Patent Publication Number: US-2016238104-A1

Title: Low mass chain link and assembly for friction reduction

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention pertains to the field of chain links More particularly, the invention pertains to low mass chain links assembled into a chain for friction reduction. 
     2. Description of Related Art 
     In a typical engine timing drive, which may include the primary drive, secondary cam drive, and oil pump drive, a chain can be used to transmit power from one sprocket and shaft to another and allow synchronized rotation between the shafts. 
       FIG. 1A  shows a typical engine timing drive layout consisting of a chain  1 , crankshaft sprocket  2 , camshaft sprocket  3 , tensioner arm  4 , tensioning device  5 , and guide  6 . Power from the crankshaft sprocket  2  is transmitted to the camshaft sprocket  3  through a flexible chain  1 , which allows synchronous rotation between the crankshaft  2   a  and camshaft  3   a , which is essential to maintaining engine timing. 
     As a torque is applied to crankshaft sprocket  2 , a resistant torque is applied to camshaft sprocket  3 , which then forces the chain  1  to generate a tight strand  7  and a slack strand  8 . Typically the chain  1  is in sliding contact between a fixed guide  6  along a portion of chain  1  in tension between the camshaft sprocket  3  and the crankshaft sprocket  2 . The chain  1  is also in sliding contact with a movable tensioning arm  4  along the portion of chain  1  between the crankshaft sprocket  2  and the camshaft sprocket  3 . The tensioning arm  4  takes up the slack in the chain  1  by pushing into the chain with a force generated by a tensioning device  5 . 
     A typical roller chain  1 , as depicted in  FIG. 2 , consists of a first set of opposed internal link plates  13  connected by a pair of bushings  11 , and a second set of opposed internal link plates  14  connected by a pair of pins  10 . The link plates  13  of the first set are arranged in an alternating relationship with the link plates  14  of the second set, with each pin  10  from the second set of links  14  extending through the bushing  11  of the first set of links  13 . A roller chain  1  will also include a roller  12  located outside the bushing  11 , while a rollerless chain would not. 
     The shapes of the sets of link plates  13 ,  14  may vary. The shapes of the link plates  13 ,  14  may be flat back links  15  with a flat back edge  15   a  as depicted in  FIG. 3  or hourglass shaped links  16  with a back edge  16   a  as depicted in  FIG. 4 . 
     The flat back edge  15   a  of the link is the contact point or surface between the link and the tensioner arm  4  or guide  5 . The contact point  15   b , where the contact occurs between the links of the chain and the tensioner arm  4  or guide  5 , is located across the entire back of the link. 
     The back edge  16   a  of the hourglass shaped links  16  is formed of two convexly curved portions  16   b  connected through a concave portion  16   c . The two convexly curved portions  16   b  are the contact points  16   b  between the hour glass shaped links  16  and the tensioner arm  4  or guide  5 . The curved portions  16   b  (contact points) are located close to the apertures  17  or joint of the link. 
     The contact points of theback edges  15   a ,  16   a  of the links  15 ,  16  of the chain  1  come into contact with the sliding surfaces  6   a ,  4   a  of the guide  6  and tensioning arm  4  respectively. The flat back links and hourglass shaped links  16  create a large contact area between the flat back edge  15   a  and the back edge  16   a  of the chain links  15 ,  16  and the sliding surfaces  4   a ,  6   a  of the tensioner arm  4  and guide  6 , creating frictional loss as depicted in  FIGS. 1B and 1C . This frictional loss results in lower fuel efficiency when used as an engine timing drive or auxiliary drive within an automotive engine. 
     Another factor influencing fuel efficiency of an automotive engine concerns the mass of the system being used. A reduction in the mass of the components used results in lower weight of the chain drive, and thus reduces fuel consumption. Specifically in regards to chain drives, lower chain mass can result in lower chain tension, which reduces the force acting upon the sliding surfaces and thus reducing frictional losses. 
     SUMMARY OF THE INVENTION 
     A roller chain or rollerless chain which comprises two distinctly different link sets, internal and external links, which could employ the low mass links and associated geometry on both link sets or just one single link set within the chain. A chain assembly may utilize this link geometry in an alternating fashion so as to allow contact with sliding surfaces on both sides of the chain or to allow contact with sliding surfaces on only one side of the chain while optimizing for friction. 
     The back edges of the external and internal links which contact the sliding surface of arms and guides within an engine timing drive, oil pump drive, or any other auxiliary drive are optimized for friction reduction. In an embodiment of the present invention, the body of the links have a convex back edge which is formed at least in part by an arc with a radius, such that the radius forms at least one high point of the arc which is centered around the middle of the link, between the apertures or holes of the links for contacting the sliding surfaces of the tensioner arms and/or guides. The radius is preferably optimized for friction reduction and forms the high point of the back edge such that the size of the radius meets pressure/velocity requirements of an application in which the chain is being applied. 
     In some embodiments, a non-contacting surface is located, opposite the contact surface, and may have a concave shape to eliminate mass from the body of the link. Reduced mass of the link and thus the chain improves the efficiency of the system, as well as improves manufacturing cost and complexity. Mass reduction of the link can also improve overall system efficiency of the chain drive, which can be accomplished with a concave edge profile or the combination of the concave edge profile with an extra hole or window within the profile boundary of the body of the link. 
     The primary mass reduction is accomplished by the profile of the concave edge, however mass reduction can be accomplished by other means. Instead of a concave profile which removes material and mass from the edge of the link, the link could contain material removal from within the link boundary in the form of an extra hole or window. A link could also contain both a profile with a concave edge combined with material removed from the inside of the link boundary of the body of the link in the form of an extra hole or window. A link could also contain both edges with a convex edge profile to maintain symmetry, combined with material removal from inside the link for mass reduction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  A shows a conventional engine timing drive. 
         FIG. 1B  shows sliding contact between the chain and tensioner arm. 
         FIG. 1C  shows sliding contact between the chain and the guide. 
         FIG. 2  shows a conventional roller chain. 
         FIG. 3  shows conventional flat back link plates of the roller chain of  FIG. 1 . 
         FIG. 4  shows conventional hourglass or dogbone link plates of the roller chain of  FIG. 1 . 
         FIG. 5A  shows a schematic of an internal link plate of an embodiment of the present invention with a convex edge. 
         FIG. 5B  shows a schematic of an external link plate of an embodiment of the present invention with a convex edge. 
         FIG. 6A  shows a schematic of an internal link plate with a hole for reducing the mass of the link of an alternate embodiment of the present invention. 
         FIG. 6B  shows a schematic of an external link plate with a hole for reducing the mass of the link of an alternate embodiment of the present invention. 
         FIG. 7A  shows a schematic of an internal link plate with a window for reducing the mass of the link of another embodiment of the present invention. 
         FIG. 7B  shows a schematic of an external link plate with a window for reducing the mass of the link of another embodiment of the present invention. 
         FIG. 8A  shows a schematic of an oval shaped internal link with a window for reducing the mass of the link in an alternate embodiment of the present invention. 
         FIG. 8B  shows a schematic of an oval shaped external link with a window for reducing the mass of the link in an alternate embodiment of the present invention. 
         FIG. 9  shows a schematic of a chain with the links arranged such that the convex edge profiles are orientated in the same direction. 
         FIG. 10  shows a schematic of a chain with the links arranged such that the convex edge profiles are orientated in opposite directions. 
         FIG. 11  shows a schematic of a chain with the links arranged such that internal links or external links have convex edge profiles and the other set of links are conventional flat back link plates of  FIG. 3 . 
         FIG. 12  shows a schematic of a chain with the links arranged such that internal links or external links have convex edge profiles and the other set of links are conventional hourglass or dog bone link plates of  FIG. 4 . 
         FIG. 13  shows a schematic of a chain of links with the convex edge profiles of links engaging a tensioner arm. 
         FIG. 14  shows an isometric three dimensional view of the chain of  FIG. 12 . 
         FIG. 15  shows a schematic of a cross-section of the links of  FIGS. 5A and 5B  along the radius R. 
         FIG. 16  shows a schematic of an alternate cross-section of embodiment of the links of  FIGS. 5A and 5B  along the radius R. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The current invention includes a link plate design that incorporates an optimized edge profile shape and link mass reduction. 
       FIG. 5A  illustrates an internal link plate  50  with a body  58  which would contain bushings  11  pressed into the link plate apertures or bushing holes  53 . The holes may also contain connecting pins (not shown). The internal link plate  50  has a convex back edge  51  for sliding contact with a guide  6  or a tensioner arm  4  as depicted in  FIG. 13 . The convex back edge  51  has a profile in which at least a portion contacts the sliding surfaces  4   a ,  6   a  of arms  4  and guides  6  within an engine timing drive, oil pump drive, or any other auxiliary drive. The profile of the convex back edge  51  is comprised of an arc with a radius R, such that a high point of the profile, formed by the radius R, contacts the sliding surfaces  4   a ,  6   a  of the arms  4  and guides  6 . The radius R is preferably optimized for friction reduction. By having a back edge  51  with a convex profile with a high point which contacts the sliding surfaces  4   a ,  6   a  of the tensioner arm and guide, frictional losses from the sliding contact of the convex shape with the tensioner arm  4  or the guide  6  are reduced. 
     In embodiments of the present invention, the high point(s) formed by a radius R is moved from around the joint location as shown in the prior art, to the middle of the link and the increase in the size of the radius R meets pressure/velocity requirements of an application as necessary. 
     The specific radius R which forms the highest point of the profile of the convex back edge is dependent on a number of system parameters such as link thickness, chain tension, plastic pressure/velocity limitations, speed of the drive, temperature of the environment, etc. If the radius is too large the friction reduction will be negligible, and if it is too small the system will reach the pressure/velocity limitations and fail. The highest point(s) formed by the radius R of the arc of the profile of the convex back edge  51  is indicated by P and is the contact point between the link and the sliding surfaces  4   a ,  6   a  of the arm  4  and guide  6 . 
     In an exemplary embodiment, the body of the link plate  50  also has a concave edge  52 . The concave edge  52  is preferably opposite the convex back edge  51 . The concave edge  52  is a non-contacting surface. The profile of the concave edge  52  allows some of the body of the link to be removed, and reduce the mass of the link, for example in comparison to the prior art link of  FIG. 3 . 
       FIG. 5B  illustrates an external link plate  54  with a body  59  which would contain pins  10  pressed into the link plate pin holes or apertures  57 . The external link plate  54  has a convex back edge  55  with a profile for slidingly contacting a guide  6  or a tensioner arm  4  as depicted in  FIG. 13 . The convex back edge  55  has a profile which contacts the sliding surfaces  4   a ,  6   a  of arms  4  and guides  6  within an engine timing drive, oil pump drive, or any other auxiliary drive. The profile of the convex back edge  55  is comprised of an arc with a radius R, such that a high point of the profile, formed by the radius R, contacts the sliding surfaces  4   a ,  6   a  of the arms  4  and guides  6 . The radius R is preferably optimized for friction reduction. By having a back edge  55  with a convex profile with a high point which contacts the sliding surfaces  4   a ,  6   a  of the tensioner arm and guide, frictional losses from the sliding contact of the convex shape with the tensioner arm  4  or the guide  6  are reduced. The highest point(s) formed by the radius R of the arc of the profile of the convex back edge  55  is indicated by P and is the contact point between the link and the sliding surfaces  4   a ,  6   a  of the arm  4  and guide  6 . 
     Mass reduction of the link can also take the form of additional holes or windows within the profile of the body of the link by removing material from within the boundary of the link profile in areas in which the material is not needed, for example between the link plate bushing holes  53  or the link plate pin holes  57 . 
     The amount of material removed for mass reduction is taken into consideration with the functional requirements of link strength and stiffness, since the links are the load carrying component of the chain assembly. The extra hole or window must also not contain a shape that could jeopardize the integrity of the link by adding stress concentrations within the link. 
     The contact surfaces P of the back edges  51 ,  55  of the links that are in sliding contact with a tensioner  4  or a guide  6  are historically flat when viewed as a cross section through the link thickness. However, the contour of the link edge when viewed through the cross section of the link thickness may be optimized for friction reduction as well. This could include a convex shape which would look like a rounding off of the link edge, for example as shown in  FIG. 15  or a concave radius which would look similar to an ice skate blade, for example as shown in  FIG. 16 . The shape may also be optimized to take advantage of the pressure/velocity properties of the materials used as the sliding surfaces of the tensioner arms  4  and guides  6 . 
     The links of the present invention may also have a shape along the profile of the link in which the convex back edge and concave edge are asymmetrical about an imaginary line perpendicular to a line (dashed line) passing through the centers of the bushing holes  53  or the pin holes  57 . 
       FIGS. 6A and 7A  show examples of internal links  60 ,  70  which have a body  91 ,  93  that defines apertures or link plate bushing holes  63 ,  73  that would receive bushings  11 . The body  91 ,  93  of the internal links  60 ,  70  each contain a convex back edge  61 ,  71  having a profile for sliding contact with a tensioner arm  4  or a guide  6  and a concave edge  62 ,  72 , opposite at least a portion of the the convex back edge  61 ,  71 . The body of the internal links also contain a hole  68  or window  78  to reduce the mass of the links  60 ,  70 . The hole  68  or window  78  is preferably located between the link plate bushing holes  63 ,  73 . The hole  68  is preferably circular in shape. The window  78  is preferably generally triangular or bell-shaped. 
     The profile of the convex back edge  61 ,  71  is comprised of an arc with a radius R, such that a high point of the profile, formed by the radius R, contacts the sliding surfaces  4   a ,  6   a  of the arms  4  and guides  6 . The radius R is preferably optimized for friction reduction. The highest point(s) formed by the radius R of the arc of the profile of the convex back edge  61 ,  71  is indicated by P and is the contact point between the link and the sliding surfaces  4   a ,  6   a  of the arm  4  and guide  6 . 
       FIGS. 6B and 7B  shows examples of external links  64 ,  74  that may be paired with internal links  60 ,  70  of  FIGS. 6A and 7A . The external link plates  64 ,  74  each have a body  92 ,  94  that defines apertures or link plate pin holes  67 ,  77  for receiving pressed pins  10 . The body  92 ,  94  of the external link plates  64 ,  74  each contain a convex back edge  65 ,  75  with a profile for sliding contact with a tensioner arm  4  or a guide  6  and a concave edge  66 ,  76  opposite at least a portion of the convex back edge  65 ,  75 . The concave edge  66 ,  76  reduces the mass of the link in addition to a hole  69  or window  79  between the link plate pin holes  67 ,  77 . The hole  69  is preferably circular in shape. The window  79  is preferably generally triangular or bell-shaped. 
     The profile of the convex back edge  65 ,  75  is comprised of an arc with a radius R, such that a high point of the profile, formed by the radius R, contacts the sliding surfaces  4   a ,  6   a  of the arms  4  and guides  6 . The radius R is preferably optimized for friction reduction. The highest point(s) formed by the radius R of the arc of the profile of the convex back edge  65 ,  75  is indicated by P and is the contact point between the link and the sliding surfaces  4   a ,  6   a  of the arm  4  and guide  6 . 
     In some instances, a chain of an engine chain drive does in fact need to contact sliding surfaces  4   a ,  6   a  of tensioner arm  4  and guide  6  along both the outer and inner periphery of the chain. In those particular cases, the internal links  80  and external links  84 , for example as shown in  FIGS. 8A-8B  may be utilized. The internal links  80  and external links  84  have a body  95 ,  96  with an outer circumference which is oval shaped, with convex back edges  81 ,  85  on opposite sides of the link. A hole or window  88 ,  89  is present between the link plate bushing holes  83  or link plate pin holes  87  for reducing the mass of the link. The hole or window  88 ,  89  is preferably hour-glass in shape. 
     The profile of the convex back edges  81 ,  85  is comprised of an arc with a radius R, such that a high point of the profile, formed by the radius R, contacts the sliding surfaces  4   a ,  6   a  of the arms  4  and guides  6 . The radius R is preferably optimized for friction reduction. The highest point(s) formed by the radius R of the arc of the profile of the convex back edge  81 ,  85  is indicated by P and is the contact point between the link and the sliding surfaces  4   a ,  6   a  of the arm  4  and guide  6 . 
     It should be noted that the placement of the holes  68 ,  69  or windows  78 ,  79 ,  88 ,  89  are such that the strength and integrity of the links are not compromised. 
     In regards to the chain assembly, the two link types (internal and external) could be arranged in a few different arrangements depending on requirements of the chain assembly. 
     1. One of the two links may use a link with a convex back edge. 
     2. Both internal and external links have a convex back edge oriented in the same direction. 
     3. Both internal and external links have a convex back edge and are oriented in an alternating or opposite direction. In other words, one link set would have all links with the convex edge in one direction while the other link set contains the convex edge in the opposite direction. 
     Depending on the application and how the chain is used, any combination of link shapes as defined within this invention record can be arranged and used to satisfy the requirements of the chain drive. 
     The internal links  50 ,  60 ,  70 ,  80  and external links  54 ,  64 ,  74 ,  84  of  FIGS. 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B  may be arranged a number of ways within the chain assembly in an optimized fashion. The link profile shapes as defined with this invention could also be combined with a traditional flat back link  15  ( FIG. 3 ) or hourglass/dog bone shaped links  16  ( FIG. 4 ) to further optimize friction loss and mass reduction. 
     For example, as depicted in  FIG. 9 , a chain assembly could contain a link plate set of an internal link  50  as depicted in  FIG. 5A  and an external link  54  as depicted in  FIG. 5B  in an alternating relationship. The convex edge  51  of the internal link  50  and the convex edge  55  of the external link  54  may be positioned in the same orientation, with the highest points P of the profiles of the convex back edges aligned. This chain assembly could be utilized in a chain drive application where the chain  1  will contact sliding surfaces along one side of the chain design, either the inner or the outer periphery of the chain, but not both. A typical application of this design is depicted in  FIG. 1A , whereby the chain  1  contacts sliding surfaces  4   a ,  6   a  of tensioner arm  4  and guide  6  along the outer periphery of the chain  1 . The internal links  51  and external links  54  would be oriented with the highest point P of the convex edges  51 ,  55  making contact with the sliding surfaces  4   a ,  6   a . It should be noted that the orientation of the links could also be made using the internal and external links of  FIGS. 6A and 6B  and the internal and external links of  FIGS. 7A and 7B . 
     In another example, a chain assembly could contain an internal link  50  as depicted in  FIG. 5A  and an external link  54  as depicted in  FIG. 5B  in an alternating relationship, as shown in  FIG. 10 , where the highest point P of the convex back edge  51  of the internal link  50  is oriented in one direction and the highest point P of the convex back edge  55  of the external link  54  is oriented in the opposite direction of convex edge  51  of the internal link  50 . This chain assembly could be utilized in a chain drive application where the chain  1  will contact sliding surfaces along both the inner and outer periphery of the chain assembly within the application. It should be noted that the orientation of the links could also be made using the internal links  60  and external links  64  of  FIGS. 6A and 6B , the internal links  70  and external links  74  of  FIGS. 7A and 7B , and internal links  80  and external links  84  of  FIGS. 8A and 8B . 
     In yet another example, as shown in  FIG. 11 , a chain assembly could contain internal links  50  as depicted in  FIG. 5A  or external links  54  as depicted in  FIG. 5B  combined with a traditional flat back link  15  as shown in  FIG. 3  in an alternating relationship. The internal links  50  or external links  54  with the convex edge  51 ,  55  contacts the sliding surfaces  6   a ,  4   a  of the guide  6  or tensioner  4  only, while the traditional flat back link  15  does not. In this case, the traditional flat back link  15  is shorter in height h 1  when measured from an imaginary line perpendicular to a line drawn from the center of one pin or bushing hole to the center of the other pin or bushing hole, than the height H of the links containing the convex edge  51 ,  55 . This similarly is true for the internal links  60  and external links  64  of  FIGS. 6A and 6B , the internal links  70  and external links  74  of  FIGS. 7A and 7B , and internal links  80  and external links  84  of  FIGS. 8A and 8B . 
     Since the flat back link  15  is shorter in height h 1 , the flat back edge  15   a  does not make contact the sliding surfaces  4   a ,  6   a  of the tensioner arm  4  or guide  6 . It should be noted that the orientation of the links could also be made using the internal links  60  and external links  64  of  FIGS. 6A and 6B  and the internal links  70  and external links  74  of  FIGS. 7A and 7B . 
     It should be noted that while the height of the links in  FIGS. 5A-8A  are indicated as “H”, the actual height measured from an imaginary line perpendicular to a line drawn from the center of one pin or bushing hole to the center of the other pin or bushing hole may vary between the links, however the height is always greater than the height h 1 , h 2  of the flat back link and the hourglass-shaped link of  FIGS. 3 and 4 . 
     In another example, as shown in  FIG. 12  a chain assembly could contain an internal links  50  as depicted in  FIG. 5A  or external links  54  as depicted in  FIG. 5B  combined with a traditional hourglass shaped links  16  as shown in  FIG. 4  arranged in an alternating relationship.  FIG. 14  is a three dimensional isometric view illustrating the chain of  FIG. 13 . 
     In this case, the highest points P of the internal links  50  or external links  54  with the convex back edges  51 ,  55  contacts the sliding surfaces  6   a ,  4   a  of the guide  6  or tensioner  4  only, while the traditional hourglass shaped or dog bone shaped link  16  does not. In this case the traditional hourglass shaped link  16  is shorter in height h 2  when measured from an imaginary link perpendicular to a line drawn from the center of one pin or bushing hole to the center of the other pin or bushing hole to than the height H of the internal links  50  or external links  54  with the convex back edge  51 ,  55 . Since the hourglass shaped link  16  is shorter in height h 2  it does not make contact with the sliding surfaces  4   a ,  6   a  of the tensioner arm  4  or guide  6 . It should be noted that the orientation of the links could also be made using the internal links  60  and external links  64  of  FIGS. 6A and 6B  and the internal links  70  and external links  74  of  FIGS. 7A and 7B . 
     Embodiments of the present invention may be used for engine timing applications where a chain is used to transfer power from one sprocket and shaft to another and the chain contacts sliding surfaces on tensioner arms and guides. Possible engine drives which are chain driven include primary drives, secondary drives, oil pump drives, balance shaft drives, fuel pump drives, and any other auxiliary drive within the engine. 
     Embodiments of the present invention could be applied to any automotive application where a chain is used to transfer power from one sprocket or shaft to another and contacts sliding surfaces for control purposes. This may include automotive transmissions, transfer cases, power transfer units, hybrid drives, transmission oil pump drives, etc. 
     Embodiments of the present invention may also be used in any application which utilizes a chain for transfer of power and also contacts guiding surfaces. 
     Embodiments of the present invention are not limited to link size, link pitch, link thickness, or any other dimensional properties related to chain design. 
     Embodiments of the present invention are not restricted to specific material properties. In most automotive applications, steel links would be used. Other industrial applications which utilize a chain drive could employ other materials such as plastics, ceramics, etc. 
     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.