JP2009138695A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine controlling an air flow in order to set an exhaust gas temperature at which the exhaust gas is reformed according to an air flow condition, and optimally reforming exhaust gas. <P>SOLUTION: This internal combustion engine includes an alcohol concentration detection step (step S11) of detecting an alcohol concentration in fuel, a step (step S12) of determining the presence or absence of abnormality of a reforming catalyst, a step (step S13) of determining respective areas of air flow areas A, B, C and D according to the alcohol concentration detected in step S11 when the reforming catalyst is normal, and a step (step S14) of switching to a map representing distribution of the air flow areas A, B, C and D with respective air flow areas determined in step S13. The air flow areas A, B, C and D are determined according to the presence or absence of abnormality of the reforming catalyst and the alcohol concentration, and strength and weakness of the air flow is determined, thereby controlling the air flow in order to set the exhaust temperature at which the exhaust gas is reformed according to the air flow condition and efficiently reforming the exhaust gas. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to 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 an internal combustion engine supplied to a 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 a system improved from this EGR system, in recent years, a part of the fuel is added to the reflux 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 the reforming catalyst is passed. Thus, the mixed gas is subjected to an endothermic reforming reaction, a reformed gas (reformer gas) containing hydrogen (H ₂ ) and carbon monoxide (CO) is generated from the mixed gas, and the reformer gas is sucked into the reformed gas. Proposals have been made for efficient exhaust heat recovery and fuel efficiency improvement by supplying to the passage.

  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.

  Further, a high-speed electromagnetic valve (Timing Control Valve: hereinafter referred to as “TCV”) such as a timing control valve is provided in a fuel passage for supplying fuel to the intake port. The EGR resistance is improved by strengthening the airflow, which is the swirling flow of the mixture, such as the vertical vortex tumble or the horizontal vortex swirl generated in the cylinder during the intake stroke of the internal combustion engine, by shortening the combustion time by TCV. The improvement of fuel consumption is aimed at (patent documents 1, 2).

  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 the reformed fuel is supplied to the intake air.

JP 2004-92520 A JP 2001-271585 A

  Here, since the reforming reaction performed by passing the mixed gas in which the exhaust gas is mixed with fuel through the reforming catalyst is an endothermic reaction, the exhaust temperature is required to be high to some extent.

  However, when the exhaust gas is reformed with the TCV in a state where the airflow in the cylinder is strengthened, the combustion time is shortened by strengthening the airflow, and the exhaust gas is compared with the same rotation and load conditions as when the airflow is weak. As the temperature decreases and the exhaust temperature required for reforming cannot be secured, there is a problem that the region where the exhaust gas can be reformed becomes narrower than when the exhaust gas is reformed with a weak airflow. is there.

  For this reason, when the air flow in the cylinder is controlled by the TCV in the FFV, there is a problem that the exhaust gas cannot be efficiently reformed because the exhaust temperature is changed by the TCV control.

  The present invention has been made in view of the above problem, and controls the air flow so as to achieve an exhaust temperature that enables the exhaust gas to be reformed according to the air flow state, thereby performing the optimal reforming of the exhaust gas. An object of the present invention is to provide an internal combustion engine that makes it possible.

  In order to achieve the above object, an internal combustion engine according to the present invention supplies an intake passage for introducing outside air into a combustion chamber, and supplies a fuel in which alcohol and gasoline are used alone or mixed to the intake passage or the combustion chamber. A first fuel supply means; 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; and the exhaust gas distribution A second fuel supply means for supplying the fuel to the 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 to generate a reformed gas by a reforming catalyst A reformer that performs, a reformed gas introduction passage that introduces the reformed gas generated in the reformer into the intake passage, an exhaust gas temperature detection means that detects a gas temperature of the exhaust gas, and the intake passage The air flow in the combustion chamber An air flow control means for controlling the strength, and combustion is performed so that the exhaust gas can be reformed by the air flow control means according to the gas temperature of the exhaust gas detected by the exhaust gas temperature detection means It is characterized by controlling the airflow in the room.

  In the internal combustion engine according to the present invention, when it is determined that the reforming catalyst is abnormal, the fuel supply for supplying fuel to the first fuel supply means and the second fuel supply means instead of the air flow control means The air flow in the combustion chamber is controlled by a high-speed solenoid valve provided in the pipe.

  The internal combustion engine according to the present invention has alcohol concentration detection means for detecting the alcohol concentration of the fuel, and controls the strength of the airflow according to the alcohol concentration detected by the alcohol concentration detection means. To do.

  According to the present invention, the exhaust gas temperature detecting means for detecting the gas temperature of the exhaust gas, and the air flow control means for controlling the air flow in the combustion chamber in the intake passage, the exhaust gas detected by the exhaust gas temperature detecting means. Depending on the gas temperature, the air flow control means can control the air flow in the combustion chamber so that the exhaust gas temperature can be changed according to the air flow state.

  As a result, if the exhaust gas temperature is lower than the temperature at which reforming is possible by strengthening the airflow in the cylinder during reforming of the exhaust gas, the airflow in the cylinder can be weakened and the exhaust gas temperature can be reformed Temperature can be increased.

  As a result, the exhaust gas can be optimally reformed by controlling the air flow so that the exhaust gas temperature can be adjusted according to the state of the air flow.

  Further, when it is determined that the reforming catalyst is abnormal, a high-speed solenoid valve provided in a fuel supply pipe for supplying fuel to the first fuel supply means and the second fuel supply means instead of the air flow control means By controlling the air flow in the combustion chamber, the exhaust gas can be reformed in accordance with the abnormal state of the reforming catalyst.

  Further, an alcohol concentration detection means for detecting the alcohol concentration of the exhaust gas is provided, and the higher the alcohol concentration, the lower the temperature of the exhaust gas can be modified. Therefore, the alcohol concentration and airflow detected by the alcohol concentration detection means The strength of the airflow can be controlled so that the exhaust gas temperature can be changed from the state so that the exhaust gas can be reformed, and the exhaust gas can be optimally reformed.

  Embodiments of an internal combustion engine according to the present invention will be described below 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 internal combustion engine according to an embodiment of the present invention.
The internal combustion engine of the present embodiment 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, and is applied to various fuel vehicles (FFV). Is.
As shown in FIG. 1, in the internal combustion engine of the present embodiment, the engine 11 as the internal combustion engine is a port injection type four-cylinder type, and a cylinder head is fastened on a cylinder block, and a plurality of cylinder bores are connected. The pistons are fitted 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, and the delivery pipe 21 is connected to a fuel pump 24 in a fuel tank 23 by a fuel supply pipe 22. The fuel supply pipe 22 is provided with a high-speed solenoid valve 38 such as a timing control valve (hereinafter referred to as “TCV”). 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.

  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.

  In addition, a cooling device 36 is provided in the reformed gas introduction passage 34 to cool the reformed gas and exhaust gas discharged from the reformer 27. 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, it is possible to suppress deterioration of the charging efficiency of the reformed gas and exhaust gas into each cylinder in the combustion chamber 12.

  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.

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, the fuel stored in the fuel tank 23 is supplied to each first injector 20 via a fuel supply pipe 22 and a delivery pipe 21 connected to the fuel supply pipe 22. 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.

Each intake port 13 is provided with an airflow control valve 37 that is an airflow control means for controlling the airflow in the combustion chamber 12. FIG. 2 is a diagram illustrating an example of the configuration of the airflow control valve. As shown in FIG. 2, the strength of the airflow generated in the combustion chamber 12 is changed by opening and closing the airflow control valve 37. Examples of the airflow generated in the combustion chamber 12 include tumble and swirl.
In the present embodiment, either or both of tumble and swirl are controlled.
The tumble refers to a vertical vortex of the air-fuel mixture generated in the cylinder during the intake stroke of the internal combustion engine. A swirl is a swirl of air-fuel mixture (lateral vortex) generated in a cylinder during the intake stroke of the engine.

  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, and an HC sensor 49 are provided in the reformed gas introduction passage 34 so as to detect the component amount of the reformed gas.

Therefore, whether or not the exhaust gas is being reformed by the reforming catalyst 31 based on the concentration detected by the H ₂ sensor 47, the CO sensor 48, the HC sensor 49, the torque fluctuation of the torque (not shown) of the flow rate adjusting valve 35, and the like. Judging. Thereby, the abnormality of the reforming catalyst 31 is detected, and the quality of the exhaust gas reforming system is judged.

  Further, as a case where the reforming catalyst 31 is in an abnormal state, for example, when carbon is deposited in the catalyst, the load on the engine 11 is small and the amount of heat from the exhaust gas applied to the reforming catalyst 31 is insufficient. In some cases, the reforming catalyst 31 does not reform the fuel.

  It can also be determined from the crank angle whether the reforming catalyst 31 is normal. When the crank angle at which the in-cylinder pressure in the cylinder of the combustion chamber 12 reaches the maximum value when the reforming catalyst 31 is in a normal state, for example, is on the advance side, the in-cylinder pressure in the cylinder is in the abnormal state when the reforming catalyst 31 is in an abnormal state. The maximum crank angle shifts to the retard side. Therefore, it is possible to determine whether the reforming catalyst 31 is normal by determining whether the crank angle is within a predetermined range.

  It is also possible to determine whether the reforming catalyst 31 is normal by detecting engine rotation fluctuations. When the reforming ratio of the fuel in the mixed gas is large when the reforming catalyst 31 is in a normal state, the rotational speed fluctuation is small, but when the reforming catalyst 31 becomes abnormal and the reforming ratio of the fuel in the mixed gas becomes small, Rotational speed fluctuation increases. Therefore, when the engine rotation fluctuation is within the predetermined value range, the reforming catalyst 31 is determined to be normal, and when the engine rotation fluctuation is outside the predetermined value range, the reforming catalyst 31 is determined to be abnormal. Thus, it can be determined whether or not the reforming catalyst 31 is normal.

  The fuel supply pipe 22 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.

  Further, an exhaust gas temperature sensor 52 which is an exhaust gas temperature detecting means for detecting the gas temperature of the exhaust gas is provided in the exhaust pipe 26. In accordance with the gas temperature of the exhaust gas detected by the exhaust temperature sensor 52, the air flow intensity in each combustion chamber 12 is controlled by the air flow control valve 37 so that the exhaust gas temperature can be modified. ing.

  When it is determined that the reforming catalyst 31 is abnormal, the exhaust gas can be reformed by a high-speed electromagnetic valve 38 such as a timing control valve provided in the fuel supply pipe 22 instead of the airflow control valve 37. The strength of the airflow in each combustion chamber 12 is controlled so that the exhaust temperature becomes a proper exhaust temperature.

[Operation control method]
Next, the operation control method in the internal combustion engine of the present embodiment 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 internal combustion engine according to this embodiment.
The operation control method in the internal combustion engine according to the present embodiment is based on the detection of the alcohol concentration of the fuel, the determination of whether or not the reforming catalyst 31 is abnormal, the presence or absence of the abnormality of the reforming catalyst 31 and the alcohol concentration of the obtained fuel. Accordingly, a map indicating the distribution of each airflow region is determined, switching to a map indicating the determined distribution of each airflow region is performed, and airflow control corresponding to each airflow region is performed.

That is, as shown in FIG. 3, the operation control method in the internal combustion engine according to the present embodiment includes an alcohol concentration detection step (step S <b> 11) in which the alcohol concentration sensor 50 detects the alcohol concentration of the fuel, and an abnormality in the reforming catalyst 31. When the reforming catalyst 31 is normal, that is, when the exhaust gas reforming system is good, the air flow region A, which will be described later, according to the alcohol concentration detected in step S11, A step of determining each region of B, C, and D (step S13), and a step of switching to a map showing the distribution of the airflow regions A, B, C, and D in which the airflow regions are determined in step S13 (step S14); It consists of
Further, when the reforming catalyst 31 is abnormal, that is, when the exhaust gas reforming system is defective, a step of determining airflow regions of airflow regions E and F (described later) according to the alcohol concentration detected in step S11 (step) S15) and a step (step S16) of switching to a map showing the distribution of the airflow regions E and F determined in step S15.

  First, in FIG. 3, in step S11, the alcohol concentration sensor 50 detects the alcohol concentration of the fuel. That is, the fuel is gasoline, alcohol, or a mixed fuel thereof, and the alcohol concentration sensor 50 reads the alcohol concentration of the fuel. Then, after reading the alcohol concentration of the fuel in step S11, the process proceeds to step S12.

In step S12, it is determined whether there is an abnormality in the reforming catalyst 31, that is, whether the exhaust gas reforming system is operating well. As described above, when the reforming catalyst 31 is in an abnormal state, for example, when carbon is deposited in the catalyst, the load on the engine 11 is small, and the amount of heat from the exhaust gas applied to the reforming catalyst 31 is small. In some cases, the reforming catalyst 31 is not sufficient to reform the fuel. Whether or not the reforming catalyst 31 is abnormal is determined from the concentration detected by the H ₂ sensor 47, the CO sensor 48, and the HC sensor 49, the torque fluctuation of the torque (not shown) of the flow rate adjustment valve 35, and the like. Further, whether or not the reforming catalyst 31 is normal can also be determined based on whether or not the crank angle is within a predetermined range and whether or not the engine rotation fluctuation is within a predetermined value range.

  If the reforming catalyst 31 is normal in step S12, that is, if it is determined that the exhaust gas reforming system is good (step S12: No), the process proceeds to step S13.

  In step S13, when the reforming catalyst 31 is normal, air flow regions A, B, C, and D, which will be described later, are determined according to the alcohol concentration detected in step S11.

  Here, a method for determining the airflow region will be described.

The airflow region is a region in which the strength of the airflow is determined according to the exhaust temperature capable of reforming the exhaust gas.
Further, not only gasoline but also fuel obtained by mixing alcohol with gasoline can be used as fuel, and the case where the alcohol concentration of fuel is 0% will be described.
FIG. 4 is a diagram showing the distribution of each airflow region when the reforming catalyst is normal.
In FIG. 4, the airflow region A is a region where the exhaust temperature does not reach the exhaust gas reference temperature at which the exhaust temperature can be reformed regardless of whether the airflow is strong or weak.
Further, the airflow region B is a region where the exhaust temperature does not reach the reference temperature at which reformation is possible when the airflow is strengthened, but the exhaust temperature exceeds the reference temperature at which reformation is possible when the airflow is weakened.
Further, the airflow region C is a region where the exhaust temperature exceeds a reference temperature at which the exhaust temperature can be reformed in a state where the airflow is strengthened.
Further, the fuel efficiency is improved when the airflow region D is weaker than when the airflow is strong.

Further, the exhaust gas reference temperature at which the exhaust gas can be reformed is T0, the exhaust gas temperature is T, the exhaust gas temperature when the tumble is weak is T1, and the exhaust gas temperature when the tumble is strong is T2.
At this time, in FIG. 4, the boundary line a (thick broken line in FIG. 4) is a line where the engine speed and torque are the same at the exhaust gas reference temperature T0 and the exhaust gas temperature T1 when the tumble is weak. is there.
Further, the boundary line b (thick solid line in FIG. 4) is a line where the engine speed and the torque are the same at the exhaust gas reference temperature T0 and the exhaust gas temperature T2 when the tumble is strong.
Further, line c (thin broken line in FIG. 4) is a line where the engine speed and the torque become the same when the fuel efficiency when the air current is weak becomes larger than the fuel efficiency when the air current is strong.

At this time, in the airflow region A, the exhaust gas temperature T1 when the tumble is weak is lower than the exhaust gas reference temperature T0, and the exhaust gas temperature T2 when the tumble is strong is also lower than the exhaust gas reference temperature T0.
In the airflow region B, the exhaust gas temperature T1 when the tumble is weak is equal to or higher than the exhaust gas reference temperature T0, and the exhaust gas temperature T2 when the tumble is strong is lower than the exhaust gas reference temperature T0.
In the airflow region C, the exhaust gas temperature T1 when the tumble is weak is equal to or higher than the exhaust gas reference temperature T0, and the exhaust gas temperature T2 when the tumble is strong is also equal to or higher than the exhaust gas reference temperature T0.

  As shown in FIG. 4, in the state of the airflow region A, that is, in the state of the region where the exhaust temperature does not reach the reformable exhaust gas reference temperature T0 regardless of whether the airflow is strong or weak, the tumble is strengthened. Like that. By strengthening the tumble in the airflow region A, the combustion becomes faster, the EGR resistance and the lean burn resistance are improved, and the fuel efficiency can be improved.

  Further, in the state of the airflow region B, that is, in the state where the airflow is strengthened, the exhaust gas temperature does not reach the exhaust gas reference temperature T0 that can be reformed, but in the state where the airflow is weakened, the exhaust gas reference temperature that can be reformed. In the case of a region exceeding T0, the tumble is weakened to reform the exhaust gas. By weakening the tumble in the airflow region B, the exhaust gas temperature rises, so that the exhaust gas can be reformed. By reforming the exhaust gas, it is possible to further increase the calorific value and the EGR resistance, thereby improving the fuel efficiency. Thereby, when the exhaust gas is not reformed in a strong tumble state, that is, when the temperature is low and the reforming cannot be performed, the fuel efficiency can be improved.

  Further, in the state of the airflow region C, that is, in the region where the exhaust temperature exceeds the exhaust gas reference temperature T0 that can be reformed with the airflow strengthened, the tumble is strengthened to reform the exhaust gas. To. By improving the exhaust gas by strengthening the tumble in the airflow region C, the combustion becomes faster, the EGR resistance and the lean burn resistance are improved, and the fuel efficiency is improved as in the airflow region A described above. Can do.

  Further, in the state of the airflow region D, that is, in the state of the region where the fuel efficiency is improved when the airflow is weaker than when the airflow is strong, the tumble is weakened to reform the exhaust gas. To do. By performing the exhaust gas reforming by weakening the tumble in the airflow region D, the exhaust gas temperature rises as in the airflow region B described above, and the reforming of the exhaust gas increases the calorific value and the EGR resistance. Since the fuel consumption can be further improved, fuel consumption can be improved.

As described above, the exhaust gas can be optimally reformed by controlling the air flow so that the exhaust gas temperature can be adjusted according to the air flow state.
Moreover, although it demonstrated using the tumble as an airflow, it is the same also in a swirl.

<Fuel consumption comparison>
Further, the air flow control is based on only the two regions of the first embodiment in which the air flow control is performed according to the diagram showing the distribution of the air flow regions A, B, C, and D as shown in FIG. The result of having compared the fuel consumption with the comparative example 1 which performs is shown.
FIG. 5 is a diagram showing the relationship between torque and fuel consumption rate.
In FIG. 5, the bold lines indicate Example 1 in which airflow control is performed according to a diagram showing the distribution of airflow regions A, B, C, and D as shown in FIG. 4.
Moreover, in FIG. 5, the thin line | wire shows the comparative example 1 which performs airflow control only based on only two area | regions with only the strength of airflow like the past.
As shown in FIG. 5, the strength of the airflow is determined in the airflow regions A to D as in the first embodiment in which the airflow control is performed according to the diagram showing the distribution of the airflow regions A, B, C, and D as shown in FIG. In addition, it was confirmed that the fuel consumption rate is reduced when the airflow control is performed as compared with the comparative example 1 in which the airflow control is performed based only on the two regions of the airflow strength and the weakness as in the related art.

  Therefore, as in the present invention, the strength of the airflow is determined in the airflow regions A to D at which the exhaust gas can be reformed according to the airflow state, and the exhaust gas is controlled by controlling the airflow. It was confirmed that this reforming can be carried out efficiently and fuel consumption can be reduced.

<Effects of EGR rate and fuel consumption rate due to the presence or absence of reforming and air flow strength>
The relationship between the EGR rate when the exhaust gas is reformed by the reforming catalyst 31 and the strength of the airflow and the fuel consumption rate at that time will be described.
Here, the EGR rate is a ratio of the exhaust gas amount fractionated in the exhaust gas distribution pipe 32 and circulated to the intake pipe 15 to the total amount of exhaust gas, and is divided into the exhaust gas distribution pipe 32. It means a value obtained by dividing the amount of exhaust gas retained by the amount of gas combined with the amount of intake air and exhaust gas flowing into the engine 11.
FIG. 6 is a diagram showing the relationship between the EGR rate and the fuel consumption rate.
In FIG. 6, a thin solid line is when the airflow is weak without reforming the exhaust gas.
A thin broken line is when the exhaust gas is not reformed and the airflow is strong.
A thick solid line is when the exhaust gas is reformed and the airflow is weak.
A thick broken line is when the exhaust gas is reformed and the airflow is strong.

  As shown in FIG. 6, by changing the airflow from a weak state to a strong state, the combustion becomes faster, so that the EGR resistance can be improved and the fuel efficiency can be improved.

  In addition, by using the reformed gas obtained by reforming the exhaust gas with the reforming catalyst 31, the calorific value is increased, and the combustion is further accelerated by hydrogen in the reformed gas, so that the EGR resistance can be improved. it can.

<Influence on combustion period and exhaust temperature due to airflow strength>
The relationship between the combustion period and the exhaust temperature when the airflow is strengthened will be described.
FIG. 7 is a diagram showing the relationship between the combustion period and the exhaust gas temperature when the airflow is strengthened.
In FIG. 7, as the tumble ratio increases, the flame propagation speed increases and combustion ends early as shown in the upper diagram. In addition, as shown in the lower diagram in FIG. 7, since combustion ends early, the in-cylinder gas temperature when the exhaust valve is opened is lowered, so that the exhaust gas temperature is also lowered.

  Therefore, the stronger the air flow and the stronger the turbulence in the cylinder, the shorter the combustion period and the lower the exhaust temperature.

<Influence on reformable area by airflow strength>
Further, the reformable region based on the airflow strength will be described.
FIG. 8 is a diagram showing the relationship between engine speed and load when the airflow is weak, and FIG. 9 is a diagram showing the relationship between engine speed and load when the airflow is strong.
As shown in FIG. 8, when the airflow is weak, it is divided into a region where the exhaust gas can be reformed and a region where the exhaust gas cannot be reformed. However, if the airflow is strengthened, the exhaust temperature decreases as described above. As shown in FIG. 9, the region where the exhaust gas can be reformed becomes narrower than the region where the exhaust gas can be modified as shown in FIG. Part) will increase.

  Therefore, if the air flow is strengthened, the region where the exhaust gas can be reformed becomes narrow, so that the exhaust gas cannot be reformed, and the EGR resistance decreases.

  Thus, by changing the airflow from a weak state to a strong state, the EGR resistance can be improved, the fuel consumption can be improved, and the reformed gas obtained by reforming the exhaust gas with the reforming catalyst 31 can be used. While increasing the calorific value, the EGR resistance can also be improved. However, by strengthening the airflow, the combustion period is shortened and the exhaust temperature is also lowered, so that the region where the exhaust gas can be reformed is narrowed.

  Therefore, for example, when the exhaust gas temperature is lower than the temperature at which reforming is possible by strengthening the tumble in the cylinder during reforming of the exhaust gas, as in the state of the airflow region B shown in FIG. By weakening the tumble, the exhaust gas temperature can be raised to a temperature at which reforming is possible, and the exhaust gas can be reformed. Therefore, the exhaust gas can be optimally reformed by controlling the air flow so that the exhaust gas temperature becomes an exhaust gas temperature at which the exhaust gas can be reformed.

<Influence on air flow area by alcohol concentration>
Moreover, the case where the alcohol fuel which mixed alcohol with gasoline is used as a fuel is demonstrated.
A map showing the distribution of airflow regions A, B, C, and D as shown in FIG. 4 changes each region according to the alcohol concentration detected in step S11 shown in FIG. This is because the higher the alcohol concentration is, the lower the exhaust gas reference temperature at which the exhaust gas can be reformed. Therefore, it is necessary to change the air flow region in accordance with the alcohol concentration.

FIGS. 10-12 is a figure which shows the relationship between the airflow area correction coefficient between each airflow area according to alcohol concentration and alcohol concentration. FIG. 10 is a diagram showing the relationship between the alcohol concentration and the airflow region correction coefficient between the airflow regions AB. FIG. 11 is a diagram illustrating the relationship between the alcohol concentration and the airflow region correction coefficient between the airflow regions BC. FIG. 12 is a diagram showing the relationship between the alcohol concentration and the airflow region correction coefficient between the airflow regions CD.
Each airflow region of airflow regions A, B, C, and D as shown in FIG. 4 is multiplied by an airflow region correction coefficient between the airflow regions as shown in FIGS. change. That is, the air flow region correction coefficient (for example, the solid line and the broken line in FIGS. 10 to 12) between the different air flow regions in FIGS. 10 to 12 indicates that the alcohol concentration becomes closer to 0%. Asymptotically approaches the value of the airflow region correction coefficient at 0%.

  Therefore, when alcohol fuel is used, each region of the airflow regions A, B, C, and D as shown in FIG. 4 can be changed by using the airflow region correction coefficient as shown in FIGS. it can.

For example, FIG. 13 is a diagram in which the airflow regions A, B, C, and D shown in FIG. 4 are changed according to the alcohol concentration.
In FIG. 13, boundary lines a ′, b ′, and c ′ are obtained by changing the boundary lines a, b, and c shown in FIG. 4 in accordance with the alcohol concentration in the fuel.
As shown in FIG. 13, for example, when the alcohol concentration in the fuel is high, reforming is possible at a low temperature, so the airflow region A is narrow and the airflow region that strengthens the airflow can be narrowed.

  Therefore, since the exhaust gas temperature T and the exhaust gas reference temperature T0 vary depending on the alcohol concentration in the fuel, the optimal modification of the exhaust gas can be achieved by changing the air flow region of the air flow in accordance with the alcohol concentration in the fuel. Quality can be improved and fuel consumption can be improved.

  Then, in step S13 shown in FIG. 3, after determining a map showing the distribution of airflow regions A, B, C, and D according to the alcohol concentration as shown in FIG. 4, the process proceeds to step S14.

  Then, in step S14 shown in FIG. 3, after switching to the map showing the distribution of the airflow regions A, B, C, and D according to the alcohol concentration as shown in FIG. 4, the operation control is finished. And airflow control according to each airflow area is implemented based on the map which shows distribution of airflow area A, B, C, D switched by step S14.

  On the other hand, when it is determined in step S12 shown in FIG. 3 that the reforming catalyst 31 is in an abnormal state, that is, the exhaust gas reforming system is defective (step S12: Yes), the process proceeds to step S15. .

  In step S15, when the reforming catalyst 31 is in an abnormal state, an airflow region is determined according to the alcohol concentration detected in step S11.

FIG. 14 is a diagram showing the distribution of each airflow region when the reforming catalyst is abnormal.
In FIG. 14, the airflow region E is a region where the exhaust gas temperature does not reach the reducible exhaust gas reference temperature T0 regardless of whether the airflow is strong or weak.
Moreover, the state where the airflow region F is weaker than when the airflow is strong is a region where fuel efficiency is improved.
Further, the boundary line d is the boundary line of the airflow regions E and F when the alcohol concentration of the fuel is 0% (solid line in FIG. 14), and the boundary line e is when the alcohol concentration of the fuel is 100%. It is the boundary line (broken line in FIG. 14) of the airflow regions E and F.

  As shown in FIG. 14, in the state of the airflow region E, that is, in the state of the region where the exhaust temperature does not reach the reformable exhaust gas reference temperature T0 regardless of whether the airflow is strong or weak, the airflow is strengthened. Like that. By strengthening the airflow in the airflow region E, the combustion becomes faster, the EGR resistance and the lean burn resistance are improved, and the fuel efficiency can be improved.

  Further, when the state of the air flow region F, that is, the state where the weak air flow is stronger than when the air flow is strong is the state where the fuel consumption is improved, the air flow is weakened to reform the exhaust gas. By reducing the airflow in the airflow region F and reforming the exhaust gas, the exhaust gas temperature rises, and the reforming of the exhaust gas can further increase the heat generation amount and further improve the EGR resistance. Can be improved.

Further, the airflow regions E and F as shown in FIG. 14 are changed in accordance with the alcohol concentration detected in step S11 shown in FIG.
FIG. 15 is a diagram illustrating the relationship between the alcohol concentration and the airflow region correction coefficient between the airflow regions EF corresponding to the alcohol concentration.
The airflow regions E and F as shown in FIG. 14 change the load region by multiplying the airflow region correction coefficient between the airflow regions EF as shown in FIG. 14 according to the alcohol concentration.

  That is, if it is determined that the reforming catalyst 31 is in an abnormal state and the exhaust gas reforming system is defective, the exhaust gas temperature need not be taken into consideration. Further, when the alcohol concentration in the fuel is high, the combustion rate is increased, and thus the EGR resistance is improved. For this reason, when the alcohol concentration in the fuel is high, the boundary line d as shown in FIG. 14 is set as the boundary line e, and the airflow region E is expanded more than when the alcohol concentration of the fuel is 0%, thereby providing an EGR region. Therefore, the fuel efficiency improvement area can be expanded.

  Therefore, when alcohol fuel is used, the airflow regions E and F as shown in FIG. 14 according to the alcohol concentration can be changed by using the airflow region correction coefficient between the airflow regions EF as shown in FIG. it can.

  Therefore, even when the reforming catalyst 31 becomes abnormal and the exhaust gas system is in a defective state, the exhaust gas temperature T and the exhaust gas reference temperature T0 change depending on the alcohol concentration in the fuel. The fuel efficiency can be improved by changing the airflow regions E and F and changing the strength of the airflow.

  Then, in step S15 shown in FIG. 3, after determining a map showing the distribution of airflow regions E and F according to the alcohol concentration as shown in FIG. 14, the process proceeds to step S16.

  Then, in step S16 shown in FIG. 3, after switching to the map showing the distribution of the airflow regions E and F according to the alcohol concentration as shown in FIG. 14, the operation control is finished. And based on the map which shows distribution of the airflow area | regions E and F switched by step S16, the airflow control according to each airflow area | region is implemented.

  As described above, in the internal combustion engine of the present embodiment, the alcohol concentration sensor 50 detects the alcohol concentration of the fuel and determines whether the reforming catalyst 31 is abnormal or not, thereby determining whether the reforming catalyst 31 is abnormal or not. The airflow region corresponding to the alcohol concentration can be determined, and the strength of the airflow can be controlled. As a result, the exhaust gas can be optimally modified by controlling the air flow so that the exhaust gas temperature can be adjusted according to the air flow state. Can be implemented efficiently.

  As described above, the internal combustion engine according to the present invention detects the alcohol concentration of the fuel and determines whether or not the reforming catalyst is abnormal, and the airflow region according to the presence or absence of the reforming catalyst and the alcohol concentration of the fuel. The exhaust gas is efficiently reformed by controlling the air flow and determining the region of the air flow intensity at which the exhaust gas temperature can be modified according to the air flow state. It is suitable for any kind of internal combustion engine.

1 is a schematic configuration diagram illustrating an internal combustion engine according to an embodiment of the present invention. It is a figure which shows an example of a structure of an airflow control valve. It is a flowchart which shows the operation control method in the internal combustion engine which concerns on a present Example. It is a figure which shows distribution of each airflow area | region when a reforming catalyst is normal. It is a figure which shows the relationship between a torque and a fuel consumption rate. It is a figure which shows the relationship between an EGR rate and a fuel consumption rate. It is a figure which shows the relationship between the combustion period when exhaust current is strengthened, and exhaust temperature. It is a figure which shows the relationship between an engine speed and load at the time of an air current weak state. It is a figure which shows the relationship between an engine speed and load when an airflow is strong. It is a figure which shows the relationship between alcohol concentration and the airflow area | region correction coefficient between airflow area AB. It is a figure which shows the relationship between alcohol concentration and the airflow area | region correction coefficient between airflow area | region BC. It is a figure which shows the relationship between alcohol concentration and the airflow area | region correction coefficient between airflow area | region CD. It is a figure which shows the relationship between the engine speed and torque which changed airflow area | region A, B, C, D according to alcohol concentration. It is a figure which shows distribution of each airflow area | region when a reforming catalyst is abnormal. It is a figure which shows the relationship between the airflow area correction coefficient between the airflow area EF according to alcohol concentration and alcohol concentration.

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 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 Airflow control valve 38 High-speed solenoid valve 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 HC Sensor 50 Alcohol Concentration Sensor 51 Air-fuel Ratio Sensor 52 Exhaust Temperature Sensor

Claims (3)

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;
Exhaust gas temperature detecting means for detecting the gas temperature of the exhaust gas;
An airflow control means for controlling the strength of the airflow in the combustion chamber in the intake passage;
An internal combustion engine characterized in that an air flow in a combustion chamber is controlled by the air flow control means so as to achieve an exhaust temperature at which the exhaust gas can be reformed according to a gas temperature of the exhaust gas detected by the exhaust gas temperature detection means. organ. In claim 1,
When it is determined that the reforming catalyst is abnormal,
An internal combustion engine that controls an air flow in a combustion chamber by a high-speed electromagnetic valve provided in a fuel supply pipe that supplies fuel to the first fuel supply unit and the second fuel supply unit instead of the air flow control unit. In claim 1 or 2,
Alcohol concentration detecting means for detecting the alcohol concentration of the fuel;
An internal combustion engine that controls the strength of the airflow in accordance with the alcohol concentration detected by the alcohol concentration detection means.

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