JP4868292B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine.

  Today, with increasing awareness of environmental protection, excellent exhaust purification performance is required for internal combustion engines. In particular, in a diesel engine, removal of so-called exhaust particulates (or particulate matter, particulate matter, PM) such as black smoke discharged from the engine is important for further spread. For this purpose, a diesel particulate filter (DPF) is often provided in the middle of the exhaust pipe.

  Although most of the PM in the exhaust gas is removed by the DPF collecting the PM, the PM continues to accumulate in the DPF, but the DPF clogs and burns the accumulated PM. It is necessary to regenerate the DPF. In order to burn the PM accumulated in the DPF, a method such as post injection after main injection in the cylinder is employed.

  Since fuel is consumed to regenerate the DPF, frequent DPF regeneration leads to deterioration of fuel consumption. On the other hand, if the number of times of DPF regeneration is too small, the amount of deposition becomes excessive, and the temperature rises during the regeneration process, which may damage the DPF. Therefore, DPF regeneration must be performed at an appropriate time. Therefore, it is necessary to develop a system that estimates the amount of PM accumulated in the DPF as accurately as possible by some method, and executes regeneration when the estimated value reaches a level that requires DPF regeneration.

  In Patent Document 1 below, a difference in pressure (pressure loss), which is a difference in pressure between the inlet and outlet of the particulate filter, increases due to an increase in ventilation resistance due to an increase in the amount of exhaust particulates deposited on the particulate filter. A technique is disclosed that detects this differential pressure and determines that it is time to regenerate when the detected differential pressure exceeds a predetermined value.

Japanese Patent Laid-Open No. 7-332065

  The inventor has obtained knowledge that the relationship between the PM deposition amount and the DPF pressure loss (differential pressure) is generally (or approximated) to the relationship shown in FIG. That is, as the PM accumulation on the DPF proceeds as the internal combustion engine continues to operate, the point indicating the PM accumulation amount and the DPF pressure loss is on the first characteristic line 21 (characteristic line) from the initial point 20 shown in FIG. Is moved to the upper right in the figure, and when the transition point 22 is reached, the second characteristic line 23 (characteristic line) is moved to the upper right in the figure.

  The first characteristic line 21 corresponds to a stage where PM accumulates in the pores of the filter wall of the DPF, and the second characteristic line 23 corresponds to a stage where PM accumulates on the wall surface of the filter wall. When PM accumulates in the wall of the filter wall, the degree of newly narrowing the exhaust gas flow path is larger than when depositing on the wall surface, thereby increasing the pressure loss value. Therefore, the first characteristic line 21 is the second characteristic line. The inclination is larger than the line 23 as shown in the figure. Note that the slope is the ratio between the increase in DPF pressure loss and the increase in PM deposition.

  If the characteristics shown in FIG. 11 are obtained in advance, the amount of PM deposited in the DPF can be estimated by obtaining the DPF pressure loss value. The DPF may be regenerated whenever the estimated amount of PM deposition reaches a level that requires regeneration.

  If it is determined that the PM accumulation amount is excessive when the point 24 in FIG. 11 is reached and the DPF regeneration is started, the subsequent PM accumulation amount and the DPF pressure loss change as indicated by the dotted line in FIG. That is, the PM accumulation amount and the DPF pressure loss value first decrease along the straight line 25, and after the transition point 26, decrease along the straight line 27 and return to the initial point 20.

  The straight line 25 is a stage where PM deposited on the wall surface of the filter wall is burning, and therefore the straight line 25 has the same inclination as the first characteristic line 21. The straight line 27 is a stage where PM deposited in the pores of the filter wall is combusting. Therefore, the straight line 27 has the same inclination as the second characteristic line 23. As described above, the PM deposition amount and the DPF pressure loss during PM deposition and PM combustion change depending on the parallelogram (or approximate) characteristics shown in FIG.

  However, the characteristics of FIG. 11 do not take into account the presence of ash. Ash is a substance in which a calcium component in engine oil is combined with a sulfur component in engine oil or fuel, and has a characteristic of being stable and difficult to burn. As the ash accumulates on the DPF, soot impedes contact with the catalyst, which is an obstacle to soot combustion.

  Further, if ash accumulates in the DPF together with PM, the presence of ash causes the true value of the pressure loss to be pushed up from the value shown in FIG. Therefore, when FIG. 11 in which ash is not taken into consideration is used, the accuracy of the estimated value of the PM accumulation amount remains low. If the characteristic line in FIG. 11 is corrected in consideration of the ash accumulation, the PM accumulation amount can be estimated with higher accuracy. However, the conventional literature including the above-mentioned Patent Document 1 does not consider such correction.

  Therefore, in view of the above problems, the problem to be solved by the present invention is to provide an exhaust gas purification apparatus for an internal combustion engine that can more accurately estimate the PM accumulation amount in the particulate filter by taking into consideration the effect of ash accumulation. There is to do.

Means for Solving the Problems and Effects of the Invention

In order to achieve the above object, an exhaust emission control device for an internal combustion engine according to the present invention includes a collector arranged in the middle of an exhaust passage to collect particulate matter, and an inlet side and an outlet side of the collector The pressure loss measuring means for measuring the pressure loss that is a pressure difference between the pressure loss, the pressure loss in the collector, and the amount of particulate matter deposited in the collector, and the amount of particulate matter deposited Characteristic storage means for storing as a characteristic line extending from an initial point where the amount of deposition on the plane with the pressure loss of the collector as two coordinate axes is zero, and the characteristics stored by the characteristic storage means And an estimation means for calculating an estimated value of the amount of the particulate matter deposited in the collector from the pressure loss measured by the pressure loss measuring means, and the estimated value calculated by the estimation means is less than a predetermined threshold value. As it grows, Reproducing means for reproducing the collector by burning the particulate matter deposited on collector unit, the stored the characteristic to the characteristic storage means, the deposition amount of the particulate matter by the reproducing means and zero Correction means for correcting according to the pressure loss after complete regeneration which is the pressure loss of the collector measured by the pressure loss measuring means when the collector is regenerated, and the particles in the collector The larger the time ratio of the self-combustion operation is, the more the time ratio of the self-combustion operation is between the time of the self-combustion operation in which the particulate matter is burned without using the regeneration means and the time of the non-self-combustion operation that is not the self-combustion operation. And a second correction means for performing correction to increase the inclination of the portion farther than the initial point out of the two portions having different inclinations .

  Thus, in the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the pressure loss of the collector and the accumulated amount of the particulate matter stored in the characteristic storage means according to the accumulated amount of the ash, which is an incombustible material, on the collector. Therefore, the amount of particulate matter deposited can be estimated more accurately by the characteristics corrected in consideration of ash accumulation. Then, the amount of particulate matter deposited on the collector is estimated based on the estimated value, and the collector is regenerated when it exceeds a predetermined value. Therefore, the collector can be regenerated at a more appropriate timing. it can. Therefore, the estimated value of the accumulated amount is excessively greater than the true value, and regeneration is too frequent, resulting in deterioration of fuel consumption. It is possible to realize an exhaust emission control device that can avoid damage to the exhaust gas.

  Further, the correction means is the pressure loss of the collector measured by the pressure loss measuring means when the collector is regenerated so that the accumulation amount of the particulate matter becomes zero by the regeneration means. The characteristics may be corrected according to the pressure loss after complete regeneration.

  Thereby, the deposition characteristic of the particulate matter in the collector is corrected using the pressure loss of the collector after complete regeneration. As will be described later, the amount of accumulated ash has a correlation with the pressure loss of the collector after complete regeneration. Therefore, by measuring the pressure loss of the collector after complete regeneration that can be easily measured, information on the amount of ash deposition is obtained and the particulate matter deposition characteristics are corrected, so regeneration of the collector at a more appropriate timing. Can do. Therefore, it can be avoided that the regeneration is too frequent and the fuel consumption is deteriorated, and that the true accumulation amount is excessive and the temperature rises during the regeneration and the collector is damaged.

  The characteristic stored in the characteristic storage means is a point where the accumulation amount is zero on a plane having two coordinate axes, the amount of accumulation of the particulate matter in the collector and the pressure loss of the collector. An initial point for performing a correction for translating the characteristic line so that the pressure loss at the initial point of the characteristic line becomes the pressure loss after the complete regeneration. Correction means may be provided.

  Thereby, the initial point of the characteristic line in the deposition characteristics of the particulate matter is corrected using the pressure loss of the collector after complete regeneration having a correlation with the ash deposition amount. Therefore, every time the regeneration is complete, the initial point is moved to an increased pressure loss value that reflects the accumulation of ash, so that a characteristic line that accurately reflects the accumulation of ash is corrected. Therefore, the collector can be regenerated at an appropriate timing by estimating the amount of particulate matter deposited using this characteristic line. Therefore, it can be avoided that the regeneration is too frequent and the fuel consumption is deteriorated, and that the true accumulation amount is excessive and the temperature rises during the regeneration and the collector is damaged.

  In the characteristic line, the ratio between the increment of the pressure loss and the increment of the deposition amount is set as an inclination, the characteristic line has two parts having different inclinations, and a boundary point between the two parts is used as a transition point. The correction unit may include a transition point correction unit that performs correction to bring the transition point closer to the initial point as the post-complete regeneration pressure loss is larger.

  As a result, the pressure drop of the collector after complete regeneration having a correlation with the ash deposition amount is used to correct the transition point in the deposition characteristics of the particulate matter so that it approaches the initial point. It is corrected to a characteristic line that accurately reflects the phenomenon in which ash accumulates in the walls of the vessel, and particulate matter no longer accumulates in the walls. Therefore, the collector can be regenerated at a more appropriate timing by the characteristic line reflecting the accumulation of ash. Therefore, it can be avoided that the regeneration is too frequent and the fuel consumption is deteriorated, and that the true accumulation amount is excessive and the temperature rises during the regeneration and the collector is damaged.

  In the characteristic line, the ratio between the increment of the pressure loss and the increment of the deposition amount is set as an inclination, the characteristic line has two parts having different inclinations, and a boundary point between the two parts is used as a transition point. The correction unit may include an inclination correction unit that performs correction to increase the inclination of the part farther from the initial point of the two parts in the characteristic line as the pressure loss after complete regeneration is larger.

  This corrects the slope of the characteristic line in the deposition characteristics of the particulate matter using the pressure loss of the collector after complete regeneration, which has a correlation with the ash deposition amount. It is corrected to a characteristic line that accurately reflects the phenomenon in which ash accumulates together with particulate matter and raises the partial pressure loss value. Therefore, the collector can be regenerated at a more appropriate timing by the characteristic line reflecting the accumulation of ash. Therefore, it can be avoided that the regeneration is too frequent and the fuel consumption is deteriorated, and that the true accumulation amount is excessive and the temperature rises during the regeneration and the collector is damaged.

  Further, the apparatus further comprises second correction means for correcting the characteristic stored in the characteristic storage means in accordance with a deposition ratio of ash, which is an incombustible substance, to the exhaust passage side wall and the exhaust passage downstream end face wall of the collector. The characteristic used in the estimation means may be the characteristic corrected by the correction means and the second correction means.

  Thereby, in addition to the correction based on the ash accumulation amount by the correction means, the second correction means also performs correction based on the deposition ratio on the side wall of the ash and the downstream end face wall. As a result, the amount of particulate matter deposited can be estimated with higher accuracy by taking into account the effect of the ash deposition ratio, so that the collector can be regenerated at a more appropriate timing. Therefore, it can be avoided that the regeneration is too frequent and the fuel consumption is deteriorated, and that the true accumulation amount is excessive and the temperature rises during the regeneration and the collector is damaged.

  In the characteristic line, the ratio between the increment of the pressure loss and the increment of the deposition amount is set as an inclination, the characteristic line has two parts having different inclinations, and a boundary point between the two parts is used as a transition point. The second correction means may increase the slope of the portion of the characteristic line farther from the initial point as the deposition ratio of the ash on the exhaust passage side wall increases.

  Thereby, since the ash accumulation ratio to the exhaust passage side wall and the exhaust passage downstream end face wall of the collector is used, and the accumulation ratio to the exhaust passage side wall is increased, the correction to increase the inclination of the characteristic line is performed. As will be described later, when the ash accumulation ratio on the exhaust passage side wall of the collector is large, the characteristic line accurately corrects the phenomenon that the pressure loss value is pushed up by the ash accumulation on the side wall. Therefore, the collector can be regenerated at an appropriate timing using this characteristic line. Therefore, it can be avoided that the regeneration is too frequent and the fuel consumption is deteriorated, and that the true accumulation amount is excessive and the temperature rises during the regeneration and the collector is damaged.

  In addition, the second correction means includes a self-combustion operation out of a self-combustion operation time and a non-self-combustion operation time that are not in the self-combustion operation and the time in which the particulate matter is burned in the collector without using the regeneration means. The larger the time ratio is, the larger the slope of the portion of the two characteristic lines that is farther from the initial point may be corrected.

  As a result, the time ratio between the self-burning operation in which the particulate matter is burned without using the regeneration means in the collector and the non-self-burning operation that is not the self-burning operation has a correlation with the ash accumulation ratio as described later. Therefore, information indicating the ash deposition ratio can be easily obtained. By using this, the second correction means can correct to the characteristic line that accurately reflects the ash deposition ratio. Therefore, the collector can be regenerated at an appropriate timing by the characteristic line. Therefore, it can be avoided that the regeneration is too frequent and the fuel consumption is deteriorated, and that the true accumulation amount is excessive and the temperature rises during the regeneration and the collector is damaged.

  Further, a first time ratio for estimating an exhaust gas temperature measuring means disposed in the exhaust passage and measuring a time ratio between the self-burning operation and the non-self-burning operation based on the exhaust temperature measured by the exhaust temperature measuring means. The time ratio used by the deposition ratio estimation means may be the time ratio estimated by the first time ratio estimation means.

  Thereby, since the time ratio between the self-combustion operation and the non-self-combustion operation is estimated from the exhaust temperature, the time ratio can be accurately obtained using the exhaust temperature that can be easily measured. The characteristic line can be corrected from the time ratio by the second correction means. Therefore, the collector can be regenerated at a more appropriate timing by using the characteristic corrected easily and appropriately. Therefore, it can be avoided that the regeneration is too frequent and the fuel consumption is deteriorated, and that the true accumulation amount is excessive and the temperature rises during the regeneration and the collector is damaged.

  Further, the rotational speed measuring means for measuring the rotational speed of the internal combustion engine, the accelerator opening measuring means for measuring the accelerator opening of the internal combustion engine, and the time ratio between the self-combustion operation and the non-self-combustion operation are set as the rotational speed. Second time ratio estimating means for estimating from the rotational speed of the internal combustion engine measured by the measuring means and the accelerator opening measured by the accelerator opening measuring means, and the time used by the deposition ratio estimating means The ratio may be the time ratio estimated by the second time ratio estimation means.

  As a result, the time ratio between the self-combustion operation and the non-self-combustion operation is estimated using the rotational speed of the internal combustion engine and the accelerator opening in the operation region, so that the time ratio is accurately obtained using a numerical value that can be easily measured. be able to. The characteristic line can be corrected from the time ratio by the second correction means. Therefore, the collector can be regenerated at a more appropriate timing by using the characteristic line corrected easily and appropriately. Therefore, it can be avoided that the regeneration is too frequent and the fuel consumption is deteriorated, and that the true accumulation amount is excessive and the temperature rises during the regeneration and the collector is damaged.

  The internal combustion engine is mounted on an automobile, and a vehicle speed measuring means for measuring the speed of the automobile and a time ratio between the self-combustion operation and the non-self-combustion operation are calculated from the speed of the automobile measured by the vehicle speed measurement means. Third time ratio estimating means for estimating, and the time ratio used by the deposition ratio estimating means may be the time ratio estimated by the third time ratio estimating means.

  Thereby, since the time ratio between the self-combustion operation and the non-self-combustion operation is estimated using the vehicle speed, the time ratio can be accurately obtained using the vehicle speed value that can be easily measured. The characteristic line can be corrected from the time ratio by the second correction means. Therefore, the collector can be regenerated at a more appropriate timing by using the characteristic line corrected easily and appropriately. Therefore, it can be avoided that the regeneration is too frequent and the fuel consumption is deteriorated, and that the true accumulation amount is excessive and the temperature rises during the regeneration and the collector is damaged.

  Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 is a schematic view of an embodiment of an exhaust gas purification apparatus 1 for an internal combustion engine according to the present invention.

  It is assumed that the exhaust emission control device 1 is configured, for example, for a four-cylinder diesel engine 2 (hereinafter simply referred to as an engine). Air is supplied to the engine 2 from an intake pipe 3 connected to the engine 2. An air flow meter 4 is disposed in the intake pipe 3 to measure the intake air amount. An intake throttle 12 is disposed in the intake pipe 3, and the amount of intake air supplied to the engine 2 is increased or decreased by adjusting the opening.

  The engine 2 is equipped with an injector 13 to supply fuel into the cylinder. Exhaust gas is discharged to an exhaust pipe 5 connected to the engine 2. The electronic control unit 10 (ECU) controls fuel injection to the engine 2 by the injector 13 and adjustment of the opening degree of the intake throttle 12. The ECU 10 has a structure including a CPU for performing various calculations, a RAM for its work area, a memory 11 for storing various information, and the like.

  A diesel particulate filter 6 (DPF) is disposed in the middle of the exhaust pipe 5. The DPF 6 carries an oxidation catalyst, which is a so-called DPF with an oxidation catalyst (C-DPF). Exhaust temperature sensors 7 and 8 are arranged on the inlet side and the outlet side of the DPF 6 respectively, and the exhaust temperature at each position is measured. Further, a differential pressure sensor 9 for measuring a differential pressure (pressure loss, DPF pressure loss) which is a difference between exhaust pressures on the inlet side and the outlet side of the DPF 6 is also provided. The measured values of the air flow meter 4, the exhaust temperature sensors 7 and 8, and the differential pressure sensor 9 are sent to the ECU 10.

  Further, the exhaust purification device 1 includes an engine speed sensor 14 and an accelerator opening sensor 15. Further, it is assumed that the exhaust purification device 1 and the engine 2 are mounted on an automobile and supplies driving force, and includes a vehicle speed sensor 16. The engine speed sensor 14 is installed in the engine 2 and measures the speed of the engine 2 or the speed per unit time and sends it to the ECU 10. The accelerator opening sensor 15 measures the degree of input to the accelerator by the user and sends it to the ECU 10. As is well known, the vehicle speed sensor 16 is mounted on, for example, a transmission, measures the vehicle speed, and sends it to the ECU 10.

  For example, the DPF 6 may have a structure in which the inlet side and the outlet side are alternately packed in a so-called honeycomb structure. The exhaust gas discharged during the operation of the engine 2 contains particulate matter (PM), and this PM is collected inside or on the surface of the DPF wall when the exhaust gas passes through the DPF wall having the above structure of the DPF 6. Is done. Every time the amount of PM deposited on the DPF 6 becomes sufficiently large, the deposited PM must be removed by burning to regenerate the DPF 6. As a method for regenerating the DPF 6, for example, a method of performing post injection from the injector 13 at a timing after main injection is used.

  In the present invention, the PM deposition characteristics shown in FIG. 11 are corrected according to the amount of ash deposited and the state of deposition. This improves the estimation accuracy of the PM accumulation amount. The overall outline of the correction is shown in FIG. 2, and the processing procedure for the correction is shown in the flowchart of FIG. Details will be described below. The procedure shown in FIG. 3 may be executed by the ECU 10.

  First, it is determined in step S10 whether the DPF 6 is being regenerated. If it is being reproduced (S10: YES), the process proceeds to S20, and if it is not being reproduced (S10: NO), this flow is terminated.

  In S20, it is determined whether or not the complete regeneration of the DPF 6 has been completed. Here, complete regeneration means that all the PM deposited on the DPF 6 is burned to return the amount of accumulated PM to zero. If complete reproduction has been completed (S20: YES), the process proceeds to S30, and if not complete (S20: NO), the process of S20 is repeated until complete reproduction is completed.

  As described above, when the process proceeds to S30, the complete regeneration of the DPF 6 has been completed. In S30, the pressure loss of the DPF 6 is measured. This may be measured by the differential pressure sensor 9.

  Next, in S40, the PM self-combustion time ratio is calculated. Here, the PM self-combustion time ratio is the ratio of the time in the PM self-combustion operation state to the total operation time. The PM self-combustion operation state is a state in which PM is deposited at the same time as PM is accumulated in the DPF 6 due to a high exhaust gas temperature discharged from the engine 2. The exhaust temperature at which the PM self-combustion operation is performed is, for example, 550 degrees Celsius or more as a guide. In the following, all temperature units are in degrees Celsius.

  In S40, the ECU 10 is equipped with a timer function, the total operation time of the engine 2 is measured, the PM self-combustion operation time is further measured, and the ratio between the PM self-combustion operation time and the total operation time is calculated. That's fine. As will be described later, since the ash accumulation state on the DPF 6 is characteristic in the PM self-combustion operation state, it is necessary to consider it when correcting the PM accumulation characteristics.

  Examples of the measurement of the PM self-burning operation time include the following three methods. First, the first method uses the exhaust temperature. As described above, if the PM self-combustion operation state is set when the exhaust gas temperature is 550 ° C. or higher, the total operation time when the exhaust temperature is 550 ° C. or higher may be set as the PM self-combustion time. The exhaust temperature may be measured by the exhaust temperature sensors 7 and 8 (sensors). At that time, the average of the measured values of the sensors 7 and 8 may be the exhaust temperature. Alternatively, a model for estimating the temperature inside the DPF 6 may be obtained from the measured values of the sensors 7 and 8, and the estimated value obtained there may be used as the exhaust temperature. Further, instead of setting 550 degrees as a threshold value, an exhaust gas temperature at which a PM self-combustion operation state is obtained in advance for the apparatus configuration to be used may be obtained and used.

  The second method uses the engine speed and the accelerator opening. On the plane showing the operating state of the engine 2 with the engine speed and the accelerator opening as coordinate axes as shown in FIG. 8, a region where the PM self-combustion operation state is obtained at a high load and high rotation is obtained. What is necessary is just to let the sum total of the operation time which has entered in the area | region be PM self-combustion time. The engine speed may be obtained by the engine speed sensor 14. The accelerator opening may be obtained by the accelerator opening sensor 15.

  The third method is a method using the vehicle speed of the automobile on which the engine 2 is mounted. If the vehicle speed is high, it is assumed that the exhaust temperature is high. Therefore, whether the vehicle speed value is large gives an indication of whether or not the PM self-combustion operation state is not. What is necessary is just to obtain | require the vehicle speed which will be in PM self-combustion driving | running state previously. For example, the driving time when the vehicle speed is 150 km / h or more may be set as the PM self-combustion time. The vehicle speed may be measured by the vehicle speed sensor 16.

  In step S50, an initial point, hysteresis, inclination, and inclination correction coefficient for correcting the PM deposition characteristic line are calculated. The PM deposition characteristic lines in a state where ash is not deposited are defined as characteristic lines 21 and 23 on the lower side of FIG. The characteristic lines corrected by the accumulation of ash are defined as characteristic lines 21 and 23 on the upper side in FIG. As shown in FIG. 2, the pressure loss of the DPF 6 at the initial point 20 before correction is P0. That is, P0 is a pressure loss under the condition that nothing is deposited on the DPF 6.

  Note that the pressure loss after complete regeneration is used in the correction described below. This is because the PM is generally burned and only ash is deposited after complete regeneration, so the pressure loss value indicates the amount of ash deposited. It will be. Therefore, as shown in FIG. 4, since the pressure loss after complete regeneration has a monotonically increasing relationship with the ash deposition amount, the pressure loss after complete regeneration becomes an index indicating the ash deposition amount.

  First, the initial point 20 is corrected. The pressure loss after complete regeneration of the DPF 6 is defined as P1. At this time, the entire characteristic line is translated upward in the drawing so that the initial point 20 of the corrected characteristic line becomes a point P1 as shown in FIG. Thus, the characteristic lines 21 and 23 having the initial point 20 corresponding to the latest ash accumulation amount are corrected.

  Next, the hysteresis is corrected. Hysteresis is the distance between the characteristic line 23 passing through the initial point 20 and the characteristic line 23, that is, the value of H0 or H1 shown in FIG. The hysteresis value is calculated according to FIG. As shown in FIG. 5, the hysteresis value monotonously decreases with respect to the pressure loss after complete regeneration.

  The reason for this will be described with reference to FIG. FIG. 9 is an enlarged view of a cross section of the filter wall of the DPF 6. As the amount of ash deposited increases, the amount of ash deposited in the pores of the filter wall also increases. This reduces the room for PM to accumulate in the filter wall. Therefore, the deposition of PM into the wall is saturated with a smaller amount of PM deposited in the wall. As described above, the first characteristic line 21 is a characteristic line corresponding to PM accumulation in the filter wall. Therefore, after all, as the amount of accumulated ash in the DPF 6 increases, the first characteristic line 21 becomes shorter and the hysteresis becomes smaller. From the above, the tendency shown in FIG. 5 is obtained.

  In FIG. 5, the hysteresis is H0 when the pressure loss after complete regeneration is P0, and H1 when the pressure loss is P1. H1 is smaller than H0. As a result, the length of the first characteristic line 21 is corrected to be short as shown in FIG.

  Next, the inclination of the second characteristic line 23 is corrected. The slope of the second characteristic line is calculated from FIG. As shown in FIG. 6, the value of the slope of the second characteristic line 23 increases monotonously with respect to the pressure loss after complete regeneration. The reason for this will be described with reference to FIG.

  FIG. 10 is a cross-sectional view of the DPF 6 in a state where both ash and PM are deposited. Ashes and PM accumulate as the engine 2 operates, only PM is burned and only ash remains each time the DPF 6 is regenerated. Therefore, after several times of DPF regeneration, ash is deposited in a low layer, and PM is deposited thereon. In general, ash tends to accumulate more on the downstream end face of the DPF 6 due to the influence of the normal exhaust flow.

  Therefore, the same effect as the axial length of the DPF 6 becomes shorter due to the ash deposited on the downstream end face side appears. Therefore, after all, the more ash is deposited, the thicker the PM is deposited on the wall surface of the filter wall with the same amount of PM deposition. Therefore, the pressure loss value becomes larger even with the same PM deposition amount. This is equivalent to increasing the slope of the second characteristic line 23. Thereby, FIG. 6 is obtained.

  In FIG. 6, when the pressure loss after complete regeneration is P0, the slope of the second characteristic line 23 is θ0, and when the pressure loss is P1, θ1. Θ1 is larger than θ0. Thereby, the inclination of the second characteristic line 23 is corrected to be larger.

  Further, the slope of the second characteristic line 23 is corrected according to the PM self-combustion operation ratio obtained in S40. This further correction follows FIG. The inclination correction coefficient shown in FIG. 7 is multiplied by the inclination value obtained in FIG. 6 to calculate the final corrected inclination value of the second characteristic line 23. As shown in FIG. 7, the slope correction coefficient monotonously increases with respect to the PM self-combustion operation ratio. The reason for this will be described below.

  In the PM self-combustion operation state, as described above, PM burns simultaneously while accumulating in the DPF 6. In this state, there is a tendency that PM is thinly and constantly deposited on the wall surface of the filter wall of the DPF 6. Since ash usually adheres to PM and flows to DPF 6, ash also accumulates on the filter sidewall. In other words, if the ratio of the amount of ash deposited on the sidewall of the DPF and the amount deposited on the downstream end face is the ash deposition ratio, the larger the PM self-combustion time ratio, the greater the deposition ratio on the ash sidewall.

  When ash is deposited on the filter wall surface together with PM, the pressure loss value is increased by the amount of ash deposited even with the same amount of PM deposited. As described above, the deposition on the filter wall surface corresponds to the second characteristic line 23. Therefore, the slope of the second characteristic line 23 increases as the PM self-combustion operation ratio eventually increases. From the above, FIG. 7 is obtained.

  Assume that the PM self-combustion operation ratio calculated in S40 is R1, and the slope correction coefficient when the PM self-combustion operation ratio is R1 as shown in FIG. 7 is k1. The product of k1 and θ1 obtained in FIG. 6 is the final corrected slope value of the second characteristic line 23.

  Finally, in S60, the PM deposition characteristic line is corrected using the hysteresis, inclination, and inclination correction coefficient obtained in S50. Thereby, the characteristic line on the upper side of FIG. 2 is obtained. The above is FIG.

  Using the corrected characteristic lines 21 and 23, the ECU 10 estimates the amount of PM deposited on the DPF 6. When the estimated value of the PM accumulation amount exceeds a predetermined threshold value, for example, post-injection may be performed from the injector 13 to regenerate the DPF. Since the characteristic line corrected by taking the ash accumulation into account is used, the PM accumulation amount can be estimated more accurately.

  The characteristics shown in FIGS. 5, 6, 7 or FIG. 8, the exhaust temperature at which the PM self-combustion operation is performed, and the threshold value of the vehicle speed are obtained and stored in the memory 11 with respect to the apparatus configuration to be used in advance, and are stored in S50. Call and use.

  In the above, the first characteristic line 21 and the second characteristic line 23 are straight lines, but this is a linear approximation, and the true characteristic may be a curve as shown in FIG. In this case, in the above description, the hysteresis, that is, the correction for reducing the distance between the initial point 20 and the transition point 22 is performed by, for example, initializing the transition point 22 along the first characteristic line which is a curve as shown in FIG. It is good also as correction | amendment which approaches the point 20. FIG. The second characteristic line 23 is corrected so as to increase the inclination of the tangent 30 at one point on the second characteristic line 23 which is the curve shown in FIG. 12, for example. What should I do?

  In the above embodiment, the procedure of S40 constitutes the first time ratio measuring means, the second time ratio measuring means, and the third time ratio measuring means. The procedures of S50 and S60 constitute correction means, initial point correction means, transition point correction means, inclination correction means, and second correction means.

1 is a schematic configuration diagram of an exhaust emission control device for an internal combustion engine in an embodiment of the present invention. The schematic diagram which shows the whole correction | amendment. The flowchart of PM deposition characteristic correction processing. The figure which shows the relationship between the pressure loss after complete reproduction | regeneration, and the amount of ash deposits. The figure which shows the relationship between a hysteresis and the pressure loss after complete reproduction | regeneration. The figure which shows the relationship between the inclination of a 2nd characteristic line, and the pressure loss after complete reproduction | regeneration. The figure which shows the relationship between an inclination correction coefficient and PM self-combustion operation ratio. The figure which shows the PM self-combustion operation area | region in all the operation areas. The figure which shows the mode of accumulation of the ash to DPF. The figure which shows the mode of accumulation of the ash to DPF. The figure which shows the PM deposition characteristic line to DPF. The figure which shows the PM deposition characteristic line to DPF.

Explanation of symbols

1 Exhaust gas purification device 2 Diesel engine (internal combustion engine)
3 Intake pipe 5 Exhaust pipe 6 Diesel particulate filter (DPF, collector)
7, 8 Exhaust temperature sensor (exhaust temperature measuring means)
9 Differential pressure sensor (pressure loss measuring means)
10 Electronic control unit (ECU, estimation means)
11 Memory (characteristic storage means)
13 Injector (regeneration means)
14 Engine speed sensor (speed measurement means)
15 Accelerator opening sensor (accelerator opening measuring means)
16 Vehicle speed sensor (vehicle speed measuring means)
21 1st characteristic line (characteristic line)
23 Second characteristic line (characteristic line)

Claims (7)

A collector arranged in the middle of the exhaust passage to collect particulate matter;
Pressure loss measuring means for measuring a pressure loss which is a pressure difference between the inlet side and the outlet side in the collector;
The characteristic between the pressure loss in the collector and the amount of particulate matter deposited in the collector is a plane with the amount of particulate matter deposited and the pressure drop of the collector as two coordinate axes. Characteristic storage means for storing as a characteristic line extending from an initial point where the amount of deposition at zero is a point ;
An estimation means for calculating an estimated value of the amount of accumulation of the particulate matter in the collector from the characteristic stored by the characteristic storage means and the pressure loss measured by the pressure loss measurement means;
Regeneration means for regenerating the collector by burning the particulate matter deposited on the collector when the estimated value calculated by the estimating means is greater than a predetermined threshold;
The said characteristic memorize | stored in the said characteristic memory | storage means is the said collection measured by the said pressure loss measurement means when the said collector was reproduced | regenerated so that the accumulation amount of the said particulate matter might be set to zero by the said reproduction | regeneration means. Correction means for correcting according to the pressure loss after complete regeneration, which is the pressure loss of the container ,
The larger the time ratio of the self-combustion operation, the longer the time ratio of the self-combustion operation, the non-self-combustion operation time that is the state in which the particulate matter is burned without using the regeneration means in the collector. A second correction means for performing correction to increase the inclination of a portion farther than the initial point among the two portions having different inclinations across the transition point in the characteristic line;
An exhaust emission control device for an internal combustion engine, comprising: Before SL correction means, as the value of the pressure loss of the initial point of the characteristic line becomes the complete regeneration after pressure drop, in claim 1 having the initial point correcting means for correcting translating the characteristic line An exhaust gas purification apparatus for an internal combustion engine as described. Before SL correction means, the full extent reproduced after the pressure loss is large, the exhaust purification system of an internal combustion engine according to the transition point to claim 1 or 2 including a transition point correcting means for correcting closer to the initial point. Before SL correcting means, the higher the complete regeneration after pressure loss is large, claim having a tilt correction means for correcting to increase the inclination of the portion that is further than the initial point of the two parts of the characteristic line The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 3 . An exhaust temperature measuring means disposed in the exhaust passage for measuring the exhaust temperature;
First time ratio estimating means for estimating the time ratio between the self-burning operation and the non-self-burning operation based on the exhaust temperature measured by the exhaust temperature measuring means;
The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 4 , wherein the time ratio used by the second correction means is the time ratio estimated by the first time ratio estimation means. A rotational speed measuring means for measuring the rotational speed of the internal combustion engine;
Accelerator opening measuring means for measuring the opening of the accelerator of the internal combustion engine;
A second time ratio for estimating the time ratio between the self-combustion operation and the non-self-combustion operation from the rotational speed of the internal combustion engine measured by the rotational speed measurement means and the accelerator opening measured by the accelerator opening measurement means An estimation means,
The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 4 , wherein the time ratio used by the second correction means is the time ratio estimated by the second time ratio estimation means. The internal combustion engine is mounted on an automobile;
Vehicle speed measuring means for measuring the speed of the car,
A third time ratio estimating means for estimating a time ratio between the self-burning operation and the non-self-burning operation from a speed of the automobile measured by the vehicle speed measuring means;
The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 4 , wherein the time ratio used by the second correction means is the time ratio estimated by the third time ratio estimation means.

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