JPH0545188A - Fluidic flowmeter - Google Patents

Abstract

PURPOSE:To precisely measure the change of a flow at high sensitivity by providing a velocity sensor utilizing an electric resistance in a passage part in which a flow cyclically fluctuates at a frequency corresponding to the flow. CONSTITUTION:Velocity sensors 11a, 11b are composed of tungsten and the like whose resistance values increase by heat generation and arranged on both sides of the outlet of a jet nozzle 5. Even in the case where an arrangement position of a deflection inducing element 7 is made the upstream side, the relation of flow-oscillation frequency is changed linearly and the same result can be obtained. The resistance of a heat ray type velocity sensor 11 is made R1, and a bridge circuit 12 is formed together with the other three resistances R2, R3, R4. In other words, R1 and R2 are made series, R3 and R4 series, and a detection circuit 13 for detecting a current I allowed to flow in respective intermediate points is provided. If the circuit 12 is regulated so that resistances may be R1XR2=R3XR4, its oscillation frequency is detected by the use of the circuit 13 and converted into a flow because the value of the resistance R1 changes and the potential and the current at each point become different when the flow to be measured collides with the sensor 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidic flow meter used for measuring the flow rate of gas or liquid.

[0002]

2. Description of the Related Art A fluidic flowmeter utilizing fluidic oscillation, which has been developed as an alternative to a conventional membrane gas meter, is small in size and has no moving parts. Research and improvement are being carried out in various fields. Further, it is desired that the conventional gas flow meter requires a rising area for mounting and is small in view of urban aesthetics and does not matter in directionality in mounting. From this point of view, there is a demand for a small and high-performance fluidic flowmeter that takes advantage of its characteristics.

As described in general textbooks, the fluidic flowmeters mentioned here focus on the fact that the flow causes vibrations by acting to control itself, and the frequency of the flowrates to the flow rate. It uses proportionality,
In general, it is known that the frequency changes almost linearly in the flow rate range of 150 liters / hour to 3000 liters / hour. Such fluidic flow meters are disclosed in, for example, Japanese Patent Laid-Open Nos. 62-30917 and 62.
-108115, JP-A-63-139214, JP-A-63-313018 and the like.

[0004]

However, in these devices, the pressure sensor is used to detect the fluctuation of the flow path portion, and the sensitivity to the change of the flow rate is insufficient and the reliability is lacking. Will be things.

[0005]

According to a first aspect of the present invention, a flow restricting portion for rectification, a jet nozzle and a flow expanding portion are sequentially provided on the same line, and the jet nozzle in the flow expanding portion faces the jet nozzle. In the fluidic flow meter provided with an end block for forming a return flow path at a position up to the discharge pipe behind the exciter in the flow path enlarged portion, the flow path is provided with a pendulum that causes a drift in the position. A speed sensor with electrical resistance is provided in the flow path part where the flow periodically changes at a frequency corresponding to the flow rate of the fluid to be measured in the flow path expansion part, and a bridge circuit is formed by four resistances including this speed sensor. A detection circuit for detecting the flow rate fluctuation based on the potential fluctuation in the bridge circuit is provided.

At this time, of the resistors forming the bridge circuit, the resistance of the speed sensor is R1, the resistance connected in series with the speed sensor is R2, and the resistance connected diagonally to this resistance R2 is R3. When the resistance connected in series with the resistance R3 is R4, in the invention according to claim 2, when the flow rate is 0, R1 × R4> R2 × R3, and when the flow rate exceeds a certain value, R1 × R4 <R2 × The values of the resistors R2, R3 and R4 are set so as to satisfy the relationship of R3, and the direction of the current or the potential difference flowing between the midpoint between the resistors R1 and R2 and the midpoint between the resistors R3 and R4 is set by the detection circuit. The flow rate fluctuation was measured by counting the number of positive and negative inversions of.

On the contrary, in the invention described in claim 3, when the flow rate is 0, R1 × R4 <R2 × R3, and when the flow rate exceeds a certain value, R1 × R4> R2 × R3 is satisfied. The values of the resistors R2, R3, and R4 are set, and the detection circuit counts the number of positive and negative inversions of the direction of the current flowing between the midpoint between the resistors R1 and R2 and the midpoint between the resistors R3 and R4. The flow rate fluctuation was measured.

[0008]

According to the first aspect of the present invention, the fluctuation detecting sensor for the flow path portion, in which the flow cyclically fluctuates at a frequency corresponding to the flow rate of the fluid to be measured, has a cyclical change with an increase in the flow rate. We focused on the point that it can be changed so as to increase linearly, and we used an electrically controlled speed sensor, so the change in flow rate can be detected with higher sensitivity than when using a pressure sensor. It will be one. In particular, since the detection circuit detects the resistance of the speed sensor based on the bridge circuit configuration having one side, it becomes possible to measure the flow rate with high sensitivity, and also to improve the responsiveness and select the level for noise. It will be easy.

At this time, according to the condition setting as claimed in claim 2 or 3, it is possible to accurately measure with extremely high sensitivity by digital circuit processing such as counting the number of inversions.

[0010]

An embodiment of the present invention will be described with reference to the drawings. First, the basic configuration and operation of a fluidic flow meter to which the present invention can be applied will be described with reference to FIG. Here, on the path connecting the inflow pipe 1 and the exhaust pipe 2, the set ring space 3, the flow path reducing unit 4, the jet nozzle 5,
The flow path expanding portion 6 is provided in order, and the pendulum 7, side blocks 8 and end blocks 9 are provided in the flow path expanding portion 6. Here, such a fluidic flowmeter has a line-symmetrical shape with respect to a straight line connecting the jet nozzle 5 and the exciter 7. The end block 9 has walls 9a and 9b extending toward the upstream side of the flow path on both sides so as to cover the side block 8. A discharge space 10 is provided behind the end block 9.

In such a structure, first, the tubular flow from the upstream side of the flow path is rectified into a two-dimensional flow in the set ring space 3 and further rectified by the flow path contracting section 4 to smoothly jet the nozzle 5. Head to. Then, the jet flow rectified by the jet nozzle 5 is divided into right and left by hitting the exciter 7, but in the space of the flow path expanding portion 6 up to the end block 9, when the flow exceeds a certain flow rate, the exciter 7 is discharged. Due to the instability of the vortex behind it, a left or right biased flow is formed. Therefore, the flow hitting the end block 9 reaches the outlet of the jet nozzle 5 along the front surface of the end block 9 and around the side block 8, and hits the jet flow at a right angle. Therefore, the direction of the jet flow is biased in the direction opposite to the initial drift by the flow returning from the side. This causes the same thing to happen again on the opposite side, with the result that the flow leaving the jet nozzle 5 changes direction in a regular and alternating manner. The frequency of this regular directional vibration increases linearly with increasing flow rate.

In such a general fluidic flowmeter, the basic components such as the jet nozzle 5, the exciter 7, the end block 9 and the like have been experimentally investigated for the principle of vibration, and as a result, it has been confirmed that It was found that the flow path contracting section 4, the jet nozzle 5, and the pendulum 7 that is the target of the flow play a large role, and the end block 9 also plays a role of a return path. Here, in this embodiment,
The inner wall 6a of the flow passage expanding portion 6 is used as a return flow passage to surely vibrate, and the end block 9 may be present in the flow passage leading to the discharge pipe 2, and the side block 8 is essential. is not.

Further, the detection sensor is provided in the flow passage portion in which the flow cyclically fluctuates at a frequency corresponding to the flow rate of the fluid to be measured in the flow passage expanding portion 6, but in the present embodiment, the speed sensor 11a,
11b is used. As the speed sensors 11a and 11b, those configured as electrical resistances by thin wires or thin films are used, and have an electrical circuit configuration. That is, a small amount of current is applied to the resistors forming the speed sensors 11a and 11b to generate heat, thereby changing the resistance value. Then, the generated heat is removed by the flow in the flow path, but the temperature of the resistor also changes depending on the degree of the heat, indicating a change in resistance value.Therefore, by detecting the potential difference, the fluctuation cycle of the flow of the fluid to be measured is detected. Can be detected. As a result, the flow rate change is obtained corresponding to the fluctuation period.

First, the speed sensors 11a and 11b are shown in FIG.
As shown in (b), FIG. 2 shows the relationship between the flow rate and the vibration frequency when the jet nozzle 5 is arranged on both sides of the outlet and measured. As described above, since it suffices that the periodical change increases linearly with the increase of the flow rate, the speed sensor 11a, which is electrically controlled as in the present embodiment,
By using 11b, the flow rate change can be measured with higher sensitivity than in the case of the pressure sensor. The speed sensors 11a and 11b are connected to the measurement points M1 and M2 in FIG.
That is, similar characteristics can be obtained when the vibration is caused by the exciter 7 and the current is measured in a region where the current flows unevenly and collides with the end block 9.

By the way, when the resistance of the speed sensor 11 is R1, this resistance R1 is equal to that of the other three as shown in FIG. 1 (a).
A bridge circuit 12 connected to the power supply V is formed together with the two resistors R2, R3 and R4. That is, the resistors R1 and R2
Are connected in series, resistors R3 and R4 are connected in series,
The bridge circuit 12 has a configuration in which the resistor R4 is diagonally located with respect to the resistor R1. A detection circuit 13 for detecting a current I flowing between the middle points of the resistors R1 and R2 and the middle points of the resistors R3 and R4 is connected.

In such a bridge circuit 12, for example, R1 × R2 = R while a slight current flows through the resistor.
Each resistance value and current value are adjusted so as to be 3 × R4. When the fluid to be measured hits the velocity sensor 11 in this state, the value of the resistance R1 changes, the potential of each point changes due to the principle of the bridge circuit 12, and the magnitude of the current also changes. In particular, if the value of the resistor R2 is set to be equal to or less than that of the resistor R1, the flow rate change can be detected with extremely high sensitivity. For example, since the current I oscillates as shown in FIG. 3, the flow rate change can be calculated with high sensitivity by detecting this oscillation cycle by the detection circuit 13.

By the way, when the material of the speed sensor 11 is properly selected and a small amount of current is applied to the resistor, R1 × R4> R2 × R3 when the flow rate is 0, and R1 × when the flow rate exceeds a certain specified value. The values of the resistors R1, R2, R3 and R4 may be set so as to satisfy the relationship of R4 <R2 × R3. In this case, a small current I initially flows between the midpoints, but the fluid to be measured flows and the resistance R of the speed sensor 11 increases.
When the value of 1 decreases, R1 × R4 <R2 × R3, and the direction of the current I becomes opposite. That is, by appropriately setting the disposition position of the speed sensor 11, the direction of the current I changes with the deflection of the fluid to be measured and vibrates positively and negatively as shown in FIG. Therefore, the flow rate change can be calculated by setting the detection circuit 13 to a digital circuit configuration and counting the number of times the direction of the current I is reversed.

This is the potential difference ΔV12 (= V1-V2) between the potential V1 at one midpoint and the potential V2 at the other midpoint.
Therefore, the flow rate can be calculated with high sensitivity even if the detection circuit 13 counts the number of positive and negative signs, and thus the number of times exceeding 0V.

As described above, as the material of the speed sensor 11, a material whose resistance value increases due to heat generation, such as tungsten or alloy, is suitable.

Further, the speed sensor 11 has the opposite property, that is, the resistance value is reduced by heat generation, for example, a thermistor is used, and R1 × R4 is used at a flow rate of 0 with a slight current flowing through the resistance. The values of the resistors R1, R2, R3 and R4 may be set so as to satisfy the relationship of <R2 × R3 and R1 × R4> R2 × R3 when the flow rate exceeds a certain specified value. In this case, a small current I first flows between the midpoints, but when the fluid to be measured flows and the resistance R1 of the speed sensor 11 decreases, R1 × R4>
R2 × R3, and the direction of the current I is opposite. That is, by appropriately setting the disposition position of the speed sensor 11, the direction of the current I changes with the deflection of the fluid to be measured and vibrates positively and negatively as shown in FIG. Therefore, the detection circuit 1
By using 3 as a digital circuit configuration and counting the number of times the direction of the current I is reversed, the flow rate change can be calculated.

In this case also, the number of positive and negative inversions of the potential difference ΔV12 may be counted.

In any case, according to the speed sensor 11 system as in this embodiment, the responsiveness can be improved by the electric circuit configuration, and the level selection for noise or the like becomes easy.

[0023]

Since the present invention is configured as described above, according to the invention of claim 1, the vibration detection of the flow path portion in which the flow periodically fluctuates at a frequency corresponding to the flow rate of the fluid to be measured. As for the sensor, we focused on the point that the periodical change increases linearly with the increase of the flow rate, and we decided to use an electrically controlled speed sensor. The flow rate change can be detected with higher sensitivity than in the case of the above, and in particular, the flow rate can be detected with higher sensitivity because it is detected by the detection circuit based on the bridge circuit configuration having the resistance of such a speed sensor on one side. The measurement can be performed, and the treatment such as improving the responsiveness and selecting the level for noise becomes easy.

At this time, according to the condition setting as claimed in claim 2 or 3, it is possible to accurately measure with extremely high sensitivity by digital circuit processing such as counting the number of inversions.

[Brief description of drawings]

1 shows an embodiment of the present invention, (a) is a circuit diagram, (b)
Is a horizontal sectional view.

FIG. 2 is a characteristic diagram showing a flow rate-frequency characteristic.

FIG. 3 is a characteristic diagram showing current change characteristics of a bridge circuit.

FIG. 4 is a characteristic diagram showing current change characteristics of a bridge circuit.

[Explanation of symbols]

 2 Discharge pipe 4 Flow path reducing section 5 Jet nozzle 6 Flow path expanding section 7 Pendulum 9 End block 11 Speed sensor 12 Bridge circuit 13 Detection circuit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Yuko Oshima Inc. 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Kenji Okada 1-3-3 Nakamagome, Ota-ku, Tokyo Stocks Inside the Ricoh Company (72) Inventor Yoshio Watanabe 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Inside Ricoh Company (72) Hisae Kondo 2-28-24 Izumi, Higashi-ku, Nagoya, Aichi Ricoh Elemex Co., Ltd. (72) Inventor Toshiyuki Takamiya 6-16-10 Minamioi, Shinagawa-ku, Tokyo Ricoh Seiki Co., Ltd.

Claims (3)

[Claims] 1. A flow reducing portion for rectifying, a jet nozzle, and a flow passage expanding portion are sequentially provided on the same line, and a pendulum for causing a drift is provided at a position facing the jet nozzle in the flow passage expanding portion. In a fluidic flowmeter provided with an end block for forming a return flow passage at a position behind the exciter in the flow passage expansion portion up to the discharge pipe, the flow rate of the fluid to be measured in the flow passage expansion portion Providing a speed sensor with electrical resistance in the flow path part where the flow periodically changes at a corresponding frequency,
A fluidic flowmeter, characterized in that a bridge circuit is formed by four resistors including the speed sensor, and a detection circuit for detecting flow rate fluctuations based on potential fluctuations in the bridge circuit is provided. 2. Among the resistors forming the bridge circuit, the resistance of the speed sensor is R1, the resistance connected in series to the speed sensor is R2, the resistance connected diagonally to this resistance R2 is R3, and this resistance is When the resistance connected in series with R3 is R4, when the flow rate is 0, R1 × R4> R2 × R3, and when the flow rate exceeds a certain value, R1 × R4 <R2 × R3 is satisfied. The values of the resistors R2, R3, R4 are set, and the center point between the resistors R1 and R2 and the resistor R are set by the detection circuit.
2. The fluidic flow meter according to claim 1, wherein the flow rate fluctuation is measured by counting the number of positive and negative inversions of a current direction or a potential difference flowing between a midpoint between R3 and R4. 3. Among resistors forming a bridge circuit, a resistance of a speed sensor is R1, a resistance connected in series with the speed sensor is R2, a resistance connected diagonally to this resistance R2 is R3, and this resistance is When the resistance connected in series with R3 is R4, when the flow rate is 0, R1 × R4 <R2 × R3, and when the flow rate exceeds a certain value, the relationship of R1 × R4> R2 × R3 is satisfied. The values of the resistors R2, R3, R4 are set, and the center point between the resistors R1 and R2 and the resistor R are set by the detection circuit.
2. The fluidic flow meter according to claim 1, wherein the flow rate fluctuation is measured by counting the number of positive and negative inversions of a current direction or a potential difference flowing between a midpoint between R3 and R4.