JP2009024528A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the emission performance during the drive with an oxygen-containing fuel or a mixed fuel containing the same. <P>SOLUTION: An exhaust emission control device comprises an exhaust main flow passage (a first exhaust emission passage 13, a second exhaust emission passage 14, a bypass passage 15, and a third exhaust emission passage 16) for allowing exhaust emission gas by the combustion of an oxygen-containing fuel, a first exhaust emission purifying catalyst 21 on the main exhaust emission flow passage, an exhaust emission sub flow passage (the first exhaust emission passage 13, the bypass passage 15, the second exhaust emission passage 14, and the third exhaust emission passage 16) for connecting the upstream side to the downstream side of the first exhaust emission purifying catalyst 21 in the exhaust emission main flow passage, a water adsorption means 31 for adsorbing water content in the exhaust emission gas on the exhaust emission sub flow passage, a second exhaust emission purifying catalyst 22 downstream of the water adsorption means 31 on the exhaust emission sub flow passage, and first and second flow passage changing valves 17, 18 for changing the flow passages of the exhaust emission gas so that the flow passage is changed to the exhaust emission sub flow passage side if the first and second exhaust emission purifying catalysts 21, 22 are not in an active state, then, changed to the exhaust emission main flow passage after the elapse of the predetermined time, and if the water adsorption means 31 reaches the temperature for dissociating water content, the exhaust emission flows at least through the exhaust emission sub flow passage. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust purification device that purifies harmful substances in exhaust gas discharged from a prime mover such as an internal combustion engine.

Generally, in the gas after combustion (exhaust gas) generated by the combustion operation of a prime mover such as an internal combustion engine, hydrocarbon (HC), unburned hydrocarbon (unburned HC), carbon monoxide (CO) And harmful substances such as nitrogen oxides (NOx). And it is not preferable to release the harmful substances to the atmosphere as they are for the reasons of the global environment and human health. Therefore, conventionally, such a prime mover is represented by a three-way catalyst for reducing or oxidizing such harmful substances into harmless water (H ₂ O), carbon dioxide (CO ₂ ), and nitrogen (N ₂ ). Exhaust gas purifying means is provided on the exhaust path through which the exhaust gas flows.

  For example, in Patent Document 1 below, an HC adsorbent made of zeolite is arranged between two exhaust gas purification catalysts (three-way catalyst) arranged in series, and the first stage exhaust gas purification catalyst is used at a low temperature. A technique is disclosed in which hydrocarbons that could not be purified are adsorbed by the HC adsorbent to prevent release to the atmosphere. Further, in the exhaust gas purification apparatus of Patent Document 1, when the exhaust gas purification catalyst reaches the catalyst activation temperature, the exhaust gas discharged from the first stage exhaust gas purification catalyst is directly flowed without flowing through the HC adsorbent. A bypass passage and a flow path switching valve are provided for flowing into the second stage exhaust gas purification catalyst.

  Further, Patent Document 2 below discloses a two-stage catalyst carrier provided in a catalyst case, a bypass passage connecting the upstream side of each catalyst carrier and the space between each catalyst carrier, And an unburned gas (hydrocarbon) adsorbent disposed on the exhaust gas purification apparatus. In this exhaust purification device of Patent Document 2, exhaust gas is allowed to flow only through the bypass passage at low temperatures to adsorb unburned gas of the unburned gas adsorbent, and the bypass passage is closed when the catalyst carrier reaches the catalyst activation temperature. Then exhaust gas flows to the catalyst carrier. At this time, in this exhaust purification device, a part of the exhaust gas leaks into the bypass passage through the leaking portion, so that the unburned gas adsorbed by the unburned gas adsorbent is desorbed and brought into an active state. It flows to a certain catalyst carrier and is purified.

Japanese Patent No. 2827546 Japanese Patent Laid-Open No. 2-17312 JP 2005-180222 A

  By the way, in recent years, in the automobile industry, various efforts have been made to cope with changes in the environment surrounding automobiles. For example, in the field of internal combustion engines, efforts have been made for so-called multi-fuel internal combustion engines that can be operated even with fuels having different fuel properties. A vehicle equipped with this kind of multi-fuel internal combustion engine is generally called a flexible fuel vehicle (FFV), and examples thereof include gasoline fuel, alcohol fuel (ethanol, methanol, butanol, etc.) or Some of these blended fuels are designed to improve environmental performance, such as the ability to operate and limit consumption of fossil fuels, such as gasoline fuel, where the limits of reserves continue to be sought. Are known. For example, Patent Document 3 discloses a multi-fuel internal combustion engine that is operated using an alcohol mixed fuel composed of gasoline fuel and alcohol fuel.

Normally, regardless of whether it is a single fuel or a mixed fuel, when it is operated using an oxygen-containing fuel such as an alcohol fuel, not only the harmful substances mentioned above but also water (specifically, Steam) is also generated. Furthermore, when the air-fuel ratio is temporarily increased even at a low temperature start or the like, the generated water and, for example, an unburned alcohol component are subjected to a steam reforming reaction (2CH ₃ OH + H ₂ O → 2CO ₂ + 4H ₂ O), so there will be more moisture in the exhaust gas than that produced by the combustion reaction. For this reason, when the catalyst carrier does not reach the catalyst activation temperature, such as when starting at a low temperature, the moisture prevents the catalyst bed temperature from rising, so that the activation of the catalyst carrier is delayed. In addition, when the prime mover is stopped in an environment where the outside air temperature is low, water vapor in the exhaust gas condenses on the inner wall surface of the exhaust passage, so that the condensed moisture increases the catalyst bed temperature at the next prime mover start. It will be a factor to further hinder. Even if the catalyst activation temperature is reached, if it is close to the lower limit temperature, the catalyst bed temperature may be lowered by the moisture, and the catalyst carrier may be removed from the active state. As described above, in a prime mover operating with an oxygen-containing fuel or a mixed fuel containing the oxygen-containing fuel, the generated moisture deteriorates the emission performance. In particular, alcohol fuels and alcohol blended fuels are poor in low-boiling components compared to gasoline fuels, and it is difficult to raise the catalyst bed temperature. Therefore, in the prime mover using alcohol fuels, the presence of generated water is a further catalyst. It becomes an inhibitory factor for the activation of the carrier.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an exhaust emission control device that improves the inconveniences of the conventional example and improves the emission performance when operating with an oxygen-containing fuel or a mixed fuel containing the same.

  In order to achieve the above object, according to the first aspect of the present invention, an exhaust main passage for flowing exhaust gas discharged from a prime mover by combustion of oxygen-containing fuel, and an exhaust main passage disposed on the exhaust main passage and flowing through the exhaust main passage. A first exhaust purification catalyst that purifies harmful components in the exhaust gas, an exhaust sub-flow path that connects the upstream side and the downstream side of the first exhaust purification catalyst in the exhaust main flow path, and the exhaust sub-flow path are disposed on the exhaust sub-flow path. Water adsorbing means for adsorbing moisture in the exhaust gas flowing through the exhaust sub-flow channel, and harmful gas in the exhaust gas flowing through the exhaust sub-flow channel disposed downstream of the water adsorbing means on the exhaust sub-flow channel If the second exhaust purification catalyst for purifying the components and the first and second exhaust purification catalysts are not in the active state, the flow path of the exhaust gas discharged from the prime mover is switched to the exhaust sub flow path side, and the exhaust gas is exhausted after a predetermined time has elapsed. Switch the gas flow path to the exhaust main flow path, After water suction means comprises a a flow path switching valve for switching the flow path of the exhaust gases to at least exhaust secondary flow channel if the moisture removable temperature flow exhaust gas.

  The exhaust emission control device according to claim 1 is configured to remove moisture in the exhaust gas when the first and second exhaust purification catalysts are not in an active state, that is, when the temperature of the exhaust gas is low, such as at a low temperature start. Adsorb to water adsorption means. Then, after that, the exhaust gas purification device switches the exhaust gas flow path to the exhaust main flow path to purify harmful substances when the first exhaust purification catalyst becomes active, and the first exhaust purification catalyst is still in the state. In the inactive state, the catalyst bed temperature is raised by the exhaust gas temperature. Further, after that, the exhaust gas purification device switches the flow path of the exhaust gas so that the exhaust gas flows through at least the exhaust sub-flow path when the water adsorbing means reaches a temperature at which moisture can be desorbed. For this reason, in this exhaust gas purification apparatus, the moisture is desorbed from the water adsorbing means to cause a water vapor reaction, and the hydrocarbon reaction and the carbon monoxide in the exhaust gas each cause an oxidation reaction by the water vapor reaction. Therefore, in this exhaust purification device, the temperature of the exhaust gas rises with the oxidation reaction, and the temperature rise efficiency of the catalyst bed temperature of the downstream second exhaust purification catalyst increases.

  In order to achieve the above object, according to the second aspect of the present invention, there is provided an exhaust main passage through which exhaust gas discharged from the prime mover due to combustion of oxygen-containing fuel flows, and the exhaust main passage disposed on the exhaust main passage. A first exhaust purification catalyst that purifies harmful components in the exhaust gas flowing through the exhaust gas, an exhaust sub-flow path that connects the upstream side and the downstream side of the first exhaust purification catalyst in the exhaust main flow path, and the exhaust sub-flow path disposed on the exhaust sub-flow path. An exhaust gas substance adsorbing means for adsorbing at least moisture and hydrocarbons or ammonia in the exhaust gas flowing through the exhaust sub flow path, and upstream of the exhaust gas substance adsorbing means on the exhaust sub flow path. And a second exhaust purification catalyst for purifying harmful components in the exhaust gas flowing through the exhaust sub-flow passage, and a lean disposed downstream of a connection point downstream of the exhaust main flow passage and the exhaust sub-flow passage. NOx catalyst and its first and second If the exhaust purification catalyst is not activated and the prime mover is executing rich spike control, the flow path of the exhaust gas discharged from the prime mover is switched to the exhaust sub-flow path side, and after a predetermined time has passed, the exhaust gas flow path becomes the main exhaust flow After that, if the exhaust gas substance adsorbing means reaches a temperature at which the adsorbed moisture and hydrocarbons or ammonia can be desorbed, at least the exhaust gas flows so that the exhaust gas flows through the exhaust sub-flow channel. A flow path switching valve for switching the flow path.

  The exhaust emission control device according to claim 2 is characterized in that at least moisture in the exhaust gas when the first and second exhaust purification catalysts are not in an active state (when the temperature of the exhaust gas is low, such as at a low temperature start). And hydrocarbon or ammonia are adsorbed by the substance adsorbing means in the exhaust gas. Then, after that, the exhaust gas purification device switches the exhaust gas flow path to the exhaust main flow path to purify harmful substances when the first exhaust purification catalyst becomes active, and the first exhaust purification catalyst is still in the state. In the inactive state, the catalyst bed temperature is raised by the exhaust gas temperature. Further, after that, the exhaust gas purification apparatus is configured so that when the exhaust gas substance adsorbing means reaches a temperature at which moisture and hydrocarbons or ammonia can be desorbed, at least the exhaust gas flows through the exhaust sub-flow path. Switch the flow path. For this reason, in this exhaust purification device, the water is desorbed from the substance adsorbing means in the exhaust gas and causes a water vapor reaction, and the hydrocarbon and carbon monoxide in the exhaust gas each cause an oxidation reaction by the water vapor reaction, Hydrocarbon or ammonia is also desorbed from the substance adsorbing means in the exhaust gas. Therefore, in this exhaust purification apparatus, even if the temperature of the original exhaust gas is low, the temperature of the exhaust gas rises due to the oxidation reaction, and hydrocarbon or ammonia flows into the downstream lean NOx catalyst together with this high temperature exhaust gas. To do. That is, in the lean NOx catalyst, the high-temperature exhaust gas and hydrocarbon or ammonia form a nitrogen oxide reducing atmosphere so that the stored nitrogen oxides can be reduced to harmless nitrogen. Become.

  When operated using an oxygen-containing fuel or a mixed fuel containing this, not only harmful substances but also moisture (water vapor) is generated in the exhaust gas. The exhaust purification apparatus according to the present invention uses the moisture. By making the steam reaction, the downstream second exhaust purification catalyst can be activated early. In addition, when the temperature of the exhaust gas is low, such as when starting at a low temperature, the exhaust gas cannot always be raised to a temperature at which the reducing atmosphere can be immediately created by rich spike control. However, the exhaust emission control device according to the present invention causes a water vapor reaction using moisture generated when an oxygen-containing fuel or a mixed fuel containing the oxygen-containing fuel or a mixed fuel containing the oxygen-containing fuel is used. As the exhaust gas temperature is raised by the oxidation reaction of the exhaust gas, and the reducing agent such as hydrocarbon is desorbed from the substance adsorbing means in the exhaust gas and put on the exhaust gas flow, the lean NOx catalyst disposed downstream is installed. A reducing atmosphere can be made efficiently. As described above, according to the exhaust emission control device of the present invention, it is possible to improve the emission performance when operating with oxygen-containing fuel or a mixed fuel containing the same.

  Embodiments of an exhaust emission control device according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the embodiments.

  A first embodiment of an exhaust emission control device according to the present invention will be described with reference to FIGS.

  First, the prime mover E to which the exhaust gas purification apparatus of the first embodiment is applied will be described. The prime mover E is an internal combustion engine that uses an oxygen-containing fuel such as an alcohol fuel alone or in combination, and does not always have to be operated using the oxygen-containing fuel. Anything that could be done is included. That is, the exhaust emission control device of the first embodiment is applied to the prime mover E in which water is generated by the combustion reaction of the oxygen-containing fuel and the water is present as water vapor in the exhaust gas.

  For example, as the prime mover E, different fuels such as an alcohol engine such as ethanol or an internal combustion engine operated with only one of a mixed fuel containing the same, a gasoline fuel, an alcohol fuel, or a mixed fuel thereof. A multi-fuel internal combustion engine mounted on a so-called flexible fuel vehicle that can be operated using any of the properties of fuel is conceivable. In the first embodiment, a V-type 6-cylinder multifuel internal combustion engine will be described as an example.

  First, as shown in FIG. 1, the exhaust purification system of the first embodiment includes first and second exhaust manifolds 11 and 12 arranged for each bank of the prime mover E, and the first and second exhausts. The first and second exhaust passages 13 and 14 connected to the manifolds 11 and 12 respectively, and the bypass passage 15 connecting the first and second exhaust passages 13 and 14 are provided. The bypass passage 15 connects the middle of each flow path of the first exhaust passage 13 and the second exhaust passage 14.

  Further, the exhaust purification device includes a first exhaust purification catalyst 21 connected to the downstream end of the first exhaust passage 13, a water adsorbing means 31 connected to the downstream end of the second exhaust passage 14, and the water adsorbing means 31. The second exhaust purification catalyst 22 disposed on the downstream side of the first exhaust gas is connected to the downstream ends of the first and second exhaust purification catalysts 21 and 22, and the exhaust gas discharged from each of them is collected together. A third exhaust passage 16 is provided. In addition, the downstream shown here shows the downstream in the flow direction of exhaust gas.

The first and second exhaust purification catalysts 21, 22 shown here are, for example, so-called three-way catalysts that purify harmful substances in the exhaust gas. Accordingly, in the first and second exhaust purification catalysts 21, 22, the hydrocarbon (HC), unburned hydrocarbon (unburned HC), carbon monoxide (CO), and nitrogen oxide (NOx) in the exhaust gas. ) And other harmful substances are reduced or oxidized to harmless water (H ₂ O), carbon dioxide (CO ₂ ), and nitrogen (N ₂ ).

  On the other hand, the water adsorbing means 31 described above adsorbs moisture (water vapor) in the exhaust gas generated in association with the combustion reaction of the oxygen-containing fuel. For example, as the water adsorbing means 31, a porous material capable of adsorbing water such as zeolite, activated carbon, and mesoporous silica can be used. The water adsorbing means 31 adsorbs moisture when the temperature of the exhaust gas is low, but desorbs the adsorbed moisture when the exhaust gas becomes high.

  Further, the exhaust purification device includes a third exhaust purification catalyst 23 connected to the downstream end of the third exhaust passage 16, and a fourth exhaust purification catalyst 24 disposed downstream of the third exhaust purification catalyst 23. , Is provided. For example, the third and fourth exhaust purification catalysts 23 and 24 are three-way catalysts if the prime mover E of the first embodiment operates mainly at the stoichiometric air fuel ratio, and the prime mover E has a lean air fuel ratio. If the operation is also performed, a so-called lean NOx catalyst is used. If all the harmful substances in the exhaust gas can be purified mainly by the theoretical air-fuel ratio operation and the upstream first and second exhaust purification catalysts 21 and 22 can be used as the three-way catalyst. The four exhaust purification catalysts 23 and 24 are not necessarily provided. In the first embodiment, since the prime mover E is exemplified as operating mainly at the stoichiometric air-fuel ratio and the lean air-fuel ratio, the third and fourth exhaust purification catalysts 23 and 24 are lean NOx catalysts.

  Here, in the exhaust purification device of the first embodiment, the first exhaust passage 13, the second exhaust passage 14, the bypass passage 15, the first exhaust purification catalyst 21, the third exhaust passage 16, the third exhaust purification catalyst 23, The flow path of the exhaust gas flowing through the fourth exhaust purification catalyst 24 is referred to as an exhaust main flow path (exhaust flow path A shown in FIG. 2), and the first exhaust passage 13, the bypass passage 15, the second exhaust passage 14, and the water adsorption means 31. The flow path of the exhaust gas flowing through the second exhaust purification catalyst 22, the third exhaust passage 16, the third exhaust purification catalyst 23, and the fourth exhaust purification catalyst 24 is referred to as an exhaust sub-flow path (exhaust flow path B shown in FIG. 3). . Further, in this exhaust purification device, the first exhaust passage 13, the first exhaust purification catalyst 21, the second exhaust passage 14, the water adsorbing means 31, the second exhaust purification catalyst 22, the third exhaust passage 16, the third exhaust purification. The flow path of the exhaust gas flowing through the catalyst 23 and the fourth exhaust purification catalyst 24 is referred to as an exhaust flow path C as shown in FIG.

  In the first embodiment, a flow path switching means is prepared to create the three exhaust flow paths A, B, and C. Specifically, in this exhaust gas purification apparatus, first and second flow path switching valves 17 and 18 are disposed in two flow paths upstream of the collecting portion in the third exhaust passage 16, respectively. That is, the first flow path switching valve 17 is disposed on the flow path downstream of the first exhaust purification catalyst 21 in the third exhaust passage 16 and upstream of the gathering portion of the third exhaust passage 16. The first flow path switching valve 17 is exemplified as one that fully opens or closes the flow path. On the other hand, the second flow path switching valve 18 is disposed on the flow path downstream of the second exhaust purification catalyst 22 in the third exhaust passage 16 and upstream of the collecting portion of the third exhaust passage 16. Here, the second flow path switching valve 18 is also exemplified as that which fully opens or closes the flow path.

  Here, the first and second flow path switching valves 17 and 18 are opened and closed according to an instruction from an electronic control unit (ECU) 41. The electronic control unit 41 is a CPU (Central Processing Unit) (not shown), a ROM (Read Only Memory) that stores in advance a predetermined control program necessary for the opening / closing operation, and temporarily stores calculation results of the CPU. A RAM (Random Access Memory), a backup RAM for storing information prepared in advance, and the like are included.

  The electronic control device 41 is configured to drive the first flow path switching valve 17 to open and to drive the second flow path switching valve 18 to close when the exhaust flow path A is selected. Thus, in this exhaust purification device, the first flow path switching valve 17 is fully opened and the second flow path switching valve 18 is fully closed, and the exhaust gas discharged from the prime mover E is discharged to the first exhaust passage 13. In addition, it flows into the first exhaust purification catalyst 21 through the second exhaust passage 14 and the bypass passage 15, and harmful substances in the exhaust gas are purified by the first exhaust purification catalyst 21. In this exhaust purification device, the exhaust gas after purification flows into the third exhaust purification catalyst 23 and the fourth exhaust purification catalyst 24 via the third exhaust passage 16, and these third and fourth exhaust purification catalysts. 23 and 24, the remaining harmful substances are purified.

  Therefore, in the case of the exhaust passage A, harmful substances in the exhaust gas cannot be purified unless at least the catalyst bed temperature of the first exhaust purification catalyst 21 reaches the activation temperature. Will be released. Therefore, in principle, the electronic control unit 41 of the first embodiment is made to select the exhaust passage A when the catalyst bed temperature of the first exhaust purification catalyst 21 reaches the activation temperature.

  The catalyst bed temperature may be detected directly from a temperature sensor (not shown) provided in the first exhaust purification catalyst 21 or may be estimated from the exhaust gas temperature or the cooling water temperature of the prime mover E. The temperature of the exhaust gas can be detected by providing an exhaust temperature sensor 51 in the exhaust manifolds 11 and 12 (here, the exhaust manifold 12). Further, the temperature of the cooling water can be detected by providing a water temperature sensor 52 in the cooling water passage of the prime mover E.

  In addition, when the exhaust passage B is selected, the electronic control device 41 is configured to drive the first passage switching valve 17 to close and to drive the second passage switching valve 18 to open. As a result, in this exhaust purification device, the first flow path switching valve 17 is fully closed and the second flow path switching valve 18 is fully opened, and the exhaust gas discharged from the prime mover E is discharged to the first exhaust passage 13. If the temperature of the exhaust gas is low, such as during cold start, the water adsorption means 31 adsorbs moisture in the exhaust gas through the bypass passage 15 and the second exhaust passage 14. Is done. In this exhaust purification device, the exhaust gas from which moisture has been removed flows into the second exhaust purification catalyst 22 and further to the third exhaust purification catalyst 23 and the fourth exhaust purification catalyst 24 via the third exhaust passage 16. And flows in.

  Therefore, when the temperature of the exhaust gas is low and the second exhaust purification catalyst 22 and the third and fourth exhaust purification catalysts 23 and 24 are not activated, the purification of harmful substances in the exhaust gas is satisfied. However, since moisture that prevents the temperature rise of the catalyst bed temperature is first adsorbed by the water adsorption means 31, the catalyst bed temperature of the second exhaust purification catalyst 22 and the like is quickly increased by the heat of the exhaust gas. Can be raised. That is, if the first exhaust purification catalyst 21 and the second exhaust purification catalyst 22 are not in the active state, the exhaust gas flow path B is selected, so that the toxic substance purification action in the second exhaust purification catalyst 22 and the like can be quickly started. It will help to raise. Therefore, in principle, the electronic control unit 41 of the first embodiment is made to select the exhaust passage B when the catalyst bed temperature of the first exhaust purification catalyst 21 has not reached the activation temperature.

  The selection of the exhaust passage B when the first exhaust purification catalyst 21 is in an inactive state is continued until the limit of the amount of moisture adsorbed by the water adsorbing means 31 is reached. If the first exhaust purification catalyst 21 has reached the activation temperature (in other words, the temperature of the exhaust gas has reached the desorption temperature of the moisture adsorbed by the water adsorption means 31) before Stop when a condition is met or after a predetermined time. For example, the predetermined condition may be when the second exhaust purification catalyst 22 reaches the activation temperature. Further, as the predetermined time, a time until the second exhaust purification catalyst 22 reaches the activation temperature (for example, an estimated time based on a past history or the like) can be considered.

  Note that there is a limit to the amount of moisture adsorbed by the water adsorbing means 31 (that is, there is a limit to the amount of exhaust gas from which moisture has been removed flowing into the second exhaust purification catalyst 22), and the exhaust gas. Since the temperature of the exhaust gas and the catalyst bed temperature of the second exhaust purification catalyst 22 also vary, the fact that the exhaust passage B is selected does not necessarily cause the second exhaust purification catalyst 22 to become active. .

  Here, since the high temperature moisture (water vapor) desorbed from the water adsorbing means 31 by the high temperature exhaust gas and the high temperature moisture (water vapor) generated by the combustion reaction cause a water vapor reaction, the water vapor reaction causes a reaction in the exhaust gas. The CO oxidation reaction and THC oxidation reaction for oxidizing and removing carbon monoxide and all hydrocarbons (THC) are promoted. At that time, the temperature of the exhaust gas is raised by the CO oxidation reaction or the like, so that the temperature rise efficiency of the catalyst bed temperature of the second exhaust purification catalyst 22 is increased, and the second exhaust purification catalyst 22 becomes early. Activation becomes possible. Further, if the water adsorbing means 31 remains adsorbed, the water adsorbing means 31 becomes inactive in the first exhaust purification catalyst 21 or the like even during operation due to a low temperature start-up or exhaust gas temperature drop. When this happens, moisture cannot be adsorbed and the second exhaust purification catalyst 22 cannot be activated early. Therefore, the electronic control unit 41 according to the first embodiment causes the exhaust passage B to be selected when the water adsorbing means 31 reaches the moisture desorption temperature in a state where the water adsorbing means 31 is adsorbing moisture. To.

  Further, the electronic control unit 41 is configured to drive both the first and second flow path switching valves 17 and 18 to be closed when the exhaust flow path C is selected. As a result, in the exhaust gas purification apparatus, both the first and second flow path switching valves 17 and 18 are fully opened, and the exhaust gas discharged from the prime mover E passes through the first exhaust passage 13 to be the first exhaust gas. While flowing into the purification catalyst 21, it flows into the water adsorption means 31 and the second exhaust purification catalyst 22 through the second exhaust passage 14.

  In principle, the electronic control unit 41 of the first embodiment is configured to select the exhaust passage C when the first exhaust purification catalyst 21 and the second exhaust purification catalyst 22 are in the active state. Thereby, when the exhaust passage C is selected, harmful substances in the exhaust gas are purified by the first exhaust purification catalyst 21 and the like. At this time, when the temperature of the exhaust gas is lowered, the water in the exhaust gas is adsorbed by the water adsorbing means 31, while the exhaust gas is at a high temperature (that is, the water adsorbing means 31 is at a moisture desorption temperature). In addition, when moisture is adsorbed, the moisture is desorbed from the water adsorption means 31. For this reason, the electronic control unit 41 may be made to select the exhaust passage C when desorbing moisture.

  Hereinafter, an example of the control operation for the exhaust emission control device according to the first embodiment will be described with reference to the flowchart of FIG.

  First, the electronic control unit 41 according to the first embodiment determines whether the fuel supplied to the combustion chamber of the prime mover E is an oxygen-containing fuel or a mixed fuel containing the oxygen-containing fuel, that is, whether an oxygen-containing fuel is used. (Step ST1).

Such determination is made, for example, because the theoretical air-fuel ratio differs between pure gasoline fuel and alcohol fuel or alcohol-mixed fuel, so that the required theoretical air-fuel ratio that the electronic control unit 41 has given an instruction to the motor E and the actual air-fuel ratio This can be done with reference to the deviation. The actual air-fuel ratio is derived from the detection value of an exhaust gas sensor (A / F sensor, O ₂ sensor, etc.) (not shown) provided in the exhaust path such as the exhaust manifolds 11 and 12. The determination may be performed by causing the driver to input the content that the oxygen-containing fuel has been supplied and sending the input information to the electronic control device 41 for holding.

  When it is determined that oxygen-containing fuel is used, the electronic control unit 41 next determines whether or not the first exhaust purification catalyst 21 and the second exhaust purification catalyst 22 are in an active state (step ST2). . For example, the case where it is determined that the engine is not in the active state here means that the idling state continues for a long time even when the prime mover E is cold-started or after the warm-up operation ends, and the temperature of the exhaust gas decreases. Cases can be considered.

  Such a determination can be made using, for example, information on the catalyst bed temperature of the first exhaust purification catalyst 21 detected or estimated as described above. This determination can also be made with reference to the temperature of the cooling water of the prime mover E detected from the water temperature sensor 52. For example, if the temperature is higher than a predetermined temperature, the first exhaust purification catalyst 21 is in an active state. Estimate that. Here, the predetermined temperature varies depending on the outside air temperature and the amount of water that can be adsorbed by the water adsorption means 31. Normally, the adsorbable amount of the water adsorbing means 31 mounted on the vehicle does not change, so this predetermined temperature is obtained by referring to map data prepared through experiments and simulations in advance, and the outside air temperature sensor shown in FIG. Each time it is changed according to the information of the outside air temperature detected at 53.

  If it is determined in step ST2 that the active state is not established, the electronic control unit 41 obtains a water adsorbable time (hereinafter referred to as “water vapor adsorbable time”) T1 to the water adsorbing means 31 (step ST3). .

  The water vapor adsorption possible time T1 is a time until an adsorbable amount of water is adsorbed in the water adsorbing means 31 in which no water is adsorbed. The adsorbable amount and the first exhaust purification catalyst 21 Estimated from catalyst bed temperature or exhaust gas temperature. Here, since the adsorbable amount is an invariable value unique to the water adsorbing means 31, the water vapor adsorbable time T1 can be estimated using only the catalyst bed temperature of the first exhaust purification catalyst 21 or the temperature of the exhaust gas. it can. For example, moisture (steam) generated by the combustion reaction is likely to cause a steam reaction as the catalyst bed temperature of the first exhaust purification catalyst 21 or the temperature of the exhaust gas becomes higher. Then, as the catalyst bed temperature of the first exhaust purification catalyst 21 or the temperature of the exhaust gas becomes higher, the CO oxidation reaction and the THC oxidation reaction are promoted, so that the moisture contained in the exhaust gas decreases. For this reason, here, as the catalyst bed temperature of the first exhaust purification catalyst 21 or the temperature of the exhaust gas is lower, a larger amount of moisture is present in the exhaust gas, so the water vapor adsorption possible time T1 becomes shorter. Further, the water vapor adsorption possible time T1 may be obtained based on the engine speed Ne of the prime mover E, the engine load KL, and the intake air amount.

  The electronic control device 41 of the first embodiment drives and controls the first and second flow path switching valves 17 and 18 so as to be the exhaust flow path B shown in FIG. 3 (step ST4). That is, here, the first flow path switching valve 17 is driven to close and the second flow path switching valve 18 is driven to open. As a result, the exhaust gas flows through the exhaust passage B, so that the moisture contained in the exhaust gas is adsorbed by the water adsorbing means 31, and the exhaust gas from which the moisture has been removed is downstream. 2 Flows through the exhaust purification catalyst 22. For this reason, the catalyst bed temperature of the second exhaust purification catalyst 22 rises without being hindered by the moisture.

  By the way, the first flow path switching valve 17 of the first embodiment is arranged downstream of the first exhaust purification catalyst 21. For this reason, the exhaust gas discharged from the prime mover E flows into the first exhaust purification catalyst 21 or the heat of the exhaust gas is transferred to the first exhaust purification catalyst 21. Can be raised. Therefore, the electronic control unit 41 of the first embodiment determines whether or not the first exhaust purification catalyst 21 is in an active state while the exhaust passage B is selected (step ST5).

  If it is determined here that the active state is established, the first exhaust purification catalyst 21 can purify the harmful substances in the exhaust gas, and therefore the electronic control unit 41 performs step ST7 described later. The process proceeds to switch to the exhaust passage A from the exhaust passage B.

  On the other hand, when it is determined that the active state is not established, the electronic control unit 41 determines whether or not the water adsorption time t of the water adsorption means 31 has passed the water vapor adsorption possible time T1. Perform (step ST6). For this reason, the electronic control device 41 according to the first embodiment starts the measurement of the adsorption time t when switching the flow path to the exhaust flow path B in step ST4.

  If it is determined that the adsorption time t has not passed the water vapor adsorption possible time T1, the electronic control unit 41 returns to step ST4 and continues the adsorption of moisture to the water adsorbing means 31.

  When the electronic control unit 41 determines that the water vapor adsorption possible time T1 has elapsed, the electronic control unit 41 drives and controls the first and second flow path switching valves 17 and 18 so that the exhaust flow path A shown in FIG. (Step ST7). That is, here, the first flow path switching valve 17 is driven to open and the second flow path switching valve 18 is driven to close. As a result, the exhaust gas flows through the exhaust passage A. Therefore, when the first exhaust purification catalyst 21 is in an active state, the first exhaust purification catalyst 21 causes harmful substances in the exhaust gas to flow. If the first exhaust purification catalyst 21 is not yet activated, the catalyst bed temperature of the first exhaust purification catalyst 21 is raised by the exhaust gas. At that time, the exhaust gas discharged from the prime mover E flows into the water adsorbing means 31 and the second exhaust purification catalyst 22, or the heat of the exhaust gas is transmitted to the water adsorbing means 31 and the second exhaust purification catalyst 22, so that the water The temperatures of the adsorption means 31 and the second exhaust purification catalyst 22 also rise.

  Subsequently, the electronic control unit 41 determines whether or not the water adsorption means 31 has reached a temperature at which the adsorbed moisture can be desorbed (hereinafter referred to as “water adsorption means desorption temperature”). Is determined (step ST8).

  Such a determination may be made by directly measuring the temperature of the water adsorbing means 31 or by substituting the temperature of the exhaust gas. Further, the determination may be made by estimating the water adsorption means desorption temperature from the engine load KL of the prime mover E. That is, when the engine load KL is a predetermined high load, it may be estimated that the water adsorbing means 31 has reached the water adsorbing means desorption temperature.

  If the water adsorbing means 31 has not reached the water adsorbing means desorption temperature, the electronic control unit 41 returns to step ST7 and maintains the state of the exhaust passage A.

  On the other hand, if the water adsorbing means 31 is at the water adsorbing means desorption temperature, the electronic control unit 41 at least causes the first and second flow path switching valves 17, so that the exhaust gas flows through the water adsorbing means 31. 18 is driven and controlled (step ST9). In the first embodiment, the first and second flow path switching valves 17 and 18 are controlled to be the exhaust flow path B shown in FIG. 3 or the exhaust flow path C shown in FIG.

  As a result, the moisture adsorbed by the water adsorbing means 31 is desorbed and a water vapor reaction is caused by the high-temperature exhaust gas, and the CO oxidation reaction and the THC oxidation reaction are promoted by the water vapor reaction. Carbon monoxide and all hydrocarbons are removed by oxidation, and the temperature of the exhaust gas is raised by the CO oxidation reaction or the like. Accordingly, here, the exhaust gas whose temperature has risen flows through the second exhaust purification catalyst 22, and the temperature rise efficiency of the catalyst bed temperature of the second exhaust purification catalyst 22 is increased. If the catalyst 22 is in an active state, the state is maintained. On the other hand, if the catalyst 22 is not in an active state, the temperature rises quickly so as to be in an active state.

  Next, the electronic control unit 41 determines whether or not all the water (water vapor) adsorbed by the water adsorbing means 31 has been desorbed (step ST10).

  Such determination can be made according to, for example, the temperature and flow rate of the exhaust gas and the amount of water that can be adsorbed by the water adsorbing means 31. However, since the amount of adsorption is unchanged, the temperature and flow rate of the exhaust gas are used as parameters. Execute using map data. The map data is obtained by setting the relationship between the exhaust gas temperature, the flow rate and the moisture desorption amount in advance through experiments and simulations. Here, the flow rate of the exhaust gas can be derived from the engine speed Ne, the engine load KL, and the intake air amount.

  If the electronic control unit 41 determines that all the moisture has not been desorbed, the electronic control unit 41 returns to step ST9 to select one of the exhaust flow path B and the exhaust flow path C. At that time, the electronic control device 41 may keep the previously set exhaust flow path B (or exhaust flow path C) as it is, and connect to the other exhaust flow path C (or exhaust flow path B). Switching may be performed.

  If it is determined in step ST10 that all moisture has been desorbed, or if it is determined in step ST1 that oxygen-containing fuel is not used, the first exhaust is determined in step ST2. When it is determined that the purification catalyst 21 and the second exhaust purification catalyst 22 are in the active state, the electronic control device 41 is one of the exhaust passage A, the exhaust passage B, and the exhaust passage C. In order to select one, drive control of the 1st and 2nd flow-path switching valves 17 and 18 is performed (step ST11). For example, when the prime mover E is operating at a high load and a high rotation speed, the exhaust gas flow rate is large and a large amount of harmful substances are contained. Therefore, the exhaust passage C is selected in order to effectively purify the exhaust gas. Thus, the two exhaust purification catalysts (first and second exhaust purification catalysts 21, 22) and the third and fourth exhaust purification catalysts 23, 24 downstream thereof are all used. Further, for example, the water adsorbing means 31 and the second exhaust purification catalyst 22 may become exhaust resistance and cause a decrease in the output of the prime mover E. Thus, the output of the prime mover E can be improved. On the other hand, if the exhaust gas does not pass through the second exhaust purification catalyst 22 for a long time, the catalyst bed temperature may be lowered and become inactive. As a result, the next time the exhaust passage B is selected, there is a possibility that the harmful substances cannot be purified and the emission performance is deteriorated. Therefore, in order to avoid such inconvenience, when the exhaust passage A is selected, it is preferable to switch to the exhaust passage B occasionally to maintain the active state of the second exhaust purification catalyst 22.

  As described above, when operating using an oxygen-containing fuel or a mixed fuel containing the same, not only harmful substances but also moisture (water vapor) is generated in the exhaust gas. If it is not in an active state, the moisture inhibits the temperature rise of the catalyst bed temperature of the exhaust purification catalyst and releases a large amount of harmful substances to the atmosphere. However, in the exhaust purification device of the first embodiment, the water is first adsorbed by the water adsorbing means 31, and the temperature of the second exhaust purification catalyst 22 disposed downstream thereof is increased. This exhaust purification device switches the exhaust flow path so as to pass the first exhaust purification catalyst 21 whose temperature is rising at the same time, and when the water adsorbing means 31 reaches the water adsorbing means desorption temperature described above. (In other words, the exhaust gas is allowed to pass through the water adsorbing means 31 again when the exhaust gas reaches a predetermined high temperature). For this reason, in this exhaust purification device, the water adsorbed by the water adsorbing means 31 causes a water vapor reaction by the high-temperature exhaust gas, and the CO oxidation reaction and the THC oxidation reaction are promoted. If the temperature becomes high and inactive, the second exhaust purification catalyst 22 is pulled up to the active state at once. As described above, according to the exhaust purification apparatus of the first embodiment, the activity of the exhaust purification catalyst is utilized using the moisture while eliminating the adverse effect of the moisture in the exhaust gas on the catalyst bed temperature of the exhaust purification catalyst. Therefore, the emission performance when operating with an oxygen-containing fuel or a mixed fuel containing the same can be improved.

  By the way, in the first embodiment, the first and second flow path switching valves 17 and 18 that are driven and controlled in the fully open state or the fully closed state are illustrated, but the first and second flow path switching valves 17 and 18 are illustrated. For 18, a valve opening angle (in other words, a desired exhaust gas flow rate) may be used. In this case, for example, when the exhaust passage C is selected, the opening angle of the first passage switching valve 17 is increased to reduce the exhaust resistance, and the temperature of the second exhaust purification catalyst 22 is prevented from being lowered. The valve opening angle of the second flow path switching valve 18 can be reduced so that a small amount of exhaust gas passes through.

  In the first embodiment, when the water adsorbing means 31 is at the water adsorbing means desorption temperature, the first and second flow path switching valves 17, 18 is driven and controlled. However, in the exhaust purification device of the first embodiment, the exhaust flow path B or the exhaust flow path C is selected even when there is a possibility of deteriorating the emission performance such as operation at a rich air-fuel ratio or high load operation, The water adsorbing means 31 may be desorbed. That is, when such emission performance deteriorates, carbon monoxide and hydrocarbons increase in the exhaust gas. Therefore, in that case, carbon monoxide and hydrocarbons are oxidized and purified by CO oxidation reaction and THC oxidation reaction accompanying the water vapor reaction of the water, and the second exhaust purification catalyst 22 (if the exhaust passage C is the first one). The exhaust purification catalyst 21) can also purify the remaining carbon monoxide and hydrocarbons.

  Next, a second embodiment of the exhaust emission control device according to the present invention will be described with reference to FIGS.

  In the second embodiment, an exhaust purification device for a prime mover E that operates mainly at a lean air-fuel ratio will be exemplified.

  The configuration of the exhaust purification apparatus of the second embodiment is obtained by replacing the positional relationship between the water adsorbing means 31 and the second exhaust purification catalyst 22 as shown in FIG. 6 with respect to the configuration of the first embodiment. Although not shown, in the second embodiment, the exhaust gas purifying apparatus is similar to the first embodiment in that the first and second flow path switching valves 17 and 18 are driven and controlled. It becomes the flow path B or the exhaust flow path C.

  Here, as the water adsorption means 31 of the second embodiment, the zeolite exemplified in the first embodiment is used. This zeolite adsorbs moisture in the exhaust gas as described in Example 1, but also adsorbs hydrocarbons and ammonia in the exhaust gas. For this reason, in the second embodiment, the water adsorbing means 31 is read as “exhaust gas substance adsorbing means 31”.

The third and fourth exhaust purification catalysts 23 and 24 of the second embodiment also use lean NOx catalysts as in the first embodiment. Here, NSR (NOx Storage Reduction) is applied as the lean NOx catalyst. To do. The NSR is a so-called NOx occlusion reduction in which a large amount of nitrogen oxides generated in a lean air-fuel ratio operation is occluded in the catalyst in the form of nitrates, and the nitrates are reduced to nitrogen (N ₂ ) in a reducing atmosphere. It is a type catalyst. In this NOx occlusion reduction type catalyst, a slight amount of NOx that has not been occluded during lean air-fuel ratio operation, and carbon monoxide and hydrocarbons in the exhaust gas are purified to nitrogen, water, and carbon dioxide by the oxidation-reduction action. .

  By the way, even if the prime mover E is operated mainly at a lean air-fuel ratio, for example, so-called rich spike control that operates at a rich air-fuel ratio at the time of cold start, medium load operation, or high load operation is performed. It is executed for the prime mover E. This is because when rich spike control is performed, the temperature of the exhaust gas becomes high, and carbon monoxide and carbonization as a reducing agent for the third and fourth exhaust purification catalysts 23 and 24 that are lean NOx catalysts. This is because the generation amount of hydrogen and ammonia increases, so that a reducing atmosphere of nitrogen oxides can be created.

  Hereinafter, the exhaust emission control device according to the second embodiment will be described together with an example of a control operation based on the flowchart of FIG. It should be noted that here, the control operation when the rich spike control is executed, that is, the control operation when the nitrogen oxides stored in the third and fourth exhaust purification catalysts 23 and 24 are reduced is referred to. explain.

  First, the electronic control unit 41 according to the second embodiment determines whether the fuel supplied to the combustion chamber of the prime mover E is an oxygen-containing fuel or a mixed fuel containing this, that is, whether an oxygen-containing fuel is used. This is performed in the same manner as Step ST1 in Example 1 (Step ST21).

  If it is determined here that oxygen-containing fuel is not used, the electronic control unit 41 once ends this control operation.

  Further, when it is determined that the oxygen-containing fuel is used, the electronic control unit 41 determines whether or not the first exhaust purification catalyst 21 and the second exhaust purification catalyst 22 are in an active state next to the first embodiment. This is performed in the same manner as step ST2 (step ST22).

  If it is determined in step ST22 that the electronic control unit 41 is in the active state, the electronic control unit 41 temporarily ends this control operation.

  Further, when it is determined that the electronic control device 41 is not in the active state in step ST22, the electronic control device 41 determines whether or not the rich spike control is being executed for the prime mover E (step ST23).

  When the electronic control device 41 determines that the rich spike control is not being executed, the electronic control device 41 temporarily ends the control operation.

  On the other hand, when it is determined that the rich spike control is being performed, the electronic control unit 41 can adsorb moisture, hydrocarbons, and ammonia to the substance adsorption means 31 in the exhaust gas (hereinafter referred to as “exhaust gas”). (Referred to as “intermediate substance adsorption time”) T2 is obtained (step ST24).

  The exhaust gas substance adsorbable time T2 is the time until the adsorbable amount is filled with moisture, hydrocarbons, or the like in the exhaust gas substance adsorbing means 31 in which no exhaust gas substance is adsorbed. It is estimated from the adsorbable amount and the catalyst bed temperature of the first exhaust purification catalyst 21 or the exhaust gas temperature. Specifically, similar to the water vapor adsorption possible time T1 of the first embodiment, the adsorbable amount is an invariable value unique to the exhaust gas substance adsorbing means 31, and therefore, the catalyst bed temperature of the first exhaust purification catalyst 21 or the exhaust gas. The time T2 during which the substance in the exhaust gas can be adsorbed is estimated using only the temperature of the gas. Here, the lower the catalyst bed temperature of the first exhaust purification catalyst 21 or the temperature of the exhaust gas, the more water is present in the exhaust gas, and more unburned fuel (that is, unburned hydrocarbons). Therefore, the substance adsorbable time T2 in the exhaust gas is shortened. Note that the substance adsorption possible time T2 in the exhaust gas may be obtained based on the engine speed Ne of the prime mover E, the engine load KL, and the intake air amount.

  Subsequently, the electronic control unit 41 of the second embodiment drives and controls the first and second flow path switching valves 17 and 18 so as to become the exhaust flow path B (step ST25). As a result, the exhaust gas flows through the exhaust passage B, and therefore, substances in the exhaust gas such as moisture, hydrocarbons, and ammonia contained in the exhaust gas are adsorbed by the substance adsorption means 31 in the exhaust gas. Is done. At that time, the exhaust gas passes through the upstream second exhaust purification catalyst 22, but the second exhaust purification catalyst 22 is not in an active state and cannot purify all hydrocarbons and ammonia in the exhaust gas. The substance adsorbing means 31 can adsorb the hydrocarbon and ammonia. Note that the catalyst bed temperatures of the first exhaust purification catalyst 21 and the second exhaust purification catalyst 22 are increased by the exhaust gas at that time.

  Next, the electronic control unit 41 determines whether or not the adsorption time t of the exhaust gas substance adsorbing means 31 of the exhaust gas substance adsorbing means 31 has passed the exhaust gas substance adsorption possible time T2 (step ST26). For this reason, the electronic control unit 41 of the second embodiment is caused to start measuring the adsorption time t when switching the flow path to the exhaust flow path B in step ST25.

  Here, when it is determined that the adsorption time t has not passed the exhaust gas substance adsorbable time T2, the electronic control unit 41 returns to step ST25 to supply moisture to the exhaust gas substance adsorbing means 31. Continue adsorption of hydrocarbons and ammonia.

  Further, when it is determined that the time T2 in which the exhaust gas substance can be adsorbed has elapsed, the electronic control unit 41 drives and controls the first and second flow path switching valves 17 and 18 so that the exhaust flow path A is obtained. (Step ST27). As a result, the exhaust gas flows through the exhaust passage A. Therefore, when the first exhaust purification catalyst 21 is in an active state, the first exhaust purification catalyst 21 causes harmful substances in the exhaust gas to flow. If the first exhaust purification catalyst 21 is not yet activated, the catalyst bed temperature of the first exhaust purification catalyst 21 is raised by the exhaust gas.

  Subsequently, the electronic control device 41 has a temperature in the exhaust gas at which the adsorbed moisture, hydrocarbons and ammonia can be desorbed (hereinafter referred to as “exhaust gas substance adsorbing means desorption temperature”). It is determined whether or not the substance adsorbing means 31 has reached (step ST28).

  Such determination may be performed by directly measuring the temperature of the substance adsorbing means 31 in the exhaust gas, or may be substituted by the temperature of the exhaust gas. Further, the determination may be made by estimating the exhaust gas substance adsorbing means desorption temperature from the engine load KL of the prime mover E. That is, when the engine load KL is equal to or higher than a predetermined medium load, at least hydrocarbons and ammonia can be desorbed, so that the exhaust gas substance adsorbing means 31 is desorbed by the exhaust gas substance adsorbing means. It may be estimated that

  If the exhaust gas substance adsorbing means 31 is not at the exhaust gas substance adsorbing means desorption temperature, the electronic control unit 41 returns to step ST27 and maintains the state of the exhaust passage A.

  On the other hand, if the exhaust gas substance adsorbing means 31 is at the exhaust gas substance adsorbing means desorption temperature, the electronic control unit 41 causes the first and The second flow path switching valves 17 and 18 are driven and controlled (step ST29). Here, the first and second flow path switching valves 17 and 18 are driven and controlled to become the exhaust flow path B.

  Thereby, here, the moisture adsorbed by the substance adsorbing means 31 in the exhaust gas is desorbed and a water vapor reaction is caused by the high temperature exhaust gas, and the CO oxidation reaction and the THC oxidation reaction are promoted by the water vapor reaction. Carbon monoxide and all hydrocarbons in the gas are oxidized and removed, and the temperature of the exhaust gas is raised by the CO oxidation reaction or the like. Here, the hydrocarbons and ammonia adsorbed by the substance adsorbing means 31 in the exhaust gas are desorbed and the third and fourth exhaust purification catalysts 23 downstream along with the high-temperature exhaust gas whose temperature has risen due to the CO oxidation reaction or the like. , 24. Further, hydrocarbons and ammonia that are generated by the rich spike operation and are not purified by the upstream second exhaust purification catalyst 22 also flow into the third and fourth exhaust purification catalysts 23 and 24. That is, here, a reducing atmosphere of nitrogen oxides is created in the third and fourth exhaust purification catalysts 23 and 24 which are lean NOx catalysts. Therefore, the nitrogen oxides stored in the third and fourth exhaust purification catalysts 23, 24 are reduced to harmless nitrogen using the hydrocarbons and ammonia as a reducing agent. For this reason, the exhaust gas substance adsorbing means 31 of the second embodiment may be configured to be capable of adsorbing at least moisture and hydrocarbons or ammonia in the exhaust gas.

  Here, some of the hydrocarbons desorbed from the substance adsorbing means 31 in the exhaust gas may be oxidized and purified by the CO oxidation reaction, so that the temperature of the exhaust gas (in other words, the magnitude of the engine load KL) is increased. However, ammonia acts as a main reducing agent in the third and fourth exhaust purification catalysts 23 and 24.

  Next, the electronic control unit 41 determines whether or not all the exhaust gas substances adsorbed by the exhaust gas substance adsorbing means 31 have been desorbed (step ST30).

  Such a determination can be made according to, for example, the temperature and flow rate of the exhaust gas, and the amount of the substance in the exhaust gas that can be adsorbed by the exhaust gas substance adsorbing means 31. And using map data with flow rate as a parameter. The map data is set in advance by conducting experiments and simulations to determine the relationship between the temperature and flow rate of the exhaust gas and the amount of desorption of each substance in the exhaust gas.

  If the electronic control unit 41 determines that all the exhaust gas substances have not been desorbed, the electronic control unit 41 returns to step ST29 and maintains the state of the exhaust flow path B.

  In addition, when it is determined in step ST30 that all the exhaust gas substances have been desorbed, the electronic control unit 41 stops the rich spike control for the prime mover E and ends this control operation. (Step ST31).

  As described above, when the temperature of the exhaust gas is low, such as when starting at a low temperature, the exhaust gas can be raised to a temperature at which the reducing atmosphere can be immediately created simply because the rich spike control is performed. There is a possibility that hydrocarbons and ammonia desorbed from the exhaust gas substance adsorbing means 31 may be released to the atmosphere. However, the exhaust gas purification apparatus of the second embodiment causes a water vapor reaction using moisture generated when an oxygen-containing fuel or a mixed fuel containing the oxygen-containing fuel or a mixed fuel containing the oxygen-containing fuel is used. Since the temperature of the exhaust gas is raised by reaction or the like, and the reducing agent such as hydrocarbon is desorbed from the exhaust gas substance adsorbing means 31 and is put on the flow of the exhaust gas, the lean NOx catalyst arranged downstream thereof The third and fourth exhaust purification catalysts 23, 24 can be efficiently put into a reducing atmosphere. Therefore, in this exhaust purification device, hydrocarbons and ammonia adsorbed on the exhaust gas substance adsorbing means 31 are desorbed to become reducing agents, and the nitrogen oxides of the third and fourth exhaust purification catalysts 23, 24 are removed. It can be reduced to nitrogen. As described above, according to the exhaust gas purification apparatus of the first embodiment, it is possible to effectively use the moisture generated when oxygen-containing fuel or a mixed fuel containing the oxygen-containing fuel is used, and to improve the emission performance at that time. .

  As described above, the exhaust emission control device according to the present invention is useful for a technique for improving the emission performance when operating with an oxygen-containing fuel or a mixed fuel containing the oxygen-containing fuel.

It is a figure shown about the structure of Example 1 of the exhaust gas purification apparatus which concerns on this invention. FIG. 6 is a diagram illustrating a route of an exhaust passage A. FIG. 6 is a diagram illustrating a route of an exhaust passage B. FIG. 5 is a diagram illustrating a route of an exhaust passage C. 3 is a flowchart for explaining a control operation of the exhaust gas purification apparatus according to the first embodiment. It is a figure shown about the structure of Example 2 of the exhaust gas purification apparatus which concerns on this invention. 6 is a flowchart illustrating a control operation during rich spike control in the exhaust purification system of the second embodiment.

Explanation of symbols

11 First exhaust manifold 12 Second exhaust manifold 13 First exhaust passage 14 Second exhaust passage 15 Bypass passage 16 Third exhaust passage 17 First flow path switching valve 18 Second flow path switching valve 21 First exhaust purification catalyst 22 First 2 Exhaust purification catalyst 23 Third exhaust purification catalyst 24 Fourth exhaust purification catalyst 31 Water adsorption means (exhaust gas substance adsorption means)
41 Electronic control device 51 Exhaust temperature sensor 52 Water temperature sensor 53 Outside air temperature sensor E Motor

Claims (2)

  An exhaust main flow path for flowing exhaust gas discharged from the prime mover by combustion of oxygen-containing fuel, and a first exhaust purification catalyst that is disposed on the exhaust main flow path and purifies harmful components in the exhaust gas flowing through the exhaust main flow path An exhaust sub-flow path connecting the upstream side and the downstream side of the first exhaust purification catalyst in the exhaust main flow path, and the exhaust gas in the exhaust gas disposed on the exhaust sub-flow path and flowing through the exhaust sub-flow path A water adsorbing means for adsorbing moisture, and a second exhaust purification catalyst that is disposed downstream of the water adsorbing means on the exhaust sub-flow path and purifies harmful components in the exhaust gas flowing through the exhaust sub-flow path; If the first and second exhaust purification catalysts are not in an active state, the exhaust gas flow path discharged from the prime mover is switched to the exhaust sub-flow path side, and the exhaust gas flow path is exhausted after a predetermined time has elapsed. Switch to the main channel, then the water An exhaust gas purification device comprising: a flow path switching valve that switches a flow path of the exhaust gas so that the exhaust gas flows through the exhaust sub-flow path when the attaching means reaches a temperature at which moisture can be desorbed. apparatus.   An exhaust main flow path for flowing exhaust gas discharged from the prime mover by combustion of oxygen-containing fuel, and a first exhaust purification catalyst that is disposed on the exhaust main flow path and purifies harmful components in the exhaust gas flowing through the exhaust main flow path An exhaust sub-flow path connecting the upstream side and the downstream side of the first exhaust purification catalyst in the exhaust main flow path, and the exhaust gas in the exhaust gas disposed on the exhaust sub-flow path and flowing through the exhaust sub-flow path Exhaust gas substance adsorbing means that adsorbs at least moisture and hydrocarbons or ammonia, and the exhaust gas disposed upstream of the exhaust gas substance adsorbing means on the exhaust sub-flow path and flowing through the exhaust sub-flow path A second exhaust purification catalyst for purifying harmful components therein, a lean NOx catalyst disposed downstream of a connection point on the downstream side of the exhaust main flow path and the exhaust sub-flow path, and the first and second The exhaust purification catalyst is not active and If the prime mover is executing rich spike control, the flow path of the exhaust gas discharged from the prime mover is switched to the exhaust sub-flow path side, and after a predetermined time has elapsed, the flow path of the exhaust gas is switched to the exhaust main flow path, After that, if the exhaust gas substance adsorbing means reaches a temperature at which the adsorbed moisture and hydrocarbons or ammonia can be desorbed, the exhaust gas flow path so that the exhaust gas flows at least through the exhaust sub flow path An exhaust gas purification apparatus comprising: a flow path switching valve for switching between.

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