Abstract:
In a transmission chain, guide plates are provided on opposite ends of guide rows. In a guide row, both of the guide plates can be contact guide plates arranged to contact sides of the transmission sprocket teeth. However, some of the guide rows are formed with one guide plate configured for contact with the sprocket teeth and the opposite guide plate configured so that it does not contact the sprocket teeth. The sprocket tooth-contacting plates can be on one side of the chain in some of the guide rows and on the opposite side of the chain in other guide rows. The guide plates in still other guide rows are configured so that they never contact the sides of the sprockets.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The disclosure of Japanese Patent Application No. 2012-056272 filed on Mar. 13, 2012, and on which this application claims priority, is herein incorporated by reference in its entirety. 
     FIELD OF THE INVENTION 
     This invention relates to a chain transmission device including an endless, flexible, transmission chain in mesh with a set of sprockets, the chain having alternating, interconnected, guide rows and link rows, each guide row having guide plates. 
     The chain can be a silent chain or any of various other kinds of transmission chains. The chain transmission device can be used as a timing chain in an automobile engine, or as a power transmission chain in a vehicle or in other kinds of machines such as industrial machinery. 
     BACKGROUND OF THE INVENTION 
     A conventional chain transmission device includes an endless chain in which a plurality of guide rows and a plurality of link rows are arranged alternately in the longitudinal direction of the chain and connected to one another flexibly. Each of the guide rows has a pair of guide plates and one or more link plates arranged between the pair of guide plates in the widthwise direction of the chain. Each of the link rows has a plurality of second link plates. The transmission includes a plurality of sprockets around which the chain is wrapped. An example of such a transmission is described in United States Patent publication 2004/0166978, published on Aug. 26, 2004. 
     As shown in  FIGS. 11 and 12 , a chain transmission  500  includes a chain  530  which has a wrapping portion  531  wrapped around and engaging with a sprocket  510  of a sprocket set. A pair of guide plates  540  of a guide row G 5  of the chain  530  guide first and second link plates  560  and  570  along the longitudinal direction of the chain. In the wrapping portion  531 , the pair of guide plates  540  may come into contact with side surfaces  512  of the sprocket  510  to restrict sideslip, i.e., movement of the chain  530  in the widthwise direction. 
     Noise is generated when the guide plates  540  come into contact with the sprocket side surfaces  512 . In addition, power transmission efficiency is impaired by friction between the guide plates  540  and the sprocket side surfaces  512 . 
     Furthermore, when a plurality of the guide rows G 5  are regularly arranged in a chain longitudinal direction, the guide plates  540  come into contact with the sprocket side surfaces  512  at regular intervals, causing generation of periodic sounds. 
     This invention addresses the above problems. It is an object of the invention to provide a chain transmission in which some of guide rows of a chain have non-contact guide plates which do not come into contact with side surfaces of the sprockets in order to decrease noise and friction caused by contact between guide plates of the guide rows and the side surfaces of the sprockets, and to reduce the weight of the chain. 
     SUMMARY OF THE INVENTION 
     The chain transmission according to the invention comprises a chain and a plurality of sprockets, at least one of the sprockets being in driving relationship with the chain, and at least one of the sprockets being in driven relationship with the chain. The chain is elongated in a lengthwise direction and has a width in a widthwise direction perpendicular to the lengthwise direction. The chain comprises a plurality of guide rows and a plurality of link rows, the guide rows and link rows being arranged alternately along the lengthwise direction of the chain and flexibly interconnected to one another. Each of the guide rows has a pair of guide plates spaced from each other in the widthwise direction and at least one first link plate disposed between the pair of guide plates. Each of the link rows has a plurality of second link plates. At any time during the operation of the transmission, the chain has a plurality of wrapping portions, a wrapping portions being in engagement with, and extending around, a portion of each of the sprockets. Each of guide plates of each of the guide rows is a guide plate from the group consisting of contact guide plates, which are able to come into contact with side surfaces of the sprockets when in a wrapping portion of the chain, and non-contact guide plates, which do not come into contact with sprocket side surfaces when in the wrapping portion of the chain. The guide rows of the chain include at least one contact guide row having at least one contact guide plate, and at least one non-contact guide row having only non-contact guide plates. 
     The contact guide plates of the contact guide rows restrict sideslip of the chain. However, because some of the guide rows of the chain are non-contact guide rows having only non-contact guide plates, the number of the guide rows that come into contact with side surfaces of the sprockets and the sprocket teeth is reduced. Consequently, noise and friction caused by the contact between guide plates and the sprocket side surfaces are reduced, and power transmission can take place more efficiently. In addition, because the non-contact guide plates are lighter in weight than the contact guide plates, impact noise generated when the contact guide plates come into contact with the sprocket side surfaces is reduced. The weight of the chain is also reduced, and therefore the overall weight of the machinery of which the chain is a part is reduced. 
     According to a second aspect of the invention, at least one of the wrapping portions of the chain always includes at least one contact guide row having at least one contact guide plate, and a plurality of non-contact guide rows each having only non-contact guide plates. Here, because at least one of the wrapping portions always includes a contact guide row, it is possible to restrict sideslip of the chain. Because at least one of the wrapping portions always includes a plurality of the non-contact guide rows, the weight of the wrapping portions is reduced, and impact noise and friction loss are reduced. 
     According to a third aspect of the invention, in each of the wrapping portions, the number of non-contact guide rows is always greater than the number of contact guide rows. Here, because the wrapping portions always include a larger number of non-contact guide rows than contact guide rows, the weight of the wrapping portions is still further reduced. Thus, it is possible to realize a further decrease in impact noise and friction. 
     According to a fourth aspect of the invention, the pair of guide plates of each of the guide rows consists of a first and second guide plates opposed to each other in the widthwise direction and provided on opposite sides of the chain. The contact guide rows of the chain comprise at least one first contact guide row, the first and second guide plates of which are contact guide plates, and a plurality of second contact guide rows one of the first and second guide plates of which is a contact guide plate and the other of the first and second guide plates of which is a non-contact guide plate. The plurality of second contact guide rows consists of guide rows from the group consisting of type 1 contact guide rows the first and second guide plates of which are respectively contact guide plates and non-contact guide plates and type 2 contact guide rows the first and second guide plates of which are respectively non-contact guide plate and contact guide plates. 
     At least one of the wrapping portions always includes at least one guide row from the group consisting of: (a) at least one first contact guide row, (b) at least one first contact guide rows and at least one second contact guide row; and (b) at least one said type 1 contact guide row and at least one said type 2 contact guide rows. 
     With this configuration the chain is restricted against chain sideslip bidirectionally. 
     According to a fifth aspect of the invention, the pair of guide plates of each of the guide rows consists of a first and second guide plates opposed to each other in the widthwise direction and provided on opposite sides of the chain. Each of the contact guide rows is a guide row from the group consisting of a type 1 contact guide row the first and second guide plates of which are respectively a contact guide plate and a non-contact guide plate, and a type 2 contact guide row the first and second guide plates of which are respectively a non-contact guide plate and a contact guide plate, and at least one of the wrapping portions always includes at least one type 1 contact guide row and at least one type 2 contact guide row. 
     Here, because at least one of the wrapping portions always includes at least one type 1 contact guide row and at least one type 2 contact guide row, it is possible to restrict sideslip of the chain bidirectionally. 
     According to a sixth aspect of the invention, each of guide plates of each contact guide row is a contact guide plate. Here again, because each of guide plates of the contact guide row is a contact guide plate, it is possible to restrict sideslip bidirectionally in the wrapping portion. 
     According to a seventh aspect of the invention, one of the pair of guide plates of at least one of the contact guide rows is a contact guide plate and the other guide plate of the pair is a non-contact guide plate. Here it is possible not only to restrict sideslip of the chain, but also to reduce the weight of the wrapping portions, and to decrease impact noise and friction. 
     According to an eighth aspect of the invention, a plurality of the contact guide rows are arranged randomly in the lengthwise direction of the chain. Here, because contact between the guide plates and the sprocket side surfaces does not occur at regular intervals, periodic contact noise is decreased. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an elevational view illustrating a chain transmission device in accordance with a first embodiment of the invention; 
         FIG. 2  is an enlarged view, partly in section, of a part of the chain in the transmission of  FIG. 1 , as viewed in the direction of arrow  2  in  FIG. 1 ; 
         FIG. 3  is a cross sectional view of the chain transmission of  FIG. 1 , taken on section plane  3   a - 3   a  or section plane  3   b - 3   b  in  FIG. 1 ; 
         FIG. 4  is an elevational view of a part of the chain of  FIG. 3 , as viewed in the direction of arrow  4  in  FIG. 3 ; 
         FIG. 5  is an elevational view illustrating a chain transmission device in accordance with a second embodiment of the invention; 
         FIG. 6  is a cross-sectional view of the second embodiment shown in  FIG. 5 , taken on section plane  6 - 6  in  FIG. 2 ; 
         FIG. 7  is an elevational view illustrating a chain transmission device in accordance with a third embodiment of the invention; 
         FIG. 8  is a sectional view, corresponding to  FIG. 6 , illustrating the third embodiment shown in  FIG. 7 ; 
         FIG. 9  is an elevational view illustrating a chain transmission device in accordance with a fourth embodiment of the invention; 
         FIG. 10  is a sectional view, corresponding to  FIG. 6 , illustrating the fourth embodiment shown in  FIG. 9 ; 
         FIG. 11  is a view, corresponding to  FIG. 2 , illustrating a part of a chain transmission of the prior art; and 
         FIG. 12  is an elevational view of a part of the chain of  FIG. 11 , as viewed in the direction of arrow  12  in  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the following description, the term “guide plate” should be understood as referring to a plate in the position of a guide plate, whether or not it Is capable of coming into contact with the side of a sprocket. The invention can be embodied in any chain transmission comprising a chain and a plurality of sprockets, at least one of the sprockets being in driving relationship with the chain, and at least one of the sprockets being in driven relationship with the chain. For example, the chain may be a silent chain or any chain having link plates corresponding to a pair of guide plates. 
     The chain transmission can be utilized not only in an automobile engine, but also in industrial machinery, conveying or carrying machines, and other machines that utilize a chain for transmission of power. While a typical chain transmission has one driven sprocket and one driving sprocket, the chain transmission can have more than one driven sprocket and can have more than one driving sprocket. The driving sprocket or sprockets can be operated by an internal combustion engine, an electric motor, or any of various other kinds of power generating devices for rotating a sprocket. 
     The transmission device  100  shown in  FIG. 1 , which can be a timing drive in an automobile engine (not shown), comprises an endless silent chain  130 . Referring to  FIGS. 1 ,  2  and  4 , the chain transmission  100  also has a sprocket set  101  in mesh with the chain. The sprocket set  101  includes a driving sprocket  110  and a driven sprocket  120 . The driving sprocket  110  is rotated by the crank shaft of an engine, and the driven sprocket  120  rotates a valve-operating camshaft in the engine or the drive shaft of an engine accessory such as an oil pump. The sprockets  110  and  120  respectively have sprocket teeth  111  and  121  which are capable of meshing engagement with the chain  130 . 
     Referring to  FIGS. 1 to 4 , the chain  130  includes a plurality of guide rows G, a plurality of link rows L, and a plurality of connecting pins  150  ( FIG. 2 ), which connect the guide rows G with the link rows L. The guide rows G are arranged alternately with the link rows L and the connecting pins allow relative articulation of the guide rows and link rows. 
     Each of the guide rows G includes a pair of guide plates  140 , and one or more first link plates  160  disposed between the pair of guide plates. In the chain shown in  FIGS. 2 and 3 , each guide row includes a plurality of first link plates  160 . Each first link plate  160  has a pair of pin holes  161  spaced from each other in the longitudinal direction of the chain, and a pair of teeth  162  ( FIG. 4 ) capable of engaging with the sprocket teeth. 
     Each of the link rows L includes a plurality of second link plates  170 , which are arranged in spaced, side-by-side relationship in the widthwise direction of the chain. The number of second link plates in each link row L exceeds by one the number of first link plates  160  in each guide row G. The second link plates  170  in each of the link rows L extend into a space between a pair of guide plates  140  of a first adjacent guide row and into a space between a pair of link plates in another adjacent guide row. Each second link plate has a pair of second pin holes  171 , spaced from each other in the longitudinal direction of the chain, and a pair of teeth  172  capable of engaging the sprocket teeth  111  and  121 . 
     Each of the connecting pins  150  is a rocker joint pin composed of a first pin  151  and a second pin  152 , which is shorter than the first pin  151 . The first and second pins  151  and  152  are inserted together through the first and second pin holes  161  and  171  and extend through the first and second link plates  160  and  170  in the widthwise direction of the chain. 
     Each of the guide plates  140  of a guide row G has a pair of pin-holding holes  149 , spaced from each other in the longitudinal direction of the chain, for holding the first pins  151 . By insertion into the pin-holding holes, each first pin  151  is fixed to the guide plates  140  at both ends thereof. Although the connecting pins in the embodiment illustrated are rocker joint pins, as an alternative, each of the connecting pins can be a single cylindrical pin. 
     As shown in  FIG. 1 , the chain  130  includes wrapping portions  131  and  132  which respectively extend in arcs around parts of sprockets  110  and  120 , and engage the sprocket teeth  111  and  121 . The portions of the chain that are not wrapped around the sprockets are free span portions  133  that extend from one sprocket to the other. 
     Referring to  FIG. 2 , the pair of guide plates  140  of each of the guide rows consists of a first guide plate  141  provided at one end of the guide row, and a second guide plate  142  at the other end of the guide row, these two guide plates being in opposed relation to each other and spaced from each other in the widthwise direction of the chain. It does not matter which of the guide plates  140  is the first guide plate  141  or the second guide plate  142 ; when one of the pair of guide plates  140  is the first guide plate  141 , the other is the second guide plate  142 . Each of the first and second guide plates  141  and  142  of each of the guide rows G is either a contact guide plate P 1  (indicated by dark hatching in  FIG. 1 ) or a non-contact guide plate P 0  (indicated by light hatching in  FIG. 1 ). 
     A contact guide plate P 1  is able to come into contact with a side surface of sprocket  110  and with a corresponding side surface of sprocket  120 . Depending on a running condition of the chain  130 , a contact guide plate P 1  may or may not come into contact with a side surface  112  or  122  of a sprocket. When restricting sideslip of the chain, which includes the prevention of meandering of the chain, a guide plate P 1  comes into contact with a sprocket side surface, e.g., side surface  112   a  or  122   a  of the respective sprockets or with a sprocket side surface  112   b  or  122   b , depending on the direction of the chain sideslip ( FIG. 3 ). The sprocket side surfaces  112  and  122  include at least side surfaces  113  and  123  of the sprocket teeth  111  and  112 , respectively. 
     A non-contact guide plate P 0  does not come into contact with the sprocket side surfaces  112  and  122  while the chain  130  is running, and is smaller and lighter than a contact guide plate P 1 . 
     In order to avoid coming into contact with the sprocket side surfaces  112  and  122 , the non-contact guide plate P 0  has a shape such that no part thereof can overlap a sprocket tooth. In the embodiment shown, in the wrapped portions  131  and  132  of the chain, the entire non-contact guide plate is positioned radially outward of the sprocket teeth  111  and  121 . This configuration reduces the weight of the non-contact guide plate P 0 . This configuration also prevents the non-contact guide plate P 0  from coming into contact not only with the sprocket side surfaces  112  and  122 , but also with the sprocket teeth  111  and  121  in the direction of the radius of a sprocket. Although the entire plate P 0  is positioned radially outward of the sprocket teeth in the embodiment shown, it is possible for portions of a non-contact guide plate that come into register with the spaces between sprocket teeth to extend radially inward relative to the tips of the sprocket teeth. 
     Referring to  FIG. 1 , all of the guide rows G of the chain  130  are categorized as either a contact guide row G 1 , in each of which at least one of the first and second guide plates  141  and  142  is a contact guide plate P 1 , or as a anon-contact guide row G 0 , in each of which both the first and second guide plates  141  and  142  are non-contact guide plates P 0 . 
     The chain  130  includes one or more non-contact guide rows G 0 . In the embodiments shown, the number of non-contact guide rows G 0  exceeds the number of contact guide rows G 1 . The weight of the chain is reduced when the number of non-contact guide rows is increased. 
     One or more non-contact guide rows G 0  are arranged between successive contact guide rows G 1 . In the embodiment shown in  FIG. 1  four non-contact guide rows are arranged between successive contact guide rows. The number of non-contact guide rows between successive contact guide rows in the chain can be a constant predetermined number, e.g., two or more, in which case the contact guide rows G 1  are arranged at regular intervals along the longitudinal direction of the chain. 
     In the embodiment shown in  FIG. 1 , all of the contact guide rows G 1  are first contact guide rows G 11  in which each of the first and second guide plates  141  and  142  ( FIG. 2 ) is a contact guide plate P 1 . 
     As is apparent from  FIG. 1 , each of the wrapping portions  131  and  132  always includes at least one first contact guide row in the embodiment of  FIG. 1 , each of the wrapping portions includes a plurality of first contact guide rows G 11  and a larger number of non-contact guide rows G 0 . 
     The weight of the chain is reduced with an increasing number of non-contact guide rows G 0  in the wrapping portions  131  and  132 . However, a minimum number of the contact guide rows G 1  in the wrapping portions is required to restrict sideslip of the chain. In the wrapping portions  131  and  132 , the number of non-contact guide rows G 0  can be more than twice as many as the number of contact guide rows G 1 . 
     Each of the guide plates  140  of each of the guide rows G is either a contact guide plate P 1  or a non-contact guide plate P 0 . 
     Each of the guide rows G of the chain  130  may be categorized as a contact guide row G 1 , having at least one contact guide plate P 1 , or a non-contact guide row G 0 , having only non-contact guide plates P 0 . 
     It is possible to restrict sideslip of the chain by utilizing a contact guide row G 1  having a contact guide plate P 1 . Because some of the guide rows G are non-contact guide rows G 0 , both guide plates  140  of which are non-contact guide plates, the number of the guide rows G that come into contact with the sprocket side surfaces  112  and  122  is decreased, and noise and friction caused by the contact between the guide plates  140  and the side surfaces  112  and  122  of the sprockets are reduced. Reduction of friction reduces power loss and improves transmission efficiency. Because the non-contact guide plates P 0  can be made lighter than the contact guide plates P 1 , the wrapping portions  131  and  132  of the chain  130  become lighter. Thus, it is possible to decrease impact and friction generated when the contact guide plates P 1  come into contact with the sprocket side surfaces  112  and  122 , and to reduce noise and frictional loss. Furthermore, the weight of the chain  130  as a whole is decreased, which contributes to reduction of the overall weight of the machine in which the chain transmission  100  is incorporated. 
     Each of the wrapping portions  131  and  132  always includes a plurality of contact guide rows G 1  and a plurality of non-contact guide rows G 0 . Because the wrapping portions  131  and  132  always include a plurality of contact guide rows G 1 , it is possible to restrict sideslip of the chain by contact between the guide plates P 1  of the contact guide rows G 1  and sprocket side surfaces  112  and  122 . 
     Because the wrapping portions  131  and  132  always include a plurality of non-contact guide rows G 0 , the weight of the wrapping portions  131  and  132  is decreased, and impact noise and friction generated when contact guide plates P 1  come into contact with the sprocket side surfaces  112  and  122  are also reduced. 
     If a guide row G 1  is a first contact guide row G 11  having a pair of contact guide plates P 1 , it is possible in each of the wrapping portions  131  and  132  to restrict chain sideslip bidirectionally in the widthwise direction of the chain. If each of the wrapping portions  131  and  132  includes a plurality of first contact guide rows G 11 , the bidirectional restriction of the chain against sideslip is enhanced. 
     If each of the wrapping portions  131  and  132  always includes a larger number of non-contact guide rows G 0  than contact guide rows G 1 , the weight of the wrapping portions  131  and  132  is further decreased. Thus, it is possible to decrease impact noise and friction generated when the contact guide plates P 1  come into contact with the sprocket side surfaces  112  and  122 . 
     In the following description of second to fourth embodiments, the same reference numerals as the first embodiment are basically used for members are used to designate components that correspond to components of the embodiment described above. 
     In the chain transmission  100  of a second embodiment, the chain  230  includes contact guide rows G 1 , which can be first contact guide row G 11 , or second contact guide row G 12 , one of the first and second guide plates  141  and  142  of which is a contact guide plate P 1 , and the other of the first and second guide plates of which is a non-contact guide plate P 0 . The chain  230  includes one or more first contact guide rows G 11  and one or more second contact guide rows G 121 . In the embodiment shown, the chain includes one first contact guide row G 11 , and a plurality of second contact guide rows G 121 . 
     Each of the second contact guide rows G 121  in the chain  230  is either a type 1 contact guide row G 121 , the first and second contact guide plates  141  and  142  of which are respectively a contact guide plate P 1  and a non-contact guide plate P 0 , or a type 2 contact guide row G 122  whose first and second guide plates  141  and  142  are respectively a non-contact guide plate P 0  and a contact guide plate P 1 . 
     Specifically, the chain  230  includes one or more type 1 contact guide rows G 121  and one or more type 2 contact guide rows G 122 . In the embodiment shown, the chain includes a plurality of type 1 contact guide rows G 121  and a plurality of type 2 contact guide rows G 122 . 
     One or more (one in the embodiment shown in  FIG. 5 ) first contact guide rows G 11  or type 1 contact guide rows G 121  are arranged between two successive type 2 contact guide rows G 122  in the longitudinal direction of the chain. The number of guide rows G arranged between a first contact guide row G 11  and a succeeding type 2 contact guide row G 122 , and between two successive type 2 contact guide rows G 122  is constant. 
     As is apparent from  FIGS. 5 and 6 , each of the wrapping portions  231  and  232  always includes one or more (one in the present embodiment) first contact guide rows G 11  and one or more second contact guide rows G 122 , or one or more type 1 contact guide rows G 121  and one or more type 2 contact guide rows G 122 . 
     Each of the wrapping portions  231  and  232  always includes a larger number of non-contact guide rows G 0  than contact guide rows G 1 . 
     In this second embodiment, the contact guide rows G 1  included in the chain  230  consist of one first contact guide row G 11  and a plurality of second contact guide rows G 12 . The plurality of the second contact guide rows G 12  consists of a plurality of the type 1 contact guide rows G 121  and a plurality of the type 2 contact guide rows G 122 . Each of the wrapping portions  231  and  232  always includes one first contact guide row G 11  and a plurality of second contact guide rows G 12 , or one or more of the type 1 contact guide rows G 121  and one or more of the type 2 contact guide rows G 122 . 
     With this configuration, because each of the wrapping portions  231  and  232  always includes at least one first guide plate  141 , which is a contact guide plate P 1 , and at least one second guide plate  142 , which is a contact guide plate P 1 , it is possible to restrict the chain sideslip bidirectionally in the widthwise direction of the chain. 
     Because each of the wrapping portions  231  and  232  always includes a second contact guide row G 12 , one of the pair of guide plates  140  of which is a contact guide plate P 1  and the other of which is a non-contact guide plate P 0 , it is possible not only to restrict sideslip, but also to reduce the weight of the wrapping portions  231  and  232 . Thus, it is possible to decrease impact noise and friction generated when the contact guide plate P 1  comes into contact with the sprocket side surfaces  121  and  122 . 
     In a third embodiment, shown in  FIGS. 7 and 8 , the chain transmission  100  includes a chain  330 . All of the contact guide rows G 1  in the chain  330  are first contact guide rows G 11 . The number of non-contact guide rows G 0  arranged between two successive first contact guide rows G 11  differs depending on the positions of the first contact guide rows G 11  in the longitudinal direction of the chain. Thus, the first contact guide rows G 11  in the chain  330  are arranged randomly in the longitudinal direction of the chain, i.e., at two or more different intervals. 
     Each of wrapping portions  331  and  332  always includes one or more (a plurality in the present embodiment) first contact guide rows G 11 , and a plurality of the non-contact guide rows G 0  the number of which exceeds the number of guide rows G 11 . 
     The contact guide rows G 11  of the chain  330  constitute one or more consecutive guide row sets and one or more single contact guide rows. The consecutive guide row set includes a plurality of first contact guide rows G 11  that are consecutive except for the link row L connecting successive guide rows. The single contact guide row includes one first contact guide row G 11 . 
     Each of the wrapping portions  331  and  332  always includes a plurality of first contact guide rows G 11 , and each of the wrapping portions  331  and  332  always includes the first and second guide plates  141  and  142 , both of which are contact guide plates P 1 . Thus, it is possible to restrict sideslip of the chain bidirectionally in the widthwise direction, and to increase the restriction of sideslip compared to the case in which some of the guide rows G 1  in the wrapping portions  331  and  332  are second contact guide row G 12 . 
     Because the first contact guide rows G 11  are arranged randomly in the chain longitudinal direction, the guide plates  140  do not come into contact with the sprocket side surfaces  112  and  122  at regular intervals when the chain  330  engages with the sprockets. Thus, periodic noise is decreased. 
     The chain transmission  100  of the fourth embodiment, shown in  FIGS. 9 and 10 , includes a chain  430 . All of the contact guide rows G 1  in the chain  430  are second contact guide rows G 12 , or more specifically, type 1 contact guide rows G 121  and type 2 contact guide rows G 122 . The arrangement of the non-contact guide rows G 0  with reference to the contact guide rows G 1  is the same as that of the third embodiment. Each of the wrapping portions  431  and  432  of the chain  430  always includes one or more type 1 contact guide rows G 121 , one or more type 2 contact guide row G 122 , and a plurality of non-contact guide rows G 0  the number of which is greater than the number of contact guide rows G 1  included therein. 
     If the guide rows G 1  are arranged randomly, the same effects as the first and third embodiments can be achieved. In addition, the following effects can be achieved. 
     Because each of the wrapping portions  431  and  432  always includes one or more type 1 contact guide rows G 121  and one or more type 2 contact guide rows, it is possible to restrict sideslip bidirectionally in the widthwise direction of the chain. 
     Because the contact guide row G 1  included in each of the wrapping portions  431  and  432  is always a second contact guide row G 12 , the weight of each of the wrapping portions  431  and  432  is reduced. Thus, it is possible to decrease impact noise and friction. 
     Many variations of the above described embodiments are possible. For example, the non-contact guide plate P 0  may have a shape such that a part is positioned radially inward of the radius of the tips of the sprocket teeth, as long as the non-contact guide plate P 0  does not come into contact with the sprocket teeth  111  and  121 , including the side surfaces  113  and  123  thereof. 
     As variations of the first embodiment, all of the guide rows G 1  of the chain  130  may consist of other combinations of first guide rows G 11  and second guide rows G 12 . In other words, all of the guide rows G 1  of the chain  130  may consist of or more first contact guide rows G 11 , one or more type 1 contact guide rows G 121  and one or more type 2 contact guide rows G 122 , one or more first contact guide rows G 11  and one or more type 1 contact guide rows G 121 , or one or more first contact guide rows G 11  and one or more type 2 contact guide rows G 122 . 
     Alternatively, all of the guide rows G 1  of the chain  130  may consist of only second contact guide rows G 12 . In other words, all of the guide rows G 1  of the chain  130  may consist of one or more type 1 contact guide rows G 121  and one or more type 2 contact guide rows G 122 , only the type 1 contact guide rows G 121  or only the type 2 contact guide rows G 122 . 
     Similarly, in the second, third and fourth embodiments, all of the guide rows G 1  of the chains  230 ,  330  and  430  may consist of any of the combinations of the first contact guide row G 11  and the second contact guide row G 12 , or only the second contact guide rows G 12 , described in the above variations of the first embodiment. In any of the variations, a plurality of the contact guide rows G 1  may be arranged either at regular intervals or randomly along the longitudinal direction of the chain. 
     In each of the embodiments, it is sufficient that all, or at least one, of the wrapping portions, always include one or more first contact guide rows G 11 , one or more first contact guide rows G 11  and one or more second contact guide rows G 12 , or one or more type 1 contact guide rows G 121  and one or more type 2 contact guide rows G 122 . 
     In the second embodiment, the first contact guide row G 11  and the type 2 contact guide row G 121  may exist between two type 2 contact guide rows  122  mutually adjacent in the longitudinal direction of the chain.