JP2009144612A - Fuel reforming device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel reforming device of an internal combustion engine having an improved detection capability of a deterioration recovery of a reforming catalyst that determines whether the reforming catalyst is deteriorated or not from the reformed gas. <P>SOLUTION: An engine system adopting the fuel reforming device of this implementation starts a recovery operation of the reforming catalyst (a step S11), reads a degree of deterioration of the reforming catalyst (a step S12), determines whether the degree of deterioration of the reforming catalyst exceeds a deterioration limit or not (a step S13), calculates extension time required for the recovery of the reforming catalyst (a step S14), stops fuel supply to the reforming catalyst (a step S15), conducts an operation as finely lean side for a stoichiometry (a step S16), determines whether NOx quantity exceeds a regulation value (a step S17), determines whether the extension time required to stably recover has elapsed or not (a step S18) and terminates the recovery operation of the reforming catalyst (a step S19). Thus, deterioration recovery of the reforming catalyst is determined and detected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel reforming apparatus for an internal combustion engine equipped with a fuel reformer, and in particular, supplies fuel to a part of the recirculation gas of exhaust gas and then reforms it with heat to generate reformed gas. The present invention relates to a fuel reformer for an internal combustion engine that supplies reformed gas to an intake passage.

Conventionally, a part of the exhaust gas of the internal combustion engine is taken out, supplied to the intake passage as a recirculation gas, and the recirculation gas is mixed with the intake air to lower the maximum temperature during combustion, so that nitrogen oxides in the exhaust gas ( NO _X) is an exhaust gas recirculation (EGR) system to reduce. As an improved system of this EGR system, in recent years, a part of fuel is added to the recirculation gas (EGR gas), and the mixed gas in which the fuel is mixed with the exhaust gas is heated using the heat of the exhaust gas and modified. By passing the porous catalyst, the mixed gas undergoes an endothermic reforming reaction, and a reformed gas (reformer gas) containing hydrogen (H ₂ ) and carbon monoxide (CO) is generated from the mixed gas. Proposals have been made to supply exhaust gas to an intake passage so as to efficiently recover exhaust heat and improve fuel efficiency.

  In such a conventional exhaust reformer system for an internal combustion engine, a fuel injection valve is provided in the intake port, and another fuel injection valve, a reforming catalyst, and a reforming gas control valve are provided in a reflux pipe branched from the exhaust pipe. ing. In a conventional internal combustion engine exhaust reformer system, fuel is injected into the recirculation pipe, and a reformed gas is generated by an endothermic reforming reaction with the reformed catalyst from the mixed gas mixed with the exhaust gas. The reformed gas is introduced into the combustion chamber.

  Thus, in the conventional exhaust reformer system for an internal combustion engine, the reform gas control valve is normally closed and fuel is injected into the intake port to introduce the air-fuel mixture into the combustion chamber, while during reforming, The reforming gas control valve is opened, fuel is injected into the reflux pipe, and reformer gas generated by the reforming catalyst is introduced into the combustion chamber and burned.

  In recent years, not only gasoline but also various fuel vehicles (FFV: Flexible Fuel Vehicles) that can use a fuel in which alcohol is mixed with gasoline have been used.

  In this FFV, in the low speed and low load region, the alcohol is separated from the mixed fuel of alcohol and gasoline and reformed fuel is supplied to the intake air (Patent Documents 1 and 2).

Japanese Patent Publication No. 3-43458 JP 2003-293867 A

However, in a conventional internal combustion engine exhaust reformer system that uses exhaust gas heat for fuel reforming, the reforming catalyst deteriorates due to fuel poisoning due to the long-time reforming operation, and the reforming performance decreases. _2. There is a problem that the generation of reformed gas containing CO and the like is reduced.

  The deterioration of the reforming catalyst occurs when the injected fuel adheres to the reforming catalyst, and further, the deterioration of the catalyst becomes more severe due to, for example, coking that the carbon (C) in the exhaust gas covers the catalyst surface. There's a problem.

  In addition, the reforming reaction by the reforming catalyst is carried out in a stoichiometric state where there is no oxygen, and the reforming catalyst is recovered by stopping the fuel supply and supplying the reflux gas to the reformer. However, if the reforming catalyst is recovered in a stoichiometric state, the amounts of HC, CO, and NOx are very small, so that it is difficult to determine the recovery of the reforming catalyst.

  In addition, since the fuel adheres to the reforming catalyst and deteriorates, or the carbon produced by coking adheres to the reforming catalyst, the fuel is more likely to adhere. However, there is a problem that the sensor cannot detect whether or not the reforming catalyst is completely recovered even if it is detected by.

  The present invention has been made in view of the above-described problem, and determines whether or not the reforming catalyst has deteriorated from the reformed gas, and improves the fuel recovery performance of the internal combustion engine in which the performance of detecting deterioration recovery of the reforming catalyst is improved. It aims to provide quality equipment.

  In order to achieve the above object, a fuel reformer for an internal combustion engine according to the present invention includes an intake passage for introducing outside air into a combustion chamber, and alcohol and gasoline alone or mixed in the intake passage or the combustion chamber. First fuel supply means for supplying the fuel, an exhaust passage for exhausting the exhaust gas discharged from the combustion chamber to the outside, an exhaust gas diversion passage for diverting a part of the exhaust gas flowing through the exhaust passage, A second fuel supply means for supplying the fuel to the exhaust gas diversion passage; and a mixed gas in which the fuel is supplied from the second fuel supply means to the exhaust gas flowing through the exhaust gas diversion passage by a reforming catalyst. A reformer that generates reformed gas; a reformed gas introduction passage that introduces the reformed gas generated by the reformer into the intake passage; and the reformed gas that is detected in the reformed gas introduction passage. A modification for detecting the degree of deterioration of the reforming catalyst. A catalyst deterioration detecting means, and when the reforming catalyst deterioration detecting means detects that the reforming catalyst is deteriorated, the fuel is supplied from the second fuel supply means to the exhaust gas branch passage. The exhaust gas is recirculated, and the exhaust gas is operated in an operation state in which the air-fuel ratio of the exhaust gas is slightly lean with respect to the stoichiometry, and the reformed gas in the reformed gas detected by the reforming catalyst deterioration detecting means is detected. The amount of NOx or oxygen in the reformed gas generated by the reforming catalyst is detected by detecting the amount of NOx or oxygen, and the amount of NOx or oxygen in the reformed gas generated by the reforming catalyst is calculated in advance. When the value is equal to or more than the prescribed value and when the value is stable, it is determined that the reforming catalyst has recovered, and the recovery of deterioration of the reforming catalyst is detected.

In the fuel reforming apparatus for an internal combustion engine according to the present invention, the amount of reduction in the amount of either or both of H ₂ and CO in the reformed gas is reduced when the reforming catalyst is in a normal state. It is characterized in that it is determined that the reforming catalyst has deteriorated when the amount of production of either one or both of H ₂ and CO in the gas is larger than the reduced amount.

  In the internal combustion engine fuel reformer according to the present invention, after the amount of NOx or oxygen in the reformed gas generated by the reforming catalyst is stabilized, the recovery time of the reforming catalyst is extended. Features.

In the fuel reforming apparatus for an internal combustion engine according to the present invention, the reforming catalyst deterioration detecting means is one or both of a NOx sensor and an O ₂ sensor.

  According to the present invention, the reforming catalyst deterioration detecting means for detecting the reforming gas by detecting the reforming gas in the reforming gas introduction passage for introducing the reforming gas generated by the reformer into the intake passage. When the reforming catalyst deterioration detecting means detects that the reforming catalyst has deteriorated, the fuel supply from the second fuel supply means to the exhaust gas branch passage is stopped, and the exhaust gas is Recirculation is performed in an operating state in which the air-fuel ratio of the exhaust gas is slightly lean with respect to stoichiometry, and the amount of NOx or oxygen in the reformed gas detected by the reforming catalyst deterioration detecting means is detected. Thus, recovery of deterioration of the reforming catalyst can be detected.

  Hereinafter, an embodiment in which a fuel reforming apparatus for an internal combustion engine according to the present invention is applied to an engine system will be described in detail with reference to the drawings. In addition, this invention is not limited by this Example.

  FIG. 1 is a schematic configuration diagram showing an engine system to which a fuel reforming apparatus for an internal combustion engine according to an embodiment of the present invention is applied. FIG. 2 is a diagram schematically showing the configuration shown in FIG.

The engine system to which the fuel reforming apparatus of the internal combustion engine of the present embodiment is applied is an internal combustion engine that can use not only gasoline but also various fuels that can use a fuel obtained by mixing ethanol with gasoline. This is applied to various fuel vehicles (FFV).
As shown in FIG. 1, in an engine system to which a fuel reforming apparatus for an internal combustion engine according to this embodiment is applied, an engine 11 as the internal combustion engine is a port injection type four-cylinder type and has a cylinder head on a cylinder block. Are fastened, and the pistons are respectively fitted to the plurality of cylinder bores so as to be movable up and down. A crankcase is fastened to the lower part of the cylinder block, a crankshaft is rotatably supported in the crankcase, and each piston is connected to the crankshaft via a connecting rod.
The engine 11 is not limited to a four-cylinder engine and may be used for other cylinder engines.

  Combustion chambers 12 are formed by cylinder blocks, cylinder heads, and pistons corresponding to four cylinders, and each combustion chamber 12 is formed with an intake port 13 and an exhaust port 14 facing each other at the top. The intake port 13 and the exhaust port 14 can be opened and closed by an intake valve and an exhaust valve (not shown).

  The downstream end of the intake pipe (intake passage) 15 is connected to each intake port 13 via an intake manifold 16, and an air cleaner 17 is attached to the upstream end of the intake pipe 15. An electronic throttle device 19 having a throttle valve 18 is provided on the downstream side of the air cleaner 17. Further, the intake manifold 16 is provided with a first injector (first fuel supply means) 20 capable of supplying fuel to the intake port 13 corresponding to each combustion chamber 12. The first injector 20 is connected to a delivery pipe 21. The delivery pipe 21 is connected to a fuel pump 24 in a fuel tank 23 by a fuel supply pipe 22-1. Although not shown, each combustion chamber 12 is equipped with a spark plug that ignites the air-fuel mixture.

On the other hand, an exhaust pipe (exhaust passage) 26 is connected to each exhaust port 14 via an exhaust manifold 25. The exhaust pipe 26 is filled with a reformer 27 and a three-way catalyst 28a. The original catalyst device 28 and the muffler 29 are mounted. As will be described later, the reformer 27 has a double-pipe structure, and a gas purification unit 27a filled with a three-way catalyst 30 and a reformer filled with a reforming catalyst 31 around it. The chamber 27b is configured to supply a fuel to a part of the exhaust gas and then reform the mixed gas by the reforming catalyst 31 using the exhaust heat to generate a reformed gas. Further, the three-way catalyst 28a, 30 are hydrocarbons contained in the exhaust gas (HC), carbon monoxide (CO), are those capable of simultaneously purifying process of harmful substances NO _X, the air-fuel ratio is stoichiometric When in the vicinity of the air-fuel ratio (stoichiometric), harmful substances in the exhaust gas can be purified. Further, the exhaust gas purified by the three-way catalysts 28 a and 30 is discharged into the atmosphere through the muffler 29.

  Here, the reformer 27 will be described in detail. The reformer 27 has a heat exchange structure, and the gas purification unit 27a of the reformer 27 connected to the exhaust pipe 26 is filled with the three-way catalyst 30, and the gas purification unit 27a is modified around the gas purification unit 27a. A quality chamber 27b is provided, and the reforming chamber 27b is filled with a reforming catalyst 31. As the reforming catalyst 31, for example, cobalt (Co), nickel (Ni), rhodium (Rh), platinum (Pt) or the like is used.

  An exhaust gas branch pipe (exhaust gas branch passage) 32 is branched from the upstream side of the reformer 27 in the exhaust pipe 26, and the downstream end of the exhaust gas branch pipe 32 is modified in the reformer 27. It is connected to one end of the mass chamber 27b. The exhaust gas branch pipe 32 is provided with a second injector (second fuel supply means) 33 for injecting fuel to a part of the exhaust gas branched from the exhaust pipe 26 to the exhaust gas branch pipe 32. ing. Similar to the first injector 20, the second injector 33 is connected to the fuel pump 24 in the fuel tank 23 by a fuel supply pipe 22-2.

  A reformed gas introduction pipe (reformed gas introduction passage) 34 for introducing the reformed gas generated by the reformer 27 into the intake pipe 15 is provided at the other end of the reforming chamber 27 b in the reformer 27. The other end of the reformed gas introduction pipe 34 is connected to the downstream side of the electronic throttle device 19 in the intake pipe 15. The reformed gas introduction pipe 34 is provided with a flow rate adjusting valve 35 that controls the amount of reformed gas introduced into the intake pipe 15 and an actuator 35 a that operates the flow rate adjusting valve 35.

  Further, a filter 37 is provided in the fuel supply pipe 22-2. After the impurities in the fuel are removed by the filter 37, the fuel is supplied to the second injector 33.

  A cooling device 36 is provided in the reformed gas introduction passage 34 to cool the reformed gas discharged from the reformer 27. A cooling pipe (not shown) is connected to the cooling device 36 so as to cool the reformed gas passing through the cooling device 36. The reformed gas discharged from the reformer 27 and the exhaust gas that has not undergone the reforming reaction are in a high temperature state, and when these are introduced into the intake passage 15 as they are, the air sucked from the outside is warmed and burned. The charging efficiency of each cylinder in the chamber 12 is deteriorated. Therefore, by cooling the reformed gas discharged from the reformer 27 by the cooling device 36, deterioration of the charging efficiency of the reformed gas into each cylinder in the combustion chamber 12 can be suppressed.

  In the engine 11 of this embodiment, fuel is injected into the intake air flowing through the intake port 13 by the first injector 20, and fuel is injected into the exhaust gas flowing through the exhaust gas branch pipe 32 by the second injector 33. The fuel injection by the first injector 20 is referred to as intake fuel injection, and the fuel injection from the second injector 33 is referred to as exhaust fuel injection.

Therefore, in a state where the flow rate adjustment valve 35 is opened, a part of the exhaust gas flowing through the exhaust pipe 26 is diverted to the exhaust gas branch pipe 32, and the second injector 33 performs fuel injection (exhaust fuel) to the exhaust gas. Injection). The mixed gas in which the fuel and the exhaust gas are mixed flows into the reforming chamber 27b of the reformer 27, and is heated by the heat of the exhaust gas flowing from the exhaust pipe 26 through the gas purification unit 27a of the reformer 27. As a result, this mixed gas is vaporized by promoting evaporation, and the vaporized mixed gas undergoes an endothermic reaction to be reformed, and a reformed gas containing hydrogen (H ₂ ), carbon monoxide (CO), and the like is formed. Generated.

  The exhaust gas distribution pipe 32 is provided with a stirring vessel 38. The exhaust gas and the fuel are mixed in the stirring vessel 38 to form an air-fuel mixture. A cooling pipe (not shown) is connected to the stirring vessel 38 so as to cool the exhaust gas and fuel in the stirring vessel 38. Alternatively, the fuel may be injected from the second injector 33 into the exhaust gas branch pipe 32 and mixed with the exhaust gas to form a mixed gas.

For example, when the exhaust gas is “7.6 CO ₂ + 6.8H ₂ O + 40.8N ₂ ” and the gasoline fuel is “C _7.6 H _13.6 ”, the endothermic reaction is
1.56 (7.6 CO ₂ +6.8 H ₂ O + 40.8 N ₂ ) +3 (C _7.6 H _13.6 ) +984.8 kcal → 31 H ₂ +34.7 CO + 63.6 N ₂
It is represented by That is, according to the endothermic reaction at this time, 31 mol of hydrogen (H ₂ ) gas and 34.7 mol of carbon monoxide (CO) gas are generated from 3 mol of gasoline fuel.

The reformed gas generated in the reformer 27 flows from the reforming chamber 27 b to the reformed gas introduction pipe 34, the supply amount thereof is adjusted by the opening degree of the flow rate adjusting valve 35, and the intake gas flowing through the intake pipe 15 is adjusted. Supplied. A mixed gas obtained by mixing the intake air and the reformed gas is introduced from the intake manifold 16 through the intake port 13 into the combustion chamber 12 and ignited by the spark plug to explode. When the exhaust valve is opened, the exhaust gas is exhausted. The gas is discharged from the port 14 to the exhaust pipe 26. In this case, since the reformed gas contains hydrogen, combustion efficiency in the combustion chamber 12 is good, fuel efficiency can be improved, and NO _x generation can be suppressed and exhaust purification efficiency can be improved. .

  Further, each first injector 20 is supplied with fuel stored in the fuel tank 23 via a fuel supply pipe 22-1 and a delivery pipe 21 connected to the fuel supply pipe 22-1. Since the engine 11 is configured so that alcohol and gasoline can be used alone or in combination as fuel, fuel having a predetermined alcohol concentration is stored in the fuel tank 23. This fuel may be 100% gasoline, a mixed fuel in which alcohol such as methanol or ethanol is mixed with gasoline, or even 100% alcohol.

  An electronic control unit (ECU) 41 is mounted on the vehicle, and the ECU 41 controls the drive of the first injector 20, the second injector 33, the spark plug, and the like, so that the fuel injection amount, the injection timing, the ignition timing, etc. Can be controlled. That is, an air flow sensor 42 is mounted on the upstream side of the intake pipe 15 and outputs the measured intake air amount to the ECU 41. The electronic throttle device 19 has a throttle position sensor 43 and outputs the current throttle opening to the ECU 41. Further, the crank angle sensor 44 outputs the detected crank angle of each cylinder to the ECU 41, and the ECU 41 determines each stroke of intake, compression, expansion (explosion), and exhaust in each cylinder based on the detected crank angle. At the same time, the engine speed is calculated.

  Accordingly, the ECU 41 determines the overall fuel injection amount, injection timing, ignition timing, and the like based on the detected intake air amount, throttle opening (or accelerator opening), engine operating state such as engine speed. Yes. In this case, the total fuel injection amount is the sum of the fuel injection amounts injected by the first injector 20 and the second injector 33.

  In addition, the ECU 41 can control the amount of reformed gas introduced into the intake pipe 15 by drivingly controlling the second injector 33, the flow rate adjusting valve 35, and the like.

  Further, a bed temperature sensor 45 is provided in the reforming chamber 27b of the reformer 27, and the current temperature (bed temperature) of the reforming chamber 27b is output to the ECU 41. Therefore, the ECU 41 determines whether or not the reformer 27 is at the activation temperature based on the detected bed temperature of the reformer 27.

  Further, the ECU 41 calculates an upper limit value of the amount of exhaust gas that can be recirculated to the intake pipe 15 based on the engine speed and the engine load (for example, throttle opening). When the ECU 41 determines that the temperature of the reformer 27 is equal to or higher than the activation temperature, the ECU 41 calculates the amount of reformed gas that can be introduced into the intake pipe 15 based on the amount of exhaust gas that can be recirculated to the intake pipe 15. The opening degree of the flow rate adjusting valve 35 is set by the actuator 35a, and the exhaust fuel injection amount by the second injector 33 is set. In this case, the first injector 20 is injected by subtracting the exhaust fuel injection amount by the second injector 33 set here from the total fuel injection amount calculated based on the intake air amount, the engine speed, and the like. The intake fuel injection amount to be set is set.

Further, a temperature sensor 46 is provided in the reformed gas introduction passage 34 so as to detect the reformed gas temperature. Further, a hydrogen (H ₂ ) sensor 47, a CO sensor 48, a NOx sensor 49, and an O ₂ (oxygen) sensor 52 are provided in the reformed gas introduction passage 34 so as to detect the component amount of the reformed gas. Further, the NOx sensor 49 and the O ₂ sensor 52 may be provided on the upstream side of the cooling device 36.

Therefore, it is determined whether or not the exhaust gas is being reformed by the reforming catalyst 31 from the concentrations detected by the H ₂ sensor 47, the CO sensor 48, the NOx sensor 49, and the O ₂ sensor 52. Thereby, it is determined whether or not the reforming catalyst 31 has deteriorated.

  The fuel supply pipe 22-1 is provided with an alcohol concentration sensor 50 that detects the alcohol concentration. The alcohol concentration sensor 50 is a capacitance type sensor that detects the alcohol concentration based on the dielectric constant of the fuel, but an optical sensor that detects the alcohol concentration based on the refractive index of the fuel is used. The detection principle is not limited.

  Further, the engine 11 of this embodiment can use not only gasoline but also fuel obtained by mixing ethanol with gasoline as fuel, and the fuel to be replenished to the fuel tank 23 is the same as the fuel used so far. The properties are not necessarily the same. Therefore, the ECU 41 feeds back the exhaust air / fuel ratio measured by the air / fuel ratio sensor 51, and determines that the fuel property has been changed when the exhaust air / fuel ratio has shifted from the stoichiometric side to the lean side or the rich side. The total fuel injection amount is corrected by controlling according to the fuel properties.

[Operation control method]
Next, an operation control method in the engine system to which the fuel reformer for the internal combustion engine of the present embodiment is applied will be described in detail with reference to FIGS.
Here, a description will be given using tumble as the airflow.
FIG. 3 is a flowchart showing an operation control method in the engine system to which the fuel reformer for the internal combustion engine according to the present embodiment is applied.
The operation control method in the engine system to which the fuel reformer for the internal combustion engine according to the present embodiment is applied determines whether or not the reforming catalyst 31 has deteriorated, and the deterioration of the reforming catalyst 31 exceeds the deterioration limit. Calculates the extension time required for the recovery of the reforming catalyst 31, stops the fuel supply from the second injector 33 to the reforming catalyst 31, and makes the air-fuel ratio of the exhaust gas slightly leaner than the stoichiometric ratio. The NOx amount measured by the NOx sensor 49 is equal to or greater than the specified value, and it is determined that the reforming catalyst 31 has recovered, and after the extended time required for recovery has elapsed, the recovery operation ends. To do.

  That is, as shown in FIG. 3, the operation control method in the engine system to which the internal combustion engine fuel reforming apparatus according to the present embodiment is applied includes the step of starting the recovery operation of the reforming catalyst 31 (step S11), A deterioration degree reading step for determining the deterioration degree of the catalyst 31 (step S12) and a step of determining whether or not the read deterioration degree of the reforming catalyst 31 exceeds the deterioration limit of the reforming catalyst 31 (step S12). Step S13), a step of calculating an extension time for extending the recovery time in order to stabilize the recovery of the reforming catalyst 31 from the degree of deterioration of the reforming catalyst 31 (Step S14), and a second injector A step of stopping supplying fuel to the reforming catalyst 31 from step 33 (step S15), and a step of operating in a state where the air-fuel ratio of the exhaust gas is slightly leaner than the stoichiometric state (step S15). 6) and a step of determining whether or not the NOx amount measured by the NOx sensor 49 is equal to or greater than a specified value (step S17), and the reforming catalyst 31 recovers when the NOx amount is equal to or greater than the specified value. A step of determining whether or not the calculated extension time required for the recovery of the reforming catalyst 31 has elapsed (step S18), and a step of ending the recovery operation of the reforming catalyst 31 (step S19). ).

  First, in FIG. 3, in step S11, the recovery operation of the reforming catalyst 31 is started. That is, the injected fuel and the exhaust gas supplied from the second injector 33 to the reforming catalyst 31 are mixed in the stirring vessel 38 to obtain a mixed gas. This mixed gas is supplied to the reforming catalyst 31 to reform the mixed gas. Then, after the recovery operation of the reforming catalyst 31 is started in step S11, the process proceeds to step S12.

In step S12, the degree of deterioration of the reforming catalyst 31 is read. Specifically, generation of either or both of H ₂ and CO for the injected fuel supplied to the reforming catalyst 31 by the second injector 33 using either or both of the H ₂ sensor 47 and the CO sensor 48. It is determined whether or not the amount by which the amount is reduced is greater than or equal to a predetermined value.
Here, the predetermined value refers to a reference amount for reducing the amount of H ₂ and / or CO produced in the reformed gas produced when the reforming catalyst 31 is in a normal state.
When the reforming catalyst 31 deteriorates, the amount of H ₂ and CO generated in the reformed gas with respect to time with respect to the fuel injection amount rapidly decreases.

Further, either or both of H ₂ and CO in the reformed gas with respect to the injected fuel supplied to the reforming catalyst 31 by the second injector 33 using either or both of the H ₂ sensor 47 and the CO sensor 48. The degree of deterioration of the reforming catalyst 31 is determined by checking whether the production rate of the reforming catalyst 31 is equal to or higher than the production rate of either or both of H ₂ and CO in the reformed gas when the reforming catalyst 31 is in a normal state. You may make it determine.

FIG. 4 is a diagram showing the presence or absence of reform recovery from the reformed product concentration.
The reforming coefficient is obtained by multiplying the flow rate of the exhaust gas supplied to the reformer 27 and the temperature coefficient at that time.
As shown in FIG. 4, there are deterioration degrees (for example, patterns 1, 2, and 3) obtained in advance from the relationship between the reforming coefficient and the reforming generation concentration. Then, any one of the deterioration degrees obtained in advance is selected according to the alcohol concentration, the operation state, etc., and whether the reforming catalyst 31 can continue the reforming as it is based on the selected deterioration degree or whether recovery is necessary. Decide whether or not.

  Then, after reading the degree of deterioration of the reforming catalyst 31, the process proceeds to step S13 shown in FIG.

  In step S13, it is determined whether the degree of deterioration of the read reforming catalyst 31 exceeds the deterioration limit. As a result of the determination in step S13, when it is determined that the degree of deterioration of the reforming catalyst 31 exceeds the deterioration limit of the reforming catalyst 31 (step S13: Yes), the process proceeds to step S14.

  In step S14, an extension time for extending the recovery time is calculated in order to stabilize the recovery of the reforming catalyst 31 from the degree of deterioration of the reforming catalyst 31. This extension time may be extended by an automatic timer. After calculating the extended time required to recover the reforming catalyst 31 more stably, the process proceeds to step S15.

  In step S15, the supply of fuel from the second injector 33 to the stirring vessel 38 is stopped, and then the process proceeds to step S16.

  In step S16, the operation is performed in a state where the air-fuel ratio of the exhaust gas is slightly lean with respect to the stoichiometry. For example, when the exhaust gas stoichiometry is 14.6, it is preferable that the air-fuel ratio in a state of being slightly leaned is about 14.7 to 14.8. After the operation is performed on the lean side with respect to the stoiki, the process proceeds to step S17.

In step S17, it is determined whether or not the amount of NOx in the reformed gas is equal to or greater than a specified value. Specifically, the NOx amount in the reformed gas is measured by the NOx sensor 49, and when the NOx amount measured by the NOx sensor 49 is equal to or higher than a specified value (step S17: Yes), the reforming is performed. It is determined that the catalyst 31 has recovered, and the process proceeds to step S18.
The specified value refers to a value at a recovery level of the NOx concentration described later.
Moreover, the case where it is stabilized means the case where the NOx concentration in the reformed gas is in a steady state.

FIG. 5 is a diagram showing the relationship between the elapsed time and the gas concentration of the gas component in the reformed gas.
As shown in FIG. 5, when the recovery of the reforming catalyst 31 is started, the operation is performed on the lean side with respect to the stoichiometry as described above. For example, when the exhaust gas stoichiometric ratio is 14.6, the air-fuel ratio slightly reduced to the lean side is set to, for example, about 14.7 to 14.8. This is because NOx is purified by the amount of HC coming out, and the NOx gas concentration becomes zero. However, when the air-fuel ratio is set to the lean side, no reaction occurs.

  In order to make the recovery of the reforming catalyst 31 more stable after the NOx concentration exceeds the recovery level, which is a specified value, and reaches a steady state where the NOx concentration change is stable, Extend the recovery time. At this time, the recovery time may be extended as a timer operation after the NOx concentration change reaches a stable level. Further, since the extension of the recovery time of the reforming catalyst 31 is performed to make the recovery of the reforming catalyst 31 more stable, the recovery time may not be extended.

Further, instead of the NOx sensor 49, an O ₂ sensor 52 may be used to detect the O ₂ concentration in the reformed gas and determine whether the reforming catalyst 31 has recovered. Further, it may be determined whether the reforming catalyst 31 has recovered by detecting the NOx concentration and the O ₂ concentration in the reformed gas using both the NOx sensor 49 and the O ₂ sensor 52.

  In step S18, it is determined whether or not the extended time required for recovery calculated from the degree of deterioration of the reforming catalyst 31 has elapsed. The extension time is, for example, 2 to 3 minutes, and may be about several minutes. If it is determined that the extended time has elapsed (step S18: Yes), it is determined that the reforming catalyst 31 is stably recovered, and the process proceeds to step S19.

  In step S19, the recovery operation of the reforming catalyst 31 is finished, and the operation control is finished. Then, as usual, fuel is supplied from the second injector 33 to the reforming catalyst 31 to perform a reforming reaction.

  On the other hand, when the deterioration degree of the read reforming catalyst 31 is determined in step S13 shown in FIG. 3, it is determined that the deterioration degree of the reforming catalyst 31 does not exceed the deterioration limit (step S13: No). ), The process proceeds to step S12. In step S12, the degree of deterioration of the reforming catalyst 31 is determined again.

  In step S17 shown in FIG. 3, when the NOx amount measured by the NOx sensor 49 is equal to or less than the specified value (step S17: No), it is determined that the reforming catalyst 31 has not recovered and NOx is again performed. The sensor 49 measures the amount of NOx until it reaches a specified value or more.

  If it is determined in step S18 shown in FIG. 3 that the extension time required for the recovery of the reforming catalyst 31 that has been calculated in advance has not elapsed (step S18: No), the reforming catalyst 31 is still stable. Thus, the reforming catalyst 31 is stably recovered until it is determined that the recovery state is not reached and the extended time required for recovery again elapses.

  As described above, in the fuel reforming apparatus for the internal combustion engine according to the present embodiment, whether or not the reforming catalyst 31 has deteriorated and whether or not the reforming catalyst 31 has deteriorated according to the operation control method in the engine system to which the fuel reforming apparatus for the internal combustion engine according to the present embodiment is applied. Determining the degree, calculating the extended time required for stable recovery of the reforming catalyst 31, and stopping the fuel supply to the reforming catalyst 31 to slightly lean the stoichiometric operation. Then, it is determined whether or not the NOx amount measured by the NOx sensor 49 is equal to or greater than a specified value, and the process is repeated until the recovery is stabilized. As a result, deterioration of the reforming catalyst 31 can be suppressed, recovery of the reforming catalyst 31 can be determined, and the reforming performance of the reforming catalyst 31 can be recovered.

  Further, the recovery of the reforming catalyst 31 is determined and the reforming performance of the reforming catalyst 31 is recovered, so that the emission can be prevented from deteriorating and the three-way catalyst 28a provided in the exhaust pipe 26 can be prevented. , 30 can be protected.

  As described above, the fuel reformer for an internal combustion engine according to the present invention detects the reformed gas generated by the reformer, detects the deterioration degree of the reforming catalyst, and the reforming catalyst is deteriorated. The fuel supply to the exhaust gas supplied to the reformer is stopped, the exhaust gas is recirculated, and the air-fuel ratio of the exhaust gas is slightly lean with respect to the stoichiometric operation state, By detecting the amount of NOx or oxygen in the reformed gas, the reforming performance of the reforming catalyst is recovered, and the deterioration recovery of the reforming catalyst is detected. Used for any type of internal combustion engine Is also suitable.

1 is a schematic configuration diagram showing an engine system to which a fuel reformer for an internal combustion engine according to an embodiment of the present invention is applied. It is a figure which shows the structure shown in FIG. 1 simply. It is a flowchart which shows the operation control method in the engine system to which the fuel reforming apparatus of the internal combustion engine which concerns on a present Example is applied. It is a figure showing the presence or absence of recovery | restoration of a modification | reformation from a modification | reformation production | generation density | concentration. It is a figure which shows the relationship between elapsed time and the gas concentration of the gas component in reformed gas.

Explanation of symbols

11 Engine (Internal combustion engine)
12 Combustion chamber 13 Intake port 14 Exhaust port 15 Intake pipe (intake passage)
16 Intake Manifold 17 Air Cleaner 18 Throttle Valve 19 Electronic Throttle Device 20 First Injector (First Fuel Supply Unit)
21 Delivery pipe 22-1, 22-2 Fuel supply pipe 23 Fuel tank 24 Fuel pump 25 Exhaust manifold 26 Exhaust pipe (exhaust passage)
27 reformer 27a gas purification unit 27b reforming chamber 28 three-way catalyst device 28a, 30 three-way catalyst 29 muffler 31 reforming catalyst 32 exhaust gas branch pipe (exhaust gas branch passage)
33 Second injector (second fuel supply means)
34 Reformed gas introduction pipe (reformed gas introduction passage)
35 Flow control valve 35a Actuator 36 Cooling device 37 Filter 38 Stirring vessel 41 Electronic control unit, ECU (fuel injection control means)
42 Air Flow Sensor 43 Throttle Position Sensor 44 Crank Angle Sensor 45 Bed Temperature Sensor 46 Temperature Sensor 47 Hydrogen (H ₂ ) Sensor 48 CO Sensor 49 NOx Sensor 50 Alcohol Concentration Sensor 51 Air-fuel Ratio Sensor 52 O ₂ (Oxygen) Sensor

Claims (4)

An intake passage for introducing outside air into the combustion chamber;
First fuel supply means for supplying fuel, which is a mixture of alcohol and gasoline, alone or mixed to the intake passage or the combustion chamber;
An exhaust passage for exhausting exhaust gas discharged from the combustion chamber to the outside;
An exhaust gas diversion passage for diverting a part of the exhaust gas flowing through the exhaust passage;
Second fuel supply means for supplying the fuel to the exhaust gas diversion passage;
A reformer for generating a reformed gas by a reforming catalyst from the mixed gas in which the fuel is supplied from the second fuel supply means to the exhaust gas flowing through the exhaust gas diversion passage;
A reformed gas introduction passage for introducing the reformed gas generated in the reformer into the intake passage;
A reforming catalyst deterioration detecting means for detecting the reforming gas in the reforming gas introduction passage and detecting the deterioration degree of the reforming catalyst;
When the reforming catalyst deterioration detecting means detects that the reforming catalyst is deteriorated, the supply of the fuel from the second fuel supply means to the exhaust gas branch passage is stopped,
The exhaust gas is recirculated, and the air-fuel ratio of the exhaust gas is minutely lean with respect to the stoichiometric operation,
Detecting the amount of NOx or oxygen in the reformed gas detected by the reforming catalyst deterioration detecting means;
The amount of NOx or oxygen in the reformed gas generated by the reforming catalyst is equal to or higher than a predetermined value of NOx or oxygen in the reformed gas generated by the reforming catalyst calculated in advance, and stable. If it is determined that the reforming catalyst has recovered,
A fuel reformer for an internal combustion engine that detects deterioration recovery of the reforming catalyst. In claim 1,
The amount of reduction in the amount of either or both of H ₂ and CO in the reformed gas is the amount of either or both of H ₂ and CO in the reformed gas when the reforming catalyst is in a normal state. A fuel reformer for an internal combustion engine, wherein when the amount of production is larger than the amount to be reduced, it is determined that the reforming catalyst has deteriorated. In claim 1 or 2,
A fuel reforming apparatus for an internal combustion engine, wherein the recovery time of the reforming catalyst is extended after the amount of NOx or oxygen in the reformed gas generated by the reforming catalyst is stabilized. In any one of Claims 1 thru | or 3,
A fuel reforming apparatus for an internal combustion engine, wherein the reforming catalyst deterioration detecting means is one or both of a NOx sensor and an O ₂ sensor.

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