JP4320586B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas purifying apparatus including a particulate filter that collects particulates contained in exhaust gas of an internal combustion engine.

  In recent years, the environmental impact of particulates (particulate matter, PM) discharged from diesel engines has become a major problem. Conventionally, a diesel particulate filter (hereinafter referred to as DPF) made of a ceramic porous body is known as a countermeasure, and is installed in the middle of the exhaust pipe to collect the particulates in the porous partition wall of the DPF. To be done. The DPF is regenerated by periodically burning and removing the collected particulates.

In general, the regeneration of the DPF calculates the particulate deposition amount (hereinafter referred to as PM deposition amount) based on the differential pressure across the DPF, and when the PM deposition amount exceeds a predetermined amount, The operation is performed by raising the temperature of the DPF above the temperature at which the particulates burn. However, depending on the operating conditions of the engine, the exhaust temperature may become a high temperature at which particulates can be spontaneously combusted. To efficiently regenerate the DPF, the temperature raising means may be operated according to the operating conditions. desirable. As this prior art, for example, Patent Document 1 is cited.
JP 2000-170521 A

  Patent Document 1 proposes a method of increasing the temperature for regenerating the DPF by selecting the temperature increasing means according to the operating condition of the engine when the PM accumulation amount reaches a predetermined value. The operating state (load state) of the engine is divided into a plurality of regions, for example, depending on the engine speed and output torque. Different regeneration operations are performed for each region, or special operations are performed in regions where natural combustion is possible. By not performing the operation, it is possible to appropriately perform the regeneration operation of the DPF while suppressing an increase in fuel consumption.

  However, in the method of Patent Document 1, it is difficult to raise the DPF to the particulate combustion temperature in the low engine speed and low load region, and even if the amount of PM deposition that needs to be regenerated is reached, Do not carry out temperature. That is, in the method of Patent Document 1, the regeneration operation is not performed in the low rotation and low load region when the amount of PM accumulation required for regeneration is exceeded, and the regeneration is performed when the low rotation and low load region is reached during the regeneration. Cancel the operation. However, in this state, if engine low speed and low load operation such as idling or traffic jam is performed for a long time, a large amount of particulates exceeding the allowable value may accumulate on the DPF.

Here, the allowable amount of particulates that can be deposited on the DPF is usually
(1) Decreased engine output as particulates accumulate on the DPF and exhaust pressure increases (2) From the viewpoint of preventing deterioration and damage of the DPF and catalyst due to reaction heat when a large amount of particulates burns at once It is determined. Therefore, when particulates exceeding the allowable amount are deposited by the method of Patent Document 1,
(1) The engine output is reduced (2) After that, a large amount of particulates may burn at a time when the engine is shifted to a middle / high load operation, and the DPF and the catalyst may be deteriorated or damaged.
There is a problem.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent accumulation of a large amount of particulates exceeding an allowable amount on the DPF in an exhaust purification device of an internal combustion engine, and It is intended to realize a safe and high-performance apparatus by preventing a decrease and a deterioration / damage of the DPF and the catalyst due to a large amount of particulates burning at once.

  In order to solve the above-mentioned problem, an exhaust emission control device for an internal combustion engine according to claim 1 is installed in an exhaust passage of the internal combustion engine to detect a particulate filter in the exhaust, and to detect an operating condition of the internal combustion engine. Operating condition detecting means, PM deposit amount detecting means for detecting the particulate amount deposited on the particulate filter, temperature raising means for raising the temperature of the particulate filter, operating condition detecting means, and PM deposit amount A temperature raising control means for operating the temperature raising means based on the detection result of the detecting means is provided. The temperature rise control means performs an operation for suppressing the accumulation of particulate matter on the particulate filter when the particulate accumulation amount on the particulate filter exceeds a predetermined value and a predetermined operating condition is satisfied. It has a deposition suppression means.

  When the particulate filter is required to be regenerated according to the detection result of the PM accumulation amount detecting means, when the operation is shifted to a low speed operation condition in which it is difficult to raise the temperature for regeneration, conventionally, regeneration or other measures are taken. Therefore, when the regeneration was performed after that, the particulate filter temperature might become very high. On the other hand, in the present invention, the PM deposition suppression means is operated when the predetermined operating condition is reached, and an operation for suppressing particulate deposition is performed, so the PM deposition amount hardly increases. Therefore, when the regeneration becomes possible after that, the temperature raising operation by the temperature raising control means can be performed, and the particulate filter can be safely regenerated, and the deterioration of the engine performance and the deterioration of the catalyst can be prevented.

For this reason, in the apparatus of claim 1, the temperature increase control means is configured to increase the temperature by the temperature increase means when the particulate accumulation amount exceeds a predetermined value and the output torque of the internal combustion engine is not less than the first predetermined value. When the temperature operation is not performed and the output torque is less than the first predetermined value and greater than or equal to the second predetermined value smaller than the first predetermined value, the temperature increasing operation by the temperature increasing means is performed, and the output torque is the second predetermined value. In the case of less than the above, the operation by the PM deposition suppressing means is performed without performing the temperature raising operation by the temperature raising means.

  Specifically, an operation according to the operating state is performed based on the output torque of the internal combustion engine. For example, since the particulates can be spontaneously combusted under a high load operation condition where the output torque is equal to or higher than the first predetermined value, it is not necessary to operate the temperature raising means. In addition, the particulate filter can be regenerated by performing a normal temperature raising operation under medium load operating conditions where the output torque is less than the first predetermined value and greater than or equal to the second predetermined value. Under low-speed and low-load operation conditions, it is difficult to raise the temperature to the normal regeneration temperature by the temperature raising means. Therefore, when the output torque is less than the second predetermined value, the effect is obtained by operating the PM accumulation suppressing means. Is obtained.

In the apparatus of claim 2 , the first predetermined value and the second predetermined value in the temperature increase control means are determined according to the rotational speed of the internal combustion engine.

  The first predetermined value is the boundary value between the region where the particulates on the filter can spontaneously burn and the region that can be regenerated by increasing the exhaust temperature because the exhaust gas temperature is high, and the second predetermined value is even if the exhaust temperature is increased. However, since these values have a correlation with the rotational speed of the internal combustion engine, the first predetermined value and the second value are taken into consideration. By setting the predetermined value, more effective temperature rise control can be performed.

According to a third aspect of the present invention, the temperature raising control means determines whether the operating condition has been maintained for a predetermined time when the particulate accumulation amount exceeds a predetermined value and the output torque of the internal combustion engine is less than a second predetermined value. Only when the determination means has a positive determination, the operation by the PM deposition suppression means is performed.

  Since the PM emission amount under the low-speed and low-load operation condition is relatively small, and the exhaust emission may be deteriorated when the operation by the PM accumulation suppressing means is performed, it is preferable that the output torque is less than the second predetermined value. Only when the predetermined time has passed since the condition is satisfied, the operation by the PM deposition suppressing means is preferably performed.

According to a fourth aspect of the present invention, the PM deposition suppressing means performs an operation of reducing the amount of particulates discharged from the internal combustion engine.

  Specifically, by performing an operation for reducing the PM emission amount from the internal combustion engine, the accumulation amount of the particulate filter can be prevented from increasing.

In the apparatus of claim 5, the PM accumulation suppression means reduces the EGR amount from a set value, reduces the upper limit guard value of the injection amount relative to the intake amount, increases the fuel injection pressure, and advances the fuel injection timing. The amount of particulates discharged from the internal combustion engine is reduced by performing any one operation selected from the corners.

  The PM emission amount from the internal combustion engine has a correlation with the EGR amount, the fuel injection amount, the fuel injection pressure, the fuel injection timing, and the like, and the PM emission amount can be reduced by changing these set values.

The apparatus according to claim 6, wherein the PM deposition suppression unit suppresses an increase in the amount of the particulate deposition by raising the temperature of the particulate filter to a temperature lower than a temperature at the time of temperature rise by the temperature raising unit. Have means.

  Preferably, in addition to operations such as increasing and decreasing the EGR amount, fuel injection amount, and fuel injection pressure, when the particulate filter is heated to a temperature lower than the normal regeneration temperature and the particulate is gradually burned, Deposition can be further suppressed. Thereby, it is possible to prevent the PM accumulation amount from exceeding an allowable amount, and to realize a safer and more reliable apparatus.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings. FIG. 1 shows the overall configuration of an exhaust emission control device for a diesel engine. In an exhaust passage of the diesel engine 1, a diesel particulate filter (hereinafter referred to as an oxidation catalyst) carrying an oxidation catalyst on the surface between exhaust pipes 2a and 2b. 3) is installed. The oxidation catalyst-attached DPF3 is formed, for example, by forming heat-resistant ceramics such as cordierite into a honeycomb structure, and sealing a number of cells serving as gas flow paths so that the inlet side or the outlet side are staggered. An oxidation catalyst such as Pt is applied to the wall surface. The exhaust gas discharged from the engine 1 flows downstream while passing through the porous partition wall of the oxidation catalyst-attached DPF 3, and particulates are collected and gradually accumulated therebetween. Note that the oxidation catalyst is supported in order to lower the regeneration temperature and perform stable combustion, and may be configured not to support the oxidation catalyst.

  An exhaust temperature sensor 41 is installed in the exhaust pipe 2b on the downstream side of the DPF 3 with an oxidation catalyst in order to know the temperature of the DPF 3 with an oxidation catalyst. The exhaust gas temperature sensor 41 is connected to the ECU 6, detects the outgas temperature of the DPF 3 with oxidation catalyst, and outputs it to the ECU 6. An air flow meter (intake air amount sensor) 42 is installed in the intake pipe 11 of the engine 1 to detect the intake air amount and output it to the ECU 6. The intake pipe 11 of the engine 1 communicates with the exhaust pipe 2a on the upstream side of the DPF 3 with the oxidation catalyst by an EGR passage 71 provided with the EGR valve 7. The driving of the EGR valve 7 is controlled by the ECU 6.

  The exhaust pipes 2a and 2b are connected to a differential pressure sensor 5 for detecting the differential pressure across the oxidation catalyst DPF 3 in order to know the amount of particulates collected and accumulated in the oxidation catalyst DPF 3 (PM accumulation amount). The One end side of the differential pressure sensor 5 is connected to the exhaust pipe 2a upstream of the DPF 3 with oxidation catalyst, and the other end side is connected to the exhaust pipe 2b downstream of the DPF 3 with oxidation catalyst via pressure introduction pipes 51 and 52, respectively. A signal corresponding to the differential pressure across the attached DPF 3 is output to the ECU 6.

  Various sensors such as an accelerator opening sensor 61 and a rotation speed sensor 62 are further connected to the ECU 6. The ECU 6 controls the fuel injection to the engine 1 by calculating the optimum fuel injection amount, injection timing, injection pressure, etc. according to the operating state based on the detection signals from these sensors. Further, by adjusting the valve opening degree of the EGR valve 7, the exhaust amount (EGR amount) recirculated to the intake air is controlled.

  In addition, the ECU 6 controls the regeneration of the oxidation catalyst-attached DPF 3 so that the PM accumulation amount does not exceed the allowable range. For this reason, in the present embodiment, the ECU 6 detects the operating conditions of the engine 1 such as the engine speed and the accelerator opening (or torque, fuel injection amount, etc.) (operating condition detecting means), and the DPF 3 with an oxidation catalyst. Calculate the PM accumulation amount from the front-rear differential pressure and the exhaust flow rate passing through the DPF 3 with oxidation catalyst, or integrate the PM emission amount from the engine 1 based on the engine operation history to obtain the PM accumulation amount on the oxidation catalyst DPF 3. Calculate (PM accumulation amount detection means). Based on the detection results of the operating condition detection means and the PM accumulation amount detection means, the DPF temperature raising means for raising the temperature of the oxidation catalyst-attached DPF 3 is operated (DPF temperature raising control means). As the DPF temperature raising means, any one or two or more means of post injection, fuel injection timing retardation, and intake throttle can be combined.

Next, the temperature rise control means which is a characteristic part of the present invention will be described. The temperature raising control means operates the DPF temperature raising means according to the operating condition of the engine 1 when the PM accumulation amount on the DPF 3 with the oxidation catalyst exceeds a predetermined value, and the temperature raising operation by the DPF temperature raising means is difficult. Under the operating conditions, an operation for suppressing the accumulation of particulates on the oxidation catalyst-attached DPF 3 is performed (PM deposition suppression means). Specifically, as shown in FIG. 2, the operating region of the engine 1 is divided into three regions A, B, and C from the engine speed and output torque. The output torque at the boundary value between region A and region B is the first predetermined value, the output torque at the boundary value between region B and region C is the second predetermined value, and these first predetermined value and second predetermined value are the engine speed. Will be decided accordingly. The operations in each area are as follows.
(1) Region A is a high load region where the output torque is greater than or equal to the first predetermined value. Under these operating conditions, the exhaust temperature is high (eg, 500 ° C. or higher), and the particulates on the DPF 3 with the oxidation catalyst spontaneously burn. No special heating operation is performed.
(2) Region B is an intermediate load region in which the output torque is less than the first predetermined value and greater than or equal to the second predetermined value, which is smaller than the first predetermined value. Under these operating conditions, the particulates deposited on the oxidation catalyst-attached DPF 3 are burned. In order to regenerate the DPF 3 with the oxidation catalyst, the temperature raising means is operated.
(3) Region C is a low-speed and low-load region where the output torque is less than the second predetermined value. Under this operating condition, even if the temperature raising means is operated, the particulates are burned and removed without significant deterioration in fuel consumption. Since it is difficult to raise the temperature of the oxidation catalyst-attached DPF 3 to a sufficient temperature (for example, 500 ° C. or higher), the same temperature raising means as that in the region B is not operated.

  However, as a result of the state of the region C being maintained for a long time under the operating condition (3), a large amount of particulates accumulated beyond a predetermined value may burn at a time when the region A subsequently moves to the region A, for example. . In this case, the temperature exceeds the allowable limit of the base material and catalyst of the DPF 3 with an oxidation catalyst (for example, 800 ° C. or more), and the DPF 3 with an oxidation catalyst or the catalyst may be deteriorated or damaged. Therefore, in the present invention, in order to avoid this, the operation by the PM deposition suppressing means is performed so as not to increase the particulates deposited on the DPF 3 with the oxidation catalyst as much as possible.

Specifically, in the region C, the PM accumulation suppression unit reduces the amount of particulates (PM emission amount) discharged from the engine 1 as much as possible, and suppresses the accumulation of new particulates on the oxidation catalyst-attached DPF 3. As a result, when the engine operating conditions change to the region A or B, the particulates deposited on the oxidation catalyst-attached DPF 3 can be burned safely. More specifically,
1) The amount of EGR is reduced from the set value to reduce the particulates discharged from the engine 1. Or
2) The upper limit guard value of the injection amount with respect to the intake amount provided for suppressing particulate discharge is reduced. Thereby, even when the intake amount is insufficient with respect to the fuel amount, such as when the vehicle is accelerated, it is possible to effectively prevent the generation of particulates in the engine 1 due to the lack of oxygen. As a result, it is possible to reduce the particulates accumulated in the DPF 3 with the oxidation catalyst even in a traffic jam that repeats acceleration / deceleration at low speed. The reduction amount of the guard value is set in a range that does not impair the acceleration performance (drivability) of the vehicle.

  In addition to the operations 1) and 2), it is also possible to increase the fuel injection pressure or advance the fuel injection timing. Further, in addition to the above-described operation for reducing the amount of particulate discharged from the engine 1, the particulates on the oxidation catalyst-attached DPF 3 are gradually burned to suppress an increase in the amount of particulates. Operations can also be performed. Specifically, when the temperature raising means is operated within a range in which the fuel consumption is not greatly deteriorated, for example, the temperature of the oxidation catalyst-attached DPF 3 is raised so as to be lower than the operation in the region B (for example, 400 ° C.). Good. In this case, deterioration of fuel consumption is suppressed, and the particulates on the oxidation catalyst-attached DPF 3 are gradually burned even before combustion removal is reached, so that it is possible to avoid accumulation of a large amount of particulates exceeding the allowable amount. As a result, when the engine operating conditions change to reach the region A or the region B, the particulates deposited on the oxidation catalyst-attached DPF 3 can be burned safely.

  Note that the engine emission and the like may be slightly deteriorated by the above operation depending on the conditions. Further, since the PM emission amount from the engine 1 in the region C is relatively small, a large amount of particulates will not suddenly accumulate on the DPF 3 with the oxidation catalyst. Accordingly, no special operation is performed immediately after entering the region C, and it is preferable to first determine whether or not the state continues for a predetermined time (determination means). Then, the above problem can be avoided by performing the operation only when the state of the region C continues for a long time.

  Next, a control routine for regenerating the DPF 3 with the oxidation catalyst by the ECU 6 will be described with reference to a flowchart shown in FIG. This routine is executed in the ECU 6 at a predetermined cycle. In step 101, first, the amount of PM deposited on the DPF 3 with the oxidation catalyst is calculated. The amount of particulate deposited on the oxidation catalyst-attached DPF 3 can be calculated from, for example, the differential pressure before and after the oxidation catalyst-attached DPF 3 detected by the differential pressure sensor 5. This utilizes the fact that the differential pressure generated when a predetermined amount of exhaust gas passes through the oxidation catalyst-attached DPF 3 has a correlation with the amount of particulates deposited on the oxidation catalyst-attached DPF 3, and these relations have been experimentally determined in advance. The obtained map data is stored in the memory of the ECU 6. The amount of exhaust is calculated from, for example, the amount of intake air detected by the air flow meter 42, the temperature of the DPF 3 with oxidation catalyst (DPF temperature) detected by the exhaust temperature sensor 41, and the like.

  Alternatively, the particulate amount accumulated on the DPF 3 with the oxidation catalyst can be calculated based on the operation history of the engine 1. For example, the amount of particulate discharged from the engine 1 per unit time is obtained from the engine speed and output torque, and this is multiplied by the particulate collection efficiency in the DPF 3 with an oxidation catalyst to add an oxidation catalyst. The amount of PM deposited on the DPF 3 can be calculated.

  In step 102, whether or not the amount of PM deposited on the oxidation-provided DPF 3 calculated in step 101 has reached a predetermined value for burning and removing particulates to regenerate the oxidation-catalyzed DPF 3 (PM accumulation amount> Whether the value is a predetermined value). This predetermined value is usually obtained by reducing the engine output as the exhaust pressure increases due to accumulation of particulates on the DPF 3 with oxidation catalyst, and the filter base material due to reaction heat when a large amount of accumulated particulates burns at once. Further, it is determined in advance from the viewpoint of preventing deterioration and breakage of the catalyst. If the determination in step 102 is negative, it is determined that regeneration is not yet necessary, and the present control routine is temporarily terminated.

  If the determination at step 102 is affirmative, the routine proceeds to step 103, where the engine speed and the accelerator opening are read from the outputs of the accelerator opening sensor 61 and the rotation speed sensor 62. In step 104, the engine output torque is obtained from the engine speed and accelerator opening read in step 103, and the current engine operating conditions are obtained based on FIG. Hereinafter, different operations are executed depending on whether the region is A, B, or C. In the region A, since the engine 1 is under a high load operation condition, the exhaust temperature is high, and the particulates on the oxidation catalyst-attached DPF 3 are naturally combusted, so that this control routine is terminated without performing any special operation.

  When the engine operating condition is the region B (medium load operating condition) in FIG. 2, the process proceeds to step 105 and the temperature raising operation for regenerating the DPF 3 with the oxidation catalyst is performed. Examples of the DPF temperature raising means include the above-described post injection, fuel injection timing delay, and intake throttle, and one or two or more of these are combined to increase the exhaust temperature and further to convert the unburned HC into an oxidation catalyst. By performing the oxidation reaction above, the temperature of the oxidation catalyst-attached DPF 3 is raised to a high temperature (for example, 500 ° C. or more). Thereby, the particulates deposited on the oxidation catalyst-attached DPF 3 can be burned and removed to recover the collection ability.

  If the engine operating condition is the area C (low speed and low load operating condition) in FIG. 2, the process proceeds to step 106 to determine whether or not the operation in the area C has continued for a predetermined time. When an operation in step 107 described later is performed, engine emission and the like may be slightly deteriorated depending on conditions. In addition, since the PM emission amount from the engine 1 in the region C is relatively small, a large amount of particulates does not suddenly accumulate on the DPF 3 with the oxidation catalyst. Therefore, no special operation is performed immediately after entering the region C, and the operation of Step 107 is performed only when the state continues for a long time. The predetermined time is set to 30 minutes, for example. If the determination at step 106 is negative, this control routine is temporarily terminated.

If the determination in step 106 is affirmative, the process proceeds to step 107, and an operation for suppressing an increase in the amount of PM deposition on the oxidation catalyst-attached DPF 3 is performed. Examples of operations for this purpose are listed below.
(First example)
As shown in FIG. 4, when the EGR amount recirculated from the EGR passage 71 of FIG. 1 to the intake air exceeds a predetermined value, the PM discharge amount increases rapidly. Therefore, the amount of particulates discharged from the engine 1 is suppressed by reducing the EGR amount from W2 (conventional set value) to W1 where the PM emission amount is relatively small.
(Second example)
As shown in FIG. 5, when the fuel injection amount exceeds a predetermined value, the PM emission amount increases rapidly. Therefore, the amount of particulates discharged from the engine 1 is suppressed by reducing the upper limit value of the fuel injection amount from X2 to X1. As described above, when the intake amount is insufficient with respect to the fuel amount, particulates are likely to be generated due to insufficient oxygen, but this can be effectively prevented.
(Third example)
As shown in FIG. 6, the PM emission amount decreases as the fuel injection pressure increases. Therefore, the amount of particulates discharged from the engine 1 is suppressed by increasing the fuel injection pressure from Y2 to Y1.
(Fourth example)
As shown in FIG. 7, when the fuel injection timing is retarded, the PM emission amount increases. Therefore, the amount of particulates discharged from the engine 1 is suppressed by advancing the fuel injection timing from Z2 to Z1.
(Fifth example)
In addition to the operations of the first example to the fourth example, as shown in FIG. A warming operation can also be performed. Here, post-injection is adopted as the DPF temperature raising means, and the increase in the PM deposition amount on the oxidation catalyst-attached DPF 3 is further suppressed by gradually burning the particulates. Thereby, compared with the case where it heats up to temperature T2, fuel consumption can be made small (M2-> M1), and the suppression effect of PM accumulation amount can be heightened, suppressing fuel consumption deterioration.

  FIG. 9 is a time chart showing the effect of the present invention when the vehicle is running. As shown in the figure, the state shifts to low speed operation (region C) in a state where the PM accumulation amount m0 that requires regeneration of the oxidation catalyst-attached DPF3 is reached. In this case, in the conventional technique that does not have the PM accumulation suppression means, the regeneration of the oxidation catalyst-attached DPF 3 or other treatment is not performed during the operation in the region C, so that the PM accumulation amount further increases. Thereafter, when the operation condition shifts to medium speed operation (region B) and regeneration is performed, the DPF temperature becomes very high and exceeds the heat resistance limit T0.

  In contrast, in the present invention, when operating in the region C, the PM emission amount from the engine 1 is reduced or the particulates on the DPF 3 with the oxidation catalyst are gradually burned, so that the PM accumulation amount hardly increases. . Therefore, when the vehicle travels in the subsequent region B, the DPF temperature does not exceed the heat resistance limit T0, and the DPF 3 with an oxidation catalyst can be safely regenerated.

1 is an overall schematic configuration diagram of an exhaust emission control device for an internal combustion engine according to a first embodiment of the present invention. FIG. 6 is a diagram for explaining that different operations are performed for regeneration of a DPF with an oxidation catalyst for each engine operating region in a graph in which engine rotation speed and output torque are both axes. It is a flowchart figure which shows the action | operation of ECU by this invention. FIG. 3 is a diagram showing a relationship between an EGR amount and a PM emission amount in an engine operation region C. In the engine operation area C, it is a figure which shows the relationship between fuel injection amount upper limit and PM emission amount. In the engine operation area C, it is a figure which shows the relationship between fuel injection pressure and PM discharge | emission amount. In the engine operation area C, it is a figure which shows the relationship between fuel-injection time and PM emission amount. In the engine operation area C, it is a figure which shows the relationship between post injection quantity, fuel consumption, and DPF temperature with an oxidation catalyst. It is a time chart figure showing the effect of the present invention at the time of vehicles run.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 11 Intake pipe 2a, 2b Exhaust pipe 3 DPF (particulate filter) with oxidation catalyst
41 Exhaust temperature sensor 42 Air flow meter 5 Differential pressure sensor 6 ECU
61 Rotational speed sensor 62 Accelerator opening sensor 7 EGR valve 71 EGR passage

Claims (6)

A particulate filter installed in the exhaust passage of the internal combustion engine for collecting particulates in the exhaust, an operating condition detecting means for detecting an operating condition of the internal combustion engine, and an amount of particulates accumulated on the particulate filter. PM deposition amount detection means, temperature rise means for raising the temperature of the particulate filter, temperature control means for operating the temperature rise means based on detection results of the operating condition detection means and the PM accumulation amount detection means The temperature raising control means performs the temperature raising operation by the temperature raising means when the amount of accumulated particulate matter on the particulate filter exceeds a predetermined value and the output torque of the internal combustion engine is not less than a first predetermined value. If the output torque is less than the first predetermined value and greater than or equal to the second predetermined value smaller than the first predetermined value, the temperature raising operation by the temperature raising means is performed. , Without performing heating operation by the heating means when the output torque is less than the second predetermined value, actuates the PM deposit control means performs an operation to suppress the deposition of particulates on the above particulate filter exhaust purification system of an internal combustion engine, characterized in that letting. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the first predetermined value and the second predetermined value in the temperature increase control means are determined in accordance with a rotational speed of the internal combustion engine. The temperature increase control means includes a determination means for determining whether or not the operating condition has been continued for a predetermined time when the particulate accumulation amount exceeds a predetermined value and the output torque of the internal combustion engine is less than a second predetermined value. a, the determination means is affirmative the determined only when, an exhaust purifying apparatus for an internal combustion engine according to claim 1 or 2, wherein performing the operation with the PM deposit control means. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the PM accumulation suppressing means performs an operation of reducing an amount of particulate discharged from the internal combustion engine. The PM accumulation suppression means performs an operation of reducing the EGR amount from a set value, reducing the upper limit guard value of the injection amount with respect to the intake air amount, increasing the fuel injection pressure, or advancing the fuel injection timing. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 4 to 5, wherein the amount of particulates discharged from the engine is reduced . The PM deposit control means, the particulate filter claims 1 having a means for suppressing the increase in the deposition amount of the particulate by raising the temperature to a temperature below the temperature during heating by the Atsushi Nobori means 5. An exhaust emission control device for an internal combustion engine according to any one of 5 above.

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