Flow rate control device

A flow rate control device comprising:

• a pressure control valve provided in a flow path;
• a flow rate control valve provided downstream of the pressure control valve;
• a first pressure sensor for measuring a pressure downstream of the pressure control valve and upstream of the flow rate control valve;
• and
• a restriction part having a fixed opening degree;
• wherein the flow rate control valve includes a valve element capable of coming in and out of contact with a valve seat, a piezoelectric element for moving the valve element to come in and out of contact with the valve seat, and a strain sensor provided on a side surface of the piezoelectric element,
• the flow rate control valve is used as a restriction part capable of changing an opening degree, the opening degree being defined by a distance between the valve seat and the valve element of the flow rate control valve,
• a driving of the piezoelectric element is controlled based on a signal output from the strain sensor while the pressure control valve is controlled based on a signal output from the first pressure sensor, and
• when performing continuous flow control, flow rate is controlled by using the restriction part having the fixed opening degree;
• and when performing intermittent flow rate control, flow rate is controlled by using the flow rate control valve as the restriction part capable of changing the opening degree.