Valve control apparatus

A valve control apparatus comprising:

• a valve that is adapted to rotate about a rotational axis of the valve;
• an actuator that includes a rod and drives the rod to reciprocate the rod in an axial direction of the rod and thereby to drive the valve;
• a link mechanism that includes a lever, which connects between the valve and the rod and converts linear motion of the rod into rotational motion of the valve;
• a magnetic movable body that is installed integrally to the rod and includes first and second magnets, which cooperate with each other to generate a magnetic field having a generally constant density of a magnetic flux, wherein a central axis of the rod is generally parallel to a center line of the first and second magnets, which is generally parallel to and is centered between an inner surface of the first magnet and an inner surface of the second magnet that are opposed to each other;
• a sensor that outputs an electric signal, which corresponds to the magnetic flux that changes in response to movement of the magnetic movable body relative to the sensor;
• and
• means for sensing an amount of displacement of the rod in a stroke direction, which coincides with the axial direction of the rod, based on the electric signal outputted from the sensor, wherein:
• the actuator is driven to control opening and closing of the valve based on the amount of displacement of the rod in the stroke direction of the rod sensed with the sensing means;
• the actuator includes a rod bearing, which slidably supports the rod to enable slide motion of the rod in the stroke direction while enabling swing motion of the rod about the rod bearing;
• the sensor includes a magnetic sensing surface, which is adapted to sense the magnetic flux of the magnetic movable body;
• the lever includes a rotational axis, which is coaxial with the rotational axis of the valve, at a valve-side connection of the lever that is rotatably connected to the valve;
• the fever includes a rod-side connection that is rotatably connected to the rod, wherein the rod-side connection is adapted to move along a rotational moving path, which is a curved path centered at the rotational axis of the valve-side connection of the lever and has a predetermined radius of curvature, when the valve is rotated through the rod;
• when an opening degree of the valve becomes a full close degree to fully close the flow passage, a rotational moving point of the rod-side connection, which is moved along the rotational moving path, is placed in a full close point along the rotational moving path;
• when the opening degree of the valve becomes a full open degree to fully open the flow passage, the rotational moving point of the rod-side connection, which moves along the rotational moving path, is placed in a full open point along the rotational moving path;
• when the opening degree of the valve becomes a half degree, which is one half of an angular degree between the full close degree and the full open degree, the rotational moving point of the rod-side connection is placed in a half point between the full close point and the full open point along the rotational moving path;
• and
• at least a portion of the magnetic sensing surface of the sensor is placed in an angular range between:
• a first imaginary line, which coincides with the center line of the first and second magnets when the rotational moving point of the rod-side connection of the lever is placed in the full close point;
• and
• a second imaginary line, which coincides with the center line of the first and second magnets when the rotational moving point of the rod-side connection of the lever is placed in the half point.