Positively guided valve drive

Abstract

In a positively guided valve drive of an internal combustion engine including a cam having a flexible belt wrapped around it and being pivotally connected to a valve shaft, the flexible belt is connected to the valve shaft by means of a carriage which has three parallel shafts two of the shafts being connected to the ends of the flexible belt and the third shaft being connected to the valve shaft for operating the valve.

1 . A positively guided valve drive ( 1 ) for an internal combustion engine comprising at least one driven cam element ( 5 ), a valve actuating element ( 2 ) actuated by the cam element ( 5 ), a flexible wrap-around element ( 11 ) extending around the cam element ( 5 )), a connecting element ( 12 ) connected to said actuating element ( 2 ) and having a connecting shaft ( 15 ) which extends parallel to an axis ( 8 ) of rotation of the element ( 5 ), the valve actuating element ( 2 ) being pivotally connected to the connecting element ( 12 ) by the connecting shaft ( 15 ), and the connecting element ( 12 ) having two additional shafts ( 13 ,  14 ) which extend parallel to the connecting shaft ( 15 ), the wrap-around element ( 11 ) being of open design and having opposite ends, each attached to one of the additional shafts ( 13 ,  14 ).  
   
   
       2 . The valve drive as claimed in  claim 1 , wherein the connecting element ( 12 ) comprises two spaced side parts ( 16 ,  17 ) which are essentially flat, are arranged parallel to one another and are connected to one another by the connecting shaft ( 15 ) and the two additional shafts ( 13 ,  14 ) which are all arranged perpendicularly to the side parts ( 16 ,  17 ).  
   
   
       3 . The valve drive as claimed in  claim 1 , wherein the side parts ( 16 ,  17 ) of the connecting element ( 12 ) are curved at their ends facing the cam element ( 5 ) with a curve radius corresponding essentially to the smallest curve radius of the cam element ( 5 ).  
   
   
       4 . The valve drive as claimed in  claim 1 , wherein the ends of the open wrap-around element ( 11 ) can be wound onto, and unwound from, the respective additional shafts ( 13 ,  14 ).  
   
   
       5 . The valve drive as claimed in  claim 1 , wherein the connecting shaft ( 15 ) and the additional shafts ( 13 ,  14 ) are arranged on the connecting element ( 12 ) in such a way that the additional shafts ( 13 ,  14 ) have a shorter radial distance from the axis ( 8 ) of rotation of the cam than the connecting shaft ( 15 ).  
   
   
       6 . The valve drive as claimed in  claim 1 , wherein the wrap-around element ( 11 ) is a finite metallic tie strap.  
   
   
       7 . The valve drive as claimed in  claim 6 , wherein the additional shafts ( 13 ,  14 ) each have a slot ( 21 ) through which the wrap-around element ( 11 ) extends and is connected to the additional shafts ( 13 ,  14 ) in a frictionally locking fashion.  
   
   
       8 . The valve drive as claimed in  claim 7 , wherein the additional shafts ( 13 ,  14 ) have entry regions at the slots ( 21 ) with a rounded contour.  
   
   
       9 . The valve drive as claimed in  claim 1 , wherein the wrap-around element ( 11 ) is embodied as a polymer tie belt with vulcanized-in tie lines ( 29 ).  
   
   
       10 . The valve drive as claimed in  claim 9 , wherein the wrap-around element ( 11 ) has bearing sections ( 27 ,  28 ) at the open ends for attachment to the additional shafts ( 13 ,  14 ) of the connecting element ( 12 ).  
   
   
       11 . The valve drive as claimed in  claim 10 , wherein regions ( 30 ) which are provided with filling material or damping material are provided between the bearing sections ( 27 ,  28 ) and the tie lines ( 29 ).