JP2005069218A - Exhaust air purifying catalyst degradation judgment method and device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase frequencies of degradation judgment practice while preserving judgment precision in judgment of a degradation of exhaust air purifying catalyst in an internal combustion engine. <P>SOLUTION: In an abnormal condition establishing judgment(S162), it is judged whether a difference between an actual measurement temperature and estimate failure floor temperature of the exhaust air is below a reference temperature difference at an abnormal period of time or not. The estimate failure floor temperature is a floor temperature in which reaction heat is not generated within an NOx occlusion reduction catalyst and therefore the estimate failure floor temperature depends on heat transmitted from the exhaust air, so that even at a transient period of time, the estimate failure floor temperature can be easily estimated depending on a running condition of the engine. Further, as the actual measurement temperature of the exhaust air reflects an actual reaction heat in the NOx occlusion reduction catalyst, if a value of "the actual measurement temperature of the exhaust air - the estimate failure floor temperature" is less than that of the reference temperature difference at the abnormal period of time, the degradation degree can be determined to be high, so that the abnormality can be determined (S170). Thus, the frequencies of the degradation judgment practice can be increased while preserving the precision of the degradation judgment. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a catalyst deterioration determination method and a deterioration determination device for determining a deterioration state of an exhaust purification catalyst provided in an exhaust system of an internal combustion engine.

  In diesel engines and lean-burn gasoline engines, NOx in the exhaust is stored in an oxidizing atmosphere, and then a reducing agent such as fuel is supplied into the exhaust to create a reducing atmosphere, and the stored NOx is released. In addition, there is an exhaust purification system using a NOx occlusion reduction catalyst that reduces and purifies. The NOx occlusion / reduction catalyst used in this exhaust purification system deteriorates when used over a long period of time, so that it becomes impossible to occlude NOx sufficiently, or NOx cannot be sufficiently reduced in a reducing atmosphere. There is a risk that it cannot be purified.

For this reason, there has been proposed a technique for addressing the above problem by accurately detecting the degree of deterioration of the NOx storage reduction catalyst. For example, there is a technique for calculating the reference temperature based on the upstream temperature of the catalyst at the start of idling and determining the degree of deterioration of the catalyst based on the difference between the temperature downstream of the catalyst and the reference temperature after a predetermined period of time during idling. (For example, refer to Patent Document 1).
JP 2001-221037 (page 7, FIG. 5)

  However, with the above technique, the deterioration degree of the NOx storage reduction catalyst cannot be detected with high accuracy unless a specific stable engine operation state such as an idle state continues. In other words, if the deterioration level is not detected within the period during which the stable operating state continues, the engine operating state changes before and after the predetermined period, and the operating state differs between when the reference temperature is set and when the temperature downstream of the catalyst is detected. This is because even if the two are compared, an accurate temperature rise due to the catalytic reaction cannot be captured.

  For this reason, the deterioration detection frequency of the NOx storage reduction catalyst has to be low, and even if the deterioration degree of the NOx storage reduction catalyst becomes high and NOx cannot be sufficiently purified, measures such as catalyst replacement cannot be performed at an early stage. There is a fear.

  An object of the present invention is to improve the frequency of execution of deterioration determination while maintaining the accuracy of deterioration determination.

In the following, means for achieving the above object and its effects are described.
The exhaust purification catalyst deterioration determination method for an internal combustion engine according to claim 1 is a catalyst deterioration determination method for determining a deterioration state of an exhaust purification catalyst provided in an exhaust system of the internal combustion engine, wherein the exhaust purification catalyst performs a catalytic reaction. Assuming that the engine is not in operation, the catalyst bed temperature estimated according to the operating state of the internal combustion engine and the reactants for purifying the exhaust purification catalyst are supplied to the exhaust purification catalyst. The deterioration degree of the exhaust purification catalyst is determined by comparing the measured catalyst bed temperature or the measured medium temperature with respect to the medium affected by the catalyst bed temperature.

  Assume that the exhaust purification catalyst is not in a catalytic reaction. This is because, for example, no reaction heat is generated in the exhaust purification catalyst because no reactant is supplied to the exhaust purification catalyst, or the exhaust purification catalyst is completely deteriorated (maximum deterioration level) and the reactant is Even if it is supplied, it corresponds to a state in which no reaction heat is generated in the exhaust purification catalyst.

  Thus, the catalyst bed temperature in a state where no heat of reaction is generated is determined only by heat transfer with the exhaust. Since the exhaust temperature can be estimated according to the operating state of the internal combustion engine, the catalyst bed temperature of the exhaust purification catalyst not performing the catalytic reaction can be easily estimated according to the operating state of the internal combustion engine.

  On the other hand, a medium measured with respect to a catalyst bed temperature measured in a state where a reactant for purifying the exhaust purification catalyst is supplied to the exhaust purification catalyst or a medium (for example, exhaust gas) affected by the catalyst bed temperature. The temperature reflects the heat of reaction at the catalyst. For this reason, it should be higher according to the heat of reaction than the catalyst bed temperature estimated as the unreacted state.

  However, it can be determined that the closer the measured temperature is to the estimated catalyst bed temperature, the less likely the reaction actually occurs despite the fact that the reactant is supplied to the exhaust purification catalyst. That is, it can be determined that the degree of deterioration is higher as the actually measured temperature is closer to the estimated catalyst bed temperature. Thus, the deterioration degree of the exhaust purification catalyst can be determined with high accuracy by comparing the estimated and calculated catalyst bed temperature with the actually measured catalyst bed temperature or medium temperature.

  Since the exhaust gas temperature can be estimated according to the operating state of the internal combustion engine, it is not necessary to limit the deterioration level detection during idling, and the reactant for purifying the exhaust gas purification catalyst is supplied to the exhaust gas purification catalyst. Therefore, it is possible to detect the degree of deterioration in a wide operation range and even in a transition period of the operation state. In this way, with respect to the exhaust purification catalyst used in the internal combustion engine, it is possible to improve the frequency of execution of deterioration determination while maintaining the accuracy of deterioration determination.

  In the exhaust gas purification catalyst deterioration determining method for an internal combustion engine according to claim 2, in claim 1, the smaller the difference between the estimated and calculated catalyst bed temperature and the measured catalyst bed temperature or measured medium temperature, It is determined that the degree of deterioration of the exhaust purification catalyst is high.

  That is, the smaller the difference between the estimated and calculated catalyst bed temperature and the measured catalyst bed temperature or the measured medium temperature, the less reaction occurs even if the reactant is supplied to the exhaust purification catalyst accordingly. Therefore, it can be determined that the deterioration of the exhaust purification catalyst is progressing as the difference is smaller.

  The exhaust purification catalyst deterioration determination method for an internal combustion engine according to claim 3 is a catalyst deterioration determination method for determining a deterioration state of an exhaust purification catalyst provided in an exhaust system of the internal combustion engine, wherein the exhaust purification catalyst has a predetermined deterioration level. The catalyst bed temperature estimated according to the operating state of the internal combustion engine and the reactants for purifying the exhaust purification catalyst are supplied to the exhaust purification catalyst. The degree of deterioration of the exhaust purification catalyst is determined by comparing the measured catalyst bed temperature in a state where the exhaust gas is being measured or the measured medium temperature with respect to the medium affected by the catalyst bed temperature.

  It is assumed that the exhaust purification catalyst is in a state of performing a catalytic reaction with a predetermined deterioration degree. This is a state in which reaction heat corresponding to a predetermined degree of deterioration is generated in the exhaust purification catalyst by the reactant supplied to the exhaust purification catalyst. For example, if the predetermined degree of deterioration is between the maximum degree of deterioration and the state in which no deterioration has occurred, the predetermined degree of deterioration can be obtained with respect to the amount of heat generated by the reaction of the reactants in the exhaust purification catalyst that has not deteriorated at all. Accordingly, the amount of heat generated is small. Further, when the predetermined deterioration degree is set to a state where no deterioration has occurred, the amount of heat generated by the reaction of the reactants in the exhaust purification catalyst which has not deteriorated at all is the same as the predetermined amount of deterioration. In this case, the calorific value is “0”.

  Assuming that the deterioration degree of the exhaust purification catalyst is a predetermined deterioration degree as described above, the calorific value for the same amount of reactants becomes a value corresponding to the predetermined deterioration degree. The catalyst bed temperature raised by this assumed heat generation amount is determined only by heat transfer with the exhaust. Since the exhaust temperature can be estimated according to the operating state of the internal combustion engine, the catalyst bed temperature of the exhaust purification catalyst can be easily estimated according to the predetermined degree of deterioration and the operating state of the internal combustion engine.

  On the other hand, a medium measured with respect to a catalyst bed temperature measured in a state where a reactant for purifying the exhaust purification catalyst is supplied to the exhaust purification catalyst or a medium (for example, exhaust gas) affected by the catalyst bed temperature. Since the temperature reflects the heat of reaction at the catalyst, it should increase with the heat of reaction.

  However, if the measured temperature is a value close to or equivalent to the estimated catalyst bed temperature, it can be determined that the heat generation amount is close to or the same as the heat generation amount at the assumed degree of deterioration. That is, it can be determined that the actual deterioration degree is closer to the predetermined deterioration degree as the measured temperature is closer to the estimated catalyst bed temperature.

Thus, the deterioration degree of the exhaust purification catalyst can be determined with high accuracy by comparing the estimated and calculated catalyst bed temperature with the actually measured catalyst bed temperature or medium temperature.
Since the exhaust gas temperature can be estimated according to the operating state of the internal combustion engine, it is not necessary to limit the deterioration level detection during idling, and the reactant for purifying the exhaust gas purification catalyst is supplied to the exhaust gas purification catalyst. Therefore, it is possible to detect the degree of deterioration in a wide operation range and even in a transition period of the operation state. In this way, with respect to the exhaust purification catalyst used in the internal combustion engine, it is possible to improve the frequency of execution of deterioration determination while maintaining the accuracy of deterioration determination.

  In the exhaust gas purification catalyst deterioration determining method for an internal combustion engine according to claim 4, in claim 3, when the actually measured catalyst bed temperature or the actually measured medium temperature is higher than the estimated catalyst bed temperature, the actually measured catalyst bed temperature is measured. The smaller the difference between the catalyst bed temperature or the measured medium temperature and the estimated catalyst bed temperature, the higher the degree of deterioration, and the measured catalyst bed temperature or measured medium temperature is greater than the estimated catalyst bed temperature calculated. When the measured catalyst bed temperature or the measured medium temperature is lower than the estimated catalyst bed temperature, the degree of deterioration is higher, and the measured catalyst bed temperature or measured medium temperature and the estimated calculation are lower. It is characterized by determining that the degree of deterioration is higher as the difference from the catalyst bed temperature is larger.

  The predetermined degree of deterioration may be set to any of the entire range from the maximum degree of deterioration to the state where no deterioration has occurred. Therefore, when the measured temperature is higher than the estimated catalyst bed temperature, the measured value It is determined that the degree of deterioration is higher as the difference between the measured temperature and the estimated catalyst bed temperature is smaller.

  When the measured temperature is lower than the estimated and calculated catalyst bed temperature, it is determined that the degree of deterioration is higher than when the measured temperature is higher than the estimated and calculated catalyst bed temperature. Furthermore, in this case, it is determined that the degree of deterioration is higher as the difference between the actually measured temperature and the estimated calculated catalyst bed temperature is larger.

  6. The exhaust gas purification catalyst deterioration judging method for an internal combustion engine according to claim 5, wherein, in any one of claims 1 to 4, if the deterioration degree of the exhaust gas purification catalyst is more deteriorated than a reference deterioration degree, the exhaust gas purification catalyst is deteriorated. It is characterized by determining that the catalyst is abnormal.

  In this way, it is possible to determine that the exhaust purification catalyst is abnormal if the reference deterioration degree is provided and the deterioration degree is higher than the reference deterioration degree. Based on the determination that the exhaust purification catalyst is abnormal, measures such as replacement of the exhaust purification catalyst can be quickly executed.

  In the exhaust gas purification catalyst deterioration determining method for an internal combustion engine according to claim 6, in claim 5, the internal combustion engine is provided with a second exhaust gas purification catalyst that is purified by the same reactant downstream of the exhaust gas purification catalyst. The exhaust purification catalyst is not judged to be abnormal if the second exhaust purification catalyst is not deteriorated even if the deterioration degree of the exhaust purification catalyst is more advanced than the reference deterioration degree. .

  In some cases, a second exhaust purification catalyst that is purified by the same reactant is provided downstream of the exhaust purification catalyst. In this case, since the second exhaust purification catalyst can reduce and purify the same component, for example, NOx, even if the upstream exhaust purification catalyst deteriorates and exhaust purification becomes insufficient, the second exhaust purification catalyst If it is not deteriorated, it may not be determined that the upstream side exhaust purification catalyst is abnormal. As a result, the operation of the internal combustion engine can be continued for a long time while maintaining a sufficient exhaust purification state.

  In particular, clogging occurs in the exhaust gas purification catalyst on the upstream side, and the catalytic reaction is biased. Depending on the measurement position, the actually measured temperature may not be accurate, which may lead to a situation where it is determined to be abnormal. However, in the case of such clogging, since the second exhaust purification catalyst often performs a sufficient purification function, it is possible to maintain a sufficient exhaust purification state by not determining that it is abnormal as described above. However, the operation of the internal combustion engine can be continued for a long time.

  The exhaust gas purification catalyst deterioration determining method for an internal combustion engine according to claim 7 is characterized in that in claim 6, the measured temperature difference between the upstream exhaust gas temperature and the downstream exhaust gas temperature of the second exhaust gas purification catalyst is abnormal. The condition that the state is smaller than the time reference temperature difference is included as a logical product condition for determining that the exhaust purification catalyst is abnormal.

  If the temperature difference between the upstream exhaust gas temperature and the downstream exhaust gas temperature of the second exhaust gas purification catalyst that are both measured is large, the second exhaust gas purification catalyst actually generates heat of reaction, and the catalytic function is It can be judged that it is normal.

  In this way, when the second exhaust purification catalyst is not deteriorated, it is not determined that there is an abnormality even if the upstream exhaust purification catalyst is deteriorated. Can be generated.

  The exhaust gas purification catalyst deterioration determining method for an internal combustion engine according to claim 8, wherein the exhaust gas purification catalyst includes a NOx occlusion reduction catalyst so that a reducing agent is supplied as the reactant. Thus, the NOx occluded in the NOx occlusion reduction catalyst is a catalyst that is purified by reduction.

  With the above-described function, it is not necessary to detect the deterioration degree of the NOx storage reduction catalyst at the time of idling, and it is sufficient if the reducing agent for reducing and purifying NOx is supplied to the NOx storage reduction catalyst. It is possible to detect the degree of deterioration within the operating range and even during the transition period of the operating state. In this way, with respect to the catalyst including the NOx storage reduction catalyst used in the internal combustion engine, the frequency of execution of deterioration determination can be improved while maintaining the accuracy of deterioration determination.

  In the exhaust gas purification catalyst deterioration determining method for an internal combustion engine according to claim 9, it is assumed in any one of claims 1 to 8 that the exhaust gas purification catalyst is in a state of performing a catalytic reaction at a first predetermined deterioration degree. Thus, it is assumed that the exhaust purification catalyst is in a state of performing a catalytic reaction at a catalyst bed temperature estimated and calculated according to an operating state of the internal combustion engine and a second predetermined deterioration level different from the first predetermined deterioration level. The difference between the estimated catalyst temperature and the estimated catalyst temperature in accordance with the operating state of the internal combustion engine is larger than the reference estimated temperature difference, which is a precondition for starting the deterioration degree determination.

  When the exhaust purification catalyst is in an inactive state or in an operating state of an internal combustion engine where the activity is not sufficient, even if the exhaust purification catalyst is not deteriorated, the estimated catalyst bed temperature and actual measurement according to the operating state of the internal combustion engine Thus, the difference between the catalyst bed temperature and the medium temperature is small, and the determination of the degree of deterioration by comparison is liable to cause an erroneous determination. Furthermore, in order to improve the determination accuracy of the deterioration level, it is necessary to always wait for a long time, and then compare the difference between the estimated catalyst bed temperature and the actually measured catalyst bed temperature or the medium temperature. It becomes difficult.

  In this claim, whether the exhaust purification catalyst is in an operating state in which a catalytic reaction sufficiently occurs depending on whether or not the difference in the estimated catalyst bed temperature is greater than the reference estimated temperature difference. It is determined whether or not. If the difference between the two estimated catalyst bed temperatures is larger than the reference estimated temperature difference, it can be determined that the internal combustion engine is in an operating state in which the exhaust purification catalyst sufficiently undergoes a catalytic reaction. I forgive you. This prevents erroneous determination of the degree of deterioration due to comparison. Further, if it can be determined that the exhaust purification catalyst is sufficiently in an operating state of the internal combustion engine in which a catalytic reaction occurs sufficiently, a highly accurate determination can be made immediately, so there is no need to always wait for a long time. Accordingly, it is possible to quickly determine the degree of deterioration with high accuracy.

  In the exhaust gas purification catalyst deterioration determining method for an internal combustion engine according to claim 10, in claim 9, the first predetermined deterioration degree is a state in which the exhaust purification catalyst has not deteriorated at all, and the second predetermined deterioration degree is The exhaust purification catalyst is in a completely deteriorated state.

  By setting the first predetermined deterioration degree and the second predetermined deterioration degree in this way, the operation state of the internal combustion engine that affects the reaction heat can be most sharply determined, and the deterioration degree can be determined more quickly and accurately. It becomes possible.

  An exhaust gas purification catalyst deterioration determination device for an internal combustion engine according to claim 11 is a catalyst deterioration determination device for determining a deterioration state of an exhaust gas purification catalyst provided in an exhaust system of the internal combustion engine, which is discharged from the exhaust gas purification catalyst. An exhaust temperature sensor for detecting the exhaust temperature, and a purification exhaust temperature detection means for measuring the exhaust temperature with the exhaust temperature sensor in a state where a reactant for purifying the exhaust purification catalyst is supplied to the exhaust purification catalyst And a catalyst bed temperature estimating means for estimating and calculating the catalyst bed temperature reached by the exhaust purification catalyst according to the operating state of the internal combustion engine, assuming that the exhaust purification catalyst is not in a catalytic reaction, and the purification Deterioration degree determination means for determining the deterioration degree of the exhaust purification catalyst by comparing the exhaust temperature measured by the exhaust gas temperature detection means and the catalyst bed temperature estimated by the catalyst bed temperature estimation means Characterized by

  The deterioration degree determination means determines the deterioration degree of the exhaust purification catalyst by comparing the exhaust temperature measured by the purification exhaust temperature detection means with the catalyst bed temperature estimated by the catalyst bed temperature estimation means. Yes. The catalyst bed temperature estimated and calculated by the catalyst bed temperature estimation means is the catalyst bed temperature when it is assumed that the exhaust purification catalyst is not performing a catalytic reaction. Therefore, the catalyst bed temperature in a state where no reaction heat is generated is determined only by heat transfer with the exhaust, and the exhaust temperature can be estimated according to the operating state of the internal combustion engine. This makes it possible to easily estimate the catalyst bed temperature of the exhaust purification catalyst that is not performing the catalytic reaction according to the operating state of the internal combustion engine.

  The exhaust temperature detected by the purification exhaust temperature detection means reflects the reaction heat in the exhaust purification catalyst, and therefore is higher in accordance with the reaction heat than the catalyst bed temperature estimated by the catalyst bed temperature estimation means. It should be. However, the closer the exhaust temperature is to the estimated and calculated catalyst bed temperature, the less reaction heat is planned, and the lower reaction heat at this time indicates the degree of deterioration of the exhaust purification catalyst. Thus, the deterioration degree determination means can determine the deterioration degree of the exhaust purification catalyst with high accuracy by comparing the estimated and calculated catalyst bed temperature with the actually measured exhaust gas temperature.

  As described above, the catalyst bed temperature estimating means estimates and calculates the catalyst bed temperature according to the operating state of the internal combustion engine. Therefore, the deterioration degree detection by the deterioration degree determining means does not need to be limited to the idling time. Any reactive substance may be used as long as the reactant for purification is supplied to the exhaust purification catalyst. Therefore, it is possible to detect the degree of deterioration in a wide operation range and even in a transition period of the operation state. In this way, with respect to the exhaust purification catalyst used in the internal combustion engine, it is possible to improve the frequency of execution of deterioration determination while maintaining the accuracy of deterioration determination.

  13. The exhaust gas purification catalyst deterioration determining apparatus for an internal combustion engine according to claim 12, wherein the deterioration degree determining means includes the exhaust gas temperature measured by the purification exhaust gas temperature detecting means and the catalyst bed temperature estimation. It is determined that the degree of deterioration of the exhaust purification catalyst is higher as the difference from the catalyst bed temperature estimated by the means is smaller.

  That is, as the difference between the exhaust temperature and the catalyst bed temperature is smaller, the reaction is not performed even if the reactant is supplied to the exhaust purification catalyst accordingly. Therefore, the deterioration degree determination means can determine that the deterioration degree is higher as the difference is smaller.

  The exhaust purification catalyst deterioration determination device for an internal combustion engine according to claim 13 is a catalyst deterioration determination device for determining the deterioration state of the exhaust purification catalyst provided in the exhaust system of the internal combustion engine, and is exhausted from the exhaust purification catalyst. An exhaust temperature sensor for detecting the exhaust temperature, and a purification exhaust temperature detection means for measuring the exhaust temperature with the exhaust temperature sensor in a state where a reactant for purifying the exhaust purification catalyst is supplied to the exhaust purification catalyst And a catalyst bed temperature estimating means for estimating and calculating the catalyst bed temperature reached by the exhaust purification catalyst in accordance with the operating state of the internal combustion engine, assuming that the exhaust purification catalyst is in a state of performing a catalytic reaction with a predetermined degree of deterioration. A deterioration degree determination that determines the deterioration degree of the exhaust purification catalyst by comparing the exhaust gas temperature measured by the purification exhaust gas temperature detection means and the catalyst bed temperature estimated by the catalyst bed temperature estimation means With the means And butterflies.

  The catalyst bed temperature estimating means assumes that the exhaust purification catalyst is in a state of performing a catalytic reaction with a predetermined deterioration degree. This is a state in which reaction heat corresponding to a predetermined degree of deterioration is generated in the exhaust purification catalyst among the reactants supplied to the exhaust purification catalyst. Assuming that the deterioration degree of the exhaust purification catalyst is a predetermined deterioration degree as described above, the calorific value for the same amount of reactants becomes a value corresponding to the predetermined deterioration degree. The catalyst bed temperature raised by this assumed heat generation amount is determined only by heat transfer with the exhaust. Since the exhaust temperature can be estimated according to the operating state of the internal combustion engine, the catalyst bed temperature estimating means can easily estimate the catalyst bed temperature of the exhaust purification catalyst having a predetermined deterioration degree according to the operating state of the internal combustion engine. .

  On the other hand, the exhaust temperature discharged from the exhaust purification catalyst during the catalyst purification detected by the exhaust temperature detection means during the purification reflects the reaction heat in the exhaust purification catalyst, so it depends on the reaction heat rather than the catalyst bed temperature. Should be high. However, if the exhaust temperature detected by the purification exhaust temperature detecting means is close to the estimated catalyst bed temperature, it can be determined that the actual deterioration degree of the exhaust purification catalyst is closer to the predetermined deterioration degree.

  Therefore, the deterioration degree determination means accurately determines the deterioration degree of the exhaust purification catalyst by comparing the exhaust temperature detected by the purification exhaust temperature detection means with the catalyst bed temperature estimated by the catalyst bed temperature estimation means. Can be determined.

  Thus, since the catalyst bed temperature estimating means calculates and calculates the catalyst bed temperature according to the predetermined deterioration level and the operating state of the internal combustion engine, the deterioration degree detection by the deterioration degree determining means does not need to be limited to the idle time, Any reactive material for purifying the exhaust purification catalyst may be supplied to the exhaust purification catalyst. For this reason, it is possible to detect the degree of deterioration in a wide operating range and even in a transition period of the operating state. In this way, with respect to the exhaust purification catalyst used in the internal combustion engine, it is possible to improve the frequency of execution of deterioration determination while maintaining the accuracy of deterioration determination.

  The exhaust gas purification catalyst deterioration determining device for an internal combustion engine according to claim 14, wherein the deterioration degree determining means is configured such that the exhaust gas temperature measured by the purification exhaust gas temperature detecting means is the catalyst bed temperature estimating means. Is higher than the estimated catalyst bed temperature, the degree of deterioration is determined to be higher as the difference between the exhaust gas temperature and the estimated catalyst bed temperature is smaller, and is measured by the purification exhaust gas temperature detecting means. When the exhaust gas temperature is lower than the catalyst bed temperature estimated by the catalyst bed temperature estimation means, the degree of deterioration is higher than when the exhaust gas temperature is higher than the estimated catalyst bed temperature, and the exhaust gas temperature is higher. It is determined that the degree of deterioration is higher as the difference between the air temperature and the estimated catalyst bed temperature is larger.

  The predetermined deterioration degree may be set to any of the entire range from the maximum deterioration degree to the state where no deterioration has occurred. In this case, when the exhaust temperature measured by the purification exhaust temperature detecting means is higher than the catalyst bed temperature estimated by the catalyst bed temperature estimating means, the deterioration degree determining means is the exhaust temperature and the estimated It is determined that the degree of deterioration is higher as the difference from the calculated catalyst bed temperature is smaller.

  When the exhaust temperature is lower than the estimated catalyst bed temperature, it is determined that the degree of deterioration is higher than when the exhaust temperature is higher than the estimated catalyst bed temperature. Furthermore, in this case, it is determined that the degree of deterioration is higher as the difference between the exhaust gas temperature and the estimated catalyst bed temperature is larger.

  16. The exhaust gas purification catalyst deterioration determining apparatus for an internal combustion engine according to claim 15, wherein the catalyst bed temperature estimating means is configured such that the operating speed of the internal combustion engine is an internal combustion engine speed and a combustion fuel. The supply amount is used.

  The exhaust temperature flowing into the exhaust purification catalyst can be estimated from the internal combustion engine speed and the amount of fuel supplied for combustion. Therefore, for example, the relationship between the rotational speed of the internal combustion engine and the amount of fuel supplied for combustion and the exhaust gas temperature is obtained in advance by experiments, and the catalyst bed temperature estimating means obtains the exhaust gas temperature based on this relationship and calculates and estimates the catalyst bed temperature. Can be used.

  The exhaust gas purification catalyst deterioration determining apparatus for an internal combustion engine according to claim 16, wherein the exhaust gas purification catalyst deterioration determination device according to any one of claims 11 to 15, if the deterioration degree of the exhaust gas purification catalyst is more advanced than a reference deterioration degree. An abnormality determining means for determining that the catalyst is abnormal is provided.

If it is determined by the abnormality determination means that the exhaust purification catalyst is abnormal, measures such as replacement of the exhaust purification catalyst can be quickly executed based on the abnormality determination.
In the exhaust gas purification catalyst deterioration judging device for an internal combustion engine according to claim 17, the internal combustion engine is provided with a second exhaust gas purification catalyst to be purified by the same reactant downstream of the exhaust gas purification catalyst. The abnormality determination means determines that the exhaust purification catalyst is abnormal if the second exhaust purification catalyst is not deteriorated even when the deterioration degree of the exhaust purification catalyst is more advanced than the reference deterioration degree. It is characterized by not.

  In some cases, a second exhaust purification catalyst that is purified by the same reactant is provided downstream of the exhaust purification catalyst. In this case, since the second exhaust purification catalyst can purify the same component, for example, NOx, even if the upstream exhaust purification catalyst deteriorates and exhaust purification becomes insufficient, the second determination unit can If the exhaust purification catalyst is not deteriorated, it may not be determined that the upstream exhaust purification catalyst is abnormal. As a result, the operation of the internal combustion engine can be continued for a long time while maintaining a sufficient exhaust purification state.

  In particular, clogging occurs in the exhaust gas purification catalyst on the upstream side, and the catalytic reaction is biased. Depending on the measurement position, the actually measured temperature may not be accurate, which may lead to a situation where it is determined to be abnormal. However, in the case of such clogging, the second exhaust purification catalyst often performs a sufficient purification function. Therefore, as described above, the abnormality determination means does not determine that there is an abnormality, so that sufficient exhaust The operation of the internal combustion engine can be continued for a long time while maintaining the purified state.

  The exhaust gas purification catalyst deterioration determining device for an internal combustion engine according to claim 18, further comprising a second exhaust temperature sensor for detecting an exhaust gas temperature discharged from the second exhaust gas purification catalyst, and the abnormality determination. And means for determining that the temperature difference between the exhaust temperature detected by the second exhaust temperature sensor and the exhaust temperature detected by the exhaust temperature sensor is smaller than the reference temperature difference at the time of abnormality. It is characterized by being one of logical product conditions for determining that the catalyst is abnormal.

  If the temperature difference between the exhaust temperature discharged from the exhaust purification catalyst measured by the exhaust temperature sensor and the exhaust temperature discharged from the second exhaust purification catalyst measured by the second exhaust temperature sensor is large The second exhaust purification catalyst actually generates heat of reaction, and it can be determined that the catalyst function is normal.

  As described above, the abnormality determining means does not determine that the second exhaust purification catalyst is abnormal even if the upstream exhaust purification catalyst is deteriorated, so that the abnormality is not abnormal. Such effects can be produced.

  In the exhaust gas purification catalyst deterioration judging device for an internal combustion engine according to claim 19, in any one of claims 11 to 18, the reactant is a fuel added to a combustion gas or an exhaust gas during an expansion stroke of the internal combustion engine. It is characterized by being.

Examples of the reactant for purifying the exhaust purification catalyst include fuel added to the combustion gas during the expansion stroke of the internal combustion engine, and fuel added to the exhaust.
The exhaust gas purification catalyst deterioration determination device for an internal combustion engine according to claim 20, wherein the deterioration degree is determined when the amount of the reactant added to the combustion gas or exhaust gas is small. A prohibiting unit for prohibiting the processing of the determining unit or the abnormality determining unit is provided.

  When the amount of the reactant added to the combustion gas or exhaust is small, sufficient heat generation will not occur even if the exhaust purification catalyst is not highly degraded. As a result, the exhaust temperature is lowered, and inaccurate exhaust temperature data is used. Therefore, when the amount of the reactant added to the combustion gas or exhaust gas is small, the prohibiting means prohibits the processing of the deterioration degree determining means or the abnormality determining means, thereby determining the deterioration degree or abnormality determination accuracy of the exhaust purification catalyst. Can be prevented from decreasing.

  In the exhaust gas purification catalyst deterioration determination device for an internal combustion engine according to claim 21, the internal combustion engine according to claim 20, wherein the internal combustion engine is provided with a plurality of catalyst control modes having different amounts of the reactant added to the combustion gas or exhaust gas, The catalyst control mode selected from the catalyst control mode according to the state of the exhaust purification catalyst is executed, and the prohibiting means executes a catalyst control mode in which the amount of the reactant added is small compared to other catalyst control modes. If it is determined that the amount of the reactant added to the combustion gas or exhaust gas is small, the processing of the deterioration degree determination means or the abnormality determination means is prohibited.

  As described above, in the catalyst control mode, when the catalyst control mode in which the amount of the reactant added is small compared to the other catalyst control modes, the processing of the deterioration degree determination unit or the abnormality determination unit is prohibited. Anyway. As a result, it is possible to execute the deterioration degree determination or abnormality determination only in the catalyst control mode in which the deterioration degree or abnormality of the exhaust purification catalyst can be detected with high accuracy. It can be prevented from lowering.

  23. The exhaust gas purification catalyst deterioration determining apparatus for an internal combustion engine according to claim 22, wherein the exhaust gas purification catalyst includes a NOx occlusion reduction catalyst and is supplied with a reducing agent as the reactant, thereby the NOx. NOx stored in the storage reduction catalyst is purified by reduction, and the catalyst control mode includes at least a particulate material regeneration control mode, a sulfur poisoning recovery control mode, and a NOx reduction control mode, and the particulate material regeneration The catalyst control mode other than the control mode and the sulfur poisoning recovery control mode is a catalyst control mode in which the amount of the reactant added is small compared to other catalyst control modes.

  Among the catalyst control modes, catalyst control modes other than the particulate material regeneration control mode and the sulfur poisoning recovery control mode can be cited as catalyst control modes in which the amount of reactant added is small compared to other catalyst control modes. Therefore, by executing the deterioration degree determination or the abnormality determination only in the particulate matter regeneration control mode and the sulfur poisoning recovery control mode, it is possible to prevent the deterioration degree or abnormality determination accuracy of the exhaust purification catalyst from being lowered.

  24. The exhaust gas purification catalyst deterioration determining apparatus for an internal combustion engine according to claim 23, wherein the catalyst bed temperature estimating means performs the catalytic reaction of the exhaust gas purification catalyst at a first predetermined deterioration degree. The catalyst bed temperature is estimated and calculated according to the operating state of the internal combustion engine, and the exhaust purification catalyst performs a catalytic reaction at a second predetermined deterioration level different from the first predetermined deterioration level. The catalyst bed temperature is estimated and calculated in accordance with the operating state of the internal combustion engine, and the prohibiting means includes the two catalyst bed temperatures estimated and calculated by the catalyst bed temperature estimation means. If the difference is smaller than the reference estimated temperature difference, the processing of the deterioration degree determining means or the abnormality determining means is prohibited.

  When the exhaust purification catalyst is in an inactive state or in an operating state of an internal combustion engine where the activity is not sufficient, even if the exhaust purification catalyst is not deteriorated, the estimated catalyst bed temperature and actual measurement according to the operating state of the internal combustion engine Thus, the difference between the catalyst bed temperature and the medium temperature is small, and the determination of the degree of deterioration by comparison is liable to cause an erroneous determination. Furthermore, in order to improve the determination accuracy of the deterioration level, it is necessary to always wait for a long time, and then compare the difference between the estimated catalyst bed temperature and the actually measured catalyst bed temperature or the medium temperature. It becomes difficult.

  In this claim, the catalyst bed temperature estimation means estimates and calculates the two catalyst bed temperatures on the assumption that the degree of deterioration is different. If the difference between the two estimated catalyst bed temperatures is smaller than the reference estimated temperature difference, the prohibiting means determines that the exhaust purification catalyst is in an inactive state or is in an operating state of an internal combustion engine where the activity is not sufficient, and determines the deterioration level. The processing of the means or the abnormality determination means is prohibited.

  On the contrary, if the difference between the two estimated catalyst bed temperatures is larger than the reference estimated temperature difference, it can be determined that the internal combustion engine is in an operating state in which the exhaust purification catalyst sufficiently undergoes a catalytic reaction. The processing of the judging means or the abnormality judging means is permitted. This prevents erroneous determination of the degree of deterioration due to comparison. Further, if it can be determined that the exhaust purification catalyst is sufficiently in an operating state of the internal combustion engine in which a catalytic reaction occurs sufficiently, a highly accurate determination can be made immediately, so there is no need to always wait for a long time. Accordingly, it is possible to quickly determine the degree of deterioration with high accuracy.

  In the exhaust gas purification catalyst deterioration determination device for an internal combustion engine according to claim 24, in claim 23, the first predetermined deterioration degree is a state in which the exhaust purification catalyst has not deteriorated at all, and the second predetermined deterioration degree is The exhaust purification catalyst is in a completely deteriorated state.

  By setting the first predetermined deterioration degree and the second predetermined deterioration degree in this way, the prohibiting means can determine the operating state of the internal combustion engine that affects the reaction heat most sensitively, and the deterioration degree determining means or abnormality determination In the processing of the means, it becomes possible to determine the degree of deterioration or abnormality with high accuracy more quickly.

  The exhaust purification catalyst deterioration determining apparatus for an internal combustion engine according to claim 25, wherein the catalyst bed temperature sensor detects the catalyst bed temperature of the exhaust purification catalyst instead of the exhaust temperature sensor. The catalyst bed temperature detected by the catalyst bed temperature sensor is used instead of the exhaust gas temperature.

  Instead of detecting the exhaust temperature, the catalyst bed temperature of the exhaust purification catalyst may be directly detected by a catalyst bed temperature sensor and used instead of the exhaust temperature in claims 11 to 24. Produces an effect.

[Embodiment 1]
FIG. 1 is a block diagram showing a schematic configuration of a vehicle diesel engine and a control device to which the above-described invention is applied. The present invention can also be applied to an engine using a NOx storage reduction catalyst such as a lean combustion gasoline engine.

  The diesel engine 2 includes a plurality of cylinders, here, four cylinders # 1, # 2, # 3, and # 4. The combustion chambers 4 of the cylinders # 1 to # 4 are connected to a surge tank 12 via an intake port 8 and an intake manifold 10 that are opened and closed by an intake valve 6. The surge tank 12 is connected via an intake passage 13 to an intercooler 14 and a supercharger, here, an outlet side of a compressor 16 a of an exhaust turbocharger 16. The inlet side of the compressor 16 a is connected to an air cleaner 18. The surge tank 12 has an EGR gas supply port 20 a of an exhaust gas recirculation (hereinafter referred to as “EGR”) path 20. A throttle valve 22 is disposed in the intake passage 13 between the surge tank 12 and the intercooler 14, and an intake air amount sensor 24 and an intake air temperature sensor 26 are disposed between the compressor 16 a and the air cleaner 18. ing.

  The combustion chambers 4 of the cylinders # 1 to # 4 are connected to the inlet side of the exhaust turbine 16b of the exhaust turbocharger 16 via an exhaust port 30 and an exhaust manifold 32 that are opened and closed by an exhaust valve 28, and the outlet of the exhaust turbine 16b. The side is connected to the exhaust path 34. The exhaust turbine 16b introduces exhaust from the fourth cylinder # 4 side in the exhaust manifold 32.

  In the exhaust path 34, three catalytic converters 36, 38 and 40 in which an exhaust purification catalyst is housed are arranged. The most upstream first catalytic converter 36 houses a NOx storage reduction catalyst. With this NOx occlusion reduction catalyst, NOx is occluded in the NOx occlusion reduction catalyst when the exhaust gas is in an oxidizing atmosphere (lean) during normal operation of the diesel engine. In a reducing atmosphere (stoichiometric or rich), NOx stored in the NOx storage reduction catalyst is released as NO and is reduced by HC or CO. In this way, NOx is purified.

  A filter having a wall portion formed in a monolith structure is accommodated in the second catalytic converter 38 disposed in the middle, and exhaust gas passes through the minute holes in the wall portion. Since the NOx occlusion reduction catalyst is coated on the surface of the filter, the NOx purification is performed as described above. Furthermore, since PM (particulate matter) in the exhaust is trapped on the filter surface, in an oxidizing atmosphere, PM starts to be oxidized by active oxygen generated when NOx is occluded, and the entire PM is oxidized by excess oxygen in the surroundings. The In a reducing atmosphere (stoichiometric or rich), oxidation of PM is promoted by a large amount of active oxygen generated from the NOx storage reduction catalyst. As a result, PM purification as well as NOx purification is performed.

The most downstream third catalytic converter 40 contains an oxidation catalyst, where HC and CO are oxidized and purified.
A first air-fuel ratio sensor 42 is disposed upstream of the first catalytic converter 36, and a first exhaust temperature sensor 44 is disposed between the first catalytic converter 36 and the second catalytic converter 38. Further, between the second catalytic converter 38 and the third catalytic converter 40, the second exhaust temperature sensor 46 is near the second catalytic converter 38, and the second air-fuel ratio sensor 48 is near the third catalytic converter 40. Is arranged.

  The first air-fuel ratio sensor 42 and the second air-fuel ratio sensor 48 are sensors that detect the air-fuel ratio of the exhaust based on the exhaust component at each position and linearly output a voltage signal proportional to the air-fuel ratio. The first exhaust temperature sensor 44 and the second exhaust temperature sensor 46 detect the exhaust temperature at their respective positions.

  A pipe for the differential pressure sensor 50 is provided on the upstream side and the downstream side of the second catalytic converter 38, respectively, and the differential pressure sensor 50 is connected to the second catalytic converter 38 in order to detect clogging inside the second catalytic converter 38. The differential pressure is detected upstream and downstream.

  The exhaust manifold 32 has an EGR gas inlet 20b of the EGR path 20 opened. The EGR gas inlet 20b is open on the first cylinder # 1 side, and is on the opposite side to the fourth cylinder # 4 side where the exhaust turbine 16b introduces exhaust.

  In the middle of the EGR path 20, an iron-based EGR catalyst 52 for reforming the EGR gas is disposed from the EGR gas inlet 20b side of the EGR path 20, and an EGR cooler 54 for cooling the EGR gas is further provided. ing. The EGR catalyst 52 also has a function of preventing the EGR cooler 54 from being clogged. An EGR valve 56 is disposed on the EGR gas supply port 20a side. By adjusting the opening degree of the EGR valve 56, the EGR gas supply amount from the EGR gas supply port 20a to the intake side can be adjusted.

  A fuel injection valve 58 disposed in each cylinder # 1 to # 4 and directly injecting fuel into each combustion chamber 4 is connected to a common rail 60 via a fuel supply pipe 58a. Fuel is supplied into the common rail 60 from an electrically controlled discharge variable fuel pump 62, and the high-pressure fuel supplied from the fuel pump 62 into the common rail 60 is supplied to each fuel injection valve 58 through each fuel supply pipe 58a. Distributed supply. A fuel pressure sensor 64 for detecting the fuel pressure is attached to the common rail 60.

  Further, low pressure fuel is separately supplied from the fuel pump 62 to the addition valve 68 via the fuel supply pipe 66. The addition valve 68 is provided in the exhaust port 30 of the fourth cylinder # 4 and injects fuel as a reducing agent toward the exhaust turbine 16b side. By the injection of the reducing agent, the exhaust gas is temporarily reduced to reduce the NOx stored in the first catalytic converter 36 and the second catalytic converter 38, and the second catalytic converter 38 simultaneously performs PM purification. To do.

  An electronic control unit (hereinafter referred to as “ECU”) 70 is mainly configured by a digital computer including a CPU, a ROM, a RAM, and the like, and a drive circuit for driving each device. The ECU 70 performs the above-described intake air amount sensor 24, intake temperature sensor 26, first air-fuel ratio sensor 42, first exhaust temperature sensor 44, second exhaust temperature sensor 46, second air-fuel ratio sensor 48, differential pressure sensor 50, fuel. The signals of the pressure sensor 64 and the throttle opening sensor 22a are read. Further, signals are read from an accelerator opening sensor 74 that detects the depression amount of the accelerator pedal 72 and a cooling water temperature sensor 76 that detects the cooling water temperature of the diesel engine 2. Further, signals are read from an engine speed sensor 80 that detects the rotational speed of the crankshaft 78, and a cylinder discrimination sensor 82 that detects the rotational phase of the crankshaft 78 or the rotational phase of the intake cam and performs cylinder discrimination.

  Based on the engine operating state obtained from these signals, the ECU 70 executes fuel injection timing control and fuel injection amount control by the fuel injection valve 58, and further controls the opening degree of the EGR valve 56 and the throttle opening degree control by the motor 22b. , And a process for determining a catalyst state to be described later is executed. For example, the throttle opening degree TA and EGR opening detected from the signal of the throttle opening sensor 22a so that the EGR rate becomes a target EGR rate set based on the engine load (or fuel injection amount) and the engine speed NE. EGR control in which the degree (the opening degree of the EGR valve 56) is adjusted is performed. Further, the intake air amount whose EGR opening is adjusted so as to become a target intake air amount (target value per one rotation of the engine 2) set based on the engine load (or fuel injection amount) and the engine speed NE. Feedback control is performed. In addition, as a combustion mode accompanying EGR control, two types of combustion modes, a normal combustion mode and a low temperature combustion mode, are executed. Here, the low-temperature combustion mode is a combustion mode in which NOx and smoke are simultaneously reduced by slowing the increase in combustion temperature by introducing a large amount of EGR gas. In the present embodiment, it is executed in the middle and high rotation region with a low load. The combustion mode other than this is a normal combustion mode in which normal EGR control (including the case where EGR is not performed) is executed.

  The catalyst control mode for executing the control process for the catalyst includes four modes: a PM regeneration control mode, a sulfur poisoning (hereinafter referred to as “S poisoning”) recovery control mode, a NOx reduction control mode, and a normal control mode. Exists. The PM regeneration control mode is a mode in which the PM accumulated in the second catalytic converter 38 is combusted and discharged as CO2 and H2O, and fuel addition from the addition valve 68 is continuously repeated. In this mode, the temperature is increased (for example, 600 to 700 ° C.). The S poison recovery control mode is a mode in which sulfur is released when the NOx storage reduction catalyst in the first catalytic converter 36 and the second catalytic converter 38 is poisoned with sulfur and the NOx storage capability is reduced. In this mode, the addition of fuel from the valve 68 is continuously repeated to increase the catalyst bed temperature (for example, 600 to 700 ° C.). The NOx reduction control mode is a mode in which NOx occluded by the NOx occlusion reduction catalyst in the first catalytic converter 36 and the second catalytic converter 38 is reduced to N2, CO2 and H2O and released. In this mode, the catalyst bed temperature becomes relatively low (for example, 250 to 500 ° C.) by intermittent fuel addition from the addition valve 68 with a relatively long time. The state other than this is the normal control mode, and the reducing agent is not added from the addition valve 68 in this normal control mode.

  Next, the process for determining normality / abnormality executed by the ECU 70 for the NOx storage reduction catalyst stored in the first catalytic converter 36 will be described. The flowchart of this process is shown in FIGS. This process is a process that is interrupted and executed at regular intervals. The steps in the flowchart corresponding to individual processes are represented by “S˜”.

  First, the catalyst state detection execution condition determination process (FIG. 2) will be described. When this process is started, it is first determined whether or not the precondition is satisfied (S102). Here, the precondition is the following condition.

  (1) The PM regeneration control mode or the S poison recovery control mode. In this mode, the reducing agent is continuously added from the addition valve 68, and the amount added is larger than that in the NOx reduction control mode.

  (2) The catalyst bed temperature of the NOx storage reduction catalyst stored in the catalytic converters 36, 38 is equal to or higher than the reference temperature. This determines that catalytic activity is occurring. The catalyst bed temperature uses the exhaust gas temperature detected by the first exhaust gas temperature sensor 44 and the second exhaust gas temperature sensor 46 as an alternative value. In addition to this, the catalyst bed temperature is estimated and calculated based on the engine operating state, for example, the engine speed and the amount of fuel injected from the fuel injection valve 58, considering the response delay due to the heat capacity, and the amount of heat given from the exhaust. Also good.

  (3) A combustion mode in which the deterioration state of the NOx storage reduction catalyst can be detected. Examples of the combustion mode include combustion modes other than the low-temperature combustion mode. In the low-temperature combustion mode, particularly when the air-fuel ratio is lowered to near the stoichiometric air-fuel ratio by EGR, the catalyst bed temperature of the NOx storage reduction catalyst in the first catalytic converter 36 may fluctuate greatly. This is to prevent a decrease in detection accuracy.

  (4) The downstream exhaust temperature detected by the second exhaust temperature sensor 46 is less than the high temperature limit temperature. This is because if the temperature is too high, the detection accuracy of the temperature rise in the second exhaust temperature sensor 46 is lowered.

  (5) The target catalyst bed temperature is equal to or higher than the reference temperature. Here, depending on the engine operating state, there is a case where control for stopping the addition of the reducing agent from the addition valve 68 and temporarily lowering the catalyst bed temperature is executed, so that the target catalyst bed temperature is set to maintain the detection accuracy. The condition is that the temperature is higher than the reference temperature.

  (6) No abnormality is detected in the first exhaust temperature sensor 44 and the second exhaust temperature sensor 46. Separately, it is determined that an abnormality such as disconnection is not detected in the abnormality detection process of each exhaust temperature sensor 44, 46 executed by the ECU 70. Note that the PM regeneration control mode and the S poison recovery control mode are not executed when the first exhaust temperature sensor 44 is abnormal. For this reason, since the establishment of the condition (1) indicates that the first exhaust temperature sensor 44 is not abnormal, the condition may be that only the second exhaust temperature sensor 46 is not detected.

  (7) The amount of attached fuel in the exhaust manifold 32 is equal to or less than the reference value. This is because the amount of attached fuel in the exhaust manifold 32 is periodically calculated in the attached fuel amount calculation processing separately executed by the ECU 70, but the detection accuracy of the catalyst state is lowered when the amount of attached fuel is large.

  (8) The deactivation phenomenon of the NOx storage reduction catalyst in the catalytic converters 36 and 38 does not occur. Even if the catalyst bed temperature is high, the catalyst activity may be deactivated when the exhaust temperature is lowered. Therefore, it is determined from the engine operating state that the catalyst temperature is deactivated so that the catalyst activity is deactivated.

(9) The output voltage from the battery is greater than or equal to the reference voltage. This is because the detection accuracy of the exhaust temperature sensors 44 and 46 is lowered at low voltage, so that the detection accuracy is maintained.
(10) The post-addition elapsed counter that counts the elapsed time from the addition of the reducing agent from the addition valve 68 is below the reference value. This is because, if a long time elapses after the addition, the reaction in the NOx occlusion reduction catalyst ends or becomes dull, and the detection accuracy decreases.

  It is assumed that the precondition is satisfied when all of these conditions (1) to (10) are satisfied. Therefore, if any one of the conditions (1) to (10) is not satisfied (“NO” in S102), the precondition completion counter that counts the duration when the precondition is satisfied is cleared (S104), and the catalyst A detection execution flag for determining whether or not to execute state detection is set to “OFF” (S106). In this way, this process is once completed. Thereafter, if the precondition is not satisfied (“NO” in S102), the execution of steps S104 and S106 is repeated.

  A case where the precondition is satisfied (“YES” in S102) will be described. First, the precondition completion counter is counted up (S108). For example, by incrementing, the time is counted in units of the control cycle of this process.

  Next, it is determined whether or not the precondition establishment counter is greater than or equal to a reference value (S110). Instead, the determination may be made based on whether or not the intake air amount integrated from the time when the precondition is satisfied is greater than or equal to the reference amount. If the precondition satisfying counter <the reference value (“NO” in S110), the normality / abnormality of the NOx storage reduction catalyst in the first catalytic converter 36 cannot be detected, so the detection execution flag is set to “OFF”. (S106), and this process is temporarily terminated.

  If the precondition fulfillment counter continues counting up (S108), and the precondition fulfillment counter ≧ reference value (“YES” in S110), the detection execution flag is set to “ON” (S112). In this way, this process is once completed.

  If the preconditions continue to be established in the next control cycle (“YES” in S102), the precondition establishment counter continues to count up (S108) and the detection execution flag = “ON” (S112) Will continue.

  If the precondition is not satisfied (“NO” in S102), the aforementioned steps S104 and S106 are executed, the precondition completion counter is returned to “0”, and the detection execution flag is returned to “OFF”. .

  Next, normality determination processing (FIG. 3) will be described. When this process is started, it is first determined whether or not a normal condition is satisfied (S132). Normal conditions are shown in the following (1) to (3). If (1) is not satisfied, “NO” is immediately determined in step S132, and the determinations (2) and (3) are not made.

(1) Detection execution flag = “ON”.
(2) The difference “thci1−thcab” between the actually measured temperature thci1 of the first exhaust temperature sensor 44 and the estimated failure bed temperature thcab is equal to or greater than the normal reference temperature difference dthcn.

(3) The estimated failure bed temperature thcab is within the reference temperature.
The estimated failure bed temperature thcab is separately calculated by the ECU 70 by the calculation process according to the equation 1 based on the operating state of the engine 2, and is repeatedly calculated in a time period. The catalyst bed of the NOx occlusion reduction catalyst in the first catalytic converter 36 is calculated. It is warm. However, the NOx occlusion reduction catalyst in the first catalytic converter 36 is estimated and calculated on the assumption that no catalytic reaction is performed.

[Equation 1]
thcab ←
thcabold + (thex-thcabold) x Kth
... [Formula 1]
In the right side of Equation 1, the previous estimated failure bed temperature thcabold represents the estimated failure bed temperature thcab calculated in the previous cycle. Here, the estimated exhaust temperature thex is a value obtained from a map from the rotational speed NE of the engine 2 and the fuel injection amount Q from the fuel injection valve 58, and this map is obtained through experiments. The annealing coefficient Kth is a coefficient of less than “1.0” reflecting a response delay with respect to the exhaust temperature caused by the heat capacity in the first catalytic converter 36, and is obtained in advance by experiments.

If the normal condition is not satisfied (“NO” in S132), the normal condition satisfaction counter is set to “0” (S134), and this process is temporarily terminated.
When the normal condition is satisfied (“YES” in S132), the normal condition satisfaction counter is incremented (S136). For example, by incrementing, the time is counted in units of the control cycle of this process.

  Next, it is determined whether or not the normal condition satisfaction counter is equal to or greater than a reference value (S138). If the normal condition satisfaction counter <the reference value (“NO” in S138), this process is terminated as it is. When the normal condition satisfaction counter continues to count up and normal condition satisfaction counter ≧ reference value (“YES” in S138), the normal determination (determination that the NOx storage reduction catalyst in the first catalytic converter 36 is normal) is made. (S140). It should be noted that when such normality determination is made continuously for the reference number of times, the normality determination may be officially made for the first time.

  Next, the abnormality determination process (FIG. 4) will be described. When this process is started, it is first determined whether or not an abnormal condition is satisfied (S162). Abnormal conditions are shown in the following (1) to (5). If (1) is not satisfied, “NO” is immediately determined in step S162, and determinations (2) to (5) are not made.

(1) Detection execution flag = “ON”.
(2) The difference “thci1-thcab” between the actually measured temperature thci1 of the first exhaust temperature sensor 44 and the estimated failure bed temperature thcab is less than the reference temperature difference dthcb (<dthcn) at the time of abnormality.

(3) The estimated failure bed temperature thcab is within the reference temperature.
(4) The actually measured temperature thci1 of the first exhaust temperature sensor 44 is within the reference value.
(5) The difference between the measured temperature thci2 of the second exhaust temperature sensor 46 and the measured temperature thci1 of the first exhaust temperature sensor 44 is within the reference difference.

  The estimated failure bed temperature thcab is a catalyst bed temperature estimated and calculated on the assumption that the NOx occlusion reduction catalyst in the first catalytic converter 36 is not performing a catalytic reaction at all, as described in the above equation 1. is there.

If the abnormal condition is not satisfied (“NO” in S162), “0” is set to the abnormal condition satisfaction counter (S164), and this process is temporarily terminated.
When the abnormal condition is satisfied (“YES” in S162), the abnormal condition satisfaction counter is incremented (S166). For example, by incrementing, the time is counted in units of the control cycle of this process.

  Next, it is determined whether or not the abnormal condition satisfaction counter is equal to or greater than a reference value (S168). If the abnormal condition establishment counter <the reference value (“NO” in S168), the present process is terminated as it is. When the abnormal condition satisfaction counter continues to count up and the abnormal condition satisfaction counter ≧ reference value (“YES” in S168), an abnormality determination (determination that the NOx storage reduction catalyst in the first catalytic converter 36 is abnormal) is made. (S170). In addition, when such abnormality determination is continuously performed for the reference number of times, it may be formally determined for the first time.

  An example of processing according to the present embodiment is shown in the timing charts of FIGS. FIG. 5 shows an example of normal determination. Here, when the precondition establishment counter reaches the reference value after the precondition is established (t0) (t1), the normal condition is established in the normal condition establishment determination (S132). When the counter reaches the reference value (t2), a normal determination is made (S140). FIG. 6 shows an example of abnormality determination. Here, when the precondition establishment counter reaches the reference value after the precondition is established (t10) (t11), the abnormal condition is established in the abnormal condition establishment determination (S162). When the counter reaches the reference value (t12), an abnormality determination is made (S170). FIG. 7 shows an example in which the deterioration of the NOx storage reduction catalyst in the first catalytic converter 36 is progressing, but the abnormality determination is not made because the purification function of the NOx storage reduction catalyst in the second catalytic converter 38 is sufficient. Is shown. After the precondition is satisfied (t20), the precondition completion counter reaches the reference value (t21). However, in the abnormal condition establishment determination (S162), the difference between the measured temperature thci2 of the second exhaust temperature sensor 46 and the measured temperature thci1 of the first exhaust temperature sensor 44 exceeds the reference difference, and the condition (5) is not satisfied. Therefore, the abnormal condition satisfaction counter does not reach the reference value (“NO” in S162). For this reason, abnormality determination is not made.

  In the configuration described above, the catalyst state detection execution condition determination process (FIG. 2), the normality determination process (FIG. 3), and the abnormality determination process (FIG. 4) are used as the exhaust purification catalyst deterioration determination method and the exhaust purification catalyst deterioration determination device. Equivalent to. Here, the estimated failure bed temperature thcab is the “catalyst bed temperature estimated according to the operating state of the internal combustion engine by assuming that the exhaust purification catalyst is not in a catalytic reaction” and the catalyst bed temperature. The estimation means corresponds to the catalyst bed temperature estimated and calculated in the same manner. The measured temperature thci1 of the first exhaust temperature sensor 44 is a medium that is affected by the measured catalyst bed temperature in a state where the reactant for purifying the exhaust purification catalyst is supplied to the exhaust purification catalyst. The medium temperature actually measured "and the exhaust temperature detected by the exhaust temperature sensor at the time of purification correspond to the exhaust temperature measured by the exhaust temperature sensor. The abnormal reference temperature difference dthcb corresponds to the reference deterioration degree in the claims. The first exhaust temperature sensor 44 corresponds to the exhaust temperature sensor in the claims. The process of detecting the actually measured temperature thci1 of the first exhaust temperature sensor 44 in order to determine the condition (2) in steps S132 and S162 corresponds to the process as the purification exhaust temperature detection means. The process of calculating the estimated failure bed temperature thcab in the above equation 1 corresponds to the process as the catalyst bed temperature estimation means. The determination of the condition (2) in steps S132 and S162 corresponds to the processing as the deterioration degree determination means. The determinations of the conditions (2) and (5) in step S162 and step S170 correspond to processing as abnormality determination means. Condition (1) in step S102 corresponds to processing as a prohibition means. The rotational speed NE of the engine 2 corresponds to the rotational speed of the internal combustion engine, and the fuel injection amount Q from the fuel injection valve 58 corresponds to the fuel supply amount for combustion.

According to the first embodiment described above, the following effects can be obtained.
(I). In the condition (2) determined in steps S132 and S162, the difference “thci1−thcab” between the actually measured temperature thci1 of the first exhaust temperature sensor 44 and the estimated failure bed temperature thcab is calculated. The measured temperature thci1 and the estimated fault bed temperature thcab are compared by a method of determining whether this difference is equal to or greater than the normal reference temperature difference dthcn or less than the abnormal reference temperature difference dthcb.

  Among these, the estimated failure bed temperature thcab is the catalyst bed temperature when it is assumed that the NOx storage reduction catalyst in the first catalytic converter 36 is not performing a catalytic reaction. This state is equivalent to a state in which the reducing agent is supplied to the completely deteriorated NOx storage reduction catalyst, or a state in which the NOx storage reduction catalyst is not completely deteriorated but no reducing agent is supplied at all. The first catalytic converter 36 is not in the NOx occlusion reduction catalyst. For this reason, the catalyst bed temperature is determined only by heat transfer with the exhaust discharged from the combustion chamber 4 of the engine 2. Since the exhaust temperature can be estimated according to the operating state of the engine 2, the estimated failure bed temperature thcab of the NOx occlusion reduction catalyst that is not performing the catalytic reaction according to the equation 1 can be easily estimated according to the operating state of the engine 2. .

  The actually measured temperature thci1 of the exhaust discharged from the first catalytic converter 36 detected by the first exhaust temperature sensor 44 reflects the actual reaction heat in the NOx storage reduction catalyst inside the first catalytic converter 36. Therefore, it should be higher than the estimated failure bed temperature thcab according to the reaction heat. Therefore, if the NOx occlusion reduction catalyst in the first catalytic converter 36 is deteriorated, the heat of reaction should be reduced according to the degree of this deterioration and reflected in the measured temperature thci1.

Therefore, the difference “thci1−thcab” is calculated and the magnitude of the reference temperature difference dthcn, dthcb is determined, thereby determining the state of reaction heat and determining the degree of deterioration.
Then, normality determination (S140) is performed on condition that the difference “thci1−thcab” ≧ normal reference temperature difference dthcn. That is, since sufficient reaction heat is generated in the NOx occlusion reduction catalyst in the first catalytic converter 36 when the reducing agent is supplied, it is determined that there is no deterioration or that the progress of the deterioration is not problematic.

  On the other hand, the abnormality determination (S170) is performed on condition that “thci1-thcab” <dthcb. That is, when the deterioration of the NOx storage reduction catalyst progresses and the difference “thci1−thcab” becomes small and sufficient reaction heat is not generated in the NOx storage reduction catalyst of the first catalytic converter 36 when the reducing agent is supplied, the deterioration occurs. It is determined that there is an abnormality because there is a possibility that the exhaust gas purification may cause a problem in exhaust gas purification.

  In this way, the degree of deterioration of the NOx storage reduction catalyst can be determined with high accuracy by the degree of the difference “thci1−thcab”. Since the estimated failure bed temperature thcab can be estimated and calculated according to the operating state of the engine 2, it is not necessary to detect the deterioration degree of the NOx occlusion reduction catalyst during idling, and a reducing agent is supplied to purify the NOx occlusion reduction catalyst. As long as it is in the state. For this reason, it is possible to detect the deterioration degree of the NOx storage reduction catalyst within a wide operating range and in a transitional period of the operating state. In this manner, the exhaust purification catalyst used in the engine 2 can improve the frequency of execution of deterioration determination while maintaining the accuracy of deterioration determination.

As a result, the abnormality determination (S170) can also be performed with high accuracy and high frequency, and measures such as replacement of the exhaust purification catalyst can be quickly executed based on the abnormality determination.
(B). In step S162, the condition for abnormality determination is that the difference between the actually measured temperature thci2 of the second exhaust temperature sensor 46 and the actually measured temperature thci1 of the first exhaust temperature sensor 44 is within the reference difference according to the condition (5). Therefore, if the difference between the measured temperature thci2 and the measured temperature thci1 exceeds the reference difference, it indicates that the abnormality determination (S170) cannot be performed. If the difference between the measured temperature thci2 and the measured temperature thci1 is large, the NOx occlusion reduction catalyst in the second catalytic converter 38 existing downstream of the first catalytic converter 36 has sufficiently generated heat in the catalytic reaction, and the NOx normally It can be purified.

  Therefore, since the comprehensive purification capacity of the first catalytic converter 36 and the second catalytic converter 38 indicates that the NOx discharged from the engine 2 can be sufficiently purified, the deterioration on the first catalytic converter 36 side proceeds considerably. Even if it is, it is prohibited to judge it as abnormal. Thus, the operation of the engine 2 can be continued for a long time while maintaining a sufficient exhaust purification state.

  In particular, when clogging occurs in the first catalytic converter 36 and the catalytic reaction is biased, the exhaust temperature does not sufficiently flow depending on the measurement position by the first exhaust temperature sensor 44, and the measured temperature thci1 is lowered and an inaccurate value is detected. Therefore, it may be determined that “thci1-thcab” <dthcb. However, in the case of clogging, the NOx occlusion reduction catalyst in the second catalytic converter 38 often performs a sufficient purification function. Therefore, as described above, the condition (5) is set as the logical product condition of the condition including (2), and if the condition (5) is not satisfied, it is not determined to be abnormal. While maintaining the above, the operation of the engine 2 can be continued over a long period of time.

  (C). In the present embodiment, the determination is performed only in the PM regeneration control mode and the S poison recovery control mode based on the determination of the precondition (S102). This PM regeneration control mode and S poisoning recovery control mode are catalyst control modes in which heat of reaction is sufficiently generated unless the reducing agent is continuously added from the addition valve 68 and the NOx storage reduction catalyst is not deteriorated. It is. In the NOx reduction control mode and the normal control mode, which are catalyst control modes other than this, the addition of the reducing agent is intermittent or not added at all, and sufficient reaction heat is not generated.

  As described above, the determination is performed in the catalyst control mode in which the addition amount of the reducing agent is sufficient, and the determination in the catalyst control mode in which the addition amount of the reducing agent is insufficient is prohibited. As a result, it is possible to prevent the deterioration degree of the exhaust purification catalyst and the determination accuracy of abnormality / normality from being lowered.

[Embodiment 2]
In the present embodiment, assuming that the NOx occlusion reduction catalyst that has not deteriorated at all is stored in the first catalytic converter 36, the estimated normal bed temperature thcax is calculated, and the estimated normal bed temperature thcax and the measured temperature thci1 are calculated. By comparing, the degree of deterioration is determined, and normality / abnormality is determined.

  In the present embodiment, the normal condition in step S132 in FIG. 3 of the first embodiment is different, and the abnormal condition in step S162 in FIG. 4 is different. The catalyst state detection execution condition determination process is the same as in FIG. Other configurations are the same as those in the first embodiment. Therefore, the same reference numerals as those in the first embodiment are used.

  The normal condition of step S132 in FIG. 3 in the present embodiment will be described. The normal conditions in this case are the same as in the first embodiment with respect to (1) and (3) among (1) to (3) described in the first embodiment. The condition (2) is as follows.

(2) The difference “thcax−thci1” between the actually measured temperature thci1 of the first exhaust temperature sensor 44 and the estimated normal bed temperature thcax is equal to or less than the normal reference temperature difference dthxn.
The estimated normal bed temperature thcax is separately calculated by the ECU 70 by the calculation process according to Equation 2 and repeatedly calculated in a time period based on the operating state of the engine 2. The catalyst bed of the NOx occlusion reduction catalyst in the first catalytic converter 36 is calculated. It is warm. As described above, it is assumed that the NOx occlusion reduction catalyst in the first catalytic converter 36 is not deteriorated at all, and the catalytic reaction is performed by supplying a sufficient reducing agent (PM regeneration control mode or S poisoning recovery control mode). The estimated calculation.

[Equation 2]
thcax ←
thcaxold + think
+ (Thex-thcaxold) × Kth ... [Formula 2]
In the right side of Equation 2, the previous estimated normal bed temperature thcaxold indicates the estimated normal bed temperature thcax calculated in the previous cycle. The reaction temperature increase rate thinc represents the temperature increase for one cycle occurring in a new NOx storage reduction catalyst that has not deteriorated in the PM regeneration control mode or the S poison recovery control mode. This temperature rise is obtained from the map by the heat capacity in the first catalytic converter 36 and the previously estimated normal bed temperature thcaxold. This map has been determined experimentally. The estimated exhaust temperature thex and the smoothing coefficient Kth are as described in the first embodiment.

  Therefore, if the measured temperature thci1 is closer to the estimated normal bed temperature thcax, that is, if the difference “thcax−thci1” is equal to or less than the normal reference temperature difference dthxn, it can be determined that the catalytic reaction is sufficient and the deterioration has not progressed.

As a result, as described in the first embodiment, it is possible to perform highly accurate determination in the normal determination process (FIG. 3).
The abnormal condition in step S162 in FIG. 4 will be described. This abnormal condition is the same as (1) and (3) to (5) in (1) to (5) described in the first embodiment, as in the first embodiment. The condition (2) is as follows.

(2) The difference “thcax−thci1” between the actually measured temperature thci1 of the first exhaust temperature sensor 44 and the estimated normal bed temperature thcax exceeds the reference temperature difference dthxb (> dthxn) at the time of abnormality.
Therefore, if the measured temperature thci1 is further away from the estimated normal bed temperature thcax to the lower temperature side, that is, if the difference “thcax−thci1” exceeds the abnormal reference temperature difference dthxb, the catalytic reaction is insufficient and the deterioration proceeds. Can be determined.

As a result, as described in the first embodiment, highly accurate determination can be performed by the abnormality determination process (FIG. 4).
An example of processing according to this embodiment is shown in the timing charts of FIGS. FIG. 8 shows an example of normal determination. The precondition is satisfied (t30), and the precondition satisfaction counter reaches the reference value (t31). At this time, since the normal condition is satisfied (“YES” in S132), when the normal condition satisfaction counter reaches the reference value (t32), a normal determination is made (S140). FIG. 9 shows an example at the time of abnormality determination. The precondition is satisfied (t40), and the precondition satisfaction counter reaches the reference value (t41). At this time, since the abnormal condition is satisfied (“YES” in S162), when the abnormal condition satisfied counter reaches the reference value (t42), an abnormality determination is made (S170). FIG. 10 shows an example in which the deterioration of the NOx storage reduction catalyst in the first catalytic converter 36 is progressing, but the abnormality determination is not made because the purification function of the NOx storage reduction catalyst in the second catalytic converter 38 is sufficient. Is shown. After the precondition is satisfied (t50), the precondition establishment counter reaches the reference value (t51). However, in the abnormal condition establishment determination (S162), the difference between the measured temperature thci2 of the second exhaust temperature sensor 46 and the measured temperature thci1 of the first exhaust temperature sensor 44 exceeds the reference difference, and the condition (5) is not satisfied. Therefore, the abnormal condition satisfaction counter does not reach the reference value (“NO” in S162). For this reason, abnormality determination is not made.

  In the above-described configuration, the estimated normal bed temperature thcax is “the catalyst bed estimated and calculated according to the operating state of the internal combustion engine by assuming that the exhaust purification catalyst is in a state of performing a catalytic reaction at a predetermined deterioration degree”. The “temperature” and the catalyst bed temperature estimating means correspond to the catalyst bed temperature estimated and calculated in the same manner. The abnormal reference temperature difference dthxb corresponds to the reference deterioration degree in the claims. The process of calculating the estimated normal bed temperature thcax in the above equation 2 corresponds to the process as the catalyst bed temperature estimation means. The relationship with the claims of other configurations is as described in the first embodiment.

According to the second embodiment described above, the following effects can be obtained.
(I). In the condition (2) determined in steps S132 and S162 in the present embodiment, the difference “thcax−thci1” between the actually measured temperature thci1 of the first exhaust temperature sensor 44 and the estimated normal bed temperature thcax is calculated. . The measured temperature thci1 and the estimated normal bed temperature thcax are compared by a method of determining whether this difference is equal to or less than the normal reference temperature difference dthxn or exceeds the abnormal reference temperature difference dthxb.

  Among these, the estimated normal bed temperature thcax is estimated and calculated on the assumption that the NOx occlusion reduction catalyst in the first catalytic converter 36 is performing a catalytic reaction with a predetermined deterioration degree. Specifically, the estimation calculation is performed on the assumption that the new article has not deteriorated at all. This state is the catalyst bed temperature when the reaction heat is sufficiently generated in the NOx occlusion reduction catalyst of the first catalytic converter 36, and the catalyst bed temperature is between the exhaust discharged from the combustion chamber 4 of the engine 2. It is determined by the heat transfer and the calorific value. The exhaust temperature can be estimated according to the operating state of the engine 2, and the heat generation amount can also be determined in advance from the state in which the reducing agent is supplied in the PM regeneration control mode or the S poison recovery control mode. From this, the estimated normal bed temperature thcax of the NOx occlusion reduction catalyst performing the catalytic reaction can be easily estimated according to the operating state of the engine 2 according to the above equation 2.

  Since the measured temperature thci1 of the exhaust discharged from the first catalytic converter 36 detected by the first exhaust temperature sensor 44 reflects the actual reaction heat in the NOx storage reduction catalyst, the estimated normal bed temperature thcax. Should be lower depending on the degree of degradation. Therefore, the difference “thcax−thci1” is calculated, and normality determination (S140) is performed on the condition that “thcax−thci1” ≦ dthxn. Also, abnormality determination (S170) is performed on the condition that “thcax−thci1”> dthxb.

  In this way, the degree of deterioration of the NOx storage reduction catalyst can be determined with high accuracy based on the degree of the difference “thcax−thci1”. Since the estimated normal bed temperature thcax can be estimated and calculated according to the operating state of the engine 2 as described above, it is not necessary to detect the deterioration degree of the NOx storage reduction catalyst during idling, and the reduction is performed to purify the NOx storage reduction catalyst. The agent may be in a state where it is supplied to the NOx storage reduction catalyst. For this reason, it is possible to detect the deterioration degree of the NOx storage reduction catalyst within a wide operating range and in a transitional period of the operating state. In this manner, the exhaust purification catalyst used in the engine 2 can improve the frequency of execution of deterioration determination while maintaining the accuracy of deterioration determination. As a result, the abnormality determination (S170) can also be performed with high accuracy and high frequency, and measures such as replacement of the exhaust purification catalyst can be quickly executed based on the abnormality determination.

(B). The same effects as (b) and (c) of the first embodiment are produced.
[Embodiment 3]
In the present embodiment, the NOx occlusion reduction has a predetermined degree of deterioration, that is, an intermediate degree of deterioration between a catalyst that has not deteriorated at all and a completely deteriorated catalyst, and is in a state of deterioration at the boundary between normal and abnormal. Assuming that the catalyst is accommodated in the first catalytic converter 36, the estimated deterioration bed temperature thcay is calculated. Then, the degree of deterioration is determined by comparing the estimated deteriorated bed temperature thcay and the actually measured temperature thci1, and normality / abnormality is determined.

  In the present embodiment, the normal condition in step S132 in FIG. 3 of the first embodiment is different, and the abnormal condition in step S162 in FIG. 4 is different. The catalyst state detection execution condition determination process is the same as in FIG. Other configurations are the same as those in the first embodiment. Therefore, the same reference numerals as those in the first embodiment are used.

  The normal condition of step S132 in FIG. 3 in the present embodiment will be described. This normal condition is the same as in the first embodiment with respect to (1) and (3) among (1) to (3) described in the first embodiment. The condition (2) is as follows.

(2) Actual temperature thci1 of first exhaust temperature sensor 44 ≧ estimated deteriorated bed temperature thcay + α. (Here α is a margin.)
The estimated deteriorated bed temperature thcay is separately calculated by the ECU 70 by the calculation process according to the equation 3 based on the operating state of the engine 2 and repeatedly calculated in a time period. The catalyst bed of the NOx storage reduction catalyst in the first catalytic converter 36 It is warm. As described above, it is assumed that the NOx occlusion reduction catalyst in the first catalytic converter 36 is performing a catalytic reaction by supplying a sufficient reducing agent in the PM regeneration control mode or the S poison recovery control mode with a predetermined deterioration degree. Estimated.

[Equation 3]
thcay ←
thcayold + thin
+ (Thex-thcayold) × Kth ... [Formula 3]
In the right side of Equation 3, the previous estimated bed temperature thcaold indicates the estimated bed temperature thcay calculated in the previous cycle. The reaction temperature increase rate thind represents a temperature increase for one cycle occurring in the NOx storage reduction catalyst having a predetermined deterioration level in the PM regeneration control mode or the S poison recovery control mode. This temperature rise is obtained from the map by the heat capacity in the first catalytic converter 36 and the previously estimated deteriorated bed temperature thcayold. This map is obtained by experiments using a NOx occlusion reduction catalyst in a predetermined deterioration state. The estimated exhaust temperature thex and the smoothing coefficient Kth are as described in the first embodiment.

  Therefore, the catalyst reaction is sufficient and the deterioration is not progressing as “thci1 ≧ thcay + α” and the measured temperature thci1 is far from the estimated deterioration bed temperature thcay, that is, the measured temperature thci1 is larger than “thcay + α”. Can be judged. As a result, as described in the first embodiment, it is possible to perform highly accurate determination in the normal determination process (FIG. 3).

  The abnormal condition in step S162 in FIG. 4 will be described. This abnormal condition is the same as (1) and (3) to (5) in (1) to (5) described in the first embodiment, as in the first embodiment. The condition (2) is as follows.

(2) Actual measured temperature thci1 of first exhaust temperature sensor 44 <estimated deteriorated bed temperature thcay.
Therefore, as the measured temperature thci1 is smaller than the estimated deterioration bed temperature thcay, it can be determined that the catalytic reaction is insufficient and the deterioration is progressing. As a result, as described in the first embodiment, highly accurate determination can be performed by the abnormality determination process (FIG. 4).

  An example of processing according to this embodiment is shown in the timing charts of FIGS. FIG. 11 shows an example of normal determination. The precondition is established (t60), and the precondition establishment counter reaches the reference value (t61). At this time, since the normal condition is satisfied (“YES” in S132), when the normal condition satisfaction counter reaches the reference value (t62), a normal determination is made (S140). FIG. 12 shows an example at the time of abnormality determination. The precondition is established (t70), and the precondition establishment counter reaches the reference value (t71). At this time, since the abnormal condition is satisfied (“YES” in S162), when the abnormal condition satisfied counter reaches the reference value (t72), an abnormality determination is made (S170). FIG. 13 shows an example in which the deterioration of the NOx storage reduction catalyst in the first catalytic converter 36 is progressing, but the abnormality determination is not made because the purification function of the NOx storage reduction catalyst in the second catalytic converter 38 is sufficient. Is shown. The precondition is satisfied (t80), and the precondition completion counter reaches the reference value (t81). However, in the abnormal condition establishment determination (S162), the difference between the measured temperature thci2 of the second exhaust temperature sensor 46 and the measured temperature thci1 of the first exhaust temperature sensor 44 exceeds the reference difference, and the condition (5) is not satisfied. Therefore, the abnormal condition satisfaction counter does not reach the reference value (“NO” in S162). For this reason, abnormality determination is not made.

  In the above-described configuration, the estimated deterioration bed temperature thcay is calculated according to the operation state of the internal combustion engine by assuming that the exhaust purification catalyst is in a state of performing a catalytic reaction at a predetermined deterioration degree. The “temperature” and the catalyst bed temperature estimating means correspond to the catalyst bed temperature estimated and calculated in the same manner. Further, the estimated deterioration bed temperature thcay corresponds to the standard deterioration degree of the claims. The process of calculating the estimated deteriorated bed temperature thcay according to Equation 3 corresponds to the process as the catalyst bed temperature estimating means. The relationship with the claims of other configurations is as described in the first embodiment.

According to the third embodiment described above, the following effects can be obtained.
(I). In the condition (2) determined in steps S132 and S162 in the present embodiment, the magnitudes of the actually measured temperature thci1 of the first exhaust temperature sensor 44 and the estimated deteriorated bed temperature thcay are compared. The estimated deterioration bed temperature thcay is estimated and calculated on the assumption that the NOx occlusion reduction catalyst in the first catalytic converter 36 is in a state of performing a catalytic reaction at a reference deterioration degree that is a boundary between normal and abnormal. Therefore, taking into account the margin α, it can be easily determined that “thci1 ≧ thcay + α” is normal and “thci1 <thcay” is abnormal.

  In this way, by comparing the measured temperature thci1 of the first exhaust temperature sensor 44 with the estimated deteriorated bed temperature thcay, the degree of deterioration of the NOx storage reduction catalyst can be determined with high accuracy. Since the estimated deterioration bed temperature thcay can be estimated and calculated according to the operating state of the engine 2, it is not necessary to detect the deterioration degree of the NOx storage reduction catalyst during idling, and the reducing agent is NOx to purify the NOx storage reduction catalyst. What is necessary is just to be the state currently supplied with respect to the storage reduction catalyst. For this reason, it is possible to detect the deterioration degree of the NOx storage reduction catalyst within a wide operating range and in a transitional period of the operating state. In this manner, the exhaust purification catalyst used in the engine 2 can improve the frequency of execution of deterioration determination while maintaining the accuracy of deterioration determination. As a result, the abnormality determination (S170) can also be performed with high accuracy and high frequency, and measures such as replacement of the exhaust purification catalyst can be quickly executed based on the abnormality determination.

(B). The same effects as (b) and (c) of the first embodiment are produced.
[Embodiment 4]
In the present embodiment, the precondition of step S102 in FIG. 2 (catalyst state detection execution condition determination process) of the first embodiment is different. Other configurations are the same as those in the first embodiment. Therefore, the same reference numerals as those of the first embodiment will be used with reference to FIGS.

In the present embodiment, there are seven preconditions for step S102 as follows.
(1) The PM regeneration control mode or the S poison recovery control mode. In this mode, the reducing agent is continuously added from the addition valve 68, and the amount added is larger than that in the NOx reduction control mode.

  (2) A combustion mode in which the deterioration state of the NOx storage reduction catalyst can be detected. Examples of the combustion mode include combustion modes other than the low-temperature combustion mode. In the low-temperature combustion mode, particularly when the air-fuel ratio is lowered to near the stoichiometric air-fuel ratio by EGR, the catalyst bed temperature of the NOx storage reduction catalyst in the first catalytic converter 36 may fluctuate greatly. This is to prevent a decrease in detection accuracy.

  (3) The downstream exhaust temperature detected by the second exhaust temperature sensor 46 is less than the high temperature limit temperature. This is because if the temperature is too high, the detection accuracy of the temperature rise in the second exhaust temperature sensor 46 is lowered.

  (4) No abnormality is detected in the first exhaust temperature sensor 44 and the second exhaust temperature sensor 46. Separately, it is determined that an abnormality such as disconnection is not detected in the abnormality detection process of each exhaust temperature sensor 44, 46 executed by the ECU 70. Note that the PM regeneration control mode and the S poison recovery control mode are not executed when the first exhaust temperature sensor 44 is abnormal. For this reason, since the establishment of the condition (1) indicates that the first exhaust temperature sensor 44 is not abnormal, the condition may be that only the second exhaust temperature sensor 46 is not detected.

  (5) The amount of fuel adhering to the exhaust manifold 32 is less than or equal to the reference value. This is because the amount of attached fuel in the exhaust manifold 32 is periodically calculated in the attached fuel amount calculation processing separately executed by the ECU 70, but the detection accuracy of the catalyst state is lowered when the amount of attached fuel is large.

(6) The output voltage from the battery is greater than or equal to the reference voltage. This is because the detection accuracy of the exhaust temperature sensors 44 and 46 is lowered at low voltage, so that the detection accuracy is maintained.
(7) The difference “thcax−thcab” between the estimated normal bed temperature thcax and the estimated failure bed temperature thcab is equal to or greater than the reference estimated temperature difference dthcx. Here, the estimated normal bed temperature thcax is the same as the estimated normal bed temperature thcax used in the second embodiment. That is, the estimated normal bed temperature thcax is separately calculated in the first catalytic converter 36 in the time period based on the operating state of the engine 2 by the calculation process according to the expression 2 of the second embodiment separately in the ECU 70. This is the catalyst bed temperature of the NOx storage reduction catalyst. As described in the second embodiment, the estimated normal bed temperature thcax is estimated and calculated on the assumption that the catalytic reaction is performed in a state in which the NOx storage reduction catalyst in the first catalytic converter 36 is not deteriorated at all.

  When all of these conditions (1) to (7) are satisfied, it is assumed that the precondition is satisfied (YES in S102). Subsequent processing in FIG. 2 (catalyst state detection execution condition determination processing), normality determination processing (FIG. 3), and abnormality determination processing (FIG. 4) are as described in the first embodiment.

  An example of processing according to this embodiment is shown in the timing charts of FIGS. The case of FIG. 14 shows a case where the conditions (1) to (6) are satisfied (t90) in a state where the NOx storage reduction catalyst in the first catalytic converter 36 is sufficiently activated. ing. It is estimated that sufficient reaction heat is generated in the NOx occlusion reduction catalyst in the first catalytic converter 36 due to the addition of the reducing agent from the addition valve 68 in the PM regeneration control mode or the S poison recovery control mode. As shown, the estimated normal bed temperature thcax rises rapidly. Further, the estimated failure bed temperature thcab is hardly changed as indicated by the one-dot chain line because the reaction heat is not generated in the NOx occlusion reduction catalyst in the first catalytic converter 36 even by the addition of the reducing agent from the addition valve 68.

  Thus, after the conditions from the preconditions (1) to (6) are satisfied (from t90), the difference “thcax−thcab” between the estimated normal bed temperature thcax and the estimated failure bed temperature thcab is determined as the reference estimate. The temperature difference is greater than or equal to dthcx (t91). Accordingly, since the remaining precondition (7) is satisfied (YES in S102), the precondition establishment counter can immediately start counting up (S108). In the case of this embodiment, the reference value for determining the precondition establishment counter may be made smaller than in the case of the first embodiment. Alternatively, if all the preconditions are satisfied without providing the precondition completion counter (YES in S102), the detection execution flag may be immediately set to “ON” (S112).

  Among the preconditions, in particular, the state where (7) is satisfied indicates that the reaction heat can be sufficiently generated unless the NOx occlusion reduction catalyst in the first catalytic converter 36 has failed. Therefore, as shown in FIG. 14, there is a clear difference between the measured temperature thci1 (solid line) of the first exhaust temperature sensor 44 at normal time and the measured temperature thci1 (broken line) at the time of failure. Therefore, in the determination of the difference “thci1−thcab” between the actually measured temperature thci1 and the estimated failure bed temperature thcab, which is performed in the normal determination process (FIG. 3) and the abnormality determination process (FIG. 4), it is determined whether the normal or abnormal with high accuracy. Can be defeated.

  As in the case of FIG. 15, the conditions from the preconditions (1) to (6) were satisfied with the NOx storage reduction catalyst in the first catalytic converter 36 deactivated or insufficiently activated. In the case of (ta), it is presumed that no or sufficient reaction heat is generated in the NOx storage reduction catalyst in the first catalytic converter 36 (two-dot chain line). Accordingly, as shown in FIG. 15, there is no clear difference between the measured temperature thci1 (solid line) of the first exhaust temperature sensor 44 at normal time and the measured temperature thci1 (broken line) at the time of failure. Therefore, if (thcax−thcab) <dthcx, the precondition is not satisfied (NO in S102), and the actually measured temperature thci1 and the estimated failure floor performed in the normal determination process (FIG. 3) and the abnormal determination process (FIG. 4). An erroneous determination is prevented in the determination of the difference “thci1−thcab” from the temperature thcab.

  In the configuration described above, the state in which the NOx occlusion reduction catalyst in the first catalytic converter 36 for which the estimated normal bed temperature thcax is estimated and calculated has not deteriorated at all corresponds to the first predetermined deterioration degree. The state in which the NOx occlusion reduction catalyst in the first catalytic converter 36 for which the estimated failure bed temperature thcab is estimated is not performing a catalytic reaction, that is, the exhaust purification catalyst is completely deteriorated, which corresponds to the second predetermined deterioration degree. To do. The relationship with the claims of other configurations is as described in the first embodiment.

According to the fourth embodiment described above, the following effects can be obtained.
(I). In the precondition determination (S102) of the present embodiment, the estimated normal bed temperature thcax calculated in a state where the NOx storage reduction catalyst is not deteriorated at all and the estimation calculated in a state where the NOx storage reduction catalyst is not performing a catalytic reaction. It is included as a condition that the difference from the fault bed temperature thcab is larger than the reference estimated temperature difference dthcx. That is, (thcax−thcab) ≧ dthcx is one of the preconditions for starting the normality determination process (FIG. 3) and the abnormality determination process (FIG. 4).

  In a state where the NOx storage reduction catalyst in the first catalytic converter 36 is deactivated or in a state where the activity is insufficient, the difference between the measured temperature thci1 and the estimated failure bed temperature thcab even if the NOx storage reduction catalyst is not deteriorated. And the determination of the degree of deterioration by comparison tends to cause erroneous determination. Furthermore, in order to improve the determination accuracy, it is necessary to compare the measured temperature thci1 with the estimated fault bed temperature thcab after always waiting for a long time, and it is difficult to make a quick determination.

  Therefore, in the present embodiment, calculation is performed on the assumption that the degree of deterioration is different, that is, the estimated normal bed temperature thcax calculated on the assumption that the NOx storage reduction catalyst is not deteriorated at all, and the state of complete deterioration. The estimated failure bed temperature thcab is used to compare (thcax−thcab) with the reference estimated temperature difference dthcx.

  If (thcax−thcab) <dthcx, it is assumed that the NOx occlusion reduction catalyst in the first catalytic converter 36 is in an inactivated state or an engine operating state in which the activity is not sufficient, and normal determination processing (FIG. 3) Processing with the determination processing (FIG. 4) is prohibited.

  On the other hand, if (thcax−thcab) ≧ dthcx, it can be determined that the engine is in an operating state in which a catalytic reaction sufficiently occurs in the NOx storage reduction catalyst. And allow processing. This prevents erroneous determination of the degree of deterioration due to comparison. Further, if it can be determined that the engine operating state in which a catalytic reaction sufficiently occurs in the NOx occlusion reduction catalyst, it is possible to immediately make a highly accurate determination, so there is no need to always wait for a long time. Accordingly, it is possible to quickly determine the degree of deterioration with high accuracy.

(B). The same effects as (a), (b) and (c) of the first embodiment are produced.
[Other embodiments]
(A). In the embodiment, instead of detecting the exhaust temperature by the first air-fuel ratio sensor 42, a temperature sensor is provided for the NOx storage reduction catalyst in the first catalytic converter 36, and the catalyst of the NOx storage reduction catalyst is directly provided. The bed temperature may be detected. The catalyst bed temperature detected in this case corresponds to “a catalyst bed temperature measured in a state where a reactant for purifying the exhaust purification catalyst is supplied to the exhaust purification catalyst”.

  (B). The supply of the reducing agent to the NOx occlusion reduction catalyst in the catalytic converters 36 and 38 is performed by adding fuel from the addition valve 68. In addition to this, the fuel injection valve 58 that is performed in the combustion chamber 4 during the expansion stroke. The reducing agent may be supplied to the NOx storage reduction catalyst by fuel injection that does not contribute to combustion from the so-called post injection. In this case, the same effect as the above-described configuration in which the reducing agent is supplied from the addition valve 68 is produced.

  (C). In the third embodiment, the estimated deteriorated bed temperature thcay is calculated by the above equation 3 assuming that the catalyst is a NOx occlusion reduction catalyst in the reference deterioration degree state. However, the NOx in which the deterioration degree progresses more than the reference deterioration degree. The calculation may be performed on the assumption that the catalyst is a storage reduction catalyst or a NOx storage reduction catalyst that has not progressed. Since the estimated deteriorated bed temperature thcay obtained by this assumption also serves as a reference, the actual degree of deterioration of the NOx storage reduction catalyst can be determined with high accuracy based on the relative relationship between the estimated deteriorated bed temperature thcay and the actually measured temperature thci1.

  That is, when the measured temperature thci1 is higher than the estimated deteriorated bed temperature thcay, it can be determined that the degree of deterioration is higher as the difference between the actually measured temperature thci1 and the estimated deteriorated bed temperature thcay is smaller. When the measured temperature thci1 is lower than the estimated deteriorated bed temperature thcay, it is determined that the degree of deterioration is higher than that when the measured temperature is thci1 and the degree of deterioration is higher as the difference between the measured temperature thci1 and the estimated deteriorated bed temperature thcay is larger. be able to.

  (D). In the fourth embodiment, the difference between the estimated normal bed temperature thcax estimated on the assumption of complete undegradation and the estimated failure bed temperature thcab calculated on the assumption of complete deterioration is determined. In addition to this, the intermediate deterioration degree between completely undeteriorated and complete deterioration is set as one or both of two kinds of deterioration degrees (corresponding to the first predetermined deterioration degree and the second predetermined deterioration degree). May be estimated and used. Thus, the active state of the NOx occlusion reduction catalyst is also reflected by the difference between the two estimated bed temperatures estimated by assuming that the degree of deterioration is in an intermediate state for one or both. For this reason, the same effect as in the fourth embodiment can be produced by making the determination on the difference between the two estimated bed temperatures a precondition for starting the determination of the degree of deterioration.

The block diagram showing schematic structure of the diesel engine for vehicles, and a control apparatus. The flowchart of the catalyst state detection execution condition determination process which ECU performs. Similarly, a flowchart of normality determination processing. The flowchart of an abnormality determination process similarly. 4 is a timing chart illustrating an example of processing according to the first embodiment. 4 is a timing chart illustrating an example of processing according to the first embodiment. 4 is a timing chart illustrating an example of processing according to the first embodiment. 9 is a timing chart illustrating an example of processing according to the second embodiment. 9 is a timing chart illustrating an example of processing according to the second embodiment. 9 is a timing chart illustrating an example of processing according to the second embodiment. 10 is a timing chart illustrating an example of processing according to the third embodiment. 10 is a timing chart illustrating an example of processing according to the third embodiment. 10 is a timing chart illustrating an example of processing according to the third embodiment. 9 is a timing chart illustrating an example of processing according to the fourth embodiment. 9 is a timing chart illustrating an example of processing according to the fourth embodiment.

Explanation of symbols

  2 ... Diesel engine, 4 ... Combustion chamber, 6 ... Intake valve, 8 ... Intake port, 10 ... Intake manifold, 12 ... Surge tank, 13 ... Intake passage, 14 ... Intercooler, 16 ... Exhaust turbocharger, 16a ... Compressor, 16b ... exhaust turbine, 18 ... air cleaner, 20 ... EGR path, 20a ... EGR gas supply port, 20b ... EGR gas intake port, 22 ... throttle valve, 22a ... throttle opening sensor, 22b ... motor, 24 ... intake air amount sensor , 26 ... Intake temperature sensor, 28 ... Exhaust valve, 30 ... Exhaust port, 32 ... Exhaust manifold, 34 ... Exhaust path, 36 ... First catalytic converter, 38 ... Second catalytic converter, 40 ... Third catalytic converter, 42 ... 1st air-fuel ratio sensor, 44 ... 1st exhaust temperature sensor, 46 ... 2nd exhaust temperature sensor, 48 ... 2nd air-fuel ratio sensor, 5 ... Differential pressure sensor, 52 ... EGR catalyst, 54 ... EGR cooler, 56 ... EGR valve, 58 ... Fuel injection valve, 58a ... Fuel supply pipe, 60 ... Common rail, 62 ... Fuel pump, 64 ... Fuel pressure sensor, 66 ... Fuel Supply pipe, 68 ... addition valve, 70 ... ECU, 72 ... accelerator pedal, 74 ... accelerator opening sensor, 76 ... cooling water temperature sensor, 78 ... crankshaft, 80 ... engine speed sensor, 82 ... cylinder discrimination sensor.

Claims (25)

A catalyst deterioration determination method for determining a deterioration state of an exhaust purification catalyst provided in an exhaust system of an internal combustion engine,
Assuming that the exhaust purification catalyst is not in a catalytic reaction, the estimated catalyst bed temperature according to the operating state of the internal combustion engine and the reactant for purifying the exhaust purification catalyst are An internal combustion engine characterized in that the degree of deterioration of the exhaust purification catalyst is determined by comparing the measured catalyst bed temperature in a state where the exhaust gas is supplied or a measured medium temperature with respect to a medium affected by the catalyst bed temperature. Of determining exhaust gas purification catalyst deterioration. 2. The internal combustion engine according to claim 1, wherein the deterioration degree of the exhaust purification catalyst is determined to be higher as the difference between the estimated and calculated catalyst bed temperature and the measured catalyst bed temperature or the measured medium temperature is smaller. Engine exhaust purification catalyst deterioration judgment method. A catalyst deterioration determination method for determining a deterioration state of an exhaust purification catalyst provided in an exhaust system of an internal combustion engine,
Assuming that the exhaust purification catalyst is in a state of performing a catalytic reaction at a predetermined deterioration level, the catalyst bed temperature estimated according to the operating state of the internal combustion engine and the reactant for purifying the exhaust purification catalyst are exhausted. Determining the degree of deterioration of the exhaust purification catalyst by comparing the measured catalyst bed temperature while being supplied to the purification catalyst or the measured medium temperature with respect to the medium affected by the catalyst bed temperature An exhaust purification catalyst deterioration determination method for an internal combustion engine. In Claim 3, when the measured catalyst bed temperature or measured medium temperature is higher than the estimated catalyst bed temperature, the measured catalyst bed temperature or measured medium temperature and the estimated calculated catalyst bed temperature The smaller the difference is, the higher the degree of degradation is,
When the actually measured catalyst bed temperature or the actually measured medium temperature is lower than the estimated catalyst bed temperature, the measured catalyst bed temperature or the actually measured medium temperature is deteriorated more than when the estimated catalyst bed temperature is higher than the estimated catalyst bed temperature. The exhaust purification catalyst deterioration determination for an internal combustion engine, wherein the deterioration degree is higher as the difference between the measured catalyst bed temperature or the measured medium temperature and the estimated calculated catalyst bed temperature is larger. Method. The exhaust gas of an internal combustion engine according to any one of claims 1 to 4, wherein the exhaust gas purification catalyst is determined to be abnormal if the deterioration level of the exhaust gas purification catalyst is more deteriorated than a reference deterioration level. Purification catalyst deterioration judgment method. 6. The internal combustion engine according to claim 5, wherein a second exhaust purification catalyst that is purified by the same reactant is provided downstream of the exhaust purification catalyst, and the deterioration degree of the exhaust purification catalyst is more advanced than the reference deterioration degree. An exhaust purification catalyst deterioration determination method for an internal combustion engine, wherein the exhaust purification catalyst is not determined to be abnormal if the second exhaust purification catalyst has not deteriorated even in the state. 7. The exhaust purification catalyst according to claim 6, wherein the measured temperature difference between the upstream exhaust temperature and the downstream exhaust temperature of the second exhaust purification catalyst is smaller than the abnormal reference temperature difference. An exhaust purification catalyst deterioration determination method for an internal combustion engine, which is included as a logical product condition in the case of determining that it is abnormal. The exhaust purification catalyst according to any one of claims 1 to 7, wherein the exhaust purification catalyst includes a NOx storage reduction catalyst and is supplied with a reducing agent as the reactant, whereby the NOx stored in the NOx storage reduction catalyst is purified by reduction. A method for determining deterioration of an exhaust gas purification catalyst for an internal combustion engine, wherein The catalyst bed temperature according to any one of claims 1 to 8, wherein the exhaust purification catalyst is assumed to be in a state in which a catalytic reaction is being performed at a first predetermined deterioration level, and estimated and calculated in accordance with an operating state of the internal combustion engine. , Assuming that the exhaust purification catalyst is performing a catalytic reaction at a second predetermined deterioration level that is different from the first predetermined deterioration level, and a catalyst bed temperature estimated according to the operating state of the internal combustion engine. An exhaust purification catalyst deterioration determination method for an internal combustion engine, wherein the difference is larger than a reference estimated temperature difference as a precondition for starting the determination of the deterioration degree. 10. The first predetermined deterioration degree is a state in which the exhaust purification catalyst is not deteriorated at all, and the second predetermined deterioration degree is a state in which the exhaust purification catalyst is completely deteriorated. An exhaust purification catalyst deterioration determination method for an internal combustion engine. A catalyst deterioration determination device for determining a deterioration state of an exhaust purification catalyst provided in an exhaust system of an internal combustion engine,
An exhaust temperature sensor for detecting the exhaust temperature discharged from the exhaust purification catalyst;
A purification-time exhaust gas temperature detecting means for measuring an exhaust gas temperature with the exhaust gas temperature sensor in a state where a reactant for purifying the exhaust gas purification catalyst is supplied to the exhaust gas purification catalyst;
Assuming that the exhaust purification catalyst is not in a catalytic reaction, catalyst bed temperature estimation means for estimating and calculating the catalyst bed temperature reached by the exhaust purification catalyst according to the operating state of the internal combustion engine;
Deterioration degree determination means for determining the degree of deterioration of the exhaust purification catalyst by comparing the exhaust temperature measured by the purification exhaust temperature detection means and the catalyst bed temperature estimated by the catalyst bed temperature estimation means; ,
An exhaust gas purification catalyst deterioration determination device for an internal combustion engine, comprising: In claim 11, the deterioration degree determination means, the smaller the difference between the exhaust temperature measured by the purification exhaust temperature detection means and the catalyst bed temperature estimated by the catalyst bed temperature estimation means, An exhaust purification catalyst deterioration determining device for an internal combustion engine, wherein the exhaust purification catalyst deterioration degree is determined to be high. A catalyst deterioration determination device for determining a deterioration state of an exhaust purification catalyst provided in an exhaust system of an internal combustion engine,
An exhaust temperature sensor for detecting the exhaust temperature discharged from the exhaust purification catalyst;
A purification-time exhaust gas temperature detecting means for measuring an exhaust gas temperature with the exhaust gas temperature sensor in a state where a reactant for purifying the exhaust gas purification catalyst is supplied to the exhaust gas purification catalyst;
Assuming that the exhaust purification catalyst is in a state of performing a catalytic reaction at a predetermined deterioration level, catalyst bed temperature estimating means for estimating and calculating the catalyst bed temperature reached by the exhaust purification catalyst according to the operating state of the internal combustion engine,
Deterioration degree determination means for determining the degree of deterioration of the exhaust purification catalyst by comparing the exhaust temperature measured by the purification exhaust temperature detection means and the catalyst bed temperature estimated by the catalyst bed temperature estimation means; ,
An exhaust gas purification catalyst deterioration determination device for an internal combustion engine, comprising: The exhaust gas temperature measured by the purifying exhaust gas temperature detecting means is higher than the catalyst bed temperature estimated by the catalyst bed temperature estimating means. The smaller the difference between the temperature and the estimated catalyst bed temperature, the higher the degree of deterioration,
When the exhaust gas temperature measured by the purification exhaust gas temperature detecting means is lower than the catalyst bed temperature estimated by the catalyst bed temperature estimating means, the exhaust gas temperature is higher than the estimated catalyst bed temperature. An exhaust purification catalyst deterioration determination device for an internal combustion engine, wherein the deterioration degree is higher than the case and the deterioration degree is higher as the difference between the exhaust temperature and the estimated catalyst bed temperature is larger. 15. The exhaust gas purification catalyst deterioration determination for an internal combustion engine according to claim 11, wherein the catalyst bed temperature estimation means uses an internal combustion engine speed and a fuel supply amount for combustion as an operating state of the internal combustion engine. apparatus. 16. The abnormality determination unit according to claim 11, further comprising: an abnormality determination unit that determines that the exhaust purification catalyst is abnormal if the deterioration degree of the exhaust purification catalyst is in a state in which the deterioration has advanced from a reference deterioration degree. An exhaust purification catalyst deterioration determination device for an internal combustion engine. 17. The internal combustion engine according to claim 16, further comprising a second exhaust purification catalyst that is purified by the same reactant downstream of the exhaust purification catalyst, and the abnormality determination means determines that the deterioration degree of the exhaust purification catalyst is a reference degradation. An exhaust purification catalyst deterioration determination device for an internal combustion engine, wherein even if the deterioration has progressed more than the degree, the exhaust purification catalyst is not determined to be abnormal unless the second exhaust purification catalyst has deteriorated. In Claim 17, while providing the 2nd exhaust gas temperature sensor which detects the exhaust gas temperature discharged from the 2nd exhaust gas purification catalyst,
The abnormality determination means is in a state where the temperature difference between the exhaust temperature detected by the second exhaust temperature sensor and the exhaust temperature detected by the exhaust temperature sensor is smaller than the reference temperature difference at the time of abnormality. An exhaust purification catalyst deterioration determination device for an internal combustion engine, characterized in that the exhaust purification catalyst is one of logical product conditions for determining that the exhaust purification catalyst is abnormal. 19. The exhaust purification catalyst deterioration determining apparatus for an internal combustion engine according to claim 11, wherein the reactant is a fuel added to a combustion gas or an exhaust gas during an expansion stroke of the internal combustion engine. 20. The prohibiting means for prohibiting the processing of the deterioration degree determining means or the abnormality determining means when the amount of the reactant added to the combustion gas or exhaust gas is small. An exhaust gas purification catalyst deterioration determining device for an internal combustion engine. 21. The catalyst according to claim 20, wherein the internal combustion engine is provided with a plurality of catalyst control modes having different amounts of the reactant added to the combustion gas or exhaust, and selected from the catalyst control modes according to the state of the exhaust purification catalyst. The control unit executes the control mode, and the prohibiting unit performs the reaction into the combustion gas or the exhaust gas when the catalyst control mode in which the amount of the reactant added is small compared to the other catalyst control modes. An exhaust purification catalyst deterioration determination device for an internal combustion engine, wherein the processing of the deterioration degree determination means or the abnormality determination means is prohibited, assuming that the amount of substance added is small. 23. The exhaust purification catalyst according to claim 21, wherein the exhaust purification catalyst includes a NOx storage reduction catalyst and is supplied with a reducing agent as the reactant, whereby the NOx stored in the NOx storage reduction catalyst is purified by reduction. The catalyst control mode includes at least a particulate material regeneration control mode, a sulfur poisoning recovery control mode, and a NOx reduction control mode, and a catalyst control mode other than the particulate material regeneration control mode and the sulfur poisoning recovery control mode is An exhaust gas purification catalyst deterioration determination device for an internal combustion engine, characterized in that the catalyst control mode is less in the amount of addition of reactants than other catalyst control modes. 23. The catalyst bed temperature estimating means according to claim 20, wherein the catalyst bed temperature estimating means assumes a state in which the exhaust purification catalyst is performing a catalytic reaction at a first predetermined deterioration level, thereby responding to an operating state of the internal combustion engine. The catalyst bed temperature is estimated and calculated, and the exhaust purification catalyst is assumed to be in a state of performing a catalytic reaction at a second predetermined deterioration level that is different from the first predetermined deterioration level. Estimate and calculate the catalyst bed temperature,
The prohibiting means prohibits the processing of the deterioration degree determining means or the abnormality determining means when the difference between the two catalyst bed temperatures estimated by the catalyst bed temperature estimating means is smaller than a reference estimated temperature difference. An exhaust gas purification catalyst deterioration determining device for an internal combustion engine. 24. The method according to claim 23, wherein the first predetermined deterioration degree is a state in which the exhaust purification catalyst is not deteriorated at all, and the second predetermined deterioration degree is a state in which the exhaust purification catalyst is completely deteriorated. An exhaust purification catalyst deterioration determination device for an internal combustion engine. 25. The catalyst bed temperature according to claim 11, further comprising a catalyst bed temperature sensor that detects a catalyst bed temperature of the exhaust purification catalyst, instead of the exhaust temperature sensor. Is used in place of the exhaust temperature, an exhaust purification catalyst deterioration determining device for an internal combustion engine.

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