Flow rate regulating device and control method of flow rate regulating device

A control method of a flow rate regulating device, the flow rate regulating device comprising:

• a valve body section that moves along an axis extending in a vertical direction in a valve chamber and has a flat valve body surface extending in a horizontal direction,
• a valve seat section having a flat valve seat surface provided around a channel opening that communicates with an inner channel and the valve chamber, disposed at a position opposite to the valve body surface and extending in the horizontal direction, and
• a regulation mechanism that moves the valve body section along the axis to regulate a distance between the valve body surface and the valve seat surface, wherein the regulation mechanism includes:
• a stepping motor that rotates a drive shaft about the axis, and
• a moving member that moves along the axis in response to the rotation of the drive shaft and is coupled to the valve body section, the method comprising:
• a control step of controlling the stepping motor, wherein in the control step, the stepping motor is controlled so that the valve body section moves in a range in which the valve body surface and the valve seat surface maintain a non-contact state, in accordance with an excitation signal that changes by a micro step unit obtained by dividing a step by a predetermined division number,
• wherein the movement range is set so that the channel cross-sectional area of the channel opening substantially matches the change amount of the minimum channel cross-sectional area of the channel formed between the valve body surface and the valve seat surface when the valve body surface is moved from a first position to a second position, the first position being a position where the valve body surface is closest to the valve seat surface and being the furthest point of motion of the valve body section in the movement range, the second position being a position where the valve body surface is farthest from the valve seat surface.