Flow rate control valve and spool position detection device for the flow rate control valve

A flow rate control valve comprising:

• a spool having a plurality of valve members and slidably accommodated in a sleeve having a plurality of ports, said flow rate control valve performing flow rate control by linearly moving the spool with an actuator;
• a generally straight target probe formed of a magnetically-responsive substance and mounted to one end of the spool, the sleeve having an opening formed at one end thereof to permit passage there through of said target probe;
• a sensor housing mounted to the one end of the sleeve for detecting a linear position of said target probe, said sensor housing having a cylinder section formed of a non-magnetic substance and defining an inner space to permit entry therein of said target probe, the inner space communicating with the opening formed in the one end of the sleeve;
• and
• first and second coils disposed around the cylinder section within said sensor housing and axially spaced from each other by a predetermined distance,
• wherein said first coil is disposed so as to respond to said target probe,
• wherein said target probe has a tapered section that is elongated in an axial direction thereof so that its volume gradually decreases toward a distal end thereof so that magnetic response of said first coil gradually varies in one direction in response to a linear position of said target probe,
• wherein said second coil is configured to not respond to linear displacement of said target probe at least within a predetermined linear displacement range of said target probe,
• wherein a linear position of said target probe, and hence a position of the spool, is detected through differential synthesis performed between outputs of the first and second coils,
• wherein said first coil is located nearer to said target probe than said second coil,
• wherein the distal end of said target probe is extendable into a sensitive region of said second coil, and
• wherein said target probe has a shape configured so that, when the distal end thereof has entered the sensitive region of said second coil, a predetermined portion of said target probe close to a proximal end thereof enters a sensitive region of said first coil and enhances a degree of sensitivity of said first coil so as to cancel out sensitivity of said second coil with the predetermined portion close to the proximal end.

A spool position detection device for a flow rate control valve that includes a spool having a plurality of valve members and slidably accommodated in a sleeve having a plurality of ports, said flow rate control valve performing flow rate control by linearly moving the spool by means of an actuator, said spool position detection device comprising:

• a generally straight target probe of a magnetically-responsive substance and mountable to one end of the spool, the sleeve having an opening formed at one end thereof to permit passage therethrough of said target probe;
• a sensor housing mountable to the one end of the sleeve for detecting a linear position of said target probe, said sensor housing having a cylinder section formed of a non-magnetic substance and defining an inner space to permit entry therein of said target probe, the inner space communicable with the opening formed at the one end of the sleeve;
• first and second coils disposed around the cylinder section within said sensor housing and axially spaced from each other by a predetermined distance;
• and
• a ring-shaped magnetically-responsive shield member inside said second coil,
• wherein said first coil is disposed so as to respond to said target probe,
• wherein said target probe has a tapered section that is elongated along an axial direction thereof so that its volume gradually decreases toward a distal end thereof so that magnetic response of said first coil gradually varies in one direction in response to a linear position of said target probe,
• said second coil is configured to not respond to linear displacement of said target probe at least within a predetermined linear displacement range of said target probe,
• wherein a linear position of said target probe, and hence a position of the spool, is detected through differential synthesis performed between outputs of the first and second coils,
• wherein said first coil is located nearer to said target probe than said second coil, and
• wherein the distal end of said target probe is extendable into a sensitive region of said second coil.