JP2010008097A - Gas detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely detect the concentration of a detection target gas component using simple processings, even for a gas of a short duration. <P>SOLUTION: The detection signal which corresponds to the concentration of the gas component contained in a detection target gas is outputted by an alcohol sensor 24. The time up to a peak from the start of a change in the detection signal of the alcohol sensor 24 is calculated by an adsorption change characteristics calculating part 32, and the time up to the completion of the change from the peak of the detection signal of the alcohol sensor 24 is calculated by a desorption change characteristic calculating part 34. Then, it is determined whether an ethanol gas component is contained in the detection target gas, on the basis of the ratio of the time up to the peak from the start of the change of the detection signal and the time up to the completion of the change from the peak by a gas component determining part 36; and when the ethanol gas component is determined as being contained in the detection target gas, the concentration of the ethanol gas component contained in the detection target gas is calculated by a gas concentration detecting part 38. <P>COPYRIGHT: (C)2010,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 has been known a gas identification device in which gas identification capability is improved by performing pattern recognition with an information device for combinations of 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. Therefore, there is a problem that the gas concentration cannot be accurately detected.

  In the technique described in Patent Document 2 described above, since the sensor temperature is periodically changed, it is sufficient when the target gas is a transient gas having a short duration such as human exhalation. There is a problem that the gas concentration cannot be accurately detected.

  The present invention has been made to solve the above problems, and can detect the concentration of a gas component to be detected with high accuracy even with a short-duration gas by a simple process. The purpose is to provide.

  In order to achieve the above object, the gas detection device according to the first aspect of the present invention increases in level as the concentration of the gas component contained in the gas to be detected increases, and as the concentration of the gas component decreases. Based on the gas sensor that outputs a detection signal whose level decreases and the detection signal output from the gas sensor, a plurality of types of change characteristics including a change characteristic of the detection signal after the detection signal has peaked are calculated. A change characteristic calculation unit that performs determination, and a determination unit that determines whether or not a gas component to be detected is included in the gas to be detected based on the plurality of types of change characteristics calculated by the change characteristic calculation unit. The detection signal output from the gas sensor when the determination unit determines that the detection target gas component is included in the detection target gas. Based on, it is configured to include a gas concentration detector for detecting the concentration of a gas component of the detection target included in the gas in the detection target.

  According to the gas detection apparatus of the first invention, the gas sensor increases the level as the concentration of the gas component contained in the gas to be detected increases, and decreases the level as the concentration of the gas component decreases. A detection signal is output. Based on the detection signal output from the gas sensor, the change characteristic calculation means calculates a plurality of types of change characteristics including the change characteristics of the detection signal after the detection signal has peaked.

  Then, the determination unit determines whether or not the detection target gas component is included in the detection target gas based on the plurality of types of change characteristics calculated by the change characteristic calculation unit. When the gas concentration detection unit determines that the gas to be detected is contained in the gas to be detected by the determination unit, the detection included in the gas to be detected based on the detection signal output from the gas sensor. The concentration of the target gas component is detected.

  As described above, when it is determined that the detection target gas component is included in the detection target gas based on a plurality of types of change characteristics including the detection signal change characteristics after the detection signal has reached a peak, By detecting the concentration of the gas component to be detected, the concentration of the gas component to be detected can be accurately detected with a simple process even for a gas having a short duration.

  The gas detection device according to the second invention has different sensitivities to the gas components, the level increases as the concentration of the gas components contained in the gas to be detected increases, and the concentration of the gas components decreases. Based on the two gas sensors that output a detection signal whose level decreases as the time goes, and the detection signal output from one of the gas sensors, the change characteristic of the detection signal after the detection signal reaches a peak is calculated. First change characteristic calculating means; second change characteristic calculating means for calculating change characteristics of the detection signal after the detection signal has reached a peak based on the detection signal output from the other gas sensor; The change characteristic calculated by the first change characteristic calculation unit is compared with the change characteristic calculated by the second change characteristic calculation unit, A determination unit that determines whether or not a gas component to be detected is included in the gas to be detected; and a case in which the gas component to be detected is determined to be included in the gas to be detected by the determination unit. And gas concentration detection means for detecting the concentration of the gas component of the detection target contained in the gas of the detection target based on the detection signal output from the gas sensor.

  According to the gas detector of the second invention, the two gas sensors each having different sensitivities to the gas component increase in level as the concentration of the gas component contained in the gas to be detected increases, and the gas component A detection signal whose level decreases as the density of the signal decreases is output. Based on the detection signal output from one of the gas sensors, the change characteristic of the detection signal after the peak of the detection signal is calculated by the first change characteristic calculation means. Further, the second change characteristic calculation means calculates the change characteristic of the detection signal after the detection signal reaches its peak, based on the detection signal output from the other gas sensor.

  The determination unit compares the change characteristic calculated by the first change characteristic calculation unit with the change characteristic calculated by the second change characteristic calculation unit, and the detection target gas component is included in the detection target gas. It is determined whether or not. When the gas concentration detection unit determines that the gas to be detected is contained in the gas to be detected by the determination unit, the detection included in the gas to be detected based on the detection signal output from the gas sensor. The concentration of the target gas component is detected.

  In this way, when it is determined that the detection target gas component is contained in the detection target gas by comparing the change characteristics of the detection signals after the detection signals of the two gas sensors have reached the peak, By detecting the concentration of the gas component to be detected, the concentration of the gas component to be detected can be accurately detected with a simple process even for a gas having a short duration.

  The change characteristic calculation means according to the first invention provides a plurality of types of change characteristics, the time from the start of change of the detection signal to the peak of the detection signal, and from the peak of the detection signal to the end of change of the detection signal. Can be calculated.

  The change characteristic calculation means according to the first invention can calculate the peak height of the detection signal and the time from when the detection signal reaches the peak until the end of the change of the detection signal as a plurality of types of change characteristics. .

  The change characteristic calculating means according to the first invention can calculate the maximum value and the minimum value of the change rate of the detection signal from the start of change of the detection signal to the end of change as a plurality of types of change characteristics.

  The change characteristic calculation means according to the first invention is the first change pattern of the detection signal when the detection signal changes so as to reach a peak as the plurality of types of change characteristics, and the detection signal after the peak. And the determination means predicts a detection signal output from the gas sensor when a gas component is continuously included in the gas to be detected based on the first change pattern. And a prediction means for predicting a detection signal output from the gas sensor when the gas component is continuously contained in the gas to be detected based on the second change pattern, and the detection signal predicted by the prediction means Based on the above, it is possible to determine whether or not the gas component to be detected is contained in the gas to be detected.

  The change characteristics of the detection signal according to the second invention are the time from the peak of the detection signal to the end of change of the detection signal, the minimum value of the change rate of the detection signal from the start of change of the detection signal to the end of change, and It can be at least one of the change patterns of the detection signal after the detection signal reaches a peak.

  The change characteristic of the detection signal according to the second invention is set as a change pattern of the detection signal after the detection signal reaches a peak, and the determination unit detects the change based on the change pattern calculated by the first change characteristic calculation unit. When the gas component is continuously contained in the target gas, the detection signal output from one gas sensor is predicted, and the detection target gas is detected based on the change pattern calculated by the second change characteristic calculation means. When a gas component is continuously contained in the gas sensor, a prediction means for predicting a detection signal output from the other gas sensor is provided, and each detection signal predicted by the prediction means is compared and detected in the detection target gas. It can be determined whether or not the target gas component is included.

  The gas sensor may be an oxide semiconductor gas sensor.

  As described above, according to the present invention, the gas to be detected is included in the gas to be detected based on a plurality of types of change characteristics including the change characteristics of the detection signal after the detection signal reaches its peak. Or by comparing the change characteristics of the detection signals after the detection signals of the two gas sensors reach the peak, and determining that the detection target gas component is included in the detection target gas In such a case, by detecting the concentration of the gas component to be detected, it is possible to accurately detect the concentration of the gas component to be detected with a simple process even if the gas has a short duration. An effect is obtained.

  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 steering column 12 provided in a driver's seat at a position where a driver's breath can reach. The ethanol concentration detection apparatus 10 includes an elongated cylindrical exhalation introduction tube 20 in which a suction port 20A having an enlarged diameter is formed at the tip, and an oxide semiconductor is used in the middle of the exhalation introduction tube 20. An alcohol sensor 24, which is an oxide semiconductor gas sensor for detecting the concentration of ethanol gas, 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 inside the breath introduction tube 20 and closer to the suction port 20A than the alcohol sensor 24. .

The alcohol sensor 24 is a sensor that detects ethanol gas contained in the gas flowing in the breath introduction pipe 20, and for example, TGS2620 (trade name, manufactured by Figaro Giken Co., Ltd.) using a metal oxide semiconductor may be used. The circuit is configured as shown in FIG. In the alcohol sensor 24, the heater voltage _{V H} and the circuit voltage _{V C} is applied, the voltage across _{V OUT} of the load resistor _{R L} connected in series with the sensor resistance _{R S,} and outputs as a detection signal. Therefore, the alcohol sensor 24 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 24 has a relatively low selectivity of gas components, 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.

  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 24 is diluted at a constant flow rate. The exhaled breath comes into contact with the alcohol sensor 24 and is then discharged out of the exhaled breath introducing tube 20.

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

  As shown in FIG. 4, the ethanol concentration detection device 10 includes an ethanol concentration determination device 30 that is connected to the alcohol sensor 24 and detects the concentration of the ethanol gas component and causes the display device 40 to display it.

  The ethanol concentration determiner 30 is based on the detection signal from the alcohol sensor 24 and the adsorption change characteristic calculation unit 32 that calculates the change characteristic of the detection signal at the time of gas adsorption, and based on the detection signal from the alcohol sensor 24. The ratio of the desorption change characteristic calculation unit 34 for calculating the change characteristic of the detection signal at the time of desorption and the calculated change characteristic of the detection signal at the time of gas adsorption and the change characteristic of the detection signal at the time of gas desorption is within a predetermined range. Depending on whether or not the gas flowing in the breath introduction pipe 20 contains an ethanol gas component, and the gas flowing in the breath introduction pipe 20 contains the ethanol gas component. A gas concentration calculation unit 38 that calculates the concentration of ethanol gas in the gas flowing in the exhalation introduction tube 20 based on the change characteristic of the detection signal at the time of gas adsorption. There.

When the adsorption change characteristic calculation unit 32 detects that the exhalation is introduced and the detection signal from the alcohol sensor 24 changes as a response to the introduced exhalation, the adsorption change characteristic calculation unit 32 detects the gas adsorption from the change in the detection signal during a predetermined measurement period Tms. As the change characteristic of the detection signal at the time, the time from the start of change of the detection signal to the peak of the detection signal (see _{Tth1-p in} FIG. 5) is calculated, and the detection signal changes so as to reach the peak. The change pattern of the detection signal at the time of being is extracted.

The time from the start of change of the detection signal to the peak of the detection signal is calculated as follows. When the value of the detection signal exceeds a threshold C _th (for example, base value + 0.2V) from the time series change of the detection signal is detected as the detection signal change start time t _th1 , and the detection signal reaches a peak _Is detected as the peak maximum time tp. Then, according to the following equation (1), a time T _th1-p from the start of change of the detection signal to the peak of the detection signal is calculated.
Time from start of change to peak T _th1-p =
Peak maximum value time t _p -change start time t _th1 (1)

When the desorption change characteristic calculation unit 34 detects that the detection signal from the alcohol sensor 24 changes, the desorption change characteristic calculation unit 34 peaks the detection signal as the change characteristic of the detection signal at the time of gas desorption from the change in the detection signal during the predetermined measurement period Tms. Then, the time (see Tp _{-th2 in} FIG. 5) until the end of the change of the detection signal is calculated.

The time from when the detection signal reaches a peak until the end of the change in the detection signal is calculated as follows. 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 C _th, as a change end time of the detection signal t _th2 To detect. Then, according to the following equation (2), a time T _p-th2 from the peak of the detection signal to the end of the change of the detection signal is calculated.
Time from peak to end of change T _p−th2 =
Change the end time _{t th2} - the peak maximum time _t p ··· (2)

  Here, the principle of the present embodiment will be described. When measuring a gas with a short duration (within a few seconds), such as human exhalation, using a sensor with relatively low selectivity, such as an oxide semiconductor sensor, the concentration of gas components Since the difference in the sensor response due to the gas component is unlikely to be detected, the concentration of the gas component to be detected may be erroneously detected based on the sensor response due to the gas component that is not the gas component to be detected. There is.

  Among the characteristics of the change pattern of the detection signal from one gas sensor, the change characteristic of the detection signal from the start of change to the peak, that is, the change characteristic at the time of gas adsorption is not only the adsorption characteristic of gas components, but also gas diffusion, Since the characteristics of the reaction are reflected, differences due to the types of gas components hardly 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.

  For this reason, it is determined whether the target gas component exists regardless of the gas concentration and other conditions by indexing the change characteristic at the time of gas desorption relative to the change characteristic at the time of gas adsorption of the detection signal from the gas sensor. can do.

Therefore, in the present embodiment, in the gas component determination unit 36, the ratio of the time from the start of change of the detected detection signal to the peak and the time from the peak of the detection signal to the end of change is as follows ( When the condition expressed by the expression 3) is satisfied, it is determined that the ethanol gas component is contained in the gas flowing in the exhalation introduction tube 20. On the other hand, when the condition represented by the following expression (3) is not satisfied, it is determined that the ethanol gas component is not contained in the gas flowing in the exhalation introduction pipe 20.
_{A 1 <T th1-p /} T p-th2 <A 2 ··· (3)

Incidentally, the threshold value A ₁ may, for example, is preferably setting the value in the range of 1.5 to 2, in this embodiment, as the threshold A _1, 1.7 is set. Further, the threshold A ₂ is preferably set to a value in the range of 2 to 2.5, for example, and in the present embodiment, 2.3 is set as the threshold A ₂ .

  The gas concentration calculation unit 38 determines the concentration of the ethanol gas component contained in the gas flowing in the breath introduction pipe 20 when it is determined that the gas flowing in the breath introduction pipe 20 contains the ethanol gas component. calculate.

  Here, the principle of calculating the concentration of the ethanol gas component will be described. The alcohol sensor used in the present embodiment is characterized in that the concentration of the alcohol component is regarded as the resistance value of the sensor resistance that changes when oxygen on the sensor surface reacts with the alcohol. From this, it is considered that the output value from the sensor is proportional to the reaction rate between alcohol and oxygen. Therefore, modeling of the excessive response of the oxide semiconductor sensor can be realized by modeling the time change of the reaction rate between alcohol and oxygen.

  Regarding the reaction rate, it is well known that the relationship with the concentration in the equilibrium state can be modeled by using the Michaelis-Menten equation. According to this modeling method, the reaction rate v is expressed by the following equation (4).

However, [S] represents the alcohol concentration, and V _max and K _m are parameters determined by the reaction.

Since the model represented by the above (4) is a model in an equilibrium state, the reaction rate in the transient response cannot be well modeled. Therefore, based on the Michaelis-Menten equation, the following reaction rate is modeled by making the following assumptions.
1. Compared to the change in alcohol concentration around the sensor, the equilibrium state is reached sufficiently quickly. That is, the change in the reaction rate is caused only by the concentration change around the sensor.
2. The change in the alcohol concentration around the sensor follows a one-dimensional diffusion equation expressed by the following equation (5) when the concentration at the entrance of the apparatus is constant.

Where λ ₁ is the diffusion coefficient, x is the distance from the entrance of the apparatus, t is the time, C ₁ is the entrance concentration, and erfc is the complementary error function.
3. The response delay of the sensor can be expressed by an nth-order lag equation expressed by the following equation (6).

Where λ ₂ is a time constant.

  Above 1. ~ 3. When the change in the sensor value over time is modeled on the basis of the above assumption, it can be expressed by the following equation (7).

  In order to calculate the above complementary error function, iterative calculation is required. Therefore, here, the concentration is estimated using the following equation (8) as a very simple approximation.

  However, a, b, and c are parameters obtained from system identification. Further, by using the above equation (8), the time required for system identification and the memory capacity to be used can be reduced.

  The gas concentration calculation unit 38 performs system identification using a change pattern of the detection signal when the extracted detection signal changes so as to have a peak. Then, the gas concentration calculation unit 38 uses the parameter obtained from the system identification, and continues the ethanol component having the same concentration as the ethanol component contained in the gas flowing in the exhalation introduction tube 20 according to the above equation (8). If included, the saturation output value of the detection signal output from the alcohol sensor 24 is predicted.

  The gas concentration calculation unit 38 then determines the ethanol corresponding to the saturated output value of the detection signal predicted based on the relationship (logarithmic function) obtained in advance between the value of the detection signal from the alcohol sensor 24 and the ethanol gas concentration. The concentration of the gas component is calculated as the concentration of the ethanol component contained in the gas flowing in the exhalation introduction tube 20.

  Next, the operation of the ethanol concentration detection apparatus 10 according to the first embodiment will be described. 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 determination device 30 of the ethanol concentration detection device 10 uses the ethanol shown in FIG. A concentration detection processing routine is executed.

  First, in step 100, it is determined whether or not a change in the gas component in the gas contained in the exhalation introduction tube 20 is detected from the change in the detection signal from the alcohol sensor 24, and the change amount of the detection signal equal to or greater than a predetermined amount. Is detected, it is determined that exhaled air is introduced into the exhalation introducing tube 20 and the gas component has changed, and the routine proceeds to step 102.

  In step 102, a detection signal for a predetermined measurement period Tms is acquired from the alcohol sensor 24. In step 104, the time from the start of change of the detection signal to the peak of the detection signal is determined as the change characteristic of the detection signal at the time of gas adsorption from the detection signal for the predetermined measurement period Tms acquired in step 102. While calculating, the change pattern of a detection signal when the detection signal changes so that it may become a peak is extracted.

  In the next step 106, from the detection signal for the predetermined measurement period Tms acquired in the above step 102, as the change characteristic of the detection signal at the time of gas desorption, the time from the peak of the detection signal to the end of the change of the detection signal Is calculated.

  Then, in step 108, according to the above equation (3), the time from the start of change of the detection signal calculated in step 104 to the peak and the change after the detection signal calculated in step 106 reaches the peak change. It is determined whether or not the ratio to the end time is within a predetermined range. If it is determined that the time ratio is not within the predetermined range, it is determined that the ethanol gas component is not contained in the gas flowing in the exhalation introduction tube 20, and the process returns to step 100.

  If it is determined in step 108 that the time ratio is within the predetermined range, it is determined that the ethanol gas component is contained in the gas flowing in the exhalation-introducing tube 20, and the process proceeds to step 110. Transition.

  In step 110, system identification is performed using the change pattern of the detection signal extracted in step 102 when the detection signal changes so as to reach a peak. The saturated output value of the detection signal output from the alcohol sensor 24 when the ethanol component having the same concentration as the ethanol component in the gas flowing in the gas 20 is continuously contained is predicted.

  In the next step 112, based on the saturation output value of the detection signal predicted in step 110, the concentration of the ethanol component contained in the gas flowing in the exhalation introduction tube 20 is calculated. The concentration of the ethanol gas component calculated in (1) is displayed on the display device 40, and the ethanol concentration detection processing routine is terminated.

  As described above, according to the ethanol concentration detection apparatus according to the first embodiment, based on the ratio of the time from the start of change of the detection signal of the alcohol sensor to the peak and the time from the peak to the end of change. Even when it is determined that an ethanol gas component is contained in the gas to be detected, by detecting the concentration of the ethanol gas component, a gas having a short duration such as exhalation is to be detected. The concentration of the ethanol gas component can be accurately detected by simple processing.

  Further, in gas measurement for a transient gas having a short duration such as human exhalation, the concentration of the gas component is detected by using a sensor having relatively low selectivity such as an oxide semiconductor sensor. Even in this case, it is possible to determine the difference in the sensor response due to the gas component and to determine whether or not the ethanol gas component as the target component exists. As a result, only the ethanol component that is the target component can be selectively quantified, and erroneous detection due to other gas components can be prevented.

  In addition, the concentration of the target component (for example, ethanol gas component) in a transient gas with a short duration such as the exhalation of the driver is distinguished from other gas components, for example, gas components contained in food. Therefore, the concentration of the ethanol gas component contained in the driver's breath can be detected with high accuracy, and the driver's drinking can be detected with high accuracy.

  In the above embodiment, the case where the change end time of the detection signal is detected using the same threshold as the threshold for detecting the change start time of the detection signal has been described as an example. However, the present invention is not limited to this. Instead of a threshold for detecting the change start time of the detection signal (for example, base value + 0.5V), when the value of the detection signal drops to this threshold, the change in the detection signal You may make it detect as end time.

  Next, an ethanol concentration detection apparatus according to the second embodiment will be described. In addition, since the ethanol concentration detection apparatus according to the second embodiment has the same configuration as that of the first embodiment, the same reference numerals are given and description thereof is omitted.

  The second embodiment is mainly different from the first embodiment in that the peak height of the detection signal is calculated as the change characteristic of the detection signal during gas adsorption.

In the ethanol concentration determination device 30 of the ethanol concentration detection apparatus according to the second embodiment, the adsorption change characteristic calculation unit 32 determines the change characteristic of the detection signal during gas adsorption from the change in the detection signal during the predetermined measurement period Tms. The peak height of the detection signal (see ΔC _{p in} FIG. 7) is calculated, and the change pattern of the detection signal when the detection signal changes so as to have a peak is extracted.

The peak height of the detection signal is calculated as follows. From the time series change of detection signals, the previous value of the detection signal change, and detects as the base value C _b of the detection signal, the detection signal to detect a peak maximum C _p when peaked. Then, the peak height ΔC _p of the detection signal is calculated according to the following equation (9).
Peak height ΔC _p of detection signal =
Peak maximum value C _p -base value C _b (9)
When the ratio between the calculated peak height of the detection signal and the time from the peak of the detection signal to the end of the change satisfies the condition expressed by the following equation (10), the gas component determination unit 36 It is determined that the ethanol gas component is contained in the gas flowing in the exhalation introduction tube 20. On the other hand, when the condition represented by the following expression (10) is not satisfied, it is determined that the ethanol gas component is not contained in the gas flowing in the exhalation introduction pipe 20.
B ₁ <LN (T _{p−th 2} / ΔC _p ) <B ₂ (10)

However, LN () represents a natural logarithm. Further, the above expression (10) can be rewritten as the following expression (10) ′.
_{B 1 <LN (T p-} th2) -LN (ΔC p) <B 2 ··· (10) '

Incidentally, the threshold value B ₁ represents, for example, is preferably setting the value in the range of 2 to 2.7, in this embodiment, as the threshold B _1, 2.3 is set. Further, the threshold value _{B 2,} for example, is preferably setting the value in the range of 2.7 to 3.3, in this embodiment, as the threshold value _{B 2,} 3.0 is set.

It is also possible to use the following expression (10) ″ instead of the above expression (10) or expression (10) ′.
_{B 1 <T p-th2 /} ΔC p <B 2 ··· (10)''

In the case of using the above (10)'' expression threshold B ₁ represents, for example, it is preferably setting the value in the range of 7 to 15, in this embodiment, as the threshold B _1, a 10 Just set it up. Further, the threshold value B _2, for example, preferably in setting the value in the range of 15 to 25, in this embodiment, as the threshold value B _2, may be set to 20.

  In addition, about the other structure and effect | action of the ethanol concentration detection apparatus which concern on 2nd Embodiment, since it is the same as that of 1st Embodiment, description is abbreviate | omitted.

  As described above, according to the ethanol concentration detection apparatus according to the second embodiment, the detection target is detected based on the ratio between the peak height of the detection signal of the alcohol sensor and the time from the peak to the end of the change. When it is determined that an ethanol gas component is contained in the gas, simple processing is possible even when a gas having a short duration, such as exhalation, is detected by detecting the concentration of the ethanol gas component. Thus, the concentration of the ethanol gas component can be accurately detected.

  Next, an ethanol concentration detection apparatus according to a third embodiment will be described. In addition, since the structure of the ethanol concentration detection apparatus which concerns on 3rd Embodiment is the structure similar to 1st Embodiment, it attaches | subjects the same code | symbol and abbreviate | omits description.

  In the third embodiment, the maximum value of the change rate of the detection signal is calculated as the change characteristic of the detection signal at the time of gas adsorption, and the change of the detection signal as the change characteristic of the detection signal at the time of gas desorption. The difference from the first embodiment is that the minimum value of the rate is calculated.

In the ethanol concentration determination device 30 of the ethanol concentration detection apparatus according to the third embodiment, the adsorption change characteristic calculation unit 32 calculates the change characteristic of the detection signal during gas adsorption from the change in the detection signal during the predetermined measurement period Tms. , to calculate the maximum value of the rate of change of the detection signal (the slope of change) (see alpha ₁ in FIG. 8), and extracts the variation pattern of the detection signal when the detection signal is changed so that the peaks.

In calculating the maximum value of the change rate of the detection signal, first, 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 detection signal is calculated from the time series change of the calculated change rate. The maximum value α _{1 of the} rate of change of the above is detected.

Further, the desorption change characteristic calculation unit 34 calculates the minimum value of the change rate of the detection signal (see α _{2 in} FIG. 8) as the change characteristic of the detection signal at the time of gas desorption from the change in the detection signal during the predetermined measurement period Tms. calculate. In calculating the minimum value of the change rate of the detection signal, first, 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 detection signal is calculated from the time series change of the calculated change rate. The minimum value α ₂ (α ₂ <0) is detected.

When the ratio between the calculated minimum value of the change rate of the detection signal and the maximum value of the change rate of the detection signal satisfies the condition expressed by the following equation (11), the gas component determination unit 36: It is determined that the ethanol gas component is contained in the gas flowing in the exhalation introduction tube 20. On the other hand, when the condition represented by the following expression (11) is not satisfied, it is determined that the ethanol gas component is not contained in the gas flowing in the exhalation introduction pipe 20.
D ₁ <-(α ₂ / α ₁ ) <D ₂ (11)

Incidentally, the threshold value _{D 1} is, for example, is preferably setting the value in the range of 0.2 to 0.5, in this embodiment, as the threshold _{D 1,} 0.3 is set. Further, the threshold value _{D 2} are, for example, is preferably setting the value in the range of 0.5 to 0.8, in this embodiment, as the threshold value _{D 2,} 0.7 is set.

  In addition, about the other structure and effect | action of the ethanol concentration detection apparatus which concern on 3rd Embodiment, since it is the same as that of 1st Embodiment, description is abbreviate | omitted.

  As described above, according to the ethanol concentration detection apparatus according to the third embodiment, ethanol is detected in the detection target gas based on the ratio between the maximum value and the minimum value of the change rate of the detection signal of the alcohol sensor. When it is determined that a gas component is contained, the concentration of the ethanol gas component is detected. The concentration of the component can be detected with high accuracy.

  Next, an ethanol concentration detection apparatus according to a fourth embodiment will be described. In addition, since the structure of the ethanol concentration detection apparatus which concerns on 4th Embodiment is the structure similar to 1st Embodiment, it attaches | subjects the same code | symbol and abbreviate | omits description.

  In the fourth embodiment, as a change characteristic of the detection signal at the time of gas adsorption, a change pattern when the detection signal changes so as to reach a peak is extracted, and a detection signal at the time of gas desorption is extracted. As a change characteristic, whether or not the ethanol gas component is included is determined based on the point of extracting the change pattern after the detection signal reaches its peak and the saturated output value of the detection signal predicted from each change pattern. The point of determination is mainly different from the first embodiment.

  In the ethanol concentration determination device 30 of the ethanol concentration detection apparatus according to the fourth embodiment, the adsorption change characteristic calculation unit 32 calculates the change characteristic of the detection signal during gas adsorption from the change in the detection signal during the predetermined measurement period Tms. Then, a change pattern of the detection signal when the detection signal changes so as to reach a peak is extracted.

  Further, the change pattern of the detection signal after the peak of the detection signal is extracted as the change characteristic of the detection signal at the time of gas desorption from the change of the detection signal in the predetermined measurement period Tms by the desorption change characteristic calculation unit 34. .

  The gas component determination unit 36 determines whether or not an ethanol gas component is contained in the gas flowing in the exhalation introduction tube 20 as described below.

First, system identification is performed based on the extracted change pattern of the detection signal when the detection signal changes so as to reach a peak. Then, using the parameter obtained from the system identification, the alcohol sensor 24 when the ethanol component having the same concentration as the ethanol component contained in the gas flowing in the exhalation introduction tube 20 is continuously contained according to the above equation (8). predicting the saturated output value of the detection signal output from the (see C ₁ in FIG. 9).

Further, based on the extracted detection signal change pattern (desorption characteristic change pattern) after the detection signal has reached its peak, ethanol having the same concentration as the ethanol component contained in the gas flowing in the exhalation introduction tube 20 predicting the saturated output value of the detection signal output from the alcohol sensor 24 (see C ₂ in FIG. 9) when the components are contained sustained.

  Here, the principle of predicting the saturation output value from the change pattern of the desorption characteristics will be described.

  Based on the Michaelis-Menten equation, the attenuation response of the alcohol sensor 24 is modeled as follows by making assumptions similar to the transient response.

Assuming that the time when the concentration starts to decrease is t ₀ , the concentration change C (x, t) at the time of desorption at the sensor position x is expressed by the following equations (12) and (13).

  When an approximate solution is used to reduce the amount of calculation, the above equation (13) is expressed by the following equation (14).

  By substituting the above equation (14) into the above equation (4) and using the reaction delay up to the third-order lag term as in the above equation (8), the output value f (t) of the sensor becomes the following (15 ) Expression.

However, a, b, c, d , t 0 is a parameter determined by system identification for the sensor.

  The gas component determination unit 36 determines the saturation output value of the detection signal output from the alcohol sensor 24 when the ethanol component having the same concentration as the ethanol component contained in the gas flowing in the breath introduction pipe 20 is continuously contained. Prediction is performed according to the above equation (15).

Then, a saturated output value C ₂ of the predicted detection signal from the change pattern of the detection signal after the peak, the saturated output value C ₁ of the predicted detection signal from the change pattern of the detection signal is changed so that the peak If the ratio satisfies the condition expressed by the following equation (16), it is determined that the ethanol gas component is contained in the gas flowing in the exhalation introduction tube 20. On the other hand, when the condition expressed by the following expression (16) is not satisfied, it is determined that the ethanol gas component is not contained in the gas flowing in the exhalation introduction pipe 20.
F ₁ <C ₂ / C ₁ <F ₂ (16)

Incidentally, the threshold F _1, for example, is preferably setting the value in the range of 0.8 to 1, in this embodiment, as the threshold F _1, 0.9 is set. Further, the threshold F _2, for example, is preferably setting the value in the range of 1-1.2, in the present embodiment, as the threshold F _2, 1.1 is set.

  The gas concentration calculation unit 38 uses the saturated output value of the detection signal predicted from the change pattern of the detection signal that changes so as to reach a peak in the gas component determination unit 36, in the gas flowing in the exhalation introduction tube 20. The concentration of the ethanol gas component contained in is calculated.

  In addition, about the other structure and effect | action of the ethanol concentration detection apparatus which concern on 4th Embodiment, since it is the same as that of 1st Embodiment, description is abbreviate | omitted.

  As described above, according to the ethanol concentration detection apparatus of the fourth embodiment, the saturated output value of the detection signal predicted from the change pattern up to the peak of the detection signal of the alcohol sensor and the change pattern after the peak If it is determined that the gas to be detected contains an ethanol gas component based on the ratio of the detected signal to the saturation output value of the detection signal, the concentration of the ethanol gas component is detected. Even when a gas with a short duration is used as a detection target, the concentration of the ethanol gas component can be accurately detected with a simple process.

  In the above embodiment, the case where the concentration of the ethanol gas component is calculated using the saturated output value of the detection signal predicted from the change pattern of the detection signal that changes so as to reach a peak will be described as an example. However, the present invention is not limited to this, and the concentration of the ethanol gas component may be calculated using the saturated output value of the detection signal predicted from the change pattern of the detection signal after the peak. .

  Next, an ethanol concentration detection apparatus according to a fifth embodiment will be described. In addition, about the part which has the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The fifth embodiment is mainly different from the first embodiment in that an alcohol sensor and a gas sensor having sensitivity to many types of gas components are used.

  As shown in FIG. 10, in the ethanol concentration detection apparatus 510 according to the fifth embodiment, an alcohol sensor 24 and a gas sensor 524 having sensitivity to many types of gas components are provided in the middle part of the exhalation introduction tube 20. And are attached. The alcohol sensor 24 and the gas sensor 524 are attached so as to face the inside of the intermediate portion of the exhalation introduction tube 20.

  Unlike the alcohol sensor 24, the gas sensor 524 has sensitivity to many types of gas components, unlike the alcohol sensor 24, in sensitivity (change characteristics) to gas components other than the target component (ethanol). As the gas sensor 524, 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 524 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 increases, 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 24 and the gas sensor 524 are reached at a constant flow rate. The exhaled breath comes into contact with the alcohol sensor 24 and the gas sensor 524 and is then discharged to the outside from the exhaled breath introducing tube 20.

  Detection signals output from each of the alcohol sensor 24 and the gas sensor 524 are input to an ethanol concentration determination unit 530 described later, and the concentration of ethanol gas as a detection target gas is detected based on the input detection signal.

  As shown in FIG. 11, the ethanol concentration determination unit 530 includes a desorption change characteristic calculation unit 34 and a desorption change characteristic calculation unit 534 that calculates a change characteristic of the detection signal at the time of gas desorption based on the detection signal from the gas sensor 524. And the ratio of the change characteristic of the detection signal at the time of gas desorption calculated based on the detection signal from each of the alcohol sensor 24 and the gas sensor 524 is within the predetermined range depending on whether or not the ratio is within a predetermined range. A gas component determination unit 536 that determines whether or not an ethanol gas component is contained in the gas, and an adsorption change extraction unit that extracts a change pattern of the detection signal at the time of gas adsorption based on the detection signal from the alcohol sensor 24. 537 and a gas concentration calculation unit 38.

The desorption change characteristic calculation unit 534 uses the change in the detection signal from the gas sensor 524 during the predetermined measurement period Tms to obtain a peak detection signal as a change characteristic of the detection signal from the gas sensor 524 during gas desorption according to the following equation (17). Then, a time T2 _p-th2 from the time until the end of the change of the detection signal is calculated.
Time from peak to end of change T2 _p-th2 =
Change end time t2 _th2 -peak maximum time t2 _p (17)
Here, the principle of the present embodiment will be described. As described above, 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 detection for a transient gas at a constant flow rate. Even the change characteristics of the signal tend to vary depending on the type of gas component. For this reason, by comparing the change characteristics at the time of gas desorption of detection signals from multiple types of gas sensors, and by indexing the change characteristics at the time of gas desorption, the target gas component can be detected regardless of conditions such as gas concentration. It can be determined whether or not it exists.

Therefore, in the present embodiment, in the gas component determination unit 536, the calculated time T _p-th2 from the start of change of the detection signal of the alcohol sensor 24 to the peak and the end of change from the peak of the detection signal of the gas sensor 524 are completed. When the ratio to the time T2 _{p-th2 up} to the condition expressed by the following expression (18) is satisfied, it is determined that the ethanol gas component is contained in the gas flowing in the exhalation introduction tube 20 . On the other hand, when the condition represented by the following expression (18) is not satisfied, it is determined that the ethanol gas component is not contained in the gas flowing in the exhalation introduction pipe 20.
_{G 1 <T p-th2 /} T2 p-th2 <G 2 ··· (18)

Incidentally, the threshold value G ₁ is preferably, for example, the previously set value in the range of 0.8 to 1, in this embodiment, as the threshold G _1, 0.9 is set. Further, the threshold value G ₂ is, for example, is preferably setting the value in the range of 1-1.2, in the present embodiment, as the threshold value G _2, 1.1 is set.

  The adsorption change extraction unit 537 has a detection signal change pattern when the detection signal changes so as to change to a peak as a change characteristic during gas adsorption from a change in the detection signal of the alcohol sensor 24 during a predetermined measurement period Tms. To extract.

  When it is determined that the ethanol gas component is contained in the gas flowing through the exhalation introduction tube 20, the gas concentration calculation unit 38 changes so that the extracted detection signal of the alcohol sensor 24 reaches a peak. The concentration of the ethanol gas component contained in the gas flowing through the exhalation-introducing tube 20 is calculated using the change pattern of the detection signal at the time.

  Next, an ethanol concentration detection processing routine according to the fifth embodiment will be described with reference to FIG. Note that the same processes as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  First, in step 100, it is determined whether or not a change in the gas component in the gas contained in the exhalation introduction tube 20 has been detected from the change in the detection signal from the alcohol sensor 24. Is detected, the process proceeds to step 550.

  In step 550, detection signals for a predetermined measurement period Tms are acquired from each of the alcohol sensor 24 and the gas sensor 524. In step 552, from the detection signal for the predetermined measurement period Tms acquired from the alcohol sensor 24 in step 550, the detection signal becomes a peak as a change characteristic of the detection signal when the alcohol sensor 24 is desorbed. The time until the end of the change of the detection signal is calculated.

  In the next step 554, from the detection signal for the predetermined measurement period Tms acquired from the gas sensor 524 in the above step 550, as the change characteristic of the detection signal when the gas sensor 524 is desorbed, the detection signal is detected after the detection signal reaches a peak. The time until the end of the change is calculated.

  In step 556, the time from the peak of the detection signal of the alcohol sensor 24 calculated in step 552 to the end of the change and the detection signal calculated in step 554 are peaked according to the above equation (18). It is determined whether the ratio of the time until the end of the change is within a predetermined range. If it is determined that the time ratio is not within the predetermined range, it is determined that the ethanol gas component is not contained in the gas flowing in the exhalation introduction tube 20, and the process returns to step 100.

  If it is determined in step 556 that the time ratio is within the predetermined range, it is determined that the gas flowing in the exhalation introduction tube 20 contains an ethanol gas component, and the process proceeds to step 558. Transition.

  In step 558, a change pattern of the detection signal when the detection signal changes so as to reach a peak is extracted from the detection signal for the predetermined measurement period Tms acquired from the alcohol sensor 24 in step 550.

  In step 110, system identification is performed using the change pattern of the detection signal when the detection signal extracted in step 558 changes so as to reach a peak, and from the alcohol sensor 24 according to the above equation (8). Predict the saturation output value of the detection signal.

  In the next step 112, based on the saturation output value of the detection signal predicted in step 110, the concentration of the ethanol component contained in the gas flowing in the exhalation introduction tube 20 is calculated. The concentration of the ethanol gas component calculated in (1) is displayed on the display device 40, and the ethanol concentration detection processing routine is terminated.

  As described above, according to the ethanol concentration detection apparatus according to the fifth embodiment, the time from when the detection signal of the alcohol sensor reaches the peak until the end of the change and the detection signal of the gas sensor reach the peak. Based on the ratio from the time until the end of the change to the end of the change, it is determined that the ethanol gas component is contained in the gas to be detected. Even when a short gas is used as a detection target, the concentration of the ethanol gas component can be accurately detected by a simple process.

  In the above-described embodiment, the case where the time from the peak to the end of the change has been described as an example for each detection signal of the alcohol sensor and the gas sensor. However, the present invention is not limited to this. For example, as the change characteristic of the detection signal at the time of gas desorption, the minimum value of the change rate of the detection signal is calculated for each detection signal of the alcohol sensor and the gas sensor, as in the third embodiment. Also good.

  Next, an ethanol concentration detection apparatus according to a sixth embodiment will be described. In addition, since the structure of the ethanol concentration detection apparatus which concerns on 6th Embodiment is the structure similar to 5th Embodiment, it attaches | subjects the same code | symbol and abbreviate | omits description.

  In the sixth embodiment, as a change characteristic of the detection signal at the time of gas desorption of the alcohol sensor, a change pattern after the detection signal of the alcohol sensor reaches a peak is extracted, and at the time of gas desorption of the gas sensor. Based on the detection signal change characteristics, the change pattern after the detection signal of the gas sensor has peaked, and the saturation output value of the detection signal predicted from the change pattern of each sensor. Is different from the fifth embodiment mainly in that it is determined whether or not is included.

  In the ethanol concentration determination device 530 of the ethanol concentration detection device according to the sixth embodiment, the desorption change characteristic calculation unit 34 detects the detection signal at the time of gas desorption from the change in the detection signal of the alcohol sensor 24 during the predetermined measurement period Tms. As a change characteristic, a change pattern of the detection signal after the detection signal of the alcohol sensor 24 reaches a peak is extracted. Further, the detection signal after the detection signal of the gas sensor 524 reaches the peak as the change characteristic of the detection signal at the time of gas desorption from the change of the detection signal of the gas sensor 524 in the predetermined measurement period Tms by the desorption change characteristic calculation unit 534. Extract change patterns.

  The gas component determination unit 536 determines whether or not an ethanol gas component is contained in the gas flowing in the exhalation introduction tube 20 as described below.

  First, based on the extracted change pattern of the detection signal after the detection signal of the alcohol sensor 24 reaches the peak, it is included in the gas flowing in the exhalation introduction tube 20 as in the first embodiment. A saturated output value of a detection signal output from the alcohol sensor 24 is predicted when an ethanol component having the same concentration as the ethanol component to be detected is continuously included.

  Moreover, based on the extracted change pattern of the detection signal after the detection signal of the gas sensor 524 reaches the peak, the gas component having the same concentration as the gas component contained in the gas flowing in the exhalation introduction tube 20 is sustained. The saturation output value of the detection signal output from the gas sensor 524 is predicted.

As in the case of the alcohol sensor 24, the saturated output value of the detection signal output from the change pattern of the detection signal after the peak of the detection signal of the gas sensor 524 (change pattern of the desorption characteristic) according to the above equation (15). Can be predicted. The parameters a, b, c, d, and t ₀ in the above equation (15) are different from the parameters relating to the alcohol sensor 24.

The alcohol sensor 24 is predicted from the change pattern of the detection signal after the peak of the alcohol sensor 24 and a saturated output value C ₂ of the detection signal, after the peak of the gas sensor 524 of the detection signal varying pattern predicted for the gas sensor 524 from determining the ratio between the saturation output value E ₂ of the detection signal, the following (19) when satisfying the formula is contained ethanol gas component in a gas flowing through the exhalation inlet pipe 20 To do. On the other hand, when the condition expressed by the following equation (19) is not satisfied, it is determined that the ethanol gas component is not contained in the gas flowing in the exhalation introduction pipe 20.
H ₁ <C ₂ / E ₂ <H ₂ (19)

Incidentally, the threshold H _1, H _2, it is sufficient to set the experimental or statistically obtained in advance determination threshold value.

  The gas concentration calculation unit 38 calculates the concentration of the ethanol gas component using the saturated output value of the detection signal predicted from the change pattern of the detection signal after the peak of the alcohol sensor 24 in the gas component determination unit 536. .

  In addition, about the other structure and effect | action of the ethanol concentration detection apparatus which concern on 6th Embodiment, since it is the same as that of 5th Embodiment, description is abbreviate | omitted.

  As described above, according to the ethanol concentration detection apparatus according to the sixth embodiment, the saturated output value of the detection signal predicted from the change pattern after the detection signal of the alcohol sensor reaches the peak, and the gas sensor When it is determined that the gas to be detected contains an ethanol gas component based on the ratio to the saturated output value of the detection signal predicted from the change pattern after the detection signal reaches its peak, the ethanol gas component By detecting the concentration of ethanol, the concentration of the ethanol gas component can be accurately detected with a simple process even when a gas having a short duration, such as exhalation, is targeted for detection.

  In the fifth embodiment and the sixth embodiment described above, the case where the alcohol sensor and the gas sensor such as the 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 in which the sensitivity with respect to a gas component differs from an alcohol sensor with 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 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.

  Further, in the first embodiment, the second embodiment, and the fifth embodiment described above, the time when the value of the detection signal has decreased to a threshold value or less is detected as the time when the detection signal change ends. Although the case has been described as an example, the present invention is not limited to this, and the time when the value of the detection signal has decreased to a value that is a constant ratio to the peak maximum value (for example, 30% of the peak maximum value) You may make it detect as the time of the end of a change of a detection signal.

  In the first to sixth embodiments, the concentration of the ethanol gas component is calculated using the saturated output value of the detection signal predicted from the change pattern of the detection signal of the alcohol sensor. However, the present invention is not limited to this, and the saturated output value of the detection signal is predicted from the base value and the peak value of the detection signal of the alcohol sensor, and the predicted saturated output value of the detection signal is used. Thus, the concentration of the ethanol gas component may be calculated.

  Moreover, although the case where it was determined as an example whether the ethanol gas component is contained using sensor output (V) was demonstrated, it is not limited to this, The concentration calculation value ( ppm or mg / L) may be used to determine whether an ethanol gas component is included. In this case, different values may be set as the determination threshold value for defining the range exemplified in each of the above embodiments.

  In the above embodiment, 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 predetermined. Control may be performed so as to prevent fraud such as preventing the engine from starting by comparing the threshold value and determining that the ethanol concentration is high when the calculated ethanol gas component concentration is equal to or greater than the threshold value.

  In the above, the example of detecting the concentration of the ethanol gas component from the exhalation of the driver has been described, but by configuring the ethanol concentration detection device to be portable, the present invention can reduce the concentration of the ethanol gas component from the exhalation of humans other than the driver. The present invention can also be applied to detection.

It is the schematic which shows the state which attached the ethanol concentration detection apparatus of the 1st Embodiment of this invention to the steering column of the driver's seat. It is the schematic which shows the 1st Embodiment of this invention. It is a circuit diagram which shows the structure of the alcohol sensor of the ethanol concentration determination device of the 1st Embodiment of this invention. It is a block diagram which shows the structure of the ethanol concentration determination device of the 1st Embodiment of this invention. It is a graph which shows the time series change of the detection signal from an alcohol sensor, the time from a change start to a peak, and the time from a peak to the end of change. It is a flowchart which shows the content of the ethanol concentration detection processing routine in the ethanol concentration detection apparatus of 1st Embodiment. It is a graph which shows the time-sequential change of the detection signal from an alcohol sensor, and the height of a peak. It is a graph which shows the time series change of the detection signal from an alcohol sensor, the minimum value of a change rate, and the maximum value of a change rate. It is a graph which shows the time series change of the detection signal from an alcohol sensor, the saturation output value estimated from the change pattern to a peak, and the saturation output value estimated from the change pattern after a peak. It is the schematic which shows the 5th Embodiment of this invention. It is a block diagram which shows the structure of the ethanol concentration determination device of the 5th Embodiment of this invention. It is a flowchart which shows the content of the ethanol concentration detection processing routine in the ethanol concentration detection apparatus of 5th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 510 Ethanol concentration detection apparatus 24 Alcohol sensor 30, 530 Ethanol concentration determination device 32 Adsorption change characteristic calculation part 34, 534 Desorption change characteristic calculation part 36, 536 Gas component determination part 38 Gas concentration calculation part 524 Gas sensor

Claims (9)

A gas sensor that outputs a detection signal whose level increases as the concentration of the gas component contained in the gas to be detected increases and decreases as the concentration of the gas component decreases;
Based on the detection signal output from the gas sensor, change characteristic calculation means for calculating a plurality of types of change characteristics including the change characteristic of the detection signal after the detection signal has reached a peak;
Determining means for determining whether or not a gas component to be detected is contained in the gas to be detected based on the plurality of types of change characteristics calculated by the change characteristic calculating means;
When it is determined by the determination means that the gas component to be detected is contained in the gas to be detected, the gas contained in the gas to be detected is based on the detection signal output from the gas sensor. Gas concentration detection means for detecting the concentration of the gas component to be detected;
A gas detection device. A detection signal is output that has different sensitivities to the gas components, increases in level as the concentration of the gas component contained in the gas to be detected increases, and decreases as the concentration of the gas component decreases. Two gas sensors,
First change characteristic calculation means for calculating a change characteristic of the detection signal after the detection signal has reached a peak based on the detection signal output from one of the gas sensors;
Second change characteristic calculating means for calculating a change characteristic of the detection signal after the detection signal reaches a peak based on the detection signal output from the other gas sensor;
The change characteristic calculated by the first change characteristic calculation means and the change characteristic calculated by the second change characteristic calculation means are compared, and the detection target gas component is included in the detection target gas. Determination means for determining whether or not,
When it is determined by the determination means that the gas component to be detected is contained in the gas to be detected, the gas contained in the gas to be detected is based on the detection signal output from the gas sensor. Gas concentration detection means for detecting the concentration of the gas component to be detected;
A gas detection device.   The change characteristic calculation means includes, as the plurality of types of change characteristics, a time from the start of change of the detection signal to the peak of the detection signal, and from the peak of the detection signal to the end of change of the detection signal. The gas detection device according to claim 1, wherein the time is calculated.   2. The change characteristic calculation unit calculates, as the plurality of types of change characteristics, a peak height of the detection signal and a time from the peak of the detection signal to the end of the change of the detection signal. Gas detection device.   The gas detection device according to claim 1, wherein the change characteristic calculation unit calculates a maximum value and a minimum value of a change rate of the detection signal from a change start to a change end of the detection signal as the plurality of types of change characteristics. The change characteristic calculation means includes a first change pattern of the detection signal when the detection signal changes to be a peak as the plurality of types of change characteristics, and after the detection signal has reached a peak. Calculating a second change pattern of the detection signal;
The determination means predicts the detection signal output from the gas sensor when a gas component is continuously included in the gas to be detected based on the first change pattern, and the second change pattern. Based on the detection signal predicted by the prediction means, the prediction means predicting the detection signal output from the gas sensor when a gas component is continuously contained in the gas to be detected The gas detection device according to claim 1, wherein it is determined whether or not the detection target gas component is contained in the detection target gas.   The change characteristic of the detection signal is the time from the peak of the detection signal to the end of change of the detection signal, the minimum value of the change rate of the detection signal from the start of change of the detection signal to the end of change, and the The gas detection device according to claim 2, wherein at least one of the change patterns of the detection signal after the detection signal reaches a peak. The change characteristic of the detection signal is a change pattern of the detection signal after the detection signal reaches a peak,
The determination means outputs the detection output from the one gas sensor when a gas component is continuously contained in the gas to be detected based on the change pattern calculated by the first change characteristic calculation means. The signal output from the other gas sensor when predicting a signal and based on the change pattern calculated by the second change characteristic calculating means when a gas component is continuously included in the gas to be detected. A prediction unit that predicts a detection signal is provided, and each of the detection signals predicted by the prediction unit is compared to determine whether or not the detection target gas component is contained in the detection target gas. Item 8. The gas detection device according to Item 7.   The gas detection device according to any one of claims 1 to 8, wherein the gas sensor is an oxide semiconductor gas sensor.

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