JP4746903B2 - Ultrasonic flow meter - Google Patents

Description

  The present invention relates to an ultrasonic flowmeter that measures the flow rate of a fluid flowing through a tubular body.

  The most widely used principle in the ultrasonic flowmeter for measuring the flow rate of the fluid flowing through the pipe is the time difference method. For example, as described in Non-Patent Document 1, this time difference method measures the flow velocity V of a fluid as a change in the propagation speed of ultrasonic waves in the fluid, that is, a propagation time difference Δt, and the known cross-sectional area of the tube body. The flow rate Q is measured by multiplying by S.

  V-shaped, Z-shaped, N-shaped, W-shaped, and the like are known for the arrangement of ultrasonic transducers using this principle.

Issued by Kogyo Shimbun Co., Ltd. Japan Measuring Instruments Industry Federation “Flow Measurement AtoZ”, pages 121-142

  The ultrasonic beam transmitted from the transmission oscillator is formed on the central axis on the plane of the flat plate vibrator when a normal flat plate piezoelectric ceramic vibrator is used. In many cases, the sound speed of the pipe body material and the internal fluid are remarkably different from each other. Therefore, compensation with an intermediate medium such as a wedge is generally performed in consideration of refraction of the ultrasonic beam.

  The positional relationship between the transmitting and receiving transducers attached to the outer peripheral surface of the tube is fixed so that an optimal position can be obtained by taking the above measures, but the fluid still has a different sound velocity than expected. The ultrasonic beam from the transmitting transducer is not necessarily the optimum beam in the receiving transducer, when the temperature dependence of the speed of sound is high, or when it changes over a wide range from a low flow velocity range to an extremely high flow velocity range. It is not always possible to receive a wave in a direction, but rather, it often deviates from a predetermined direction.

  An object of the present invention is to solve the above-described problems and to provide an ultrasonic flowmeter capable of transmitting and receiving an ultrasonic beam with an optimal direction by controlling the direction of ultrasonic waves.

In order to achieve the above object, an ultrasonic flowmeter according to the present invention includes a tubular body for flowing a fluid to be measured, and a vibration for transmitting and receiving an ultrasonic beam via a fluid attached to an outer peripheral surface of the tubular body. Each of the transducer groups is composed of a plurality of ultrasonic transducers, and ultrasonic waves are applied by performing predetermined electrical phase control between the ultrasonic transducers. The transmission direction and the reception direction of the beam can be controlled, and the plurality of ultrasonic transducers are arranged in a line in the transmission transducer group and the reception transducer group, and the transmission transducer group The ultrasonic beam transmission azimuth is controlled by applying a phase difference to each of the arranged ultrasonic transducers and aligning the wavefronts, and transmitting the ultrasonic beam synthesized in the direction perpendicular to the wavefront. The ultrasonic beam by the receiving transducer group Control of reception orientation aligns the wavefront by providing a phase difference to individual ultrasonic transducers and the sequence was carried out by reception ultrasonic beam from the wave face and vertically vibrating the transmitting It is characterized in that the receiving direction of the ultrasonic beam by the receiving transducer group coincides with the transmitting direction of the ultrasonic beam by the child group.

  According to the ultrasonic flowmeter of the present invention, it is possible to electrically control the direction of the ultrasonic beam without adjusting the transducer group by mechanically shifting the position of the transducer group. Can send and receive waves.

  The present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 1 is a configuration diagram, in which first and second transducer groups 2 and 3 are arranged at a distance L at positions facing each other through a fluid F of a tube body 1. Each of the first vibrator group 2 and the second vibrator group 3 includes a plurality of vibrators 2a, 2b, 2c,..., 2n and vibrators 3a, 3b,. ing.

  The first vibrator group 2 will be described. As shown in FIG. 2, the plurality of vibrators 2a, 2b, 2c,..., 2n of the first vibrator group 2 include phase shift circuits 4a, 4b, .. 4n are connected to each other and connected to the signal source 6 through the switch circuit 5.

  In FIG. 2, the vibrators 2a, 2b, 2c,..., 2n are repeatedly given phase differences, that is, delay times corresponding to the line segments a to a ′, from the phase shift circuits 4a, 4b,. When excited, the ultrasonic beams from the respective vibrators 2a, 2b, 2c,..., 2n interfere with each other and are phase-synthesized so that the wave fronts are aligned in line segments A to A ′ and perpendicular to the wave fronts A to A ′. The main axis of the ultrasonic beam is deflected and emitted in the θ direction.

In order to deflect the ultrasonic beam in this azimuth θ, if the distance between the transducers 2a, 2b,..., 2n is d and λ is the wavelength of the ultrasonic wave, Should be given.
φ _n = (n−1) (2πd / λ) sin θ

  Therefore, the transmission direction of the ultrasonic beam can be arbitrarily controlled by controlling the phase amount of the phase shift circuits 4a, 4b,.

  FIG. 3 is a graph showing the relationship between the azimuth θ and the phase difference when the frequency f = 1 MHz and the transducer groups 2 and 3 are separated by a distance L = 10 mm in water. When the main axis of the beam is formed, a phase difference φ = 7.3 degrees may be given between the vibrators.

  The same applies to the case where the second transducer group 3 is on the receiving side. As shown in FIG. 4, each transducer 3a, 3b,. ... There is a phase difference for the ultrasonic beam that reaches 3n from the direction of the azimuth θ to reach the transducers 3a, 3b,. Accordingly, the phase difference corresponding to the line segment bb ′, that is, the delay time, is switched from the phase shift circuits 7a, 7b,..., 7n to the transducers 3a, 3b,. If the phase difference of the ultrasonic beam that arrives earlier is increased and the wave fronts are aligned in the line segment BB ′, the ultrasonic beam from the θ direction can be received efficiently.

  In an ultrasonic flowmeter, since it is usual to transmit ultrasonic beams alternately in the forward and reverse directions with respect to the flow direction of the fluid F and use the difference in ultrasonic arrival time, the first and first The two transducer groups 2 and 3 perform transmission and reception by switching between transmission and reception.

  In this way, when the first and second vibrator groups 2 and 3 are arranged on the outer periphery of the tubular body 1 and the vibrator is excited by giving a phase difference at a predetermined frequency, the first vibrator group 2 The main axis of the ultrasonic beam can be obtained in the selected front direction, and the second transducer group 3 can receive the main axis from this direction.

  Therefore, if the principal axes of the ultrasonic beams of the first and second transducer groups 2 and 3 are both directed toward the second and first transducer groups 3 and 2 on the counterpart side, the ultrasonic wave is transmitted at the shortest distance. Is transmitted, the signal-to-noise ratio of the signal is improved, and high accuracy is obtained as an ultrasonic flowmeter.

It is a block diagram. It is a principle explanatory drawing in transmission of an ultrasonic beam. It is a graph figure of the relationship of the phase amount corresponding to an azimuth | direction. It is a principle explanatory drawing in reception of an ultrasonic beam.

Explanation of symbols

1 Tubular body 2, 3 vibrator group 2a, 2b, ... 2n, 3a, 3b, ..., 3n vibrator 4a, 4b, ..., 4n, 7a, 7b, ..., 7n Phase circuit 5, 8 Switch circuit 6 Signal source

Claims (2)

These vibrators are provided with a tubular body through which a fluid to be measured flows, a transmitting transducer group for transmitting and receiving an ultrasonic beam via a fluid attached to the outer peripheral surface of the tubular body, and a receiving transducer group. each group composed of a plurality of ultrasonic transducers, and can control the transmit direction and reception direction of the ultrasonic beam, respectively, by subjecting each of a predetermined electrical phase control between the ultrasonic transducers, said feeding In the transducer group for wave and the transducer group for reception, the plurality of ultrasonic transducers are arranged in a line, and the transmission direction of the ultrasonic beam by the transducer group for transmission is controlled by the arranged ultrasonic wave The transducer is excited by giving a phase difference to each other, aligning the wavefront, transmitting an ultrasonic beam synthesized in a direction perpendicular to the wavefront, and receiving the ultrasonic beam by the receiving transducer group. Wave direction control is performed individually on the arranged ultrasonic transducers. Align the wavefront by providing phase difference, said corrugated surface and carried by reception ultrasonic beam from the vertical direction, the reception for the transducer groups to transmitting direction of ultrasonic beam by the transmitting for transducer groups The ultrasonic flowmeter is characterized in that the receiving direction of the ultrasonic beam is matched.   The ultrasonic flowmeter according to claim 1, wherein the transmitting transducer group and the receiving transducer group are alternately switched between transmitting and receiving functions.

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