Two-step roller finger cam follower

Abstract

A two-step roller finger follower assembly for shifting between high-lift and low-lift valve modes in a valve train of an internal combustion engine includes a body having side members defining coaxially disposed shaft orifices, a pallet end, a socket end, a slider arm aperture, and a latch pin channel. The socket end is mountable to a hydraulic lash adjuster, and the pallet end is matable with a valve stem. A slider arm for engaging a high-lift cam lobe is disposed in the aperture, is pivotably mounted to a rotatable cross-shaft extending through the shaft orifices, and includes a slider tip for selectively engaging a latch pin to latch or unlatch the slider arm from the body. Dual rollers on the cross-shaft follow dual low-lift cam lobes. Preferably, the slider arm has a compound radial surface to provide compound lost motion of the slider arm, thereby minimizing rotational inertia.

1 . A roller finger follower assembly for use in conjunction with a cam shaft and valve train of an internal combustion engine, the camshaft having at least one first lobe and at least one second lobe, said roller finger follower assembly comprising:
 a) a body having a first side member and a second side member defining coaxial first and second shaft orifices, said body further defining a slider arm aperture;   b) a shaft supported in said shaft orifices and extending across said slider arm aperture and supportive of at least one roller for engaging said first cam lobe;   c) a slider arm disposed in said slider arm aperture and mounted for pivotal motion about an axis of said shaft and having a surface for engaging said second cam lobe and having an end; and   d) a latch pin disposed in said latch pin channel for selectively engaging said slider end to switch modes of the roller finger follower assembly.   
   
   
       2 . A roller finger follower assembly in accordance with  claim 1  wherein said first cam lobe is a low-lift lobe and said second cam lobe is a high-lift lobe. 
   
   
       3 . A roller finger follower assembly in accordance with  claim 2  comprising two of said rollers for following two of said low-lift cam lobes. 
   
   
       4 . A roller finger follower assembly in accordance with  claim 3  wherein said shaft extends through said body and wherein said two rollers are disposed on said shaft on opposite sides respectively of said body. 
   
   
       5 . A roller finger follower assembly in accordance with  claim 1  further including a bushing disposed between the shaft and at least one of said shaft orifices. 
   
   
       6 . A roller finger follower assembly in accordance with  claim 5  wherein said bushing is fixed in said at least one of said shaft orifices to prevent relative rotational motion between said bushing and said at least one of said shaft orifices. 
   
   
       7 . A roller finger follower assembly in accordance with  claim 1  wherein said slider arm surface is a compound surface. 
   
   
       8 . A roller finger follower assembly in accordance with  claim 7  wherein said compound surface comprises a plurality of arcuate portions having differing radii. 
   
   
       9 . A roller finger follower assembly in accordance with  claim 1  wherein at least one of said body and said slider arm includes at least one rotational limiter. 
   
   
       10 . A roller finger follower assembly in accordance with  claim 1  further comprising a bias spring grounded to said body and said slider arm. 
   
   
       11 . A camshaft-engaging element in a two-step roller finger follower assembly comprising a slider surface for making contact with a cam lobe, said slider surface having a compound surface. 
   
   
       12 . An element in accordance with  claim 11  wherein said compound surface comprises a plurality of arcuate sections having differing radii. 
   
   
       13 . An internal combustion engine including a camshaft having high-lift and low-lift cam lobes, comprising a roller finger follower assembly for selectively adjusting the lift of an associated engine valve, wherein said roller finger follower assembly includes,
 a body having a first side member and a second side member defining coaxial first and second shaft orifices, said body further defining a slider arm aperture,   a shaft supported in said shaft orifices and extending across said slider arm aperture and supportive of at least one roller for engaging said first cam lobe,   a slider arm disposed in said slider arm aperture and mounted for pivotal motion about an axis of said shaft and having a surface for engaging said second cam lobe and having an end, and   a latch pin disposed in said latch pin channel and for selectively engaging said slider end to switch modes of said roller finger follower assembly.