Engine brake lash adjuster device and method

Abstract

A compression brake device and method are provided that include a lash member coupled to a rocker arm. The lash member has a first position that forces opening of the valve when the rocker arm is at the lower position. The brake also includes a lost motion cylinder at least partially defined within the rocker arm. The cylinder is biased towards a position of greatest internal displacement volume. The lost motion cylinder has a first operational mode wherein the lost motion cylinder permits compression thereof such that the ability of the rocker arm to open an exhaust valve is a function of the position of the lash member. The lost motion cylinder has a second operational mode wherein the lost motion cylinder retards compression thereof such that the ability of the rocker arm to open an exhaust valve is independent of the position of the lash member.

1 . A compression brake including:
 a rocker arm pivotable about a rocker arm shaft to selectively force an exhaust valve to an open condition, the rocker arm having a lower position, an upper position, and a plurality of positions intermediate the lower and upper positions;   a lash member coupled to the rocker arm, the lash member being configurable to define a plurality of positions relative to the rocker arm, the lash member having a first position that forces opening of the valve when the rocker arm is at the lower position, and   a lost motion cylinder at least partially defined within the rocker arm, the cylinder biased towards a position of greatest internal displacement volume, the lost motion cylinder having a first operational mode wherein the lost motion cylinder permits compression thereof such that the ability of the rocker arm to open an exhaust valve is a function of the position of the lash member, the lost motion cylinder having a second operational mode wherein the lost motion cylinder retards compression thereof such that the ability of the rocker arm to open an exhaust valve is independent of the position of the lash member.   
     
     
         2 . The engine of  claim 1 , wherein the second operational mode of the lost motion cylinder is an engine compression braking mode and the first operational mode of the lost motion cylinder is a non-engine compression braking mode. 
     
     
         3 . The engine of  claim 1 , further including a seal valve within the rocker arm that, when closed, places the lost motion cylinder into the second operational mode. 
     
     
         4 . The engine of  claim 3 , wherein the seal valve is biased towards a closed position. 
     
     
         5 . The engine of  claim 3 , wherein the seal valve includes an actuator that abuts a portion of an engine when the rocker arm is in the lower position to place the seal valve in the open position and to place the lost motion cylinder in the second operational mode. 
     
     
         6 . The engine of  claim 3 , further including a lock that holds the seal valve in the open position. 
     
     
         7 . The engine of  claim 6 , further including a solenoid that selectively releases the lock. 
     
     
         8 . A compression brake mechanism including:
 a rocker arm operable to selectively engage an engine valve;   a lash member having a plurality of settings that define lash between rocker arm movement and engine valve movement; and   a lost motion mechanism disposed between the lash member and the engine valve; the lost motion mechanism having a first operational mode and a second operational mode, the first operational mode providing an ability to open an engine valve as a function of the lash member setting, the second operational mode providing an ability to open an engine valve independent of the lash member setting.   
     
     
         9 . The brake mechanism of  claim 8 , further comprising an engine valve upon which the lash member acts, wherein the engine valve is an exhaust valve and the second operational mode provides engine compression braking. 
     
     
         10 . The brake mechanism of  claim 8 , further including at least one seal valve within the rocker arm, the at least one seal valve being operable such that the second operational mode of the lost motion mechanism traps fluid within a portion of the rocker arm. 
     
     
         11 . The brake mechanism of  claim 10 , wherein the trapping of fluid prevents loss of motion by the lost motion mechanism. 
     
     
         12 . The brake mechanism of  claim 10 , further including a lock operable to hold the lost motion mechanism in the first operational mode. 
     
     
         13 . The brake mechanism of  claim 12 , wherein the seal valve is biased to a closed position corresponding to the second operational mode, and releasing the hold provided by the lock permits the biasing of the seal valve to assume the closed position. 
     
     
         14 . The brake mechanism of  claim 13 , further including a reset pin that is selectively locked by the lock, the reset pin having a first portion extending outside of the rocker arm, force applied to the first portion urging opening of the seal valve. 
     
     
         15 . The brake mechanism of  claim 8 , wherein the lost motion mechanism includes a cylinder, the first operational mode permitting egress of fluid from the cylinder, the second operational mode preventing egress of fluid from the cylinder. 
     
     
         16 . The brake mechanism of  claim 15 , wherein the lash member provides a limit on the travel of the cylinder. 
     
     
         17 . The brake mechanism of  claim 15 , wherein the lash member provides a limit on the minimum interior volume of the cylinder. 
     
     
         18 . The brake mechanism of  claim 8 , wherein the brake is operational on a 4-stroke engine, wherein the lost motion mechanism is in the first operational mode during an exhaust stroke and the lost motion mechanism, when in the second operational mode, releases fluid compressed during a compression stroke. 
     
     
         19 . The brake mechanism of  claim 8 , wherein the brake mechanism is part of an internal combustion engine. 
     
     
         20 . A method of operating an exhaust valve on an internal combustion engine including:
 providing a lost motion cylinder at least partially within a rocker arm operable to open the exhaust valve;   providing a lash member to define a maximum travel of a piston of the cylinder that defines a first internal volume of the cylinder;   providing a seal valve within the rocker arm to selectively seal and open the internal volume of the cylinder;   closing the seal valve when the internal volume of the cylinder is a second internal volume that is greater than a the first volume defined by the lash member thereby sealing fluid within the cylinder;   rotating the rocker arm with the seal valve closed to force open the exhaust valve;   opening the seal valve to release fluid from the cylinder; and   rotating the rocker arm with the seal valve open such that the cylinder assumes the first internal volume to force open the exhaust valve.   
     
     
         21 . The method of  claim 20 , wherein rotating the rocker arm with the seal valve closed causes opening of the exhaust valve. 
     
     
         22 . A method of adjusting lash between an exhaust valve and a rocker arm on an operating internal combustion engine including:
 providing a rocker arm having a first lash member defining a first lash amount between the rocker arm and the exhaust valve, the first lash amount defining a first point during downward travel of the rocker arm at which the exhaust valve is opened;   providing a lash variance member defining a second lash amount between the rocker arm and the exhaust valve that is smaller than the first lash amount, the second last amount defining a second point in the downward travel of the rocker arm at which the exhaust valve is opened, the second point being higher than the first point; and   toggling between the first and second lash amounts within a cycle of the engine.   
     
     
         23 . The method of  claim 22 , wherein the lash variance member includes a hydraulic piston. 
     
     
         24 . The method of  claim 23 , wherein the hydraulic piston includes a displacement, the displacement being limited by the first lash member to define a first displacement. 
     
     
         25 . The method of  claim 23 , wherein the second lash amount is defined by a second displacement of the hydraulic piston that is greater than the first displacement.