Electromechanical transducer controlling device

DETAILED DESCRIPTION It is a primary object of the present invention to obviate the prior art problems pointed out above and to provide a novel and improved control device for an electromechanical transducer of the kind which provides a mechanical output proportional to an electrical input quantity so that such a transducer can respond accurately to the input.
The present invention is applied specifically to the control of the electromechanical transducer or the proportional electromagnetic valve described in (1) and is featured by the provision of control means which controls an electrical input signal to the electromechanical transducer as follows: (a) The transducer is controlled by a cyclic electrical input signal so as to alleviate the material wear due to the striking of the sliding parts against the associated parts and to reduce the level of the crashing sound.
(b) On-off of the electrical quantity applied as the input to the transducer is repeated at a constant period shorter than the minimum response time required for the full stroke of the plunger urged by the mechanical output of the transducer, and the duty cycle of the electrical input is controlled so as to provide an analog mechanical output or quantity, for example, displacement which can be controlled by a digital electrical signal.
(c) By virtue of the manner of control described in (b), the analog mechanical quantity includes a very small digital quantity component or a very small vibratory stroke component which is effective in eliminating the hysteresis occurring in the mechanical output of the transducer.
(d) Two switching elements are provided for the cyclic on-off of the electrical quantity applied to the transducer, and electrical signals having opposite duty cycles such that one of them is in its on-state while the other is in its off-state are applied to these two switching elements respectively.
Therefore, current supplied to the member or the coil generating an electromagnetic force corresponding to the magnitude of the electrical quantity input can flow in either the positive direction or the negative direction depending on the ratio between the duty cycles of the electrical inputs applied to the respective switching elements so as to provide the analog mechanical quantity, for example, the displacement of both the positive direction and the negative direction