Verfahren und Vorrichtung zum elektrischen Ventilantrieb bei Brennkraftmaschinen

Each valve (18) of an internal combustion engine is driven by a separate rotary electric motor (10). The valves are preferably either rotary valves, driven directly, or poppet valves (18), driven through a cam (16). Each motor (10) may run at half the engine speed to open and close a valve (18) at a basic profile during each engine cycle. Valve operation is shaped to engine conditions by slowing the motor speed in the valve-open period to increase the valve-open period, or increasing the motor speed in the valve-open period to decrease the valve-open period. The motor speed is oppositely controlled when the valve is closed to compensate for phase changes of the motor (10) relative to the engine. Valve phase as well as opening and closing velocity of the valve (18) are controlled by motor speed. A cam mechanism (16) for poppet valves (18) comprises a cylindrical cam (24) in line with the motor axis (20) and the valve stem (21), the mechanism (16) having inner and outer cylinders (24,30), one cylinder (24) rotating with the motor (10) and carrying a cam (36) and the other containing a cam follower (42) and reciprocating with the valve (18). A motor control includes position transducers for generating crankshaft position and motor position pulse trains. The pulse trains are compared to detect any phase difference between engine and motor (10). Tables are generated to define the desired phase difference needed for particular valve characteristics. The phase difference represents the instantaneous deviation from the basic profile. One of the tables is selected according to the engine conditions and the motor (10) is driven to achieve the desired phase differences.