Ultrasonic measurement unit and gas meter

Abstract

To reduce the dispersion of measurement without changing the flow passage itself of a fluid to be measured.SOLUTION: The ultrasonic flow meter includes a flow path 2 through which a fluid to be measured flows, a pair of ultrasonic transceivers 10A and 10B disposed upstream and downstream of the flow path, respectively, and a seat 21 provided outside the flow path. The seat has a pair of hollow cylindrical connecting parts 21A and 21B, and each of the pair of hollow cylindrical connecting parts holds each of the pair of ultrasonic transceivers on one end T1, and the other end T2 is connected to the flow passage.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an ultrasonic measurement unit and a gas meter. [Background technology]

[0002] A gas meter using an ultrasonic measuring unit measures the flow rate of gas by utilizing the fact that the propagation time of ultrasonic waves changes depending on the flow rate of gas. An example of this type of gas meter is described in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2023-153539 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide an ultrasonic measurement unit that can reduce measurement variations without making any changes to the flow path itself of the fluid to be measured, and a gas meter equipped with this ultrasonic measurement unit. [Means for solving the problem]

[0005] In order to achieve the above-mentioned object, the ultrasonic measurement unit according to the present invention has the following features. a flow path through which a fluid to be measured flows; a pair of ultrasonic transmitters and receivers arranged upstream and downstream of the flow path, respectively, for transmitting and receiving ultrasonic waves into the flow path; a base provided outside the flow path and holding the pair of ultrasonic transmitter-receivers, The seat has a pair of hollow cylindrical connecting portions, Each of the pair of hollow cylindrical connecting parts holds the pair of ultrasonic transmitter-receivers at one end, and is connected to the flow path at the other end. Ultrasonic measurement unit. [Effects of the Invention]

[0006] According to the present invention, it is possible to reduce the variation in measurement without making any changes to the flow path itself of the fluid to be measured.

[0007] The present invention has been briefly described above. The details of the present invention will become clearer by reading the following detailed description of the invention (hereinafter referred to as "embodiments") with reference to the accompanying drawings. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is an external view of a measurement unit of a gas meter according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the measurement unit. [Figure 3] FIG. 3 is an external view of the base of the measurement unit. [Figure 4] FIG. 4 is a cross-sectional view of the seat. [Figure 5] FIG. 5 is a block diagram showing the functions of a gas meter. [Figure 6] FIG. 6 is a graph showing the results of a flow rate measurement test using the gas meter of this embodiment, a graph showing the results of a flow rate measurement test using a conventional gas meter as a comparative example, and a graph comparing the measurement variation between this embodiment and the comparative example (conventional example). [Figure 7] FIG. 7 is a schematic diagram for explaining an example of the measurement principle of an ultrasonic gas meter. DETAILED DESCRIPTION OF THE INVENTION

[0009] First, with reference to FIG. 7, the problem that the inventors have investigated will be described in detail. FIG. 7 is a schematic diagram for explaining an example of the measurement principle of an ultrasonic gas meter. 7, the ultrasonic measurement unit 8 included in this gas meter has a flow path 2 inside a pipe 1 through which the fluid to be measured flows linearly in a fixed direction (the direction of arrow A), and also has a pair of ultrasonic transmitters and receivers 10A, 10B on the upstream and downstream sides outside the flow path 2. These ultrasonic transmitters and receivers 10A, 10B are held by bases 41A, 41B, and transmit ultrasonic waves so as to diagonally cross the flow direction of the fluid to be measured flowing inside the flow path 2.

[0010] The pair of ultrasonic transmitter-receivers 10A, 10B are arranged in a positional relationship such that an ultrasonic wave transmitted from one ultrasonic transmitter-receiver 10A (10B) is reflected by the inner wall 1A of the flow path 2 and received by the other ultrasonic transmitter-receiver 10B (10A). The two ultrasonic transmitter-receivers 10A, 10B alternately transmit and receive ultrasonic waves in the same direction (forward direction) as the flow of the fluid to be measured (see arrow C1) and ultrasonic waves in the opposite direction to the flow of the fluid to be measured (see arrow C1). Then, calculation means (not shown) converts the flow rate from the difference in propagation time of the ultrasonic waves in the two directions.

[0011] When the fluid to be measured is not flowing in the flow path 2, the ultrasonic waves simply propagate between the two ultrasonic transmitters and receivers 10A and 10B, and there is no difference in the propagation time of the ultrasonic waves in the two directions. However, when the fluid to be measured is flowing in the same direction as the ultrasonic waves (forward direction), the speed of the ultrasonic waves emitted from the upstream ultrasonic transmitter and receiver 10A increases, and the time it takes to reach the receiving (downstream) ultrasonic transmitter and receiver 10B becomes shorter.

[0012] On the other hand, when the flow of the fluid to be measured and the ultrasonic waves are in the opposite direction, the speed of the ultrasonic waves emitted from the downstream ultrasonic transmitter / receiver 10B is reduced, and the time it takes for the ultrasonic waves to reach the receiving (upstream) ultrasonic transmitter / receiver 10A is lengthened. The time it takes for the ultrasonic waves to reach each ultrasonic transmitter / receiver 10A, 10B varies depending on the flow direction and speed of the fluid to be measured. Therefore, the calculation means calculates the flow velocity of the fluid to be measured from this change and converts the flow velocity into the flow rate.

[0013] When attempting to measure the flow rate of hydrogen gas using the above-mentioned gas meter, it is difficult to ensure the difference in propagation time between the ultrasonic waves traveling in the forward and reverse directions of the gas flow because the propagation speed of ultrasonic waves in hydrogen gas is significantly faster than that in air (approximately three times that of air). This makes it easy for measurement variability to occur, especially in areas with low flow rates. While enlarging the flow path is one way to increase the propagation time, doing so can have an adverse effect on the gas flow, resulting in significant diffuse reflection from the reflective surface, making it difficult to obtain a stable propagation time difference and resulting in little improvement in the variability of measurement results. Furthermore, enlarging the flow path increases the ultrasonic propagation distance, amplifying the ultrasonic output, which can lead to increased noise, leading to erroneous measurements, and can also accelerate battery consumption and increase costs.

[0014] As a result of the above investigation, the inventors have come up with the embodiment.

[0015] Specific embodiments of the present invention will be described below with reference to the accompanying drawings. Fig. 1 is an external view of a measurement unit of a gas meter according to an embodiment of the present invention, Fig. 2 is a cross-sectional view of the measurement unit, Fig. 3 is an external view of a base of the measurement unit, and Fig. 4 is a cross-sectional view of the base. Fig. 5 is a block diagram showing the functions of the gas meter.

[0016] The gas meter 100 includes the ultrasonic measurement unit 7 shown in FIGS. 1 and 2, and a control unit 30 (see FIG. 5) connected to the ultrasonic measurement unit 7.

[0017] The ultrasonic measurement unit 7 includes a flow path 2 through which a fluid to be measured flows, a pair of ultrasonic transmitters and receivers 10A and 10B disposed on the upstream and downstream sides of the flow path 2, respectively, for transmitting and receiving ultrasonic waves into the flow path 2, and a base 21 disposed outside the flow path 2 and for holding the pair of ultrasonic transmitters and receivers 10A and 10B. The flow path 2 is disposed inside a tubular body 1. The fluid to be measured flows linearly through the flow path 2 in the direction of arrow A. The pair of ultrasonic transmitters and receivers 10A and 10B propagate ultrasonic waves so as to diagonally cross the flow direction of the fluid to be measured flowing through the flow path 2. The pair of ultrasonic transmitters and receivers 10A and 10B receive ultrasonic waves traveling from upstream to downstream and from downstream to upstream. Specifically, the ultrasonic transmitter and receiver 10B receives ultrasonic waves in the forward direction indicated by arrow C1 in FIG. 2, and the ultrasonic transmitter and receiver 10A receives ultrasonic waves in the reverse direction indicated by arrow C2 in FIG. 2.

[0018] 1 and 2, the seat 21 is fixed to the outer side of the tubular body 1. As shown in Fig. 1 to Fig. 4, the seat 21 has a pair of hollow cylindrical connectors 21A and 21B. Each of the pair of hollow cylindrical connectors 21A and 21B holds a pair of ultrasonic transmitter / receivers 10A and 10B at one end T1, and has the other end T2 connected to the flow path 2 (see Fig. 2).

[0019] 2, the pair of ultrasonic transmitter-receivers 10A, 10B are arranged in a positional relationship such that an ultrasonic wave transmitted from one ultrasonic transmitter-receiver 10A (10B) is reflected by the inner wall 1A of the flow path 2 and received by the other ultrasonic transmitter-receiver 10B (10A). That is, the pair of ultrasonic transmitter-receivers 10A, 10B are arranged on the same side of the flow path 2.

[0020] Furthermore, the inner peripheral walls 22 of the hollow cylindrical connecting parts 21A, 21B are formed in a tapered shape (conical surface shape) such that the opening 22T2 on the other end T2 side connected to the flow path 2 is larger than the opening 22T1 on the one end T1 side. The hollow cylindrical connecting parts 21A, 21B have the opening 22T1 on the one end T1 side which has a shape corresponding to the shape of the vibration part 11 of the ultrasonic transmitter / receiver 10A, 10B, and the ultrasonic transmitter / receiver 10A, 10B is embedded in the opening 22T1 on the one end T1 side, thereby holding the ultrasonic transmitter / receiver 10A, 10B. Note that the inner peripheral walls 22 of the hollow cylindrical connecting parts 21A, 21B do not necessarily have to be formed in a tapered shape, and the openings 22T1 and 22T2 may be formed in a cylindrical surface shape having the same size.

[0021] The functions of the control unit 30 will be described. The control unit 30 has a propagation time calculation unit 31, a flow velocity calculation unit 32, and a flow rate calculation unit 33. The propagation time calculation unit 31 calculates the propagation time of ultrasonic waves between the pair of ultrasonic transmitters and receivers 10A and 10B based on detection data from the pair of ultrasonic transmitters and receivers 10A and 10B included in the ultrasonic measurement unit 7. The flow velocity calculation unit 32 calculates the difference between the propagation time of ultrasonic waves when one ultrasonic transmitter and receiver 10A transmits ultrasonic waves and the other ultrasonic transmitter and receiver 10B receives them, based on the data calculated by the propagation time calculation unit. The flow velocity calculation unit 32 calculates the flow velocity of the fluid to be measured based on this difference. The flow rate calculation unit 33 calculates the flow rate of the fluid to be measured based on the flow velocity calculated by the flow velocity calculation unit 32.

[0022] In the above configuration, the ultrasonic transmitters and receivers 10A and 10B are held at one end T1 of the hollow cylindrical connecting portions 21A and 21B in the seat 21 provided outside the flow path 2. Therefore, the ultrasonic measuring unit 7 can have a larger distance between the ultrasonic transmitters and receivers 10A and 10B and the flow path 2 compared to when the ultrasonic transmitters and receivers 10A and 10B are provided at locations that contact the flow path 2. Therefore, the ultrasonic transmitters and receivers 10A and 10B can measure the propagation characteristics of the ultrasonic waves in a state where they are less susceptible to the influence of the gas flow in the flow path 2.

[0023] Furthermore, since the ultrasonic propagation distance can be increased depending on the length of the hollow cylindrical connecting portions 21A and 21B, it is possible to measure the ultrasonic propagation characteristics with the propagation distance set to a long value. As a result, even when the fluid to be measured is, for example, hydrogen gas, which has a fast ultrasonic propagation speed and is unlikely to produce a difference in propagation time, it is possible to ensure a large difference in the propagation time of the ultrasonic waves in the two directions, forward and backward, relative to the flow of the fluid to be measured. This reduces the measurement variation in the flow rate, enabling stable metering. Furthermore, since no changes are required to the flow path 2, there is no need to change the rectification mechanism or sensor components within the flow path 2, resulting in cost savings.

[0024] Furthermore, the tapered inner peripheral wall 22 of the hollow cylindrical connecting parts 21A, 21B can improve the ultrasonic emission and incidence characteristics and prevent measurement errors. That is, the tapered inner peripheral wall 22 makes it easier to pick up reflected waves from the inner wall 1A of the flow path 2 even if the flow path 2 is turbulent, and the collected reflected waves can be converged toward the vibration parts 11 of the ultrasonic transmitter / receivers 10A, 10B. This has the effect of preventing measurement errors caused by refraction that occurs when ultrasonic waves exit the flow path 2.

[0025] Furthermore, since the ultrasonic transmitter / receivers 10A, 10B are embedded and held in the openings 22T1 at the one ends T1 of the hollow cylindrical connecting parts 21A, 21B, diffusion of ultrasonic waves can be prevented and the holding force of the ultrasonic transmitter / receivers 10A, 10B by the base 21 can be improved. Therefore, it is possible to reduce disturbance noise. Furthermore, since the shape of the openings 22T1 at the one ends T1 of the hollow cylindrical connecting parts 21A, 21B is determined in accordance with the shape of the vibration parts (matching layers) 11 of the ultrasonic transmitter / receivers 10A, 10B, the effect of preventing diffusion of the transmitted ultrasonic waves can be obtained.

[0026] FIG. 6 is a graph showing the results of a flow rate measurement test using the gas meter of this embodiment, a graph showing the results of a flow rate measurement test using a conventional gas meter as a comparative example, and a graph comparing the measurement variation between this embodiment and the comparative example (conventional example).

[0027] Comparing the measurement results of the gas meter of this embodiment with the measurement results of the gas meter of the comparative example, it can be seen that the gas meter of this embodiment has less variation in measurement. As can be seen from the comparison of standard deviations, the variation (σ) of flow rate measurement of this embodiment is reduced by approximately 32% compared to the comparative example.

[0028] The present invention is not limited to the above-described embodiments, and can be appropriately modified, improved, etc. In addition, the material, shape, dimensions, numerical values, form, number, location, etc. of each component in the above-described embodiments are arbitrary and not limited as long as they can achieve the present invention.

[0029] Here, the features of the ultrasonic measuring unit and the gas meter according to the above-described embodiments of the present invention will be briefly summarized and listed below in [1] to [6]. [1] A flow path (2) through which a fluid to be measured flows; a pair of ultrasonic transmitters / receivers (10A, 10B) disposed upstream and downstream of the flow path, respectively, for transmitting and receiving ultrasonic waves into the flow path; a seat (21) provided outside the flow path and holding the pair of ultrasonic transmitter-receivers, The seat has a pair of hollow cylindrical connecting parts (21A, 21B), Each of the pair of hollow cylindrical connecting parts holds the pair of ultrasonic transmitter-receivers at one end (T1), and the other end (T2) is connected to the flow path. Ultrasonic measurement unit (7).

[0030] According to the configuration [1] above, the ultrasonic transmitter / receivers (10A, 10B) are held at one end (T1) of the hollow cylindrical connector (21A, 21B) in the base (21) provided outside the flow path (2). Therefore, the distance between the ultrasonic transmitter / receiver and the flow path can be increased compared to when the ultrasonic transmitter / receiver is provided at a location adjacent to the flow path. This allows the ultrasonic transmitter / receiver to measure the ultrasonic propagation characteristics in a state where it is less affected by the flow field in the flow path. Furthermore, since the ultrasonic propagation distance can be increased depending on the length of the hollow cylindrical connector, it is possible to measure the ultrasonic propagation characteristics with a long propagation distance. As a result, it is possible to ensure a difference in the propagation time of the ultrasonic waves measured by the pair of ultrasonic transmitter / receivers. Therefore, even when the measured fluid has a fast ultrasonic propagation velocity and is unlikely to experience a difference in propagation time, such as hydrogen gas, it is possible to reduce variation in flow rate measurement and enable stable metering. Furthermore, since no modifications are required to the flow path, there is no need to change the rectifying mechanism or sensor components in the flow path, resulting in cost savings.

[0031] [2] The pair of ultrasonic transmitters and receivers propagate ultrasonic waves so as to cross obliquely the flow direction of the fluid to be measured flowing through the flow channel, and receive ultrasonic waves traveling from the upstream to the downstream and ultrasonic waves traveling from the downstream to the upstream. The ultrasonic measurement unit according to [1] above.

[0032] According to the configuration [2] above, the flow rate of the fluid to be measured can be measured based on the difference in propagation time of ultrasonic waves in two directions, forward and backward, relative to the flow of the fluid to be measured.

[0033] [3] The pair of ultrasonic transmitter-receivers (10A, 10B) are arranged in a positional relationship such that ultrasonic waves transmitted from one ultrasonic transmitter-receiver are reflected by the inner wall (1A) of the flow path and received by the other ultrasonic transmitter-receiver. The ultrasonic measurement unit according to [1] or [2] above.

[0034] According to the configuration [3] above, a pair of ultrasonic transmitters and receivers can be arranged on the same side of the flow path, thereby achieving a more compact structure than when a pair of ultrasonic transmitters and receivers are arranged on either side of the flow path.

[0035] [4] The inner peripheral wall (22) of the hollow cylindrical connecting part is formed in a tapered shape such that an opening (22T2) on the other end (T2) side connected to the flow path is larger than an opening (22T1) on the one end (T1) side. An ultrasonic measurement unit according to any one of [1] to [3] above.

[0036] According to the configuration [4] above, the inner peripheral wall of the hollow cylindrical connecting part is tapered, which improves the ultrasonic emission and incidence characteristics and prevents measurement errors. That is, the tapered inner peripheral wall makes it easier to pick up reflected waves from the inner wall of the flow path even if the flow path is turbulent. Furthermore, the collected reflected waves can be focused toward the vibration part of the ultrasonic transmitter / receiver, which also prevents measurement errors caused by refraction when the ultrasonic waves exit the flow path.

[0037] [5] The hollow cylindrical connecting part has an opening (22T1) on the one end (T1) side that has a shape corresponding to the shape of the vibration part (11) of the ultrasonic transmitter-receiver, and the ultrasonic transmitter-receiver is embedded in the opening on the one end (T1) side, thereby holding the ultrasonic transmitter-receiver. An ultrasonic measurement unit according to any one of [1] to [4] above.

[0038] According to the configuration [5] above, since the ultrasonic transmitter / receiver is embedded and held in one end of the hollow cylindrical connecting part, it is possible to prevent diffusion of ultrasonic waves and improve the holding force of the ultrasonic transmitter / receiver by the base. Therefore, it is possible to reduce disturbance noise. Furthermore, since the shape of one end of the hollow cylindrical connecting part is determined according to the shape of the vibration part (matching layer) of the ultrasonic transmitter / receiver, it is possible to obtain the effect of preventing diffusion of the transmitted ultrasonic waves.

[0039] [6] The ultrasonic measurement unit according to any one of [1] to [5] above; a propagation time calculation unit that calculates a propagation time of an ultrasonic wave between the pair of ultrasonic transmitters and receivers based on detection data of the pair of ultrasonic transmitters and receivers included in the ultrasonic measurement unit; a flow velocity calculation unit that calculates the difference between the propagation time of an ultrasonic wave when one of the ultrasonic transmitter-receivers transmits an ultrasonic wave and the other ultrasonic transmitter-receiver receives the ultrasonic wave, and the propagation time of an ultrasonic wave when the other ultrasonic transmitter-receiver transmits an ultrasonic wave and the one ultrasonic transmitter-receiver receives the ultrasonic wave, based on the calculated data of the propagation time calculation unit, and calculates the flow velocity of the fluid to be measured based on the difference; a flow rate calculation unit that calculates a flow rate of the fluid to be measured based on the flow rate calculated by the flow rate calculation unit, Gas meter.

[0040] According to the configuration [6] above, the ultrasonic transmitter / receiver is held at one end of the hollow-tubular connector on a base installed outside the flow path. This allows for a greater distance between the ultrasonic transmitter / receiver and the flow path compared to when the ultrasonic transmitter / receiver is installed at a location adjacent to the flow path. This allows the ultrasonic transmitter / receiver to measure the ultrasonic propagation characteristics in a state less affected by the flow field within the flow path. Furthermore, the ultrasonic propagation distance can be increased depending on the length of the hollow-tubular connector, making it possible to measure the ultrasonic propagation characteristics with a long propagation distance. As a result, it is possible to ensure a difference in the propagation time of the ultrasonic waves measured by each of the pair of ultrasonic transmitter / receivers. Therefore, even when the measured fluid has a fast ultrasonic propagation velocity and is unlikely to experience a difference in propagation time, such as hydrogen gas, flow rate measurement variability can be reduced, enabling stable metering. Furthermore, since no modifications to the flow path are required, there is no need to change the rectifying mechanism or sensor components within the flow path, resulting in cost savings. [Explanation of symbols]

[0041] 1. Body 1A Inner wall 2 Flow path 7 Ultrasonic measurement unit 10A, 10B ultrasonic transmitter / receiver 11 Vibration unit 21 Pedestal 21A, 21B Hollow cylindrical connection part 22 Inner wall 22T1 Opening on one end 22T2 Opening on the other end T1 one end T2 other end

Claims

1. a flow path through which a fluid to be measured flows; a pair of ultrasonic transmitters and receivers arranged upstream and downstream of the flow path, respectively, for transmitting and receiving ultrasonic waves into the flow path; a base provided outside the flow path and holding the pair of ultrasonic transmitter-receivers, The seat has a pair of hollow cylindrical connecting portions, Each of the pair of hollow cylindrical connecting parts holds the pair of ultrasonic transmitter-receivers at one end, and is connected to the flow path at the other end. Ultrasonic measurement unit.

2. the pair of ultrasonic transmitters / receivers propagate ultrasonic waves so as to cross obliquely the flow direction of the fluid to be measured flowing through the flow channel, and receive ultrasonic waves traveling from the upstream to the downstream and ultrasonic waves traveling from the downstream to the upstream. The ultrasonic measurement unit according to claim 1 .

3. the pair of ultrasonic transmitter-receivers are arranged in a positional relationship such that ultrasonic waves transmitted from one of the ultrasonic transmitter-receivers are reflected by an inner wall of the flow path and received by the other ultrasonic transmitter-receiver; The ultrasonic measurement unit according to claim 1 .

4. an inner peripheral wall of the hollow cylindrical connecting portion is tapered so that an opening on the other end connected to the flow path is larger than an opening on the one end. The ultrasonic measurement unit according to claim 1 .

5. The hollow cylindrical connecting part has an opening on one end side that has a shape corresponding to the shape of a vibration part of the ultrasonic transmitter-receiver, and the ultrasonic transmitter-receiver is embedded in the opening on the one end side, thereby holding the ultrasonic transmitter-receiver. The ultrasonic measurement unit according to claim 1 .

6. The ultrasonic measurement unit according to any one of claims 1 to 5, a propagation time calculation unit that calculates a propagation time of an ultrasonic wave between the pair of ultrasonic transmitters and receivers based on detection data of the pair of ultrasonic transmitters and receivers included in the ultrasonic measurement unit; a flow velocity calculation unit that calculates the difference between the propagation time of ultrasonic waves when one of the ultrasonic transmitter-receivers transmits ultrasonic waves and the other ultrasonic transmitter-receiver receives them, and the propagation time of ultrasonic waves when the other ultrasonic transmitter-receiver transmits ultrasonic waves and the one ultrasonic transmitter-receiver receives them, based on the calculated data of the propagation time calculation unit, and calculates the flow velocity of the fluid to be measured based on the difference; a flow rate calculation unit that calculates a flow rate of the fluid to be measured based on the flow rate calculated by the flow rate calculation unit, Gas meter.

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