JPH05233069A - Mass flow controller - Google Patents

Abstract

PURPOSE:To enable detection and correction even when any deviation is generated in the value of one flow rate sensor by providing plural flow rate sensors, variable valve and control part and providing a mechanism to correct respective flow rate sensor values. CONSTITUTION:The thermal amount move of gas branched by a bypass pipe 4 is detected by respective flow rate sensors 3. The values of a flow rate detection circuit 5 inputting signals from the respective flow rate sensors 3 are respectively inputted to a correcting circuit 9 for correcting the values from these plural flow rate sensors 3 and detecting abnormality, and error is corrected. The correcting circuit 9 outputs this result to a comparator circuit 6 as an exact value showing the quantity of gas. This signal is compared with a signal from a flow rate setting circuit 7 to set a prescribed flow rate by the comparator circuit 6, and the result is fed back and inputted to a valve control circuit 8. The variable valve 2 is driven by the output signal of the valve control circuit 8, and the flow rate is controlled. Thus, even when any deviation is generated in the value of one flow rate sensor 3, detection or correction is enabled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to mass flow controller flow control.

[0002]

2. Description of the Related Art In a conventional mass flow controller, as shown in FIG. 3, a bypass pipe 4 is provided only in front of a variable valve 2 of a main pipe 1, and a flow sensor 3 is installed there. The output signal from the flow rate detection circuit 5 for inputting the signal from the flow rate sensor 3 and the output signal from the flow rate setting circuit 7 for setting a predetermined flow rate are input and the signal from the comparison circuit 6 for comparing the two is controlled by the valve. The variable valve 2 is driven by a signal from the valve control circuit 8 which is input to the circuit 8 to control the flow rate.

[0003]

In such a conventional mass flow controller, there is a 1
Since the control is performed by only one flow rate sensor, there is a problem that the sensitivity of the flow rate sensor is deviated and the flow rate is not recognized.

[0004]

A feature of the present invention is to provide a mass flow controller for controlling the flow rate of a gas, which comprises a flow rate sensor, a variable valve and a control section, and has a plurality of the flow rate sensors, and each flow rate is The mass flow controller has a mechanism for calibrating the sensor value.
The plurality of flow rate sensors can be arranged in series before the variable valve. Alternatively, the plurality of flow rate sensors can be arranged at the front stage and the rear stage of the variable valve.

[0005]

The present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a mass flow controller according to a first embodiment of the present invention. The gas flowing through the main pipe 1 is diverted by bypass pipes 4 for partially flowing the gas, which are respectively provided in the front stage (upstream) and the rear stage (downstream) of the variable valve 2 that changes the flow rate. The amount of heat transfer is detected by each flow sensor 3. The value output from the flow rate detection circuit 5 to which the signal from each flow rate sensor 3 is input is input to a calibration circuit 9 that calibrates values from a plurality of flow rate sensors and detects an abnormality, and the error is calibrated there. A signal is sent from the calibration circuit 9 to the comparison circuit 6 as one accurate value indicating the gas amount after the values from both flow rate sensors are calibrated. This signal and the signal from the flow rate setting circuit 7 for setting a predetermined flow rate are compared by the comparison circuit 6, the result is output and fed back to the valve control circuit 8, and is varied by the output signal of the valve control circuit 8 thereby. The valve 2 is driven to control the flow rate.

FIG. 2 is a block diagram of the mass flow controller of the second embodiment of the present invention. 2 that are the same as or similar to those in FIG. 1 are denoted by the same reference numerals. In the second embodiment, the plurality of flow rate sensors 3 are arranged in series in the preceding stage (upstream).

[0007]

According to the present invention described above, a plurality of flow rate sensors, a variable valve and a control unit are provided,
Since there is a mechanism for calibrating each flow sensor value, there is an effect that detection and calibration can be performed when the value of one flow sensor is deviated.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a conventional technique.

[Explanation of symbols]

 1 Main Pipe 2 Variable Valve 3 Flow Sensor 4 Bypass Pipe 5 Flow Rate Detection Circuit 6 Comparison Circuit 7 Flow Rate Setting Circuit 8 Valve Control Circuit 9 Calibration Circuit

Claims (3)

[Claims] 1. A mass flow controller having a flow sensor, a variable valve, and a control unit for controlling the flow rate of a gas, comprising a plurality of the flow sensors and a mechanism for calibrating each flow sensor value. Characteristic mass flow controller. 2. The mass flow controller according to claim 1, wherein the plurality of flow rate sensors are arranged in series in front of the variable valve. 3. The mass flow controller according to claim 1, wherein the plurality of flow rate sensors are arranged in a front stage and a rear stage of the variable valve.