WO2014024621A1 - Thermal flow measurement device and control device using same - Google Patents

Thermal flow measurement device and control device using same Download PDF

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Publication number
WO2014024621A1
WO2014024621A1 PCT/JP2013/068803 JP2013068803W WO2014024621A1 WO 2014024621 A1 WO2014024621 A1 WO 2014024621A1 JP 2013068803 W JP2013068803 W JP 2013068803W WO 2014024621 A1 WO2014024621 A1 WO 2014024621A1
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flow rate
output
characteristic
correction
detection unit
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PCT/JP2013/068803
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French (fr)
Japanese (ja)
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和紀 鈴木
半沢　恵二
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日立オートモティブシステムズ株式会社
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Publication of WO2014024621A1 publication Critical patent/WO2014024621A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/696—Circuits therefor, e.g. constant-current flow meters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/696—Circuits therefor, e.g. constant-current flow meters
    • G01F1/6965—Circuits therefor, e.g. constant-current flow meters comprising means to store calibration data for flow signal calculation or correction

Definitions

  • the present invention relates to a thermal type flow rate measuring apparatus that measures a flow rate or flow rate of a fluid using a heating resistor.
  • the thermal flow rate measuring device is used for measuring the air flow rate of intake air required for, for example, automobile engine control.
  • the heating resistor is heated and controlled so as to have a certain temperature difference with respect to the intake air temperature, and the flow rate is detected from the current flowing through the heating resistor.
  • a detection resistor is arranged and the flow rate is detected from a temperature difference detected by the temperature detection resistor.
  • Both types have a non-linear characteristic that the detection output for the flow rate is high at low flow rates and low at high flow rates.
  • the current automobile engine control device is mainly digital processing by a microcomputer, and the detection output of the flow rate is also converted into a digital value by the A / D converter, and the digital value versus flow rate table stored in a preset division. Thus, the flow rate value is obtained.
  • the accuracy of the flow value referring to the table increases as the number of table divisions increases, but there is a problem that the memory capacity to be stored becomes large. Therefore, there is a method of calculating the flow rate value by linearly interpolating two points between the divisions, but the linear interpolation has a limit in improving accuracy particularly in a portion where the curve of the nonlinear characteristic is large.
  • the technique described in Patent Document 1 obtains a flow rate value by performing A / D conversion on a detection output using a flow rate as a logarithmic axis, that is, an output obtained by converting a nonlinear characteristic into a linear characteristic by logarithmic conversion. Yes.
  • the present invention is to provide a thermal flow measuring device with good measurement accuracy.
  • the thermal flow measurement device of the present invention is a thermal flow measurement device including a flow rate detection unit for measuring the flow rate of the fluid to be measured, wherein the flow rate detection unit is measured by the flow rate detection unit.
  • a correction unit that corrects the output of the flow rate detection unit in an effective flow rate range, the correction unit corrects the sensitivity to be larger than the sensitivity of the flow rate detection unit, and the sensitivity is a flow rate
  • the output is always corrected to a constant gradient, and the output can be switched to either voltage output or frequency output.
  • thermo flow measuring device of the present invention it is possible to provide a thermal flow measuring device with good measurement accuracy.
  • the block diagram of the thermal type flow measuring apparatus which shows the 1st Example of this invention Output characteristic diagram of the present invention Characteristics of the oscillator according to the first embodiment of the present invention Variation characteristics of the oscillator according to the first embodiment of the present invention Correction table of the present invention Characteristics of measured correction amount Calculation of lattice point correction Calculation of lattice points
  • Block diagram of a thermal flow measuring device showing a third embodiment of the present invention Arrangement diagram of resistors of flow rate detector according to the present invention Flow rate (logarithmic axis) -output voltage characteristic diagram according to the third embodiment of the present invention Flow rate (logarithmic axis) -flow rate 1% error voltage characteristic diagram according to the third embodiment of the present invention Correction table characteristic chart according to the fourth embodiment of the present invention Flow rate (logarithmic axis) vs.
  • the flow rate detection unit 10 includes a heating resistor 11 and resistance temperature detectors 12, 13, 14, 15, and 16. An example of the structure of the flow rate detection unit 10 is illustrated in FIG. 10.
  • the resistance temperature detector 12 is disposed on the substrate, the heating resistor 11 is disposed on the silicon diaphragm, and the heating resistor 11.
  • the resistance temperature detectors 13 and 14 are arranged on the upstream side, and the resistance temperature detectors 15 and 16 are arranged on the downstream side of the heating resistor 11.
  • the heating resistor 11 uses a bridge circuit composed of the resistance temperature detector 12 and the resistances 17 and 18 to change the partial pressure value of the resistance temperature detector 12 and the resistance 17 to a reference value (temperature value).
  • the differential amplifier 19 outputs so that the divided voltage value with respect to the resistor 18 becomes equal to the reference value, and a current is applied so as to reach a constant temperature.
  • the resistance thermometers 13, 14, 15, and 16 change in resistance value due to the heat transfer of the heating resistor, and the heat transfer from the heating resistor 11 cooled by the flow (flow rate) of the fluid Fa to be measured. Is lower in the resistance thermometers 13 and 14 on the upstream side and decreases in resistance value, and is higher in the resistance thermometer resistors 15 and 16 on the downstream side and increases in resistance value.
  • the resistance temperature detectors 13, 14, 15, and 16 are configured by a bridge circuit that supplies current from the constant voltage power supply 20, and detects the flow rate Q based on a potential difference Vdet when the resistance value changes due to the flow of fluid. It has become.
  • Such a flow rate detection method is generally called a temperature difference detection method.
  • the output of the bridge circuit that is, the potential difference Vdet is internally processed by the flow rate processing circuit 30, and the flow rate Q is converted into the voltage value Vout or the frequency Fout and output to the engine control device 100 for low idle rotation control and A / F. It serves for control of engine rotation as a control air flow rate.
  • 31 indicates the result of zero span adjustment of the potential difference Vdet detected by the bridge circuit.
  • 31a is the characteristic before the zero span adjustment
  • 31b is the characteristic after the zero span adjustment.
  • Reference numeral 34 denotes the difference between the target output characteristic and the characteristic 31b obtained by adjusting the potential difference Vdet detected by the bridge circuit to zero span. By adding this difference as a correction amount ⁇ FQ, the target output is corrected to 32.
  • the potential difference Vdet detected by the bridge circuit becomes a characteristic 31a shown in a characteristic diagram 31 in which the horizontal axis and the vertical axis are proportional axes with respect to the flow rate Q.
  • This characteristic is highly sensitive in the low flow rate region and low in the high flow rate region, and has a characteristic of non-linear characteristics.
  • the output voltage Vout or the output frequency Fout becomes the characteristic 32b 'in the characteristic diagram 32.
  • the engine control apparatus 100 mainly has a circuit configuration in which the output voltage Vout of the flow rate processing circuit 30 is input to the A / D converter 101 and the flow rate Q is obtained by a digital output value.
  • the output characteristic 32b ' is determined from the reading resolution of the engine control apparatus 100 and the characteristics of the oscillator in the integrated circuit in the flow rate detection apparatus.
  • FIG. 3 shows the characteristics of the oscillator. Assuming that the initial characteristic is C1, the characteristic of the oscillator changes such as C2 and C3 due to resistance deterioration or capacitor deterioration. Since the frequency generated by the oscillator is divided into a flow rate output signal, when the characteristics of the oscillator vary, the output characteristics of the flow also vary.
  • 1% error indicates the amount of change in output when the flow rate changes by 1%.
  • a table correction 34a (see FIG. 1) is provided for correction.
  • correction can be performed by setting arbitrary grid points.
  • the calculation method of the grid point correction amount in this table correction is such that the grid points that can be arbitrarily changed are arranged so that the resolution is high in a sharply curved area, and the resolution is coarse in a slowly curved area.
  • a curve is created by spline interpolation for the target correction value. The intersection of the curve by the spline and the lattice point is determined as a correction amount.
  • the lattice interval can be arbitrarily selected for each sample.
  • it is necessary to determine the lattice interval in advance In this case, since the lattice interval cannot be optimized for each sample, the effect of improving the measurement accuracy is smaller than described below, but the measurement accuracy is improved as compared with the correction using the equidistant lattice.
  • a correction amount calculation method for optimizing the lattice spacing for each sample is described below. Measure the output characteristics with respect to the flow rate for each sample. The difference between the output characteristic and the target characteristic is used as a correction amount, and the relationship of the correction amount to the flow rate is shown in FIG. At this time, the correction amount with respect to the flow rate is different for each sample. For this correction amount, the position of the grid point and the correction amount are determined from the low flow rate side. First, a straight line is drawn from two low flow characteristics. Next, a straight line is drawn from two or more points on the low flow rate side other than the two points used to draw the straight line first. At this time, when the calculation is performed at two points, a straight line is calculated from two points, and when the straight line is calculated from three or more points, a straight line that minimizes the error is calculated using the least square method. This calculated straight line is shown in FIG.
  • the correction between the lattice points of the correction table is an example of linear interpolation.
  • the correction is not limited to this, and correction may be performed by secondary interpolation. Thereby, the nonlinearity after correction
  • the resistance temperature detectors 13, 14, 15, and 16 are configured by a bridge circuit that supplies a current from the constant voltage power supply 20, and the potential difference Vdet when the resistance value changes when the fluid flows.
  • the flow rate Q is detected.
  • the potential difference Vdet detected by the bridge circuit becomes the characteristic 31a of the characteristic diagram 31 in which the horizontal axis and the vertical axis are represented by the proportional axis with respect to the flow rate Q, and the sensitivity is high in the low flow range and low in the high flow range. Characteristics are non-linear characteristics.
  • the output voltage Vout or the output frequency Fout obtained by converting the flow rate Q on the horizontal axis of the characteristic 31a into a logarithmic axis becomes the characteristic 32a in the characteristic diagram 32.
  • FIG. 11 shows the characteristics of the output Vout of the flow rate processing circuit 30 with the logarithmic axis representing the flow rate Q on the horizontal axis, which is a reprint of the characteristic diagram 32 of FIG. 9, and the characteristics 32a of the flow rate Q and the potential difference Vdet are detected in the low flow rate range.
  • the output voltage Vout is output in the range of 0 V to the reference voltage Vref of the A / D converter 101, and the flow rate is calculated in units of resolution Vadr determined by the bit length of the A / D converter 101.
  • an FRC free running counter
  • FIG. 12 shows the characteristics of the resolution Vadr of the A / D converter 101 and the 1% error equivalent voltage VEr (1% Error) of the flow rate Q of the evaluation index described above with the characteristic 32a of FIG. Shown as 100%.
  • the correction characteristic 34a of FIG. 34 is a correction amount ⁇ FQ that increases the voltage in the low flow rate region and decreases the voltage in the high flow rate region with respect to the flow rate Q.
  • the output of the characteristic diagram 31, that is, the potential difference Vdet is a digital value.
  • the output voltage Vout or the output frequency Fout is output by adding the value converted to ⁇ and the correction amount ⁇ FQ.
  • the characteristic 32b is a result of expressing the output voltage Vout or the output frequency Fout obtained by adding the value obtained by converting the potential difference Vdet into a digital value and the correction amount ⁇ FQ with the flow rate Q as a logarithmic axis, and is more linearized with respect to the characteristic 32a. It is characteristic 32b.
  • FIG. 11 shows the characteristic diagram 32 again.
  • the flow rate Q obtained by the A / D converter 101 is a flow rate change of 1%. Can be reliably detected, and the S / N ratio is increased, so that a stable flow rate measuring apparatus that is highly accurate and is not affected by noise or the like can be obtained.
  • the characteristic 32b is a more linear characteristic than the characteristic 32a, and the 1% error equivalent voltage VEr is a substantially constant characteristic. This is apparent from the following.
  • the output VEr obtained by converting the output voltage Vout to the flow rate error ⁇ in the monotonically increasing characteristics on the graph is .
  • the correction characteristic 34a is corrected so that the output voltage Vout or the output frequency Fout with respect to the flow rate Q having the horizontal axis as a logarithmic axis becomes a characteristic 32b that approaches a straight line.
  • the resolution of the output voltage Vout or the output frequency Fout in the low flow rate region can be improved.
  • Example 3 will be described with reference to FIGS.
  • the resolution could be improved in the low flow rate range, but when the characteristics 32a and 32b shown in FIG. 11 are compared, the gradient of the characteristic 32b is smaller than the gradient of the characteristic 32a in the high flow rate range. Therefore, it also has an aspect that the resolution is lowered.
  • the operation of the A / D converter 101 changing the input voltage in the range from 0 to the reference voltage can be operated with a wide dynamic range and a large resolution.
  • the dynamic range is about half of that. This is because the output voltage characteristic 32b is larger in the vicinity of the target minimum flow rate Qmin than the output voltage characteristic 32a.
  • the correction characteristic 34a in FIG. 9 is changed to the correction characteristic 34c shown in FIG. 13 so that the characteristics of the flow rate Q and the output voltage Vout with the horizontal axis as a logarithmic axis are substantially linear.
  • FIG. 14 shows the characteristics of the output voltage Vout with respect to the logarithmic axis flow Q in the entire flow range (Qstart to Qmax), and FIG. 15 shows the 1% error equivalent voltage VEr (1% Error) of the flow Q with respect to the logarithmic axis flow Q.
  • VEr 1% Error
  • the flow rate processing circuit 30 is shown as a block diagram, but the processing means can be applied to either an analog processing method or a digital processing method.
  • the analog processing method the potential difference Vdet and the correction voltage Vcomp characteristic generated by the function generator are added to obtain the characteristic 32b or 32c by the log amplifier.
  • the digital processing method can simplify the circuit configuration and improve the drift of the analog amplifier circuit.
  • a dedicated IC ASIC
  • the potential difference Vdet is converted into a digital value by the A / D converter, the correction characteristic 34a or 34c, the addition / logarithmic axis conversion characteristic 32b or 32c is calculated by a program, and the calculation result is analog by the D / A converter.
  • the output voltage Vout or the output frequency Fout is output to the engine control apparatus 100 as a value.
  • ⁇ Y is created in advance with respect to the flow rate Q using a correction table, and ⁇ Y is obtained by referring to the table with the flow rate Q, or the correction table is set with a polynomial. There is a method of obtaining ⁇ Y by calculation each time.
  • the block of the flow rate processing circuit 30 shown in FIG. 9 is not necessarily configured as it is.
  • the input of the flow rate detection unit 10 is performed in the usage range of the flow rate Q.
  • the output of the fourth root with respect to the flow rate, or the output Vout or the output frequency of the flow rate processing circuit 30 with the logarithmic axis as the flow rate is corrected so that it becomes a straight line, and the percentage of the flow rate error is constant over the entire use range.
  • the operation and the effect are the same as long as the error value included in the output voltage Vout or the output frequency Fout is a substantially constant value.
  • the actual flow rate range used that is, the target minimum flow rate Qmin, in the range (Qarea) of Qmax (1000 kg / h) with Qmin> Qstart including the margin as the starting point.
  • the characteristics of the flow rate Q and the output voltage Vout or the output frequency Fout with the logarithmic axis as an axis are almost linear.
  • the characteristics that are almost straight lines have the same operation and effect even if the conversion is made with the target minimum flow rate Qmin as the starting point.
  • Example 4 will be described with reference to FIGS.
  • the flow rate Q is corrected so as to be close to a straight line on the logarithmic axis to improve the resolution in the low flow rate region.
  • the potential difference Vdet is nonlinearly processed, and the nonlinearity is obtained.
  • the resolution in the low flow rate region is improved by referring to the correction table from the processing output.
  • FIG. 16 is a block diagram of the flow rate processing circuit 30 of the present embodiment, showing an example of digital processing, and the numerical values in the following figures are represented by binary digits.
  • the nonlinear processing 35 converts the potential difference Vdet detected by the bridge circuit of the resistance temperature detectors 13, 14, 15, 16 into a variable by a quadratic function ((a ⁇ Vdet) ⁇ 2 + b ⁇ Vdet + c), and corrects the correction table.
  • table argument Vmpin is output.
  • the correction table 36 is divided in the entire region of the table argument Vmpin, and the correction output Vmpout corresponding to the table argument Vmpin to be referred to is the output Vout or Fout of the flow rate processing circuit 30.
  • the gradient of the region where the potential difference Vdet is small is increased by the non-linear processing 35 so that the table argument Vmpin of the correction table 36 is divided equally.

Abstract

In order to provide a thermal flow measurement device with superior measurement accuracy, in a thermal flow measurement device provided with a flow detection unit which measures flow of a fluid to be measured, the flow detection unit has correction means which corrects output of the flow detection unit in a valid flow range capable of being measured with the flow detection unit, wherein the correction means performs the correction so as to achieve a greater sensitivity compared to the sensitivity of the flow detection unit, said sensitivity being corrected so that the output always forms a uniform gradient with respect to the flow. The output is made to be switchable between either voltage output or frequency output.

Description

熱式流量測定装置及びこれを用いた制御装置Thermal flow measurement device and control device using the same
　本発明は、発熱抵抗体を用いて流体の流量あるいは流速を測定する熱式流量測定装置に関する。 The present invention relates to a thermal type flow rate measuring apparatus that measures a flow rate or flow rate of a fluid using a heating resistor.
　熱式流量測定装置は、例えば自動車エンジン制御の際に必要となる吸入空気の空気流量の測定に使用されている。 The thermal flow rate measuring device is used for measuring the air flow rate of intake air required for, for example, automobile engine control.
　流量の検出方法としては、発熱抵抗体を吸入空気温度に対して一定の温度差になるように加熱制御し、発熱抵抗体に流れる電流から流量を検出する方式と、発熱抵抗体の両側に温度検出抵抗体を配置して、温度検出抵抗体で検出する温度差から流量を検出する方式がある。 As a method of detecting the flow rate, the heating resistor is heated and controlled so as to have a certain temperature difference with respect to the intake air temperature, and the flow rate is detected from the current flowing through the heating resistor. There is a method in which a detection resistor is arranged and the flow rate is detected from a temperature difference detected by the temperature detection resistor.
　両方式ともに流量に対する検出出力は、低流量では感度が高く、高流量では感度が低くなる非線形特性を有している。 Both types have a non-linear characteristic that the detection output for the flow rate is high at low flow rates and low at high flow rates.
　ところで、現在の自動車エンジン制御装置は、マイコンによるデジタル処理が主流であり、流量の検出出力もＡ／Ｄ変換器によりデジタル値に変換し、あらかじめ設定した分割で記憶されたデジタル値対流量のテーブルにより流量値を得るようになっている。 By the way, the current automobile engine control device is mainly digital processing by a microcomputer, and the detection output of the flow rate is also converted into a digital value by the A / D converter, and the digital value versus flow rate table stored in a preset division. Thus, the flow rate value is obtained.
　テーブルを参照する流量値は、テーブルの分割数が多いほど精度が向上するが、記憶するメモリ容量が大きくなる問題がある。そこで、分割間の２点を直線補間して流量値を算出する方法もあるが、直線補間では特に非線形特性の湾曲が大きい部分において精度の向上に限界があった。特許文献１に記載の技術は、流量の検出出力から流量を対数軸とした検出出力、すなわち対数変換により非線形特性を直線特性に変換した出力をＡ／Ｄ変換して流量値を得るようにしている。このように、対数軸上で直線特性に変換することにより、テーブルを参照して２点間を直線補間する場合よりも、上述した非線形特性の場合で比較すると、より流量値の精度を向上させることを可能としている。 The accuracy of the flow value referring to the table increases as the number of table divisions increases, but there is a problem that the memory capacity to be stored becomes large. Therefore, there is a method of calculating the flow rate value by linearly interpolating two points between the divisions, but the linear interpolation has a limit in improving accuracy particularly in a portion where the curve of the nonlinear characteristic is large. The technique described in Patent Document 1 obtains a flow rate value by performing A / D conversion on a detection output using a flow rate as a logarithmic axis, that is, an output obtained by converting a nonlinear characteristic into a linear characteristic by logarithmic conversion. Yes. In this way, by converting to a linear characteristic on the logarithmic axis, the accuracy of the flow rate value is further improved as compared with the case of the nonlinear characteristic described above, compared to the case of linear interpolation between two points with reference to the table. Making it possible.
特開平４―１１６２４８号公報JP-A-4-116248
　近年、自動車の走行において環境問題が重要な課題であり、アイドル運転時の燃料消費の低減、排気ガスの低減のため、低アイドル回転化が必要となっている。低アイドル回転化のためには、空気流量を従来よりも更に低流量域までの流量検出が必要となる。従来の最小流量に対して低アイドル回転化の最小流量は半分以下の流量になる。 In recent years, environmental problems are an important issue in driving a car, and low idling speed is required to reduce fuel consumption and exhaust gas during idling. In order to reduce the idling speed, it is necessary to detect the air flow rate to a lower flow rate range than before. The minimum flow rate for low idle rotation is less than half the conventional minimum flow rate.
　上述した特許文献１によれば、流量の検出出力の範囲全体を対数変換した直線特性であるため、直線特性における流量が無限小で元の非線形特性と一致する。そのため、最小流量での出力は元の非線形特性に比較して大きな値となり、最大流量の範囲で直線特性の勾配が緩やかになるため、流量変化に対する検出出力、すなわち分解能が小さくなる。 According to Patent Document 1 described above, since the linear characteristic is obtained by logarithmically converting the entire flow rate detection output range, the flow rate in the linear characteristic is infinitely small and matches the original nonlinear characteristic. For this reason, the output at the minimum flow rate becomes a larger value than the original non-linear characteristic, and the gradient of the linear characteristic becomes gentle in the range of the maximum flow rate, so that the detection output for the flow rate change, that is, the resolution becomes small.
　分解能が小さい検出出力をエンジン制御装置のＡ／Ｄ変換器に入力した時、Ａ／Ｄ変換器の分解能によっては、上述した例の最小流量を３．６ｋｇ／ｈとするとその付近の流量変化に対してＡ／Ｄ変換器の出力でこの変化を検出することが困難であったり、検出が可能であってもＳ／Ｎが低下して誤差を含んだ流量を検出する可能性がある。 When a detection output with a small resolution is input to the A / D converter of the engine control device, depending on the resolution of the A / D converter, if the minimum flow rate in the above example is 3.6 kg / h, the flow rate changes in the vicinity. On the other hand, it is difficult to detect this change in the output of the A / D converter, or even if it can be detected, there is a possibility that the S / N is lowered and a flow rate including an error is detected.
　また、最小流量から最大流量の範囲、すなわちダイナミックレンジが縮小し、Ａ／Ｄ変換器の利用効率が低下するという問題もある。 Also, there is a problem that the range from the minimum flow rate to the maximum flow rate, that is, the dynamic range is reduced, and the use efficiency of the A / D converter is lowered.
　本発明は、計測精度のよい熱式流量測定装置を提供することである。 The present invention is to provide a thermal flow measuring device with good measurement accuracy.
　上記課題を解決するため、本発明の熱式流量測定装置は、被計測流体の流量を計測する流量検出部を備えた熱式流量測定装置において、前記流量検出部は、前記流量検出部で計測できる有効流量範囲において前記流量検出部の出力を補正する補正手段を有し、前記補正手段は、前記流量検出部の感度に比べて大きい感度となるように補正し、かつ、この感度は、流量に対して常に一定の勾配となる出力に補正し、　前記出力を電圧出力あるいは周波数出力のどちらかに切り替え可能とした。 In order to solve the above problem, the thermal flow measurement device of the present invention is a thermal flow measurement device including a flow rate detection unit for measuring the flow rate of the fluid to be measured, wherein the flow rate detection unit is measured by the flow rate detection unit. A correction unit that corrects the output of the flow rate detection unit in an effective flow rate range, the correction unit corrects the sensitivity to be larger than the sensitivity of the flow rate detection unit, and the sensitivity is a flow rate The output is always corrected to a constant gradient, and the output can be switched to either voltage output or frequency output.
　本発明の熱式流量測定装置によれば、計測精度のよい熱式流量測定装置を提供することが可能となる。 According to the thermal flow measuring device of the present invention, it is possible to provide a thermal flow measuring device with good measurement accuracy.
本発明の第一の実施例を示す熱式流量測定装置のブロック図The block diagram of the thermal type flow measuring apparatus which shows the 1st Example of this invention 本発明の出力特性図Output characteristic diagram of the present invention 本発明の第一の実施例の発振器の特性Characteristics of the oscillator according to the first embodiment of the present invention 本発明の第一の実施例の発振器の変動特性Variation characteristics of the oscillator according to the first embodiment of the present invention 本発明の補正テーブルCorrection table of the present invention 測定した補正量の特性Characteristics of measured correction amount 格子点補正量の計算Calculation of lattice point correction 格子点の計算Calculation of lattice points 本発明の第三の実施例を示す熱式流量測定装置のブロック図Block diagram of a thermal flow measuring device showing a third embodiment of the present invention 本発明に係る流量検出部の抵抗体の配置図Arrangement diagram of resistors of flow rate detector according to the present invention 本発明の第三の実施例による流量（対数軸）－出力電圧特性図Flow rate (logarithmic axis) -output voltage characteristic diagram according to the third embodiment of the present invention 本発明の第三の実施例による流量（対数軸）－流量１％誤差電圧特性図Flow rate (logarithmic axis) -flow rate 1% error voltage characteristic diagram according to the third embodiment of the present invention 本発明の第四の実施例による補正テーブル特性図Correction table characteristic chart according to the fourth embodiment of the present invention 本発明の第四の実施例による流量（対数軸）－出力電圧特性図Flow rate (logarithmic axis) vs. output voltage characteristic diagram according to the fourth embodiment of the present invention 本発明の第四の実施例による流量（対数軸）－流量１％誤差電圧特性図Flow rate (logarithmic axis) -flow rate 1% error voltage characteristic diagram according to the fourth embodiment of the present invention 本発明の第五の実施例を示す流量処理回路のブロック図Block diagram of a flow rate processing circuit showing a fifth embodiment of the present invention 本発明の第五の実施例による補正テーブルの一例An example of a correction table according to the fifth embodiment of the present invention
　以下、本発明の実施例について図面を用いて説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
　図１において、流量検出部１０は、発熱抵抗体１１と測温抵抗体１２、１３、１４、１５、１６で構成されており、流量検出部１０の構造の一例を図１０で示している。 1, the flow rate detection unit 10 includes a heating resistor 11 and resistance temperature detectors 12, 13, 14, 15, and 16. An example of the structure of the flow rate detection unit 10 is illustrated in FIG. 10.
　図１０に示されるように、流量検出部１０は、被計測流体Ｆａに対して、基板上に測温抵抗体１２が配置され、シリコンダイヤフラム上に発熱抵抗体１１が配置され、発熱抵抗体１１の上流側に測温抵抗体１３、１４、発熱抵抗体１１の下流側に測温抵抗体１５、１６が配置されている。 As shown in FIG. 10, in the flow rate detection unit 10, with respect to the fluid Fa to be measured, the resistance temperature detector 12 is disposed on the substrate, the heating resistor 11 is disposed on the silicon diaphragm, and the heating resistor 11. The resistance temperature detectors 13 and 14 are arranged on the upstream side, and the resistance temperature detectors 15 and 16 are arranged on the downstream side of the heating resistor 11.
　図１において、発熱抵抗体１１は、測温抵抗体１２と抵抗体１７、１８で構成されるブリッジ回路の作用によって、測温抵抗体１２と抵抗体１７の分圧値を基準値（温度の目標値）として、抵抗体１８との分圧値が基準値と等しくなるように、差動増幅器１９が出力し、一定の温度になるように電流が通電される。 In FIG. 1, the heating resistor 11 uses a bridge circuit composed of the resistance temperature detector 12 and the resistances 17 and 18 to change the partial pressure value of the resistance temperature detector 12 and the resistance 17 to a reference value (temperature value). As a target value), the differential amplifier 19 outputs so that the divided voltage value with respect to the resistor 18 becomes equal to the reference value, and a current is applied so as to reach a constant temperature.
　そして、測温抵抗体１３、１４、１５、１６は、発熱抵抗体の伝熱によって抵抗値に変化が生じ、被計測流体Ｆａの流れ（流量）で冷却された発熱抵抗体１１からの伝熱は、上流側の測温抵抗体１３、１４では低くなって抵抗値が小さくなり、下流側の測温抵抗体１５、１６では高くなって抵抗値が大きくなる。 The resistance thermometers 13, 14, 15, and 16 change in resistance value due to the heat transfer of the heating resistor, and the heat transfer from the heating resistor 11 cooled by the flow (flow rate) of the fluid Fa to be measured. Is lower in the resistance thermometers 13 and 14 on the upstream side and decreases in resistance value, and is higher in the resistance thermometer resistors 15 and 16 on the downstream side and increases in resistance value.
　測温抵抗体１３、１４、１５、１６は、定電圧電源２０から電流を供給するブリッジ回路で構成されており、流体が流れて抵抗値が変化した時の電位差Ｖｄｅｔによって流量Ｑを検出するようになっている。 The resistance temperature detectors 13, 14, 15, and 16 are configured by a bridge circuit that supplies current from the constant voltage power supply 20, and detects the flow rate Q based on a potential difference Vdet when the resistance value changes due to the flow of fluid. It has become.
　このような流量検出方式は、一般に温度差検出方式と言われている。 Such a flow rate detection method is generally called a temperature difference detection method.
　ブリッジ回路の出力、すなわち電位差Ｖｄｅｔは流量処理回路３０によって内部処理を行い、流量Ｑを電圧値Ｖｏｕｔあるいは周波数Ｆｏｕｔに変換して、エンジン制御装置１００に出力されて、低アイドル回転制御やＡ／Ｆ制御の空気流量としてエンジン回転の制御に供される。 The output of the bridge circuit, that is, the potential difference Vdet is internally processed by the flow rate processing circuit 30, and the flow rate Q is converted into the voltage value Vout or the frequency Fout and output to the engine control device 100 for low idle rotation control and A / F. It serves for control of engine rotation as a control air flow rate.
　次に、流量処理回路３０について説明する。 Next, the flow rate processing circuit 30 will be described.
　図１において、３１はブリッジ回路で検出される電位差Ｖｄｅｔをゼロスパン調整した結果をしめす。３１ａはゼロスパン調整前、３１ｂはゼロスパン調整後の特性である。また、３４は目標の出力特性とブリッジ回路で検出される電位差Ｖｄｅｔをゼロスパン調整した特性３１ｂとの差分を示す。この差分を補正量ΔＦＱとして加えることで目標出力である３２に補正する。 In FIG. 1, 31 indicates the result of zero span adjustment of the potential difference Vdet detected by the bridge circuit. 31a is the characteristic before the zero span adjustment, and 31b is the characteristic after the zero span adjustment. Reference numeral 34 denotes the difference between the target output characteristic and the characteristic 31b obtained by adjusting the potential difference Vdet detected by the bridge circuit to zero span. By adding this difference as a correction amount ΔFQ, the target output is corrected to 32.
　ブリッジ回路で検出される電位差Ｖｄｅｔは、流量Ｑに対して、横軸、縦軸を比例軸で示した特性図３１に示す特性３１ａとなることは知られている。本特性は、低流量域では感度が高く、高流量域では感度が低い特性で、非直線特性となる特徴を持っている。 It is known that the potential difference Vdet detected by the bridge circuit becomes a characteristic 31a shown in a characteristic diagram 31 in which the horizontal axis and the vertical axis are proportional axes with respect to the flow rate Q. This characteristic is highly sensitive in the low flow rate region and low in the high flow rate region, and has a characteristic of non-linear characteristics.
　これを特性３１ｂとなるようにゼロスパン調整する。このとき、ゼロスパン調整は、補正係数をｋｚｅｒｏ，ｋｓｐａｎとしたとき、Ｆｚ＝ｋｓｐａｎ＊Ｖｄｅｔ＋ｋｚｅｒｏで計算され補正される。その後、３４ａの補正量ΔＦＱを加えることで、特性３２ｂ’に補正する。 ¡Adjust the zero span so that it becomes the characteristic 31b. At this time, the zero span adjustment is calculated and corrected by Fz = kspan * Vdet + kzero when the correction coefficients are kzero and kspan. Thereafter, the correction amount ΔFQ of 34a is added to correct the characteristic 32b ′.
　次に、調整におけるノイズの影響について図２を用いて説明する。流量検出部の検出ノイズをａＱとするとゼロスパン調整後の出力Ｆｚにおいては、Ｆｚ　＝ｋｓｐａｎ＊（Ｖｄｅｔ＋ａＱ）＋ｋｚｅｒｏとなり、検出ノイズが調整により増大してしまう。その後、３４ａのΔＦＱを加算し、最終出力に調整する。このとき、加えられるΔＦＱはＬＳＩ内部でデジタル値として加算されるため、ノイズは無い。従って、最終出力のノイズは、ゼロスパン調整後のｋｓｐａｎ＊　ａＱ’がそのまま出力ノイズとなる。
このことから、ゼロスパン調整のｋｓｐａｎで感度を大きくするのではなく、ΔＦＱを加算する工程で、感度を大きくすることで、出力ノイズを小さくすることが可能となる。 Next, the influence of noise in adjustment will be described with reference to FIG. If the detection noise of the flow rate detector is aQ, the output Fz after zero span adjustment is Fz = kspan * (Vdet + aQ) + kzero, and the detection noise increases due to the adjustment. Thereafter, ΔFQ of 34a is added to adjust to the final output. At this time, the added ΔFQ is added as a digital value inside the LSI, so there is no noise. Therefore, as the final output noise, kspan * aQ ′ after the zero span adjustment becomes the output noise as it is.
Therefore, the output noise can be reduced by increasing the sensitivity in the step of adding ΔFQ, rather than increasing the sensitivity by kspan of zero span adjustment.
　補正後の、出力電圧Ｖｏｕｔあるいは出力周波数Ｆｏｕｔは特性図３２の特性３２ｂ’となる。 After the correction, the output voltage Vout or the output frequency Fout becomes the characteristic 32b 'in the characteristic diagram 32.
　次に、エンジン制御装置１００は、流量処理回路３０の出力電圧ＶｏｕｔをＡ／Ｄ変換器１０１の入力とし、デジタル出力値によって流量Ｑを得るようにした回路構成が主流である。 Next, the engine control apparatus 100 mainly has a circuit configuration in which the output voltage Vout of the flow rate processing circuit 30 is input to the A / D converter 101 and the flow rate Q is obtained by a digital output value.
　そのため、Ａ／Ｄ変換器１０１の分解能によっては特性３２ｂ’の感度が大きくなる特性にしてしまうと、読み取り誤差が大きくなってしまう。 Therefore, depending on the resolution of the A / D converter 101, if the sensitivity of the characteristic 32b 'is increased, a reading error increases.
　そこで、出力特性３２ｂ’は、エンジン制御装置１００の読み取り分解能と流量検出装置内の集積回路内の発振器の特性から決定する。 Therefore, the output characteristic 32b 'is determined from the reading resolution of the engine control apparatus 100 and the characteristics of the oscillator in the integrated circuit in the flow rate detection apparatus.
　図３に発振器の特性を示す。初期特性をＣ１とすると、発振器の特性は抵抗劣化あるいはコンデンサの劣化などから、Ｃ２やＣ３のように特性変化が発生する。
発振器によって生成された周波数を分周して流量出力の信号としているため、発振器の特性が変動すると流量の出力特性にも変動が発生する。 FIG. 3 shows the characteristics of the oscillator. Assuming that the initial characteristic is C1, the characteristic of the oscillator changes such as C2 and C3 due to resistance deterioration or capacitor deterioration.
Since the frequency generated by the oscillator is divided into a flow rate output signal, when the characteristics of the oscillator vary, the output characteristics of the flow also vary.
　そこで、図４に示すような発振器の変動分を１％ＥＲＲＯＲとして割り当て、各流量に割りあてられる１％ＥＲＲＯＲを発振器の変動分よりも大きな１％ＥＲＲＯＲとなるような出力特性とすることで、発振器の変動が流量特性に与える影響を１％以下にすることができる。 Therefore, by assigning the fluctuation of the oscillator as shown in FIG. 4 as 1% ERROR, and setting the output characteristics such that 1% ERROR allocated to each flow rate becomes 1% ERROR larger than the fluctuation of the oscillator. The influence of fluctuation of the oscillator on the flow rate characteristic can be reduced to 1% or less.
　ここで、１％ｅｒｒｏｒとは、流量が１％変化したときの出力の変化量を示す。 Here, 1% error indicates the amount of change in output when the flow rate changes by 1%.
　さらに、補正する際にテーブル補正３４ａ（図１参照。）が設けられており、このテーブルにおいては、任意の格子点を設定して補正をすることができる。 Furthermore, a table correction 34a (see FIG. 1) is provided for correction. In this table, correction can be performed by setting arbitrary grid points.
　続けて、図５を用いてテーブル補正について説明する。格子点間隔が等間隔である等間隔格子３６ａと格子点間隔が任意に変更することができる不等間隔格子３６ｂがある。等間隔格子では、局所的な特性曲がりに対して、分解能を任意に変更できないため、誤差が大きくなってしまうことがある。それに対して、不等間隔格子を用いて特性曲がりの大きな部分の格子間隔を小さくして分解能をあげることで、特性曲がりの大きな部分での補正を可能としている。 Next, table correction will be described with reference to FIG. There are an equidistant lattice 36a in which the lattice point intervals are equal and an unequally spaced lattice 36b in which the lattice point interval can be arbitrarily changed. In the equidistant lattice, the resolution cannot be arbitrarily changed with respect to the local characteristic curve, and the error may increase. On the other hand, by using a non-uniformly spaced grating to reduce the lattice spacing of the portion with the large characteristic curve and increase the resolution, correction at the portion with the large characteristic curve is possible.
　このテーブル補正における格子点補正量の算出方法は、任意に変更できる格子点を曲がりの急な領域には分解能が高くなるように配置し、曲がりの緩やかな領域には、分解能が粗くなるように配置しておき、目標の補正値に対してスプライン補間によりカーブを作る。このスプラインによるカーブと格子点との交点を補正量として決定する。ただし、不等間隔格子の場合、サンプル毎に格子間隔を任意に選択できるが、このスプライン補間により格子点の補正量を決定する場合、予め格子間隔を決定しておく必要がある。この場合、格子間隔をサンプル毎に最適化することができないため、計測精度の向上の効果が下記に記載するよりも小さいが等間隔格子を使った補正よりも計測精度が向上する。 The calculation method of the grid point correction amount in this table correction is such that the grid points that can be arbitrarily changed are arranged so that the resolution is high in a sharply curved area, and the resolution is coarse in a slowly curved area. A curve is created by spline interpolation for the target correction value. The intersection of the curve by the spline and the lattice point is determined as a correction amount. However, in the case of an unequal interval lattice, the lattice interval can be arbitrarily selected for each sample. However, when determining the correction amount of the lattice point by this spline interpolation, it is necessary to determine the lattice interval in advance. In this case, since the lattice interval cannot be optimized for each sample, the effect of improving the measurement accuracy is smaller than described below, but the measurement accuracy is improved as compared with the correction using the equidistant lattice.
　次に、格子間隔をサンプル毎に最適化する補正量算出方法を以下に記載する。サンプル毎に流量に対する出力の特性を測定する。出力特性と目標特性との差を補正量とし、流量に対する補正量の関係を図６に示す。このとき、サンプル毎に流量に対する補正量が異なる。この補正量に対して、低流量側から格子点の位置と補正量を決定していく。まず、低流量特性２点から直線を引く。次に、最初に直線を引くのに用いた２点以外で低流量側の２点以上から直線を引く。このとき、２点で計算された場合は２点から直線が算出され、３点以上から直線が算出される場合は、最小二乗法を用いて誤差が最小となるような直線を計算する。この算出された直線を図７に示す。 Next, a correction amount calculation method for optimizing the lattice spacing for each sample is described below. Measure the output characteristics with respect to the flow rate for each sample. The difference between the output characteristic and the target characteristic is used as a correction amount, and the relationship of the correction amount to the flow rate is shown in FIG. At this time, the correction amount with respect to the flow rate is different for each sample. For this correction amount, the position of the grid point and the correction amount are determined from the low flow rate side. First, a straight line is drawn from two low flow characteristics. Next, a straight line is drawn from two or more points on the low flow rate side other than the two points used to draw the straight line first. At this time, when the calculation is performed at two points, a straight line is calculated from two points, and when the straight line is calculated from three or more points, a straight line that minimizes the error is calculated using the least square method. This calculated straight line is shown in FIG.
　このようにして、低流量側から高流量側にかけて直線を求め、これらの直線の交点が（格子点座標、補正量）となる。このように算出された補正量を図８に示す。この算出方法は、サンプル毎に格子点位置及び格子点間隔を任意に決定することができるため、精度が落ちることなく高精度に補正することができる。これにより、計測精度のよい熱式流量測定装置を提供することが可能となる。 In this way, straight lines are obtained from the low flow rate side to the high flow rate side, and the intersection of these straight lines becomes (lattice point coordinates, correction amount). The correction amount calculated in this way is shown in FIG. Since this calculation method can arbitrarily determine the grid point position and the grid point interval for each sample, it can be corrected with high accuracy without lowering accuracy. As a result, it is possible to provide a thermal flow rate measuring apparatus with good measurement accuracy.
　なお、本実施例では、補正テーブルの格子点間の補正が線形補間の例を示したがこれに限られるものではなく、２次補間によって補正してもよい。これにより、同様に格子点間の補正後の非線形性を緩和することができる。 In the present embodiment, the correction between the lattice points of the correction table is an example of linear interpolation. However, the correction is not limited to this, and correction may be performed by secondary interpolation. Thereby, the nonlinearity after correction | amendment between lattice points can be relieved similarly.
　次に、他の実施例の一例である実施例２について図９、図１１、図１２を用いて説明する。実施例１と同様に測温抵抗体１３、１４、１５、１６は、定電圧電源２０から電流を供給するブリッジ回路で構成されており、流体が流れて抵抗値が変化した時の電位差Ｖｄｅｔによって流量Ｑを検出するようになっている。 Next, a second embodiment, which is an example of another embodiment, will be described with reference to FIG. 9, FIG. 11, and FIG. As in the first embodiment, the resistance temperature detectors 13, 14, 15, and 16 are configured by a bridge circuit that supplies a current from the constant voltage power supply 20, and the potential difference Vdet when the resistance value changes when the fluid flows. The flow rate Q is detected.
　以下、流量処理回路３０の詳細について説明する。ブリッジ回路で検出される電位差Ｖｄｅｔは、流量Ｑに対して、横軸、縦軸を比例軸で示した特性図３１の特性３１ａとなり、低流量域では感度が高く、高流量域では感度が低い特性で、非直線特性となる。そして、特性３１ａの横軸の流量Ｑを対数軸に変換した出力電圧Ｖｏｕｔあるいは出力周波数Ｆｏｕｔは特性図３２の特性３２ａとなる。 Hereinafter, details of the flow rate processing circuit 30 will be described. The potential difference Vdet detected by the bridge circuit becomes the characteristic 31a of the characteristic diagram 31 in which the horizontal axis and the vertical axis are represented by the proportional axis with respect to the flow rate Q, and the sensitivity is high in the low flow range and low in the high flow range. Characteristics are non-linear characteristics. The output voltage Vout or the output frequency Fout obtained by converting the flow rate Q on the horizontal axis of the characteristic 31a into a logarithmic axis becomes the characteristic 32a in the characteristic diagram 32.
　図１１は、図９の特性図３２を再掲した横軸の流量Ｑを対数軸とした流量処理回路３０の出力Ｖｏｕｔの特性であり、流量Ｑと電位差Ｖｄｅｔの特性３２ａは、低流量域では検出感度が低いままの非線形特性となっている。出力電圧Ｖｏｕｔは、０ＶからＡ／Ｄ変換器１０１の基準電圧Ｖｒｅｆの範囲で出力され、Ａ／Ｄ変換器１０１のビット長で決まる分解能Ｖａｄｒの単位で流量が算出される。また、Ａ／Ｄ変換器１０１の代わりにＦＲＣ（フリーランニングカウンタ）を用いることで、出力周波数Ｆｏｕｔを出力することができる。なお、図１１の縦軸の出力電圧Ｖｏｕｔは、Ａ／Ｄ変換器１０１の基準電圧Ｖｒｅｆを１００％とした場合の割合（％）で示している。 FIG. 11 shows the characteristics of the output Vout of the flow rate processing circuit 30 with the logarithmic axis representing the flow rate Q on the horizontal axis, which is a reprint of the characteristic diagram 32 of FIG. 9, and the characteristics 32a of the flow rate Q and the potential difference Vdet are detected in the low flow rate range. Non-linear characteristics with low sensitivity. The output voltage Vout is output in the range of 0 V to the reference voltage Vref of the A / D converter 101, and the flow rate is calculated in units of resolution Vadr determined by the bit length of the A / D converter 101. Further, by using an FRC (free running counter) instead of the A / D converter 101, the output frequency Fout can be output. Note that the output voltage Vout on the vertical axis in FIG. 11 is shown as a ratio (%) when the reference voltage Vref of the A / D converter 101 is 100%.
　ところで、流量測定装置ではＡ／Ｄ変換器１０１の分解能Ｖａｄｒに対して、流量Ｑの１％誤差相当電圧ＶＥｒ（以下１％誤差相当電圧、１％Ｅｒｒｏｒと同義）にどれだけの余裕があるかが評価指標の１つとなっている。すなわち、分解能Ｖａｄｒに比較して１％誤差相当電圧ＶＥｒが大きくできれば、流量Ｑの１％変化を確実に検出できると共に、信号／ノイズ（Ｓ／Ｎ）比が大きくなり、高精度で安定した流量測定装置として評価されることになる。 By the way, in the flow rate measuring apparatus, how much margin is available for the 1% error equivalent voltage VEr of the flow rate Q (hereinafter, synonymous with 1% error equivalent voltage and 1% Error) with respect to the resolution Vadr of the A / D converter 101. Is one of the evaluation indicators. That is, if the 1% error equivalent voltage VEr can be increased as compared with the resolution Vadr, a 1% change in the flow rate Q can be reliably detected, and the signal / noise (S / N) ratio is increased, so that the flow rate is highly accurate and stable. It will be evaluated as a measuring device.
　図１２は、Ａ／Ｄ変換器１０１の分解能Ｖａｄｒと、図９の特性３２ａを上述した評価指標の流量Ｑの１％誤差相当電圧ＶＥｒ（１％Ｅｒｒｏｒ）の特性であり、最大となるＶＥｒを１００％として示している。 FIG. 12 shows the characteristics of the resolution Vadr of the A / D converter 101 and the 1% error equivalent voltage VEr (1% Error) of the flow rate Q of the evaluation index described above with the characteristic 32a of FIG. Shown as 100%.
　目標最小流量をＱｍｉｎにおける１％誤差相当電圧ＶＥｒ＝ＶＥｒａｍｉｎは６％程度であり、Ａ／Ｄ変換器１０１の分解能Ｖａｄｒ＝１５％より小さな値となり、流量Ｑが１％変化した場合の検出が不可能であることを示している。そこで、流量処理回路３０では、最大流量Ｑｍａｘ（約１０００ｋｇ／ｈ）までの範囲において、横軸の流量Ｑを対数軸にした出力電圧Ｖｏｕｔあるいは出力周波数Ｆｏｕｔの特性がほぼ直線に近づくように線形化の補正をするようにした。 The 1% error equivalent voltage VEr = VERamin at the target minimum flow rate at Qmin is about 6%, which is smaller than the resolution Vadr = 15% of the A / D converter 101, and detection is not possible when the flow rate Q changes by 1%. It shows that it is possible. Therefore, in the flow rate processing circuit 30, in the range up to the maximum flow rate Qmax (about 1000 kg / h), linearization is performed so that the characteristics of the output voltage Vout or the output frequency Fout using the flow rate Q on the horizontal axis as a logarithmic axis are almost linear. The correction was made.
　図９の補正図３４の補正特性３４ａは、流量Ｑに対して低流量域で電圧を増加させ、高流量域で電圧を減少させる補正量ΔＦＱとし、特性図３１の出力すなわち電位差Ｖｄｅｔをデジタル値に変換した値と補正量ΔＦＱを加算して出力電圧Ｖｏｕｔあるいは出力周波数Ｆｏｕｔを出力するようにしている。電位差Ｖｄｅｔをデジタル値に変換した値と補正量ΔＦＱの加算された出力電圧Ｖｏｕｔあるいは出力周波数Ｆｏｕｔを流量Ｑを対数軸として表した結果が特性３２ｂであり、特性３２ａに対してより直線化された特性３２ｂとなっている。 The correction characteristic 34a of FIG. 34 is a correction amount ΔFQ that increases the voltage in the low flow rate region and decreases the voltage in the high flow rate region with respect to the flow rate Q. The output of the characteristic diagram 31, that is, the potential difference Vdet is a digital value. The output voltage Vout or the output frequency Fout is output by adding the value converted to と and the correction amount ΔFQ. The characteristic 32b is a result of expressing the output voltage Vout or the output frequency Fout obtained by adding the value obtained by converting the potential difference Vdet into a digital value and the correction amount ΔFQ with the flow rate Q as a logarithmic axis, and is more linearized with respect to the characteristic 32a. It is characteristic 32b.
　図１１は特性図３２を再掲した図であり、特性３２ｂは特性３２ａに対して、最小流量Ｑｍｉｎにおける出力電圧ＶｏｕｔがＶｏｕｔａ＝２５％からＶｏｕｔｂ＝３９％に大きくなり、ほぼ流量Ｑ＝２０ｋｇ／ｈまでの範囲で出力電圧Ｖｏｕｔの勾配が大きくなる特性であることから分解能が向上していることが解る。これは、出力周波数Ｆｏｕｔでも同じである。 FIG. 11 shows the characteristic diagram 32 again. In the characteristic 32b, the output voltage Vout at the minimum flow rate Qmin increases from Vouta = 25% to Voutb = 39% with respect to the characteristic 32a, and the flow rate Q = 20 kg / h. It can be seen that the resolution is improved due to the characteristic that the gradient of the output voltage Vout increases in the range up to. The same applies to the output frequency Fout.
　図１２の流量Ｑの１％誤差相当電圧ＶＥｒ（１％Ｅｒｒｏｒ）の特性において、補正特性３４ａで補正された特性を特性３３ｂで示しており、目標最小流量ＱｍｉｎにおいてＶＥｒｂｍｉｎ＝４６％程度まで大きくなり、特性３３ａのＶＥｒａｍｉｎ＝６％に比較してほぼ８倍に大きくすることができる。 In the characteristic of 1% error equivalent voltage VEr (1% Error) of the flow rate Q in FIG. 12, the characteristic corrected by the correction characteristic 34a is shown by the characteristic 33b, and increases to about VErbmin = 46% at the target minimum flow rate Qmin. , The characteristic 33a can be increased by approximately 8 times compared to VERamin = 6%.
　このことは、Ａ／Ｄ変換器１０１の分解能Ｖａｄｒ＝１５％に対してもほぼ２．５倍に大きくなっているので、Ａ／Ｄ変換器１０１で得られる流量Ｑは、１％の流量変化が確実に検出でき、さらにＳ／Ｎが大きくなるので、高精度でノイズ等の影響を受けない安定した流量測定装置にすることができる。なお、特性３２ａに比較して特性３２ｂはより直線化された特性となり、１％誤差相当電圧ＶＥｒはほぼ一定の特性となっているが、これは次のことから明らかである。 This is about 2.5 times larger than the resolution Vadr = 15% of the A / D converter 101. Therefore, the flow rate Q obtained by the A / D converter 101 is a flow rate change of 1%. Can be reliably detected, and the S / N ratio is increased, so that a stable flow rate measuring apparatus that is highly accurate and is not affected by noise or the like can be obtained. The characteristic 32b is a more linear characteristic than the characteristic 32a, and the 1% error equivalent voltage VEr is a substantially constant characteristic. This is apparent from the following.
　横軸の流量Ｑを対数軸ｘ、縦軸の出力電圧Ｖｏｕｔを比例軸ｙとして、グラフ上で単調増加の特性において、出力電圧Ｖｏｕｔを流量の誤差εに換算した出力ＶＥｒは下記で算出される。
特性：Ａ・ｌｏｇｘ＋Ｂ
傾き：ｄ（Ａ・ｌｏｇｘ＋Ｂ）／ｄｘ＝Ａ／ｘ
ｘ（＝Ｑ）のΔｘ変化に対するｙ（＝Ｖｏｕｔ）の変化Δｙ＝Ａ／ｘ・Δｘ
ｘ（＝Ｑ）の誤差εにおける変化Δｘ＝ε・ｘ
ｙ（＝誤差換算出力ＶＥｒ）＝（Ａ／ｘ）・ε・ｘ＝Ａ・ε
（Ａ、Ｂは定数）
　すなわち、横軸の流量Ｑを対数軸として、流量の誤差εがある値のとき出力電圧Ｖｏｕｔは一定値となるので、図１２の特性３３ｂがε＝１％に換算した出力電圧Ｖｏｕｔでほぼ一定値を示している。これは、出力周波数Ｆｏｕｔで算出しても同様に一定値となる。 With the flow rate Q on the horizontal axis as the logarithmic axis x and the output voltage Vout on the vertical axis as the proportional axis y, the output VEr obtained by converting the output voltage Vout to the flow rate error ε in the monotonically increasing characteristics on the graph is .
Characteristic: A ・ logx + B
Inclination: d (A · logx + B) / dx = A / x
Change in y (= Vout) with respect to Δx change in x (= Q) Δy = A / x · Δx
Change in error (ε) of x (= Q) Δx = ε · x
y (= error conversion output Ver) = (A / x) · ε · x = A · ε
(A and B are constants)
That is, the output voltage Vout is a constant value when the flow rate Q on the horizontal axis is a logarithmic axis and the flow rate error ε is a certain value. Therefore, the characteristic 33b in FIG. 12 is substantially constant at the output voltage Vout converted to ε = 1%. The value is shown. Even if this is calculated by the output frequency Fout, it becomes a constant value similarly.
　実施例２によれば、熱式流量測定装置において、横軸を対数軸とした流量Ｑに対する出力電圧Ｖｏｕｔあるいは出力周波数Ｆｏｕｔが、直線に近づく特性３２ｂとなるように、補正特性３４ａで補正することにより、低流量域での出力電圧Ｖｏｕｔあるいは出力周波数Ｆｏｕｔの分解能を向上できる効果がある。これにより、より計測精度のよい熱式流量測定装置を提供することが可能となる。 According to the second embodiment, in the thermal type flow rate measuring device, the correction characteristic 34a is corrected so that the output voltage Vout or the output frequency Fout with respect to the flow rate Q having the horizontal axis as a logarithmic axis becomes a characteristic 32b that approaches a straight line. As a result, the resolution of the output voltage Vout or the output frequency Fout in the low flow rate region can be improved. As a result, it is possible to provide a thermal flow rate measuring apparatus with better measurement accuracy.
　次に、実施例３について図１３乃至図１５を用いて説明する。先の実施例２では、低流量域で分解能を向上することができたが、図１１に示す特性３２ａと３２ｂを比較した時、高流量域において特性３２ｂの勾配が特性３２ａの勾配より小さくなるので、分解能が低下してしまう側面も併せて持っている。 Next, Example 3 will be described with reference to FIGS. In the previous Example 2, the resolution could be improved in the low flow rate range, but when the characteristics 32a and 32b shown in FIG. 11 are compared, the gradient of the characteristic 32b is smaller than the gradient of the characteristic 32a in the high flow rate range. Therefore, it also has an aspect that the resolution is lowered.
　流量全域で流量Ｑの１％誤差相当電圧ＶＥｒ（１％Ｅｒｒｏｒ）の特性を示す図１２において、最大流量Ｑｍａｘ＝１０００ｋｇ／ｈでは、補正特性３４ａがない場合の特性３３ａをＶＥｒ＝１００％で示したのに対して、補正特性３４ａで補正した特性３３ｂはほぼ５０％まで分解能が低下している。 In FIG. 12 showing the characteristics of the 1% error equivalent voltage VEr (1% Error) of the flow rate Q over the entire flow rate range, the maximum flow rate Qmax = 1000 kg / h shows the characteristic 33a without the correction characteristic 34a as VEr = 100%. On the other hand, the resolution of the characteristic 33b corrected by the correction characteristic 34a is reduced to almost 50%.
　ところで、Ａ／Ｄ変換器１０１の動作として、０から基準電圧の範囲で入力電圧を変化させることが、ダイナミックレンジが広く分解能を大きくして動作させることができる。実施例２の出力電圧の特性３２ｂでは、目標最小流量Ｑｍｉｎと最大流量Ｑｍａｘの電圧差ΔＶｏｕｔｂ＝５２％に対して、補正特性３４ａがない場合の電圧差ΔＶｏｕｔａ＝６５％より小さくなり、基準電圧Ｖｒｅｆの半分程度のダイナミックレンジとなっている。これは、出力電圧の特性３２ａに比較して出力電圧の特性３２ｂが目標最小流量Ｑｍｉｎ付近で大きくなっていることに起因している。 Incidentally, as the operation of the A / D converter 101, changing the input voltage in the range from 0 to the reference voltage can be operated with a wide dynamic range and a large resolution. In the output voltage characteristic 32b of the second embodiment, the voltage difference ΔVoutb = 52% between the target minimum flow rate Qmin and the maximum flow rate Qmax is smaller than the voltage difference ΔVouta = 65% when there is no correction characteristic 34a, and the reference voltage Vref. The dynamic range is about half of that. This is because the output voltage characteristic 32b is larger in the vicinity of the target minimum flow rate Qmin than the output voltage characteristic 32a.
　そこで、本実施例では、実際に使用される使用流量範囲、すなわち目標最小流量Ｑｍｉｎに対して、誤差分等の余裕分を含めたＱｍｉｎ＞Ｑｓｔａｒｔを始点としてＱｍａｘ（１０００ｋｇ／ｈ）の範囲（Ｑａｒｅａ）において、横軸を対数軸とした流量Ｑと出力電圧Ｖｏｕｔの特性がほぼ直線となるように、図９の補正特性３４ａから図１３に示す補正特性３４ｃに変更している。 Therefore, in the present embodiment, a range of Qmax (1000 kg / h) starting from Qmin> Qstart including a margin such as an error with respect to the actually used working flow range, that is, the target minimum flow rate Qmin (Qarea). 9), the correction characteristic 34a in FIG. 9 is changed to the correction characteristic 34c shown in FIG. 13 so that the characteristics of the flow rate Q and the output voltage Vout with the horizontal axis as a logarithmic axis are substantially linear.
　図１４は、全流量域（ＱｓｔａｒｔからＱｍａｘ）で対数軸の流量Ｑに対する出力電圧Ｖｏｕｔの特性、図１５は、対数軸の流量Ｑに対する流量Ｑの１％誤差相当電圧ＶＥｒ（１％Ｅｒｒｏｒ）の特性である。図１４、図１５において、特性図３２、図１１、図１２と同一特性、及び同一部分については同一符号で示してあり、補正特性３４ａがない場合が特性３２ａと特性３３ａ、実施例２の補正特性３４ａで補正した場合が特性３２ｂと特性３３ｂ、本実施例の補正特性３４ｃで補正した場合が特性３２ｃと特性３３ｃである。 FIG. 14 shows the characteristics of the output voltage Vout with respect to the logarithmic axis flow Q in the entire flow range (Qstart to Qmax), and FIG. 15 shows the 1% error equivalent voltage VEr (1% Error) of the flow Q with respect to the logarithmic axis flow Q. It is a characteristic. 14 and 15, the same characteristics and the same parts as those in the characteristic diagrams 32, 11, and 12 are denoted by the same reference numerals. When there is no correction characteristic 34 a, the characteristics 32 a and the characteristics 33 a are corrected. The characteristics 32b and 33b are corrected by the characteristic 34a, and the characteristics 32c and 33c are corrected by the correction characteristic 34c of this embodiment.
　図１４に示す出力電圧Ｖｏｕｔの特性から目標最小流量Ｑｍｉｎと最大流量Ｑｍａｘの電圧差ΔＶｏｕｔは、実施例３のΔＶｏｕｔｂ＝５２％からΔＶｏｕｔｃ＝６１％に改善され、ダイナミックレンジを大きくすることができる。その結果、図１５の流量Ｑの１％誤差相当電圧ＶＥｒ（１％Ｅｒｒｏｒ）の特性で示すように、低流量域から高流量域の範囲で、実施例３の特性３３ｂのＶＥｒ＝４９％程度から５８％程度まで大きくすることができ、Ａ／Ｄ変換器の分解能Ｖａｄｒ＝１５％に対して十分大きな値となり、１％の流量変化が確実に検出でき、さらにＳ／Ｎが大きくなるので、高精度でノイズ等の影響を受けない安定した流量測定装置にすることができる。 From the characteristics of the output voltage Vout shown in FIG. 14, the voltage difference ΔVout between the target minimum flow rate Qmin and the maximum flow rate Qmax is improved from ΔVoutb = 52% in Example 3 to ΔVoutc = 61%, and the dynamic range can be increased. As a result, as shown by the characteristic of the 1% error equivalent voltage VEr (1% Error) of the flow rate Q in FIG. 15, in the range from the low flow rate range to the high flow rate range, VEr of the characteristic 33b of Example 3 is about 49%. To 58%, which is a sufficiently large value for the resolution Vadr = 15% of the A / D converter, and a 1% flow rate change can be reliably detected, and the S / N is further increased. A highly accurate and stable flow rate measuring device that is not affected by noise or the like can be obtained.
　実施例２や本実施例では流量処理回路３０をブロック図として示しているが、処理手段は、アナログ処理方法、デジタル処理方法のどちらの方法にも適用することができる。アナログ処理方法では、電位差Ｖｄｅｔと関数発生器で発生させた補正電圧Ｖｃｏｍｐ特性を加算して、ログ増幅器で特性３２ｂ、あるいは３２ｃを得るようにする方法である。一方デジタル処理方法は、回路構成の簡易化やアナログ増幅回路のドリフトが改善でき、特にセンサ処理においては、専用のＩＣ（ＡＳＩＣ）が採用される傾向にある。デジタル処理方法では、電位差ＶｄｅｔをＡ／Ｄ変換器でデジタル値として、補正特性３４ａあるいは３４ｃ、加算、対数軸変換の特性３２ｂあるいは３２ｃをプログラムで演算し、演算結果をＤ／Ａ変換器でアナログ値として、出力電圧Ｖｏｕｔあるいは出力周波数Ｆｏｕｔをエンジン制御装置１００に出力するようにしている。 In the second embodiment and the present embodiment, the flow rate processing circuit 30 is shown as a block diagram, but the processing means can be applied to either an analog processing method or a digital processing method. In the analog processing method, the potential difference Vdet and the correction voltage Vcomp characteristic generated by the function generator are added to obtain the characteristic 32b or 32c by the log amplifier. On the other hand, the digital processing method can simplify the circuit configuration and improve the drift of the analog amplifier circuit. In particular, in the sensor processing, a dedicated IC (ASIC) tends to be employed. In the digital processing method, the potential difference Vdet is converted into a digital value by the A / D converter, the correction characteristic 34a or 34c, the addition / logarithmic axis conversion characteristic 32b or 32c is calculated by a program, and the calculation result is analog by the D / A converter. The output voltage Vout or the output frequency Fout is output to the engine control apparatus 100 as a value.
　さらに、図９の補正図３４や図１３の補正図は、あらかじめ流量Ｑに対してΔＹを補正テーブルで作成し、流量Ｑによってテーブルを参照しΔＹを得る方法や、補正テーブルを多項式で設定し、その都度演算によってΔＹを得る方法等がある。 Further, in the correction diagrams of FIG. 34 and FIG. 13, ΔY is created in advance with respect to the flow rate Q using a correction table, and ΔY is obtained by referring to the table with the flow rate Q, or the correction table is set with a polynomial. There is a method of obtaining ΔY by calculation each time.
　また、必ずしも図９に示した流量処理回路３０のブロックがそのまま構成される必要はなく、発熱抵抗体による流量の計測にあって、流量Ｑの使用範囲において、流量検出部１０の入力に対して、流量に対して４乗根の出力、あるいは、流量を対数軸とした流量処理回路３０の出力Ｖｏｕｔあるいは出力周波数が直線に近づく補正が成され、また使用範囲全域で流量誤差の百分率が一定値の場合、出力電圧Ｖｏｕｔあるいは出力周波数Ｆｏｕｔに含まれる誤差の値がほぼ一定値となる処理であれば、作用、効果は同等である。 Further, the block of the flow rate processing circuit 30 shown in FIG. 9 is not necessarily configured as it is. In the flow rate measurement by the heating resistor, the input of the flow rate detection unit 10 is performed in the usage range of the flow rate Q. The output of the fourth root with respect to the flow rate, or the output Vout or the output frequency of the flow rate processing circuit 30 with the logarithmic axis as the flow rate is corrected so that it becomes a straight line, and the percentage of the flow rate error is constant over the entire use range. In this case, the operation and the effect are the same as long as the error value included in the output voltage Vout or the output frequency Fout is a substantially constant value.
　なお、本実施例では、実際に使用される使用流量範囲、すなわち目標最小流量Ｑｍｉｎに対して、余裕分を含めたＱｍｉｎ＞Ｑｓｔａｒｔを始点としてＱｍａｘ（１０００ｋｇ／ｈ）の範囲（Ｑａｒｅａ）において、横軸を対数軸とした流量Ｑと出力電圧Ｖｏｕｔあるいは出力周波数Ｆｏｕｔの特性がほぼ直線となるようにした。しかし、目標最小流量Ｑｍｉｎの測定誤差が皆無、又は非常に小さい場合には、ほぼ直線とする特性は、目標最小流量Ｑｍｉｎを始点とした変換であっても、作用、効果は同等である。 In the present embodiment, the actual flow rate range used, that is, the target minimum flow rate Qmin, in the range (Qarea) of Qmax (1000 kg / h) with Qmin> Qstart including the margin as the starting point. The characteristics of the flow rate Q and the output voltage Vout or the output frequency Fout with the logarithmic axis as an axis are almost linear. However, when there is no or very small measurement error of the target minimum flow rate Qmin, the characteristics that are almost straight lines have the same operation and effect even if the conversion is made with the target minimum flow rate Qmin as the starting point.
　次に、実施例４について図１６、１７を用いて説明する。先の実施例２あるいは３では、流量Ｑを対数軸で直線に近づく特性となるように補正して低流量域の分解能を向上させたが、本実施例では、電位差Ｖｄｅｔを非線形処理し、非線形処理の出力から補正テーブルを参照して低流量域の分解能を向上させるようにしている。 Next, Example 4 will be described with reference to FIGS. In the previous embodiment 2 or 3, the flow rate Q is corrected so as to be close to a straight line on the logarithmic axis to improve the resolution in the low flow rate region. However, in this embodiment, the potential difference Vdet is nonlinearly processed, and the nonlinearity is obtained. The resolution in the low flow rate region is improved by referring to the correction table from the processing output.
　図１６は本実施例の流量処理回路３０のブロック図であり、デジタル処理の例を示し、以下の図中の数値は２進数のｄｉｇｉｔで表してある。 FIG. 16 is a block diagram of the flow rate processing circuit 30 of the present embodiment, showing an example of digital processing, and the numerical values in the following figures are represented by binary digits.
　非線形処理３５は、測温抵抗体１３、１４、１５，１６のブリッジ回路で検出される電位差Ｖｄｅｔを変数として２次関数（（ａ・Ｖｄｅｔ）×２　＋ｂ・Ｖｄｅｔ＋ｃ）で変換して、補正テーブル３６のテーブル引数Ｖｍｐｉｎを出力する。補正テーブル３６は、テーブル引数Ｖｍｐｉｎの全領域で分割されており、参照するテーブル引数Ｖｍｐｉｎに該当する補正出力Ｖｍｐｏｕｔを流量処理回路３０の出力ＶｏｕｔあるいはＦｏｕｔとしている。 The nonlinear processing 35 converts the potential difference Vdet detected by the bridge circuit of the resistance temperature detectors 13, 14, 15, 16 into a variable by a quadratic function ((a · Vdet) × 2 + b · Vdet + c), and corrects the correction table. 36 table argument Vmpin is output. The correction table 36 is divided in the entire region of the table argument Vmpin, and the correction output Vmpout corresponding to the table argument Vmpin to be referred to is the output Vout or Fout of the flow rate processing circuit 30.
　ここで、本発明の課題である流量Ｑの低流量域の分解能を大きくする手段の１つとして、補正テーブルの全入力範囲でテーブル引数Ｖｍｐｉｎの分割を均等に細分化した補正テーブルを用いる例があるが、補正テーブルのデータ数が増大するのでメモリ容量が増大しコスト、信頼性に問題が生ずる。また、他の手段として、図１７に示すように、電位差Ｖｄｅｔの小さい領域（低流量域）でテーブル分割数を多く（細分化）し、電位差Ｖｄｅｔが大きくなるに従ってテーブル分割数を少なくする不均等な分割にする例がある。しかし、電位差Ｖｄｅｔの大きい領域（高流量域）で分解能を所定の範囲内にするためには、テーブル分割数を少なくするにも限度があり、テーブル分割数の増大が避けられない。そこで、本実施例では、非線形処理３５によって、電位差Ｖｄｅｔの小さい領域の勾配を大きくし、補正テーブル３６のテーブル引数Ｖｍｐｉｎを均等な分割にするようにした。 Here, as one of means for increasing the resolution of the low flow rate region of the flow rate Q, which is the subject of the present invention, there is an example using a correction table in which the division of the table argument Vmpin is equally subdivided in the entire input range of the correction table. However, since the number of data in the correction table increases, the memory capacity increases, causing problems in cost and reliability. As another means, as shown in FIG. 17, the number of table divisions is increased (subdivided) in a region where the potential difference Vdet is small (low flow rate region), and the number of table divisions is reduced as the potential difference Vdet increases. There is an example to make a simple division. However, in order to make the resolution within a predetermined range in a region where the potential difference Vdet is large (high flow rate region), there is a limit in reducing the number of table divisions, and an increase in the number of table divisions is unavoidable. Therefore, in this embodiment, the gradient of the region where the potential difference Vdet is small is increased by the non-linear processing 35 so that the table argument Vmpin of the correction table 36 is divided equally.
１０…流量検出部
１１…発熱抵抗体
１２～１６…測温抵抗体
１７，１８…抵抗体
１９…差動増幅器
２０…定電圧電源
３０…流量処理回路
３１…流量（比例軸）―センサ出力電圧特性
３２…流量（対数軸）－流量処理回路出力電圧特性
３３…流量（対数軸）－流量１％誤差電圧特性
３６…補正テーブル
１００…エンジン制御装置
１０１…Ａ／Ｄ変換器 DESCRIPTION OF SYMBOLS 10 ... Flow rate detection part 11 ... Heating resistors 12-16 ... Resistance temperature detectors 17, 18 ... Resistor 19 ... Differential amplifier 20 ... Constant voltage power supply 30 ... Flow rate processing circuit 31 ... Flow rate (proportional axis)-sensor output voltage Characteristic 32 ... Flow rate (logarithmic axis)-Flow rate processing circuit output voltage characteristic 33 ... Flow rate (logarithmic axis)-Flow rate 1% error voltage characteristic 36 ... Correction table 100 ... Engine controller 101 ... A / D converter

Claims (5)

  1. 　被計測流体の流量を計測する流量検出部を備えた熱式流量測定装置において、
    　前記流量検出部は、前記流量検出部で計測できる有効流量範囲において前記流量検出部の出力を補正する補正手段を有し、
    　前記補正手段は、
    　前記流量検出部の感度に比べて大きい感度となるように補正し、かつ、この感度は、流量に対して常に一定の勾配となる出力に補正し、
    　前記出力を電圧出力あるいは周波数出力のどちらかに切り替え可能なことを特徴とする熱式流量測定装置及びこれを用いた制御装置。     In a thermal flow measuring device equipped with a flow rate detection unit for measuring the flow rate of the fluid to be measured
    The flow rate detection unit has correction means for correcting the output of the flow rate detection unit in an effective flow rate range that can be measured by the flow rate detection unit,
    The correction means includes
    The sensitivity is corrected so as to be greater than the sensitivity of the flow rate detector, and this sensitivity is corrected to an output that always has a constant gradient with respect to the flow rate,
    A thermal flow rate measuring device capable of switching the output to either voltage output or frequency output, and a control device using the same.
  2. 　前記流量検出部に比べて大きい感度への変換は、各流量において発振器の特性変化以上の勾配を持った感度へ変換することを特徴とする請求項１に記載の熱式流量測定装置及びこれを用いた制御装置。 2. The thermal flow rate measuring device according to claim 1, wherein the conversion to a sensitivity higher than that of the flow rate detection unit is converted to a sensitivity having a gradient equal to or greater than a characteristic change of an oscillator at each flow rate. Control device used.
  3. 　前記補正手段は、前記流量を変数とする多項式で変換する手段であることを特徴とする請求項１または２に記載の熱式流量測定装置及びこれを用いた制御装置。 3. The thermal flow rate measuring device according to claim 1 or 2, and a control device using the thermal flow rate measuring device according to claim 1, wherein the correction means is a means for converting with a polynomial having the flow rate as a variable.
  4. 　前記補正手段は、前記流量で参照する補正テーブルによって出力を補正する手段であることを特徴とする請求項１または２に記載の熱式流量測定装置及びこれを用いた制御装置。 3. The thermal flow rate measuring device according to claim 1 or 2, and a control device using the thermal flow rate measuring device according to claim 1, wherein the correction means is means for correcting an output by a correction table referred to by the flow rate.
  5. 　前記補正テーブルは、不等間隔で任意に格子点間を決定できることを特徴とする請求項４に記載の熱式流量測定装置及びこれを用いた制御装置。 5. The thermal flow rate measuring device according to claim 4, and a control device using the thermal flow rate measuring device according to claim 4, wherein the correction table can arbitrarily determine the interval between grid points at unequal intervals.
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