Abstract:
Disclosed is a method for manufacturing an element for a CVT belt, comprising a body portion ( 22 L,  22 R) having right and left sides and a tapered portion with a downwardly reducing width, a neck portion extending upward from the body portion, and a head portion extending upward from the neck portion. The manufacturing method comprises a first punching step in which a metal strip blank ( 31 ) which has a uniform thickness and a width which makes it possible obtain elements arrayed on an even number of lines in an arrangement in which the head portions are opposed to each other or an arrangement in which the body portions are opposed to each other, is punched along an outline (( 33 L,  33 R) of an excess material ( 21   b ) added to profiles of the left and right sides ( 21 L,  21 R) of the body portions, and along an outline ( 58 L,  58 R) of an excess material ( 32   b ) added to a profile of a lower side ( 32 L,  32 R) of the body portion; a plastic deformation step in which the blank is compressed in the thickness direction to form a predetermined projection and depression, and form the tapered portion while displacing the material in the outline directions; and a second punching step in which the element is obtained as a product by punching the blank.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a method of manufacturing an element that is a constituent component of a belt housed in a continuously variable transmission (CVT). 
       BACKGROUND ART 
       [0002]    The CVT has widely been employed in a vehicle driving system. The CVT incorporates a metal belt that includes a metal member called an element. Prior art techniques related to the element are disclosed in Patent Documents 1 and 2. 
         [0003]    The technique disclosed in Patent Document 1 will be described with reference to  FIG. 17  hereof. 
         [0004]      FIG. 17  is a diagram for explaining a conventional method of manufacturing an element for a CVT belt, in which a coiled material  100  is fed as indicated by an arrow  101 , during which a large U-shaped relief opening  102  is first punched and then a plurality of recesses  103 ,  104 , and  105  are formed. Finally, an element  110  is cut out from the coiled material  100 , the element  110  including a body portion  107 , a neck portion  108  extending from the body portion  107 , and a head portion  109  disposed at the tip of the neck portion  108 . 
         [0005]    This is advantageous in the mass-productivity of the element  110  due to the continuous manufacture of the element  110  from the coiled material  100 . 
         [0006]    However, the ratio of the area of the element  110  to the area of the coiled material  100  is small, resulting in a poor yield. 
         [0007]    A measure to improve the yield is proposed in Patent Document 2. 
         [0008]    A technique disposed in Patent Document 2 will be described with reference to  FIG. 18 . 
         [0009]      FIG. 18  is a diagram for explaining another conventional method of manufacturing an element for a CVT belt. 
         [0010]    As depicted in (a) of  FIG. 18 , an element  120  includes a body portion  121 , a neck portion  122  extending upwardly from the body portion  121 , and a head portion  123  disposed on top of the neck portion  122 . 
         [0011]    As depicted in (b) of  FIG. 18  that is a cross-sectional view taken along line b-b of (a), the body portion  121  is provided with a downwardly projecting taper portion  124 , and the head portion  123  is provided with a raised portion called a nose  125  and a recessed portion called a hole  126 . 
         [0012]    The element  120  having such a shape is manufactured through (c) and (d) of  FIG. 18 . 
         [0013]    That is, as depicted in (c), the taper portions  124 ,  124  are formed on the underside of a strip stock  127 . This forming is carried out by causing the strip stock  127  to pass through between specialized reduction rolls. 
         [0014]    Next, as depicted in (d), the nose  125  and the hole  126  are formed, and finally, left and right, two elements  120 ,  120  are obtained by blanking. 
         [0015]    The yield is improved since the left and right, two elements  120 ,  120  can be obtained. However, the production cost increases due to the necessity of a specialized rolling machine to form the taper portions  124 ,  124 . That is, the presence of a separate taper portion forming step induces an increase of the production cost. 
         [0016]    An element manufacturing method is thus required in which the taper portion forming step depicted in (c) can be omitted. 
       PRIOR ART LITERATURE 
     Patent Literature 
       [0000]    
       
         
           
             Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2002-213539 
             Patent Document 2: Japanese Patent Publication No. 3703678 
           
         
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0019]    To meet the above requirement, an object of the present invention is to provide an element manufacturing method capable of omitting the taper portion forming step. 
       Solution to Problem 
       [0020]    According to an aspect of the present invention, there is provided a method of manufacturing an element for a continuously variable transmission belt, the element including a body portion having left and right lateral sides abutting respectively against left and right pulley halves of a pulley of a continuously variable transmission and having a downwardly tapered taper portion; a neck portion extending upwardly from the body portion; and a head portion extending upwardly from the neck portion, the method comprising a step of preparing a metal strip-shaped stock having a uniform thickness and a width enough to acquire even columns of elements in one form of a form where the head portions confront each other and a form where the body portions confront each other; a first blanking step of blanking the metal strip-shaped stock along contour lines of excess metals added to contours of the left and right lateral sides of the body portion for promoting subsequent working steps and along a contour line of an excess metal added to a contour of the bottom side of the body portion for promoting subsequent working steps; a plastic working step of compressing the stock in a thickness direction to form predetermined recessed and raised portions and to form the taper portion while causing the metals to flow to the edge; and a second blanking step of cutting out the element as a product from the stock. 
         [0021]    The manufacturing method preferably further comprises a slit forming step of punching and forming a slit between the confronting head portions in the form where the head portions confront each other. 
         [0022]    Preferably, the first blanking step in the form where the head portions confront each other is carried out by setting an actual plastic working volume corresponding to a volume of the product to 80% or less of a reference plastic working volume, the actual plastic working volume being defined by multiplying by a thickness of the stock an area that is enclosed by the contour lines of the excess metals added to the contours of the left and right lateral sides of the body portion, the contour line of the excess metal added to the contour of the bottom side of the body portion, and a taper starting line of the taper portion, the reference plastic working volume being defined by multiplying by the thickness of the stock an area that is enclosed by the contour lines of the excess metals added to the left and right lateral sides of the body portion, an edge in a width direction of the stock before the blanking work, and the taper starting line of the taper portion. 
         [0023]    Desirably, the first blanking step in the form where the head portions confront each other is carried out by setting an actual plastic working volume corresponding to a volume of the product to 48% or less of a reference plastic working volume, the actual plastic working volume being defined by multiplying by a thickness of the stock an area that is enclosed by the contour lines of the excess metals added to the contours of the left and right lateral sides of the body portion, the contour line of the excess metal added to the contour of the bottom side of the body portion, and a taper starting line of the taper portion, the reference plastic working volume being defined by multiplying by the thickness of the stock an area that is enclosed by the contour lines of the excess metals added to the contours of the left and right lateral sides of the body portion, an edge in a width direction of the stock before the blanking work, and the taper starting line of the taper portion. 
       Advantageous Effects of Invention 
       [0024]    According to the method of manufacturing an element for a continuously variable transmission belt of the present invention, there is included the first blanking step of blanking the metal strip-shaped stock along lines described by adding excess metals to contours of the left and right lateral sides of the body portion and along a contour line described by adding an excess metal to a contour of the bottom side thereof. Then, at the next plastic working step, the stock is compressed in a thickness direction to form predetermined recessed and raised portions and to form the taper portion while causing the metals to flow to the edge. That is, according to the present invention, the taper portion is also formed at the plastic working step for forming the predetermined recessed and raised portions. As a result, a separate taper portion forming step can be omitted. 
         [0025]    If the prepared stock is immediately subjected to the plastic working, the flow of metals to the bottom side is impeded, so that the body portion becomes thick. 
         [0026]    In this respect, in the present invention, blanking was performed along the lines described by adding excess metals to the contours of the left and right lateral sides of the body portion and along the contour line described by adding an excess metal to the contour of the bottom side thereof. By virtue of this blanking, a sufficient flow of the metals to the bottom side is achieved. 
         [0027]    As a result, an element with a high dimensional accuracy can be manufactured in spite of the omission of the separate taper portion forming step. 
         [0028]    Further included is the slit forming step of punching and forming a slit between the opposed head portions in the form where the head portions confront each other. Due to the formation of the slit between the head portion and the head portion, the stock can have a predetermined thickness without an increase in the thickness of the body portion. 
         [0029]    As a result, an element with a still higher dimensional accuracy can be manufactured in spite of the omission of the separate taper portion forming step. 
         [0030]    Furthermore, by setting (actual plastic working volume/reference plastic working volume) to 80% or less, a smooth metal flow is ensured enabling an element with a high dimensional accuracy to be manufactured. 
         [0031]    Preferably, by setting (actual plastic working volume/reference plastic working volume) to 48% or less, a more smooth metal flow is ensured enabling an element with a still higher dimensional accuracy to be manufactured. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0032]      FIG. 1  is a schematic view illustrating an essential part of a continuously variable transmission; 
           [0033]      FIG. 2  is a cross-sectional view illustrating a continuously variable transmission belt; 
           [0034]      FIG. 3  is a diagram illustrating a preparation step in a manufacturing method of the present invention; 
           [0035]      FIG. 4  is a diagram illustrating another mode of the preparation step of  FIG. 3 ; 
           [0036]      FIG. 5  is a diagram illustrating a further mode of the preparation step of  FIG. 3 ; 
           [0037]      FIG. 6  is a diagram illustrating a still further mode of the preparation step of  FIG. 3 ; 
           [0038]      FIG. 7  is a diagram illustrating a first blanking step in the manufacturing method of the present invention; 
           [0039]      FIG. 8  is a diagram illustrating another mode of the first blanking step of  FIG. 4 ; 
           [0040]      FIG. 9  is a diagram illustrating a slit forming step in the manufacturing method of the present invention; 
           [0041]      FIG. 10  is a diagram illustrating a plastic working step in the manufacturing method of the present invention; 
           [0042]      FIG. 11  is a top plan view illustrating the plastic working step; 
           [0043]      FIG. 12  is a diagram illustrating a proper value of an actual plastic working volume used in the manufacturing method of the present invention; 
           [0044]      FIG. 13  is a diagram illustrating a step of forming a hole and a nose of an element of the belt; 
           [0045]      FIG. 14  is a diagram illustrating a second blanking step in the manufacturing method of the present invention; 
           [0046]      FIG. 15  is a front view of a preferred element; 
           [0047]      FIG. 16  is a side view of the preferred element; 
           [0048]      FIG. 17  is a diagram illustrating a conventional method of manufacturing an element for a CVT belt; and 
           [0049]      FIG. 18  is a diagram illustrating another conventional method of manufacturing an element for a CVT belt. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0050]    Certain modes for carrying out the present invention will now be described with reference to the accompanying drawings. 
         [0051]    An embodiment of the present invention will be described referring to the drawings. 
         [0052]    As depicted in  FIG. 1 , a continuously variable transmission (CVT)  10  includes as its main components a pair of pulleys  11  (only one is shown), and a belt  13  wound around the pulleys  11 . 
         [0053]    The belt  13  includes layered rings  14 ,  14  composed of endless metal rings laid one upon another, and an element  20  supported by the layered rings  14 ,  14 . 
         [0054]    The element  20  includes a laterally elongated body portion  22  having left and right lateral sides  21 ,  21  abutting against left and right halves  12 L,  12 R of the pulley  11 , a reduced-width neck portion  23  extending upwardly from the body portion  22 , and a triangular head portion  24  disposed on top of the neck portion  23 . 
         [0055]    As depicted in (a) of  FIG. 2 , the body portion  22  has a downwardly tapered taper portion  25 , and the head portion  24  has a hole  26  and a complementarily shaped nose  27  that can enter the hole  26 . 
         [0056]    The taper portion  25  may have a downwardly extending parallel-thin-walled portion  25   b  as depicted in (b) of  FIG. 2 . 
         [0057]    Since the body portion  22  is provided with the downwardly tapered taper portion  25 , the head portions  24  are spaced apart from each other while coming into point-contact at black points  28  and bend so as to have a radius of curvature corresponding to the diameter (pitch circle diameter) of the pulley. For this reason, the belt  14  exerts a bending function similar to that of the ordinary chain or belt. 
         [0058]    A method of manufacturing the element  20  will next be described. 
         [0059]    First, a stock  31  depicted in  FIG. 3  is prepared. The stock  31  is called also the coiled material or a steel strip. A metal strip-shaped stock  31  is prepared that has a uniform thickness (plate thickness) and a width enough to cut out two elements  20 L and  20 R (L and R are added for convenience to distinguish the positions. L represents left and R represents right. The same applies hereinafter) in such a manner that the respective head portions  24 L and  24 R confront each other (preparation step). 
         [0060]    The prepared stock  31  may be of a form described hereinbelow. 
         [0061]    That is, as depicted in  FIG. 4 , the stock  31  may be prepared such that body portions  22 L and  22 R confront each other. 
         [0062]    Alternatively, as depicted in  FIG. 5 , the stock  31  may be prepared such that four rows of elements are arranged in the width direction with the head portions  24 L and  24 R confronting each other and with the body portions  22 L and  22 R confronting each other. 
         [0063]    Furthermore, as depicted in  FIG. 6 , the stock  31  may be prepared such that six rows of elements are arranged in the width direction with the head portions  24 L and  24 R confronting each other and with the body portions  22 L and  22 R confronting each other. 
         [0064]    An important thing here is that the metal strip-shaped stock  31  having a uniform thickness is prepared in such a manner that the adjacent elements  20 L and  20 R are arranged with their respective head portions  24 L and  24 R facing each other or with their respective body portions  22 L and  22 L facing each other. 
         [0065]    Next, the stock  31  is partially notched (first blanking step). 
         [0066]    The size of a notched region (area or volume) is important for carrying out the invention. Thus, to clarify and facilitate the description of the notched region (area or volume), definition will be given of a reference plastic working volume and an actual plastic working volume. 
         [0067]    The reference plastic working volume will be described with reference to (a) of  FIG. 7 . A region (a hatched region) is determined that is enclosed by contour lines  33 L,  33 L described by adding excess metals  21   a,    21   a  to contours of the left and right lateral sides (upper and lower in the diagram)  21 L,  21 L of the body portion  22 L on the left of the diagram, an edge  57 L in the width direction of the stock, and a taper portion starting line  39 L. The taper portion starting line  39 L will be described in detail referring to  FIG. 11 . 
         [0068]    A volume is obtained by multiplying the area of the region (hatched region) enclosed by the four lines  33 L,  33 L,  57 L, and  39 L by the thickness of the stock. This volume is defined as the reference plastic working volume of the stock, and the volume at that time is represented as 100 percent. The same applies to the right part of the diagram, in which L is replaced with R. 
         [0069]    The actual plastic working volume will next be described with reference to (b) of  FIG. 7 . A region (a hatched region) is determined that is enclosed by contour lines  33 L,  33 L described by adding excess metals  21   b,    21   b  to contours of the left and right lateral sides  21 L,  21 L of the body portion  22 L on the left of the diagram, a line  58 L described by adding an excess metal  32   b  to a contour of a bottom side  32 L of the body portion  22 L, and the taper portion starting line  39 L. A volume is obtained by multiplying the area of the region (hatched region) enclosed by the four lines  33 L,  33 L,  32 L, and  39 L by the thickness of the stock. This volume is defined as the actual plastic working volume of the stock. The same applies to the right part of the diagram, in which L is replaced with R. 
         [0070]    To obtain the form of (b) of  FIG. 7 , the stock  31  is blanked along the lines  33 L,  58 L, and  33 L and the lines  33 R,  58 R, and  33 R used as blanking lines (blanking step). 
         [0071]    The lines  58 L and  58 R are determined based on the actual plastic working volume, and, although the reason thereof will be described later, a desired value of the actual plastic working volume is 80 percent or less, more preferably, 48 percent or less of the reference plastic working volume. 
         [0072]    As depicted in  FIG. 8 , a stock in the form of opposing the body portions  22 L and  22 R to each other may be blanked along the contour lines  33 L,  58 L, and  33 L that are described by adding the excess metals  21   b,    21   b  to the contours of the lateral sides  21 L,  21 L and by adding an excess metal to the contour  32   b  of the bottom side  32 L, and along the contour lines  33 R,  58 R, and  33 R. In this case as well, the desired value of the actual plastic working volume was 80 percent or less, more preferably, 48 percent or less of the reference plastic working volume. 
         [0073]    Next, as depicted in  FIG. 9 , a substantially rectangular slit  35  is punched and formed between the opposed head portions  24 L and  24 R (slit forming step). 
         [0074]    Although (the first blanking step) and (the slit forming step) are separately described in sequence, (the first blanking step) and (the slit forming step) may be performed at the same time in a press machine. At that time, the press machine can be of a compact size. 
         [0075]    Next, the stock  31  is placed on a die  36  depicted in (a) of  FIG. 10 , and a punch  38  having slant surfaces  37 L and  37 R on the left and right is lowered so that the stock  31  is subjected to a plastic forming to reduce the plate thickness. The positional relationship between the die  36  and the punch  38  may be different from (a) of  FIG. 10  in that the punch  38  is positioned below, that the stock  31  is placed on the punch  38 , and that the die  36  is disposed above the punch  38  so as to subject the stock  31  to a plastic forming to reduce the plate thickness. 
         [0076]    Then, as depicted in (b) of  FIG. 10 , the stock  31  is formed with a pair of taper portions  25 L and  25 R, and the slit  35  at the center has a reduced width (plastic working step). 
         [0077]    In the plastic working step, as depicted in  FIG. 11 , the portion of the stock  31  on the left hand from a taper portion starting line  39 L on the left of the diagram projects leftward as indicated by an arrow ( 1 ) to thereby ensure a smooth formation of the left taper portion  25 L. 
         [0078]    Similarly, a portion on the left hand from a taper portion starting line  39 R on the right of the diagram projects rightward as indicated by an arrow ( 2 ) to thereby ensure a smooth formation of the right taper portion  25 R. 
         [0079]    Here, (actual plastic working volume/reference plastic working volume) will be considered. 
         [0080]    For this consideration, multiple types of the plastic working part described in  FIG. 11  were fabricated that include ones with the hatched region of 100 percent as described in (a) of  FIG. 7  and ones with the hatched region less than 100 percent as described in (b) of  FIG. 7 . 
         [0081]    Next, as depicted in (a) of  FIG. 12 , thicknesses T( 1 ) and T( 2 ) at left and right ends of the head portion  24 L were measured and a thickness T( 3 ) of the neck portion was measured. Then, from the calculation of (T( 1 )+T( 2 ))/2−T( 3 ), a vertical difference among three points is found. 
         [0082]    More detailedly, in (actual plastic working volume/reference plastic working volume), measurement points were employed every 5 percent, and seven test pieces were prepared per one point. 
         [0083]    Thus, 147 test pieces were subjected to the blanking step and the plastic working step of the present invention, to obtain the result depicted in (b) of  FIG. 12  where an interpolation is made so that the points are smoothly joined together. 
         [0084]    When the hatched region is large as depicted in (a) of  FIG. 7 , the flow of the metal upon the plastic working operation is prevented in the directions indicated by the arrows ( 1 ) and ( 2 ) of  FIG. 11 , resulting in an uneven finish thickness. On the other hand, when the hatched region is small as depicted in (b) of  FIG. 7 , the flow of the metal upon the plastic working operation becomes smooth in the directions indicated by the arrows ( 1 ) and ( 2 ) of  FIG. 11 , resulting in an even finish thickness. For this reason, in (b) of  FIG. 12 , the three-point vertical difference was zero within the range of 0 to 48% (where the hatched portion is small), whereas the three-point vertical difference increased accordingly as approaching 100% after 48% was exceeded. 
         [0085]    Thus, the desired value of the actual plastic working volume was set to 80 percent or less. Then, the three-point vertical difference fell within the range of −0.050 mm to +0.050 mm. More preferably, it was set to 48 percent or less. Then, the three-point vertical difference had a difference of 0 μm with respect to a target value 0 μm. 
         [0086]    As depicted in  FIG. 11 , a portion of the left element on the right hand from the taper portion starting line  39 L projects rightward as indicated by an arrow ( 3 ) and enters the slit  35 . Similarly, a portion of the right element on the left hand from the taper portion starting line  39 R projects leftward as indicated by an arrow ( 4 ) and enters the slit  35 . 
         [0087]    Next, as depicted in  FIG. 13 , the stock  31  advanced in forming is retained by a lower die  41  and an upper die  42 , and pins  43 ,  43  are thrust up from the low die  41  to form the hole and the nose (reference numerals  26  and  27  in  FIG. 2 ). Since the formation of the hole and the nose is included in the plastic working operation, it may naturally be carried out at the same time in  FIG. 10 . 
         [0088]    Accordingly, in the plastic working step, the taper portions  25 L and  25 R and the predetermined recessed and raised portions (the hole  26  and the nose  27 ) are formed while compressing the stock  31  with the notched portions  33 L and  33 R and the slit  35  in the thickness direction while causing the metal to flow to the notched portions  33 L and  33 R and the slit  35 , whereupon an even plate thickness can easily be achieved. 
         [0089]    Next, as depicted in  FIG. 14 , the elements  20 L and  20 R are cut out as products from the stock  31  (second blanking step). This step may be performed at the same time in  FIG. 13 . In that case, the positioning accuracy of the hole and nose is improved. 
         [0090]    As a result, the elements with a high dimensional accuracy can be manufactured irrespective of omission of the separate taper portion forming step. 
         [0091]    Description will next be given of a more preferred mode of the element for the continuously variable transmission manufactured by the manufacturing method as set forth hereinabove. 
         [0092]    As depicted in  FIG. 15 , in an element  20 B including the body portion  22  having the left and right lateral sides  21 ,  21  in contact with the pulley of the continuously variable transmission and having the taper portion  25  that is downwardly convex in section, the neck portion  23  extended upwardly from the body portion  22 , and the head portion  24  disposed on top of the neck portion  23 , there are defined a point B at a center of the body portion  22  except the taper portion  25 , points A, A at left and right ends of the body portion  22  except the taper portion  25 , and points C, C at left and right ends of the head portion  24 . 
         [0093]    Then, the plate thicknesses at the points A, B, and C are denoted by Ta, Tb, and Tc, respectively. The plate thickness of the neck portion  23  is Tb equal to that at the point B. The plate thickness at the center of the head portion is denoted by Td ( FIG. 16 ). 
         [0094]    The mutual relationship among the plate thicknesses is represented as Ta&lt;Tb≦Tc and Td&lt;Tc as depicted in  FIG. 16 . 
         [0095]    That is, in the element  20 B including the body portion  22  that is positioned inside when arrayed overlapping one another annularly in the thickness direction while being in contact with the pulley of the continuously variable transmission and that is formed with the left and right lateral sides  21 ,  21  in contact with the pulley, the neck portion  23  that is formed extending toward the outer periphery of the body portion  22  and that has a width narrower than that of the body portion  22 , and the head portion  24  that is positioned outside when laid annularly overlapping one another and that is disposed contiguously via the neck portion  23 , the body portion  22  having at its substantially lower half the taper portion  25  that is formed to be thinner in plate thickness than the other portions, 
         [0096]    the head portion  24  has the plate thickness Tc at its left and right ends lying on both sides of a region (the center of the head portion  24 ) on top of the neck portion, the plate thickness Tc being larger than the plate thickness Td of the region on top of the neck portion, 
         [0097]    the neck portion  23  and the body portion  22  have the plate thicknesses Tb and Ta, respectively, that are smaller than the plate thickness Tc at the left and right ends of the head portion  24 , and 
         [0098]    in the body portion  22  except the taper portion  25 , the plate thickness Ta at the left and right ends of the body portion  22  is smaller than the plate thickness of a region under the neck portion, that is, the plate thickness Tb at the center of the body portion  22 . 
         [0099]    A belt obtained by arraying a plurality of the thus formed elements  20 B in an annularly overlapping manner ensures a smooth curving deformation toward the inner periphery of the continuously variable transmission belt, thereby providing an excellent overlapping form without the overlapping direction of the elements bending toward the head potion. 
         [0100]    Thus, when the continuously variable transmission belt is formed and passed around the pulleys of the continuously variable transmission, a deflection toward the outer periphery of the continuously variable transmission belt can be prevented so that a stable power transmission can be achieved in the continuously variable transmission without causing any damage to the metal rings and the elements making up the belt. 
         [0101]    Additionally, when the plurality of elements are arrayed in an annularly overlapping manner, the adjacent elements contact one another at their respective relatively thick portions, that is, at their respective three sites (three points) consisting of the left and right ends (the points C, C) of the head and the region (the point B) under the neck, so that an extremely stable overlapping state can be achieved so as to prevent the meandering, etc., to ensure an effective power transmission when the continuously variable transmission belt is formed. 
         [0102]    It is thus assured as depicted in  FIGS. 15 and 16  that the plate thickness Ta at the point A is smaller securely than the plate thickness Tb at the point B and that the plate thickness Tb at the point B is equal to or smaller than the plate thickness Tc at the point C. As a result, when the continuously variable transmission belt is formed by arraying the plurality of elements in an annularly overlapping manner, a stable overlapping state can be obtained by virtue of the contacts of the points C and B. In addition, since the elements can securely be prevented from curving as to converge toward the head portions, a stable power transmission is ensured in the continuously variable transmission, free from any damage to the elements caused by an undesired contact with the endless multilayer ring when passed around the pulleys of the continuously variable transmission. 
       INDUSTRIAL APPLICABILITY 
       [0103]    The present invention is best suited to the manufacture of the element that is a main component of the continuously variable transmission. 
       LIST OF REFERENCE SIGNS 
       [0104]      10  continuously variable transmission (CVT) 
         [0105]      11  pulley 
         [0106]      12 L,  12 R pulley half 
         [0107]      20 ,  20 L,  20 R,  20 B element 
         [0108]      21 ,  21 L,  21 R lateral side of body portion 
         [0109]      21   b  excess metal added to contour of lateral side 
         [0110]      22 ,  22 L,  22 R body portion 
         [0111]      23  neck portion 
         [0112]      24 ,  24 L,  24 R head portion 
         [0113]      25  taper portion 
         [0114]      31  stock 
         [0115]      32 L,  32 R bottom side of body portion 
         [0116]      32   b  excess metal added to contour of bottom side 
         [0117]      33 L,  33 R notched portion 
         [0118]      35  slit 
         [0119]      36  die 
         [0120]      38  punch 
         [0121]      57 L,  57 R left and right edges of stock