JP2016065512A - Ozone supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress release of ozone into atmospheric air.SOLUTION: An ozone supply device includes an air pump 30p sucking atmospheric air and distributing the air, an air duct 26, an ozonizer 30, and air pump control means 41a. The air duct 26 guides the air distributed by the air pump 30p to an exhaust passage 10ex of an internal combustion engine 10. The ozonizer 30 is disposed in the air duct 26, and produces ozone from oxygen included in the air distributed by the air pump 30p. The air pump control means 41a controls an operation of the air pump 30p so that the air distribution by the air pump 30p is continued for a prescribed time from the time of stop of the production of ozone, and then stops the air distribution when the production of ozone by the ozonizer 30 is stopped.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ozone supply device.

  2. Description of the Related Art Conventionally, there has been known a system in which hydrocarbon (fuel) as a reducing agent is added to an upstream portion of a NOx catalyst in an exhaust passage of an internal combustion engine, and NOx in the exhaust is reduced and purified on the NOx catalyst. Yes. When this type of fuel is partially oxidized and reformed in an ozone environment, the NOx purification rate is improved. Therefore, Patent Document 1 discloses an ozone supply including a blower pipe connected to an exhaust passage, an air pump that blows air to the blower pipe, and an ozonizer that generates ozone from oxygen contained in the air blown by the air pump. An apparatus is disclosed. According to this, the fuel injected into the blower pipe can be reformed in an ozone environment.

JP 2000-54833 A

  However, the present inventors have found that the following problems occur when the ozone supply device is stopped. That is, immediately after the ozone generation by the ozonizer is stopped and the air pump is stopped, ozone remains in the ozonizer or in the air duct. This residual ozone may flow back through the air pipe over time and be released from the air pump inlet to the atmosphere. In particular, high concentrations of ozone may adversely affect the human body, so ozone release to the atmosphere is undesirable.

  This invention is made | formed in view of the said problem, The objective is to provide the ozone supply apparatus aiming at suppression of atmospheric | air emission of ozone.

  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. .

  The disclosed first invention includes an air pump (30p) that sucks and blows air and an air pipe (23, 26) that guides air blown by the air pump to an exhaust passage (10ex) of the internal combustion engine (10). When the ozone generation by the ozonizer (30) that is provided in the blower pipe and is generated by air contained in the air pumped by the air pump, and when the ozone generation by the ozonizer is stopped, the air blow by the air pump for a predetermined time from the time when the ozone generation is stopped. Air pump control means (41a) for controlling the operation of the air pump so as to stop the air blowing after continuing the operation.

  According to this invention, the period which continues ventilation by an air pump only for the predetermined time from the ozone production | generation stop time is provided. Therefore, the ozone (residual ozone) remaining in the ozonizer and the blower pipe at the time when the ozone generation is stopped is pushed out to the exhaust passage during the above-described blowing duration. Therefore, since residual ozone is scavenged during the ventilation period, it is possible to suppress the possibility that residual ozone is released from the air pump inlet to the atmosphere after the air pump is stopped.

  The disclosed second invention includes an air pump (30p) that sucks and blows air, and a blower pipe (23, 26) that guides air blown by the air pump to an exhaust passage (10ex) of the internal combustion engine (10). The ozonizer (30) for generating ozone from oxygen contained in the air blown by the air pump in the blower pipe, and the ozonizer in the upstream part of the ozonizer in the blower pipe, And an ozone check valve (30v) for preventing the generated ozone from flowing back through the blower pipe.

  According to this invention, the check valve for ozone is provided in the upstream side portion of the ozonizer in the blower pipe. Therefore, ozone remaining in the ozonizer at the time when ozone generation is stopped (residual ozone) can be prevented from flowing back into the air after the air pump is stopped to the atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing a reducing agent addition device having a function as an ozone supply device according to a first embodiment of the present invention and a combustion system to which this device is applied. The graph explaining that an oxidation reaction arises in two steps, a cold flame reaction and a hot flame reaction. The figure explaining the reaction path | route of a cold flame reaction. The figure which shows the range which two-step oxidation reaction produces of atmospheric temperature and equivalent ratio. The flowchart explaining the process sequence of control based on the reducing agent addition apparatus shown in FIG. The flowchart which shows the procedure of the subroutine process regarding the strong oxidation control shown in FIG. The flowchart which shows the procedure of the subroutine process regarding the all stop control shown in FIG. The timing chart showing the one aspect | mode of the relationship between an ozonizer stop time and an air pump stop time at the time of implementing all stop control of FIG. The schematic diagram which shows the ozone supply apparatus which concerns on 2nd Embodiment of this invention, and the combustion system to which this apparatus is applied. The schematic diagram which shows the reducing agent addition apparatus which has a function as an ozone supply apparatus which concerns on 3rd Embodiment of this invention, and the combustion system to which this apparatus is applied. The schematic diagram which shows the reducing system addition apparatus which has a function as an ozone supply apparatus which concerns on 4th Embodiment of this invention, and the combustion system to which this 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 NOx purification device 12, a particulate collection device (DPF 13), and a reducing agent addition device, which will be described in detail below. 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 type diesel engine, and light oil which is a hydrocarbon compound is used as a fuel used for combustion. The internal combustion engine 10 basically operates to burn in a lean state. That is, combustion is performed (lean combustion) in a state where the air-fuel ratio, which is the ratio between the fuel injected into the combustion chamber and the air sucked into the combustion chamber, is set to an excess of air.

  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 (not shown) for cooling the intake air (pressurized 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 is adjusted in flow rate by a throttle valve (not shown) and distributed to a plurality of combustion chambers of the internal combustion engine 10. A NOx purification device 12 is disposed downstream of the turbine 11a in the exhaust passage 10ex, and a DPF 13 (Diesel Particulate Filter) is disposed further downstream. The DPF 13 collects fine particles contained in the exhaust.

  A supply pipe 23 of the reducing agent addition device is connected to the exhaust passage 10ex on the upstream side of the NOx purification device 12. The reformed fuel generated by the reducing agent addition device is added as a reducing agent from the supply pipe 23 to the exhaust passage 10ex. The reformed fuel is obtained by partially oxidizing a hydrocarbon compound (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 with reference to FIG. Further, the reducing agent addition device has a function of supplying ozone from the supply pipe 23 to the exhaust passage 10ex, and provides an ozone supply device.

The NOx purification device 12 is configured by accommodating a honeycomb-shaped carrier in a housing. A coating material is provided on the surface of the carrier, and a reduction catalyst is supported on the coating material. The NOx purification device 12 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 . The exhaust gas contains O ₂ (oxygen) in addition to NOx, but 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. For example, the NOx purification device 12 having a NOx adsorption function is provided by a reduction catalyst made of silver alumina supported on a carrier. Specifically, it is a structure in which silver as a reduction catalyst is supported on alumina coated on the support surface. The adsorbed NOx is desorbed from the reduction catalyst when the catalyst temperature is equal to or higher than the activation temperature. The desorbed NOx is reduced and purified by the reformed fuel.

  Next, a reducing agent addition device that generates reformed fuel and adds it to the exhaust passage 10ex from the supply pipe 23 will be described. The reducing agent addition apparatus includes a reaction vessel 20, a heater 21, an injection valve 22, an ozonizer 30, and an air pump 30p described in detail below. Further, the reducing agent addition device includes a supply pipe 23 and a blower pipe 26, which will be described in detail below, and further includes an electronic control unit (ECU 40).

  The ozonizer 30 includes a housing 32 that forms a flow passage 32a therein, and a plurality of electrodes 31 are disposed in the flow passage 32a. These electrodes 31 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 31 is controlled by a microcomputer (microcomputer 41) provided in the ECU 40.

  The air blown by the air pump 30p flows into the housing 32 of the ozonizer 30. The air pump 30p is a centrifugal air pump, and is configured by housing an impeller driven by an electric motor in a case. This electric motor is controlled by the microcomputer 41. The air pump 30p sucks and pressurizes the air from the suction port 30in formed in the case, and blows air to the ozonizer 30. The air blown to the ozonizer 30 flows into the flow passage 32 a in the housing 32 and flows through the interelectrode passage 31 a that is a passage between the electrodes 31.

  The ozonizer 30 is connected to the reaction vessel 20 through the blower pipe 26. An electromagnetically driven check valve 26v is attached to the blower pipe 26. The microcomputer 41 controls the opening / closing drive of the check valve 26v. Specifically, the valve body of the check valve 26v is controlled to be switched between a fully open position and a fully closed position. Therefore, when the air pump 30p is driven to open the check valve 26v, the air that has flowed through the interelectrode passage 31a flows through the blower pipe 26, the reaction vessel 20, and the supply pipe 23 in order and flows into the exhaust passage 10ex. Will be. That is, the supply pipe 23 and the blower pipe 26 provide a blower pipe that guides the air blown by the air pump 30p to the exhaust passage 10ex.

  A heater 21 and an injection valve 22 are attached to the reaction vessel 20, and a reaction chamber 20a communicating with the inflow port 20in and the outflow port 20out is formed inside the reaction vessel 20. The heater 21 has a heat generating portion that generates heat when energized, and power supply to the heat generating portion is controlled by the microcomputer 41. Specifically, the amount of heat generated is controlled by the microcomputer 41 performing duty control on the amount of power supplied to the heat generating unit. The heat generating portion is disposed in the reaction chamber 20a and heats the fuel injected from the injection valve 22 to the reaction chamber 20a. The temperature of the reaction chamber 20 a is detected by a reaction chamber temperature sensor 27. The reaction chamber temperature sensor 27 outputs the detected temperature information (reaction chamber temperature Th) to the ECU 40.

  The injection valve 22 has a body in which an injection hole is formed, an electric actuator, and a valve body. When the electric actuator is energized, the valve body opens and fuel is injected from the nozzle hole into the reaction chamber 20a. When the electric actuator is turned off, the valve body closes and fuel injection is stopped. The microcomputer 41 controls the amount of fuel injected per unit time into the reaction chamber 20a by controlling energization to the electric actuator. Liquid fuel in a fuel tank (not shown) is supplied to the injection valve 22 by a fuel pump (not shown). The fuel in the fuel tank is also used as the fuel for combustion 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 injected from the injection valve 22 into the reaction chamber 20a collides with the heat generating portion and is heated and vaporized. The vaporized fuel is mixed with the air flowing into the reaction chamber 20a from the inflow port 20in. As a result, the gaseous fuel is partially oxidized by oxygen in the air and reformed into partially oxidized hydrocarbons such as aldehydes. The reformed gaseous fuel (reformed fuel) flows into the exhaust passage 10ex through the supply pipe 23.

  When the electrode 31 of the ozonizer 30 is energized, electrons emitted from the electrode 31 collide with oxygen molecules contained in the air in the interelectrode passage 31a. Then, ozone is generated from oxygen molecules. That is, the ozonizer 30 generates oxygen as active oxygen by bringing oxygen molecules into a plasma state by discharge. Therefore, ozone is contained in the air flowing through the blower pipe 26 when the ozonizer 30 is energized.

  In the reaction chamber 20a, a cold flame reaction described in detail below occurs. This cold flame reaction is a reaction in which gaseous fuel is partially oxidized by oxygen in the air flowing in from the inlet 20in. Specific examples of such partially oxidized fuel (reformed fuel) include partial oxides (for example, aldehydes) in which a part of the fuel (hydrocarbon compound) is oxidized to aldehyde groups (CHO). It is done.

  Here, the cold flame reaction will be described in detail with reference to FIGS.

  FIG. 2 is a simulation result simulating a phenomenon in which fuel (hexadecane) is sprayed on the heater 21 to be vaporized, and the vaporized fuel stays in the vicinity of the heater 21 and is reformed. Specifically, it shows changes in various physical quantities with respect to the elapsed time from the start of exposure when gaseous fuel (hexadecane) is exposed to 430 ° C. That is, (a) in the figure shows the change in ambient temperature. (B) shows the change in the molar concentration of fuel (hexadecane). (C) shows the change in the molar concentration of each of oxygen molecules consumed by oxidation, water molecules generated by oxidation, and carbon dioxide molecules. (D) shows the change in the molar concentration of acetaldehyde and propionaldehyde, which are reformed fuels produced by the cold flame reaction. Initial conditions at the start of fuel injection are 1 atm, hexadecane concentration 2200 ppm, oxygen concentration 20%, carbon dioxide concentration 9%, and water concentration 2%.

  As shown in FIG. 2, as soon as fuel is injected, the ambient temperature increases, the molar concentration of the fuel decreases, and the molar concentration of the reformed fuel increases. This phenomenon means that the fuel is oxidized to oxygen and generates heat, and reformed fuel is generated from the fuel. That is, a cold flame reaction is occurring. However, such a temperature rise and changes in various molar concentrations are temporary, and during the period of about 4 seconds from the start of fuel injection, no temperature rise and no change in molar concentration appear.

  When about 4 seconds elapse, the atmospheric temperature further rises, the reformed fuel molar concentration decreases, and the amount of carbon dioxide and water produced and the amount of oxygen consumed increase. This phenomenon means that the reformed fuel is oxidized to oxygen and generates heat, and the reformed fuel is completely burned to generate carbon dioxide and water. That is, a hot flame reaction is occurring. Note that the amount of temperature increase due to the cold flame reaction is smaller than the amount of temperature increase due to the hot flame reaction. Moreover, the oxygen consumption by a cold flame reaction is less than the oxygen consumption by a hot flame reaction.

  When the oxidation reaction occurs in two stages, the reformed fuel appears as an intermediate product during the period from the start of the cold flame reaction to the start of the hot flame reaction. Specific examples of the intermediate product include various hydrocarbon compounds such as aldehydes and ketones. FIG. 3 shows an example of a main reaction route through which aldehyde is generated.

  First, as shown in (1) in the figure, hydrocarbon (light oil) reacts with oxygen molecules to generate hydrocarbon peroxy radicals. This hydrocarbon peroxy radical is decomposed into an aldehyde and a hydrocarbon radical (see (2)). This hydrocarbon radical reacts with oxygen molecules to generate another hydrocarbon peroxy radical (see (3)). This hydrocarbon peroxy radical is decomposed into an aldehyde and a hydrocarbon radical (see (4)). This hydrocarbon radical reacts with oxygen molecules to generate another hydrocarbon peroxy radical (see (5)). In this way, hydrocarbon peroxy radicals are repeatedly generated while reducing the number of carbon atoms, and aldehydes are generated each time the carbon peroxy radical is generated. In the hot flame reaction, the fuel is completely burned to generate carbon dioxide and water, and no intermediate product appears. That is, the intermediate product produced by the cold flame reaction is oxidized to carbon dioxide and water.

  In the simulation shown in FIG. 2, the exposure temperature was 430 ° C. On the other hand, the present inventors further conducted analysis by simulation with different exposure temperatures. As a result, when the exposure temperature is 530 ° C., there is almost no period of staying in the cold flame reaction, and the oxidation reaction is completed in one stage. When the exposure temperature is set to 330 ° C., the start time of the cold flame reaction is delayed as compared with the case where the exposure temperature is set to 430 ° C. When the exposure temperature is 230 ° C. or lower, neither a cold flame reaction nor a hot flame reaction occurs, and no oxidation reaction occurs.

  In the simulation shown in FIG. 2, the equivalence ratio, which is the ratio between the injected fuel and the supplied air, is 0.23. On the other hand, the present inventors further performed analysis by simulation with different equivalence ratios. If the equivalence ratio is strictly defined, it is a value obtained by dividing "the weight of fuel contained in the actual air-fuel mixture" by "the weight of fuel capable of complete combustion". When the equivalence ratio is 1.0, there is almost no period of staying in the cold flame reaction, and the oxidation reaction is completed in one stage. In addition, when the equivalent ratio is 0.37, the start time of the cold flame reaction is earlier than when the equivalent ratio is 0.23. In addition, the cold flame reaction rate is increased and the cold flame reaction period is shortened. In addition, the atmospheric temperature at the time when the cold flame reaction ends is increased.

  FIG. 4 summarizes these analysis results. That is, the relationship between the exposure temperature (atmosphere temperature) and the equivalence ratio and the presence / absence of the occurrence of a cold flame reaction is shown. The horizontal axis in FIG. A region with dots in the figure represents a region where a two-stage oxidation reaction occurs. As shown in the figure, in the region where the ambient temperature is lower than the lower limit value, it becomes a non-reactive region where no oxidation reaction occurs. Even if the atmospheric temperature is higher than the lower limit, if the equivalent ratio is in the region of 1.0 or more, it becomes a one-step oxidation reaction region where the oxidation reaction is completed in one step.

  Further, the boundary line between the two-stage oxidation reaction region and the first-stage oxidation reaction region varies depending on the ambient temperature and the equivalence ratio. That is, a two-stage oxidation reaction occurs when the ambient temperature is in a predetermined temperature range and the equivalent ratio is in a predetermined equivalent ratio range. These temperature range and equivalent ratio range correspond to the range of the region with dots in FIG. When the atmospheric temperature is adjusted to an optimum temperature (for example, 370 ° C.) within a predetermined temperature range, the equivalent ratio at the boundary line becomes the maximum value (for example, 1.0). Therefore, in order to cause the cold flame reaction at an early stage, the heater temperature is adjusted to the optimum temperature and the equivalence ratio is set to 1.0. However, since the cold flame reaction does not occur when the equivalent ratio exceeds 1.0, it is desirable to adjust the equivalent ratio to a value smaller than the margin by 1.0.

  In the simulation shown in FIG. 2, the ozone concentration in the air is zero. On the other hand, the present inventors further performed an analysis by simulation with different ozone concentrations in the air. The initial conditions in this simulation are 1 atm, hexadecane concentration 2200 ppm, and ambient temperature 330 ° C. As a result, it was confirmed that the start time of the cold flame reaction was earlier as the ozone concentration was higher. Such a phenomenon caused by ozone occurs for the following reason. That is, in (1), (3), and (5) in FIG. 3, hydrocarbon radicals and oxygen molecules react, but when ozone is contained in the air, this reaction is promoted, and aldehyde Will be generated in a short time.

  The microcomputer 41 provided in the ECU 40 includes a storage device that stores a program, and a central processing unit that executes arithmetic processing according to the stored program. The ECU 40 controls the operation of the internal combustion engine 10 based on various detected values such as an accelerator pedal depression amount (engine load), an engine speed (engine speed), an intake pressure, an exhaust pressure, and the like.

  Further, the ECU 40 controls the operation of the reducing agent addition device based on the physical quantities detected by the reaction chamber temperature sensor 27, the catalyst temperature sensor 42 and the exhaust pressure sensor 43. The catalyst temperature sensor 42 is attached to the NOx purification device 12 and detects the atmospheric temperature (catalyst temperature) of the reduction catalyst. The exhaust pressure sensor 43 is attached to the exhaust pipe and detects the exhaust pressure (exhaust pressure) at the portion of the exhaust passage 10ex where the supply pipe 23 is connected.

  In general, the ECU 40 controls the operation of the reducing agent adding device as follows. That is, the operation of the reducing agent addition device and the stop control are switched based on the exhaust pressure. Further, when the apparatus is operated, switching between a reducing agent supply control for supplying a reducing agent to the exhaust passage 10ex and an ozone supply control for supplying ozone is performed based on the reaction chamber temperature Th. Further, when carrying out the reducing agent addition control, strong oxidation control, weak oxidation control, and oxidation stop control are switched based on the reaction chamber temperature Th.

  Specifically, during the operation period of the internal combustion engine 10, the microcomputer 41 repeatedly executes the program of the procedure shown in FIG. 5 at a predetermined cycle, thereby controlling the operation of the reducing agent addition device. First, in step S10 of FIG. 5, it is determined whether or not the pressure in the exhaust pipe (exhaust pressure) detected by the exhaust pressure sensor 43 is less than a predetermined threshold value Pth. The threshold value Pth is set to a maximum discharge pressure by the air pump 30p or a value slightly smaller than the maximum discharge pressure. If the exhaust pressure is less than the threshold value Pth, it can be considered that the exhaust pressure is sufficiently smaller than the air pump discharge pressure and that air containing fuel or ozone can be supplied to the exhaust passage 10ex.

  If it is determined in step S10 that the exhaust pressure is not less than the threshold value Pth, that is, if it is determined that the supply to the exhaust passage 10ex by the air pump 30p is not possible, a full stop that stops the operation of the reducing agent addition device in step S18. Implement control. The total stop control is a control for stopping supply of both ozone and the reducing agent to the exhaust passage 10ex, and details will be described later with reference to FIG.

  On the other hand, if it is determined in step S10 that the exhaust pressure is less than the threshold value Pth, that is, if it is determined that supply to the exhaust passage 10ex by the air pump 30p is possible, in step S11, is the catalyst temperature higher than the predetermined temperature T1? Determine whether or not. When it is determined that the temperature is lower than the predetermined temperature T1, it is determined in subsequent step S12 whether or not the catalyst temperature is higher than the second predetermined temperature T2. When it is determined that the temperature is lower than the second predetermined temperature, it is determined in subsequent step S13 whether or not the catalyst temperature is higher than the activation temperature T3.

  The predetermined temperature T1 and the second predetermined temperature T2 are set to be higher than the activation temperature T3. The predetermined temperature T1 is set to be higher than the second predetermined temperature T2. For example, when the activation temperature T3 is 250 ° C., the second predetermined temperature T2 is set to 350 ° C., and the predetermined temperature T1 is set to 400 ° C. Here, the activation temperature T3 of the reduction catalyst is the lowest temperature at which NOx can be reduced and purified on the reduction catalyst.

  If it is determined in steps S11, S12, and S13 that the catalyst temperature is lower than the activation temperature T3, ozone supply control is performed in step S14. When it is determined that the catalyst temperature is higher than the activation temperature T3 and lower than the second predetermined temperature T2, strong oxidation control is performed in step S15. When it is determined that the catalyst temperature is higher than the second predetermined temperature T2 and lower than the predetermined temperature T1, weak oxidation control is performed in step S16. When it is determined that the catalyst temperature is higher than the predetermined temperature T1, oxidation stop control is performed in step S17.

  When the ozone supply control is performed in step S14 of FIG. 5, the air pump 30p is operated with a preset amount of power, and the electrode 31 of the ozonizer 30 is energized and discharged with a preset amount of power. Cause it to occur. Further, the energization to the heater 21 is stopped, and the energization to the injection valve 70 is stopped to stop the fuel injection.

  According to the ozone supply control described above, ozone is generated by the ozonizer 30, and the generated ozone is added to the exhaust passage 10ex through the 23 supply pipe 23 and the blower pipe 26. Here, if the heater 21 is energized, the ozone is heated and collapses. Moreover, if fuel injection is performed, ozone will react with fuel. In view of these points, in the ozone generation mode, the heating by the heater 21 is stopped and the fuel injection is stopped, so that it is possible to avoid ozone reacting with the fuel and heating collapse. Therefore, the generated ozone is added to the exhaust passage 10ex as it is.

  In the strong oxidation control according to step S15 in FIG. 5, a subroutine process shown in FIG. 6 is performed. First, in step S20 of FIG. 6, a detection value (reaction chamber temperature Th) by the reaction chamber temperature sensor 27 is acquired. In subsequent step S21, the heater 21 is feedback-controlled so that the obtained reaction chamber temperature Th matches the preset target temperature Ttrg. The target temperature Ttrg is set to an atmospheric temperature (for example, 370 ° C.) at which the equivalence ratio is maximum in the two-stage oxidation reaction region shown in FIG.

  In subsequent step S22, when all the NOx flowing into the NOx purification device 12 is reduced, a reducing agent addition amount for supplying the NOx purification device 12 without excess or deficiency is set as a target fuel amount Ftrg. The target fuel amount Ftrg is the mass of fuel supplied to the NOx purification device 12 per unit time.

  Specifically, the target fuel amount Ftrg is set based on the NOx inflow amount and the catalyst temperature described below. The NOx inflow amount is the mass of NOx flowing into the NOx purification device 12 per unit time. For example, the NOx inflow amount can be estimated based on the operating state of the internal combustion engine 10. The target fuel amount Ftrg is increased as the NOx inflow amount increases. Further, since the amount (reducing power) in which NOx is reduced on the reduction catalyst varies depending on the catalyst temperature, the target fuel amount Ftrg is set according to the difference in the reducing power depending on the catalyst temperature.

  In the subsequent step S23, fuel injection is performed by controlling the operation of the injection valve 22 based on the target fuel amount Ftrg set in step S22. Specifically, the valve opening time of the injection valve 22 is lengthened as the target fuel amount Ftrg increases. Alternatively, the interval from the end of the current injection to the start of the next injection is shortened.

  In the subsequent step S24, the target equivalent ratio φtrg is calculated so as to cause a cold flame reaction based on the reaction chamber temperature Th. Specifically, a maximum value of the equivalent ratio in the two-stage oxidation reaction region, which is a maximum value of the equivalent ratio corresponding to the ambient temperature, or a value obtained by subtracting a predetermined margin from the maximum value is a target equivalent ratio φtrg. As a map and stored in the microcomputer 41. A target equivalent ratio φtrg corresponding to the detected reaction chamber temperature Th is calculated with reference to the map. By setting the target equivalent ratio φtrg in consideration of the margin as described above, even if the actual equivalent ratio becomes larger than the target equivalent ratio φtrg, the possibility of exceeding the maximum value of the equivalent ratio can be reduced. The risk of reaching a hot flame reaction can be reduced.

  In the subsequent step S25, the target air amount Atrg is calculated based on the target equivalent ratio φtrg set in step S24 and the target fuel amount Ftrg set in step S22. Specifically, the target air amount Atrg is calculated so that φtrg = Ftrg / Atrg. In the following step S26, the operation of the air pump 30p is controlled based on the target air amount Atrg calculated in step S25. Specifically, the duty ratio for energizing the air pump 30p is increased as the target air amount Atrg is larger.

  As described above, the target air amount Atrg is set according to the target fuel amount Ftrg and the target temperature Ttrg is set, and the air pump 30p and the heater 21 are controlled, whereby the reaction chamber temperature Th and the equivalence ratio are set to the two-stage oxidation reaction. Adjusted to the area. Therefore, the above-described reformed fuel is generated by causing a cold flame reaction. The lower limit of the temperature range in which the reaction chamber temperature Th is adjusted is 260 ° C. serving as a boundary line between the first-stage oxidation region and the second-stage oxidation region and the non-reaction region. The upper limit of the temperature range is the maximum temperature on the boundary line between the first stage oxidation region and the second stage oxidation region. The upper limit of the range in which the equivalence ratio is adjusted is the maximum value of the boundary lines between the first stage oxidation region and the second stage oxidation region, and is an equivalent ratio corresponding to 370 ° C.

  In the subsequent step S27, the power supplied to the ozonizer 30 is controlled in accordance with the fuel concentration in the reaction vessel 20. Specifically, the target ozone amount Otrg is calculated based on the target fuel amount Ftrg. Specifically, the target ozone amount Otrg is calculated so that the ratio of the ozone concentration to the fuel concentration in the vaporizing chamber 25a becomes a predetermined value (for example, 0.2). For example, the ratio is set so that the cold flame reaction is completed within a predetermined time (for example, 0.02 seconds). Also, the target ozone amount Otrg is set to increase as the temperature of the reduction catalyst decreases.

  Then, based on the target air amount Atrg and the target ozone amount Otrg, a target energization amount Ptrg to the ozonizer 30 is calculated. Specifically, as the target air amount Atrg increases, the residence time of the air in the interelectrode passage 21a is shortened, so that the target energization amount Ptrg is increased. Further, the target energization amount Ptrg is increased as the target ozone amount Otrg is increased. Next, the energization amount to the ozonizer 30 is controlled based on the target energization amount Ptrg. Specifically, as the target energization amount Ptrg is larger, the energization duty ratio to the ozonizer 30 is increased. Alternatively, the interval from the end of current energization to the start of next energization is shortened.

  By executing the process in step S27, ozone is generated and supplied to the reaction vessel 20, so that the start timing of the cool flame reaction is advanced and the cool flame reaction time is shortened. It is done. Therefore, even if the reaction vessel 20 is downsized so that the residence time of the fuel in the reaction vessel 20 is shortened, the cold flame reaction can be completed within the residence time. Therefore, the reaction vessel 20 can be downsized. In the subsequent step S28, the check valve 26v is controlled to open.

  As described above, according to the strong oxidation control of FIG. 6, the ozone generated by the ozonizer 30, the oxygen in the air, and the fuel vaporized by the heater 21 are mixed, and the fuel is partially oxidized in an environment where ozone exists. Is done. On the other hand, in the weak oxidation control in step S16 of FIG. 5, the fuel is partially oxidized in an environment where ozone is not present by stopping the ozonizer 30 and stopping ozone generation. Further, in the oxidation stop control in step S17, the ozonizer 30 and the heater 21 are stopped to stop the ozone generation and the fuel heating, so that the fuel that is not partially oxidized without being oxidized by oxygen or ozone is obtained. It is added to the exhaust passage 10ex. The fuel added in this way is exposed to high-temperature exhaust gas in the exhaust passage 10ex or the NOx purification device 12 and partially oxidized.

  More specifically, in the weak oxidation control, the process of step S27 is abolished while performing the same process as steps S20 to S26 shown in FIG. That is, the heater control, fuel injection control, air pump control, valve opening control in steps S21, S23, S26, and S28, and the target fuel amount Ftrg, target equivalent ratio φtrg, and target air amount Atrg in steps S22, S24, and S25 are set. carry out. However, the discharge control in step S27 is not performed, and energization to the ozonizer 30 is stopped to stop ozone generation.

  Further, in the oxidation stop control, the processes in steps S21 and S27 in FIG. 6 are abolished while the processes similar to S20 and S22 to S26 shown in FIG. 6 are performed. That is, fuel injection control, air pump control, valve opening control in steps S23, S26, and S28, and setting of the target fuel amount Ftrg, target equivalent ratio φtrg, and target air amount Atrg in steps S22, S24, and S25 are performed. However, the discharge control in step S27 is not performed, and energization to the ozonizer 30 is stopped to stop ozone generation. Further, the heater control in step S21 is not performed, and the energization to the heater 21 is stopped to stop the heating of the fuel.

  FIG. 7 shows a subroutine process of the all stop control in step S18 of FIG. 6 is repeatedly executed at a predetermined cycle, while the process of FIG. 7 is performed during the execution of any of the ozone supply control, strong oxidation control, weak oxidation control, and oxidation stop control. If a negative determination is made in step S10, it is executed only once.

  First, in step S30 of FIG. 7, it is determined whether or not the internal combustion engine 10 is in operation. If a negative determination is made that the vehicle is not in operation, power supply to the heater 21 is stopped in step S33. On the other hand, if it is determined that the vehicle is in operation, the reaction chamber temperature Th detected by the reaction chamber temperature sensor 27 is acquired in the subsequent step S31. In subsequent step S32, the heater 21 is feedback-controlled so that the acquired reaction chamber temperature Th coincides with a predetermined temperature Tp set in advance. For example, the predetermined temperature Tp is set to the maximum value of the assumed temperature. As a result, when the exhaust pressure decreases below the threshold value Pth and heating by the heater 21 is started, the reaction chamber temperature Th can be quickly set to the target temperature Ttrg.

  In continuing step S34, electricity supply to the injection valve 22 is stopped and fuel injection is stopped. In the subsequent step S35, the energization to the ozonizer 30 is stopped to stop the ozone generation. When the process of FIG. 7 is executed after switching from the weak oxidation control or the oxidation stop control to the full stop control, the stop of ozone generation is continued in step S35.

  In a succeeding step S36, it is determined whether or not the ozonizer stop time is equal to or longer than the predetermined time Eth. In other words, it is determined whether or not the predetermined time Eth has elapsed since the ozone generation stop point. If it is determined that the predetermined time Eth has elapsed, energization to the air pump 30p is stopped in the subsequent step S39 to stop blowing. In step S40, the exhaust check valve 26v is controlled to close. When the process of FIG. 7 is executed after switching from the weak oxidation control or the oxidation stop control to the full stop control, the start time of the full stop control is regarded as the ozone generation stop time. In this case, it is determined whether or not the predetermined time Eth has elapsed from the start time of the all stop control.

  On the other hand, if it is determined that the predetermined time Eth has not elapsed, the target air amount Atrg is set to the maximum value in the subsequent step S37. In the following step S38, the energization amount to the air pump 30p is controlled based on the target air amount Atrg set in step S37, and the air pump 30p is operated with the maximum air volume. Then, the process of step S36 is performed again. Thus, during a period from when ozone generation is stopped until the predetermined time Eth elapses, the air pump 30p is operated at the maximum air volume, and when the predetermined time Eth is reached, the air pump 30p is stopped. As described above, the microcomputer 41 when the operation of the air pump 30p is controlled so as to stop the air blowing after continuing the air blowing by the air pump 30p for a predetermined time Eth from the ozone generation stop time ta is the air pump control means 41a (FIG. 1). Reference).

  FIG. 8 is an example showing a state in which the strong oxidation control in step S16 and the full stop control in step S18 are repeatedly switched as the exhaust pressure Pex fluctuates across the threshold value Pth. That is, when the vehicle speed changes as shown in the (a) column and the exhaust pressure Pex changes as shown in the (b) column, the determination result in step S10 is switched. When the total stop control is performed in accordance with this determination change, the energization state of the ozonizer 30 and the amount of air blown by the air pump 30p change as shown in columns (c) and (d). That is, when the exhaust pressure Pex changes below the threshold Pth when the exhaust pressure Pex changes below the threshold Pth while the strong oxidation control is being performed, the energization of the ozonizer 30 is turned off from on. Switch to

  Then, the operation of the air pump 30p is continued until the predetermined time Eth has elapsed from the ozone generation stop time ta. The amount of air flow is maximized during this air blowing duration. In the example of FIG. 8, since the air flow rate is not maximized at the ozone generation stop time ta, the air flow rate during the air blowing duration is increased compared to the ozone generation stop time ta. Then, the operation of the air pump 30p is stopped at the time tb when the predetermined time Eth has elapsed from the ozone generation stop time ta, and the air flow rate is quickly reduced.

  As described above, according to the present embodiment, there is provided a period in which air blowing by the air pump 30p is continued for a predetermined time Eth from the ozone generation stop time ta. Therefore, the ozone remaining at the ozone generation stop time ta is pushed out to the exhaust passage 10ex and scavenged during the ventilation continuation period (predetermined time Eth). Therefore, after the air pump 30p is stopped, it is possible to suppress the possibility that residual ozone is released from the suction port 30in of the air pump 30p to the atmosphere. The residual ozone described above is ozone remaining in the housing 32 of the ozonizer 30 and in the case of the blower pipe 26 and the air pump 30p.

  Further, according to the present embodiment, the air pump control means 41a controls the operation of the air pump 30p so as to maximize the amount of air blow during the period (predetermined time Eth) in which air blow by the air pump 30p is continued from the ozone generation stop time ta. . Here, if the amount of air blown during the air blowing duration is reduced, there is a concern that when the exhaust pressure Pex suddenly increases to exceed the air blowing pressure by the air pump 30p, the exhaust gas flows backward to the supply pipe 23 and scavenging becomes insufficient. The In this embodiment, the risk of scavenging being insufficient can be reduced because the amount of air blown during the air blowing duration is maximized in this embodiment.

  Furthermore, according to the present embodiment, the ozone generation by the ozonizer 30 is stopped based on the fact that the pressure (exhaust pressure Pex) in the exhaust passage 10ex is equal to or higher than the predetermined pressure (threshold value Pth). Therefore, it is possible to avoid using a large air pump 30p whose maximum blowing pressure greatly exceeds the threshold value Pth. Therefore, it is possible to reduce the size of the air pump 30p and reduce the power consumption of the air pump 30p. When ozone generation is stopped in the case of such a high exhaust pressure, the exhaust pressure Pex is likely to further increase after the ozone generation is stopped, as illustrated in FIG. 8B. Therefore, the effect by maximizing the above-mentioned air flow rate is remarkably exhibited. In the case of a high exhaust pressure, the catalyst temperature is high and there are few opportunities for ozone to be required. Therefore, even if ozone generation is stopped in the case of high exhaust pressure as described above, the opportunities for performing ozone supply control and strong oxidation control are hardly reduced.

  Furthermore, according to the present embodiment, the exhaust pipe 26 includes the exhaust check valve 26v that is provided on the downstream side of the ozonizer 30 in the blower pipe 26 and prevents the exhaust gas from flowing into the ozonizer 30 through the supply pipe 23 and the blower pipe 26. . Therefore, it can suppress that the ozonizer 30 is exposed to exhaust gas and deteriorates. As a specific example of the deterioration, dirt contained in exhaust gas such as unburned fuel components adheres to the electrode 31 and the discharge state is deteriorated.

  Furthermore, according to this embodiment, even when the total stop control is performed after the execution of the weak oxidation control or the oxidation stop control that does not generate ozone, the exhaust check valve 26v is controlled to be closed for a predetermined time. Air blowing continues for Eth. Therefore, the gaseous fuel remaining in the reaction chamber 20a is also pushed out to the exhaust passage 10ex and scavenged at a predetermined time Eth.

  Furthermore, according to this embodiment, the reduction catalyst is a substance containing at least silver. Specifically, a silver catalyst is supported on alumina coated on a carrier. By employing a silver catalyst in this way, the partial oxidation reaction of FIG. 3 is more likely to occur than when a platinum catalyst is employed, for example. Therefore, according to this embodiment that employs a silver catalyst, the NOx purification rate can be improved as compared with the case where a platinum catalyst is employed. In particular, the effect of improving the NOx purification rate is remarkably exhibited in the low temperature region of the temperature region where the catalyst temperature Tcat is activated.

  Furthermore, in this embodiment, the reducing agent heated to a predetermined temperature or higher by the heater 21 is partially oxidized by oxygen contained in the air to be reformed. According to this, partial oxidation of the fuel can be easily realized, and reforming of the reducing agent can be easily realized. Further, by heating the fuel with the heater 21, cracking that causes the fuel to decompose into a hydrocarbon compound having a small number of carbon atoms occurs. And since the boiling point of the hydrocarbon whose carbon number decreased by cracking becomes low, it is suppressed that the vaporized fuel returns to a liquid.

  Further, in the present embodiment, the ozonizer 30 is provided, and ozone generated by the ozonizer 30 is supplied when a cold flame reaction is caused by strong oxidation control. Therefore, it is possible to accelerate the start time of the cold flame reaction and shorten the cold flame reaction time. Therefore, even if the reaction vessel 20 is downsized so that the residence time of the fuel in the reaction chamber 20a is shortened, the cold flame reaction can be completed within the residence time. Therefore, the reaction vessel 20 can be downsized.

Furthermore, in the present embodiment, when the catalyst temperature Tcat is lower than the activation temperature, the fuel generated by the injection valve 22 is stopped and the ozone generated by the ozonizer 30 is supplied to the air passage 23b, whereby the exhaust gas is discharged. Ozone is added to the passage 10ex. According to this, it is possible to prevent the reducing agent from being added even though the reduction catalyst of the NOx purification device 12 is not activated. Then, by adding ozone, NO in the exhaust is oxidized to NO ₂ and adsorbed to the NOx purification catalyst, so that the amount of NOx adsorption to the NOx purification device 12 can be increased.

(Second Embodiment)
In the first embodiment, the reducing agent addition device having a function of supplying ozone provides the ozone supply device according to the present invention. In contrast, in the present embodiment, the ozone supply device shown in FIG. 9 is provided, which is a device in which the reaction vessel 20, the heater 21, and the injection valve 22 shown in FIG. 1 are eliminated. The ozone supply device includes an ozonizer 30, an air pump 30p, a blower pipe 26, a supply pipe 23, an exhaust check valve 26v, and an ECU 40.

  In the control according to the present embodiment, the processing contents shown in FIGS. 5, 6, and 7 are changed as follows. That is, the determinations in steps S11 and S12 shown in FIG. 5 are abolished, and the reducing agent supply control in steps S15, S16, and S17 is abolished. When it is determined in step S13 that the catalyst temperature is higher than T3, the full stop control in step S18 is performed.

  Further, the processing of steps S20, S21, S22, and S25 shown in FIG. 6 is abolished. The target air amount Atrg used for the air pump control in step S26 is set according to the NO concentration in the exhaust. In step S27, the power supplied to the ozonizer 30 is controlled according to the NO concentration in the exhaust gas. In short, the higher the NO concentration in the exhaust, the greater the amount of ozone supplied.

  Also, steps S30 to S34 shown in FIG. 7 are abolished. In steps S36 to S40, as in the first embodiment, the continuous air blowing by the air pump 30p is performed for a predetermined time Eth from the ozone generation stop time ta, and then the exhaust check valve 26v is controlled to be closed. Therefore, also in the present embodiment, the residual ozone can be scavenged in the same manner as in the first embodiment, and the possibility that the residual ozone is released from the inlet 30in of the air pump 30p to the atmosphere can be suppressed.

(Third embodiment)
The reducing agent addition apparatus according to this embodiment includes a pressurized air pipe 25 and a metering valve 25v shown in FIG. The upstream end of the pressurized air pipe 25 is connected to the downstream side portion of the turbine 11a in the intake passage 10in, and the downstream end of the pressurized air pipe 25 is downstream of the exhaust check valve 26v in the blower pipe 26. Side and upstream of the inlet 20in.

  An electromagnetically driven metering valve 25 v is attached to the pressurized air pipe 25. The microcomputer 41 controls the opening / closing drive of the metering valve 25v. Therefore, when the metering valve 25v is driven to open, a part of the pressurized air flowing through the intake passage 10in flows through the pressurized air pipe 25, the reaction vessel 20 and the supply pipe 23 in this order and flows into the exhaust passage 10ex. Will be. When the metering valve 25v is opened, the exhaust check valve 26v is controlled to be closed so that the pressurized air is prevented from flowing into the ozonizer 30 and the air pump 30p through the blower pipe 26.

  The valve body of the exhaust check valve 26v is controlled to be switched between a fully open position and a fully closed position. On the other hand, for the valve body of the metering valve 25v, the opening position of the valve body is controlled (metering control) so as to adjust the flow rate of the pressurized air flowing into the reaction vessel 20. Further, when one of the exhaust check valve 26v and the metering valve 25v is opened, the other is closed so that both the exhaust check valve 26v and the metering valve 25v are not opened simultaneously. Thus, the microcomputer 41 controls.

  The microcomputer 41 controls to switch between the air pump mode and the supercharger mode based on the catalyst temperature and the exhaust pressure. The air pump mode is a mode in which air blown from the air pump 30p is supplied to the reaction chamber 20a through the blower pipe 26. In the air pump mode, ozone-containing air containing ozone generated by the ozonizer 30 may be supplied by the air pump 30p, or air that does not contain ozone may be supplied by the air pump 30p by stopping the ozonizer 30. The supercharger mode is a mode in which a part of the intake air (pressurized air) pressurized by the turbine 11a is supplied to the reaction chamber 20a through the pressurized air pipe 25. The metering valve 25v and the check valve 26v provide a switching device that switches between the air pump mode and the supercharger mode.

  In the control according to the present embodiment, the processing content shown in FIG. 5 is changed as follows. That is, when it is determined positive in step S10 that the exhaust pressure Pex is less than Pth (S10: YES), the mode is switched to the air pump mode. And the process of step S11-S17 is performed similarly to the said 1st Embodiment. On the other hand, if it is determined in step S10 that the exhaust pressure Pex is not less than Pth (S10: NO), if there is a request for weak oxidation control or oxidation stop control, the supercharger mode is switched to perform full stop control. The weak oxidation control or the oxidation stop control is executed without executing. And if there is no said request | requirement, all the stop control shown in FIG. 7 will be performed similarly to the said 1st Embodiment.

  As described above, also in the present embodiment, as in the first embodiment, the continuous air blowing by the air pump 30p is performed for a predetermined time Eth from the ozone generation stop time ta, and then the exhaust check valve 26v is controlled to be closed. Therefore, also in the present embodiment, the residual ozone can be scavenged in the same manner as in the first embodiment, and the possibility that the residual ozone is released from the inlet 30in of the air pump 30p to the atmosphere can be suppressed.

  Furthermore, according to this embodiment, the supercharger mode can be executed in addition to the air pump mode. Therefore, it is possible to improve the NOx purification rate by ozone and to enable the addition of the reforming reducing agent even when the exhaust pressure Pex is high while suppressing contamination of the air pump 30p and the ozonizer 30.

(Fourth embodiment)
The reducing agent addition apparatus according to the present embodiment includes an ozone check valve 30v shown in FIG. 11 and eliminates the air pump control means 41a according to the first embodiment. The check valve for ozone 30 v is provided in the blower pipe 26 on the downstream side of the air pump 30 p and the upstream side of the ozonizer 30. The ozone check valve 30v is a mechanical check valve, and the elastic force of the elastic member is applied to the valve body. When the upstream pressure of the valve body becomes higher than the downstream pressure by a predetermined amount or more, the valve body opens the valve against the elastic force. That is, when the air pump 30p is operated, the valve is opened with the blowing pressure. On the other hand, when the downstream pressure of the valve body becomes higher than the upstream pressure, the valve body is not opened and the valve closed state is maintained. Therefore, the ozone check valve 30v prevents the ozone generated by the ozonizer 30 from flowing back into the air pump 30p through the air duct 26.

  In the control according to the present embodiment, the same control as in FIGS. 5 and 6 is performed, and the processing content shown in FIG. 7 is changed as follows. That is, if the processes of steps S36, S37, and S38 are abolished and the ozonizer 30 is stopped in step S36, the air pump 30p is quickly stopped in the subsequent step S39. That is, the air pump control means 41a is abolished.

  As described above, according to the present embodiment, the ozone check valve 30 v is provided on the upstream side of the ozonizer 30. Therefore, ozone (residual ozone) remaining in the ozonizer 30 at the time when ozone generation is stopped can be prevented from flowing back to the air through the air duct 26 after the air pump 30p is stopped. Further, in the present embodiment, the ozone check valve 30v is disposed on the downstream side of the air pump 30p, so that the residual ozone is also prevented from flowing into the air pump 30p. Therefore, it is possible to suppress the deterioration of the air pump 30p due to residual ozone.

  In addition, according to the reducing agent addition apparatus shown in FIG. 1, it can be said that by providing the air pump control means 41a provided by the microcomputer 41, it is possible to suppress the release of residual ozone into the atmosphere without requiring the ozone check valve 30v.

(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. Is also possible.

  In the air pump control means 41a according to the first embodiment, the air flow rate at the predetermined time Eth is maximized, but the present invention is not limited to the maximum air flow rate. For example, the air blowing amount at the predetermined time Eth may be set so that the air blowing amount at the ozone generation stop time ta is increased by a predetermined amount. In this case, if the blown air volume at the ozone generation stop time ta is the maximum air volume, the maximum air volume is maintained without increasing the blown air volume during the predetermined time Eth.

  In the air pump control means 41a according to the first embodiment, the predetermined time Eth for scavenging is set to a preset time, but the predetermined time Eth may be variably set. For example, the residual ozone amount at the ozone generation stop time ta may be estimated, and the predetermined time Eth may be set longer as the estimated residual ozone amount increases. According to this, excess and deficiency of the predetermined time Eth can be suppressed, and both reduction in power consumption of the air pump 30p required for scavenging and improvement in the certainty of scavenging can be achieved.

  Although the electromagnetically driven exhaust check valve 26v is employed in the first embodiment, a mechanical check valve similar to the ozone check valve 30v shown in FIG. 11 may be employed. Further, the mechanical ozone check valve 30v shown in FIG. 11 may be changed to an electromagnetically driven check valve.

  In the first embodiment, the air pump 30p is disposed on the upstream side of the ozonizer 30, but may be disposed on the downstream side of the ozonizer 30. However, the arrangement of the air pump 30p on the upstream side of the ozonizer 30 reduces the degree to which the air pump 30p is exposed to ozone, so that the possibility of the air pump 30p being deteriorated by ozone can be reduced.

  The present invention can also be applied to a reducing agent addition apparatus that eliminates the ozone supply control in step S14 of FIG. The present invention can also be applied to an ozone supply device that supplies ozone to the exhaust passage 10ex and promotes the temperature increase during regeneration control in which the temperature of the DPF 13 is increased and regenerated.

  In the ozone supply control according to step S14 in FIG. 5, the air pump 30p is operated with a preset amount of power, and the electrode 31 of the ozonizer 30 is energized with a preset amount of power to cause discharge. On the other hand, the power supplied to the ozonizer 30 and the amount of air blown by the air pump 30p may be controlled according to the NO concentration in the exhaust gas. In short, the higher the NO concentration in the exhaust, the greater the amount of ozone supplied by the ozone supply control.

  In the first embodiment, when any one of the ozone supply control, the strong oxidation control, the weak oxidation control, and the oxidation stop control is performed, the exhaust pressure is switched to Pth, that is, the negative determination is performed in step S10. In this case, the full stop control of FIG. 7 is executed only once. On the other hand, when the exhaust pressure is switched to Pth or greater during the ozone supply control or the strong oxidation control, the total stop control is executed once, and the exhaust pressure is equal to or greater than Pth during the weak oxidation control or the oxidation stop control. In the case of switching, all stop control may not be executed. In short, at least when exhaust gas pressure is switched to Pth while ozone is being generated, full stop control may be executed.

  In each of the above embodiments, the exhaust pressure sensor 43 is provided, and the exhaust pressure Pex that is the pressure in the exhaust passage 10ex is directly detected. On the other hand, the exhaust pressure sensor 43 may be eliminated, and the exhaust pressure Pex may be estimated based on, for example, the operating state of the internal combustion engine 10 or the pressure loss in the DPF 13. In each of the above embodiments, the catalyst temperature sensor 42 attached to the NOx purification device 12 is provided, and the atmospheric temperature (catalyst temperature) of the reduction catalyst is directly detected. On the other hand, the catalyst temperature sensor 42 may be eliminated, and the catalyst temperature may be estimated based on, for example, the operating state of the internal combustion engine 10.

  In the third embodiment shown in FIG. 10, the metering valve 25v and the exhaust check valve 26v are configured separately, but may be configured integrally. In the embodiment shown in FIG. 10, the supercharger 11 rotates the compressor 11c by the kinetic energy of the exhaust, but a supercharger that drives the compressor 11c by an electric motor may be adopted.

  In the case where the intake passage 10in shown in FIG. 10 is provided with a cooler that cools the intake air pressurized by the compressor 11c, the pressurized air pipe 25 is connected to the upstream side of the cooler to suck the intake air before cooling. It is desirable to configure to supply to the reaction vessel 20. However, the pressurized air pipe 25 may be connected to the downstream side of the cooler so that the cooled intake air is supplied to the reaction vessel 20.

  In the fourth embodiment shown in FIG. 11, the ozone check valve 30v is provided on the downstream side of the air pump 30p and on the upstream side of the ozonizer 30, but if it is on the upstream side of the ozonizer 30, the upstream side of the air pump 30p is provided. An ozone check valve 30v may be provided.

  In each of the above embodiments, the DPF 13 is disposed on the downstream side of the NOx purification device 12 in the exhaust passage 10ex, but may be disposed on the upstream side of the NOx purification device 12. In each of the above embodiments, a catalyst containing silver is used as the reduction catalyst. However, the present invention is not limited to such a silver catalyst. For example, a catalyst containing copper or iron is used as the reduction catalyst. It may be used. In each of the above embodiments, a reduction catalyst that physically captures (that is, adsorbs) NOx is employed. However, in a combustion system that employs a reduction catalyst that captures (that is, stores) NOx by chemical bonding, A reducing agent addition apparatus may be applied. Specific examples of the reduction catalyst that occludes in this way include platinum and vanadium.

  In the modification according to the first embodiment, the modification is performed so that the ratio of the aldehyde contained in the reducing agent is a predetermined ratio (for example, 10%). On the other hand, you may modify | reform so that the ratio of an aldehyde may become about 100%. Further, the modified reducing agent according to the present invention is not limited to containing an aldehyde. For example, a reducing agent addition apparatus using alcohol, acetate, carbon monoxide, or hydrogen as a partial oxide may be used.

  When the internal combustion engine 10 is burning in a state leaner than the stoichiometric air-fuel ratio, the reducing agent addition device is applied to a combustion system in which the NOx purification device 12 adsorbs NOx and reduces NOx in other than lean combustion. Also good. In this case, ozone may be generated during lean combustion, and reformed fuel may be generated 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 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, 23 ... Supply pipe (blower pipe), 26 ... Blower pipe, 30 ... Ozonizer, 30p ... Air pump, 30v ... Check valve for ozone, 41a ... Air pump control means.

Claims (7)

An air pump (30p) for sucking and blowing air,
Blower pipes (23, 26) for guiding the air blown by the air pump to the exhaust passage (10ex) of the internal combustion engine (10);
An ozonizer (30) that is provided in the blower pipe and generates ozone from oxygen contained in the air blown by the air pump;
An air pump control means (41a) for controlling the operation of the air pump so as to stop the air blowing after continuing the air blowing by the air pump for a predetermined time from the ozone generation stop time when the ozone generation by the ozonizer is stopped;
An ozone supply device comprising:   2. The ozone supply according to claim 1, wherein the air pump control unit controls the operation of the air pump so as to maximize the amount of air blow during a period in which the air pump continues to blow air from the time when the ozone generation is stopped. apparatus.   The said air pump control means controls the action | operation of the said air pump so that it may increase ventilation volume compared with the said ozone generation stop time in the period which continues ventilation by the said air pump from the said ozone generation stop time. Item 2. The ozone supply device according to Item 1.   The ozone supply device according to claim 2 or 3, wherein the ozone generation by the ozonizer is stopped based on a pressure in the exhaust passage being equal to or higher than a predetermined pressure.   The exhaust check valve (26v) provided in the downstream part of the said ozonizer among the said ventilation pipes, and preventing exhaust_gas | exhaustion flowing into the said ozonizer through the said ventilation pipe is provided. The ozone supply device according to any one of the above. An air pump (30p) for sucking and blowing air,
Blower pipes (23, 26) for guiding the air blown by the air pump to the exhaust passage (10ex) of the internal combustion engine (10);
An ozonizer (30) that is provided in a downstream portion of the air pump in the blower pipe and generates ozone from oxygen contained in the air blown by the air pump;
A check valve for ozone (30v) provided in an upstream portion of the ozonizer in the air duct, and preventing ozone generated by the ozonizer from flowing back through the air duct;
An ozone supply device comprising:   The ozone supply device according to claim 6, wherein the check valve for ozone is provided on the downstream side of the air pump in the blower pipe.

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