JPH05233068A - Mass flow controller - Google Patents

Mass flow controller

Info

Publication number
JPH05233068A
JPH05233068A JP2983592A JP2983592A JPH05233068A JP H05233068 A JPH05233068 A JP H05233068A JP 2983592 A JP2983592 A JP 2983592A JP 2983592 A JP2983592 A JP 2983592A JP H05233068 A JPH05233068 A JP H05233068A
Authority
JP
Japan
Prior art keywords
pressure
gas
flow rate
oriffice
pressure gauge
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
JP2983592A
Other languages
Japanese (ja)
Inventor
Toshiaki Sango
利明 三五
Original Assignee
Nec Corp
日本電気株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nec Corp, 日本電気株式会社 filed Critical Nec Corp
Priority to JP2983592A priority Critical patent/JPH05233068A/en
Publication of JPH05233068A publication Critical patent/JPH05233068A/en
Withdrawn legal-status Critical Current

Links

Abstract

PURPOSE:To prevent a gas duct from being clogged, transformation with the passage of time and gas from being residual by structuring the gas duct almost as a single pipe, measuring a flow rate by a fixed oriffice and two pressure gauges and loading feedback to a variable valve. CONSTITUTION:A fixed oriffice 2 is provided at a gas duct 1 constituted almost as a single pipe. A first pressure gauge 3 provided at this oriffice 2 measures pressure by using the capacity change of a diaphragm to be deformed by the change of pressure. A second pressure gauge 4 is provided in the front step part of the fixed oriffice 2. The differential pressure of pressure measured by the first and second pressure gauges 3 and 4 is converted to the flow rate and outputted as a signal. This output signal is compared with a set signal by a comparator circuit 6, a variable valve 7 is controlled by a control circuit 6 so that the differential signal can be turned to zero, and the flow rate is controlled from 0SLM to 20SLM. Thus, the clogging can be prevented by constituting the gas duct 1 almost as the single pipe, the change with the passage of time can be prevented by using the pressure gauges 3 and 4, and gas can be prevented from being residual by omitting a bypass line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass flow controller for controlling a gas flow rate, and more particularly to a flow sensor and a shape of a gas flow path.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, a mass flow controller for controlling a gas flow rate has a flow rate sensor 10,
It is composed of a bypass element 11, a comparison circuit 5, a control circuit 6, and a variable valve 7. The flow sensor 10 is the gas flow path 1
2 on the outside of a capillary tube with a diameter of about 0.2 mm
One self-heating type resistor 12 is wound, and this line is preheated, the temperature change when the gas passes through the line is electrically detected, and the gas flowing through the gas flow path is detected from the specific heat. Is measured and converted into a flow rate.

A bypass line is provided in parallel with the flow rate sensor 10 to support a wide range of flow rate measurements, and a bypass element 11 such as a laminar flow element is used to maintain a correct diversion ratio. The output signal from the flow rate sensor 10 is compared with the set value by the comparison circuit 5, and the control circuit 6 controls the variable valve 7 so that the difference signal becomes zero, thereby controlling the flow rate.

[0004]

The McFlow controller according to the prior art uses a thin tube having a sensor portion of about 0.2 mm through which gas passes, so that liquefied gas is liquefied due to temperature change and is clogged. There's a problem.
Further, since the flow rate sensor changes with time due to temperature change, periodic calibration is required. Furthermore, the gas flow path becomes complicated to form a bypass line, gas retention occurs, purge gas such as nitrogen gas remains in the mass flow controller, the regular mass flow rate is no longer measured, and the actual flow rate is If it becomes unstable or rust occurs when a corrosive gas such as chlorine gas is used, or if rust occurs with a powder product such as boron trichloride, the mass flow controller's flow sensor section There was a problem that there was a possibility of clogging in the pipe. The breakdown of the mass flow controller due to this sensor abnormality accounts for about 60% of the total number of breakdowns.

[0005]

A mass flow controller of the present invention is provided with a fixed orifice in a gas flow path having a shape close to a single pipe, and one pressure gauge is provided in the fixed orifice portion and one pressure gauge is provided in a preceding stage portion thereof. And a variable valve controlled by an output signal obtained from the pressure gauge.

[0006]

The present invention will be described below with reference to the drawings. FIG. 1 is a structural diagram of a mass flow controller according to a first embodiment of the present invention. Fixed orifice 2 in gas channel 1
Is provided, the first pressure gauge 3 for measuring the pressure is provided in the fixed orifice portion 2 by using the change in the capacity of the diaphragm that is deformed by the change in the pressure, and the second pressure gauge 4 is provided in front of the fixed orifice 2. The first and second pressure gauges 3 and 4 are provided.
The differential pressure of the pressure measured by is converted into a flow rate and output as a signal. This output signal and the setting signal are compared by the comparison circuit 5, and the control circuit 6 is set so that the difference signal becomes zero.
Is used to control the variable valve 7 to control the flow rate from 0 to 20 SLM.

FIG. 2 is a structural diagram of the second embodiment of the present invention. A fixed orifice 2 is provided in the gas flow path 1 and two silicon chips are welded to each other, and the upper chip is an integrated circuit having a diffusion resistance at the end of a pressure diaphragm formed in the IC chip. The piezoresistive pressure element 8 is provided as the first pressure gauge in the fixed orifice section 2, and the pressure difference measured by the piezoresistive element in front of the fixed orifice section 2 is converted into a flow rate and compared with the set value by the comparison circuit 5. Then, the variable valve 7 is controlled by the control circuit 6 so that the difference signal becomes zero, and the flow rate from 0 to 20 SLM is controlled. By using the piezoresistive pressure elements 8 and 9, the gas flow path 1 has a shape closer to a single tube.

[0008]

As described above, according to the present invention, since the gas passage has a shape close to a single tube, the gas passage is not clogged. Further, since the pressure gauge is used as the sensor for measuring the flow rate, there is an effect that the change with time due to the temperature change is small and the calibration is unnecessary. Further, since the bypass line is not provided, the gas does not stay, the purge gas does not stay, and the mass flow controller does not become unstable. Further, there is an effect that there is no possibility of clogging due to generation of rust when a corrosive gas is used and fine particles of a gas that produces a product such as boron trichloride.

Further, in the second embodiment, since the piezoresistive pressure element is used as the pressure gauge, the gas flow rate has a shape closer to that of a single tube, and the effect of preventing clogging is further enhanced.

According to the present invention, the problems of sensor clogging and aging can be solved, so that the failure of the mass flow controller due to the sensor can be reduced by 80% or more.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing a conventional technique.

[Explanation of symbols]

 1 Gas Flow Path 2 Fixed Orifice 3 Pressure Gauge 4 Pressure Gauge 5 Comparison Circuit 6 Control Circuit 7 Variable Valve 8 Piezoresistive Pressure Element 9 Piezoresistive Pressure Element 10 Flow Sensor 11 Bypass Element 12 Self-Heating Resistor

Claims (2)

[Claims]
1. A fixed orifice is provided in a gas flow path having a shape close to that of a single tube, a first pressure gauge is provided at the fixed orifice portion, and a second pressure gauge is provided at a preceding stage thereof. A mass flow controller, wherein a variable valve controlled by an output signal obtained from the second pressure gauge controls an amount of gas flowing into a flow path in which the second pressure gauge is provided.
2. The mass flow controller according to claim 1, wherein a piezoresistive pressure element is used for the first and second pressure gauges.
JP2983592A 1992-02-18 1992-02-18 Mass flow controller Withdrawn JPH05233068A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2983592A JPH05233068A (en) 1992-02-18 1992-02-18 Mass flow controller

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2983592A JPH05233068A (en) 1992-02-18 1992-02-18 Mass flow controller

Publications (1)

Publication Number Publication Date
JPH05233068A true JPH05233068A (en) 1993-09-10

Family

ID=12287077

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2983592A Withdrawn JPH05233068A (en) 1992-02-18 1992-02-18 Mass flow controller

Country Status (1)

Country Link
JP (1) JPH05233068A (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6708945B2 (en) 2001-07-12 2004-03-23 Smc Kabushiki Kaisha Flow rate control valve
JP2006043775A (en) * 2004-08-06 2006-02-16 Trumpf Werkzeugmaschinen Gmbh & Co Kg Laser beam machining head
EP2144043A1 (en) 2008-07-08 2010-01-13 Surpass Industry Co., Ltd. Differential-pressure flow meter and flow-rate controller
US8307845B2 (en) 2009-02-10 2012-11-13 Surpass Industry Co., Ltd. Flow rate controller
US8490645B2 (en) 2010-03-05 2013-07-23 Surpass Industry Co., Ltd. Pressure sensor, pressure-differential flow rate meter, and flow rate controller
JP2014132188A (en) * 2013-01-07 2014-07-17 Horiba Ltd Fluid control valve and mass flow controller

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6708945B2 (en) 2001-07-12 2004-03-23 Smc Kabushiki Kaisha Flow rate control valve
JP2006043775A (en) * 2004-08-06 2006-02-16 Trumpf Werkzeugmaschinen Gmbh & Co Kg Laser beam machining head
EP2144043A1 (en) 2008-07-08 2010-01-13 Surpass Industry Co., Ltd. Differential-pressure flow meter and flow-rate controller
US8006572B2 (en) 2008-07-08 2011-08-30 Surpass Industry Co., Ltd. Differential-pressure flow meter and flow-rate controller
US8307845B2 (en) 2009-02-10 2012-11-13 Surpass Industry Co., Ltd. Flow rate controller
US8490645B2 (en) 2010-03-05 2013-07-23 Surpass Industry Co., Ltd. Pressure sensor, pressure-differential flow rate meter, and flow rate controller
JP2014132188A (en) * 2013-01-07 2014-07-17 Horiba Ltd Fluid control valve and mass flow controller

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Legal Events

Date Code Title Description
A300 Withdrawal of application because of no request for examination

Free format text: JAPANESE INTERMEDIATE CODE: A300

Effective date: 19990518