JP2005054631A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for detecting the abnormality of a PM exhaust amount resulting from an engine. <P>SOLUTION: A regeneration frequent time when a regeneration interval to determine a forcible regeneration timing for a DPF 25 in accordance therewith is shorter than a threshold value is determined, a continuous regeneration frequency where the regeneration frequent time continuously occurs is counted, the abnormality of the PM exhaust amount resulting from the engine 10 is determined when the counted continuous regeneration frequency exceeds a threshold value. <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 of a diesel engine.

In recent years, development of an exhaust emission control device (CR-DPF) has attracted attention as one promising means for reducing PM contained in exhaust gas from a diesel engine (see Patent Documents 1 to 7). The exhaust purification device collects PM contained in the exhaust of the engine in a filter and continuously burns and removes the collected PM by 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 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 enters the activation temperature range of the catalyst when the amount of PM accumulated on the filter is excessive, there is a possibility that the PM accumulated excessively on the filter may burn rapidly, It tends to cause melting and cracking. Therefore, forced removal of 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 JP 2003-83035 A JP 2003-49633 A

  However, these perform control to detect the amount of PM accumulated in the filter from the engine, but management of the engine that exhausts PM is not performed, and PM is not generated due to engine abnormality or deterioration. There was a problem that it was not possible to cope with a large number of occurrences.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an exhaust emission control device that detects an abnormality in PM emission due to an engine.

  The first invention is applied to an exhaust emission control device that collects PM contained in engine exhaust gas in a filter and burns the collected PM by catalytic action.

  The first determination means for determining the forced regeneration timing of the filter when the exhaust pressure upstream of the filter or the differential pressure before and after the filter exceeds the set value, and the forced regeneration of the filter based on a method different from the first determination means Second determination means for determining the timing, reproduction interval time determination means for determining the regeneration frequent time when the regeneration interval time for determining the forced regeneration time of the filter is shorter than the threshold, and the continuous regeneration time continuously It is characterized by comprising counting means for counting the number of regenerations and engine abnormality determining means for judging that the PM emission amount is abnormal when the counted number of continuous regenerations exceeds a threshold value.

  The second invention is characterized in that, in the first invention, the second judging means judges the forced regeneration time when the PM accumulation amount of the filter is not less than a predetermined value.

  According to a third aspect, in the first aspect, the second determination means performs the filter operation when the operation time or the operation distance measured from the forced release of the temperature rise control reaches the set interval for forced regeneration. The forced regeneration timing is determined when there is no history of forced temperature increase control.

  In a fourth aspect based on the first aspect, the second determination means is for 0 reset forced regeneration in which the operation time or the operation distance or the number of times of forced temperature increase control of the filter initializes the PM accumulation amount periodically. A feature is that the forced regeneration time is determined when the set interval is reached.

  According to the first invention, when a large amount of PM is generated due to engine abnormality or deterioration, the differential pressure before and after the filter is increased, and the forced regeneration start is determined. Since it becomes shorter than the normal interval (for example, 50 hours), the number of continuous regenerations that occur continuously during this frequent regeneration is counted, and when the counted number of continuous regenerations exceeds the threshold, the PM emission abnormality caused by the engine is abnormal Can be judged accurately. By notifying the determination result, it is urged to inspect and repair the engine, and it is possible to prevent the engine from being left while the fuel consumption of the engine is deteriorated.

  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 for determining the forced regeneration timing. It is possible to increase the probability of avoiding an excessive amount of PM deposition.

  In the determination method based on the PM accumulation amount, the regeneration interval time becomes equal to or longer than a normal interval (for example, 50 hours), so the continuous determination number is cleared, and this case is erroneously determined as an abnormality in the PM emission amount caused by the engine. You can avoid that.

  In the third invention, the determination method based on the exhaust pressure upstream of the filter or the differential pressure before and after the filter and the determination method based on the interval for forced regeneration are used in combination to determine the forced regeneration timing, and these checks work. It is possible to increase the probability that the PM accumulation amount of the filter can be avoided in advance.

  In the determination method based on the interval for forced regeneration, since the regeneration interval time is longer than a normal interval (for example, 50 hours), the number of continuous determinations is cleared, and this case is mistaken for an abnormality in PM emission due to the engine. Judgment can be avoided.

  In the fourth aspect of the invention, the determination method based on the exhaust pressure upstream of the filter or the differential pressure before and after the filter and the determination method based on the zero reset forced regeneration interval are used in combination to determine the forced regeneration timing. Therefore, it is possible to increase the probability of avoiding an excessive amount of PM accumulated on the filter.

  In the determination method based on the interval for 0 reset forced regeneration, the regeneration interval time is equal to or greater than a normal interval (for example, 50 hours), so the number of continuous determinations is cleared, and this case is regarded as abnormal PM emission due to the engine. Incorrect determination can be avoided.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  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 (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 25 and an oxidation catalyst 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 with a catalyst (alumina or the like) is employed in order to set the combustible ignition temperature of PM collected in the partition walls to a low value. The oxidation catalyst 26 is formed in the honeycomb structure carrying the catalyst, and mainly oxidizes HC (hydrocarbon) contained in the exhaust gas that passes through the flow path partitioned in a lattice shape of the honeycomb structure. The heat of reaction raises 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 the engine load q, the inlet pressure and outlet pressure of the CR-DPF 17 There are provided a differential pressure sensor 30 for detecting the differential pressure, 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 air flow sensor 32 for detecting the intake flow rate, and the like.

  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 the time when the forced regeneration of the DPF 25 is necessary is determined, the normal control map is switched to the temperature increase map for forced regeneration. 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 the means, if necessary, a fuel injection signal for performing after injection at a combustible timing following the main injection of fuel is determined based on the temperature increase map, while the atmospheric temperature of the CR-DPF is predetermined. When the value is equal to or greater than the value, a fuel injection signal for performing post injection at a timing significantly delayed from the main injection is determined based on the temperature increase map.

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

  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 mode (see FIG. 4) corresponding to the determination method at that time is used as the PM accumulation amount. A means (S9 in FIG. 2) for setting the corresponding forced regeneration temperature and forced regeneration time 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 CR-DPF 17), a level 1 and a level 2 higher than this are set as a predetermined value as a criterion for the forced regeneration timing. 1. The forced regeneration time and the forced regeneration temperature corresponding to the PM accumulation amount are set as different forced regeneration modes for each forced regeneration time determination based on Level 1 and Level 2.

  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 condition where the combustion of the deposited PM is started by the oxidation 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 calculated 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 of the DPF 25) and the space velocity. Is 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.

  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. In S3, the differential pressure before and after the DPF 25 is read. In S4, it is determined whether or not the differential pressure exceeds level 1 or level 2. In S5, the measured value of driving time (or driving distance) is read. In S6, it is determined whether or not the measured value of the driving time (or driving distance) has reached the forced regeneration interval. In S7, a measured value of driving time (or driving distance or forced regeneration count) is read. In S8, it is determined whether or not the measured value of the driving time (or the 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. When 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 according to whether the forced regeneration timing determination (yes) depends on any of the determinations in S2 to S84 (see FIG. 4). 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 in 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 controlled so that the post injection is performed at a timing substantially delayed from the main injection based on the temperature rise map while monitoring the outlet temperature of the DPF 25 To do. When operating below the exhaust temperature required for the oxidation reaction of the catalyst, the catalyst preheating means is controlled while monitoring the atmospheric temperature of the CR-DPF 17, and if necessary, the main injection is performed based on the temperature increase map. Subsequently, the fuel injection device is controlled to perform after injection at a combustible timing. 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 unburned fuel added to the exhaust is oxidized on the catalyst by post-injection by switching the temperature increase map, and the catalyst heat is raised by the reaction heat. The combustion process of the deposited PM is promoted.

  In S11, it is determined whether or not the outlet temperature of the DPF 25 reaches the forced regeneration temperature. If the determination in S11 is yes, the process proceeds to S12, while if the determination in S11 is no, the determination is repeated until yes. In S12, it is determined whether or not the duration time at which the outlet temperature of the DPF 25 is equal to or higher than the forced regeneration temperature has reached the forced regeneration time. 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.

  The system abnormality of the CR-DPF 17 including the differential pressure sensor 30, the temperature sensor 31a, the temperature sensor 31b, the air flow sensor 32, etc. is processed in another routine, and it is not shown when it is determined that there is an abnormality in this system. An abnormal lamp is lit to inform you of this.

  In the present invention, in order to detect an abnormality in the PM emission amount caused by the engine 10, a regeneration interval time determining means for determining a regeneration frequent time in which the regeneration interval time for determining the forced regeneration timing of the DPF 25 is shorter than a threshold value. And a counting means for counting the number of times of continuous regeneration that occurs frequently during regeneration, and an engine abnormality determination for determining that the PM emission amount is abnormal due to the engine 10 when the counted number of continuous regeneration exceeds a threshold value. Means. If it is determined that the playback interval time is equal to or greater than the threshold value, the continuous playback count is cleared.

  The flowchart of FIG. 5 shows a routine for detecting an abnormality in the PM emission amount caused by the engine 10 and is executed in the control unit 20 at regular intervals.

  This will be described. First, in step 1, it is determined whether or not there is a determination of the forced regeneration start of the DPF 25.

  When the forced regeneration start is determined, the process proceeds to step 2 to measure the regeneration interval time at which the forced regeneration timing of the DPF 25 is determined, and the regeneration frequent time when the regeneration interval time becomes shorter than a threshold (for example, 50 hours). Determine whether or not. The process performed in step 2 corresponds to a reproduction interval time determination unit.

  If it is determined in step 2 that the reproduction is frequent, the process proceeds to step 3 to count the number of continuous reproductions in which the frequent reproduction occurs continuously. Note that the processing performed in step 2 corresponds to counting means.

  On the other hand, if it is determined in step 2 that the playback interval time is equal to or greater than the threshold, the number of continuous playbacks is cleared.

  Subsequently, the process proceeds to step 4 to determine whether or not the counted number of continuous reproductions exceeds a threshold value (for example, 3 times). The process performed in step 4 corresponds to engine abnormality determination means.

  Here, when the number of times of continuous reproduction is equal to or less than the threshold value, the process proceeds to step 6 to execute forced regeneration based on the above-described forced regeneration mode.

  On the other hand, if the number of continuous regenerations exceeds the threshold value, it is determined that an abnormality in the PM emission amount caused by the engine 10 has occurred, and the process proceeds to step 5 to turn on the abnormal lamp. This prompts the engine 10 to be inspected and repaired, and can prevent the engine 10 from being left with the fuel economy and the like deteriorated.

  As described above, when a large amount of PM is generated due to an abnormality or deterioration of the engine, the differential pressure before and after the DPF 25 is increased and the forced regeneration start is determined, and this regeneration interval time is normal. Since it becomes shorter than the interval (for example, 50 hours), the number of continuous regenerations that occur continuously during this regeneration frequency is counted, and when the counted number of continuous regenerations exceeds a threshold value, an abnormality in PM emission caused by the engine 10 is detected. Can be judged accurately.

On the other hand, when the following conditions are satisfied and the forced regeneration start determination of the DPF 25 is performed, the regeneration interval time becomes equal to or longer than a normal interval (for example, 50 hours), and thus the continuous determination count is cleared. .
-When the amount of accumulated PM (estimated amount) in the DPF 25 exceeds a predetermined value and forced regeneration is reached.
-When the operation time (or operation distance) measured from the completion of forced regeneration based on the PM accumulation amount reaches an interval set for forced regeneration, forced regeneration is reached when there is no history of forced regeneration.
-When the operation time (or operation distance or the number of forced regenerations) reaches the zero reset forced regeneration interval that periodically initializes the PM accumulation amount and reaches forced regeneration.
Thereby, it can be avoided that these cases are erroneously determined as abnormal PM emission due to the engine 10.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The present invention can be used for an exhaust purification device provided in a diesel engine.

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 an example of forced regeneration mode setting which concerns on the control content of a control unit. It is a flowchart explaining the control content of a control unit.

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 CR-DPF (Exhaust gas purification device)
20 Control unit 21 EGR valve 22 Open / close valve for turbo bypass 25 DPF (filter)
26 Oxidation catalyst 30 Differential pressure sensor 31a, 31b Temperature sensor 32 Air flow sensor

Claims (4)

In an exhaust purification device that collects PM contained in the exhaust of an engine in a filter and burns the collected PM by a catalytic action,
The first determination means for determining the forced regeneration timing of the filter when the exhaust pressure upstream of the filter or the differential pressure before and after the filter exceeds the set value, and the forced regeneration timing of the filter based on a method different from the first determination means. Second determination means for determining, reproduction interval time determining means for determining a regeneration frequent time when the regeneration interval time for determining the forced regeneration timing of the filter is shorter than a threshold, and the number of times of continuous regeneration in which this frequent regeneration time occurs continuously An exhaust emission control device comprising: a counting means for counting the amount of exhaust gas; and an engine abnormality determining means for determining that the PM emission amount is abnormal when the counted number of continuous regenerations exceeds a threshold value.   2. The exhaust emission control device according to claim 1, wherein the second determination unit is configured to determine a forced regeneration timing when a PM accumulation amount of the filter is equal to or greater than a predetermined value.   When the operation time or operation distance measured from the cancellation of the forced temperature rise control of the filter reaches an interval set for forced regeneration, the second determination means has a history of forced temperature rise control of the filter during that time. 2. The exhaust emission control device according to claim 1, wherein the forced regeneration timing is determined when there is not.   The second determination means sets the forced regeneration timing when the operation time or the operation distance or the number of times of forced temperature increase control of the filter reaches an interval set for 0 reset forced regeneration that initializes the PM accumulation amount periodically. The exhaust emission control device according to claim 1, wherein the exhaust gas purification device is configured to determine.

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