JP2014051896A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform PM removal control with optimal timing.SOLUTION: A particulate filter 24 for collecting particulates included in exhaust gas is arranged within an engine exhaust passage. The particulate filter includes exhaust gas inflow passages and exhaust gas outflow passages that are arranged alternately via porous partition walls. Movement promoting control for promoting movement of ash that is accumulated on inner peripheral faces of the exhaust gas inflow passages to back parts of the exhaust gas inflow passages is performed. Pressure loss of the particulate filter is detected. When the detected pressure loss is larger than a predetermined upper limit value, PM removal control for removing particulates from the particulate filter is performed.

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine.

  There is known an internal combustion engine in which a particulate filter for collecting particulate matter contained in exhaust gas is disposed in an engine exhaust passage. This particulate filter includes exhaust gas inflow passages and exhaust gas outflow passages that are alternately arranged via porous partition walls. As a result, the exhaust gas first flows into the exhaust gas inflow passage, then passes through the partition wall and flows out into the exhaust gas outflow passage. Accordingly, the particulate matter contained in the exhaust gas is collected in the partition wall or on the partition wall surface constituting the inner peripheral surface of the exhaust gas inflow passage.

  As the amount of particulate matter deposited on the particulate filter increases, the pressure loss of the particulate filter increases. When the pressure loss of the particulate filter increases, the engine output may decrease. Therefore, an exhaust emission control device for an internal combustion engine is known that performs PM removal control for removing particulate matter from the particulate filter when the pressure loss of the particulate filter is detected and the pressure loss exceeds the upper limit value ( Patent Document 1).

JP 2005-76462 A

  By the way, incombustible components called ash are also contained in the exhaust gas, and this ash is collected by the particulate filter together with the particulate matter. However, ash does not burn or vaporize even when PM removal control is performed. That is, the ash is not removed from the particulate filter and remains on the particulate filter. As a result, the pressure loss of the particulate filter is increased by the amount of ash accumulated on the particulate filter. For this reason, when PM removal control is performed because the pressure loss of the particulate filter has exceeded the upper limit value, the PM removal control is performed despite the relatively small amount of particulate matter deposited on the particulate filter. May occur. That is, there is a possibility that the execution timing of PM removal control may be made earlier than the optimal timing. Therefore, the PM removal control is undesirable and frequently performed, and there is a possibility that the energy consumed for the PM removal control increases.

  According to the present invention, the particulate filter for collecting the particulate matter contained in the exhaust gas is disposed in the engine exhaust passage, and the particulate filter is an exhaust gas that is alternately disposed via the porous partition walls. In the exhaust gas purification apparatus for an internal combustion engine having a gas inflow passage and an exhaust gas outflow passage, a movement for promoting the movement of the ash deposited on the inner peripheral surface of the exhaust gas inflow passage to the back of the exhaust gas inflow passage PM that removes particulate matter from the particulate filter when the detected pressure loss is larger than a predetermined upper limit value, the movement promoting means that performs acceleration control, the detection means that detects the pressure loss of the particulate filter An exhaust gas purification apparatus for an internal combustion engine is provided, which includes a PM removal unit that performs removal control.

  Preferably, the movement promoting means determines whether or not the amount of ash accumulated on the inner peripheral surface of the exhaust gas inflow passage is larger than a predetermined upper limit amount, and the ash amount is determined in advance. When it is determined that the amount is larger than the limit amount, the movement promotion control is performed.

  Preferably, the movement promoting means supplies a liquid to the particulate filter in order to perform movement promotion control. More preferably, the liquid is composed of at least one of water, an aqueous solution, and a liquid fuel. More preferably, condensed water generated in the internal combustion engine is stored in at least one of the engine intake passage, the engine exhaust passage upstream of the particulate filter, and the exhaust gas recirculation passage connecting the engine intake passage and the engine exhaust passage. A condensate water storage part is formed, and the movement promoting means supplies the condensed water stored in the condensate water storage part to the particulate filter in order to perform movement promotion control. More preferably, a NOx reduction catalyst disposed in the particulate filter or in the engine exhaust passage downstream of the particulate filter, and a reducing agent addition for secondarily adding a liquid reducing agent in the engine exhaust passage upstream of the particulate filter And a NOx reduction means for adding a liquid reducing agent from the reducing agent addition valve with an addition pressure for NOx reduction and an addition time for NOx reduction for NOx reduction. In order to perform this, the liquid reducing agent is added from the reducing agent addition valve with an addition pressure lower than the NOx reduction addition pressure or an addition time longer than the NOx reduction addition time.

  Preferably, the movement promoting means generates a pulsation in the pressure in the particulate filter in order to perform movement promotion control.

  Preferably, the movement promoting means vibrates the particulate filter in order to perform movement promotion control.

  Preferably, the movement promoting means raises the temperature of the particulate filter to a temperature higher than that during PM removal control in order to perform movement promotion control.

  Preferably, the movement promoting means supplies the liquid to the particulate filter and coagulates the liquid in order to perform movement promotion control.

  PM removal control can be performed at an optimal timing.

1 is an overall view of an internal combustion engine. It is the schematic of a cooling device. It is a front view of a particulate filter. It is side surface sectional drawing of a particulate filter. It is a time chart explaining PM removal control. It is a map which shows an increase part. It is a map which shows a decreasing part. It is a flowchart which shows the routine which performs PM removal control. It is a flowchart which shows the routine which performs calculation of particulate matter deposition amount QPM. It is a diagram which shows the relationship between pressure difference PD and particulate matter deposition amount QPM. It is a diagram which shows the relationship between pressure difference PD and particulate matter deposition amount QPM. It is a diagram which shows the relationship between pressure difference PD and particulate matter deposition amount QPM. It is a diagram which shows the relationship between pressure difference PD and particulate matter deposition amount QPM. It is a partial expanded sectional view of the particulate filter which shows the ash deposited on the inner peripheral surface of an exhaust gas inflow passage. It is a partial expanded sectional view of the particulate filter which shows the ash deposited in the back part of an exhaust gas inflow passage. It is a time chart explaining movement promotion control. It is a diagram explaining the difference of the intercept of two asymptotic lines. It is a diagram explaining the difference of the intercept of two asymptotic lines. It is a flowchart which shows the routine which performs engine starting control. It is a flowchart which shows the routine which performs movement promotion control. It is a flowchart which shows the routine which performs idling control. It is a flowchart which shows the routine which performs calculation of ratio R. It is a diagram explaining another Example of ratio R. It is a figure which shows another Example of a condensed water storage part. It is a figure which shows another Example of a condensed water storage part. It is a figure which shows another Example of a condensed water storage part. It is a general view of the internal combustion engine which shows another Example by this invention. It is a time chart explaining the movement promotion control of the Example shown by FIG. FIG. 20 is a flowchart showing a routine for executing movement promotion control shown in FIG. 19. FIG. It is a general view of the internal combustion engine which shows another Example by this invention. It is a time chart explaining the movement promotion control of the Example shown by FIG. It is a flowchart which shows the routine which performs the movement promotion control shown by FIG. It is a general view of the internal combustion engine which shows another Example by this invention. It is a general view of the internal combustion engine which shows another Example by this invention. It is a general view of the internal combustion engine which shows another Example by this invention. It is a general view of the internal combustion engine which shows another Example by this invention. It is a time chart explaining the movement promotion control of the Example shown by FIG. It is a flowchart which shows the routine which performs the movement promotion control shown by FIG. It is a general view of the internal combustion engine which shows another Example by this invention. It is a time chart explaining the movement promotion control of the Example shown by FIG. FIG. 30 is a flowchart showing a routine for executing movement promotion control shown in FIG. 29. FIG. It is a time chart explaining another Example by this invention. FIG. 32 is a flowchart showing a routine for performing exhaust purification control shown in FIG. 31. FIG. FIG. 32 is a flowchart showing a routine for executing movement promotion control shown in FIG. 31. It is a time chart explaining another Example by this invention. It is a flowchart which shows the routine which performs the engine stop control shown by FIG. FIG. 35 is a flowchart showing a routine for executing engine start control shown in FIG. 34. FIG. It is a flowchart which shows the routine which performs the movement promotion control at the time of a stop shown by FIG. It is a flowchart which shows the routine which performs the movement promotion control at the time of a start shown by FIG. It is a general view of the internal combustion engine which shows another Example by this invention. It is a time chart explaining the movement promotion control of the Example shown by FIG. It is a flowchart which shows the routine which performs the movement promotion control at the time of a stop shown by FIG.

  Referring to FIG. 1, 1 is a main body of a compression ignition internal combustion engine, 2 is a combustion chamber of each cylinder, 3 is an electronically controlled fuel injection valve for injecting fuel into each combustion chamber 2, and 4 is an intake manifold. Reference numeral 5 denotes an exhaust manifold. The intake manifold 4 is connected to the outlet of the compressor 7 c of the exhaust turbocharger 7 via the intake duct 6, and the inlet of the compressor 7 c is connected to the air cleaner 9 via the air flow meter 8. An electrically controlled throttle valve 10 is disposed in the intake duct 6, and a cooling device 11 for cooling intake air flowing in the intake duct 6 is disposed in the intake duct 6. On the other hand, the exhaust manifold 5 is connected to the inlet of the exhaust turbine 7 t of the exhaust turbocharger 7, and the outlet of the exhaust turbine 7 t is connected to the exhaust aftertreatment device 20.

  The exhaust manifold 5 and the intake manifold 4 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 12, and an electrically controlled EGR control valve 13 is disposed in the EGR passage 12. A cooling device 14 for cooling the EGR gas flowing in the EGR passage 12 is disposed in the EGR passage 12. On the other hand, each fuel injection valve 3 is connected to a common rail 16 through a fuel supply pipe 15. Fuel is supplied into the common rail 16 from an electronically controlled fuel pump 17 with variable discharge amount, and the fuel supplied into the common rail 16 is supplied to the fuel injection valve 3 through each fuel supply pipe 15. In the embodiment shown in FIG. 1, this fuel is composed of light oil. In another embodiment, the internal combustion engine comprises a spark ignition internal combustion engine in which combustion is performed under a lean air-fuel ratio. In this case, the fuel is composed of gasoline.

  The exhaust aftertreatment device 20 includes an exhaust pipe 21 connected to the outlet of the exhaust turbine 7t, a catalytic converter 22 connected to the exhaust pipe 21, and an exhaust pipe 23 connected to the catalytic converter 22. A wall flow type particulate filter 24 is disposed in the catalytic converter 22.

  The catalytic converter 22 is provided with a temperature sensor 25 for detecting the temperature of the particulate filter 24. In another embodiment, a temperature sensor for detecting the temperature of the exhaust gas flowing into the particulate filter 24 is disposed in the exhaust pipe 21. In yet another embodiment, a temperature sensor for detecting the temperature of the exhaust gas flowing out from the particulate filter 24 is disposed in the exhaust pipe 23. The temperature of these exhaust gases represents the temperature of the particulate filter 24.

  The catalytic converter 22 is further provided with a pressure loss sensor 26 for detecting the pressure loss of the particulate filter 24. In the embodiment shown in FIG. 1, the pressure loss sensor 26 includes a pressure difference sensor for detecting a pressure difference upstream and downstream of the particulate filter 24. In another embodiment, the pressure loss sensor 26 is a sensor that is attached to the exhaust pipe 21 and detects the engine back pressure.

  On the other hand, a fuel addition valve 27 is attached to the exhaust manifold 5. Fuel is supplied to the fuel addition valve 27 from the common rail 16, and fuel is added from the fuel addition valve 27 into the exhaust manifold 5. In another embodiment, the fuel addition valve 27 is disposed in the exhaust pipe 21.

  FIG. 2 shows the cooling device 14 provided in the EGR passage 12. The cooling device 14 includes a main passage 14a connected to the EGR passage 12, a cooler 14b arranged around the main passage 14a, and a main passage downstream from the cooler 14b by branching from the main passage 14a upstream of the cooler 14b. A bypass passage 14c that returns to 14a, and a bypass control valve 14d that selectively guides EGR gas to one of the main passage 14a and the bypass passage 14c. When the EGR gas is to be cooled, the bypass control valve 14d is controlled to the cooling position indicated by the solid line in FIG. 2, and thus the EGR gas is guided into the cooler 14b. On the other hand, when the EGR gas should not be cooled as in the cold operation, the bypass control valve 14d is controlled to the bypass position indicated by the broken line in FIG. 2, and thus the EGR gas is bypassed the cooler 14b. Further, the bypass passage 14 c is provided with a condensed water storage portion 14 e for storing condensed water generated in the EGR passage 12 and the cooling device 14. In the embodiment shown in FIG. 2, the condensed water storage part 14e is constituted by a recess formed on the bottom surface of the bypass passage 14c.

  Referring again to FIG. 1, the electronic control unit 30 is composed of a digital computer and is connected to each other by a bidirectional bus 31, a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, and a CPU (Microprocessor) 34. The input port 35 and the output port 36 are provided. Output signals of the air flow meter 8, the temperature sensor 25, and the pressure difference sensor 26 are input to the input port 35 via corresponding AD converters 37, respectively. The accelerator pedal 39 is connected to a load sensor 40 that generates an output voltage proportional to the depression amount L of the accelerator pedal 39. The output voltage of the load sensor 40 is input to the input port 35 via the corresponding AD converter 37. Is done. A water temperature sensor 41 for detecting the engine cooling water temperature and an oil temperature sensor 42 for detecting the engine lubricating oil temperature are attached to the engine main body 1, and the output voltages of these sensors 41, 42 respectively correspond to corresponding AD converters 37. To the input port 35. Further, a crank angle sensor 43 that generates an output pulse every time the crankshaft rotates, for example, 15 ° is connected to the input port 35. The CPU 34 calculates the engine speed Ne based on the output pulse from the crank angle sensor 43. The input port 35 further receives signals indicating whether the ignition switch 44 and the starter switch 45 are on or off. The starter motor 46 is operated when the starter switch 45 is turned on. On the other hand, the output port 36 is connected to the fuel injection valve 3, the throttle valve 10 drive device, the EGR control valve 13, the bypass control valve 14 d, the fuel pump 17, the fuel addition valve 27, and the starter motor 46 through corresponding drive circuits 38. Is done.

  3A and 3B show the structure of the wall flow type particulate filter 24. FIG. 3A shows a front view of the particulate filter 24, and FIG. 3B shows a side sectional view of the particulate filter 24. As shown in FIG. As shown in FIGS. 3A and 3B, the particulate filter 24 has a honeycomb structure, and a plurality of exhaust flow passages 71i and 71o extending in parallel to each other, and a partition wall that separates the exhaust flow passages 71i and 71o from each other. 72. In the embodiment shown in FIG. 3A, the exhaust flow passages 71i and 71o include an exhaust gas inflow passage 71i having an upstream end opened and a downstream end closed by a plug 73d, and an upstream end closed by a plug 73u and a downstream end. The exhaust gas outflow passage 71o is opened. In addition, the hatched part in FIG. 3A shows a plug 73u. Therefore, the exhaust gas inflow passages 71 i and the exhaust gas outflow passages 71 o are alternately arranged via the thin partition walls 72. In other words, in the exhaust gas inflow passage 71i and the exhaust gas outflow passage 71o, each exhaust gas inflow passage 71i is surrounded by four exhaust gas outflow passages 71o, and each exhaust gas outflow passage 71o is surrounded by four exhaust gas inflow passages 71i. Arranged so that. In another embodiment, the exhaust flow passage is constituted by an exhaust gas inflow passage whose upstream end and downstream end are opened, and an exhaust gas outflow passage whose upstream end is closed by a plug and whose downstream end is opened.

  The partition wall 72 is formed of a porous material, for example, a ceramic such as cordierite, silicon carbide, silicon nitride, zirconia, titania, alumina, silica, mullite, lithium aluminum silicate, zirconium phosphate. Therefore, as shown by an arrow in FIG. 3B, the exhaust gas first flows into the exhaust gas inflow passage 71i, and then flows into the adjacent exhaust gas outflow passage 71o through the surrounding partition wall 72. Thus, the partition 72 constitutes the inner peripheral surface of the exhaust gas inflow passage 71i. The average pore diameter of the partition wall 72 is about 10 to 25 μm.

  A catalyst having an oxidation function is supported on both side surfaces of the partition wall 72 and the inner surfaces of the pores. The catalyst having an oxidation function is composed of a noble metal such as platinum Pt, rhodium Rh, or palladium Pd. In another embodiment, the catalyst having an oxidation function is composed of a complex oxide containing a base metal such as cerium Ce, praseodymium Pr, neodymium Nd, and lanthanum La. In yet another embodiment, the catalyst is composed of a combination of noble metals and composite oxides.

  Now, the exhaust gas contains particulate matter mainly formed from solid carbon. This particulate matter is collected on the particulate filter 24. Combustion is performed in the combustion chamber 2 under excess oxygen. Therefore, unless the fuel is secondarily supplied from the fuel injection valve 3 and the fuel addition valve 27, the particulate filter 24 is in an oxidizing atmosphere. Further, the particulate filter 24 carries a catalyst having an oxidation function. As a result, the particulate matter collected by the particulate filter 24 is sequentially oxidized. However, when the amount of particulate matter collected per unit time is larger than the amount of particulate matter oxidized per unit time, the amount of particulate matter collected on the particulate filter 24 is reduced. It increases with the passage of engine operating time.

  Therefore, in the embodiment according to the present invention, the PM removal control for removing the particulate matter from the particulate filter 24 is repeatedly performed. As a result, the particulate matter on the particulate filter 24 is removed, and the pressure loss of the particulate filter 24 is reduced.

  In the embodiment shown in FIG. 1, the PM removal control is constituted by a temperature increase control that raises and holds the temperature of the particulate filter 24 to the PM removal temperature (for example, 600 ° C.) in order to oxidize and remove the particulate matter. . In order to execute the temperature raising control, in one embodiment, fuel is added from the fuel addition valve 27, and this fuel is burned in the exhaust passage or the particulate filter 24. In another embodiment, fuel is injected from the fuel injection valve 3 into the compression stroke or the exhaust stroke, and this fuel is burned in the combustion chamber 2, the exhaust passage, or the particulate filter 24.

  That is, as shown in FIG. 4, when the pressure loss of the particulate filter 24, that is, the pressure difference PD becomes larger than the upper limit value UPD at time ta1, PM removal control, that is, temperature increase control is started. Therefore, the temperature TF of the particulate filter 24 is raised to the PM removal temperature TFPM and held. As a result, the pressure difference PD is reduced. In addition, the amount QPM of particulate matter deposited on the particulate filter 24 is also reduced. Next, when the particulate matter deposition amount QPM becomes smaller than the lower limit LQPM at time ta2, the PM removal control is ended. Therefore, the temperature TF of the particulate filter 24 decreases. Next, at time ta3, when the pressure difference PD becomes larger than the upper limit value UPD, PM removal control is started. Next, when the particulate matter deposition amount QPM becomes smaller than the lower limit LQPM at time ta4, the PM removal control is ended. In this way, PM removal control is repeatedly performed.

  In one embodiment, the particulate matter accumulation amount QPM is obtained based on the engine operating state for an increase qPMi per unit time and a decrease qPMd per unit time, and the sum of the increase qPMi and the decrease qPMd is integrated. (QPM = QPM + qPMi−qPMd). As shown in FIG. 5A, the increase qPMi is stored in advance in the ROM 32 (FIG. 1) in the form of a map as a function of the fuel injection amount QF and the engine speed Ne. The fuel injection amount QF represents the engine load. On the other hand, the decrease qPMd is stored in advance in the ROM 32 in the form of a map as a function of the intake air amount Ga and the temperature TF of the particulate filter 24 as shown in FIG. 5B. The intake air amount Ga represents the flow rate of exhaust gas or oxygen flowing into the particulate filter 24.

  FIG. 6 shows a routine for executing the PM removal control shown in FIG. Referring to FIG. 6, in step 101, it is determined whether or not the pressure difference PD of the particulate filter 24 is larger than the upper limit value UPD. When PD> UPD, the routine proceeds to step 102 where temperature increase control is performed. That is, the target value TTF of the temperature TF of the particulate filter 24 is set to the PM removal temperature TFPM. In the embodiment shown in FIG. 1, the temperature of the particulate filter 24 is controlled so that the actual temperature of the particulate filter 24 becomes the target value TTF. In the following step 103, it is determined whether or not the particulate matter deposition amount QPM is smaller than the lower limit value LQPM. When QPM ≧ LQPM, the process returns to step 102. When QPM <LQPM, the processing cycle is terminated. Therefore, the temperature increase control is terminated. In step 101, when PD ≦ UPD, the processing cycle is terminated. In this case, temperature increase control is not performed.

  FIG. 7 shows a routine for calculating the particulate matter deposition amount QPM. Referring to FIG. 7, in step 111, an increase qPMi is calculated from the map of FIG. 5A. In the following step 112, the decrease qPMd is calculated from the map of FIG. 5B. In the following step 113, the particulate matter accumulation amount QPM is calculated (QPM = QPM + qPMi−qPMd).

  In another embodiment, the PM removal control includes NOx increase control for increasing the amount of NOx in the exhaust gas flowing into the particulate filter 24 in order to oxidize and remove particulate matter by NOx. In order to increase the amount of NOx, for example, the amount of EGR gas is decreased. In still another embodiment, the PM removal control is configured to supply ozone to the particulate filter 24 from an ozone supply device connected to an exhaust passage upstream of the particulate filter 24 in order to oxidize and remove particulate matter by ozone. Consists of supply control.

By the way, ash is contained in the exhaust gas, and this ash is also collected by the particulate filter 24 together with the particulate matter. It has been confirmed by the present inventors that this ash is mainly formed from calcium salts such as calcium sulfate CaSO ₄ and zinc phosphate calcium Ca ₁₉ Zn ₂ (PO ₄ ) ₁₄ . Calcium Ca, zinc Zn, phosphorus P and the like are derived from engine lubricating oil, and sulfur S is derived from fuel. That is, taking calcium sulfate CaSO ₄ as an example, engine lubricating oil flows into combustion chamber 2 and burns, and calcium Ca in the lubricating oil combines with sulfur S in the fuel to produce calcium sulfate CaSO _4. Is done.

  However, even if PM removal control is performed, the ash does not burn or vaporize. That is, the ash remains on the particulate filter 24 without being removed from the particulate filter 24. As a result, the pressure loss or pressure difference PD of the particulate filter 24 increases by the amount of ash accumulated on the particulate filter 24.

  That is, when the engine operation is started from a state where the particulate filter 24 is new, as shown in FIG. 8A, the pressure difference PD is from its initial value PD0, and the particulate matter deposition amount QPM is from its initial value of zero. Each increases along the curve CT1. Next, when the pressure difference PD becomes larger than the upper limit value UPD, PM removal control is started. As a result, as shown in FIG. 8B, the pressure difference PD decreases from the upper limit value UPD, and the particulate matter deposition amount QPM decreases from the value QPM1 along the curve CR1. Next, when the particulate matter accumulation amount QPM becomes smaller than the lower limit LQPM, the PM removal control is terminated. As a result, as shown in FIG. 8C, the pressure difference PD increases from the value PD1, and the particulate matter deposition amount QPM increases from the lower limit value LQPM along the curve CT2. Next, when the pressure difference PD becomes larger than the upper limit value UPD, PM removal control is started. As a result, as shown in FIG. 8D, the pressure difference PD decreases from the upper limit value UPD, and the particulate matter deposition amount QPM decreases from the value QPM2 along the curve CR2. Next, when the particulate matter accumulation amount QPM becomes smaller than the lower limit LQPM, the PM removal control is terminated. In this way, the increase and decrease of the pressure difference PD and the particulate matter accumulation amount QPM are alternately repeated.

  From another viewpoint, FIG. 8A shows the first increase action of the pressure difference PD and the particulate matter deposition amount QPM, and FIG. 8B shows the first decrease action of the pressure difference PD and the particulate matter deposition amount QPM. 8C shows a second increase action of the pressure difference PD and the particulate matter deposition amount QPM, and FIG. 8D shows a second decrease action of the pressure difference PD and the particulate matter deposition amount QPM. Yes.

  As described above, as the engine operation time becomes longer, the particulate matter deposition amount QPM at the time when the increase of the pressure difference PD and the particulate matter deposition amount QPM is stopped, that is, when the PM removal control is started, decreases. (QPM1> QPM2), the pressure difference PD at the time when the pressure difference PD and the particulate matter accumulation amount QPM start to increase is increased (PD0 <PD1 <PD2). As a result, there is a possibility that the execution timing of PM removal control may be made earlier than the optimal timing. In this case, the PM removal process is undesirable and frequently performed, and the fuel consumption is undesirably increased.

  On the other hand, roughly speaking, the ash on the particulate filter 24 is dispersed in the ash A on the inner peripheral surface 71is of the exhaust gas inflow passage 71i as shown in FIG. 9A, and in FIG. 9B. As shown in the drawing, it is considered that the ash A is formed from one or both of the ash A locally deposited in the back or bottom 71ir of the exhaust gas inflow passage 71i. In addition, the ash A accumulated on the inner peripheral surface 71is of the exhaust gas inflow passage 71i has a great influence on the pressure loss or pressure difference PD of the particulate filter 24. On the other hand, the ash A accumulated in the inner portion 71ir of the exhaust gas inflow passage 71i has little influence on the pressure loss or pressure difference PD of the particulate filter 24.

  Then, if the ash A accumulated on the inner peripheral surface 71is is moved to the inner portion 71ir, the influence of the ash on the pressure difference PD can be weakened. In this regard, for example, when the amount of exhaust gas flowing into the particulate filter 24 is large, such as during engine high load operation, a part of the ash A accumulated on the inner peripheral surface 71is is caused by the exhaust gas flow. It may be moved to 71ir. However, in this case, it is difficult to move a sufficient amount of ash.

  Therefore, in the embodiment according to the present invention, movement promotion control is performed to promote the movement of the ash A accumulated on the inner peripheral surface 71is of the exhaust gas inflow passage 71i to the inner portion 71ir of the exhaust gas inflow passage 71i. As a result, the amount of ash accumulated on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is reduced, and the influence of the ash on the pressure difference PD can be kept small. Therefore, the execution timing of PM removal control can be maintained at an optimal timing.

  In the embodiment shown in FIG. 1, movement promotion control is performed by supplying liquid to the particulate filter 24. This liquid is composed of condensed water stored in the condensed water storage part 14e.

  Further, in the embodiment shown in FIG. 1, it is determined whether or not the amount of ash deposited on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is larger than a predetermined upper limit amount, and on the inner peripheral surface 71is. When it is determined that the amount of ash deposited on the engine is larger than the upper limit, movement promotion control is performed at the time of engine cold start. On the other hand, the movement promotion control is not performed when it is not determined that the amount of ash deposited on the inner peripheral surface 71is is larger than the upper limit amount. This movement promotion control will be described with reference to FIG.

  In FIG. 10, the solid line indicates the case where the movement promotion control is performed, and the broken line indicates the case where the movement promotion control is not performed. Referring to FIG. 10, at time tb1, the ignition switch 44 is turned on and the starter switch 45 is turned on, so that the engine start is started. As a result, the engine speed Ne increases. Next, at time tb2, complete explosion occurs when the engine speed Ne exceeds a predetermined set value NeC (for example, 900 rpm). Next, when the movement promotion control is not performed, normal idling control is performed as shown by a broken line in FIG. That is, when the engine operation is a cold operation, the engine rotation speed Ne is maintained at a cold idling rotation speed NeIC (for example, 1000 rpm at the highest). Further, the EGR control valve 13 is closed, and therefore the supply of EGR gas is prohibited. Next, when the engine operation is switched to the warm operation at time tb4, the engine rotational speed Ne is maintained at the idling rotational speed NeIW (for example, 700 to 800 rpm). In addition, supply of EGR gas is allowed. That is, the opening degree DEGR of the EGR control valve 13 is controlled according to the engine operating state. In the embodiment shown in FIG. 1, when both the engine cooling water temperature and the engine lubricating oil temperature are lower than a preset temperature (for example, 20 ° C.), it is determined that the engine operation is a cold operation, and the engine When one or both of the cooling water temperature and the engine lubricating oil temperature is higher than the set temperature, it is determined that the engine operation is a warm operation.

  On the other hand, when the movement promotion control is performed, as shown by a solid line in FIG. 10, after the complete explosion at time tb2, the engine speed Ne is set to a predetermined movement promotion idling speed NeIT (for example, 1500 rpm). ) Is maintained. The movement promoting idling rotational speed NeIT is set higher than the normal idling rotational speeds NeIC and NeIW. As a result, the amount of gas flowing through the intake manifold 4, the combustion chamber 2, the exhaust manifold 5, the exhaust pipe 21, and the particulate filter 24 is increased. Further, the opening degree DEGR of the EGR control valve 13 is opened. In the example shown in FIG. 10, the opening degree DEGR is set to 100%, that is, the EGR control valve 13 is fully opened. At this time, since the engine operation is a cold operation, the bypass control valve 14d of the cooling device 14 is controlled to the bypass position (FIG. 2). As a result, a relatively large amount of EGR gas flows in the bypass passage 14c, and condensed water is discharged from the condensed water storage portion 14e by this large amount of EGR gas. This condensed water flows through the intake manifold 4, the combustion chamber 2, the exhaust manifold 5, and the exhaust pipe 21 together with the EGR gas, and is supplied into the particulate filter 24.

  As a result, the ash on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is caused to flow by the condensed water and is moved to the inner portion 71ir. Alternatively, the ash is swollen by the condensed water, the ash layer formed on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is destroyed, and the ash is easily separated from the inner peripheral surface 71is. The ash peeled from the inner peripheral surface 71is is easily moved to the inner portion 71ir by the exhaust gas during the subsequent engine operation.

  In this case, since the engine operation is a cold operation, the condensed water is supplied to the particulate filter 24 in a liquid state, and therefore the ash movement can be surely promoted. Note that the amount of condensed water passing through the combustion chamber 2 by the movement promotion control is relatively small, and the water hammer phenomenon does not occur. Further, when the movement promotion control is performed, the particulate matter deposited on the inner peripheral surface 71is is also moved to the inner portion 71ir. The particulate matter thus moved is removed during the subsequent PM removal process.

  Next, when a predetermined set time tB has elapsed at time tb3, normal idling control is started. That is, when the engine operation is the cold operation, the engine speed Ne is maintained at the cold idling speed NeIC, and the EGR control valve 13 is closed. Next, when the engine operation is switched to the warm operation at time tb4, the engine rotational speed Ne is maintained at the warm idling rotational speed NeIW, and the supply of EGR gas is allowed.

  When the fuel consumption rate when the particulate filter 24 is new is referred to as a new fuel consumption rate, according to the present inventors, the amount of ash deposited on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is determined in advance. When the amount exceeds the upper limit amount, the increase in the fuel consumption rate with respect to the fuel consumption rate when new is about 13%. Next, after the movement promotion control was performed, the increase in the fuel consumption rate relative to the fuel consumption rate at the time of new article was about 3%. Thus, the increase in fuel consumption can be reliably suppressed by the movement promotion control.

Whether or not the amount of ash accumulated on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is larger than a predetermined upper limit is determined, for example, as follows. That is, as shown in FIG. 11A, the pressure difference PD and the particulate matter deposition amount QPM change along the curve CT1 during the first increasing action. An asymptote AST1 of the curve CT1 is expressed by the following equation.
PD = A1 · QPM + (B1 + C1)

Further, the pressure difference PD and the particulate matter deposition amount QPM change along the curve CR1 during the first decreasing action. The asymptote ASR1 of the curve CR1 is expressed by the following equation.
PD = A1 ・ QPM + B1

  The difference between the intercepts of these two equations is represented by C1. B1 represents the pressure loss of the particulate filter 24 itself and corresponds to PD0.

Similarly, as shown in FIG. 11B, the pressure difference PD and the particulate matter deposition amount QPM change along the curve CTi during the i-th increasing action (i = 1, 2,...). The asymptotic line ASTi of the curve CTi is expressed by the following equation.
PD = Ai · QPM + (Bi + Ci)

Further, the pressure difference PD and the particulate matter accumulation amount QPM change along the curve CRi during the i-th decreasing action. The asymptote ASRi of the curve CRi is expressed by the following equation.
PD = Ai · QPM + Bi

  The difference between the intercepts of these two equations is represented by Ci.

  The intercept difference Ci represents the amount of particulate matter deposited on the particulate filter 24 during the i-th increase in the pressure difference PD and particulate matter deposition amount QPM, or the pressure difference PD and particulate matter deposition amount. This represents the amount of particulate matter removed from the particulate filter 24 during the i-th decreasing action of QPM. The amount of the particulate matter decreases as the amount of ash deposited on the inner peripheral surface 71is of the exhaust gas inflow passage 71i increases. Therefore, the difference Ci or the ratio R (= Ci / C1) decreases as the amount of ash accumulated on the inner peripheral surface 71is of the exhaust gas inflow passage 71i increases. 11A shows a case where the difference Ci or the ratio R is large, and FIG. 11B shows a case where the difference Ci or the ratio R is small.

  Therefore, in the embodiment shown in FIG. 1, when the ratio R is smaller than a predetermined lower limit value RL, the amount of ash accumulated on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is determined in advance. When the ratio R is larger than the lower limit RL, it is determined that the amount of ash deposited on the inner peripheral surface 71is is smaller than the upper limit.

  FIG. 12 shows a routine for executing engine start control in the embodiment shown in FIG. This routine is executed only once when the ignition switch 44 is turned on. Referring to FIG. 12, in step 121, the flag X is reset (X = 0). This flag X is set when the normal idling control routine (FIG. 14) is to be executed (X = 1), and is reset otherwise (X = 0). In the following step 122, it is determined whether or not the engine speed Ne is higher than the set speed NeC. When Ne ≦ NeC, the process returns to step 122. When Ne> NeC, that is, when a complete explosion has occurred, the routine proceeds to step 123, where it is determined whether the ratio R is smaller than the lower limit value RL. When R <RL, the routine proceeds to step 124 where it is judged if the engine operation is a cold operation. When the engine operation is a cold operation, the routine proceeds to step 125, where a movement promotion control routine is executed. In the following step 126, the flag X is set (X = 1). When R ≧ RL at step 123 and when engine operation is warm in step 125, the routine proceeds to step 126. Therefore, movement promotion control is not performed in these cases.

  FIG. 13 shows a routine for executing the movement promotion control in the embodiment shown in FIG. This routine is executed in step 125 of FIG. 12, for example. Referring to FIG. 13, in step 131, the target rotational speed TNe is set to the movement promotion idling rotational speed NeIT. In the embodiment shown in FIG. 1, the engine speed is controlled so that the actual engine speed becomes the target speed TNe. In the following step 132, the EGR control valve 13 is opened. In the following step 133, it is determined whether or not the set time tB has elapsed. When the set time tB has not elapsed, the process returns to step 131. When the set time tB has elapsed, the processing cycle is terminated. That is, the movement promotion control is terminated, and the process proceeds to step 126 in FIG.

  FIG. 14 shows a routine for executing normal idling control. Referring to FIG. 14, in step 141, it is determined whether or not the depression amount L of the accelerator pedal 39 is zero, that is, whether or not the engine operation is an idling operation. When L> 0, that is, when the engine operation is not the idling operation, the processing cycle is terminated. When L = 0, that is, when the engine operation is the idling operation, the routine proceeds to step 142 where it is determined whether or not the flag X is set. When the flag X is reset (X = 0), the processing cycle ends. On the other hand, when the flag X is set (X = 1), the process proceeds to step 143. Therefore, the routine does not proceed to step 143 until the flag X is set in step 126 of the routine of FIG. In step 143, it is determined whether or not the engine operation is a cold operation. Next, when the engine operation is the cold operation, the routine proceeds to step 144, where the target rotational speed TNe is set to the cold idling rotational speed NeIC. In the following step 146, the EGR control valve 13 is closed. On the other hand, when the engine operation is the warm operation, the routine proceeds to step 146, where the target engine speed TNe is set to the warm idling engine speed NeIW. In the subsequent step 147, the supply of EGR gas is allowed.

  FIG. 15 shows a routine for calculating the ratio R. Referring to FIG. 15, in step 151, the pressure difference PD is read. In the following step 152, the particulate matter amount QPM is read. In the following step 153, it is determined whether or not the PM removal control is switched from execution to stop. When the PM removal control has not been switched from execution to stop, the routine proceeds to step 154, where it is determined whether or not the PM removal control has been switched from stop to execution. When the PM removal control is not switched from stop to execution, the processing cycle is terminated. When the PM removal control is switched from stop to execution, that is, when the i-th increase action of the pressure difference PD and the particulate matter deposition amount QPM is finished, the process proceeds to step 155, and the curve CTi of the i-th increase action is asymptotic. Line ASTi is determined. Next, when the PM removal control is switched from execution to stop, that is, when the i-th reduction action of the pressure difference PD and the particulate matter deposition amount QPM is completed, the process proceeds from step 153 to step 156 to proceed to the i-th reduction action. Asymptotic line ASRi of the curve CRi is determined. In the subsequent step 157, the intercept difference Ci is calculated. In the following step 158, the ratio R is calculated (R = Ci / C1). In the subsequent step 159, the parameter i is incremented by 1 (i = i + 1). The parameter i is set to 1 when the engine is started.

  Next, another embodiment of the ratio R will be described with reference to FIG. As shown in FIG. 16, the pressure difference PD decreases by Di (= UPD−PD (i + 1)) at the time of the i-th decreasing action. The decrease Di or the ratio Di / D1 decreases as the amount of ash deposited on the inner peripheral surface 71is of the exhaust gas inflow passage 71i increases. Therefore, the ratio R is calculated in the form of Di / D1. In yet another embodiment, when the difference Ci or the decrease Di is smaller than a predetermined lower limit value, the amount of ash deposited on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is a predetermined upper limit amount. When the difference Ci or the decrease Di is larger than the lower limit value, it is determined that the amount of ash deposited on the inner peripheral surface 71is is smaller than the upper limit amount.

  FIG. 17A to FIG. 17C show another embodiment of the condensed water reservoir 14e. In the embodiment shown in FIG. 17A, the bypass passage 14c of the cooling device 14 is bent downward, and the condensed water storage portion 14e is formed of a bent portion of the bypass passage 14c. In the embodiment shown in FIG. 17B, the condensed water storage portion 14 e is configured by a recess formed on the bottom surface of the intake manifold 4. In the embodiment shown in FIG. 17C, the condensed water storage part 14 e is configured by a recess formed on the bottom surface of the exhaust manifold 5. In the embodiment shown in FIGS. 17B and 17C, the EGR control valve 13 is closed during the movement promotion control. In yet another embodiment, the condensate water storage portion 14e is constituted by a recess formed on the bottom surface of the housing of the exhaust turbocharger 7 or a recess formed on the bottom surface of the exhaust pipe 21.

  FIG. 18 shows another embodiment according to the present invention. Referring to FIG. 18, the particulate filter 24 carries a NOx reduction catalyst 24a. The NOx reduction catalyst 24a has a function of reducing NOx in the exhaust gas with a reducing agent in an oxidizing atmosphere containing the reducing agent. The NOx reduction catalyst 24a is composed of, for example, a vanadium / titania catalyst in which vanadium oxide is supported on a support formed from titania or a copper zeolite catalyst in which copper is supported on a support formed from zeolite. In another embodiment, the NOx reduction catalyst is disposed downstream of the particulate filter 24.

  The exhaust pipe 21 upstream of the NOx reduction catalyst 24a is provided with a reducing agent addition valve 50 for secondary addition of a reducing agent into the exhaust gas. The reducing agent addition valve 50 is connected to a reducing agent tank 52 via a reducing agent supply pipe 51, and a reducing agent pump 53 capable of adjusting the discharge pressure is disposed in the reducing agent supply pipe 51. In the example shown in FIG. 18, the reducing agent is composed of a urea aqueous solution, and the reducing agent tank 52 contains the urea aqueous solution.

  During normal operation after the engine start is completed, a reducing agent is added from the reducing agent addition valve 50 in order to reduce NOx. This reducing agent is then supplied to the NOx reduction catalyst 24a. As a result, NOx is reduced in the NOx reduction catalyst 24a. In this case, the reducing agent is added from the reducing agent addition valve 50 with the NOx reduction addition pressure and the NOx reduction addition time. The NOx reduction addition pressure and the NOx reduction addition time are selected according to the engine operating state so that the reducing agent, that is, the urea aqueous solution can be sufficiently atomized.

  In the embodiment shown in FIG. 18, the liquid supplied by the movement promotion control is composed of a reducing agent added from the reducing agent addition valve 50, that is, an aqueous urea solution. That is, as shown in FIG. 19, after a start of the engine at time tc1, when a complete explosion occurs at time tc2, the engine speed Ne is maintained at the movement promoting idling speed NeIT. As a result, the amount of exhaust gas flowing through the particulate filter 24 is increased. At this time, the reducing agent is added in liquid form from the reducing agent addition valve 50 with the addition pressure for promoting movement. This liquid reducing agent is supplied to the particulate filter 24 by exhaust gas. As a result, the ash on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is promoted to move to the inner portion 71r. Next, when the movement promotion addition time tC has elapsed at time tc3, normal idling control is started. Further, the addition of the liquid reducing agent is stopped. That is, the movement promotion control is stopped.

  The movement promoting addition pressure and the movement promoting addition time are set so that the reducing agent is hardly atomized and is supplied to the particulate filter 24 in a liquid form. That is, the reducing agent is added with a movement promotion addition pressure lower than the NOx reduction addition pressure or a movement promotion addition time longer than the NOx reduction addition time. The movement promoting addition pressure and the movement promoting addition time are set according to the engine operating state. In the embodiment shown in FIG. 18, the movement promoting addition pressure increases as the amount of intake air increases, and increases as the temperature of the exhaust gas flowing into the particulate filter 24 increases. Further, the movement promoting addition time becomes longer as the pressure in the exhaust pipe 21 becomes higher, and becomes longer as the amount of ash deposited on the inner peripheral surface 71is of the exhaust gas inflow passage 71i increases.

  FIG. 20 shows a routine for executing the movement promotion control shown in FIG. This routine is executed in step 125 of FIG. 12, for example. Referring to FIG. 19, in step 161, the target rotational speed TNe is set to the movement promotion idling rotational speed NeIT. In the following step 162, the movement promoting addition pressure is calculated. In the following step 163, the movement promoting addition time is calculated. In the subsequent step 164, the reducing agent is added from the reducing agent addition valve 50 with the movement promoting addition pressure for the movement promoting addition time. The processing cycle is then terminated. That is, the movement promotion control is terminated, and the process proceeds to step 126 in FIG.

  Next, another embodiment of the movement promotion control in the embodiment shown in FIG. 1 or FIG. 18 will be described. In this embodiment, the liquid supplied by the movement promotion control is constituted by the fuel added from the fuel addition valve 27. The fuel added from the fuel addition valve 27 is used to reduce NOx by the catalyst supported on the particulate filter 24, or is used to perform the temperature increase control described above.

  When the movement promotion control is to be performed, the liquid fuel is added from the fuel addition valve 27. In this case, the fuel is added with an addition pressure lower than the addition pressure for NOx reduction or temperature rise control or an addition time longer than the addition time for NOx reduction or temperature rise control. As a result, fuel is added to the particulate filter 24 in liquid form.

  As described above, when the liquid is added from the reducing agent addition valve 50 (FIG. 18) or the fuel addition valve 27 (FIG. 1) in order to perform the movement promotion control, no additional configuration is required.

  FIG. 21 shows still another embodiment according to the present invention. Referring to FIG. 21, the EGR passage 12 is provided with a liquid addition valve 55 for secondarily adding a liquid into the EGR gas. The liquid addition valve 55 is connected to a liquid tank 57 via a liquid supply pipe 56, and a liquid pump 58 capable of adjusting the discharge pressure is disposed in the liquid supply pipe 56. In the example shown in FIG. 21, the liquid is composed of water, and the liquid tank 57 contains water. In another embodiment, the liquid is composed of an aqueous solution or a liquid fuel.

  In the embodiment shown in FIG. 21, the liquid supplied by the movement promotion control is composed of the liquid added from the liquid addition valve 55, that is, water. That is, as shown in FIG. 22, when a complete explosion occurs at time td2 after engine start at time td1, the engine speed Ne is maintained at the movement promoting idling speed NeIT. Further, the EGR control valve 13 is opened. At this time, water is added from the liquid addition valve 55 with an addition pressure for promoting movement. This water is supplied to the particulate filter 24 by exhaust gas. As a result, the ash on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is promoted to move to the inner portion 71r. In this case, the movement promoting addition pressure and the movement promoting addition time are set so that water is supplied to the particulate filter 24 in a liquid form. Next, when the movement promotion addition time tD has elapsed at time td3, normal idling control is started. Also, the addition of water is stopped. That is, the movement promotion control is stopped.

  FIG. 23 shows a routine for executing the movement promotion control shown in FIG. This routine is executed in step 125 of FIG. 12, for example. Referring to FIG. 23, in step 171, the target rotational speed TNe is set to the movement promotion idling rotational speed NeIT. In the subsequent step 172, the EGR control valve 13 is opened. In the subsequent step 173, the movement promoting addition pressure is calculated. In the subsequent step 174, the movement promotion addition time is calculated. In the subsequent step 175, the liquid is added from the liquid addition valve 55 with the movement promoting addition pressure for the movement promoting addition time. The processing cycle is then terminated. That is, the movement promotion control is terminated, and the process proceeds to step 126 in FIG.

  In the embodiment shown in FIG. 24A, a liquid addition valve 55 is arranged in the intake duct 6. In the embodiment shown in FIG. 24B, a liquid addition valve 55 is arranged in the exhaust manifold 5. In the embodiment shown in FIG. 24C, the liquid addition valve 55 is disposed in the exhaust pipe 21. In the embodiment shown in FIGS. 24A to 24C, the EGR control valve 13 is closed during the movement promotion control.

  FIG. 25 shows still another embodiment according to the present invention. Referring to FIG. 25, an exhaust control valve 60 capable of opening and closing the inside of the exhaust pipe 23 is disposed in the exhaust pipe 23 downstream of the particulate filter 24. The exhaust control valve 60 is normally fully opened.

  In the embodiment shown in FIG. 25, the movement promotion control is constituted by generation of pressure pulsation in the particulate filter 24. That is, as shown in FIG. 26, after the engine is started at time te1, when a complete explosion occurs at time te2, the engine speed Ne is maintained at the movement promoting idling speed NeIT. At this time, the exhaust control valve 60 is repeatedly opened and closed alternately. As a result, pulsation is generated in the pressure in the particulate filter 24. By this pressure pulsation, the ash layer formed on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is destroyed, and the ash is easily separated from the inner peripheral surface 71is. The ash peeled from the inner peripheral surface 71is is easily moved to the inner portion 71ir by the exhaust gas during the subsequent engine operation. Next, when a predetermined set time tE elapses at time te3, normal idling control is started. Further, the exhaust control valve 60 is kept fully open. That is, the movement promotion control is stopped.

  FIG. 27 shows a routine for executing the movement promotion control shown in FIG. This routine is executed in step 125 of FIG. 12, for example. Referring to FIG. 27, in step 181, the target rotational speed TNe is set to the movement promoting idling rotational speed NeIT. In the subsequent step 182, the exhaust control valve 60 is opened and closed. In the following step 183, it is determined whether or not the set time tE has elapsed. When the set time tE has not elapsed, the process returns to step 181. When the set time tE has elapsed, the processing cycle is terminated. That is, the movement promotion control is stopped, and the process proceeds to Step 126 in FIG.

  FIG. 28 shows still another embodiment according to the present invention. Referring to FIG. 28, a vibrator 61 is attached to the catalytic converter 22.

  In the embodiment shown in FIG. 28, the movement promotion control is constituted by generation of vibration of the particulate filter 24. That is, as shown in FIG. 29, after the engine is started at time tf1, when a complete explosion occurs at time tf2, the engine speed Ne is maintained at the movement promoting idling speed NeIT. At this time, the vibrator 61 is activated. As a result, vibration is applied to the particulate filter 24. By this vibration, the ash layer formed on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is broken, and the ash is easily separated from the inner peripheral surface 71is. The ash peeled from the inner peripheral surface 71is is easily moved to the inner portion 71ir by the exhaust gas during the subsequent engine operation. Next, when a predetermined set time tF has elapsed at time tf3, normal idling control is started. Further, the vibrator 61 is stopped. That is, the movement promotion control is stopped.

  FIG. 30 shows a routine for executing the movement promotion control shown in FIG. This routine is executed in step 125 of FIG. 12, for example. Referring to FIG. 30, in step 191, the target rotational speed TNe is set to the movement promoting idling rotational speed NeIT. In the following step 192, the vibrator 61 is activated. In the following step 193, it is determined whether or not the set time tF has elapsed. When the set time tF has not elapsed, the process returns to step 191. When the set time tF has elapsed, the processing cycle ends. That is, the movement promotion control is stopped, and the process proceeds to Step 126 in FIG.

  FIG. 31 shows still another embodiment according to the present invention. In the movement promotion control of the embodiment shown in FIG. 31, first, movement promotion temperature rise control is performed in which the temperature TF of the particulate filter 24 rises to a movement promotion temperature TFT higher than the PM removal temperature TFPM during PM removal control. Is called. Next, exhaust gas increase control is performed to temporarily increase the amount of exhaust gas flowing through the particulate filter 24. As a result, the ash is contracted by heating, the ash layer formed on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is destroyed, and the ash is easily separated from the inner peripheral surface 71is. The ash peeled from the inner peripheral surface 71is is easily and reliably moved to the inner portion 71ir by the increased amount of exhaust gas. The movement promoting temperature TFT is, for example, about 630 ° C. to 1100 ° C.

  The movement promotion control of this embodiment is performed during normal operation after the engine start is completed. That is, as shown in FIG. 31, at time tg1, PM removal control is started, and the temperature TF of the particulate filter 24 is raised to the PM removal temperature TFPM. Next, at time tg2, the particulate matter accumulation amount QPM becomes smaller than the lower limit LQPM, and the PM removal control is ended. Subsequent to the PM removal control, movement promotion control is started. Specifically, first, movement promotion temperature rise control is started. That is, the temperature TF of the particulate filter 24 is raised from the PM removal temperature TFPM to the movement promotion temperature TFT and held. If it does in this way, energy required for temperature control for movement promotion can be reduced. Next, when a predetermined time tG1 elapses at time tg3, the movement promotion temperature increase control is terminated. Next, exhaust gas amount increase control is started. As a result, the exhaust gas amount QEX flowing through the particulate filter 24 is increased. Next, when a predetermined set time tG2 elapses at time tg4, the exhaust gas increase control is terminated. Therefore, the movement promotion control is terminated.

  In order to execute the temperature promotion control for promoting movement, in one embodiment, fuel is added from the fuel addition valve 27 and this fuel is combusted in the exhaust passage or the particulate filter 24. In another embodiment, fuel is injected from the fuel injection valve 3 into the compression stroke or the exhaust stroke, and this fuel is burned in the combustion chamber 2, the exhaust passage, or the particulate filter 24. On the other hand, the engine speed or the throttle opening is increased in order to perform the exhaust gas increase control.

  FIG. 32 shows a routine for executing the exhaust purification control shown in FIG. Referring to FIG. 32, in step 201, the PM removal control routine shown in FIG. 6 is executed. In the following step 202, it is determined whether or not the ratio R is smaller than the lower limit value RL. When R <RL, the routine proceeds to step 203 where a movement promotion control routine is executed. On the other hand, when R ≧ RL, the processing cycle is terminated. Therefore, in this case, the movement promotion control routine is not executed.

  FIG. 33 shows a routine for executing the movement promotion control shown in FIG. This routine is executed in step 203 of FIG. 32, for example. Referring to FIG. 33, in step 211, the target value TTF of the temperature TF of the particulate filter 24 is set to the movement promoting temperature TFT. In the following step 212, it is determined whether or not the set time tG1 has elapsed. When the set time tG1 has not elapsed, the process returns to step 211. When the set time tG1 has elapsed, the routine proceeds to step 213, where exhaust gas increase control is performed. In the following step 214, it is determined whether or not the set time tG2 has elapsed. When the set time tG2 has not elapsed, the process returns to step 213. When the set time tG2 has elapsed, the processing cycle is terminated. That is, the exhaust gas increase control is terminated, and therefore the movement promotion control is terminated.

  In another embodiment, the exhaust gas amount increase control is omitted. In this case, the ash peeled from the inner peripheral surface 71is by the movement promoting temperature increase control is easily moved to the inner portion 71ir by the exhaust gas during the subsequent engine operation.

  FIG. 34 shows another embodiment of the movement promotion control in the embodiment shown in FIG. 24C. In the embodiment shown in FIG. 34, the movement promotion control is composed of a stop movement promotion control performed when the engine is stopped and a start movement promotion control performed when the engine is subsequently started.

  That is, as shown in FIG. 34, when the ignition switch 44 is turned off at time th1, the engine operation is stopped. As a result, the engine speed Ne decreases to zero. Next, when a predetermined set time tH1 elapses, stop-time movement promotion control is performed. That is, the liquid is added from the liquid addition valve 55 with the movement promoting addition pressure. As a result, the ash on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is caused to flow by the condensed water and is moved to the inner portion 71ir. Alternatively, the ash is swollen by the condensed water, the ash layer formed on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is destroyed, and the ash is easily separated from the inner peripheral surface 71is. The set time tH1 is set to a time necessary for lowering the temperature TF of the particulate filter 24 so that the liquid added from the liquid addition valve 55 is not vaporized by the particulate filter 24. Next, at the time th3, when the addition of the liquid is performed only for the movement promoting addition time tH2, the addition of the liquid is stopped. That is, the stop movement promotion control is stopped.

  Next, at time th4, the ignition switch 44 is turned on and the engine is started. Next, when a complete explosion occurs at time th5, start-up movement promotion control is started. In other words, the engine speed Ne is maintained at the movement promoting idling speed NeIT. As a result, the amount of exhaust gas flowing through the particulate filter 24 is increased. Therefore, the ash peeled from the inner peripheral surface 71is of the exhaust gas inflow passage 71i is easily moved to the inner portion 71ir. Next, when a predetermined set time tH3 has elapsed at time th6, normal idling control is started. That is, the start-up movement promotion control is stopped.

  FIG. 35 shows a routine for executing the engine stop control shown in FIG. This routine is executed only once when the ignition switch 44 is turned off. Referring to FIG. 35, in step 221, the flag XX is reset (XX = 0). This flag XX is set when the start-up movement promotion control is to be executed (XX = 1), and is otherwise reset (XX = 0). In the subsequent step 222, the engine operation is stopped. In the following step 223, it is determined whether or not the ratio R is smaller than the lower limit value RL. When R <RL, the routine proceeds to step 224, where the stop-time movement promotion control routine is executed. In the following step 225, the flag XX is set (XX = 1). In the subsequent step 226, energization to the electronic control unit 30 is stopped. The processing cycle is then terminated. On the other hand, when R ≧ RL, the process proceeds from step 223 to step 226. Therefore, in this case, movement promotion control is not performed.

  FIG. 36 shows a routine for executing the engine start control shown in FIG. This routine is executed only once when the ignition switch 44 is turned on. Referring to FIG. 36, in step 231, the flag X described with reference to FIG. 12 is reset (X = 0). In the following step 232, it is determined whether or not the engine speed Ne is higher than the set speed NeC. When Ne ≦ NeC, the process returns to step 232. When Ne> NeC, that is, when a complete explosion has occurred, the routine proceeds to step 233, where it is determined whether the flag XX described with reference to FIG. 35 is set. When the flag XX is set (XX = 1), next, the routine proceeds to step 234, where the starting movement promotion control routine is executed. In the subsequent step 235, the flag X is set (X = 1). When the flag XX is reset in step 233 (XX = 0), the process proceeds to step 235. Therefore, in this case, start-up movement promotion control is not performed.

  FIG. 37 shows a routine for executing the stop-time movement promotion control shown in FIG. This routine is executed in step 224 of FIG. 35, for example. Referring to FIG. 37, in step 241, it is determined whether or not a set time tH1 has elapsed since the ignition switch 44 was turned off. When the set time tH1 has not elapsed, the process returns to step 241. When the set time tH1 has elapsed, the routine proceeds to step 242 where the movement promoting addition pressure is calculated. In the subsequent step 243, the movement promotion addition time is calculated. In the subsequent step 244, the liquid is added from the liquid addition valve 55 with the movement promoting addition pressure for the movement promoting addition time. The processing cycle is then terminated. That is, the stop movement promotion control is terminated, and the process proceeds to Step 225 in FIG.

  FIG. 38 shows a routine for executing the start-up movement promotion control shown in FIG. This routine is executed in step 234 of FIG. 36, for example. Referring to FIG. 38, in step 251, the target rotational speed TNe is set to the movement promoting idling rotational speed NeIT. In the following step 252, it is determined whether or not the set time tH3 has elapsed. When the set time tH3 has not elapsed, the process returns to step 251. When the set time tH3 has elapsed, the processing cycle is terminated. That is, the start-up movement promotion control is stopped, and the process proceeds to Step 235 in FIG.

  FIG. 39 shows still another embodiment according to the present invention. The embodiment shown in FIG. 39 is different from the embodiment shown in FIG. 34 in that a cooler 62 is attached to the catalytic converter 24 and the liquid added to the particulate filter 24 is solidified by the cooler 62. Yes.

  That is, as shown in FIG. 40, when the ignition switch 44 is turned off at time tj1 to stop the engine operation, and when a predetermined set time tJ1 elapses, the stop-time movement promotion control is performed. That is, the liquid is added from the liquid addition valve 55 with the movement promoting addition pressure. As a result, the ash on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is caused to flow by the condensed water and is moved to the inner portion 71ir. Alternatively, the ash is swollen by the condensed water, the ash layer formed on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is destroyed, and the ash is easily separated from the inner peripheral surface 71is. The set time tJ1 is set in the same manner as the set time tH1 described above.

  Next, at the time tj3, when the addition of the liquid is performed only for the movement promoting addition time tJ2, the addition of the liquid is stopped. Next, at tj4, when a predetermined set time tJ3 elapses from the stop of the liquid addition, the cooler 62 is activated and the liquid added to the particulate filter 24 is solidified. As a result, since the liquid expands, the ash layer formed on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is further destroyed. Therefore, the ash is more easily separated from the inner peripheral surface 71is. Next, when a predetermined set time tJ4 elapses at time tj5, the cooler 62 is stopped. That is, the stop movement promotion control is stopped. The set time tJ4 is set to a time necessary for the liquid added to the particulate filter 24 to sufficiently solidify.

  Next, at time tj6, the ignition switch 44 is turned on and the engine is started. At this point, the solidified liquid has melted. Next, when a complete explosion occurs at time tj7, start-up movement promotion control is started. In other words, the engine speed Ne is maintained at the movement promoting idling speed NeIT. As a result, the amount of exhaust gas flowing through the particulate filter 24 is increased. Therefore, the ash peeled from the inner peripheral surface 71is of the exhaust gas inflow passage 71i is easily moved to the inner portion 71ir. Next, when a predetermined set time tJ5 elapses at time tj8, normal idling control is started. That is, the start-up movement promotion control is stopped.

  FIG. 41 shows a routine for executing the stop-time movement promotion control shown in FIG. This routine is executed in step 224 of FIG. 35, for example. Referring to FIG. 41, in step 261, it is determined whether or not a set time tJ1 has elapsed since the ignition switch 44 was turned off. When the set time tJ1 has not elapsed, the process returns to step 261. When the set time tJ1 has elapsed, the routine proceeds to step 262, where the movement promoting addition pressure is calculated. In the subsequent step 263, the movement promotion addition time is calculated. In the subsequent step 264, the liquid is added from the liquid addition valve 55 with the movement promoting addition pressure for the movement promoting addition time. In the following step 265, it is determined whether or not the set time tJ3 has elapsed since the liquid addition was stopped. When the set time tJ3 has not elapsed, the process returns to step 265. When the set time tJ3 has elapsed, the routine proceeds to step 266, where the cooler 62 is activated. In the subsequent step 267, it is determined whether or not the set time tJ4 has elapsed since the cooler 63 was operated. When the set time tJ4 has not elapsed, the process returns to step 266. When the set time tJ4 has elapsed, the processing cycle is then terminated. That is, the stop movement promotion control is terminated, and the process proceeds to Step 225 in FIG.

  In the embodiment shown in FIG. 34, the atmospheric temperature may become considerably low during the engine operation stop, and the liquid added to the particulate filter 24 may solidify. Also in this case, the ash layer formed on the inner peripheral surface 71is of the exhaust gas inflow passage 71i is further broken, and therefore the ash is easily moved to the inner portion 71ir.

DESCRIPTION OF SYMBOLS 1 Engine main body 12 EGR channel | path 14e Condensate water storage part 21 Exhaust pipe 24 Particulate filter 26 Pressure difference sensor 71i Exhaust gas inflow channel 71o Exhaust gas outflow channel 72 Bulkhead

Claims (10)

A particulate filter for collecting particulate matter contained in the exhaust gas is arranged in the engine exhaust passage, and the particulate filter is arranged in an exhaust gas inflow passage and exhaust gas alternately arranged through porous partition walls. In an exhaust gas purification apparatus for an internal combustion engine, comprising an outflow passage,
A movement promoting means for performing movement promotion control for promoting the ash deposited on the inner peripheral surface of the exhaust gas inflow passage to move to the inner part of the exhaust gas inflow passage;
Detection means for detecting pressure loss of the particulate filter;
PM removal means for performing PM removal control for removing particulate matter from the particulate filter when the detected pressure loss is larger than a predetermined upper limit;
An exhaust purification device for an internal combustion engine, comprising:   The movement promoting means determines whether or not the amount of ash accumulated on the inner peripheral surface of the exhaust gas inflow passage is larger than a predetermined upper limit amount, and the ash amount is larger than a predetermined upper limit amount. The exhaust emission control device for an internal combustion engine according to claim 1, wherein the movement promotion control is performed when it is determined that the amount is large.   The exhaust purification device of an internal combustion engine according to claim 1 or 2, wherein the movement promoting means supplies liquid to the particulate filter in order to perform movement promotion control.   The exhaust gas purification apparatus for an internal combustion engine according to claim 3, wherein the liquid is composed of at least one of water, an aqueous solution, and liquid fuel.   Condensation for storing condensed water generated in the internal combustion engine in at least one of the engine intake passage, the engine exhaust passage upstream of the particulate filter, and the exhaust gas recirculation passage connecting the engine intake passage and the engine exhaust passage to each other The internal combustion engine according to claim 3 or 4, wherein a water storage part is formed, and the movement promoting means supplies the condensed water stored in the condensed water storage part to the particulate filter in order to perform movement promotion control. Exhaust purification device.   A NOx reduction catalyst disposed in the engine exhaust passage in the particulate filter or downstream of the particulate filter, a reducing agent addition valve for secondary addition of liquid reducing agent in the engine exhaust passage upstream of the particulate filter, and NOx NOx reduction means for adding a liquid reducing agent from the reducing agent addition valve with a NOx reduction addition pressure and a NOx reduction addition time for reduction, and the movement promoting means for performing movement promotion control The liquid reducing agent is added from the reducing agent addition valve with an addition pressure lower than the NOx reduction addition pressure or an addition time longer than the NOx reduction addition time. An exhaust purification device for an internal combustion engine.   The exhaust purification device for an internal combustion engine according to any one of claims 1 to 6, wherein the movement promoting means generates pulsation in the pressure in the particulate filter in order to perform movement promotion control.   The exhaust purification device for an internal combustion engine according to any one of claims 1 to 7, wherein the movement promoting means vibrates the particulate filter in order to perform movement promotion control.   The exhaust purification device for an internal combustion engine according to any one of claims 1 to 8, wherein the movement promoting means raises the temperature of the particulate filter to a temperature higher than that during PM removal control in order to perform movement promotion control. .   The exhaust purification device for an internal combustion engine according to any one of claims 1 to 9, wherein the movement promoting means supplies the liquid to the particulate filter and coagulates the liquid in order to perform movement promotion control.

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