Systems and Methods for Timing of Valve Lift Events

Abstract

A rocker arm assembly is configured to selectively actuate one or more exhaust valves. A method for timing valve lift events comprises actuating an exhaust rocker arm based on an exhaust lift profile and actuating an engine brake rocker arm based on an engine brake profile. The exhaust lift profile and the engine brake lift profile can have cross points. A method disclosed comprises minimizing an angle defined between the exhaust lift profile and the engine brake lift profile at a cross point.

What is claimed is: 
     
         1 . A method for timing valve lift events of a rocker arm assembly of an internal combustion engine, the rocker arm assembly comprising an exhaust rocker arm and an engine brake rocker arm and configured to selectively actuate one or more of a first exhaust valve or a second exhaust valve, the method comprising:
 enabling actuation of the first exhaust valve and the second exhaust valve by the exhaust rocker arm;   actuating the exhaust rocker arm based on an exhaust lift profile;   enabling actuation of the second exhaust valve by the engine brake rocker arm independent of actuation of the first exhaust valve; and   actuating the engine brake rocker arm based on an engine brake lift profile,   wherein the exhaust lift profile and the engine brake lift profile have a first cross point and a second cross point, and   wherein an angle defined between a tangent to the exhaust lift profile and a tangent to the engine brake lift profile is minimized at the first cross point and the second cross point so as to respectively minimize a velocity difference between the first exhaust valve and the second exhaust valve at each of the first cross point and the second cross point.   
     
     
         2 . The method of  claim 1 , wherein the engine brake lift profile comprises a first engine brake lift sub-profile, a second engine brake lift sub-profile, a third engine brake lift sub-profile, and a fourth engine brake lift sub-profile. 
     
     
         3 . The method of  claim 2 , wherein the exhaust lift profile is subsequent to the second engine brake lift sub-profile and overlaps with the third engine brake lift sub-profile at the first cross point and with the fourth engine brake lift sub-profile at the second cross point, wherein the exhaust lift profile is tangent with the third engine brake lift sub-profile at the first cross point and is tangent with the fourth engine brake lift sub-profile at the second cross point. 
     
     
         4 . The method of  claim 2 , wherein, when the actuation of the first exhaust valve and the second exhaust valve by the exhaust rocker arm is enabled and the actuation of the second exhaust valve by the engine brake rocker arm is enabled, the actuation of the first exhaust valve is based on the exhaust lift profile, and the actuation of the second exhaust valve is based on the first engine brake lift sub-profile, the second engine brake lift sub-profile, and the exhaust lift profile. 
     
     
         5 . The method of  claim 2 , wherein, when the actuation of the first exhaust valve and the second exhaust valve by the exhaust rocker arm is enabled and the actuation of the second exhaust valve by the engine brake rocker arm is enabled, one cylinder pressure peak is generated in a four-stroke cycle of the internal combustion engine. 
     
     
         6 . The method of  claim 5 , wherein the second engine brake lift sub-profile is configured to release cylinder pressure such that the one cylinder pressure peak is generated in a compression stroke of the four-stroke cycle of the internal combustion engine. 
     
     
         7 . The method of  claim 1 , wherein, at the first cross point or the second cross point, the engine brake lift profile is configured to deliver valve lift in a same direction as the exhaust lift profile. 
     
     
         8 . The method of  claim 7 , wherein, at the first cross point or the second cross point, the engine brake lift profile is configured to deliver valve lift at a similar velocity as the exhaust lift profile. 
     
     
         9 . The method of  claim 2 , further comprising:
 disabling actuation of the first exhaust valve and the second exhaust valve by the exhaust rocker arm.   
     
     
         10 . The method of  claim 9 , wherein, when the actuation of the first exhaust valve and the second exhaust valve by the exhaust rocker arm is disabled and the actuation of the second exhaust valve by the engine brake rocker arm is enabled, the first exhaust valve is unactuated, and the actuation of the second exhaust valve is based on the engine brake lift profile. 
     
     
         11 . The method of  claim 9 , wherein, when the actuation of the first exhaust valve and the second exhaust valve by the exhaust rocker arm is disabled and the actuation of the second exhaust valve by the engine brake rocker arm is enabled, two cylinder pressure peaks are generated in a four-stroke cycle of the internal combustion engine. 
     
     
         12 . The method of  claim 11 , wherein the second engine brake lift sub-profile is configured to release cylinder pressure such that a first cylinder pressure peak is generated in a compression stroke of the four-stroke cycle of the internal combustion engine, wherein the fourth engine brake lift sub-profile is configured to release cylinder pressure such that a second cylinder pressure peak is generated before an intake stroke of the four-stroke cycle of the internal combustion engine. 
     
     
         13 . The method of  claim 1 , wherein the rocker arm assembly further comprises an intake rocker arm configured to activate at least two intake valves, the method further comprising:
 enabling actuation of the at least two intake valves by the intake rocker arm based on an intake lift profile.   
     
     
         14 . A method for timing valve lift events of a rocker arm assembly of an internal combustion engine, the rocker arm assembly comprising an exhaust rocker arm and an engine brake rocker arm and configured to selectively actuate one or more of a first exhaust valve or a second exhaust valve, the method comprising:
 enabling actuation of the first exhaust valve and the second exhaust valve by the exhaust rocker arm;   actuating the exhaust rocker arm based on an exhaust lift profile;   enabling actuation of the second exhaust valve by the engine brake rocker arm independent of actuation of the first exhaust valve;   actuating the engine brake rocker arm based on an engine brake lift profile;   maintaining the actuation of the exhaust rocker arm and the engine brake rocker arm for at least one engine cycle following an initial actuation of the engine brake rocker arm; and   disabling actuation of the first exhaust valve and the second exhaust valve by the exhaust rocker arm.   
     
     
         15 . The method of  claim 14 , wherein the exhaust lift profile and the engine brake lift profile have a first cross point and a second cross point, and wherein an angle defined between a tangent to the exhaust lift profile and a tangent to the engine brake lift profile is minimized at the first cross point and the second cross point so as to respectively minimize a velocity difference between the first exhaust valve and the second exhaust valve at each of the first cross point and the second cross point. 
     
     
         16 . The method of  claim 15 , wherein the engine brake lift profile comprises a first engine brake lift sub-profile, a second engine brake lift sub-profile, a third engine brake lift sub-profile, and a fourth engine brake lift sub-profile, and wherein the exhaust lift profile is subsequent to the second engine brake lift sub-profile and overlaps with the third engine brake lift sub-profile at the first cross point and with the fourth engine brake lift sub-profile at the second cross point, wherein the exhaust lift profile is tangent with the third engine brake lift sub-profile at the first cross point and is tangent with the fourth engine brake lift sub-profile at the second cross point. 
     
     
         17 . The method of  claim 15 , wherein, at the first cross point or the second cross point, the engine brake lift profile is configured to deliver valve lift in a same direction as the exhaust lift profile. 
     
     
         18 . The method of  claim 17 , wherein, at the first cross point or the second cross point, the engine brake lift profile is configured to deliver valve lift at a similar velocity as the exhaust lift profile. 
     
     
         19 . The method of  claim 16 , wherein, when the actuation of the first exhaust valve and the second exhaust valve by the exhaust rocker arm is disabled and the actuation of the second exhaust valve by the engine brake rocker arm is enabled, two cylinder pressure peaks are generated in a four-stroke cycle of the internal combustion engine. 
     
     
         20 . The method of  claim 19 , wherein the second engine brake lift sub-profile is configured to release cylinder pressure such that a first cylinder pressure peak of the two cylinder pressure peaks is generated in a compression stroke of the four-stroke cycle of the internal combustion engine, wherein the fourth engine brake lift sub-profile is configured to release cylinder pressure such that a second cylinder pressure peak of the two cylinder pressure peaks is generated before an intake stroke of the four-stroke cycle of the internal combustion engine.