WO2014196559A1 - ガスセンサ制御装置 - Google Patents

ガスセンサ制御装置 Download PDF

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Publication number
WO2014196559A1
WO2014196559A1 PCT/JP2014/064825 JP2014064825W WO2014196559A1 WO 2014196559 A1 WO2014196559 A1 WO 2014196559A1 JP 2014064825 W JP2014064825 W JP 2014064825W WO 2014196559 A1 WO2014196559 A1 WO 2014196559A1
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WIPO (PCT)
Prior art keywords
abnormality
oxygen supply
current
solid electrolyte
electrolyte layer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
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PCT/JP2014/064825
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English (en)
French (fr)
Japanese (ja)
Inventor
克英 秋元
秀一 中野
雄史 福田
朝文 藤井
隆仁 増子
俊英 鈴村
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Denso Corp
Original Assignee
Denso Corp
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Publication date
Application filed by Denso Corp filed Critical Denso Corp
Priority to US14/896,100 priority Critical patent/US10082482B2/en
Priority to EP14807068.3A priority patent/EP3006930B1/en
Publication of WO2014196559A1 publication Critical patent/WO2014196559A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • G01N27/416—Systems
    • G01N27/4163—Systems checking the operation of, or calibrating, the measuring apparatus
    • 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
    • G01N27/417—Systems using cells, i.e. more than one cell and probes with solid electrolytes
    • G01N27/4175—Calibrating or checking the analyser
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/22—Safety or indicating devices for abnormal conditions
    • F02D41/222—Safety or indicating devices for abnormal conditions relating to the failure of sensors or parameter detection devices
    • 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
    • G01N27/4065—Circuit arrangements specially adapted therefor
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Definitions

  • the present invention relates to a control device for a gas sensor that generates a sensor output in accordance with the oxygen concentration in exhaust gas.
  • gas sensors using solid electrolytes such as stabilized zirconia have been used as sensors for detecting the oxygen concentration contained in the exhaust of in-vehicle engines, for example, and various techniques for eliminating detection errors of the gas sensors have been proposed. ing.
  • a sensor output value is acquired under a situation where fuel cut is performed in the engine, and a deviation of the sensor output value is determined as an output correction value by comparing the sensor output value with a known reference output value in an atmospheric state.
  • require is known (for example, refer patent document 1).
  • the correction gain is calculated using the output correction value (atmospheric output error) obtained in the atmospheric correction process, and when the air-fuel ratio deviates from the stoichiometric (theoretical air-fuel ratio), the sensor output is output using the correction gain. The value is corrected.
  • the gain correction of the sensor output value can be performed by using the correction gain calculated by the atmospheric correction process as described above.
  • a gain error occurs when the diffusion layer is clogged or cracked.
  • a gain error can be corrected. Become.
  • abnormalities in the gas sensor may include cracking of the solid electrolyte layer in addition to clogging or cracking of the diffusion layer.
  • a crack occurs in the solid electrolyte layer
  • the exhaust gas flows into the atmosphere chamber through the crack and an output error due to the exhaust occurs.
  • a deviation (error) of the sensor output value occurs even if stoichiometric.
  • the determination of such a crack abnormality in the solid electrolyte layer has not been performed, and it has not been possible to specify the abnormality type for the crack abnormality in the solid electrolyte layer.
  • the main object of the present invention is to provide a gas sensor control device that can appropriately determine the occurrence of cracking abnormality in a solid electrolyte layer in a gas sensor.
  • the gas sensor control device includes a solid electrolyte layer, a first electrode disposed on one side of the solid electrolyte layer so as to be exposed to the exhaust gas of the internal combustion engine, and the other side of the solid electrolyte layer facing the air chamber.
  • a gas sensor that includes a sensor element having a second electrode arranged and generates a sensor output according to the oxygen concentration in the exhaust gas is a control target.
  • the gas sensor control device includes oxygen supply means for supplying oxygen from the second electrode side to the first electrode side via the solid electrolyte layer by applying a predetermined voltage or a predetermined current between the first electrode and the second electrode.
  • an abnormality determining means for determining an abnormality in cracking of the solid electrolyte layer based on a current or an electromotive force between the first electrode and the second electrode generated when the oxygen supply by the oxygen supply means is started.
  • the exhaust enters the atmosphere chamber through the crack, and the oxygen concentration in the atmosphere chamber decreases.
  • the oxygen concentration in the air chamber is lower than that in the normal state
  • the oxygen supply amount (oxygen pumping amount) generated by the voltage application is The current is less likely to flow between the first electrode and the second electrode.
  • the supply amount of oxygen (oxygen pumping amount) generated by the application of the current is small, and the sensor electromotive force generated by the supply of oxygen increases.
  • Sectional drawing which shows the structure of a sensor element.
  • the conceptual diagram which shows the output characteristic of an A / F sensor.
  • the conceptual diagram which shows the normal time of a sensor element, and the time of a Zr crack.
  • the time chart which shows the time change of the applied voltage and element current at the time of normal time and a Zr crack.
  • the flowchart which shows the procedure of the abnormality determination process of the diffused resistance layer which concerns on 1st Embodiment.
  • the flowchart which shows the procedure of the determination process of Zr crack abnormality which concerns on 1st Embodiment.
  • the time chart which shows the time change of the applied voltage and element current at the time of the normal time which concerns on a 1st modification, and a Zr crack.
  • the conceptual diagram which shows the whole structure of the gas sensor control apparatus which concerns on a 2nd modification.
  • the conceptual diagram which shows the relationship between the air fuel ratio which concerns on a 3rd modification, and a negative voltage.
  • the conceptual diagram which shows the structure of the sensor control circuit which concerns on 2nd Embodiment.
  • the conceptual diagram which shows the normal time of a sensor element, and the time of a Zr crack.
  • the time chart which shows the time change of the element current and the voltage between terminals at the time of normal time and a Zr crack.
  • the flowchart which shows the procedure of the determination process of Zr crack abnormality which concerns on 2nd Embodiment.
  • the conceptual diagram which shows the whole structure of the gas sensor control apparatus which concerns on 3rd Embodiment.
  • the time chart which shows the time change of the applied voltage and element current at the time of the normal time which concerns on a 6th modification, and a Zr crack.
  • the conceptual diagram which shows the relationship between the air fuel ratio which concerns on a 6th modification, and the determination threshold value.
  • the conceptual diagram which shows the relationship between the element temperature which concerns on an 8th modification, and the determination threshold value.
  • the present embodiment embodies an air-fuel ratio detection device that detects the oxygen concentration (air-fuel ratio: A / F ratio) in the exhaust gas using exhaust gas discharged from an on-vehicle engine (internal combustion engine) as a detected gas.
  • the detection result of the fuel ratio is used in an air-fuel ratio control system constituted by an engine ECU or the like.
  • air-fuel ratio control system stoichiometric air-fuel ratio control for feedback control of the air-fuel ratio in the vicinity of the stoichiometric control, lean air-fuel ratio control for feedback control of the air-fuel ratio in a predetermined lean region, and the like are appropriately performed.
  • the A / F sensor is provided in the exhaust pipe of the engine, and generates sensor output corresponding to the oxygen concentration in the exhaust gas with the exhaust gas flowing in the exhaust pipe as a detection target.
  • the A / F sensor includes a sensor element 10 that has a solid electrolyte body and flows an element current in accordance with the oxygen concentration in the exhaust gas in a state where a voltage is applied. 10 shows a cross-sectional configuration.
  • the sensor element 10 is actually formed in a long shape extending in the direction orthogonal to the paper surface of FIG. 2, and the entire element is accommodated in a housing or an element cover.
  • the sensor element 10 includes a solid electrolyte layer 11, a diffusion resistance layer 12, a shielding layer 13, and an insulating layer 14, which are stacked in the vertical direction in the figure.
  • a protective layer (not shown) is provided around the element.
  • the rectangular solid electrolyte layer 11 is a partially stabilized zirconia sheet, and a pair of upper and lower electrodes 15 and 16 are disposed opposite to each other with the solid electrolyte layer 11 interposed therebetween.
  • the electrode 15 is a first electrode (exhaust side electrode)
  • the electrode 16 is a second electrode (atmosphere side electrode).
  • the diffusion resistance layer 12 is made of a porous sheet for introducing exhaust gas to the electrode 15, and the shielding layer 13 is made of a dense layer for suppressing permeation of exhaust gas.
  • the diffusion resistance layer 12 is provided with an exhaust chamber 17 so as to surround the electrode 15.
  • Both the diffusion resistance layer 12 and the shielding layer 13 are made of a ceramic such as alumina, spinel, zirconia or the like by a sheet forming method or the like, but have different gas permeability depending on the average pore diameter and porosity. It has become.
  • the insulating layer 14 is made of a high thermal conductive ceramic such as alumina, and an air duct 18 serving as an air chamber is formed at a portion facing the electrode 16.
  • a heater 19 is embedded in the insulating layer 14.
  • the heater 19 is composed of 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 12 and then flows into the exhaust chamber 17 through the diffusion resistance layer 12 and reaches the electrode 15.
  • the exhaust gas is lean, oxygen in the exhaust gas is decomposed by the electrode 15 and discharged from the electrode 16 to the atmospheric duct 18.
  • oxygen in the atmospheric duct 18 is decomposed by the electrode 16 and discharged from the electrode 15 to the exhaust side.
  • the exhaust electrode 15 is a negative electrode and the atmospheric electrode 16 is a positive electrode.
  • the electrode 15 is negative ( ⁇ ) and the electrode 16 is positive (+).
  • the applied voltage VP applied between them is a positive voltage. Therefore, conversely, the applied voltage VP applied between these electrodes with the electrode 15 being positive (+) and the electrode 16 being negative ( ⁇ ) is a negative voltage.
  • FIG. 3 is a drawing showing the output characteristics (VI characteristics) of the sensor element 10.
  • the applied voltage VP of the sensor element 10 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 VP axis, which 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 is the increase / decrease in the air / fuel ratio.
  • Ie the degree of lean / rich
  • LX in FIG. 3 represents an applied voltage characteristic line for determining the applied voltage VP, and the slope thereof substantially coincides with the resistance dominant region (the slope portion on the lower voltage side than the limit current region). For example, if the air-fuel ratio is stoichiometric, “Va” is applied between both electrodes of the sensor element 10.
  • the gas sensor control apparatus mainly includes a microcomputer (hereinafter abbreviated as “microcomputer 20”) and a sensor control circuit 30, thereby providing the sensor element 10 of the A / F sensor AS. Measurement of flowing element current, calculation of A / F value based on the element current value, and the like are performed.
  • the microcomputer 20 is configured by a well-known logical operation circuit including a CPU, various memories, an A / D converter, and the like.
  • the microcomputer 20 inputs an A / F output voltage corresponding to the element current value from the sensor control circuit 30, and 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 20 is sequentially output to an engine ECU (not shown).
  • the reference voltage power supply 33 is connected to the positive terminal (S + terminal connected to the atmospheric electrode 16) of the sensor element 10 via the operational amplifier 31 and the current detection resistor 32 (current measurement resistor).
  • the applied voltage control circuit 35 is connected to the negative terminal (S-terminal connected to the exhaust-side electrode 15) of the sensor element 10 via an operational amplifier 34.
  • the point A at one end of the current detection resistor 32 is held at the same voltage as the reference voltage Vf (eg, 2.2 V).
  • the element current flows through the current detection resistor 32, 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 10, so that the B point voltage increases. When the exhaust gas is rich, a current flows from the S ⁇ terminal to the S + terminal, so the B point voltage decreases. .
  • the applied voltage control circuit 35 as a basic configuration, the B point voltage is monitored and a voltage to be applied to the sensor element 10 is determined according to the voltage value (for example, determined based on the applied voltage straight line LX in FIG. 3).
  • the D point voltage is controlled via the operational amplifier 34.
  • the applied voltage can be fixed.
  • An amplifier circuit 37 is connected to points A and B at both ends of the current detection resistor 32, and an A / F output voltage that is an output of the amplifier circuit 37 is taken into an A / D input terminal of the microcomputer 20. .
  • the A / F value is calculated based on the A / D value of the A / F output voltage that is sequentially taken.
  • oxygen supply oxygen pumping
  • the electrode 16 side reference electrode side
  • the electrode 15 side gas detection electrode side
  • a predetermined voltage is applied, and a Zr crack (that is, crack of the solid electrolyte layer 11) abnormality of the sensor element 10 is determined based on the element current detected in the voltage application state.
  • the voltage applied so that oxygen is supplied from the electrode 16 side to the electrode 15 side is a negative voltage, for example, “Vn” in FIG. 3.
  • the sensor control circuit 30 As a configuration for switching the voltage applied to the sensor element 10 to a negative voltage, the following configuration is added to the sensor control circuit 30 in FIG. That is, the sensor control circuit 30 is provided with a switch circuit 38 between the element current measurement point (point B in the figure) and the applied voltage control circuit 35, and the switch circuit 38 receives a control command ( The switching operation is performed according to the switching control signal.
  • the switch circuit 38 is normally connected at the s1 point, and the A / F sensor AS is normally controlled in this state. That is, the point B voltage is input to the applied voltage control circuit 35, and the applied voltage is variably adjusted based on the point B voltage.
  • FIG. 4 shows the sensor element 10 during normal operation and during Zr cracking.
  • FIG. 5 shows changes over time in applied voltage and device current during normal operation and during Zr cracking.
  • the sensor applied voltage is changed from a positive voltage (for example, Va in FIG. 3) to a negative voltage (for example, Vn in FIG. 3) in the stoichiometric detection state is illustrated.
  • the peak value of the negative current immediately after switching the applied voltage to the negative voltage is “Ia1”
  • the negative current when the time T1 has elapsed from the voltage switching is “Ia2”. That is, the negative current changes from Ia1 to Ia2 at T1, which is a period of transient change of the element current.
  • the Zr cracking will be described.
  • the exhaust chamber 17 and the air duct 18 are communicated by the crack of the solid electrolyte layer 11, and the exhaust gas flows into the air duct 18 so that the oxygen concentration in the air duct 18 is lower than the air (20.9%) Less).
  • the applied voltage VP is changed from a positive voltage to a negative voltage in this state
  • the element current IL is changed to a negative current all at once by oxygen pumping from the air duct 18 side to the exhaust chamber 17 side, and then gradually becomes a negative current. (Negative current decreases). Then, it converges to the current value Ib0 corresponding to the Vn application state on the sensor characteristics.
  • the peak value of the negative current immediately after switching the applied voltage to the negative voltage is “Ib1”
  • the negative current when the time T1 has elapsed from the voltage switching is “Ib2”. That is, the negative current changes from Ib1 to Ib2 at T1, which is a period of transient change of the element current.
  • the exhaust gas flows into the air duct 18 and the oxygen concentration in the air duct 18 is low. Therefore, when oxygen pumping from the air duct 18 side to the exhaust chamber 17 side is performed, The oxygen in the duct 18 is quickly reduced, and a negative current is difficult to flow. That is, when Zr cracking, a negative current is less likely to flow when a negative voltage is applied than when it is normal. Therefore, the return (convergence) from the current peak value after switching the applied voltage is accelerated. In the present embodiment, it is determined that a Zr crack abnormality has occurred in the sensor element 10 based on the difference in the convergence speed of the negative current.
  • the abnormality determination process performed by the microcomputer 20 will be described.
  • two abnormality determination processes are performed.
  • the atmospheric detection value of the A / F sensor AS is calculated when the engine fuel is cut, and diffusion is performed based on the atmospheric detection value.
  • the clogging abnormality of the resistance layer 12 and the cracking abnormality of the diffusion resistance layer 12 are determined.
  • the crack abnormality of the solid electrolyte layer 11 is determined at the time of engine stoichiometric operation.
  • FIG. 6 is a flowchart showing the procedure of the abnormality determination process of the diffusion resistance layer 12, and this process is repeatedly performed by the microcomputer 20 at a predetermined cycle.
  • step S11 it is determined whether or not the fuel is currently being cut.
  • step S12 it is determined whether or not the state in the engine exhaust pipe is stable after the start of the fuel cut. And if both step S11 and S12 are YES, it will progress to subsequent step S13 and will acquire the present sensor output value as an atmospheric detection value.
  • step S14 it is determined whether or not the atmospheric detection value acquired in step S13 is within a normal range.
  • the normal range is determined based on the known oxygen concentration. If the atmospheric detection value is within the normal range, step S14 is affirmed.
  • step S15 it is determined that the A / F sensor AS is normal.
  • step S14 is denied.
  • step S16 it is determined whether or not the atmospheric detection value is out of the lower limit value side between the upper limit value side and the lower limit value side of the normal range. If the atmospheric detection value is outside the lower limit value of the normal range, the process proceeds to step S17, where it is determined that the diffusion resistance layer 12 is clogged abnormally in the sensor element 10. Further, when step S16 is NO, that is, when the atmospheric detection value is out of the upper limit value side of the normal range, the process proceeds to step S18 and it is determined that a cracking abnormality of the diffusion resistance layer 12 has occurred in the sensor element 10.
  • FIG. 7 is a flowchart showing the procedure of the Zr crack abnormality determination process. This process is repeatedly performed by the microcomputer 20 at a predetermined cycle.
  • step S21 it is determined whether or not the engine is currently in a stoichiometric operation state. At this time, step S21 may be affirmed when the air-fuel ratio is stable and stable.
  • step S22 it is determined whether or not an abnormality determination execution condition described below is satisfied.
  • the implementation conditions are: (1) The state of exhaust in the exhaust pipe (exhaust flow rate, exhaust pressure) is stable. (2) The temperature of the sensor element 10 is constant. (3) Not during or immediately after fuel cut, (4) the exhaust temperature is within a predetermined range; (5) The atmospheric pressure is within a predetermined range; If all these conditions are satisfied, step S22 is affirmed.
  • the condition for performing the abnormality determination only needs to include at least one of the above (1) to (5), and the setting thereof is arbitrary.
  • (1) is a condition for satisfying that the amount of oxygen in the air duct 18 is stable.
  • the amount of oxygen in the air duct 18 fluctuates under a situation where the exhaust flow rate and the exhaust pressure change, and the oxygen pumping amount from the air duct 18 to the exhaust chamber 17 is affected accordingly.
  • the exhaust flow rate and the exhaust pressure are in a stable state, the oxygen pumping amount can be maintained at a desired amount.
  • the exhaust flow rate is stable can be determined from the fact that the engine speed is stable at a constant value.
  • the element temperature may be obtained by using, for example, a known impedance detection method. Specifically, the sensor applied voltage or the applied current is temporarily changed at a predetermined AC frequency, and the device current or the device electromotive force that changes in response thereto is detected. Then, the element impedance is calculated based on the element current or the element electromotive force.
  • the temperature of the sensor element 10 is affected when the exhaust gas temperature is too high or too low.
  • the oxygen pumping amount is maintained at a desired amount. It is a condition. This is a condition that focuses on the same decrease as the condition (2).
  • the exhaust temperature may be detected using an exhaust sensor provided in the engine exhaust pipe, or may be estimated based on an engine operating state such as an engine rotation speed or an engine load.
  • (5) is a condition for keeping the oxygen concentration in the atmosphere constant, paying attention to the fact that the atmospheric oxygen concentration affects the oxygen concentration in the atmosphere. For example, it is considered that when the atmospheric pressure decreases, the oxygen pumping amount decreases due to a decrease in oxygen concentration, and conversely when the atmospheric pressure increases, the oxygen pumping amount increases due to an increase in oxygen concentration.
  • steps S21 and S22 are YES, the process proceeds to step S23, and if any of steps S21 and S22 is NO, the process is terminated.
  • an abnormality determination execution interval may be set, and the success or failure of the abnormality determination execution condition is determined on the condition that a predetermined time (for example, 10 minutes) has elapsed since the previous execution. Also good.
  • step S23 a negative voltage is applied to the pair of electrodes 15 and 16 of the sensor element 10, and in the subsequent step S24, the value of the element current flowing in the negative voltage application state is acquired.
  • the acquisition of the element current value is repeatedly performed at a predetermined time period until a predetermined abnormality determination period elapses (that is, until step S25 is affirmed).
  • the negative voltage value is preferably, for example, ⁇ 0.8 V or more.
  • the negative voltage application time is preferably 500 msec or less.
  • step S26 the presence or absence of an abnormality in Zr cracking is determined based on the change rate of the element current (corresponding to the speed parameter) after oxygen pumping is started by switching the sensor applied voltage to a negative voltage. Specifically, at this time, it is determined whether the change rate of the element current is equal to or higher than a predetermined determination threshold value K1.
  • the change rate of the element current may be a parameter indicating the speed of change of the element current with the passage of time, and is, for example, a time differential value (change slope) of the element current obtained every predetermined time.
  • the current change amount within a predetermined time after the start of oxygen pumping may be used. The amount of current change is “Ia2-Ia1” and “Ib2-Ib1” in FIG.
  • a current threshold is set as a negative current, and the time required for the device current to reach the current threshold in the process of the negative current converging to the convergence value after the start of oxygen pumping It is good also as speed (speed parameter). In this case, the larger the change rate of the device current, the shorter the time required until the device current reaches the current threshold value.
  • the determination threshold value K1 is determined based on the change speed of the element current at the normal time. If the sensor element 10 is normal, step S26 is denied, and if the Zr crack is abnormal, step S26 is affirmed. Is done.
  • step S26 if step S26 is YES, it will progress to step S27 and will determine with the Zr crack abnormality having arisen in the sensor element 10.
  • FIG. In this case, according to each abnormality determination process of FIG.6 and FIG.7, about A / F sensor AS, any of the clogging abnormality of the diffusion resistance layer 12, a cracking abnormality, and the cracking abnormality (Zr cracking abnormality) of the solid electrolyte layer 11 It is possible to identify whether or not
  • a stoichiometric correction value is calculated based on the deviation amount of the element current (negative current) from the normal time, and the stoichiometric correction value is used. Then, the sensor output value may be corrected.
  • the crack abnormality of the solid electrolyte layer 11 can be determined appropriately by using it.
  • the abnormality of the clogging and cracking of the diffusion resistance layer 12 is determined when the fuel of the engine is cut, and the solid electrolyte is used during the operation other than the fuel cut (in the stoichiometric operation in this embodiment). It was set as the structure which determines the crack abnormality of the layer 11. FIG. Therefore, each of these abnormalities can be suitably specified while being distinguished from each other.
  • the microcomputer 20 (element current detection unit), when the A / F output voltage output from the amplifier circuit 37 is AD-converted, conversion processing is performed in a predetermined voltage range (for example, 0 to 5 V).
  • the value exceeding the upper limit value or lower limit value of the voltage range is stuck at the upper limit value or lower limit value.
  • the sticking time Th when the element current sticks to the lower limit value Vmin is relatively long in the normal state, but the sticking time Th is short (or sticking occurs in the case of Zr cracking compared to the normal time).
  • the microcomputer 20 calculates the sticking time when the detected value of the element current (A / F output voltage) is stuck to the limit value (lower limit value Vmin) of the AD voltage range after the oxygen pumping is started. And when the pasting time is less than predetermined time, it determines with Zr crack abnormality having arisen.
  • the negative voltage may be variably set.
  • a negative voltage control circuit 41 is newly provided, and application voltage control is performed by the application voltage control circuit 35 or by the negative voltage control circuit 41. Whether the applied voltage control is performed is switched by the switch circuit 42.
  • the switch circuit 42 is switched to the s1 point side, the applied voltage control circuit 35 performs the applied voltage control, and when the switch circuit 42 is switched to the s2 point side, the negative voltage control circuit 41 performs the applied voltage control. .
  • Control commands from the microcomputer 20 are input to the negative voltage control circuit 41 and the switch circuit 42, respectively.
  • the microcomputer 20 is configured to determine whether or not the Zr crack is abnormal other than during the stoichiometric operation (except when the fuel is cut), and the negative voltage is variably set according to the air-fuel ratio (exhaust oxygen concentration). Specifically, in step S23 of FIG. 7, the negative voltage is set based on the air-fuel ratio in each case using the relationship of FIG. In FIG. 10, the negative voltage is increased on the rich side with respect to the stoichiometry, and the negative voltage is decreased on the lean side. The negative voltage is applied between the pair of electrodes 15 and 16 to perform oxygen pumping.
  • the air-fuel ratio exhaust oxygen concentration
  • the oxygen pumping amount at normal time and at Zr cracking changes.
  • the accuracy of abnormality determination can be increased.
  • the negative voltage may be variably set according to the temperature (element temperature) of the sensor element 10. Specifically, the negative voltage is increased when the element temperature is lower than the activation temperature, and the negative voltage is decreased when the element temperature is higher than the activation temperature.
  • the negative voltage may be variably set according to the atmospheric pressure. In this case, it is preferable to increase the negative voltage when the atmospheric pressure is low and decrease the negative voltage when the atmospheric pressure is high.
  • oxygen pumping from the atmospheric duct 18 to the exhaust chamber 17 is performed by applying a negative voltage between the pair of electrodes 15 and 16 of the sensor element 10, and based on the change of the negative current in that state. In this embodiment, this is changed, and a negative current is passed between the pair of electrodes 15 and 16 of the sensor element 10 to flow from the air duct 18 to the exhaust chamber 17. In this state, the cracking abnormality of the solid electrolyte layer 11 is determined based on the sensor electromotive force.
  • a constant current as a constant current generating means is provided on an electric path connected to one of the electrodes 15 and 16 in the sensor control circuit 30.
  • a circuit is provided, and oxygen is supplied from the air duct 18 to the exhaust chamber 17 by the constant current circuit.
  • 11 (a) and 11 (b) the same reference numerals are given to the same components as those in FIG. 1 described above, and some of the common components (such as the microcomputer 20) are omitted or simplified.
  • a switch circuit 51 is connected to the positive terminal (S + terminal) of the sensor element 10, and the switch circuit 51 responds to a control command (switching control signal) from a microcomputer (not shown). Switching operation. In such a case, the switch circuit 51 is normally connected at the s1 point, and the A / F sensor AS is normally controlled in this state. On the other hand, when the switch circuit 51 is connected at s2 points, the constant current circuit 52 is connected to the positive terminal (S + terminal) of the sensor element 10.
  • the constant current circuit 52 is a suction type constant current circuit, and the identification current circuit 52 causes a negative current In flowing from the electrode 15 (S ⁇ ) to the electrode 16 (S +) to flow in the sensor element 10.
  • a switch circuit 53 and a constant current circuit 54 are provided at the negative terminal (S-terminal) of the sensor element 10.
  • the constant current circuit 54 is a discharge type constant current circuit, and the identification current circuit 54 causes a negative current In flowing in the direction from the electrode 15 (S ⁇ ) to the electrode 16 (S +) in the sensor element 10.
  • FIG. 12 shows the sensor element 10 at the normal time and at the time of Zr cracking.
  • FIG. 13 shows the time change of the element current during normal time and Zr cracking, and the time change of the voltage between the terminals of the sensor element 10 which is the voltage between the pair of electrodes 15 and 16.
  • the sensor applied voltage positive voltage
  • the element current is changed from 0 mA to a predetermined negative current.
  • the Zr cracking will be described.
  • the exhaust chamber 17 and the air duct 18 are communicated by the crack of the solid electrolyte layer 11, and the exhaust gas flows into the air duct 18 so that the oxygen concentration in the air duct 18 is lower than the air (20.9%) Less).
  • the element current is changed from 0 mA to a negative current in this state, a negative electromotive force is generated between the pair of electrodes 15 and 16 as a voltage between terminals due to oxygen pumping from the air duct 18 side to the exhaust chamber 17 side. Thereafter, the electromotive force gradually increases to the negative side.
  • the exhaust gas flows into the air duct 18 and the oxygen concentration in the air duct 18 is low. Therefore, when oxygen pumping from the air duct 18 side to the exhaust chamber 17 side is performed, The oxygen in the duct 18 decreases quickly, and the sensor electromotive force increases. In the present embodiment, it is determined that a Zr crack abnormality has occurred in the sensor element 10 based on the difference in the change rate of the sensor electromotive force.
  • FIG. 14 is a flowchart showing the procedure of the Zr crack abnormality determination process, and this process is repeatedly performed by the microcomputer 20 at a predetermined cycle.
  • step S31 it is determined whether or not the engine is currently in a stoichiometric operation state.
  • step S32 it is determined whether or not an abnormality determination execution condition is satisfied.
  • steps S31 and S32 are the same as steps S21 and S22 in FIG. And if both step S31 and S32 are YES, it will progress to step S33, and if either of step S31 and S32 is NO, this process will be complete
  • step S33 a negative current is applied to the pair of electrodes 15 and 16 of the sensor element 10, and in subsequent step S34, the value of the sensor electromotive force generated in the negative current application state is acquired.
  • the acquisition of the electromotive force value is repeatedly performed at a predetermined time period until a predetermined abnormality determination period elapses (that is, until step S35 is affirmed).
  • step S36 the presence / absence of Zr cracking abnormality is determined based on the rate of change of sensor electromotive force (corresponding to the speed parameter) after oxygen pumping is started. Specifically, at this time, it is determined whether the change rate of the sensor electromotive force is equal to or higher than a predetermined determination threshold value K2.
  • the change rate of the sensor electromotive force may be a parameter indicating the speed of change in electromotive force with the passage of time, and is, for example, a time differential value (inclination of change) of the electromotive force obtained every predetermined time. Alternatively, it may be the amount of voltage change within a predetermined time after the start of oxygen pumping. The amount of voltage change is “Va2-Va1” and “Vb2-Vb1” in FIG.
  • a voltage threshold value may be determined as a negative electromotive force, and the time required for the sensor electromotive force to reach the voltage threshold after the start of oxygen pumping may be set as the change rate of the sensor electromotive force.
  • the larger the change rate of the sensor electromotive force the shorter the time required until the sensor electromotive force reaches the voltage threshold value.
  • the determination threshold value K2 is determined based on the change rate of the sensor electromotive force at the normal time. If the sensor element 10 is normal, Step S36 is denied, and if the Zr crack is abnormal, Step S36 is determined. Affirmed.
  • step S36 if step S36 is YES, it will progress to step S37 and will determine with the Zr crack abnormality having arisen in the sensor element 10.
  • the negative current may be variably set.
  • the negative current may be variably set according to the air-fuel ratio, element temperature, and atmospheric pressure.
  • FIG. 15 shows the overall configuration of the gas sensor control device according to the present embodiment.
  • an applied voltage control circuit 61 is connected to the positive terminal (S + terminal) of the sensor element 10.
  • the applied voltage control circuit 61 includes two power supply circuits 62 and 63, a switch circuit 64 that switches between the two power supply circuits 62 and 63, and a non-inverting amplifier circuit 65 connected to one end of the switch circuit 64.
  • the non-inverting amplifier circuit 65 includes an operational amplifier 65a and a feedback resistor 65b connected to its inverting input terminal ( ⁇ input terminal). Further, the resistors included in the power supply circuits 62 and 63 are input resistors of the non-inverting amplifier circuit 65.
  • a capacitor 65c is connected in parallel with the feedback resistor 65b. That is, in this configuration, an LPF for preventing applied voltage oscillation is provided integrally with the non-inverting amplifier circuit 65.
  • the cut-off frequency fc of the LPF is, for example, 2.7 Hz.
  • an AC power supply circuit 67, a buffer 68, and a current detection resistor 69 are connected in series to the negative terminal (S-terminal) of the sensor element 10.
  • the AC power supply circuit 67 is an AC voltage generating means for outputting an AC voltage of about 10 to 20 kHz, for example, and is configured by an AC voltage generating circuit and an LPF for filtering the AC voltage output of the generating circuit.
  • An AC voltage is applied to the sensor element 10 by the AC power supply circuit 67.
  • the AC power supply circuit 67 corresponds to a voltage application unit for impedance detection.
  • the AC power supply circuit 67 outputs an AC voltage amplified by 1 V on both positive and negative sides with 2.2 V as a reference.
  • the current detection resistor 69 is provided on the current path between the AC power supply circuit 67 and the sensor element 10, and the terminal on the opposite side to the sensor element 10 has a reference voltage (the center voltage of the AC voltage of the AC power supply circuit 67). ).
  • the element current is measured at an intermediate point A between the current detection resistor 69 and the negative terminal of the sensor element 10.
  • an LPF 70 composed of a resistor and a capacitor is connected to an intermediate point A between the current detection resistor 69 and the negative terminal of the sensor element 10, and the LPF 70 is further non-inverting of the operational amplifier 65 a of the non-inverting amplifier circuit 65. It is connected to the input terminal (+ input terminal).
  • an intermediate voltage between the current detection resistor 69 and the sensor element 10 that is, a voltage divided by the current detection resistor 69 and the sensor element 10) is non-inverted and amplified by the applied voltage control circuit 61 via the LPF 70. Input to the circuit 65.
  • the cut-off frequency fc of the LPF 70 is, for example, 150 Hz.
  • one power supply circuit 62 corresponds to a voltage application unit for A / F detection
  • the other power supply circuit 63 corresponds to a voltage application unit for negative voltage control.
  • the switch circuit 64 is switched according to a control command (switching control signal) from the microcomputer 78. In such a case, the switch circuit 64 is normally connected at the s1 point, and the A / F sensor is normally controlled in that state.
  • the power supply voltage is input from the power supply circuit 62 to the operational amplifier 65a of the non-inverting amplifier circuit 65, and the output voltage (point B voltage in the figure) of the non-inverting amplifier circuit 65 is fixed at 2.6V, for example.
  • the switch circuit 64 when the switch circuit 64 is connected to the s2 point, the power supply voltage is input from the power supply circuit 63 to the operational amplifier 65a of the non-inverting amplifier circuit 65, and the output voltage of the non-inverting amplifier circuit 65 (B in the figure).
  • the point voltage is fixed at 1.7V, for example.
  • the intermediate point voltage (that is, the voltage divided by the current detection resistor 69 and the sensor element 10) is individually captured.
  • Two signal output units are provided.
  • One is an A / F signal output unit 71 for outputting an A / F detection signal corresponding to the element current, and the other is an impedance signal output unit 72 for outputting an impedance detection signal.
  • the A / F signal output unit 71 includes a non-inverting amplifier circuit in which an operational amplifier 73 and an LPF unit 74 are integrally provided.
  • the non-inverting input terminal (+ input terminal) of the operational amplifier 73 receives the point A voltage via the LPF 70. At this time, the fluctuation of the voltage at the point A, which fluctuates in an AC manner for impedance detection, is removed by the LPF 70.
  • the impedance signal output unit 72 includes an HPF 75 and a peak hold circuit 76. The peak hold circuit 76 is integrally provided with a signal amplifier. Both the A / F detection signal output from the A / F signal output unit 71 and the impedance detection signal output from the impedance signal output unit 72 are input to the microcomputer 78.
  • the switch circuit 64 when the Zr cracking abnormality is determined, the switch circuit 64 is connected to the s2 point, and the applied voltage control circuit 61 applies a negative voltage generated by using the power supply circuit 63 as a power source to the sensor element 10. Is done. As a result, oxygen is forcibly supplied from the atmospheric duct 18 to the exhaust chamber 17.
  • the switch circuit 64 When the predetermined negative voltage control end timing is reached, the switch circuit 64 is switched from the s2 point connection to the s1 point connection, and the negative voltage control is switched to the normal control.
  • a constant current circuit may be provided in the sensor control circuit, and oxygen pumping may be performed by a predetermined current (negative current) generated by the constant current circuit.
  • a difference occurs in the rate of change of the sensor electromotive force after the start of oxygen pumping. Therefore, by using this, it is possible to appropriately determine the crack abnormality of the solid electrolyte layer 11. it can.
  • the air-fuel ratio (the value of the oxygen concentration of the exhaust gas) at the time of performing oxygen pumping is acquired, and the crack abnormality of the solid electrolyte layer 11 is obtained based on the air-fuel ratio. It is good also as a structure which sets the determination threshold value which determines whether it is variable. That is, when the air-fuel ratio is different, the oxygen pumping amount at the time of Zr cracking changes. In this case, when the air-fuel ratio is rich, the decrease in oxygen concentration in the atmospheric duct 18 is relatively large, and when the air-fuel ratio is lean, the decrease in oxygen concentration in the atmospheric duct 18 is relatively small. This is shown in the time chart of FIG.
  • the change of the negative current in the normal state is indicated by a solid line
  • the change in the negative current in the case of the rich air-fuel ratio at the time of Zr cracking is indicated by a two-dot chain line
  • the negative current in the case of the lean air-fuel ratio at the time of Zr cracking is indicated by a dashed line.
  • the negative currents at the time when the time T1 has elapsed since the voltage switching are represented as Ic1, Ic2, and Ic3 (
  • the determination threshold value may be set using the relationship of FIG. In FIG. 17, the determination threshold value is increased on the rich side with respect to the stoichiometry, and the determination threshold value is decreased on the lean side.
  • the determination threshold value can be variably set according to the atmospheric pressure.
  • the atmospheric pressure is low, as shown in FIG. 16 as a case of a rich air-fuel ratio, the decrease in the oxygen concentration in the air duct 18 becomes relatively large. Therefore, taking this into consideration, the determination threshold value may be set variably.
  • the temperature (element impedance) of the sensor element 10 when oxygen pumping is performed is acquired, and the crack abnormality of the solid electrolyte layer 11 is determined based on the element temperature. It is good also as a structure which sets the determination threshold value to determine variably. That is, when the element temperature is different, the active state of the sensor element 10 is changed, so that the oxygen pumping amount at the time of Zr cracking is changed. In this case, it is considered that the oxygen pumping amount decreases as the element temperature decreases. Therefore, as shown in FIG. 18, the determination threshold value is increased when the element temperature is low, and the determination threshold value is decreased when the element temperature is high.
  • the accuracy of abnormality determination can be increased by changing the determination threshold value for abnormality determination according to the element temperature (element impedance) each time.
  • the abnormality determination is not limited to the element activation temperature, it is possible to increase the chances of performing the abnormality determination.
  • the degree of cracking abnormality of the solid electrolyte layer 11 changes, and the oxygen pumping amount at the time of abnormality determination is also affected. For example, as the crack of the solid electrolyte layer 11 is larger, the amount of decrease in the oxygen concentration in the air duct 18 is larger and the amount of oxygen pumping is smaller. In this case, since the degree of abnormality is reflected in the change rate of the device current and the change rate of the sensor electromotive force, whether the failure can be dealt with by correcting the sensor output value when the cracking abnormality of the solid electrolyte layer 11 occurs. It is possible to determine whether or not the sensor output value is disabled as an occurrence.
  • the present invention can be applied to a so-called O2 sensor that changes the electromotive force output in accordance with the oxygen concentration in the exhaust gas.
  • the gas sensor may be used for applications other than automobiles.
  • SYMBOLS 10 Sensor element, 11 ... Solid electrolyte layer, 12 ... Diffusion resistance layer (diffusion layer), 15 ... Electrode (first electrode), 16 ... Electrode (second electrode), 18 ... Air duct (atmosphere chamber), 20 ... Microcomputer (oxygen supply means, abnormality determination means) 30 ... sensor control circuit (gas sensor control device), AS ... A / F sensor.

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JP6048442B2 (ja) * 2014-04-11 2016-12-21 株式会社デンソー 酸素濃度センサの素子インピーダンス検出装置
JP2016121880A (ja) * 2014-12-24 2016-07-07 株式会社デンソー センサ制御装置
JP6551386B2 (ja) * 2016-12-26 2019-07-31 トヨタ自動車株式会社 排気センサの診断装置
JP6805072B2 (ja) * 2017-05-08 2020-12-23 日本特殊陶業株式会社 ガス濃度検出装置
JP7081387B2 (ja) 2018-08-10 2022-06-07 株式会社デンソー 酸素センサ制御装置
JP7312095B2 (ja) * 2019-11-25 2023-07-20 日本碍子株式会社 ガスセンサ及びクラック検出方法
JP7286518B2 (ja) * 2019-11-25 2023-06-05 日本碍子株式会社 ガスセンサ及びクラック検出方法
JP7286519B2 (ja) * 2019-11-25 2023-06-05 日本碍子株式会社 ガスセンサ及びクラック検出方法
JP7301781B2 (ja) * 2020-03-26 2023-07-03 日本碍子株式会社 センサ素子のクラック検出方法及びセンサ素子の評価方法
JP2024082357A (ja) 2022-12-08 2024-06-20 日本碍子株式会社 ガスセンサ及びガスセンサの制御方法

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JP2014235107A (ja) 2014-12-15
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US10082482B2 (en) 2018-09-25
US20160123922A1 (en) 2016-05-05
JP6123498B2 (ja) 2017-05-10
EP3006930A4 (en) 2017-02-22

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