DE10251686B4 - Emission control system and method for an internal combustion engine - Google Patents

Abstract

An exhaust purification system for an internal combustion engine comprising: a particulate filter device (42, 142) for trapping foreign matter contained in the exhaust gas of the internal combustion engine, the filter device (42, 142) being recoverable by burning the foreign matter trapped by the filter; by adding fuel to the exhaust gas and increasing the temperature of the filter by burning the fuel; a combustion chamber fuel injection device (13) which is provided in a combustion chamber of the engine, which can perform not only a main fuel injection, which is provided for generating a torque, but also a secondary fuel injection, which is provided for increasing the temperature of the filter device (42, 142) by burning this fuel in the exhaust passage; and an exhaust passage fuel injection device (17) provided in an exhaust passage of the engine upstream of the filter device (42, 142); characterized in that when a recovery process of the filter device (42, 142) is to be performed, fuel is supplied through the combustion chamber fuel injector (13) when a bed temperature ...

Description

The invention relates to an exhaust gas purification system and a method for an internal combustion engine and in particular to a fuel delivery control or regulation.

In view of internal combustion engines used in automobiles, it has become necessary in recent years to reduce the exhaust emissions by eliminating harmful gas components such as carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx) contained in the exhaust gas which is discharged from an internal combustion engine before the exhaust gas is released into the ambient air.

In a diesel engine as a self-igniting engine using light oil as a fuel, it is particularly important to eliminate fine particles (foreign matter) such as soot and SOF (soluble organic fraction) contained in the exhaust gas, and carbon monoxide (CO). Hydrocarbons (HC), nitrogen oxides (NOx) and so on.

Each impurity is a mixture containing soot as its main component and a variety of other substances. The soot has its origin in the fuel and forms a black smoke. These ingredients are classified into insoluble substances such as carbon black and sulfates, and soluble substances (SOF) such as unburned fuel components and unburned oil components depending on whether they are soluble in an organic solvent.

As a result, it is believed that soot is produced as complicated as the reactions that occur when combusting fuel with an insufficient amount of air. In particular, fuel molecules are pyrolyzed to be dehydrated, thereby producing cores of foreign matter (precursors of carbon black). The cores then stick together to adhere to each other, thereby producing soot. In diesel combustion, a large amount of soot is generated during diffusion combustion of fuel. However, when air is introduced into a flame at a late stage of combustion, afterburning occurs and the generated soot is immediately reduced. Sulfates are produced in the form of sulfuric acid mist when sulfur components are oxidized to bind water during combustion.

In a known method, however, a particulate filter is arranged in an exhaust passage of a diesel engine. The particulate filter is formed of a substrate including a large number of fine pores formed by entrained air bubbles to increase its specific surface area per unit volume. As the exhaust gas passes through the pores of the filter, foreign substances contained in the exhaust gas are adsorbed and thus trapped on the surfaces of the filter.

However, if excess impurities are accumulated and accumulated on the particulate filter, the trajectories of the exhaust gas in the filter become clogged, thereby blocking the flow of the exhaust gas.

When the flow of the exhaust gas is blocked at the particulate filter as described above, the pressure of the exhaust gas increases in a portion of the exhaust passage, which is upstream of the particulate filter and thus the increased exhaust pressure acts as a back pressure on the internal combustion engine.

Thus, it is necessary to recover the particulate filter by eliminating the foreign matter accumulated there before the amount thereof becomes excessively large.

One method of restoring a particulate filter is to create an oxidizing atmosphere in the particulate filter to oxidize or burn contaminants trapped thereon.

However, the foreign substances ignite at a high temperature of about 500 to 700 ° C. For oxidizing the trapped impurities in the above manner, therefore, it is necessary to raise the temperature of the atmosphere in the particulate filter to 500 to 700 ° C and to generate an oxygen surplus atmosphere in the vicinity of the particulate filter.

However, since a diesel engine generally performs lean combustion in most operating ranges by generating excessively rich atmospheres, the combustion temperature of the air-fuel mixture tends to be low and the temperature of the exhaust gas accordingly exhibits a tendency to be low. Accordingly, in diesel engines, it is difficult to raise the temperature of the atmosphere in the particulate filter to 500 ° C or higher merely by applying the heat of the exhaust gas.

In this regard, a diesel exhaust particulate filter has been proposed, as in the published patent application of Japanese Patent Application No. 7-106290 is disclosed, the exhaust particulate filter disclosed in this publication can cause ignition of the foreign matters even at a relatively low temperature of about 350 to 400 ° C by carrying catalytic substances including a mixture of a platinum group metal and an alkaline earth metal oxide.

However, in diesel engines, the exhaust gas temperature hardly increases to 350 ° C or higher in a low load operating range, although it may increase to 350 ° C or higher in a high load operating range. Therefore, when the diesel engine is operated at a low load, particularly when the fuel injection is stopped or stopped, such as in the deceleration of the vehicle, a low-temperature exhaust gas is discharged from the diesel engine. It is assumed that the particulate filter is cooled down by the exhaust gas, resulting in a reduction of the oxidation capacity of the particulate filter with respect to the foreign matters.

Accordingly, when the impurities at the particulate filter are oxidized while the engine is operated at a low load, it is necessary to heat the particulate filter to at least a minimum temperature for causing the oxidation of the impurities.

One method of increasing the temperature of the particulate filter is to apply fuel to the particulate filter. In this method, the bed temperature of the particulate filter is increased by the heat generated in the oxidation of the applied fuel to thereby burn and oxidize the foreign matter on the filter.

For the supply of the fuel for raising the bed temperature of the particulate filter, the following methods are used. One method is to perform a secondary fuel injection. In this method, a part of the fuel to be injected into each cylinder of the engine is secondarily injected as a power source after the combustion process of the fuel is finished. Thus, the fuel is applied to the filter by discharging the exhaust gas to which unburned fuel is supplied as described above into the exhaust passage. The other method is to provide a fuel injection device in the exhaust passage to inject the fuel directly into the exhaust gas.

The former method, wherein the fuel is supplied into the cylinders as unburned fuel, is characterized in that the supplied fuel can be sufficiently atomized. Specifically, the fuel in the form of a mist is injected into each combustion chamber at a high temperature. The fuel is sufficiently atomized by evaporation in each combustion chamber. Thus, the combustion reactivity of the fuel on the particulate filter is improved so that the fuel can react even when the bed temperature of the particulate filter is in the range of the minimum temperature for causing a combustion reaction of the fuel.

According to this method, the atomized fuel passes through the upstream portion to react in the downstream portion even if the temperature distribution in the particulate filter is uneven, the temperature of a downstream portion of the filter reaches the reaction temperature, whereas the temperature of an upstream portion thereof does not do. Thus, it is possible to heat the particulate filter as a whole to a temperature required for causing the oxidation of the impurities.

However, the above method wherein the fuel is supplied into each cylinder as unburned fuel involves the following problems. First, because part of the fuel to be converted into energy is used, the absolute amount of the fuel to be supplied is limited. Second, if the engine is operated at a high load, it may be that the supply of the fuel is not allowed because a resulting decrease in torque is feared.

In contrast, according to the other method, wherein fuel is injected and thus supplied into the exhaust passage, the fuel is supplied via a system other than that used for supplying the fuel in each cylinder of the engine. Therefore, it is possible to supply a large amount of fuel and execute on the fuel injection regardless of the operating state of the engine.

However, this method wherein the fuel is injected into the exhaust passage involves the following problems. Since fuel is injected in a liquid state in the form of a mist, the exhaust gas temperature at a fuel injection portion, that is, a portion where the fuel is injected, must be high enough to atomize the fuel in a short time. Furthermore, the fuel can not be completely atomized during the feed. Therefore, in the reaction of the fuel thereto, the heat of the particulate filter is removed as latent heat to convert the fuel in a liquid state to a fuel gas. Accordingly, the bed temperature of the particulate filter must be higher than the minimum temperature for causing the reaction of the fuel. When injecting the fuel also a part of the fuel adheres to the exhaust pipes. If the exhaust gas temperature is low, the adhering fuel may accumulate in a liquid state. Thus, a countermeasure is required in particular if the Fuel is injected at a portion having a trap shape such as a manifold.

DE 41 17 676 A1 discloses an exhaust system for regenerating a particulate filter in which combustor fuel injection or exhaust manifold fuel injection is performed. Further, also reveal EP 0 070 619 A2 and JP-A 2003 120 373 Exhaust system with a filter whose temperature is increased by adding unburned fuel.

In view of the above problems, the invention has been made to provide an exhaust gas purifying system according to claim 1 and a method according to claim 10 for an internal combustion engine suitable for selecting an efficient fuel supply method based on various states of an internal combustion engine and an exhaust system to foreign matters eliminate that are accumulated on a particulate filter.

The exhaust gas purification system of the invention includes a filter disposed in an exhaust passage of the internal combustion engine and for trapping foreign matter contained in the exhaust gas, combustor fuel supply means for injecting a secondary fuel in addition to a main injection of fuel converted to energy in each Combustion chamber of the internal combustion engine, and a Abgaskanalkellstoffzufuhreinrichtung, which is arranged in the exhaust passage and the injection of fuel into the exhaust gas inside. When the secondary fuel injection can be performed and the bed temperature of the filter is equal to or higher than a first temperature, a temperature that causes oxidation of a fuel gas, the exhaust gas purification system constructed as described above injects fuel through the combustor fuel supply. On the other hand, when the temperature is equal to or higher than a second temperature, a temperature that does not cause condensation of the fuel injected into the exhaust passage, and a third temperature, a temperature that causes oxidation of the fuel gas including fuel droplets, the exhaust purification system injects Fuel through the Abgaskanalkinnstoffzufuhreinrichtung.

The exhaust gas purification system is adapted to apply fuel to the filter by selectively performing the secondary fuel injection into each combustion chamber and injecting fuel into the exhaust passage in accordance with thermal states of the peripheral elements that change depending on the operating state of the internal combustion engine, respectively.

That is, when the condition regarding the internal combustion engine that requires the internal combustion engine to run at a low load so that the secondary fuel injection can be performed and the condition regarding the bed temperature of the filter requires that the bed temperature be equal to or higher than a predetermined one When both are satisfied, the exhaust purification system performs the supply of the fuel by performing the secondary fuel injection into each combustion chamber. On the other hand, when the condition regarding the exhaust passage that requires the temperature of the exhaust passage is equal to or higher than a predetermined temperature, and the condition regarding the bed temperature of the filter requires that the bed temperature of the filter be equal to or higher than the predetermined temperature When both are met, the exhaust gas purifying system carries out the supply of the fuel by injecting fuel into the exhaust passage.

It may also happen that the conditions allow the supply of the fuel to be performed by each of the above two fuel supply devices. Namely, this is the case when the secondary fuel injection into each combustion chamber is permitted and the bed temperature of the filter is equal to or higher than both the first temperature causing oxidation of a fuel gas and the third temperature causing oxidation of a fuel gas including fuel droplets and the temperature in the exhaust passage is equal to or higher than the second temperature, which does not cause condensation of the fuel to be injected into the exhaust passage. At this time, the exhaust gas purifying system performs the supply of the fuel by one or both of the combustor fuel supply device and the exhaust gas piping fuel supply device.

As described above, the bed temperature of the filter is employed as a state for carrying out the supply of the fuel either through the combustor fuel supply means or the exhaust gas fuel supply means. The first temperature to be met in the supply of the fuel through the combustor fuel supply means is a minimum temperature for causing the oxidation of the fuel at the filter. On the other hand, the third temperature to be satisfied upon supply of the fuel by the exhaust gas fuel supply means is a minimum temperature for causing the oxidation of the fuel even after the latent heat has been extracted from the filter to completely atomize a fuel gas including the fuel droplets. Due to the latent heat generated when converting the fuel into a fuel gas as described above, therefore, the third temperature to be higher than the first temperature.

When the fuel is supplied through the combustor fuel supply, the fuel is completely atomized in each combustion chamber at a high temperature prior to application to the filter, thereby achieving a desirable fuel burn reactivity. Thus, a combustion reaction of the fuel can be caused even at the first temperature in a low-temperature region. On the other hand, when the fuel is supplied by being injected into the exhaust passage, the fuel is injected in the form of a mist and then atomized by the atmosphere in the vicinity of the fuel injection portion before being applied to the filter. In some cases, however, the injected fuel is not completely atomized depending on the state of the surrounding atmosphere. Therefore, the supply of the fuel is allowed only when the bed temperature of the filter is equal to or higher than the third temperature in a high-temperature region.

In the context of the first and third temperatures, the second temperature must be a temperature that does not cause condensation of the fuel injected into the exhaust passage, namely, a temperature at which the fuel injected into the exhaust passage is maintained can be without collecting as a liquid fuel in the channel.

The filter carries a storage reduction NOx catalyst. This catalyst can store nitrogen oxides contained in the exhaust gas when the oxygen concentration in the exhaust gas is high, and release the stored nitrogen oxides when the oxygen concentration decreases and there is fuel serving as a reducing agent.

Besides the above-described properties, the storage-reduction type NOx catalyst also serves to activate oxygen in the exhaust gas when the oxygen concentration in the exhaust gas is high, and to reduce the nitrogen oxides and generate active oxygen when the oxygen concentration decreases and fuel is present. which serves as a reducing agent. The active oxygen thus generated is used for removing nitrogen oxides in the exhaust gas and also acts as an oxidizing agent used in the combustion of the foreign matters.

In the invention, foreign matters collected at the particulate filter can be effectively eliminated in accordance with various conditions relating to the internal combustion engine and the exhaust system.

The above-mentioned exemplary embodiment or other exemplary embodiments, objects, features, advantages, technical and industrial significance of this invention will be better understood by reading the following detailed description of the exemplary embodiments of the invention when considered in conjunction with the accompanying drawings.

1 shows a schematic view of a construction of a diesel engine system including an exhaust gas purification system according to an embodiment of the invention.

2 shows a schematic view of a construction of an ECU of the exhaust gas purification system according to the embodiment of an invention and its peripheral configuration.

3 shows a schematic view of a cross section of a catalyst housing of the exhaust gas purification system according to an embodiment of the invention.

4 shows schematic cross sections of an internal combustion engine and an exhaust system when a combustion chamber fuel injection is performed according to an embodiment of the invention.

5 shows a schematic view of cross-sections of the internal combustion engine and the exhaust system when an exhaust gas fuel injection is performed according to an embodiment of the invention.

6 FIG. 10 is a flowchart of a foreign matter elimination control routine used in an embodiment of the invention. FIG.

And 7 shows a schematic view of a cross section of a catalyst housing including a filter device according to a modified example of the embodiment of the invention and agrees 3 match.

In the following description and the accompanying drawings, the invention will be described in more detail with respect to the exemplary embodiments.

The invention will be described below with reference to its embodiments. In the embodiments, the exhaust gas purification system and the method according to the invention are incorporated in a diesel engine system.

With reference to 1 is an internal combustion engine 1 (hereinafter referred to as an engine a four-cylinder diesel engine system. The motor 1 includes as its main components a fuel supply system 10 , Combustion chambers 20 , an intake system 30 , an exhaust system 40 Etc.

The fuel delivery system 10 includes a feed pump 11 , a store 12 (Common rail), fuel injection valves 13 , a shut-off valve 14 , a fuel supply nozzle 17 , an engine fuel passage P1, a supply fuel passage P2, and other components.

The feed pump 11 is adapted to pressurize high pressure fuel supplied from a fuel tank (not shown) to the common rail 12 to be supplied via the engine fuel passage P1. The common rail 12 serves as a reservoir for holding the high pressure fuel from the feed pump 11 is supplied at a predetermined high pressure and distributes the stored fuel to the fuel injection valves 13 , Each of the fuel injection valves 13 is an electromagnetic valve with an electromagnetic solenoid (not shown) provided inside and is controlled to open, if necessary, to fuel in a corresponding one of the combustion chambers 20 inject.

The feed pump 11 carries a part of the fuel from the fuel tank to the fuel supply nozzle 17 to via the feed fuel passage P2. In the feed fuel passage P2 is the check valve 14 between the feed pump 11 and the fuel supply nozzle 17 arranged. The shut-off valve 14 is used to shut off the supply fuel passage P2 to stop the fuel supply in an emergency. Like the fuel injectors 13 is the fuel supply nozzle 17 an electromagnetic valve and suitable for injecting the fuel serving as a reducing agent into the exhaust system 40 into it.

The intake system 30 forms a channel (an intake passage) of the intake air to each combustion chamber 20 to be fed. On the other hand, the exhaust system forms 40 a passage (exhaust passage) of the exhaust gas coming from the combustion chamber 20 is delivered.

The motor 1 By the way, with a known charging device 50 (ie a turbocharger) provided. The turbocharger 50 includes a turbine wheel 52 and a compressor 53 that over a wave 51 coupled together. The compressor 53 is the intake air in the intake system 30 whereas the turbine wheel 52 the exhaust gas in the exhaust system 40 is exposed. The thus constructed turbocharger 50 Serves (a charging function) increasing the pressure of the intake air by turning the compressor 53 wherein the hydrodynamic energy is applied to the flow of the exhaust gas, which is the turbine wheel 52 is exposed.

In the intake system 30 is an intercooler 31 in the turbocharger 50 provided for suitably forcibly cooling the intake air, which is heated when charging. A throttle 32 is downstream of the intercooler 31 intended. The throttle 32 is an electronically controlled on-off valve that can continuously change its opening amount and adjusting (decreasing) the supply amount of the intake air is used to reduce the area of a flow path of the intake air at predetermined conditions.

In the engine 1 is also an exhaust gas recirculation channel 60 (an EGR channel) provided. The EGR channel 60 serves as a bypass for connecting sections upstream and downstream of the combustors 20 (Sections in the intake system 30 and the exhaust system 40 ). In particular, the EGR channel connects 60 an exhaust manifold 40a upstream of the turbocharger 50 in the exhaust system 40 with a section of the intake system 30 downstream of the throttle 32 , During operation of the engine 1 becomes a part of the exhaust gas through the EGR channel 60 to the intake system 30 returned as necessary. The EGR channel 60 is with an EGR valve 61 which is electronically controlled to be continuously and continuously opened and closed, and thus is able to flexibly adjust the amount of exhaust gas in the EGR passage 60 flows. The EGR channel 60 is also with an EGR cooler 62 provided for cooling the exhaust gas passing through the EGR passage 60 flows through it while it is returned.

Further, on the downstream side of a portion of the exhaust system 40 in which the exhaust manifold 40a that with the respective combustion chambers 20 connected, and the turbine wheel 52 are provided, an exhaust passage 40b , a NOx catalyst housing 2 , and an exhaust duct 40c arranged sequentially along the flow of the exhaust gas. The catalyst housing 42 takes a storage reduction NOx catalyst 42b for eliminating harmful components contained in the exhaust gas, such as NOx, and a particulate filter 42a for removing foreign matter (PM) contained in the exhaust gas, such as soot together with harmful components such as NOx, as described later (see 3 ). In the embodiment, the catalyst housing 42 also as a filter device 42 designated.

Furthermore, there are different sensors in the respective sections of the engine 1 built-in. Each of the sensors generates a signal representing an environmental condition of a corresponding one Section of the engine 1 or the operating condition of the engine 1 suggests.

In particular, generates a common rail pressure sensor 70 a detection signal indicative of the pressure of the fuel in the common rail 12 is stored. A fuel pressure sensor 71 generates a detection signal indicative of a pressure PG (a fuel pressure) of the fuel passing through the supply fuel passage P2 and into the fuel supply nozzle 17 is introduced. An air flow meter 72 is in a section of the intake system 30 provided upstream of the throttle 32 and generates a detection signal indicating an intake air amount GA. An air fuel sensor 73 is in a section of the exhaust system 40 upstream of the catalyst housing 43 and generates a detection signal that changes continuously in accordance with the oxygen concentration in the exhaust gas. An exhaust gas temperature sensor 74 is also in a section of the exhaust system 40 downstream of the catalyst housing 42 and generates a detection signal indicative of exhaust gas temperature TEX of the exhaust gas. A NOx sensor 75 is also in a section of the exhaust system 40 downstream of the catalyst housing 42 and generates a detection signal that changes continuously in accordance with the NOx concentration in the exhaust gas. A catalyst inlet exhaust gas temperature sensor 78 is in a section of the exhaust system 40 an inlet of the catalyst housing 42 and generates a detection signal indicative of the temperature of the exhaust gas entering the catalyst housing 42 into flows. A filter bed temperature sensor 79 is in the catalyst housing 42 and generates a detection signal indicating the bed temperature of the catalyst. A pressure sensor 90 is upstream of the catalyst housing 42 and generates a detection signal indicative of the pressure in the exhaust passage.

In addition, an accelerator opening sensor 76 attached to an accelerator pedal (not shown) and generates a detection signal indicative of a depression amount ACC of the accelerator pedal used as a basis for determining the required operation load. A crank angle sensor 77 is suitable for generating a detection signal (pulse) every time an output shaft (a crankshaft) of the engine 1 turns around a predetermined angle. Each of these sensors 70 to 79 and 90 is electric with an electronic control unit (ECU) 80 connected.

As in 2 is shown, the ECU includes 80 a central processing unit 81 (CPU), a read-only memory 82 (ROM), a volatile random access memory 83 (RAM), a backup RAM 84 , the recorded information stops after the operation is stopped, a time counter 85 and so on. These components 81 to 85 , an external input circuit 86 including an analog-to-digital converter and an external output circuit 87 are through a bidirectional bus 88 connected together, whereby a logical calculation circuit is formed.

The ECU 80 is arranged to receive detection signals from the respective sensors via the external input circuit and perform basic controls such as a fuel injection control on the engine 1 by executing a program stored in the ROM 82 in the CPU 81 is stored. When feeding the ECU leads 80 various other controls and regulations based on the operating condition of the engine 1 such as a reduction feed control (fuel), a control performed upon the supply of a reducing agent (for example, fuel serving as a reducing agent) for determining the amount of fuel to be injected and a timing for supplying the fuel.

As described above, the exhaust gas purification system of the engine is 1 through the fuel supply system 10 arranged to supply the fuel to each cylinder via a corresponding one of the fuel injection valves 13 , the NOx catalyst and the particulate filter used in the exhaust system 40 is arranged, the ECU 80 which is operable to control and regulate the functions of the fuel supply system 10 , the NOx catalyst, the particulate filter and other components. Thus, the controls including the above-described fuel supply control by the operations of the ECU 80 which generates instruction signals related to the controls and the other components constituting the exhaust gas purification system.

Next, the construction and function of the catalyst housing 42 that in the exhaust system 40 as one of the components that the engine 1 form, is provided, described in detail.

3 FIG. 10 is an enlarged sectional view of a portion of the internal structure of FIG 1 shown catalyst housing 42 , The catalyst housing 42 takes the particle filter 42a on which the storage reduction NOx catalyst 42b wearing.

The NOx catalyst 42b comprises a support formed, for example, of aluminum (Al 2 O 3) as its main material, at least one element supported on the surface of the support and selected from alkali metals such as potassium (K), sodium (Na), lithium (Li) and cesium (Cs), alkaline earth metals, such as Barium (Ba), calcium (Ca) and rare earth metals such as yttrium (Y), and at least one noble metal serving as an oxidation catalyst (noble metal catalyst) such as platinum (Pt) supported on the support.

The particle filter 42a is formed of a porous material such as cordierite. As each end of the particulate filter 42a is closed, the exhaust gas, which has flowed into an inlet exhaust passage, passes through an environmental partition formed of a porous material and enters an adjacent exhaust outlet passage, as indicated by arrows in FIG 3 is shown.

In the embodiment, in the particulate filter 42a a layer of the support formed of aluminum or the like provided on a surface of the partition and on an internal surface of each pore of the partition. At this support, the NOx catalyst 42b supported, which is formed of the noble metal catalyst and a NOx absorbent.

The NOx absorbent has a storage property (absorption) with respect to NOx when the oxygen concentration in the exhaust gas is high, and a release property with respect to the NOx when the oxygen concentration in the exhaust gas is low. When the NO x is released into the exhaust gas with substances such as HC and CO, the noble metal catalyst also promotes the oxidation of HC and CO, thus causing the oxidation reduction reactions between NO x as an oxidizing substance and HC and CO as a reduction substance. As a result, HC and CO are oxidized to CO2 and H2O, respectively, whereas NOx is reduced to N2.

In the oxidation of HC, which is promoted by the noble metal catalyst, the NOx catalyst 42b As described above, a heat of reaction is generated here around the bed temperature of the NOx catalyst 42b to increase.

Incidentally, when the NOx absorbent has absorbed the NOx with a predetermined limit amount, it will continue to store further NOx even if the oxygen concentration in the exhaust gas is high. In the engine 1 Therefore, a reducing agent to a portion of the exhaust passage upstream of the catalyst housing 42 fed to the NOx catalyst 42b to reactivate by reducing and thus eliminating the absorbed NOx. This control is repeatedly performed at predetermined intervals to a NOx storage capacity (a NOx absorption capacity) of the NOx catalyst 42b restore before NOx is stored with the limit amount (absorbed).

The NOx catalyst 42b that is attached to the particulate filter 42a is carried, while a series of the processes for catching, reducing and eliminating the NOx is repeatedly performed as described above. The NOx catalyst generates secondary oxygen in a secondary way. When the exhaust gas through the particulate filter 42a As a result, foreign matter contained in the exhaust gas such as soot is trapped by the porous material. The trapped impurities immediately react with the active oxygen, which acts as an oxidant with extremely high reactivity (activity). Thus, the impurities become without generation of luminous flames on the NOx catalyst 42b eliminated, which is mentioned as a result of the supply of the fuel.

In the following, processes and methods of NOx removal will be described in detail.

In diesel engines, in general, the oxygen concentration in the air-fuel mixtures to be burned in the combustion chambers is high in most engine operating ranges. Normally, the oxygen concentration in an air-fuel mixture before combustion in the combustion chambers is directly reflected by the oxygen concentration in the exhaust gas. In particular, the oxygen concentration in the air-fuel mixture after combustion thereof decreases by one degree in accordance with the amount of oxygen used in the combustion. Therefore, when the oxygen concentration (air-fuel ratio) in the air-fuel mixture is high, the oxygen concentration in the exhaust gas basically becomes high in a similar manner.

As described above, the NOx catalyst has 42b a storage property with respect to NOx when the oxygen concentration in the exhaust gas is high and a reduction property with respect to NOx at NO2 or NO when the oxygen concentration in the exhaust gas is low. Thus, the NOx catalyst continues to absorb NOx as long as the oxygen concentration in the exhaust gas is high. However, the amount of NOx that can be stored in the NOx catalyst is limited as described above. When the NOx catalyst 42b Already NOx has absorbed with the limit amount, the NOx from the exhaust gas will not be trapped therefore by the NOx catalyst, but will enter as they are through the catalyst housing 42 therethrough.

In the above case, a reducing agent needs to be applied to the NOx absorbent for restoring the NOx storage capacity of the NOx catalyst as described above. If the fuel is normal However, it is difficult to generate an exhaust gas containing much fuel serving as a reducing agent with respect to the engine construction.

In the embodiment, therefore, the fuel is supplied into the exhaust gas using the methods described above. One method is to supply unburned fuel by injecting a secondary fuel in addition to a main fuel for conversion to energy in each combustion chamber of the internal combustion engine and the other method is injecting fuel into the exhaust gas using the fuel supply device located in the exhaust passage is provided. Using one or both of these methods, the amount of reducing agent in the exhaust gas is increased to restore the NOx storage capacity of the NOx catalyst.

The ECU 80 of the motor 1 continuously detects the NOx concentration in the exhaust gas in a portion of the exhaust system 40 downstream of the NOx catalyst 42b based on an output signal from the NOx sensor 75 , The NOx storage capacity (the NOx storage efficiency) of the NOx catalyst 42b decreases as the amount of in the NOx catalyst 42b stored NOx, in other words when in the NOx catalyst 42b NO x amount stored closer to a maximum amount (a saturation amount) of the NO x coming into the NO x catalyst 42b can be stored. That is, when the amount of in the NOx catalyst 42b stored NOx increases, a larger amount of NOx passes through the catalyst housing 42 through, as it is to be discharged on the downstream side, whereby the NOx concentration in the exhaust gas is increased. With such a correlative relationship between the NOx concentration in the exhaust gas and that in the NOx catalyst 42b stored NOx amount, it is possible to determine the amount of NOx contained in the NOx catalyst 42b is stored on the basis of the detected NOx concentration.

Thus, in the embodiment, the ECU 80 arranged to determine that in the NOx catalyst 42b stored NOx amount has reached a predetermined amount when the NOx concentration in a portion of the exhaust system 40 downstream of the catalyst housing 42 exceeds a predetermined value. When it is determined that NOx is stored at the predetermined amount, fuel becomes a portion of the exhaust system 40 upstream of the catalyst housing 42 fed. Specifically, fuel is supplied into the exhaust gas as unburned fuel using the fuel supply device, whereby the amount of the reducing agent in the exhaust gas is temporarily increased. At this time, the air-fuel ratio decreases to cause NOx stored in the catalyst to react with the fuel serving as a reducing agent to thereby be eliminated.

Next, the processes and methods for removing foreign matters (to be referred to as PM hereinafter) included in the exhaust gas will be described.

Like NOx, the foreign matter is eliminated using the fuel. The elimination of the NOx is effected by using chemical reactions between HC as a main component of the fuel and NOx as described above. On the other hand, in the removal of the foreign matters, HC is mainly used as a heat source to increase the bed temperature of the catalyst so that foreign matters and oxygen (O2) are activated to cause oxidation of the foreign matters and thus eliminate them.

That is, the elimination of the foreign matters is effected by using the fuel as a heat source in the particulate filter 42a namely by applying the combustion reactivity of the fuel.

In an example of a control method for removing foreign matters in the above manner, the ECU performs 81 a program made in the ROM 82 is stored to make a comparison judgment on a history of operation stored in the backup RAM 84 is recorded, a signal from the pressure sensor 90 which is disposed in the exhaust passage and so on. The operating history is established based on the output signals from the accelerator opening sensor 76 , the crank angle sensor 77 , the time counter 85 and other components. According to the result of the judgment, it is determined whether the supply of the fuel is to be performed as a process for removing the foreign matter.

In removing the foreign matter, the fuel is also supplied in the same process as used for removing NOx. That is, a method is to perform a secondary fuel injection (combustor fuel supply device). In the secondary fuel injection, a part of the main fuel to be converted into energy is injected into each combustion chamber of the internal combustion engine after the combustion process of the main fuel is finished, whereby unburned fuel is supplied into the exhaust gas, as in FIG 4 is shown. The other method is to provide a fuel injector or device in the exhaust passage (FIG. Exhaust duct fuel supply means). In this method, the fuel is injected directly into the exhaust gas as in 5 is shown. These methods have different characteristics and the characteristic of each method is one of reflected factors in the above judgment as to whether the supply of the fuel should be carried out.

Hereinafter, the characteristics of the combustor fuel supply device and the exhaust gas fuel supply device will be described, respectively.

• (1) Da der Kraftstoff in jede Brennkammer hinein eingespritzt wird, wird der Kraftstoff ausreichend zerstäubt.
• (2) Da der Kraftstoff zerstäubt wird und somit in aktiviertem Zustand in das Katalysatorgehäuse 42 eingeführt wird, tritt eine Verbrennungsreaktion des Kraftstoffs auf, selbst wenn die Betttemperatur des Katalysators bei einer ersten Temperatur liegt (die bei etwa 200°C angenommen wird), einer Minimaltemperatur, die erforderlich ist zum Veranlassen einer Verbrennungsreaktion des Kraftstoffs, der zerstäubt und somit aktiviert ist.
• (3) Die Kraftstoffeinspritzmenge kann nicht direkt gesteuert werden, da sie von der erforderlichen Kraftstoffmenge abhängig ist, die bestimmt wird auf der Grundlage des Niederdrückungsbetrags des Gaspedals. Eine große Kraftstoffmenge kann übrigens nicht verwendet werden.
• (4) Der Kraftstoff kann nicht zugeführt werden, wenn der Motor mit einer hohen Last betrieben wird oder wenn der Motor gestartet wird, um das Erzeugen einer Drehmomentabstufung oder dergleichen zu vermeiden.

First, the combustion chamber fuel supply device has the following characteristics:

• (1) Since the fuel is injected into each combustion chamber, the fuel is sufficiently atomized.
• (2) Since the fuel is atomized and thus in the activated state in the catalyst housing 42 is introduced, a combustion reaction of the fuel occurs even if the bed temperature of the catalyst is at a first temperature (assumed to be about 200 ° C), a minimum temperature required to cause a combustion reaction of the fuel, which is atomized and thus activated is.
• (3) The fuel injection amount can not be controlled directly because it depends on the required amount of fuel that is determined based on the depression amount of the accelerator pedal. Incidentally, a large amount of fuel can not be used.
• (4) The fuel can not be supplied when the engine is operated at a high load or when the engine is started to avoid generating a torque step or the like.

• (1) Da der Kraftstoff in den Abgaskanal hinein eingespritzt wird, wird befürchtet, dass der Kraftstoff nicht zerstäubt wird, sondern an der Innenfläche des Abgaskanals anhaftet, um daran zu kondensieren, außer wenn die Temperatur des Abgases gleich oder höher als eine zweite Temperatur ist (die bei etwa 300°C angenommen wird).
• (2) Es kann passieren, dass der Kraftstoff nicht vollständig zerstäubt wird und deshalb ein Teil des Kraftstoffs in das Katalysatorgehäuse 42 hineinfließt in der Gestalt von Kraftstofftröpfchen. Dabei wird dem Filter die Wärme als latente Wärme entzogen zum vollständigen Zerstäuben des Kraftstoffgases einschließlich der Kraftstofftröpfchen. Deshalb wird eine dritte Temperatur (die bei etwa 250°C angenommen wird), die höher als die erste Temperatur ist, als die Minimaltemperatur eingesetzt, die erforderlich ist zum Veranlassen einer Verbrennungsreaktion des Kraftstoffs an dem Filter.
• (3) Der Kraftstoff wird von einem separaten Kraftstoffzufuhrsystem zugeführt, gegenüber dem für die Zufuhr des Kraftstoffs, der bei der Motorverbrennung verwendet wird, deshalb ist es möglich, die Zufuhr des Kraftstoffs unabhängig von dem Betrieb des Motors auszuführen und die Einspritzmenge direkt zu steuern. Des Weiteren kann eine große Kraftstoffmenge verwendet werden.

On the other hand, the exhaust gas fuel supply device has the following characteristics:

• (1) Since the fuel is injected into the exhaust passage, it is feared that the fuel will not be atomized but will adhere to the inner surface of the exhaust passage to condense thereon unless the temperature of the exhaust gas is equal to or higher than a second temperature (which is assumed at about 300 ° C).
• (2) It may happen that the fuel is not completely atomized and therefore part of the fuel is in the catalyst housing 42 flows in the form of fuel droplets. The heat is removed from the filter as latent heat to completely atomize the fuel gas including the fuel droplets. Therefore, a third temperature (assumed to be about 250 ° C) higher than the first temperature is used as the minimum temperature required to cause a combustion reaction of the fuel to the filter.
• (3) The fuel is supplied from a separate fuel supply system to that for the supply of the fuel used in the engine combustion, therefore, it is possible to carry out the supply of the fuel independently of the operation of the engine and to directly control the injection amount. Furthermore, a large amount of fuel can be used.

The characteristics of the combustor fuel supply system and the exhaust gas fuel supply device are summarized as follows. First, according to the combustor fuel supply device, the fuel may be supplied even if the bed temperature of the catalyst is low, although the addition of the fuel is applied depending on the operating state of the engine. However, a large amount of fuel can not be used and the injection amount can not be easily adjusted. On the other hand, according to the exhaust gas fuel supply device, the fuel can be supplied regardless of the operating state of the engine, and the injection amount can be easily adjusted. However, the bed temperature of the catalyst must be high and the temperature of the exhaust passage is limited.

Next, controls will be described that are performed to determine whether the supply of the fuel is to be performed. The programs are determined based on the characteristics of the respective fuel supply methods. When it is determined that it is necessary to eliminate the stored foreign matters, first, a catalyst exit exhaust temperature, that is, a temperature of the exhaust gas flowing out from the catalyst is detected by the exhaust gas temperature sensor 74 measured. When the fuel is supplied, when the temperature in the catalyst housing 42 is in a high temperature range (≥ 700 ° C), the temperature further increases, resulting in heat deterioration of the NOx catalyst 42b can lead. The above measurement is mainly performed to prohibit the supply of the fuel when the temperature in the catalyst housing 42 in the high temperature range.

Next, a control for determining whether to supply the fuel by the combustor fuel supply means will be described. After the catalyst exit exhaust gas temperature is measured as described above, it is determined whether the engine is in a high load state based on signals from the accelerator opening sensor 76 and the crank angle sensor 77 and the Temperature of an engine coolant is measured by means of a water temperature gauge (not shown). The engine speed is particularly unstable immediately after the start of the engine and therefore the fuel is not supplied. Accordingly, in the embodiment, the measured coolant temperature is used as one of the criteria for determining whether the engine has been warmed up after starting the engine. Next, the bed temperature of the catalyst by means of the filter bed temperature sensor 79 measured. When it is determined that the bed temperature is equal to or higher than the first temperature (200 ° C), the fuel is supplied into the combustion chambers.

Next, a control for determining whether to supply the fuel through the exhaust gas fuel supply means will be described. After the catalyst exit exhaust gas temperature is measured as described above, a catalyst input exhaust temperature, that is, a temperature of the exhaust gas that enters the catalyst housing 42 flows in, by means of the catalyst input exhaust gas temperature sensor 78 measured. Although it is actually preferable to actually measure the temperature of the exhaust gas in the fuel injection portion, it is difficult to arrange the sensors. In the embodiment, therefore, the catalyst input temperature is measured, and the temperature of the exhaust gas at the fuel injection portion is estimated from the detected catalyst input exhaust gas temperature. If the catalyst input exhaust gas temperature is equal to or higher than the second temperature (300 ° C), then the bed temperature of the catalyst by means of the filter bed temperature sensor 79 measured. When the bed temperature is equal to or higher than the third temperature (250 ° C), the fuel is supplied into the exhaust passage and the fuel supply control for removing the foreign matters is stopped.

Hereinafter, the procedure of "fuel supply control" will be described in detail with reference to a flowchart of FIG 6 described by the ECU 80 of the motor 1 to be performed in the embodiment.

6 FIG. 12 is a flowchart showing processes of a "particulate filter removal routine", a routine to be used for controlling the fuel supply method and the fuel supply amount when performing particulate removal control. The ECU 80 starts the application of a routine at the same time as the start of the engine 1 ,

When this routine is started, the ECU determines 80 first at step S101, if necessary, the particulate removal control based on the operation history of a signal from the pressure sensor 90 and other components. The operation history is established by accumulating operation data obtained via the accelerator opening sensor 76 , the crank angle sensor 77 , the time counter 85 and so on. If it is determined that it is unnecessary to perform the particulate removal control, then the ECU proceeds 80 to step S112 and to step S113 to perform normal combustion without executing either the combustor fuel supply or the exhaust fuel supply and the ECU 80 then finish the routine. In contrast, when it is determined in step S101 that the particulate removal control needs to be performed, the ECU proceeds 80 to step S102.

In step S102, the ECU determines 80 the state of the catalyst housing 42 based on the catalyst exit exhaust temperature. When the catalyst exit exhaust temperature is equal to or higher than 700 ° C, the ECU advances 80 to step S112 and to step S113 to perform normal combustion without executing either the combustor fuel supply or the exhaust gasoline fuel supply and the ECU 80 then finish the routine. In contrast, when it is determined in step S102 that the catalyst exit exhaust gas temperature is lower than 700 ° C, the ECU advances 80 to step S103.

In the following steps after the step S102, processes are performed to determine whether the combustor fuel supply can be performed. First, the coolant temperature of the engine 1 measured at step S103. If the coolant temperature is lower than 60 ° C, the ECU will advance 80 to step S107 and to step S108 without executing the combustor fuel supply. In contrast, when the coolant temperature is equal to or higher than 60 ° C, the ECU advances 80 to step S104.

In step S104, the ECU determines 80 the load condition of the engine. When it is determined that the engine is operating at a high load, the ECU advances 80 to step S107 and to step S108 without executing the combustor fuel supply. Conversely, when the engine is operated at low load, the ECU advances 80 to step S105.

In step S105, the bed temperature of the catalyst is measured. When the bed temperature is lower than 200 ° C, the ECU advances 80 to step S107 and to step S108 without executing the combustor fuel supply. In contrast, when the bed temperature is equal to or higher than 200 ° C, the ECU advances 80 to step S106 continues to perform the combustion chamber fuel supply and then proceeds to step S108.

From S108, processes are performed to determine if the exhaust gas fueling can be performed. First, the catalyst input exhaust gas temperature is measured at step S108. When the catalyst input exhaust gas temperature is lower than 300 ° C, the ECU advances 80 to step S111 to complete the routine without performing the exhaust gas fueling. In contrast, when the catalyst input exhaust gas temperature is equal to or higher than 300 ° C, the ECU advances 80 to step S109.

At the step 109 the bed temperature of the catalyst is measured. When the bed temperature is lower than 250 ° C, the ECU advances 80 to step S111 to complete the routine without performing the exhaust gas fueling. In contrast, when the bed temperature is equal to or higher than 250 ° C, the ECU advances 80 to step S110 to perform the exhaust gas fueling and thereafter terminate the routine.

In the routine described above, the ECU determines 80 first, whether the combustor fuel supply is being executed, and then determines whether the exhaust gas fuel supply device is being executed. In fact, these two fueling controls are preferably performed independently of each other and are represented in separate control routines. In the routine of the embodiment, the ECU determines 80 however, performing the combustor fueling and then the exhaust gasoline fueling for ease of control. If, in contrast, the ECU 80 is arranged to perform the execution of the Abgaskanalkraftstoffzufuhr and then the combustion chamber fuel supply, this makes thus no difference in the actual control.

Hereinafter, a modified example of the embodiment described above will be described, wherein a catalyst housing 110 including a filter device 142 as it is in 7 is shown in place of the catalyst housing 42 (Filter device) is used. 7 By the way, that's right 3 match.

This modified example differs from the embodiment in that a catalyst 120 with an oxidation property such as a so-called oxidation catalyst upstream of the filter 42a ( 142a in 7 ) of the filter device 42 ( 142 in 7 ) is arranged; an exhaust gas temperature sensor 178 is provided between the catalyst 120 and the filter 142a ; and the filter bed temperature sensor 79 is not provided. In the modified example, therefore, the catalyst housing 110 through the catalyst 120 , the filter 142a and the exhaust gas temperature sensor 178 educated.

In the catalyst housing 110 are in particular the filter 142a the filter device 142 and the catalyst 120 which is a catalyst of a honeycomb structure having an oxidation property (for example, an oxidation catalyst carrying platinum Pt) and the upstream of the filter 142a is arranged in series with each other while being spaced from each other, and the exhaust gas temperature sensor 178 is between the catalyst 120 and the filter 142a intended.

With this arrangement, the fuel gas supplied into the exhaust gas in the secondary fuel injection and / or the fuel gas including the fuel droplets injected into the exhaust passage are burned (oxidized) on the oxidation catalyst 120 , whereby the temperature of the exhaust gas is increased, which passes. When the thus heated exhaust gas in the filter 142a flows into it, causing the trapped and collected foreign matter on the filter 142a oxidized and thus eliminated.

Incidentally, a catalyst having an oxidation property such as a NOx catalyst carrying platinum or the like may be used as the catalyst 120 be used, the upstream of the filter 142a is arranged.

The oxidation catalyst 120 is upstream of the filter 142a In the modified example, therefore, it is unnecessary to add a catalyst to the filter 142a to wear. A filter carrying a NOx catalyst, which in 3 can be shown, however, as the filter 142a be used.

Hereinafter, a control procedure used in the modified example will be described.

First, it determines if the secondary fuel injection into the combustion chamber 20 the internal combustion engine 1 to be carried out in it. Here is the secondary fuel injection in the combustion chamber 20 the internal combustion engine 1 performed when the exhaust gas temperature passing through the exhaust gas temperature sensor 178 is reached, reaches a temperature that causes fuel gas in the exhaust gas to be oxidized on the oxidation catalyst 120 (For example, 200 ° C or higher).

Next, it is determined whether fuel is to be injected into the exhaust passage based on the following two conditions. The first condition requires that the exhaust gas temperature passing through the exhaust temperature sensor 178 is high enough to cause a fuel gas including fuel droplets in the exhaust gas to the oxidation catalyst 120 is oxidized (for example, 250 ° C or higher). The second condition requires that the temperature (exhaust gas temperature) in a portion of the exhaust passage into which fuel is injected from the fuel supply nozzle 17 whose temperature is estimated based on the operating conditions of the engine 1 (that is, load and engine speed), is a temperature that does not cause condensation of the fuel that is in the portion of the engine 1 is injected (for example, 300 ° C or higher). If these two conditions are not met, fuel will leak from the fuel delivery nozzle 17 injected into the exhaust duct.

Furthermore, in the modified example with the exhaust gas temperature sensor 178 that is between the oxidation catalyst 120 and the filter 142a It is possible to directly detect the temperature of the exhaust gas that is heated by the oxidation of the fuel contained therein on the oxidation condenser upstream of the exhaust gas temperature sensor 178 is arranged.

Incidentally, the temperatures used in the respective processes of the routine of the embodiment are not limited, but may be changed depending on the engine and the exhaust system used. At step S108, the bed temperature is also measured and used for estimating the temperature of the exhaust gas at the fuel injection portion. However, this is only one method of estimating the temperature of the exhaust gas at the fuel injection portion. Thus, the temperature of the exhaust gas in the fuel injection portion may be estimated by another method, for example, based on the coolant temperature, the intake air temperature, the injection amount, the rotational speed, and so on. Any method can be used as long as the temperature can be estimated. This also applies to the other processes. For example, the coolant temperature and the load of the engine are respectively determined at steps S103 and S104 of the routine. However, each of these processes is just one example of the processes for determining if the secondary fuel injection of the engine is to be performed.

If the combustor fuel supply and the exhaust gas fuel supply are both allowable, one or both may also be performed. For example, if the predetermined temperatures used in the respective thermal states for performing the exhaust gas fuel supply are sufficiently satisfied when the engine is idling, it is not necessary to carry out the exhaust gas fuel supply. At this time, the foreign matters collected in the catalyst can be sufficiently removed only by performing the combustor fuel supply. Also, when the engine is alternately operated at a high load and a low load, the foreign matters can be sufficiently removed only by performing the exhaust gasoline fuel supply during the operation of the low load engine without performing the combustor fuel supply.

As described above, the exhaust gas purification system of the invention performs the supply of the fuel depending on the conditions of the engine of the exhaust system to increase the temperature of the particulate filter, which serves to oxidize the foreign matters contained in the exhaust gas. Thus, the foreign matter can be reliably eliminated with efficiency.

In particular, the exhaust gas purification system of the invention selects a suitable fueling method based on the operating state of the internal combustion engine and the thermal state of the exhaust system. Thus, the foreign matters can stably be burned on the filter without causing deterioration of the constituents of the exhaust gas flowing into the catalyst case, and clogging of the catalyst case by the supplied fuel is prevented.

An exhaust gas purification system and method for an internal combustion engine is provided, which includes a combustion chamber fuel supply device ( 13 ) suitable for the supply of a part of a fuel, which into respective combustion chambers ( 20 ), as a secondary injected fuel, and an exhaust gas fuel supply device ( 17 ) suitable for directly feeding fuel into an exhaust passage. The combustion chamber fuel supply device ( 13 ) is used when a secondary fuel injection can be performed and a bed temperature of a particulate filter ( 42a ) is equal to or higher than a first temperature. The exhaust gas fuel feed device ( 17 ) is used when a temperature of the exhaust passage is equal to or higher than a second temperature and the bed temperature of the filter ( 42a ) is equal to or higher than a third temperature.

Claims (12)

An exhaust purification system for an internal combustion engine, comprising: a particulate filter device ( 42 . 142 ) for capturing foreign matter contained in the exhaust gas of the internal combustion engine, wherein the filter device ( 42 . 142 ) can be recovered by burning the foreign matter caught by the filter by means of the supply of fuel to the exhaust gas and raising the temperature of the filter by burning the fuel; a combustion chamber fuel injection device ( 13 ) provided in a combustion chamber of the engine capable of performing not only a main fuel injection provided for generating a torque but also a secondary fuel injection provided for raising the temperature of the filtering device (FIG. 42 . 142 by burning this fuel in the exhaust passage; and an exhaust gas fuel injection device ( 17 ) located in an exhaust passage of the engine upstream of the filter device ( 42 . 142 ) is provided; characterized in that when a recovery process of the filter device ( 42 . 142 ) fuel through the combustion chamber fuel injection device ( 13 ) is supplied when a bed temperature of the filter device ( 42 . 142 ) is equal to or higher than a first temperature, and fuel through the exhaust gas fuel injection device ( 17 ) is supplied when a temperature of the exhaust gas is equal to or higher than a second temperature and the bed temperature of the filter device ( 42 . 142 ) is equal to or higher than a third temperature. Exhaust gas purification system according to claim 1, characterized in that fuel is supplied by one or both of the combustion chamber fuel injection device ( 13 ) and the exhaust gas fuel injection device ( 17 ), when the bed temperature of the filter device ( 42 . 142 ) is equal to or higher than the first temperature that causes oxidation of the fuel gas, and the third temperature that causes oxidation of the fuel gas including the fuel droplets and a temperature of the exhaust gas in the exhaust passage is equal to or higher than the second temperature Condensation of the fuel injected into the exhaust passage does not cause. Exhaust gas purification system according to claim 1 or 2, characterized in that the filter device ( 42 . 142 ) a filter ( 42a . 142a ) carrying a catalyst. An exhaust gas purification system according to claim 3, characterized in that the first temperature is equal to or higher than 200 ° C and the third temperature is equal to or higher than 250 ° C. An exhaust gas purification system according to any one of claims 1 to 4, characterized in that the second temperature is equal to or higher than 300 ° C. Exhaust gas purification system according to one of claims 1 to 5, characterized in that the filter ( 42a . 142a ) a storage reduction NOx catalyst ( 42b ) capable of storing nitrogen oxides contained in the exhaust gas when an oxygen concentration in the exhaust gas is high, and for reducing the stored nitrogen oxides when the oxygen concentration decreases and there is fuel serving as a reducing agent. An exhaust gas purification system according to any one of claims 1 to 6, further characterized by a filter bed temperature sensor ( 79 ) inside the filter device ( 42 ) is arranged to detect its temperature. An exhaust purification system according to any one of claims 1 to 7, further characterized by an exhaust gas temperature sensor ( 78 . 178 ) located upstream of the filter device ( 42 . 142 ) is arranged to detect the temperature of the exhaust gas. Exhaust gas purification system according to one of claims 3 to 8, further characterized by an exhaust gas sensor ( 74 ) located downstream of the filter device ( 42 . 142 ) is provided, which is suitable for detecting a temperature of the exhaust gas, which flows out of the catalyst. An exhaust gas purification method for an internal combustion engine, the internal combustion engine comprising: a particulate filter device ( 42 . 142 ) for capturing foreign matter contained in the exhaust gas of the internal combustion engine, wherein the filter device ( 42 . 142 ) can be restored by burning. the foreign matter trapped by the filter by means of the supply of fuel to the filter and raising the temperature of the filter by burning the fuel; a combustion chamber fuel injection device ( 13 ) provided in a combustion chamber of the engine capable of performing not only a main fuel injection provided for generating a torque but also a secondary fuel injection provided for raising the temperature of the filtering device (FIG. 42 . 142 by burning this fuel in the exhaust passage; and an exhaust gas fuel injection device ( 17 ) located in an exhaust passage of the engine upstream of the filter device ( 42 . 142 ) is provided; characterized by the following steps: determining the need for a filter device recovery process ( 42 . 142 ) and if the need for a recovery process is determined: determining a bed temperature of the filter device ( 42 . 142 ); Determining an exhaust gas temperature; Performing fuel injection by the combustor fuel injection device (10) 13 ), when a bed temperature of the filter device ( 42 . 142 ) is equal to or higher than a first temperature; and performing fuel injection by the exhaust gas fuel injection device (10) 17 ) when a temperature of the exhaust gas is equal to or higher than a second temperature and the bed temperature of the filter device ( 42 . 142 ) is equal to or higher than a third temperature. An exhaust purification method according to claim 10, further characterized by the step of: injecting fuel through one or both of said combustion chamber fuel injection device (10); 13 ) and the exhaust gas fuel injection device ( 17 ), when the bed temperature of the filter ( 42 . 142 ) is equal to or higher than the first temperature that causes oxidation of the fuel gas, and the third temperature that causes oxidation of the fuel gas including the fuel droplets and a temperature of the exhaust gas in the exhaust passage is equal to or higher than the second temperature does not cause condensation of the fuel injected into the exhaust passage. An exhaust gas purification method according to claim 10 or 11, further characterized by the steps of: detecting a temperature of the exhaust gas discharged from the filter device (10); 42 . 142 ) flows out; and prohibiting the supply of the fuel from the combustor fuel supply device ( 13 ) and the exhaust gas fuel feed device ( 17 ), when the detected temperature of the exhaust gas is equal to or higher than a predetermined temperature, an upper limit temperature for ensuring that heat deterioration of the catalyst is not caused.

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