JP2008261255A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To excellently reduce exhaust emissions in a cold start, in an internal combustion engine for receiving supply of alcohol fuel and gasoline fuel, in an exhaust emission control device of the internal combustion engine. <P>SOLUTION: This internal combustion engine 10 receives supply of the gasoline fuel and the alcohol fuel, and has a main exhaust passage 14, a first bypass passage 20 and a second bypass passage 22 bypassing the main exhaust passage 14, and has an exhaust switching valve 26 capable of switching an inflow destination of exhaust gas to any of the main exhaust passages 14, the first bypass passage 20 and the second bypass passage 22. The first bypass passage 20 is provided with a first adsorbent unit 30 suitable for adsorbing a predetermined component included in the exhaust gas when using low alcohol concentration fuel. The second bypass passage 22 is provided with a second adsorbent unit 40 suitable for adsorbing the predetermined component included in the exhaust gas when using high alcohol concentration fuel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly, to an exhaust gas purification apparatus suitable for suppressing emission of HC and NOx when an internal combustion engine receiving supply of gasoline fuel and alcohol fuel is in a cold state.

  Conventionally, for example, Patent Document 1 discloses an internal combustion engine that uses alcohol as a fuel, and an internal combustion engine that includes an adsorbent that adsorbs an unburned component (HC) contained in exhaust gas in a bypass passage upstream of an exhaust purification catalyst. An exhaust emission control device for an engine is disclosed. In this conventional exhaust purification device, HC flowing in the exhaust passage is adsorbed by the adsorbent before the exhaust purification catalyst is activated. After the exhaust purification catalyst is activated, the HC adsorbed on the adsorbent is desorbed from the adsorbent and purified by the exhaust purification catalyst.

  For example, Patent Document 2 discloses an automobile exhaust gas purification system including an HC adsorption catalyst that adsorbs HC and a NOx adsorption catalyst that adsorbs NOx on the upstream side of the exhaust purification catalyst. In this conventional purification system, the exhaust gas before the exhaust purification catalyst is activated is adsorbed by the HC adsorption catalyst and the NOx adsorption catalyst. After the exhaust purification catalyst is activated, HC and NOx adsorbed on the HC adsorption catalyst and NOx adsorption catalyst are desorbed from these adsorption catalysts and purified by the exhaust purification catalyst.

JP-A-6-93848 JP-A-2005-299631

  By the way, characteristics of exhaust gas components differ between alcohol fuel and gasoline fuel. However, in the above conventional technology, no consideration is given to the difference in the characteristics of the exhaust gas components caused by the difference in the fuel used. In this regard, the conventional technique described above still leaves room for improvement in appropriately reducing exhaust emission even when a fuel with a high alcohol concentration is used.

  The present invention has been made in order to solve the above-described problems. An internal combustion engine exhaust purification apparatus capable of satisfactorily reducing exhaust emissions during cold operation in an internal combustion engine that is supplied with alcohol fuel and gasoline fuel. The purpose is to provide.

1st invention is provided in the exhaust passage of the internal combustion engine which receives supply of gasoline fuel and alcohol fuel, adsorb | sucking means which adsorb | sucks the predetermined component contained in exhaust gas, and the said exhaust_gas | exhaustion downstream from the said adsorbing means An exhaust gas purification apparatus for an internal combustion engine, comprising a purification catalyst that is provided in a passage and purifies the predetermined component,
The adsorption means includes a moisture adsorption means for adsorbing a water component contained in exhaust gas, and an HC adsorption means for adsorbing an HC component contained in exhaust gas,
The moisture adsorbing means includes a moisture adsorbing material having a capacity larger than that of a water adsorbing material used in an internal combustion engine having the same displacement with only gasoline fuel as fuel,
The HC adsorbing means includes an HC adsorbent for low alcohol concentration fuel and an HC adsorbent for high alcohol concentration fuel as HC adsorbents having different adsorption characteristics.

  In a second aspect based on the first aspect, the HC adsorbent for low alcohol concentration fuel is an HC adsorbent suitable for adsorbing relatively high-grade HC components, and the HC adsorption for high alcohol concentration fuel. The material is characterized in that it is an HC adsorbent suitable for adsorbing a lower HC component than an HC component adsorbed by the low alcohol concentration fuel HC adsorbent.

The third invention is the first or second invention, wherein the exhaust passage includes a main exhaust passage through which exhaust gas discharged from the internal combustion engine flows, and a bypass passage that bypasses the main exhaust passage,
The exhaust gas purification apparatus for an internal combustion engine further includes flow path switching means capable of switching an inflow destination of exhaust gas between the main exhaust passage and the bypass path, and control means for controlling the flow path switching means. ,
The adsorption means is disposed in the bypass passage.

Further, in a fourth aspect based on the third aspect, the alcohol concentration acquisition means for acquiring the alcohol concentration in the fuel,
The apparatus further comprises period setting means for setting an inflow period of the exhaust gas to the adsorption means according to the acquired alcohol concentration.

The fifth invention provides a main exhaust passage through which exhaust gas discharged from an internal combustion engine that receives supply of gasoline fuel and alcohol fuel flows,
A first bypass passage that bypasses the main exhaust passage;
A second bypass passage that bypasses the main exhaust passage;
A flow path switching means capable of switching an inflow destination of the exhaust gas to any of the main exhaust passage, the first bypass passage, and the second bypass passage;
An adsorbing means for low alcohol concentration fuel, which is disposed in the first bypass passage and is suitable for adsorbing a predetermined component contained in exhaust gas when low alcohol concentration fuel is used;
An adsorbing means for high alcohol concentration fuel, which is disposed in the second bypass passage and is suitable for adsorbing a predetermined component contained in exhaust gas when high alcohol concentration fuel is used;
Alcohol concentration acquisition means for acquiring the alcohol concentration in the fuel;
Control means for controlling the flow path switching means according to the acquired alcohol concentration;
It is characterized by providing.

Further, a sixth invention is the fifth invention, wherein the low alcohol concentration fuel adsorbing means includes a low alcohol concentration fuel moisture adsorbing material that adsorbs a water component contained in the exhaust gas,
The high alcohol concentration fuel adsorbing means includes a water adsorbent for high alcohol concentration fuel that adsorbs a water component contained in exhaust gas,
The capacity of the moisture adsorbent for high alcohol concentration fuel is larger than the capacity of the moisture adsorbent for low alcohol concentration fuel.

The seventh invention is the fifth or sixth invention, wherein the low alcohol concentration fuel adsorbing means includes an HC adsorbent for low alcohol concentration fuel that adsorbs an HC component contained in exhaust gas,
The high alcohol concentration fuel adsorbing means includes an HC adsorbent for high alcohol concentration fuel that adsorbs an HC component contained in exhaust gas,
The HC adsorbent for low alcohol concentration fuel and the HC adsorbent for high alcohol concentration fuel have different adsorption characteristics.

  The eighth invention is the seventh invention, wherein the HC adsorbent for low alcohol concentration fuel is an HC adsorbent suitable for adsorbing a relatively high-grade HC component, and the HC adsorption material for high alcohol concentration fuel. The material is characterized in that it is an HC adsorbent suitable for adsorbing a lower HC component than an HC component adsorbed by the low alcohol concentration fuel HC adsorbent.

In a ninth aspect based on any one of the fifth to eighth aspects, the low alcohol concentration fuel adsorbing means includes a low alcohol concentration fuel NOx adsorbent that adsorbs NOx components contained in the exhaust gas. Including
The high alcohol concentration fuel adsorbing means includes a NOx adsorbent for high alcohol concentration fuel that adsorbs a NOx component contained in exhaust gas,
The capacity of the NOx adsorbent for high alcohol concentration fuel is smaller than the capacity of the NOx adsorbent for low alcohol concentration fuel.

  According to a tenth aspect of the present invention, in any one of the fifth to ninth aspects, exhaust to the high alcohol concentration fuel adsorbing means and / or the low alcohol concentration fuel adsorbing means according to the acquired alcohol concentration. It further comprises period setting means for setting a gas inflow period.

  According to the first invention, even when a high alcohol concentration fuel is used, moisture that inhibits adsorption of a predetermined component of the exhaust gas to the adsorption means other than the moisture adsorption means is present in the other adsorption means. It is possible to reliably prevent the inflow, and thus it is possible to satisfactorily reduce exhaust emission during cold start. Further, according to the present invention, it is possible to satisfactorily prevent the HC component from being released into the atmosphere during cold start regardless of the alcohol concentration in the fuel.

  According to the second aspect of the present invention, when a low alcohol concentration fuel is used, the HC component atmosphere at the time of cold start is obtained by the low alcohol concentration fuel HC adsorbent suitable for adsorption of a relatively high grade HC component. The release into the inside can be satisfactorily suppressed. In addition, when a high alcohol concentration fuel is used, the low alcohol concentration fuel HC adsorbent, which is suitable for adsorption of HC components lower than the HC component adsorbed by the low alcohol concentration fuel HC adsorbent, It is possible to satisfactorily suppress the release of HC components into the atmosphere at the time of starting.

  According to the third aspect, since the adsorbing means is arranged in the bypass passage, the purge operation can be performed at an arbitrary timing.

  According to the fourth aspect of the invention, it is possible to appropriately set the adsorption execution period regardless of the alcohol concentration in the fuel.

  According to the fifth invention, according to the alcohol concentration in the fuel, the adsorption means suitable for the alcohol concentration at that time is selected from the adsorption means for the low alcohol concentration fuel and the adsorption means for the high alcohol concentration fuel. Is possible.

  According to the sixth aspect of the invention, even when a high alcohol concentration fuel is used, moisture that inhibits adsorption of a predetermined component of the exhaust gas to the adsorption means other than the moisture adsorption means is present in the other adsorption means. It is possible to reliably prevent the inflow, and thus it is possible to satisfactorily reduce exhaust emission during cold start.

  According to the seventh aspect of the invention, it is possible to satisfactorily prevent the HC component from being released into the atmosphere at the time of cold start regardless of the alcohol concentration in the fuel.

  According to the eighth aspect of the present invention, when a low alcohol concentration fuel is used, the HC component atmosphere at the time of cold start is achieved by the low alcohol concentration fuel HC adsorbent suitable for adsorption of a relatively high-grade HC component. The release into the inside can be satisfactorily suppressed. In addition, when a high alcohol concentration fuel is used, the low alcohol concentration fuel HC adsorbent, which is suitable for adsorption of HC components lower than the HC component adsorbed by the low alcohol concentration fuel HC adsorbent, It is possible to satisfactorily suppress the release of HC components into the atmosphere at the time of starting.

  According to the ninth aspect of the invention, the capacity of the NOx adsorbent for high alcohol concentration fuel is set to a size suitable for the NOx emission amount when the fuel having a high ethanol concentration is used. For this reason, it is possible to efficiently purge NOx from the NOx adsorbent while ensuring adequate NOx adsorption capability at the time of cold start in which fuel with a high ethanol concentration is used.

  According to the tenth aspect, it is possible to appropriately set the adsorption execution period regardless of the alcohol concentration in the fuel.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a configuration of an internal combustion engine system including an exhaust purification device according to Embodiment 1 of the present invention. An internal combustion engine 10 shown in FIG. 1 includes an intake passage 12 for taking air into the cylinder and an exhaust passage through which exhaust gas discharged from the cylinder flows.

  The exhaust passage of the present embodiment includes a main exhaust passage 14 for discharging exhaust gas from the cylinder, and a first bypass passage 20 and a second bypass passage 22 which will be described later. A pre-stage catalyst (SC) 16 and an underfloor catalyst (UF) 18 capable of purifying exhaust gas are arranged in series in the main exhaust passage 14 in order from the upstream side.

  The system of the present embodiment includes a first bypass passage 20 and a second bypass passage 22 as passages that bypass the main exhaust passage 14. The first bypass passage 20 branches from the main exhaust passage 14 at the upstream connection portion 24a located downstream of the pre-stage catalyst 16, and is again at the downstream connection portion 24b located downstream of the upstream connection portion 24a. 14 to join. Similarly to the first bypass passage 20, the second bypass passage 22 is configured to branch from the main exhaust passage 14 at the upstream connection portion 24 a and merge with the main exhaust passage 14 again at the downstream connection portion 24 b. ing.

  An exhaust switching valve 26 for switching the inflow destination of the exhaust gas to any of the main exhaust passage 14, the first bypass passage 20, and the second bypass passage 22 is disposed in the upstream connection portion 24 a. A first adsorbent unit 30 having a function of adsorbing water components, HC components, and NOx components contained in the exhaust gas is disposed in the middle of the first bypass passage 20, and the second bypass passage. A second adsorbent unit 40 having a function of adsorbing the water component, HC component, and NOx component contained in the exhaust gas is also disposed in the middle of 22. Detailed configurations of the first adsorbent unit 30 and the second adsorbent unit 40 will be described later with reference to FIG.

  The system of this embodiment includes an ECU (Electronic Control Unit) 50. The ECU 50 detects the concentration of ethanol contained in the fuel supplied to the internal combustion engine 10 together with various sensors used to control the internal combustion engine 10 such as an air flow meter 52 that measures the amount of air Ga taken into the internal combustion engine 10. An ethanol sensor 54 is connected. The ethanol sensor 54 is disposed in a fuel tank or a fuel pipe. The ECU 50 is connected to various actuators for controlling the internal combustion engine 10 such as the exhaust switching valve 26 described above.

  The system of the present embodiment described above is mounted on a system capable of operating the internal combustion engine 10 with either gasoline fuel or alcohol fuel (ethanol in this case), that is, a so-called flexible fuel vehicle (FFV). System. In such a system, the fuel to be finally supplied to the internal combustion engine 10 includes the type of fuel selected by the user of the vehicle (in this embodiment, gasoline, ethanol, or a predetermined proportion of ethanol). Depending on the amount and type of fuel remaining in the fuel tank when refueling is performed at a timing desired by the user. That is, in FFV, the ethanol content (ethanol concentration) in the fuel that is finally supplied to the internal combustion engine 10 can be arbitrarily changed between 0% and 100%.

  FIG. 2 is a diagram for explaining a specific configuration of the first adsorbent unit 30 and the second adsorbent unit 40. The first adsorbent unit 30 is configured to be an adsorbent suitable for use when a fuel having a relatively low ethanol concentration is used. More specifically, as shown in FIG. 2, the first adsorbent unit 30 includes the first moisture adsorbent 32, the first HC adsorbent 34, and the first NOx adsorbent 36 from the side close to the upstream connection portion 24a. The three adsorbents arranged on the first bypass passage 20 are provided in this order.

  The other second adsorbent unit 40 is configured to be an adsorbent suitable for use when a fuel having a relatively high ethanol concentration is used. More specifically, as shown in FIG. 2, the second adsorbent unit 40 is referred to as a second moisture adsorbent 42, a second HC adsorbent 44, and a second NOx adsorbent 46 from the side closer to the upstream connection portion 24a. Three adsorbents arranged on the second bypass passage 22 in order are provided.

  As the 1st moisture adsorption material 32 and the 2nd moisture adsorption material 42, Na-Y type zeolite with a low Si / Al ratio can be used, for example. These moisture adsorbents 32 and the like are provided for the purpose of removing in advance upstream of the NOx adsorbent 36 and the like water that inhibits the adsorption of NOx and HC (particularly NOx) to the NOx adsorbent 36 and the like. It is a thing. The capacities of these moisture adsorbents 32 and the like vary depending on the required level of NOx adsorption to the NOx adsorbent 36 etc. in each vehicle. This NOx adsorption requirement level is determined from the viewpoint of what percentage of NOx contained in the exhaust gas needs to be adsorbed according to the target suppression level of the NOx emission amount.

  More specifically, in the present embodiment, the capacity of the first moisture adsorbing material 32 is the NOx adsorption request level as described above when the internal combustion engine 10 is operated with a fuel whose gasoline fuel is 100%. As a reference, it is determined to be an amount that can secure a capacity necessary for removing water. The capacity of the second moisture adsorbing material 42 is determined to be about 1.5 times (1.2 to 1.8 times) the capacity of the first moisture adsorbing material 32 determined as described above. ing. In other words, the capacity of the second moisture adsorbent 42 to be used when the internal combustion engine 10 is operated with a fuel having a high ethanol concentration is the capacity of the moisture adsorbent required for a gasoline vehicle having the same displacement. It is determined to be 1.5 times the value.

  Further, the first HC adsorbent 34 is configured to be an adsorbent suitable for adsorbing higher HC components having a larger number of carbons than the second HC adsorbent 44. As such first HC adsorbent 34, for example, Y-type zeolite having a high Si / Al ratio can be used. The other second HC adsorbent 44 is configured to be an adsorbent suitable for adsorbing lower HC components having a carbon number of C4 or less, which is smaller than that of the first HC adsorbent 34. As such second HC adsorbent 44, for example, zeolite such as ferrierite or ZSM5 can be used. The second HC adsorbent 44 preferably carries a noble metal such as silver Ag or platinum Pt that is advantageous for adsorption of the lower HC component.

  Further, as the first NOx adsorbent 36 and the second NOx adsorbent 46, for example, ZSM5 carrying iron Fe can be used. More specifically, the capacity of the first NOx adsorbent 36 is such that when the internal combustion engine 10 is operated with a fuel whose gasoline fuel is 100%, the NOx removal is performed based on the above-mentioned NOx adsorption requirement level. It is determined so that the required capacity can be secured. The capacity of the second NOx adsorbent 46 is determined to be 0.5 times the capacity of the first NOx 36 determined as described above. In other words, the capacity of the second NOx 46 to be used when the internal combustion engine 10 is operated with fuel having a high ethanol concentration is 0.5% of the capacity of the NOx adsorbent required for a gasoline vehicle having the same displacement. It has been decided to double.

FIG. 3 is a diagram for explaining the system operation according to the first embodiment of the present invention.
(First channel form)
As shown in FIG. 3 (A), the first flow path configuration is realized by controlling the exhaust switching valve 26 so that the main exhaust passage 14 and the first bypass passage 20 are in communication with each other. When such a first flow path configuration is selected, all of the exhaust gas discharged from the internal combustion engine 10 is introduced from the main exhaust passage 14 into the first bypass passage 20 via the upstream connection portion 24a. Become so. The exhaust gas introduced into the first bypass passage 20 passes through the first adsorbent unit 30, is then returned to the main exhaust passage 14, passes through the underfloor catalyst 18, and then released into the atmosphere.

  If the first flow path configuration is selected at the time of cold start of the internal combustion engine 10, moisture is well removed from the exhaust gas by the most upstream first moisture adsorbent 32, and then in the exhaust gas. HC and NOx contained in the catalyst are removed by being adsorbed by the first HC adsorbent 34 and the first NOx adsorbent 36 (adsorption operation). Thereby, it is possible to suppress the release of HC and NOx into the atmosphere during a cold start when the pre-stage catalyst 16 or the like has not yet been activated. Further, if the first flow path configuration is selected again at a predetermined timing after the activation of the front catalyst 16 or the like, the exhaust gas that has been relatively warmed after starting is supplied to the first adsorbent unit 30. Thus, HC and NOx can be desorbed from the HC adsorbent 34 and the desorbed HC and NOx can be purified by the underfloor catalyst 18 (purge operation).

(Second flow path form)
As shown in FIG. 3B, the second flow path form is realized by controlling the exhaust switching valve 26 so that the main exhaust passage 14 and the second bypass passage 22 are in communication with each other. When such a second flow path configuration is selected, all of the exhaust gas discharged from the internal combustion engine 10 is introduced from the main exhaust passage 14 to the second bypass passage 22 via the upstream connection portion 24a. Become so. The exhaust gas introduced into the second bypass passage 22 passes through the second adsorbent unit 40, then returns to the main exhaust passage 14 again, passes through the underfloor catalyst 18, and is then released into the atmosphere. By selecting the second mode as described above, the adsorption operation to the second adsorbent unit 40 can be realized when the internal combustion engine 10 is cold started, and the purge operation is performed after the catalyst is activated. Can be realized.

(3rd channel form)
The third flow path form is realized by controlling the exhaust gas switching valve 26 so that the main exhaust passage 14 is not blocked by the exhaust gas switching valve 26 as shown in FIG. Such a third flow path form is a flow path form used during normal operation of the internal combustion engine 10, and in this case, the exhaust gas discharged from the internal combustion engine 10 is sent to the first adsorbent unit 30 or the first adsorbent unit 30. 2 Without passing through the adsorbent unit 40, it passes through the main exhaust passage 14 and is released into the atmosphere.

  By the way, in FFV, the characteristic of the exhaust gas component at the time of cold start differs greatly when a fuel with a high ethanol concentration is used and when a normal gasoline fuel is used. With reference to FIG. 4 and FIG. 5, the difference in the characteristics of such exhaust gas components will be described in detail.

  FIG. 4 is a diagram showing the ratio of the lower HC component of C4 or less in non-methane HC (NMHC) contained in the exhaust gas in relation to the ethanol concentration in the fuel. 4 that the lower HC component ratio increases as the ethanol concentration increases. As an ordinary HC adsorbent for gasoline fuel, a material suitable for adsorbing HC components higher than C4 is used. For this reason, when a fuel having a high ethanol concentration is used in the FFV, the ordinary HC adsorbent for gasoline fuel cannot sufficiently adsorb the lower HC component.

  FIG. 5 is a graph comparing the amount of NMHC (excluding unburned ethanol) discharged during cold start due to the difference in fuel properties. As shown in FIG. 5, in the case of fuel (E100) in which ethanol is 100%, NMHC emissions during cold start increase compared to the case of fuel (LFG-3) in which gasoline is 100%. . This is due to the following reasons. That is, since ethanol is less likely to vaporize and ignite than gasoline, combustion is less stable at cold start, and the time required to stabilize combustion is longer. Therefore, in the case of ethanol (E100), it is necessary to stabilize combustion by supplying more fuel than gasoline (LFG-3). As a result, the amount of NMHC discharged increases, and the NMHC discharge time during cold start also increases.

  FIG. 6 is a diagram comparing NOx emissions during cold start due to differences in fuel properties. Since ethanol (E100) has a large latent heat of vaporization, the combustion temperature is lower than when gasoline (LFG-3) is used. For this reason, as shown in FIG. 6, the amount of NOx emission is smaller for ethanol (E100).

  Therefore, in the system of this embodiment, considering the difference in the characteristics of the exhaust gas components due to the difference in the ethanol concentration contained in the fuel, each of the case where the ethanol concentration in the fuel is low and the case where the ethanol concentration is high As described above, the adsorbent units 30 and 40 suitable for the characteristics of the exhaust gas components are provided in the bypass passages 20 and 22, respectively.

  Then, the adsorbent to be used is selected between the first adsorbent unit 30 and the second adsorbent unit 40 according to the ethanol concentration in the fuel. Furthermore, when it is determined that fuel with a high ethanol concentration is used, the time for performing adsorption of HC and NOx on the second adsorbent unit 40 at the time of cold start is extended.

FIG. 7 is a flowchart of a routine executed by the ECU 50 in order to realize the above function. This routine is started when the ignition switch is turned ON (IG ON) when the internal combustion engine 10 is in the cold state.
In the routine shown in FIG. 7, first, the ethanol concentration a in the fuel is determined using the ethanol sensor 54 (step 100).

  Next, it is determined whether or not the ethanol concentration a is equal to or higher than a preset specified value A (step 102). As a result, when it is determined that the ethanol concentration a is not equal to or higher than the specified value A, the first adsorbent unit 30 configured as an adsorbent suitable for a fuel having a relatively low ethanol concentration is selected. That is, the exhaust gas switching valve 26 is controlled so that the first flow path configuration is realized (step 104). In this case, the internal combustion engine 10 is started with the first flow path configuration selected (step 106).

  On the other hand, if it is determined in step 102 that the ethanol concentration a is equal to or greater than the specified value A, the second adsorbent unit 40 configured as an adsorbent suitable for fuel having a relatively high ethanol concentration is selected. In other words, the exhaust gas switching valve 26 is controlled so that the second flow path configuration is realized (step 108). In this case, the internal combustion engine 10 is started with the second flow path configuration selected (step 106).

  Next, it is determined whether or not the ethanol concentration a is zero or less than a preset specified value B (step 110). As a result, if it is determined that the ethanol concentration a is zero or less than the specified value B, is the integrated value of the intake air amount Ga from the starting time of the internal combustion engine 10 in step 106 equal to or greater than a predetermined value C? It is determined whether or not (step 112). As a result, when the cumulative intake air amount Ga ≧ C is established, the exhaust gas switching valve is configured so that the exhaust gas is discharged through the main exhaust passage 14 as it is, that is, the third flow path configuration is selected. 26 is controlled (step 114). Thereby, the adsorption operation is terminated.

  On the other hand, if it is determined in step 100 that the ethanol concentration a is not zero or less than the specified value B, that is, if it can be determined that fuel with a high ethanol concentration is being used, the end timing of the adsorption operation is determined. In order to be extended, the predetermined value C is corrected so as to increase by a value corresponding to the ethanol concentration a (step 116). More specifically, the predetermined value C is a base value C that is determined in advance as a value for determining the adsorption execution time when the fuel uses 100% gasoline. The value C is corrected to be a value obtained by adding a product (C ′ × a) of the ethanol concentration a and a predetermined increment C ′. In this case, the adsorption operation is continued until the integrated intake air amount Ga reaches the corrected value C (steps 112 and 114).

  According to the routine shown in FIG. 7 described above, when a fuel having a relatively low ethanol concentration is used, including the case where only gasoline fuel is used, the first adsorbent unit suitable for such fuel is used. 30 is selected. As described above, the first adsorbent unit 30 includes the first HC adsorbent 34 suitable for adsorbing higher HC components having a carbon number larger than that of C4. When a fuel with a relatively low ethanol concentration is used, the characteristics of the HC component discharged at the cold start are not much different from those when only ordinary gasoline fuel is used. For this reason, when a low ethanol concentration fuel is used at the time of cold start, the first HC adsorbent 34 having the same configuration as that for ordinary gasoline fuel can effectively release HC into the atmosphere. Can be prevented.

  Further, according to the above routine, when a fuel having a relatively high ethanol concentration is used, the second adsorbent unit 40 is selected as an adsorbent suitable for such fuel. As described above, the second adsorbent unit 40 is provided with the second HC adsorbent 44 suitable for adsorbing lower HC components of C4 or lower. For this reason, when a high ethanol concentration fuel is used during cold start, the second HC adsorbent 44 releases C4 or lower HC components, which are the main components of the discharged HC, into the atmosphere. It can prevent well.

  Further, when ethanol fuel is used, the concentration of water in the exhaust gas increases due to combustion of ethanol, compared to when gasoline fuel is used. For this reason, when a fuel having a relatively high ethanol concentration is used, a moisture adsorbent having a capacity equivalent to that of a normal gasoline fuel adsorbent is not sufficient, and the NOx adsorbing capacity of the NOx adsorbent is remarkably increased. It will decrease. On the other hand, according to the above routine, when a fuel having a relatively high ethanol concentration is used, the second moisture adsorbent having a capacity 1.5 times that of the first moisture adsorbent 32 is secured. 42 is selected. For this reason, even when a fuel having a high ethanol concentration is used, it is possible to reliably prevent moisture that inhibits NOx adsorption from flowing into the second NOx adsorbent 46.

  Further, the capacity of the second NOx adsorbent 46 is 0.5 times the capacity of the first NOx adsorbent 36. That is, the capacity of the second NOx adsorbent 46 is set to a size suitable for the NOx emission amount when a fuel having a high ethanol concentration is used. When the capacity of the adsorbent increases, it takes a long time to raise the temperature of the adsorbent during the purge operation, and the time required to purge the adsorbed component from the adsorbent becomes longer. On the other hand, according to the second NOx adsorbent 46, the NOx purge from the second NOx adsorbent 46 is ensured after adequately securing the NOx adsorbing capacity at the time of cold start in which the fuel having a high ethanol concentration is used. Can be performed efficiently.

  Further, according to the above routine, when the ethanol concentration a in the fuel is higher than the specified value B, the inflow time of the exhaust gas to the second adsorbent unit 40 at the cold start becomes higher as the ethanol concentration a becomes higher. The exhaust gas switching valve 26 is controlled so as to be longer, that is, so that the adsorption execution period is longer. For this reason, it is possible to appropriately set the adsorption execution period in accordance with the change in the discharge time and discharge amount of NMHC caused by the difference in the ethanol concentration in the fuel.

  By the way, in the above-described first embodiment, the first adsorbent unit 30 suitable for use when the ethanol concentration in the fuel is relatively low, and suitable for use when the ethanol concentration in the fuel is relatively high. The second adsorbent unit 40 is provided in separate and independent bypass passages 20 and 22, respectively. However, in the present invention, the configuration for ensuring the target adsorption capacity regardless of the change in the ethanol concentration in the fuel is not limited to the above, and for example, as shown in FIG. It may be configured as shown.

  FIG. 8 is a view for explaining a modified example of the exhaust gas purification apparatus according to Embodiment 1 of the present invention. In FIG. 8, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted or simplified. The configuration shown in FIG. 8 includes a single bypass passage 60 as a passage that bypasses the main exhaust passage 14. The bypass passage 60 is configured to branch from the main exhaust passage 14 at the upstream connection portion 24a and to merge with the main exhaust passage 14 again at the downstream connection portion 24b. Further, an exhaust gas switching valve 62 for switching the inflow destination of the exhaust gas between the main exhaust passage 14 and the bypass passage 60 is disposed in the upstream side connection portion 24a.

  As shown in FIG. 8, in the middle of the bypass passage 60, three adsorbents are arranged in the order of the moisture adsorbent 64, the HC adsorbent 66, and the NOx adsorbent 68 from the side close to the upstream connection portion 24a. ing. The moisture adsorbing material 64 is composed of the same material and capacity as the second moisture adsorbing material 42 described above. That is, the capacity of the moisture adsorbent 64 is 1.5 times the capacity of the moisture adsorbent required for a gasoline vehicle with the same displacement so as to cover the case where fuel with a high ethanol concentration is used. Has been determined.

  Further, the HC adsorbent 66 is configured to include the first HC adsorbent 34 and the second HC adsorbent 44 described above. That is, the HC adsorbent 66 is made of a material suitable for adsorption of lower C4 or lower HC components (for example, ferrierite carrying silver Ag) and a material suitable for adsorption of higher grade HC components (for example, Y-type zeolite).

  Further, the NOx adsorbent 68 is composed of the same material and capacity as the first NOx adsorbent 36 described above. That is, the capacity of NOx68 is set so as to cover the case where fuel with a low ethanol concentration is used.

  Also in the configuration shown in FIG. 8 described above, if the exhaust gas switching valve 62 is controlled so that the exhaust gas is introduced into the bypass passage 60 at the cold start, HC and the like contained in the exhaust gas are removed. It can be adsorbed by the HC adsorbent 66 or the like. Further, if the exhaust gas switching valve 62 is controlled again so that the exhaust gas is introduced into the bypass passage 60 after the catalyst is activated, HC and the like are desorbed from the HC adsorbent 66 and the underfloor catalyst. 18 can be purified.

In the above-described first embodiment and its modifications, the exhaust switching valves 26 and 62 correspond to the “flow path switching means” in the third or fifth invention. Further, the “control means” in the third or fifth aspect of the present invention is realized by the ECU 50 executing the routine processing shown in FIG.
Further, when the ECU 50 executes the process of step 100, the “alcohol concentration acquisition means” in the fourth or fifth aspect of the invention executes the series of processes of steps 110 to 116, thereby executing the fourth or The “period setting means” in the fifth invention is realized.

It is a figure for demonstrating the structure of an internal combustion engine system provided with the exhaust gas purification apparatus in Embodiment 1 of this invention. It is a figure for demonstrating the specific structure of a 1st adsorbent unit and a 2nd adsorbent unit. It is a figure for demonstrating the system operation | movement of Embodiment 1 of this invention. It is the figure which represented the ratio of the lower HC component below C4 in the nonmethane HC (NMHC) contained in exhaust gas with the ethanol concentration in a fuel. It is the figure which compared the discharge | emission amount of NMHC (except unburned ethanol) at the time of the cold start by the difference in a fuel property. It is the figure which compared NOx discharge | emission amount at the time of the cold start by the difference in a fuel property. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the modification of the exhaust gas purification apparatus in Embodiment 1 of this invention.

Explanation of symbols

10 Internal combustion engine 14 Main exhaust passage 16 Pre-stage catalyst (SC)
18 Underfloor catalyst (UF)
20 first bypass passage 22 second bypass passage 24a upstream connection portion 24b downstream connection portions 26, 62 exhaust switching valve 30 first adsorbent unit 32 first moisture adsorbent 34 first HC adsorbent 36 first NOx adsorbent 40 first 2 adsorbent unit 42 second moisture adsorbent 44 second HC adsorbent 46 second NOx adsorbent 50 ECU (Electronic Control Unit)
54 Ethanol sensor 60 Bypass passage 64 Water adsorbent 66 HC adsorbent 68 NOx adsorbent

Claims (10)

Provided in an exhaust passage of an internal combustion engine receiving supply of gasoline fuel and alcohol fuel, adsorbing means for adsorbing a predetermined component contained in exhaust gas, provided in the exhaust passage downstream of the adsorbing means, An exhaust gas purification apparatus for an internal combustion engine comprising a purification catalyst for purifying a predetermined component,
The adsorption means includes a moisture adsorption means for adsorbing a water component contained in exhaust gas, and an HC adsorption means for adsorbing an HC component contained in exhaust gas,
The moisture adsorbing means includes a moisture adsorbing material having a capacity larger than that of a water adsorbing material used in an internal combustion engine having the same displacement with only gasoline fuel as fuel,
The exhaust purification device for an internal combustion engine, wherein the HC adsorption means includes an HC adsorbent for low alcohol concentration fuel and an HC adsorbent for high alcohol concentration fuel as HC adsorbents having different adsorption characteristics.   The HC adsorbent for low alcohol concentration fuel is an HC adsorbent suitable for adsorbing relatively high grade HC components, and the HC adsorbent for high alcohol concentration fuel is adsorbed by the HC adsorbent for low alcohol concentration fuel. 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the exhaust gas purification apparatus is an HC adsorbent suitable for adsorbing an HC component lower than the HC component to be absorbed. The exhaust passage includes a main exhaust passage through which exhaust gas discharged from the internal combustion engine flows, and a bypass passage that bypasses the main exhaust passage,
The exhaust gas purification apparatus for an internal combustion engine further includes flow path switching means capable of switching an inflow destination of exhaust gas between the main exhaust passage and the bypass path, and control means for controlling the flow path switching means. ,
The exhaust purification device for an internal combustion engine according to claim 1 or 2, wherein the adsorption means is disposed in the bypass passage. Alcohol concentration acquisition means for acquiring the alcohol concentration in the fuel;
The exhaust emission control device for an internal combustion engine according to claim 3, further comprising period setting means for setting an inflow period of exhaust gas to the adsorption means in accordance with the acquired alcohol concentration. A main exhaust passage through which exhaust gas discharged from an internal combustion engine that is supplied with gasoline fuel and alcohol fuel flows;
A first bypass passage that bypasses the main exhaust passage;
A second bypass passage that bypasses the main exhaust passage;
A flow path switching means capable of switching an inflow destination of the exhaust gas to any of the main exhaust passage, the first bypass passage, and the second bypass passage;
An adsorbing means for low alcohol concentration fuel, which is disposed in the first bypass passage and is suitable for adsorbing a predetermined component contained in exhaust gas when low alcohol concentration fuel is used;
An adsorbing means for high alcohol concentration fuel, which is disposed in the second bypass passage and is suitable for adsorbing a predetermined component contained in exhaust gas when high alcohol concentration fuel is used;
Alcohol concentration acquisition means for acquiring the alcohol concentration in the fuel;
Control means for controlling the flow path switching means according to the acquired alcohol concentration;
An exhaust emission control device for an internal combustion engine, comprising: The low alcohol concentration fuel adsorbing means includes a low alcohol concentration fuel moisture adsorbing material that adsorbs a water component contained in exhaust gas,
The high alcohol concentration fuel adsorbing means includes a water adsorbent for high alcohol concentration fuel that adsorbs a water component contained in exhaust gas,
6. The exhaust emission control device for an internal combustion engine according to claim 5, wherein the capacity of the moisture adsorbent for high alcohol concentration fuel is larger than the capacity of the moisture adsorbent for low alcohol concentration fuel. The low alcohol concentration fuel adsorbing means includes an HC adsorbent for low alcohol concentration fuel that adsorbs an HC component contained in exhaust gas,
The high alcohol concentration fuel adsorbing means includes an HC adsorbent for high alcohol concentration fuel that adsorbs an HC component contained in exhaust gas,
The exhaust purification device for an internal combustion engine according to claim 5 or 6, wherein the HC adsorbent for low alcohol concentration fuel and the HC adsorbent for high alcohol concentration fuel have different adsorption characteristics.   The HC adsorbent for low alcohol concentration fuel is an HC adsorbent suitable for adsorbing relatively high grade HC components, and the HC adsorbent for high alcohol concentration fuel is adsorbed by the HC adsorbent for low alcohol concentration fuel. 8. The exhaust gas purification apparatus for an internal combustion engine according to claim 7, wherein the exhaust gas purification apparatus is an HC adsorbent suitable for adsorbing an HC component lower than the HC component to be absorbed. The low alcohol concentration fuel adsorbing means includes a NOx adsorbent for low alcohol concentration fuel that adsorbs a NOx component contained in exhaust gas,
The high alcohol concentration fuel adsorbing means includes a NOx adsorbent for high alcohol concentration fuel that adsorbs a NOx component contained in exhaust gas,
The internal combustion engine according to any one of claims 5 to 8, wherein a capacity of the NOx adsorbent for high alcohol concentration fuel is smaller than a capacity of the NOx adsorbent for low alcohol concentration fuel. Engine exhaust purification system.   The apparatus further comprises period setting means for setting an inflow period of exhaust gas to the high alcohol concentration fuel adsorbing means and / or the low alcohol concentration fuel adsorbing means according to the acquired alcohol concentration. Item 10. The exhaust emission control device for an internal combustion engine according to any one of Items 5 to 9.

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