JP2006291837A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device of an internal combustion engine capable of increasing the estimated accuracy of the temperature of a catalyst device. <P>SOLUTION: This exhaust emission control device calculates the estimated value of the catalyst floor temperature of a catalyst carrying type PM filter 73 by combining a first estimated catalyst floor temperature calculated based on the measured value of a first exhaust gas temperature sensor 91 with a second estimated catalyst floor temperature calculated based on the measured value of a second exhaust gas temperature sensor 92. Furthermore, the degree of the reflection the first estimated catalyst floor temperature on the estimated value of the catalyst floor temperature and the degree of the reflection of the second estimated catalyst floor temperature on the estimated value of the catalyst floor temperature are set according to an exhaust gas flow. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification device for an internal combustion engine that performs exhaust gas purification based on an estimated value of the temperature of a catalyst device.

  2. Description of the Related Art As an exhaust gas purification device for an internal combustion engine, an exhaust gas purification device that includes a fuel addition valve that injects fuel into exhaust gas and a catalyst device that supports a catalyst that stores nitrogen oxide (NOx) in the exhaust gas is known. (See Patent Document 1).

  In such an exhaust purification device, the NOx storage capacity of the device is reduced by storing sulfur oxide (SOx) together with NOx in the catalyst device, so the amount of SOx stored in the catalyst device exceeds the limit value. When it is estimated that there is, reduction control for reducing SOx is performed. In this reduction control, the temperature of the catalytic device (catalyst bed temperature) is raised to the target temperature through the supply of fuel into the exhaust, and then the air-fuel ratio of the exhaust is made rich through the supply of fuel into the exhaust. The SOx of the catalyst device is reduced to recover the NOx storage capacity.

  Further, as the exhaust gas purification device for the internal combustion engine, a fuel addition valve for injecting fuel into the exhaust, a first catalyst device for promoting the oxidation reaction of the fuel supplied into the exhaust, and a function for promoting the oxidation reaction of the fuel And a second catalyst device having a function of capturing particulate matter (PM) in exhaust gas is known (see Patent Document 2).

In such an exhaust purification device, when it is estimated that the amount of PM trapped in the second catalyst device exceeds a limit value, purification control for purifying PM is performed. In this purification control, the trapped PM is burned by raising the catalyst bed temperature to the target temperature through the supply of fuel into the exhaust.
JP 2002-122019 A JP 2004-143988 A

  Incidentally, as described above, in the SOx reduction control and the PM purification control, the fuel is supplied based on the catalyst bed temperature. Therefore, the exhaust purification device is required to accurately estimate the catalyst bed temperature. .

  In the exhaust purification device of Patent Document 1, the catalyst bed temperature is estimated based on the measured value of the exhaust temperature sensor provided downstream of the catalyst device, but the measured value of the exhaust temperature sensor is the actual catalyst bed. Since the response delay to the temperature is large, the estimation accuracy of the catalyst bed temperature may not be sufficiently ensured.

  In the exhaust purification device of Patent Document 2, an exhaust temperature sensor is provided in the exhaust passage downstream of the first catalyst device and upstream of the second catalyst device, and the catalyst is obtained by grasping the second catalyst bed temperature through the measured value of this sensor. The estimation accuracy of the bed temperature is improved.

  In the exhaust emission control device, a part of the fuel supplied into the exhaust gas passes through the first catalyst device and is combusted in the second catalyst device. In the exhaust emission control device, the fuel in the second catalyst device is burned. Since the temperature cannot be estimated in consideration of combustion, it is conceivable that the estimation accuracy of the catalyst bed temperature is remarkably deteriorated when the amount of fuel supplied to the catalyst device is large.

  It should be noted that the exhaust purification device of Patent Document 1 and Patent Document 2 described above is not limited to the exhaust gas purification device that purifies the exhaust gas based on the estimated value of the catalyst bed temperature, but there is still room for improvement regarding the estimation of the catalyst bed temperature. It is to leave.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an exhaust gas purification apparatus for an internal combustion engine that can further improve the temperature estimation accuracy of the catalyst apparatus.

In the following, means for achieving the above object and its effects are described.
<Claim 1>
The invention according to claim 1 is an additive supply means for supplying an additive into exhaust, a catalyst device having a function of promoting an oxidation reaction of the additive, and an exhaust temperature provided upstream of the catalyst device. A first exhaust temperature sensor that measures the exhaust gas, a second exhaust temperature sensor that is provided downstream of the catalyst device and measures the exhaust temperature, and a condition for purifying exhaust gas through the catalyst device is satisfied, Control means for purifying exhaust gas by controlling an additive supply mode by the additive supply means based on an estimated value of the temperature of the catalyst device, a measured value of the first exhaust temperature sensor, and the second exhaust gas The gist of the invention is that it includes an estimation unit that calculates an estimated value of the temperature of the catalyst device in combination with a measured value of a temperature sensor. The “catalyst bed temperature” used in the following description indicates the temperature of the catalyst device.

  Since the first exhaust temperature sensor measures the temperature of the exhaust gas before flowing into the catalyst device, basically, the measured value has a high correlation with the actual catalyst bed temperature (measured value with little deviation from the actual catalyst bed temperature). Can be output. On the other hand, the measured value does not reflect the increase in the catalyst bed temperature accompanying the oxidation reaction of the additive in the catalyst device.

  Since the second exhaust temperature sensor measures the temperature of the exhaust gas after flowing out of the catalyst device, the second exhaust temperature sensor can output a measurement value reflecting an increase in the catalyst bed temperature due to the oxidation reaction of the additive in the catalyst device. . On the other hand, the measured value basically increases the response delay with respect to the actual catalyst bed temperature.

  In the first aspect of the invention, in consideration of the characteristics of the measured values of each exhaust gas temperature sensor, the catalyst bed temperature is estimated by combining the measured value of the first exhaust gas temperature sensor and the measured value of the second exhaust gas temperature sensor. The value is calculated. As a result, while maintaining an appropriate correlation between the estimated value of the catalyst bed temperature and the actual catalyst bed temperature, the estimated value reflects the increase in the catalyst bed temperature accompanying the oxidation reaction of the additive in the catalyst device. Therefore, the estimation accuracy of the catalyst bed temperature can be further improved. Note that, according to the invention described in claim 11, it is possible to achieve an effect similar to the effect of the invention described in claim 1.

<Claim 2>
According to a second aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the first aspect, the degree to which the measured value of the first exhaust temperature sensor is reflected on the estimated value of the temperature of the catalytic device is first. When the measured value reflection rate is set and the degree of reflecting the measured value of the second exhaust temperature sensor with respect to the estimated value of the temperature of the catalyst device is set as the second measured value reflection rate, the estimation means includes the exhaust purification device. The gist is that the first measurement value reflection rate and the second measurement value reflection rate are set based on the operation mode.

  Since the first exhaust temperature sensor and the second exhaust temperature sensor have the output characteristics as described above, when the response delay of the measured value of the second exhaust temperature sensor with respect to the actual catalyst bed temperature is small, the first exhaust temperature sensor The measured value of the second exhaust temperature sensor reflects the actual catalyst bed temperature more appropriately than the measured value. Therefore, in order to improve the estimation accuracy of the catalyst bed temperature, the first measurement value reflection rate and the second measurement value reflection rate are taken into account by taking into account the response delay of the measurement value of the second exhaust temperature sensor with respect to the actual catalyst bed temperature. It can be said that it is desirable to set. On the other hand, the response delay of the measured value of the second exhaust temperature sensor tends to change according to the operation mode of the exhaust purification device.

  In the second aspect of the invention, in consideration of the above, the first measured value reflection rate and the second measured value reflection rate are set based on the operation mode of the exhaust gas purification apparatus. The estimation accuracy can be further improved. In addition, according to the twelfth aspect of the present invention, the operational effect of the second aspect of the invention can be achieved.

<Claim 3>
According to a third aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the first aspect, the degree to which the measured value of the first exhaust temperature sensor is reflected on the estimated value of the temperature of the catalytic device is first. When the measurement value reflection rate is used and the degree of reflection of the measurement value of the second exhaust temperature sensor with respect to the estimated value of the temperature of the catalyst device is the second measurement value reflection rate, the estimation means The gist is that the first measured value reflection rate and the second measured value reflection rate are set based on the equivalent value.

  Since the first exhaust temperature sensor and the second exhaust temperature sensor have the output characteristics as described above, when the response delay of the measured value of the second exhaust temperature sensor with respect to the actual catalyst bed temperature is small, the first exhaust temperature sensor The measured value of the second exhaust temperature sensor reflects the actual catalyst bed temperature more appropriately than the measured value. Therefore, in order to improve the estimation accuracy of the catalyst bed temperature, the first measurement value reflection rate and the second measurement value reflection rate are taken into account by taking into account the response delay of the measurement value of the second exhaust temperature sensor with respect to the actual catalyst bed temperature. It can be said that it is desirable to set. On the other hand, the response delay of the measured value of the second exhaust temperature sensor shows a tendency to change according to the flow rate of the exhaust.

  In the third aspect of the invention, in consideration of the above, the first measured value reflection rate and the second measured value reflection rate are set based on the flow rate of the exhaust gas or its equivalent value. The temperature estimation accuracy can be further improved. Note that, according to the invention described in claim 13, it is possible to achieve an effect similar to the effect of the invention described in claim 3.

<Claim 4>
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, the estimating means is configured to reflect the first measured value reflection rate as the flow rate of the exhaust gas or an equivalent value thereof changes to the increase side. The main point is that the second measured value reflection rate is increased while the value is reduced.

  Since the thermal energy applied to the catalyst device increases as the exhaust gas flow rate increases, the response delay of the measured value of the second exhaust temperature sensor with respect to the temperature of the catalyst device tends to decrease as the exhaust gas flow rate increases. Indicates.

  In the invention according to claim 4, in consideration of the above, the first measured value reflection rate is decreased and the second measured value reflection rate is increased as the flow rate of the exhaust gas or its equivalent value changes to the increase side. Therefore, the estimation accuracy of the catalyst bed temperature can be further improved. According to the invention as set forth in claim 14, it is possible to achieve an effect similar to the effect of the invention as set forth in claim 4.

<Claim 5>
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, the catalyst device carries a catalyst that stores nitrogen oxides in the exhaust gas, and the control means includes When the conditions for reducing the sulfur oxides stored in the catalyst device are satisfied, the sulfur reduction is performed by reducing the sulfur oxides by enriching the air-fuel ratio of the exhaust through the supply of the additive And the estimation means reflects the first measurement value reflection rate and the second measurement value reflection rate during execution of the sulfur reduction treatment and the first measurement value reflection during suspension of the sulfur reduction treatment. The gist is that the rate and the second measured value reflection rate are set to different values.

  The degree of divergence between the actual catalyst bed temperature and the measured value of the first exhaust temperature sensor due to the large difference in the amount of additive supplied to the catalyst device between the execution of the sulfur reduction process and the stop of the sulfur reduction process A big difference appears. Incidentally, the measured value of the first exhaust temperature sensor does not reflect the temperature rise caused by the oxidation reaction of the additive in the catalyst device. Therefore, as the amount of additive supplied to the catalyst device increases, the actual catalyst bed temperature and 1 The degree of deviation from the measured value of the exhaust temperature sensor tends to increase. Therefore, in order to ensure the estimation accuracy of the catalyst bed temperature, it is necessary to set the first measurement value reflection rate and the second measurement value reflection rate to values suitable for the processing at that time.

  In the invention according to claim 5, in consideration of the above, the first measured value reflection rate and the second measured value reflection rate during execution of the sulfur reduction treatment and the first measured value reflection rate during suspension of the sulfur reduction treatment. Since the second measured value reflection rate is set to a different value, the estimation accuracy of the catalyst bed temperature can be further improved. According to the invention as set forth in claim 15, it is possible to achieve an effect similar to that of the invention according to claim 5.

<Claim 6>
According to a sixth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the fifth aspect of the invention, the estimation means uses the second measured value reflection rate during the execution of the sulfur reduction process to stop the sulfur reduction process. And the first measured value reflection rate during execution of the sulfur reduction treatment is set smaller than the first measured value reflection rate during suspension of the sulfur reduction treatment. The gist is to do.

  During execution of the sulfur reduction treatment, a larger amount of additive is supplied to the catalyst device than when the sulfur reduction treatment is stopped, and therefore the degree of divergence between the actual catalyst bed temperature and the measured value of the first exhaust temperature sensor is large. Become.

  In the invention according to claim 6, in consideration of such a situation, the second measured value reflection rate during execution of the sulfur reduction treatment is set larger than the second measured value reflection rate during suspension of the sulfur reduction treatment, Since the first measured value reflection rate during the execution of the sulfur reduction treatment is set to be smaller than the first measured value reflection rate during the stop of the sulfur reduction treatment, the estimation accuracy of the temperature of the catalyst device is further improved. Will be able to. In addition, according to the invention described in claim 16, it is possible to achieve an effect equivalent to the effect of the invention described in claim 6.

<Claim 7>
The invention according to claim 7 is the exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein the exhaust gas purification apparatus is disposed upstream of the catalyst device to oxidize the additive. An upstream catalytic device having a function of promoting a reaction, wherein the first exhaust temperature sensor is provided in an exhaust passage downstream of the upstream catalytic device and upstream of the catalytic device; The gist of the invention is that the temperature sensor is provided downstream of the catalyst device.

<Claim 8>
According to an eighth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the seventh aspect, the estimation means reflects a measured value of the first exhaust temperature sensor with respect to an estimated value of the temperature of the catalytic device. The degree to which the upstream catalyst device reflects the measured value of the second exhaust temperature sensor with respect to the estimated value of the temperature of the catalyst device as the second measured value reflection rate. The gist is that the first measured value reflection rate is set to “0” when a condition indicating that the catalyst function is deteriorated is established.

  When the catalytic function of the upstream catalytic device is deteriorated, the amount of additive flowing into the catalytic device without being oxidized by the catalytic device becomes excessively large, so that the actual catalyst bed temperature and the first exhaust temperature sensor are measured. The degree of deviation from the value tends to be remarkably large.

  In the invention according to claim 8, in consideration of the above, when the condition indicating that the catalytic function of the upstream catalytic device is deteriorated, the first measured value reflection rate is set to “0”. Therefore, it is possible to suppress a decrease in the estimation accuracy of the catalyst bed temperature. In addition, according to the twentieth aspect of the present invention, it is possible to achieve an operational effect similar to that of the eighth aspect of the invention.

<Claim 9>
According to a ninth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to any one of the first to eighth aspects, the estimation means includes the measured value of the first exhaust temperature sensor and the second exhaust temperature. The gist is that an estimated value of the temperature of the catalyst device at a plurality of locations from the upstream to the downstream of the catalyst device is calculated through a combination with the measured value of the sensor.

In the catalyst device, a temperature gradient is generated from upstream to downstream.
In the invention according to claim 9, by calculating the estimated value of the catalyst bed temperature at a plurality of locations from the upstream to the downstream of the catalyst device, the temperature gradient of the catalyst device is taken into account when controlling the supply mode of the additive. To be able to. As a result, more precise supply control of the additive can be realized. According to the invention as set forth in claim 21, it is possible to achieve an effect similar to the effect of the invention as set forth in claim 9.

<Claim 10>
According to a tenth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the ninth aspect, the estimation means is a representative of the plurality of estimated values based on estimated values of the temperature of the catalyst device at the plurality of locations. The control means is for controlling the supply mode of the additive by the additive supply means based on the representative value.

  In the invention according to claim 10, since the estimated value (representative value) of the catalyst bed temperature is calculated in consideration of the temperature gradient of the catalyst device, the estimated accuracy of the temperature can be further improved. Moreover, since the supply mode of the additive is controlled based on such an estimated value, the exhaust gas is more appropriately purified. Note that, according to the invention described in claim 22, it is possible to achieve an effect similar to the effect of the invention described in claim 10.

<Claim 11>
The invention according to claim 11 is an additive supply means for supplying an additive into exhaust, a catalyst device having a function of promoting an oxidation reaction of the additive, and an exhaust temperature provided upstream of the catalyst device. A first exhaust temperature sensor that measures the exhaust gas, a second exhaust temperature sensor that is provided downstream of the catalyst device and measures the exhaust temperature, and a condition for purifying exhaust gas through the catalyst device is satisfied, Based on the measured value of the first exhaust temperature sensor, the control means for purifying the exhaust by controlling the supply mode of the additive by the additive supply means based on the estimated value of the temperature of the catalyst device. The estimated value of the temperature of the catalyst device is a first estimated value, the estimated value of the temperature of the catalyst device calculated based on the measured value of the second exhaust temperature sensor is a second estimated value, and the control means For exhaust purification And an estimation means for calculating the third estimated value by combining the first estimated value and the second estimated value with the estimated value of the temperature of the catalyst device used as the third estimated value. It is a summary.

<Claim 12>
According to a twelfth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the eleventh aspect, a degree of reflecting the first estimated value with respect to the third estimated value is a first estimated value reflection rate, and When the degree of reflecting the second estimated value with respect to the third estimated value is defined as a second estimated value reflecting rate, the estimating means determines the first estimated value reflecting rate and the first estimated value reflecting rate based on the operation mode of the exhaust purification device. The gist is that the second estimated value reflection rate is set.

<Claim 13>
According to a thirteenth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the eleventh aspect, a degree of reflecting the first estimated value with respect to the third estimated value is a first estimated value reflection rate, and When the second estimated value reflection rate is a degree of reflecting the second estimated value with respect to the third estimated value, the estimating means is configured to determine the first estimated value reflection rate and the estimated value based on the flow rate of exhaust gas or an equivalent value thereof. The gist is that the second estimated value reflection rate is set.

<Claim 14>
According to a fourteenth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the thirteenth aspect, the estimation means includes the first estimated value reflection rate as the flow rate of the exhaust gas or an equivalent value thereof changes to the increase side. The main point is that the second estimated value reflection rate is increased while the value is reduced.

<Claim 15>
The invention according to claim 15 is the exhaust gas purification apparatus for an internal combustion engine according to claim 14, wherein the catalyst device carries a catalyst for storing nitrogen oxides in the exhaust gas, and the control means includes When the conditions for reducing the sulfur oxides stored in the catalyst device are satisfied, the sulfur reduction is performed by reducing the sulfur oxides by enriching the air-fuel ratio of the exhaust through the supply of the additive Processing, and the estimation means reflects the first estimated value reflection rate and the second estimated value reflection rate during execution of the sulfur reduction treatment and the first estimated value reflection during suspension of the sulfur reduction treatment. The gist is that the rate and the second estimated value reflection rate are set to different values.

<Claim 16>
According to a sixteenth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the fifteenth aspect, the estimation means uses the second estimated value reflection rate during the execution of the sulfur reduction process to stop the sulfur reduction process. The first estimated value reflection rate during execution of the sulfur reduction treatment is set to be smaller than the first estimated value reflection rate during suspension of the sulfur reduction treatment. The gist is to do.

<Claim 17>
According to a seventeenth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to any one of the eleventh to sixteenth aspects, the estimation means determines the measured value of the first exhaust temperature sensor as the flow rate of the exhaust gas or the exhaust gas flow rate. The gist is that the first estimated value is calculated by correcting based on the equivalent value.

  Since the thermal energy applied to the catalyst device increases as the exhaust gas flow rate increases, the degree of divergence between the actual catalyst bed temperature and the measured value of the first exhaust gas temperature sensor decreases as the exhaust gas flow rate increases. Show the trend.

  In the invention according to claim 17, in consideration of the above, the first estimated value is calculated by correcting the measured value of the first exhaust temperature sensor based on the flow rate of exhaust gas or its equivalent value. Therefore, it becomes possible to improve the estimation accuracy of the same temperature.

<Claim 18>
According to an eighteenth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to any one of the eleventh to eleventh aspects, the estimation means determines the measured value of the second exhaust temperature sensor as the flow rate of exhaust gas or the The gist is that the second estimated value is calculated by correcting based on the equivalent value.

  Since the thermal energy applied to the catalyst device increases as the exhaust flow rate increases, the degree of divergence between the actual catalyst bed temperature and the measured value of the second exhaust temperature sensor decreases as the exhaust flow rate changes to the increase side. Show the trend.

  In the invention according to claim 18, in consideration of the above, the second estimated value is calculated by correcting the measured value of the second exhaust temperature sensor based on the flow rate of exhaust gas or its equivalent value. Therefore, it becomes possible to improve the estimation accuracy of the same temperature.

<Claim 19>
The invention according to claim 19 is the exhaust gas purification apparatus for an internal combustion engine according to any one of claims 11 to 18, wherein the exhaust gas purification apparatus is disposed upstream of the catalyst device to oxidize the additive. An upstream catalytic device having a function of promoting a reaction, wherein the first exhaust temperature sensor is provided in an exhaust passage downstream of the upstream catalytic device and upstream of the catalytic device; The gist of the invention is that the temperature sensor is provided downstream of the catalyst device.

<Claim 20>
According to a twentieth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the nineteenth aspect, the estimation means determines the degree of reflection of the first estimated value with respect to the third estimated value. A condition indicating that the catalyst function of the upstream catalytic device is deteriorated is established by setting the reflection rate and the second estimated value reflection rate to which the second estimated value is reflected with respect to the third estimated value. The first estimated value reflection rate is set to “0”.

<Claim 21>
According to a twenty-first aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to any one of the eleventh to twentieth aspects, the estimating means is configured to combine the first estimated value and the second estimated value. The gist is that the third estimated value is calculated at a plurality of locations from upstream to downstream of the catalyst device.

<Claim 22>
According to a twenty-second aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the twenty-first aspect, the estimating means calculates a representative value of the plurality of estimated values based on the third estimated value at the plurality of locations. The control means is to control the supply mode of the additive by the additive supply means based on the representative value.

An embodiment of the present invention will be described with reference to FIGS.
In this embodiment, the case where this invention is actualized as a control apparatus of a diesel engine is assumed.

<Diesel engine structure>
FIG. 1 shows a schematic structure of a diesel engine to which the present invention is applied.
The diesel engine 1 includes an engine body 11, a turbocharger 4, a common rail fuel supply device 5, an exhaust gas recirculation device 6, and an exhaust gas purification device 7. Various devices are controlled through the electronic control device 9.

The engine body 11 is provided with a plurality of cylinders 12.
A combustion chamber 13 for burning a mixture of air and fuel is formed in the cylinder 12.

  In the diesel engine 1, an intake passage 23 through which external air is circulated into the combustion chamber 13 is configured by the intake port of the engine body 11, the intake manifold 21, and the intake pipe 22.

  In the intake passage 23, an air cleaner 24, a compressor wheel 41 of the turbocharger 4, an intercooler 25, and a throttle valve 26 are arranged in this order from the upstream side in the air flow direction.

  In the diesel engine 1, an exhaust passage 33 through which the gas in the combustion chamber 13 circulates to the outside is configured by the exhaust port of the engine body 11, the exhaust manifold 31, and the exhaust pipe 32.

  In the exhaust passage 33, the fuel addition valve 71 of the exhaust purification device 7, the turbine wheel 42 of the turbocharger 4, the NOx catalytic converter 72 of the exhaust purification device 7, and the catalyst-carrying PM filter 73 are arranged in this order from the upstream side in the exhaust flow direction. Is arranged. In the present embodiment, the fuel addition valve 71 corresponds to the additive supply means. The NOx catalytic converter 72 corresponds to a catalyst device. The catalyst-carrying PM filter 73 corresponds to the second catalyst device.

[1] “Structure of turbocharger”
The turbocharger 4 increases the amount of air supplied into the combustion chamber 13 by compressing the air in the intake pipe 22 using the energy of the exhaust.

  The turbocharger 4 includes a compressor wheel 41 disposed in the intake passage 23, a turbine wheel 42 disposed in the exhaust passage 33, and a rotor shaft 43 connecting these wheels 41, 42. The intake air is compressed by rotating the compressor wheel 41 together with the turbine wheel 42 through the energy of the exhaust.

[2] “Structure of common rail fuel supply system”
The common rail fuel supply device 5 burns fuel in the combustion chamber 13 by injecting high-pressure fuel into the combustion chamber 13.

The common rail fuel supply device 5 includes a fuel injection valve 51, a fuel tank 52, a fuel pump 53, and a common rail 54.
The fuel injection valve 51 injects fuel into the combustion chamber of the corresponding cylinder 12.

The fuel pump 53 sucks the fuel in the fuel tank 52, pressurizes the sucked fuel to a predetermined pressure, and supplies it to the common rail 54.
The common rail 54 maintains the fuel supplied from the fuel pump 53 in a high pressure state. The fuel in the common rail 54 is injected from the fuel injection valve 51 into the combustion chamber of the cylinder 12 as each fuel injection valve 51 is opened.

[3] “Structure of exhaust gas recirculation device”
The exhaust gas recirculation device 6 supplies a part of the exhaust gas into the intake pipe 22, thereby lowering the combustion temperature of the air-fuel mixture and reducing the generation amount of nitrogen oxides (NOx).

The exhaust gas recirculation device 6 includes a communication pipe 61, an EGR cooler 62, and an EGR valve 63.
The communication pipe 61 communicates the exhaust passage 33 upstream of the turbine wheel 42 and the intake passage 23 downstream of the throttle valve 26. Further, an EGR cooler 62 and an EGR valve 63 are arranged in the communication pipe 61 in order from the upstream side in the exhaust flow direction.

The EGR cooler 62 cools the exhaust gas supplied to the intake pipe 22 via the communication pipe 61.
The EGR valve 63 adjusts the flow rate of exhaust gas supplied to the intake pipe 22 via the communication pipe 61.

[4] “Structure of exhaust emission control device”
The exhaust purification device 7 purifies particulate matter (PM), nitrogen oxides (NOx), hydrocarbons (HC) and carbon monoxide (CO) in the exhaust.

  The exhaust purification device 7 includes a fuel addition valve 71, a NOx catalytic converter 72, and a catalyst-carrying PM filter 73. In this embodiment, the NOx catalytic converter 72 corresponds to the upstream catalytic device.

The NOx catalytic converter 72 includes a catalyst carrier on which an NOx storage reduction catalyst is supported.
In the NOx catalytic converter 72, NOx purification is performed as follows.
(A) When the exhaust is in an oxidizing atmosphere (lean), NOx in the exhaust is stored in the NOx catalyst.
(B) When the exhaust is in a reducing atmosphere (stoichiometric or rich), NOx stored in the NOx catalyst is released as nitrogen monoxide (NO) and is reduced by HC or CO.

  “Stoichi” is the state where the air-fuel ratio of the exhaust corresponds to the stoichiometric air-fuel ratio, “Lean” is the state where the air-fuel ratio of the exhaust is larger than the stoichiometric air-fuel ratio, “Rich” is the state where the air-fuel ratio of the exhaust is the stoichiometric air-fuel ratio Each smaller state is shown.

  The catalyst-carrying PM filter 73 includes a porous ceramic structure (PM filter) that can capture PM in the exhaust gas. The PM filter carries a NOx storage reduction catalyst.

In the catalyst-carrying PM filter 73, PM is captured and purified as follows.
(A) When exhaust passes through the wall of the porous ceramic structure, PM in the exhaust is captured by the wall of the ceramic structure.
(B) When the exhaust gas is hot, the trapped PM is oxidized by oxygen in the exhaust gas.
(C) The trapped PM is oxidized by active oxygen generated during NOx storage and release.

The catalyst-carrying PM filter 73 purifies NOx in the same manner as the NOx catalytic converter 72.
The fuel addition valve 71 adds fuel into the exhaust through injection of fuel (additive). The fuel addition valve 71 is supplied with fuel having a lower pressure than the fuel supplied to the common rail 54 through the fuel pump 53.

  The fuel injected from the fuel addition valve 71 is supplied to the NOx catalytic converter 72 and the catalyst-carrying PM filter 73 together with the exhaust gas. In the diesel engine 1, fuel injection (fuel addition) is performed by the fuel addition valve 71 for the purpose of supplying fuel to the NOx catalytic converter 72 and the catalyst-carrying PM filter 73. Details of the fuel addition mode by the fuel addition valve 71 will be described later.

[5] "Control system structure"
The electronic control unit 9 temporarily stores a central processing unit that executes arithmetic processing related to engine control, a read-only memory in which programs and maps necessary for engine control are stored in advance, calculation results of the central processing unit, etc. A random access memory, an input port for inputting an external signal, an output port for outputting a signal to the outside, and the like.

  A first exhaust temperature sensor 91, a second exhaust temperature sensor 92, an exhaust air / fuel ratio sensor 93, an air flow meter 94, a rotational speed sensor 95, and the like for detecting the engine operating state are connected to the input port of the electronic control unit 9. ing.

  The first exhaust temperature sensor 91 is provided in the exhaust passage 33 downstream of the NOx catalytic converter 72 and upstream of the catalyst-carrying PM filter 73, and the temperature of the exhaust gas flowing into the catalyst-carrying PM filter 73 (first exhaust temperature TE1). ) Is output. After the output signal of the first exhaust temperature sensor 91 is input to the electronic control unit 9, it is used for various controls as the first exhaust temperature measurement value TE1M.

  The second exhaust temperature sensor 92 is provided in the exhaust passage 33 downstream of the catalyst-carrying PM filter 73, and an electric signal corresponding to the temperature of the exhaust gas flowing out from the catalyst-carrying PM filter 73 (second exhaust temperature TE2). Is output. The output signal of the second exhaust temperature sensor 92 is input to the electronic control unit 9, and then used as various control values as the second exhaust temperature measurement value TE2M.

  The exhaust air / fuel ratio sensor 93 is provided in the exhaust passage 33 downstream of the turbine wheel 42 and upstream of the NOx catalytic converter 72, and outputs an electric signal corresponding to the air / fuel ratio (exhaust air / fuel ratio EFA) of the exhaust flowing in the exhaust pipe 32. Output. The output signal of the exhaust air / fuel ratio sensor 93 is input to the electronic control unit 9 and then used for various controls as the exhaust air / fuel ratio measured value EAFM.

  The air flow meter 94 is provided in the intake passage 23 downstream of the air cleaner 16 and upstream of the compressor wheel 41, and outputs an electrical signal corresponding to the flow rate of air flowing through the intake pipe 22 (intake flow rate GA). After the output signal of the air flow meter 94 is input to the electronic control unit 9, it is used for various controls as an intake flow rate measurement value GAM.

  The rotational speed sensor 95 is provided in the vicinity of the crankshaft and outputs an electrical signal corresponding to the rotational speed of the crankshaft (engine rotational speed NE). The output signal of the rotational speed sensor 95 is input to the electronic control unit 9 and then used for various controls as the engine rotational speed measurement value NEM.

Drive circuits such as the throttle valve 26, the EGR valve 63, the fuel pump 53, the fuel injection valve 51, and the fuel addition valve 71 are connected to the output port of the electronic control unit 9.
The electronic control unit 9 determines the required value of each control parameter (for example, the fuel injection amount (fuel injection amount FI) by the fuel injection valve 51 or the fuel addition valve) based on the engine operation state grasped from the detection signal of each sensor. The fuel addition amount by 71 (fuel addition amount FA)) is set. Then, a command signal corresponding to the required value is output to the drive circuit of each device connected to the output port.

  The electronic control device 9 controls the drive circuit so that the throttle control for adjusting the opening of the throttle valve 26, the EGR control for adjusting the opening of the EGR valve 63, the discharge pressure control for adjusting the discharge pressure of the fuel pump 53, Various controls such as fuel injection control for injecting fuel from the fuel injection valve 51 and fuel addition control for injecting fuel from the fuel addition valve 71 are performed. Note that the control means includes the electronic control device 9.

<Exhaust gas purification control>
In this embodiment, as control for purifying exhaust, “PM regeneration control” for burning PM on the catalyst-carrying PM filter 73, and reducing and releasing sulfur oxide (SOx) stored in the NOx catalyst. “S poisoning recovery control” to be performed and “NOx reduction control” to reduce and release NOx stored in the NOx catalyst are performed.

  In order to perform PM regeneration that burns PM and S poison recovery that reduces and releases SOx, it is necessary to sufficiently raise the temperature (catalyst bed temperature) of the NOx catalytic converter 72 and the catalyst-carrying PM filter 73. Therefore, in PM regeneration control and S poison recovery control, temperature increase control is performed to increase the catalyst bed temperature to a temperature (for example, 600 to 700 ° C.) required for PM regeneration and S poison recovery.

  In the temperature raising control, fuel supply to the exhaust gas by the fuel addition valve 71 is continuously repeated at relatively short intervals to increase the amount of fuel supplied to the NOx catalyst (NOx catalyst converter 72 and catalyst-carrying PM filter 73). I try to let them. As a result, the catalyst bed temperature can be increased due to heat generated by the oxidation reaction of the fuel in the exhaust gas or on the catalyst.

[1] "PM regeneration control"
In the exhaust purification device 7, the pressure loss in the PM filter 73 increases as the amount of PM trapped in the catalyst-carrying PM filter 73 increases. Therefore, it is necessary to purify the PM accumulated on the filter before the pressure loss increases to such a degree as to deteriorate the engine operating condition.

Therefore, when it is estimated that the amount of PM accumulated on the catalyst-carrying PM filter 73 has reached the limit value, the electronic control unit 9 performs temperature increase control through PM regeneration control.
Since high-temperature exhaust gas is supplied to the catalyst-carrying PM filter 73 by the oxidation reaction of fuel in the NOx catalytic converter 72, PM is combusted through the high temperature of the catalyst-carrying PM filter 73. Further, since the fuel that has passed through the NOx catalytic converter 72 is oxidized by the catalyst-carrying PM filter 73, PM is combusted through heat generated by the oxidation reaction.

[2] "S poison recovery control"
The NOx catalyst of the NOx catalytic converter 72 and the catalyst-carrying PM filter 73 has the property of absorbing SOx generated from the sulfur content derived from fuel and lubricating oil together with NOx. On the other hand, since the storage amount of the NOx catalyst has a limit, when the SOx storage amount becomes excessively large, the NOx storage capacity is reduced (S poisoning). Therefore, the exhaust purification device 7 needs to reduce the SOx stored in the NOx catalyst before it interferes with NOx storage due to an increase in the SOx storage amount.

Therefore, when it is estimated that the amount of SOx occluded in the NOx catalyst has reached the limit value, the electronic control device 9 performs the temperature rise control and the SOx reduction control through the S poison recovery control.
As a result, after the NOx catalytic converter 72 and the catalyst-carrying PM filter 73 are heated through the temperature rise control, the exhaust air-fuel ratio is made rich through the SOx reduction control. The periphery of 73 is maintained in a high-temperature reducing atmosphere. Then, the SOx stored in the NOx catalyst is reduced and then released from the NOx catalyst.

[3] "NOx reduction control"
In the exhaust purification device 7, it is necessary to reduce and release the NOx stored in the NOx catalyst before the NOx storage amount of the NOx catalytic converter 72 and the catalyst-carrying PM filter 73 reaches the limit.

  Therefore, when it is estimated that the amount of NOx stored in the NOx catalyst has reached the limit value, the electronic control device 9 performs intermittent fuel addition by the fuel addition valve 71 through NOx reduction control.

  As a result, the air-fuel ratio of the exhaust gas surrounding the NOx catalyst is temporarily stoichiometric or rich, so that NOx in the NOx catalytic converter 72 and the catalyst-carrying PM filter 73 is reduced. During NOx reduction control, the catalyst bed temperature is maintained at a relatively low temperature (for example, 250 to 500 ° C.).

  During the execution of the temperature raising control through the PM regeneration control and the S poison recovery control, after injection by the fuel injection valve 51 can be performed as necessary. This after injection is fuel injection executed during the compression stroke and exhaust stroke after the pilot injection and the main injection are performed, and is used for combustion in the combustion chamber 13 such as pilot injection and main injection. The fuel injection is different from the fuel injection. As a result, most of the fuel injected in the after injection is discharged into the exhaust system without being combusted in the combustion chamber 13, so that the amount of fuel in the exhaust is increased and the catalyst bed temperature is increased.

<S poison recovery control process>
The “S poisoning recovery control process” will be described with reference to FIG. This process is repeatedly executed by the electronic control device 9 at regular intervals. In the following description, the converter catalyst bed temperature TC is the catalyst bed temperature of the NOx catalyst converter 72, the filter catalyst bed temperature TF is the catalyst bed temperature of the catalyst-carrying PM filter 73, and the target catalyst bed temperature TFT is “temperature rise”. The target values of the filter catalyst bed temperature TF in the “control processing” are respectively shown.

[Step S110] It is determined whether the “SOx reduction control process” (FIG. 7) for reducing the SOx stored in the catalyst-carrying PM filter 73 is being executed.
When the “SOx reduction control process” is not executed, the process of step S120 is performed.
When the “SOx reduction control process” is being executed, the process of step S150 is performed.

[Step S120] It is determined whether or not “temperature increase control processing” (FIG. 5) for increasing the filter catalyst bed temperature TF to the target catalyst bed temperature TFT is being executed.
When the “temperature increase control process” is not executed, the process of step S130 is performed.
When the “temperature increase control process” is being executed, the process of step S140 is performed.

[Step S130] It is determined whether or not an execution condition (condition for reducing SOx) of S poison recovery control is satisfied.
When the execution condition is satisfied, the process of step S132 is performed.
When the execution condition is not satisfied, the “S poisoning recovery control process” is temporarily ended.

In the process of step S130, when the following conditions [a] and [b] are satisfied, it is determined that the execution condition of the S poison recovery control is satisfied.
[A] The amount of SOx stored in the catalyst-carrying PM filter 73 (SOx storage amount) has reached a limit value. The SOx occlusion amount can be estimated based on, for example, the operation history of the diesel engine 1 (intake flow rate GA or fuel injection amount FI).
[B] The estimated value of converter catalyst bed temperature TC (estimated converter catalyst bed temperature eTC) is equal to or higher than the temperature required to cause the oxidation reaction of fuel. The estimated converter catalyst bed temperature eTC can be estimated based on the operating state of the diesel engine 1 (intake flow rate GA or fuel injection amount FI).

  [Step S132] The “temperature increase control process” (FIG. 5) is started. Thereby, in the next control cycle of the “S poisoning recovery control process”, the process proceeds from the process of step S120 to the process of step S140.

[Step S140] It is determined whether the estimated filter catalyst bed temperature eTF (third estimated value) is equal to or higher than the target catalyst bed temperature TFT.
When the target catalyst bed temperature TFT is equal to or higher than the target catalyst temperature TFT, the process of step S142 is performed.
When the temperature is lower than the target catalyst bed temperature TFT, the “S poisoning recovery control process” is temporarily ended.

The estimated filter catalyst bed temperature eTF is calculated through the “catalyst bed temperature estimation process” (FIG. 8). Further, it is calculated as a value representative of the catalyst bed temperature of the catalyst-carrying type PM filter 73.
[Step S142] The “temperature increase control process” (FIG. 5) is terminated and the “SOx reduction control process” (FIG. 7) is started. As a result, in the next control cycle of the “S poisoning recovery control process”, the process proceeds from step S110 to step S150.

[Step S150] It is determined whether or not an end condition for S poison recovery control (a condition indicating that the reduction of SOx has been completed) is satisfied.
When the end condition is satisfied, the process of step S152 is performed.
When the termination condition is not satisfied, the “S poisoning recovery control process” is temporarily terminated.

  In the process of step S150, when the estimated value of the SOx occlusion amount is less than the determination value, it is determined that the termination condition for the S poison recovery control is satisfied. During the execution of the “SOx reduction control process”, the estimated value of the SOx occlusion amount can be updated based on, for example, the SOx reduction amount per unit time.

  [Step S152] The “SOx reduction control process” (FIG. 7) is terminated. Note that the execution condition of the S poison recovery control is not limited to the conditions exemplified above, and appropriate conditions can be adopted. Similarly, the end condition of the S poison recovery control is not limited to the above-exemplified conditions, and appropriate conditions can be adopted.

<Temperature control process>
The “temperature increase control process” will be described with reference to FIG. This process is repeatedly executed at regular intervals by the electronic control unit 9 from the start to the end in the “S poisoning recovery control process”.

[Step S210] It is determined whether or not the target value (target catalyst bed temperature TFT) of the filter catalyst bed temperature TF has been set after the “temperature increase control process” is started through the “S poisoning recovery control process”. .
When the target catalyst bed temperature TFT is not set, the process of step S212 is performed.
When the target catalyst bed temperature TFT is set, the process of step S214 is performed.

  [Step S212] The target catalyst bed temperature TFT is set based on the engine operating state (for example, the engine speed NE and the fuel injection amount FI). Here, the target catalyst bed temperature TFT is calculated from a map in which the relationship between the engine operating state and the target catalyst bed temperature TFT is set in advance.

  The target catalyst bed temperature TFT is set as a catalyst bed temperature necessary for appropriately reducing the SOx of the catalyst-carrying PM filter 73 when the NOx catalyst converter 72 is normal. Therefore, when the NOx catalytic converter 72 is normal, the filter catalyst bed temperature TF is maintained at a temperature higher than the target catalyst bed temperature TFT through the “temperature rise control process”, so that the reduction of SOx is appropriately performed. .

  [Step S214] Based on the target catalyst bed temperature TFT, the amount of fuel added to the exhaust by the fuel addition valve 71 (fuel addition amount FA) is set. Here, based on the difference between the target catalyst bed temperature TFT and the estimated value of the filter catalyst bed temperature TF (estimated filter catalyst bed temperature eTF), the filter catalyst bed temperature TF is maintained at a temperature higher than the target catalyst bed temperature TFT. Therefore, the fuel addition amount FA required for this is calculated. The estimated filter catalyst bed temperature eTF is calculated through the “catalyst bed temperature estimation process” (FIG. 8). Further, it is calculated as a value representative of the catalyst bed temperature of the catalyst-carrying type PM filter 73.

  In the fuel addition control separately executed in the electronic control unit 9, the fuel addition valve 71 is controlled so that fuel of the same addition amount FA is injected from the fuel addition valve 71 every time the fuel addition amount FA is set through this step S214. To do. Thus, the fuel addition by the fuel addition valve 71 is repeatedly executed, so that the filter catalyst bed temperature TF is maintained at a temperature higher than the target catalyst bed temperature TFT.

<SOx reduction control processing>
With reference to FIG. 6, the outline of the “SOx reduction control process” will be described.
FIG. 6 shows an example of how the fuel addition amount FA and the exhaust air-fuel ratio EAF change during the execution of the “SOx reduction control process”.

  In the “SOx reduction control process”, the exhaust air-fuel ratio EAF is changed through intermittent fuel addition by the fuel addition valve 71 (fuel addition in a mode in which execution of fuel addition and stop of fuel addition are repeated at a relatively short period in a predetermined period) I try to make it rich. In FIG. 6, a period t6A corresponds to an execution period of intermittent fuel addition.

  On the other hand, when the intermittent fuel addition is executed, the catalyst bed temperature of the catalyst-carrying PM filter 73 is greatly increased. Therefore, in the “SOx reduction control process”, an excessive increase in the catalyst bed temperature is suppressed through a periodic stop of intermittent fuel addition. In FIG. 6, the period t6B corresponds to a period during which intermittent fuel addition is stopped.

  During execution of the “SOx reduction control process”, execution of intermittent fuel addition and stop of intermittent fuel addition are repeated in this way, so the exhaust air-fuel ratio EAF reverses between rich and lean in accordance with the fuel addition mode. To come. When the exhaust air-fuel ratio EAF is made rich, SOx stored in the NOx catalyst of the catalyst-carrying PM filter 73 is reduced and released from the catalyst.

  A detailed processing procedure of the “SOx reduction control process” will be described with reference to FIG. This process is repeatedly executed by the electronic control unit 9 from the start to the end in the “S poisoning recovery control process”. That is, the process of step S302 is started again with the end of step S320.

  [Step S302] A fuel addition amount FA of the fuel addition valve 71 is set based on the measured exhaust air-fuel ratio EAFM. That is, the fuel addition amount FA per injection required to make the exhaust air-fuel ratio EAF rich through intermittent fuel addition is set. In addition, when the estimated filter catalyst bed temperature eTF is excessively high (for example, when the upper limit catalyst bed temperature TFlmt is exceeded), the fuel addition amount FA is limited based on the estimated filter catalyst bed temperature eTF. The upper limit catalyst bed temperature TFlmt corresponds to the highest temperature among the filter catalyst bed temperatures TF that do not cause damage to the catalyst-carrying PM filter 73 due to heat.

  [Step S304] The intermittent fuel addition stop period (required stop period tst) is set based on the estimated filter catalyst bed temperature eTF. That is, the intermittent fuel addition stop period necessary to prevent the filter catalyst bed temperature TF from becoming excessively high (for example, a temperature equal to or higher than the upper limit catalyst bed temperature TFlmt) is set.

[Step S306] The intermittent fuel addition by the fuel addition valve 71 is started.
[Step S310] It is determined whether or not the elapsed period (addition execution period ti) from the start of intermittent fuel addition has reached the request execution period tit.
When the requested execution period tit has not been reached, the process of step S310 is performed again.
When the request execution period tit has been reached, the process of step S312 is performed.

  The required execution period tit corresponds to an execution period of intermittent fuel addition required for appropriately reducing SOx through enrichment of the exhaust air-fuel ratio EAF. In this process, a preset request execution period tit is adopted, but the request execution period tit may be set based on an estimated value of the SOx amount occluded in the catalyst-carrying PM filter 73 or the like. it can.

[Step S312] The intermittent fuel addition by the fuel addition valve 71 is stopped.
[Step S320] It is determined whether or not the elapsed period (addition stop period ts) after stopping the intermittent fuel addition has reached the required stop period tst.
When the request stop period tst has not been reached, the process of step S320 is performed again.
When the request stop period tst has been reached, the process of step S302 is performed.

  During the execution of the “SOx reduction control process”, the exhaust air-fuel ratio EAF can be enriched by reducing the intake flow rate GA. For example, the exhaust air-fuel ratio EAF can be changed to the rich side by reducing the intake flow rate GA through the supply of exhaust gas into the intake pipe 22 by EGR control.

<Estimated aspect of catalyst bed temperature>
In the “catalyst bed temperature estimation process” of the present embodiment, in order to estimate the filter catalyst bed temperature TF with higher accuracy, the following [1] “estimation process configuration 1” and [2] “estimation process configuration 2” The filter catalyst bed temperature TF is estimated including the process described in FIG.

[1] “Configuration 1 of estimation processing”
Since the first exhaust temperature sensor 91 measures the temperature of the exhaust gas immediately before flowing into the catalyst-carrying PM filter 73, basically the measured value (actual filter catalyst bed temperature) having a high correlation with the actual filter catalyst bed temperature TF. Measurement value with a small deviation from TF) can be output. On the other hand, the measured value does not reflect the increase in the filter catalyst bed temperature TF accompanying the fuel oxidation reaction in the catalyst-carrying PM filter 73.

  Since the second exhaust temperature sensor 92 measures the temperature of the exhaust gas immediately after flowing out from the catalyst-carrying PM filter 73, the increase in the filter catalyst bed temperature TF accompanying the fuel oxidation reaction in the catalyst-carrying PM filter 73 is reflected. The measured value can be output. On the other hand, the measured value basically has a large response delay with respect to the actual filter catalyst bed temperature TF.

  In the “catalyst bed temperature estimation process” of the present embodiment, the characteristics of the measured values of the exhaust gas temperature sensors 91 and 92 are taken into consideration, and the filter catalyst bed temperature TF (based on the first exhaust gas temperature measured value TE1M) is estimated. The estimated value of the filter catalyst bed temperature TF (the first estimated catalyst bed temperature eTF1) and the filter catalyst bed temperature TF (second estimated catalyst bed temperature eTF2) estimated based on the second exhaust temperature measured value TE2M are combined ( The estimated filter catalyst bed temperature eTF) is calculated.

[2] “Configuration 2 of the estimation process”
Since the first exhaust temperature sensor 91 and the second exhaust temperature sensor 92 have the output characteristics as described above, when the response delay of the measured value of the second exhaust temperature sensor 92 with respect to the actual filter catalyst bed temperature TF is small, The measured value of the second exhaust temperature sensor 92 reflects the actual filter catalyst bed temperature TF more appropriately than the measured value of the first exhaust temperature sensor 91. That is, in order to improve the estimation accuracy of the filter catalyst bed temperature TF, each response to the estimated filter catalyst bed temperature eTF is taken into account by taking into account the response delay of the measured value of the second exhaust temperature sensor 92 with respect to the actual filter catalyst bed temperature TF. It is desirable to set the degree of reflection of the estimated catalyst bed temperatures eTF1, eTF2. On the other hand, the response delay of the measured value of the second exhaust temperature sensor 92 tends to change according to the operation mode of the exhaust purification device 7.

  In the “catalyst bed temperature estimation process” of the present embodiment, in consideration of the above, the degree of reflecting the first estimated catalyst bed temperature eTF1 to the estimated filter catalyst bed temperature eTF (first estimated value reflection rate DP1) and The degree of reflecting the second estimated catalyst bed temperature eTF2 to the estimated filter catalyst bed temperature eTF (second estimated value reflection rate DP2) is set in accordance with the operation mode of the exhaust purification device 7.

<Catalyst bed temperature estimation process>
A detailed processing procedure of the “catalyst bed temperature estimation process” will be described with reference to FIGS. This process is repeatedly executed by the electronic control device 9 at regular intervals.

  [Step S402] An estimated value of the filter catalyst bed temperature TF is calculated based on the first exhaust gas temperature measurement value TE1M and the exhaust gas flow rate GE. In the “catalyst bed temperature estimation process”, the estimated value of the filter catalyst bed temperature TF calculated using only the first exhaust temperature measured value TE1M as the measured value of the exhaust temperature TE is set as the first estimated catalyst bed temperature eTF1.

In the process of step S402, the first estimated catalyst bed temperature eTF1 is specifically calculated through the following processes (a) and (b).
(A) From the first correction amount calculation map (FIG. 9) in which the relationship between the exhaust flow rate GE and the first correction amount TEge1 is set in advance, the first correction amount TEge1 suitable for the exhaust flow rate GE in the current control cycle is calculated. . In this process, the intake flow rate GA is used as the equivalent value of the exhaust flow rate GE. That is, when calculating the first correction amount TEge1, the intake flow rate measurement value GAM of the current control cycle is applied to the first correction amount calculation map.

  (B) The first estimated catalyst bed temperature eTF1 is calculated by correcting the first exhaust temperature measurement value TE1M based on the first correction amount TEge1. That is, a value obtained through the addition of the first exhaust temperature measurement value TE1M and the first correction amount TEge1 is set as the first estimated catalyst bed temperature eTF1.

Here, the setting mode of the first correction amount calculation map will be described.
The first correction amount TEge1 is calculated as a value for correcting the deviation between the first exhaust temperature measurement value TE1M and the actual filter catalyst bed temperature TF. Therefore, it is necessary to set the first correction amount TEge1 in accordance with the degree of deviation between the first exhaust temperature measurement value TE1M and the actual filter catalyst bed temperature TF.

  On the other hand, as the exhaust gas flow rate GE increases, the amount of thermal energy supplied to the catalyst-carrying PM filter 73 increases, so the degree of deviation between the first exhaust temperature measurement value TE1M and the actual filter catalyst bed temperature TF is: The exhaust gas flow rate GE tends to become smaller as it increases.

  In the first correction amount calculation map, the relationship between the exhaust gas flow rate GE and the first correction amount TEge1 is set in accordance with such a change tendency of the degree of deviation. That is, the map is configured such that the first correction amount TEge1 decreases as the exhaust flow rate GE changes to the increase side.

  [Step S404] An estimated value of the filter catalyst bed temperature TF is calculated based on the second measured exhaust gas temperature value TE2M and the exhaust gas flow rate GE. In the “catalyst bed temperature estimation process”, the estimated value of the filter catalyst bed temperature TF calculated using only the second exhaust temperature measurement value TE2M as the measurement value of the exhaust temperature TE is set as the second estimated catalyst bed temperature eTF2.

In the process of step S404, the second estimated catalyst bed temperature eTF2 is specifically calculated through the following processes (a) and (b).
(A) From the second correction amount calculation map (FIG. 10) in which the relationship between the exhaust flow rate GE and the second correction amount TEge2 is set in advance, the second correction amount TEge2 suitable for the exhaust flow rate GE in the current control cycle is calculated. . In this process, the intake flow rate GA is used as the equivalent value of the exhaust flow rate GE. That is, when calculating the second correction amount TEge2, the intake flow rate measurement value GAM of the current control cycle is applied to the second correction amount calculation map.

  (B) The second estimated catalyst bed temperature eTF2 is calculated by correcting the second exhaust temperature measurement value TE2M based on the second correction amount TEge2. That is, a value obtained through addition of the second exhaust temperature measurement value TE2M and the second correction amount TEge2 is set as the second estimated catalyst bed temperature eTF2.

Here, the setting mode of the second correction amount calculation map will be described.
The second correction amount TEge2 is calculated as a value for correcting the deviation between the second exhaust temperature measurement value TE2M and the actual filter catalyst bed temperature TF. Accordingly, it is necessary to set the second correction amount TEge2 in accordance with the degree of deviation between the second exhaust temperature measurement value TE2M and the actual filter catalyst bed temperature TF.

  On the other hand, since the amount of thermal energy supplied to the catalyst-carrying PM filter 73 increases as the exhaust flow rate GE increases, the degree of divergence between the second exhaust temperature measurement value TE2M and the actual filter catalyst bed temperature TF is: The exhaust gas flow rate GE tends to become smaller as it increases.

  In the second correction amount calculation map, the relationship between the exhaust gas flow rate GE and the second correction amount TEge2 is set in accordance with such a change tendency of the degree of deviation. That is, the map is configured so that the second correction amount TEge2 becomes smaller as the exhaust flow rate GE changes to the increase side.

  [Step S406] The first estimated value reflection rate DP1 is set based on the operation mode of the exhaust emission control device 7. Specifically, the first estimated value reflection rate DP1 is set through the processing from the next step S406-1 to step S406-4.

[Step S406-1] It is ascertained which of the following "state A" to "state C" the state of the exhaust gas purification device 7 belongs to.
“State A”: The catalytic function of the NOx catalytic converter 72 is deteriorated.
“State B”: Other than the above “State A” and the SOx reduction control process is being executed.
“State C”: Other than the above “State B”.

  Note that whether or not the catalytic function of the NOx catalytic converter 72 has deteriorated is determined by a deterioration determination process separately performed through the electronic control unit 9. In the determination process, when the degree of deviation between the estimated converter catalyst bed temperature eTC and the first exhaust temperature measurement value TE1M is larger than the reference degree, it is determined that the catalyst function of the NOx catalytic converter 72 has deteriorated.

  [Step S406-2] When the exhaust purification device 7 belongs to "state A", the first estimated value reflection rate DP1 is set to "0". The first estimated value reflection rate DP1 can be set to any value near “0”.

  [Step S406-3] When the exhaust purification device 7 belongs to "state B", the first estimated value reflection rate DP1 is set based on the exhaust flow rate GE. Specifically, the first estimated value reflection rate DP1 is set through the following processing.

  From the reduction control reflection rate calculation map (FIG. 11) in which the relationship between the exhaust gas flow rate GE and the first estimated value reflection rate DP1 when the exhaust purification device 7 belongs to “state B” is set in this control cycle. A first estimated value reflection rate DP1 suitable for the exhaust gas flow rate GE is calculated. In this process, the intake flow rate GA is used as the equivalent value of the exhaust flow rate GE. That is, when calculating the first estimated value reflection rate DP1, the intake flow rate measurement value GAM in the current control cycle is applied to the reduction rate reflection rate calculation map.

  [Step S406-4] When the exhaust purification device 7 belongs to "state C", the first estimated value reflection rate DP1 is set based on the exhaust flow rate GE. Specifically, the first estimated value reflection rate DP1 is set through the following processing.

  From the normal control reflection rate calculation map (FIG. 12) in which the relationship between the exhaust gas flow rate GE and the first estimated value reflection rate DP1 when the exhaust purification device 7 belongs to “state C” is set in this control cycle. A first estimated value reflection rate DP1 suitable for the exhaust gas flow rate GE is calculated. In this process, the intake flow rate GA is used as the equivalent value of the exhaust flow rate GE. That is, when calculating the first estimated value reflection rate DP1, the intake flow rate measurement value GAM of the current control cycle is applied to the normal control reflection rate calculation map.

[Step S408] A second estimated value reflection rate DP2 is set based on the first estimated value reflection rate DP1. That is, the second estimated value reflection rate DP2 is calculated through the following [Equation 1].

[Formula 1]

DP2 ← 1-DP1

In addition, the relationship between the exhaust flow rate GE and the second estimated value reflection rate DP2 is preliminarily incorporated into the reduction control reflection rate calculation map and the normal control reflection rate calculation map, and the first estimated value is obtained in the process of step S406. The reflection rate DP1 and the second estimated value reflection rate DP2 can also be calculated.

Here, the setting mode of the reflection rate calculation rate calculation map and the normal control rate calculation map will be described.
First, the relationship between the exhaust gas flow rate GE and the first estimated value reflection rate DP1 in each calculation map will be described.

  Since the amount of thermal energy supplied to the catalyst-carrying PM filter 73 increases as the exhaust flow rate GE increases, the degree of divergence between the second exhaust temperature measurement value TE2M and the actual filter catalyst bed temperature TF depends on the exhaust flow rate GE. Shows a tendency to decrease as the value increases toward the increasing side.

  Therefore, as described in the “estimation processing configuration 2”, the second estimated value reflection rate DP2 is set to a larger value as the exhaust flow rate GE changes to the increase side, that is, the first estimated value reflection rate DP1. By setting to a smaller value, it is possible to improve the estimation accuracy of the filter catalyst bed temperature TF.

  Based on this, in the reduction rate reflection rate calculation map and the normal control rate reflection rate calculation map, the exhaust flow rate GE and the exhaust gas flow rate GE are reduced so that the first estimated value reflection rate DP1 decreases as the exhaust flow rate GE changes to the increase side. A relationship with the first estimated value reflection rate DP1 is set.

Next, the relationship between the return control rate calculation map and the normal control rate calculation map will be described.
Since the amount of fuel supplied to the catalyst-carrying PM filter 73 differs greatly between the execution and stop of the SOx reduction control process, the actual filter catalyst bed temperature TF and the measured value of the first exhaust temperature sensor 91 A big difference also appears in the degree of divergence. Incidentally, the measured value of the first exhaust gas temperature sensor 91 does not reflect the increase in the filter catalyst bed temperature TF accompanying the oxidation reaction of the fuel in the catalyst-carrying PM filter 73, so the fuel supplied to the catalyst-carrying PM filter 73. As the amount increases, the degree of deviation between the actual filter catalyst bed temperature TF and the measured value of the first exhaust gas temperature sensor 91 tends to increase.

  During execution of the SOx reduction control process, intermittent fuel addition for enriching the exhaust air-fuel ratio EAF is performed, so that a larger amount of fuel is supplied to the catalyst-carrying PM filter 73 than when the SOx reduction control process is stopped. Therefore, the degree of deviation between the actual filter catalyst bed temperature TF and the measured value of the first exhaust temperature sensor 91 increases.

  Accordingly, in the reduction control reflection rate calculation map, the first estimated value reflection rate DP1 is set to a smaller value than the normal control reflection rate calculation map. That is, when the first estimated value reflection rate DP1 at the same exhaust flow rate GE is compared, the first estimated value reflection rate DP1 of the reduction control reflection rate calculation map is reflected in the first control value reflection rate calculation map. The value is smaller than the rate DP1.

[Step S410] An estimated filter catalyst bed temperature eTF is calculated based on the first estimated catalyst bed temperature eTF1, the first estimated value reflection rate DP1, the second estimated catalyst bed temperature eTF2, and the second estimated value reflection rate DP2. That is, the estimated filter catalyst bed temperature eTF is calculated through the following [Equation 2].

[Formula 2]

eTF ← eTF1 × DP1 + eTF2 × DP2

The estimated filter catalyst bed temperature eTF calculated through the above [Equation 2] includes the estimated filter catalyst bed temperature including the “temperature increase control process” and “SOx reduction control process” of the “S poisoning recovery control process”. Reference is made as appropriate in each control process using eTF.

<Effect of embodiment>
As described above in detail, according to the exhaust gas purification apparatus for an internal combustion engine according to this embodiment, the following effects can be obtained.

  (1) In the exhaust purification system of this embodiment, the estimated filter catalyst bed temperature eTF is calculated by combining the first estimated catalyst bed temperature eTF1 and the second estimated catalyst bed temperature eTF2. Accordingly, while maintaining a moderate correlation between the estimated filter catalyst bed temperature eTF and the actual filter catalyst bed temperature TF, the catalyst bed accompanying the oxidation reaction of fuel in the catalyst-carrying PM filter 73 with respect to the estimated value eTF. Since the rise in temperature can be reflected, the estimation accuracy of the filter catalyst bed temperature TF can be further improved.

  (2) In the exhaust purification system of this embodiment, the first estimated value reflection rate DP1 and the second estimated value reflection rate DP2 are set based on the exhaust flow rate GE (intake flow rate GA). Thereby, the estimation accuracy of the filter catalyst bed temperature eTF can be further improved.

  (3) In the exhaust purification system of the present embodiment, the first estimated value reflection rate DP1 is decreased and the second estimated value reflection rate DP2 is increased as the exhaust flow rate GE (intake flow rate GA) changes to the increase side. ing. Thereby, the estimation accuracy of the filter catalyst bed temperature eTF can be further improved.

  (4) In the exhaust purification system of this embodiment, the first estimated value reflection rate DP1 and the second estimated value reflection rate DP2 during execution of the SOx reduction control process and the first estimated value reflection rate during stoppage of the SOx reduction control process DP1 and second estimated value reflection rate DP2 are set to different values. Thereby, the estimation accuracy of the filter catalyst bed temperature eTF can be further improved.

  (5) In the exhaust purification system of the present embodiment, the second estimated value reflection rate DP2 during execution of the SOx reduction control process is set larger than the second estimated value reflection rate DP2 during stoppage of the SOx reduction control process, The first estimated value reflection rate DP1 during the execution of the SOx reduction control process is set to be smaller than the first estimated value reflection rate DP1 during the stop of the SOx reduction control process. Thereby, the estimation accuracy of the filter catalyst bed temperature eTF can be further improved.

  (6) When the catalytic function of the NOx catalytic converter 72 is deteriorated, the amount of fuel flowing into the catalyst-carrying PM filter 73 without being oxidized by the NOx catalytic converter 72 is excessively increased. The degree of deviation between the temperature TF and the measured value of the first exhaust temperature sensor 91 is remarkably increased.

  In the exhaust purification apparatus of the present embodiment, in consideration of the above, when the condition indicating that the catalytic function of the NOx catalytic converter 72 is deteriorated, the first estimated value reflection rate DP1 is set to “0”. It is set to. Thereby, the fall of the estimation precision of the filter catalyst bed temperature TF can be suppressed.

  (7) In the exhaust purification system of this embodiment, the first estimated catalyst bed temperature eTF1 is calculated by correcting the measured value of the first exhaust temperature sensor 91 based on the exhaust flow rate GE. Further, the second estimated catalyst bed temperature eTF2 is calculated by correcting the measured value of the second exhaust temperature sensor 92 based on the exhaust flow rate GE. This makes it possible to improve the estimation accuracy of each estimated catalyst bed temperature and thus the filter catalyst bed temperature TF.

<Example of change>
In addition, the said embodiment can also be implemented as the following forms which changed this suitably, for example.

In the above embodiment, the state to which the exhaust purification device 7 belongs is classified into “state A”, “state B”, and “state C” in step S406 of the “catalyst bed temperature estimation process”. Further, it can be divided into the following “state D” and “state E”.
“State D”: Other than “State B” and the temperature increase control process is being executed.
“State E”: Other than “State D”.

  In this case, a reflection rate calculation map in which the relationship between the exhaust gas flow rate GE and the first estimated value reflection rate DP1 when the exhaust purification device 7 belongs to “state D”, and the exhaust purification device 7 “state E” are set. The first estimated value reflection rate DP1 in each state can be calculated through a reflection rate calculation map in which the relationship between the exhaust gas flow rate GE and the first estimated value reflection rate DP1 is set in advance. .

  In the above embodiment, the estimated filter catalyst bed temperature eTF is calculated by combining the first estimated catalyst bed temperature eTF1 and the second estimated catalyst bed temperature eTF2. However, for example, the following changes may be made. That is, the estimated filter catalyst bed temperature eTF can be calculated by combining the first exhaust temperature measurement value TE1M and the second exhaust temperature measurement value TE2M.

In this case, the calculation mode of the estimated filter catalyst bed temperature eTF can be realized by changing the “catalyst bed temperature estimation process” of the embodiment as follows.
(A) The process of step S402 and S404 is abbreviate | omitted.
(B) The first estimated catalyst bed temperature eTF1 is replaced with the first exhaust temperature measurement value TE1M.
(C) The second estimated catalyst bed temperature eTF2 is replaced with the second exhaust gas temperature measurement value TE2M.
(D) The first estimated value reflection rate DP1 is replaced with a first measured value reflection rate (a degree of reflecting the first exhaust temperature measured value TE1M with respect to the estimated filter catalyst bed temperature eTF). The first measured value reflection rate is set in a manner according to the first estimated value reflection rate DP1.
(E) The second estimated value reflection rate DP2 is replaced with a second measured value reflection rate (a degree of reflecting the second exhaust temperature measured value TE2M with respect to the estimated filter catalyst bed temperature eTF). The second measured value reflection rate is set in a manner according to the second estimated value reflection rate DP2.

  In the above embodiment, the estimated filter catalyst bed temperature eTF is calculated as a value representative of the catalyst bed temperature of the catalyst-carrying PM filter 73. However, the estimated filter catalyst bed temperature eTF can be changed as follows, for example. That is, the estimated filter catalyst bed temperature eTF at individual positions at a plurality of locations from upstream to downstream of the catalyst-carrying PM filter 73 through a combination of the first estimated catalyst bed temperature eTF1 and the second estimated catalyst bed temperature eTF2. Can also be calculated.

  In this case, when the first estimated catalyst bed temperature eTF1 and the second estimated catalyst bed temperature eTF2 are combined, the estimated filter catalyst bed temperature at each of the above positions is taken into account by adding a temperature gradient in the catalyst-carrying PM filter 73. eTF can be calculated. In each control for exhaust purification including the “S poisoning recovery control process”, an estimated value suitable for the control is selected from the plurality of estimated filter catalyst bed temperatures eTF, so that a finer fuel can be obtained. Addition can be realized.

  Further, a representative value of these catalyst bed temperatures eTF (for example, an average value of the plurality of estimated filter catalyst bed temperatures eTF) is calculated based on the plurality of estimated filter catalyst bed temperatures eTF, and a fuel addition mode is calculated based on these values. Can also be controlled. The configuration for calculating the estimated filter catalyst bed temperature eTF at such a plurality of locations is a configuration for calculating the estimated filter catalyst bed temperature eTF by combining the first exhaust temperature measurement value TE1M and the second exhaust temperature measurement value TE2M. It can also be applied to.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the whole structure of the diesel engine provided with the exhaust-gas purification apparatus about embodiment which actualized the exhaust-gas purification apparatus of the internal combustion engine concerning this invention. The flowchart which shows the process sequence of the "S poisoning recovery control process" performed through the electronic controller in the same embodiment. The flowchart which shows the process sequence of the "S poisoning recovery control process" performed through the electronic controller in the same embodiment. The flowchart which shows the process sequence of the "S poisoning recovery control process" performed through the electronic controller in the same embodiment. 7 is a flowchart showing a processing procedure of “temperature increase control processing” executed through the electronic control device in the embodiment. 5 is a time chart showing an example of a fuel addition mode and an exhaust air-fuel ratio change mode during execution of the “SOx reduction control process” of the same embodiment. 4 is a flowchart showing a processing procedure of “SOx reduction control processing” executed through the electronic control device in the embodiment. The flowchart which shows the process sequence of the "catalyst bed temperature estimation process" performed through the electronic controller in the same embodiment. The figure which shows the 1st correction amount calculation map used in the "catalyst bed temperature estimation process" of the embodiment. The figure which shows the 2nd correction amount calculation map used in the "catalyst bed temperature estimation process" of the embodiment. The figure which shows the reflection rate calculation ratio calculation map used in the "catalyst bed temperature estimation process" of the embodiment. The figure which shows the reflection rate calculation map at the time of normal control used in the "catalyst bed temperature estimation process" of the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Diesel engine, 11 ... Engine main body, 12 ... Cylinder, 13 ... Combustion chamber.
21 ... Intake manifold, 22 ... Intake pipe, 23 ... Intake passage, 24 ... Air cleaner, 25 ... Intercooler, 26 ... Throttle valve.

31 ... Exhaust manifold, 32 ... Exhaust pipe, 33 ... Exhaust passage.
4 ... Turbocharger, 41 ... Compressor wheel, 42 ... Turbine wheel, 43 ... Rotor shaft.

DESCRIPTION OF SYMBOLS 5 ... Common rail type fuel supply apparatus, 51 ... Fuel injection valve, 52 ... Fuel tank, 53 ... Fuel pump, 54 ... Common rail.
6 ... Exhaust gas recirculation device, 61 ... Communication pipe, 62 ... EGR cooler, 63 ... EGR valve.

DESCRIPTION OF SYMBOLS 7 ... Exhaust gas purification apparatus, 71 ... Fuel addition valve, 72 ... NOx catalytic converter, 73 ... Catalyst carrying type PM filter
DESCRIPTION OF SYMBOLS 9 ... Electronic controller, 91 ... 1st exhaust temperature sensor, 92 ... 2nd exhaust temperature sensor, 93 ... Exhaust air-fuel ratio sensor, 94 ... Eflow meter, 95 ... Rotational speed sensor.

Claims (22)

An additive supply means for supplying the additive into the exhaust;
A catalyst device having a function of promoting an oxidation reaction of the additive;
A first exhaust temperature sensor provided upstream of the catalyst device and measuring the exhaust temperature;
A second exhaust temperature sensor provided downstream of the catalyst device and measuring an exhaust temperature;
When the conditions for purifying exhaust gas through the catalyst device are satisfied, the exhaust gas is purified by controlling the supply mode of the additive by the additive supply means based on the estimated value of the temperature of the catalyst device. Control means to perform,
An exhaust gas purification system for an internal combustion engine, comprising: an estimation unit that calculates an estimated value of the temperature of the catalyst device by combining the measured value of the first exhaust temperature sensor and the measured value of the second exhaust temperature sensor. apparatus. The exhaust gas purification apparatus for an internal combustion engine according to claim 1,
The degree to which the measured value of the first exhaust temperature sensor is reflected on the estimated value of the temperature of the catalyst device is defined as a first measured value reflection rate, and the second exhaust temperature sensor is reflected on the estimated value of the temperature of the catalyst device. When the degree of reflecting the measured value is the second measured value reflection rate,
The estimation means sets the first measurement value reflection rate and the second measurement value reflection rate based on an operation mode of the exhaust purification device. The exhaust gas purification apparatus for an internal combustion engine according to claim 1,
The degree to which the measured value of the first exhaust temperature sensor is reflected on the estimated value of the temperature of the catalyst device is defined as a first measured value reflection rate, and the second exhaust temperature sensor is reflected on the estimated value of the temperature of the catalyst device. When the degree of reflecting the measured value is the second measured value reflection rate,
The exhaust gas purifying apparatus for an internal combustion engine, wherein the estimating means sets the first measured value reflection rate and the second measured value reflection rate based on an exhaust flow rate or an equivalent value. The exhaust gas purification apparatus for an internal combustion engine according to claim 3,
The estimation means reduces the first measured value reflection rate and increases the second measured value reflection rate as the flow rate of the exhaust gas or an equivalent value thereof changes to the increase side. Engine exhaust purification system. The exhaust gas purification apparatus for an internal combustion engine according to claim 4,
The catalyst device carries a catalyst that occludes nitrogen oxides in exhaust gas,
When the condition for reducing the sulfur oxides stored in the catalyst device is satisfied, the control means makes the sulfur oxides rich by making the air-fuel ratio of the exhaust rich by supplying the additive. It is to perform sulfur reduction treatment to reduce,
The estimation means includes the first measurement value reflection rate and the second measurement value reflection rate during execution of the sulfur reduction treatment, and the first measurement value reflection rate and the second measurement value during suspension of the sulfur reduction treatment. An exhaust emission control device for an internal combustion engine, wherein the reflection rate is set to a different value. The exhaust gas purification apparatus for an internal combustion engine according to claim 5,
The estimation means sets the second measured value reflection rate during execution of the sulfur reduction treatment to be larger than the second measured value reflection rate during suspension of the sulfur reduction treatment and performs the sulfur reduction treatment. The exhaust gas purification apparatus for an internal combustion engine, wherein the first measured value reflection rate is set to be smaller than the first measured value reflection rate when the sulfur reduction process is stopped. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 6,
The exhaust purification device includes an upstream catalyst device that is disposed upstream of the catalyst device and has a function of promoting an oxidation reaction of the additive,
The first exhaust temperature sensor is provided in an exhaust passage downstream of the upstream catalyst device and upstream of the catalyst device,
The exhaust gas purification apparatus for an internal combustion engine, wherein the second exhaust temperature sensor is provided downstream of the catalyst device. The exhaust gas purification apparatus for an internal combustion engine according to claim 7,
The estimation means sets the degree of reflection of the measured value of the first exhaust temperature sensor to the estimated value of the temperature of the catalyst device as a first measured value reflection rate and the estimated value of the temperature of the catalyst device. When the condition indicating that the catalyst function of the upstream catalytic device is deteriorated is established with the degree of reflecting the measurement value of the second exhaust temperature sensor as the second measurement value reflection rate, the first measurement value An exhaust emission control device for an internal combustion engine, wherein the reflection rate is set to "0". The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 8,
The estimation means estimates the temperature of the catalytic device at a plurality of locations from upstream to downstream of the catalytic device through a combination of the measured value of the first exhaust temperature sensor and the measured value of the second exhaust temperature sensor. An exhaust purification device for an internal combustion engine, characterized in that a value is calculated. The exhaust gas purification apparatus for an internal combustion engine according to claim 9,
The estimation means calculates a representative value of the plurality of estimated values based on an estimated value of the temperature of the catalyst device at the plurality of locations,
The exhaust gas purification apparatus for an internal combustion engine, wherein the control means controls an additive supply mode by the additive supply means based on the representative value. An additive supply means for supplying the additive into the exhaust;
A catalyst device having a function of promoting an oxidation reaction of the additive;
A first exhaust temperature sensor provided upstream of the catalyst device and measuring the exhaust temperature;
A second exhaust temperature sensor provided downstream of the catalyst device and measuring an exhaust temperature;
When the conditions for purifying exhaust gas through the catalyst device are satisfied, the exhaust gas is purified by controlling the supply mode of the additive by the additive supply means based on the estimated value of the temperature of the catalyst device. Control means to perform,
The estimated value of the temperature of the catalyst device calculated based on the measured value of the first exhaust temperature sensor is set as a first estimated value, and the temperature of the catalyst device calculated based on the measured value of the second exhaust temperature sensor The estimated value is a second estimated value, the estimated value of the temperature of the catalyst device used when purifying exhaust gas by the control means is the third estimated value, and the first estimated value and the second estimated value are combined. An exhaust emission control device for an internal combustion engine, comprising: an estimation unit that calculates the third estimated value. The exhaust gas purification apparatus for an internal combustion engine according to claim 11,
The degree of reflecting the first estimated value with respect to the third estimated value is defined as a first estimated value reflecting rate, and the degree of reflecting the second estimated value with respect to the third estimated value is defined as a second estimated value reflecting rate. When
The exhaust gas purifying apparatus for an internal combustion engine, wherein the estimating means sets the first estimated value reflection rate and the second estimated value reflection rate based on an operation mode of the exhaust purification device. The exhaust gas purification apparatus for an internal combustion engine according to claim 11,
The degree of reflecting the first estimated value with respect to the third estimated value is defined as a first estimated value reflecting rate, and the degree of reflecting the second estimated value with respect to the third estimated value is defined as a second estimated value reflecting rate. When
The exhaust gas purification apparatus for an internal combustion engine, wherein the estimating means sets the first estimated value reflection rate and the second estimated value reflection rate based on an exhaust flow rate or an equivalent value thereof. The exhaust gas purification apparatus for an internal combustion engine according to claim 13,
The estimation means decreases the first estimated value reflection rate and increases the second estimated value reflection rate as the flow rate of the exhaust gas or an equivalent value thereof changes to the increase side. Engine exhaust purification system. The exhaust gas purification apparatus for an internal combustion engine according to claim 14,
The catalyst device carries a catalyst that occludes nitrogen oxides in exhaust gas,
When the condition for reducing the sulfur oxides stored in the catalyst device is satisfied, the control means makes the sulfur oxides rich by making the air-fuel ratio of the exhaust rich by supplying the additive. It is to perform sulfur reduction treatment to reduce,
The estimation means includes the first estimated value reflection rate and the second estimated value reflection rate during execution of the sulfur reduction treatment, and the first estimated value reflection rate and the second estimated value during suspension of the sulfur reduction treatment. An exhaust emission control device for an internal combustion engine, wherein the reflection rate is set to a different value. The exhaust emission control device for an internal combustion engine according to claim 15,
The estimation means sets the second estimated value reflection rate during execution of the sulfur reduction treatment to be larger than the second estimated value reflection rate during suspension of the sulfur reduction treatment and performs the sulfur reduction treatment. The exhaust gas purification apparatus for an internal combustion engine, wherein the first estimated value reflection rate is set to be smaller than the first estimated value reflection rate when the sulfur reduction process is stopped. The exhaust emission control device for an internal combustion engine according to any one of claims 11 to 16,
The estimation means calculates the first estimated value by correcting a measured value of the first exhaust temperature sensor based on an exhaust flow rate or an equivalent value thereof. apparatus. The exhaust emission control device for an internal combustion engine according to any one of claims 11 to 17,
The estimation means calculates the second estimated value by correcting the measured value of the second exhaust temperature sensor based on the flow rate of exhaust gas or an equivalent value thereof. apparatus. The exhaust emission control device for an internal combustion engine according to any one of claims 11 to 18,
The exhaust purification device includes an upstream catalyst device that is disposed upstream of the catalyst device and has a function of promoting an oxidation reaction of the additive,
The first exhaust temperature sensor is provided in an exhaust passage downstream of the upstream catalyst device and upstream of the catalyst device,
The exhaust gas purification apparatus for an internal combustion engine, wherein the second exhaust temperature sensor is provided downstream of the catalyst device. The exhaust emission control device for an internal combustion engine according to claim 19,
The estimating means sets a degree of reflecting the first estimated value to the third estimated value as a first estimated value reflection rate and a degree of reflecting the second estimated value to the third estimated value. When the condition indicating that the catalyst function of the upstream catalytic device is deteriorated is established as the second estimated value reflection rate, the first estimated value reflection rate is set to “0”. An exhaust gas purification apparatus for an internal combustion engine characterized by the above. The exhaust emission control device for an internal combustion engine according to any one of claims 11 to 20,
The estimation means calculates the third estimated value at a plurality of locations from upstream to downstream of the catalyst device through a combination of the first estimated value and the second estimated value. An exhaust purification device for an internal combustion engine. The exhaust gas purification apparatus for an internal combustion engine according to claim 21,
The estimation means calculates a representative value of the plurality of estimated values based on the third estimated value at the plurality of locations,
The exhaust gas purification apparatus for an internal combustion engine, wherein the control means controls an additive supply mode by the additive supply means based on the representative value.

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