One method to control intake and exhaust valve operation during engine operation is described in French Patent application. No. FR 2851367 A1. This method presents a means to control a dual coil electromagnetically actuated valve using a single coil. The approach attempts to open an electrically actuated valve by controlling current to one of the two valve actuator coils, namely, the closing coil. By reducing current to the valve closing coil, a closed valve can accelerate from a closed position to an open position, and then oscillate in a damped trajectory. The valve can be set to a closed position by energizing a closing coil, at least during a portion of the valve oscillation period. This mode of valve control is sometimes referred to as “Ballistic” mode.
The above-mentioned method can also have a disadvantage due to changes in the valve apparatus, for example. In this mode of operation, the valve opening duration can be affected by the collective mass of the actuator armature and valve, actuator spring forces, cylinder pressure, and the friction forces of the apparatus because the before-mentioned method can be influenced by the natural response (i.e., the behavior of an electrical or mechanical system due to internal energy storage) of the valve actuator system during the valve opening period. Consequently, a change to the valve actuator system can alter the valve opening duration and a corresponding cylinder air charge that may be inducted during a valve opening period. For example, deposits can form on intake valves during the course of engine operation. These deposits can increase the weight of the valve and may cause the natural response of the valve to change. In addition, lower temperatures can cause friction forces of the valve actuator assembly to increase, thereby changing the natural response and/or opening period of the valve.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method of electromechanical valve control that offers substantial improvements.