JP2013145207A - Gas detection sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas detection sensor being mountable on a vehicle and capable of retaining measuring accuracy.SOLUTION: The gas sensor includes a detection cell 16 including: a light source 11 for emitting infrared light; light receiving parts 13 and 15 for receiving the infrared light; and filters 12 and 14 for transmitting the infrared light. The filters 12 and 14 transmit infrared light with a first specific wavelength that is absorbed by alcohol and infrared light with a second specific wavelength that is absorbed by water vapor. The light receiving part 13 measures concentration of alcohol contained in a detecting object gas as an alcohol sensor by the infrared light with the first specific wavelength having transmitted through the filter 12. The light receiving part 15 measures humidity contained in the detecting object gas as a humidity sensor by the infrared light with the second specific wavelength having transmitted through the filter 14. Another humidity sensor 21 for measuring the humidity by a different detection principle from the measurement of the humidity by measuring the infrared light with the second specific wavelength is further provided at a path 20 for guiding the detecting object gas to the detection cell 16.

Description

  The present invention relates to a gas detection sensor that detects gas based on an absorption wavelength of light such as infrared rays, and more particularly to a gas detection sensor that is suitable for use in detecting the concentration of alcohol contained in exhaled breath.

  In response to the recent trend of drunk driving prevention, when the alcohol concentration in the exhalation of the vehicle driver is higher than the regulation value, a device that disables the start of the vehicle engine (hereinafter referred to as “alcohol interface”). "Rock".) Is attracting attention. The alcohol interlock is equipped with an alcohol detection sensor that measures the alcohol concentration contained in exhaled breath. The alcohol interlock determines whether the engine is permitted to start or not based on the measurement result of the alcohol detection sensor. Yes.

  As a gas sensor for detecting alcohol, sensors using various alcohol detection methods are known, and as one of them, an infrared absorption type gas sensor is known (for example, see Patent Document 1). The infrared absorption type gas sensor is a sensor that focuses on infrared rays in a wavelength band that is absorbed by alcohol among infrared rays, and measures alcohol concentration based on the degree of absorption of infrared rays in the wavelength band.

  High detection accuracy is required for gas sensors used for alcohol interlocks. In the case of an infrared absorption type gas sensor, there is a problem that the alcohol concentration cannot be measured accurately due to contamination inside the sensor due to the expiration of the detection target. That is, there is a problem that the accuracy of alcohol concentration measurement deteriorates because it cannot be determined whether the change in the amount of infrared light detected by the sensor is due to absorption by alcohol or due to contamination inside the sensor.

JP 2005-292009 A

  In order to solve the above-described problem and maintain high detection accuracy of the gas sensor, calibration of the sensor using a calibration gas whose concentration of a measurement target gas such as alcohol is known in advance is generally performed. As the calibration gas, for example, a gas cylinder filled with gas or a gas generated by heating a solid material is used.

  However, in the case of a gas sensor that is included in an alcohol interlock mounted on a vehicle and whose measurement object is alcohol, there is a problem that it is difficult to use a calibration gas due to the following restrictions.

  That is, when a solid material is heated to generate calibration alcohol, the solid material becomes a combustible material. In general, since it is not desirable to mount a combustible material on a vehicle, it has been difficult to use a gas sensor used for alcohol interlock as a calibration gas generation source.

  Furthermore, since alcohol is a volatile substance, the alcohol content of the solid material may change (decrease) due to the volatilization of the alcohol over time. That is, there is a problem in the long-term stability of the alcohol concentration contained in the calibration gas generated from the solid material, and it has been difficult to accurately calibrate the gas sensor.

  Further, when the calibration gas filled in the gas cylinder is used, the gas cylinder is filled with a high-pressure calibration gas. Generally, since it is not desirable to mount a high-pressure gas cylinder on a vehicle, it has been difficult to use a gas sensor used for alcohol interlock as a calibration gas generation source.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a gas detection sensor that can be mounted on a vehicle and can maintain measurement accuracy.

In order to achieve the above object, the present invention provides the following means.
The gas detection sensor of the present invention includes a detection cell including a light source that emits infrared light, a light receiving unit that receives the infrared light, and a filter that is disposed between the light source and the light receiving unit and transmits infrared light of a specific wavelength. The gas detection sensor provided, wherein the filter transmits infrared light having a first specific wavelength that is absorbed by alcohol and infrared light having a second specific wavelength that is absorbed by water vapor, and receives the light. The unit measures the concentration of alcohol contained in the gas to be detected as an alcohol sensor by measuring the infrared of the first specific wavelength that has passed through the filter, and measures the infrared of the second specific wavelength that has passed through the filter. By measuring the humidity contained in the gas to be detected as a humidity sensor, the path to guide the gas to be detected to the detection cell Wherein the other of the humidity sensor for measuring the humidity is further provided by the different detection principle and the measurement of the humidity by measuring the infrared of a specific wavelength.

  According to the gas detection sensor of the present invention, the alcohol concentration and humidity of the gas to be detected measured by the infrared absorption method using the light source, the light receiving unit, and the filter, and the gas to be detected measured by a method different from the infrared absorption method Can be obtained. Since humidity is measured by the infrared absorption method and a different method, it is possible to determine whether or not an error has occurred in the measurement value by the infrared absorption method by paying attention to the difference between the two values. Furthermore, by using the humidity measured by a method different from the infrared absorption method, the measurement value can be calibrated by the infrared absorption method, and the measurement accuracy can be maintained.

  Further, in order to calibrate the measurement value by the infrared absorption method using another humidity sensor having a different detection principle, the gas detection sensor is mounted on the vehicle as compared with the methods of Patent Documents 1 and 2 using the calibration gas. Becomes easy. In other words, there is no need to use components that may become obstacles when mounted on a vehicle, such as the flammable solid material described in Patent Document 1 or the high-pressure gas cylinder described in Patent Document 2.

  In the above invention, the alcohol concentration value measured by the light receiving unit is corrected based on the humidity value measured by the light receiving unit and the humidity value measured by the other humidity sensor. It is preferable that an operation unit for performing the above is further provided.

  Thus, by providing a calculating part in a gas detection sensor, the measured value of the calibrated alcohol concentration can be directly output from a gas detection sensor. In other words, measurement accuracy can be maintained with a single gas detection sensor.

  In the above invention, the calculation unit performs correction processing of the alcohol concentration value using the humidity value measured by the light receiving unit and the humidity value measured by the other humidity sensor as parameters. Is preferred.

  In this way, correction processing of the alcohol concentration value measured by the infrared absorption method is performed using the humidity value measured by the infrared absorption method and the humidity value measured by a method different from the infrared absorption method as parameters. By doing so, the correction process is performed accurately and the correction process is facilitated.

  For example, a calibration coefficient for calibrating the humidity value measured by the infrared absorption method based on the humidity value measured by a method different from the infrared absorption method is obtained, and the measurement is performed by the infrared absorption method using the calibration coefficient. A method of correcting the alcohol concentration value, a method of correcting the alcohol concentration value based on an arithmetic expression using both humidity values as parameters, and an alcohol concentration value using both humidity values as parameters. A method of performing correction processing using a table in which correction values of values are collected can be mentioned.

  In the above invention, the calculation unit compares the humidity value measured by the light receiving unit with the humidity value measured by the other humidity sensor, and compares the humidity value with two measured humidity values. If there is, it is preferable to perform correction processing of the alcohol concentration value.

  In this way, the humidity value measured by the infrared absorption method is compared with the humidity value measured by a method different from the infrared absorption method, and only when there is a difference between the two values, the infrared absorption method is used. By performing the correction process of the measured alcohol concentration value, it is possible to suppress the excessive correction process from being performed. In other words, it is possible to suppress an erroneous correction process in which the measured alcohol concentration value deviates from the actual alcohol concentration value.

  In other words, if there is no difference between the humidity value measured by the infrared absorption method and the humidity value measured by a method different from the infrared absorption method, the humidity value measured by the infrared absorption method is It is considered that errors due to filter contamination etc. are not included. It is considered that the error of alcohol concentration measured by the same infrared absorption method does not include an error due to filter fouling or the like. In this case, the accuracy of the measured alcohol concentration value can be maintained by not performing the correction process for removing the error included in the measured alcohol concentration value.

  According to the gas detection sensor of the present invention, the gas for calibration is measured by measuring the humidity of the gas to be detected by a method other than the infrared absorption method and the infrared absorption method, and by measuring the alcohol concentration of the gas to be detected by the infrared absorption method. Since the measured value of the alcohol concentration can be configured without using, there is an effect that it can be mounted on a vehicle and the measurement accuracy can be maintained.

It is a schematic diagram explaining the structure of the gas detection sensor which concerns on one Embodiment of this invention. It is a graph explaining the change with progress of time of the sensor output of humidity. It is a flowchart explaining the correction process in the calculating part of FIG. It is a graph explaining the relationship before and behind correction | amendment in the sensor output of alcohol concentration.

A gas detection sensor 1 according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram illustrating the configuration of a gas detection sensor 1 according to the present embodiment.
The gas detection sensor 1 of this embodiment is used for an alcohol interlock mounted on a vehicle such as an automobile, and measures the alcohol concentration contained in the breath (detected gas) of the driver of the vehicle. .

  As shown in FIG. 1, the gas detection sensor 1 includes a detection cell 10 that measures alcohol concentration and humidity contained in exhaled breath, a path 20 that guides exhalation to the detection cell 10, and a path humidity sensor that measures the humidity of the exhaled breath. (Other humidity sensor) 21, a calculation unit 22 that performs correction processing of the value of the alcohol concentration measured by the detection cell 10, and the detection cell 10, the path 20, the path humidity sensor 21, and the calculation unit 22 are housed inside. A housing 23 is mainly provided.

  The detection cell 10 includes a light source 11 that emits light including infrared rays, a first filter (filter) 12 and a first light receiving portion (light receiving portion) 13 that function as an infrared absorption alcohol sensor, and an infrared absorption humidity sensor. A second filter (filter) 14 and a second light receiving part (light receiving part) 15 that function as a light source 11, a first filter 12, a second filter 14, a first light receiving part 13 and a second light receiving part 15 are housed inside. The cell container 16 is mainly provided.

  The light source 11 is disposed inside the cell container 16 and irradiates light including infrared rays to the exhaled breath introduced into the internal space of the cell container 16. More specifically, the light source 11 is formed on the upper end surface (the upper end surface in FIG. 1) of the inner surface of the cell container 16 forming the internal space. The upper end surface is a reflecting surface that reflects light emitted from the light source 11 and is preferably formed in a parabolic shape having the light source 11 as a focal point. The “light” described in the present embodiment includes not only electromagnetic waves whose wavelength belongs to the visible light band but also electromagnetic waves that belong to the infrared wavelength band.

  The first filter 12 and the second filter 14 are wavelengths that are provided on a surface facing the light source 11 in the storage unit 17 that stores the first light receiving unit 13 and the second light receiving unit 15 therein, and transmit light having a specific wavelength. It is a selection filter. The storage unit 17 is a member disposed at the lower end of the internal space of the cell container 16, and light other than the light transmitted through the first filter 12 and the second filter 14 is transmitted to the first light receiving unit 13 and the first light receiving unit 13. 2 to prevent the light receiving unit 15 from receiving the light.

  The first filter 12 transmits infrared rays having a wavelength or wavelength band (first specific wavelength: hereinafter referred to as “wavelength”) that is absorbed by alcohol among infrared rays, and blocks light of other wavelengths and the like. It is. The first filter 12 is disposed at a position between the light source 11 and the first light receiving unit 13 in the storage unit 17.

  The 2nd filter 14 permeate | transmits infrared rays of the wavelength etc. (2nd specific wavelength) absorbed by water vapor | steam among infrared rays, and blocks | interrupts light of other wavelengths. The second filter 14 is disposed at a position between the light source 11 and the second light receiving unit 15 in the storage unit 17. As a material constituting the first filter 12 and the second filter 14, a known material can be used, and the kind thereof is not particularly limited.

  In addition, as a wavelength etc. absorbed by alcohol of infrared rays, a wavelength etc. absorbed by water vapor | steam, a well-known absorption wavelength etc. can be used, In this embodiment, the wavelength etc. limited in detail are not used. Absent.

  The first light receiving unit 13 measures the intensity of infrared light transmitted through the first filter 12, and measures how much the intensity of infrared light transmitted through the first filter 12 is weakened by alcohol contained in exhaled breath. Is. The second light receiving unit 15 measures the light intensity of the infrared light transmitted through the second filter 14, and measures how much the intensity of the infrared light transmitted through the second filter 14 is weakened by the water vapor contained in the exhalation. Is.

  In addition, as the 1st light-receiving part 13 and the 2nd light-receiving part 15, the well-known optical sensor which measures the intensity | strength etc. of light can be used, Especially the detection method of a light, and the structural feature of a sensor It is not limited.

  The cell container 16 houses therein the light source 11, the first filter 12, the first light receiving unit 13, the second filter 14, and the second light receiving unit 15 that constitute an infrared absorption alcohol sensor and a humidity sensor. Inside the cell container 16 is provided an internal space through which the driver's breath is guided. The cell container 16 is configured so that light is not inserted into the internal space from the outside. Further, a discharge hole 18 is provided on the side surface of the cell container 16 to connect the internal space to the outside and discharge the exhaled air guided to the internal space to the outside.

  The path 20 is a flow path that guides the driver's breath to the internal space of the cell container 16. The end of the path 20 on the cell container 16 side is connected to the cell container 16, and the opposite end protrudes from the housing 23 of the gas detection sensor 1. The portion of the path 20 that protrudes from the housing 23 may be connected to a mouthpiece that the driver gives when breathing in, or the portion may directly form a mouthpiece.

  The path humidity sensor 21 is a sensor that is provided in the middle of the path 20 and measures water vapor contained in exhaled air flowing through the path 20. The path humidity sensor 21 is a method other than a humidity measurement method using infrared absorption by water vapor, for example, a humidity measurement using a change in impedance or capacity due to moisture adsorption / desorption in a polymer film or ceramic sintered body. A sensor for measuring humidity using a method. The path humidity sensor 21 is desirably a small and highly reliable sensor because the number of installation locations is limited.

  Based on the sensor output IR, which is a humidity measurement signal output from the second light receiving unit 15, and the sensor output RT, which is a humidity measurement signal output from the path humidity sensor 21, the calculation unit 22 13 is a calculation unit that performs a correction process of the sensor output AL that is a measurement signal of the alcohol concentration output from 13. The calculation unit 22 is a microcomputer having a CPU (Central Processing Unit), ROM, RAM, input / output interface, and the like, and executes the above-described correction processing by executing a control program stored in a storage device such as a ROM. Etc. are executed. Details of the above-described correction processing will be described below.

Next, measurement of alcohol concentration and calibration of sensor output in the gas detection sensor 1 having the above-described configuration will be described with reference to FIGS.
When exhalation is blown into the path 20 of the gas detection sensor 1 by the driver, the exhalation is guided to the internal space of the detection cell 10 via the path 20. The path humidity sensor 21 measures the concentration of water vapor contained in the exhaled breath passing through the path 20, that is, the humidity of the exhaled breath, and outputs a sensor output RT corresponding to the humidity contained in the exhaled breath to the computing unit 22.

  In the detection cell 10, light including infrared rays is irradiated from the light source 11 to the exhaled breath guided to the internal space. Of the light emitted to the exhaled breath, a part of the wavelength or wavelength band light is absorbed by alcohol or water vapor contained in the exhaled breath.

  The first light receiving unit 13 measures the intensity of light transmitted through the first filter 12 among the light irradiated to the exhalation, in other words, the intensity of infrared rays such as a wavelength absorbed by the alcohol, and the alcohol contained in the exhalation. A sensor output AL corresponding to the concentration is output to the calculation unit 22. The second light receiving unit 15 measures the intensity of light that has passed through the second filter 14 out of the light irradiated to the exhalation, in other words, the intensity of infrared rays such as wavelengths absorbed by water vapor, and the humidity contained in the exhalation. The sensor output IR corresponding to is output to the calculation unit 22.

  Note that the values of the sensor output RT and the sensor output IR change over time as shown in FIG. That is, the sensor output IR, which is a measurement result based on the infrared absorption method, shows a tendency that the value decreases with time due to contamination of the second filter 14 or the like. On the other hand, the sensor output RT, which is the measurement result of the path humidity sensor 21 based on a method other than the infrared absorption method, tends to show substantially the same value regardless of the passage of time.

  As shown in FIG. 3, the calculation unit 22 to which the sensor output RT of the path humidity sensor 21 and the sensor output IR of the second light receiving unit 15, which are sensor outputs obtained by measuring the humidity included in the exhalation, are input. Correction processing is performed on the sensor output AL obtained by measuring the alcohol concentration contained in the.

  First, the calculation unit 22 compares the humidity sensor output RT and the sensor output IR, and determines whether or not the values of both outputs are different (S11). When it is determined that the value of the sensor output RT is equal to the value of the sensor output IR (in the case of NO), it is considered that the sensor output AL does not include an error due to contamination of the first filter 12, etc. Correction calculation for the sensor output AL is not performed.

  Note that the determination process of whether or not the values of the two outputs are different in S11 is not limited to the determination of whether or not the difference between the two outputs is a strict meaning, but the value in a sense that includes a predetermined allowable range. What performs the determination process of whether it is different is also included.

  When it is determined that the value of the sensor output RT is different from the value of the sensor output IR (in the case of YES), the calculation unit 22 corrects the correction coefficient that makes the value of the sensor output IR equal to the value of the sensor output RT. (Or a calibration coefficient) is obtained and a calculation process for correcting the value of the sensor output IR is performed (S12). Thereafter, the calculation unit 22 performs calculation processing for correcting (calibrating) the value of the sensor output AL using the correction coefficient obtained in S12 (S13).

  The relationship between the sensor output AL before correction and the sensor output AL after correction after the correction processing in S13 is as shown in FIG. That is, the sensor output AL before correction indicated by the dotted line in FIG. 4 becomes the sensor output AL after correction indicated by the solid line in FIG. 4 by the correction processing in S13.

  According to the gas detection sensor 1 having the above-described configuration, the alcohol concentration and humidity of exhaled breath measured by the light source 11, the first filter 12, the first light receiving unit 13, the second filter 14, and the second light receiving unit 15, and the path humidity. The humidity of the breath measured by the sensor 21 is obtained. Since humidity is measured by the infrared absorption method and a different method, it is possible to determine whether or not an error has occurred in the measurement value by the infrared absorption method by paying attention to the difference between the two values. Furthermore, by using the expiration humidity measured by the path humidity sensor 21, the measurement value can be calibrated by the infrared absorption method, and the measurement accuracy of the alcohol concentration by the gas detection sensor 1 can be maintained.

  Also, since the sensor output AL and sensor output IR are calibrated by the infrared absorption method using the sensor output RT of the path humidity sensor 21 having a different detection principle, it is compared with the methods of Patent Documents 1 and 2 using calibration gas. The gas detection sensor 1 can be easily mounted on the vehicle. In other words, there is no need to use components that may become obstacles when mounted on a vehicle, such as the flammable solid material described in Patent Document 1 or the high-pressure gas cylinder described in Patent Document 2.

  Since the calculation unit 22 is provided in the gas detection sensor 1, the measured value of the calibrated alcohol concentration can be directly output from the gas detection sensor 1. In other words, the measurement accuracy can be maintained with the gas detection sensor 1 alone.

  The sensor output IR value (humidity value) output from the second light receiving unit 15 and the sensor output RT value (humidity value) output from the path humidity sensor 21 are compared, and the difference between the two values is obtained. By performing the correction process of the value of the sensor output AL (value of the alcohol concentration) output from the first light receiving unit 13 only when there is, it is possible to suppress the excessive correction process from being performed. In other words, it is possible to suppress an erroneous correction process in which the alcohol concentration value measured by the first light receiving unit 13 deviates from the actual alcohol concentration value.

  That is, when there is no difference between the value of the sensor output IR output from the second light receiving unit 15 and the value of the sensor output RT output from the path humidity sensor 21, the value is output from the second light receiving unit 15. It is considered that the sensor output IR value does not include an error due to contamination of the second filter 14 or the like. It is considered that the error due to contamination of the first filter 12 is not included in the alcohol concentration value measured by the same infrared absorption method. In this case, the accuracy of the measured alcohol concentration value can be maintained by not performing the correction process for removing the error included in the measured alcohol concentration value.

  Correction of the value of the sensor output AL output from the first light receiving unit 13 by using the value of the sensor output IR output from the second light receiving unit 15 and the value of the sensor output RT output from the road humidity sensor 21 as parameters. By performing the process, the correction process can be performed accurately and the correction process can be easily performed.

  As in the present embodiment, a calibration coefficient (correction coefficient) for calibrating the value of the sensor output IR output from the second light receiving unit 15 based on the value of the sensor output RT output from the path humidity sensor 21 is obtained. A method of correcting the value of the sensor output AL output from the first light receiving unit 13 using the calibration coefficient may be used, or the sensor may be based on an arithmetic expression using the sensor output RT and the sensor output IR value as parameters. You may use the method of performing the arithmetic processing which correct | amends output AL, and the method of performing correction processing using the table which put together the correction value of the value of sensor output AL which used sensor output RT and sensor output IR value as a parameter, There is no particular limitation.

  Further, a series of correction processes compares the sensor output IR value (humidity value) output from the second light receiving unit 15 with the sensor output RT value (humidity value) output from the path humidity sensor 21. In addition to performing only when there is a difference between the two values, a mode in which correction processing is performed when a predetermined time has elapsed, and a mode in which correction processing is periodically performed at a predetermined timing are also possible. It is not limited.

  In addition, the sensor output AL of the alcohol concentration may be corrected using the sensor output of the humidity measured according to different detection principles as in the above-described embodiment, or the sensor output of oxygen or carbon dioxide may be used instead of the sensor output of humidity. Can be used to correct the sensor output AL of the alcohol concentration.

  DESCRIPTION OF SYMBOLS 1 ... Gas detection sensor, 10 ... Detection cell, 11 ... Light source, 12 ... 1st filter (filter), 13 ... 1st light-receiving part (light-receiving part), 14 ... 2nd filter (filter), 15 ... 2nd light-receiving part (Light receiving unit), 20... Path, 21... Path humidity sensor (other humidity sensor), 22.

Claims (4)

A gas detection sensor comprising a detection cell including a light source that emits infrared light, a light receiving unit that receives the infrared light, and a filter that is disposed between the light source and the light receiving unit and transmits infrared light of a specific wavelength. ,
The filter transmits infrared light having a first specific wavelength, which is a wavelength absorbed by alcohol, and infrared light having a second specific wavelength, which is a wavelength absorbed by water vapor,
The light receiving unit measures the concentration of alcohol contained in the gas to be detected as an alcohol sensor by measuring infrared light having the first specific wavelength that has passed through the filter, and infrared light having the second specific wavelength that has passed through the filter. By measuring the humidity contained in the detected gas as a humidity sensor,
The path for guiding the gas to be detected to the detection cell is further provided with another humidity sensor for measuring humidity based on a detection principle different from the measurement of the humidity by measuring the infrared of the second specific wavelength. Gas detection sensor.   An arithmetic unit for correcting the value of the alcohol concentration measured by the light receiving unit based on the humidity value measured by the light receiving unit and the humidity value measured by the other humidity sensor; The gas detection sensor according to claim 1, wherein the gas detection sensor is provided.   The arithmetic unit performs correction processing of the alcohol concentration value using the humidity value measured by the light receiving unit and the humidity value measured by the other humidity sensor as parameters. The gas detection sensor according to claim 2.   The arithmetic unit compares the humidity value measured by the light receiving unit with the humidity value measured by the other humidity sensor, and there is a difference between two measured humidity values. The gas detection sensor according to claim 2, wherein correction processing for the value of the alcohol concentration is performed.

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