JP2009300088A - Gas detector and secular change correcting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor which can reduce the complicatedness of calibration work without interrupting the detection of the concentration of a polarized gas in correcting the concentration of the gas, and a secular change correcting method. <P>SOLUTION: A sensor driving control part 11 repeatedly performs high temperature control for driving a catalytic combustion type gas sensor at a high temperature and low temperature control for driving the catalytic combustion type gas sensor 21 at a low temperature in a gas sensor device 1. A deterioration determining part 15 determines the deterioration state of the catalytic combustion type gas sensor 21 from the output difference between the output voltage of the catalytic combustion type gas sensor 21 during the low-temperature control and the output voltage of the catalytic combustion type gas sensor 21 during the high-temperature control in a case that the calculated concentration of the gas is a predetermined concentration or below. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a gas detection device and an aging correction method.

  Conventionally, a catalytic combustion type gas sensor that detects the concentration of a polar gas such as acetic acid or ethanol is known. In this contact combustion type gas sensor, the resistance value of platinum is changed by burning the polar gas on the catalyst, and the concentration of the polar gas is detected from the output voltage obtained based on this change. Yes. However, in such a contact combustion type gas sensor, polar gas is burned on the catalyst, and therefore, when used for a long period of time, the aging changes in the output voltage due to debris adhering to the catalyst surface. In addition, secular change is caused by silicone poisoning.

  In view of this, there has been proposed a gas detection device that corrects an output voltage that has changed over time so that the concentration of a polar gas can be accurately detected. The first apparatus is configured to detect the concentration of a calibration gas whose concentration has been clarified in advance, and to obtain a calibration calculation formula for correcting the detected concentration so as to match the clarified concentration. ing. In the subsequent detection, the first apparatus performs density detection while performing a correction operation using a calibration calculation formula (see Patent Document 1).

The second apparatus includes two sensors: a measurement sensor that detects the concentration of the gas to be detected that is a measurement target, and a reference measurement sensor that detects the concentration of the gas to be detected in the atmosphere. And the 2nd apparatus is the structure which correct | amends the output value of a measurement sensor with the output value of a reference | standard sensor on the assumption that both sensors change similarly aged (refer patent document 2).
JP 2006-194776 A JP-A-7-270315

  However, in the gas detection device described in Patent Document 1, calibration gas is required to obtain a calibration formula for correction, and work for obtaining the calibration formula is complicated and complicated. turn into. Furthermore, the gas detection device described in Patent Document 1 cannot be used to detect the gas concentration during the period until the calibration calculation formula is obtained, and is a gas detection device (for example, a gas alarm device) that needs to detect the concentration continuously. Is unsuitable.

  Further, the gas detection device described in Patent Document 2 is configured to perform correction based on the premise that both sensors change with time, so that a detection sensor and a reference sensor, such as a contact combustion gas sensor, are used. It is not possible to apply to a sensor having a sensor with a large change over time.

  The present invention has been made to solve such a conventional problem, and an object of the present invention is to reduce the complexity of the calibration work without interrupting the concentration detection of the polar gas in the concentration correction. It is an object of the present invention to provide a gas detection device and an aging correction method that can perform the above-described operation.

  The gas detection device of the present invention is a gas detection device provided with a catalytic combustion type gas sensor, and outputs a high level signal to drive the catalytic combustion type gas sensor at a high temperature and drives the catalytic combustion type gas sensor at a low temperature. Sensor driving control means for repeatedly performing low temperature control for outputting a low level signal, concentration calculating means for calculating the concentration of polar gas from the output of the catalytic combustion type gas sensor driven by the sensor driving control means, When the concentration calculated by the calculating means is equal to or lower than the predetermined concentration, the degradation of the catalytic combustion gas sensor is determined from the output difference between the output of the catalytic combustion gas sensor during low temperature control and the output of the catalytic combustion gas sensor during high temperature control. Deterioration determination means for determining the state, the concentration calculation means is contact combustion driven by the sensor drive control means The output of the gas sensor, and corrected according to the deterioration state of has been catalytic combustion type gas sensor determined by the deterioration determining means, and calculates the concentration of the polar gas.

  In the gas detection device of the present invention, the sensor drive control means is configured to perform combustion in a combustion period in which the polar gas adsorbed by driving the catalytic combustion gas sensor at a high temperature is burned, and in a combustion period in which the catalytic combustion gas sensor is driven at a low temperature. A temperature drop period for lowering the temperature of the contact combustion gas sensor whose temperature has increased, a base value detection period for driving the contact combustion gas sensor whose temperature has dropped during the temperature drop period at a high temperature, and a contact combustion type driven at a high temperature during the base value detection period The adsorption period in which the gas sensor is driven at a low temperature to adsorb the polar gas is repeated, and the deterioration judgment means outputs the difference between the output of the contact combustion gas sensor during the temperature drop period and the output of the contact combustion gas sensor during the base value detection period. It is preferable that

  Further, in the gas detection device of the present invention, the deterioration determination means includes an output in a steady state where the output of the catalytic combustion type gas sensor is stable during the temperature drop period, and a steady state where the output of the catalytic combustion type gas sensor is stable during the base value detection period. It is preferable that the difference from the output at is the output difference.

  Further, in the gas detection device of the present invention, in the deterioration determination step, the difference between the output difference, the output of the initial catalytic combustion gas sensor during the low temperature control, and the output of the initial catalytic combustion gas sensor during the high temperature control. It is preferable to determine the deterioration state of the catalytic combustion type gas sensor from the initial difference.

  In the gas detection device of the present invention, it is preferable that the initial difference is zero.

  The gas detection device of the present invention further includes an initial difference storage unit that stores an initial difference in advance, and the deterioration determination unit uses a contact combustion gas sensor based on the output difference and the initial difference stored in the initial difference storage unit. It is preferable to determine the deterioration state of the.

  Further, the aging correction method of the present invention is a aging correction method for a catalytic combustion type gas sensor, wherein the high temperature control for outputting a high level signal to drive the catalytic combustion type gas sensor at a high temperature and the catalytic combustion type gas sensor at a low temperature. A sensor driving control step for repeatedly performing low temperature control for outputting a low level signal for driving, and a concentration calculating step for calculating the concentration of the polar gas from the output of the catalytic combustion type gas sensor driven in the sensor driving control step; When the concentration calculated in the concentration calculation step is equal to or lower than a predetermined concentration, a contact combustion gas sensor is obtained from an output difference between the output of the contact combustion gas sensor during low temperature control and the output of the contact combustion gas sensor during high temperature control. A deterioration determination step for determining the deterioration state of the sensor, and in the concentration calculation step, the drive in the sensor drive control step is performed. It has been the output of the catalytic combustion type gas sensor, and corrected according to the deterioration state of the determined catalytic combustion type gas sensor in a deteriorated decision process, and calculates the concentration of the polar gas.

  In the aging correction method of the present invention, in the sensor drive control step, the combustion period in which the catalytic combustion gas sensor is driven at a high temperature to burn the adsorbed polar gas and the contact combustion gas sensor is driven at a low temperature to burn in the combustion period. The temperature drop period during which the temperature of the contact combustion gas sensor whose temperature has increased due to the temperature drop is decreased, the base value detection period during which the contact combustion gas sensor whose temperature has dropped during the temperature drop period is driven at a high temperature, and the contact combustion driven at a high temperature during the base value detection period The adsorption period in which polar gas is adsorbed by driving the gas sensor at low temperature is repeated, and in the deterioration judgment process, the difference between the output of the contact combustion gas sensor during the temperature drop period and the output of the contact combustion gas sensor during the base value detection period is output. It is preferable to use a difference.

  In the aging correction method of the present invention, in the deterioration determination step, the output in a steady state where the output of the catalytic combustion type gas sensor is stable during the temperature drop period and the steady state where the output of the catalytic combustion type gas sensor is stable during the base value detection period. The difference from the output in the state is preferably the output difference.

  Further, in the aging correction method of the present invention, in the deterioration determination step, the difference between the output difference, the output of the initial catalytic combustion gas sensor during the low temperature control, and the output of the initial catalytic combustion gas sensor during the high temperature control. It is preferable to determine the deterioration state of the catalytic combustion type gas sensor from a certain initial difference.

  In the aging correction method of the present invention, the initial difference is preferably set to zero.

  In the aging correction method of the present invention, in the deterioration determination step, it is preferable to read an initial difference stored in advance and determine a deterioration state of the catalytic combustion type gas sensor from the output difference and the stored initial difference. .

  According to the gas detection device of the present invention, when the concentration of the polar gas is equal to or lower than the predetermined concentration, the output difference between the output of the catalytic combustion type gas sensor during the low temperature control and the output of the catalytic combustion type gas sensor during the high temperature control. From this, the deterioration state of the catalytic combustion type gas sensor is determined. Here, when the concentration of the polar gas is less than or equal to the predetermined concentration, for example, when the concentration of the polar gas is nearly zero, the output is not affected by the concentration of the polar gas and is close to the initial setting value. Should be. However, when the contact combustion type gas sensor is deteriorated, the resistance value of the detection sensor among the contact combustion type gas sensors is lowered. As a result, a change occurs in the output difference. For this reason, it is possible to determine the deterioration state of the catalytic combustion type gas sensor from the output difference. In particular, since the concentration correction is performed by determining the deterioration state of the catalytic combustion type gas sensor while calculating the concentration of the polar gas, it is troublesome to use the calibration gas without interrupting the detection of the concentration of the polar gas. Does not occur. Therefore, in the concentration correction, it is possible to reduce the complexity of the calibration operation without interrupting the detection of the concentration of the polar gas.

  In addition, since the difference between the output of the catalytic combustion type gas sensor during the temperature drop period and the output of the catalytic combustion type gas sensor during the base value detection period is used as the output difference, from the output during the two periods that are not easily affected by the concentration of the polar gas, The deterioration state is determined, and the determination accuracy of the deterioration state can be improved.

  The difference between the output in the steady state where the output of the catalytic combustion type gas sensor is stable during the temperature drop period and the output in the steady state where the output of the catalytic combustion type gas sensor is stable during the base value detection period is defined as the output difference. For this reason, it is possible to prevent the use of the output in the transition period immediately after switching between the high temperature control and the low temperature control. Accordingly, it is possible to improve the determination accuracy of the deterioration state.

  In addition, since the deterioration state of the catalytic combustion type gas sensor is judged from the output difference and the initial difference, it is possible to know how much the output has changed from the state without the initial deterioration, and to improve the determination accuracy of the deterioration state. Can do.

  Further, since the initial difference is set to zero, it can be determined from the output difference only how much the output has changed from the state without the initial deterioration. Therefore, the processing load can be reduced in determining the deterioration state.

  Further, the initial difference is stored in advance, and the deterioration state of the catalytic combustion type gas sensor is determined from the output difference and the stored initial difference. This eliminates the need for circuit adjustment or the like for making the initial difference zero, and makes it possible to easily perform the initial setting of the gas detection device.

  Further, according to the aging correction method of the present invention, when the concentration of the polar gas is equal to or lower than the predetermined concentration, the output of the catalytic combustion gas sensor during the low temperature control and the output of the catalytic combustion gas sensor during the high temperature control From this output difference, the deterioration state of the catalytic combustion type gas sensor is determined. Here, when the concentration of the polar gas is less than or equal to the predetermined concentration, for example, when the concentration of the polar gas is nearly zero, the output is not affected by the concentration of the polar gas and is close to the initial setting value. Should be. However, when the contact combustion type gas sensor is deteriorated, the resistance value of the detection sensor among the contact combustion type gas sensors is lowered. As a result, a change occurs in the output difference. For this reason, it is possible to determine the deterioration state of the catalytic combustion type gas sensor from the output difference. In particular, since the concentration correction is performed by determining the deterioration state of the catalytic combustion type gas sensor while calculating the concentration of the polar gas, it is troublesome to use the calibration gas without interrupting the detection of the concentration of the polar gas. Does not occur. Therefore, in the concentration correction, it is possible to reduce the complexity of the calibration operation without interrupting the detection of the concentration of the polar gas.

  In addition, since the difference between the output of the catalytic combustion type gas sensor during the temperature drop period and the output of the catalytic combustion type gas sensor during the base value detection period is used as the output difference, from the output during the two periods that are not easily affected by the concentration of the polar gas, The deterioration state is determined, and the determination accuracy of the deterioration state can be improved.

  The difference between the output in the steady state where the output of the catalytic combustion type gas sensor is stable during the temperature drop period and the output in the steady state where the output of the catalytic combustion type gas sensor is stable during the base value detection period is defined as the output difference. For this reason, it is possible to prevent the use of the output in the transition period immediately after switching between the high temperature control and the low temperature control. Accordingly, it is possible to improve the determination accuracy of the deterioration state.

  In addition, since the deterioration state of the catalytic combustion type gas sensor is judged from the output difference and the initial difference, it is possible to know how much the output has changed from the state without the initial deterioration, and to improve the determination accuracy of the deterioration state. Can do.

  Further, since the initial difference is set to zero, it can be determined from the output difference only how much the output has changed from the state without the initial deterioration. Therefore, the processing load can be reduced in determining the deterioration state.

  Further, the initial difference is stored in advance, and the deterioration state of the catalytic combustion type gas sensor is determined from the output difference and the stored initial difference. This eliminates the need for circuit adjustment or the like for making the initial difference zero, and makes it possible to easily perform the initial setting of the gas detection device.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. FIG. 1 is a configuration diagram illustrating a gas detection device according to an embodiment of the present invention. As shown in FIG. 1, the gas detection device 1 detects the concentration of polar gas based on the sensor output, and includes a control unit 10 and a gas sensor unit 20 having a catalytic combustion type gas sensor 21. ing. Here, the polar gas is a gas in which the molecules have an electric dipole because the centers of gravity of the positive charge and the negative charge do not coincide with each other in the molecule, and are also simply referred to as a polar gas. Examples of such a polar gas include ethanol, acetic acid, formaldehyde, and toluene.

  The control unit 10 performs drive control of the gas sensor unit 20 and calculates a gas concentration, and is configured by, for example, an MPU (Microprocessor Unit). The control unit 10 includes a sensor drive control unit (sensor drive control unit) 11, a sensor output acquisition unit 12, a storage unit (initial difference storage unit) 13, a concentration calculation unit (concentration calculation unit) 14, and a deterioration determination unit ( Degradation determination means) 15.

  The sensor drive control unit 11 drives and controls the catalytic combustion type gas sensor 21, and repeatedly performs high temperature control and low temperature control. The high temperature control is a control for driving the catalytic combustion gas sensor 21 at a high temperature (for example, driving at about 400 ° C.). The low temperature control is a control for driving the catalytic combustion gas sensor 21 at a low temperature (for example, driving at about 200 ° C.). The sensor drive controller 11 is configured to output high-level and low-level drive pulses, thereby performing high-temperature control and low-temperature control.

  The sensor output acquisition unit 12 acquires information on the output voltage of the catalytic combustion gas sensor 21 that has been subjected to high temperature control and low temperature control by the sensor drive control unit 11. The sensor output acquisition unit 12 is connected to the concentration calculation unit 14 and the deterioration determination unit 15, and is configured to transmit the acquired output voltage information to the concentration calculation unit 14 and the deterioration determination unit 15.

  The storage unit 13 stores information necessary for calculating the gas concentration and information necessary for determining the deterioration state of the catalytic combustion type gas sensor 21. The concentration calculation unit 14 calculates the concentration of the polar gas based on the output voltage value of the catalytic combustion gas sensor 21 acquired by the sensor output acquisition unit 12. In calculating the concentration, the concentration calculation unit 14 uses the information stored in the storage unit 13 to obtain the concentration.

  Further, the deterioration determination unit 15 determines a deterioration state of the catalytic combustion type gas sensor 21. Here, in the contact combustion type gas sensor 21, burnout adheres to the catalyst surface due to long-term use, and the resistance value decreases and the output voltage changes. In addition, the resistance value decreases due to silicone poisoning, and the output voltage changes. The deterioration determination unit 15 determines such a deterioration state.

  The gas sensor unit 20 includes various resistors Rb, R1 to R3, a bridge current control unit 22, an instrumentation amplifier 23, and an A / D converter 24 in addition to the contact combustion type gas sensor 21.

  As shown in FIG. 1, the contact combustion type gas sensor 21 has two resistors Rr and Rs, and these resistors Rr and Rs together with the resistors R1 and R2 form a bridge circuit. The resistor R2 has one end connected to the power supply voltage side and the other end connected to the connection point A. The sensor resistor Rs is connected in series with the resistor R2, one end is connected to the connection point A, and the other end is connected to the bridge current control unit 22.

  The resistor R1 has one end connected to the power supply voltage side and the other end connected to the connection point B. The reference resistor Rr is connected in series with the resistor R 1, one end is connected to the connection point B, and the other end is connected to the bridge current control unit 22.

  Details of such a catalytic combustion type gas sensor 21 are shown in FIG. FIG. 2 is an external view showing details of the catalytic combustion type gas sensor 21 shown in FIG. 1, wherein (a) shows a top view and (b) shows a cross-sectional view. FIG. 2B shows a cross section taken along the line AA in FIG.

  A catalytic combustion type gas sensor 21 shown in FIG. 2A and FIG. 2B is a micro sensor manufactured using a semiconductor manufacturing process technology. In this contact combustion type gas sensor 21, an insulating film 21b made of a silicon oxide film, a silicon nitride film, a hafnium oxide film or the like is formed on a silicon wafer 21a, and a sensor resistance Rs and a reference resistance Rr are formed on the insulating film 21b. Is provided.

The sensor resistor Rs is a resistor made of platinum, and a catalyst layer 21s is provided so as to enclose the resistor. The catalyst layer 21 s is made of, for example, Pd / Al ₂ O ₃ made of alumina supporting palladium. The reference resistor Rr is a resistor made of platinum like the sensor resistor Rs, and an alumina layer 21r is provided so as to enclose the resistor.

  In addition, three bonding pads 21c to 21e are formed on the silicon wafer 21a. The first bonding pad 21c is a connection point A. The second bonding pad 21d is connected to the bridge current control unit 22 shown in FIG. Further, the third bonding pad 21e becomes the connection point B.

  Further, in the silicon wafer 21a, concave portions 21f and 21g are formed by anisotropic etching from the back surface at positions corresponding to the sensor resistance Rs and the reference resistance Rr. The catalytic combustion type gas sensor 21 has a small heat capacity due to the recesses 21f and 21g.

  Reference is again made to FIG. As shown in FIG. 1, the resistor Rb has one end connected to the sensor drive control unit 11 and the other end connected to the bridge current control unit 22. The bridge current control unit 22 controls the value of the current flowing through the catalytic combustion type gas sensor 21. The bridge current control unit 22 is configured to control the current value according to the drive pulse from the sensor drive control unit 11. Specifically, when a high level pulse voltage is input from the sensor drive control unit 11, the bridge current control unit 22 controls the contact combustion type gas sensor 21 to flow a current having a predetermined current value. Further, the bridge current control unit 22 performs control so that a current having a current value lower than a predetermined current value flows through the contact combustion gas sensor 21 when a low-level pulse voltage is applied from the sensor drive control unit 11.

  In this way, the sensor drive control unit 11 controls the amount of current flowing through the catalytic combustion gas sensor 21 to drive the catalytic combustion gas sensor 21 at a high temperature or a low temperature. In the present embodiment, a current is supplied to the contact combustion gas sensor 21 during low temperature driving. However, the present invention is not limited thereto, and a current may not be supplied during low temperature driving.

  The instrumentation amplifier 23 amplifies the difference between the voltages input to the non-inverting input terminal and the inverting input terminal. The instrumentation amplifier 23 has a non-inverting input terminal connected to the connection point A and an inverting input terminal connected to the connection point B. For this reason, the instrumentation amplifier 23 amplifies the voltage difference between the connection point A and the connection point B. The instrumentation amplifier 23 is connected to a variable resistor R3. The variable resistor R3 is adjusted so that the output from the instrumentation amplifier 23 becomes “0” when the concentration of the polar gas to be detected is “0”. The A / D converter 24 receives the analog voltage output from the instrumentation amplifier 23, performs A / D conversion, and outputs the analog voltage to the sensor output acquisition unit 12.

  Since it becomes such composition, gas sensor part 20 operates as follows. First, it is assumed that a low-level pulse voltage is output from the sensor drive control unit 11. As a result, the catalytic combustion type gas sensor 21 is driven at a low temperature to be lower than the combustion temperature of the polar gas, and the polar gas adheres to the catalyst layer 21s provided so as to surround the sensor resistance Rs.

  Thereafter, it is assumed that a high-level pulse voltage is output from the sensor drive control unit 11. Thereby, the catalytic combustion type gas sensor 21 is driven at a high temperature to reach the combustion temperature of the polar gas, and the polar gas adhering to the catalyst layer 21s is combusted. Moreover, the sensor resistance Rs is warmed with this combustion, and the resistance value of the sensor resistance Rs changes. As a result, the balance of the bridge circuit is lost, and the output from the instrumentation amplifier 23 shows a value corresponding to the molecular weight (ie, concentration) of the attached polar gas.

  Next, the basic operation of the control unit 10 will be described. FIG. 3 is a diagram illustrating an operation of the control unit 10 illustrated in FIG. In FIG. 3, the vertical axis represents the drive pulse from the sensor drive control unit 11, and the horizontal axis represents time.

  As shown in FIG. 3, the sensor drive control unit 11 first outputs a high-level pulse voltage to the bridge current control unit 22 only during the period A0. Thereby, the contact combustion type gas sensor 21 burns the attached polar gas. Next, the sensor drive control unit 11 outputs a low-level drive pulse to the bridge current control unit 22 for the period (adsorption period) b1. Thereby, polar gas adheres to the contact combustion type gas sensor 21. At this time, a number of gas molecules corresponding to the concentration of the polar gas adhere to the catalytic combustion type gas sensor 21. The period b1 is set to about 1 to 60 seconds depending on the gas type to be specified.

  Then, the sensor drive control unit 11 outputs a high-level pulse voltage to the bridge current control unit 22 during the period (combustion period) B1. Thereby, the gas molecules adhering to the contact combustion type gas sensor 21 burn. In particular, since gas molecules are attached in the number corresponding to the concentration, the value of the voltage acquired by the sensor output acquisition unit 12 changes according to the concentration. The sensor output acquisition unit 12 acquires the voltage VgB in this period B1. Here, the voltage VgB is a peak voltage in the period B1.

  Next, the sensor drive control unit 11 outputs a low-level drive pulse to the bridge current control unit 22 for a period (temperature decrease period) a1. As a result, the temperature of the catalytic combustion gas sensor 21 that has been warmed in period B1 and increased to about 400 ° C. is decreased to about 200 ° C. This period a1 is a time sufficient for the temperature of the catalytic combustion type gas sensor 21 (about 400 ° C.) to return to about 200 ° C., and is set to about 0.05 to 0.5 seconds.

  Thereafter, the sensor drive control unit 11 outputs a high-level pulse voltage to the bridge current control unit 22 for a period (base value detection period) A1. As a result, the catalytic combustion gas sensor 21 is driven at a high temperature in a state where the polar gas is not substantially adsorbed by the catalytic combustion gas sensor 21. The sensor output acquisition unit 12 acquires the voltage VgA obtained in this period A1 as a base voltage. Here, the voltage VgA is a peak voltage in the period A1.

  In the gas detection apparatus 1 according to the present embodiment, the period from the period b1 to the period A1 is set as the detection period, and these detection periods are repeated.

  Next, a density calculation method by the density calculation unit 14 will be described. 4A and 4B are diagrams for explaining a concentration calculation method by the concentration calculation unit 14 shown in FIG. 1, in which FIG. 4A shows the output voltage VgA obtained in the base value detection period A1, and FIG. 4B shows the combustion period B1. (C) shows the output voltage VgB-VgA. 4A to 4C, the vertical axis indicates the output voltage, and the horizontal axis indicates time.

  As shown in FIG. 4A, the output voltage VgA obtained in the base value detection period A1 is substantially the same when the concentration of the polar gas is 10 ppm and when it is 100 ppm. The output voltage VgA in the base value detection period A1 is obtained in a state in which almost no polar gas is attached to the catalytic combustion type gas sensor 21, and therefore shows almost the same value regardless of the concentration difference of 10 ppm and 100 ppm. .

  However, when the concentration is 1000 ppm, the output voltage VgA obtained in the base value detection period A1 is higher than those at 10 ppm and 100 ppm. This is because, since the concentration is as high as 1000 ppm, polar gas molecules adhere to the catalytic combustion type gas sensor 21 and burn during the base value detection period A1.

  Further, as shown in FIG. 4B, the output voltage VgB obtained in the combustion period B1 varies depending on the concentration of the polar gas. That is, the output voltage VgB shows a higher value as the concentration of the polar gas becomes higher.

  Further, as shown in FIG. 4C, the voltage VgB-VgA also differs depending on the concentration of the polar gas, and shows a higher value as the concentration of the polar gas increases. Here, the storage unit 13 stores an arithmetic expression or a map for calculating the concentration according to the value of VgB-VgA. For this reason, the concentration calculation unit 14 calculates the concentration based on the value of VgB−VgA shown in FIG. 4C and the arithmetic expression and map stored in the storage unit 13. Note that the concentration calculation unit 14 may calculate the concentration based on the integrated value of the output voltage.

  Next, a deterioration determination method by the deterioration determination unit 15 will be described. First, the deterioration judgment is based on the following principle. That is, if debris adheres to the catalyst layer 21 s of the catalytic combustion type gas sensor 21, the heat capacity increases, and the heat dissipation is further promoted during high temperature driving and the temperature reached by the sensor resistance Rs is lowered as compared with low temperature driving. When the ultimate temperature decreases in this way, the resistance value of platinum does not increase as the ultimate temperature decreases, and as a result, the resistance value of the sensor resistance Rs decreases. In addition, silicon oxide adheres to the catalyst layer 21s due to the silicone poisoning, and the resistance value of the sensor resistance Rs decreases as described above. For this reason, the following phenomenon occurs.

  FIG. 5 is a diagram for explaining a change in the output voltage due to deterioration of the catalytic combustion type gas sensor 21. First, as shown in FIG. 5, it is assumed that the transistor Q1 is installed instead of the bridge current control unit 22, and the voltage input to the base of the transistor Q1 is 0 V (low level) and the predetermined voltage E0 (high level). . It is further assumed that the bridge circuit is ideal and balanced, and that the catalytic combustion gas sensor 21 is not in a polar gas atmosphere.

  In this case, in the contact combustion gas sensor 21 that has not deteriorated, when a voltage of 0 V is applied to the base of the transistor Q1, the transistor Q1 is turned off. For this reason, the voltage at the connection points A and B is 0V, and the output voltage from the instrumentation amplifier 23 is 0V.

  On the other hand, when the predetermined voltage E0 is applied to the base of the transistor Q1, the transistor Q1 becomes conductive. Here, since the balance of the bridge circuit is adjusted and the catalytic combustion gas sensor 21 is not in a polar gas atmosphere, the output voltage from the instrumentation amplifier 23 is 0V. Accordingly, the voltage difference (output difference) between high temperature driving and low temperature driving is 0V.

  On the other hand, in the deteriorated catalytic combustion type gas sensor 21, the resistance value of the sensor resistance Rs is reduced, and the following occurs. First, it is assumed that a voltage of 0 V is applied to the base of the transistor Q1. In this case, the transistor Q1 is turned off, and the voltages at the connection points A and B are 0V. Therefore, the output voltage from the instrumentation amplifier 23 is 0V.

  On the other hand, when the predetermined voltage E0 is applied to the base of the transistor Q1, the transistor Q1 becomes conductive. Here, since the resistance value of the sensor resistance Rs is lowered, the partial pressure at the connection point A is lowered. On the other hand, the partial pressure at the connection point B is the same as in the case where there is no deterioration. Accordingly, a voltage lower than 0V is output from the instrumentation amplifier 23, and the voltage difference (output difference) between the high temperature driving and the low temperature driving becomes a value where the absolute value exceeds 0V.

  More specifically, when the catalytic combustion type gas sensor 21 is not deteriorated, the partial pressure at the connection point A during high temperature driving is Vcc · Rs / (R2 + Rs). On the other hand, the partial pressure at the connection point B is Vcc · Rr / (R1 + Rr). Here, since the bridge circuit is balanced, (Vcc · Rs / (R2 + Rs)) = (Vcc · Rr / (R1 + Rr)) and (Vcc · Rs / (R2 + Rs)) − (Vcc · Rr). / (R1 + Rr)) = 0. Therefore, the voltage difference between the high temperature driving and the low temperature driving is 0V.

  On the other hand, when the contact combustion type gas sensor 21 has deteriorated over time, the partial pressure at the connection point A during high temperature driving is Vcc · Rs ′ / (R2 + Rs ′). On the other hand, the partial pressure at the connection point B is Vcc · Rr / (R1 + Rr). Here, Rs ′ is a resistance value of the deteriorated sensor resistance Rs, and is a value lower than Rs. Therefore, (Vcc · Rs ′ / (R2 + Rs ′)) <(Vcc · Rr / (R1 + Rr)) is established. Therefore, (Vcc · Rs ′ / (R2 + Rs ′)) − (Vcc · Rr / (R1 + Rr)) = N (N is a number less than 0). Therefore, the voltage difference between the high temperature driving and the low temperature driving is an absolute value exceeding 0V.

  In particular, as is apparent from the equation (Vcc · Rs ′ / (R2 + Rs ′)), as the sensor resistance Rs further deteriorates and the value of Rs ′ decreases, (Vcc · Rs ′ / (R2 + Rs ′) ) Decreases and the absolute value of N increases. Therefore, the voltage difference (output difference) between the high temperature driving and the low temperature driving indicates the degree of deterioration of the catalytic combustion type gas sensor 21.

  The above voltage difference is obtained when the catalytic combustion type gas sensor 21 is not in a polar gas atmosphere. When the catalytic combustion type gas sensor 21 is in a polar gas atmosphere, the voltage difference is affected by the polar gas. Change. Therefore, the above theory is valid only when the concentration of the polar gas is zero or small.

  FIG. 6 is a diagram showing a waveform of an output voltage obtained under each condition. FIG. 6A shows a waveform when the initial (not deteriorated) catalytic combustion gas sensor 21 is not in a polar gas atmosphere. (B) has shown the waveform in case the initial catalytic combustion type gas sensor 21 exists in the polar gas atmosphere of a specific density | concentration. Further, (c) shows a waveform when the catalytic combustion gas sensor 21 deteriorated to some extent is not in the polar gas atmosphere, and (d) shows a waveform when the catalytic combustion gas sensor 21 deteriorated to some extent is in the polar gas atmosphere of a specific concentration. The waveform in a certain case is shown. Further, (e) shows a waveform when the further deteriorated catalytic combustion type gas sensor 21 is not in the polar gas atmosphere, and (f) shows a waveform when the further deteriorated catalytic combustion type gas sensor 21 is in the polar gas atmosphere having a specific concentration. The waveform in the case of is shown. In FIG. 6, the vertical axis represents the output voltage, and the horizontal axis represents time. Moreover, the scale of the vertical axis | shaft of FIG. 6 (a), FIG.6 (c), and FIG.6 (e) is the same, and the vertical axis | shaft of FIG.6 (b), FIG.6 (d), and FIG.6 (f). The scales are the same, but the scales of the vertical axes of these two are different. Further, it is assumed that the balance of the bridge circuit is adjusted by the variable resistor R3 and the initial difference is 0V.

  First, as shown in FIG. 6A, since the catalytic combustion type gas sensor 21 is not in a polar gas atmosphere, the output voltage is in the adsorption period b1, the combustion period B1, the temperature drop period a1, and the base value detection period A1. The specific voltage E1 is obtained. Since the catalytic combustion type gas sensor 21 is not deteriorated, the output voltage in a polar gas atmosphere having a specific concentration is compared with that in FIGS. 6D and 6F, as shown in FIG. Indicates a large value.

  Further, as shown in FIG. 6C, when the catalytic combustion type gas sensor 21 has deteriorated to some extent, and when it is not in a polar gas atmosphere, as described above, the output voltage is less than the specific voltage E1 during high temperature driving. Become. Therefore, the output voltage shows the specific voltage E1 in the adsorption period b1 and the temperature decrease period a1, but shows a value lower than the specific voltage E1 in the combustion period B1 and the base value detection period A1. Since the catalytic combustion type gas sensor 21 has deteriorated to some extent, the output voltage in a polar gas atmosphere having a specific concentration is smaller than that in FIG. 6B, as shown in FIG. 6D. .

  Further, as shown in FIG. 6 (e), when the contact combustion type gas sensor 21 is deteriorated, when it is not in a polar gas atmosphere, as described above, the output voltage is less than the specific voltage E1 during high temperature driving. Become. In addition, the output voltage is lower than the value shown in FIG. Therefore, as shown in FIG. 6 (e), the output voltage shows the specific voltage E1 in the adsorption period b1 and the temperature decrease period a1, but in the combustion period B1 and the base value detection period A1, the output voltage is shown in FIG. 6 (c). The voltage value is lower than the indicated value. Since the catalytic combustion type gas sensor 21 is further deteriorated, the output voltage in a polar gas atmosphere having a specific concentration is smaller than that shown in FIG. 6 (d), as shown in FIG. 6 (f). .

  The deterioration determination unit 15 determines the degree of deterioration of the catalytic combustion type gas sensor 21 based on the voltage change shown in FIGS. 6 (a), 6 (c) and 6 (e). That is, the deterioration determination unit 15 determines the deterioration state of the contact combustion type gas sensor 21 from the output difference between the output voltage of the contact combustion type gas sensor 21 during low temperature control and the output voltage of the contact combustion type gas sensor 21 during high temperature control. To do.

  The deterioration determining unit 15 determines deterioration when the concentration of the polar gas is zero or small. As described above, when the concentration is high, the output voltage as shown in FIG. 6A, FIG. 6C, and FIG. An output voltage as shown in FIG. 6B, FIG. 6D, and FIG. 6F is obtained. For this reason, the deterioration determination unit 15 cannot determine deterioration. Therefore, the deterioration determination unit 15 performs the deterioration determination only when the concentration calculated by the concentration calculation unit 14 is equal to or lower than the predetermined concentration.

  Further, when the deterioration determination unit 15 obtains the output voltage as shown in FIGS. 6A, 6C, and 6E, the deterioration state is determined according to the stored contents stored in the storage unit 13. to decide. FIG. 7 is a diagram showing the storage contents stored in the storage unit 13 shown in FIG. In FIG. 7, the vertical axis represents sensor sensitivity (degraded state), and the horizontal axis represents the voltage difference. As illustrated in FIG. 7, the storage unit 13 stores a map indicating the correlation between the deterioration state and the voltage difference. For this reason, when determining the voltage difference between the high temperature driving and the low temperature driving, the deterioration determining unit 15 determines the deterioration state with reference to a map as shown in FIG.

  In addition, as shown in FIG. 1, the density calculation unit 14 includes a correction unit 14a. The correction unit 14 a corrects the output voltage obtained from the catalytic combustion gas sensor 21 according to the deterioration state determined by the deterioration determination unit 15. In other words, when the deterioration determination unit 15 determines the deterioration state, the concentration calculation unit 14 calculates the concentration based on the output voltage corrected by the correction unit 14a.

  FIG. 8 is a diagram showing another example of the stored contents stored in the storage unit 13 shown in FIG. In the example shown in FIG. 7, an example is shown in which the voltage difference between the low temperature driving and the high temperature driving of the catalytic combustion gas sensor 21 that is not deteriorated is 0 V (that is, the initial difference is 0 V). However, the present invention is not limited to this, and as shown in FIG. 8, the voltage difference between the low temperature driving and the high temperature driving of the non-degraded catalytic combustion gas sensor 21 is 90 mV (that is, the initial difference is 90 mV). May be indicated.

  In this case, as shown in FIG. 8A, the storage unit 13 stores a map in which the sensor sensitivity is 100% when the voltage difference is 90 mV in advance. The storage unit 13 stores that the initial voltage difference of the catalytic combustion gas sensor 21 is 90 mV, and the deterioration determination unit 15 subtracts 90 mV from the voltage difference between the high temperature driving and the low temperature driving, The deterioration state may be determined from the value obtained by subtraction and the map as shown in FIG.

  In addition, the storage unit 13 may not store a map, and may store an arithmetic expression obtained by linear approximation of map data as shown by a broken line in FIG. That is, as illustrated in FIG. 8B, the storage unit 13 may store an arithmetic expression y = −1.9126x + 268.5 when the sensor sensitivity is y and the voltage difference is x. Good. In this case, the deterioration determination unit 15 determines the deterioration state from the arithmetic expression approximated by a straight line. In addition, the storage unit 13 may store a logarithmically approximated arithmetic expression in order to improve accuracy over a linearly approximated arithmetic expression. That is, as shown in FIG. 8C, the storage unit 13 stores an arithmetic expression y = −215.08Ln (x) +1066.4 when the sensor sensitivity is y and the voltage difference is x. You may keep it. In this case, the deterioration determination unit 15 determines the deterioration state from a logarithmically approximated arithmetic expression.

  FIG. 9 is a diagram illustrating an output voltage after correction by the arithmetic expression approximated by the straight line and the arithmetic expression approximated by the logarithm shown in FIG. When the deterioration determination unit 15 determines the deterioration state, the correction unit 14a corrects the output voltage of the catalytic combustion gas sensor 21 according to the deterioration state and calculates the concentration, thereby correcting the concentration.

  For example, when the deterioration determination unit 15 determines that the sensor sensitivity is 60%, the correction unit 14a corrects (VgB−VgA) by an arithmetic expression of (VgB−VgA) /0.60, The density is calculated from the obtained value. As shown in FIG. 9, the corrected value is closer to 1300 mV, which is the sensor output when the sensor sensitivity is 100%, rather than the output voltage is not corrected, and it can be seen that it can cope with the deterioration state.

  Further, the deterioration determination unit 15 includes the output voltage Va of the catalytic combustion gas sensor 21 during the temperature decrease period a1 and the output voltage VA of the catalytic combustion gas sensor 21 during the base value detection period A1 among the periods shown in FIG. From this difference, it is preferable to determine the deterioration state of the catalytic combustion type gas sensor 21. This is because the output voltage obtained in the above two periods is not easily affected by the concentration of the polar gas.

  In particular, as shown in FIG. 6, the deterioration determination unit 15 stabilizes the output voltage Va in a steady state in which the output voltage of the catalytic combustion gas sensor 21 in the temperature decrease period a1 is stable and the output voltage in the base value detection period A1. It is preferable to determine the deterioration state of the catalytic combustion type gas sensor 21 from the difference from the output voltage VA of the catalytic combustion type gas sensor 21 in the steady state. This is to prevent the use of the output voltage in the transition period immediately after the temperature drop period a1 and the base value detection period A1.

  Next, a method for correcting aging of the gas detection device 1 according to this embodiment will be described. FIG. 10 is a flowchart showing the aging correction method according to this embodiment. As shown in FIG. 10, first, the control unit 10 determines whether or not the initial difference has been calculated (S1). When it is determined that the initial difference has not been calculated (S1: NO), the control unit 10 outputs the output voltage VA of the catalytic combustion gas sensor 21 in the steady state where the output voltage of the base value detection period A1 is stable, and the temperature decrease period a1. The output voltage Va in a steady state where the output voltage of the catalytic combustion type gas sensor 21 is stable is acquired n times (n is an integer of 2 or more) (S2).

  And the control part 10 calculates n times average value of VA-Va, and makes this memorize | store in the memory | storage part 13 as an initial difference (S3). Then, the process proceeds to step S4. The acquisition of the initial difference is completed by the processing of step S1 to step S3. The initial difference may be set to “0” by adjusting the resistances R1 and R2 to adjust the balance of the bridge circuit, and the processing of Steps S1 to S3 may not be executed. In particular, when VA is increased or Va is decreased, the resistor R1 may be increased or the resistor R2 may be decreased.

  If it is determined that the initial difference has been calculated (S1: YES), the sensor output acquisition unit 12 acquires the peak voltage VgB in the combustion period B1 (S4). Next, the sensor output acquisition unit 12 acquires the steady-state output voltage Va in the temperature decrease period a1 (S5). Thereafter, the sensor output acquisition unit 12 acquires the peak voltage VgA in the base value detection period A1 (S4). Next, the sensor output acquisition unit 12 detects the steady-state output voltage VA in the base value detection period A1 (S7).

  Thereafter, the control unit 10 determines whether or not the deterioration state of the catalytic combustion gas sensor 21 has been determined (S8). If it is determined that the deterioration state has not been determined (S8: NO), the process proceeds to step S10. On the other hand, when it is determined that the deterioration state has been determined (S8: YES), the correction unit 14a corrects the peak voltages VgB and VgA (S9). And the density | concentration calculation part 14 calculates a density | concentration from the arithmetic expression of VgB-VgA, and the memory content memorize | stored in the memory | storage part 13 (S10).

  Next, the deterioration determination unit 15 determines whether or not the concentration calculated in step S10 is equal to or lower than a predetermined concentration (S11). Here, the predetermined density is a numerical value determined by the deterioration determination accuracy, and the smaller the value, the higher the deterioration determination accuracy.

  If it is determined that the concentration calculated in step S10 is not less than the predetermined concentration (S11: NO), the process proceeds to step S4. On the other hand, when it is determined that the concentration calculated in step S10 is equal to or lower than the predetermined concentration (S11: YES), the deterioration determination unit 15 determines from the arithmetic expression VA-Va and the stored content stored in the storage unit 13. Judge the deterioration state. Then, the degradation determination unit 15 updates the determined degradation state information (S13). Thereafter, the process proceeds to step S4.

  In addition, the flowchart shown in FIG. 10 is repeatedly performed until the power supply of the gas detection apparatus 1 is turned off. If the power is turned on again after the power is turned off, the process is executed from step S4.

  Thus, according to the gas detector 1 and the aging correction method according to the present embodiment, when the concentration of the polar gas is equal to or lower than the predetermined concentration, the output voltage of the catalytic combustion gas sensor 21 during the low temperature control The deterioration state of the catalytic combustion type gas sensor 21 is determined from the output difference from the output voltage of the catalytic combustion type gas sensor 21 during the high temperature control. Here, when the concentration of the polar gas is equal to or lower than the predetermined concentration, for example, when the concentration of the polar gas is nearly zero, the difference in output voltage is not affected by the concentration of the polar gas, and the initial setting is not affected. Should be close to the value. However, when the catalytic combustion type gas sensor 21 is deteriorated, the resistance value of the sensor resistance Rs of the catalytic combustion type gas sensor 21 becomes low. As a result, a change occurs in the output difference. For this reason, the deterioration state of the catalytic combustion type gas sensor 21 can be determined from the output difference. In particular, since the concentration correction is performed by determining the deterioration state of the catalytic combustion type gas sensor 21 while calculating the concentration of the polar gas, it is complicated to use the calibration gas without interrupting the detection of the concentration of the polar gas. Will not occur. Therefore, in the concentration correction, it is possible to reduce the complexity of the calibration operation without interrupting the detection of the concentration of the polar gas.

  Further, since the difference between the output voltage Va of the catalytic combustion type gas sensor 21 in the temperature decrease period a1 and the output voltage VA of the catalytic combustion type gas sensor 21 in the base value detection period A1 is set as an output difference, the concentration of the polar gas is affected. The deterioration state is determined from the outputs in two periods that are difficult to receive, and the determination accuracy of the deterioration state can be improved.

  Further, an output voltage Va in a steady state where the output voltage of the catalytic combustion type gas sensor 21 is stable during the temperature drop period a1, and an output voltage VA in a steady state where the output voltage of the contact combustion type gas sensor 21 is stable during the base value detection period A1. Difference (VA−Va) is defined as an output difference. For this reason, it is possible to prevent the use of the output in the transition period immediately after switching between the high temperature control and the low temperature control. Accordingly, it is possible to improve the determination accuracy of the deterioration state.

  Further, since the deterioration state of the catalytic combustion type gas sensor 21 is determined from the output difference and the initial difference, it is possible to know how much the output has changed from the state without the initial deterioration, and improve the determination accuracy of the deterioration state. be able to.

  Further, since the initial difference is set to zero, it can be determined from the output difference only how much the output has changed from the state without the initial deterioration. Therefore, the processing load can be reduced in determining the deterioration state.

  Further, the initial difference is stored in advance, and the deterioration state of the catalytic combustion type gas sensor 21 is determined from the output difference and the stored initial difference. For this reason, the circuit adjustment for making an initial difference zero is unnecessary, and the initial setting of the gas detection apparatus 1 can be performed easily.

  As described above, the present invention has been described based on the embodiment, but the present invention is not limited to the above embodiment, and may be modified without departing from the gist of the present invention. For example, in the above-described embodiment, the contact combustion type gas sensor 21 includes the reference resistor Rr and the sensor resistor Rs connected in series, and the resistor R1 and the resistor R2 connected in series. Rr may be connected in series, and resistor R2 and sensor resistor Rs may be connected in series.

  In this embodiment, the determination of deterioration is performed when the concentration of the polar gas is equal to or lower than the predetermined concentration. However, the present invention is not limited to this, and even if the concentration of the polar gas exceeds the predetermined concentration, the concentration is determined. A plurality of (for each density) maps and formulas may be prepared so as to correspond to each density calculated by the calculation unit 14, and the deterioration determination may be performed.

It is a block diagram which shows the gas detection apparatus which concerns on embodiment of this invention. It is an external view which shows the detail of the contact combustion type gas sensor shown in FIG. 1, (a) shows the top view, (b) has shown sectional drawing. It is a figure which shows operation | movement of the control part shown in FIG. 2A and 2B are diagrams for explaining a concentration calculation method by a concentration calculation unit shown in FIG. 1, in which FIG. 1A shows an output voltage VgA obtained in a base value detection period, and FIG. 2B shows an output voltage VgB obtained in a combustion period. (C) shows the output voltage VgB-VgA. It is a figure explaining the change of the output voltage by deterioration of a contact combustion type gas sensor. It is a figure which shows the waveform of the output voltage obtained in each condition, Comprising: (a) shows a waveform when an initial (not deteriorated) catalytic combustion type gas sensor is not in a polar gas atmosphere, (b) shows The waveform when the initial catalytic combustion type gas sensor is in a polar gas atmosphere having a specific concentration is shown. (C) shows the waveform when the catalytic combustion type gas sensor deteriorated to some extent is not in the polar gas atmosphere. ) Shows the waveform when the catalytic combustion gas sensor deteriorated to some extent is in a polar gas atmosphere of a specific concentration, and (e) shows the waveform when a further deteriorated catalytic combustion gas sensor is not in the polar gas atmosphere. , (F) shows a waveform when the further deteriorated catalytic combustion type gas sensor is in a polar gas atmosphere having a specific concentration. It is a figure which shows the memory content memorize | stored in the memory | storage part shown in FIG. It is a figure which shows the other example of the memory content memorize | stored in the memory | storage part shown in FIG. It is a figure which shows the output voltage after correction | amendment by the arithmetic expression by which the linear approximation shown in FIG. 8 and the arithmetic expression by logarithm approximation were carried out. It is a flowchart which shows the secular change correction method which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Gas detection apparatus 10 ... Control part 11 ... Sensor drive control part (sensor drive control means)
12 ... Sensor output acquisition unit 13 ... Storage unit (initial difference storage means)
14 ... Density calculation section (concentration calculation means)
14a ... Correction unit 15 ... Degradation judgment unit (degradation judgment means)
DESCRIPTION OF SYMBOLS 20 ... Gas sensor part 21 ... Contact combustion type gas sensor 21a ... Silicon wafer 21b ... Insulating film 21c-21e ... Bonding pad 21f, 21g ... Recess 21s ... Catalyst layer 21r ... Alumina layer 22 ... Bridge current control part 23 ... Instrumentation amplifier 24 ... A / D converter Rs ... sensor resistance Rr ... reference resistance R1-R3, Rb ... resistance Q1 ... transistor b1 ... adsorption period B1 ... combustion period a1 ... temperature drop period A1 ... base value detection period

Claims (12)

A gas detection device including a catalytic combustion type gas sensor,
Sensor drive control means for repeatedly performing high temperature control for outputting a high level signal for driving the catalytic combustion gas sensor at a high temperature and low temperature control for outputting a low level signal for driving the contact combustion gas sensor at a low temperature;
Concentration calculation means for calculating the concentration of the polar gas from the output of the catalytic combustion gas sensor driven by the sensor drive control means;
When the concentration calculated by the concentration calculating means is equal to or lower than a predetermined concentration, from the output difference between the output of the catalytic combustion gas sensor during the low temperature control and the output of the catalytic combustion gas sensor during the high temperature control, Deterioration determining means for determining a deterioration state of the catalytic combustion type gas sensor,
The concentration calculating means corrects the output of the catalytic combustion type gas sensor driven by the sensor drive control means in accordance with the deterioration state of the catalytic combustion type gas sensor determined by the deterioration determining means. A gas detector characterized by calculating a concentration. The sensor drive control means is a contact combustion type in which the catalytic combustion type gas sensor is driven at a high temperature to burn the adsorbed polar gas, and the catalytic combustion type gas sensor is driven at a low temperature to increase the temperature by combustion in the combustion period. A temperature drop period for lowering the temperature of the gas sensor, a base value detection period for driving the catalytic combustion gas sensor whose temperature has dropped during the temperature drop period at a high temperature, and the contact combustion gas sensor driven at a high temperature during the base value detection period. Repeat the adsorption period to adsorb polar gas by driving at low temperature,
The said deterioration judgment means makes the difference of the output of the said contact combustion type gas sensor in the said temperature fall period and the output of the said contact combustion type gas sensor in the said base value detection period an output difference. Gas detection device. The deterioration determining means is a difference between an output in a steady state where the output of the catalytic combustion type gas sensor is stable during the temperature drop period and an output in a steady state where the output of the catalytic combustion type gas sensor is stable during the base value detection period. The gas detection device according to claim 2, wherein the difference is an output difference. The deterioration determining means is based on the output difference, an initial difference which is a difference between an initial contact combustion gas sensor output during the low temperature control and an initial contact combustion gas sensor output during the high temperature control. The gas detection device according to any one of claims 1 to 3, wherein a deterioration state of the catalytic combustion type gas sensor is determined. The gas detection device according to claim 4, wherein the initial difference is zero. An initial difference storage means for storing the initial difference in advance;
The gas detection according to claim 4, wherein the deterioration determination unit determines a deterioration state of the catalytic combustion type gas sensor from the output difference and the initial difference stored by the initial difference storage unit. apparatus. A method for correcting aging of a catalytic combustion type gas sensor,
A sensor drive control step for repeatedly performing a high temperature control for outputting a high level signal to drive the catalytic combustion gas sensor at a high temperature and a low temperature control for outputting a low level signal to drive the contact combustion gas sensor at a low temperature;
A concentration calculating step of calculating the concentration of the polar gas from the output of the catalytic combustion type gas sensor driven in the sensor driving control step;
When the concentration calculated in the concentration calculation step is equal to or lower than a predetermined concentration, from the output difference between the output of the catalytic combustion gas sensor during the low temperature control and the output of the catalytic combustion gas sensor during the high temperature control, A deterioration determining step of determining a deterioration state of the catalytic combustion type gas sensor,
In the concentration calculation step, the output of the catalytic combustion type gas sensor driven in the sensor drive control step is corrected according to the deterioration state of the catalytic combustion type gas sensor determined in the deterioration determination step, An aging correction method characterized by calculating a concentration. In the sensor drive control step, the catalytic combustion type gas sensor is driven at a high temperature to burn a polar gas adsorbed, and the catalytic combustion type gas sensor is driven at a low temperature to increase the temperature by combustion in the combustion period. A temperature drop period for lowering the temperature of the gas sensor, a base value detection period for driving the catalytic combustion gas sensor whose temperature has dropped during the temperature drop period at a high temperature, and the contact combustion gas sensor driven at a high temperature during the base value detection period. Repeat the adsorption period to adsorb polar gas by driving at low temperature,
The difference between the output of the catalytic combustion type gas sensor in the temperature decrease period and the output of the catalytic combustion type gas sensor in the base value detection period is set as an output difference in the deterioration determination step. Correction method for aging. In the deterioration determination step, a difference between an output in a steady state where the output of the catalytic combustion type gas sensor is stable during the temperature decrease period and an output in a steady state where the output of the catalytic combustion type gas sensor is stable during the base value detection period. The aging deterioration correction method according to claim 8, wherein the difference is an output difference. In the deterioration determination step, from the output difference, the initial difference that is the difference between the initial contact combustion gas sensor output during the low temperature control and the initial contact combustion gas sensor output during the high temperature control, The method for correcting aging deterioration according to any one of claims 7 to 9, wherein the deterioration state of the catalytic combustion type gas sensor is determined. The aging deterioration correction method according to claim 10, wherein the initial difference is zero. The deterioration determination step reads the initial difference stored in advance, and determines the deterioration state of the catalytic combustion type gas sensor from the output difference and the stored initial difference. Aged deterioration correction method described.

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