JP4804178B2 - Liquid level sensor - Google Patents

Liquid level sensor Download PDF

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JP4804178B2
JP4804178B2 JP2006061469A JP2006061469A JP4804178B2 JP 4804178 B2 JP4804178 B2 JP 4804178B2 JP 2006061469 A JP2006061469 A JP 2006061469A JP 2006061469 A JP2006061469 A JP 2006061469A JP 4804178 B2 JP4804178 B2 JP 4804178B2
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利雄 大池
泰典 川口
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Description

本発明は、液体に浸漬された電極対の両電極間の静電容量により液面レベルを検出する静電容量式の液面レベルセンサに関する。   The present invention relates to a capacitance-type liquid level sensor that detects a liquid level by the capacitance between both electrodes of an electrode pair immersed in a liquid.

近年、自動車等の車両の燃料タンクには、液体に浸漬された電極対の両電極間の静電容量により液面レベルを検出する静電容量式の液面レベルセンサが用いられている。電極対の両電極間の静電容量は液体の誘電率により変化し、液体の誘電率は液体の種類や温度等の条件により変化する。そこで従来、静電容量式の液面レベルセンサにおいて、液体の誘電率に応じて補正を行うようにした液面レベルセンサが知られている（例えば、特許文献１参照）。   2. Description of the Related Art In recent years, a capacitance-type liquid level sensor that detects a liquid level based on capacitance between both electrodes of an electrode pair immersed in a liquid has been used in a fuel tank of a vehicle such as an automobile. The capacitance between both electrodes of the electrode pair varies depending on the dielectric constant of the liquid, and the dielectric constant of the liquid varies depending on conditions such as the type of liquid and temperature. In view of this, a liquid level sensor that performs correction according to the dielectric constant of a liquid in a capacitance type liquid level sensor has been known (for example, see Patent Document 1).

特許文献１に開示されたセンサは、平坦面が鉛直となるように対向配置された平板状の測定用電極対と、対向配置された平板状の参照用電極対とを備え、測定用電極対の両電極間の静電容量及び参照用電極対の両電極間の静電容量に基づいて水位を検出するものである。参照用電極対は液体に浸漬され、参照用電極対の両電極間の液中及び気中における静電容量の比から液体の誘電率が求められる。そして、測定用電極対の両電極間の静電容量に対し、求められた液体の誘電率を用いて補正を行い、水位を高精度に検出するようにしている。   The sensor disclosed in Patent Document 1 includes a flat plate-like measurement electrode pair arranged so that a flat surface is vertical, and a flat plate-like reference electrode pair arranged so as to face each other. The water level is detected based on the capacitance between the two electrodes and the capacitance between the two electrodes of the reference electrode pair. The reference electrode pair is immersed in the liquid, and the dielectric constant of the liquid is obtained from the ratio of the capacitance in the liquid and in the air between the two electrodes of the reference electrode pair. Then, the capacitance between the electrodes of the measurement electrode pair is corrected using the obtained dielectric constant of the liquid, and the water level is detected with high accuracy.

特開平１１−１０８７３５号公報Japanese Patent Laid-Open No. 11-108735

しかし、特許文献１に開示されたセンサでは、参照用電極対が少しでも気中に露出すると参照用電極対により求められる液体の誘電率に誤差を生じ、水位の検出精度が低下する原因となる。よって、参照用電極対は常に液中に配置される必要があるが、このことは測定用電極対による水位の検出範囲を参照用電極対が完全に浸漬する水位よりも上方に限定することとなる。そして、測定用電極対による水位の検出範囲を下方に拡大すべく参照用電極対を小型化すると、参照用電極対の出力が不安定となり、やはり液体の誘電率に誤差を生じる。   However, in the sensor disclosed in Patent Document 1, if the reference electrode pair is exposed to the air even a little, an error occurs in the dielectric constant of the liquid obtained by the reference electrode pair, which causes a decrease in water level detection accuracy. . Therefore, the reference electrode pair must always be placed in the liquid, which limits the water level detection range by the measurement electrode pair above the water level at which the reference electrode pair is completely immersed. Become. Then, if the reference electrode pair is downsized to expand the water level detection range by the measurement electrode pair downward, the output of the reference electrode pair becomes unstable, and an error also occurs in the dielectric constant of the liquid.

このように、特許文献１に開示されたセンサでは、液体容器の底までの液面レベルの検出、つまり液面レベルが低いときの液面レベルの検出は困難であった。そして、薄型の燃料タンクが求められる近年の自動車において、液面レベルセンサの検出不能な範囲がタンク底部にあることは車両性能上大きな問題であり、タンクの底まで検出可能な液面レベルセンサが求められている。   Thus, with the sensor disclosed in Patent Document 1, it is difficult to detect the liquid level to the bottom of the liquid container, that is, to detect the liquid level when the liquid level is low. And in recent automobiles where a thin fuel tank is required, it is a big problem in terms of vehicle performance that there is a range where the liquid level sensor cannot be detected at the bottom of the tank, and there is a liquid level sensor that can detect up to the bottom of the tank. It has been demanded.

さらに、特許文献１に開示されたセンサは、測定用電極対及び参照用電極対の２組の電極対を必要とし、センサの小型化が難しい。また、これら２組の電極対は露出しているため電磁波等の影響を受けやすく、それにより両電極間の静電容量が変化して液面レベルの検出精度が低下する虞がある。さらに、自動車等の車両では、走行時には振動で燃料が揺さぶられ、燃料の飛沫が露出した電極対に付着することも考えられるが、この場合、電極対の両電極間の静電容量が正規より高い値となり液面レベルの検出精度が低下する。また、走行時には燃料が揺さぶられ、その液面が安定せず、露出した電極対はその影響を直接に受けるため、検出される液面レベルが安定しない。   Furthermore, the sensor disclosed in Patent Document 1 requires two electrode pairs, a measurement electrode pair and a reference electrode pair, and it is difficult to reduce the size of the sensor. In addition, since these two electrode pairs are exposed, they are easily affected by electromagnetic waves or the like, which may change the capacitance between the two electrodes and reduce the detection accuracy of the liquid level. Furthermore, in vehicles such as automobiles, the fuel may be shaken by vibration during driving, and fuel droplets may adhere to the exposed electrode pair.In this case, the capacitance between the electrodes of the electrode pair is more than normal. The value becomes high and the detection accuracy of the liquid level is lowered. Further, during running, the fuel is shaken, the liquid level is not stable, and the exposed electrode pair is directly affected by the influence, so that the detected liquid level is not stable.

本発明は、上述した事情に鑑みてなされたものであり、その目的は、小型化を図り、さらには液面レベルの検出精度を高めた液面レベルセンサを提供することにある。   The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a liquid level sensor that is downsized and further increases the detection accuracy of the liquid level.

上記目的は、本発明に係る下記（１）〜（５）の液面レベルセンサにより達成される。 The above object is achieved by the following liquid level sensors according to the present invention (1) to ( 5 ).

（１）絶縁性基体の外周に互いに平行に螺旋状に巻きつけられた第１電極及び第２電極と、前記第１電極及び前記第２電極に対向するように前記絶縁性基体の外周を取り囲む第３電極と、を備え、
前記第１電極及び前記第２電極の螺旋軸が鉛直となるように配置され、前記第１電極及び前記第２電極の螺旋ピッチが、上端から下端に向かうに従って徐々に密となるように設定され、
前記第３電極が筒状に形成され、前記第１電極及び前記第２電極並びに前記絶縁性基体が、前記第３電極内に収容され、
前記第１電極と前記第２電極とから成る第１の電極対、及び、前記第１電極または第２電極と前記第３電極とから成る第２の電極対の２組の電極対がそれぞれ液体に浸漬された際の両電極間の静電容量に基づいて、該液体の液面レベルを検出することを特徴とする液面レベルセンサ。 (1) Surrounding the outer periphery of the insulating base so as to face the first electrode and the second electrode, and the first electrode and the second electrode spirally wound in parallel with each other on the outer periphery of the insulating base A third electrode;
The first electrode and the second electrode are arranged so that the spiral axes thereof are vertical, and the spiral pitch of the first electrode and the second electrode is set so as to gradually become denser from the upper end toward the lower end. ,
The third electrode is formed in a cylindrical shape, and the first electrode, the second electrode, and the insulating substrate are accommodated in the third electrode,
Two electrode pairs, the first electrode pair composed of the first electrode and the second electrode, and the second electrode pair composed of the first electrode or the second electrode and the third electrode, are liquids, respectively. A liquid level sensor that detects a liquid level of the liquid based on a capacitance between both electrodes when immersed in the liquid.

（２）筒状の前記第３電極が、その周壁を軸に沿って分断されて開閉可能に構成されていることを特徴とする上記（１）に記載の液面レベルセンサ。 ( 2 ) The liquid level sensor according to ( 1 ), wherein the cylindrical third electrode is configured to be opened and closed by dividing a peripheral wall thereof along an axis.

（３）筒状の前記第３電極の下端の開口を塞ぐ底板を有し、
前記底板にオリフィスが穿設されていることを特徴とする上記（１）又は（２）に記載の液面レベルセンサ。 ( 3 ) having a bottom plate that closes the opening at the lower end of the cylindrical third electrode;
The liquid level sensor according to ( 1 ) or ( 2 ) above, wherein an orifice is formed in the bottom plate.

（４）前記オリフィスの外側に該オリフィスを覆うフィルタを有していることを特徴とする上記（３）に記載の液面レベルセンサ。 ( 4 ) The liquid level sensor according to ( 3 ), wherein a filter that covers the orifice is provided outside the orifice.

（５）２組の前記電極対それぞれの両電極間の静電容量に基づいて前記液体の液面レベルを演算するための回路が、筒状の前記第３電極に収容されていることを特徴とする上記（１）〜（４）のいずれかに記載の液面レベルセンサ。 ( 5 ) The circuit for calculating the liquid level of the liquid based on the capacitance between both electrodes of the two sets of electrode pairs is accommodated in the cylindrical third electrode. The liquid level sensor according to any one of ( 1 ) to ( 4 ) above.

上記（１）の構成の液面レベルセンサによれば、２組の電極対を構成する電極は、第１の電極対を構成する第１電極及び第２電極、並びに、第２の電極対を構成する第１電極（または第２電極）及び第３電極である。よって、２組の電極対それぞれの液体に浸漬された際の両電極間の静電容量の変化は互いに異なる。そして、これら２組の電極対それぞれの両電極間の静電容量の比に基づいて、液体の誘電率の影響を補正して液面レベルを精度よく検出することができる。
ここで、液面レベルの検出は２組の電極対それぞれの一部が液体に浸漬されていれば可能であり、その検出範囲は２組の電極対の水平方向の重複部分となる。これによれば、従来のように参照用電極対を常に液中に配置しておく必要がなく、液体容器の底もしくはその近傍まで液面レベルを検出することができる。
そして、従来は測定用電極対と参照用電極対とに独立した計４つの電極が必要であったのに対し、２組の電極対を第１〜第３電極の組み合わせで構成することで部品点数を削減することができ、液面レベルセンサの小型化を図ることができる。 According to the liquid level sensor having the above configuration (1), the electrodes constituting the two electrode pairs include the first electrode and the second electrode constituting the first electrode pair, and the second electrode pair. It is the 1st electrode (or 2nd electrode) and 3rd electrode which comprise. Therefore, the capacitance changes between the two electrodes when immersed in the liquids of the two electrode pairs are different from each other. The liquid level can be detected with high accuracy by correcting the influence of the dielectric constant of the liquid on the basis of the capacitance ratio between the two electrodes of the two pairs of electrodes.
Here, the detection of the liquid level is possible if a part of each of the two pairs of electrodes is immersed in the liquid, and the detection range is an overlapping portion of the two pairs of electrodes in the horizontal direction. According to this, it is not necessary to always arrange the reference electrode pair in the liquid as in the prior art, and the liquid level can be detected up to the bottom of the liquid container or the vicinity thereof.
Conventionally, a total of four electrodes are required for the measurement electrode pair and the reference electrode pair, whereas the two electrode pairs are configured by combining the first to third electrodes. The number of points can be reduced, and the liquid level sensor can be downsized.

また、第１電極及び第２電極の螺旋ピッチが下端ほど密とされ、液面が下端部にあるとき、即ち液面レベルが低いときの液面変位に対する２組の電極対それぞれの両電極間の静電容量の変化率が比較的大きくなる。これにより、液面レベルが低いときの液面レベルの検出精度を向上させることができる。 Further , when the spiral pitch of the first electrode and the second electrode is closer to the lower end and the liquid level is at the lower end, that is, between the two electrodes of each of the two electrode pairs with respect to the liquid level displacement when the liquid level is low The rate of change of the electrostatic capacity becomes relatively large. Thereby, the detection accuracy of the liquid level when the liquid level is low can be improved.

また、筒状の第３電極内に第１電極及び第２電極を収容することで第１電極及び第２電極を電気的にシールドし、第１電極及び第２電極に作用する電磁波等の影響を排除することができる。さらには、液体容器内で液体が激しく揺さぶられたとしても筒状の第３電極内では液体の揺れが軽減され、液体の飛沫が飛び難く、また液面も安定する。これにより、液面レベルを精度よく、安定して検出することができる。 In addition , by housing the first electrode and the second electrode in the cylindrical third electrode, the first electrode and the second electrode are electrically shielded, and the influence of electromagnetic waves acting on the first electrode and the second electrode is affected. Can be eliminated. Furthermore, even if the liquid is vigorously shaken in the liquid container, the liquid shake is reduced in the cylindrical third electrode, so that the liquid splash is difficult to fly and the liquid level is stabilized. Thereby, the liquid level can be detected accurately and stably.

上記（２）の構成の液面レベルセンサによれば、第３電極を開くことで該第３電極内に第１電極及び第２電極並びに絶縁性基体を容易に収容することができる。 According to the liquid level sensor having the configuration ( 2 ), the first electrode, the second electrode, and the insulating base can be easily accommodated in the third electrode by opening the third electrode.

上記（３）の構成の液面レベルセンサによれば、ダンパー効果を得ることができ、液体容器内で液体が激しく揺さぶられたとしても筒状の第３電極内では液体の揺れが軽減され、液面が安定する。これにより、液面レベルを安定して検出することができ。 According to the liquid level sensor having the above configuration ( 3 ), a damper effect can be obtained, and even if the liquid is vigorously shaken in the liquid container, the liquid shake is reduced in the cylindrical third electrode, The liquid level is stable. Thereby, a liquid level can be detected stably.

上記（４）の構成の液面レベルセンサによれば、ごみ等でオリフィスが詰まることを防止することができ、筒状の第３電極内に異物が侵入し電極間が短絡することを未然に防ぐことができる。 According to the liquid level sensor having the above configuration ( 4 ), it is possible to prevent the orifice from being clogged with dust or the like, and to prevent foreign matter from entering the third cylindrical electrode and shorting between the electrodes. Can be prevented.

上記（５）の構成の液面レベルセンサによれば、演算回路も第３電極で電気的にシールドし、電磁波等の影響を排除することができ、また、液面レベルセンサをコンパクトにまとめることができる。 According to the liquid level sensor having the above configuration ( 5 ), the arithmetic circuit can also be electrically shielded by the third electrode to eliminate the influence of electromagnetic waves and the like, and the liquid level sensor can be compactly integrated. Can do.

本発明によれば、小型化を図り、さらには液面レベルの検出精度を高めた液面レベルセンサを提供することができる。   According to the present invention, it is possible to provide a liquid level sensor that is miniaturized and further increases the detection accuracy of the liquid level.

以下、本発明に係る好適な実施形態を図面に基づいて詳細に説明する。
図１は本発明に係る液面レベルセンサの一実施形態の正面図、図２は図１の液面レベルセンサの底面図、図３は図１の液面レベルセンサにおいて液面変位と２組の電極対それぞれの両電極間の静電容量との関係を示すグラフである。 DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
FIG. 1 is a front view of an embodiment of a liquid level sensor according to the present invention, FIG. 2 is a bottom view of the liquid level sensor of FIG. 1, and FIG. It is a graph which shows the relationship with the electrostatic capacitance between both electrodes of each electrode pair.

図１及び図２に示すように、本実施形態の液面レベルセンサ１０は、容器１内の液体Ｌに浸漬されて液体Ｌの液面Ｓのレベルを検出するものである。この液面レベルセンサ１０は、絶縁性基体１２の外周に互いに平行に螺旋状に巻きつけられた第１電極１３及び第２電極１４と、第１電極１３及び第２電極１４に対向するように絶縁性基体１２の外周を取り囲む第３電極１５と、を備えている。   As shown in FIGS. 1 and 2, the liquid level sensor 10 of the present embodiment detects the level of the liquid level S of the liquid L by being immersed in the liquid L in the container 1. The liquid level sensor 10 is opposed to the first electrode 13 and the second electrode 14 that are spirally wound around the outer periphery of the insulating substrate 12 in parallel with each other, and the first electrode 13 and the second electrode 14. And a third electrode 15 surrounding the outer periphery of the insulating substrate 12.

絶縁性基体１２は、角柱状の中央部の周面から四方に放射状にリブ２１が突設されて長手方向に垂直な断面において略十字状に形成された棒状部材であり、その長手方向を鉛直として配置される。絶縁性基体１２の材料は特に限定されないが、強度や液体（車両燃料等）に対する耐性などを考慮して、例えばポリアセタール樹脂等の合成樹脂を用いることが好ましい。   The insulative base 12 is a rod-like member that is formed in a substantially cross shape in a cross section perpendicular to the longitudinal direction, with ribs 21 projecting radially from the peripheral surface of the central portion of the prismatic shape, and the longitudinal direction is vertical. Arranged as. The material of the insulating substrate 12 is not particularly limited, but it is preferable to use, for example, a synthetic resin such as a polyacetal resin in consideration of strength and resistance to liquid (vehicle fuel and the like).

第１電極１３及び第２電極１４は、絶縁性基体１２の４つのリブ２１の外周に互いに平行に螺旋状に巻きつけられており、その螺旋ピッチは、電極１３，１４がそれぞれ接続される端子１６，１７が設けられた絶縁性基体１２の長手方向の上端から、下端に向けて徐々に密となるように設定されている。   The first electrode 13 and the second electrode 14 are spirally wound around the outer periphery of the four ribs 21 of the insulating base 12 in parallel with each other, and the helical pitch is a terminal to which the electrodes 13 and 14 are connected, respectively. The insulating base 12 provided with 16 and 17 is set so as to become denser gradually from the upper end in the longitudinal direction toward the lower end.

各リブ２１の外縁には、第１電極１３及び第２電極１４の螺旋ピッチに対応して複数の保持溝がそれぞれ刻設されており、電極１３，１４は、これらの保持溝に差し込まれながら各リブ２１の外縁に巻きつけられている。尚、電極１３，１４の材料には、液体（車両燃料等）に対する耐性を考慮して、ＳＵＳや洋白などを用いることが好ましい。   A plurality of holding grooves are formed on the outer edges of the ribs 21 corresponding to the helical pitches of the first electrode 13 and the second electrode 14, and the electrodes 13 and 14 are inserted into these holding grooves. It is wound around the outer edge of each rib 21. Note that it is preferable to use SUS, white or the like as the material of the electrodes 13 and 14 in consideration of resistance to liquid (vehicle fuel or the like).

第３電極１５は、略円筒状に形成された金属パイプであり、内部に第１電極１３及び第２電極１４並びに絶縁性基体１２を収容しており、その内周面は、電極１３，１４と隙間をおいて半径方向に対向している。第３電極１５の材料には、液体（車両燃料等）に対する耐性を考慮して、ＳＵＳや洋白などを用いることが好ましい。   The third electrode 15 is a metal pipe formed in a substantially cylindrical shape, and accommodates the first electrode 13, the second electrode 14, and the insulating base 12 therein, and the inner peripheral surface thereof has electrodes 13, 14. With a gap in the radial direction. For the material of the third electrode 15, it is preferable to use SUS, white or the like in consideration of resistance to liquid (vehicle fuel or the like).

第３電極１５の下端の開口は底板２２により塞がれている。底板２２と容器１の底面との間には僅かに隙間がおかれ、そして底板２２には少なくとも１つ（本実施形態では２つ）のオリフィス（小孔）２３が穿設されており、液体Ｌはオリフィス２３を通して第３電極１５内へ流入し、もしくは第３電極１５外へ流出する。オリフィス２３により液体Ｌの流入及び流出は緩慢なものとなり、つまり、ダンパーの如く振舞う。尚、図示は省略するが、オリフィス２３の外側に該オリフィス２３を覆うフィルターが設けられている。   The opening at the lower end of the third electrode 15 is closed by the bottom plate 22. A slight gap is provided between the bottom plate 22 and the bottom surface of the container 1, and at least one (two in this embodiment) orifices (small holes) 23 are formed in the bottom plate 22. L flows into the third electrode 15 through the orifice 23 or out of the third electrode 15. The orifice 23 makes the inflow and outflow of the liquid L slow, that is, it behaves like a damper. Although not shown, a filter that covers the orifice 23 is provided outside the orifice 23.

液面Ｓの変位に伴い、第１電極１３と第２電極１４とで構成される電極対の両電極間、第２電極１４と第３電極１５とで構成される電極対の両電極間、あるいは第３電極１５と第１電極１３とで構成される電極対の両電極間に液体が介在している部分の長さが変化し、これらの電極対それぞれの両電極間の静電容量が変化する。これらの電極対それぞれの両電極間の静電容量は、回路ユニット１９にて測定される。   Along with the displacement of the liquid level S, between both electrodes of the electrode pair composed of the first electrode 13 and the second electrode 14, between both electrodes of the electrode pair composed of the second electrode 14 and the third electrode 15, Alternatively, the length of the portion where the liquid is interposed between both electrodes of the electrode pair constituted by the third electrode 15 and the first electrode 13 is changed, and the capacitance between both electrodes of each of these electrode pairs is changed. Change. The capacitance between both electrodes of each of these electrode pairs is measured by the circuit unit 19.

回路ユニット１９は、絶縁性基体１２の上方に位置し、第３電極１５内に収容されている。尚、第３電極１５の上端の開口は、蓋板２４により塞がれており、この蓋板２４には空気抜きのための小孔２５が穿設されている。電極１３，１４，１５は、それぞれ端子１６，１７，１８を介して、回路ユニット１９内の測定回路に接続されている。   The circuit unit 19 is located above the insulating base 12 and is accommodated in the third electrode 15. Note that the opening at the upper end of the third electrode 15 is closed by a cover plate 24, and a small hole 25 for venting air is formed in the cover plate 24. The electrodes 13, 14, and 15 are connected to a measurement circuit in the circuit unit 19 via terminals 16, 17, and 18, respectively.

回路ユニット１９の測定回路では、電極１３，１４，１５の群から互いに異なる組み合わせで選ばれる２組の電極対を構成するように回路が適宜切換えられ、これら２組の電極対それぞれの両電極間の静電容量が測定され、測定された静電容量に基づいて所定の演算がなされ液面Ｓのレベルが検出される。この演算は、例えば以下のようにして行われる。   In the measurement circuit of the circuit unit 19, the circuits are appropriately switched so as to form two electrode pairs selected from the group of the electrodes 13, 14, 15 in different combinations, and between the two electrodes of each of these two electrode pairs. , And a predetermined calculation is performed based on the measured capacitance to detect the level of the liquid level S. This calculation is performed as follows, for example.

第１電極１３と第２電極１４とで構成される電極対（以下で第１電極対という）の両電極間の静電容量が測定される。次いで、回路が切換えられ、第２電極１４と第３電極１５とで構成される電極対（以下で第２電極対という）の両電極間の静電容量が測定される。尚、第３電極１５は常に接地電位とされ、第１電極１３及び第２電極１４のシールドとして機能している。   The capacitance between both electrodes of an electrode pair (hereinafter referred to as a first electrode pair) composed of the first electrode 13 and the second electrode 14 is measured. Next, the circuit is switched, and the capacitance between both electrodes of an electrode pair (hereinafter referred to as a second electrode pair) composed of the second electrode 14 and the third electrode 15 is measured. The third electrode 15 is always at ground potential and functions as a shield for the first electrode 13 and the second electrode 14.

図３に、容器１の底面からの液面Ｓの高さｈに対する第１電極対の静電容量Ｃ１及び第２電極対の静電容量Ｃ２の関係を示す。図中、一点差線が第１電極対の静電容量Ｃ１の特性曲線であり、二点鎖線が第２電極対の静電容量Ｃ２の特性曲線である。図３に示すように、第１電極１３及び第２電極１４の螺旋ピッチは下端ほど密とされており、液面Ｓの変位に対し、液面Ｓが下端部にあるときほど静電容量Ｃ１，Ｃ２の変化率が大きくなる。 FIG. 3 shows the relationship between the capacitance C 1 of the first electrode pair and the capacitance C 2 of the second electrode pair with respect to the height h of the liquid level S from the bottom surface of the container 1. In the figure, dashed-dotted line is a characteristic curve of the capacitance C 1 of the first electrode pair, the two-dot chain line is a characteristic curve of the capacitance C 2 of the second electrode pair. As shown in FIG. 3, the spiral pitch of the first electrode 13 and the second electrode 14 is closer to the lower end, and with respect to the displacement of the liquid level S, the capacitance C increases as the liquid level S is at the lower end. 1, C 2 of the change rate becomes large.

第１電極対の静電容量Ｃ１及び第２電極対の静電容量Ｃ２は、それぞれ次式で表される。

Figure 0004804178
ここで、ｋは定数であり、εｒは液体の誘電率であり、ｇ１（ｈ），ｇ２（ｈ）はそれぞれ図３に示す第１電極対の静電容量Ｃ１又は第２電極対の静電容量Ｃ２の特性曲線を原点に平行移動したものであってｈの関数であり、Ｃ０１，Ｃ０２はそれぞれ第１電極対又は第２電極対の気中（ｈ＝０）における静電容量である。 The capacitance C 2 of the capacitance C 1 and the second electrode pair of the first electrode pair are indicated by the following formulas, respectively.
Figure 0004804178
 Here, k is a constant, ε r is the dielectric constant of the liquid, and g 1 (h) and g 2 (h) are the capacitance C 1 or the second electrode of the first electrode pair shown in FIG. A characteristic curve of the capacitance C 2 of the pair is translated from the origin and is a function of h, and C 01 and C 02 are the air in the first electrode pair or the second electrode pair (h = 0), respectively. It is an electrostatic capacity in.

式（１）において両辺をＣ０１で割り、次式を得る。

Figure 0004804178
Both sides divided by C 01 in formula (1), the following equation is obtained.
Figure 0004804178

式（３）を整理して次式を得る。

Figure 0004804178
The following equation is obtained by rearranging equation (3).
Figure 0004804178

同様に式（２）において両辺をＣ０２で割り、整理して次式を得る。

Figure 0004804178
Similarly both sides divided by C 02 in formula (2), the following expression is obtained by organizing.
Figure 0004804178

式（４）で式（５）を辺々割り、次式を得る。

Figure 0004804178
Dividing equation (5) side by side with equation (4), the following equation is obtained.
Figure 0004804178

式（６）はεｒを含んでおらず、即ち、式（６）より液体の誘電率によらず液面レベルが算出される。尚、第１電極対及び第２電極対のいずれにも該当しない組み合わせで構成される電極対、即ち第３電極１５と第１電極１３とで構成される電極対の両電極間の静電容量を、第１電極対の静電容量Ｃ１及び第２電極対の静電容量Ｃ２の双方に加算するようにして、上記演算に供される両静電容量の値を全体的に上げるようにしてもよい。 Equation (6) does not include the epsilon r, that is, liquid level regardless the equation (6) the dielectric constant of the liquid is calculated. Note that the capacitance between both electrodes of an electrode pair constituted by a combination that does not correspond to either the first electrode pair or the second electrode pair, that is, an electrode pair constituted by the third electrode 15 and the first electrode 13. and so as to add both the capacitance C 2 of the capacitance C 1 and the second electrode pair of the first electrode pair, as generally increasing the values of both the capacitance to be used for the calculation It may be.

このように、本実施形態の液面レベルセンサ１０によれば、２組の電極対を構成する電極は、第１電極１３、第２電極１４、第３電極１５の群から互いに異なる組み合わせで選ばれる。よって、２組の電極対それぞれの液体Ｌに浸漬された際の両電極間の静電容量の変化は互いに異なる。そして、これら２組の電極対それぞれの両電極間の静電容量の比に基づいて、液体Ｌの誘電率の影響を補正して液面レベルを精度よく検出することができる。
ここで、液面レベルの検出は２組の電極対それぞれの一部が液体に浸漬されていれば可能であり、その検出範囲は２組の電極対の水平方向の重複部分となる。これによれば、従来のように参照用電極対を常に液中に配置しておく必要がなく、液体容器の底もしくはその近傍まで液面レベルを検出することができる。
そして、従来は測定用電極対と参照用電極対とに独立した計４つの電極が必要であったのに対し、２組の電極対を第１電極１３、第２電極１４、第３電極１５の組み合わせで構成することで部品点数を削減することができ、液面レベルセンサ１０の小型化を図ることができる。 Thus, according to the liquid level sensor 10 of the present embodiment, the electrodes constituting the two electrode pairs are selected from different combinations from the group of the first electrode 13, the second electrode 14, and the third electrode 15. It is. Therefore, the change in capacitance between both electrodes when immersed in the liquid L of each of the two pairs of electrodes is different from each other. Then, based on the capacitance ratio between the two electrodes of each of these two pairs of electrodes, the influence of the dielectric constant of the liquid L can be corrected and the liquid level can be detected accurately.
Here, the detection of the liquid level is possible if a part of each of the two pairs of electrodes is immersed in the liquid, and the detection range is an overlapping portion of the two pairs of electrodes in the horizontal direction. According to this, it is not necessary to always arrange the reference electrode pair in the liquid as in the prior art, and the liquid level can be detected up to the bottom of the liquid container or the vicinity thereof.
Conventionally, a total of four electrodes are required for the measurement electrode pair and the reference electrode pair, whereas the two electrode pairs are the first electrode 13, the second electrode 14, and the third electrode 15. Thus, the number of parts can be reduced, and the liquid level sensor 10 can be downsized.

また、本実施形態の液面レベルセンサ１０によれば、第１電極１３及び第２電極１４の螺旋ピッチが下端ほど密とされ、液面Ｓが下端部にあるとき、即ち液面レベルが低いときの液面変位に対する２組の電極対それぞれの両電極間の静電容量の変化率が比較的大きくなる。これにより、液面レベルが低いときの液面レベルの検出精度を向上させることができる。   Further, according to the liquid level sensor 10 of the present embodiment, when the spiral pitch of the first electrode 13 and the second electrode 14 is closer to the lower end and the liquid level S is at the lower end, that is, the liquid level is low. The change rate of the capacitance between the two electrodes of each of the two electrode pairs with respect to the liquid level displacement is relatively large. Thereby, the detection accuracy of the liquid level when the liquid level is low can be improved.

また、本実施形態の液面レベルセンサ１０によれば、筒状の第３電極１５内に第１電極１３及び第２電極１４を収容することで第１電極１３及び第２電極１４を電気的にシールドし、第１電極１３及び第２電極１４に作用する電磁波等の影響を排除することができる。さらには、液体容器内１で液体Ｌが激しく揺さぶられたとしても筒状の第３電極１５内では液体Ｌの揺れが軽減され、液体Ｌの飛沫が飛び難く、また液面Ｓも安定する。これにより、液面レベルを精度よく、安定して検出することができる。   Further, according to the liquid level sensor 10 of the present embodiment, the first electrode 13 and the second electrode 14 are electrically connected by housing the first electrode 13 and the second electrode 14 in the cylindrical third electrode 15. Thus, the influence of electromagnetic waves or the like acting on the first electrode 13 and the second electrode 14 can be eliminated. Furthermore, even if the liquid L is vigorously shaken in the liquid container 1, the liquid L is less shaken in the cylindrical third electrode 15, so that the splash of the liquid L is difficult to fly and the liquid level S is stabilized. Thereby, the liquid level can be detected accurately and stably.

また、本実施形態の液面レベルセンサ１０によれば、底板２２のオリフィス２３によりダンパー効果を得ることができ、液体容器１内で液体Ｌが激しく揺さぶられたとしても筒状の第３電極１５内では液体Ｌの揺れが軽減され、液面Ｓが安定する。これにより、液面レベルを安定して検出することができ。   Further, according to the liquid level sensor 10 of the present embodiment, the damper effect can be obtained by the orifice 23 of the bottom plate 22, and the cylindrical third electrode 15 can be obtained even if the liquid L is shaken violently in the liquid container 1. Inside, the shaking of the liquid L is reduced and the liquid level S is stabilized. Thereby, a liquid level can be detected stably.

また、本実施形態の液面レベルセンサ１０によれば、オリフィス２３の外側に該オリフィス２３を覆うフィルターを設けたので、ごみ等でオリフィス２３が詰まることを防止することができ、筒状の第３電極１５内に異物が侵入し電極間が短絡することを未然に防ぐことができる。   Further, according to the liquid level sensor 10 of the present embodiment, since the filter that covers the orifice 23 is provided outside the orifice 23, the orifice 23 can be prevented from being clogged with dust or the like, and the cylindrical first It is possible to prevent foreign matters from entering the three electrodes 15 and short-circuiting between the electrodes.

また、本実施形態の液面レベルセンサ１０によれば、回路ユニット１９までも第３電極１５内に収容されており、演算回路も第３電極１５で電気的にシールドし、電磁波等の影響を排除することができ、また、液面レベルセンサをコンパクトにまとめることができる。   Further, according to the liquid level sensor 10 of the present embodiment, even the circuit unit 19 is accommodated in the third electrode 15, and the arithmetic circuit is also electrically shielded by the third electrode 15, so that the influence of electromagnetic waves or the like is affected. In addition, the liquid level sensor can be compactly integrated.

尚、本発明は、上述した実施形態に限定されるものではなく、適宜、変形、改良、等が可能である。その他、上述した実施形態における各構成要素の材質、形状、寸法、数値、形態、数、配置箇所、等は本発明を達成できるものであれば任意であり、限定されない。   In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. In addition, the material, shape, dimension, numerical value, form, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary and not limited as long as the present invention can be achieved.

例えば、上述した液面レベルセンサ１０では、第３電極１５は金属パイプとして説明したが、これに限定されず、絶縁性材料からなるパイプの内周面に金属を電解・非電解メッキしたものでもよく、また、図４に示すように、軸に沿って分割してもよい。   For example, in the liquid level sensor 10 described above, the third electrode 15 has been described as a metal pipe. However, the present invention is not limited to this, and the inner peripheral surface of a pipe made of an insulating material may be electroless / electroless plated. Alternatively, as shown in FIG. 4, it may be divided along an axis.

図４に示す第３電極１５´は、内周面に金属メッキされた絶縁性の合成樹脂材料からなるパイプの周方向の一箇所を軸に沿って分断したものであって、軸に関して分断箇所と対称な箇所に設けられた薄肉のヒンジ部３１を変形させながら開閉する。これによれば、第３電極１５´を開いくことで、第３電極１５´内に第１電極１３及び第２電極１４並びに絶縁性基体１２を容易に収容することができる。尚、分断箇所の両縁には、閉じられた際に互いに係合するロック手段としての係止突起３２及び係止部３３がそれぞれ設けられている。尚、上述した実施形態の金属パイプの第３電極１５では、軸に沿って２分割し、両者を金属製のヒンジで物理的にも電気的にも接続するようにすればよい。   The third electrode 15 ′ shown in FIG. 4 is obtained by dividing one place in the circumferential direction of a pipe made of an insulating synthetic resin material plated with metal on the inner circumferential surface along the axis, and is divided with respect to the axis. Are opened and closed while deforming the thin hinge portion 31 provided in a symmetrical place. According to this, the 1st electrode 13, the 2nd electrode 14, and the insulating base | substrate 12 can be easily accommodated in 3rd electrode 15 'by opening 3rd electrode 15'. Note that a locking projection 32 and a locking portion 33 are provided as locking means that engage with each other when closed when both edges of the dividing portion are closed. The third electrode 15 of the metal pipe of the above-described embodiment may be divided into two along the axis, and both may be physically and electrically connected with a metal hinge.

本発明に係る液面レベルセンサの一実施形態の正面図である。It is a front view of one embodiment of a liquid level sensor according to the present invention. 図１の液面レベルセンサの底面図である。It is a bottom view of the liquid level sensor of FIG. 図１の液面レベルセンサにおいて液面変位と２組の電極対それぞれの両電極間の静電容量との関係を示すグラフである。2 is a graph showing a relationship between a liquid level displacement and capacitance between both electrodes of two pairs of electrodes in the liquid level sensor of FIG. 1. 図１の液面レベルセンサの第３電極の変形例の平面図である。It is a top view of the modification of the 3rd electrode of the liquid level sensor of FIG.

符号の説明Explanation of symbols

１ 容器
１０ 液面レベルセンサ
１２ 絶縁性基体
１３ 第１電極
１４ 第２電極
１５ 第３電極
２２ 底板
２３ オリフィス
Ｌ 液体
Ｓ 液面 DESCRIPTION OF SYMBOLS 1 Container 10 Liquid level sensor 12 Insulating base | substrate 13 1st electrode 14 2nd electrode 15 3rd electrode 22 Bottom plate 23 Orifice L Liquid S Liquid level

Claims (5)

絶縁性基体の外周に互いに平行に螺旋状に巻きつけられた第１電極及び第２電極と、前記第１電極及び前記第２電極に対向するように前記絶縁性基体の外周を取り囲む第３電極と、を備え、
前記第１電極及び前記第２電極の螺旋軸が鉛直となるように配置され、前記第１電極及び前記第２電極の螺旋ピッチが、上端から下端に向かうに従って徐々に密となるように設定され、
前記第３電極が筒状に形成され、前記第１電極及び前記第２電極並びに前記絶縁性基体が、前記第３電極内に収容され、
前記第１電極と前記第２電極とから成る第１の電極対、及び、前記第１電極または第２電極と前記第３電極とから成る第２の電極対の２組の電極対がそれぞれ液体に浸漬された際の両電極間の静電容量に基づいて、該液体の液面レベルを検出することを特徴とする液面レベルセンサ。 A first electrode and a second electrode spirally wound around the outer periphery of the insulating substrate, and a third electrode surrounding the outer periphery of the insulating substrate so as to face the first electrode and the second electrode And comprising
The first electrode and the second electrode are arranged so that the spiral axes thereof are vertical, and the spiral pitch of the first electrode and the second electrode is set so as to gradually become denser from the upper end toward the lower end. ,
The third electrode is formed in a cylindrical shape, and the first electrode, the second electrode, and the insulating substrate are accommodated in the third electrode,
Two electrode pairs, the first electrode pair composed of the first electrode and the second electrode, and the second electrode pair composed of the first electrode or the second electrode and the third electrode, are liquids, respectively. A liquid level sensor that detects a liquid level of the liquid based on a capacitance between both electrodes when immersed in the liquid. 筒状の前記第３電極が、その周壁を軸に沿って分断されて開閉可能に構成されていることを特徴とする請求項１に記載の液面レベルセンサ。 2. The liquid level sensor according to claim 1 , wherein the cylindrical third electrode is configured to be able to be opened and closed by dividing its peripheral wall along an axis. 筒状の前記第３電極の下端の開口を塞ぐ底板を有し、
前記底板にオリフィスが穿設されていることを特徴とする請求項１又は２に記載の液面レベルセンサ。 A bottom plate for closing the opening at the lower end of the cylindrical third electrode;
Liquid level sensor according to claim 1 or 2, characterized in that the orifice is formed in the bottom plate. 前記オリフィスの外側に該オリフィスを覆うフィルタを有していることを特徴とする請求項３に記載の液面レベルセンサ。 4. The liquid level sensor according to claim 3 , further comprising a filter that covers the orifice outside the orifice. ２組の前記電極対それぞれの両電極間の静電容量に基づいて前記液体の液面レベルを演算するための回路が、筒状の前記第３電極に収容されていることを特徴とする請求項１〜請求項４のいずれかに記載の液面レベルセンサ。 The circuit for calculating the liquid level of the liquid based on the capacitance between both electrodes of each of the two pairs of electrodes is accommodated in the cylindrical third electrode. Item 5. The liquid level sensor according to any one of Items 1 to 4 .
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