JP2001355433A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the regeneration disabled state of a filter by estimating the accumulation quantity of particulates on the filter, and heightening the temperature of exhaust gas to oxidize the particulates before the particulates are accumulated in a layered state on the filter. SOLUTION: This engine exhaust emission control device is constituted to once collect the particulates included in the exhaust gas, by the filter 22 disposed in an exhaust pipe 70 to remove the particulates, and to remove the collected particulates by oxidation to regenerate the filter. The filter 22 removes the collected particulates by oxidation without generating a luminous flame when the quantity of engine exhaust particulates per unit time is less than the quantity of oxidation removable particulates. A smoke sensor 102 is installed downstream of the filter in the exhaust pipe 70 to detect the concentration of the particulates in the exhaust gas, and an oxidation removal accelerating means is provided for accelerating the oxidation removal of the particulates on the filter when the output value of the smoke sensor 102 exceeds the threshold value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas purification device for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in a diesel engine, a particulate filter is arranged in an engine exhaust passage in order to remove fine particles such as soot contained in exhaust gas. Then, the particulate filter once collects the fine particles in the exhaust gas, and removes the fine particles collected on the particulate filter to regenerate the particulate filter.

However, the fine particles collected on the particulate filter do not ignite unless they reach a high temperature of about 600 ° C. or more, whereas the exhaust gas temperature of a diesel engine is usually much lower than 600 ° C. Therefore, it is difficult to ignite the fine particles on the particulate filter with the heat of the exhaust gas. Therefore, in order to ignite the fine particles collected on the particulate filter even with the exhaust gas heat considerably lower than 600 ° C, the ignition temperature of the fine particles must be lowered.

[0004] By the way, it has been conventionally known that a catalyst can be carried on a particulate filter to reduce the ignition temperature of fine particles. Therefore, various particulate filters carrying a catalyst are known.

For example, Japanese Patent Publication No. Hei 7-106290 discloses a particulate filter in which a mixture of a platinum group metal and an alkaline earth metal oxide is supported on the particulate filter. The particulate filter disclosed in this publication is capable of igniting fine particles even at a relatively low temperature of approximately 350 ° C. to 400 ° C., and is capable of continuous combustion depending on the operating conditions.

[0006]

As described above, a diesel engine whose exhaust gas temperature is usually much lower than 600 ° C., but when the load is high, the exhaust gas temperature is increased from 350 ° C.
Reach up to 400 ° C. Therefore, at first glance, it can be seen that a particulate engine can be ignited and burned by the exhaust gas heat when the engine load becomes high, in the case of a diesel engine to which the particulate filter disclosed in the above publication is applied.

However, even if the temperature of the exhaust gas reaches 350 ° C. to 400 ° C., the fine particles may not actually ignite.
Further, even if the fine particles are ignited, only a part of the fine particles burn, and a large amount of fine particles remains unburned.

When the amount of fine particles contained in the exhaust gas is small, the amount of fine particles adhering to the particulate filter is small. Therefore, when the temperature of the exhaust gas changes from 350 ° C. to 400 ° C., the fine particles on the particulate filter It ignites and then burns continuously. However, if the amount of fine particles contained in the exhaust gas is large, other fine particles accumulate on the particulate filter before the fine particles attached to the particulate filter completely burn, and the fine particles are laminated on the particulate filter. Will be deposited. Then, some of the fine particles that are likely to come into contact with active oxygen burn, but fine particles that are hardly in contact with active oxygen do not burn, and thus a large amount of fine particles remain unburned.

Therefore, if the amount of fine particles contained in the exhaust gas increases depending on the operating state of the engine, a large amount of fine particles will continue to accumulate on the particulate filter even if the particulate filter described in the above-mentioned publication is used.

On the other hand, when a large amount of fine particles accumulate on the particulate filter, the fine particles on the filter gradually become difficult to ignite and burn. This is probably because the carbon in the fine particles changes to a substance that is difficult to burn such as graphite while the fine particles are being deposited.

In fact, if a large amount of fine particles continue to accumulate on the particulate filter, the fine particles do not ignite in a low-temperature exhaust gas of 350 ° C. to 400 ° C. High temperature exhaust gas is required.
However, as described above, in a diesel engine, the exhaust gas temperature does not usually exceed 600 ° C. Therefore, if the particulates continue to deposit on the particulate filter, it becomes difficult to ignite the deposited particulates with the heat of the exhaust gas.

On the other hand, the exhaust gas temperature can be raised to a high temperature of 600 ° C. or more, and therefore, even if the deposited fine particles ignite, another problem arises in this case. That is, when the fine particles ignite at a high temperature of 600 ° C. or more, the fine particles emit a bright flame and burn. As a result, the temperature of the particulate filter rises to 800 ° C. or more for a long time until the burning of the fine particles deposited on the particulate filter is completed.

As a result, the particulate filter deteriorates early, so that the particulate filter must be replaced with a new one early. Further, when the deposited fine particles burn, the ash, ie, ash, which is a burning residue, is condensed to form a large lump, and the lump blocks the pores of the particulate filter and causes clogging. The number of clogged pores gradually increases over time. Therefore, the pressure loss of the exhaust gas flow in the particulate filter gradually increases, and as a result, the engine output decreases. Therefore, even if this point is taken into consideration, the particulate filter must be replaced with a new one at an early stage.

[0014] Once such a large amount of fine particles are deposited in a layered manner, the various problems described above occur. Therefore, in consideration of the balance between the amount of fine particles contained in the exhaust gas and the amount of fine particles that can be burned on the particulate filter, it is necessary to prevent the fine particles from being deposited on the stack.

However, if a particulate filter with a catalyst is provided in the exhaust pipe and a continuous combustion process is performed in which exhaust gas purification is left to the operating conditions of the engine, the above problem cannot always be avoided.

Accordingly, the exhaust gas is switched alternately from the upstream side and the downstream side of the exhaust flow to the particulate filter of the purifier so that the particulates can be continuously burned as much as possible irrespective of the operating condition. As a result, the fine particles accumulate on both side surfaces of the particulate filter. In this way, the amount of the deposited fine particles per unit area can be reduced, and by switching the exhaust gas flow, the fine particles to be deposited can be disturbed and blown off. Is provided, the fine particles move around the inside, the chance of contact with the active oxygen releasing agent is increased, and the amount of oxidizable fine particles can be increased.

However, even in this case, the exhaust gas temperature is not always at the above-mentioned particulate combustion temperature, and a large amount of particulates may be emitted from the diesel engine depending on the operating condition. Therefore, in such a case, the fine particles that cannot be eliminated in a short time gradually accumulate on the particulate filter.

When the deposition proceeds to some extent and the deposition proceeds, the ability to oxidize the particulates is extremely reduced. If the exhaust gas is passed through the particulate filter in this state, the deposition of the particulates further progresses, and the particulate filter is regenerated. It becomes difficult. Therefore, it is important to regenerate the particulate filter before the particulate filter oxidizing ability of the particulate filter is extremely reduced.

However, in the prior art, there is no technique for accurately measuring or estimating the amount of accumulated particulate before the particulate filter oxidizing ability of the particulate filter is extremely reduced.

Further, in the particulate filter described in the above publication, when the exhaust gas temperature becomes lower than 350 ° C., the fine particles do not ignite, so that the fine particles accumulate on the particulate filter. Exhaust gas temperature of 350 ° C if the amount of accumulated fine particles is small
Although particles can be burned even at temperatures of 400 ° C to 400 ° C, if the amount of particles is large enough to deposit
At temperatures between ° C and 400 ° C, the particles cannot be ignited, if at all, but only some of them. Therefore, most of the deposited fine particles are left unburned.

The present invention has been made in view of the above points, and the problem to be solved is to estimate the amount of fine particles deposited on the filter from the amount of desorbed smoke, and to deposit the fine particles on the filter in a layered manner. It is an object of the present invention to provide an exhaust gas purifying apparatus for an internal combustion engine, in which the temperature of an exhaust gas is increased before burning to burn fine particles, and a situation in which regeneration of a filter becomes impossible can be avoided.

[0022]

Means for Solving the Problems To achieve the above object, an exhaust gas temperature raising apparatus for an internal combustion engine according to the present invention employs the following means.

That is, in the exhaust gas purifying apparatus for an internal combustion engine of the present invention, the particulates in the exhaust gas are once collected by a filter arranged in the engine exhaust passage in order to remove the fine particles contained in the exhaust gas. In the exhaust gas purifying apparatus for an internal combustion engine for regenerating the filter by oxidizing and removing the generated particulates, the filter may be configured such that the amount of particulates discharged from the internal combustion engine per unit time by the filter is reduced by the filter. When the amount is smaller than the amount, the filter oxidizes and removes the trapped fine particles without generating a bright flame. The filter is installed downstream of the filter in the engine exhaust passage and is included in exhaust gas at the installation location. A fine particle concentration sensor for detecting the concentration of fine particles; and a fine particle on the filter when an output value of the fine particle concentration sensor exceeds a specific set value. Having an oxidation removal facilitating means for facilitating the removal by oxidation.

Here, an ECU for controlling the entire internal combustion engine is provided.
And a brief description of the components of the present invention. The ECU consists of a digital computer as is well known, and is connected to each other by a bidirectional bus.
OM, random access memory RAM, backup R
It comprises an AM, an input port, an output port, and the like.

The input ports are electrically connected to various sensors mounted on the internal combustion engine or the vehicle. When output signals of these sensors enter the ECU from the input ports, the parameters relating to these sensors are temporarily random-accessed. It is stored in the memory RAM.

Then, based on these parameters, C
The CPU performs an arithmetic process required by the PU. In executing the arithmetic process, the CPU calls the parameters stored in the random access memory RAM via the bidirectional bus as needed.

The "filter" is preferably a particulate filter for removing fine particles such as soot contained in exhaust gas. The “particulate concentration sensor” may be a known smoke sensor, a transmission type smoke meter, an opacimeter, or the like, which detects the concentration of the particulates contained in the exhaust gas.

Regarding "when the set value is exceeded",
A so-called threshold value can be exemplified as an example of the set value. As is well known, the threshold is the minimum value required for a particular process to occur. In the case of the present invention, the fine particles are deposited on the filter at the minimum value of the exhaust smoke concentration required for being deposited on the filter, in other words, the amount of the deposited particles continues to increase, and when the amount of the deposited particles exceeds a certain amount, This is the limit of the amount of fine particles at which oxidation removal of fine particles cannot be performed immediately. The exhaust smoke concentration means a ratio of smoke that has flowed downstream of a portion of the engine exhaust passage where a filter is installed, in the exhaust gas (so-called desorption smoke concentration).

The exhaust smoke concentration in such a case differs depending on the type of the internal combustion engine and the type of the vehicle on which the internal combustion engine is mounted.
The case where it exceeds 5% is mentioned.

As another example of the case where the set value is exceeded, the average value of the exhaust smoke concentration when the vehicle has traveled for a certain time or distance regardless of the engine operating condition exceeds the threshold value. There are cases.

The "oxidation removal accelerating means" can be exemplified by an application program which is stored in the ROM of the ECU and is an execution routine for accelerating oxidation removal. Specifically, an application program for executing a heating control for raising the exhaust gas heat so as to periodically oxidize the fine particles collected by the filter by utilizing heat, and an application for operating an electric heating means such as an electric heater. A program can be exemplified.

As means for executing the temperature raising control, for example, a fuel injection valve or an intake throttle valve installed in an intake passage can be mentioned. The amount of fuel combusted in the cylinder is determined by changing the amount of fuel injected from the fuel injection valve and the amount of intake air flowing through the intake passage by controlling the intake throttle valve, and thus the temperature of exhaust gas changes. Since the attributes of the ROM for storing these programs are in the ECU, it can be said that the ECU is a means for promoting oxidation and removal.

Therefore, it can be said that the oxidation removal promoting means raises the filter temperature. Further, the filter temperature is measured by temperature detecting means such as a temperature sensor.

Further, as another example of the oxidation removal promoting means, a means for reversing the flow of exhaust gas flowing in the filter can be mentioned. Reversing refers to flowing the exhaust gas from the opposite side to the filter so that the exhaust gas flowing from one side of the filter flows from the other side. Flowing the exhaust gas from one side and the other side of the filter will be referred to as a forward flow and a backward flow, respectively, for convenience.

By reversing the flow of the exhaust gas with respect to the filter, fine particles such as soot move around in the base material of the filter, so that oxidation of the fine particles can be promoted to purify the fine particles efficiently. become able to. The means for reversing the flow direction of the exhaust gas in this way is called "exhaust flow switching means".

The case where this exhaust flow switching means is applied to the present invention will be described below. That is, in order to remove the fine particles contained in the exhaust gas, the fine particles in the exhaust gas are once collected by a filter arranged in the engine exhaust passage, and the collected fine particles are oxidized and removed to regenerate the filter. In the exhaust gas purifying apparatus for an internal combustion engine, the filter emits the collected fine particles when the amount of the particulates discharged from the internal combustion engine per unit time is smaller than the amount of the oxidizable and removable fine particles per unit time by the filter. A filter for oxidizing and removing in a state in which no flame is generated, wherein the filter is provided downstream of the filter in the engine exhaust passage and detects a concentration of particulates contained in exhaust gas at the installation location; A first flow of exhaust gas flowing from one side to the other side and a second flow of exhaust gas flowing from the other side to the one side. Exhaust flow switching means for alternately switching the flow, and oxidation removal promoting means for promoting the oxidation removal of the fine particles on the filter when the output value of the fine particle concentration sensor exceeds a specific set value. .

More specifically, immediately after the operation of the exhaust gas switching means, the fine particles deposited on the filter are easily separated by the flow from the opposite side, and are discharged from the filter at once. Therefore, by detecting the output value of the particle concentration sensor at this time, it is possible to determine how much particles have accumulated on the filter. When the output value of the fine particle concentration sensor exceeds a set value, the control is performed so that the oxidation promoting means operates.

The "exhaust flow switching means" includes an exhaust switching valve provided in the exhaust passage at a location upstream of the filter installation location, the exhaust switching valve and the one side of the filter, and the exhaust switching valve and the exhaust switching valve. It is preferable that the apparatus has a pair of communication paths respectively connecting the other side and control means for performing switching control of the exhaust switching valve.

The exhaust switching valve has a valve element operated by a driving device such as an actuator. One of the pair of communication paths is connected to the one side of the filter in accordance with opening and closing of the valve element. Or the other communication path connecting the other side of the filter, every time the internal combustion engine decelerates the exhaust gas flowing through the exhaust passage toward the filter, at an appropriate predetermined time, at an appropriate predetermined travel distance, or the like. , A valve device for branching as required.

The control means is one of various application programs stored in the ROM for implementing various routines for executing control of the internal combustion engine. Further, since the attribute of the ROM for storing the program relating to the control means is in the ECU, the ECU can be said to be the control means.

The output port is electrically connected to various operating devices such as the exhaust switching valve, and operates the various operating devices based on output signals of necessary sensors among the various sensors. .

When the operation of the exhaust switching valve is controlled based on the calculation result of the CPU, one of the pair of communication paths, which connects the exhaust switching valve and one side of the filter, is connected to the first passage of the exhaust gas. 1 flow or a second flow of exhaust gas in the other communication path connecting the other side of the exhaust switching valve and the filter.

In the present invention having such a configuration, the accumulation amount of fine particles is estimated by the fine particle concentration sensor, and the estimated value (detected value by the fine particle concentration sensor) is a concentration value exceeding the set value. At the time, the oxidation removal promoting means is operated. Therefore, the particulates can be burned before the particulates are deposited so that the filter cannot be regenerated, so that a situation in which the particulate filter cannot be regenerated can be avoided.

Since the exhaust flow switching means also functions as the oxidation removal promoting means as described above, when the exhaust gas switching means reverses the flow of the exhaust gas flowing through the filter, the value detected by the particle concentration sensor is reduced. When it is determined that the threshold value is exceeded, the exhaust gas switching device, which is a component of the exhaust gas flow switching device, is frequently switched to promote oxidation of the fine particles, and thus to efficiently purify the fine particles. The function as an oxidation removal accelerating means may be enhanced, but at the same time, as described above, the application program for executing the temperature increase control or the application program for operating the electric heating means such as an electric heater is executed as the oxidation removal accelerating means. May be promoted.

By doing so, the oxidizing and removing ability is doubled, and the efficiency is further improved. Further, the present invention once traps particulates in the exhaust gas by a filter arranged in the engine exhaust passage to remove particulates contained in the exhaust gas,
In the exhaust gas purifying apparatus for an internal combustion engine for regenerating the filter by oxidizing and removing the collected particulates, the filter may be configured such that an amount of particulates discharged per unit time from the internal combustion engine per unit time by the filter is reduced. A filter that oxidizes and removes the trapped fine particles without producing a bright flame when the amount is smaller than the amount of fine particles that can be oxidized and removed. A fine particle concentration sensor for detecting the concentration of fine particles contained in the gas, and a first flow for flowing exhaust gas from one side to the other side of the filter when an output value of the fine particle concentration sensor exceeds a specific set value. Exhaust flow switching means for alternately switching a second flow of exhaust gas flowing from the other side toward the one side; and an output of the fine particle concentration sensor. And bypass means value to flow exhaust gas to the engine exhaust passage in a state where the filter is bypassed when exceeds a certain set value, may have a.

Also in this case, the output value of the particle concentration sensor is obtained as an instantaneous value or as an average value at predetermined intervals of time and distance, and when these values exceed the specific set values, the oxidation removal promoting means is activated. You may make it.

It is preferable to use a part of the engine exhaust passage as the "bypass means". The allowable amount that the filter can continuously oxidize and remove fine particles is predetermined to a certain extent. If the allowable amount is exceeded, the accumulation of fine particles increases at once,
Under such circumstances, the exhaust gas is bypassed to prevent the accumulation of fine particles more than currently accumulated. While bypassed, oxidation is gradually promoted over time.

[0048]

Embodiments of the present invention will be described below with reference to the accompanying drawings. <Outline of Apparatus Configuration> FIG. 1 shows a case where the present invention is applied to a compression ignition type internal combustion engine. The present invention can also be applied to a spark ignition type internal combustion engine.

Referring to FIG. 1, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston,
5 is a combustion chamber, 6 is an electric control type fuel injection valve, 7 is an intake valve,
Reference numeral 8 denotes an intake port, 9 denotes an exhaust valve, and 10 denotes an exhaust port.

The intake port 8 is connected to a surge tank 12 via a corresponding intake branch 11, and the surge tank 12 is connected to a compressor 15 of an exhaust turbocharger 14 via an intake duct 13.

A step motor 16 is provided in the intake duct 13.
And a cooling device 18 for cooling the intake air flowing through the intake duct 13 around the intake duct 13. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 18 and cools the intake air by the engine cooling water.

On the other hand, the exhaust port 10 is connected to the exhaust turbocharger 1 through an exhaust manifold 19 and an exhaust pipe 20.
4 and an outlet of the exhaust turbine 21 is connected to an exhaust purification device A having a casing 23 having a built-in particulate filter 22.

Exhaust manifold 19 and surge tank 12
Are connected to each other via an exhaust gas recirculation (hereinafter, referred to as EGR) passage 24, and an electrically controlled EGR control valve 25 is disposed in the EGR passage 24.

A cooling device 2 for cooling the EGR gas flowing in the EGR passage 24 is provided around the EGR passage 24.
6 is arranged. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 26, and the engine cooling water cools the EGR gas.

On the other hand, the fuel injection valve 6 is connected to a fuel reservoir, a so-called common rail 27, via a fuel supply pipe 6a. An electric control type variable discharge fuel pump 28 supplies fuel into the common rail 27,
The fuel supplied into the fuel injection valve 7 is supplied to the fuel injection valve 6 through a fuel supply pipe 6a. Common rail 27 has common rail 2
A fuel pressure sensor 29 for detecting the fuel pressure in the fuel cell 7 is attached, and the discharge amount of the fuel pump 28 is adjusted based on the output signal of the fuel pressure sensor 29 so that the fuel pressure in the common rail 27 becomes the target fuel pressure. Control.

Electronic control unit (hereinafter referred to as “ECU”) 30
Consists of a digital computer, a bidirectional bus 31
(Read only memory) connected to each other by
32, RAM (random access memory) 33, CPU
(Microprocessor) 34, input port 35 and output port 36.

The output signal of the fuel pressure sensor 29 is
The data is input to the input port 35 via the D converter 37. Further, the particulate filter 22 is provided with a temperature sensor 39 as temperature detecting means for detecting the internal temperature of the particulate filter 22, and an output signal of the temperature sensor 39 is input to an input port 35 via a corresponding AD converter 37. Is done.

The accelerator pedal 40 includes an accelerator pedal 4
A load sensor 41 that generates an output voltage proportional to the amount of depression L of 0 (see FIG. 2) is connected, and the output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37.
Is input to Further, the input port 35 is connected to a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, by 30 °.

On the other hand, the output port 36 is connected to the fuel injection valve 6, the throttle valve driving step motor 16, the EGR control valve 25, the fuel pump 28, and an actuator 72 described later via a corresponding drive circuit 38.

FIG. 2A shows the relationship between the required torque TQ, the depression amount L of the accelerator pedal 40, and the engine speed N. In FIG. 2A, each curve represents an equal torque curve, a curve indicated by TQ = 0 indicates that the torque is zero, and the remaining curves are TQ = a, TQ
= B, TQ = c, TQ = d in order of increasing required torque.

The required torque TQ shown in FIG.
As shown in (B), the ROM 32 is previously stored in the form of a map as a function of the depression amount L of the accelerator pedal 40 and the engine speed N.
Is stored in In the present embodiment, first, a required torque TQ corresponding to the depression amount L of the accelerator pedal 40 and the engine speed N is calculated from the map shown in FIG. 2B, and the fuel injection amount and the like are calculated based on the required torque TQ. calculate. <Structure of Exhaust Purification Apparatus> As shown in FIGS. 1, 3 and 4, the exhaust purification apparatus A has an exhaust pipe 70 as an engine exhaust passage connected to the outlet side of the exhaust turbine 21.

A first branch branched from the exhaust pipe 70 and connected to one surface (one side) and the other surface (the other side) of the particulate filter 22 in the casing 23 containing the particulate filter 22. An exhaust passage 76 and a second exhaust passage 77 are provided.

Further, the exhaust pipe 70 is connected to the first exhaust passage 7.
A bypass passage 73 is provided as a bypass unit that bypasses the particulate filter 22 and discharges the exhaust gas without passing through the particulate filter 22 from the branch point between the sixth and second exhaust passages 77.

An exhaust switching valve 71 is installed at a branch point between the first exhaust passage 76 and the second exhaust passage 77, that is, at a location on the exhaust pipe 70 upstream of the location where the particulate filter 22 is installed. I have. Exhaust switching valve 71
Includes a valve body 71a driven by an actuator 72, and selects a first exhaust passage 76 according to the position of movement of the valve body 71a to discharge exhaust gas from one side of the particulate filter 22 to the other side. A first flow (forward flow) to flow and a second flow (backflow) to select the second exhaust passage 77 and flow exhaust gas from the other side to the one side of the particulate filter 22 are alternately switched. It has become.

Here, the casing 23 for accommodating the particulate filter 22 is disposed just above the exhaust pipe 70 forming the bypass passage 73, and the exhaust switching valve 71 is provided on both sides of the casing 23 from the exhaust pipe 70. Exhaust passage 76 and second exhaust passage 77 branched through
Are connected. That is, the first exhaust passage 76 and the second exhaust passage 77 are formed by a pair of communication lines respectively connecting the exhaust switching valve 71 and the one side of the particulate filter 22 and the exhaust switching valve 71 and the other side of the particulate filter 22. It can be called a passage.

In the exhaust pipe 70, a pressure sensor 100 and a smoke sensor 102 are installed near the upstream side and the downstream side of the exhaust gas purification device A, respectively. The pressure sensor 100 detects the exhaust pressure on the upstream side of the exhaust gas purification device A, and the smoke sensor 102 detects the concentration of the particles contained in the exhaust gas on the downstream side of the exhaust gas purification device A as a particle concentration sensor. It should be noted that a well-known transmission type smoke meter, opacimeter, or the like may be used instead of the smoke sensor 102. Pressure sensor 100 and smoke sensor 102
Is input to the input port 35 via the corresponding AD converter 37.

The exhaust switching valve 71 is connected to the filter temperature and pressure sensor 1 detected by the temperature sensor 39.
00, exhaust pressure detected by the smoke sensor 102
Concentration of fine particles contained in the exhaust gas detected by
The switching is performed so as to generate the first flow or the second flow in the particulate filter 22 in accordance with an output signal indicating an operating state of the engine. This switch is
This is performed when necessary, such as every time the engine decelerates, every predetermined time, or every predetermined traveling distance.

The switching by the exhaust switching valve 71 is performed by E
It is controlled by the CU 30. And the casing 23
In the particulate filter 22, the length in the width direction orthogonal to the length direction is longer than the length in the length direction when the passing direction of the exhaust gas is the length direction. With such a configuration, the particulate filter 22
The space required for mounting the exhaust gas purifying device A, which includes the casing 23 enclosing the vehicle, on the vehicle can be reduced.

The actuator 72 is connected to the CP of the ECU 30.
It is driven and controlled by control means 75 implemented on U34, and driven by a control signal from output port 36. Further, the actuator 72 is driven by a negative pressure formed as the internal combustion engine is driven. When the negative pressure is not applied, the actuator 72 moves the valve body 71a to a position (a forward flow position) where the first exhaust passage 76 is selected. When the first negative pressure is applied, the valve body 71a is controlled to the neutral position. When the second negative pressure stronger than the first negative pressure is applied, the second exhaust passage 77 is controlled.
The valve element 71a is controlled to a position (reverse flow position) where is selected.

When the valve body 71a is in the forward flow position shown by the broken line in FIG. 3, the exhaust switching valve 71 connects the exhaust pipe 70 to the first exhaust passage 76 and connects the second exhaust passage 77 to the bypass passage 73. To the exhaust pipe 7
0 → first exhaust passage 76 → particulate filter 2
It flows in the order of 2 → second exhaust passage 77 → bypass passage 73 and is discharged to the atmosphere.

When the valve body 71a is at the reverse flow position shown by the solid line in FIG. 3, the exhaust switching valve 71 connects the exhaust pipe 70 to the second exhaust passage 77 and connects the first exhaust passage 76 to the bypass passage. Since it is connected to the exhaust gas 73, the exhaust gas flows in the order of the exhaust pipe 70 → the second exhaust passage 77 → the particulate filter 22 → the first exhaust passage 76 → the bypass passage 73 and is discharged to the atmosphere.

When the valve body 71a is at the neutral position parallel to the axis of the exhaust pipe 70, the exhaust gas is discharged from the exhaust pipe 70 because the exhaust switching valve 71 connects the exhaust pipe 70 directly to the bypass passage 73. Flows through the bypass passage 73 without passing through the particulate filter 22, and is released to the atmosphere (see FIG. 12).

As described above, by switching the valve body 71a,
By repeating the forward flow and the backward flow, fine particles such as soot move around in the base material of the particulate filter 22, so that oxidation of the fine particles such as soot can be promoted, and thus, fine particles can be efficiently purified.

A program (not shown) constituting an operation control execution routine of the exhaust gas switching valve 71 is provided by
Since the ROM is stored in the OM and the attribute of the ROM is in the ECU 30, the ECU 30 to which the program for controlling the operation of the exhaust switching valve 71 belongs is referred to as control means for controlling the switching of the exhaust switching valve 71.

The ECU 30, which is the control means for performing the switching control of the exhaust switching valve 71, the exhaust switching valve 71, and the exhaust gas including at least the first exhaust passage 76 and the second exhaust passage 77 which are a pair of communication passages are exhausted. It is referred to as flow switching means.

<Structure of Particulate Filter and Continuous Oxidation Process of Fine Particles> FIG. 5A is an image diagram in the case where exhaust gas is flown into the particulate filter 22 from only one direction. It accumulates only on the surface and does not move, causing not only a rise in exhaust gas pressure loss, but also a hindrance to the purification of particulates such as soot.

FIG. 5B is an image diagram in the case where exhaust gas flows from both directions to the particulate filter 22. Since fine particles are disturbed on both sides of the particulate filter in the forward flow direction and the backward flow direction, the particulate filter is not used. 22 can move around on both sides or inside the base material to promote oxidation of fine particles such as soot using active points of the entire filter base material.
2 can reduce the accumulation of fine particles. Therefore, an increase in the pressure loss of the exhaust gas can be avoided.

FIG. 6 shows the structure of the particulate filter 22. 6A shows a front view of the particulate filter 22, and FIG. 6B shows a side sectional view of the particulate filter 22. As shown in FIGS. 6A and 6B, the particulate filter 22 has a honeycomb structure, and includes a plurality of exhaust gas passages 50 and an exhaust gas outflow passage 51 extending in parallel with each other. It is a so-called wall flow type provided with:

The exhaust gas passage has an exhaust gas inflow passage 50 whose downstream end is closed by a plug 52 and an exhaust gas outflow passage 51 whose upstream end is closed by a plug 53. In FIG. 6A, the hatched portion is the plug 5
3 is shown.

Therefore, the exhaust gas inflow passages 50 and the exhaust gas outflow passages 51 are alternately arranged via the thin partition walls 54. In other words, the exhaust gas inflow passage 50 and the exhaust gas outflow passage 51 are each surrounded by four exhaust gas outflow passages 51, and each exhaust gas outflow passage 51 is surrounded by five exhaust gas inflow passages 50. So that

The particulate filter 22 is formed from a porous material such as cordierite. Therefore, the exhaust gas that has flowed into the exhaust gas inflow passage 50 flows through the surrounding partition wall 54 into the adjacent exhaust gas outflow passage 51 as indicated by an arrow in FIG. 6B.

In this embodiment, the peripheral wall surface of each exhaust gas inflow passage 50 and each exhaust gas outflow passage 51, that is, each partition 54
A support layer made of, for example, alumina is formed on both side surfaces of the substrate and on the inner wall surfaces of the pores in the partition walls 54. When a noble metal catalyst is present on the support and excess oxygen is And an active oxygen releasing agent that releases the stored oxygen in the form of active oxygen when the ambient oxygen concentration is reduced.

In this case, in this embodiment, platinum Pt is used as a noble metal catalyst, and potassium K, sodium Na, lithium Li, cesium Cs,
An alkali metal such as rubidium Rb, barium Ba,
At least one selected from the group consisting of alkaline earth metals such as calcium Ca and strontium Sr, rare earths such as lanthanum La and yttrium Y, and transition metals is used.

In this case, as the active oxygen releasing agent, an alkali metal or an alkaline earth metal having a higher ionization tendency than calcium Ca, ie, potassium K, lithium Li,
It is preferable to use cesium Cs, rubidium Rb, barium Ba, and strontium Sr.

Next, the action of the particulate filter 22 for removing fine particles in the exhaust gas will be described.
The case where potassium and potassium K are carried will be described as an example. However, the use of other noble metals, alkali metals, alkaline earth metals, rare earths, and transition metals has the same effect of removing fine particles.

In a compression ignition type internal combustion engine as shown in FIG. 1, combustion is performed under excess air, and thus the exhaust gas contains excess air. That is, when the ratio of air and fuel supplied to the intake passage, the combustion chamber 5 and the exhaust passage is referred to as the air-fuel ratio of the exhaust gas, the air-fuel ratio of the exhaust gas in the compression ignition type internal combustion engine as shown in FIG. It has become.

Since NO is generated in the combustion chamber 5, the exhaust gas contains NO. In addition, sulfur S in the fuel
This sulfur S reacts with oxygen in the combustion chamber 5 to become SO ₂ . Therefore, the exhaust gas contains SO ₂ . Therefore, exhaust gas containing excess oxygen, NO and SO ₂ flows into the exhaust gas inflow passage 50 of the particulate filter 22.

FIGS. 7A and 7B schematically show enlarged views of the inner peripheral surface of the exhaust gas inflow passage 50 and the surface of the carrier layer formed on the inner wall surface of the pores in the partition wall 54. FIG. 7A and 7B, reference numeral 60 denotes platinum Pt particles, and reference numeral 61 denotes an active oxygen releasing agent containing potassium K.

As described above, since the exhaust gas contains a large amount of excess oxygen, when the exhaust gas flows into the exhaust gas inflow passage 50 of the particulate filter 22, FIG.
As shown in (A), these oxygens O ₂ are converted to O ₂ ^- or O ^2-
On the surface of platinum Pt.

[0090] On the other hand, NO in the exhaust gas on the surface of the platinum Pt O ₂ ^- reacting or O ^2- and becomes NO ₂ (2NO + O
₂ → 2NO ₂ ). Next, a part of the generated NO ₂ is absorbed in the active oxygen releasing agent 61 while oxidizing on the platinum Pt,
While bonding with the potassium K FIG 7 (A) to nitrate ion NO ₃ as shown ^- diffused into the form the active oxygen release agent 61,
Some of the nitrate ions NO ₃ ^- produces potassium nitrate KNO _3.

As described above, the exhaust gas contains SO
₂ also contains, the SO ₂ is absorbed in the active oxygen release agent 61 by a NO similar mechanisms. That is, the oxygen O ₂ as described above O ₂ ^- are attached to or O ^2- form on the surface of the platinum Pt in, SO ₂ in the exhaust gas on the surface of the platinum Pt O ₂ ^- or O ^2- and Reacts to SO ₃ .

Next, a part of the produced SO ₃ is made of platinum Pt.
Absorbed in the active oxygen releasing agent 61 while further oxidizing above,
While being bound to potassium K, it diffuses into the active oxygen releasing agent 61 in the form of sulfate ions SO ₄ ^2- to generate potassium sulfate K ₂ SO ₄ . Thus, potassium nitrate KNO ₃ and potassium sulfate K ₂ SO ₄ are generated in the active oxygen release catalyst 61.

Further, fine particles mainly composed of carbon C are generated in the combustion chamber 5, and therefore, these fine particles are contained in the exhaust gas. These fine particles contained in the exhaust gas are exhausted from the particulate filter 2.
2B, when flowing in the exhaust gas inflow passage 50 or when going from the exhaust gas inflow passage 50 to the exhaust gas outflow passage 51, as shown by reference numeral 62 in FIG. It comes into contact with and adheres to the surface of the active oxygen releasing agent 61.

As described above, the fine particles 62 are
1 and the fine particles 62 and the active oxygen releasing agent 6
At the contact surface with No. 1, the oxygen concentration decreases. Then, a concentration difference occurs between the inside of the active oxygen releasing agent 61 having a high oxygen concentration and the oxygen in the active oxygen releasing agent 61 tends to move toward the contact surface between the fine particles 62 and the active oxygen releasing agent 61. I do.
As a result, potassium nitrate KNO ₃ formed in the active oxygen releasing agent 61 is decomposed into potassium K, oxygen O and NO, and the oxygen O moves toward the contact surface between the fine particles 62 and the active oxygen releasing agent 61, and NO becomes active oxygen It is released from the release agent 61 to the outside.

The NO released to the outside is the platinum Pt on the downstream side.
It is oxidized at the top and is again absorbed in the active oxygen releasing agent 61. At this time, potassium sulfate K ₂ SO ₄ formed in the active oxygen releasing agent 61 is also decomposed into potassium K, oxygen O and SO _2, and the oxygen O moves toward the contact surface between the fine particles 62 and the active oxygen releasing agent 61, and SO 2 ₂ is released from the active oxygen releasing agent 61 to the outside.

The SO ₂ released to the outside is platinum P on the downstream side.
It is oxidized on t and is again absorbed in the active oxygen releasing agent 61. However, since potassium sulfate K ₂ SO ₄ is stabilized, active oxygen is hardly released as compared with potassium nitrate KNO ₃ .

On the other hand, the oxygen O heading to the contact surface between the fine particles 62 and the active oxygen releasing agent 61 is oxygen decomposed from a compound such as potassium nitrate KNO ₃ or potassium sulfate K ₂ SO ₄ .

The oxygen O decomposed from the compound has a high energy and an extremely high activity. Therefore, the oxygen that goes to the contact surface between the fine particles 62 and the active oxygen releasing agent 61 is active oxygen O. When the active oxygen O comes into contact with the fine particles 62, the fine particles 62 oxidize within a short period of time without emitting a bright flame, and the fine particles 62 almost disappear. Therefore, the fine particles 62 do not accumulate on the particulate filter 22.

The particulate filter 2 as in the prior art
When the fine particles deposited in a stack on the second burn, the particulate filter 22 glows red and burns with a flame. Such combustion with a flame cannot be sustained unless it is at a high temperature. Therefore, in order to maintain the combustion with such a flame, the temperature of the particulate filter 22 must be maintained at a high temperature.

On the other hand, in the present embodiment, the fine particles 62 are oxidized without emitting a bright flame as described above, and the surface of the particulate filter 22 does not glow at this time. That is, in the present invention, the fine particles 62 are oxidized and removed even at a considerably lower temperature than in the prior art.

Therefore, the function of removing fine particles 62 by oxidation of the fine particles 62 that do not emit bright flame according to the present embodiment is completely different from the function of removing fine particles by conventional combustion accompanied by a flame. Further, the action of removing fine particles by oxidation of the fine particles is performed at a considerably low temperature. Therefore, the temperature of the particulate filter 22 does not rise so much, and there is almost no risk of the particulate filter 22 being deteriorated. In addition, since particles hardly accumulate on the particulate filter 22, there is little danger that ash, which is a burning residue of the particles, is agglomerated, and therefore, there is less danger that the particulate filter 22 is clogged.

The clogging is mainly caused by calcium sulfate CaSO ₄ . That is, the fuel and the lubricating oil contain calcium Ca, and therefore contain calcium Ca in the exhaust gas. This calcium Ca produces calcium sulfate CaSO ₄ when SO ₃ is present. This calcium sulfate CaSO ₄ is solid and does not thermally decompose even at high temperatures. Therefore, when calcium sulfate CaSO ₄ is generated and the pores of the particulate filter 22 are closed by the calcium sulfate CaSO ₄ , clogging occurs.

However, in this case, the active oxygen releasing agent 6
When an alkali metal or an alkaline earth metal having a higher ionization tendency than calcium Ca, such as potassium K, is used, SO ₃ diffused into the active oxygen releasing agent 61 combines with potassium K to form potassium sulfate K ₂ SO ₄ . Calcium Ca passes through the partition wall 54 of the particulate filter 22 without binding to SO _3, and
Outflow into 1.

Therefore, the particulate filter 22
No pores are clogged. Therefore, as described above, as the active oxygen releasing agent 61, an alkali metal or alkaline earth metal having a higher ionization tendency than calcium Ca, that is, potassium K, lithium Li, cesium Cs, rubidium Rb, barium Ba, and strontium Sr is used. It will be preferable.

Incidentally, platinum Pt and active oxygen releasing agent 6
1 is activated as the temperature of the particulate filter 22 increases, so that the amount of active oxygen O that the active oxygen releasing agent 61 can release per unit time increases as the temperature of the particulate filter 22 increases. Therefore, the amount of fine particles that can be oxidized and removed by the particulate filter 22 without emitting a luminous flame per unit time on the particulate filter 22 (the amount of fine particles that can be oxidized and removed by the particulate filter 22 per unit time:
Hereinafter, simply “the amount of fine particles that can be removed by oxidation”) increases as the temperature of the particulate filter 22 increases.

In FIG. 8, the vertical axis represents the amount G of particles that can be oxidized and removed per unit time, and the horizontal axis represents the particulate filter 22.
FIG. 5 is a graph of the amount G of particulates that can be removed by oxidation and the temperature TF of the particulate filter obtained at the temperature TF of FIG.

Assuming that the amount of the particulates discharged from the combustion chamber 5 per unit time is the amount M of the particulates discharged from the engine, an area where the particulates M discharged from the engine is smaller than the particulates G that can be removed by oxidation is indicated by the symbol I, An operation region in which the fine particles M are larger than the fine particles G that can be removed by oxidation is indicated by reference numeral II.

In the region I of FIG. 8, as soon as all the fine particles discharged from the combustion chamber 5 come into contact with the particulate filter 22, the collected fine particles generate a bright flame on the particulate filter 22 in a short time. Means the operating region in which oxidization and removal are carried out without the need.

On the other hand, the region II in FIG. 8 is caused by a shortage of active oxygen when the engine discharge in the operation region in which the engine exhaust particulates M are larger than the oxidation-removable particulates G, that is, when the engine is continued in the region II. Operating area in which fine particles accumulate on the stack.

FIGS. 9A to 9C show how the fine particles are oxidized in the region II of FIG. That is, in the case where the amount of active oxygen is insufficient to oxidize all the fine particles, when the fine particles 62 adhere to the active oxygen releasing agent 61 as shown in FIG. As a result, the fine particles that have not been sufficiently oxidized remain on the carrier layer. Next, when the state of the shortage of the active oxygen is continued, the fine particles which were not oxidized one after another remain on the carrier layer. As a result, as shown in FIG. Covered by part 63.

The remaining fine particle portion 6 covering the surface of the carrier layer
3 gradually changes to a carbon material that is hardly oxidized, and thus the residual fine particle portion 63 tends to remain as it is. When the surface of the carrier layer is covered with the residual fine particle portion 63, the oxidizing action of NO and SO ₂ by platinum Pt and the releasing action of active oxygen by the active oxygen releasing agent 61 are suppressed. As a result, as shown in FIG. 9C, another fine particle 64 is deposited on the remaining fine particle portion 63 one after another. That is, the fine particles are deposited in a layered manner.

When the fine particles are deposited in a layered manner as described above, since these fine particles are separated from the platinum Pt and the active oxygen releasing agent 61, even if they are easily oxidized, they can no longer be oxidized by the active oxygen O. Therefore, further fine particles are deposited on the fine particles 64 one after another. That is, if the state in which the engine discharge fine particles M are larger than the oxidizable / removable fine particle amount G continues, the fine particles accumulate on the particulate filter 22 in a stacked state.

Thus, unless the temperature of the exhaust gas is raised or the temperature of the particulate filter 22 is raised, the deposited particulates cannot be ignited and burned.

In summary, in the region I of FIG. 8, the fine particles are oxidized within a short time without emitting a bright flame on the particulate filter 22, but in the region II of FIG. It can be said that they accumulate in a shape. Particulate filter 2
In order to prevent the particulate matter M from being accumulated in a layered manner on the substrate 2, it is desirable that the particulate matter M discharged from the engine is always smaller than the amount G of the particulates that can be removed by oxidation.

The particulate filter 22 used in the present embodiment can oxidize the fine particles even if the temperature TF is considerably low. Therefore, the engine discharge fine particles M and the temperature TF of the particulate filter 22 can be maintained such that the engine discharge fine particles M become smaller than the amount G of particles that can be removed by oxidation. If the operating state is maintained such that the engine discharge fine particles M become smaller than the oxidizable and removable fine particle amount G, almost no fine particles are deposited on the particulate filter 22.

As a result, the particulate filter 22
The pressure loss of the exhaust gas flow at is almost unchanged. In this way, a reduction in engine power can be kept to a minimum. In the present embodiment, the engine operation state is basically maintained such that the amount of particulates M discharged from the engine is smaller than the amount G of particulates that can be removed by oxidation in all operation states.

However, in practice, it is impossible to reduce the amount of particulates M discharged from the engine to be smaller than the amount G of particulates that can be removed by oxidation in all operating states. Therefore, if the engine exhaust particulates M become larger than the oxidizable / removable particulate matter G for some reason, such as a sudden change in the engine operating state, the non-oxidized particulates on the particulate filter 22 begin to remain, and as a result, Particulate filter 2
The fine particles are deposited in a layered manner on 2.

In this case, the particulate filter 22
If the particulates continue to accumulate on the particulate filter 22, it becomes difficult to oxidize and remove the particulates discharged by the engine on the particulate filter 22 thereafter. Therefore, in order to continuously oxidize and remove the particulates discharged from the engine on the particulate filter 22, when the amount of particulates deposited on the particulate filter 22 exceeds a threshold which is a predetermined limit deposited particulate quantity, the particulate matter is accumulated. A state must be created in which the fine particles are quickly oxidized and removed.

However, actually, the particulate matter M
It is difficult to determine whether or not the amount is larger than the amount G of particles that can be removed by oxidation. Therefore, in this embodiment, the exhaust pipe 7
0, a smoke sensor 102 as a particulate concentration sensor is installed on the downstream side of the exhaust gas purification device A including the particulate filter 22, and the concentration of the particulates contained in the exhaust gas is detected at the place where the smoke sensor 102 is installed. When the value exceeds the threshold value, which is a specific set value, instantaneously or when compared with an average value during a certain period (a predetermined interval) such as an engine operation time or a vehicle mileage, the fine particles on the particulate filter 22 are removed. Oxidation removal is promoted to create a state in which fine particles deposited on the particulate filter 22 are promptly oxidized and removed (see FIGS. 10 and 11). 10 and FIG.
The vertical axis represents the desorption smoke concentration and the average desorption smoke concentration, and the horizontal axis represents the time, and the desorption smoke concentration-time diagram and the desorption smoke concentration-time diagram are plotted. FIG. 10 shows that the oxidation removal accelerating means is activated when the desorbed smoke concentration instantaneously exceeds the threshold value. FIG. 11 shows that the oxidation removal accelerating means is activated when the average concentration of smoke desorbed from the threshold exceeds the threshold. When the oxidation removal promoting means is activated, the temperature of the particulate filter 22 increases.

More specifically, if the amount G of particles that can be oxidized and removed is, for example, within the region II in FIG. 8 depending on the operating state of the engine, the particles are deposited on the particulate filter 22 in a layered manner and the threshold value is reduced. As a result, the particulate matter M discharged from the engine is reduced, and the amount of particulates G that can be removed by oxidation is reduced.
Is controlled so as to be within the region I in which is increased.

In order to remove the accumulated fine particles by oxidation, the switching valve 71 disposed in the exhaust pipe 70 is switched. Switching valve 7
When 1 is switched, the exhaust upstream side and the exhaust downstream side of the particulate filter 22 are reversed, and the flow of the exhaust gas flowing in the filter is reversed. At the portion of the particulate filter 22 downstream of the exhaust before the switching, the fine particles adhere to the surface of the active oxygen releasing agent 61 and release the active oxygen O, and the fine particles are oxidized and removed.

A part of the released active oxygen O moves with the exhaust gas to the exhaust gas downstream of the particulate filter 22, and oxidizes and removes fine particles deposited there. Here, as described above, the fine particles are disturbed in the forward flow direction and the reverse flow direction on both surfaces of the particulate filter 22, move around on both surfaces of the particulate filter 22, or inside the base material, and meet the active points of the entire filter base material. Oxidizes and raises filter temperature.

When the unoxidized fine particles start to accumulate on the particulate filter 22, the fine particles can be oxidized and removed from the particulate filter 22 by reversing the upstream and downstream sides of the exhaust of the particulate filter 22.

When particulates accumulate on the particulate filter 22, the air-fuel ratio of a part or the whole of the exhaust gas is temporarily made rich to oxidize the deposited particulates without producing a bright flame. When the air-fuel ratio of the exhaust gas becomes rich, that is, when the oxygen concentration in the exhaust gas decreases, active oxygen O is released from the active oxygen releasing agent 61 to the outside at a stretch, and the fine particles deposited by the active oxygen O released at a dash emit bright. It is oxidized and removed in a short time without generating a flame.

Since the flow of the exhaust gas flowing through the particulate filter is reversed to promote the oxidization and removal, the exhaust gas switching device provided in the exhaust pipe 70 at a location upstream of the location where the particulate filter 22 is installed is provided. A first exhaust passage 7, which is a valve 71 and a pair of communication passages connecting the exhaust switching valve 71 and the particulate filter 22 to one side and the exhaust switching valve 71 and the other side, respectively.
The exhaust gas purifying apparatus A including the sixth and second exhaust passages 77 and control means 75 for performing switching control of the exhaust switching valve is provided by:
It can be said that it has an exhaust flow switching means and also has an oxidation removal promoting means.

When judging from the viewpoint that the oxidation removal promoting means raises the filter temperature as described above, another example of the oxidation removal promoting means is stored in the ROM of the ECU and executed in the execution routine for promoting the oxidation removal. An example of an application program can be given.

More specifically, an application program for executing a temperature rise control for raising the temperature of the exhaust gas so as to periodically burn the fine particles collected by the particulate filter by utilizing heat, and an electric heating means such as an electric heater. Can be exemplified. As means for executing the temperature rise control, for example, a fuel injection valve or an intake throttle valve installed in an intake passage can be mentioned. By controlling the amount of fuel injected from the fuel injection valve and the control of the intake throttle valve, the amount of intake air flowing through the intake passage changes to determine the amount of fuel to be burned in the cylinder, and, consequently, the temperature of exhaust gas. Since the attributes of the ROM for storing these programs are in the ECU, the ECU can also be referred to as an oxidation removal accelerating means.

Hereinafter, an application example of the method for promoting the oxidation removal of fine particles using the output value of the smoke sensor will be described. (1) The amount of fine particles deposited on the particulate filter 22 is estimated from the desorbed smoke concentration measured by the smoke sensor, the temperature of the particulate filter 22, and the flow rate of exhaust gas, and the above-described estimation is performed based on the estimation result. The regeneration control timing and period of the particulate filter 22 are determined by the temperature raising control means and the exhaust flow switching means.
From the temperature of the particulate filter 22 and the flow rate of the exhaust gas, it is possible to roughly determine the amount that can process the fine particles. In addition, if the concentration of the desorbed smoke is known, the difference between the two can be seen, and the fine particles remaining in the particulate filter 22 can be determined. The amount can be estimated. If the remaining amount is known, it is possible to effectively determine the regeneration control timing and the processing period for the temperature rise control. (2) PM regeneration when the desorption smoke concentration actually measured by the smoke sensor 102 exceeds an allowable desorption smoke concentration (threshold value) corresponding to a change in engine conditions such as a change in exhaust gas flow rate or a change in accelerator opening. Perform processing.

By changing the threshold value (comparison value) of the allowable desorption smoke concentration in accordance with the operating conditions at each time, it is possible to obtain a more optimal timing of the PM regeneration processing. (3) The regeneration process is performed when the instantaneous value or the average value of the desorption smoke concentration under certain predetermined operating conditions such as idle exceeds a certain threshold value. In this case, only one threshold value (comparison value) to be compared with the value detected by the smoke sensor needs to be set in advance. (4) The pressure on the inlet side of the particulate filter 22 is measured by the pressure sensor 100, and when the desorption smoke concentration due to the instantaneous high-pressure wave exceeds the threshold value of the desorption amount corresponding to the pressure, the regeneration process I do. Fine particles such as soot have the property of desorbing at a certain pressure, and are used. (5) When the average amount of desorption smoke during a certain period exceeds a threshold value of the average desorption amount corresponding to the average pressure on the inlet side of the particulate filter 22, the regeneration process is performed. in this case,
For example, the average desorption smoke amount when acceleration or deceleration is performed several times during a certain period is a target. (6) In the exhaust gas purifying apparatus for an internal combustion engine having the exhaust gas flow switching means, the valve body 71a of the exhaust gas switching valve 71 is switched at a constant time interval under a predetermined operating condition such as idling to flow the exhaust gas. When the instantaneous value or the average value of the amount of the desorbed fine particles when the flow rate is alternately changed to the forward flow and the reverse flow exceeds a certain threshold value, the regeneration process is performed. (7) In the case where the desorbed particles in the exhaust gas purifying apparatus A for the internal combustion engine having the exhaust flow switching means are desorbed due to any of the above-described operating states or a combination thereof. The valve body 71a of the exhaust switching valve 71
Is set to a neutral state (see FIG. 12), and the exhaust gas is bypassed through the bypass passage 73 to prevent further accumulation of fine particles. At the same time, a measure for the abnormality of the particulate filter 22 is performed.

Here, an example of the abnormality of the particulate filter 22 will be described. The maximum amount that the particulate filter 22 can oxidize the fine particles is determined, but if the fine particles are deposited beyond this maximum amount, the fine particles will self-ignite if no action is taken, There is a possibility that the particulate filter 22 may be melted. Therefore, when there is a possibility that such an abnormal situation may occur, the situation is bypassed in advance to prevent the occurrence of the abnormal situation. (8) In the exhaust gas purifying apparatus for an internal combustion engine having the exhaust flow switching means, for example, when the amount of desorption smoke exceeds a certain threshold during the execution of a steady operation such as an idling operation, the accumulation is performed by executing the engine operation such as rapid acceleration. In an engine operating state in which a large amount of smoke is released at once, the bypass passage 73 is set to the neutral position to suppress the released smoke.

The particulates such as soot are trapped in the particulate filter 22 by the paste-like SOF component in many cases. However, if the exhaust gas temperature rises rapidly due to the operating state of the engine, the SOF component will not burn due to the temperature. It is conceivable that the fine particles cannot be captured by the particulate filter 22, and as a result, the fine particles are separated. In addition, depending on the engine operating conditions, the flow rate of the exhaust gas may be high, which may promote the desorption of the fine particles. (9) In the exhaust gas purifying apparatus A for the internal combustion engine having the exhaust flow switching means, when the desorption smoke causes particulates to be desorbed due to any of the above-described operating states or a combination thereof, the exhaust gas is exhausted. The switching valve 71a is set to an appropriate tilt position (a halfway open state in which the switch valve 71a is not tilted but tilted to some extent).
And the temperature rise control is performed such that only a part of the gas flows through the particulate filter 22. By doing so, the deposited PM is removed and the emission of the desorbed smoke is suppressed.

When the amount of fine particles in the particulate filter 22 is large, oxidation is promoted because the oxidation treatment of the particulate filter 22 must be promoted. However, the amount of fine particles entering the particulate filter 22 later is reduced by the amount of the particulate filter. It may be more than 22 oxidation treatment capacities. Therefore, in such a case, the valve body 71a of the exhaust gas switching valve 71 is slightly inclined to allow a part of the exhaust gas to flow through the bypass passage 73. If fine particles accumulate on the particulate filter 22 more than this, if the regeneration of the particulate filter 22 would be hindered, the particulate filter 22 would flow down neutrally.
This is because if the oxidation has progressed to some extent, the exhaust gas switching valve 71a can be dealt with by slightly tilting it. (10) In the exhaust gas purifying apparatus A for the internal combustion engine having the exhaust flow switching means, the desorbed smoke causes particulates to be desorbed due to any of the above-described operating states or a combination thereof, and the temperature of the particulate filter becomes lower. If the temperature is sufficiently high (300 ° C. or higher), the particulates are bypassed while the valve body 71 a of the exhaust gas switching valve 71 is in the neutral position for a certain period, and the particulates deposited on the particulate filter 22 are oxidized during that time. After that, the valve body 71a is alternately switched. (11) In the exhaust gas purifying apparatus A for an internal combustion engine having the exhaust flow switching means, when the desorption smoke causes particulates to desorb due to any of the above-described operating states or a combination thereof, By frequently switching the valve body 71a, the oxidation of the fine particles deposited on the particulate filter 22 is promoted. Then, when the amount of desorption smoke falls below a certain threshold value, the valve body 71a is switched alternately. By switching the valve body 71a, vibration is appropriately generated in the particulate filter 22, and as a result, the fine particles search for active sites by themselves, which is preferable because oxidation is promoted.

If the movement of the valve body 71a is too slow, the amount of bypassed particles will increase more than necessary. Therefore, it is important to execute the valve body 71a at an opening / closing speed that can prevent such adverse effects. become.

In the internal combustion engine having such a configuration, the amount of accumulated fine particles is estimated by the smoke sensor 102, and the estimated value (detected value by the fine particle concentration sensor) is a concentration value that exceeds the threshold value. At one time, the oxidation removal promoting means is activated. Accordingly, the particulates can be oxidized before the particulates are deposited so much that the particulate filter cannot be regenerated, thereby avoiding a situation in which the particulate filter cannot be regenerated.

By operating the exhaust flow switching means, the fine particles attached to the particulate filter 22 can be burned as continuously as possible. That is, since the exhaust gas can be alternately flown from both sides of the particulate filter 22 by providing the exhaust switching valve 71, when the exhaust gas is flown into the particulate filter 22 from only one direction, only one partition surface and only the inside of the partition are oxidized. While the reaction is not used, the amount of fine particles that accumulate in a unit area increases, and the oxidizing performance decreases. On the other hand, in the exhaust gas purifying apparatus for an internal combustion engine of the present embodiment, a forward flow and a backward flow are used alternately. As a result, the exhaust gas flows from both sides of the particulate filter, so that the fine particles are agitated and move around on the partition wall surface and inside the partition wall of the particulate filter, and effectively use the catalytic active points on the partition wall surface of the particulate filter and the entire inside of the partition wall. be able to. Therefore, the oxidation of the fine particles can be promoted, the purification can be performed more continuously, and the exhaust gas purification performance can be enhanced.

In this embodiment, the exhaust gas purifying device A
Which employs the exhaust flow switching means and the bypass means, but does not have these means, that is, the particulate filter 22 is formed as a part of the exhaust pipe 70,
An exhaust gas purifying apparatus A having a configuration as shown in a modification of FIG. 13 in which exhaust gas is directly introduced into the particulate filter 22.
Of course.

[0137]

According to the exhaust gas purifying apparatus for an internal combustion engine of the present invention,
Estimate the amount of particulates deposited on the filter from the amount of desorbed smoke and raise the exhaust gas temperature to burn the particulates before the particulates accumulate on the filter, making it impossible to regenerate the filter. Situations can be avoided.

[Brief description of the drawings]

FIG. 1 is an overall view of an internal combustion engine to which an exhaust gas purification device for an internal combustion engine of the present invention is applied.

FIG. 2 is a diagram showing a required torque of an engine.

FIG. 3 is a plan view showing an exhaust gas purification device.

FIG. 4 is a side view showing an exhaust gas purification device.

5 (A) is an image diagram showing a state in which fine particles are deposited on a filter substrate, and FIG. 5 (B) is an image diagram showing a state in which fine particles are disturbed due to a forward flow and a backward flow of exhaust gas.

FIG. 6A is a front view of a particulate filter,
(B) is a side sectional view of the particulate filter.

FIG. 7 is a conceptual diagram showing the oxidizing action of fine particles.

FIG. 8 is a diagram showing the relationship between the amount of fine particles that can be removed by oxidation and the temperature of a particulate filter.

FIG. 9 is a conceptual diagram showing a deposition action of fine particles.

FIG. 10: Desorption smoke concentration-time diagram

FIG. 11: Desorption smoke concentration-time diagram

FIG. 12 is a diagram showing a state where the valve body is at a neutral position parallel to the axis of the exhaust pipe.

FIG. 13 is a diagram showing a modification of the exhaust emission control device.

[Description of Signs] A Exhaust gas purifier 1 Engine main body 2 Cylinder block 3 Cylinder head 4 Piston 5 Combustion chamber 6 Electric control type fuel injection valve 6a Fuel supply pipe 7 Intake valve 8 Intake port 9 Exhaust valve 10 Exhaust port 11 Intake branch pipe DESCRIPTION OF SYMBOLS 12 Surge tank 13 Intake duct 14 Exhaust turbocharger 15 Compressor 16 Step motor 17 Throttle valve 18 Cooling device 19 Exhaust manifold 20 Exhaust pipe 21 Exhaust turbine 22 Particulate filter (filter) 23 Casing 24 EGR passage 25 Electric control type EGR control valve 26 Cooling device 27 Common rail 28 Fuel pump 29 Fuel pressure sensor 30 ECU (oxidation removal promoting means) 31 Bidirectional bus 32 ROM 33 RAM 34 CPU 35 Input port 36 Output port 37 A / D converter 3 Reference Signs List 8 drive circuit 39 temperature sensor 40 accelerator pedal 41 load sensor 42 crank angle sensor 50 exhaust gas inflow passage 51 exhaust gas outflow passage 52 plug 53 plug 54 partition wall 60 particles of platinum Pt 61 active oxygen releasing agent 62 particles 63 fine particles 63 residual fine particles 64 70 Exhaust pipe (engine exhaust passage) 71 Exhaust switching valve 71a Valve element 72 Actuator 73 Bypass passage (Bypass means) 75 Control means 76 First exhaust passage 77 Second exhaust passage 100 Pressure sensor 102 Smoke sensor (Particle concentration Sensor) G Amount of particulates that can be removed by oxidation L Amount of depression of accelerator pedal N Engine speed M Amount of exhaust particulates O Active oxygen TF Temperature of particulate filter TQ Required torque

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinya Hirota 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Kazuhiro Ito 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation ( 72) Inventor Takamitsu Asanuma 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Koichi Kimura 1 Toyota Town Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 3G090 AA03 CA01 CB24 DA01 DA10 DA13 DA18 DA20 EA03 EA05 EA06 EA07 3G091 AA02 AA10 AA11 AA17 AA18 AB02 AB13 BA00 BA11 BA33 BA38 CA13 CB02 CB07 CB08 DA03 DB10 EA00 GB EA01 EA03 EA07 EA30 EA31 GB02 GA19 FB32 GB10X GB17X HA14 HA36 HA37 HA38 HB01 HB03 HB05 HB06 4D058 JA32 JB02 KC01 KC52 MA41 MA42 MA51 MA52 P A01

Claims (7)

[Claims] 1. A filter disposed in an engine exhaust passage for removing fine particles contained in exhaust gas, the fine particles in the exhaust gas are once collected, and the collected fine particles are oxidized and removed. In the exhaust gas purifying apparatus for an internal combustion engine for regeneration, the filter collects the exhaust gas when the amount of particulates discharged from the internal combustion engine per unit time is smaller than the amount of particulates that can be removed by oxidation per unit time by the filter. A filter for oxidizing and removing particles in a state in which a bright flame is not generated, a particle concentration sensor installed downstream of the filter in the engine exhaust passage and detecting the concentration of the particles contained in exhaust gas at the installation location. Means for promoting oxidation removal of particulates on the filter when the output value of the particulate concentration sensor exceeds a specific set value; , An exhaust purification device for an internal combustion engine. 2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein said oxidation removal promoting means raises the temperature of a filter. 3. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein said oxidation removal promoting means reverses the flow of exhaust gas flowing through the filter. 4. A filter disposed in an engine exhaust passage for removing fine particles contained in the exhaust gas once collects fine particles in the exhaust gas, and oxidizes and removes the collected fine particles to remove the fine particles from the filter. In the exhaust gas purifying apparatus for an internal combustion engine for regeneration, the filter collects the exhaust gas when the amount of particulates discharged from the internal combustion engine per unit time is smaller than the amount of particulates that can be removed by oxidation per unit time by the filter. A filter for oxidizing and removing particles in a state in which a bright flame is not generated, a particle concentration sensor installed downstream of the filter in the engine exhaust passage and detecting the concentration of the particles contained in exhaust gas at the installation location. A first flow of exhaust gas flowing from one side to the other side of the filter and an exhaust gas flowing from the other side to the one side; An internal combustion engine comprising: an exhaust flow switching unit that alternately switches a second flow; and an oxidation removal promotion unit that promotes oxidation removal of particulates on the filter when an output value of the particulate concentration sensor exceeds a specific set value. Engine exhaust purification device. 5. An output value of the particle concentration sensor is obtained as an instantaneous value or an average value at a predetermined interval of time or distance, and when these values exceed the specific set value, the oxidation removal promoting means is operated. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein: 6. A filter disposed in an engine exhaust passage for removing fine particles contained in the exhaust gas, once collecting the fine particles in the exhaust gas, oxidizing and removing the collected fine particles to remove the fine particles from the filter. In the exhaust gas purifying apparatus for an internal combustion engine to be regenerated, the filter is configured to collect the particulates discharged from the internal combustion engine per unit time when the amount of the particulates discharged from the engine per unit time is smaller than the amount of particulates that can be removed by oxidation per unit time. A filter configured to oxidize and remove the generated fine particles without causing a bright flame, wherein the fine particle concentration sensor is installed downstream of the filter in the engine exhaust passage and detects the concentration of fine particles contained in exhaust gas at the installation location. A first flow of exhaust gas from one side of the filter to the other side when an output value of the particulate concentration sensor exceeds a specific set value; Exhaust gas switching means for alternately switching the flow of the exhaust gas and the second flow of exhaust gas flowing from the other side toward the one side; and the filter when the output value of the particulate matter concentration sensor exceeds a specific set value. An exhaust purification device for an internal combustion engine, comprising: bypass means for flowing exhaust gas into the engine exhaust passage in a bypassed state. 7. An output value of the particle concentration sensor is obtained as an instantaneous value or an average value at predetermined intervals of time and distance, and when these values exceed the specific set value, the oxidation removal promoting means is operated. The exhaust gas purifying apparatus for an internal combustion engine according to claim 6, wherein: