JP6156238B2 - Reducing agent addition device - Google Patents

Description

  The present invention relates to a reducing agent addition apparatus for adding a hydrocarbon compound (fuel) as a reducing agent used for NOx reduction.

  2. Description of the Related Art Conventionally, a reducing agent addition device that adds fuel (reducing agent) to an upstream side of a reduction catalyst in an exhaust passage is known with respect to a technique for purifying NOx (nitrogen oxide) contained in exhaust gas from an internal combustion engine. According to this addition device, NOx is reduced and purified by the fuel on the reduction catalyst.

  With regard to this type of addition apparatus, Patent Document 1 discloses a technique in which an ozonizer that generates ozone by discharge is provided upstream of a catalyst in an exhaust passage. According to this, the reaction on the catalyst is activated by ozone and the purification rate is improved. In view of the fact that ozone is easily destroyed in a high-temperature environment, Patent Document 1 also discloses a technique for air-cooling an ozonizer. Specifically, when the ozonizer reaches a high temperature exceeding the upper limit value, the flow rate of the cooling air is increased to suppress the rise in the temperature of the ozonizer.

JP 2011-85086 A

  Now, the present inventors add a reducing agent that heats the fuel with a heater and mixes it with air to partially oxidize the fuel to produce reformed fuel and add the reformed fuel to the exhaust passage. The device was examined. Furthermore, the present inventors have studied to promote partial oxidation of fuel by changing the air used for such partial oxidation to air containing ozone by discharge of an ozonizer. Also in the apparatus according to this study, when the ozonizer becomes high temperature, it is desirable to increase the flow rate of air supplied to the ozonizer to cool the ozonizer and to suppress thermal destruction of ozone.

  However, in the apparatus according to the above study, the air supplied to the ozonizer is mixed with fuel on the downstream side of the ozonizer and used for oxidation (reforming) of the fuel. For this reason, when air cooling is attempted by increasing the flow rate of the air supplied to the ozonizer, the temperature of the fuel heated by the heater is lowered, and there is a concern that partial oxidation of the fuel is inhibited.

  In short, if the air cooling of the ozonizer is promoted by increasing the air flow rate, the ozone for promoting the fuel reforming can be increased, but the fuel temperature is lowered and the fuel reforming is hindered.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a reducing agent addition apparatus that promotes reforming of a fuel used as a reducing agent.

  The invention disclosed herein employs the following technical means to achieve the above object. Note that the reference numerals in parentheses described in the claims and in this section indicate the correspondence with the specific means described in the embodiments described later, and do not limit the technical scope of the invention. .

  One of the disclosed inventions is provided in a combustion system in which an NOx purification device (15) for purifying NOx contained in exhaust gas of an internal combustion engine (10) on a reduction catalyst is provided in an exhaust passage (10ex). Of these, it is assumed that the reducing agent is added to the upstream side of the reduction catalyst.

And, an ozonizer (20) that discharges the supplied air to generate air containing ozone, a fuel injection valve (40) that injects fuel that is a hydrocarbon compound,
A heater (50) for heating the fuel injected from the fuel injection valve;
A mixing chamber (30a) for mixing the ozone-containing air generated by the ozonizer and the fuel heated by the heater is formed inside, and the mixing container (30a) that partially oxidizes the fuel by mixing to generate the reformed fuel ( 30),
Fuel addition control means (S12) for controlling the fuel injection valve, the heater, and the ozonizer to generate reformed fuel and to add the reformed fuel as a reducing agent to the exhaust passage;
Ozone addition control means (S13) for controlling the generation of ozone by operating the ozonizer while stopping the operation of the fuel injection valve and the heater and adding the ozone to the exhaust passage;
When the internal temperature of the ozonizer exceeds the upper limit value (Tu1, Tu2) and becomes a high temperature, the air increase control means (S25, S25, S2) suppresses the increase in the internal temperature by increasing the flow rate of the air supplied to the ozonizer. S50), and
The upper limit value (Tu2) at the time of control by the fuel addition control means is set to a value higher than the upper limit value (Tu1) at the time of control by the ozone addition control means.

According to the above invention, the ozonizer operates as follows in the control of the fuel addition control means and the ozone addition control means. That is, at the time of control by the fuel addition control means, the fuel as the reducing agent is reformed by the ozone-containing air, so that NOx reduction on the reduction catalyst can be promoted. In addition, since ozone is added to the exhaust passage during the control by the ozone addition control means, NO in the exhaust is oxidized to NO ₂ and the amount of NOx adsorbed to the NOx purification device can be increased. That is, the ozonizer used for promoting the reforming of the fuel can be used for increasing the adsorption amount due to NO oxidation, for example, when the catalyst is not activated and cannot be reduced even when the fuel is added.

  Further, according to the above invention, when the internal temperature of the ozonizer becomes higher than the upper limit value, the flow rate of air supplied to the ozonizer is increased, so that air cooling of the ozonizer is promoted and temperature rise is suppressed. , Ozone destruction due to high temperature is suppressed.

  Here, if the air cooling is promoted at the time of fuel addition, the temperature of the fuel is lowered and the reforming is inhibited. In the above-described invention in view of this point, the upper limit value used for determining whether or not to increase the air flow rate is set to a higher value when adding reformed fuel than when adding ozone. Therefore, at the time of fuel addition, an increase in the air flow rate is not executed at a certain high temperature, so that the concern that the reforming is hindered due to a decrease in fuel temperature can be reduced. In other words, the upper limit value can be set so that the demerit of the fuel temperature decrease due to the increase in the air flow rate does not become greater than the advantage due to the increase in ozone due to the increase in the air flow rate.

  As described above, according to the present invention, it is possible to avoid the air increase control as in the case of ozone addition until the time of fuel addition, and to sufficiently promote the reforming of fuel at the time of fuel addition.

1 is a schematic diagram showing a reducing agent addition apparatus according to a first embodiment of the present invention and a combustion system to which the apparatus is applied. Sectional drawing which shows typically the reducing agent addition apparatus which concerns on 1st Embodiment. The flowchart which shows the process sequence of control for switching the operation mode of the reducing agent addition apparatus shown in FIG. The figure which shows the optimal temperature of an ozonizer in each of the operation mode shown in FIG. The flowchart which shows the procedure of the subroutine process based on the ozone production | generation control shown in FIG. The flowchart which shows the procedure of the subroutine process regarding the reformed fuel production | generation control shown in FIG. The flowchart which shows the procedure of the subroutine process regarding the reformed fuel production | generation control shown in FIG. The flowchart which shows the procedure of the subroutine process regarding the standby control shown in FIG. The flowchart which shows the process sequence of standby control in 2nd Embodiment of this invention. The flowchart which shows the process sequence of ozone production | generation control in 3rd Embodiment of this invention. The flowchart which shows the process sequence of reformed fuel production | generation control in 4th Embodiment of this invention. The schematic diagram which shows the reducing system which concerns on 5th Embodiment of this invention, and the combustion system to which the apparatus is applied. The schematic diagram which shows the reducing system which concerns on 6th Embodiment of this invention, and the combustion system to which the apparatus is applied.

  Hereinafter, a plurality of modes for carrying out the invention will be described with reference to the drawings. In each embodiment, portions corresponding to the matters described in the preceding embodiment may be denoted by the same reference numerals and redundant description may be omitted. In each embodiment, when only a part of the configuration is described, the other configurations described above can be applied to other portions of the configuration.

(First embodiment)
The combustion system shown in FIG. 1 includes an internal combustion engine 10, a supercharger 11, a particulate collection device (DPF 14), a DPF regeneration device (regeneration DOC 14 a), a NOx purification device 15, a reducing agent purification device (purification). DOC16) and a reducing agent adding device A1. The combustion system is mounted on a vehicle, and the vehicle travels using the output of the internal combustion engine 10 as a drive source. The internal combustion engine 10 is a compression self-ignition diesel engine, and light oil is used as a fuel for combustion.

  The supercharger 11 includes a turbine 11a, a rotating shaft 11b, and a compressor 11c. The turbine 11a is disposed in the exhaust passage 10ex of the internal combustion engine 10 and rotates by the kinetic energy of the exhaust. The rotating shaft 11b couples the impellers of the turbine 11a and the compressor 11c to transmit the rotational force of the turbine 11a to the compressor 11c. The compressor 11c is disposed in the intake passage 10in of the internal combustion engine 10, compresses the intake air, and supercharges the internal combustion engine 10.

  A cooler 12 for cooling the intake air compressed by the compressor 11c is disposed on the downstream side of the compressor 11c in the intake passage 10in. The compressed intake air cooled by the cooler 12 is adjusted in flow rate by a throttle valve 13 and then distributed to a plurality of combustion chambers of the internal combustion engine 10 by an intake manifold.

  A regeneration DOC 14a (Diesel Oxidation Catalyst), a DPF 14 (Diesel Particulate Filter), a NOx purification device 15, and a purification DOC 16 are arranged in this order on the downstream side of the turbine 11a in the exhaust passage 10ex. The DPF 14 collects fine particles contained in the exhaust. The regeneration DOC 14a has a catalyst that oxidizes and burns unburned fuel in the exhaust. Due to this combustion, the fine particles collected by the DPF 14 are burned, and the DPF 14 is regenerated to maintain the collection ability. Note that combustion by supplying unburned fuel to the regeneration DOC 14a is not always performed, but temporarily performed at a time when regeneration is necessary.

  A supply pipe 32 of the reducing agent adding device A1 is connected to the downstream side of the DPF 14 and the upstream side of the NOx purification device 15 in the exhaust passage 10ex. The reformed fuel generated by the reducing agent adding device A1 is added as a reducing agent from the supply pipe 32 to the exhaust passage 10ex. The reformed fuel is obtained by partially oxidizing a hydrocarbon (fuel) used as a reducing agent and reforming it into a partially oxidized hydrocarbon such as an aldehyde, which will be described in detail later.

The NOx purification device 15 includes a honeycomb-shaped carrier 15b that carries a reduction catalyst, and a housing 15a that houses the carrier 15b. The NOx purification device 15 purifies NOx contained in the exhaust by reacting NOx in the exhaust with the reformed fuel on the reduction catalyst and reducing it to N ₂ . Although exhaust gas contains O ₂ in addition to NOx, the reformed fuel reacts selectively with NOx in the presence of O ₂ .

  A reduction catalyst having a function of adsorbing NOx is used. Specifically, when the catalyst temperature is lower than the activation temperature at which the reduction reaction is possible, the reduction catalyst exhibits a function of adsorbing NOx in the exhaust. When the catalyst temperature is equal to or higher than the activation temperature, the adsorbed NOx is reduced by the reformed fuel and released from the reduction catalyst. For example, the NOx purification device 15 having a NOx adsorption function is provided by a reduction catalyst made of silver alumina supported on the carrier 15b.

  The purification DOC 16 is configured by accommodating a carrier carrying an oxidation catalyst in a housing. The purification DOC 16 oxidizes the reducing agent that has not been used for NOx reduction on the reduction catalyst and has flowed out of the NOx purification device 15 on the oxidation catalyst. This prevents the reducing agent from being released into the atmosphere from the outlet of the exhaust passage 10ex. Note that the activation temperature of the oxidation catalyst (eg, 200 ° C.) is lower than the activation temperature of the reduction catalyst (eg, 250 ° C.).

  Next, the reducing agent adding device A1 that generates reformed fuel and adds it to the exhaust passage 10ex from the supply pipe 32 will be described. The reducing agent addition apparatus A1 includes an ozonizer 20, an air pump 20p, a mixing container 30, a fuel injection valve 40, and a heater 50, which will be described in detail below.

  As shown in FIG. 2, the ozonizer 20 includes a housing 22 that forms a flow passage 22a therein, and a plurality of electrodes 21 are disposed in the flow passage 22a. Specifically, the electrode 21 is held in the housing 22 via the electrical insulating member 23. These electrodes 21 have a flat plate shape arranged so as to face each other in parallel, and electrodes to which a high voltage is applied and electrodes having a ground voltage are alternately arranged. The voltage application to the electrode 21 is controlled by a microcomputer (microcomputer 81) included in the electronic control unit (ECU 80).

  Air blown by the air pump 20p flows into the housing 22 of the ozonizer 20. The air pump 20p is driven by an electric motor, and the electric motor is controlled by the microcomputer 81. The air blown by the air pump 20 p flows into the flow passage 22 a in the housing 22 and flows through the interelectrode passage 21 a that is a passage between the electrodes 21. The flow rate of air blown by the air pump 20p and the mass of air supplied to the ozonizer 20 per unit time (hereinafter referred to as air flow rate) is controlled by the microcomputer 81. For example, the microcomputer 81 controls the air flow rate by duty-controlling the electric motor.

  On the downstream side of the ozonizer 20, a mixing container 30 that forms a mixing chamber 30a is attached. The mixing container 30 is formed with an air inlet 30b through which air flowing through the interelectrode passage 21a flows into the mixing chamber 30a. Further, the mixing container 30 is formed with a jet port 30c through which the air flowing into the mixing chamber 30a is jetted to the supply pipe 32.

  A fuel injection valve 40 is attached to the mixing container 30. The liquid fuel in the fuel tank 40t shown in FIG. 1 is supplied to the fuel injection valve 40 by the pump 40p, and injected from the injection hole (not shown) of the fuel injection valve 40 into the mixing chamber 30a. The fuel in the fuel tank 40t is also used as the combustion fuel described above, and the fuel used for combustion of the internal combustion engine 10 and the fuel used as the reducing agent are shared. The fuel injection valve 40 is configured to open by an electromagnetic force generated by an electromagnetic solenoid, and power supply to the electromagnetic solenoid is controlled by the microcomputer 81.

  A heater 50 is attached to the mixing container 30. The heater 50 includes a heating element (not shown) that generates heat when energized, and a heat transfer cover 51 that houses the heating element. The energization state of the heating element is controlled by the microcomputer 81. The outer peripheral surface of the heat transfer cover 51 corresponds to the heating surface 51a, and the heating surface 51a rises in temperature when the heat transfer cover 51 is heated by the heating element.

  The heating surface 51a is disposed at a position facing the injection hole of the fuel injection valve 40 in the mixing chamber 30a so that the liquid fuel injected from the fuel injection valve 40 directly adheres to the heating surface 51a. The liquid fuel heated by the heater 50 is vaporized in the mixing chamber 30a. Further, the vaporized fuel is heated to a predetermined temperature or higher by the heater 50. As a result, cracking occurs in which the fuel is decomposed into hydrocarbons having a small number of carbon atoms. The heated gaseous fuel is mixed with the air flowing in from the air inlet 30b in the mixing chamber 30a. As a result, the fuel is partially oxidized by oxygen in the air, and the fuel is reformed to partially oxidized hydrocarbons such as aldehydes.

  A temperature sensor 31 for detecting the temperature of the mixing chamber 30 a is attached to the mixing container 30. Specifically, the temperature sensor 31 is arranged in the upper part of the heating surface 51a in the mixing chamber 30a. The temperature detected by the temperature sensor 31 is the temperature after the reaction between the vaporized fuel and air. The temperature sensor 31 outputs detected temperature information (detected temperature) to the ECU 80.

  When the energizer 20 is energized, the electrons emitted from the electrodes 21 collide with oxygen molecules contained in the air in the interelectrode passage 21a. Then, ozone is generated from oxygen molecules. In other words, the ozonizer 20 generates oxygen as active oxygen by changing oxygen molecules into a plasma state by discharge. Accordingly, the air flowing into the mixing container 30 from the air inlet 30b contains ozone generated by the ozonizer 20.

  In the mixing chamber 30a, a cold flame reaction occurs in which gaseous fuel is partially oxidized by oxygen or ozone in the air. Such a partially oxidized fuel is called a reformed fuel. As a specific example of the reformed fuel, a partial oxide in a state where a part of the fuel (hydrocarbon compound) is oxidized to an aldehyde group (CHO) ( For example, aldehyde). And if the ozone produced | generated by the ozonizer 20 is contained in the air, the oxidation reaction rate of the fuel in the mixing chamber 30a will become quick.

  Here, the fuel in the high temperature environment oxidizes and reacts with oxygen contained in the surrounding air even if it is atmospheric pressure, and self-ignition combustion. Such an oxidation reaction by self-ignition combustion is also called a hot flame reaction in which carbon dioxide and water are generated while generating heat. However, when the ratio of fuel to air (equivalent ratio) and the ambient temperature are within a predetermined range, the period of staying in the cold flame reaction described below becomes longer, and then a hot flame reaction occurs. That is, an oxidation reaction occurs in two stages, a cold flame reaction and a hot flame reaction.

  This cold flame reaction is a reaction that easily occurs when the ambient temperature is low and the equivalence ratio is small, and is a reaction in which the fuel is partially oxidized by oxygen contained in the surrounding air. Then, when the ambient temperature rises due to heat generated by the cold flame reaction and then a certain period of time elapses, the partially oxidized fuel (for example, aldehyde) is oxidized and the above-described hot flame reaction occurs. Therefore, if the fuel stays in the mixing chamber 30a for a long time, a hot flame reaction also occurs after the cold flame reaction occurs in the mixing chamber 30a.

  In the present embodiment, the atmospheric temperature, the equivalence ratio, and the fuel residence time in the mixing chamber 30a are adjusted so that the cold flame reaction occurs but the hot flame reaction does not occur. Further, by using a partially oxidized fuel such as aldehyde generated by the cold flame reaction as a reducing agent for NOx purification, the NOx purification rate by the NOx purification device 15 can be improved. Further, the higher the concentration of ozone contained in the air flowing into the mixing chamber 30a, the more the fuel oxidation reaction is promoted, and the start timing of the cold flame reaction is advanced. Therefore, by generating a sufficient amount of ozone by the ozonizer 20, it is possible to reduce the amount of fuel flowing out of the mixing chamber 30a without being reformed to aldehyde or the like.

  The microcomputer 81 provided in the ECU 80 includes a storage device that stores a program and a central processing unit that executes arithmetic processing according to the stored program. The ECU 80 controls the operation of the internal combustion engine 10 based on detection values of various sensors. Specific examples of the various sensors include an engine rotation speed sensor 92, a throttle opening sensor 93, an intake pressure sensor 94, an intake air amount sensor 95, an exhaust temperature sensor 96, an outside air temperature sensor 91, and the like.

  The engine rotation speed sensor 92 detects the rotation speed (engine speed) of the output shaft 10 a of the internal combustion engine 10. The throttle opening sensor 93 detects the opening of the throttle valve 13. The intake pressure sensor 94 detects the pressure on the downstream side of the throttle valve 13 in the intake passage 10in. The intake air amount sensor 95 detects the mass flow rate of intake air.

  In general, the ECU 80 controls the injection amount and injection timing of combustion fuel injected from a fuel injection valve (not shown) according to the rotation speed of the output shaft 10a and the load of the internal combustion engine 10. Further, the ECU 80 controls the operation of the reducing agent adding device A1 based on the exhaust temperature detected by the exhaust temperature sensor 96. That is, the microcomputer 81 performs control so as to switch between generation of reformed fuel and generation of ozone by repeatedly executing the program of the procedure shown in FIG. 3 at a predetermined period. The above program is triggered by the ignition switch being turned on, and is always executed during the operation period of the internal combustion engine 10.

  First, in step S10 of FIG. 3, it is determined whether or not NOx is generated due to combustion in the internal combustion engine 10. If it is determined that NOx is being generated, the reducing agent adding device A1 is operated according to the temperature of the reduction catalyst (NOx catalyst temperature) of the NOx purification device 15.

  Specifically, first, in step S11, it is determined whether or not the NOx catalyst temperature is lower than the reduction catalyst activation temperature Tact (for example, 250 ° C.). The NOx catalyst temperature is estimated based on the exhaust temperature detected by the exhaust temperature sensor 96. Here, the activation temperature of the reduction catalyst indicates a temperature at which NOx can be reduced and purified by the reformed fuel.

  If it is determined that the NOx catalyst temperature is not lower than the activation temperature Tact, a reformed fuel generation control subroutine process (see FIGS. 6 and 7) described later is performed in step S12. If it is determined that the NOx catalyst temperature is lower than the activation temperature Tact, a subroutine process of ozone generation control (see FIG. 5) described later is performed in step S13. Hereinafter, the operation mode of the reducing agent addition device A1 based on reformed fuel generation control is referred to as a reformed fuel mode, and the operation mode of the reducing agent addition device A1 based on ozone generation control is referred to as an ozone mode.

  On the other hand, if it is determined in step S10 that NOx is not generated, the process proceeds to step S14, and it is determined whether it is necessary to prepare so that the NOx purification by the NOx purification device 15 can be started quickly. . For example, when the internal combustion engine 10 is automatically stopped by idle stop control, or when the internal combustion engine 10 is automatically stopped when the vehicle is driven by an electric motor, it is considered that there is a high possibility that NOx will occur within a predetermined time. It is determined that preparation for NOx purification is necessary.

  If it is determined in step S14 that preparation for purification is necessary, in step S15, a standby control subroutine process (see FIG. 8) described later is performed. Hereinafter, the operation mode of the reducing agent adding apparatus A1 by the standby control is referred to as a standby mode. On the other hand, if it is determined in step S14 that preparation for purification is unnecessary, the operation of the reducing agent adding apparatus A1 is stopped in step S16. Specifically, when energization is performed on the ozonizer 20, the air pump 20p, the fuel injection valve 40, and the heater 50, the energization thereof is stopped.

  Since ozone is easily destroyed in a high temperature environment, when the temperature of the ozonizer 20 exceeds the upper limit and becomes high, the supply flow rate (air flow rate) of air to the ozonizer 20 is increased, and the ozonizer 20 is increased. It is desirable to air-cool. However, the air supplied to the ozonizer 20 is mixed with fuel on the downstream side of the ozonizer 20 and used for fuel oxidation (reformation). Therefore, when air cooling is attempted by increasing the air flow rate, the temperature in the mixing chamber 30a (the temperature of the vaporized fuel) decreases, and there is a concern that partial oxidation of the fuel is hindered.

  In view of the air cooling due to the air flow rate and the decrease in the fuel temperature that occurs as a contradiction, the optimum temperature range of the internal temperature of the ozonizer 20, that is, the air temperature of the flow passage 22a, is set as shown in FIG. Specifically, the optimum temperature range R1 in the ozone mode is 120 ° C. or less, the optimum temperature range R2 in the reformed fuel mode is 80 ° C. or more and 200 ° C. or less, and the optimum temperature range R3 in the standby mode (standby state). It is set to 80 ° C. or higher and 120 ° C. or lower. Then, the air flow rate is controlled in each mode so that the internal temperature of the ozonizer 20 falls within these optimum temperature ranges R1, R2, and R3.

  In the ozone mode, first, in step S20 shown in FIG. 5, the energization to the fuel injection valve 40 is stopped to stop the fuel injection, and the energization to the heater 50 is stopped to stop the heating of the mixing chamber 30a. In the subsequent step S21, a required ozone flow rate Oreq, which is the amount of ozone added to the exhaust passage 10ex required per unit time, is calculated. Specifically, the NOx flow rate discharged based on the operating state of the internal combustion engine 10 such as the load of the internal combustion engine 10 and the engine speed is estimated, and the required ozone flow rate Oreq is calculated based on the estimated NOx flow rate.

  In subsequent step S22, a base air flow rate Abase, which is a base value of the air flow rate, is calculated based on the required ozone flow rate Oreq calculated in step S21. The base air flow rate Abase is a flow rate necessary for the ozone generation amount corresponding to the required ozone flow rate Oreq. If there is no destruction of ozone due to high temperature, when the air at the base air flow rate Abase flows into the ozonizer 20, ozone can be generated with the required ozone flow rate Oreq without excess or deficiency.

  In subsequent step S23, the internal temperature (ozonizer temperature Ta) of the ozonizer 20 is acquired. For example, the ozonizer temperature Ta is estimated on the basis of the outside air temperature detected by the outside air temperature sensor 91, the air flow rate, the amount of heat generated by discharge, and the like. In subsequent step S24, it is determined whether or not the ozonizer temperature Ta exceeds the upper limit value Tu1 (upper limit value when ozone is added) and is at a high temperature. The upper limit value Tu1 is a preset value and corresponds to the upper limit value Tu1 of the optimum temperature range R1 shown in FIG. The upper limit value Tu1 in the ozone mode is set to a value smaller than the upper limit value Tu2 (upper limit value at the time of fuel addition) of the optimum temperature range R2 in the reformed fuel mode.

  If it is determined that the ozonizer temperature Ta is higher than the upper limit Tu1, the value obtained by adding the predetermined value α to the base air flow rate Abase is set as the target air flow rate Atrg in the next step S25. On the other hand, when it is determined that the ozonizer temperature Ta is equal to or lower than the upper limit value Tu1, the temperature of the mixing chamber 30a (mixing chamber temperature Tb) is acquired in the next step S26. Specifically, the detection value of the temperature sensor 31 is acquired. Thereafter, in step S27, it is determined whether or not the mixing chamber temperature Tb is equal to or higher than a predetermined temperature Tx.

  If it is determined that the mixing chamber temperature Tb is lower than the predetermined temperature Tx, a value obtained by subtracting the predetermined value α from the base air flow rate Abase is set as the target air flow rate Atrg in the next step S28. On the other hand, if it is determined that the mixing chamber temperature Tb is equal to or higher than the predetermined temperature Tx, the base air flow rate Abase is set as the target air flow rate Atrg in the next step S29.

  In the subsequent step S30, the operation of the air pump 20p is controlled based on the target air flow rate Atrg set in steps S25, S28, and S29. Specifically, control is performed so that the air flow rate becomes the target air flow rate Atrg by supplying power corresponding to the target air flow rate Atrg to the electric motor of the air pump 20p.

  Next, in step S31, it is determined whether or not the state (Ta> Tu1) denied in step S24 continues for a predetermined time or more. If a negative determination is made that the operation is not continued, the process proceeds to step S32 where normal power is supplied to the ozonizer 20 to discharge (normal discharge). On the other hand, when an affirmative determination is made that the state of Ta> Tu1 has continued for a predetermined time or longer, the process proceeds to step S33, and power lower than the normal power in step S32 is supplied to the ozonizer 20 for discharge (low power discharge). ) Specifically, the voltage applied to the electrode 21 is changed to a lower value during low power discharge than during normal discharge. Note that if the voltage applied to the electrode 21 is excessively low, the discharge becomes unstable, and if it is excessively high, the ratio of the amount of ozone generated relative to the amount of power supply decreases and the power consumption deteriorates. Therefore, the applied voltage is set to a value within the range in consideration of these balances, that is, a value at which the power consumption does not fall below a predetermined value while ensuring stable discharge.

  According to the ozone generation control described above, ozone is generated by the ozonizer 20, and the generated ozone is added to the exhaust passage 10ex through the mixing chamber 30a and the supply pipe 32. Here, when the heater 50 is energized, the ozone is heated and collapses. Moreover, if fuel injection is performed, ozone will react with fuel. In view of these points, since the heating and fuel injection by the heater 50 are stopped in the control of FIG. 5, it is possible to avoid the reaction of ozone with the fuel and the collapse of the heating, and the generated ozone is added to the exhaust passage 10ex as it is. The Rukoto.

  In the reformed fuel mode, first, in step S40 shown in FIG. 6, a required fuel amount Freq, which is a fuel injection amount into the mixing chamber 30a required per unit time, is calculated. Specifically, the NOx flow rate discharged based on the operating state of the internal combustion engine 10 such as the load and engine speed of the internal combustion engine 10 is estimated, and the required fuel amount Freq is calculated based on the estimated NOx flow rate.

  In subsequent step S41, the operation of the fuel injection valve 40 is controlled based on the required fuel amount Freq calculated in step S40, and an amount of fuel corresponding to the required fuel amount Freq is injected into the mixing chamber 30a. In subsequent step S42, the mixing chamber temperature Tb detected by the temperature sensor 31 is acquired. In subsequent step S43, a deviation ΔTb between the detected mixing chamber temperature Tb and the target mixing chamber temperature Tbtrg is calculated. The target mixing chamber temperature Tbtrg is set to a temperature at which the above-described cold flame reaction occurs but no hot flame reaction occurs.

  In the subsequent step S45, the amount of power supplied to the heater 50 is controlled based on the deviation ΔTb calculated in step S43. That is, for example, the amount of power supplied to the heater 50 is feedback-controlled so that the deviation ΔTb becomes zero. In the subsequent step S46, the target equivalent ratio φtrg is set based on the mixing chamber temperature Tb acquired in step S42. The target equivalent ratio φtrg is set to an equivalent ratio in which a cold flame reaction occurs but a hot flame reaction does not occur. Since the equivalent ratio that causes only the cold flame reaction in this way varies depending on the ambient temperature of the fuel, the equivalent ratio that causes only the cold flame reaction is calculated based on the actually detected mixing chamber temperature Tb. The target equivalent ratio φtrg is set so that the equivalent ratio is obtained.

  In the subsequent step S47, a base air flow rate Abase that is a base value of the air flow rate is calculated based on the target equivalent ratio φtrg set in step S46 and the required fuel amount Freq calculated in step S40. When the air having the base air flow rate Abase flows into the mixing chamber 30a, the ratio of the gaseous fuel and air in the mixing chamber 30a becomes the target equivalent ratio φtrg.

  In the subsequent step S48 of FIG. 7, the ozonizer temperature Ta is acquired. For example, the ozonizer temperature Ta is estimated based on the outside air temperature detected by the outside air temperature sensor 91, the air flow rate, the amount of heat generated by the discharge, the radiant heat from the mixing container 30, and the like. In a succeeding step S49, it is determined whether or not the ozonizer temperature Ta exceeds the upper limit value Tu2. The upper limit value Tu2 is a preset value and corresponds to the upper limit value Tu2 of the optimum temperature range R2 shown in FIG. The upper limit value Tu2 in the reformed fuel mode is set to a value larger than the upper limit value Tu1 of the optimum temperature range R1 in the ozone mode.

  When it is determined that the ozonizer temperature Ta is higher than the upper limit value Tu2, a value obtained by adding the predetermined value β to the base air flow rate Abase is set as the target air flow rate Atrg in the next step S50. On the other hand, if it is determined that the ozonizer temperature Ta is equal to or lower than the upper limit value Tu2, it is determined in the next step S51 whether or not the ozonizer temperature Ta exceeds the lower limit value Td. The lower limit value Td is a preset value and corresponds to the lower limit value Td of the optimum temperature range R2 shown in FIG. The lower limit value d in the reformed fuel mode is set to a value smaller than the upper limit value Tu1 of the optimum temperature range R1 in the ozone mode.

  If it is determined that the ozonizer temperature Ta is lower than the lower limit value Td, a value obtained by subtracting the predetermined value β from the base air flow rate Abase is set as the target air flow rate Atrg in the next step S52. On the other hand, if it is determined that the ozonizer temperature Ta is equal to or higher than the lower limit value Td, the base air flow rate Abase is set as the target air flow rate Atrg in the next step S53.

  In subsequent step S54, the operation of the air pump 20p is controlled based on the target air flow rate Atrg set in steps S50, S52, and S53. Specifically, control is performed so that the air flow rate becomes the target air flow rate Atrg by supplying power corresponding to the target air flow rate Atrg to the electric motor of the air pump 20p.

  Next, in step S55, it is determined whether the state denied in step S49 (Ta> Tu2) continues for a predetermined time or more. If a negative determination is made that the operation has not continued, the process proceeds to step S56, where normal power is supplied to the ozonizer 20 and discharged (normal discharge). On the other hand, if an affirmative determination is made that the state of Ta> Tu2 continues for a predetermined time or longer, the process proceeds to step S57, and power lower than the normal power in step S56 is supplied to the ozonizer 20 for discharge (low power discharge). ) Specifically, the voltage applied to the electrode 21 is changed to a lower value during low power discharge than during normal discharge. Note that if the voltage applied to the electrode 21 is excessively low, the discharge becomes unstable, and if it is excessively high, the ratio of the amount of ozone generated relative to the amount of power supply decreases and the power consumption deteriorates. Therefore, the applied voltage is set to a value within the range in consideration of these balances, that is, a value at which the power consumption does not fall below a predetermined value while ensuring stable discharge.

  According to the reformed fuel generation control explained above, the mixing chamber temperature Tb and the equivalence ratio are adjusted so that the cool flame reaction occurs, and the partially oxidized fuel (reformed fuel) by the cool flame reaction is converted into NOx. It is added to the exhaust passage 10ex as a reducing agent for purification. Therefore, the NOx purification rate can be improved compared to the case where fuel that is not partially oxidized is used as it is as a reducing agent. Further, by including ozone in the air used for oxidizing the fuel, the start timing of the cool flame reaction can be advanced and the cool flame reaction time can be shortened.

  In the standby mode, first, when energization of the ozonizer 20, the fuel injection valve 40, and the heater 50 is performed in step S60 shown in FIG. 8, the energization of these is stopped. In the subsequent step S61, the ozonizer temperature Ta is acquired in the same manner as in step S23 of FIG. In a succeeding step S62, it is determined whether or not the ozonizer temperature Ta acquired in the step S61 is lower than a lower limit value Td. The lower limit value Td used in this determination is the same as the lower limit value Td used in the determination in step S51 of FIG.

  If a negative determination is made that Ta <Td is not satisfied, in the following step S63, the power supply amount to the air pump 20p is controlled so that the ozonizer temperature Ta becomes equal to or lower than the upper limit value Tu1. The upper limit value Tu1 used in this control is the same as the upper limit value Tu1 used in the determination in step S24 of FIG. On the other hand, when an affirmative determination is made that Ta <Td, the air cooling of the ozonizer temperature Ta is suppressed by stopping energization of the air pump 20p.

  The microcomputer 81 functions as various control means described below when executing various steps.

  That is, in steps S25 and S50, when the ozonizer temperature Ta becomes higher than the upper limit values Tu1 and Tu2, it functions as “air increase control means” that increases the air flow rate and suppresses the rise of the ozonizer temperature Ta. . In step S52, when the ozonizer temperature Ta exceeds the lower limit value Td and becomes a low temperature, it functions as “air reduction control means” that reduces the air flow rate and suppresses the decrease in the ozonizer temperature Ta. Steps S33 and S57 function as “power reduction control means” that reduces the amount of power supplied to the ozonizer 20 during control by the air increase control means.

  In step S12, it functions as “fuel addition control means” for generating and adding reformed fuel. In step S13, it functions as “ozone addition control means” for generating and adding ozone. In steps S62, S63, and S64, it functions as “standby flow rate control means” for controlling the air flow rate so that Td <Ta ≦ Tu1.

  In steps S21, S22, and S29, “ozone air control means” that calculates a base air flow rate Abase (target flow rate) based on the required ozone flow rate Oreq (required flow rate) and controls the air flow rate to be the base air flow rate Abase. Function as. In steps S40, S47, and S53, a “fuel air control means” that calculates a base air flow rate Abase (target flow rate) based on the required fuel amount Freq (required flow rate) and controls the air flow rate to become the base air flow rate Abase. Function as.

  As described above, according to the present embodiment, the flow rate of the air supplied to the ozonizer 20 is increased when the ozonizer temperature Ta becomes higher than the upper limit values Tu1 and Tu2. Therefore, air cooling of the ozonizer 20 is promoted to suppress a temperature rise, and ozone destruction due to a high temperature is suppressed. And upper limit Tu1 used for the determination at the time of reformed fuel addition is set to a value higher than upper limit Tu2 used for the determination at the time of ozone addition. Therefore, at the time of fuel addition, an increase in the air flow rate is not executed at a certain high temperature, so that the concern that the reforming is hindered due to a decrease in fuel temperature can be reduced. In other words, the upper limit value Tu1 used for the determination at the time of adding the reformed fuel can be set so that the demerit of the fuel temperature decrease due to the increase in the air flow rate does not become larger than the merit due to the increase in ozone due to the increase in the air flow rate.

  Further, in the present embodiment, when the ozonizer temperature Ta exceeds the lower limit value Td and becomes a low temperature during the control by the fuel addition control means (S51: NO), the air reduction control means (S52) for reducing the air flow rate is provided. . According to this, inhibition of the cold flame reaction due to a decrease in the mixing chamber temperature Tb can be suppressed, and a decrease in the amount of reformed fuel generated can be suppressed. In other words, the power consumption by the heater 50 for setting the mixing chamber temperature Tb to the target mixing chamber temperature Tbtrg can be reduced by reducing the air flow rate.

  Furthermore, in this embodiment, standby flow rate control means (S62 to S64) for controlling the air flow rate so as to satisfy Td <Ta ≦ Tu1 in the standby mode is provided. According to this, regardless of whether the reformed fuel mode or the ozone mode is requested next time, it is possible to quickly realize the control of the ozonizer temperature Ta to the optimum temperature range R1, R2 at the time of the request.

  Further, in the present embodiment, the above-described ozone air control means (S21, S22, S29) is provided. When the ozonizer temperature Ta becomes higher than the upper limit value Tu1 in the ozone mode, the control by the air increase control (S25) is performed in preference to the control by the ozone air control means. According to this, since the efficiency of ozone generation is improved by setting the ozonizer temperature Ta to the optimum temperature range R1, the amount of ozone generation can be increased as compared with controlling the air flow rate while ignoring the ozonizer temperature Ta.

  Furthermore, in this embodiment, the above-mentioned fuel air control means (S40, S47, S53) is provided. When the ozonizer temperature Ta becomes higher than the upper limit value Tu2 in the reformed fuel mode, the control by the air increase control (S50) is performed in preference to the control by the fuel air control means. According to this, since the efficiency of reformed fuel generation is improved by setting the ozonizer temperature Ta to the optimum temperature range R2, the reformed fuel generation amount is larger than controlling the air flow rate ignoring the ozonizer temperature Ta. it can.

  Furthermore, in this embodiment, when the mixing chamber temperature Tb is lower than the predetermined temperature Tx in the ozone mode, the air flow rate is decreased on the condition that the ozonizer temperature Ta does not exceed the upper limit value Tu1 and is not high. According to this, it is possible to avoid the mixing chamber temperature Tb from becoming excessively low during the ozone mode. Therefore, immediately after switching from the ozone mode to the reformed fuel mode, the mixing chamber temperature Tb can be quickly set to the target mixing chamber temperature Tbtrg. Therefore, it is possible to suppress the generation amount of the reformed fuel from decreasing immediately after switching to the reformed fuel mode.

  Furthermore, in the present embodiment, power reduction control means for reducing the amount of power supplied to the ozonizer 20 at the time of control by the air increase control means is provided. According to this, in addition to the air cooling of the ozonizer 20 due to an increase in the air flow rate, the amount of heat generated due to the power supply to the ozonizer 20 is reduced, so the ozonizer temperature Ta can be lowered more quickly.

  Further, in the present embodiment, by including ozone in the air used for fuel oxidation, the start timing of the cool flame reaction can be advanced and the cool flame reaction time can be shortened. Therefore, even if the mixing container 30 is downsized so that the residence time of the fuel in the mixing container 30 is shortened, the cold flame reaction can be completed within the residence time. Therefore, the size of the mixing container 30 can be reduced.

Further, in the present embodiment, when the reduction catalyst is lower than the activation temperature Tact, the ozone generated by the ozonizer 20 is supplied to the mixing chamber 30a while stopping the fuel injection by the fuel injection valve 40, so that the exhaust gas is exhausted. Ozone is added to the passage 10ex. According to this, although the reduction catalyst of the NOx purification device 15 is not activated, it can be prevented that the reformed fuel as the reducing agent is added. Then, by adding ozone, NO in exhaust gas is oxidized to NO ₂ and adsorbed to the NOx purification catalyst, so that the amount of NOx adsorption to the NOx purification device 15 can be increased.

  Further, in the present embodiment, a heater 50 that heats the fuel and a temperature sensor 31 that detects the mixing chamber temperature Tb are provided. In steps S43 and S45 of FIG. 6, the operation of the heater 50 is controlled in accordance with the detected mixing chamber temperature Tb, thereby adjusting the mixing chamber temperature Tb to a predetermined temperature range. According to this, the temperature of the mixing chamber 30 a is directly detected by the temperature sensor 31. Further, the fuel in the mixing chamber 30 a is directly heated by the heater 50. Therefore, it is possible to accurately adjust the temperature of the mixing chamber 30a to a predetermined temperature range.

  Here, the equivalence ratio range in which the cold flame reaction occurs varies depending on the mixing chamber temperature Tb. In this embodiment in view of this point, the target equivalent ratio φtrg is changed in step S46 according to the detected mixing chamber temperature Tb. Therefore, even if the detected mixing chamber temperature Tb is deviated from the target mixing chamber temperature Tbtrg, the equivalence ratio is adjusted according to the actual mixing chamber temperature Tb, so that a cool flame reaction is surely generated. You can

  Furthermore, in the present embodiment, cracking is performed in which the fuel is decomposed into a hydrocarbon compound having a small number of carbon atoms by the heater 50. Since the hydrocarbon having a reduced number of carbon atoms due to cracking has a low boiling point, the vaporized fuel is suppressed from returning to a liquid.

(Second Embodiment)
In the standby control of FIG. 8 described above, the air flow rate is controlled so that the ozonizer temperature Ta is within the overlapping range of the optimum temperature range R1 in the ozone mode and the optimum temperature range R2 in the reformed fuel mode. That is, the air flow rate is controlled so as to satisfy Td <Ta ≦ Tu1, and the optimum temperature ranges R1 and R2 are quickly set in any of the modes to be executed next time. On the other hand, in the standby control according to the present embodiment, which mode is to be executed next time is predicted, and the air flow rate is controlled to be within the optimum temperature range for the predicted mode.

  Specifically, as shown in FIG. 9, first, in step S70, when energization is performed on the ozonizer 20, the fuel injection valve 40, and the heater 50, the energization is stopped. In a succeeding step S71, the NOx catalyst temperature Tcat is acquired. Specifically, the NOx catalyst temperature Tcat is estimated based on the exhaust temperature detected by the exhaust temperature sensor 96.

  In the subsequent step S72, it is predicted which of the ozone mode and the reformed fuel mode will be required next time based on the transition of the NOx catalyst temperature Tcat acquired in step S71. For example, when the internal combustion engine 10 is automatically stopped by idle stop control or when the internal combustion engine 10 is automatically stopped and the motor is driven by the electric motor, the standby mode is set because NOx is not discharged from the internal combustion engine 10.

  If the NOx catalyst temperature Tcat is equal to or higher than the activation temperature Tact during the standby mode in such a situation, it is predicted that the reformed fuel mode will be requested next time. On the other hand, if the NOx catalyst temperature Tcat is lower than the activation temperature Tact during the standby mode in the above situation, it is predicted that the ozone mode will be requested next time.

  In subsequent step S73, the ozonizer temperature Ta is acquired in the same manner as in step S48 of FIG. In subsequent step S74, the target air flow rate Atrg is set based on the prediction result in step S72 and the ozonizer temperature Ta acquired in step S73. For example, if the reformed fuel mode is predicted, the target air flow rate Atrg is set so that the ozonizer temperature Ta is adjusted to the optimum temperature range R2 of the reformed fuel mode. For example, if the ozone mode is predicted, the target air flow rate Atrg is set so that the ozonizer temperature Ta is adjusted to the optimum temperature range R1 of the ozone mode.

  In the subsequent step S75, the operation of the air pump 20p is controlled based on the target air flow rate Atrg set in step S74. Specifically, control is performed so that the air flow rate becomes the target air flow rate Atrg by supplying power corresponding to the target air flow rate Atrg to the electric motor of the air pump 20p.

  Note that the microcomputer 81 when executing the process of step S72 provides “standby prediction means” for predicting whether the control mode to be executed next is the ozone mode or the reformed fuel mode. The microcomputer 81 when executing the processes of steps S74 and S75 provides “standby flow rate control means” for controlling the air flow rate based on the result of the prediction and the ozonizer temperature Ta.

  According to the reformed fuel generation control described above, the standby time prediction means (S72) and the standby flow rate control means (S74, S75) described above are provided. Therefore, the ozonizer temperature Ta can be set to the optimum temperature ranges R1 and R2 in advance regardless of whether the reformed fuel mode or the ozone mode is requested next time. Therefore, it is possible to sufficiently suppress the ozone thermal destruction immediately after switching from the standby mode to another mode.

(Third embodiment)
In the present embodiment, the ozone generation control shown in FIG. 5 is modified as shown in FIG. Specifically, after acquiring the ozonizer temperature Ta in step S23, if it is determined in step S24 that the ozonizer temperature Ta is equal to or lower than the upper limit value Tu1, the following determination (prediction) is performed in step S241. carry out. That is, it is determined whether or not switching from the current ozone generation control to the reformed fuel generation control in step S12 of FIG. 3 is performed within a predetermined time. In other words, it is determined whether or not the shift to the reformed fuel generation control is in a state immediately before the fuel shift that is performed within a predetermined time.

  In step S241, similarly to steps S71 and S72 of FIG. 9, it is predicted whether the reformed fuel mode is required within a predetermined time based on the transition of the NOx catalyst temperature Tcat. For example, if the NOx catalyst temperature Tcat is predicted to rise to the activation temperature Tact within a predetermined time, it is determined that the state is just before fuel transfer.

  If it is determined that the state is immediately before the fuel transfer, it is determined in subsequent step S242 whether or not the ozonizer temperature Ta is equal to or higher than the first temperature set to a value lower than the upper limit value Tu1. . In the present embodiment, the first temperature is set to the same value as the lower limit value Td used in the reformed fuel generation control. If it is determined in step S242 that the temperature is equal to or higher than the first temperature, or if it is determined in step S241 that the state is not immediately before the fuel transfer, the process proceeds to step S29, and the base air flow rate Abase is set as the target air flow rate Atrg. Set.

  On the other hand, when it is determined that the state is immediately before the fuel transfer and the ozonizer temperature Ta is determined not to be equal to or higher than the first temperature, a value obtained by subtracting the predetermined value α from the base air flow rate Abase is set as the target air flow rate Atrg. Set. In the present embodiment, the processing of steps S26 and S27 in FIG. 5 is abolished.

  In short, in the ozone generation control according to the present embodiment, the air flow rate is controlled so that the ozonizer temperature Ta is within the optimum temperature range R1 unless it is in a state immediately before fuel transfer. On the other hand, if it is predicted and determined that the state is immediately before the fuel transfer, the air flow rate is controlled so as to be in a high temperature region not lower than the first temperature in the optimum temperature range R1.

  The microcomputer 81 at the time of executing the process of step S241 determines whether or not it is in a state immediately before fuel transfer in which the shift to the reformed fuel mode is performed within a predetermined time in the ozone mode. Means "are provided. The microcomputer 81 at the time of executing the process of step S243 controls the air flow rate so that the ozonizer temperature Ta becomes equal to or higher than the first temperature when it is determined that the state is immediately before the fuel shift. Means "are provided.

  As described above, according to the present embodiment, since the fuel transition prediction unit and the control unit immediately before fuel transition are provided, the ozonizer temperature Ta is set to the optimum temperature range R2 of the reformed fuel mode before switching to the reformed fuel mode. Can do. Alternatively, the temperature can be close to the optimum temperature range R2. Therefore, immediately after switching from the standby mode to another mode, the time during which the ozonizer temperature Ta is lower than the optimum temperature range R2 can be eliminated. Alternatively, the time can be shortened.

(Fourth embodiment)
In the present embodiment, the reformed fuel generation control shown in FIG. 7 is modified as shown in FIG. Specifically, when it is determined in steps S49 and S51 that the ozonizer temperature Ta is not more than the upper limit value Tu2 and not less than the lower limit value Td, the following determination (prediction) is performed in step S511. To do. That is, it is determined whether or not switching from the present reformed fuel generation control to the ozone generation control in step S13 in FIG. 3 is performed within a predetermined time. In other words, it is determined whether or not the shift to the ozone generation control is in a state immediately before the shift to ozone within a predetermined time.

  In step S511, similarly to steps S71 and S72 of FIG. 9, it is predicted whether the ozone mode is required within a predetermined time based on the transition of the NOx catalyst temperature Tcat. For example, if the NOx catalyst temperature Tcat is predicted to fall below the activation temperature Tact within a predetermined time, it is determined that the state is immediately before ozone transfer.

  If it is determined to be in a state immediately before ozone transfer, it is determined in subsequent step S512 whether or not the ozonizer temperature Ta is equal to or lower than a second temperature set to a value higher than the lower limit value Td by a predetermined temperature. . In the present embodiment, the second temperature is set to the same value as the upper limit value Tu1 used in ozone generation control. If it is determined in step S512 that the temperature is equal to or lower than the second temperature, the process proceeds to step S53, where the base air flow rate Abase is set as the target air flow rate Atrg. On the other hand, when it is determined that the state is immediately before the ozone transfer and it is determined that the ozonizer temperature Ta is not equal to or lower than the second temperature, a value obtained by adding the predetermined value β from the base air flow rate Abase is set as the target air flow rate Atrg. Set.

  In short, in the reformed fuel generation control according to the present embodiment, the air flow rate is controlled so that the ozonizer temperature Ta is within the optimum temperature range R2 unless the state is just before ozone transfer. On the other hand, if it is predicted and determined that the state is immediately before ozone transfer, the air flow rate is controlled so that the temperature is in the low temperature region below the second temperature in the optimum temperature range R2.

  The microcomputer 81 at the time of executing the process of step S511 determines whether or not it is a state immediately before the ozone transfer in which the shift to the ozone mode is performed within a predetermined time in the reformed fuel mode. Means "are provided. The microcomputer 81 when executing the process of step S513 controls the air flow rate so that the ozonizer temperature Ta becomes equal to or lower than the second temperature when it is determined that the state is immediately before ozone transfer. Means "are provided.

  As described above, according to the present embodiment, since the ozone transition prediction unit and the control unit immediately before the ozone transition are provided, the ozonizer temperature Ta can be set to the optimum temperature range R1 of the ozone mode before switching to the ozone mode. Alternatively, the temperature can be close to the optimum temperature range R1. Therefore, immediately after switching from the reformed fuel mode to the ozone mode, the time during which the ozonizer temperature Ta is higher than the optimum temperature range R1 can be eliminated. Alternatively, the time can be shortened.

(Fifth embodiment)
In the reducing agent addition apparatus A1 shown in FIG. 1, air is supplied to the ozonizer 20 by an air pump 20p. In contrast, in the reducing agent addition apparatus A2 of the present embodiment shown in FIG. 12, a part of the intake air of the internal combustion engine 10 is branched and flows into the ozonizer 20.

  Specifically, in the intake passage 10in, the downstream portion of the compressor 11c and the upstream portion of the cooler 12 and the flow passage 22a of the ozonizer 20 are connected by a branch pipe 36h. Further, the downstream portion of the cooler 12 in the intake passage 10in and the flow passage 22a are connected by a branch pipe 36c. The branch pipe 36 h supplies the high-temperature intake air before being cooled by the cooler 12 to the ozonizer 20. The branch pipe 36 c supplies the low temperature intake air after being cooled by the cooler 12 to the ozonizer 20.

  An electromagnetic valve 36 for opening and closing the internal passage is attached to the branch pipes 36h and 36c. The operation of the electromagnetic valve 36 is controlled by the microcomputer 81. When the electromagnetic valve 36 is operated so as to open the branch pipe 36h and close the branch pipe 36c, the high-temperature intake air flows into the ozonizer 20. When the electromagnetic valve 36 is operated so as to open the branch pipe 36c and close the branch pipe 36h, the low temperature intake air flows into the ozonizer 20.

  The operation of the electromagnetic valve 36 causes the high-temperature mode to branch the high-temperature intake air before being cooled by the cooler 12 from the upstream portion of the cooler 12, and the low-temperature intake air after being cooled by the cooler 12 from the downstream portion of the cooler 12 The low-temperature mode for branching can be switched. In the ozone mode, the low temperature mode is set to suppress destruction of the generated ozone by the heat of the intake air. Further, in the reformed fuel mode, the high temperature mode is set to suppress the fuel heated by the heater 50 from being cooled by the intake air in the mixing chamber 30a.

  Further, the flow rate of the air supplied to the ozonizer 20 is controlled by adjusting the opening degree of the electromagnetic valve 36. Also in the present embodiment, as in the first embodiment, the upper limit value Tu1 used for determination in the reformed fuel mode is set to a value higher than the upper limit value Tu2 used for determination in the ozone mode. . Therefore, the same effects as those of the first embodiment can be obtained by this embodiment.

  Furthermore, according to the present embodiment, a part of the intake air supercharged by the supercharger 11 is supplied to the ozonizer 20. Therefore, it becomes possible to supply oxygen-containing air to the ozonizer 20 without using the air pump 20p shown in FIG.

  Furthermore, according to this embodiment, the temperature of the air supplied to the ozonizer 20 can be changed by switching between the high temperature mode and the low temperature mode, so that the ozonizer temperature Ta can be quickly realized within the optimum temperature ranges R1 and R2. .

(Sixth embodiment)
In the fifth embodiment shown in FIG. 12, two branch pipes 36 h and 36 c are provided, and are switched between the high temperature mode and the low temperature mode by the electromagnetic valve 36. On the other hand, in the reducing agent addition apparatus A3 of the present embodiment, as shown in FIG. 13, the branch pipe 36c that supplies the low-temperature intake air to the ozonizer 20 is eliminated. And the flow volume of the air supplied to the ozonizer 20 is controlled by adjusting the opening degree of the electromagnetic valve 36.

  Also in the present embodiment, similarly to the first embodiment, the upper limit value Tu1 used for determination in the reformed fuel mode is set to a value higher than the upper limit value Tu2 used for determination in the ozone mode. Therefore, the same effects as those of the first embodiment can be obtained by this embodiment.

(Other embodiments)
The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made as illustrated below. Not only combinations of parts that clearly show that combinations are possible in each embodiment, but also combinations of the embodiments even if they are not explicitly stated unless there is a problem with the combination. In steps S62 and S64 in FIG. 8, the air pump 20p is stopped when the ozonizer temperature Ta is lower than Td, but the air pump 20p is stopped when the mixing chamber temperature Tb is lower than a predetermined value. You may let them.

  In the first embodiment, in the ozone mode, if Ta <Tu1, the air flow rate is controlled based on the required ozone flow rate Oreq corresponding to the exhausted NOx flow rate, and if Ta ≧ Tu1, the above control is performed. As a priority, the air flow rate is increased (S25). On the other hand, when Ta <Tu1, control may be performed with a preset air flow rate.

  In the first embodiment, in the reformed fuel mode, when Ta <Tu2, the air flow rate is controlled based on the target equivalent ratio φtrg suitable for the cold flame reaction, and when Ta ≧ Tu1, the above control is performed. The air flow rate is increased with higher priority (S50). On the other hand, when Ta <Tu2, control may be performed with a preset air flow rate.

  In step S23 of FIG. 5, the ozonizer temperature Ta is estimated based on the amount of heat generated by the discharge, the outside air temperature, and the air flow rate. On the other hand, a temperature sensor may be attached to the ozonizer 20 to directly detect the ozonizer temperature Ta.

  In steps S25, S28, and S29 of FIG. 5, the air flow rate is changed in three stages. That is, the base air flow rate is changed in three stages of Abase, Abase + α, and Abase−α. On the other hand, the air flow rate may be changed steplessly in accordance with the difference between the ozonizer temperature Ta and the upper limit value Tu1.

  In the third embodiment and the fourth embodiment, the optimum temperature range R1 in the ozone mode and the optimum temperature range R2 in the reformed fuel mode are partially overlapped. On the other hand, when these optimum temperature ranges R1 and R2 do not overlap, the first temperature used for the determination in step S242 in FIG. 10 is set to a temperature lower than the upper limit value Tu1 by a predetermined temperature (for example, 10 ° C.). do it. Further, the second temperature used for the determination in step S512 in FIG. 11 may be set to a temperature that is higher than the lower limit value Td by a predetermined temperature (for example, 10 ° C.).

  In the above embodiment shown in FIG. 1, a reduction catalyst that physically captures (that is, adsorbs) NOx is employed. However, the combustion system employs a reduction catalyst that traps (that is, stores) NOx by chemical bonding. A reducing agent addition device may be applied.

  When the internal combustion engine 10 is burning in a state leaner than the stoichiometric air-fuel ratio, the NOx purifying device 15 adsorbs NOx and reduces the NOx when it is not lean combustion to the reducing agent adding devices A1, A2, A3 may be applied. In this case, ozone may be added to the exhaust passage 10ex in the ozone mode during lean combustion, and the reformed fuel may be added to the exhaust passage 10ex in reformed fuel mode at times other than lean combustion. As a specific example of the catalyst that captures NOx during lean combustion in this way, an occlusion reduction catalyst using platinum and barium supported on a carrier can be cited.

  In the first embodiment, the NOx catalyst temperature used in step S <b> 11 of FIG. 3 is estimated from the exhaust temperature detected by the exhaust temperature sensor 96. On the other hand, a temperature sensor may be attached to the NOx purification device 15 to directly measure the NOx catalyst temperature. Alternatively, the NOx catalyst temperature may be estimated based on the rotation speed of the output shaft 10a, the load of the internal combustion engine 10, and the like.

  In the embodiment shown in FIG. 1, the ozonizer 20 is configured by arranging flat-plate electrodes 21 so as to face each other in parallel. On the other hand, the discharge reactor may be constituted by a needle-like electrode protruding in a needle shape and an annular electrode surrounding the needle-like electrode in an annular shape.

  In the embodiment shown in FIG. 1, a reducing agent addition device is applied to a combustion system mounted on a vehicle. On the other hand, a reducing agent addition device may be applied to a stationary combustion system. In the embodiment shown in FIG. 1, a reducing agent addition device is applied to a compression self-ignition diesel engine, and light oil used as a fuel for combustion is used as a reducing agent. On the other hand, gasoline used as a fuel for combustion may be used as a reducing agent by applying a reducing agent addition device to an ignition ignition type gasoline engine.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 10ex ... Exhaust passage, 15 ... NOx purification apparatus, 20 ... Ozonizer, 30 ... Mixing container, 30a ... Mixing chamber, 40 ... Fuel injection valve, 50 ... Heater, S12 ... Fuel addition control means, S13 ... Ozone Addition control means, S25, S50 ... Air increase control means, Tu1 ... Upper limit value in ozone mode, Tu2 ... Upper limit value in reformed fuel mode, A1, A2, A3 ... Reducing agent addition device.

Claims (10)

A NOx purification device (15) for purifying NOx contained in the exhaust gas of the internal combustion engine (10) on the reduction catalyst is provided in a combustion system provided in the exhaust passage (10ex), and upstream of the reduction catalyst in the exhaust passage. In the reducing agent addition device for adding the reducing agent to the side,
An ozonizer (20) that discharges into supplied air to generate air containing ozone;
A fuel injection valve (40) for injecting fuel which is a hydrocarbon compound;
A heater (50) for heating the fuel injected from the fuel injection valve;
A mixing chamber (30a) for mixing the ozone-containing air generated by the ozonizer and the fuel heated by the heater is formed therein, and the fuel is partially oxidized by the mixing to generate a reformed fuel. A mixing vessel (30);
Fuel addition control means (S12) for controlling the fuel injection valve, the heater and the ozonizer to generate the reformed fuel and to add the reformed fuel as the reducing agent to the exhaust passage; ,
Ozone addition control means (S13) for controlling the generation of ozone by operating the ozonizer while stopping the operation of the fuel injection valve and the heater and adding the ozone to the exhaust passage;
When the internal temperature of the ozonizer exceeds the upper limit value (Tu1, Tu2) and becomes a high temperature, the air increase control means for suppressing an increase in the internal temperature by increasing the flow rate of the air supplied to the ozonizer. (S25, S50),
With
The reducing agent addition apparatus characterized in that the upper limit value (Tu2) at the time of control by the fuel addition control means is set to a value higher than the upper limit value (Tu1) at the time of control by the ozone addition control means. .   When the internal temperature of the ozonizer becomes lower than the lower limit (Td) during the control by the fuel addition control means, the flow rate of the air supplied to the ozonizer is reduced to reduce the internal temperature. The reducing agent adding device according to claim 1, further comprising an air reduction control means (S52) for suppressing. An ozone transition predicting means (S511) for determining whether or not it is a state immediately before the ozone transition when the shift to the control by the ozone addition control means is performed within a predetermined time during the control by the fuel addition control means;
The flow rate of air supplied to the ozonizer so that the internal temperature of the ozonizer becomes equal to or lower than a temperature set to a value higher than the lower limit value by a predetermined temperature when it is determined that the state is immediately before the ozone transfer. Control means (S513) immediately before ozone transfer for controlling
The reducing agent addition apparatus according to claim 2, comprising: The upper limit value at the time of ozone addition, which is the upper limit value (Tu1) at the time of control by the ozone addition control means, is set to a value higher than the lower limit value,
In a standby state in which the fuel addition control unit and the ozone addition control unit do not perform any control, the internal temperature of the ozonizer is in a range between the ozone addition upper limit value and the lower limit value. The reducing agent addition apparatus according to claim 2 or 3, further comprising standby flow rate control means (S62, S63, S64) for controlling a flow rate of air supplied to the ozonizer. A standby time prediction means (S72) for predicting which control is performed next time in a standby state where the fuel addition control means and the ozone addition control means do not perform the control in a standby state;
Standby flow rate control means (S74, S75) for controlling the flow rate of air supplied to the ozonizer based on the prediction result by the standby prediction means and the internal temperature of the ozonizer in the standby state;
The reducing agent addition apparatus according to any one of claims 1 to 3, further comprising: A fuel transition predicting means (S241) for determining whether or not it is in a state immediately before the fuel transition when the shift to the control by the fuel addition control means is performed within a predetermined time during the control by the ozone addition control means;
When it is determined that the state is immediately before the fuel transfer, the internal temperature of the ozonizer is equal to or higher than a temperature set to a value lower than the upper limit value at the time of control by the ozone addition control means. Immediately before fuel transfer control means (S243) for controlling the flow rate of air supplied to the ozonizer;
The reducing agent adding device according to any one of claims 1 to 5, wherein the reducing agent adding device is provided. Based on the required flow rate of ozone added to the exhaust passage, a target flow rate of air supplied to the ozonizer is calculated, and an ozone air control means (S21, S22, S29)
When the internal temperature of the ozonizer becomes higher than the upper limit (Tu1) during the control by the ozone addition control means, the air increase control (prior to the control by the ozone air control means) Control by S25) is implemented, The reducing agent addition apparatus as described in any one of Claims 1-6 characterized by the above-mentioned. Based on the required flow rate of the reformed fuel added to the exhaust passage, a target flow rate of air supplied to the ozonizer is calculated, and an air control means for fuel (S40, S40, S40, S40, S47, S53)
When the internal temperature of the ozonizer becomes higher than the upper limit (Tu2) during the control by the fuel addition control means, the air increase control has priority over the control by the fuel air control means. Control by means (S50) is implemented, The reducing agent addition apparatus as described in any one of Claims 1-7 characterized by the above-mentioned.   When the temperature of the mixing chamber is lower than a predetermined temperature (Tx) during the control by the ozone addition control means, the condition is that the internal temperature of the ozonizer does not exceed the upper limit and does not reach a high temperature. The reducing agent addition apparatus according to claim 1, wherein the flow rate of supplied air is reduced.   The reducing agent according to any one of claims 1 to 9, further comprising power reduction control means (S33, S57) for reducing the amount of power supplied to the ozonizer during control by the air increase control means. Addition equipment.

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