Abstract:
A chain guide, including a chain guide member and a guide holder, in which deformation and/or scarring of the guide holder can be controlled, and which is easy to assemble and disassemble, is described. The position of a front end of the guide holder is brought in contact with a flange provided at the front end of the chain guide member. Left and right side surfaces of the chain guide member are formed on the backside of the flange. The leading edge of the front end of the guide holder abuts and confronts the left and right side surface of the backside of the flange of the chain guide member so that a chain entering the chain guide contacts the chain guide member rather than the guide holder. A method of manufacturing the guide holder is presented.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present invention claims priority under 35 USC 119 based on Japanese patent application No. 2003-307343, filed Aug. 29, 2003. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a chain guide for a motorcycle, which is useful for preventing a drive chain from coming off a sprocket on the motorcycle&#39;s rear wheel due to a swinging motion of a rear swing arm. 
     2. Description of the Background Art 
     Certain chain guides for motorcycle drive chains have been known. For example, a chain guide has been provided at the rear portion of the a motorcycle&#39;s rear swing arm, for preventing a chain from coming off a sprocket due to vibrations of the rear swing arm or the like under harsh traveling conditions. There is an increased risk of the chain coming off the sprocket where the vertical amplitude of vibrations of the rear swing arm becomes significantly large. 
     However, during travel, the known chain guide is adapted to be contacted by the moving chain at the position of installation thereof. Therefore, abrasion of the chain guide is a problem with the known designs. 
     A chain guide which is formed of plastic resin, with an attached guide holder to increase the strength and the rigidity thereof, is proposed in Japanese published Patent Document JP-UM-B-5-20637. 
       FIGS. 7 and 8  of the drawings in the present document are reproductions of FIG. 4 and FIG. 2, respectively, from Japanese published Patent Document JP-UM-B-5-20637. However, components of  FIGS. 7 and 8  hereof have been renumbered from the original, and the names of the components are partly changed. 
     In the prior art chain guide  100  from Japanese published Patent Document JP-UM-B-5-20637, as illustrated in  FIGS. 7-8 , the chain guide  100  includes a guide holder  101  formed of a metal such as aluminum, and having a substantially U-shape in cross-section. The chain guide  100  also includes a chain guide member  102  formed of plastic resin or the like for fitting inside of the guide holder  101 . The chain guide  100  is attached to the lower rear surface  107  of the rear swing arm  106  via a mounting stay  108 . 
     During operation of the motorcycle, the chain  109  is adapted to be contacted by the moving chain guide member  102 . When these components come into contact many times, abrasion of the chain guide member  102  results. At a chain-introducing portion  105  of the chain guide  100 , the chain guide member  102  is subjected to a large amount of abrasion. 
     Once the chain guide member has become abraded, since the chain guide member  102  and the guide holder  101  are oriented flush with each other on the side surface of the introducing portion, the chain  109  may come into contact with the guide holder  101 , in association with a swinging motion of the rear swing arm  106 . When durability is considered, it would be best to avoid interaction between the guide holder  101  and the chain  109 , since these components are both formed of metal. When it is found that these metal components come into contact after a certain amount of usage, replacement of the device with a larger chain guide, or increased costs are likely. 
     Also, when the guide holder  101  becomes s deformed or scarred due to contact or the like between the guide holder and the chain, it takes time for replacement thereof, and during this time, the vehicle becomes temporarily unusable. In the case of off-road motorcycle racing, for example, it may affect the result of the race. Therefore, easy assembly and disassembly of the guide holder are desired. 
     Although the known motorcycle chain guides are useful for their intended purposes, there is still a need for an improved chain guide, designed to minimize contact between a guide holder and a motorcycle chain during use. It would be advantageous if such a chain guide were easy to maintain and service. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a chain guide including a guide holder in which deformation and scarring of the guide holder is minimized by design. 
     It is another object of the present invention to provide a chain guide which can be assembled and disassembled easily. 
     The present invention, according to a first aspect hereof, provides a chain guide including a chain guide member, formed of tough, durable material, where the chain guide member is designed to come into contact with a moving chain during use. The chain guide hereof also includes a guide holder for supportively holding the chain guide member, wherein the guide holder is mountable to the swing arm. In the chain guide according to the first aspect hereof, an enlarged flange is provided at a front end of the chain guide member, and a cutout portion is formed in a front end portion of the guide holder. In use, the front end portion of the guide holder is retained behind the chain guide member by the flange at the front of the chain guide member. 
     The flange is provided at the front end of the chain guide member where the chain is introduced, and the front end portion of the guide holder is brought in contact with the flange. 
     The flange at the front end of the chain guide member is adapted to shield the front end of the guide holder from contacting the chain. Accordingly, the chain is adapted to be contacted by the moving chain guide member, and does not come into direct contact with the front end of the guide holder. In other words, the chain guide member absorbs the impact generated by contact of the chain. 
     During off-road traveling on rough, uneven ground, interference between the guide holder and the surface of the ground may occur. (In the prior art, since the guide holder and the surface of the ground could potentially interfere directly with each other, scarring and/or deformation of the guide holder could occur.) According to the first aspect of the present invention, in a situation where the chain guide contacts the ground surface, it will be the non-metal chain guide member which makes such contact, since the front end of the chain guide is defined by the chain guide member, and therefore, scarring and/or deformation of the guide holder is minimized or avoided. 
     Consequently, a lightweight and compact chain and guide holder can be formed, and in addition, occurrence of scarring and/or deformation of the guide holder due to contact with the chain can be reduced or eliminated. Furthermore, since the occurrence of scarring on the guide holder is reduced, frequency of maintenance such as repair and/or replacement of the guide holder may be reduced. 
     The present invention, according to a second embodiment hereof, is characterized in that the guide holder is formed such that the lower ends of the left and right walls thereof bend inwardly and are connected at the bottom, so as to be formed into a modified trough having a U-shape as viewed in cross-section, with the left and right walls tapered downwardly. 
     Since the guide holder is formed substantially into the cross-sectional U-shape with the left and right walls tapered downwardly, the possibility of reception of impact from below or from sides by, for example, stones or obstacles, may be reduced. As a consequence, the possibility of deformation and breakage of the guide holder or of the mounting stay may be reduced. 
     The present invention, according to a third embodiment hereof, is further characterized in that the guide holder is formed from an extruded tubular member made of an aluminum alloy. In other words, the guide holder can be formed by cutting and machining only, and thus a pressing process is not necessary. Since an extruded member of an aluminum alloy is used, the portion which requires machining is small, and simultaneously, dimensional accuracy is achieved, which is higher than the accuracy which can be obtained by stamping or press processing. 
     Consequently, the chain guide member can be positioned accurately with respect to the guide holder and assembled easily. 
     By using the extruded member of aluminum alloy, required processes are cutting and machining only, and many processes including heat processing or pressing, as in the related art, are not necessary. Since a die for stamping or press processing is not necessary, it is advantageous in terms of cost, particularly when manufacturing few components. 
     The present invention, according to a fourth embodiment hereof, is characterized in that the guide holder is formed in a modified trough shape with a substantially U-shaped cross-section, by dividing a hollow extruded tubular member, having a substantially rectangular cross-sectional shape, into two parts. 
     Since the guide holder is obtained by dividing a hollow extruded tubular member of substantially rectangular cross-sectional shape into two parts, the cross-sectional shape, in particular, the dimensional accuracy in the direction of width of the extruded tubular member can be utilized as is. As a result, a predetermined dimensional accuracy of the guide holder can be easily and reliably secured. 
     Also, since the guide holder is formed by using an extruded tubular member of substantially rectangular cross-sectional shape, the packed state for transportation is stable in comparison with material of irregular cross-sectional shape, and thus the possibility of collapse of cargo piles can be reduced. 
     As a further consequence of the guide holder shape, the chain guide member can be positioned accurately and assembled easily with respect to the guide holder. 
     The present invention, according to a fifth embodiment hereof, is characterized in that the left and right walls and the bottom portion extending between these walls of guide holder are configured in such a manner that the bottom portion is thinner than either of the left and right walls. 
     Since the guide holder is formed from the extruded tubular member, the bottom portion can be made thinner than either of the left and right walls. By forming the bottom portion of the guide holder to be thinner than either of the left and right walls, which corresponds to the stay mounting portion, the strength of the stay mounting portion is maintained, while reducing the weight of the guide holder. 
     The present invention, according to a sixth embodiment hereof, provides a chain guide including a chain guide member which is adapted to be contacted by the moving chain, and a guide holder for holding the chain guide member. When installed on a vehicle, the guide holder is mounted to the swing arm. The sixth embodiment of the chain guide hereof is characterized in that the guide holder is formed in a modified trough shape with a substantially U-shaped cross-section, by dividing an extruded tubular member of substantially rectangular cross-sectional shape into two parts. 
     Since the guide holder is obtained by dividing an extruded tubular member having a substantially rectangular cross-sectional shape into two parts, the cross-sectional shape, in particular, the dimensional accuracy in the direction of width of the extruded member can be utilized as is, and thus a predetermined dimensional accuracy required by the guide holder can be secured easily and reliably. 
     Also, since the guide holder is formed from an extruded tubular member of substantially rectangular cross-sectional shape, the packed state for transportation is stable in comparison with material of irregular cross-sectional shape, and thus the possibility of collapse of cargo piles can be reduced. 
     As a consequence, the chain guide member can be positioned accurately and assembled easily with respect to the guide holder. 
     The present invention, according to a seventh embodiment hereof, is characterized in that the left and right walls and the bottom portion connecting the lower ends of these walls, constituting the guide holder, are formed in such a manner that the bottom portion is thinner than either of the left and right walls. 
     Since the guide holder is formed from the extruded member, the bottom portion can be easily made thinner than either of the left and right walls. By forming the bottom portion of the guide holder to be thinner than either of the left and right walls, which corresponds to the stay mounting portion, the strength of the stay mounting portion is maintained, while reducing the overall weight of the guide holder. 
     According to the first aspect of the present invention, since scarring of the guide holder due to contact with the chain is reduced or eliminated, frequency of maintenance of the guide holder can advantageously be reduced. 
     According to the second aspect of the present invention, since the guide holder is formed in a modified trough shape with a substantially U-shaped cross-section in which the left and right walls are tapered downward, deformation and damages of the guide holder or the mounting stay can be advantageously reduced. 
     According to the third aspect of the present invention, since an extruded member of aluminum alloy is used, the amount of machining may be less than when a method of cutting out a guide holder from a plate member is employed. Since machining is employed to form the guide holder, the guide holder is advantageously obtained with a high degree of accuracy. 
     According to the fourth aspect of the present invention, since the predetermined dimensional accuracy of the guide holder can be secured easily and reliably by forming it in a modified trough shape with a substantially U-shaped cross-section by dividing a hollow extruded tubular member of substantially rectangular cross-sectional shape into two parts, the chain guide member can advantageously be positioned accurately in the guide holder, and the chain guide can be assembled easily. 
     According to the fifth aspect of the present invention, since the bottom portion of the guide holder is formed to be thinner than either of the left and right walls, the weight of the guide holder can advantageously be reduced while maintaining the strength of the side walls. 
     According to the sixth aspect of the present invention, since the predetermined dimensional accuracy of the guide holder can be secured easily and reliably by forming it in a modified trough shape with a substantially U-shaped cross-section as a result of dividing the hollow, extruded tubular member of substantially rectangular cross-sectional shape into two parts, the chain guide member can be positioned accurately and assembled easily with respect to the guide holder. 
     According to the seventh aspect of the present invention, since the bottom portion of the guide holder is formed to be thinner than either of the left and right walls, the weight of the guide holder can advantageously be reduced, while maintaining the strength of the side walls. 
     For a more complete understanding of the present invention, the reader is referred to the following detailed description section, which should be read in conjunction with the accompanying drawings. Throughout the following detailed description and in the drawings, like numbers refer to like parts. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of an off-road type motorcycle to which the present invention is applied. 
         FIG. 2  is an enlarged side detail view of a portion designated within a circle  2  of FIG.  1 , illustrating the inventive chain guide, including a chain guide member and guide holder, mounted to a swing arm of an off-road type motorcycle. 
         FIG. 3  is a cross-sectional view of the assembled chain guide, taken along the line  3 - 3  in  FIG. 2 . 
         FIG. 4  is an exploded perspective view of a chain guide according to the present invention. 
         FIG. 5  is a cross-sectional view of the assembled chain guide, taken along the line  5 - 5  in  FIG. 2 . 
         FIG. 6  illustrates a series of manufacturing steps for forming a guide holder according to a method of the present invention. 
         FIG. 7  is an exploded view drawing from  FIG. 4  in Patent Document JP-UM-B-5-20637 illustrating a prior art chain guide, including a chain guide member and guide holder. 
         FIG. 8  is an assembled view drawing from  FIG. 2  in Patent Document JP-UM-B-5-20637 illustrating a prior art chain guide, including a chain guide member and guide holder, mounted to a swing arm. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the attached drawings, a number of presently contemplated embodiments hereof will be described, including the best mode for carrying out the invention. 
       FIG. 1  is a side view of an off-road type motorcycle to which the present invention is applied. The motorcycle  10  includes a main frame  11 , a front fork  12  steerably attached at the front of the main frame  11 , and a front wheel  13  attached to the lower end of the front fork  12 . The motorcycle  10  also includes an engine  14  suspended from the main frame  11 , and an exhaust pipe  16  extending rearwardly from the engine, for flowing exhaust gas discharged from the engine  14  to a muffler  15 . The motorcycle  10  further includes a fuel tank  17  and a rider&#39;s seat  18  disposed on the main frame  11  from the front to the rear. The motorcycle  10  also includes a swing arm  21  pivotally attached to the rear of the main frame  11  via a rear cushion  19  so as to be capable of a reciprocating vertical movement, and a rear wheel  22  attached to the back end of the swing arm  21 . 
     A power transmission system is provided for moving the motorcycle  10 , and mainly includes the engine  14 , a transmission  23  provided below the engine  14 , a drive gear  25  attached to an output shaft  24  of the transmission  23 , a sprocket  26  attached to the rear wheel  22 , and a chain  27 . The chain  27  is an endless chain loop wound around the sprocket  26  and the drive gear  25 . 
     A chain guide  30  according to the present invention is also provided on the motorcycle  10 , attached to the lower surface of the rear portion of the swing arm  21 , so as to be capable of vertical movement via a mounting stay  28 . 
     In the drawings, reference numeral  31  designates a chain cover, reference numeral  32  designates a front fender, and reference numeral  33  designates a handlebar. 
     It will be apparent from a review of  FIG. 1  that during forward movement of the motorcycle  10 , the rear wheel  22  will rotate in a counter-clockwise direction as viewed in the drawing. Accordingly, due to this counterclockwise direction of wheel rotation, the drive gear  25  and sprocket  26  will each also move in the counter-clockwise direction during forward movement, since the sprocket  26  is affixed to the wheel  22 , and the drive gear  25  is connected to the sprocket via the chain  27 . Therefore, due to both sprockets moving in this way, it is clear that the lower portion of the chain  27  will move in a rearward direction during normal vehicle operation under power, as shown by the arrow A in  FIG. 2 . The chain guide  30  surrounds an area at the lower portion of the chain  27 , which is wound around the sprocket  26 . Since the lower part of the chain  27  moves rearwardly, and the chain guide surrounds a lower part of the chain, it will be seen that the front end of the chain guide  30  defines a chain-receiving end where the chain first enters the chain guide. The chain guide  30  prevents the chain  27  from coming off the sprocket  26  during vertical movement of the swing arm  21 . The chain guide  30  also controls deflection of the chain  27 , so that it does not exceed a predetermined extent. In other words, its function is to guide the chain  27 , and prevent it from coming off the sprocket  26 , by controlling deflection of the chain  27 . 
       FIG. 2  is an enlarged detail view of the chain guide hereof, taken in a portion indicated inside of a circle  2  in  FIG. 1 . The chain guide  30  includes a chain guide member  34  formed of resilient, abrasion-resistant material such as a polyurethane elastomer. The chain guide  30  also includes a guide holder  35 , formed of high-strength aluminum alloy. The guide holder  35  substantially surrounds and encloses the chain guide member  34 , as shown. Mounting stays  28   a ,  28   b  are mounted to the lower surface  36  of the swing arm, and the chain guide member  34  and the guide holder  35  are each respectively fixed to the stays  28   a ,  28   b  via bolts  38  and nuts  39  ( FIG. 3 ). 
     The chain guide member  34  includes a medial portion  34   m  having a first width extending between opposed side walls  46 L,  46 R thereof. An enlarged flange  41  is provided at the front end of the chain guide member  34  forward of the medial portion  34   m , and the flange  41  is disposed so as to protrude forwardly from the front end  42  of the guide holder  35 . As seen in  FIGS. 4 and 5 , the flange  41  is wider than the medial portion  34   m  of the chain guide member on both sides thereof. Due to its width, the flange  41  functions as a stop member to limit rearward movement of the chain guide member  34  in the guide holder  35 . It will be understood that, due to its increased width and location in front of the guide holder  35 , the flange  42  shields the front end of the guide holder  35 , and tends to prevent or limit contact between the chain  27  and the guide holder  35  during vehicle operation. 
       FIG. 3  is a cross-sectional view of the chain guide hereof taken along the line  3 - 3  in  FIG. 2 . As seen in  FIGS. 2-3 , the chain guide  30  includes the chain guide member  34  attached to the mounting stay  28   a , which is mounted to the lower surface  36  of the swing arm via the bolts  38  and the nuts  39 . The chain guide  30  also includes the guide holder  35  attached to the mounting stay  28   a  via the bolt  38  and nut  39  while fitting around the outer surface  43 L,  43 R of the chain guide member  34 . In the depicted embodiment, a collar  44  is fitted into the center of the chain guide member  34  via the bolt  38  and the nut  39 . 
     The drawing also shows that the chain  27  is passed through an opening  45  formed at the center of the chain guide member  34 . 
     The guide holder  35  is configured with a substantially U-shaped cross-section, as shown, wherein the lower ends of right and left walls  46 L,  46 R bend inwardly and are connected at the bottom portion  47 , so that the left and right walls are downwardly tapered. 
     Since the guide holder  35  is configured with the left and right walls  46 L,  46 R tapered downwardly, the possibility of reception of impact from below or from the sides by, for example, stones or obstacles, may be reduced. As a consequence, the possibility of deformation and scarring of the guide holder  35  may be reduced. 
     In addition, the left and right walls  46 L,  46 R and the bottom portion  47  connecting the walls constituting the guide holder  35  are configured such that the bottom portion  47  is formed to be thinner than either of the left and right walls. 
     Since the guide holder  35  is formed from an extruded tubular member of substantially rectangular cross-sectional shape, the thickness of the bottom portion  47  can easily be made thinner than the thickness of either of the left and right walls  46 L,  46 R. 
     Consequently, by forming the left and right walls  46 L,  46 R of the guide holder  35 , which corresponds to a mounting portion for the mounting stay  28   a , thicker than the thickness of the bottom portion  47 , and forming the bottom portion  47  thinner in relation thereto, the weight of the guide holder  35  can be reduced, while maintaining the strength of the left and right walls  46 L,  46 R. 
       FIG. 4  is an exploded perspective view of a chain guide  30  according to the present invention, and the chain guide  30  can be formed by fitting the guide holder  35  to the chain guide member  34  as indicated by an arrow a. The front of the chain guide  30  is shown on the left in the drawing. 
     As noted above, the integral enlarged flange  41  is provided at the front end of the chain guide member  34 . The front end  42  of the guide holder  35  is provided with a cutout portion formed therein that receives the flange  41 . The flange  41  is wider than the inside space between the side walls  46 L,  46 R, and therefore, the flange  41  blocks the guide holder  35  from moving therepast. As a result, the front end  42  of the guide holder is retained rearwardly of the flange  41 , by bringing the front end  42  of the guide holder  35  in contact with the flange  41 . 
     A guide member extension boss  37  is extended on top of the chain guide member  34 , and the guide member extension boss is formed with guide member mounting holes  37   a ,  37   b  extending therethrough. 
     Additionally, the guide holder  35  is formed with guide holder mounting holes  40   a ,  40   b ,  40   c  formed through the upper portion thereof. The guide member mounting hole  37   a  is alignable with the guide holder mounting hole  40   a , and the guide member mounting hole  37   b  is alignable with the guide holder mounting hole  40   b , so as to be attachable to the mounting stay  28   a  via the bolt  38  and the nut  39  (See  FIG. 3 ). 
     The guide holder mounting holes  40   a ,  40   b  are formed to be alignable with the holes of the mounting stay  28   a  (See  FIG. 3 ), so that the guide holder can be attached to the mounting stay  28   a  via the bolt  38  and the nut  39 . In the same manner, the guide holder mounting hole  40   c  is formed to be alignable with the hole on the mounting stay  28   b  (See  FIG. 2 ), so as to be capable of being fixed to the mounting stay  28   b  via the bolt  38  and the nut  39 . 
     The guide holder  35  is formed from an extruded tubular member made out of aluminum alloy. That is, only cutting and machining are needed to transform the tubular member into guide holders, and a pressing process is unnecessary. Since an extruded tubular member of aluminum alloy is used, the portion requiring machining is small, and simultaneously, a higher dimensional accuracy is achieved than if stamping or press processing is used. 
     Consequently, since the guide holder  35  can obtain higher dimensional accuracy than can be obtained by stamping or press processing, the chain guide member  34  can be accurately positioned and easily assembled with the guide holder  35 . 
       FIG. 5  is a cross-sectional view of the chain guide hereof, taken along the line  5 - 5  in  FIG. 2 .  FIG. 5  clearly shows that the integral enlarged flange  41  is provided at a front end of the chain guide member  34 , and a front end  42  of the guide holder  35  is retained rearwardly of the flange  41  by bringing the front end  42  of the guide holder  35  in contact with the flange  41 , as described above. 
     The integral flange  41  includes formed left and right back side surfaces  48 L,  48 R, and the back bottom surface  49  (see  FIG. 2 ) clamped between the left and right back side surfaces  48 L,  48 R. Then, the chain guide  30  is formed by bringing the left and right walls  46 L,  46 R of the front end  42  of the guide holder  35  into abutment with the left and right back side surfaces  48 L,  48 R, and bringing the bottom portion  47  at the front end  42  of the guide holder  35  into abutment with the back bottom surface  49 . 
     A method for manufacturing the guide holder will now be described, with reference to  FIG. 6 .  FIG. 6  illustrates the manufacturing steps for forming a guide holder according to an aspect of the present invention. 
     The drawing (a) shows that the extruded tubular member  52 , formed from an aluminum alloy and having a predetermined cross-sectional shape, is formed by an extruding die  51 . In other words, the extruded tubular member  52  of the aluminum alloy is formed with a substantially rectangular cross-sectional shape with the left and right walls  46 L,  46 R tapered downwardly, and the thickness of the bottom portion  47  is made thinner than the thickness of either of the left and right walls  46 L,  46 R. 
     Since the guide holder is formed from the hollow extruded tubular member  52  of substantially rectangular cross-sectional shape, the packed state for transportation is stable in comparison with material of irregular cross-sectional shape, and thus the possibility of collapse of cargo piles can be reduced. 
     The drawing (b) shows that the extruded tubular member of aluminum alloy  52  can be divided lengthwise into two parts by a cutting tool  53 , such as a revolving saw or other appropriate cutting tool. 
     Since the hollow extruded tubular member  52  of substantially rectangular cross-sectional shape can be formed into a pair of modified trough-shaped members, each having a substantially U-shaped cross-section by dividing the tubular member into two parts, the entire extruded member  52  can be utilized effectively. 
     Since the hollow extruded tubular member  52  of substantially rectangular cross-sectional shape is used by dividing a single member into two parts, the cross-sectional shape or the dimensional accuracy of the extruded member  52  can be effectively utilized as is, and a predetermined dimensional accuracy required for the guide holder  35  (See  FIG. 2 ) can be secured easily and reliably. 
     Means for dividing the extruded tubular member  52  is not limited to the cutting tool described above. For example, it may be cut by a thermal processing means such as laser or welding. 
       FIG. 6(   c ) shows that the extruded tubular member  52 , formed into substantially U-shape by dividing into two parts, can be processed to a predetermined shape by removing means such as cutting. 
     Since the extruded tubular member  52  is used, the portion requiring machining is small, and a higher dimensional accuracy is obtained than when a method of stamping or press processing is used. 
     By utilizing the extruded tubular member  52  of aluminum alloy, thermal processing which corresponds to T 5  is performed simultaneously during the extruding process, and hence a strength equivalent to the high-strength aluminum alloy which is used in the guide holder in the related art is secured. Therefore, the only required post-process is machining, and hence a number of processes such as thermal processing, pressing, bending, solution annealing, aging treatment, precision alignment are not necessary. Since a die for a pressing process is not necessary, in particular, it is advantageous in terms of cost, particularly when manufacturing a few components. 
     Although the preferred removing means for processing the extruded tubular member  52 , divided into two parts into a predetermined shape, is cutting, the method is not limited thereto. For example, it is also possible to process by thermal processing means such as laser or welding. An optimal method is selected by considering constraint conditions in manufacture such as processing accuracy, equipment held, or cycle time required for processing. 
       FIG. 6(   d ) shows a completed guide holder  35 . 
     The operation of the chain guide thus constructed will be described below. 
     Referring again to  FIG. 5 , in the chain guide  30 , the integral enlarged flange  41  is provided at a front end of the chain guide member  34 , and the front end  42  of the guide holder  35  is retained rearwardly of the flange  41  by bringing the front end  42  of the guide holder  35  in contact with the flange  41 . 
     Since it is constructed such that the flange  41  at the front end of the chain guide member  34  covers the front end of the guide holder, the chain  27  advances as indicated by an arrow b, and part of the chain  27  is adapted to be contacted by the moving chain guide member  34  due to external causes, so that a force is exerted on the flange  41  of the chain guide member  34  as indicated by an arrow b. 
     Since the flange  41  is applied against the leading edge  42  of the guide holder  35  with the force of arrow b, the chain guide member  34  is fixed to the guide holder  35  by the flange  41 , the bolt  38  (see  FIG. 3 ), and the nut  39 . The chain guide member  34  is covered by the guide holder  35  along the outer surfaces  43 L,  43 R thereof, and the chain guide member  34  is prevented from coming off during normal use. 
     In the chain-introducing portion at the front of the chain guide  30 , since the outside front edge of the guide holder  35  is substantially covered by the chain guide member  34 , the chain  27  does not come into direct contact with the front end  42  of the guide holder  35 . In other words, an impact due to contact of the chain  27  can be absorbed by the chain guide member  34 . In addition, impact due to contact of the chain guide  30  with respect to the surface of the road during off-road travel can also be absorbed and alleviated by the chain guide member  34 . Further, by using a resilient, abrasion-resistant material such as a polyurethane elastomer for forming the chain guide member  34 , its impact absorbing property may be improved. 
     Consequently, scarring, deformation, and the like of the guide holder  35  can be reduced. Since scarring of the guide holder  35  is reduced, frequency of maintenance such as repair and/or replacement of the guide holder  35  may be reduced. 
     Although the material of the guide holder is extruded material of aluminum alloy in the described embodiment the present invention, iron, magnesium, titanium, or an alloy thereof are also usable, and may be substituted for the described alloy. Selection of the material is made considering required durability, strength, weight, dimensional accuracy, processability, and/or costs. 
     It is also possible to apply the chain guide of the present invention for a general vehicle having a chain and sprocket, for preventing the chain from coming apart. 
     Also, the chain guide of the invention can be widely applied to a motorcycle, a tricycle, and to chain-driven utility vehicles. 
     While a working example of the present invention has been described, the present invention is not limited to the working example described above but can be modified in various manners without departing from the spirit and scope of the present invention, as set forth in the claims.