Valve drive for an internal combustion engine

Abstract

The invention relates to a valve drive for internal combustion engines, comprising at least one cam assembly which can be axially displaced on a camshaft. The assembly consists of at least two cams having different profiles and actuating optionally at least one gas exchange valve for adjusting different valve lifts and/or valve timing. The aim of the invention is to create a space-saving and simple valve drive for an internal combustion engine of the aforementioned type, which allows valve lift and/or valve timing to be adjusted without an additional actuation stage. For this purpose, one cam is connected to the camshaft so as to rotate with the camshaft and the other cam is mounted so as to be rotated on the camshaft. The cam that is rotationally mounted on the camshaft can be positively connected to and released from the cam that is connected so as to rotate with the camshaft via a controlled pilot and main locking plunger. The rotationally fixed cam has a larger profile height than the rotationally mounted cam. The larger profile height is designed for a relatively large lift of the gas exchange valve, while the lower cam profile height is designed for smaller lift heights. By displacing the cam assembly when the cams are coupled, the cam with the larger or the smaller profile height can be engaged with the gas exchange valve. A zero lift of the gas exchange valve can be adjusted, when the cam with the smaller profile height engages, by decoupling the rotational cam from the cam that is arranged on the camshaft so as to rotate therewith.

1 . Valve drive for an internal combustion engine, with at least one cam assembly that is axially displaceable on a camshaft and consists of at least two cams, which are provided with different profiles and which selectively actuate at least one gas-exchange valve for adjustment of different valve lifts and/or valve control times,
 wherein   one cam ( 2 ;  2 ′) is connected to the camshaft ( 1 ) so as to rotate with it, and the other cam ( 3 ;  3 ′) is mounted rotatably on the camshaft ( 1 ) and, can be connected, with shape fit, with the cam ( 2 ;  2 ′) disposed on the camshaft ( 1 ) so as to rotate with it, by way of a controllable main locking plunger ( 6 ;  6 ), and separated from it.   
   
   
       2 . Valve drive according to  claim 1 ,
 wherein   the profile height of the cam ( 2 ;  2 ′) is larger, as compared with the profile height of the cam ( 3 ;  3 ′) mounted rotatably on the camshaft ( 1 ).   
   
   
       3 . Valve drive according to  claim 1 ,
 wherein   a groove-like guide ( 8 ;  8 ′) is disposed in the region of the base circle ( 15 ;  15 ′) of the cam ( 3 ;  3 ′) disposed rotatably on the camshaft ( 1 ), with which guide a pilot locking plunger ( 16 ;  16 ′) can be engaged and disengaged, which is mounted and is controllably displaceable in a blind-hole bore ( 17 ;  17 ′) of the base circle ( 14 ;  14 ′) of the cam ( 2 ;  2 ′) connected with the camshaft so as to rotate with it.   
   
   
       4 . Valve drive according to  claim 1 ,
 wherein   the blind-hole bore ( 17 ;  17 ′) is in communication, by way of supply ducts, with a controllable pressurized-oil supply for displacement of the pilot locking plunger ( 16 ;  16 ′) in the direction of the groove-like guide ( 8 ;  8 ′).   
   
   
       5 . Valve drive according to  claim 1 ,
 wherein   a spring ( 18 ;  18 ′) is disposed on the bottom of the pilot locking plunger ( 16 ;  16 ′), which spring acts against the oil pressure acting to displace the pilot locking plunger ( 16 ;  16 ′) in the direction of the groove-like guide ( 8 ;  8 ′), and displaces the pilot locking plunger ( 16 ;  16 ′) in the direction of the bottom of the blind-hole bore ( 17 ;  17 ′) upon disconnection of the oil pressure for displacing the pilot locking plunger ( 16 ;  16 ′) in the direction of the groove-like guide ( 8 ;  8 ′), and the connection of the cam ( 3 ;  3 ′) with the cam ( 2 ;  2 ′) is de-interlocked by means of the pilot locking plunger ( 16 ;  16 ′).   
   
   
       6 . Valve drive according to  claim 1 ,
 wherein   the groove-like guide ( 8 ;  8 ′) extends over approximately 180° in the region of the base circle ( 15 ;  15 ′) of the cam ( 3 ;  3 ′).   
   
   
       7 . Valve drive according to  claim 1 ,
 wherein   a blind-hole bore ( 20 ;  20 ′) is disposed, in the region of the cam ( 2 ;  2 ′), in which bore a displaceable main locking plunger ( 6 ;  6 ′) is controllably mounted, which can be engaged with and disengaged from a blind-hole bore ( 13 ;  13 ′) disposed in the region of the cam ( 3 ;  3 ′).   
   
   
       8 . Valve drive according to  claim 1 ,
 wherein   the blind-hole bore ( 20 ;  20 ′) in the cam ( 2 ;  2 ′) and the blind-hole bore ( 13 ;  13 ′) in the cam ( 3 ;  3 ′) are in communication with a controllable pressurized-oil supply for displacement of the main locking plunger ( 6 ;  6 ′).   
   
   
       9 . A valve drive according to  claim 1 ,
 wherein   a spring ( 7 ) is disposed between the bottom of the main locking plunger ( 6 ;  6 ′) and the bottom of the blind-hole bore ( 20 ;  20 ′) in the cam ( 2 ;  2 ′).