JP3557930B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust gas purification technology for an internal combustion engine provided with a combustion heater.
[0002]
[Prior art]
2. Description of the Related Art In recent years, internal combustion engines mounted on automobiles and the like have been required to reduce a relatively large amount of unburned hydrocarbons (HC), white smoke, and the like discharged at the time of a cold start for reasons such as environmental protection.
[0003]
In response to such demands, a combustion device (combustion heater) independent of the internal combustion engine is provided, and the combustion heat generated by the combustion heater is used to heat the intake air and cooling water of the internal combustion engine, so that the fuel Techniques have been proposed for promoting vaporization, increasing the temperature of the combustion chamber of the internal combustion engine, and warming up, and reducing unburned HC, white smoke, and the like discharged from the internal combustion engine during a cold start.
[0004]
In an internal combustion engine, nitrogen oxides (NO_X) And harmful gas components such as unburned HC to improve exhaust emissions. In particular, in the case of a diesel engine, NO_XIt is also required to reduce particulate matter (PM: Particulate Matter) such as soot contained in exhaust gas in addition to HC and HC.
[0005]
In response to such a request, when the air-fuel ratio of the exhaust gas is lean, the NO_XIs absorbed when the oxygen concentration in the exhaust gas is reduced and reducing components such as HC and carbon monoxide (CO) are present._XReduction type lean NO that releases and reduces and purifies_XWhen the exhaust gas is formed of a catalyst, porous ceramics, etc., it traps PM in the exhaust gas when the exhaust gas passes through the holes, and when the air-fuel ratio of the exhaust gas is lean and the exhaust gas temperature is high (for example, 500C to 700C) There has been proposed a technique of providing a DPF or the like for burning PM trapped in an exhaust passage of an internal combustion engine.
[0006]
By the way, in a diesel engine that burns light oil containing a relatively large amount of sulfur component, sulfur oxide (SO_x) Is generated, so that relatively large amount of SO_xWill exist.
[0007]
SO contained in exhaust_xIs NO_XOcclusion reduction type lean NO by the same mechanism as_XAbsorbed by the catalyst. At that time, SO_xIs occlusion reduction type lean NO_XNO to form stable sulfate in the catalyst_XIt is hard to be released compared to_XIt tends to accumulate in the catalyst.
[0008]
Storage NO lean type NO_XSO in catalyst_xWhen the accumulated amount increases, the storage reduction type lean NO_XNO that can be absorbed by the catalyst_XNO in the exhaust_XSo-called SO that cannot completely purify_xPoisoning occurs and exhaust emissions deteriorate.
[0009]
To solve such a problem, an exhaust gas purifying apparatus for an internal combustion engine as described in Japanese Patent Application Laid-Open No. 6-272541 has been proposed. This exhaust gas purification device has NO_XA reducing agent supply device that arranges the absorbing agent and the particulate filter at a position where heat can be transmitted to each other, and that supplies a reducing agent to an exhaust passage upstream of the particulate filter;_XWhen the condition for regeneration of the absorbent is satisfied, the reducing agent is supplied from the reducing agent supply device and NO_XNO absorbed by the absorbent_XIs discharged and reduced, and then the particulate matter collected by the particulate filter is burned using the reducing agent supplied from the reducing agent supply device as an ignition source, and NO generated by the combustion heat generated at that time._XRaise the temperature of the absorbent to NO_XWhen the absorbent becomes hot, SO_xSupplying a reducing agent for reduction to SO_xTo release and reduce.
[0010]
[Problems to be solved by the invention]
However, the exhaust gas purifying device as described above has NO_XNO absorbed by the absorbent_XAnd SO_xNO when releasing and reducing_XA dedicated device such as a reducing agent supply device that supplies the reducing agent to the absorbent is required, and a space for the reducing agent supply device and the like must be secured when the exhaust gas purification device is mounted on a vehicle.
[0011]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems. In an internal combustion engine provided with a combustion-type heater, NO is added without adding a dedicated device such as a reducing agent supply device._X, PM, or SO_xIt is an object of the present invention to provide a technology that can efficiently purify the like.
[0012]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above-described problems. That is, the exhaust gas purifying apparatus for an internal combustion engine according to the present invention burns fuel independently of the internal combustion engine.And a combustion heater for raising the temperature of related elements of the internal combustion engineAnd a harmful gas component in the exhaust provided in the exhaust system of the internal combustion engine.At least nitrogen oxides, particulate matter, sulfur oxidesExhaust purification means for purifying the exhaust gas, and the state of the exhaust purification meansWhich harmful gas components among nitrogen oxides, particulate matter, and sulfur oxides are in a state to be purifiedState determination means for determining,Combustion heaterThe properties of the combustion gas emitted fromThe combustion type heater has a property corresponding to the harmful gas component determined by the state determination means.Combustion condition changing means for changing the combustion conditions of the above,Combustion heaterAnd combustion gas introduction means for introducing the combustion gas discharged from the exhaust gas into the exhaust gas purification means.
[0013]
In the exhaust gas purification device configured as described above, the state determination unit determines the state of the exhaust gas purification unit. And the combustion condition changing means,Combustion heaterIn order to make the properties of the combustion gas discharged from theCombustion heaterChange the combustion conditions. Combustion gas introduction means, combustion conditions have been changedCombustion heaterThe combustion gas discharged from the exhaust gas into the exhaust gas purifying means.
[0014]
In this case, a combustion gas having a property corresponding to the state of the exhaust gas purifying means is introduced into the exhaust gas purifying means. Here, the property of the combustion gas refers to, for example, the temperature of the combustion gas, the air-fuel ratio of the combustion gas, the amount of each component constituting the combustion gas, and the like. Various harmful gas components can be efficiently purified in the exhaust gas purifying means by setting the optimum properties according to the properties, for example, the properties suitable for purifying the predetermined harmful gas components by the exhaust gas purifying means.
[0015]
Further, the exhaust gas purifying means purifies nitrogen oxides, particulate matter, and sulfur oxides. In this case, the state determination means determines whether the exhaust purification means is in a state to purify nitrogen oxides, whether the exhaust purification means is in a state to purify particulate matter, or whether the exhaust purification means It is determined whether or not the oxide is in a state to be purified.
[0016]
Also,The combustion condition changing means may change the combustion condition of the combustion heater so that purification is performed in the order of nitrogen oxide, particulate matter, and sulfur oxide.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, specific embodiments of the exhaust gas purifying apparatus for an internal combustion engine according to the present invention will be described with reference to the drawings.
[0018]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. In FIG. 1, an internal combustion engine 1 is a water-cooled diesel engine having a plurality of cylinders.
The internal combustion engine 1 is provided with one fuel injection valve 10 for each cylinder. Each fuel injection valve 10 is mounted so that its injection hole faces a combustion chamber (not shown) of each cylinder, so that fuel can be directly injected into the combustion chamber. The fuel injection valve 10 communicates with a pressure accumulation chamber (common rail) 12 via a fuel distribution pipe 11, and the common rail 12 communicates with a fuel pump (not shown) via a fuel passage 13.
[0019]
In the fuel injection system configured as described above, the fuel discharged from the fuel pump is supplied to the common rail 12 through the fuel passage 13 and accumulated in the common rail 12 to a predetermined pressure. Is applied to the fuel injection valve 10. Then, when the fuel injection valve 10 is opened, the accumulated fuel is injected into the combustion chamber of each cylinder.
[0020]
Further, an intake branch pipe 2 is connected to the internal combustion engine 1, and each branch pipe of the intake branch pipe 2 communicates with a combustion chamber of each cylinder via an intake port (not shown). The intake branch pipe 2 is connected to an intake pipe 3, and the intake pipe 3 is connected to an air cleaner box 4 containing an air filter. An intake throttle valve 26 is provided in the middle of the intake pipe 3 and is driven to open and close to adjust the intake flow rate in the intake pipe 3. The intake throttle valve 26 is provided with an actuator 27 that includes a step motor or the like and drives the intake throttle valve 26 to open and close.
[0021]
In the intake system configured as described above, fresh air that has flowed into the air cleaner box 4 is guided to the intake branch pipe 2 through the intake pipe 3 after dust and dust are removed by the air filter, and then the intake branch pipe 2. Are distributed to the combustion chamber of each cylinder through the respective branch pipes, and are mixed with the fuel injected from the fuel injection valve 10 in the combustion chamber to form an air-fuel mixture.
[0022]
Further, an exhaust branch pipe 6 is connected to the internal combustion engine 1, and each branch pipe of the exhaust branch pipe 6 communicates with a combustion chamber of each cylinder via an exhaust port (not shown). The exhaust branch pipe 6 is connected to an exhaust pipe 7, and in the middle of the exhaust pipe 7, a storage-reduction type lean NO as an exhaust purification means according to the present invention is provided._XA catalyst 8 is arranged.
[0023]
Storage NO lean type NO_XThe catalyst 8 includes a carrier having a plurality of flow channels arranged in a honeycomb shape, and a NO._XAnd an absorbent.
The carrier is made of a porous ceramic. The flow path of the carrier includes a flow path in which the upstream end is open and the downstream end is closed, and a flow path in which the upstream end is closed and the downstream end is open. The roads are arranged alternately.
[0024]
NO_XExamples of the absorbent include alkali metals such as potassium (K), sodium (Na), lithium (Li) or cesium (Cs), alkaline earths such as barium (Ba) and calcium (Ca), and lanthanum (La). ) Or a rare earth element such as yttrium (Y) and a noble metal such as platinum (Pt). In the present embodiment, it is composed of Ba and Pt. NO_XThis will be described by taking an absorbent as an example.
[0025]
The storage reduction type lean NO thus configured_XIn the catalyst 8, the storage reduction type lean NO_XWhen the air-fuel ratio of the exhaust gas flowing into the catalyst 8 becomes lean, the NO_XIs NO_XAbsorbed by absorbent. On the other hand, when the oxygen concentration in the exhaust decreases, NO_XNO absorbed by the absorbent_XIs released. At this time, the storage reduction type lean NO_XIf a reducing component is present in the catalyst 8, NO_XNO released from absorbent_XReacts with the reducing component to be reduced and purified.
[0026]
NO as described above_XNO in absorbent_XAlthough the detailed mechanism of the absorption / desorption action of is not clear, it is considered that the action is carried out by the following mechanism.
[0027]
That is, the storage reduction type lean NO_XWhen the air-fuel ratio of the exhaust gas flowing into the catalyst 8 becomes lean and the oxygen concentration in the exhaust gas increases, the oxygen O₂Is NO_XO on the Pt surface of the absorbent_2-Or O^2-As NO, and then NO in the exhaust gas becomes O 2 on the surface of Pt._2-Or O^2-Reacts with nitrogen dioxide (NO₂). Then, NO₂Is bonded to barium oxide (BaO) while being oxidized on the surface of Pt, and nitrate ions (NO_3-) Is formed. Thus, the NO in the exhaust_XIs NO_3-As NO_XAbsorbed by absorbent.
[0028]
NO as described above_XThe absorption action of the storage-reduction type lean NO_XThe air-fuel ratio of the exhaust gas flowing into the catalyst 8 is lean and NO_XAbsorbent NO_XContinued as long as the absorption capacity is not saturated.
[0029]
Next, the storage reduction type lean NO_XWhen the concentration of oxygen in the exhaust gas flowing into the catalyst 8 decreases, NO_XNO in absorbent₂NO reduced in production and bound to BaO_3-Is NO₂Becomes NO_XRelease from absorbent. That is, the storage reduction type lean NO_XWhen the concentration of oxygen in the exhaust gas flowing into the catalyst 8 decreases, NO_3-NO in the form of_XNO absorbed by the absorbent_XIs NO₂Becomes NO_XIt will be released from the absorbent.
[0030]
NO_XNO released from absorbent_XRepresents a reducing component (for example, NO_XOxygen O on Pt of absorbent_2-Or oxygen O^2-Reacts with active species such as HC and CO partially oxidized to react with nitrogen (N₂) Etc. are reduced and purified.
[0031]
On the other hand, the storage reduction type lean NO_XIn the catalyst 8, particulate matter (PM) in the exhaust gas is collected in the pores of the porous ceramic. The PM collected in this manner is stored occlusion reduction type lean NO._XWhen the temperature of the exhaust gas flowing into the catalyst 8 becomes high (for example, 500 ° C. to 700 ° C.) and the air-fuel ratio of the exhaust gas becomes lean, the O₂Reacts with and is combusted and processed.
[0032]
By the way, the storage reduction type lean NO_XNO of catalyst 8_XThe absorbent includes sulfur oxides (SO_x) Is NO_XIs absorbed by a similar mechanism. That is, the storage reduction type lean NO_XWhen the air-fuel ratio of the exhaust gas flowing into the catalyst 8 is lean, the SO_xIs NO_XSOx oxidized on the Pt surface of the absorbent_3-And SO_4-And these SO_3-, SO_4-Is NO_XBarium sulfate (BaSO) is combined with BaO as an absorbent.₄) Is formed.
[0033]
BaSO₄Is NO_3-More stable than BaSO₄The crystals are easily coarsened, so that once formed, they are difficult to decompose and release. Therefore, NO_XBaSO in absorbent₄When the production amount of NO increases, NO_XThe amount of BaO that can be combined with_XAbsorbent NO_XSo-called SO with reduced absorption capacity_xPoisoning occurs.
[0034]
SO_xAs a method for eliminating poisoning, occlusion reduction type lean NO_XThe temperature in the catalyst 8 is raised to a high temperature (for example, 500 ° C. to 700 ° C.), and the storage reduction type lean NO_XBy making the air-fuel ratio of the exhaust gas flowing into the catalyst 8 rich, NO_XBaSO formed in the absorbent₄To SO_3-And SO_4-Pyrolyzed to_3-, SO_4-Reacts with reducing components such as HC and CO to form gaseous SO₂To NO_XA method of releasing from an absorbent can be exemplified.
[0035]
Next, the internal combustion engine 1 is provided with a combustion heater 14 according to the present invention. The combustion heater 14 is connected to an intake passage 15 and a combustion gas discharge passage 17.
[0036]
The intake passage 15 is connected to the intake pipe 3 so that a part of intake air flowing through the intake pipe 3 can be supplied to the combustion heater 14. Further, an air pump 16 for forcibly sending a part of the intake air flowing through the intake pipe 3 to the combustion heater 14 is provided in the intake passage 15.
[0037]
The combustion gas discharge passage 17 is provided with the storage reduction type lean NO._XThe combustion gas discharged from the combustion type heater 14 is connected to the exhaust pipe 7 upstream of the catalyst 8 and is used for storing and reducing the lean NO._XIt can be introduced into the catalyst 8. Thus, the combustion gas discharge passage 17 and the exhaust pipe 7 realize the combustion gas introduction means according to the present invention.
[0038]
Subsequently, the combustion type heater 14 has a cooling water introduction passage 18 for guiding the cooling water of the internal combustion engine 1 to the combustion type heater 14, and a cooling water for guiding the cooling water heated in the combustion type heater 14 to the internal combustion engine 1. The discharge passage 19 is connected.
[0039]
Further, a fuel introduction passage 20 is connected to the combustion type heater 14, and the fuel introduction passage 20 is connected to the fuel passage 13 described above. Thereby, a part of the fuel flowing through the fuel passage 13 can be supplied to the combustion heater 14.
[0040]
Here, a specific configuration of the combustion heater 14 will be described with reference to FIG. The combustion type heater 14 communicates with a water jacket (not shown) of the internal combustion engine 1 via a cooling water introduction passage 18 and a cooling water discharge passage 19, and inside the combustion type heater 14, cooling water from the water jacket is provided. The cooling water passage 14a inside the heater for flowing the water is formed.
[0041]
The heater internal cooling water passage 14a is configured to circulate around a combustion chamber 14d formed inside the combustion type heater 14, and cooling water flowing through the heater internal cooling water passage 14a receives heat from the combustion chamber 14d. To increase the temperature. This will be described sequentially.
[0042]
The combustion chamber 14d includes a combustion tube 14b as a combustion source for generating a flame, and a cylindrical partition 14c that covers the combustion tube 14b to prevent the flame from leaking outside. By covering the combustion cylinder 14b with the partition 14c in this manner, the combustion chamber 14d is defined inside the partition 14c. The partition wall 14c is covered by an outer wall 43a of the combustion chamber main body 43 of the combustion type heater 14, and an annular gap is provided between the partition wall 14c and the outer wall 43a. It functions as a cooling water passage 14a.
[0043]
The combustion type heater 14 has an air supply port 14d.₁And exhaust outlet 14d₂Are formed, and these air supply ports 14d are formed.₁And exhaust outlet 14d₂Communicate with the combustion chamber 14d. The air supply port 14d₁Is connected to the intake passage 15 described above, and the exhaust outlet 14d₂Is connected to the above-described combustion gas discharge passage 17.
[0044]
Subsequently, the combustion type heater 14 has a cooling water inlet 14a.₁And cooling water outlet 14a₂Are formed, and these cooling water inlets 14a are formed.₁And cooling water outlet 14a₂Are connected to the heater internal cooling water passage 14a. The cooling water inlet 14a₁The cooling water introduction passage 18 described above is connected to the cooling water discharge port 14a.₂Is connected to the cooling water discharge passage 19 described above.
[0045]
Further, the fuel introduction passage 20 described above is connected to the combustion cylinder 14b, and a part of the fuel discharged from the fuel pump is supplied to the combustion cylinder 14b. The combustion cylinder 14b includes a vaporizing glow plug (not shown) for vaporizing the fuel supplied through the fuel introduction passage 20, and an ignition glow plug (not shown) for igniting the vaporized fuel. ing. The vaporizing glow plug and the ignition glow plug may be shared by a single glow plug.
[0046]
In the combustion type heater 14 configured as described above, the air supply port 14 d₁The intake air flowing into the combustion chamber 14d is guided to the combustion chamber 14d, and the fuel supplied to the combustion cylinder 14b by the fuel introduction passage 20 is vaporized by a vaporizing glow plug (not shown). Then, the intake air and the vaporized fuel are mixed to form an air-fuel mixture, and the air-fuel mixture is ignited by an ignition glow plug (not shown) in the combustion chamber 14d and burns.
[0047]
The gas burned in the combustion chamber 14d flows from the combustion chamber 14d to the exhaust outlet 14d.₂To the exhaust outlet 14d₂Is discharged to the combustion gas discharge passage 17. The combustion gas discharged to the combustion gas discharge passage 17 passes through the combustion gas discharge passage 17 and stores and reduces the lean NO._XIt is led to the exhaust pipe 7 upstream of the catalyst 8. The combustion gas guided to the exhaust pipe 7 is mixed with the exhaust gas flowing from the upstream side of the exhaust pipe 7 while storing and storing the lean NO._XIt flows into the catalyst 8.
[0048]
On the other hand, the combustion heat generated by the combustion in the combustion chamber 14d is transmitted to the cooling water flowing in the heater internal cooling water passage 14a via the partition wall 14c, and raises the temperature of the cooling water.
[0049]
Returning to FIG. 1, the internal combustion engine 1 is provided with an electronic control unit (ECU: Electronic Control Unit) 21 for engine control. The ECU 21 includes a CPU, a ROM, a RAM, an input interface circuit, an output interface circuit, and the like, which are interconnected by a bidirectional bus. Various sensors are connected to the input interface circuit via electric wiring, The fuel injection valve 10, the combustion heater 14, the air pump 16, the actuator 27, and the like are connected to the output interface circuit via electric wiring.
[0050]
The various sensors described above include an air flow meter 5 attached to the intake pipe 3 and a storage reduction type lean NO._XA catalyst temperature sensor 9 mounted on the catalyst 8, a crank position sensor 22 and a water temperature sensor 23 mounted on the internal combustion engine 1, an accelerator position sensor mounted on an accelerator pedal (not shown) or an accelerator lever operated in conjunction with the accelerator pedal, etc. 24, a common rail pressure sensor 25 attached to the common rail 12, and the like.
[0051]
The air flow meter 5 is a sensor that outputs an electric signal corresponding to the mass of intake air flowing through the intake pipe 3. The catalyst temperature sensor 9 is a storage reduction type lean NO_XThe sensor outputs an electric signal corresponding to the catalyst bed temperature of the catalyst 8. The crank position sensor 22 is a sensor that outputs a pulse signal each time a crankshaft (not shown) of the internal combustion engine 1 rotates by a predetermined angle. The water temperature sensor 23 is a sensor that outputs an electric signal corresponding to the temperature of the cooling water flowing through the water jacket of the internal combustion engine 1. The accelerator position sensor 24 is a sensor that outputs an electric signal corresponding to the operation amount of the accelerator pedal. The common rail pressure sensor 25 is a sensor that outputs an electric signal corresponding to the fuel pressure in the common rail 12.
[0052]
The ECU 21 determines the operating state of the internal combustion engine 1 and the storage reduction type lean NO based on the output signal values of the various sensors as described above._XThe state of the catalyst 8 is determined, and based on the determination result, the fuel injection control and the combustion type heater control are performed, and the exhaust gas purification control which is the gist of the present invention is performed.
[0053]
In the fuel injection control, for example, the ECU 21 inputs output signals of the air flow meter 5, the crank position sensor 22, the accelerator position sensor 24, and the common rail pressure sensor 25.
[0054]
The ECU 21 calculates the engine speed of the internal combustion engine 1 based on the time interval at which the crank position sensor 22 outputs the pulse signal, and the torque to be output from the internal combustion engine 1 based on the output signal of the accelerator position sensor 24. That is, the engine torque required by the driver is calculated. Then, the ECU 21 controls the discharge amount of the fuel pump so that the output signal value of the common rail pressure sensor 25 becomes an optimum value corresponding to the engine speed and the engine torque, and outputs the output signal value of the air flow meter 5 and the engine speed. The fuel injection amount (fuel injection time) and the fuel injection start timing are calculated using the parameters and the required engine torque as parameters.
[0055]
Subsequently, the ECU 21 refers to the output signal value (the rotational position of the crankshaft) of the crank position sensor 22 and applies a drive current to the fuel injection valve 10 when the rotational position of the crankshaft coincides with the fuel injection start timing. Then, the fuel injection valve 10 is opened. The application of the drive current to the fuel injection valve 10 is continued for a period corresponding to the fuel injection time.
[0056]
Further, in the combustion heater control, when the temperature of the cooling water is lower than a predetermined temperature, such as at the time of a cold start of the internal combustion engine 1, the ECU 21 activates the air pump 16 so that a part of the intake air is supplied to the combustion heater 14. Along with the supply, a part of the fuel is supplied to the combustion heater 14, and then the vaporization glow plug and the ignition glow plug of the combustion heater 14 are energized to operate the combustion heater 14. Then, when the temperature of the cooling water rises due to the operation of the combustion type heater 14 and the output signal value of the water temperature sensor 23 becomes a predetermined value or more, the ECU 21 stops the operation of the combustion type heater 14.
[0057]
Next, the exhaust gas purification control according to the present embodiment will be described.
In the exhaust gas purification control, the ECU 21 determines that the storage reduction type lean NO_XNO of catalyst 8_XPurification time, PM purification time, and SO_xThe purification timing is determined, and the combustion conditions of the combustion type heater 14 are controlled such that the mixed gas of the exhaust gas from the internal combustion engine 1 and the combustion gas from the combustion type heater 14 has properties corresponding to the respective purification times.
[0058]
For example, storage reduction type lean NO_XCatalyst 8 is NO_XIf it is during the purification time, the ECU 21 needs to lower the oxygen concentration in the mixed gas and increase the concentration of the reducing components (HC and CO) in the mixed gas. The combustion condition of the combustion heater 14 is controlled so that the air-fuel ratio of the gas becomes rich.
[0059]
Storage NO lean type NO_XWhen the catalyst 8 is in the PM purification time, it is necessary to make the air-fuel ratio of the mixed gas lean and raise the temperature of the mixed gas, so that the ECU 21 determines the air-fuel ratio of the combustion gas discharged from the combustion heater 14. The combustion conditions of the combustion heater 14 are controlled such that the gas is in a lean state and the temperature of the combustion gas is high.
[0060]
Storage NO lean type NO_XWhen the catalyst 8 is at the time of SOx purification, the air-fuel ratio of the mixed gas needs to be made rich and the temperature of the mixed gas must be increased, so the ECU 21 determines the air-fuel ratio of the combustion gas discharged from the combustion heater 14. The combustion conditions of the combustion type heater 14 are controlled so that is rich and the temperature of the combustion gas becomes high.
[0061]
Here, when making the air-fuel ratio of the combustion gas rich, the ECU 21 increases, for example, the discharge amount of the fuel pump to increase the amount of fuel supplied to the combustion heater 14.
[0062]
When increasing the temperature of the combustion gas, the ECU 21 increases, for example, the air volume of the air pump 16 to increase the amount of fresh air supplied to the combustion heater 14, and increases the amount of fresh air in proportion to the increase in the amount of fresh air. The amount of fuel supplied to the combustion heater 14 is increased by increasing the discharge amount of the fuel pump. That is, the ECU 21 increases the amount of heat discharged from the combustion heater 14 per unit time by increasing the flow rate of combustion gas discharged from the combustion heater 14 per unit time.
[0063]
By the way, since the proportion of exhaust gas in the mixed gas is greater than the proportion of combustion gas, when the air-fuel ratio of the mixed gas is set to a desired rich state, the combustion is performed to make the air-fuel ratio of the combustion gas excessively rich. It is necessary to supply a large amount of fuel to the type heater 14, and the fuel consumption will be deteriorated.
[0064]
Therefore, in the present embodiment, when the air-fuel ratio of the mixed gas is made rich, the ECU 21 reduces the exhaust amount of the internal combustion engine 1 to reduce the proportion of the exhaust gas in the mixed gas, The amount of fuel to be supplied to the car was minimized.
[0065]
Furthermore, SO_xThe timing for purifying PM is preferably immediately after purifying PM. This is SO_xNO to purify_XAlthough the absorbent needs to be heated to a high temperature, NO_XSince the temperature of the absorbent is increased, the SO_xThis is because if the purification is performed, the load on the combustion heater 14 can be reduced.
[0066]
Hereinafter, the operation and effect of the present embodiment will be described.
In executing the exhaust gas purification control, the ECU 21 executes an exhaust gas purification control routine as shown in FIG. This exhaust gas purification control routine is a routine that is repeatedly executed at predetermined time intervals (for example, every time the crank position sensor 22 outputs a pulse signal).
[0067]
In the exhaust gas purification control routine, first, in S301, the storage reduction type lean NO_XNO absorbed by catalyst 8_XIt is determined whether or not the purification condition of the above is satisfied.
[0068]
NO mentioned above_XThe purification conditions for (1) occlusion reduction type lean NO_XThe catalyst 8 is in an active state. (2) Storage-reduction type lean NO_XNO of catalyst 8_XConditions such as the absorption capacity being just before saturation can be exemplified.
[0069]
As a method of determining whether the condition (1) is satisfied or not, the storage reduction type lean NO is determined by determining whether the output signal value of the catalyst temperature sensor 9 is equal to or greater than a predetermined value._XA method for determining whether or not the catalyst 8 is in an active state can be exemplified.
[0070]
As a method of determining whether the condition (2) is satisfied or not, the previous NO_XBy determining whether or not the operation history of the internal combustion engine 1 from the purification completion time to the present time, for example, the integrated value of the intake air amount or the fuel injection amount exceeds a predetermined determination value, the storage reduction lean NO_XNO of catalyst 8_XA method of estimating whether or not the absorption capacity is immediately before saturation can be exemplified.
[0071]
The ECU 21 determines NO in S301._XWhen it is determined that the purification condition is not satisfied, the execution of this routine is temporarily terminated, and the determination in S301 is NO._XWhen it is determined that the purification condition is satisfied, the process proceeds to S302.
[0072]
In S302, the ECU 21 controls the actuator 27 to close the intake throttle valve 26 by a predetermined amount, thereby reducing the intake air amount of the internal combustion engine 1 by a predetermined amount, and thereby reducing the exhaust amount of the internal combustion engine 1 by a predetermined amount. .
[0073]
In S303, the ECU 21 determines that the storage reduction type lean NO_XThe temperature and composition (air-fuel ratio) of the combustion gas discharged from the combustion heater 14 are adjusted so that the temperature of the mixed gas flowing into the catalyst 8 becomes 300 ° C. to 500 ° C. and the air-fuel ratio of the mixed gas becomes a predetermined rich state. ) Control. That is, the ECU 21 increases the air flow of the air pump 16 and increases the discharge amount of the fuel pump. At this time, the ECU 21 increases the rate of increase in the discharge rate of the fuel pump with respect to the rate of increase in the flow rate of the air pump 16 to increase the amount of combustion gas discharged per unit time from the combustion type heater 14 while increasing the amount of combustion gas. Make the air-fuel ratio rich.
[0074]
At this time, the storage reduction type lean NO_XThe mixed gas in a rich state of 300 ° C. to 500 ° C. flows into the catalyst 8, and NO_XNO absorbed by the absorbent_XIs released and reduced.
[0075]
Subsequently, the ECU 21 proceeds to S304,_XIt is determined whether or not purification has been completed. As this determination method, occlusion reduction type lean NO_XMaximum amount of NO that can be absorbed by catalyst 8_XIs occlusion reduction type lean NO_XWhen absorbed in the catalyst 8, all of these NO_XThe time required for the release and reduction of NO (NO_XPurification time) is determined in advance by experiments, etc._XThe time elapsed since the start of the purification control for NO_XA method of determining whether or not the time is equal to or longer than the purification time can be exemplified.
[0076]
In addition, the above-mentioned NO_XThe purification time varies depending on the flow rate of the mixed gas per unit time when the air-fuel ratio of the mixed gas is constant (predetermined rich state), and the flow rate of the mixed gas per unit time is determined by the intake air amount of the internal combustion engine 1. And the air flow rate of the air pump 16,_XThe relationship between the purification time, the intake air amount, and the air volume of the air pump 16 may be obtained in advance by experiments or the like, and the relationship may be mapped. In this case, the ECU 21 accesses the map using the intake air amount and the air amount of the air pump 16 as parameters, and determines the NO specified from the intake air amount and the air amount of the air pump 16._XCalculate the purification time.
[0077]
NO at S304_XNO since the time when the purification control was started_XLess than the purification time, NO_XIf it is determined that the purification has not been completed, the ECU 21 once ends the execution of this routine. Then, the ECU 21 re-executes this routine after a predetermined time has elapsed,_XNO since the time when the purification control was started_XIf it is determined that the time is longer than the purification time, the process proceeds to S305.
[0078]
In S305, the ECU 21 determines that the storage reduction type lean NO_XIt is determined whether the conditions for purifying the PM absorbed by the catalyst 8 are satisfied.
The above-described PM purification conditions include, for example, (1) occlusion reduction type lean NO_XThe catalyst 8 is in an active state. (2) Storage-reduction type lean NO_XConditions such as the PM trapping ability of the catalyst 8 immediately before saturation can be exemplified.
[0079]
As a method for determining whether the condition (2) is satisfied / unsatisfied, there is a method of determining whether the integrated value of the intake air amount or the fuel injection amount from the previous PM purification completion time to the present time exceeds a predetermined determination value. Is determined, the storage reduction type lean NO_XA method for estimating whether or not the PM collection capacity of the catalyst 8 is immediately before saturation, a method for storing and reducing the lean NO_XIn order to detect the degree of increase in exhaust resistance due to an increase in the amount of PM trapped by the catalyst 8, the storage reduction type lean NO_XA pressure sensor is provided in the exhaust pipe 7 upstream of the catalyst 8, and it is determined whether or not the output signal value of the pressure sensor exceeds a predetermined determination value._XA method for estimating whether or not the PM collection ability of the catalyst 8 is immediately before saturation can be exemplified.
[0080]
The ECU 21 once terminates the execution of this routine when determining in S305 that the PM purification condition is not satisfied, and proceeds to S306 when determining in S305 that the PM purification condition is satisfied.
[0081]
In S306, the ECU 21 controls the actuator 27 to return the opening of the intake throttle valve 26 closed in S302 to the normal opening, thereby increasing the intake air amount of the internal combustion engine 1, thereby increasing the internal combustion engine 1 1 is returned to the normal displacement.
[0082]
When purifying PM, the storage reduction type lean NO_XAlthough it is necessary to increase the temperature of the mixed gas flowing into the catalyst 8, the proportion of exhaust gas in the mixed gas is greater than the proportion of combustion gas. Therefore, the load on the air pump 16 increases and the fuel consumption of the combustion heater 14 increases. Therefore, the ECU 21 may execute the process of S307 without performing the process of S306.
[0083]
In S307, the ECU 21 determines that the storage reduction type lean NO_XThe temperature and the air-fuel ratio of the combustion gas discharged from the combustion heater 14 are controlled such that the temperature of the mixed gas flowing into the catalyst 8 becomes 500 ° C. to 700 ° C. and the air-fuel ratio of the mixed gas becomes lean. Specifically, the ECU 21 increases the air flow of the air pump 16 and increases the discharge amount of the fuel pump in proportion thereto, thereby increasing the amount of combustion gas discharged from the combustion heater 14 per unit time.
[0084]
At this time, the storage reduction type lean NO_XThe lean mixed gas of 500 ° C. to 700 ° C. flows into the catalyst 8, and the storage reduction type lean NO_XThe PM trapped in the catalyst 8 becomes O₂Reacts with and is combusted and processed.
[0085]
Subsequently, the ECU 21 proceeds to S308, and determines whether or not the purification of PM has been completed. As this determination method, occlusion reduction type lean NO_XThe maximum amount of PM that can be collected by the catalyst 8 is stored and reduced lean NO_XThe time required for all the PM to be burned and processed (PM purification time) when the PM is trapped by the catalyst 8 is determined in advance by an experiment or the like, and the time from when the PM purification control is started is determined. A method for determining whether or not the elapsed time is equal to or longer than the PM purification time;_XIn order to detect the degree of decrease in exhaust resistance due to the decrease in the amount of PM trapped in the catalyst 8, the storage reduction type lean NO_XA method of providing a pressure sensor in the exhaust pipe 7 upstream of the catalyst 8 and determining whether or not the output signal value of the pressure sensor has dropped below a predetermined determination value can be exemplified.
[0086]
Note that the above-mentioned PM purification time varies depending on the flow rate of the mixed gas per unit time when the air-fuel ratio of the mixed gas is constant (predetermined lean state). The relationship between the PM purification time, the intake air amount, and the air flow rate of the air pump 16 is determined in advance by experiments or the like, and the relationship may be mapped in advance because the relationship varies depending on the intake air amount and the air flow rate of the air pump 16. Good. In this case, the ECU 21 accesses the map using the intake air amount and the air volume of the air pump 16 as parameters, and calculates the PM purification time specified from the intake air volume and the air volume of the air pump 16.
[0087]
When it is determined in S308 that the elapsed time from the start of the PM purification control is less than the PM purification time and that the PM purification is not completed, the ECU 21 ends the execution of this routine once. Then, the ECU 21 re-executes this routine after a predetermined time has elapsed, and when it is determined in S308 that the elapsed time from the start of the PM purification control is equal to or longer than the PM purification time and that the PM purification has been completed, the process proceeds to S309. move on.
[0088]
In S309, the ECU 21 determines that the storage reduction type lean NO_XSO absorbed in catalyst 8_xIt is determined whether or not the purification condition of the above is satisfied.
SO mentioned above_xThe purification conditions for (1) occlusion reduction type lean NO_XThe catalyst 8 is in an active state. (2) Storage-reduction type lean NO_XSO of catalyst 8_xConditions such as the absorption amount reaching an upper limit value within an allowable range can be exemplified.
[0089]
As a method of determining whether the condition (2) is satisfied or not, the amount of the sulfur component contained in the fuel per unit amount and the amount of the SO_xThe storage-reduction type lean NO is determined based on the intake air amount and the integrated value of the fuel injection amount from the purification completion time to the present time._XSO absorbed in catalyst 8_xEstimate the quantity and estimate the estimated SO_xA method of determining whether the amount exceeds the upper limit can be exemplified.
[0090]
The ECU 21 determines in step S309 that the SO_xIf it is determined that the purification condition is not satisfied, the execution of this routine is temporarily terminated, and the SO_xWhen it is determined that the purification condition is satisfied, the process proceeds to S310.
[0091]
In step S310, the ECU 21 controls the actuator 27 so as to close the intake throttle valve 26, which has been returned to the normal opening degree in step S306, by a predetermined amount, thereby reducing the intake air amount of the internal combustion engine 1 and thereby the internal combustion engine 1 1 is reduced by a predetermined amount.
[0092]
In S311, the ECU 21 determines that the storage reduction type lean NO_XThe temperature and the air-fuel ratio of the combustion gas discharged from the combustion heater 14 are controlled so that the temperature of the mixed gas flowing into the catalyst 8 becomes 500 ° C. to 700 ° C. and the air-fuel ratio of the mixed gas becomes a rich state. Specifically, the ECU 21 increases the air flow of the air pump 16 and increases the discharge amount of the fuel pump. At this time, the ECU 21 increases the rate of increase in the discharge rate of the fuel pump with respect to the rate of increase in the flow rate of the air pump 16 to increase the amount of combustion gas discharged per unit time from the combustion type heater 14 while increasing the amount of combustion gas. Make the air-fuel ratio rich.
[0093]
In this case, the storage reduction type lean NO_XSince a mixed gas in a rich state of 500 ° C. to 700 ° C. flows into the catalyst 8, NO_XBaSO formed in the absorbent₄Is SO_3-And SO_4-Etc., then those SO_3-, SO_4-Reacts with HC, CO, etc. in the mixed gas to form gaseous SO.₂Is reduced to NO_XReleased from absorbent.
[0094]
Subsequently, the ECU 21 proceeds to S312,_xIt is determined whether or not purification has been completed. As this determination method, occlusion reduction type lean NO_XSO of catalyst 8_xIf the amount of absorption reaches the upper limit within the allowable range,_xThe time required for reduction and release (SO_x(Purification time) is determined in advance by experiments, etc._xThe time elapsed from the start of the purification control of the SO_xA method of determining whether or not the time is equal to or longer than the purification time can be exemplified.
[0095]
It should be noted that the aforementioned SO_xThe purification time varies depending on the mixed gas flow rate per unit time when the air-fuel ratio of the mixed gas is constant (predetermined rich state), and the mixed gas flow rate per unit time is determined by the intake air amount of the internal combustion engine 1. And the air flow rate of the air pump 16,_xThe relationship between the purification time, the intake air amount, and the air volume of the air pump 16 may be obtained in advance by experiments or the like, and the relationship may be mapped. In this case, the ECU 21 accesses the map using the intake air amount and the air flow amount of the air pump 16 as parameters, and determines the SO that is specified from the intake air amount and the air amount of the air pump 16._xCalculate the purification time.
[0096]
In S312, SO_xThe time elapsed from the start of the purification control of the SO_xLess than the purification time, SO_xIf it is determined that the purification has not been completed, the ECU 21 once ends the execution of this routine. Then, the ECU 21 re-executes this routine after the elapse of the predetermined time, and in S312, the SO 21_xThe time elapsed from the start of the purification control of the SO_xIt is longer than the purification time and SO_xIf it is determined that the purification has been completed, the process proceeds to S313.
[0097]
In S313, the ECU 21 stops the operation of the combustion heater 14 and the air pump 16, and controls the actuator 27 to return the opening of the intake throttle valve 26 to the normal opening, thereby stopping the exhaust gas purification control.
[0098]
By executing the exhaust gas purification control routine by the ECU 21 in this way, the state determining means and the combustion condition changing means according to the present invention are realized.
Therefore, according to the present embodiment, in the internal combustion engine 1 including the combustion heater 14, NO_XAnd PM and SO_xBy changing the combustion conditions of the combustion type heater 14 according to the respective purification timings, the occlusion reduction type lean NO_XThe property of the mixed gas flowing into the catalyst 8 is changed to NO_XAnd PM and SO_xAnd the properties according to the respective purification conditions.
[0099]
As a result, in the internal combustion engine provided with the combustion type heater 14, the NO._X, PM, and SO_xIt is possible to purify the wastewater, and it is not necessary to provide a dedicated device such as a reducing agent supply device.
[0100]
【The invention's effect】
The exhaust gas purifying apparatus for an internal combustion engine according to the present invention,Combustion heaterIn the internal combustion engine equipped with, according to the time when the exhaust gas purification means purifies various harmful gas components,Combustion heaterBy changing the combustion conditions, the property of the combustion gas flowing into the exhaust gas purifying means can be made to correspond to the property of purifying various harmful gas components.
[0101]
Thus, according to the present invention,Combustion heaterIn an internal combustion engine withCombustion heaterOf various harmful gas components by using the combustion gas discharged from the vehicle, it is not necessary to provide a dedicated device such as a reducing agent supply device, and the effect of being excellent in mountability on a vehicle is obtained. Can be.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas purification device according to the present invention is applied;
FIG. 2 is a diagram showing an internal configuration of a combustion type heater.
FIG. 3 is a flowchart illustrating an exhaust gas purification control routine according to the embodiment;
[Explanation of symbols]
1 ... internal combustion engine
2. Intake branch pipe
3 ... intake pipe
6 ... exhaust branch pipe
7 ... exhaust pipe
8: lean NO storage-reduction type_Xcatalyst
9 Catalyst temperature sensor
14. Combustion heater
15 ... Intake passage
16. Air pump
17. Combustion gas discharge passage
20 ・ ・ Fuel introduction passage
21..ECU
26 .. Intake throttle valve
27..Actuators

Claims (2)

A combustion heater for burning fuel independently of the internal combustion engine and for raising the temperature of related components of the internal combustion engine ;
Exhaust purification means provided in the exhaust system of the internal combustion engine, and purifies at least nitrogen oxides, particulate matter, and sulfur oxides, which are harmful gas components in the exhaust gas,
State determination means for determining which harmful gas component among the nitrogen oxides, particulate matter, and sulfur oxides is in a state to be purified ,
Combustion condition changing means for changing the combustion condition of the combustion heater so as to make the property of the combustion gas discharged from the combustion heater a property corresponding to the harmful gas component determined by the state determination means ,
Combustion gas introduction means for introducing the combustion gas discharged from the combustion heater to the exhaust gas purification means,
An exhaust gas purifying apparatus for an internal combustion engine, comprising: 2. The internal combustion engine according to claim 1, wherein the combustion condition changing unit changes the combustion condition of the combustion heater so that purification is performed in the order of nitrogen oxide, particulate matter, and sulfur oxide. 3. Exhaust gas purification device.

Images