Patent Publication Number: US-2005130779-A1

Title: Chain with a mark

Description:
REFERENCE TO RELATED APPLICATIONS  
      This application claims an invention, which was disclosed in Japanese Application No. 2003-419107, filed Dec. 17, 2003, entitled “CHAIN WITH A MARK” and in Japanese Application No. 2003-411727, filed Dec. 10, 2003, entitled “CHAIN WITH A MARK.” The benefit under 35 USC §119(a)-(d) or §365(b) is hereby claimed, and the aforementioned applications are hereby incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a timing chain wrapped around a plurality of sprockets that require synchronistic operation in an internal combustion engine and a random chain having at least two kinds of link plates that are arranged in a random pattern. More particularly, the present invention relates to a chain where the position that should correspond to the timing mark of the sprocket or the position that is a starting point of a random pattern is shown by a guide plate.  
      2. Description of Related Art  
      In a timing chain used for cam timing in an internal combustion engine, a predetermined timing mark is provided to drive a plurality of sprockets in a synchronistic manner. The timing mark is provided on the timing chain as well as on the sprocket. Synchronistic operation of a plurality of sprockets is achieved by conforming the timing mark of the timing chain to the timing mark of the sprocket.  
      A method of providing a timing mark on a timing chain by coloring an outside plate by applying a baking finish or plating to distinguish the outside plate from the other remaining outside plates is known in the art, as shown in Japanese patent application laid-open publication No. 9-242829. Since additional process such as applying a baking finish or plating is required in the manufacturing process of timing chains. A special facility for such a process is necessary, thus increasing manufacturing cost.  
      Japanese patent application laid-open publication No. 2003-240061 shows a chain where a link plate acts as a timing plate having a notch formed on the engaging side with the sprocket provided at a position corresponding to the timing mark of the sprocket in lieu of a guide plate.  
      In this case, since the link plate acts as a timing mark, additional processes such as baking finish or plating are not required, however, because the link plate has a notch formed on the engaging side with the sprocket is used as a timing plate, there is no guiding portion for the sprocket where the timing plate is present. Therefore, a chain may disengage from the sprocket. Furthermore, the tensile strength of the guide rows having the guide plate differs from the tensile strength of guide rows having a link plate in lieu of the guide plate. Therefore, after pre-stress operation, in which the excessive tensile load is applied, the chain pitches will vary.  
      The present invention is directed to providing a marked chain that can not only reduce manufacturing cost but can also prevent disengagement of the chain from the sprocket and maintain the strength of the chain uniformly.  
     SUMMARY OF THE INVENTION  
      A marked chain according to the present invention is includes of a plurality of link plates for engagement with a sprocket and a plurality of guide plates disposed on opposite sides of the chain to guide the chain on the sprocket in the width direction during engagement with the sprocket. At a marked position, a guide plate is provided that has a backside shape different from those of the other remaining guide plates.  
      According to the present invention, the guide plate acting as a mark only has a backside shape different from those of the other remaining guide plates. The guide plate with the mark also provides a guiding function of a chain relative to the sprocket in the same manner as the other remaining guide plates. Thereby, the chain is securely guided on the sprocket and prevented from being disengaged from the sprocket. Moreover, no baking finish or plating of a guide plate is required, thereby decreasing manufacturing cost.  
      The marked chain may be a timing chain for driving a plurality of sprockets in a synchronistic manner. A guide plate is provided at a marked position corresponding to a timing mark of a sprocket a guide plate (or a timing plate) having a different backside shape from those of the other remaining guide plates.  
      Alternatively, the marked chain is a random chain where at least two types of link plates having different engagement pitches are arranged in a random pattern in the longitudinal direction of the chain. At a position corresponding to the starting position of the random pattern is a guide plate having a different backside shape from those of the other remaining guide plates.  
      The guide plate disposed at the marked position may have a crotch portion on the backside. Alternatively, the guide plate disposed at the marked position may have a flat backside surface and the other remaining guide plates may have crotch portions on their backsides.  
      In a third embodiment of the present invention, the guide plate disposed at the marked position may have a flat backside surface and have not been subject to pre-stressing. The other remaining guide plates may have crotch portions on the backsides thereof and have been pre-stressed.  
      In this case, the guide plate having the flat backside surface has a greater rigidity than the other remaining guide plates that have not been pre-stressed. The other remaining guide plates having crotch portions with relatively low rigidities, that have been pre-stressed, equalizes the yield loads of all of the guide plates with each other, thus making the strength of the entire chain uniform.  
      In the manufacturing process of a marked chain of the present invention, first, pre-stressing of a chain with the other remaining guide plates interlaced is conducted, and thereafter, the guide plate is installed at the marked position of the chain.  
      In a fourth embodiment, each of the guide plates has a generally flat surface on one side of the chain across the pin aperture centerline and a crotch portion on the other side of the chain across from the pin aperture centerline. At a marked position, an upside-down guide plate is provided to form a different backside shape from the other guide plates disposed adjacent to the upside-down guide plate.  
      In this case, the guide plate disposed at the marked position is the same kind of plate as the other guide plates, thereby equalizing the tensile strength of the guide rows and maintaining a uniform tensile strength of the whole chain. Also, since the guide plate does not require a baking finish or plating, manufacturing cost is reduced. Moreover, because all of the guide plates are the same, just placed in a different orientation, the manufacturing cost is further reduced.  
      In a fifth embodiment, the distance between the pin aperture centerline of the guide plate and the outermost edge portion of either the backside edge portion or the opposite edge portion of the guide plate is equal to or smaller than the distance between the pin aperture centerline of the link plates forming the chain and the backside surface.  
      In this case, even when a guide plate is assembled into the chain upside down, the outermost edge portion of the guide plate on the backside do not protrude outwardly from the backside of the link plates, which thereby prevents local wear of the tensioner arm or chain guide contacting the backside of the chain during operation.  
      Alternatively, the distance between the pin aperture centerline of the guide plate and the backside edge portion of the guide plate is equal to the distance between the pin aperture centerline of the guide plate and the opposite edge portion of the guide plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       FIG. 1  is a schematic view of an engine timing system employing a timing chain of the present invention.  
       FIG. 2  is a front elevational view of a portion of a timing chain according to a first embodiment of the present invention.  
       FIG. 3  is a front elevational view of a portion of a timing chain according to a second embodiment of the present invention.  
       FIG. 4  is a front elevational view of a portion of a timing chain according to a third embodiment of the present invention.  
       FIG. 5  is a schematic view of an engine timing system employing a timing chain according to a fourth embodiment of the present invention.  
       FIG. 6  is a front elevational view of a portion of a timing chain according to a fifth embodiment of the present invention.  
       FIG. 7  is a front elevational enlarged view of a timing plate according to a sixth embodiment. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIG. 1  shows an engine timing system employing a timing chain as a marked chain of the present invention. As shown in  FIG. 1 , the timing system  1  is constructed from a crank sprocket  3  mounted on a crankshaft  2 , cam sprockets  6 ,  7  mounted on camshafts  4 ,  5 , respectively, and a timing chain  10  wrapped around the sprockets  3 ,  6  and  7 .  
      A timing mark  30  is marked on the crank sprocket  3  and timing marks  60 ,  70  on the cam sprockets  6 ,  7 , respectively. The timing chain  10  has a guide plate  11  and a plurality of guide plates  12  on the outermost sides thereof. The guide plate  11  is disposed at a position corresponding to the timing mark  60  of the cam sprocket  6  and functions as a timing mark of the chain. A guide plate similar to the guide plate  11  may be disposed at positions corresponding to the other timing marks  30 ,  70 .  
       FIG. 2  shows a portion of the timing chain  10 , which represents a first embodiment of the present invention. As shown in  FIG. 2 , the timing chain  10  includes of a plurality of rows of interleaved link plates  15  each having a pair of pin apertures  16  and teeth  17  and pivotably connected to each other by connecting pins  18  inserted into the pin apertures  16 . The timing chain  1  also has guide plates  11 ,  12  disposed outside the outermost link plates  15  and fixedly connected to the ends of the connecting pins  18 .  
      Each of the guide plates  11 ,  12  has a flat portion  11 A,  12 A, respectively, on the engagement side with a sprocket. These flat portions  11 A,  12 A are disposed on opposite sides of the sprocket during engagement with the sprocket and maintain the chain centrally on the sprocket teeth.  
      The guide plate  11  has a crotch portion  11 C on the backside of the plate opposite the engaging side. The bottom portion of the crotch  11 C extends below the upper edges of the openings of the pin apertures  16 . The guide plate  12  is of a general trapezoid shape and includes a flat portion  12 B on the backside.  
      In the timing system  1  incorporating the above-mentioned timing chain  10 , the guide plate  11  or timing plate acting as a timing mark is the same as the other guide plates  12 , except for the backside shape, which provides a guiding function of the chain  10  relative to the sprocket in the same manner as the other guide plates  12  during engagement with the sprocket. Thereby, the chain  10  can be securely guided on the sprocket and disengagement of the chain  10  from the sprocket is securely prevented. Also, since the guide plate  11  does not require a baking finish or plating, manufacturing cost is reduced.  
       FIG. 3  shows a timing chain according to a second embodiment of the present invention. In  FIG. 3 , like reference numbers indicate identical or functionally similar elements. The second embodiment differs from the first embodiment in that the backside shapes of the guide plate  11 ′ or timing plate and the other guide plates  12 ′ are reversed.  
      That is, in this case, the guide plate  11 ′ has a trapezoidal shape with a flat portion  11 ′B on the backside. Each of the other guide plates  12 ′ has a crotch portion  12 ′C on the backside.  
      Similar to the first embodiment, the guide plate  11 ′ or timing plate acts as a timing mark in the same as way as the other guide plate  12 ′, except the backside shape provides a guiding function of the chain  10 ′ relative to the sprocket in the same manner as the other guide plates  12 ′ during engagement with the sprocket. Thereby, the chain  10 ′ is securely guided on the sprocket and disengagement of the chain  10 ′ from the sprocket is securely prevented. Also, since the guide plate  11 ′ does not require a baking finish or plating, manufacturing cost is reduced.  
       FIG. 4  shows a timing chain according to a third embodiment of the present invention. In  FIG. 4 , like reference numbers indicate identical or functionally similar elements. As with the second embodiment, the third embodiment also differs from the first embodiment in that the backside shapes of the guide plate  11 ″ or timing plate and the other guide plates  12 ″ are reversed.  
      That is, the guide plate  11 ″ has a trapezoidal shape with a flat portion  11 ″B on the backside. Each of the other guide plates  12 ″ has a crotch portion  12 ″C on the backside.  
      Moreover, in the third embodiment, the guide plate  12 ″ has been pre-stressed but the guide plate  11 ″ has not been pre-stressed. That is, in this case, during assembly of the chain  10 ″, a pre-stress load or excessive tensile load is applied to the chain  10 ″ with the guide plates  12 ″ installed and the guide plate  11 ″ not installed. After pre-stress operation, the guide plate  11 ″ is installed into the chain  10 ″ to complete the entire chain.  
      According to the third embodiment, the guide plate  11 ″ is of relatively high rigidity without a crotch portion on the backside even though the plate has not been pre-stressed, whereas the other guide plate  12 ″ is of relatively low rigidity with a crotch portion on the backside that has been pre-stressed and subject to a residual compressive stress. As a result, the yield load of the guide plate  11 ″ or the timing plate can be made equal to that of the other guide plate  12 ″. In such a manner, the strength of the entire chain may be made uniform.  
      In the first and second embodiments, the guide plate is the timing plate, and the other guide plates have both been pre-stressed and subjected to a residual compressive stress, however in this case, the yield load of each of the guide plates differs from each other due to the differences in the backside shape of each of the guide plates.  
       FIG. 5  shows an engine timing system of another embodiment employing a timing chain as a marked chain of the present invention. As shown in  FIG. 5 , the timing system  101  is constructed from a crank sprocket  103  mounted on a crankshaft  102 , cam sprockets  106 ,  107  mounted on camshafts  104 ,  105 , respectively, and a timing chain  110  wrapped around the sprockets  103 ,  106  and  107 .  
      A timing mark  130  is marked on the crank sprocket  103  and timing marks  160 ,  170  on the cam sprockets  106 ,  107 , respectively. The timing chain  1   10  has a guide plate  111  and a plurality of guide plates  112  on the outermost sides thereof. The guide plate  111  is disposed at a position corresponding to the timing mark  160  of the cam sprocket  106  and functions as a timing mark of the chain. A guide plate similar to the guide plate  111  may be disposed at positions corresponding to the other timing marks  130 ,  170 .  
       FIG. 6  shows a portion of the timing chain  1   10 , which represents a fifth embodiment of the present invention. As shown in  FIG. 6 , the timing chain  110  includes of a plurality of rows of interleaved link plates  115  each having a pair of pin apertures  116  and teeth  117  and pivotably connected to each other by connecting pins  118  inserted into the pin apertures  116 . The timing chain  101  also has guide plates  111 ,  111 ′ disposed outside the outermost link plates  115  and fixedly connected to the ends of the connecting pins  118 .  
      The guide plate  111  has a crotch portion  111 C on the engaging side and a flat portion  111 A on the backside opposite the engaging side. The bottom portion of the crotch  111 C of the guide plate  111  extends below the bottom portion of the crotch portion of the link plate  115 . Thereby, as shown in  FIG. 7 , a hatched portion g of the crotch portion  111 C has a guiding function to locate the chain  110  centrally on the sprocket during engagement with the sprocket.  
      The guide plate  111 ′ is the same plate as the guide plate  111  but placed upside down. That is, the guide plate  111 ′ has a flat portion  111 ′A on the engaging side and a crotch portion  111 ′C on the backside opposite the engaging side. The flat portion  111 ′A is disposed below the crotch portion  111 C of the guide plate  111  to display a guiding function of the chain  110  during engagement with the sprocket.  
      As shown in  FIG. 7 , the length or distance extending from the pin aperture centerline C of the guide plate  111  to the flat surface  111 A on the backside is h. The length extending from the pin aperture centerline C to the outer edge portion on the engaging side is also h. The lengths or distances h are the same. On the other hand, the length extending from the pin aperture centerline of the link plate  115  to the backside surface is h 0 , and the distance h 0  is greater than or equals the distance h.  
      In the timing system  1  incorporating the above-mentioned timing chain  110 , the guide plate disposed at a position corresponding to the timing mark of the sprocket is the same type of plate as the guide plate placed upside down. By using the same guide plates in different positions, the tensile strength of the guide rows and of the whole chain is equalized and uniformly maintained. Also, since the guide plate does not require a baking finish or plating, the manufacturing cost is reduced.  
      Moreover, in this case, when the guide plate is placed upside down, the outermost edge portion of the guide plate on the backside will not protrude outwardly from the backside surface of the link plate  115 , thereby preventing the backside surface of the chain from locally contacting the tensioner arm or chain guide during operation. In such a way, local wear to the tensioner arm or chain guide is prevented.  
      In the above-mentioned embodiment, flat, generally U-shaped crotch portions  111 A,  111 ′C were shown, but the present invention can be applied to various shapes including generally V-shape, round shape, or the like.  
      Also, the guide plate  111 ′ may be employed as a timing plate. That is, in this case, in  FIG. 6 , the positions of the guide plates  111 ,  111 ′ are exchanged.  
      Similar to the above-mentioned embodiment, all the guide plates have the same shape, thereby equalizing the tensile strength of the entire guide rows which uniformly maintains the tensile strength of the entire chain.  
      In the example of the above-mentioned embodiment, both of the lengths extending from the pin aperture centerline C of the guide plate to the backside surface and the engaging side surface are the same h, but the backside surface to the pin aperture centerline C or the engaging surface of the guide plate to the pin aperture centerline C may be shorter than the other.  
      In the above-mentioned first through sixth embodiments, a timing chain was shown as an example of the marked chain of the present invention. The present invention may also be applied to a random chain, where at least two kinds of link plates with different engagement pitches are arranged in a random pattern along the length of the chain. Here, the engagement pitch means a distance between the corresponding flank surfaces of the adjacent link plates along the engagement pitch line.  
      In this case, a guide plate (e.g. guide plate  11 ,  11 ′,  11 ″,  111 ,  111 ′, in each of the above-mentioned embodiments) having a different backside shape from the other guide plates may be disposed at a starting position of the random pattern.  
      Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.