Patent Publication Number: US-2009233745-A1

Title: Power transmission chain and power transmission device

Description:
TECHNICAL FIELD 
     The present invention relates to a power transmission chain and a power transmission device. 
     BACKGROUND ART 
     As an endless power transmission chain used in a power transmission device, such as a pulley-type continuously variable transmission (CVT) in an automobile, there is a type including plural link plates aligned in the chain travel direction. Respective link plates adjacent to each other in the chain travel direction are coupled to each other with a pair of pins that are allowed to undergo rolling motions with respect to each other (see, for example, Patent Documents 1 and 2). 
     Patent Document 1: Japanese Unexamined Patent Publication No. 2005-226831 
     Patent Document 2: Japanese Unexamined Patent Publication No. 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     The link plates forming the power transmission chains disclosed in Patent Documents 1 and 2 are, when viewed in the chain width direction, of a shape asymmetric with respect to the front and the rear in the chain travel direction, and the orientation of the link plates with respect to the chain travel direction is determined. Accordingly, one of the things necessary for these power transmission chains when the power transmission chains are fabricated by inserting pins through the link plates is to align the link plates in the correct orientation. In addition, because the travel direction (rotation direction) of the power transmission chain is determined, it is necessary to place the chain in the correct direction when the chain is wound around the pulleys. 
     The invention was devised under the circumstances described above, and has an object to provide a power transmission chain and a power transmission device with which not only can the assemble direction of the link plates be discriminated, but also the travel direction can be discriminated. 
     Means for Solving the Problems 
     In order to achieve the above object, one likeable aspect of the invention provides a power transmission chain including plural link plates aligned in a chain travel direction, and plural coupling members that extend in a chain width direction orthogonal to the chain travel direction and couple the plural link plates one with another. When the link plates are viewed along the chain width direction, each of the link plates has a discrimination portion to discriminate the chain travel direction. 
     According to this aspect, by providing the discrimination portions, it is possible to discriminate the orientations of the link plates with respect to the chain travel direction. For example, when the link plates are viewed along the chain width direction, in a case where each link plate is of a shape asymmetric with respect to the front and the rear in the chain travel direction and the orientation of the link plate with respect to the chain travel direction is determined, the assemble direction of the link plates can be discriminated. It is thus possible to prevent the link plates from being assembled in a wrong orientation. In addition, it is possible to discriminate the travel direction of the power transmission chain (the rotation direction of the power transmission chain) using the discrimination portion. Thus, it is possible to prevent the power transmission chain from being wound around the pulleys or the like in a wrong direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial broken perspective view schematically showing the configuration of a major portion of a chain-type continuously variable transmission as a power transmission device provided with a power transmission chain according to one embodiment of the invention. 
         FIG. 2  is an enlarged section of a major portion of a drive pulley (driven pulley) and a chain of  FIG. 1 . 
         FIG. 3  is a section of a major portion of the chain. 
         FIG. 4  is a section taken on line IV-IV of  FIG. 3 . 
         FIG. 5  is a section of a major portion in another embodiment of the invention. 
         FIG. 6  is a partial section of a major portion in still another embodiment of the invention. 
         FIG. 7  is a section of a major portion in still another embodiment of the invention. 
         FIG. 8  is a section of a major portion in still another embodiment of the invention. 
         FIG. 9  is a section of a major portion in still another embodiment of the invention. 
         FIG. 10  is a section of a major portion in still another embodiment of the invention. 
         FIG. 11  is a section of a major portion in still another embodiment of the invention. 
         FIG. 12  is a section of a major portion in still another embodiment of the invention. 
         FIG. 13  is a section of a major portion in still another embodiment of the invention. 
         FIG. 14  is a section of a major portion in still another embodiment of the invention. 
         FIG. 15  is a partial section of a major portion in still another embodiment of the invention. 
         FIG. 16  is a view of a major portion in still another embodiment of the invention when viewed along the chain width direction. 
         FIG. 17  is a view of a major portion in still another embodiment of the invention when viewed along the chain width direction. 
         FIG. 18  is a partial section of a major portion in still another embodiment of the invention. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Preferred embodiments of the invention will be described with reference to the accompanying drawings. 
       FIG. 1  is a partial broken perspective view schematically showing the configuration of a major portion of a chain-type continuously variable transmission (hereinafter, also referred to simply as the continuously variable transmission) as a power transmission device provided with a power transmission chain according to one embodiment of the invention. 
     Referring to  FIG. 1 , a continuously variable transmission  100  is mounted on a vehicle, such as an automobile. The continuously variable transmission  100  includes a drive pulley  60  made of metal (structural steel or the like) as one of a pair of pulleys, a driven pulley  70  made of metal (structural steel or the like) as the other one of a pair of pulleys, and an endless power transmission chain  1  (hereinafter, also referred to simply as the chain) wound around these pulleys  60  and  70 . 
     The drive pulley  60  and the driven pulley  70  are formed of variable diameter pulleys.  FIG. 2  is an enlarged section of a major portion of the drive pulley  60  (driven pulley  70 ) and the chain  1  of  FIG. 1 . Referring to  FIG. 1  and  FIG. 2 , the drive pulley  60  is attached in a together rotatable manner to an input shaft  61  that is coupled to a vehicle driving source in such a manner that power can be transmitted from the driving source. The drive pulley  60  includes a stationary sheave  62  and a movable sheave  63 . The stationary sheave  62  and the movable sheave  63  have a pair of mutually opposing sheave surfaces  62   a  and  63   a , respectively. Each of the sheave surfaces  62   a  and  63   a  includes a slope surface in the form of a circular conical surface. A groove is defined between these sheave surfaces  62   a  and  63   a  and the chain  1  is caught tightly and held in this groove. 
     A hydraulic actuator (not shown) to change the groove width is connected to the movable sheave  63 , so that the groove width is varied at speed change by moving the movable sheave  63  in the axial direction of the input shaft  61  (right-left direction in  FIG. 2 ). The chain  1  is thus allowed to move in the radial direction of the input shaft  61  (top-bottom direction in  FIG. 2 ), which makes it possible to change an effective radius of the pulley  60  with respect to the chain  1 . 
     In  FIG. 2 , reference characters to denote components of the driven pulley  70  corresponding to the counterparts of the drive pulley  60  are shown in parentheses. As are shown in  FIG. 1  and  FIG. 2 , the driven pulley  70  is attached in a together rotatable manner to an output shaft  71  that is coupled to a drive wheel (not shown) in such a manner that power can be transmitted to the drive wheel. As with the drive pulley  60 , the driven pulley  70  includes a stationary sheave  73  and a movable sheave  72  respectively having a pair of mutually opposing sheave surfaces  73   a  and  72   a  each in the form of a circular conical surface to define a groove in which the chain  1  is caught tightly. 
     As with the movable sheave  63  of the drive pulley  60 , a hydraulic actuator (not shown) is connected to the movable sheave  72  of the driven pulley  70 , so that the groove width is varied at speed change by moving the movable sheave  72 . It is thus possible to change an effective radius of the pulley  70  with respect to the chain  1  by moving the chain  1 . 
     According to the configuration as described above, power is transmitted between a pair of the pulleys  60  and  70  via the chain  1 . 
       FIG. 3  is a section of a major portion of the chain  1 .  FIG. 4  is a section taken on line IV-IV of  FIG. 3 . Hereinafter, the chain  1  will be described in reference to the linear region of the chain  1 . Referring to  FIG. 3  and  FIG. 4 , the chain  1  includes plural link plates  2  and plural coupling members  50  that couple these link plates  2  in such a manner that they are allowed to bend with respect to one another. 
     Hereinafter, a direction along the travel direction of the chain  1  is defined as the chain travel direction X 1 , a direction orthogonal to the chain travel direction X 1  and along the longitudinal direction of the coupling members  50  is defined as the chain width direction W 1 , and a direction orthogonal to both the chain travel direction X 1  and the chain width direction W 1  is defined as the orthogonal direction V 1 . 
     Each link plate  2  is in the form of a plate, and includes a front end portion  5  and a rear end portion  6  as a pair of end portions aligned from front to rear in the chain travel direction X 1 , and an intermediate portion  7  disposed between the front end portion  5  and the rear end portion  6 . 
     The front end portion  5  and the rear end portion  6  are provided with a front through-hole  9  as a first through-hole and a rear through-hole  10  as a second through-hole, respectively. The intermediate portion  7  has a pillar portion  8  as a partition between the front through-hole  9  and the rear through-hole  10 . The pillar portion  8  has a specific thickness in the chain travel direction X 1 . The rigidity of the link plate  2  is increased by disposing the pillar portion  8  between the front through-hole  9  and the rear through-hole  10 . An outer peripheral portion  25  of each link plate  2  shapes a smooth curve, which is deemed as a shape that hardly causes stress concentration. 
     When the chain  1  is viewed along the chain width direction W 1 , the link plate  2  is of a shape asymmetric with respect to the front and the rear in the chain travel direction X 1  (asymmetric with respect to the right-left direction in  FIG. 4 ) and has the directivity. The orientation of the link  2  with respect to the chain travel direction X 1  is determined. 
     First, second, and third link lines  51 ,  52 , and  53  are formed using the link plates  2 . To be more specific, the first link line  51 , the second link  52 , and the third link line  53  respectively include plural link plates  2  aligned in the chain width direction W 1 . 
     In each of the first through third link lines  51  through  53 , the link plates  2  in the same link line are aligned so that all are lined up at the same position in the chain travel direction X 1 . The first through third link lines  51  through  53  are aligned in the chain travel direction X 1 . 
     The respective link plates  2  in the first through third link lines  51  through  53  are coupled to the corresponding link plates  2  in the first through third link lines  51  through  53  using the corresponding coupling members  50  in a relatively rotatable (bendable) manner. 
     To be more concrete, the front through-hole  9  made in the like plate  2  in the first link line  51  and the rear through-hole  10  made in the link plate  2  in the second link line  52  are aligned in the chain width direction W 1  and correspond to each other. The link plates  2  in the first and second link lines  51  and  52  are coupled so as to be bendable with respect to each other in the chain travel direction X 1  using the coupling member  50  that is inserted through these through-holes  9  and  10 . 
     Likewise, the front through-hole  9  made in the link plate  2  in the second link line  52  and the rear through-hole  10  made in the link plate  2  in the third link line  53  are aligned in the chain width direction W 1  and correspond to each other. The link plates  2  in the second and third link lines  52  and  53  are coupled so as to be bendable with respect to each other in the chain travel direction X 1  with the coupling member  50  that is inserted through these through-holes  9  and  10 . 
     In  FIG. 3 , the first through third link lines  51  through  53  are shown one for each. However, the first through third link lines  51  through  53  are disposed repetitively along the chain travel direction X 1 . The respective link plates  2  adjacent to each other in the chain travel direction X 1  are successively coupled to each other with the corresponding coupling members  50  to form the endless chain  1 . 
     Referring to  FIG. 3  and  FIG. 4 , each coupling member  50  includes first and second pins  3  and  4 , and these first and second pins  3  and  4  make a pair. The first pin  3  comes into contact with the second pin  4 , which is the counterpart of the pair, in a contact state including at least one of rolling contact and sliding contact in association with bending of the link plates  2  with respect to each other. 
     The first pin  3  is a first power transmission member that extends long in the chain width direction W 1 . The peripheral surface  11  of the first pin  3  extends in parallel with the chain width direction W 1 . 
     The peripheral surface  11  is formed as a smooth surface and has a front portion  12  as a counter portion facing frontward in the chain travel direction X 1 . The front portion  12  opposes the second pin  4  and comes into contact with a rear portion  19  of the second pin  4  described below at a contact portion T (a contact point when viewed along the chain width direction W 1 ). The contact portion T is in the form of a long line in the chain width direction W and it looks like a point when viewed along the chain width direction W 1 . 
     A pair of end portions  16  of the first pin  3  with respect to the longitudinal direction (chain width direction W 1 ) respectively protrude in the chain width direction W 1  from the link plates  2  disposed at a pair of end areas in the chain width direction W 1 . The pair of end portions  16  are respectively provided with end faces  17  as a pair of power transmission portions. 
     Referring to  FIG. 2 , these end faces  17  are brought into frictional contact (engagement) with the corresponding sheave surfaces  62   a  and  63   a  and sheave surfaces  72   a  and  73   a  of the pulleys  60  and  70 , respectively. 
     The first pin  3  is pinched between the corresponding sheave surfaces  62   a  and  63   a  or sheave surfaces  72   a  and  73   a . This configuration allows power to be transmitted between the first pin  3  and the respective pulleys  60  and  70 . Because the first pin  3  makes a direct contribution to power transmission at the end faces  17 , it is made of a high-strength material with excellent wear resistance, for example, bearing steel. Examples of such bearing steel include but is not limited to a SUJ 2  material according to the Japan Industrial Standard. 
     Referring to  FIG. 3  and  FIG. 4 , the second pin  4  (called also as a strip or an interpiece) is a second power transmission member made of the same material as the first pin  3  and extending long in the chain width direction W 1 . 
     The second pin  4  is formed shorter than the first pin  3  with respect to the chain width direction W 1  to prevent a pair of the end portions thereof from coming into contact with the sheave surfaces of the respective pulleys. The second pin  4  is disposed ahead in the chain travel direction X 1  with respect to the first pin  3  which is the counterpart of the pair. The second pin  4  is made thinner than the first pin  3  with respect to the chain travel direction X 1 . 
     The peripheral surface  18  of the second pin  4  extends in the chain width direction W 1 . The peripheral surface  18  has the rear portion  19  as the counter portion facing backwards in the chain travel direction X 1 . The rear portion  19  is orthogonal to the chain travel direction X 1  and flat. As has been described, the rear portion  19  opposes the front portion  12  of the firs pin  3  as the counterpart of the pair. 
     The chain  1  is a so-called press-fit type chain. To be more concrete, the corresponding first pin  3  is fit into the front through-holes  9  in the respective link plates  2  in a relatively movable manner through loose-fit, whereas the second pin  4  making a pair with the first pin  3  is press-fit fixedly therein in a relatively immovable manner. Also, the corresponding first pin  3  is press-fit fixedly in the rear through-holes  10  in the respective plate links  2  in a relatively immovable manner, whereas the second pin  4  making a pair with the first pin  3  is fit therein in a relatively movable manner through loose-fit. 
     According to the configuration as described above, the front portion  12  of the first pin  3  and the rear portion  19  of the second pin  4  as the counterpart of the pair come into contact with each other on the contact portion T in association with the bending between the respective link plates  2  adjacent to each other in the chain travel direction X 1 . The contact in this instance is in a contact state that includes at least one of rolling contact and sliding contact. 
     The chain  1  has a predetermined alignment pitch P. The alignment pitch P is defined as a pitch between the adjacent first pins  3  of the chain  1  in the linear region. To be more concrete, it is a distance in the chain travel direction X 1  between the contact portion T 1  of the first and second pins  3  and  4  inside the front through-hole  9  in the link plate  2  and the contact portion T 1  of the first and second pins  3  and  4  inside the rear through-hole  10  in the same link plate  2  of the chain  1  in the linear region. In this embodiment, the alignment pitch P is set, for example, to 8 mm. 
     When viewed along the chain width direction W 1 , of the front portion  12 , a part that is allowed to come into contact with the rear portion  19  of the second pin  4  shapes an involute curve. Accordingly, when the adjacent link plates  2  bend with respect to each other, the corresponding first and second pins  3  and  4  are allowed to come into rolling contact smoothly with each other, which in turn allows the link plates  2  to bend smoothly with respect to each other. When the chain  1  is viewed along the chain width direction W 1 , movement locus of the contact portion T in this instance draw an involute curve. 
     The front portion  12  of the first pin  3  when viewed in the chain width direction W 1  may shape a curve other than an involute curve. Examples of such a shape include a curve having one or more than one curvature radius. 
     The pillar portion  8  of the link plate  2  has a pair of side portions  20  and  21  that oppose each other in the chain travel direction X 1 . One side portion  20  is positioned relatively on the front side in the chain travel direction X 1 . This one side portion  20  is configured in such a manner so as not to interfere with a rolling motion of the first pin  3  loosely fit into the corresponding front through-hole  9  (with bending between the corresponding link plates  2 ). 
     Also, this one side portion  20  functions as a guide that limits further bending of the chain  1  by coming into contact with the corresponding first pin  3  when the bending angle between the corresponding link plates  2  reaches the maximum design bending angle. 
     The other side portion  21  is positioned relatively on the rear side in the chain travel direction X 1 . The other side portion  21  is configured in such a manner so as not to interfere with a rolling motion of the second pin  4  loosely fit into the corresponding rear through-hole  10  (with bending between the corresponding link plates  2 ). 
     In addition, the other side portion  21  functions as a guide that limits further bending of the chain  1  by coming into contact with the corresponding second pin  4  when the bending angle between the corresponding link plates  2  reaches the maximum design bending angle. 
     This embodiment is characterized in that the chain travel direction X 1  can be discriminated when the link plate  2  is viewed along the chain width direction W 1 . 
     To be more concrete, when the link plate  2  is viewed along the chain width direction W 1 , the link plate  2  is of an generally rectangular shape that is relatively long in the chain travel direction X 1  and relatively short in the orthogonal direction V 1 , and includes four corners  31 ,  32 ,  33 , and  34 . First and second corners  31  and  32  are disposed at the front end in the chain travel direction X 1 , and third and fourth corners  33  and  34  are disposed at the rear end in the chain travel direction X 1 . 
     When the link plate  2  is viewed along the chain width direction W 1 , the link plate  2  includes a discrimination portion  22  to discriminate the chain travel direction X 1 . The discrimination portion  22  includes a small curvature radius portion  23  as a first circular arc portion and a large curvature radius portion  24  as a second circular arc portion provided to the first through fourth corners  31  through  34 . 
     The small curvature radius portion  23  is provided to only one of the four corners  31  through  34  of the link plate  2  (the first corner  31  in this embodiment), and faces frontward in the chain travel direction X 1 . In other words, of the link plate  2 , the side on which the small curvature radius portion  23  is present is the side that is to face frontward in the chain travel direction X 1 . A curvature radius r 1  of the small curvature radius portion  23  is made smaller than a curvature radius r 2  of the large curvature radius portions  24 , and is set to a range, for example, of 0.2 to 2.0 mm. 
     When the curvature radius r 1  is less than 0.2 mm, the small curvature radius portion  23  has an acute shape, which easily causes stress concentration. Conversely, when the radius curvature r 1  exceeds 2.0 mm, the small curvature radius portion  23  becomes rounder, which makes it difficult to discriminate between the small curvature radius portion  23  and the large curvature radius potions  24 . It is therefore preferable to set the curvature radius r 1  to the range specified above. 
     The large curvature radius portion  24  is provided to each of the remaining three corners among the four corners  31  through  34  of the link plate  2  (the second through fourth corners  32  through  34  in this embodiment). As has been described, the curvature radius r 2  of the large curvature radius portions  24  is set larger than the curvature radius r 1  of the small curvature radius portion  23 , and is set, for example, to 3.0 mm or greater. In other words, the curvature radius r 2  of the large curvature radius portion  24  is set to at least 150% of the curvature radius r 1  of the small curvature radius portion  23 . 
     Alternatively, the curvature radii r 2  of the respective large curvature radius portions  24  may be set to values different from one another. 
     Linear portions  26  are formed to a pair of the end portions of the small curvature radius portion  23  with respect to the circumferential direction of the outer peripheral portion  25  of the link plate  2 . The linear portions  26  form a part of the outer peripheral portion  25  of the link plate  2  and are connected smoothly with the small curvature radius portion  23 . By providing the linear portions  26 , the small curvature radius portion  23  can be discriminated more readily. 
     According to this embodiment, the function and the effect as follows can be achieved. That is, by providing the discrimination portion  22  to the link plate  2 , it is possible to discriminate the orientation of the link plate  2  with respect to the chain travel direction X 1 . 
     When the link plate  2  is viewed along the chain width direction W 1 , the link plate  2  is of a shape asymmetric with respect to the front and the rear in the chain travel direction X 1 . According to this configuration, although the orientation of the link plate  2  with respect to the chain travel direction X 1  is determined, it is possible to discriminate the assemble direction of the link plates  2  due to such link plates  2 . It is thus possible to prevent the link plates  2  from being assembled in a wrong orientation. 
     In addition, the travel direction of the chain  1  (rotation direction of the chain  1 ) can be discriminated by the discrimination portion  22 . It is thus possible to prevent the chain  1  from being wound around the respective pulleys  60  and  70  in a wrong direction. For example, in a case where the link plates  2  are aligned and the coupling members  50  are inserted into the corresponding link plates  2  by a machine, it is possible to prevent an error when assembling the link plates  2 . 
     In addition, by providing the small curvature radius portion  23  to the discrimination portion  22 , it is possible to align the link plates  2  in the correct orientation with respect to the chain travel direction X 1  in a reliable manner by a job as simple as pointing the small curvature radius portion  23  of the link plate  2  in the chain travel direction X 1 . 
     Further, the first pin  3  is loosely fit into the front through-hole  9  in the link plate  2  and the second pin  4  is press-fit fixedly therein, whereas the first pin  3  is press-fit fixedly in the rear through-hole  10  and the second pin  4  is loosely fit therein. Accordingly, when the end faces  17  of the first pin  3  come into contact with the corresponding sheave surfaces  62   a  and  63   a  or sheave surfaces  72   a  and  73   a  of the pulleys  60  and  70 , respectively, the second pin  4  that makes a pair comes into contact with the first pin  3  in a contact state including at least one of rolling contact and the sliding contact, which allows the link plates  2  to bend with respect to each other. 
     In this instance, the sliding contact components can be lessened by increasing the mutual rolling contact components between the first and second pins  3  and  4  making a pair. Consequently, the end faces  17  of the first pin  3  are allowed to come into contact with the corresponding sheave surfaces  62   a  and  63   a  or sheave surfaces  72   a  and  73   a  while they hardly rotate. It is thus possible to ensure higher transmission efficiency by reducing a frictional loss. 
     In addition, when the link plates  2  that bend with respect to each other are viewed along the chain width direction W 1 , movement locus of the contact portion T of the corresponding first and second pins  3  and  4  draw an involute curve in reference to the first pin  3 . It is thus possible to suppress the occurrence of a chordal action in the chain  1  when the first pins  3  are successively meshed with the pulleys  60  and  70 . Consequently, noises while the chain  1  is driven can be reduced. 
     In this manner, it is possible to achieve the continuously variable transmission  100  excellent in transmission efficiency and silence, with which not only can the assemble direction of the link plates  2  be readily discriminated, but also the travel direction of the chain  1  can be readily discriminated. 
     It may be configured in such a manner that the large curvature radius portion  24  is provided instead of the small curvature radius portion  23  of this embodiment and the small curvature radius portion  23  is provided instead of the large curvature radius portion  24 . In this case, as is shown in  FIG. 5 , the small curvature radius portion  23  is provided to three points and the large curvature radius portion  24  is provided to one point. 
       FIG. 6  is a partial section of a major portion in still another embodiment of the invention. In this embodiment, differences from the embodiment shown in  FIG. 1  through  FIG. 4  will be chiefly described. Like components are labeled with like reference characters and descriptions thereof are omitted herein. 
     Referring to  FIG. 6 , this embodiment is characterized in that plural types of link plates having different alignment pitches (specifications) in the linear region of the chain are provided so as to randomize engagement cycles in which the end faces  17  of the first pins  3  successively engage with the respective pulleys  60  and  70 , and that the discrimination portion to discriminate the specification of the link plate is provided. 
     To be more concrete, as plural types of link plates having specifications different from each other, link plates  2  as a first type of link plates having a relatively short alignment pitch, and long link plates  2 A as a second type of link plates having a relatively long alignment pitch are provided. 
     In the long link plate  2 A, the length of a pillar portion  8 A in the chain travel direction X 1  is made longer than the length of the pillar portion  8  of the link plate  2  in the chain travel direction X 1 . Accordingly, an alignment pitch PA of the long link plates  2 A is longer than the alignment pitch P of the link plates  2  (PA&gt;P). 
     The link plates  2  and the long link plates  2 A are aligned randomly in the chain travel direction X 1 . In this case, the phrase, “aligned randomly”, means that at least one of the link plates  2  and the long link plates  2 A are disposed on an irregular base at least in a partial region in the chain travel direction X 1 . The phrase, “on an irregular base”, means that at least one of the periodicity and the regularity is absent. 
     The link plates  2  and the long link plates  2 A may be aligned randomly in all the regions of the chain  1  in the chain travel direction X 1 . 
     As one example of such random alignment, there is a case where the link plates  2  and the long link plates  2 A are aligned in the order of  2 A,  2 ,  2 ,  2 A,  2 ,  2 ,  2 ,  2 A,  2 ,  2 ,  2 ,  2 ,  2 ,  2 A,  2 ,  2 ,  2 ,  2 ,  2 ,  2 ,  2 , . . . with respect to the chain travel direction X 1 . 
     The link plates  2  and the long link plates  2 A are provided with discrimination portions  22  and  22 A, respectively. A curvature radius r 1 A of a small curvature radius portion  23 A of the discrimination portion  22 A of the long link plates  2 A is made smaller than the curvature radius r 1  of the small curvature radius portion  23  of the discrimination portion  22  of the link plates  2  (r 1 A&lt;r 1 ). This configuration makes it possible to discriminate between the link plates  2  and the long link plates  2 A. In addition, it is possible to discriminate the orientations of the respective link plates  2  and long link plates  2 A with respect to the chain travel direction X 1 . 
     Alternatively, the curvature radius r 1 A of the small curvature radius portion  23 A of the discrimination portion  22 A may be made larger than the curvature radius r 1  of the small curvature radius portion  23  of the discrimination portion  22 . 
     Further, the curvature radius r 2  of the large curvature radius portion  24  may differ between the link plates  2  and the long link plates  2 A. 
     According to this embodiment, the function and the effect as follows can be achieved. That is, by providing the discrimination portions  22  and  22 A to the link plates  2  and the long link plates  2 A, respectively, it is possible to discriminate the types of the link plates (between the link plates  2  and the long link plates  2 A) with ease, which can prevent the link plates  2  from being assembled erroneously. 
     In addition, plural types of link plates  2  and  2 A having different alignment pitches are provided, and these link plates  2  and  2 A are aligned randomly. Accordingly, the engagement cycles of the chain  1  and the respective pulleys  60  and  70  while the chain  1  is driven can be randomized. It is thus possible to distribute the frequencies of engaging sounds of the chain  1  and the respective pulleys  60  and  70  over a wide range by randomizing the occurrence cycles of the engaging sounds, which can consequently reduce noises accompanying the driving of the chain  1 . 
     Further, in the embodiment described above, the small curvature radius portions  23  and  23 A may be provided to only any one of the second through fourth corners  32  through  34 . 
       FIG. 7  is a section of a major portion in still another embodiment of the invention. In this embodiment, differences from the embodiment shown in  FIG. 1  through  FIG. 4  will be chiefly described. Like components are labeled with like reference characters and descriptions thereof are omitted herein. 
     This embodiment is characterized in that, as is shown in  FIG. 7 , a discrimination portion  22 B is formed by providing a concave portion  35  instead of the small curvature radius portion  23  shown in  FIG. 4 . 
     The concave portion  35  is formed in only one of the four corners of the link plate (for example, in the first corner  31 ) as with the small curvature radius portion described above. A curvature radius r 3  of the concave portion  35  is equal to the curvature radius r 1  of the small curvature radius portion  23  (see  FIG. 4 ). 
     According to this embodiment, it is possible to align link plates  2 B in the correct orientation with respect to the chain travel direction X 1  in a reliable manner by a job as simple as pointing the concave portion  35  in the chain travel direction X 1 . 
     In a case where plural types of link plates having different alignment pitches are used as plural types of link plates having specifications different from each other, it is possible to discriminate the type of link plates by changing the position and the shape of the discrimination portion  22 B from one type of link plates to another. 
       FIG. 8  is a section of a major portion in still another embodiment of the invention. In this embodiment, differences from the embodiment shown in  FIG. 1  through  FIG. 4  will be chiefly described. Like components are labeled with like reference characters and descriptions thereof are omitted herein. 
     Referring to  FIG. 8 , this embodiment is characterized in that, when a link plate  2 C is viewed along the chain width direction W 1 , the link plate  2 C includes a discrimination portion  22 C to discriminate the chain travel direction X 1 , and that the discrimination portion  22 C is disposed in a pair of the side portions  20  and  21  of a pillar portion  8 C of the link plate  2 C. 
     The discrimination portion  22 C has a flat portion  36  provided to one side portion  20  and a mountain portion  37  provided to the other side portion  21 . The flat portion  36  extends linearly generally in parallel with the orthogonal direction V 1 . The mountain portion  37  is formed by allowing the intermediate portion of the other side portion  21  with respect to the orthogonal direction V 1  to protrude in a direction opposite to the chain travel direction X 1 , and it is in the form of a mountain when viewed along the chain width direction W 1 . 
     A curvature radius r 4  of the mountain portion  37  is set, for example, to a range of 0.3 mm to 2.0 mm. When the curvature radius r 4  of the mountain portion  37  is less than the lower limit specified above, the mountain portion  37  has an acute shape, which easily causes stress concentration. Conversely, when the curvature radius r 4  is larger than the upper limit specified above, the mountain portion  37  becomes rounder, which makes it difficult to discriminate between the flat portion  36  and the mountain portion  37 . It is therefore preferable to set the curvature radius r 4  to the range specified above. According to the configuration described above, the shapes of the pair of side portions  20  and  21  of the pillar portion  8 C become different from each other. 
     According to this embodiment, by providing the discrimination portion  22 C to the pillar portion  8 C positioned between the front through-hole  9  and the rear through-hole  10 , it is possible to make the position of the discrimination portion  22 C easy to be recognized so that it can be readily found. In addition, while the chain is driven, the link plates  2 C undergo a tensile force induced by the first and second pins  3  and  4  (the coupling members  50 ) inserted through the respective front through-holes  9  and rear through-holes  10 . However, a load from the first and second pins  3  and  4  will not directly act on the pillar portions  8 C of the link plates  2 C. Accordingly, stress developed in the pillar portion  8 C is small in comparison with the other portions of the link plate  2 C. Hence, even when the discrimination portion  22 C is formed by changing the shape of the pillar portion  8 C, the durability of the link plate  2 C will not be deteriorated. 
     Alternatively, as is shown in  FIG. 9 , a recess portion  38  may be provided instead of the mountain portion  37  of  FIG. 8 . It is preferable to set a curvature radius r 5  of the recess portion  38  to a numerical range same as that of the radius curvature r 4  of the mountain portion  37  of  FIG. 8 . 
     Further, as is shown in  FIG. 10 , it may be configured in such a manner that the mountain portion  37  is provided to the one side portion  20  and the flat portion  36  to the other side portion  21 . Moreover, as is shown in  FIG. 11 , it may be configured in such a manner that the mountain portion  37  is provided to the one side portion  20  and the recess portion  38  to the other side portion  21 . 
     In addition, as is shown in  FIG. 12 , it may be configured in such a manner that the recess portion  38  is provided to the one side surface  20  and the mountain portion to the other side portion  21 . Further, as is shown in  FIG. 13 , it may be configured in such a manner that the recess portion is provided to the one side portion  20  and the flat portion to the other side portion  21 . 
     In a case where plural types of link plates having different alignment pitches are used as plural types of link plates having specifications different from each other, it is possible to discriminate the type of link plates by changing the shapes of the one side portion and the other side portion of the pillar portion from one type of link plates to another. 
       FIG. 14  is a section of a major portion in still another embodiment of the invention. In this embodiment, differences from the embodiment shown in  FIG. 1  through  FIG. 4  will be chiefly described. Like components are labeled with like reference characters and descriptions thereof are omitted herein. 
     Referring to  FIG. 14 , this embodiment is characterized in that, when a link plate  2 G is viewed along the chain width direction W 1 , the link plate  2 G includes a discrimination portion  22 G to discriminate the chain travel direction X 1 . When the link plate  2 G is viewed along the chain width direction W 1 , the discrimination portion  22 G includes a punching hole which is a concave portion as a marker provided to the front surface of the pillar portion  8 . 
     The discrimination portion  22 G is formed when molding the link plate  2 G by pressing a material (steel plate or the like) of the link plate  2 G. The discrimination portion  22 G is formed on the pillar portion  8  on the front side with respect to the chain travel direction X 1 . When the link plate  2 G is viewed along the chain width direction W 1 , the center of the discrimination portion  22 G with respect to the chain travel direction X 1  is disposed so as to avoid the center of the pillar portion  8  with respect to the chain travel direction X 1 . In the pillar portion  8 , the shape on the periphery of the one side portion  20  and the shape on the periphery of the other side portion  21  are different from each other. 
     According to this embodiment, the discrimination portion  22 G is provided to the pillar portion  8  positioned between the front through-hole  9  and the rear through-hole  10 . This configuration makes the position of the discrimination portion  22 G easy to be recognized so that it can be readily found. The chain travel direction X 1  can be readily discriminated according to the shape of the pillar portion  8 . 
     In the respective embodiments shown in  FIG. 8  through  FIG. 14 , even when the respective shapes of the pair of side portions  20  and  21  of the pillar portion are symmetrical with respect to the front and the rear in the chain travel direction X 1 , it is still possible to discriminate the chain travel direction X 1  by providing the discrimination portion  22 G. 
     The discrimination portion  22 G may be formed on the rear side of the pillar portion  8  with respect to the chain travel direction X 1 . Also, a plurality of discrimination portions  22 G may be provided. Further, in a case where plural types of link plates having different alignment pitches are used as plural types of link plates having specifications different from each other, it is possible to discriminate the type of link plates by changing the position, the size, and the shape of the discrimination portion  22 G from one type of link plates to another. 
       FIG. 15  is a partial section of a major portion in still another embodiment of the invention. In this embodiment, differences from the embodiment shown in  FIG. 1  through  FIG. 4  will be chiefly described. Like components are labeled with like reference characters and descriptions thereof are omitted herein. 
     Referring to  FIG. 15 , this embodiment is characterized in that, when a link plate  2 H is viewed along the chain width direction W 1 , the link plate  2 H includes a discrimination portion  22 H to discriminate the chain travel direction X 1 . When the link plate  2 H is viewed along the chain width direction W 1 , the discrimination portion  22 H includes a symbol as a marker provided to the front surface of the pillar portion  8  of the link plate  2 H. 
     The discrimination portion  22 H includes, for example, an arrow symbol formed by irradiating a laser beam to the link plate  2 H. This arrow symbol indicates the chain travel direction X 1 . 
     According to this embodiment, the discrimination portion  22 H is provided to the pillar portion  8  positioned between the front through-hole  9  and the rear through-hole  10 . This configuration makes the position of the discrimination portion  22 H easy to be recognized so that it can be readily found. 
     In a case where plural types of link plates having different alignment pitches are used as plural types of link plates having specifications different from each other, it is possible to discriminate the type of link plates by changing the position, the shape, and the size of the discrimination portion  22 H from one type of link plates to another. 
     In this embodiment, as is shown in  FIG. 16 , it may be configured in such a manner that, instead of the arrow symbol described above, a symbol in the shape of an inequality sign is provided to the surface of the pillar portion  8  when viewed in the chain width direction W 1  and used as a discrimination portion  22 J indicating the chain travel direction X 1 . Alternatively, it may be configured in such a manner that, instead of the arrow symbol described above, a triangle symbol is provided to the surface of the pillar portion  8  when viewed from the chain width direction W 1  as is shown in  FIG. 17  and used as a discrimination portion  22 K indicating the chain travel direction X 1 . 
     In the respective embodiments above, the first pin  3  may be loosely fit into the corresponding rear through-holes  10 . Also, the second pin  4  may be loosely fit into the corresponding front through-holes  9 . Further, the second pin  4  may be engaged with the respective pulleys  60  and  70 . 
       FIG. 18  is a partial section of a major portion in still another embodiment of the invention. In this embodiment, differences from the embodiment shown in  FIG. 1  through  FIG. 4  will be chiefly described. Like components are labeled with like reference characters and descriptions thereof are omitted herein. 
     Referring to  FIG. 18 , this embodiment is characterized in that respective link plates  2 J adjacent to each other in the chain travel direction X 1  are coupled so that they can bend with respect to each other, using the single first pins  3  as the coupling members. To be more concrete, a corresponding first pin  3  is loosely fit into front through-holes  9 J in the respective link plates  2 J in a relatively movable manner, whereas another corresponding first pin  3  is press-fit fixedly into rear through-holes  10 J in the respective link plates  2 J. 
     Of the peripheral portion of the front through-hole  9 J, the section of a front portion  39  (counter portion) positioned on the front side with respect to the chain travel direction X 1  is of a linear shape extending generally straight in the orthogonal direction V 1 . The front portion  39  opposes the front portion  12  of the first pin  3  loosely fit into the front through-holes  9 J. The front portion  12  of the first pin  3  and the front portion  39  come into contact with each other at the contact portion T in a contact state including at least one of rolling contact and sliding contact. 
     Accordingly, the link plate  2 J and the first pin  3  loosely fit into this link plate  2 J come into rolling and sliding contact with each other in association with the bending of the link plates  2 J with respect to each other. Also, when the first pin  3  is viewed along the chain width direction W 1 , the movement locus of the contact portion T in association with the bending between the link plates  2 J draw an involute curve in reference to the first pin  3 . 
     According to this embodiment, it is possible to make the alignment pitch between the first pins  3  shorter, which makes it possible to provide more first pins  3  to be meshed with the respective pulleys at a time. Accordingly, a load per first pin  3  can be reduced. It is thus possible to reduce colliding forces with the respective pulleys, which can in turn reduce noises. 
     In a case where plural types of link plates having different alignment pitches are used as plural types of link plates having specifications different from each other, it is possible to discriminate the type of link plates by changing the position and the shape of the discrimination portion  22  from one type of link plates to another. 
     Further, any one of the discrimination portions  22 A through  22 H,  22 J, and  22 K may be provided instead of the discrimination portion  22 . Furthermore, the first pin  3  may be loosely fit into the rear through-holes  10 J in the respective link plates  2 J. 
     While the embodiments of the invention have been described, it should be appreciated that the invention is not limited to the embodiments above. For example, in the respective embodiments shown in  FIG. 8  through  FIG. 13 , it may be configured in such a manner that the discrimination portion is provided to only one of the pair of side portions  20  and  21  of the pillar portion, so that the pillar portion of the link plate is of a shape asymmetric with respect to the front and the rear in the chain travel direction X 1 . 
     In the respective embodiments above, a lot symbol may be inscribed on the surface of the link plate  2 , so that this lot symbol is used as the discrimination portion by disposing the lot symbol on the pillar portion of the link plate at a position closer to either the front through-hole or the rear through-hole. 
     The discrimination portions of the respective embodiments can be discriminated by an individual visually or by various types of discrimination devices. For example, by imaging the link plate with a camera to capture the image and apply image processing thereon, automatic discrimination is enabled swiftly in a reliable manner. This is suitable for automating the fabrication of chains. For example, the discrimination is enabled using a sensor that utilizes optical, electrical, or acoustic actions. 
     In addition, the invention may be applied to a so-called block-type power transmission chain, in which members having power transmission portions same as the end faces of the first pins are provided in the vicinity of a pair of the end portions of the first pin. The block-type power transmission chain includes power transmission blocks, and the power transmission blocks are fixed to the link plates or the pins so as to protrude toward the both ends in the chain width direction W 1  with respect to the pins. 
     The shapes of the front through-hole and the rear through-holes of the link plate may be changed with each other. Further, a connecting groove (slit) may be provided to the pillar portion between the front through-hole and the rear through-hole in the link plate. In this case, an amount of elastic deformation (flexibility) of the link plate can be increased, and stress developing in the link plate can be reduced further. 
     It should also be noted that the invention is not limited to the configuration in which the groove widths of both the drive pulley  60  and the driven pulley  70  are variable, and it may configured in such a manner that the groove width of either one of the pulleys is variable whereas the groove width of the other is fixed. Further, the above described are the embodiments in which the groove widths vary continuously (in a stepless manner). However, the invention may be applied to other power transmission devices in which the groove widths are varied step-wise or are fixed (invariable). 
     While the embodiments of the invention have been described in detail, modifications, alterations and equivalents of the invention will readily occur to anyone skilled in the art who understands the contents. The sprit and the scope of the invention, therefore, are limited solely by the scope and equivalents of the appended claims. 
     This application corresponds to the prior Japanese Patent Application No. 2005-301031 filed with the Japanese Patent Office on Oct. 14, 2005, the entire contents of which are incorporated herein by reference.