Methods and apparatus for measuring NOx gas concentration, for detecting exhaust gas concentration and for calibrating and controlling gas sensor
First Claim
Patent Images
1. A method for measuring the nitrogen oxide concentration using a nitrogen oxide concentration detector having:
- a first measurement chamber into which is introduced a measurement gas via a first diffusion resistance;
an oxygen concentration detection electrode for measuring the oxygen concentration in the detection gas in said first measurement chamber;
a first oxygen ion pump cell for pumping oxygen contained in the measurement gas from said first measurement chamber to outside and/or from outside to inside of said first measurement chamber based on the potential of said oxygen concentration detection electrode;
a second measurement chamber into which the gas is introduced from said first measurement chamber via a second diffusion resistance; and
a second oxygen ion pump cell having a pair of electrodes across which a voltage is applied to decompose the nitrogen oxide in said second measurement chamber to pump out dissociated oxygen to cause a current corresponding to the nitrogen oxide concentration, referred to as second oxygen pump current, to flow in the second oxygen ion pump cell;
wherein said first oxygen ion pump cell sufficiently pumps out oxygen from the first measurement chamber to an extent not to allow all nitrogen oxide to decompose oxygen in said measurement gas;
wherein the nitrogen oxide concentration obtained based on said second oxygen pump current is corrected responsive to the oxygen concentration in the detection gas.
0 Assignments
0 Petitions
Accused Products
Abstract
A method for detecting the concentration of a specific gas (NOx) in an engine exhaust gas using a gas sensor and a process of correcting the gas sensor. According to the correcting process, the amount of moisture in the exhaust gas is estimated, then a gas concentration detection signal output by the gas sensor on the basis of an estimated amount of moisture is corrected.
Finally, the effect of the amount of moisture in the exhaust gas is removed or reduced from the detected value of gas concentration.
-
Citations
41 Claims
-
1. A method for measuring the nitrogen oxide concentration using a nitrogen oxide concentration detector having:
-
a first measurement chamber into which is introduced a measurement gas via a first diffusion resistance;
an oxygen concentration detection electrode for measuring the oxygen concentration in the detection gas in said first measurement chamber;
a first oxygen ion pump cell for pumping oxygen contained in the measurement gas from said first measurement chamber to outside and/or from outside to inside of said first measurement chamber based on the potential of said oxygen concentration detection electrode;
a second measurement chamber into which the gas is introduced from said first measurement chamber via a second diffusion resistance; and
a second oxygen ion pump cell having a pair of electrodes across which a voltage is applied to decompose the nitrogen oxide in said second measurement chamber to pump out dissociated oxygen to cause a current corresponding to the nitrogen oxide concentration, referred to as second oxygen pump current, to flow in the second oxygen ion pump cell;
wherein said first oxygen ion pump cell sufficiently pumps out oxygen from the first measurement chamber to an extent not to allow all nitrogen oxide to decompose oxygen in said measurement gas;
wherein the nitrogen oxide concentration obtained based on said second oxygen pump current is corrected responsive to the oxygen concentration in the detection gas. - View Dependent Claims (2, 3, 4, 5, 6, 7, 27)
-
-
8. An apparatus for measuring the nitrogen oxide concentration comprising:
-
(a) a nitrogen oxide concentration detector having (a1) a first measurement chamber into which a detection gas is introduced via a first diffusion resistance;
(a2) an oxygen concentration detection electrode measuring the oxygen concentration in the detection gas in said first measurement chamber;
(a3) a first oxygen ion pump cell sufficiently pumping oxygen contained in the detection gas from said first measurement chamber to outside and/or from outside to inside of said first measurement chamber based on the potential of said oxygen concentration detection electrode to an extent not to allow all nitrogen oxide to decompose oxygen in said measurement gas;
(a4) a second measurement chamber into which the gas is introduced from said first measurement chamber via a second diffusion resistance; and
(a5) a second oxygen ion pump cell having a pair of electrodes across which a voltage is applied to decompose the oxygen nitride in said second measurement chamber to pump out dissociated oxygen to cause the current corresponding to the nitrogen oxide concentration referred to as second oxygen pump current, to flow in the second oxygen ion pump cell;
(b) gain selection means for selecting a coefficient, referred to as gain, of variation of said second oxygen pump current in a function responsive to an output of said oxygen concentration detection electrode, provided that said variation in said nitrogen oxide concentration is said function of variation of said second oxygen pump current; and
(c) operation means for calculating the nitrogen oxide concentration based on said second oxygen pump current and the gain selected by said gain selection means.
-
-
9. A method for controlling a nitrogen oxide concentration detector having:
-
a first measurement chamber into which a measurement gas is introduced via a first diffusion resistance;
a first oxygen ion pump cell sufficiently pumping oxygen in the measurement gas from said first measurement chamber to outside and/or from outside to inside of said measurement chamber to an extent not to allow all the nitrogen oxide to decompose in the gas under measurement;
a second measurement chamber into which a measurement gas is introduced from the first measurement chamber via a second diffusion resistance; and
a second oxygen ion pump cell having a pair of electrodes provided on the inside and outside of the second measurement chamber, an electrical voltage being applied across said electrodes to decompose the nitrogen oxide in said second measurement chamber to dissociate oxygen, said second oxygen ion pump cell pumping out dissociated oxygen to cause a flow of current corresponding to the nitrogen oxide concentration, referred to as second oxygen ion pump current;
said method comprising;
correcting a detection output of the nitrogen oxide concentration of said nitrogen oxide concentration detector derived from said second oxygen ion pump current responsive to changes caused in the oxygen partial pressure in the measurement gas. - View Dependent Claims (10, 11)
-
-
12. A method for controlling a nitrogen oxide concentration detector having:
-
a first measurement chamber into which a measurement gas is introduced via a first diffusion resistance;
a first oxygen ion pump cell sufficiently pumping oxygen in the measurement gas from said first measurement chamber to outside and/or from outside to inside of said measurement chamber to an extent not to allow all the nitrogen oxide to decompose oxygen in the gas under measurement;
a second measurement chamber into which a measurement gas is introduced from the first measurement chamber via a second diffusion resistance; and
a second oxygen ion pump cell having a pair of electrodes provided on the inside and outside of the second measurement chamber, an electrical voltage being applied across said electrodes to decompose the nitrogen oxide in said second measurement chamber to dissociate oxygen, said second oxygen ion pump cell pumping out dissociated oxygen to cause a flow of current corresponding to the nitrogen oxide concentration, referred to as second oxygen ion pump current;
said method comprising;
controlling the voltage applied across the second oxygen ion pump cell depending on variations in the oxygen partial pressure in the measurement gas.
-
-
13. The method as defined in claim B4 wherein, if the oxygen partial pressure is low or high, the voltage applied across the second oxygen ion pump cell is lowered or raised, respectively.
-
14. An apparatus for measuring nitrogen oxide concentration comprising:
-
(a) a nitrogen oxide concentration detector having;
(a1) a first measurement chamber into which a measurement gain is introduced via a first diffusion resistance;
(a2) a first oxygen ion pump cell sufficiently pumping oxygen in the measurement gas from said first measurement chamber to outside and/or from outside to inside of said measurement chamber to an extent not to allow all the nitrogen oxide to decompose in the gas under measurement;
(a3) a second measurement chamber into which a measurement gas is introduced from the first measurement chamber via a second diffusion resistance; and
(a4) a second oxygen ion pump cell having a pair of electrodes provided on the inside and outside of the second measurement chamber an electrical voltage being applied across said electrodes to decompose the nitrogen oxide in said second measurement chamber to provide dissociated oxygen, said second oxygen ion pump cell pumping out the dissociated oxygen to cause a flow of current corresponding to the nitrogen oxide concentration, referred to as second oxygen ion pump current;
said apparatus further comprising;
(b) an oxygen partial pressure detection cell detecting the oxygen partial pressure in said first measurement chamber or in said second measurement chamber; and
(c) a nitrogen oxide concentration processor receiving an output of said oxygen partial pressure detection cell and an output of said second oxygen ion pump cell as an input, said nitrogen oxide concentration processor correcting a detection output of the nitrogen oxide concentration of the nitrogen oxide concentration detector derived from the second oxygen ion pump current when the output of said oxygen partial pressure detection cell is changed. - View Dependent Claims (15)
-
-
16. A method for detecting the concentration of exhaust gas using a gas sensor which detects the concentration of a specific component in a gas discharged from an internal combustion engine, the method comprising:
-
calibrating a zero point of a detection output of the gas sensor specifying the zero concentration of said specific component, based on a detection output of the gas sensor in atmosphere, and detecting the concentration of said specific component based on the calibrated detection output. - View Dependent Claims (19, 20, 21)
-
-
17. A method for detecting the concentration of exhaust gas using a gas sensor which detects the concentration of a specific component in a gas discharged from an internal combustion engine, comprising:
-
calibrating the zero point of a detection output of the gas sensor specifying the zero concentration of the specific component, based on a detection output of the gas sensor obtained on cutting fuel supply to said internal combustion engine for setting the concentration of said specific component in the gas introduced into said gas sensor substantially to zero or to substantially the same level as the atmosphere; and
detecting the concentration of said specific component based on the calibrated detection output.
-
-
18. A method for detecting the concentration of exhaust gases using a gas sensor which detects the concentration of a specific component in a gas discharged from an internal combustion engine, the method comprising:
-
calibrating the zero point of a detection output of the gas sensor specifying the zero concentration of the specific component, based on a detection output of the gas sensor obtained on setting a rich air-to-fuel ratio for said internal combustion engine to reduce said specific component and to set the concentration of said specific component in the gas introduced into said gas sensor substantially to zero or to substantially the same level as the atmosphere; and
detecting the concentration of said specific component based on the calibrated detection output.
-
-
22. A method for detecting the concentration of exhaust gases using a gas sensor which detects the concentration of a specific component in a gas discharged from an internal combustion engine, comprising:
-
driving the internal combustion engine under conditions which enable the concentration of said specific component to be estimated or which render said concentration know;
calibrating a detection output of said gas sensor based on a detection output of said gas sensor under a driving condition for said engine; and
detecting the concentration of said specific component based on the calibrated detection output.
-
-
23. An apparatus for detecting the concentration of exhaust gases comprising:
-
a gas sensor detecting the concentration of a specific component in a gas discharged from an internal combustion engine;
driving condition setting means for setting driving conditions for the engine which enable the concentration of said specific component to be estimated or which render said concentration known; and
calibration means for calibrating a detection output of said gas sensor based on a detection output of said gas sensor under said driving conditions as set by said driving condition setting means.
-
-
24. An apparatus for detecting the concentration of exhaust gases comprising:
-
a NOx occlusion catalyst disposed in an exhaust pipe of an internal combustion engine;
a NOx sensor mounted downstream of said NOx occlusion catalyst in the exhaust pipe to detect the NOx concentration in the exhaust gases;
driving condition setting means for transiently providing a rich air-to-fuel ratio for cleaning NOx occluded in said NOx occlusion catalyst; and
means for detecting a state of deterioration of said NOx occlusion catalyst based on changes in a detection output of said NOx sensor before and after setting the rich air-to-fuel ratio.
-
-
25. An apparatus for detecting the concentration of exhaust gases comprising:
-
a selectively NOx reducing catalyst arranged in an exhaust pipe of an internal combustion engine;
a NOx sensor mounted downstream of said catalyst in the exhaust pipe to detect the NOx concentration in the exhaust gases;
means for adding HC to exhaust gases of said internal combustion engine; and
means for detecting the state of deterioration of said catalyst based on changes in a detection output of said NOx sensor before and after HC addition.
-
-
26. In a method for detecting the concentration of a specific gas in an engine exhaust gas, a method for correcting a gas sensor comprising:
-
estimating the amount of moisture in the exhaust gas from driving conditions of the engine;
correcting a gas concentration detection signal output by the gas sensor responsive to an estimated amount of moisture; and
removing or reducing the effect of the amount of moisture in said exhaust gas from the detected value of the gas concentration.
-
-
28. The method for correcting the gas sensor as defined in claim D1 or D2 wherein said gas sensor is a sensor exploiting the oxygen ion pumping action of a solid electrolyte.
-
29. The method for correcting the gas sensor as defined in any one of claims D1 to D3 further comprising:
-
estimating an air to fuel ratio supplied to said engine to be corresponding to the amount of moisture in said exhaust gas;
pre-formulating a map containing correction data for said gas concentration detection signal corresponding to said estimated ratio based on said estimated ratio, said gas concentration detection signal and true gas concentration value;
reading out, from said map, specific correction data corresponding to said estimated ratio as determined by an engine driving condition; and
correcting said gas concentration detection signal by the read-out correction data.
-
-
30. In a method for detecting the NOX concentration using a NOx sensor having at least two solid electrolyte oxygen ion pump cells, in which a voltage is applied across a first oxygen ion pump cell for pumping out oxygen in the measurement gas, a current corresponding to the oxygen concentration in the measurement gas is caused to flow in said first oxygen ion pump cell, a second oxygen ion pump cell decomposes NOx in the gas not pumped by the first oxygen ion pump cell to pump out dissociated oxygen, with a current corresponding to the NOx gas concentration flowing in the second oxygen ion pump cell, a method for correcting a gas sensor;
-
wherein the voltage is applied across the first oxygen ion pump cell for sufficiently pumping out oxygen in the measurement gas to an extent not to allow all NOx to decompose in the measurement gas;
wherein a NOx gas concentration detection signal corresponding to the electric current value obtained from said second oxygen ion pump cell is corrected, responsive to a signal corresponding to an electric current value obtained from the first oxygen ion pump cell; and
wherein the effect of the amount of moisture in said measurement gas is removed or reduced from the NOx gas concentration as found based on said NOx gas concentration detection signal.
-
-
31. The method for correcting the gas sensor as defined in claim D5,
wherein the electric current value in said first oxygen ion pump cell is estimated to correspond to the amount of the moisture in said measurement gas, wherein a map containing correction data of said NOx gas concentration detection signal corresponding to the electric current value of the first oxygen ion pump cell is pre-formulated based on the electric current value of said first oxygen ion pump cell, wherein electric current value obtained from said second oxygen ion pump cell and a true NOx gas concentration, pre-set correction data corresponding to the electric current value of the first oxygen ion pump cell is read out from said map, and wherein the NOx gas concentration detection signal is corrected by the read-out correction data.
-
32. The method as defined in claim D5 wherein the voltage is applied across the first oxygen ion pump cell for sufficiently pumping out oxygen in the measurement gas to an extent substantially not to allow NOX in the measurement gas to decompose.
-
33. Apparatus for detecting the concentration of a specific gas in an engine exhaust gas comprising:
-
a gas sensor;
means for estimating the amount of moisture in the exhaust gas from driving conditions of an engine;
means for correcting a gas concentration detection signal output from the gas sensor responsive to an estimated amount of moisture; and
means for removing or reducing the effect of the amount of moisture in said exhaust gas from the detected value of the gas concentration.
-
-
34. The apparatus as defined in claim D8 wherein said gas sensor is a NOx sensor.
-
35. D10. The apparatus as defined in claim D8 further comprising:
-
means for estimating an air to fuel ratio supplied to said engine to be corresponding to the amount of moisture in said exhaust gas;
memory means for storing a map containing correction data for said gas concentration detection signal corresponding to said estimated ratio based on said estimated ratio, said gas concentration detection signal and true gas concentration value;
reading means for reading out from said map, specific correction data corresponding to said estimated ratio as determined by an engine driving condition; and
correcting means for correcting said gas concentration detection signal by the read-out correction data.
-
-
36. Apparatus for detecting the NOx concentration comprising a NOx sensor having at least two solid electrolyte oxygen ion pump cells, in which a voltage is applied across a first oxygen ion pump cell for pumping out oxygen in the measurement gas, a current corresponding to the oxygen concentration in the measurement gas is caused to flow in said first oxygen ion pump cell, a second oxygen ion pump cell decomposes NOx in the gas not pumped by the first oxygen ion pump cell to pump out dissociated oxygen, with a current corresponding to the NOx gas concentration flowing in the second oxygen ion pump cell;
-
wherein the voltage is applied across the first oxygen ion pump cell for sufficiently pumping out oxygen in the measurement gas to an extent not to allow all NOx to decompose oxygen in the measurement gas;
wherein a NOx gas concentration detection signal corresponding to the electric current value obtained from said second oxygen ion pump cell is corrected, responsive to a signal corresponding to an electric current value obtained from the first oxygen ion pump cell; and
wherein the effect of the amount of moisture in said measurement gas is removed or reduced from the NOx gas concentration as found based on said NOx gas concentration detection signal.
-
-
37. A method for determining NOx concentration in a measurement gas, under a varying condition of the NOx gas concentration in the measurement gas in the course that the measurement gas is allowed to travel through a flow channel facing a ceramic body having an electrically controllable conducting state of oxygen ions, comprising:
-
(1) introducing the measurement gas into the flow channel;
(2) forming in said flow channel a residual gas having a NOx concentration different from that before entrance into said flow channel by extracting an oxygen gas from the measurement gas of step (1) through the ceramic body to outside of the flow channel;
(3) dissociating NOx of said NOx-concentrated residual gas into nitrogen and oxygen by applying a voltage across electrodes formed on the ceramic body;
(4) measuring an electric current flowing through the ceramic body between the electrodes, said electric current being generated by the electrochemical action of the oxygen dissociated from NOx in step (3);
(5) determining a basic NOx concentration of the measurement gas, based on the electric current measurement in step (4), and (6) correcting said basic NOx concentration determined by step (5) responsive to the oxygen concentration in the measurement gas.
-
-
38. A method for determining NOx concentration in a measurement gas, under a varying condition of the NOx gas concentration in the measurement gas in the course that the measurement gas is allowed to travel through a flow channel facing a ceramic body having an electrically controllable conducting state of oxygen ions, comprising:
-
(1) introducing the measurement gas into the flow channel;
(2) forming in said flow channel a residual gas having a NOx concentration different from that before entrance into said flow channel by extracting an oxygen gas from the measurement gas of step (1through the ceramic body to outside of the flow channel;
(3) dissociating NOx of said NOx-concentrated residual gas into nitrogen and oxygen by applying a voltage across electrodes formed on the ceramic body;
(4) measuring an electric current flowing through the ceramic body between the electrodes, said current being generated by the electrochemical action of the oxygen dissociated from NOx in step (3);
(5) determining a basic NOx concentration of the measurement gas, based on the electric current measured in step (4). and (6) correcting said basic NOx concentration of step (5) responsive to said change if the oxygen partial pressure in the measurement gas is changed.
-
-
39. A method for determining NOx concentration in a measurement gas, under a varying condition of the NOx gas concentration in the measurement gas in the course that the measurement gas is allowed to travel through a flow channel facing a ceramic body having an electrically controllable conducting state of oxygen ions, comprising:
-
(1) introducing the measurement gas into the flow channel;
(2) forming in said flow channel a residual gas having a NOx concentration different from that before entrance into said flow channel by extracting an oxygen gas from the measurement gas of the step (1) through the ceramic body to outside of the flow channel;
(3) dissociating NOx of said NOx-concentrated residual gas into nitrogen and oxygen by applying a voltage across electrodes formed on the ceramic body;
(4) measuring an electric current flowing through the ceramic body between the electrodes, said electric current being generated by the electrochemical action of the oxygen dissociated from NOx in step (3);
(5) determining a basic NOx concentration of the measurement gas based on the electric current measured in step (4); and
(6) measuring an output in step (4) introducing atmospheric air, and calibrating zero point of said basic NOx concentration.
-
-
40. A method for determining the NOx concentration in a measurement gas, under a varying condition of the NOx gas concentration in the measurement gas in the course that the measurement gas is allowed to travel through a flow channel facing a ceramic body having an electrically controllable conducting state of oxygen ions, comprising:
-
(1) introducing the measurement gas into the flow channel;
(2) forming in said flow channel a residual gas having a NOx concentration different from that before entrance into said flow channel by extracting an oxygen gas from the measurement gas of step (1) through the ceramic body to outside of the flow channel;
(3) dissociating NOx of said NOx-concentrated residual gas into nitrogen and oxygen by applying a voltage across electrodes formed on the ceramic body;
(4) measuring an electric current flowing through the ceramic body between the electrodes, said electric current being generated by the electrochemical action of the oxygen dissociated from NOx in step (3);
(5) determining a basic NOx concentration of the measurement gas, based on the electric current measured in step (4); and
(6) correcting the basic NOx concentration wherein the amount of moisture in said measurement gas is estimated from a driving condition of an engine, and said NOx concentration of step (5) is corrected depending on an estimated amount of moisture.
-
-
41. A method for measuring a nitrogen oxide concentration using a nitrogen oxide concentration detector having:
-
a first measurement chamber formed in said detector, into which fast measurement chamber a measurement gas is introduced via a first diffusion resistance formed on an entrance of the first measurement chamber;
an oxygen concentration detection electrode for measuring an oxygen concentration in the measurement gas in said first measurement chamber;
a first oxygen ion pump cell for pumping out oxygen from said first measurement chamber to form a residual gas in the first measurement chamber in accordance with the potential of said oxygen concentration detection electrode;
a second measurement chamber formed in said detector into which second measurement chamber the residual gas is introduced via a second diffusion resistance formed between the first and second chambers; and
a second oxygen ion pump cell having two output electrodes across which electrodes a voltage is applied to decompose the oxygen nitride in the residual gas and to pump out oxygen dissociated from the oxygen nitride to cause a current that corresponds to the nitrogen oxide concentration, said current being referred to as a second oxygen pump current flowing in the second oxygen ion pump cell;
wherein said first oxygen ion pump cell sufficiently pumps out oxygen from the first measurement chamber to an extent not to allow all nitrogen oxide in the residual gas to decompose; and
wherein the nitrogen oxide concentration obtained responsive to said second oxygen pump current is corrected in accordance to the oxygen concentration in the measurement gas, said oxygen concentration being detected by a current flowing through the first oxygen ion pump cell.
-
Specification