DE102015116257B4 - Ozone supply device - Google Patents

Abstract

Ozone supply device for a combustion system, which has a NOx purification device (12, 12A) which is arranged in an exhaust gas passage (10ex) of an internal combustion engine (10), the NOx purification device (12, 12A) purifying NOx in an exhaust gas, wherein ozone is supplied by the ozone supply device upstream of the NOx purification device (12, 12A) in the exhaust passage (10ex) to oxidize NOx in the exhaust gas into NO, the ozone supply device comprising: an ozonizer (30) which generates ozone by electric discharges; a detection unit (41a) which obtains an NO reduction correlation value, the NO reduction correlation value being a physical quantity correlated with a primary cause of NO reduction in NO, the NO reduction in NO at a portion of the exhaust passage ( 10ex) occurs which is upstream of the NOx purification device (12, 12A) or within the NOx purification device (12, 12 A) occurs; and a controller (41b) that controls an amount of ozone generated by the ozonizer (30) according to the NO reduction correlation value obtained by the detection unit (41a).

Description

TECHNICAL AREA

The present disclosure relates to an ozone supply device that supplies ozone upstream of a NOx purification device in an exhaust passage of an internal combustion engine, whereby NO is converted into exhaust gas into NO ₂ .

BACKGROUND SKILLS

One type of exhaust gas NOx (nitrogen oxide) cleaning system stores NOx from the exhaust gas and then purifies the NOx. NO ₂ (nitrogen dioxide) is actively stored in this way compared to NO (nitrogen oxide or nitrogen monoxide). For this reason, as in the JP 2008-163887 A when ozone is supplied into an exhaust passage by an ozone supply device to oxidize NO into NO ₂ , the storage efficiency can be improved.

Furthermore, another type of NOx purification system uses a reducing agent to reduce and purify NOx in the presence of a reduction catalyst. In this type of system, aqueous urea or urea water solution is fed to the exhaust passage. Then ammonia is supplied to the reduction catalyst as the reducing agent. Alternatively, hydrocarbons are supplied to the exhaust passage as the reducing agent. In these systems, it is known that if the NO to NO ₂ ratio of the exhaust gas is optimized, then the NOx purification rate will improve. For this reason, an ozone supply device preferably supplies ozone to the exhaust passage to oxidize NO to NO ₂ , thereby optimizing the NO to NO ₂ ratio and improving the NOx purification rate.

US 2009/0 120 070 A1 discloses an exhaust gas purification system for an internal combustion engine having a plurality of Diesel Particulate Filters (DPF) leading to an exhaust duct for collecting particulate matter in an exhaust gas and an ozone supplier for supplying ozone to the upstream side of each of the Branch off and are connected to a large number of DPFs. The system changes a ratio of a supply amount of the exhaust gas and a ratio of a supply amount of the ozone, respectively, between the plurality of DPFs.

According to DE 198 59 201 A1 it is known, in particular for cleaning exhaust gases from internal combustion engines, to add a gaseous or liquid reducing agent to the exhaust gas. According to the invention, in addition to the reducing agent, an oxidizing agent with low heat of formation is also used to increase the catalytic reduction at low temperatures, in particular below 150 KJ / mol at room temperature. In the associated device, there are means for supplying the reducing agent on the one hand and the oxidizing agent on the other hand to an exhaust line of an engine or another internal combustion engine.

SHORT VERSION

Typically, ozone is generated by electrical discharges. There is a need to reduce the electrical discharge power consumption by generating the minimum amount of ozone required. In this regard, the aforementioned various types of NOx purification systems use conventional ozone supply devices that generate an ozone amount and supply it to the exhaust passage based on the amount of NO in the exhaust gas.

However, the present inventors recognized that in an upstream section of the NOx purifying device in the exhaust passage or within the NOx purifying device, a phenomenon occurs where NO ₂ generated from NO by the supply of ozone is reduced and returns to NO. Furthermore, when this phenomenon occurs, there are concerns that the actual amount of NO ₂ may fall below the desired amount of NO ₂ and the NOx purification rate may deteriorate as a result.

In view of the above, it is an object of the present disclosure to provide an ozone supply device that suppresses over-generation and under-generation of ozone.

In one aspect of the present disclosure, there is provided an ozone supply device for a combustion system, which includes a NOx purification device disposed in an exhaust passage of an internal combustion engine, the NOx purification device purifying NOx in an exhaust gas, with ozone by the ozone supply device upstream of the NOx purification device is supplied in the exhaust passage to oxidize NO in the exhaust gas to NO ₂ , the ozone supply device having an ozonizer that generates ozone by electric discharges, a detection unit that obtains an NO reduction correlation value, the NO reduction correlation value being a physical quantity , which is correlated with a primary cause of the NO ₂ reduction in NO, the NO ₂ reduction in NO occurring at a portion of the exhaust passage that is upstream of the NOx purifier or within the NOx purifier, and a controller respectively one Control, which controls which amount of ozone, which is generated by the ozonizer, according to the NO reduction correlation value, which is obtained by the detection unit.

According to the present disclosure, the amount of ozone that is generated is controlled in accordance with a physical quantity that is correlated with a primary cause of NO ₂ reduction in NO (i.e., an NO reduction correlation value). For this reason, in response to a primary cause of NO ₂ reduction in NO, the amount of ozone that is generated can be increased to accelerate a reaction in which NO is oxidized in NO ₂ . As such, the amount of ozone generation can be adjusted by considering the cause of the reduction in NO, and the over-generation and under-generation of ozone due to the above-mentioned phenomenon can be suppressed.

Figure list

• 1 eine schematische Ansicht einer Reduktionsmittelzuführvorrichtung, welche als eine Ozonzuführvorrichtung fungiert, sowie eines Verbrennungssystems, welches diese Vorrichtung aufweist, in Übereinstimmung mit einer ersten Ausführungsform der vorliegenden Offenbarung ist;
• 2 ein Graph ist, welcher auf eine Zweischritt-Oxidationsreaktion einer Kaltflammenreaktion und einer Heißflammenreaktion bezogen ist;
• 3 ein Diagramm ist, welches einen Reaktionsvorgang der Kaltflammenreaktion zeigt;
• 4 ein Diagramm ist, welches einen Bereich veranschaulicht, welcher durch eine Umgebungstemperatur und ein Äquivalenzverhältnis, in dem die Zweischritt-Oxidationsreaktion auftritt, definiert ist;
• 5 ein Flussdiagramm ist, welches einen Steuervorgang durch die Reduktionsmittelzufuhrvorrichtung, welche in 1 gezeigt ist, zeigt;
• 6 ein Flussdiagramm ist, welches einen Unter-Routinenvorgang bezogen auf den Starkoxidationssteuerschritt, welcher in 5 gezeigt ist, zeigt;
• 7 ein Flussdiagramm ist, welches einen Unter-Routinenvorgang bezogen auf den Ozonzuführ-Steuerschritt, welcher in 5 gezeigt ist, zeigt;
• 8 ein Kennfeld bzw. eine Übersichtstafel ist, welches für den Vorgang der 7 eine Beziehung zwischen einer HC-Konzentration und einem Faktor, welcher eine Ozonzuführmenge korrigiert, zeigt;
• 9 ein Kennfeld ist, welches für den Vorgang der 7 eine Beziehung zwischen einer CO-Konzentration und einem Faktor, welcher eine Ozonzuführmenge korrigiert, zeigt;
• 10 ein Kennfeld ist, welches für den Vorgang der 7 eine Beziehung zwischen einer Abgastemperatur und einem Faktor, welcher eine Ozonzuführmenge korrigiert, zeigt;
• 11 ein Kennfeld ist, welches für den Vorgang der 7 eine Beziehung zwischen einer Katalysatortemperatur und einem Faktor, welcher eine Ozonzuführmenge korrigiert, zeigt, während eine Reaktionsgeschwindigkeit an einem Reduktionskatalysator berücksichtigt wird;
• 12 ein Kennfeld ist, welches für den Vorgang der 7 eine Beziehung zwischen einer Katalysatortemperatur und einem Faktor, welcher eine Ozonzuführmenge korrigiert, zeigt, während eine Adsorptionskraft berücksichtigt wird;
• 13 ein Diagramm von experimentellen Ergebnissen ist, welches eine Beziehung zwischen einer CO-Konzentration und einer NOx-Adsorptionsrate zeigt;
• 14 ein Diagramm von experimentellen Ergebnissen ist, welches eine Beziehung zwischen einer HC-Konzentration und einer NOx-Adsorptionsrate zeigt;
• 15 ein Diagramm von experimentellen Ergebnissen ist, welches zeigt, dass Ozon eine NOx-Adsorptionsrate verbessert, wenn die NOx-Adsorptionsrate durch CO verringert wird;
• 16 ein Diagramm von experimentellen Ergebnissen ist, welches zeigt, dass Ozon eine NOx-Adsorptionsrate verbessert, wenn die NOx-Adsorptionsrate durch HC verringert wird; und
• 17 eine schematische Ansicht einer Ozonzuführvorrichtung, sowie eines Verbrennungssystems, welches diese Vorrichtung aufweist, gemäß einer zweiten Ausführungsform der vorliegenden Offenbarung ist.

The disclosure, along with additional objects, features, and advantages thereof, will best be understood from the following description, the appended claims, and the accompanying drawings, in which:

• 1 FIG. 2 is a schematic view of a reductant supply device that functions as an ozone supply device and a combustion system having this device in accordance with a first embodiment of the present disclosure;
• 2nd Fig. 12 is a graph related to a two-step oxidation reaction of a cold flame reaction and a hot flame reaction;
• 3rd Fig. 12 is a diagram showing a reaction process of the cold flame reaction;
• 4th FIG. 12 is a diagram illustrating a range defined by an ambient temperature and an equivalence ratio in which the two-step oxidation reaction occurs;
• 5 FIG. 14 is a flowchart showing a control process by the reducing agent supply device shown in FIG 1 shown shows;
• 6 FIG. 14 is a flowchart showing a subroutine process related to the strong oxidation control step shown in FIG 5 shown shows;
• 7 FIG. 11 is a flowchart showing a subroutine process related to the ozone supply control step shown in FIG 5 shown shows;
• 8th is a map or an overview table, which is for the process of 7 shows a relationship between an HC concentration and a factor that corrects an ozone supply amount;
• 9 is a map, which is for the process of 7 shows a relationship between a CO concentration and a factor that corrects an ozone supply amount;
• 10th is a map, which is for the process of 7 shows a relationship between an exhaust gas temperature and a factor that corrects an ozone supply amount;
• 11 is a map, which is for the process of 7 shows a relationship between a catalyst temperature and a factor that corrects an ozone supply amount while considering a reaction rate on a reduction catalyst;
• 12 is a map, which is for the process of 7 shows a relationship between a catalyst temperature and a factor that corrects an ozone supply amount while considering an adsorption force;
• 13 Fig. 11 is a graph of experimental results showing a relationship between a CO concentration and a NOx adsorption rate;
• 14 Fig. 11 is a graph of experimental results showing a relationship between an HC concentration and a NOx adsorption rate;
• 15 FIG. 4 is a graph of experimental results showing that ozone improves a NOx adsorption rate when the NOx adsorption rate is increased by CO is reduced;
• 16 FIG. 4 is a graph of experimental results showing that ozone improves a NOx adsorption rate when the NOx adsorption rate is increased by HC is reduced; and
• 17th is a schematic view of an ozone supply device, and a combustion system having this device, according to a second embodiment of the present disclosure.

DETAILED DESCRIPTION

A plurality of embodiments of the present disclosure will be described hereinafter with reference to the drawings. In the embodiments, a part, which corresponds to an object described in a previous embodiment are assigned the same reference numerals, and a redundant explanation can be omitted for that part. If only part of a configuration is described in one embodiment, another previous embodiment can be applied to the other parts of the configuration. The parts can be combined even if it is not explicitly described that the parts can be combined. The embodiments can be partially combined, although it is not explicitly described that the embodiments can be combined, provided there is no harm in the combination.

(First embodiment)

A combustion system like the one in 1 an internal combustion engine 10th , a loader 11 , a NOx purification device 12 , a Diesel Particulate Filter (DPF 13 = Diesel Particulate Filter = Diesel Particulate Filter) and a reducing agent adding device. The combustion system is attached to a vehicle and the vehicle is powered by an output from the internal combustion engine 10th operated. In the present embodiment, the internal combustion engine 10th a compression compression ignition diesel engine and diesel fuel (light oil), which is a hydrocarbon compound, is used as a fuel for combustion. The internal combustion engine 10th is generally operated in a lean condition. In other words, is in the internal combustion engine 10th Fuel burned in a state in which an air / fuel ratio, which is a ratio of air supplied into the combustion chamber to fuel injected into the combustion chamber, is set such that air is excessive, that is, into a lean burn state.

The loader 11 has a turbine 11a , a rotating shaft 11b and a compressor 11c on. The turbine 11a is in an exhaust passage 10ex the internal combustion engine 10th arranged and rotated by kinetic energy of exhaust gas. The rotating shaft 11b or rotary shaft 11b connects an impeller of the turbine 11a with an impeller of the compressor 11c and transmits a torque of the turbine 11a on the compressor 11c . The compressor 11c is in an intake passage 10 in the internal combustion engine 10th arranged and leads intake air into the internal combustion engine 10th after compressing (i.e. loading) the intake air.

A cooler (not shown) is in the intake passage 10 in downstream of the compressor 11c arranged. The cooler cools intake air (compressed air) which passes through the compressor 11c is compressed, and the compressed air, which is cooled by the radiator, is in combustion chambers of the internal combustion engine 10th distributed after a flow amount of the compressed intake air is adjusted by a throttle valve (not shown). The NOx purification device 12 is in the exhaust passage 10ex downstream of the turbine 11a arranged. Then the DPF 13 in the exhaust passage 10ex downstream of the NOx purification device 12 arranged. The DPF 13 filters out particles contained in the exhaust gas.

A feed passage 23 of the reducing agent supplying device is with the exhaust passage 10ex upstream of the NOx purification device 12 connected. Reformed fuel generated by the reducing agent adding device is used as a reducing agent of the exhaust passage 10ex through the feed passage 23 fed. The reformed fuel is made by partially oxidizing hydrocarbon (i.e., fuel) used as a reducing agent in partially oxidized hydrocarbon such as aldehyde, as later referred to in FIG 3rd will be described. Furthermore, the reducing agent adding device has a function of supplying ozone from the supply passage 23 to the exhaust passage 10ex and provides an ozone supply device.

The NOx purification device 12 has a honeycomb carrier, which is housed within a housing. A coating is provided on a surface of the carrier and a reduction catalyst is carried through the coating. The NOx purification device 12 purifies NOx contained in the exhaust gas by a reaction of NOx with the reformed fuel in the presence of the reduction catalyst, that is, by a reduction process of NOx in N ₂ . It should be noted that although O _{2 is} also contained in the exhaust gas in addition to NOx, the reformed reducing agent reacts selectively (preferably) with NOx in the presence of O ₂ .

In the present embodiment, the reduction catalyst has an adsorptivity to adsorb NOx. More specifically, the reduction catalyst shows the adsorptivity to adsorb NOx in the exhaust gas when a catalyst temperature Tcat is lower than an activation temperature. The activation temperature is defined as a temperature at which a reduction reaction can occur. For example, the NOx purification device 12 provide the NOx adsorption function with a silver / alumina catalyst carried by the carrier. More specifically, silver, which acts as a reduction catalyst, is made by Alumina, which is coated on the surface of the carrier, worn. The adsorbed NOx is desorbed from the reduction catalyst when the catalyst temperature Tcat is equal to or above the activation temperature. Then the desorbed NOx is reduced by the reformed fuel and it is cleaned accordingly.

Next, the reducing agent adding device that generates reformed fuel and the reformed fuel from the supply passage 23 to the exhaust passage 10ex feeds, are explained. The reducing agent adding device has a reaction container 20th as explained below, a heater 21st , an injector 22 , an ozonizer 30th and an air pump 30p on. Furthermore, the reducing agent adding device also has the feed passage 23 and a ventilation passage 26 , which is described below, and also has an electronic control unit (ECU 40 ) on.

The ozonizer 30th has a housing 32 on which is a fluid passage 32a has in it. A plurality of pairs of electrodes 31 are within the fluid passage 32a arranged. The electrodes 31 are plate-shaped and are arranged to face each other to be in parallel with each other, and ground electrodes are alternately arranged with high voltage application electrodes. The ECU 40 has a microcomputer 41 on which is the application of voltage to the electrodes 31 controls.

Air flowing through the air pump 30p is blown, flows into the housing 32 of the ozonizer 30th . The air pump 30p is an air pump of the centrifuge type and is formed by an impeller, which is operated by an electric motor and is housed within a housing. This electric motor is powered by the microcomputer 41 controlled. The housing of the air pump 30p has an inlet 30in formed therein. The air pump 30p receives atmospheric air through inlet 30in, compresses or compresses the atmospheric air, and then blows the atmospheric air to the ozonizer 30th . The air leading to the ozonizer 30th is blown, flows into the fluid passage 32a in the housing and then flows through electrode passages 31a between the electrodes 31 are formed.

The ozonizer 30th is with the reaction vessel 20th via the ventilation passage 26 connected. A check valve 26v which is an electromagnetic type valve is in the ventilation passage 26 Installed. The microcomputer 41 controls the opening and closing of the check valve 26v . In particular, a valve body of the check valve 26v controlled to switch between a fully open position and a fully closed position. As a result, when the air pump flows 30p is on, and the check valve 26v is controlled to open up the air passing through the electrode passages 31a has passed through the ventilation passage in this order 26 , the reaction vessel 20th and the feed passage 23 . Then the air flows into the exhaust passage 10ex . In other words, see the feed passage 23 and the ventilation passage 26 a ventilation passage in front of the air passing through the air pump 30p is blown into the exhaust passage 10ex leads.

The stoker 21st and the injector 22 are on the reaction vessel 20th attached, and a reaction chamber 20a is inside the reaction vessel 20th educated. The reaction chamber 20a is in fluid communication with an inlet 20in and an outlet 20out. The stoker 21st has a heating section that generates heat when it is supplied with power, and a supply of the heating section with power is provided by the microcomputer 41 controlled. The microcomputer controls more precisely 41 a heating amount of the heating section via control of the duty ratio of a power supply amount to the heating section. The heating section is in the reaction chamber 20a arranged to fuel from the injector 22 into the reaction chamber 20a injected or injected to heat. A temperature in the reaction chamber 20a is through a chamber temperature sensor 27th detected. The chamber temperature sensor 27th gives information about the detected temperature (reaction chamber temperature Th) to the ECU 40 out.

The injector 22 has a body that has injection ports formed thereon, an eclectic actuator, and a valve member. When the electrical actuator is powered, the valve element moves to open the injection ports, causing fuel to enter the reaction chamber through the injection ports 20a is injected. When the electric actuator is turned off or disconnected from the power supply, the valve element moves to close the injection openings, thereby stopping the fuel injection. The microcomputer 41 controls an amount of fuel injection to the reaction chamber 20a per unit time by controlling the power supply to the electric actuator. Liquid fuel inside a fuel tank (not shown) is fed to the injector 22 supplied by a fuel pump (not shown). The fuel within the fuel tank is also used as the fuel for combustion as described above. That is, the fuel in the fuel tank is called both, fuel for combustion in the internal combustion engine 10th and fuel is used as the reducing agent.

Fuel coming from the injector 22 into the reaction chamber 20a is injected, collides with the heating section and is heated and evaporated by the heating section. The vaporized fuel is mixed with the air that enters the reaction chamber 20a from the inlet 20in flows, mixed. As a result, the vaporized fuel is partially oxidized with oxygen in the air, and thus the vaporized fuel is reformed into partially oxidized hydrocarbons such as aldehyde. The vaporized fuel which is reformed in this way (i.e., reformed fuel) is in the exhaust passage 10ex through the feed passage 23 fed.

If electrical power the electrodes 31 of the ozonizer 30th supplied, electrons collide, which from the electrodes 31 are imitated with oxygen molecules that are in the air in the electrode passages 31a are included. As a result, ozone is generated from the oxygen molecules. That is, the ozonizer 30th brings the oxygen molecules into a plasma state by means of electrical discharges, whereby ozone is generated as a reactive oxygen. Accordingly, when electrical power instructs the ozonizer 30th The air that is supplied through the ventilation passage 26 pours ozone.

A cold flame reaction occurs within the reaction chamber 20a on. In the cold flame reaction, vaporized fuel is partially oxygenated in the air from the inlet 20in flows in, oxidizes. A partial oxide (e.g., aldehyde) may be an example of the fuel that is partially oxidized in this manner, in which a portion of the fuel (hydrocarbon compound) is oxidized with an aldehyde group (CHO).

Next, the cold flame reaction will be described in detail with reference to FIG 2nd and 3rd to be discribed.

2nd illustrates simulation results showing a phenomenon in the fuel (hexadecane) on the heater 21st is sprayed and vaporized, and the vaporized fuel which is around the heater 21st remaining around is being reformed. In particular, in a case where the vaporized fuel (hexadecane) is exposed to an environment at 430 ° C, each graph shows changes in a variety of physical quantities in terms of an elapsed time after exposure. In 2nd graph (a) illustrates a change in ambient temperature, graph (b) illustrates a change in molarity of the fuel (hexadecane), graph (c) illustrates changes in a molarity of (i) oxygen consumed by the oxidation process, ( ii) water molecules generated by the oxidation process and (iii) carbon dioxide molecules generated by the oxidation process, and graph (d) illustrates changes in a molarity of alcetaldehyde and propionaldehyde, each of which is a reformed fuel produced by the Cold flame reaction is generated. Initial conditions at the start of fuel injection are set at 1 atmospheric pressure, 2,200 ppm hexadecane concentration, 20% oxygen concentration, 9% carbon dioxide concentration and 2% water concentration.

As in 2nd is shown, immediately after the injection of the fuel, the ambient temperature increases, the molarity of the fuel decreases, and the molarity of the reformed fuel increases. This means that fuel generates heat by being oxidized with oxygen and that the reformed fuel is generated from the fuel, ie the cold flame reaction occurs. However, such an increase in temperature and change in molarities are transient, and there is no increase in temperature or change in molar concentration for a period of about 4 seconds from the start of fuel injection.

When approximately 4 seconds have passed, the ambient temperature continues to increase, the molarity of the reformed fuel decreases, the amounts of carbon dioxide and water that are generated increase, and the consumption amount of oxygen increases. This means that the reformed fuel generates heat by being oxidized with oxygen and that the reformed fuel burns completely to produce carbon dioxide and water, i.e. the hot flame reaction occurs. A temperature increase amount or a temperature increase amount by the cold flame reaction is less than that by the hot flame reaction. Furthermore, an oxygen consumption amount by the cold flame reaction is less than that by the hot flame reaction.

When the two-step oxidation reaction occurs, the reformed fuel is generated as an intermediate during a period between the cold flame reaction and the hot flame reaction. Examples of intermediates can be a plurality of hydrocarbon compounds such as aldehyde, ketone or the like. 3rd illustrates an example of a major reaction pathway through which aldehyde is produced.

As by (1) in 3rd is indicated, hydrocarbon (light oil, such as diesel fuel) reacts with an oxygen molecule and a hydrocarbon-peroxyl radical is generated. The hydrocarbon peroxyl radical is decomposed into aldehyde and a hydrocarbon radical (refer to (2) in 3rd ). The hydrocarbon radical reacts with an oxygen molecule and another hydrocarbon-peroxyl radical is generated (refer to (3) in FIG 3rd ). The hydrocarbon peroxyl radical is decomposed into aldehyde and a hydrocarbon radical (refer to (4) in 3rd ). The hydrocarbon radical reacts with an oxygen molecule and another hydrocarbon-peroxyl radical is also generated (refer to (5) in FIG 3rd ). In this way, a hydrocarbon-peroxyl radical is generated repeatedly while reducing the carbon number, and aldehyde is generated every time the hydrocarbon-peroxyl radical is generated. It should be noted that in the hot flame reaction, fuel is completely burned, and carbon dioxide and water are generated, and therefore intermediate products are not generated. In other words, the intermediates generated by the cold flame reaction are oxidized in carbon dioxide and water during the hot flame reaction. Accordingly, according to the present disclosure, various controls are performed so that the cold flame reaction occurs and the hot flame reaction does not occur.

In the simulation, which in 2nd is shown, the exposure temperature is set to 430 ° C. However, the inventors of the present disclosure continued to perform simulation with various exposure temperatures. As a result, it was found that when the exposure temperature is 530 ° C, the duration of the cold flame reaction is minimal, and the oxidation reaction is accomplished in one step. In contrast, when the exposure temperature is set to 330 ° C, a start setting or a start time of the cold flame reaction is delayed compared to a case where the exposure temperature is set to 430 ° C. Similarly, when the exposure temperature is set to 230 ° C or lower, none of the cold flame reaction and the hot flame reaction occur, that is, the oxidation reaction does not occur.

In the simulation, which in 2nd is illustrated, the equivalence ratio, which is a ratio of the injected fuel and the supplied air, is set to be 0.23. In this connection, the present inventors have obtained results of the simulation with different equivalence ratios. It should be noted that the equivalence ratio can be defined as a value by dividing the “weight of fuel contained in an air-fuel mixture” by the “weight of fuel that can be completely burned”. When the equivalence ratio is set to 1.0, the duration of the cold flame reaction is minimal, and the oxidation reaction is accomplished in one step. Also, when the equivalence ratio is set to 0.37, compared to a case where the equivalence ratio is set to 0.23, the cold flame reaction starts earlier, the reaction rate of the cold flame reaction increases, the duration of the cold flame reaction decreases, and the ambient temperature at the time of completion of the cold flame reaction increases.

4th illustrates a summary of the analysis results as described above. 4th indicates a relationship between the exposure temperature (ambient temperature), the equivalence ratio, and an occurrence / non-occurrence of the cold flame reaction. In 4th the horizontal axis of the graph shows the heater temperature (ambient temperature) and the vertical axis of the graph shows the equivalence ratio. The dotted area in 4th is a range in which a two-step oxidation reaction occurs. As in 4th is shown, a region in which the ambient temperature is lower than a lower limit is a non-reaction region in which the oxidation reaction does not occur. Furthermore, even if the ambient temperature is higher than the lower limit, a range in which the equivalence ratio is equal to or greater than 1.0 is a one-step oxidation reaction range in which the oxidation is accomplished with only one step.

A boundary line between the two-step oxidation reaction area and the one-step oxidation reaction area varies according to an ambient temperature and the equivalence ratio. That is, when the ambient temperature falls within a predetermined temperature range and the equivalence ratio falls within a certain equivalence ratio range, the two-step oxidation reaction occurs. That is, the specified temperature range and the equivalence ratio range correspond to the dotted range in FIG 4th . If the ambient temperature is set to an optimal temperature (e.g. 370 ° C) within the specified temperature range, the equivalence ratio on the boundary line has a maximum value (e.g. 1.0). Accordingly, in order to generate the cold flame reaction earlier, the heater temperature is adjusted to the optimum temperature, and the equivalence ratio is set to 1.0. However, if the equivalence ratio is larger than 1.0, the Cold flame reaction does not occur. Accordingly, the equivalence ratio is preferably set to a value of less than 1.0 by a sufficiently small margin.

In the simulation as in 2nd an ozone concentration in air is set to zero. The present inventors further carried out a simulation with different concentrations of ozone in the air. In the simulation, an initial condition with 1 atmospheric pressure, a hexadecane concentration of 2,200 ppm and the ambient temperature of 330 ° C was set. As a result, it was found that the cold flame reaction started earlier when the ozone concentration increased. Such a phenomenon can be explained as below. As described above, a hydrocarbon radical reacts with an oxygen molecule in (1), (3) and (5) in 3rd and this reaction is accelerated with ozone contained in air. As a result, aldehyde is generated in a short time.

The microcomputer 41 the ECU 40 has a storage unit for storing programs and a central processing unit which performs arithmetic processing according to the programs stored in the storage unit. The ECU 40 controls the operation of the internal combustion engine 10th based on various detection values such as an accelerator pedal depression amount (that is, the engine load), a rotational speed of the internal combustion engine 10th (i.e., a rotational speed of the engine), an intake air pressure, an exhaust pressure, or the like.

The ECU also controls 40 the operation of the reducing agent adding device in addition to detection values of the operating state of the internal combustion engine 10, such as engine load or engine rotation speed, based on physical quantities determined by the chamber temperature sensor 27th and a catalyst temperature sensor 42 be recorded. In addition, the catalyst temperature sensor 42 on the NOx purification device 12 attached and detects the ambient temperature of the reduction catalyst (that is, the catalyst temperature Tcat ).

The ECU 40 controls the operation of the reducing agent adding device in the following manner. Based on the catalyst temperature Tcat switches the ECU 40 between a reducing agent addition control process, which reducing agent to the exhaust passage 10ex and an ozone supply control process which adds ozone to the exhaust passage 10ex adds to. The ECU also switches 40 when performing the reductant supply control process based on the catalyst temperature Tcat between a strong oxidation control process, a weak oxidation control process, and a stop oxidation control process.

In particular controls the microcomputer 41 the operation of the reducing agent adding device by periodically executing, with a predetermined period, a program corresponding to the process steps described in 5 are shown. First at step S10 of the 5 determines whether the internal combustion engine 10th is in operation. If the internal combustion engine 10th When not determined to be in operation, it is assumed that NOx, which is the cleaning target, in the exhaust passage 10ex does not exist, and at step S18 a complete stop control operation is performed to stop the operation of the reducing agent adding device. The full stop control process stops the supply of both ozone and reducing agent to the exhaust passage 10ex . In other words, the air pump 30p , the ozonizer 30th , the stoker 21st and the injector 22 all stopped, and the check valve 26v will be closed.

In contrast, if at step S10 it is determined that the internal combustion engine 10th is in operation, then at step S11 determines whether the catalyst temperature Tcat above a first predetermined temperature T1 is. When the catalyst temperature is determined to be below the first predetermined temperature T1 to be, the process progresses to step S12 where it is determined whether the catalyst temperature Tcat above a second predetermined temperature T2 is. If the catalyst temperature Tcat is determined to be below the second predetermined temperature T2 the process goes to step S13 where it is determined whether the catalyst temperature Tcat above an activation temperature T3 is.

The first predetermined temperature T1 and the second predetermined temperature T2 are set to be higher than the activation temperature T3 . Furthermore, the first predetermined temperature T1 set to be higher than the second predetermined temperature T2 . For example, if the activation temperature T3 Is 200 ° C, then the second predetermined temperature T2 set to 350 ° C, and the first predetermined temperature T1 can be set to 400 ° C. Here is the activation temperature T3 of the reduction catalyst is a minimum temperature at which NOx can be reduced or cleaned in the presence of the reduction catalyst.

Based on the provisions of the steps S11 , S12 and S13 will when the Catalyst temperature Tcat is determined to be lower than the activation temperature T3 , then the ozone supply control process at step S14 executed. If the catalyst temperature Tcat is determined to be higher than the activation temperature T3 and lower than the second predetermined temperature T2 then the strong oxidation control process at step S15 executed. If the catalyst temperature Tcat is determined to be higher than the second predetermined temperature T2 and lower than the first predetermined temperature T1 , then the weak oxidation control process at step S16 executed. If the catalyst temperature Tcat is determined to be higher than the first predetermined temperature T1 , then the stop oxidation control process at step S17 executed.

For the step oxidation strong oxidation control process S15 of the 5 becomes the sub-routine process, which in 6 shown is executed. First at step S20 of the 6 a detection value (the reaction chamber temperature Th) from the chamber temperature sensor 27th acquired. Next up at step S21 a feedback control on the heater 21st carried out in order to adapt the obtained reaction chamber temperature Th to a preset target temperature Ttrg. The target temperature Ttrg is set to an ambient temperature within the two-step oxidation reaction range, which is in 4th is shown to be where the equivalence ratio is maximized (e.g. 370 ° C).

Next up at step S22 a reducing agent addition amount or a reducing agent addition amount as a target fuel flow rate (or target fuel quantity) Ftrg set. Here, the reducing agent addition amount refers to the amount of reducing agent supplied to the NOx purification device 12 which is just sufficient to add all of the NOx to the NOx purification device 12 flows to reduce. The target fuel flow rate also relates Ftrg on the mass of fuel sent to the NOx purifier 12 per unit time is added.

In particular, the target fuel flow rate Ftrg based on a NOx inflow rate, which will be described below, and the catalyst temperature Tcat . The NOx inflow rate refers to the mass of NOx that is in the NOx purification device 12 flows per unit time. For example, the NOx inflow rate can be based on operating states of the internal combustion engine 10th can be estimated. The target fuel flow rate Ftrg is increased as the NOx inflow rate increases. Also, since there is a reduction amount (reduction ability) of NOx in the presence of the reduction catalyst according to the catalyst temperature Tcat varies, the target fuel flow rate Ftrg according to changes in the reducibility due to the catalyst temperature Tcat set.

Next up at step S23 the operation of the injector 22 is controlled and fuel injection is based on the target fuel flow rate Ftrg which in step S22 is set. In particular, the injector 22 controlled to open for a longer period of time when the target fuel flow rate Ftrg increases. Alternatively, a time interval between the termination of an injection or injection and the start of a subsequent injection can be shortened.

Next up at step S24 set a target equivalence ratio φtrg based on the reaction chamber temperature Th such that the cold flame reaction occurs. In particular, a maximum value of the equivalence ratio within the two-step oxidation reaction range, which is the maximum value of the equivalence ratio, which corresponds to the ambient temperature (i.e. the chamber temperature), or a value which is calculated by subtracting a given margin from this maximum value is used as an overview table or a map of the target equivalence ratio (φtrg in the microcomputer 41 saved. The target equivalence ratio (φtrg, which corresponds to the recorded chamber temperature, is calculated using the map.) If the target equivalence ratio (φtrg is set with a given margin as described above, it is possible even if the current or actual equivalence ratio exceeds the target equivalence ratio (φtrg to avoid a situation where the current equivalence ratio exceeds the maximum value of the equivalence ratio described above, and thereby reduce the likelihood of the cold flame response being missed to directly achieve the hot flame response.

Next up at step S25 a target air flow rate (or target air amount) Atrg calculated based on the target equivalence ratio φtrg, which in step S24 is set, and the target fuel flow rate Ftrg which in step S22 is set. In particular, the target air flow rate Atrg is calculated such that φtrg = Ftrg / Atrg. Next up at step S26 the operation of the air pump 30p based on the target air flow rate Atrg, which at step S25 is calculated, controlled. In particular, a relative power supply duty cycle of the air pump 30p increases as the target air flow rate Atrg increases.

As a result of setting the target air flow rate Atrg and the target temperature Ttrg according to the target fuel flow rate Ftrg and as a result of controlling the air pump 30p and the heater 21st based on this, the reaction chamber temperature Th and the equivalence ratio are adjusted to be in the two-step oxidation reaction range. As a result, the cold flame reaction occurs and the reformed fuel mentioned above is generated. The lower limit of the adjustment range of the reaction chamber temperature Th is 260 ° C, which is the boundary line between the one-step / two-step oxidation area and the non-reaction area. The upper limit of this temperature range is the highest temperature on the boundary between the one-step oxidation area and the two-step oxidation area. The upper limit of the adjustment range or setting range of the equivalence ratio is the maximum value on the boundary line between the one-step reaction area and the two-step reaction area and is the equivalence ratio, which corresponds to 370 ° C.

Next up at step S27 the supply of electrical power to the ozonizer 30th based on the fuel concentration within the reaction tank 20th controlled. Here, a target flow ozone flow rate (or target ozone amount) Otrg is calculated based on the target fuel flow rate Ftrg . In particular, the target ozone flow rate Otrg is calculated such that the ratio of the ozone concentration to the fuel concentration in the reaction tank 20th is a predetermined value (e.g. 0.2). This ratio can be set such that the cold flame reaction is completed within a predetermined time period (for example 0.02 seconds). Furthermore, the target ozone flow rate Otrg is increased as the temperature of the reduction catalyst decreases.

Furthermore, a target energy supply rate or target power supply rate (or target energy supply amount) becomes Ptrg for the ozonizer 30th calculated based on the target air flow rate Atrg and the target ozone flow rate Otrg. In particular, as the target air flow rate Atrg increases, the amount of time that air in the electrode passages shortens 31a remains, and accordingly, the target energy supply rate Ptrg is increased. Furthermore, as the target ozone flow rate Otrg increases, the target energy supply rate Ptrg is increased. Next is the target energy delivery rate of the ozonizer 30th controlled based on the target energy supply rate Ptrg. Specifically, as the target energy supply rate Ptrg increases, the ozonizer's relative energy supply duty becomes 30th elevated. Alternatively, a time interval after an energy supply period ends and before a subsequent energy supply period begins can be shortened.

If the process from step S27 When carried out in this manner, ozone is generated and this ozone becomes the reaction vessel 20th added. As a result, the cold flame reaction starts earlier and the duration of the cold flame reaction is reduced. As a result, even if the size of the reaction container 20th is reduced in such a way that an amount of time or the length of time that the fuel within the reaction container 20th remains, is reduced, the cold flame reaction is completed within this period. Accordingly, the size of the reaction container 20th be reduced. Next up at step S28 the check valve 26v controlled to open.

In this way, due to the strong oxidation control process, the 6 Ozone, which is generated by the ozonizer 30th is generated with oxygen in the air and fuel generated by the heater 21st is evaporated, mixed, and the fuel is partially oxidized in the presence of ozone. In contrast, during the weak oxidation control process according to step S16 of the 5 the ozonizer 30th stopped and the generation of ozone is stopped, and the fuel is partially oxidized without being in the presence of ozone. Furthermore, during the stop oxidation control process according to step S17 the ozonizer 30th and the stoker 21st stopped, and the generation of ozone and the heating of fuel are both stopped. As such, without the oxygen and the ozone for the oxidation of the fuel in the exhaust passage 10ex added without being partially oxidized. Then this added fuel becomes high temperature exhaust gas inside the exhaust passage 10ex and NOx purification device 12 exposed and is thereby partially oxidized.

More specifically, during the weak oxidation control process, the same processes as those of the steps become S20 to S26 , what a 6 are shown performed during the process of step S27 is not carried out. In other words, the heater control, the fuel injection control, the air pump control, the valve opening control of the steps S21 , S23 , S26 , S28 and setting the target fuel flow rate Ftrg , the target equivalence ratio φtrg, the target air flow rate Atrg of the steps S22 , S24 , S25 carried out. The electrical discharge process of the step S27 however, the ozonizer is not energized and energized 30th is or is stopped so that ozone is not generated.

Furthermore, during the stop oxidation control process, the same processes as those of the steps become S20 and S22 to S26 , what a 6 are shown performed during the operations of the steps S21 and S27 of the 6 not be carried out. In other words, the fuel injection control, the air pump control, the valve opening control of the steps S23 , S26 , S28 and setting the target fuel flow rate Ftrg , the target equivalence ratio φtrg, the target air flow rate Atrg of the steps S22 , S24 , S25 carried out. The electrical discharge process of the step S27 however, the ozonizer is not energized and energized 30th is stopped so that ozone is not generated. Furthermore, the heater control according to step S21 not carried out and an energy supply of the heater 21st is stopped so that the fuel is not heated.

During the ozone supply control process according to step S14 of the 5 becomes an energy supply of the heater 21st and the injector 22 stopped, and accordingly the injection of fuel is stopped. During this condition, ozone becomes in the ozonizer 30th generated. Then the generated ozone becomes the exhaust passage 10ex through the ventilation passage 26 and the feed passage 23 fed. Accordingly, when the reduction catalyst of the NOx purification device 12 is not activated, the NO in the exhaust gas is oxidized by the ozone in NO ₂ and the amount of NOx which is adsorbed by the reduction catalyst is increased.

But when HC or CO , which is contained in the exhaust gas, reacts with NO ₂ (for example, an inhibition reaction), reduces the NO ₂ to NO. This inhibition reaction occurs upstream of the NOx purification device 12 in the exhaust passage 10ex occurs or occurs in the presence of the reduction catalyst. In particular, if HC reacts with NO ₂ , partly oxides of HC (HC-O) and NO generated. If CO reacts with NO ₂ , NO and CO2 are generated.

Further responds HC with ozone (i.e. an inhibition reaction) to become oxides such as aldehydes. As a result, part of the added ozone undergoes an inhibition reaction with the HC and this part of the ozone cannot be used to oxidize the NO into NO ₂ . As a result, when this inhibition reaction occurs, the NO ₂ concentration is reduced and the amount of NOx adsorbed by the reduction catalyst is reduced. In addition, when an exhaust gas temperature increases Tex or the catalyst temperature Tcat increases, the reaction rate of the above-mentioned inhibition reactions increases. As a result, the NO ₂ concentration is further reduced, and hence the amount of NOx that is adsorbed is further reduced.

Accordingly, when the HC concentration and the CO concentration increase, or when the exhaust gas temperature becomes Tex and the catalyst temperature Tcat increase, the inhibition reactions accelerated. In this regard, the HC concentration, the CO concentration, the exhaust gas temperature Tex and the catalyst temperature Tcat are regarded as physical quantities, which are correlated with the primary cause of the NO ₂ reduction in NO (in other words, “NO reduction correlation values”). As mentioned above, this NO ₂ reduction in NO occurs at a portion of the exhaust passage 10ex which upstream of the NOx purification device 12 is or occurs within the NOx purification device 12 on. Furthermore, the catalyst temperature Tcat Reference is made to the temperature of the NOx purifier 12 . As a countermeasure to these inhibition reactions, when the amount of ozone that is supplied is increased, the reduction in the amount of NOx that is adsorbed can be suppressed in the following manner.

In particular, in addition to the ozone that is used to oxidize NO into NO ₂ , an excess amount of ozone is used to cope with CO to react in the exhaust gas and in the presence of the adsorption catalyst CO to oxidize in CO ₂ . Furthermore, this excess amount of ozone to be with HC to respond to that HC to oxidize in aldehydes and the like. Here they are CO and the HC primary causes of the inhibition reactions. By causing oxidations to occur in this manner, the concentrations of the CO and the HC is reduced, and as a result, the inhibition reactions can be suppressed.

Furthermore, when the catalyst temperature Tcat increases, the reduction catalyst is activated to a high degree and reaction rates are increased. As a result, as explained above, the inhibition reactions are accelerated. In contrast, it weakens even when the catalyst temperature Tcat is low, the adsorption force of the catalyst decreases to NO ₂ and accordingly any adsorbed NO ₂ becomes easier with CO or HC react (i.e. go through the inhibition reactions). As a countermeasure to this weakening of the adsorption force which causes inhibition reactions, the amount of ozone that is supplied can be increased in the following manner to suppress a decrease in the amount of NOx that is adsorbed.

In particular, the excess amount of ozone (that is, in addition to the ozone used to oxidize NO in NO ₂ ) further oxidizes NO ₂ in N ₂ O ₅ (di-nitrogen pentoxide) and HNO ₃ (nitric acid). N ₂ O ₅ and HNO ₃ have a greater adsorption capacity with the catalyst compared to NO ₂ . Accordingly, the above-mentioned excess amount of ozone can increase both the adsorbability with respect to NO ₂ and the inhibition reaction of adsorbed NO ₂ with CO or HC to suppress.

In view of the above, the microcomputer controls 41 the ozone supply amount according to the NO reduction correction values. In other words, when the HC concentration increases, when the CO concentration increases, and when the exhaust gas temperature Tex increases, the amount of ozone passed through the ozonizer becomes 30th is generated, and accordingly the ozone supply amount is increased. Regarding the catalyst temperature Tcat becomes the ozone supply amount by taking into account the effects of the catalyst temperature Tcat modified both on the reaction rates and on the adsorption force.

A subroutine routine of the ozone supply control process is described with reference to FIG 7 be explained. First, be as a step S30 the NO concentration, the HC concentration and the CO concentration of the exhaust gas. In particular, these concentrations can be based on the operating conditions of the internal combustion engine 10th can be estimated. Next up at step S31 the catalyst temperature Tcat and the exhaust temperature reaches Tex. Here is the catalyst temperature Tcat detected and by the catalyst temperature sensor 42 obtained, and the exhaust gas temperature Tex is based on the operating conditions of the internal combustion engine 10th estimated. If the HC concentration, the CO concentration, the catalyst temperature Tcat and the exhaust gas temperature Tex can be obtained in this way, the microcomputer sees 41 a registration unit 41a (please refer 1 ) which obtains these physical quantities which are correlated with the primary cause of the inhibition reactions mentioned above (i.e. the NO reduction correlation values).

Next up at step S32 a base ozone flow rate (or base ozone quantity) obase based on the NO concentration obtained at step S30 is obtained, calculated. In particular, a flow rate of the exhaust gas is based on the operating conditions of the internal combustion engine 10th estimated. Then, based on the flow rate and the NO concentration, an amount of NO which is in the NOx purification device 12 flows per unit time, estimated. The base ozone flow rate Obase is the amount of ozone needed to oxidize all of the NO to NO ₂ .

Next up at step S33 a correction factor K1 for the base ozone flow rate Obase based on the HC concentration, which at step S30 is obtained, calculated. The correction factor K1 is a real number equal to or greater than one. If the correction factor K1 increases, the base ozone flow rate Obase is corrected to increase by a larger amount. For example, optimal values for the correction factor K1 in terms of HC concentration can be obtained from previous experiments, and these optimal values can be presented as an overview table or map format, such as the one described in 8th is shown in the ECU 40 get saved. Then, while referring to this map, the correction factor K1 determined based on the HC concentration obtained.

Next up at step S34 a correction factor K2 for the base ozone flow rate Obase based on the CO concentration, which at step S30 is obtained, calculated. The correction factor K2 is a real number equal to or greater than one. If the correction factor K2 increases, the base ozone flow rate Obase is corrected to increase by a larger amount. For example, optimal values of the correction factor K2 in terms of CO concentration can be obtained from previous experiments, and these optimal values can be used as an overview table or map format, such as the one described in 9 is shown in the ECU 40 get saved. Then, while referring to this map, the correction factor K2 determined based on the CO concentration obtained.

Here, by increasing the amount of ozone as the HC concentration or the NO concentration increases, an oversupply and an undersupply of ozone can be avoided while the above-mentioned inhibition reactions are still suppressed. However, if the HC concentration or the NO concentration exceeds a predetermined concentration, there is no expectation that further increases in ozone will suppress the inhibition reactions. Regarding this point, as soon as the HC concentration or the CO concentration exceeds a predetermined concentration, the correction factors become K1 and K2 to maximum values K1a and K2a (please refer 8th and 9 ) regardless of any changes in the HC concentration or the CO concentration.

Next up at step S35 a correction factor K3 for the base ozone flow rate Obase calculated based on the exhaust temperature Tex, which at step S31 is obtained. The correction factor K3 is a real number equal to or greater than one. If the correction factor K3 increases, the base ozone flow rate Obase is corrected to increase by a larger amount. For example, optimal values of the correction factor K3 with respect to the exhaust gas temperature Tex can be obtained from previous experiments and these optimal values can be stored as a map format like the one shown in 10th is shown, namely in the ECU 40 . Then, while referring to this map, the correction factor K3 determined based on the exhaust gas temperature Tex obtained.

In the example shown in 10th is shown, the correction factor is set such that when the exhaust gas temperature Tex increases, the amount of ozone is increased by a larger amount or a larger amount. The characteristic line, however, which in 10th shown may differ according to various factors such as the type of reduction catalyst used. For example, it is contemplated that based on the various factors, the amount of ozone can be increased by a smaller amount as the exhaust gas temperature increases, the characteristic line of 10th can be curved with a convex shape on the upper side of the diagram, or the characteristic line can be curved with a convex shape on the lower side of the diagram.

Next up at step S36 a correction factor K4 for the base ozone flow rate Obase based on the catalyst temperature Tcat which at step S31 is obtained, calculated. If the correction factor K4 increases, the base ozone flow rate Obase is corrected to increase by a larger amount. The correction factor K4 is used as two correction factors K4a and K4b set in the following way.

In particular, as explained above, when the catalyst temperature increases Tcat increases, the reaction rate of inhibition reactions on the reduction catalyst also increases. In contrast, when the catalyst temperature weakens Tcat decreases, the adsorption force of NO ₂ on the reduction catalyst decreases. Accordingly, with regard to the reaction speed point, the correction factor becomes above K4a preferably set such that the amount of ozone is increased when the catalyst temperature Tcat increases as in 11 is shown. In contrast, with regard to the adsorption force point, the correction factor above K4b preferably set such that the amount of ozone is increased when the catalyst temperature Tcat decreases as in 12 is shown.

For example, optimal values for the correction factors K4a and K4b regarding the catalyst temperature Tcat from previous experiments, and these optimal values can be used as a map format such as the one used in the 11 and 12 is shown in the ECU 40 get saved. Then, while referring to these maps, the correction factors K4a and K4b based on the catalyst temperature obtained Tcat calculated by what the correction factor K4 is determined. As a result, the correction factor K4 which on the catalyst temperature Tcat have a temperature range in which ozone is increased as the temperature increases and another temperature range in which ozone is decreased as the temperature increases.

Next up at step S37 the base ozone flow rate Obase, which at step S32 is calculated based on the correction factors K1 , K2 , K3 and K4 which with the steps S33 to S36 be calculated, corrected. For example, a target ozone flow rate Otrg can be obtained by multiplying the base ozone flow rate Obase by each of the correction factors K1 , K2 , K3 and K4 be calculated. In other words, the target ozone flow rate Otrg is set so that the easier it is for the inhibition reactions to occur, the more the ozone flow rate Obase is increased. Furthermore, the target ozone flow rate Otrg is a target value of the amount of ozone, which the exhaust passage 10ex is supplied per unit time.

Next up at step S38 an electrical discharge control process related to the ozonizer 30th based on the target ozone flow rate performed at step S37 is calculated. In particular, when the target ozone flow rate Otrg increases, the amount of electric power that the electrodes receive 31 is fed increased. Next up at step S39 the operation of the air pump 30p controlled based on the target ozone flow rate Otrg. In particular, when the target ozone flow rate Otrg increases, the amount of electric power given to the air pump electric motor 30p is increased, so the amount of air that is supplied by the air pump 30p is blown, increases.

Next up at step S40 the check valve 26v controlled to open. Then the next step is S41 the energy supply of the heater 21st stopped, and the energy supply of the injector 22 is stopped to stop fuel injection. In contrast to the present embodiment, when the Stoker 21st Energy is supplied, then the ozone warms up and breaks up or decays. Furthermore, when fuel injection is performed, the ozone can react with the fuel. Regarding these points, step S41 the heating or heating by the heater 21st is stopped and the fuel injection is stopped, and thus a reaction of the ozone with the fuel or a thermal breakdown or breakdown of the ozone can be avoided. As a result, the generated ozone can exhaust passage 10ex can be added without a change.

In view of the above, the present embodiment has the detection unit 41a which are the physical quantities which are correlated with the primary cause of the NO ₂ reduction in NO (that is to say NO reduction correlation values), and a controller 41b on which is the amount of ozone that passes through the ozonizer 30th is generated based on the NO reduction correlation values obtained. Specifically, the amount of ozone that is generated is based on the HC concentration, the CO concentration, the exhaust gas temperature Tex and the catalyst temperature Tcat increases, which are the primary causes of NO ₂ reduction in NO. As a result, the oxidation reaction of NO to NO _{2 is} accelerated. In this regard, the amount of ozone that is generated can be adjusted while considering the primary reasons for the reduction in NO, and thus under-generation and over-generation of ozone due to inhibition reactions can be suppressed.

The present inventors recognized the following points. As explained above, as the HC concentration and the CO concentration increase, there are concerns that the NO ₂ concentration may decrease due to inhibition reactions. As for this, the amount of ozone that is supplied is increased to increase the ratio under which HC and CO be oxidized by ozone and alleviate the above concerns. Furthermore, increasing the amount of ozone supplied further oxidizes NO ₂ and increases the adsorption force. With regard to these points, in the present embodiment, the HC concentration and the CO concentration of the exhaust gas are included in the NO reduction correlation values by the detection unit 41a can be obtained. Then the controller or controller increases 41b the amount of ozone that is generated as the HC or CO concentration obtained increases. As a result, over-generation and under-generation of ozone can be suppressed.

The present inventors recognized the above effects of increasing the amount of ozone that is generated from experimental results shown in the 13 to 16 are shown. Furthermore, the reduction catalyst, which in 1 a type of catalyst which selectively (preferably) causes a reducing agent to react with NOx in the presence of O ₂ . In this regard, the catalyst used for these experiments is a type of catalyst that stores NOx in a lean environment in which O ₂ exists and causes a reducing agent to react with NOx under a rich environment.

For the experiment of 13 the NO concentration is 100 ppm, the ozone concentration is 100 ppm, the HC concentration is zero, the catalyst temperature is 180 ° C and the NOx adsorption rate is measured while the CO concentration is varied. The experimental results, which in 13 show that as the CO concentration increases, the NOx adsorption rate decreases. For the experiment of 14 the NO concentration is 100 ppm, the ozone concentration is 100 ppm, the CO concentration is zero, the catalyst temperature is 180 ° C and the NOx adsorption rate is measured while varying a C ₃ H ₆ concentration. The experimental results, which in 14 show that as the C ₃ H ₆ concentration increases, the NOx adsorption rate decreases.

For the experiment of 15 the NO concentration is 100 ppm, the CO concentration is 300 ppm, the HC concentration is zero, the catalyst temperature is 180 ° C, and the NOx adsorption rate is measured while the ozone concentration is varied. The experimental results, which in 15 show that when the CO concentration is 300 ppm, the NOx adsorption rate is approximately zero when the ozone concentration is zero. Then, when the ozone concentration is increased, the NOx adsorption rate is greatly improved.

For the experiment of 16 the NO concentration is 100 ppm, the C ₃ H ₆ concentration is 300 ppm, the CO concentration is zero, the catalyst temperature is 180 ° C, and the NOx adsorption rate is measured while the ozone concentration is varied. The experimental results, which in 16 show that when the C ₃ H ₆ concentration is 300 ppm, the NOx adsorption rate is approximately zero when the ozone concentration is zero. Then, when the ozone concentration is increased, the NOx adsorption rate is greatly improved. With regard to the experimental results of the 13 to 16 above it is clear that the NOx adsorption rate due to HC and CO is reduced, but is improved by adding ozone.

The present inventors further recognized the following points. As above with reference to the 8th and 9 explains, when the HC concentration or the NO concentration exceeds a predetermined concentration, there is no expectation that further increases in ozone will suppress the inhibition reactions. With regard to these points, in the present embodiment, as soon as the obtained HC concentration or the obtained CO concentration exceeds a predetermined concentration, the controller sets 41b the amount of ozone generated by bracketing or holding the correction factors K1 and K2 regardless of any changes in HC concentration or CO concentration. As a result, it is possible to avoid excessive generation of unnecessary ozone.

The present inventors further recognized the following points. As explained above, as the exhaust gas temperature Tex increases, there are concerns that the NO ₂ concentration may decrease due to an acceleration of inhibition reactions. In this regard, when the ozone supply amount is increased, the ratio under which HC and CO be oxidized by ozone, and the above concerns can be alleviated. With regard to this point, in the present embodiment, the NO reduction correlation values given by the detection unit 41a the exhaust gas temperature Tex is obtained, and the amount of ozone that is generated is controlled in accordance with the exhaust gas temperature Tex. As a result, over-generation and under-generation of ozone can be suppressed.

The present inventors further recognized the following points. As explained above, when the catalyst temperature increases Tcat decreases, the adsorptive power of NO ₂ decreases, and there are concerns that the NO _{2 can} desorb and can be reduced to NO ₍ i.e., under an inhibition reaction), thereby reducing the NO ₂ concentration. In this regard, if the ozone supply amount is increased, the NO _{2 can be} further oxidized in nitric acids with a strong adsorption force, and the above concerns can be alleviated. With regard to this point, in the present embodiment, the NO reduction correlation values given by the detection unit 41a be obtained, the catalyst temperature Tcat on, and the amount of ozone that is generated becomes according to the catalyst temperature Tcat controlled. As a result, over-generation and under-generation of ozone can be suppressed.

During normal operation of the internal combustion engine 10th are the exhaust gas temperature Tex and the catalyst temperature Tcat essentially the same. During transitional operations or a transitional operation, however, in which the load of the internal combustion engine 10th increases rapidly, the catalyst temperature Tcat lag behind the increases in the exhaust gas temperature Tex, and a temperature difference can be generated. At this point, in the present embodiment, each of the exhaust gas temperature Tex and the catalyst temperature Tcat acquired, and the correction factors K3 and K4 are set in accordance with each temperature. Accordingly, even if there is a temperature difference between the exhaust gas temperature Tex and the catalyst temperature Tcat as described above exists, under-generation and over-generation of ozone can be precisely suppressed.

Furthermore, in the present embodiment, the reduction catalyst is a material which has at least silver. In particular, a silver catalyst is carried by an aluminum oxide which is coated on a support. By using such a silver catalyst, the partial oxidation reaction of the 3rd more easily compared to using, for example, a platinum catalyst. Accordingly, in the present embodiment using a silver catalyst, the NOx purification ratio is increased compared to using a platinum catalyst. In particular, the catalyst temperature is within an activated temperature range Tcat a remarkable increase in the NOx purification ratio was observed at the lower end of the temperature range.

Furthermore, in the present embodiment, the reducing agent is supplied by the heater 21st heated above a predetermined temperature and partially oxidized with oxygen in the air to be reformed. As a result, the fuel can be partially oxidized more easily, and thus the reducing agent is reformed more easily. Furthermore, by heating the fuel with the heater 21st the fuel decomposes or breaks up in hydrocarbon compounds with low carbon numbers, i.e. by cracking. The low carbon hydrocarbons due to cracking have low boiling points, and thus the vaporized fuel is suppressed from returning to a liquid state.

Further, in the present embodiment, during the cold flame reaction of the strong oxidation control process, ozone generated by the ozonizer 30th is generated, supplied. Accordingly, the cold flame reaction starts earlier and the duration the cold flame reaction is reduced. As a result, even if the size of the reaction container 20th is reduced in such a way that an amount of time that the fuel has inside the reaction container 20a remains, is reduced, the cold flame reaction can be completed within this period. Accordingly, the size of the reaction container 20th be reduced.

(Second embodiment)

In the first embodiment described above, the reducing agent adding device has a function of supplying ozone and provides the ozone supply device of the present disclosure. However, the ozone supply device of the present embodiment, which is shown in 17th is shown has the reaction container 20th , the stoker 21st and the injector 22 of the 1 not on. The ozone supply device has the ozonizer 30th , the air pump 30p who have favourited Ventilation Passage 26 who have favourited Feeding Passage 23 , the check valve 26v and the ECU 40 on.

It also uses the NOx purification device 12 , what a 1 a reduction catalyst which causes a reducing agent to react selectively (preferably) with NOx in the presence of O ₂ . In this regard, the NOx purifier uses 12a In the present embodiment, a reduction catalyst that stores NOx under a lean environment in which NO _{2 is} present and causes a reducing agent to react with NOx under a rich environment.

Furthermore, the control operations of the present embodiment are different from those of the 5 and 6 in the following way. In particular, the determination steps in the steps S11 and S12 of the 5 not performed and the reducing agent supply control steps in the steps S15 to S17 of the 5 are not carried out. Furthermore, when the catalyst temperature in the steps S13 is determined to be larger than T3, the full stop control operation of step S18 carried out.

The steps continue S20 to S25 of the 6 not done. The target air flow rate Atrg, which is used for the air pump control process of the step S26 is used is adjusted according to the NO concentration in the exhaust gas. At step S27 becomes the energy supply of the ozonizer 30th controlled according to the NO concentration in the exhaust gas. In other words, as the NO concentration in the exhaust gas increases, the amount of ozone that is supplied is also increased.

Furthermore, regarding the control process, the 7 the present embodiment performs the same control operation as that of the first embodiment described above. In other words, the amount of ozone that is generated is controlled based on the NO reduction correlation values. For this reason, the present embodiment suppresses over-generation and under-generation of ozone due to inhibition reactions in the same manner as the first embodiment described above.

(Other embodiments)

Preferred embodiments of the present disclosure are described above. However, the present disclosure is not limited to the above-described embodiments, and a variety of modifications as exemplified below are contemplated. Furthermore, the embodiments are not limited to combinations with one another only in the manner which is explicitly described. Instead, as long as a specific combination is not difficult, the embodiments can be combined in whole or in part, even if the specific combination is not explicitly described.

The present inventors observed the following point. If sulfur components are present in the exhaust gas, these sulfur components can adsorb on the adsorption catalyst. Adsorbed sulfur components are too difficult to desorb from the adsorption catalyst compared to NO ₂ and can easily accumulate in the adsorption catalyst. If the amount of sulfur adsorbed by the adsorption catalyst is large, then the amount of NO ₂ adsorbed can be reduced, that is, the so-called sulfur poisoning problem. Then, as the sulfur poisoning progresses, the adsorbability with respect to NO ₂ weakens. In this case, adsorbed NO ₂ can easily with CO or HC react, that is, go through inhibition reactions. As a result, if the amount of sulfur adsorbed (i.e., the amount of sulfur poisoning) is large, then the adsorbability of NO ₂ decreases. In other words, the amount of sulfur that is adsorbed can be viewed as a physical quantity that is correlated with a trapping force of NO ₂ (i.e., a trapping force correlation value). With regard to this point, the detection unit 41a the amount of sulfur that is adsorbed, and then the controller can 41b the amount of ozone that is generated based on control the amount of sulfur that is adsorbed.

The characteristic lines, which in the 10th and 11 are shown may change according to a relationship between the HC concentration and the CO concentration. With regard to this point, the correction factors K3 and K4 , which is the ozone supply amount according to the catalyst temperature Tcat and correct the exhaust gas temperature Tex, are also modified or modified based on the above-mentioned ratio. Furthermore, a function that defines the relationship between an overall correction factor and the various NO reduction correlation values such as the HC concentration, the CO concentration, the exhaust gas temperature Tex, the catalyst temperature Tcat or the like represents in the microcomputer 41 be saved in advance. Then the various NO reduction correlation values are obtained and substituted into this equation to calculate the total correction factor. In this case, the target ozone flow rate Otrg can be calculated by multiplying the base ozone flow rate Obase by the total correction factor.

In each of the above-described embodiments, when the ozone supply amount is controlled based on the NO reduction correlation values, these NO reduction correlation values include the HC concentration, the CO concentration, the exhaust gas temperature Tex, and the catalyst temperature Tcat on. However, the present disclosure is not limited to controlling the ozone supply amount by obtaining all of these NO reduction correlation values. Instead, at least one of the NO reduction correlation values can be obtained, and the ozone supply amount can be controlled based on the at least one of these values obtained.

In each of the embodiments described above, the catalyst temperature sensor is 42 in the NOx purification device 12 , 12A, and the ambient temperature of the reduction catalyst (that is, the catalyst temperature) is directly detected. In contrast, the catalyst temperature sensor 42 not be provided, and instead the catalyst temperature can be estimated based on, for example, operating conditions or operating states of the internal combustion engine 10th .

At step S30 of the 7 the NO concentration, the HC concentration and the CO concentration of the exhaust gas based on the operating states of the internal combustion engine 10th estimated. Instead, these concentrations can be detected directly by sensors. At step S31 of the 7 becomes the catalyst temperature Tcat through the catalyst temperature sensor 42 detected. The catalyst temperature Tcat can, however, based on the operating conditions of the internal combustion engine 10th instead be estimated. At step S31 of the 7 becomes the exhaust gas temperature Tex based on the operating conditions of the internal combustion engine 10th estimated. However, the exhaust gas temperature Tex can be directly detected by an exhaust gas temperature sensor instead.

In the first embodiment described above, a catalyst having silver is used as the reduction catalyst. However, the present disclosure is not limited to using a silver catalyst in this manner, and catalysts including copper or iron, for example, may be used as the reduction catalyst instead. Further, in the first embodiment described above, a reduction catalyst is used which physically traps NOx (that is, by adsorption). However, the reducing agent adding device can be used for a combustion system having a reduction catalyst that chemically binds (i.e., by occlusion) with NOx to trap the NOx. Such a storage reduction catalyst can be, for example, a catalyst which is formed by combining platinum with an alkali earth metal such as barium or an alkali metal such as lithium.

The reducing agent adding device can be applied to a combustion system in which the NOx purifying device 12 NOx adsorbs when the internal combustion engine 10th burns in a state leaner than a theoretical air-fuel ratio and reduces NOx outside of lean combustion. In this case, ozone can be generated during lean combustion and reformed fuel can be generated outside of lean combustion. A catalyst that traps NOx in this manner during lean combustion may be, for example, a storage reduction catalyst made of platinum and barium carried on a carrier. Further, in the first embodiment described above, fuel is used as the reducing agent, which is the exhaust passage 10ex will be added. However, the ozone supply device of the present disclosure can be applied to a combustion system that uses ammonia as the reducing agent by adding aqueous urea or urea-water solution.

In the first embodiment described above, a check valve 26v of the electromagnetic type used. However, a mechanical type check valve can be used instead. In the first embodiment described above, the air pump is 30p upstream of the ozonizer 30th arranged. The air pump 30p can, however, downstream of the ozonizer 30th be arranged instead. In each embodiment described above is the DPF 13 downstream of the NOx purification device 12 in the exhaust passage 10ex arranged. The DPF 13 can, however, upstream of the NOx purifier 12 be arranged instead.

In the reforming process of the first embodiment described above, when the reductant supply control process is performed, reforming is performed such that aldehydes contained in the reductant reach a predetermined ratio (e.g. 10%). However, the reforming process may be such that the aldehyde ratio is variable according to the amount of NOx added to the NOx purification device 12 flows or the reduction catalyst temperature is set. Furthermore, the reformed reducing agent of the present disclosure is not limited to substances having aldehydes. For example, the reducing agent adding device can use alcohol, acetate, carbon monoxide, hydrogen or partial oxides.

In the embodiment of the 1 the reducing agent adding device is applied to a combustion system mounted on a vehicle. However, the reducing agent adding device can be applied to a stationary combustion system instead. In the embodiment of the 1 The reducing agent adding device is applied to a compression ignition type diesel engine, and light oil (diesel fuel) used as a fuel for combustion is used as the reducing agent. However, the reducing agent adding device can instead be applied to a spark ignition type gasoline engine, and gasoline used as a fuel for combustion can be used as the reducing agent.

The units and functions provided by the ECU 40 (Controller) can be provided by software recorded on a non-transitory recording medium and a computer executing this software only by software, only hardware, or a combination thereof. For example, if the controller is provided by hardware circuits, these circuits can be digital circuits that have a plurality of logic circuits or analog circuits.

Claims (5)

Ozone supply device for a combustion system, which has a NOx purification device (12, 12A) which is arranged in an exhaust gas passage (10ex) of an internal combustion engine (10), the NOx purification device (12, 12A) purifying NOx in an exhaust gas, wherein ozone is supplied by the ozone supply device upstream of the NOx purification device (12, 12A) in the exhaust passage (10ex) to oxidize NOx in the exhaust gas into NO ₂ , the ozone supply device comprising: an ozonizer (30) which discharges ozone by electrical discharges generated; a detection unit (41a) which obtains a NO reduction correlation value, the NO reduction correlation value being a physical quantity correlated with a primary cause of NO ₂ reduction in NO, the NO ₂ reduction in NO at a portion of the Exhaust gas passage (10ex) occurs which is upstream of the NOx purification device (12, 12A) or inside the NOx purification device (12, 12A); and a controller (41b) that controls an amount of ozone generated by the ozonizer (30) according to the NO reduction correlation value obtained by the detection unit (41a). Ozone supply device after Claim 1 , wherein the NO reduction correlation value obtained by the detection unit (41a) has at least one of an HC concentration of the exhaust gas and a CO concentration of the exhaust gas, and the controller (41b) increases the amount of ozone that is generated when the HC concentration or the CO concentration obtained by the detection unit (41a) increases. Ozone supply device after Claim 2 , wherein when the HC concentration or the CO concentration obtained by the detection unit (41a) is at or above a predetermined concentration, the controller (41b) controls the amount of ozone generated regardless of any changes in the HC concentration or the CO concentration. Ozone supply device according to one of the Claims 1 to 3rd , wherein the NO reduction correlation value obtained by the detection unit (41a) has an exhaust gas temperature. Ozone supply device according to one of the Claims 1 to 4th , wherein the NOx purification device (12, 12A) has a function of trapping NO ₂ in the exhaust gas, and the NO reduction correlation value obtained by the detection unit (41a) is a temperature of the NOx purification device (12, 12A) having.

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