JP3329783B2 - Laminar flow meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminar flow meter, and more particularly, to a method for generating a laminar flow, which uses a honeycomb pipe composed of a large number of thin tubes, and fills some of the thin tubes constituting the honeycomb pipe with packing. The present invention relates to a laminar flow meter that changes the measurement range by adjusting the flow rate flowing through the honeycomb pipe by performing the above-described steps, and its calibration.

[0002]

2. Description of the Related Art A differential pressure type flow meter used in a laminar flow region having a Re (Reynolds) number of 2320 or less is called a laminar flow meter. Conventionally, this laminar flow meter has a linear honeycomb pipe composed of a number of thin tubes parallel to the axis, and a differential pressure sensor that outputs a differential pressure signal proportional to the differential pressure of the fluid flowing through the honeycomb pipe. Things are known.

[0003]

However, in the conventional laminar flow meter described above, when the measurement range is changed in the manufacturing process, a honeycomb pipe is required for each measurement range, and as a result, the outer shape of the honeycomb pipe changes. Oops. The present invention provides a laminar flow meter with a desired measurement range without changing the outer shape of the honeycomb pipe by filling some of the thin tubes constituting the honeycomb pipe, and the calibration means in that case. It is an object of the present invention to provide a laminar flow meter having the same.

[0004]

According to a first aspect of the present invention, there is provided a honeycomb pipe formed of a large number of thin tubes for laminar flow, and a pressure difference between an upstream pressure and a downstream pressure of the honeycomb pipe is detected. and a differential pressure sensor, a layer in which the said capillary so as to change the measurement range by and a padding to prevent the fluid to be measured flows, to prevent the flow of a desired number of fluid in the capillary at該詰Me thereof In the flow meter, the honeycomb
The upstream joint connected to the upstream side of the
The downstream joint and the upstream pressure introduction pipe
The downstream pressure introduction pipe connected to the joint is connected to the downstream joint.
The connected differential pressure sensor is integrally formed,
The physically formed member is formed on a laminar flow meter body.
It is characterized in that it is detachably fitted to the
It is.

[0005]

[0006]

According to a second aspect of the present invention, in the first aspect of the present invention, there is provided a flow control valve for controlling a flow rate of the fluid flowing through the honeycomb pipe, and a power supply of the laminar flow meter is operated in conjunction with the flow control valve. The battery is controlled to be turned on and off, and the power supply battery is turned on when the flow control valve is opened, and the power supply battery is turned off when the flow control valve is closed.

[0008] The invention according to claim 3, the laminar flow generating pipe for generating a laminar flow, a laminar flow meter and a differential pressure sensor for detecting a pressure differential across the layer flow generating pipe, the Means for reading in the memory each calibration flow rate and the output value of the differential pressure sensor for each calibration flow rate in accordance with the calibration flow rate flowing through the laminar flow meter, and an output memory table storing each calibration flow rate and the sensor output. has, during the measurement flow measurement, in the layer flowmeter so as to output the calculated calibrating the measured flow rate based on the memory value in the memory table, the flow
The output value of the differential pressure sensor at the time of the amount 0 is read into the memory.
Zero-point calibration means, and
And a table for adjusting each memory value of the memory table.
And the flow rate is set to 0, and the zero point calibration is performed.
Means to perform zero point calibration, and
It is characterized in that the moly value is adjusted.

[0009]

[0010]

[0011]

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a view for explaining an example of an embodiment of a laminar flow meter according to the present invention.
1 is a laminar flow meter main body, 2 is a honeycomb pipe, 3 is a large number of thin tubes constituting the honeycomb pipe, 3a is a padding for closing the thin tube 3, 6a, 6b, 6c, 6d, 6e, 6f, 6
g, 6h are retaining members provided in the case 4 of the laminar flow meter main body 1, 4 is a case of the laminar flow meter main body 1, 5 is a differential pressure sensor, 7a, 7b, 7c, 7d are O-rings, 8a is A flow control valve, 8b is a knob for a flow control valve with a power switch, and 9a, 9b are joints.

FIG. 2 is a side view of the laminar flow meter of FIG. 1. In FIG. 2, reference numeral 10 denotes a display, 11 denotes a PC board, 12 denotes a power supply battery, and 13a and 13b denote process connectors.
As shown in FIG. 2, on the wall surface of the case 4 of the laminar flow meter,
The process connector 13a serving as an inlet of the fluid to be measured is
A power supply battery 12, which is a power supply of a laminar flow meter for detecting a pressure difference between the pressure on the upstream side and the pressure on the downstream side of the honeycomb pipe 2, is attached to the wall surface. A process connector 13b serving as an outlet for the fluid to be measured is attached to the wall surface. A joint 9a connected to the differential pressure sensor 5 is connected to the process connector 13a, and a joint 9b connected to the differential pressure sensor 5 is connected to the process connector 13b.

The joints 9a and 9b have, as shown in FIG.
The honeycomb pipe 2 is formed of a number of thin tubes, has a U-shape, and is connected to a honeycomb pipe 2 for generating a differential pressure by flowing a fluid to be measured in a laminar flow. The shape of the honeycomb pipe 2 does not have to be a U-shape. In addition, a filling 3a for preventing a fluid to be measured from flowing through the thin tube 3 constituting the honeycomb pipe 2 is attached, and a flow of a desired number of fluids in the thin tube is prevented by the filling so that the measurement range is reduced. Can be changed. Although FIG. 1 shows two paddings, the present invention is not limited to this, and a necessary number may be attached according to the measurement range. In addition, if the filling is a member that can prevent the measured fluid from flowing through the thin tube,
Any member may be used.

The upstream side of the honeycomb pipe 2 and the pressure sensor 5
The upstream side of the O-rings 7a, 7c
The honeycomb pipe 2
The downstream side of the pressure sensor 5 and the downstream side of the pressure sensor 5 are integrally attached in a liquid-tight manner by joints 9b by respective O-rings 7b and 7d, and these are configured as an integral member. As will be described, the laminar flow meter body 1 is detachably attached to the case 4.

The honeycomb pipe 2 is detachably fitted on the case 4 of the laminar flow meter main body 1, and detaching stoppers 6c and 6d for preventing the honeycomb pipe 2 from coming off are attached. The joint 9a is fitted around the periphery of the downstream side joint 9a, and the joint 9b is fitted around the downstream side joint 9b to prevent the joint 9a from coming off. The stoppers 6e, 6f, 6g, and 6h for preventing the 9b from coming off are attached. Note that in FIG.
Although eight of a, 6b, 6c, 6d, 6e, 6f, 6g, and 6h are illustrated, the number is not limited thereto, and the number required to fix the honeycomb pipe 2 and the joints 9a and 9b is provided. You only have to attach.

The retainer may be made integral with the case 4 by injection molding. With the structure as described above, the joints 9a and 9b are connected to both ends of the differential pressure sensor 5, and the honeycomb pipe 2 is further connected to the joints 9a and 9b to form an integrated body. , 6c, 6
d, 6e, 6f, 6g, and 6h can be easily assembled simply by fitting them.

An O-ring 7a as a packing for sealing the honeycomb pipe 2 is provided inside the joint 9a.
O which is a packing for sealing the differential pressure sensor 5
Similarly, an O-ring 7b serving as a seal for sealing the honeycomb pipe 2 and an O-ring 7d serving as a seal for sealing the differential pressure sensor 5 are incorporated in the joint 9b. Have been. For this reason, the differential pressure sensor 5 and the honeycomb pipe 2 can be easily replaced.

On the side of the case 4, a flow rate with a power switch for controlling the turning on and off of the power supply battery 12 shown in FIG. 2 in conjunction with the movement of the flow rate control valve 8a for adjusting the flow rate of the fluid to be measured. When the control valve knob 8b is attached and the flow control valve 8a is closed (that is, when the flow rate is not measured), the power supply battery 12 is disconnected.
The consumption of the power supply battery 12 is reduced.

Next, an application example of the laminar flow meter according to the present invention will be described. In a laminar flow meter, if the viscosity of the fluid is constant, the flow rate can be obtained as an amount proportional to the reciprocal of the viscosity and the differential pressure, so that the flow calculation is simplified. Gases having a pressure from a few atmospheres to a few millimeters of mercury are suitable for flow measurement using a laminar flow meter, since the effect of viscosity on pressure change is small. Therefore, the laminar flow meter of the present invention is applied particularly as a flow meter for gases such as oxygen. However, the present invention is not limited to gas, and the laminar flow meter of the present invention is a type of differential pressure type flow meter, and therefore can be applied to flow measurement of liquid, vapor, and the like.

FIG. 3 is a main part configuration diagram for explaining a calibration means suitable for application to the above-described laminar flow meter.
Using U, actual flow calibration, linearization correction, and 0
Enables point calibration, simplifies calibration, improves accuracy, and
This enables cost reduction.

Output of differential pressure sensor in laminar flow meter
There is an individual difference in the relationship between the flow rates. Normally, the adjustment of the zero point and the full scale is individually performed by an electric circuit. Further, when the linearity is poor, adjustment of the linearizer and the like require time for calibration and the like. Further, the differential pressure sensor is an analog output, and the zero point shift may be caused by the external atmosphere, a change in the fluid, a change with time, or the like, but the present invention has solved these problems.

FIG. 3 is a block diagram for explaining an embodiment of a laminar flow meter provided with a calibration means according to the present invention.
In the figure, 21 is a CPU, 22 is a sensor output table stored in a memory of the CPU 21, 23 is a display, 24 is a differential pressure sensor, 25 is an amplifier circuit, 26 is a power control unit, 27 is a flow rate display and an integrated display. The mode switching switch 28 for switching the display mode of the calibration mode (Cal) and the measurement mode (R)
(Calibration) / Run (measurement)
A changeover switch 29 changes a flow rate value of a fluid flowing for calibration (for changing a flow rate value in a table when the flow rate value cannot be accurately set). A sensor output reading button 31 is a button for zero point Cal, which is a button for zero point calibration. When the sensor output reading button 30 is pressed, the output of the differential pressure sensor 4 at that time is read into the sensor output table 22,
The zero-point calibration is performed by pressing the zero-point Cal button 31.

In FIG. 3, first, Cal (calibration) / R
The un (measurement) switch SW 28 is set to the Cal side (calibration mode), and calibration is performed while the sensor output table 22 is sequentially displayed on the display 23. For example, when the flow rate is 0, pressing the sensor output reading button 30 causes the differential pressure sensor 2
4 is read and stored in V ₀ of the sensor output table 22. Next, the flow rate flowing through the flow meter
After the _1, and then by pressing the sensor output read button 30, the sensor output V ₁ is loaded into the sensor output table 22. Hereinafter, similarly, V ₂ , V ₃ , V
Read up to ₄ (maximum flow).

FIG. 4 shows the sensor output table 22 at that time.
Is a diagram showing an example of each of the flow rates F ₀ , F ₁ ,
Output voltages V ₀ , V of differential pressure sensors corresponding to F ₂ , F ₃ , F _4
1 , V ₂ , V ₃ and V ₄ are stored. In FIG. 4, the number of measurement points is five, but this is an arbitrary number of points and is not limited to this. Further, when an accurate actual flow rate cannot be supplied, F _{0 to} F ₄ can be rewritten to the flow rate value at that time. The calibration flow rate changing unit 29 is for this purpose, and is for changing the calibration flow rate value in the table when the calibration flow rate value cannot be set accurately. Next, the Cal (calibration) / Run (measurement) switch SW 28 is set to R
By setting to the un side (measurement mode), the CPU reads the sensor output of the differential pressure
The flow rate display, the integration display, and the like are switched as required by 27 and an analog output, a pulse output, and an alarm output are output.

As described above, in the present invention, actual measurement is performed only at a plurality of predetermined flow points where the flow rate is accurately determined, and the measured value is used as the predetermined flow rate at the time of measuring the flow rate to be measured. Although the flow rate at points other than the predetermined flow rate point is unknown, in the present invention, the flow rate between each predetermined flow rate (between each calibration flow rate) is measured by linear interpolation.

FIG. 5 is a diagram for explaining an example.
The black circles in the figure are the actual measured values when the actual flow calibration was performed as described above, and the dotted lines in the figure are those obtained by interpolating the actual measured values with a straight line. It is possible to linearly increase the accuracy to improve the accuracy.

Next, the zero-point calibration will be described. In the present invention, zero point calibration by pressing the 0-point Cal button 31 when the flow rate 0, reads the V ₀ which time, if the V ₀ is shifted to V ₀ of the sensor output table 22, the can be performed as many automatic V ₁ ~V ₄ also 0 point adjustment by shifting the shift.

According to the present invention, as described above, the output values for several accurate flow rates (calibration flow rates) are stored, and the flow rate is measured over the entire measurement range by interpolating between these output values. However, when the laminar flow meter is a battery-driven type, the differential pressure sensor usually uses a large current, so that the battery-driven type cannot be used for a long time. Therefore, as shown in FIG. , A power supply control unit 26,
The power supply control unit 26 is controlled by the CPU 21 and, for example, at a pulse rate of several + milliSec, several tens of μsec.
During this time, the power supply is turned on to perform measurement, and the power supply battery is driven intermittently to reduce battery consumption.

[0030]

According to the present invention, the measurement range can be adjusted without changing the outer shape of the honeycomb pipe. Therefore, it is not necessary to prepare a honeycomb pipe for each measurement range, and only one type is required except for the filling of the laminar flow meter body regardless of the measurement range, so that the structure is simplified,
The cost in the manufacturing process can be reduced. In particular, the structure
Simplified, easy to assemble and differential pressure sensor
And the honeycomb pipe can be prevented from coming off.

[0031]

[0032]

[0033] Claim 2 to the corresponding effect: In the prior art, the power source is entered or has expired power supply battery of laminar flow meter for fluid is flowing, though not fluid flows in opposite Therefore, there is a problem that the life of the battery is shortened, but the present invention can solve this problem. In addition, since the opening and closing of the valve for flowing the fluid and the turning on and off of the power supply of the laminar flow meter power supply battery can be performed by one flow control valve, the operation is simplified.

An effect corresponding to claim 3 is that the laminar flow meter has C
The provision of the actual flow calibration function using PU enables simple intermittent measurement to be performed, eliminating the need for full-scale adjustment of the sensor output of the differential pressure sensor, making calibration and the like simple and in a short time. . In addition, simplification of work such as calibration
By reducing the time, the cost of the product can be reduced. Also,
Since the user can easily perform the calibration, there is an effect that the expense of requesting the manufacturer to perform the calibration is unnecessary. Furthermore, a zero-point calibrator using a CPU for a laminar flow meter
Function allows zero point adjustment with one touch,
It can be easily adjusted locally.

[0035]

[0036]

[0037]

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an example of an embodiment of a laminar flow meter according to the present invention.

FIG. 2 is a diagram showing a side view of the laminar flow meter of FIG. 1;

FIG. 3 is a block diagram illustrating an embodiment of a laminar flow meter having a calibration unit according to the present invention.

FIG. 4 is a diagram illustrating an example of a sensor output table when performing actual flow calibration.

FIG. 5 is a diagram showing flow rate-output characteristics after correction of linearity between respective predetermined flow rates using the calibration result shown in FIG. 4;

[Explanation of symbols]

1: laminar flow meter main body, 2: honeycomb pipe, 3: thin tube,
3a: padding, 4: case, 5, 24 ... differential pressure sensor, 6
a, 6b, 6c, 6d, 6e, 6f, 6g, 6h: retaining, 7a, 7b, 7c, 7d: O-ring, 8a: flow control valve, 8b: knob for flow control valve with power switch, 9a, 9b ... Joints, 10, 23 ... Indicators, 11 ...
PC board, 12: Power battery, 13a, 13b: Process connector, 21: CPU, 22: Sensor output table, 25: Amplifier circuit, 26: Power control unit, 27: Mode switching SW, 28: Cal / Run switching SW, 29: Calibration flow rate change unit, 30: Sensor output read button, 31 ...
Button for 0 point Cal.

Continuation of the front page (56) References JP-A-8-178722 (JP, A) JP-A-8-136326 (JP, A) JP-A-10-122918 (JP, A) JP-A-8-14981 (JP) , A) Japanese Utility Model Showa 61-206821 (JP, U) Japanese Utility Model Showa 52-7656 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01F 1/00-9/02

Claims (3)

(57) [Claims] 1. A honeycomb pipe for generating a laminar flow comprising a large number of thin tubes, a differential pressure sensor for detecting a pressure difference between an upstream pressure and a downstream pressure of the honeycomb pipe, and a fluid to be measured And a laminar flow meter adapted to change the measurement range by blocking the flow of the desired number of fluids in said capillary tube .
And an upstream side connected to an upstream side of the honeycomb pipe.
A downstream joint connected to the joint and the downstream side, and an upstream pressure guide
The inlet pipe is connected to the upstream joint and the downstream pressure introduction pipe
Is connected to the differential pressure sensor connected to the downstream joint.
And the integrally formed member is a laminar flow rate.
Is removably fitted to a receiving member formed on the meter body.
A laminar flow meter. 2. A pre-SL has a flow regulating valve for adjusting the flow rate of the fluid flowing through the honeycomb pipes, and controls the turning on and off of the power supply battery of the layer flow meter in conjunction with the flow rate control valve, the flow rate The laminar flow meter according to claim 1 , wherein the power supply battery is turned on when the control valve is opened, and the power supply battery is turned off when the control valve is closed. A laminar flow generating pipes that generates wherein laminar flow, a laminar flow meter and a differential pressure sensor for detecting a pressure differential across the layer flow generating pipe, the laminar flow meter Means for reading in a memory each calibration flow rate and the output value of the differential pressure sensor for each calibration flow rate in accordance with the flowing calibration flow rate ;
An output memory table that stores the calibration flow rate and sensor output
When measuring the measured flow rate, in a laminar flow meter configured to calculate and output the measured flow rate based on each memory value in the memory table and output the difference,
Zero point calibration means for reading the output value of the pressure sensor into the memory
Based on the calibration result by the zero-point calibration means.
Table adjustment means for adjusting each memory value of memory table
And the flow rate is set to 0, and the zero point calibration means sets the flow rate to 0.
Perform point calibration and adjust each memory value in the memory table
Laminar flow meter and performs.