WO2014024621A1 - Dispositif de mesure de flux thermique et dispositif de régulation associé - Google Patents

Dispositif de mesure de flux thermique et dispositif de régulation associé 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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WO
WIPO (PCT)
Prior art keywords
flow rate
output
characteristic
correction
detection unit
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PCT/JP2013/068803
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English (en)
Japanese (ja)
Inventor
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/fr

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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

Selon l'invention, pour obtenir un dispositif de mesure de flux thermique avec une précision de mesure supérieure, dans un dispositif de mesure de flux thermique équipé d'une unité de détection de flux qui mesure le flux d'un fluide à mesurer, l'unité de détection de flux a un moyen de correction qui corrige la sortie de l'unité de détection de flux dans une plage de flux valide susceptible d'être mesurée avec l'unité de détection de flux, le moyen de correction réalisant la correction de manière à obtenir une sensibilité supérieure par comparaison à la sensibilité de l'unité de détection de flux, ladite sensibilité étant corrigée de sorte que la sortie forme toujours un gradient uniforme par rapport au flux. La sortie est faite pour être permutable entre soit une sortie de tension, soit une sortie de fréquence.
PCT/JP2013/068803 2012-08-10 2013-07-10 Dispositif de mesure de flux thermique et dispositif de régulation associé WO2014024621A1 (fr)

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JP2012177694A JP5814884B2 (ja) 2012-08-10 2012-08-10 熱式流量測定装置及びこれを用いた制御装置
JP2012-177694 2012-08-10

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018116676A1 (fr) * 2016-12-20 2018-06-28 日立オートモティブシステムズ株式会社 Dispositif de mesure de vitesse d'écoulement gazeux

Families Citing this family (1)

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Publication number Priority date Publication date Assignee Title
WO2016017300A1 (fr) 2014-07-30 2016-02-04 日立オートモティブシステムズ株式会社 Dispositif de détection de quantité physique

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JPS62288578A (ja) * 1986-06-06 1987-12-15 Nippon Kagaku Kogyo Kk 熱線流速計の直線化装置
JPS63208714A (ja) * 1987-02-25 1988-08-30 Kokuritsu Kogai Kenkyu Shocho 高速デジタルリニヤライザ−
JPH01105108A (ja) * 1987-10-17 1989-04-21 Ohkura Electric Co Ltd 直線化回路を含む変換増幅器
JPH0894406A (ja) * 1994-09-27 1996-04-12 Tokyo Gas Co Ltd 流速センサの出力補正装置および流量計
JPH11183231A (ja) * 1997-12-25 1999-07-09 Tokyo Gas Co Ltd 積算流量計及びそれを利用したガスメータ
JP2005106723A (ja) * 2003-10-01 2005-04-21 Hitachi Ltd 熱式流量計及び制御システム
JP2007071889A (ja) * 2006-11-27 2007-03-22 Hitachi Ltd 熱式空気流量計

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Publication number Priority date Publication date Assignee Title
JPS62288578A (ja) * 1986-06-06 1987-12-15 Nippon Kagaku Kogyo Kk 熱線流速計の直線化装置
JPS63208714A (ja) * 1987-02-25 1988-08-30 Kokuritsu Kogai Kenkyu Shocho 高速デジタルリニヤライザ−
JPH01105108A (ja) * 1987-10-17 1989-04-21 Ohkura Electric Co Ltd 直線化回路を含む変換増幅器
JPH0894406A (ja) * 1994-09-27 1996-04-12 Tokyo Gas Co Ltd 流速センサの出力補正装置および流量計
JPH11183231A (ja) * 1997-12-25 1999-07-09 Tokyo Gas Co Ltd 積算流量計及びそれを利用したガスメータ
JP2005106723A (ja) * 2003-10-01 2005-04-21 Hitachi Ltd 熱式流量計及び制御システム
JP2007071889A (ja) * 2006-11-27 2007-03-22 Hitachi Ltd 熱式空気流量計

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018116676A1 (fr) * 2016-12-20 2018-06-28 日立オートモティブシステムズ株式会社 Dispositif de mesure de vitesse d'écoulement gazeux
JPWO2018116676A1 (ja) * 2016-12-20 2019-07-04 日立オートモティブシステムズ株式会社 気体流量測定装置
US11009379B2 (en) 2016-12-20 2021-05-18 Hitachi Automotive Systems, Ltd. Gas flow rate measurement device

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