JP6512535B2 - Exhaust purification system for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust purification system of an internal combustion engine.

  Urea SCR (Selective Catalytic Reduction) system is known as one of the systems for purifying the exhaust gas emitted from an internal combustion engine. In the urea SCR system, a selective reduction catalyst (SCR catalyst) that stores ammonia generated from urea in the exhaust pipe of an internal combustion engine and selectively reduces NOx in the exhaust by the ammonia, and exhaust of the selective reduction catalyst An addition valve for adding urea is provided on the upstream side (see, for example, Patent Document 1).

  Also, the exhaust pipe may be provided with a filter for collecting particulate matter (particulate matter, PM) in the exhaust gas. When particulate matter of a certain amount or more is deposited on the filter, the filter is heated to carry out a regeneration treatment for burning the deposited particulate matter. As the regeneration process, for example, after injection or post injection for raising the temperature of the exhaust gas is performed following the main injection for obtaining the torque of the internal combustion engine. In addition, as the deposition amount of particulate matter on the filter increases, the pressure difference (pressure loss) across the filter gradually increases. Therefore, whether or not the regeneration process is to be performed is determined based on the value acquired by the differential pressure sensor, for example, by providing a differential pressure sensor that acquires the differential pressure before and after the filter.

JP, 2010-270624, A

  By the way, in the urea SCR system, depending on conditions such as the addition amount of urea added from the addition valve and the temperature of the selective reduction catalyst, urea or an intermediate product (cyanuric acid) may be formed on the inner wall of the exhaust pipe or the front end of the selective reduction catalyst. Deposits derived from urea, which are precipitated solids of melamine, melamine, etc.).

  On the other hand, there is a catalyst-carrying filter in which the selective reduction catalyst is supported on the filter. When this catalyst-carrying filter is employed, deposits from the urea water are deposited on the exhaust pipe, the mixer, and the front end of the catalyst because urea water is added from the upstream of the catalyst-carrying filter. When the urea-derived deposit is deposited on the front end of the catalyst-supporting filter, the urea-derived deposit increases the pressure difference across the catalyst-supporting filter. Due to the increase in differential pressure due to the deposition of the urea-derived deposit, the temperature rise for burning the particulate matter is carried out even when the deposition amount of the particulate matter on the catalyst-carrying filter is small, and the unnecessary temperature rise is repeated Problem of getting worse.

  The present invention has been made in view of the above problems, and is an internal combustion that can suppress frequent implementation of temperature rise for burning particulate matter by deposition of a urea-derived deposit on the front end of a catalyst-carrying filter. An object of the present invention is to provide an exhaust gas purification device for an engine.

In order to solve the above-mentioned subject, the exhaust gas purification device of the internal combustion engine of the present invention,
A catalyst provided in an exhaust pipe (3) of an internal combustion engine (2) and carrying a selective reduction catalyst that selectively reduces NOx in exhaust gas on a filter that collects particulate matter in the exhaust gas of the internal combustion engine A supported filter (7),
An addition valve (5) for adding urea for reducing NOx in the catalyst supporting filter on the exhaust upstream side of the catalyst supporting filter;
A differential pressure sensor (8) for acquiring a differential pressure before and after the catalyst-carrying filter;
A determination unit (S31, 1) that determines regeneration of the catalyst-carrying filter based on the value acquired by the differential pressure sensor;
An index detection unit (S1, 1) for detecting an influence index indicating the magnitude of the influence on the differential pressure by the deposition of the urea-derived deposit on the front end of the catalyst-carrying filter;
When the determination unit determines that the catalyst supporting filter is to be regenerated, the catalyst supporting filter is heated so that the particulate matter deposited on the catalyst supporting filter is burned when the influence index is less than a predetermined value. A first reproduction control unit (S32, S34, S4, 1) for performing a first reproduction process;
When the determination unit determines that the catalyst supporting filter is to be regenerated, if the influence index is equal to or more than the predetermined value, the urea regeneration process removes the urea-derived deposit accumulated on the catalyst supporting filter instead of the first regeneration process. A second reproduction control unit (S32, S33, S5, 1) for performing a second reproduction process;
Equipped with

  According to the present invention, the influence index indicating the magnitude of the influence on the differential pressure due to the deposition of the urea-derived deposit on the front end of the catalyst-carrying filter is detected. Then, when it is determined that the regeneration of the catalyst supporting filter is performed based on the differential pressure before and after the catalyst supporting filter, the influence index is confirmed before the regeneration is performed. When the influence index is less than the predetermined value, the temperature raising (first regeneration processing) for burning the accumulated particulate matter is performed. On the other hand, when the influence index is equal to or more than the predetermined value, the execution of the first regeneration treatment is stopped and the second regeneration treatment for removing the urea-derived deposit is performed, so that the particulate matter is burned by the deposition of the urea-derived deposit It can be suppressed that the temperature rise (first regeneration process) is frequently performed. In addition, since the urea-derived deposit deposited on the catalyst-loaded filter can be removed by the second regeneration treatment, it is possible to suppress an increase in differential pressure before and after the catalyst-loaded filter due to the deposition of the urea-derived deposit.

It is a block diagram of the exhaust gas purification device of an internal combustion engine. It is the figure which showed the state which the urea depot deposited on the SCRF front end. FIG. 6 is a diagram showing a breakdown of a differential pressure due to PM deposition and a differential pressure due to urea deposition when the differential pressure reaches a threshold. It is the figure which showed the state which the urea depot deposited in the narrow range of the SCRF front end. It is a block diagram of each process which comprises the regeneration process of SCRF. It is the block diagram which showed the process of calculating an influence index from SCRF temperature and the amount of urea addition. It is the figure which showed the relationship between SCRF temperature and an influence index. It is the figure which showed the relationship of the amount of urea addition, and an influence index in case the SCRF temperature is low. It is the figure which showed the relationship of the amount of urea addition, and an influence index when the SCRF temperature is high. It is the figure which showed transition of the SCRF temperature to the upper part and illustrated transition of the influence index in the form made to respond to the transition of the temperature in the lower part. It is the block diagram which showed the process of calculating the influence index in which the NOx purification rate was considered in addition to the SCRF temperature and the amount of urea addition. It is a figure showing the relation between the NOx purification rate and the correction term of an influence index. It is the figure which showed the relationship between SCRF temperature and NOx purification capacity in SCRF. It is the block diagram which showed the process of calculating the influence index which considered engine stop time in addition to the SCRF temperature and the amount of urea addition. It is a figure showing the relation between engine stop time and the correction term of influence index. It is a flow chart of temperature rise execution decision whether it carries out temperature rise for PM removal or temperature rise for urea depot removal. It is a time chart of each parameter relevant to regeneration processing of SCRF.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an exhaust gas purification apparatus for an internal combustion engine to which the present invention is applied. The exhaust gas purification apparatus shown in FIG. 1 is mounted on a vehicle to remove harmful substances in the exhaust gas discharged from an engine 2 (internal combustion engine) of the vehicle. The exhaust gas purification apparatus includes a urea SCR system that purifies NOx in the exhaust gas. Furthermore, the exhaust gas purification device is also a device for removing PM (Soot, soot) in the exhaust gas.

  The engine 2 is, for example, a diesel engine that includes an injector that directly injects fuel into a cylinder, and the fuel injected from the injector self-ignites in the cylinder to generate a torque for driving a vehicle.

  In the exhaust pipe 3 of the engine 2, an oxidation catalyst 4 (DOC: Diesel Oxidation Catalyst) for oxidizing and purifying HC or CO, which is one of the harmful components in the exhaust gas, is disposed. The oxidation catalyst 4 supports, for example, a catalyst component (for example, Pt (platinum), Pd (palladium), etc.) that accelerates the oxidation reaction of HC and CO on a wall-through type ceramic honeycomb or metal mesh. It has a structure. Further, the oxidation catalyst 4 raises the temperature of the exhaust by the oxidation reaction with the unburned fuel (unburned HC) supplied to the oxidation catalyst 4 in order to burn and remove the PM and the urea-derived deposit accumulated in the below-mentioned SCRF 7 It also plays a role.

  In the exhaust pipe 3 downstream of the oxidation catalyst 4, an addition valve 5 for adding urea water as a reducing agent is disposed in the exhaust pipe 3. The addition valve 5 has the same structure as a fuel injection valve (injector) that injects fuel into a cylinder of a gasoline engine or into an intake port. That is, the addition valve 5 is an electromagnetic on-off valve provided with a nozzle in which an injection hole is formed, a drive unit including an electromagnetic solenoid and the like, and a urea water passage for circulating urea water and a needle for opening and closing the nozzle. It is configured. Then, when the electromagnetic solenoid is energized, the needle moves in the valve opening direction with the energization, and urea water is injected from the injection hole formed at the tip of the nozzle with the movement of the needle.

  A mixer 6 is disposed in the exhaust pipe 3 downstream of the addition valve 5. The mixer 6 is a device that atomizes the urea water added from the addition valve 5 and disperses it in the exhaust gas. The mixer 6 is configured, for example, as a passage for generating a swirling or meandering flow of exhaust.

  In the exhaust pipe 3 downstream of the mixer 6, a selective catalytic reduction filter (SCRF) 7 as a catalyst-carrying filter is disposed. The SCRF 7 collects PM in exhaust gas, for example, an SCR as a selective reduction catalyst that selectively reduces NOx in exhaust gas to a filter (DPF: Diesel Particulate Filter) configured on a wall-through type ceramic honeycomb. The catalyst has a supported structure. That is, the SCRF 7 has both the function of removing PM and the function of reducing and purifying NOx. Exhaust gas flows downstream while passing through the porous partition walls of the SCRF 7, while PM in the exhaust gas is collected by the SCRF 7.

The SCR catalyst supported on SCRF 7 promotes, for example, the reduction reactions of the following formulas 1, 2 and 3 as a reduction reaction of ammonia (NH 3) generated from urea water and NO x, for example, vanadium, Base metal oxides such as molybdenum and tungsten, zeolites and noble metals. Thus, while the exhaust gas passes through the SCRF 7, NOx is decomposed (purified) into water or nitrogen according to, for example, the following formulas 1, 2, and 3.
4NO + 4NH3 + O2 → 4N2 + 6H2O (Equation 1)
6 NO 2 + 8 NH 3 → 7 N 2 + 3 H 2 O (Equation 2)
NO + NO 2 + 2 NH 3 → 2 N 2 + 3 H 2 O (Equation 3)

  Further, the exhaust gas purification device is provided with a urea water supply device (not shown) that supplies urea water to the addition valve 5. The urea water supply device includes a urea water tank for storing urea water, a pipe connecting the urea water tank and the addition valve 5, and a pump for drawing up urea water from the urea water tank and discharging it to the addition valve 5 side through the pipe And a regulator for adjusting the pressure of the urea water in the pipe to a predetermined pressure.

  Furthermore, various sensors are provided in the exhaust gas purification device. Specifically, a differential pressure sensor 8 is provided which detects a differential pressure before and after the SCRF 7 (a difference between a pressure upstream of the SCRF 7 and a pressure downstream of the SCRF 7). Further, an exhaust temperature sensor 9 for detecting the temperature of exhaust flowing into the SCRF 7 and an upstream NOx sensor 10 for detecting the NOx concentration are provided upstream of the SCRF 7. If the function of estimating the concentration of NOx flowing into the SCRF 7 is in the ECU 1, the upstream NOx sensor 10 may be omitted. The sensor 9 is provided downstream of the mixer 6. When the sensor 10 is mounted, it is provided upstream of the addition valve 5. Further, downstream of the SCRF 7, a downstream NOx sensor 11 is provided which detects the concentration of NOx in the exhaust gas flowing out of the SCRF 7. Furthermore, an airflow meter 12 for detecting the flow rate (for example, mass flow rate) of intake gas flowing through the intake pipe of the engine 2, a rotation speed sensor 13 for detecting the rotation speed of the engine 2, and a vehicle side The accelerator pedal sensor 14 etc. which detect the operation amount (depression amount) of the accelerator pedal for this are provided. The detection values of these sensors 8 to 14 are input to the ECU 1.

  The exhaust gas purification apparatus includes an ECU (Electronic Control Unit) 1 that controls the overall control of the exhaust gas purification apparatus. The ECU 1 has a normal computer structure, and includes a CPU (not shown) that performs various calculations, and a memory 15 such as a ROM and a RAM that store various information. The ECU 1 detects, for example, the operating conditions of the engine 2 based on detection signals from the various sensors described above, calculates the optimal fuel injection amount, injection timing, injection pressure, etc. according to the operating conditions, Control fuel injection. Further, the ECU 1 may have a function of estimating the concentration of NOx flowing into the SCRF 7.

  Further, the ECU 1 calculates the addition amount of urea water necessary for NOx purification in the SCRF 7 and drives the addition valve 5 so that the addition amount of urea water is added. With regard to calculation of the addition amount of urea water, for example, the ammonia supply amount to SCRF 7 determined from the amount of ammonia necessary to purify NOx flowing into SCRF 7 and the addition amount of urea water added so far, ammonia consumption in SCRF 7 The ammonia adsorption amount at SCRF 7 is calculated based on the balance with the amount. Then, the urea water addition amount corresponding to the deviation between the ammonia adsorption amount and the target adsorption amount is calculated as the addition amount at this time. The ammonia consumption amount in the SCRF 7 is based on, for example, the operating conditions of the upstream NOx sensor 10 and the engine 2 (engine speed obtained from the speed sensor 13 and engine load (fuel injection amount) obtained from the accelerator pedal sensor 14). The amount of NOx flowing into the SCRF 7 is calculated, the concentration of NOx flowing out of the SCRF 7 from the downstream NOx sensor 11 is calculated, and the amount of NOx upstream of the SCRF and the amount of NOx downstream of the SCRF are obtained.

  Furthermore, when the differential pressure detected by the differential pressure sensor 8 becomes large, the ECU 1 executes a regeneration process to burn off the PM deposited on the SCRF 7 and regenerate the SCRF 7. Details of this reproduction process will be described later.

  Before describing the details of the regeneration process, the urea-derived deposit will be described. The urea water added from the addition valve 5 is thermally decomposed by the exhaust heat to generate ammonia and cyanuric acid. Here, in the process of generating ammonia and cyanuric acid from urea water, an intermediate product such as melamine and melm is generated. The intermediate product usually decomposes by heat, but may solidify without disappearing under certain conditions. Moreover, only the water content of the urea water may be evaporated to precipitate urea and solidify. Below, the urea origin deposit which is a precipitation solid substance of the intermediate product derived from urea or urea is called urea depot. Urea deposits tend to occur, for example, when the temperature of SCRF 7 is low (specifically, for example, 250 ° C. or less). Also, the urea depot is more likely to occur as the amount of urea water added by the addition valve 5 increases.

  The urea deposit is deposited on the inner wall of the exhaust pipe 3, the mixer 6, the SCRF 7 and the like. As for SCRF7, as shown in FIG. 2, the urea deposit tends to be deposited on the front end (end on the exhaust upstream side) of the SCRF 7. This is because when the evaporation or decomposition of the aqueous urea solution is not completed by the front end of the SCRF 7, the urea water is accumulated at the front end of the SCRF and a solidified urea deposit is generated.

  When the urea deposit is deposited on SCRF7, the deposition blocks the flow of exhaust gas, resulting in an increase in pressure difference (pressure loss) before and after SCRF7. At this time, even if the differential pressure reaches the determination threshold value for carrying out the regeneration process (the temperature rise for PM removal) of the SCRF 7, as shown in FIG. In some cases, the pressure may be large and the differential pressure due to the urea deposition may be small, or conversely, the differential pressure due to the amount of PM may be small and the differential pressure due to the urea deposition may be large. The temperature elevation for burning and removing the PM may be performed when the amount of PM deposited on the SCRF 7 is as large as possible as shown in the breakdown on the left of FIG. Because the temperature required to remove the PM is higher than the temperature required to remove the urea depot, there is more fuel needed to heat the exhaust. Therefore, if the temperature increase is performed even when the amount of PM is small as shown in the right of FIG. 3, the fuel is wastefully used to raise the temperature of the exhaust gas, resulting in the deterioration of the fuel efficiency.

  As shown in FIG. 4, when the urea deposit is deposited in a narrow area at the front end of the SCRF 7, the extent to which the urea deposit inhibits the flow of exhaust gas in the SCRF 7 is smaller than in the case of FIG. The influence on the differential pressure is small. In this case, when the differential pressure reaches the determination threshold, it is considered that the breakdown in the left of FIG. 3 is not significant.

  The regeneration process of SCRF 7 described below suppresses that the temperature rise for PM removal is carried out in the breakdown of the right in FIG. 3 due to the deposition of the urea deposit at the front end of SCRF 7 as shown in FIG. It is configured for the purpose of Hereinafter, the details of the regeneration process of the SCRF 7 executed by the ECU 1 will be described.

  FIG. 5 shows a block diagram of each step of the regeneration process. The regeneration process shown in FIG. 5 starts, for example, simultaneously with the start of the engine 2 and is repeatedly executed in a predetermined cycle. In the regeneration process of FIG. 5, an influence index indicating the magnitude of the influence on the differential pressure due to the deposition of urea on the front end of the SCRF 7 is calculated (S1). The influence index is, in other words, an index showing the degree of contribution to differential pressure by deposition of urea on the front end of SCRF 7, and is an index showing that the larger the value, the larger the degree of contribution.

  Specifically, the influence index is calculated according to the process of FIG. In FIG. 6, the temperature of the SCRF 7 at each time point is acquired (S11). Specifically, since the temperature of the SCRF 7 changes according to the temperature of the exhaust gas, the temperature of the SCRF 7 is estimated based on the temperature of the exhaust gas detected by the exhaust gas temperature sensor 9, for example. More specifically, for example, the inside of the SCRF 7 is virtually divided into a plurality of regions (cells) from the upstream side to the downstream side, and the temperature distribution in the SCRF 7 is obtained by estimating the temperature of each cell. Then, for example, the average value of the obtained temperature distribution is taken as the temperature of the SCRF 7. As for the number of cell divisions, the more the number of divisions, the more accurate the temperature can be obtained, but the amount of calculation increases. In consideration of the accuracy of the temperature and the amount of calculation, the number of cell divisions is appropriately set.

  Hereinafter, a method of estimating the temperature of each cell will be described. The estimation of the temperature of each cell is performed, for example, sequentially from the upstream side. The temperature of the cell may be the temperature of the base material of the cell portion. The process of estimating all cell temperatures at each time point is regarded as one process, and the process performed one time before is referred to as the previous process and the process currently performed is referred to as the present process. Further, one cell to be a target of cell temperature estimation is referred to as the cell, one upstream cell adjacent to the cell is referred to as an upstream cell, and one downstream cell adjacent to the cell is referred to as a downstream cell.

  Specifically, the heat transfer amount Q1 from the exhaust flowing through the cell to the cell is determined. The heat transfer amount Q1 is a heat transfer coefficient indicating the temperature of the exhaust flowing through the cell (hereinafter referred to as the cell gas temperature), the temperature of the cell, the flow rate of the exhaust flowing through the cell, and the heat transfer between the exhaust and the cell. Obtained by The exhaust flow rate is obtained by the detection value of the air flow meter 12. The cell gas temperature may be the value obtained in the previous process or the cell gas temperature in the upstream cell obtained in the current process. The method of determining the cell gas temperature will be described later. Further, the temperature of the cell may be a value obtained in the previous processing. The heat transfer coefficient may be a predetermined fixed value or a value corresponding to the exhaust gas flow rate. The relationship between the cell gas temperature, the temperature of the cell and the exhaust gas flow rate, and the heat transfer amount Q1 is determined in advance, and stored in the memory 15 as a map, for example, and the heat transfer amount Q1 is calculated using the map.

  Further, the heat transfer amount Q2 from the cell adjacent to the upstream and downstream of the cell to the cell is obtained. The heat transfer amount Q2 is obtained by the heat transfer coefficient indicating the temperature of the upstream cell, the temperature of the downstream cell, the temperature of the cell, and the heat transfer in the SCRF 7. As the temperature of the upstream cell, a value obtained by the process of this time may be used, assuming that the cell temperature is determined sequentially from the upstream cell. As the temperature of the downstream cell and the temperature of the cell, values obtained by the previous processing may be used. The heat transfer coefficient may be a predetermined fixed value. The relationship between the temperature of the upstream cell, the temperature of the downstream cell and the temperature of the cell, and the heat transfer amount Q2 is determined in advance, and stored, for example, in the memory 15 as a map. Calculate

  A total value of the obtained two heat transfer amounts Q1 and Q2 is calculated. This determines the total heat transferred to the cell. Next, the temperature rise value of the cell is calculated from the total value of the heat transfer amount to the cell. In this calculation, the total value of the heat transfer amount may be divided by the heat capacity of a predetermined cell. Furthermore, the obtained temperature rise value is added to the previously calculated temperature of the cell. This determines the current temperature of the cell.

  Next, how to determine the cell gas temperature required to determine the temperature of each cell will be described. The basic idea of the calculation of the cell gas temperature of the cell can be obtained by dividing the temperature decrease by the heat transfer amount Q1 from the gas flowing through the cell to the cell (dividing the heat transfer amount Q by the heat capacity of the gas ) Is subtracted from the cell gas temperature of the upstream cell. That is, the cell gas temperature of the cell is obtained by the heat transfer amount Q1 and the cell gas temperature of the upstream cell. The heat transfer amount Q1 and the cell gas temperature of the upstream cell are already obtained in this process. If there is no cell upstream from the cell, that is, if the cell is the most upstream cell, the detection value of the exhaust temperature sensor 9 may be used as the cell gas temperature of the upstream cell. The relationship between the heat transfer amount Q1 and the cell gas temperature of the upstream cell, and the cell gas temperature of the cell are obtained in advance and stored, for example, in the memory 15 as a map, and the cell gas temperature of the cell is calculated using the map. .

  After all, the temperature of the SCRF 7 becomes a value corresponding to the temperature and flow rate of the exhaust flowing into the SCRF 7. Therefore, in S11, it is meant that the estimated model of the temperature of the SCRF 7 based on the exhaust temperature and flow rate is stored in the memory 15, and the temperature of the SCRF 7 is estimated based on the estimated model.

  Note that although the calculation of the temperature of the SCRF 7 is described above as the PM accumulated in the SCRF 7 does not burn, when the temperature of the SCRF 7 is high and the PM burns, the temperature of the SCRF 7 also changes depending on the amount of heat generated by the combustion. . Therefore, the temperature of the SCRF 7 may be estimated in consideration of the amount of heat generation due to PM combustion. Further, in the process of S11 in FIG. 6, a temperature sensor may be provided inside the SCRF 7 and the detection value of the temperature sensor may be acquired as the temperature of the SCRF 7.

  Returning to the explanation of FIG. 6, the urea addition amount per unit time added from the addition valve 5 at each time point is acquired (S12). The addition amount of urea may be the addition amount command value to the addition valve 5 that the ECU 1 itself has obtained at each time point.

  Based on the temperature of SCRF 7 and the amount of urea added (conditions related to urea depot deposition) obtained at S11 and S12, the influence index to the differential pressure by the urea depot at each time is calculated (S13). The impact index calculated here is an index corresponding to the amount of change per unit time of the amount of urea deposit deposited on the SCRF 7 at each time point, that is, the deposition rate of the urea deposit. In other words, the influence index of S13 is an index indicating the ease of deposition of the urea depot on the SCRF 7 at each time point.

  Here, FIGS. 7 to 9 illustrate the relationship between the SCRF temperature or the amount of urea added and the influence index. Urea deposits tend to occur at low temperatures and decompose at high temperatures. Therefore, as shown in FIG. 7, the influence index becomes a large value in the region where the SCRF temperature is low, and the influence index becomes smaller as the SCRF temperature becomes higher. In addition, when the SCRF temperature rises to a certain degree, the deposited urea depot decomposes and disappears. Therefore, in FIG. 7, in the region where the SCRF temperature is equal to or higher than the predetermined temperature, the influence index is a negative value indicating that the urea depot disappears. The influence index indicates that the larger the value on the positive side, the larger the deposition amount of urea depot, and the larger the value on the negative side, the larger the decomposition amount of the deposited urea depot and the more it disappears.

  Further, as shown in FIGS. 8 and 9, the influence index becomes larger as the amount of addition of urea is larger. This is because as the amount of urea added increases, the amount of intermediate products that cause the urea depot increases. In addition, when the amount of urea added is large, the temperature of SCRF 7 is easily lowered by the aqueous urea solution supplied to SCRF 7 as compared with the case where the amount is small, and the temperature drop tends to generate urea depot.

  Comparing FIG. 8 with FIG. 9, when the SCRF temperature in FIG. 8 is low, the degree of increase in the influence index with respect to the increase in the urea addition amount is large, while when the SCRF temperature in FIG. In other words, even if the amount of urea water addition is the same, the influence index when the SCRF temperature is low in FIG. 8 becomes a larger value than the influence index when the SCRF temperature is high in FIG. This is because, as described with reference to FIG. 7, when the SCRF temperature is low, urea deposition is likely to occur. Also in FIG. 8 and FIG. 9, the influence index can take a negative value. For example, when the amount of urea added is small, the decomposition of the urea deposit already deposited under the influence of the SCRF temperature is superior to the new deposit of the urea deposit. In this case, the impact index is negative.

  In the process of S13, the relationship between the SCRF temperature and the urea addition amount, and the influence index is obtained in advance, and stored in the memory 15 as, for example, the map 101 (see FIG. 6). Then, an influence index corresponding to the SCRF temperature and the urea addition amount is calculated for each time point from the map 101 and the SCRF temperature and the urea addition amount obtained in S11 and S12. The map 101 corresponds to an integrated one of the relationships shown in FIGS.

  After carrying out the step of S13, next, the influence index at each time point obtained in S13 is integrated (S14). That is, the influence index obtained at S13 at the present time point is added to the integrated value of the influence index obtained at S14 up to the previous time point to be an integrated value at the current time point. This integrated value corresponds to the integrated amount of urea depot deposited at the front end of the SCRF 7. The integrated value obtained by S14 is taken as the output value in the process of S1 of FIG. The integrated value changes between the lower limit and the upper limit, for example, with the lower limit being zero and the upper limit being a predetermined value (for example, 100).

  Here, FIG. 10 is a diagram illustrating transition of the influence index obtained in the step S1 (step of FIG. 6) with respect to time, and in detail, transition of the SCRF temperature is illustrated in the upper part, and transition of the temperature The lower half shows the transition of the impact indicator in a form that corresponds to the In addition, the code | symbol "m" of FIG. 10 has shown the influence parameter | index calculated by S13 of FIG. In the example of FIG. 10, when the SCRF temperature is low, the influence index (integrated value) gradually increases with the passage of time, and the increase amount per unit time (the influence index m at each time point) is the SCRF temperature It is larger than when it is medium or high. Further, when the SCRF temperature is medium, the influence index (integrated value) gradually increases with the passage of time, but the increase amount per unit time is smaller than when the SCRF temperature is low. Further, when the SCRF temperature is high, the influence index (integrated value) gradually decreases with the passage of time. Thus, the integrated value of the influence index does not continue to increase monotonically with the passage of time, but depending on the conditions of the SCRF temperature and the amount of added urea, the rate of increase may change or may decrease.

  In addition, the start point (zero point) of integration of the influence index of FIG. 10, that is, when calculation of the influence index of S13 of FIG. 6 and start of integration of S14 are carried out, temperature rise for PM removal by S4 of FIG. Or when the temperature rise for removing the urea deposit in S5 is performed. That is, in the process of S1, the integral value of the influence index to the present time after temperature rising of S4 or S5 was implemented last time is calculated. This is because by performing the temperature raising, the urea deposit deposited on the SCRF 7 is removed and the influence index is reset to zero.

  Thus, in FIG. 6, the influence index is obtained from the SCRF temperature and the urea addition amount at each time point, and in other words, the influence index based on the history of the SCRF temperature and the history of the urea addition amount Seeking.

  By the way, in addition to the SCRF temperature and the amount of urea addition, the urea depot is influenced by the NOx purification rate in SCRF 7 and the recent engine stop time. Therefore, in addition to the SCRF temperature and the urea addition amount, the influence index may be determined in consideration of the NOx purification rate and the engine stop time as described below.

  First, calculation of the influence index in consideration of the NOx purification rate will be described. When the urea deposit is deposited at the front end of the SCRF 7 as shown in FIG. 2, the deposition narrows the flow range of the exhaust gas in the SCRF 7 and as a result, the NOx purification rate lowers than expected. Conversely, when the NOx purification rate is lower than expected, it can be considered that the effect of urea deposit deposition is large. Based on this concept, the influence index obtained from the SCRF temperature and the urea addition amount is corrected according to the NOx purification rate.

  FIG. 11 is a block diagram in which a process related to the correction by the NOx purification rate is added to each process of FIG. In FIG. 11, the NOx purification rate at each time point of SCRF 7 is acquired (S15). The NOx purification rate is obtained by acquiring the NOx amount B1 flowing into the SCRF 7 and the NOx amount B2 flowing out from the SCRF 7 and dividing the difference between the NOx amounts B1 and B2 by the inflowing NOx amount B1. That is, the NOx purification rate = (B1-B2) / B1 is calculated. Here, the inflow NOx amount B1 may be obtained from, for example, a detection value of the upstream NOx sensor 10, or may be estimated from engine operating conditions (engine speed, engine load, etc.). Further, the outflowing NOx amount B2 is obtained from, for example, the detection value of the downstream NOx sensor 11. When the inflow NOx amount B1 is estimated from the engine operating condition, the engine rotational speed as the engine operating condition is obtained from the rotational speed sensor 13. The engine load may be a command value of the fuel injection amount to the injector set by the ECU 1 itself based on the detection value of the accelerator pedal sensor 14 (operation amount of the accelerator pedal), the engine speed, and the like. The relationship between the engine operating condition and the inflow NOx amount B1 can be obtained in advance and stored, for example, in the memory 15 as a map, and the inflow NOx amount B1 can be obtained based on this map.

  Next, a correction term (correction coefficient) for correcting the influence index obtained in the steps of S11 to S14 is calculated based on the NOx purification rate (S16). The correction term is a coefficient for correcting the influence index to the increase side by multiplying the influence index, and is set to a value of 1 or more. When the correction term = 1, it means that the correction of the influence index is not performed.

  Here, FIG. 12 shows the relationship between the NOx purification rate and the correction term. In FIG. 12, line 103 shows the relationship when the SCRF temperature is high, and line 104 shows the relationship when the SCRF temperature is low. Further, FIG. 13 shows the relationship between the SCRF temperature and the NOx purification capacity (NOx purification rate) in SCRF7. As shown in FIG. 13, in the region where the SCRF temperature is low (region below the temperature T1), the NOx purification capacity is low because the catalyst activity in the SCRF 7 is low. In addition, when the SCRF temperature is increased to a certain extent, the activity of the catalyst is increased, so the NOx purification capacity is increased. However, if the SCRF temperature becomes too high (in the range of temperature T2 or more), the NOx purification capacity decreases.

  When the SCRF temperature is high (the temperature is between T1 and T2 in the example of FIG. 13), although the NOx purification capacity is normally high, the actual NOx purification rate is low. It can be considered that the NOx purification rate is decreasing due to the influence of deposition. In addition, it can be considered that the lower the NOx purification rate, the higher the degree of influence due to the accumulation of urea depot. Based on this idea, in the line 103 of FIG. 12, the correction term is larger as the NOx purification rate is lower. On the other hand, when the NOx purification rate is high when the SCRF temperature is high, the NOx purification capacity is originally high (see FIG. 13), and the urea depot is necessary to correct the influence index obtained from the SCRF temperature and the urea water addition amount. Assuming that deposition is not performed, the correction term is 1 in the region where the NOx purification rate is a certain value or more in the line 103.

  In addition, when the SCRF temperature is low (temperature T1 or lower in FIG. 13), the NOx purification ability is originally low, so it can not be judged that the influence of urea deposit deposition is large even if the actual NOx purification rate is low. . Therefore, in the line 104 of FIG. 12, the correction term is set smaller than that of the line 103.

  In the process of S16, the relationship of FIG. 12, that is, the relationship between the SCRF temperature and the NOx purification rate, and the correction term is obtained in advance and stored in the memory 15 as the map 102 (see FIG. 11). Then, the correction term is calculated based on the map 102 and the SCRF temperature and the NOx purification rate acquired in the steps of S11 and S15. Although FIG. 12 exemplifies two of the relationship 103 when the SCRF temperature is high and the relationship 104 when the SCRF temperature is low, the map 102 shows the NOx purification rate and the correction term for each region of more than two SCRF temperatures. Is a map in which the relationship of Since the necessity of correcting the influence index is particularly high when the NOx purification rate is low when the SCRF temperature is high, the map 102 is configured only with the line 103 in FIG. 12 and the SCRF temperature acquired in S11 is a predetermined value or more In this case, the calculation of the correction term in S16 and the correction in S17 described later may be performed, and if the SCRF temperature is less than the predetermined value, the processes in S16 and S17 may be omitted.

  After the correction term is calculated in the process of S16, next, the influence index is corrected by multiplying the influence index obtained in the process of S14 (S17). By this, in addition to the SCRF temperature and the urea addition amount, it is possible to obtain an influence index in which the NOx purification rate is also taken into consideration. For example, when the SCRF temperature is high and the NOx purification rate is low, the influence index is corrected to increase. The influence index after correction is taken as an output value in the step S1 of FIG.

  Next, calculation of the influence index in consideration of the recent engine stop time will be described. When the engine 2 stops, the SCRF temperature decreases, but as the engine stop time is longer, that is, as the state where the SCRF temperature decreases continues longer, urea deposition tends to occur. Therefore, the influence index obtained from the SCRF temperature and the urea addition amount is corrected according to the recent engine stop time.

  Specifically, as shown in FIG. 14, the latest engine stop time is acquired (S18). The ECU 1 has a clock, and calculates the engine stop time, which is the time from when the engine 2 is stopped to when the engine 2 is next started, every time the engine 2 stops, and stores it in the memory 15 deep. In the process of S18, the engine stop time stored in the memory 15 is read.

  Next, a correction term (correction coefficient) for correcting the influence index obtained in the process of S11 to S14 is calculated based on the engine stop time (S19). Similarly to the correction term calculated in S16, this correction term is also a coefficient for correcting the influence index to the increase side by multiplying the influence index, and is set to one or more values.

  Here, FIG. 15 shows the relationship between the engine stop time and the correction term. As shown in FIG. 15, the correction term has a value close to 1 or 1 in a region where the engine stop time is short, but the correction term increases rapidly as the engine stop time becomes longer. This is because when the engine stop time is short, such as when the engine is stopped by an idle stop function that causes the engine to stop automatically while waiting for a signal, urea deposition hardly occurs while the engine is stopped. On the other hand, when the engine stop time is long, for example, when the vehicle is stopped overnight, the urea supplied from the addition valve 5 and remaining in the SCRF 7 before the engine stop does not solidify at the time of engine operation Even if it is a urea addition amount, it may be solidified by the state where the SCRF temperature is low continuing for a long time. At this time, the differential pressure across the SCRF 7 at the end of the engine stop (when starting the engine) is a value obtained by increasing the differential pressure before and after the engine stop by the amount corresponding to the amount of urea deposit accumulation generated during the engine stop. . This increase corresponds to the correction term in FIG.

  In the process of S19, the relationship of FIG. 15 is obtained in advance and stored in the memory 15 as the map 105 (see FIG. 14). Then, the correction term is calculated based on the map 105 and the engine stop time acquired in S18.

  Next, the influence index is corrected by multiplying the effect index obtained in the process of S14 by the correction term obtained in the process of S19 (S20). Thereby, in addition to the SCRF temperature and the amount of added urea, it is possible to obtain an impact indicator that also takes into account the recent engine shutdown time. For example, when the engine stop time is long, the influence index is corrected to increase. The influence index after correction is taken as an output value in the step S1 of FIG.

  In addition, as long as the engine stop time acquired by S15 is the engine stop time with respect to the engine stop which generate | occur | produced at the same time, correction | amendment of S20 based on this engine stop time is performed only once. That is, for example, when the engine is stopped at a certain time t1, the correction of S20 based on the engine stop time for the engine stop is performed only once. Thereafter, when the engine is stopped at another time t2, the correction of S20 based on the engine stop time with respect to the engine stop is also performed only once.

  Furthermore, in the case of engine stop based on the idle stop function, the engine stop time is very short, and there is almost no occurrence of urea deposition during engine stop. Therefore, in the processes of S18 to S20, the influence index may be corrected in consideration of only the engine stop based on the key-off of the vehicle excluding the engine stop by the idle stop function. In this case, in the process of S18, the engine stop time at the latest engine stop of the engine stop based on the key-off of the vehicle is acquired. Even when correction is performed in consideration of the engine stop based on the idle stop function, the engine stop time based on the idle stop function is very short, so the correction term calculated in S19 is 1 and it is substantially The correction of the influence index may not be performed.

  The correction of the influence index based on the NOx purification rate and the correction of the influence index based on the engine stop time may be performed only one or both. When both are performed, for example, both the correction term calculated in S16 of FIG. 11 and the correction term calculated in S19 of FIG. 14 are multiplied by the influence index calculated in S14. Alternatively, a map of the SCRF temperature, the NOx purification rate, the engine stop time, and the correction term, in which the map 102 of FIG. 11 and the map 105 of FIG. 14 are integrated, is obtained and stored in the memory 15. Then, one correction term may be calculated according to the SCRF temperature, the NOx purification rate, and the engine stop time based on this map, and the influence index may be corrected based on this correction term.

  Thus, in addition to the SCRF temperature and the amount of urea addition, a high accuracy influence index can be obtained by considering the NOx purification rate and the engine stop time.

  The above is the content of the process of S1 of FIG. In addition, ECU1 which performs the process of S1 corresponds to an index detection part. Moreover, ECU1 which performs the process of S11 corresponds to a temperature acquisition part. The ECU 1 that executes the process of S12 corresponds to the addition amount acquisition unit. The ECU 1 that executes the process of S13 corresponds to a calculation unit. The ECU 1 that executes the process of S14 corresponds to the integration unit. The ECU 1 that executes the process of S15 corresponds to the purification rate acquisition unit. The ECU 1 that executes the steps of S16 and S17 corresponds to a correction unit. The ECU 1 that executes the process of S18 corresponds to the stop time acquisition unit. The ECU 1 that executes the processes of S19 and S20 corresponds to the correction unit.

  Returning to the explanation of FIG. 5, the front and rear differential pressure of the SCRF 7 is acquired from the differential pressure sensor 8 (S2). After acquiring the influence index and the differential pressure in S1 and S2, next, based on these, the temperature raising execution judgment of whether to carry out the temperature raising for PM removal or to carry out the temperature rise for urea deposit removal is performed (S3). Specifically, the process of the flowchart of FIG. 16 is performed.

  In FIG. 16, first, it is determined whether or not the differential pressure acquired in the process of S2 is equal to or greater than a predetermined threshold (S31). The differential pressure changes depending on the flow rate of the exhaust gas passing through the SCRF 7 even when the same amount of PM is deposited, and specifically, the higher the flow rate, the larger the differential pressure. So, in S31, in order to exclude the influence of the differential pressure by the flow of exhaust, for example, the threshold according to the flow of exhaust is set. The threshold is set to a larger value as the flow rate is higher. The flow rate of the exhaust is obtained by the air flow meter 12, the exhaust temperature sensor 9 upstream of the SCRF, and the differential pressure sensor 8. Then, the threshold value corresponding to the flow rate is compared with the differential pressure. Alternatively, the detected value of the differential pressure sensor 8 may be converted to a differential pressure per unit flow rate based on the flow rate of the exhaust gas, and the differential pressure per unit flow rate may be compared with the threshold. In addition, ECU1 which implements the process of S31 corresponds to a judgment part.

  If the differential pressure is less than the threshold (S31: No), the process waits until the differential pressure becomes equal to or greater than the threshold. If the differential pressure becomes equal to or higher than the threshold (S31: Yes), then it is determined whether the influence index obtained in the step of S1 is equal to or higher than a predetermined threshold. If it is less than the threshold value (S32: No), it is determined that the temperature increase execution for PM removal is performed, assuming that the influence on differential pressure due to urea deposition is small and the breakdown of differential pressure is the breakdown on the left of FIG. S34). Thereafter, the process of FIG. 16 is ended.

  On the other hand, if the influence index is equal to or higher than the threshold (S32: Yes), it is assumed that urea deposition has a large effect on differential pressure, and the breakdown of differential pressure is the breakdown on the right in FIG. It is determined that the warm operation is performed (S33). Thereafter, the process of FIG. 16 is ended.

  Referring back to FIG. 5, either one of the temperature increase for PM removal (S4) or the temperature increase for urea deposit removal (S5) is performed based on the result of the implementation determination of S3. Specifically, when it is determined in S34 of FIG. 16 that the temperature rise for PM removal is performed, the temperature rise for PM removal is performed (S4). For example, after the main injection for obtaining the torque of the engine 2, this temperature rise is carried out after injection or post injection. Here, the after injection is a small amount of fuel injection performed immediately after the main injection for the purpose of raising the temperature of the exhaust gas. The post injection is a small amount of fuel injection performed immediately before the exhaust valve opens in order to feed the unburned fuel into the exhaust pipe 3. Further, a fuel addition valve for adding fuel may be provided upstream of the oxidation catalyst 4 of the exhaust pipe 3 and the unburned fuel may be directly added into the exhaust pipe 3 by this fuel addition valve.

  Unburned fuel is supplied to the oxidation catalyst 4 by after injection, post injection, or fuel addition by the fuel addition valve, and the unburned fuel is oxidized in the oxidation catalyst 4 to raise the temperature of the exhaust gas. The exhaust gas that has been heated flows into the SCRF 7 to raise the temperature of the SCRF. The target temperature of the SCRF temperature at the time of temperature rise for PM removal is set to a temperature higher than the target temperature at the time of temperature rise for deposit removal described later, specifically the temperature at which PM burns out (about 600 ° C. to 700 ° C. Set to). The ECU 1 monitors the SCRF temperature while performing the temperature rise for removing the PM, and adjusts the post injection amount and the like so that the SCRF temperature becomes the target temperature. For example, when the SCRF temperature is lower than the target temperature, the post injection amount is increased, and conversely, when the SCRF temperature is higher than the target temperature, the post injection amount is reduced. The monitoring (acquisition) of the SCRF temperature may be performed in the same manner as the process of S11 in FIG. Further, since the SCRF temperature is correlated with the exhaust temperature, the injection amount may be adjusted so that the detection value of the exhaust temperature sensor 9 becomes the target temperature. As described above, by performing temperature raising while monitoring the SCRF temperature, it is possible to suppress the temperature rise of the SCRF 7 and to suppress that the SCRF 7 is melted by heat due to the temperature rise.

  Further, the temperature rise for PM removal may continue for a fixed time (for example, 20 minutes to 30 minutes) determined in advance, or the detection value of the differential pressure sensor 8 is a predetermined value (more than the threshold of S31 in FIG. 16). You may continue until it becomes less than a small value). The duration of the temperature rise for PM removal is longer than the duration of the temperature rise for urea depot removal.

  Thus, by carrying out the temperature rise for PM removal, it is possible to burn and remove the PM deposited on the SCRF 7. In addition, because the urea depot burns at a lower temperature than PM, the urea depot can also be burned off.

  On the other hand, when it is determined in S33 of FIG. 16 that the temperature raising for removing the urea deposit is performed, the temperature raising for removing the urea depot is performed (S5). This temperature increase is also performed, for example, after injection, post injection, or fuel addition by a fuel addition valve, similarly to the temperature increase for PM removal. However, the target temperature of the SCRF temperature and the duration of the temperature rise are different from the temperature rise for PM removal. Specifically, the target temperature of the SCRF temperature at the time of temperature rise for removing the urea depot is set to a temperature lower than the target temperature at the time of temperature rise for PM removal. Specifically, it is permitted that PM is not burned and removed Meanwhile, the urea depot is set to a temperature (for example, about 350 ° C. to 400 ° C.) at which combustion removal is performed.

  Since it is difficult to predict that the SCRF temperature will be excessive when raising the temperature for removing the urea deposit, for example, the amount of fuel injection such as post injection is fixed in advance for each operating condition to achieve the target temperature. It will be a value. That is, monitoring of the SCRF temperature during the temperature raising process and adjustment of the injection amount based on the SCRF temperature are not performed. Note that, similarly to the temperature increase for PM removal, the SCRF temperature may be monitored to adjust the injection amount so that the SCRF temperature becomes the target temperature.

  Moreover, the continuation time of temperature rising for urea depot removal is set to time (for example, about 5 minutes-about 10 minutes) shorter than the continuation time for PM removal. That is, the temperature rise for removing the urea deposit is ended after continuing for a predetermined fixed time which is shorter than the duration of the temperature rise for PM removal. Note that the duration of the temperature rise for removing the urea deposit may be set to a time according to the influence index, and specifically, may be set to a longer time as the influence index is larger. Even when the duration is set in accordance with the influence index, the duration is set to be shorter than the duration in the temperature rise for PM removal. As described above, by setting the duration according to the influence index, it is possible to suppress the termination of the temperature rise before the combustion removal of the urea deposit deposited on the SCRF 7 completely, and also the combustion removal of the urea deposit It can be suppressed that the temperature rise is continued needlessly despite the completion of. Thus, by carrying out the temperature rise for removing the urea deposit, the urea deposit deposited on the SCRF 7 can be burned and removed.

  The ECU 1 that executes the processes of S32, S34 and S4 corresponds to a first regeneration control unit. The ECU 1 executing the processes of S32, S33 and S5 corresponds to a second regeneration control unit. Further, the temperature rise for PM removal corresponds to the first regeneration process, and the temperature rise for urea deposit removal corresponds to the second regeneration process.

  Here, FIG. 17 is a diagram for explaining the operation of the present embodiment, and shows a time chart of each parameter related to the regeneration processing of the SCRF 7. More specifically, FIG. 17 shows, from the top, the differential pressure before and after the SCRF (FIG. 17A), the PM amount in the SCRF (FIG. 17B), and the differential pressure due to urea deposition to the front end of the SCRF (impact index) FIG. 6C shows a time chart of the SCRF temperature (FIG. 7D) and the injection amount for temperature rise (FIG. 7E). Further, in FIG. 17, the dotted line indicates the present embodiment, and the solid line indicates the conventional example.

  As shown in FIG. 17, when the differential pressure reaches the threshold, conventionally, as shown by the solid lines in FIGS. 17 (d) and 17 (e), the temperature rise for PM removal is necessarily performed. In the example, before performing the temperature rise, the influence index by the urea deposit to the front end of the SCRF is confirmed. If the influence index has reached the predetermined value (see FIG. 17C), the temperature increase for urea deposit removal is performed instead of the temperature increase for PM removal (FIGS. 17D and 17D). see dotted line in e)). Although the amount of PM in the SCRF does not decrease by performing the temperature rise for removing the urea depot (see the dotted line in FIG. 17B), the differential pressure due to the urea depot decreases (see FIG. 17C). As a result, the differential pressure indicated by the dotted line in FIG. 17 (a) decreases by the amount by which the differential pressure in FIG. 17 (c) decreases. However, since the amount of PM is not burned and removed, the dotted line in FIG. 17A is higher than the solid line.

  As described above, according to the present embodiment, the influence index due to the urea deposition on the front end of the SCRF is calculated, and when the differential pressure reaches the threshold value, the influence index is confirmed. In place of the temperature rise for PM removal, the temperature rise for urea deposit removal is carried out. Thereby, it can suppress that temperature rising for PM removal is implemented frequently under the influence of urea deposit deposition. Since the target temperature is lower and the duration time is shorter than the temperature increase for PM removal, the temperature increase for urea deposit removal is a temperature increase with good fuel efficiency. By suppressing the frequent implementation of the temperature rise for PM removal, the deterioration of the fuel efficiency can be suppressed. Further, by carrying out the temperature rise for removing the urea deposit, it is possible to remove the urea deposit deposited on the SCRF, and it is possible to suppress the increase in the differential pressure due to the urea deposit deposition.

  In addition, although it is difficult to accurately detect the accumulation amount of urea deposit on the SCRF, in the present embodiment, since both the detection value of the differential pressure sensor and the influence index are used, the SCRF as shown in FIG. A large amount of deposition of urea deposit on the front end can accurately capture a state where the differential pressure due to the urea deposit is large. Further, as shown in FIG. 4, there is a possibility that the temperature rise for removing the urea deposit may be carried out even when the urea deposit is deposited in a narrow range at the front end of the SCRF and the differential pressure by the urea deposit is small. In this case, although the influence on the vehicle performance and the SCRF catalyst performance is small, the temperature rise for removing the urea depot is frequently performed, and the fuel efficiency is deteriorated. In this embodiment, frequent (wasted) temperature increase for removing the urea deposit can be suppressed.

  The present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the claims. For example, in the above embodiment, as a means for removing the urea deposit deposited on the SCRF, temperature increase processing of the SCRF temperature based on post injection etc. has been exemplified, but for example, the flow rate of the exhaust is increased and the urea deposit is You may fly from SCRF. An increase in the flow rate of exhaust causes, for example, the engine to operate at high speed and high load conditions.

  Moreover, although the example which arrange | positioned the oxidation catalyst upstream of SCRF was shown in the said embodiment, you may carry | support an oxidation catalyst on the base material of SCRF. Also by this, it is possible to raise the SCRF temperature by supplying the unburned fuel to the oxidation catalyst supported on the SCRF.

1 ECU (determination unit, index detection unit, temperature acquisition unit, addition amount acquisition unit, calculation unit, integration unit, purification rate acquisition unit, stop time acquisition unit, correction unit, first regeneration control unit, second regeneration control Department)
2 Engine (internal combustion engine)
3 Exhaust pipe 5 Addition valve 7 SCRF (catalyst-carrying filter)
8 Differential pressure sensor

Claims (7)

A catalyst provided in an exhaust pipe (3) of an internal combustion engine (2) and carrying a selective reduction catalyst that selectively reduces NOx in exhaust gas on a filter that collects particulate matter in the exhaust gas of the internal combustion engine A supported filter (7),
An addition valve (5) for adding urea for reducing NOx in the catalyst supporting filter on the exhaust upstream side of the catalyst supporting filter;
A differential pressure sensor (8) for acquiring a differential pressure before and after the catalyst-carrying filter;
A determination unit (S31, 1) that determines regeneration of the catalyst-carrying filter based on the value acquired by the differential pressure sensor;
An index detection unit (S1, 1) for detecting an influence index indicating the magnitude of the influence on the differential pressure by the deposition of the urea-derived deposit on the front end of the catalyst-carrying filter;
When the determination unit determines that the catalyst supporting filter is to be regenerated, the catalyst supporting filter is heated so that the particulate matter deposited on the catalyst supporting filter is burned when the influence index is less than a predetermined value. A first reproduction control unit (S32, S34, S4, 1) for performing a first reproduction process;
When the determination unit determines that the catalyst supporting filter is to be regenerated, if the influence index is equal to or more than the predetermined value, the urea regeneration process removes the urea-derived deposit accumulated on the catalyst supporting filter instead of the first regeneration process. A second reproduction control unit (S32, S33, S5, 1) for performing a second reproduction process;
An exhaust purification system of an internal combustion engine comprising:   The index detection unit obtains the temperature of the catalyst-supporting filter and the addition amount of urea added from the addition valve, and calculates the influence index based on the temperature and the addition amount. An exhaust gas purification device for an internal combustion engine as described above. The index detection unit
A temperature acquisition unit (S11) for acquiring temperatures at respective points in time of the catalyst-carrying filter;
An addition amount acquisition unit (S12) for acquiring the addition amount of urea at each time point added from the addition valve;
A calculation unit (S13) for calculating the influence index according to the temperature and the addition amount at each time point;
And an integration unit (S14) for integrating the influence index at each time point calculated by the calculation unit, and
The first regeneration control unit executes the first regeneration process based on the time when the influence index of the integration obtained by the integration unit is less than the predetermined value,
The exhaust gas purification apparatus according to claim 2, wherein the second regeneration control unit implements the second regeneration process when the influence index of integration obtained by the integration unit is equal to or more than the predetermined value. The index detection unit
A purification rate acquisition unit (S15) for acquiring the NOx purification rate of the catalyst-carrying filter;
The exhaust gas purification apparatus for an internal combustion engine according to claim 2 or 3, further comprising: a correction unit (S16, S17) that corrects the influence index based on the NOx purification rate acquired by the purification rate acquisition unit. The index detection unit
A stop time acquisition unit (S18) for acquiring the latest stop time of the internal combustion engine;
The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 2 to 4, further comprising: a correction unit (S19, S20) that corrects the influence index based on the stop time acquired by the stop time acquisition unit.   The second regeneration process is a process of raising the temperature of the catalyst supporting filter so that the urea-derived deposit is burned, and a target temperature of the catalyst supporting filter at the time of performing the second regeneration process is the value of the first regeneration process. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein the temperature is lower than a target temperature of the catalyst-carrying filter at the time of implementation. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein the second regeneration control unit ends the second regeneration process after continuing for a predetermined time.

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