67results about How to "High accuracy of flow control" patented technology

An electromagnetic proportional flow rate control valve capable of performing precise flow rate control in a low flow rate side of an operating region is provided. In an electromagnetic proportional flow rate control valve 32, in which a valve member 2 is driven in a valve closing direction in accordance with the increase in a driving current I of a solenoid coil 15, a solenoid driving force F is set such that it decreases accompanying the displacement of the valve member 2 in the valve closing direction with respect to an identical driving current in the solenoid coil 15. Thus, an amount of change in an area of a valve opening with respect to unit changes in the driving current I becomes smaller in a region at which the stroke is small compared to a case of having flat characteristics, whereby the flow rate control precision in the low flow rate region can be improved.

The invention provides a composite valve which can achieve both an improvement of a flow rate control precision in a small flow rate region and an increase of a controllable flow rate (a reduction of a pressure loss), and can enhance a sealing performance of a pilot passage by a pilot valve body, whereby it is possible to securely prevent a malfunction and it is possible to enhance a reliability. When a lift amount of a second valve body (24) for a small flow rate control is equal to or less than a predetermined amount (Tc), a pilot passage (19) is closed by a pilot valve body (60) which is slidable on an inner wall of a bush retention body (28), and a first valve port (13) is closed by a first valve body (15) for a large flow rate control, thereby taking a small flow rate control state in which a flow rate is controlled in correspondence to a lift amount of the second valve body (24). When the lift amount of the second valve body (24) goes beyond the predetermined amount (Tc), a pilot valve body (20) is raised in correspondence to a rising motion of a valve shaft (25) so as to open the pilot passage (19), thereby taking a large flow rate control state in which the first valve body (15) opens the first valve port (13). The pilot valve body (60) is outward inserted slidably to the valve shaft (25), and is energized downward by a spring member (26) so as to close the pilot passage (19). Further, when the lift amount of the second valve body (24) is increased more than the predetermined amount Tc, the pilot valve body (60) is caught on the valve shaft (25) so as to be pulled up.