WO2021251036A1 - Capteur de concentration en ammoniac - Google Patents

Capteur de concentration en ammoniac Download PDF

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Publication number
WO2021251036A1
WO2021251036A1 PCT/JP2021/017627 JP2021017627W WO2021251036A1 WO 2021251036 A1 WO2021251036 A1 WO 2021251036A1 JP 2021017627 W JP2021017627 W JP 2021017627W WO 2021251036 A1 WO2021251036 A1 WO 2021251036A1
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Prior art keywords
ammonia
nox
concentration
correction
corrected
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PCT/JP2021/017627
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English (en)
Japanese (ja)
Inventor
敏彦 原田
弘宣 下川
勇樹 村山
大樹 市川
Original Assignee
株式会社Soken
株式会社デンソー
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Publication of WO2021251036A1 publication Critical patent/WO2021251036A1/fr

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • 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
    • G01N27/416—Systems

Definitions

  • This disclosure relates to an ammonia concentration detector.
  • a catalyst for purifying NOx nitrogen oxides
  • NOx nitrogen oxides
  • NO and NO 2 contained in exhaust gas exhausted from a diesel engine as an internal combustion engine
  • SCR selective catalytic reduction catalyst
  • a reducing agent supply device for supplying ammonia as a reducing agent to the selective reducing catalyst is arranged at a position upstream of the flow of the exhaust gas from the selective reducing catalyst.
  • a NOx sensor for detecting the NOx concentration in the exhaust gas and an ammonia sensor for detecting the ammonia concentration in the exhaust gas are arranged at a position downstream of the flow of the exhaust gas of the selective reduction catalyst in the exhaust pipe. Then, by using the NOx sensor and the ammonia sensor, a device is made to improve the purification rate of NOx by ammonia while suppressing the outflow of ammonia from the selective reduction catalyst.
  • the multi-gas sensor of Patent Document 1 utilizes an ammonia sensor unit configured to calculate the ammonia concentration, a NOx sensor unit configured to calculate the NOx concentration, and an uncorrected NOx concentration by the NOx sensor unit. It is provided with a calculation control unit configured to calculate the ammonia concentration.
  • the calculation control unit is configured to switch the ammonia output concentration used for the output from the multi-gas sensor between the case where the ammonia concentration in the exhaust gas is low and the case where the ammonia concentration is high.
  • the calculation control unit sets the ammonia output concentration to the ammonia concentration by the ammonia sensor unit corrected by the NOx concentration of the NOx sensor unit.
  • the calculation control unit sets the ammonia output concentration to the ammonia concentration calculated by using the uncorrected NOx concentration of the NOx sensor unit.
  • the hybrid potential indicating the ammonia concentration in the ammonia sensor section becomes close to the saturated state. Therefore, in the multi-gas sensor of Patent Document 1, when the ammonia concentration is high, the NOx sensor unit indirectly detects the ammonia concentration by detecting NOx produced by oxidative decomposition of ammonia.
  • the ammonia output concentration is detected separately for the case where the ammonia concentration in the exhaust gas is low and the case where the ammonia concentration is high. Therefore, the ammonia concentration near the boundary between the case where the ammonia concentration in the exhaust gas is low and the case where the ammonia concentration is high is not continuous, and the calculated ammonia output concentration may change rapidly.
  • the present disclosure is obtained in an attempt to provide an ammonia concentration detecting device capable of detecting the concentration of ammonia in a detection target gas in a state of continuously or stepwise changing over a wide concentration range.
  • a hybrid potential type ammonia detector that outputs an ammonia voltage according to the concentration of ammonia in the detection target gas
  • An oxygen detection unit that outputs an oxygen current according to the oxygen concentration in the detection target gas
  • a first correction unit that corrects the ammonia voltage based on the oxygen current to obtain the corrected ammonia voltage
  • a NOx detector of the limit current type that outputs a NOx current according to the concentration of NOx in the gas to be detected and the concentration of NOx generated by oxidative decomposition of ammonia in the gas to be detected.
  • a second correction unit for further correcting the corrected ammonia voltage by the first correction unit based on the NOx current to obtain the ammonia output concentration is provided.
  • the second correction unit is in an ammonia concentration detecting device configured to increase the correction ratio by the NOx current as the corrected ammonia voltage by the first correction unit increases.
  • the ammonia concentration detection device of the above aspect uses the concentration of NOx to detect the concentration of ammonia, and changes the correction ratio according to the concentration of NOx so that the concentration of ammonia changes continuously.
  • the ammonia concentration detecting device includes a second correction unit for obtaining the ammonia output concentration by increasing the correction ratio by the NOx current as the corrected ammonia voltage by the first correction unit is higher.
  • the NOx current according to the concentration of NOx generated by the oxidative decomposition of ammonia detected in the NOx detection unit can be reflected more in the ammonia output concentration. can.
  • the concentration of ammonia in the detection target gas can be detected in a state of continuously or stepwise changing over a wide concentration range.
  • the "continuously or stepwise changing state” does not mean a state in which the method of detecting ammonia completely changes at a specific boundary of the corrected ammonia voltage, but is subject to a change in the corrected ammonia voltage. It refers to a state in which the method of detecting ammonia changes continuously or stepwise.
  • each component shown in one aspect of the present disclosure indicate the correspondence with the reference numerals in the figure in the embodiment, but each component is not limited to the content of the embodiment.
  • FIG. 1 is an explanatory diagram showing a configuration of an ammonia concentration detecting device according to the first embodiment.
  • FIG. 2 is a sectional view taken along line II-II of FIG. 1, showing a sensor element of the ammonia concentration detection device according to the first embodiment.
  • FIG. 3 is a sectional view taken along line III-III of FIG. 1 showing a sensor element of the ammonia concentration detection device according to the first embodiment.
  • FIG. 4 is a sectional view taken along line IV-IV of FIG. 1, showing a sensor element of the ammonia concentration detection device according to the first embodiment.
  • FIG. 1 is an explanatory diagram showing a configuration of an ammonia concentration detecting device according to the first embodiment.
  • FIG. 2 is a sectional view taken along line II-II of FIG. 1, showing a sensor element of the ammonia concentration detection device according to the first embodiment.
  • FIG. 3 is a sectional view taken along line III-III of FIG. 1 showing a sensor element of the ammonia concentration detection device
  • FIG. 5 is an explanatory diagram showing a part of the electrical configuration of the ammonia concentration detecting device according to the first embodiment.
  • FIG. 6 is an explanatory diagram showing an exhaust pipe of an internal combustion engine to which an ammonia concentration detecting device is applied according to the first embodiment.
  • FIG. 7 is a graph showing the relationship between the injection amount of urea water and the concentration of ammonia and the concentration of NOx at the outlet of the selective reduction catalyst according to the first embodiment.
  • FIG. 8 is a graph showing the relationship between the concentration of ammonia and the concentration of oxygen in the detection target gas and the ammonia voltage by the ammonia detection unit according to the first embodiment.
  • FIG. 9 is a graph showing the relationship between the concentration of ammonia in the detection target gas and the NOx current by the NOx detection unit according to the first embodiment.
  • FIG. 10 is a graph showing a map showing the relationship between the ammonia voltage and the corrected ammonia voltage when the oxygen concentration in the detection target gas changes according to the first embodiment.
  • FIG. 11 is a graph showing a relationship map between the corrected ammonia voltage, the ammonia correction ratio, and the NOx correction ratio according to the first embodiment.
  • FIG. 12 is a graph showing the hybrid potential generated in the ammonia electrode according to the first embodiment.
  • FIG. 13 is a graph showing the hybrid potential generated in the ammonia electrode when the concentration of ammonia in the detection target gas changes according to the first embodiment.
  • FIG. 14 is a graph showing the hybrid potential generated in the ammonia electrode when the oxygen concentration in the detection target gas changes according to the first embodiment.
  • FIG. 15 is a flowchart showing a control method of the ammonia concentration detecting device according to the first embodiment.
  • FIG. 16 is an explanatory diagram showing an exhaust pipe of an internal combustion engine to which an ammonia concentration detecting device is applied according to another embodiment.
  • the ammonia concentration detection device 1 of the present embodiment includes an ammonia detection unit 2, an oxygen detection unit 3, a first correction unit 54, a NOx detection unit 4, and a second correction unit 55.
  • the ammonia detection unit 2 is of a hybrid potential type, and is configured to output an ammonia voltage Va corresponding to the concentration of ammonia in the detection target gas G.
  • the oxygen detection unit 3 is of the limit current type, and is configured to output an oxygen current Io according to the oxygen concentration in the detection target gas G.
  • the first correction unit 54 is configured to correct the ammonia voltage Va based on the oxygen current Io and obtain the corrected ammonia voltage Vb.
  • the NOx detection unit 4 is of the limit current type, and outputs a NOx current In according to the concentration of NOx in the detection target gas G and the concentration of NOx generated by oxidative decomposition of ammonia in the detection target gas G. It is configured as.
  • the second correction unit 55 is configured to further correct the corrected ammonia voltage Vb by the first correction unit 54 based on the NOx current In to obtain the ammonia output concentration Na. Further, the second correction unit 55 is configured to increase the correction ratio by the NOx current In as the correction ammonia voltage Vb by the first correction unit 54 increases.
  • ammonia concentration detecting device 1 of the present embodiment will be described in detail.
  • Ammonia concentration detector 1 As shown in FIG. 6, the ammonia concentration detecting device 1 is used in a vehicle, and the exhaust gas flowing through the exhaust pipe 71 connected to the internal combustion engine (engine) 7 of the vehicle is set as the detection target gas G, and the concentration of ammonia in the exhaust gas is measured. It is configured to detect.
  • the internal combustion engine 7 of this embodiment is a diesel engine that performs combustion operation by utilizing self-ignition of light oil.
  • the ammonia concentration detection device 1 is a composite sensor 10 as a detection device (sensor) arranged in the exhaust pipe 71, a detection circuit using the composite sensor 10, and a sensor control unit (which receives signals from the detection circuit and performs arithmetic processing). It is composed of SCU) 5.
  • the composite sensor 10 is configured by using the sensor element 11, and the sensor control unit 5 is configured by using an electronic circuit and a computer.
  • the sensor of the ammonia concentration detection device 1 of the present embodiment is a composite sensor (multi-gas sensor) 10 capable of not only detecting the concentration of ammonia in the gas G to be detected but also the concentration of oxygen and the concentration of NOx in the gas G to be detected. Is formed as.
  • the ammonia detection unit 2, the oxygen detection unit 3, and the NOx detection unit 4 of the present embodiment are configured by using the composite sensor 10.
  • the detection target gas G in the same environment can be used for detecting the concentrations of ammonia, oxygen, and NOx, and the detection accuracy of the ammonia concentration can be improved.
  • the composite sensor 10 of the ammonia concentration detection device 1 is attached to the sensor element 11, the housing for holding the sensor element 11 and attaching it to the exhaust pipe 71, and the sensor element 11 attached to the tip end side of the housing. It is provided with a front end side cover for protecting the sensor element 11 and a base end side cover attached to the base end side of the housing to protect the electrical wiring portion of the sensor element 11.
  • the concentrations of the ammonia output concentrations Na and NOx by the ammonia concentration detection device 1 are the selective reduction catalysts arranged in the exhaust pipe 71 by the engine control unit (ECU) 6 as the control device of the internal combustion engine 7 to reduce NOx. It is used to control the state of 72. More specifically, the concentrations of the ammonia output concentrations Na and NOx by the ammonia concentration detection device 1 are used to determine the timing of supplying ammonia as the reducing agent K from the urea water injection device 73, which will be described later, to the exhaust pipe 71. Will be done.
  • the exhaust pipe 71 of the internal combustion engine 7 is located on the upstream side of the exhaust gas flow of the selective catalytic reduction catalyst (SCR) 72 that reduces NOx using ammonia as the reducing agent K and the selective catalytic reduction catalyst 72.
  • a urea water injection device (reducing agent supply device) 73 and a composite sensor 10 located on the downstream side of the exhaust gas flow of the selective reduction catalyst 72 are arranged.
  • ammonia as a reducing agent K for NOx is attached to the catalyst carrier.
  • the selective reduction catalyst 72 chemically reacts NOx (nitrogen oxide) with ammonia (NH 3 ) to reduce it to nitrogen (N 2 ) and water (H 2 O). The amount of ammonia adhered to the catalyst carrier of the selective reduction catalyst 72 decreases with the reduction reaction of NOx.
  • the urea water injection device 73 is configured to supply the ammonia gas generated when urea water is injected into the exhaust pipe 71 to the selective reduction catalyst 72 in the exhaust pipe 71. Specifically, when the amount of ammonia adhered to the catalyst carrier of the selective reduction catalyst 72 becomes small, ammonia is newly replenished from the urea water injection device 73 to the catalyst carrier. Ammonia gas is produced by hydrolyzing urea water.
  • a urea water tank 731 is connected to the urea water injection device 73.
  • the engine control unit 6 supplies reduction from the urea water injection device 73 to the selective reduction catalyst 72 so that both the concentration of ammonia contained in the detection target gas G and the concentration of NOx contained in the detection target gas G are the lowest.
  • the amount of agent K can be adjusted.
  • the engine control unit 6 can monitor the concentration of ammonia and the concentration of NOx to determine the amount of the reducing agent K supplied to the selective reduction catalyst 72, and the reduction reaction of NOx in the selective reduction catalyst 72 can be performed. It can be performed more optimally while suppressing the outflow of ammonia.
  • the composite sensor 10 of the ammonia concentration detection device 1 of the present embodiment is arranged at a position downstream of the exhaust gas flow of the selective reduction catalyst 72 for reducing NOx, which is arranged in the exhaust pipe 71.
  • the concentration of ammonia gas flowing out from the selective reduction catalyst 72 is detected.
  • a NOx sensor 12 for detecting the concentration of NOx in the exhaust gas may be arranged at a position in the exhaust pipe 71 on the upstream side of the flow of the exhaust gas of the selective reduction catalyst 72.
  • the oxidation catalyst (DOC) 74, the filter (DPF) 75 and the like may be arranged at the upstream position of the selective reduction catalyst 72 in the exhaust pipe 71.
  • the oxidation catalyst reduces the conversion (oxidation) of NO (nitric oxide) to NO 2 (nitrogen dioxide), CO (carbon monoxide), HC (hydrocarbon), and the like.
  • the filter collects fine particles.
  • FIG. 7 shows the relationship between the amount of urea water injected by the urea water injection device 73 and the concentration of ammonia and the concentration of NOx at the outlet (downstream position) of the selective reduction catalyst 72 in the exhaust pipe 71.
  • the concentration of ammonia at the outlet of the selective reduction catalyst 72 increases, and when the injection amount of urea water is small, the concentration of NOx at the outlet of the selective reduction catalyst 72 increases.
  • NOx is ammonia in the detection target gas G existing at the position of the ammonia concentration detection device 1 at the outlet of the selective reduction catalyst 72.
  • a state in which the amount of NOx outflow is larger than the amount of ammonia outflow, and a state in which the amount of ammonia outflow is larger than the amount of NOx outflow occur at different times. become. In other words, when the amount of NOx outflow is large, the amount of ammonia outflow is small, and when the amount of ammonia outflow is large, the amount of NOx outflow is small.
  • FIG. 8 shows the relationship between the concentration of ammonia in the detection target gas G and the ammonia voltage Va detected by the ammonia detection unit 2.
  • concentration of ammonia in the detection target gas G becomes high
  • the ammonia voltage Va becomes saturated.
  • concentration of ammonia in the detection target gas G becomes high, it becomes difficult to accurately detect the concentration of ammonia only by the ammonia detection unit 2.
  • the oxygen concentration in the detection target gas G becomes high, the ammonia voltage Va is detected low even if the actual ammonia concentration does not change.
  • FIG. 9 shows the relationship between the concentration of ammonia in the detection target gas G and the NOx current In detected by the NOx detection unit 4.
  • the NOx current In increases as the concentration of ammonia in the detection target gas G increases. Even if the concentration of ammonia in the detection target gas G becomes high, the NOx detection unit 4 makes it possible to detect the concentration of ammonia as accurately as possible.
  • ammonia detection unit 2 As shown in FIGS. 1 and 5, the ammonia detection unit 2 has an ammonia sensor unit 20 which is a part of the sensor element 11 and an ammonia control unit 51 which is a part of the sensor control unit 5.
  • the ammonia sensor unit 20 includes a first solid electrolyte body 21, an ammonia electrode 22 provided on the outer surface 211 of the first solid electrolyte body 21 and exposed to the detection target gas G, and an inner side surface 212 of the first solid electrolyte body 21. It is composed of a reference electrode 23 provided in the above and exposed to the reference gas A.
  • the sensor of the ammonia concentration detection device 1 of the present embodiment is configured as a composite sensor 10 having a function of detecting each concentration of ammonia, oxygen, and NOx.
  • the ammonia sensor unit 20 is formed as a part of the composite sensor 10.
  • the ammonia control unit 51 is set when the reduction current due to the electrochemical reduction reaction of oxygen (hereinafter referred to as reduction reaction) and the oxidation current due to the electrochemical oxidation reaction of ammonia (hereinafter referred to as oxidation reaction) become equal to each other.
  • the generated potential difference between the ammonia electrode 22 and the reference electrode 23 is configured to be detected as a mixed potential having an ammonia voltage Va. Since the hybrid potential by the ammonia control unit 51 changes depending on the oxygen concentration in the detection target gas G, it is corrected and used according to the oxygen concentration.
  • the oxygen detection unit 3 has an oxygen sensor unit 30 which is a part of the sensor element 11 and an oxygen control unit 52 which is a part of the sensor control unit 5.
  • the oxygen sensor unit 30 is provided on the second solid electrolyte 31 laminated on the first solid electrolyte 21 via the insulator 25, and on the first surface 311 of the second solid electrolyte 31, and is used as a detection target gas G. It is composed of an oxygen electrode 32 to be exposed and a reference electrode 33 provided on the second surface 312 of the second solid electrolyte body 31 and exposed to the reference gas A.
  • the oxygen sensor unit 30 is formed as a part of the composite sensor 10.
  • the oxygen control unit 52 flows between the voltage application unit 521 that applies a predetermined DC voltage between the oxygen electrode 32 and the reference electrode 33, and between the oxygen electrode 32 and the reference electrode 33 when the DC voltage is applied. It has a current detection unit 522 for detecting the oxygen current Io. When a predetermined DC voltage is applied between the oxygen electrode 32 and the reference electrode 33, oxygen in the detection target gas G is discharged to the reference gas duct 24. By integrating the oxygen current Io by the current detection unit 522, the amount of oxygen contained in the detection target gas G can be obtained.
  • the oxygen detection unit 3 of the present embodiment is a state in which the flow rate of the detection target gas G passing through the diffusion resistor 45 is limited, and the oxygen flowing between the electrodes 32 and 33 when a DC voltage showing a limit current characteristic is applied. It is a limit current type that detects the current Io.
  • the oxygen detection unit 3 is of an electromotive force type that detects an electromotive force generated between a pair of electrodes according to the difference in oxygen concentration between the detection target gas G and the reference gas A, and this electromotive force.
  • the oxygen current Io may be detected based on.
  • the NOx detection unit 4 has a NOx sensor unit 40 which is a part of the sensor element 11 and a NOx control unit 53 which is a part of the sensor control unit 5.
  • the NOx sensor unit 40 includes a second solid electrolyte body 31, a NOx electrode 42 provided on the first surface 311 of the second solid electrolyte body 31 and exposed to the detection target gas G, and a second solid electrolyte body 31. It is composed of a reference electrode 43 provided on the surface 312 and exposed to the reference gas A.
  • the NOx sensor unit 40 is formed as a part of the composite sensor 10.
  • the NOx electrode 42 is arranged at a position on the first surface 311 of the second solid electrolyte body 31 on the downstream side of the flow of the detection target gas G from the position where the oxygen electrode 32 is provided.
  • the reference electrode 43 of the NOx sensor unit 40 may be integrated with the reference electrode 43 of the oxygen sensor unit 30.
  • the NOx control unit 53 flows between the voltage application unit 531 that applies a predetermined DC voltage between the NOx electrode 42 and the reference electrode 43, and between the NOx electrode 42 and the reference electrode 43 when the DC voltage is applied. It has a current detection unit 532 for detecting the NOx current In. When a predetermined DC voltage is applied between the NOx electrode 42 and the reference electrode 43, NOx in the detection target gas G is decomposed. In the NOx control unit 53, both the concentration of NOx directly contained in the detection target gas G and the concentration of NOx produced by oxidative decomposition of ammonia in the detection target gas G are detected as the NOx current In.
  • the first correction unit 54 affects the ammonia voltage Va detected by the hybrid potential type ammonia detection unit 2 due to the difference in the concentration of oxygen contained in the detection target gas G. It is to correct.
  • the corrected ammonia voltage Vb indicates the ammonia voltage corrected according to the magnitude of the oxygen current Io.
  • the first correction unit 54 is built in the sensor control unit 5. The corrected ammonia voltage Vb by the first correction unit 54 is corrected higher as the oxygen current Io by the oxygen detection unit 3 increases.
  • the oxygen current Io (the concentration of oxygen in the detection target gas G) by the oxygen detection unit 3 is used as a parameter, and the correction according to the ammonia voltage Va and the oxygen current Io is performed.
  • the relationship map M1 for which the relationship with the corrected ammonia voltage Vb is obtained is set.
  • the relationship map M1 is created as a relationship between the ammonia voltage Va and the corrected ammonia voltage Vb when the oxygen concentration is at a predetermined value.
  • the first correction unit 54 collates the oxygen current Io by the oxygen detection unit 3 and the ammonia voltage Va by the ammonia detection unit 2 with the relationship map M1 to obtain the correction ammonia voltage Vb.
  • FIG. 10 shows a relationship map M1 when the oxygen concentration in the detection target gas G is 5 [volume%], 10 [volume%], and 20 [volume%].
  • the relationship map M1 can be obtained at the time of trial production / experiment of the ammonia concentration detecting device 1.
  • the second correction unit 55 corrects the ammonia output concentration Na, which is the sensor output of the ammonia concentration detection device 1, by using the concentration of NOx contained in the detection target gas G. Is.
  • the second correction unit 55 is built in the sensor control unit 5.
  • the second correction unit 55 utilizes the property that the NOx detection unit 4 also detects the concentration of NOx generated by oxidative decomposition of ammonia, and the higher the concentration of ammonia contained in the detection target gas G, the higher the ammonia output concentration Na. It is configured to increase the ratio of reflecting the NOx current In by the NOx detection unit 4.
  • the corrected ammonia concentration based on the corrected ammonia voltage Vb is Oa [ppm]
  • the ammonia correction ratio indicating the ratio reflecting the corrected ammonia concentration Oa in the ammonia output concentration Na is Aa [-]
  • the NOx concentration based on the NOx current In is the NOx concentration.
  • An [ ⁇ ] is a NOx correction ratio indicating a ratio of On [ppm] and NOx concentration On reflected in the ammonia output concentration Na.
  • D [ppm] is a constant term and is appropriately determined according to the characteristics of the ammonia detection unit 2.
  • the ammonia correction ratio Aa is set smaller as the corrected ammonia voltage Vb is higher.
  • the ammonia correction ratio Aa of this embodiment is set to 1 as a reference when the corrected ammonia voltage Vb is 0 (zero), and decreases exponentially as the corrected ammonia voltage Vb increases, and the corrected ammonia voltage Vb Is set to be 0 (zero) when it reaches the expected maximum value.
  • the ammonia correction ratio Aa may be set to be smaller as the corrected ammonia voltage Vb is higher.
  • the NOx correction ratio An is set larger as the corrected ammonia voltage Vb is higher.
  • the NOx correction ratio An of the present embodiment is set to 0 (zero) as a reference when the corrected ammonia voltage Vb is 0 (zero), and increases exponentially as the corrected ammonia voltage Vb increases, and is corrected. It is set to 1 when the ammonia voltage Vb reaches the expected maximum value.
  • the NOx correction ratio An may be set to be larger as the corrected ammonia voltage Vb is higher.
  • the ammonia correction ratio Aa and the NOx correction ratio An may be values that change continuously according to the correction ammonia voltage Vb, or may be values that change stepwise according to the correction ammonia voltage Vb. In this case, the ammonia correction ratio Aa and the NOx correction ratio An can be changed in three or more steps.
  • the correction function of the ammonia output concentration Na the influence of various substance amounts depending on the combustion state in the internal combustion engine 7 may be taken into consideration.
  • the concentration of NOx in the exhaust gas as the detection target gas G becomes high when the air-fuel ratio of the internal combustion engine is in the fuel lean state. Therefore, the correction function may take into account parameters according to the air-fuel ratio of the internal combustion engine.
  • the second correction unit 55 of this embodiment is configured to obtain the ammonia correction ratio Aa and the NOx correction ratio An using the relationship maps Ma and Mn.
  • the second correction unit 55 has a setting unit 56, and the setting unit 56 includes an ammonia-related map Ma showing the relationship between the corrected ammonia concentration Oa and the ammonia correction ratio Aa, and the corrected ammonia concentration.
  • a NOx relationship map Mn showing the relationship between Oa and the NOx correction ratio An is set.
  • the second correction unit 55 collates the corrected ammonia concentration Oa with the ammonia relation map Ma to determine the ammonia correction ratio Aa, and collates the corrected ammonia concentration Oa with the NOx relation map Mn to determine the NOx correction ratio An. It is configured to do so.
  • the ammonia relation map Ma and the NOx relation map Mn the ammonia correction ratio Aa and the NOx correction ratio An can be easily obtained.
  • the relation maps Ma and Mn can be obtained at the time of trial production / experiment of the ammonia concentration detecting device 1.
  • the sensor element 11 As shown in FIGS. 1 and 6, the sensor element 11 is held in a housing and is covered by a plurality of covers attached to the housing.
  • the ammonia sensor unit 20, the oxygen sensor unit 30, and the NOx sensor unit 40 are formed in a portion on the tip end side of the sensor element 11 arranged in the exhaust pipe 71.
  • the tip end side portion of the sensor element 11 is covered with a porous protective layer.
  • an atmosphere as a reference gas A is formed between the inner side surface 212 of the first solid electrolyte body 21 and the second surface 312 of the second solid electrolyte body 31 by the insulator 25.
  • the reference gas duct 24 to be introduced is formed.
  • the reference gas duct 24 is formed from the base end portion of the sensor element 11, and the atmosphere taken into the cover of the composite sensor 10 from the outside is introduced into the reference gas duct 24.
  • the reference electrode 23 of the ammonia sensor unit 20, the reference electrode 33 of the oxygen sensor unit 30, and the reference electrode 43 of the NOx sensor unit 40 are arranged in the reference gas duct 24.
  • the exhaust gas as the detection target gas G is introduced into the first surface 311 of the second solid electrolyte 31 via the diffusion resistor 45 by the insulator 25.
  • the gas chamber 44 is formed.
  • the diffusion resistor 45 is formed of a porous material of ceramics, and limits the flow velocity of the detection target gas G introduced into the gas chamber 44.
  • the diffusion resistor 45 may be formed by a pinhole provided in the insulator 25.
  • the first and second solid electrolytes 21 and 31 are formed in a plate shape and are configured by using a zirconia material having a property of conducting oxygen ions at a predetermined temperature.
  • the zirconia material can be composed of various materials containing zirconia as a main component.
  • zirconia material stabilized zirconia or partially stabilized zirconia in which a part of zirconia is replaced with a rare earth metal element such as yttria (yttrium oxide) or an alkaline earth metal element can be used.
  • the outer surface 211 of the first solid electrolyte 21 forms the outermost surface of the sensor element 11.
  • the ammonia electrode 22 provided on the outer surface 211 is formed in a state in which the detection target gas G can easily come into contact with the ammonia electrode 22.
  • the surface of the ammonia electrode 22 of this embodiment is not provided with a protective layer made of a porous body of ceramics or the like. Then, the detection target gas G comes into contact with the ammonia electrode 22 without being diffusion-controlled. It is also possible to provide a protective layer on the surface of the ammonia electrode 22 so as not to reduce the flow velocity of the detection target gas G as much as possible.
  • the ammonia electrode 22 contains a noble metal having catalytic activity for ammonia and oxygen, and a zirconia material which is a co-material when sintering with the first solid electrolyte body 21.
  • a noble metal having catalytic activity for ammonia and oxygen
  • a zirconia material which is a co-material when sintering with the first solid electrolyte body 21.
  • gold (Au) gold
  • platinum (Pt) -gold alloy platinum-palladium alloy
  • palladium-gold alloy palladium-gold alloy and the like
  • the ammonia electrode 22 may contain a metal oxide, an oxide having a perovskite structure (perovskite type oxide), a composite oxide, or the like, in addition to the noble metal and the zirconia material, or instead of the noble metal.
  • the oxygen electrode 32 contains a noble metal having a catalytic activity for oxygen and a zirconia material which is a co-material when sintering with the second solid electrolyte body 31. Platinum, palladium, gold or the like can be used as the noble metal constituting the oxygen electrode 32.
  • the NOx electrode 42 contains a noble metal having catalytic activity for NOx and oxygen, and a zirconia material which is a co-material when sintering with the second solid electrolyte body 31.
  • a platinum-rhodium (Rh) alloy or the like can be used as the noble metal constituting the NOx electrode 42.
  • Each reference electrode 23, 33, 43 contains a noble metal having catalytic activity for oxygen, and a zirconia material that serves as a co-material when sintering with the first solid electrolyte 21 or the second solid electrolyte 31. Platinum, palladium, gold or the like can be used as the noble metal constituting each reference electrode 23, 33, 43.
  • the heating element 111 embedded in the insulator 25 is laminated on the first solid electrolyte 21 and the second solid electrolyte 31.
  • the insulator 25 is made of an insulating ceramic material such as alumina.
  • the reference gas duct 24 and the gas chamber 44 are formed by a space provided in the insulator 25.
  • the heating element 111 has a heating element that generates heat when energized by the energizing control unit 57 in the sensor control unit 5.
  • the heating element 111 contains a conductive metal material. The heat generated by the heating element of the heating element 111 causes the ammonia detection unit 2, the oxygen detection unit 3, and the NOx detection unit 4 to be heated to a target temperature.
  • Hybrid potential of ammonia detection unit 2 As shown in FIG. 1, the ammonia voltage Va by the ammonia detection unit 2 is detected by the potential difference (voltage) ⁇ V as a mixed potential generated between the ammonia electrode 22 and the reference electrode 23. As shown in FIG. 12, the ammonia detection unit 2 is generated when the reduction current due to the reduction reaction of oxygen and the oxidation current due to the oxidation reaction of ammonia in the ammonia electrode 22 become equal to each other. The potential difference ⁇ V between them is detected. The potential difference ⁇ V generated between the ammonia electrode 22 and the reference electrode 23 indicates the mixed potential generated in the ammonia electrode 22 by the detection target gas G containing ammonia and oxygen.
  • the ammonia oxidation reaction and the oxygen reduction reaction proceed at the same time.
  • Oxidation of ammonia typically, 2NH 3 + 3O 2- ⁇ N 2 + 3H 2 O + 6e - represented by.
  • Reduction reaction of oxygen is typically, O 2 + 4e - ⁇ 2O represented by 2-.
  • the mixed potential of ammonia and oxygen in the ammonia electrode 22 is generated as a potential when the oxidation reaction (rate) of ammonia and the reduction reaction (rate) of oxygen in the ammonia electrode 22 become equal.
  • FIG. 12 is a diagram for explaining the hybrid potential generated in the ammonia electrode 22.
  • the horizontal axis represents the potential of the ammonia electrode 22 with respect to the reference electrode 23 (potential difference ⁇ V), and the vertical axis represents the current flowing between the ammonia electrode 22 and the reference electrode 23 to change the mixed potential. I will show you how to do it.
  • the first line L1 showing the relationship between the potential and the current when the oxidation reaction of ammonia is carried out at the ammonia electrode 22 and the potential and the current when the reduction reaction of oxygen is carried out at the ammonia electrode 22
  • the second line L2 showing the relationship is shown. Both the first line L1 and the second line L2 are indicated by an upward-sloping line.
  • the mixed potential is the potential when the positive current on the first line L1 showing the oxidation reaction of ammonia and the negative current on the second line L2 showing the reduction reaction of oxygen are balanced. Then, the hybrid potential in the ammonia electrode 22 is detected as a potential on the negative side with respect to the reference electrode 23.
  • ammonia voltage is shown as the potential on the positive side for the sake of simplicity.
  • the ammonia voltage Va can be treated as an absolute value.
  • the corrected ammonia concentration Oa in the correction function of the ammonia output concentration Na of the second correction unit 55 described above is shown as a positive value.
  • the ammonia concentration detecting device 1 detects the concentration of ammonia flowing out from the selective reduction catalyst 72 and the concentration of NOx when purifying the NOx contained in the exhaust gas exhausted to the exhaust pipe 71 of the internal combustion engine (diesel engine) 7. Used for When the internal combustion engine 7 is started, the engine control unit 6 and the sensor control unit 5 are also started, and the detection by the ammonia concentration detection device 1 is started.
  • the ammonia detection unit 2 detects the ammonia voltage Va according to the concentration of ammonia contained in the detection target gas G (step S101 in FIG. 15). Further, the oxygen detection unit 3 detects the oxygen current Io according to the concentration of oxygen contained in the detection target gas G (step S102). Further, the NOx detection unit 4 detects the NOx current In according to the concentration of NOx contained in the detection target gas G (step S103).
  • the detected ammonia voltage Va and the detected oxygen current Io are substituted into the relationship map, and the corrected ammonia voltage Vb is obtained from the relationship map (step S104).
  • the corrected ammonia concentration Oa based on the corrected ammonia voltage Vb is substituted into the ammonia relation map Ma, and the ammonia correction ratio Aa is obtained by the ammonia relation map Ma (step S105).
  • the corrected ammonia concentration Oa based on the corrected ammonia voltage Vb is substituted into the NOx relation map Mn, and the NOx correction ratio An is obtained from the NOx relation map Mn (step S106).
  • the ammonia concentration detection device 1 having the composite sensor 10 can output the ammonia output concentration Na as the sensor output indicating the ammonia concentration and the NOx concentration On as the sensor output indicating the NOx concentration.
  • the ammonia concentration detection device 1 may output an oxygen concentration based on the oxygen current Io as a sensor output indicating the oxygen concentration.
  • the ammonia concentration detecting device 1 of the present embodiment uses the concentration of NOx to detect the concentration of ammonia, and changes the correction ratio according to the concentration of NOx so that the concentration of ammonia changes continuously. be. Specifically, in the second correction unit 55 of the ammonia concentration detection device 1, the higher the correction ammonia voltage Vb by the first correction unit 54, the smaller the utilization ratio of the correction ammonia voltage Vb and the correction ratio by the NOx current In. Is increased to obtain the ammonia output concentration Na.
  • the concentration of ammonia in the detection target gas G increases, the NOx current In corresponding to the concentration of NOx generated by the oxidative decomposition of ammonia detected by the NOx detection unit 4 increases to the ammonia output concentration Na. It can be reflected. Further, as the concentration of ammonia in the detection target gas G increases, the ratio of the corrected ammonia voltage Vb obtained by the first correction unit 54 reflected in the ammonia output concentration Na can be reduced.
  • the ratio of the corrected ammonia voltage Vb (corrected ammonia concentration Oa) and the ratio of the NOx current In (NOx concentration On) reflected in the ammonia output concentration Na correct the ammonia output concentration Na in the entire range of the corrected ammonia voltage Vb. Obtained based on the function.
  • the ammonia output concentration Na changes continuously or stepwise over the entire range of the corrected ammonia voltage Vb (corrected ammonia concentration Oa), and when the corrected ammonia voltage Vb (corrected ammonia concentration Oa) reaches a predetermined value. In addition, it does not switch suddenly. In other words, there is no boundary where the method of detecting the ammonia concentration changes abruptly, and the ammonia concentration can be detected more appropriately.
  • the concentration of ammonia in the detection target gas G can be detected in a state of continuously or stepwise changing over a wide concentration range.
  • This embodiment shows a case where the method of calculating the ammonia output concentration Na by the second correction unit 55 is different from that of the first embodiment.
  • the corrected ammonia concentration based on the corrected ammonia voltage Vb is Oa
  • the NOx concentration based on the NOx current In is On
  • the NOx correction ratio indicating the ratio reflecting the NOx concentration On in the ammonia output concentration Na is An
  • D is a constant term.
  • the corrected ammonia concentration Oa, the NOx concentration On, the NOx correction ratio An, and the constant term D are obtained in the same manner as in the first embodiment. Further, as shown in FIG. 11 of the first embodiment, the NOx correction ratio An is set to be larger as the corrected ammonia voltage Vb is higher.
  • the NOx correction ratio An is set to 0 (zero) as a reference when the corrected ammonia voltage Vb is 0 (zero), and increases exponentially as the corrected ammonia voltage Vb increases, and the corrected ammonia voltage Vb Is set to 1 when it reaches the expected maximum value.
  • the relationship between the corrected ammonia concentration Oa and the NOx correction ratio An is set as the NOx relationship map Mn.
  • the second correction unit 55 is configured to collate the NOx concentration On with the NOx relationship map Mn to determine the NOx correction ratio An.
  • the ratio of the corrected ammonia voltage Vb (corrected ammonia concentration Oa) reflected in the ammonia output concentration Na is always the same, and the ratio of the NOx current In reflected in the ammonia output concentration Na is the corrected ammonia voltage Vb.
  • the ammonia output concentration Na changes continuously in the entire range of the corrected ammonia voltage Vb, and switches discontinuously when the corrected ammonia voltage Vb reaches a predetermined value, as in the first embodiment. There is no.
  • the other configurations, actions and effects, etc. of the ammonia concentration detection device 1 of the present embodiment are the same as the configurations, actions and effects, etc. of the first embodiment. Further, also in this embodiment, the components indicated by the same reference numerals as those shown in the first embodiment are the same as those of the first embodiment.
  • the ammonia concentration detection device 1 is separately configured instead of having the composite sensor 10 at the position on the downstream side of the flow of the exhaust gas as the detection target gas G of the selective reduction catalyst 72.
  • the ammonia sensor 13 and the NOx sensor 14 may be provided.
  • the ammonia sensor 13 has a function of detecting the concentration of ammonia contained in the exhaust gas.
  • the NOx sensor 14 has a function of detecting the concentration of NOx and the concentration of oxygen contained in the detection target gas G.
  • the ammonia detection unit 2 is configured by using the ammonia sensor 13, and the oxygen detection unit 3 and the NOx detection unit 4 are configured by using the NOx sensor 14.
  • the ammonia concentration detection device 1 may be configured by using the existing NOx sensor. Further, in this case as well, the same effect as that of the first embodiment can be obtained. Further, the oxygen detection unit 3 may be configured by using an oxygen sensor different from the NOx sensor 14.
  • present disclosure is not limited to each embodiment, and further different embodiments can be configured without departing from the gist thereof.
  • the present disclosure includes various modifications, modifications within an equal range, and the like.
  • the technical idea of the present disclosure also includes combinations, forms, etc. of various components assumed from the present disclosure.

Abstract

L'invention concerne un capteur de concentration en ammoniac (1) qui comprend : une unité de détection d'ammoniac (2) qui délivre en sortie une tension d'ammoniac (Va) ; une unité de détection d'oxygène (3) qui délivre en sortie un courant d'oxygène (Io) ; et une unité de détection de NOx (4) qui délivre en sortie un courant de NOx (In) correspondant à la concentration en NOx qui comprend des NOx produits par la décomposition oxydante d'ammoniac. De plus, ce capteur de concentration en ammoniac (1) comprend : une première unité de correction (54) qui obtient une tension d'ammoniac corrigée (Vb) par la correction de la tension d'ammoniac (Va) conformément au courant d'oxygène (Io) ; et une seconde unité de correction (55) qui obtient une concentration de sortie en ammoniac (Na) par l'augmentation du taux de correction au moyen du courant de NOx (In) lorsque la tension d'ammoniac corrigée (Vb) par la première unité de correction (54) devient supérieure.
PCT/JP2021/017627 2020-06-08 2021-05-10 Capteur de concentration en ammoniac WO2021251036A1 (fr)

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JP2020-099340 2020-06-08
JP2020099340A JP7304317B2 (ja) 2020-06-08 2020-06-08 アンモニア濃度検出装置

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009511859A (ja) * 2005-10-07 2009-03-19 デルファイ・テクノロジーズ・インコーポレーテッド マルチセルアンモニアセンサーおよびその使用方法
JP2010071195A (ja) * 2008-09-18 2010-04-02 Toyota Motor Corp ＮＯｘセンサの出力較正装置及び出力較正方法
JP2019203835A (ja) * 2018-05-25 2019-11-28 株式会社Ｓｏｋｅｎ マルチガスセンサ

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009511859A (ja) * 2005-10-07 2009-03-19 デルファイ・テクノロジーズ・インコーポレーテッド マルチセルアンモニアセンサーおよびその使用方法
JP2010071195A (ja) * 2008-09-18 2010-04-02 Toyota Motor Corp ＮＯｘセンサの出力較正装置及び出力較正方法
JP2019203835A (ja) * 2018-05-25 2019-11-28 株式会社Ｓｏｋｅｎ マルチガスセンサ

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