Ultrasonic flow meter

Abstract

This ultrasonic flow meter comprises: a measurement flow path forming unit that has a rectangular cross section and forms a measurement flow path in which a fluid being measured flows from an upstream side to a downstream side; a first ultrasonic wave transmitter / receiver that is disposed on an outer surface related to one short edge of the rectangular cross section, includes an ultrasonic wave transmission / reception surface having dimensions greater than or equal to the dimensions of an inner surface related to the one short edge, and transmits and receives ultrasonic waves; three or more reflection units that are disposed in the measurement flow path and reflect the ultrasonic waves from the first ultrasonic wave transmitter / receiver in the measurement flow path; and a second ultrasonic wave transmitter / receiver that is disposed on the outer surface related to the one short edge and located downstream of the first ultrasonic wave transmitter / receiver in the extending direction of the measurement flow path, includes an ultrasonic wave transmission / reception surface having dimensions greater than or equal to the dimensions of the inner surface related to the one short edge, and receives the ultrasonic waves reflected by the three or more reflection units and transmits the ultrasonic waves.

Description

ultrasonic flow meter

[0001] The present disclosure relates to ultrasonic flow meters.

[0002] A conventional flow velocity measurement device is known that measures the flow velocity of a fluid to be measured in a measurement flow path formed between a coaxially arranged inner pipe and an outer pipe (see Patent Document 1). This flow velocity measurement device includes two ultrasonic transmitter-receivers, and ultrasonic waves transmitted from one of the ultrasonic transmitter-receivers are received by the other ultrasonic transmitter-receiver via a plurality of reflectors provided in the measurement flow path. The measurement flow path is formed between the inner pipe and the outer pipe, and the entire flow path, including the measurement flow path, has a circular shape.

[0003] Japanese Unexamined Patent Publication No. 61-40512

[0004] The two ultrasonic transmitter-receivers are arranged on the outer surface of the outer tube, and one of the ultrasonic transmitter-receivers transmits ultrasonic waves in a direction perpendicular to the extension direction of the measurement flow path. However, when performing flow rate measurement using ultrasonic waves, there is room for improvement in the accuracy of the flow rate measurement.

[0005] Therefore, an object of the present disclosure is to provide an ultrasonic flowmeter that is capable of measuring flow rates using ultrasonic waves with high accuracy.

[0006] The ultrasonic flowmeter disclosed herein comprises: a measurement flow path forming section that forms a measurement flow path through which the fluid to be measured flows from upstream to downstream and has a rectangular cross section; a first ultrasonic transmitter / receiver that is arranged on the outer surface of one of the short sides of the rectangular cross section and includes an ultrasonic transmitting / receiving surface having dimensions equal to or greater than the dimensions of the inner surface of the one short side, and that transmits and receives ultrasonic waves; three or more reflecting sections that are arranged in the measurement flow path and reflect ultrasonic waves from the first ultrasonic transmitter / receiver in the measurement flow path; and a second ultrasonic transmitter / receiver that is arranged on the outer surface of the one short side and downstream of the first ultrasonic transmitter / receiver in the extension direction of the measurement flow path, and includes an ultrasonic transmitting / receiving surface having dimensions equal to or greater than the dimensions of the inner surface of the one short side, and that receives ultrasonic waves reflected by the three or more reflecting sections and transmits ultrasonic waves.

[0007] According to the present disclosure, the first ultrasonic transmitter / receiver has an ultrasonic transmitting / receiving surface having a dimension equal to or larger than the dimension of the inner surface of one of the short sides, and the second ultrasonic transmitter / receiver has an ultrasonic transmitting / receiving surface having a dimension equal to or larger than the dimension of the inner surface of one of the short sides, so that ultrasonic waves can be propagated uniformly throughout the entire measurement flow path, thereby achieving high-precision flow rate measurement.

[0008] In the above disclosure, the reflecting section may include a first reflecting section that is arranged on an inner surface related to the other short side of the rectangular cross section so as to face the first ultrasonic transmitter / receiver and reflects ultrasonic waves from the first ultrasonic transmitter / receiver toward one of the short sides, a second reflecting section that is arranged on the inner surface related to the one short side and downstream of the first reflecting section and reflects ultrasonic waves reflected by the first reflecting section toward the other short side, and a third reflecting section that is arranged on the inner surface related to the other short side and downstream of the second reflecting section and reflects ultrasonic waves reflected by the second reflecting section toward one of the short sides.

[0009] According to the above configuration, the ultrasonic wave propagation path can be made M-shaped (M-path configuration). This allows the inclination angles of the reflecting surfaces of the first reflecting portion and the third reflecting portion to be small. This makes it possible to suppress the occurrence of turbulence in the flow of the fluid to be measured, reducing changes in flow direction and thereby contributing to stabilization of the flow.

[0010] In the above disclosure, the first ultrasonic transducer and the second ultrasonic transducer may each be a thickness vibration type ultrasonic transducer.

[0011] According to the above configuration, ultrasonic waves can be transmitted more uniformly from the first ultrasonic transmitter / receiver or the second ultrasonic transmitter / receiver throughout the entire flow path, and the transmitted ultrasonic waves can be received more accurately by the second ultrasonic transmitter / receiver or the first ultrasonic transmitter / receiver.

[0012] In the above disclosure, the first ultrasonic transmitter / receiver and the second ultrasonic transmitter / receiver may transmit or receive ultrasonic waves in a direction perpendicular to the measurement flow path.

[0013] According to the above configuration, no refraction occurs during propagation of ultrasonic waves into the fluid to be measured, and therefore accurate measurement can be achieved even for fluids whose refraction pattern can change depending on temperature and density.

[0014] In the above disclosure, the ultrasonic flowmeter may further include a diffuse reflection portion located between the first reflection portion and the third reflection portion in the extension direction and provided on the inner surface relating to the other short side of the rectangular cross section.

[0015] According to the above configuration, among the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver (or the ultrasonic waves transmitted from the second ultrasonic transmitter / receiver), those that do not pass through the first reflecting section (or the third reflecting section) are diffusely reflected by the diffuse reflecting section. This makes it possible to prevent the ultrasonic waves that do not pass through the first reflecting section (or the third reflecting section) from being received by the second ultrasonic transmitter / receiver (or the first ultrasonic transmitter / receiver). Therefore, it is possible to prevent unnecessary ultrasonic waves from being received in a configuration in which the ultrasonic propagation path is M-shaped (M-path configuration).

[0016] In the above disclosure, the first reflecting portion may have a first converging reflecting surface that reflects ultrasonic waves from the first ultrasonic transmitter / receiver so as to converge toward the second reflecting portion, and the third reflecting portion may have a second converging reflecting surface that reflects ultrasonic waves from the second ultrasonic transmitter / receiver so as to converge toward the second reflecting portion.

[0017] According to the above configuration, a portion of the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver (or the second ultrasonic transmitter / receiver) can be reflected by the first converging reflecting surface (or the second converging reflecting surface) so as to converge toward the second reflecting portion, thereby increasing the signal strength of the ultrasonic waves received by the second ultrasonic transmitter / receiver (or the first ultrasonic transmitter / receiver).

[0018] The ultrasonic flowmeter of the present disclosure includes a measurement flow path forming section having a rectangular cross section that forms a measurement flow path through which a fluid to be measured flows from an upstream side to a downstream side; a first ultrasonic transmitter-receiver that is disposed on one of the short sides of the rectangular cross section and on an outer surface related to one of the long sides of the rectangular cross section, and transmits and receives ultrasonic waves; a first deflection-reflection section that deflects and reflects ultrasonic waves from the first ultrasonic transmitter-receiver toward the other short side; a first reflection section that is disposed on an inner surface related to the other short side, and reflects ultrasonic waves reflected by the first deflection-reflection section toward the one short side; The ultrasonic transducer comprises: a second reflecting section that is arranged downstream of the first reflecting section and that reflects the ultrasonic waves reflected by the first reflecting section toward the other short side; a third reflecting section that is arranged on the inner surface related to the other short side and downstream of the second reflecting section and that reflects the ultrasonic waves reflected by the second reflecting section toward one of the short sides; a second deflection-reflection section that deflects and reflects the ultrasonic waves from the third reflecting section; and a second ultrasonic transmitter / receiver that is arranged on the side of the one short side and on the outer surface related to the one long side and that receives the ultrasonic waves reflected by the second deflection-reflection section and transmits ultrasonic waves.

[0019] According to the present disclosure, by arranging the first ultrasonic transmitter / receiver and the second ultrasonic transmitter / receiver on the outer surface of one of the long sides of the rectangular cross section of the measurement flow path forming portion, which has a relatively large space, it is possible to improve the design freedom of the control board including each ultrasonic transmitter / receiver and the signal processing unit. This simplifies the component configuration by integrating each ultrasonic transmitter / receiver with the control board, thereby realizing cost reduction, and also enables a compact design by effectively utilizing space.

[0020] In the above disclosure, the first ultrasonic transducer and the second ultrasonic transducer may each be a thickness vibration type ultrasonic transducer.

[0021] According to the above configuration, ultrasonic waves can be transmitted more uniformly from the first ultrasonic transmitter / receiver or the second ultrasonic transmitter / receiver throughout the entire flow path, and the transmitted ultrasonic waves can be received more accurately by the second ultrasonic transmitter / receiver or the first ultrasonic transmitter / receiver.

[0022] In the above disclosure, the first deflection reflection unit may deflect the direction of travel of the ultrasonic waves from the first ultrasonic transmitter / receiver by 90 degrees and reflect them toward the first reflection unit, and the second deflection reflection unit may deflect the direction of travel of the ultrasonic waves from the third reflection unit by 90 degrees and reflect them toward the second ultrasonic transmitter / receiver.

[0023] According to the above configuration, ultrasonic waves transmitted from the first ultrasonic transmitter / receiver or the second ultrasonic transmitter / receiver arranged on the outer surface of one of the long sides of the rectangular cross section can travel from one short side to the other short side of the rectangular cross section. This makes it possible to propagate ultrasonic waves throughout the entire flow path from one short side to the other short side of the rectangular cross section, even when an embodiment is adopted in which each ultrasonic transmitter / receiver is arranged on the outer surface of the long sides of the rectangular cross section.

[0024] In the above disclosure, the ultrasonic flowmeter may further include a diffuse reflection portion located between the first reflection portion and the third reflection portion in the extension direction and provided on the inner surface relating to the other short side of the rectangular cross section.

[0025] According to the above configuration, among the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver (or the ultrasonic waves transmitted from the second ultrasonic transmitter / receiver), those that do not pass through the first reflecting section (or the third reflecting section) are diffusely reflected by the diffuse reflecting section. This makes it possible to prevent the ultrasonic waves that do not pass through the first reflecting section (or the third reflecting section) from being received by the second ultrasonic transmitter / receiver (or the first ultrasonic transmitter / receiver). Therefore, it is possible to prevent unnecessary ultrasonic waves from being received in a configuration in which the ultrasonic propagation path is M-shaped (M-path configuration).

[0026] In the above disclosure, the first reflecting portion may have a first converging reflecting surface that reflects ultrasonic waves from the first ultrasonic transmitter / receiver so as to converge toward the second reflecting portion, and the third reflecting portion may have a second converging reflecting surface that reflects ultrasonic waves from the second ultrasonic transmitter / receiver so as to converge toward the second reflecting portion.

[0027] According to the above configuration, a portion of the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver (or the second ultrasonic transmitter / receiver) can be reflected by the first converging reflecting surface (or the second converging reflecting surface) so as to converge toward the second reflecting portion, thereby increasing the signal strength of the ultrasonic waves received by the second ultrasonic transmitter / receiver (or the first ultrasonic transmitter / receiver).

[0028] According to the present disclosure, it is possible to provide an ultrasonic flowmeter that is capable of measuring flow rates using ultrasonic waves with high accuracy.

[0029] Fig. 3 is a cross-sectional view showing the configuration of an ultrasonic flowmeter in one embodiment. Fig. 4 is a side view of an ultrasonic flowmeter viewed from an arrow A in Fig. 1. Fig. 4 is a cross-sectional view showing the configuration of an ultrasonic flowmeter in one embodiment. Fig. 5 is a cross-sectional view taken along line D-D in Fig. 3. Fig. 5 is a cross-sectional view showing the configuration of an ultrasonic flowmeter in one embodiment. Fig. 6 is a cross-sectional view showing the configuration of an ultrasonic flowmeter in one embodiment.

[0030] An ultrasonic flowmeter according to an embodiment of the present disclosure will be described below with reference to the drawings. The ultrasonic flowmeter described below is merely one embodiment of the present disclosure. Therefore, the present disclosure is not limited to the following embodiment, and additions, deletions, and modifications are possible within the scope of the present disclosure.

[0031] (First embodiment) A first embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a cross-sectional view showing the configuration of an ultrasonic flowmeter 50 in the first embodiment, and Fig. 2 is a side view of the ultrasonic flowmeter 50 as viewed from the arrow A in Fig. 1.

[0032] 1 and 2 , the ultrasonic flowmeter 50 includes a measurement flow path forming unit 20, a first ultrasonic transmitter / receiver 4, a first reflecting unit 6, a second reflecting unit 10, a third reflecting unit 7, a second ultrasonic transmitter / receiver 5, and a signal processing unit 11. The first ultrasonic transmitter / receiver 4 and the second ultrasonic transmitter / receiver 5 are each capable of transmitting and receiving ultrasonic waves. The second ultrasonic transmitter / receiver 5 can receive ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 4, and the first ultrasonic transmitter / receiver 4 can receive ultrasonic waves transmitted from the second ultrasonic transmitter / receiver 5. In this embodiment, unless otherwise noted, a mode in which ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 4 are received by the second ultrasonic transmitter / receiver 5 will be described.

[0033] Measurement flow path forming portion 20 forms measurement flow path 1 through which the fluid to be measured flows from the upstream side (left side in FIG. 1) to the downstream side (right side in FIG. 1), and has a rectangular cross section (transverse cross section of measurement flow path forming portion 20). That is, measurement flow path forming portion 20 has an inner surface B1 and an outer surface B3 associated with one short side SS1, and an inner surface B2 and an outer surface B4 associated with the other short side SS2. Measurement flow path forming portion 20 also has an inner surface C1 and an outer surface C3 associated with one long side LS1, and an inner surface C2 and an outer surface C4 associated with the other long side LS2. Examples of the fluid to be measured include a liquid such as water or a gas such as air.

[0034] The measurement flow path 1 has a dimension W between an inner surface C1 associated with one long side LS1 and an inner surface C2 associated with the other long side LS2, and a dimension H (<<W) between an inner surface B1 associated with one short side SS1 and an inner surface B2 associated with the other short side SS2. The measurement flow path 1 has a large aspect ratio (W / H). The measurement flow path 1 extends in one direction and has an inlet 2 and an outlet 3. The fluid to be measured flows into the measurement flow path 1 through the inlet 2 and then flows out through the outlet 3.

[0035] The first ultrasonic transmitter / receiver 4 is disposed on the outer surface B3 associated with one of the short sides SS1. The first ultrasonic transmitter / receiver 4 is disposed so that the direction of ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 4 is perpendicular to the extension direction of the measurement flow path 1. An example of the first ultrasonic transmitter / receiver 4 is a thickness vibration type ultrasonic transmitter / receiver. The first ultrasonic transmitter / receiver 4 has an ultrasonic transmitting / receiving surface US that transmits and receives ultrasonic waves. The ultrasonic transmitting / receiving surface US has a dimension E that is equal to or greater than the dimension H of the inner surface B1 associated with one of the short sides SS1. Note that the ultrasonic transmitting / receiving surface US may have a dimension equal to the dimension of the outer surface B3 associated with one of the short sides SS1.

[0036] The first reflecting unit 6 is disposed on the inner surface B2 associated with the other short side SS2 so as to face the first ultrasonic transmitter / receiver 4. The first reflecting unit 6 has a triangular shape with a height of T at its vertex. Specifically, the first reflecting unit 6 has a reflecting surface 8 with an inclination angle θ1 relative to the direction in which the fluid to be measured flows, i.e., the extension direction of the measurement flow path 1. The first reflecting unit 6 also has an upstream surface 6a located upstream of the reflecting surface 8. In this configuration, the reflecting surface 8 of the first reflecting unit 6 reflects ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 4 toward one short side SS1. More specifically, the reflecting surface 8 reflects ultrasonic waves toward the second reflecting unit 10 located on the inner surface B1 associated with the one short side SS1 and downstream of the reflecting surface 8. In this manner, by adopting a configuration in which ultrasonic waves received by the reflecting surface 8 are reflected downstream of the reflecting surface 8, the inclination angle θ1 of the reflecting surface 8 can be set to an angle smaller than 45°. Therefore, the dimension T of the first reflecting unit 6 can be sufficiently small. The dimension T is sufficiently small compared to the dimension W (T<<W). Furthermore, by reducing the dimension T of the first reflecting portion 6, the inclination angle of the upstream surface 6a of the first reflecting portion 6 can also be reduced. Therefore, the upstream surface 6a can guide the fluid to be measured that has flowed in from the inlet 2 downstream so that the fluid is focused toward the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 4.

[0037] The second reflecting portion 10 is disposed on the inner surface B1 associated with one of the short sides SS1 and downstream of the first reflecting portion 6. In this embodiment, the second reflecting portion 10 may be the inner surface B1 associated with one of the short sides SS1 itself, or a separate protrusion may be provided as the second reflecting portion 10. The second reflecting portion 10 reflects ultrasonic waves reflected by the first reflecting portion 6 toward the other short side. More specifically, the second reflecting portion 10 reflects ultrasonic waves toward the third reflecting portion 7 located on the inner surface B2 associated with the other short side SS2 and downstream of the second reflecting portion 10. The reflection angle of ultrasonic waves by the second reflecting portion 10, i.e., the angle between the propagation path of the ultrasonic waves reflected by the second reflecting portion 10 toward the third reflecting portion 7 and the inner surface B1 (or the angle between the propagation path of the ultrasonic waves reflected by the second reflecting portion 10 toward the first reflecting portion 6 and the inner surface B1), is defined as θ2. The reflection angle θ2 can be calculated based on the above-mentioned tilt angle θ1, as follows: θ2=90−2*θ1.

[0038] The third reflecting unit 7 has basically the same configuration as the first reflecting unit 6 described above. The third reflecting unit 7 is disposed on the inner surface B2 related to the other short side SS2 so as to face the second ultrasonic transmitter / receiver 5. The third reflecting unit 7 is disposed downstream of the second reflecting unit 10 so as to face the second ultrasonic transmitter / receiver 5. The third reflecting unit 7 has a triangular shape with a height dimension of T at its apex. Specifically, the third reflecting unit 7 has a reflecting surface 9 with an inclination angle θ1 with respect to the direction in which the fluid to be measured flows, i.e., the extension direction of the measurement flow path 1. The third reflecting unit 7 also has a downstream surface 7a provided downstream of the reflecting surface 9. In this configuration, the reflecting surface 9 of the third reflecting unit 7 reflects ultrasonic waves reflected by the second reflecting unit 10 toward one short side SS1. More specifically, the reflecting surface 9 reflects ultrasonic waves toward the second ultrasonic transmitter / receiver 5, which is provided on the inner surface B1 related to one short side SS1 and at a position facing the third reflecting unit 7. In this manner, in a configuration in which ultrasonic waves transmitted from the second ultrasonic transmitter-receiver 5 are received by the first ultrasonic transmitter-receiver 4, by adopting a configuration in which ultrasonic waves received by the reflecting surface 9 are reflected upstream of the reflecting surface 9, it is possible to set the inclination angle θ1 of the reflecting surface 9 to an angle smaller than 45°. Therefore, the dimension T of the third reflecting portion 7 can be made sufficiently small. The dimension T is sufficiently small relative to the dimension W (T<<W). Furthermore, by making the dimension T of the third reflecting portion 7 small, the inclination angle of the downstream surface 7a of the third reflecting portion 7 can also be made small. Therefore, the downstream surface 7a can smoothly guide the measured fluid toward the outlet 3. The first reflecting portion 6, the second reflecting portion 10, and the third reflecting portion 7 correspond to reflecting portions.

[0039] The second ultrasonic transmitter / receiver 5 has basically the same configuration as the first ultrasonic transmitter / receiver 4 described above. The second ultrasonic transmitter / receiver 5 is arranged on the outer surface B3 associated with one short side SS1 so as to face the third reflecting portion 7. The second ultrasonic transmitter / receiver 5 is arranged spaced apart from the first ultrasonic transmitter / receiver 4 in the extension direction of the measurement flow path 1. The second ultrasonic transmitter / receiver 5 is arranged so that the direction of ultrasonic waves transmitted from the second ultrasonic transmitter / receiver 5 is perpendicular to the extension direction of the measurement flow path 1. The second ultrasonic transmitter / receiver 5 receives ultrasonic waves reflected by the reflecting surface 9 of the third reflecting portion 7. An example of the second ultrasonic transmitter / receiver 5 is a thickness vibration type ultrasonic transmitter / receiver. The second ultrasonic transmitter / receiver 5 has an ultrasonic transmitting / receiving surface US that transmits and receives ultrasonic waves. The ultrasonic transmitting / receiving surface US has a dimension E that is equal to or greater than the dimension H of the inner surface B1 associated with one short side SS1.

[0040] The signal processing unit 11 includes at least one of a processor such as a CPU and an integrated circuit such as an ASIC. The first ultrasonic transmitter / receiver 4 and the second ultrasonic transmitter / receiver 5 are each electrically connected to the signal processing unit 11. The signal processing unit 11 receives signals from the first ultrasonic transmitter / receiver 4 and the second ultrasonic transmitter / receiver 5 and calculates the flow velocity and flow rate of the fluid to be measured.

[0041] In the above configuration, the ultrasonic propagation path 12 in the ultrasonic flowmeter 50 is a path that passes through the first ultrasonic transmitter / receiver 4, the first reflecting section 6, the second reflecting section 10, and the third reflecting section 7 to the second ultrasonic transmitter / receiver 5, or a path that follows the reverse path, and forms an M-shape (inverted M-shape) overall as shown by the dashed line in Figure 1.

[0042] Next, the operation of the ultrasonic flowmeter 50 is as follows: The fluid to be measured flowing through the measurement flow path 1 flows in from the inlet 2 as shown by the white arrow in Fig. 1, passes through the above-mentioned ultrasonic propagation path 12, and flows out from the outlet 3. The signal processing unit 11 uses the pair of ultrasonic transmitter / receivers 4, 5 to measure the propagation time of the ultrasonic waves in the ultrasonic propagation path 12 between the first ultrasonic transmitter / receiver 4 and the second ultrasonic transmitter / receiver 5, and calculates the flow velocity and flow rate of the fluid to be measured based on the propagation time using a known method.

[0043] As described above, according to the ultrasonic flowmeter 50 of this embodiment, the first ultrasonic transmitter / receiver 4 has an ultrasonic transmitting / receiving surface US having a dimension E that is equal to or larger than the dimension H of the inner surface B1 associated with one of the short sides SS1, and the second ultrasonic transmitter / receiver 5 has an ultrasonic transmitting / receiving surface US having a dimension E that is equal to or larger than the dimension H of the inner surface B1 associated with one of the short sides SS1. This allows ultrasonic waves to propagate uniformly throughout the entire measurement flow path 1. This makes it possible to achieve high-precision flow rate measurement.

[0044] Furthermore, since the first ultrasonic transmitter / receiver 4 and the second ultrasonic transmitter / receiver 5 transmit and receive ultrasonic waves in a direction perpendicular to the measurement flow path 1, no refraction occurs during propagation to the fluid to be measured. Therefore, accurate measurement can be achieved even for fluids whose refraction pattern can change depending on temperature and density.

[0045] Furthermore, the dimension T of the first reflecting portion 6 is sufficiently small compared to the dimension W. Therefore, it is possible to suppress the occurrence of turbulence in the flow of the fluid to be measured due to the presence of the upstream surface 6a, and in addition, it is also possible to prevent the occurrence of separation vortices in the fluid to be measured after it has passed the apex of the first reflecting portion 6, thereby preventing the occurrence of large turbulence.

[0046] Furthermore, the dimension T of the third reflecting portion 7 is sufficiently small compared to the dimension W. Therefore, it is possible to suppress the occurrence of turbulence in the flow of the fluid to be measured due to the presence of the third reflecting portion 7. In addition, it is also possible to prevent the occurrence of separation vortices in the fluid to be measured after it has passed the apex of the third reflecting portion 7, thereby preventing the occurrence of significant turbulence.

[0047] Furthermore, because the measurement flow path 1 is a two-dimensional flow path with a large aspect ratio (W / H), the dimension W can be made larger and the dimension H can be made smaller than when the aspect ratio is small. As a result, the dimension T of each of the first reflecting portion 6 and the third reflecting portion 7 is sufficiently small compared to the dimension W, so even if the first reflecting portion 6 and the third reflecting portion cause disturbances in the flow of the fluid to be measured, the influence of the disturbances on the overall flow is small. Furthermore, the dimension H of the short side SS1 on which the ultrasonic transmitters and receivers 4 and 5 are installed is reduced, making it easy to make the dimensions of the ultrasonic transmitters and receivers 4 and 5 larger than the dimension H.

[0048] Furthermore, when a thickness vibration type ultrasonic transmitter / receiver having a thickness vibration mode is adopted as the ultrasonic transmitter / receiver 4, 5, it becomes possible to transmit ultrasonic waves more uniformly to the fluid to be measured in the measurement flow path 1, thereby further improving the measurement accuracy.

[0049] Furthermore, by forming the ultrasonic propagation path 12 in an M-shape, it is possible to reduce the inclination angle θ1 of the first reflecting portion 6 and the third reflecting portion 7. This makes it possible to prevent large disturbances from occurring in the flow of the fluid to be measured, thereby reducing changes in the direction of the flow and stabilizing the flow.

[0050] In the above embodiment, the first ultrasonic transmitter / receiver 4 is arranged so that the direction of the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 4 is perpendicular to the extension direction of the measurement flow path 1, and the second ultrasonic transmitter / receiver 5 is arranged so that the direction of the ultrasonic waves reflected by the third reflecting unit 7 and received by the second ultrasonic transmitter / receiver 5 is perpendicular to the extension direction of the measurement flow path 1. However, this is not limited to this. The first ultrasonic transmitter / receiver 4 may be arranged so that the direction of the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 4 intersects the extension direction of the measurement flow path 1, and the second ultrasonic transmitter / receiver 5 may be arranged so that the direction of the ultrasonic waves reflected by the third reflecting unit 7 and received by the second ultrasonic transmitter / receiver 5 intersects the extension direction of the measurement flow path 1. In this case, for example, the ultrasonic transmitting / receiving surface US of the first ultrasonic transmitter / receiver 4 can be tilted slightly downstream, and the ultrasonic transmitting / receiving surface US of the second ultrasonic transmitter / receiver 5 can be tilted slightly upstream. This allows the inclination angle θ1 to be further reduced, thereby enabling the dimensions T of the first reflecting portion 6 and the third reflecting portion 7 to be further reduced. As a result, it is possible to further suppress turbulence in the flow of the fluid to be measured in the measurement flow path 1, thereby further improving the reliability of stabilizing the flow and improving the measurement accuracy. At the same time, it is possible to further reduce pressure loss in the flow direction.

[0051] In addition, in this embodiment, the first reflecting portion 6, the second reflecting portion 10, and the third reflecting portion 7 are provided as reflecting portions, but the present invention is not limited to this. The number of reflecting portions may be three or more, and may be, for example, five.

[0052] Second Embodiment A second embodiment will be described with reference to Figures 3 and 4. Figure 3 is a cross-sectional view showing the configuration of an ultrasonic flowmeter 150 in the second embodiment, and Figure 4 is a cross-sectional view taken along line D-D in Figure 3. Among the components of the ultrasonic flowmeter 150 of the second embodiment, the same components as those of the ultrasonic flowmeter 50 of the first embodiment are given the same reference numerals as in the first embodiment, and descriptions thereof will be omitted unless otherwise noted.

[0053] 3 and 4 , the ultrasonic flowmeter 150 of the second embodiment includes a measurement flow path forming unit 20, a first ultrasonic transmitter / receiver 4, a first reflecting unit 6, a second reflecting unit 10, a third reflecting unit 7, a second ultrasonic transmitter / receiver 5 (not shown), and a signal processing unit 11, similar to the ultrasonic flowmeter 50 of the first embodiment, and further includes a control board 13 and two deflection reflecting units 14 (deflection reflecting units 14a and 14b). The deflection reflecting unit 14a corresponds to the first deflection reflecting unit, and the deflection reflecting unit 14b corresponds to the second deflection reflecting unit. The measurement flow path 1 of the ultrasonic flowmeter 150 has an aspect ratio (W / H) of 3 or more to form a two-dimensional flow of the fluid to be measured within the cross section.

[0054] As in the first embodiment, measurement flow path forming section 20 has an inner surface B1 and an outer surface B3 associated with one short side SS1, and an inner surface B2 and an outer surface B4 associated with the other short side SS2. Also, as in the first embodiment, measurement flow path forming section 20 has an inner surface C1 and an outer surface C3 associated with one long side LS1, and an inner surface C2 and an outer surface C4 associated with the other long side LS2.

[0055] The present embodiment differs from the first embodiment in that the first ultrasonic transmitter / receiver 4 and the second ultrasonic transmitter / receiver 5 (not shown) are each disposed on an outer surface C3 of one of the long sides LS1. The second ultrasonic transmitter / receiver 5 is disposed at a distance from the first ultrasonic transmitter / receiver 4 in the extension direction of the measurement flow path 1.

[0056] 4, the first ultrasonic transmitter / receiver 4 and the second ultrasonic transmitter / receiver 5 are integrally mounted on a control board 13 on which a signal processing unit 11 is provided. In this manner, the first ultrasonic transmitter / receiver 4 and the second ultrasonic transmitter / receiver 5 are integrally mounted on the control board 13 arranged on one long side LS1 side where a relatively large space is available.

[0057] The deflecting reflectors 14a and 14b are formed in the shape of thin plates. The deflecting reflectors 14a and 14b are disposed in the measurement flow path 1. Specifically, the deflecting reflector 14a is disposed opposite the first ultrasonic transmitter / receiver 4, and the deflecting reflector 14b is disposed opposite the second ultrasonic transmitter / receiver 5. The deflecting reflector 14a has a reflecting surface 14c that reflects the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 4 toward the first reflecting unit 6. That is, the deflecting reflector 14a deflects the traveling direction of the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 4 by 90°. The deflecting reflector 14b has a reflecting surface 14c that reflects the ultrasonic waves reflected by the third reflecting unit 7 toward the second ultrasonic transmitter / receiver 5. That is, the deflecting reflector 14b deflects the traveling direction of the ultrasonic waves reflected by the third reflecting unit 7 by 90°.

[0058] The deflecting reflectors 14a, 14b are arranged in the measurement flow path 1 so that the main surfaces of the deflecting reflectors 14a, 14b are aligned along the flow direction of the fluid to be measured. Furthermore, in order to propagate ultrasonic waves over the entire area on the short sides SS1, SS2 sides, the dimensions of the deflecting reflectors 14a, 14b (dimensions in the direction of the short sides SS1, SS2) are set equal to the dimensions of the inner surfaces B1, B2. Furthermore, on the back surface 14d of each reflecting surface 14c, a back passage portion 15 is formed as a partial partition of the measurement flow path 1 to suppress a reduction in the cross-sectional area of ​​the measurement flow path 1 and reduce the effect on the flow of the fluid to be measured in the measurement flow path 1.

[0059] The ultrasonic propagation path 12 (dashed line shown in Figure 3) in the ultrasonic flowmeter 150 is a path that passes through the first ultrasonic transmitter / receiver 4, the deflection reflection unit 14a, the first reflection unit 6, the second reflection unit 10, the third reflection unit 7, and the deflection reflection unit 14b to the second ultrasonic transmitter / receiver 5, or a path that goes in the opposite direction.

[0060] In the above configuration, in the case where ultrasonic waves transmitted by the first ultrasonic transmitter / receiver 4 are received by the second ultrasonic transmitter / receiver 5, the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 4 have their traveling direction deflected by 90° by the deflecting reflector 14a and head towards the first reflector 6. The ultrasonic waves reflected by the first reflector 6 head towards the deflecting reflector 14b via the second reflector 10 and the third reflector 7. The ultrasonic waves reflected by the deflecting reflector 14b are then received by the second ultrasonic transmitter / receiver 5. The second ultrasonic transmitter / receiver 5 then receives an ultrasonic signal. On the other hand, in the case where ultrasonic waves transmitted by the second ultrasonic transmitter / receiver 5 are received by the first ultrasonic transmitter / receiver 4, the ultrasonic waves travel along a propagation path in the opposite direction to that described above. The signal processing unit 11 uses a pair of ultrasonic transmitter / receivers 4, 5 to measure the propagation time of ultrasonic waves in the ultrasonic propagation path 12 between the first ultrasonic transmitter / receiver 4 and the second ultrasonic transmitter / receiver 5, and calculates the flow velocity and flow rate of the measured fluid based on the propagation time using a known method.

[0061] As described above, according to the second embodiment, the first ultrasonic transmitter / receiver 4 and the second ultrasonic transmitter / receiver 5 are arranged on the outer surface C3 associated with one of the long and short sides LS1 of the rectangular cross section of the measurement flow path forming section 20, which allows a relatively large amount of space to be secured. This improves the degree of freedom in designing the control board 13 including the ultrasonic transmitters / receivers 4, 5 and the signal processing section 11. This simplifies the component configuration by integrating the ultrasonic transmitters / receivers 4, 5 with the control board 13, thereby realizing cost reductions, and also allows for a compact design by effectively utilizing space.

[0062] Furthermore, in this embodiment, the deflective reflectors 14a and 14b are arranged in the measurement flow path 1 so that the main surfaces of the deflective reflectors 14a and 14b are aligned along the flow direction of the fluid to be measured, and further, the back passage portion 15 is formed on the back surface 14d side of the reflecting surface 14c, so that the fluid to be measured can flow without stagnation in the measurement flow path 1 while suppressing a reduction in the cross-sectional area of ​​the measurement flow path 1. Furthermore, the deflective reflectors 14a and 14b effectively function as regulators that stabilize the flow direction of the fluid to be measured, so that it is possible to further suppress turbulence in the flow of the fluid to be measured.

[0063] Third Embodiment A third embodiment will be described with reference to Fig. 5. Fig. 5 is a cross-sectional view showing the configuration of an ultrasonic flowmeter 250 according to the third embodiment. Among the components of the ultrasonic flowmeter 250 according to the third embodiment, the same components as those of the ultrasonic flowmeter 50 according to the first embodiment are given the same reference numerals as those in the first embodiment, and descriptions thereof will be omitted unless otherwise noted.

[0064] 5, the ultrasonic flowmeter 250 of the third embodiment differs from the ultrasonic flowmeter 50 of the first embodiment in that it further includes a diffuse reflection portion 21. The diffuse reflection portion 21 is located between the first reflection portion 6 and the third reflection portion 7 in the extension direction of the measurement flow path 1, and is provided on the inner surface B2 associated with the other short side SS2 of the rectangular cross section of the measurement flow path forming portion 20. The diffuse reflection portion 21 may be located, for example, at a central position between the first reflection portion 6 and the third reflection portion 7 in the extension direction of the measurement flow path 1, facing the second reflection portion 10.

[0065] An example of the configuration of the diffuse reflection unit 21 is as follows. For example, the diffuse reflection unit 21 is formed by forming the inner surface B2 of the measurement flow path forming unit 20 unevenly in the thickness direction of the measurement flow path forming unit 20. In this case, the depth of the diffuse reflection unit 21 (i.e., the depth dimension in the thickness direction based on the inner surface B2 where the diffuse reflection unit 21 is not provided) may be approximately the same as the wavelength of the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 4 (or the second ultrasonic transmitter / receiver 5). Alternatively, the diffuse reflection unit 21 may be formed by dispersing a plurality of granular bodies having a diameter approximately the same as the wavelength of the ultrasonic waves in a recess formed by scraping the inner surface B2 of the measurement flow path forming unit 20 in the thickness direction of the measurement flow path forming unit 20. However, the configuration of the diffuse reflection unit 21 is not limited to the above. For example, the diffuse reflection unit 21 may be formed by dispersing a plurality of granular bodies having a diameter approximately the same as the wavelength of the ultrasonic waves in a recess formed by scraping the inner surface B2 of the measurement flow path forming unit 20 in the thickness direction of the measurement flow path forming unit 20.

[0066] In the ultrasonic flowmeter 250 of this embodiment, among the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 4 (or the ultrasonic waves transmitted from the second ultrasonic transmitter / receiver 5), those that do not pass through the first reflecting unit 6 (or the third reflecting unit 7) are diffusely reflected by the diffuse reflecting unit 21. This makes it possible to prevent the ultrasonic waves (ultrasonic waves indicated by the dashed dotted line in FIG. 5) that do not pass through the first reflecting unit 6 (or the third reflecting unit 7) from being received by the second ultrasonic transmitter / receiver 5 (or the first ultrasonic transmitter / receiver 4). Therefore, in a configuration in which the ultrasonic propagation path is M-shaped (M-path configuration), it is possible to suppress the reception of unnecessary ultrasonic waves.

[0067] The diffuse reflection portion 21 may be provided not only in the measurement flow path forming portion 20 having a rectangular cross section, but also in a measurement flow path forming portion having, for example, a circular cross section or an elliptical cross section. In this case, the same effect is achieved. Furthermore, the diffuse reflection portion 21 may be provided in the ultrasonic flowmeter 150 of the second embodiment and the ultrasonic flowmeter 350 of the fourth embodiment described below, as described above.

[0068] (Fourth embodiment) A fourth embodiment will be described with reference to Fig. 6. Fig. 6 is a cross-sectional view showing the configuration of an ultrasonic flowmeter 350 according to the fourth embodiment. Among the components of the ultrasonic flowmeter 350 according to the fourth embodiment, the same components as those of the ultrasonic flowmeter 50 according to the first embodiment are given the same reference numerals as those in the first embodiment, and descriptions thereof will be omitted unless otherwise noted.

[0069] 6 , an ultrasonic flowmeter 350 of the fourth embodiment differs from the ultrasonic flowmeter 50 of the first embodiment in that the first reflecting portion 6 further includes a first converging-reflecting surface 31, and the third reflecting portion 7 further includes a second converging-reflecting surface 33. In this embodiment, the first converging-reflecting surface 31 is provided on the first reflecting portion 6, and the second converging-reflecting surface 33 is provided on the third reflecting portion 7, but this is not limitative. The first converging-reflecting surface 31 may be provided on a component separate from the first reflecting portion 6, and the second converging-reflecting surface 33 may be provided on a component separate from the third reflecting portion 7.

[0070] The first converging-reflecting surface 31 of the first reflecting unit 6 is arranged so as to overlap at least a portion of the reflecting surface 8 in the extension direction of the measurement flow path 1. At least a portion of the first converging-reflecting surface 31 is located upstream of a vertical line extending in the up-down direction with the first ultrasonic transmitter / receiver 4 as the base point. The inclination angle of the first converging-reflecting surface 31 with respect to the extension direction is larger than the above-mentioned inclination angle θ1. Although not shown, the first reflecting unit 6 may have another converging-reflecting surface, at least a portion of which is located downstream of the above-mentioned vertical line. The inclination angle of the other converging-reflecting surface with respect to the extension direction is smaller than the above-mentioned inclination angle θ1.

[0071] Similar to the first converging-reflecting surface 31, the second converging-reflecting surface 33 of the third reflecting unit 7 is disposed so as to overlap at least a portion of the reflecting surface 9 in the extension direction of the measurement flow path 1. At least a portion of the second converging-reflecting surface 33 is located downstream of a vertical line extending in the up-down direction with the second ultrasonic transmitter / receiver 5 as the base point. The inclination angle of the second converging-reflecting surface 33 with respect to the extension direction is larger than the inclination angle θ1 described above. Although not shown, the third reflecting unit 7 may have another converging-reflecting surface, at least a portion of which is located upstream of the vertical line. The inclination angle of the another converging-reflecting surface with respect to the extension direction is smaller than the inclination angle θ1 described above.

[0072] In the ultrasonic flowmeter 350 of this embodiment, some of the ultrasonic waves (ultrasonic waves indicated by dashed lines in FIG. 6 ) transmitted from the first ultrasonic transmitter / receiver 4 (or ultrasonic waves transmitted from the second ultrasonic transmitter / receiver 5) can be reflected by the first converging reflecting surface 31 (or the second converging reflecting surface 33) so as to converge toward the second reflecting section 10. This makes it possible to increase the signal strength of the ultrasonic waves received by the second ultrasonic transmitter / receiver 5 (or the first ultrasonic transmitter / receiver 4).

[0073] The first converging-reflecting surface 31 and the second converging-reflecting surface 33 may be provided not only on the measurement flow-path forming portion 20 having a rectangular cross section, but also on a measurement flow-path forming portion having, for example, a circular cross section or an elliptical cross section. In this case, the same effect is achieved. Furthermore, the first converging-reflecting surface 31 and the second converging-reflecting surface 33 may be provided in the ultrasonic flowmeter 150 of the second embodiment and the ultrasonic flowmeter 250 of the third embodiment, as described above.

[0074] (Additional Notes) The following techniques are disclosed by the above description of the embodiments.

[0075] (Technology 1) An ultrasonic flow meter comprising: a measurement flow path forming section that forms a measurement flow path through which a fluid to be measured flows from upstream to downstream and that has a rectangular cross section; a first ultrasonic transmitter / receiver that is arranged on an outer surface related to one short side of the rectangular cross section and includes an ultrasonic transmitting / receiving surface having dimensions equal to or larger than the dimensions of the inner surface related to the one short side, and that transmits and receives ultrasonic waves; three or more reflecting sections that are arranged in the measurement flow path and reflect ultrasonic waves from the first ultrasonic transmitter / receiver in the measurement flow path; and a second ultrasonic transmitter / receiver that is arranged on the outer surface related to the one short side and downstream of the first ultrasonic transmitter / receiver in the extension direction of the measurement flow path, and includes an ultrasonic transmitting / receiving surface having dimensions equal to or larger than the dimensions of the inner surface related to the one short side, and that receives ultrasonic waves reflected by the three or more reflecting sections and transmits ultrasonic waves.

[0076] (Technology 2) The reflecting section is an ultrasonic flowmeter described in Technology 1, including: a first reflecting section that is arranged on an inner surface related to the other short side of the rectangular cross section so as to face the first ultrasonic transmitter / receiver and reflects ultrasonic waves from the first ultrasonic transmitter / receiver toward one of the short sides; a second reflecting section that is arranged on the inner surface related to the one short side and downstream of the first reflecting section and reflects ultrasonic waves reflected by the first reflecting section toward the other short side; and a third reflecting section that is arranged on the inner surface related to the other short side and downstream of the second reflecting section and reflects ultrasonic waves reflected by the second reflecting section toward the one short side.

[0077] (Technology 3) The ultrasonic flowmeter according to Technology 1 or 2, wherein the first ultrasonic transducer and the second ultrasonic transducer are thickness vibration type ultrasonic transducers.

[0078] (Technology 4) The ultrasonic flowmeter according to Technology 1 or 2, wherein the first ultrasonic transmitter / receiver and the second ultrasonic transmitter / receiver transmit or receive ultrasonic waves in a direction perpendicular to the measurement flow path.

[0079] (Technology 5) An ultrasonic flowmeter according to any one of technologies 2 to 4, further comprising a diffuse reflection portion located between the first reflection portion and the third reflection portion in the extension direction and provided on the inner surface relating to the other short side of the rectangular cross section.

[0080] (Technology 6) An ultrasonic flowmeter described in any one of technologies 2 to 5, wherein the first reflecting portion has a first converging reflecting surface that reflects ultrasonic waves from the first ultrasonic transmitter / receiver so as to converge toward the second reflecting portion, and the third reflecting portion has a second converging reflecting surface that reflects ultrasonic waves from the second ultrasonic transmitter / receiver so as to converge toward the second reflecting portion.

[0081] (Technology 7) A measurement flow path forming section having a rectangular cross section that forms a measurement flow path through which a fluid to be measured flows from upstream to downstream, a first ultrasonic transmitter-receiver that is disposed on one of the short sides of the rectangular cross section and on an outer surface related to one long side of the rectangular cross section, and transmits and receives ultrasonic waves, a first deflection reflection section that deflects and reflects ultrasonic waves from the first ultrasonic transmitter-receiver toward the other short side, a first reflection section that is disposed on an inner surface related to the other short side and reflects ultrasonic waves reflected by the first deflection reflection section toward one of the short sides, and a second reflection section that is disposed on an inner surface related to the one short side and reflects the ultrasonic waves reflected by the first deflection reflection section toward the one short side. a second reflecting section arranged downstream of a reflecting section and reflecting the ultrasonic waves reflected by the first reflecting section toward the other short side; a third reflecting section arranged on an inner surface related to the other short side and downstream of the second reflecting section and reflecting the ultrasonic waves reflected by the second reflecting section toward the one short side; a second deflection-reflection section that deflects and reflects the ultrasonic waves from the third reflecting section; and a second ultrasonic transmitter / receiver arranged on the one short side and on an outer surface related to the one long side and receiving the ultrasonic waves reflected by the second deflection-reflection section and transmitting ultrasonic waves.

[0082] (Technology 8) The ultrasonic flowmeter according to Technology 7, wherein the first ultrasonic transducer and the second ultrasonic transducer are thickness vibration type ultrasonic transducers.

[0083] (Technology 9) An ultrasonic flowmeter described in Technology 7 or 8, wherein the first deflection reflection unit deflects the ultrasonic waves from the first ultrasonic transmitter / receiver by 90° in the direction of travel of the ultrasonic waves and reflects them toward the first reflection unit, and the second deflection reflection unit deflects the ultrasonic waves from the third reflection unit by 90° in the direction of travel of the ultrasonic waves and reflects them toward the second ultrasonic transmitter / receiver.

[0084] (Technology 10) An ultrasonic flowmeter described in any one of technologies 7 to 9, further comprising a diffuse reflection portion located between the first reflection portion and the third reflection portion in the extension direction and provided on the inner surface relating to the other short side of the rectangular cross section.

[0085] (Technology 11) An ultrasonic flowmeter described in any one of Technologies 7 to 10, wherein the first reflecting portion has a first converging reflecting surface that reflects ultrasonic waves from the first ultrasonic transmitter / receiver so as to converge toward the second reflecting portion, and the third reflecting portion has a second converging reflecting surface that reflects ultrasonic waves from the second ultrasonic transmitter / receiver so as to converge toward the second reflecting portion.

[0086] 1 Measurement flow path 2 Inlet of measurement flow path 3 Outlet of measurement flow path 4 First ultrasonic transducer 5 Second ultrasonic transducer 6 First reflecting section 6a Upstream surface 7 Third reflecting section 7a Downstream surface 8, 9 Reflecting surface 10 Second reflecting section 11 Signal processing section 12 Ultrasonic propagation path 13 Control board 14, 14a, 14b Deflecting reflecting section 14c Reflecting surface 14d Back surface 15 Back passage section 20 Measurement flow path forming section 21 Diffuse reflecting section 31 First converging reflecting surface 33 Second converging reflecting surface 50, 150 Ultrasonic flowmeter B1 Inner surface relating to one short side B2 Inner surface relating to the other short side B3 Outer surface relating to one short side B4 Outer surface relating to the other short side C1 Inner surface relating to one long side C2 Inner surface relating to the other long side C3 Outer surface relating to one long side C4 Outer surface related to the other long side LS1 One long side LS2 The other long side SS1 One short side SS2 The other short side US Ultrasonic wave transmitting and receiving surface

Claims

1. An ultrasonic flow meter comprising: a measurement flow path forming section which forms a measurement flow path through which a fluid to be measured flows from upstream to downstream and which has a rectangular cross-section; a first ultrasonic transmitter / receiver which is arranged on an outer surface relating to one of the short sides of the rectangular cross-section and which includes an ultrasonic transmitting / receiving surface having a dimension equal to or greater than the dimension of the inner surface relating to the one short side, and which transmits and receives ultrasonic waves; three or more reflecting sections which are arranged in the measurement flow path and which reflect ultrasonic waves from the first ultrasonic transmitter / receiver in the measurement flow path; and a second ultrasonic transmitter / receiver which is arranged on the outer surface relating to the one short side and which is arranged downstream of the first ultrasonic transmitter / receiver in the extension direction of the measurement flow path, and which includes an ultrasonic transmitting / receiving surface having a dimension equal to or greater than the dimension of the inner surface relating to the one short side, and which receives ultrasonic waves reflected by the three or more reflecting sections and transmits ultrasonic waves.

2. The ultrasonic flowmeter of claim 1, wherein the reflecting section includes: a first reflecting section that is arranged on the inner surface related to the other short side of the rectangular cross section so as to face the first ultrasonic transmitter / receiver and reflects ultrasonic waves from the first ultrasonic transmitter / receiver toward the one short side; a second reflecting section that is arranged on the inner surface related to the one short side and downstream of the first reflecting section and reflects ultrasonic waves reflected by the first reflecting section toward the other short side; and a third reflecting section that is arranged on the inner surface related to the other short side and downstream of the second reflecting section and reflects ultrasonic waves reflected by the second reflecting section toward the one short side.

3. The ultrasonic flowmeter according to claim 1 or 2, wherein the first ultrasonic transmitter / receiver and the second ultrasonic transmitter / receiver are thickness vibration type ultrasonic transmitter / receivers.

4. An ultrasonic flowmeter according to claim 1 or 2, wherein the first ultrasonic transmitter / receiver and the second ultrasonic transmitter / receiver transmit or receive ultrasonic waves in a direction perpendicular to the measurement flow path.

5. An ultrasonic flowmeter as described in claim 2, further comprising a diffuse reflection portion located between the first reflection portion and the third reflection portion in the extension direction and provided on the inner surface relating to the other short side of the rectangular cross section.

6. An ultrasonic flowmeter as described in claim 2, wherein the first reflecting portion has a first converging reflecting surface that reflects ultrasonic waves from the first ultrasonic transmitter / receiver so as to converge toward the second reflecting portion, and the third reflecting portion has a second converging reflecting surface that reflects ultrasonic waves from the second ultrasonic transmitter / receiver so as to converge toward the second reflecting portion.

7. A measurement flow path forming section having a rectangular cross section and forming a measurement flow path through which a fluid to be measured flows from upstream to downstream; a first ultrasonic transmitter / receiver arranged on one of the short sides of the rectangular cross section and on the outer surface related to one of the long sides of the rectangular cross section, transmitting and receiving ultrasonic waves; a first deflection reflection section that deflects and reflects ultrasonic waves from the first ultrasonic transmitter / receiver toward the other short side; a first reflection section that is arranged on the inner surface related to the other short side and downstream of the first reflection section, reflecting ultrasonic waves reflected by the first deflection reflection section toward the one short side; a second reflection section that is arranged on the inner surface related to the one short side and downstream of the first reflection section, reflecting ultrasonic waves reflected by the first reflection section toward the other short side; a third reflection section that is arranged on the inner surface related to the other short side and downstream of the second reflection section, reflecting ultrasonic waves reflected by the second reflection section toward the one short side; and a second deflection reflection section that deflects and reflects ultrasonic waves from the third reflection section. an ultrasonic flowmeter comprising: a second ultrasonic transmitter / receiver arranged on the side of the one short side and on an outer surface related to the one long side, receiving ultrasonic waves reflected by the second deflection reflection portion and transmitting ultrasonic waves.

8. The ultrasonic flowmeter according to claim 7, wherein the first ultrasonic transducer and the second ultrasonic transducer are each a thickness vibration type ultrasonic transducer.

9. An ultrasonic flowmeter as described in claim 7 or 8, wherein the first deflection reflection unit reflects ultrasonic waves from the first ultrasonic transmitter / receiver toward the first reflection unit by deflecting the direction of travel of the ultrasonic waves by 90 degrees, and the second deflection reflection unit reflects ultrasonic waves from the third reflection unit toward the second ultrasonic transmitter / receiver by deflecting the direction of travel of the ultrasonic waves by 90 degrees.

10. An ultrasonic flowmeter as described in claim 7, further comprising a diffuse reflection portion located between the first reflection portion and the third reflection portion in the extension direction and provided on the inner surface relating to the other short side of the rectangular cross section.

11. An ultrasonic flowmeter as described in claim 7, wherein the first reflecting portion has a first converging reflecting surface that reflects ultrasonic waves from the first ultrasonic transmitter / receiver so as to converge toward the second reflecting portion, and the third reflecting portion has a second converging reflecting surface that reflects ultrasonic waves from the second ultrasonic transmitter / receiver so as to converge toward the second reflecting portion.

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