CN112505127A - Gas sensor control device, gas sensor device, and internal combustion engine control device - Google Patents
Gas sensor control device, gas sensor device, and internal combustion engine control device Download PDFInfo
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- CN112505127A CN112505127A CN202010948212.8A CN202010948212A CN112505127A CN 112505127 A CN112505127 A CN 112505127A CN 202010948212 A CN202010948212 A CN 202010948212A CN 112505127 A CN112505127 A CN 112505127A
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- 238000002485 combustion reaction Methods 0.000 title claims abstract description 42
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 655
- 239000007789 gas Substances 0.000 claims abstract description 348
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 331
- 239000001301 oxygen Substances 0.000 claims abstract description 144
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 144
- 238000001514 detection method Methods 0.000 claims abstract description 143
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 139
- 238000000034 method Methods 0.000 claims abstract description 105
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- 238000005086 pumping Methods 0.000 description 82
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 51
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- 239000011241 protective layer Substances 0.000 description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
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- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 6
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- 238000000354 decomposition reaction Methods 0.000 description 6
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- 238000006243 chemical reaction Methods 0.000 description 5
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- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
-
- 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
- G01N27/419—Measuring voltages or currents with a combination of oxygen pumping cells and oxygen concentration cells
-
- 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
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
- F01N13/008—Mounting or arrangement of exhaust sensors in or on exhaust 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
Abstract
The invention provides a gas sensor control device, a gas sensor device, and an internal combustion engine control device, which reduce the influence of the pressure of the gas to be measured and improve the measurement accuracy of the ammonia concentration. The gas sensor control device is provided with a control unit that executes: a first reception process of receiving a first detection result corresponding to a concentration of ammonia output from an ammonia detection unit of a mixed potential type for detecting ammonia contained in a gas to be measured; a second reception process of receiving a second detection result corresponding to the concentration of oxygen output from an oxygen detection unit for detecting oxygen contained in the measurement target gas; a first concentration calculation process of calculating a first ammonia concentration contained in the measurement target gas based on the first detection result and the second detection result; the pressure correction process corrects the first ammonia concentration based on pressure information indicating the pressure of the gas to be measured, which is acquired from an external device, to acquire a second ammonia concentration of the gas to be measured, in order to reduce the influence of the pressure of the gas to be measured on ammonia.
Description
Technical Field
The invention relates to a gas sensor control device, a gas sensor device, and an internal combustion engine control device.
Background
An ammonia sensor that detects the concentration of ammonia contained in a gas to be measured (for example, an exhaust gas from an internal combustion engine) is known (for example, patent document 1). This ammonia sensor includes a mixed potential unit having a solid electrolyte and a pair of electrodes (a detection electrode and a reference electrode). The mixed potential unit outputs an electromotive force corresponding to the concentration of ammonia in the measurement target gas, but this electromotive force also reflects the concentration of oxygen in the measurement target gas.
For example, as shown in patent document 2, a relational expression between the ammonia concentration, the oxygen concentration, and the electromotive force of the mixed potential unit in the gas to be measured is known. By using such a relational expression, the ammonia concentration in the measurement gas is calculated based on the information of the electromotive force of the mixed potential unit and the oxygen concentration in the measurement gas.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2015-34814
Patent document 2: japanese patent laid-open publication No. 2018-72315
Disclosure of Invention
Problems to be solved by the invention
The pressure of the gas to be measured is not always constant and may vary. For example, when a throttle valve for adjusting the intake air amount of an internal combustion engine is fully opened, the pressure of exhaust gas (measured gas) from the internal combustion engine is higher than the pressure before the throttle valve is fully opened.
The inventors of the present invention found that: when the pressure of the gas to be measured changes in this manner, the output (electromotive force) of the mixed potential unit changes. In the conventional ammonia sensor, the influence of the pressure of the gas to be measured is not taken into consideration when the ammonia concentration is obtained.
The purpose of the present invention is to improve the accuracy of ammonia concentration measurement by reducing the influence of the pressure of the gas to be measured in a gas sensor control device, a gas sensor device, and an internal combustion engine control device.
Means for solving the problems
The inventors of the present invention found that: when the pressure of the gas to be measured changes, the output (electromotive force) of the mixed-potential-type ammonia detecting unit changes (that is, the output of the mixed-potential-type ammonia detecting unit is affected by the pressure of the gas to be measured). The reason for this is presumed to be as follows.
As shown in patent document 2, ammonia (2/3 NH) is contained in the probe electrode of the mixed potential cell3) With oxygen ions (O)2-) React to produce nitrogen (1/3N)2) Water (H)2O) and electrons (2 e)-) And oxygen (1/2O)2) And electron (2 e)-) React to generate oxygen ions (O)2-) The cathodic reactions of (a) are simultaneous. Then, the equilibrium point of the anodic reaction with respect to the cathodic reaction was observed as an electromotive force of the mixed potential unit. In such a situation, for example, when the pressure of the gas to be measured becomes high, the electromotive force of the mixed potential means becomes small. It is considered that when the pressure of the gas to be measured becomes high, the apparent oxygen concentration becomes higher than the oxygen concentration before the pressure of the gas to be measured becomes high, and as a result, it is estimated that the sensing electrode of the mixed potential cell easily reacts with oxygen and relatively easily causes a cathode reaction.
The means for solving the above problems are as follows. Namely:
<1> a gas sensor control device, comprising a control unit that executes: a first reception process of receiving a first detection result corresponding to a concentration of ammonia output from a mixed-potential-type ammonia detection unit for detecting ammonia contained in a measurement target gas; a second reception process of receiving a second detection result corresponding to a concentration of oxygen output from an oxygen detection unit for detecting oxygen contained in the measurement target gas; a first concentration calculation process of calculating a first ammonia concentration in the measurement target gas based on the first detection result and the second detection result; and a pressure correction process of correcting the first ammonia concentration based on pressure information indicating the pressure of the gas to be measured acquired from an external device to acquire a second ammonia concentration of the gas to be measured, in order to reduce an influence of the pressure of the gas to be measured on the ammonia.
<2> in the gas sensor control device according to <1>, the pressure correction process is a process of obtaining the second ammonia concentration by correcting the first ammonia concentration using a correction coefficient based on the pressure information.
<3> in the gas sensor control device according to the above <1> or <2>, when the oxygen is affected by the pressure of the gas under measurement, the control unit performs an oxygen pressure correction process for correcting the second ammonia concentration based on the pressure information of the gas under measurement to obtain a third ammonia concentration of the gas under measurement in order to reduce the effect of the pressure.
<4> in the gas sensor control device according to any one of <1> to <3>, in a case where the oxygen is affected by the pressure of the gas under measurement, the control unit performs a simultaneous correction process of correcting a first ammonia concentration based on the pressure information of the gas under measurement to acquire a fourth ammonia concentration of the gas under measurement, instead of the pressure correction process, in order to reduce the effect of the pressure of the gas under measurement on the ammonia and reduce the effect of the pressure of the gas under measurement on the oxygen.
<5> A gas sensor device, comprising: a mixed potential type ammonia detection unit for detecting that ammonia is contained in a gas to be measured; an oxygen detection unit for detecting oxygen contained in the measurement target gas; and the gas sensor control device according to any one of the above <1> to <4 >.
<6> an internal combustion engine control device for controlling an operating state of an internal combustion engine, the internal combustion engine control device comprising a control unit that executes: a first reception process of receiving a first detection result corresponding to a concentration of ammonia detected by a mixed-potential-type ammonia detection unit for detecting that ammonia is contained in a gas to be measured from the internal combustion engine; a second reception process of receiving a second detection result corresponding to a concentration of oxygen output from an oxygen detection unit for detecting oxygen contained in the measurement target gas; a first concentration calculation process of calculating a first ammonia concentration in the measurement target gas based on the first detection result and the second detection result; and a pressure correction process of correcting the first ammonia concentration based on pressure information indicating the pressure of the gas to be measured acquired from an external device to acquire a second ammonia concentration of the gas to be measured, in order to reduce an influence of the pressure of the gas to be measured on the ammonia.
<7> in the internal combustion engine control device according to <6>, the pressure correction process is a process of acquiring the second ammonia concentration by correcting the first ammonia concentration using a correction coefficient based on the pressure information.
<8> in the internal combustion engine control device according to <6> or <7>, when the oxygen is affected by the pressure of the gas under measurement, the control unit performs an oxygen pressure correction process for correcting the second ammonia concentration based on the pressure information of the gas under measurement to obtain a third ammonia concentration of the gas under measurement in order to reduce the effect of the pressure.
<9> in the internal combustion engine control device according to any one of <6> to <8>, when the oxygen is affected by the pressure of the measurement gas, the control unit performs a simultaneous correction process for correcting a first ammonia concentration based on the pressure information of the measurement gas and acquiring a fourth ammonia concentration of the measurement gas, instead of the pressure correction process, in order to reduce the effect of the pressure of the measurement gas on the ammonia and reduce the effect of the pressure of the measurement gas on the oxygen.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, in the gas sensor control device, the gas sensor device, and the internal combustion engine control device, the accuracy of measuring the ammonia concentration can be improved by reducing the influence of the pressure of the gas to be measured.
Drawings
Fig. 1 is a longitudinal sectional view of a multi-gas sensor according to embodiment 1.
Fig. 2 is an explanatory diagram showing a schematic configuration of the multi-gas sensor device.
Fig. 3 is a sectional view showing the structure of the ammonia sensor portion.
Fig. 4 is a flowchart showing the content of the ammonia concentration detection process.
Fig. 5 is an explanatory diagram illustrating an installation location of a pressure sensor for detecting the pressure of the gas to be measured.
Fig. 6 is a graph showing a relationship between the pressure of the gas to be measured and the ammonia concentration affected by the pressure of the gas to be measured.
Fig. 7 is a graph showing a relationship between the pressure of the gas to be measured and the oxygen concentration affected by the pressure of the gas to be measured.
Fig. 8 is a graph showing a relationship between the pressure of the gas under measurement and the ammonia concentration in which the influence of the pressure of the gas under measurement on ammonia is reduced.
Fig. 9 is an explanatory diagram showing a schematic configuration of the internal combustion engine control system according to embodiment 2.
Fig. 10 is a flowchart showing the contents of the ammonia concentration detection process in the ECU.
Fig. 11 is a flowchart showing the content of the ammonia concentration detection process according to embodiment 3.
Fig. 12 is a flowchart showing the content of the ammonia concentration detection process according to embodiment 4.
Fig. 13 is a flowchart showing the content of the ammonia concentration detection process according to embodiment 5.
Fig. 14 is a flowchart showing the content of the ammonia concentration detection process according to embodiment 6.
Description of the reference numerals
2: a first pumping unit (oxygen detection unit); 42: an ammonia sensor unit (ammonia detection unit); 42 x: a first ammonia sensor unit; 42 y: a second ammonia sensor unit; 60: a microcomputer (SCU); 61: a CPU (control unit); 100A: a multi-gas sensor element section; 200A: a multi-gas sensor; 220: an ECU; 221: an ECU (internal combustion engine control device); 222: a CPU (control unit); 300: a gas sensor control device; 400: multiple gas sensor devices (gas sensor devices); 500: a pressure sensor; 600: an internal combustion engine control system; l: an axis.
Detailed Description
< embodiment 1>
Fig. 1 is a cross-sectional view of multi-gas sensor 200A according to embodiment 1 along the longitudinal direction (direction of axis L), and fig. 2 is an explanatory diagram illustrating a schematic configuration of multi-gas sensor device 400 according to embodiment 1. Note that, in fig. 2, for convenience of explanation, only a cross section along the longitudinal direction (the axis L direction) of the multi-gas sensor element portion 100A housed in the multi-gas sensor 200A is shown.
The multi-gas sensor device 400 is used in a urea SCR (selective catalytic reduction) system for detecting Nitrogen Oxides (NO) contained in exhaust gas (an example of a gas to be measured) discharged from a diesel engine (an example of an internal combustion engine) of an automobilex) And (5) purifying. The urea SCR system is ammonia (NH)3) With Nitrogen Oxides (NO)x) A chemical reaction takes place to reduce the nitrogen oxides to nitrogen (N)2) And a system for purifying nitrogen oxides contained in the exhaust gas. In urea SCR systems, when nitrogen oxides are suppliedIf the amount of ammonia is excessive, unreacted ammonia may be contained in the exhaust gas and may be directly discharged to the outside. The multi-gas sensor device 400 measures the concentration of ammonia contained in the exhaust gas (measurement target gas) in order to monitor the emission of ammonia. The multi-gas sensor device 400 is configured to be able to measure NO in addition to the ammonia concentration as described laterxConcentration, etc.
As shown in FIG. 1, a multi-gas sensor 200A is provided for measuring ammonia concentration and NOxThe components of the multi-gas sensor element portion 100A for detecting the concentration.
The multi-gas sensor 200A includes: a plate-shaped multi-gas sensor element portion 100A extending in the direction of the axis L; a cylindrical main metal fitting member 138 having a threaded portion 139 formed on an outer surface thereof for fixing to an exhaust pipe; a cylindrical ceramic sleeve 106 disposed so as to surround the periphery of the multiple gas sensor element portion 100A in the radial direction; an insulating contact member 166 disposed in a state in which the inner wall surface of a contact insertion hole 168 penetrating in the direction of the axis L surrounds the periphery of the rear end portion of the multi-gas sensor element portion 100A; and a plurality of (only 2 are illustrated in fig. 1) connection terminals 110 arranged between the multi-gas sensor element portion 100A and the insulating contact member 166.
The main metal fitting member 138 is formed into a substantially cylindrical shape having a through hole 154 penetrating in the direction of the axis L and a frame portion 152 protruding inward in the radial direction of the through hole 154. The main metal fitting member 138 holds the multi-gas sensor element portion 100A in a state in which the distal end side of the multi-gas sensor element portion 100A is disposed outside the distal end side of the through hole 154 and the electrode terminal portions 80A and 82A are disposed outside the rear end side of the through hole 154. Moreover, the shelf portion 152 is formed as an inward tapered surface having an inclination with respect to a plane perpendicular to the direction of the axis L.
Further, inside the through hole 154 of the main metal fitting member 138, the ceramic holder 151 having an annular shape, the powder filling layers 153, 156 (hereinafter also referred to as "talc rings 153, 156"), and the ceramic sleeve 106 described above are laminated in this order from the distal end side to the rear end side in a state of surrounding the periphery of the multi-gas sensor element portion 100A in the radial direction. Further, a pressure seal 157 is disposed between the ceramic sleeve 106 and the rear end portion 140 of the main metal fitting member 138, and a metal holder 158 for holding the talc ring 153 and the ceramic holder 151 to maintain airtightness is disposed between the ceramic holder 151 and the mount portion 152 of the main metal fitting member 138. Further, the rear end portion 140 of the main metal fitting member 138 is pressed, so that the ceramic sleeve 106 is pressed toward the tip end side via the press seal 157.
On the other hand, a double-layer outer protector 142 and an inner protector 143 made of metal (e.g., stainless steel) covering the protruding portions of the multiple gas sensor element portion 100A and having a plurality of hole portions are attached to the outer periphery of the main metal fitting member 138 on the tip end side (lower side in fig. 1) by welding or the like.
An outer cylinder 144 is fixed to the outer periphery of the main fitting member 138 on the rear end side. Further, a gasket 150 is disposed in an opening portion on the rear end side (upper side in fig. 1) of the outer tube 144, the gasket 150 is formed with lead insertion holes 161 through which a plurality of leads 146 (only 3 leads are shown in fig. 1) are inserted, and the plurality of leads 146 are electrically connected to the electrode terminal portions 80A and 82A of the multi-gas sensor element portion 100A, respectively. Note that, for simplicity, the electrode terminal portions on the front and back surfaces of the multi-gas sensor element portion 100A are denoted by reference numerals 80A and 82A in fig. 1, respectively, but actually, NO described later is used as a basisxThe sensor portion 30A, the first ammonia sensor portion, and the second ammonia sensor portions 42x and 42y have a plurality of electrodes and the like.
Further, an insulating contact member 166 is disposed on the rear end side (upper side in fig. 1) of the multi-gas sensor element portion 100A protruding from the rear end portion 140 of the main metal fitting member 138. The insulating contact member 166 is disposed around the electrode terminal portions 80A and 82A formed on the front and rear surfaces of the multi-gas sensor element portion 100A on the rear end side. The insulating contact member 166 is formed in a cylindrical shape having a contact insertion hole 168 penetrating in the direction of the axis L, and includes a flange portion 167 protruding radially outward from the outer surface. The insulating contact member 166 is disposed inside the outer cylinder 144 by the flange portion 167 coming into contact with the outer cylinder 144 via the holding member 169. Connection terminal 110 on the side of insulating contact member 166 is electrically connected to electrode terminal portions 80A and 82A of multi-gas sensor element portion 100A, and is electrically connected to the outside through lead wire 146.
As shown in fig. 2, the gas sensor control device 300 is electrically connected to an ECU (engine controller unit) 220. An end of lead wire 146 extending from gas sensor 200A is connected to a connector configured to be electrically connected to a connector on the side of gas sensor control device 300.
Next, the structure of the multi-gas sensor element unit 100A included in the multi-gas sensor 200A will be described. The multi-gas sensor element portion 100A has a structure having a known NOxNO of the same construction as the sensorx A sensor portion 30A and an ammonia sensor portion 42.
NOxThe sensor unit 30A mainly includes NO including the first pumping means 2, the oxygen concentration detection means 6, and the second pumping means 4xA detection section. In addition, NOxThe sensor section 30A has a structure in which an insulating layer 23e, a first solid electrolyte body 2a, an insulating layer 23d, a third solid electrolyte body 6a, an insulating layer 23c, a second solid electrolyte body 4a, and insulating layers 23b and 23a are laminated in this order. As shown in fig. 2, a first measurement chamber S1 is formed between the first solid electrolyte body 2a and the third solid electrolyte body 6 a. Further, the exhaust gas is introduced from the outside through the first diffusion resistor 8a disposed at the left end (inlet) of the first measurement chamber S1. Further, a protective layer 9 made of a porous material is disposed outside the first diffusion resistor 8 a.
A second diffusion resistor 8b is disposed at one end of the first measurement chamber S1 opposite to the entrance. In fig. 2, a second measurement chamber S2 communicating with the first measurement chamber S1 through a second diffusion resistor 8b is formed on the right side of the first measurement chamber S1. The second measurement chamber S2 is formed between the first solid electrolyte body 2a and the second solid electrolyte body 4a so as to penetrate the third solid electrolyte body 6 a.
A long heating resistor 21 extending in the longitudinal direction of the multi-gas sensor element portion 100A is embedded between the insulating layers 23b, 23 a. The heat-generating resistor 21 has a heat-generating portion provided on the tip end side in the axial direction (longitudinal direction), and a pair of lead portions provided from the heat-generating portion toward the rear end side in the axial direction. The heat-generating resistor 21 and the insulating layers 23b and 23a correspond to a heater. The heater is used to raise the temperature of the gas sensor to an active temperature to increase the oxygen ion conductivity of the solid electrolyte body, thereby stabilizing the operation.
Each of the insulating layers 23a to 23e is mainly made of alumina, and the first diffusion resistor 8a and the second diffusion resistor 8b are made of a porous material such as alumina. The heating resistor 21 is made of platinum or the like. The heat generating portion of the heat generating resistor 21 may be formed in a serpentine pattern, for example.
The first pumping unit 2 is used to pump out or pump in oxygen in the exhaust gas (measured gas) introduced into the first measurement chamber S1. The first pumping means 2 includes a first solid electrolyte body 2a mainly composed of zirconia having oxygen ion conductivity, an inner first pumping electrode 2b disposed so as to sandwich the first solid electrolyte body 2a, and an outer first pumping electrode 2c serving as a counter electrode. The inner first pumping electrode 2b faces the first measurement chamber S1. The inner first pumping electrode 2b and the outer first pumping electrode 2c are each mainly made of platinum, and the surface of the inner first pumping electrode 2b is covered with a protective layer 11 made of a porous body.
The insulating layer 23e corresponding to the upper surface of the outer first pumping electrode 2c is hollowed out, and the hollowed-out portion is filled with the porous body 13. The porous body 13 allows the outer first pumping electrode 2c to communicate with the outside, thereby allowing gas (oxygen) to enter and exit.
Further, the oxygen concentration in the exhaust gas (the gas to be measured) can be grasped based on the first pumping current Ip1 flowing through the first pumping means (an example of the oxygen detection portion) 2. As will be described later, the oxygen concentration in the exhaust gas obtained based on the first pumping current Ip1 is used for the detection of the ammonia concentration in the exhaust gas.
The oxygen concentration detection cell 6 includes a third solid electrolyte body 6a mainly composed of zirconia, and a probe electrode 6b and a reference electrode 6c disposed so as to sandwich the third solid electrolyte body 6 a. The detection electrode 6b faces the first measurement chamber S1 at a position downstream of the inner first pumping electrode 2 b. The detection electrode 6b and the reference electrode 6c are each mainly made of platinum.
The insulating layer 23c is cut so that the reference electrode 6c in contact with the third solid electrolyte body 6a is disposed inside, and the cut portion (cut portion) is filled with a porous body to form the reference oxygen chamber 15. Then, by using the Icp supply circuit 54, a current of a weak constant value is supplied to the oxygen concentration detection cell 6 in advance, and oxygen is fed from the first measurement chamber S1 into the reference oxygen chamber 15.
The second pumping means 4 includes a second solid electrolyte body 4a mainly composed of zirconia, an inner second pumping electrode 4b disposed on a surface of the second solid electrolyte body 4a facing the second measurement chamber S2, and a second pumping counter electrode 4c serving as a counter electrode. The inner second pumping electrode 4b and the second pumping counter electrode 4c are both mainly made of platinum. The second pumping counter electrode 4c is disposed at a position of the cut portion of the insulating layer 23c on the second solid electrolyte body 4a, faces the reference electrode 6c, and faces the reference oxygen chamber 15.
As shown in fig. 2, the inner first pumping electrode 2b, the detection electrode 6b, and the inner second pumping electrode 4b are connected to a reference potential. In addition, NOxThe portions (for example, the first pumping means 2, the oxygen concentration detection means 6, the second pumping means 4, and the like) other than the heating resistor 21 and the insulating layers 23b, 23a in the sensor section 30A constitute NOxA detection section.
Next, the ammonia sensor unit 42 will be described. The ammonia sensor unit 42 includes two ammonia sensor units (a first ammonia sensor unit 42x and a second ammonia sensor unit 42y) of a mixed potential system. Fig. 3 is a sectional view showing the structure of the ammonia sensor portion 42. As shown in fig. 3, the multi-gas sensor element portion 100A has, as ammonia sensor portions, a first ammonia sensor portion 42x and a second ammonia sensor portion 42y that are separated from each other in the width direction. The first ammonia sensor unit 42x and the second ammonia sensor unit 42y each include a mixed potential unit.
First ammonia sensor portion 42x andthe second ammonia sensor portion 42y is formed to constitute NOxOn the insulating layer 23a of the outer surface (lower surface) of the sensor portion 30A. In the first ammonia sensor unit 42x, a first reference electrode 42ax is formed on the insulating layer 23a, and a first solid electrolyte body 42dx is formed so as to cover the lower surface and the side surface of the first reference electrode 42 ax. Further, a first detection electrode 42bx is formed on the surface of the first solid electrolyte body 42 dx. The ammonia concentration in the measurement target gas is detected by the electromotive force change between the first reference electrode 42ax and the first detection electrode 42 bx. In addition, similarly, the second ammonia sensor portion 42y has the second reference electrode 42ay formed on the insulating layer 23a, and the second solid electrolyte body 42dy is formed so as to cover the lower surface and the side surface of the second reference electrode 42 ay. Further, a second detection electrode 42by is formed on the surface of the second solid electrolyte body 42 dy. The ammonia concentration in the measurement target gas is detected by the electromotive force change between the second reference electrode 42ay and the second detection electrode 42 by.
In the present embodiment, NO is disposed so as to sandwich the heater (the heating resistor 21, the insulating layer 23b, and the insulating layer 23a) in the stacking directionxThe detection unit, the ammonia sensor unit 42 (the first ammonia sensor unit 42x and the second ammonia sensor unit 42y), and therefore NOxThe detection section and the two ammonia sensor sections 42x, 42y are both adjacent to the heater (at substantially the same distance from the heater). As a result, the temperatures of the two ammonia sensor portions 42x and 42y can be controlled more accurately.
The first ammonia sensor unit 42x and the second ammonia sensor unit 42y are integrally covered with a porous protection layer 23 g. The protective layer 23g is for preventing the toxic substance from adhering to the first and second detection electrodes 42bx and 42by, and for adjusting the diffusion rate of the measurement target gas flowing from the outside into the first and second ammonia sensor units 42x and 42 y. Examples of the material for forming the protective layer 23g include alumina (alumina) and spinel (MgAl)2O4) At least one material selected from the group consisting of silica-alumina and mullite. By appropriately setting the thickness, particle diameter, particle size distribution, porosity, blending ratio and the like of the protective layer 23gThe diffusion rate of the gas to be measured is adjusted by the protective layer 23g under the condition.
In other embodiments, the first ammonia sensor 42x and the second ammonia sensor 42y may be exposed without providing the protective layer 23g, or protective layers may be provided separately for the first ammonia sensor 42x and the second ammonia sensor 42 y.
The first detection electrode 42bx and the second detection electrode 42by can be formed of a material containing Au as a main component (for example, 70 mass% or more). The first reference electrode 42ax and the second reference electrode 42ay may be formed of a Pt single body or a material containing Pt as a main component (for example, 70 mass% or more). The first detection electrode 42bx and the second detection electrode 42by are electrodes in which ammonia gas is hard to burn on the electrode surface. After passing through the detection electrode 42bx (42by), the ammonia reacts with oxygen ions at the interface between the detection electrode 42bx (42by) and the reference electrode 42ax (42ay) (electrode reaction), so as to detect the concentration of the ammonia. The content of the specific detection process of the ammonia concentration will be described later.
In the present embodiment, the resistance of the oxygen concentration detection means 6 is measured, and the heater (heat generation resistor 21) is heated based on the resistance. Therefore, the temperature of the multi-gas sensor element portion 100A is maintained at the most stable value (value at which the temperature can be estimated) in the vicinity of the oxygen concentration detection means 6. Therefore, the first ammonia sensor unit 42x and the second ammonia sensor unit 42y are disposed in the vicinity of the oxygen concentration detection means 6, and the temperatures of the two ammonia sensor units 42x and 42y are maintained at stable values.
Next, an example of the structure of the gas sensor control device 300 will be described with reference to fig. 2. The gas sensor control device 300 includes an (analog) control circuit 59 and a microcomputer (sensor control unit, SCU)60 on a circuit board. The microcomputer 60 controls the entire gas sensor control device 300, and includes a CPU (central processing unit) 61, a RAM 62, a ROM 63, a signal input/output unit 64, an a/D converter 65, and blocks (not shown). In the microcomputer 60, a program stored in advance in the ROM 63 or the like is executed by the CPU 61.
The control circuit 59 includes a reference voltage comparison circuit 51, an Ip1 driver circuit 52, a Vs detection circuit 53, an Icp supply circuit 54, an Ip2 detection circuit 55, a Vp2 application circuit 56, a heater drive circuit 57, a first electromotive force detection circuit 58a, and a second electromotive force detection circuit 58 b.
The first electromotive force detection circuit 58a and the second electromotive force detection circuit 58b detect the ammonia concentration output (electromotive force) between the electrodes of the first ammonia sensor unit 42x and the second ammonia sensor unit 42y, and output the detected ammonia concentration output (electromotive force) to the microcomputer 60.
NOxThe outer first pumping electrode 2c of the sensor portion 30A is connected to the Ip1 driver circuit 52, and the reference electrode 6c is connected in parallel to the Vs detection circuit 53 and the Icp supply circuit 54. In addition, the second pumping counter electrode 4c is connected in parallel with the Ip2 detection circuit 55 and the Vp2 application circuit 56. The heater drive circuit 57 is connected to the heater (specifically, the heating resistor 21).
The pair of electrodes 42ax and 42bx of the first ammonia sensor unit 42x are connected to the first electromotive force detection circuit 58a, respectively. Similarly, the pair of electrodes 42ay and 42by of the second ammonia sensor unit 42y are connected to the second electromotive force detection circuit 58b, respectively.
Each of the circuits 51 to 57 has the following functions. The Ip1 driver circuit 52 supplies a first pumping current Ip1 between the inner first pumping electrode 2b and the outer first pumping electrode 2c, and detects the first pumping current Ip1 at that time. The Vs detection circuit 53 detects a voltage Vs between the detection electrode 6b and the reference electrode 6c, and outputs the detection result to the reference voltage comparison circuit 51.
The reference voltage comparison circuit 51 compares a reference voltage (e.g., 425mV) with the output (voltage Vs) of the Vs detection circuit 53, and outputs the comparison result to the Ip1 driver circuit 52. The Ip1 driver circuit 52 controls the direction and magnitude of the current flow of the Ip1 such that the voltage Vs becomes equal to the reference voltage, thereby adjusting the oxygen concentration in the first measurement chamber S1 to NOxA predetermined value of the degree of non-decomposition.
The Icp supply circuit 54 causes a weak current Icp to flow between the probe electrode 6b and the reference electrode 6c, and oxygen is fed from the first measurement chamber S1 into the reference oxygen chamber 15 to expose the reference electrode 6c to a predetermined oxygen concentration serving as a reference.
The Vp2 applying circuit 56 applies NO in the gas to be measured between the inner second pumping electrode 4b and the second pumping counter electrode 4cxDecomposition of gas to oxygen and N2Constant voltage Vp2 (e.g. 450mV) of gas level to convert NOxDecomposing into nitrogen and oxygen.
The Ip1 driver circuit 52 outputs the detected value of the first pumping current Ip1 to the a/D converter 65. Further, the Ip2 detection circuit 55 outputs the detected value of the second pumping current Ip2 to the a/D converter 65. The a/D converter 65 digitally converts these values and outputs the converted values to the CPU61 via the signal input/output unit 64.
Next, an example of control performed by the control circuit 59 provided in the gas sensor control device 300 will be described. First, when the engine is started and electric power is supplied from the external power supply, the heater is operated via the heater drive circuit 57, and the first pumping means 2, the oxygen concentration detection means 6, and the second pumping means 4 are heated to the activation temperature. The Icp supply circuit 54 supplies a weak current Icp between the probe electrode 6b and the reference electrode 6c, and feeds oxygen from the first measurement chamber S1 into the reference oxygen chamber 15. In addition, when NO is fed by the heaterxWhen the sensor portion 30A is heated to an appropriate temperature, NO followsxThe first ammonia sensor unit 42x and the second ammonia sensor unit 42y in the sensor unit 30A are also heated to desired temperatures.
When the cells are heated to the activation temperature, the first pumping cell 2 pumps out oxygen in the exhaust gas flowing into the first measurement chamber S1 from the inner first pumping electrode 2b toward the outer first pumping electrode 2 c. At this time, the oxygen concentration in the first measurement chamber S1 becomes the oxygen concentration detection means6 (inter-terminal voltage), the Ip1 driver circuit 52 controls the first pumping current Ip1 flowing through the first pumping cell 2 so that the inter-electrode voltage Vs becomes the reference voltage (e.g., 425mV), thereby adjusting the oxygen concentration in the first measurement chamber S1 to NOxDegree of non-decomposition. Further, the oxygen concentration in the exhaust gas flowing into the first measurement chamber S1 is determined based on the first pumping current Ip1 detected by the Ip1 driver circuit 52, and the oxygen concentration is used for detection of the ammonia concentration described later.
The gas to be measured whose oxygen concentration has been adjusted further flows toward the second measurement chamber S2. The Vp2 applying circuit 56 applies NO in the gas to be measuredxDecomposition of gas to oxygen and N2A constant voltage Vp2 (a voltage higher than the value of the control voltage of the oxygen concentration detection cell 6, for example, 450mV) of the degree of gas is used as the inter-electrode voltage (inter-terminal voltage) of the second pumping cell 4 to convert NO into NOxDecomposing into nitrogen and oxygen. Then, a second pumping current Ip2 is supplied to the second pumping means 4, so that NO is pumped from the second measuring chamber S2xOxygen generated by the decomposition of (a). At this time, by detecting the second pumping current Ip2, NO in the gas to be measured can be detectedxAnd (4) concentration.
The ammonia concentration output (electromotive force) between the pair of electrodes 42ax and 42bx is detected by the first electromotive force detection circuit 58a, whereby the ammonia concentration in the gas to be measured can be detected as described later. Further, the ammonia concentration in the gas to be measured can be detected by detecting the ammonia concentration output (electromotive force) between the pair of electrodes 42ay, 42by the second electromotive force detection circuit 58 b.
Next, the calculation process for the concentration of each gas (particularly, the concentration of ammonia) by the microcomputer (SCU)60 of the gas sensor control device 300 will be described.
Further, the ammonia sensor portion 42 detects not only ammonia but also NO2Therefore, when the gas to be measured contains NO other than ammonia2In the case of gas, the detection accuracy of ammonia may be lowered. Thus, by using sensitivity to ammonia versus NOxTwo ammonia sensor units 42 having different sensitivity ratios of (1) as ammoniaA sensor section 42 for calculating ammonia gas and NO2Each concentration of (a).
For example, the sensor output of the ammonia sensor portion 42 is for x: ammonia concentration, y: NO2Gas concentration, D: o is2The concentration is represented by F (x, y, D). When two ammonia sensor units having different sensitivity ratios are used, F is obtained1(mx、ny、D)、F2(sx, ty, D) (m, n, s, t are coefficients). Since F1, F2, and D are obtained from the sensor output, two unknowns (x, y) may be solved from two equations.
In the present specification, the detection of ammonia and the calculation of the ammonia concentration by the ammonia sensor unit 42 will be described in detail. Further, the NO control by the ammonia sensor unit 42 is omitted2And detection of NO2The details of the calculation process of the concentration of (2).
An electromotive force is generated between the first reference electrode 42ax and the first detection electrode 42bx of the first ammonia sensor unit (an example of an ammonia detection unit) 42x in accordance with the concentration of ammonia contained in the exhaust gas (measurement target gas). The first electromotive force detecting circuit 58a detects an electromotive force between the first reference electrode 42ax and the first detection electrode 42bx as a first ammonia electromotive force EMF 1.
Similarly, an electromotive force is generated between the second reference electrode 42ay and the second detection electrode 42by of the second ammonia sensor unit (an example of the ammonia detection unit) 42y in accordance with the concentration of ammonia in the measurement target gas. Also, the second electromotive force detecting circuit 58b detects an electromotive force between the second reference electrode 42ay and the second detecting electrode 42by as a second ammonia electromotive force EMF 2.
The ROM 63 of the microcomputer 60 stores various data (relational expressions and the like) shown below, for example. The CPU61 reads various data from the ROM 63, and performs various arithmetic processes in accordance with the value of the first pumping current Ip1, the value of the second pumping current Ip2, the first ammonia electromotive force EMF1, and the second ammonia electromotive force EMF 2.
The ROM 63 stores "first ammonia electromotive force&O2Concentration output-ammonia concentration output relation, second ammonia electromotive force&O2Concentration output-Ammonia concentration output relation `, ` second `A pumping current Ip1-O2Concentration output relation expression, second pumping current Ip2-NOxConcentration output relation "and the like.
First Ammonia electromotive force&O2The concentration output-ammonia concentration output relation represents the first ammonia electromotive force EMF1 output from the first ammonia sensor unit 42x, and is based on the "first pumping current Ip 1-O" described later2Concentration output relation "derived O2An expression of the relationship between the concentration output and the ammonia concentration output (first ammonia concentration) related to the ammonia concentration of the gas to be measured that does not reduce (does not take into account) the influence of the pressure of the gas to be measured.
"second Ammonia electromotive force&O2The concentration output-ammonia concentration output relation represents the second ammonia electromotive force EMF2 output from the second ammonia sensor unit 42y, and is based on the "first pumping current Ip 1-O" described later2Concentration output relation "derived O2An expression of the relationship between the concentration output and the ammonia concentration output (first ammonia concentration) related to the ammonia concentration of the gas to be measured that does not reduce (does not take into account) the influence of the pressure of the gas to be measured.
"first Pumping Current Ip1-O2The concentration output relation "represents the first pumping current Ip1 and the O of the gas to be measured2The formula of the relationship between concentrations.
"second Pumping Current Ip2-NOxThe concentration output relation "represents the second pumping current Ip2 and the NO of the measured gasxThe relationship between concentrations.
The various data may be set to a predetermined relational expression as described above, and may be set to a table, for example, as long as the data calculates the concentration of each gas from the output of the sensor. Alternatively, a value obtained by using a gas model having a known gas concentration (relational expression, table, or the like) may be used in advance.
Next, an ammonia concentration detection process for detecting the ammonia concentration (an example of the second ammonia concentration) performed by the CPU (an example of the control unit) 61 of the microcomputer 60 will be described. Here, a process of detecting the ammonia concentration in the gas to be measured using the first ammonia electromotive force EMF1 detected by the first ammonia sensor unit 42x, the first pumping current Ip1, and the like will be described.
Fig. 4 is a flowchart showing the content of the ammonia concentration detection process. First, in the multi-gas sensor device 400 (see fig. 2), the first ammonia electromotive force EMF1 (an example of a first detection result) output from the first ammonia sensor unit 42x is detected by the first electromotive force detection circuit 58a, and information on the first ammonia electromotive force EMF1 is received by the microcomputer 60 of the gas sensor control device 300 (first reception processing, step 1 in fig. 4).
On the other hand, the first pumping current Ip1 (an example of a second detection result) output from the first pumping unit 2 is detected via the Ip1 driver circuit 52, and information on the first pumping current Ip1 is received by the microcomputer 60 (second receiving processing, step 1 of fig. 4). As the first pumping current Ip1, a current detected at the same timing (at the same time) as the first ammonia electromotive force is detected is used.
When information on the first pumping current Ip1 is input to the CPU61 of the microcomputer 60, the CPU61 calls "the first pumping current Ip 1-O" from the ROM 632Concentration output relation ", the first pumping current Ip is converted into the first oxygen concentration Y (an example of the second detection result) using the relation (output conversion processing, step 2 of fig. 4).
Subsequently, the CPU61 calls "first ammonia electromotive force" from the ROM 63&O2A concentration output-ammonia concentration output relational expression "is used to calculate a first ammonia concentration, which is a tentative ammonia concentration without reducing (not considering) the influence of the pressure of the measured gas, using the relational expression, the first ammonia electromotive force EMF1, and the first oxygen concentration Y (first concentration calculation processing, step 3 in fig. 4).
Then, the CPU61 acquires pressure information of the exhaust gas (measured gas) from the ECU 220 as the external device (pressure information acquisition processing, step 4 of fig. 4). Here, the pressure sensor 500 and the like for detecting the pressure of the gas to be measured will be described with reference to fig. 5. Fig. 5 is an explanatory diagram illustrating an installation location of the pressure sensor 500 for detecting the pressure of the gas to be measured. In fig. 5, an oxidation catalyst 503, a DPF (Diesel Particulate Filter) 504, and an SCR (Selective Catalytic Reduction) catalyst 505 are provided in this order from the upstream side in an exhaust pipe 502 of a Diesel engine (internal combustion engine) 501. The pressure sensor 500 is provided in a position of the exhaust pipe 502 between the DPF504 and the SCR catalyst 505, and detects the pressure of the exhaust gas (gas to be measured) flowing through the exhaust pipe 502. Further, multi-gas sensor 200A of multi-gas sensor device 400 is provided at a position on the downstream side of exhaust pipe 502 adjacent to SCR catalyst 505.
The pressure (measured value) detected by pressure sensor 500 is stored in a memory device (ROM such as EPROM and EEPROM) provided in ECU 220. The CPU61 of the gas sensor control device 300 (microcomputer 60) executes processing for acquiring information on the pressure detected by the pressure sensor 500 from the ECU 220. The pressure information of the gas to be measured acquired by the microcomputer 60 is an absolute pressure (101.325+ P) (P is a measurement value of the pressure sensor 500). As the pressure information of the pressure sensor 500, pressure information detected at the same timing (at the same time) as the timing of detecting the first ammonia electromotive force EMF1 or pressure information detected after a predetermined time from the timing of detecting the first ammonia electromotive force EMF1 is used.
Next, as shown in fig. 4, the CPU61 executes a process of calculating a correction coefficient Z' for correcting the first ammonia concentration in order to reduce the influence of the pressure of the gas to be measured (correction coefficient calculation process, step 5 in fig. 4). Here, first, the first oxygen concentration Y is pressure-corrected to obtain a second oxygen concentration Y'. Specifically, for example, the second oxygen concentration Y' is calculated based on the relational expression (1) shown below and the first oxygen concentration Y.
[ relational expression (1) ]
Y’＝Y×(101.325+P+k)/(101.325+P)×101.325/(101.325+k)
(in the above formula, P represents a measured value (measured pressure) of a gas to be measured, and k represents a pressure correction coefficient.)
Next, the temporary correction coefficient Z is calculated based on the second oxygen concentration Y' and the relational expression (2) shown below.
[ relational expression (2) ]
Z＝a×Y’＾2+b×Y’+c
(in the above formula, a, b and c are each a coefficient.)
Then, when the provisional correction coefficient Z is corrected, a correction coefficient Z' for correcting the first ammonia concentration is obtained. Specifically, the correction coefficient Z' for correcting the first ammonia concentration is obtained based on, for example, the relational expression (3) shown below and the provisional correction coefficient Z.
[ relational expression (3) ]
Z’＝Z×((101.325+P+k’)/(101.325+P)×101.325/(101.325+k’))×(a×ln(Y’)+b)
(in the above formula, P represents a measured value (measured pressure) of a gas to be measured, k' represents a pressure correction coefficient, and a and b represent coefficients, respectively.)
Next, as shown in step 6 of fig. 4, the following processing (pressure correction processing) is executed in the CPU 61: the first ammonia concentration is corrected by a correction coefficient Z' based on the pressure information of the gas to be measured, and a second ammonia concentration of the gas to be measured is acquired. Here, the second ammonia concentration in which the influence of the pressure of the gas to be measured is reduced is obtained by multiplying (multiplying) the first ammonia concentration by the correction coefficient Z'. In this way, the second ammonia concentration with a reduced influence of the pressure of the gas to be measured can be obtained easily.
In the case of the present embodiment, the first pumping means 2 pumps out or draws in oxygen from the gas to be measured (exhaust gas) introduced from the outside (inside the exhaust pipe) to the first measurement chamber S1 through the protective layer 9 and the first diffusion resistor 8a, which are formed of porous material, as shown in fig. 2. Therefore, the first pumping current Ip1 output from the first pumping cell 2 is affected by the pressure of the measured gas. Therefore, in the present embodiment, as shown in step 7 of fig. 4, in order to reduce the influence of such pressure on oxygen, for example, the following processing (oxygen pressure correction processing) is performed: the second ammonia concentration is corrected based on the pressure information of the gas to be measured. As a result of this processing, a third ammonia concentration of the gas under measurement is acquired, which reduces the influence of the pressure of the gas under measurement on oxygen.
As described above, the ammonia concentration (the second ammonia concentration, the third ammonia concentration) in which the influence of the pressure of the gas to be measured on the ammonia is reduced is obtained using the first ammonia electromotive force EMF1 (an example of the first detection result) detected by the first ammonia sensor unit 42x, the first pumping current Ip1 (an example of the second detection result), the pressure information of the gas to be measured, and the like. Further, the third ammonia concentration is reduced not only by the influence of the pressure of the measured gas on ammonia but also by the influence of the pressure of the measured gas on oxygen.
Similarly, the second ammonia sensor unit 42y obtains an ammonia concentration (second ammonia concentration) in which the influence of the pressure of the gas to be measured on the ammonia is reduced, and an ammonia concentration (third ammonia concentration) in which the influence of the pressure of the gas to be measured on both the ammonia and the oxygen is reduced, using the second ammonia electromotive force EMF2 (an example of the first detection result), the first pumping current Ip1 (an example of the second detection result), the pressure information of the gas to be measured, and the like.
Further, the third ammonia concentrations obtained from the first ammonia sensor unit 42x and the second ammonia sensor unit 42y, and the like are used to determine NO2Gas concentration, etc.
As described above, according to the multi-gas sensor device 400 (gas sensor control device 300) of the present embodiment, the influence of the pressure of the gas to be measured on the ammonia can be reduced, and the accuracy of measuring the ammonia concentration can be improved. In particular, in the case of the present embodiment, the influence of the pressure of the measurement gas on oxygen can be further reduced, and the measurement accuracy of the ammonia concentration can be further improved.
[ Ammonia detection test 1]
The following ammonia detection test was performed using the multi-gas sensor device 400 of embodiment 1. A predetermined exhaust pipe is prepared, and the multi-gas sensor device 400 is provided in the middle of the exhaust pipe. Then, the pressure condition of the gas to be measured is changed while the gas to be measured (gas) containing ammonia at a constant concentration is supplied to the exhaust pipe, and the ammonia concentration under each pressure condition is detected by the multi-gas sensor device 400. Here, for the purpose of the test, the multi-gas sensor device 400 is set to detect the ammonia concentration (first ammonia concentration) to which the pressure correction process and the oxygen correction process are not performed and the ammonia concentration (second ammonia concentration) to which the pressure correction process and the oxygen correction process are performed.
Fig. 6 is a graph showing a relationship between the pressure of the gas to be measured and the ammonia concentration affected by the pressure of the gas to be measured. In FIG. 6, the horizontal axis represents pressure (kPa) and the vertical axis represents ammonia concentration (ppm). As shown in fig. 6, regarding the ammonia concentration (first ammonia concentration) that has not been subjected to the pressure correction process and the oxygen correction process, it can be confirmed that the ammonia concentration is detected as a value smaller than the original value (set value) as the pressure of the gas to be measured is larger.
[ oxygen concentration detection test ]
Next, the oxygen concentration detection test described below was performed using the multi-gas sensor device 400 of embodiment 1. An exhaust pipe similar to the ammonia detection test 1 was prepared, and the multi-gas sensor device 400 was installed in the middle of the exhaust pipe. Then, the pressure condition of the gas to be measured (air) containing oxygen at a constant concentration is changed while the gas to be measured (air) is supplied to the exhaust pipe, and the oxygen concentration under each pressure condition is detected by the multi-gas sensor device 400. Here, for the purpose of experiment, it is set to detect the oxygen concentration (first oxygen concentration Y) obtained by the output conversion processing of the first pumping current Ip1 and the second oxygen concentration Y' obtained by pressure-correcting the first oxygen concentration Y.
Fig. 7 is a graph showing a relationship between the pressure of the gas to be measured and the oxygen concentration affected by the pressure of the gas to be measured. In FIG. 7, the horizontal axis represents pressure (kPa) and the vertical axis represents oxygen concentration (ppm). As shown in fig. 7, it can be confirmed that, as the pressure of the gas to be measured is higher, the oxygen concentration Y, which is not pressure-corrected, is detected as a value higher than the original value (set value).
[ Ammonia detection test 2]
The following ammonia detection test was performed using the multi-gas sensor device 400 of embodiment 1. A predetermined exhaust pipe is prepared, and the multi-gas sensor device 400 is provided in the middle of the exhaust pipe. Then, while the gas to be measured (air) containing ammonia at a constant concentration is supplied to the exhaust pipe, the pressure condition of the gas to be measured is changed, and the ammonia concentration under each pressure condition is detected by the multi-gas sensor device 400. Here, for the purpose of the test, the ammonia concentration (second ammonia concentration) at which only the pressure correction process described above has been performed and the oxygen correction process has not been performed, and the ammonia concentration (third ammonia concentration) at which the pressure correction process and the oxygen correction process have been performed are set to be detected by the multi-gas sensor device 400. The pressure conditions of the gas to be measured are used as pressure information of the gas to be measured.
Fig. 8 is a graph showing a relationship between the pressure of the gas under measurement and the ammonia concentration in which the influence of the pressure of the gas under measurement on ammonia is reduced. In fig. 8, the horizontal axis represents pressure (kPa) and the vertical axis represents ammonia concentration (ppm). Due to the influence of the pressure of the gas to be measured on oxygen, an error of about several ppm is observed between the second ammonia concentration, which has been subjected to only the pressure correction process but not the oxygen correction process, and the original value (set value).
< embodiment 2>
Next, embodiment 2 of the present invention will be described with reference to fig. 9 and 10. In the present embodiment, an internal combustion engine control system 600 that is provided in an internal combustion engine (for example, a diesel engine) of an automobile and controls an operation state of the internal combustion engine will be described. Fig. 9 is an explanatory diagram showing a schematic configuration of an internal combustion engine control system 600 according to embodiment 2. The engine control system 600 includes the multi-gas sensor device 400 as a device for detecting NO in exhaust gas (gas to be measured) from the enginexAnd a sensor for detecting ammonia. The internal combustion engine control system 600 includes the ECU 221 as an internal combustion engine control device and the pressure sensor 500 that detects the pressure of the exhaust gas, in addition to the multi-gas sensor device 400.
The basic structure of the multi-gas sensor device 400 is the same as that of embodiment 1 described above. However, in the present embodiment, the process of detecting the ammonia concentration in the exhaust gas is not performed in the gas sensor control device 300 provided in the multi-gas sensor device 400, but is performed in the ECU (internal combustion engine control device) 221 provided in the internal combustion engine control system 600. The ECU 221 includes a CPU (an example of a control unit) 222, a ROM 223, a RAM 224, a signal input/output unit 225, an a/D converter 226, a timer, and the like. In the case of the present embodiment, various data, programs, and the like necessary for detecting the ammonia concentration and the like are stored in the ROM 223 of the ECU 221, and various processes are executed by the CPU 222.
Further, the ECU 221 is electrically connected to the gas sensor control device 300 of the multi-gas sensor device 400. The ECU 221 appropriately acquires (receives) various information required for the ammonia concentration detection process from the microcomputer (SCU)60, such as the first ammonia electromotive force EMF1 and the second ammonia electromotive force EMF2 detected by the ammonia sensor unit 42 (the first ammonia sensor unit 42x and the second ammonia sensor unit 42y) of the multi-gas sensor device 400, and the first pumping current Ip1 detected by the first pumping means 2.
Further, the pressure sensor 500 is provided in the exhaust pipe 502 at a position between the DPF504 and the SCR catalyst 505 (see fig. 5) as in embodiment 1. The detection result of the pressure sensor 500 is stored in a ROM (EPROM, EEPROM, etc.) 223 of the ECU 221. The CPU 222 of the ECU 221 retrieves pressure information of the gas to be measured from the ROM 223 as needed. In this manner, the ECU 221 acquires pressure information (detection result) of the gas to be measured from the pressure sensor 500 as the external device.
Here, a process of detecting the ammonia concentration in the gas to be measured using the first ammonia electromotive force EMF1, the first pumping current Ip1, and the like detected by the first ammonia sensor unit 42x of the multi-gas sensor device 400 will be described.
Fig. 10 is a flowchart showing the content of the ammonia concentration detection process in the ECU 221. As shown in steps 11 to 13 of fig. 10, the CPU 222 of the ECU 221 obtains the first ammonia concentration by executing the same processes as those in embodiment 1 described above, in addition to the processes.
Then, at step 14 in fig. 10, the CPU 222 retrieves pressure information (absolute pressure) of the exhaust gas by calling out the pressure information of the exhaust gas (gas under measurement) detected by the pressure sensor 500 stored in the ROM 223.
As shown in steps 15 to 17 of fig. 10, the CPU 222 of the ECU 221 executes the processes similar to those of embodiment 1 described above in addition to the processes, and finally obtains a third ammonia concentration at which both the influence of the pressure of the gas under measurement on ammonia and the influence of the pressure of the gas under measurement on oxygen are reduced.
As described above, the ECU 221 may perform the same ammonia concentration detection process as in embodiment 1.
< embodiment 3>
Next, embodiment 3 of the present invention will be described with reference to fig. 11 and the like. In the present embodiment, the process of detecting the ammonia concentration in the gas to be measured is performed in the microcomputer (SCU) of the multi-gas sensor device, as in embodiment 1. However, in the ammonia concentration detection process of the present embodiment, the pressure correction process is performed to reduce the influence of the pressure of the gas to be measured on the ammonia, but the oxygen pressure correction is not performed in consideration of the influence of the pressure of the gas to be measured on the oxygen.
Fig. 11 is a flowchart showing the content of the ammonia concentration detection process according to embodiment 3. As shown in steps 21 to 24 in fig. 11, the CPU of the microcomputer (SCU) executes the same processes as steps 1 to 4 (see fig. 4) in embodiment 1.
As shown in step 25 of fig. 11, in the present embodiment, the correction coefficient Z' is also calculated in the same manner as in step 5 of embodiment 1. However, in the case of the present embodiment, since the influence of the pressure of the gas to be measured on the oxygen is not considered, the pressure correction of the first oxygen concentration Y obtained by the above-described relational expression (1) for calculating the provisional correction coefficient Z is not performed. Therefore, "(second oxygen concentration) Y'" in the above relational expression (2) for calculating the temporary correction coefficient Z is replaced with "(first oxygen concentration) Y". In the above relational expression (3) for calculating the correction coefficient Z ', the "(second oxygen concentration) Y'" is also replaced with "(first oxygen concentration) Y".
Then, as shown in step 26 of fig. 11, the first ammonia concentration is corrected by using the correction coefficient Z' in the same manner as in step 6 of embodiment 1, and a second ammonia concentration in which the influence of the pressure of the gas to be measured on the ammonia is reduced is obtained.
As described above, when it is not necessary to consider the influence of the pressure of the gas to be measured on oxygen, only the pressure correction process for the purpose of reducing the influence of the pressure of the gas to be measured on ammonia may be performed (step 26).
In the multi-gas sensor device of the present embodiment, the first pumping means pumps out or pumps in oxygen in the gas to be measured (exhaust gas) introduced from the outside (into the exhaust pipe) to the first measurement chamber via the porous protection layer and the first diffusion resistor, as in embodiment 1. In contrast, for example, in another embodiment, when the first measurement chamber is directly communicated with the outside without passing through the first diffusion resistor or the like, there is no need to consider the influence of the pressure of the measurement target gas on oxygen. Therefore, the oxygen pressure correction process for reducing the influence of the pressure of the gas to be measured on oxygen may be performed as necessary.
< embodiment 4>
Next, embodiment 4 of the present invention will be described with reference to fig. 12 and the like. In the present embodiment, the detection process for the ammonia concentration in the exhaust gas is performed in an ECU (internal combustion engine control device) as in embodiment 2. In the ammonia concentration detection process of the present embodiment, only the pressure correction process for the purpose of reducing the influence of the pressure of the gas to be measured on the ammonia is performed, as in embodiment 3.
Fig. 12 is a flowchart showing the content of the ammonia concentration detection process according to embodiment 4. As shown in steps 31 to 33 in fig. 12, the CPU of the ECU executes the same processes as those in embodiment 3 described above in addition to the processes to obtain the first ammonia concentration.
Then, in step 34 of fig. 12, the CPU of the ECU calls out the pressure information of the exhaust gas (gas to be measured) detected by the pressure sensor, which is stored in the ROM (EPROM, EEPROM, etc.) of the ECU, to acquire the pressure information (absolute pressure) of the exhaust gas (the same as in step 14 of embodiment 2 of fig. 10).
As shown in steps 35 and 36 of fig. 12, the CPU of the ECU executes the processes similar to those of embodiment 3 described above in addition to the processes, and finally obtains a second ammonia concentration at which the influence of the pressure of the measurement gas on ammonia is reduced.
As described above, the same ammonia concentration detection process as in embodiment 4 may be performed in an ECU (internal combustion engine control device).
< embodiment 5>
Next, embodiment 5 of the present invention will be described with reference to fig. 13 and the like. In the present embodiment, the process of detecting the ammonia concentration in the gas to be measured is performed in the microcomputer (SCU) of the multi-gas sensor device, as in embodiment 1. However, in the ammonia concentration detection process according to the present embodiment, a simultaneous correction process is performed in which the decrease in the influence of the pressure of the gas to be measured on ammonia and the decrease in the influence of the pressure of the gas to be measured on oxygen are performed together.
Fig. 13 is a flowchart showing the content of the ammonia concentration detection process according to embodiment 5. As shown in steps 41 to 44 in fig. 13, the CPU of the microcomputer (SCU) executes the same processes as steps 1 to 4 (see fig. 4) in embodiment 1.
In the present embodiment, the simultaneous correction processing is performed at step 45 in fig. 13, instead of steps 5 to 7 (the pressure correction processing, the oxygen pressure correction processing, and the like in fig. 4) in embodiment 1. In the simultaneous correction processing, the simultaneous correction coefficient α for reducing the influence of the pressure of the gas to be measured on the ammonia and the influence of the pressure of the gas to be measured on the oxygen are determined based on the pressure information (absolute pressure) of the exhaust gas (gas to be measured) acquired in step 44.
The simultaneous correction coefficient α is obtained, for example, using relational expressions determined based on the results of the ammonia detection test 1, the ammonia detection test 2, the oxygen detection test, and the like. Then, the first ammonia concentration calculated in step 43 is corrected using the simultaneous correction coefficient α, and thereby a fourth ammonia concentration is obtained in which both the influence of the pressure of the gas under measurement on ammonia and the influence of the pressure of the gas under measurement on oxygen are reduced.
As described above, the reduction of the influence of the pressure of the gas to be measured on ammonia and the reduction of the influence of the pressure of the gas to be measured on oxygen can be performed in one step. In this manner, the load of processing in the CPU can be suppressed by concentrating the correction processing for the first ammonia concentration in one step.
< embodiment 6>
Next, embodiment 6 of the present invention will be described with reference to fig. 14 and the like. In the present embodiment, the detection process for the ammonia concentration in the exhaust gas is performed in an ECU (internal combustion engine control device) as in embodiment 2. In the ammonia concentration detection process of the present embodiment, a simultaneous correction process is performed in which the decrease in the influence of the pressure of the gas to be measured on ammonia and the decrease in the influence of the pressure of the gas to be measured on oxygen are performed in a concentrated manner, as in embodiment 5.
Fig. 14 is a flowchart showing the content of the ammonia concentration detection process according to embodiment 6. As shown in step 51 to step 54 in fig. 14, the CPU of the ECU executes the same processes as those in step 11 to step 14 (see fig. 10) in embodiment 2.
In the present embodiment, in step 55 in fig. 14, the CPU of the ECU performs the simultaneous correction process similar to that of embodiment 5 to obtain a fourth ammonia concentration at which both the influence of the pressure of the gas under measurement on ammonia and the influence of the pressure of the gas under measurement on oxygen are reduced.
As described above, the same ammonia concentration detection process as in embodiment 5 may be performed in an ECU (internal combustion engine control device).
< other embodiment >
The present invention is not limited to the embodiments described above and illustrated in the drawings, and for example, the following embodiments are also included in the technical scope of the present invention.
(1) In the above embodiments, a diesel engine is exemplified as the internal combustion engine, but the gas sensor control device, the gas sensor device, and the internal combustion engine control device of the present invention can be applied to, for example, a gasoline engine.
(2) In the above embodiments, the multi-gas sensor device including two mixed-potential ammonia sensor units has been exemplified, but the present invention is not limited thereto, and for example, the present invention can be applied to a gas sensor device including one mixed-potential ammonia sensor unit.
(3) In each of the above embodiments, the pressure sensor is a pressure sensor provided in the exhaust pipe at a position between the DPF and the SCR catalyst, but the present invention is not limited to this, and a pressure sensor disposed at another position may be used.
(4) In the above embodiments, a multi-gas sensor device including an oxygen detection unit and an ammonia detection unit (i.e., a device in which the oxygen detection unit and the ammonia detection unit are integrated) is used, but the present invention is not limited thereto, and for example, the oxygen detection unit and the ammonia detection unit may be configured as separate and independent devices.
(5) In each of the above embodiments, the correction coefficient Z' calculated by the relational expressions (1) to (3) and the like is used for the pressure information of the gas to be measured in the process (pressure correction process) for reducing the influence of the pressure of the gas to be measured on the ammonia, but the present invention is not limited to this, and in other embodiments, for example, the relationship between the first ammonia concentration and the pressure of the gas to be measured may be prepared in advance in the form of a table, and the pressure correction process may be performed using the table. In addition, the oxygen pressure correction processing and the simultaneous correction processing may be performed by using a table prepared in advance in the same manner.
Claims (9)
1. A gas sensor control device is provided with a control unit that executes:
a first reception process of receiving a first detection result corresponding to a concentration of ammonia output from a mixed-potential-type ammonia detection unit for detecting ammonia contained in a measurement target gas;
a second reception process of receiving a second detection result corresponding to a concentration of oxygen output from an oxygen detection unit for detecting oxygen contained in the measurement target gas;
a first concentration calculation process of calculating a first ammonia concentration contained in the measurement target gas based on the first detection result and the second detection result; and
and a pressure correction process of correcting the first ammonia concentration based on pressure information indicating the pressure of the gas to be measured acquired from an external device to acquire a second ammonia concentration of the gas to be measured, in order to reduce the influence of the pressure of the gas to be measured on the ammonia.
2. The gas sensor control device according to claim 1,
the pressure correction processing is processing for acquiring the second ammonia concentration by correcting the first ammonia concentration using a correction coefficient based on the pressure information.
3. The gas sensor control device according to claim 1 or 2,
in the case where the oxygen is affected by the pressure of the measurement gas, the control unit executes an oxygen pressure correction process for correcting the second ammonia concentration based on the pressure information of the measurement gas to acquire a third ammonia concentration of the measurement gas in order to reduce the effect of the pressure.
4. The gas sensor control device according to any one of claims 1 to 3,
in the case where the oxygen is affected by the pressure of the measurement gas, the control unit executes a simultaneous correction process, in which a first ammonia concentration is corrected based on the pressure information of the measurement gas, and a fourth ammonia concentration of the measurement gas is acquired, instead of the pressure correction process, in order to reduce the effect of the pressure of the measurement gas on the ammonia and reduce the effect of the pressure of the measurement gas on the oxygen.
5. A gas sensor device is provided with:
a mixed potential type ammonia detection unit for detecting ammonia contained in a gas to be measured;
an oxygen detection unit for detecting oxygen contained in the measurement target gas; and
the gas sensor control device according to any one of claims 1 to 4.
6. An internal combustion engine control device for controlling an operation state of an internal combustion engine, the internal combustion engine control device comprising a control unit that executes:
a first reception process of receiving a first detection result corresponding to a concentration of ammonia detected by a mixed-potential-type ammonia detection unit for detecting ammonia contained in a gas to be measured from the internal combustion engine;
a second reception process of receiving a second detection result corresponding to a concentration of oxygen output from an oxygen detection unit for detecting oxygen contained in the measurement target gas;
a first concentration calculation process of calculating a first ammonia concentration contained in the measurement target gas based on the first detection result and the second detection result; and
and a pressure correction process of correcting the first ammonia concentration based on pressure information indicating the pressure of the gas to be measured acquired from an external device to acquire a second ammonia concentration of the gas to be measured, in order to reduce the influence of the pressure of the gas to be measured on the ammonia.
7. The internal combustion engine control apparatus according to claim 6,
the pressure correction processing is processing for acquiring the second ammonia concentration by correcting the first ammonia concentration using a correction coefficient based on the pressure information.
8. The control device of the internal combustion engine according to claim 6 or 7,
in the case where the oxygen is affected by the pressure of the measurement gas, the control unit executes an oxygen pressure correction process for correcting the second ammonia concentration based on the pressure information of the measurement gas to acquire a third ammonia concentration of the measurement gas in order to reduce the effect of the pressure.
9. The internal combustion engine control apparatus according to any one of claims 6 to 8,
in the case where the oxygen is affected by the pressure of the measurement gas, the control unit executes a simultaneous correction process, in which a first ammonia concentration is corrected based on the pressure information of the measurement gas, and a fourth ammonia concentration of the measurement gas is acquired, instead of the pressure correction process, in order to reduce the effect of the pressure of the measurement gas on the ammonia and reduce the effect of the pressure of the measurement gas on the oxygen.
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| JP2019166843 | 2019-09-13 | ||
| JP2020125048A JP7252921B2 (en) | 2019-09-13 | 2020-07-22 | Gas sensor control device, gas sensor device and internal combustion engine control device |
| JP2020-125048 | 2020-07-22 |
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| JP7252921B2 (en) | 2023-04-05 |
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