JP5098479B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine that performs a deterioration determination process for determining the degree of deterioration of an exhaust gas purification catalyst provided in an exhaust passage of the internal combustion engine.

  In order to promote the exhaust purification action of the exhaust purification catalyst provided in the exhaust passage of the internal combustion engine, a fuel addition process in which an unburned fuel component is added to the exhaust purification catalyst as a reactant has been proposed. ing. In this fuel addition process, for example, a method of injecting fuel from a fuel addition valve provided in a portion upstream of the exhaust purification catalyst in the exhaust passage, or an exhaust stroke from the in-cylinder fuel injection valve after normal fuel injection is performed. The fuel is added to the exhaust gas by a method of performing post injection for injecting the fuel therein.

  By the way, in general, the exhaust purification catalyst gradually deteriorates with long-term use, and the exhaust purification capability is lowered. If the exhaust purification catalyst thus deteriorated is continuously used as it is, the exhaust property deteriorates. Therefore, in order to suppress this, appropriate maintenance such as replacement of the deteriorated exhaust purification catalyst with a new one is performed. Here, in order to perform such maintenance at an appropriate timing, it is necessary to accurately grasp the degree of deterioration of the exhaust purification catalyst.

  When the unburned fuel component is supplied to the exhaust purification catalyst by the fuel addition process described above, the catalyst bed temperature rises due to the reaction heat, and the temperature of the exhaust gas passing through the exhaust purification catalyst rises due to the influence of the reaction heat. It becomes like this. Here, since the reaction heat becomes larger as the deterioration degree of the exhaust purification catalyst becomes lower, the temperature of the exhaust gas that has passed through the exhaust purification catalyst changes in correlation with the deterioration degree of the exhaust purification catalyst.

  Therefore, in the apparatus described in Patent Document 1, when the fuel addition process is being performed, based on the exhaust temperature detected by the exhaust temperature sensor provided in the downstream side of the exhaust purification catalyst in the exhaust passage. The degree of reaction heat in the catalyst is estimated, and deterioration determination processing for determining the degree of deterioration of the catalyst based on the magnitude of the reaction heat is executed.

  Specifically, the temperature of the exhaust gas that has passed through the exhaust purification catalyst is detected by an exhaust temperature sensor, and the virtual catalyst bed temperature is calculated on the assumption that the exhaust purification catalyst has deteriorated to a state where no reaction heat is generated. To do. Then, based on the magnitude of the deviation between the detected exhaust temperature and the calculated virtual catalyst bed temperature, it is determined that the smaller the deviation, the smaller the reaction heat in the catalyst and the greater the degree of deterioration of the catalyst. I have to.

Thus, by comparing the exhaust temperature actually detected by the exhaust temperature sensor with the virtual catalyst bed temperature, the degree of deterioration of the exhaust purification catalyst can be determined based on the difference.
JP 2005-69218 A

  By the way, although the value of the exhaust temperature detected by the exhaust temperature sensor provided on the downstream side of the exhaust purification catalyst as described above has a correlation with the degree of deterioration of the catalyst, the magnitude of the correlation is in the vicinity of the exhaust temperature sensor. Varies with exhaust flow rate. For example, when the exhaust flow rate is very small, the flow of exhaust is not uniform, so the exhaust temperature rises due to the reaction heat of the exhaust purification catalyst depending on the exhaust temperature sensor mounting position, the shape of the exhaust passage, etc. However, the exhaust gas may pass without contacting the detection part of the exhaust gas temperature sensor, and the temperature of the exhaust gas may not be detected accurately. In such a case, although the reaction in the catalyst is performed well and the actual catalyst bed temperature has risen sufficiently, the exhaust temperature detected by the exhaust temperature sensor is less likely to rise. There is a risk that the correlation between the exhaust temperature and the degree of deterioration of the catalyst is lowered, and an erroneous determination is made that the exhaust purification catalyst has deteriorated.

  The present invention has been made in view of the above circumstances, and its purpose is to reduce the correlation between the exhaust gas temperature detected by the exhaust gas temperature sensor and the degree of deterioration of the exhaust gas purification catalyst due to the exhaust gas flow rate, thereby deteriorating the exhaust gas purification catalyst. An object of the present invention is to provide an exhaust emission control device for an internal combustion engine that can prevent an erroneous determination to be made.

In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 is a fuel addition means for performing a fuel addition process for adding an unburned fuel component as a reactant to an exhaust purification catalyst provided in an exhaust passage of an internal combustion engine, and the exhaust purification catalyst in the exhaust passage. An exhaust gas temperature sensor provided at a downstream side of the exhaust gas sensor, and is calculated on the assumption that the exhaust purification catalyst has deteriorated to a predetermined degree of deterioration when the fuel addition process is being performed. In the exhaust gas purification apparatus for an internal combustion engine that performs a deterioration determination process for determining a deterioration degree of the exhaust gas purification catalyst based on a magnitude of a deviation between a virtual catalyst bed temperature and an exhaust gas temperature detected by the exhaust gas temperature sensor. comprising an exhaust flow rate estimation means for estimating the exhaust gas flow in the vicinity of the temperature sensor, the inflow exhaust temperature estimation means for estimating, based on the engine operating state the temperature of the exhaust gas flowing into the exhaust purification catalyst, Wherein when the exhaust flow rate is estimated by the exhaust flow rate estimation means while prohibiting the deterioration determination process when it is less than the lower limit flow rate value, the temperature of the exhaust gas estimated by the inflow exhaust temperature estimating means is lower than a predetermined temperature The gist is that the deterioration determination process is prohibited, and the predetermined temperature is set to a higher temperature as the estimated exhaust flow rate is larger .

  When the exhaust flow rate is very small, the flow of exhaust is not uniform, so depending on the exhaust temperature sensor mounting position, the shape of the exhaust passage, etc., even if the exhaust gas temperature rises due to the reaction heat of the exhaust purification catalyst, The exhaust gas may pass without contacting the detection part of the exhaust gas temperature sensor, and the temperature of the exhaust gas may not be detected accurately. In such a case, the correlation between the exhaust temperature detected by the exhaust temperature sensor and the degree of deterioration of the exhaust purification catalyst is reduced, so that the reliability of the determination result obtained through the deterioration determination process is reduced. In the first aspect of the invention described above, when the correlation between the exhaust temperature and the degree of deterioration of the exhaust purification catalyst is reduced, that is, the exhaust flow rate in the vicinity of the exhaust temperature sensor estimated by the exhaust flow rate estimating means is the lower limit flow rate value. If it is less, the deterioration determination process is prohibited. As a result, an erroneous determination that the exhaust purification catalyst has deteriorated can be suppressed.

  The lower limit flow rate value is a lower limit value of the exhaust flow rate that can determine the degree of deterioration of the exhaust purification catalyst with sufficient accuracy based on the exhaust temperature detected by the exhaust temperature sensor. It is set in consideration of the shape of the passage.

Further, the predetermined degree of deterioration includes a state in which the exhaust purification catalyst has not deteriorated at all, and a state in which no reaction heat is generated even when unburned fuel components are supplied.
Further, when the temperature of the exhaust gas flowing into the exhaust purification catalyst is low, the exhaust purification catalyst is difficult to activate, and thus reaction heat is unlikely to be generated. Thus, in a state where reaction heat is unlikely to be generated regardless of the degree of deterioration of the exhaust purification catalyst, the reliability of the determination result obtained through the deterioration determination process decreases. In the above configuration, when the reliability of the determination result obtained through the deterioration determination process is lowered, that is, when the temperature of the exhaust gas flowing into the exhaust purification catalyst is lower than a predetermined temperature, the deterioration determination process is prohibited. ing. As a result, it is possible to suppress an erroneous determination that the exhaust purification catalyst has deteriorated.
Further, as the exhaust gas flow rate increases, the exhaust gas flow velocity increases, and the time taken for the exhaust gas containing the unburned fuel component to pass through the exhaust gas purification catalyst becomes shorter. Becomes shorter. Therefore, even when the temperature of the exhaust gas flowing into the exhaust purification catalyst is the same, the reaction heat decreases as the exhaust gas flow rate increases, and the reliability of the determination result obtained through the deterioration determination process decreases. Therefore, in the above configuration, the predetermined temperature at which the deterioration determination process is prohibited is set to a higher temperature as the exhaust gas flow rate is higher. As a result, the predetermined temperature for prohibiting the execution of the deterioration degree determination process can be set in a manner that matches the change in the reliability of the determination result obtained through the deterioration determination process associated with the change in the exhaust gas flow rate.

According to a second aspect of the present invention, in the first aspect of the invention, the deterioration determination process is performed when the exhaust flow rate estimated by the exhaust flow rate estimating means is greater than or equal to an upper limit flow rate value greater than the lower limit flow rate value. The gist is to prohibit it.

  As the exhaust gas flow rate increases, the exhaust gas flow rate increases, and the time taken for the exhaust gas to pass through the exhaust gas purification catalyst is shortened. Therefore, the period for heat exchange between the exhaust gas purification catalyst and the exhaust gas is shortened. Therefore, when the exhaust flow rate is very high, even if the reaction heat in the catalyst is large, the exhaust temperature is less likely to rise, and the correlation between the degree of catalyst deterioration and the exhaust temperature decreases, so the deterioration determination process The reliability of the determination result obtained through the process will be reduced. In the invention according to the second aspect, when the correlation between the exhaust temperature and the degree of deterioration of the exhaust purification catalyst is thus lowered, that is, when the exhaust flow rate estimated by the exhaust flow rate estimation means is equal to or higher than the upper limit flow rate value. The deterioration determination process is prohibited. As a result, the correlation between the exhaust temperature and the degree of deterioration of the exhaust purification catalyst is lowered, and it is possible to suppress erroneous determination that the exhaust purification catalyst is deteriorated.

  The upper limit flow rate value is an upper limit value of the exhaust gas flow rate that can determine the degree of deterioration of the exhaust gas purification catalyst with sufficient accuracy based on the exhaust gas temperature detected by the exhaust gas temperature sensor. It is set in consideration of the passage area and the like.

Similar to the first aspect of the present invention, the predetermined deterioration degree of the second aspect of the present invention includes a state in which the exhaust purification catalyst is not deteriorated at all or an unburned fuel component is supplied. It shall include the state of deterioration until no heat of reaction is generated.

According to a third aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the first or second aspect , the predetermined degree of deterioration is such that the exhaust purification catalyst has reached a state where no reaction heat is generated by the fuel addition process. The deterioration determination process indicates that the deterioration degree of the exhaust purification catalyst is larger as the difference between the calculated virtual catalyst bed temperature and the exhaust temperature detected by the exhaust temperature sensor is smaller. The gist is to judge.

  According to the above configuration, since it is assumed that the exhaust purification catalyst has deteriorated to a state where no reaction heat is generated by the fuel addition process, the magnitude of the reaction heat that varies depending on the amount of fuel added by the fuel addition process, etc. Therefore, the virtual catalyst bed temperature can be calculated without taking the above into consideration, and the calculation of the virtual catalyst bed temperature is facilitated and the accuracy thereof can be increased. As a result, the degree of deterioration of the exhaust purification catalyst can be determined with higher accuracy. By the way, when the virtual catalyst bed temperature is calculated on the assumption that the exhaust purification catalyst has deteriorated to a state where no reaction heat is generated by the fuel addition treatment as described above, the virtual catalyst bed temperature is It can be determined that the degree of deterioration of the exhaust purification catalyst is larger as the deviation from the exhaust temperature detected by the exhaust temperature sensor is smaller.

According to a fourth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the third aspect , a deviation between the virtual catalyst bed temperature and the exhaust temperature detected by the exhaust temperature sensor through the deterioration determination process is a predetermined amount. The gist of the present invention is to provide an abnormality determining means for determining that an abnormality has occurred in the exhaust purification catalyst when the state of being less than or equal to a predetermined period has continued.

Further, as described in the fourth aspect of the invention, the state where the difference between the virtual catalyst bed temperature and the detected exhaust temperature is less than a predetermined amount, that is, the state where the degree of deterioration of the catalyst is relatively large continues for a predetermined period or longer. By adopting a configuration that sometimes determines that an abnormality occurs in the exhaust purification catalyst, it is possible to accurately determine that the catalyst is in an abnormal state that may deteriorate the exhaust properties due to deterioration of the catalyst. Become.

According to a fifth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the fourth aspect of the present invention, an abnormality notifying means for notifying that the exhaust purification catalyst is informed when it is determined that an abnormality has occurred. The gist is to provide it.

  According to the above configuration, the fact can be notified based on the determination that an abnormality has occurred in the exhaust purification catalyst. As a result, it is possible to urge the implementation of measures such as exchanging the exhaust purification catalyst, and consequently, it is possible to suppress the deterioration of the exhaust properties accompanying the deterioration of the exhaust purification catalyst.

Hereinafter, an embodiment in which an exhaust gas purification apparatus for an internal combustion engine according to the present invention is applied to an exhaust gas purification apparatus for an on-vehicle diesel engine will be described with reference to FIGS.
FIG. 1 is a schematic diagram illustrating a schematic configuration of a diesel engine and an exhaust purification device thereof according to the present embodiment. As shown in FIG. 1, an intake passage 20 and an exhaust passage 30 are connected to the diesel engine 10. The intake passage 20 is provided with an intake throttle valve 21 that is opened and closed by a motor 21a. By changing the opening of the intake throttle valve 21, the amount of air introduced into the combustion chamber 11 is adjusted. The

  The combustion chamber 11 of the diesel engine 10 is provided with a fuel injection valve 12 for each cylinder. These fuel injection valves 12 are connected to a common rail 13 and inject fuel filled in the common rail 13 into the combustion chamber 11. The common rail 13 is supplied with fuel stored in a fuel tank (not shown) by a supply pump 14.

  As shown in FIG. 1, the intake passage 20 and the exhaust passage 30 are connected to a turbocharger 22. The turbocharger 22 rotates the turbine 22 a with the energy of the exhaust gas flowing through the exhaust passage 30 to pressurize the air in the intake passage 20 and send it into the combustion chamber 11.

  Further, as shown in FIG. 1, an exhaust gas recirculation passage that communicates with the intake passage 20 and recirculates a part of the exhaust gas in the exhaust passage 30 to the intake passage 20 at a portion upstream of the turbocharger 22 in the exhaust passage 30. 43 is connected. The exhaust gas recirculation passage 43 is provided with an EGR valve 44 that is opened and closed by a linear solenoid 44a. By changing the opening degree of the EGR valve 44, the exhaust gas recirculated from the exhaust passage 30 to the intake air passage 20 is provided. The quantity is metered.

  As shown in FIG. 1, a catalytic converter 41 and a PM filter 42 are provided in a portion of the exhaust passage 30 downstream of the turbocharger 22. Each of these catalytic converter 41 and PM filter 42 carries a NOx storage reduction catalyst.

The NOx occlusion reduction catalyst occludes NOx in the lean state, while in the rich state, the NOx occluded reacts with CO contained in the exhaust and HC of the unburned fuel component to reduce NOx, _2. Exhaust gas is purified by using CO ₂ and H ₂ O.

  The PM filter 42 is a monolithic filter formed of a porous material, and captures particulate matter (PM) mainly composed of soot and the like in the exhaust gas. As described above, since the NOx storage reduction catalyst is also carried on the PM filter, the PM trapped by the PM filter 42 is oxidized and removed by the oxidation action of the NOx storage reduction catalyst.

  Further, as shown in FIG. 1, a first exhaust temperature sensor 55 is provided in a portion of the exhaust passage 30 downstream of the catalytic converter 41, more specifically, between the catalytic converter 41 and the PM filter 42. Further, a second exhaust temperature sensor 56 is provided in a portion of the exhaust passage 30 downstream of the PM filter 42. These exhaust temperature sensors 55 and 56 detect the temperature of the exhaust gas that has passed through the catalytic converter 41 and the temperature of the exhaust gas that has passed through the PM filter 42, respectively.

  The output signals of these exhaust temperature sensors 55 and 56 are taken into the electronic control unit 50 that controls the diesel engine 10 in an integrated manner. The electronic control unit 50 includes a digital computer having a CPU, ROM, RAM, and the like, and a drive circuit for driving each device of the diesel engine 10. In addition to the exhaust temperature sensors 55 and 56 described above, the electronic control unit 50 includes the amount of air provided in the intake passage 20 and introduced into the diesel engine 10 and its temperature, that is, the intake air amount GA and the intake temperature THA. An air flow meter 51 for detecting, an accelerator opening sensor 52 for detecting an accelerator opening TA indicating the depression amount of an accelerator pedal, a water temperature sensor 53 for detecting an engine cooling water temperature THW of the diesel engine 10, and a rotation for detecting an engine rotational speed NE. A speed sensor 54 and the like are connected. The output signals of these various sensors 51 to 56 are taken into the electronic control device 50.

  The electronic control unit 50 is connected to a catalyst abnormality lamp 60 provided on the instrument panel of the driver's seat. The catalyst abnormality lamp 60 is turned on by the electronic control unit 50 when an abnormality determination is made that an abnormality has occurred in the NOx storage reduction catalyst through an abnormality determination process described later.

  The electronic control unit 50 performs fuel injection timing control and fuel injection amount control by the fuel injection valve 12 based on the output signals of the various sensors 51 to 56. Further, as part of the EGR control for adjusting the amount of exhaust gas recirculated to the intake passage 20 by adjusting the opening degree of the EGR valve 44 and the opening degree of the intake throttle valve 21, and as part of the exhaust purification process, the catalytic converter 41 and the PM A fuel addition process for supplying unburned fuel component HC as a reactant to the filter 42 is executed.

  Note that in the diesel engine 10 of the present embodiment, the combustion mode associated with EGR control is switched between a normal combustion mode and a low-temperature combustion mode. Here, the low-temperature combustion mode is a combustion mode in which a large amount of exhaust gas is recirculated to the intake passage 20 through the exhaust gas recirculation passage 43 to slow combustion and simultaneously reduce NOx and smoke due to HC of the unburned fuel component. In the diesel engine 10 of the present embodiment, this low temperature combustion mode is executed in a low load, medium and high rotation range. On the other hand, it is the normal combustion mode that executes normal EGR control (including the case where the exhaust gas is not recirculated).

Further, there are four types of control modes related to the fuel addition process: a PM removal control mode, a sulfur poisoning recovery control mode, a NOx reduction control mode, and a normal control mode. The PM removal control mode is a mode in which PM accumulated on the PM filter 42 is burned to make CO ₂ and H ₂ O. After normal fuel injection, fuel is injected from the fuel injection valve 12 in the exhaust stroke. In this mode, post-injection for adding fuel to the exhaust gas is continuously repeated to increase the catalyst bed temperature (for example, 600 to 700 ° C.). The sulfur poisoning recovery control mode is a mode in which sulfur is released from the NOx occlusion reduction catalyst when the NOx occlusion reduction catalyst in the catalytic converter 41 and the PM filter 42 is poisoned with sulfur and the NOx occlusion capacity is reduced. In this mode, the addition of fuel to the exhaust by post-injection is continuously repeated to raise the catalyst bed temperature (for example, 600 to 700 ° C.), and the exhaust gas is in a rich state in which a large amount of HC is contained. The NOx reduction control mode, NOx stored in the NOx storage reduction catalyst in the catalytic converter 41 and the PM filter 42 is a mode for reducing the _{N 2.} In this mode, the post-injection is intermittently executed for a relatively long time to keep the catalyst bed temperature at a relatively low temperature (for example, 250 to 500 ° C.) and to make the exhaust gas rich. The state other than this is the normal control mode, and in this normal control mode, fuel is not added to the exhaust by post injection. In the normal control mode, since the exhaust gas is in a lean state, NOx contained in the exhaust gas is stored in the NOx storage reduction catalyst.

  By the way, in general, the exhaust purification catalyst gradually deteriorates with long-term use, and the exhaust purification capability is lowered. In the NOx occlusion reduction catalyst, when the deterioration progresses, it becomes impossible to occlude NOx even in the lean state, or NOx cannot be reduced even in the rich state in the NOx reduction control mode. To do. If the catalyst thus deteriorated is continuously used as it is, the exhaust property deteriorates. Therefore, in order to suppress this, it is necessary to perform appropriate maintenance such as replacing the deteriorated catalyst with a new one. Here, in order to perform such maintenance at an appropriate timing, it is necessary to accurately grasp the deterioration state of the catalyst.

  Therefore, in the exhaust purification device of the present embodiment, the deterioration determination for determining the deterioration state of the NOx storage reduction catalyst based on the magnitude of reaction heat when HC is supplied to the catalytic converter 41 by the fuel addition process. The process is executed. Then, the deterioration state of the catalyst is determined through the deterioration determination process, and it is determined based on the determination result that an abnormality has occurred in the exhaust purification catalyst.

  Hereinafter, control related to determination of deterioration of the NOx storage reduction catalyst will be described with reference to FIGS. 2 is a flowchart showing a flow of a series of processes related to the execution condition determination process for determining whether or not an execution condition of the deterioration determination process is satisfied, and FIG. 3 is a flow of a series of processes related to the normality determination process. FIG. 4 is a flowchart showing a flow of a series of processes related to the abnormality determination process. The processing shown in the flowcharts of FIGS. 2 to 4 is repeatedly executed at a predetermined cycle by the electronic control unit 50 during engine operation.

  First, the execution condition determination process shown in FIG. 2 will be described. When this process is started, it is first determined whether or not an execution condition for executing the deterioration determination process is established through steps S100 to S160.

  Specifically, in step S100, it is determined whether the catalyst control mode is the PM removal control mode or the sulfur poisoning recovery control mode. In these modes, since post injection is continuously executed as described above, the amount of fuel added to the exhaust gas is larger than that in the NOx reduction control mode, and the reaction heat is also increased. As described above, in step S100, it is determined whether or not it is a catalyst control mode in which the amount of fuel added is relatively large and the deterioration state of the catalyst can be determined based on the magnitude of reaction heat.

  In step S110, it is determined whether or not the first exhaust temperature sensor 55 is normal. Here, it is confirmed that an abnormality such as disconnection is not detected in the abnormality detection process of the first exhaust temperature sensor 55 that is separately executed by the electronic control unit 50.

  In step S120, it is determined whether the catalyst bed temperature of the catalytic converter 41 is equal to or higher than the reference temperature. Here, it is confirmed that the NOx storage reduction catalyst is activated based on the catalyst bed temperature being equal to or higher than the reference temperature. Here, the exhaust temperature detected by the first exhaust temperature sensor 55 is used as an alternative value for the catalyst bed temperature of the catalytic converter 41. In addition to this, the catalyst bed temperature may be estimated and calculated based on the operating state of the engine, for example, the engine speed NE and the fuel injection amount Q from the fuel injection valve 12, by the amount of heat given from the exhaust to the catalytic converter 41. .

  In step S130, it is determined whether or not the combustion mode is the normal combustion mode. When the air-fuel ratio is lowered to near the stoichiometric air-fuel ratio by recirculating a large amount of exhaust gas to the intake passage 20 in the low-temperature combustion mode, the catalyst bed temperature of the NOx storage reduction catalyst in the catalytic converter 41 may vary greatly. . Thus, in a state where the catalyst bed temperature fluctuates greatly, the determination accuracy of the deterioration state based on the magnitude of the reaction heat decreases. Therefore, it is confirmed through step S130 that the combustion mode is the normal combustion mode.

  In step S140, it is determined whether or not a post-addition elapsed counter that counts an elapsed time from fuel addition by post-injection is equal to or less than a reference value, that is, whether or not the post-injection execution is within a predetermined period. This is because the reaction in the NOx occlusion reduction catalyst ends or becomes dull after a long time has elapsed after the fuel addition, and the determination accuracy of the deterioration determination process decreases.

  In step S150, the exhaust flow rate in the vicinity of the first exhaust temperature sensor 55 is not less than the lower limit flow rate value EXmin and less than the upper limit flow rate value EXmax. It is determined whether it is in the region.

  When the exhaust gas flow rate is very small, the flow of the exhaust gas is not uniform, so even if the exhaust gas temperature rises due to the reaction heat in the NOx storage reduction catalyst, the exhaust gas contacts the detection part of the first exhaust gas temperature sensor 55. The exhaust temperature may not be detected accurately. Further, as the exhaust gas flow rate increases, the exhaust gas flow rate increases and the time taken for the exhaust gas to pass through the catalytic converter 41 is shortened. Therefore, when the exhaust gas flow rate is very high, the reaction heat in the catalyst is large. However, the exhaust temperature is less likely to rise. Therefore, the execution condition is that the estimated exhaust flow rate is within a predetermined flow rate range from the lower limit flow rate value EXmin to the upper limit flow rate value EXmax. Here, the exhaust flow rate in the vicinity of the first exhaust temperature sensor 55 is estimated based on the value of the intake air amount GA detected by the air flow meter 51.

  The lower limit flow rate value EXmin is a lower limit value of the exhaust flow rate that can determine with sufficient accuracy the degree of deterioration of the NOx storage reduction catalyst in the catalytic converter 41 based on the exhaust temperature detected by the first exhaust temperature sensor 55. Is set in consideration of the mounting position of the first exhaust temperature sensor 55, the shape of the exhaust passage 30, and the like. The upper limit flow rate value EXmax is an upper limit value of the exhaust flow rate that can determine the deterioration degree of the NOx storage reduction catalyst in the catalytic converter 41 with sufficient accuracy based on the exhaust temperature detected by the first exhaust temperature sensor 55. Is set in consideration of the dimensions of the catalytic converter 41, the passage area of the exhaust passage 30, and the like.

  In step S160, it is determined whether the inflow exhaust gas temperature, which is the temperature of the exhaust gas flowing into the catalytic converter 41, is equal to or higher than a predetermined temperature THst. Even if the catalyst bed temperature of the catalytic converter 41 is high, if the temperature of the inflowing exhaust gas flowing into the catalytic converter 41 decreases, the catalyst may not be activated and the reaction may not easily occur, and the deterioration based on the magnitude of the reaction heat There is a risk that the accuracy of the degree determination will decrease. Therefore, the inflow exhaust gas temperature is estimated based on the engine operating state, and it is determined whether there is a possibility that the reaction is less likely to occur based on the estimated temperature. Even if the inflowing exhaust gas temperature is the same, if the exhaust gas flow rate increases, the reaction heat decreases, and the reliability of the determination result obtained through the deterioration determination process decreases. Therefore, here, as the exhaust gas flow rate increases, the predetermined temperature THst Is set to a large value to ensure the determination accuracy of the deterioration determination process.

  If all of these execution conditions are satisfied (steps S100 to S160: all YES), the process proceeds to step S200, and the execution condition satisfaction counter is incremented by a predetermined amount, for example, “1”. Next, in step S210, it is determined whether or not the execution condition satisfaction counter is greater than or equal to a reference value. If it is determined in step S210 that the execution condition satisfaction counter is less than the reference value (step S210: NO), the process proceeds to step S225, the determination execution flag is set to “OFF”, and the process is temporarily terminated. To do. On the other hand, if it is determined in step S210 that the execution condition satisfaction counter is greater than or equal to the reference value (step S210: YES), the process proceeds to step S220, the determination execution flag is set to “ON”, and this process is temporarily performed. finish.

  On the other hand, if any one of the above execution conditions is not satisfied (steps S100 to S160: any one is NO), the process proceeds to step S205 and the execution condition satisfaction counter is set to “0”. Reset to. In step S225, the determination execution flag is set to “OFF”, and this process is temporarily terminated.

  By repeatedly executing the execution condition determination process in this way, if the state where all the execution conditions are satisfied continues, the execution condition satisfaction counter continues to be incremented and the determination execution flag is set to “ON”. After that, the state in which the determination execution flag is set to “ON” continues.

On the other hand, if even one execution condition is not satisfied, the precondition completion counter is reset to “0” and the determination execution flag is set to “OFF”.
Next, the normality determination process shown in FIG. 3 will be described. When this process is started, it is first determined whether or not a normal condition is established through steps S300 and S310.

  Specifically, in step S300, it is determined whether or not the determination execution flag is set to “ON”. If it is determined in step S300 that the determination execution flag is set to “ON” (step S300: YES), the process proceeds to step S310. Then, a difference “TH1−THcat” between the exhaust temperature TH1 detected by the first exhaust temperature sensor 55 and the virtual catalyst bed temperature THcat is calculated, and the difference “TH1−THcat” is equal to or greater than the normal reference temperature difference ΔTHn. It is determined whether or not. Here, the virtual catalyst bed temperature THcat is the catalyst bed temperature of the catalytic converter 41 that is repeatedly calculated at a predetermined cycle based on the engine operating state by the calculation of Equation 1 shown below. However, here, the hypothetical catalyst bed temperature THcat is estimated and calculated on the assumption that the NOx storage reduction catalyst has deteriorated to a state where no reaction heat is generated. That is, in this step S310, the difference between the virtual catalyst bed temperature THcat calculated on the assumption that no reaction heat is generated and the exhaust temperature TH1 actually detected by the first exhaust temperature sensor 55 is large. A deterioration determination process for determining the degree of deterioration of the catalyst based on the above is executed.

THcat ←
THcatold + (THex-THcatold) x Kth ... [Formula 1]
The previous virtual catalyst bed temperature THcatold on the right side of Equation 1 indicates the virtual catalyst bed temperature THcat calculated in the previous cycle. Here, the estimated exhaust temperature THex is a value obtained by referring to the calculation map from the engine speed NE and the fuel injection amount Q. The annealing coefficient Kth is a coefficient of less than “1.0” reflecting the response delay of the exhaust temperature caused by the heat capacity of the catalytic converter 41, and is set based on the results of experiments performed in advance.

  When it is determined that the difference “TH1−THcat” between the calculated virtual catalyst bed temperature THcat and the exhaust temperature TH1 detected by the first exhaust temperature sensor 55 is equal to or larger than the normal reference temperature difference ΔTHn (step S310: YES), it is determined that the reaction heat in the catalytic converter 41 is sufficiently large and the deterioration degree of the NOx storage reduction catalyst is low.

  In step S320, it is determined that the normal condition is satisfied, and the normal condition satisfaction counter is incremented by a predetermined amount, for example, “1”. Next, it progresses to step S330 and it is determined whether a normal condition satisfaction counter is more than a reference value.

  If it is determined in step S330 that the normal condition satisfaction counter is less than the reference value (step S330: NO), this process is once terminated. On the other hand, when it is determined in step S330 that the normal condition establishment counter is equal to or greater than the reference value (step S330: YES), the process proceeds to step S340, and the NOx occlusion reduction catalyst in the catalytic converter 41 is normal. A normal determination is made, the catalyst abnormality lamp 60 is turned off, and this process is temporarily terminated. If the catalyst abnormality lamp 60 is not lit at this time, the process is temporarily terminated while the catalyst abnormality lamp 60 is turned off.

  On the other hand, when it is determined in step S300 that the determination execution flag is “OFF” (step S300: NO), the process proceeds to step S325 without executing the deterioration determination process in step S310. In step S310, if it is determined that the difference “TH1−THcat” between the exhaust temperature TH1 detected by the first exhaust temperature sensor 55 and the virtual catalyst bed temperature THcat is less than the normal reference temperature difference ΔTHn (step S310). (S310: NO), the process proceeds to step S325.

In step S325, the normal condition satisfaction counter is reset to “0”, and this process is temporarily terminated.
By repeatedly executing the normality determination process as described above, a normal determination that the NOx storage reduction catalyst is normal is performed based on the fact that the period during which the normal condition is satisfied continues for a predetermined period or longer. become.

  Next, the abnormality determination process shown in FIG. 4 will be described. When this process is started, it is first determined whether or not an abnormal condition is established through steps S400 and S410.

  Specifically, in step S400, it is determined whether or not the determination execution flag is set to “ON”. If it is determined in step S400 that the determination execution flag is set to “ON” (step S400: YES), the process proceeds to step S410. Then, the difference “TH1−THcat” between the exhaust temperature TH1 detected by the first exhaust temperature sensor 55 and the virtual catalyst bed temperature THcat is calculated, and this difference “TH1−THcat” is less than the abnormality reference temperature difference ΔTHt. It is determined whether or not. The virtual catalyst bed temperature THcat is a virtual catalyst bed temperature THcat calculated on the assumption that no heat of reaction is generated at all by the calculation shown in Expression 1 as described above. That is, in step S410, the virtual catalyst bed temperature THcat calculated on the assumption that no reaction heat is generated at all as in step S310 in the normality determination process described above and the exhaust gas temperature TH1 actually detected by the first exhaust gas temperature sensor 55. A deterioration determination process for determining the degree of deterioration of the catalyst based on the magnitude of the deviation from is executed.

  When it is determined that the difference “TH1−THcat” between the virtual catalyst bed temperature THcat and the exhaust temperature TH1 detected by the first exhaust temperature sensor 55 is less than the abnormal reference temperature difference ΔTHt (step S410: YES). It is determined that the reaction heat in the catalytic converter 41 is very small and the NOx storage reduction catalyst is deteriorated. The abnormal-time reference temperature difference ΔTHt is set to a value smaller than the normal-time reference temperature difference ΔTHn.

  In step S420, it is determined that the abnormal condition is satisfied, and the abnormal condition satisfaction counter is incremented by a predetermined amount, for example, “1”. Next, it progresses to step S430 and it is determined whether the abnormal condition satisfaction counter is more than a reference value. In step S430, when it is determined that the abnormal condition satisfaction counter is less than the reference value (step S430: NO), this process is once terminated. On the other hand, if it is determined in step S430 that the abnormal condition establishment counter is greater than or equal to the reference value (step S430: YES), the process proceeds to step S440, where an abnormality occurs in the NOx storage reduction catalyst in the catalytic converter 41. The abnormality is determined to be present, the catalyst abnormality lamp 60 is turned on, and this process is temporarily terminated. If the catalyst abnormality lamp 60 has already been lit at this time, the process is temporarily terminated while the catalyst abnormality lamp 60 remains lit.

  On the other hand, when it is determined in step S400 that the determination execution flag is “OFF” (step S400: NO), the process proceeds to step S425 without executing the deterioration determination process in step S410. Further, when it is determined in step S410 that the difference “TH1−THcat” between the exhaust temperature TH1 detected by the first exhaust temperature sensor 55 and the virtual catalyst bed temperature THcat is equal to or larger than the abnormality reference temperature difference ΔTHt (step S410). Also in S410: NO), the process proceeds to Step S425.

In step S425, the abnormal condition establishment counter is reset to “0”, and this process is temporarily terminated.
By repeatedly executing this abnormality determination process in this way, an abnormality determination is made that an abnormality has occurred in the NOx storage reduction catalyst based on the fact that the period during which the abnormal condition is satisfied continues for a predetermined period or longer. Then, the catalyst abnormality lamp 60 is turned on.

In the exhaust purification device of this embodiment, the abnormality of the NOx occlusion reduction catalyst is determined by repeatedly executing the processing described with reference to FIGS.
In the exhaust purification apparatus of this embodiment, as described with reference to FIG. 2, the exhaust flow rate in the vicinity of the first exhaust temperature sensor 55 is within a predetermined flow rate range (step S150) and flows into the catalytic converter 41. That the temperature of the exhaust gas to be performed is equal to or higher than the predetermined temperature THst (step S160) is included in the execution condition of the deterioration determination process. Therefore, as shown in FIG. 5, the determination execution region for executing the deterioration determination process is limited based on the exhaust flow rate and the inflow exhaust gas temperature flowing into the catalytic converter 41. Specifically, when the exhaust flow rate is outside a predetermined flow rate range from the lower limit flow rate value EXmin to the upper limit flow rate value EXmax, or when the inflow exhaust gas temperature is lower than the predetermined temperature THst, the deterioration determination process is prohibited.

According to the embodiment described above, the following effects can be obtained.
(1) When the exhaust gas flow rate is very small, the flow of exhaust gas becomes non-uniform, and the correlation between the exhaust gas temperature TH1 detected by the first exhaust gas temperature sensor 55 and the deterioration degree of the NOx storage reduction catalyst decreases. Thus, the reliability of the determination result obtained through the deterioration determination process is reduced. In the exhaust purification apparatus of the above embodiment, when the correlation between the exhaust temperature TH1 and the deterioration degree of the NOx storage reduction catalyst is thus reduced, that is, the estimated exhaust flow rate in the vicinity of the first exhaust temperature sensor 55 is the lower limit flow rate value EXmin. If it is less, the deterioration determination process is prohibited. Therefore, it is possible to suppress an erroneous determination that the NOx storage reduction catalyst is deteriorated.

  (2) As the exhaust gas flow rate increases, the exhaust gas flow velocity increases, and the time taken for the exhaust gas to pass through the catalytic converter 41 is shortened. Therefore, the period for heat exchange between the catalytic converter 41 and the exhaust gas is shortened. . Therefore, when the exhaust gas flow rate is very high, even if the reaction heat in the NOx occlusion reduction catalyst is large, the exhaust gas temperature is less likely to rise, and the correlation between the degree of catalyst deterioration and the exhaust gas temperature TH1 decreases. Thus, the reliability of the determination result obtained through the deterioration determination process is reduced. In the exhaust purification device of the above embodiment, when the correlation between the exhaust temperature TH1 and the deterioration degree of the NOx storage reduction catalyst is thus lowered, that is, when the estimated exhaust flow rate is equal to or higher than the upper limit flow rate value EXmax, the deterioration determination is performed. Processing is prohibited. As a result, the correlation between the exhaust temperature TH1 and the degree of deterioration of the NOx storage reduction catalyst is reduced, and it is possible to suppress an erroneous determination that the NOx storage reduction catalyst is deteriorated.

  (3) In the above embodiment, the hypothetical catalyst bed temperature THcat is calculated on the assumption that the NOx storage reduction catalyst has deteriorated to a state where no reaction heat is generated by the fuel addition process. Therefore, the virtual catalyst bed temperature THcat can be calculated without considering the magnitude of the reaction heat that changes depending on the amount of fuel added by the fuel addition process, and the calculation can be facilitated and the accuracy can be increased. . As a result, the degree of deterioration of the NOx storage reduction catalyst can be determined with higher accuracy.

  (4) NOx occlusion reduction when the difference between the virtual catalyst bed temperature THcat and the detected exhaust temperature TH1 is less than the abnormal reference temperature difference ΔTHt, that is, when the degree of deterioration of the catalyst is relatively large for a predetermined period or longer. It is determined that an abnormality has occurred in the catalyst. Therefore, it can be accurately determined that the catalyst is in an abnormal state where the exhaust properties may deteriorate due to deterioration.

  (5) Since the catalyst abnormality lamp 60 is provided on the instrument panel of the driver's seat and the catalyst abnormality lamp 60 is lit based on the abnormality determination, it is determined that an abnormality has occurred in the NOx storage reduction catalyst. This can be notified based on the above. As a result, it is possible to urge the implementation of measures such as exchanging the catalyst, and as a result, it is possible to suppress the deterioration of the exhaust properties due to the catalyst deterioration.

  (6) When the temperature of the exhaust gas flowing into the catalytic converter 41 is low, the exhaust purification catalyst is difficult to activate, so that reaction heat is unlikely to be generated. Thus, in the state where reaction heat is unlikely to be generated regardless of the degree of deterioration of the NOx storage reduction catalyst, the reliability of the determination result obtained through the deterioration determination process is lowered. In the above embodiment, when the reliability of the determination result obtained through the deterioration determination process is lowered, that is, when the temperature of the exhaust gas flowing into the catalytic converter 41 is lower than the predetermined temperature Thst, the deterioration determination process is prohibited. I am doing so. As a result, it is possible to suppress erroneous determination that the NOx storage reduction catalyst is deteriorated.

  Further, as the exhaust gas flow rate increases, the exhaust gas flow rate increases, and the time taken for the exhaust gas containing the unburned fuel component to pass through the catalytic converter 41 is shortened. Therefore, the unburned fuel component reacts in the NOx storage reduction catalyst. The period is shortened. Therefore, even when the temperature of the exhaust gas flowing into the catalytic converter 41 is the same, the reaction heat decreases as the exhaust gas flow rate increases, and the reliability of the determination result obtained through the deterioration determination process decreases. Therefore, in the above embodiment, the predetermined temperature THst for prohibiting the deterioration determination process is set to a higher temperature as the exhaust flow rate is higher. As a result, the predetermined temperature THst that prohibits execution of the deterioration degree determination process can be set in a manner that matches the change in the reliability of the determination result obtained through the deterioration determination process that accompanies the change in the exhaust flow rate. .

In addition, the said embodiment can also be implemented with the following forms which changed this suitably.
Although one of the conditions for executing the deterioration determination process is that the temperature of the inflowing exhaust gas flowing into the catalytic converter 41 is equal to or higher than the predetermined temperature THst, the configuration is shown in which the predetermined temperature THst is set to a higher temperature as the exhaust flow rate increases. It is also possible to adopt a configuration in which the predetermined temperature THst is set as a constant value regardless of the exhaust gas flow rate.

  In the above embodiment, the exhaust flow rate in the vicinity of the first exhaust temperature sensor 55 is estimated, and it is determined that the estimated exhaust flow rate is in a predetermined flow rate range that is equal to or higher than the lower limit flow rate value EXmin and lower than the upper limit flow rate value EXmax. The configuration is shown as one of the execution conditions (step S150 in FIG. 2). On the other hand, if the exhaust flow rate in the vicinity of the first exhaust temperature sensor 55 is less than the lower limit flow rate value EXmin or greater than or equal to the upper limit flow rate value EXmax, the exhaust flow rate of the exhaust flow rate is prohibited. It is possible to suppress an erroneous determination that the NOx storage reduction catalyst is deteriorated due to a decrease in the determination accuracy of the deterioration determination process associated with the change. Therefore, referring to FIG. 2, if the exhaust flow rate in the vicinity of the first exhaust temperature sensor 55 is at least when it is less than the lower limit flow rate value EXmin or more than the upper limit flow rate value EXmax, the execution of the deterioration determination process is prohibited. Other execution conditions in the execution condition determination process described can be changed as appropriate. For example, a configuration in which step S160 is omitted and the deterioration determination process is executed regardless of the inflow exhaust gas temperature of the exhaust gas flowing into the catalytic converter 41 may be employed. Further, as shown in FIG. 2, in the present embodiment, in steps S100 to S160, the process of sequentially determining whether or not each execution condition is satisfied is shown. It is not limited by the determination order. Therefore, a configuration in which these determinations are performed in another order, or a configuration in which it is determined at a time whether all the conditions are satisfied can be employed.

  -Although the NOx occlusion reduction catalyst was illustrated as an exhaust purification catalyst, this invention can be applied even if it is a catalyst which generate | occur | produces reaction heat by a fuel addition process also in an exhaust purification apparatus provided with another catalyst. For example, the present invention can also be applied to an exhaust purification device that includes an oxidation catalyst that generates oxidation heat by supplying unburned fuel components by fuel addition processing.

  As the fuel addition means, a configuration has been shown in which post-injection is performed and fuel is added to the exhaust gas. In addition, a fuel addition valve is provided in the exhaust passage 30 and fuel is injected from the fuel addition valve so that unburned fuel components It is also possible to adopt a configuration for supplying the exhaust purification catalyst to the exhaust purification catalyst. Further, the amount of unburned fuel contained in the exhaust gas is increased by increasing the fuel injection amount Q in the normal fuel injection from the fuel injection amount at the stoichiometric air-fuel ratio, and the unburned fuel component is supplied to the exhaust purification catalyst. A configuration or the like that performs rich spikes can also be employed.

  In addition to the configuration for determining the degree of deterioration of the catalyst based on the virtual catalyst bed temperature THcat calculated on the assumption that the exhaust purification catalyst has deteriorated to a state where no reaction heat is generated as in the above embodiment, If the magnitude of the reaction heat associated with the fuel addition process is known, the virtual catalyst bed temperature THcat can be calculated on the assumption that the exhaust purification catalyst has an arbitrary degree of deterioration. In this case, the smaller the difference between the virtual catalyst bed temperature THcat and the exhaust gas temperature TH1 detected by the first exhaust gas temperature sensor 55, the closer the actual deterioration degree of the exhaust purification catalyst is to the assumed deterioration degree. can do. For example, the catalyst is based on the magnitude of the difference between the virtual catalyst bed temperature THcat calculated on the assumption that the exhaust purification catalyst is not deteriorated at all and the exhaust temperature TH1 detected by the first exhaust temperature sensor 55. When the degree of deterioration of the exhaust gas is determined, it can be determined that the degree of deterioration of the exhaust purification catalyst is smaller as the difference is smaller.

  -Although the structure which determines the deterioration degree of a catalyst based on the difference of the calculated virtual catalyst bed temperature THcat and the exhaust temperature TH1 detected by the 1st exhaust temperature sensor 55 was shown, calculated virtual catalyst bed temperature THcat In addition to this, as a method for obtaining the magnitude of the difference between the exhaust gas temperature TH1 detected by the first exhaust gas temperature sensor 55, the ratio between the virtual catalyst bed temperature THcat and the detected exhaust gas temperature TH1, for example, “virtual” A configuration in which “catalyst bed temperature THcat / exhaust temperature TH1” is calculated and the degree of deterioration of the catalyst is determined based on the magnitude of this ratio can be mentioned. In the case of adopting such a configuration, it can be determined that the deterioration is progressing as the value is larger. If this value is “1.0”, the actual degree of deterioration of the catalyst is increased. It can be determined that the degree of deterioration is approximately equal to the assumed degree of deterioration.

  In the above embodiment, as the abnormality determination means, the state where the difference between the exhaust temperature TH1 detected by the first exhaust temperature sensor 55 and the virtual catalyst bed temperature THcat is less than the abnormality reference temperature difference ΔTHt continues for a predetermined period or longer. A configuration is sometimes shown in which an abnormality is determined. On the other hand, regardless of whether or not the state where the difference between the virtual catalyst bed temperature THcat and the exhaust gas temperature TH1 is less than a predetermined amount has continued for a predetermined period or longer, the virtual catalyst bed temperature and detection calculated through the deterioration determination process It is also possible to adopt a configuration for determining that an abnormality has occurred in the exhaust purification catalyst when the deviation from the exhaust temperature is less than a predetermined amount.

  In the above embodiment, the configuration in which the deterioration degree of the NOx storage reduction catalyst in the catalytic converter 41 is determined based on the exhaust gas temperature TH1 of the exhaust gas that has passed through the catalytic converter 41 detected by the first exhaust gas temperature sensor 55 has been described. On the other hand, a configuration for determining the deterioration degree of the NOx storage reduction catalyst in the PM filter 42 based on the exhaust gas temperature of the exhaust gas that has passed through the PM filter 42 detected by the second exhaust gas temperature sensor 56, or a second exhaust gas temperature sensor It is also possible to employ a configuration that collectively estimates the degree of deterioration of the NOx storage reduction catalyst in the catalytic converter 41 and the PM filter 42 based on the exhaust gas temperature detected by the engine 56.

  When the abnormality determination is made, the configuration has been shown in which the abnormality of the driver is informed by turning on the catalyst abnormality lamp 60 provided on the instrument panel of the driver's seat. The configuration of the notification means for notifying that it has occurred can be changed as appropriate. For example, a method of displaying a catalyst abnormality warning on a monitor of a car navigation system, a method of notifying the occurrence of abnormality by voice guidance, or a method of notifying the occurrence of abnormality by a warning sound may be employed.

  -Moreover, it is not necessary to provide the alerting | reporting means which alert | reports that abnormality has occurred in this way. For example, even when the notification means is not provided, the abnormality determination result is held in the memory of the electronic control unit 50 and the catalyst is checked when the vehicle state is checked at a dealer or a repair shop. It is only necessary to output a determination result indicating that an abnormality has occurred.

  In the above embodiment, the example in which the exhaust gas purification apparatus for an internal combustion engine according to the present invention is applied to the exhaust gas purification apparatus for an in-vehicle diesel engine has been described, but the present invention is not limited to the in-vehicle engine. Further, it can be applied to a gasoline engine or the like in addition to a diesel engine.

1 is a schematic diagram showing a schematic configuration of a diesel engine and an exhaust purification device thereof according to an embodiment of the present invention. The flowchart which shows the flow of a series of processes concerning the execution condition determination process of the embodiment. The flowchart which shows the flow of a series of processes concerning the normal determination process of the embodiment. The flowchart which shows the flow of a series of processes concerning the abnormality determination process of the embodiment. The graph which shows the relationship between the determination execution area | region of the deterioration determination process concerning the same embodiment, exhaust flow volume, and inflow exhaust gas temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Diesel engine, 11 ... Combustion chamber, 12 ... Fuel injection valve, 13 ... Common rail, 14 ... Supply pump, 20 ... Intake passage, 21 ... Intake throttle valve, 21a ... Motor, 22 ... Turbocharger, 22a ... Turbine, 30 DESCRIPTION OF SYMBOLS ... Exhaust passage, 41 ... Catalytic converter, 42 ... PM filter, 43 ... Exhaust recirculation passage, 44 ... EGR valve, 44a ... Linear solenoid, 50 ... Electronic control unit, 51 ... Air flow meter, 52 ... Accelerator opening sensor, 53 ... Water temperature sensor 54... Rotational speed sensor 55. First exhaust temperature sensor 56. Second exhaust temperature sensor 60.

Claims (5)

Fuel addition means for performing a fuel addition process for adding an unburned fuel component as a reactant to an exhaust purification catalyst provided in an exhaust passage of an internal combustion engine, and a portion downstream of the exhaust purification catalyst in the exhaust passage. An exhaust temperature sensor, and a virtual catalyst bed temperature calculated on the assumption that the exhaust purification catalyst has deteriorated to a predetermined degree of deterioration when the fuel addition process is being performed, and the exhaust temperature. In an exhaust gas purification apparatus for an internal combustion engine that performs a deterioration determination process for determining a degree of deterioration of the exhaust gas purification catalyst based on a magnitude of a deviation from an exhaust gas temperature detected by a sensor,
Exhaust flow rate estimating means for estimating the exhaust flow rate in the vicinity of the exhaust temperature sensor, and inflow exhaust temperature estimating means for estimating the temperature of the exhaust gas flowing into the exhaust purification catalyst based on the engine operating state ,
When the exhaust flow rate estimated by the exhaust flow rate estimation means is less than the lower limit flow rate value, the deterioration determination process is prohibited, and when the exhaust gas temperature estimated by the inflow exhaust gas temperature estimation means is less than a predetermined temperature Prohibiting the deterioration determination process;
The exhaust gas purification apparatus for an internal combustion engine, wherein the predetermined temperature is set to a higher temperature as the estimated exhaust flow rate is larger . The exhaust gas purification apparatus for an internal combustion engine according to claim 1,
The exhaust gas purification apparatus for an internal combustion engine, wherein the deterioration determination process is prohibited when an exhaust flow rate estimated by the exhaust flow rate estimation means is equal to or greater than an upper limit flow rate value larger than the lower limit flow rate value . The exhaust gas purification apparatus for an internal combustion engine according to claim 1 or 2 ,
The predetermined deterioration degree is a deterioration degree when the exhaust purification catalyst has deteriorated to a state where no reaction heat is generated by the fuel addition process.
The internal combustion engine characterized in that the deterioration determination processing determines that the degree of deterioration of the exhaust purification catalyst is larger as the difference between the calculated virtual catalyst bed temperature and the exhaust temperature detected by the exhaust temperature sensor is smaller. Exhaust purification equipment. The exhaust gas purification apparatus for an internal combustion engine according to claim 3 ,
That the exhaust purification catalyst is abnormal when the difference between the virtual catalyst bed temperature and the exhaust temperature detected by the exhaust temperature sensor is less than a predetermined amount through the deterioration determination process for a predetermined period or longer An exhaust gas purifying device for an internal combustion engine, comprising: an abnormality determining means for determining The exhaust gas purification apparatus for an internal combustion engine according to claim 4 ,
An exhaust gas purifying apparatus for an internal combustion engine, comprising: an abnormality notifying means for notifying that an abnormality has occurred in the exhaust purification catalyst.

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