Pressure-type flow rate control device and flow rate self-diagnosis method

A flow rate self-diagnosis method performed in a pressure-type flow rate control device that includes a restriction part, a control valve provided upstream of the restriction part, an upstream pressure sensor that detects a pressure of a flow passage between the restriction part and the control valve, a downstream pressure sensor that detects a pressure of a flow passage downstream of the restriction part, with a shutoff valve being provided downstream of the downstream pressure sensor, and a controller having a flow rate self-diagnostic function of diagnosing flow control by using pressure drop data on the flow passage between the control valve and the restriction part and reference pressure drop data stored in advance,

• the flow rate self-diagnosis method comprising the steps of:
• issuing a close command to the control valve and the shutoff valve during a flow rate of gas flowing is controlled at a set flow rate;
• after the close command is issued, determining whether a critical expansion condition is satisfied based on outputs of the upstream pressure sensor and the downstream pressure sensor;
• if the critical expansion condition is satisfied, storing pressure drop data measured during a period in which the critical expansion condition is satisfied;
• and
• carrying out self-diagnosis of flow rate control by comparing pressure drop data acquired during the period in which the critical expansion condition is satisfied with the reference pressure drop data.

A pressure-type flow rate control device comprising:

• a restriction part;
• a control valve provided upstream of the restriction part;
• an upstream pressure sensor that detects a pressure of a flow passage between the restriction part and the control valve;
• and
• a controller having a flow rate self-diagnostic function of diagnosing flow rate control by using pressure drop data on the flow passage between the control valve and the restriction part and reference pressure drop data,
• wherein, in a case where the flow rate self-diagnostic function is executed, the controller acquires the pressure drop data by measuring a drop in upstream pressure with the upstream pressure sensor after the control valve is closed, and uses, as the reference pressure drop data, reference pressure drop data that is based on either an initial upstream pressure that is an upstream pressure at a time when the control valve is closed or an initial flow rate that is a flow rate determined using the initial upstream pressure.

A flow rate self-diagnosis method performed in a pressure-type flow rate control device that includes a restriction part, a control valve provided upstream of the restriction part, an upstream pressure sensor that detects a pressure of a flow passage between the restriction part and the control valve, and a controller having a flow rate self-diagnostic function of diagnosing flow rate control by using pressure drop data on the flow passage between the control valve and the restriction part and reference pressure drop data,

• the flow rate self-diagnosis method comprising the steps of:
• acquiring the pressure drop data by measuring a drop in upstream pressure with the upstream pressure sensor after the control valve is closed;
• and
• diagnosing flow rate control by comparing the pressure drop data and the reference pressure drop data,
• wherein a slope α of a straight line defined by ln(P(t)/P0)=−αt, where P(t) is a function of a pressure with respect to time, P0 is an initial pressure, and t is time, is used as the pressure drop data and the reference pressure drop data.