JP2011027464A - Gas detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely detect concentration of a detecting object gas component by reducing erroneous detection even if detecting object gas and those other than the detecting object gas are included in the detecting object gas. <P>SOLUTION: By a presumed concentration calculation section 32, presumed concentration C<SB>pre</SB>when a gas component within exhalation is presumed to be ethanol gas is calculated, based on detection signals from an alcohol sensor 24A and a gas sensor 24B. When a reliability necessity determination section 34 determines that the presumed concentration is larger than a threshold and reliability R needs to be calculated, a reliability calculation section 36 calculates the reliability R where the gas component within exhalation is ethanol gas for a variable x represented by a ratio of the presumed concentrations C<SB>pre1</SB>to C<SB>pre2</SB>obtained from change characteristics of detection signals from the respective sensors. An ethanol concentration calculation section 38 calculates ethanol gas concentration by multiplying the presumed concentrated C<SB>pre</SB>by the reliability R. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a gas detection device, and more particularly to a gas detection device capable of detecting the concentration of alcohol contained in a driver's breath.

  2. Description of the Related Art Conventionally, there is known a gas identification device that improves gas identification capability by performing pattern recognition using an information device when identifying gas by combining outputs of a plurality of gas sensors having different characteristics (Patent Document 1).

  There is also known a gas detection device that periodically changes the temperature of an oxide semiconductor gas sensor and determines a gas type from a parameter of a response waveform with respect to the temperature change (Patent Document 2).

JP-A-6-242039 JP-A-7-311170

  However, the technique described in Patent Document 1 requires complicated information processing for pattern recognition, and can cope with a case where the output pattern from the gas sensor does not match the output pattern stored in advance. If the gas to be detected contains a gas to be detected and a gas other than the gas to be detected, the gas to be detected cannot be distinguished from the gas component other than the gas to be detected. There is a problem that.

  Further, in the technique described in Patent Document 2, since it is necessary to periodically change the sensor temperature, the target gas is a transient gas having a short duration such as human exhalation. However, there is a problem that the gas concentration cannot be sufficiently detected and the gas concentration cannot be accurately detected. In such a case, it is desirable to use a gas sensor having good response such as a metal oxide semiconductor gas sensor in a stable state. However, since the metal oxide semiconductor gas sensor is not high in gas selectivity, it also responds to gas components other than the detection target gas contained in the detection target gas, which is higher than the actual gas concentration of the detection target gas. However, it is detected as a high quantitative value, resulting in a false detection.

  The present invention has been made to solve the above-described problems. Even when the gas to be detected contains a gas to be detected and a gas other than the gas to be detected, the detection object can be reduced by reducing false detection. An object of the present invention is to provide a gas detection device capable of accurately detecting the concentration of the gas component.

  In order to achieve the above object, each of the gas detection devices of the first invention has sensitivity to each detection target gas component, and has different sensitivity to gas components other than the detection target gas component. A plurality of gas sensors that detect a physical quantity related to the concentration of a gas component contained in the gas and output a detection signal; and a detection target gas in the detection target gas using each of the detection signals of the plurality of gas sensors A feature amount is calculated from the same characteristics obtained for each of the detection signals of the plurality of gas sensors, and an assumed gas concentration calculation unit that calculates the concentration of none gas only when it is assumed that a component is included, and a plurality of features in advance The reliability of the detected gas component obtained for each of the quantities, and the reliability of the deemed gas concentration being the detected gas component based on the calculated feature quantity A reliability calculation means for calculating; and a gas concentration calculation means for calculating the gas concentration of the detection target gas by multiplying the deemed gas concentration by the reliability calculated by the reliability calculation means. Yes.

  According to the gas detection device of the first invention, a plurality of gas sensors each having sensitivity to a detection target gas component and having different sensitivities to gas components other than the detection target gas component are each in the detection target gas. A physical quantity related to the concentration of the gas component contained in the gas is detected and a detection signal is output. The deemed gas concentration calculating means calculates the none gas concentration only when it is determined that the detection target gas component is contained in the detection target gas using each of the detection signals of the plurality of gas sensors. In addition, the reliability calculation means calculates the feature amount from the same characteristic obtained for each of the detection signals of the plurality of gas sensors, and the reliability of being a detection target gas component obtained in advance for each of the plurality of feature amounts, Based on the calculated feature amount, the reliability that the deemed gas concentration is the detection target gas component is calculated. Then, the gas concentration calculating means calculates the gas concentration of the detection target gas by multiplying the deemed gas concentration by the reliability calculated by the reliability calculating means.

  In this way, the detection target gas concentration is calculated only based on the characteristic amount obtained from the characteristics of the gas sensors and the characteristics of the plurality of gas sensors only when it is assumed that the detection target gas component is contained in the detection target gas. By calculating the gas concentration of the detection target gas component by multiplying the reliability of being a gas component, the gas concentration taking into account the reliability of being the detection target gas is calculated, and in the detection target gas Even when a gas other than the detection target gas and the detection target gas is included, it is possible to reduce the erroneous detection and to accurately detect the concentration of the detection target gas component.

  In the gas detection device of the first invention, the feature amount may be a ratio of the same characteristics obtained for each of detection signals of the plurality of gas sensors.

  A gas detection device according to a second aspect of the invention is a gas sensor that detects a detection target gas component contained in a detection target gas and a physical quantity related to the concentration of a gas component other than the detection target gas component and outputs a detection signal; The assumed gas concentration calculating means for calculating the gas concentration only when the detection target gas component is considered to be contained in the detection target gas using the detection signal of the gas sensor, and the detection signal of the gas sensor A feature amount is calculated from a plurality of types of obtained characteristics, and the deemed gas concentration is calculated based on the reliability of the detection target gas component obtained in advance for each of the plurality of feature amounts and the calculated feature amount. A reliability calculation means for calculating the reliability of the gas component to be detected; and the detection target by multiplying the deemed gas concentration by the reliability calculated by the reliability calculation means. It is configured to include a gas concentration calculating means for calculating the gas concentration of the scan.

  According to the gas detection device of the second invention, the gas sensor detects the physical quantity related to the concentration of the detection target gas component contained in the detection target gas and the gas component other than the detection target gas component, and detects the detection signal. Is output. The deemed gas concentration calculation means calculates the none gas concentration only when it is determined that the detection target gas component is contained in the detection target gas using the detection signal of the gas sensor. Further, the reliability calculation means calculates a feature amount from a plurality of types of characteristics obtained with respect to the detection signal of the gas sensor, and calculates the reliability of being a detection target gas component obtained for each of the plurality of feature amounts in advance. Based on the obtained feature amount, the reliability that the deemed gas concentration is the detection target gas component is calculated. Then, the gas concentration calculating means calculates the gas concentration of the detection target gas by multiplying the deemed gas concentration by the reliability calculated by the reliability calculating means.

  In this way, only when it is assumed that the detection target gas component is contained in the detection target gas, the detected gas concentration and the assumed gas concentration calculated based on the characteristic amount obtained from the multiple types of characteristics of the gas sensor are detected. The gas concentration of the detection target gas component is calculated by multiplying the reliability of the detection target gas component by multiplying the reliability of the detection target gas component, and the detection target gas is calculated. Even when a gas other than the detection target gas and the detection target gas is contained therein, the detection error can be reduced and the concentration of the detection target gas component can be accurately detected.

  In the gas detection device of the second invention, the plurality of types of characteristics include characteristics dependent on the concentration of a gas component contained in the gas to be detected, and types of gas components contained in the gas to be detected. Dependent properties can be included.

  In the gas detection device of the first and second inventions, the characteristics include the peak value of the detection signal, the maximum value of the change rate of the detection signal, the minimum value of the change rate of the detection signal, and the detection signal. The time from the start of change until the peak value is reached, the time from when the detection signal reaches the peak value to the end of the change, the detection signal from the start of change until the peak value is reached A change pattern of the signal or a change pattern of the detection signal from when the detection signal reaches a peak value until the change ends can be used.

  In the gas detectors of the first and second inventions, when the deemed concentration is greater than a predetermined value, the gas concentration calculation unit uses the reliability calculated by the reliability calculation unit. When the gas concentration of the detection target gas component is calculated and the assumed concentration is smaller than a predetermined value, the assumed concentration can be set as the gas concentration of the detection target gas component.

  As described above, according to the present invention, only when it is assumed that the detection target gas component is contained in the gas to be detected, and the reliability of the deemed gas concentration being the detection target gas component. To calculate the gas concentration of the detection target gas component, the gas concentration taking into account the reliability of the detection target gas is calculated, and the detection target gas and the detection target gas are included in the detection target gas. Even when other gases are included, it is possible to reduce the erroneous detection and to accurately detect the concentration of the detection target gas component.

It is the schematic which shows the state which attached the ethanol concentration detection apparatus which concerns on this Embodiment to the steering column of a driver's seat. It is the schematic which shows 1st Embodiment. It is a circuit diagram which shows the structure of the alcohol sensor of the ethanol concentration detection apparatus of this Embodiment. It is a block diagram which shows the structure of the ethanol concentration detection apparatus of 1st Embodiment. It is a graph which shows the time series change of the detection signal of an alcohol sensor or a gas sensor, the height of a peak, the time from the change start to the peak, and the time from the peak to the end of the change. It is a graph which shows an example of reliability function R (x). It is a flowchart which shows the content of the ethanol gas concentration calculation processing routine in the ethanol concentration detection apparatus of 1st Embodiment. It is the schematic which shows 2nd Embodiment. It is a block diagram which shows the structure of the ethanol concentration detection apparatus of 2nd Embodiment. It is a flowchart which shows the content of the ethanol gas concentration calculation processing routine in the ethanol concentration detection apparatus of 2nd Embodiment. It is a graph which shows the time series change of the detection signal of an alcohol sensor or a gas sensor, the maximum value of the change rate of a detection signal, and the minimum value. It is a graph which shows the time-sequential change of the detection signal of an alcohol sensor or a gas sensor, and the predicted saturated output value.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, a case where the present invention is applied to an ethanol concentration detection device that detects the concentration of ethanol, which is a kind of alcohol, from the breath of a driver will be described as an example.

  As shown in FIG. 1, the ethanol concentration detection apparatus 10 according to the first embodiment is attached to a position where the driver's exhalation of the steering column 12 provided in the driver's seat can reach. The ethanol concentration detection apparatus 10 includes an elongate cylindrical exhalation introduction tube 20 having a suction port 20A having an enlarged diameter at the tip, and an alcohol sensor 24A, which will be described later, is disposed inside the exhalation introduction tube 20. And the gas sensor group 24 provided with the gas sensor 24B is attached.

  As shown in FIG. 2, a suction fan 22 that is driven in order to suck the breath of the driver from the suction port 20A is provided in the breath introduction pipe 20 and on the suction port 20A side of the gas sensor group 24. .

  An alcohol sensor 24A, which is an oxide semiconductor gas sensor that detects the concentration of ethanol gas using an oxide semiconductor, and a gas sensor 24B that is sensitive to many types of gas components are attached inside the middle part of the exhalation introduction tube 20. It has been. The alcohol sensor 24 </ b> A and the gas sensor 24 </ b> B are attached so as to face the inside of the intermediate portion of the exhalation introduction tube 20.

The alcohol sensor 24A is a sensor that detects ethanol gas contained in the gas flowing through the breath introduction pipe 20, and for example, a TGS 2620 (trade name, manufactured by Figaro Giken Co., Ltd.) using a metal oxide semiconductor can be used. The circuit is configured as shown in FIG. In the alcohol sensor 24A, the heater voltage V _H and the circuit voltage V _C are applied, and the voltage V _OUT across the load resistor _RL connected in series to the sensor resistor _RS is output as a detection signal. Therefore, the alcohol sensor 24 </ b> A outputs a detection signal having a higher level as the concentration of ethanol gas contained in the gas flowing in the exhalation introduction tube 20 becomes higher, and ethanol contained in the gas flowing in the exhalation introduction tube 20. As the gas concentration decreases, a detection signal having a lower level is output.

  Further, the alcohol sensor 24A has a relatively low gas component selectivity, and has sensitivity to, for example, hydrogen, carbon monoxide, methane, isobutane, etc. in addition to ethanol gas, and has different sensitivity characteristics for each gas component. have.

  Unlike the alcohol sensor 24A, the gas sensor 24B has a sensitivity (variation characteristic) to gas components other than the target component (ethanol) and is sensitive to many types of gas components. As the gas sensor 24B, for example, an air quality sensor (a sensor that detects air dirt) can be used, and TGS2600 (trade name, manufactured by Figaro Giken Co., Ltd.) can be used.

  The gas sensor 24 </ b> B outputs a detection signal having a higher level as the concentration of the sensitive gas component contained in the gas flowing in the exhalation introduction pipe 20 becomes higher, and is included in the gas flowing in the exhalation introduction pipe 20. As the concentration of the sensitive gas component decreases, a detection signal having a lower level is output.

  According to this embodiment, when the suction fan 22 is driven, the exhaled air exhaled from the driver is drawn into the exhalation introduction tube 20 from the intake port 20A of the exhalation introduction tube 20, and the exhalation is mixed with the air. As a result, the alcohol sensor 24A and the gas sensor 24B are reached at a constant flow rate. Then, after the exhaled breath comes into contact with the alcohol sensor 24A and the gas sensor 24B, the exhaled breath is discharged to the outside from the exhaled breath introducing pipe 20.

  When a gas component having sensitivity to the alcohol sensor 24A and the gas sensor 24B comes into contact with the alcohol sensor 24A and the gas sensor 24B, a detection signal corresponding to the concentration of the gas component in the gas is output by the alcohol sensor 24A and the gas sensor 24B. Detection signals output from each of the alcohol sensor 24A and the gas sensor 24B are input to an ethanol concentration detector 30 described later, and the concentration of ethanol gas as the detection target gas is detected based on the input detection signal.

  As shown in FIG. 4, the ethanol concentration detection device 10 includes an ethanol concentration detector 30 that is connected to the alcohol sensor 24A and the gas sensor 24B and detects the concentration of the ethanol gas component and displays it on the display device 50. Yes.

  The ethanol concentration detector 30 includes a CPU that controls the entire ethanol concentration detection device 10, a ROM as a storage medium that stores various programs such as an ethanol concentration calculation processing routine that will be described later, a RAM that temporarily stores data as a work area, And a microcomputer including a bus connecting them.

  The ethanol concentration detector 30 is based on detection signals from the alcohol sensor 24A and the gas sensor 24B, and an assumed concentration calculation unit 32 that calculates a no-concentration only when the gas component in exhalation is assumed to be ethanol gas. A reliability necessity determination unit 34 that determines whether or not it is necessary to calculate the reliability that the gas component in the exhalation is ethanol gas based on the assumed concentration calculated by the calculation unit 32, and an alcohol sensor Based on the detection signals from 24A and the gas sensor 24B, a reliability calculation unit 36 that calculates the reliability that the gas component in the expiration is ethanol gas, and the ethanol gas concentration is calculated based on the assumed concentration and the reliability. Control to display the ethanol concentration calculation unit 38 and the calculation result by the ethanol concentration calculation unit 38 on the display device 50. And a display control unit 40 that.

The deemed concentration calculation unit 32 considers that the gas component contained in the exhalation is ethanol gas, and calculates the peak height of the detection signal as the change characteristic of the detection signal from the alcohol sensor 24A. The detection signal peak height Δf _p (see FIG. 5) detects the peak maximum value f _p when the detection signal reaches a peak, and the peak maximum value f _p and the detection signal threshold f _th (for example, change) When the value of the previous detection signal is the base value f _b of the detection signal, the calculation is performed according to the following equation (1) using the base value f _b +0.2 V).

Δf _p = f _p −f _th (1)

Then, based on the previously obtained relation between the height Delta] f _p and ethanol gas concentration peaks, it calculates the concentration C _pre1 considered based on the detection signal of the alcohol sensor 24A. Similarly, to calculate the height of the peak of the detection signal as a change characteristic of the detection signal of the gas sensor 24B, on the basis of the previously obtained relationship between the height Delta] f _p and ethanol gas concentration peaks in the detection signal of the gas sensor 24B Based on the assumed concentration C _pre2 is calculated. Then, according to the multiple regression equation (equation (2) below) expressed using the quantitative coefficients a, b, and c calculated in advance, the ethanol gas-only concentration C _pre is calculated.

C _pre = a × C _pre1 + b × C _pre2 + c (2)

The reliability necessity determination unit 34 determines whether or not the ethanol gas only concentration C _pre calculated by the deemed concentration calculation unit 32 is greater than the threshold value C _th , thereby allowing the reliability calculation unit 36 described later to determine the reliability. It is determined whether or not it is necessary to calculate. When the assumed concentration calculation unit 32 calculates the ethanol gas only concentration C _pre , the gas component contained in the exhalation is considered to be ethanol gas, but in reality, a gas component other than ethanol gas is included. There is a possibility. In this case, there is a possibility that the sensor response to the gas component other than the ethanol gas which is the target component is superimposed on the detection signal, and the ethanol gas-only concentration C _pre is calculated as a quantitative value higher than the gas concentration of the ethanol gas. is there. Therefore, when the ethanol gas-only concentration C _pre is larger than the threshold C _th (for example, 0.15 mg / L), it is determined that the reliability needs to be calculated. When the deemed concentration C _pre is equal to or less than the threshold value C _th , it is determined that the calculation of reliability is unnecessary, and the deemed concentration C _pre is used as the ethanol gas concentration C as it is.

As represented by the following equation (3), the reliability calculation unit 36 considers the assumed concentration C _pre1 based on the detection signal of the alcohol sensor 24A calculated by the assumed concentration calculation unit 32 and the detection signal of the gas sensor 24B. The ratio of the density C _pre2 is set as a variable x.

x = C _pre2 / C _pre1 (3)

Here, the deemed concentration C _pre1 and the deemed concentration C _pre2 are calculated based on the peak height, which is a change characteristic of the detection signals of the alcohol sensor 24A and the gas sensor 24B, and the deemed concentration C _pre1 and the deemed concentration C. _{It can be said that pre2} itself is a change characteristic of each detection signal of the alcohol sensor 24A and the gas sensor 24B.

For the variable x, a reliability function R (x) indicating the reliability that the gas component in the exhalation is the target component, ethanol gas, is determined in advance. Here, the reliability function R (x) is defined by the following equation (4) using the parameters a and b, and the reliability R for the deemed density C _pre is calculated based on this R (x). .

For example, FIG. 6 shows a graph representing the reliability function R (x) when a = 1 and b = 0.5. If the gas component contained in the exhalation is ethanol gas, the assumed concentration C _pre1 and the assumed concentration C _pre2 should be substantially the same value, so the reliability R is the largest when the variable x is “1”. Become.

  Note that the smaller the value of the parameter b, the fewer false detections and the more undetected. On the other hand, the larger the value of the parameter b, the more false detections and the fewer undetected. Therefore, the values of the parameters a and b are set in accordance with the purpose such as the actual measurement value of the detection signal from each sensor and how much undetection is allowed to reduce false detection.

The ethanol concentration calculation unit 38 calculates the product of the ethanol gas _endless concentration C _pre calculated by the deemed concentration calculation unit 32 and the reliability R calculated by the reliability calculation unit 36 in accordance with the following equation (5). Calculated as concentration C.

C = C _pre × R (5)

  When the reliability R is large, the ethanol gas concentration C is also increased. When the reliability R is small, the ethanol gas concentration C is also decreased so that the reliability of the target component is reflected in the gas concentration. ing.

  Next, an ethanol gas concentration calculation processing routine in the ethanol concentration detection apparatus 10 according to the first embodiment will be described with reference to FIG. When the driver is seated on the vehicle seat, the exhalation of the driver is blown into the exhalation introduction tube 20, and when the ignition switch is turned on by the driver, the ethanol concentration detector 30 of the ethanol concentration detecting device 10 uses the ethanol shown in FIG. A concentration calculation processing routine is executed.

  In step 100, detection signals from the alcohol sensor 24A and the gas sensor 24B are acquired.

Next, in step 102, the peak height is calculated as the change characteristic of the detection signal of the alcohol sensor 24A based on the time series change of the detection signal acquired in step 100, and the peak height and the ethanol gas concentration are calculated. Based on the relationship obtained in advance, the assumed concentration C _pre1 based on the detection signal of the alcohol sensor 24A is calculated. Similarly, the peak height is calculated as a change characteristic of the detection signal of the gas sensor 24B, and the assumed concentration C _pre2 based on the detection signal of the gas sensor 24B is calculated based on the relationship obtained in advance between the peak height and the ethanol gas concentration. calculate.

Next, in step 104, according to the above (2), with a concentration _{C pre2} considered based on the detection signal of the detection signal based on the considered concentration _{C pre1,} and the gas sensor 24B of the alcohol sensor 24A which is calculated in step 102, The concentration C _pre without ethanol gas is calculated.

Next, in step 106, it is determined whether or not the calculation of the reliability is necessary by determining whether or not the ethanol gas only concentration C _pre calculated in step 104 is larger than the threshold value C _th. . If the ethanol gas only concentration C _pre is larger than the threshold C _th (for example, 0.15 mg / L), it is determined that the calculation of the reliability is necessary, and the process proceeds to Step 108. On the other hand, if the deemed concentration C _pre is equal to or less than the threshold C _th , it is determined that the calculation of the reliability is unnecessary, and the process proceeds to step 114, where the ethanol gas non- _removed concentration C _pre calculated in step 104 is used as it is. Substituting the ethanol gas concentration C, the process proceeds to step 116.

In step 108, according to the above (3), with a concentration _{C pre2} considered based on the detection signal of the detection signal based on the considered concentration _{C pre1,} and the gas sensor 24B of the alcohol sensor 24A which is calculated in step 102, these ratios Is calculated as a variable x. Next, in step 110, the reliability R for the variable x calculated in step 108 is calculated according to the above equation (4).

Next, in step 112, the product of the ethanol gas _endless concentration C _pre calculated in step 104 and the reliability R calculated in step 110 is calculated as the ethanol gas concentration C in accordance with the above equation (5). To do.

  Next, in step 116, the ethanol gas concentration C calculated in step 112 or the ethanol gas concentration C replaced in step 114 is displayed on the display device 50, and this routine ends.

  As described above, according to the ethanol concentration detection apparatus according to the first embodiment, it is assumed that the gas component in the exhalation is ethanol gas, and the ethanol gas is detected from the change characteristics of the detection signal of the alcohol sensor and the gas sensor. The assumed concentration is calculated, and based on the assumed concentration based on the detection signal of the alcohol sensor and the assumed concentration based on the detection signal of the gas sensor, the reliability of the gas component in the expiration is ethanol gas is calculated. The ethanol gas concentration is calculated from the product of the deemed concentration and the reliability. This makes it possible to calculate the ethanol gas concentration taking into account the reliability that the target component is ethanol gas, thus reducing false detection even when exhaled gas contains gas other than ethanol gas. Thus, the ethanol gas concentration can be detected with high accuracy.

  In addition, by calculating the reliability only when the calculated concentration of only ethanol gas is greater than a predetermined threshold, the calculation time when the calculation of the reliability is unnecessary can be shortened.

  In addition, by determining the parameters a and b of the reliability function based on the false detection and undetected target levels, a flexible detection result according to the purpose can be obtained.

  Next, an ethanol concentration detection apparatus according to the second embodiment will be described. Although the case where two gas sensors are used has been described in the first embodiment, the second embodiment is different in that two change characteristics are used for detection signals of one gas sensor. In addition, about the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 8, the ethanol concentration detection device 210 according to the second embodiment includes an oxide semiconductor that detects the concentration of ethanol gas using an oxide semiconductor inside an intermediate portion of the exhalation introduction tube 20. An alcohol sensor 24A, which is a gas sensor, is attached.

  According to this embodiment, when the suction fan 22 is driven, the exhaled air exhaled from the driver is drawn into the exhalation introduction tube 20 from the intake port 20A of the exhalation introduction tube 20, and the exhalation is mixed with the air. As a result, the alcohol sensor 24A is diluted at a constant flow rate. Then, after contacting the alcohol sensor 24A, the exhaled breath is discharged to the outside from the exhalation introducing pipe 20.

  When a gas component having sensitivity to the alcohol sensor 24A comes into contact with the alcohol sensor 24A, a detection signal corresponding to the concentration of the gas component in the gas is output by the alcohol sensor 24A. The detection signal output from the alcohol sensor 24A is input to an ethanol concentration detector 230 described later, and the concentration of ethanol gas as the detection target gas is detected based on the input detection signal.

  As shown in FIG. 9, the ethanol concentration detection device 210 includes an ethanol concentration detector 230 that is connected to the alcohol sensor 24 </ b> A and detects the concentration of the ethanol gas component and displays it on the display device 50.

  The ethanol concentration detector 230 includes a CPU that controls the entire ethanol concentration detection device 210, a ROM as a storage medium that stores various programs such as an ethanol concentration calculation processing routine described later, a RAM that temporarily stores data as a work area, And a microcomputer including a bus connecting them.

  The ethanol concentration detector 230, based on the detection signal from the alcohol sensor 24A, an assumed concentration calculation unit 232 that calculates the concentration only when it is assumed that the gas component in the exhalation is ethanol gas, and the necessity of reliability determination A reliability calculation unit 236 that calculates a reliability that the gas component in the exhalation is ethanol gas based on a detection signal from the unit 34, the alcohol sensor 24A, an ethanol concentration calculation unit 38, and a display control unit 40 And.

The deemed concentration calculation unit 232 is _assumed to be calculated in the same manner as the assumed concentration calculation unit 32 of the ethanol concentration detection device 10 according to the first embodiment calculates the assumed concentration C _pre1 based on the detection signal of the alcohol sensor 24A. The concentration is ethanol gas and the concentration is C _pre .

The reliability calculation unit 236 sets the time from the start of change of the detection signal to the peak of the detection signal as a change characteristic of the detection signal at the time of gas adsorption from the change of the detection signal of the alcohol sensor 24A (T _{th1- p} ). Further, as a change characteristic of the detection signal at the time of gas desorption from the change of the detection signal of the alcohol sensor 24A, the time from the peak of the detection signal to the end of the change of the detection signal (see T _{p-th2 in} FIG. 5). calculate.

  Among the change characteristics of the detection signal of one gas sensor, the change characteristics of the detection signal from the start of change to the peak, that is, the change characteristics at the time of gas adsorption reflect not only the adsorption characteristics of gas components but also the characteristics of gas diffusion and reaction. Therefore, differences due to the types of gas components are unlikely to occur. On the other hand, the change characteristic of the detection signal from the peak to the end of the change, that is, the change characteristic at the time of gas desorption mainly reflects the desorption characteristic of the gas component, and the change of the detection signal for the transient gas at a constant flow rate Even if it is a characteristic, the difference by the kind of gas component tends to arise. Therefore, the variable x is calculated using the change characteristics of both detection signals.

First, the time from when the change of the detection signal starts until the detection signal reaches a peak is calculated as follows. As shown in FIG. 5, when the detection signal value exceeds a threshold value f _th (for example, base value f _b +0.2 V), the detection signal change start time t _th1 is detected from the time series change of the detection signal. and, when the detection signal reaches a peak, it is detected as the peak maximum time t _p. Then, according to the following equation (6), a time T _th1-p from the start of the change of the detection signal to the peak of the detection signal is calculated.

T _th1−p = t _p −t _th1 (6)

Further, the time from when the detection signal reaches a peak until the end of the change of the detection signal is calculated as follows. As shown in FIG. 5, from the time series change of detection signals, when the detection signal reaches a peak, is detected as the peak maximum time t _p, when the value of the detection signal is lowered to the threshold value f _th, detection signal The change end time t _th2 is detected. Then, according to the following expression (7), a time T _p-th2 from the peak of the detection signal to the end of the change of the detection signal is calculated.

_{T p-th2 = t th2 -t} p ··· (7)

Then, as represented by the following equation (8), the detection signal from the change start of the time T _p-th2 to change in the detection signal exits a time T _th1-p and the peak until the peak Let the ratio be a variable x.

x = Tp _-th2 / _Tth1-p (8)

  Next, an ethanol gas concentration calculation processing routine in the ethanol concentration detection device 210 of the second embodiment will be described with reference to FIG. When the driver is seated on the vehicle seat, the exhalation of the driver is blown into the exhalation introduction tube 20, and when the ignition switch is turned on by the driver, the ethanol concentration detector 230 of the ethanol concentration detection device 210 performs the ethanol shown in FIG. A concentration calculation processing routine is executed.

  In step 250, a detection signal of the alcohol sensor 24A is acquired.

Next, in step 252, the peak height is calculated as a change characteristic of the detection signal of the alcohol sensor 24A based on the time-series change of the detection signal acquired in step 250, and the peak height and the ethanol gas concentration are calculated. Based on the relationship obtained in advance, the ethanol gas concentration C _pre is calculated.

Next, in step 106, it is determined whether or not the calculation of the reliability is necessary by determining whether or not the ethanol gas only concentration C _pre calculated in step 252 is greater than the threshold value C _th. . If the ethanol gas only concentration C _pre is larger than the threshold C _th (for example, 0.15 mg / L), it is determined that the calculation of the reliability is necessary, and the process proceeds to Step 254. On the other hand, if the deemed concentration C _pre is equal to or less than the threshold C _th , it is determined that the calculation of the reliability is unnecessary, and the process proceeds to step 114, where the ethanol gas _{nonconcentration} concentration C _pre calculated in step 252 is used as it is. Substituting the ethanol gas concentration C, the process proceeds to step 116.

In step 254, the time T _th1-p from the start of change to the peak of the detection signal and the time T _p-th2 from the peak to the end of change of the detection signal are calculated according to the above equations (6) and (7). calculate. Next, in step 256, according to the above equation (8), the time T _th1-p from the start of change calculated in step 254 to the peak of the detection signal and the time from the peak to the end of change of the detection signal. A ratio with the time T _p-th2 is calculated as a variable x.

  Thereafter, in steps 112 and 116, processing similar to the ethanol concentration calculation processing routine in the ethanol concentration detection apparatus 10 of the first embodiment is performed, and this routine is terminated.

  As described above, according to the ethanol concentration detection apparatus according to the second embodiment, it is assumed that the gas component in the exhalation is ethanol gas, and the concentration of only ethanol gas is determined from the change characteristic of the detection signal of the alcohol sensor. As a change characteristic of the detection signal of the alcohol sensor, calculate the reliability that the gas component in the exhalation is ethanol gas based on the change characteristic at the time of gas adsorption and desorption. The ethanol gas concentration is calculated from the product of the reliability and the reliability. This makes it possible to calculate the ethanol gas concentration taking into account the reliability that the target component is ethanol gas, thus reducing false detection even when exhaled gas contains gas other than ethanol gas. Thus, the ethanol gas concentration can be detected with high accuracy.

In the first embodiment, when the assumed density obtained from the peak height of the detection signal is used as the change characteristic of the detection signal, in the second embodiment, from the start of the change until the detection signal reaches the peak. Although the case of using the time from the peak and the time until the end of the change of the detection signal has been described, the change characteristic of the detection signal is not limited to this. For example, the time-series change of the change rate of the detection signal is calculated from the time-series change of the detection signal, and the maximum value α ₁ of the change rate of the detection signal obtained from the time-series change of the calculated change rate (α in FIG. 11). ₁ ) may be used. Alternatively, the minimum value α ₂ (see α _{2 in} FIG. 11) of the detection signal change rate obtained from the time-series change of the calculated change rate may be used. Further, a change pattern of the detection signal when the detection signal changes so as to reach a peak is extracted, system identification is performed based on this change pattern, and the detection signal is included in the gas flowing in the exhalation introduction tube 20. saturated output value of the detection signal output from the sensor when ethanol components of the same concentration as the ethanol component is contained by sustained (see f ₁ in FIG. 12) may be used in prediction. Also, extracting a change pattern of the detection signal after the detection signal becomes a peak, on the basis of the change pattern, by performing a system identification, to predict the saturation output value of the detection signal (see f ₂ in FIG. 12) May be used.

In the second embodiment, the case where the change of the detection signal ends when the value of the detection signal decreases to the threshold f _{th has} been described. However, when the change rate of the detection signal shows a minimum value. Alternatively, the detection signal may be reduced by a certain percentage with respect to the peak value (for example, f _b + 1 / 2Δf _p ).

  In the first embodiment, the case where an alcohol sensor and a gas sensor such as an air quality sensor are used has been described as an example. However, the present invention is not limited to this. What is necessary is just to comprise using the gas sensor different from a sensor. For example, an oxygen sensor, a water vapor sensor, or a carbon dioxide sensor can be used together with an alcohol sensor. As the oxygen sensor, an oxygen sensor that detects the oxygen concentration using a solid electrolyte can be used. As the water vapor sensor, a water vapor sensor that detects the concentration of water vapor using an oxide semiconductor or polymer film capacitance is used. Can be used. Moreover, as a carbon dioxide sensor, the carbon dioxide sensor which detects the density | concentration of a carbon dioxide using a solid electrolyte can be used.

  In the first and second embodiments, the case where the calculated concentration of the ethanol gas component is displayed has been described as an example. However, the present invention is not limited to this. For example, the calculated concentration of the ethanol gas component Is compared with a predetermined threshold value, and when the calculated ethanol gas component concentration is equal to or higher than the threshold value, it is determined that the ethanol concentration is high, and control is performed to prevent fraud such as preventing the engine from starting. May be.

  In the first and second embodiments, the example in which the concentration of the ethanol gas component is detected from the exhalation of the driver has been described. However, the present invention is not limited to the driver by configuring the ethanol concentration detection device to be portable. The present invention can also be applied to the case where the concentration of ethanol gas components is detected from human breath.

10, 210 Ethanol concentration detector 24A Alcohol sensor 24B Gas sensor 30, 230 Ethanol concentration detectors 32, 232 Deemed concentration calculator 34 Reliability necessity determination unit 36, 236 Reliability calculator 38 Ethanol concentration calculator

Claims (6)

Sensitivity to each detection target gas component and sensitivity to gas components other than the detection target gas component are different, and detection is performed by detecting a physical quantity related to the concentration of the gas component contained in each detection target gas. A plurality of gas sensors for outputting signals;
Using each of the detection signals of the plurality of gas sensors, an assumed gas concentration calculating means for calculating a gas concentration only when it is assumed that the detection target gas component is contained in the detection target gas;
A feature amount is calculated from the same characteristic obtained for each of the detection signals of the plurality of gas sensors, and the reliability of the detection target gas component obtained for each of the plurality of feature amounts in advance and the calculated feature amount are calculated. A reliability calculation means for calculating the reliability that the deemed gas concentration is the detection target gas component;
Gas concentration calculating means for calculating the gas concentration of the detection target gas by multiplying the deemed gas concentration by the reliability calculated by the reliability calculating means;
A gas detection device.   The gas detection device according to claim 1, wherein the feature amount is a ratio of the same characteristics obtained for each of detection signals of the plurality of gas sensors. A gas sensor that detects a detection target gas component contained in a detection target gas and a physical quantity related to the concentration of a gas component other than the detection target gas component and outputs a detection signal;
Using the detection signal of the gas sensor, an assumed gas concentration calculating means for calculating a gas concentration only when it is considered that the detection target gas component is contained in the detection target gas;
A feature amount is calculated from a plurality of types of characteristics obtained for the detection signal of the gas sensor, based on the reliability of the detection target gas component obtained for each of the plurality of feature amounts, and the calculated feature amount, A reliability calculation means for calculating a reliability of the deemed gas concentration being the detection target gas component;
Gas concentration calculating means for calculating the gas concentration of the detection target gas by multiplying the deemed gas concentration by the reliability calculated by the reliability calculating means;
A gas detection device.   The characteristic of depending on the density | concentration of the gas component contained in the gas of the said detection object in the said multiple types of characteristic, and the characteristic depending on the kind of gas component contained in the gas of the said detection object are included. Gas detection device.   The characteristics include the peak value of the detection signal, the maximum value of the change rate of the detection signal, the minimum value of the change rate of the detection signal, the time from when the detection signal starts to change to the peak value, The time from when the detection signal reaches the peak value until the change ends, the change pattern of the detection signal from when the detection signal starts changing to the peak value, or the detection signal reaches the peak value The gas detection device according to any one of claims 1 to 4, wherein the change pattern of the detection signal is from the start to the end of the change.   When the deemed concentration is larger than a predetermined value, the gas concentration calculating unit calculates the gas concentration of the detection target gas component using the reliability calculated by the reliability calculating unit, and the assumed concentration is The gas detection device according to any one of claims 1 to 5, wherein, when the value is smaller than a predetermined value, the assumed concentration is the gas concentration of the detection target gas component.

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