JP6255948B2 - Gas sensor control device - Google Patents

Description

  The present invention relates to a gas sensor control device.

  For example, there is known a gas sensor that detects exhaust gas discharged from an in-vehicle engine and detects the NOx concentration in the exhaust gas. The gas sensor (NOx sensor) includes a pump cell, a monitor cell, and a sensor cell each having a solid electrolyte body and a pair of electrodes disposed on the solid electrolyte body, and oxygen in the exhaust gas introduced into the chamber. A gas that is discharged by a pump cell, detects the amount of residual oxygen by a monitor cell, and detects the NOx concentration by a sensor cell from the gas after the oxygen discharge has been put into practical use.

  Various techniques for performing abnormality determination on this type of gas sensor have been proposed. For example, in the technique described in Patent Document 1, a deterioration detection cell is provided in the vicinity of a sensor cell, and an output equivalent to a deterioration product of the sensor cell is obtained by the deterioration detection cell. Then, the output of the sensor cell is compared with the output of the deterioration detection cell to determine whether or not the NOx sensor is deteriorated.

JP 2009-175014 A

  However, the conventional technique requires a deterioration detection cell for detecting sensor deterioration in addition to the pump cell, the monitor cell, and the sensor cell, resulting in a complicated configuration.

  The main object of the present invention is to provide a gas sensor control device that can appropriately determine abnormality of a gas sensor without causing complication of the configuration.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

  The gas sensor control device (40) of the present invention includes a pump cell (31) having a solid electrolyte body (11, 12) and a pair of electrodes (32, 33, 36 to 38) arranged on the solid electrolyte body. ), Which is applied to a gas sensor (10) including a monitor cell (34) and a sensor cell (35), in which the pump cell discharges oxygen in the gas to be detected introduced into the gas chamber (14, 16). After the oxygen is discharged, the monitor cell outputs a signal corresponding to the concentration of residual oxygen in the gas chamber, and the sensor cell outputs a signal corresponding to the concentration of a specific component other than oxygen in the gas chamber. ing. And, when the monitor cell detection value obtained from the output signal of the monitor cell and the sensor cell detection value obtained from the output signal of the sensor cell, the sensor cell detection value is smaller than the monitor cell detection value, An abnormality determining means for determining that an abnormality has occurred in the gas sensor.

  The gas sensor having the above configuration is, for example, a NOx sensor that detects NOx concentration in exhaust gas discharged from the engine, and has a configuration including a pump cell, a monitor cell, and a sensor cell. In such a gas sensor, the residual oxygen concentration in the gas chamber is detected by the monitor cell from the gas after the oxygen is discharged by the pump cell, and the concentration of a specific component other than oxygen is detected by the sensor cell. In this case, a detection output corresponding to the amount of residual oxygen is obtained according to the monitor cell, whereas a detection output corresponding to the amount of residual oxygen and other specific components is obtained according to the sensor cell. Therefore, originally, it is assumed that the sensor cell detection value> the monitor cell detection value. On the contrary, if the sensor cell detection value <the monitor cell detection value, it can be determined that an abnormality has occurred in the gas sensor. In such abnormality determination, the configuration of the gas sensor is not forced to change. As described above, it is possible to appropriately determine abnormality of the gas sensor without causing complication of the configuration.

The block diagram which shows the element internal structure of a NOx sensor, and a sensor control circuit. The block diagram which shows the outline | summary of an engine system. The figure which shows the output characteristic of a NOx sensor. The flowchart which shows the abnormality determination process of a NOx sensor. The flowchart which shows the setting process for setting a determination value.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment embodying a gas sensor control device of the present invention will be described with reference to the drawings. In the present embodiment, a NOx concentration detection device that uses a NOx sensor provided in an exhaust pipe of an in-vehicle engine (internal combustion engine) and detects the NOx concentration in the exhaust based on the output of the NOx sensor will be described. A configuration shown in FIG. 2 is assumed as an engine system to which the NOx concentration detection device is applied.

  In FIG. 2, an engine 50 is a multi-cylinder diesel engine, for example, and has a plurality of injectors 51 for injecting fuel. An exhaust purification device 53 is provided in the exhaust pipe 52 of the engine 50. The exhaust purification device 53 is a NOx purification catalyst such as a NOx occlusion reduction type catalyst or an ammonia selective reduction catalyst, and NOx and the like are purified when the exhaust passes through the exhaust purification device 53. Further, at least one of the upstream side and the downstream side of the exhaust gas purification device 53 is provided with a NOx sensor 10 that detects the NOx concentration in the exhaust gas. In FIG. 2, the NOx sensor 10 is provided on both the upstream side and the downstream side of the exhaust purification device 53, but the configuration may be provided only on one of them.

  The ECU 60 is an electronic control device including a known microcomputer including a CPU, various memories, and the like. The ECU 60 receives a detection signal from the NOx sensor 10 and also detects a rotation speed of the engine 50. A detection signal is input from 61 or a load sensor 62 that detects an engine load such as an accelerator opening. The ECU 60 performs fuel injection control of the injector 51, deterioration determination of the exhaust purification device 53, and the like based on these detection signals and the like.

  Next, the sensor element 10a constituting the NOx sensor 10 will be described with reference to FIG. The sensor element 10a has a so-called laminated structure, and its internal structure is shown in FIG. The horizontal direction in the figure corresponds to the longitudinal direction of the sensor element 10a. The right side of the figure is the element base end side (exhaust pipe attachment site side), and the left side of the figure is the element tip side. The sensor element 10a has a so-called three-cell structure including a pump cell, a sensor cell, and a monitor cell, and each cell is stacked and configured. Since the monitor cell has a function of discharging oxygen in the gas like the pump cell, the monitor cell may be referred to as an auxiliary pump cell or a second pump cell.

  In the sensor element 10a, the solid electrolyte bodies 11 and 12 made of an oxygen ion conductive material such as zirconia are formed in a sheet shape, and are stacked at a predetermined interval above and below the figure via spacers 13 made of an insulating material such as alumina. ing. Among these, an exhaust inlet 11a is formed in the solid electrolyte body 11 on the upper side of the figure, and exhaust around the sensor element is introduced into the first chamber 14 through the exhaust inlet 11a. The first chamber 14 communicates with the second chamber 16 via the throttle unit 15. Both chambers 14 and 16 correspond to gas chambers. On the upper surface side of the solid electrolyte body 11 in the figure, a porous diffusion layer 17 for taking in and out the exhaust gas with a predetermined diffusion resistance is provided, and an insulating layer 19 for partitioning the air passage 18 is provided. .

  Further, an insulating layer 21 made of alumina or the like is provided on the lower surface side of the solid electrolyte body 12 in the figure, and an atmospheric passage 22 is formed by the insulating layer 21. A heater (heating element) 23 is embedded in the insulating layer 21 for heating the entire sensor. In this case, the pump 23, the monitor cell 34, and the sensor cell 35 are heated by the heater 23, and activation of each of these cells 31, 34, 35 is promoted. The heater 23 generates thermal energy by power supply from a battery power source (not shown).

  The solid electrolyte body 12 on the lower side of the figure is provided with a pump cell 31 so as to face the first chamber 14. The pump cell 31 takes in and out oxygen in the exhaust gas introduced into the first chamber 14. The residual oxygen concentration in the chamber 14 is adjusted to a predetermined concentration. The pump cell 31 has a pair of upper and lower electrodes 32 and 33 provided with the solid electrolyte body 12 sandwiched therebetween, and in particular, the electrode 32 on the first chamber 14 side is a NOx inert electrode (an electrode that is difficult to decompose NOx). Yes. The pump cell 31 decomposes oxygen present in the first chamber 14 in a state where a voltage is applied between the electrodes 32 and 33 and discharges it from the electrode 33 to the atmosphere passage 22 side.

  Further, a monitor cell 34 and a sensor cell 35 are provided in the upper solid electrolyte body 11 in the drawing so as to face the second chamber 16. After the surplus oxygen is discharged by the pump cell 31 described above, the monitor cell 34 generates a current output in accordance with the electromotive force or voltage application according to the residual oxygen concentration in the second chamber 16. The sensor cell 35 detects the NOx concentration from the gas in the second chamber 16 as the “specific component concentration”.

  The monitor cell 34 and the sensor cell 35 are arranged side by side at positions close to each other, and have a configuration in which electrodes 36 and 37 are provided on the second chamber 16 side and a common electrode 38 is provided on the atmosphere passage 18 side. That is, the monitor cell 34 is constituted by the solid electrolyte body 11, the electrode 36 and the common electrode 38 disposed so as to face each other, and the sensor cell 35 is similarly configured to face the solid electrolyte body 11 and the electrode 37 disposed so as to face it. And the common electrode 38. The electrode 36 (electrode on the second chamber 16 side) of the monitor cell 34 is made of a noble metal such as Au—Pt that is inactive to NOx, whereas the electrode 37 (electrode on the second chamber 16 side) of the sensor cell 35 is active for NOx. It consists of noble metals such as platinum Pt and rhodium Rh. For convenience, in the drawing, the monitor cell 34 and the sensor cell 35 are shown side by side with respect to the exhaust flow direction (the left-right direction in the drawing). It is arranged to become.

  Here, the pump cell 31, the monitor cell 34, and the sensor cell 35 are provided side by side in the longitudinal direction of the sensor element 10a, the pump cell 31 is provided at the distal end side of the sensor element 10a, and the base end side (exhaust pipe attachment side) ) Are provided with a monitor cell 34 and a sensor cell 35.

  In the sensor element 10a configured as described above, the exhaust gas is introduced into the first chamber 14 through the porous diffusion layer 17 and the exhaust gas inlet 11a. When this exhaust gas passes through the vicinity of the pump cell 31, a decomposition reaction occurs by applying a pump cell voltage Vp between the pump cell electrodes 32 and 33, and the exhaust cell passes through the pump cell 31 according to the oxygen concentration in the first chamber 14. Oxygen is taken in and out. At this time, since the electrode 32 on the first chamber 14 side is a NOx inactive electrode, NOx in the exhaust gas is not decomposed in the pump cell 31, but only oxygen is decomposed and discharged from the electrode 33 to the atmospheric passage 22. By the action of the pump cell 31, the inside of the first chamber 14 is maintained in a predetermined low oxygen concentration state.

  The gas that has passed through the vicinity of the pump cell 31 (the gas after the oxygen concentration adjustment) flows into the second chamber 16, and the monitor cell 34 generates an output corresponding to the residual oxygen concentration in the gas. The output of the monitor cell 34 is detected as a monitor cell current Im when a predetermined monitor cell voltage Vm is applied between the monitor cell electrodes 36 and 38. Further, when a predetermined sensor cell voltage Vs is applied between the sensor cell electrodes 37 and 38, NOx in the gas is reduced and decomposed, and oxygen generated at that time is discharged from the electrode 38 to the atmospheric passage 18. At this time, the NOx concentration in the exhaust gas is detected by the current (sensor cell current Is) flowing through the sensor cell 35.

  The sensor control circuit 40 includes a microcomputer 41 that is a main body for sensor control, and a circuit unit having a voltage application unit, a current detection unit, and the like. The microcomputer 41 and the circuit unit are used to connect the electrodes 32 and 33 of the pump cell 31. The pump cell voltage Vp applied to the monitor cell 34, the monitor cell voltage Vm applied between the electrodes 36 and 38 of the monitor cell 34, and the sensor cell voltage Vs applied between the electrodes 37 and 38 of the sensor cell 35 are controlled. Detection values (detection signals) of the pump cell current Ip, the monitor cell current Im, and the sensor cell current Is are sequentially input to the microcomputer 41, and the microcomputer 41 determines the oxygen concentration and NOx concentration in the exhaust based on these detection values. calculate. For example, the microcomputer 41 may be provided in the ECU 60 of FIG.

  In the microcomputer 41, the current detection signal of each cell is input via an A / D converter (not shown). In this case, a current is detected within a current detection range (corresponding to a concentration detection range) determined for each cell, and the current detection value is converted within the voltage conversion range (for example, 0 to 5 V) of the A / D converter. Are taken into the microcomputer 41.

  Next, the characteristics of the pump cell 31, the monitor cell 34, and the sensor cell 35 will be described with reference to FIG. 3A to 3C show basic characteristics under constant oxygen concentration and NOx concentration.

  FIG. 3A is a VI characteristic diagram showing the relationship between the pump cell voltage Vp and the pump cell current Ip as the pump cell characteristic. In FIG. 3A, a flat portion substantially parallel to the voltage axis (horizontal axis) is a limit current region for specifying the pump cell current Ip, and the increase / decrease of the pump cell current Ip corresponds to the oxygen concentration in the exhaust gas. . That is, the pump cell current Ip increases as the oxygen concentration in the exhaust gas increases, and the pump cell current Ip decreases as the oxygen concentration in the exhaust gas decreases. The limit current region shifts to the higher voltage side as the oxygen concentration increases, and accordingly, the applied voltage characteristic (applied voltage line LX1) for determining the pump cell voltage Vp is shifted to the higher voltage side. Yes. Further, the slope portion on the lower voltage side than the limit current region is the resistance dominant region. The slope of the resistance dominating region depends on the element temperature, and the slope is smaller as the element temperature is lower.

  FIG. 3B is a VI characteristic diagram showing the relationship between the monitor cell voltage Vm and the monitor cell current Im as the monitor cell characteristic. In FIG. 3B, a flat portion substantially parallel to the voltage axis (horizontal axis) is a limit current region for specifying the monitor cell current Im, and the increase or decrease in the monitor cell current Im is the residual oxygen concentration in the second chamber 16. It corresponds to. That is, the monitor cell current Im increases as the residual oxygen concentration in the second chamber 16 increases, and the monitor cell current Im decreases as the oxygen concentration decreases. The monitor cell voltage Vm is set to a predetermined value Vm0 that allows the monitor cell current Im corresponding to a predetermined oxygen concentration to be detected in the limit current region.

  Further, FIG. 3C is a VI characteristic diagram showing the relationship between the sensor cell voltage Vs and the sensor cell current Is as the sensor cell characteristic. In FIG. 3B, a flat portion substantially parallel to the voltage axis (horizontal axis) is a limit current region for specifying the sensor cell current Is, and the increase or decrease in the sensor cell current Is is exhausting (in the second chamber 16). Corresponds to the NOx concentration. That is, the sensor cell current Is increases as the NOx concentration in the exhaust gas increases, and the sensor cell current Is decreases as the NOx concentration in the exhaust gas decreases. However, in this case, since residual oxygen exists in the second chamber 16 in addition to NOx, the sensor cell current Is corresponds to the amount of NOx and residual oxygen. The sensor cell voltage Vs is set at a predetermined value Vs0 that enables detection of a sensor cell current Is corresponding to a predetermined NOx concentration in the limit current region.

  Meanwhile, in the NOx sensor 10, the monitor cell current Im has a value corresponding to the amount of oxygen in the second chamber 16, whereas the sensor cell current Is has a value corresponding to the amounts of oxygen and NOx in the second chamber 16. Therefore, if the monitor cell current Im and the sensor cell current Is are compared, it should be essentially Im <Is. However, if an abnormality occurs in the NOx sensor 10, the magnitude relationship between Im and Is may be reversed. Therefore, in the present embodiment, the monitor cell current Im and the sensor cell current Is are compared, and the presence or absence of abnormality of the NOx sensor 10 is determined based on the comparison result.

  FIG. 4 is a flowchart showing an abnormality determination process of the NOx sensor 10, and this process is repeatedly performed by the microcomputer 41 at a predetermined cycle.

  In FIG. 4, in step S <b> 11, it is determined whether or not an abnormality determination execution condition is satisfied. The execution conditions include that the NOx sensor 10 is in an active state, that the engine 50 is performing lean combustion, and the like. And when all these are satisfy | filled, it determines with the implementation conditions being satisfied, and progresses to subsequent step S12.

  In step S12, the monitor cell current Im and the sensor cell current Is are acquired. In subsequent step S13, the characteristic deviation is corrected for the monitor cell current Im and the sensor cell current Is. That is, in the NOx sensor 10, there may be a characteristic deviation (initial characteristic deviation) due to individual differences or a characteristic deviation (characteristic deterioration) due to changes over time. Under such circumstances, sensor abnormality determination There is a concern about the decrease in accuracy. Therefore, each current value is corrected in order to suppress a decrease in determination accuracy due to characteristic deviation.

  Specifically, the monitor cell current Im and the sensor cell current Is when the engine is stopped in the sensor active state (for example, immediately after the IG is turned off) and the difference between the Im and Is and a predetermined reference value are calculated. It is stored as a characteristic error (correction value). Alternatively, the amount of sulfur poisoning (or the amount of oil additive such as Pb) associated with the long-term use of the NOx sensor 10 is estimated, and a characteristic error (correction value) corresponding to the estimated amount is set. Is also possible. For example, it is conceivable to set the characteristic error (correction value) based on the cumulative integrated value of the fuel injection amount, the cumulative exhaust amount, the total travel distance of the vehicle, and the like. In step S13, each time Im and Is are corrected by a characteristic error (correction value). It should be noted that the correction of the characteristic deviation only needs to be performed on at least one of Im and Is, and the configuration may be such that only Im or only Is is corrected.

  Thereafter, in step S14, an output difference ΔI is calculated by subtracting the sensor cell current Is from the monitor cell current Im (ΔI = Im−Is). This output difference ΔI corresponds to the relative difference of the monitor cell detection value with respect to the sensor cell detection value. In the following step S15, it is determined whether or not the output difference ΔI is equal to or greater than a predetermined determination value K. In this case, the determination value K is a positive value. However, it is also possible to set K = zero.

  If ΔI <K, it is determined that the NOx sensor 10 is in a normal state, and this process is terminated. If ΔI ≧ K, the process proceeds to step S16, where it is determined that an abnormality has occurred in the NOx sensor 10. When it is determined that there is an abnormality in the NOx sensor 10, various fail-safe processes such as storing diagnosis data and stopping the catalyst deterioration diagnosis using the NOx sensor output are appropriately performed.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  In the NOx sensor 10, the sensor cell current Is> the monitor cell current Im should be originally satisfied. On the other hand, if the sensor cell current Is <the monitor cell current Im, it can be determined that an abnormality has occurred in the NOx sensor 10. . In such abnormality determination, the configuration change as the NOx sensor 10 is not forced. As described above, it is possible to appropriately determine the abnormality of the NOx sensor 10 without complicating the configuration.

  The monitor cell current Im and the sensor cell current Is are corrected for characteristic deviation, and the sensor abnormality determination is performed using the corrected Im and Is. As a result, even if a characteristic deviation occurs in the NOx sensor 10, the influence of the characteristic deviation can be suppressed and the accuracy of abnormality determination can be increased.

  The sensor abnormality determination is performed based on the monitor cell current Im and the sensor cell current Is acquired under the condition determined to be the lean combustion state. When the engine 50 is in the lean combustion state, NOx is surely contained in the exhaust, unlike the stoichiometric combustion state and the rich combustion state. Therefore, the accuracy of the abnormality determination performed based on the comparison between the monitor cell current Im and the sensor cell current Is can be increased by setting the lean combustion state as the abnormality determination execution condition.

(Other embodiments)
You may change the said embodiment as follows, for example.

  In the above abnormality determination process, the determination value K for abnormality determination may be variably set according to the situation every time, and a specific example is shown below. FIGS. 5A and 5B are flowcharts showing a setting process for setting the determination value K. FIG. This process only needs to be performed before the comparison determination of Im and Is is performed in the abnormality determination process of FIG. 4, and is performed, for example, immediately before step S15 in FIG. When the process of FIG. 5 is applied, the condition for performing the abnormality determination is different from that described above, and in the case of FIG. 5A, the abnormality determination is performed regardless of whether the lean combustion state is present. In the case of (b), an abnormality determination is further carried out regardless of whether or not the fuel cut state. That is, the abnormality determination process is performed even in a state other than the lean combustion state. It is the same that the condition for performing the abnormality determination includes that the NOx sensor 10 is in an active state.

  In FIG. 5A, in step S21, it is determined whether or not a lean combustion state is currently set. If the combustion state is lean, the process proceeds to step S22. If the combustion state is other than lean combustion, the process proceeds to step S23. . In step S22, the determination value K is set to “a”, and in step S23, the determination value K is set to “b”. In this case, since a <b, the determination value K is set to a smaller value in the lean combustion state than in the combustion state other than the lean combustion state.

  That is, when the engine 50 is in the lean combustion state, the amount of NOx in the exhaust gas is increased compared to the case where the engine 50 is in a combustion state other than the lean combustion. For this reason, it is desirable to change the determination value K in order to make the determination accuracy equal when performing abnormality determination in the lean combustion state and in the state where it is not. In the present embodiment, as described above, the determination value K is set to a smaller value in the lean combustion state than in the combustion state other than the lean combustion, so whether the combustion state is lean or not. Therefore, it is possible to improve the accuracy of sensor abnormality determination.

  In FIG. 5B, in step S31, it is determined whether or not the fuel is currently being cut. If the fuel is being cut, the process proceeds to step S32. If not, the process proceeds to step S33. In step S32, the determination value K is set to “c”, and in step S33, the determination value K is set to “d”. In this case, since c> d, the determination value K is set to a larger value when the fuel is being cut than when the fuel is not being cut. Then, the comparison determination of Im and Is is performed using the determination value K set as shown in FIGS.

  That is, when the engine 50 is in the fuel cut state, NOx in the exhaust becomes almost zero. For this reason, it is desirable to change the determination value K in each case in order to make the determination accuracy equal when performing the abnormality determination in the fuel cut state and the state (normal operation state) that is not. In the present embodiment, as described above, when the fuel cut state is set, the determination value K is set to a larger value than when the fuel cut state is not set. The accuracy can be increased.

  In FIG. 5B, the process for determining whether or not the fuel is being cut may be any process that determines whether or not the engine 50 is in the combustion state, and immediately after the operation of the engine 50 is stopped (warm up). You may change to the process which determines that it is a machine stop state).

  Each process of FIGS. 5A and 5B can be realized as one process. In such a case, the determination value K is set separately for three states of a lean combustion state, a combustion state other than lean combustion, and a fuel cut state (combustion stop state), and the determination values in these states are set as Ka, Kb, Kc. In this case, it is preferable that Ka <Kb <Kc.

  In the above embodiment, in determining the sensor abnormality, the output difference ΔI obtained by subtracting the sensor cell current Is from the monitor cell current Im is used as the abnormality determination parameter. However, this may be changed, for example, the monitor cell for the sensor cell current Is The ratio of current Im (= Im / Is) can also be used as an abnormality determination parameter. In any case, any configuration that uses the relative difference between the monitor cell detection value and the sensor cell detection value as the abnormality determination parameter may be used.

  The configuration of the NOx sensor 10 may be different from the configuration shown in FIG. For example, instead of the configuration in which the exhaust gas is introduced into the first chamber 14 via the exhaust gas inlet 11a provided in the solid electrolyte body 11, a diffusion resistance layer is provided between the solid electrolyte bodies 11 and 12 arranged opposite to each other ( For example, a part of the spacer 13 may be a diffusion resistance layer), and the exhaust gas may be introduced into the first chamber 14 through the diffusion resistance layer. In addition, instead of a configuration in which the first chamber 14 and the second chamber 16 are provided as gas chambers and they are communicated with each other via the throttle portion 15, the chambers 14 and 16 are provided as one gas having no throttle portion. You may comprise as a chamber.

  The specific component to be detected may be other than NOx. For example, a gas sensor that uses HC or CO in the exhaust as a detection target (specific component) may be used. In this case, surplus oxygen in the exhaust is discharged by the pump cell, and HC and CO are decomposed from the gas after the surplus oxygen is discharged by the sensor cell to detect HC concentration and CO concentration. In addition, the concentration of ammonia in the gas to be detected may be detected.

  -It can also be embodied as a sensor control device applied to a gas sensor provided in an intake passage of an engine or a gas sensor used in other types of engines such as a gasoline engine in addition to a diesel engine. The gas sensor may be one that detects gas other than exhaust or is used for purposes other than automobiles.

  DESCRIPTION OF SYMBOLS 10 ... NOx sensor (gas sensor), 11, 12 ... Solid electrolyte body, 14, 16 ... Chamber (gas chamber), 31 ... Pump cell, 34 ... Monitor cell, 35 ... Sensor cell, 32, 33, 36-38 ... Electrode, 40 ... Sensor control circuit (acquisition means, abnormality determination means).

Claims (7)

A pump cell (31), a monitor cell (34), and a sensor cell (35) each having a solid electrolyte body (11, 12) and a pair of electrodes (32, 33, 36 to 38) disposed on the solid electrolyte body. In the gas sensor, the pump cell discharges oxygen in the gas to be detected introduced into the gas chamber (14, 16), and after the oxygen is discharged, the monitor cell While outputting a signal according to the residual oxygen concentration in the gas chamber, the sensor cell is adapted to output a signal according to the concentration of a specific component other than oxygen in the gas chamber ,
The gas sensor is a NOx sensor (10) that detects the concentration of NOx in the exhaust gas with the exhaust gas discharged from the internal combustion engine (50) as a detection target, and the sensor cell outputs a signal corresponding to the NOx concentration. A gas sensor control device (40) comprising:
An acquisition means for acquiring a monitor cell detection value obtained from the output signal of the monitor cell and a sensor cell detection value obtained from the output signal of the sensor cell;
An abnormality determining means for determining that an abnormality has occurred in the gas sensor when the sensor cell detection value is smaller than the monitor cell detection value;
Lean determination means for determining that the internal combustion engine is in a lean combustion state;
With
The abnormality determination means performs sensor abnormality determination on the basis of the monitor cell detection value and the sensor cell detection value acquired by the acquisition means under a condition determined to be the lean combustion state. Gas sensor control device. The abnormality determination means performs the abnormality determination regardless of whether or not the internal combustion engine is in a rich combustion state with the NOx sensor being activated, and a relative difference between the monitor cell detection value and the sensor cell detection value is When it is a predetermined determination value or more, it is determined that an abnormality has occurred in the sensor cell,
The gas sensor control device according to claim 1 , further comprising means for setting the determination value to a smaller value when the internal combustion engine is in a lean combustion state than in a combustion state other than lean combustion. The abnormality determination means performs the abnormality determination regardless of whether or not the internal combustion engine is in a combustion stop state with the NOx sensor being activated, and a relative difference between the monitor cell detection value and the sensor cell detection value Is determined to be abnormal in the sensor cell, when is greater than or equal to a predetermined determination value,
Wherein when the internal combustion engine is in a stopped state combustion, gas sensor control device according to claim 1 or 2 comprising means for setting a larger value the determination value than when not in a state of stopping combustion. A pump cell (31), a monitor cell (34), and a sensor cell (35) each having a solid electrolyte body (11, 12) and a pair of electrodes (32, 33, 36 to 38) disposed on the solid electrolyte body. In the gas sensor, the pump cell discharges oxygen in the gas to be detected introduced into the gas chamber (14, 16), and after the oxygen is discharged, the monitor cell While outputting a signal according to the residual oxygen concentration in the gas chamber, the sensor cell is adapted to output a signal according to the concentration of a specific component other than oxygen in the gas chamber ,
The gas sensor is a NOx sensor (10) that detects the concentration of NOx in the exhaust gas with the exhaust gas discharged from the internal combustion engine (50) as a detection target, and the sensor cell outputs a signal corresponding to the NOx concentration. A gas sensor control device (40) comprising:
An acquisition means for acquiring a monitor cell detection value obtained from the output signal of the monitor cell and a sensor cell detection value obtained from the output signal of the sensor cell;
An abnormality determining means for determining that an abnormality has occurred in the gas sensor when the sensor cell detection value is smaller than the monitor cell detection value;
Equipped with a,
The abnormality determination means performs the abnormality determination regardless of whether or not the internal combustion engine is in a rich combustion state with the NOx sensor being activated, and a relative difference between the monitor cell detection value and the sensor cell detection value is When it is a predetermined determination value or more, it is determined that an abnormality has occurred in the sensor cell,
A gas sensor control device comprising: means for setting the determination value to a smaller value when the internal combustion engine is in a lean combustion state than in a combustion state other than lean combustion . The abnormality determination means performs the abnormality determination regardless of whether or not the internal combustion engine is in a combustion stop state with the NOx sensor being activated, and a relative difference between the monitor cell detection value and the sensor cell detection value Is determined to be abnormal in the sensor cell, when is greater than or equal to a predetermined determination value,
The gas sensor control device according to claim 4 , further comprising means for setting the determination value to a larger value when the internal combustion engine is in a combustion stopped state than in a case where the internal combustion engine is not in a combustion stopped state. A pump cell (31), a monitor cell (34), and a sensor cell (35) each having a solid electrolyte body (11, 12) and a pair of electrodes (32, 33, 36 to 38) disposed on the solid electrolyte body. In the gas sensor, the pump cell discharges oxygen in the gas to be detected introduced into the gas chamber (14, 16), and after the oxygen is discharged, the monitor cell While outputting a signal according to the residual oxygen concentration in the gas chamber, the sensor cell is adapted to output a signal according to the concentration of a specific component other than oxygen in the gas chamber ,
The gas sensor is a NOx sensor (10) that detects the concentration of NOx in the exhaust gas with the exhaust gas discharged from the internal combustion engine (50) as a detection target, and the sensor cell outputs a signal corresponding to the NOx concentration. A gas sensor control device (40) comprising:
An acquisition means for acquiring a monitor cell detection value obtained from the output signal of the monitor cell and a sensor cell detection value obtained from the output signal of the sensor cell;
An abnormality determining means for determining that an abnormality has occurred in the gas sensor when the sensor cell detection value is smaller than the monitor cell detection value;
Equipped with a,
The abnormality determination means performs the abnormality determination regardless of whether or not the internal combustion engine is in a combustion stop state with the NOx sensor being activated, and a relative difference between the monitor cell detection value and the sensor cell detection value Is determined to be abnormal in the sensor cell, when is greater than or equal to a predetermined determination value,
A gas sensor control device comprising means for setting the judgment value to a larger value when the internal combustion engine is in a combustion stopped state than in a case where the internal combustion engine is not in a combustion stopped state . Correction means for correcting a characteristic deviation for at least one of the monitor cell detection value and the sensor cell detection value;
The abnormality determining means, the gas sensor control device according to any one of claims 1 to 6 to implement the abnormality determination of the gas sensor using the detected value corrected by said correction means.

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