Abstract: A drive unit for a gate valve controls a flow rate of fluid passing through an opening in a valve seat by forward and backward moving a valve plate against the opening in the valve seat. This drive unit includes a shaft connected to the valve plate, a linear motor for driving the shaft and drive control means to control the drive of the linear motor. The linear motor has a plurality of coils for generating a magnetic field by electric current and a permanent magnet assembly to react to the magnetic field generated by the plurality of coils. The plurality of coils forms a stator while the permanent magnet assembly is connected to the shaft and displaced together with the shaft to form a mover to forward and backward move the valve plate. Each of the plurality of coils is connected to its own control circuit and the drive control means individually controls the current flowing through each of the plurality of coils via the control circuit.

Abstract: A gas pressure within a treatment chamber 2 can be more accurately regulated to a predicted target pressure whereby there can be provided a pressure control apparatus which can easily and speedily regulate the gas pressure for various combination of the treatment chamber 2, a sanction chamber 3 and a valve 4. A required inflow rate (Qi) at which it is necessary for gas to flow into the treatment chamber 2 in order to reach a preset target pressure (Psp) within the treatment chamber is calculated on the basis of the expression of Qi=Qo+(P/?t)V and the thus calculated required inflow rate (Qi) is flown into the treatment chamber 2 to control the pressure within the treatment chamber 2 to the required pressure (Psp).