JP5332575B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to regeneration of a diesel particulate filter (DPF) provided in an exhaust passage of an internal combustion engine.

  Exhaust gas from a diesel engine that burns in a lean air-fuel ratio environment contains particulate matter containing carbon (C) as a main component called particulates. A diesel particulate filter (DPF) is a filter that traps particulates in an exhaust passage of an internal combustion engine so that the particulates are not released into the atmosphere. The trapped particulate is deposited on the DPF. The accumulated particulates are combusted by the temperature rise of the exhaust and are removed from the DPF. This process is called DPF regeneration.

  Although it is necessary to raise the exhaust gas temperature for DPF regeneration, raising the exhaust gas temperature raises the problem of increased nitrogen oxide (NOx) emissions. Patent Document 1 makes a proposal for improving temperature rise during DPF regeneration and suppressing NOx emission.

The prior art of Patent Document 1 discloses an exhaust gas recirculation (EGR) passage that recirculates part of exhaust gas from a diesel engine to intake air, an EGR cooler that cools the recirculated exhaust gas in the EGR passage, a bypass passage that bypasses the EGR cooler, and an EGR cooler. And a bypass valve for switching the bypass passage. This prior art controls the exhaust temperature of the diesel engine to a temperature suitable for DPF regeneration while suppressing the generation of NOx by selecting the cooling and non-cooling of the recirculated exhaust or the degree of cooling by operating the bypass valve.
JP 2006-152891 A

  In order to burn the particulates, a temperature of 450 ° C. or higher is necessary. However, the temperature raising method disclosed in Patent Document 1 may be difficult to apply depending on the operating conditions of the diesel engine. For example, if the exhaust temperature is forcibly increased by fuel injection control such as post-injection or retarded fuel injection timing in the low-load / low-rotation region of a diesel engine, it may cause oil dilution inside the diesel engine, It is likely to worsen consumption.

  On the other hand, if the diesel engine is continuously operated under low temperature conditions, particulates may accumulate excessively on the DPF and the DPF may not be able to trap the particulates.

  An object of the present invention is to realize DPF regeneration at a low exhaust temperature in order to solve the above-mentioned problems related to regeneration of DPF.

  In order to achieve the above object, the present invention provides an exhaust gas purification apparatus for an internal combustion engine that purifies exhaust gas from an internal combustion engine, a diesel particulate filter that traps particulates contained in the exhaust gas, and an exhaust gas temperature increase that raises the exhaust gas temperature. Means, upstream of the diesel particulate filter and generating nitrogen dioxide so that nitrogen dioxide is included in the exhaust, and the amount of particulates deposited on the diesel particulate filter reaches a predetermined amount A means for determining whether or not the accumulated amount of particulates has reached a predetermined amount, and whether or not the operating state of the internal combustion engine is in an operating region suitable for regeneration of a diesel particulate filter by combustion Operating region judgment means to perform and the trapped amount of particulates When the operating state of the internal combustion engine is in an operating region suitable for regeneration of the diesel particulate filter due to combustion, the means for operating the exhaust temperature raising means and the trapped amount of the particulate have reached a predetermined amount. When the operating state of the internal combustion engine is not in an operating range suitable for regeneration of a diesel particulate filter due to combustion, the means for operating the nitrogen dioxide generating means and the dilution of the engine oil for lubricating the internal combustion engine with fuel Dilution degree determination means for determining. The operating region determination means is a low-load low-rotation region where the load of the internal combustion engine is equal to or lower than the predetermined load and the rotational speed of the internal combustion engine is equal to or lower than the predetermined rotational speed, and It is configured to determine that the operating state is not in an operating region suitable for regeneration of a diesel particulate filter due to combustion.

  When the trapped amount of particulates reaches a predetermined amount and the operating state of the internal combustion engine is not in the operating range suitable for regeneration of the diesel particulate filter by combustion, nitrogen dioxide is generated by the nitrogen dioxide generating means. The generated nitrogen dioxide reacts with the carbon contained in the particulate trapped in the diesel particulate filter, and oxidizes the carbon that is the main component of the particulate to remove it from the diesel particulate filter. Even in the operating state of the internal combustion engine where the exhaust temperature does not reach the particulate combustion temperature, the regeneration of the diesel particulate filter becomes possible, so the operating range of the internal combustion engine that can regenerate the diesel particulate filter is expanded, and the diesel particulate filter is expanded. It is possible to prevent excessive accumulation of particulates on the curate filter without deteriorating exhaust composition and fuel consumption.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an internal combustion engine provided with an exhaust gas recirculation apparatus according to a first embodiment of the present invention. FIG. 2 is a diagram for explaining the DPF regeneration concept of the exhaust gas recirculation apparatus according to the first embodiment of the present invention. FIG. 3 is a flowchart for explaining a DPF regeneration routine executed by the controller according to the first embodiment of the present invention. FIG. 4 is a flowchart for explaining a DPF regeneration subroutine by NO ₂ executed by the controller according to the first embodiment of the present invention. FIG. 5 is a diagram showing the relationship between the EGR rate, the amount of smoke generated, and the amount of NOx generated with respect to the reflux exhaust temperature and the excess air ratio λ.

  Referring to FIG. 1, in a four-cylinder compression ignition type internal combustion engine 1 for a vehicle, a fuel injection valve 40 injects fuel into the air sucked into the combustion chamber 6 of each cylinder through an intake valve 4 through an intake passage 10. By doing so, an air-fuel mixture is generated in the cylinder. The air-fuel mixture is compressed by the reciprocating motion of the piston 2 accommodated in the cylinder, and is ignited and combusted in the combustion chamber 6 due to the temperature rise accompanying the compression. Combustion gas generated in the combustion chamber 6 by combustion is discharged from the exhaust valve 5 through the exhaust passage 20. The internal combustion engine 1 is constituted by a four-stroke cycle engine that repeats the steps of intake, compression, expansion, and exhaust in each cylinder in order.

  The intake passage 10 is provided with a compressor of a turbocharger 50 that supercharges intake air and an intake throttle 32 that adjusts the intake air flow rate. The intake passage 10 is connected to each cylinder via an intake collector 11.

  The exhaust passage 20 is provided with an exhaust turbine of the turbocharger 50, an oxidation catalyst 22, and a diesel particulate filter (DPF) 21 that traps particulates in the exhaust.

  The exhaust turbine of the turbocharger 50 includes a variable nozzle 24. The variable nozzle 24 increases the flow rate of the exhaust gas flowing into the exhaust turbine when the internal combustion engine 1 rotates at a low speed to increase the supercharging effect of the intake air, while fully opening at the time of high speed rotation to reduce the inflow resistance of the exhaust gas to the exhaust turbine. It has. An exhaust gas recirculation (EGR) passage 30 that recirculates part of the exhaust gas to the intake collector 11 is connected to the exhaust passage 20 from the upstream side of the exhaust turbine.

  The EGR passage 30 is provided with a water-cooled cooler 34 that cools the recirculated exhaust gas and an exhaust recirculation (EGR) valve 31 that adjusts the exhaust recirculation (EGR) flow rate. Furthermore, a bypass passage 37 that bypasses the water-cooled cooler 34 and a bypass valve 38 that changes the flow rate of the exhaust gas between the bypass passage 37 and the water-cooled cooler 34 according to the opening degree are provided.

  In order to supply fuel to the fuel injection valve 40, a high-pressure fuel pump 43 driven by the crankshaft of the internal combustion engine 1 and a common rail 41 for temporarily storing high-pressure fuel discharged from the high-pressure fuel pump 43 are provided. The high-pressure fuel pump 43 and the common rail 41 are connected by a fuel pipe 42. The fuel injection valve 40 is connected to the common rail 41 and injects fuel stored in the common rail 41 into the combustion chamber 6 in accordance with a pulse width modulation signal input from the controller 70.

  The fuel injection of the fuel injection valve 40, the opening of the intake throttle 32, the opening of the variable nozzle 24 of the turbocharger 50, the opening of the EGR valve 31, and the opening of the bypass valve 38 are controlled by the controller 70, respectively. The The controller 70 regenerates the DPF 21 through these controls.

  The controller 70 includes a programmable microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). It is also possible to configure the controller with a plurality of microcomputers.

  For fuel injection control, the controller 70 includes an accelerator pedal depression amount sensor 61 for detecting an accelerator pedal depression amount Acc provided in the vehicle, a crank angle sensor 60 for detecting the rotational speed and crank angle of the internal combustion engine 1, and an exhaust temperature. A temperature sensor 62 to detect, a differential pressure sensor 63 to detect the differential pressure upstream and downstream of the DPF 21, a temperature sensor 64 to detect the bed temperature of the DPF 21, a temperature sensor 65 to detect the bed temperature of the oxidation catalyst 22, and the exhaust passage 20 The air-fuel ratio sensor 66, the air flow meter 67 for detecting the intake fresh air amount of the internal combustion engine 1, the flow rate sensor 68 for detecting the recirculated exhaust amount of the EGR passage 30, and the NOx concentration in the exhaust discharged from the combustion quality 6 are detected. Detection data is input as signals from the NOx concentration sensor 69.

  The concept of the regeneration control of the DPF 21 executed by the controller 70 will be described with reference to FIG.

  In a high load region where the load of the internal combustion engine 1 is high, the exhaust temperature is high. In this case, it is possible to achieve the exhaust temperature required to burn the particulates accumulated in the DPF 21 only by opening the intake throttle 32 and increasing the intake air amount.

  In the low load and high rotation range where the load of the internal combustion engine 1 is low and the rotation speed is high, the exhaust temperature necessary for burning the particulates accumulated in the DPF 21 is the post injection by the fuel injection valve 40 and the main injection. Obtained by timing delay operation.

  On the other hand, if the exhaust temperature is raised in the same way as in the low load and high rotation range in the low load and low rotation range where both the load and the rotation speed of the internal combustion engine 1 are low, oil dilution inside the diesel engine and fuel consumption of the diesel engine will occur. There is a high possibility of incurring deterioration.

Therefore, in this low load low rotation region, the controller 70 supplies NO ₂ to the DPF 21 instead of regenerating the DPF 21 by burning the particulates, and the following equation (1) is added to the carbon (C) that is the main component of the particulates. The particulates are removed from the DPF 21 by causing the chemical reaction of

2NO ₂ + C → 2NO + CO ₂ (1)

  As described above, high temperature of 450 ° C. is necessary for burning particulates, but the above reaction is started at about 200 ° C.

The NO ₂ supplied to the DPF 21 is obtained by converting the NO in the exhaust to NO ₂ by the catalytic reaction of the following equation (2) in the upstream oxidation catalyst 22.

2NO + O ₂ → 2NO ₂ (2)

  The controller 70 activates the oxidation catalyst 22 by increasing the bed temperature of the oxidation catalyst 22 in order to promote the chemical reaction of the equation (2) in the oxidation catalyst 22. For this purpose, the controller 70 controls the opening degree of the variable nozzle 24, the EGR valve 31, and the bypass valve 38, the excess air ratio λ of the air-fuel mixture supplied to the combustion chamber 6, the exhaust gas recirculation (EGR) rate, and the recirculation. The exhaust temperature (EGR temperature) is controlled.

The oxidation catalyst 22 is activated when the bed temperature reaches about 200 ° C., and generates NO ₂ from NO under an excess air atmosphere enhanced by an increase in the excess air ratio λ.

  With reference to FIG. 3, the DPF regeneration routine executed by the controller 70 in order to realize the above control will be described next. The controller 70 executes this routine during the operation of the internal combustion engine 1 at regular time intervals, for example, every 10 milliseconds.

  In step S1, the controller 70 determines whether there is a regeneration request for the DPF 21. The regeneration request for the DPF 21 is issued when the particulate accumulation amount of the DPF 21 exceeds a predetermined amount. The particulate accumulation amount of the DPF 21 is estimated from the differential pressure upstream and downstream of the DPF 21 detected by the differential pressure sensor 63.

  If there is no request for regeneration of the DPF 21, the controller 70 does nothing and ends the routine.

  If there is a regeneration request for the DPF 21, the controller 70 reads the bed temperature of the DPF 21, the load and rotation speed of the internal combustion engine 1, and the bed temperature of the oxidation catalyst 22 in step S2.

  Here, the bed temperature of the DPF 21 is detected by the temperature sensor 64. The bed temperature of the oxidation catalyst 22 is detected by the temperature sensor 65. The load of the internal combustion engine 1 is expressed as the accelerator pedal depression amount Acc detected by the accelerator pedal depression amount sensor 61. The rotational speed of the internal combustion engine 1 is detected by a crank angle sensor 60.

  In step S3, the controller 70 determines whether the operating state of the internal combustion engine 1 is suitable for regeneration of the DPF 21 by particulate combustion. Specifically, the controller 70 searches the operation region map stored in advance in the ROM having the characteristics shown in FIG. 2 on the basis of the load and the rotational speed of the internal combustion engine, so that the operation state of the internal combustion engine 1 is the above-described high level. It is determined whether the load region, the low load high rotation region, or the low load low rotation region.

  As a result of the determination, when the operating state of the internal combustion engine 1 is in the low load and low rotation region, the operating state of the internal combustion engine 1 is a region that is not suitable for regeneration of the DPF 21 by particulate combustion. On the other hand, when the operating state of the internal combustion engine 1 is in another region, the operating state of the internal combustion engine 1 is a region suitable for regeneration of the DPF 21 by particulate combustion.

  If the operating state of the internal combustion engine 1 is suitable for regeneration of the DPF 21 by particulate combustion based on the determination result of step S3, the controller 70 performs a normal forced temperature increase operation of the DPF 21 in step S6. That is, the fuel injection valve 40 is caused to perform post injection, and the main injection timing of the fuel injection valve 40 is retarded. Further, if necessary, the intake throttle 32 is opened to increase the intake air amount. These operations are known DPF regeneration operations. After the process of step S6, the controller 70 ends the routine.

  On the other hand, if the operating state of the internal combustion engine 1 is not suitable for regeneration of the DPF 21 by particulate combustion, the process of step S4 is performed.

In step S <b> 4, the controller 70 prohibits forced DPF 21 temperature raising operation by fuel injection control of the fuel injection valve 40 and opening control of the intake throttle 32. In the next step S5, the controller 70 executes the DPF regeneration subroutine using NO ₂ shown in FIG. 4 to regenerate the DPF 21 using NO ₂ .

  Referring to FIG. 4, in step S21, the controller 70 adds the excess air ratio λ, EGR rate in addition to the bed temperature of the oxidation catalyst 22, the bed temperature of the DPF 21, and the load and rotation speed of the internal combustion engine 1 read in step S1. Read the exhaust temperature. The excess air ratio λ is detected by an air-fuel ratio sensor 66 provided in the exhaust passage 20. The EGR rate is the ratio of the recirculation exhaust amount and the intake fresh air amount. The intake fresh air amount is detected by the air flow meter 67 and the recirculation exhaust amount is detected by the flow sensor 68. The exhaust temperature is detected by the temperature sensor 62.

  In step S22, the controller 70 determines whether the excess air ratio λ is equal to or greater than a predetermined value.

  If the excess air ratio λ is equal to or greater than the predetermined value, the controller 70 performs the process of step S24. If the excess air ratio λ is not equal to or greater than the predetermined value, the controller 70 increases the excess air ratio λ in step S23, that is, closes the EGR valve 38 and decreases the opening of the variable nozzle 24. By this operation, the EGR is stopped, and the compressor supercharges the intake air in the intake passage 10 by the exhaust turbine of the turbocharger 50 driven by the exhaust flow accelerated by the variable nozzle 24.

  As a result, only the air supercharged by the compressor is sucked into the combustion chamber 6 of the internal combustion engine 1. By this operation, the excess air ratio λ increases, generation of particulates due to air-fuel mixture combustion in the combustion chamber 6 is suppressed, and an environment in which NOx is likely to be generated due to air-fuel combustion.

  According to the studies by the inventors, the EGR rate, the amount of smoke generated, and the amount of NOx generated change as shown in FIG. 5 with respect to the reflux exhaust temperature and the excess air ratio λ. That is, as a result of the processing in step S23, when the excess air ratio λ increases, the amount of NOx generated increases.

  After the process of step S23, the controller 70 performs the process of step S24.

In step S24, the controller 70 determines whether the NOx concentration detected by the NOx concentration sensor 69 is equal to or higher than a predetermined concentration. Note that NO ₂ used for regeneration of the DPF 21 is a part of NOx and not all, but a high NOx concentration means a high NO ₂ concentration.

  If the NOx concentration is equal to or higher than the predetermined concentration, the controller 70 performs the process of step S26. If the NOx concentration is not equal to or higher than the predetermined concentration, the controller 70 performs NOx emission control as follows in step S25. That is, the bypass valve 38 is opened and the EGR valve 31 is set to a small opening. Thereby, an EGR rate falls. Further, the reflux exhaust temperature rises.

  Referring to FIG. 5, a low EGR rate causes an increase in the excess air ratio λ, and an increase in the excess air ratio λ and an increase in the recirculation exhaust temperature increase the amount of NOx produced by the internal combustion engine 1.

  After the process of step S25, the controller 70 performs the process of step S26.

In step S26, the controller 70 determines whether the bed temperature of the DPF 21 and the bed temperature of the oxidation catalyst 22 are each equal to or higher than a predetermined temperature. When the bed temperature of the oxidation catalyst 22 is equal to or higher than a predetermined temperature, the oxidation catalyst 22 is activated and promotes oxidation of NO to increase NO ₂ in the exhaust. Further, when the bed temperature of the DPF 21 becomes a predetermined temperature or more, the particulates deposited on the DPF 21 are removed from the DPF 21 by causing the oxidation reaction of the above formulas (1) and (2) by the NO ₂ generated in the oxidation catalyst 22. Is done. Therefore, the controller 70 ends the routine when the condition of step S26 is satisfied.

If the determination in step S26 is negative, that is, if either or both of the bed temperature of the DPF 21 and the bed temperature of the oxidation catalyst 22 are not equal to or higher than the predetermined temperature, the controller 70 performs exhaust gas temperature control as follows.
In other words, the bypass valve 38 is opened while the EGR valve 31 is opened as in the process of step S25. As a result, the amount of EGR increases and the temperature of the exhaust discharged from the combustion chamber 1 increases due to the high-temperature reflux exhaust. After the process of step S26, the controller 70 ends the subroutine.

Referring to FIG. 3 again, if it is determined in step S3 that the operating state of the internal combustion engine 1 is not suitable for regeneration of the DPF 21 by particulate combustion, that is, the load and rotational speed of the internal combustion engine 1 are low as shown in FIG. When it is determined that the engine is in the low load rotation region, the processing of steps S4 and S5, that is, the temperature rise control for burning the particulates is always prohibited, while the regeneration control of the DPF 21 using NO ₂ is performed. It is.

Therefore, even when the internal combustion engine 1 is in a low load and low rotation region, that is, at a low temperature when the exhaust temperature is not suitable for regeneration of the DPF 21 due to particulate combustion, the DPF 21 can be reliably regenerated using NO ₂ . Also, under this condition, the DPF 21 is not forcibly raised in temperature, so that dilution of engine oil and deterioration of fuel consumption can be prevented.

  Since the DPF 21 can be regenerated at a low temperature in this way, the operating range of the internal combustion engine 1 that can regenerate the DPF 21 can be expanded. As a result, even when the internal combustion engine 1 continues to operate in the low load and low rotation region, it is possible to reliably prevent excessive accumulation of particulates on the DPF 21.

Further, in the low load and low rotation region, the excess air ratio λ, the NO ₂ concentration, and the exhaust temperature are controlled under the subroutine of FIG. 4, so that the particulates due to the combustion of the air-fuel mixture in the combustion chamber 6 are controlled. The generation of NO ₂ necessary for the regeneration of the DPF 21 in the oxidation catalyst 22 and the operation for raising the bed temperature of the DPF 21 necessary for the regeneration of the DPF 21 by NO ₂ are suppressed once in a single subroutine while suppressing the generation. Is feasible.

  Next, a second embodiment of the present invention will be described with reference to FIG. The controller 70 according to this embodiment executes a DPF regeneration routine shown in FIG. 6 instead of the DPF regeneration routine of FIG.

  Referring to FIG. 6, in step S31, the controller 70 determines whether there is a regeneration request for the DPF 21 as in the process of step S1.

  If there is no request for regeneration of the DPF 21, the controller 70 does nothing and ends the routine.

  If there is a regeneration request for the DPF 21, the controller 70 reads the bed temperature of the DPF 21 and the load and rotation speed of the internal combustion engine 1 in step S32.

  In step S33, the controller 70 determines whether the bed temperature of the DPF 21 is equal to or lower than a predetermined temperature, the load of the internal combustion engine 1 is equal to or lower than the predetermined load, and the rotational speed of the internal combustion engine 1 is equal to or lower than the predetermined speed. Here, the predetermined load and the predetermined speed are values for determining the low-load low-rotation region in FIG.

  If the determination in step S33 is negative, the controller 70 performs the forced temperature raising operation of the DPF 21 in step S40 as in step S6, and then ends the routine.

If the determination in step S33 is affirmative, in step S34, the controller 70 estimates the particulate deposition rate on the DPF 21 under the current operating conditions. Specifically, the particulate discharge amount per unit time of the internal combustion engine 1 is calculated with reference to a map stored in advance in ROM using the excess air ratio λ and the load and rotation speed of the internal combustion engine 1 as parameters. The particulate discharge amount per unit time calculated in this way is regarded as the particulate deposition rate on the DPF 21 when the regeneration control of the DPF 21 using NO ₂ is not performed.

In step S35, the controller 70 estimates the particulate inflow speed to the DPF 21 when the regeneration control of the DPF 21 using NO ₂ is performed. Specifically, based on the excess air ratio λ and the load and rotation speed of the internal combustion engine 1 under the regeneration control of the DPF 21 using NO ₂ , the map referred to in step S34 is searched, and the unit of the internal combustion engine 1 is searched. Calculate particulate emissions per hour. Then, the particulate discharge amount per unit time is regarded as the particulate inflow rate to the DPF 21. The method for regeneration control of the DPF 21 is as described in the first embodiment, and the change of the excess air ratio λ under the regeneration control of the DPF 21 is known.

In step S36, the controller 70 estimates the regeneration speed of the DPF 21 when the regeneration control of the DPF 21 using NO ₂ is performed based on the bed temperature of the DPF 21. Here, the reproduction speed means a decrease amount of the particulate per unit time.

In step S37, the controller 70 subtracts the regeneration speed of the DPF 21 estimated in step S35 from the particulate inflow speed estimated in step S34 to the DPF 21 under the regeneration control of the DPF 21 using NO ₂ . Calculate the particulate deposition rate.

  In step S38, the controller 70 calculates the particulate deposition rate on the DPF 21 when the regeneration control of the DPF 21 estimated in step S34 is not performed, and the particulate deposition on the DPF 21 under the regeneration control of the DPF 21 calculated in step S37. Compare speed.

When the former is larger than the latter, it means that regeneration control of the DPF 21 using NO ₂ is effective. In this case, in step S39, the controller 70 executes the DPF regeneration subroutine using NO ₂ shown in FIG. 4 to regenerate the DPF 21 using NO ₂ in the same manner as step S5 in FIG.

On the other hand, when the former is not larger than the latter, it means that the regeneration control of the DPF 21 using NO ₂ is not effective. In this case, the controller 70 ends the routine without regenerating the DPF 21 using NO ₂ .

According to this embodiment, prior to the regeneration of the DPF 21 using NO ₂ in the low load and low speed region of the internal combustion engine 1 shown in FIG. 2, it is determined in advance whether the regeneration of the DPF 21 using NO ₂ is effective. Therefore, the regeneration of the DPF 21 can be performed more reliably.

  A third embodiment of the present invention will be described with reference to FIG. The controller 70 according to this embodiment executes a DPF regeneration routine shown in FIG. 7 instead of the DPF regeneration routine of FIG.

  Referring to FIG. 7, in step S41, the controller 70 determines whether there is a regeneration request for the DPF 21 as in the process of step S1 of FIG.

  If there is no request for regeneration of the DPF 21, the controller 70 does nothing and ends the routine.

  If there is a regeneration request for the DPF 21, the controller 70 reads the bed temperature of the DPF 21 and the load and rotation speed of the internal combustion engine 1 in step S42 as in step S32 of FIG. 6, and in step S43, FIG. As in step S33, it is determined whether the bed temperature of the DPF 21 is equal to or lower than a predetermined temperature, the load of the internal combustion engine 1 is equal to or lower than the predetermined load, and the rotational speed of the internal combustion engine 1 is equal to or lower than the predetermined speed.

If the determination in step S43 is affirmative, the controller 70 performs the processes in steps S47 to S51 as in steps S34 to S38 in FIG. When the particulate deposition rate on the DPF 21 when the regeneration control of the DPF 21 is not performed in step S51 exceeds the particulate deposition rate on the DPF 21 under the regeneration control of the DPF 21, the step of FIG. 6 is performed at step S52. Similar to S39, the DPF regeneration subroutine using NO ₂ shown in FIG. 4 is executed to regenerate the DPF 21 using NO ₂ . After the process of step S52, the controller 70 ends the routine.

  If the particulate deposition rate on the DPF 21 when the regeneration control of the DPF 21 is not performed in step S51 does not exceed the particulate deposition rate on the DPF 21 under the regeneration control of the DPF 21, the controller 70 regenerates the DPF 21. The routine is terminated without performing.

  On the other hand, if the determination in step S43 is negative, the controller 70 detects the dilution of the engine oil in step S44. The controller 70 detects the engine oil dilution by the following method. That is, based on the post-injection amount executed by the fuel injection valve 40 and the period for executing post-injection, the dilution is obtained by referring to the dilution map stored in advance in the ROM. The dilution map is set so that the dilution increases as the post injection amount increases and the post injection execution period increases. Both the post injection amount and the post injection execution period are known values for the controller 70 because the controller 70 determines the fuel injection control of the fuel injection valve 40.

  In step S45, the controller 70 determines whether or not the dilution of the engine oil is equal to or greater than a predetermined dilution. When the engine oil dilution is not equal to or higher than the predetermined dilution, it is considered that the regeneration of the DPF 21 due to particulate combustion is not hindered. In this case, the controller 70 ends the routine after performing the forced temperature raising operation of the DPF 21 as in step S6 of FIG.

  On the other hand, if the dilution of the engine oil is equal to or greater than the predetermined dilution, the process after step S47 is performed without performing the forced temperature increase operation of the DPF 21 even if the determination in step S43 is negative. When engine oil dilution is high, if the DPF 21 is forced to warm up, including post injection and retarded main injection, the engine oil will be further diluted and the lubricating effect of the engine oil may be lost. Because there is sex.

In this embodiment, in such a case, the DPF 21 regeneration control using NO ₂ is performed as necessary without performing the forced temperature raising operation of the DPF 21, thereby preventing dilution of the engine oil and preventing the DPF 21 from being diluted. Playback can be performed.

  In each of the above embodiments, the intake throttle 32 and the fuel injection valve 40 constitute an exhaust temperature raising means, and steps S6, S40, and S46 of the controller 70 constitute a means for operating the exhaust temperature raising means. The oxidation catalyst 22 constitutes the nitrogen dioxide generating means, the intake throttle 32 and the variable nozzle 24 constitute the excess air ratio control means, the exhaust gas recirculation valve 31 and the bypass valve 38 constitute the exhaust gas recirculation control means, and step of the controller 70 S5, S39, and S50 constitute a means for operating the nitrogen dioxide generating means. The differential pressure sensor 63 and steps S1, S31, and S41 of the controller 70 constitute a deposition amount determining means. The accelerator pedal depression amount sensor 61, the crank angle sensor 60, and steps S3, S33, and S43 of the controller 70 constitute an operation region determination means. Step S43 of the controller 70 constitutes engine oil dilution determination means. Steps S34 and S47 of the controller 70 constitute a first calculation means. Steps S35-S37 and steps S48-S50 of the controller 70 constitute the second calculation means.

  As mentioned above, although this invention has been demonstrated through some specific embodiment, this invention is not limited to each said embodiment. Those skilled in the art can make various modifications or changes to these embodiments within the scope of the claims.

1 is a schematic configuration diagram of an internal combustion engine including an exhaust gas recirculation device according to a first embodiment of the present invention. It is a diagram explaining the DPF regeneration concept of the exhaust gas recirculation apparatus according to the first embodiment of the present invention. It is a flowchart explaining the DPF regeneration routine which the controller by 1st Embodiment of this invention performs. Is a flowchart illustrating DPF regeneration subroutine by NO ₂ by the controller according to the first embodiment of the present invention performs. It is a diagram which shows the relationship between an EGR rate, the amount of smoke generation, and the amount of NOx generation with respect to recirculation | reflux exhaust temperature and excess air ratio (lambda). It is a flowchart explaining the DPF regeneration routine which the controller by 2nd Embodiment of this invention performs. It is a flowchart explaining the DPF regeneration routine which the controller by 3rd Embodiment of this invention performs.

Explanation of symbols

1 Internal combustion engine 10 Intake passage 20 Exhaust passage 21 Diesel particulate filter (DPF)
22 Oxidation catalyst 24 Variable nozzle 31 EGR valve 32 Intake throttle 34 EGR cooler 37 Bypass passage 38 Bypass valve 40 Fuel injection valve 50 Turbo supercharger 60 Crank angle sensor 61 Accelerator pedal depression sensor 62 Temperature sensor 63 Differential pressure sensor 64 Temperature sensor 65 Temperature sensor 66 Air-fuel ratio sensor 67 Air flow meter 68 Flow rate sensor 69 NOx concentration sensor 70 Controller

Claims (5)

In an exhaust gas purification apparatus for an internal combustion engine for purifying exhaust gas from the internal combustion engine,
A diesel particulate filter that traps particulates contained in the exhaust;
Exhaust temperature raising means for raising the exhaust temperature;
Nitrogen dioxide generating means provided upstream of the diesel particulate filter and generating nitrogen dioxide so that nitrogen dioxide is contained in the exhaust,
A deposition amount judging means for judging whether or not a particulate deposition amount on the diesel particulate filter has reached a predetermined amount;
An operation region determination means for determining whether or not the operation state of the internal combustion engine is in an operation region suitable for regeneration of the diesel particulate filter by combustion when the amount of accumulated particulates reaches a predetermined amount;
Means for operating the exhaust gas temperature raising means when the particulate trap amount reaches a predetermined amount and the operating state of the internal combustion engine is in an operating region suitable for regeneration of the diesel particulate filter by combustion;
Means for operating the nitrogen dioxide generating means when the trapped amount of the particulate has reached a predetermined amount and the operating state of the internal combustion engine is not in an operating region suitable for regeneration of the diesel particulate filter by combustion;
Dilution determination means for determining dilution of engine oil for lubricating an internal combustion engine;
With
The operating region determining means is a low load low rotation region where the load of the internal combustion engine is equal to or lower than a predetermined load and the rotational speed of the internal combustion engine is equal to or lower than the predetermined rotational speed, and An exhaust purification device for an internal combustion engine, characterized in that it is determined that the operating state of the engine is not in an operating region suitable for regeneration of a diesel particulate filter by combustion.   First calculation means for calculating the particulate deposition rate of the diesel particulate filter when the nitrogen dioxide generation means is not operated, and calculation of the particulate deposition rate of the diesel particulate filter when the nitrogen dioxide generation means is operated And a second calculation unit, and the operation region determination unit prohibits the operation of the nitrogen dioxide generation unit when the calculation result of the first calculation unit does not exceed the calculation result of the second calculation unit. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, further comprising means.   The internal combustion engine includes an exhaust gas recirculation mechanism that recirculates a part of the exhaust gas to the intake air, and the nitrogen dioxide generating means includes an oxidation catalyst provided upstream of the diesel particulate filter with respect to the flow of the exhaust gas, and an air mixture gas burned by the internal combustion engine The exhaust purification of an internal combustion engine according to claim 1 or 2, further comprising: an excess air ratio control means for controlling an excess ratio; and an exhaust gas recirculation control means for controlling an exhaust gas recirculation rate and a temperature of the recirculated exhaust gas. apparatus.   The internal combustion engine includes a supercharger having a variable nozzle and an intake throttle, and the exhaust gas recirculation mechanism includes an exhaust gas recirculation passage, an exhaust gas recirculation valve that adjusts the flow rate of the exhaust gas recirculation passage according to the opening, and an exhaust gas recirculation passage. A cooler that cools the exhaust, a bypass passage that bypasses the cooler, and a bypass valve that changes a ratio of the exhaust passing through the cooler and the bypass passage, and the excess air ratio control means controls the opening of the intake throttle And means for controlling the opening degree of the variable nozzle, the exhaust gas recirculation control means comprising means for controlling the opening degree of the exhaust gas recirculation valve and means for controlling the ratio of the bypass valve. An exhaust emission control device for an internal combustion engine according to claim 3.   The internal combustion engine includes a fuel injection valve that injects fuel for combustion, and an intake throttle that adjusts the intake air amount. The exhaust temperature raising means controls the injection timing of the fuel injection valve, and the opening degree of the intake throttle. The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 4, wherein the exhaust gas purification device is configured by control means.

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