WO2017068919A1

WO2017068919A1 - Exhaust gas sensor control device and exhaust gas sensor system

Info

Publication number: WO2017068919A1
Application number: PCT/JP2016/078605
Authority: WO
Inventors: 攻田中
Original assignee: 株式会社デンソー
Priority date: 2015-10-19
Filing date: 2016-09-28
Publication date: 2017-04-27
Also published as: JP2017078579A

Abstract

A NOx detection device (10) as an exhaust gas sensor control device is a device that controls a NOx sensor (100) that detects the NOx concentration in an exhaust gas of internal combustion engines. Corresponding to an electron conduction change quantity (c) generated in the NOx sensor (100), the device corrects a second pumping current (Ip2), i.e., a sensor output of the NOx sensor (100).

Description

Exhaust gas sensor control device and exhaust gas sensor system

Cross-reference of related applications

This application is based on Japanese Patent Application No. 2015-205393 filed on October 19, 2015, and claims the benefit of its priority. Which is incorporated herein by reference.

The present disclosure relates to a control device and an exhaust gas sensor system connected to an exhaust gas sensor that detects a concentration of a specific gas component in exhaust gas of an internal combustion engine.

As an exhaust gas sensor that detects the concentration of a specific gas component in the exhaust gas of an internal combustion engine, for example, as described in Patent Document 1, a NOx sensor that detects NOx (nitrogen oxide) concentration is known. The NOx sensor described in Patent Document 1 includes a gas sensor element including one or a plurality of cells formed by forming a pair of electrodes on the surface of an oxygen ion conductive solid electrolyte layer such as zirconia. The NOx sensor measures the oxygen concentration in the first measurement chamber communicating with the gas space to be measured by an oxygen concentration detection cell, and the oxygen in the first measurement chamber is first measured so that the first measurement chamber has a predetermined oxygen concentration. Control (pump in and out) by pumping cell. Further, the NOx sensor is configured such that the gas to be measured whose oxygen concentration is controlled flows from the first measurement chamber into the second measurement chamber, and applies a constant voltage to the second pumping cell to thereby change the gas to be measured in the second measurement chamber. The contained NOx is decomposed into N ₂ and O ₂ . At this time, the NOx concentration in the measurement gas is detected by measuring the second pumping current flowing between the pair of electrodes of the second pumping cell.

JP 2009-265085 A

By the way, in the exhaust gas sensor described in Patent Document 1, even if the specific gas component (NOx) to be measured is not included in the exhaust gas, the second pumping current corresponding to the specific gas component is predetermined. Current value (so-called offset value). For this reason, it is common to calculate the concentration of the specific gas component by performing correction such as subtracting the offset value from the second pumping current. However, this offset value changes due to the influence of temperature change, aging change, manufacturing variation, and the like, causing a shift in sensor output (second pumping current).

Among exhaust gas sensors, for example, an O2 (oxygen concentration) sensor or an A / F (air-fuel ratio) sensor, such as a sensor whose sensor output has a relatively large current value, the above-described deviation has a small ratio to the sensor output. small. On the other hand, when the sensor output is a small current value such as a NOx sensor, the above-described deviation has a large influence on the sensor output because the ratio increases with respect to the sensor output. For this reason, it is desirable that the above-described deviation amount can be corrected appropriately and the detection accuracy of the sensor output can be improved.

This disclosure is intended to provide an exhaust gas sensor control device and an exhaust gas sensor system that can improve the detection accuracy of sensor output.

An exhaust gas sensor control device according to an aspect of the present disclosure is a control device that controls an exhaust gas sensor that detects a concentration of a specific gas component in exhaust gas of an internal combustion engine, and that controls the amount of electron conduction generated in the exhaust gas sensor. The sensor output of the exhaust gas sensor is corrected according to the amount of change.

Similarly, an exhaust gas sensor system according to an aspect of the present disclosure includes an exhaust gas sensor that detects the concentration of a specific gas component in the exhaust gas of an internal combustion engine, and the above-described control device.

The sensor output offset amount of the exhaust gas sensor fluctuates due to various influences such as element temperature and aging, and the cause is considered to be mainly the influence of the amount of electron conduction generated in the exhaust gas sensor. According to the above configuration of one aspect of the present disclosure, the sensor output of the exhaust gas sensor can be appropriately corrected according to the amount of change in the electron conduction amount. It can suppress suitably and can improve the detection accuracy of a sensor output.

According to the present disclosure, it is possible to provide an exhaust gas sensor control device and an exhaust gas sensor system that can improve detection accuracy of sensor output.

FIG. 1 is a diagram showing a schematic configuration of a NOx sensor system as an example of an exhaust gas sensor system according to the first embodiment. FIG. 2 is a diagram illustrating an example of element temperature-sensor output characteristics of the NOx sensor. FIG. 3 is a flowchart showing a sensor output correction amount update process according to the first embodiment. FIG. 4 is a flowchart showing a sensor output correction amount update process according to the second embodiment.

Hereinafter, the present embodiment will be described with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same constituent elements in the drawings will be denoted by the same reference numerals as much as possible, and redundant description will be omitted.

[First Embodiment]
The first embodiment will be described with reference to FIGS. In the first embodiment, as an example of an exhaust gas sensor that detects the concentration of a specific gas component in the exhaust gas of an internal combustion engine (engine), a NOx sensor that measures the NOx concentration in the exhaust gas will be described.

As shown in FIG. 1, the NOx sensor system 1 includes a NOx sensor control device (hereinafter also referred to as “NOx detection device 10”) and a NOx sensor 100. The NOx sensor system 1 measures the NOx concentration and the oxygen concentration in the exhaust gas based on the sensor output of the NOx sensor 100 by controlling the operation of the NOx sensor 100 by the NOx detection device 10. That is, the NOx detection device 10 corresponds to a control device for an exhaust gas sensor (NOx sensor) in the present embodiment. Further, the NOx sensor system 1 corrects the sensor output of the NOx sensor 100 by the NOx detection device 10.

The NOx detection device 10 is mounted on a vehicle including an engine (not shown), and is electrically connected to the NOx sensor 100 via a connector or the like.

Further, the NOx detection device 10 is electrically connected to a vehicle-side control device (ECU) (not shown). The ECU receives the oxygen concentration and NOx concentration data corrected by the NOx detection device 10 and executes processing such as control of the operating state of the engine and purification of NOx accumulated in the catalyst based on the received data. .

The NOx detection device 10 includes a microcomputer 51 and a control circuit 52 on a circuit board. The microcomputer 51 controls the entire NOx detection device 10. In particular, in the present embodiment, the microcomputer 51 performs output correction of the sensor output of the NOx sensor 100 measured by the control circuit 52. Details of the output correction will be described later with reference to FIGS.

The microcomputer 51 physically includes a CPU, a RAM, a ROM, a signal input / output unit, an A / D converter, a clock, and the like, and a program stored in advance in the ROM or the like is executed by the CPU, which will be described later. Various functions can be exhibited.

The control circuit 52 controls the NOx sensor 100, detects the first pumping current Ip1 and the second pumping current Ip2 flowing through the NOx sensor 100, and outputs them to the microcomputer 51.

Next, the configuration of the NOx sensor 100 will be described. The NOx sensor 100 includes a NOx sensor element 101, a housing that houses the NOx sensor element 101, a connector for connecting the NOx sensor element 101 and the NOx detection device 10, and a lead wire connected to the NOx sensor element 101. However, the configuration of the sensor itself is known. Therefore, the following description will be made with reference to a cross-sectional view of the NOx sensor element 101 shown in FIG.

The NOx sensor element 101 has a structure in which a first solid electrolyte layer 111, an insulating layer 140, a second solid electrolyte layer 121, an insulating layer 145, a third solid electrolyte layer 131, and

insulating layers

162 and 163 are stacked in this order. A first measurement chamber 150 is defined between the first solid electrolyte layer 111 and the second solid electrolyte layer 121, and a first diffusion resistor 151 disposed at the entrance (left end in FIG. 1) of the first measurement chamber 150. The measurement gas GM is introduced from the outside via

A second diffusion resistor 152 is disposed at the end of the first measurement chamber 150 opposite to the inlet, and communicates with the first measurement chamber 150 on the right side of the first measurement chamber 150 via the second diffusion resistor 152. A second measurement chamber 160 is defined. The second measurement chamber 160 is formed between the first solid electrolyte layer 111 and the third solid electrolyte layer 131 through the second solid electrolyte layer 121.

A long plate-like heater 164 extending along the longitudinal direction of the NOx sensor element 101 is embedded between the

insulating layers

162 and 163. The heater 164 is used to raise the temperature of the gas sensor to the activation temperature, increase the conductivity of oxygen ions in the solid electrolyte layer, and stabilize the operation of the gas sensor.

The

insulating layers

140 and 145 are mainly made of alumina, and the first diffusion resistor 151 and the second diffusion resistor 152 are made of a porous material such as alumina. The heater 164 is made of platinum or the like.

The first pumping cell 110 includes a first solid electrolyte layer 111 mainly composed of zirconia having oxygen ion conductivity, an inner first pumping electrode 113 disposed so as to sandwich the first solid electrolyte layer 111, and an outer first pumping electrode serving as a counter electrode. 112. The inner first pumping electrode 113 faces the first measurement chamber 150. Both the inner first pumping electrode 113 and the outer first pumping electrode 112 are mainly made of platinum, and the surface of each electrode is covered with a protective layer 114 made of a porous material.

The oxygen concentration detection cell 120 includes a second solid electrolyte layer 121 mainly composed of zirconia, and a detection electrode 122 and a reference electrode 123 arranged so as to sandwich the second solid electrolyte layer 121. The detection electrode 122 faces the first measurement chamber 150 on the downstream side of the inner first pumping electrode 113. Both the detection electrode 122 and the reference electrode 123 are mainly made of platinum.

The insulating layer 145 is cut out so that the reference electrode 123 in contact with the second solid electrolyte layer 121 is disposed inside, and the cut-out portion is filled with a porous body to form the reference oxygen chamber 170. . Then, a weak constant value of current is supplied to the oxygen concentration detection cell 120 in advance by using the control circuit 52, so that oxygen is sent from the first measurement chamber 150 into the reference oxygen chamber 170 to be an oxygen reference.

The second pumping cell 130 includes a third solid electrolyte layer 131 mainly composed of zirconia, an inner second pumping electrode 133 disposed on the surface of the third solid electrolyte layer 131 facing the second measurement chamber 160, and a counter electrode. And a second pumping counter electrode 132. Both the inner second pumping electrode 133 and the second pumping counter electrode 132 are mainly composed of platinum.

The second pumping counter electrode 132 is disposed in the cutout portion of the insulating layer 145 on the third solid electrolyte layer 131 and faces the reference oxygen chamber 170 so as to face the reference electrode 123.

The inner first pumping electrode 113, the detection electrode 122, and the inner second pumping electrode 133 are each connected to a reference potential. The outer first pumping electrode 112, the reference electrode 123, and the second pumping counter electrode 132 are connected to the control circuit 52. The heater 164 is connected to the control circuit 52.

The control circuit 52 has the following functions.

The control circuit 52 supplies the first pumping current Ip1 between the inner first pumping electrode 113 and the outer first pumping electrode 112, and detects the first pumping current Ip1 at that time. At this time, a voltage Vp1 is generated between the inner first pumping electrode 113 and the outer first pumping electrode 112.

The control circuit 52 detects the interelectrode voltage Vs between the detection electrode 122 and the reference electrode 123.

The control circuit 52 compares the reference voltage (for example, 425 mV) with the above-described interelectrode voltage Vs. Then, the Ip1 current is controlled so that the interelectrode voltage Vs becomes equal to the reference voltage, and the oxygen concentration in the first measurement chamber 150 is adjusted so that NOx is not decomposed.

The control circuit 52 causes a weak current Icp to flow between the detection electrode 122 and the reference electrode 123, sends oxygen from the first measurement chamber 150 into the reference oxygen chamber 170, and the reference electrode 123 has a predetermined oxygen concentration as a reference. To expose.

The control circuit 52 has a constant voltage Vp2 between the inner second pumping electrode 133 and the second pumping counter electrode 132 such that the NOx gas in the measurement gas GM is decomposed into oxygen (O ₂ ) and nitrogen (N ₂ ). (Eg, 450 mV) is applied to decompose NOx into nitrogen and oxygen.

The control circuit 52 detects the second pumping current Ip2 flowing through the second pumping cell 130 so that oxygen generated by the decomposition of NOx is pumped out of the second measurement chamber 160.

The control circuit 52 outputs the detected values of the first pumping current Ip1 and the second pumping current Ip2 to the microcomputer 51.

Next, an example of control of the NOx sensor 100 using the control circuit 52 will be described. First, when the engine is started and supplied with electric power from an external power source, the heater 164 to which the heater voltage Vh is applied is activated via the control circuit 52, and the first pumping cell 110, the oxygen concentration detection cell 120, the second The pumping cell 130 is heated to the activation temperature. In addition, the control circuit 52 causes a weak current Icp to flow between the detection electrode 122 and the reference electrode 123, and sends oxygen from the first measurement chamber 150 into the reference oxygen chamber 170 to obtain an oxygen reference.

When each of the

cells

110, 120, and 130 is heated to the activation temperature, the first pumping cell 110 converts the oxygen in the measurement gas (exhaust gas) GM that has flowed into the first measurement chamber 150 into the first inner pumping. Pumping from the electrode 113 toward the outer first pumping electrode 112.

At this time, the oxygen concentration in the first measurement chamber 150 corresponds to the interelectrode voltage Vs (interterminal voltage Vs) of the oxygen concentration detection cell 120. For this reason, the control circuit 52 controls the first pumping current Ip1 flowing through the first pumping cell 110 so that the interelectrode voltage Vs becomes the reference voltage, so that the oxygen concentration in the first measurement chamber 150 can be NOx. Adjust so as not to disassemble as much as possible.

The gas GM to be measured whose oxygen concentration is adjusted further flows toward the second measurement chamber 160. Then, the control circuit 52 uses a constant voltage Vp2 (the oxygen concentration detection cell 120) as an inter-electrode voltage (inter-terminal voltage) of the second pumping cell 130 such that the NOx gas in the measurement gas GM is decomposed into oxygen and N 2 gas. A voltage higher than the control voltage value (for example, 450 mV) is applied to decompose NOx into nitrogen and oxygen. Then, the second pumping current Ip2 flows through the second pumping cell 130 so that oxygen generated by the decomposition of NOx is pumped out of the second measurement chamber 160. At this time, there is a linear relationship between the second pumping current Ip2 and the NOx concentration. Therefore, when the control circuit 52 detects the second pumping current Ip2, the microcomputer 51 can detect the NOx concentration in the gas to be measured based on the detected second pumping current Ip2.

However, even if the NOx concentration in the exhaust gas is 0, the second pumping current Ip2 corresponding to this NOx concentration generates a predetermined current value (so-called offset value). Further, this offset value tends to change due to the influence of temperature change, aging change, manufacturing variation, and the like. For this reason, the microcomputer 51 of the NOx detection device 10 is configured to correct the second pumping current Ip2 (sensor output) detected by the control circuit 52 and improve the detection accuracy of the sensor output and the NOx concentration.

Referring to FIGS. 2 and 3, a method for correcting the sensor output of the NOx sensor 100 implemented by the NOx detection device 10 will be described. In the following description, the second pumping current Ip2 is also expressed as “sensor electrode current”.

FIG. 2 shows an example of the element temperature and sensor electrode current characteristics of the NOx sensor 100. The horizontal axis in FIG. 2 represents the element temperature [° C.], and more specifically, the operating temperature of the NOx sensor element 101. The vertical axis in FIG. 2 indicates the sensor electrode current [μA], that is, the second pumping current Ip2. A graph I1 connecting the rhombus plots shows an example of the characteristics of the NOx sensor 100 in use under an arbitrary condition, and a graph I2 connecting the square plots shows an example of the characteristics in the initial state when the sensor is manufactured. A graph connecting the circle plots shows a difference (I1-I2) between these characteristics. In the example shown in FIG. 2, the NOx concentration as the specific gas component is 0 ppm. That is, each characteristic shown in FIG. 2 corresponds to the offset value output without depending on the NOx concentration in the exhaust gas.

As shown in graphs I1 and I2 in FIG. 2, the sensor electrode current increases as the element temperature increases, and conversely, the sensor electrode current tends to decrease as the element temperature decreases. Further, at any element temperature (for example, A ° C.), the sensor electrode current at the same element temperature tends to increase as the usage time elapses from the initial state. That is, the characteristic between the element temperature and the sensor electrode current is, as indicated by a graph I2-I1 in FIG. 2, for example, a transition from the graph I2 to the graph I1, and the entire characteristic as the sensor usage time elapses. Tends to base up in the direction of increasing current value.

Thus, the characteristic between the element temperature of the NOx sensor 100 and the sensor electrode current shown in FIG. 2, that is, the offset amount of the sensor output of the NOx sensor 100 varies due to various influences such as the element temperature and aging. This causes a shift in the sensor output.

The reason why such characteristics occur in the sensor output of the NOx sensor 100 is mainly due to the influence of the amount of electron conduction. The amount of electron conduction is the amount of electrons flowing through the device electrode regardless of the gas atmosphere when a voltage is applied to the sensor. It is known that the amount of electron conduction varies due to various effects such as variations in sensor solids, aging, and temperature. Therefore, in this embodiment, attention is paid to the characteristics of the electron conduction amount. By sequentially measuring the amount of electron conduction and updating the correction amount of the sensor output in accordance with the change in the amount of change in the amount of electron conduction within a predetermined range, the NOx concentration is accurately derived. Specifically, in the NOx sensor system 1 of the first embodiment, as shown in FIG. 2, the correction amount d according to the increase or decrease in the difference c between the sensor electrode currents a and b at two predetermined element temperatures A and B. Update.

Hereinafter, the sensor output correction amount update process will be described along the procedure of the flowchart of FIG. A series of processing of the flowchart shown in FIG. 3 is performed by the microcomputer 51 of the NOx detection apparatus 10 at predetermined intervals, for example.

In step S101, it is confirmed whether or not a predetermined operation condition for performing the correction amount update process is satisfied. This operating condition can be set under the operating environment where the output amount and temperature of the exhaust gas in the engine exhaust pipe are relatively stable. For example, when the engine is turned off, during fuel cut control, idling operation Time can be included. As a result of the determination in step S101, if the predetermined operating condition is satisfied, the process proceeds to step S102, and if not, the control flow ends.

In step S102, the heater 164 is controlled through the control circuit 52 so that the element temperature becomes a predetermined A ° C. When the process of step S102 is completed, the process proceeds to step S103.

In step S103, the sensor electrode current a at the element temperature A ° C. is measured via the control circuit 52, and this current value is recorded. The sensor electrode current a is output information of the NOx sensor 100 used by the microcomputer 51 to calculate the NOx concentration in the measurement gas GM, and corresponds to the second pumping current Ip2 described above. When the process of step S103 is completed, the process proceeds to step S104.

In step S104, the heater 164 is controlled via the control circuit 52 so that the element temperature becomes a predetermined B ° C. When the process of step S104 is completed, the process proceeds to step S105.

In step S105, the sensor electrode current b at the element temperature B ° C. is measured via the control circuit 52, and this current value is recorded. When the process of step S105 is completed, the process proceeds to step S106.

Here, the element temperature A used in steps S102 to S105 is preferably the activation temperature of each

cell

110, 120, 130 in the NOx sensor element 101. Since the activation temperature in the case of the NOx sensor 100 is in the range of 750 to 850 ° C., for example, the element temperature A can be set to 800 ° C. Further, it is preferable that the element temperature B is higher than the element temperature A and does not overlap with a steady deviation (for example, ± 50 ° C.) of temperature control of the element temperature A. Therefore, the element temperature B can be set to 900 ° C. which is 100 ° C. higher than the element temperature A, for example. By setting the element temperatures A and B in this way, it is possible to easily produce a difference in the change amount c of the electron conduction amount between the two temperatures.

In step S106, the change amount c of the electron conductivity is calculated based on the sensor electrode currents a and b recorded in steps S103 and S105. The microcomputer 51 calculates, for example, the difference (c = b−a) between the sensor electrode currents a and b as the amount of change in electron conduction c. The amount of change in electronic conductivity c may be a relative difference between the sensor electrode currents at two predetermined temperatures. In addition to the difference, the ratio, or the difference or ratio multiplied by a coefficient, a , B can also be used for calculation. When the process of step S106 is completed, the process proceeds to step S107.

In step S107, a correction amount d corresponding to the electron conduction amount change amount c calculated in step S106 is set. For example, the microcomputer 51 stores in advance a map including a plurality of sets of the change amount c and the correction amount d corresponding to the change amount c, and refers to the map based on the change amount c calculated in step S106. Thus, the correction amount d can be selected. The correspondence between the change amount c and the correction amount d can set the correction amount d in a direction in which the corrected sensor output value approaches the reference value in the initial state according to the change amount c. For example, on the basis of the correction amount d0 when the amount of change in electron conduction c0 in the initial state at the time of sensor fabrication is used as a reference, the correction amount is decreased when the change amount c is larger than the initial value c0, and the change amount c is the initial value. When it decreases from c0, the correction amount d can be increased.

In step S108, the sensor output value is corrected using the correction amount d set in step S107. For example, the microcomputer 51 multiplies the second pumping current Ip2 (sensor electrode current) measured via the control circuit 52 by the correction amount d, or adds or subtracts the sensor output value to the NOx concentration. Convert to. When the process of step S108 is completed, this control flow ends.

Next, the effect of the first embodiment will be described. According to the NOx detection device 10 (control device of the NOx sensor 100) and the NOx sensor system 1 of the first embodiment, the microcomputer 51 of the NOx detection device 10 sets the change amount c of the amount of electron conduction generated in the NOx sensor 100. Accordingly, the second pumping current Ip2 measured by the control circuit 52, which is the sensor output of the exhaust gas sensor 100, is corrected.

As described with reference to FIG. 2, the offset amount of the sensor output of the NOx sensor 100 fluctuates due to various influences such as element temperature and aging, and the cause is mainly the electrons generated in the NOx sensor 100. The effect of conductivity is considered. According to the configuration of the first embodiment, the sensor output of the NOx sensor 100 can be appropriately corrected in accordance with the change amount c of the electron conduction amount. It can suppress suitably and can improve the detection accuracy of a sensor output. Further, by improving the detection accuracy of the sensor output, it is possible to improve the measurement accuracy of the NOx concentration that is output from the sensor output.

Further, according to the NOx detection device 10 and the NOx sensor system 1 of the first embodiment, the microcomputer 51 of the NOx detection device 10 calculates the change amount c of the electron conduction amount based on the sensor output at a predetermined element temperature. Then, the correction amount d is changed in accordance with the change amount c, and the sensor output is corrected using the changed correction amount d to be output as the NOx concentration. More specifically, the sensor outputs (sensor electrode currents a and b) at the two element temperatures A and B are measured, and the change amount c of the electron conduction amount is calculated based on these two sensor output values.

With this configuration, both the current sensor electrode currents a and b are used to calculate the amount of change in electronic conductivity c. Therefore, the element temperature-sensor output characteristics described with reference to FIG. The amount of change in electron conduction c can be calculated, and the correction amount d can be changed. In addition, the element temperature-sensor output characteristics shown in FIG. 2 are mainly due to the amount of electron conduction as described above, but as other factors, the

cell

110, 120, 130 of the NOx sensor element 101 has the other factors. The influence of oxygen remaining inside (residual O ₂ ) is also conceivable. In both cases, by calculating the amount of change in electronic conductivity c using the two current sensor electrode currents a and b, the occurrence of sensor output deviation due to residual O ₂ can be suitably suppressed, and the detection accuracy of the sensor output can be improved. It can be further improved.

Further, according to the NOx detection device 10 and the NOx sensor system 1 of the first embodiment, the microcomputer 51 of the NOx detection device 10 is in a predetermined operating environment in which the exhaust gas in the exhaust pipe is stable when the engine is operating. When the engine is off (for example, when the engine is off, during fuel cut control, during idling, etc.), the correction amount d is changed.

With this configuration, the sensor outputs (sensor electrode currents a and b) of the element temperatures A and B are measured in a predetermined operating environment where the exhaust gas is stable and the fluctuation of the NOx concentration in the exhaust gas is extremely small. Therefore, it is possible to improve the detection accuracy of the change amount c of the electron conductivity calculated based on these. Therefore, the correction amount d can be changed with high accuracy, and the measurement accuracy of the NOx concentration can be further improved.

In the first embodiment, the configuration in which the change amount c of the electron conduction amount is calculated using the sensor electrode currents a and b at the two element temperatures A and B is not limited to this. The change amount may be calculated using the sensor electrode current at the element temperature described above. Thereby, the amount of change can be calculated with higher accuracy. In this case, the change amount c of the electron conduction amount can be calculated using a function having three current values as arguments.

[Second Embodiment]
A second embodiment will be described with reference to FIGS. The configuration of the second embodiment is the same as that of the first embodiment, but the method for updating the sensor output correction amount is different. Specifically, in the first embodiment, the microcomputer 51 of the NOx detection device 10 measures sensor outputs (sensor electrode currents a and b) at two element temperatures A and B, and outputs these two sensor output values. In the second embodiment, as shown in FIG. 2, the sensor output (sensor electrode current a) at a single element temperature A is measured as shown in FIG. Then, based on the measured sensor electrode current a and the reference current value, a change amount f of the electron conduction amount is calculated. As the reference current value, for example, an initial value (sensor electrode current initial value e) of the sensor output at the same element temperature A as previously described, which is measured and stored in advance when the NOx sensor 100 is manufactured, can be used. .

The update process of the sensor output correction amount in the second embodiment will be described along the procedure of the flowchart of FIG. A series of processing of the flowchart shown in FIG. 4 is performed by the microcomputer 51 of the NOx detection device 10 at predetermined intervals, for example. Note that steps S201 to S203 and S207 are the same as steps S101 to S103 and S108 in FIG.

In step S204, the sensor electrode current initial value e at the time of sensor fabrication is read. As the sensor electrode current initial value e, for example, when the sensor fabrication operation is completed, the sensor electrode current at the same element temperature A ° C. as in step S203 is measured, and this current value is recorded in the microcomputer 51 in advance. ing. When the process of step S204 is completed, the process proceeds to step S205.

In step S205, based on the sensor electrode current a and the sensor electrode current initial value e recorded and read in steps S203 and S204, a change amount f of the electron conduction amount is calculated. For example, as described in step S106 of FIG. 3, the microcomputer 51 calculates the amount of change in electron conduction f by the difference between the two (f = ae) and various calculations. When the process of step S205 is completed, the process proceeds to step S206.

In step S206, a correction amount g corresponding to the electron conduction amount change amount f calculated in step S205 is set. For example, the microcomputer 51 stores in advance a map including a plurality of sets of the change amount f and the correction amount g corresponding to the change amount f, and refers to the map based on the change amount f calculated in step S205. Thus, the correction amount g can be selected. In addition, the correspondence between the change amount f and the correction amount g can be set such that the corrected sensor output value approaches the reference value in the initial state according to the change amount f. For example, when the change amount f increases in the positive direction with reference to the correction amount g0 when the change amount f is 0 (when the sensor electrode current a is the same as the sensor electrode current initial value e), the correction amount is decreased. When the change amount f decreases in the negative direction, the correction amount g can be increased.

As described above, also in the second embodiment, similarly to the first embodiment, the sensor output of the exhaust gas sensor 100 can be appropriately corrected in accordance with the change amount f of the electron conduction amount generated in the NOx sensor 100. Therefore, the same effect as the first embodiment can be obtained.

In the second embodiment, the sensor electrode current initial value e is used as the reference current value for calculating the difference from the sensor output at the single element temperature A. However, the reference current value is caused by secular change. It is only necessary that the output deviation of the sensor output at the same element temperature A can be clearly grasped. In this case, for example, when the correction amount update process of FIG. 4 has been performed a plurality of times in the past, the sensor electrode current a measured a predetermined number of times can be used as the reference current value.

The embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. That is, those specific examples modified by appropriate design by those skilled in the art are also included in the scope of the present disclosure as long as they have the features of the present disclosure. For example, the elements included in each of the specific examples described above and their arrangement, materials, conditions, shapes, sizes, and the like are not limited to those illustrated, and can be changed as appropriate. Moreover, each element with which each embodiment mentioned above is provided can be combined as long as technically possible, and the combination of these is also included in the scope of the present disclosure as long as it includes the features of the present disclosure.

Claims

A control device (10) for controlling an exhaust gas sensor (100) for detecting a concentration of a specific gas component in exhaust gas of an internal combustion engine,
The sensor output (Ip2) of the exhaust gas sensor is corrected according to the amount of change (c) in the amount of electron conduction generated in the exhaust gas sensor.
Control device for exhaust gas sensor.
A change amount (c, f) of the electron conduction amount is calculated based on the sensor output (a, b) at a predetermined element temperature (A, B), and a correction amount (d, g) according to the change amount. The sensor output is corrected using the changed correction amount and output as the concentration of the specific gas component.
The exhaust gas sensor control device according to claim 1.
The sensor outputs (a, b) at at least two element temperatures (A, B) are measured, and the change amount (c) of the electron conduction amount is calculated based on the at least two sensor output values. The correction amount (d) is changed according to
The exhaust gas sensor control device according to claim 2.
The sensor output (a) at a predetermined element temperature (A) is measured, the change amount (f) of the electron conduction amount is calculated based on the measured sensor output and a reference current value (e), Change the correction amount (g) according to the amount of change,
The exhaust gas sensor control device according to claim 2.
The reference current value is an initial value (e) of a sensor output at the element temperature when the exhaust gas sensor is manufactured.
The exhaust gas sensor control device according to claim 4.
The correction amount is changed when the operating state of the internal combustion engine is in a predetermined operating environment in which the exhaust gas in the exhaust pipe is stable.
The exhaust gas sensor control device according to any one of claims 2 to 5.
An exhaust gas sensor (100) for detecting the concentration of a specific gas component in the exhaust gas of the internal combustion engine;
A control device (10) according to any one of claims 1 to 6;
An exhaust gas sensor system (1) comprising: