Abstract
This paper describes a cam-drive type proportional valve for water hydraulics and its dynamic characteristics. A spool in a conventional proportional valve is balanced by forces generated by the proportional solenoid and the spring. To cope with large force acting on the spool, it requires a strong solenoid and heavy core. Thus fast response of the valve is hardly realized. In the developed valve, the spool is driven by positive cam mechanism, in which a heart-like cam is placed between two cam-followers and the cam is driven by a stepping motor. The spool displacement is feed backed by microcomputer-based system and the stepping motor is proportionally controlled. The static characteristics are measured without the feedback control system. Non-linearity of the spool displacement against the rotational angle of the cam was below 0.2% and the hysteresis was hardly observed even though no feedback control loop was added. As for measurement of dynamic characteristics, the step and ramp responses are measured using the constructed controller with microcomputer.
