JP7507657B2 - Ultrasonic Flow Meter - Google Patents

Description

The present invention relates to an ultrasonic flow meter.

In general, periodic and regular pressure fluctuations are likely to occur in gas piping due to the usage state of gas appliances such as gas heat pump air conditioners, or due to pressure fluctuations on the gas supply side, and flow speed changes are likely to occur in the forward and reverse flow directions. Ultrasonic flowmeters calculate the flow volume passing through based on the instantaneous flow speed measured at a constant cycle. For this reason, when gas is not used or when used in a low flow rate range, if the flow speed changes as described above become large, the error in the gas usage amount will increase due to the variation in the measured flow rate, which may result in unfair results in the gas fee charged, so an ultrasonic flowmeter with small variation in the measured flow rate is required.
Conventionally, there has been an ultrasonic flow meter in which, for example, gas flowing in from the inlet 12 passes through the passage hole 36b of the straightening plate 36 via the shut-off valve 34, flows into and passes through the measuring tube 40, and then flows out from the outlet 14 via the passage hole 38b of the straightening plate 38 (see Patent Document 1).

JP 2009-186429 A

However, in the ultrasonic flowmeter, the straightening plate 36 having the passage hole 36b for obtaining the orifice effect and the straightening plate 38 having the passage hole 38b are separate from the gas meter 10, which poses the problem of a large number of parts and assembly steps.
In view of the above problems, an object of the present invention is to provide an ultrasonic flowmeter having a reduced number of parts and assembly steps.

In order to solve the above problems, the ultrasonic flowmeter according to the present invention comprises:
Case and
an inlet buffer portion which is a partitioned space on the upstream side of the case;
an outlet buffer portion which is a space partitioned on the downstream side within the case;
a measuring unit that is housed in the case and has a cylindrical body having an inlet portion that communicates with the inlet buffer portion and an outlet portion that communicates with the outlet buffer portion,
an ultrasonic flowmeter for measuring a flow rate of gas passing through the measuring unit, the gas flowing in from an inlet communicating with an inlet portion of the case, flowing in from an inlet portion of the measuring unit communicating with the inlet buffer portion, circulating through a flow passage in the measuring unit, and flowing out from an outlet portion via an outlet buffer portion communicating with the outlet portion,
an inlet flow passage portion separated from the inlet buffer portion by a partition wall protruding from an inner surface of the case, and through which gas flowing in from the inlet flows downstream;
a central space portion disposed between the inlet buffer portion and the outlet buffer portion and configured to accommodate the measuring unit;
the central space formed between the inlet buffer and the outlet buffer is in communication with the inlet flow path,
The gas that flows in through the inlet and flows down to the downstream side of the inlet flow passage section flows into the inlet buffer section through an inlet communication hole provided in the partition wall.

According to the present invention, since the partition wall having the inlet communication hole is provided on the inner surface of the case to protrude therefrom, an ultrasonic flowmeter having a reduced number of parts and assembly steps can be obtained.
Furthermore, the gas retained in the central space acts as a sort of cushion to absorb and mitigate the pulsation of the inflowing gas, thereby making it possible to reduce variations in the measured flow rate.

In an embodiment of the present invention, the inlet communication hole may be disposed on the inside of the inlet portion of the measurement unit.
According to this embodiment, the creeping distance along which the gas flows is increased, and gas pulsation can be reduced, so that an ultrasonic flowmeter with small variation in the measured flow rate can be obtained.

In another embodiment of the present invention, an inlet buffer partition wall separating the inlet buffer from the central space may be provided with a notch that allows liquid that has flowed into the inlet buffer to flow out into the central space.
According to this embodiment, even if a large amount of liquid enters the inlet buffer together with the gas, the liquid can be stored at the bottom of the central space, preventing the liquid from entering the measurement unit and preventing the variation in the measured flow rate from increasing.

In another embodiment of the present invention, a partition wall having an outlet communication hole may be provided on the inward surface of the case between the outlet buffer portion and the outlet portion of the case to protrude therefrom.
According to this embodiment, an ultrasonic flowmeter with a small number of parts and assembly steps can be obtained.

In another embodiment of the present invention, the outlet buffer portion may be in direct communication with the outlet portion of the case.
According to this embodiment, so-called gas escape is improved, and pressure loss can be reduced.

In another embodiment of the present invention, the outlet buffer portion may be formed so that the cross-sectional area increases toward the downstream side.
According to this embodiment, so-called gas escape is further improved, and pressure loss can be further reduced.

In another embodiment of the present invention, at least one of the opening edge of the inlet portion and the opening edge of the outlet portion of the cylindrical body of the measurement unit may be disposed flush with the outward surface of the buffer portion.
According to this embodiment, the outward surface of the buffer section is flush with the opening edge of the inlet section and/or the opening edge of the outlet section of the measuring unit, which facilitates the inflow and outflow of gas, reduces pressure loss, and reduces variation in the measured flow rate.

In another embodiment of the present invention, a shielding plate may be provided on the inward surface of the case, and positioned between the inlet port and the inlet communication hole.
According to this embodiment, the gas flowing in from the inlet collides with the shielding plate and is detouring, which increases the creepage distance and absorbs and reduces gas pulsation, thereby reducing variation in the measured flow rate.

As a new embodiment of the present invention, at least one of the side walls that form the front and back surfaces of the case and face each other across the central space may be provided with a bulge that bulges outward.

According to this embodiment, the volume of the central space is increased, which has the effect of increasing the amount of fluid that can be stored.

1 is an overall perspective view of an ultrasonic flowmeter according to a first embodiment; FIG. 2 is an overall perspective view of the ultrasonic flowmeter shown in FIG. 1 as viewed from a different angle. 2 is a perspective view showing a state in which a cover is removed from the ultrasonic flowmeter shown in FIG. 1. 2 is a perspective view of the cover shown in FIG. 1 as seen from the rear side. FIG. 2 is a perspective view of a case body shown in FIG. 1 . FIG. 2 is a vertical sectional perspective view of the ultrasonic flowmeter shown in FIG. 1 . FIG. 2 is a cross-sectional view of the ultrasonic flowmeter shown in FIG. 1 . 2 is another cross-sectional view of the ultrasonic flowmeter shown in FIG. 1. FIG. 2 is a vertical sectional perspective view of the measurement unit shown in FIG. 1 . 2 is a right side vertical cross-sectional view of the measurement unit shown in FIG. 1 . FIG. 11 is a partial cross-sectional view of the measurement unit shown in FIG. 10 . FIG. 11 is a perspective view showing a state in which a cover body is removed from an ultrasonic flowmeter according to a second embodiment. FIG. 11 is a perspective view of a cover of the ultrasonic flowmeter according to the second embodiment, as viewed from the rear side. FIG. 13 is a perspective view of the case body shown in FIG. 12 . FIG. 11 is a vertical sectional perspective view of an ultrasonic flowmeter according to a second embodiment. FIG. 11 is a perspective view showing a state in which a cover body is removed from an ultrasonic flowmeter according to a third embodiment. FIG. 17 is a perspective view of the case body shown in FIG. 16 . FIG. 11 is an overall perspective view of an ultrasonic flowmeter according to a fourth embodiment. FIG. 19 is an overall perspective view of the ultrasonic flowmeter shown in FIG. 18 as viewed from a different angle. 19 is a perspective view showing a state in which a cover body is removed from the ultrasonic flowmeter shown in FIG. 18. FIG. 19 is a perspective view of the case body shown in FIG. 18 . FIG. 19 is a vertical cross-sectional view of the ultrasonic flowmeter shown in FIG. 18. FIG. 19 is a cross-sectional view of the ultrasonic flowmeter shown in FIG. 18. FIG. 13 is an overall perspective view of an ultrasonic flowmeter according to a fifth embodiment. FIG. 25 is an overall perspective view of the ultrasonic flowmeter shown in FIG. 24 as viewed from a different angle. 25 is an overall perspective view showing a state in which a cover body is removed from the ultrasonic flowmeter shown in FIG. 24. 25 is a perspective view of the cover shown in FIG. 24 as seen from the rear side. FIG. 27 is an overall perspective view showing a state in which a gasket is removed from the ultrasonic flowmeter shown in FIG. 26. FIG. 25 is a perspective view of the case body shown in FIG. 24 . FIG. 25 is a vertical cross-sectional view of the ultrasonic flowmeter shown in FIG. 24. 25 is a central vertical cross-sectional view of the ultrasonic flowmeter shown in FIG. 24. FIG. 25 is a front vertical cross-sectional view of the ultrasonic flowmeter shown in FIG. 24. FIG. 11 is a bar graph showing the results of Example 1 in which the flow rate of the ultrasonic flowmeter according to the first embodiment was obtained by calculation. FIG. 1 is a graph showing the results of Example 1 in which the pressure loss of the ultrasonic flowmeter according to the first embodiment was calculated. FIG. 11 is a bar graph showing the results of Example 2 in which the flow rate of the ultrasonic flowmeter according to the second embodiment was calculated. FIG. 13 is a bar graph showing the results of Example 3 in which the flow rate of the ultrasonic flowmeter according to the third embodiment was obtained by calculation. FIG. 11 is a graph showing the results of Examples 2 and 3 in which the pressure losses of the ultrasonic flowmeters according to the second and third embodiments were calculated. FIG. 13 is a bar graph showing the results of Example 4 in which the flow rate of the ultrasonic flowmeter according to the fourth embodiment was obtained by calculation. FIG. 13 is a graph showing the results of Example 4 in which the pressure loss of the ultrasonic flowmeter according to the fourth embodiment was calculated. FIG. 13 is a bar graph showing the results of Example 5 in which the flow rate of the ultrasonic flowmeter according to the fifth embodiment was calculated. FIG. 13 is a graph showing the results of Example 5 in which the pressure loss of the ultrasonic flowmeter according to the fifth embodiment was calculated. FIG. 11 is a bar graph showing the results of calculating the flow rate of the ultrasonic flowmeter according to the comparative example. FIG. 13 is a graph showing the results of Examples 6 and 7 in which pressure fluctuations that differ depending on the frequency of the first and fourth embodiments are measured, respectively. FIG. 13 is a graph showing the results of Example 8 in which pressure fluctuations that differ depending on the frequency of the fifth embodiment are measured. FIG. 13 is a trajectory diagram of Example 9 in which the flow of gas according to the first embodiment is visualized. FIG. 13 is a trajectory diagram of Example 10 in which the flow of gas according to the third embodiment is visualized.

An ultrasonic flowmeter according to a first embodiment of the present invention will be described with reference to the accompanying drawings shown in FIGS.
The ultrasonic flowmeter according to the first embodiment is generally composed of a case 10, a shutoff valve 40, and a measurement unit 50.

The case 10 is formed from a metal material such as aluminum or an aluminum alloy, and as shown in Figures 1 and 2, is box-shaped with an inlet portion 11 located at one end of the upper surface and an outlet portion 12 located at the other end.
The case 10 is composed of a case body 20 and a lid 30. A shutoff valve 40 having a valve body 41 is disposed in an inlet 13 (see FIG. 6) located at the lower end of the inlet portion 11 in order to prevent gas from flowing into the internal space of the case 10 in the event of an abnormality.

As shown in FIG. 5, the internal space of the case body 20 is divided into three spaces on the left and right by an outlet flow path partition wall 21 and an outlet buffer partition wall 22 that protrude vertically and continuously, and an inlet flow path partition wall 23 and an inlet buffer partition wall 24 that protrude vertically and continuously. In particular, an inlet side space portion 10a is located on the right side of the case body 20, an outlet side space portion 10b is located on the left side of the case body 20, and a central space portion 10c is located in the center of the case body 20.

The inlet side space 10a is divided into two sections, the inlet flow passage section 14 and the inlet buffer section 16, by a horizontally extending first partition wall 25 that is integrally protruded from the case body 20. An inlet communication hole 25a is formed in the first partition wall 25. By providing the inlet communication hole 25a, an approximately orifice structure is formed, and an ultrasonic flowmeter is obtained that can prevent erroneous measurement by the measurement unit due to pressure fluctuations. In addition, the inlet communication hole 25a is positioned inside the inlet section 52a of the measurement unit 50 described later, and the creepage distance is long.

As shown in FIG. 5, the inlet buffer partition wall 24 is provided with an engagement receiving portion 24a for supporting the measuring unit 50 described below. Furthermore, the inlet buffer partition wall 24 is provided with a notch portion 24b for guiding liquid that flows in at the same time as the gas from the inlet buffer 16 to the central space 10c (FIG. 6). Therefore, even if a large amount of liquid flows into the inlet side space 10a, the liquid can be prevented from entering the measuring unit 50 by collecting the liquid on the bottom surface of the inlet buffer 16 and the central space 10c.

3, the outlet side space 10b is divided into upper and lower two sections, an outlet buffer section 17 and an outlet flow path section 18, by a horizontally extending second partition wall 26 which is integrally provided to protrude from the case body 20. An outlet communication hole 26a for allowing gas to flow out is provided in the second partition wall 26. By providing the outlet communication hole 26a, a substantial orifice structure is formed, and an ultrasonic flowmeter capable of preventing erroneous measurement by the measuring unit due to pressure fluctuations is obtained.
In addition, the outlet communication hole 26a is disposed inside an outlet portion 52b of a measuring unit 50, which will be described later, and the creepage distance is long.

As shown in FIG. 5, a third partition wall 27 is horizontally protruded from the central space 10c so as to bridge the outlet buffer partition wall 22 and the inlet buffer partition wall 24, forming a water collection space 10d that communicates with the inlet buffer section 16 via the cutout portion 24b. In addition, an engagement receiving portion 22a is provided on the outlet buffer partition wall 22 to support the measuring unit 50 described later.

As shown in FIG. 4, the cover 30 has a front shape capable of covering the opening of the case body 20. On the inner surface of the cover 30, the outlet flow path partition wall 31 and the outlet buffer partition wall 32, the inlet flow path partition wall 33 and the inlet buffer partition wall 34, the first partition wall 35, the second partition wall 36 and the third partition wall 37 are respectively protruding at positions that butt against the outlet flow path partition wall 21 and the outlet buffer partition wall 22, the inlet flow path partition wall 23 and the inlet buffer partition wall 24, the first partition wall 25, the second partition wall 26 and the third partition wall 27. Furthermore, the first partition wall 35 is formed with an inlet communication hole 35a. Also, the second partition wall 36 is formed with an outlet communication hole 36a.

As shown in FIG. 9, the measurement unit 50 is composed of a cylindrical body 51 having a generally rectangular cross section and an inlet portion 52a and an outlet portion 52b at both ends, and a measurement circuit section 53 located in the center of the upper surface of the cylindrical body 51.

As shown in Figures 10 and 11, the cylinder 51 has five flow straightening plates 56a, 56b, 56c, 56d, and 56e arranged at equal intervals in the center of the flow passage inside the cylinder 51, forming six layers of measurement flow passages 57a, 57b, 57c, 57d, 57e, and 57f. In addition, the cylinder 51 has two pairs of annular ribs 58a, 58b formed on its outer surface to prevent the O-ring 59 from coming off (Figure 9). Furthermore, a reinforcing rib 58c is protruded from the outer surface of the cylinder 51 (see Figure 3).

As shown in FIG. 9, the measurement circuit section 53 is composed of a pair of ultrasonic transducers 54a, 54b arranged in an approximately V-shape, and a control circuit board 55 arranged above the ultrasonic transducers 54a, 54b.
Then, the propagation time is measured for the ultrasonic wave emitted from one ultrasonic transducer 54a to pass through the measurement flow paths 57a to 57f formed between the flow straightening plates 56a, 56b, 56c, 56d, and 56e, to be reflected, and to be received by the other ultrasonic transducer 54b. Also, the propagation time is measured for the ultrasonic wave emitted from the other ultrasonic transducer 54b to pass through the measurement flow paths 57a to 57f formed between the flow straightening plates 56a, 56b, 56c, 56d, and 56e, to be reflected, and to be received by the one ultrasonic transducer 54a. From the difference between these propagation times, the flow velocity of the gas in each of the measurement flow paths 57a to 57f is detected, and the flow rate of the gas passing through each of the measurement flow paths 57a to 57f is calculated.

3, one O-ring 59 is engaged with the engagement receiving portion 24a of the inlet buffer partition wall 24 to position the measurement unit 50. The remaining O-ring 59 is engaged with the engagement receiving portion 22a of the outlet buffer partition wall 22 of the case body 20 to position the measurement unit 50. The O-rings 59 are then sandwiched between the inlet buffer partition wall 24 of the case body 20 and the inlet buffer partition wall 34 of the lid body 30. When the attachment of the lid body 30 to the case body 20 is completed, the inlet communication holes 25a and 35a are formed (see FIG. 7). As a result, the inlet portion 52a of the measurement unit 50 is positioned in the inlet buffer 16 as shown in FIG. 8. The outlet portion 52b of the measurement unit 50 is positioned in the outlet buffer 17. The measurement circuit portion 53 of the measurement unit 50 is then disposed in the central space portion 10c.
For ease of explanation, the case 10 is not shown with a structure for pulling out a connection wire connected to the measuring unit 50 and/or a structure for leading a portion of the gas to the outside in order to measure the gas pressure, but it goes without saying that these may be provided as appropriate if necessary.

Next, a method for measuring the flow rate of a gas will be described.
As shown in Fig. 3, by driving the valve body 41 of the shutoff valve 40 to open the inlet 13, the gas flowing in from the inlet 11 flows from the inlet 13 into the inlet flow passage 14 of the inlet side space 10a. Then, the gas flowing in from the inlet communication hole 25a of the first partition wall 25 flows into the inlet buffer 16. The gas flowing in the inlet buffer 16 flows into the cylindrical body 51 from the trumpet-shaped inlet 52a of the measurement unit 50. Furthermore, the gas that passes through the measurement flow passages 57a to 57f while being rectified along the five rectifying plates 56a to 56e has its propagation time measured via ultrasonic waves emitted by a pair of ultrasonic transducers 54a and 54b. Based on the measured propagation time, a central processing unit (CPU) mounted on the control circuit board 55 calculates the flow rate of the gas that has passed through. Next, the gas that has passed through each measurement flow path 57a to 57f flows out from the outlet portion 52b of the cylindrical body 51 to the outlet buffer portion 17, passes through the outlet communication hole 26a provided in the second partition wall 26 and flows into the outlet flow path portion 18, and then flows out to the outside from the outflow portion 12.

As shown in Figures 12 to 15, the second embodiment is almost similar to the first embodiment described above, except that an outlet buffer portion 17 which becomes the outlet side space portion 10b is formed by an outlet flow path partition wall 21 and an outlet buffer partition wall 22 which are arranged above and below within a case body 20.
14, the outlet flow path partition wall 21 is inclined so that the cross-sectional area of the outlet buffer 17 increases downstream. The outlet buffer partition wall 22 is provided with an engagement receiving portion 22a for supporting an outlet portion 52b of a measuring unit 50, which will be described later.

Furthermore, as shown in FIG. 13, the cover 30 of the second embodiment has a front shape capable of covering the opening of the case body 20. On the inner surface of the cover 30, the outlet flow path partition wall 31 and the outlet buffer partition wall 32, the inlet flow path partition wall 33 and the inlet buffer partition wall 34, the first partition wall 35 and the third partition wall 37 are respectively protruding at positions that abut the outlet flow path partition wall 21 and the outlet buffer partition wall 22, the inlet flow path partition wall 23 and the inlet buffer partition wall 24, and the first partition wall 25 and the third partition wall 27. Furthermore, the outlet buffer partition wall 32 is provided with an engagement receiving portion 32a for supporting the outlet portion 52b of the measurement unit 50. The first partition wall 35 is formed with an inlet communication hole 35a.

12, a ring-shaped first flange 60 is attached to the measurement unit 50 at a position corresponding to the engagement receiving portion 22a of the outlet buffer partition wall 22. Therefore, the outlet portion 52b of the measurement unit 50 is flush with the outward surface of the outlet buffer partition wall 22. As a result, there are advantages in that the gas flows out smoothly, pressure loss is reduced, and variation in the measured flow rate is reduced.
Since the rest is similar to the first embodiment described above, the same parts are given the same numbers and the description will be omitted.

In this embodiment, the cross-sectional area of the outlet buffer section 17 increases toward the downstream side. This not only improves gas escape and reduces pressure loss, but also improves the flow of gas in the measurement flow paths 57a to 57f, thereby reducing variation in the measured flow rate.

As shown in Figures 16 and 17, the third embodiment is almost the same as the second embodiment described above, except that a shielding plate 28 that extends horizontally within the inlet flow passage 14 and is located between the inlet 13 and the inlet communication hole 25a is provided on the inward surface of the case body 20. The inlet communication hole 25a is located approximately in the center of the first partition wall 25.

According to this embodiment, by providing the shielding plate 28, the gas flowing in from the inlet 13 is temporarily blocked, thereby making it possible to reduce the pulsation of the gas.
It goes without saying that the position, size and shape of the shielding plate 28 can be appropriately selected according to need.
Since the rest of the configuration is substantially the same as the second embodiment described above, the same parts are designated by the same reference numerals and the description thereof will be omitted.

In the fourth embodiment, as shown in Figs. 18 to 21, the inlet flow passage 14 of the inlet side space 10a is communicated with the central space 10c.
That is, as shown in FIG. 18, the case 10 is box-shaped, with an inlet portion 11 disposed at one end of the upper surface thereof and an outlet portion 12 disposed at the other end thereof.
The case 10 is composed of a case body 20 and a lid 30. A shutoff valve 40 having a valve body 41 is disposed in an inlet 13 (see FIG. 22) located at the lower end of the inlet portion 11 in order to adjust the inflow of gas into the internal space of the case 10.

As shown in FIG. 21, the internal space of the case body 20 is formed with an outlet side space portion 10b on the left side of the case body 20 by an outlet flow path partition wall 21 and an outlet buffer partition wall 22 that protrude continuously from top to bottom.

The outlet side space 10b is divided into upper and lower two sections, an outlet buffer section 17 and an outlet flow path section 18, by a second partition wall 26 extending horizontally and protruding from the inward surface of the case body 20. The second partition wall 26 is provided with an outlet communication hole 26a for allowing gas to flow out. By providing the outlet communication hole 26a, a substantial orifice structure is formed, and an ultrasonic flowmeter is obtained that can prevent erroneous measurement by the measurement unit due to pressure fluctuations. Furthermore, the outlet communication hole 26a is positioned more inward than an outlet section 52b of a measurement unit 50 described later, and the creepage distance is longer.
The outlet communication hole 26a may be formed by post-processing after molding by die casting as in this embodiment, or, as in the previously described embodiment, it may be formed so that a portion of the outlet communication hole 26a opening to the front side is closed by a protrusion provided on the inward surface of the lid body.
The outlet buffer partition wall 22 is provided with an engagement receiving portion 22a for engaging and positioning a measuring unit 50 (described later), and a pair of upper and lower fitting grooves 22c are provided on the opposing surfaces of the opening edge of the engagement receiving portion 22a for mounting a spacer 61 (described later).
In order to attach the spacer, a pair of upper and lower engaging protrusions may be provided on the opposing surfaces of the opening edge of the engaging portion 22a for actual joining. Furthermore, it is of course possible to assemble the two by making the opposing surface of the opening edge of the engaging portion 22a flat and shaping it so that the joining portion of the spacer straddles this.

The case body 20 also has a generally L-shaped inlet flow passage partition wall 23 integrally protruding from its inward surface so as to be continuous with the outlet flow passage partition wall 21, and a central space 10c is formed directly below the inlet flow passage partition wall 23. The front of the space surrounded by the outlet flow passage partition wall 21 and the inlet flow passage partition wall 23 is partitioned by an inner wall 23a, forming a storage section 10e (Figure 19).

The inlet side space 10a is partitioned by the inlet flow passage partition wall 23 and the inlet buffer partition wall 24 that protrudes from the inlet flow passage partition wall 23 and is not continuous with the inlet buffer partition wall 24. The inlet side space 10a is partitioned into two levels, the inlet flow passage 14 and the inlet buffer 16, by providing a first partition wall 25 that extends horizontally and is continuous only with the inlet buffer partition wall 24. Therefore, the inlet flow passage 14 and the central space 10c are connected to each other. An inlet communication hole 25a is formed in the first partition wall 25. By providing the inlet communication hole 25a, an approximately orifice structure is formed, and an ultrasonic flowmeter that can prevent erroneous measurement by the measurement unit due to pressure fluctuations is obtained. The inlet communication hole 25a is located inside the inlet portion 52a of the measurement unit 50 described later, and the creepage distance is long.
The inlet communication hole 25a may be formed by post-processing after molding by die casting as in this embodiment, or, as shown in the above-described embodiment, it may be formed so that a portion of the inlet communication hole 25a opening toward the front is closed by a protrusion provided on the inward surface of the lid body.
21, the inlet buffer partition wall 24 is provided with an engagement receiving portion 24a for engaging and positioning a measuring unit 50 (described later), and a pair of upper and lower fitting grooves 24c are provided on the opposing surfaces of the opening edge of the engagement receiving portion 24a for mounting a spacer 62 (described later).
In order to attach the spacer, a pair of upper and lower engaging ridges may be provided on the opposing surfaces of the opening edge of the engaging portion 24a, and the actual joining may be performed. Furthermore, it is of course possible to assemble the two by making the opposing surface of the opening edge of the engaging portion 24a flat and shaping it so that the joining portion of the spacer straddles this.
Furthermore, the inlet buffer partition wall 24 is provided with a notch 24b for guiding the liquid that flows in together with the gas from the inlet buffer 16 to the central space 10c (FIG. 22). Therefore, even if a large amount of liquid flows into the inlet side space 10a, the liquid can be collected on the bottom surface of the inlet buffer 16 and the central space 10c, and can be prevented from entering the measurement unit 50.

As shown in Figures 18 and 19, the lid 30 is a plate-like body having a front shape capable of covering the opening of the case body 20.

As shown in FIG. 20, the measurement unit 50 is almost the same as the embodiment described above, so the same parts are given the same numbers and their explanations are omitted.

Then, as shown in FIG. 20, the measurement unit 50 is engaged with the engagement receiving portion 22a (FIG. 29) of the case body 20 via one O-ring 59 (FIG. 23) to position it. Furthermore, the measurement unit 50 is engaged with the engagement receiving portion 24a of the case body 20 via one O-ring 59 to position it. Next, a spacer 61 is fitted into the fitting groove 22c of the outlet buffer partition wall 22, and a spacer 62 is fitted into the fitting groove 24c of the inlet buffer partition wall 24. Finally, the cover 30 is attached to the case body 20 to form the notch portion 24b (see FIG. 22). As a result, as shown in FIG. 23, the inlet portion 52a of the measurement unit 50 is positioned in the inlet buffer portion 16. Also, the outlet portion 52b of the measurement unit 50 is positioned in the outlet buffer portion 17. Then, the measurement circuit portion 53 of the measurement unit 50 is disposed in the central space portion 10c.

The corners of the inlet space 10a, the outlet space 10b, and the central space 10c are rounded to ensure a smooth flow of gas. Of course, the size of the roundness can be selected as needed. For example, the radius of curvature of the rounded surface is preferably in the range of R0.5 to 30 mm. If R is less than 0.5 mm, the rate of defects during casting increases significantly, and if R exceeds 30 mm, the wall becomes too thick, increasing manufacturing costs and making it unrealistic.

As shown in Figures 24 to 32, the fifth embodiment is almost the same as the fourth embodiment described above, and is generally composed of a case 10, a shutoff valve 40, and a measuring unit 50. For this reason, the same parts will be described with the same numbers.

In addition, since the shutoff valve 40 and the measuring unit 50 are almost the same as those in the above-mentioned embodiment, the same parts are given the same numbers and the description will be omitted.
However, the measuring unit 50 is engaged with the engaging receiving portion 22a of the outlet buffer partition 22 shown in Fig. 29 and the engaging receiving portion 24a of the inlet buffer partition 24 via O-rings 59, 59 shown in Fig. 32. Furthermore, as shown in Fig. 28, spacers 61, 62 are disposed in the engaging receiving portion 22a of the outlet buffer partition 22 and the engaging receiving portion 24a of the inlet buffer partition 24, respectively.

As shown in Figures 24 and 25, the case 10 is box-shaped and is composed of a case main body 20 and a case holder 21.

As shown in FIGS. 26 and 27, the case body 20 is integrally joined to the cover 30 via a gasket 63 by screws (not shown).
In this embodiment, the screw pitch may be a predetermined distance to ensure sealing, for example, the pitches of adjacent screws on either side may be approximately equal, for example, 70 mm, in order to reduce the number of screws and increase productivity while ensuring sealing.

As shown in Figures 28 and 29, the inside of the case body 20 is divided into three spaces, an inlet space 10a, an outlet space 10b, and a central space 10c, as in the previous embodiment.

The inlet side space 10a is divided into two sections, an inlet flow path section 14 and an inlet buffer section 16, by a horizontally extending first partition wall 25 which is integrally provided to protrude from the case body 20. An inlet communication hole 25a is formed in the first partition wall 25. By providing the inlet communication hole 25a, a substantial orifice structure is formed, and an ultrasonic flowmeter capable of preventing erroneous measurement by the measurement unit due to pressure fluctuations is obtained.
In addition, the inlet side space 10a is divided into the inlet buffer 16 and the central space 10c on the left and right sides by an inlet buffer partition wall 24 that is continuous with the first partition wall 25 and extends vertically and is integrally provided on the case body 20 so as to protrude therefrom. Therefore, the inlet flow path 14 and the central space 10c are in communication with each other. As a result, a part of the gas that has flowed in from the inlet 13 flows into the central space 10c via the inlet flow path 14, and then flows into the inlet buffer 16.

28, the outlet side space 10b is partitioned into upper and lower two stages, an outlet buffer section 17 and an outlet flow path section 18, by a horizontally extending second partition wall 26 which is integrally provided to protrude from the case body 20. An outlet communication hole 26a for allowing gas to flow out is provided in the second partition wall 26. By providing the outlet communication hole 26a, a substantial orifice structure is formed, and an ultrasonic flowmeter capable of preventing erroneous measurement by the measuring unit due to pressure fluctuations is obtained.
In addition, since the outlet communication hole 26a is disposed on the inside of an outlet portion 52b of a measuring unit 50, which will be described later, the creepage distance is long. A pressure sensor 45 is attached to the side wall of the outlet flow passage portion 18.

As shown in Figures 30 and 31, the inward protrusion capacity of the inlet flow passage partition wall 23 and the inner wall 23a of the central space 10c is smaller than that of the fourth embodiment. This is to facilitate the flow of gas from the inlet flow passage 14 into the central space 10c. This embodiment has the advantages of simplifying the structure of the mold, facilitating die casting, and saving die casting material. Furthermore, a relay connector 46 is provided on the inner wall 23a.
In addition, the side wall located below the inlet flow passage partition wall 23 is bulged outward to form the bulging portion 20a. Therefore, according to this embodiment, the bottom area of the central space 10c is increased, which has the advantage of increasing the amount of water that can be stored in the central space 10c.

As shown in Figure 27, the cover body 30 has bulges 38a, 38b, 38c, 38d, and 38e at positions facing the inlet flow path section 14, the inlet buffer section 16, the central space section 10c, the outlet buffer section 17, and the outlet flow path section 18 of the case main body 20, respectively.
According to this embodiment, the provision of the bulges 38a, 38b, 38c, 38d, and 38e increases the rigidity of the entire lid 30. In particular, the bulge 38c provided at a position opposite the central space 10c not only prevents the lid 30 from colliding with the measurement circuit unit 53 (FIG. 31), but also has the advantage of substantially increasing the volume of the central space 10c, thereby increasing the amount of water stored.

In any of the first to fifth embodiments described above, the inlet communication hole 25a communicating with the inlet buffer 16 is located above the inlet buffer 16. Therefore, the inlet communication hole 25a is located above the inlet portion 52a of the measurement unit 50 located within the inlet buffer 16. The measured fluid that flows down from the inlet communication hole 25a into the inlet buffer 16 is separated into gas and moisture, etc. within the inlet buffer 16, and the moisture, etc. is removed and managed.
Example 1

A simulation was performed for the first embodiment to obtain the flow rates and pressure losses in the six measurement flow paths 57a to 57f. The results of Example 1 are shown in the bar graph of FIG. 33 and the graph of FIG.
The ideal volumetric flow rate per layer was assumed to be 1,000 (L/h).

As is clear from Fig. 33, the difference between the maximum flow rate (1,028 (L/h)) and the minimum flow rate (969 (L/h)) is 59 (L/h). When the ideal flow rate is used as the standard, the difference is 5.9%, and it was confirmed that the variation in this embodiment is smaller than the variation in the comparative example described later.
Also, as shown in FIG. 34, it was confirmed that the pressure loss was 185.3 (Pa), which was below the in-house standard value (190 (Pa)).
Example 2

A simulation was performed for the second embodiment to obtain the flow rates and pressure losses in the six measurement flow paths 57a to 57f. The results of Example 2 are shown in the bar graph of FIG. 35 and the graph of FIG.
The ideal volumetric flow rate per layer was assumed to be 1,000 (L/h).

As is clear from Fig. 35, the difference between the maximum flow rate (1,022 (L/h)) and the minimum flow rate (988 (L/h)) is 34 (L/h). When the ideal flow rate is used as the standard, the difference is 3.4%, and it was confirmed that the variation in this embodiment is smaller than the variation in the comparative example described later.
Also, as shown in FIG. 36, it was confirmed that the pressure loss was 159.7 (Pa), which was below the in-house standard value (190 (Pa)).
Example 3

A simulation was performed for the third embodiment to obtain the flow rates and pressure losses in the six measurement flow paths 57a to 57f. The simulation results are shown in the bar graph of FIG. 36 and the graph of FIG.
The ideal volumetric flow rate per layer was assumed to be 1,000 (L/h).

As is clear from Fig. 36, the difference between the maximum flow rate (1,016 (L/h)) and the minimum flow rate (972 (L/h)) is 44 (L/h). When the ideal flow rate is used as the standard, the difference is 4.4%, and it was confirmed that the variation in this embodiment is smaller than the variation in the comparative example described later.
Also, as shown in FIG. 37, it was confirmed that the pressure loss was 169.6 (Pa), which was below the in-house standard value (190 (Pa)).
Example 4

A simulation was performed for the fourth embodiment to obtain the flow rates and pressure losses in the six measurement flow paths 57a to 57f. The simulation results are shown in the bar graph of FIG. 38 and the graph of FIG.
The ideal volumetric flow rate per layer was assumed to be 1,000 (L/h).

As is clear from Fig. 38, the difference between the maximum flow rate (1,023 (L/h)) and the minimum flow rate (981 (L/h)) is 42 (L/h). When the ideal flow rate is used as the standard, the difference is 4.2%, and it was confirmed that the variation in this embodiment is smaller than the variation in the comparative example described later.
Also, as shown in FIG. 39, it was confirmed that the pressure loss was 177.6 (Pa), which was below the in-house standard value (190 (Pa)).

Even though the inlet flow passage 14 and the central space 10c are connected, there is little variation in the measured flow rate. This is thought to be because even if the gas flowing in from the inlet 13 pulsates, the gas remaining in the central space 10c acts as a cushion, so to speak, and absorbs and mitigates the gas pulsation before the flowing in gas passes through the inlet communication hole 25a.
Example 5

A simulation was performed for the fifth embodiment to obtain the flow rates and pressure losses in the six measurement flow paths 57a to 57f. The results of Example 5 are shown in the bar graph of FIG. 40 and the graph of FIG.
The ideal volumetric flow rate per layer was assumed to be 1,000 (L/h).

As is clear from Fig. 40, the difference between the maximum flow rate (1,033 (L/h)) and the minimum flow rate (973 (L/h)) is 60 (L/h). When the ideal flow rate is used as the standard, the difference is 5.8%, and it was confirmed that the variation in this embodiment is smaller than the variation in the comparative example described later.
Also, as shown in FIG. 41, it was confirmed that the pressure loss was 184.6 (Pa), which was below the in-house standard value (190 (Pa)).

Even though the inlet flow passage 14 and the central space 10c are connected, there is little variation in the measured flow rate. This is thought to be because even if the gas flowing in from the inlet 13 pulsates, the gas remaining in the central space 10c acts as a cushion, so to speak, and absorbs and mitigates the gas pulsation before the flowing in gas passes through the inlet communication hole 25a.
Comparative Example

An ultrasonic flowmeter modeled after an existing model was simulated to determine the flow rates in the six measurement channels 57a to 57f. The simulation results are shown in the bar graph in Figure 42.

As is clear from Figure 42, the difference between the maximum flow rate (1,095 (L/h)) and the minimum flow rate (968 (L/h)) is 127 (L/h). The degree of variation when the ideal flow rate is used as the standard was 12.7%.
Therefore, it was found that the variation in the measured flow rate according to each of the above-mentioned embodiments was smaller than the variation in the measured flow rate according to the existing ultrasonic flowmeter.
(Examples 6 and 7)

In contrast to the first and fourth embodiments, low-frequency (several Hz), medium-frequency (approximately 20 Hz), and high-frequency (several tens of Hz) sinusoidal pressure fluctuations were applied to a non-flowing gas via a speaker, and the fluctuations in the measured flow rate were measured, resulting in Examples 6 and 7. The measurement results of the measured flow rates in Examples 6 and 7 are shown in FIG.
In this embodiment, the ideal measured flow rate is zero (L/h).

As is clear from FIG. 43, the average value of the measured flow rate was within ±1 (L/h), and was found to be smaller than the reference value of 5 (L/h), which is the minimum value of the measured flow rate that must be detected.
In particular, for Example 6 according to the fourth embodiment, it was found that the average value of the measured flow rate at medium frequency was one order of magnitude smaller than the other average values. This is because the fluctuation of the measured flow rate fluctuates around the median value, so there is little deviation from the median value and there is little false detection.

As described above, the average value of the measured flow rate at medium frequency in Examples 6 and 7, especially in Example 7, is significantly smaller than the average value of the other measured flow rates. This is thought to be because when gas flows from the inlet 13 to the inlet communication hole 25a, even if the gas pressure is pulsating, the gas remaining in the central space 10c acts as a cushioning material to absorb and reduce the gas pulsation.
Therefore, it was found that by appropriately selecting the position, shape and volume of the central space 10c communicating with the inlet flow passage 14, the variation in the average measured flow rates at low, medium and high frequencies can be reduced.
(Example 8)

In contrast to the fifth embodiment, low-frequency (several Hz), medium-frequency (approximately 20 Hz) and high-frequency (several tens of Hz) sinusoidal pressure fluctuations were applied to a non-flowing gas via a speaker, and the fluctuations in the measured flow rate were measured, resulting in Example 8. The measurement results of the measured flow rate in Example 8 are shown in FIG.
In this embodiment, the ideal measured flow rate is zero (L/h).

As is clear from FIG. 44, the average value of the measured flow rate was within ±1 (L/h), and was found to be smaller than the reference value of 5 (L/h), which is the minimum value of the measured flow rate that must be detected.
In particular, for Example 8 according to the fifth embodiment, it was found that the average value of the measured flow rate at high frequencies was one order of magnitude smaller than the other average values. This is because the fluctuations in the measured flow rate fluctuate around the median value, so there is little deviation from the median value and there is little false detection.

Note that the above-mentioned Examples 7 and 8 show the relationship between the measured flow rate and time when pressure fluctuations are applied when no gas is flowing through the gas meter, and it is desirable for the measured flow rate to be 0 L/h. Furthermore, the measured flow rates in Examples 7 and 8 are within approximately ±1 L/h, and in particular, the average measured flow rate in Example 8 is -0.04 L/h to -0.52 L/h, so it was found that the two have equivalent performance. Furthermore, while the gas meter must detect flow rates exceeding 5 L/h, it was found that this is fully possible as long as it is within the error range mentioned above.

As described above, the average value of the measured flow rate at high frequency in Example 8 is significantly smaller than the average values of the other measured flow rates. This is thought to be because when gas flows from the inlet 13 to the inlet communication hole 25a, even if the gas pressure is pulsating, the gas remaining in the central space 10c efficiently absorbs and reduces the gas pulsation as a cushioning material, so to speak.
Therefore, it was found that by appropriately selecting the position, shape and volume of the central space 10c communicating with the inlet flow passage 14, the variation in the average measured flow rates at low, medium and high frequencies can be reduced.
Example 9

Figure 45 shows a trajectory diagram that visualizes the fluid flow through a simulation for the first embodiment.

As is clear from Fig. 45, it was found that the gas flowing in from the inlet 13 is throttled as it passes through the inlet communication hole 25a, and then diffuses again before flowing in from the inlet 52a of the measurement unit 50. For this reason, it was found that the gas pulsation is absorbed when it is throttled and diffused in the inlet communication hole 25a, and the creeping distance is lengthened by the detour, thereby mitigating the pressure fluctuation of the gas.
Example 10

Figure 46 shows a trajectory diagram that visualizes the fluid flow through a simulation for the third embodiment.

As is clear from Figure 46, the gas flowing in from the inlet 13 collides with the shield plate 28, diffuses, and is diverted, is constricted as it passes through the inlet communication hole 25a, and then diffuses again and flows in from the inlet portion 52a of the measurement unit 50.

As is clear from the above trajectory diagram, the gas pulsation is absorbed and mitigated by the gas colliding with the shielding plate 28 and being redirected, or by the gas being throttled and diffused by the inlet communication hole 25a.

The present invention is of course applicable not only to city gas but also to flow measurement of other gases.

LIST OF SYMBOLS 10 Case 10a Inlet side space 10b Outlet side space 10c Central space 10d Water collection space 10e Storage section 11 Inflow section 12 Outlet section 13 Inlet 14 Inlet flow passage section 16 Inlet buffer section 17 Outlet buffer section 18 Outlet flow passage section 19 Intermediate buffer section 20 Case body 20a Bulging section 21 Outlet flow passage partition wall 22 Outlet buffer partition wall 22a Engagement receiving section 23 Inlet flow passage partition wall 23a Inner wall 24 Inlet buffer partition wall 24a Engagement receiving section 24b Cutout section 25 First partition wall 25a Inlet communication hole 26 Second partition wall 26a Outlet communication hole 27 Third partition wall 28 Shielding plate 30 Lid body 31 Outlet flow passage partition wall 32 Outlet buffer partition wall 33 Inlet flow passage partition wall 34 Inlet buffer partition wall 34a Inlet communication hole 35 First partition wall 36 Second partition wall 36a Outlet communication hole 37 Third partition wall 38a to 38e Bulging portion 40 Shutoff valve 41 Valve body 45 Pressure sensor 46 Relay connector 50 Measurement unit 51 Cylinder 52a Inlet portion 52b Outlet portion 53 Measurement circuit portion 54a Ultrasonic transducer 54b Ultrasonic transducer 55 Control circuit board 56a to 56e Flow straightening plate 57a to 56f Measurement flow passage 60 First flange portion 61 Spacer 62 Spacer 63 Gasket

Claims (9)

Case and
an inlet buffer portion which is a partitioned space on the upstream side of the case;
an outlet buffer portion which is a space partitioned on the downstream side within the case;
a measuring unit that is housed in the case and has a cylindrical body having an inlet portion that communicates with the inlet buffer portion and an outlet portion that communicates with the outlet buffer portion,
an ultrasonic flowmeter for measuring a flow rate of gas passing through the measuring unit, the gas flowing in from an inlet communicating with an inlet portion of the case, flowing in from an inlet portion of the measuring unit communicating with the inlet buffer portion, circulating through a flow passage in the measuring unit, and flowing out from an outlet portion via an outlet buffer portion communicating with the outlet portion,
an inlet flow passage portion separated from the inlet buffer portion by a partition wall protruding from an inner surface of the case, and through which gas flowing in from the inlet flows downstream;
a central space portion disposed between the inlet buffer portion and the outlet buffer portion and configured to accommodate the measuring unit;
the central space formed between the inlet buffer and the outlet buffer is in communication with the inlet flow path,
An ultrasonic flowmeter characterized in that gas flowing in from the inlet and flowing down to the downstream side of the inlet flow passage portion flows into the inlet buffer portion through an inlet communication hole provided in the partition wall. An ultrasonic flowmeter as described in claim 1, characterized in that the inlet communication hole is located inside the inlet portion of the measurement unit. An ultrasonic flowmeter according to claim 1 or 2, characterized in that the inlet buffer partition wall separating the inlet buffer section and the central space section is provided with a notch that allows liquid that has flowed into the inlet buffer section to flow out into the central space section. An ultrasonic flowmeter according to any one of claims 1 to 3, characterized in that an outlet flow passage is formed by providing a partition wall with an outlet communication hole on the inner surface of the case between the outlet buffer section and the outflow section of the case. An ultrasonic flowmeter according to any one of claims 1 to 3, characterized in that the outlet buffer portion is directly connected to the outflow portion of the case. The ultrasonic flowmeter according to claim 5, characterized in that the outlet buffer portion is formed so that its cross-sectional area increases toward the downstream side. An ultrasonic flowmeter according to any one of claims 1 to 6, characterized in that at least one of the opening edges of the inlet and the outlet of the cylindrical body of the measurement unit is disposed flush with the outward surface of the buffer section. An ultrasonic flowmeter according to at least one of claims 1 to 7, characterized in that a shielding plate is provided on the inner surface of the case between the inlet and the inlet communication hole. 9. The ultrasonic flowmeter according to claim 1, wherein at least one of the side walls that form the front and back surfaces of the case and that face each other across the central space is provided with a bulging portion that bulges outward.

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