CN204613784U - A kind of nitrogen oxide sensor add heat detecting device - Google Patents
A kind of nitrogen oxide sensor add heat detecting device Download PDFInfo
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- CN204613784U CN204613784U CN201520282665.6U CN201520282665U CN204613784U CN 204613784 U CN204613784 U CN 204613784U CN 201520282665 U CN201520282665 U CN 201520282665U CN 204613784 U CN204613784 U CN 204613784U
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Abstract
What the utility model provided a kind of nitrogen oxide sensor adds heat detecting device, comprises heating detection module, voltage transformation module and single-chip microcomputer; Heating detection module is used for for the heating of nitrogen oxide sensor zone of heating Pt thermal resistance and the resistance value of Real-Time Monitoring nitrogen oxide sensor zone of heating Pt thermal resistance; Heating detection module comprises the first K switch 1, second switch K2, constant current source, the first resistance R1 and the second resistance R2; Single-chip microcomputer is used for the temperature obtaining nitrogen oxide sensor according to the voltage gathered, and the folding controlling the first K switch 1 or second switch K2 makes the working temperature of nitrogen oxide sensor remain on 600 DEG C ~ 800 DEG C.The utility model is owing to separately carrying out heating part and detecting portion, and when ensure that measurement, nitrogen oxide sensor is not at heated condition, thus can measure its specified temp under a certain state accurately.The utility model adopts the Pt thermal resistance of three-wire type to measure, and reduces Pt thermal resistance heat lead to the impact of measurement result, makes measurement result more accurate.
Description
Technical field
The utility model belongs to vehicle maintenance service technical field, and more specifically, what relate to a kind of nitrogen oxide sensor adds heat detecting device.
Background technology
The tail gas of motor vehicle emission has become the main source of air NOx pollutant, due to the raising of national exhaust emission standard, need to detect in real time the NOx discharge in tail gas and process, and nitrogen oxide sensor is one of core component in this detection system.
Nitrogen oxide sensor is combined by electrochemical layer and zone of heating, and electrochemical layer mainly completes a series of galvanochemistry and cartalytic decomposition effect, to realize the measurement to NOx gas; Zone of heating mainly to nitrogen oxide sensor heating, makes it to reach the temperature needed for electrochemical layer galvanochemistry and catalytic reaction.The zone of heating of nitrogen oxide sensor adopts Pt thermal resistance structure, judges the working temperature of nitrogen oxide sensor, thus control the working temperature of nitrogen oxide sensor further, to ensure the normal work of nitrogen oxide sensor according to the resistance value of the Pt thermal resistance measured.But, in existing method, the heating process of nitrogen oxide sensor and testing process are carried out simultaneously, cannot measure the resistance value of nitrogen oxide sensor zone of heating Pt thermal resistance under a certain specified temp accurately, thus cannot measure the temperature of nitrogen oxide sensor accurately; Secondly, because existing nitrogen oxide sensor adopts constant voltage laser heating, on its control circuit, so just need the fixed value resistance adding one 0.2 Ω ~ 0.5 Ω in addition, the electric current of 1A ~ 2A is had by this fixed value resistance in control circuit, this resistance is caused to produce larger power consumption, circuit board temperature is raised, and the chip affected on control circuit normally works.And Pt thermal resistance takes twin wire measuring method, the Pt thermoelectricity resistance out of true recorded usually, therefore there is no a kind of method that can ensure nitrogen oxide sensor normal work at the temperature of 600 DEG C ~ 800 DEG C at present.
Utility model content
For the defect of prior art, what the utility model provided a kind of nitrogen oxide sensor adds heat detecting device, its object is to ensure that nitrogen oxide sensor normally works at the temperature of 600 DEG C ~ 800 DEG C.
What the utility model provided a kind of nitrogen oxide sensor adds heat detecting device, comprises heating detection module, voltage transformation module and single-chip microcomputer; Described heating detection module is used for for the heating of nitrogen oxide sensor zone of heating Pt thermal resistance and the resistance value of Real-Time Monitoring nitrogen oxide sensor zone of heating Pt thermal resistance; Described heating detection module comprises the first K switch 1, second switch K2, constant current source, the first resistance R1 and the second resistance R2; One end of described first K switch 1 is used for being connected with the first output terminal of external power supply, and the described control end of the first K switch 1 is connected with the first control end of described single-chip microcomputer; The input end of described constant current source is connected with the other end of described first K switch 1, and one end of described second switch K2 is used for being connected with the first output terminal of described external power supply, and the control end of described second switch K2 is connected with the second control end of described single-chip microcomputer; The output terminal of described constant current source and the other end of described second switch K2 are all connected to the positive pole of the Pt thermal resistance of nitrogen oxide sensor; Described first resistance R1 and described second resistance R2 is sequentially connected in series between the other end and ground of described second switch K2, and being connected in series to hold of described first resistance R1 and described second resistance R2 is connected with the first voltage acquisition end of described single-chip microcomputer; The input end of described voltage transformation module is connected to the second output terminal of described external power supply, the power input of described single-chip microcomputer is connected with the output terminal of described voltage transformation module, and the second voltage acquisition end of described single-chip microcomputer is connected with the reference pole of the Pt thermal resistance of described nitrogen oxide sensor; Described single-chip microcomputer is used for the temperature obtaining nitrogen oxide sensor according to the voltage gathered, and the folding controlling described first K switch 1 or described second switch K2 makes the working temperature of nitrogen oxide sensor remain on 600 DEG C ~ 800 DEG C.
Wherein, described heating detection module also comprises the stabilivolt D1 be connected in parallel with described second resistance R2.
The principle of work adding heat detecting device of the nitrogen oxide sensor that the utility model provides is as follows: single-chip microcomputer closes according to frequency control first K switch 1 of 50Hz ~ 200Hz or second switch K2; During heating, Single-chip Controlling second switch K2 closes and the first K switch 1 turns off; During detection, Single-chip Controlling first K switch 1 conducting and second switch K2 turn off, single-chip microcomputer carrys out the dutycycle of feedback adjusting heating signal according to the nitrogen oxide sensor real time temperature detected, the adjustment heat time, thus nitrogen oxide sensor is remained in the working range of 600 DEG C ~ 800 DEG C.Wherein, the thermal control signals that sends of described single-chip microcomputer and detection control signal are rectangular pulse signal.Wherein, single-chip microcomputer first sends temperature detection signal before sending heating signal each time, thus obtains nitrogen oxide sensor real time temperature.
The utility model is owing to separately carrying out heating part and detecting portion in time, and when ensure that measurement, nitrogen oxide sensor is not at heated condition, thus can measure its specified temp under a certain state accurately.Secondly, do not need the fixed value resistance adding 0.2 Ω ~ 0.5 Ω in addition in control circuit of the present utility model, decrease the thermal value of control circuit board, ensure that the chip on circuit board normally works within the scope of operating temperature ratings.Again, adopt the Pt thermal resistance of three-wire type to measure, reduce Pt thermal resistance heat lead to the impact of measurement result, make measurement result more accurate.
Accompanying drawing explanation
The circuit diagram adding heat detecting device of the nitrogen oxide sensor that Fig. 1 provides for the utility model embodiment.
The heating voltage schematic diagram that Fig. 2 applies for the utility model.
The detection current diagram that Fig. 3 applies for the utility model.
Fig. 4 is nitrogen oxide sensor zone of heating Pt thermal resistance schematic diagram of the present utility model.
Embodiment
In order to make the purpose of this utility model, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the utility model is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the utility model, and be not used in restriction the utility model.
The utility model detects the working temperature of nitrogen oxide sensor by the resistance value detecting zone of heating Pt thermal resistance in nitrogen oxide sensor, and controlled the temperature of nitrogen oxide sensor by the heat time of control Pt thermal resistance, to ensure that nitrogen oxide sensor accurately can measure the content of NOx in tail gas at the temperature of 600 DEG C ~ 800 DEG C.
Fig. 1 shows the circuit diagram adding heat detecting device of the nitrogen oxide sensor that the utility model embodiment provides, and for convenience of explanation, illustrate only the part relevant to the utility model embodiment.
The heat detecting device 1 that adds of the nitrogen oxide sensor that the utility model provides comprises heating detection module 11, voltage transformation module 12 and single-chip microcomputer 13, external power supply 2 is powered for heating detection module 11, is controlled closed realization heating and the detection control of the first K switch 1 and second switch K2 by single-chip microcomputer 13.
Wherein heat detection module 11 for being the heating of nitrogen oxide sensor zone of heating Pt thermal resistance, external power supply 2 is connected with the positive pole of nitrogen oxide sensor zone of heating Pt thermal resistance through second switch K2, the minus earth of Pt thermal resistance, the reference pole of Pt thermal resistance is connected with single-chip microcomputer 13.Wherein, external power supply 2 can provide the heating voltage of nitrogen oxide sensor, and external power supply 2 can for single-chip microcomputer 13 provides stable normal working voltage after voltage transformation module 12.
Heating detection module 11 is for the resistance value of Real-Time Monitoring nitrogen oxide sensor zone of heating Pt thermal resistance, external power supply 2 is connected with Constant current input end through the first K switch 1, constant current source output terminal is connected with the positive pole of Pt thermal resistance, the output terminal of constant current source is connected with the first resistance R1, first resistance R1 connects with the second resistance R2, one end of second resistance R2 is connected with single-chip microcomputer 13, the other end ground connection of the second resistance R2.
Computer heating control and detection control are provided separately by heating detection control method of the present utility model, and by the duty that chip microcontroller heating process and testing process are separated from each other, thus make the resistance value of the nitrogen oxide sensor zone of heating Pt thermal resistance measured more accurate.
The utility model adopts the measuring method of three-wire type to measure nitrogen oxide sensor zone of heating Pt thermal resistance, being heat lead between the positive pole of Pt thermal resistance and the reference pole of Pt thermal resistance, is heat lead and heating resistor between the reference pole of Pt thermal resistance and the negative pole of Pt thermal resistance.Compare and twin wire measuring method in the past, the impact of heat lead on the Pt thermal resistance resistance value recorded can be removed, make measurement result more accurate.
Single-chip microcomputer judges the working temperature of nitrogen oxide sensor according to the resistance value of Pt thermal resistance, thus the heat time of adjustment to Pt thermal resistance, under ensureing that nitrogen oxide sensor always works in stable temperature reliably, improve the measurement of NOx in tail gas further.
Below in conjunction with specific embodiment and accompanying drawing, the utility model is further elaborated.
Heating detection module 11 for providing heating voltage for nitrogen oxide sensor zone of heating Pt thermal resistance, thus makes nitrogen oxide sensor heat up, and reaches working temperature.The second switch K2 of external power supply 2 in switch module is connected with the positive pole of nitrogen oxide sensor zone of heating Pt thermal resistance, the minus earth of Pt thermal resistance, and the reference pole of Pt thermal resistance is connected with single-chip microcomputer.
Heating detection module 11 for detecting the resistance value of nitrogen oxide sensor zone of heating Pt thermal resistance in real time, namely the working temperature Real-time Feedback of nitrogen oxide sensor to single-chip microcomputer 13, constantly regulated by single-chip microcomputer 13, make nitrogen oxide sensor always work in fixed temperature.External power supply 2 is connected with Constant current input end through the first K switch 1, constant current source output terminal is connected with the positive pole of nitrogen oxide sensor zone of heating Pt thermal resistance, the output terminal of constant current source is connected with the first resistance R1, first resistance R1 connects with the second resistance R2, one end of second resistance R2 is connected with single-chip microcomputer, the other end ground connection of the second resistance R2.
In testing process, because the cathode voltage value of nitrogen oxide sensor zone of heating Pt thermal resistance is larger, exceed the measurement range of single-chip microcomputer, therefore adopt the mode of the first resistance R1 and the second resistance R2 series connection dividing potential drop, calculated the cathode voltage value U1 of Pt thermal resistance by the magnitude of voltage detecting the second resistance R2.
A stabilivolt D1 in parallel at the two ends of the second resistance R2, be used for protecting single-chip microcomputer, the high pressure preventing the second resistance R2 two ends unexpected damages single-chip microcomputer.
Nitrogen oxide sensor heating detection control method described in the utility model comprises the following steps:
Single-chip microcomputer closes according to frequency control first K switch 1 of 50Hz ~ 200Hz or second switch K2.When the first K switch 1 disconnects, second switch K2 closes, be then heated condition, can be nitrogen oxide sensor zone of heating Pt thermal resistance and provide heating voltage U4, as shown in Figure 2; When the first K switch 1 closes, second switch K2 disconnects, be then detected state, and constant current source provides the setting examination electric current I of 200 ~ 400mA for nitrogen oxide sensor zone of heating Pt thermal resistance, as shown in Figure 3.
During heating, single-chip microcomputer 13 controls second switch K2 and closes, and the first K switch 1 turns off.External power supply 2 is connected with the positive pole of nitrogen oxide sensor zone of heating Pt thermal resistance through second switch K2, and the negative pole then through Pt thermal resistance arrives with reference to ground, completes heating process.
In heating process, the heat time adopts dutycycle voltage applying mode, and the ON time that the heat time controls second switch K2 by single-chip microcomputer 13 determines.Dutycycle is larger, and ON time is longer.At the heating initial stage, regulate dutycycle, nitrogen oxide sensor zone of heating Pt thermal resistance is heated up with the firing rate of 5 ~ 20 DEG C per second, reaches working temperature; After reaching working temperature, regulate dutycycle, make it remain on stable working temperature.The adjustment of dutycycle size is having arranged of the PWM generator by carrying single-chip microcomputer.
Nitrogen oxide sensor in the course of the work, when the environment temperature residing for nitrogen oxide sensor fluctuates to some extent, single-chip microcomputer also can be in good time change heating voltage dutycycle, namely control the ON time of second switch K2, make the working temperature of nitrogen oxide sensor stabilize to 600 DEG C ~ 800 DEG C.
During detection, single-chip microcomputer 13 controls the first K switch 1 conducting, and second switch K2 turns off, and namely makes nitrogen oxide sensor heater circuit quit work.Constant current source output terminal is connected with the positive pole of nitrogen oxide sensor zone of heating Pt thermal resistance, and the reference pole of Pt thermal resistance is connected with single-chip microcomputer, and the negative pole of Pt thermal resistance is received and reached with reference to ground.Because the cathode voltage value of nitrogen oxygen Pt thermal resistance is larger, exceed the measurement range of single-chip microcomputer, therefore the mode of the first resistance R1 and the second resistance R2 series connection dividing potential drop is adopted, by detecting the magnitude of voltage U2 of the second resistance R2, voltage U 1 between Pt thermal resistance positive pole and negative pole is U2/R2* (R2+R1)
The reference of Pt thermal resistance is extremely directly connected with single-chip microcomputer, can record the reference pole of Pt thermal resistance and the voltage U 3 of negative pole, then the voltage at nitrogen oxide sensor zone of heating Pt thermal resistance two ends is U0=U1-2 í U3.
Now constant current source outputting standard electric current I, then the resistance value R0=U0/I of Pt thermal resistance.
Single-chip microcomputer regulates the dutycycle of heating voltage according to the difference comparing Pt thermal resistance resistance value R0 and standard electric resistance, namely controls the ON time of second switch K2, makes the working temperature that well heater keeps stable.
Those skilled in the art will readily understand; the foregoing is only preferred embodiment of the present utility model; not in order to limit the utility model; all do within spirit of the present utility model and principle any amendment, equivalent to replace and improvement etc., all should be included within protection domain of the present utility model.
Claims (2)
1. nitrogen oxide sensor add a heat detecting device, it is characterized in that, comprise heating detection module (11), voltage transformation module (12) and single-chip microcomputer (13);
Described heating detection module (11) comprises the first K switch 1, second switch K2, constant current source, the first resistance R1 and the second resistance R2; One end of described first K switch 1 is used for being connected with the first output terminal of external power supply (2), and the control end of described first K switch 1 is connected with the first control end of described single-chip microcomputer (13); The input end of described constant current source is connected with the other end of described first K switch 1, one end of described second switch K2 is used for being connected with the first output terminal of described external power supply (2), and the control end of described second switch K2 is connected with the second control end of described single-chip microcomputer (13); The output terminal of described constant current source and the other end of described second switch K2 are all connected to the positive pole of the Pt thermal resistance of nitrogen oxide sensor (3); Described first resistance R1 and described second resistance R2 is sequentially connected in series between the other end and ground of described second switch K2, and being connected in series to hold of described first resistance R1 and described second resistance R2 is connected with the first voltage acquisition end of described single-chip microcomputer (13);
The input end of described voltage transformation module (12) is connected to the second output terminal of described external power supply (2);
The power input of described single-chip microcomputer (13) is connected with the output terminal of described voltage transformation module (12), and the second voltage acquisition end of described single-chip microcomputer (13) is connected with the reference pole of the Pt thermal resistance of described nitrogen oxide sensor (3); Described single-chip microcomputer (13) obtains the temperature of nitrogen oxide sensor according to the voltage gathered, and the folding controlling described first K switch 1 or described second switch K2 makes the working temperature of nitrogen oxide sensor remain on 600 DEG C ~ 800 DEG C.
2. add heat detecting device as claimed in claim 1, it is characterized in that, described heating detection module (11) also comprises the stabilivolt D1 be connected in parallel with described second resistance R2.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN201520282665.6U CN204613784U (en) | 2015-04-30 | 2015-04-30 | A kind of nitrogen oxide sensor add heat detecting device |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201520282665.6U CN204613784U (en) | 2015-04-30 | 2015-04-30 | A kind of nitrogen oxide sensor add heat detecting device |
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| CN204613784U true CN204613784U (en) | 2015-09-02 |
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| CN201520282665.6U Active CN204613784U (en) | 2015-04-30 | 2015-04-30 | A kind of nitrogen oxide sensor add heat detecting device |
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