JP4193808B2 - Exhaust purification device for internal combustion engine and method for estimating thermal deterioration of exhaust purification catalyst - Google Patents

Description

  The present invention relates to an exhaust purification device for an internal combustion engine and a method for estimating thermal deterioration of an exhaust purification catalyst.

  In recent years, NOx purification catalysts for purifying NOx (nitrogen oxides) have been disposed in the exhaust passages of some internal combustion engines. In addition, a PM filter that collects PM (Particulate Matter) and a DPNR (Diesel Particulate-NOx Reduction system) catalyst that functions as a NOx purification catalyst have been provided.

  Such various catalysts may be supplied with additives in order to recover and maintain the exhaust purification function. For example, in a NOx purification catalyst, engine fuel or the like is supplied as an additive for reducing and releasing NOx stored therein.

  Moreover, if PM collected in the PM filter is accumulated, pressure loss in the PM filter increases. Therefore, PM collected by supplying fuel as an additive to the PM filter is burned out and the PM filter is regenerated.

  By the way, the temperature of the catalyst is raised by high-temperature exhaust, the oxidation reaction heat of the additive, the heat of combustion of the additive, etc., but the catalyst undergoes thermal degradation in a high-temperature atmosphere. It gradually decreases.

Thus, various devices for estimating the thermal degradation of such a catalyst have been proposed. For example, in the apparatus described in Patent Document 1, thermal degradation of the catalyst is detected based on the temperature history received by the catalyst. More specifically, the degree of progress of thermal degradation of the catalyst based on the temperature of the catalyst (hereinafter referred to as the bed temperature) is calculated every predetermined time. Each time the degree of progress of the same heat deterioration is calculated, the values are sequentially integrated to obtain the degree of heat deterioration, thereby estimating the heat deterioration of the catalyst.
Japanese Patent Laid-Open No. 7-119447

  By the way, in the above-described conventional apparatus, the calculation of the degree of thermal deterioration and the integration of the degree of thermal deterioration are performed at preset time intervals, and the calculation and integration are performed at predetermined time intervals that are fixed values. Done.

  Here, if such a time interval is too long, there is a concern that the following problems occur. That is, even if the catalyst excessive temperature rises temporarily within the time interval, the bed temperature is increased by the low temperature after the excessive temperature increase. Therefore, such an excessive temperature rise is less likely to be reflected in the bed temperature that is referred to when calculating the degree of progress of thermal degradation, and it is difficult to appropriately estimate the thermal degradation of the catalyst.

  On the other hand, if the time interval is shortened, the bed temperature can be referred to before the temperature of the excessively high catalyst is lowered. Accordingly, such an excessive temperature rise is easily reflected in the bed temperature referred to when calculating the degree of progress of thermal deterioration, and the thermal deterioration of the catalyst can be estimated appropriately.

  However, if the time interval is shortened in this way, there is a concern that the following new problems may occur. That is, the integrated value of the degree of progress of thermal deterioration is generally stored in a storage device such as a RAM (Random Access Memory). Here, since the numerical value is processed in the binary system in the storage device, the numerical value that can be processed is an integer. Therefore, the minimum value of the increment of the integrated value of the degree of progress of the thermal deterioration is “1”. The maximum value that can be processed is limited by the number of bits for processing the numerical value. For example, when processing a numerical value by 16 bits, an integer from “0” to “63535 (= 2 ^ 16)” is processed. Possible number. The numerical capacity that can be processed by the storage device in this manner is hereinafter referred to as numerical processing capacity.

  Here, when the time interval is shortened, the integrated value is calculated more times than when the time interval is long. Therefore, the integrated value reaches the maximum value of the numerical processing capacity at an earlier stage. It will end up. Therefore, there is a possibility that the numerical processing capacity may be exhausted at a stage where the thermal degradation is not progressing so much, and the estimated limit amount of the thermal degradation is reduced. The occurrence of such a problem can be avoided by reducing the increment of the integrated value, in other words, by reducing the minimum value. However, since the minimum value of the increase width is limited to “1” as described above, there is actually a limit even if this minimum value is reduced, and a minimum value corresponding to shortening of the time interval is set. It may not be possible.

  Thus, when calculating the degree of thermal degradation within a predetermined time interval based on the bed temperature of the catalyst and integrating the degree of thermal degradation to estimate the thermal degradation of the catalyst, setting the estimation mode At this time, there are various restrictions, and in some cases, there is a possibility that heat deterioration cannot be estimated appropriately.

  The present invention has been made in view of such circumstances, and its purpose is to suitably estimate thermal degradation by increasing the degree of freedom in setting the estimation mode when estimating thermal degradation of a catalyst. It is an object of the present invention to provide an exhaust gas purification apparatus for an internal combustion engine and a method for estimating thermal deterioration of an exhaust gas purification catalyst.

  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, when the time interval is shortened, the estimation means sets the average value of the bed temperature within the time interval. The gist is to calculate the degree of progress of the thermal deterioration based on the above.

In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 is applied to an internal combustion engine including a catalyst for exhaust purification, and calculates the degree of progress of thermal degradation of the catalyst within a predetermined time interval based on the bed temperature of the catalyst. In the exhaust gas purification apparatus for an internal combustion engine provided with estimation means for estimating the thermal deterioration of the catalyst based on the calculated integrated value of the degree of thermal deterioration, the estimation means is configured when the rate of change in the bed temperature is small. While calculating the degree of thermal deterioration based on the average value of the bed temperature within the time interval, when the rate of change of the bed temperature is large, based on the maximum value of the bed temperature within the time interval The gist is to calculate the degree of progress of thermal degradation.

  According to this configuration, in a situation where the rate of change of the bed temperature is small and it is difficult for the catalyst to overheat, the degree of progress of thermal deterioration is calculated based on the average value of the bed temperature within the time interval. Therefore, it becomes possible to suppress the influence of the fluctuation of the bed temperature within the same time interval on the calculation of the degree of progress of the thermal deterioration as much as possible, so that the thermal deterioration of the catalyst can be accurately estimated.

  Further, according to this configuration, in a situation where the rate of change of the bed temperature is large and the catalyst is likely to overheat, the degree of progress of the thermal deterioration is calculated based on the maximum value of the bed temperature within the time interval. . Therefore, when the catalyst overheats within the same time interval, the degree of progress of thermal deterioration is calculated based on the bed temperature at the time of overheating. For this reason, even when the catalyst is overheated, it is possible to accurately estimate the thermal deterioration of the catalyst.

  Thus, in the same configuration, either the average value or the maximum value within the time interval is selected for the bed temperature for calculating the degree of thermal deterioration progress. That is, when estimating the thermal degradation of the catalyst, the degree of freedom regarding the setting of the bed temperature for calculating the thermal degradation progress in the estimation mode is increased, so that the thermal degradation can be suitably estimated. become.

  In addition, in order to accurately estimate the thermal deterioration of the catalyst when an excessive temperature rise occurs in the catalyst, one mode in which the time interval is set short can be considered. However, if the time interval is shortened in this manner, the estimated limit amount of thermal deterioration is likely to be insufficient as described above, and thus the numerical processing capacity has to be increased in order to compensate for the shortage. In this respect, in the same configuration, the degree of progress of thermal degradation is calculated based on the maximum value of the bed temperature within the above time interval, so that the thermal degradation of the catalyst when an excessive temperature rise occurs is accurately estimated. Therefore, it is not necessary to increase the numerical processing capacity in particular, and even if it is increased, the amount of increase can be reduced.

The invention according to claim 2 is applied to an internal combustion engine including an exhaust purification catalyst, and calculates the degree of progress of thermal degradation of the catalyst within a predetermined time interval based on the bed temperature of the catalyst. In the method for estimating the thermal deterioration of the catalyst based on the calculated integrated value of the thermal deterioration progress, when the numerical processing capacity of the storage device storing the integrated value of the thermal deterioration progress is small, the time interval The thermal deterioration progress is calculated based on the maximum value of the bed temperature within the time interval, and when the numerical processing capacity of the storage device is large, the numerical processing capacity is small and The gist of the invention is to shorten the time interval in comparison and calculate the degree of progress of the thermal deterioration based on the average value of the bed temperature within the time interval. As described above, the numerical processing capacity refers to a numerical capacity that can be processed by the storage device that stores the integrated value of the degree of progress of thermal deterioration.

  In this method, when the numerical processing capacity of the storage device that stores the integrated value of the degree of progress of thermal deterioration is small, the time interval is lengthened. Therefore, compared with the case where the time interval is short, the number of times of thermal deterioration progress is reduced, and the estimated limit amount of thermal deterioration can be increased. In addition, when the time interval is lengthened in this way, the degree of progress of the thermal deterioration is calculated based on the maximum value of the bed temperature within the time interval. Therefore, when the time interval is lengthened in this way, and the catalyst overheats within the same time interval, the degree of progress of thermal degradation is calculated based on the bed temperature at the time of overheating. Will come to be. For this reason, even when the catalyst is overheated, it is possible to accurately estimate the thermal deterioration of the catalyst.

  On the other hand, when the numerical processing capacity of the storage device is large, the time interval is shortened. In this case, the following effects can be obtained. In other words, the degree of progress of the thermal deterioration is calculated based on the bed temperature, but when the catalyst is excessively heated, the bed temperature is reduced before the temperature of the excessively high catalyst decreases. You can refer to it. Therefore, such an excessive temperature rise is likely to be reflected in the bed temperature referred to when calculating the degree of progress of the thermal deterioration, so that even when the excessive temperature rise of the catalyst occurs, the thermal deterioration of the catalyst is appropriately estimated. Will be able to. Further, when the time interval is shortened in this way, the degree of progress of the thermal deterioration is calculated based on the average value of the bed temperature within the time interval. Therefore, it becomes possible to suppress the influence of the fluctuation of the bed temperature within the same time interval on the calculation of the degree of progress of the thermal deterioration as much as possible, so that the thermal deterioration of the catalyst can be accurately estimated.

  As described above, in this configuration, when estimating the thermal deterioration of the catalyst, the time interval is set according to the numerical processing capacity of the storage device. That is, the degree of freedom in setting the same time interval in the thermal deterioration estimation mode is increased, thereby making it possible to set an appropriate time interval according to the numerical processing capacity, and thus making it preferable to estimate thermal deterioration. To be able to do that. In addition, for the bed temperature for calculating the degree of thermal deterioration progress, either an average value or a maximum value within the time interval is selected in correspondence with the set time interval. Therefore, when estimating the thermal deterioration of the catalyst, the bed temperature for calculating the degree of progress of thermal deterioration in the estimation mode is appropriately selected, so that the thermal deterioration can be estimated appropriately.

  In addition, in an internal combustion engine equipped with an exhaust purification catalyst, a deterioration estimation method in the case where the numerical processing capacity is large as described above is used as a catalyst deterioration estimation method in an engine provided with a storage device having a large numerical processing capacity. By applying the method, the thermal deterioration of the catalyst can be accurately estimated appropriately. In addition, by applying the deterioration estimation method in the case where the numerical processing capacity is small as described above as a method for estimating the deterioration of the catalyst in the engine in which the storage device having a small numerical processing capacity is provided, the numerical processing capacity is thus increased. Even when the amount of the catalyst is small, the thermal deterioration of the catalyst can be estimated accurately and appropriately. That is, by appropriately selecting the deterioration estimation method according to the numerical processing capacity of the storage device that is different for each engine, it is possible to perform an appropriate thermal deterioration estimation according to the numerical processing capacity of the storage device.

(First embodiment)
A first embodiment of an internal combustion engine exhaust gas purification apparatus according to the present invention will be described below with reference to FIGS.

FIG. 1 is a schematic configuration diagram illustrating a control device for a diesel engine including an exhaust purification device according to the present embodiment, an engine 1 to which the control device is applied, and peripheral configurations thereof.
The engine 1 is provided with a plurality of cylinders # 1 to # 4. A plurality of fuel injection valves 4 a to 4 d are attached to the cylinder head 2. These fuel injection valves 4a to 4d inject fuel into the combustion chambers of the cylinders # 1 to # 4. In addition, the cylinder head 2 is provided with intake ports for introducing outside air into the cylinders and exhaust ports 6a to 6d for discharging combustion gas to the outside of the cylinders corresponding to the respective cylinders # 1 to # 4. ing.

  The fuel injection valves 4a to 4d are connected to a common rail 9 that accumulates high-pressure fuel. The common rail 9 is connected to the supply pump 10. The supply pump 10 sucks fuel in the fuel tank and supplies high-pressure fuel to the common rail 9. The high-pressure fuel supplied to the common rail 9 is injected into the cylinder from the fuel injection valves 4a to 4d when the fuel injection valves 4a to 4d are opened.

  An intake manifold 7 is connected to the intake port. The intake manifold 7 is connected to the intake passage 3. A throttle valve 16 for adjusting the intake air amount is provided in the intake passage 3.

An exhaust manifold 8 is connected to the exhaust ports 6a to 6d. The exhaust manifold 8 is connected to the exhaust passage 26.
In the middle of the exhaust passage 26, there is provided a turbocharger 11 that supercharges intake air introduced into the cylinder using exhaust pressure. An intercooler 18 is provided in the intake passage 3 between the intake side compressor of the turbocharger 11 and the throttle valve 16. The intercooler 18 cools the intake air whose temperature has risen due to supercharging of the turbocharger 11.

  Further, in the middle of the exhaust passage 26, on the downstream side of the exhaust side turbine of the turbocharger 11, there is provided an exhaust purification member 30 that constitutes an exhaust purification device and purifies exhaust components. Inside the exhaust purification member 30, two catalysts are arranged in series.

  Of these two catalysts, the first catalyst provided upstream of the exhaust carries a NOx storage-reduction catalyst (hereinafter referred to as NSR (NOx storage-reduction) catalyst) that purifies NOx in the exhaust. This is the NSR catalyst 31.

  The second catalyst provided downstream of the NSR catalyst 31 is a NOx purification catalyst with a filter function that collects PM (particulate matter) in the exhaust, so-called DPNR (Diesel Particulate-NOx Reduction). system) catalyst 32. The DPNR catalyst 32 is a porous ceramic structure carrying an NSR catalyst, and PM in the exhaust gas is collected when passing through the porous wall. Further, when the air-fuel ratio of the exhaust is lean, NOx in the exhaust is stored in the NSR catalyst, and when the air-fuel ratio becomes rich, the NOx stored in the NSR catalyst is reduced and released by HC, CO, and the like.

  In addition, the engine 1 is provided with an EGR device. This EGR device is a device that reduces the combustion temperature in the cylinder by introducing a part of the exhaust gas into the intake air, thereby reducing the amount of NOx generated. This device includes an EGR passage 13 that connects the intake passage 3 and the exhaust passage (exhaust manifold 8), an EGR valve 15 provided in the EGR passage 13, an EGR cooler 14, and the like. The EGR valve 15 adjusts the exhaust gas recirculation amount introduced into the intake passage 3 from the exhaust passage 26, that is, the EGR amount, by adjusting the opening degree thereof. The EGR cooler 14 reduces the temperature of the exhaust gas flowing in the EGR passage 13. The EGR valve 15 is provided with an EGR valve opening sensor 22, and the EGR valve opening sensor 22 detects the opening of the EGR valve 15 (EGR valve opening EA).

  Various sensors for detecting the engine operation state are attached to the engine 1. For example, the air flow meter 19 detects the intake air amount GA in the intake passage 3. The throttle opening sensor 20 detects the opening of the throttle valve 16 (throttle opening TA). A first exhaust temperature sensor 33 provided on the exhaust downstream side of the NSR catalyst 31 measures a first exhaust temperature Ta that is the temperature of the exhaust immediately after passing through the NSR catalyst 31. A second exhaust temperature sensor 34 provided on the exhaust downstream side of the DPNR catalyst 32 detects a second exhaust temperature Tb that is the temperature of the exhaust immediately after passing through the DPNR catalyst 32. The engine rotation speed sensor 23 detects the rotation speed of the crankshaft, that is, the engine rotation speed NE. The accelerator sensor 24 detects an accelerator pedal depression amount, that is, an accelerator operation amount ACCP. The air-fuel ratio sensor 21 detects the air-fuel ratio λ of the exhaust.

  The outputs of these various sensors are input to the control device 25. The control device 25 includes a central processing control device (CPU), a read only memory (ROM) that stores various programs and maps in advance, a random access memory (RAM) that temporarily stores CPU calculation results, a timer counter, an input The microcomputer is mainly configured with an interface, an output interface, and the like. In the RAM, numerical values are processed in binary. In the same RAM, numerical values are processed with 16 bits. Therefore, the numerical capacity that can be processed by the RAM, that is, the numerical processing capacity is “2 ^ 16 = 63535”.

  The control device 25 controls, for example, the fuel injection amount control and fuel injection timing control of the fuel injection valves 4a to 4d, the discharge pressure control of the supply pump 10, the drive amount control of the actuator 17 that opens and closes the throttle valve 16, and the EGR valve. Various controls of the engine 1 such as opening degree control of 15 are performed. The control device 25 also performs various types of exhaust purification control such as estimation of thermal deterioration of the catalyst disposed in the exhaust purification member 30 and control of fuel addition from an injection nozzle 5 described later.

  The injection nozzle 5 is provided in the cylinder head 2 and supplies fuel as an additive to the exhaust purification member 30, that is, the NSR catalyst 31 and the DPNR catalyst 32. The injection nozzle 5 and the supply pump 10 are connected by a fuel supply pipe 27, and fuel is injected from the injection nozzle 5 into the exhaust port 6d of the fourth cylinder # 4. The injected fuel reaches the NSR catalyst 31 and the DPNR catalyst 32 together with the exhaust gas. The injection nozzle 5 has the same structure as the fuel injection valves 4a to 4d, and its injection amount and injection timing are controlled by the control device 25. Further, the arrangement position of the injection nozzle 5 can be changed as appropriate as long as it is in the exhaust passage and upstream of the exhaust purification member 30. In this embodiment, the injection nozzle 5 and the like are also members constituting the exhaust purification device.

In the present embodiment, the above-described fuel addition is performed on the NSR catalyst 31 and the DPNR catalyst 32. The reason will be described below.
A. In the case of a diesel engine, the air-fuel ratio of the exhaust gas is normally lean. Therefore, before the NOx storage amount of the NSR catalyst 31 or the DPNR catalyst 32 reaches the limit, the air-fuel ratio of the exhaust gas is made rich so that It is necessary to reduce and release the stored NOx. Therefore, when the NOx occlusion amount estimated based on the engine operating state or the like reaches a predetermined limit value, the control device 25 executes the NOx reduction process through the fuel addition by the injection nozzle 5. When the fuel injected at this time reaches the NSR catalyst 31 or the DPNR catalyst 32, it acts as a NOx reducing agent. Further, when the fuel is burned by the NSR catalyst 31 and the DPNR catalyst 32, oxygen is consumed, and the air-fuel ratio of the exhaust gas becomes rich. By such NOx reduction treatment, the NOx purification function of the NSR catalyst 31 and the DPNR catalyst 32 is maintained.

  B. When the amount of PM trapped in the DPNR catalyst 32 increases, the pressure loss in the DPNR catalyst 32 increases. Therefore, it is necessary to perform a so-called DPNR catalyst regeneration process that reduces the accumulated PM before the pressure loss increases so as to adversely affect the engine operating state and the like. Therefore, when the PM accumulation amount estimated based on the engine operating state, the difference between the upstream exhaust pressure and the downstream exhaust pressure of the DPNR catalyst 32, etc. reaches a predetermined limit value, the control nozzle 25 The DPNR catalyst regeneration process is performed through the fuel addition according to the above. The fuel injected at this time is combusted when it reaches the DPNR catalyst 32, whereby PM is ignited and finally burned off. That is, this injected fuel acts as a PM combustion accelerator. By such a regeneration process of the DPNR catalyst, the amount of PM deposited on the DPNR catalyst 32 is reduced.

  C. The NOx occlusion reduction type catalyst has a property of absorbing SOx (sulfur oxide) generated from a sulfur content derived from fuel or lubricating oil. Here, since the storage amount of the NOx storage reduction catalyst is limited, a decrease phenomenon of the NOx purification function due to so-called SOx poisoning occurs such that when the SOx absorption amount increases, the storable NOx amount decreases. . On the other hand, SOx absorbed by the NOx occlusion reduction catalyst is known to be released in a reduced state from the catalyst under a high-temperature reducing atmosphere close to 600 ° C. Under such conditions, the NOx occlusion is released. The amount of SOx absorbed by the reduced catalyst can be reduced. Therefore, the control device 25 executes the SOx poisoning recovery process through the fuel addition by the injection nozzle 5 when the SOx absorption amount estimated based on the engine operating state or the like reaches a predetermined limit value. The fuel injected at this time is burned in the NSR catalyst 31 and the DPNR catalyst 32, and the temperature of each catalyst is raised by the heat. In addition, the oxygen around each catalyst is consumed by the combustion of the fuel, the oxygen concentration around the NSR catalyst 31 and the DPNR catalyst 32 is lowered, the conditions such as the high temperature and the reducing atmosphere are satisfied, and the SOx deposited on each catalyst is reduced. -Released. This fuel also functions as a reducing agent for SOx.

For the reasons A to C described above, fuel is added to the NSR catalyst 31 and the DPNR catalyst 32.
Note that the NSR catalyst 31 and the DPNR catalyst 32 may be damaged if the temperature becomes excessively high. In particular, since the exhaust gas heated by the NSR catalyst 31 flows into the DPNR catalyst 32, the temperature of the DPNR catalyst 32 tends to be higher than that of the NSR catalyst 31. Therefore, the amount of fuel supplied from the injection nozzle 5 is adjusted so that the temperature of the DPNR catalyst 32 becomes a predetermined target temperature.

  On the other hand, HC (hydrocarbon), which is a component of the added fuel, is purified during NOx reduction and PM combustion. However, as the thermal deterioration of each catalyst proceeds, the HC purification rate (the amount of HC purified by the catalyst / the amount of HC flowing into the catalyst) decreases, and along with this, the NOx purification rate (catalyst) The amount of NOx purified in step 1 / the amount of NOx flowing into the catalyst) also decreases. The exhaust purification function of the exhaust purification member 30 as a whole gradually decreases due to the progress of thermal deterioration in each catalyst.

  The thermal deterioration that affects the exhaust purification function of the exhaust purification member 30 is correlated with the temperature history of the heat received by the catalyst, in other words, the integrated value of the bed temperature that is the temperature of the catalyst, and the heat increases as the integrated value increases. It can be determined that the deterioration is progressing. Therefore, in this embodiment, the control device 25 is used to estimate the thermal deterioration of the catalyst in the following manner.

  First, when the NSR catalyst 31 and the DPNR catalyst 32 are regarded as one catalyst, the bed temperature T when the exhaust purification member 30 is regarded as one catalyst is estimated. More specifically, the bed temperatures at a plurality of locations are estimated for the NSR catalyst 31 and the DPNR catalyst 32, and the average value of the respective estimated bed temperatures is set as the bed temperature T. The bed temperature T may be estimated as appropriate, but can be estimated in the following manner, for example.

  That is, as shown in FIG. 2, three bed temperatures such as a first bed temperature T 1, a second bed temperature T 2, and a third bed temperature T 3 are in order from the exhaust upstream portion to the exhaust downstream portion in the NSR catalyst 31. Is estimated. These bed temperatures T1 to T3 are the fuel addition amount Qhc from the injection nozzle 5, the intake air amount GA, the temperature gradient in the NSR catalyst 31, and the first exhaust temperature Ta measured by the first exhaust temperature sensor 33. Can be estimated. More specifically, the bed temperatures T1 to T3 are estimated so that the values of the bed temperatures T1 to T3 increase as the fuel addition amount Qhc and the intake air amount GA increase. Further, in the estimation, the temperature gradient in the NSR catalyst 31 is taken into consideration, and the estimation is basically performed so that the magnitude relationship between the bed temperatures T1 to T3 is “T1 <T2 <T3”. Further, by correcting each bed temperature T1 to T3 based on the first exhaust temperature Ta, the estimation accuracy of each bed temperature can be further increased. For example, when the temperature of the exhaust gas immediately after passing through the NSR catalyst 31 is estimated based on the third bed temperature T3 and the like and the estimated temperature is lower than the first exhaust gas temperature Ta, the temperature difference is determined according to the temperature difference. Each bed temperature T1 to T3 is corrected to the high temperature side. Thus, when estimating each bed temperature T1-T3, the estimated accuracy of each bed temperature is further improved by feedback-correcting each bed temperature T1-T3 using the detected value of the exhaust temperature sensor, that is, the measured value of the exhaust temperature. Can be enhanced.

  Further, as shown in FIG. 2, the fourth bed temperature T4, the fifth bed temperature T5, the sixth bed temperature T6, and the seventh bed temperature are in order from the exhaust upstream portion to the exhaust downstream portion in the DPNR catalyst 32. Estimate the bed temperature at four locations such as T7. Each of these bed temperatures T4 to T7 is also equal to the fuel addition amount Qhc from the injection nozzle 5, the intake air amount GA, the temperature gradient in the DPNR catalyst 32, and the second exhaust temperature Tb measured by the second exhaust temperature sensor 34. Can be estimated. That is, the bed temperatures T4 to T7 can also be estimated in the same manner as the estimation of the bed temperatures T1 to T3 described above.

And the calculated value becomes the said bed temperature T by calculating the average value of each said estimated bed temperature T1-T7.
In such a manner or the like, the bed temperature T is calculated every predetermined time, and the degree of thermal degradation dK within the calculation interval time is calculated based on the bed temperature T. In calculating the degree of thermal degradation dK, a larger value is calculated as the bed temperature T is higher. Then, the heat deterioration progress dK obtained every predetermined time is sequentially integrated, and the integrated value is used as a heat deterioration counter K, and the integrated value is stored in a RAM which is a storage device in the control device 25. Thus, if the thermal degradation progress dK within a predetermined time interval is calculated and the thermal degradation progress dK is sequentially accumulated, the value of the latest thermal degradation counter K stored in the RAM becomes the current heat degradation. It becomes an index value indicating the degree of deterioration, and it is possible to estimate the thermal deterioration of the exhaust purification member 30 based on the value.

  Incidentally, the deterioration of the exhaust gas purification function of the catalyst due to thermal deterioration tends to slow down as the heat deterioration progresses. Conversely, the deterioration of the exhaust gas purification function of the catalyst due to thermal deterioration greatly decreases in the early stage of the thermal deterioration. . Therefore, the thermal degradation progress dK is set so that the value of the thermal degradation progress dK calculated based on the bed temperature T increases as the value of the thermal degradation counter K at the time of calculating the bed temperature T decreases. By doing so, the degree of thermal deterioration can be estimated more accurately.

  By the way, when the calculation of the thermal degradation progress dK and the integration of the thermal degradation progress dK (update of the thermal degradation counter K) are performed at a predetermined time interval, various restrictions as described above regarding the setting of the time interval. Exists.

  That is, the numerical processing capacity of the RAM is consumed by increasing the integrated value (thermal deterioration counter K) of the thermal deterioration progress dK, but the time interval is a fixed value and the interval is set to be long. As compared with the case where the same time interval is set short, the number of integration of the thermal deterioration progress dK is reduced. Therefore, in this case, the degree of consumption of the numerical processing capacity is lowered, and thereby the estimated limit amount of thermal degradation is increased. That is, when the time interval is set long, there is an advantage that an estimated limit amount of thermal deterioration can be appropriately secured. However, the floor temperature referred to when calculating the degree of progress of the heat deterioration is less likely to reflect the excessive temperature rise of the exhaust purification member 30, and it is difficult to appropriately estimate the heat deterioration of the exhaust purification member 30. There is.

  On the other hand, when the time interval is a fixed value and the interval is set short, the excessive temperature rise of the exhaust purification member 30 is easily reflected in the floor temperature referred to when calculating the degree of progress of thermal deterioration, and the exhaust purification is performed. While there is an advantage that the thermal degradation of the member 30 can be appropriately estimated, there is a disadvantage that the estimation limit amount of the thermal degradation is reduced.

  In this way, when the time interval is a fixed value, although an advantage corresponding to the set time is obtained, an adverse effect due to the disadvantage corresponding to the set time also occurs. Therefore, in some cases, the thermal degradation of the exhaust purification member 30 such as the thermal degradation of the exhaust purification member 30 due to excessive temperature rise cannot be properly estimated, or the estimated limit amount of the thermal degradation is reduced. There is a risk that estimation cannot be performed properly.

  Therefore, in the present embodiment, when estimating the thermal degradation of the NSR catalyst 31 and the DPNR catalyst 32, that is, the thermal degradation of the exhaust purification member 30, the above-described time during which the thermal degradation progress degree dK is calculated and the thermal degradation counter K is integrated. An interval (hereinafter referred to as an interval), that is, a period time for calculation and integration is variably set in the following manner. Furthermore, the bed temperature for calculating the degree of progress of thermal deterioration is switched according to the variably set interval. And the thermal deterioration estimation of the exhaust purification member 30 can be appropriately performed by increasing the degree of freedom regarding the setting of the estimation mode in this way.

First, the variable setting of the interval will be described with reference to FIGS.
FIG. 3 shows the procedure of the interval setting process executed by the control device 25. This process constitutes the setting means.

  When this process is started, the rate of change R of the bed temperature T (the average value of the bed temperature of each part of the exhaust purification member 30) is calculated (S100). The rate of change R is the amount of change in the bed temperature T per unit time.

  Next, the interval INTc is set based on the calculated change rate R (S110). Here, as shown in FIG. 4, the interval INTc increases as the rate of change R increases, and conversely, the interval INTc decreases as the rate of change R decreases. Thus, the interval INTc is variably set.

The reason why the interval INTc is variably set in this manner is as follows.
That is, when the rate of change R of the bed temperature T is small, it is difficult for the exhaust purification member 30 to overheat, and the floor temperature referenced when calculating the degree of thermal deterioration dK is within the exhaust purification member 30 within the interval. The heat receiving state of is properly reflected. Therefore, in such a situation, it is possible to appropriately estimate the thermal deterioration of the exhaust purification member 30 even if the interval INTc is lengthened. Further, if the interval INTc is lengthened, the number of times of the thermal deterioration progress dK is reduced as compared with the case where the interval INTc is short. Therefore, the degree of consumption of the numerical processing capacity of the RAM consumed by the increase in the heat deterioration counter K is lowered, and the estimated limit amount of heat deterioration is increased.

  On the other hand, the degree of progress of thermal degradation dK is calculated based on the bed temperature T. However, in the situation where the rate of change R of the bed temperature T is large and the exhaust purification member 30 is likely to overheat, the interval INTc is set. If it is shortened, the same bed temperature T can be referred to before the temperature of the exhaust purification member 30 that has become excessively high decreases. Therefore, such an excessive temperature rise tends to be reflected in the bed temperature referred to when calculating the degree of thermal degradation progress dK, and even if the exhaust purification member 30 is excessively heated, Thermal degradation can be estimated appropriately.

When the interval INTc is set in this way, this process is terminated.
When the interval INTc is set, the heat deterioration progress dK based on the bed temperature T is calculated, and the heat deterioration counter K is updated. Here, in this embodiment, instead of referring to the bed temperature T at the calculation timing of the heat deterioration progress dK as it is, the heat deterioration progress is based on the maximum value or the average value of the bed temperature T in the interval INTc. The degree dK is calculated.

FIG. 4 shows a procedure for the thermal deterioration counter calculation process executed by the control device 25. This process is repeatedly executed at predetermined intervals, for example, every second.
When this process is started, first, the average bed temperature Tav and the maximum bed temperature Tmax are calculated (S200). This average bed temperature Tav is an average value of the bed temperature T within the interval INTc, and is calculated from the following equation (1). The initial value is “0”.

Tav (i) = Tav (i-1) + T / INTc (1)
Tav (i): Average bed temperature Tav in the current execution cycle
Tav (i-1): Average bed temperature Tav in the previous execution cycle
T: Floor temperature T when step S200 is executed
INTc: Interval INTc currently set

The maximum bed temperature Tmax is the maximum value of the bed temperature T within the interval INTc, and is calculated from the following equation (2). The initial value is “0”.

Tmax (i) = MAX (Tmax (i−1), T) (2)
Tmax (i): Maximum bed temperature Tmax in the current execution cycle
Tmax (i-1): Maximum bed temperature Tmax in the previous execution cycle
T: Floor temperature T when step S200 is executed

According to “MAX (Tmax (i−1), T)” on the right side of the above equation (2), the larger one of the maximum bed temperature Tmax in the previous execution cycle and the bed temperature T at the time of execution of step S200 is determined this time. Is set as the maximum bed temperature Tmax in the execution cycle.

  Next, it is determined whether or not the time counter CNT is equal to or greater than the set interval INTc (S210). The time counter CNT is a value repeatedly calculated in another process, and the value is incremented by “1” every second. When the sequentially incremented value reaches the interval INTc, the time counter CNT is cleared and the value is set to “0”.

  If it is determined in step S210 that the time counter CNT is less than the interval INTc, that is, it is determined that the time counter CNT has not reached the interval INTc (S210: NO), this process is temporarily terminated.

  On the other hand, if it is determined that the time counter CNT is equal to or greater than the interval INTc, that is, the time counter CNT has reached the interval INTc (S210: YES), the average bed temperature Tav and the maximum bed temperature Tmax are set in step S200. It is determined whether or not the interval INTc set at the time of calculation is greater than or equal to the selection determination value A (S220). Note that the values of the average bed temperature Tav and the maximum bed temperature Tmax when it is determined that the time counter CNT has reached the interval INTc are final values within the interval INT.

  If the interval INTc is greater than or equal to the selection determination value A (S220: YES), the thermal deterioration progress dK within the interval INTc is calculated based on the maximum bed temperature Tmax (S230). As described above, when the interval INTc is equal to or greater than the selection determination value A, that is, when the interval INTc is increased, the thermal deterioration progress dK is calculated based on the maximum bed temperature Tmax, whereby the interval INTc is calculated. When the exhaust purification member 30 is excessively heated, the degree of progress of thermal degradation dK is calculated based on the bed temperature at the time of the excessive temperature increase. Accordingly, in the present embodiment, when the rate of change R is small, it is difficult to cause excessive temperature rise, and the interval INTc is lengthened. However, a sudden temperature rise that cannot be captured by such rate of change R is exhausted. Even if it occurs in the purification member 30, it is possible to accurately estimate the thermal deterioration of the exhaust purification member 30.

  On the other hand, when the interval INTc is less than the selection determination value A (S220: NO), the thermal deterioration progress dK in the interval INTc is calculated based on the average bed temperature Tav (S240). As described above, when the interval INTc is less than the selection determination value A, that is, when the interval INTc is shortened, the thermal deterioration progress dK is calculated based on the average bed temperature Tav. The influence of the fluctuation of the bed temperature T on the calculation of the thermal deterioration progress dK can be suppressed as much as possible. As a result, the thermal deterioration of the exhaust purification member 30 can be accurately estimated. Incidentally, when the interval INTc is shortened as described above, even when the exhaust purification member 30 is excessively heated as described above, the thermal deterioration of the exhaust purification member 30 is appropriately estimated.

  As described above, when the thermal degradation progress dK is calculated in step S230 or step S240, the thermal degradation counter K is updated (S250). Here, the heat deterioration counter K is updated by integrating the heat deterioration progress dK based on the following equation (3).

K (i) = K (i-1) + dK (3)
K (i): Updated thermal deterioration counter K
K (i-1): Thermal deterioration counter K before update
dK: degree of progress of thermal degradation calculated in step S230 or step S240

The heat deterioration counter K is updated when the time counter CNT reaches the interval INTc. Accordingly, the heat deterioration counter K is updated every time the interval INTc elapses.

Then, the average bed temperature Tav is cleared to “0”, and the maximum bed temperature Tmax is also cleared to “0” (S260), and this process is temporarily terminated.
FIG. 6 shows an example of the change of the interval INTc that is changed through the execution of the interval setting process and the selection of the bed temperature for calculating the degree of thermal deterioration progress that is performed through the execution of the thermal deterioration counter calculation process. In addition, the dashed-dotted line shown in FIG. 6 has shown the change of the value in the middle of the calculation about the average bed temperature Tav calculated for every section.

  As shown in FIG. 6, in the section where the rate of change R of the bed temperature T is small (sections A, B, J, P), the number of updates of the thermal deterioration counter K is reduced by increasing the interval INTc. Therefore, the degree of consumption of the numerical processing capacity of the RAM consumed by the increase in the heat deterioration counter K is lowered, and the estimated limit amount of heat deterioration is increased accordingly.

  Further, when the interval INTc is lengthened in this way, the thermal deterioration progress dK is calculated based on the maximum bed temperature Tmax within the interval INTc. Therefore, even if a rapid temperature rise that cannot be detected by the change rate R occurs in the exhaust purification member 30, the thermal deterioration of the exhaust purification member 30 is accurately estimated.

  On the other hand, in the section where the change rate R of the bed temperature T is large (section C to section H, section K to section N), even if an excessive temperature rise occurs in the exhaust purification member 30 by shortening the interval INTc. The thermal deterioration of the exhaust purification member 30 is appropriately estimated.

  When the interval INTc is shortened in this way, the thermal deterioration progress dK is calculated based on the average bed temperature Tav in the interval INTc. Therefore, it is possible to suppress the influence of the fluctuation of the bed temperature T in the interval INTc on the calculation of the thermal deterioration progress dK as much as possible, and the thermal deterioration of the exhaust purification member 30 is accurately estimated.

As described above, according to the present embodiment, the following effects can be obtained.
(1) While calculating the thermal deterioration progress dK of the exhaust purification member 30 (NSR catalyst 31 and DPNR catalyst 32) within a predetermined time interval based on the bed temperature, the integrated value (heat) of the thermal deterioration progress dK When estimating the thermal deterioration of the exhaust purification member 30 based on the deterioration counter K), the time interval (interval INTc) is variably set. Therefore, while obtaining the advantages according to the set time, the adverse effects due to the disadvantages according to the set time can be suppressed. As described above, the time interval is variably set when estimating the thermal degradation of the catalyst, thereby increasing the degree of freedom in setting the same time interval in the thermal degradation estimation mode. Can be suitably performed.

  (2) When the rate of change R of the bed temperature T is small, the interval INTc is set so that the interval INTc (time interval) becomes longer than when the change rate R is not. Therefore, it is possible to appropriately estimate the thermal deterioration of the exhaust purification member 30 and to appropriately secure the estimated limit amount of the thermal deterioration.

  (3) When the interval INTc is lengthened, the thermal deterioration progress dK is calculated based on the maximum value (maximum bed temperature Tmax) of the bed temperature T within the interval INTc. Therefore, even if a sudden temperature rise that cannot be captured by the change rate R occurs in the exhaust purification member 30, the thermal deterioration of the exhaust purification member 30 can be accurately estimated.

  (4) When the rate of change R of the bed temperature T is large, the interval INTc is set so that the interval INTc (time interval) is shorter than when the change rate R is not. Therefore, even when an excessive temperature rise of the exhaust purification member 30 occurs, the thermal deterioration of the exhaust purification member 30 can be appropriately estimated.

(5) When the interval INTc is shortened, the thermal deterioration progress dK is calculated based on the average value (average bed temperature Tav) of the bed temperature T within the interval INTc. Therefore, it becomes possible to suppress the influence of the fluctuation of the bed temperature T in the interval INTc on the calculation of the thermal deterioration progress dK as much as possible, so that the thermal deterioration of the exhaust purification member 30 can be accurately estimated. Become.
(Second Embodiment)
Next, a second embodiment that embodies an exhaust emission control device for an internal combustion engine according to the present invention will be described with reference to FIGS.

  In the present embodiment, the interval is a fixed value set appropriately. Then, either the average value or the maximum value in the interval is selected for the bed temperature for calculating the thermal deterioration progress dK. That is, when estimating the heat deterioration of the exhaust purification member 30, the heat deterioration estimation is suitably performed by increasing the degree of freedom regarding the setting of the bed temperature for calculating the heat deterioration progress in the estimation mode. The configuration is basically the same as that of the first embodiment except that the setting processing is omitted and a part of the thermal deterioration counter calculation processing is different. Therefore, hereinafter, the exhaust gas purification apparatus for an internal combustion engine according to the present embodiment will be described focusing on these differences.

FIG. 7 shows the procedure of the thermal deterioration counter calculation process executed in the present embodiment. This process is also repeatedly executed by the control device 25 at predetermined intervals, for example, every second.
When this process is started, first, the average bed temperature Tav and the maximum bed temperature Tmax are calculated (S300). The calculation mode of the average bed temperature Tav and the maximum bed temperature Tmax here is the same as the calculation mode in step S200 in the first embodiment.

  Next, it is determined whether or not the time counter CNT is equal to or greater than an interval INT that is a fixed value set appropriately (S310). The time counter CNT is the same as the time counter CNT in the first embodiment, and when the value reaches the interval INT, the time counter CNT is cleared.

  When it is determined in step S310 that the time counter CNT is less than the interval INT, that is, it is determined that the time counter CNT has not reached the interval INT (S310: NO), this process is temporarily ended.

  On the other hand, when it is determined that the time counter CNT is equal to or greater than the interval INT, that is, it is determined that the time counter CNT has reached the interval INT (S310: YES), the floor temperature T (the average of the floor temperature of each part of the exhaust purification member 30) It is determined whether the rate of change R, which is the amount of change per unit time, is greater than or equal to the determination value B (S320). The values of the average bed temperature Tav and the maximum bed temperature Tmax when it is determined that the time counter CNT has reached the interval INT are final values within the interval INT.

  When the rate of change R is equal to or greater than the determination value B, that is, when the change in the bed temperature T is large (S320: YES), the degree of thermal deterioration dK within the interval INT is calculated based on the maximum bed temperature Tmax. (S330).

  In such a situation where the rate of change R is large and the exhaust purification member 30 is likely to overheat, the interval of time between the thermal deterioration progress dK is calculated based on the maximum value of the bed temperature T in the interval INT. When an excessive temperature rise occurs in the exhaust purification member 30 within the INT, the thermal deterioration progress dK is calculated based on the bed temperature T at the time of the excessive temperature increase. Therefore, even when an excessive temperature rise occurs in the exhaust purification member 30, it is possible to accurately estimate the thermal deterioration of the exhaust purification member 30.

  On the other hand, when the rate of change R is less than the determination value B, that is, when the change in the bed temperature T is small (S320: NO), the degree of thermal deterioration dK within the interval INT is calculated based on the average bed temperature Tav. (S340).

  In such a situation where the rate of change R is small and it is difficult for the exhaust purification member 30 to overheat, by calculating the thermal deterioration progress dK based on the average value of the bed temperature T in the interval INT, It becomes possible to suppress as much as possible the influence of the fluctuation of the bed temperature T in the interval INT on the calculation of the degree of progress of thermal degradation dK. As a result, the thermal deterioration of the exhaust purification member 30 can be accurately estimated.

  As described above, when the thermal degradation progress dK is calculated in step S330 or step S340, the thermal degradation counter K is updated (S350). The update mode of the thermal deterioration counter K here is the same as the update mode in step S250 in the first embodiment.

Then, the average bed temperature Tav is cleared to “0”, and the maximum bed temperature Tmax is also cleared to “0” (S360), and this process is temporarily terminated.
FIG. 8 shows an example of the selection of the bed temperature for calculating the degree of progress of heat deterioration performed through the execution of the heat deterioration counter calculation process. In addition, the dashed-dotted line shown in FIG. 8 has shown the change of the value in the middle of the calculation about the average bed temperature Tav calculated for every section.

  As shown in FIG. 8, in a section where the rate of change R of the bed temperature T is small (sections A, B, F, J), the thermal deterioration progress dK is calculated based on the average bed temperature Tav within the interval INT. . Therefore, it is possible to suppress the influence of the fluctuation of the bed temperature T in the interval INT on the calculation of the degree of progress of thermal degradation dK as much as possible, and the thermal degradation of the exhaust purification member 30 is accurately estimated.

  On the other hand, in a section where the change rate R of the bed temperature T is large (section C to section E, section G, section H), the thermal deterioration progress dK is calculated based on the maximum bed temperature Tmax within the interval INT. Therefore, even when the exhaust purification member 30 is excessively heated, the thermal deterioration of the exhaust purification member 30 is accurately estimated.

  In addition, in order to accurately estimate the thermal deterioration of the exhaust purification member 30 when an excessive temperature rise occurs in the exhaust purification member 30, one mode in which the interval INT is set short can be considered. However, if the interval INT is shortened in this manner, the estimated limit amount of thermal degradation is likely to be insufficient as described above. For this reason, there is a problem that the numerical value processing capacity has to be increased, for example, the numerical value processing capacity of the RAM is changed to 32 bits in order to compensate for the shortage. In this regard, if the heat deterioration counter calculation process is executed, the heat deterioration progress dK is calculated based on the maximum bed temperature Tmax in the interval INT in a situation where the exhaust purification member 30 is likely to overheat. It is possible to accurately estimate the thermal deterioration of the exhaust purification member 30 when an excessive temperature rise occurs. Therefore, it is not necessary to increase the numerical processing capacity in particular, and even if the numerical processing capacity is increased, the amount of increase can be reduced.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The thermal deterioration progress dK of the exhaust purification member 30 (NSR catalyst 31 and DPNR catalyst 32) within a preset time interval (interval INT) is calculated based on the bed temperature, and the thermal deterioration progress dK When the thermal degradation of the exhaust purification member 30 is estimated based on the integrated value (thermal degradation counter K), the thermal degradation progress dK is calculated in the following manner.

  That is, when the rate of change R of the bed temperature T is small, the thermal deterioration progress dK is calculated based on the average value of the bed temperature T (average bed temperature Tav) within the interval INT. In such a situation where the rate of change R is small and it is difficult for the exhaust purification member 30 to overheat, the degree of progress of thermal degradation dK is calculated based on the average bed temperature Tav, so that the bed temperature T within the interval INT is calculated. The influence of the fluctuation on the calculation of the thermal deterioration progress dK can be suppressed as much as possible. As a result, the thermal deterioration of the exhaust purification member 30 can be accurately estimated.

  When the rate of change R is large, the thermal deterioration progress dK is calculated based on the maximum value (maximum bed temperature Tmax) of the bed temperature T within the interval INT. In such a situation where the rate of change R is large and the exhaust purification member 30 is likely to overheat, the exhaust purification member 30 is calculated within the interval INT by calculating the degree of thermal deterioration dK based on the maximum bed temperature Tmax. When the excessive temperature rise occurs, the thermal deterioration progress dK is calculated based on the bed temperature T at the time of the excessive temperature rise. Therefore, even when the exhaust purification member 30 is excessively heated, the thermal deterioration of the exhaust purification member 30 can be accurately estimated.

  As described above, in the present embodiment, either the average value or the maximum value in the interval INT is selected for the bed temperature for calculating the thermal deterioration progress dK. That is, when estimating the thermal deterioration of the exhaust purification member 30, the degree of freedom regarding the setting of the bed temperature for calculating the degree of progress of thermal deterioration in the estimation mode is increased, and thereby the thermal deterioration is preferably estimated. Will be able to.

(2) Further, by calculating the degree of thermal deterioration dK based on the maximum bed temperature Tmax within the interval INT, the thermal deterioration of the exhaust purification member 30 when an excessive temperature rise occurs can be accurately estimated. Therefore, it is not necessary to increase the numerical processing capacity of the RAM, and even if it is increased, the amount of increase can be reduced.
(Third embodiment)
Next, a third embodiment in which the method for estimating thermal deterioration of an exhaust purification catalyst according to the present invention is applied to an exhaust purification apparatus for an internal combustion engine will be described with reference to FIGS.

  In the present embodiment, different thermal deterioration estimation methods are applied to different engines having different numerical processing capacities of the RAM. More specifically, different intervals are set for each engine having a different numerical processing capacity of the RAM, and different thermal deterioration counter calculation processes corresponding to the set intervals are executed.

Note that the configurations of the internal combustion engine and the exhaust purification device in which the respective heat deterioration counter calculation processes are executed are basically the same as those in the first embodiment except that the numerical processing capacity of the RAM is different. Therefore, in the following, the method for estimating the heat deterioration of the exhaust purification catalyst according to the present embodiment will be described with a focus on the respective heat deterioration counter calculation processes executed in accordance with the numerical processing capacity.
[Thermal degradation counter calculation processing when the numerical processing capacity of the RAM is small]
First, thermal deterioration counter calculation processing that is executed when the numerical processing capacity of the RAM included in the control device 25 is small will be described with reference to FIGS. 9 and 10 together.

  FIG. 9 shows the procedure of the thermal deterioration counter estimation process executed when the numerical processing capacity of the RAM is small. This process is repeatedly executed by the control device 25 at predetermined intervals, for example, every second.

  When this process is started, first, the maximum bed temperature Tmax is calculated (S400). The calculation mode of the maximum bed temperature Tmax here is the same as the calculation mode in step S200 in the first embodiment.

  Next, it is determined whether or not the time counter CNT is equal to or greater than an interval INTa that is a fixed value set according to the numerical processing capacity (S410). The time counter CNT is the same as the time counter CNT in the first embodiment, and when the value reaches the interval INTa, the time counter CNT is cleared. In addition, the interval INTa at this time is set in advance according to the numerical storage capacity of the RAM so as to be longer than that provided with a RAM having a large numerical processing capacity.

  If it is determined in step S410 that the time counter CNT is less than the interval INTa, that is, the time counter CNT has not reached the interval INTa (S410: NO), this process is temporarily terminated.

  On the other hand, if it is determined that the time counter CNT is equal to or greater than the interval INTa, that is, it is determined that the time counter CNT has reached the interval INTa (S410: YES), the degree of progress of thermal deterioration in the interval INTa based on the maximum bed temperature Tmax. dK is calculated (S430). Note that the value of the maximum bed temperature Tmax at this time is a final value within the interval INTa.

  Then, when the thermal degradation progress dK is calculated, the thermal degradation counter K is updated (S430). The update mode of the thermal deterioration counter K here is the same as the update mode in step S250 in the first embodiment.

Then, the maximum bed temperature Tmax is cleared to “0” (S440), and this process is temporarily terminated.
FIG. 10 shows one mode of the bed temperature for calculating the degree of progress of heat deterioration when the heat deterioration counter calculation process is executed.

When the numerical processing capacity of the RAM is small, the interval INTa is set long. As shown in FIG. 10, in each section (section A to section J), based on the maximum bed temperature Tmax in the interval INTa. The thermal degradation progress dK is calculated. Therefore, when the interval INTa is lengthened in this way and the exhaust purification member 30 is excessively heated within the interval INTa, the thermal deterioration is caused based on the bed temperature T at the excessive temperature increase. The degree of progress dK is calculated. Therefore, as shown by the alternate long and short dash line in FIG. 10, the thermal deterioration progress dK is calculated based on the average value (average bed temperature Tav) of the bed temperature T in each section (section A to section J). Therefore, it is possible to grasp the excessive temperature rise of the exhaust purification member 30 more accurately, and even when the excessive temperature rise occurs in the exhaust purification member 30, it is possible to accurately estimate the thermal deterioration of the exhaust purification member 30. .
[Heat degradation counter calculation process when RAM has a large numerical processing capacity]
Next, thermal deterioration counter calculation processing executed when the numerical processing capacity of the RAM included in the control device 25 is large will be described with reference to FIGS. 11 and 12 together.

  FIG. 11 shows the procedure of the thermal deterioration counter estimation process executed when the numerical processing capacity of the RAM is large. This process is repeatedly executed by the control device 25 at predetermined intervals, for example, every second.

  When this process is started, first, an average bed temperature Tav is calculated (S500). The calculation mode of the average bed temperature Tav here is the same as the calculation mode in step S200 in the first embodiment.

  Next, it is determined whether or not the time counter CNT is equal to or greater than an interval INTb that is a fixed value set according to the numerical processing capacity (S510). The time counter CNT is the same as the time counter CNT in the first embodiment, and when the value reaches the interval INTb, the time counter CNT is cleared. Further, the interval INTb at this time is set in advance according to the numerical storage capacity of the RAM so as to be shorter than that provided with the RAM having a small numerical processing capacity, and the value is shorter than the interval INTa. Has been.

  If it is determined in step S510 that the time counter CNT is less than the interval INTb, that is, it is determined that the time counter CNT has not reached the interval INTb (S510: NO), this process is temporarily terminated.

  On the other hand, when it is determined that the time counter CNT is equal to or greater than the interval INTb, that is, it is determined that the time counter CNT has reached the interval INTb (S510: YES), the degree of progress of thermal deterioration in the interval INTb based on the average bed temperature Tav. dK is calculated (S530). Note that the value of the average bed temperature Tav at this time is a final value in the interval INTb.

  When the thermal degradation progress dK is calculated, the thermal degradation counter K is updated (S530). The update mode of the thermal deterioration counter K here is the same as the update mode in step S250 in the first embodiment.

Then, the average bed temperature Tav is cleared to “0” (S540), and this process is temporarily terminated.
FIG. 12 shows one mode of the bed temperature for calculating the degree of progress of heat deterioration when the heat deterioration counter calculation process is executed. In addition, the dashed-dotted line shown in the same figure has shown the change of the value in the middle of the calculation about the average bed temperature Tav calculated for every section.

  When the numerical processing capacity of the RAM is large, the interval INTb is set short, and as shown in FIG. 12, in each section (section A to section T), the average bed temperature Tav in the interval INTb is used. The thermal degradation progress dK is calculated. Therefore, the influence of the fluctuation of the bed temperature T in the interval INTb on the calculation of the degree of thermal deterioration dK can be suppressed as much as possible, so that the thermal deterioration of the exhaust purification member 30 can be accurately estimated.

  Thus, in this embodiment, when the numerical processing capacity of the RAM that stores the thermal deterioration counter K is small, the interval is set to be long. Therefore, as described in the first embodiment, the number of integrations of the thermal degradation progress dK decreases, and the estimated limit amount of thermal degradation increases. Further, when the interval is lengthened in this way, the thermal deterioration progress dK is calculated based on the maximum value of the bed temperature T within the interval (the maximum bed temperature Tmax). Accordingly, when the interval is lengthened and the exhaust purification member 30 is excessively heated within the interval, the thermal deterioration progress dK is calculated based on the bed temperature T at the excessive temperature increase. Is done. Therefore, even when an excessive temperature rise of the exhaust purification member 30 occurs, thermal deterioration of the exhaust purification member 30 can be accurately estimated.

  On the other hand, when the numerical processing capacity of the RAM is large, the interval is set to be short. Thus, when the interval is set short, the following effects can be obtained. That is, the degree of thermal degradation dK is calculated based on the bed temperature, but if the exhaust purification member 30 is overheated, the temperature of the exhaust purification member 30 that has become excessively high decreases. You can refer to its bed temperature before. Therefore, such an excessive temperature rise tends to be reflected in the bed temperature referred to when calculating the degree of thermal degradation progress dK, and even when the exhaust purification member 30 is excessively heated, Thermal degradation can be estimated appropriately. Further, when the interval is shortened in this way, the thermal deterioration progress dK is calculated based on the average value of the bed temperature T within the interval (the average bed temperature Tav). Therefore, it is possible to suppress as much as possible the influence of the fluctuation of the bed temperature T in the interval on the calculation of the degree of progress of thermal degradation dK, so that the thermal degradation of the exhaust purification member 30 can be accurately estimated.

  Thus, in this embodiment, when estimating the thermal deterioration of the exhaust purification member 30, the interval is set according to the numerical processing capacity of the RAM. In other words, the degree of freedom in setting the same interval in the thermal deterioration estimation mode is increased, whereby an appropriate interval according to the numerical processing capacity can be set, and thus the thermal deterioration is appropriately estimated. be able to. In addition, regarding the bed temperature for calculating the thermal degradation progress dK, either an average value or a maximum value in the interval is selected in correspondence with the set interval. Therefore, when estimating the heat deterioration of the exhaust purification member 30, the bed temperature for calculating the heat deterioration progress dK in the estimation mode is appropriately selected, and thus the heat deterioration can be estimated appropriately.

As described above, according to the present embodiment, the following effects can be obtained.
(1) While calculating the thermal degradation progress dK of the exhaust purification member 30 (NSR catalyst 31 and DPNR catalyst 32) within a predetermined time interval (interval INT) based on the floor temperature, the thermal degradation progress dK When estimating the thermal degradation of the exhaust purification member 30 based on the integrated value (thermal degradation counter K), the thermal degradation is estimated in the following manner.

  That is, when the numerical processing capacity of the RAM storing the heat deterioration counter K is small, the interval is set to be long, and the heat deterioration progress dK is set based on the maximum bed temperature Tmax within the set interval. I am trying to calculate. Therefore, it is possible to increase the estimated limit amount of the heat deterioration, and it is possible to accurately estimate the heat deterioration of the exhaust purification member 30 even when the exhaust purification member 30 is excessively heated.

  On the other hand, when the numerical processing capacity of the RAM storing the heat deterioration counter K is large, the interval is set short and the heat deterioration progress dK is set based on the average bed temperature Tav within the set interval. I am trying to calculate. Therefore, even when the exhaust purification member 30 is excessively heated, the thermal deterioration of the exhaust purification member 30 can be appropriately estimated, and the fluctuation of the bed temperature T within the interval is calculated as the degree of progress of thermal deterioration dK. Thus, the thermal deterioration of the exhaust purification member 30 can be accurately estimated.

  As described above, in the present embodiment, when estimating the thermal deterioration of the exhaust purification member 30, the degree of freedom in setting the interval in the thermal deterioration estimation mode is increased. Further, regarding the bed temperature for calculating the thermal degradation progress dK, either an average value or a maximum value in the interval is selected in correspondence with the set interval. For this reason, it is possible to suitably estimate the thermal deterioration of the exhaust purification member 30.

  Further, as a method for estimating the deterioration of a catalyst in an internal combustion engine including the exhaust purification member 30 and provided with a RAM having a large numerical processing capacity, a deterioration estimating method in the case where the numerical processing capacity is large as described above. Since it is applied, the thermal deterioration of the exhaust purification member 30 can be accurately estimated appropriately. Further, since the deterioration estimation method in the case where the numerical processing capacity is small as described above is applied as the catalyst deterioration estimation method in the engine in which the RAM having a small numerical processing capacity is arranged, the numerical processing capacity is thus increased. Even if there is little, the thermal deterioration of the exhaust purification member 30 can be estimated accurately and appropriately. In other words, the deterioration estimation method is appropriately selected according to the numerical processing capacity of the RAM that is different for each engine, and accordingly, it is possible to perform appropriate thermal deterioration estimation according to the numerical processing capacity of the RAM. .

In addition, each said embodiment can also be changed and implemented as follows.
In the first embodiment, the interval INTc is variably set and the bed temperature for calculating the thermal degradation progress dK is switched. In addition, only variable setting of the interval INTc may be performed, and the bed temperature for calculating the thermal degradation progress dK may be fixed to either the average bed temperature Tav or the maximum bed temperature Tmax. Also in this case, the effect by variably setting the interval INTc can be obtained.

-The estimation aspect regarding the bed temperature of several places of the NSR catalyst 31 and the DPNR catalyst 32 can be changed arbitrarily.
-Although the said additive was the fuel of the engine 1, what kind of thing may be sufficient as long as the effect | action similar to this is acquired.

The injection nozzle 5 may be attached at any position as long as it is on the exhaust upstream side of the exhaust purification member.
-In each embodiment, the case where this invention was applied to the exhaust gas purification apparatus provided with the exhaust gas purification member 30 by which two catalysts were arrange | positioned was demonstrated. In addition, the present invention can be similarly applied to an exhaust purification member provided with an exhaust purification member provided with one catalyst or an exhaust purification member provided with three or more catalysts.

  The NSR catalyst 31 is not limited to the NOx storage reduction catalyst as described above. In short, any catalyst that can purify NOx may be used. In each embodiment, the catalyst disposed in the exhaust purification member is the NSR catalyst 31 or the DPNR catalyst 32, and the catalyst to which the additive is supplied. However, the catalyst disposed in the exhaust purification member is The present invention is not limited to this, and the present invention can be similarly applied to any exhaust purification member provided with a catalyst that causes thermal degradation.

  The internal combustion engine to which the present invention is applied is not limited to a diesel engine. For example, the present invention can be similarly applied to a gasoline engine including a catalyst that is thermally deteriorated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing an internal combustion engine to which the exhaust gas purifying apparatus for an internal combustion engine according to a first embodiment of the present invention is applied and a peripheral configuration thereof. The schematic diagram which shows the estimated location of the bed temperature in the same embodiment. The flowchart which shows the procedure of the interval setting process in the embodiment. The graph which shows the correspondence of the change rate of a bed temperature, and an interval. The flowchart which shows the procedure of the heat deterioration counter calculation process in the embodiment. The time chart which shows the example about the change of the interval in the same embodiment, and selection of the bed temperature for thermal degradation progress degree calculation. The flowchart which shows the procedure of the heat deterioration counter calculation process in 2nd Embodiment. The time chart which shows the example about selection of the bed temperature for the thermal deterioration progress calculation in the embodiment. The flowchart which shows the procedure of the heat deterioration counter calculation process corresponding to the case where numerical processing capacity is small in 3rd Embodiment. The time chart which shows the one aspect | mode about the bed temperature for heat deterioration progress calculation when the same heat deterioration counter calculation process is performed. The flowchart which shows the procedure of the thermal deterioration counter calculation process corresponding to the case where there is much numerical processing capacity in 3rd Embodiment. The time chart which shows the one aspect | mode about the bed temperature for heat deterioration progress calculation when the same heat deterioration counter calculation process is performed.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cylinder head, 3 ... Intake passage, 4a-4d ... Fuel injection valve, 5 ... Injection nozzle, 6a-6d ... Exhaust port, 7 ... Intake manifold, 8 ... Exhaust manifold, 9 ... Common rail, 10 ... Supply pump, 11 ... turbocharger, 13 ... EGR passage, 14 ... EGR cooler, 15 ... EGR valve, 16 ... throttle valve, 17 ... actuator, 18 ... intercooler, 19 ... air flow meter, 20 ... throttle opening sensor, 21 DESCRIPTION OF SYMBOLS ... Air-fuel ratio sensor, 22 ... EGR valve opening sensor, 23 ... Engine rotational speed sensor, 24 ... Accelerator sensor, 25 ... Control device (estimating means), 26 ... Exhaust passage, 27 ... Fuel supply pipe, 30 ... Exhaust purification member 31 ... NSR catalyst, 32 ... DPNR catalyst, 33 ... first exhaust temperature sensor, 34 ... second exhaust temperature sensor

Claims (2)

Applied to an internal combustion engine equipped with an exhaust purification catalyst, the degree of progress of thermal deterioration of the catalyst within a predetermined time interval is calculated based on the bed temperature of the catalyst, and the calculated degree of progress of thermal deterioration is integrated In an exhaust gas purification apparatus for an internal combustion engine comprising estimation means for estimating thermal degradation of the catalyst based on a value,
  When the rate of change in the bed temperature is small, the estimating means calculates the degree of progress of the thermal deterioration based on the average value of the bed temperature within the time interval, while the rate of change in the bed temperature is large. Calculating the degree of progress of the thermal degradation based on the maximum value of the bed temperature within the time interval.
  An exhaust emission control device for an internal combustion engine. Applied to an internal combustion engine equipped with an exhaust purification catalyst, the degree of progress of thermal deterioration of the catalyst within a predetermined time interval is calculated based on the bed temperature of the catalyst, and the calculated degree of progress of thermal deterioration is integrated In a method for estimating thermal degradation of the catalyst based on a value,
  When the numerical processing capacity of the storage device that stores the integrated value of the degree of progress of thermal degradation is small, the time interval is lengthened and the progress of thermal degradation is based on the maximum value of the bed temperature within the time interval. Calculate the degree,
  When the numerical processing capacity of the storage device is large, the time interval is shortened as compared with the case where the numerical processing capacity is small, and the thermal degradation is based on the average value of the bed temperature within the time interval. Calculate progress
  A method for estimating thermal deterioration of an exhaust purification catalyst.

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