JP2000234509A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To separate ash deposited on a particulate filter without influencing on the driving condition of an engine. SOLUTION: This device is individually placed with a particulate filter (DPF) 40 on each exhaust branch pipe 41 which connects an exhaust manifold 31 of a diesel engine 1 to an exhaust port of each cylinder, and DPF upper steam side part of the exhaust branch pipe of an adjacent cylinder is connected each other with a communicating path 41 with providing a communication valve 43 which can close each communication path. When an amount of ash deposited on DPF is increased, the communication valve 43 is closed at the end of acceleration or the start of deceleration in driving of the engine under a specified load condition. A condition where pressure is lower in the exhaust port than in the exhaust manifold 31 is thereby generated and exhaust air flows backward in DPF. The ash deposited on DPF can be easily separated from DPF by the back flow of the exhaust air without influencing on a driving condition of the engine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, and more particularly to an exhaust gas purifying apparatus for an internal combustion engine provided with a particulate filter for trapping particulates in exhaust gas.

[0002]

2. Description of the Related Art The exhaust gas of an internal combustion engine, particularly the exhaust gas of a diesel engine, contains exhaust particulates mainly composed of carbon (soot). For this reason, various exhaust purification devices have been devised for purifying exhaust gas using a particulate filter in order to prevent the release of the particulates to the atmosphere.

As the particulate filter, a filter using a filter material such as ceramic, porous metal, or metal fiber non-woven fabric is usually used. For example, in the case where a metal fiber nonwoven fabric is used as a filter member, Fe-Cr-Al
A particulate filter is formed by winding a belt-shaped nonwoven fabric using a heat-resistant metal fiber such as an alloy or a Ni-Cr-Al alloy on a corrugated sheet of a heat-resistant metal of the same material alternately and winding it in a roll shape. (See JP-A-9-262414). In this particulate filter, since the metal fiber nonwoven fabrics are held with a gap therebetween by the corrugated sheet, the axial passages along the corrugated sheet are arranged in a spiral shape. At one end of the particulate filter, the ends of the nonwoven fabric facing each other are continuously spirally welded every other layer so as to close half of the ends of the axial passage. At the opposite end of the particulate filter, the ends of the nonwoven fabric of a layer different from the one end are spirally welded to each other to close the end of the axial passage. Thereby, in the roll-shaped particulate filter, the axial passage closed at one end and the axial passage closed at the other end are alternately arranged in the radial direction across the wall of the metal fiber nonwoven fabric. Become.

By arranging the particulate filter in the exhaust passage, the exhaust gas flows into the axial passage in which the upstream end of the particulate filter is opened, passes through the nonwoven fabric separating the passages, and opens the downstream end. Into the defined axial passage, and is discharged downstream through this passage. Therefore, when passing through the nonwoven fabric, the particulates in the exhaust gas are collected by the nonwoven fabric.

[0005] Generally, the pore size of the filter material of the particulate filter is set to a relatively large value of about 15 to 50 microns in order to reduce the exhaust resistance of the particulate filter itself, and carbon particles (soot) as the main component of the particulate filter are formed. It is much larger than the diameter (about 0.1 micron). Therefore, at the start of use of the particulate filter, a considerable amount of the particulates in the exhaust gas pass through the filter, so that the collection efficiency of the particulate filter is relatively low. However, with use, particulates adhere around the pores of the filter material, and the attached particulate particles grow together with each other to form a deposited layer of particulates. The effective filter hole diameter becomes smaller. Therefore, the trapping efficiency of the filter increases with the accumulation of particulates, and at the same time, the exhaust pressure loss of the filter also increases.

In the particulate filter, the exhaust pressure loss increases as the accumulation (collection amount) of the particulate increases. Therefore, the particulate (carbon particles) deposited on the filter by a method such as periodically raising the exhaust temperature. It is necessary to prevent engine performance from being deteriorated due to excessive increase in exhaust pressure loss. An example of an exhaust gas purifying apparatus using such a particulate filter is described in, for example, Japanese Utility Model Laid-Open No. 5-69311. The device disclosed in the publication has a configuration in which a small-capacity particulate filter is arranged on an exhaust branch pipe that connects between an exhaust port of each cylinder of a diesel engine and an exhaust collecting portion. In the device of the publication, the particulate filter is provided near the exhaust port having the highest exhaust temperature in the exhaust system, and the particulate filter is provided individually for each cylinder to reduce the heat capacity of each particulate filter. If the exhaust gas temperature rises due to an increase in load during operation of the engine, the particulates deposited on the particulate filter easily burn. For this reason, it is possible to efficiently burn the particulates without providing a separate heating device for burning the particulates.

[0007]

However, in the apparatus disclosed in Japanese Utility Model Application Laid-Open No. 5-69311, although the particulates accumulated on the particulate filter can be satisfactorily burned, the ash accumulated on the particulate filter is removed. Since the filter cannot be desorbed, the pressure loss of the filter gradually increases due to the accumulation of ash.

Exhaust gas contains ash mainly composed of combustion products such as lubricating oil, in addition to particulates mainly composed of carbon particles (soot). Ash is mainly composed of an inorganic component such as calcium sulfate, and has a size of about 0.1 μm, similarly to particulates. Ash also forms a deposited layer in which particles are bonded to each other on the filter material of the particulate filter by the same mechanism as for particulates. Although the amount of ash contained in the exhaust gas is extremely small compared to the particulate matter, even if the exhaust gas temperature rises, it does not burn like the particulate matter mainly composed of carbon, so the use period of the particulate filter is limited. As it gets longer, it gradually accumulates on the particulate filter.

In addition, the ash deposit layer has a higher mechanical strength than the particulate deposit layer and does not spontaneously detach from the filter with the vibration caused by the operation of the engine. The pressure loss of the filter will gradually increase due to the accumulation of ash, and the engine performance will be affected. For this reason, an operation for detaching the ash deposited on the particulate filter and restoring the pressure loss of the filter is required separately. However, the apparatus disclosed in the above publication does not consider this point.

Since the deposited layer of ash does not burn, it is necessary to apply a large mechanical impact to disintegrate the deposited layer in order to desorb the ash from the particulate filter. This mechanical shock can theoretically also be given, for example, by increasing the exhaust flow velocity through the particulate filter. However, as described above, the ash deposition layer has a relatively high mechanical strength, and in order to desorb the ash by increasing the exhaust flow velocity, an operation in which the engine speed and the load are significantly increased is required. Is impractical because the influence on the engine operation state becomes large.

In view of the above problems, an object of the present invention is to provide an exhaust gas purifying apparatus for an internal combustion engine capable of removing ash accumulated on a particulate filter without significantly affecting a normal engine operating state. And

[0012]

According to the first aspect of the present invention, there is provided on each exhaust branch pipe connecting an exhaust port of each cylinder of an internal combustion engine and an exhaust collecting portion where exhaust of each cylinder joins. A particulate filter disposed to trap particulates in the exhaust gas, and an exhaust gas flowing backward from the exhaust collecting portion to the exhaust port side through the respective particulate filters, thereby accumulating the particulate filter. Ash desorbing means for desorbing ash composed of non-combustible components, and when the internal combustion engine ends acceleration or starts deceleration in a predetermined load region, the ash desorbing operation is performed by operating the ash desorbing means. An exhaust gas purification device for an internal combustion engine, comprising: That is, in the first aspect of the present invention, the ash deposited on the particulate filter is desorbed by causing the exhaust gas to flow backward from the exhaust collecting portion toward the exhaust port. In normal operation, the ash accumulation state has the least resistance to the exhaust flow in the direction from the exhaust port side to the exhaust collecting section, and the ash accumulation state is opposite to the normal exhaust flow. The resistance of the layers is relatively large. For this reason, a large force acts on the ash deposition layer due to the backflow of the exhaust gas, and the ash deposition layer is easily collapsed and detached from the filter even when the exhaust gas flows at a relatively small flow rate. Since the collapsed ash deposit becomes fine particles, when the exhaust gas flows in the forward direction, it passes through the holes of the filter and is discharged downstream of the particulate filter.

The ash desorbing means for back-flowing the exhaust gas includes, for example, closing a communication passage of an exhaust branch pipe, stopping combustion in a cylinder, and the like, an exhaust throttle, and a variable nozzle (inlet of a turbocharger) as described later. (Guide vane) Any one or a combination of two or more means such as a pressure increase in the exhaust collecting section due to closure or EGR stop, a decrease in intake air amount due to a change in intake throttle, valve timing, etc. can be used. is there.

[0014] When the exhaust gas is caused to flow backward using such means, the operating state of the engine may be affected. But,
At the end of acceleration or at the start of deceleration, the amount of fuel supplied to the cylinder of the engine decreases, so at the end of acceleration or at the start of deceleration, the pressure of exhaust gas discharged from the cylinder is lower than during acceleration or before the start of deceleration. . On the other hand, the exhaust pressure of the exhaust collecting portion at the end of acceleration or at the start of deceleration is still relatively high during acceleration or before the start of deceleration. For this reason, at the end of acceleration and at the start of deceleration, the exhaust collecting section pressure becomes higher than the exhaust port pressure, so that a condition is established in which exhaust gas easily flows back through the particulate filter without using the above-described units.
In this state, the use of the ash desorbing means allows a relatively large amount of exhaust gas to flow back through the filter without significantly affecting the operation of the engine.
For this reason, when the acceleration is completed or the deceleration is started, the exhaust gas is caused to flow backward by using the ash desorbing means, so that the deposited ash is desorbed from the filter without affecting the operation of the engine.

According to the second aspect of the present invention, the ash desorbing means includes a portion upstream of the particulate filter of the exhaust branch pipe and a portion upstream of the particulate filter of the exhaust branch pipe of at least one other cylinder. 2. The exhaust system according to claim 1, further comprising: a communication path that communicates with the portion, and a communication valve that can close the communication path, wherein the exhaust path is generated in the particulate filter by closing the communication path during an ash desorption operation. 3. The present invention provides an exhaust gas purifying apparatus for an internal combustion engine.

In other words, according to the second aspect of the present invention, the ash desorbing means includes a communication path that connects the upstream side of the particulate filter of each exhaust branch pipe to the exhaust branch pipe of at least one other cylinder, and this communication path. And a communication valve capable of closing the passage. When the communication passage is opened, the exhaust branch pipe upstream of the particulate filter communicates with other exhaust branch pipes, so that the volume of the exhaust branch pipe upstream of the particulate matter is substantially large, but the communication valve closes the communication passage. Then, the exhaust branch pipe volume on the upstream side of the particulates becomes small.

On the other hand, when the exhaust valve of each cylinder is opened, high-pressure exhaust gas is discharged from the cylinder and the exhaust port pressure rises in the initial stage of valve opening. The pressure drops. When the communication valve is opened, the volume of the exhaust branch pipe upstream of the particulate filter is increased due to communication with the other exhaust branch pipes. Therefore, even if the exhaust pressure decreases after the exhaust valve is opened, the exhaust port pressure is not so large. Does not drop. However, when the communication valve is closed, the pressure drop in the exhaust port after the discharge of the high-pressure exhaust gas is increased due to a decrease in the volume of the exhaust branch pipe. Considering the case where the exhaust port pressure of a certain cylinder is greatly reduced when the communication valve is closed, the exhaust collecting section pressure at this time is maintained at a high pressure due to the inflow of high-pressure exhaust from another cylinder. A pressure difference will occur between the exhaust port and the exhaust port. This pressure difference becomes larger at the end of acceleration or at the start of deceleration. For this reason, by closing the communication valve at the end of acceleration or at the start of deceleration, a large pressure difference can be generated between the exhaust collecting portion and the exhaust port, and a large amount of exhaust can flow back through the particulate filter. . As a result, the ash is detached from the filter without significantly affecting the operating state of the engine.

According to the third aspect of the present invention, the ash desorbing means includes a cylinder deactivating means for stopping combustion of any one of the cylinders of the internal combustion engine. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the exhaust gas backflow is generated in a particulate filter arranged in an exhaust branch pipe of the one cylinder by stopping combustion of the cylinder.

That is, in the invention of claim 3, the ash desorbing means desorbs ash from the filter by stopping the combustion of some cylinders of the engine at the end of acceleration or at the start of deceleration. By stopping combustion in the cylinder, the minimum pressure of exhaust gas exhausted from the cylinder becomes almost equal to the intake pressure of the engine.Therefore, a large pressure difference occurs between the exhaust collecting portion and the exhaust port, and a large amount of exhaust gas is generated. Backflow can be achieved through a particulate filter. On the other hand, at the end of acceleration and at the start of deceleration, the rotational speed and load of the engine are usually large, so even if some cylinders are stopped, there is no significant effect on the operation of the engine.

According to the fourth aspect of the present invention, the exhaust pressure of the exhaust collecting section is increased by suppressing the outflow of exhaust from the exhaust collecting section, or the amount of intake air flowing into each cylinder. Ash forced desorption that causes an exhaust flow to flow back from the exhaust collecting section to the exhaust port side through the respective particulate filters and thereby desorb ash from the particulate filters by either or both of the following. Equipped with separation means,
If the ash desorption operation is not performed within a predetermined ash desorption operation execution period, the desorption control unit operates the ash forced desorption unit after the elapse of the desorption operation execution period. An exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 3, wherein the forced ash removal operation is performed.

That is, in the invention according to the fourth aspect, the execution period of the ash desorption operation is determined. For example, when the ash accumulation amount becomes equal to or more than a predetermined value, the engine is started during the desorption operation execution period. When the vehicle is accelerated or decelerated under the load condition, the ash detachment operation is performed. In addition, in the present invention, apart from the ash desorption operation performed at the end of acceleration or deceleration start under the predetermined load state, the load is increased by either or both of increasing the exhaust collecting section pressure or decreasing the cylinder intake pressure. An ash forcible detachment means for forcibly detaching the ash independently of the ash is provided.
Since the ash desorption operation is performed when the engine is accelerated or decelerated under a predetermined load condition, if these conditions are not satisfied, the engine may be operated for a long time in a state where the ash accumulation amount is large (a state in which the filter pressure loss is high). May be driven.
In the present invention, a period during which the ash detachment operation is to be performed, that is, a detachment operation execution period is determined. If the ash detachment operation is not performed within this period, the ash is removed even if the above conditions are not satisfied. Ash is detached from the filter using a forced detachment means. In this case, although the operating state of the engine is slightly affected, this prevents the engine from being operated for a long time with a high filter pressure loss.

[0022]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a schematic configuration in a case where the exhaust emission control device of the present invention is applied to an automobile diesel engine. In FIG. 1, reference numeral 1 denotes an automobile internal combustion engine. In the present embodiment, the engine 1 is a four-cylinder diesel engine, and each cylinder is provided with an in-cylinder fuel injection valve 111 that injects fuel directly into the cylinder. The fuel is pumped from a high-pressure fuel injection pump 113 to a common rail (accumulator) 115 to which each fuel injection valve 111 is connected, and is injected from the common rail into each cylinder by the fuel injection valve 111 at a predetermined timing.

In FIG. 1, reference numeral 21 denotes an intake manifold connecting the intake port of each cylinder to the intake passage 2, and reference numeral 31 denotes an exhaust manifold (exhaust collecting portion) connecting the exhaust port of each cylinder to the exhaust passage 3. In the present embodiment, a supercharger 35 for supercharging the engine 1 is provided. The exhaust passage 3 is provided at an exhaust outlet of the supercharger 35, and the intake passage 2 is provided at an intake outlet of the supercharger 35. It is connected.

In this embodiment, a variable nozzle (inlet guide vane) 36 capable of changing the nozzle opening area is provided at the exhaust inlet of the exhaust turbine 35a of the supercharger 35.
Is provided. The variable nozzle 36 is connected to an ECU 3 described later.
A suitable type of actuator 36 such as a stepper motor or a negative pressure actuator which operates in response to a control signal from 0.
The angle is controlled according to a signal from the ECU 30. When the nozzle opening area of the variable nozzle 36 is changed, the flow rate of the exhaust gas passing through the nozzle and flowing into the exhaust wheel of the exhaust turbine changes even at the same exhaust flow rate, so that the turbine rotational speed changes. Therefore, the variable nozzle 36
, The turbine speed can be maintained substantially constant even when the exhaust flow rate changes. When the exhaust flow rate is constant, the pressure in the exhaust manifold 31 increases as the nozzle opening area of the variable nozzle 36 is reduced (squeezed).

The intake passage 2 is provided with an intercooler 25 for cooling intake air supplied from a supercharger 35 and an intake throttle valve 27. The intake throttle valve 27 includes an actuator 27a of an appropriate type such as a stepper motor or a negative pressure actuator that operates in accordance with a signal from the ECU 30 described later, takes an opening degree in accordance with the signal from the ECU 30, and adjusts the intake flow rate of the engine. Restrict.

When the intake flow rate is restricted by the intake throttle valve 27, the intake pressure of each cylinder decreases and the amount of intake air flowing into the cylinder decreases, so that the minimum value of the exhaust port pressure when the exhaust valve is opened decreases. Further, in this embodiment, an exhaust throttle valve 37 provided with an actuator 37a similar to the intake throttle valve 27 is provided in the exhaust passage 3 downstream of the supercharger 35.
The exhaust throttle is performed by setting the opening in accordance with the signal from the CU 30.

When the exhaust throttle valve 37 performs exhaust throttle, the exhaust pressure in the exhaust manifold 31 increases. In FIG. 1, reference numeral 33 denotes an EGR passage which connects the engine exhaust system and the intake system and recirculates part of the engine exhaust to the intake system, and 23 denotes an EGR valve arranged in the EGR passage. The EGR valve 23 includes an appropriate actuator (not shown) such as a stepper motor, a negative pressure actuator, or the like. The EGR valve 23 has an opening in accordance with a signal from the ECU 30 and returns to the intake system through the EGR passage 33 (EGR gas). ) The flow rate is controlled according to the operating state of the engine.

During the EGR operation, when the EGR valve opening decreases, the flow rate of exhaust gas recirculated from the exhaust manifold 31 to the intake system decreases, so that the pressure in the exhaust manifold 31 increases even if other conditions are constant. In the present embodiment, a particulate filter (diesel particulate filter, hereinafter referred to as “DPF”) 40 is provided in an exhaust branch pipe connecting the exhaust manifold 31 to each exhaust port. The DPF 40 is formed of a heat-resistant porous material such as a ceramic or a metal fiber nonwoven fabric, and has a number of flow paths that form an exhaust flow path in the axial direction (the exhaust flow direction). Each of these flow paths is closed at one of the upstream end and the downstream end in the exhaust flow direction, and the flow path whose upstream end is closed and the flow path whose downstream end is closed are alternately arranged adjacent to each other. Have been. For this reason, the exhaust gas discharged from the exhaust port of each cylinder flows into the flow path in which the upstream end of each DPF is open (the downstream end is closed), and passes through the porous partition separating the flow paths. Then, the downstream end flows into the open flow path and flows out of the DPF from the downstream end. Particulates contained in the exhaust gas are collected when the exhaust gas passes through the porous partition.

In this embodiment, the DPF 4 having a relatively small capacity is used.
0 is provided adjacent to the exhaust port of each cylinder,
Because high-temperature exhaust from the cylinder flows directly into the DPF,
The temperature of the PF 40 can be kept high. In addition, since each DPF 40 has a small capacity, the amount of particulates that can be collected is also small, and it is necessary to set a relatively short interval for performing the burning operation of the particulates. As a result, the DPF temperature rises and particulate combustion starts. Further, since the amount of collected particulates is small, the combustion of the collected particulates can be completed in a short time, and the time required for the regeneration operation can be reduced. In this embodiment, since a diesel engine is used as the engine 1, the engine exhaust temperature during normal operation is relatively low. In this embodiment,
A small-capacity DPF 40 is arranged at the exhaust port of each cylinder,
By employing a so-called separated DPF, it is possible to satisfactorily complete the regeneration of each DPF 40 even in an engine operating state in which the exhaust gas temperature rises for a short time during acceleration or the like.

In this embodiment, the exhaust manifold 3
Of the branch pipe connecting the exhaust port 1 to the exhaust port of each cylinder
The upstream side (exhaust port side) is connected to the upstream side of the DPF 40 of the adjacent exhaust branch pipe by a communication passage 41, and each communication passage is provided with a communication valve 43 capable of closing the communication passage 40. The communication valve 43 includes an appropriate type of actuator (not shown) that is activated by a signal from the ECU 30, and closes the communication passage 41 in response to a signal from the ECU 30. The communication valve 41 is kept open during normal operation (when the ash desorption operation is not being performed).

In FIG. 1, reference numeral 30 denotes an electronic control unit (ECU) of the engine 1. In the present embodiment, the ECU 30 is a microcomputer having a known configuration including a RAM, a ROM, and a CPU. The ECU 30 performs basic control such as fuel injection control of the engine 1, and also controls the DPF 40 according to an engine operating state as described later. It functions as a desorption control unit for performing a desorption operation of the deposited ash.

To perform these controls, an input port of the ECU 30 receives a signal corresponding to the engine intake air amount from an air flow meter 51 provided in the engine intake passage and a temperature sensor 53 provided in the exhaust manifold 31. A signal corresponding to the engine exhaust temperature is input, and a pulse signal is input from the rotation speed sensor 55 disposed near the engine crankshaft (not shown) at every constant rotation angle of the engine crankshaft. Further, in the present embodiment, the ECU
A signal representing the accelerator pedal depression amount (accelerator opening) of the driver is input to an input port 30 from an accelerator opening sensor 57 arranged near an accelerator pedal (not shown) of the engine 1. The ECU 30 converts the output of the air flow meter 51, the output of the accelerator opening sensor 57, and the output of the temperature sensor 53 at predetermined intervals into an A / D conversion of the intake air amount Ga, the accelerator opening ACCP, and the exhaust temperature T in a predetermined area of the RAM of the ECU 30. While storing, the rotation speed sensor 5
The engine speed NE is calculated from the interval of the pulse signal from the step 5 and stored in a predetermined area of the RAM. ECU 30
Calculates the engine basic fuel injection amount and the fuel injection timing based on the accelerator opening ACCP detected by the accelerator opening sensor 57 and the engine speed NE based on a relationship previously stored in the ROM. The fuel injection amount QINJ and the fuel injection timing of the engine are set by adding a correction according to the engine operating state to the amount. In the present invention, the method for setting the fuel injection amount and the fuel injection timing is not particularly limited, and any of the known methods for a diesel engine can be used.

On the other hand, the output port of the ECU 30 is connected to the fuel injection valve 11 of each cylinder via a fuel injection circuit (not shown) in order to control the amount and timing of fuel injection into each cylinder.
1, and is connected to a high-pressure fuel pump 113 via a drive circuit (not shown) to control the amount of fuel pumped from the pump 113 to the common rail 115. Also,
The output port of the ECU 30 is further connected to an actuator 27 of the intake throttle valve 27 via a drive circuit (not shown).
a, which is connected to the variable nozzle actuator 36a of the supercharger exhaust turbine 35a, the actuator 37a of the exhaust throttle valve 37, and the actuator of the EGR valve 23 to open the intake throttle valve 27, the variable nozzle 36, the exhaust throttle valve 37, and the EGR valve 23; Each degree is controlled.

Next, the operation of detaching ash from the DPF 40 in this embodiment will be described. As described above, ash mainly composed of an inorganic substance such as calcium sulfate contained in the exhaust gas accumulates in the DPF 40, and the pressure loss gradually increases regardless of the particulate combustion operation. Although the amount of ash in the exhaust gas is very small, the increase in pressure loss due to ash accumulation is relatively slow, but the pressure loss of the DPF 40 increases after long-term use.
Perform ash desorption operation every 2,000 kilometers
It is necessary to reduce the pressure loss of PF40. As mentioned above, the exhaust manifold 3
It has been found that it is effective to create a state in which the pressure in 1 becomes higher than the cylinder exhaust port pressure (hereinafter, referred to as “a state in which a negative pressure difference occurs in the DPF”) and flow exhaust gas back through the DPF 40.

As a method for generating a negative pressure difference in the DPF, for example, there is the following method. (A) The communication valve 43 is closed. When the exhaust valve is opened during the cylinder exhaust stroke, high-pressure exhaust gas is exhausted from the cylinder and the exhaust port pressure increases, but when exhaust of the high-pressure exhaust gas ends, the exhaust port pressure decreases. Further, when the communication valve 43 is closed, the volume on the upstream side of the DPF decreases, so that the pressure drop of the exhaust port increases.
On the other hand, in the exhaust manifold downstream of the DPF, the exhaust pressure is always kept high because high-pressure exhaust gas from other cylinders flows in. Therefore, when the communication valve 43 is closed, a negative pressure difference occurs before and after the DPF during opening of the exhaust valve of the cylinder. In the method by closing the communication valve, the output, vibration and noise of the engine hardly change, so that the operability of the engine is hardly affected.

(B) Partial cylinder deactivation. In the present embodiment, since the fuel injection valve for individually injecting the fuel into each cylinder is provided, it is possible to stop the fuel injection of any part of the cylinders and prevent the combustion in the cylinders. . In this case, since combustion does not occur in the cylinder at rest, the maximum pressure of the exhaust gas discharged to the exhaust port is significantly reduced, and the minimum pressure in the exhaust port pressure change when the exhaust valve is opened further decreases, and the cylinder intake pressure is reduced. It will be a nearby value. on the other hand,
Also in this case, the exhaust manifold 31 pressure is maintained at a high pressure by exhaust from cylinders other than the idle cylinder. Therefore, when the combustion of some of the cylinders is stopped, a large negative pressure difference occurs in the DPF of the stopped cylinder.

The generation of a negative pressure difference due to partial cylinder deactivation is short and has little effect on the engine output, but changes in engine vibration and noise cause a sense of incongruity to the driver. Will be affected. (C) Suppression of exhaust flowing out of the exhaust manifold. If the exhaust gas flowing out of the exhaust manifold is suppressed, the exhaust pressure in the manifold increases. As a result, a period occurs in which the exhaust manifold pressure is higher than the exhaust port pressure of each cylinder, and a negative pressure difference occurs in the DPF.

The specific method for suppressing the outflow of exhaust gas from the exhaust manifold is as follows: (a) Exhaust throttle by closing exhaust throttle valve 37. (B) The opening degree of the variable nozzle 36 of the turbocharger 35 is reduced. (C) Reducing the amount of recirculated exhaust gas by closing the EGR valve 23. Etc.

When the exhaust manifold pressure is increased, the output of the engine is reduced and the fuel consumption is deteriorated due to the increase of the exhaust back pressure. In addition, the exhaust noise is greatly changed. Relatively large. (D) Reduction of cylinder intake air amount. When the amount of intake air taken into the cylinder is reduced, the combustion pressure in the cylinder is reduced, so that the exhaust pressure when the exhaust valve is opened becomes lower as a whole. In this case, as compared with the exhaust pressure when the exhaust valve is opened, the minimum pressure drop due to the earlier completion of the discharge of the high-pressure exhaust is larger. Therefore, the pressure drop in the exhaust port becomes larger than the pressure drop in the exhaust manifold, and a negative pressure difference is generated in the DPF.

As a means for reducing the cylinder intake air amount, in this embodiment, an intake throttle using an intake air amount throttle valve 27 is used. However, in an engine having a variable valve timing capable of changing the engine intake valve timing, the intake air is restricted. The cylinder intake air amount can also be reduced by retarding the valve closing timing to lower the intake volume efficiency of the cylinder.

The method based on the reduction of the cylinder intake air amount causes a decrease in the engine output and the deterioration of the fuel efficiency similarly to the method based on the increase in the exhaust pressure, so that the influence on the engine operability is increased. D
As a specific method of generating a negative pressure difference in PF,
Although there is a method described in the above (A) to (D), in the actual operation, if the method (A) to (D) is used alone during the steady operation, the negative pressure difference generated in the DPF is relatively small. As a result, the ash desorption effect becomes insufficient. For this reason, when the ash desorption operation is performed by using the above-described methods (A) to (D) during the steady operation of the engine, two or more of the above-described methods are performed in combination and the negative generated in the DPF is performed. Needs to be increased.

However, as described in the description of each method, since the method other than the method by closing the communication valve slightly affects the operability of the engine, the method by closing the communication valve and the other method during the steady operation are used. If implemented in combination, the operability of the engine will be affected. Therefore, in this embodiment, in order to minimize the effect of the ash desorption operation on the engine operability, the ash desorption operation is performed alone or in combination at the end of acceleration or deceleration of the engine. ing.

As described above, the amount of fuel supplied to each cylinder is sharply reduced at the end of acceleration and at the start of deceleration of the engine. For this reason, at the end of acceleration and at the start of deceleration, the combustion pressure in each cylinder drops sharply, and the minimum pressure of the exhaust port when the exhaust valve is opened also drops relatively large. On the other hand, at the end of acceleration and at the start of deceleration, since the exhaust manifold still has relatively high exhaust pressure during acceleration or before the start of deceleration, the pressure at the exhaust port falls below the exhaust manifold pressure and negative pressure is applied to the DPF. A difference comes into play. At this time, if any of the above methods is executed, the negative pressure difference generation effect by these operations is added to the negative pressure difference generation effect by acceleration / deceleration, and the generated negative pressure difference becomes extremely large, and the ash The desorption becomes complete.

Moreover, the end of acceleration and the start of deceleration are performed in an operation region where the engine speed and output are relatively high, and the engine output sharply decreases at the end of both acceleration and deceleration. For this reason, in this state, the driver hardly perceives fluctuations in engine output, changes in vibration and noise even if other methods that affect the engine operability are performed in steady operation, as well as closing the communication passage. There is no effect on engine operability.

A specific embodiment for performing the ash detachment operation at the end of acceleration or at the start of deceleration will be described below. (1) First Embodiment In this embodiment, when the amount of ash accumulated on the DPF 40 increases, the acceleration of the engine ends in a predetermined load region of the engine.
Alternatively, when deceleration is started, the ash desorbing operation is performed by closing the communication valve 43 that communicates the exhaust branch pipe on the upstream side of the DPF 40 with another exhaust branch pipe.

As described above, according to the closing of the communication valve 43, a negative pressure difference can be generated in the DPF 40 without affecting the operability of the engine even during a steady operation. The negative pressure difference that occurs is relatively small. In this embodiment, the DPF 40 is closed by closing the communication valve 43 when the acceleration of the engine ends or when the engine starts to decelerate.
The ash desorption effect is greatly improved without affecting the engine operability by amplifying the negative pressure difference that occurs in the engine. FIG. 2 is a flowchart illustrating the ash detachment operation of the present embodiment.

This operation is carried out by a routine executed by the ECU 30 at regular intervals. In FIG.
When the operation starts, in step 201, the ECU
The engine fuel injection amount QINJ, the engine speed NE, the accelerator opening ACCP, and the vehicle travel distance KM since the previous ash desorption operation were performed are read. In the present embodiment, the ECU 30 accumulates and stores the vehicle travel distance after performing the ash detachment operation by a separately executed routine. This traveling distance KM is used for determining whether or not the ash detachment operation is necessary.

Next, at step 203, the current DPF4
It is determined whether an ash detachment operation of 0 is necessary. DP
It is considered that the ash accumulation amount on F40 increases in proportion to the operating time of the engine (the traveling distance of the vehicle). Therefore, in the present embodiment, when the vehicle travel distance since the previous detachment operation was executed becomes equal to or more than a predetermined value (for example, 1000 km), it is determined that the ash accumulation amount on the DPF 40 has increased to the allowable upper limit value and the ash removal is performed. Perform a release operation. The ash accumulation amount may be determined by using, for example, the integrated value of the engine speed or the integrated value of the engine fuel injection amount after the previous desorption operation, instead of the vehicle travel distance.

If it is determined in step 203 that the ash desorption operation is currently required, it is next determined in step 205 whether the engine is currently operating in a load region in which the ash desorption operation is to be performed. . Ash desorption operation is DP
This must be performed under conditions where a sufficiently large negative pressure difference occurs in F40. For this purpose, it is preferable to carry out the operation in a state where the engine load is large to some extent and the exhaust pressure is sufficiently high. Therefore, in the present embodiment, an engine load condition in which a sufficiently high negative pressure difference is generated by closing the communication valve 43 at the time of acceleration / deceleration is determined in advance by experiments or the like, and the engine ends acceleration in this load region or stops deceleration. The ash desorption operation by closing the communication valve 43 is executed only when the operation is started.

FIG. 3 is a diagram schematically showing a load region in which the ash desorption operation is performed in the present embodiment. The vertical axis of FIG. 3 is the engine output torque (that is, the fuel injection amount QINJ), and the horizontal axis is the engine. The rotation speed NE is shown. In the present embodiment, the ash desorbing operation by closing the communication valve 43 is performed only in a region where the engine exhaust pressure is sufficiently increased (region I in FIG. 3).

If it is determined in step 205 that the engine has been operating in the region I of FIG. 3, it is next determined in step 207 whether or not the present time corresponds to the time when the acceleration of the engine has ended or the deceleration has started. . In the present embodiment, the acceleration is terminated by a change in the accelerator opening ACCP read in step 201,
Judge the start of deceleration. Since the driver returns the accelerator pedal at the end of acceleration and at the start of deceleration, the accelerator opening ACCP decreases. Therefore, in step 207, when the current accelerator opening ACCP has decreased by a predetermined value or more with respect to the accelerator opening ACCP read at the time of the previous execution of this operation, it is determined that the current acceleration has ended or the deceleration has just started. ing.

At both the end of acceleration and the start of deceleration, the fuel injection amount QINJ to the engine is reduced as compared with the previous value. Therefore, it may be determined that the acceleration end or the deceleration start has been performed when the fuel injection amount QINJ from the previous operation execution has decreased by a predetermined amount or more instead of the accelerator opening ACCP. When it is determined in step 207 that the acceleration end or the deceleration start has been performed in the predetermined load region, the communication valve 43 is closed in step 209. As a result, a negative pressure difference due to the closing of the communication valve 43 is added to the pressure difference at the end of acceleration and at the start of deceleration.
A large negative pressure difference acts on F40, and the ash layer deposited on DPF 40 collapses and desorbs due to the backflow of exhaust gas. In step 209, together with closing the communication valve 43,
In step 211, the value of the traveling distance KM for determining whether or not the ash detachment operation is necessary is cleared, and the integration of the value of KM is newly started.

If a negative determination is made in any of steps 203 to 207, the communication valve 43 is opened in step 213, and this operation ends. For this reason, the communication valve 43 is closed at the end of acceleration or at the start of deceleration, and the communication valve 43 is kept open after the ash is completely removed. As a result, the ash that has been desorbed from the DPF 40 by the ash desorbing operation and has become fine particles passes through the pores of the DPF 40 and is discharged downstream of the DPF 40 by the forward exhaust flow passing through the DPF 40.

(2) Second Embodiment In this embodiment, instead of closing the communication valve 43 of the first embodiment, the DPF 40 is stopped by stopping a part of the cylinder of the engine at the end of acceleration and at the start of deceleration. Increase the resulting negative pressure differential. In the present embodiment, the cylinder is stopped by stopping fuel injection from the fuel injection valve of each cylinder, and only one cylinder is stopped in one ash desorption operation. That is, in the present embodiment, the D of one cylinder is determined by one ash desorption operation.
Ash desorption of only the PF is performed, and the ash desorption of all cylinders from the DPF is completed by performing the ash desorption operation four times.

FIG. 4 is a flowchart for explaining the ash detaching operation of the present embodiment. This operation is performed by a routine executed by the ECU 30 at regular intervals. In the flowchart of FIG. 4, steps 401 to 407 indicate the same operations as steps 201 to 207 in FIG. Also in this operation, the ash accumulation due to the partial cylinder deactivation in step 409 and subsequent steps is performed only when the ash accumulation amount of the DPF 40 is increased and the acceleration is completed or the deceleration is started while the engine is operating in the predetermined load region. A separation operation is performed.

That is, in step 409, the value of the counter i representing the cylinder number is incremented by one. The value of the counter i represents the number of the cylinder in which the operation is suspended this time and the ash desorption operation is performed. In the present embodiment, steps 403 to 40
When the condition of 7 is satisfied, the value of the counter i is increased by one each time the operation is performed, so that the ash desorption operation is sequentially performed from the first cylinder to the fourth cylinder. When the value of i becomes 4 or more (step 411), it means that the ash desorption operation of all the cylinders has been completed, so step 41 is performed.
At 9, the value of i is cleared and is ready for the next ash desorption operation start.

If i.ltoreq.4 in step 411, the process proceeds to step 413, where the next fuel injection to the i-th cylinder of the engine is stopped, and the cylinder operation is stopped. As a result, a large negative pressure difference acts on the DPF of the i-th cylinder, and the ash deposited on the DPF collapses and desorbs. Since the negative pressure difference of the DPF generated by suspending the cylinder operation during acceleration / deceleration is extremely large, in the present embodiment, the cylinder rest period is set to only one cycle. DPF
The ash layer deposited on the cylinder is released by one cylinder operation stop, but it is also possible to completely remove the ash by stopping one cylinder for a plurality of cycles.

In step 415, it is determined whether or not the number i of the cylinder stopped in step 413 is 4. If the fourth cylinder has been deactivated in step 413 (i = 4), the ash desorption operation has been completed for all of the first to fourth cylinders. The travel distance integrated value KM for determining whether or not the separation operation is necessary is cleared, and the integration of KM is newly started. If i ≠ 4 in step 413, the value of KM is not cleared because ash desorption of all cylinders has not been completed yet. Therefore, in this case, steps 403 to 407
As long as the condition is satisfied, the ash desorption operation of the next cylinder is continuously executed.

In the first embodiment and the second embodiment, the ash desorption operation is performed by executing the closing operation of the communication valve 43 or the operation of partially stopping the cylinder independently. If the closing of the valve 43 and the partial cylinder deactivation operation are performed simultaneously, the negative pressure difference of the DPF 40 can be further increased, so that the ash can be more completely desorbed.

(3) Third Embodiment Next, a third embodiment of the present invention will be described. In the present embodiment, the engine load region for performing the ash desorption operation is:
As shown in FIG. 6, it is set in two areas. The load region I in FIG. 6 is a load region where the engine exhaust pressure is sufficiently high, similarly to the load region I in FIG. In addition, FIG.
I is a load region in which the exhaust pressure is lower than in the load region I, but a negative pressure difference sufficient for desorbing ash can be generated in the DPF by performing an exhaust pressure increasing operation as described later. The load ranges I and II are preferably determined by experiments using an actual engine and DPF.

In this embodiment, similarly to the first embodiment, when the end of acceleration or the start of deceleration occurs while the engine is operating in the load region I, only the communication valve 43 is closed. Perform the ash desorption operation. On the other hand, in the first embodiment, when the engine was operated in a region other than the load region I, the ash desorption operation was not performed, whereas in the present embodiment, the engine was operated in the load region II. When the vehicle is decelerating, the ash detachment operation is performed. Further, in this case, the DPF is required only by closing the communication valve 43.
Since there is a possibility that a negative pressure difference large enough cannot be generated, any one of the methods ((a) to (c)) described in the above (C) is used together with the closing of the communication valve 43. Perform the operation to increase the pressure of the exhaust manifold. As a result, it is possible to perform the ash desorption operation even in the engine load region II. In this case, in the steady operation state, when the exhaust manifold pressure increasing operation is performed, the deterioration of the drivability due to a decrease in the engine output and a change in vibration and noise is increased,
At the start of deceleration, the output of the engine has just begun to decrease, and the engine load area II is set to a relatively high speed and high load. Relatively small. Thus, in the present embodiment, the area in which the ash detachment operation can be performed is expanded as compared with the first embodiment, and the probability that the ash detachment operation is performed when the ash detachment operation is required increases. .

In this embodiment, the engine is in the load region II.
Does not perform the ash desorption operation at the start of acceleration of the engine. This is because, during acceleration, the engine output needs to be increased, and when the exhaust manifold pressure is increased, the operability of the engine may be significantly deteriorated due to a decrease in the engine output. FIG. 5 is a flowchart illustrating the ash detachment operation of the present embodiment. This operation is performed as a routine executed by the ECU 30 at regular intervals.

In FIG. 5, in steps 501 and 503, parameters such as the fuel injection amount QINJ are read and it is determined whether or not the ash desorption operation is currently required. Steps 501 and 503 correspond to steps 201 and 2 in FIG.
03 is the same operation. If the ash desorption operation is currently required in step 501, it is next determined in step 505 whether or not the engine is currently operating in the load region I of FIG. If the engine is currently operating in the load region I, it is determined in step 507 whether or not the present time corresponds to the end of acceleration or the start of deceleration. The communication valve 43 is closed to execute the ash desorption operation. Steps 507 and 509
Is the same operation as steps 207 and 209 in FIG. Then, after execution of step 509, step 511 is executed.
Clears the value of the running distance integrated value KM.

On the other hand, if it is determined in step 505 that the engine is not operating in the load region I of FIG. 6, the routine proceeds to step 513, where it is determined whether the engine is currently operating in the load region II of FIG. If the engine is running, it is determined in step 515 whether or not the engine has just started to decelerate. In the present embodiment, for example, it is determined that the deceleration has been started when the amount of decrease in the accelerator opening ACCP read in step 501 from the previous time is equal to or greater than a predetermined value and the current accelerator opening is smaller than the predetermined value. That is,
In the present embodiment, when the driver returns the accelerator pedal and the accelerator opening after the return is a small value, it is determined that the deceleration has been started.

In steps 513 and 515, the current load area I
If it is determined that the deceleration at I has been started, the exhaust manifold pressure is increased in step 517.
In the present embodiment, as described above, (a) the exhaust throttle valve 37
(B) reducing the opening of the variable nozzle 36 of the turbocharger 35 and (c) reducing the amount of recirculated exhaust gas by closing the EGR valve 23 by one or more methods. An operation of increasing the pressure of the exhaust manifold 31 is performed. Then, in step 519, the communication valve 43 is closed at the same time as the exhaust manifold pressure increasing operation. As a result, even in the load region II where the exhaust pressure is relatively low, the DP
A sufficiently large negative pressure difference can be generated in F40, and the ash deposited on DPF 40 collapses and desorbs.

Steps 521 to 523 correspond to step 51
7 shows the determination of the ending condition of the ash detachment operation based on Nos. 7 and 519. In the present embodiment, the ash desorption operation by the exhaust manifold pressure increasing operation and the communication valve closing valve is performed in step 5.
At 17, the operation is continued for a predetermined time after the exhaust manifold pressure increasing operation is started. That is, the value of the time counter t at step 521 is increased by 1, ash removal operation is continued by the step 517 and 519 until it reaches the value t ₀ the value of the counter t is determined in advance at step 523. As described above, in the present embodiment, the exhaust throttle valve 37,
The exhaust manifold pressure rises by means of the turbocharger variable nozzle 36 and the EGR valve 23, but since these means all have relatively slow operating speeds, there is a time delay from the start of operation to the rise of the exhaust manifold pressure. Therefore, in the present embodiment, the DPF 40 is activated when a certain margin (time corresponding to t ₀ in step 523) has elapsed from the start of the operation of the exhaust throttle valve 37, the turbocharger variable nozzle 36, the EGR valve 23, and the like. Therefore, it is determined that a sufficiently large negative pressure difference has occurred and the ash has detached.

If t ≧ t ₀ at step 523, the ash detachment operation has been completed, and the routine proceeds to step 511, where the mileage integrated value KM is cleared. If the ash desorption operation is not required in step 503 (for example, K
If the value of M has not reached the predetermined value) and step 5
If the engine is not currently operating in the load region I or II at 13, if it is not at the end of acceleration or deceleration at step 507, and if it is not at the time of deceleration start at step 515, the operation of steps 525 to 529 is not performed. Then, the value of the time counter t is cleared, the communication valve 43 is maintained in the open state, and the exhaust manifold pressure increasing operation is stopped.

In this embodiment, the ash desorbing operation is performed using the communication valve 43. However, as described in the second embodiment (FIG. 4), the communication valve 43 is replaced with a partial cylinder stop. It is also possible to perform the ash desorption operation for each cylinder. Further, at the start of deceleration in the load region II, the intake air pressure restricting valve 27 is replaced with an exhaust manifold pressure increasing operation.
A similar effect can be obtained by using both the cylinder intake air amount reduction operation and the valve closing operation of the communication valve 43, or using the cylinder intake air amount reduction operation and the partial cylinder deactivation operation together.

Further, at the start of deceleration in the load region II, if the throttle such as the exhaust throttle valve 37 or the intake air amount throttle valve 23 is made relatively small (the opening degree is made relatively large), the engine operability is given. The effect can be further reduced. (4) Fourth Embodiment Next, a fourth embodiment of the present invention will be described.

In each of the above-described embodiments, the ash detachment operation is executed only when the acceleration ends or the deceleration starts in a specific load region. In this case, when the engine is continuously operated in a region other than the specific load region, or when the engine is operated in the specific load region and no acceleration or deceleration is performed, even if the ash accumulation amount increases, The separation operation is not executed, and the engine is operated for a long time in a state where the pressure loss of the DPF 40 is large.

In the present embodiment, if the ash detachment operation is not performed within a predetermined detachment operation execution period after it is determined that the ash detachment operation needs to be executed to prevent this, The ash is forcibly detached even if the conditions for performing the ash detachment operation are not satisfied. In this case, since the exhaust pressure may be low depending on the engine operating condition, in this embodiment, the exhaust manifold pressure increasing operation and the communication valve closing operation are used in combination to ensure the exhaust gas pressure even under a low exhaust pressure. A large negative pressure difference is generated in the DPF.
As a result, when the ash accumulation amount increases, the ash desorption operation is reliably performed, and thus the engine is prevented from being operated for a long time in a state where the pressure loss of the DPF is high.

FIG. 7 is a flowchart for explaining the ash detaching operation of the present embodiment. This operation is performed by a routine executed by the ECU 30 at regular intervals. In FIG. 7, step 701 indicates an operation for reading each parameter, and step 703 indicates an operation for determining whether or not the ash detachment operation is necessary. Steps 701 and 703 are the same operations as steps 201 and 203 in FIG. 2, respectively.

If the current ash detachment operation is required in step 703, the value of the detachment operation execution period counter ct is increased in step 705. The counter ct is:
When it is determined in step 703 that the ash desorption operation is not necessary, that is, when it is determined that the ash accumulation amount is within the allowable range, the ash is always cleared in step 727, and thus the calculation is performed in step 707. Counter c
The value of t is a value corresponding to the elapsed time since it was determined that the ash desorption operation was necessary.

Next, at step 707, the counter ct
Is determined to have reached the predetermined value ct ₀ . c
The value of t _{0 is} a value corresponding to the desorption operation execution period, and is set as an upper limit time during which the engine operation with the ash accumulation amount increased is permitted. In step 707, ct <c
If t ₀ , that is, if the detachment operation execution period has not elapsed, the value of the time counter t is cleared in step 709, and then steps 711 to 717 are executed. Steps 711 to 717 are the same operations as steps 205 to 201 in FIG. 2, whereby the engine is operating in a predetermined load region (FIG. 3, the same load region as load region I), and the acceleration of the engine is terminated. Alternatively, when deceleration starts, the ash desorbing operation is performed only by closing the communication valve 43. Further, when the ash detachment operation is performed by the operations of steps 711 to 715, the mileage integrated value KM for determining whether or not the detachment operation needs to be executed is cleared, and at the next operation execution, the detachment operation execution is performed at step 727. While the value of the period counter ct is cleared, the communication valve 43 is kept open in step 729, and the exhaust manifold pressure increasing operation is stopped in step 731.

On the other hand, if the conditions for executing the ash desorption operation in steps 711 and 713 are not satisfied despite the necessity of the ash desorption operation, the value of the counter ct increases in step 705 each time the operation is performed. Then, while ash desorption operation is not executed, so that the desorption operation execution period becomes ct ≧ ct ₀ At step 707 the elapsed, steps 719 725 are performed. Steps 719 to 721 show the same operation as steps 517 to 523 in FIG. That is, in step 719, the exhaust manifold pressure is increased, and in step 721, the communication valve 43 is closed. As a result, the ash detachment operation is forcibly executed even when the detachment operation execution conditions in steps 711 and 713 are not satisfied. This state is maintained for a predetermined time (time until the value of the time counter t increases from 0 to t ₀ ) (steps 723 and 725). When the predetermined time elapses, step 717 is executed to change the value of KM. Cleared. That is, the ash forcible detachment operation is performed for a predetermined time (t ₀ ) after the start.
Is terminated when elapses. Also in this case, at the next operation execution, steps 727 to 731 are executed after step 703, and the normal operation of the engine is restarted.

Also in this embodiment, the operation of reducing the cylinder intake air amount by the intake throttle valve 27 is performed instead of the operation of increasing the exhaust manifold pressure, and the operation of partially stopping the cylinder is performed instead of the operation of closing the communication valve 43. It is needless to say that it is also possible to perform ash desorption by the following method.

[0077]

According to the invention described in each of the claims, there is a common effect that the ash accumulated on the particulate filter can be surely desorbed without greatly affecting the operation state of the engine. . Further, according to the invention of claim 4, in addition to the above-mentioned common effect, there is an effect that the engine can be prevented from being operated for a long time in a state where the exhaust pressure loss is high.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment when the present invention is applied to an automobile diesel engine.

FIG. 2 is a flowchart illustrating a first embodiment of an ash detachment operation according to the present invention.

FIG. 3 is a diagram showing an engine load region in which the ash desorption operation of FIG. 2 is performed.

FIG. 4 is a flowchart illustrating a second embodiment of the ash detachment operation according to the present invention.

FIG. 5 is a flowchart illustrating a third embodiment of the ash detachment operation according to the present invention.

6 is a diagram showing an engine load region in which the ash desorption operation of FIG. 5 is performed.

FIG. 7 is a flowchart illustrating a fourth embodiment of the ash detachment operation according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Diesel engine 23 ... EGR valve 27 ... Intake throttle valve 30 ... Electronic control unit (ECU) 31 ... Exhaust manifold 35 ... Turbocharger 36 ... Variable nozzle 37 ... Exhaust throttle valve 40 ... Particulate filter 41 ... Communication passage 43 ... Communication valve

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G090 AA01 AA02 AA04 BA01 BA08 CA00 CB24 CB25 DA00 DA18 DA20 DB06 DB07 EA04 EA05 EA07

Claims (4)

[Claims] A particulate filter disposed on each exhaust branch pipe connecting an exhaust port of each cylinder of the internal combustion engine and an exhaust collecting part where the exhaust of each cylinder joins, for collecting particulates in the exhaust gas; Ash desorbing means for desorbing ash composed of non-combustible components deposited on the particulate filter by generating an exhaust flow that flows backward from the exhaust collecting portion to the exhaust port side through the respective particulate filters, Desorption control means for operating the ash desorption means to perform an ash desorption operation when the internal combustion engine ends acceleration or starts deceleration in a predetermined load region, apparatus. 2. The ash desorbing means includes: a communication passage that communicates a portion upstream of the particulate filter of the exhaust branch pipe with a portion upstream of the particulate filter of the exhaust branch pipe of at least one other cylinder; 2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, further comprising: a communication valve capable of closing the communication path, wherein the exhaust path is generated in the particulate filter by closing the communication path during an ash desorption operation. 3. The ash desorption means includes a cylinder deactivation means for stopping combustion of an arbitrary part of the cylinder of the internal combustion engine. The ash desorption means stops the combustion of one part of the cylinder during the ash desorption operation. 2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the exhaust gas reverse flow is generated in a particulate filter arranged in an exhaust branch pipe of a part of the cylinder. 3. 4. Either increasing the exhaust pressure of the exhaust collecting section by suppressing the outflow of exhaust from the exhaust collecting section, or reducing the amount of intake air flowing into each cylinder. Or ash forced desorption means for desorbing ash from the particulate filter by generating an exhaust flow that flows backward from the exhaust collecting portion to the exhaust port side through the respective particulate filters by the respective particulate filters, or the both; If the ash detachment operation is not executed within the predetermined ash detachment operation execution period, the ash forcible detachment unit is operated after the elapse of the detachment operation execution period to forcibly remove the ash. The exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 3, which performs a separating operation.