A valve actuation system includes a rocker for conveying motion to an engine valve, a motion source arranged to impart motion to the rocker, rocker stop assembly configured to operate in an activated mode, in which the rocker stop assembly maintains the rocker in a position corresponding to partial valve lift, and a deactivated mode, in which the rocker stop assembly allows the rocker to move to a position corresponding to a fully closed valve position, and a rocker stop reset assembly for resetting the rocker stop assembly to the deactivated mode subsequent to a main event peak lift to thereby achieve late valve closing. A damper assembly may interact with the rocker stop assembly to provide a smooth transition of the rocker and valve motion to a late intake valve closing dwell. A valve catch assembly may control the seating velocity of the at least one valve.

Various embodiments include a method for actuating a camshaft adjuster of an internal combustion engine, in which a current is generated in an electric motor of the camshaft adjuster comprising: measuring an instantaneous strength of the current; calculating a mean value of the measured strength of the current over a predefined elapsed time; measuring a temperature of the camshaft adjuster; comparing the mean value of the measured strength of the current to a threshold value obtained from a characteristic diagram stored in a memory based on the measured temperature and the predefined elapsed time; and reducing the current if the calculated mean value of the strength of the current is higher than the threshold value.

Various embodiments include a method for actuating a camshaft adjuster of an internal combustion engine, in which a current is generated in an electric motor of the camshaft adjuster comprising: measuring an instantaneous strength of the current; calculating a mean value of the measured strength of the current over a predefined elapsed time; measuring a temperature of the camshaft adjuster; comparing the mean value of the measured strength of the current to a threshold value obtained from a characteristic diagram stored in a memory based on the measured temperature and the predefined elapsed time; and reducing the current if the calculated mean value of the strength of the current is higher than the threshold value.

Systems and methods for unsticking intake and exhaust valves of an engine are described. In one example, valves that may be adjustably timed relative to an engine crankshaft position may be adjusted to unstick intake and/or exhaust valve that are stuck open or closed. In addition, fuel injection timing and spark timing may be adjusted in an effort to unstick intake and/or exhaust valves.

An actuator for operating a poppet valve (30) of an internal combustion engine. The actuator comprises a rotary portion (4) and a body portion (2), and the rotary portion defines a cam surface (50, 60). A cam follower (10) is engaged with the cam surface, and a linkage is coupled to the cam follower at one end and coupled to a valve stem (12) at its other end. The cam surface (50, 60) is shaped such that exertion of a closing force on the valve stem, by a piston of the engine following failure of the actuator for example, causes the cam follower (10) to exert a turning force on the rotary portion (4).

An internal combustion engine (10) with variable valve timing has one or more valve shafts (38, 44) connected to stepper motors (54) for angularly positioning the one or more valve shafts (38, 44) relative to an engine block (12). Flow passages (50, 52) are formed into the one or more valve shafts (38, 44) for passing intake air and exhaust gases into and from the engine (10). Sensors (58, 60 and 62) are located adjacent a crankshaft (28) and the one or more valve shafts (38, 44) for determining crankshaft positions and valve shaft positions relative to the engine block (12). An engine control unit (56) receives crank shaft and valve shaft position signals and emits control signals to the stepper motors (54) to selectively operate the engine in two stroke, four stroke, six stroke, eight stroke, and ten stroke modes. Electrically controlled clutches (74 and 76) are mounted to respective ones of the crankshaft (28) and the valve shafts (38, 44), and connected by a timing chain (72) for actuating to provide backup valve shaft.