Abstract:
To provide a metal chain having reduced weight and size but uncompromised strength, and manufacturable/assemblable with reduced work burden and cost. A metal chain is formed by coupling together a plurality of inner links and outer links alternately and pivotably in a longitudinal direction of the chain. Each of the outer link includes a pair of front and back pins and a pair of left and right outer plates. Each of the inner links includes a pair of front and back bushings and a pair of left and right inner plates. The pair of front and back bushings and the pair of left and right inner plates of the inner link are integrally formed as one component.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a metal chain formed by coupling together a plurality of inner links and outer links alternately and pivotably in the longitudinal direction of the chain. 
         [0003]    2. Description of the Related Art 
         [0004]      FIG. 16  shows a conventionally known metal chain formed by coupling together a plurality of inner links and outer links alternately and pivotably in the longitudinal direction of the chain. The chain  900  is formed by coupling together outer links  920  and inner links  910  alternately, each outer link  920  having a pair of outer plates  922  with pins  921  fixed in pin holes of the outer plates  922 , and each inner link  910  having a pair of inner plates  912  with bushings  911  fixed in bushing holes of the inner plates  912 , with the pins  921  of the outer links  920  loosely fitted in the bushings  911  of the inner links  910  (see, for example, Japanese Patent Application Laid-open No. 2007-107583). 
       SUMMARY OF THE INVENTION 
       [0005]    Press-fitting, whereby the bushings  911  are press-fitted into the bushing holes of the inner plates  912 , is a commonly used technique to join the inner plates  912  with the bushings  911  for the metal chain such as the chain  900  of Japanese Patent Application Laid-open No. 2007-107583. 
         [0006]    However, press-fitting the bushings  911  to the inner plate  912  lowers the strength of the inner plate  912 , as it causes portions A of the inner plate  912  shown in  FIG. 16  to easily rupture because tensile force generated by the chain tension tends to concentrate on these portions. Increasing the rigidity of the inner plate  912  to make up for the reduced strength thereof would lead to an increase in size or weight of the inner plate  912 , which is a problem characteristic to metal chains. 
         [0007]    In order to press-fit bushings  911  to the inner plate  912 , the inner plate  912  needs a portion of at least a certain width around the bushing holes, which is also a problem characteristic to metal chains, and this results in an increase in the size in the chain height direction, and weight, of the inner plate  912  corresponding to the increased plate portions. 
         [0008]    Another problem with the conventional chain  900  is that the outer plates  922 , pins  921 , inner plates  912 , and bushings  911  need to be separately subjected to forming, thermal treatment, and finishing processes, so that the burden and cost of manufacturing the chain are high. 
         [0009]    Furthermore, the conventional chain  900  is assembled through a large number of process steps such as press-fitting pairs of front and back bushings  911  to pairs of left and right inner plates  912  to form inner links  910 , inserting pairs of front and back pins  921  that are press-fitted to the outer plates  922  into the bushings  911 , and connecting the outer plates  922  with the pairs of front and back pins  921  by press-fitting, and so on, so that work burden in assembling the chain is high. 
         [0010]    The present invention solves these problems and it is an object of the invention to provide a metal chain having reduced weight and size but uncompromised strength, and manufacturable/assemblable with reduced work burden and cost. 
         [0011]    The present invention solves the problems described above by providing a metal chain formed by coupling together a plurality of inner links and outer links alternately and pivotably in a longitudinal direction of the chain. Each of the outer links includes a pair of front and back pins, and a pair of left and right outer plates that connect the pair of front and back pins. Each of the inner links includes a pair of front and back bushings that axially support the pins, and a pair of left and right inner plates that connect the pair of front and back bushings. The pair of front and back bushings and the pair of left and right inner plates of the inner link are integrally formed as one component. 
         [0012]    According to the invention as set forth in claim  1 , the pair of front and back bushings and the pair of left and right inner plates of the inner link are integrally formed as one component, so that hardly any rupture occurs in the inner plates that may result from press-fitting. Thus the inner link can have enhanced strength without increasing weight or size. 
         [0013]    While the conventional inner plate needed a portion of more than a certain width around the bushing hole if the bushing is to be press-fitted to the inner plate, the inner plate does not need such a portion according to the invention as set forth in claim  1 . Thus the inner plate can be reduced in its chain height direction and weight. 
         [0014]    Since the inner link is formed as one component, the number of components is reduced, so that the work burden and cost in the manufacture or assembling of the chain are reduced. 
         [0015]    According to the invention as set forth in claim  2 , an outer edge of the bushing and an outer edge of the inner plate in a chain width direction overlap with each other in some regions. The inner link is thus reduced in weight, and has less irregularities in its contour, so that the inner link can be manufactured more easily. 
         [0016]    According to the invention as set forth in claim  3 , an outer edge of the bushing overlaps an outer edge of the inner plate in a chain width direction at least in a pair of front and back outer regions. Therefore, in addition to the reduction in the weight and burden in the manufacture of the inner link, the inner link can also be reduced in size in the chain height direction. 
         [0017]    According to the invention as set forth in claim  4 , the inner link further includes a reinforcement portion that extends from one of the pair of front and back bushings to the other one of the pair of front and back bushings on a side that does not mesh with a sprocket. The inner link can thus have enhanced strength without the possibility of inhibiting the meshing with the sprocket. 
         [0018]    According to the invention as set forth in claim  5 , the outer link is formed by two components, which are a first outer link part and a second outer link part that are each formed integrally, so that the number of components is further reduced, and the work burden and cost in the manufacture or assembling of the chain are reduced. Moreover, since the outer link has fewer portions where the pins are press-fitted to the outer plates, the outer link can have higher strength. 
         [0019]    According to the invention as set forth in claim  6 , the first outer link part and the second outer link part are formed in the same shape. As there are less types of components forming the chain, the work burden and cost in the manufacture or assembling of the chain are reduced. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a diagram for explaining a metal chain according to a first embodiment; 
           [0021]      FIG. 2  is a cross-sectional plan view showing a part of the metal chain according to the first embodiment; 
           [0022]      FIG. 3  is a diagram for explaining a metal chain according to a second embodiment; 
           [0023]      FIG. 4  is a cross-sectional plan view showing a part of the metal chain according to the second embodiment; 
           [0024]      FIG. 5  is a diagram for explaining an inner link according to the second embodiment; 
           [0025]      FIG. 6  is a diagram for explaining a metal chain according to a third embodiment; 
           [0026]      FIG. 7  is a partially cross-sectional plan view of the metal chain according to the third embodiment; 
           [0027]      FIG. 8  is a cross-sectional view of an inner link according to the third embodiment; 
           [0028]      FIG. 9  is a diagram for explaining an inner link according to a variation example of the third embodiment; 
           [0029]      FIG. 10  is a diagram for explaining an example of a failure in the forming of the inner link; 
           [0030]      FIG. 11  is a diagram for explaining a metal chain according to a fourth embodiment; 
           [0031]      FIG. 12  is a partially cross-sectional plan view of the metal chain according to the fourth embodiment; 
           [0032]      FIG. 13  is a diagram for explaining an outer link according to a variation example of the fourth embodiment; 
           [0033]      FIG. 14  is a diagram for explaining a metal chain according to a fifth embodiment; 
           [0034]      FIG. 15  is a partially cross-sectional plan view of the metal chain according to the fifth embodiment; and 
           [0035]      FIG. 16  is a diagram for explaining a conventional chain. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Examples 
       [0036]    A metal chain  100  according to a first embodiment of the present invention will be hereinafter described with reference to the drawings. 
         [0037]    The metal chain  100  of the first embodiment is configured as a timing chain incorporated in a timing system of a car engine, and includes a plurality of inner metal links  110  and a plurality of outer metal links  120 , as shown in  FIG. 1  or  FIG. 2 . These inner links  110  and outer links  120  are alternately connected to each other along the longitudinal direction of the chain by inserting pins  121  of the outer links  120  into bushings  111  of the inner links  110 . 
         [0038]    Each inner link  110  includes a pair of front and back bushings  111  for axially supporting pins  121 , and a pair of left and right inner plates  112  that connect the pair of front and back bushings  111  in the longitudinal direction of the chain. The inner link  110  is integrally formed, each as an independent component, by plastic working such as forging or pressing, or casting, or metal injection molding, or machining. The bushing  111  has a bushing hole, and the inner plate  112  has a plate hole of the same diameter as that of the bushing hole. The bushing  111  and the inner plate  112  are connected to each other such that their holes are concentric. 
         [0039]    Each outer link  120  includes a pair of front and back pins  121  and a pair of left and right outer plates  122  that connect the pair of front and back pins  121  in the longitudinal direction of the chain, these being formed as separate components. The pins  121  are fixed both ends thereof in pin holes of the outer plates  122  at by press-fitting or the like. 
         [0040]    Next, a metal chain  200  according to a second embodiment of the present invention will be described with reference to  FIG. 3  to  FIG. 5 . The second embodiment is basically the same as the previously described first embodiment except for some parts. Therefore, elements of the second embodiment that are identical to those of the first embodiment denoted by numerals beginning with “1” herein and in the drawings will be numbered the same but beginning with “2” instead of “1”, and will not be described again. 
         [0041]    First, the metal chain  200  of the second embodiment is different from that of the first embodiment in the size of the inner plate  212  of the inner link  210 . Namely, in the metal chain  200  of the second embodiment, as shown in  FIG. 5 , when the inner link  210  is divided into three regions—a pair of front and rear outer regions Ro and an inner region Ri—by imaginary lines L passing through centers C of the bushing holes  211   a  of the bushings  211  (plate holes  212   a  of the inner plates  212 ) and extending along a chain height direction, outer edges of the bushings  211  overlaps with, in a chain width direction, outer edges of the inner plates  212  in the pair of front and rear outer regions Ro. 
         [0042]    In this embodiment, as described above, the outer edges of the bushings  211  overlap with the outer edges of the inner plates  212  entirely in the outer regions Ro, but they may overlap with each other only partly in the outer regions Ro, or also in part of the inner region Ri. 
         [0043]    The outer edges of the inner plates  212  are straight in the inner region Ri as shown in  FIG. 5  in this embodiment, but they may be curved outward or inward in the inner region Ri. 
         [0044]    Next, a metal chain  300  according to a third embodiment of the present invention will be described with reference to  FIG. 6  to  FIG. 10 . The third embodiment is basically the same as the previously described second embodiment except for some parts. Therefore, elements of the third embodiment that are identical to those of the second embodiment denoted by numerals beginning with “2” herein and in the drawings will be numbered the same but beginning with “3” instead of “2”, and explanation thereof will be omitted except for constitutions exhibiting differences from those in the second embodiment. 
         [0045]    In the metal chain  300  of the third embodiment, as shown in  FIG. 6  or  FIG. 8 , the inner link  310  includes a total of two reinforcement portions  313  each extending from one bushing  311  toward the other bushing  311  on the side that does not mesh with a sprocket (not shown), more specifically on a radially outer side of a pitch circle P of the sprocket (not shown). 
         [0046]    As the reinforcement portions  313  are formed on a radially outer side of the pitch circle P of the sprocket (not shown), the reinforcement portions  313  do not inhibit meshing with the sprocket (not shown), so the reinforcement portions  313  may be formed in any shapes. For example, a reinforcement portion  313 ′ may be formed such as to connect one bushing  311  with the other bushing  311  as shown in  FIG. 9 . 
         [0047]    The metal chain  300  of the third embodiment thus formed not only has inner links  310  with higher strength enhanced by the reinforcement portions  313 , but also, since the inner link  310  has a different shape on the side that meshes with the sprocket from the side that does not mesh with the sprocket due to formation of the reinforcement portions  313 , the inner link  310  offers clear indication of its orientation when assembling the chain, with the reinforcement portions  313  serving as a distinguishing mark. This, in turn, allows easy establishment of positional accuracy between the bushing hole  311   a  and plate hole  312   a  of the inner link  310 , and an outer circumferential portion of the bushing  311  on the side that meshes with the sprocket. 
         [0048]    Namely, with reference to  FIG. 10  that shows an example of a failure in the forming of the inner link  210  according to the second embodiment, when the inner link  210  is molded with the use of an upper mold, a lower mold, and a core for forming a hole (bushing hole  211   a  and plate hole  212   a ), sometimes the inner link  210  may be formed to have an upper side U and a lower side D displaced from each other in the chain height direction because of a misalignment between the upper mold and lower mold during the molding of the inner link  210 . If the upper side U and the lower side D in the chain height direction of the inner link  210  are symmetrical as in the second embodiment, it is not clear which of the upper side U or the lower side D in the chain height direction of the inner link  210  is the side that is to mesh with the sprocket. Therefore, there is a possibility that the displaced side (upper side U or lower side D in the chain height direction of the inner link  210 ) where the bushing hole  211   a  and the plate hole  212   a  are misaligned may be mistaken as the side that is to mesh with the sprocket. In this regard, with the metal chain  300  of the third embodiment, the side that is to mesh with the sprocket can be distinguished easily by the reinforcement portions  313  of the inner link  310  as a mark. Therefore, by molding the inner link with a precise positional relationship between the outer circumferential portion of the bushing  311  on the side that meshes with the sprocket and the bushing hole  311   a /plate hole  312   a,  positional accuracy between the bushing hole  311   a /plate hole  312   a  and the outer circumferential portion of the bushing  311  on the side that meshes with the sprocket can readily be established. 
         [0049]    Next, a metal chain  400  according to a fourth embodiment of the present invention will be described with reference to  FIG. 11  and  FIG. 12 . The fourth embodiment is basically the same as the previously described second embodiment except for some parts. Therefore, elements of the fourth embodiment that are identical to those of the second embodiment denoted by numerals beginning with “2” herein and in the drawings will be numbered the same but beginning with “4” instead of “2”, and explanation thereof will be omitted expect for constitutions exhibiting differences from those of the second embodiment. 
         [0050]    In the metal chain  400  of the fourth embodiment, as shown in  FIG. 11  or  FIG. 12 , the outer link  420  is formed by two components, a first outer link part  420 A and a second outer link part  420 B, each integrally formed by plastic working such as forging or pressing, or casting, or metal injection molding, or machining. 
         [0051]    The outer link parts  420 A and  420 B each have one outer plate  422 A or  422 B and one pin  421 A or  421 B, and formed in an identical shape. 
         [0052]    The outer link parts  420 A and  420 B are not limited to the specific form described above. For example, as shown in  FIG. 13 , an outer link  420 ′ may be configured to have a first outer link part  420 A′ having one outer plate  422 A′ and two pins  421 A′, and the second outer link part  420 B′ having one outer plate  422 B′. 
         [0053]    As one alternative, as shown in  FIG. 14  and  FIG. 15 , a metal chain  500  may be formed by combining outer links  520  configured similarly to that of the fourth embodiment and inner links  510  configured similarly to that of the third embodiment. 
         [0054]    While the metal chain was described as a timing chain of a car engine in the embodiments above, the purpose of use of the metal chain of the present invention is not limited to this application, and may be used as a transmission chain or a conveyor chain. 
         [0055]    While the chains in the embodiments above have one inner link in the chain width direction, they may have a plurality of inner links arranged in the chain width direction. 
         [0056]    Various embodiments and variation examples shown above may be freely combined to form other metal chains. 
         [0057]    Various parts of the metal chain may be made of any of ferrous metals such as iron, steel and the like, or non-ferrous metals such as aluminum, copper, and the like.