Abstract:
There is provided a valve actuation linkage mechanism for use in an internal combustion engine that reduces friction wear on the valve assembly during engine operation and can be pre-assembled to reduce manufacturing time and costs. The valve actuation linkage mechanism comprises a rocker arm having a pivot rod cup, a pivot rod, a valve bridge having a pivot rod chamber, and a pivot rod retainer. The pivot rod comprises a pivot rod head, a pivot rod neck, a pivot rod body, and a pivot rod bottom. The valve bridge comprises a middle valve bridge section having the pivot rod chamber and a pair of pivot rod retainer securing bore, a bottom valve bridge section, and a lubricant dimple in the pivot rod chamber. The pivot rod retainer is comprised of a pivot rod orifice having pivot rod prongs and at least one securing orifice.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to valve trains in internal combustion engines. More particularly, this invention relates to valve actuation mechanisms using rocker arms and valve bridges to actuate intake and exhaust valves in a diesel engine.  
         BACKGROUND OF THE INVENTION  
         [0002]    Internal combustion engines typically have rocker arms to actuate intake and exhaust valves, which permit air to enter and exit each cylinder. Commonly there are separate rocker arms to actuate a valve or pair of valves. Push rods cause the rocker arms to rotate or pivot and thereby actuate the valves. The push rods extend through the engine to connect to a camshaft. As the camshaft rotates, the push rods move the rocker arms to open and close the valves. The camshaft is designed to open and close the valves in conjunction with the cycling of the piston in the cylinder.  
           [0003]    Recent valve actuation mechanism designs use rocker carriers and rocker arm assemblies with rocker arms made of plate material. For example, those disclosed in patent applications Ser. No. 09/768,520 filed on Jan. 24, 2001, by Martin Zielke for a Rocker Carrier, and Ser. No. 09/769,610 filed on Jan. 25, 2001 by Danesh et al. for a Rocker Arm Assembly, which are hereby incorporated by reference. These patent applications are both assigned to the assignee of the present patent application, International Truck and Engine Corporation. The recent designs though improved over earlier designs have some drawbacks.  
           [0004]    [0004]FIG. 1 illustrates a perspective view of a partial prior art valve actuation mechanism. There is shown a valve actuation linkage mechanism  100  generally comprising a valve bridge  10 , a pivot foot  20 , a pivot foot fastener  30  and a rocker arm  40 .  
           [0005]    [0005]FIG. 2 shows how the partial valve actuation mechanism of FIG. 1, without the valve bridge, mounted on a rocker carrier  200  which will be mounted on a cylinder head (not shown) in an internal combustion engine. The rocker arms  40  and  240  are cooperatively mounted on the rocker carrier  200  through a corresponding rocker arm pedestal or fulcrum plate  220  and fastened to the rocker carrier  200  by hold down bolts  210 . The hold down bolts  210  allow the rocker arms  40  and rocker arm fulcrum plate  220  to be pre-installed to the rocker carrier  200  thereby decreasing engine manufacturing time and costs. The rocker carrier  200  shown would be mounted on one side or bank of a V-8 type engine. The rockers arms  40  and  240  shown in FIG. 2 typically have the same configuration but differ in size. FIG. 2 shows the exhaust rocker arm  40  longer and larger than the intake rocker arm  240 . However, length and size of the rocker arms  40  and  240  is determined by the location of the intake and exhaust valves in relation to the rocker arm assembly. The rocker arms could be the same or different sizes depending on a particular engine application.  
           [0006]    Referring again to FIG. 1, the valve actuation linkage mechanism  100  could be used in an engine application having four valves per cylinder. The valve bridge  10  when actuated by the rocker arm  40  via the pivot foot  25  will act on a pair of valves, e.g., a pair of intake or exhaust valves (not shown). The rocker arm generally comprises a push rod cup  60 , a pivot ball cup  70 , a rocker arm aperture  80 , and a pivot foot end  55  having a pivot foot cup  50 . The pivot foot cup  50  accepts a pivot foot  20  secured by a pivot foot fastener  30 . The pivot foot fastener  30  secures the pivot foot  20  to the pivot foot cup  50  via a set of opposing pivot foot clamps  37  which are clamp or crimped on to the exterior surface of the pivot foot cup  50 .  
           [0007]    During engine operation, a push rod (not shown) actuates the rocker arm  40  via the push rod cup  60 . The rocker arm  40  will pivot via a gage or pivot ball (not shown) in the pivot ball cup  70 . The pivot foot  20  will in turn actuate the valves (not shown) via the Valve Bridge  10 . The pivot foot  20  contacts and acts on the valve bridge  10  to actuate valve movement (not shown) in a particular cylinder. In particular, the pivot foot bottom  25  contacts the valve bridge  10  at a top bridge contact surface area  15  to actuate valve movement. The physical makeup and positioning of the valve actuation linkage mechanism  100  is such that the of the pivot foot bottom  25  is continuously sitting on or contacting the valve bridge  10  top contact surface area  15 . In this manner, rocker arm  40  movement and force is immediately translated, via the pivot foot  20 , to the valve bridge  10 .  
           [0008]    As the rocker arm  40  moves and pivots during engine operation, the attached pivot foot pivot travels or cycles upward or downward in an arc motion. The pivot foot&#39;s  25  arcing motion and simultaneous mechanical contact on the valve bridge  10  results in friction wear between the pivot foot  20  and the bridge contact area  15 . In essence, the pivot foot bottom surface  25  travels on the bridge contact area  15  and exerts a force with both vertical  13  and horizontal  17  elements. As the rocker arm  40  pivots during engine operation, the pivot foot bottom surface  25  exerts both a vertical force  13  and a back and forth horizontal force  17 . The mechanical action between the pivot foot  20  and the valve bridge  10  results in excessive friction wear between the pivot foot contact surface  27  and the bridge contact area  15 . Additionally, the pivot foot fastener  30  encounters vertical  13  and horizontal  17  forces. This degrades and loosens the connection securing the pivot foot  20  to the rocker arm  40  pivot foot cup  50 . Moreover, the physical orientation and configuration of the rocker arm  40 , pivot foot  20 , pivot foot fastener  30  and valve bridge  10  prevent adequate oil lubrication of these interconnected and interactive parts, adding to the friction wear drawback of this design.  
           [0009]    Thus, existing valve actuation linkage mechanisms suffer from excessive wear between the pivot foot and valve bridge at the point of contact or contact area. Accordingly, there is a need for a valve actuation linkage mechanism that can be pre-assembled and that reduces friction wear on the valve assembly during operation.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention provides a valve actuation linkage mechanism for use in an internal combustion engine that reduces friction wear on the valve assembly during engine operation and can be pre-assembled resulting in decreased manufacturing time and cost. The valve actuation linkage mechanism comprises a rocker arm having a pivot rod cup, a pivot rod, a valve bridge having a pivot rod chamber, and a pivot rod retainer. The pivot rod comprises a pivot rod head, a pivot rod neck, a pivot rod body, and a pivot rod bottom. The valve bridge comprises a middle valve bridge section having the pivot rod chamber and at least one adjacent pivot rod retainer securing bore, a bottom valve bridge section, and a lubricant dimple in the pivot rod chamber. The pivot rod retainer is comprised of a pivot rod orifice having at least one pivot rod prong and at least one securing orifice.  
           [0011]    The following drawings and description set forth additional advantages and benefits of the invention. More advantages and benefits are obvious from the description and may be learned by practice of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The present invention may be better understood when read in connection with the accompanying drawings, of which:  
         [0013]    [0013]FIG. 1 shows a perspective view of a prior art valve actuation assembly;  
         [0014]    [0014]FIG. 2 shows a perspective view of the prior art valve actuation linkage mechanism of FIG. 1 installed on a rocker carrier;  
         [0015]    [0015]FIG. 3 shows a perspective view of an embodiment of a valve actuation linkage mechanism according to the present invention;  
         [0016]    [0016]FIG. 4 shows a side view of the embodiment of a valve actuation linkage mechanism shown in FIG. 3;  
         [0017]    [0017]FIG. 5 shows a perspective view of another embodiment of the valve actuation linkage mechanism according to the present invention;  
         [0018]    [0018]FIG. 6 shows a perspective view of a pivot rod and valve bridge of the valve actuation linkage mechanism of FIG. 3; and  
         [0019]    [0019]FIG. 7 shows a side view of the pivot rod and valve bridge of the valve actuation linkage mechanism of FIG. 6. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0020]    [0020]FIG. 3 illustrates a perspective view of a preferred embodiment of a valve actuation linkage mechanism  300  according to the present invention. The valve actuation linkage mechanism  300  comprises a valve bridge  310 , a pivot rod  320 , a pivot rod retainer  330  and a rocker arm  40 . The valve actuation linkage mechanism  300  depicted in FIG. 3 is preferably used in a 4-valve per cylinder engine application. Those of skill in the art will readily recognize that other engine applications are possible.  
         [0021]    The rocker arm  40  of the valve actuation linkage mechanism  300  shown in FIG. 3 retains substantially the same function and physical configuration as existing prior art rocker arms  40  (shown in FIG. 1). The rocker arm  40  will cooperate with the pivot rod  320  in the valve actuation linkage mechanism  300  to actuate the valve bridge  310 . The novel pivot foot preferably comprises a pivot rod head  329 , a pivot rod neck  327 , and a pivot rod body  325  with a pivot rod bottom  425  (shown in FIG. 4). The pivot rod head  329  preferably has a curved shape in the form of a “mushroom” head. In this manner, the pivot rod head  329  will complimentarily cooperate with a pivot rod cup  350  in the rocker arm  40 . The complimentary shapes of the curved pivot rod head  329  and the pivot rod cup  350  allow for easier motion between the two part and tend to reduce wear between them as the valve actuation linkage mechanism  300  operates.  
         [0022]    [0022]FIG. 3 also illustrates a novel valve bridge  310  that will act simultaneous on a pair of intake or exhaust valves (not shown). The valve bridge in this embodiment, the valve bridge  310  preferably comprises a pivot rod chamber  315 , a pair of fastener bores  314 , valve stem chambers  405  (shown in FIG. 4), a bottom valve bridge section  312  and a middle valve bridge section  316 . The pivot rod chamber  315  is preferably configured to be a hollow cylindrical void or chamber with a complimentary pivot rod body  325  configuration that allows insertion of the pivot rod  320 . Significantly, the configuration of the pivot rod bottom  425  and corresponding pivot rod chamber bottom  415  (shown in FIG. 4) in the valve bridge  310  will eliminate the flat surface rubbing contact  15  present in prior designs thereby substantially reducing friction wear between linkage mechanism  300  components, particularly between the pivot foot bottom  25  and the valve bridge contact surface area  15  (shown in FIG. 1). Additionally, the pivot rod chamber  315  is preferably configured such that there is a divot or dimple  417  (shown in FIG. 4) at the pivot chamber bottom  415 . The pivot or dimple  417  will preferably hold engine oil or some other lubricant to provide lubrication between the pivot rod  320  and the valve bridge  310 . In particular, lubrication between the pivot rod bottom  425  and the pivot chamber bottom  415  (shown in FIG. 4), thereby substantially reducing friction wear between the pivot rod  320  and the valve bridge  310 .  
         [0023]    The pivot rod chamber  315  is preferably located in the middle valve bridge section  316  and can be cast as part of or drilled into the valve bridge  310 . The middle valve bridge section  316  can be either a raised body portion as shown here in FIG. 3 or flush as illustrated in FIG. 1 depending on the engine application. The bottom valve bridge section  312  is preferably a raised body portion that extends away and downward from the valve bridge  310 . The bottom valve bridge section  312  is preferable since it will provide the valve bridge  310  with added structural support and strength, as there is now a pivot rod chamber  315  in the valve bridge  310 . The actual configuration of the bottom valve bridge section  312  will be determined by the particular engine application used. Also, the fastener bores  314  are typically bored into the valve bridge  310  adjacent to the pivot rod chamber  315 . The fastener bores  314  allow the pivot rod  310  to be secured in the pivot rod chamber  315  via the pivot rod retainer  330  (shown in FIGS. 6 &amp; 7).  
         [0024]    The pivot rod retainer  330  is preferably flat and comprises a pivot rod retaining area  335 , a pair of pivot rod retaining prongs  337 , and a pair of opposing fastener orifices  334 . The pivot rod retainer  330  will have a thickness, length and width that will be dependent on the particular engine application where it  330  is to be used. The pivot rod retaining prongs  337  are preferably situated in opposing positions in the pivot rod retaining area  335  adjacent to the fastener orifices  334 . The pivot rod  320  can be preferably inserted into the pivot rod retainer  320  either before or after the pivot rod retainer is secured to the valve bridge  310 . The pivot rod retaining area  335  is configured in a manner so that the pivot rod  320 , once inserted, can move as necessary as the rocker arm  40  goes through its motion during engine operation. The novel pivot rod retainer  330  and the valve bridge  310  have moved the previous prior retaining or securing location of the pivot foot  20  from the rocker arm  40  pivot foot cup  50  to the valve bridge  310 .  
         [0025]    In a first case, the pivot rod  320  is inserted into the pivot rod retainer  330  before the retainer  330  is fastened to the valve bridge  310 . The pivot rod body  325  is inserted into and travels in the pivot rod retaining area  335 . The retaining prongs  337  are resilient and flex or move to allow the pivot rod body  325  to travel in pivot rod retaining area  335 . Once the pivot rod body  325  has traveled sufficiently, the retaining prongs  337  will resiliently rebound or flex to secure the pivot rod retainer  330  to the pivot rod  320  around the pivot rod neck  327 . The connected pivot rod  320  and pivot rod retainer  330  tandem would now be fastened to the valve bridge  310  (shown in FIGS. 6 &amp; 7). The pivot rod  320  is inserted into the pivot rod chamber  315  of the valve bridge  310 . The retainer  330 /pivot rod  320  combination is then preferably secured to the valve bridge by using a pair of valve bridge fasters  614  (shown in FIGS. 6 &amp; 7), e.g., drill screws or rivets.  
         [0026]    In a second case, the pivot rod retainer  330  is first secured to the valve bridge  310  by a pair of fasters  614  inserted into the valve bridge fastener bores  314 (shown in FIGS. 6 &amp; 7). The pivot rod  320  is next inserted into the pivot rod retainer  330  so that the pivot rod body  325  travels in the pivot rod retaining area  335 . The resilient retaining prongs  337  flex or move to allow the pivot rod body  325  to travel in the pivot rod retaining area  335 . Once the pivot rod body  325  has traveled sufficiently, the retaining prongs  337  will resiliently rebound or flex to secure the pivot rod  320 , about the pivot rod neck  327 , to the valve bridge  310  in the pivot rod chamber  315  (shown in FIGS. 6 &amp; 7).  
         [0027]    Once the pivot rod  320  has been secured to the valve bridge  310 , the rocker arm  40  can interact or cooperate with the pivot rod  320 /valve bridge  310  combination in the valve actuation linkage mechanism  300  to actuate corresponding valves (not shown). During operation of the valve actuation linkage mechanism  300 , the pivot rod  320  will operate in a manner substantially similar to that of a push rod (not shown). The pivot rod  320  rotates freely and moves about the pivot rod head  329  and pivot rod bottom  425  (shown in FIG. 4) as necessary to account for the rotation and translation required for a 4-valve per cylinder engine requiring a valve bridge  310 . There is enough play or space in the pivot rod retaining area  335  so that the pivot rod body  325  can move back and forth or vertically to translate the motion of the rocker arm  40  to the valve bridge  310  to appropriately actuate the valves (not shown) during engine operation.  
         [0028]    [0028]FIG. 4 illustrates a side view of the valve actuation linkage mechanism  300  shown in FIG. 3. There is shown the rocker arm  40 , the pivot rod  320 , the pivot rod retainer  330 , and the valve bridge  310 . The pivot foot  320  comprising a pivot rod head  329 , a pivot rod neck  327 , and a pivot rod body  325  with a pivot rod bottom  425  is more clearly illustrated. Also shown is the pivot rod head  329  with the preferred curved shape in the form of a “mushroom” head.  
         [0029]    [0029]FIG. 4 shows, in better detail, the valve bridge  310  comprising a pivot rod chamber  315 , a pair of fastener bores  314 , valve stem chambers  405 , a bottom valve bridge section  312  and a middle valve bridge section  316 . There is shown the pivot rod chamber  315  hollow cylindrical void or chamber configuration, which will complimentarily interact or cooperate with the pivot rod body  325 . The complimentary configurations of the pivot rod bottom  425  and the corresponding pivot rod chamber bottom  415  will eliminate the flat surface rubbing contact  15  present in prior designs to substantially reduce friction wear between the pivot rod  320  and the valve bridge  310 . Additionally, there is shown the divot or dimple  417  at the pivot chamber bottom  415  which will hold engine oil or some other lubricant to provide lubrication between the pivot rod  320  and the valve bridge  310 . The lubrication between the pivot rod bottom  425  and the pivot chamber bottom  415  will further reduce friction wear between the pivot rod  320  and the valve bridge  310 .  
         [0030]    [0030]FIG. 4 also shows, the pivot rod chamber  315  preferably located in the middle valve bridge section  316 . The middle valve bridge section  316  may be either a raised body portion as shown here or flush as illustrated in FIG. 1, depending on the particular engine application. The bottom valve bridge section  312  provides the valve bridge  310  added structural support and strength as there is now a pivot rod chamber  315  in the valve bridge  310 . The bottom valve bridge section  312  is preferably a raised body portion that extends away and downward from the valve bridge  310 . Also, shown are the fastener bores  314  typically bored into the valve bridge  310  adjacent to the pivot rod chamber  315 . The fastener bores  314  allow the pivot rod  310  to be secured in the pivot rod chamber  315  via the pivot rod retainer  330  (shown in FIGS. 6 &amp; 7). FIG. 4 also shows the preferred flat shape of the pivot rod retainer  330 .  
         [0031]    [0031]FIG. 5 illustrates a perspective view of a second embodiment of the valve actuation linkage mechanism  500  according to the present invention. The second embodiment of the valve actuation linkage mechanism  500  is identical to the first embodiment of the valve actuation linkage mechanism  500  shown in FIG. 1. There is one main exception, there is no use of the pivot rod retainer  330  (show in FIGS. 3 &amp; 4). The valve actuation linkage mechanism  500  here is preferably held in proper positioning by the close tolerances between the rocker arm  40 , the pivot rod  320  and the valve bridge  310  once the valve actuation linkage mechanism  500  is operationally installed in an engine using this embodiment.  
         [0032]    The valve actuation linkage mechanism  500  will operate in a manner substantially similar to that described for the first embodiment of the valve actuation linkage mechanism  300 (FIG. 3). Once the pivot rod  320  has been installed in the valve bridge  310 , the rocker arm  40  will cooperate with the pivot rod  320 /valve bridge  310  combination to actuate corresponding valves (not shown). The pivot rod  320  rotates freely and moves about the pivot rod head  329  and pivot rod bottom  425  (shown in FIG. 4) as necessary to account for the rotation and translation required for a 4-valve per cylinder engine requiring a valve bridge  310 . There is enough play or space in the pivot rod chamber  315  so that the pivot rod body  325  can move back and forth to translate the motion of the rocker arm  40  to the valve bridge  310  to appropriately actuate the valves (not shown) during engine operation.  
         [0033]    [0033]FIG. 6 shows a perspective view of a pivot rod  320  and valve bridge  310  of the valve actuation linkage mechanism  300  shown in FIG. 3. FIG. 6 shows the pivot rod  320  and pivot rod retainer  330  secured to the valve bridge  310  by a pair of fasteners  614  inserted into the valve bridge fastener bores  314 . The resilient retaining prongs  337  are shown securing the pivot rod  320  about the pivot rod neck  327  to the valve bridge  310  in the pivot rod chamber  315  (shown in FIG. 7). Also, the pivot rod retainer  330  comprises a pivot rod retainer area  335  that is configured to allow the pivot rod  320  movement or play within the pivot rod area  335  during valve actuation. Once the pivot rod  320  has been secured to the valve bridge  310 , the rocker arm  40  cooperates with the pivot rod  320 /valve bridge  310  combination to actuate corresponding valves (not shown). The pivot rod body  325  will preferably move back and forth in the pivot rod chamber and vertically to translate the motion of the rocker arm  40  to the valve bridge  310  and thereby actuate the valves (not shown) during engine operation.  
         [0034]    [0034]FIG. 7 shows a side view of a pivot rod  320  and valve bridge  310  of the partial valve actuation linkage mechanism  300  shown in FIG. 6. There is shown the pivot rod  320  appropriately positioned in the pivot rod chamber  315  and secured to the valve bridge  310  by the pivot rod retainer  330  by a pair of fasteners  614 . The fasteners are preferably inserted into a pair of opposing the valve bridge fastener bores  314  located adjacent to the pivot rod chamber  315 . The pivot rod retainer  330  is shown securing the pivot rod  320  about the pivot rod neck  327  to the valve bridge  310 . Once the pivot rod  320  has been secured to the valve bridge  310 , the rocker arm  40  cooperates with the pivot rod  320 /valve bridge  310  combination to actuate corresponding valves (not shown).  
         [0035]    [0035]FIG. 7 shows a pivot rod chamber movement area  715  that allows the pivot rod to move back and forth inside the pivot rod chamber  315  to compensate for the arc motion of the rocker arm  40  (shown in FIG. 3) during engine operation. In this manner the vertical motion of the rocker arm  40  can be translated to the to the valve bridge  310  during engine operation. There is also shown the complimentary round nature of the pivot rod bottom  425  and the pivot rod chamber bottom  415 . The complimentary configurations of the pivot rod bottom  425  and the corresponding pivot rod chamber bottom  415  eliminate the flat surface rubbing contact  15  present in prior designs such as shown in FIG. 1. Instead of the flat surface contact area  15  (shown in FIG. 1), the complimentary curved surfaces of the pivot rod bottom  425  and the corresponding pivot rod chamber bottom  415  result in a contact line or contact line area  725  between both components. The resultant contact line area  725  is smaller than the flat surface rubbing contact  15  shown in FIG. 1 and thus substantially reduces friction wear between the pivot rod  320  and the valve bridge  310 . Additionally, the pivot rod chamber  315  has a divot or dimple  417  at the pivot rod chamber bottom  415  which will hold engine oil or some other lubricant to provide lubrication between the pivot rod  320  and the valve bridge  310 . The lubrication between the pivot rod bottom  425  and the pivot chamber bottom  415  further reduces friction wear between the pivot rod  320  and the valve bridge  310 .  
         [0036]    The invention has been described and illustrated with respect to certain preferred embodiments by way of example only. Those skilled in that art will recognize that the preferred embodiments may be altered or amended without departing from the true spirit and scope of the invention. Therefore, the invention is not limited to the specific details, representative devices, and illustrated examples in this description. The present invention is limited only by the following claims and equivalents.