JP6083373B2 - Highly active substance addition equipment - Google Patents

Description

  The present invention relates to a highly active substance addition apparatus for adding a reducing agent used for NOx reduction.

  2. Description of the Related Art Conventionally, a technique for purifying NOx (nitrogen oxide) contained in exhaust gas of an internal combustion engine by reacting with a reducing agent on a catalyst is known. With regard to this technique, the highly active substance addition device described in Patent Document 1 uses a fuel (hydrocarbon) used for combustion of an internal combustion engine as a reducing agent. Then, liquid fuel is injected from the injection valve in the form of a mist and reformed by passing between the discharging electrodes, and the reformed liquid fuel is added to the exhaust passage.

JP 2009-162173 A

  However, in the apparatus for reforming the reducing agent by discharging as described above, the amount of power required for discharging is large, and reduction of power consumption is required. In particular, when the internal combustion engine is mounted on a vehicle, the capacity of the in-vehicle battery that supplies power to the electrodes is limited, so that further reduction in power consumption is required.

  This invention is made | formed in view of the said problem, The objective is to provide the highly active substance addition apparatus aiming at reduction of power consumption.

  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 a highly active substance adding device. This highly active substance addition device 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). It is assumed that a highly active substance is added upstream of the reduction catalyst. A reducing agent supply means (33) for supplying a reducing agent as a fuel, and an electrode (21) for ionizing oxygen gas containing at least oxygen by discharging, the reducing agent supplied by the reducing agent supply means The state of the reduction catalyst during the operation of the discharge reactor (20) that is oxidized by the ionized oxygen gas to generate the reforming and reducing agent as the highly active substance and the power is supplied to the electrode and the discharge reactor is operated. And an electric power adjustment means (S38) for adjusting electric power supplied to the electrode according to at least one of the exhaust states.

  When the ratio of the reforming amount to the reducing agent supply amount to the discharge reactor is referred to as a reforming rate, the reforming rate increases as the power supplied to the electrode increases. However, the present inventors have found that the required reforming rate varies depending on the state of the reduction catalyst and the state of the exhaust. Specific examples of the state of the reduction catalyst include the temperature of the reduction catalyst. Specific examples of the exhaust state include the ratio of NO to NOx flowing into the NOx purification device, the flow rate of the exhaust gas flowing through the NOx purification device, and the like.

According to the above invention in view of this knowledge, while supplying electric power to the electrode and operating the discharge reactor, the electric power supplied to the electrode is adjusted according to at least one of the state of the reduction catalyst and the state of the exhaust. Therefore, the supplied power is adjusted according to the required reforming rate. Therefore, wasteful power supply is suppressed even when the required reforming rate is low, and power consumption can be reduced.

The schematic diagram which shows the combustion system to which the highly active substance addition apparatus which concerns on one Embodiment of this invention, and its apparatus are applied. The schematic diagram explaining the mechanism in which ozone is produced | generated in the highly active substance addition apparatus shown in FIG. The schematic diagram explaining the mechanism in which the reformed HC is produced | generated in the highly active substance addition apparatus shown in FIG. The flowchart which shows the procedure of the control which switches ozone production | generation and reformed HC production | generation in the highly active substance addition apparatus shown in FIG. The flowchart which shows the procedure of the subroutine process based on the ozone production | generation control shown in FIG. 5 is a flowchart showing a procedure of a subroutine process related to reforming / reducing agent generation control shown in FIG. 4. The test result showing that the effect of NOx purification rate improvement by discharge changes according to NOx catalyst temperature. The figure which shows an example of control of the discharge electric power according to the NOx catalyst temperature in the highly active substance addition apparatus shown in FIG. The test result showing that the effect of NOx purification rate improvement by discharge changes according to NO ratio. The figure which shows an example of control of the discharge electric power according to NO ratio in the highly active substance addition apparatus shown in FIG. The flowchart which shows the procedure of the subroutine process based on NO ratio estimation control shown in FIG. The figure which shows the one aspect | mode of the change of NO ratio with respect to the change of DOC temperature, when base DOC temperature is lower than DOC active temperature. The figure which shows the one aspect | mode of the change of NO ratio with respect to the change of DOC temperature, when base DOC temperature is higher than DOC active temperature.

  Hereinafter, an embodiment of the invention will be described with reference to the drawings. 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 highly active substance adding device. 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 35 of a highly active substance addition device is connected to the exhaust passage 10ex downstream of the DPF 14 and upstream of the NOx purification device 15. The reforming / reducing agent generated by the highly active substance adding device is added from the supply pipe 35 to the exhaust passage 10ex. The reforming / reducing agent is obtained by partially oxidizing a hydrocarbon (fuel) used as a reducing agent to reform it into a partially oxidized hydrocarbon, which will be described in detail later with reference to FIG.

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 purifying device 15 purifies NOx contained in the exhaust by reacting NOx in the exhaust with the reforming reducing agent on the reduction catalyst and reducing it to N ₂ . The exhaust gas contains O ₂ in addition to NOx, but the reforming / reducing agent 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 reforming reducing agent 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, a highly active substance adding device that generates a reforming and reducing agent and adds it to the exhaust passage 10ex from the supply pipe 35 will be described. The highly active substance addition apparatus includes a discharge reactor 20, an air pump 31, a fuel injection valve 33, and an electric heater 34, which will be described in detail below. The discharge reactor 20 includes a plurality of pairs of a pair of electrodes 21 that have a ground voltage and a high voltage. Each electrode 21 has a flat plate shape and is disposed so as to face each other in parallel. The voltage application to the electrode 21 is controlled by a microcomputer (microcomputer 81) included in the electronic control unit (ECU 80).

  A case 30 that forms a mixing chamber 30 a is attached to the upstream side of the discharge reactor 20. The air blown by the air pump 31 flows into the mixing chamber 30a through the blow pipe 32. The air pump 31 is driven by an electric motor, and the electric motor is controlled by the microcomputer 81. The air blown by the air pump 31 is a normal temperature and normal pressure atmosphere existing around the highly active substance adding device. Since air contains oxygen molecules, it can be said that the air pump 31 supplies oxygen-containing gas to the mixing chamber 30a. Hereinafter, such a gas containing at least oxygen is simply referred to as oxygen gas. The air pump 31 provides “oxygen supply means” for supplying oxygen gas to the discharge reactor 20.

  The liquid fuel in the fuel tank 33t is supplied to the fuel injection valve 33 by the pump 33p and injected from the injection hole of the fuel injection valve 33 into the mixing chamber 30a. The fuel in the fuel tank 33t 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 injection valve 33 is structured to open by an electromagnetic force generated by an electromagnetic solenoid, and the energization of the electromagnetic solenoid is controlled by the microcomputer 81. The fuel injection valve 33 provides “reducing agent supply means” for supplying hydrocarbons to the discharge reactor 20 by injecting fuel.

  The electric heater 34 is disposed in the mixing chamber 30 a and heats the liquid fuel injected from the fuel injection valve 33. The state of energization to the electric heater 34 is controlled by the microcomputer 81. The liquid fuel heated by the electric heater 34 is vaporized in the mixing chamber 30a, and the vaporized fuel is heated to a predetermined temperature or higher by the electric heater 34. As a result, cracking occurs in which the fuel is decomposed into hydrocarbons having a small number of carbon atoms. 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.

  In the mixing chamber 30a, the fuel vaporized and cracked by the electric heater 34 and the air containing the oxygen gas supplied by the air pump 31 are mixed. The air-fuel mixture flows through the flow passage 21 a between the electrodes 21 of the discharge reactor 20 and is added to the exhaust passage 10 ex through the supply pipe 35. The discharge reactor 20 oxidizes hydrocarbons contained in the air-fuel mixture to generate a reforming reducing agent. Hereinafter, the production reaction will be described with reference to FIG.

  First, as indicated by reference numeral (1) in FIG. 2, electrons emitted from the electrode 21 collide with oxygen gas (oxygen molecules) contained in the air-fuel mixture. Then, the oxygen molecules are ionized and become active oxygen (see symbol (2)). Next, the active oxygen reacts with the gaseous fuel (hydrocarbon) contained in the air-fuel mixture to partially oxidize the hydrocarbon (see symbol (3)). Thereby, the reforming / reducing agent in a state where the hydrocarbons are partially oxidized is generated (see reference numeral (4)). Specific examples of the reforming / reducing agent include partial oxides in a state in which a part of the hydrocarbon is oxidized to a hydroxy group (OH) or an aldehyde group (CHO).

  Further, the discharge reactor 20 actively generates ozone as shown in FIG. 3 in a state where the fuel injection by the fuel injection valve 33 is stopped and no fuel flows. That is, first, electrons emitted from the electrode 21 collide with oxygen gas (oxygen molecules) blown by the air pump 31 (see reference numeral (1)). Then, the oxygen molecules are ionized and become active oxygen (see symbol (2)). Then, the active oxygen reacts with the oxygen molecules that are blown and oxidizes (see symbols (5) and (6)).

  In short, if a voltage is applied to the electrode 21 to activate the air pump 31, the discharge reactor 20 turns oxygen gas into a plasma state by glow discharge and ionizes oxygen molecules into active oxygen. If the fuel is injected in this state, the discharge reactor 20 partially oxidizes the fuel with active oxygen to generate a reforming and reducing agent. On the other hand, if fuel injection is stopped, the discharge reactor 20 generates ozone from oxygen gas by active oxygen. The generated reforming / reducing agent or ozone flows out of the flow passage 21a between the electrodes 21 due to the blowing pressure of the air pump 31, and is added to the exhaust passage 10ex through the supply pipe 35.

  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 accelerator pedal sensor 91, an engine speed sensor 92, a throttle opening sensor 93, an intake pressure sensor 94, an intake air amount sensor 95, an exhaust temperature sensor 96, and the like.

  The accelerator pedal sensor 91 detects a user's accelerator pedal depression amount. 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 highly active substance adding device based on the exhaust temperature detected by the exhaust temperature sensor 96. That is, the microcomputer 81 performs control so as to switch between the generation of the reforming reducing agent and the generation of ozone by repeatedly executing the program of the procedure shown in FIG. 4 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. 5, it is determined whether or not the internal combustion engine 10 is in operation. If it is determined that it is not in operation, the operation of the reducing agent addition device is stopped in step S15. Specifically, when the air pump 31, the fuel injection valve 33, and the electric heater 34 are energized, the energization is stopped. On the other hand, if it is determined that the internal combustion engine 10 is in operation, the reducing agent adding device is operated according to the temperature of the reducing catalyst (NOx catalyst temperature) of the NOx purification device 15.

  Specifically, first, in step S11, the air pump 31 is operated with a preset amount of power. In subsequent step S12, it is determined whether or not the NOx catalyst temperature is lower than the activation temperature T1 (for example, 250 ° C.) of the reduction catalyst. The NOx catalyst temperature is estimated from 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 lower than the activation temperature T1, the subroutine for ozone generation control shown in FIG. 5 is performed in the next step S13. That is, first, in step S20 in FIG. 5, the electrode 21 of the discharge reactor 20 is energized with a preset amount of electric power to cause discharge. In continuing step S21, electricity supply to the electric heater 34 is stopped, and in continuing step S22, electricity supply to the fuel injection valve 33 is stopped and fuel injection is stopped.

  According to the ozone generation control described above, discharge is performed in a state where air is supplied to the discharge reactor 20 without supplying fuel. Therefore, ozone is generated as shown in FIG. 3, and the generated ozone is added to the exhaust passage 10 ex through the supply pipe 35.

  Returning to the description of FIG. 4, when it is determined that the NOx catalyst temperature is equal to or higher than the activation temperature T <b> 1, in the next step S <b> 14, the reforming / reducing agent generation control subroutine shown in FIG. 6 is performed. That is, first, in step S30 of FIG. 6, the electric heater 34 is operated with a preset amount of power. In subsequent step S31, based on the operating state of the internal combustion engine 10, the amount of NOx contained in the exhaust gas flowing into the NOx purification device 15 and the amount of NOx adsorbed by the NOx purification device 15 are calculated.

  A specific example of calculating the NOx amount will be described below. The amount of NOx in the exhaust gas changes according to the operating state of the internal combustion engine 10. For example, the output torque and engine speed of the internal combustion engine 10 and the NOx amount are highly correlated. Therefore, the NOx amount corresponding to the output torque and the engine speed is tested and mapped in advance and stored in the microcomputer 81. Then, during operation of the internal combustion engine 10, the actual output torque or the target output torque and the engine speed are acquired. Based on the acquired output torque and engine speed, the NOx amount is calculated with reference to the stored map.

  Strictly speaking, the NOx amount is the NOx amount per unit time, that is, the NOx flow rate. Further, the NOx adsorption amount is calculated based on the transition of the NOx amount calculated in this way. For example, the integrated value of the NOx amount during the warm-up operation period in which the NOx catalyst temperature rises to the activation temperature T1 from the start of the internal combustion engine 10 is calculated as the NOx adsorption amount.

  In the next step S32, the required amount of the return agent is calculated based on the NOx amount and the NOx adsorption amount calculated in step S31. For example, the NOx amount is added to the NOx adsorption amount, and the required amount of the reductant is calculated by multiplying the added value by a predetermined coefficient. In the subsequent step S33, the operation of the fuel injection valve 33 is controlled based on the necessary reducing agent amount set in step S32. Specifically, the time during which the fuel injection valve 33 is open per predetermined time is lengthened as the amount of necessary reducing agent increases. The microcomputer 81 when executing the process of step S33 provides “reducing agent control means” for controlling the amount of reducing agent supplied by the fuel injection valve 33 based on the flow rate of NOx flowing into the NOx purification device 15. .

  In the subsequent step S34, the NOx catalyst temperature is acquired. The NOx catalyst temperature is estimated from the exhaust temperature detected by the exhaust temperature sensor 96. In subsequent step S35, the ratio of the NO amount to the NOx amount flowing into the NOx purification device 15 is estimated as the NO ratio. The estimation procedure will be described later in detail with reference to FIG. In subsequent step S36, the flow velocity of the exhaust gas flowing through the exhaust passage 10ex is acquired. For example, the flow rate of exhaust gas is calculated based on the intake air amount detected by the intake air amount sensor 95. The microcomputer 81 provides “reduction catalyst temperature acquisition means”, “NO ratio estimation means”, and “exhaust gas flow rate acquisition means” at the time of execution of each of steps S34, S35, and S36.

  In the subsequent step S37, the electric power supplied to the electrode 21 is calculated based on the required amount of the return agent calculated in step S32, the NOx catalyst temperature acquired in step S34, the NO ratio estimated in step S35, and the exhaust flow velocity acquired in step S36. Set. As the supplied power is increased, the ratio (reformation rate) of the amount of the modified reducing agent to the amount of the reducing agent supplied to the discharge reactor 20 is increased.

  In this step S37, the larger the necessary amount of the reducing agent and the more reducing agent injected from the fuel injection valve 33, the larger the power supplied to the electrode 21 and the higher the reforming rate. Thus, basically, the supplied power is set in proportion to the required amount of return agent. However, the supplied power is corrected according to the NOx catalyst temperature, the NO ratio, and the exhaust flow rate. The technical significance of these corrections will be described below with reference to FIGS.

The bar graph with dots in FIG. 7 indicates the NOx purification rate when discharge is performed, and the bar graph with hatching indicates the NOx purification rate when discharge is not performed. The NOx purification rate is the ratio of the NOx amount purified by the NOx purification device 15 to the NOx amount flowing into the NOx purification device 15. In the test of FIG. 7, the test is performed in a state where the ratio of the NO ₂ amount to the NOx amount (NO ₂ ratio) is 1, that is, the NO amount is zero, and the fuel used as the reducing agent is C ₃ H ₆ . In any test, the amount of reducing agent supplied to the discharge reactor 20 and the amount of air are the same.

  As shown in the figure, when the NOx catalyst temperature is 300 ° C., the NOx purification rate is improved by about three times by performing discharge to reform the reducing agent. However, when the NOx catalyst temperature is 400 ° C., it is clear from the test results of FIG. 7 that even if the discharge is not performed, the NOx purification rate equivalent to that when the discharge is performed can be obtained. .

  In view of this test result, the discharge power is corrected as shown in FIG. That is, after the NOx catalyst temperature rises to the activation temperature T1 and the catalyst warm-up is completed, correction is made so that the discharge power is reduced as the NOx catalyst temperature rises. When the NOx catalyst temperature rises to a discharge unnecessary temperature T2 (for example, 400 ° C.), the discharge power is corrected to zero. When the NOx catalyst temperature is the activation temperature T1, the discharge power correction based on the NOx catalyst temperature is not performed.

The bar graph with dots in FIG. 9 shows the NOx purification rate when discharged with the NO ₂ ratio being 1 and the NO amount being zero, and the shaded bar graph is the NO ratio being 1 and NO ₂ The NOx purification rate when discharged in a state where the amount is zero is shown. The fuel used as the reducing agent is C ₃ H ₆ and the NOx catalyst temperature is 300 ° C. In any test, the amount of reducing agent supplied to the discharge reactor 20 and the amount of air are the same.

As shown, even in conditions such as a reducing agent amount and the air amount is the same, NOx purification rate for NO ratio is often lower the NO ₂ amount that increases, apparent from the test results of FIG. 9 became. This is because NO ₂ has a higher reduction reactivity with the reducing agent than NO. In view of this test result, the discharge power is corrected as shown in FIG. In other words, correction is performed such that the lower the NO ratio, the lower the discharge power. When the NO ratio is 1, correction of discharge power based on the NO ratio is not performed.

  Furthermore, the higher the exhaust gas flow rate, the higher the possibility that NOx in the exhaust gas will pass through the reduction catalyst without being purified, so correction is made to increase the discharge power. In short, the correction is made such that the higher the NOx catalyst temperature, the lower the discharge power, the lower the NO ratio, the lower the discharge power, and the faster the exhaust gas flow rate, the higher the discharge power.

  Returning to the description of FIG. 6, in step S38 of FIG. 6, the power supplied to the electrode 21 is controlled so as to be the discharge power set in step S37 as described above. For example, a booster circuit that boosts the voltage of the battery is provided on the vehicle, and a high voltage boosted by the booster circuit is applied to the electrode 21. Then, the supplied power is controlled by controlling the duty ratio for applying the high voltage. Note that the microcomputer 81 when executing the process of step S38 provides “power adjusting means” that adjusts the discharge power according to the state of the reduction catalyst and the state of the exhaust.

  FIG. 11 is a subroutine process showing the NO ratio estimation procedure. First, in step S40 of FIG. 11, the output torque and engine speed of the internal combustion engine 10 are acquired as the engine operating state. In the subsequent step S41, a base NO ratio that is a reference value for the current NO ratio is acquired.

  The base NO ratio is the NO ratio in a steady operation state in which a predetermined time or more has passed without the output torque of the internal combustion engine 10 and the engine speed changing. The output torque, engine speed, and NO ratio are highly correlated. Therefore, the NO ratio corresponding to the output torque and the engine speed is tested and mapped in advance and stored in the microcomputer 81. Then, based on the output torque and engine speed acquired in step S40, the base NO ratio is calculated with reference to the stored map.

Since the regeneration DOC 14a is disposed upstream of the NOx purification device 15, when the NO in the exhaust is oxidized to NO ₂ by the regeneration DOC 14a, the NO ratio of the exhaust flowing into the NOx purification device 15 is increased. Change. Such a change in the NO ratio is reflected in the NO ratio map described above. However, the value of the NO ratio stored in this map is a value when the internal combustion engine 10 is in steady operation, and when the engine operating state changes and the temperature of the regeneration DOC 14a (DOC temperature) changes, Deviation occurs between the actual NO ratio and the base NO ratio. Therefore, in the following steps S44 to S47, the deviation is corrected according to the DOC temperature.

  Specifically, first, in step S42, the base DOC temperature that is the reference temperature of the regeneration DOC 14a at the present time is acquired. The base DOC temperature is the DOC temperature in the steady operation state described above. Note that the DOC temperature increases as the values of the output torque and the engine speed increase. In subsequent step S43, the actual DOC temperature at the present time is acquired. The DOC temperature is estimated from the exhaust temperature detected by the exhaust temperature sensor 96.

In subsequent step S44, the base DOC temperature acquired in step S42 and the DOC temperature acquired in step S43 are compared in magnitude. In the following step S45, the decomposition start temperature described below and the DOC temperature are compared in magnitude. Here, when the exhaust gas temperature is in a high temperature range equal to or higher than a predetermined temperature, a phenomenon occurs in which NO ₂ is thermally decomposed and changed to NO. The minimum value (for example, 500 ° C.) in this high temperature region is called the decomposition start temperature. In the subsequent step S46, the activation temperature (DOC activation temperature) of the regeneration DOC 14a is compared with the DOC temperature. The DOC activation temperature is a temperature at which NO in exhaust gas can be oxidized to NO ₂ (for example, 200 ° C.).

  In the subsequent step S47, the base NO ratio acquired in step S41 is corrected according to the method described in detail later based on the comparison results in steps S44, S45, and S46. Then, the NO ratio corrected in step S47 is used as the estimated value of the NO ratio in step S35 of FIG.

  Note that the microcomputer 81 when executing the process of step S41 provides a “base value calculation unit” that calculates a base value of the NO ratio (base NO ratio) based on the engine operating state. The microcomputer 81 when executing the process of step S42 provides “reference temperature setting means” for setting the reference temperature (base DOC temperature) of the regeneration DOC 14a based on the engine operating state. The microcomputer 81 at the time of executing the process of step S47 provides “correction means” that corrects the base NO ratio so as to decrease when the DOC temperature is higher than the base DOC temperature.

Next, the correction method in step S47 will be described in detail. Basically, the rate at which the regeneration DOC 14a oxidizes NO to NO ₂ is higher as the DOC temperature is higher unless an exceptional condition described later is satisfied. Then, the NO ratio becomes low. Therefore, the base NO ratio is set lower as the base DOC temperature is higher. However, this base NO ratio is a value that assumes a case where the base DOC temperature is constant and the internal combustion engine 10 is in steady operation.

  Therefore, when the DOC temperature is transiently higher than the base DOC temperature, the actual NO ratio is lower than the base NO ratio. Therefore, in step S47, the base NO ratio is corrected so that the NO ratio is decreased if the DOC temperature is higher than the base DOC temperature, and is increased if the DOC temperature is lower than the base DOC temperature. That is, the base NO ratio is corrected based on the comparison result in step S44. However, this is not the case when the high temperature exception condition or inactive exception condition described below is met.

When the exhaust gas temperature is in a high temperature region that is equal to or higher than the predetermined temperature, NO ₂ is thermally decomposed and changed to NO as described above, so the NO ratio increases. Therefore, when the DOC temperature is higher than the decomposition start temperature, the base NO ratio is corrected to increase the NO ratio exceptionally.

However, when the base DOC temperature is higher than the decomposition start temperature, that is, when the high temperature exception condition is not met, the base NO ratio is set to a value assuming NO ₂ thermal decomposition. Therefore, in this case, even if the DOC temperature is higher than the decomposition start temperature, the increase correction of the base NO ratio is unnecessary.

  In view of this point, in step S47, whether or not the high temperature exception condition that the base DOC temperature is lower than the decomposition start temperature and the DOC temperature is higher than the decomposition start temperature is satisfied based on the comparison result in steps S44 and S45. Determine whether. When it is determined that the high temperature exception condition is satisfied, the base NO ratio is corrected so that the NO ratio is increased even though the DOC temperature is higher than the base DOC temperature.

If the regeneration DOC 14a is not activated at a low temperature, NO is not oxidized to NO ₂ , so the NO ratio increases. Therefore, when the base DOC temperature is lower than the DOC activation temperature, the base NO ratio is set to a value that assumes that NO is not oxidized to NO ₂ . This value is the NO ratio (DOC inlet NO ratio) of the exhaust gas flowing into the regeneration DOC 14a. Therefore, when the base DOC temperature is lower than the DOC activation temperature, the NO ratio is not increased and corrected in spite of the fact that the DOC temperature is lower than the base DOC temperature.

  However, when the base DOC temperature is higher than the DOC activation temperature (see FIG. 13), that is, when the inactive exception condition is not met, the base NO ratio is set to a value lower than the DOC inlet NO ratio. Therefore, in this case, if the DOC temperature is lower than the base DOC temperature, the base NO ratio increase correction is performed. In this increase correction, the base NO ratio is corrected with the DOC inlet NO ratio as an upper limit.

  In view of this point, in step S47, whether or not the inactive exception condition that the base DOC temperature is lower than the DOC activation temperature and the DOC temperature is lower than the DOC activation temperature is satisfied based on the comparison result in steps S44 and S46. Determine whether or not. If it is determined that the inactive exception condition is satisfied, the base NO ratio is not corrected even if the DOC temperature deviates from the base DOC temperature (see FIG. 12).

  12 and 13 are diagrams showing measured values of the actual NO ratio (actual NO ratio) under the test conditions in which the DOC temperature changes when the internal combustion engine 10 is not in steady operation. The upper row shows the change in DOC temperature, and the lower row shows the change in NO ratio. FIG. 12 shows an example when the base DOC temperature is lower than the DOC activation temperature, and FIG. 13 shows an example when the base DOC temperature is higher than the DOC activation temperature.

  First, the example of FIG. 12 will be described. In the example of FIG. 12, since the base DOC temperature is lower than the DOC activation temperature, the inactivity exception condition may be satisfied. First, the actual NO ratio coincides with the base NO ratio in the period up to the time t2 when the DOC temperature rises and reaches the base DOC temperature (see t1), and further reaches the activation temperature. Therefore, it is not necessary to correct the base NO ratio in step S47 in FIG. Since the inactive exception condition is satisfied during the period up to the time point t2, the correction in step S47 is not performed although the DOC temperature is deviated from the base DOC temperature.

After the time t2, the amount of NO that is oxidized to NO ₂ by the regeneration DOC 14a is larger in the period up to the time t3 when the DOC temperature further rises and reaches the decomposition start temperature as compared with that in the steady operation. Therefore, the actual NO ratio is smaller than the base NO ratio. Therefore, during the period from time t2 to time t3, the base NO ratio is corrected to decrease according to the comparison in step S44.

During the period from the time point t3 to the time point t4, the DOC temperature becomes equal to or higher than the decomposition start temperature, and a phenomenon occurs in which NO ₂ is thermally decomposed and changed to NO. Therefore, the actual NO ratio becomes larger than the base NO ratio. During this period, the high temperature exception condition is satisfied, and the base NO ratio is increased and corrected according to the comparison in step S45.

  Since the actual NO ratio is smaller than the base NO ratio in the period from the time t4 to the time t5 when the DOC temperature decreases and reaches the activation temperature, as in the period from the time t2 to the time t3. Reduce the NO ratio. After the time point t5, the inactive exception condition is satisfied in the same manner as the period up to the time point t2, so that the correction in step S47 is not performed although the DOC temperature is different from the base DOC temperature.

Next, the example of FIG. 13 will be described. In the example of FIG. 13, since the base DOC temperature is higher than the DOC activation temperature, the inactivity exception condition is not satisfied. First, the DOC temperature rises to reach the activation temperature (see t11), and the DOC temperature is lower than the base DOC temperature in a period until t12 when the base DOC temperature is reached. Therefore, the amount that NO is oxidized to NO ₂ by the regeneration DOC 14a is smaller than that in the steady operation. Therefore, the actual NO ratio is larger than the base NO ratio. Therefore, the base NO ratio is increased and corrected according to the comparison in step S44. In this increase correction, the base NO ratio is corrected with the DOC inlet NO ratio as an upper limit.

After the time point t12, during the period from the time point t12 until the time point t13 when the DOC temperature further rises and reaches the decomposition start temperature, the amount of NO oxidized to NO ₂ by the regeneration DOC 14a is larger than that in the steady operation. Therefore, the actual NO ratio is smaller than the base NO ratio. Therefore, during the period from the time t12 to the time t13, the base NO ratio is corrected to decrease according to the comparison in step S44.

In the period from the time point t13 to the time point t14, a phenomenon occurs in which the DOC temperature becomes equal to or higher than the decomposition start temperature, and NO ₂ is thermally decomposed and changed to NO. Therefore, the actual NO ratio becomes larger than the base NO ratio. During this period, the high temperature exception condition is satisfied, and the base NO ratio is increased and corrected according to the comparison in step S45. After the time point t14, the correction is performed according to the comparison in step S44 according to the difference between the DOC temperature and the base DOC temperature in the same manner as the period up to the time point t13.

As described above, the highly active substance addition device according to the present embodiment adjusts the power supplied to the electrode 21 according to the state of the reduction catalyst and the state of the exhaust. That is, the NO ratio is estimated as a physical quantity representing the exhaust state, the exhaust flow rate is obtained, and the NOx catalyst temperature is obtained as the physical quantity representing the state of the reduction catalyst. Then, the higher the acquired NOx catalyst temperature, the lower the estimated NO ratio, and the slower the acquired exhaust gas flow rate, the smaller the power supplied to the electrode 21. Hereinafter, the technical significance of adjusting the power supply in this way will be described.

  When the reducing agent is reformed by the discharge reactor 20, the NOx purification rate in the NOx purification device 15 is improved. However, as described above with reference to FIG. 7, when the NOx catalyst temperature rises to the discharge unnecessary temperature T2, a NOx purification rate equivalent to the case of reforming can be obtained without reforming. In this embodiment in view of this point, the higher the NOx catalyst temperature is, the smaller the supplied electric power is, and when the temperature becomes equal to or higher than the discharge unnecessary temperature T2, the supplied electric power is made zero (see FIG. 8). Therefore, since the supplied power is adjusted according to the required reforming rate, it is possible to suppress wasteful power supply even when the required reforming rate is low, thereby reducing power consumption. Can be planned.

  As described above with reference to FIG. 9, the NOx purification rate increases as the NO ratio decreases. In this embodiment in view of this point, the lower the NO ratio, the smaller the supplied power (see FIG. 10). Therefore, since the supplied power is adjusted according to the required reforming rate, it is possible to suppress wasteful power supply even when the required reforming rate is low.

  As described above, the higher the exhaust gas flow rate, the higher the possibility that NOx in the exhaust gas passes through the reduction catalyst without being purified. In other words, when the exhaust gas flow rate is slow, a sufficient NOx purification rate can be ensured even if the reforming rate is low. Therefore, in the present embodiment, the lower the exhaust flow rate, the smaller the supplied power. Therefore, since the supplied power is adjusted according to the required reforming rate, it is possible to suppress wasteful power supply even when the required reforming rate is low.

Furthermore, in this embodiment, when estimating the NO ratio, if the exhaust gas temperature is equal to or higher than the decomposition start temperature, the NO ratio is corrected and estimated so as to increase. Therefore, even if a phenomenon in which NO ₂ is thermally decomposed and changes to NO occurs, it is possible to suppress a decrease in the accuracy of NO ratio estimation. Therefore, it is possible to adjust with high accuracy in adjusting the supply power according to the NO ratio.

Further, in this embodiment, the base NO ratio is calculated based on the engine operating state in step S41 of FIG. 11, and the base DOC temperature is set based on the engine operating state in step S42. Then, based on the comparison between the actual DOC temperature and the base DOC temperature in step S46, the base NO ratio is corrected and the NO ratio is estimated. Therefore, the NO ratio is estimated in view of the fact that NO is oxidized to NO ₂ by the regeneration DOC 14a, so that the estimation accuracy of the NO ratio can be improved. Therefore, it is possible to adjust with high accuracy in adjusting the supply power according to the NO ratio.

  Further, in the present embodiment, in steps S31, S32, and S33 in FIG. 6, fuel (reducing agent) is injected by the amount of the necessary reducing agent according to the engine operating state. Then, the larger the amount of injected reducing agent, the larger the supplied power. Therefore, even when the injection amount of the reducing agent increases with the increase in the necessary reducing agent amount, it is possible to avoid the reforming rate from decreasing. In other words, wasteful power supply can be suppressed by reducing the supply power when the amount of reducing agent injection decreases as the required amount of reducing agent decreases.

  Further, in the present embodiment, if fuel injection is stopped, ozone is generated by active oxygen, and if fuel is injected, fuel is oxidized (reformed) by active oxygen and a reforming / reducing agent is generated. Therefore, both the reforming of the reducing agent and the generation of ozone can be realized with one discharge reactor 20.

Furthermore, in this embodiment, the reduction catalyst has a function of adsorbing NOx. Therefore, when ozone generated in the discharge reactor 20 is added to the exhaust passage 10ex, NO in the exhaust is oxidized to NO ₂ and is easily adsorbed by the reduction catalyst. Therefore, the generated ozone can be used for improving NOx adsorption on the reduction catalyst.

Further, in the present embodiment, ozone is generated on the condition that the reduction catalyst is lower than the activation temperature, and the reforming reducing agent is generated on the condition that the reduction catalyst is higher than the activation temperature. Therefore, it can be avoided that the reforming reducing agent is added to the exhaust passage 10ex at a low temperature when the reduction catalyst cannot exhibit the reducing ability. And, at the low temperature, ozone is added to the exhaust passage 10ex to oxidize NO to NO ₂ and improve NOx adsorption, so that NOx can be prevented from flowing out of the NOx purification device 15 without being purified at low temperatures.

  Further, although ozone is more likely to be thermally decomposed as the temperature is higher, in the present embodiment, ozone is added to the exhaust passage 10ex when the temperature is low, and is not added except when the temperature is low. Therefore, the possibility that the added ozone is thermally decomposed by exhaust heat can be reduced.

  Here, if the liquid fuel injected from the fuel injection valve 33 adheres to the electrode 21, the timing for supplying the reformed fuel to the exhaust passage 10ex may not be controlled as intended. For example, there is a concern that the supply of the reforming / reducing agent is delayed or the reforming / reducing agent is added unintentionally at a low exhaust temperature. In response to this concern, in the present embodiment, the liquid fuel injected from the fuel injection valve 33 is heated by the electric heater 34. Therefore, the vaporization of the liquid fuel is promoted, the liquid fuel can be prevented from adhering to the electrode 21, and the above concerns can be reduced.

  Furthermore, in this embodiment, since liquid fuel is heated with the electric heater 34, the cracking mentioned above can be produced and the boiling point of fuel can be reduced. Accordingly, it is possible to suppress the vaporized fuel from being cooled by the oxygen gas and returning to the liquid, and thus it is possible to suppress the liquid fuel from adhering to the electrode 21.

(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 embodiment shown in FIG. 6, the power supplied to the electrode 21 is adjusted according to both the state of the reduction catalyst and the state of exhaust. On the other hand, the supplied power may be adjusted according to one of the state of the reduction catalyst and the state of the exhaust. In other words, instead of adjusting the supply power to the electrode 21 based on the three parameters of the NOx catalyst temperature, the NO ratio, and the exhaust gas flow rate, the supply power is adjusted based on one or two of the three parameters. May be.

  In the embodiment shown in FIG. 1, the fuel injection valve 33 is employed as the atomizing means for atomizing the liquid fuel and supplying it to the heating means. On the other hand, a vibrating device that vibrates the liquid fuel and makes it atomize by bringing the liquid fuel into contact with a vibration plate that vibrates at a high frequency such as ultrasonic waves may be employed as the atomizing means.

  In the embodiment shown in FIG. 1, an air pump 31 that blows air is used as oxygen supply means for supplying oxygen gas to the discharge reactor 20. On the other hand, a part of the intake air of the internal combustion engine 10 may be branched and allowed to flow into the discharge reactor 20. In this case, in the intake passage 10in located on the downstream side of the compressor 11c, the intake air may be branched from the upstream portion of the cooler 12, or the intake air may be branched from the downstream portion of the cooler 12.

  Further, a mode in which the high-temperature intake air before being cooled by the cooler 12 is branched from the upstream portion of the cooler 12 and a mode in which the low-temperature intake air after being cooled by the cooler 12 from the downstream portion of the cooler 12 are branched. You may make it switch. In this case, it is desirable to suppress the destruction of the generated ozone by the heat of the intake air by setting a mode in which the low-temperature intake air is branched when ozone is generated. In addition, it is desirable to suppress the cooling of the fuel heated by the electric heater 34 by the intake air in the mixing chamber 30a by setting the mode in which the high temperature intake air is branched when the reforming / reducing agent is generated.

  In the case of a complete stop in which both the generation of ozone and the generation of the reforming reducing agent are stopped, the discharge by the discharge reactor 20 may be stopped to suppress wasteful power consumption. Specific examples of the case of complete stop include a case where the NOx catalyst temperature is lower than the activation temperature and the NOx adsorption amount is saturated, or the NOx catalyst temperature exceeds the reducible range and becomes high. There are cases. In the case of the complete stop, power consumption may be reduced by stopping the operation of the air pump 31 and stopping the supply of oxygen gas.

  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. Alternatively, a highly active substance addition apparatus may be applied.

  When the internal combustion engine 10 is burned in a state leaner than the stoichiometric air-fuel ratio, the highly active substance addition device is applied to a combustion system in which the NOx purification device 15 adsorbs NOx and reduces NOx in other than lean combustion. May be. In this case, ozone may be generated at the time of lean combustion, and a reforming reducing agent 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.

The highly active substance addition device may be applied to a combustion system in which the NOx purification device 15 that does not have an adsorption or storage function is employed. In this case, ozone generated in the discharge reactor 20 may be used for regeneration of the DPF 14. That is, by adding ozone upstream of the DPF 14, NO in the exhaust is oxidized to NO ₂ and flows into the DPF 14. Then, the carbon component of the fine particles collected and deposited by the DPF 14 reacts with NO ₂ and is oxidized. Thereby, the fine particles deposited on the DPF 14 are removed, and the DPF 14 is regenerated.

  In the first embodiment, the NOx catalyst temperature used in step S <b> 12 of FIG. 4 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 discharge reactor 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 highly active substance addition device is applied to a combustion system mounted on a vehicle. On the other hand, a highly active substance addition device may be applied to a stationary combustion system. In the embodiment shown in FIG. 1, a highly active substance 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 highly active substance addition device to an ignition ignition type gasoline engine.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 10ex ... Exhaust passage, 15 ... NOx purification device, 20 ... Discharge reactor, 21 ... Electrode, 31 ... Air pump (oxygen supply means), 33 ... Fuel injection valve (reducing agent supply means), S38 ... Power adjustment means.

Claims (11)

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 a highly active substance addition device that adds a highly active substance to the side,
Reducing agent supply means (33) for supplying a reducing agent as fuel ;
It has an electrode (21) for ionizing oxygen gas containing at least oxygen by discharge, and the reducing agent supplied by the reducing agent supply means is oxidized by the ionized oxygen gas to be modified as the highly active substance. A discharge reactor (20) for producing a reducing agent;
A power adjusting means (S38) that adjusts the power supplied to the electrode according to at least one of the state of the reduction catalyst and the state of the exhaust gas while supplying power to the electrode and operating the discharge reactor. )When,
A highly active substance adding device comprising: Reduction catalyst temperature acquisition means (S34) for acquiring the temperature of the reduction catalyst as a physical quantity representing the state of the reduction catalyst;
2. The highly active substance adding device according to claim 1, wherein the power adjustment unit reduces the power supplied to the electrode as the temperature acquired by the reduction catalyst temperature acquisition unit increases. 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 a highly active substance addition device that adds a highly active substance to the side,
Reducing agent supply means (33) for supplying a reducing agent as fuel ;
It has an electrode (21) for ionizing oxygen gas containing at least oxygen by discharge, and the reducing agent supplied by the reducing agent supply means is oxidized by the ionized oxygen gas to be modified as the highly active substance. A discharge reactor (20) for producing a reducing agent;
Power adjusting means (S38) for adjusting the power supplied to the electrode according to at least one of the state of the reduction catalyst and the state of the exhaust;
Reduction catalyst temperature acquisition means (S34) for acquiring the temperature of the reduction catalyst as a physical quantity representing the state of the reduction catalyst,
The high-activity substance addition device according to claim 1, wherein the power adjustment means reduces the power supplied to the electrode as the temperature acquired by the reduction catalyst temperature acquisition means increases. NO ratio estimation means (S35) for estimating the ratio of NO to NOx flowing into the NOx purification device as a physical quantity representing the state of the exhaust,
Said power adjusting means, the lower the said ratio estimated by the NO ratio estimating means, high activity according to any one of claims 1 to 3, characterized in that to reduce the power supplied to the electrode Substance addition equipment. 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 a highly active substance addition device that adds a highly active substance to the side,
Reducing agent supply means (33) for supplying a reducing agent as fuel ;
It has an electrode (21) for ionizing oxygen gas containing at least oxygen by discharge, and the reducing agent supplied by the reducing agent supply means is oxidized by the ionized oxygen gas to be modified as the highly active substance. A discharge reactor (20) for producing a reducing agent;
Power adjusting means (S38) for adjusting the power supplied to the electrode according to at least one of the state of the reduction catalyst and the state of the exhaust;
NO ratio estimation means (S35) for estimating a ratio of NO to NOx flowing into the NOx purification device as a physical quantity representing the state of the exhaust,
The highly active substance adding device according to claim 1, wherein the power adjusting means reduces the power supplied to the electrode as the ratio estimated by the NO ratio estimating means is lower. In the case where the lowest value of the temperature region where the phenomenon that NO ₂ is thermally decomposed and changed to NO occurs is called the decomposition start temperature,
The highly active substance addition according to claim 4 or 5 , wherein the NO ratio estimating means performs correction so as to increase the ratio when the exhaust gas temperature is equal to or higher than the decomposition start temperature. apparatus. The combustion system includes an oxidation catalyst (14a) on the upstream side of the NOx purification device,
The NO ratio estimation means includes
Base value calculation means (S41) for calculating a base value of the ratio based on the operating state of the internal combustion engine;
Reference temperature setting means (S42) for setting a reference temperature of the oxidation catalyst based on the operating state of the internal combustion engine;
Correction means (S44, S47) for correcting the base value based on a comparison between the temperature of the oxidation catalyst and the reference temperature, and estimating the corrected base value as the ratio;
The highly active substance adding device according to claim 4 , wherein the high active substance adding device is provided. An exhaust gas flow rate acquisition means (S36) for acquiring the flow rate of the exhaust gas flowing through the NOx purification device as a physical quantity representing the state of the exhaust gas;
The highly active substance according to any one of claims 1 to 7 , wherein the power adjustment unit decreases the power supplied to the electrode as the flow rate acquired by the exhaust flow rate acquisition unit decreases. Addition equipment. 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 a highly active substance addition device that adds a highly active substance to the side,
Reducing agent supply means (33) for supplying a reducing agent as fuel ;
It has an electrode (21) for ionizing oxygen gas containing at least oxygen by discharge, and the reducing agent supplied by the reducing agent supply means is oxidized by the ionized oxygen gas to be modified as the highly active substance. A discharge reactor (20) for producing a reducing agent;
Power adjusting means (S38) for adjusting the power supplied to the electrode according to at least one of the state of the reduction catalyst and the state of the exhaust;
An exhaust gas flow rate acquisition means (S36) for acquiring a flow rate of the exhaust gas flowing through the NOx purification device as a physical quantity representing the state of the exhaust gas,
The high-active substance addition device according to claim 1, wherein the power adjustment means decreases the power supplied to the electrode as the flow rate acquired by the exhaust flow rate acquisition means decreases. Reducing agent control means (S33) for controlling the amount of reducing agent supplied by the reducing agent supply means based on the flow rate of NOx flowing into the NOx purification device,
Said power adjusting means, wherein the more the supply amount of the controlled reducing agent by the reducing agent control unit, according to any one of claims 1 to 9, characterized in that to increase the power supplied to the electrode Highly active substance addition equipment. 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 a highly active substance addition device that adds a highly active substance to the side,
Reducing agent supply means (33) for supplying a reducing agent as fuel ;
It has an electrode (21) for ionizing oxygen gas containing at least oxygen by discharge, and the reducing agent supplied by the reducing agent supply means is oxidized by the ionized oxygen gas to be modified as the highly active substance. A discharge reactor (20) for producing a reducing agent;
Power adjusting means (S38) for adjusting the power supplied to the electrode according to at least one of the state of the reduction catalyst and the state of the exhaust;
Reducing agent control means (S33) for controlling the amount of reducing agent supplied by the reducing agent supply means based on the flow rate of NOx flowing into the NOx purification device,
The high-active substance addition device according to claim 1, wherein the power adjustment means increases the power supplied to the electrode as the supply amount of the reducing agent controlled by the reducing agent control means increases.

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