JPS63235800A - Mass flow controller - Google Patents

Abstract

PURPOSE:To get rid of any measuring failure in an actual flow rate, by comparing each output value out of plural flow measuring parts installed in a pipeline, and detecting the mass flow abnormality. CONSTITUTION:A flow control valve 11 is installed in the point midway in a pipeline 1, and each of flow measuring parts A and A is set up in front and in the rear of this valve. The flow measuring part A has a laminar flow element 2, a sensor pipe 3 and a glidge circuit 6. In addition, there is provided with a mass flow malfunction detecting element 13 which compares flow measured values out of each amplification correcting part 7 comprised in these flow measuring parts A and A and detects a mass flow malfunction. Accordingly, the mass flow malfunction is detectable by the flow measured value, so that slippage failure in the actual flow rate to the set value due to the clogging of a sensor part is checkable.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to mass flow controllers.

[Conventional technology]

Conventionally, this type of mass flow controller has a flow rate measuring section that measures the flow rate in the piping, a flow rate control valve that controls the flow rate in the piping, and a flow rate measurement value from the flow rate measuring section and a set flow rate value that are compared. The control unit outputs an opening/closing signal for the valve, and the flow rate in the piping was only measured at one point.

[Problem that the invention seeks to solve]

Since the above-mentioned conventional mass flow controller has only one flow rate measuring section, if the laminar flow element of the flow rate measuring section becomes clogged or the sensor pipe becomes clogged.

There will be a difference between the actual flow rate and the measured value, and the flow rate will be controlled based on the measured value with an error, and the actual flow rate that you want to control will not be achieved, and the measured value will be different from the set value. There was a problem in that it was not possible to detect a sensor defect because the numbers matched.

An object of the present invention is to provide a mass flow controller that solves the above problems.

[Means for solving problems]

The present invention includes a flow rate measurement section that measures the flow rate in piping, a flow rate control valve that controls the flow rate in the piping, and a flow rate measurement value from the flow rate measurement section and a set flow rate value that are compared with each other to generate an opening/closing signal for the valve. A mass flow controller having a control unit that outputs a flow rate, wherein a plurality of the flow rate measurement units are provided in the piping, and a mass flow controller that detects a mass flow abnormality by comparing the flow rate measurement values output by each of the plurality of flow rate measurement units. This is a mass flow controller characterized by being equipped with an abnormality detection section.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

In Figure 1, a flow control valve 1 is installed in the middle of piping 1.
1 is installed, and flow rate measurement units A, A are placed before and after the flow rate control valve 11 with the flow rate control valve 11 in between. Each flow rate measuring section A has a laminar flow element 2 installed in a pipe 1.

A sensor tube 3 that bypasses the laminar flow element 2 and connects the front and back of it
, self-heating resistors 4 and 5 wrapped around the front and rear ends of the sensor tube 3, a bridge circuit 6 that includes the self-heating resistors 4 and 5 on each side and detects the flow rate value based on the temperature difference, and a detected signal. It consists of an amplification correction section 7 that performs amplification correction and a control section 8. 9 is a flow rate setting section that outputs a set flow rate value.

Further, the front and rear flow rate measurement units A, amplification correction unit 7 included in A
The system is equipped with a mass flow abnormality detection section 13 that detects a mass flow abnormality by comparing measured flow values from the flow rate and a flow rate display section 12.

In the embodiment, it is assumed that the gas to be controlled flows within the gas pipe 1 in the direction of the arrow. A laminar flow element 2 is installed in the pipe 1 and is called a bypass section. There are thin sensor tubes 3 on both sides of this laminar flow element 2 (bypass section), and when gas flows from the IN side to the 00T side, it is divided into the laminar flow element 2 side and the sensor tube 3 side at a certain ratio. It flows. The sensor tube 3 side has a structure in which two self-heating resistors 4 and 5 are wound around the outside of the sensor tube 3. When gas flows, the upstream resistor 4 is deprived of heat, and the downstream Heat will be applied to the resistor 5 on the side. Therefore, there is a temperature difference between the self-heating resistors 4 and 5 on the upstream and downstream sides, and there is a correlation between the temperature difference and the mass flow rate, so the temperature difference is detected by the bridge circuit 6 and the mass flow rate is Measure. The signal detected by the bridge circuit 6 is sent to the amplification correction section 7
The signal is amplified and corrected and then enters the control section 8. The control unit 8 compares the set flow rate value from the flow rate setting unit 9 and the measured flow rate value from the amplification correction unit 7, outputs a valve opening/closing signal according to the difference between the set flow rate value and the measured flow rate value, and adjusts the set value. control so that the measured flow rate and the measured flow rate match. The valve control signal output from the control section 8 is amplified by the amplification section IO and then sent to the drive section 1.
1a, the control valve 11 is driven, and the flow rate is adjusted.6 or above is the general operation of the conventional mass flow.According to the present invention, another flow rate measuring section is provided after the control valve 11. It is designed to measure mass flow rate. Here, the measured flow rate signal is input to the mass flow measurement flow rate display section 12 and the mass flow abnormality detection circuit section 13. The mass flow abnormality detection circuit section 13 compares the signal from the mass flow rate setting section 9 in the previous stage, the flow rate measurement signal 14 in the previous stage, and the flow rate measurement signal 15 in the subsequent stage, and when the three do not match, displays a mass flow abnormality on the flow rate display section 12. It is designed to be displayed.

Therefore, if the laminar flow element 2 in the upper or lower sensor bypass section is clogged or the sensor tube 3 is clogged, the flow measurement signal 14 in the previous stage and the flow measurement signal 15 in the lower stage will no longer match, and the flow rate will be displayed immediately. At section 12, mass flow abnormality can be detected.

Regarding the positional relationship of the two flow rate measuring sections, it does not matter where they are installed, and they can be installed anywhere in front or behind the control valve, or the flow rate measuring section can be separated into a bypass section and a sensor pipe section. was used in the explanation as an example, but any type of sensor can be used as long as it can measure the flow rate. Of course, there is no problem even if the upper and lower tiers use different sensor types.

〔Effect of the invention〕

As explained above, the present invention measures the flow rate in piping at two or more locations and compares the measured values.

It has the effect of being able to detect abnormalities in the mass flow, allowing the mass flow controller alone to check for deviations in the actual flow rate from the set value due to clogging of a part of the sensor, failures in the flow control valve, failures in mass flow calibration, etc.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the mass flow controller of the present invention.

Claims (1)

[Claims] (1) A flow rate measuring section that measures the flow rate in the piping, a flow rate control valve that controls the flow rate in the piping, and a flow rate measurement value from the flow rate measuring section and a set flow rate value are compared and an opening/closing signal for the valve is generated. In the mass flow controller, a plurality of the flow rate measurement units are provided in the piping, and a mass flow abnormality is detected by comparing the flow rate measurement values output by each of the plurality of flow rate measurement units. A mass flow controller characterized by being equipped with a detection section.