JP2005054634A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for efficiently and accurately performing the forcible regeneration of a continuously regenerative filter device using catalytic action for burning PM contained in exhaust gas from an engine while trapping it to prevent the worsening of fuel consumption due to excessive forcible regeneration and the deterioration of a filter and a catalyst due to the abnormal combustion of the accumulated PM. <P>SOLUTION: This exhaust emission control device comprises a means S1 for estimating a PM accumulation amount for the filter, means S2-S8 for determining forcible regeneration timings of the filter in accordance with a plurality of different methods, a means S9 for setting a forcible regeneration temperature and a forcible regeneration temperature corresponding to the PM accumulation amount for the filter as forcible regeneration modes corresponding to the determining methods when receiving the determination of the forcible regeneration timings, a means S10 for performing temperature rise control to forcibly increase the temperature of the filter in accordance with the forcible regeneration modes when receiving the determination of the forcible regeneration timings, and means S11-S14 for cancelling the forcible temperature rise control of the filter when the condition of the temperature of the filter higher than the forcible regeneration temperature is continued until the forcible regeneration time is reached. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exhaust emission control device for removing PM (particulate matter) contained in exhaust gas from a diesel engine.

In recent years, development of a continuous regenerative filter device (CR-DPF: continuous Regeneratoin-Diesel Particulate Filter) has attracted attention as one of the promising means for reducing PM contained in the exhaust of diesel engines (Patent Document 1 to Patent Document) 5). The continuous regeneration type filter device collects PM contained in the exhaust of the engine in a filter and continuously burns and removes the collected PM by a catalytic action. Even in such a filter device, the catalyst has an active temperature region, and if the operation state at an exhaust temperature lower than this is continued for a long time, the filter cannot be continuously regenerated sufficiently, and the amount of accumulated PM becomes excessive. May adversely affect engine performance. In addition, when shifting to an operation state at an exhaust temperature that falls within the activation temperature region of the catalyst, PM that accumulates excessively in the filter may burn rapidly, and the filter is liable to be melted or cracked. For this reason, forced removal of the deposited PM (forced regeneration of the filter) is performed at a necessary time.
JP 2003-155915 A JP 2003-155916 A JP 2003-155919 A JP 2003-129835 A JP 2003-3833

  Regarding the method for determining the time required for forced regeneration (forced regeneration time), the method for determining the forced regeneration time from the PM accumulation amount of the filter estimated from the engine operation history, the exhaust pressure upstream of the filter or the A method of determining the forced regeneration time from the differential pressure is tried. In the former case, it is difficult to accurately estimate the amount of PM deposited on the filter due to environmental factors such as environmental conditions, and the difference between the estimated amount of PM and the actual value may increase over time. . In the latter case, the amount of accumulated PM is not sensitively reflected in the exhaust pressure upstream of the filter (or the differential pressure before and after the filter), and cannot be detected unless the clogged state of the filter proceeds beyond a certain level. Therefore, the combined use of both is assumed, but the amount of PM accumulation may vary greatly depending on the method for determining the forced regeneration timing. When forced regeneration is controlled to a uniform pattern, fuel consumption deteriorates and accumulates due to excessive forced regeneration. There is also concern about the induction of filter and catalyst deterioration due to abnormal combustion of PM.

  An object of the present invention is to provide means for efficiently and accurately processing forced regeneration while avoiding such problems.

  According to a first aspect of the present invention, there is provided an exhaust gas purification apparatus that collects PM contained in engine exhaust gas and combusts it by catalytic action, and means for estimating the PM accumulation amount of the filter, and a plurality of different methods, respectively. Means for determining forced regeneration time, means for setting forced regeneration temperature and forced regeneration time according to the PM accumulation amount of the filter as forced regeneration mode corresponding to the determination method upon receiving the judgment of forced regeneration time, When the regeneration time is received, a means for controlling the temperature rise to forcibly increase the filter temperature based on the forced regeneration mode, and forcing the filter when the continuation state where the filter temperature exceeds the forced regeneration temperature reaches the forced regeneration time And a means for canceling an appropriate temperature rise control.

  According to a second aspect of the present invention, in the exhaust gas purification apparatus according to the first aspect, the means for determining the forced regeneration timing of the filter based on a plurality of different methods is the forced regeneration when the PM accumulation amount of the filter is a predetermined value or more. Means for determining the timing, and means for determining the forced regeneration timing when the exhaust pressure upstream of the filter or the differential pressure before and after the filter is greater than or equal to a predetermined value.

  According to a third aspect of the present invention, in the exhaust purification apparatus according to the first aspect, the means for determining the forced regeneration timing of the filter based on a plurality of different methods is the forced regeneration when the PM accumulation amount of the filter is a predetermined value or more. Means to determine the timing and when the operating time or operating distance measured from the cancellation of the forced temperature rise control of the filter reaches the set interval for forced regeneration, the history of forced temperature rise control of the filter is Means for determining a forced regeneration time when there is not.

  According to a fourth aspect of the present invention, in the exhaust emission control device according to the first aspect, the means for determining the forced regeneration timing of the filter based on a plurality of different methods is the forced regeneration when the PM accumulation amount of the filter is a predetermined value or more. Means to determine the timing, and the forced regeneration timing when the operating time or distance or the number of forced temperature rise control of the filter reaches the interval set for 0 reset forced regeneration that periodically initializes the PM accumulation amount And means for determining.

  According to a fifth aspect of the present invention, in the exhaust purification apparatus according to the first aspect, the means for determining the forced regeneration timing of the filter based on a plurality of different methods is the forced regeneration when the PM accumulation amount of the filter is equal to or greater than a predetermined value. Means to determine the timing and when the operating time or operating distance measured from the cancellation of the forced temperature rise control of the filter reaches the set interval for forced regeneration, the history of forced temperature rise control of the filter is Means to determine the forced regeneration time when there is not, the operating time or operating distance or the number of forced temperature rise control of the filter reaches the interval set for 0 reset forced regeneration to initialize the PM accumulation amount periodically Then, means for determining the forced regeneration time is provided.

  According to a sixth aspect of the present invention, in the exhaust purification apparatus according to the second aspect of the invention, the means for determining the forced regeneration time when the exhaust pressure upstream of the filter or the differential pressure before and after the filter is greater than or equal to a predetermined value is And a means for setting a plurality of different level values as predetermined values.

  According to a seventh aspect of the present invention, in the exhaust purification apparatus according to the second aspect of the invention, the means for determining the forced regeneration timing when the exhaust pressure upstream of the filter or the differential pressure before and after the filter is greater than or equal to a predetermined value is the exhaust pressure upstream of the filter or Means for limiting the determination based on the differential pressure before and after the filter to a specific operating condition.

  According to an eighth aspect of the present invention, in the exhaust purification apparatus according to the second aspect of the invention, the means for determining the forced regeneration timing when the exhaust pressure upstream of the filter or the differential pressure before and after the filter is greater than or equal to a predetermined value is the exhaust pressure upstream of the filter or And means for correcting the differential pressure before and after the filter based on the exhaust gas temperature.

  According to a ninth aspect of the present invention, in the exhaust emission control device according to the first aspect, the means for estimating the PM accumulation amount of the filter is a means for obtaining the PM emission amount per unit time based on the excess air ratio as the engine operating state And means for obtaining the PM combustion amount per unit time based on the temperature and space velocity of the filter, and means for obtaining the PM accumulation amount of the filter by sequentially integrating the subtraction value obtained by subtracting the PM combustion amount from the PM emission amount. It is characterized by that.

  According to a tenth aspect of the present invention, in the exhaust gas purification apparatus according to the first aspect of the present invention, the means for performing the temperature rise control for forcibly increasing the filter temperature based on the forced regeneration mode when the determination is made with the forced regeneration timing, When the temperature is below a predetermined temperature required for the catalyst reaction, means for performing a temperature increase control 1 that actively increases the exhaust temperature of the engine to preheat the catalyst, and when the filter temperature is equal to or higher than the predetermined temperature required for the catalyst reaction And means for performing temperature rise control 2 for adding unburned fuel to the exhaust gas so as to promote the reaction of the catalyst.

  According to an eleventh aspect of the present invention, in the exhaust gas purification apparatus according to the tenth aspect of the present invention, means for performing a temperature rise control for forcibly increasing the filter temperature based on the forced regeneration mode upon receiving the forced regeneration timing And a means for waiting for the transition to the temperature raising control 1 while performing normal control when the temperature or the engine load is lower than the lower limit value.

  According to a twelfth aspect of the present invention, in the exhaust gas purification apparatus according to the tenth aspect of the present invention, means for performing a temperature rise control for forcibly increasing the filter temperature based on the forced regeneration mode upon receiving the determination of the forced regeneration time is an engine exhaust Means for canceling the temperature rise control 2 when the temperature exceeds the upper limit value.

  In a thirteenth aspect of the present invention, in the exhaust gas purification apparatus according to any one of the first to fifth aspects of the present invention, means for actively controlling the amount of oxygen in the exhaust gas so as to keep the exhaust gas temperature downstream of the filter below the upper limit value. And.

  In the first invention, since a plurality of methods are used in combination for determining the forced regeneration time, a plurality of checks work, so that it is possible to increase the probability of avoiding an excessive amount of PM accumulation on the filter. Since the forced regeneration mode corresponding to multiple judgment methods is selected, and the release condition based on the forced regeneration temperature and the forced regeneration time according to the PM accumulation amount at that time is satisfied, the temperature rise control of the filter is performed. is there. For this reason, forced regeneration of the filter can be processed efficiently and appropriately with a combustion mode (combustion time and combustion temperature) that matches the amount of PM deposition at that time. The deterioration of the filter and catalyst due to abnormal combustion can be effectively prevented.

  In the second aspect of the invention, the determination method based on the PM accumulation amount and the determination method based on the exhaust pressure upstream of the filter or the differential pressure before and after the filter are used in combination to determine the forced regeneration timing. It is possible to increase the probability of avoiding excessive PM deposition. Since the forced regeneration mode corresponding to these judgment methods is selected, the temperature rise control of the filter is performed until the release condition based on the forced regeneration temperature and the forced regeneration time according to the PM accumulation amount at that time is satisfied. is there. For this reason, forced regeneration of the filter can be processed efficiently and appropriately with a combustion mode (combustion time and combustion temperature) that matches the amount of PM deposition at that time. Deterioration of the filter and catalyst due to abnormal combustion can be prevented.

  In the third aspect of the invention, the determination method based on the PM accumulation amount and the determination method based on the forced regeneration interval are used in combination for the determination of the forced regeneration timing, and these checks work, so the PM accumulation amount of the filter is excessive. Probability that can be avoided in advance. Since the forced regeneration mode corresponding to these judgment methods is selected, the temperature rise control of the filter is performed until the release condition based on the forced regeneration temperature and the forced regeneration time according to the PM accumulation amount at that time is satisfied. is there. For this reason, forced regeneration of the filter can be processed efficiently and appropriately with a combustion mode (combustion time and combustion temperature) that matches the amount of PM deposition at that time. Deterioration of the filter and catalyst due to abnormal combustion can be prevented. Regarding the judgment method based on the interval for forced regeneration, there is no history of forced regeneration based on the PM accumulation amount during the operation time or driving distance measured from the release of forced regeneration based on the PM accumulation amount reaches the set interval The forced regeneration time is sometimes determined, and this regeneration process can be expected to correct the deviation between the actual value and the estimated value of the PM accumulation amount.

  In the fourth aspect of the invention, the determination method based on the PM accumulation amount and the determination method based on the zero reset forced regeneration interval are used in combination for the determination of the forced regeneration timing, and these checks work, so the PM accumulation amount of the filter is reduced. It is possible to increase the probability of avoiding excess. The forced regeneration mode corresponding to these determination methods is selected, and the temperature rise control of the filter is performed until the release condition based on the forced regeneration temperature and the forced regeneration time according to the PM accumulation amount at that time is satisfied. . For this reason, forced regeneration of the filter can be processed efficiently and appropriately with a combustion mode (combustion time and combustion temperature) that matches the amount of PM deposition at that time. Deterioration of the filter and catalyst due to abnormal combustion can be prevented. The determination method based on the interval for 0 reset forced regeneration is to determine the forced regeneration timing when the number of forced regenerations based on the operating time, the operating distance, or the PM accumulation amount reaches the set interval. By the forced regeneration, the PM accumulation amount of the filter is completely combusted, and the estimated value of the PM accumulation amount can be initialized (the deviation between the actual value and the estimated value can be corrected to 0).

  In the fifth invention, the judgment method based on the PM accumulation amount, the judgment method based on the forced regeneration interval, and the judgment method based on the zero reset forced regeneration interval are used in combination for the judgment of the forced regeneration timing. Therefore, it is possible to increase the probability that the amount of PM accumulated on the filter can be avoided in advance. The forced regeneration mode corresponding to these determination methods is selected, and the temperature rise control of the filter is performed until the release condition based on the forced regeneration temperature and the forced regeneration time according to the PM accumulation amount at that time is satisfied. . For this reason, forced regeneration of the filter can be processed efficiently and appropriately with a combustion mode (combustion time and combustion temperature) that matches the amount of PM deposition at that time. Deterioration of the filter and catalyst due to abnormal combustion can be prevented. The regeneration process based on the forced regeneration interval and the regeneration process based on the zero reset forced regeneration interval correct the deviation between the actual value and estimated value of the PM deposition amount, and maintain a high level of accuracy in estimating the PM deposition amount. It is.

  In the sixth invention, the forced regeneration timing can be determined based on the exhaust pressure upstream of the filter or the differential pressure before and after the filter at a plurality of different levels, and by setting the forced regeneration mode corresponding to these determinations, The combustion form (combustion time and combustion temperature) that matches the PM accumulation amount at that time can be processed efficiently and appropriately, and fuel and fuel deterioration due to excessive forced regeneration and filter and catalyst deterioration due to abnormal combustion of accumulated PM Can be prevented.

  In the seventh invention, the detection value (exhaust pressure or exhaust pressure) used for the determination of the forced regeneration timing is limited by limiting the determination of the forced regeneration timing based on the exhaust pressure upstream of the filter or the differential pressure before and after the filter to a specific operating condition. Since the differential pressure is also stable, the forced regeneration time can be accurately determined.

  In the eighth aspect of the invention, the exhaust pressure upstream of the filter or the differential pressure before and after the filter is corrected (temperature compensated) according to the exhaust temperature of the engine, so that it changes depending on the exhaust temperature even in the same clogged state. Since variations in exhaust pressure and differential pressure are suppressed, forced regeneration timing can be accurately determined.

  In the ninth aspect of the invention, an accurate PM emission amount is obtained from the excess air ratio closely corresponding to the smoke concentration, and an accurate PM combustion rate is obtained from the temperature and space velocity of the filter. By subtracting the PM combustion amount (PM combustion rate x unit time) from the value, a high estimate of the PM deposition amount can be obtained.

  In the tenth aspect of the invention, when shifting to forced regeneration, when the filter temperature falls below a predetermined temperature, the exhaust temperature is raised by the temperature raising control 1 to preheat the catalyst. When the filter temperature is equal to or higher than the predetermined temperature, unburned fuel is added to the exhaust gas by the temperature raising control 2 and reacts on the catalyst, so that the combustion of the deposited PM is promoted by using the reaction heat as a heat source for raising the temperature of the exhaust gas. .

  In the eleventh aspect of the invention, when the engine exhaust temperature or the engine load is in an operating state below the lower limit value, the routine does not shift to the temperature raising control 1 but stands by with the normal control. In such an operating state where the exhaust temperature is low, it is difficult to raise the exhaust gas, and it takes time to raise the temperature. Therefore, the combustion efficiency is poor by waiting in the normal control regardless of the determination of the forced regeneration timing. The temperature increase control 1 is avoided.

  In the twelfth aspect of the invention, when the exhaust gas temperature downstream of the filter exceeds the upper limit value, the temperature rise exceeding the allowable range of the filter due to abnormal combustion of the accumulated PM can be suppressed by stopping the temperature rise control 2. It can contribute to prevention of catalyst deterioration.

  In the thirteenth aspect of the invention, since the oxygen concentration in the exhaust gas is actively controlled so as to keep the exhaust gas temperature downstream of the filter below the upper limit value, abnormal combustion of the deposited PM that causes a rapid temperature rise can be suppressed. It can contribute to prevention of deterioration and catalyst deterioration.

  In FIG. 1, reference numeral 10 denotes a diesel engine, which includes a common rail fuel injection device (not shown). A compressor 12 a, an intercooler 13, and an intake throttle valve 14 of a turbocharger 12 are interposed in the intake passage 11 of the engine 10. A turbine 12 b of the turbocharger 12, an exhaust throttle valve 16, and a continuous regenerative filter device (CR-DPF) 17 are interposed in the exhaust passage 15 of the engine 10. The common rail fuel injection device includes a high-pressure pump that accumulates fuel in the common rail, and a fuel supply pipe that connects the injection nozzle of each cylinder to the common rail. The control unit 20 controls the fuel injection device and the preheating means described later, and stores a temperature increase control map for forced regeneration in addition to a normal control map. Reference numeral 21 denotes an EGR valve of an EGR (exhaust gas recirculation) device, and reference numeral 22 denotes a turbo bypass opening / closing valve that bypasses the turbine 12 b of the turbocharger 12.

  The CR-DPF 17 includes a DPF (Diesel Particulate Filter) 25 and an oxidation catalyst 26 (DOC: Diesel Oxidation Catalyst). The DPF 25 is formed in a honeycomb structure, and the inlets and outlets of flow paths (cells) partitioned in a lattice shape are alternately sealed. That is, the flow path sealed at the inlet and the flow path sealed at the outlet are alternately adjacent to each other, and the porous partition walls that partition these allow passage of the exhaust gas. In this example, a filter with a catalyst (alumina or the like) (CSF: Catalyst Soot Filter) is employed in order to set a combustible ignition temperature of PM collected in the partition walls. DOC26 is formed in a honeycomb structure carrying a catalyst, and mainly oxidizes HC (hydrocarbon) contained in exhaust gas that passes through the flow path partitioned in a lattice shape of the honeycomb structure. Heat increases the catalyst temperature and promotes the combustion of the deposited PM.

  As detection means necessary for control of the control unit 20, in addition to a rotation sensor (also serving as a crank angle sensor) for detecting the engine speed Ne and a load sensor for detecting an engine load q (for example, fuel injection amount), the CR-DPF 17 A differential pressure sensor 30 for detecting the differential pressure between the inlet pressure and the outlet pressure of the DPF 25, a temperature sensor 31a for detecting the inlet temperature of the DPF 25, a temperature sensor 31b for detecting the outlet temperature of the DPF 25, an airflow sensor 32 for detecting the intake flow rate, etc. Is provided.

  FIG. 15 exemplifies the relationship between the PM accumulation amount and the exhaust gas temperature. When the exhaust gas temperature exceeds the reference temperature at which the PM emission amount = the PM combustion amount, the PM fuel amount> the PM emission amount. PM accumulation amount (or differential pressure before and after DPF decreases, but when the exhaust gas temperature is lower than the reference temperature, the PM combustion amount <PM emission amount and the PM accumulation amount increases. If the PM accumulation amount exceeds a predetermined value due to continued operation at an exhaust temperature lower than the required value, forced regeneration is required to avoid deterioration in engine performance. The relationship with the exhaust temperature is the same as the relationship between the PM deposition amount and the exhaust temperature.

  The control unit 20 determines a fuel injection signal (injection amount command and injection timing command) to the injection nozzle based on the normal control map from the engine speed Ne and the engine load q. When it is determined when the forced regeneration of the DPF 25 is necessary, the normal control map is switched to the forced regeneration temperature increase map. When the atmospheric temperature of the CR-DPF 17 falls below a predetermined value (for example, 230 ° C.), the catalyst preheating is performed. In addition to driving means, if necessary, a fuel injection signal for performing after injection at a combustible timing subsequent to the main injection of fuel is determined based on the temperature rise map 1, while the atmospheric temperature of the CR-DPF is When the value is equal to or greater than the predetermined value, a fuel injection signal for performing post-injection is determined based on the temperature increase map 2 at a timing significantly delayed from the main injection.

  As for the catalyst preheating means, the EGR valve 21, the intake throttle valve 14 or the exhaust throttle valve 16, and the turbo bypass opening / closing valve 22 are used for the control of positively increasing the exhaust temperature of the engine 10. When the turbocharger 12 is a variable nozzle type, it is conceivable to control the variable nozzle as catalyst preheating means instead of the turbo bypass opening / closing valve 22.

  Regarding the determination of the time when forced regeneration of the DPF 25 is necessary, the difference between the means for determining the forced regeneration time when the PM accumulation amount (estimated value) of the DPF 25 is equal to or greater than a predetermined value (S2 in FIG. 2) and the CR-DPF 17 Means (S4 in FIG. 2) for determining the forced regeneration timing when the pressure (or inlet pressure of the CR-DPF 17) is equal to or higher than a predetermined value, and the operation time (or operation) measured from the completion of the forced regeneration based on the PM accumulation amount When the distance) reaches the interval set for forced regeneration, means for determining the forced regeneration time when there is no forced regeneration history (S6 in FIG. 2) and operation time (or driving distance or number of forced regenerations) Means for determining forced regeneration when an interval for 0 reset forced regeneration for periodically initializing the PM accumulation amount is reached (S8 in FIG. 2).

  In FIG. 12, T is an interval for forced regeneration, T0int is an interval for 0 reset regeneration, ☆ is 0 reset forced regeneration for each T0int, ○ is forced regeneration based on the PM accumulation amount, and ◇ is an interval for forced regeneration The execution of forced regeneration based on T is illustrated. T1 <T, T3 <T, T2 = T, T4 = T, T5 <T.

  The forced regeneration time of the DPF 25 is determined based on a plurality of such different methods. When any one of these determinations is received, the forced regeneration temperature corresponding to the PM deposition amount is set as a forced regeneration mode corresponding to the determination method at that time. And means for setting the forced regeneration time (S9 in FIG. 2) is set. In the means for determining the forced regeneration time from the differential pressure before and after the CR-DPF 17, level 1 and a higher level 2 are set as predetermined values as criteria for determining the forced regeneration time. The forced regeneration temperature and the forced regeneration temperature corresponding to the PM accumulation amount are set as different forced regeneration modes for each regeneration time determination.

  The forced regeneration mode is for determining the forced regeneration time based on excess PM accumulation, determining the forced regeneration time based on exceeding differential pressure level 1, determining the forced regeneration time based on exceeding differential pressure level 2, and for forced regeneration. It is selected from the determination of the forced regeneration time based on the interval and the determination of the forced regeneration time based on the interval for 0 reset forced regeneration (see FIG. 11). The forced regeneration temperatures Treg1 to Treg5 corresponding to these modes are target temperatures for the temperature rise control based on the map 2, and are set according to the PM accumulation amount (see FIG. 13). The forced regeneration times T1 to T5 are set according to the PM deposition and the forced regeneration temperatures Treg1 to Treg5 (see FIG. 14). When the DPF outlet temperature reaches the forced regeneration temperature Treg1 to T5 and reaches the forced regeneration time T1 to T5, means for canceling the fuel injection control based on the temperature rise map 2 (see S11 and S12 in FIG. 3). ) Is set.

  Regarding the calculation of the PM accumulation amount (S1 in FIG. 2), the excess air ratio is obtained from the intake flow rate (detection signal of the air flow sensor 32) and the fuel flow rate (detection signal of the engine load q), and the smoke concentration is calculated from the excess air ratio. The PM emission amount per unit time is obtained from the smoke concentration and the intake flow rate. On the other hand, based on the PM combustion characteristic map of the DPF, the PM combustion amount per unit time is obtained under the exhaust conditions where the combustion of the deposited PM is started by the oxidation action of the catalyst. Specifically, the space velocity that affects the efficiency of the oxidation reaction by the catalyst is obtained, and the PM combustion rate is obtained from the catalyst temperature of the DPF 25 (the outlet temperature of the DPF 25 or the average value of the inlet temperature and the outlet temperature) and the space velocity. Convert to PM combustion amount per unit time. Then, the PM accumulation amount of the DPF is obtained by sequentially integrating the subtraction value obtained by subtracting the PM combustion amount from the PM emission amount. Since the subtraction value may be negative, processing for correcting the negative subtraction value = 0 is set.

  2 and 3 are flowcharts for explaining the control contents of the control unit 20. In S1, the PM accumulation amount of the DPF 25 is calculated. In S2, it is determined whether the calculated value (estimated amount) of the PM accumulation amount is equal to or greater than a predetermined value (threshold value). In S3, the differential pressure before and after CR-DPF 17 is read. In S4, it is determined whether the differential pressure exceeds level 1 or level 2. In S5, the count value of driving time (or driving distance) is read. In S6, it is determined whether the count value of the driving time (or driving distance) has reached the forced regeneration interval and whether there is no forced regeneration history during that time. In S7, the count value of the driving time (or driving distance or forced regeneration count) is read. In S8, it is determined whether or not the count value of the driving time (or driving distance or the number of forced regenerations) has reached the zero reset forced regeneration interval.

  If the determination of S2 is no, the determination of S4 is no, the determination of S6 is no, and the determination of S8 is no, the process returns to S1. If the determination of S2 is yes or the determination of S4 is yes or the determination of S6 is yes or the determination of S8 is yes, the process proceeds to S9. In S9, the forced regeneration mode is selected depending on whether the forced regeneration timing determination (yes) depends on any of the determinations in S2 to S8. When based on the determination of S2, the forced regeneration temperature Treg1 and the forced regeneration time T1 are set according to the PM deposition amount in the forced regeneration mode corresponding to the excess of the PM deposition amount. Based on the determination of S4, the forced regeneration temperature Treg2 or Treg3 and the forced regeneration time T2 or T3 are deposited in the forced regeneration mode corresponding to the differential pressure level 1 excess or the forced regeneration mode corresponding to the differential pressure level 2 excess. Set according to the amount. When based on the determination of S6, the forced regeneration temperature Treg4 and the forced regeneration time T4 are set according to the PM accumulation amount by the forced regeneration mode corresponding to the forced regeneration interval. When based on the determination of S8, the forced regeneration temperature Treg5 and the forced regeneration time T5 are set according to the PM accumulation amount in the forced regeneration mode corresponding to the zero reset forced regeneration interval.

  In S10, forced regeneration is executed based on the selected forced regeneration mode. When the exhaust gas temperature is sufficient for the oxidation reaction of the catalyst, the fuel injection device is set so that the post-injection is performed at a timing significantly delayed from the main injection based on the temperature increase map 2 while monitoring the outlet temperature of the DPF 25. Control (temperature increase control 2). When operating below the exhaust temperature required for the oxidation reaction of the catalyst, the pre-heating means of the catalyst is controlled while monitoring the ambient temperature of the CR-DPF 17, and if necessary, the main injection is performed based on the temperature rise map 1 Subsequently, the fuel injection device is controlled to perform after injection at a combustible timing (temperature increase control 1). In the after-injection, the amount of heat that is not used for power in the calorific value of the fuel increases and the exhaust temperature rises, so the catalyst of the DPF 25 is also raised to the temperature required for the oxidation treatment of the deposited PM. When the catalyst temperature reaches the temperature required for the oxidation treatment, the temperature rise map 1 is switched to the temperature rise map 2, and post-injection causes the unburned fuel added to the exhaust gas to undergo an oxidation reaction on the catalyst, and the reaction heat causes the catalyst to react. In order to raise temperature, the combustion process of deposition PM is accelerated | stimulated (refer FIG. 10).

  In S11, it is determined whether or not the outlet temperature of the DPF reaches the forced regeneration temperature (threshold value). If the determination in S11 is yes, the process proceeds to S12. If the determination in S11 is no, the determination is repeated until yes. In S12, it is determined whether or not the duration of the DPF outlet temperature equal to or greater than the forced regeneration temperature has reached the forced regeneration time (threshold value). If the determination in S12 is yes, the process proceeds to S13. If the determination in S12 is no, the determination is repeated until yes. In S13, the forced regeneration mode is reset. In S14, the temperature increase control for forced regeneration is canceled and the routine returns to normal fuel injection.

  FIG. 4 is a flowchart for explaining the processing of S1 (see FIG. 2). In S1.1, the excess air ratio is calculated from the intake flow rate and the fuel flow rate. In S1.2, the smoke concentration is obtained from the excess air ratio based on the map. In S1.3, the PM discharge amount is calculated from the smoke concentration and the intake flow rate. Since the relationship between the smoke concentration and the excess air ratio also affects the engine speed Ne, it is preferable to obtain the smoke density from the excess air ratio and the engine speed Ne based on a three-dimensional map.

  In S1.4, the exhaust flow rate = the intake flow rate / the exhaust density is calculated from the intake flow rate and the exhaust density. The exhaust density is determined from the exhaust temperature (average value of the inlet temperature and outlet temperature of the DPF 25) and the differential pressure before and after the CR-DPF 17 based on the assumption that it is equivalent to the air density. In S1.5, space velocity = exhaust flow rate / filter capacity is calculated from the exhaust flow rate and the filter capacity of the DPF 25. In S1.6, the PM combustion speed is obtained based on the map from the space velocity and the ambient temperature of the DPF 25 (the outlet temperature or the inlet temperature of the DPF 25 or the average value of the outlet temperature and the inlet temperature), and the PM combustion per unit time is obtained. Convert to quantity.

  In S1.7, the PM accumulation amount of the DPF 25 is calculated by sequentially integrating the subtraction value obtained by subtracting the PM combustion amount from the PM emission amount. The subtraction value = PM emission amount−PM combustion amount may be negative. In such a case, the subtraction value = 0 is corrected.

  FIG. 5 is a flowchart for explaining the processing of S3 (see FIG. 2). In S3.1, the detection signal of the differential pressure sensor 30 and the detection signals of the temperature sensors 31a and 31b are read. In S3.2, based on the inlet temperature and outlet temperature of the DPF 25, the differential pressure before and after the CR-DPF 17, which is compared with the judgment reference value of the forced regeneration timing, is corrected.

  Since the differential pressure before and after the CR-DPF 17 varies greatly depending on the operating conditions even when the PM accumulation amount of the DPF 25 is the same, the detection of the differential pressure may be limited to specific operating conditions. FIG. 6 is a flowchart for explaining the specific processing. In S3.01, it is determined whether or not the operating state of the engine satisfies the permission condition for detecting the differential pressure. When the determination of S3.01 is yes, the process proceeds to S3.02 and S3.03, and the same processing as S3.1 and S3.2 of FIG. 5 is performed, while when the determination of S3.01 is no, The determination as to whether or not the permission condition for detecting the differential pressure is satisfied is repeated. As a result, the detection value (exhaust pressure or differential pressure) used to determine the forced regeneration time is also stabilized, so that the forced regeneration time can be accurately determined.

  FIG. 7 is a flowchart for explaining the processing of S5 (see FIG. 2). In S5.1, it is determined whether or not forced regeneration is completed. When the determination in S5.1 is yes, in S5.2, the operation time (or operation distance) is counted from 0. In S5.3, the counting (measurement) of the driving time (or driving distance) is processed. In S5.4, it is determined whether or not forced regeneration is started. If the determination in S5.4 is yes, the count value of the driving time (or driving distance) is reset to 0 in S5.5. If the determination in S5.1 is no, repeat the determination of whether forced regeneration is complete. If the determination in S5.4 is no, the process returns to S5.3, and the operation time (or operation distance) counting process is continued.

  FIG. 8 is a flowchart for explaining the processing of S7 (see FIG. 2). In S7.1, it is determined whether or not the zero reset forced regeneration is completed. When the determination in S7.1 is yes, in S7.2, the counting of the driving time (or driving distance or the number of forced regenerations) starts from 0. In S7.3, the counting (measurement) of the driving time (or driving distance or forced regeneration count) is processed. In S7.4, it is determined whether or not zero reset forced regeneration is started. If the determination in S7.4 is yes, the count value of the driving time (or driving distance or the number of forced regenerations) is reset to 0 in S7.5. If the determination in S7.1 is no, the determination whether or not the zero reset forced regeneration is complete is repeated. If the determination in S7.4 is no, the process returns to S7.3 and continues the counting process of the driving time (or driving distance or the number of forced regenerations).

  FIG. 9 is a flowchart for explaining the processing of S10 (see FIG. 2). In S10.1, it is determined whether or not the temperature raising control 1 is in the operating state of the exhaust temperature below the effective lower limit value. If the determination in S10.1 is yes, the process proceeds to S10.2. If the determination in S10.1 is no, in S10.5, while continuing fuel injection based on the normal control map, temperature increase control Wait for transition to 1.

  In S10.2, it is determined whether the exhaust gas temperature is sufficient for the catalyst oxidation reaction. When the determination in S10.2 is yes, in S10.3, the normal control map is switched to the temperature increase map 2 to control the fuel injection device so that post injection is performed at a timing significantly delayed from the main injection. (Temperature rise control 2). On the other hand, when the determination of S10.2 is no, in S10.4, the fuel pre-heating means is controlled, and if necessary, the fuel injection is performed so that after-injection is performed at a combustible timing following the main injection. The apparatus is controlled (temperature increase control 1).

  In the temperature rise control 2 (S10.3), there is no possibility that the ambient temperature of the DPF 25 suddenly rises due to abnormal combustion of the accumulated PM, so when the DPF outlet temperature reaches the upper limit of the allowable range, It is better to set to stop the fuel post-injection.

  The determination of the forced regeneration timing of the DPF 25 is based on the determination method based on the estimation of the PM accumulation amount, the determination method based on the differential pressure level, the determination method based on the forced regeneration interval, and the zero reset forced regeneration interval. The determination method is used in combination, and since these checks work, the probability of avoiding an excessive amount of PM deposition can be increased. The temperature increase control of the CR-DPF 17 is performed until the forced regeneration mode corresponding to these determination methods is selected and the release condition based on the forced regeneration temperature and the forced regeneration time corresponding to the PM accumulation amount is satisfied. For this reason, even if the judgment level of the PM accumulation amount differs depending on the judgment method of the forced regeneration timing, the forced regeneration can be processed efficiently and appropriately with a combustion mode (combustion time and combustion temperature) that matches the PM accumulation amount at that time. Thus, it is possible to prevent deterioration of the fuel efficiency due to excessive forced regeneration and deterioration of the filter and catalyst due to abnormal combustion of the accumulated PM.

  Specifically, as the assumed PM accumulation amount increases, the target temperature (forced regeneration temperature) of the temperature raising control 2 is set lower (see FIG. 13), so that abnormal combustion of the accumulated PM is prevented, Forced regeneration can be controlled efficiently and appropriately. In addition, the deviation between the actual value and the estimated value of the PM accumulation amount is corrected by the regeneration process based on the forced regeneration interval and the regeneration process based on the zero reset forced regeneration interval. It can be maintained at a high level.

  As means for avoiding abnormal combustion of accumulated PM, by controlling the oxygen concentration in the exhaust gas according to the outlet temperature or inlet temperature of the DPF 25 or the average value thereof, the atmospheric temperature of the DPF 25 is kept below the upper limit of the allowable range. It is also possible. In that case, in the control unit 20, the oxygen concentration in the exhaust gas is controlled for the EGR valve 21, the intake throttle valve 14 or the exhaust throttle valve 15, the turbo bypass opening / closing valve 22, or the variable nozzle of the variable nozzle turbocharger. A control function for decreasing the temperature of the DPF 25 according to the temperature rise is set.

  The target of the temperature rise control 2 is not limited to fuel post-injection, and a device for adding fuel to the exhaust passage 15 upstream of the CR-DPF 17 can be set. The target of the temperature raising control 1 may be the use of a device (for example, a retarder brake) for forcibly increasing the engine load in addition to the preheating means described above.

It is a schematic diagram explaining the structure of a system. It is a flowchart explaining the control content of a control unit. It is a flowchart explaining the control content of a control unit. It is a flowchart explaining the control content of a control unit. It is a flowchart explaining the control content of a control unit. It is a flowchart explaining the control content of a control unit. It is a flowchart explaining the control content of a control unit. It is a flowchart explaining the control content of a control unit. It is a flowchart explaining the control content of a control unit. It is a characteristic view explaining the control content of a control unit. It is an example of forced regeneration mode setting which concerns on the control content of a control unit. It is a characteristic view explaining the control content of a control unit. It is a characteristic view explaining the control content of a control unit. It is a characteristic view explaining the control content of a control unit. It is a characteristic view explaining the control content of a control unit.

Explanation of symbols

10 Diesel Engine 11 Intake Passage 12 Turbocharger 14 Intake Throttle Valve 15 Exhaust Passage 16 Exhaust Throttle Valve 17 CR-DPF (Continuous Regenerative Filter Device)
20 Control unit 21 EGR valve 22 Turbo bypass opening / closing valve 25 DPF (CSF)
26 DOC (oxidation catalyst)
30 Differential pressure sensor 31a, 31b Temperature sensor 32 Air flow sensor

Claims (13)

  In an exhaust purification device that collects PM contained in engine exhaust and burns by catalytic action, a means for estimating the amount of PM accumulated on the filter and a forced regeneration time for each filter are determined based on a plurality of different methods. When a determination is made on the means and the forced regeneration time, the forced regeneration temperature and forced regeneration time corresponding to the PM accumulation amount of the filter are set as the forced regeneration mode corresponding to the judgment method, and the forced regeneration time is determined. When this is received, the temperature rise control is forcibly raised based on the forced regeneration mode, and the forced temperature rise control of the filter is canceled when the continuation state where the filter temperature is higher than the forced regeneration temperature reaches the forced regeneration time. And an exhaust gas purifying device.   The means for determining the forced regeneration timing of the filter based on a plurality of different methods is different from the means for determining the forced regeneration timing when the PM accumulation amount of the filter is a predetermined value or more, and the difference between the exhaust pressure upstream of the filter or the difference between before and after the filter. The exhaust emission control device according to claim 1, further comprising means for determining a forced regeneration timing when the pressure is equal to or greater than a predetermined value.   The means for determining the forced regeneration time of the filter based on a plurality of different methods is the means for determining the forced regeneration time when the PM accumulation amount of the filter is equal to or greater than a predetermined value, and the cancellation of the forced temperature rise control of the filter Means for determining the forced regeneration time when the operating time or the driving distance measured from the time reaches the set interval for forced regeneration when there is no forced temperature increase control history of the filter during that time. The exhaust emission control device according to claim 1.   The means for determining the forced regeneration time of the filter based on a plurality of different methods is the means for determining the forced regeneration time when the PM accumulation amount of the filter is equal to or greater than a predetermined value, and the forced time of the filter. 2. Means for determining the forced regeneration timing when the number of times of temperature rise control reaches the set interval for 0 reset forced regeneration for periodically initializing the PM accumulation amount. Exhaust purification equipment.   The means for determining the forced regeneration time of the filter based on a plurality of different methods is the means for determining the forced regeneration time when the PM accumulation amount of the filter is equal to or greater than a predetermined value, and the cancellation of the forced temperature rise control of the filter Means for determining the forced regeneration time when the operating time or driving distance measured from the time reaches the set interval for forced regeneration and there is no forced temperature rise control history during that time, and the operating time or driving distance Or a means for determining a forced regeneration timing when the number of times of forced temperature increase control of the filter reaches an interval set for zero reset forced regeneration that periodically initializes the PM accumulation amount. The exhaust emission control device according to claim 1.   The means for determining the forced regeneration timing when the exhaust pressure upstream of the filter or the differential pressure before and after the filter is equal to or greater than a predetermined value includes a means for setting a plurality of different level values as predetermined values that serve as criteria for determining the forced regeneration timing. The exhaust emission control device according to claim 2, wherein the exhaust purification device is provided.   The means for determining the forced regeneration timing when the exhaust pressure upstream of the filter or the differential pressure before and after the filter is equal to or greater than a predetermined value is a means for limiting the determination based on the exhaust pressure upstream of the filter or the differential pressure before and after the filter to a specific operating condition. The exhaust emission control device according to claim 2, further comprising:   The means for determining the forced regeneration timing when the exhaust pressure upstream of the filter or the differential pressure before and after the filter is greater than or equal to a predetermined value includes means for correcting the exhaust pressure upstream of the filter or the differential pressure before and after the filter by the exhaust temperature. The exhaust emission control device according to claim 2.   The means for estimating the PM accumulation amount of the filter is a means for obtaining the PM emission amount per unit time based on the excess air ratio as the engine operating state, and the PM combustion per unit time based on the filter temperature and space velocity. The exhaust emission control device according to claim 1, further comprising: means for obtaining an amount; and means for obtaining a PM accumulation amount of the filter by sequentially integrating a subtraction value obtained by subtracting the PM combustion amount from the PM emission amount.   When the forced regeneration timing is received, the temperature increase control means for forcibly increasing the filter temperature based on the forced regeneration mode is to preheat the catalyst when the filter temperature falls below a predetermined temperature required for the reaction of the catalyst. Means for performing temperature rise control 1 that actively increases the exhaust temperature of the engine, and a rise in which unburned fuel is added to the exhaust to promote the reaction of the catalyst when the filter temperature is higher than a predetermined temperature required for the reaction of the catalyst. The exhaust emission control device according to claim 1, comprising means for performing temperature control 2.   When the forced regeneration timing is received, the means to perform temperature rise control that forcibly increases the filter temperature based on the forced regeneration mode is the normal control when the engine exhaust temperature or engine load is below the lower limit. The exhaust emission control device according to claim 10, further comprising: a unit that waits for the transition to the temperature rise control 1 while performing the operation.   The means for performing the temperature raising control to forcibly increase the filter temperature based on the forced regeneration mode when receiving the determination of the forced regeneration time, means for stopping the temperature raising control 2 when the exhaust temperature of the engine exceeds the upper limit value, The exhaust emission control device according to claim 10, comprising:   An exhaust emission control device according to any one of claims 1 to 5, further comprising means for positively controlling the amount of oxygen in the exhaust gas so as to keep the exhaust gas temperature downstream of the filter below an upper limit value.

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