Abstract:
A pendulum absorber fixed to the crankshaft of an engine comprises a pendulum and a pendulum carrier attached to the pendulum carrier attachment boss of the crankshaft. Each pendulum carrier has a pair of parallel ears extending therefrom. The carrier is tightly attached to the attachment boss such that the attachment boss is captured between the ears of the carrier. Attachment of the pendulum carrier to the sides of the attachment boss allows for feasibility in production, unlike known arrangements which require attachment of the pendulum carrier to the top of the crankshaft web. The fastener may be a pair of pressed-in pins, a single shrink-fit pin, shoulder bolts, Z-Form™ fastener assemblies, or rivets. Regardless of the type of fastener used, the side attachment arrangement of the disclosed inventive concept is sufficient to carry the load in sheer and prevent the pendulum assemblies from moving relative to the crankshaft.

Description:
TECHNICAL FIELD 
     The disclosed inventive concept relates generally to absorbers to reduce torsional vibration in an internal combustion engine. More particularly, the disclosed inventive concept relates to pendulum absorbers mounted by fasteners including one or more pressed-in pins, bolts or rivets attached to the side of the crankshaft to facilitate production assembly. 
     BACKGROUND OF THE INVENTION 
     Internal combustion engines having a relatively small number of cylinders provide automobile makers with an attractive solution to the need for improved fuel economy. In order to compensate for reduction of cubic capacity vehicle manufacturers developed technologies to improve engine power, such as direct fuel injection, turbocharging, and variable timing for inlet and exhaust camshafts. In this way six- and eight-cylinder engines can be scaled down without losing available horsepower. 
     An undesirable consequence of engines with a small number of cylinders is high crankshaft torsional vibration and high engine block vibration caused by forces, such as first and second order forces, that are not cancelled. Such vibrations are ultimately transmitted through the engine mounts and driveline to the vehicle structure. 
     Engineers managed these vibrations to one extent or another through a variety of approaches, many of which increase the cost of construction and reduce fuel economy. One accepted solution to overcome excessive vibration is the provision of one or more pendulums on the crankshaft to lower the torsional vibration of the crankshaft and the consequent driveline vibration. Such crankshaft-mounted pendulums function as vibration absorbers as they are tuned to address and thus cancel out vibrations generated by crankshaft rotation, thus smoothing torque output of the crankshafts. This approach is taken as well by designers of some airplane piston engines where the pendulums smooth output torque and reduce rigid body motion. 
     An example of a pendulum vibration absorber associated with an engine crankshaft is set forth in U.S. Pat. No. 4,739,679, assigned to the assignee of the instant application. According to the arrangement set forth in this patent, the pendulum is bolted to the crankshaft so that the shoulder bolts carry the load in sheer along the shoulder. However, the pendulum of this design is intended for an I-4 engine that does not require counterweights for balancing insofar as an I-4 is balanced in first order. Accordingly, so long as the pendulums are symmetric, the I-4 will still be balanced. 
     Such is not the case for the I-3 engine. In this engine, pendulums are necessary as counterweights for balance since the I-3 engine has a first order pitching moment. To obtain the necessary balance without adding the large inertia of U.S. Pat. No. 4,739,679, the pendulums must be designed in a similar shape as a conventional counterweight. 
     However, attachment to the crankshaft has been calculated to result in bolt failure at high speed due to sheer. The prototype method of attaching a pendulum crankshaft is not feasible in production. One method conceived was to bolt on the pendulums along the sides. This method is not feasible since the clamp load is not sufficient to prevent the pendulum from moving radially. The clamp load interface would slip and bolts would fail in sheer. 
     Thus a new approach to the attachment of the pendulum to the crankshaft in smaller engines is needed to address the problems associated with known arrangements and to reduce the amount of torsional vibration produced by the internal combustion engine. 
     SUMMARY OF THE INVENTION 
     The disclosed inventive concept overcomes the problems associated with known approaches to reducing torsional vibrations generated in operating internal combustion engines having a small displacement, such as three cylinder engines. The disclosed inventive concept accomplishes this step by providing a pair of opposed fasteners positioned coaxially on both sides of the pendulum carrier for attachment to the pendulum carrier attachment boss of the crankshaft. 
     Particularly, the vibrational absorber assembly of the disclosed inventive concept includes a rotational element typically in the form of a crankshaft and pendulum assemblies attached to the crankshaft. Each pendulum assembly includes a pendulum and a pendulum carrier to which the pendulum is attached. The crankshaft has pendulum carrier attachment bosses to which the pendulum carriers are attached. 
     Each pendulum carrier has a pair of parallel ears extending therefrom. The carrier is tightly attached to the crankshaft pendulum carrier attachment boss such that the pendulum carrier attachment boss is captured between the ears of the carrier. Fastener-passing holes are formed in the ears while fastener-receiving holes are formed in the pendulum carrier attachment boss. All of these holes are coaxial. 
     The fastener may include one or more of pressed pins, a single shrink-fit pin, shoulder bolts, Z-Form™ fastener assemblies, or rivets. The pressed pins and the shrink-fit pin define an interference fit whereas the shoulder bolts and the rivets define a tight fit for the fastener. Regardless of the type of fastener used, the arrangement of the disclosed inventive concept wherein the fasteners attach the pendulum carrier to the pendulum carrier attachment boss from the side are sufficient to carry the load in sheer and prevent the pendulum assemblies from moving relative to the crankshaft. Attachment of the pendulum carrier to the sides of the pendulum carrier attachment boss allows the disclosed inventive concept to be feasible in production, unlike known arrangements which require attachment of the pendulum carrier to the top of the crankshaft web. Accordingly, the disclosed inventive concept overcomes the problems associated with known arrangements in which the clamp load interface is known to slip and attachment bolts fail in sheer. 
     The above advantages and other advantages and features will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention wherein: 
         FIG. 1  is a perspective view of a crankshaft having pendulum assemblies attached to the side of the crankshaft by one or more pins, bolts or rivets according to the disclosed inventive concept; 
         FIG. 2  is an end view of a pendulum assembly attached to a crankshaft by pins according to one embodiment of the disclosed inventive concept; 
         FIG. 3  is an end view of a pendulum assembly attached to a crankshaft by a single, shrink-fit pin according to one embodiment of the disclosed inventive concept; 
         FIG. 4  is an end view of a pendulum assembly attached to a crankshaft by shoulder bolts according to another embodiment of the disclosed inventive concept; 
         FIG. 5  is an end view of a pendulum assembly attached to a crankshaft by Z-Form™ fasteners according to an additional embodiment of the disclosed inventive concept; and 
         FIG. 6  is an end view of a pendulum assembly attached to a crankshaft by a rivets according to a further embodiment of the disclosed inventive concept. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the following figures, the same reference numerals will be used to refer to the same components. In the following description, various operating parameters and components are described for different constructed embodiments. These specific parameters and components are included as examples and are not meant to be limiting. 
     Referring to  FIG. 1 , a perspective view of a crankshaft assembly for an internal combustion engine is illustrated. Referring to  FIGS. 2 through 6 , end views of alternate embodiments of the disclosed inventive concept are illustrated in which a pendulum-carrier assembly is attached to the crankshaft by pins in  FIG. 2 , by a single pressed pin in  FIG. 3 , by shoulder bolts in  FIG. 4 , by Z-Form™ fasteners in  FIG. 5 , and by rivets in  FIG. 6 . It is to be understood that the overall configuration of the illustrated crankshaft assembly shown in the figures is set forth for suggestive purposes only as the overall configuration may be altered from that illustrated without deviating from the spirit or scope of the invention. 
     As illustrated in  FIG. 1 , the crankshaft assembly  10  includes a crankshaft  12 . The crankshaft  12  has a rotational axis  14 . Rotation of the crankshaft  12  about its rotational axis  14  is made possible by the provision of main journals  16 ,  16 ′,  16 ″ and  16 ′″. The journals  16 ,  16 ′,  16 ″ and  16 ′″ are integrally formed as part of the crankshaft  10  and are restrained within the engine block (not shown) by crankshaft bearings (not shown). 
     The connecting rods (not shown) are attached as is known in the art to rod journals  18 ,  18 ′ and  18 ″ by rod bearings. The rod journals  18 ,  18 ′ and  18 ″ are integrally formed on the crankshaft  12 , again as is known in the art. 
     The crankshaft  12  includes a first end  20  and a second end  22 . Conventionally provided extending from one end, in this case the first end  20 , is a post  24 . The post  24  serves as a mount for any number of engine components, such as an absorber, a fan belt pulley and a drive mechanism for a camshaft. These components are not shown but these components and their methods of attachment are known to those skilled in the art. 
     Conventionally attached to the other end of the crankshaft  12 , in this case the second end  22 , is a flywheel (not shown). The flywheel, which assists in reducing torsional fluctuations in the crankshaft  12 , is in operative engagement with the drive shaft or transaxle of the vehicle. 
     Counterweights are formed as integral components of the crankshaft  12 . Counterweight  26  is illustrated while an identical counterweight (not shown) is provided for in spaced apart relation from the counterweight  26 . It is understood that the conventional modern internal combustion engine includes one or more such counterweights to provide balance to the crankshaft  12 , the connecting rods, and their associated pistons. 
     To each side of the rod journal  18  is provided a spaced apart pair of crank webs  28  and  28 ′. Extending from the crank web  28  is a pendulum carrier attachment boss  30  and extending from the crank web  28 ′ is a pendulum carrier attachment boss  30 ′. 
     To each side of the rod journal  18 ″ is provided a spaced apart pair of crank webs  32  and  32 ′. Extending from the crank web  32  is a pendulum carrier attachment boss  34  and extending from the crank web  32 ′ is a pendulum carrier attachment boss  34 ′. It is to be understood that more pendulums may be provided than are shown in  FIG. 1  up to the number of crank webs. 
     The disclosed inventive concept provides pendulum assemblies for attachment to the crankshaft  12 . Particularly, a pendulum assembly  40  is attached to the pendulum carrier attachment boss  30 , a pendulum assembly  40 ′ is attached to the pendulum carrier attachment boss  30 ′, a pendulum assembly  40 ″ is attached to the pendulum carrier attachment boss  34 , and a pendulum assembly  40 ″′ is attached to the pendulum carrier attachment boss  34 ′. 
     Each of the pendulum assemblies  40 ,  40 ′,  40 ″ and  40 ″′ includes a pendulum and a pendulum carrier. The pendulum carrier is attached to the pendulum carrier attachment boss of the crank. Particularly, the pendulum assembly  40  includes a pendulum  42  attached to a pendulum carrier  44 , the pendulum assembly  40 ′ includes a pendulum  42 ′ attached to a pendulum carrier  44 ′, the pendulum assembly  40 ″ includes a pendulum  42 ″ attached to a pendulum carrier  44 ″, and the pendulum assembly  40 ″′ includes a pendulum  42 ″′ attached to a pendulum carrier  44 ″′. 
     The pendulum carrier  44  is attached to the pendulum carrier attachment boss  30 . The pendulum carrier  44 ′ is attached to the pendulum carrier attachment boss  30 ′. The pendulum carrier  44 ″ is attached to the pendulum carrier attachment boss  34 . And the pendulum carrier  44 ″′ is attached to the pendulum carrier attachment boss  34 ′. 
     According to the disclosed inventive concept, the pendulum carriers are attached to their respective pendulum carrier attachment bosses by elongated, mechanical fasteners positioned through the pendulum carriers and into the pendulum carrier attachment bosses. The disclosed inventive concept provides for two methods of mechanical fastening that may be used alone or in combination. 
     One embodiment of mechanical attachment according to the disclosed inventive concept is illustrated in  FIG. 2  in which an end view of the pendulum assembly  40 ″′ attached to the crankshaft  12  is attached by pressed-in pins  46  and  46 ′ is shown. The pressed-in pins  46  and  46 ′ pass through holes formed in parallel ears  48  and  48 ′ that extend from the pendulum carrier  44 ″′ and into holes formed in alignment in the pendulum carrier attachment boss  34 ′. The pressed-in pins  46  and  46 ′ may be of a variety of diameters, though a non-limiting diameter may be 8.0 mm. The pressed-in pins  46  and  46 ′ are pressed in to assure good attachment by way of an interference fit. This method of attachment, coupled with the tight fit of the pendulum carrier  44 ″′ to the pendulum carrier attachment boss  34 ′, restricts movement of the pendulum assembly  40 ″′ relative to the crankshaft  12 . 
     A number of tools may be used for pressing the pressed-in pins  46  and  46 ′ through the holes formed in parallel ears  48  and  48 ′ and into the holes formed in alignment in the pendulum carrier attachment boss  34 ′. One such tool, illustrated as T, is shown. The tool T is suggestive and is not intended as being limiting. 
     A variation of the mechanical attachment of the pendulum assembly  40 ″′ to the crankshaft  12  illustrated in  FIG. 2  in which two pressed-in pins  46  and  46 ′ are illustrated is shown in  FIG. 3  in which a single, shrink-fit pin  50  is applied. The shrink-fit pin  50  passes through holes formed in parallel ears  48  and  48 ′ that extend from the pendulum carrier  44 ″′ and through a hole formed in the pendulum carrier attachment boss  34 ′. A cap  52  formed at one end of the shrink-fit pin  50  limits the depth to which the shrink-fit pin  50  may be inserted. 
     The shaft of the shrink-fit pin  50  may be of a variety of diameters, though a non-limiting diameter may be 8.0 mm. The shrink-fit pin  50  is pressed in to assure good attachment by way of an interference fit using a tool similar to that illustrated in  FIG. 2 . This method of attachment, coupled with the tight fit of the pendulum carrier  44 ″′ to the pendulum carrier attachment boss  34 ′, again restricts movement of the pendulum assembly  40 ″′ relative to the crankshaft  12 . 
     A third embodiment of mechanical attachment according to the disclosed inventive concept is illustrated in  FIG. 4  in which an end view of the pendulum assembly  40 ″′ attached to the crankshaft  12  is attached by shoulder bolts  60  and  60 ′ is shown. The shoulder bolt  60  includes a shoulder  62  and a threaded end  64 . The shoulder bolt  60 ′ includes a shoulder  60 ′ and a threaded end  64 ′. The bolts  60  and  60 ′ may be of a variety of diameters, though a non-limiting diameter may be 8.0 mm. 
     The shoulder bolts  60  and  60 ′ pass through holes formed in the ears  48  and  48 ′ of the pendulum carrier  44 ″′ and into threaded holes formed in alignment in the pendulum carrier attachment boss  34 ′. The shoulders  62  and  62 ′ have a tight fit relative to the holes formed in the ears  48  and  48 ′ of the pendulum carrier  44 ″′ and in the pendulum carrier attachment boss  34 ′. 
     A fourth embodiment of mechanical attachment according to the disclosed inventive concept is illustrated in  FIG. 5  in which an end view of the pendulum assembly  40 ″′ attached to the crankshaft  12  is attached by Z-Form™ fastener assemblies  70  and  70 ′ is shown. (Z-Form™ is a product of Acument Global Technologies.) The fastener assembly  70  includes a shoulder bolt  72  and a pre-assembled deformable sleeve  74 . The shoulder bolt  72  includes a shoulder  76  and a threaded end  78 . The fastener assembly  70 ′ includes a shoulder bolt  72 ′ and a pre-assembled deformable sleeve  74 ′. The shoulder bolt  72 ′ includes a shoulder  76 ′ and a threaded end  78 ′. The shoulder bolts  72  and  72 ′ may be of a variety of diameters, though a non-limiting diameter may be 8.0 mm. 
     The pre-assembled deformable sleeves  74  and  74 ′ pass through holes formed in the ears  48  and  48 ′ of the pendulum carrier  44 ″′ and into holes formed in the pendulum carrier attachment boss  34 ′. The shoulder bolts  72  and  72 ′ are then inserted into and through the pre-assembled deformable sleeves  74  and  74 ′ and are threaded into the pendulum carrier attachment boss  34 ′. The fastener assemblies  70  and  70 ′ eliminate undesirable clearance between the shoulder bolts  72  and  72 ′ and the bolt-passing holes formed in the pendulum carrier  44 ′″. 
     A fifth embodiment of mechanical attachment according to the disclosed inventive concept is illustrated in  FIG. 6  in which an end view of the pendulum assembly  40 ″′ attached to the crankshaft  12  is attached by blind rivets  80  and  80 ′ is shown. The blind rivet  80  includes a rivet head  82  and a shank  84  extending therefrom. An upset head  86  is formed at the end of the shank  84  after the blind rivet  80  is attached. A cavity  88  is formed in the pendulum carrier attachment boss  34 ′ to accommodate the upset head  86 . A retained mandrel head  90  forms the upset head  86  as is known in the art. 
     The blind rivet  80 ′ includes a rivet head  82 ′ and a shank  84 ′ extending therefrom. An upset head  86 ′ is formed at the end of the shank  84 ′ after the blind rivet  80 ′ is attached. A cavity  88 ′ is formed in the pendulum carrier attachment boss  34 ′ to accommodate the upset head  86 ′. A retained mandrel head  90 ′ forms the upset head  86 ′, again as is known in the art. 
     Whether pressed pins  46  and  46 ′, the shrink-fit pin  50 , the shoulder bolts  60  and  60 ′, the fastener assemblies  70  and  70 ′, or the rivets  80  and  80 ′ are used, the disclosed inventive concept are sufficient to carry the load in sheer and prevent the pendulum assemblies  40 ,  40 ′,  40 ″, and  40 ″′ from moving relative to the crankshaft  12 . 
     The disclosed inventive concept provides a method of fixedly and efficiently attaching a pendulum assembly to a crankshaft having sufficient strength to carry the load in sheer while preventing movement of the pendulum assembly relative to the crankshaft. Thus the disclosed inventive concept overcomes the problems associated with known arrangements in which the clamp load interface is known to slip and attachment bolts fail in sheer. 
     One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.