Patent Publication Number: US-2022228649-A1

Title: Chain guide mechanism

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a chain guide mechanism suitable for a timing system of an engine, for example, in which chain guides keep tension and slidably guide a chain that is passed over sprockets respectively provided to a crankshaft and camshafts inside the engine room. 
     2. Description of the Related Art 
     A chain guide mechanism for a timing system is known, which is installed in a car engine room to slidably guide a running chain and keep correct tension between sprockets. 
     One type of chain guide mechanism is configured to include, for example, a pivoting chain guide pivotably attached to an engine block, which is a mounting target, on the slack side of the chain run line, and a fixed chain guide fixedly attached to the engine block on the tight side of the chain run line. 
     One problem with such a chain guide mechanism was poor work efficiency during assembly or maintenance, since it was necessary to install or remove each of a plurality of sprockets, pivoting chain guide, and fixed chain guide, and to lay or remove the chain, separately. 
     For better work efficiency during assembly or maintenance, there has been proposed a timing system that adopts a chain guide mechanism that integrally holds a pivoting chain guide and a fixed chain guide by connecting these guides (see, for example, Japanese Patent Application Publication No. 2018-179086). 
     The chain guide mechanism described in Japanese Patent Application Publication No. 2018-179086 joins the pivoting chain guide and fixed chain guide together by a connection unit, which is composed of a pair of arm members extending from both sides, across the chain, of the chain run side of the fixed chain guide toward the pivoting chain guide, and a joint member having a pair of connection arms extending from both sides, across the chain, of the chain run side of the pivoting chain guide toward the arm members. 
     In the chain guide mechanism, the arm members are formed integrally with the guide shoe of the fixed chain guide, and the guide shoe is fixed to a fixed guide support member, so that the fixed chain guide and the arm members are united. Amounting boss on the pivoting chain guide is fitted into a fitting hole in the joint member to unite them, and engaging protrusions provided on the joint member are inserted in and engaged with engaging holes formed in the arm members. In this way, the chain guide mechanism is able to integrally hold the fixed chain guide and the pivoting chain guide. 
     SUMMARY OF THE INVENTION 
     However, the abovementioned chain guide mechanism has an increased number of components because the joint member, which is provided with the fitting hole in which the mounting boss of the pivoting chain guide is fitted, is provided as a separate part from the arm members that are formed integrally with the fixed chain guide. 
     Another problem is that, when connecting the fixed chain guide with the pivoting chain guide, the process of inserting the engaging protrusions on the joint member into the engaging holes of the arm members is not easy and time-consuming. 
     After the fixed chain guide has been connected with the pivoting chain guide, the pivoting chain guide, which is not fixed but freely movable, tends to make it more difficult to install other components. Moreover, the overall large number of steps to unite the fixed chain guide, pivoting chain guide, and other components make it harder to achieve a significant improvement in work efficiency. 
     The present invention has been made in view of the circumstances described above, its object being to provide a chain guide mechanism that can readily integrate all the components in a simple structure for better work efficiency during assembly or maintenance. 
     The present invention solves the above problems by providing a chain guide mechanism capable of integrally supporting components on a frame, the components including a plurality of sprockets, a chain that is passed over the plurality of sprockets, and a fixed chain guide and a pivoting chain guide that slidably guide the chain. The pivoting chain guide includes a cylindrical mounting boss protruding outward from one side in a guide width direction. The frame includes a sprocket support part that supports each of the plurality of sprockets when the chain is passed over the sprockets, a fixed chain guide support part that supports the fixed chain guide, and a pivoting chain guide holding part that holds the mounting boss in a state of a loose fit. The pivoting chain guide holding part is configured to allow the mounting boss to be fitted therethrough from one side. 
     According to the chain guide mechanism set forth in claim  1 , the components including a plurality of sprockets, chain, fixed chain guide, and pivoting chain guide are integrally supported on a frame and can be assembled into a unit. The pivoting chain guide holding part of the frame is configured to allow the mounting boss of the pivoting chain guide to be fitted therethrough from one side. In this way, the pivoting chain guide can be connected to and separated from the frame easily with a simple structure. As this facilitates integration of the frame and the pivoting chain guide, the work efficiency during assembly or maintenance can be improved. 
     Since there is no need to prepare a separate joint member for uniting the pivoting chain guide with other components, there is no weight increase caused by an increased number of components, and a fuel economy loss can be avoided. 
     According to the configuration set forth in claim  2 , the mounting boss, has, on an outer circumferential surface, a double flat side part, while the pivoting chain guide holding part includes a loose fit part and guide portions. The pivoting chain guide holding part is configured so as to hold the pivoting chain guide in a pivotable manner when the double flat side part is inserted between opposite inner side faces of the guide portions and the pivoting chain guide is rotated. This configuration prevents the pivoting chain guide from separating from the frame and reliably unites them, which helps improve the work efficiency during assembly or maintenance. 
     According to the configuration set forth in claim  3 , an outer circumferential surface at a distal end of the mounting boss is formed with a retainer part, which, when one side of the pivoting chain guide is in surface contact with one face of the pivoting chain guide holding part, engages with another face of the pivoting chain guide holding part. This configuration reliably prevents the pivoting chain guide from tilting when the pivoting chain is attached to the frame, which helps improve the work efficiency during assembly or maintenance. 
     According to the configuration set forth in claim  4 , the retainer part is made up of a plurality of locking tabs circumferentially spaced apart on the mounting boss such that at least two locking tabs always engage with the other face of the pivoting chain guide holding part. This helps simplify the structure of the assembly and improves its formability. 
     According to the configuration set forth in claim  5 , the pivoting chain guide holding part includes a planar restricting part on an outer side on a rear side in a chain running direction of the loose fit part to restrict pivoting movement of the pivoting chain guide during assembly, and the restricting part is formed with an engaging notch on a face thereof positioned on the pivoting chain guide side. The pivoting chain guide is formed with, on one side thereof, an engaging protrusion, which is to be engaged with the engaging notch and configured to be able to engage with a side face of the restricting part when the pivoting chain guide is rotated. When assembling the components into a unit, the engaging protrusion of the pivoting chain guide is engaged with the engaging notch to fasten the pivoting chain guide. When installing the chain guide mechanism into an internal combustion engine, the engaging protrusion is engaged with the side face of the restricting part so that the pivoting chain guide is prohibited from rotating in a direction away from the chain. This function that fastens the pivoting chain guide in two stages restricts free pivoting of the pivoting chain guide and further helps improve the work efficiency during assembly or maintenance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view illustrating one mode of use of a chain guide mechanism according to one embodiment of the present invention; 
         FIG. 2  is a perspective view illustrating a configuration of a frame in the chain guide mechanism illustrated in  FIG. 1 ; 
         FIG. 3  is a perspective view illustrating a configuration of a top guide in the chain guide mechanism illustrated in  FIG. 1 ; 
         FIG. 4  is a perspective view illustrating a configuration of a fixed chain guide in the chain guide mechanism illustrated in  FIG. 1 ; 
         FIG. 5  is a perspective view illustrating a configuration of a pivoting chain guide in the chain guide mechanism illustrated in  FIG. 1 ; 
         FIG. 6  is a cross-sectional view illustrating the mounting boss of the pivoting chain guide illustrated in  FIG. 5 , with a pivoting chain guide holding part of the frame; 
         FIG. 7A  is a schematic plan view illustrating a state in which the mounting boss of the pivoting chain guide is inserted in the pivoting chain guide holding part of the frame; 
         FIG. 7B  is a cross-sectional view of a region surrounded by the two-dot chain line in  FIG. 7A , seen from one side of the frame; 
         FIG. 8A  is a schematic plan view illustrating a state in which an engaging protrusion of the pivoting chain guide is engaged with an engaging notch in the frame; 
         FIG. 8B  is a cross-sectional view of a region surrounded by the two-dot chain line in  FIG. 8A , seen from one side of the frame; 
         FIG. 9A  is a schematic plan view illustrating a state in which an engaging protrusion of the pivoting chain guide is engaged with a side face of a restricting part of the frame; and 
         FIG. 9B  is a cross-sectional view of a region surrounded by the two-dot chain line in  FIG. 9A , seen from one side of the frame. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention can have any specific forms of embodiment as long as it provides a chain guide mechanism capable of integrally supporting components on a frame, the components including a plurality of sprockets, a chain passed over the plurality of sprockets, and a fixed chain guide and a pivoting chain guide that slidably guide the chain, the pivoting chain guide including a cylindrical mounting boss protruding outward from one side in a guide width direction, the frame including a sprocket support part that supports each of the plurality of sprockets when the chain is passed over the sprockets, a fixed chain guide support part that supports the fixed chain guide, and a pivoting chain guide holding part that holds the mounting boss with a loose fit, and the pivoting chain guide holding part being configured to allow the mounting boss to be fitted thereto from one side. 
     The chain running surfaces of the fixed chain guide and pivoting chain guide in the chain guide mechanism of the present invention may be formed integrally with the chain guides of a material having favorable sliding properties, or a guide shoe that allows favorable sliding of the chain may be removably attached to the chain guides. 
     The fixed chain guide, pivoting chain guide, and guide shoes in the chain guide mechanism of the present invention may be made of any material that has low friction resistance. Specifically, materials that exhibit durability in high-temperature environments and can allow the chain to run smoothly in sliding contact are preferable. For example, synthetic resin materials such as polyamide 6 resin, polyamide 46 resin, polyamide 66 resin, and polyacetal resin can be preferably used. 
     In a case where the fixed chain guide and pivoting chain guide have a guide shoe, the guide body that supports the guide shoe may be made of metal such as iron or aluminum. 
     A chain guide mechanism according to the present invention will be hereinafter described in more detail with reference to the drawings. 
     As illustrated in  FIG. 1 , the chain guide mechanism  100  according to the present invention is configured to be able to integrally support, on a metal plate frame  110 , components including a drive-side sprocket  101  provided to a crankshaft, two driven-side sprockets  102  and  103  each provided to each of two cam shafts, a chain  105  passed over the drive-side sprocket  101  and the driven-side sprockets  102  and  103 , a top guide  150  and a fixed chain guide  160  each slidably guiding the running chain  105 , and a pivoting chain guide  170  keeping correct chain tension while slidably guiding the running chain  105 . Reference numeral  106  in  FIG. 1  denotes a tensioner. 
     The frame  110  is formed by processing a metal plate member and includes, as illustrated in  FIG. 2 , a drive-side sprocket support part  111 , driven-side sprocket support parts  115  and  120 , a top guide support part  125 , a fixed chain guide support part  130 , and a pivoting chain guide holding part  140 . 
     The drive-side sprocket support part  111  is formed at one end of a planar frame substrate, and includes a locking tab  112  that engages with one side of a gear part of the drive-side sprocket  101 , and a pair of pressing tabs  113  on both sides of the locking tab  112  for supporting the other side of the gear part of the drive-side sprocket  101 . The locking tab  112  and pressing tabs  113  are each formed to have a side face in a zigzag shape and tips positioned at different heights. 
     The driven-side sprocket support parts  115  and  120  are provided side by side on the other end of the frame substrate. The driven-side sprocket support part  115  includes a locking tab  116  that engages with one side of a gear part of the driven-side sprocket  102 , and a pair of pressing tabs  117  on both sides of the locking tab  116  along a circular arc for supporting the other side of the gear part of the driven-side sprocket  102 . 
     The other driven-side sprocket support part  120  is configured similarly to the driven-side sprocket support part  115  and includes a locking tab  121  and two pressing tabs  122 . 
     The top guide support part  125  is formed by a support wall  126 , which is an edge portion at the other end of the frame substrate (top-side edge portion) bent substantially at right angles to one side and extends along a guide longitudinal direction. 
     In the bent corner of the frame substrate, in a center part in the guide longitudinal direction, is formed an engaging hole  127 , which is an elongated slot extending in the guide longitudinal direction. 
     The fixed chain guide support part  130  is formed by a support wall  131 , which is a side edge portion of the frame substrate on the tight side of the chain run line bent substantially at right angles to one side and extends along the chain run line. 
     In the bent corner of the frame substrate are formed a plurality of engaging holes  132  spaced apart from each other along the guide longitudinal direction. Each of the engaging holes  132  is formed as an elongated slot extending in the guide longitudinal direction, for example. 
     The pivoting chain guide holding part  140  is formed in a side edge portion at one end (bottom end) of the frame substrate on the slack side of the chain run line. 
     The pivoting chain guide holding part  140  includes a substantially C-shape loose fit part  141  and guide portions  142  each continuous with each of both ends of the loose fit part  141 . 
     Inner side faces  143  of the guide portions  142  include flat parts facing and extending parallel to each other. The guide portions  142  are formed such that the distance D 2  between the inner side faces  143  is smaller than the inside diameter D 1  of the loose fit part  141  (see  FIG. 6 ). 
     One of the guide portions  142  positioned on a rear side in the chain running direction is formed with a restricting part  144  that restricts pivoting movement of the pivoting chain guide  170  on an outer side face thereof. The restricting part  144  is planar and formed with an engaging notch  145  on one face. 
     The top guide  150  includes, as illustrated in  FIG. 3 , a planar sliding surface forming part  151  extending along the guide longitudinal direction and having a sliding surface thereon for guiding the chain  105 , a side wall  152  upright at one side edge in the guide width direction of the sliding surface and extending over the entire guide length, engaging hooks  153  provided at both ends in the guide longitudinal direction on the back side of the sliding surface forming part  151 , and an engaging protrusion  154  formed at the other side edge in the guide width direction on the back side of the sliding surface forming part  151 . 
     The engaging hooks  153  each have a hook structure with a square U-shape cross section to be able to slide relative to the support wall  126  of the top guide support part  125  in a direction perpendicular to the guide longitudinal direction, so as to restrict movement of the top guide  150  in the guide longitudinal direction. 
     The fixed chain guide  160  includes, as illustrated in  FIG. 4 , a sliding surface forming part  161  extending along the guide longitudinal direction and having a sliding surface thereon for guiding the chain  105 , a side wall  162  upright at one side edge in the guide width direction of the sliding surface and extending over the entire guide length, a first engaging hook  163  provided at one end in the guide longitudinal direction on the back side of the sliding surface forming part  161 , a plurality of second engaging hooks  164  provided at one side edge in the guide width direction on the back side of the sliding surface forming part  161  and spaced apart in the guide longitudinal direction, and a plurality of engaging protrusions  165  formed at the other side edge in the guide width direction on the back side of the sliding surface forming part  161  and spaced apart in the guide longitudinal direction. 
     The first engaging hook  163  has a hook structure with a square U-shape cross section to be able to slide relative to the support wall  131  of the fixed chain guide support part  130  in a direction perpendicular to the guide longitudinal direction. 
     The second engaging hook  164  includes a base part extending perpendicularly to the sliding surface from the back side of the sliding surface forming part  161 , and a catch portion extending from the distal end of the base part toward inside in the guide width direction. 
     The pivoting chain guide  170  has a guide shoe  171  slidably guiding the running chain  105 , and a guide body  175  attached to the guide shoe  171  and supporting the guide shoe  171  along the guide longitudinal direction, as illustrated in  FIG. 5 . 
     The guide body  175  includes a cylindrical mounting boss  180  at one end in the guide longitudinal direction, which serves as the pivot shaft. 
     As illustrated in  FIG. 6 , the mounting boss  180  has an outside diameter D 3  that is smaller than the inside diameter D 1  of the loose fit part  141  of the pivoting chain guide holding part  140  and larger than the distance D 2  between the inner side faces  143  of the guide portions  142 , and protrudes outward from one side in the guide width direction. 
     The mounting boss  180  has a double flat side part  181  which is a pair of flat surfaces parallel to each other. 
     The width D 4  of the double flat side part  181  is smaller than the distance D 2  between the inner side faces  143  of the guide portions  142 , so that the mounting boss  180  with its double flat side part  181  parallel to the inner side faces  143  of the guide portions  142  can be fitted to the pivoting chain guide holding part  140  from one side. 
     On the outer circumferential surface at the distal end of the mounting boss  180  is formed a retainer part  182  which, when one side of the pivoting chain guide  170  is in surface contact with one face of the pivoting chain guide holding part  140 , engages with the other face of the pivoting chain guide holding part  140 . 
     The retainer part  182  is made up of, for example, a plurality of locking tabs  183  circumferentially spaced apart on the mounting boss  180  such that at least two locking tabs  183  always engage with the other face of the pivoting chain guide holding part  140 . 
     The pivoting chain guide  170  is formed with an engaging protrusion  176  on one side thereof, which is to be engaged with the engaging notch  145  in the pivoting chain guide holding part  140  and configured to be able to engage with a side face of the restricting part  144  when the pivoting chain guide  170  is rotated. 
     Various components of the chain guide mechanism  100  described above are assembled into a unit as described below. 
     The drive-side sprocket  101  and two driven-side sprockets  102  and  103  are supported respectively on the drive-side sprocket support part  111  and the driven-side sprocket support parts  115  and  120  and are united with the frame  110  by laying the chain  105  over them. 
     The top guide  150  is slid from one side of the frame  110  to bring the engaging hooks  153  into engagement with the support wall  126  of the top guide support part  125  and to insert the engaging protrusion  154  into the engaging hole  127  of the top guide support part  125 , whereby the top guide  150  is united with the frame  110  while being restricted from moving in the guide longitudinal direction. 
     The fixed chain guide  160  is slid from one side of the frame  110  to bring the first engaging hook  163  and second engaging hooks  164  into engagement with the support wall  131  of the fixed chain guide support part  130  and to insert the engaging protrusions  165  into the engaging holes  132  of the fixed chain guide support part  130 , whereby the fixed chain guide  160  is united with the frame  110  while being restricted from moving in the guide longitudinal direction. 
     The pivoting chain guide  170  is installed such that, with the double flat side part  181  of the mounting boss  180  being set parallel with the inner side faces  143  of the guide portions  142  of the pivoting chain guide holding part  140 , the pivoting chain guide  170  is moved along one side face thereof to fit the mounting boss  180  to the pivoting chain guide holding part  140  as illustrated in  FIG. 7A  and  FIG. 7B . The width D 4  of the double flat side part  181  is smaller than the distance D 2  between the inner side faces  143  of the guide portions  142 , so that the pivoting chain guide  170  can be smoothly attached to the frame  110 . The two locking tabs  183  engage with the other face of the pivoting chain guide holding part  140  to prevent the pivoting chain guide  170  from tilting. 
     Next, as illustrated in  FIG. 8A  and  FIG. 8B , the pivoting chain guide  170  is rotated to a direction in which it presses the chain  105  to bring the engaging protrusion  176  on the guide body  175  into engagement with the engaging notch  145  of the pivoting chain guide holding part  140 , to fasten the pivoting chain guide  170  in position with a loose fit on the pivoting chain guide holding part  140 . In this state, since the outside diameter D 3  of the mounting boss  180  is larger than the distance D 2  between the inner side faces  143  of the guide portions  142 , the pivoting chain guide  170  can be prevented from separating from the frame  110 , i.e., the pivoting chain guide  170  is thus united with the frame  110 . The two locking tabs  183  kept in engagement with the other face of the pivoting chain guide holding part  140  prevent the pivoting chain guide  170  from tilting when the pivoting chain guide  170  is rotated. 
     Moreover, as the pivoting chain guide  170  is rotated it presses the chain  105 , which ensures that the drive-side sprocket  101  and two driven-side sprockets  102  and  103  are supported more firmly respectively on the drive-side sprocket support part  111  and the driven-side sprocket support parts  115  and  120 . 
     Thus the drive-side sprocket  101 , two driven-side sprockets  102  and  103 , chain  105 , top guide  150 , fixed chain guide  160 , and pivoting chain guide  170  can be configured as one assembly, all integrally supported on the frame  110 . 
     The chain guide mechanism  100  according to this embodiment is inserted into the engine block, with all the components united. At this time, as illustrated in  FIG. 9A  and  FIG. 9B , the pivoting chain guide  170  is rotated further to the direction in which it presses the chain  105  to bring the engaging protrusion  176  on the guide body  175  into engagement with one side face of the restricting part  144  of the pivoting chain guide holding part  140 , to fasten the pivoting chain guide  170  in a state in which it is prohibited from rotating in a direction away from the chain  105 . This restricts the pivoting chain guide  170  from pivoting freely, which helps improve the work efficiency during assembly or maintenance. 
     The drive-side sprocket  101  is then attached to the crankshaft, and the two driven-side sprockets  102  and  103  are each attached to the cam shafts. Amounting shaft is inserted into the mounting boss  180  of the pivoting chain guide  170 , to secure the chain guide mechanism  100  inside the engine room. 
     As described above, the chain guide mechanism  100  according to the embodiment supports the components including the drive-side sprocket  101 , two driven-side sprockets  102  and  103 , chain  105 , top guide  150 , fixed chain guide  160 , and pivoting chain guide  170  integrally on the frame  110  so that they can be assembled into one unit. The pivoting chain guide  170 , in particular, can be united with the frame  110  by inserting the mounting boss  180  from one side and by rotating the pivoting chain guide  170  on the frame  110 . Thus the operation of integrating various components is made easy with a simple structure, and the work efficiency during assembly or maintenance can be improved. 
     While one embodiment of the present invention has been described in detail, the present invention is not limited to the embodiment described above and may be carried out with various design changes without departing from the scope of the present invention set forth in the claims. 
     For example, the chain guide mechanism of the present invention may not necessarily include the top guide, in which case the top guide support part need not be provided to the frame. 
     The retainer part of the mounting boss maybe formed all around the mounting boss. 
     The frame need not necessarily be formed by processing a metal plate. 
     While the chain guide mechanism described above is provided for a timing system inside an engine in the embodiment described above, the chain guide mechanism is applicable not only to this but to various equipment. 
     The chain guide mechanism is applicable in various industrial fields including similar drive mechanisms using not only chains, but also belts, ropes and the like.