JP2002168112A - Exhaust emission control device, and controlling method for exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To securely prevent a filter, which collects suspended particles in an internal combustion engine, from being clogged. SOLUTION: Suspended particles in exhaust gas inside an internal combustion engine are collected by the filter. A hydrocarbon compound and carbon-contained suspended particles, contained in the exhaust gas, are dispersively collected on a filter member. It is judged whether or not the level of suspended particles collected by the filter exceeds the prescribed allowance. If it exceeds the allowance, either oxygen or hydrocarbon compound in the exhaust gas is increased. This accelerates the combustion of hydrocarbon compound and carbon-contained suspended particles on the filer, thereby preventing the filter from being clogged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a technique for purifying carbon-containing suspended particulates contained in exhaust gas of an internal combustion engine.

[0002]

2. Description of the Related Art The exhaust gas of an internal combustion engine, especially a diesel engine, contains carbon-containing suspended particulates such as black smoke (soot), and reduces the total amount of particulates discharged in order to prevent air pollution. It is strongly requested to do so. Also,
A similar requirement exists from a so-called in-cylinder injection gasoline engine that directly injects gasoline into the combustion chamber, because carbon-containing suspended particulates may be emitted together with exhaust gas depending on operating conditions.

As a technique capable of greatly reducing the suspended carbon-containing particles discharged from the internal combustion engine, a heat-resistant filter is provided in the exhaust passage of the engine, and the suspended carbon-containing particles discharged together with the exhaust gas are filtered. The technique of collecting with is proposed.

[0004] If the carbon-containing suspended particulates in the exhaust gas are collected by using such a method, the particulates discharged to the atmosphere such as soot can be significantly reduced. It must be processed in.
As a typical method of treating the collected carbon-containing suspended particulates, using an auxiliary means such as an electric heater or a burner,
A technique for periodically burning the collected carbon-containing suspended particulates (Japanese Patent Application Laid-Open No. H5-296027) and a technique for burning the particulates by intentionally increasing the exhaust gas temperature of the engine (Japanese Patent Application Laid-Open No. 2000-161444) ) Etc. have been proposed. If these techniques are used, the collected carbon-containing suspended particles can be treated relatively easily.

[0005]

However, if the trapped carbon-containing suspended particulates do not burn sufficiently for some reason, the filter tends to be clogged due to the accumulation of the unburned particulates. Alternatively, even if the emission of carbon-containing suspended particulates suddenly increases for some reason, such as an engine malfunction,
The filter is easily clogged. When the filter is clogged, there is a problem that not only the engine performance is reduced but also an excessive force due to the exhaust pressure of the engine may be applied to the filter.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art, and provides a technique capable of reliably avoiding clogging of a filter even under conditions where the filter is likely to be clogged for some reason. With the goal.

[0007]

Means for Solving the Problems and Their Functions and Effects In order to solve at least a part of the above problems, the first exhaust gas purifying apparatus of the present invention has the following structure. That is, in an exhaust gas purifying apparatus for purifying carbon-containing suspended particulates contained in exhaust gas of an internal combustion engine, the hydrocarbon-based compound and the carbon-containing suspended particulates contained in the exhaust gas are combined with oxygen in the exhaust gas. By collecting and dispersing so as to be capable of contacting, the exhausted gas whose inflow temperature is lower than the flammable temperature of the carbon-containing suspended particulates is used to separate the collected hydrocarbon-based compound and the carbon-containing suspended particulates. A trapping filter to be burned, trapping amount determining means for determining whether or not the trapping amount of the carbon-containing suspended particulates in the trapping filter exceeds a predetermined allowable value; and An oxygen supply amount increasing means for increasing the supply amount of oxygen to the collection filter when the collection amount exceeds the predetermined allowable value.

[0008] A first exhaust gas purifying method of the present invention corresponding to the above first exhaust gas purifying apparatus is a method for purifying carbon-containing suspended particulates contained in exhaust gas of an internal combustion engine. A collection filter provided in an exhaust passage of the internal combustion engine to trap the hydrocarbon-based compound and the carbon-containing suspended fine particles contained in the exhaust gas in a state where the hydrocarbon-based compound and the carbon-containing suspended fine particles are dispersed so as to come into contact with oxygen in the exhaust gas. Collecting, using an exhaust gas whose temperature flowing into the collection filter is lower than the flammable temperature of the carbon-containing suspended particulates, and burning the collected hydrocarbon-based compound and carbon-containing suspended particulates, Determine whether the trapping amount of the carbon-containing suspended particulates in the trapping filter exceeds a predetermined allowable value,
When the trapping amount exceeds the predetermined allowable value, the supply amount of oxygen to the trapping filter is increased.

In the first exhaust gas purifying apparatus and the first exhaust gas purifying method, when the trapped amount of the carbon-containing suspended particulates on the trapping filter exceeds a predetermined allowable value, The supply amount of oxygen to the collection filter is increased. In this case, the combustion of the hydrocarbon-based compound on the collection filter is promoted, and the combustion of the carbon-containing suspended fine particles is further promoted, so that the trapped amount of the carbon-containing suspended particulates is reduced. As a result, clogging of the collection filter can be easily avoided.

[0010] In the internal combustion engine to which the first exhaust gas purifying apparatus is applied, a recirculation passage for extracting a part of the exhaust gas from the exhaust passage and recirculating the exhaust gas to the intake passage, and a recirculation passage for exhaust gas provided on the recirculation passage. When an exhaust gas recirculation valve for controlling recirculation is provided, the exhaust gas recirculation valve may be controlled to reduce the amount of recirculated exhaust gas.

When the amount of recirculation of exhaust gas decreases, the amount of intake air flowing into the combustion chamber of the internal combustion engine increases accordingly,
The amount of oxygen in the exhaust gas increases. Therefore, this method is preferable because the supply amount of oxygen to the collection filter can be easily increased.

When the internal combustion engine to which the first exhaust gas purifying apparatus is applied is provided with a supercharger for increasing the amount of air taken in by the internal combustion engine using the flow energy of the exhaust gas, The intake air amount of the internal combustion engine may be increased by controlling the operation state of the supercharger.

By controlling the operating state of the supercharger, the amount of intake air of the internal combustion engine can be easily increased, and the amount of oxygen supplied to the collection filter can be easily increased. Is preferred.

[0014] In the first exhaust gas purifying device, the amount of intake air of the internal combustion engine may be increased by increasing the flow energy of the exhaust gas. In particular, the flow energy may be increased by increasing the temperature of the exhaust gas.

Since the supercharger increases the amount of intake air of the internal combustion engine using the flow energy of the exhaust gas, the amount of intake air can be increased by increasing the flow energy of the exhaust gas. . In particular, the temperature of the exhaust gas
For example, the fuel injection timing can be easily increased by adjusting the fuel injection timing, so that the amount of oxygen supplied to the collection filter can be easily increased, which is preferable.

In order to solve at least a part of the problems in the prior art, the second exhaust gas purifying apparatus of the present invention employs the following configuration. That is, in an exhaust gas purifying apparatus for purifying carbon-containing suspended particulates contained in exhaust gas of an internal combustion engine, the hydrocarbon-based compound and the carbon-containing suspended particulates contained in the exhaust gas are combined with oxygen in the exhaust gas. By collecting and dispersing so as to be capable of contacting, the exhausted gas whose inflow temperature is lower than the flammable temperature of the carbon-containing suspended particulates is used to separate the collected hydrocarbon-based compound and the carbon-containing suspended particulates. A trapping filter for burning, trapping amount determining means for determining whether or not the trapping amount of the carbon-containing suspended particulates in the trapping filter exceeds a predetermined allowable value; and collecting the carbon-containing suspended particulates. When the amount exceeds the predetermined allowable value, a hydrocarbon compound supply amount increasing means for increasing the supply amount of the hydrocarbon compound to the collection filter is provided.

A second exhaust gas purifying method according to the present invention corresponding to the above exhaust gas purifying apparatus is the exhaust gas purifying method for purifying carbon-containing suspended particulates contained in exhaust gas of an internal combustion engine. A collection filter is provided in an exhaust passage of the engine, and the hydrocarbon-based compound and the carbon-containing suspended fine particles contained in the exhaust gas are collected in a state where they are dispersed so as to be able to contact oxygen in the exhaust gas, Using an exhaust gas whose temperature flowing into the trapping filter is lower than the flammable temperature of the carbon-containing suspended particulates, the trapped hydrocarbon-based compound and the carbon-containing suspended particulates are burned, and the trapping filter is used. It is determined whether or not the trapping amount of the carbon-containing suspended fine particles in the trapping filter exceeds a predetermined allowable value, and when the trapping amount exceeds the predetermined threshold value, Charcoal Characterized in that to increase the supply amount of the hydrogen-based compounds.

In the second exhaust gas purifying apparatus and the second exhaust gas purifying method according to the present invention, when the trapped amount of the carbon-containing suspended particulates on the trapping filter exceeds a predetermined allowable value. Then, the supply amount of the hydrocarbon-based compound to the collection filter is increased. In this case, the combustion of the hydrocarbon-based compound on the collection filter is promoted, and the combustion of the carbon-containing suspended fine particles is further promoted, so that the trapped amount of the carbon-containing suspended particulates is reduced. As a result, clogging of the collection filter can be easily avoided.

A system in which the internal combustion engine to which the second exhaust gas purifying apparatus is applied injects a main fuel corresponding to a majority of a fuel amount determined according to a required value of an engine output and a residual auxiliary fuel into a combustion chamber. In the case of the above-described engine, the supply amount of the hydrocarbon-based compound may be increased by injecting the main fuel and the sub-fuel at intervals of a predetermined value or more.

This is preferable because the amount of the hydrocarbon compound discharged can be easily and quickly increased. Further, it is preferable to change the ratio between the auxiliary fuel and the main fuel because the supply amount of the hydrocarbon compound can be easily adjusted.

In the second exhaust gas purifying apparatus, the supply amount of the hydrocarbon-based compound may be increased by injecting the auxiliary fuel earlier than the main fuel by a predetermined period or more. Alternatively, the supply amount of the hydrocarbon-based compound may be increased by injecting the sub-fuel at a time later than the main fuel by a predetermined period or more. Further, the supply amount of the hydrocarbon-based compound may be increased by increasing the amount of the auxiliary fuel.

This is preferable because the supply amount of the hydrocarbon compound to the collection filter can be easily increased. Further, it is preferable to adjust the proportion of the auxiliary fuel because the supply amount of the hydrocarbon compound can be easily and accurately adjusted.

In the above-described first or second exhaust gas purifying apparatus of the present invention, the trapped amount of the carbon-containing suspended particulates is determined based on the pressure in the exhaust passage upstream of the trapping filter. It may be determined whether or not the allowable value is exceeded.

[0024] If the trapping amount in the trapping filter increases, the pressure in the exhaust pipe upstream of the filter increases with the trapping amount. Is preferable because it is possible to easily determine whether or not the number exceeds the limit.

In this exhaust gas purifying apparatus, the trapping amount exceeds the predetermined allowable value based on the pressure in the exhaust passage on the upstream side of the trapping filter and the pressure in the exhaust passage on the downstream side. It is also possible to determine whether or not it is.

If the trapping amount of the suspended particulates on the trapping filter exceeds a predetermined allowable value, the pressure difference between before and after the trapping filter increases, and therefore, based on the pressure on the downstream side in addition to the pressure on the upstream side. This is preferable because it is possible to reliably determine whether or not the amount collected by the filter exceeds a predetermined allowable value.

In the exhaust gas purifying apparatus, the trapping amount exceeds the predetermined allowable value based on the operating conditions of the internal combustion engine in addition to the pressure in the exhaust passage on the upstream side of the trapping filter. It may be determined whether or not there is.

When the operating conditions of the internal combustion engine are determined, if the amount of trapped carbon-containing suspended particulates on the trapping filter increases,
The pressure in the exhaust pipe upstream of the trapping filter increases. From this, if it is determined based on the operating conditions of the internal combustion engine in addition to the pressure in the exhaust pipe upstream of the collection filter, it is possible to reliably determine whether the collection amount exceeds a predetermined allowable amount. This is preferable because it can be detected. Of course, in order to make the determination based on the operating conditions of the internal combustion engine, the determination may be made based on the pressure upstream of the trapping filter under predetermined operating conditions.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to more clearly explain the operation and effect of the present invention, embodiments of the present invention will be described in the following order. A. Apparatus configuration: A-1. Configuration of Engine: A-2. Outline of particulate filter: A-3. Overview of engine control: B. Filter regeneration promotion processing: B-1. EGR control: B-2. Supercharging pressure control: B-3. Fuel injection control: B-4. Modification:

A. Apparatus Configuration: An embodiment in which the exhaust gas purifying apparatus of the present invention is applied to a diesel engine will be described below. Of course, not limited to diesel engines,
The present invention can be applied to other internal combustion engines such as a gasoline engine in which fuel is directly injected into a cylinder. Also,
INDUSTRIAL APPLICABILITY The present invention can be applied to all types of internal combustion engines such as those mounted on a vehicle or a ship, or those for stationary use.

A-1. Engine Configuration: FIG. 1 is an explanatory diagram showing a schematic configuration of a diesel engine 10 equipped with the exhaust gas purifying apparatus of the first embodiment. The diesel engine 10 is a so-called four-cylinder engine, and has four combustion chambers # 1 to # 4. Air is supplied to each combustion chamber via an intake pipe 12, and when fuel is injected from a fuel injection valve 14 provided in each combustion chamber, the air and fuel burn in the combustion chamber to form an exhaust pipe 16. The exhaust gas is exhausted from.

A supercharger 20 is provided in the exhaust pipe 16. The supercharger 20 includes a turbine 21 provided in the exhaust pipe 16, a compressor 22 provided in the intake pipe 12, and a shaft 23 connecting the turbine 21 and the compressor 22. When the exhaust gas discharged from the combustion chamber rotates the turbine 21 of the supercharger 20, the compressor 22 rotates via the shaft 23, compresses the air, and supplies the air to each combustion chamber. The supercharger 20 of the present embodiment
Is provided with an actuator 70, and the turbine 2
It is possible to change the opening area (hereinafter, referred to as turbine opening area) of a portion where the exhaust gas flows into the exhaust gas inlet 1. By appropriately controlling the turbine opening area according to the exhaust gas flow rate, the efficiency of the supercharger 20 can be improved. A bypass valve called a wastegate valve 72 is provided on the upstream side of the turbine 21.
The performance of the supercharger 20 can be controlled by adjusting the opening degree of the wastegate valve 72 using the wastegate actuator 74 and controlling the ratio of the exhaust gas that bypasses the turbine 21.

An air cleaner 26 is provided upstream of the compressor 22. The compressor 22 compresses air taken from the air cleaner 26 and supplies the compressed air to the combustion chamber. Since the temperature of the air rises when compressed by the compressor 22, an intercooler 24 for cooling the air is provided downstream of the compressor 22, and the compressed air is cooled by the intercooler 24 before being supplied to the combustion chamber. It is also possible.

In the exhaust pipe 16 on the upstream side of the turbine 21, a particulate filter 100 is provided for each of the combustion chambers # 1 to # 4. The particulate filter 100 traps the suspended particulates and the hydrocarbon compound contained in the exhaust gas and uses the reaction heat of the hydrocarbon compound to remove the collected suspended particulates at a relatively low temperature. Can be burned in gas. The particulate filter 100 will be described later.

The exhaust pipe 16 and the intake pipe 12 on the upstream side of each particulate filter 100 are connected by an EGR passage 60, and a part of the exhaust gas can be introduced into the intake pipe 12. By adjusting the opening of the EGR valve 62 provided in the EGR passage 60, the amount of exhaust gas introduced into the intake pipe 12 can be controlled.

Fuel supply pump 18 and fuel injection valve 14
Injects an appropriate amount of fuel into the combustion chamber at an appropriate timing under the control of the engine control ECU 30.

The engine control ECU 30 detects the operating conditions of the engine, such as the engine speed Ne and the accelerator opening θac, and according to the operating conditions, the fuel supply pump 1
8, the fuel injection valve 14, the EGR valve 62, the supercharger 20, and the like are appropriately controlled. Further, when the pressure in the exhaust pipe is detected and it is detected that the particulate filter 100 is slightly clogged, as described later, the EGR valve 62, the supercharger 20, the fuel supply pump 18, the fuel injection valve 14, By performing such control, filter regeneration promotion processing is performed. Therefore, in the diesel engine 10 of the present embodiment, there is no possibility that the filter is clogged even under the condition where the filter is easily clogged for some reason.

A-2. Outline of Particulate Filter: FIG. 2 is a perspective view showing an external shape of the particulate filter 100 attached to the exhaust pipe 16. In order to facilitate understanding, a partial cross section is taken and the internal structure is enlarged and displayed. Particulate filter 1
Reference numeral 00 denotes a cylindrical case 102 and an element 104 inserted into the case 102 and having an outer periphery welded to the case. The element 104 has a roll structure in which a nonwoven fabric 106 made of a heat-resistant metal and a corrugated sheet 108 made of the same heat-resistant metal are stacked and wound around a center rod 110 as a core. The element 104 used in the particulate filter 100 of this embodiment has an outer diameter of about 55
mm and a length of about 40 mm are used. Of course, these dimensions can be appropriately changed according to the displacement of the diesel engine, the inner diameter of the exhaust pipe 16, and the like.

Since the nonwoven fabric 106 is wound together with the corrugated sheet 108, the interval between the nonwoven fabrics 106 is
08, the predetermined interval is maintained.
A large number of passages are formed between the corrugated plate 108 and the corrugated plate 108 along the axial direction of the center rod 110. On both sides of the element 104, sealing plates 112 are welded. Sealing plate 112
Forms a structure in which the passage formed between the nonwoven fabric 106 and the corrugated sheet 108 is alternately closed, so that the exhaust gas passes through the nonwoven fabric 106. With reference to FIG. 3, a description will be given of how the structure in which the exhaust gas passes through the nonwoven fabric 106 is formed by the sealing plate 112.

FIG. 3 shows the structure of the particulate filter 100.
FIG. 3 is an explanatory view conceptually showing a cross-sectional structure of FIG. Note that, in order to prevent the figure from being complicated, the display of the corrugated sheet 108 is omitted in FIG. As shown in the figure, the sealing plate 112 closes the passages formed between the adjacent nonwoven fabrics 106 at predetermined intervals so as to be alternately arranged. For this reason, as shown by the arrow in the figure, when the exhaust gas flows from the left side of the figure, the exhaust gas once flows into the passage not closed by the sealing plate 112, but the outlet side of the passage is sealed. The plate 112 is closed. Therefore, the exhaust gas passes through the nonwoven fabric 106 forming the side surface of the passage and passes through the passage whose outlet side is not closed, as indicated by the thick arrow in the drawing. Thus, when the exhaust gas passes through the nonwoven fabric 106, the carbon-containing suspended particulates such as soot contained in the exhaust gas can be collected by the nonwoven fabric 106.

Here, as the nonwoven fabric 106, a nonwoven fabric made of an iron-based heat-resistant alloy having specifications within a predetermined range as shown in FIG. 4 is used. , Can be collected in a state of being dispersed so as to be able to contact oxygen in the exhaust gas. As described above, when the suspended fine particles are collected in a three-dimensionally dispersed state, they can be ignited and burned spontaneously when the collected fine particles reach a certain amount, as described later. The mechanism in which the carbon-containing suspended fine particles and the hydrocarbon-based compound are collected in a dispersed state, and the mechanism in which the carbon-containing suspended fine particles collected by being dispersed and collected naturally burn will be described later.

"Fiber diameter" shown in FIG. 4 indicates the average diameter of the metal fibers forming the nonwoven fabric. The metal nonwoven fabric is formed by innumerable metal fibers being intricately intertwined with each other, and three-dimensionally branched paths are formed between the metal fibers. The “pore diameter” is an index indicating the size of a passage cross section formed between metal fibers, and indicates the inner diameter (diameter) of a circular passage having an equivalent cross-sectional area. The value of the “pore diameter” can be most simply measured visually based on a photograph of the surface or cross section of the metal nonwoven fabric taken with a scanning electron microscope.

Incidentally, the element 104 of the present embodiment described above is used.
Has been described as being formed by welding the sealing plates 112 to both ends of the element 104, but a structure without the sealing plates 112 may be used as described below.

FIG. 5 is a cross-sectional view of a particulate filter 100 including an element having a structure without using a sealing plate. In FIG. 5, in order to avoid the figure from being complicated,
The illustration of the corrugated plate 108 is omitted. In FIG. 3 described above,
Although the sealing plates 112 were alternately welded to both ends of the nonwoven fabric 106, instead of welding the sealing plates, as shown in FIG.
The nonwovens may be welded together at the end 113. In this case, since the sealing plate 112 can be omitted, the particulate filter 100 can be manufactured more easily.

The specifications of the nonwoven fabric shown in FIG. 4 are merely examples, and the specifications of the nonwoven fabric are not limited to the values illustrated in the drawing. In this embodiment,
Although a metal non-woven fabric made of an iron-based heat-resistant alloy is used, other known heat-resistant metal non-woven fabrics may be used.

As described above, the nonwoven fabric 106 of the particulate filter 100 can collect carbon-containing suspended fine particles in the exhaust gas in a three-dimensionally dispersed state inside the nonwoven fabric 106. When the fine particles are collected, they can be ignited spontaneously to burn the fine particles. Therefore, the particulate filter 100 of the present embodiment can naturally regenerate the filter without performing a special operation such as intentionally increasing the exhaust gas temperature. In the present specification, such a function of the particulate filter 100 of the present embodiment is referred to as a “natural reproduction function”. Although the mechanism of the natural regeneration function has not been completely elucidated, the mechanism presumed at the present time will be described briefly.

It is known that the exhaust gas of a diesel engine contains carbon-containing suspended particulates and hydrocarbon compounds in the proportions as shown in FIG. That is,
Roughly speaking, suspended particulates such as soot, hydrocarbon-based compounds derived from fuel, and hydrocarbon-based compounds derived from lubricating oil are contained in substantially the same ratio. It is said that suspended particulates such as soot will not burn even in an exhaust gas atmosphere containing oxygen unless the temperature reaches 550 ° C. or higher. On the other hand, a hydrocarbon-based compound derived from a fuel or a lubricating oil can cause some oxidation reaction even at a temperature lower than 550 ° C. as long as oxygen is supplied.

The particulate filter 10 of the present embodiment
0, the metal nonwoven fabric 10 having a pore size distribution in a predetermined range.
6, and the carbon-containing suspended fine particles and the hydrocarbon compound in the exhaust gas are collected in a three-dimensionally dispersed state inside the nonwoven fabric. For this reason, a part of the collected hydrocarbon compounds is collected in a state where oxygen in the exhaust gas is sufficiently supplied, and a slow oxidation reaction (exothermic reaction) occurs depending on the temperature of the exhaust gas. To begin, gradually increase the filter temperature. As a result, when the carbon-containing suspended fine particles and the hydrocarbon-based compound are collected to some extent by the filter, the filter temperature becomes 550 ° C. or higher, and the fine particles on the filter and the hydrocarbon-based compound can be burned at once.

FIG. 7 is an explanatory diagram conceptually showing how the particulate filter 100 of this embodiment performs natural reproduction. FIG. 7A schematically illustrates a state in which the particulate filter 100 is mounted in the exhaust pipe 16 of the diesel engine 10. FIG. 7B is a diagram conceptually showing a result obtained by measuring the differential pressure dP before and after the filter, the exhaust gas temperature Tg flowing into the filter, and the filter temperature Tf while operating the diesel engine 10 under a constant condition. FIG.

When the operation of the diesel engine 10 is started, the exhaust gas temperature Tg and the filter temperature Tf immediately rise to reach a steady temperature. At this time, the filter temperature Tf is actually a value higher than the exhaust gas temperature Tg, but from the viewpoint of simplifying the explanation, it is assumed here that there is no significant difference between the two temperatures.

When the particulate filter 100 is new, the differential pressure dP before and after the filter gradually increases during the beginning, but eventually stabilizes at a constant value. The reason why the differential pressure before and after the filter stabilizes to a constant value is that the particulate filter 100 of the present embodiment three-dimensionally collects suspended particulates in the exhaust gas not only on the filter surface but also inside the filter. . The value at which the differential pressure stabilizes mainly depends on the design specifications of the filter, but typically becomes a value that is about 3 to 4 times the differential pressure when new. For convenience of explanation,
The period from the start of the operation of the diesel engine 10 until the differential pressure before and after the filter stabilizes will be referred to as “first period”.

When the diesel engine 10 has been operated for a while after the pressure difference before and after the filter has stabilized, the filter temperature Tf has not changed even though the exhaust gas temperature Tg has not changed.
Begins to rise little by little. The difference between the filter temperature Tf and the exhaust gas temperature Tg gradually increases, and finally the filter temperature Tf reaches around 550 ° C. During this time, the differential pressure dP before and after the filter tends to increase very slightly as the carbon-containing suspended fine particles such as soot and the hydrocarbon-based compound are collected by the filter, but a significant increase cannot be measured. In some cases.

When the filter temperature Tf rises to about 550 ° C., the carbon-containing suspended particulates such as soot trapped in the filter start to burn, and when all the trapped particulates burn, the filter temperature Tf becomes lower than the exhaust gas. The temperature quickly decreases to a temperature near the temperature Tg. If it is possible to detect an increase in the differential pressure dP before and after the filter due to the collection of soot and the like in the exhaust gas, it is possible to detect a decrease in the differential pressure dP when soot and the like burn on the filter. it can. After the end of the first period, the period during which the filter temperature Tf gradually deviates from the exhaust gas temperature Tg and decreases to the exhaust gas temperature Tg again will be referred to as a “second period”. Note that the period of the first period is considerably shorter than the period of the second period, but in FIG. 7, the period of the first period is displayed longer than the actual period of the second period for display reasons.

Even if the soot and the like trapped in the filter have burned and the filter temperature Tf has dropped to a temperature near the exhaust gas temperature Tg, the filter temperature Tf will be restored again after a while.
Begins to rise and eventually reaches 550 ° C., and the collected soot and the like burn. In this way, the filter is forever
, And the collection and combustion of soot and the like contained in the exhaust gas are repeated. The above is the first mode of the natural reproduction function of the particulate filter 100.

Under the condition that the exhaust gas temperature Tg is high, the second mode of the natural regeneration function appears. FIG. 7 (c)
The filter temperature Tf and the differential pressure d before and after the filter when the diesel engine 10 is operated under the condition that the exhaust gas temperature is slightly higher (typically 50 ° C.) than the condition of (b).
It is explanatory drawing which showed transition of P notionally. Similar results can be obtained not only with the exhaust gas temperature but also when the soot concentration is changed to be slightly higher than the condition of FIG. 7B.

Under the condition of high exhaust gas temperature Tg, FIG.
As shown in (c), after the end of the second period, the filter temperature T
f is stabilized at a slightly higher temperature without decreasing to around the exhaust gas temperature Tg. After the end of the second period, the filter temperature T
A period during which f is stabilized at a temperature higher than the exhaust gas temperature Tg will be referred to as a “third period”. In the third period, it is expected that the collection and combustion of soot and the like are locally repeated or performed simultaneously. As described above, in the second mode of the natural regeneration function, collection and combustion of suspended particulates are performed in parallel.

As described above, since the particulate filter 100 of this embodiment uses a nonwoven fabric for the predetermined specifications, the particulate filter 100 in a state in which the carbon-containing suspended fine particles and the hydrocarbon compound in the exhaust gas are dispersed. Thus, the collected fine particles can be naturally burned without performing a special operation. The reason why the particulate filter 100 can collect fine particles such as soot in a dispersed state is considered to be that the fine particles are collected while being actively incorporated into the nonwoven fabric by the mechanism described below. Hereinafter, the trapping mechanism estimated at the present time will be briefly described.

FIG. 8 is an explanatory view conceptually showing the structure of a cross section of a nonwoven fabric made of a heat-resistant metal. Each of the hatched circles in the figure indicates the cross section of the nonwoven fabric fiber. The nonwoven fabric is formed by innumerable fibers intricately intertwined with each other, and has an infinite number of three-dimensional passages intricately communicating with each other.

FIG. 8A conceptually shows the cross-sectional structure of a new nonwoven fabric. The exhaust gas flows downward from above. Openings of various sizes are formed on the surface of the non-woven fabric due to the uneven distribution of fibers, but even small openings are sufficiently large for the gas molecules of the exhaust gas. It is considered that the light passes through the entire surface almost evenly. In FIG. 8A, the exhaust gas passing between the fibers of the nonwoven fabric is schematically displayed using thick arrows.

When the exhaust gas passes through the nonwoven fabric, fine particles such as soot contained in the exhaust gas are trapped between the fibers, and the opening on the surface of the nonwoven fabric gradually closes. For this reason, as shown in FIG. 8B, the small openings on the surface of the nonwoven fabric are blocked by fine particles such as soot, and the exhaust gas concentrates on the relatively large openings remaining without being blocked. As a result, the flow of the exhaust gas passing through the nonwoven fabric is concentrated on the flow starting from the large opening remaining without being blocked on the surface. In FIG. 8B, fine particles such as soot are schematically displayed by small black circles.

When the exhaust gas flows intensively, the flow velocity increases accordingly, and a large pressure gradient is generated in the passage. This phenomenon may be considered that the flow collides with the fibers of the non-woven fabric and a large pressure is generated. As described above, since the passages formed inside the nonwoven fabric are intricately communicated with each other, if the pressure of the passages that are collectively flowing increases, the passages immediately branch to other passages. For this reason, the pressure difference before and after the nonwoven fabric is maintained in a certain range without increasing to a predetermined value or more.

FIG. 8C conceptually shows how the main stream branches off and flows to another passage. As described above, as a result of the flow of the exhaust gas diverging inside the nonwoven fabric, the carbon-containing suspended particulates such as soot contained in the exhaust gas are collected throughout the inside of the nonwoven fabric. Even if a certain portion inside the nonwoven fabric is closed with soot, the passages are three-dimensionally and intricately communicated with each other, so that it is possible to immediately branch to another passage. That is, even if a certain portion is closed by soot or the like inside the nonwoven fabric, the passage is automatically switched and the exhaust gas flows through a new passage, so that the soot and the like are collected in a dispersed state. .

As described above, the particulate filter 100 provided on the upstream side of the turbine 21 has a natural regeneration function, and separates the suspended particulates and the hydrocarbon-based compound in the collected exhaust gas from each other. It can be spontaneously burned without performing a complicated operation.

As described above, the particulate filter 100 of the present embodiment allows the carbon-containing suspended particulates and the hydrocarbon-based compound in the collected exhaust gas to be naturally burned without performing any special operation. Can be. In the particulate filter 100 of this embodiment, the carbon-containing suspended particulates and the like in the exhaust gas are collected by using the metal nonwoven fabric 106. However, the particulate filter is not limited to the metal nonwoven fabric, and may be, for example, a cordierite honeycomb. Even if a filter such as a filter, such as a filter, having the same pore size distribution is used, it is considered that the filter exhibits the same natural regeneration function as the filter of the present embodiment.

A-3. Outline of Engine Control: FIG. 9 is a flowchart showing an outline of an engine control routine performed by the engine control ECU 30. In this control routine, the power is turned “ON” when a start key is inserted into the engine.
It starts when the state is reached.

When it is detected that the key inserted into the engine has been turned to the starting position, the engine control ECU 30
Starts the engine start control (step S10). In this process, the engine is started by injecting fuel at appropriate timing while cranking the engine with the starter motor. When starting the engine, the intake air temperature and the engine water temperature are detected, and if the temperature is so low that it is difficult to start the engine, the intake air and the combustion chamber are appropriately heated by a heater. When the injected fuel burns in the combustion chamber, a large torque is generated and the engine rotation speed increases. The engine control ECU 30 detects that the engine rotation speed has reached a predetermined rotation speed and performs engine start control. To end.

When the engine start control is completed, an engine operating condition is detected (step S20). The main parameters that define the operating conditions of the engine are the engine rotation speed Ne and the accelerator opening θac, and other auxiliary parameters such as intake air temperature, engine cooling water temperature, fuel temperature, intake pressure, etc. In step S20, these parameters are detected. The engine rotation speed Ne can be detected by a crank angle sensor 32 mounted on a crankshaft of the engine.
The accelerator opening θac is detected by an accelerator opening sensor 34 attached to the accelerator pedal. As will be described in detail later, the differential pressure across the particulate filter 100 is also detected in the engine operating condition detecting process.

When the engine operating conditions are detected, a process for setting the engine control mode is performed according to the detected operating conditions (step S30). As will be described in detail later,
In the diesel engine 10 of the present embodiment, various controls such as control for injecting fuel into the combustion chamber, EGR control for recirculating a part of the exhaust gas to the intake passage, and control for operating efficiency of the supercharger 20 are performed. Although these controls are performed, these controls are not performed independently, but as a whole, they constitute one system in relation to each other so that the engine is maintained in an optimum state. Further, as described later, when the differential pressure across the particulate filter 100 increases to a value exceeding an allowable value, the fuel injection, E
By performing control in cooperation with various factors such as the GR amount and the supercharging pressure, the natural regeneration function of the filter of the present embodiment can be promoted, and the pressure difference between before and after can be restored to the normal range. In the diesel engine 10 of the present embodiment, in order to enable the cooperative control of the respective elements, the control mode is first set based on the operating conditions of the engine, and the respective elements are controlled based on the control mode. It adopts the method of doing.

When the control mode is set in this way, fuel injection control is performed based on the control mode (step S
40). The fuel injection control is a control for injecting an appropriate amount of fuel at an appropriate timing according to the operating conditions of the engine. The outline of the control is as follows. First,
The basic fuel injection amount and fuel injection timing are calculated based on the engine rotation speed Ne and the accelerator opening θac. Next, this value is corrected taking into account the effects of the intake air temperature, engine cooling water temperature, fuel temperature, etc.
An optimum injection amount and an optimum injection timing according to the engine operating conditions are calculated. In order to inject fuel at the injection amount and timing calculated in this way, the fuel supply pump 18
And the fuel injection valve 14 are controlled.

More specifically, the basic fuel injection amount and the basic fuel injection timing are used as a map for the engine rotation speed Ne and the accelerator opening θac as an engine control E
It is stored in a ROM built in the CU 30. Also,
Various correction coefficients such as the intake air temperature and the engine cooling water temperature are also stored as a map in the ROM in the engine control ECU 30. The engine control ECU 30 acquires the basic fuel injection amount, injection timing, and various correction coefficients by referring to these maps. The optimum fuel injection amount and fuel injection timing are calculated based on the obtained fuel injection amount, injection timing, and various correction coefficients, and the fuel supply pump 18 and the fuel injection valve 14 are controlled.

When the fuel injection control is completed, the EGR
The control is started (step S50). EGR is Ex
Abbreviation for hust gas recirculation, which refers to the intentional return of part of the exhaust gas into the intake pipe in order to reduce the concentration of nitrogen oxides contained in the exhaust gas. . If a part of the exhaust gas is recirculated to the intake air, the combustion speed in the combustion chamber is reduced, so the maximum combustion temperature is lowered and the concentration of nitrogen oxides in the exhaust gas can be reduced. When the gas recirculation amount increases, combustion tends to be unstable. Therefore, depending on the operating conditions of the engine,
It is necessary to control the amount of exhaust gas recirculation to be optimal. Such control is performed in the EGR control.

When the fuel injection control is completed, the boost pressure control is subsequently performed (step S60). As described above with reference to FIG. 1, the supercharger 20 is provided in the diesel engine 10, and a large amount of air is supplied to the combustion chamber by making the pressure in the intake pipe 12 higher than the atmospheric pressure. be able to. As described above, increasing the pressure in the intake pipe higher than the atmospheric pressure is referred to as “supercharging”, and a pressure increase from the intake pipe before the supercharging is referred to as “supercharging pressure”. Increasing the boost pressure will increase the amount of oxygen available for combustion,
The effect of improving the maximum output of the engine, or reducing the amount of carbon-containing suspended particulates such as soot even under a constant output condition can be obtained. In the diesel engine 10 of the present embodiment, the opening area of the portion where the exhaust gas flows into the turbine 21 of the supercharger is controlled so that an appropriate supercharging pressure according to the operating conditions of the engine can be obtained. . Further, when the exhaust gas flow rate is large and the supercharging pressure is too high, a control is performed such that the supercharging pressure is not excessively increased by opening the waste gate valve 72 to bypass a part of the exhaust gas.

When the supercharging pressure control is completed as described above, it is detected whether or not the starting key inserted into the engine has been returned to the "OFF" position (step S7).
0), if it has not been returned to the "off" position, the process returns to step S20 and repeats a series of subsequent processes. The engine control ECU 30 repeats the above-described processing until the start key is returned to the “off” position. As a result, the engine is always optimally controlled according to changes in the operating conditions.

Further, as will be described in detail later, in the diesel engine 10 of the present embodiment, when it is detected that the differential pressure across the particulate filter 100 has increased and there is a concern that the filter may be clogged, the fuel injection control is performed. , EGR control, supercharging pressure control, etc., are appropriately performed to promote the natural regeneration function of the particulate filter 100 of the present embodiment, and to prevent clogging of the filter.

B. Filter regeneration promotion processing: As described above, the diesel engine 10 of the present embodiment detects a differential pressure across the particulate filter 100 and, when there is a possibility of filter clogging, performs an automatic filter regeneration function. Perform processing to promote. This filter regeneration promotion process is not a single process but a combination of various controls such as fuel injection, EGR, and supercharging pressure. If the filter regeneration mode is set during the control mode setting process described above, the combustion Filter regeneration promotion control is performed by injection, EGR control, supercharging pressure control, and the like. Therefore, first, the process of setting the filter regeneration mode during the control mode setting process will be described.

B-1. Control mode setting process: FIG.
It is a flowchart which shows the flow of a control mode setting process. This process is performed after detecting the engine operating conditions in step S20 in the engine control routine shown in FIG. Hereinafter, the contents of the processing will be described with reference to FIG.

When the control mode setting process is started, first, it is determined whether or not the operating condition of the engine is in the unibus combustible region (step S100). Unibus combustion is a special combustion method based on the premise that fuel is injected multiple times during one cycle of a diesel engine.
The diesel engine 10 according to the present embodiment performs the unibus combustion, whereby it is possible to suppress the emission of carbon-containing suspended particulates such as soot and nitrogen oxides. Unibus combustion will be described later. FIG. 11 is an explanatory diagram conceptually showing an engine operating condition in which unibus combustion is possible, with the horizontal axis representing the engine rotation speed Ne and the vertical axis representing the accelerator opening θac. Possible operating conditions of the engine, that is, from the engine speed 0 rpm to the maximum speed MAX rpm,
The hatched area within the range of the accelerator opening from 0% to 100% is an area where unibus combustion is possible. As shown in the figure, in the extremely low rotational speed range where combustion is likely to be unstable, and in the remaining regions excluding the high rotational speed range and the high accelerator opening range where the load on the engine is high, Unibus combustion control is performed. .

If it is determined that the engine operating conditions are in the unibus combustible region (step S100: yes)
s) The flag Fu indicating that the unibus combustion control is to be performed is set to "ON" (high voltage state) (step S102).
Here, the flag Fu will be described. An address for displaying the above-described control mode of the engine is provided in a RAM incorporated in the engine control ECU 30, and in the data of the address, each bit corresponds to a flag. FIG. 12 is an explanatory diagram conceptually showing address data indicating a control mode. As shown in the figure, one byte (8 bits) of memory is allocated to the address, and the first bit is a flag Fu.
Is a bit corresponding to. Address flag Fu
Are two bits for a spare flag. The remaining five bits are flags used in filter regeneration promotion control described later. The first bit is a flag Ff indicating that filter regeneration promotion control is to be performed, and the other bits are flags F1 to F1 indicating a filter regeneration level. This bit indicates F4. The flags Ff to F4 will be described later.

If it is determined in step S100 of FIG. 10 that the operating condition of the engine is in the region where the unibus combustion is performed, the flag Fu is set to “ON” (high voltage state) in step S102. Conversely, when it is determined that the region is not in the region where the unibus combustion is performed, the flag F
u is set to “OFF” (low voltage state) (step S
104).

In the control mode setting process of FIG. 10, the setting of the flag Fu is changed each time the engine operating condition enters or exits the unibus combustible region. However, instead of immediately changing the flag Fu even when the operating state is switched, the setting of the flag Fu may be changed only after confirming that the switched state has continued for a predetermined period. In this case, for example, when the operating condition of the engine happens to be near the boundary of the unibus combustible region, the control state of the engine is frequently switched by a slight change in the operating condition, and the operating condition may become unstable. Is preferred because it is eliminated. Also, in FIG. 12, it has been described that one-byte memory is allocated to the address indicating the control mode of the engine, but it is needless to say that more memory may be allocated.

Next, the particulate filter 100
Is calculated (step S106). Pressure sensors 64 and 66 are provided upstream and downstream of the particulate filter 100. In the process of step S106, the differential pressure dP before and after the filter is calculated from the outputs of these sensors detected in advance in the above-described engine operating condition detection process (step S20 of FIG. 9).

Although the pressure difference dP before and after the filter is calculated from the pressures before and after the filter detected by using the pressure sensors 64 and 66, the pressure values before and after the filter need not always be detected. . For example, a plurality of types of pressure switches that close the contacts depending on the pressure difference before and after the filter may be provided, and the pressure difference before and after the filter may be detected depending on which of the contacts is closed. Alternatively, a pressure sensor may be provided only upstream of the filter, and the pressure upstream of the filter may be detected when the engine is operating under predetermined conditions. If the pressure difference before and after the filter increases, the pressure upstream of the filter increases accordingly. From this,
By detecting that the pressure upstream of the filter has increased under predetermined operating conditions, it is also possible to detect an increase in the differential pressure across the filter.

After calculating the differential pressure dP before and after the filter, the allowable differential pressure dPc of the differential pressure before and after the filter and the return differential pressure dPr are obtained (step S106). Allowable differential pressure d
Pc is a pressure value used as a reference for determining whether or not the particulate filter 100 may be clogged. The return differential pressure dPr is a pressure value serving as a criterion for determining whether or not to terminate the filter regeneration promotion process described later. Allowable differential pressure dPc and return differential pressure d
Pr is an engine control ECU in the form of a map for the engine speed Ne and the accelerator opening θac, respectively.
30 is stored in the ROM. In the process of step S106, by referring to the map, the allowable differential pressure dPc and the return differential pressure dP in accordance with the engine operating conditions are determined.
Get the value of r.

In this embodiment, the allowable differential pressure dPc
Alternatively, the return differential pressure dPr is set to an optimal value according to the engine operating conditions using a map. However, when the carbon-containing suspended particulates accumulate and the filter starts to be clogged, the differential pressure across the filter tends to increase rapidly, so that the allowable differential pressure dPc or the return differential pressure d
The value of Pr may be a constant value regardless of the engine operating conditions. This eliminates the need for a map,
This is preferable because the storage capacity of the ROM can be saved accordingly.

Next, the magnitude relationship between the differential pressure dP before and after the filter and the allowable differential pressure dPc is compared (step S108).
When the differential pressure dP is larger than the allowable differential pressure dPc (step S108: no), it is considered that the deposited amount of the carbon-containing suspended fine particles is large, and the particulate filter 100 may be clogged. Therefore, in such a case, the flag Ff described with reference to FIG. 12 is set to the “ON” state in order to avoid clogging of the filter. When the flag Ff is set to “ON”, filter regeneration promotion control described below is performed, and the carbon-containing suspended particulates deposited on the filter burn, so that clogging of the filter can be avoided.

If it is determined in step S108 that the differential pressure dP before and after the filter is smaller than the allowable differential pressure dPc, it is determined whether the flag Ff is set (step S110). That is, when the differential pressure dP before and after the filter exceeds the allowable differential pressure dPc (step SS108: no), the differential pressure dP before and after the filter decreases as a result of performing the filter regeneration promotion control. If the filter regeneration promotion control is immediately stopped just because it becomes smaller than dPc, the filter differential pressure d
P may immediately exceed the allowable differential pressure dPc again. In order to avoid such a situation, when the filter regeneration promotion control is started, the differential pressure across the filter becomes equal to the allowable differential pressure dPc.
The control is not interrupted even if the value becomes below, and is continued until the value becomes smaller than the return differential pressure dPr. Therefore, when the differential pressure dP before and after the filter is smaller than the allowable differential pressure dPc, it is determined whether or not the flag Ff is set. When the flag Ff is set (when the filter regeneration control is being performed), Then, the differential pressure dP before and after the filter is compared with the return differential pressure dPr (step S114).

As a result of comparison between the differential pressure dP and the return pressure dPr, if the differential pressure dP has not decreased to a value smaller than the return pressure dPr (step S114: n)
o) Assuming that the filter regeneration promotion control is continued, the filter regeneration level setting process is started (step S12).
0). As will be described in detail later, in the filter regeneration promotion control of the present embodiment, it is possible to set various degrees of promoting the natural regeneration function of the particulate filter 100, and when the pressure difference before and after the filter becomes large. First, a light control of the degree of promotion is performed, and if the differential pressure does not decrease, the control content is gradually changed to a control of a heavy degree of promotion. In response to this, in step S120, a process of setting the degree of promoting the natural reproduction function of the particulate filter 100 is performed.

On the other hand, if the differential pressure dP before and after the filter is smaller than the return differential pressure dPr (step S114: yes), the carbon-containing suspended particulates deposited on the filter burn. It is determined that the filter has been sufficiently regenerated, and the value of the flag Ff indicating the filter regeneration promotion control and the values of the flags F1 to F4 indicating the filter regeneration level are set to "OFF" (step S1).
16). Next, the counter n used in the filter regeneration level setting process is reset. The counter n and the flags F1 to F4 indicating the filter regeneration level will be described later.

FIG. 13 is a flowchart showing the flow of the above-described filter reproduction level setting process. When the process is started, first, the value of the counter n is increased by "1" (step S200). Here, the meaning of the counter n will be described. As described above, the engine control ECU 30 controls the engine operation state to be optimal by repeatedly executing the engine control routine of FIG. The counter n is a variable used to count the number of times the engine control routine is executed while performing the filter regeneration promotion control. That is, as described above with reference to FIG. 10, when the filter regeneration promotion control is not performed (flag Ff: OFF), the counter n is always reset, and when the filter regeneration promotion control is performed (flag Ff). : ON), every time the filter regeneration level setting process is performed once, the value of the counter n is incremented by "1" in step S200 in FIG. As is apparent from this, it is possible to detect how many times the engine control routine has been executed based on the value of the counter n while performing the filter regeneration promotion control.

When the value of the counter n is increased by "1", it is determined whether or not the counter n has reached a predetermined first threshold number th1 (step S202). Counter n is the first
If the threshold number th1 has not been reached (step S20)
2: no), after setting the flag F1 to "ON" (step S204), the process exits the filter regeneration level setting process and returns to the engine control routine via the control mode setting process of FIG. EGR performed following the control mode setting process in the engine control routine
In the control, a process of decreasing the EGR amount is performed in response to the setting of the flag F1. As will be described in detail later, by performing such control, the natural regeneration function of the particulate filter 100 can be promoted, and the carbon-containing suspended particulates deposited on the filter can be burned. This control is the lightest control of the filter regeneration promotion control, and is performed until the value of the counter n reaches the predetermined threshold number th1.

Normally, while performing the filter regeneration promotion control corresponding to the flag F1, the engine control routine is executed for a while, so that the differential pressure dP before and after the filter decreases to a value equal to or less than the return differential pressure dPr. As a result, the flag Ff indicating the filter regeneration promotion control and the flags F1 to F4 indicating the filter regeneration level are reset (see step S116 in FIG. 10).

Even if the value of the counter n reaches the first threshold number th1, the differential pressure dP before and after the filter does not decrease to a value equal to or lower than the return differential pressure dPr (step S202 in FIG. 13).
If yes, the counter n is compared with the second threshold number th2 (step S206). If the counter n has not reached the second threshold number th2, the flag F2 is turned “ON”.
(Step S208), the process exits the filter regeneration level setting process, and returns to the engine control routine via the control mode setting process of FIG. Since the flag F1 has already been set to "ON" in step S204, the counter n is set to the first threshold number t.
When the value becomes h1 or more, the flag F2 is set to "ON" in addition to the flag F1.

When the flag F1 is "ON", the engine control routine performs control to decrease the EGR amount.
When the flag F2 is set to "ON", control is performed to set the supercharging pressure to a higher value. As will be described in detail later, by controlling the supercharging pressure to be higher, the natural regeneration function of the particulate filter 100 can be promoted. If the differential pressure across the filter does not sufficiently decrease even when the counter n reaches the first threshold number th1 in this manner, the natural regeneration function of the filter is controlled by controlling the supercharging pressure in addition to the EGR control. The carbon-containing suspended particulates deposited on the filter are further promoted to burn.

If the engine control routine is executed for a while while performing the EGR control and the supercharging pressure control in response to the setting of the flag F1 and the flag F2, the differential pressure across the filter can be obtained. dP is the return differential pressure dP
r, the flag Ff indicating the filter regeneration promotion control and the flag F indicating the filter regeneration level.
1 to F4 are reset (see step S116 in FIG. 10).

When the differential pressure dP before and after the filter does not decrease to a value equal to or lower than the return differential pressure dPr even if the value of the counter n reaches the second threshold number th2 (step S206: yes).
Compares the counter n with the third threshold number th3 (step S210). When the counter n is equal to the third threshold number t
If it has not reached h3, the flag F3 is set to "ON" (step S212), and the process exits the filter regeneration level setting process and returns to the engine control routine. When the flag F3 is set to "ON", control for retarding the fuel injection timing is performed in the engine control routine. As will be described later in detail, by performing such control, the particulate filter 10
0 natural regeneration function can be promoted. Counter n
If the differential pressure before and after the filter does not sufficiently decrease even if reaches the second threshold number th2, the fuel injection timing is retarded in addition to the EGR control and the supercharging pressure control, whereby the natural regeneration of the filter is performed. The function is further promoted, and the carbon-containing suspended particulates deposited on the filter are burned. That is, if the fuel injection timing is retarded, the temperature of the exhaust gas rises, so that the effect of the supercharging pressure control is more likely to appear, and the natural regeneration function of the filter can be promoted accordingly.

When the differential pressure dP before and after the filter does not decrease to a value equal to or lower than the return differential pressure dPr even when the value of the counter n reaches the third threshold number th3 (step S210: yes).
Compares the counter n with the fourth threshold number th4 (step S214). When the counter n is the fourth threshold number t
If h4 has not been reached, the flag F4 is set to "ON" (step S212), then the flags F1 to F3 are set to "OFF", and the routine returns to the engine control routine. When the flag F4 is set to "ON", in the engine control routine, control is performed to promote the natural regeneration function of the filter while performing unibus combustion described later. As will be described in detail later, by performing a special unibus combustion control, the particulate filter 1 is controlled.
00 natural regeneration function can be promoted.

When the differential pressure dP before and after the filter does not decrease to a value equal to or lower than the return differential pressure dPr even when the value of the counter n reaches the fourth threshold number th4 (step S214: yes).
Sets the flag F2 to "ON" while keeping the flag F4 set to "ON" (step S21).
8). In other words, by increasing the supercharging pressure while performing the unibus combustion control for filter regeneration, the natural regeneration function of the particulate filter 100 is further promoted.

As described above, when the flags F1 to F4 are set to either "ON" or "OFF", the filter regeneration level setting process shown in FIG. 13 is terminated, and the control mode shown in FIG. After the setting process, the process returns to the engine control routine. As described above, the fuel injection control and EGR performed following the control mode setting process
In various controls such as control and supercharging pressure control, processing according to the control mode is performed. That is, when the flag Fu in the address indicating the control mode shown in FIG. 12 is “ON”, these elements are appropriately controlled to perform the unibus combustion control. When the flag Ff indicating that the filter regeneration promotion control is to be performed is “ON”,
Filter regeneration promotion control is performed in accordance with the settings of flags F1 to F4. Hereinafter, various controls performed according to the setting of these flags will be described.

B-2. EGR control: As described above, in the filter regeneration promotion control, a plurality of controls are combined in a stepwise manner. At the stage immediately after the rise in the differential pressure across the filter is detected, the following control is first performed in the EGR control. Is performed, combustion of the carbon-containing suspended particulates deposited on the particulate filter 100 is attempted.

FIG. 14 is a flowchart showing the flow of the EGR control process performed in the above-described engine control routine. When the EGR control process is started, first, it is determined whether or not the flag F1 is set to "ON" (step S300). That is, as described above,
If it is set in the control mode setting process (see FIG. 10) performed prior to the EGR control process to perform the filter regeneration promotion control, the filter regeneration level setting process (FIG. 1)
3), the content of the regeneration promotion control is set, and when the EGR control is used, the flag F1 is set. Therefore, when the EGR control process is started, first, the flag F
It is determined whether or not 1 is set to “ON”.

If the flag F1 is not set to "ON" (step S300: no), it is determined that normal EGR control is to be performed, and the valve opening degree θegr of the EGR valve 62 is set to a value determined by the operating conditions of the engine. (Step S302). The valve opening degree θegr of the EGR valve is stored in the ROM in the engine control ECU as a map using the engine rotation speed Ne and the accelerator opening degree θac as parameters. By outputting the valve opening degree θegr set in the map to the EGR valve 62, the EGR amount can be controlled to an optimum EGR amount according to the engine operating conditions.

On the other hand, if the flag F1 is "ON" (step S300: yes), the value of the EGR valve opening θegr is set to "0", and the EGR valve 62 is fully closed. (Step S304). By doing so, the natural regeneration function of the particulate filter 100 can be promoted for the following reasons, and the carbon-containing suspended particulates deposited on the filter can be burned.

When the EGR valve 62 is closed, the amount of EGR flowing back into the intake pipe decreases. In a diesel engine, EG which is usually drawn into the combustion chamber by every intake air
Since the total value of the R amount and the air amount is constant, if the EGR amount decreases, the intake air amount increases accordingly. here,
Since the amount of fuel injected into the combustion chamber is the same, if the amount of intake air increases, the amount of oxygen discharged without being used for combustion increases, and eventually the amount of oxygen in the exhaust gas increases. As described above with reference to FIG. 7, the particulate filter 100 of the present embodiment disperses and collects the carbon-containing suspended fine particles and the hydrocarbon-based compound in the exhaust gas so as to be able to contact oxygen in the exhaust gas. In addition, carbon-containing suspended particulates are burned in a relatively low temperature exhaust gas by utilizing a relatively mild oxidation reaction of a hydrocarbon compound. Therefore, if the amount of oxygen in the exhaust gas is increased by closing the opening of the EGR valve, the oxidation reaction of the hydrocarbon-based compound collected on the filter is promoted, and the combustion of the carbon-containing suspended particulates is extended. It can be promoted.

In the above description, the flag F1 is set to “O”
In the case of "N", the EGR valve 62 is set to the fully closed state. However, as long as the EGR amount decreases and the air amount increases, the above-described filter regeneration promoting effect can be obtained. Therefore, the EGR valve 62 does not necessarily need to be fully closed, and for example, the EGR valve 62 may be closed by a predetermined opening degree.

B-3. Supercharging pressure control: If the differential pressure dP before and after the particulate filter 100 does not sufficiently decrease even after the above-described EGR control is performed for a predetermined time, the following control is performed in the supercharging pressure control described below. Is performed, combustion of the carbon-containing suspended particulates deposited on the particulate filter 100 is attempted.

FIG. 15 is a flowchart showing the flow of the supercharging pressure control process performed in the above-described engine control routine. As described above with reference to FIG. 1, the diesel engine 10 of the present embodiment is provided with the supercharger 20 capable of controlling the area of the opening (turbine opening area) through which the exhaust gas flows into the turbine 21 by the actuator 70. I have. When the supercharging pressure control process is started, first, the turbine opening area of the supercharger 20 is set to an optimum value according to the engine operating conditions (step S400). In the ROM in the engine control ECU, an optimal turbine opening area according to the engine operating conditions is stored as a map using the engine rotation speed Ne and the accelerator opening θac as parameters. By reading the values set in this map and outputting them to the actuator 70 of the supercharger 20, the turbine opening area can be controlled to an optimum value according to the engine operating conditions.

Next, it is determined whether or not the flag F2 is set to "ON" (step S402). As described above, the filter reproduction level setting process (see FIG. 13)
If it is determined that the filter regeneration promotion control is to be performed using the boost pressure control, the flag F2 is set to “ON”. Therefore, based on the setting of the flag F2, it is determined whether or not to perform the filter regeneration promotion control using the supercharging pressure control.

If the flag F2 is not set to "ON" (step S402: no), it is determined that normal control is to be performed, and the control directly exits from the supercharging pressure control and proceeds to the engine control routine shown in FIG. Return to.

On the other hand, when the flag F2 is set to "ON" (step S402: yes), the filter regeneration promoting control using the supercharging pressure control is performed.
A process for correcting the set value of the turbine opening area is performed (Step S404). As a preparation for describing the content of such processing, a set value of the turbine opening area used in normal supercharging pressure control will be described.

Generally, when the opening area of the turbine is reduced, the flow rate of the exhaust gas flowing into the turbine 21 increases, so that the rotation speed of the turbine 21 increases, and the supercharging pressure increases accordingly. However, since the exhaust resistance increases as the turbine opening area decreases, the turbine opening area has an optimal value determined according to the engine operating conditions. In the ROM in the engine control ECU, such an optimum value of the turbine opening area is stored in the form of a map in accordance with the operating conditions of the engine. In a normal supercharging pressure control, the map is read out. , The turbine opening area is controlled to an appropriate value.

In the process of step S404, control is performed to correct the turbine opening area set in the map to a small value by a predetermined amount and increase the supercharging pressure. Of course, the correction amount of the turbine opening area is determined by the engine rotation speed N
The map may be set using e and the accelerator opening θac as parameters, and the turbine opening area may be corrected using the values set in the map. This is preferable because the correction amount can be optimized according to the engine operating conditions. After the completion of the supercharging pressure control, the process returns to the engine control routine shown in FIG.

As described above, the flag F2 is set to "O"
If "N" is set, the supercharging pressure is set to a higher value.
When the supercharging pressure increases, the amount of air taken into the combustion chamber increases accordingly. The amount of fuel to be injected does not change depending on the setting of the flag F2. Therefore, as the intake air amount increases, the oxygen amount in the exhaust gas increases accordingly. As a result, the natural regeneration function of the particulate filter 100 is promoted, and the carbon-containing suspended particulates deposited on the filter burn.

In the above description, the actuator 70
Is used, and when the flag F2 is "ON", the turbine opening area is reduced to increase the supercharging pressure. The present invention is not limited to the case where a turbocharger capable of controlling the turbine opening area is mounted. For example, when the exhaust gas amount exceeds a predetermined amount in an engine operating condition, the wastegate valve 72 is slightly opened so that the exhaust gas always bypasses the turbine 21 and the flag F2 is turned “ON”. Alternatively, the boost pressure may be increased by fully closing the wastegate valve 72.

B-4. Fuel injection control: Even if the above-described supercharging pressure control is performed for a predetermined time, the particulate filter 100
If the differential pressure dP before and after is not sufficiently reduced, the following control is performed in the fuel injection control to burn the carbon-containing suspended particulates deposited on the particulate filter 100. That is, the diesel engine 10 of the present embodiment employs a combustion method called Unibus combustion, and the natural regeneration function of the particulate filter 100 is promoted by changing the control parameters of the Unibus combustion.

Here, a description will be given of a combustion method called “unibus combustion” in comparison with a combustion method generally used in diesel engines. A diesel engine employs a method in which aspirated air sucked into a combustion chamber is adiabatically compressed by a piston, and fuel is injected into the obtained high-temperature and high-pressure compressed air to burn. The injected fuel is sprayed and travels while diffusing in the air, and the fine particles of the fuel constituting the spray are vaporized by the temperature.As a result, a fuel mixture is formed around each fine particle of the fuel. You. Since the intake air is compressed to a sufficiently high temperature, when the fuel mixture formed around the fuel particulates reaches the flammable concentration, it is ignited spontaneously and combustion starts. As described above, the combustion mode of the diesel engine employs a mode of diffusion of fuel spray, followed by vaporization and self-ignition, and is therefore also called a diffusion combustion mode. In diffusion combustion, it is desirable that self-ignition be effected as soon as the fuel mixture reaches a combustible concentration, so that a so-called high cetane number fuel is often used.

In recent years, so-called pilot injection is often performed in which fuel is injected a plurality of times.
That is, when the fuel is injected at once, the injected fuel is ignited at the same time and the combustion pressure rises rapidly, resulting in a problem that a combustion noise peculiar to the diesel engine may be generated. By injecting the fuel, it is intended to avoid these problems. Even when pilot injection is performed, since fuel is injected into air compressed to high temperature and high pressure, diffusion combustion is performed for each injected fuel.

On the other hand, in a combustion system called unibus combustion, a part of fuel is injected into air in the middle of compression in which a combustible air-fuel mixture cannot self-ignite, and the remaining fuel is compressed to a high temperature. This is a combustion system that injects into high-pressure air.
When such a combustion method is adopted, it is possible to significantly reduce the amount of carbon-containing suspended particulates such as soot and nitrogen oxides contained in exhaust gas as described below.

FIG. 16 is an explanatory view conceptually showing the principle by which the emission of carbon-containing suspended particulates such as soot and nitrogen oxides can be reduced by performing unibus combustion. The large circle in the figure schematically shows the combustion chamber viewed from above, and the small circle at the approximate center of the combustion chamber is
FIG. 3 schematically shows a tip portion (a nozzle portion) of a fuel injection valve 14 provided in a combustion chamber. Fuel injection valve 14
Are provided with a plurality of small nozzles for injecting fuel, and fuel spray is radially ejected from each nozzle of the nozzle. Here, it is assumed that four nozzles are provided in the nozzle.

FIG. 16A is an explanatory diagram schematically showing a state in which a part of the fuel is injected into the combustion chamber during the compression of the intake air. The fuel spray ejected at a high pressure from the injection port travels straight through the combustion chamber while diffusing little by little as shown in the figure. Hereinafter, the fuel injection performed during the compression in the Unibus combustion will be referred to as “auxiliary injection”, and the fuel spray formed by the auxiliary injection will be referred to as “auxiliary fuel spray 80”. In contrast, fuel injection performed in high-temperature, high-pressure air in the latter half of compression is referred to as “main injection”, and fuel spray formed by main injection is referred to as main fuel spray 84. In the Unibus combustion, the auxiliary injection is performed in the relatively low-temperature intake air during compression, so that the auxiliary fuel spray 80 is diffused and vaporized in the combustion chamber without self-ignition. FIG. 16B schematically illustrates a state in which the diffusion and vaporization of the auxiliary fuel spray 80 progresses in the combustion chamber to form a fuel mixture 82. of course,
While the fuel spray is diffusing and vaporizing, the temperature of the air-fuel mixture rises with the compression of the intake air, but when it reaches a self-ignitable temperature, the fuel spreads and the flammable concentration increases. Since the fuel concentration is lower than that, the auxiliary fuel spray 80 does not self-ignite.

FIG. 16C is an explanatory diagram schematically showing a state in which the main fuel spray 84 is formed by performing the main injection. As shown, the main fuel spray 84 is formed at a position overlapping with the fuel mixture 82 formed by the auxiliary injection. In addition, since the main injection is performed in the fuel mixture 82 which has been compressed and has a high temperature and a high pressure, the injected fuel spray is quickly diffused, and is vaporized and self-ignited. When the main fuel spray 84 self-ignites in this manner, the fuel mixture 82 formed by the auxiliary injection also starts burning by using this flame as a fire, and eventually all the injected fuel is burned.

If the above-described unibus combustion method is employed, carbon-containing suspended particulates such as soot and nitrogen oxides contained in the exhaust gas are greatly reduced as compared with the combustion method employed in a normal diesel engine. It is possible to reduce. Hereinafter, the reason will be described.

In the unibus combustion, the fuel to be injected is divided into two injections, an auxiliary injection and a main injection, and the fuel injected by the auxiliary injection is burned after being sufficiently diffused and vaporized. In general, if it burns in a sufficiently vaporized state, carbon-containing suspended particulates such as soot hardly occur, but so-called diffusion combustion in which fuel particles burn from the vaporized end generates carbon-containing suspended particulates such as soot. It is difficult to burn without. For this reason, in Unibus combustion, part of the fuel is supplementarily injected to diffuse and diffuse sufficiently.
By burning after vaporization, the proportion of the fuel to be diffused and burned is reduced, so that the amount of carbon-containing suspended particulates such as soot can be significantly suppressed.

The fuel mixture 82 formed by the auxiliary injection has such a low fuel concentration that it does not self-ignite unless the main injection is performed to supply the ignition. In general, the burning speed of a fuel mixture largely depends on the fuel concentration, and the burning speed increases as the fuel concentration of the mixture increases. For this reason, the fuel mixture 82 formed by the auxiliary injection has a lower combustion speed due to the lower fuel concentration. The lower the burning rate, the lower the flame temperature. It is believed that most of the nitrogen oxides contained in the exhaust gas are generated by the oxidation of the nitrogen in the air when exposed to high temperatures in a flame,
Even a slight decrease in the flame temperature can greatly reduce the emission of nitrogen oxides.

In the diesel engine 10 of this embodiment,
If the pressure difference dP before and after the particulate filter 100 does not sufficiently decrease even after the above-described supercharging pressure control is performed for a predetermined time, the natural regeneration function of the particulate filter 100 is changed by changing the control parameters of the unibus combustion. To promote the combustion of carbon-containing suspended particulates deposited on the filter.

FIG. 17 is a flowchart showing the flow of the fuel injection control process performed in the engine control routine described above. When the fuel injection control process is started, first, a basic fuel injection amount is acquired with reference to a map (step S500). As described above, the basic fuel injection amount is stored in the ROM incorporated in the engine control ECU 30 as a map for the engine rotation speed Ne and the accelerator opening θac. Next, various correction coefficients such as the intake air temperature and the engine cooling water temperature are acquired from the map (step S502). These maps are also stored in the ROM in the engine control ECU. The actual fuel injection amount is calculated using the basic fuel injection amount thus obtained and the various correction coefficients (step S504).

Next, it is determined whether or not the flag Ff indicating that the unibus combustion control is to be performed is "ON" (step S506). That is, as shown in FIG. 12, since the unibus combustion is not possible under all operating conditions, it is determined whether or not the engine is operating in the unibus combustible region by referring to the flag Fu. is there.

If the flag Fu is not "ON" (step S506: no), it is determined that the same fuel injection as that of a normal diesel engine is to be performed, and the fuel injection timing is acquired by referring to the map (step S506). Step S50
8). Next, it is determined whether or not the flag F3 is "ON" (step S510). That is, as described above in the filter regeneration level setting process, the fuel injection timing is retarded while increasing the supercharging pressure.
Since the natural regeneration function of the particulate filter 100 may be promoted, whether or not such control is performed is determined by setting the flag F3. If the flag F3 is "ON", a process of retarding the fuel injection timing by a predetermined amount is performed (step S51).
2) If the flag F3 is not "ON", the process directly exits the fuel injection control and returns to the engine control routine shown in FIG.

On the other hand, when the flag Fu is "ON" (step S506: yes), it is determined that the unibus combustion control is to be performed, and the fuel amount of the auxiliary injection and the fuel amount of the main injection are determined. Is calculated (step S514). That is, the ratio between the fuel amount of the auxiliary injection and the fuel amount of the main injection is
Since the map is set according to the engine operating conditions, by distributing the actual fuel injection amount at such a ratio,
The fuel amount of the auxiliary injection and the fuel amount of the main injection are calculated. Of course, for simplicity, the ratio between the fuel amount of the auxiliary injection and the fuel amount of the main injection may be set to a constant value.

Next, the injection timing of the auxiliary injection and the injection timing of the main injection are obtained (step S51).
6). These injection timings are also set in the ROM in the engine control ECU as maps for the engine operating conditions. Unibus combustion can be performed by injecting fuel at the fuel amount and the injection timing calculated for each of the auxiliary injection and the main injection.

Here, the diesel engine 1 of this embodiment
In the case of 0, it is possible to promote the natural regeneration function of the particulate filter 100 by changing the control parameters of the unibass combustion. In response to this, it is determined whether the flag F4 is "ON". Is determined (step S518). The flag F4 is a flag indicating whether or not to perform the filter regeneration acceleration control using the combustion of the unibus.

If the flag F4 is "ON" (step S518: yes), the auxiliary injection timing is corrected and advanced by a predetermined amount (step S52).
0). If the auxiliary injection timing is advanced, the emission amount of the hydrocarbon compound increases for the reason described later. As described above, the particulate filter 100 uses the oxidation reaction of the collected hydrocarbon-based compound to burn the carbon-containing suspended particulates. Therefore, as the emission of the hydrocarbon-based compound increases, the natural amount of the filter increases. The reproduction function can be promoted. The same effect can be obtained by retarding the timing of the main injection instead of advancing the auxiliary injection timing. The reason for this will be described later.
It is also preferable to increase the amount of fuel to be auxiliaryly injected in accordance with the change of the injection timing.

If the flag F4 is not "ON" (step S518: no), the values calculated in steps S514 and S516 are not changed.
After exiting the fuel injection control, the process returns to the engine control routine shown in FIG.

Here, by advancing the timing of the auxiliary injection or delaying the timing of the main injection,
The reason why the emission amount of the hydrocarbon compound increases will be described. FIG. 18 is an explanatory diagram schematically showing a state in which the main injection is performed after the auxiliary injection is performed at the advanced timing. The period up to the main injection is extended by the advance of the auxiliary injection timing, and the fuel spray formed by the auxiliary injection is diffused over a wide range. As the diffusion range of the fuel becomes wider, the fuel concentration becomes lower, and if the fuel concentration becomes too low, a region where the main injected fuel is ignited and the ignition is supplied will not be burned. FIG. 18 shows a state in which an incombustible mixture 88 having a fuel concentration lower than the flammable limit is formed outside the mixture 86 having a combustible fuel concentration.
In addition, since the intake air actually flows in the combustion chamber, as shown conceptually in FIG. 18, the low-concentration air-fuel mixture 88 that cannot be burnt exists around the outer periphery of the air-fuel mixture 86 in the combustible range. Although not necessarily, for ease of understanding, the thin non-combustible air-fuel mixture 88 is shown as being present on the outer peripheral portion for convenience.

Further, if the diffusion range of the fuel injected by the auxiliary injection is widened, the isolated mixture 89 which is isolated and in which the flame by the main injection cannot propagate is likely to be generated. In other words, if the fuel mixture stays in a narrow range during the diffusion of fuel, such an isolated fuel mixture is unlikely to be generated, but if the diffusion range is wide, the effect of the flow of air flowing into the fuel chamber will increase. Such an isolated fuel mixture is more likely to be generated.

As shown in FIG. 18, even when the timing of the auxiliary injection is advanced and the main injection is performed, the non-combustible mixture 88 whose fuel concentration is lower than the flammable limit, or the flame exists because it exists in isolation. The isolated mixture 89 that cannot be propagated is discharged together with the exhaust gas without burning. For this reason, when the auxiliary injection timing is advanced, the emission amount of the hydrocarbon compound increases. The principle described above holds true in the case where the main injection timing is retarded instead of advancing the auxiliary injection timing. For this reason, even if the main injection timing is retarded, it is possible to increase the emission amount of the hydrocarbon compound.

When the amount of fuel for auxiliary injection is increased,
Since the fuel concentration of the isolated mixture 89 as shown in FIG. 18 increases, the amount of emission of hydrocarbon compounds tends to increase accordingly.

As described above, at the time of the unibus combustion control, the amount of the hydrocarbon compound in the exhaust gas can be immediately increased by changing the timing of the auxiliary injection or the main injection. As described above, the particulate filter 100 uses the oxidation reaction of the hydrocarbon-based compound in the exhaust gas to burn the collected carbon-containing suspended particulates, so that the amount of the hydrocarbon-based compound discharged can be reduced quickly. If it can be increased to, the particulate filter 10
This is preferable because the natural regeneration function can be promptly promoted.

In the above-described method, the amount of the hydrocarbon-based compound in the exhaust gas can be accurately controlled by adjusting parameters such as the timing of the auxiliary injection or the main injection. Therefore, it is preferable because a sufficient and necessary amount can be supplied to promote the natural regeneration function of the particulate filter 100.

As described above, in addition to changing the control parameters of the unibass combustion to increase the emission of hydrocarbon compounds, for example, by increasing the supercharging pressure,
If the amount of oxygen in the exhaust gas is also increased, the natural regeneration function of the particulate filter 100 can be further promoted. Instead of increasing the supercharging pressure, it goes without saying that air may be introduced into the exhaust pipe using, for example, an air pump or a reed valve.

The hydrocarbon-based compound discharged by changing the control parameters of the Unibus combustion is injected into the combustion chamber and discharged after being exposed to a high-temperature and high-pressure environment. Since the fuel is decomposed and burnt easily, the natural regeneration function of the particulate filter 100 can be effectively promoted.

As a matter of course, instead of changing the control parameters of the unibus combustion as described above, the method of so-called post-injection, that is, by significantly delaying the fuel injection timing from the normal timing, the It is also possible to increase emissions.

B-5. Modifications Although various embodiments have been described above, the present invention is not limited to all the above embodiments, and can be implemented in various modes without departing from the gist thereof.

For example, in the above-described embodiment, the particulate filter has been described as having a metal nonwoven fabric. However, the present invention can be applied to other well-known filters such as ceramic filters.

Further, in the above-described embodiment, in the EGR control, the oxygen amount in the exhaust gas is increased by fully closing the EGR valve 62. However, for example, in the operating condition where the supercharging pressure is high, The EGR valve 62 may be opened. If the EGR valve 62 is opened when the supercharging pressure is high,
It is possible to directly supply air from the intake side to the exhaust side through the passage 60 to increase the amount of oxygen supplied to the particulate filter 100.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a diesel engine to which an exhaust gas purification device of the present embodiment is applied.

FIG. 2 is an explanatory diagram showing the external shape and structure of the particulate filter of the present embodiment.

FIG. 3 is an explanatory view conceptually showing a state in which particulates in exhaust gas are collected in the particulate filter of the present embodiment.

FIG. 4 is an explanatory diagram illustrating the specifications of a nonwoven fabric used in the particulate filter of the present embodiment.

FIG. 5 is an explanatory view conceptually showing a state in which particulates in exhaust gas are collected in a particulate filter according to a modification of the present embodiment.

FIG. 6 is an explanatory view exemplifying compositions of carbon-containing suspended particulates and hydrocarbon compounds contained in exhaust gas of a diesel engine.

FIG. 7 is an explanatory view conceptually showing how the particulate filter according to the present embodiment burns the collected fine particles.

FIG. 8 is an explanatory view conceptually showing a mechanism by which the particulate filter of the present embodiment disperses and collects carbon-containing suspended particulates and the like in exhaust gas.

FIG. 9 is a flowchart illustrating an engine control routine of a diesel engine to which the exhaust gas purifying apparatus of the embodiment is applied.

FIG. 10 is a flowchart showing a flow of processing for setting a control mode in an engine control routine.

FIG. 11 is an explanatory diagram showing an engine operating region in which a unibus combustion control is performed in a diesel engine to which the exhaust gas purification device of the present embodiment is applied.

FIG. 12 is an explanatory diagram showing a configuration of 1-byte data indicating a control mode of an engine.

FIG. 13 is a flowchart showing a flow of processing for setting a reproduction level when performing filter regeneration control.

FIG. 14 shows EGR performed in an engine control routine.
It is a flowchart which shows the flow of control.

FIG. 15 is a flowchart showing a flow of supercharging pressure control performed in an engine control routine.

FIG. 16 is an explanatory diagram conceptually showing the principle of the unibus combustion control.

FIG. 17 is a flowchart showing a flow of fuel injection control performed in an engine control routine.

FIG. 18 is an explanatory diagram showing the reason why the emission amount of the hydrocarbon-based compound increases by changing the control parameter of the unibus combustion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Diesel engine 12 ... Intake pipe 14 ... Fuel injection valve 16 ... Exhaust pipe 18 ... Fuel supply pump 20 ... Supercharger 21 ... Turbine 22 ... Compressor 23 ... Shaft 24 ... Intercooler 26 ... Air cleaner 30 ... Engine control ECU 32 ... Crank angle sensor 34 ... Accelerator opening sensor 60 ... EGR passage 62 ... EGR valves 64 and 66 ... Pressure sensor 70 ... Actuator 72 ... Waste gate valve 74 ... Waste gate actuator 80 ... Auxiliary fuel spray 82 ... Fuel mixture 84 ... Main Fuel spray 86 ... Air-fuel mixture 88 ... Incombustible air-fuel mixture 89 ... Isolated air-fuel mixture 100 ... Particulate filter 102 ... Case 104 ... Element 106 ... Non-woven fabric 108 ... Corrugated plate 110 ... Center rod 112 ... Seal plate 113 ... End

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 25/00 F02M 25/00 HK ST 25/07 570 25/07 570P 570J // B01D 46/42 B01D 46/42 A (72) Inventor Zenichiro Kato 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Toshihisa Sugiyama 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Yoshimitsu Henda 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Kazuhiko 1 Toyota Town Toyota City, Aichi Prefecture Inside Toyota Motor Corporation F-term (reference) 3G062 AA01 AA05 BA04 BA05 DA02 FA08 GA06 3G090 AA01 AA02 AA04 BA01 CA01 CA02 CB18 DA01 DA03 DA04 DA11 DA12 DA13 DA18 DA20 EA04 EA05 EA06 3G301 HA02 HA11 HA13 L B11 MA11 MA18 MA23 MA26 MA27 NC02 ND05 NE12 PA16A PB01Z PD15A PE01Z PE08Z PF03Z 4D058 JA32 MA41 MA51 MA52 PA01 QA25 SA08

Claims (15)

[Claims] 1. An exhaust gas purifying apparatus for purifying carbon-containing suspended particulates contained in exhaust gas of an internal combustion engine, wherein the hydrocarbon-based compound and the carbon-containing suspended particulates contained in the exhaust gas are removed from the exhaust gas. By dispersing and collecting so as to be capable of contacting with the oxygen of the exhaust gas, the temperature at the time of inflow is lower than the flammable temperature of the carbon-containing suspended fine particles using exhaust gas,
A trapping filter for burning the trapped hydrocarbon-based compound and the carbon-containing suspended particulates, and determining whether or not the trapping amount of the carbon-containing suspended particulates in the trapping filter exceeds a predetermined allowable value. Trapping amount determining means, and an oxygen supply amount increasing means for increasing the supply amount of oxygen to the trapping filter when the trapping amount of the carbon-containing suspended particulates exceeds the predetermined allowable value. An exhaust gas purification apparatus comprising: 2. The exhaust gas purifying apparatus according to claim 1, wherein the internal combustion engine is provided on the recirculation passage, and a recirculation passage for extracting a part of the exhaust gas from the exhaust passage and recirculating the exhaust gas to the intake passage. An exhaust gas recirculation valve for controlling the recirculation of the exhaust gas. The oxygen supply amount increasing means controls the exhaust gas recirculation valve to reduce the amount of the exhaust gas recirculated. Purification device. 3. The exhaust gas purifying apparatus according to claim 1, wherein the internal combustion engine includes a supercharger that increases the amount of air taken in by the internal combustion engine using flow energy of the exhaust gas. The exhaust gas purifying device, wherein the oxygen supply amount increasing unit is a unit that controls an operating state of the supercharger to increase an intake air amount of the internal combustion engine. 4. The exhaust gas purifying apparatus according to claim 3, wherein the oxygen supply amount increasing unit increases the intake air amount of the internal combustion engine by increasing a flow energy of the exhaust gas. There is an exhaust gas purification device. 5. The exhaust gas purifying apparatus according to claim 4, wherein the flow energy of the exhaust gas is increased by increasing the temperature of the exhaust gas. 6. An exhaust gas purifying apparatus for purifying carbon-containing suspended particulates contained in exhaust gas of an internal combustion engine, wherein the hydrocarbon-based compound and the carbon-containing suspended particulates contained in the exhaust gas are removed from the exhaust gas. By dispersing and collecting so as to be able to contact oxygen, the temperature at the time of inflow is lower than the flammable temperature of the carbon-containing suspended particulates using exhaust gas,
A collection filter for burning the collected hydrocarbon-based compound and the carbon-containing suspended fine particles, and determining whether or not the collection amount of the carbon-containing suspended fine particles in the collection filter exceeds a predetermined allowable value. A trapping amount determination unit, and a hydrocarbon compound that increases a supply amount of the hydrocarbon compound to the trapping filter when the trapping amount of the carbon-containing suspended particulates exceeds the predetermined allowable value. An exhaust gas purifying apparatus comprising: a supply amount increasing unit. 7. The exhaust gas purifying apparatus according to claim 6, wherein the internal combustion engine separates a main fuel corresponding to a majority of a fuel amount determined according to a required value of an engine output and a remaining auxiliary fuel into a combustion chamber. The hydrocarbon-based compound supply amount increasing means is configured to inject the main fuel and the sub-fuel at intervals of a predetermined value or more, so that the supply amount of the hydrocarbon-based compound is increased. Exhaust gas purifying device, which is means for increasing the amount of exhaust gas. 8. The exhaust gas purifying apparatus according to claim 7, wherein the hydrocarbon compound supply amount increasing means injects the auxiliary fuel earlier than the main fuel to thereby increase the hydrocarbon-based compound supply amount. An exhaust gas purifying device, which is a means for increasing a supply amount of a compound. 9. The exhaust gas purifying apparatus according to claim 7, wherein the hydrocarbon compound supply amount increasing means injects the auxiliary fuel at a later time than the main fuel to thereby provide the hydrocarbon-based compound. An exhaust gas purifying device, which is a means for increasing a supply amount of a compound. 10. The exhaust gas purifying apparatus according to claim 7, wherein the hydrocarbon compound supply amount increasing means increases the supply amount of the hydrocarbon compound by increasing the auxiliary fuel. Is an exhaust gas purification device. 11. The exhaust gas purifying apparatus according to claim 1, wherein the trapping amount determination unit determines whether the trapping amount of the carbon-containing suspended particulates exceeds the predetermined allowable value. An exhaust gas purifying device, which is a means for determining whether or not to perform the determination based on a pressure in an exhaust passage on an upstream side of the collection filter. 12. The exhaust gas purifying apparatus according to claim 11, wherein the trapping amount determining unit is configured to detect a pressure in a downstream exhaust passage in addition to a pressure in an upstream exhaust passage of the trapping filter. An exhaust gas purification device that is means for making a determination based on the exhaust gas. 13. The exhaust gas purifying apparatus according to claim 11, wherein the trapping amount determining unit is configured to determine a trapping amount based on an operating condition of the internal combustion engine in addition to a pressure in an exhaust passage on an upstream side of the trapping filter. Exhaust gas purifying device, which is a means for making a judgment. 14. An exhaust gas purifying method for purifying carbon-containing suspended particulates contained in exhaust gas of an internal combustion engine, wherein a trapping filter is provided in an exhaust passage of the internal combustion engine, and carbonization contained in the exhaust gas is provided. The hydrogen-based compound and the carbon-containing suspended particulates are collected in a state of being dispersed so as to be able to contact oxygen in the exhaust gas, and the temperature flowing into the collection filter is lower than the flammable temperature of the carbon-containing suspended particulates. Using the exhaust gas, the collected hydrocarbon-based compound and the carbon-containing suspended particulates are burned, and whether or not the trapping amount of the carbon-containing suspended particulates in the collection filter exceeds a predetermined allowable value. And determining if the trapping amount exceeds the predetermined allowable value, increasing the supply amount of oxygen to the trapping filter. 15. An exhaust gas purifying method for purifying carbon-containing suspended particulates contained in exhaust gas of an internal combustion engine, wherein a trapping filter is provided in an exhaust passage of the internal combustion engine, and carbonization contained in the exhaust gas is provided. The hydrogen-based compound and the carbon-containing suspended particulates are collected in a state of being dispersed so as to be able to contact oxygen in the exhaust gas, and the temperature flowing into the collection filter is lower than the flammable temperature of the carbon-containing suspended particulates. Using the exhaust gas, the collected hydrocarbon-based compound and the carbon-containing suspended particulates are burned, and whether or not the trapping amount of the carbon-containing suspended particulates in the collection filter exceeds a predetermined allowable value. And determining that the amount of the hydrocarbon-based compound supplied to the collection filter is increased when the collection amount exceeds the predetermined allowable value.