JP4894948B2 - Exhaust gas sensor deterioration detection device - Google Patents

Description

  The present invention relates to an exhaust gas sensor deterioration detection device that detects deterioration of an exhaust gas sensor of an internal combustion engine.

  The exhaust gas discharged from the internal combustion engine of the vehicle is regulated so that the concentration of NOx or the like (hereinafter referred to as a specific gas) contained in the exhaust gas is not more than a predetermined value, so that the vehicle is equipped with a gas concentration sensor. The specific gas concentration in the exhaust gas is monitored. The gas concentration sensor is provided in the solid electrolyte element, and the temperature control is performed by heating the solid electrolyte element by a heater so that the activation temperature of the specific gas is reached. Therefore, if the performance of the heater is lowered and the solid electrolyte element is excessively heated or insufficiently heated, the specific gas cannot be brought into a desired active state, and it is difficult to detect the specific gas with high accuracy.

For this reason, it is required to detect the performance degradation of the heater, and as such detection means, a method for detecting the performance degradation of the heater by comparing the initial state of the heater with the current state has been proposed (for example, (See Patent Document 1). In the detection method described in Patent Document 1, the initial internal resistance of the gas concentration sensor and the heater and the current internal resistance are compared, and when there is a large change, it is determined that the performance has deteriorated and a predetermined abnormality is detected. Process.
JP 2002-15596A

  However, the method for detecting a decrease in heater performance described in Patent Document 1 uses the gas concentration sensor and the internal resistance of the heater in actual use as the current internal resistance. However, since the internal resistance of the gas concentration sensor and heater may vary greatly depending on the usage conditions, the current internal resistance of the gas concentration sensor and heater in use is not accurately detected. There is. Therefore, if the internal resistance of the gas concentration sensor and the heater in the state of use is the current internal resistance, it is difficult to accurately compare with the initial internal resistance of the heater.

  In view of the above problems, an object of the present invention is to provide a deterioration detection device for an exhaust gas sensor that accurately detects a decrease in the performance of the exhaust gas sensor.

In view of the above problems, the present invention, the heater for heating the element resistance detection circuit for detecting the element resistance of the element of the exhaust gas sensor is heated by a heater, the exhaust gas sensor based on the element resistance which the element resistance detection circuit detects The exhaust gas sensor has deteriorated by comparing the heater current estimated by the first heater current estimating means, the heater current estimated by the first heater current estimating means, and the heater current detected by the heater current detecting means. There is provided a deterioration detection device for an exhaust gas sensor, characterized by comprising deterioration determination means for determining whether or not.

  It is possible to provide an exhaust gas sensor deterioration detection device that accurately detects a reduction in performance of an exhaust gas sensor.

It is the schematic of an exhaust gas sensor. It is a functional block diagram in the deterioration detection apparatus of an exhaust gas sensor. It is an example of element temperature-element resistance MAP and heater temperature-heater resistance MAP. It is a flowchart figure which shows the procedure of the deterioration detection of an exhaust gas sensor. It is an example which shows the relationship between element temperature and heater resistance by which heater resistance was calculated larger than a threshold value. It is a flowchart figure which shows the procedure which detects abnormality of a solid electrolyte element based on element temperature. It is a functional block diagram in the deterioration detection apparatus of an exhaust gas sensor. It is an example of the relationship between the outside air temperature, the temperature of the A / F sensor heater, the temperature of the sub O ₂ sensor heater, the engine cooling water temperature, and the intake air temperature with respect to the soak time. It is a flowchart figure which shows the procedure which detects deterioration of a heater using progress of soak time.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. In the present embodiment, an exhaust gas sensor deterioration detection device 100 that detects deterioration of the heater performance based on the resistance value of the exhaust gas sensor heater will be described.

The exhaust gas sensor will be briefly described. FIG. 1 shows a schematic view of an exhaust gas sensor. The exhaust gas sensor 1 includes an exhaust gas chamber 9 which is formed between a pair of partition walls 2 and 3 including a solid electrolyte and into which exhaust gas is introduced, and is disposed with the partition wall 2 interposed therebetween. released oxygen pump electrodes 8 to release the exhaust gas outside the chamber, the oxygen ions with release of decomposition resulting oxygen ions exhaust gas chamber 9 inside of the NO _X by applying a voltage is arranged to sandwich the partition wall 3 in the exhaust-gas chamber external has a NO _X sensing electrode 25 NO _X concentration is measured from a current value that occurs when the.

  A heater wall 27 is arranged so as to face the partition wall 3 with the spacer 26 interposed therebetween. The heater wall 27 is made of alumina, and a plurality of heaters 28 for heating are arranged inside the heater wall 27. The heater 28 is connected to an external power source (not shown), and the exhaust gas sensor 1 is heated to a predetermined temperature by the heater 28.

  In the exhaust gas chamber 9, exhaust gas is introduced into the exhaust gas flow path formed between the pair of partition walls 2 and 3. The exhaust gas chamber 9 is partitioned by at least a pair of partition walls 2 and 3 and is simultaneously partitioned by the diffusion-controlling wall 5 and the spacer 6 to be shielded from the outside. The diffusion-controlling wall 5 is made of a porous material such as alumina, or a material in which pores are formed in a porous material or a non-porous material, which can introduce exhaust gas into the exhaust gas chamber 9 with a predetermined diffusion-controlling resistance. The spacer 6 is formed of a normal material such as alumina.

  As the solid electrolyte, one having oxygen ion conductivity can be used, for example, a normal solid such as zirconia, bismuth oxide, cerium oxide, or a material obtained by adding yttria, calcia, ceria, magnesia or the like to these materials. Use electrolyte.

  The oxygen pump electrode 8 uses Pt or a known alloy having oxygen sensitivity. Among the oxygen pump electrodes 8, one electrode 4 is disposed on the exhaust gas chamber side surface of the partition wall 2, and the other electrode 7 is disposed on the outer surface of the exhaust gas chamber 9 to constitute the oxygen pump electrode 8. Therefore, by applying a voltage to the oxygen pump electrode 8, the oxygen in the exhaust gas chamber comes into contact with the internal electrode 4 which is an electrode disposed on the exhaust gas chamber side surface of the partition wall 2, and the solid electrolyte contained in the partition wall 2 is removed. Via the external electrode 7 disposed on the outer surface of the exhaust gas chamber, and discharged outside the exhaust gas chamber. The oxygen partial pressure inside the exhaust gas chamber is lowered by the action of the oxygen pump electrode 8.

As the oxygen partial pressure decreases, NO is generated from NO _x inside the exhaust gas chamber, and this NO is detected by the NO _X detection electrode 25. The oxygen partial pressure of oxygen contained in the exhaust gas by reduction is reduced to be in contact to the NO _X sensing electrode 25, the measurement error of the NO _X sensing electrodes caused by the interference of the oxygen is reduced.

As the NO _X detection electrode 25, for example, a Pt / Rh electrode or the like having NO _X selective reduction is used. Similarly to the oxygen pump electrode 8, the NO _X detection electrode 25 has an internal NO _X detection electrode 30 that is one electrode disposed on the exhaust gas chamber side of the partition wall 3, and the external detection electrode 20 that is the other electrode is an exhaust gas chamber. constitute the NO _X sensing electrode disposed 9 external.

When a voltage is applied to the NO _X detection electrode 25, the NO inside the exhaust gas chamber generated by the action of the oxygen pump described above is decomposed by the internal NO _X detection electrode 30 to generate oxygen ions. The oxygen ions are transported to the external detection electrode 20 through the solid electrolyte contained in the partition wall 3 and released to the outside of the exhaust gas chamber, and the NO _x concentration is measured by the current value generated at this time. The NO _X detection electrode 25 is disposed on the most downstream side of the exhaust gas flow, at the same level as the oxygen pump electrode 8 or further downstream. Not only the NO _X detection electrode 25 but also various electrodes for detecting other exhaust gas components may be simultaneously disposed in the exhaust gas chamber.

  In this embodiment, the resistance value of the heater 28 calculated from the resistance value of the heater 28 estimated based on the electrical resistance (hereinafter referred to simply as element resistance) of the solid electrolyte element (hereinafter also referred to simply as element) and the current value of the heater 28. The deterioration detection device 100 of the exhaust gas sensor 1 that detects the deterioration of the heater 28 based on the resistance value will be described.

  FIG. 2 is a functional block diagram of the deterioration detection device 100 for the exhaust gas sensor 1 according to the present embodiment. The exhaust gas sensor deterioration detection device 100 is controlled by an exhaust gas sensor deterioration detection ECU (hereinafter simply referred to as a deterioration detection ECU) 10. An element resistance sensor 11, a heater current sensor 12, and a battery voltage sensor 13 are connected to the deterioration detection ECU 10. Further, the deterioration detection ECU 10 is configured to include first heater resistance estimating means 16, heater resistance calculating means 17, deterioration determining means 18, element temperature-element resistance MAP14, and heater temperature-heater resistance MAP15.

  The element resistance sensor 11 detects the electrical resistance of the solid electrolyte element based on the relationship between the applied voltage and the current, and sends a signal corresponding to the value of the electrical resistance to the deterioration detection ECU 10. For example, the control of the oxygen pump electrode 8 as a pump is temporarily suspended (several microseconds to several milliseconds), and the current I1 when the voltage V1 is applied and the current I2 when the voltage V2 is applied are measured. Then, (V1-V2) / (I1-I2) is calculated as the element resistance. By detecting the element resistance in a state where the oxygen pump electrode 8 is not controlled as a pump, the element resistance can be detected without being affected by the change in the internal resistance of the solid electrolyte element.

  The heater current sensor 12 detects the current of one or more heaters 28 among the currents flowing through the plurality of heaters 28 and sends a signal corresponding to the current value to the deterioration detection ECU 10. The battery voltage sensor 13 detects the voltage of the battery that supplies power to the heater 28 and sends a signal corresponding to the detected voltage value to the deterioration detection ECU 10.

  The element temperature-element resistance MAP14 shows the relationship between the element temperature and the element resistance as shown in FIG. Therefore, by referring to the element temperature-element resistance MAP14, the element resistance is extracted if the element temperature is detected, and the element resistance is extracted if the element resistance is detected. The element temperature-element resistance MAP14 is generated by measuring the element resistance in advance with respect to a predetermined element temperature range, and the deterioration detection ECU 10 holds the generated element temperature-element resistance MAP14.

  The heater temperature-heater resistance MAP15 indicates the relationship between the heater temperature of the normal heater 28 and the heater resistance, as shown in FIG. Therefore, by referring to the heater temperature-heater resistance MAP15, the heater resistance is extracted if the heater temperature is detected, and the heater temperature is extracted if the heater resistance is detected. The heater temperature-heater resistance MAP15 is generated by measuring the heater resistance with respect to a predetermined heater temperature range in advance.

  Since the relationship between the heater temperature and the heater resistance varies depending on individual differences, it is preferable that the heater temperature-heater resistance MAP15 has a width that takes into account the variation due to individual differences. In FIG. 3B, the heater temperature and the resistance lower limit product showing a low resistance, the resistance center product showing a substantially central resistance, and the resistance upper limit product showing a high resistance with respect to the heater temperature are taken as an example. The relationship of heater resistance is shown. Since the heater temperature-heater resistance MAP15 is generated in consideration of the variation as shown in FIG. 3B, a normal range of heater resistance (or heater temperature) is extracted between the widths of the lower limit product and the upper limit product. The

  The first heater resistance estimating means 16 extracts the element temperature from the element temperature-element resistance map 14 based on the element resistance of the exhaust gas sensor, estimates the temperature of the heater 28 based on the extracted element temperature, and estimates the estimated heater 28 The resistance value of the heater 28 that heats the exhaust gas sensor is estimated from the element resistance of the exhaust gas sensor by extracting the resistance of the heater 28 from the heater temperature-heater resistance map 15 based on the temperature. The heater resistance calculation means 17 calculates the resistance value of the heater based on the current value of the heater 28 and the voltage of the battery supplying power to the heater 28. Further, the deterioration determining means 18 compares the two resistance values estimated by the first heater resistance estimating means 16 and the heater resistance calculating means 17 and determines whether or not the exhaust gas sensor has deteriorated.

  Based on the above configuration, the operation of the gas sensor deterioration detection apparatus 100 will be described. FIG. 4 is a flowchart showing a procedure for detecting deterioration of the exhaust gas sensor. The detection of the deterioration of the exhaust gas sensor is performed, for example, in anticipation of the time when the heater and the element temperature are stabilized after the automobile engine is started.

  First, the element resistance sensor 11 detects the electric resistance of the solid electrolyte element, and sends the value of the element resistance to the deterioration detection ECU 10. The deterioration detection ECU 10 refers to the element temperature-element resistance MAP14 and extracts the element temperature corresponding to the element resistance (S11).

  Incidentally, since the solid electrolyte element such as the partition wall 3 is heated by the heater 28, the element temperature is estimated to be approximately the same as the temperature of the heater 28. The deterioration detection ECU 10 estimates the heater temperature of the heater 28 from the extracted element temperature (S12).

  Next, the deterioration detection ECU 10 refers to the heater temperature-heater resistance MAP15 and extracts the heater resistance corresponding to the heater temperature (S13). Since the heater temperature-heater resistance MAP15 is generated for the heater in a normal state, the heater resistance extracted from the heater temperature-heater resistance MAP15 is the heater resistance when the heater 28 is normal.

  Once the heater resistance is extracted, the deterioration detection ECU 10 processes the heater resistance (hereinafter referred to as the element resistance) in which variations due to individual differences of the heaters 28, a difference between the heater temperature and the element temperature, and errors resulting from the measurement of the element resistance are processed. The heater resistance is referred to as heater resistance A) (S14).

  Next, the heater current sensor 12 detects the current value of the heater 28 and sends it to the deterioration detection ECU 10 (S15). Further, the deterioration detection ECU 10 detects the voltage of the battery that supplies power to the heater 28, and based on the battery voltage and the current value of the heater 28, the heater resistance (hereinafter referred to as the heater resistance obtained from the heater current) (Referred to as resistance B) (S16).

  When the heater resistance A and the heater resistance B are calculated, the deterioration detection ECU 10 determines whether or not the difference between them is larger than a predetermined threshold (S17). The heater resistance A is a heater resistance when the heater 28 is normal, and the heater resistance B is the heater resistance of the heater 28 detected by the heater current sensor 12 and calculated by a predetermined procedure. If it is different from the threshold value, it can be determined that an abnormality has occurred in the heater 28 or has deteriorated in the present embodiment (Yes in step S17).

  For example, if the performance of the heater 28 deteriorates or is disconnected, the heater resistance B is calculated to be larger than in a normal state. In this case, even if the element is not heated and a low heater temperature is estimated (S12) and a low heater resistance is extracted (S13), the heater resistance A is in a normal value range, so that the deterioration detection ECU 10 Can be detected. When the performance of one of the plurality of heaters 28 is deteriorated or disconnected, the element is heated by another normal heater 28, so that the heater resistance A is within a normal value range. Since it becomes larger than the resistance A by a predetermined threshold or more, the deterioration detection ECU 10 can detect that the heater 28 has deteriorated.

  For example, when the heater 28 is short-circuited, the heater resistance B is calculated to be smaller than the normal state. In this case, the element may be heated or not heated. However, since the heater resistance A extracted based on the heater temperature is within a normal value range, the deterioration detection ECU 10 indicates that the heater 28 has deteriorated. It can be detected.

  FIG. 5 is a graph showing the relationship between the element temperature and the heater resistance when the heater resistance B is largely calculated. In FIG. 5, the heater resistance (Y axis) is plotted against the element temperature (X axis). A line a in FIG. 5 indicates the heater resistance A, and a line b indicates the heater resistance B. A line c between the lines a and b is a threshold value for determining whether or not the line is deteriorated. Therefore, if the heater resistance B is larger than the line c at the element temperature detected from the element resistance, it is determined that the heater 28 has deteriorated.

  FIG. 5 shows the relationship with the heater resistance in a predetermined range of the element temperature, but the heater resistance B of the deteriorated heater 28 is larger than the threshold value c in the entire temperature range of FIG. The deterioration of the heater 28 can be detected without depending on the element temperature. Further, as shown in FIG. 3B, the threshold value may be provided as shown by a line d in consideration of errors due to individual differences of the heaters 28 or the like. If the threshold value is set small (provided closer to the line a) in consideration of individual differences, heater deterioration can be detected at an early stage even if there are individual differences.

  As described above, according to the present embodiment, when the heater performance decreases and the heater resistance increases, the heater resistance in a normal state can be compared, so that a deteriorated heater can be detected accurately. Further, since errors due to individual differences are processed in the heater resistance in a normal state, it is possible to detect deterioration by reducing the influence due to individual differences in heaters. Further, since the number of steps for calculating the heater resistances A and B is small and the number of newly added parts is small, it is possible to detect the deterioration of the heater while reducing the cost.

  In FIG. 4, the deterioration is determined based on the heater resistance. However, if the relationship between the heater temperature and the heater current is previously measured and the heater temperature and the heater current MAP are generated as shown in FIG. The comparison of S17 is performed based on the heater current, and the deterioration of the heater can be detected. Similarly, if the relationship between the heater temperature and the heater voltage is measured in advance, the deterioration of the heater can be detected based on the heater voltage.

  If this embodiment is applied, not only the deterioration of the heater 28 but also the abnormality of the solid electrolyte element can be detected. FIG. 6 is a flowchart showing a procedure for detecting an abnormality of the solid electrolyte element based on the element temperature.

  First, the deterioration detection ECU 10 calculates the heater resistance B based on the heater current detected by the heater current sensor 12 and the battery voltage detected by the battery voltage sensor 13 (S101). Based on the calculated heater resistance B, the heater temperature is extracted with reference to the heater temperature-heater resistance MAP15 in FIG. 3B (S102). Since the heater temperature is estimated to be approximately the same as the element temperature, the element temperature (hereinafter referred to as element temperature A) is estimated based on the heater temperature (S103).

  Next, the deterioration detection ECU 10 extracts an element temperature corresponding to the element resistance (hereinafter referred to as element temperature B) with reference to the element temperature-element resistance MAP14 based on the electric resistance of the solid electrolyte element (S104). If there is any abnormality in the solid electrolyte element, the extracted element temperature B is expected to be different from the element temperature A by a predetermined threshold or more. Therefore, the deterioration detection ECU 10 compares the element temperatures A and B to determine the solid temperature. Abnormality of the electrolyte element can be detected (S105).

  In this embodiment, a description will be given of a deterioration detection device 100 for an exhaust gas sensor that detects deterioration of a heater based on an intake air temperature or an outside air temperature. FIG. 7 shows a functional block diagram of the exhaust gas sensor deterioration detection apparatus 100 of the present embodiment. In FIG. 7, the same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.

The exhaust gas sensor deterioration detection device 100 is controlled by an exhaust gas sensor deterioration detection ECU (hereinafter simply referred to as a deterioration detection ECU) 10. A soak timer 51, an intake air temperature sensor 52, an A / F sensor heater 53, a sub O ₂ sensor heater 54, an outside air temperature sensor 55, and a water temperature sensor 56 are connected to the deterioration detection ECU 10.

The soak timer 51 measures a time after the engine is stopped (hereinafter referred to as a soak time (a time for stabilizing the component temperature to the environmental temperature)), and sends the measured time to the deterioration detection ECU 10. Further, the intake air temperature sensor 52 detects the temperature of air taken in by the engine and sends it to the deterioration detection ECU 10. The A / F sensor heater 53 is a heater for heating the A / F sensor, detects the temperature of the heater, and sends it to the deterioration detection ECU 10. The sub O ₂ sensor heater 54 is a heater that heats the sub O ₂ sensor, detects the temperature of the heater, and sends the detected temperature to the deterioration detection ECU 10. The outside air temperature sensor 55 and the water temperature sensor 56 detect the temperature of the outside air and the temperature of the engine cooling water, respectively, and send them to the deterioration detection ECU 10.

By the way, when the engine is stopped, heat generation from the engine and power supply to the heater are stopped. For this reason, the temperature of the heater 28 of the exhaust gas sensor deterioration detection device 100, the A / F sensor heater, and the sub O ₂ sensor heater gradually approaches the outside air temperature and the intake air temperature as time elapses after the engine is stopped. . FIG. 8 shows an example of the relationship between the outside air temperature, the temperature of the A / F sensor heater, the temperature of the sub O ₂ sensor heater, the engine cooling water temperature, and the intake air temperature with respect to the soak time. Only the outside air temperature is taken on the right axis, and the outside air temperature shows a substantially constant value.

According to FIG. 8, the temperature of the sub O ₂ sensor heater and the outside air temperature are close to each other after elapse of t1 minutes (for example, 60 minutes), and A / F after elapse of t2 minutes (for example, 120 minutes). Sensor heater temperature and intake air temperature are close to each other. Therefore, when a certain amount of time has elapsed after the engine is stopped, it can be estimated that the temperature of the A / F sensor heater and the temperature of the sub O ₂ sensor heater are approximately the same as the outside air temperature and the intake air temperature.

Similarly to the temperature of the A / F sensor heater and the temperature of the sub O ₂ sensor heater, the temperature of the heater 28 of the exhaust gas sensor deterioration detection device 100 is the same as the outside air temperature and the intake air temperature after a certain period of time has elapsed after the engine is stopped. It can be presumed that the level has reached. Therefore, if the relationship between the soak time and the temperature of the A / F sensor heater is used, the heater 28 is based on the outside air temperature, the temperature of the A / F sensor heater, the temperature of the sub O ₂ sensor heater, the engine cooling water temperature, or the intake air temperature. Can be estimated. If the temperature of the heater 28 is estimated, the heater resistance can be extracted in the same manner as in the first embodiment to detect the deterioration of the exhaust gas sensor. The second heater resistance estimation means 19 in FIG. 7 estimates the resistance value of the heater 28 that heats the exhaust gas sensor based on the temperature detected by the temperature sensor provided in each part of these vehicles.

  FIG. 9 is a flowchart showing a procedure for detecting the deterioration of the heater 28 after the elapse of a predetermined soak time. The detection procedure in FIG. 9 starts, for example, immediately after the automobile engine is stopped. When the detection procedure of FIG. 9 starts, the deterioration detection ECU 10 determines whether or not the soak time has passed a predetermined time TS (S21). The time TS is determined in advance by measuring the relationship between the soak time as shown in FIG. 8 and the temperature of the A / F sensor heater or the like according to the outside air temperature or the season. The deterioration detection ECU 10 repeats the determination in step S21 until the soak time reaches the time TS.

When the soak time elapses time TS, the deterioration detection ECU 10 determines the temperature detected by each sensor from the intake air temperature sensor 52, the A / F sensor heater 53, the sub-O ₂ sensor heater 54, the outside air temperature sensor 55, and the water temperature sensor 56. Obtain (S22).

  The deterioration detection ECU 10 extracts, as the temperature of the heater 28, a temperature suitable for estimating the temperature of the heater 28 of the exhaust gas sensor deterioration detection device 100 among the acquired temperatures (S23). Based on the extracted temperature of the heater 28, the heater resistance (hereinafter referred to as the heater resistance C estimated from the intake air temperature or the like) is extracted with reference to the heater temperature-heater resistance MAP in FIG. .

As the temperature suitable for estimating the temperature of the heater 28 of the exhaust gas sensor deterioration detection device 100, the lowest temperature among the acquired temperatures may be used, the temperature of the A / F sensor heater or the sub O ₂ sensor heater. A lower temperature may be used.

  Next, the deterioration detection ECU 10 calculates a heater resistance (hereinafter, the heater resistance obtained from the heater current is referred to as a heater resistance D) based on the heater current detected by the heater current sensor 12 and the battery voltage detected by the battery voltage sensor 13. (S24).

When the heater resistance C and the heater resistance D are calculated, the deterioration detection ECU 10 compares them (S25). Since the heater resistance C is a resistance value estimated from the temperature of the A / F sensor heater other than the heater 28, the temperature of the sub-O ₂ sensor heater, and the like, it is assumed that the heater resistance C indicates a normal heater resistance. Further, since the heater resistance D is the heater resistance of the heater 28 detected by the heater current sensor 12 and calculated in a predetermined procedure, if these differences are different from a predetermined threshold (Yes in step S25), the heater resistance It can be determined that an abnormality has occurred in 28, or has deteriorated in the present embodiment (S26).

  For example, when the performance of the heater 28 is degraded or disconnected, the heater resistance D is calculated to be larger than the normal state. In this case, since the heater resistance C is estimated from the temperature of another heater such as an A / F sensor heater, the heater resistance C becomes a normal value. Therefore, the heater resistance D is greater than the heater resistance C by a predetermined threshold or more, and the deterioration detection ECU 10 can detect that the heater 28 has deteriorated.

  For example, when the heater 28 is short-circuited, the heater resistance D is calculated to be smaller than the normal state. In this case, since the heater resistance C is estimated from another temperature sensor, the heater resistance C becomes a normal value. Accordingly, the heater resistance D is smaller than the heater resistance C by a predetermined threshold or more, and the deterioration detection ECU 10 can detect that the heater 28 has deteriorated.

  As a result of the comparison between the heater resistances C and D, if the difference between the heater resistances C and D is not greater than or equal to the threshold value, it is determined that the heater 28 has not deteriorated, and the detection procedure of FIG.

  According to the present embodiment, the heater resistance (heater resistance D) is obtained by providing the soak timer 51, and the heater 28 (heater resistance C) calculated based on the heater resistance and the heater current is accurately determined. Deterioration can be detected. Further, since the number of steps for calculating the heater resistance C and D is small and the number of newly added parts is small, it is possible to detect the deterioration of the heater while reducing the cost.

  As described above, according to the exhaust gas sensor deterioration detection device 100 in the present embodiment, it is possible to detect the deterioration of the heater based on the heater resistance and accurately detect the deterioration of the exhaust gas sensor. Further, it is possible to detect the deterioration of the exhaust gas sensor based not only on the heater resistance but also on the heater current and the heater current. Further, not only the deterioration of the exhaust gas sensor due to the deterioration of the heater but also the deterioration of the exhaust gas sensor can be detected based on the abnormality of the solid electrolyte element.

DESCRIPTION OF SYMBOLS 1 Exhaust gas sensor 2,3 Partition 5 Diffusion-controlled wall 8 Oxygen pump electrode 9 Exhaust gas chamber 10 Exhaust gas sensor deterioration detection ECU
11 Element Resistance Sensor 12 Heater Current Sensor 13 Battery Voltage Sensor 14 Element Temperature-Element Resistance MAP
15 Heater temperature-Heater resistance MAP
51 Soak timer
100 Deterioration detection device

Claims (2)

An element resistance detection circuit for detecting the element resistance of the element of the exhaust gas sensor heated by the heater ;
A first heater current estimating means for estimating the current of the heater in which the element resistance detection circuit heats the exhaust gas sensor based on the device resistance was detected,
Heater current detecting means for detecting a heater current of the heater;
A deterioration determining means for comparing the heater current estimated by the first heater current estimating means with the heater current detected by the heater current detecting means to determine whether or not the exhaust gas sensor has deteriorated;
A deterioration detection device for an exhaust gas sensor, comprising: An element resistance detection circuit for detecting the element resistance of the element of the exhaust gas sensor heated by the heater;
A first heater voltage estimating means for estimating a voltage of the heater in which the element resistance detection circuit heats the exhaust gas sensor based on the device resistance was detected,
Heater voltage detecting means for detecting the heater voltage of the heater;
A deterioration determining means for comparing the heater voltage estimated by the first heater voltage estimating means with the heater voltage detected by the heater voltage detecting means to determine whether or not the exhaust gas sensor has deteriorated;
A deterioration detection device for an exhaust gas sensor, comprising:

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