Abstract:
A bumper for a pendulum that cannot inadvertently become loose is disclosed. The pendulum has at least one and preferably a pair of spaced apart, elongated bumpers. The elongated bumpers generally have an L-shape. The pendulum is comprised of two halves. L-shaped channels are formed in each pendulum half. The bumpers are fitted into channels of the same shape formed in the pendulum halves. When the two halves are fitted together, the L-shaped bumper is captured therebetween. Each pendulum half includes an elevated central area and a pair of recessed areas with each recessed area formed on one side of the elevated area. Side walls are formed at the intersections of the elevated area and the recessed areas. A base wall is formed along the lower edge of the elevated area. The bumper ends extend from the elevated area beyond the side walls and base wall.

Description:
TECHNICAL FIELD 
       [0001]    The disclosed inventive concept relates generally to pendulum crankshafts for internal combustion engines. More particularly, the disclosed inventive concept relates to a bumper arrangement that prevents metal-to-metal impact of the pendulum assembly on the pendulum carrier by providing bumpers that cannot slip from their positions as assembled. 
       BACKGROUND OF THE INVENTION 
       [0002]    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. 
         [0003]    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 engine order forces, that are not cancelled. Such torsional vibrations are ultimately transmitted through the engine mounts and to the vehicle structure. 
         [0004]    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 vehicle noise and harshness. Such crankshaft-mounted pendulums function as vibration absorbers as they are tuned to address and thus reduce vibrations generated by oscillating torque, 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 stress within the crankshaft itself. 
         [0005]    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, a pendulum includes an inner curved cam follower surface that is alternately engaged and disengaged from a pin type cam fixed on the pendulum carrier. 
         [0006]    The crankshaft pendulum is interconnected with the pendulum carrier by pairs of rollers that are movable on mating curved tracks. While there are a number of variations of the movable relationship between the pendulum and the crankshaft, it is common to incorporate rolling pins as the points of contact between these two components. 
         [0007]    Each rolling pin requires a pendulum rolling pin track in which the rollers can roll. Known rolling pin tracks have a great distance between the walls of the track and the rolling pin. When the engine is running and the crankshaft is rotating, centrifugal force keeps the pendulum in its full out position. The pendulum responds to the oscillating torque by moving side to side. This reduces the oscillating torque to the transmission to improve NVH. The pendulum can hit the bumpers if the oscillating torque is too high. In this case, the pendulums would need to be detuned. The other time the pendulums hit is during start up and shut down when there is not enough centrifugal force to overcome gravity. The bumpers are intended to reduce the NVH of metal hitting metal in these three cases. In this position, the centrifugal force is sufficient to overcome gravity and the torsionals are so low as not to cause the pendulum to move back and forth. However, when the engine is turned off and rotational movement of the crankshaft stops, centrifugal motion stops as well and the pendulum, no longer held in its full out position, may move to its full travel condition in which the pendulum experiences a drop caused by gravity if the stopped position of the pendulum is “up” or is generally above the midline of the crankshaft. If the pendulum is stopped in this position, then it will drop before hitting metal-on-metal, thus increasing undesirable NVH in the engine and, consequently, in the vehicle. 
         [0008]    To compensate for this drop, rubber bumpers are located on the pendulum or on the pendulum carrier to dampen the metal-on-metal contact. When the pendulums are over-excited or during engine start-up or shut-down, the bumpers hit their stops. In known designs, the bumpers are inserted into blind pockets formed in either the pendulum or in the pendulum carrier. Because of insufficient grip length, these bumpers are prone to falling out of their pockets, thus not only failing to achieve their intended purpose, but also creating a risk of clogged oil lines and thus causing early engine failure. 
         [0009]    Thus a new approach to the pendulum bumpers is needed to address the problems associated with known arrangements. 
       SUMMARY OF THE INVENTION 
       [0010]    The disclosed inventive concept overcomes the challenges faced by known pendulum arrangements for internal combustion engines by providing a bumper that cannot inadvertently become loose from the pendulum. Regardless of engine operation, the bumper stays attached to the pendulum. 
         [0011]    The pendulum assembly for attachment to the crankshaft of an internal combustion engine of the disclosed inventive concept comprises a pendulum having at least one and preferably a pair of spaced apart, elongated bumpers. The elongated bumpers generally have an L-shape. 
         [0012]    The pendulum is comprised of two halves. L-shaped channels are formed in each pendulum half. The bumpers are fitted into channels of the same shape formed in the pendulum halves. When the two halves are fitted together, the L-shaped bumper is captured therebetween. 
         [0013]    Each pendulum half includes an elevated central area and a pair of recessed areas with each recessed area formed on one side of the elevated area. Side walls are formed at the intersections of the elevated area and the recessed areas. A base wall is formed along the lower edge of the elevated area. The bumpers are long enough so that the bumper ends extend from the elevated area beyond the side walls and base wall. 
         [0014]    The bumpers are composed of a polymerized material including, but not limited to, natural rubber, synthetic rubber, or any other flexible and resilient material that is able to withstand oil. 
         [0015]    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 
         [0016]    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: 
           [0017]      FIG. 1  is a side view of a pendulum assembly for attachment to a crankshaft according to the prior art; 
           [0018]      FIG. 2  is an end view of a crankshaft having the pendulum assembly of  FIG. 1  attached thereto according to the prior art; 
           [0019]      FIG. 3  is a side view of a pendulum assembly having pendulum bumpers according to the disclosed inventive concept with the pendulum shown in its full out position relative to the pendulum carrier; 
           [0020]      FIG. 4  is a perspective view of the pendulum assembly of  FIG. 3 ; 
           [0021]      FIG. 5  is an exploded view of the pendulum assembly of  FIG. 3 ; and 
           [0022]      FIG. 6  is a view similar to that of  FIG. 3  but illustrating the pendulum assembly moved to its full travel position relative to the pendulum carrier whereby the bumpers of the pendulum may be in contact with the pendulum carrier as illustrated. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]    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. 
         [0024]    Referring to  FIGS. 1 and 2 , views of a known pendulum assembly and the pendulum assembly attached to a crankshaft are illustrated. Referring to  FIG. 3 through 6 , the pendulum assembly according to the disclosed inventive concept is illustrated. 
         [0025]      FIG. 1  is an end view of a pendulum assembly  10  as is known in the art for attachment to a crankshaft. The pendulum assembly  10  includes two pendulum halves, of which only a first pendulum half  12  is illustrated. A second pendulum half that is a mirror image of the pendulum half  12  is fitted over the first pendulum half  12 . The first pendulum half  12  and the second pendulum half are typically attached to one another by mechanical fasteners. 
         [0026]    The first pendulum half  12  (and the second pendulum half) includes an elevated area  14  and spaced apart recessed areas  16  and  16 ′. A kidney-shaped cycloid pathway  18  is formed in the recessed areas  16 . A kidney-shaped cycloid pathway  18 ′ is formed in the recessed areas  16 ′. 
         [0027]    The elevated area  14  includes outer walls  20  and  20 ′. A rubber stop-receiving pocket  22  is formed in the outer wall  20 . A rubber stop-receiving pocket  22 ′ is formed in the outer wall  20 ′. A rubber stop  24  is fitted into the rubber stop-receiving pocket  22 . A rubber stop  24 ′ is fitted into the rubber stop-receiving pocket  22 ′. 
         [0028]      FIG. 2  illustrates the known pendulum assembly  10  attached to a crankshaft  30 . The crankshaft  30  conventionally includes a pair of spaced-apart lobes  32  and  32 ′. The spaced-apart lobes  32  and  32 ′ function as a carrier for the pendulum assembly  10 . Particularly, the lobe  32  includes an insert-receiving aperture  34  into which is conventionally fitted an insert (not shown) having a kidney-shaped pathway formed therein. In the same way, the lobe  32 ′ includes an insert-receiving aperture  34 ′ into which is conventionally fitted an insert (not shown) having a kidney-shaped pathway formed therein. 
         [0029]    The rubber stops  24  and  24 ′ function as bumpers to prevent the first pendulum half  12  (and the second pendulum half) from making direct, metal-on-metal contact with the spaced-apart lobes  32  and  32 ′. While preventing such metal-on-metal contact is desired, the rubber stops  24  and  24 ′ are known to become separated from their rubber stop-receiving pockets  22  and  22 ′ respectively during engine operation as discussed above. The disclosed inventive concept, discussed in detail hereinafter in relation to  FIGS. 3 through 6 , provides a solution to this problem. 
         [0030]    Referring to  FIGS. 3 through 6 , a pendulum assembly according to the disclosed inventive concept, generally illustrated as  40 , is shown. The pendulum assembly  40  includes a first pendulum half  42  and a second pendulum half  44 . The first pendulum half  42  and the second pendulum half  44  are typically attached to one another by mechanical fasteners, such as a first bolt  46  and a second bolt  46 ′. 
         [0031]    The first pendulum half  42  includes an elevated area  48  and a pair of spaced-apart recessed areas  50  and  50 ′. A kidney-shaped cycloid pathway  52  is formed in the recessed area  50 . A kidney-shaped cycloid pathway  52 ′ is formed in the recessed area  50 ′. 
         [0032]    The second pendulum half  44  includes an elevated area  54  and a pair of spaced-apart recessed areas  56  and  56 ′. A kidney-shaped cycloid pathway  58  is formed in the recessed area  56 . A kidney-shaped cycloid pathway  58 ′ is formed in the recessed area  56 ′. 
         [0033]    The pendulum assembly  40  is attached to a crankshaft (not shown) by a pendulum carrier  60 . It is to be understood that the pendulum carrier  60  is one of several possible design configurations intended to connect the pendulum assembly  40  to the crankshaft. Thus the configuration of the pendulum carrier  60  as illustrated in  FIGS. 3 through 6  is not intended to be limiting but is only intended as being suggestive. 
         [0034]    The pendulum carrier  60  includes a first carrier ear  62  and a second carrier ear  62 ′. As shown particularly in  FIG. 5 , a kidney-shaped cycloid pathway  64  is formed in the first carrier ear  62  and a kidney-shaped cycloid pathway  64 ′ is formed in the second carrier ear  62 ′. 
         [0035]    The pendulum carrier  60  further includes a pair of crankshaft attachment arms  66  and  66 ′. The crankshaft attachment arm  66  has a bolt hole  68  formed therethrough. The crankshaft attachment arm  66 ′ has a bolt hole  68 ′ formed therethrough. Mechanical fasteners such as shoulder bolts  70  and  70 ′ attach the pendulum carrier  60  to the crankshaft. 
         [0036]    Fitted between each pendulum half  42  and  44  are rolling pins  72  and  72 ′. The rolling pin  72  is fitted through the kidney-shaped cycloid pathway  64  of the first carrier ear  62  of the pendulum carrier  60  and into the kidney-shaped cycloid pathway  52  of the first pendulum half  42  and into the kidney-shaped cycloid pathway  58  of the second pendulum half  44 . The rolling pin  72 ′ is fitted through the kidney-shaped cycloid pathway  64 ′ of the second carrier ear  62 ′ of the pendulum carrier  60  and into the kidney-shaped cycloid pathway  52 ′ of the first pendulum half  42  and into the kidney-shaped cycloid pathway  58 ′ of the second pendulum half  44 . 
         [0037]    The kidney-shaped rolling tracks  64  and  64 ′ of the pendulum carrier  60  are inverted relative to the kidney-shaped rolling tracks  52  and  52 ′ of the first pendulum half  42  and the kidney-shaped rolling tracks  58  and  58 ′ of the second pendulum half  44 . This arrangement allows the desired pendulum motion of the pendulum assembly  40  relative to the pendulum carrier  60 . 
         [0038]      FIG. 3  illustrates the pendulum assembly  40  in its full out position in which the centrifugal force is sufficient to overcome gravity and the torsionals are low so as not to cause the pendulum to move back and forth. In this position, the rolling pin  72  is centered relative to the kidney-shaped cycloid pathway  64  of the first carrier ear  62  of the pendulum carrier  60 , the kidney-shaped cycloid pathway  52  of the first pendulum half  42 , and the kidney-shaped cycloid pathway  58  of the second pendulum half  44 . In addition, in this centered position the rolling pin  72 ′ is centered relative to the kidney-shaped cycloid pathway  64 ′ of the second carrier ear  62 ′ of the pendulum carrier  60 , the kidney-shaped cycloid pathway  52 ′ of the first pendulum half  42 , and the kidney-shaped cycloid pathway  58 ′ of the second pendulum half  44 . The illustrated centered position arises when centrifugal force is reduced such as during engine shut down in which the pendulum assembly  40  experiences a “drop” whereby the pendulum assembly  40  is pulled away from the pendulum carrier  60 . In this position, no metal-to-metal contact between the pendulum assembly  40  and the pendulum carrier  60  is experienced. 
         [0039]    When the centrifugal force of acting upon the pendulum assembly  40  is sufficient to overcome gravity at a relatively low RPM (such as  130  RPM) and the torque oscillation is sufficient, the pendulum  44  may be moved relative to the pendulum carrier  60  from its full out condition illustrated in  FIG. 3  to a full travel condition where the pendulum  44  may come into contact with the pendulum carrier  60 . While this ordinarily does not happen, if the oscillating torque of the pendulum  44  is too high, it is possible n for the pendulum  44  may come into contact with the pendulum carrier  60 . 
         [0040]    The full travel position is illustrated in  FIG. 6 . In this position, the rolling pin  72  is positioned at one end of the kidney-shaped cycloid pathway  64  of the first carrier ear  62  of the pendulum carrier  60  and is at the other end of the kidney-shaped cycloid pathway  52  of the first pendulum half  42  and the kidney-shaped cycloid pathway  58  of the second pendulum half  44 . In the same way, the rolling pin  72 ′ is at one end of the kidney-shaped cycloid pathway  64 ′ of the second carrier ear  62 ′ of the pendulum carrier  60  and is at the other end of the kidney-shaped cycloid pathway  52 ′ of the first pendulum half  42  and the kidney-shaped cycloid pathway  58 ′ of the second pendulum half  44 . 
         [0041]    To avoid possible undesirable metal-to-metal contact when the pendulum  44  is in its full travel condition as shown in  FIG. 6 , impact-dampening elements in the form of a first angled bumper  74  and a second angled bumper  74 ′ are provided. The first angled bumper  74  and a second angled bumper  74 ′ are sandwiched between the first pendulum half  42  and the second pendulum half  44 . The first angled bumper  74  and the second angled bumper  74 ′ may be made of any durable and oil-resistant polymerized material, such as, but not limited, to rubber. 
         [0042]    The elevated area  48  of the first pendulum half  42  includes a pair of side walls  76  and  76 ′ and a base wall  78 . A first bumper channel  80  and a second bumper channel  80 ′ are formed in the elevated area  48 . In the same manner, the elevated area  54  of the second pendulum half  44  includes a pair of side walls  82  and  82 ′ and a base wall  84 . A first bumper channel  86  and a second bumper channel  86 ′ are formed in the elevated area  54 . 
         [0043]    The first angled bumper  74  is fitted in the first bumper channel  80  of the first pendulum half  42  and the first bumper channel  86  of the second pendulum half  44  such that one end of the first angled bumper  74  extends beyond the side wall  76  of the elevated area  48  and the side wall  82  of the elevated area  54  while the other end of the first angled bumper  74  extends beyond the base wall  78  of the elevated area  48  and the base wall  84  of the elevated area  54 . In a like manner, the second angled bumper  74 ′ is fitted in the second bumper channel  80 ′ of the first pendulum half  42  and the second bumper channel  86 ′ of the second pendulum half  44  such that one end of the second angled bumper  74 ′ extends beyond the side wall  76 ′ of the elevated area  48  and the side wall  82 ′ of the elevated area  54  while the other end of the second angled bumper  74 ′ extends beyond the base wall  78  of the elevated area  48  and the base wall  84  of the elevated area  54 . 
         [0044]    As illustrated in  FIG. 6 , when the pendulum assembly  40  is in its full travel condition relative to the pendulum carrier  60 , the first angled bumper  74  and the second angled bumper  74 ′ prevent metal-to-metal contact between the pendulum assembly  40  and the pendulum carrier  60 . Because the angled bumpers are angled, have ends that extend beyond the side walls and base walls of the elevated areas of the pendulum halves, and are captured between the pendulum halves, the possibility that one or the other of the angled bumpers slipping from their positions as assembled is virtually eliminated by the disclosed inventive concept. 
         [0045]    The disclosed inventive concept as set forth above overcomes the challenges faced by known pendulum crankshaft arrangements for internal combustion engines by providing an improved impact-dampening arrangement that avoids the possibility of the bumpers slipping from their assembled positions. Accordingly, 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.