CN104897851A - Control circuit and method for nitrogen oxide sensor oxygen determination chamber oxygen pump - Google Patents
Control circuit and method for nitrogen oxide sensor oxygen determination chamber oxygen pump Download PDFInfo
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Abstract
The invention discloses a control circuit and method for nitrogen oxide sensor oxygen determination chamber oxygen pump. The oxygen pump control circuit includes a first receiving module, a voltage superimposed module, a second receiving module, a signal processing module and an oxygen pump module. The input terminal of the voltage superimposed module is connected to the output terminal of the first receiving module; a first signal input terminal of the signal processing module is connected to the output terminal of the voltage superimposed module; a second signal input terminal is connected to the output terminal of the second receiving module; a feedback signal input terminal is connected to a negative feedback terminal of the oxygen pump module; and the input terminal of the oxygen pump module is connected the output terminal of the signal processing module. The control circuit and method for nitrogen oxide sensor oxygen determination chamber oxygen pump achieve dynamic adaptive real-time adjustment of oxygen concentration in the nitrogen oxide sensor oxygen determination chamber, and maintain the oxygen concentration of in the oxygen determination chamber at a threshold concentration, in order to achieve the prerequisites for using the nitrogen oxygen sensor for test of NOx content in exhaust.
Description
Technical field
The invention belongs to sensor technical field, more specifically, relate to a kind of nitrogen oxide sensor and determine oxygen cavity pump oxygen control circuit and method.
Background technology
Along with economic growth, use the vehicle of diesel motor to increase gradually, discharge exceeds standard and causes China's urban air environmental pollution serious; Therefore emission compliance has become the long-term and urgent task of of Chinese society.Nitrogen oxide sensor is mainly used in the NOx emission content measuring exhaust gas from diesel vehicle, is the critical component of diesel engine aftertreatment system.
In NOx emission content detection process, after being heated by nitrogen oxide sensor, discharge the oxygen in NOx detection chambers, make within oxygen concentration remains on 5ppm in NOx detection chambers; Under NOx atmosphere, the atmosphere to be checked containing NOx enters detection chambers carry out NOx emission content detection via determining oxygen chamber; Wherein, NOx detection chambers refers to the reduction chamber of nitrogen oxide sensor chip; This detection method is responsive to detection chambers oxygen concentration, if external oxygen infiltrates detection chambers with NOx gas, causes detection chambers oxygen concentration to transfinite, then can affect the accuracy of NOx emission content detection result to a great extent; Because atmosphere to be checked enters NOx detection chambers via determining oxygen chamber, therefore carry out in the process of NOx emission content detection at employing nitrogen oxide sensor chip, the oxygen concentration of determining in oxygen chamber is most crucial, needs to be controlled within the scope of 1 ~ 5ppm.
Summary of the invention
For above defect or the Improvement requirement of prior art, the invention provides a kind of nitrogen oxide sensor and determine oxygen cavity pump oxygen control circuit and method, its object is to, the oxygen concentration electric potential difference between nitrogen oxide sensor reduction chamber and reference chamber is controlled in pump oxygen process, with control pump oxygen voltage, thus the oxygen concentration difference of being reduced by nitrogen oxide sensor between chamber and reference chamber maintains in certain concentration difference, realize the real-time control to determining oxygen chamber oxygen concentration.
For achieving the above object, according to one aspect of the present invention, provide a kind of nitrogen oxide sensor and determine oxygen cavity pump oxygen control circuit, comprise the first receiver module, voltage superposition module, the second receiver module, signal processing module and pump oxygen module;
Wherein, the input end of voltage superposition module connects the output terminal of the first receiver module; First signal input part of signal processing module connects the output terminal of voltage superposition module, and secondary signal input end connects the output terminal of the second receiver module, and feedback signal input terminal connects the negative feedback end of pump oxygen module; The output terminal of the input end connection signal processing module of pump oxygen module, the output terminal of pump oxygen module determines the pump oxygen voltage output end of oxygen cavity pump oxygen control circuit as described nitrogen oxide sensor;
Wherein, the first receiver module is for receiving and nursing one's health the comparison electrode signal of nitrogen oxide sensor; Second receiver module is for receiving and nursing one's health the reference electrode signal of nitrogen oxide sensor; Voltage superposition module will be used for according to comparing electrode signal and superimposed voltage obtains correction voltage; Signal processing module obtains pump oxygen control signal according to the comparative result of this correction voltage and reference electrode signal; Pump oxygen module according to this pump oxygen control signal rear pump oxygen voltage, driving pump oxygen.
Preferably, superimposed voltage is 430mV ~ 600mV.
Preferably, voltage superposition module comprises zener diode D1, the first resistance R1, the second resistance R2 and the 3rd resistance R3; Voltage stabilizing diode D1 adopts accurate stabilivolt; More stable to make by the superimposed voltage of resistance R2, R3 dividing potential drop acquisition;
Wherein, the first end of the first resistance connects 5V voltage source, and the first end of the second resistance R2 connects second end of the first resistance R1, and the first end of the 3rd resistance R3 connects second end of the second resistance R2; The positive pole of described voltage stabilizing diode D1 connects second end of the 3rd resistance R3;
Wherein, the negative pole of voltage stabilizing diode D1 connects the end of connecting of the first resistance R1 and the second resistance R2; The positive pole of voltage stabilizing diode D1 as the input end of voltage superposition module, the output terminal of end as voltage superposition module of connecting of the second resistance R2 and the 3rd resistance R3.
Preferably, first receiver module comprises the first operational amplifier OP1, its input anode is as the input end of the first receiver module, its input negative terminal connects second end of the 3rd resistance R3 in voltage superposition module, its first output terminal is as the output terminal of the first receiver module, connect the input end of voltage superposition module, the second output terminal connects second end of the 3rd resistance R3 in voltage superposition module;
Wherein, the first operational amplifier OP1 is used as voltage follower, and according to the short principle of the void of operational amplifier, the output signal of the first operational amplifier OP1 equals the comparison electrode voltage signal that OP1 inputs anode.
Preferably, signal processing module comprises the second operational amplifier OP2, the 4th resistance R4, the 5th resistance R5 and the 6th resistance R6;
Wherein, the input negative terminal of the second operational amplifier OP2 as the first signal input part of signal processing module, its input anode as the secondary signal input end of signal processing module, for inputting reference electrode voltage;
The first end of the 4th resistance R4 connects the output terminal of the second operational amplifier OP2; The first end of the 6th resistance R6 connects second end of the 4th resistance R4, the second end ground connection of the 6th resistance R6; The first end of the 5th resistance R5 connects the input negative terminal of the second operational amplifier OP2;
4th resistance R4 and the output terminal of end as signal processing module of connecting of the 6th resistance R6, be connected with the oxygen electrode of determining of nitrogen oxide sensor; Second end of the 5th resistance R5 as the feedback signal input terminal of signal processing module, with the determining oxygen electrode and be connected of nitrogen oxide sensor;
Second operational amplifier OP2 is according to the comparative result rear pump oxygen control signal of its anode input signal and negative terminal input signal; During pump oxygen, pump oxygen control signal raises gradually from negative value, and pump oxygen voltage then reduces gradually.
Preferably, the first resistance value is 1K Ω ~ 5K Ω; If resistance is less than this scope, then makes by the electric current of D1 too large, cause D1 to generate heat and produce temperature drift; If be greater than this scope, then D1 may be caused to lose pressure stabilization function without enough electric currents.
Preferably, the resistance of the 5th resistance R5 is in megohm magnitude; 5th resistance R5 is for guaranteeing the stable output of the second operational amplifier OP2, and get its resistance in megohm magnitude, farthest can reduce the electric current that the 5th resistance R5 flows through, to eliminate the impact of the 5th resistance R5 self on the second operational amplifier OP2 input negative terminal.
According to another aspect of the present invention, provide a kind of nitrogen oxide sensor and determine oxygen cavity pump oxygen control method, determine oxygen cavity pump oxygen control circuit based on above-mentioned nitrogen oxide sensor, specific as follows:
(1) by controlling heating voltage, the perform region of nitrogen oxide sensor is heated to target temperature;
(2) by control pump oxygen voltage, the oxygen determined in oxygen chamber discharge is determined outside oxygen chamber, make to determine oxygen chamber equal with the oxygen content in reduction chamber;
Due to reduction chamber with determine oxygen chamber only phase alternating floor diffusion barrier, therefore determine oxygen chamber oxygen emptying after, the oxygen reduced in chamber enters under diffusion to be determined oxygen chamber and is discharged subsequently and determines outside oxygen chamber; Thus, oxygen chamber is determined equal with the oxygen content in reduction chamber;
And reduce between chamber and reference cavity indoor there is difference in oxygen concentration, therefore compare the electric potential difference existing between electrode and reference electrode and produced by oxygen concentration difference; Wherein, compare electrode and be arranged in reduction chamber, reference electrode is arranged on reference cavity indoor, and reference electrode communicates with air;
(3) adjust pump oxygen voltage with driving pump oxygen according to above-mentioned oxygen concentration electric potential difference, oxygen chamber indoor oxygen will be determined and discharge, until determine oxygen chamber oxygen concentration to be reduced to concentration threshold;
Along with pump oxygen carries out, determine oxygen concentration in oxygen chamber and reduce gradually, determine oxygen chamber and increase gradually with reference to the difference in oxygen concentration between chamber, compare oxygen concentration electric potential difference between electrode and reference electrode and strengthen gradually thereupon, pump oxygen voltage reduces gradually, and pump oxygen slows down; When this electric potential difference increases 430mV ~ 600mV, determine oxygen chamber oxygen concentration and reach concentration threshold; Wherein, oxygen concentration electric potential difference is that the Zirconia electrolytic concentration potential of generation is poor by oxygen concentration difference in two chambers.
Preferably, along with pump oxygen slows down, the oxygen concentration electric potential difference compared between electrode and reference electrode reduces gradually; Higher than concentration threshold when determining oxygen concentration in oxygen chamber, by the self-adjusting of oxygen concentration electric potential difference control pump oxygen voltage, strengthen driving pump oxygen, pumping outside chamber by determining oxygen unnecessary in oxygen chamber, maintaining concentration threshold by determining oxygen concentration in oxygen chamber.
Preferably, the threshold value of determining oxygen concentration in oxygen chamber is 1ppm ~ 5ppm, determines oxygen concentration in oxygen chamber and reaches 1ppm ~ 5ppm, then reach the requirement of tail gas NOx content detection; After this, the pump oxygen amount of determining oxygen chamber enters into the external world amount of oxygen determining oxygen chamber and reaches mobile equilibrium.
In general, the above technical scheme conceived by the present invention compared with prior art, can obtain following beneficial effect:
(1) nitrogen oxide sensor provided by the invention determines oxygen cavity pump oxygen control circuit, and module is simple, element is few, volume is little, can embed in the nitrogen oxide sensor of millimeter magnitude, and the fast and stable realized determining oxygen chamber oxygen concentration controls;
(2) because nitrogen oxide sensor provided by the invention determines oxygen cavity pump oxygen control circuit and method, realize regulating in real time the dynamic self-adapting determining oxygen concentration in oxygen chamber: once the oxygen concentration of determining oxygen chamber is greater than threshold value, unnecessary oxygen will be pumped determines outside oxygen chamber, maintains in threshold value thus by determining oxygen concentration in oxygen chamber.
Accompanying drawing explanation
Fig. 1 is nitrogen oxide sensor ceramic chip structural representation;
Fig. 2 is the system chart that a kind of nitrogen oxide sensor that the embodiment of the present invention provides determines oxygen cavity pump oxygen control circuit;
Fig. 3 is that a kind of nitrogen oxide sensor that the embodiment of the present invention provides determines oxygen cavity pump oxygen control circuit.
Embodiment
In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.In addition, if below in described each embodiment of the present invention involved technical characteristic do not form conflict each other and just can mutually combine.
If Fig. 1 is nitrogen oxide sensor ceramic chip structural representation, in Fig. 1, IP1 and IP2 all represents current measuring device, and E1 represents earth terminal, V
frepresent oxygen concentration voltage difference; Ceramic chip is six layers of zirconia material, and the gray area in ground floor and the second layer is diffusion barrier; Ceramic chip is divided into 3 chambers: with reference to chamber: this chamber fills air, introduces reference electrode in this chamber; Determine oxygen chamber: in this chamber, atmosphere is variable, introduce in this chamber and determine oxygen electrode, by determining the size of the voltage difference determination pump oxygen voltage of oxygen electrode and central electrode, to determining oxygen cavity pump oxygen; Reduction chamber: with determine oxygen chamber phase alternating floor diffusion barrier, the atmosphere of chamber interior because of diffusion similar to the atmosphere determining oxygen chamber.
When carrying out pump oxygen and measure oxygen content, ceramic chip has 3 pairs of electrode participation work: compare electrode and reference electrode, for measuring reduction chamber with poor with reference to chamber oxygen concentration; Central electrode and determine oxygen electrode, controls within the specific limits for the oxygen concentration determining oxygen chamber and reduction chamber; Potential electrode and central electrode, the concentration of NOx in the voltage response tail gas that potential electrode obtains.
Before tail gas NOx content detection starts, the perform region of nitrogen oxide sensor is heated to target temperature, the oxygen determined in oxygen chamber discharged determines outside oxygen chamber by comparing electrode and determining the pump oxygen voltage that formed between oxygen electrode; Oxygen in reduction chamber enters under diffusion to be determined oxygen chamber and is discharged subsequently and determines outside oxygen chamber, thus, determine oxygen chamber and the oxygen content approximately equal of reducing in chamber; And reduce between chamber and reference cavity indoor there is oxygen concentration difference;
According to the principle of Nernst equation, be arranged on reduction chamber in comparison electrode and the reference electrode being arranged on reference cavity indoor between there is oxygen concentration voltage difference delta U, automatically control this oxygen concentration voltage difference delta U by pump oxygen control circuit, make it to remain on preset value; Oxygen concentration voltage difference delta U remains on preset value, then show that determining oxygen chamber reaches with the oxygen concentration of reduction chamber the condition precedent that nitrogen oxide sensor detects tail gas NOx content;
Determine oxygen chamber O
2concentration then meets this condition precedent in the threshold range of 1 ~ 5ppm; Owing to determining oxygen chamber O
2concentration, lower than 1 ~ 5ppm, can make NOx react determining oxygen electrode, cause NOx concentration in reduction chamber not enough, thus the NOx concentration causing potential electrode to measure is inaccurate; If determine oxygen chamber O
2concentration, higher than 1 ~ 5ppm, is determined oxygen chamber oxygen and is entered reduction chamber, affects NOx concentration measurement result equally;
Tail gas NOx content detection starts, and nitrogen oxide sensor ceramic chip is placed in vehicle exhaust atmosphere, and the NOx gas in tail gas enters determines oxygen chamber and reduction chamber; In reduction chamber, NOx is decomposed into O under the catalytic action of potential electrode
2with N
2; According to the O that potential electrode detects
2the electric current that ion produces determines the concentration of NOx in chamber, reaches the NOx emission content object measuring exhaust gas from diesel vehicle.
It is the system chart that a kind of nitrogen oxide sensor that the embodiment of the present invention provides determines oxygen cavity pump oxygen control circuit shown in Fig. 2; The pump oxygen control circuit that this embodiment provides comprises the first receiver module, voltage superposition module, the second receiver module, signal processing module and pump oxygen module;
Wherein, the first receiver module receives the comparison electrode signal of nitrogen oxide sensor and carries out denoising conditioning to it; Second receiver module is for receiving the reference electrode signal of nitrogen oxide sensor and carrying out denoising conditioning to it; The input end of voltage superposition module connects the output terminal of the first receiver module, the comparison electrode signal after access process; First signal input part of signal processing module connects the output terminal of voltage superposition module, access correction voltage; Secondary signal input end connects the output terminal of the second receiver module, the reference electrode signal after access process; Feedback signal input terminal connects the negative feedback end of pump oxygen module; The output terminal of the input end connection signal processing module of pump oxygen module.
Be that a kind of nitrogen oxide sensor that the embodiment of the present invention provides determines oxygen cavity pump oxygen control circuit shown in Fig. 3, comprise zener diode D1, the first operational amplifier OP1, second operational amplifier OP2,5V voltage source, the 3rd resistance R3 of second resistance R2,1.6K ohm of first resistance R1,2.8K ohm of 1K ohm, the 6th resistance R6 of the 5th resistance R5 and 300 ohm of the 4th resistance R4,1M ohm of 200 ohm;
The input anode electrode Vc voltage input end of making comparisons of the first operational amplifier OP1, input negative terminal connects one end of the 3rd resistance R3; OP1 is used as voltage follower in circuit, and the output voltage of OP1 is and compares electrode Vc voltage;
The output of the first operational amplifier OP1 is divided into two branch roads; Wherein, the first branch road connects the positive pole of voltage stabilizing diode D1, and the second branch road is connected to the first end of the 3rd resistance R3; The first end of the second resistance R2 connects second end of the 3rd resistance R3; The first end of the first resistance R1 connects the crossing end of the second resistance R2 second end and voltage stabilizing diode D1 negative pole; Second end of the first resistance connects 5V voltage source anode;
The input negative terminal of the second operational amplifier OP2 connects second end of the 3rd resistance R3, and input negative terminal is used as reference electrode Vr voltage input end; Thus, compare electrode voltage and input with the negative pole that the voltage that the 3rd resistance R3 assigns to is added as OP2, reference electrode voltage inputs as positive pole; Both compare on the second operational amplifier OP2, output signal to act on after the 4th resistance R4 and the 6th resistance R6 to determine oxygen electrode; During pump oxygen, the output end voltage of the second operational amplifier OP2 is elevated to 0mV gradually from negative value; Operational amplifier OP2 in the present embodiment for controlling the oxygen concentration electric potential difference Δ U making to compare between electrode and reference electrode;
The first end of the 4th resistance R4 connects the output terminal of the second operational amplifier OP2; The first end of the 6th resistance R6 connects second end of the 4th resistance R4, the second end ground connection of the 6th resistance R6; Determine the end of connecting that oxygen electrode connects the 4th resistance R4 and the 6th resistance R6;
The voltage of the 4th resistance R4 second end acts on determines oxygen electrode V
0; Apply 2.3V fixed voltage at central electrode Vi end, central electrode Vi terminal voltage with determine oxygen electrode V
0voltage difference between terminal voltage is pump oxygen voltage U o
2;
The first end of the 5th resistance R5 connects the input negative terminal of the second operational amplifier OP2; Determine the second end that oxygen electrode connects the 5th resistance R5; Wherein, D1 both end voltage is stabilized in 1.25V, and the voltage that the 3rd resistance R3 assigns to is preset in 450mV, as superimposed voltage.
Specifically set forth nitrogen oxide sensor provided by the invention below in conjunction with Fig. 1 and Fig. 3 and determine oxygen cavity pump oxygen control method:
(1) evenly increase heating voltage slowly until target heating voltage, the perform region of nitrogen oxide sensor is heated to target temperature;
(2) oxygen determined in oxygen chamber is discharged and is determined outside oxygen chamber by control pump oxygen voltage, makes to determine oxygen chamber equal with the oxygen content in reduction chamber;
Due to reduction chamber with determine oxygen chamber only phase alternating floor diffusion barrier, therefore determine oxygen chamber oxygen emptying after, the oxygen reduced in chamber enters under diffusion to be determined oxygen chamber and is discharged subsequently and determines outside oxygen chamber; Thus, oxygen chamber is determined equal with the oxygen content in reduction chamber;
And reduce between chamber and reference cavity indoor there is oxygen concentration difference, therefore compare between electrode and reference electrode and there is oxygen concentration electric potential difference; Wherein, compare electrode and be arranged in reduction chamber, reference electrode is arranged on reference cavity indoor, and reference electrode communicates with air;
(3) pump oxygen voltage is adjusted with driving pump oxygen, until determine oxygen chamber oxygen concentration to be reduced to 1ppm ~ 5ppm according to above-mentioned oxygen concentration electric potential difference;
Along with pump oxygen carries out, determine oxygen concentration in oxygen chamber and reduce gradually, determine oxygen chamber and increase gradually with reference to the difference in oxygen concentration between chamber; Thus, compare oxygen concentration electric potential difference between electrode and reference electrode and strengthen gradually thereupon, pump oxygen voltage reduces gradually, and pump oxygen slows down; When this electric potential difference is 430mV ~ 600mV, determine oxygen chamber oxygen concentration for arriving 1ppm ~ 5ppm; Wherein, oxygen concentration electric potential difference is the electric potential difference that the ion motion produced by oxygen concentration difference in two chambers causes;
(4) along with pump oxygen slows down, when determining in oxygen chamber, oxygen concentration is higher than 1ppm ~ 5ppm, and the oxygen concentration electric potential difference compared between electrode and reference electrode increases; By this electric potential difference control pump oxygen voltage self-adjusting, with driving pump oxygen, pumping outside chamber by determining oxygen unnecessary in oxygen chamber, maintaining 1ppm ~ 5ppm by determining oxygen chamber oxygen concentration;
Determine oxygen chamber oxygen concentration and reach 1ppm ~ 5ppm, namely reach the requirement that nitrogen oxide sensor carries out tail gas NOx content detection; After this, the pump oxygen amount of determining oxygen chamber enters into the external world amount of oxygen determining oxygen chamber and reaches mobile equilibrium; Thus achieve the Automatic adjusument determining oxygen chamber oxygen concentration.
Those skilled in the art will readily understand; the foregoing is only preferred embodiment of the present invention; not in order to limit the present invention, all any amendments done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within protection scope of the present invention.
Claims (10)
1. nitrogen oxide sensor determines an oxygen cavity pump oxygen control circuit, it is characterized in that, comprises the first receiver module, voltage superposition module, the second receiver module, signal processing module and pump oxygen module;
The input end of described voltage superposition module connects the output terminal of described first receiver module; First signal input part of described signal processing module connects the output terminal of described voltage superposition module, and secondary signal input end connects the output terminal of described second receiver module, and feedback signal input terminal connects the negative feedback end of described pump oxygen module; The input end of described pump oxygen module connects the output terminal of described signal processing module, and the output terminal of described pump oxygen module determines the pump oxygen voltage output end of oxygen cavity pump oxygen control circuit as described nitrogen oxide sensor;
Described first receiver module is for receiving and nursing one's health the comparison electrode signal of nitrogen oxide sensor; Second receiver module is for receiving and nursing one's health the reference electrode signal of nitrogen oxide sensor; Described voltage superposition module is used for according to comparing electrode signal and superimposed voltage obtains correction voltage, and described signal processing module obtains pump oxygen control signal according to the comparative result of described correction voltage and reference electrode signal; Pump oxygen module according to described pump oxygen control signal rear pump oxygen voltage, driving pump oxygen.
2. pump oxygen control circuit as claimed in claim 1, it is characterized in that, described superimposed voltage is 430mV ~ 600mV.
3. pump oxygen control circuit as claimed in claim 1 or 2, it is characterized in that, described voltage superposition module comprises zener diode D1, the first resistance R1, the second resistance R2 and the 3rd resistance R3;
The first end of described first resistance connects 5V voltage source, and the first end of the second resistance R2 connects second end of the first resistance R1, and the first end of the 3rd resistance R3 connects second end of the second resistance R2; The positive pole of described voltage stabilizing diode D1 connects second end of the 3rd resistance R3;
The negative pole of described voltage stabilizing diode D1 connects the end of connecting of the first resistance R1 and the second resistance R2; The positive pole of voltage stabilizing diode D1 as the input end of voltage superposition module, the output terminal of end as voltage superposition module of connecting of the second resistance R2 and the 3rd resistance R3.
4. pump oxygen control circuit as claimed in claim 3, it is characterized in that, described first receiver module comprises the first operational amplifier OP1, its input anode is as the input end of the first receiver module, its input negative terminal connects second end of the 3rd resistance R3 in voltage superposition module, its first output terminal, as the output terminal of the first receiver module, connects the input end of voltage superposition module, and the second output terminal connects second end of the 3rd resistance R3 in voltage superposition module.
5. the pump oxygen control circuit as described in claim 3 or 4, is characterized in that, described signal processing module comprises the second operational amplifier OP2, the 4th resistance R4, the 5th resistance R5 and the 6th resistance R6;
The input negative terminal of described second operational amplifier OP2 as the first signal input part of signal processing module, its input anode as the secondary signal input end of signal processing module, for inputting reference electrode voltage;
The first end of described 4th resistance R4 connects the output terminal of the second operational amplifier OP2; The first end of the 6th resistance R6 connects second end of the 4th resistance R4, the second end ground connection of the 6th resistance R6; The first end of the 5th resistance R5 connects the input negative terminal of the second operational amplifier OP2;
Described 4th resistance R4 and the output terminal of end as signal processing module of connecting of the 6th resistance R6, be connected with the oxygen electrode of determining of nitrogen oxide sensor; Second end of the 5th resistance R5 as the feedback signal input terminal of signal processing module, with the determining oxygen electrode and be connected of nitrogen oxide sensor.
6. the pump oxygen control circuit as described in any one of claim 3 to 5, is characterized in that, the resistance of described first resistance R1 is 1K Ω ~ 5K Ω.
7. the pump oxygen control circuit as described in claim 5 or 6, is characterized in that, the resistance of described 5th resistance R5 is in megohm magnitude.
8. determine a pump oxygen control method for oxygen cavity pump oxygen control circuit based on the nitrogen oxide sensor described in any one of claim 1 to 7, it is characterized in that, described method is specific as follows:
(1) by controlling heating voltage, the perform region of nitrogen oxide sensor is heated to target temperature;
(2) by control pump oxygen voltage, the oxygen determined in oxygen chamber discharge is determined outside oxygen chamber, make to determine oxygen chamber equal with the oxygen content in reduction chamber, and compare the electric potential difference existing between electrode and reference electrode and produced by oxygen concentration difference;
(3) adjust pump oxygen voltage with driving pump oxygen according to described oxygen concentration electric potential difference, oxygen chamber indoor oxygen will be determined and discharge, until determine oxygen chamber oxygen concentration to be reduced to concentration threshold.
9. pump oxygen control method as claimed in claim 8, is characterized in that, reducing, slowing down the speed of pump oxygen along with determining oxygen concentration in oxygen chamber; Along with pump oxygen slows down, the oxygen concentration electric potential difference compared between electrode and reference electrode reduces gradually; Higher than concentration threshold when determining oxygen concentration in oxygen chamber, by the self-adjusting of oxygen concentration electric potential difference control pump oxygen voltage, strengthen driving pump oxygen, pumping outside chamber by determining oxygen unnecessary in oxygen chamber, maintaining concentration threshold by determining oxygen concentration in oxygen chamber.
10. pump oxygen control method as claimed in claim 8 or 9, it is characterized in that, described method concentration threshold is 1ppm ~ 5ppm.
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| US5034112A (en) * | 1988-05-19 | 1991-07-23 | Nissan Motor Company, Ltd. | Device for measuring concentration of nitrogen oxide in combustion gas |
| US20040238378A1 (en) * | 2002-03-29 | 2004-12-02 | Shinji Kumazawa | Nox measurement device, nox sensor self-diagnosis device, and self-diagnosis method thereof |
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| CN104897851B (en) | 2016-08-24 |
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