WO2017212950A1 - Gas sensor control device - Google Patents

Gas sensor control device Download PDF

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Publication number
WO2017212950A1
WO2017212950A1 PCT/JP2017/019729 JP2017019729W WO2017212950A1 WO 2017212950 A1 WO2017212950 A1 WO 2017212950A1 JP 2017019729 W JP2017019729 W JP 2017019729W WO 2017212950 A1 WO2017212950 A1 WO 2017212950A1
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current
gas
humidity
voltage
sensor
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PCT/JP2017/019729
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French (fr)
Japanese (ja)
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中江　誠
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株式会社デンソー
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/406—Cells and probes with solid electrolytes
    • G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases
    • G01N27/41—Oxygen pumping cells
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/416—Systems

Definitions

  • the present disclosure relates to a gas sensor control device used for a vehicle or the like.
  • oxygen sensors that detect oxygen concentration in exhaust gas are known as sensors used in automobiles.
  • the oxygen sensor detects the oxygen concentration and thus detects the air-fuel ratio of the exhaust gas by utilizing the fact that the magnitude of the current flowing through the sensor element changes according to the oxygen concentration in the exhaust gas.
  • the detection result of the air-fuel ratio is used in an air-fuel ratio control system constituted by an engine ECU or the like, and the stoichiometric combustion control for feedback control of the air-fuel ratio in the vicinity of the stoichiometric (theoretical air-fuel ratio) or the air-fuel ratio in a predetermined lean region.
  • Lean combustion control with feedback control is realized.
  • the sensor output of an oxygen sensor changes due to the influence of humidity in the air atmosphere.
  • the oxygen partial pressure in the atmosphere is lower than in a low humidity state, so the number of oxygen molecules detected by the oxygen sensor is substantially reduced and the sensor output Decreases.
  • the sensor output error caused by the influence of humidity is reduced when the sensor is calibrated using the atmosphere. That is, in a state where the fuel supply of the engine is stopped and the exhaust in the exhaust pipe is completely replaced with the atmosphere, the humidity of the atmosphere is detected, and the sensor output is corrected according to the humidity of the atmosphere.
  • the timing of atmospheric humidity detection is limited when the fuel supply is stopped, that is, when the fuel is cut. Since the atmosphere has a known oxygen concentration, the humidity of the sensor output can be corrected by filling the exhaust pipe with the atmosphere when the fuel is cut. It should be noted that a certain amount of time is required until the exhaust in the exhaust pipe is completely replaced with the atmosphere when the fuel is cut. Therefore, atmospheric humidity detection cannot be performed every time a fuel cut is performed, and the opportunities for humidity detection are more limited. On the other hand, the atmospheric humidity may change during the drive cycle, and it is desirable to frequently detect the atmospheric humidity in order to increase the accuracy of detection by the gas sensor.
  • the present disclosure has been made to solve the above-described problems, and has as its main purpose to provide a gas sensor control device that can increase the chance of humidity detection by a sensor and appropriately perform gas concentration measurement.
  • the gas sensor control device of the present disclosure includes a solid electrolyte layer and at least a pair of electrodes sandwiching the solid electrolyte layer, and a first electrode to which a gas to be detected, which is exhaust gas or a mixed gas including exhaust gas, is guided to one of the pair of electrodes.
  • the sensor element is the second electrode provided in the reference gas chamber for introducing the reference gas, and the limit current corresponding to the concentration of the specific gas in the detected gas is output by applying a voltage in the limit current region.
  • the first current that is output when a voltage is applied in the limit current region and the water decomposition on the higher voltage side than the limit current region under a predetermined operating state in which fuel is burned in the internal combustion engine.
  • An acquisition unit that acquires a second current that is output when a voltage is applied in a region; a humidity estimation unit that estimates the humidity of the detected gas based on a difference between the first current and the second current; and Humidity estimation section Based on the humidity of more estimated detection target gas, and a correction unit for correcting the detected density of the particular gas.
  • the sensor output of the gas sensor changes depending on the amount of moisture contained in the exhaust gas, for example. Therefore, in order to improve the detection accuracy of the sensor, it is desirable to grasp the humidity and correct the sensor current or the like according to the humidity.
  • the exhaust contains moisture generated by combustion of the internal combustion engine in addition to atmospheric moisture. If the amount of moisture is almost constant, the humidity of the atmosphere can be determined by detecting the humidity of the exhaust. I think it can be done.
  • Other than the exhaust gas may be a gas to be detected by the gas sensor.
  • the first current associated with the voltage application in the limit current region and the second current associated with the voltage application in the water splitting region are acquired in a predetermined operation state of the internal combustion engine, and the exhaust gas is determined based on the difference between the currents.
  • the humidity was estimated. Therefore, it is possible to estimate the humidity of the exhaust gas in a state where the amount of water generated by combustion is constant.
  • the change in the gas concentration detection value due to the moisture content in the exhaust is based on the change in the moisture content contained in the atmosphere. That is, since the exhaust humidity depends on the atmospheric humidity, the sensor output can be corrected according to the atmospheric humidity by using the exhaust humidity estimated in the predetermined operation state. That is, in this configuration, it is possible to capture a change in atmospheric humidity even during operation of the internal combustion engine, and to correct the sensor output according to the humidity. Thereby, the opportunity of humidity detection by a sensor can be increased and gas concentration measurement can be implemented appropriately.
  • FIG. 1 is a configuration diagram showing the entire engine control system
  • FIG. 2 is a block diagram showing the sensor element
  • FIG. 3 is a configuration diagram showing an electrical configuration of the sensor control circuit
  • FIG. 4 is a diagram showing output characteristics of the A / F sensor.
  • FIG. 5 is a flowchart showing a humidity detection processing procedure according to the first embodiment.
  • FIG. 6 is a correlation diagram between the humidity of the gas to be detected and ⁇ I.
  • FIG. 7 is a flowchart showing a processing procedure for acquiring an A / F value according to the first embodiment.
  • FIG. 8 is a correlation diagram between the A / F value and the element current IL under humidity conditions.
  • FIG. 9 is a flowchart illustrating a humidity detection processing procedure according to the second embodiment.
  • an engine control system according to the present embodiment will be described with reference to the drawings.
  • an exhaust gas discharged from an engine mounted on a vehicle is used as a detected gas
  • an A / F sensor that detects the concentration of oxygen or unburned gas (air-fuel ratio: A / F) in the exhaust gas is used.
  • An engine control system that performs various engine controls based on the output of the A / F sensor will be described.
  • stoichiometric combustion control is performed in which the air-fuel ratio is feedback-controlled at or near the stoichiometric air-fuel ratio.
  • the engine 10 is, for example, a gasoline engine, and includes an electronically controlled throttle valve 11, a fuel injection valve 12, an ignition device 13, and the like.
  • the engine 10 is connected to a starter 16 that applies initial rotation (cranking rotation) to the engine 10 when the engine is started.
  • the exhaust pipe 14 of the engine 10 is provided with a catalyst 15 made of, for example, a three-way catalyst as an exhaust purification device.
  • An A / F sensor 20 is provided upstream of the catalyst 15 in the exhaust pipe 14 and outputs a detection signal corresponding to the concentration of oxygen or unburned gas in the exhaust to the ECU 17.
  • the ECU 17 is provided with a sensor control circuit 50.
  • the ECU 17 is connected to a crank angle sensor 18 for detecting the rotational position of the engine output shaft and the engine rotational speed Ne, an accelerator sensor (not shown), and the like, and signals from these sensors are sequentially input to the ECU 17. It has become so.
  • the A / F sensor 20 includes a sensor element 30 having a stacked structure.
  • FIG. 2 shows a cross-sectional configuration of the sensor element 30.
  • the sensor element 30 has a long shape extending in the direction perpendicular to the paper surface of FIG. 2, and the entire element is accommodated in a housing or an element cover.
  • the sensor element 30 includes a solid electrolyte layer 31, a diffusion resistance layer 32, a shielding layer 33, and an insulating layer 34, which are stacked on the top and bottom of the drawing.
  • a protective layer (not shown) is provided around the element.
  • the rectangular plate-shaped solid electrolyte layer 31 is a partially stabilized zirconia sheet, and a pair of upper and lower electrodes 35 and 36 are disposed opposite to each other with the solid electrolyte layer 31 interposed therebetween.
  • the diffusion resistance layer 32 is made of a porous sheet for introducing exhaust into the electrode 35, and the shielding layer 33 is made of a dense layer for suppressing the permeation of exhaust.
  • a chamber 37 is provided in the diffusion resistance layer 32 so as to surround the electrode 35.
  • Both of the diffusion resistance layer 32 and the shielding layer 33 are formed of a ceramic such as alumina, spinel, zirconia or the like by a sheet forming method or the like, but have different gas permeability due to differences in the average pore diameter and porosity of the porosity. It has become.
  • the insulating layer 34 is made of high thermal conductive ceramics such as alumina, and an air duct 38 is formed as a reference gas chamber at a portion facing the electrode 36.
  • a heater 39 is embedded in the insulating layer 34.
  • the heater 39 is a linear heating element that generates heat when energized from a battery power source, and heats the entire element by the generated heat.
  • the surrounding exhaust gas is introduced from the side portion of the diffusion resistance layer 32 and then flows into the chamber 37 through the diffusion resistance layer 32 and reaches the electrode 35.
  • the exhaust gas is lean, oxygen in the exhaust gas is decomposed by the electrode 35 and discharged from the electrode 36 to the atmospheric duct 38.
  • oxygen in the atmospheric duct 38 is decomposed by the electrode 36 and discharged to the electrode 35 side.
  • the electrode 35 is a negative electrode and the electrode 36 is a positive electrode. As shown in FIG. 2, the electrode 35 is negative ( ⁇ ) and the electrode 36 is positive (+). It is said. Therefore, conversely, the applied voltage applied between these electrodes with the electrode 35 being positive (+) and the electrode 36 being negative (-) is a negative voltage.
  • a lead wire (not shown) is connected to each electrode 35, 36, and the sensor element 30 is connected to the sensor control circuit 50 through the lead wire.
  • the sensor control circuit 50 includes a microcomputer 40 and a detection circuit unit, thereby measuring the element current IL flowing through the sensor element 30 of the A / F sensor 20 and calculating the A / F value based on the element current value. Etc. are implemented.
  • the microcomputer 40 is composed of a well-known logic operation circuit including a CPU, a RAM, a ROM, an A / D converter, etc., and inputs an A / F output voltage corresponding to the element current value from the detection circuit unit.
  • the A / F value is calculated from the A / D value of the A / F output voltage.
  • the A / F value calculated by the microcomputer 40 is sequentially output to another microcomputer for engine control provided in the ECU 17.
  • the ROM of the microcomputer 40 stores a control program for causing the CPU to execute each process, a conversion map for performing humidity correction described later, and the like.
  • a reference voltage power supply 53 is connected to the positive terminal of the sensor element 30 (S + terminal connected to the atmospheric electrode 36) via an operational amplifier 51 and a current detection resistor 52 (current measurement resistor).
  • the applied voltage control circuit 54 is connected to the negative terminal (S-terminal connected to the exhaust-side electrode 35) of the sensor element 30.
  • the point A at one end of the current detection resistor 52 is held at the same voltage as the reference voltage Vf (for example, 2.2 V).
  • the element current flows through the current detection resistor 52, and the voltage at the point B changes according to the element current. For example, when the exhaust gas is lean, a current flows from the S + terminal to the S ⁇ terminal in the sensor element 30, so that the point B voltage rises. .
  • the applied voltage control circuit 54 monitors the B point voltage as a basic configuration, determines a voltage to be applied to the sensor element 30 according to the voltage value, and controls the S-side voltage.
  • An amplifier circuit is connected to points A and B at both ends of the current detection resistor 52, and an A / F output voltage that is an output of the amplifier circuit is taken into the A / D input terminal of the microcomputer 40.
  • the sensor current flowing through the A / F sensor varies depending on the humidity in the gas to be detected.
  • the humidity in the gas to be detected when the gas to be detected is in a high humidity state, the oxygen partial pressure in the atmosphere is lower than that in a low humidity state.
  • the number of oxygen molecules detected by the sensor is substantially reduced, and the sensor output is reduced. Therefore, in order to accurately detect the gas concentration, it is preferable to grasp the humidity and correct the sensor current or the like according to the humidity.
  • the A / F sensor 20 is installed in the exhaust pipe 14, the opportunity to directly detect the atmospheric humidity has been limited to cases such as when the fuel is cut. For this reason, it is difficult to frequently grasp atmospheric humidity with the A / F sensor 20 during operation.
  • the amount of water contained in the exhaust passing through the exhaust pipe 14 after combustion of the engine 10 is calculated as the sum of the amount of water generated by the combustion of the engine and the amount of water contained in the air used for combustion. From this, it can be said that there is a correlation between the humidity of the exhaust and the humidity of the atmosphere. As a result, if the amount of water generated by combustion is almost constant, the humidity of the atmosphere can be grasped by detecting the humidity of the exhaust. That is, even when the engine 10 is in operation, a change in atmospheric humidity can be captured, and the sensor output can be corrected according to the humidity.
  • the humidity of the exhaust gas is estimated, and the influence of the humidity on the sensor output is corrected, so that the oxygen concentration in the exhaust gas, that is, A / F value is calculated.
  • the voltage-current characteristic (VI characteristic) shown in FIG. 4 is used to estimate the humidity of the exhaust gas.
  • the applied voltage VP of the sensor element 30 is shown on the horizontal axis
  • the element current IL is shown on the vertical axis.
  • a straight line portion (flat portion) parallel to the voltage axis that is the horizontal axis is a limit current region that specifies the element current IL as a limit current.
  • the increase / decrease in the element current IL in the limit current region corresponds to the increase / decrease in the air-fuel ratio (that is, the degree of lean / rich). That is, the element current IL increases as the air-fuel ratio becomes leaner, and the element current IL decreases as the air-fuel ratio becomes richer.
  • the region where the element current IL is almost stable on the higher voltage side than the limit current region is the water decomposition region.
  • the water splitting area exists as a flat area.
  • water contained in the exhaust gas is decomposed by voltage application, and an element current IL corresponding to oxygen ions generated by the decomposition is detected. Therefore, it is possible to calculate the amount of moisture in the exhaust gas and hence the humidity of the exhaust gas from the value obtained by subtracting the device current IL in the limit current region from the device current IL in the water decomposition region.
  • the current that flows when a voltage V1 (for example, 0.4 to 0.5 V) corresponding to the limit current region is applied is acquired as I1, and subsequently corresponds to the water decomposition region.
  • a current that flows when a voltage V2 (for example, 1.0 V to 1.2 V) is applied is acquired as I2.
  • the humidity of the exhaust is calculated from ⁇ I which is the difference between them.
  • ⁇ I and the humidity (absolute humidity) of the gas to be detected have a substantially proportional relationship, and the humidity can be easily calculated.
  • the oxygen concentration detection value is corrected based on the obtained humidity of the exhaust gas. As a result, an appropriate A / F value that is not affected by humidity can be calculated.
  • a voltage in the limit current region (eg, voltage V1) is always used as the reference voltage, and the oxygen concentration in the exhaust gas is calculated based on the detected element current IL (eg, current I1). Is done.
  • the voltage (for example, voltage V2) in the water splitting region is used only when estimating the humidity of exhaust gas, that is, when the vehicle is in a predetermined operating state.
  • step S11 it is determined whether or not the engine 10 is in a combustion state and is in a predetermined operation state.
  • the predetermined operating state is preferably a state where the combustion of the engine 10 is stable, that is, a state where the composition of the gas generated by the combustion is stable.
  • step S11 is affirmed, the process proceeds to step S12.
  • the frequency of humidity calculation may be added to the execution conditions. For example, when a predetermined time has elapsed since the previous humidity calculation, step S12 and subsequent steps may be performed.
  • step S12 the applied voltage control circuit 54 applies the voltage V1. Then, the element current IL flowing between the electrodes 35 and 36 under the voltage V1 is acquired as the current I1 (step S13). Subsequently, in step S14, the applied voltage is changed from the voltage V1 to the voltage V2, and the applied voltage control circuit 54 applies the voltage V2. Then, the element current IL flowing between the electrodes 35 and 36 under the voltage V2 is acquired as the current I2 (step S15).
  • the current I1 acquired in step S13 is preferably acquired immediately before the voltage is changed from the voltage V1 to the voltage V2. Thereby, the time difference of the acquisition timing of the electric current I1 and the electric current I2 can be made small, and a more exact humidity can be estimated.
  • step S16 ⁇ I is calculated by subtracting the current I1 from the current I2.
  • ⁇ I is a value corresponding to the oxygen concentration derived from water molecules contained in the exhaust gas.
  • step S17 the humidity of the exhaust is estimated based on ⁇ I.
  • the humidity of the exhaust can be estimated based on the relationship between ⁇ I and humidity shown in FIG. 6, for example.
  • the relationship in FIG. 6 is based on data obtained by measuring I1 and I2 while changing the humidity condition under a predetermined temperature condition due to, for example, adaptation.
  • ⁇ I tends to increase as the humidity increases. This is because the higher the humidity, the more water molecules contained in the exhaust gas, and the more oxygen ions dissociated from the water molecules. If the humidity of the exhaust gas is estimated, this process is terminated.
  • step S11 determines whether the vehicle is not in the predetermined driving state.
  • step S13 and step S15 correspond to an “acquisition unit”
  • step S17 corresponds to a “humidity estimation unit”.
  • step S21 an element current IL when a voltage in the limit current region is applied is acquired.
  • step S22 the humidity of the exhaust gas estimated in step S17 is read.
  • step S23 the oxygen concentration in the exhaust gas and thus the A / F value is calculated based on the IL and the humidity of the exhaust gas with reference to the conversion map stored in advance in the ROM (step S24).
  • FIG. 8 is an example of a conversion map, which defines the relationship among the air-fuel ratio (A / F), the element current IL, and the humidity condition. In this case, because the oxygen partial pressure decreases as the humidity increases, the A / F value is calculated as a small value even for the same element current IL.
  • Step S23 and Step S24 correspond to a “correction unit”.
  • the current I1 associated with the voltage application in the limit current region and the current I2 associated with the voltage application in the water decomposition region are acquired in a predetermined operating state of the engine 10, and the exhaust humidity is determined based on the difference between these currents. Was estimated. Therefore, it is possible to estimate the humidity of the exhaust gas in a state where the amount of water generated by combustion is constant. In this case, if the moisture content due to combustion is constant, the change in the gas concentration detection value due to the moisture content in the exhaust is based on the change in the moisture content contained in the atmosphere. That is, since the exhaust humidity depends on the atmospheric humidity, the sensor output can be corrected according to the atmospheric humidity by using the exhaust humidity estimated in the predetermined operation state.
  • the humidity was estimated from the difference between the current I2 output in the water decomposition region and the current I1 output in the limit current region. Therefore, the humidity of the exhaust can be accurately grasped, and humidity correction can be performed appropriately.
  • each of the current I1 and the current I2 is acquired in an idle operation state in which the fuel injection amount is a predetermined amount.
  • the amount of water generated by combustion becomes substantially constant, and the humidity of the exhaust gas, and hence the humidity of the atmosphere, can be detected with high accuracy.
  • the second embodiment will be described focusing on the differences from the first embodiment.
  • the amount of water contained in the exhaust gas is calculated as the sum of the amount of water generated by the combustion of the engine 10 and the amount of water contained in the air used for combustion.
  • the exhaust humidity depends on the amount of combustion moisture. Therefore, even in an operation state other than the idle operation state, the humidity of the exhaust gas can be estimated by estimating the amount of combustion moisture in the operation state.
  • FIG. 9 is a flowchart showing the humidity detection process in the present embodiment. This process is executed by the microcomputer 40 in place of the above-described FIG. Here, only differences from FIG. 5 will be described.
  • step S31 it is determined in step S31 whether or not the vehicle is in a predetermined driving state. Specifically, it is determined whether it is any of a plurality of predetermined operating states.
  • the predetermined operation state includes an operation state at an idle rotation speed and an operation state at another rotation speed (for example, 2000 rpm) higher than the idle rotation speed.
  • step S31 is affirmed, it progresses to step S12, and the process similar to FIG. 5 is performed after that to step S16. And when progressing to step S32, the moisture content which generate
  • the moisture amount can be estimated based on the fuel injection amount by the fuel injection valve 12 or a parameter (such as the engine rotational speed Ne or the load) correlated with the fuel injection amount for each operation state. Specifically, a predetermined moisture amount corresponding to the fuel injection amount is determined in advance by adaptation or the like. Incidentally, the amount of water generated by combustion tends to increase as the fuel injection amount increases.
  • the humidity of the exhaust gas is estimated in consideration of the amount of combustion moisture corresponding to each of a plurality of different operating states. Specifically, the difference between the amount of combustion moisture in the operation state and the amount of combustion moisture in the reference operation state (for example, idle operation state) is added to the humidity of the exhaust gas in the reference operation state. Thereby, the humidity in the driving
  • the humidity of the exhaust gas can be estimated by using the combustion moisture amount even in the operation state other than the idle operation state. Therefore, humidity detection can be performed even in various operating states, and opportunities for humidity detection can be increased.
  • the idling operation state is set as the predetermined operation state when detecting the humidity.
  • the predetermined operation state is limited to this as long as the composition of the gas generated by the combustion of the engine 10 is stable. Absent. For example, a state where the fuel injection amount by the fuel injection valve 12 is constant for a predetermined time can be considered.
  • the configuration may be such that the humidity is detected when the inside of the exhaust pipe is replaced with the atmosphere.
  • the inside of the exhaust pipe is replaced with the atmosphere, for example, the case of fuel cut or the case where the engine 10 is stopped can be considered.
  • the humidity of the atmosphere can be directly detected. Thereby, the opportunity of atmospheric humidity detection can be increased.
  • the A / F value is calculated using the conversion map, but the A / F value may be calculated using a correlation function corresponding to the element current IL instead of the map. In this case, in step S23, arithmetic processing is performed based on the function.
  • the A / F value is calculated corresponding to the combination of the element current IL and the exhaust humidity.
  • the error ⁇ IL of the element current IL that is, The correction value of the element current IL may be calculated.
  • the error ⁇ IL is used as a correction value for the element current IL. That is, the oxygen concentration and the A / F value are calculated on the basis of the element current IL taking this correction value into consideration.
  • an adjustment resistor or an identification resistor including information on individual sensor differences may be connected to the sensor control circuit 50.
  • the sensor individual difference information is stored in the code storage unit by QR code (registered trademark) or the like, and the code storage unit is attached to the A / F sensor 20, and the sensor control circuit 50 reads the code information and the sensor individual circuit It is good also as a structure which recognizes difference information. As a result, variations in individual sensor characteristics can be suppressed.
  • the humidity of exhaust gas may be estimated based on the individual difference information.
  • the microcomputer 40 is configured to correct the conversion map based on the sensor individual difference information in step S23 of FIG. Or it is set as the structure which correct
  • the A / F sensor 20 is provided in the exhaust pipe 14 and the exhaust gas in the exhaust pipe is the gas to be detected by the A / F sensor 20, but this may be changed.
  • an A / F sensor 20 is provided in the engine intake pipe downstream of the connection portion with the EGR pipe, and the gas in the intake pipe (that is, exhaust and A new gas mixture) may be used as a gas to be detected by the A / F sensor 20.
  • the reference gas introduced into the reference gas chamber of the sensor element 30 is not limited as long as the oxygen concentration is known and may be other than the atmosphere.
  • the gas sensor may be a so-called two-cell gas sensor including an electromotive force cell and a pump cell in addition to the A / F sensor 20 of the above embodiment. Further, as the sensor element 30, a cup-type structure can be used in addition to the stacked-type structure.
  • the gas sensor may detect a specific gas concentration different from the oxygen concentration.
  • a NOx sensor that detects the NOx concentration in the exhaust gas (the gas to be detected) may be used.
  • the NOx sensor includes a pump cell that keeps the oxygen concentration in the chamber constant by pumping oxygen and a sensor cell that detects the NOx concentration using the gas after oxygen pumping. By applying this voltage, it is possible to detect the oxygen concentration and the NOx concentration. In this case, it is possible to estimate the amount of water based on the pump cell output or to estimate the amount of water based on the sensor cell output.
  • the microcomputer 40 of the said embodiment may be applied to the gas sensor used for a diesel engine and another type engine other than a gasoline engine.

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Abstract

A gas sensor control device (50) is applied to a gas sensor (20) which outputs a limiting current corresponding to the concentration of a specific gas in a detected gas, by applying a voltage in a limiting current zone. Furthermore, the gas sensor control device (50) is provided with: an acquiring unit which acquires a first current that is output when the voltage is applied in the limiting current zone in a prescribed operating state in which fuel is being combusted in an internal-combustion engine (10), and a second current that is output when the voltage is applied in a water decomposition zone on the higher voltage side of the limiting current zone; a humidity estimating unit which estimates the humidity of the detected gas on the basis of the difference between the first current and the second current; and a correcting unit which corrects the detected value of the concentration of the specific gas on the basis of the humidity of the detected gas as estimated by the humidity estimating unit.

Description

ガスセンサ制御装置Gas sensor control device 関連出願の相互参照Cross-reference of related applications
　本出願は、２０１６年６月６日に出願された日本出願番号２０１６－１１２９３５号に基づくもので、ここにその記載内容を援用する。 This application is based on Japanese Application No. 2016-112935 filed on June 6, 2016, the contents of which are incorporated herein by reference.
　本開示は、車両等に用いられるガスセンサ制御装置に関するものである。 The present disclosure relates to a gas sensor control device used for a vehicle or the like.
　従来、自動車に使用されるセンサとして、排気中の酸素濃度を検出する酸素センサ等が知られている。酸素センサは、センサ素子を流れる電流の大きさが排気中の酸素濃度に応じて変化することを利用して、酸素濃度の検出、ひいては排気の空燃比を検出するものである。空燃比の検出結果はエンジンＥＣＵ等により構成される空燃比制御システムにて用いられ、空燃比をストイキ（理論空燃比）近傍でフィードバック制御するストイキ燃焼制御や、同空燃比を所定のリーン領域でフィードバック制御するリーン燃焼制御等が実現される。 Conventionally, oxygen sensors that detect oxygen concentration in exhaust gas are known as sensors used in automobiles. The oxygen sensor detects the oxygen concentration and thus detects the air-fuel ratio of the exhaust gas by utilizing the fact that the magnitude of the current flowing through the sensor element changes according to the oxygen concentration in the exhaust gas. The detection result of the air-fuel ratio is used in an air-fuel ratio control system constituted by an engine ECU or the like, and the stoichiometric combustion control for feedback control of the air-fuel ratio in the vicinity of the stoichiometric (theoretical air-fuel ratio) or the air-fuel ratio in a predetermined lean region. Lean combustion control with feedback control is realized.
　例えば、酸素センサは、大気雰囲気中の湿度の影響によってセンサ出力が変化することが知られている。具体的には、大気雰囲気が高湿度状態である場合は、低湿度状態に比べて大気中の酸素分圧が低いため、酸素センサによって検出される酸素の分子数が実質的に少なくなりセンサ出力が低下する。特許文献１に記載の技術では、大気を用いたセンサの校正にあたり、湿度影響によって生じるセンサ出力の誤差の低減を図っている。すなわち、エンジンの燃料供給を停止して、排気管内の排気が完全に大気に入れ替わった状態において、大気の湿度を検出し、その大気の湿度に応じてセンサ出力を補正している。 For example, it is known that the sensor output of an oxygen sensor changes due to the influence of humidity in the air atmosphere. Specifically, when the atmospheric atmosphere is in a high humidity state, the oxygen partial pressure in the atmosphere is lower than in a low humidity state, so the number of oxygen molecules detected by the oxygen sensor is substantially reduced and the sensor output Decreases. In the technique described in Patent Document 1, the sensor output error caused by the influence of humidity is reduced when the sensor is calibrated using the atmosphere. That is, in a state where the fuel supply of the engine is stopped and the exhaust in the exhaust pipe is completely replaced with the atmosphere, the humidity of the atmosphere is detected, and the sensor output is corrected according to the humidity of the atmosphere.
特開２０１０－２８１７３２号公報JP 2010-281732 A
　しかしながら、上記技術では、大気の湿度検出のタイミングが、燃料の供給が停止された時、つまり燃料カット時に限られることとなる。大気は酸素濃度が既知であるため、燃料カット時に排気管内が大気に満たされることで、センサ出力の湿度補正を行うことができる。なお、燃料カット時において、排気管内の排気が完全に大気に入れ替わるまでにはある程度の時間が必要となる。そのため、燃料カットが行われる度に大気の湿度検出が実施できるわけではなく、湿度検出の機会はより限定的である。一方で、大気の湿度は、ドライブサイクル中において変化が生じることがあり、ガスセンサの検出の高精度化を図る上では、大気の湿度検出を頻繁に行うことが望ましい。 However, in the above-described technology, the timing of atmospheric humidity detection is limited when the fuel supply is stopped, that is, when the fuel is cut. Since the atmosphere has a known oxygen concentration, the humidity of the sensor output can be corrected by filling the exhaust pipe with the atmosphere when the fuel is cut. It should be noted that a certain amount of time is required until the exhaust in the exhaust pipe is completely replaced with the atmosphere when the fuel is cut. Therefore, atmospheric humidity detection cannot be performed every time a fuel cut is performed, and the opportunities for humidity detection are more limited. On the other hand, the atmospheric humidity may change during the drive cycle, and it is desirable to frequently detect the atmospheric humidity in order to increase the accuracy of detection by the gas sensor.
　本開示は、上記課題を解決するためになされたものであり、センサによる湿度検出の機会を増やし、ガス濃度測定を適正に実施することができるガスセンサ制御装置を提供することを主目的とする。 The present disclosure has been made to solve the above-described problems, and has as its main purpose to provide a gas sensor control device that can increase the chance of humidity detection by a sensor and appropriately perform gas concentration measurement.
　本開示のガスセンサ制御装置は、固体電解質層及びそれを挟む少なくとも一対の電極を有し、前記一対の電極のうち一方を、排気又は排気を含む混合ガスである被検出ガスが導かれる第１電極、他方を基準ガスを導入する基準ガス室に設けられる第２電極とするセンサ素子を備え、限界電流域での電圧印加により、前記被検出ガス中の特定ガスの濃度に応じた限界電流を出力するガスセンサに適用され、内燃機関で燃料の燃焼が行われる所定運転状態下において、前記限界電流域での電圧印加時に出力される第１電流と、前記限界電流域よりも高電圧側の水分解域での電圧印加時に出力される第２電流とを取得する取得部と、前記第１電流及び前記第２電流の差に基づいて、前記被検出ガスの湿度を推定する湿度推定部と、前記湿度推定部により推定した前記被検出ガスの湿度に基づいて、前記特定ガスの濃度検出値を補正する補正部と、を備える。 The gas sensor control device of the present disclosure includes a solid electrolyte layer and at least a pair of electrodes sandwiching the solid electrolyte layer, and a first electrode to which a gas to be detected, which is exhaust gas or a mixed gas including exhaust gas, is guided to one of the pair of electrodes. The sensor element is the second electrode provided in the reference gas chamber for introducing the reference gas, and the limit current corresponding to the concentration of the specific gas in the detected gas is output by applying a voltage in the limit current region. The first current that is output when a voltage is applied in the limit current region and the water decomposition on the higher voltage side than the limit current region under a predetermined operating state in which fuel is burned in the internal combustion engine. An acquisition unit that acquires a second current that is output when a voltage is applied in a region; a humidity estimation unit that estimates the humidity of the detected gas based on a difference between the first current and the second current; and Humidity estimation section Based on the humidity of more estimated detection target gas, and a correction unit for correcting the detected density of the particular gas.
　ガスセンサは、例えば排気中に含まれる水分量によってセンサ出力が変化する。そのため、センサの検出精度の向上を図るためには、湿度を把握し、その湿度に応じてセンサ電流等を補正することが望ましい。また、排気には、大気中の水分以外に内燃機関の燃焼により発生する水分が含まれ、その水分量がほぼ一定の状態であれば、排気の湿度を検出することで、大気の湿度を把握することができると考えられる。なお、排気以外をガスセンサの被検出ガスとしてもよい。 The sensor output of the gas sensor changes depending on the amount of moisture contained in the exhaust gas, for example. Therefore, in order to improve the detection accuracy of the sensor, it is desirable to grasp the humidity and correct the sensor current or the like according to the humidity. In addition, the exhaust contains moisture generated by combustion of the internal combustion engine in addition to atmospheric moisture. If the amount of moisture is almost constant, the humidity of the atmosphere can be determined by detecting the humidity of the exhaust. I think it can be done. Other than the exhaust gas may be a gas to be detected by the gas sensor.
　上記構成では、内燃機関の所定運転状態で限界電流域での電圧印加に伴う第１電流と水分解域での電圧印加に伴う第２電流とを取得し、それら電流の差に基づいて、排気の湿度を推定するようにした。そのため、燃焼により生じる水分量を一定にした状態下で、排気の湿度を推定することができる。この場合、燃焼による水分量が一定であれば、排気の水分量に起因するガス濃度検出値の変化は、大気中に含まれる水分量の変化に基づくものとなる。すなわち、排気の湿度は大気の湿度に依存したものとなるため、所定運転状態で推定した排気の湿度を用いることにより、大気の湿度に応じたセンサ出力の補正を実現できる。つまり本構成では、内燃機関の運転中であっても、大気の湿度変化を捉えることができ、その湿度に応じてセンサ出力を補正することができる。これにより、センサによる湿度検出の機会を増やし、ガス濃度測定を適正に実施することができる。 In the above configuration, the first current associated with the voltage application in the limit current region and the second current associated with the voltage application in the water splitting region are acquired in a predetermined operation state of the internal combustion engine, and the exhaust gas is determined based on the difference between the currents. The humidity was estimated. Therefore, it is possible to estimate the humidity of the exhaust gas in a state where the amount of water generated by combustion is constant. In this case, if the moisture content due to combustion is constant, the change in the gas concentration detection value due to the moisture content in the exhaust is based on the change in the moisture content contained in the atmosphere. That is, since the exhaust humidity depends on the atmospheric humidity, the sensor output can be corrected according to the atmospheric humidity by using the exhaust humidity estimated in the predetermined operation state. That is, in this configuration, it is possible to capture a change in atmospheric humidity even during operation of the internal combustion engine, and to correct the sensor output according to the humidity. Thereby, the opportunity of humidity detection by a sensor can be increased and gas concentration measurement can be implemented appropriately.
　本開示についての上記目的およびその他の目的、特徴や利点は、添付の図面を参照しながら下記の詳細な記述により、より明確になる。その図面は、
図１は、エンジン制御システムの全体を示す構成図であり、 図２は、センサ素子を示す構成図であり、 図３は、センサ制御回路の電気的構成を示す構成図であり、 図４は、Ａ／Ｆセンサの出力特性を示す図であり、 図５は、第１実施形態の湿度検出の処理手順を示すフローチャートであり、 図６は、被検出ガスの湿度とΔＩの相関図であり、 図７は、第１実施形態のＡ／Ｆ値取得の処理手順を示すフローチャートであり、 図８は、湿度条件下におけるＡ／Ｆ値と素子電流ＩＬの相関図であり、 図９は、第２実施形態の湿度検出の処理手順を示すフローチャートである。 The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings. The drawing
FIG. 1 is a configuration diagram showing the entire engine control system, FIG. 2 is a block diagram showing the sensor element, FIG. 3 is a configuration diagram showing an electrical configuration of the sensor control circuit, FIG. 4 is a diagram showing output characteristics of the A / F sensor. FIG. 5 is a flowchart showing a humidity detection processing procedure according to the first embodiment. FIG. 6 is a correlation diagram between the humidity of the gas to be detected and ΔI. FIG. 7 is a flowchart showing a processing procedure for acquiring an A / F value according to the first embodiment. FIG. 8 is a correlation diagram between the A / F value and the element current IL under humidity conditions. FIG. 9 is a flowchart illustrating a humidity detection processing procedure according to the second embodiment.
　（第１実施形態）
　以下、本実施形態に係るエンジン制御システムを図面に従って説明する。本実施形態では、車両に搭載されるエンジンにより排出される排気を被検出ガスとし、同排気中の酸素又は未燃ガスの濃度（空燃比：Ａ／Ｆ）を検出するＡ／Ｆセンサを用い、Ａ／Ｆセンサの出力に基づいてエンジンの各種制御等を実施するエンジン制御システムについて説明する。当該制御システムでは、空燃比をストイキ又はストイキ付近で空燃比フィードバック制御するストイキ燃焼制御が実施される。 (First embodiment)
Hereinafter, an engine control system according to the present embodiment will be described with reference to the drawings. In this embodiment, an exhaust gas discharged from an engine mounted on a vehicle is used as a detected gas, and an A / F sensor that detects the concentration of oxygen or unburned gas (air-fuel ratio: A / F) in the exhaust gas is used. An engine control system that performs various engine controls based on the output of the A / F sensor will be described. In the control system, stoichiometric combustion control is performed in which the air-fuel ratio is feedback-controlled at or near the stoichiometric air-fuel ratio.
　まず、エンジン制御システムの全体概要を図１を用いて説明する。エンジン１０は、例えばガソリンエンジンであり、電子制御式のスロットルバルブ１１や、燃料噴射弁１２、点火装置１３等を備えている。また、エンジン１０にはエンジン始動時において当該エンジン１０に初期回転（クランキング回転）を付与する始動装置１６が接続されている。エンジン１０の排気管１４には排気浄化装置として例えば三元触媒よりなる触媒１５が設けられている。排気管１４において触媒１５の上流側にはＡ／Ｆセンサ２０が設けられており、排気中の酸素又は未燃ガスの濃度に対応した検出信号をＥＣＵ１７に出力する。ＥＣＵ１７には、センサ制御回路５０が設けられている。その他に、ＥＣＵ１７には、エンジン出力軸の回転位置及びエンジン回転速度Ｎｅを検出するクランク角センサ１８や、図示しないアクセルセンサ等が接続されており、これら各センサからの信号がＥＣＵ１７に逐次入力されるようになっている。 First, the overall outline of the engine control system will be described with reference to FIG. The engine 10 is, for example, a gasoline engine, and includes an electronically controlled throttle valve 11, a fuel injection valve 12, an ignition device 13, and the like. The engine 10 is connected to a starter 16 that applies initial rotation (cranking rotation) to the engine 10 when the engine is started. The exhaust pipe 14 of the engine 10 is provided with a catalyst 15 made of, for example, a three-way catalyst as an exhaust purification device. An A / F sensor 20 is provided upstream of the catalyst 15 in the exhaust pipe 14 and outputs a detection signal corresponding to the concentration of oxygen or unburned gas in the exhaust to the ECU 17. The ECU 17 is provided with a sensor control circuit 50. In addition, the ECU 17 is connected to a crank angle sensor 18 for detecting the rotational position of the engine output shaft and the engine rotational speed Ne, an accelerator sensor (not shown), and the like, and signals from these sensors are sequentially input to the ECU 17. It has become so.
　次に、Ａ／Ｆセンサ２０の構成を図２を用いて説明する。本Ａ／Ｆセンサ２０は積層型構造のセンサ素子３０を有している。図２はそのセンサ素子３０の断面構成を示す。実際には当該センサ素子３０は図２の紙面直交方向に延びる長尺状をなし、素子全体がハウジングや素子カバー内に収容される構成となっている。センサ素子３０は、固体電解質層３１、拡散抵抗層３２、遮蔽層３３及び絶縁層３４を有し、これらが図の上下に積層されて構成されている。同素子の周囲には図示しない保護層が設けられている。長方形板状の固体電解質層３１は部分安定化ジルコニア製のシートであり、その固体電解質層３１を挟んで上下一対の電極３５，３６が対向配置されている。拡散抵抗層３２は電極３５へ排気を導入するための多孔質シートからなり、遮蔽層３３は排気の透過を抑制するための緻密層からなる。拡散抵抗層３２には、電極３５を囲むようにしてチャンバ３７が設けられている。拡散抵抗層３２と遮蔽層３３は何れも、アルミナ、スピネル、ジルコニア等のセラミックスをシート成形法等により成形したものであるが、ポロシティの平均孔径及び気孔率の違いによりガス透過率が相違するものとなっている。 Next, the configuration of the A / F sensor 20 will be described with reference to FIG. The A / F sensor 20 includes a sensor element 30 having a stacked structure. FIG. 2 shows a cross-sectional configuration of the sensor element 30. Actually, the sensor element 30 has a long shape extending in the direction perpendicular to the paper surface of FIG. 2, and the entire element is accommodated in a housing or an element cover. The sensor element 30 includes a solid electrolyte layer 31, a diffusion resistance layer 32, a shielding layer 33, and an insulating layer 34, which are stacked on the top and bottom of the drawing. A protective layer (not shown) is provided around the element. The rectangular plate-shaped solid electrolyte layer 31 is a partially stabilized zirconia sheet, and a pair of upper and lower electrodes 35 and 36 are disposed opposite to each other with the solid electrolyte layer 31 interposed therebetween. The diffusion resistance layer 32 is made of a porous sheet for introducing exhaust into the electrode 35, and the shielding layer 33 is made of a dense layer for suppressing the permeation of exhaust. A chamber 37 is provided in the diffusion resistance layer 32 so as to surround the electrode 35. Both of the diffusion resistance layer 32 and the shielding layer 33 are formed of a ceramic such as alumina, spinel, zirconia or the like by a sheet forming method or the like, but have different gas permeability due to differences in the average pore diameter and porosity of the porosity. It has become.
　絶縁層３４はアルミナ等の高熱伝導性セラミックスからなり、電極３６に対面する部位には基準ガス室として大気ダクト３８が形成されている。また、同絶縁層３４にはヒータ３９が埋設されている。ヒータ３９は、バッテリ電源からの通電により発熱する線状の発熱体よりなり、その発熱により素子全体を加熱する。 The insulating layer 34 is made of high thermal conductive ceramics such as alumina, and an air duct 38 is formed as a reference gas chamber at a portion facing the electrode 36. A heater 39 is embedded in the insulating layer 34. The heater 39 is a linear heating element that generates heat when energized from a battery power source, and heats the entire element by the generated heat.
　上記構成のセンサ素子３０において、その周囲の排気は拡散抵抗層３２の側方部位から導入された後、拡散抵抗層３２内を経由してチャンバ３７に流れ込み、電極３５に達する。排気がリーンの場合、排気中の酸素が電極３５で分解され、電極３６より大気ダクト３８に排出される。また、排気がリッチの場合、逆に大気ダクト３８内の酸素が電極３６で分解され、電極３５側に排出される。 In the sensor element 30 having the above configuration, the surrounding exhaust gas is introduced from the side portion of the diffusion resistance layer 32 and then flows into the chamber 37 through the diffusion resistance layer 32 and reaches the electrode 35. When the exhaust gas is lean, oxygen in the exhaust gas is decomposed by the electrode 35 and discharged from the electrode 36 to the atmospheric duct 38. On the other hand, when the exhaust gas is rich, oxygen in the atmospheric duct 38 is decomposed by the electrode 36 and discharged to the electrode 35 side.
　本実施形態では、電極３５を負極、電極３６を正極としており、図２のように電極３５を負（－）、電極３６を正（＋）としてこれら電極間に印加される印加電圧を正電圧としている。ゆえに、その逆に、電極３５を正（＋）、電極３６を負（－）としてこれら電極間に印加される印加電圧が負電圧である。各電極３５，３６には図示しないリード線が接続され、そのリード線を介してセンサ素子３０がセンサ制御回路５０に接続されている。 In this embodiment, the electrode 35 is a negative electrode and the electrode 36 is a positive electrode. As shown in FIG. 2, the electrode 35 is negative (−) and the electrode 36 is positive (+). It is said. Therefore, conversely, the applied voltage applied between these electrodes with the electrode 35 being positive (+) and the electrode 36 being negative (-) is a negative voltage. A lead wire (not shown) is connected to each electrode 35, 36, and the sensor element 30 is connected to the sensor control circuit 50 through the lead wire.
　次に、センサ制御回路５０の具体的な構成について図３を用いて説明する。センサ制御回路５０は、マイコン４０と検出回路部とを有しており、これらによりＡ／Ｆセンサ２０のセンサ素子３０に流れる素子電流ＩＬの計測やその素子電流値に基づくＡ／Ｆ値の演算などが実施される。マイコン４０は、ＣＰＵ、ＲＡＭ、ＲＯＭ、Ａ／Ｄ変換器等を備える周知の論理演算回路にて構成されており、素子電流値に相応するＡ／Ｆ出力電圧を検出回路部から入力し、同Ａ／Ｆ出力電圧のＡ／Ｄ値によりＡ／Ｆ値を算出する。そして、マイコン４０により演算されたＡ／Ｆ値は、ＥＣＵ１７内に設けられたエンジン制御用の別のマイコンに逐次出力される。なお、マイコン４０のＲＯＭには、ＣＰＵに各処理を実行させるための制御プログラムや、後述する湿度補正を行うための換算マップ等が記憶されている。 Next, a specific configuration of the sensor control circuit 50 will be described with reference to FIG. The sensor control circuit 50 includes a microcomputer 40 and a detection circuit unit, thereby measuring the element current IL flowing through the sensor element 30 of the A / F sensor 20 and calculating the A / F value based on the element current value. Etc. are implemented. The microcomputer 40 is composed of a well-known logic operation circuit including a CPU, a RAM, a ROM, an A / D converter, etc., and inputs an A / F output voltage corresponding to the element current value from the detection circuit unit. The A / F value is calculated from the A / D value of the A / F output voltage. Then, the A / F value calculated by the microcomputer 40 is sequentially output to another microcomputer for engine control provided in the ECU 17. The ROM of the microcomputer 40 stores a control program for causing the CPU to execute each process, a conversion map for performing humidity correction described later, and the like.
　センサ制御回路５０において、センサ素子３０の正側端子（大気側の電極３６に接続されるＳ＋端子）にはオペアンプ５１及び電流検出抵抗５２（電流計測用抵抗）を介して基準電圧電源５３が接続され、同センサ素子３０の負側端子（排気側の電極３５に接続されるＳ－端子）には印加電圧制御回路５４が接続されている。この場合、電流検出抵抗５２の一端のＡ点は基準電圧Ｖｆ（例えば２．２Ｖ）と同じ電圧に保持される。素子電流は電流検出抵抗５２を介して流れ、素子電流に応じてＢ点の電圧が変化する。例えば排気がリーンの場合、センサ素子３０においてＳ＋端子からＳ－端子に電流が流れるためＢ点電圧が上昇し、リッチの場合、Ｓ－端子からＳ＋端子に電流が流れるためＢ点電圧が低下する。 In the sensor control circuit 50, a reference voltage power supply 53 is connected to the positive terminal of the sensor element 30 (S + terminal connected to the atmospheric electrode 36) via an operational amplifier 51 and a current detection resistor 52 (current measurement resistor). The applied voltage control circuit 54 is connected to the negative terminal (S-terminal connected to the exhaust-side electrode 35) of the sensor element 30. In this case, the point A at one end of the current detection resistor 52 is held at the same voltage as the reference voltage Vf (for example, 2.2 V). The element current flows through the current detection resistor 52, and the voltage at the point B changes according to the element current. For example, when the exhaust gas is lean, a current flows from the S + terminal to the S− terminal in the sensor element 30, so that the point B voltage rises. .
　印加電圧制御回路５４では、基本構成として、Ｂ点電圧をモニタするとともにその電圧値に応じてセンサ素子３０に印加すべき電圧を決定し、Ｓ－側の電圧を制御する。また、電流検出抵抗５２の両端のＡ点及びＢ点には増幅回路が接続されており、その増幅回路の出力であるＡ／Ｆ出力電圧がマイコン４０のＡ／Ｄ入力端子に取り込まれる。 The applied voltage control circuit 54 monitors the B point voltage as a basic configuration, determines a voltage to be applied to the sensor element 30 according to the voltage value, and controls the S-side voltage. An amplifier circuit is connected to points A and B at both ends of the current detection resistor 52, and an A / F output voltage that is an output of the amplifier circuit is taken into the A / D input terminal of the microcomputer 40.
　ところで、Ａ／Ｆセンサに流れるセンサ電流は、被検出ガス中の湿度によって変動することが知られている。例えば、被検出ガスが高湿度状態である場合は、低湿度状態の場合に比べて大気中の酸素分圧が低くなる。その結果、センサによって検出される酸素の分子数が実質的に少なくなり、センサ出力が低下することとなる。そのため、ガス濃度検出を精度よく実施するためには湿度を把握し、その湿度に応じてセンサ電流等を補正することが好ましい。 Incidentally, it is known that the sensor current flowing through the A / F sensor varies depending on the humidity in the gas to be detected. For example, when the gas to be detected is in a high humidity state, the oxygen partial pressure in the atmosphere is lower than that in a low humidity state. As a result, the number of oxygen molecules detected by the sensor is substantially reduced, and the sensor output is reduced. Therefore, in order to accurately detect the gas concentration, it is preferable to grasp the humidity and correct the sensor current or the like according to the humidity.
　しかしながら、Ａ／Ｆセンサ２０は排気管１４に設置されているため、大気の湿度を直接検出できる機会は、燃料カット時などの場合に限られていた。そのため、運転中にＡ／Ｆセンサ２０で大気の湿度を頻繁に把握することは困難であった。ここで、エンジン１０の燃焼後に排気管１４を通過する排気に含まれる水分量は、エンジンの燃焼で発生する水分量と燃焼に用いた空気に含まれる水分量の和として算出される。このことから、排気の湿度と大気の湿度との間には、相関関係があるといえる。その結果、燃焼により発生する水分量がほぼ一定の状態であれば、排気の湿度を検出することで、大気の湿度を把握することができる。すなわち、エンジン１０の運転中であっても、大気の湿度変化を捉えることができ、その湿度に応じてセンサ出力を補正することができる。 However, since the A / F sensor 20 is installed in the exhaust pipe 14, the opportunity to directly detect the atmospheric humidity has been limited to cases such as when the fuel is cut. For this reason, it is difficult to frequently grasp atmospheric humidity with the A / F sensor 20 during operation. Here, the amount of water contained in the exhaust passing through the exhaust pipe 14 after combustion of the engine 10 is calculated as the sum of the amount of water generated by the combustion of the engine and the amount of water contained in the air used for combustion. From this, it can be said that there is a correlation between the humidity of the exhaust and the humidity of the atmosphere. As a result, if the amount of water generated by combustion is almost constant, the humidity of the atmosphere can be grasped by detecting the humidity of the exhaust. That is, even when the engine 10 is in operation, a change in atmospheric humidity can be captured, and the sensor output can be corrected according to the humidity.
　そこで、本実施形態では、所定運転状態において、排気の湿度を推定し、その湿度によるセンサ出力への影響を補正することで、大気の湿度変化に対応して、排気中の酸素濃度、ひいてはＡ／Ｆ値を算出する。なお、排気の湿度の推定には、図４に示す電圧－電流特性（Ｖ－Ｉ特性）を利用している。図４では、センサ素子３０の印加電圧ＶＰを横軸に示し、素子電流ＩＬを縦軸に示している。図４の特性線において、横軸である電圧軸に平行な直線部分（フラット部分）は限界電流としての素子電流ＩＬを特定する限界電流域である。なお、限界電流域での素子電流ＩＬの増減は、空燃比の増減（すなわち、リーン・リッチの程度）に対応している。つまり、空燃比がリーン側になるほど素子電流ＩＬは増大し、空燃比がリッチ側になるほど素子電流ＩＬは減少する。 Therefore, in the present embodiment, in a predetermined operation state, the humidity of the exhaust gas is estimated, and the influence of the humidity on the sensor output is corrected, so that the oxygen concentration in the exhaust gas, that is, A / F value is calculated. Note that the voltage-current characteristic (VI characteristic) shown in FIG. 4 is used to estimate the humidity of the exhaust gas. In FIG. 4, the applied voltage VP of the sensor element 30 is shown on the horizontal axis, and the element current IL is shown on the vertical axis. In the characteristic line of FIG. 4, a straight line portion (flat portion) parallel to the voltage axis that is the horizontal axis is a limit current region that specifies the element current IL as a limit current. Note that the increase / decrease in the element current IL in the limit current region corresponds to the increase / decrease in the air-fuel ratio (that is, the degree of lean / rich). That is, the element current IL increases as the air-fuel ratio becomes leaner, and the element current IL decreases as the air-fuel ratio becomes richer.
　一方、限界電流域よりも高電圧側で素子電流ＩＬがほぼ安定した領域は水分解域となっている。なお、水分解域は、フラット域として存在している。この水分解域では、電圧印加により排気に含まれる水が分解され、その分解により発生した酸素イオンに応じた素子電流ＩＬが検出される。そのため、水分解域での素子電流ＩＬから限界電流域での素子電流ＩＬを減じた値から、排気中の水分量、ひいては排気の湿度を算出することができる。具体的には、所定運転状態において、限界電流域に対応する電圧Ｖ１（例えば、０．４～０．５Ｖ）を印加した際に流れる電流をＩ１として取得し、続いて、水分解域に対応する電圧Ｖ２（例えば、１．０Ｖ～１．２Ｖ）を印加した際に流れる電流をＩ２として取得する。次に、これらの差であるΔＩから排気の湿度を算出する。ここでΔＩと被検出ガスの湿度（絶対湿度）は略比例関係にあり、容易に湿度を算出することができる。そして、得られた排気の湿度に基づいて、酸素濃度検出値を補正する。これにより湿度に影響されない適正なＡ／Ｆ値を算出することができる。 On the other hand, the region where the element current IL is almost stable on the higher voltage side than the limit current region is the water decomposition region. The water splitting area exists as a flat area. In this water decomposition region, water contained in the exhaust gas is decomposed by voltage application, and an element current IL corresponding to oxygen ions generated by the decomposition is detected. Therefore, it is possible to calculate the amount of moisture in the exhaust gas and hence the humidity of the exhaust gas from the value obtained by subtracting the device current IL in the limit current region from the device current IL in the water decomposition region. Specifically, in a predetermined operating state, the current that flows when a voltage V1 (for example, 0.4 to 0.5 V) corresponding to the limit current region is applied is acquired as I1, and subsequently corresponds to the water decomposition region. A current that flows when a voltage V2 (for example, 1.0 V to 1.2 V) is applied is acquired as I2. Next, the humidity of the exhaust is calculated from ΔI which is the difference between them. Here, ΔI and the humidity (absolute humidity) of the gas to be detected have a substantially proportional relationship, and the humidity can be easily calculated. The oxygen concentration detection value is corrected based on the obtained humidity of the exhaust gas. As a result, an appropriate A / F value that is not affected by humidity can be calculated.
　なお、本実施形態では、基準電圧として常時は限界電流域における電圧（例えば、電圧Ｖ１）が用いられ、検出される素子電流ＩＬ（例えば、電流Ｉ１）に基づいて、排気中の酸素濃度が算出される。一方で、排気の湿度を推定する場合、つまり車両が所定運転状態となった場合にのみ水分解域における電圧（例えば、電圧Ｖ２）が用いられることとなる。 In the present embodiment, a voltage in the limit current region (eg, voltage V1) is always used as the reference voltage, and the oxygen concentration in the exhaust gas is calculated based on the detected element current IL (eg, current I1). Is done. On the other hand, the voltage (for example, voltage V2) in the water splitting region is used only when estimating the humidity of exhaust gas, that is, when the vehicle is in a predetermined operating state.
　以下、マイコン４０により実施される湿度検出の処理手順について、図５のフローチャートを用いて説明する。本処理は、マイコン４０により所定周期（例えば、１０ｍｓ）で繰り返し実行される。 Hereinafter, the humidity detection processing procedure performed by the microcomputer 40 will be described with reference to the flowchart of FIG. This process is repeatedly executed by the microcomputer 40 at a predetermined cycle (for example, 10 ms).
　まず、ステップＳ１１では、エンジン１０が燃焼状態であり、かつ所定運転状態であるか否かを判定する。所定運転状態としては、エンジン１０の燃焼が安定している状態、つまり燃焼により発生するガスの組成が安定している状態であることが好ましい。本実施形態では、例えば、車両がアイドル運転状態である場合に、所定運転状態であると判定する。そして、ステップＳ１１が肯定されると、ステップＳ１２に進む。なお、湿度算出の頻度を実施条件に加えてもよく、例えば、前回の湿度算出から所定時間が経過している場合に、ステップＳ１２以降を実施するようにしてもよい。 First, in step S11, it is determined whether or not the engine 10 is in a combustion state and is in a predetermined operation state. The predetermined operating state is preferably a state where the combustion of the engine 10 is stable, that is, a state where the composition of the gas generated by the combustion is stable. In the present embodiment, for example, when the vehicle is in an idle operation state, it is determined that the vehicle is in a predetermined operation state. If step S11 is affirmed, the process proceeds to step S12. Note that the frequency of humidity calculation may be added to the execution conditions. For example, when a predetermined time has elapsed since the previous humidity calculation, step S12 and subsequent steps may be performed.
　ステップＳ１２では、印加電圧制御回路５４により電圧Ｖ１を印加する。そして、電圧Ｖ１のもとで電極３５，３６間に流れる素子電流ＩＬを電流Ｉ１として取得する（ステップＳ１３）。続いて、ステップＳ１４では、印加電圧を電圧Ｖ１から電圧Ｖ２へ変更し、印加電圧制御回路５４により電圧Ｖ２を印加する。そして、電圧Ｖ２のもとで電極３５，３６間に流れる素子電流ＩＬを電流Ｉ２として取得する（ステップＳ１５）。 In step S12, the applied voltage control circuit 54 applies the voltage V1. Then, the element current IL flowing between the electrodes 35 and 36 under the voltage V1 is acquired as the current I1 (step S13). Subsequently, in step S14, the applied voltage is changed from the voltage V1 to the voltage V2, and the applied voltage control circuit 54 applies the voltage V2. Then, the element current IL flowing between the electrodes 35 and 36 under the voltage V2 is acquired as the current I2 (step S15).
　なお、ステップＳ１３で取得される電流Ｉ１は、電圧を電圧Ｖ１から電圧Ｖ２へ変更する直前に取得されることが好ましい。これにより、電流Ｉ１及び電流Ｉ２の取得タイミングの時間差を小さくし、より正確な湿度を推定することができる。 Note that the current I1 acquired in step S13 is preferably acquired immediately before the voltage is changed from the voltage V1 to the voltage V2. Thereby, the time difference of the acquisition timing of the electric current I1 and the electric current I2 can be made small, and a more exact humidity can be estimated.
　続くステップＳ１６では、電流Ｉ２から電流Ｉ１を減算することによって、ΔＩを算出する。ここで、ΔＩは、排気中に含まれる水分子由来の酸素濃度に応じた値となる。ステップＳ１７に進むと、ΔＩに基づいて排気の湿度を推定する。ここで、排気の湿度は、例えば図６に示すΔＩと湿度との関係により推定することができる。図６の関係は、例えば適合により、所定の温度条件下において湿度条件を変化させつつＩ１，Ｉ２を計測することで得られたデータに基づくものである。図６に示されるように、湿度が高くなるほどΔＩは大きくなる傾向となる。これは、湿度が高いほど排気中に含まれる水分子が多くなり、その水分子から解離される酸素イオンが多くなるためである。なお、排気の湿度を推定すると、本処理を終了する。 In the subsequent step S16, ΔI is calculated by subtracting the current I1 from the current I2. Here, ΔI is a value corresponding to the oxygen concentration derived from water molecules contained in the exhaust gas. In step S17, the humidity of the exhaust is estimated based on ΔI. Here, the humidity of the exhaust can be estimated based on the relationship between ΔI and humidity shown in FIG. 6, for example. The relationship in FIG. 6 is based on data obtained by measuring I1 and I2 while changing the humidity condition under a predetermined temperature condition due to, for example, adaptation. As shown in FIG. 6, ΔI tends to increase as the humidity increases. This is because the higher the humidity, the more water molecules contained in the exhaust gas, and the more oxygen ions dissociated from the water molecules. If the humidity of the exhaust gas is estimated, this process is terminated.
　一方、ステップＳ１１で車両が所定運転状態でないと判定した場合は、そのまま本処理を終了する。ここで、ステップＳ１３及びステップＳ１５が「取得部」に相当し、ステップＳ１７が「湿度推定部」に相当する。 On the other hand, if it is determined in step S11 that the vehicle is not in the predetermined driving state, this processing is terminated as it is. Here, step S13 and step S15 correspond to an “acquisition unit”, and step S17 corresponds to a “humidity estimation unit”.
　次に、マイコン４０により実施されるＡ／Ｆ値取得の処理手順について、図７のフローチャートを用いて説明する。本処理は、マイコン４０により所定周期（例えば、１０ｍｓ）で繰り返し実行される。 Next, an A / F value acquisition process performed by the microcomputer 40 will be described with reference to the flowchart of FIG. This process is repeatedly executed by the microcomputer 40 at a predetermined cycle (for example, 10 ms).
　まず、ステップＳ２１では、限界電流域における電圧を印加した際の素子電流ＩＬを取得する。続くステップＳ２２では、ステップＳ１７で推定した排気の湿度を読み込む。そして、ステップＳ２３に進み、ＲＯＭに予め記憶されている換算マップを参照し、ＩＬ及び排気の湿度に基づいて、排気中の酸素濃度、ひいてはＡ／Ｆ値を算出する（ステップＳ２４）。図８は、換算マップの一例であり、空燃比（Ａ／Ｆ）と、素子電流ＩＬと、湿度条件との関係を規定したものである。この場合、湿度が高くなるほど酸素分圧が低くなることに起因して、同じ素子電流ＩＬであっても、Ａ／Ｆ値が小さい値として算出されるようになっている。 First, in step S21, an element current IL when a voltage in the limit current region is applied is acquired. In the subsequent step S22, the humidity of the exhaust gas estimated in step S17 is read. Then, the process proceeds to step S23, and the oxygen concentration in the exhaust gas and thus the A / F value is calculated based on the IL and the humidity of the exhaust gas with reference to the conversion map stored in advance in the ROM (step S24). FIG. 8 is an example of a conversion map, which defines the relationship among the air-fuel ratio (A / F), the element current IL, and the humidity condition. In this case, because the oxygen partial pressure decreases as the humidity increases, the A / F value is calculated as a small value even for the same element current IL.
　このように、排気の湿度、ひいては大気の湿度の影響を補正した空燃比が算出される。ここで、ステップＳ２３及びステップＳ２４が「補正部」に相当する。 In this way, the air-fuel ratio is corrected by correcting the influence of the humidity of the exhaust gas, and consequently the humidity of the atmosphere. Here, Step S23 and Step S24 correspond to a “correction unit”.
　以上、詳述した本実施形態によれば、以下の優れた効果が得られる。 As described above, according to the embodiment described in detail, the following excellent effects can be obtained.
　上記構成では、エンジン１０の所定運転状態で限界電流域での電圧印加に伴う電流Ｉ１と水分解域での電圧印加に伴う電流Ｉ２とを取得し、それら電流の差に基づいて、排気の湿度を推定するようにした。そのため、燃焼により生じる水分量を一定にした状態下で、排気の湿度を推定することができる。この場合、燃焼による水分量が一定であれば、排気の水分量に起因するガス濃度検出値の変化は、大気中に含まれる水分量の変化に基づくものとなる。すなわち、排気の湿度は大気の湿度に依存したものとなるため、所定運転状態で推定した排気の湿度を用いることにより、大気の湿度に応じたセンサ出力の補正を実現できる。つまり、本構成では、エンジン運転中であっても、大気の湿度変化を捉えることができ、その湿度に応じてセンサ出力を補正することができる。これにより、Ａ／Ｆセンサ２０による湿度検出の機会を増やし、ガス濃度測定を適正に実施することができる。 In the above configuration, the current I1 associated with the voltage application in the limit current region and the current I2 associated with the voltage application in the water decomposition region are acquired in a predetermined operating state of the engine 10, and the exhaust humidity is determined based on the difference between these currents. Was estimated. Therefore, it is possible to estimate the humidity of the exhaust gas in a state where the amount of water generated by combustion is constant. In this case, if the moisture content due to combustion is constant, the change in the gas concentration detection value due to the moisture content in the exhaust is based on the change in the moisture content contained in the atmosphere. That is, since the exhaust humidity depends on the atmospheric humidity, the sensor output can be corrected according to the atmospheric humidity by using the exhaust humidity estimated in the predetermined operation state. That is, in this configuration, even when the engine is operating, a change in atmospheric humidity can be captured, and the sensor output can be corrected according to the humidity. Thereby, the opportunity of humidity detection by A / F sensor 20 can be increased, and gas concentration measurement can be implemented appropriately.
　また、水分解域で出力される電流Ｉ２と限界電流域で出力される電流Ｉ１との差から湿度を推定するようにした。そのため、排気の湿度を精度良く把握でき、湿度補正を適正に実施することができる。 Also, the humidity was estimated from the difference between the current I2 output in the water decomposition region and the current I1 output in the limit current region. Therefore, the humidity of the exhaust can be accurately grasped, and humidity correction can be performed appropriately.
　具体的には、燃料噴射量が所定量であるアイドル運転状態において、電流Ｉ１及び電流Ｉ２のそれぞれを取得するようにした。この場合、燃焼によって発生する水分量がほぼ一定となり、排気の湿度、ひいては大気の湿度を精度良く検出することができる。 Specifically, each of the current I1 and the current I2 is acquired in an idle operation state in which the fuel injection amount is a predetermined amount. In this case, the amount of water generated by combustion becomes substantially constant, and the humidity of the exhaust gas, and hence the humidity of the atmosphere, can be detected with high accuracy.
　（第２実施形態）
　次に、第２実施形態について第１実施形態との相違点を中心に説明する。上述のとおり、排気に含まれる水分量は、エンジン１０の燃焼で発生する水分量と燃焼に用いた空気に含まれる水分量の和として算出される。この場合、大気の湿度が安定している状態では、排気の湿度は、燃焼水分量に依存したものとなる。そのため、アイドル運転状態以外の運転状態であっても、その運転状態における燃焼水分量を推定することで、排気の湿度を推定することができる。 (Second Embodiment)
Next, the second embodiment will be described focusing on the differences from the first embodiment. As described above, the amount of water contained in the exhaust gas is calculated as the sum of the amount of water generated by the combustion of the engine 10 and the amount of water contained in the air used for combustion. In this case, when the atmospheric humidity is stable, the exhaust humidity depends on the amount of combustion moisture. Therefore, even in an operation state other than the idle operation state, the humidity of the exhaust gas can be estimated by estimating the amount of combustion moisture in the operation state.
　図９は、本実施形態における湿度検出の処理を示すフローチャートであり、本処理は、上述の図５に置き換えてマイコン４０により実行される。ここでは、図５との相違点のみを説明する。 FIG. 9 is a flowchart showing the humidity detection process in the present embodiment. This process is executed by the microcomputer 40 in place of the above-described FIG. Here, only differences from FIG. 5 will be described.
　図９では、ステップＳ３１で、車両が所定運転状態であるか否かを判定する。具体的には、予め定められた複数の運転状態のうちいずれかであるかを判定する。例えば、所定運転状態には、アイドル回転速度の運転状態と、アイドル回転速度よりも高回転の別の回転速度（例えば、２０００ｒｐｍ）の運転状態とが含まれる。ステップＳ３１が肯定された場合は、ステップＳ１２へ進み、それ以降ステップＳ１６までは、図５と同様の処理が実行される。そして、ステップＳ３２へ進むと、燃焼により発生する水分量を推定する。ここで、水分量の推定は、運転状態ごとに、燃料噴射弁１２による燃料噴射量、又はそれと相関するパラメータ（エンジン回転速度Ｎｅや負荷など）に基づいて推定することができる。具体的には、燃料噴射量に応じた所定の水分量が、予め適合などにより定められている。ちなみに、燃料噴射量が増大するほど、燃焼により生成する水分量は増える傾向となる。 In FIG. 9, it is determined in step S31 whether or not the vehicle is in a predetermined driving state. Specifically, it is determined whether it is any of a plurality of predetermined operating states. For example, the predetermined operation state includes an operation state at an idle rotation speed and an operation state at another rotation speed (for example, 2000 rpm) higher than the idle rotation speed. When step S31 is affirmed, it progresses to step S12, and the process similar to FIG. 5 is performed after that to step S16. And when progressing to step S32, the moisture content which generate | occur | produces by combustion is estimated. Here, the moisture amount can be estimated based on the fuel injection amount by the fuel injection valve 12 or a parameter (such as the engine rotational speed Ne or the load) correlated with the fuel injection amount for each operation state. Specifically, a predetermined moisture amount corresponding to the fuel injection amount is determined in advance by adaptation or the like. Incidentally, the amount of water generated by combustion tends to increase as the fuel injection amount increases.
　続いて、ステップＳ３３に進むと、各々異なる複数の運転状態のうちそれぞれに応じた燃焼水分量を考慮して、排気の湿度を推定する。具体的には、その運転状態における燃焼水分量と基準となる運転状態（例えば、アイドル運転状態）における燃焼水分量との差分を、基準となる運転状態での排気の湿度に加味する。これにより、その運転状態での湿度を推定することができる。なお、推定された湿度は、第１実施形態と同様に、図７のＡ／Ｆ値取得の処理に用いられる。 Subsequently, when the process proceeds to step S33, the humidity of the exhaust gas is estimated in consideration of the amount of combustion moisture corresponding to each of a plurality of different operating states. Specifically, the difference between the amount of combustion moisture in the operation state and the amount of combustion moisture in the reference operation state (for example, idle operation state) is added to the humidity of the exhaust gas in the reference operation state. Thereby, the humidity in the driving | running state can be estimated. Note that the estimated humidity is used in the A / F value acquisition process of FIG. 7 as in the first embodiment.
　上記の構成によれば、アイドル運転状態以外の運転状態であっても、燃焼水分量を用いることで、排気の湿度を推定することができる。これにより、様々な運転状態においても湿度検出をすることができ、湿度検出の機会を増やすことができる。 According to the above configuration, the humidity of the exhaust gas can be estimated by using the combustion moisture amount even in the operation state other than the idle operation state. Thereby, humidity detection can be performed even in various operating states, and opportunities for humidity detection can be increased.
　本開示は上記実施形態に限らず、例えば次のように実施されてもよい。 The present disclosure is not limited to the above embodiment, and may be implemented as follows, for example.
　・上記第１実施形態では、湿度を検出する際の所定運転状態として、アイドル運転状態としたが、エンジン１０の燃焼により発生するガスの組成が安定している状態であれば、これに限られない。例えば、燃料噴射弁１２による燃料噴射量が所定時間一定である状態が考えられる。 In the first embodiment, the idling operation state is set as the predetermined operation state when detecting the humidity. However, the predetermined operation state is limited to this as long as the composition of the gas generated by the combustion of the engine 10 is stable. Absent. For example, a state where the fuel injection amount by the fuel injection valve 12 is constant for a predetermined time can be considered.
　また、所定運転状態の場合に加え、排気管内が大気に置換された場合にも湿度を検出する構成であってもよい。排気管内が大気に置換された場合は、例えば、燃料カットの場合やエンジン１０を停止した場合が考えられる。この構成によれば、排気が大気となるため、大気の湿度を直接検出することができる。これにより、大気の湿度検出の機会を増やすことができる。 Further, in addition to the case of a predetermined operation state, the configuration may be such that the humidity is detected when the inside of the exhaust pipe is replaced with the atmosphere. When the inside of the exhaust pipe is replaced with the atmosphere, for example, the case of fuel cut or the case where the engine 10 is stopped can be considered. According to this configuration, since the exhaust becomes the atmosphere, the humidity of the atmosphere can be directly detected. Thereby, the opportunity of atmospheric humidity detection can be increased.
　・上記実施形態では、換算マップを用いて、Ａ／Ｆ値を算出したが、マップに代えて、素子電流ＩＬに対応する相関関数を用いてＡ／Ｆ値を算出してもよい。この場合、ステップＳ２３では、関数に基づいて演算処理を行う。 In the above embodiment, the A / F value is calculated using the conversion map, but the A / F value may be calculated using a correlation function corresponding to the element current IL instead of the map. In this case, in step S23, arithmetic processing is performed based on the function.
　・上記実施形態では、素子電流ＩＬと排気の湿度との組み合わせに対応して、Ａ／Ｆ値を算出する構成としたが、例えば、Ａ／Ｆ値に代えて素子電流ＩＬの誤差ΔＩＬ、つまり素子電流ＩＬの補正値を算出する構成としてもよい。この場合、誤差ΔＩＬは、素子電流ＩＬの補正値として用いられる。すなわち、この補正値を加味した素子電流ＩＬに基づいて、酸素濃度やＡ／Ｆ値が算出される。 In the above embodiment, the A / F value is calculated corresponding to the combination of the element current IL and the exhaust humidity. For example, instead of the A / F value, the error ΔIL of the element current IL, that is, The correction value of the element current IL may be calculated. In this case, the error ΔIL is used as a correction value for the element current IL. That is, the oxygen concentration and the A / F value are calculated on the basis of the element current IL taking this correction value into consideration.
　・センサ出力の精度を向上させるために、センサ制御回路５０にセンサ個体差の情報を含む調整抵抗や識別抵抗を接続する構成であってもよい。また、センサ個体差情報をＱＲコード（登録商標）等によりコード記憶部に記憶させるとともに、そのコード記憶部をＡ／Ｆセンサ２０に張り付けておき、コード情報の読み取りによりセンサ制御回路５０においてセンサ個体差情報を認識させる構成としてもよい。これにより個々のセンサ特性のばらつきを抑制することができる。 In order to improve the accuracy of the sensor output, an adjustment resistor or an identification resistor including information on individual sensor differences may be connected to the sensor control circuit 50. Further, the sensor individual difference information is stored in the code storage unit by QR code (registered trademark) or the like, and the code storage unit is attached to the A / F sensor 20, and the sensor control circuit 50 reads the code information and the sensor individual circuit It is good also as a structure which recognizes difference information. As a result, variations in individual sensor characteristics can be suppressed.
　このようにセンサ個体差情報を取得できる構成において、その個体差情報に基づいて、排気の湿度を推定する構成としてもよい。具体的には、マイコン４０は、図７のステップＳ２３において、センサ個体差情報に基づいて換算マップを補正する構成とする。又は、換算マップの参照結果を、センサ個体差情報により補正する構成とする。これにより、センサ個体差を吸収した上で、適正に湿度の推定を実施できる。 In such a configuration in which sensor individual difference information can be acquired, the humidity of exhaust gas may be estimated based on the individual difference information. Specifically, the microcomputer 40 is configured to correct the conversion map based on the sensor individual difference information in step S23 of FIG. Or it is set as the structure which correct | amends the reference result of a conversion map by sensor individual difference information. Thereby, it is possible to appropriately estimate the humidity after absorbing the sensor individual difference.
　・上記実施形態では、Ａ／Ｆセンサ２０を排気管１４に設け、その排気管内の排気をＡ／Ｆセンサ２０の被検出ガスとしたが、これを変更してもよい。例えば、エンジン排気側と吸気側とＥＧＲ配管により接続する構成において、エンジン吸気管においてＥＧＲ配管との接続部よりも下流側にＡ／Ｆセンサ２０を設け、その吸気管内のガス（すなわち、排気と新規との混合ガス）をＡ／Ｆセンサ２０の被検出ガスとしてもよい。 In the above embodiment, the A / F sensor 20 is provided in the exhaust pipe 14 and the exhaust gas in the exhaust pipe is the gas to be detected by the A / F sensor 20, but this may be changed. For example, in a configuration in which the engine exhaust side and the intake side are connected by EGR piping, an A / F sensor 20 is provided in the engine intake pipe downstream of the connection portion with the EGR pipe, and the gas in the intake pipe (that is, exhaust and A new gas mixture) may be used as a gas to be detected by the A / F sensor 20.
　・センサ素子３０の基準ガス室に導入される基準ガスは、酸素濃度が既知であればよく、大気以外であってもよい。ガスセンサは、上記実施形態のＡ／Ｆセンサ２０以外に、起電力セルとポンプセルとを備える、いわゆる２セル構造のガスセンサであってもよい。さらに、センサ素子３０として、積層型構造のもの以外に、コップ型構造のものを用いることも可能である。 The reference gas introduced into the reference gas chamber of the sensor element 30 is not limited as long as the oxygen concentration is known and may be other than the atmosphere. The gas sensor may be a so-called two-cell gas sensor including an electromotive force cell and a pump cell in addition to the A / F sensor 20 of the above embodiment. Further, as the sensor element 30, a cup-type structure can be used in addition to the stacked-type structure.
　・ガスセンサは、酸素濃度とは異なる特定ガス濃度を検出するものであってもよい。例えば、排気（被検出ガス）中のＮＯｘ濃度を検出するＮＯｘセンサであってもよい。ＮＯｘセンサは、酸素のポンピングによりチャンバ内の酸素濃度を一定とするポンプセルと、酸素ポンピング後のガスを用いてＮＯｘ濃度を検出するセンサセルとを有する構成からなり、これら各セルでは、限界電流域での電圧印加により酸素濃度の検出、ＮＯｘ濃度の検出が可能となっている。この場合、ポンプセル出力に基づいて水分量の推定を行うこと、又はセンサセル出力に基づいて水分量の推定を行うことが可能である。 · The gas sensor may detect a specific gas concentration different from the oxygen concentration. For example, a NOx sensor that detects the NOx concentration in the exhaust gas (the gas to be detected) may be used. The NOx sensor includes a pump cell that keeps the oxygen concentration in the chamber constant by pumping oxygen and a sensor cell that detects the NOx concentration using the gas after oxygen pumping. By applying this voltage, it is possible to detect the oxygen concentration and the NOx concentration. In this case, it is possible to estimate the amount of water based on the pump cell output or to estimate the amount of water based on the sensor cell output.
　・上記実施形態のマイコン４０は、ガソリンエンジン以外にも、ディーゼルエンジンや他の形式のエンジンに用いられるガスセンサに適用されてもよい。 -The microcomputer 40 of the said embodiment may be applied to the gas sensor used for a diesel engine and another type engine other than a gasoline engine.
　本開示は、実施例に準拠して記述されたが、本開示は当該実施例や構造に限定されるものではないと理解される。本開示は、様々な変形例や均等範囲内の変形をも包含する。加えて、様々な組み合わせや形態、さらには、それらに一要素のみ、それ以上、あるいはそれ以下、を含む他の組み合わせや形態をも、本開示の範疇や思想範囲に入るものである。 Although the present disclosure has been described based on the embodiments, it is understood that the present disclosure is not limited to the embodiments and structures. The present disclosure includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more or less, are within the scope and spirit of the present disclosure.

Claims (6)

  1. 　固体電解質層（３１）及びそれを挟む少なくとも一対の電極（３５，３６）を有し、前記一対の電極のうち一方を、排気又は排気を含む混合ガスである被検出ガスが導かれる第１電極（３５）、他方を基準ガスを導入する基準ガス室（３８）に設けられる第２電極（３６）とするセンサ素子（３０）を備え、限界電流域での電圧印加により、前記被検出ガス中の特定ガスの濃度に応じた限界電流を出力するガスセンサ（２０）に適用され、
    　内燃機関（１０）で燃料の燃焼が行われる所定運転状態下において、前記限界電流域での電圧印加時に出力される第１電流と、前記限界電流域よりも高電圧側の水分解域での電圧印加時に出力される第２電流とを取得する取得部と、
    　前記第１電流及び前記第２電流の差に基づいて、前記被検出ガスの湿度を推定する湿度推定部と、
    　前記湿度推定部により推定した前記被検出ガスの湿度に基づいて、前記特定ガスの濃度検出値を補正する補正部と、
    を備えるガスセンサ制御装置（５０）。     A first electrode having a solid electrolyte layer (31) and at least a pair of electrodes (35, 36) sandwiching the solid electrolyte layer (31), to which a gas to be detected, which is exhaust gas or a mixed gas containing exhaust gas, is guided to one of the pair of electrodes. (35) comprising a sensor element (30) having a second electrode (36) provided in a reference gas chamber (38) for introducing a reference gas as the other, and applying a voltage in a limit current region, Applied to a gas sensor (20) that outputs a limiting current according to the concentration of a specific gas of
    In a predetermined operation state in which fuel is burned in the internal combustion engine (10), a first current that is output when a voltage is applied in the limit current region, and a water decomposition region that is higher in voltage than the limit current region. An acquisition unit for acquiring a second current output when a voltage is applied;
    A humidity estimation unit that estimates the humidity of the gas to be detected based on the difference between the first current and the second current;
    A correction unit that corrects the concentration detection value of the specific gas based on the humidity of the detected gas estimated by the humidity estimation unit;
    A gas sensor control device (50).
  2. 　前記取得部は、前記内燃機関における燃料噴射量が所定量である前記所定運転状態下において、前記第１電流及び前記第２電流を取得する請求項１に記載のガスセンサ制御装置。 The gas sensor control device according to claim 1, wherein the acquisition unit acquires the first current and the second current under the predetermined operation state in which a fuel injection amount in the internal combustion engine is a predetermined amount.
  3. 　前記取得部は、アイドル運転状態を前記所定運転状態とし、そのアイドル運転状態下において、前記第１電流及び前記第２電流を取得する請求項１又は２に記載のガスセンサ制御装置。 The gas sensor control device according to claim 1 or 2, wherein the acquisition unit sets the idle operation state to the predetermined operation state, and acquires the first current and the second current under the idle operation state.
  4. 　前記取得部は、各々異なる複数の前記所定運転状態下でそれぞれ前記第１電流と前記第２電流とを取得し、
    　前記湿度推定部は、前記各所定運転状態下での前記第１電流及び前記第２電流の差と、当該各所定運転状態での燃焼水分量の差とに基づいて、前記被検出ガスの湿度を推定する請求項１乃至３のいずれか１項に記載のガスセンサ制御装置。     The acquisition unit acquires the first current and the second current, respectively, under a plurality of different predetermined operating states,
    The humidity estimation unit is configured to determine a humidity of the gas to be detected based on a difference between the first current and the second current under each predetermined operating state and a difference in the amount of combustion moisture in each predetermined operating state. The gas sensor control device according to any one of claims 1 to 3, wherein
  5. 　前記ガスセンサの出力特性を示す個体差情報を取得する情報取得部を備え、
    　前記湿度推定部は、前記個体差情報に基づいて、前記被検出ガスの湿度を推定する請求項１乃至４のいずれか１項に記載のガスセンサ制御装置。     An information acquisition unit that acquires individual difference information indicating the output characteristics of the gas sensor,
    The gas sensor control device according to any one of claims 1 to 4, wherein the humidity estimation unit estimates the humidity of the detection target gas based on the individual difference information.
  6. 　前記取得部は、前記所定運転状態に加え、前記被検出ガスが大気となる状態においても、前記第１電流及び前記第２電流を取得する請求項１乃至５のいずれか１項に記載のガスセンサ制御装置。 The gas sensor according to any one of claims 1 to 5, wherein the acquisition unit acquires the first current and the second current even in a state where the detected gas is in the atmosphere in addition to the predetermined operation state. Control device.
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JP7430116B2 (en) 2020-07-09 2024-02-09 日本特殊陶業株式会社 Gas sensor unit, internal combustion engine control system and oxygen information acquisition method

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP7122935B2 (en) * 2018-10-26 2022-08-22 株式会社Soken carbon dioxide detector
JP2020076361A (en) * 2018-11-07 2020-05-21 株式会社豊田自動織機 Humidity estimation device

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10267885A (en) * 1997-03-21 1998-10-09 Ngk Spark Plug Co Ltd Correcting method of gas sensor
JP2004138486A (en) * 2002-10-17 2004-05-13 Toyota Motor Corp NOx SENSOR
JP2011180042A (en) * 2010-03-02 2011-09-15 Ngk Spark Plug Co Ltd Device for control of gas sensor, and control system of gas sensor
JP2012077732A (en) * 2010-10-06 2012-04-19 Nippon Soken Inc Output correction device for air-fuel ratio
WO2013179545A1 (en) * 2012-05-31 2013-12-05 日本特殊陶業株式会社 Gas sensor control device

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10267885A (en) * 1997-03-21 1998-10-09 Ngk Spark Plug Co Ltd Correcting method of gas sensor
JP2004138486A (en) * 2002-10-17 2004-05-13 Toyota Motor Corp NOx SENSOR
JP2011180042A (en) * 2010-03-02 2011-09-15 Ngk Spark Plug Co Ltd Device for control of gas sensor, and control system of gas sensor
JP2012077732A (en) * 2010-10-06 2012-04-19 Nippon Soken Inc Output correction device for air-fuel ratio
WO2013179545A1 (en) * 2012-05-31 2013-12-05 日本特殊陶業株式会社 Gas sensor control device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP7430116B2 (en) 2020-07-09 2024-02-09 日本特殊陶業株式会社 Gas sensor unit, internal combustion engine control system and oxygen information acquisition method

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