JP5088849B2 - Flow meter and its impeller - Google Patents

Flow meter and its impeller Download PDF

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JP5088849B2
JP5088849B2 JP2006113240A JP2006113240A JP5088849B2 JP 5088849 B2 JP5088849 B2 JP 5088849B2 JP 2006113240 A JP2006113240 A JP 2006113240A JP 2006113240 A JP2006113240 A JP 2006113240A JP 5088849 B2 JP5088849 B2 JP 5088849B2
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impeller
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blade
measuring chamber
flow rate
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将範 川西
鉄平 大山
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Ricoh Elemex Corp
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Description

本発明は、水道メータ等に使用される流量計と、その羽根車に関するものである。   The present invention relates to a flow meter used for a water meter or the like and an impeller thereof.

水道メータ等に使用されている流量計では、流入側から流入した流体（ほとんどの場合、水）が、羽根車に設けられた羽根の間を通過する際に、前記羽根において流体の圧力を受ける側の面を押し回すことにより、該羽根車を回転させる。このときの羽根車の回転数は、流体の流量に比例するため、前記回転数を歯車等でアナログ的に、あるいはセンサー等でデジタル的に変換し、更に表示機構において一定の常数を加えることによって積算流量値に変換して、流体の流量が計測される。   In a flow meter used in a water meter or the like, fluid (in most cases, water) flowing in from the inflow side receives fluid pressure at the blade when passing between the blades provided in the impeller. The impeller is rotated by pushing around the side surface. Since the rotational speed of the impeller at this time is proportional to the flow rate of the fluid, the rotational speed is converted to analog by a gear or the like or digitally by a sensor or the like, and a constant constant is added to the display mechanism. The flow rate of the fluid is measured by converting into an integrated flow rate value.

通常の流量計では、流量−器差曲線の特定流量域（特に小流量域）で、器差がプラス傾向を示す。即ち、小流量域では、実際の流量よりも計測流量の方が多くなってしまう。この結果、特定流量域において、器差の「ピーク」と呼ばれる領域が発生してしまう。このピークをなくすために、特許文献１に開示された技術が存している。   In a normal flow meter, the instrumental difference shows a positive tendency in a specific flow rate range (particularly a small flow rate range) of the flow rate-instrument difference curve. That is, in the small flow rate range, the measured flow rate is larger than the actual flow rate. As a result, a region called “peak” of instrumental error occurs in the specific flow rate region. In order to eliminate this peak, a technique disclosed in Patent Document 1 exists.

しかし、特許文献１に開示された技術では、羽根車の羽根のねじり角を途中で変化させることによって器差のピークをなくしているため、羽根車の製作が難しいという不具合がある。   However, the technique disclosed in Patent Literature 1 has a problem that it is difficult to manufacture the impeller because the instrumental error peak is eliminated by changing the torsion angle of the impeller blade in the middle.

ところで、器差をどれくらいフラットにする必要があるかを考えると、国際規格及び日本工業規格から判断して流量ポイントＱ３での器差を０％としたときに、流量ポイントＱ２〜Ｑ４の流量範囲において前記器差が±２％に入っていることが必要であると考えられる。更には、流量ポイントＱ１〜Ｑ４の流量範囲においても器差が±２％に入っていることが、器差がフラットであると判断する上で最適と考えられる。
特開２００４−１４４５７６号公報 By the way, considering how flat the instrumental difference needs to be, when the instrumental difference at the flow point Q3 is 0% as judged from international standards and Japanese industry standards, the flow rate range of the flow points Q2 to Q4 It is considered necessary that the instrumental error is within ± 2%. Furthermore, it is considered optimal that the instrumental difference is within ± 2% even in the flow rate range of the flow points Q1 to Q4 in order to judge that the instrumental difference is flat.
JP 2004-144576 A

本発明は、従来の流量計に使用されているような製作容易なねじり羽根を使用し、羽根車と該羽根車を内装している計量室の寸法を一定の関係に保つことによって、器差をフラットにすることを目的としている。   The present invention uses a torsional blade that is easy to manufacture as used in conventional flowmeters, and keeps the dimensions of the impeller and the measurement chamber that houses the impeller in a certain relationship, thereby reducing the instrumental error. The purpose is to make it flat.

課題を解決するための手段及び発明の効果Means for Solving the Problems and Effects of the Invention

上記した課題を解決するための請求項１の発明は、流入口と流出口を有し、ボス部から半径方向に延設され、流体の流れによって回転する羽根車の羽根が、前記流体の流れ方向の中心軸を中心としてねじれた形状の流量計において、前記羽根車が内装される計量室を、前記流体の流れ方向と直交する面で切断し、計量室の内径をＤ１、羽根車のボス部の外径をＤ２、羽根の枚数をｎ、羽根の厚みをｔ、円周率をπとしたとき、
０．０５＜２ｔｎ（Ｄ１−Ｄ２）／［Ｄ１ ２π−Ｄ２ ２π−２ｔｎ（Ｄ１−Ｄ２）］＜０．１１
の関係が成立することを特徴としている。 The invention of claim 1 for solving the above-mentioned problem is characterized in that an impeller blade having an inflow port and an outflow port, extending in a radial direction from the boss portion, and rotating by the flow of the fluid is the flow of the fluid. In a flow meter having a twisted shape about the central axis of the direction, the measuring chamber in which the impeller is built is cut along a plane orthogonal to the fluid flow direction, and the inner diameter of the measuring chamber is set to D 1 . When the outer diameter of the boss portion is D 2 , the number of blades is n, the thickness of the blades is t, and the circumference is π,
0.05 <2tn (D 1 -D 2 ) / [D 1 2 π-D 2 2 π-2tn (D 1 -D 2)] <0.11
Is characterized by the fact that

請求項１の発明の式は、計量室における流体の流れ方向と直交する面で、流体が通過する面積と羽根が占める面積との割合（面積割合）を示している。ここで、流量計において、流量−器差曲線の特定流量域（特に小流量域）で器差がプラス傾向を示す原因として、流体の流量を計測するために設置された羽根車が、前記流体の流れを阻害することが考えられる。乱流、層流の違いにより、流れの中に置かれた各羽根に対する抵抗が流量に比例せず、乱流域である大流域において抵抗が増し、羽根車の回転を阻害させる。ところが、層流となる小流域においては、各羽根への抵抗が小さくなり、羽根車の回転がスムーズとなる。この結果、小流域での器差が大流域と比較して、みかけ上大きくなり、これがピークとなる。この推察から展開すると、計量室における流体の流れ方向と直交する面で、流体が通過する面積と該流体の通過を阻害する各羽根が占める面積との割合が、器差のピークに影響を与えると考えられる。   The equation of the first aspect of the invention shows the ratio (area ratio) between the area through which the fluid passes and the area occupied by the blades on the plane perpendicular to the fluid flow direction in the measuring chamber. Here, in the flow meter, the impeller installed to measure the flow rate of the fluid is the cause of the instrumental difference showing a positive tendency in a specific flow rate range (especially the small flow rate range) of the flow rate-instrument difference curve. It is conceivable that the flow of water is obstructed. Due to the difference between turbulent flow and laminar flow, the resistance to each blade placed in the flow is not proportional to the flow rate, and the resistance increases in the large flow region, which is a turbulent flow region, impeding the rotation of the impeller. However, in a small flow area that is a laminar flow, the resistance to each blade is reduced, and the impeller rotates smoothly. As a result, the instrumental difference in the small basin is apparently larger than that in the large basin, and this peaks. From this inference, the ratio of the area through which the fluid passes and the area occupied by each blade impeding the passage of the fluid on the surface perpendicular to the fluid flow direction in the measuring chamber affects the peak of the instrumental error. it is conceivable that.

即ち、上記した式の値（面積割合）が、０．０５(５％)より大きく、かつ、０．１１(１１％)よりも小さくなることが必要である。上記した関係を保つことが、流量ポイントＱ３における器差を０％としたときに、流量ポイントＱ１〜Ｑ４における器差が２％を超えないようなフラットな器差特性を得るための最低限の要件となる。 That is, it is necessary that the value (area ratio) of the above formula is larger than 0.05 (5%) and smaller than 0.11 (11%) . Maintaining the above-described relationship is the minimum for obtaining a flat instrumental error characteristic such that the instrumental error at the flow rate points Q1 to Q4 does not exceed 2% when the instrumental error at the flow rate point Q3 is set to 0%. It becomes a requirement.

請求項２の発明は、請求項１の発明を前提として、請求項１の関係が、前記計量室の内径が最小である断面において成立することを特徴としている。   The invention of claim 2 is characterized in that, based on the invention of claim 1, the relationship of claim 1 is established in a cross section in which the inner diameter of the measuring chamber is minimum.

請求項２の発明は、計量室の内径が流体の流れ方向に対して変化している場合、請求項１の関係が、前記計量室の内径が最小の断面において成立する必要があることを示している。即ち、計量室において羽根車が設置してある部分の内径が羽根車のボス部の外径に比べて十分に大きい場合、流体が通過する面積は十分に大きくなるため、請求項１の関係は容易に満たされる。しかし、流体が羽根車を通過するまでに計量室の内径が小さくなると、請求項１の関係が満たされなくなり、器差のピークをなくす効果も小さくなる。そこで、計量室の内径が流体の流れ方向に対して変化している場合には、該計量室の内径が最小である断面において請求項１の関係が満たされる必要がある。これにより、器差のピークがなくなり、フラットな器差特性が得られる。   The invention of claim 2 shows that when the inner diameter of the measuring chamber changes with respect to the flow direction of the fluid, the relationship of claim 1 must be established in a cross section with the smallest inner diameter of the measuring chamber. ing. That is, when the inner diameter of the portion where the impeller is installed in the measuring chamber is sufficiently larger than the outer diameter of the boss portion of the impeller, the area through which the fluid passes becomes sufficiently large. Filled easily. However, if the inner diameter of the measuring chamber is reduced before the fluid passes through the impeller, the relationship of claim 1 is not satisfied and the effect of eliminating the instrumental error peak is reduced. Therefore, when the inner diameter of the measuring chamber changes with respect to the fluid flow direction, the relationship of claim 1 needs to be satisfied in the cross section where the inner diameter of the measuring chamber is the smallest. Thereby, the peak of the instrumental error is eliminated and a flat instrumental error characteristic is obtained.

請求項３の発明は、請求項１又は２の発明を前提として、請求項１の関係が、前記羽根車のボス部の外径が最大である断面において成立することを特徴としている。   The invention of claim 3 is characterized in that, based on the invention of claim 1 or 2, the relationship of claim 1 is established in a cross section in which the outer diameter of the boss portion of the impeller is maximum.

請求項３の発明は、請求項２の発明と同様の考えであり、計量室の内径ではなく、羽根車のボス部の外径が最大の部分で請求項１の関係が満たされる必要があることを示している。これにより、器差のピークがなくなり、フラットな器差特性が得られる。   The invention of claim 3 is the same idea as the invention of claim 2, and it is necessary that the relationship of claim 1 is satisfied not at the inner diameter of the measuring chamber but at the portion where the outer diameter of the boss portion of the impeller is the largest. It is shown that. Thereby, the peak of the instrumental error is eliminated and a flat instrumental error characteristic is obtained.

請求項４の発明は、請求項１ないし３のいずれかに記載の流量計に内装されたことを特徴とする羽根車である。   According to a fourth aspect of the present invention, there is provided an impeller characterized in that the flowmeter according to any one of the first to third aspects is internally provided.

請求項４の発明に係る羽根車は、請求項１の関係を満たす流量計の計量室に内装されている。このため、羽根のねじれ形状が簡単なものになり、羽根車の製作が容易である。   An impeller according to a fourth aspect of the invention is housed in a metering chamber of a flow meter that satisfies the relationship of the first aspect. For this reason, the twisted shape of the blade becomes simple, and the manufacture of the impeller is easy.

本明細書では、流量計の一実施例である縦型軸流羽根車式流量計（以下、単に「流量計」と記載する）について説明する。図１は本発明の実施例の流量計１の正面断面図、図２の（ａ）は羽根車１０の斜視図であり、（ｂ）は同じく正面図、図３の（ａ）は厚みｔが一定の羽根１１の断面図であり、（ｂ）は厚みｔ１，ｔ２が基端部から先端部にかけて漸減する羽根１１の断面図、図４は羽根車１０が内装された計量室７の拡大断面図、図５は図４のＸ−Ｘ線断面図である。 In the present specification, a vertical axial flow impeller type flow meter (hereinafter simply referred to as “flow meter”) which is an embodiment of the flow meter will be described. FIG. 1 is a front sectional view of a flow meter 1 according to an embodiment of the present invention, FIG. 2A is a perspective view of an impeller 10, FIG. 1B is a front view, and FIG. Is a cross-sectional view of a fixed blade 11, (b) is a cross-sectional view of the blade 11 in which the thicknesses t 1 and t 2 are gradually reduced from the base end portion to the tip end portion, and FIG. 4 is a measuring chamber 7 in which the impeller 10 is housed. FIG. 5 is a sectional view taken along line XX of FIG.

図１に示されるように、本実施例の流量計１は、流体（本実施例の場合、水）の上流側に配置される補足管２と、それに合体された下ケース３とを備え、それらにまたがって流入口４から流出口５に至る水の流路が形成される。下ケース３の中央部には、ほぼ垂直上方へ導かれる水流に対する整流器６が位置すると共に、それに付随する調整器８があり、それらの上側に計量室７が設けられている。   As shown in FIG. 1, the flow meter 1 of the present embodiment includes a supplementary pipe 2 disposed on the upstream side of the fluid (in the case of the present embodiment, water), and a lower case 3 combined therewith, A water flow path from the inflow port 4 to the outflow port 5 is formed across them. In the central part of the lower case 3, there is a rectifier 6 for a water flow guided substantially vertically upward, and there is a regulator 8 associated therewith, and a measuring chamber 7 is provided above them.

前記計量室７の内部には羽根車１０が、整流器６に固定された垂直方向のピボット軸９に上側からわずかな隙間をもって挿入された状態で、垂直方向の軸線回りに回転自在に設置されている。羽根車１０の中心線の回りには、その中心線に対して複数枚（本実施例の場合、１２枚）の羽根１１がボス部１２と一体に形成され、それらの羽根１１は、羽根車１０の中心線を中心とするらせん状の面に沿ってねじれて形成されている。下ケース３の管路において上方へ導かれた水は、整流器６で整流された後、下側から羽根車１０に当たり、その羽根１１のねじれに基づき羽根車１０を回転させつつ、羽根車１０の軸方向に通過し、その後、方向を変えて流出口５から下流側に流出される。   An impeller 10 is installed inside the measuring chamber 7 so as to be rotatable about a vertical axis while being inserted into a vertical pivot shaft 9 fixed to the rectifier 6 with a slight gap from above. Yes. Around the center line of the impeller 10, a plurality of (12 in this embodiment) blades 11 are formed integrally with the boss portion 12 with respect to the center line. It is formed by twisting along a spiral surface centered on 10 center lines. The water guided upward in the conduit of the lower case 3 is rectified by the rectifier 6, hits the impeller 10 from below, and rotates the impeller 10 based on the twist of the blade 11, After passing in the axial direction, the direction is changed, and then it flows out from the outlet 5 to the downstream side.

羽根車１０の回転は、電子式流量計の場合、羽根車１０の上部に内蔵された磁石（図示せず）により、その回転をＭＲセンサーなどで検知して電気信号に置き換え、電子カウンター１３で積算される。電子カウンター１３は、遮水ケース１４内に納められていて、開閉式の蓋１５で被われている。羽根車１０の下方に配置される整流器６には、中心線から放射状に延びる複数の整流羽根１６が取付けられた調整器８が付属して設けられている。そして、各整流羽根１６のうちの１枚を、垂直軸に対して微小角度だけ調整することで、羽根車１０の羽根１１に当たる水流の向きをわずかに変えて、羽根車１０の回転数を微調整することができる。なお、機械式流量計の場合、羽根車１０の回転が歯車等により回転積算計に伝達されることにより、回転数がカウントされる構成である。   In the case of an electronic flow meter, the rotation of the impeller 10 is detected by an MR sensor or the like using a magnet (not shown) built in the upper portion of the impeller 10 and replaced with an electric signal. Accumulated. The electronic counter 13 is housed in a water shielding case 14 and is covered with an openable / closable lid 15. The rectifier 6 disposed below the impeller 10 is provided with an adjuster 8 to which a plurality of rectifying blades 16 extending radially from the center line are attached. Then, by adjusting one of the rectifying blades 16 by a minute angle with respect to the vertical axis, the direction of the water flow hitting the blades 11 of the impeller 10 is slightly changed, and the rotational speed of the impeller 10 is slightly changed. Can be adjusted. In the case of a mechanical flow meter, the rotation speed is counted by transmitting the rotation of the impeller 10 to a rotation accumulator by a gear or the like.

図２に示されるように、羽根車１０は、外周面に各羽根１１が延設された斜め円筒形状のボス部１２と、該ボス部１２に連結されて羽根車１０全体を回転支持するための回転軸１７とを有している。前記回転軸１７の外径は、前記ボス部１２の外径よりも小さい。前記各羽根１１は、水流の乱れを生じさせにくくするために、回転軸１７の軸線に対して等間隔で、かつ同じ方向にねじれた状態で取付けられている。羽根車１０の各羽根１１に水の圧力が作用することにより、回転軸１７の軸心を中心に羽根車１０が回転される。このときの回転数が換算されて電子カウンター１３に表示されることにより、水の通過量が計測される。なお、羽根車１０の羽根１１には、図３の（ａ），（ｂ）に示されるように、厚みｔが延設方向の全長に亘って一定であるものと、基端部から先端部にかけての厚みｔ１，ｔ２が漸減するもの（徐々に薄くなっているもの）とが存している。 As shown in FIG. 2, the impeller 10 is configured to rotate and support the impeller 10 as a whole by being connected to the boss portion 12 having an oblique cylindrical shape in which each blade 11 is extended on the outer peripheral surface. Rotation shaft 17. The outer diameter of the rotating shaft 17 is smaller than the outer diameter of the boss portion 12. Each of the blades 11 is attached in a state of being twisted in the same direction at equal intervals with respect to the axis of the rotating shaft 17 in order to make it difficult to disturb the water flow. When the pressure of water acts on each blade 11 of the impeller 10, the impeller 10 is rotated about the axis of the rotation shaft 17. The amount of water passing is measured by converting the number of rotations at this time and displaying it on the electronic counter 13. As shown in FIGS. 3A and 3B, the blade 11 of the impeller 10 has a thickness t that is constant over the entire length in the extending direction, and from the proximal end portion to the distal end portion. In some cases, the thicknesses t 1 and t 2 gradually decrease (thickness gradually decreases).

ここで、流量計１において、流量−器差曲線の特定流量域（特に小流量域）で器差がプラス傾向を示す原因として、水の流量を計測するために設置された羽根車１０が、水の流れを阻害するためと考えられる。乱流、層流の違いにより、流れの中に置かれた各羽根１１に対する抵抗が流量（面積が一定のため、流速でも同じになる）に比例せず、乱流域である大流域において抵抗が増し、羽根車１０の回転を阻害させる。ところが、層流となる小流域においては、各羽根１１への抵抗が小さくなり、羽根車１０の回転がスムーズとなり、小流域での器差が大流域と比較して、みかけ上大きくなり、これがピークとなる。この推察から展開すると、計量室７における水の流れ方向と直交する面で、水が通過する面積Ｓ１と、該水の通過を阻害する各羽根１１が占める面積Ｓ２との割合（面積割合Ｒ）が、器差のピークに影響を与えると考えられる。 Here, in the flow meter 1, the impeller 10 installed to measure the flow rate of water as a cause of the instrumental difference showing a positive tendency in a specific flow rate region (particularly a small flow rate region) of the flow rate-instrument difference curve This is considered to inhibit the flow of water. Due to the difference between turbulent flow and laminar flow, the resistance to each blade 11 placed in the flow is not proportional to the flow rate (because the area is constant, and the flow velocity is the same), and the resistance is large in the turbulent flow area. The rotation of the impeller 10 is inhibited. However, in the small basin where the flow is laminar, the resistance to each blade 11 is reduced, the rotation of the impeller 10 is smooth, and the instrumental difference in the small basin is apparently larger compared to the large basin. It becomes a peak. When deployed from the inferred, in a plane perpendicular to the flow direction of water in the measuring chamber 7, the area S 1 that the water passes through the proportion (area ratio between the area S 2 occupied by each vane 11 to inhibit the passage of water R) is considered to affect the peak of instrumental error.

図４及び図５を参照しながら、流量計１の計量室７において各羽根１１が占める面積Ｓ１と、水が通過する領域の面積Ｓ２とを求める。計量室７の内径をＤ１、ボス部１２の外径をＤ２、羽根１１の厚みをｔ、羽根１１の枚数をｎ（本実施例の場合、ｎ＝１２）、羽根１１の長さをＬとすると、図５より、各羽根１１が占める面積Ｓ１と、水が通過する領域の面積Ｓ２は、それぞれ以下のようになる。
Ｓ１＝ｔ×ｎ×Ｌ 式（１）
Ｓ２＝[(Ｄ１ ２−Ｄ２ ２)×π／４]−Ｓ１ 式（２） 4 and 5, the area S 1 occupied by each blade 11 in the measuring chamber 7 of the flow meter 1 and the area S 2 of the region through which water passes are obtained. The inner diameter of the measuring chamber 7 is D 1 , the outer diameter of the boss part 12 is D 2 , the thickness of the blade 11 is t, the number of blades 11 is n (in this embodiment, n = 12), and the length of the blade 11 is Assuming that L, the area S 1 occupied by each blade 11 and the area S 2 of the region through which water passes are as follows from FIG.
S 1 = t × n × L Formula (1)
S 2 = [(D 1 2 −D 2 2 ) × π / 4] −S 1 formula (2)

ここで、各羽根１１の先端部と計量室７の内壁面との隙間ｅが極めて小さい（１〜３mm）。しかも、前記隙間ｅは、流れてきた異物との噛み込み等を防ぐために設けられているものであり、流量計１の器差をフラットにするという機能に関するものではない。よって、隙間ｅを無視できるとすると、Ｌ≒(Ｄ１−Ｄ２)／２となる。これを、式（１）に代入すると、各羽根１１が占める面積Ｓ１は以下のように表される。
Ｓ１＝ｔ×ｎ×(Ｄ１−Ｄ２)／２ 式（３） Here, the gap e between the tip of each blade 11 and the inner wall surface of the measuring chamber 7 is extremely small (1 to 3 mm). Moreover, the gap e is provided in order to prevent biting with the foreign material that has flowed, and is not related to the function of flattening the instrumental error of the flow meter 1. Therefore, if the gap e can be ignored, L≈ (D 1 −D 2 ) / 2. When this is substituted into the equation (1), the area S 1 occupied by each blade 11 is expressed as follows.
S 1 = t × n × ( D 1 -D 2) / 2 Equation (3)

上記した式（３）を式（２）に代入すると、水が通過する領域の面積Ｓ２は以下のように表される。
Ｓ２＝(Ｄ１ ２−Ｄ２ ２)×π／４−ｔ×ｎ×(Ｄ１−Ｄ２)／２ 式（４） Substituting equation (3) described above in equation (2), the area S 2 of a region where water passes is expressed as follows.
S 2 = (D 1 2 -D 2 2 ) × π / 4−t × n × (D 1 -D 2 ) / 2 Formula (4)

式（３）と式（４）より、各羽根１１が占める面積Ｓ１と水が通過する領域の面積Ｓ２との割合（面積割合Ｒ）を求める。
Ｒ＝Ｓ１／Ｓ２
＝[ｔｎ(Ｄ１−Ｄ２)／２]／[π(Ｄ１ ２−Ｄ２ ２)／４−ｔｎ(Ｄ１−Ｄ２)／２]
＝２ｔｎ(Ｄ１−Ｄ２)／[Ｄ１ ２π−Ｄ２ ２π−２ｔｎ(Ｄ１−Ｄ２)]
なお、上式においては、乗算の記号（「×」）の表示を省略している。 From the expressions (3) and (4), the ratio (area ratio R) between the area S 1 occupied by each blade 11 and the area S 2 of the region through which water passes is obtained.
R = S 1 / S 2
= [Tn (D 1 -D 2 ) / 2] / [π (D 1 2 -D 2 2 ) / 4-tn (D 1 -D 2 ) / 2]
= 2tn (D 1 -D 2 ) / [D 1 2 π-D 2 2 π-2tn (D 1 -D 2 )]
In the above equation, the display of the symbol for multiplication (“×”) is omitted.

そして、図３の（ｂ）に示されるように、羽根車１０における各羽根１１の厚みが長さ方向に漸減している場合、各羽根１１における最も厚い部分の厚みｔ１と、最も薄い部分の厚みｔ２との平均値をとって、羽根１１の厚みｔとする。即ち、この場合の羽根１１の厚みｔは、ｔ＝(ｔ１−ｔ２)／２で表される。 As shown in FIG. 3B, when the thickness of each blade 11 in the impeller 10 is gradually reduced in the length direction, the thickness t 1 of the thickest portion and the thinnest portion in each blade 11 The thickness t 2 of the blade 11 is taken as an average value. That is, the thickness t of the blade 11 in this case is represented by t = (t 1 −t 2 ) / 2.

また、各羽根１１とボス部１２との接続部分には、各羽根１１の強度を増すために丸面取り（Ｒ面取り）をするのが普通であるが、上式では丸面取りがないものとして羽根の厚みｔを決定している。   In addition, the connecting portion between each blade 11 and the boss portion 12 is usually rounded (R chamfered) in order to increase the strength of each blade 11, but in the above formula, the blade is assumed to have no round chamfering. The thickness t is determined.

本出願人は、各種の大きさの流量計１において、水が通過する領域の面積Ｓ１と羽根車１０の各羽根１１が占める面積Ｓ２を調べ、それらの面積割合Ｒを算出した。そして、流量ポイントＱ１−Ｑ３の器差を測定した。更に、水の流量を変えたときの器差を測定した。その結果を、図６に示す。 The present applicant examined the area S1 of the region through which water passes and the area S2 occupied by each blade 11 of the impeller 10 in the flowmeters 1 of various sizes, and calculated their area ratio R. And the instrumental difference of the flow point Q1-Q3 was measured. Furthermore, the instrumental error when the flow rate of water was changed was measured. The result is shown in FIG .

図６の(ａ)に示される各測定データを、図６の（ｂ）においてグラフに示す。このグラフより、面積割合Rが１８％の場合には、小流量域において器差のピークが発生するが、１１％以下の場合には、小流量域であってもピークが発生していないことがわかる。   Each measurement data shown in FIG. 6A is shown in a graph in FIG. From this graph, when the area ratio R is 18%, an instrumental error peak occurs in the small flow rate range, but when it is 11% or less, no peak occurs even in the small flow rate range. I understand.

なお、計量室７の内径Ｄ１が水の流れ方向に対して変化している場合には、該計量室７の内径Ｄ１が最小である断面において、面積割合Ｒが０．０５〜０．１１の範囲に存することが必要である。なぜならば、計量室７の内径Ｄ１が最も小さい部分において、水が通過する領域の面積Ｓ１が最小になる（即ち、面積割合Ｒが最大になる）からである。換言すれば、断面が最小の部分で面積割合Ｒが０．０５〜０．１１の範囲に存すれば、それよりも大きな断面の部分では、面積割合Ｒが０．０５〜０．１１の範囲に存することが確実だからである。同様にして、羽根車１０のボス部１２の外径が最大である断面において、面積割合Ｒが０．０５〜０．１１の範囲に存することが必要である。 In the case where the inner diameter D 1 of the metering chamber 7 is changed relative to the direction of flow of the water, the cross-sectional inner diameter D 1 of the metering chamber 7 is the smallest, the area ratio R is from 0.05 to 0. It is necessary to be in the range of 11 . This is because the area S 1 of the region through which water passes is minimized (that is, the area ratio R is maximized) in the portion where the inner diameter D 1 of the measuring chamber 7 is the smallest. In other words, if Sonsure a range of cross-section area ratio R with minimal parts 0.05 to 0.11, in the portion of larger cross-section than, the area ratio R is from 0.05 to 0.11 range It is because it is certain that it exists. Similarly, in the cross section in which the outer diameter of the boss portion 12 of the impeller 10 is maximum, the area ratio R needs to be in the range of 0.05 to 0.11 .

上記した面積割合Ｒをできるだけ小さくする方法として、羽根車１０の羽根１１の枚数ｎを減らして面積割合Ｒを小さくすること、あるいは羽根車１０の各羽根１１の厚みｔを薄くして面積割合Ｒを小さくすることも効果的である。ただし、羽根車１０の各羽根１１の枚数ｎを減らして面積割合Ｒを小さくする方法の場合、前記羽根１１の枚数ｎを極端に減らすと、計量室７内において羽根車１０の回転に作用しない水の量（不感水量）が多くなり、微小流領域において羽根車１０が自身の回転負荷抵抗に負けてしまい、その結果、前記羽根車１０が流量に比例して回転しなくなり、器差特性が大きくマイナスになったり、羽根車１０が不動になったりするおそれがある。また、羽根車１０の各羽根１１の厚みｔを薄くしすぎると、各羽根１１が強度不足によって破損したり、器差異常等を発生したりするおそれがある。このため、上記した各種の方法を組み合わせながら、面積割合Ｒが０．０５〜０．１１の範囲になるように流量計１を設計することが必要である。 As a method for reducing the above-described area ratio R as much as possible, the area ratio R is reduced by reducing the number n of the blades 11 of the impeller 10 or the area ratio R is decreased by reducing the thickness t of each blade 11 of the impeller 10. It is also effective to reduce. However, in the method of reducing the area ratio R by reducing the number n of each blade 11 of the impeller 10, if the number n of the blade 11 is extremely reduced, it does not affect the rotation of the impeller 10 in the measuring chamber 7. The amount of water (insensitive water amount) increases, and the impeller 10 loses its rotational load resistance in the micro flow region. As a result, the impeller 10 does not rotate in proportion to the flow rate, and the instrumental error characteristic is There is a risk that it will be greatly negative or the impeller 10 may become immobile. Further, if the thickness t of each blade 11 of the impeller 10 is made too thin, each blade 11 may be damaged due to insufficient strength, or an instrumental error or the like may occur. For this reason, it is necessary to design the flow meter 1 so that the area ratio R is in the range of 0.05 to 0.11 while combining the various methods described above.

本明細書では、縦型軸流羽根車式流量計について説明した。しかし、本発明に係る面積割合Ｒの関係を、横型軸流羽根車式流量計に適用することもできる。   In the present specification, the vertical axial flow impeller flow meter has been described. However, the relationship of the area ratio R according to the present invention can also be applied to a horizontal axial flow impeller flow meter.

本発明の実施例の流量計１の正面断面図である。It is front sectional drawing of the flowmeter 1 of the Example of this invention. （ａ）は羽根車１０の斜視図であり、（ｂ）は同じく正面図である。(A) is a perspective view of the impeller 10, (b) is also a front view. （ａ）は厚みｔが一定の羽根１１の断面図であり、（ｂ）は厚みｔ１，ｔ２が基端部から先端部にかけて漸減する羽根１１の断面図である。(A) is sectional drawing of the blade | wing 11 with constant thickness t, (b) is sectional drawing of the blade | wing 11 from which thickness t1, t2 decreases gradually from a base end part to a front-end | tip part. 羽根車１０が内装された計量室７の拡大断面図である。It is an expanded sectional view of the measurement chamber 7 with which the impeller 10 was equipped. 図４のＸ−Ｘ線断面図である。FIG. 5 is a sectional view taken along line XX in FIG. 4. （ａ）は水の流量を変化させたときの面積割合Ｒに対する器差を測定したものであり、（ｂ）は各面積割合Ｒにおける流量−器差曲線である。 (A) it is obtained by measuring the instrumental error for the area ratio R when changing the flow rate of the water, (b) the flow rate in each area ratio R - is instrumental error curve.

符号の説明Explanation of symbols

Ｄ１：計量室の内径
Ｄ２：ボス部の外径
ｎ：羽根の枚数
ｔ：羽根の厚み
１：流量計
４：流入口
５：流出口
７：計量室
１０：羽根車
１１：羽根
１２：ボス部 D 1 : Inner diameter of measuring chamber
D 2 : outer diameter of the boss
n: Number of blades
t: Thickness of the blade
1: Flow meter
4: Inlet
5: Outlet
7: Weighing room
10: Impeller
11: Feather
12: Boss

Claims (4)

流入口と流出口を有し、ボス部から半径方向に延設され、流体の流れによって回転する羽根車の羽根が、前記流体の流れ方向の中心軸を中心としてねじれた形状の流量計において、
前記羽根車が内装される計量室を、前記流体の流れ方向と直交する面で切断し、計量室の内径をＤ１、羽根車のボス部の外径をＤ２、羽根の枚数をｎ、羽根の厚みをｔ、円周率をπとしたとき、
０．０５＜２ｔｎ（Ｄ１−Ｄ２）／［Ｄ１ ２π−Ｄ２ ２π−２ｔｎ（Ｄ１−Ｄ２）］＜０．１１
の関係が成立することを特徴とする流量計。 In a flowmeter having an inlet and an outlet, extending in a radial direction from a boss portion and rotating with a fluid flow, the blades of an impeller twisted about a central axis in the fluid flow direction,
The measuring chamber in which the impeller is built is cut along a plane perpendicular to the fluid flow direction, the inner diameter of the measuring chamber is D 1 , the outer diameter of the boss portion of the impeller is D 2 , the number of blades is n, When the thickness of the blade is t and the circumference is π,
0.05 <2tn (D 1 -D 2 ) / [D 1 2 π-D 2 2 π-2tn (D 1 -D 2)] <0.11
A flowmeter characterized by the fact that the relationship is established. 請求項１の関係が、前記計量室の内径が最小である断面において成立することを特徴とする請求項１に記載の流量計。   The flowmeter according to claim 1, wherein the relationship according to claim 1 is established in a cross section in which the inner diameter of the measuring chamber is minimum. 請求項１の関係が、前記羽根車のボス部の外径が最大である断面において成立することを特徴とする請求項１又は２に記載の流量計。   The flowmeter according to claim 1, wherein the relationship of claim 1 is established in a cross section in which the outer diameter of the boss portion of the impeller is maximum. 請求項１ないし３のいずれかに記載の流量計に内装されたことを特徴とする羽根車。   An impeller mounted on the flowmeter according to any one of claims 1 to 3.
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