JP2007064881A - Ultrasonic flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter for enabling long time use by a battery and low in power consumption in the ultrasonic flowmeter for measuring a flow rate, using direct propagation time and reflection propagation time of ultrasonic waves. <P>SOLUTION: The ultrasonic flowmeter measures the direct propagation time and the reflection propagation time of the ultrasonic waves, propagating between an upstream side ultrasonic element 2 and a downstream side ultrasonic element in a time measuring means 5. A flow rate calculation means finds the flow rate by using the measured time. When a flow rate determining means 9 determines that the flow rate is a constant value or lower, a power source is continuously supplied to a receiving detection means 4. When the flow rate is a constant value or higher, a control means 7 controls so as to shut off power source supply to the receiving detection means 4, in the time zone that receives the reflection propagation time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic flowmeter.

JP 2004-239868 A

  2. Description of the Related Art Conventionally, an ultrasonic flowmeter using ultrasonic waves is known as a flow rate measuring device that measures a flow rate of city gas or water. For example, the following method is employed for measuring the flow rate. That is, a pair of ultrasonic elements is provided on the upper and lower sides in the flow direction of the flow path, and ultrasonic waves (from one ultrasonic element (transmitting-side ultrasonic element) to the other ultrasonic element (receiving-side ultrasonic element) ( Measure the direct propagation time that the direct wave reaches, measure the reflected propagation time until the direct wave reflects off the surface of the receiving ultrasonic element, and measure the flow rate using these propagation times. It is.

  A piezoelectric element is used as the ultrasonic element, and a drive voltage circuit is often used for transmitting ultrasonic waves. In addition, a voltage detection circuit for detecting the received ultrasonic waves is used, and the drive voltage circuit and the voltage detection circuit have a problem that power consumption is large. Since conventional ultrasonic flowmeters (for example, gas meters) are operated using batteries, there is a problem that if the power consumption is large, the batteries will not be used even if they are used for a long time (for example, about 10 years). Therefore, an ultrasonic flowmeter that has low power consumption and can be used for a long time with a battery has been demanded.

  The present invention has been made in the background as described above. In particular, the present invention is an ultrasonic flowmeter that performs flow measurement using the direct propagation time and reflected propagation time of ultrasonic waves, and has low power consumption and is based on a battery. It is an object to provide an ultrasonic flowmeter that can be used for a long time.

Means for Solving the Problems and Effects of the Invention

The present invention
A flow path for passing fluid;
A pair of ultrasonic elements provided with a composite of an ultrasonic transmission function and an ultrasonic reception function, disposed on the upper and lower sides in the flow direction of the flow path, from one ultrasonic element to the other ultrasonic wave Transmitting an ultrasonic wave toward the element, receiving the transmitted ultrasonic wave with the other ultrasonic element and outputting an electrical signal; and an upper ultrasonic element and a lower ultrasonic element,
Transmitting means for applying a driving voltage to the upper ultrasonic element or the lower ultrasonic element to transmit ultrasonic waves;
Receiving detection means for detecting that the upper ultrasonic element or the lower ultrasonic element has received the ultrasonic wave when the electrical signal from the ultrasonic element is input;
After the transmission means applies the drive voltage to the upper ultrasonic element, the transmitted ultrasonic wave propagates directly toward the lower ultrasonic element, and the lower ultrasonic element The forward direct propagation time until the reception detection means detects that a direct wave has been received, and the transmitted ultrasonic wave after the transmission means applies the drive voltage to the lower-side ultrasonic element. A reverse direct propagation time until the reception detecting means detects that the sound wave propagates directly toward the upper ultrasonic element and the direct wave is received by the upper ultrasonic element; After the transmission means applies the driving voltage to the side ultrasonic element, the transmitted ultrasonic wave propagates toward the lower ultrasonic element and is reflected on the surface of the lower ultrasonic element. Reflected wave, above The upper-side reflection propagation time until the reception detection means detects that the reflected wave is received by the side ultrasonic element, and the transmission means applies the drive voltage to the lower-side ultrasonic element. The transmitted ultrasonic wave propagates toward the upper ultrasonic element and is reflected on the surface of the upper ultrasonic element to become a reflected wave, and the reflected wave is received by the lower ultrasonic element. Time measuring means for measuring the lower-side reflection propagation time until the reception detecting means detects that,
A high-precision calculation that calculates the flow rate of the fluid with relatively high accuracy by using the forward direct propagation time, the reverse direct propagation time, the upper-side reflection propagation time, and the lower-side reflection propagation time; A flow rate calculation means capable of switching between simple calculation for simply calculating the flow rate of the fluid by using the forward direct propagation time and the reverse direct propagation time;
A flow rate determining means for determining whether or not the flow rate calculated by the flow rate calculating means is a predetermined value or more;
When it is determined by the flow rate determination means that the flow rate of the fluid is equal to or less than a predetermined value, by supplying power to the reception detection means in a time zone for detecting the direct wave and the reflected wave, When both the direct wave and the reflected wave are detected, and the flow rate determining means determines that the fluid flow rate is equal to or higher than a predetermined value, the time period for detecting the direct wave is reached. By supplying power to the reception detection means and cutting off the power supply to the reception detection means in a time zone during which the reflected wave is detected, the reflected wave is not detected and the reflected wave is not detected. Control means;
It is an ultrasonic flowmeter characterized by providing.

  According to the present invention, the flow rate determining means for determining whether the flow rate is equal to or higher than a predetermined value is provided. Then, when the flow rate is less than a predetermined value by the flow rate determination means, both the direct wave and the reflected wave are detected (both detection states), and when the flow rate is determined to be higher than the predetermined value, the direct wave is detected. Power is supplied to the reception detection means only for the time, and while the reflected wave is propagating, the power supply of the reception detection means is cut off (reflected wave non-detection state). Thereby, the power consumption of the reception detection means can be reduced.

  When the flow rate is equal to or lower than the predetermined value, both detection states are set, and when the flow rate is equal to or lower than the predetermined value, the reflected wave non-detection state is set as follows. That is, the flow rate can be obtained with relatively high accuracy in the case of both detection states (high accuracy calculation), and the flow rate can be easily obtained with slightly less accuracy in the case of no reflected wave detection state (simple calculation). . Normally, high measurement accuracy is required when the flow rate is low, and when the flow rate is high, even if the accuracy is somewhat deteriorated, it is often acceptable. Therefore, when the flow rate is small, both detection states are set and high-precision calculation is performed to measure the flow rate with relatively high accuracy. Also, when the flow rate is large, the reflected wave is not detected and simple calculation is performed to keep power consumption low. The detailed contents of the high-precision calculation and simple calculation will be described later.

Further, the present invention can be as follows.
When the reflected wave non-detection state continues for a predetermined time or more, the control means sets the both-state detection state for a certain period of time, and performs the high-precision calculation by the flow rate calculation means to control the flow rate of the fluid. Ultrasonic flowmeter that measures relatively accurately.
In other words, since the measurement accuracy is low while the reflected wave is not detected, if the reflected wave non-detected state continues for a predetermined time or longer, the reception detection means is used as both detection means and high-precision calculation is performed. Thus, the flow rate is confirmed. Thereby, the reliability and measurement accuracy with respect to the measured flow rate can be increased.

Furthermore, the present invention provides
The control unit causes the flow rate calculation unit to perform the high-accuracy calculation when the two-way detection state is set, and causes the flow rate calculation unit to perform the simple calculation when the reflected wave non-detection state is set. A sonic flow meter may be used. In other words, during the non-detected state of the reflected wave, the calculation time can be shortened by performing simple calculation, and the power consumption can be reduced. In addition, as described above, since the power source of the reception detection unit is periodically cut off during the reflected wave non-detection state, low power consumption is achieved. That is, low power consumption by shortening the calculation time and low power consumption by turning off the power of the reception detection means are achieved in a superimposed manner, and it is possible to further reduce the power consumption.

Moreover, you may employ | adopt the following structure.
A flow rate stability determination unit that determines whether or not the temporal variation rate of the flow rate calculated by the flow rate calculation unit falls within a predetermined numerical value;
When it is determined by the flow rate stability determining means that the temporal variation rate of the flow rate is within a predetermined numerical value, one of the upper ultrasonic element and the lower ultrasonic element is used. Only the ultrasonic wave is transmitted, and the other ultrasonic element receives the direct wave of the ultrasonic wave, and supplies power to the reception detection means only in the time zone corresponding to the reception of the direct wave. An ultrasonic flowmeter configured to be in a one-sided detection state in which power supply to the reception detection unit is cut off during a time period when reception is not performed.

  According to the above invention, when the flow rate stability determining means determines that the flow rate is stable for a certain time or more, one ultrasonic element is dedicated for transmission and the other ultrasonic element is dedicated for reception until flow rate fluctuation occurs. To do. Then, the direct propagation time from one side is measured, and the flow rate is obtained by estimating the direct propagation time on the opposite side. Thereby, the frequency | count of a drive and reception frequency of an ultrasonic element can be reduced, and power consumption can be made low. The flow rate calculation method in this case will be described in detail later.

The present invention also provides:
When the one-side detection state continues for a predetermined time or longer, the both-side detection state is set for a certain period of time, and the high-precision calculation is performed by the flow rate calculation means, thereby measuring the flow rate of the fluid with relatively high accuracy. An ultrasonic flow meter can be used. That is, while the one-side detection state is set, the accuracy of the flow rate measurement is somewhat deteriorated. Therefore, the both-side detection state is returned every certain time, and high-precision calculation is performed to check the flow rate. This makes it possible to increase the reliability and measurement accuracy for the measured flow rate.

Furthermore, the present invention may be as follows.
The value directly stored in the forward direct propagation time immediately before the one-side detection state is T1 ″, and the ultrasonic wave reaches the surface of the lower ultrasonic element from the surface of the upper ultrasonic element. And the value stored in advance is defined as t1 ′, and the time that the ultrasonic wave reaches the surface of the upper ultrasonic element from the surface of the lower ultrasonic element is stored in advance. t2 ′, the forward direct propagation time measured while the one-side detection state is set to TT1, and from the surface of the upper-side ultrasonic element to the surface of the lower-side ultrasonic element in the one-side detection state The time that the ultrasonic wave reaches is tt1, the time that the ultrasonic wave reaches the surface of the upper ultrasonic element from the surface of the lower ultrasonic element in the one-side detection state is tt2, and the flow velocity of the fluid is V. ,in front When the flow rate of the fluid is Q and the cross-sectional area of the flow path and the value stored in advance is S, the flow rate calculation in the one-side detection state is
ΔT = T1 ″ −TT1
tt1 = t1′−ΔT
tt2 = t2 ′ + ΔT
And V = (L / 2) × (1 / tt1-1 / tt2)
Q = S × V
An ultrasonic flowmeter that calculates the flow rate Q by calculating.

  By employing the above calculation method, the calculation time can be shortened and low power consumption can be achieved. Further, as described above, while the one-side detection state is set, the number of times the ultrasonic element is driven and the number of receptions can be reduced, and the power consumption can be reduced. That is, low power consumption by shortening the calculation time and low power consumption by reducing the number of times of driving the ultrasonic element are achieved in a superimposed manner, and it is possible to further reduce the power consumption.

On the other hand, the present invention
While the reception detection means is in the one-side detection state, an ultrasonic flowmeter that switches between the transmission-side ultrasonic element and the reception-side ultrasonic element every predetermined time can be used. As a result, it is possible to prevent fatigue and failure caused by transmitting ultrasonic waves from only one side of the ultrasonic element, thereby improving reliability and measuring accuracy.

Further, the present invention may be as follows.
The forward direct propagation time is T1, the reverse direct propagation time is T2, the upper-side reflection propagation time is τ1, the lower-side reflection propagation time is τ2, and the transmission means applies the drive voltage. TT1 is a transmission delay time from when the upper ultrasonic element is transmitted until the ultrasonic wave is transmitted until the ultrasonic wave is transmitted from the lower ultrasonic element after the transmission means applies the drive voltage. The transmission delay time is tT2, the reception delay time from when the upper ultrasonic element receives the ultrasonic wave until the reception detecting means detects the reception is tR1, and the lower ultrasonic element is the ultrasonic wave TR2 is a reception delay time from when the reception detecting unit detects the reception until t1 is a time required for the ultrasonic wave to reach the surface of the lower ultrasonic element from the surface of the upper ultrasonic element. A time from which the ultrasonic wave reaches the surface of the upper ultrasonic element from the surface of the lower ultrasonic element to t2, and a distance from the surface of the upper ultrasonic element to the surface of the lower ultrasonic element The value stored in advance is L, the flow velocity of the fluid is V, the flow rate of the fluid is Q, the cross-sectional area of the flow path and the value stored in advance is S, and the fluid When the value stored in advance, which is a value obtained by subtracting the backward direct propagation time T2 from the forward direct propagation time T1 and Δδ0 in a state where the current does not flow, is Δδ0,
t1 = (τ1 + τ2-2 × T2-Δδ0) / 2
t2 = (τ1 + τ2-2 × T2 + Δδ0) / 2
To obtain the above-mentioned t1 and t2, and further V = (L / 2) × (1 / t1-1 / t2)
Q = S × V
The ultrasonic flowmeter is supposed to obtain the flow rate Q by calculating

On the other hand, the present invention can employ the following configurations.
The forward direct propagation time in the reflected wave non-detection state is T1 ′, the reverse direct propagation time in the reflected wave non-detection state is T2 ′, and is a value obtained by subtracting t1 from T1 and stored in advance. When the obtained value is J1, the value obtained by subtracting t2 from T2 and the value stored in advance is G1, the simple calculation is
V = (L / 2) × {1 / (T1′−J1) −1 / (T2′−G1)}
Q = S × V
The ultrasonic flowmeter is supposed to obtain the flow rate Q by calculating

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of an ultrasonic flowmeter according to the present invention. As described above, the ultrasonic flowmeter 1 includes a flow path through which a fluid flows, an upper ultrasonic element 2 disposed on the upper side of the flow path, a lower ultrasonic element 3 disposed on the lower side, and a drive voltage circuit. Transmission means 6 comprised of, etc., reception detection means 4 comprised of voltage detection circuits, etc., time measurement means 5, flow rate calculation means 8, control means 7, flow rate judgment means 9, flow rate stability judgment means 10, transmission side switch 11 and the reception side switch 12 are included. Among these, the flow rate calculation means 8, the control means 7, the flow rate determination means 9, and the flow rate stability determination means 10 are configured using a microcomputer or the like as will be described later.

  The upper-side ultrasonic element 2 and the lower-side ultrasonic element 3 are composed of piezoelectric elements or the like, and are provided with a composite of an ultrasonic transmission function and an ultrasonic reception function. The transmission side switch 11 and the reception side switch 12 are controlled by the control means 7 and used to switch between the transmission side ultrasonic element and the reception side ultrasonic element. The transmission means 6 applies a drive voltage to the ultrasonic element on the transmission side under the control of the control means. Then, the transmission means 6 notifies the time measurement means 5 of the timing at which the drive voltage is applied. On the other hand, when the ultrasonic elements 2 and 3 receive an ultrasonic wave, the ultrasonic element outputs an electric signal, and the electric signal is input to the reception detection means 4 through the reception side switch 12. The reception detection means 4 detects this electric signal, thereby detecting that the ultrasonic wave has reached the ultrasonic element on the reception side, and notifies the time measurement means 5 of the timing. The time measurement unit 5 measures the ultrasonic propagation time based on the application timing of the drive voltage sent from the transmission unit 6 and the timing of the reception signal sent from the reception detection unit 4.

  More specifically, the time measuring means 5 measures four types of time shown in the timing chart of FIG. That is, from the timing (1) when the transmission means 6 applies the driving voltage to the upper ultrasonic element 2, the transmitted ultrasonic wave reaches the lower ultrasonic element 3 as a direct wave, and the reception detection means 4 From the forward direct propagation time until the detection (2) and the timing (1), the transmitted ultrasonic wave is reflected on the surface of the lower ultrasonic element 3 to become a reflected wave, and the reflected wave becomes the upper ultrasonic wave. Transmission from the upper side reflection propagation time until reaching the element 2 and (3) when the reception detection means 4 detects it, and the timing (4) when the transmission means 6 applied the drive voltage to the lower side ultrasonic element 3 The transmitted ultrasonic wave reaches the upper ultrasonic element 2 as a direct wave and is transmitted from the reverse direct propagation time until the reception detection means 4 detects (5) and the timing (4). On the surface of the upper ultrasonic element 2 It reflected and becomes a reflected wave, the reflected wave reaches the downstream side ultrasonic element 3, a downstream side reflection propagation time until it receives the detection means 4 detects (6).

  Returning to FIG. The flow rate calculation means 8 is a high-precision calculation capable of calculating the flow velocity V with relatively high accuracy using the forward direct propagation time, reverse direct propagation time, upper-side reflection propagation time, and lower-side reflection propagation time (for details, see Two types of operations can be switched and executed using the forward direct propagation time and the backward direct propagation time, and a simple operation that can be performed at high speed, although the accuracy is somewhat worse. . This calculation is switched by the control means 7.

  The flow rate obtained by the flow rate calculation unit 8 is sent to the flow rate determination unit 9 and the flow rate stability determination unit 10. The flow rate determining means 9 determines whether or not the flow rate is equal to or greater than a predetermined value. When the flow rate determining means 9 determines that the flow rate is below a predetermined value, the control means 7 continuously supplies power to the reception detecting means 4 as shown in FIG. A state where both can be detected (both detection state) is set. In other words, high-accuracy flow measurement is performed by making the forward direct propagation time, backward direct propagation time, upper-side reflection propagation time, and lower-side reflection propagation time all measurable and performing the above-described high-precision calculation. . On the other hand, when the flow rate determination unit 9 determines that the flow rate is equal to or higher than the predetermined value, the control unit 7 cuts off the power supply to the reception detection unit 4 during the time period for detecting the reflected wave. A state in which the reflected wave is not detected (reflected wave non-detected state) is set.

  FIG. 3 shows a specific timing chart in the reflected wave non-detection state. First, an ultrasonic wave is transmitted from the upper ultrasonic element 2 in (7), and the ultrasonic wave (direct wave) is received by the lower ultrasonic element 3 in (8). The control means 7 starts to supply power to the reception detection means 4 shortly before the direct wave arrives, and turns off the power of the reception detection means 4 immediately after detecting the direct wave of (8). During the time period until the reflected wave reaches the upper ultrasonic element 2, the power supply to the reception detection means 4 is not performed. After the reflected wave arrives, an ultrasonic wave is emitted from the lower ultrasonic element 3 at (9), and the ultrasonic wave (direct wave) is received by the upper ultrasonic element 2 at (10). The control means 7 starts to supply power to the reception detection means 4 shortly before the direct wave arrives, and turns off the power of the reception detection means 4 immediately after detecting the direct wave of (10). In the time period until the reflected wave reaches the lower ultrasonic element 3, power supply to the reception detection means 4 is not performed. Thereafter, this measurement is repeated when the flow rate is equal to or greater than the predetermined value. If it is determined by the flow rate determination means 9 that the flow rate has changed to a predetermined value or less, the two-way detection state is restored.

  Thus, in the reflected wave non-detection state, since the power supply of the reception detection part 4 is cut | disconnected periodically, power consumption can be made low. In addition, when the flow rate is large, the allowable amount of measurement error increases (even if the measurement accuracy is somewhat deteriorated), the flow rate can be calculated by simple calculation. As a result, the operating time of the CPU is reduced and the power consumption can be further reduced. On the other hand, when the flow rate is small, high accuracy is required for the flow rate measurement. Therefore, the flow rate is measured with relatively high accuracy by performing the high-accuracy calculation in the detection state.

  When the reflected wave non-detection state continues for a predetermined time or more, the flow rate may be confirmed and measured by periodically returning to the both detection state. For example, as shown in FIG. 4, when the reflected wave non-detection state continues for a predetermined time, both detection states are set between (13) and (14). During this time, the power supply to the reception detection means 4 is controlled so that both the direct wave and the reflected wave received by the ultrasonic elements 2 and 3 can be detected. And the reliability of flow measurement is improved by calculating the flow rate with high precision calculation. When the flow rate determining means 9 determines that the flow rate is equal to or higher than the predetermined value, the reflected wave is not detected again from (14) as shown in FIG. Moreover, when it determines with a flow volume being below a predetermined value, it does not return to a reflected wave detection state, but both detection states are continued.

  On the other hand, when the flow rate stability determining means 10 determines that the temporal fluctuation rate of the flow rate is within the predetermined range (the flow rate is stable), as shown in FIG. It is possible to dedicate transmission, and the other ultrasonic element can be dedicated to reception. More specifically, an ultrasonic wave is transmitted only from one ultrasonic element, a direct wave is received by the other ultrasonic element, and power is supplied to the reception detection means 4 only in a time zone corresponding to the direct wave. The control means 7 is controlled so as to cut off the power supply to the reception detection means during a time period when no ultrasonic waves are received (one-side detection state). Thereby, the frequency | count of transmission of an ultrasonic wave and the frequency | count of reception can be reduced, and a reduction in power consumption can further be advanced. The flow rate calculation method in the one-side detection state will be described in detail later. If the flow rate stability determination unit 10 determines that the flow rate is not stable while the one-side detection state is set, the two-side detection state is restored.

  Moreover, it can also be as shown in FIG. That is, until (16), ultrasonic waves are transmitted only from the upper ultrasonic element 3 (one-side detection state), and when a certain period of time has passed, ultrasonic waves are also transmitted from the lower ultrasonic element 3 in (16). Transmitting, detecting direct waves and reflected waves, and performing high-precision calculation once. Thereby, the reliability of flow measurement can be improved. In response to this measurement result, when the flow rate stability determination means 10 determines that the flow rate is stable, the one-side detection state continues. And after predetermined time passes, the same measurement as the above is performed again in (17).

  Moreover, you may make it like FIG. That is, when the one-side detection state is continued, the upper ultrasonic element 2 is exclusively used for transmission and the lower ultrasonic element 3 is exclusively used for reception until (19). The sonic element 3 is dedicated to transmission, and the upper ultrasonic element 2 is switched to reception only. Thereby, fatigue of the ultrasonic element due to the transmission state lasting for a long time can be prevented, leading to a reduction in failure rate. When the flow rate stability determining means 10 determines that the flow rate is not stable, it returns to the both detection state.

Next, a method for calculating the flow rate will be described with reference to FIG. First, the definitions of the symbols shown in FIG. 8 are shown below.
T1 Forward direct propagation time T2 Reverse direct propagation time τ1 Upper-side reflection propagation time τ2 Lower-side reflection propagation time tT1 From the time when the transmission means 6 applies the drive voltage to the time when ultrasonic waves are transmitted from the upper-side ultrasonic element 2 Transmission delay time tT2 Transmission delay time tR1 from when the transmission means 6 applies the drive voltage to when the ultrasonic wave is transmitted from the lower ultrasonic element 3 Reception after the upper ultrasonic element 2 receives the ultrasonic wave Reception delay time tR2 until the detection means 4 detects the reception Reception delay time t1 until the reception detection means 4 detects the reception after the lower ultrasonic element 3 receives the ultrasonic wave The upper ultrasonic element Time t2 at which the ultrasonic wave reaches the surface of the lower ultrasonic element 3 from the surface 2 The time L at which the ultrasonic wave reaches the surface of the upper ultrasonic element 2 from the surface of the lower ultrasonic element 3 L Upper ultrasonic element Table of 2 Distance V to surface of lower ultrasonic element 3 Fluid flow velocity Q Fluid flow rate S Cross-sectional area of flow path Δδ0 = T1-T2 = (tT1-tT2) − (tR1-tR2) (flow rate = 0) value)
Of these values, L, S, and Δδ0 are stored in advance in a ROM or the like.

First, high-precision calculation will be described. From FIG. 8 and the above definition,
T1 = tT1 + t1 + tR2 (Formula 1)
T2 = tT2 + t2 + tR1 (Formula 2)
τ1 = tT1 + t1 + t2 + tR1 (Formula 3)
τ2 = tT2 + t1 + t2 + tR2 (Formula 4)
It can be expressed. From these equations,
From (Expression 3) + (Expression 4) -2 × (Expression 2) t1 = (τ1 + τ2-2 × T2-Δδ0) / 2
t2 = (τ1 + τ2-2 × T2 + Δδ0) / 2
T1 and t2 can be obtained by calculating. The flow velocity V is V = (L / 2) × (1 / t1-1 / t2)
From the cross-sectional area S, the flow rate Q can be obtained from Q = S × V
Can be obtained as

Next, simple calculation will be described. First, the symbols are defined below.
T1 ′ Forward direct propagation time T2 ′ in reflected wave non-detected state Reverse direct propagation time J1 T1-t1 in reflected wave non-detected state
G1 T2-t2
J1 and G1 are stored in advance as delay terms. Using these values,
V = (L / 2) × {1 / (T1′−J1) −1 / (T2′−G1)}
Q = S × V
Is calculated, the flow velocity V and the flow rate Q can be obtained.

Next, a flow rate calculation method in the one-side detection state will be described. First, symbols are defined as follows.
T1 ″ Forward direct propagation time T2 ″ immediately before the one-side detection state T1 ′ Reverse direct propagation time t1 ′ immediately before the one-side detection state Ultrasonic waves from the surface of the upper ultrasonic element 2 to the surface of the lower ultrasonic element 3 Time t2 ′ when the ultrasonic wave reaches the surface of the upper ultrasonic element 2 from the surface of the lower ultrasonic element 3 TT1 Forward direct propagation time tt1 measured while the one-side detection state is set Time tt2 when ultrasonic waves reach the surface of the lower ultrasonic element 3 from the surface of the upper ultrasonic element 2 in the detection state From the surface of the lower ultrasonic element 3 to the surface of the upper ultrasonic element 2 in the one-side detection state Time of arrival of ultrasonic wave Among these values, T1 ″, T2 ″, t1 ′, t2 ′ are stored in advance.
ΔT = T1 ″ −TT1
tt1 = t1′−ΔT (Formula 5)
tt2 = t2 ′ + ΔT (Formula 6)
Using the above (formula 5) and (formula 6), V = (L / 2) × (1 / tt1-1 / tt2)
Q = S × V
The flow velocity V and the flow rate Q can be obtained as follows.

  The control means 7, the flow rate calculation means 8, the flow rate determination means 9, and the flow rate stability determination means 10 shown in FIG. 1 are specifically configured using a microcomputer 13 as shown in FIG. The microcomputer 13 includes a CPU, ROM, RAM, and I / O. Inside the ROM, as shown in FIG. 10, a control program P7, a flow rate calculation program P8, a flow rate determination program P9, and a flow rate stability determination program P10 are stored. It is remembered. When the CPU reads and executes these programs, the functions of the control means 7, the flow rate calculation means 8, the flow rate determination means 9, and the flow rate stability determination means 10 are realized.

1 is a schematic block diagram of an ultrasonic flow meter according to the present invention. The timing chart in a both-sides detection state. The timing chart in a reflected wave non-detection state. The timing chart which returns to a both detection state temporarily after continuing a reflected wave non-detection state for a fixed time. The timing chart in the one-side detection state. The timing chart which returns to a both-sides detection state temporarily after continuing the one-sided detection state for a fixed time. The timing chart which switches the ultrasonic element of a transmission side and the ultrasonic element of a reception side after continuing a one-sided detection state for a fixed time. The figure for demonstrating the flow volume calculating method. An embodiment in which FIG. A schematic representation of the ROM storage area.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ultrasonic flow meter 2 Upper side ultrasonic element 3 Lower side ultrasonic element 4 Reception detection means 5 Time measurement means 6 Transmission means 7 Control means 8 Flow rate calculation means 9 Flow rate determination means 10 Flow rate stability determination means 11 Transmission side switch 12 Reception Side switch V Flow velocity

Claims (9)

A flow path for passing fluid;
A pair of ultrasonic elements that are provided with a combination of an ultrasonic transmission function and an ultrasonic reception function and are arranged on the upper and lower sides in the flow direction of the flow path, from one ultrasonic element to the other ultrasonic wave Transmitting an ultrasonic wave toward the element, receiving the transmitted ultrasonic wave with the other ultrasonic element and outputting an electrical signal; and an upper ultrasonic element and a lower ultrasonic element,
Transmitting means for applying a driving voltage to the upper ultrasonic element or the lower ultrasonic element to transmit ultrasonic waves;
Receiving detection means for detecting that the upper ultrasonic element or the lower ultrasonic element has received the ultrasonic wave when the electrical signal from the ultrasonic element is input;
After the transmission means applies the drive voltage to the upper ultrasonic element, the transmitted ultrasonic wave propagates directly toward the lower ultrasonic element, and the lower ultrasonic element The forward direct propagation time until the reception detection means detects that a direct wave has been received, and the transmitted ultrasonic wave after the transmission means applies the drive voltage to the lower-side ultrasonic element. A reverse direct propagation time until the reception detecting means detects that the sound wave propagates directly toward the upper ultrasonic element and the direct wave is received by the upper ultrasonic element; After the transmission means applies the driving voltage to the side ultrasonic element, the transmitted ultrasonic wave propagates toward the lower ultrasonic element and is reflected on the surface of the lower ultrasonic element. Reflected wave, above The upper-side reflection propagation time until the reception detection means detects that the reflected wave is received by the side ultrasonic element, and the transmission means applies the drive voltage to the lower-side ultrasonic element. The transmitted ultrasonic wave propagates toward the upper ultrasonic element and is reflected on the surface of the upper ultrasonic element to become a reflected wave, and the reflected wave is received by the lower ultrasonic element. Time measuring means for measuring the lower-side reflection propagation time until the reception detecting means detects that,
A high-precision calculation that calculates the flow rate of the fluid with relatively high accuracy by using the forward direct propagation time, the reverse direct propagation time, the upper-side reflection propagation time, and the lower-side reflection propagation time; A flow rate calculation means capable of switching between simple calculation for simply calculating the flow rate of the fluid by using the forward direct propagation time and the reverse direct propagation time;
A flow rate determining means for determining whether or not the flow rate calculated by the flow rate calculating means is a predetermined value or more;
When it is determined by the flow rate determination means that the flow rate of the fluid is equal to or less than a predetermined value, by supplying power to the reception detection means in a time zone for detecting the direct wave and the reflected wave, When both the direct wave and the reflected wave are detected, and the flow rate determining means determines that the fluid flow rate is equal to or higher than a predetermined value, the time period for detecting the direct wave is reached. By supplying power to the reception detection means and cutting off the power supply to the reception detection means in a time zone during which the reflected wave is detected, the reflected wave is not detected and the reflected wave is not detected. Control means;
An ultrasonic flowmeter comprising:   When the reflected wave non-detection state continues for a predetermined time or more, the control means sets the both-state detection state for a certain period of time, and performs the high-precision calculation by the flow rate calculation means to control the flow rate of the fluid. The ultrasonic flowmeter according to claim 1, which measures with relatively high accuracy.   The control unit causes the flow rate calculation unit to perform the high-accuracy calculation when the two-way detection state is set, and causes the flow rate calculation unit to perform the simple calculation when the reflected wave non-detection state is set. Item 3. The ultrasonic flowmeter according to Item 1 or 2. A flow rate stability determination unit that determines whether or not the temporal variation rate of the flow rate calculated by the flow rate calculation unit falls within a predetermined numerical value;
When it is determined by the flow rate stability determining means that the temporal variation rate of the flow rate is within a predetermined numerical value, one of the upper ultrasonic element and the lower ultrasonic element is used. Only the ultrasonic wave is transmitted, and the other ultrasonic element receives the direct wave of the ultrasonic wave, and supplies power to the reception detection means only in the time zone corresponding to the reception of the direct wave. The ultrasonic flowmeter according to any one of claims 1 to 3, wherein the ultrasonic flowmeter is in a one-sided detection state in which power supply to the reception detection unit is cut off during a time period in which reception is not performed.   When the one-side detection state continues for a predetermined time or longer, the both-side detection state is set for a certain period of time, and the high-precision calculation is performed by the flow rate calculation means, thereby measuring the flow rate of the fluid with relatively high accuracy. The ultrasonic flowmeter according to claim 4. The value directly stored in the forward direct propagation time immediately before the one-side detection state is T1 ″, and the ultrasonic wave reaches the surface of the lower ultrasonic element from the surface of the upper ultrasonic element. And the value stored in advance is defined as t1 ′, and the time that the ultrasonic wave reaches the surface of the upper ultrasonic element from the surface of the lower ultrasonic element is stored in advance. t2 ′, the forward direct propagation time measured while the one-side detection state is set to TT1, and from the surface of the upper-side ultrasonic element to the surface of the lower-side ultrasonic element in the one-side detection state The time that the ultrasonic wave reaches is tt1, the time that the ultrasonic wave reaches the surface of the upper ultrasonic element from the surface of the lower ultrasonic element in the one-side detection state is tt2, and the flow velocity of the fluid is V. ,in front When the flow rate of the fluid is Q and the cross-sectional area of the flow path and the value stored in advance is S, the flow rate calculation in the one-side detection state is
ΔT = T1 ″ −TT1
tt1 = t1′−ΔT
tt2 = t2 ′ + ΔT
And V = (L / 2) × (1 / tt1-1 / tt2)
Q = S × V
The ultrasonic flowmeter according to claim 4 or 5, wherein the flow rate Q is obtained by calculating.   7. The ultrasonic wave according to claim 4, wherein the ultrasonic wave element on the transmission side and the ultrasonic wave element on the reception side are switched every predetermined time while the reception detection unit is in the one-side detection state. Flowmeter. The forward direct propagation time is T1, the reverse direct propagation time is T2, the upper-side reflection propagation time is τ1, the lower-side reflection propagation time is τ2, and the transmission means applies the drive voltage. TT1 is a transmission delay time from when the upper ultrasonic element is transmitted until the ultrasonic wave is transmitted until the ultrasonic wave is transmitted from the lower ultrasonic element after the transmission means applies the drive voltage. The transmission delay time is tT2, the reception delay time from when the upper ultrasonic element receives the ultrasonic wave until the reception detecting means detects the reception is tR1, and the lower ultrasonic element is the ultrasonic wave TR2 is a reception delay time from when the reception detecting unit detects the reception until t1 is a time required for the ultrasonic wave to reach the surface of the lower ultrasonic element from the surface of the upper ultrasonic element. A time from which the ultrasonic wave reaches the surface of the upper ultrasonic element from the surface of the lower ultrasonic element to t2, and a distance from the surface of the upper ultrasonic element to the surface of the lower ultrasonic element The value stored in advance is L, the flow velocity of the fluid is V, the flow rate of the fluid is Q, the cross-sectional area of the flow path and the value stored in advance is S, and the fluid When the value stored in advance, which is a value obtained by subtracting the backward direct propagation time T2 from the forward direct propagation time T1 and Δδ0 in a state where the current does not flow, is Δδ0,
t1 = (τ1 + τ2-2 × T2-Δδ0) / 2
t2 = (τ1 + τ2-2 × T2 + Δδ0) / 2
To obtain the above-mentioned t1 and t2, and further V = (L / 2) × (1 / t1-1 / t2)
Q = S × V
The ultrasonic flowmeter according to any one of claims 1 to 7, wherein the flow rate Q is obtained by calculating. The forward direct propagation time in the reflected wave non-detection state is T1 ′, the reverse direct propagation time in the reflected wave non-detection state is T2 ′, and is a value obtained by subtracting t1 from T1 and stored in advance. When the obtained value is J1, the value obtained by subtracting t2 from T2 and the value stored in advance is G1, the simple calculation is
V = (L / 2) × {1 / (T1′−J1) −1 / (T2′−G1)}
Q = S × V
The ultrasonic flowmeter according to any one of claims 1 to 8, wherein the flow rate Q is obtained by calculating.

Images