JP2004156943A - Measuring instrument and measuring method for charged pressure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charged pressure measuring instrument wherein a pressure change, time, a flow rate, and temperature are measured to calculate the charged pressure from the physical properties of a gas, thereby enhancing the measurement accuracy of the charged pressure. <P>SOLUTION: This charged pressure measuring instrument 1 for measuring a charged pressure in a pressure vessel 21 such as an accumulator, has a means for pressurizing the interior of the pressure vessel by pressing a fluid into a fluid chamber 25 of the pressure vessel 21, a means for measuring a flow rate, time, pressure, and temperature during the pressurization by the pressurizing means, and a personal computer 8 for collecting and computing measurement data obtained by the measuring means. <P>COPYRIGHT: (C)2004,JPO

Description

上記（１）式により演算処理を実行することを特徴とするものである。
【０００９】
また、本発明の請求項３による測定方法は、アキュムレータ等の圧力容器における封入圧を測定する封入圧測定方法において、前記圧力容器のフルード室にフルードを圧入して前記圧力容器内を加圧し、加圧中に流量、時間、圧力および温度を測定し、得られた測定データをパソコンを用いて演算処理することにより前記封入圧を測定することを特徴とするものである。
【００１０】
更にまた、本発明の請求項４による測定方法は、上記した請求項３の封入圧測定方法において、封入圧をＰ_０、封入ガスボリュームをＶ_０、流量をＱ、時間をｔ、圧力をＰ、ポリトロープ指数をｎとして、

上記（１）式により演算処理を実行することを特徴とするものである。
【００１１】
【発明の実施の形態】
つぎに本発明の実施例を図面にしたがって説明する。
【００１２】
図１は、本発明の実施例に係る封入圧測定装置１の概略を示しており、この測定装置１はアキュムレータ２１の封入圧を測定するものである。アキュムレータ２１は、シェル２２の内部にブラダ２３を架設することによってシェル２２の内部をガス室２４とフルード室２５とに区画しており、このうちのガス室２４に封入されたガスの圧力すなわち封入圧を測定する。
【００１３】
構成としては先ず、アキュムレータ２１のフルード室２５にフルード（作動油）を圧入してアキュムレータ２１内を加圧する加圧手段として、タンク２、ポンプ３および配管４などが設けられており、加圧手段による加圧中に、流量、圧力および温度を測定する測定手段として、流量計５、圧力計６および温度計７などが設けられており、測定手段による測定データを収集し演算処理する手段としてパソコン８が設けられている。ポンプ３は定流量ポンプである。流量計５は流量をアナログ電圧で出力する。圧力計６は圧力をアナログ電圧で出力する。温度計７は温度をアナログ電圧で出力する。パソコン８はデータ収集用であり、流量計５、圧力計６および温度計７からの電圧値をＡ／Ｄボードで変換し、内部クロックで時間を測定する。取り込んだデータはパソコン８内で処理を行ない、封入圧を算出する。フルードとしてはブレーキフルードを使用する。
【００１４】
ポンプ３から吐き出されたフルードは、流量計５および圧力計６を経てアキュムレータ２１に流れる。そのときの時間、流量および圧力の変化をパソコン８によって測定する。容積の変化は、ガスボリューム（初期容積）が分かっていれば時間と流量の関係から導き出すことができる。また、温度計７により規定温度での封入圧値に換算する。
【００１５】
演算処理は以下のようにして行なわれる。
【００１６】
（１）理論式
時間ｔ、圧力Ｐ、容積Ｖ、流量Ｑとし、時間ｔ_０、ｔ_１、ｔ_２におけるそれぞれの値を添え字１、２、３で表わすとする。このとき、圧力Ｐ_０は封入圧、容積Ｖ_０はガスボリュームとなる。
【００１７】
圧縮を受ける気体の状態式は、ポリトロープ指数をｎとすると、

上の式より

以上の式より、封入圧Ｐ_０は以下のように表わされる。

【００１８】
また、理論圧力変化は以下の式で表わすことができる。

【００１９】
（２）データ処理
実験は流量を一定とした上で行なった。
【００２０】
図２の「圧力−時間線図」参照。
【００２１】
この図２の測定時間９秒弱のあたりにある特性が変わっている点が変曲点であり、アキュムレータの内圧とポンプから送られた作動油の圧力が平衡し、アキュムレータのポートが開く点である。
【００２２】
上記従来の変曲点検出による測定方法は、上記変曲点におけるデータをもとに圧力変化値を微分して、変化のタイミングで変曲点圧力を決定していた。
【００２３】
図３の「従来技術における封入圧の検出」参照。
【００２４】
しかし、この方法では、ポートの張付きによる誤差や、開いたあとのノイズの影響により、測定精度は数ｋｇｆ／ｃｍ^２程度であった。
【００２５】
これに対して、本発明による測定方法では、上記変曲点を開始時間ととっているが、変曲点のばらつきによる時間的誤差はほとんど影響がない。
【００２６】
図４の「ポリトロープ指数算出」参照。
【００２７】
そこから、任意の２点以上での圧力および時間を選択し、以下の式を用いることでポリトロープ指数を算出する。
すなわち、任意の２点（添え字１、２）における時間と圧力より、ポリトロープ指数は

となる。
求めたポリトロープ指数をフィードバックし、それぞれの測定値を（１）式に代入することで、任意の点において封入圧を求めることができる。
【００２８】
図５の「封入圧算出結果」参照。
【００２９】
本発明方法における封入圧測定の精度はそれぞれの誤差の影響にもよるが、±０．５ｋｇｆ／ｃｍ^２と良く、封入圧の測定誤差を抑えることができる。
【００３０】
（３）評価実験
▲１▼評価実験の構成
アキュムレータ内の圧力および温度を測定できるサンプルを用意し、本発明方法の評価を行なった。
【００３１】
評価実験装置１１の構成は図６に示すとおりであり、ポンプの代わりに、ピストン１３の移動量をコントロールできる設備（ハイドロパルス試験機）１２を用い、圧力計は装置側圧力検出センサ（センサＡ）１４、流量計の代わりにレーザー変位計１５を用いてピストン１３の移動量から流量を求めた。また、アキュムレータ２１内に取り付けたＡＣＣ内圧力検出センサ（センサＢ）１６および温度センサ（センサＣ）１７により、アキュムレータ２１内の圧力と温度の変化を測定することで、本発明方法の評価に用いる指標とした。
【００３２】
評価実験には３種類のワークを用意し、流量６０、５０、４０、１３．５ｃｃ／ｓｅｃの条件において繰り返し測定を行なった。
【００３３】
封入圧として、センサＢ１６により測定した加圧前の圧力を正とし、そこからの誤差を、従来方式である変曲点検出方法との比較を行なうことで評価する。
【００３４】
図７の「測定画面と封入圧算出結果」参照。
【００３５】
▲２▼評価実験の結果
図８ないし図１１のグラフは、それぞれの流量において、ＡＣＣ内圧力検出センサ１６より求めた封入圧を正とし、そこからの誤差の絶対値を比較したものである。それぞれの流量において、図上上側のグラフが本発明方法の結果、図上下側のグラフが従来方法の結果を示している。また、プロットは平均値を示しており、バーは最大値および最小値の幅を示している。
【００３６】
▲３▼評価実験の結論
流量の高低やワークに関係なく、従来技術である変曲点検出による測定方法に比べて、本発明の測定方法は格段に封入圧検出精度が高いことが確認できた。また、再現性があることも確認することができた。
【００３７】
【発明の効果】
本発明は、以下の効果を奏する。
【００３８】
すなわち、上記構成を備えた本発明の各請求項による測定装置および測定方法によれば、圧力変化、時間、流量および温度を測定することにより気体の物性から封入圧を算出するようにしたので、封入圧の測定精度を向上させることができる。
【図面の簡単な説明】
【図１】本発明の実施例に係る封入圧測定装置の構成説明図
【図２】圧力および時間の関係を示すグラフ図
【図３】従来技術における封入圧検出方法を示すグラフ図
【図４】ポリトロープ指数算出方法を示すグラフ図
【図５】封入圧算出結果を示すグラフ図
【図６】評価実験装置の構成説明図
【図７】測定画面および封入圧算出結果を示すグラフ図
【図８】評価実験結果（６０ｃｃ／ｓｅｃ）を示すグラフ図
【図９】評価実験結果（５０ｃｃ／ｓｅｃ）を示すグラフ図
【図１０】評価実験結果（４０ｃｃ／ｓｅｃ）を示すグラフ図
【図１１】評価実験結果（１３．５ｃｃ／ｓｅｃ）を示すグラフ図
【符号の説明】
１ 封入圧測定装置
２ タンク
３ ポンプ
４ 配管
５ 流量計
６ 圧力計
７ 温度計
８ パソコン
１１ 評価実験装置
１２ ハイドロパルス試験機
１３ ピストン
１４ 装置側圧力検出センサ
１５ レーザー変位計
１６ ＡＣＣ内圧力検出センサ
１７ 温度センサ
２１ アキュムレータ（圧力容器）
２２ シェル
２３ ブラダ
２４ ガス室
２５ フルード室[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sealing pressure measuring device and a sealing pressure measuring method for measuring the magnitude of a sealing pressure in a pressure vessel such as an accumulator.
[0002]
[Prior art]
It is extremely important to measure the pressure of a gas sealed in an accumulator used as a pressure accumulator or a pulse pressure absorbing device, that is, a sealed pressure, in specifying operating characteristics of an accumulator and setting specifications. The filling pressure refers to the pressure of the filling gas in a specified temperature atmosphere under atmospheric pressure.
[0003]
Conventionally, when measuring the filling pressure of an accumulator, a method of measuring the filling pressure by injecting fluid into a fluid chamber of the accumulator, pressurizing the inside of the accumulator, and finding an inflection point of the pressure (a point at which a port opens). Has been developed (see Patent Document 1).
[0004]
This prior art is an excellent technique that can relatively easily measure the sealing pressure, but has the following disadvantages.
{Circle around (1)} When the port is opened, sticking may occur and the value may be higher than the sealing pressure.
{Circle around (2)} The gas pressure becomes unstable until a transition to an equilibrium state from the pressure difference from the external pressure due to sticking, noise is generated due to pressure fluctuation, and it is difficult to detect an accurate sealing pressure.
[0005]
[Patent Document 1]
JP-A-7-139501 [Patent Document 2]
JP 2001-13044 A
[Problems to be solved by the invention]
In view of the above, the present invention calculates the sealing pressure from the physical properties of gas by measuring pressure change, time, flow rate, and temperature, instead of the above-described conventional measuring method using inflection point detection, and thereby measuring the sealing pressure. It is an object of the present invention to provide a sealing pressure measuring device and a sealing pressure measuring method capable of improving accuracy.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a measuring apparatus according to claim 1 of the present invention is an enclosure pressure measuring apparatus for measuring an enclosure pressure in a pressure vessel such as an accumulator, wherein the pressure vessel is press-fitted into a fluid chamber of the pressure vessel. Means for pressurizing the inside, means for measuring flow rate, time, pressure and temperature during pressurization by the pressurizing means, and a personal computer for collecting and measuring data measured by the measuring means, Is what you do.
[0008]
The measuring apparatus according to claim 2 of the present invention is the same as the above-described filling pressure measuring apparatus according to claim 1, wherein the filling pressure is P ₀ , the filling gas volume is V ₀ , the flow rate is Q, the time is t, the pressure is P, Assuming that the polytropic index is n,

It is characterized in that the arithmetic processing is executed by the above equation (1).
[0009]
In addition, the measuring method according to claim 3 of the present invention is a method for measuring a sealing pressure in a pressure vessel such as an accumulator, wherein a fluid is press-fitted into a fluid chamber of the pressure vessel to pressurize the inside of the pressure vessel, The method is characterized in that the flow rate, time, pressure and temperature are measured during pressurization, and the obtained measurement data is subjected to arithmetic processing using a personal computer to measure the sealing pressure.
[0010]
Furthermore, the measuring method according to claim 4 of the present invention is the same as the above-described method for measuring filling pressure according to claim 3, wherein the filling pressure is P ₀ , the filling gas volume is V ₀ , the flow rate is Q, the time is t, and the pressure is P. , And the polytropic index is n,

It is characterized in that the arithmetic processing is executed by the above equation (1).
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0012]
FIG. 1 schematically shows a sealing pressure measuring device 1 according to an embodiment of the present invention. The measuring device 1 measures the sealing pressure of an accumulator 21. The accumulator 21 divides the inside of the shell 22 into a gas chamber 24 and a fluid chamber 25 by bridging a bladder 23 inside the shell 22, and the pressure of the gas sealed in the gas chamber 24, that is, the sealing of the gas chamber 24. Measure the pressure.
[0013]
First, a tank 2, a pump 3, a pipe 4, and the like are provided as pressurizing means for pressurizing the inside of the accumulator 21 by pressing fluid (hydraulic oil) into the fluid chamber 25 of the accumulator 21. A flow meter 5, a pressure gauge 6, a thermometer 7 and the like are provided as measuring means for measuring a flow rate, a pressure and a temperature during pressurization by a personal computer. 8 are provided. The pump 3 is a constant flow pump. The flow meter 5 outputs the flow rate as an analog voltage. The pressure gauge 6 outputs the pressure as an analog voltage. The thermometer 7 outputs the temperature as an analog voltage. The personal computer 8 is for data collection, converts voltage values from the flow meter 5, the pressure gauge 6, and the thermometer 7 with an A / D board, and measures time with an internal clock. The acquired data is processed in the personal computer 8 to calculate the sealing pressure. Use brake fluid as fluid.
[0014]
Fluid discharged from the pump 3 flows to the accumulator 21 via the flow meter 5 and the pressure gauge 6. The changes in time, flow rate and pressure at that time are measured by the personal computer 8. The change in volume can be derived from the relationship between time and flow if the gas volume (initial volume) is known. Further, the pressure is converted into a sealed pressure value at a specified temperature by the thermometer 7.
[0015]
The arithmetic processing is performed as follows.
[0016]
(1) The theoretical formulas are assumed to be time t, pressure P, volume V, and flow rate Q, and respective values at times t ₀ , t ₁ , and t ₂ are represented by subscripts 1, 2, and 3. At this time, the pressure P ₀ is the sealing pressure, and the volume V ₀ is the gas volume.
[0017]
The state equation of a gas undergoing compression is as follows, where the polytropic index is n.

From the above formula

From the above equations, filling pressure P ₀ is expressed as follows.

[0018]
The theoretical pressure change can be expressed by the following equation.

[0019]
(2) The data processing experiment was performed with the flow rate kept constant.
[0020]
See "Pressure-Time Diagram" in FIG.
[0021]
The inflection point is where the characteristic around the measurement time of less than 9 seconds in FIG. 2 changes, and the point at which the internal pressure of the accumulator and the pressure of the hydraulic oil sent from the pump are balanced and the port of the accumulator opens. is there.
[0022]
In the conventional measurement method using inflection point detection, the pressure change value is differentiated based on the data at the inflection point, and the inflection point pressure is determined at the timing of the change.
[0023]
See "Detection of sealing pressure in prior art" in FIG.
[0024]
However, in this method, the measurement accuracy was about several kgf / cm ² due to an error due to sticking of the port and the influence of noise after opening.
[0025]
On the other hand, in the measuring method according to the present invention, the inflection point is taken as the start time, but the time error due to the variation of the inflection point has almost no influence.
[0026]
See "Polytropic Index Calculation" in FIG.
[0027]
From there, the pressure and time at any two or more points are selected, and the polytropic index is calculated by using the following equation.
That is, from the time and pressure at any two points (subscripts 1 and 2), the polytropic index is

It becomes.
By feeding back the obtained polytropic index and substituting the respective measured values into the equation (1), the sealing pressure can be obtained at an arbitrary point.
[0028]
See “Results of calculation of sealing pressure” in FIG.
[0029]
Although the accuracy of the sealing pressure measurement in the method of the present invention depends on the influence of each error, it is preferably ± 0.5 kgf / cm ^2, and the measurement error of the sealing pressure can be suppressed.
[0030]
(3) Evaluation experiment (1) Construction of evaluation experiment A sample capable of measuring the pressure and temperature in the accumulator was prepared, and the method of the present invention was evaluated.
[0031]
The configuration of the evaluation experiment apparatus 11 is as shown in FIG. 6. Instead of a pump, an equipment (hydropulse tester) 12 capable of controlling the movement amount of a piston 13 is used, and a pressure gauge is used as a device-side pressure detection sensor (sensor A). 14) The flow rate was determined from the amount of movement of the piston 13 using a laser displacement meter 15 instead of the flow meter. The pressure and temperature changes in the accumulator 21 are measured by the ACC pressure detection sensor (sensor B) 16 and the temperature sensor (sensor C) 17 mounted in the accumulator 21, and are used for evaluating the method of the present invention. The index was used.
[0032]
Three types of works were prepared for the evaluation experiment, and the measurement was repeatedly performed under the conditions of flow rates of 60, 50, 40, and 13.5 cc / sec.
[0033]
As the sealing pressure, the pressure before pressurization measured by the sensor B16 is set to be positive, and an error therefrom is evaluated by comparing with an inflection point detection method which is a conventional method.
[0034]
See “Measurement screen and sealing pressure calculation result” in FIG. 7.
[0035]
(2) Results of evaluation experiment The graphs in FIGS. 8 to 11 are obtained by making the sealing pressure obtained by the ACC internal pressure detection sensor 16 positive at each flow rate and comparing the absolute value of the error therefrom. At each flow rate, the upper graph shows the results of the method of the present invention, and the upper and lower graphs show the results of the conventional method. The plot shows the average value, and the bar shows the range between the maximum value and the minimum value.
[0036]
(3) Conclusion of the evaluation experiment Regardless of the flow rate and the work, it was confirmed that the measurement method of the present invention has a significantly higher sealing pressure detection accuracy than the conventional measurement method using the inflection point detection. . In addition, it was confirmed that there was reproducibility.
[0037]
【The invention's effect】
The present invention has the following effects.
[0038]
That is, according to the measuring device and the measuring method according to the claims of the present invention having the above-described configuration, since the pressure change, time, flow rate, and temperature are measured to calculate the sealing pressure from the physical properties of the gas, Measurement accuracy of the sealing pressure can be improved.
[Brief description of the drawings]
FIG. 1 is a configuration explanatory view of a sealing pressure measuring apparatus according to an embodiment of the present invention. FIG. 2 is a graph showing a relationship between pressure and time. FIG. 3 is a graph showing a sealing pressure detecting method in the prior art. FIG. 5 is a graph showing the method of calculating the polytropic index. FIG. 5 is a graph showing the result of calculating the sealing pressure. FIG. 6 is a diagram illustrating the configuration of the evaluation experiment apparatus. FIG. 7 is a graph showing the measurement screen and the result of calculating the filling pressure. FIG. 9 is a graph showing evaluation test results (60 cc / sec). FIG. 9 is a graph showing evaluation experiment results (50 cc / sec). FIG. 10 is a graph showing evaluation experiment results (40 cc / sec). Graph showing experimental results (13.5 cc / sec).
DESCRIPTION OF SYMBOLS 1 Enclosure pressure measuring device 2 Tank 3 Pump 4 Piping 5 Flow meter 6 Pressure gauge 7 Thermometer 8 Personal computer 11 Evaluation experimental device 12 Hydropulse tester 13 Piston 14 Device side pressure detection sensor 15 Laser displacement meter 16 ACC pressure detection sensor 17 Temperature sensor 21 Accumulator (pressure vessel)
22 shell 23 bladder 24 gas chamber 25 fluid chamber

Claims (4)

In an enclosure pressure measuring device that measures the enclosure pressure in a pressure vessel such as an accumulator,
Means for pressurizing the inside of the pressure vessel by injecting fluid into the fluid chamber of the pressure vessel, means for measuring flow rate, time, pressure and temperature during pressurization by the pressurizing means, and measurement data by the measuring means And a personal computer that collects and performs arithmetic processing. The sealing pressure measuring device according to claim 1,
When the filling pressure is P ₀ , the filling gas volume is V ₀ , the flow rate is Q, the time is t, the pressure is P, and the polytropic index is n,

An enclosure pressure measuring device, which performs arithmetic processing by the above equation (1). In an enclosure pressure measuring method for measuring an enclosure pressure in a pressure vessel such as an accumulator,
By pressurizing the inside of the pressure vessel by injecting fluid into the fluid chamber of the pressure vessel, measuring the flow rate, time, pressure and temperature during the pressurization, and performing arithmetic processing on the obtained measurement data using a personal computer. A method for measuring the filling pressure, comprising measuring the filling pressure. In the method for measuring a sealing pressure according to claim 3,
When the filling pressure is P ₀ , the filling gas volume is V ₀ , the flow rate is Q, the time is t, the pressure is P, and the polytropic index is n,

A method of measuring an enclosed pressure, wherein the arithmetic processing is performed by the above equation (1).

Images