JP2009114908A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of preventing the deterioration of fuel economy for post injection, and reducing the discharging amount of SOx. <P>SOLUTION: The exhaust emission control device is equipped with a DPF 12 filtering exhaust discharged from an engine 1, and collecting soot in the exhaust, in an exhaust pipe 4 of the engine 1. The exhaust emission control device is equipped with a fuel additive supplying device 16 supplying fuel additive for lowering the combustion temperature of the soot in the exhaust and collecting SOx in the exhaust, and an ECU 20 controlling the fuel additive supplying device 16. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine. More specifically, the present invention relates to an exhaust gas purification apparatus for an internal combustion engine having a filter that collects particulates (particulate matter) in the exhaust gas of the internal combustion engine.

  2. Description of the Related Art Conventionally, a technique for reducing particulate emissions by providing a DPF (Diesel Particulate Filter) that collects particulates in exhaust gas in an exhaust system of an internal combustion engine has been widely used. Since there is a limit to the amount of particulates that can be collected by the DPF, a DPF regeneration process for burning the particulates deposited on the DPF is appropriately executed. In this regeneration process, fuel injection (hereinafter referred to as “post-injection”) is performed during the exhaust process, the fuel injected by the oxidation catalyst or the like is burned, and the DPF is brought into a high-temperature atmosphere so that the accumulated particulates are removed. Force to burn.

  However, although the solubilizing organic component (hereinafter referred to as “SOF”) of the accumulated particulates can be purified by a catalyst having an oxidation function, the soot occupying most of the components constituting the particulates is burned and removed. In this case, since it is necessary to keep the DPF at a soot combustion temperature of 600 ° C. or more for a long time, there is a possibility that the fuel efficiency is deteriorated by performing the post injection. Therefore, in recent years, a technique for suppressing fuel consumption by post injection has been proposed.

  For example, Patent Document 1 proposes to use a colloidal dispersion composed of particles of a cerium compound, an acid, and an organic acid, and further containing at least one of rhodium and palladium as a fuel additive. According to this proposal, by adding the fuel additive as described above to the fuel, the combustion temperature of the soot can be lowered, the consumption of fuel for post injection can be reduced, and nitrogen oxide (hereinafter referred to as “NOx”). ) Emissions can also be reduced.

  On the other hand, in the exhaust gas discharged from the internal combustion engine, in addition to the particulates and NOx as described above, sulfur oxides (hereinafter referred to as “SOx”) generated by oxidizing the sulfur content in the fuel and oil. included. Here, in order to purify NOx in the exhaust, as shown in Patent Document 2, the NOx is absorbed when the air-fuel ratio of the exhaust is lean, and the absorbed NOx is released when the oxygen concentration in the exhaust is lowered. A NOx absorbent may be provided in the exhaust system. However, even if such an NOx absorbent is provided in the exhaust system, it may be poisoned by SOx in the exhaust and the function of the NOx absorbent may be lowered. Therefore, a plurality of techniques for reducing SOx in exhaust gas have been proposed.

For example, Patent Document 3 discloses an exhaust passage provided with a SOx trap catalyst. This SOx trap catalyst carries a SOx holding agent having a function of holding SOx in the exhaust gas inside. By providing such a SOx trap catalyst upstream of the NOx absorbent, it is possible to prevent the NOx absorbent from being poisoned by SOx.
In addition, for example, Patent Document 4 discloses a system in which a sulfur content capturing material for capturing sulfur content is supported on the DPF, thereby preventing poisoning due to SOx of the NOx absorbent provided on the downstream side of the DPF. There are also proposals to make the compact.
Special table 2007-509193 gazette Japanese Patent No. 2600492 JP 2006-138223 A JP 2006-346605 A

  Therefore, in order to prevent deterioration of fuel consumption due to post-injection of DPF regeneration processing and reduce the amount of SOx emission, the exhaust purification device is configured by combining the techniques disclosed in Patent Documents 1 to 4 described above. Can be considered.

  However, for example, if the SOx trap catalyst of Patent Document 3 is provided in the exhaust passage, the exhaust purification device may be increased in size. This is because, due to the diffusibility of the exhaust gas, it is difficult to efficiently collect SOx in the entire region of the SOx trap catalyst, and a large carrier is required to collect a large amount of SOx. Moreover, when the SOx trap catalyst is supported on the DPF as shown in Patent Document 4, the pressure loss of the exhaust gas in the DPF may increase.

  An object of the present invention is to provide an exhaust emission control device that can prevent deterioration in fuel consumption associated with post-injection and that can reduce SOx emissions. It has been made.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a filtering means (12) for filtering exhaust gas discharged from an internal combustion engine (1) and collecting soot in the exhaust gas. In the exhaust gas purification apparatus for an internal combustion engine provided in (4), a fuel addition that lowers the combustion temperature of soot in the exhaust and collects SOx in the exhaust to the fuel before being injected into the combustion chamber of the internal combustion engine An additive supply means (16, 21) for supplying the agent is provided.

  According to a second aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the first aspect, the fuel additive includes a compound including at least one of an alkali metal and an alkaline earth metal. It is characterized by that.

  According to a third aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the second aspect, the additive supply means has an alkali metal and alkaline earth metal content of 5 ppm or more in terms of ion mass ratio and a saturated solubility. The fuel additive is supplied to the fuel so as to be less than the above.

  According to a fourth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the second or third aspect, a catalyst for reducing the amount of soot in the exhaust gas upstream of the filtering means in the exhaust passage ( 11) is provided.

  According to a fifth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the fourth aspect, the catalyst for reducing the amount of soot in the exhaust gas includes a three-way catalyst or an oxidation catalyst.

  According to a sixth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to any of the first to fifth aspects, the NOx in the exhaust gas is purified downstream of the filtering means in the exhaust passage. A NOx purification device (14) is provided.

  According to a seventh aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the sixth aspect, the NOx purification apparatus generates ammonia when the air-fuel ratio of the exhaust gas is rich, and the generated ammonia And a catalyst for reducing NOx by the held ammonia when the air-fuel ratio of the exhaust gas is lean.

  According to an eighth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to any one of the first to seventh aspects, the filtering means includes a purification filter through which exhaust gas is filtered. It is characterized in that platinum, palladium, and rhodium are not substantially supported on the upstream surface.

  According to a ninth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the eighth aspect, an SOx trap material (127) having a function of absorbing SOx is provided on a downstream surface of the purification filter. It is characterized by that.

  A tenth aspect of the present invention is the exhaust gas purification apparatus for an internal combustion engine according to any one of the first to ninth aspects, wherein the additive supply means is an operating state of the internal combustion engine or an exhaust gas discharged from the internal combustion engine. The supply amount of the fuel additive is controlled according to the state.

According to the first aspect of the present invention, the fuel additive having a function of reducing the combustion temperature of the soot in the exhaust gas and collecting SOx in the exhaust gas before being injected into the combustion chamber of the internal combustion engine. Supplied in fuel. Accordingly, it is possible to suppress the consumption of fuel when the soot accumulated on the filtering means is burned and the filtering means is regenerated by reducing the combustion temperature of the soot. It is also possible to prevent thermal deterioration of the device provided downstream of the filtering means.
Further, by supplying the fuel additive described above to the fuel and collecting SOx in the exhaust gas, SOx can be deposited together with soot by the filtering means. As a result, it is possible to prevent the device provided downstream of the filtering means from being poisoned by SOx in the exhaust gas.
Thus, in order to reduce the combustion temperature of soot and prevent poisoning by SOx, it is only necessary to supply the fuel additive described above to the fuel. Therefore, according to the present invention, as compared with the above-described conventional exhaust purification device, the exhaust purification device does not increase in size and the exhaust pressure loss does not increase.

According to the invention described in claim 2, the fuel additive contains an alkali metal or an alkaline earth metal. By burning the fuel to which such a fuel additive is added in an internal combustion engine, oxides and carbonates can be generated in the exhaust gas and deposited on the filtering means. The oxides and carbonates deposited on these filtering means react with SOx in the exhaust gas, and change to sulfate to act as a trap material that captures SOx. Therefore, the SOx in the exhaust gas is deposited on the filtering means. be able to. Further, the alkali metal or alkaline earth metal contained in the fuel additive reacts with SOx in the exhaust to produce a sulfate compound, thereby removing SOx in the exhaust.
Due to the action of the alkali metal and alkaline earth metal as described above, poisoning due to SOx of the apparatus provided on the downstream side of the filtering means can be prevented. Here, in particular, a catalyst provided with a function of adsorbing NOx such as alkali metal, alkaline earth metal, ceria, zirconia, or the like, that is, a catalyst that is vulnerable to poisoning by SOx, is provided in the apparatus provided downstream of the filtering means. If included, it is possible to reduce the frequency of executing the process of desorbing SOx from such a catalyst, and the fuel efficiency can be further improved.

In addition, the soot generated by burning the fuel in the internal combustion engine is in a state of being intimately intertwined with the alkali metal or alkaline earth metal contained in the fuel additive in the combustion chamber and the exhaust passage of the internal combustion engine, that is, It becomes a tight contact state, and can reduce the combustion temperature of soot by this.
By the way, the soot discharged from the internal combustion engine is hardly burned by a three-way catalyst, an oxidation catalyst, or the like. However, the soot and the fuel additive are in a tight contact state in this manner. It becomes possible to burn soot with the original catalyst or the oxidation catalyst.

  According to the third aspect of the invention, it is possible to achieve the effect of lowering the combustion temperature of the soot and the effect of collecting SOx while preventing the fuel additive from being wasted. In addition, the influence of the addition of the fuel additive to the fuel on the operating state of the internal combustion engine can be minimized.

  According to the fourth aspect of the present invention, the amount of soot accumulated on the filtering means can be reduced by providing the catalyst for reducing the amount of soot in the exhaust gas upstream of the filtering means. Therefore, it is possible to further reduce the consumption of fuel for performing the regeneration process for burning the soot deposited on the filtering means.

  According to the fifth aspect of the present invention, the catalyst containing the three-way catalyst or the oxidation catalyst is provided on the upstream side of the filtering means in the exhaust passage, so that the soot is burned by this catalyst and is deposited on the filtering means. The amount of soot can be reduced. As described above, when the fuel additive is added, the soot produced is intimately intertwined with the alkali metal or alkaline earth metal and contacts the catalyst in a tight contact state. In addition, since the alkali metal and the alkaline earth metal itself in the fuel additive are excellent in soot combustibility, it is possible to burn soot with such a catalyst. As a result, the amount of soot that accumulates on the filtering means can be reduced, the frequency of executing the regeneration processing of the filtering means can be reduced, and fuel efficiency can be further improved.

  According to the sixth aspect of the present invention, the NOx in the exhaust gas can be purified by providing the NOx purification device that purifies the NOx in the exhaust gas. In particular, by providing such a NOx purification device downstream of the filtering means in the exhaust passage, the NOx purification device is prevented from being poisoned by SOx in the exhaust gas, and SOx is desorbed from the NOx purification device. The frequency of executing the process can be reduced. Therefore, fuel efficiency can be improved and thermal degradation of the NOx purification device can be suppressed.

  According to the seventh aspect of the present invention, a catalyst that generates ammonia when the air-fuel ratio is rich and reduces NOx when the air-fuel ratio is lean is used in the NOx purification device. The separation temperature can be lowered. Therefore, it is possible to suppress fuel consumption for executing the process of desorbing SOx from the NOx purification device and further suppress thermal deterioration of the NOx purification device.

  According to the invention described in claim 8, platinum, palladium, and the surface on the inside and upstream side of the purification filter of the filtering means, that is, the portion where the soot and fuel additive are deposited when the exhaust gas is filtered, Noble metals such as rhodium are substantially not supported. When the soot deposited on the purification filter is burned and the filtering means is regenerated, if the purification filter contains noble metals as described above, SOx deposited on the purification filter as sulfide may be desorbed. According to the present invention, there is no possibility of such poisoning by SOx. Here, it is possible to carry an oxidation catalyst, a three-way catalyst, or the like containing the above-mentioned noble metal on the downstream surface of the purification filter where the fuel additive cannot reach.

  According to the ninth aspect of the present invention, the SOx trap material having a function of absorbing SOx is provided on the downstream surface of the purification filter, so that the device provided downstream of the filtering means is poisoned by SOx. Can be prevented more effectively. Further, by providing such a SOx trap material on the downstream surface of the purification filter of the filtration means, it is possible to reduce the size of the exhaust purification device as compared with the case where it is provided separately from the filtration means.

  According to the tenth aspect of the present invention, the supply amount of the fuel additive is controlled according to the operating state of the internal combustion engine or the state of the exhaust discharged from the internal combustion engine. Here, the operating state of the internal combustion engine includes a rotational speed, a torque value, a cumulative travel distance, and the like. Further, the exhaust state includes SOx concentration, NOx concentration, air-fuel ratio, and the like in the exhaust. By controlling the supply amount of the fuel additive according to such a state, the fuel additive is prevented from being consumed unnecessarily, and the effect of lowering the combustion temperature of the above-mentioned soot and collecting SOx. The effect to do can be show | played.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a diagram showing a configuration of an internal combustion engine and an exhaust purification device thereof according to a first embodiment of the present invention. An internal combustion engine (hereinafter simply referred to as “engine”) 1 is a diesel engine that directly injects fuel into each cylinder, and each cylinder is provided with a fuel injection valve.

  The fuel (light oil) stored in the fuel tank 15 is appropriately supplied to these fuel injection valves via a pump and a common rail (not shown). These fuel injection valves are electrically connected by an electronic control unit (hereinafter referred to as “ECU”) 20, and the valve opening time and valve closing time of the fuel injection valve are controlled by the ECU 20. The fuel tank 15 is connected to an additive supply device 16 for supplying a fuel additive to the fuel stored in the fuel tank 15.

  The additive supply device 16 supplies a fuel additive having a predetermined function into the fuel before being injected by the fuel injection valve into each cylinder of the engine 1. The fuel additive has a function of lowering the combustion temperature of soot contained in the particulates in the exhaust gas and capturing SOx in the exhaust gas by being burned together with the fuel.

  More specifically, the fuel additive includes any one of an alkali metal and an alkaline earth metal, or a compound containing an alkali metal and an alkaline earth metal. The additive supply device 16 supplies the fuel additive containing the alkali metal and the alkaline earth metal to the fuel after mixing a compound soluble in the fuel. The additive supply device 16 is electrically connected to the ECU 20 to adjust the supply amount of the fuel additive. The supply amount of the fuel additive is adjusted so that the content of these alkali metals and alkaline earth metals is 5 ppm or more and less than the saturation solubility in terms of ion mass ratio in a state where the fuel additive is supplied to the fuel.

  Further, the engine 1 is provided with an intake pipe 2 through which intake air flows and an exhaust pipe 4 through which exhaust flows. The intake pipe 2 is connected to an intake port of each cylinder of the engine 1. The exhaust pipe 4 is connected to the exhaust port of each cylinder of the engine 1.

  In the intake pipe 2, an intercooler for cooling the pressurized air and a throttle valve for controlling the intake air amount are provided. The throttle valve is connected to the ECU 20 via an actuator, and its opening degree is electromagnetically controlled by the ECU 20.

  In the exhaust pipe 4, in order from the upstream side to the downstream side, a catalytic converter 11, a particulate matter collection device (hereinafter referred to as “DPF”) (Diesel Particulate Filter) 12 as a filtering means, and a NOx purification device 14. And are provided.

  The catalytic converter 11 is configured by supporting an oxidation catalyst made of platinum or the like on a carrier having a honeycomb structure, and promotes oxidation of hydrocarbons (HC) and carbon monoxide (CO) contained in exhaust gas and removes them. To do. As a result, the catalytic converter 11 reduces the amount of soot in the exhaust gas composed of hydrocarbons or the like. The catalyst supported by the catalytic converter 11 is not limited to the oxidation catalyst, and a three-way catalyst may be used.

  The DPF 12 includes a purification filter that collects particulates in the exhaust gas by filtering the exhaust gas flowing through the exhaust passage 4. More specifically, the DPF 12 collects particulates in the exhaust gas by depositing them on the surface of the purification filter and the holes inside the purification filter when the exhaust gas passes through the fine holes of the purification filter. As this purification filter, a wall flow type having a honeycomb structure is used. Moreover, as a constituent material of the purification filter, for example, ceramics such as silicon carbide (SiC) or a porous metal body is used. Here, noble metals such as platinum, palladium, and rhodium are substantially not supported on the inside and upstream surfaces of the purification filter.

  When the particulates are collected up to the limit of the soot collecting ability of the DPF 12, that is, the deposition limit, the pressure loss increases. Therefore, it is necessary to appropriately perform the DPF regeneration process for burning the accumulated particulates. This DPF regeneration process is performed by performing post injection to raise the temperature of the exhaust gas to the combustion temperature of soot that occupies the most of the components constituting the particulates. This post-injection is fuel injection performed in the exhaust process by the fuel injection valve of the engine 1.

  The NOx purification device 14 captures NOx in the exhaust when the air-fuel ratio of the exhaust discharged from the engine 1 is lean, and reduces the captured NOx when the air-fuel ratio of the exhaust is rich. Purifies NOx inside.

More specifically, the NOx purification device 14 is composed of platinum (Pt) acting as a catalyst, supported on an alumina (Al ₂ O ₃ ) carrier, ceria having NOx adsorption capability, and ammonia (NH _{3) in} exhaust gas. ) And zeolite having a function of holding ammonium ions (NH ₄ ⁺ ).

  When the amount of adsorbed ammonia in the NOx purifying device 14 decreases, the NOx purifying ability decreases. Therefore, in order to appropriately reduce NOx, a reducing agent is supplied to the NOx purifying device 14 (hereinafter referred to as “reduction”). . In this reduction, the reducing agent is reduced by making the air-fuel ratio of the air-fuel mixture in the combustion chamber richer than the stoichiometric air-fuel ratio by increasing the amount of fuel injected from the fuel injection valve and decreasing the amount of intake air by the throttle valve. The NOx purification device 14 is supplied. That is, by enriching the air-fuel ratio, the reducing agent concentration in the exhaust gas flowing into the NOx purification device 14 becomes higher than the oxygen concentration, and reduction is performed.

The NOx purification in the NOx purification device 14 will be described.
First, when the air-fuel ratio of the air-fuel mixture combusted in the engine 1 is set to be leaner than the stoichiometric air-fuel ratio, so-called lean burn operation is performed, the reducing agent concentration in the exhaust gas flowing into the NOx purification device 14 is lower than the oxygen concentration. Become. As a result, carbon monoxide (NO) and oxygen (O ₂ ) in the exhaust gas react with each other by the action of the catalyst and are adsorbed on the ceria as NO ₂ . Carbon monoxide (CO) that has not reacted with oxygen is also adsorbed by ceria.

Next, when reduction is performed to make the reducing agent concentration in the exhaust gas higher than the oxygen concentration, carbon monoxide (CO) in the exhaust gas reacts with water (H ₂ O), and carbon dioxide (CO ₂ ) and hydrogen (H ₂ ) is generated, and unit hydrogen (HC) in the exhaust gas reacts with water to generate hydrogen together with carbon monoxide (CO) and carbon dioxide (CO ₂ ). Furthermore, NOx (NO, NO ₂ ) adsorbed on NOx and ceria (and platinum) contained in the exhaust gas and the generated hydrogen react by the action of the catalyst, and ammonia (NH ₃ ) and water Is generated. Further, the ammonia generated here is adsorbed on the zeolite in the form of ammonium ions (NH ₄ ⁺ ).

Next, when lean burn operation is performed in which the air-fuel ratio is set to be leaner than the stoichiometric air-fuel ratio, and the reducing agent concentration in the exhaust gas flowing into the NOx purification device 14 is set to be lower than the oxygen concentration, NOx is adsorbed by ceria. Is done. Further, when ammonium ions are adsorbed on the zeolite, NOx and oxygen in the exhaust gas react with ammonia to generate nitrogen (N ₂ ) and water.

  Thus, according to the NOx purification device 14, ammonia generated during the supply of the reducing agent is adsorbed by the zeolite, and the ammonia adsorbed during the lean burn operation reacts with NOx, so that the NOx is efficiently purified. be able to.

  In the exhaust pipe 4, an SOx sensor 13 is provided between the DPF 12 and the NOx purification device 14. The SOx sensor 13 detects the SOx concentration of the exhaust gas flowing between the DPF 12 and the NOx purification device 14 in the exhaust pipe 4 and supplies a detection signal substantially proportional to the detected SOx concentration to the ECU 20.

  The ECU 20 shapes input signal waveforms from various sensors, corrects a voltage level to a predetermined level, converts an analog signal value into a digital signal value, and a central processing unit (hereinafter referred to as “a processing unit”). CPU ”). In addition, the ECU 20 includes a storage circuit that stores various calculation programs and calculation results executed by the CPU, and an output circuit that outputs a control signal to the fuel injection valve of the engine 1.

  The ECU 20 includes a plurality of control blocks that function according to the hardware configuration such as the input circuit, the CPU, the storage circuit, and the output circuit. Specifically, the ECU 20 includes a supply device control unit 21 that controls the additive supply device 16.

  The supply device control unit 21 controls the supply amount of the fuel additive of the additive supply device 16 according to the output from the SOx sensor 13. More specifically, the supply device control unit 21 includes a control map indicating the relationship between the SOx concentration between the DPF 12 and the NOx purification device 14 and the optimum supply amount of the fuel additive. Based on this, the supply amount of the fuel additive is controlled. Here, the optimal supply amount of the fuel additive is, for example, an optimal supply amount for reducing poisoning due to SOx of the NOx purification device 14, but is not limited thereto.

As described above in detail, according to the exhaust gas purification apparatus of the present embodiment, the fuel additive having the function of lowering the combustion temperature of soot in exhaust gas and collecting SOx in exhaust gas is It is supplied into the fuel before being injected into each cylinder. As a result, the consumption of fuel when the soot accumulated on the DPF 12 is burned and the DPF 12 is regenerated can be suppressed by reducing the soot combustion temperature. Further, thermal deterioration of the NOx purification device 14 provided downstream of the DPF 12 can be prevented.
Further, by supplying the fuel additive described above to the fuel and collecting SOx in the exhaust gas, SOx can be deposited together with soot by the DPF 12. Thereby, it is possible to prevent the NOx purification device 14 from being poisoned by SOx in the exhaust gas.
Thus, in order to reduce the combustion temperature of soot and prevent poisoning by SOx, it is only necessary to supply the fuel additive described above to the fuel. Therefore, according to the exhaust purification device of the present embodiment, the exhaust purification device does not increase in size or the exhaust pressure loss does not increase as compared with the case where the SOx trap material that absorbs SOx is provided in the exhaust passage 4. .

The fuel additive includes an alkali metal or an alkaline earth metal. By burning the fuel to which such a fuel additive is added in the engine 1, oxides and carbonates can be generated in the exhaust gas and can be deposited on the DPF 12. The oxides and carbonates deposited on the DPF 12 react with SOx in the exhaust gas, and change to sulfate to act as a trap material that captures SOx. Therefore, the SOx in the exhaust gas can be deposited on the DPF 12. it can. Further, the alkali metal or alkaline earth metal contained in the fuel additive reacts with SOx in the exhaust to produce a sulfate compound, thereby removing SOx in the exhaust.
Here, in particular, when the NOx purification device 14 includes a catalyst having a function of adsorbing NOx such as alkali metal, alkaline earth metal, ceria, zirconia, that is, a catalyst vulnerable to poisoning by SOx, It is possible to reduce the frequency of executing the process of desorbing SOx from such a catalyst, and the fuel consumption can be further improved.

  In addition, the soot generated by burning the fuel in the engine 1 is in a state of being closely intertwined with the alkali metal or alkaline earth metal contained in the fuel additive in the cylinder and the exhaust passage 4 of the engine 1, that is, Thus, a tight contact state is obtained, and thus the combustion temperature of the soot can be lowered.

Further, by providing the catalytic converter 11 including the oxidation catalyst on the upstream side of the DPF 12 in the exhaust passage 4, the catalytic converter 11 can burn soot and the amount of soot deposited on the DPF 12 can be reduced.
By the way, the soot discharged from the engine 1 is usually hardly burned by a three-way catalyst or an oxidation catalyst. However, when the fuel additive is added as described above, the generated soot is intimately intertwined with the alkali metal or alkaline earth metal and contacts the catalytic converter 11 in a tight contact state. In addition to this, since the alkali metal and the alkaline earth metal itself in the fuel additive are excellent in the soot combustibility, the soot can be combusted by such a catalytic converter 11. As a result, the amount of soot that accumulates on the DPF 12 can be reduced, the frequency of executing the regeneration process of the DPF 12 can be reduced, and fuel efficiency can be further improved.

  The supply amount of the fuel additive is adjusted so that the content of the alkali metal and the alkaline earth metal is 5 ppm or more and less than the saturation solubility in an ion mass ratio in a state where the fuel additive is supplied to the fuel. . Thereby, while preventing the fuel additive from being consumed unnecessarily, the effect of lowering the soot combustion temperature and the effect of collecting SOx can be achieved. Moreover, the influence which it has on the driving | running state of the engine 1 by adding a fuel additive to a fuel can also be minimized.

  Further, by providing the NOx purification device 14 that purifies NOx in the exhaust, NOx in the exhaust can be purified. In particular, by providing such a NOx purification device 14 on the downstream side of the DPF 12 in the exhaust passage 4, the NOx purification device 14 is prevented from being poisoned by SOx in the exhaust, and SOx is removed from the NOx purification device 14. The frequency of executing the desorption process can be reduced. Therefore, fuel efficiency can be improved and thermal deterioration of the NOx purification device 14 can be suppressed.

  Further, by using a catalyst that generates ammonia when the air-fuel ratio is rich and reduces NOx when it is lean for the NOx purification device 14, the SOx desorption temperature of the NOx purification device 14 can be lowered. Accordingly, it is possible to suppress the fuel consumption for executing the process of desorbing SOx from the NOx purification device 14 and further suppress the thermal deterioration of the NOx purification device 14.

  Also, noble metals such as platinum, palladium, and rhodium are not substantially supported on the inside and upstream surfaces of the purification filter of the DPF 12, that is, on the portion where soot and fuel additives are deposited when the exhaust gas is filtered. . When the soot accumulated on the purification filter is burned and the DPF 12 is regenerated, the SOx deposited on the purification filter as sulfide may be desorbed if the purification filter contains the above-mentioned noble metal. According to the exhaust gas purification apparatus of the present embodiment, there is no possibility of such poisoning due to SOx.

  Further, the supply amount of the fuel additive is controlled according to the SOx concentration between the DPF 12 detected by the SOx sensor 13 and the NOx purification device 14. Thereby, while preventing the fuel additive from being wasted, the effect of lowering the combustion temperature of the soot and the effect of collecting SOx can be achieved. Further, it is possible to prevent the NOx purification device 14 from being poisoned by SOx.

  In the present embodiment, the DPF 12 constitutes a filtering means, and the additive supply device 16 and the supply device control unit 21 of the ECU 20 constitute an additive supply means.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIG. The exhaust purification device of this embodiment differs from the exhaust purification device according to the first embodiment in the configuration of the DPF 12A.

FIG. 2 is a cross-sectional view of the purification filter 122 of the DPF 12A.
As shown in FIG. 2, the purification filter 122 has a honeycomb shape and includes a plurality of passages through which exhaust flows. Each passage has an upstream seal 123 that blocks exhaust from flowing into the passage from the upstream side, and a downstream seal 124 that blocks exhaust from flowing from the interior of the passage to the downstream side, respectively. It is provided alternately. Thereby, the inflow side cell 125 into which exhaust flows in and the outflow side cell 126 from which exhaust flows out are alternately formed.

  That is, the exhaust gas discharged from the engine 1 and flowing into the DPF 12A first flows into the inflow side cell 125, passes through the purification filter 122, flows into the outflow side cell 126, and flows out of the DPF 12A. Here, when the exhaust gas passes through the purification filter 122, particulates contained in the exhaust gas accumulate on the upstream surface of the purification filter 122 and the holes formed in the purification filter 122.

  On the other hand, a SOx trap material 127 having a function of absorbing SOx in the exhaust is provided on the downstream surface of the purification filter 122. By providing such a SOx trap material 127 in addition to the fuel additive for reducing the SOx amount as described above, the amount of SOx discharged can be further reduced, and the NOx purification device 14 provided on the downstream side of the DPF 12A. The poisoning by SOx can be prevented more effectively. Further, by providing such an SOx trap material 127 on the downstream surface of the purification filter of the DPF 12A, the exhaust purification device can be downsized as compared with the case where it is provided separately from the DPF 12A.

  Next, Examples 1 to 3 of the first embodiment of the present invention and Comparative Examples 1 to 3 to be compared with Examples 1 to 3 will be described.

[Example 1]
In Example 1, what supplied the fuel additive to the standard light oil so that content of calcium stearate and magnesium stearate might be 130 ppm and 60 ppm by ion mass ratio, respectively is used as fuel.
The DPF is a wall flow type made of SiC and having a pore diameter of 10.7 μm, a porosity of 42%, a cell density of 300 cpsi, and a wall thickness of 12 mm.

[Example 2]
In Example 2, what supplied the fuel additive to the standard light oil so that content of calcium stearate and magnesium stearate may be 65 ppm and 30 ppm by ion mass ratio, respectively is used as fuel.
The DPF is a wall flow type made of SiC and having a pore diameter of 10.7 μm, a porosity of 42%, a cell density of 300 cpsi, and a wall thickness of 12 mm.

[Example 3]
In Example 3, what supplied the fuel additive to the standard light oil so that content of calcium stearate and magnesium stearate might be 11 ppm and 5 ppm by ion mass ratio, respectively is used as fuel.
The DPF is a wall flow type made of SiC and having a pore diameter of 10.7 μm, a porosity of 42%, a cell density of 300 cpsi, and a wall thickness of 12 mm.

[Comparative Example 1]
In Comparative Example 1, standard light oil is used as the fuel. Unlike the above-described Examples 1 to 3, no fuel additive is added.
The DPF is a wall flow type made of SiC and having a pore diameter of 10.7 μm, a porosity of 42%, a cell density of 300 cpsi, and a wall thickness of 12 mm.

[Comparative Example 2]
In Comparative Example 2, standard light oil is used as the fuel. Unlike the above-described Examples 1 to 3, no fuel additive is added.
Further, the DPF is made of SiC, having a pore diameter of 10.7 μm, a porosity of 42%, a cell density of 300 cpsi, and a wall thickness of 12 mm and having an oxidation catalyst supported on a wall flow type made by Ibiden. Use. More specifically, the DPF has a purity of 99% dinitrodiamine platinic acid, a purity of 99% palladium nitrate, an alumina having a specific surface area of 130 m ² / g, and 10% by weight of the total amount of alumina. A solution prepared by adding alumina sol 520 manufactured by Chemical Industry Co., Ltd. was impregnated with the above-mentioned DPF manufactured by Ibiden Co., Ltd., and further obtained by baking at 550 ° C., with an alumina loading of 30 g / L and a platinum loading of 3.2 g / L and the amount of palladium supported are 1.8 g / L.

[Comparative Example 3]
In the comparative example 3, what added EOLYS176 by Rhodia to standard light oil so that a content metal content might be 12 ppm is used as a fuel.
The DPF is a wall flow type made of SiC and having a pore diameter of 10.7 μm, a porosity of 42%, a cell density of 300 cpsi, and a wall thickness of 12 mm.

  Next, Tests 1 to 3 for comparing the above Examples 1 to 3 and Comparative Examples 1 to 3 will be described with reference to FIGS.

[Test 1 (soot emissions test)]
Test 1 verifies the soot emission reduction effect of the catalytic converter (oxidation catalyst). More specifically, the engine is operated in a steady state, the particulates are collected from the exhaust gas that has passed through the oxidation catalyst, and the particle size distribution of the collected particulates is measured using a high-speed response fineness distribution meter (type DMS500). To measure.

FIG. 3 is a diagram showing the particle size distribution of the particulates that have passed through the oxidation catalyst, and shows the results of Test 1. FIG. In FIG. 3, the horizontal axis is the particle size of the particulates, and the vertical axis is the number of particles per unit volume.
As shown in FIG. 3, when the particle size is between about 60 nm and 120 nm, Examples 1 to 3 of the present invention have less particulate emissions, that is, soot emissions than Comparative Example 1. Yes.

FIG. 4 is a diagram showing the number of particles having a particle size of 87 nm among the particulates that have passed through the oxidation catalyst, and is a diagram showing the results of Test 1. FIG. In FIG. 4, the vertical axis represents the number of particles when the number of particles in Comparative Example 1 is 1.
As shown in FIG. 4, in Examples 1 to 3 of the present invention in which the fuel additive is added to the fuel, compared with Comparative Example 1 in which the fuel additive is not added, the particulate discharge amount, that is, the soot amount Emissions are low.

  As described above, as the result of Test 1 shows, by adding the fuel additive to the fuel as in the present invention, combustion of soot in the oxidation catalyst can be promoted, and soot emission can be reduced.

[Test 2 (soot combustion temperature test)]
Test 2 verifies the effect of reducing the soot combustion temperature by the DPF.
In this test, first, the engine is operated in a steady state, and the exhaust gas that has passed through the catalytic converter is filtered with a DPF to deposit 2 g / L of exhaust. Here, in Examples 1 to 3, since the fuel additive is added to the fuel, the emissions include combustion products of the fuel additive in addition to the soot.

Next, the DPF on which the discharge is accumulated is set in a test apparatus as shown in FIG. 5, and a combustion test of the soot accumulated on the DPF is performed. More specifically, while circulating the model gas through the exhaust passage at a predetermined linear velocity, the DPF is heated from room temperature to 690 ° C. at a rate of 20 ° C./min in the heating furnace, and CO generated by combustion of soot during this period The concentration of CO ₂ is measured with MEXA-7500D manufactured by Horiba. Here, a mixed gas containing 10% oxygen and 90% nitrogen is used as the model gas, and the linear velocity is 23000 m / h.

FIG. 6 is a diagram showing the combustion temperature of soot, and is a diagram showing the results of Test 2. In FIG. 6, the horizontal axis represents the temperature of the DPF, and the vertical axis represents the concentrations of CO and CO ₂ .
As shown in FIG. 6, in Comparative Examples 1 and 2 in which the fuel additive is not added to the fuel, there is a peak of CO and CO ₂ concentration when the DPF temperature is between about 660 ° C. and 680 ° C. That is, in these comparative examples 1 and 2, soot burns most efficiently at about 660 ° C to 680 ° C.

On the other hand, in Examples 1 to 3 in which the fuel additive is added to the fuel, there is a peak of CO and CO ₂ concentration when the temperature of the DPF is between about 520 ° C. and 580 ° C. Therefore, comparing Examples 1 to 3 with Comparative Examples 1 and 2, it can be said that Examples 1 to 3 of the present invention can efficiently burn soot at a lower temperature.
Here, in Comparative Example 3, there are peaks of CO and CO ₂ concentration when the temperature of the DPF is around 520 ° C. This is because the additive as described above is added to the fuel.

  As described above, as shown by the results of Test 2, the soot combustion temperature in the DPF can be reduced by adding the fuel additive to the fuel as in the present invention.

[Test 3 (SOx capture test)]
Test 3 verifies the SOx trapping effect of DPF.
In this test, first, as in Test 2, the engine is operated in a steady state, and the exhaust gas that has passed through the catalytic converter is filtered with DPF to deposit 10 g / L of exhaust.
Next, the DPF on which the effluent is accumulated is set in the test apparatus shown in FIG. More specifically, while the DPF is heated to about 550 ° C. in a heating furnace, the SOx concentration on the downstream side of the DPF is adjusted for 30 minutes while passing the model gas through the exhaust passage at a predetermined linear velocity. It measures by MEXA-6000FT made.
Here, the model gas includes N ₂ as a balance gas, SOx 30 ppm, O ₂ 6%, CO ₂ 6%, C ₃ H ₆ 500 ppm C, CO ₂ 900 ppm, H ₂ O 7% Use gas mixed in proportions. The linear velocity is 25000 m / h.

FIG. 7 is a diagram showing the results of Test 3, which is a diagram showing the collection rate of SOx by DPF. In FIG. 7, the horizontal axis represents time, and the vertical axis represents the SOx collection rate.
As shown in FIG. 7, in Comparative Examples 1 and 2 in which no fuel additive is added to the fuel, the SOx collection rate is about 0% from the start to the end of the measurement.

In contrast, in Examples 1 to 3 in which the fuel additive is added to the fuel, the SOx collection rate is maintained at about 100% from the start to the end of the measurement. Therefore, comparing Examples 1 to 3 and Comparative Examples 1 and 2, it can be said that Examples 1 to 3 of the present invention have a high ability to collect SOx by DPF.
Here, in Comparative Example 3, an SOx collection rate of about 5% to 15% is shown for about 10 minutes after the measurement is started. This can be said to be because the above-mentioned additive contains ceria.

  As described above, as the result of Test 3 shows, SOx in the exhaust gas can be collected by the DPF by adding the fuel additive to the fuel as in the present invention.

The present invention is not limited to the above-described embodiments and examples, and various modifications can be made.
In the above-described embodiment, the supply device control unit 21 adjusts the supply amount of the fuel additive based on the SOx concentration detected by the SOx sensor 13, but is not limited thereto. For example, a NOx sensor or an air-fuel ratio sensor may be provided downstream of the NOx purification device, and the amount of fuel additive supplied may be controlled based on the output of these sensors. In addition, the supply amount of the fuel additive may be controlled in accordance with the operating state of the engine 1, that is, the rotational speed, the torque number, the cumulative travel distance, and the like.

  In the above-described embodiment, the fuel additive is supplied to the fuel after the compound soluble in the fuel is mixed into the fuel additive containing the alkali metal or the alkaline earth metal. However, the present invention is not limited to this. . When the fuel additive is a water-soluble substance, the fuel additive may be dissolved in water and a surfactant may be added to form an emulsion, and then supplied to the fuel.

  Further, in the above-described embodiment, the fuel additive includes a compound composed of either alkali metal and alkaline earth metal or alkali metal and alkaline earth metal. Preferably it contains only earth metals. For example, even if the fuel additive contains an alkali metal, the above-described effects can be achieved. However, when the DPF carrier contains cordierite or silicon carbide, the alkali metal is supported during the regeneration process of the DPF. There is a risk of getting inside.

  In the second embodiment described above, the SOx trap material is provided on the downstream surface of the purification filter 122. However, the present invention is not limited to this, and an oxidation catalyst or a three-way catalyst may be provided as necessary.

  The present invention can also be applied to an exhaust emission control device such as a marine vessel propulsion engine such as an outboard motor having a vertical crankshaft.

1 is a diagram illustrating a configuration of an internal combustion engine and an exhaust purification device thereof according to a first embodiment of the present invention. It is sectional drawing of DPF which concerns on the 2nd Embodiment of this invention. It is a figure which shows distribution of the particle size of the particulates which passed the oxidation catalyst. It is a figure which shows the particle number with a particle size of 87 nm among the particulates which passed the oxidation catalyst. It is a figure which shows the structure of a test apparatus. It is a figure which shows the combustion temperature of soot. It is a figure which shows the collection rate of SOx by DPF.

Explanation of symbols

1 ... Internal combustion engine (internal combustion engine)
2 ... Intake pipe 4 ... Exhaust pipe (exhaust passage)
11 ... Catalytic converter 12 ... DPF (filtering means)
127 ... SOx trap material (SOx trap material)
13 ... SOx sensor (SOx sensor)
14 ... NOx purification device (NOx purification device)
16 ... Additive supply device (additive supply means)
20 ... Electronic control unit 21 ... Supply device controller (additive supply means)

Claims (10)

In the exhaust gas purification apparatus for an internal combustion engine, the exhaust gas filtering apparatus for filtering the exhaust gas discharged from the internal combustion engine and collecting the soot in the exhaust gas in the exhaust passage of the internal combustion engine,
Additive supply means for supplying a fuel additive for lowering the combustion temperature of soot in exhaust gas and collecting SOx in exhaust gas to fuel before being injected into the combustion chamber of the internal combustion engine. An exhaust purification device for an internal combustion engine.   2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the fuel additive includes a compound including at least one of an alkali metal and an alkaline earth metal.   The said additive supply means supplies the said fuel additive to a fuel so that content of an alkali metal and an alkaline earth metal may be 5 ppm or more and less than saturation solubility by ion mass ratio. 2. An exhaust gas purification apparatus for an internal combustion engine according to 1.   The exhaust purification device for an internal combustion engine according to claim 2 or 3, wherein a catalyst for reducing the amount of soot in the exhaust is provided upstream of the filtering means in the exhaust passage.   The exhaust purification device for an internal combustion engine according to claim 4, wherein the catalyst for reducing the amount of soot in the exhaust includes a three-way catalyst or an oxidation catalyst.   The exhaust purification device for an internal combustion engine according to any one of claims 1 to 5, wherein a NOx purification device for purifying NOx in the exhaust is provided downstream of the filtering means in the exhaust passage. .   The NOx purification device generates ammonia when the air-fuel ratio of exhaust gas is rich, holds the generated ammonia, and reduces NOx by the held ammonia when the air-fuel ratio of exhaust gas is lean The exhaust emission control device for an internal combustion engine according to claim 6, further comprising a catalyst. The filtering means includes a purification filter for filtering exhaust gas,
The exhaust purification device for an internal combustion engine according to any one of claims 1 to 7, wherein platinum, palladium, and rhodium are substantially not carried on the inside and upstream surfaces of the purification filter. .   The exhaust purification device of an internal combustion engine according to claim 8, wherein a SOx trap material having a function of absorbing SOx is provided on a downstream surface of the purification filter.   The additive supply means controls the supply amount of the fuel additive in accordance with the operating state of the internal combustion engine or the state of exhaust discharged from the internal combustion engine. 2. An exhaust gas purification apparatus for an internal combustion engine according to 1.

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