JP4662236B2 - Flow meter - Google Patents

Description

  The present invention relates to a flow meter.

An impeller-type flow meter is known as a conventional flow meter. This flow meter includes an impeller that rotates by receiving fluid, and measures a flow rate based on the rotation of the impeller (see, for example, Non-Patent Document 1).
Yutaka Matsuyama, “Practical flow rate measurement”, 1st edition, Energy Conservation Center, June 15, 1999, p. 155-156

  Incidentally, in recent years, there has been a demand for a flow meter having higher measurement performance. However, the above-described conventional flow meter has a problem that a so-called “instrument difference” (ratio of a value obtained by subtracting a true value from an actual measurement value to a true value) increases in a small flow region.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a flow meter with higher measurement accuracy than before.

In order to achieve the above object, a flow meter comprising a meter body assembled to an outer case attached in the middle of a water pipe, a pair of cylindrical portions arranged vertically on the meter body and connected by a plurality of ribs The rectifier is joined to the lower part of the lower cylindrical part, and the impeller is rotatably supported by a support pin standing from the center of the upper surface of the rectifier, and the impeller blades are accommodated in the lower cylindrical part. In addition, the support pin housing shaft protruding upward from the center of the impeller has a structure housed in the shaft housing portion provided at the center of the lower surface of the upper cylindrical portion, and the fluid that has flowed from the inlet of the outer case, The rectifier and the lower cylindrical part are directed upward in this order, and the impeller is rotated by flowing from the upper surface of the lower cylindrical part to the outlet of the outer case through a plurality of ribs. For flow meter to measure There are, rotational locus drawn by the plurality of blades with the impeller along with the rotation of the impeller, constructed from the end surface of the upstream side so that the truncated cone shape that is reduced in diameter in a linear taper shape toward the end face of the downstream However, it has characteristics.

In the flow meter according to claim 1, when the outer diameter of the end portion on the lower end side of the impeller is P and the outer diameter of the end portion on the upper end side is S, R = S It is characterized by the ratio obtained by / P being 0.96 to 0.98.

The invention of claim 3 is characterized in that, in the flow meter of claim 2, the outer diameter P of the end portion on the lower end side of the impeller is P = 50 mm.

  According to the invention according to claim 1 configured as described above, the measurement accuracy can be made higher than that of the conventional flow meter.

Here, the ratio R (= S / P) of the outer diameter P at the lower end of the impeller and the outer diameter S at the upper end of the impeller is effectively 0.96 to 0.98. In addition, the measurement accuracy can be improved (invention of claim 2). Further, if the outer diameter of the end portion on the lower end side of the impeller is 50 mm, the measurement accuracy can be improved more effectively (the invention of claim 3) .

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
The flow meter 10 of the present invention is a so-called vertical axial flow impeller flow meter, and the meter main body 12 shown in FIG. 2 is assembled to an outer case 11 (see FIG. 1) attached in the middle of a water pipe. It becomes.

  In the outer case 11, an inflow port 11A opened on the left side in FIG. 1 and an outflow port 11B opened on the right side are formed, and a lower chamber 13 extending downward from the inflow port 11A, and a lower chamber 13 An upper room 14 located above is provided. Further, the upper room 14 and the lower room 13 communicate with each other in the vertical direction via the communication port 16. A meter body 12 is inserted and assembled from above into an upper surface opening 15 formed on the upper surface of the upper chamber 14, and a lower end portion of the meter body 12 is joined to an edge portion of the communication port 16.

In the meter main body 12, reference numeral 50 in FIG. 2 is a cylindrical housing, and a pair of cylindrical portions 50A and 50B arranged vertically are connected by a plurality of ribs 52. The lower cylindrical portion 50B is opened up and down, and the blade 43 of the impeller 40 is accommodated in the lower cylindrical portion 50B, and the rectifier 20 is joined to the lower portion of the lower cylindrical portion 50B. ing. And as shown with the thick line arrow of FIG. 1, the water which flowed upwards in order of the rectifier 20 and the lower cylindrical part 50B from the lower room 13 of the outer case 11 from the upper surface of the lower cylindrical part 50B from the upper surface of the rib 52, Passing through 52, proceed to the upper chamber 14 of the outer case 11 and head toward the outlet 11B .

  As shown in FIG. 2, a shaft accommodating portion 53 hangs down on the lower surface of the upper cylindrical portion 50A so as to taper toward the center of the lower cylindrical portion 50B. A shaft 41 extending from an impeller 40 described later is accommodated.

  On the other hand, a meter unit 60 is attached to the upper surface of the upper cylindrical portion 50A, and the meter unit 60 counts and displays the integrated flow rate of water that has passed through the flow meter 10 in conjunction with the rotation of the impeller 40. Note that when the upper lid 61 provided at the upper part of the meter unit 60 is opened, the flow rate display unit 63 can be seen through the glass window 62.

  The rectifier 20 includes a central rectifier 22 in the center of the inner side of the cylindrical cylindrical body 27, and has a structure in which, for example, six rectifying walls 70 extend radially from the central rectifier 22 toward the cylindrical body 27. (See FIG. 2).

  The cylindrical body 27 is opened up and down, and a slide ring 32 is assembled to an upper end edge thereof. Specifically, the slide ring 32 is formed with long holes 35 and 35 at two positions separated by 180 °, and a screw inserted into the long holes 35 and 35 is screwed into the upper end portion of the cylindrical body 27. . Then, the slide ring 32 can be rotated on the cylinder 27 by loosening the screw, and the slide ring 32 can be fixed to the cylinder 27 by tightening the screw at a desired position. Further, in the slide ring 32, lateral grooves 33, 33 that open toward the inside are formed at positions that are approximately 90 ° apart from the long holes 35, 35. In FIG. 2, for convenience of explanation, both a portion where the long hole 35 is formed and a portion where the lateral groove 33 is formed are shown.

The central rectifier 22 is disposed at a position closer to the upper end (downstream end) of the cylindrical body 27. The central rectifier 22 has a dome shape that is rounded downward and tapered. Further, a support hole 22U penetrating in the vertical direction is formed at the center of the dome, that is, the center of the central rectifier 22, and the shaft core portion 22A is fixed to the support hole 22U. The support pins 2 1 vertically from the upper end of the shaft portion 22A is erected.

  Each of the plurality of rectifying walls 70 is parallel to the axial direction of the cylindrical body 27 in the vertical direction. Further, the lower end edge of the rectifying wall 70 is inclined so as to gradually go downward from the central rectifying body 22 toward the cylindrical body 27, and the lower end edge 70 U of the rectifying wall 70 on the cylindrical body 27 side is inclined to the central rectifying body 22. It is located below the lower end of. Of the plurality (six) of rectifying walls 70, for example, two rectifying walls 70 </ b> B arranged to face each other are provided with movable blades 29. In FIG. 2, only one of the two rectifying walls 70B arranged to face each other is shown.

  The rectifying wall 70 </ b> B provided with the movable blade 29 has a recess 71 opened toward the impeller 40 in a portion near the cylindrical body 27. The movable blade 29 has a substantially rectangular flat plate shape corresponding to the recess 71 and is assembled in the recess 71. Specifically, the pin 34 inserted from the outer surface of the cylindrical body 27 is inserted into the lower end portion of the movable blade 29, and the movable blade 29 can tilt around the pin 34. An emboss 30 is projected and engaged with the upper end of the movable blade 29 toward the inside of the lateral grooves 33 and 33 of the cylindrical body 27. Thereby, as the slide ring 32 rotates, the movable blades 29 and 29 (only one movable blade 29 is shown in FIG. 2) tilted symmetrically.

  Now, in FIG. 3, the impeller 40 is shown. As shown in the figure, the impeller 40 includes, for example, twelve blades 43 projecting radially from the outer peripheral surface of the cylindrical body 42. When viewed from above in FIG. 3, that is, from the downstream side, each blade 43 is twisted in its entirety with the lower edge 43 </ b> B preceding the upper edge 43 </ b> A of each blade 43 in the counterclockwise direction. It has a shape. Thereby, when water pressure is applied to the blades 43 from the upstream side (downward in FIG. 3), the impeller 40 rotates so that the lower end edge 43 </ b> B of the blades 43 precedes. That is, the impeller 40 rotates counterclockwise as viewed from above.

  The shaft 41 rises vertically upward from the center of the bottom surface of the cylindrical body 42, and the space between the shaft 41 and the inner surface of the cylindrical body 42 is reinforced by ribs 46.

  As shown in FIG. 4, a hollow at the lower end is formed in the core portion of the shaft 41, and a bearing 47 is assembled at a position near the upper end in the cavity. And the support pin 21 with which the rectifier 20 was mentioned above is inserted in the cavity from the lower end of the shaft 41, and the front-end | tip of the support pin 21 is abutted against the bearing 47 (refer FIG. 2). Thereby, the impeller 40 is rotatably supported by the support pin 21.

  One end of the magnet coupling 44 is provided at the upper end portion of the shaft 41, and is disposed opposite to the other magnet coupling 44 fixed to the gear 64 constituting the meter unit 60 as shown in FIG. 2. Thereby, the rotation of the impeller 40 is transmitted as the rotation of the gear 64 of the meter unit 60.

  A cap 45 is attached to the upper end of the shaft 41 so as to cover the magnet coupling 44, and a convex portion 48 is formed at the center of the cap 45. And the bearing member 49 is provided in the position facing this convex part 48 among the meter units 60 (refer FIG. 2).

  By the way, the impeller 40 has a flat truncated cone shape as a whole. That is, the outer diameter of the impeller 40 is gradually reduced from the upstream end 80 toward the downstream end 81. Specifically, the side edge 43G of the blade 43 provided in the impeller 40 is a taper that is linearly inclined so as to approach the center of the impeller 40 from the lower end edge 43B of the blade 43 toward the upper end edge 43A. It has a shape. In other words, the side edge 43G of the blade 43 obliquely intersects the upper edge 43A and the lower edge 43B of the blade 43 parallel to each other (see FIG. 4).

Here, in the present embodiment, the outer diameter at the upstream end 80 of the impeller 40 is, for example, 50 mm. And when the outer diameter at the end 80 on the upstream side of the impeller 40 is P and the outer diameter at the end 81 on the downstream side of the impeller 40 is S,
R = S / P
The ratio R obtained in (1) is 0.96 to 0.98.

Next, the operation of this embodiment configured as described above will be described.
1, the water that has flowed into the lower chamber 13 from the inlet 11A of the outer case 11 flows upward along the rectifying wall 70 of the rectifier 20 and toward the impeller 40. . The impeller 40 rotates by receiving the water guided by the rectifying wall 70 by each blade 43. The water that has passed through the impeller 40 along the shaft 41 (support pin 21) flows out between the ribs 52, 52 of the cylindrical housing 50 to the side of the meter body 12, and passes through the upper chamber 14 of the outer case 11. Head to the outlet 11B. Then, the rotation of the impeller 40 is transmitted to the meter unit 60 through the magnet couplings 44 and 44, and the flow rate of water is measured and displayed.

[Example]
A flow meter (No. 1, No. 2) as an implementation product of the present invention in which the shape of the impeller is the same as that of the above-described embodiment, and the outer diameter of the impeller from the upstream end to the downstream end A conventional flow meter (No. 3) that is different from the above-described embodiment only in that it is constant up to the part was manufactured. Here, the dimensions of the impeller in each flow meter (No. 1 to 3) were the conditions shown in Table 1 below.

  Next, water was passed through each of these flow meters (No. 1 to 3) at a preset flow rate, and the measured value of each flow meter (No. 1 to 3) at each set flow rate value was obtained.

  Furthermore, the instrumental difference of each flow meter (No.1-No.3) was calculated for every set flow rate, and it was made into a graph (instrumental difference curve) as shown in FIG.

Here, in this embodiment, the “instrument difference” is obtained by the following equation, where X is the measured value and Y is the true value.
Instrumental difference (%) = ((X−Y) / Y) · 100

  Each flow meter (No. 1 to No. 3) is provided with a movable blade 29. In this experiment, each movable blade 29 is set substantially vertically.

  When the flow meter (No. 1, No. 2), which is an embodiment of the present invention, is compared with the conventional flow meter (No. 3) based on the graph of FIG. In the medium to large flow rate range (400 to 20000 L / h), the instrumental error can be reduced to almost 0%. However, in the small flow rate range (90 to 400 L / h), the instrumental difference greatly deviates to the plus side. Yes. That is, it was found that the linearity of the instrumental difference curve is low. Note that, in the small flow rate range (90 to 400 L / h), the ratio (= K / T) of the frictional resistance force T of water applied to the impeller and the rotational force K that causes the water to rotate the impeller is increased. However, it is presumed that the impeller easily rotates as compared with a large flow rate range (400 to 20000 L / h).

  On the other hand, in the flow meter (No. 1, No. 2) which is the product of the present invention, the instrumental error can be almost 0% even in a small flow rate range (90 to 400 L / h). It was found that the linearity of the curve was improved. This is because the outer diameter of the impeller 40 is gradually reduced from the upstream end portion 80 toward the downstream end portion 81, so that the impeller 40 in the small flow rate region (90 to 400 L / h). 40 is prevented from increasing the ratio (= K / T) between the frictional resistance T of water applied to 40 and the rotational force K that causes the water to rotate the impeller 40, and the frictional resistance T It is presumed that the ratio to the rotational force K (= K / T) is almost constant.

  From this, it was found that the measurement accuracy of the flow meter is improved as compared with the conventional one by gradually reducing the diameter of the impeller 40 from the upstream end 80 toward the downstream end 81. .

  Furthermore, in the flow meter (No. 1, No. 2) which is the product of the present invention, the rotational speed of the impeller 40 did not increase as compared with the conventional flow meter (No. 3). Thereby, the durability performance of the flow meter 10 (specifically, the durability performance of the bearing 47 and the bearing member 49) is not impaired, and can be equivalent to the conventional flow meter.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.
(1) In the above embodiment, the outer diameter at the upstream end 80 of the impeller 40 is 50 mm. However, the outer diameter is not limited to this, and may be larger or smaller than 50 mm. Note that, as in this embodiment, the lower end side of the impeller 40 is upstream, the outer diameter of the upstream end portion 80 of the impeller 40 is 50 mm, and the outer diameter of the upstream end portion 80 of the impeller 40 is When the ratio R (= S / P) between P and the outer diameter S at the downstream end 81 is 0.96 to 0.98, the measurement accuracy can be improved particularly effectively.

(2) In the above embodiment, when the impeller 40 is viewed from the downstream side, the lower end edge 43B is configured to have a shape that precedes the upper end edge 43A of each blade 43 in the counterclockwise direction. However, the present invention is not limited to this, and the lower end edge 43 </ b> B may have a shape that precedes one of the circumferential directions of the cylindrical body 42 with respect to the upper end edge 43 </ b> A of each blade 43.

(3) In the above embodiment, the ratio R (= S / P) between the outer diameter P at the upstream end portion 80 of the impeller 40 and the outer diameter S at the downstream end portion 81 of the impeller 40 is “ Although it was set as "0.9726" or "0.9646", if it is a value included in 0.96-0.98, it will not restrict to this.

Side sectional view of a flow meter according to an embodiment of the present invention. Cross section of meter body Perspective view of impeller Cross section of impeller The graph which showed the experimental result with respect to an Example

Explanation of symbols

10 Flow meter 21 Support pin (Rotating shaft)
40 Impeller 80 Upstream end 81 Downstream end

Claims (3)

A flow meter in which a meter main body is assembled to an outer case attached in the middle of a water pipe, the meter main body comprising a pair of cylindrical portions arranged vertically and connected by a plurality of ribs, the lower side A rectifier is joined to the lower part of the cylindrical part of the rectifier, and the impeller is rotatably supported by a support pin standing from the center of the upper surface of the rectifier, and the blades of the impeller are accommodated in the lower cylindrical part, The support pin housing shaft that protrudes upward from the center of the impeller has a structure housed in the shaft housing portion provided at the center of the lower surface of the upper cylindrical portion, and the fluid that has flowed from the inlet of the outer case, Rotating the impeller by flowing upwards in the order of the rectifier and the lower cylindrical part and flowing from the upper surface of the lower cylindrical part through the plurality of ribs toward the outlet of the outer case Let the fluid In the flow meter for measuring the flow rate,
The rotation trajectory drawn by the plurality of blades provided in the impeller as the impeller rotates is configured to have a truncated cone shape that is reduced in diameter to a linear taper from the upstream end surface toward the downstream end surface. A flow meter characterized by that. When the outer diameter of the lower end side of the impeller is P and the outer diameter of the upper end side is S,
R = S / P
The flow meter according to claim 1, wherein the ratio obtained by the above is 0.96 to 0.98. The outer diameter P of the lower end side of the impeller is:
P = 50mm
The flow meter according to claim 2, wherein

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