Abstract: An object of the invention is to provide a flow rate control valve assembly capable of preventing a flow rate from varying in a direction opposite to the desired direction upon flow rate control As shown in FIG. 1, the flow rate control valve assembly comprises a sliding shaft and a sliding cylindrical surface which fit slidably in with each other in an axial direction, and a moving mechanism for moving the sliding shaft in an axial direction. At least one of the sliding surface of the sliding shaft and the sliding cylindrical surface is provided with one or a plurality of tapered grooves having its specific area defining a fluid passage. The tapered groove is configured such that flow passage resistance increases or decreases gradually along a lengthwise direction, and a cavity formed at an end of the sliding shaft for making sure of a sliding area is formed at a site isolated or shut off from the fluid passage.

Abstract: An object of the invention is to provide a flow rate control valve assembly capable of preventing a flow rate from varying in a direction opposite to the desired direction upon flow rate control As shown in FIG. 1, the flow rate control valve assembly comprises a sliding shaft and a sliding cylindrical surface which fit slidably in with each other in an axial direction, and a moving mechanism for moving the sliding shaft in an axial direction. At least one of the sliding surface of the sliding shaft and the sliding cylindrical surface is provided with one or a plurality of tapered grooves having its specific area defining a fluid passage. The tapered groove is configured such that flow passage resistance increases or decreases gradually along a lengthwise direction, and a cavity formed at an end of the sliding shaft for making sure of a sliding area is formed at a site isolated or shut off from the fluid passage.