JP4070687B2 - Exhaust purification device - Google Patents

Description

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

  In recent years, development of an exhaust purification device has attracted attention as one of the promising means for reducing PM contained in the exhaust of a diesel engine vehicle (see Patent Document 1). The exhaust purification device collects PM contained in the exhaust of the engine on a filter, continuously removes the collected PM by catalytic action, and continuously regenerates it. 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 is not sufficiently continuously regenerated 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 active temperature range of the catalyst, PM that accumulates excessively in the filter may burn rapidly, and the filter is liable to be melted or cracked.

As described above, since the continuous regeneration failure of the exhaust gas purification device causes a serious problem, the amount of PM accumulated in the exhaust gas purification device is managed, and the forced removal of the deposited PM (hereinafter referred to as the accumulated PM) is performed at a necessary time. , Forced regeneration). As a forced regeneration method, fuel is added to the exhaust upstream from the exhaust purification device, and the unburnt fuel is burned by the action of the oxidation catalyst, so that the exhaust is exhausted to a temperature sufficient for burning the deposited PM (550 ° C or higher). Techniques for raising the temperature are widely studied. Also, under conditions where the effect of such an oxidation catalyst cannot be used (exhaust temperature is 230 ° C. or less), EGR, intake / exhaust throttle, turbo bypass, turbo with variable nozzle mechanism (hereinafter referred to as VNT), injection timing The exhaust must be heated to a temperature where catalysis can be used, using various techniques such as retarding and adding after-injection. All these exhaust temperature raising techniques release heat to the exhaust, which is a factor that greatly deteriorates fuel consumption.
JP 2003-155915 A

  In the prior art, the case of stopping the engine due to the driver's intention during forced regeneration is not taken into account. For example, when the engine is started again, the exhaust temperature is raised to a temperature sufficient for PM combustion once again (forced regeneration). This will lead to an increase in fuel cost. Further, since the PM combustion efficiency decreases as the accumulated PM decreases (see FIG. 17), the forced regeneration retry at the end of the forced regeneration period is uneconomical because the PM combustion efficiency with respect to the fuel consumption deterioration rate becomes low (see FIG. 18). .

  An object of the present invention is to provide an exhaust emission control device having a forced regeneration retry control that suppresses deterioration of fuel consumption even when the engine stops during forced regeneration.

According to a first aspect of the present invention, there is provided a filter for collecting particulate matter in exhaust gas from a diesel engine, and forcibly regenerating the filter by removing the particulate matter collected by the filter by a chemical reaction using combustion or a catalyst. In the exhaust emission control device comprising the regeneration control means,
Engine stop determination means for determining stop of the diesel engine;
An elapsed time measuring means for measuring a forced regeneration elapsed time from the start of forced regeneration of the filter until the diesel engine is stopped and forced regeneration of the filter is interrupted;
A time difference measuring means for calculating a difference between a forced regeneration time for completely removing the particulate matter set by the forced regeneration control means and a measured forced regeneration elapsed time;
The forced regeneration control means performs the forced regeneration of the filter at the next diesel engine start based on the difference between the calculated forced regeneration time and the forced regeneration elapsed time ,
When it is determined that the forced regeneration of the filter has been completed, a forced regeneration completion permission time shorter than the forced regeneration time is set, and when the forced regeneration elapsed time is longer than the forced regeneration completion permission time, the next time the diesel engine is started The forced regeneration of the filter is not performed .

In a second aspect based on the first aspect, the forced regeneration completion permission time is a time set in accordance with a PM regeneration rate of the filter.

  In the first aspect of the invention, when forced regeneration is stopped by stopping the engine during forced regeneration of the filter of the exhaust gas purification apparatus, forced regeneration of the filter is continued at the next diesel engine start, so that the filter PM is reliably Can be removed.

In addition , if the forced regeneration elapsed time is longer than the forced regeneration completion permission time, the forced regeneration of the filter is not performed at the next diesel engine start, so by canceling the forced regeneration at the next engine start, Deterioration of fuel consumption can be suppressed, and fuel consumption as a vehicle can be improved.

In the second aspect of the invention , the forced regeneration completion permission time is set as the time set according to the PM regeneration rate of the filter, so that a region where the regeneration efficiency of the filter is low can be avoided.

  In FIG. 1, reference numeral 10 denotes a diesel engine, which includes a common rail fuel injection device (not shown). A compressor 12a, 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 an exhaust purification device 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 exhaust purification device 17 includes a DPF 25 and an oxidation catalyst (DOC) 26. 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 plugged. 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 (CSF) with a catalyst (alumina or the like) is used to set a combustible ignition temperature of PM collected by the partition walls. The DOC 26 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. The catalyst temperature is increased by heat, and combustion of the deposited PM is promoted.

  As a detection means required for control of the control unit 20, a rotation sensor (also serving as a crank angle sensor) for detecting the engine speed Ne and a load sensor for detecting a fuel injection amount q corresponding to the engine load are provided. Further, a differential pressure sensor 30 that detects the differential pressure between the inlet pressure and the outlet pressure of the exhaust purification device 17, a temperature sensor 31a that detects the inlet temperature of the DPF 25, a temperature sensor 31b that detects the outlet temperature of the DPF 25, and an intake air flow rate are detected. An airflow sensor 32 is provided.

  FIG. 2 exemplifies the relationship between the PM accumulation amount (or the differential pressure before and after the DPF) and the exhaust temperature. When the exhaust gas temperature is higher than the reference temperature at which the PM combustion amount is equal to the PM combustion amount, , PM combustion amount> PM emission amount, and PM accumulation amount (or differential pressure before and after DPF) decreases, but when the exhaust gas temperature is lower than the reference temperature, PM combustion amount <PM emission amount and PM accumulation The amount increases. For this reason, if the operation state of the exhaust temperature lower than the reference temperature continues, if the PM accumulation amount exceeds a predetermined value, forced regeneration is necessary to avoid a decrease in engine performance.

  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, and when the ambient temperature of the exhaust purification device 17 falls below a predetermined value (for example, 230 ° C.), In addition to driving the preheating means, if necessary, a fuel injection signal for performing after injection at a combustible timing following main fuel injection is determined based on the temperature increase map 1, while the ambient temperature of the exhaust purification device When is equal to or greater than a 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 open / close valve 22 are used for control to positively increase the exhaust temperature of the engine 10. When the turbocharger 12 is of a variable nozzle type, it is conceivable to control the variable nozzle as a 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, means for determining the forced regeneration time (S2 in FIG. 3) when the PM accumulation amount (estimated amount) of the DPF 25 is equal to or greater than a predetermined value, and the differential pressure across the DPF 25 ( Alternatively, a means for determining the forced regeneration timing (S5 in FIG. 3) when the inlet pressure of the exhaust gas purification device 17 is equal to or higher than a predetermined value, and an operation time (or operation distance) measured from completion of the forced regeneration based on the PM accumulation amount. ) Reaches an interval set for forced regeneration, and means for determining the forced regeneration time (S7 in FIG. 3) when there is no forced regeneration history, and the operation time (or driving distance or the number of forced regenerations) Means (S9 in FIG. 3) for determining forced regeneration when the zero reset forced regeneration interval for periodically initializing the PM accumulation amount is reached.

  In FIG. 5, 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 timing of the DPF 25 is determined based on such a plurality of different methods, and when any one of these determinations is received, the forced regeneration temperature corresponding to the PM deposition amount as a forced regeneration mode corresponding to the determination method at that time. And means for setting the forced regeneration time (S10 in FIG. 3) is set. In the means for determining the forced regeneration timing from the differential pressure before and after the DPF 25 (or the inlet pressure of the exhaust gas purification device 17), level 1 and level 2 higher than this are set as predetermined values that serve as criteria for determining the forced regeneration timing. The forced regeneration temperature and the forced regeneration temperature corresponding to the PM accumulation amount are set as different forced regeneration modes for each judgment of the forced regeneration time based on the level 1 and the level 2.

  The forced regeneration mode is a forced regeneration timing determination based on an excess of the PM accumulation amount, a forced regeneration timing determination based on an excess of the differential pressure level 1, a forced regeneration timing determination based on an excess of the differential pressure level 2, and a 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. 6). The forced regeneration temperatures Treg1 to Treg5 corresponding to these modes are target temperatures for temperature increase control based on the map 2, and are set according to the PM accumulation amount (see FIG. 7). The forced regeneration times T1 to T5 are set according to the PM deposition and forced regeneration temperatures Treg1 to Treg5 (see FIG. 8). When the average state of the detected temperatures of the temperature sensors 31a and 31b and the detected temperature of the temperature sensors 31a and 31b reaches the forced regeneration temperatures Treg1 to Treg5 or more reaches the forced regeneration times T1 to T5, the temperature rise map 2 is used. A means (see S12 and S13 in FIG. 3) for canceling the fuel injection control is set.

  Regarding the calculation of the PM accumulation amount (S1 in FIG. 3), 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, the intake flow rate, and the fuel 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 condition where the combustion of the deposited PM is started by the oxidizing action of the catalyst. Specifically, the space velocity that affects the efficiency of the oxidation reaction by the catalyst is obtained, the catalyst temperature of the DPF 25 (the inlet temperature of the DPF 25, the outlet temperature of the DPF 25, or the average value of the inlet temperature and the outlet temperature of the DPF 25) and the space velocity. From this, the PM combustion rate is obtained and converted into a 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.

  3 and 4 show the control contents of the control unit 20, specifically, forced regeneration control, and forced regeneration control performed at the next engine start after the engine is stopped during forced regeneration, which is a characteristic control of the present invention. It is a flowchart explaining (forced regeneration retry control).

  In S1, the PM accumulation amount of the DPF 25 is calculated. The calculation of the PM deposition amount will be described later in detail with reference to FIG. 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 subsequent S4, it is determined whether or not the differential pressure determination condition before and after the exhaust gas purification device 17 is satisfied. If the determination is yes, the process proceeds to S5, and if no, the process proceeds to S7.

  In S4, the differential pressure across the exhaust purification device 17 is read. The calculation of the front-rear differential pressure will be described with reference to FIG. In S5, it is determined whether or not the differential pressure exceeds level 1 or level 2. In S6, the count value of driving time (or driving distance) is read. The reading of the count value will be described later with reference to FIG. In S7, it is determined whether or not the count value of the driving time (or driving distance) has reached the forced regeneration interval. In S8, the count value of driving time (or driving distance or forced regeneration) is read. The reading of the count value will be described later with reference to FIG. In S9, 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 S5 is no, the determination of S7 is no, and the determination of S9 is no, the process returns to S1. If the determination of S2 is yes or S5 is yes or S7 is yes or the determination of S9 is yes, the process proceeds to S10. In S10, the forced regeneration mode is selected depending on whether the forced regeneration timing determination (yes) depends on any of the determinations in S2 to S9. 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. In the case of the determination in S5, the forced regeneration temperature Treg2 or Treg3 and the forced regeneration time T2 or T3 are accumulated in the PM by the forced regeneration mode corresponding to exceeding the differential pressure level 1 or the forced regeneration mode corresponding to exceeding the differential pressure level 2. Set according to the amount. When based on the determination in S7, the forced regeneration temperature Treg4 and the forced regeneration time T4 are set according to the PM accumulation amount in the forced regeneration mode corresponding to the forced regeneration interval. When based on the determination of S9, 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 S11, forced regeneration is executed based on the selected forced regeneration mode. The forced regeneration control will be described later with reference to FIG. When the exhaust gas temperature is sufficient for the oxidation reaction of the catalyst, the main injection is performed on the basis of the temperature increase map 2 while monitoring the detected temperature of the temperature sensors 31a and 31b and the average value of the detected temperatures of the temperature sensors 31a and 31b. The fuel injection device is controlled so as to perform the post injection at a timing significantly delayed from the start (temperature increase control 2). In the operating state below the exhaust temperature required for the oxidation reaction of the catalyst, the catalyst preheating means is controlled while monitoring the ambient temperature of the exhaust purification device 17, and if necessary, the main temperature is based on the temperature increase map 1. The fuel injection device is controlled so as to perform after injection at a combustible timing following injection (temperature increase control 1). In the after-injection, the amount of heat not used for power in the calorific value of the fuel increases and the exhaust gas temperature rises, so that the catalyst of the DPF 25 is also raised to the temperature necessary 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. 9).

  In S12, it is determined whether or not the outlet temperature of the DPF reaches the forced regeneration temperature (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, 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 S13 is yes, the process proceeds to S14. If the determination in S13 is no, the determination is repeated until yes. In S14, the forced regeneration mode is reset. In S15, the temperature increase control for forced regeneration is canceled and the routine returns to normal fuel injection.

  S16 and subsequent steps subsequent to S15 are flowcharts for explaining forced regeneration control that is performed at the next engine start when the engine 10 is stopped during forced regeneration.

  First, in S16, it is determined whether or not the main switch for stopping the engine 10 has been turned off. If yes, the process proceeds to S17. If no, the engine 10 is in operation and the process returns to S1, and normal forced regeneration control is performed. repeat.

  In S17, it is determined whether or not forced regeneration is being performed. If the forced regeneration is being performed, the process proceeds to S18, and if the forced regeneration is not being performed, the control is terminated. In subsequent S18, it is determined whether or not the forced regeneration elapsed time in which forced regeneration has been performed exceeds the forced regeneration completion permission time. Here, the forced regeneration completion permission time is set from the relationship between the filter regeneration rate and the forced regeneration elapsed time as shown in FIG.

  As shown in FIG. 10, the filter regeneration efficiency decreases immediately after the forced regeneration is started and before the forced regeneration is completed. Therefore, by setting the forced regeneration completion permission time to a regeneration rate at which the regeneration efficiency decreases, the PM in the filter is substantially eliminated and the forced regeneration elapsed time is prevented from becoming longer.

  If the determination in S18 is yes, the process proceeds to S19, where it is determined that forced regeneration has been completed, and in S20 that follows, it is determined that forced regeneration is unnecessary at the next engine 10 start, the forced regeneration elapsed time is reset, and the control ends. .

  On the other hand, if the determination in S18 is no, the process proceeds to S21, and it is determined that the forced regeneration retry control for continuing the forced regeneration at the next start of the engine 10 is necessary, and the remaining time for forced regeneration is calculated in S22. Here, the forced regeneration remaining time is calculated by subtracting the forced regeneration elapsed time from the forced regeneration time set in the forced regeneration mode. In S23, the remaining forced regeneration time is stored in the memory. In this way, the forced regeneration retry control according to the forced regeneration remaining time is performed at the next engine 10 start.

  As described above, when forced regeneration is stopped by stopping the engine during forced regeneration of the filter, forced regeneration is continuously performed when the engine 10 is started next time, so that PM of the filter can be reliably removed.

  In addition, if there is an engine stop request during forced regeneration, the forced regeneration elapsed time is set to a predetermined time to determine whether to perform forced regeneration retry at the next engine start according to the forced regeneration elapsed time until engine stop. If it exceeds (the forced regeneration completion permission time), the forced regeneration retry is not performed at the next engine start, so that deterioration of the fuel efficiency due to the forced regeneration retry can be suppressed, and the fuel efficiency of the vehicle can be improved.

  FIG. 11 is a flowchart for explaining the processing of S1 (see FIG. 3). In S1.1, the excess air ratio is calculated from the intake air flow rate and the fuel flow rate. In S1.2, the smoke concentration is obtained based on the map from the excess air ratio. In S1.3, the PM discharge amount is calculated from the smoke concentration, the intake flow rate, and the fuel flow rate. Since the relationship between the smoke concentration and the excess air ratio is also influenced by 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, exhaust flow rate = intake flow rate / exhaust density is calculated from the intake flow rate and the exhaust density. Based on the assumption that the density of the exhaust is equal to the density of the air, the exhaust temperature (the average value of the detected temperatures of the temperature sensors 31a and 31b and the detected temperature of the temperature sensors 31a and 31b) and the exhaust purification device 17 Obtained from the differential pressure. In S1.5, space velocity = exhaust gas flow rate / filter capacity is calculated from the exhaust gas 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 detected temperature of the temperature sensors 31a and 31b and the detected temperature of the temperature sensors 31a and 31b), and the unit per unit time Convert to the amount of PM combustion.

  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. 12 is a flowchart for explaining the process of S4 (see FIG. 3). In S4.1, the detection signal of the differential pressure sensor 30 and the detection signals of the temperature sensors 31a and 31b are read. In S4.2, based on the inlet temperature and outlet temperature of the DPF 25, the differential pressure before and after the exhaust purification device 17 is compared with the judgment reference value of the forced regeneration timing.

  Since the differential pressure before and after the exhaust gas purification device 17 varies greatly depending on the operating conditions even when the PM accumulation amount of the DPF 25 is the same, it is conceivable to limit the detection of the differential pressure to specific operating conditions. FIG. 13 is a flowchart for explaining the specific processing. In S4.01, 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 S4.01 is yes, the process proceeds to S4.02 and S4.03, and the same processing as S4.1 and S4.2 of FIG. 12 is performed, while when the determination of S4.01 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. 14 is a flowchart for explaining the processing of S6 (see FIG. 3). In S6.1, it is determined whether or not forced regeneration is completed. When the determination in S6.1 is yes, the operation time (or operation distance) is counted from 0 in S6.2. In S6.3, the counting (measurement) of the driving time (or driving distance) is processed. In S6.4, it is determined whether or not forced regeneration is started. When the determination in S6.4 is yes, the count value of the driving time (or driving distance) is reset to 0 in S6.5. If the determination in S6.1 is no, the determination of whether or not forced regeneration is complete is repeated. When the determination in S6.4 is no, the process returns to S6.3 and the operation time (or operation distance) counting process is continued.

  FIG. 15 is a flowchart for explaining the process of S8 (see FIG. 3). In S8.1, it is determined whether or not the zero reset forced regeneration is completed. When the determination in S8.1 is yes, in S8.2, the counting of the driving time (or the driving distance or the number of forced regenerations) is started from 0. In S8.3, a count (measurement) of driving time (or driving distance or forced regeneration count) is processed. In S8.4, it is determined whether or not zero reset forced regeneration is started. If the determination in S8.4 is yes, the count value of the driving time (or driving distance or forced regeneration count) is reset to 0 in S8.5. If the determination in S8.1 is no, the determination of whether or not the zero reset forced regeneration is complete is repeated. If the determination in S8.4 is no, the process returns to S8.3, and the operation time (or operation distance or forced regeneration count) counting process is continued.

  FIG. 16 is a flowchart for explaining the processing of S11 (see FIG. 3). In S11.1, 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 S11.1 is yes, the process proceeds to S11.2. If the determination in S11.1 is no, the temperature increase control is performed in S11.5 while continuing fuel injection based on the normal control map. Wait for transition to 1.

  In S11.2, it is determined whether or not the exhaust gas temperature is sufficient for the catalyst oxidation reaction. When the determination in S11.2 is yes, in S11.3, the fuel injection device is controlled to perform post-injection at a timing significantly delayed from main injection by switching the normal control map to the temperature increase map 2 in S11.3. (Temperature rise control 2). On the other hand, when the determination in S11.2 is no, the catalyst preheating means is controlled, and if necessary, the fuel injection device is controlled to perform after injection at a combustible timing following the main injection (if necessary) Temperature rise control 1).

  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. Since the determination method is used in combination, and these checks work, the probability of avoiding an excessive PM deposition amount can be increased. The temperature increase control of the exhaust emission control device 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 deposition 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 deposition amount at that time. As a result, 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 deposition amount increases, the target temperature (forced regeneration temperature) of the temperature raising control 2 is set lower and the forced regeneration time is set longer, so that abnormal combustion of the deposited PM is prevented, Forced regeneration can be controlled efficiently and appropriately. In addition, since 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, the estimation accuracy of the PM accumulation amount is also improved. It can be maintained at a high level.

  As a means for avoiding abnormal combustion of the deposited PM, it is conceivable to control the oxygen concentration in the exhaust gas according to the outlet temperature of the DPF 25, thereby suppressing the ambient temperature of the DPF 25 to be equal to or lower than the upper limit value of the allowable range. In that case, in the control unit, depending on the temperature rise of the DPF 25, the oxygen concentration in the exhaust is targeted for the EGR valve, the intake throttle valve or the exhaust throttle valve, the on-off valve of the turbo bypass or the variable nozzle of the variable nozzle turbocharger, etc. Thus, a control function that decreases the value is set.

  The target of the temperature raising control 2 is not limited to the fuel post-injection, and a fuel addition device to the exhaust passage upstream of the exhaust purification device can also be set. In addition to the preheating means described above, use of a braking device (such as a drive system retarder brake) that increases the engine load is also conceivable as the target of the temperature raising control 2.

  Since the forced regeneration retry can be performed efficiently even when the engine is stopped during the forced regeneration of the exhaust purification device, it is useful for a low-pollution diesel vehicle.

It is a schematic diagram explaining the composition of an exhaust emission control device. It is a figure which shows the relationship between PM deposition amount and exhaust temperature. It is a flowchart explaining the content of the forced regeneration control of a control unit. It is a flowchart explaining the content of the forced regeneration control of a control unit similarly. It is a figure which shows the relationship between driving time and a forced regeneration interval. It is a figure which shows an example of the forced regeneration time and forced regeneration temperature for every forced regeneration mode. It is a figure which shows the relationship between forced regeneration temperature and PM deposition amount. It is an example of the map of forced regeneration temperature. It is a figure explaining temperature rising control. It is a figure which shows the relationship between a filter regeneration rate and forced regeneration elapsed time. It is a flowchart which calculates PM deposition amount. It is a flowchart which confirms a front-back differential pressure difference. It is a flowchart which confirms the differential pressure difference before and behind in consideration of driving conditions. It is a flowchart which confirms a forced regeneration interval. It is a flowchart which confirms a 0 reset forced regeneration interval. It is a flowchart for demonstrating forced regeneration implementation. It is a figure which shows the relationship between PM combustion efficiency and PM deposition amount. It is a figure which shows the relationship between forced regeneration elapsed time and PM combustion efficiency.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Diesel engine 11 Intake passage 12 Turbo supercharger 14 Intake throttle valve 15 Exhaust passage 16 Exhaust throttle valve 17 Exhaust purification device 20 Control unit 21 EGR valve 22 Open / close valve of turbo bypass 25 DPF
26 Oxidation catalyst 30 Differential pressure sensor 31a, 31b Temperature sensor 32 Air flow sensor

Claims (2)

Exhaust gas comprising a filter for collecting particulate matter in exhaust gas from a diesel engine, and forced regeneration control means for forcibly regenerating the filter by burning and removing the particulate matter collected by the filter by a chemical reaction using a catalyst. In the purification device,
Engine stop determination means for determining stop of the diesel engine;
An elapsed time measuring means for measuring a forced regeneration elapsed time from the start of forced regeneration of the filter until the diesel engine is stopped and forced regeneration of the filter is interrupted;
A time difference measuring means for calculating a difference between a forced regeneration time for completely removing the particulate matter set by the forced regeneration control means and a measured forced regeneration elapsed time;
The forced regeneration control means performs the forced regeneration of the filter at the next diesel engine start based on the difference between the calculated forced regeneration time and the forced regeneration elapsed time ,
When it is determined that the forced regeneration of the filter has been completed, a forced regeneration completion permission time shorter than the forced regeneration time is set, and when the forced regeneration elapsed time is longer than the forced regeneration completion permission time, the next time the diesel engine is started exhaust gas purification apparatus characterized by not carrying out the forced regeneration of the filter. The exhaust purification device according to claim 1, wherein the forced regeneration completion permission time is a time set according to a PM regeneration rate of the filter .

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