JP2009138525A - Sulfur accumulation degree estimation device of exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sulfur accumulation estimation device of an exhaust emission control device which more accurately estimates the sulfur accumulation degree of an NOx occlusion reduction catalyst. <P>SOLUTION: A sulfur accumulation degree of an exhaust emission control device 16 including a NOx occluding/reducing catalyst for occluding nitrogen oxides in exhaust under oxidizing atmosphere and for reducing the occluded nitrogen oxides under reductive atmosphere, is estimated based on the degree of rise in catalyst floor temperature of the NOx occluding/reducing catalyst associated with the introduction of a reducing agent which is detected by floor temperature sensors S1-Sn. Consequently, the sulfur accumulation degree can be directly estimated from the detection result of the degree of rise in the catalyst floor temperature at that time. The estimation of more accumulate sulfur accumulation degree of the NOx occluding/reducing catalyst can be realized without accumulating errors in an integration process. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sulfur deposition degree estimation device for an exhaust purification apparatus that estimates a sulfur deposition degree of a NOx storage reduction catalyst provided in an exhaust purification apparatus.

  As an exhaust purification device applied to an internal combustion engine that performs lean combustion, an exhaust purification device including a NOx occlusion reduction catalyst that purifies exhaust nitrogen oxide (NOx) is known. The NOx occlusion reduction catalyst is obtained by adding an alkaline substance as a NOx occlusion material to a conventional three-way catalyst. For example, a monolith support is coated with alumina, platinum (Pt), rhodium (Rh), and various alkalis. In addition, those carrying an alkaline earth or rare earth oxide are used.

  Such NOx purification using the NOx occlusion reduction catalyst is performed in the following manner. In the oxidizing atmosphere, NOx in the exhaust is oxidized on the noble metal of the catalyst, and is combined with the NOx storage material adjacent thereto to form nitrate, and is stored in the catalyst. On the other hand, at the equivalent point and reducing atmosphere, nitrates stored in the catalyst are decomposed and reacted with reducing gases such as hydrocarbon (HC) and carbon monoxide (CO) on noble metals and reduced to nitrogen. The Therefore, in a lean combustion engine that employs a NOx occlusion reduction catalyst in an exhaust purification device, NOx reduction control for reducing and purifying NOx occluded in the catalyst with the exhaust air-fuel ratio rich is performed intermittently, so that occlusion and reduction are repeated. To purify NOx.

  By the way, the NOx occlusion reduction catalyst occludes the sulfur oxide (SOx) of the exhaust gas as well as NOx in an oxidizing atmosphere. SOx occluded as a sulfate in the catalyst is not released at the catalyst bed temperature (about 250 ° C.) at the time of NOx reduction control, so that it gradually accumulates in the catalyst and deteriorates the NOx occlusion capacity of the catalyst. become. Therefore, in order to eliminate the deterioration of the NOx storage capacity of the catalyst due to SOx deposition, so-called catalyst sulfur poisoning, the catalyst bed temperature is increased to a temperature at which sulfur content can be released (600 ° C or higher). It is necessary to periodically perform sulfur release control for adding a fuel serving as an agent to the exhaust and releasing the sulfur content deposited on the catalyst.

Conventionally, as can be seen, for example, in Patent Documents 1 and 2, devices for estimating the degree of sulfur deposition of the NOx storage reduction catalyst have been proposed in order to know the timing of such sulfur release control. In such a conventional sulfur deposition degree estimation device, the amount of sulfur newly deposited on the NOx storage reduction catalyst in the unit time (new sulfur deposition amount per unit time) is obtained from the vehicle travel distance per unit time, As an integrated value of the obtained amount, the amount of sulfur (the amount of sulfur accumulation) accumulated in the current NOx storage reduction catalyst is estimated.
JP 2002-364349 A JP 2003-343243 A

  However, in the conventional estimation method as described above, if there is even a slight estimation error of the new sulfur deposition amount per unit time, the error is accumulated, so that the estimation error of the sulfur deposition amount finally obtained is large. turn into. If the estimation error of the sulfur accumulation amount becomes large, the execution timing of the sulfur release control becomes inappropriate, and problems such as excessive or insufficient sulfur release occur.

  The present invention has been made in view of such a situation, and the problem to be solved is a sulfur accumulation amount estimation device for an exhaust purification device capable of more accurately estimating the degree of sulfur accumulation of a NOx storage reduction catalyst. Is to provide.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
In order to solve the above-mentioned problem, the invention according to claim 1 is an apparatus for estimating a sulfur deposition degree of the NOx occlusion reduction catalyst in an exhaust gas purification apparatus provided with an NOx occlusion reduction catalyst, wherein Detection means for detecting the temperature rise of the catalyst bed temperature of the NOx storage reduction catalyst, and estimation for estimating the estimated sulfur degree of the NOx storage reduction catalyst based on the temperature rise of the catalyst bed temperature detected by the detection means The gist is to provide the means.

  The NOx occlusion reduction catalyst provided in the exhaust purification device occludes NOx in the exhaust under an oxidizing atmosphere, and reduces and purifies the occluded NOx under a reducing atmosphere. In such a NOx occlusion reduction catalyst, SOx in the exhaust gas gradually accumulates together with NOx. And if the amount of sulfur deposits in the NOx storage reduction catalyst increases, the low-temperature activity ability of the catalyst decreases, so that the temperature rise of the catalyst bed temperature when a reducing agent such as an unburned fuel component is introduced decreases. Therefore, the degree of sulfur deposition in the exhaust purification device can be estimated from the temperature rise of the catalyst bed temperature accompanying the introduction of the reducing agent. Specifically, it can be estimated that the sulfur deposition degree of the exhaust purification device is larger as the catalyst bed temperature rise accompanying the introduction of the reducing agent is smaller. According to such an estimation method, since the degree of sulfur deposition is directly estimated from the detection result of the temperature rise of the catalyst bed temperature at that time, the accumulation process is not performed, and errors may be accumulated as a result of the accumulation process. Absent. Therefore, according to the above configuration, the sulfur accumulation degree of the NOx storage reduction catalyst can be estimated more accurately.

  The current NOx occlusion capacity of the NOx occlusion reduction catalyst is obtained by subtracting the decrease in NOx occlusion capacity due to sulfur deposition from the original NOx occlusion capacity of the NOx occlusion reduction catalyst (amount of NOx that can be occluded). Therefore, the current NOx storage capacity can be uniquely determined from the sulfur accumulation amount of the NOx storage reduction catalyst. Therefore, in the above configuration, it is possible to estimate the current NOx storage capacity instead of the sulfur accumulation amount as an index value of the degree of sulfur deposition of the NOx storage reduction catalyst.

  According to a second aspect of the present invention, in the sulfur deposition degree estimating device for the exhaust gas purification device according to the first aspect, the detection means includes a detected value of the temperature of the exhaust gas introduced into the exhaust gas purification device and the catalyst bed temperature. The gist is to detect the temperature rise based on the deviation from the detected value.

The temperature rise of the catalyst bed temperature when the reducing agent is introduced can be easily detected based on the deviation between the detected value of the temperature of the exhaust gas introduced into the exhaust purification device and the detected value of the catalyst bed temperature.
According to a third aspect of the present invention, in the sulfur purification degree estimating device for the exhaust purification apparatus according to the first or second aspect, the estimation of the sulfur deposition degree by the estimating means is performed on the exhaust gas introduced into the exhaust purification apparatus. The gist is that the detection is performed based on the detection result of the temperature rise by the detection means when the temperature is in the light-off temperature range of the NOx storage reduction catalyst.

  When the temperature of the exhaust gas introduced into the exhaust gas purification device is gradually increased, when the temperature of the exhaust gas to be introduced reaches a certain temperature range, the NOx storage reduction catalyst is activated and the catalyst bed temperature rapidly increases. The light-off temperature range of the NOx storage reduction catalyst is such a temperature range. By the way, in such a light-off temperature range, the temperature rise of the catalyst bed accompanying the introduction of the reducing agent becomes remarkable. Therefore, if it is based on the temperature rise of the catalyst bed temperature accompanying the introduction of the reducing agent when the temperature of the exhaust gas introduced into the exhaust purification device is in the light-off temperature range of the NOx storage reduction catalyst, the NOx storage reduction catalyst It becomes possible to estimate the degree of sulfur deposition of the water more accurately.

  According to a fourth aspect of the present invention, in the sulfur deposition degree estimating device for an exhaust purification apparatus according to any one of the first to third aspects, the estimation of the sulfur deposition degree by the estimating means is performed by using the catalyst bed temperature. The gist of the present invention is that the detection is performed based on the detection result of the degree of increase in temperature during the control for increasing the temperature.

  In an exhaust purification device equipped with a NOx storage reduction catalyst, for example, PM regeneration control for removing particulate matter (PM) collected in the exhaust purification device, NOx reduction control for reducing and purifying NOx stored in the catalyst, etc. Control is implemented. During the execution of such control, the catalyst bed temperature is raised by introducing the reducing agent, and accordingly, it is possible to estimate the degree of sulfur deposition in the above-described manner.

  According to a fifth aspect of the present invention, in the sulfur purification degree estimation device of the exhaust purification device according to any one of the first to third aspects, the estimation of the sulfur deposition degree by the estimating means is performed by the exhaust purification device. The gist is that the detection is performed based on the detection result of the temperature rise of the detection means during the execution of the PM regeneration control for removing the collected particulate matter.

  During the execution of the PM regeneration control as described above, the catalyst bed temperature is actively raised by introducing the reducing agent. Therefore, it is possible to suitably estimate the degree of sulfur deposition in the above-described manner in conjunction with the implementation of such PM regeneration control.

  The invention according to claim 6 is the sulfur accumulation degree estimation device for the exhaust gas purification device according to any one of claims 1 to 5, wherein the estimation means has a temperature increase degree equal to or less than a prescribed poisoning determination value. The gist of the present invention is to estimate that the degree of sulfur deposition of the exhaust purification device is large.

  As described above, if the amount of sulfur deposited on the NOx storage reduction catalyst increases, the low-temperature activity of the catalyst decreases, so the temperature rise of the catalyst bed temperature when a reducing agent such as an unburned fuel component is introduced decreases. To do. Therefore, it is possible to estimate whether or not the degree of sulfur deposition of the NOx storage reduction catalyst is large depending on whether or not the temperature rise of the catalyst bed temperature accompanying the introduction of the reducing agent is equal to or less than a predetermined determination value. .

  According to a seventh aspect of the present invention, in the sulfur deposition degree estimating device of the exhaust purification device according to the sixth aspect, the poisoning determination value is smaller as the flow rate of the exhaust gas introduced into the exhaust purification device is larger. The gist is that the value is set.

  Even if the temperature of the exhaust gas introduced into the exhaust gas purification device is the same, the catalyst bed temperature becomes more difficult to rise as the flow rate of the introduced exhaust gas increases. Therefore, by setting the poisoning determination value to a smaller value as the flow rate of the exhaust gas introduced into the exhaust gas purification device increases, it is possible to more appropriately estimate whether the sulfur accumulation degree of the NOx storage reduction catalyst is larger. Will be able to do.

  The invention according to claim 8 is the sulfur accumulation degree estimation device of the exhaust purification device according to claim 6 or 7, wherein the poisoning judgment value is higher when the temperature of the exhaust gas introduced into the exhaust purification device is higher. The gist is that it is set to a large value.

  The higher the temperature of the exhaust gas introduced into the exhaust gas purification device, the higher the catalyst bed temperature. Therefore, the higher the temperature of the exhaust gas introduced into the exhaust gas purification device, the more appropriately the estimation of whether or not the sulfur accumulation degree of the NOx storage reduction catalyst is large by setting the poisoning determination value to a larger value. Will be able to do.

  A ninth aspect of the present invention is the sulfur deposition degree estimating apparatus according to any one of the first to eighth aspects, wherein the detecting means is configured to increase the temperature of the catalyst bed at each part of the exhaust gas purification apparatus. And the estimation means individually estimates the degree of sulfur deposition in each part of the exhaust purification device based on the degree of increase in the catalyst bed temperature of each detected part. It is a summary.

  In the above configuration, the degree of sulfur deposition is individually estimated for each part of the exhaust purification device. Therefore, it is possible to estimate the degree of sulfur deposition for each part of the exhaust purification device, and in turn, to estimate the sulfur deposition distribution of the exhaust purification device.

DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment in which a sulfur deposition degree estimating device for an exhaust gas purification device according to the present invention is embodied will be described in detail with reference to FIGS.
FIG. 1 schematically shows a configuration of a diesel engine to which a sulfur deposition degree estimation device of an exhaust purification device according to the present embodiment is applied. As shown in the figure, the diesel engine includes an intake passage 10, a combustion chamber 11 and an exhaust passage 12. An injector 13 is installed in the combustion chamber 11 into which outside air is introduced through the intake passage 10, and the fuel injected from the injector 13 is combusted inside. Exhaust gas generated by the combustion is discharged to the exhaust passage 12. In the exhaust passage 12, a fuel addition valve 14 for adding fuel to the exhaust, an exhaust temperature sensor 15 for detecting the temperature of exhaust, and an exhaust purification device 16 are installed in this order from the upstream side. The exhaust gas temperature sensor 15 provided upstream of the exhaust gas purification device 16 detects the temperature of the exhaust gas introduced into the exhaust gas purification device 16.

  The exhaust purification device 16 carries a NOx occlusion reduction catalyst therein, and this NOx occlusion reduction catalyst occludes NOx in the exhaust in the oxidizing atmosphere, and occludes in the equivalent point and the reducing atmosphere. NOx is reduced. The exhaust purification device 16 is also configured to function as a filter that collects particulate matter (PM) in the exhaust.

  Inside the exhaust purification device 16, a plurality (n) of temperature sensors (bed temperature sensors S <b> 1 to Sn) are arranged at equal intervals in the exhaust flow direction inside. The bed temperature sensors S1 to Sn detect the catalyst bed temperature of each part of the exhaust purification device 16 individually.

  Such control of the diesel engine is performed by the electronic control unit 17. The electronic control unit 17 is a central processing unit (CPU) that performs various arithmetic processes related to engine control, a read-only memory (ROM) in which programs and data for engine control are stored in advance, and temporary calculation results of the CPU. A random access memory (RAM), and an input / output port (I / O) for inputting and outputting signals. In addition to the exhaust temperature sensor 15 and floor temperature sensors S1 to Sn, for example, a diesel engine such as an NE sensor 18 that detects an engine rotation speed or an accelerator sensor 19 that detects an accelerator operation amount is provided at an input port of the electronic control unit 17. Various sensors for detecting the driving situation are connected. The electronic control unit 17 performs various controls such as fuel injection amount control and fuel injection timing control of the injector 13 based on the detection results of these sensors.

  In this diesel engine, the electronic control unit 17 performs NOx reduction control, PM regeneration control, sulfur release control, and the like as control related to the exhaust purification device 16. The NOx reduction control is control for reducing NOx occluded in the NOx occlusion reduction catalyst, and is performed by supplying unburned fuel components serving as a reducing agent to the exhaust through addition of fuel from the fuel addition valve 14. The PM regeneration control is a control for removing PM trapped in the exhaust purification device 16 and raises the catalyst bed temperature to a temperature at which PM can be removed through fuel addition from the fuel addition valve 14 to collect the PM. This is done by burning the PM that has been released. Furthermore, the sulfur release control is a control for releasing SOx deposited on the NOx storage reduction catalyst. The catalyst bed temperature is raised to a temperature (600 ° C. or higher) at which SOx can be released, This is done by supplying unburned fuel components that serve as a reducing agent to the exhaust through the addition of fuel.

  In the present embodiment, the sulfur deposition degree of the NOx occlusion reduction catalyst of the exhaust purification device 16 is estimated in order to determine the execution timing, the execution period, etc. of the sulfur release control as described above. In the present embodiment, the estimation of the degree of sulfur deposition is performed based on the temperature rise of the catalyst bed accompanying the introduction of the reducing agent.

  The principle of such estimation is as follows. That is, the NOx occlusion reduction catalyst generates heat by a reduction reaction when a reducing agent (unburned fuel component such as HC or CO) is introduced. Therefore, the catalyst bed temperature of the NOx storage reduction catalyst rises with the introduction of the reducing agent. Here, when the amount of sulfur accumulation in the NOx storage reduction catalyst increases, the low temperature activity of the NOx storage reduction catalyst decreases, and the temperature rise of the catalyst bed temperature accompanying the introduction of the reducing agent becomes slow. Therefore, as shown in FIG. 2, it can be estimated that the sulfur deposition amount increases as the temperature increase (temperature increase amount) of the catalyst bed temperature at the time of introducing the reducing agent decreases.

  The estimation of the degree of sulfur deposition based on the temperature increase of the catalyst bed accompanying the introduction of the reducing agent is desirably performed under the following exhaust temperature conditions. FIG. 3 shows the relationship between the exhaust temperature and the catalyst bed temperature. As shown in the figure, when the temperature of the exhaust gas introduced into the exhaust purification device 16 is gradually increased, when the temperature of the exhaust gas introduced exceeds a certain temperature (for example, 200 ° C.), the NOx storage reduction catalyst When activated, the catalyst bed temperature rises rapidly. Such a temperature range (for example, a temperature range of 200 to 300 ° C.) where the catalyst bed temperature rapidly increases is called a light-off temperature range of the NOx storage reduction catalyst. In such a light-off temperature range, the catalyst bed temperature rises significantly with the introduction of the reducing agent. Therefore, if it is based on the temperature rise of the catalyst bed temperature accompanying the introduction of the reducing agent when the temperature of the exhaust gas introduced into the exhaust purification device 16 is in the light-off temperature range of the NOx storage reduction catalyst, NOx storage reduction The degree of sulfur deposition of the catalyst can be estimated more accurately.

  Moreover, it is preferable to perform the estimation of the degree of sulfur deposition as described above when control for greatly increasing the catalyst bed temperature is performed. During the execution of such control, the catalyst bed temperature is raised by introducing the reducing agent, and accordingly, it is possible to estimate the degree of sulfur deposition in the above-described manner. In addition, if such control is being performed, a difference in the bed temperature degree of the catalyst bed temperature due to the degree of sulfur deposition appears significantly. For example, during the above-described PM regeneration control, the catalyst bed temperature is actively raised by introducing the reducing agent, and therefore the sulfur deposition degree is accurately estimated based on the catalyst bed temperature rise. Can do.

  Therefore, in the present embodiment, when the temperature of the exhaust gas introduced into the exhaust purification device 16 is in the light-off temperature range of the NOx storage reduction catalyst and the PM regeneration control is being performed, the catalyst bed temperature in the above aspect is used. The degree of sulfur deposition is estimated based on the temperature rise. Therefore, it is possible to accurately estimate the degree of sulfur deposition of the NOx storage reduction catalyst.

  As described above, in the present embodiment, each of the bed temperature sensors S1 to Sn detects the degree of temperature increase of the catalyst bed temperature at each part of the exhaust purification device 16. In the present embodiment, the sulfur deposition degree for each part of the exhaust purification device 16 is individually estimated based on the detected temperature rise of the catalyst bed temperature of each part, and from the estimation results, The sulfur accumulation distribution of the exhaust purification device 16 is estimated. FIG. 4 shows an example of the distribution mode of the heating allowance of the catalyst bed temperature at each part of the exhaust purification device 16 when the sulfur deposition degree is small and large. In addition, “P1”, “P2”, “P3”,... “Pn−1”, “Pn” on the horizontal axis of the graph are the installation of the bed temperature sensors S1, S2, S3,. Indicates the position. In the example shown in the figure, as the sulfur deposition progresses, the temperature increase of the catalyst bed temperature at the front end portion of the exhaust gas purification device 16 is significantly reduced, and the sulfur deposition progresses particularly at the front end portion. It has become a state.

  Further, in the present embodiment, based on the estimation result of the sulfur accumulation amount, the present NOx occlusion ability (amount of NOx that can be occluded) of the NOx occlusion reduction catalyst is also estimated. The current NOx storage capacity can be obtained by subtracting the decrease in NOx storage capacity due to sulfur deposition from the original NOx storage capacity of the NOx storage reduction catalyst in the absence of sulfur deposition. Therefore, from the estimation result of the sulfur accumulation amount, it is possible to estimate the current NOx storage capacity of the NOx storage reduction catalyst.

  In the present embodiment, whether or not the sulfur deposition of the NOx storage reduction catalyst proceeds beyond an allowable level based on the temperature increase of the catalyst bed temperature at each part of the exhaust purification device 16 as described above. Is determined. This determination is made based on whether or not the temperature increase of the catalyst bed temperature at each part is below a prescribed poisoning determination value. More specifically, if the temperature increase of the catalyst bed temperature in any part of the exhaust purification device 16 is equal to or less than the poisoning determination value, sulfur deposition exceeding an allowable level has occurred. Judgment is made.

  Incidentally, in this embodiment, the poisoning determination value is variably set according to the temperature and flow rate of the exhaust gas introduced into the exhaust gas purification device 16. Here, the poisoning determination value is set using an arithmetic map based on the temperature and flow rate of the exhaust gas introduced into the exhaust gas purification device 16 as shown in FIG. In the present embodiment, the flow rate of the exhaust gas introduced into the exhaust gas purification device 16 is estimated based on the engine speed detected by the NE sensor 18 and the engine load obtained from the fuel injection amount of the injector 13. And ask for it.

  This calculation map is set so that the poisoning determination value becomes smaller as the temperature of the exhaust gas introduced into the exhaust purification device 16 is lower or as the flow rate of the exhaust gas introduced into the exhaust purification device 16 is higher. Has been. The catalyst bed temperature is likely to increase as the temperature of the exhaust gas introduced into the exhaust gas purification device 16 is higher, and becomes difficult to increase as the flow rate of the introduced exhaust gas is higher. Therefore, if the poisoning determination value is set in the above-described manner, whether or not the sulfur accumulation degree of the NOx occlusion reduction catalyst is large according to the temperature and flow rate of the exhaust gas introduced into the exhaust purification device 16, that is, sulfur poisoning. Thus, it is possible to appropriately estimate whether or not the vehicle is in the advanced state.

  In addition, the temperature rising tendency of the catalyst bed temperature may vary depending on the portion of the exhaust purification device 16. When such a difference in temperature rising tendency is significant, a calculation map as described above is provided for each part of the exhaust purification device 16, and a poisoning determination value is individually set for each part of the exhaust purification device 16. You may make it do.

  In the present embodiment, when it is confirmed by the above determination that the sulfur accumulation of the NOx occlusion reduction catalyst is proceeding beyond an allowable level, the NOx reduction control, the PM regeneration control, the sulfur release is performed. The embodiment of each exhaust purification control such as control is changed. For example, when the NOx occlusion capacity of the NOx occlusion reduction catalyst is reduced due to sulfur accumulation, the execution interval of the NOx reduction control is shortened. Further, as the sulfur deposition progresses, the low temperature activity of the NOx occlusion reduction catalyst decreases and the reduction reaction of NOx decreases. Therefore, when it is estimated that the amount of sulfur deposition is large, the execution time of the NOx reduction control is increased, The amount of fuel added to the exhaust during the reduction control and the number of additions are also increased. Further, in the PM regeneration control, when it is estimated that the amount of accumulated sulfur is large, the target temperature of the catalyst bed temperature under control is made higher to promote sulfur release during control. In addition, when it is estimated that the amount of accumulated sulfur is large, the embodiment of the control is changed such that the timing of performing the sulfur release control is advanced or the execution time of the control is lengthened.

  Further, in the present embodiment, when it is estimated that the amount of sulfur accumulation in the front end portion of the exhaust purification device 16 is particularly large, the catalyst end face burnout control is performed. This catalyst end burn-out control is originally performed to eliminate clogging of the front end face of the exhaust purification device 16 due to PM, and by adjusting the interval of fuel addition into the exhaust appropriately, exhaust purification. This is performed by intensively raising the temperature of the front end surface of the device 16. Here, by such control, the catalyst bed temperature in the front end face of the exhaust purification device 16 and in the vicinity thereof is raised, so that sulfur accumulated in the site is released.

  FIG. 6 shows a flowchart of a sulfur deposition degree estimation routine for estimating the sulfur deposition degree in the present embodiment. The processing of this routine is repeatedly performed periodically by the electronic control unit 17 during operation of the diesel engine.

  When this routine is started, the electronic control unit 17 first checks in steps S10 and S20 whether or not an execution condition for estimating the degree of sulfur deposition is satisfied. More specifically, the electronic control unit 17 at this time determines whether or not the temperature of the exhaust gas introduced into the exhaust gas purification device 16 is in the light-off temperature range of the NOx storage reduction catalyst and the PM regeneration control is being performed. Check. If the exhaust gas temperature is not in the light-off temperature range (S10: NO) or the PM regeneration control is not being performed (S20: NO), the electronic control unit 17 continues the process of this routine as it is. finish.

  On the other hand, if the conditions for estimating the degree of sulfur deposition are satisfied (S10: YES and S20: YES), the electronic control unit 17 detects the respective bed temperature sensors S1 to Sn at that time in step S30. The catalyst bed temperatures T1 to Tn of the respective parts of the exhaust purification device 16 to be acquired are acquired. Then, the difference between the obtained catalyst bed temperature T1 to Tn of each part and the temperature Tex of the exhaust gas introduced into the exhaust gas purification device 16 is obtained, respectively, and the temperature increase ΔT1 to ΔTn (= Ti− Tex: “i” is an integer from “1” to “n”).

  Subsequently, in step S40, the electronic control unit 17 calculates the poisoning determination value based on the temperature and flow rate of the exhaust gas introduced into the exhaust gas purification device 16 using the calculation map as shown in FIG. In step S50, the electronic control unit 17 allows the sulfur accumulation of the NOx storage reduction catalyst by comparing the previously calculated temperature rise ΔTi (ΔT1 to ΔTn) of the catalyst bed temperature with the poisoning determination value. Check if it is progressing beyond a possible level. More specifically, here, the electronic control unit 17 has any one of the catalyst bed temperature temperature increases ΔT1 to ΔTn of each part of the exhaust purification device 16 that is equal to or lower than the poisoning determination value, It is determined that the sulfur accumulation of the NOx storage reduction catalyst is proceeding beyond an acceptable level.

  Here, if the sulfur accumulation of the NOx occlusion reduction catalyst remains within an allowable range (S50: NO), the electronic control unit 17 once ends the processing of this routine as it is. On the other hand, if not (S50: YES), in step S60, the electronic control unit 17 determines each part of the exhaust gas purification device 16 based on the previously calculated catalyst bed temperature temperature increase ΔTi (ΔT1 to ΔTn). The sulfur deposition amount, sulfur deposition distribution, and current NOx storage capacity are calculated, and the processing of this routine is terminated. Depending on the amount of sulfur deposition calculated in this way, the sulfur deposition distribution, and the current NOx storage capacity, the embodiments of each exhaust purification control such as NOx reduction control, PM regeneration control, and sulfur release control are changed as described above. become.

  In this embodiment, the exhaust temperature sensor 15 and the bed temperature sensors S1 to Sn correspond to the “detection means” that detects the temperature rise of the catalyst bed temperature accompanying the introduction of the reducing agent. Yes. Further, the processing of steps S50 and S60 of the sulfur deposition degree estimation routine performed by the electronic control unit 17 corresponds to the processing performed by the “estimating means”.

According to the sulfur deposition degree estimation device for the exhaust gas purification apparatus of the present embodiment described above, the following effects can be achieved.
(1) In the present embodiment, the temperature increase of the catalyst bed temperature of the NOx storage reduction catalyst accompanying the introduction of the reducing agent is detected, and more specifically, based on the detected temperature increase of the catalyst bed temperature. Is configured to estimate the sulfur estimation degree of the NOx occlusion reduction catalyst based on the deviation between the detected value of the temperature of the exhaust gas introduced into the exhaust gas purification device 16 and the detected value of the catalyst bed temperature. When the amount of sulfur deposited on the NOx storage reduction catalyst increases, the low-temperature activity ability of the catalyst decreases, so that the temperature rise of the catalyst bed temperature when a reducing agent such as an unburned fuel component is introduced decreases. Therefore, the degree of sulfur deposition of the exhaust purification device 16 can be estimated from the temperature increase of the catalyst bed temperature when the reducing agent is introduced. Specifically, it can be estimated that the degree of sulfur deposition of the NOx occlusion reduction catalyst is larger as the degree of increase in the catalyst bed temperature during introduction of the reducing agent is smaller. According to such an estimation method, since the degree of sulfur deposition is directly estimated from the detection result of the temperature rise of the catalyst bed temperature at that time, the accumulation process is not performed, and errors may be accumulated as a result of the accumulation process. Absent. Therefore, according to the present embodiment, the degree of sulfur deposition of the NOx storage reduction catalyst can be estimated more accurately.

  (2) In the present embodiment, the above aspect is based on the detection result of the temperature rise of the catalyst bed temperature when the temperature of the exhaust gas introduced into the exhaust purification device 16 is in the light-off temperature range of the NOx storage reduction catalyst. The degree of sulfur deposition at is estimated. In the light-off temperature range of the NOx occlusion reduction catalyst, the catalyst bed temperature rises with the introduction of the reducing agent. Therefore, according to the sulfur deposition degree estimating device of the exhaust purification apparatus of the present embodiment that estimates the sulfur deposition degree based on the temperature rise of the catalyst bed temperature in such a light-off temperature range, the sulfur of the NOx storage reduction catalyst The degree of deposition can be estimated more accurately.

  (3) In the present embodiment, the degree of sulfur deposition in the above embodiment is based on the detection result of the temperature rise of the catalyst bed temperature during the control of raising the catalyst bed temperature, specifically, the PM regeneration control. We are trying to estimate. The estimation of the degree of sulfur deposition in the above-described aspect can be performed in conjunction with the control for raising the catalyst bed temperature by introducing the reducing agent, such as PM regeneration control. In particular, during the PM regeneration control, the catalyst bed temperature is actively raised by introducing the reducing agent, so that the degree of sulfur deposition can be estimated appropriately.

  (4) In the present embodiment, it is estimated that the degree of sulfur deposition of the exhaust purification device 16 exceeds a permissible level when the temperature increase ΔT1 to ΔTn of the catalyst bed temperature is equal to or less than a specified poisoning determination value. Like to do. As described above, if the amount of sulfur deposited on the NOx storage reduction catalyst increases, the low-temperature activity of the catalyst decreases, so the temperature rise of the catalyst bed temperature when a reducing agent such as an unburned fuel component is introduced decreases. To do. Therefore, it is possible to estimate whether or not the degree of sulfur deposition of the NOx storage reduction catalyst is large depending on whether or not the temperature rise of the catalyst bed temperature accompanying the introduction of the reducing agent is equal to or less than a predetermined determination value. .

  (5) In this embodiment, the poisoning determination value is set to a smaller value as the flow rate of the exhaust gas introduced into the exhaust gas purification device 16 increases. Even if the temperature of the exhaust gas introduced into the exhaust gas purification device 16 is the same, the catalyst bed temperature of the NOx storage reduction catalyst becomes more difficult to increase as the flow rate of the introduced exhaust gas increases. Therefore, as the flow rate of the exhaust gas introduced into the exhaust gas purification device 16 is larger, the poisoning determination value is set to a smaller value, thereby more appropriately estimating whether the sulfur accumulation degree of the NOx storage reduction catalyst is larger. To be able to do that.

  (6) In this embodiment, the poisoning determination value is set to a larger value as the temperature of the exhaust gas introduced into the exhaust gas purification device is higher. The higher the temperature of the exhaust gas introduced into the exhaust gas purification device 16, the higher the catalyst bed temperature. Therefore, the higher the temperature of the exhaust gas introduced into the exhaust gas purification device 16, the more appropriate the estimation of whether or not the sulfur accumulation degree of the NOx storage reduction catalyst is large by setting the poisoning determination value to a larger value. To be able to do that.

  (7) In the present embodiment, the respective bed temperature sensors S1 to Sn detect the degree of increase in the catalyst bed temperature at each part of the exhaust gas purification device 16, and the increase in the catalyst bed temperature at each detected part is detected. The degree of sulfur deposition for each part of the exhaust purification device 16 is individually estimated based on the temperature. Therefore, it is possible to estimate the degree of sulfur deposition for each part of the exhaust purification device 16 and thus to estimate the sulfur deposition distribution of the exhaust purification device 16.

  (8) In this embodiment, according to the estimated degree of sulfur deposition, embodiments of each exhaust purification control such as NOx reduction control, PM regeneration control, and sulfur release control are changed. Therefore, each exhaust purification control can be carried out accurately according to the degree of sulfur accumulation of the NOx storage reduction catalyst, avoiding deterioration of emissions, suppressing deterioration of controllability of the catalyst bed temperature, function of the catalyst It becomes possible to prevent failure.

  (9) In the present embodiment, when it is estimated that the NOx occlusion ability of the NOx occlusion reduction catalyst is lowered due to sulfur deposition, the execution interval of the NOx reduction control is shortened. Therefore, even when the NOx occlusion ability of the NOx occlusion reduction catalyst is reduced due to sulfur deposition, the NOx reduction control can be performed before it becomes impossible to occlude more NOx.

  (10) In the present embodiment, when it is estimated that the amount of sulfur accumulation is large, the execution time of the NOx reduction control is lengthened, or the amount of fuel added to the exhaust during NOx reduction control or the number of additions is increased. Like to do. Therefore, it is possible to accurately perform the reduction and purification of NOx stored in the catalyst regardless of the decrease in the low-temperature activity of the NOx storage and reduction catalyst due to sulfur deposition.

  (11) In this embodiment, when it is estimated that the amount of accumulated sulfur is large, the target temperature of the catalyst bed temperature in the PM regeneration control is made higher. As a result, sulfur release can be promoted during the PM regeneration control, and the sulfur component deposited on the NOx storage reduction catalyst can be suitably released even during the PM regeneration control.

  (12) In this embodiment, when it is estimated that the amount of accumulated sulfur is large, the execution timing of the sulfur release control is advanced or the execution time of the control is lengthened. Therefore, excessive sulfur accumulation of the NOx storage reduction catalyst can be suitably suppressed.

In addition, the said embodiment can also be changed and implemented as follows.
-In above-mentioned embodiment, each bed temperature sensor S1-Sn detects the temperature increase degree of the catalyst bed temperature of each site | part of the exhaust gas purification apparatus 16, respectively, and the temperature increase degree of the catalyst bed temperature of each detected site | part is detected. On the basis of the above, the degree of sulfur deposition in each part of the exhaust purification device 16 is individually estimated. However, if it is not necessary to estimate the sulfur deposition distribution of the exhaust purification device 16, only one bed temperature sensor is installed in the exhaust purification device 16, and only the sulfur deposition amount of the entire exhaust purification device 16 is estimated. Anyway.

  In the above embodiment, the poisoning determination value is variably set based on the temperature and flow rate of the exhaust gas introduced into the exhaust gas purification device 16, but the exhaust gas temperature or flow rate is the bed temperature of the catalyst bed temperature. When the influence on the tendency is small, the poisoning determination value may be set based on only one of the exhaust gas temperature and the flow rate, excluding the one with the smaller influence. When the influence of both is small, the poisoning determination value may be set to a fixed value without being variably set.

  In the above embodiment, the amount of sulfur deposition, the sulfur deposition distribution, the current NOx storage capacity, and the occurrence of sulfur deposition exceeding an acceptable level are estimated from the combined increase in the catalyst bed temperature accompanying the introduction of the reducing agent. To do each. However, if it is not necessary, any one or more of the above estimations may be omitted and only the necessary estimation may be performed. For example, in the above embodiment, the sulfur accumulation amount is estimated, and the current NOx storage capacity is estimated based on the estimation result. However, without introducing the sulfur accumulation amount, the introduction of the reducing agent is not performed. The current NOx storage capacity may be directly estimated from the accompanying increase in the catalyst bed temperature.

  In the above embodiment, the degree of sulfur deposition of the exhaust purification device 16 is estimated during the PM regeneration control. However, if the catalyst bed temperature is raised by the introduction of the reducing agent, it is possible to estimate the degree of sulfur deposition in the same manner. For example, even during the execution of NOx reduction control, the target temperature of the catalyst bed temperature being controlled is lower than that during PM regeneration control, but the catalyst bed temperature can be raised by introducing a reducing agent. It is possible to estimate the degree of sulfur deposition based on the rise in bed temperature.

  In the above embodiment, the degree of sulfur deposition is estimated when the temperature of the exhaust gas introduced into the exhaust purification device 16 is in the light-off temperature range of the NOx storage reduction catalyst. However, although the difference in the temperature rise tendency of the catalyst bed temperature according to the degree of sulfur deposition is not as significant as in the light-off temperature range, it is possible to estimate the degree of sulfur deposition in other temperature ranges. Therefore, when the temperature of the exhaust gas introduced into the exhaust gas purification device 16 is less frequently in the light-off temperature range, the degree of sulfur deposition is estimated in a temperature range other than the light-off temperature range. Also good.

  In the above embodiment, the catalyst bed temperature heating allowance ΔT1 to ΔTn as the deviation between the detected value (Tex) of the exhaust gas introduced into the exhaust purification device 16 and the detected value (T1 to Tn) of the catalyst bed temperature. And the sulfur deposition degree of the NOx storage reduction catalyst is estimated based on the calculated temperature increase allowances ΔT1 to ΔTn. However, if the temperature of the exhaust gas introduced into the exhaust gas purification device 16 at the time of estimation is made substantially constant, the degree of sulfur deposition can be directly estimated from the detected catalyst bed temperature.

  In the above embodiment, the case where the present invention is applied to an exhaust gas purification device installed in a diesel engine has been described. However, in an oxidizing atmosphere, exhaust nitrogen oxides are stored, and in a reducing atmosphere, the stored nitrogen oxides are stored. The present invention can be similarly applied to an exhaust purification device installed in an internal combustion engine other than a diesel engine as long as the exhaust purification device includes a NOx storage reduction catalyst to be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic which shows typically the structure of the diesel engine applied about one Embodiment of the sulfur deposition degree estimation apparatus of the exhaust gas purification apparatus which concerns on this invention. The graph which shows the relationship between the temperature increase of the catalyst bed temperature of a NOx occlusion reduction catalyst at the time of a reducing agent introduction | transduction, and sulfur deposition amount. The graph which shows the relationship between the temperature of the exhaust_gas | exhaustion introduce | transduced into an exhaust gas purification apparatus, and the catalyst bed temperature of a NOx storage reduction catalyst. The graph which shows the distribution of the temperature increase of the catalyst bed temperature of each part of the exhaust gas purification apparatus when the degree of sulfur deposition is small and when it is large. The graph which shows the relationship between the exhaust gas flow volume and exhaust temperature in the calculation map of the poisoning determination value employ | adopted as the said embodiment, and a sulfur poisoning determination value. The flowchart which shows the process sequence of the sulfur deposition degree estimation routine employ | adopted as the said embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Intake passage, 11 ... Combustion chamber, 12 ... Exhaust passage, 13 ... Injector, 14 ... Fuel addition valve, 15 ... Exhaust temperature sensor, 16 ... Exhaust gas purification device, 17 ... Electronic control unit, 18 ... NE sensor, 19 ... Accelerator sensor, S1-Sn ... floor temperature sensor.

Claims (9)

An apparatus for estimating the degree of sulfur deposition of the NOx occlusion reduction catalyst in an exhaust gas purification apparatus comprising a NOx occlusion reduction catalyst,
Detecting means for detecting the temperature increase of the catalyst bed temperature of the NOx storage reduction catalyst accompanying the introduction of the reducing agent;
Estimating means for estimating a sulfur estimation degree of the NOx storage reduction catalyst based on the temperature increase detected by the detecting means;
An apparatus for estimating the degree of sulfur accumulation in an exhaust emission control device. 2. The exhaust gas purification device according to claim 1, wherein the detection unit detects the temperature increase based on a deviation between a detected value of the temperature of exhaust gas introduced into the exhaust gas purification device and a detected value of the catalyst bed temperature. Sulfur deposition degree estimation device. The estimation of the degree of sulfur deposition by the estimation unit is based on the detection result of the temperature increase by the detection unit when the temperature of the exhaust gas introduced into the exhaust purification device is in the light-off temperature range of the NOx storage reduction catalyst. The sulfur accumulation degree estimation device for an exhaust emission control device according to claim 1, wherein the sulfur accumulation degree estimation device is performed. The estimation of the degree of sulfur deposition by the estimation means is performed based on a detection result of the temperature increase degree of the detection means during execution of control for raising the catalyst bed temperature. The sulfur deposition degree estimation apparatus of the exhaust gas purification apparatus according to the item. The estimation of the degree of sulfur deposition by the estimation unit is performed based on the detection result of the temperature increase level of the detection unit during the execution of PM regeneration control for removing the particulate matter collected in the exhaust purification device. The sulfur accumulation degree estimation device for an exhaust emission control device according to any one of claims 1 to 3. The exhaust emission control device according to any one of claims 1 to 5, wherein the estimation means estimates that the degree of sulfur accumulation of the exhaust emission control device is large when the temperature rise is equal to or less than a prescribed poisoning determination value. Equipment for estimating the degree of sulfur deposition. The sulfur deposition degree estimation device for an exhaust purification device according to claim 6, wherein the poisoning determination value is set to a smaller value as the flow rate of exhaust gas introduced into the exhaust purification device is larger. The sulfur deposition degree estimation device for an exhaust purification device according to claim 6 or 7, wherein the poisoning determination value is set to a larger value as the temperature of exhaust gas introduced into the exhaust purification device is higher. The detection means detects the temperature rise of the catalyst bed temperature at each part of the exhaust purification device,
The estimation means individually estimates the degree of sulfur deposition in each part of the exhaust gas purification apparatus based on the detected temperature rise of the catalyst bed temperature in each part. The sulfur deposition degree estimation apparatus according to item 1.

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