  of the winding core  20  extends is the same as that of the end face  21  shown in  FIG. 1 . Axis X is the center of rotating shaft  27 , that is, the center of rotation of the winding core  20 . 
     The winding core  20  has a predetermined length in the extending direction of axis X. Here, the predetermined length is greater than or equal to a length required to wind up the electrode plate  5 . The structure of the winding core  20  will be specifically described later. 
     The core drive device  30  comprises for example an electric motor  31 , for use as a drive source, and a connection mechanism  32  that connects the shaft of the electric motor  31  to rotating shaft  27  of the winding core  20 . The connection mechanism  32  comprises, for example, a plurality of gears and the like, and serves to transmit the rotation of the shaft of the electric motor  31  to rotating shaft  27  of the winding core  20 . The connection mechanism  32  may be, for example, a speed reducer. 
     The electric motor  31  and connection mechanism  32  are indicated by dotted lines in  FIG. 1 . As the motor  31  is driven, the rotation of its shaft is transmitted to rotating shaft  27  of the winding core  20  through the connection mechanism  32 . Thereupon, the winding core  20  rotates about axis X. In  FIG. 1 , the winding core  20  rotated through a predetermined angle relative to the full-line image is indicated by a two-dot chain line. 
     The holding device  40  comprises first and second rollers  41  and  42  and support block  43 . The first roller  41  is an example of a first holding section. The second roller  42  is an example of a second holding section.  FIG. 2  is a view of the holding device  40  taken from a direction F 2  in  FIG. 1 .  FIG. 2  is a side view of the holding device  40 . As shown in  FIG. 2 , the first and second rollers  41  and  42  are rotatably supported by the support block  43 . As an example of a support structure, the support block  43  rotatably supports a rotating shaft  46  of the first roller  41 . A rotating shaft  47  of the second roller  42  is rotatably supported by the support block  43 . Alternatively, the first and second rollers  41  and  42  may be supported for rotation about rotating shafts  46  and  47  that are secured to the support block  43 . 
     Each of the first and second rollers  41  and  42  has a circular shape in a direction perpendicular to axes Y and Z. The rollers  41  and  42  are equal in diameter. 
     The respective axes Y and Z of rotating shafts  46  and  47  of the first and second rollers  41  and  42  extend parallel to axis X of the winding core  20 . The axes Y and Z are the respective centers of rotating shafts  46  and  47 , that is, the respective centers of rotation of the rollers  41  and  42 . The extending direction D of the axes X, Y and Z is a linear direction. 
     In the present embodiment, as shown in  FIG. 1 , the first and second rollers  41  and  42  are located so that axis Y of rotating shaft  46  of the first roller  41  overlaps axis Z of rotating shaft  47  of the second roller  42  in a vertical direction G. According to the present embodiment, the vertical direction G is parallel to the direction of gravitational action, which is downward. The second roller  42  is located above the first roller  41 . The extending direction D is perpendicular to the vertical direction G. 
     As shown in  FIG. 1 , the electrode plate  5  is held between the first and second rollers  41  and  42 .  FIG. 3  is an enlarged view showing respective end faces  44  and  45  of the rollers  41  and  42  between which the electrode plate  5  is not held. When the electrode plate  5  is not held between the rollers  41  and  42 , as shown in  FIG. 3 , the rollers  41  and  42  are supported on the support block  43  in such a manner that they are pressed against each other in the vertical direction G. Thus, the first and second rollers  41  and  42  contact each other in the vertical direction G when the electrode plate  5  is not held between them. 
     An outer peripheral portion  41   a  of the first roller  41  is made of a material softer than that of an outer peripheral portion  42   a  of the second roller  42 . In the present embodiment, the first and second rollers  41  and  42  are made of, for example, rubber and metal, respectively. 
     Thus, the outer peripheral portion  41   a  of the first roller  41  that is pressed against the second roller  42  is elastically deformed and dented along the outer peripheral portion  42   a  of the second roller  42 . In  FIG. 3 , contact portions of the first and second rollers  41  and  42  are shown in an enlarged scale. That part of the outer peripheral portion  41   a  which is released from the contact with the outer peripheral portion  42   a  of the second roller  42  is elastically restored from the dented state as the first roller  41  rotates. The elastic deformation of the first roller  41  is exaggeratedly shown in  FIG. 3 . In fact, the amount of elastic deformation of the first roller  41  is small. 
     The following is a description of the materials of the outer peripheral portions  41   a  and  42   a  of the first and second rollers  41  and  42 . 
     The outer peripheral portion  41   a  of the first roller  41  is made of, for example, urethane rubber and its Shore hardness should only be A40 or more. For example, the entire first roller  41  may be made of urethane rubber with the Shore hardness of A40 or more. 
     For example, aluminum and hard anodized aluminum are used for the outer peripheral portion  42   a  of the second roller  42 . The outer peripheral portion  42   a  of the second roller  42  is practicable only if it is as hard as iron, aluminum, or stainless steel. Aluminum is preferred because of its adaptation to low inertia. To improve its longevity, however, the aluminum is anodized. Alternatively, the entire second roller  42  may be made of aluminum and hard anodized aluminum. 
     The holding device  40  holds the electrode plate  5  between the first and second rollers  41  and  42 . As described previously, the electrode plate  5  is formed by laminating the positive- and negative-electrode sheets and separator. Further, the first and second rollers  41  and  42  contact each other and are freely rotatable. Accordingly, the electrode plate  5  is held between and pressed by the first and second rollers  41  and  42  as it passes between the rollers  41  and  42  from one side to the other. Thereupon, the sheet members that constitute the electrode plate  5  are brought into close contact with one another. 
     After having passed between the first and second rollers  41  and  42  from the one side to the other, the electrode plate  5  is secured to the winding core  20 . In other words, the holding device  40  is located upstream relative to the winding core  20  in the moving direction of the electrode plate  5 . 
     As shown in  FIG. 2 , the holding-device position adjustment device  50  is located below the support block  43 . The holding-device position adjustment device  50  is an example of a position adjustment device. The position adjustment device  50  serves to move the support block  43  in the vertical direction G, thereby adjusting its position in the vertical direction G. The position adjustment device  50  may be, for example, a motor-driven type or comprise a pneumatic actuator. As the position of the support block  43  is changed by the position adjustment device  50 , the positions of the first and second rollers  41  and  42  in the vertical direction G change. 
     The following is a specific description of the structure of the winding core  20 . The winding core  20  comprises first and second sections  22  and  23 . The first section  22  is one half of the winding core  20  divided along a minor axis S of the end face  21 , and the second section  23  is the other half. 
     The core drive device  30  comprises a fixing mechanism  35 , which connects the first and second sections  22  and  23  to each other and fixes them so that the end face  21  is elliptical. Further, the fixing mechanism  35  has the function of fixing the first and second sections  22  and  23  in such a manner that the two sections are spaced apart from each other along a major axis L.  FIG. 4  shows the first and second sections  22  and  23  in a spaced state. The fixing mechanism  35  is shown in  FIG. 4 . 
     Further, a chuck mechanism  25  for fixing the electrode plate  5  is disposed between the first and second sections  22  and  23  of the winding core  20 . The chuck mechanism  25  is an example of a fixing device. When the first and second sections  22  and  23  are connected to each other so that the end face  21  is elliptical, the chuck mechanism  25  is accommodated between the first and second sections  22  and  23 . Therefore, in this state, the electrode plate  5  is held between the first and second sections  22  and  23 . 
     The following is a specific description of correlations between the positions of the winding core  20  and holding device  40 . The correlation in a driving state where the winding core  20  rotates so that the electrode plate  5  is wound around it will be described first.  FIG. 1  shows the state wherein the winding core  20  rotates thereby the electrode plate  5  is wound around the winding core  20 . As shown in  FIG. 1 , the correlation between the positions of the winding core  20  and holding device  40  in the driving state satisfies the following two conditions. 
     Condition 1: An imaginary line V that passes between the first and second rollers  41  and  42  and extends perpendicular to the direction in which the electrode plate  5  is introduced between the rollers  41  and  42  and the extending direction D of axis X of the winding core  20  passes through a position off axis X coincident with the center of rotation of the winding core  20 . In the present embodiment, the direction in which the electrode plate  5  is introduced between the first and second rollers  41  and  42  is coincident with the extending direction of a line that connects the axes Y and X of the rollers  41  and  42 , that is, the vertical direction G. Thus, according to the present embodiment, the imaginary line V is a straight line perpendicular to the vertical direction G and extending direction D. The imaginary line V is indicated by a two-dot chain line in  FIG. 2 . 
     Here, the position between the first and second rollers  41  and  42  through which the imaginary line V passes is a leading end position P 1  in the moving direction of the electrode plate  5 , within a range  90  where the rollers  41  and  42  contact each other without the electrode plate  5  between them. The contact range  90  and leading end position P 1  are shown in  FIG. 3 . 
     Condition 2: While the winding core  20  is rotating about axis X so that the electrode plate  5  is wound around it, at least part of the winding core  20  overlaps the imaginary line V. 
     To satisfy Condition 1, according to the present embodiment, the winding core  20  is located in a position where the minor axis S does not overlap the imaginary line V. To satisfy Condition 2, an end portion of the winding core  20  overlaps the imaginary line V just before and after the major axis L of the end face  21  of the winding core  20  becomes perpendicular to the imaginary line V. 
       FIG. 5  shows the first and second rollers  41  and  42  and their surroundings in one state where the winding core  20  does not overlap the imaginary line V, out of states where the winding core  20  shown in  FIG. 1  is rotating in a rotation direction R so that the electrode plate  5  is wound around it. When the winding core  20  does not overlap the imaginary line V, as shown in  FIG. 5 , that part of the electrode plate  5  which has passed between the rollers  41  and  42  is pulled to that side of the imaginary line V where the winding core  20  is located. Accordingly, an angle a defined by that part of the electrode plate  5  which has not yet passed between the rollers  41  and  42  and that part which has passed through there is an obtuse angle. 
     Thus, the part of the electrode plate  5  having passed between the first and second rollers  41  and  42  is slightly wound around that one of the rollers  41  and  42  which is located on that side of the imaginary line V where the winding core  20  is located. In the present embodiment, the roller which is located on that side of the imaginary line V where the winding core  20  is located is the second roller  42 . 
       FIG. 6  shows the first and second rollers  41  and  42  and their surroundings in one state where the winding core  20  overlaps the imaginary line V, out of the states where the winding core  20  shown in  FIG. 1  is rotating in the rotation direction R so that the electrode plate  5  is wound around it. 
     When the winding core  20  overlaps the imaginary line V, as shown in  FIG. 6 , that part of the electrode plate  5  which has passed between the rollers  41  and  42  is pulled away from the side of the imaginary line V where the winding core  20  is located. Accordingly, an angle p defined by that part of the electrode plate  5  which has not yet passed between the rollers  41  and  42  and that part which has passed through there is an obtuse angle. Thus, the part of the electrode plate  5  having passed between the first and second rollers  41  and  42  is slightly wound around that one of the rollers  41  and  42  which is located on the side opposite to that side of the imaginary line V where the winding core  20  is located. In the present embodiment, the roller on the side opposite to that side of the imaginary line V where the winding core  20  is located is the first roller  41 . 
     As shown in  FIG. 1 , the feeding device  65  feeds the electrode plate  5  toward the winding core  20  when the electrode plate  5  is to be secured to the winding core  20 , as described later. The feeding device  65  does not feed the electrode plate  5  while the electrode plate  5  is being wound around the winding core  20 . As an example according to the present embodiment, the feeding device  65  feeds the electrode plate  5  in a direction perpendicular to the vertical direction G. 
     For example, the feeding device  65  comprises a pair of rollers rotatable therein such that the electrode plate  5  is introduced between these rollers. The electrode plate  5  is delivered as the pair of rollers rotate. The feeding device  65  may be configured to deliver the electrode plate  5  by means of a different structure. When the feeding device  65  is not feeding the electrode plate  5 , the rollers are freely rotatable and never hinder the movement of the electrode plate  5  being wound around the winding core  20 . 
     The feeding-device position adjustment device  80  is located below the feeding device  65 . The position adjustment device  80  serves to adjust the position of the feeding device  65  in the vertical direction G. 
     The control unit  70  controls the core drive device  30 , holding-device position adjustment device  50 , and feeding device  65 . 
     The following is a description of steps of procedure for securing the electrode plate  5  to the winding core  20 .  FIG. 7  shows a state before the electrode plate  5  is secured to the winding core  20 . As shown in  FIG. 4 , the control unit  70  first controls the core drive device  30  to adjust the posture of the winding core  20  so that the major axis L of the end face  21  extends in the vertical direction G. This is done because the first and second sections  22  and  23  can be separated with the minor axis S therebetween and that the electrode plate  5  is secured to the chuck mechanism  25 , which is disposed between the first and second sections  22  and  23  that are spaced apart from each other. 
     Then, as shown in  FIG. 4 , the control unit  70  controls the holding-device position adjustment device  50  to align the positions of the first and second rollers  41  and  42  so that the imaginary line V overlaps the chuck mechanism  25 . Subsequently, the control unit  70  controls the feeding-device position adjustment device  80  to adjust the position of the feeding device  65  in the vertical direction G depending on the movement of the rollers  41  and  42 . Then, the control unit  70  controls the feeding device  65  to feed the electrode plate  5  toward the winding core  20 . 
     The fed electrode plate  5  moves between the first and second rollers  41  and  42  toward the winding core. The electrode plate  5  overlaps the imaginary line V. As the imaginary line V overlaps the chuck mechanism  25 , the electrode plate  5  reaches the chuck mechanism  25 . When the electrode plate  5  reaches the chuck mechanism  25 , it is secured to the chuck mechanism  25 . The chuck mechanism  25  may be operated directly by a human operator or its operation may be controlled by the control unit  70 . 
     Then, the control unit  70  controls the fixing mechanism  35  of the core drive device  30  to connect the first and second sections  22  and  23  of the winding core  20  to each other, thereby making the end face  21  elliptical and fixing the winding core  20  in this state.  FIG. 8  shows a state where the first and second sections  22  and  23  are connected to each other so that the end face  21  is elliptical. In this state, the electrode plate  5  is held between the first and second sections  22  and  23 . 
     Subsequently, as shown in  FIG. 1 , the control unit  70  controls the holding-device position adjustment device  50  to move the holding device  40  so that Conditions 1 and 2 are satisfied. Then, the control unit  70  controls the core drive device  30  to rotate the winding core  20  in the rotation direction R. As the winding core  20  is thus rotated, the electrode plate  5  is wound around the winding core  20 . The rotation of the winding core  20  is controlled so that the length of the electrode plate  5  wound around the winding core  20  per unit time is constant. This is done because the length of the electrode plate  5  wound around the winding core  20  per unit time becomes irregular due to the elliptical end face  21  if the winding core  20  rotates at a constant speed. 
     When the winding core  20  is rotating so that the electrode plate  5  is wound around it, in the winding device  10  constructed in this manner, the electrode plate  5  is slightly wound around the first or second roller  41  or  42 , as shown in  FIGS. 5 and 6 . Thereupon, the electrode plate  5  is pulled on either side of the first and second rollers  41  and  42 , as indicated by arrows in  FIGS. 5 and 6 . The resultant of these two tensile forces serves to press the electrode plate  5  against the first or second roller  41  or  42 . 
     When the winding core  20  is rotating so that the electrode plate  5  is wound around it, therefore, the electrode plate  5  is pressed against the first or second roller  41  or  42 . As the electrode plate  5  is pressed against the first or second roller  41  or  42 , that part of the electrode plate  5  which has passed between the rollers  41  and  42  can be kept from flapping. 
     As that part of the first roller  41  which is pressed against the second roller  42  is elastically deformed and dented along the outer peripheral portion  42   a  of the second roller  42 , moreover, the electrode plate  5  is held between the first and second rollers  41  and  42  throughout the range  90 . Thus, the adhesion of the electrode plate  5  can be improved. 
     Further, the relative positions of the winding core  20  and holding device  40  can be efficiently adjusted by regulating the position of the holding device  40 . The following is a specific description of this point. As described above, the winding core  20  is connected to the core drive device  30 . In order to move the core drive device  30 , therefore, other devices connected to it should be moved simultaneously. Since the holding device  40  comprises the support block  43  and the first and second rollers  41  and  42  rotatably supported thereon, however, only the holding device  40  should be moved. Thus, the relative positions of the winding core  20  and holding device  40  can be efficiently adjusted by regulating the position of the holding device  40 . 
     A winding device according to a second embodiment will now be described with reference to  FIG. 9 . Like reference numbers are used to designate like constituent elements of the first and second embodiments having the same functions, and a repeated description of those elements is omitted. The present embodiment differs from the first embodiment in the structure of a holding device  40 . Other structures are the same as those of the first embodiment. The following is a description of the different point. 
       FIG. 9  shows part of the holding device  40  of the present embodiment. In the present embodiment, first and second pressing sections  101  and  102  are provided in place of the first and second rollers  41  and  42 . The pressing sections  101  and  102  have the same shape and size and face each other in a vertical direction G. 
     The first pressing section  101  is made of the same material as the outer peripheral portion  41   a  of the first roller  41 . The first pressing section  101  is an example of a first holding section. The second pressing section  102  is made of the same material as the outer peripheral portion  42   a  of the second roller  42 . The second pressing section  102  is an example of a second holding section. The first and second pressing sections  101  and  102  are secured to a support block  43  in such a manner that they are pressed against each other in the vertical direction G. 
     A range of the first and second pressing sections  101  and  102  facing each other is formed to be arc-shaped. When an electrode plate  5  is not held between the pressing sections  101  and  102 , therefore, that part of the first pressing section  101  which contacts the second pressing section  102 , like the counterpart in the first embodiment, is elastically deformed so that it is dented along the second pressing section  102 . In  FIG. 9 , contact portions of the first and second pressing sections  101  and  102  are shown in an enlarged scale. 
     The relative positions of a winding core  20  and the holding device  40  where the electrode plate  5  is wound around the winding core  20  are set so as to satisfy the following conditions. 
     Condition 1: An imaginary line V that passes between the first and second pressing sections  101  and  102  and extends perpendicular to the direction in which the electrode plate  5  is introduced between the pressing sections  101  and  102  and an extending direction D of an axis X of the winding core  20  passes through a position off axis X coincident with the center of rotation of the winding core  20 . In the present embodiment, the direction in which the electrode plate  5  is introduced between the first and second pressing sections  101  and  102  is coincident with the vertical direction G in which the pressing sections  101  and  102  are arranged. Thus, according to the present embodiment, the imaginary line V is perpendicular to the vertical direction G and extending direction D. The imaginary line V is indicated by a two-dot chain line in  FIG. 9 . 
     Here, the position between the first and second pressing sections  101  and  102  through which the imaginary line V passes is a leading end position P 2  in the moving direction of the electrode plate  5 , within a range  91  where the pressing sections  101  and  102  contact each other without the electrode plate  5  between them. The contact range  91  and leading end position P 2  are shown in  FIG. 9 . 
     Condition 2: While the winding core  20  is rotating about axis X so that the electrode plate  5  is wound around it, at least part of the winding core  20  overlaps the imaginary line V. 
     Conditions 1 and 2 described above are the same as those of the first embodiment provided that the first and second pressing sections  101  and  102  are used in place of the first and second rollers  41  and  42 . 
     The present embodiment provides the same effects as those of the first embodiment. 
     A winding device according to a third embodiment will now be described with reference to  FIG. 10 . Like reference numbers are used to designate like constituent elements of the first and third embodiments having the same functions, and a repeated description of those elements is omitted. The present embodiment differs from the first embodiment in the shape of an end face  21  of a winding core  20 . Other structures are the same as those of the first embodiment. 
       FIG. 10  is a schematic view showing a winding device  10  of the present embodiment. As shown in  FIG. 10 , the end face  21  of the winding core  20  has a rhombic shape. The rhombic shape is an example of the non precise circle shape. The present embodiment provides the same effects as those of the first embodiment. Thus, the shape of the end face  21  of the winding core  20  should only be non precise circle. The winding core  20  of the present embodiment may also be used in the second embodiment. 
     A winding device according to a fourth embodiment will now be described with reference to  FIG. 11 . Like reference numbers are used to designate like constituent elements of the first and fourth embodiments having the same functions, and a repeated description of those elements is omitted. In the present embodiment, a core-drive-device position adjustment device  110  is provided in place of the holding-device position adjustment device  50 . Other structures are the same as those of the first embodiment. The following is a description of the different point. 
       FIG. 11  is a schematic view showing a winding device  10  of the present embodiment. As shown in  FIG. 11 , the core-drive-device position adjustment device  110  is located below a core drive device  30 . The core-drive-device position adjustment device  110  is an example of the position adjustment device. The position adjustment device  110  serves to adjust the position of the core drive device  30  in a vertical direction G. Thus, the position of a winding core  20  can be adjusted in the vertical direction G. 
     The core-drive-device position adjustment device  110  may be configured to adjust the position of the core drive device  30  in the vertical direction G by using, for example, a driving force of an electric motor. Alternatively, a pneumatic actuator may be used to adjust the position of the core drive device  30  in the vertical direction G. 
     In  FIG. 11 , the winding core  20  moved to a position where an electrode plate  5  is secured to a chuck mechanism  25  by the core-drive-device position adjustment device  110  is indicated by a two-dot chain line. In  FIG. 11 , the winding core  20  in a position where it rotates in a rotation direction R so that the electrode plate  5  is wound around it is indicated by a full line. 
     In securing the electrode plate  5  to the chuck mechanism  25  of the winding core  20 , according to the present embodiment, the core-drive-device position adjustment device  110  is used to adjust the position of the winding core  20  so that the chuck mechanism  25  overlaps an imaginary line V. Thus, the holding-device position adjustment device  50  is not used in the present embodiment. 
     The present embodiment provides the same effects as those of the first embodiment. The core-drive-device position adjustment device  110  described in connection with the present embodiment may also be used in the second and third embodiments. 
     A winding device according to a fifth embodiment will now be described with reference to  FIG. 12 . Like reference numbers are used to designate like constituent elements of the first and fifth embodiments having the same functions, and a repeated description of those elements is omitted. The present embodiment differs from the first embodiment in the structure of a winding core  20 . Other structures are the same as those of the first embodiment. The following is a description of the different point. 
       FIG. 12  is a schematic view showing a winding device  10  of the present embodiment. In the present embodiment, as shown in  FIG. 12 , first and second sections  22  and  23  are divided along an imaginary line V in place of the minor axis S. Specifically, as shown in  FIG. 12 , the positional relationship between the winding core  20  and a holding device  40  is such that an electrode plate  5  is wound around the winding core  20 . If the winding core  20  is in such a posture that its major axis L extends parallel to a vertical direction G, the boundary between the first and second sections  22  and  23  overlaps the imaginary line V. 
     In securing the electrode plate  5  to a chuck mechanism  25  disposed between the first and second sections  22  and  23 , therefore, the relative positions of the winding core  20  and holding device  40  need not be adjusted so that the chuck mechanism  25  and imaginary line V overlap each other. Thus, the holding-device position adjustment device  50  is unnecessary in the present embodiment. 
     According to the present embodiment, based on the effects of the first embodiment, the holding-device position adjustment device  50  need not be used, so that the configuration of the winding device  10  can be simplified. 
     The winding core  20  of the present embodiment may also be used in the second to fourth embodiments. The core-drive-device position adjustment device  110  is unnecessary if the winding core  20  of the present embodiment is used in the fourth embodiment. 
     In the first, third, fourth and fifth embodiments, the first and second rollers  41  and  42  as an example of the first and second holding sections contact each other throughout the range  90  when the electrode plate  5  is not held between them. The position between the first and second rollers  41  and  42  through which the imaginary line V passes is assumed to be the leading end position P 1  in the moving direction of the electrode plate  5  within the range  90 . In the second embodiment, the first and second pressing sections  101  and  102  as an example of the first and second holding sections contact each other throughout the range  91  when the electrode plate  5  is not held between them. The position between the first and second pressing sections  101  and  102  through which the imaginary line V passes is assumed to be the center position P 2  in the moving direction of the electrode plate  5  within the range  91 . 
     Thus, the position between the first and second holding sections through which the imaginary line passes is the leading end position in the moving direction of the windable material, such as the electrode plate  5 , within a predetermined range if the holding sections contact each other throughout the range, not at a single point, in a cross-section perpendicular to the extending direction of the holding sections when the windable material is not held between them. 
     If the first and second holding sections contact each other at a single point in the cross-section perpendicular to the extending direction of the holding sections, in contrast, this point is assumed to be the position between the first and second holding sections through which the imaginary line passes. 
     Although the electrode plate  5  is used as the windable material in the first to fifth embodiments, moreover, it may be replaced with some other material. 
     According to the first to fifth embodiments, furthermore, the end portion of the winding core  20  along the major axis L overlaps the imaginary line V, and other portions do not. This represents an example where at least part of the winding core overlaps the imaginary line while the winding core is rotating. Alternatively, the imaginary line V may be set so that it always overlaps the winding core. 
     This invention is not limited directly to the embodiments described herein, and in carrying out the invention, its constituent elements may be embodied in modified forms without departing from the spirit of the invention. Further, various inventions may be made by suitably combining a plurality of constituent elements described in connection with the foregoing embodiments. For example, some of the constituent elements according to the foregoing embodiments may be omitted. Furthermore, constituent elements according to different embodiments may be combined as required. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.