Electric valve

An electric valve comprising:

• a valve body that has a valve port and a valve seat enclosing the valve port;
• a valve member that faces the valve port;
• a valve stem;
• a stepping motor;
• and
• a controller configured to control the stepping motor,
• wherein the valve stem and the valve body constitute a screw-feed mechanism, or the valve stem and the valve member constitute a screw-feed mechanism,
• wherein the valve stem is coaxially secured to a magnet rotor of the stepping motor,
• wherein an end of the valve stem is connected to the valve member,
• wherein when the magnet rotor rotates in a valve closing direction, the valve member moves toward the valve port,
• wherein when the valve member comes into contact with the valve seat, the valve seat restricts the valve member from moving toward the valve port,
• wherein, in an initialization operation mode, the controller is configured to input pulses to the stepping motor to rotate the magnet rotor in the valve closing direction and obtain, as a reference position, a position of the magnet rotor when rotation of the magnet rotor in the valve closing direction is restricted,
• wherein, in a normal operation mode, the controller is configured to position the magnet rotor based on the reference position and manage the position of the magnet rotor by using a number of pulses input to the stepping motor,
• wherein when the magnet rotor is at the reference position, inputting a maximum number of pulses to the stepping motor causes the magnet rotor to travel from the reference position to a full-open position,
• wherein a valve-member movement command received by the controller contains a valve opening degree corresponding to a target position of the magnet rotor, a valve opening degree of 0 [%] corresponds to the reference position, and a valve opening degree of 100 [%] corresponds to the full-open position,
• wherein the controller is configured to receive the valve-member movement command from an external device,
• wherein the controller is configured to rotate the magnet rotor to reach the position of the magnet rotor to the target position corresponding to the valve opening degree when the valve opening degree is greater than or equal to 0 [%] and less than or equal to 100 [%],
• wherein the controller is configured to transmit a command result indicating a reception of an out-of-range valve opening degree to the external device when the valve opening degree contained in the valve-member movement command received by the controller is less than 0 [%] or greater than 100 [%].