Variable valve actuation system configurations

Abstract

Valve actuation systems are disclosed herein that allow valve closing timing to be varied using a lost-motion system. In some embodiments, an actuation system is provided that has a locked configuration in which a bearing element is held in place between first and second valve train components to transmit cam motion to an engine valve. The actuation system also has an unlocked configuration in which the bearing element is permitted to be at least partially ejected from between the first and second valve train components, such that cam motion is not transmitted to the engine valve. A number of valve train configurations are disclosed, including a pushrod with a translating follower, a pushrod with an end-pivoted follower, a center-pivoted rocker, an end-pivoted rocker, and a direct attack valve train with a bucket tappet.

What is claimed is: 
     
         1 . A lost-motion variable valve actuation system, comprising:
 a rocker arm having a first rocker pad that engages an engine valve and a second rocker pad;   a pushrod having a first end in engagement with the second rocker pad and a second end in engagement with a follower; and   an actuation system configured to selectively permit a bearing element to be at least partially ejected from between the follower and a cam to allow the engine valve to close.   
     
     
         2 . The system of  claim 1 , wherein the follower comprises a cylindrical canister with a closed end that defines a contact surface that engages the bearing element. 
     
     
         3 . The system of  claim 1 , wherein the follower is configured to rotate about an axis of rotation and wherein the follower comprises a first end having a bore formed therein through which a shaft extends along the axis of rotation and a second end opposite the first end that engages the bearing element. 
     
     
         4 . The system of  claim 3 , wherein the second end comprises a roller rotatably mounted therein such that the roller engages the bearing element. 
     
     
         5 . The system of  claim 3 , wherein the second end of the pushrod engages the follower at a location intermediate to the first and second ends of the follower. 
     
     
         6 . The system of  claim 3 , wherein the pushrod is coupled to the follower by a ball and socket coupling. 
     
     
         7 . The system of  claim 1 , wherein the engine valve is inwardly-opening. 
     
     
         8 . The system of  claim 1 , wherein the actuation system has a locked configuration in which the bearing element is maintained between the follower and the cam and an unlocked configuration in which the bearing element can be at least partially ejected from between the follower and the cam. 
     
     
         9 . A lost-motion variable valve actuation system, comprising:
 a rocker arm having a first rocker pad that engages an engine valve and a second rocker pad; and   an actuation system configured to selectively permit a bearing element to be at least partially ejected from between the second rocker pad and a cam to allow the engine valve to close;   wherein the rocker arm is configured to rotate about an axis of rotation.   
     
     
         10 . The system of  claim 9 , wherein the first and second rocker pads are formed at opposed ends of the rocker arm and wherein the axis of rotation is disposed intermediate to the first and second rocker pads. 
     
     
         11 . The system of  claim 9 , wherein the axis of rotation is disposed at a first end of the rocker arm, the first rocker pad is formed at a second, opposite end of the rocker arm, and the second rocker pad is formed at a location intermediate to the first and second ends of the rocker arm. 
     
     
         12 . The system of  claim 9 , wherein the second rocker pad comprises a roller rotatably mounted in the rocker arm. 
     
     
         13 . The system of  claim 9 , wherein the engine valve is inwardly-opening. 
     
     
         14 . The system of  claim 9 , wherein the actuation system has a locked configuration in which the bearing element is maintained between the rocker arm and the cam and an unlocked configuration in which the bearing element can be at least partially ejected from between the rocker arm and the cam.