JP4178797B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification device for an internal combustion engine, and preferably to an exhaust gas purification device that suppresses SOx poisoning of a catalyst in an exhaust passage of a diesel engine.
[0002]
[Prior art]
As a technology for purifying NOx from exhaust gas exhausted from a lean burnable vehicle internal combustion engine, there is an exhaust purification device using a NOx storage reduction catalyst.
[0003]
This NOx storage reduction catalyst is disposed in an exhaust passage of an internal combustion engine capable of lean combustion. When exhaust gas having a lean air-fuel ratio (that is, under an oxygen-excess atmosphere) flows, NOx in the exhaust gas is occluded by the catalyst. When exhaust gas having stoichiometric (theoretical air / fuel ratio) or rich air / fuel ratio (that is, in an oxygen lean atmosphere) flows, the NOx stored in the catalyst is NO. ₂ Released as. Furthermore, N is reduced by reducing components such as HC and CO in the exhaust gas. ₂ Reduced to Currently, techniques for purifying such NOx have been developed.
[0004]
By the way, since the fuel of the internal combustion engine generally contains a sulfur content, when the fuel is combusted in the internal combustion engine, the sulfur content in the fuel is combusted and SO. ₂ Or SO _Three Sulfur oxide (SOx) is generated. The NOx storage reduction catalyst stores SOx in exhaust gas by the same mechanism as the NOx storage function. Therefore, when a NOx catalyst is disposed in the exhaust passage of the internal combustion engine, this NOx catalyst stores not only NOx but also SOx.
[0005]
The SOx stored in the NOx storage reduction catalyst forms a stable sulfate with time. For this reason, under the same conditions as when NOx is released and reduced from the NOx catalyst, decomposition or release is difficult, and the NOx catalyst tends to accumulate. As a result, when the amount of SOx accumulated in the NOx storage reduction catalyst increases, the NOx storage capacity of the catalyst decreases, and NOx in the exhaust gas cannot be sufficiently removed, and the NOx purification efficiency decreases. This is so-called S poisoning.
[0006]
Therefore, in order to maintain the exhaust purification capacity of the NOx storage reduction catalyst high for a long period of time, it is necessary to decompose the SOx stored in the catalyst, release it from the catalyst, and recover from the S poison.
[0007]
In view of this, Japanese Patent Application Laid-Open No. 6-725541 and the like disclose that the NOx catalyst is heated to a higher temperature (for example, 600 ° C. or higher) than that during normal regeneration operation and the air-fuel ratio of the exhaust gas is recovered. A technique is disclosed in which S is poisoned and the S poisoning recovery process is periodically performed.
[0008]
In the processing technique disclosed in the above publication, a NOx catalyst that stores NOx when the air-fuel ratio of the exhaust gas flowing into the NOx catalyst is lean and releases NOx stored when the oxygen concentration of the exhaust gas decreases is used. In the exhaust passage of the internal combustion engine. Then, NOx in the exhaust is occluded, and then the exhaust air-fuel ratio flowing into the NOx catalyst is made rich, and the occluded NOx is released from the NOx catalyst.
[0009]
Furthermore, the NOx catalyst and the particulate filter that collects the particulates in the exhaust gas are arranged at positions where heat can be mutually transmitted. Then, the air-fuel ratio of the exhaust gas flowing into the NOx catalyst is made rich to perform NOx release and reduction purification. Thereafter, the particulates collected by the particulate filter are burned, the air-fuel ratio of the exhaust gas flowing into the NOx catalyst again after the particulate combustion operation is made rich, and the NO poisoning of the NOx catalyst is recovered.
[0010]
However, the cause of sulfur poisoning of the exhaust catalyst is considered other than the sulfur content in the fuel. The main thing is blow-by gas resulting from engine oil (lubricating oil).
[0011]
The blow-by gas is such that the combustion gas in the combustion chamber leaks from the gap between the piston ring and the cylinder wall due to the pressure of combustion and flows into the crankcase. Therefore, the blow-by gas needs to be purified to prevent contamination in the crankcase and deterioration of the oil.
[0012]
Therefore, as disclosed in Japanese Patent Application Laid-Open No. 10-103039, the blow-by gas purification device collects the oil content in the blow-by gas with a filter and decomposes it into water and oxygen dioxide by the decomposition action of the photocatalyst. The technology that purifies the oil and discharges it to the atmosphere has been developed.
[0013]
[Problems to be solved by the invention]
However, the blow-by gas contains a sulfur content in the lubricating oil in the crankcase. Therefore, the blow-by gas is circulated through the intake system, then flows into the exhaust passage through the combustion chamber, and poisons the exhaust catalyst. As a process for recovering the sulfur poisoning of the exhaust catalyst, not only the conventional purification of the sulfur content in the exhaust passage, but also the purification of the sulfur content in the blow-by gas becomes a problem.
[0014]
The present invention has been made in view of such problems of the prior art, and the problem to be solved by the present invention is to trap the sulfur content in the blow-by gas, thereby trapping the S coverage of the catalyst in the exhaust passage. An object of the present invention is to provide an exhaust purification device for an internal combustion engine that suppresses poison.
[0015]
[Means for Solving the Problems]
In order to solve the above problems, the present invention employs the following means. Examples of the internal combustion engine according to the present invention include a diesel engine and a gasoline engine.
[0016]
The blow-by gas passage that recirculates the blow-by gas of the internal combustion engine from the crankcase to the intake system is equipped with a SOx trap agent that traps sulfur content in the blow-by gas, and the SOx in the blow-by gas is removed in advance to the intake system By recirculating, S poisoning of the exhaust catalyst can be suppressed.
[0017]
This SOx trapping agent is made of, for example, copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), on a support made of sintered metal coated with a metal oxide such as alumina, titanium or zirconia. And at least one selected from transition metals such as sodium (Na), potassium (K), lithium (Li), and alkali or alkaline earth metals such as barium (Ba). . Furthermore, by supporting a metal such as platinum (Pt), palladium (Pd), rhodium (Rh) on the support, SOx is easily trapped in the form of sulfate ions.
[0018]
As an exhaust catalyst, an oxidation catalyst and a NOx catalyst can be exemplified as a catalyst having oxidation ability, and as a NOx catalyst, a selective reduction type NOx catalyst and an occlusion reduction type NOx catalyst can be exemplified. The selective reduction type NOx catalyst includes a catalyst in which a transition metal such as Cu is supported on zeolite by ion exchange, a catalyst in which a noble metal is supported on zeolite or alumina, and the like. The NOx storage reduction catalyst uses, for example, alumina as a carrier, and an alkali metal such as potassium (K), sodium (Na), lithium (Li), cesium (Cs), barium (Ba), calcium, for example. A catalyst comprising at least one selected from an alkaline earth such as (Ca), a rare earth such as lanthanum (La) and yttrium (Y) and a noble metal such as platinum (Pt). . This NOx storage reduction catalyst stores (absorbs / adsorbs) NOx when the air-fuel ratio of the inflowing exhaust gas is lean, and releases the stored NOx when the oxygen concentration of the inflowing exhaust gas decreases.
[0019]
In order to perform the S poison recovery treatment (release the trapped SOx) of the SOx trapping agent, a heating means for heating the SOx trapping agent may be provided. As this heating means, a part or the whole of the filter carrier made of sintered metal may be constituted by an electric heating element that generates heat when energized, or an electric heating element is placed on a sintered metal part where no catalyst is supported. It may be configured to be embedded and integrated.
[0020]
Further, by releasing SOx trapped in the SOx trapping agent at a predetermined time, re-poisoning of the NOx catalyst in the exhaust system can be suppressed.
[0021]
The predetermined time is a time when the released sulfur component flows into the exhaust passage and the NOx catalyst in the exhaust system is not re-poisoned. That is, it is when the air-fuel ratio of the exhaust gas is stoichiometric at or near the stoichiometric air-fuel ratio, or rich when it is richer than the stoichiometric air-fuel ratio.
[0022]
Furthermore, immediately after the completion of the S poisoning recovery process, the SOx trapping agent temperature is extremely high, so that the occlusion performance is lowered. Thus, after the SO poisoning recovery process of the SOx trapping agent is completed, a structure having a cooling means may be provided in order to quickly cool the SOx trapping agent to a temperature with high occlusion performance.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings. In addition, embodiment described below is the aspect which applied the exhaust gas purification apparatus which concerns on this invention to the diesel engine 1 for vehicles as an internal combustion engine.
[0024]
As shown in FIG. 1, the diesel engine 1 has an intake passage 2, a blow-by gas passage 3, an exhaust passage 4, a piston / crank mechanism 5, and a valve mechanism 6. It is ignited and burned by injecting heavy oil or light oil fuel.
[0025]
In this engine combustion process, the gas leaked from the gap between the piston ring and the cylinder block 7 is blow-by gas 9. The blowby gas 9 is recirculated from the crankcase 8 to the intake system (intake passage 2) through the blowby gas passage 3. The blow-by gas passage 3 is provided with an S trap 11 capable of trapping (absorbing / adsorbing) sulfur.
[0026]
As shown in FIG. 2, the S trap 11 has a SOx trap agent 15 referred to in the present invention. The SOx trap agent 15 is formed on a surface of a filter made of sintered metal 14 with a basic substance (zeolite, zirconia). , Li, Na alkali metal, etc.) are supported to trap the sulfur content in the blow-by gas 9.
[0027]
By the way, there is a limit to the sulfur trapping ability of the SOx trapping agent 15, and when a predetermined amount of sulfur is trapped, it is saturated and cannot be trapped any further and the sulfur is passed as it is. Therefore, it is necessary to raise the temperature of the SOx trap agent 15 in order to release the sulfur component at a predetermined timing before the sulfur trap capability of the SOx trap agent 15 is saturated.
[0028]
Therefore, the sintered metal carrier 14 of the S trap 11 has a heater function, and generates heat when an electric current is passed to heat the SOx trap agent 15. That is, the S trap 11 may be integrated with heating means. The sintered metal carrier 14 of the S trap 11 is electrically connected to a heater relay 22, and this heater relay 22 is ON / OFF controlled by a command signal from an electronic control unit (ECU 21). The heater consisting of is controlled ON / OFF.
[0029]
Further, an inlet gas temperature sensor 23 and an outlet gas temperature sensor 24 are attached to the blow-by gas passage 3 in order to measure the catalyst bed temperature of the SOx trap agent 15. The inlet gas temperature sensor 23 and the outlet gas temperature sensor 24 are arranged near the inlet and the outlet of the S trap 11. Then, an output signal corresponding to the temperature of the exhaust gas flowing into the S trap 11 or the temperature of the exhaust gas flowing out of the S trap 11 is output to the ECU 21. Based on the output signals of these inlet gas temperature sensor 23 and outlet gas temperature sensor 24, the ECU 21 calculates the catalyst bed temperature of the SOx trap agent 15.
[0030]
Alternatively, only the inlet gas temperature sensor 23 may be attached in the vicinity of the inlet of the S trap 11. Then, an output signal corresponding to the temperature of the blow-by gas 9 flowing into the S trap 11 is output to the ECU 21. This is because the blow-by gas temperature detected by the incoming gas temperature sensor 23 is substantially equal to the catalyst bed temperature of the SOx trap agent 15 and can be substituted for the catalyst bed temperature of the SOx trap agent 15.
[0031]
Immediately after the completion of the S poisoning recovery process, the catalyst bed temperature of the SOx trap agent 15 is extremely high, so that the trap performance is lowered. Therefore, after the S poisoning recovery process control is completed, that is, after the energization of the S trap 11 is turned off, a cooling means for quickly cooling the catalyst bed temperature of the SOx trap agent 15 to a temperature having a high trapping performance is provided. The cooling means may be air-cooled or water-cooled.
[0032]
In this embodiment, the exhaust catalyst 12 is a DPNR catalyst 12 that can simultaneously reduce particulate matter (PM), NOx, SOx, HC, and CO contained in the exhaust gas of the diesel engine 1 with one catalyst. The DPNR catalyst 12 is a particulate filter made of a porous ceramic structure and carrying an NOx storage reduction catalyst.
[0033]
The reducing agent supply device 13 supplies the reducing agent to the exhaust passage 4 on the upstream side of the particulate filter, and enriches the air-fuel ratio of the exhaust gas flowing into the NOx catalyst.
[0034]
Since this embodiment is applied to the diesel engine 1, the fuel of the diesel engine 1 is used as a reducing agent. In addition, the reducing agent supply device 13 includes a nozzle that injects fuel supplied from the engine fuel system into the exhaust passage 4 in the form of a mist.
[0035]
An exhaust temperature sensor 25 is disposed in the exhaust passage 4 between the particulate filter and the reducing agent supply device 13. The detection signal from the exhaust temperature sensor 25 is input to the electronic control unit (ECU 21). The ECU 21 includes a known type of digital computer in which a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and an input / output port are connected by a bidirectional bus. In addition to executing basic engine control such as fuel injection amount control, recovery processing of the S trap 11, regeneration of the NOx storage reduction catalyst, combustion of particulates, recovery of S poisoning of the NOx storage reduction catalyst, etc. The control is also executed.
[0036]
Although not shown, an exhaust throttle valve that opens and closes the exhaust passage 4 and an actuator that opens and closes the throttle valve are disposed in the exhaust passage 4. This intake throttle valve is normally fully opened and is closed when the NOx storage reduction catalyst is regenerated to reduce the amount of exhaust air flowing into the DPNR catalyst 12 by restricting the intake air amount of the internal combustion engine. As a result, oxygen in the exhaust is consumed, so that the amount of reducing agent necessary to reduce the oxygen concentration in the DPNR catalyst 12 atmosphere is reduced. The actuator may be of an appropriate type such as a solenoid for driving the intake throttle valve or a negative pressure actuator.
[0037]
In this embodiment, since the diesel engine 1 is applied, the air-fuel ratio of the exhaust at normal time is lean, and the DPNR catalyst 12 occludes NOx in the exhaust. When the reducing agent is supplied from the reducing agent supply device 13 to the exhaust passage 4 upstream of the particulate filter and the air-fuel ratio of the inflowing exhaust gas becomes rich, the DPNR catalyst 12 releases the stored NOx.
[0038]
Here, the NOx absorption / release action will be described with reference to FIG. Although the detailed mechanism of this absorption / release action is not clear, it is considered that the mechanism is as follows. In the present embodiment, the case where platinum Pt and barium Ba are supported will be described as an example, but the same mechanism can be obtained by using other noble metals, alkali metals, alkaline earths, and rare earths.
[0039]
When the exhaust gas flowing into the DPNR catalyst 12 becomes considerably lean, the oxygen concentration in the exhaust gas greatly increases. Then, as shown in FIG. 3A, these oxygen O ₂ Is O ₂ ー or O ² It adheres to the surface of platinum Pt in the form of-. On the other hand, NO in the exhaust gas is O on the surface of platinum Pt. ₂ ー or O ² Reacts with NO ₂ (2NO + O ₂ → 2NO ₂ ). Then the generated NO ₂ Part of this is occluded in the DPNR catalyst 12 while being further oxidized on platinum Pt, and is combined with barium oxide BaO. As shown in FIG. 3A, nitrate ion NO _Three It diffuses into the DPNR catalyst 12 in the form of-. In this way, NOx is occluded in the DPNR catalyst 12.
[0040]
As long as the oxygen concentration in the exhaust gas flowing into the DPNR catalyst 12 is high, NO on the surface of the platinum Pt ₂ Is generated. As long as the NOx storage capacity of the DPNR catalyst 12 is not saturated, NO ₂ Is stored in the DPNR catalyst 12 and nitrate ions NO. _Three Is generated.
[0041]
On the other hand, the oxygen concentration in the exhaust gas flowing into the DPNR catalyst 12 decreases and NO ₂ The reaction proceeds in the reverse direction (NO _Three -→ NO ₂ ) Thus, nitrate ion NO in the DPNR catalyst 12 _Three -NO ₂ From the DPNR catalyst 12. That is, when the oxygen concentration in the exhaust gas flowing into the DPNR catalyst 12 decreases, NOx is released from the DPNR catalyst 12. If the degree of leanness of the inflowing exhaust gas decreases, the oxygen concentration in the exhaust gas decreases. Therefore, if the degree of leanness of the exhaust gas flowing into the DPNR catalyst 12 is lowered, NOx is released from the DPNR catalyst 12.
[0042]
On the other hand, when the air-fuel ratio of the exhaust gas flowing into the DPNR catalyst 12 at this time is made rich, HC and CO are oxygen O on platinum Pt. ₂ ー or O ² It is oxidized by reacting with-. Further, when the air-fuel ratio of the exhaust gas is made rich, the oxygen concentration in the exhaust gas extremely decreases, so that NO from the DPNR catalyst 12 ₂ Is released. This NO ₂ As shown in FIG. 3B, it is reduced and purified by reacting with unburned HC and CO. In this way, NO on the surface of platinum Pt. ₂ When the NO is present, NO from the DPNR catalyst 12 one after another ₂ Is released. Therefore, when the air-fuel ratio of the exhaust gas flowing into the DPNR catalyst 12 is made rich, NOx is released from the DPNR catalyst 12 in a short time and is reduced and purified.
[0043]
The air-fuel ratio of the exhaust gas flowing into the DPNR catalyst 12 here refers to the ratio of air and fuel supplied to the exhaust passage 4 and the combustion chamber or intake passage 2 upstream of the DPNR catalyst 12. Therefore, when air or a reducing agent is not supplied to the exhaust passage 4, the exhaust air-fuel ratio becomes equal to the operating air-fuel ratio (combustion air-fuel ratio in the combustion chamber). The reducing agent used in the present invention may be any reducing agent that generates reducing components such as hydrocarbons and carbon monoxide in the exhaust gas. That is, a gas such as hydrogen or carbon monoxide, a liquid such as propane, propylene, or butane, or a liquid hydrocarbon such as gas, gasoline, light oil, or kerosene can be used. In the present embodiment, light oil, which is the fuel of the diesel engine 1, is used as a reducing agent as described above in order to avoid complications during storage, replenishment, and the like.
[0044]
Next, the mechanism of S poisoning of the DPNR catalyst 12 will be described. When the SOx component is contained in the exhaust gas flowing into the DPNR catalyst 12, the DPNR catalyst 12 stores SOx in the exhaust by the same mechanism as the NOx storage described above. That is, when the air-fuel ratio of the exhaust gas flowing into the DPNR catalyst 12 is lean, the SOx (for example, SO ₂ ) Is oxidized on platinum Pt to form SO ^Three -SO ^Four It becomes. And combined with barium oxide BaO, BaSO _Four Is generated. BaSO _Four Is relatively stable, and since crystals are likely to be coarse, once produced, they are difficult to decompose and release. For this reason, BaSO in the DPNR catalyst 12 _Four When the production amount of NO increases, the amount of BaO that can participate in the storage of NOx decreases, so the storage capacity of NOx decreases. In order to recover this S poisoning, BaSO produced in the DPNR catalyst 12 is used. _Four Is decomposed at a high temperature and the SO produced thereby ^Three -SO ^Four -Sulfuric acid ions are reduced in a rich atmosphere to form gaseous SO ₂ To be released from the DPNR catalyst 12.
[0045]
Therefore, in order to recover the SOx poisoning, the DPNR catalyst 12 needs to be in a high temperature and rich atmosphere state.
[0046]
Here, the sulfur poisoning recovery process of the exhaust catalyst will be described. The S poisoning recovery process is not particularly limited as long as the air-fuel ratio of the exhaust gas flowing into the exhaust catalyst can be made rich. In the present embodiment, since the DPNR catalyst 12 is used as the exhaust catalyst 12, a particulate filter carrying an NOx storage reduction catalyst is disposed in the exhaust passage 4, and the particulate matter collected by the particulate filter is disposed. After the combustion of (PM: Particulate Matter), the throttle valve is closed, and the reducing agent is supplied from the reduction supply device to the particulate filter. Since the NOx storage reduction catalyst is heated by heat generated during particulate matter combustion, the NOx storage reduction catalyst is placed in a high temperature and rich atmosphere. In this way, S poisoning is quickly recovered.
[0047]
The particulate filter is made of porous ceramic. In the particulate filter, first passages with plugs on the upstream side and second passages with plugs on the downstream side are alternately arranged to form a honeycomb shape. When the exhaust gas flows from the upstream side toward the downstream side, the exhaust gas passes through the flow path wall surface of the porous ceramic from the second passage, flows into the first passage, and flows downstream. At this time, since the particulate matter in the exhaust gas is collected by the porous ceramic, the release of the particulate matter to the atmosphere is prevented.
[0048]
Next, the control system of this embodiment will be described with reference to FIGS. FIG. 4 is a flowchart showing a control routine of S poison recovery processing of the S trap. This routine is executed by the ECU 21 by interruption every predetermined time.
[0049]
First, in step 110, it is determined whether or not to start the S poisoning recovery process control of the NOx storage reduction catalyst that is the exhaust catalyst 12. For example, the start condition of the S poisoning recovery process control of the NOx storage reduction catalyst is at the time of deceleration, the NOx catalyst is at an activation temperature or higher, and a predetermined time or more has elapsed since the previous regeneration was executed. Etc.
[0050]
When it is determined that the S poisoning recovery process control of the NOx storage reduction catalyst should not be started, the process returns to the main program.
[0051]
On the other hand, if it is determined in step 110 that the S poisoning recovery process control of the NOx storage reduction catalyst that is the exhaust catalyst 12 is started, the process proceeds to step 120 and the S poison recovery process control of the S trap is started. By executing the S poison recovery process of the S trap during the S poison recovery process of the NOx storage reduction catalyst, the S re-poisoning of the NOx storage reduction catalyst is suppressed.
[0052]
Next, at step 130, it is determined whether or not a condition that the sulfur content released from the engine exhaust gas is not stored in the NOx catalyst is satisfied. In this step, it is determined whether or not conditions necessary for recovering S poisoning, that is, whether or not the NOx storage reduction catalyst is in a high temperature and rich atmosphere state. In the present embodiment, this condition is that the bed temperature of the NOx catalyst is 600 ° C. or higher and the air-fuel ratio of the intake exhaust gas is 14.5 or lower.
[0053]
If this condition is satisfied, that is, if it is determined that the NOx storage reduction catalyst is in a high temperature and rich atmosphere, the routine proceeds to step 140. Then, the S trap 11 disposed in the blow-by gas passage 3 is energized to heat the SOx trap agent 15 in the S trap 11. Then, the electric power is controlled so that the temperature of the SOx trapping agent 15 is 600 ° C. to 650 ° C.
[0054]
On the other hand, if the above condition is not satisfied, that is, if it is determined that the NOx storage reduction catalyst is not in a high temperature and rich atmosphere, the process returns to the main program.
[0055]
Next, in step 150, it is determined whether or not the poisoning recovery process control of the S trap 11 is to be ended.
[0056]
When this condition is satisfied, the process proceeds to step 160, the energization of the S trap 11 is turned off, and the heating of the SOx trap agent 15 is finished. Then, return to the main program.
[0057]
On the other hand, if this condition is not satisfied, the process proceeds to step 170. Then, the S trap 11 is energized, and it is determined whether or not the time when the SOx trap agent 15 is heated is equal to or longer than a predetermined time. That is, it is determined whether or not the sulfur content stored in the SOx trap agent 15 is released from the SOx trap agent 15.
[0058]
When this condition is satisfied, the process proceeds to step 160, the energization of the S trap 11 is turned off, and the heating of the SOx trap agent 15 is finished. Then, return to the main program.
[0059]
On the other hand, if this condition is not satisfied, the routine returns to step 130, and it is determined again whether or not the condition that the sulfur content released from the engine exhaust gas is not stored in the NOx catalyst is satisfied. Then, the above steps are repeated.
[0060]
Next, the control of the cooling means of this embodiment will be described with reference to FIG. FIG. 5 is a flowchart showing a control routine of the cooling means.
[0061]
First, in step 210, it is determined whether or not the S-poisoning recovery control of the S-trap has ended.
[0062]
Immediately after the S poison recovery process of the S trap is completed, the catalyst bed temperature of the SOx trap agent 15 is high and the trap performance is low. Therefore, after the S poison recovery control of the S trap is completed, the catalyst bed temperature of the SOx trap agent 15 is quickly cooled to a temperature with high trapping performance.
[0063]
First, in step 210, it is determined whether or not the S-poisoning recovery process control of the S-trap has ended. This condition may be that the energization of the S trap 11 is turned off. In this case, this routine is executed after the control routine of the S poison recovery recovery process of the S trap is completed.
[0064]
If it is determined that the S-poisoning recovery process control of the S trap has not ended, the process returns to the main program.
[0065]
On the other hand, if it is determined in step 210 that the S-poisoning recovery process control of the S trap has been completed, the process proceeds to step 220 and control of the cooling means of the S trap 11 is started.
[0066]
Next, the routine proceeds to step 230, where it is determined whether or not the control of the cooling means of the S trap 11 is to be terminated.
[0067]
When this condition is satisfied, the process proceeds to step 240, the control of the cooling means of the S trap 11 is finished, and the cooling of the S trap 11 is finished. Then, return to the main program.
[0068]
On the other hand, if this condition is not satisfied, the process proceeds to step 250. And it is judged whether the time which cooled SOx trap agent 15 is more than predetermined time. That is, it is determined whether or not the catalyst bed temperature of the SOx trap agent 15 has dropped to a temperature with high trapping performance.
[0069]
When this condition is satisfied, the process proceeds to step 240, the control of the cooling means of the S trap 11 is finished, and the cooling of the S trap 11 (SOx trap agent 15) is finished. Then, return to the main program.
[0070]
On the other hand, when this condition is not satisfied, the process returns to step 230, and it is determined again whether or not the control of the cooling means of the S trap 11 is to be ended. Then, the above steps are repeated.
[0071]
Note that, according to the present embodiment, the SOx trapping agent captures the sulfur content in the blow-by gas, so that the ash deposited on the exhaust catalyst can be reduced. Furthermore, since the SOx trapping agent can collect not only the sulfur content in the blow-by gas but also the phosphorus content, it suppresses a decrease in the oxidation activity of the catalyst due to phosphorus deposition.
[0072]
【The invention's effect】
As is clear from the above detailed description, the internal combustion engine equipped with the exhaust emission control device according to the present invention traps the sulfur content in the blow-by gas by the SOx trapping agent. As a result, the S poisoning of the catalyst in the exhaust passage can be suppressed, and an excellent effect that the frequency of performing the S poisoning recovery process can be greatly reduced is exhibited.
[Brief description of the drawings]
FIG. 1 is a schematic structural diagram of an internal combustion engine shown in the present embodiment.
FIG. 2 is an enlarged view of an S trap.
FIG. 3 is a view showing a mechanism of NOx absorption / release action of the NOx storage reduction catalyst.
FIG. 4 is a flowchart showing a control routine of S poison recovery processing of an S trap.
FIG. 5 is a flowchart showing a control routine for cooling means of the S trap.
[Explanation of symbols]
1 ... Vehicle diesel engine
2 ... Intake passage
3 ... Blow-by gas passage
4 ... Exhaust passage
5 ... Piston crank mechanism
6 ... Valve mechanism
7 ... Cylinder block
8 ... Crankcase
9 ... Blow-by gas
11 ... S trap
12 ... DPNR catalyst
13 ... Reducing agent supply device
14 ... Sintered metal
15 ... SOx trapping agent
21 ... ECU
22 ... Heater relay
23 ... Inlet gas temperature sensor
24 ... Outgas temperature sensor
25 ... Exhaust temperature sensor

Claims (4)

In an internal combustion engine having a blowby gas passage for recirculating blowby gas of an internal combustion engine from a crankcase to an intake system, and an exhaust catalyst in the exhaust passage, an SOx trap agent for trapping sulfur components in the blowby gas is used as the blowby gas. An exhaust purification device for an internal combustion engine , provided in a passage, wherein the internal combustion engine is a diesel engine and the exhaust catalyst is a NOx catalyst. 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, further comprising a heating unit that heats the SOx trapping agent. It said heating means, when the air-fuel ratio of the exhaust gas is rich is rich of stoichiometry, or stoichiometric air-fuel ratio is stoichiometric or near the claim 2, characterized in that heating the SOx trap agent Exhaust gas purification device for internal combustion engine. The exhaust emission control device for an internal combustion engine according to claim 3 , further comprising a cooling means for cooling the SOx trapping agent.

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