JP6083374B2 - Reducing agent addition device - Google Patents

Description

  The present invention relates to a reducing agent 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 reducing agent addition apparatus described in Patent Document 1 uses 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 above-described conventional apparatus, the following problems occur due to the mist of liquid fuel adhering to the electrodes. That is, the liquid fuel attached to the electrode remains attached until it is vaporized, and the timing at which it is vaporized and discharged from the electrode becomes uncertain. Therefore, it becomes difficult to add the reducing agent to the exhaust passage at a desired timing.

  In order to solve this problem, the present inventors have examined a configuration in which liquid fuel is heated by a heater and vaporized, and then passed between electrodes. In the case of this configuration, there arises a response delay problem that the timing at which the reformed fuel is added to the exhaust passage is delayed from the timing at which the liquid fuel is injected from the injection valve. Therefore, in order to suppress such a response delay, it is required to quickly vaporize the liquid fuel injected from the injection valve.

  Even in an apparatus that does not reform the fuel by the electrode, it may be required to add the liquid fuel to the exhaust passage after being heated and vaporized by the heater. Even in this case, the problem of the above-mentioned response delay occurs unless it is vaporized quickly.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a reducing agent addition apparatus that can suppress a response delay in the addition timing of the reducing agent.

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

One of the disclosed inventions is a reducing agent addition device. This reducing agent 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 reducing agent is added upstream of the reduction catalyst. And the injection valve (33) which has the injection hole (D1, D2, D3, D4) which injects a liquid reducing agent in a spray state, and the heating surface (34a) arrange | positioned so as to oppose an injection hole Heating means (34, 34p, 34q, 34r) for heating and vaporizing the liquid reducing agent adhering to the heating surface, and a spraying center line (C1, C2) of the reducing agent injected from the nozzle hole , C3, C4) and the injection valve are arranged so that the crossing angles (θ1, θ2, θ3, θ4) between the heating surface and the heating surface are acute angles, and the heating means (34q, 34r) generate heat when heated. A heat transfer cover (342, 343) for accommodating the body (34b) and the heating element, the injection valve is disposed on the upper side of the heating surface, and is opposed to the nozzle hole in the heating surface on the surface (341a), the recess (342a, 343a) is being formed It features a.
Furthermore, one of the disclosed inventions is a reducing agent addition device. This reducing agent 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 reducing agent is added upstream of the reduction catalyst. And the injection valve (33) which has the injection hole (D1, D2, D3, D4) which injects a liquid reducing agent in a spray state, and the heating surface (34a) arrange | positioned so as to oppose an injection hole A heating means (34, 34p, 34q, 34r) for heating and vaporizing the liquid reducing agent attached to the heating surface, and a vaporizing chamber (36a) for vaporizing the reducing agent injected from the injection valve. And a holding member (35) for holding the heating means so that the heating surface is positioned in the vaporization chamber, and the heating means is inserted into an insertion hole (35c) formed in the holding member, The surface has a shape extending in the insertion direction (A) into the insertion hole, and a plurality of injection holes are provided in the injection valve, and the plurality of injection holes are arranged in the insertion direction and are injected from the injection hole. Spraying center line (C1, C2, C3, C4) Intersection angle between the surface (θ1, θ2, θ3, θ4 ) is an acute angle, and the Katamukuru so the spray center line insertion direction, the injector is characterized in that it is arranged.

According to these inventions, since the intersection angle between the spray center line and the heating surface of the reducing agent injected is an acute angle, so that the spray is deposited obliquely with respect to the heating surface. Therefore, since the adhesion area of the spray is enlarged as compared with the case where the crossing angle is a right angle, the heating of the reducing agent by the heating surface is promoted, and the rapid evaporation of the liquid reducing agent can be promoted. Therefore, it is possible to suppress a response delay problem such that the timing at which the reducing agent vaporized by the heating means is added to the exhaust passage is delayed from the timing at which the liquid reducing agent is injected from the injection valve.

1 is a schematic diagram showing a reducing agent addition apparatus according to a first embodiment of the present invention and a combustion system to which the apparatus is applied. Sectional drawing which shows typically the reducing agent addition apparatus shown in FIG. Sectional drawing which follows the III-III line | wire in FIG. It is sectional drawing of the injection valve which concerns on 1st Embodiment, Comprising: The figure which shows the cross-sectional shape of a nozzle hole. The figure which shows typically the crossing angle of the spray centerline of a fuel and a heater heating surface in 1st Embodiment. The figure which shows typically the projection range of the fuel spray in a heater heating surface in 1st Embodiment. The schematic diagram explaining the mechanism in which reformed HC is generated in a 1st embodiment. The schematic diagram explaining the mechanism by which ozone is produced | generated in 1st Embodiment. The flowchart which shows the procedure of the control which switches ozone production | generation and reformed HC production | generation in 1st Embodiment. The flowchart which shows the process sequence which controls fuel supply amount and heater temperature in 1st Embodiment. Sectional drawing of the electric heater which concerns on 2nd Embodiment of this invention. Sectional drawing of the electric heater which concerns on 3rd Embodiment of this invention. Sectional drawing of the electric heater which concerns on 4th Embodiment of this invention.

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

(First embodiment)
The combustion system shown in FIG. 1 includes an internal combustion engine 10, a supercharger 11, a particulate collection device (DPF 14), a NOx purification device 15, a reducing agent purification device (DOC 16), 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 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.

  The exhaust discharged from the plurality of combustion chambers is collected by the exhaust manifold 10m. The exhaust manifold 10m is provided with a return pipe 10egr for returning a part of the exhaust gas to the intake passage 10in as EGR (Exhaust Gas Recirculation) gas. By mixing EGR gas into the intake air in this way, the combustion temperature in the combustion chamber is lowered and NOx reduction is achieved. An EGR cooler 17 and an EGR valve 18 are attached to the reflux pipe 10 egr. The EGR cooler 17 further reduces the combustion temperature by cooling the EGR gas and promotes NOx reduction. The EGR valve 18 is controlled by the ECU 80 and controls the flow rate of the EGR gas according to the operating state of the internal combustion engine 10.

  In the exhaust passage 10ex, on the downstream side of the turbine 11a, a DPF 14 (Diesel Particulate Filter), a NOx purification device 15, and a DOC 16 (Diesel Oxidation Catalyst) are arranged in this order. The DPF 14 collects fine particles contained in the exhaust. A supply pipe 24 of a reducing agent addition device is connected to the exhaust passage 10ex on the downstream side of the DPF 14 and the upstream side of the NOx purification device 15. The reforming / reducing agent generated by the reducing agent adding device is added from the supply pipe 24 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 purification device 15 purifies NOx contained in the exhaust by reacting NOx in the exhaust with fuel on the reduction catalyst and reducing it to N ₂ . The exhaust gas contains O ₂ in addition to NOx, but the added 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 fuel and released from the reduction catalyst. For example, the NOx purification device 15 having a NOx adsorption function is provided by a reduction catalyst made of silver alumina supported on the carrier 15b.

  The DOC 16 is configured by accommodating a carrier carrying an oxidation catalyst in a housing. The 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 reducing agent addition device that generates a modified reducing agent and adds it to the exhaust passage 10ex from the supply pipe 24 will be described with reference to FIGS.

  The reducing agent addition device is disposed outside the exhaust passage 10ex, and includes a discharge reactor 20, an air pump 32p, an injection valve 33, an electric heater 34, and an electronic control unit (ECU 80) which will be described in detail below. Energization of the discharge reactor 20, the air pump 32p, the injection valve 33, and the electric heater 34 is controlled by a microcomputer (microcomputer 81) provided in the ECU 80.

  The discharge reactor 20 includes a housing 22 that forms a flow passage 22a therein, and a plurality of electrodes 21 are disposed in the flow passage 22a. These electrodes 21 have a flat plate shape arranged so as to face each other in parallel, and electrodes to which a high voltage is applied and electrodes having a ground voltage are alternately arranged.

  A connecting member 30 is attached to the upstream side of the discharge reactor 20, and a cylindrical mixing container 31 that forms a mixing chamber 31 a is disposed in the internal space 30 a of the connecting member 30. The downstream opening of the mixing container 31 is connected to a flow passage 22 a formed by the housing 22. The upstream opening of the mixing container 31 faces the opening of the cylindrical member 30b provided in the connecting member 30 via a predetermined gap CL.

  Therefore, the mixing chamber 31a and the internal space 30a communicate with each other through the gap CL formed between the mixing container 31 and the cylindrical member 30b. Specifically, an internal space 30a exists around the mixing chamber 31a communicating with the flow passage 22a. The air in the internal space 30 a flows into the mixing chamber 31 a through the annular gap CL, and flows in order to the flow passage 22 a and the supply pipe 24.

  A holding member 35 that holds a vaporizing case 36, an injection valve 33, and an electric heater 34, which will be described in detail later, is attached to the upstream side of the connecting member 30. An air passage 35 a is formed in a lower portion of the holding member 35. The air blown by the air pump 32p flows into the air passage 35a through the blower pipe 32. The air blown by the air pump 32p is a normal temperature and normal pressure atmosphere existing around the reducing agent adding device. Since air contains oxygen molecules, it can be said that the air pump 32p supplies oxygen gas containing at least oxygen to the mixing chamber 31a. As described above, the air introduced from the air pump 32p to the blower pipe 32 sequentially flows through the air passage 35a, the internal space 30a, and the gap CL and flows into the mixing chamber 31a.

  As shown in FIG. 3, the vaporizing case 36 has a vaporizing chamber 36a having a circular cross section formed therein. A heating surface 34a of the electric heater 34 is disposed in the vaporizing chamber 36a. The heater includes a heating element 34b that generates heat when energized, and a heat transfer cover 340 that accommodates the heating element 34b therein. The outer peripheral surface of the heat transfer cover 340 corresponds to the heating surface 34a described above, and the heating surface 34a rises in temperature as the heat transfer cover 340 is heated by the heating element 34b.

  The heat transfer cover 340 and the heating element 34b are inserted into an insertion hole 35c formed in the holding member 35, and the heat transfer cover 340 extends in the insertion direction A (left and right direction in FIG. 2) into the insertion hole 35c. Shape. This insertion direction A is a horizontal direction in the state which mounted the reducing agent addition apparatus in the vehicle. That is, the center line Ch of the heat transfer cover 340 extends in the horizontal direction. The length of the heat transfer cover 340 in the insertion direction A, that is, the length in the longitudinal direction is longer than the length of the heat transfer cover 340 in the direction perpendicular to the insertion direction A.

  An opening 36c is formed in the upper part of the peripheral wall of the vaporizing case 36, and the injection valve 33 is arranged above the opening 36c. The injection valve 33 includes an injection hole plate 33a in which a plurality of injection holes D1, D2, D3, and D4 (see FIGS. 3 and 4) are formed. The plurality of nozzle holes D1 to D4 are arranged side by side in the insertion direction A of the heat transfer cover 340, that is, the direction of the center line Ch.

  The injection valve 33 is held by being inserted into an insertion hole 35 b formed in the holding member 35. The injection valve 33 has a rod-like shape extending in the insertion direction B into the insertion hole 35b. This insertion direction B coincides with the direction in which the center line Ci of the injection valve 33 extends, and is inclined with respect to the vertical direction when the reducing agent addition device is mounted on the vehicle. That is, the center line Ch of the electric heater 34 and the center line Ci of the injection valve 33 cross each other at an angle.

  As shown in FIG. 4, the nozzle holes D1 to D4 have a shape extending straight. The passage sectional shape of the nozzle holes D1 to D4 is circular, and the passage sectional area is constant. Center lines C1, C2, C3, and C4 of the injection holes D1 to D4 are inclined with respect to the center line Ci of the injection valve 33. The spray which is the mist-like liquid fuel injected from each of the nozzle holes D1 to D4 has a conical shape which expands as it goes downstream. The center lines of this spray are the center lines C1, C2, C3, and C4 of the nozzle holes D1 to D4.

  As shown in FIG. 5, the spray injected from the nozzle holes D1 to D4 flows into the vaporizing chamber 36a through the opening 36c and is sprayed onto the heating surface 34a. The intersection angles θ1, θ2, θ3, and θ4 between the spray center lines C1, C2, C3, and C4 and the heating surface 34a are acute angles of less than 90 degrees. Strictly speaking, the crossing angles θ1 to θ4 are angles between the horizontal plane at the uppermost end portion of the heating surface 34a and the spray center lines C1 to C4.

  The positions of the nozzle holes D1 to D4 in the insertion direction A are located closer to the front side (left side in FIG. 5) in the insertion direction A than the heating surface 34a. And the crossing angle (theta) 1- (theta) 4 of spray is so large that the nozzle hole located in the near side of the insertion direction A among several nozzle holes D1-D4. In the vertical direction, the nozzle holes D1 to D4 are positioned above the heating surface 34a.

  Since the intersection angles θ1 to θ4 are acute angles, the conical spray is sprayed obliquely on the heating surface 34a. Therefore, as shown in FIG. 6, areas A1, A2, A3, and A4 of the heating surface 34a where the spray is sprayed have an elliptical shape with the insertion direction A as the longitudinal direction. The smaller the crossing angles θ1 to θ4 are, the longer the elliptical longitudinal direction of the spray areas A1 to A4 becomes. Further, when the diameter of the nozzle holes D1 to D4 is increased or the distance between the nozzle holes D1 to D4 and the heating surface 34a is increased, the areas of the regions A1, A2, A3, and A4 are increased, and the area from the heating surface 34a is increased. It will protrude. The diameter and the distance are set so as not to protrude in this way.

  The liquid fuel that has flowed into the vaporizing chamber 36a is heated by the electric heater 34 and vaporized. Further, the heating surface 34a further heats the vaporized fuel, thereby generating cracking that decomposes the fuel into hydrocarbons having a small number of carbon atoms. For example, the microcomputer 81 controls energization of the electric heater 34 so that the fuel is heated to a temperature at which light oil is cracked (350 ° C. to 500 ° C.). Cracked fuel has a low boiling point and is difficult to condense. The fuel that has been vaporized and cracked is ejected from a plurality of ejection ports 36 b formed at the tip of the vaporizing case 36 in the axial direction. The gaseous fuel ejected from the ejection port 36 b is mixed with the air introduced from the gap CL in the mixing chamber 31 a and then flows into the discharge reactor 20.

  The injection valve 33 and the electric heater 34 are attached to the vaporizing case 36 via a sealing material (not shown). Therefore, a portion of the vaporizing chamber 36a excluding the jet port 36b is a sealed space. Therefore, the vaporization chamber 36a becomes a high pressure as the fuel vaporizes. With this pressure, the gaseous fuel in the vaporization chamber 36a is ejected from the ejection port 36b to the mixing chamber 31a.

  The liquid fuel in the fuel tank 33t is supplied to the injection valve 33 by the pump 33p, and is supplied from the injection holes D1 to D4 of the injection valve 33 to reduce the pressure, thereby supplying the atomized state to the vaporization chamber 36a. Is done. In other words, the injection valve 33 provides a “atomization device” for atomizing the liquid fuel into the liquid fuel. For example, the injection valve 33 injects the liquid fuel in a spray state of 60 μm or less.

  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 injection valve 33 is configured to open by an electromagnetic force generated by an electromagnetic solenoid, and power supply to the electromagnetic solenoid is controlled by the microcomputer 81.

  When the injection amount per unit time of the liquid fuel injected into the vaporization case 36 is larger than the vaporization amount vaporized per unit time, the fuel sags from the spray areas A1, A2, A3, A4, It falls from the heating surface 34a by its own weight. Then, the liquid fuel is stored in the vaporizing case 36. In this case, the vaporizing case 36 provides a storage tank that temporarily stores the injected liquid fuel until it is vaporized. However, the fuel injection amount from the nozzle holes D1 to D4 is controlled so that the liquid level of the stored fuel does not reach the opening 36c.

  The air-fuel mixture obtained by mixing gaseous fuel and air in the mixing chamber 31 a flows through the interelectrode 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 24. The discharge reactor 20 oxidizes fuel (hydrocarbon) contained in the air-fuel mixture to generate reformed fuel. Hereinafter, the production reaction will be described with reference to FIG.

  First, as indicated by reference numeral (1) in FIG. 7, the 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. 8 in a state where the fuel injection by the injection valve 33 is stopped and no fuel flows. That is, first, electrons emitted from the electrode 21 collide with the introduced oxygen gas (oxygen molecules) (see reference numeral (1)). Then, the oxygen molecules are ionized and become active oxygen (see symbol (2)). Then, the active oxygen is oxidized by reacting with the oxygen molecules that are blown (see symbol (5)).

  In short, when a voltage is applied to the electrode 21 to introduce oxygen gas, the discharge reactor 20 turns the oxygen gas into a plasma state by glow discharge and ionizes oxygen molecules into active oxygen. If fuel is ejected from the ejection port 36b in this state, the discharge reactor 20 partially oxidizes the fuel with active oxygen to generate a reforming reducing agent. On the other hand, if fuel ejection from the ejection port 36b is stopped, the discharge reactor 20 generates ozone from oxygen gas by active oxygen. The generated aldehyde or ozone flows out of the interelectrode passage 21a by the supply pressure of air, that is, the pressure by the air pump 32p, and is added to the exhaust passage 10ex through the supply pipe 24.

  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 (not shown), an engine speed sensor (not shown), a throttle opening sensor (not shown), an intake pressure sensor (not shown), and an intake air amount sensor 95. Exhaust temperature sensor 96 etc. are mentioned.

  The accelerator pedal sensor detects a user's accelerator pedal depression amount. The engine rotation speed sensor detects the rotation speed of the output shaft of the internal combustion engine 10. The throttle opening sensor detects the opening of the throttle valve 13. The intake pressure sensor detects the pressure on the downstream side of the throttle valve 13 in the intake passage 10in. The intake air amount sensor 95 detects the mass flow rate of intake air.

  In general, the ECU 80 controls the injection amount and injection timing of combustion fuel injected from a fuel injection valve (not shown) according to the rotation speed of the output shaft 10a and the load of the internal combustion engine 10. Further, the ECU 80 controls the operation of the reducing agent addition device based on the exhaust temperature detected by the exhaust temperature sensor 96. That is, the microcomputer 81 performs control so that the generation of the reforming / reducing agent and the generation of ozone are switched by repeatedly executing the program of the procedure shown in FIGS. 9 and 10 at a predetermined period. These programs are triggered by the ignition switch being turned on as a trigger, and are always executed during the operation period of the internal combustion engine 10.

  First, in step S10 of FIG. 9, the microcomputer 81 operates the air pump 32p. In subsequent step S <b> 11, a voltage is applied to the electrode 21 to discharge in the discharge reactor 20. In subsequent step S12, it is determined whether or not the temperature of the reduction catalyst (NOx catalyst temperature) of the NOx purification device 15 is lower than the activation temperature. 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 reforming reducing agent.

  If it is determined that the NOx catalyst temperature is lower than the activation temperature, the ozone generation flag is set to ON in step S13. This ozone generation flag instructs to generate ozone as shown in FIG. On the other hand, if it is determined that the NOx catalyst temperature is not lower than the activation temperature, the reforming flag is set to ON in step S14. This reforming flag instructs to generate a reforming reducing agent as shown in FIG.

  Next, in step S20 of FIG. 10, it is determined whether or not the reforming flag is set to ON. If it is determined that the reforming flag is not on, energization to the electric heater 34 is stopped in the subsequent step S21, and the injection valve 33 is closed so as to stop fuel injection in step S22. The microcomputer 81 at the time of executing the process of step S22 provides “ozone generation control means”.

  On the other hand, if it is determined that the reforming flag is on, in the subsequent step S23, the amount of reforming reducing agent (necessary reducing agent amount) required by the NOx purification device 15 per unit time is calculated. The microcomputer 81 at the time of executing the process of step S23 provides “necessary amount calculation means”. Hereinafter, a specific example of calculating the necessary reducing agent amount will be described.

  First, the NOx concentration in the exhaust gas and the exhaust amount are calculated based on the operating state of the internal combustion engine 10 such as the load of the internal combustion engine 10, the rotational speed of the output shaft 10a, and the amount of fuel injected for combustion. Next, the NOx amount (NOx emission amount) in the exhaust gas is calculated based on the calculated NOx concentration and the exhaust gas amount. Next, the amount of NOx adsorbed by the NOx purification device 15 (NOx adsorption amount) is calculated based on the calculated NOx emission amount, the supplied amount of reforming / reducing agent, NOx catalyst temperature, and the like. Next, the total NOx amount is calculated by adding the current NOx emission amount to the calculated NOx adsorption amount. Next, the amount of reforming / reducing agent necessary to purify the total NOx amount is calculated as the necessary reducing agent amount.

  After calculating the required reducing agent amount in step S23 as described above, in the subsequent step S24, the target heater temperature is calculated based on the calculated required reducing agent amount. Specifically, the target heater temperature is set higher as the required amount of reducing agent is larger. However, the lower limit value of the target heater temperature is set to be equal to or higher than the crackable temperature.

  In the subsequent step S25, the power supplied to the electric heater 34 is controlled so as to reach the target heater temperature. For example, the supply power is controlled by duty-controlling the pulse width of the voltage applied to the electric heater 34. When the fuel is vaporized, heat is removed from the heating surface 34a due to the latent heat of vaporization. Therefore, electric power is supplied to the electric heater 34 so as to reach the target heater temperature in consideration of the temperature decrease due to the latent heat of vaporization. In the subsequent step S26, fuel injection is performed by controlling the valve opening time of the injection valve 33 so that the fuel injection amount per unit time becomes the required reducing agent amount. The microcomputer 81 when executing the process of step S26 provides “reforming control means”.

  As described above, the reducing agent addition apparatus according to this embodiment supplies liquid fuel to the discharge reactor 20 after the liquid fuel is vaporized by the electric heater 34, thereby suppressing the problem of liquid fuel adhering to the electrode 21. The fuel can be reformed. In addition, the intersection angles θ1, θ2, θ3, and θ4 of the fuel spray center lines C1, C2, C3, and C4 injected from the nozzle holes D1, D2, D3, and D4 and the heating surface 34a of the electric heater 34 are acute angles. is there. Therefore, compared with the case where the intersection angles θ1 to θ4 are right angles, the spray adhesion area is enlarged. Specifically, in the case of the right angle, the spray areas A1 to A4 are circular, whereas in the present embodiment in which the intersection angles θ1 to θ4 are acute angles, the spray areas A1 to A4 are enlarged in the injection direction. Become an ellipse. Therefore, heating of the reducing agent by the heating surface 34a is promoted, and rapid vaporization of the liquid reducing agent can be promoted. Therefore, it is possible to reform the fuel while suppressing the adhesion of the fuel to the electrode 21 and to suppress the response delay of the fuel addition timing.

  Furthermore, in the present embodiment, the electric heater 34 is inserted into the insertion hole 35c formed in the holding member 35, and the heating surface 34a has a shape extending in the insertion direction A to the insertion hole 35c. Now, since it is necessary to seal between the electric heater 34 and the holding member 35 in the insertion hole 35c, it is desirable to reduce the opening area of the insertion hole 35c to shorten the seal length. On the other hand, it is desirable to increase the area of the heating surface 34a to promote rapid vaporization.

  Therefore, in the present embodiment, the heating surface 34a is formed in a shape extending in the insertion direction A, so that the area of the heating surface 34a is expanded without increasing the opening area of the insertion hole 35c. Further, in the present embodiment, the injection valve 33 is arranged so that the spray center lines C1 to C4 are inclined in the insertion direction A. For this reason, the direction in which the spray adhesion area is enlarged matches the insertion direction A, that is, the direction in which the heating surface 34a extends. Therefore, since the area | region to which spray does not adhere decreases in the heating surface 34a, the heating surface 34a expanded in the insertion direction A can be utilized effectively.

  Further, in the present embodiment, a plurality of injection holes D1 to D4 are provided in the injection valve 33, and the plurality of injection holes D1 to D4 are arranged in the insertion direction A of the electric heater 34. According to this, spraying area | region A1-A4 can be expanded in the insertion direction A, making the shape of the nozzle hole D1-D4 circular and making spray into a cone shape. Therefore, it is unnecessary to drill a non-circular injection hole in the injection hole plate 33a, and the area where the spray does not adhere can be reduced in the heating surface 34a, and the heating surface 34a expanded in the insertion direction A is effectively used. it can.

  Here, when the liquid fuel injected from the 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 injection valve 33 is heated by the electric heater 34 and vaporized. Therefore, it can suppress that liquid fuel adheres to the electrode 21, and can reduce the said concern.

  Furthermore, in this embodiment, the discharge reactor 20 which ionizes the supplied oxygen gas by discharge and makes it active oxygen, and the injection valve 33 which supplies a fuel to the discharge reactor 20 are provided. Then, the microcomputer 81 provides the ozone generation control means in step S13 and the reforming control means in step S14. Therefore, if fuel injection is stopped by the ozone generation control means, ozone is generated by active oxygen, and if fuel is injected by the reforming control means, the fuel is oxidized (reformed) by active oxygen and reformed and reduced. An agent is produced. Therefore, both the reforming of the reducing agent and the generation of ozone can be realized with one discharge reactor 20.

  Here, when the liquid fuel adheres to the electrode 21, when switching from the generation of the reforming / reducing agent to the generation of ozone, the adhering fuel is vaporized and the electrode is vaporized even though the fuel supply is stopped. There will be fuel in the inter-passage 21a. Then, the active oxygen generated by the discharge oxidizes the fuel to generate a reforming and reducing agent, and the amount of ozone that is generated by oxidizing oxygen molecules is reduced. On the other hand, according to this embodiment, since the fuel adhesion to the electrode 21 can be suppressed as described above, it is possible to suppress the problem that the reforming / reducing agent is generated when the ozone generation flag is on.

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.

  Further, in the present embodiment, the atmosphere is used as an oxygen gas containing at least oxygen, and the atmosphere is supplied to the discharge reactor 20 by the air pump 32p. Therefore, for example, oxygen gas having a high oxygen concentration can be supplied to the discharge reactor 20 as compared with the case where the exhaust gas from the internal combustion engine 10 is used as oxygen gas.

  Further, in the present embodiment, the fuel cracked by the electric heater 34 is supplied to the discharge reactor 20, so that the fuel is partially oxidized with the oxygen gas ionized by the discharge reactor 20 to generate the reformed fuel. . Therefore, since the boiling point of the fuel is lowered by being cracked, the fuel is suppressed from being liquefied again when the vaporized fuel is cooled by oxygen gas and the temperature is lowered. As a result, suppression of the gaseous fuel condensing and adhering to the electrode 21 can be promoted.

  Furthermore, in this embodiment, the injection valve 33 which supplies to the electric heater 34 in the state which atomized the liquid fuel is provided. Therefore, the time required to vaporize and crack the liquid fuel with the electric heater 34 is shortened. Therefore, the responsiveness of the addition of the reformed fuel to the necessary reducing agent amount can be accelerated.

(Second Embodiment)
In the embodiment shown in FIG. 3, the heat transfer cover 340 of the electric heater 34 has a cylindrical shape. Therefore, the part of area | region A1-A4 to which spray is sprayed among the heating surfaces 34a is circular arc shape which makes the upper side convex. On the other hand, the heat transfer cover 341 of the electric heater 34p according to the present embodiment shown in FIG. 11 has a cylindrical shape in which an insertion hole for the heating element 34b is formed inside the square pillar. And the part of the opposing surface 341a which opposes the nozzle holes D1-D4 among the heating surfaces 34a, Comprising: The part of spraying area | region A1-A4 to which spray is sprayed is a flat shape extended in a horizontal direction. In addition, the arrow which shows the up-down direction in a figure shows the up-down direction in the state which mounted the reducing agent addition apparatus in the vehicle.

  In the case of the embodiment shown in FIG. 3, the heating surface 34a has a curved shape that protrudes upward, so that the fuel adhering to the spray areas A1 to A4 flows down by its own weight along the circumferential direction of the heating surface 34a. Liquid sag is likely to occur. On the other hand, according to this embodiment shown in FIG. 11, the opposing surface 341a which is a part of spraying area | region A1-A4 among the heating surfaces 34a is a flat shape extended in a horizontal direction. Therefore, it is possible to suppress the fuel adhering to the facing surface 341a from flowing down by its own weight along the short side direction (the left-right direction in FIG. 11) of the heating surface 34a. Therefore, it is possible to promote rapid vaporization of the liquid fuel.

(Third embodiment)
As shown in FIG. 12, in the heat transfer cover 342 of the electric heater 34q according to the present embodiment, recesses 342a are formed in the spray areas A1 to A4 of the heating surface 34a. In addition, the arrow which shows the up-down direction in a figure shows the up-down direction in the state which mounted the reducing agent addition apparatus in the vehicle.

  Therefore, according to this embodiment, it can suppress that the fuel adhering to spraying area | region A1-A4 flows down with dead weight along the transversal direction (left-right direction of FIG. 12) of the heating surface 34a. Therefore, it is possible to promote rapid vaporization of the liquid fuel.

(Fourth embodiment)
As shown in FIG. 13, in the heat transfer cover 343 of the electric heater 34r according to the present embodiment, portions of the spray areas A1 to A4 of the heating surface 34a are formed in an uneven shape having a plurality of recesses 343a. Yes. In addition, the arrow which shows the up-down direction in a figure shows the up-down direction in the state which mounted the reducing agent addition apparatus in the vehicle.

  Therefore, according to this embodiment, it can suppress that the fuel adhering to spraying area | region A1-A4 flows down with dead weight along the transversal direction (left-right direction of FIG. 13) of the heating surface 34a. And since the surface area of the heating surface 34a is increasing by forming in uneven | corrugated shape, vaporizing liquid fuel rapidly can be accelerated | stimulated.

(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. 3, the plurality of nozzle holes D <b> 1 to D <b> 4 are arranged in one row, but may be arranged in two or more rows. Alternatively, there may be one nozzle hole. Further, it is not necessary that all of the plurality of crossing angles θ1 to θ4 are acute angles, and at least one crossing angle may be an acute angle. Further, in the embodiment shown in FIG. 6, it is set so that the spray does not protrude from the heating surface 34a, but it may be set to protrude.

  In the embodiment shown in FIG. 5, the spray center lines C <b> 1 to C <b> 1 in the direction in which fuel is injected from the longitudinal direction of the heating surface 34 a, that is, the insertion direction A of the electric heater 34 from the front side (left side in FIG. 5). Tilt C4. On the other hand, the spray center lines C1 to C4 may be inclined in a direction in which fuel is injected from the back side in the insertion direction A (right side in FIG. 5). In the embodiment shown in FIG. 5, the heating surface 34 a has a shape extending in the insertion direction A, but the heating surface 34 a does not have to have a shape extending in one direction.

  In the embodiment shown in FIG. 4, the nozzle holes D <b> 1 to D <b> 4 have a shape that extends straight, and the passage cross-sectional shape of the nozzle holes D <b> 1 to D <b> 4 is circular. On the other hand, the nozzle hole may have a tapered shape that expands as the passage cross section is on the downstream side. Further, the cross-sectional shape of the passage is not limited to being circular, and may be, for example, an ellipse. In this case, it is desirable to match the longitudinal direction of the ellipse with the extending direction of the heating surface 34a.

  In the embodiment shown in FIG. 2, the vaporizing case 36 and the holding member 35 are formed separately, and the vaporizing case 36 is assembled inside the holding member 35. However, the vaporizing case and the holding member are made of resin. It may be integrally formed with.

  In the embodiment shown in FIG. 1, an air pump 32 p that blows air is used as means for supplying air to the discharge reactor 20. On the other hand, the air pump 32p may be abolished by branching a part of the intake air of the internal combustion engine 10 to flow into the discharge reactor 20. For example, high-temperature intake air may be branched from the downstream portion of the compressor 11c and the upstream portion of the cooler 12 in the intake passage 10in. Alternatively, low temperature intake air may be branched from the downstream portion of the compressor 11c and the cooler 12 in the intake passage 10in. Means for heating the air supplied to the discharge reactor 20 may be provided to suppress the vaporized fuel from being cooled by the air.

  In the embodiment shown in FIG. 1, an injection valve 33 is employed as atomizing means for atomizing 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, the electric heater 34 is adopted as a heating means for heating and vaporizing the liquid fuel, but a heat exchanger using waste heat of the internal combustion engine 10 may be adopted as the heating means. .

  In the case of a complete stop in which both the generation of ozone and the generation of reformed fuel 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. Further, in the case of the complete stop, the power consumption may be reduced by stopping the air supply by stopping the operation of the air pump 32p.

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

  When the internal combustion engine 10 is burning in a state leaner than the stoichiometric air-fuel ratio, the reducing agent 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. 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.

The reducing agent addition device may be applied to a combustion system in which the NOx purification device 15 having no 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 embodiment shown in FIG. 9, the NOx catalyst temperature used in step S <b> 12 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, 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, the discharge reactor 20 is arranged on the downstream side of the electric heater 34, but the discharge reactor 20 may be arranged on the upstream side of the electric heater 34. Further, the discharge reactor 20 may be eliminated.

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

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 10ex ... Exhaust passage, 15 ... NOx purification device, 20 ... Discharge reactor, 21 ... Electrode, 33 ... Injection valve, 34 ... Heater, 34a ... Heating surface, C1, C2, C3, C4 ... Spray center line , D1, D2, D3, D4... Injection hole, θ1, θ2, θ3, θ4.

Claims (6)

A NOx purification device (15) for purifying NOx contained in the exhaust gas of the internal combustion engine (10) on the reduction catalyst is provided in a combustion system provided in the exhaust passage (10ex), and upstream of the reduction catalyst in the exhaust passage. In the reducing agent addition device for adding the reducing agent to the side,
An injection valve (33) having injection holes (D1, D2, D3, D4) for injecting a liquid reducing agent in a spray state;
A heating means (34, 34p, 34q, 34r) having a heating surface (34a) disposed so as to face the nozzle hole and heating and vaporizing the liquid reducing agent attached to the heating surface; With
The injection valve is arranged so that the crossing angles (θ1, θ2, θ3, θ4) of the spraying center lines (C1, C2, C3, C4) of the reducing agent injected from the injection holes and the heating surface become acute angles. Has been placed ,
The heating means (34q, 34r) includes a heating element (34b) that generates heat when energized, and a heat transfer cover (342, 343) that houses the heating element therein.
The injection valve is disposed above the heating surface,
A reducing agent addition apparatus , wherein concave portions (342a, 343a) are formed on an opposing surface (341a) of the heating surface facing the nozzle hole . It has a vaporizing chamber (36a) in which the reducing agent injected from the injection valve vaporizes, and a holding member (35) for holding the heating means so that the heating surface is located in the vaporizing chamber,
The heating means is inserted into an insertion hole (35c) formed in the holding member,
The heating surface has a shape extending in the insertion direction (A) into the insertion hole,
The reducing agent addition apparatus according to claim 1, wherein the injection valve is arranged such that the spray center line is inclined in the insertion direction. A plurality of the nozzle holes are provided in the injection valve,
The reducing agent adding device according to claim 2, wherein the plurality of nozzle holes are arranged side by side in the insertion direction. A NOx purification device (15) for purifying NOx contained in the exhaust gas of the internal combustion engine (10) on the reduction catalyst is provided in a combustion system provided in the exhaust passage (10ex), and upstream of the reduction catalyst in the exhaust passage. In the reducing agent addition device for adding the reducing agent to the side,
An injection valve (33) having injection holes (D1, D2, D3, D4) for injecting a liquid reducing agent in a spray state;
A heating means (34, 34p, 34q, 34r) having a heating surface (34a) disposed so as to face the nozzle hole and heating and vaporizing the liquid reducing agent attached to the heating surface;
A holding member (35) for holding the heating means so that the heating surface is located in the vaporizing chamber, as well as having a vaporizing chamber (36a) for vaporizing the reducing agent injected from the injection valve. ,
The heating means is inserted into an insertion hole (35c) formed in the holding member,
The heating surface has a shape extending in the insertion direction (A) into the insertion hole,
A plurality of the nozzle holes are provided in the injection valve,
The plurality of nozzle holes are arranged side by side in the insertion direction,
The spray center line of the reducing agent injected from the injection hole (C1, C2, C3, C4 ) and the intersection angle between the heating surface (θ1, θ2, θ3, θ4 ) Ri is Do an acute angle, and the spray center line The reducing agent adding device is characterized in that the injection valve is arranged so that the valve is inclined in the insertion direction . The injection valve is disposed above the heating surface;
The reducing agent addition apparatus according to claim 4 , wherein an opposing surface (341a) of the heating surface that faces the nozzle hole has a flat shape that extends in a horizontal direction. A discharge reactor (21) having an electrode (21) for ionizing at least oxygen gas containing oxygen by discharge, and oxidizing the reducing agent vaporized by the heating means with the ionized oxygen gas to generate a modified reducing agent. 20) The reducing agent adding device according to any one of claims 1 to 5 , further comprising: 20).

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