Rocker arm with outwardly sprung hydraulic actuator piston

Abstract

A rocker arm comprises a hydraulic actuator piston slidably disposed in an actuator bore. An actuator spring is configured to bias the hydraulic actuator piston out of actuator bore and into contact with a valve train component or at least one engine valve, wherein reaction of the hydraulic actuator piston against the valve train component or the at least one engine valve biases a motion receiving portion of the rocker arm into contact with the valve actuation motion source. In an unactuated state of the hydraulic actuator piston, hydraulic fluid is permitted to flow out of the actuator bore and, in an actuated state of the hydraulic actuator piston, hydraulic fluid is locked in the actuator bore.

What is claimed is: 
     
         1 . A rocker arm for conveying valve actuation motions, the rocker arm comprising a motion receiving portion configured to receive the valve actuation motions from a valve actuation motion source and a motion imparting portion configured to convey the valve actuation motions to a valve train component or at least one engine valve, the rocker arm further comprising:
 a hydraulic actuator piston slidably disposed in an actuator bore; and   an actuator spring configured to bias the hydraulic actuator piston out of actuator bore and into contact with the valve train component or the at least one engine valve, wherein reaction of the hydraulic actuator piston against the valve train component or the at least one engine valve biases the motion receiving portion of the rocker arm into contact with the valve actuation motion source,   wherein, in an unactuated state of the hydraulic actuator piston, hydraulic fluid is permitted to flow out of the actuator bore and, in an actuated state of the hydraulic actuator piston, hydraulic fluid is locked in the actuator bore.   
     
     
         2 . The rocker arm of  claim 1 , wherein the actuator spring is configured to absorb the valve actuation motions received from the valve actuation motions source during the unactuated state. 
     
     
         3 . The rocker arm of  claim 1 , wherein the rocker arm is a center pivot rocker arm. 
     
     
         4 . The rocker arm of  claim 1 , wherein the actuator bore is formed in the motion imparting portion of the rocker arm. 
     
     
         5 . The rocker arm of  claim 1 , wherein the at least one engine valve comprises at least one exhaust valve and the valve actuation motion source is an auxiliary valve actuation motion source separate from a main valve actuation motion source. 
     
     
         6 . The rocker arm of  claim 1 , further comprising:
 a control valve comprising a control valve piston slidably disposed in a control valve bore;   a first hydraulic fluid passage in fluid communication with the control valve bore and the actuator bore;   a second hydraulic passage in fluid communication with the control valve bore and configured to receive hydraulic fluid from a constant hydraulic fluid supply; and   a vent port in fluid communication with the first hydraulic passage and the control valve bore,   wherein, in the unactuated state, the control valve piston is positioned within the control valve bore to permit flow of hydraulic fluid from the second hydraulic passage to the first hydraulic passage and the actuator bore and to permit flow of hydraulic fluid from the first hydraulic passage to the control valve bore through the vent port,   and wherein, in the actuated state, the control valve piston is positioned within the control valve bore to occlude the first hydraulic passage and the vent port thereby locking hydraulic fluid in the first hydraulic passage and the actuator bore.   
     
     
         7 . The rocker arm of  claim 6 , wherein the control valve bore is formed in the motion imparting portion of the rocker arm. 
     
     
         8 . The rocker arm of  claim 6 , further comprising:
 a selectable hydraulic fluid passage in fluid communication with the control valve bore and configured to receive hydraulic fluid from a selectable hydraulic fluid supply.   
     
     
         9 . The rocker arm of  claim 8 , wherein the control valve piston has a piston bore formed therein, an annular channel formed on an outer diameter of the control valve piston and a radial opening in fluid communication with the piston bore and the annular channel, and wherein the piston bore is configured to receive hydraulic fluid from the selectable hydraulic fluid passage via the control valve bore. 
     
     
         10 . The rocker arm of  claim 9 , wherein the annular channel is configured to provide fluid communication between the first and second hydraulic passages during the unactuated state. 
     
     
         11 . The rocker arm of  claim 9 , further comprising:
 a checking element disposed in the control valve piston between the piston bore and the radial opening and configured to permit flow of hydraulic fluid from the piston bore to the annular channel via the radial opening, but not vice versa.