JP4770753B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine.

  Japanese Patent Application Laid-Open No. 2004-92520 discloses an exhaust reformer system. The exhaust reformer system includes a fuel reforming catalyst that is disposed in the middle of the EGR path of the internal combustion engine and is installed so as to be able to absorb the heat of the exhaust gas. Fuel is supplied to the fuel reforming catalyst. The fuel and steam in the EGR gas undergo a steam reforming reaction to generate hydrogen, carbon monoxide, and the like. This steam reforming reaction is a reaction that occurs by absorbing the heat of the exhaust gas. For this reason, the calorie | heat amount of the produced | generated reformed gas is more than the calorie | heat amount of the fuel before reaction. Therefore, when the reformed gas is recirculated to the intake passage as EGR gas and burned in the internal combustion engine, exhaust heat is recovered, so that the thermal efficiency of the internal combustion engine can be improved.

JP 2004-92520 A Japanese Utility Model Publication No. 61-21565 JP 2006-226172 A Japanese Patent Laid-Open No. 10-101301

  When reforming gasoline with a fuel reforming catalyst, if the temperature of the fuel reforming catalyst is low (for example, about 650 to 700 ° C. or less), a reaction in which carbon in the fuel is deposited is likely to occur. When this carbon deposition reaction occurs, the production amount of hydrogen and carbon monoxide decreases, and the exhaust heat recovery effect becomes small. Further, the deposited carbon adhering to the catalyst absorbs the reforming fuel, and the carbon burns, so that the fuel reforming catalyst is deteriorated. For this reason, when gasoline is used as a reforming fuel, there is a problem that fuel reforming cannot be performed in a low temperature range, and the fuel efficiency improvement effect cannot be sufficiently exhibited.

  On the other hand, in recent years, the use of alcohol extracted from sugarcane, corn, wood and the like has been promoted as fuel for automobiles. For this reason, the spread of alcohol fuel or mixed fuel in which gasoline and alcohol are mixed is expected. Therefore, a flexible fuel vehicle that can use various kinds of fuels with a mixture of alcohol has been developed.

  Japanese Utility Model Publication No. 61-21566 discloses a system that is similar to the exhaust reformer system and uses alcohol fuel as the reforming fuel. Alcohol fuels are less susceptible to carbon deposition reaction even at low temperatures, so fuel reforming can be carried out even at low temperatures. However, alcohol fuel has a smaller amount of reformed gas produced than gasoline, and the energy density of the fuel itself is also low. For this reason, there is a problem that it is difficult to obtain a sufficient fuel economy improvement effect as compared with the case of using gasoline reforming.

  The present invention has been made in view of the above points, and provides a control device for an internal combustion engine capable of suppressing deterioration of a fuel reforming catalyst and sufficiently exhibiting a fuel efficiency improvement effect by fuel reforming. For the purpose.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
An EGR path for extracting a part of the exhaust gas passing through the exhaust passage of the internal combustion engine and recirculating it to the intake passage;
A fuel reforming catalyst that is arranged in the middle of the EGR path and is provided so as to be able to absorb heat of exhaust gas passing through the exhaust passage and to reform the fuel;
A reforming fuel supply means for mixing a main fuel containing hydrocarbons and an alcohol fuel, and supplying the mixture as a reforming fuel to the fuel reforming catalyst;
The lower the temperature of the fuel reforming catalyst, the higher the proportion of alcohol in the reforming fuel, and the higher the temperature of the fuel reforming catalyst, the higher the proportion of hydrocarbons in the reforming fuel. A mixing ratio control means for controlling a mixing ratio of the main fuel and the alcohol fuel,
It is characterized by providing.

The second invention is the first invention, wherein
A supply amount control means for increasing the supply amount of the reforming fuel to the fuel reforming catalyst as the mixing ratio of the alcohol fuel increases is provided.

The third invention is a control device for an internal combustion engine,
An EGR path for extracting a part of the exhaust gas passing through the exhaust passage of the internal combustion engine and recirculating it to the intake passage;
A fuel reforming catalyst that is arranged in the middle of the EGR path and is provided so as to be able to absorb heat of exhaust gas passing through the exhaust passage and to reform the fuel;
Reforming fuel supply means for supplying reforming fuel to the fuel reforming catalyst;
Mixing ratio detection means for detecting a mixing ratio of alcohol and hydrocarbon in the reforming fuel;
Execution condition setting means for setting conditions for executing the supply of the reforming fuel to the fuel reforming catalyst;
With
The execution condition setting means sets the condition so that the higher the proportion of alcohol in the reforming fuel is, the more the reforming fuel is supplied to a region where the temperature of the fuel reforming catalyst is lower. It is characterized by relaxation.

Moreover, 4th invention is set in 3rd invention,
A supply amount control means for increasing the supply amount of the reforming fuel to the fuel reforming catalyst as the proportion of alcohol in the reforming fuel increases is provided.

  According to the first invention, a mixture obtained by mixing a main fuel containing hydrocarbons and an alcohol fuel can be supplied as a reforming fuel to a fuel reforming catalyst disposed in the middle of the EGR path. The lower the temperature of the fuel reforming catalyst, the higher the alcohol ratio in the reforming fuel, and the higher the temperature of the fuel reforming catalyst, the higher the hydrocarbon ratio in the reforming fuel. The mixing ratio of the fuel and the alcohol fuel can be controlled. Thereby, when the temperature of the fuel reforming catalyst is low and the carbon deposition reaction is likely to occur, it is possible to reliably suppress the carbon deposition reaction from occurring by increasing the alcohol ratio in the reforming fuel. . For this reason, even when the temperature of the fuel reforming catalyst is low, it is possible to prevent a reduction in reforming efficiency and deterioration of the fuel reforming catalyst, so that fuel reforming is executed up to an operation region where the exhaust gas temperature is relatively low. be able to. Further, when the temperature of the fuel reforming catalyst is high and the carbon deposition reaction is difficult to occur, the exhaust heat recovery efficiency can be further increased by increasing the hydrocarbon ratio in the reforming fuel. For this reason, according to the first aspect of the present invention, the fuel efficiency improvement effect by fuel reforming can be greatly exhibited while reliably suppressing the occurrence of the carbon deposition reaction. Furthermore, according to the first invention, when the reforming fuel having a high alcohol ratio is reformed by the fuel reforming catalyst, sulfur poisoning of the fuel reforming catalyst can be easily recovered.

  According to the second invention, the larger the mixing ratio of the alcohol fuel, the larger the amount of reforming fuel supplied to the fuel reforming catalyst. Thereby, even if the alcohol ratio in the reforming fuel changes, the properties of the gas sucked into the internal combustion engine can be kept constant. For this reason, it is possible to reliably prevent adverse effects such as combustion instability and emission deterioration.

  According to the third invention, it is possible to detect the mixing ratio of alcohol and hydrocarbon in the reforming fuel supplied to the fuel reforming catalyst arranged in the middle of the EGR path. The higher the proportion of alcohol in the reforming fuel is, the more the fuel reforming execution region can be expanded to a region where the temperature of the fuel reforming catalyst is low. As a result, the fuel reforming execution region can be set as wide as possible within a range in which the carbon deposition reaction does not occur according to the proportion of alcohol in the reforming fuel. For this reason, the exhaust heat recovery effect by fuel reforming can be enjoyed in a wide operation region, and the fuel consumption can be greatly improved. Moreover, even if the alcohol ratio in the reforming fuel changes due to the supply of different types of fuel, it is possible to reliably suppress the carbon precipitation reaction, resulting in a decrease in reforming efficiency. And deterioration of the fuel reforming catalyst can be prevented.

  According to the fourth aspect of the invention, the higher the proportion of alcohol in the reforming fuel is, the more the amount of reforming fuel supplied to the fuel reforming catalyst can be increased. Thereby, even if the alcohol ratio in the reforming fuel changes, the properties of the gas sucked into the internal combustion engine can be kept constant. For this reason, it is possible to reliably prevent adverse effects such as combustion instability and emission deterioration.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a schematic diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system according to the present embodiment includes an internal combustion engine 10 that serves as a power source for an automobile, for example. The internal combustion engine 10 is provided with a fuel injector 14 that injects fuel into the intake manifold 12. The fuel injector is not limited to such a configuration, and may be installed so as to directly inject fuel into the cylinder.

  Air is sucked into the intake passage 18 through the air cleaner 16. In the middle of the intake passage 18, an intake compressor of the turbocharger 20 is disposed. The intake air compressed by the turbocharger 20 is cooled by the intercooler 22, then distributed by the intake manifold 12 and flows into each cylinder of the internal combustion engine 10.

  Exhaust gas discharged from each cylinder flows into the exhaust passage 26 through the exhaust manifold 24. In the middle of the exhaust passage 26, an exhaust turbine of the turbocharger 20 is disposed.

  A first EGR introduction pipe 28 for performing external EGR (Exhaust Gas Recirculation) branches off from the exhaust passage 26 on the downstream side of the turbocharger 20. The first EGR introduction pipe 28 can take out a part of the exhaust gas flowing through the exhaust passage 26 as EGR gas.

  The first EGR introduction pipe 28 is connected to a fuel reforming catalyst (reformer) 30. A reforming fuel injection device 32 that injects reforming fuel is installed in the first EGR introduction pipe 28 in front of the fuel reforming catalyst 30.

  The catalyst carrier installed in the EGR gas passage inside the fuel reforming catalyst 30 carries catalyst components such as Rh, Co, and Ni, for example. The fuel reforming catalyst 30 is installed so as to be able to absorb the heat of the exhaust gas passing through the exhaust passage 26. The fuel reforming catalyst 30 is provided with a temperature sensor 34 that detects the temperature of the fuel reforming catalyst 30.

In the fuel reforming catalyst 30, hydrogen (H ₂ ) and carbon monoxide (CO) are generated by causing a reforming reaction (steam reforming reaction) between the reforming fuel and water vapor and carbon dioxide in the EGR gas. Generated.

  One end of a second EGR introduction pipe 36 is connected to the fuel reforming catalyst 30. The other end of the second EGR introduction pipe 36 is connected to the intake passage 18 upstream of the turbocharger 20. An EGR cooler 38 is installed in the middle of the second EGR introduction pipe 36. EGR gas containing hydrogen and carbon monoxide (hereinafter referred to as “reformed gas”) generated by the fuel reforming catalyst 30 is introduced into the intake passage 18 through the second EGR introduction pipe 36. An EGR valve 40 for controlling the amount of reformed gas introduced into the intake passage 18 is installed at a connection portion between the second EGR introduction pipe 36 and the intake passage 18.

  The system includes a first fuel tank 42 that stores main fuel, and a second fuel tank 44 that stores alcohol fuel (fuel mainly composed of alcohol such as ethanol). The system according to the present embodiment enables refueling with any fuel of 100% hydrocarbon fuel (referred to as gasoline in the present embodiment) and a mixed fuel of gasoline and alcohol (hereinafter simply referred to as “mixed fuel”). It has become. In the first fuel tank 42, mixed fuel or 100% gasoline fuel is stored as the main fuel according to the fuel selected by the user. The first fuel tank 42 is provided with a fuel property sensor 56 capable of detecting the mixing ratio of alcohol and gasoline in the main fuel.

The system includes a device (not shown) for separating and extracting alcohol fuel from the mixed fuel. The separated and extracted alcohol fuel is stored in the second fuel tank 44. The separation / extraction method in this case is not particularly limited. For example, the separation / extraction can be performed by any of the following methods: (1) A method of separation using a separation membrane.
(2) A method in which the mixed fuel is heated and separated using the difference in boiling points (fractional distillation).
(3) A method of separating water by adding water to the mixed fuel and transferring alcohol having high affinity with water to the aqueous phase.

  In the present invention, unlike the above, alcohol fuel may be separately supplied to the second fuel tank 44.

  The main fuel stored in the first fuel tank 42 is supplied to the fuel injector 14 through the main fuel line 46. A branch line 48 branches from the main fuel line 46. The branch line 48 is connected to the mixing ratio controller 50. On the other hand, the alcohol fuel stored in the second fuel tank 44 is supplied to the mixture ratio controller 50 through the alcohol fuel line 52.

  The main fuel supplied through the branch line 48 and the alcohol fuel supplied through the alcohol fuel line 52 are mixed by the mixing ratio controller 50. This mixed fuel becomes the reforming fuel. The reforming fuel is supplied to the reforming fuel injection device 32 through the reforming fuel line 54. The mixing ratio controller 50 is configured to freely adjust the mixing ratio of the main fuel and the alcohol fuel.

  In the present embodiment, the crankshaft of the internal combustion engine 10 is connected to the motor generator 58. The internal combustion engine 10 and the motor generator 58 constitute a hybrid system. The present invention is not limited to such a hybrid system, and the internal combustion engine 10 may be used alone as a power source.

  The system of this embodiment further includes an ECU (Electronic Control Unit) 60. The ECU 60 is electrically connected to various actuators and sensors such as the above-described reforming fuel injection device 32, EGR valve 40, mixing ratio controller 50, temperature sensor 34, and fuel property sensor 56.

The gasoline in the reforming fuel causes a reforming reaction represented by the following formula in the fuel reforming catalyst 30.
1.56 (7.6CO ₂ + 6.8H ₂ O + 40.8N ₂ ) + 3C _7.6 H _13.6 + Q1
→ 31H ₂ + 34.7CO + 63.6N ₂ (1)

On the other hand, alcohol (ethanol in this case) in the reforming fuel causes a reforming reaction represented by the following formula in the fuel reforming catalyst 30.
C ₂ H ₅ OH + 0.4CO ₂ + 0.6H ₂ O + 2.3N ₂ + Q2 → 3.6H ₂ + 2.4CO + 2.3N ₂ (2)

  Q1 and Q2 in the above formulas (1) and (2) are reaction heat absorbed by the reforming reaction. In the fuel reforming catalyst 30, the reforming reaction is performed by absorbing the heat of the exhaust gas flowing through the exhaust passage 26 as reaction heat. The amount of heat of hydrogen and carbon monoxide generated by such a reforming reaction is larger than the amount of heat of the original fuel by the amount of the reaction heat. Therefore, in this system, the reformed gas containing hydrogen and carbon monoxide is recirculated to the internal combustion engine 10 and burned, thereby increasing the output as compared with the case where the reforming fuel is burned as it is. it can. In other words, in this system, the heat efficiency of the internal combustion engine 10 can be improved by recovering the heat of the exhaust gas by the fuel reforming catalyst 30. For this reason, fuel consumption performance can be improved.

[Features of Embodiment 1]
When reforming 100% gasoline fuel, if the temperature of the fuel reforming catalyst 30 is low (for example, about 650 to 700 ° C. or less), a reaction in which carbon in the fuel is precipitated easily occurs. When this carbon deposition reaction occurs, the amount of reformed gas (hydrogen, carbon monoxide) produced decreases, so the exhaust heat recovery effect (fuel efficiency improvement effect) becomes small. Further, the deposited carbon adhering to the fuel reforming catalyst 30 absorbs the reforming fuel, and the carbon burns, so that the fuel reforming catalyst 30 is deteriorated. In order to avoid such a carbon precipitation reaction, when using 100% gasoline as the reforming fuel, the exhaust gas temperature at which the temperature of the fuel reforming catalyst 30 becomes high (eg, 700 ° C. or higher). Fuel reforming can only be carried out in a high operating range.

  On the other hand, in the case of alcohol fuel, which is an oxygen-containing fuel, the carbon deposition reaction hardly occurs even when the temperature of the fuel reforming catalyst 30 is low. For this reason, there is a merit that fuel reforming can be performed even in an operation region where the exhaust gas temperature is low. However, alcohol fuel has a smaller amount of reformed gas produced than gasoline, and therefore has a small exhaust heat recovery effect (thermal efficiency improvement effect). Furthermore, the alcohol fuel has a lower energy density than the gasoline itself. For this reason, in order to keep the property of the gas sucked into the internal combustion engine 10 constant, it is necessary to increase the amount of fuel to be reformed. For this reason, as long as no carbon deposition reaction occurs, the use of gasoline reforming is more effective in improving fuel economy.

  According to the system of the present embodiment, a mixture of gasoline and alcohol can be used as a reforming fuel. Then, by changing the mixing ratio in the mixing ratio controller 50, the alcohol ratio in the reforming fuel can be changed. In the present embodiment, in view of the above-described circumstances, the alcohol ratio in the reforming fuel is controlled according to the temperature of the fuel reforming catalyst 30.

  That is, in the present embodiment, the lower the temperature of the fuel reforming catalyst 30, the higher the alcohol ratio in the reforming fuel. The higher the alcohol ratio, the lower the gasoline ratio, so that the carbon deposition reaction is less likely to occur. For this reason, according to this embodiment, even when the temperature of the fuel reforming catalyst 30 is relatively low, the carbon deposition reaction can be reliably suppressed. Therefore, since the operating region where fuel reforming is performed can be expanded to a region where the exhaust gas temperature is low, the fuel efficiency improvement effect can be enhanced.

  In the present embodiment, the higher the temperature of the fuel reforming catalyst 30, the lower the alcohol ratio in the reforming fuel. The lower the alcohol ratio, the higher the gasoline ratio and the more reformed gasoline. For this reason, the exhaust heat recovery rate can be further increased. Further, when the temperature of the fuel reforming catalyst 30 is high, even if the reforming amount of gasoline increases, the carbon deposition reaction hardly occurs. Therefore, according to this embodiment, the reforming amount of gasoline can be increased as much as possible while preventing the carbon deposition reaction. As a result, the fuel efficiency improvement effect can be further enhanced.

  In the present embodiment, the injection amount of the reforming fuel injection device 32 is increased as the mixing ratio of the alcohol fuel in the mixing ratio controller 50 is higher. Thereby, the fuel amount reformed by the fuel reforming catalyst 30 can be increased as the alcohol ratio in the reforming fuel is higher. As described above, when using reforming of alcohol fuel instead of gasoline, it is necessary to increase the amount of fuel to be reformed in order to keep the properties of the gas sucked into the internal combustion engine 10 constant. In the present embodiment, by controlling the injection amount of the reforming fuel injection device 32 as described above, the properties of the gas sucked into the internal combustion engine 10 can be changed even if the alcohol ratio in the reforming fuel changes. Can be kept constant. For this reason, it is possible to reliably prevent adverse effects such as combustion instability and emission deterioration.

[Specific Processing in Embodiment 1]
FIG. 2 is a flowchart of a routine executed by the ECU 60 in the present embodiment in order to realize the above function. This routine is repeatedly executed every predetermined time. According to the routine shown in FIG. 2, first, fuel determination is performed based on the signal from the fuel property sensor 56 (step 100), and the main fuel stored in the first fuel tank 42 is determined based on the determination result. It is determined whether the fuel is a mixed fuel or a gasoline 100% fuel (step 102).

  When the main fuel is 100% gasoline, it is not preferable to consume alcohol fuel because alcohol fuel cannot be separated and extracted. Therefore, if it is determined in step 102 that the main fuel is 100% gasoline, gasoline control using only gasoline (main fuel) as reforming fuel is executed (step 104). In this gasoline control, the mixture ratio controller 50 is controlled so that only the main fuel is supplied to the reforming fuel injection device 32. Further, in order to prevent the carbon deposition reaction from occurring, control is performed so that fuel is injected from the reforming fuel injection device 32 only when the temperature of the fuel reforming catalyst 30 is high (eg, 700 ° C. or higher). The

  On the other hand, if it is determined in step 102 that the main fuel is a mixed fuel, then the mixing ratio of gasoline and alcohol in the main fuel is calculated based on the signal from the fuel property sensor 56 (step). 106).

  Next, it is determined whether or not the temperature of the fuel reforming catalyst 30 detected by the temperature sensor 34 is equal to or higher than a specified temperature (step 108). This specified temperature is a lower limit temperature at which fuel reforming is executed. When it is determined that the temperature of the fuel reforming catalyst 30 is lower than the specified temperature, the processing from step 102 onward is executed again.

  On the other hand, if it is determined in step 108 that the temperature of the fuel reforming catalyst 30 is equal to or higher than the specified temperature, then the temperature range of the fuel reforming catalyst 30 is read (step 110). For each temperature range of the fuel reforming catalyst 30, the ECU 60 stores a map that defines an optimal alcohol ratio in the reforming fuel in the temperature range. In this map, based on the reasons described above, the alcohol ratio is set higher as the fuel reforming catalyst 30 is in the lower temperature range, and the alcohol ratio is set lower as the fuel reforming catalyst 30 is in the higher temperature range. Yes. In step 110, the map is read, and an optimal alcohol ratio in the reforming fuel with respect to the current temperature of the fuel reforming catalyst 30 is obtained.

  Subsequently, the mixing ratio in the mixing ratio controller 50 is determined (step 112). In this step 112, based on the mixing ratio of gasoline and alcohol in the main fuel calculated in step 106 so that the alcohol ratio in the reforming fuel becomes the value obtained in step 110, the mixing ratio is determined. The mixing ratio in the controller 50 is calculated. Next, it is determined whether or not the storage amount in the second fuel tank 44 is normal (step 114). When it is determined that the storage amount in the second fuel tank 44 is normal, the mixture ratio controller 50 is operated so that the mixture ratio determined in step 112 is realized (step 116). .

  Subsequent to step 116, the injection amount of the reforming fuel injection device 32 is determined (step 118). Specifically, in the mixing ratio determined in step 112, the injection amount is determined so as to increase as the alcohol fuel mixing ratio increases. When the injection amount is determined, injection from the reforming fuel injection device 32 is executed. Thereby, the fuel reforming by the fuel reforming catalyst 30 is performed (step 120).

  On the other hand, if it is determined in step 114 that the amount stored in the second fuel tank 44 is not normal (the amount stored is small), the mixing ratio controller 50 Constant mixture ratio control is performed with the mixture ratio as a predetermined value (step 122).

  As described above, according to the routine processing shown in FIG. 2 of the present embodiment, the alcohol ratio in the reforming fuel can be increased as the temperature of the fuel reforming catalyst 30 is lower. For this reason, even in the operation region where the exhaust gas temperature is low and the temperature of the fuel reforming catalyst 30 is low, the fuel reforming can be carried out while reliably suppressing the carbon deposition reaction.

  On the other hand, when the temperature of the fuel reforming catalyst 30 is high, the proportion of alcohol in the reforming fuel can be reduced and the proportion of gasoline can be increased. That is, under conditions where the carbon deposition reaction is unlikely to occur, the reforming amount of gasoline can be increased as much as possible, so that the exhaust heat recovery rate can be further increased. For this reason, the big fuel-consumption improvement effect is acquired.

  Thus, according to the present embodiment, fuel reforming can be performed in a wide operation region, and the fuel efficiency improvement effect by fuel reforming can be exhibited greatly. Moreover, since it is possible to reliably suppress the carbon precipitation reaction, it is possible to reliably suppress the reduction in reforming efficiency and the deterioration of the fuel reforming catalyst 30. For this reason, according to the present embodiment, the fuel efficiency can be sufficiently improved.

  Further, according to the present embodiment, there is an advantage that the sulfur poisoning of the fuel reforming catalyst 30 can be easily recovered. When gasoline is used as a reforming fuel, there is a problem in that the fuel reforming catalyst 30 is poisoned by sulfur contained in the gasoline. According to this embodiment, when the fuel for reforming with a high alcohol ratio is reformed by the fuel reforming catalyst 30, sulfur poisoning of the fuel reforming catalyst 30 can be easily recovered.

  Further, according to this embodiment, the higher the mixing ratio of alcohol fuel in the mixing ratio controller 50, the more the injection amount of the reforming fuel injection device 32 can be increased. Thereby, even if the alcohol ratio in the reforming fuel changes, the properties of the gas sucked into the internal combustion engine 10 can be kept constant. For this reason, it is possible to reliably prevent adverse effects such as combustion instability and emission deterioration.

  In the first embodiment described above, the temperature sensor 34 is installed in the fuel reforming catalyst 30 to directly detect the temperature of the fuel reforming catalyst 30, but a temperature sensor is installed in the exhaust passage 26. May be. Since the fuel reforming catalyst 30 is heated by the exhaust gas as described above, the temperature of the fuel reforming catalyst 30 becomes substantially the same as the exhaust gas temperature. Therefore, in the present invention, the mixing ratio of the main fuel and the alcohol fuel in the reforming fuel may be controlled based on the exhaust gas temperature detected by the temperature sensor installed in the exhaust passage 26.

  Further, after the internal combustion engine 10 is warmed up, the mixing ratio of the main fuel and the alcohol fuel in the reforming fuel may be controlled based on conditions such as the engine speed and the load. Generally, after the internal combustion engine 10 is warmed up, the exhaust gas temperature correlates with the engine speed and the load. That is, the higher the rotation speed and the higher the load side, the higher the exhaust gas temperature, and the higher the temperature of the fuel reforming catalyst 30. Therefore, after the internal combustion engine 10 is warmed up, the mixing ratio between the main fuel and the alcohol fuel in the reforming fuel may be controlled based on the engine speed and the load, regardless of the temperature sensor. The same effect can be obtained.

  In the first embodiment described above, the first EGR introduction pipe 28 and the second EGR introduction pipe 36 are connected to the reforming fuel injection device 32 and the mixing ratio control in the “EGR path” in the first invention. The vessels 50 respectively correspond to the “reforming fuel supply means” in the first invention. Further, when the ECU 60 executes the process of the routine shown in FIG. 2, the “mixing ratio control means” in the first invention executes the process of the above step 118, thereby the “supply amount” in the second invention. "Control means" is realized respectively.

Embodiment 2. FIG.
Next, the second embodiment of the present invention will be described with reference to FIG. 3 to FIG. 5. The description will focus on the differences from the first embodiment described above, and the same matters will be described. Simplify or omit.

[Description of system configuration]
FIG. 3 is a diagram for explaining a system configuration according to the second embodiment of the present invention. In FIG. 3, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted or simplified. As shown in FIG. 3, the system according to the second embodiment includes a single fuel tank 62 without including the second fuel tank. The fuel tank 62 stores fuel selected by the user for refueling, that is, mixed fuel or 100% gasoline fuel.

  The fuel stored in the fuel tank 62 is supplied to the fuel injector 14 through the fuel line 64. A branch line 66 branches from the fuel line 64. The branch line 66 is connected to the reforming fuel injection device 32. That is, in the present embodiment, the fuel stored in the fuel tank 62 is used as it is as the reforming fuel.

[Features of Embodiment 2]
In the present embodiment, the alcohol ratio in the reforming fuel changes according to the type of fuel that the user has selected to refuel. As described above, when the alcohol ratio is high, the carbon deposition reaction hardly occurs, so that the fuel reforming can be performed up to a region where the fuel reforming catalyst 30 is at a relatively low temperature. On the contrary, if the temperature of the fuel reforming catalyst 30 is not so high that the alcohol ratio in the reforming fuel is low and approaches 100% of gasoline, the carbon deposition reaction occurs. Therefore, in this embodiment, the region where fuel reforming is performed is changed according to the alcohol ratio in the reforming fuel. Further, as in the first embodiment, the injection amount of the reforming fuel injection device 32 is changed according to the alcohol ratio in the reforming fuel.

[Specific Processing in Second Embodiment]
FIG. 4 is a flowchart of a routine executed by the ECU 60 in the present embodiment in order to realize the above function. According to the routine shown in FIG. 4, first, fuel determination of the reforming fuel is performed (step 130). This fuel determination can be made based on the signal from the fuel property sensor 56 installed in the fuel tank 62. Next, based on the result of the fuel determination, it is determined whether the reforming fuel is a mixed fuel or a gasoline 100% fuel (step 132).

  If it is determined in step 132 that the reforming fuel is 100% gasoline, gasoline control is executed as in step 104 of FIG. 2 (step 134).

  On the other hand, if it is determined in step 132 that the reforming fuel is a mixed fuel, the alcohol ratio in the reforming fuel is then calculated based on the signal from the fuel property sensor 56 (step). 136).

  Next, it is determined whether or not the temperature of the fuel reforming catalyst 30 detected by the temperature sensor 34 is equal to or higher than a specified temperature (step 138). This specified temperature is a lower limit temperature at which fuel reforming is executed. When it is determined that the temperature of the fuel reforming catalyst 30 is lower than the specified temperature, the processing from step 132 onward is executed again.

  On the other hand, if it is determined in step 138 that the temperature of the fuel reforming catalyst 30 is equal to or higher than the specified temperature, the reforming region in which fuel reforming is to be performed next is the reformation calculated in step 136. It is changed according to the alcohol ratio in the quality fuel (step 140). The ECU 60 stores a map that defines the relationship between the alcohol ratio in the reforming fuel and the temperature range of the fuel reforming catalyst 30 that should perform the fuel reforming. In this map, for the reason described above, the temperature range of the fuel reforming catalyst 30 to be subjected to fuel reforming is set to expand toward the low temperature side as the alcohol ratio is higher. In step 140, the temperature range of the fuel reforming catalyst 30 to be subjected to fuel reforming is changed based on this map. For example, when the proportion of alcohol in the reforming fuel is 0%, that is, gasoline 100%, the temperature range of the fuel reforming catalyst 30 to be subjected to fuel reforming is set to 700 ° C. or higher. Then, as the alcohol ratio increases, the temperature range is expanded to the low temperature side. When the alcohol ratio is 100%, the temperature range of the fuel reforming catalyst 30 to be subjected to fuel reforming is set to 450 ° C. or higher. The The ECU 60 permits fuel injection from the reforming fuel injection device 32 on the condition that the temperature of the fuel reforming catalyst 30 detected by the temperature sensor 34 is within the temperature range set in step 140. .

  Subsequent to step 140, the injection amount of the reforming fuel injection device 32 is changed (step 142). Specifically, based on the alcohol ratio in the reforming fuel calculated in step 136, the injection amount is changed so as to increase as the alcohol ratio increases.

  As described above, according to the routine processing shown in FIG. 4, the alcohol ratio in the reforming fuel is detected, and the higher the alcohol ratio, the more the fuel reforming catalyst 30 reaches a lower temperature region. The area where the reforming is performed can be expanded. For this reason, according to the alcohol ratio in the reforming fuel, the fuel reforming execution region can be expanded as much as possible within a range in which no carbon precipitation reaction occurs. As a result, a great fuel economy improvement effect can be obtained. Moreover, even if the alcohol ratio of the fuel to be refueled changes, it is possible to reliably suppress the carbon precipitation reaction. Therefore, it is possible to reliably suppress the reduction of the reforming efficiency and the deterioration of the fuel reforming catalyst 30.

  Moreover, according to this embodiment, the injection amount of the reforming fuel injection device 32 can be increased as the alcohol ratio in the reforming fuel is higher. Thereby, even if the alcohol ratio in the reforming fuel changes, the properties of the gas sucked into the internal combustion engine 10 can be kept constant. For this reason, it is possible to reliably prevent adverse effects such as combustion instability and emission deterioration.

  By the way, in Embodiment 2 mentioned above, the temperature sensor 34 is installed in the fuel reforming catalyst 30, and the temperature of the fuel reforming catalyst 30 detected by the temperature sensor 34 is a temperature range determined according to the alcohol ratio. However, in the present invention, a temperature sensor may be installed in the exhaust passage 26. Since the fuel reforming catalyst 30 is heated by the exhaust gas as described above, the temperature of the fuel reforming catalyst 30 becomes substantially the same as the exhaust gas temperature. Therefore, in the present invention, when the exhaust gas temperature detected by the temperature sensor installed in the exhaust passage 26 is within the temperature range determined according to the alcohol ratio, execution of fuel reforming is permitted. Also good.

  In the present invention, after the internal combustion engine 10 is warmed up, the fuel reform execution condition may be set based on the engine speed, the load, and the like. An example thereof will be described with reference to FIG. Generally, after the internal combustion engine 10 is warmed up, the exhaust gas temperature correlates with the engine speed and the load. FIG. 5 is a diagram showing the correlation. The horizontal axis in FIG. 5 is the engine speed, and the vertical axis is the load (engine torque). In addition, a large number of lower right lines in FIG. 5 are isotherms formed by connecting points having the same exhaust gas temperature. In FIG. 5, the exhaust gas temperature is 700 ° C. or higher in the operation region on the high rotation high load side from the isotherm A. Therefore, when the reforming fuel is 100% gasoline, execution of fuel reforming is permitted when the engine speed and the load are on the high-rotation high-load side from the isotherm A. Then, as the alcohol ratio in the reforming fuel increases, the isotherm permitting the execution of fuel reforming is expanded to the low temperature side, and when the alcohol ratio is 100%, the isothermal in FIG. Expand to line B (450 ° C). That is, when the alcohol ratio is 100%, execution of fuel reforming is permitted when the engine speed and the load are higher than the isotherm B on the higher rotation and higher load side. Thus, the same effect can be obtained even when the control is performed based on the engine speed and the load, regardless of the temperature sensor.

  In the second embodiment described above, the first EGR introduction pipe 28 and the second EGR introduction pipe 36 are provided in the “EGR path” in the third invention, and the reforming fuel injection device 32 is provided in the third embodiment. The fuel property sensor 56 corresponds to the “reforming fuel supply means” in the present invention, and the “mixing ratio detecting means” in the third invention. Further, when the ECU 60 executes the process of step 140, the “execution condition setting control means” in the third aspect of the invention executes the process of step 142, whereby the “supply amount control” of the fourth aspect of the invention is performed. Each means is realized.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the system configuration | structure of Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a figure which shows the relationship between an engine speed and load, and exhaust gas temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Intake manifold 14 Fuel injector 16 Air cleaner 18 Intake passage 20 Turbo supercharger 22 Intercooler 24 Exhaust manifold 26 Exhaust passage 28 First EGR introduction pipe 30 Fuel reforming catalyst 32 Reforming fuel injection device 34 Temperature sensor 36 Second EGR introduction pipe 38 EGR cooler 40 EGR valve 42 First fuel tank 44 Second fuel tank 50 Mixing ratio controller 56 Fuel property sensor 58 Motor generator 60 ECU
62 Fuel tank

Claims (4)

An EGR path for extracting a part of the exhaust gas passing through the exhaust passage of the internal combustion engine and recirculating it to the intake passage;
A fuel reforming catalyst that is arranged in the middle of the EGR path and is provided so as to be able to absorb heat of exhaust gas passing through the exhaust passage and to reform the fuel;
A reforming fuel supply means for mixing a main fuel containing hydrocarbons and an alcohol fuel, and supplying the mixture as a reforming fuel to the fuel reforming catalyst;
The lower the temperature of the fuel reforming catalyst, the higher the proportion of alcohol in the reforming fuel, and the higher the temperature of the fuel reforming catalyst, the higher the proportion of hydrocarbons in the reforming fuel. A mixing ratio control means for controlling a mixing ratio of the main fuel and the alcohol fuel,
A control device for an internal combustion engine, comprising:   2. The control apparatus for an internal combustion engine according to claim 1, further comprising supply amount control means for increasing the supply amount of the reforming fuel to the fuel reforming catalyst as the mixing ratio of the alcohol fuel increases. . An EGR path for extracting a part of the exhaust gas passing through the exhaust passage of the internal combustion engine and recirculating it to the intake passage;
A fuel reforming catalyst that is arranged in the middle of the EGR path and is provided so as to be able to absorb heat of exhaust gas passing through the exhaust passage and to reform the fuel;
Reforming fuel supply means for supplying reforming fuel to the fuel reforming catalyst;
Mixing ratio detection means for detecting a mixing ratio of alcohol and hydrocarbon in the reforming fuel;
Execution condition setting means for setting conditions for executing the supply of the reforming fuel to the fuel reforming catalyst;
With
The execution condition setting means sets the condition so that the higher the proportion of alcohol in the reforming fuel is, the more the reforming fuel is supplied to a region where the temperature of the fuel reforming catalyst is lower. A control device for an internal combustion engine, characterized by mitigating.   4. The internal combustion engine according to claim 3, further comprising supply amount control means for increasing the supply amount of the reforming fuel to the fuel reforming catalyst as the proportion of alcohol in the reforming fuel is higher. Engine control device.

Images