JP4235509B2 - Exhaust purification equipment - 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, attention has been focused on the development of a continuous regeneration filter device (CR-DPF) as one of exhaust emission control devices for reducing PM contained in exhaust gas from a diesel engine. The continuous regeneration 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 for regeneration. 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 region of the catalyst when the amount of PM accumulated on the filter is excessive, there is a possibility that PM accumulated excessively on the filter may burn suddenly. It tends to cause melting and cracking. Therefore, forced combustion removal of the deposited PM (forced regeneration of the filter) is performed at a necessary time according to the PM accumulation amount and the differential pressure across the filter. However, it is difficult to control the combustion temperature of the deposited PM, and there is a technique for detecting the combustion temperature during forced regeneration and determining that the filter has melted when the detected temperature exceeds a predetermined temperature (see Patent Document 1). ).
JP 2003-155912 A

  In the prior art, the abnormal state is only estimated from the detected combustion temperature and dealt with, and the cause of the abnormality cannot be specified.

  An object of the present invention is to accurately detect that an abnormality has occurred in forced regeneration control, identify the cause of the abnormality, and maintain the performance of the filter device.

A first aspect of the present invention is an exhaust purification apparatus having a continuously regenerating filter that collects PM contained in engine exhaust and combusts by catalytic action, and a forced regeneration state determining means for determining a forced regeneration state of the filter. In the case where the temperature detecting means for detecting the temperature of the filter, the heating control means for controlling the heating state of the filter according to the detected temperature of the filter at the time of forced regeneration of the filter, and the filter is not in the heating state, The detection temperature of the filter is compared with a predetermined temperature, the counting means for counting the number of times that the detection temperature of the filter exceeds the predetermined temperature, and when the abnormality occurs in the filter when the number of counts exceeds the predetermined number of times Abnormality occurrence determination means for determining.

  In a second aspect based on the first aspect, the predetermined temperature is set according to an abnormal state of the filter.

  In a third aspect based on the second aspect, the predetermined temperature is set according to at least one of an allowable temperature during forced regeneration, a deterioration temperature of the oxidation catalyst, and a melting temperature of the filter.

According to a fourth aspect of the present invention, in any one of the first to third aspects, when the abnormality occurrence determination unit determines that the filter is abnormal, the abnormality notification unit notifies the outside of the abnormality of the filter.

  According to a fifth invention, in the fourth invention, the notification method differs according to the abnormal state of the filter.

  In the first invention, when the filter is not heated, the number of times the detected temperature of the filter exceeds the predetermined temperature is counted, and when the count exceeds the predetermined number, an abnormality has occurred in the filter device. Therefore, it is possible to accurately determine abnormality in the filter device. In addition, since the abnormality determination is performed when the abnormality determination is in forced regeneration and the filter is not in a heated state, the cause of the abnormality can be specified in the engine injection system or the forced regeneration control logic.

  In the second and third inventions, since the predetermined temperature is set according to the abnormal state of the filter, that is, the allowable temperature at the time of forced regeneration, the deterioration temperature of the oxidation catalyst, and the melting temperature of the filter, The state can be recognized, and the countermeasure after the abnormality recognition can be promptly performed.

  According to the fourth aspect of the invention, the abnormality of the filter is surely notified to the driver or the like when the abnormality occurs, so that the driver or the like can recognize the abnormality immediately after the occurrence of the abnormality and the deterioration of the exhaust gas or the deterioration of the fuel consumption due to the abnormality can be recognized. Can be suppressed.

  In the fifth aspect of the invention, since the notification method is changed according to the abnormal state of the filter, the abnormal state of the filter can be recognized when the abnormality of the filter occurs, and the countermeasure after the abnormality recognition can be performed quickly.

  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 a continuous regeneration 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 diesel particulate removing device (DPF) 25 and an oxidation catalyst 26 installed on the upstream side thereof. 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 subsequent to the main injection of fuel is determined, while the CR-DPF ambient temperature is equal to or higher than a predetermined value, A fuel injection signal for performing post injection at a timing significantly delayed from the main injection is determined.

  As the preheating means for the catalyst, 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 to perform control to positively increase the exhaust temperature of the engine 10 to heat the catalyst. . 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. 2) when the PM accumulation amount (estimated amount) of the DPF 25 is equal to or larger than a predetermined value, and the differential pressure across the DPF 25 ( Alternatively, the means for determining the forced regeneration timing when the inlet pressure of the CR-DPF 17 is equal to or greater than a predetermined value (S4 in FIG. 2), and the operation time (or operation distance) measured from the completion of the forced regeneration based on the PM accumulation amount. Means that the forced regeneration timing is determined when there is no forced regeneration history during the interval set for forced regeneration (S6 in FIG. 2) and the operation time (or the driving distance or the number of forced regenerations) is PM Means (S8 in FIG. 2) for determining forced regeneration when the zero reset forced regeneration interval for periodically initializing the accumulation amount is reached is set.

  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 predetermined values 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.

  In 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 obtained from the excess air ratio. The PM emission amount per unit time is obtained from the smoke concentration and the intake air 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, 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.

  FIG. 2 is a flowchart for explaining the control content of the forced regeneration control of the control unit 20, and 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 across the DPF 25 is read. In S4, it is determined whether the front-rear differential pressure has exceeded a predetermined pressure. In S5, the count value of driving time (or driving distance) is read. In S6, it is determined whether or not the count value of the driving time (or driving distance) has reached the forced regeneration interval. In S7, the count value of driving time (or driving distance or forced regeneration) 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. 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 depending on whether the forced regeneration timing determination (yes) depends on any of the determinations in S2 to S8 (see FIG. 3).

  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 as to perform post injection at a timing significantly delayed from the main injection while monitoring the outlet temperature of the DPF 25. In an operating state 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 timing at which combustion is possible following the main injection The fuel injection device is controlled to perform after-injection. 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 post-injection is switched to the post-injection. By the post-injection, the unburned fuel added to the exhaust is oxidized on the catalyst, and the reaction heat increases the catalyst temperature. As a result, the combustion process of the deposited PM is promoted.

  In S11, it is determined whether or not the outlet temperature of the DPF 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.

  FIG. 4 is a flowchart for explaining the control contents of the abnormally high temperature determination of the CR-DPF 17 performed during forced regeneration, which is characteristic control of the present invention. This control content is controlled by the control unit 20 and is performed when the CR-DPF 17 is in the forced regeneration state.

  In S20, it is determined whether or not the CR-DPF 17 is in the forced regeneration state, for example, based on whether or not the forced regeneration mode is set. If yes, the process proceeds to S21, and if no, the control is terminated. In S21, the detected temperature of the temperature sensor 31b that detects the outlet temperature of the DPF 25 is read, and it is determined whether or not the detected temperature exceeds a first predetermined temperature (for example, 650 ° C.). Here, the first predetermined temperature is the regeneration temperature in the forced regeneration mode, and it is determined in this step whether or not the DPF 25 should be heated. If the temperature exceeds the first predetermined temperature, the process proceeds to S22, where temperature control is performed based on a standard map for performing temperature control for decreasing the temperature of the DPF 25, and the process proceeds to S24. On the other hand, if the temperature is equal to or lower than the first predetermined temperature, the process proceeds to S23, and the temperature control of the DPF 25 is performed based on the temperature increase map for heating the DPF 25.

  In S24, the temperature of the DPF 25 whose temperature is controlled based on the standard map in S22 is read from the sensor 31b, and it is determined whether or not the detected temperature of the DPF 25 exceeds the second predetermined temperature. Here, the second predetermined temperature is an allowable upper limit temperature of the forced regeneration temperature, and is set to a temperature at which the DPF 25 does not melt, for example, 700 ° C. When the detected temperature exceeds the second predetermined temperature, the process proceeds to S25.

  In S25, the number of times that the detected temperature of the DPF 25 exceeds the second predetermined temperature is counted (see FIGS. 5 and 6). FIG. 5 shows a normal temperature control state, and FIG. 6 shows a state where an abnormality has occurred in the temperature state of the DPF 25. In subsequent S26, it is determined whether or not the count number exceeds the first predetermined number. Here, the first predetermined number of times is set to 3 times, for example. That is, the fact that the temperature of the DPF 25 exceeds the second predetermined temperature for the first predetermined number of times despite the temperature control for lowering the temperature of the DPF 25 based on the standard map means that the temperature control of the DPF 25 If an abnormality has occurred and the first predetermined number of times has been exceeded, the driver is notified of the abnormality of the DPF 25 by, for example, the lighting of a lamp or the sound of a buzzer in S27.

  Here, although the temperature control of the DPF 25 is a temperature control for lowering the DPF 25, the temperature of the DPF 25 is rising, so the cause of the abnormality in the temperature control of the DPF 25 is the amount of fuel to the engine 10 and the fuel It can be identified as an abnormality in the injection system of the engine, which is an abnormality in the injection timing, or an abnormality in the forced regeneration control logic of the DPF 25, and the time from identification of the cause of the abnormality to resolution of the problem can be shortened. Thereby, the purification performance as a system of CR-DPF17 can be maintained, and the deterioration of exhaust gas and the deterioration of fuel consumption due to abnormality of DPF25 can be suppressed.

  Although the number of times the second predetermined temperature has been exceeded is counted in S26, the time exceeding the second predetermined temperature may be measured, and it may be determined that an abnormality has occurred in the DPF 25 when the predetermined time is exceeded.

  FIG. 7 is a flowchart for explaining the control contents of the abnormal high temperature determination of the CR-DPF 17 performed during the forced regeneration as the second embodiment. This control content is controlled by the control unit 20 and is performed when the CR-DPF 17 is in the forced regeneration state.

  In contrast to the control of the first embodiment shown in FIG. 4, the present embodiment is different in that the control is made to determine the influence of the abnormal temperature of the CR-DPF 17 on the CR-DPF 17.

  The control contents from S20 to S25 are the same as those in the first embodiment. In S30 following S25, is the number of times the temperature of the DPF 25 exceeds the second predetermined temperature described above less than the first predetermined number (for example, three times)? Determine if. If it is less than the first predetermined number of times, the process proceeds to S31 to determine whether or not the temperature of the DPF 25 exceeds the third predetermined temperature. If it is the first predetermined number of times or more, the process proceeds to S32, and the lamp is turned on to notify the driver or the like of the abnormality.

  In S31, the temperature of the oxidation catalyst 26 is read from the temperature sensor 31a that detects the inlet temperature of the DPF 25, and the temperature of the oxidation catalyst 26 is compared with a third predetermined temperature. Here, the third predetermined temperature is set to a temperature at which the catalyst of the oxidation catalyst 26 deteriorates, for example, 800 ° C. If the temperature of the oxidation catalyst 26 exceeds the third predetermined temperature, the process proceeds to S33, and the number of times the temperature exceeds the third predetermined temperature is counted. In subsequent S34, it is determined whether or not the number counted in S33 is less than a second predetermined number (for example, two times). If less than the second predetermined number, the process proceeds to S35, and if it is equal to or greater than the second predetermined number, the process proceeds to S36. The lamp is lit to notify the driver of the abnormality. Note that the temperature of the oxidation catalyst 26 may be estimated from the detected temperature of the sensor 31b.

  In S35, the temperature of the DPF 25 is compared with a fourth predetermined temperature. Here, the fourth predetermined temperature is set to a temperature at which the DPF 25 melts, for example, 1000 ° C. If the temperature of the DPF 25 exceeds the fourth predetermined temperature, the process proceeds to S37, and the number of times of exceeding the fourth predetermined temperature is counted. In S38, it is determined whether or not the number counted in S37 is less than a third predetermined number (for example, two times). If the number is less than the third predetermined number, the control is repeated. The lamp is lit to notify the driver of the abnormality.

  The lamps are turned on in S32, S36, and S39, respectively, but the cause of the abnormality can be specified by changing the color. FIG. 8 shows the relationship between the predetermined temperatures.

  Thus, by setting a threshold value (predetermined temperature) for each abnormal state of CR-DPF 17 and comparing it with the detected temperature of DPF 25 or oxidation catalyst 26, the abnormal state of CR-DPF 17 can be grasped more accurately. , It is possible to efficiently deal with abnormalities.

  Since it is possible to reliably determine the abnormality of the exhaust gas purification device, it is useful for low-pollution diesel vehicles.

It is a schematic diagram explaining the composition of an exhaust emission control device. It is a flowchart explaining the control content of a control unit. It is a figure which shows an example of forced regeneration mode. It is a flowchart explaining the control content which detects the abnormally high temperature at the time of forced regeneration. It is a figure which shows the relationship between 1st predetermined temperature and 2nd predetermined temperature. It is a conceptual diagram of the count at the time of abnormally high temperature. It is another flowchart explaining the control content which detects the abnormally high temperature at the time of forced regeneration. It is a figure which shows the relationship of each predetermined temperature.

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
20 Control unit 21 EGR valve 22 Turbo bypass opening / closing valve 25 DPF
26 Oxidation catalyst 30 Differential pressure sensor 31a, 31b Temperature sensor 32 Air flow sensor

Claims (5)

In an exhaust purification device having a continuously regenerating filter that collects PM contained in the exhaust of an engine and burns it by catalytic action,
Forced regeneration state determination means for determining the forced regeneration state of the filter;
Temperature detecting means for detecting the temperature of the filter;
Heating control means for controlling the heating state of the filter according to the detected temperature of the filter during forced regeneration of the filter;
When the filter is not in a heated state, the detection temperature of the filter is compared with a predetermined temperature, and the counting means for counting the number of times the detection temperature of the filter exceeds the predetermined temperature;
An abnormality occurrence determination means for determining that an abnormality has occurred in the filter when the number of counts exceeds a predetermined number;
An exhaust emission control device comprising:   The exhaust emission control device according to claim 1, wherein the predetermined temperature is set according to an abnormal state of the filter.   The exhaust emission control device according to claim 2, wherein the predetermined temperature is set according to at least one of an allowable temperature during forced regeneration, a deterioration temperature of the oxidation catalyst, and a melting temperature of the filter. The exhaust gas purification according to any one of claims 1 to 3, further comprising abnormality notifying means for notifying the outside of the filter abnormality when the abnormality occurrence determining means determines an abnormality of the filter. apparatus.   The exhaust emission control device according to claim 4, wherein the abnormality notification unit has a different notification method according to an abnormal state of the filter.

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