JP2002047956A - Exhaust emission control method for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control method for an internal combustion engine capable of suppressing SOx poisoning phenomenon of exhaust gas purifying catalyst of NOx storage reduction type and improving a purification rate of exhaust gas further. SOLUTION: In this exhaust emission control method for the internal combustion engine, sulfur content which becomes the cause for generating sulfur oxide SOx after combustion in the internal combustion engine 1 is solidified before exhaust gas flows into the exhaust gas purifying catalyst 39 of NOx storage reduction type provided in an exhaust passage 7 using sulfur content solidifying agent (stored in a solidifying agent tank 41) containing metallic element having a function for oxidizing sulfur component and basic metallic element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas for an internal combustion engine capable of suppressing a decrease in an exhaust gas purification rate due to SOx poisoning of a NOx storage reduction type exhaust gas purification catalyst and further increasing the exhaust gas purification rate. It relates to a purification method.

[0002]

2. Description of the Related Art The exhaust gas of an internal combustion engine is released to the atmosphere after being purified by an exhaust purification catalyst such as a three-way catalyst. Then, as one of such an exhaust gas purifying catalyst, oxygen O ₂ is occluded nitrogen oxides NOx when in excess, nitrogen oxides occluded when less oxygen O ₂ in the exhaust gas in the exhaust gas NOx is released and reduced (at this time, carbon monoxide CO and hydrocarbons HC in the exhaust gas are oxidized), and an NOx storage reduction type exhaust purification catalyst has been used.

[0003] By using such an exhaust purification catalyst, nitrogen oxides NOx in exhaust gas during lean operation are stored, and nitrogen oxides stored during stoichiometric or rich operation are stored.
By releasing and reducing NOx, the exhaust gas purification rate can be further improved. Such NOx storage-reduction type exhaust purification catalysts are useful for improving the exhaust purification rate of lean burn engines that perform lean operation more aggressively than ordinary engines, and also contribute to improving fuel economy. I have.

[0004]

However, these NOx
The storage reduction type exhaust purification catalyst has the property of storing sulfur oxides SOx more stably than nitrogen oxides NOx. Sulfur oxide SOx in exhaust gas is generated by oxidizing a sulfur component contained in fuel or engine oil by combustion of an internal combustion engine. Although the sulfur component contained in fuel and engine oil is very small,
Since the NOx storage-reduction type exhaust purification catalyst is stably stored, the amount of storage is gradually accumulated and increased. If a large amount of sulfur oxide SOx is stored in the NOx storage reduction type exhaust purification catalyst, it becomes impossible to properly store, release, and reduce nitrogen oxide NOx. This is the so-called NO
This is the "SOx poisoning" phenomenon in x-reduction-type exhaust purification catalysts.

[0005] In a conventional NOx storage reduction type exhaust purification catalyst, most of the storage capacity is nitrogen oxide NOx when it is new.
Although it is used for occlusion of x, when it is subjected to SOx poisoning, only a small amount of occlusion capacity is used for occlusion of nitrogen oxides NOx. If this SOx poisoning phenomenon can be suppressed, the storable and desorbable amounts of nitrogen oxide NOx can be increased, and the exhaust purification performance of the NOx storage-reduction type exhaust purification catalyst can be significantly improved. it can. In addition, such
Japanese Patent Application Laid-Open
Although those described in 2000-27712 publication are also known,
The effect is not yet sufficient, and the inventors have achieved the present invention with the aim of further improving exhaust gas purification performance.

Accordingly, an object of the present invention is to provide a method of purifying exhaust gas of an internal combustion engine which can suppress the SOx poisoning phenomenon of a NOx storage reduction type exhaust gas purification catalyst and further improve the purification rate of exhaust gas. It is in.

[0007]

According to a first aspect of the present invention, there is provided an exhaust gas purifying method for an internal combustion engine for purifying exhaust gas of an internal combustion engine, the method comprising the steps of: Using a sulfur component solidifying agent containing a basic metal element, a NOx occlusion reduction type exhaust purification catalyst installed on the exhaust passage is used to reduce the sulfur component that causes the formation of sulfur oxides after combustion of the internal combustion engine. It is characterized in that it is solidified before the exhaust gas flows into it.

[0008] A method for purifying exhaust gas of an internal combustion engine according to a second aspect is characterized in that, in the first aspect of the invention, a sulfur component solidifying agent is previously mixed with the fuel.

According to a third aspect of the present invention, there is provided the exhaust gas purifying method for an internal combustion engine according to the first aspect, wherein the sulfur component solidifying agent is added to the intake passage, the combustion chamber, or the exhaust passage separately from the fuel. It is characterized by doing.

According to a fourth aspect of the present invention, there is provided a method for purifying exhaust gas of an internal combustion engine according to any one of the first to third aspects, wherein the metal element has a function of oxidizing a sulfur component contained in the sulfur component solidifying agent. Is a transition element.

According to a fifth aspect of the present invention, there is provided the exhaust gas purification method for an internal combustion engine according to any one of the first to fourth aspects, wherein the basic metal element contained in the sulfur component solidifying agent is an alkali metal element. Alternatively, it is an alkaline earth metal element.

According to a sixth aspect of the present invention, there is provided the exhaust gas purifying method for an internal combustion engine according to the fifth aspect, wherein the basic metal element contained in the sulfur component solidifying agent is an atom having an atomic number equal to or higher than that of potassium. It is characterized by being an alkali metal element having a number.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the exhaust gas purifying method of the present invention will be described below. FIG. 1 shows an internal combustion engine (engine) 1 having a purification device for performing the purification method of the present embodiment.

The engine 1 described below is a multi-cylinder engine. Here, only one of the cylinders is shown as a sectional view. The engine 1 is an in-cylinder injection engine that injects fuel directly into the cylinder 3, and is a lean burn (lean burn) engine. The engine 1 has a spark plug 2
Thus, a driving force is generated by igniting the air-fuel mixture in each cylinder 3. At the time of combustion of the engine 1, air taken in from the outside passes through the intake passage 4 and is mixed with fuel injected from the injector 5 to form an air-fuel mixture. The interior of the cylinder 3 and the intake passage 4 are opened and closed by an intake valve 6. The air-fuel mixture burned inside the cylinder 3 is exhausted to the exhaust passage 7 as exhaust gas.
An exhaust valve 8 is provided between the inside of the cylinder 3 and the exhaust passage 7.
Is opened and closed by

On the intake passage 4, a throttle valve 9 for adjusting the amount of intake air taken into the cylinder 3 is provided. The throttle valve 9 is connected to a throttle position sensor 10 for detecting the opening degree. Accelerator pedal 1 attached to throttle valve 9
An accelerator position sensor 12 for detecting the depression position of the throttle valve 1 and a throttle motor 13 for driving the throttle valve 9 are also provided. Although not shown in FIG. 1, an intake air temperature sensor for detecting the temperature of intake air is also provided on the intake passage 4.

On the downstream side of the throttle valve 9,
A surge tank 14 is formed.
, A vacuum sensor 15 and a cold start injector 17 are provided. The vacuum sensor 15 detects the pressure in the intake passage 4 (intake pipe pressure). The cold start injector 17 is connected to the engine 1
The fuel is diffused and sprayed into the surge tank 14 at the time of a cold start to form a homogeneous air-fuel mixture.

A swirl control valve 18 is provided further downstream of the surge tank 14. The swirl control valve 18 is used for lean combustion (stratified combustion).
This is for generating a stable swirl inside the cylinder 3 at times. Along with the swirl control valve 18, an SCV position sensor 19 for detecting the opening of the swirl control valve 18, a DC motor 20 for driving the swirl control valve 18, and the like are also provided.

The opening and closing timing of the intake valve 6 of the engine 1 of the present embodiment can be variably controlled by a variable valve timing mechanism 21. The open / close state of the intake valve 6 can be detected by a cam position sensor 22 that detects the rotational position of a camshaft on which a cam for opening and closing the intake valve 6 is formed. further,
Near the crankshaft of the engine 1 is a crank position sensor 2 for detecting the rotational position of the crankshaft.
3 is attached. Crank position sensor 2
From the output of 3, the position of the piston 24 in the cylinder 3 and the engine speed can also be obtained. Engine 1
A knock sensor 25 for detecting the knocking of the engine 1 and a water temperature sensor 26 for detecting the temperature of the cooling water are also attached.

On the other hand, on the exhaust passage 7, on the side close to the main body of the engine 1, a starting catalyst 27, which is a normal three-way catalyst, is disposed. Since the start-up catalyst 27 is close to the combustion chamber (cylinder 3) of the engine 1, the temperature is easily raised by the exhaust gas. It is arranged to be. The engine 1 is a four-cylinder engine, and is provided with two start-up catalysts 27, one for each two cylinders. An exhaust gas temperature sensor 28 is attached to each starting catalyst 27, and the exhaust gas temperature sensor 28 detects the temperature of the exhaust gas.

On the downstream side of the start-up catalyst 27, an exhaust pipe is integrated and an exhaust purification catalyst 39 of the NOx storage reduction type is disposed. This NOx storage reduction type exhaust purification catalyst 39
Will be described in detail later. Exhaust purification catalyst 39
An air-fuel ratio sensor 40 for detecting the exhaust air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst 39 is mounted on the upstream side of the exhaust gas purification catalyst 39. As the air-fuel ratio sensor 40, a linear air-fuel ratio sensor capable of linearly detecting the exhaust air-fuel ratio from a rich region to a lean region, and an on-off detection of whether the exhaust air-fuel ratio is in a rich region or a lean region. An O ₂ sensor (oxygen sensor) or the like is used.

Further, an external EGR (Exhaust Gas Recirculation) for recirculating exhaust gas from the exhaust passage 7 to the intake passage 4 is provided.
ulation) passage 43 is formed. External EGR passage 43
The intake passage 4 is connected to the surge tank 14, and the exhaust passage 7 is connected to the upstream side of the starting catalyst 27. An EGR valve 44 for adjusting the amount of exhaust gas to be recirculated is provided on the external EGR passage 43. The EGR mechanism uses the negative pressure of the intake pipe in the intake passage 4 to return a part of the exhaust gas to the intake passage 4, thereby obtaining an effect of suppressing NOx generation and improving fuel efficiency. It should be noted that internal EGR control for obtaining the same effect by controlling the opening / closing timing of the intake valve 6 may be used together.

The fuel stored in the fuel tank 29 is delivered to the injector 5 of the engine 1 by a low-pressure fuel pump 30 for delivery, passes through a fuel filter 31, and is supplied after being pressurized by a high-pressure fuel pump 32. Is done. The engine 1 is capable of lean burn, and in order to perform good lean burn (stratified combustion), fuel is not directly injected into the cylinder 3 during the compression stroke to form a state suitable for stratified combustion. Therefore, the fuel is injected by the injector 5 after the pressure is increased.

Along with the injector 5, a fuel pressure sensor 33 for detecting the pressure of the fuel for precise control is also provided. The high-pressure fuel pump 32 is connected to the engine 1
, That is, the rotation of the camshaft on the exhaust valve 8 side to increase the pressure of the fuel. The fuel delivered by the low-pressure fuel pump 30 is supplied to the cold start injector 17 as it is.

Along with the fuel tank 29, the fuel tank 2
Charcoal canister 3 for collecting fuel evaporated in 9
4 are provided. The charcoal canister 34 has an activated carbon filter inside, and the activated carbon filter collects evaporated fuel. The collected fuel is purged into the intake passage 4 and burned in the cylinder 3 while the purge amount is controlled by the purge control valve 35. The fuel tank 29 has a return pipe 36 for returning the remaining fuel not injected into the fuel tank.
Is also attached.

The above-described spark plug 2, injector 5,
Throttle position sensor 10, accelerator position sensor 12, throttle motor 13, vacuum sensor 15, cold start injector 17, DC motor 2
0, the actuator of the variable valve timing mechanism 21;
The cam position sensor 22, crank position sensor 23, knock sensor 25, water temperature sensor 26, exhaust temperature sensor 28, purge control valve 35, air-fuel ratio sensor 40, EGR valve 44, intake temperature sensor, and other actuators and sensors It is connected to an electronic control unit (ECU) 37 that comprehensively controls the engine 1.

In the system shown in FIG.
An electronic control drive unit (EDU) 38 is provided between the U37 and the injector 5. EDU38 is E
The drive current from the CU 37 is amplified to drive the injector 5 with a high voltage and a large current. These actuators and sensors are controlled based on a signal from the ECU 37, or the detection result is obtained by an EC.
It is sent to U37. The ECU 37 includes a CPU for performing calculations therein, a RAM for storing various amounts of information such as calculation results, a backup RAM for storing the stored contents by a battery, and a ROM for storing each control program.
Etc. The ECU 37 controls the engine 1 based on various information amounts such as the intake passage pressure and the air-fuel ratio.

The NOx storage reduction type exhaust purification catalyst 39 will be described.

The exhaust gas purifying catalyst 39 is provided on a carrier having a surface coated with a thin film of alumina, a noble metal such as platinum, palladium and rhodium, and an alkali coating (K, Na, Li, Cs) on an alumina coating layer. ), Alkaline earth metals (Ba, Ca, etc.) or rare earth elements (L
a, Y, etc.) and the NOx contained in the exhaust gas when the engine is operated at a lean air-fuel ratio.
Can be occluded. For this reason, the exhaust purification catalyst 39 has a function as a normal three-way catalyst, that is, a function to purify HC, CO, and NOx in exhaust gas when burned in the vicinity of the stoichiometric air-fuel ratio. Can store NOx contained in the exhaust gas.

The NOx stored in the exhaust purification catalyst 39 is released when burned at a rich air-fuel ratio or a stoichiometric air-fuel ratio (stoichiometric air-fuel ratio), and is reduced and purified by HC and CO in the exhaust gas ( At this time, HC and CO are simultaneously oxidized and purified. Therefore, the NOx of the exhaust purification catalyst 39
When it is determined that the occluded amount is almost full, a so-called rich spike operation, in which the stored NOx is reduced by operating the engine for a short time at the rich air-fuel ratio, may be forcibly performed.

As described above, the exhaust gas purifying catalyst 39 has NO
It has the property of storing SOx more stably than x, which causes SOx poisoning. In the present embodiment, such a sulfur component causing SOx is solidified, the SOx concentration in the exhaust gas is reduced, and the amount of SOx stored in the NOx storage reduction type exhaust purification catalyst 39 is reduced. As a result, the capacity (NOx storable amount) of the exhaust purification catalyst 39 used for NOx occluding and reducing is increased, and N2 in the exhaust gas is reduced.
The purification rate of Ox can be improved.

For example, the above-described rich spike operation may not be performed depending on the operation state. Therefore, it is better that the NOx storable amount of the exhaust purification catalyst 39 is large, and if the storable amount is large, NOx cannot be completely absorbed. Thus, it is possible to prevent NOx from flowing downstream. The purification method of the present embodiment uses a sulfur component solidifying agent to solidify the sulfur component.

The sulfur component in the exhaust gas is solidified using a sulfur component solidifying agent (hereinafter, also simply referred to as “solidifying agent”). It should just be. In this case, the sulfur component solidifying agent may be added to the intake air upstream of the cylinder 3, may be added in the cylinder 3, or may be added to the exhaust gas discharged from the cylinder 3. You may add to it.
Further, it may be added to fuel (gasoline) in advance, or may be added to a fuel tank.

The solidifying agent of the present embodiment contains a metal element having a function of oxidizing a sulfur component (hereinafter, also simply referred to as “metal element having an oxidation function”) and a basic metal element. By having both components, the sulfur component can be effectively solidified. Here, it is effective that the metal element having an oxidation function is a transition element. Further, the basic metal element is preferably an alkali metal element or an alkaline earth metal element, and particularly preferably an alkali metal having an atomic number higher than that of potassium.

Specific examples of the metal element having an oxidation function include Pt, Pd, Rh, Fe, Ce, In, Ag,
There are Au and Ir. Among them, those other than In are transition elements. On the other hand, as the basic metal element, specifically, Li, Na, K, Rb, Cs, Fr, Be, Mg,
There are Ca, Sr, Ba, Ra, Al, Zn, Zr, and La. Of these, alkali metals are Li, Na, K, R
b, Cs, and Fr. Among them, those having an atomic number equal to or greater than that of potassium are K, Rb, Cs, and Fr. Alkaline earth metals are Be, Mg, Ca, Sr,
Ba and Ra.

It is considered that the solidification of the sulfur component is performed as follows (where the metal element having an oxidizing function is M
_1, and the basic metal element and M _2). SO ₂ and SO ₃ are generated by the combustion of the engine 1. These react as follows: SO ₂ − (M ₁ ) → SO ₃ → M ₂ SO ₃ → M ₂ SO ₄ .

As described above, by adding a metal element having an oxidizing function to the solidifying agent, the oxidation reaction of the sulfur component can easily proceed. That is, as described above, SO ₂ is likely to become SO ₃ , and the solidification rate of sulfur can be improved. Then, the oxidized sulfur oxide is solidified as a sulfite or a sulfate by the basic metal element.

At this time, by using an alkali metal having an atomic number equal to or greater than that of potassium as the basic metal element, the solidification rate of the sulfur component can be improved. This is because an alkali metal having an atomic number higher than that of potassium has a strong basicity and is easily associated with a sulfur component. In addition to the above, SO ₂ → M ₂ SO ₂ − (M ₁ ) → M ₂ SO ₃ → It is considered that a reaction such as M ₂ SO ₄ occurs, and as a result, the solidification rate of the sulfur component is improved. (In the above description, the metal element M ₁ having an oxidizing function is considered to oxidize a compound M ₂ SO ₂ of sulfur dioxide gas SO ₂ and a basic metal element M _2. )

Normally, during combustion of an internal combustion engine such as the engine 1
Under high temperature during combustion such as _TwoIs once SO_ThreeAcid
But chemically equilibrated with SO_ThreeSulfurous gas rather than gas
SO_TwoThe above-mentioned reaction does not occur because it is in the state
Therefore, an improvement in the solidification rate of sulfur cannot be expected. In addition, as SOx
Can be SO etc., but this is due to oxidation
Tte SO_TwoAnd SO_ThreeThen, as described above,
It is solidified.

The effect of the solidifying agent described above was experimentally verified. In the experiment, a fuel containing a solid content of 500 ppm by weight in a sulfur content was used as a test fuel. Measure the SOx concentration in the exhaust gas when the engine was operated under the conditions of an engine speed of 2000 rpm and a load of 60 Nm, and calculated the SOx concentration in the exhaust gas when the engine was operated with normal fuel without the addition of a solidifying agent. The decrease was calculated as the solidification rate of the sulfur component. The amount of the solidifying agent is calculated from the theoretical number of moles of a sulfur salt (M ₂ SO ₄ ) formed by the basic metal element (M ₂ ) contained in the solidifying agent and the sulfur contained in the fuel. You. The solidification rate of the sulfur component when each element is contained as each solidifying agent is shown in the following [Table 1].

[0040]

[Table 1]

As is evident from Table 1, when the metal element (Ce, Fe) having an oxidizing function is used alone, there is no partner for forming a salt, and therefore, there is of course little effect. When only the basic metal elements (Ca, Ba, K, Cs) are included, the effect of the solidification rate of about 20% to 30% is obtained, but when both are contained, further effects are obtained. In particular, the use of an alkali metal element (K, Cs) having an atomic number equal to or greater than that of potassium as a basic metal has a remarkable effect. Furthermore, among the metal elements (Ce, Fe) having an oxidation function used here, when Ce is used in combination with a basic metal, the solidification rate is better, and the combination of K and Ce has the best solidification rate. Was.

The solidifying agent may contain a metal element having an oxidizing function or a metal element having a basic property as an ion or a soluble compound.
The solidifying agent may be a solid or a liquid, or may be a gas, and the above-mentioned soluble compound dissolved in a solvent,
It can be provided in various forms such as a solid that dissolves gasoline as a solvent as a solvent.

For example, it is conceivable to dissolve potassium citrate or calcium naphthenate, which is a compound of a basic metal, in ethanol to form ions in a solution, and to add the ions to gasoline as a fuel. Alternatively, it is conceivable to dissolve potassium carbonate, sodium carbonate, or calcium hydroxide, which is a compound of a basic metal, with water to form ions in an aqueous solution, and to spray and add the ions onto an intake passage, a cylinder, or an exhaust passage.

As described above, by solidifying most of the sulfur components contained in the exhaust gas, NO
Since it becomes difficult for SOx to be stored in the x-storage-reduction type exhaust purification catalyst 39, the storage capacity of the exhaust purification catalyst 39 can be used for storing NOx, and the purification rate of NOx can be improved.

As described above, there are several methods for adding the solidifying agent. First, the case where the above-described sulfur component solidifying agent is mixed with fuel will be briefly described. The above-described internal combustion engine shown in FIG. 1 shows the configuration in this case. In this case, the entire engine 1 including the intake / exhaust system and the fuel system functions as a sulfur component solidifying means for solidifying the solidifying agent. Here, potassium is used as a basic alkali metal element, and a solution in which potassium citrate is dissolved in ethanol is used as a fixing agent. This fixing agent further contains Ce as a transition metal element having an oxidizing function as cerium octylate.

The solidifying agent was charged into the fuel tank 29. If the solidifying agent is added immediately after the gasoline tank is replenished with fuel, the mixing ratio with gasoline, which is the fuel, can be easily set to a predetermined mixing ratio, which is convenient. As described above, when the solidifying agent is added to gasoline as the fuel, the fuel is injected into the cylinder 3 and burned, whereby the above-described reaction of solidifying the sulfur component occurs, and the sulfur component in the exhaust gas ( Originally, the fuel or the sulfur component in the engine oil) is solidified and is no longer stored in the exhaust purification catalyst 39.

Next, the case where the above-mentioned sulfur component solidifying agent is added by spraying onto the intake passage 4 will be briefly described. FIG. 2 shows the configuration of the engine 1 and its periphery in this case. Note that the same or equivalent components as those shown in FIG. 1 described above are denoted by the same reference numerals, and detailed description thereof will be omitted. Here, potassium is used as a basic alkali metal element, and an aqueous solution of potassium hydroxide is used as a fixing agent. This fixing agent further contains Ce as a transition metal element having an oxidizing function as cerium octylate.

A solidifying agent tank 41 for storing the solidifying agent is provided in association with the engine 1. A pipe is provided from the solidifying agent tank 41 to the surge tank 14, and a surge tank 1 is provided at a tip of the pipe.
A spray nozzle 16 for spraying the solidifying agent toward the inside of the nozzle 4 is connected. A spray pump 42 for spraying the solidifying agent is provided in the middle of the pipe. The spray pump 42 is driven by the electric power of the battery or a part of the output of the engine 1. Further, the spray nozzle 16
Is connected to the ECU 37 described above.
The spray timing and spray amount of the solidifying agent are controlled by this.

When the solidifying agent is sprayed on the intake air using the spray nozzle 16, the solidifying agent is directly sucked into the cylinder 3 and burned together with the fuel injected from the injector 5. As a result, the above-mentioned reaction for solidifying the sulfur component occurs, and the sulfur component in the exhaust gas (originally in the fuel or in the engine oil) is solidified and is not stored in the exhaust purification catalyst 39. . in this case,
The entire engine 1 including the intake / exhaust system and the fuel system, the spray nozzle 16 for supplying the solidifying agent, the solidifying agent tank 41, the spray pump 42, etc. function as a sulfur component solidifying means for solidifying the solidifying agent. I have.

Next, the case where the above-mentioned sulfur component solidifying agent is added by spraying into the cylinder 3 will be briefly described. FIG. 3 shows the configuration of the engine 1 and its periphery in this case. The same or similar components as those shown in FIGS. 1 and 2 are denoted by the same reference numerals, and detailed description thereof will be omitted. Again, potassium is used as the basic alkali metal element, and an aqueous solution of potassium hydroxide is used as the fixing agent. This immobilizing agent includes C as a transition metal element having an oxidizing function.
e is further contained as cerium octylate.

Further, a solidifying agent tank 41 for storing the solidifying agent is provided in association with the engine 1. A pipe is provided from the solidifying agent tank 41 to the cylinder 3, and a spray nozzle 16 for spraying the solidifying agent toward the inside of the cylinder 3 is connected to a tip of the pipe. A spray pump 42 for spraying the solidifying agent is provided in the middle of the pipe. Spray pump 42
Is driven by the power of the battery or a part of the output of the engine 1. Further, the spray nozzle 16 is connected to the above-mentioned ECU 37, and the spray timing and the spray amount of the solidifying agent are controlled by the ECU 37.

When the solidifying agent is sprayed into the cylinder 3 using the spray nozzle 16, the above-described reaction for solidifying the sulfur component occurs, and the sulfur component in the exhaust gas (originally in the fuel or engine oil) The sulfur component therein is solidified and no longer stored in the exhaust purification catalyst 39. Also in this case, the entire engine 1 including the intake / exhaust system and the fuel system, the spray nozzle 16 for supplying the solidifying agent, the solidifying agent tank 41,
The spray pump 42 and the like function as a sulfur component solidifying means for solidifying the solidifying agent.

Next, the case where the above-mentioned sulfur component solidifying agent is added by spraying onto the exhaust passage 7 will be briefly described. FIG. 4 shows the configuration of the engine 1 and its surroundings in this case. The same or similar components as those shown in FIGS. 1 to 3 are denoted by the same reference numerals, and detailed description thereof will be omitted. Again, potassium is used as the basic alkali metal element, and an aqueous solution of potassium hydroxide is used as the fixing agent. This fixing agent includes Ce as a transition metal element having an oxidizing function.
As cerium octylate.

A solidifying agent tank 41 for storing the solidifying agent is provided in association with the engine 1. A pipe is provided from the solidifying agent tank 41 to the exhaust passage 7, and a spray nozzle 1 for spraying the solidifying agent onto the exhaust passage 7 on the upstream side of the exhaust purification catalyst 39 is provided at a tip of the pipe.
6 are connected. A spray pump 42 for spraying the solidifying agent is provided in the middle of the pipe. The spray pump 42 is driven by the electric power of the battery or a part of the output of the engine 1. Further, the spray nozzle 16 is connected to the ECU 37 described above,
The spray timing and spray amount of the solidifying agent are controlled by the ECU 37.

When the solidifying agent is sprayed onto the exhaust passage 7 using the spray nozzle 16, the solidifying agent mixes with the exhaust gas containing the sulfur component, and the above-described reaction for solidifying the sulfur component occurs. During this reaction, the heat of the exhaust gas can accelerate the reaction. By this reaction, the sulfur component in the exhaust gas (originally in the fuel or in the engine oil) is solidified and is not stored in the exhaust purification catalyst 39. Also in this case, the entirety of the engine 1 including the intake / exhaust system and the fuel system, the spray nozzle 16 for supplying the solidifying agent, the solidifying agent tank 41, the spray pump 42, and the like solidify the sulfur component solidifying means for solidifying the solidifying agent. Functioning as

Next, the above-mentioned sulfur component solidifying agent was added to the external EG.
The case of adding by spraying on the R passage 43 will be briefly described. FIG. 5 shows the configuration of the engine 1 and its periphery in this case. The same or equivalent components as those shown in FIGS. 1 to 4 are denoted by the same reference numerals, and detailed description thereof will be omitted. even here,
Potassium is used as a basic alkali metal element, and an aqueous solution of potassium hydroxide is used as a fixing agent.
This fixing agent further contains Ce as a transition metal element having an oxidizing function as cerium octylate.

A solidifying agent tank 41 for storing the solidifying agent is provided in association with the engine 1. A pipe is arranged from the solidifying agent tank 41 to above the external EGR passage 43, and a spray nozzle 16 for spraying the solidifying agent into the inside of the external EGR passage 43 is connected to a tip of the pipe. A spray pump 42 for spraying the solidifying agent is provided in the middle of the pipe. The spray pump 42 is driven by the electric power of the battery or a part of the output of the engine 1. Further, the spray nozzle 1
6 is connected to the ECU 37 described above,
7 controls the spray timing and spray amount of the solidifying agent.

Using the spray nozzle 16, the external EGR passage 4
When the solidifying agent is sprayed on the exhaust gas 3, the solidifying agent mixes with the exhaust gas containing the sulfur component, and further mixes with the intake air on the intake passage 4, which is directly sucked into the cylinder 3 and injected from the injector 5. The fuel is burned together with the fuel. As a result, the above-described reaction for solidifying the sulfur component occurs. By this reaction, the sulfur component in the exhaust gas (originally in the fuel or in the engine oil) is solidified and is not stored in the exhaust purification catalyst 39. Also in this case, the entirety of the engine 1 including the intake / exhaust system and the fuel system, the spray nozzle 16 for supplying the solidifying agent, the solidifying agent tank 41, the spray pump 42, and the like solidify the sulfur component solidifying means for solidifying the solidifying agent. Functioning as

[0059]

According to the first aspect of the present invention, the sulfur component causing the formation of sulfur oxides after the combustion of the internal combustion engine is reduced by the sulfur component solidifying agent into the NOx storage provided in the exhaust passage. Since the exhaust gas is solidified before flowing into the reduction type exhaust purification catalyst, the SOx poisoning of the NOx storage reduction type exhaust purification catalyst can be suppressed, and the purification of the exhaust gas can be further improved. It is important that the above-mentioned sulfur component solidifying agent contains a metal element having a function of oxidizing a sulfur component and a basic metal element.
As a result, the sulfur oxides that cause SOx poisoning of the exhaust purification catalyst can be effectively solidified, and the purification performance can be reliably improved.

According to the second aspect of the present invention, by adding the sulfur component solidifying agent to the fuel, the ratio of the amount of the sulfur component solidifying agent added to the fuel amount can be easily adjusted. On the other hand, according to the third aspect of the present invention, the sulfur component solidifying agent is added separately from the fuel in the intake passage, the combustion chamber, or the exhaust passage. The addition time can be selected, and the addition amount (including the case where the addition is not desired) can be adjusted according to the operation state of the internal combustion engine and the like. Either case contributes to the improvement of the solidification rate of the sulfur component. The best one should be adopted according to the situation.

According to the fifth aspect of the present invention, a basic metal element, which is an alkali metal element or an alkaline earth metal element, easily reacts with a sulfur component and easily forms a salt (solid). The solidification rate of the component can be improved. In this case, when the basic metal element is an alkali metal element having an atomic number equal to or larger than the atomic number of potassium as described in claim 6, it is particularly easy to form a salt (solid) with a sulfur component. The solidification rate of the sulfur component can be further improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an internal combustion engine that implements a first embodiment of an exhaust gas purification method of the present invention and its periphery.

FIG. 2 is a configuration diagram showing an internal combustion engine for implementing a second embodiment of the exhaust gas purification method of the present invention and its periphery.

FIG. 3 is a configuration diagram showing an internal combustion engine that implements a third embodiment of the exhaust gas purification method of the present invention and its periphery.

FIG. 4 is a configuration diagram showing an internal combustion engine that implements a fourth embodiment of the exhaust gas purification method of the present invention and the periphery thereof.

FIG. 5 is a configuration diagram showing an internal combustion engine implementing a fifth embodiment of the exhaust gas purification method of the present invention and its periphery.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine (internal combustion engine), 3 ... Cylinder, 4 ... Intake passage, 7 ... Exhaust passage, 8 ... Exhaust valve, 16 ... Spray nozzle, 27 ... Start catalyst, 29 ... Fuel tank, 39 ... Exhaust purification catalyst (NOx Storage reduction type), 41 ... solidifying agent tank,
42: spray pump, 43: external EGR passage.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B01D 53/36 102Z (72) Inventor Tatsushi Mizuno 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation ( 72) Inventor Shinji Tsuji 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Masahiko 1 Toyota Town Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Kenji Kato Aichi Prefecture 1 Toyota Town, Toyota City Inside Toyota Motor Co., Ltd. (72) Inventor Takasen Ito 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Yoshitsugu Ogura 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (72) Inventor Tetsuo Kawamura 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Norio Kimura No. 41, 41, Chochu, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture F-term in Toyota Central R & D Laboratories Co., Ltd. 3G091 AA11 AA12 AA17 AA24 AB03 AB06 AB11 AB15 BA11 BA13 BA20 CA15 CB01 EA01 EA06 EA07 EA08 EA09 EA10 EA16 EA17 EA19 EA34 FB10 GA06 GB02Z GB03Z GB04Z GB05Z GB06Z GB07Z HA03 HA10 3G092 AA01 AA06 AA09 AA10 AA11 AA17 AB02 AB16 CB01 DC14 DE14Y DF01 FA02Z01 DF02 FA03Z HE03Z HE08Z 4D048 AA06 AB01 AB02 AB03 AB05 BA02X BA02Y BA03X BA03Y BA08Y BA14X BA15X BA16Y BA17Y BA18X BA19X BA19Y BA30Y BA31Y BA33Y BA34Y BA36X BA36Y BA41X BC01 BC04 CC32 CC38 CC46 EA04

Claims (6)

[Claims] 1. An exhaust gas purification method for an internal combustion engine for purifying exhaust gas of an internal combustion engine, comprising: using a sulfur component solidifying agent containing a metal element having a function of oxidizing a sulfur component and a basic metal element. Internal combustion characterized by solidifying a sulfur component that causes the generation of sulfur oxides after combustion of an internal combustion engine before exhaust gas flows into a NOx storage reduction type exhaust purification catalyst installed on an exhaust passage. Engine exhaust purification method. 2. The method for purifying exhaust gas of an internal combustion engine according to claim 1, wherein said sulfur component solidifying agent is previously mixed with fuel. 3. The exhaust gas purification method for an internal combustion engine according to claim 1, wherein the sulfur component solidifying agent is added to the intake passage, the combustion chamber, or the exhaust passage separately from the fuel. 4. The internal combustion engine according to claim 1, wherein the metal element having a function of oxidizing a sulfur component contained in the sulfur component solidifying agent is a transition element. Exhaust gas purification method. 5. The internal combustion engine according to claim 1, wherein the basic metal element contained in the sulfur component solidifying agent is an alkali metal element or an alkaline earth metal element. Engine exhaust purification method. 6. The method according to claim 5, wherein the basic metal element contained in the sulfur component solidifying agent is an alkali metal element having an atomic number higher than that of potassium.
An exhaust gas purification method for an internal combustion engine according to claim 1.