Drive unit for gate valve

A drive unit for a gate valve for controlling a flow rate of fluid flowing through an opening of a valve seat by moving a valve plate forward and backward against said valve seat having said opening provided therein, said drive unit comprising a shaft connected to said valve plate, a linear motor for driving said shaft and drive control means to control the drive of said linear motor, characterized in that said linear motor has a plurality of coils that generate a magnetic field by an electric current and permanent magnets that react to the magnetic field generated by said plurality of coils;

• wherein said plurality of coils are a stator while said permanent magnets are a mover which is connected to said shaft and moves together with said shaft to thereby move said valve plate forward and backward, wherein said plurality of coils are each connected to their own individual control circuits and said drive control means individually controls the electric current flowing through each of said plurality of coils through said drive control circuits and further comprises a linear encoder to detect the current position of said permanent magnets of said mover, wherein said linear encoder comprises a plurality of laser sources to irradiate lasers of different wavelengths toward said permanent magnets, which are the mover, and an image sensor to receive said lasers reflected from said permanent magnets of the mover, said plurality of laser sources are installed so as to face different orientation directions, and said image sensor detects the current position of said permanent magnets of the mover depending on the type of said lasers received by said image sensor and the position at which said lasers are received and wherein said drive control means controls the electric current through said plurality of coils by determining the coil or coils necessary for flowing the electric current therethrough to thereby display said permanent magnets to a desired position in accordance with the magnet position detected by said linear encoder and the electric current to flow through said coil or coils.