JP2809495B2 - Flow meter correction device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a correction device for a flow meter, and in particular, is configured to accurately measure a flow rate even when a sudden increase or decrease of a fluid to be measured is repeated in a short time. The present invention relates to a correction device for a flow meter.

2. Description of the Related Art A flowmeter for measuring a fluid to be measured (in this case, a gas to be measured is referred to as a gas hereinafter) is provided in a pipe for supplying a measured fluid such as city gas to each home. Has been established. As this type of flow meter, for example,
A turbine type flow meter disclosed in Japanese Patent No. 15520, which can measure a wide range from a small flow rate to a large flow rate, is used. In this turbine type flow meter, a turbine rotor as a rotating body rotates in proportion to the flow rate, detects the number of rotations, and outputs a rotation detection pulse (hereinafter simply referred to as a pulse).

When a gas appliance that consumes a large amount of gas, such as a gas water heater, is used, the flow rate of the gas rapidly increases at the same time as the start of use, and the gas appliance is switched to an unused state. And the flow rate drops sharply.

As described above, when the gas flow rate is rapidly reduced, in the turbine type flow meter, it takes time until the rotation of the turbine rotor is reduced by the inertia of the turbine rotor to a rotation corresponding to the reduced flow rate, During this time, there is a problem that the measured flow rate is measured more than the actual flow rate.

Therefore, it is conceivable to correct the overmeter amount by monitoring the change in the rotation speed of the turbine rotor and multiplying the integrated value of the flow pulse generated by the overspeed at the time of the rapid decrease of the flow rate by a correction rate corresponding to the overmeter time. I have.

However, if the gas appliance is frequently used, the time from the rapid decrease in gas flow to the rapid increase is short, and the use of the next gas is started while the gas flow is rapidly decreased and the turbine rotor is over-rotating. In this case, there is a problem that a correction value is calculated assuming that there is a flow rate even while the flow rate is reduced to zero, and an accurate flow rate cannot be obtained even if the flow rate is corrected in accordance with the overmeter time.

Therefore, an object of the present invention is to provide a flowmeter correction device that solves the above-mentioned problems.

Means for Solving the Problems The present invention detects a rotation of a rotating body that rotates according to a flow rate of a fluid to be measured, generates a pulse, and integrates the pulse to measure a flow rate of the fluid to be measured. A correction device for the meter, wherein a decrease rate of the flow rate is calculated from a cycle of the pulse, a first time point at which the decrease rate is equal to or more than a predetermined value, and a second time point at which the decrease rate is less than a predetermined value. Detecting means for detecting; pressure detecting means for detecting the pressure of the fluid to be measured; and input of a signal from the first time point to the second time point of the detecting means to generate a pressure detection signal from the pressure detecting means. Correction value generating means for generating a correction value based on the pulse, and integrating means for adding the pulse excluding the period from the first time point to the second time point and the correction value from the correction value generating means. It becomes.

Action Even if the flow rate suddenly increases and decreases in a short time, the pressure of the fluid to be measured, which fluctuates according to the flow rate of the fluid to be measured, is detected by the pressure detecting means, and the rotating body is over-rotated based on the pressure detection signal. By correcting the integrated value of the pulse by the (over meter), an accurate flow meter can be performed even when the flow rate suddenly increases to zero while the rotor is over-rotating.

Embodiment FIG. 1 shows an embodiment of a flow meter correcting device according to the present invention. In the figure, a flow meter main body 2 of a turbine type flow meter 1 is disposed in the middle of a pipe for feeding a fluid to be measured such as a gas with its axial center aligned vertically. The fluid is supplied as indicated by the arrow in the figure.

Reference numeral 3 denotes an upstream cone, which is inserted from below into the flow path 2a of the flowmeter main body 2, and is held by a column 3a. Reference numeral 4 denotes a downstream cone, which is inserted into the flow path 2a of the flowmeter main body 2 from above, and is attached to and held by the column 4a. Bearing holes 3b, 4b having a predetermined depth are formed in the axes of the opposing surfaces of the upstream and downstream cones 3, 4, and each bearing hole 3b, 4b has a superalloy, a jewel (artificial sapphire). ), For example, a hemispherical bearing portion is formed at the center of the pivot bearings 5, 6.

Reference numeral 7 denotes a turbine rotor, in which a rotary shaft 9 is inserted and fitted and fixed in a central hole of a rotor hub 8, and a plurality of blades 10 are integrally formed on an outer periphery of the rotor hub 8. The rotating shaft 9 is made of, for example, cemented carbide or steel, and has an upstream end 9a and a downstream end 9b.
Are each formed in a hemispherical shape, and are slidably supported at low friction on the bearing portions of the pivot bearings 5 and 6 of the upstream and downstream cones 3 and 4, respectively.

Reference numeral 11 denotes two magnets provided inside the upper surface of the rotor hub 8. Reference numeral 12 denotes a rotation detecting pickup made up of a magnetoresistive element or the like, which is embedded in the downstream cone 4 so as to face the magnet 11.

In addition, the said turbine type flowmeter 1 is arrange | positioned in the middle of the gas piping (not shown) to each household. Therefore, when a household gas appliance (not shown) is used, a flow rate corresponding to the usage amount flows through the flow path 2a. Then, the turbine rotor 7 rotates at a rotation speed proportional to the gas flow rate.

That is, the pickup 12 outputs a pulse corresponding to the rotation speed of the turbine rotor 7, in other words, a pulse having a period proportional to the flow rate.

A correction device 13 is supplied with a pulse from the pickup 12. The pulse supplied from the pickup 12 to the correction device 13 is amplified by the amplifier 14, and then the correction operation circuit 15
And is converted to a flow rate. Then, the converted flow rate is integrated by the integration circuit 16, and the integrated value is displayed on the display device 17.

The pulse amplified by the amplifier 14 is also supplied to an overmeter start detection circuit 18 and an overmeter end detection circuit 19 as detection means. The overmeter start detection circuit 18 measures the pulse period and supplies an overmeter start signal OMS to the correction operation circuit 15 as described later. The overmeter end detection circuit 19 supplies an overmeter end signal OME to the correction operation circuit 15 based on the rate of change of the pulse period, as described later.

Reference numeral 20 denotes an overmeter elapsed time measuring circuit, which is supplied with the signal OMS from the overmeter start detection circuit 18 and the signal OME from the overmeter end detection circuit 19, and measures the time from when the signal OMS is supplied until the signal OME is supplied. The measured value is supplied to the correction operation circuit 15.

Reference numeral 21 denotes a pressure sensor as pressure detecting means, which is provided in the flow meter main body 2 so as to detect the pressure of gas flowing in the flow path 2a. In this embodiment, the pressure sensor 21 is buried in the inner wall of the flow path 2a facing the downstream cone 4, but may be provided on the inner wall of the flow path 2a facing the upstream cone 3.
Alternatively, it may be provided above the flow meter 1 and in the middle of the downstream pipe. The pressure detection signal output from the pressure sensor 21 is input to the correction operation circuit 15 of the correction device 13. Then, the correction operation circuit 15 corrects the integrated value of the flow rate due to the excessive rotation (overmeter) of the turbine rotor 7 when the flow rate is rapidly decreased based on the pressure detection signal from the pressure sensor 21. The correction operation circuit 15
Numerical predetermined pressure P ₀ of the zero flow is preset to.

Here, for example, such use of the above as a gas appliance is repeated if the use amount of gas decreases rapidly, to zero from the Q _B in the actual flow rate at time T ₁ as shown in FIG. 2 (A) Declines sharply. However, the rotation speed of the turbine rotor 7 is shown in FIG.
Reaches a rotational speed proportional to the actual flow rate at the time of gradually becomes reduced to the time T _2, from time T ₁ rather than falls in proportion to the rapid decrease of the flow rate (zero) as shown in. That is, from time T ₁
Rotational speed does not represent a flow rate between T _2.

The overmeter start detection circuit 18 and the overmeter end detection circuit 19 shown in FIG. 1 always measure the period of the pulse by counting the number of pulses that arrive at a certain time. That is, as shown in FIG. 2 (C), the rotation speeds N ₀ , N ₁ ,... At the respective times t ₁ , t ₂ ,.

Further, the overmeter start detection circuit 18 detects the previous rotation speed N
subtracts the rotational speed N ₁ of the current from the _i-1, the difference N _{when i-1} -N _i is equal to or greater than a predetermined amount .DELTA.N (first time point), the correction calculation circuit generates a Obameta start signal OMS 15 And supplies it to the overmeter elapsed time measuring circuit 20. The constant value ΔN is a positive value, and is set to a value corresponding to a rapid change in the flow rate.

Also, the overmeter end detection circuit 19 detects the previous rotation speed Ni _-1.
If when the difference N _i-1 -N _i between the current rotational speed N _i reaches a constant value less than ΔN or below zero (the second time), the correction to generate a Obameta end signal OME arithmetic circuit 15 and Obameta It is supplied to the elapsed time measuring circuit 20.

Therefore, the overmeter elapsed time measuring circuit 20 outputs the signal OMS
The elapsed time from the arrival of the signal to the arrival of the signal OME is measured, and the measured value is output to the correction operation circuit 15.

For example, as shown in FIG. 3, the time T when the signal OMS is incoming to the time T _B by the signal OME is incoming at _A, the correction calculation circuit 15 area N _B of the hatched portion in the figure (T _B -T _A excess flow rate V of Obameta time integrated value corresponding to _{a) = N B (T B -T} a) · K ( where, K is integrated seeking once per flow rate) that correction value the rotor circuit 16
To supply.

The integration circuit 16 integrates the pulses from the amplifier 14, but interrupts the above integration during the period from the arrival of the signal OMS to the arrival of the signal OME. Furthermore, after the signal OMS is received, the integrated value is added by adding the integrated value at the time of overmeter.

The integrated value output by the integrating circuit 16 is supplied to a display device 17, where the integrated value is displayed as a flow rate.

After generation of such a signal OMS, period integrating circuit 16 to the generation of the signal OME since not performed cumulative excess accumulation of the flow rate can be prevented, and also when the rotational speed N _i at the time point of generation of signals OME not zero Since the over-meter integrated value in the above period is obtained by the correction arithmetic circuit 15 and added to the integrated value of the pulse, the insufficient integration of the flow rate is corrected and prevented.

As a result, the flow rate measurement accuracy of the turbine type flow meter 1 is improved, and the turbine type flow meter 1 can be applied to a place where the flow rate fluctuation is large, and the applicable range is expanded.

By the way, after the signal OME is received, if the integrated value at the time of over meter is added at once by the integrating circuit 16, the flow rate display value of the display device 17 changes abruptly, so that the pulse from the amplifier 14 enters the integrating circuit 16. The above-mentioned integrated value at the time of over-meter may be divided into several times and added.

As shown in FIG. 4 (A) ~ (C), rapid increase of the flow rate, after the sudden decrease even flow rate rapidly decreases is repeated (time t ₂₎ to the turbine rotor 7 is stopped (time t _3), the flow rate is rapidly increased Even at (time t ₄ ), the integrated value of the pulse is corrected as described above.

However, as shown in FIG. 5 (A) ~ (C), rapid increase of the flow rate, if the rapid decrease is repeated in a short time, the turbine rotor 7 flow decreases rapidly (time t ₁₂₎ is still rotating by inertia During this period, the flow rate will increase rapidly (time t ₁₃ ). In this case, as shown in FIG. 5 (B), the flow rate sharply increases while the rotation of the turbine rotor 7 is decreasing. Therefore, the turbine rotor 7 continues to rotate even while the flow rate is zero. Will rise.

Therefore, the hatched portion in FIG. 3, that is, FIG. 5 (B)
Hatched portion V _X amount of is excessively accumulated than the actual flow rate.

However, in the present embodiment, the pressure of the fluid flowing through the flow path 2a is detected by the pressure sensor 21, and a change in this pressure appears in proportion to a change in the flow rate. That is, the pressure at the pressure when the flow rate increases rapidly from zero to Q _A at time t ₁₁ is the zero flow rate as in the FIG. 5 when measuring the pressure in the flow path 2a (C)
Changes from P ₀ to P _1, the flow rate at time t ₁₂ is changed from the pressures P ₁ when rapidly decreases from Q _A to zero to P _0.

Here, over-metering quantity to be measured from the rotational speed of the turbine rotor 7 from the time t ₁₂ in FIG. 5 (B) to t ₁₃ is V _Y + V _X.

This excess flow V _T from the time t ₁₂ to t ₁₃ is calculated from the following equation multiplying the V _Y + V _X by the correction value _{F (P 0 -P X / P} 0).

V _T = (V _Y + V _X ) × F (P ₀ −P _X / P ₀ ) (However, P _X : Measurement pressure) …… From the formula, when P _X = P ₀ , F (P ₀ −P _X / P ₀ ) = 0.

When P _X ≠ P _0, the _value of F (P ₀ −P _X / P ₀ ) is obtained by a function F determined for each flow meter.

Therefore, the correction operation circuit 15 uses the pressure P ₀
Is detected, the above equation is calculated and the turbine rotor 7
Excess flow (correction value) V _T due to excessive rotation (over meter)
= 0. And the integrated flow rate is integrated to from time t ₁₁ in the integrating circuit 16 to t ₁₂ by adding an excess flow V _T = 0 to the display device 17 the true flow rate measurements.

In addition to the above, as a means for correcting an excessive flow rate at the time of an overmeter by using a pressure detection signal from the pressure sensor 21, the following method may be used.

The correction operation circuit 15 outputs the OM signal from the overmeter start detection circuit 18
When S arrives, the pulse from the amplifier 14 is not integrated, and the calculation of the above expression is performed. In this case, the integrating circuit 16 supplies the integrated value of the pulse to the display device 17 when P _X = P ₀ , and adds the corrected flow rate calculated by the equation to the integrated value of the pulse when P _X ≠ P _0. A true flow value is obtained and supplied to the display device 17.

Thus, the pressure sensor 21 that detects the pressure in the flow path 2a
Even if the flow rate suddenly increases or decreases in a short period of time based on the pressure detection signal from the controller, accurate correction can be performed, and the flow rate measurement accuracy of the flow meter 1 can be improved.

The operation of the circuit shown in FIG. 1 may be performed by a microcomputer. FIG. 6 shows the flowchart.

In the figure, after step S1 (initial setting for omitting steps), the rotation speed _Ni is measured (S2), and the previous rotation speed _Ni-1
(S3), and the current rotational speed _Ni is used as the previous rotational speed.
Put in N _i-1 (S4).

Next, the difference D is compared with a constant value ΔN (S5). If the difference D is equal to or greater than the constant value ΔN, the timer OT is incremented (S6).
Set the overmeter flag OF (S7) and set the integration counter
The value of SC is displayed as a flow rate (S8), and the process returns to S2.

If the difference is less than the fixed value ΔN, the flag OF is determined (S9),
If the flag OF is not set, the number of revolutions _Ni × K is added to the integration counter SC (S10), and the value of the counter SC is displayed as a flow rate (S11).

If the flag OF is set in S9, it is determined whether or not the pressure in the flow passage 2a from the pressure detection signal from the pressure sensor 21 is a predetermined pressure P ₀ of the zero flow (S12), the pressure P If it is ₀ , the flow rate is zero, so the flow proceeds to S14.

However, if the pressure is equal to or higher than P _{0 in} S12, the rotation speed N _i
(The integrated value at the time of overmeter) of the timer OT and the flow rate K per one rotation of the rotor is added to the value of the counter SC (S1
3) The value of the counter SC is displayed as a flow rate (S14), and the timer OT and the flag OF are reset (S15). S11, S above
After the execution of 15, the process returns to S2.

When the operation of the first circuit is performed by a microcomputer, it may be performed by a processing method as shown in FIG.

In Figure 7, after the initial setting (S1), to check the pressure in the first flow path 2a without measuring the rotational speed N _i (S2 ').
Since the pressure in the S2 'is the zero flow when a predetermined pressure P ₀ and proceeds to S14 without accumulating the pulses from the amplifier 14. However, in the case of FIG. 6 described above when the pressure in the S2 'is at a predetermined pressure P ₀ the following P ₁ as well as after S2 (where, S12 is excluded) processing is executed.

Although the above embodiment has been described by taking a turbine type flow meter as an example, it goes without saying that the correction device of the present invention can also be applied to other types of flow meters.

Effect of the Invention As described above, the flowmeter correction device according to the present invention generates a correction value based on a pressure detection signal from a pressure detection unit that detects the pressure of a fluid to be measured. Even if the flow rate suddenly increases and decreases in a short time, the flow rate is accurately detected when the flow rate is zero, and the correction value is integrated assuming that there is a flow rate from the pulse cycle even though the flow rate is zero. Can be prevented. Therefore, even if the flow rate suddenly decreases to zero and the flow rate suddenly increases while the rotating body is in the over-meter state due to over-rotation, the pressure change is detected by the pressure detection means to accurately determine the presence or absence of the flow rate, and the flow rate is measured. It has features such as higher accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic structural view for explaining an embodiment of a flow meter correcting device according to the present invention, and FIGS. 2 and 3 show changes in the number of revolutions of a turbine rotor according to a flow rate change and a correction device. 4 and 5 are diagrams showing changes in flow rate, turbine rotor speed, and pressure, and FIG. 6 is an embodiment of a microcomputer for executing the operation of the apparatus of the present invention. FIG. 7 is a flowchart of a modification of the microcomputer. DESCRIPTION OF SYMBOLS 1 ... Turbine type flow meter, 2 ... Flow meter main body, 2a ... Flow path, 7 ... Turbine rotor, 10 ... Blade, 12 ... Pickup, 13 ... Correction device, 15 ... Correction arithmetic circuit, 16 ……
Integrating circuit, 17 display device, 18 overmeter start detection circuit, 19 overmeter end detection circuit, 20 overmeter elapsed time measurement circuit, 21 pressure sensor.

Claims (1)

(57) [Claims] An apparatus for correcting a flow meter for detecting a rotation of a rotating body that rotates according to a flow velocity of a fluid to be measured, generating a pulse, integrating the pulses, and measuring a flow rate of the fluid to be measured. Detecting means for calculating a rate of decrease in the flow rate from the cycle of the pulse, and detecting a first time point when the rate of decrease is equal to or more than a predetermined value and a second time point when the rate of decrease is less than a predetermined value; Pressure detection means for detecting the pressure of the fluid to be measured; and a correction value is generated based on a pressure detection signal from the pressure detection means by inputting a signal from the first time point to a second time point of the detection means. Correction value generation means, and integration means for adding the pulse excluding the period from the first time point to the second time point and the correction value from the correction value generation means. Flow meter correction device.