JP2010014060A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize fuel supply action and improve a combustion state and exhaust emission in an internal combustion engine using a biofuel. <P>SOLUTION: An internal combustion engine 10 is provided with a fuel tank 30, a deteriorated fuel separation device 40, a branched fuel pipe 42, and a combustion device 46. Biofuel used as fuel for the internal combustion engine 10 is stored in the fuel tank 30. The deteriorated fuel separation device 40 separates deteriorated fuel contained in the biofuel. The separated deteriorated fuel is supplied to the combustion device 46 via the branched fuel pipe 42 and a deteriorated fuel tank 44. The combustion device 46 burns the deteriorated fuel at an upstream side of a catalyst 24 and warms up the catalyst 24 by the combustion gas. Consequently, normal fuel injection can be done by separating deteriorated fuel in the biofuel, and the catalyst 24 can be efficiently warmed up by using deteriorated fuel. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device suitably used for controlling the operating state of an internal combustion engine, and more particularly to a control device for an internal combustion engine that can be applied to biofuel.

  As a conventional technique, for example, as disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2006-144736), the biofuel is used as a fuel for an internal combustion engine, and the biofuel is used for exhaust gas purification. System is known. Prior art systems reform bioethanol containing ethanol and use the reformed gas as fuel. In the prior art, biofuel is also supplied into the exhaust gas, and NOx in the exhaust gas is purified by using the purification ability of ethanol.

JP 2006-144736 A

  By the way, in the above-described conventional technology, the biofuel and the reformed gas are combusted in the cylinder of the internal combustion engine, or the biofuel is supplied into the exhaust gas. In this case, biofuel is often injected from an injector such as a fuel injection valve or an exhaust addition valve. However, since biofuel contains unsaturated organic compounds and the like, oxidation degradation is likely to occur particularly in an environment exposed to high temperatures such as an internal combustion engine. When biofuel is oxidatively deteriorated, the density and viscosity of the fuel increase due to the formation of polymer and the like.

  As a result, when the biofuel used in the internal combustion engine is oxidized and deteriorated, the fuel injection valve, the exhaust addition valve, or the like may be clogged. For this reason, in the prior art, there is a problem that the fuel injection amount becomes unstable or the exhaust emission deteriorates according to the deterioration level of the biofuel.

  The present invention has been made in order to solve the above-described problems, and the object of the present invention is to stably perform fuel injection even when degraded fuel is contained in biofuel, An object of the present invention is to provide a control device for an internal combustion engine capable of improving exhaust emission.

The first invention comprises a deteriorated fuel separating means for separating deteriorated fuel from biofuel used as fuel for an internal combustion engine,
A catalyst for purifying unpurified components contained in the exhaust gas of the internal combustion engine;
A deteriorated fuel supply means for supplying deteriorated fuel separated from the biofuel to the upstream side of the catalyst;
It is characterized by providing.

According to a second invention, in the first invention,
It is configured to include deteriorated fuel combustion means for burning the deteriorated fuel supplied to the upstream side of the catalyst.

According to a third invention, in the second invention,
Temperature detecting means for detecting the temperature of the catalyst;
Combustion control means for burning the deteriorated fuel by the deteriorated fuel combustion means when the temperature of the catalyst is lower than a judgment value for combustion;
It is set as the structure provided with.

According to a fourth invention, in any one of the first to third inventions,
A deteriorated fuel heating means for heating the deteriorated fuel supplied to the upstream side of the catalyst is provided.

According to a fifth invention, in the fourth invention,
The deteriorated fuel heating means is configured to heat the deteriorated fuel using heat of exhaust gas.

According to a sixth invention, in the fourth or fifth invention,
The deteriorated fuel heating means includes
A bypass passage connecting the exhaust port of the internal combustion engine and the upstream side of the catalyst at a shorter distance than the normal exhaust passage;
A bypass on-off valve for opening and closing the bypass passage;
It is set as the structure provided with.

According to a seventh invention, in any of the fourth to sixth inventions,
Temperature detecting means for detecting the temperature of the catalyst;
Heating control means for heating the deteriorated fuel by the deteriorated fuel heating means when the temperature of the catalyst is lower than a heating judgment value;
It is set as the structure provided with.

An eighth invention is any one of the first to seventh inventions,
A deteriorated fuel tank is provided for storing the deteriorated fuel separated from the biofuel.

  According to the first invention, even if the biofuel used in the internal combustion engine contains the deteriorated fuel, the deteriorated fuel can be separated from the normal fuel by the deteriorated fuel separating means. Accordingly, it is possible to prevent the deteriorated fuel from being supplied to the fuel injection system, and to perform fuel injection stably. Moreover, according to the deteriorated fuel supply means, the separated deteriorated fuel can be supplied to the upstream side of the catalyst. By burning this fuel, for example, inside or upstream of the catalyst, the catalyst temperature can be increased efficiently. For this reason, even in a low temperature state such as during a cold start, the catalyst can be quickly warmed up using the deteriorated fuel that is an unnecessary separation product. Therefore, the catalyst can be activated at an early stage, and the exhaust emission at the start can be improved with certainty.

  According to the second aspect of the invention, the deteriorated fuel combustion means can burn the separated deteriorated fuel upstream of the catalyst. In this case, for example, by using a dedicated burner or the like, the deteriorated fuel having reduced volatility can be reliably burned. Moreover, since a high temperature combustion gas can be obtained, the heating efficiency of a catalyst can be improved.

  According to the third invention, the combustion control means can control the deteriorated fuel combustion means in accordance with the magnitude relationship between the catalyst temperature and the combustion determination value. Thereby, the deteriorated fuel can be burned on the upstream side of the catalyst only in a low temperature state where the catalyst activity is lower than the allowable limit. In other cases, it is not necessary to burn the deteriorated fuel, so that useless combustion can be prevented, and the influence of the deterioration fuel combustion on the exhaust emission can be minimized.

  According to the fourth invention, when the deteriorated fuel is burned in a state where it is difficult to vaporize, such as at a low temperature start, a relatively large amount of HC is likely to be generated because the combustion state is bad. On the other hand, the deteriorated fuel heating means can efficiently heat the deteriorated fuel supplied to the deteriorated fuel combustion means by using high-temperature exhaust gas. Thereby, vaporization of a deteriorated fuel can be accelerated | stimulated and this can be burned in a favorable state. Therefore, HC generated during combustion of the deteriorated fuel can be suppressed to a minimum, and exhaust emission at the time of starting can be improved.

  According to the fifth aspect of the present invention, the deteriorated fuel can be easily heated using the heat of the exhaust gas without using a special heating device or heating neelgi. For this reason, the heating structure mounted on the system can be simplified, and the operating efficiency of the system can be increased.

  According to the sixth invention, when the exhaust gas is supplied to the deteriorated fuel combustion means through the normal exhaust path, the exhaust gas passes through a relatively long exhaust path or passes through a device such as a turbocharger. The temperature of the exhaust gas decreases accordingly. In contrast, the bypass passage can quickly supply the exhaust gas having a high temperature discharged from the internal combustion engine to the position of the deteriorated fuel combustion means.

  According to the seventh aspect, the heating control means can control the deteriorated fuel heating means in accordance with the magnitude relationship between the catalyst temperature and the heating determination value. As a result, the fuel can be heated accurately only at low temperatures when the deteriorated fuel is difficult to vaporize. In other cases, it is not necessary to carry out the heating control, so that the system can be operated in a normal state.

  According to the eighth aspect, the deteriorated fuel separated during the operation of the internal combustion engine can be temporarily stored in the deteriorated fuel tank. When the deteriorated fuel is required by the deteriorated fuel combustion means, the deteriorated fuel stored in the tank can be supplied quickly.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
The first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an overall configuration diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in this figure, the system of the present embodiment includes a multi-cylinder internal combustion engine 10 made of, for example, a diesel engine. The internal combustion engine 10 includes an intake passage 12 through which intake air flows and an exhaust passage 14 through which exhaust gas flows.

  The intake passage 12 is connected to an intake port of each cylinder via an intake manifold 16. The intake passage 12 is provided with an air flow meter 18 for detecting the intake air amount, an electric throttle valve 20 for adjusting the intake air amount, and the like. On the other hand, the exhaust passage 14 is connected to an exhaust port of each cylinder via an exhaust manifold 22.

  The exhaust passage 14 is provided with a catalyst 24 that purifies unpurified components in the exhaust gas. As the catalyst 24, for example, a general catalyst such as a three-way catalyst or a NOx storage reduction catalyst is used. Further, the exhaust manifold 22 is provided with an exhaust addition valve 26 made of an electromagnetic valve or the like. The exhaust addition valve 26 is for increasing the temperature of the catalyst 24, regenerating it, etc. by adding fuel to the exhaust gas. Further, the intake passage 12 and the exhaust passage 14 are provided with a turbocharger 28 that supercharges intake air using the exhaust pressure of the internal combustion engine.

  Next, the fuel supply system of this embodiment will be described. The fuel supply system includes a fuel tank 30 for storing biofuel. The biofuel is a fuel containing alcohols produced using, for example, various vegetable oils, plant materials, and the like as raw materials. A common rail 34 is connected to the fuel tank 30 via a fuel pipe 32, and a fuel injection valve 36 for each cylinder is connected to the common rail 34.

  During the operation of the internal combustion engine, the fuel pump disposed in the fuel tank 30 is operated to supply biofuel in the tank to the common rail 34. This fuel is injected into each cylinder from the fuel injection valve 36 and combusts together with the intake air sucked into the cylinder from the intake passage 12. Further, the exhaust gas after combustion flows through the exhaust passage 14 and the unpurified components in the exhaust gas are purified by the catalyst 24 and then released to the outside.

  Here, since biofuel contains oxygen atoms, unsaturated organic compounds, and the like, oxidation degradation is likely to occur particularly in an environment exposed to high temperatures such as an internal combustion engine. When biofuel is oxidatively deteriorated, the density and viscosity of the fuel increase due to the formation of polymer and the like. If the deteriorated fuel is supplied to the fuel injection valve 36, the injection valve may be clogged.

  In order to cope with such a problem, the system of the present embodiment is equipped with a fuel deterioration sensor 38, a deteriorated fuel separator 40, a deteriorated fuel tank 44, and a combustion device 46. The fuel deterioration sensor 38 detects the deterioration level of biofuel. More specifically, the fuel deterioration sensor 38 detects the concentration of a deterioration component (polymer or the like) contained in the biofuel, or the density, viscosity, etc. of the fuel, and the deterioration level of the biofuel based on the detection result. A detection signal corresponding to is output.

  The deteriorated fuel separator 40 separates the deteriorated fuel contained in the biofuel from normal fuel (fuel that has not deteriorated), and sends this deteriorated fuel to the branch fuel pipe 42. As an example of a specific structure of the deteriorated fuel separator 40, the device 40 includes an electromagnetic switching valve (three-way valve) and the like. This switching valve is configured to switch the connection destination of the fuel tank 30 to either the common rail 34 or the deteriorated fuel tank 44.

  In the present embodiment, the deteriorated fuel separation device 40 provided with a switching valve has been described as an example of the deteriorated fuel separation means. However, the present invention is not limited to this, and the deteriorated fuel separation device 40 may be realized using, for example, a separation membrane that separates fuel. In this case, the separation membrane is, for example, a filter having a selective permeability for only one of normal fuel and deteriorated fuel.

  The branch fuel pipe 42 is connected between the deteriorated fuel separator 40 and the combustion device 46, and constitutes the deteriorated fuel supply means of the present embodiment. That is, the branch fuel pipe 42 supplies the deteriorated fuel separated from the biofuel to the upstream side of the catalyst 24. The deteriorated fuel tank 44 is a tank for temporarily storing the separated deteriorated fuel, and is provided in the middle of the branch fuel pipe 42. A fuel pump or the like (not shown) is disposed in the deteriorated fuel tank 44, and this fuel pump supplies deteriorated fuel stored in the tank 44 to the combustion device 46 as necessary.

  In this embodiment, since the deteriorated fuel tank 44 is installed, the deteriorated fuel separated during operation of the engine can be temporarily stored in the deteriorated fuel tank 44. When the deteriorated fuel is required by the combustion device 46, the deteriorated fuel stored in the tank 44 can be supplied quickly.

  The combustion device 46 burns the deteriorated fuel supplied from the deteriorated fuel tank 44 on the upstream side of the catalyst 24, and constitutes the deteriorated fuel combustion means of the present embodiment. The combustion device 46 includes an ignition burner installed in the exhaust passage 14. During the operation of the burner, high temperature combustion gas is generated by burning the deteriorated fuel, and this combustion gas is configured to heat the catalyst 24 on the downstream side.

  Further, the system of the present embodiment includes a sensor system including an air flow meter 18, a fuel deterioration sensor 38, a catalyst temperature sensor 48, and the like, and an ECU (Electronic Control Unit) 50 that controls the operation of the internal combustion engine 10. Here, the catalyst temperature sensor 48 detects the temperature (bed temperature) of the catalyst 24 and constitutes the temperature detection means of the present embodiment. The sensor system includes a water temperature sensor that detects the cooling water temperature of the internal combustion engine, an A / F sensor that detects the air-fuel ratio of the exhaust gas, an accelerator opening sensor that detects the accelerator opening, and the like. These sensors are connected to the input side of the ECU 50.

  On the other hand, the internal combustion engine 10 includes various actuators including a throttle valve 20, an exhaust addition valve 26, a fuel injection valve 36, a switching valve for a deteriorated fuel separator 40, a fuel pump in tanks 30 and 44, a combustion device 46, and the like. ing. These actuators are connected to the output side of the ECU 50. The ECU 50 drives each actuator based on various parameters detected by the sensor system, thereby controlling the operating state of the internal combustion engine. This operation control includes fuel separation control described below and combustion control of deteriorated fuel.

(Fuel separation control)
In the fuel separation control, the deteriorated fuel contained in the biofuel is separated and stored in the deteriorated fuel tank 44. More specifically, in the fuel separation control, first, when biofuel in the fuel tank 30 is supplied to the common rail 34, the fuel deterioration sensor 38 detects the biofuel deterioration level Vfuel. Then, the deterioration level Vfuel is compared with a deterioration determination value Vd described later to determine whether or not the deterioration degree of the biofuel is within a normal range. When the fuel is normal, it is supplied to the common rail 34 as it is. When the fuel has deteriorated, the fuel is stored in the deteriorated fuel tank 44 by the deteriorated fuel separator 40.

  According to this configuration, even if the biofuel contains degraded fuel, the degraded fuel can be separated from normal fuel by the degraded fuel separator 40. Thereby, it can prevent that a deteriorated fuel is supplied to the fuel injection valve 36, and can perform fuel injection stably. In this case, in the process of separating the deteriorated fuel, since it is determined whether or not the fuel is deteriorated according to the magnitude relationship between the deterioration level Vfuel and the deterioration determination value Vd, only the deteriorated fuel of the biofuel is reliably and easily separated. can do.

  Moreover, according to the present embodiment, the separated deteriorated fuel can be combusted on the upstream side of the catalyst 24, and the catalyst temperature can be efficiently increased by the combustion gas. In particular, since the dedicated combustion device 46 is used, the deteriorated fuel having reduced volatility can be reliably burned by a burner or the like, and a high-temperature combustion gas can be obtained. Therefore, the catalyst 24 can be quickly warmed up by using the deteriorated fuel that is an unnecessary separation product even in a low temperature state such as during cold start. Thereby, the catalyst 24 can be activated at an early stage, and the exhaust emission especially at the time of starting can be improved reliably.

(Deterioration fuel combustion control)
This combustion control is characterized in that the catalyst 24 is warmed up using deteriorated fuel in a low temperature state where the catalyst activity is not sufficiently exhibited. FIG. 2 is a characteristic diagram showing the relationship between the NOx occlusion amount of the catalyst 24 and the catalyst temperature. As shown in this figure, the NOx occlusion ability of the catalyst 24 is extremely lowered in a low temperature region than the activation temperature (about 300 ° C.). Therefore, in the present embodiment, when the temperature Tc detected by the catalyst temperature sensor 48 is lower than a combustion determination value Td described later, the deteriorated fuel in the deteriorated fuel tank 44 is supplied to the combustion device 46, and this fuel Is combusted upstream of the catalyst 24.

  FIG. 3 is a characteristic diagram showing the relationship between the elapsed time after starting and the catalyst temperature for each of the case where the deteriorated fuel is burned and the case where it is not burned. As shown in this figure, it can be seen that when the deteriorated fuel is burned, the catalyst temperature rises more quickly than when the deteriorated fuel is not burned, and the catalyst 24 is activated early.

  According to the above configuration, the combustion device 46 can be controlled in accordance with the magnitude relationship between the catalyst temperature Tc and the combustion determination value Td. As a result, the deteriorated fuel can be burned on the upstream side of the catalyst 24 only in a low temperature state where the catalyst activity falls below the allowable limit. In other cases, it is not necessary to carry out the combustion control, so that useless combustion can be prevented and the influence of the combustion control on the exhaust emission can be minimized.

[Specific Processing for Realizing Embodiment 1]
FIG. 4 is a flowchart of control executed by the ECU 50 in the first embodiment of the present invention. Note that the routine of FIG. 4 is repeatedly executed during operation of the internal combustion engine. In this routine, first, the deterioration level Vfuel of the biofuel is detected by the fuel deterioration sensor 38 (step 100). Then, it is determined whether or not the deterioration level Vfuel is equal to or higher than the deterioration determination value Vd (step 102).

  Here, the deterioration determination value Vd is the minimum value of the deterioration level at which the fuel injection valve 36 and the like are adversely affected, and is stored in the ECU 50 in advance. That is, when the fuel deterioration level Vfuel is equal to or higher than the deterioration determination value Vd, if this fuel is supplied to the common rail 34, the injection valve may be clogged.

  Therefore, when the determination in step 102 is satisfied, the deteriorated fuel separator 40 is switched to store the deteriorated fuel supplied from the fuel tank 30 in the deteriorated fuel tank 44 (step 104). Further, when the determination in step 102 is not established, the deterioration level of the biofuel is relatively light, so that the fuel is supplied to the common rail 34 by the deteriorated fuel separator 40 (step 106).

  Next, the temperature Tc of the catalyst 24 is detected by the catalyst temperature sensor 48 (step 108), and it is determined whether or not the catalyst temperature Tc is equal to or higher than the combustion determination value Td (step 110). The combustion determination value Td is a temperature set corresponding to the activation temperature of the catalyst 24, for example, and is stored in the ECU 50 in advance. That is, when the catalyst temperature Tc is equal to or higher than the combustion determination value Td, sufficient catalyst performance can be obtained without warming up the catalyst 24. Therefore, when the determination in step 110 is established, the above-described deterioration fuel combustion control is not performed, and the process ends.

  On the other hand, when the determination in step 110 is not established, the catalyst 24 is in a low temperature state where the purification capability is not sufficiently exhibited, and thus the combustion control of the deteriorated fuel is started by operating the combustion device 46 (step 112). This combustion control is continued until the determination in step 110 is satisfied, and is terminated when the determination is satisfied. Thereby, the catalyst 24 can be warmed up quickly.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is an overall configuration diagram for explaining a system configuration according to the second embodiment of the present invention. As shown in this figure, the present embodiment employs a system configuration substantially similar to that of the first embodiment. However, in this embodiment, a bypass passage 60 and a bypass opening / closing valve 62 serving as deteriorated fuel heating means are provided between the exhaust passage 14 and the exhaust manifold 22, and this is a different configuration from the first embodiment. have.

[Features of Embodiment 2]
The internal combustion engine 10 includes a normal exhaust path from the exhaust manifold 22 to the exhaust passage 14 via the turbocharger 28. The bypass passage 60 short-circuits the exhaust manifold 22 and the exhaust passage 14 without passing through the turbocharger 28 with respect to the exhaust passage. That is, the bypass passage 60 connects the exhaust port of the internal combustion engine and the upstream side of the catalyst 24 at a shorter distance than the normal exhaust path.

  The combustion device 46 described above is provided at a position where the bypass passage 60 joins the exhaust passage 14. Thereby, the exhaust gas flowing through the bypass passage 60 can heat the burner of the combustion device 46 and the deteriorated fuel supplied to the burner. Further, the bypass passage 60 is provided with a bypass opening / closing valve 62 made of an electromagnetic valve or the like. The bypass opening / closing valve 62 opens and closes the bypass passage 60 in accordance with a control signal input from the ECU 50.

(Heating control of deteriorated fuel)
This heating control is to heat the deteriorated fuel supplied to the combustion device 46 by the heat of the exhaust gas in a low temperature state where the deteriorated fuel is difficult to vaporize. More specifically, in the heating control, the bypass on-off valve 62 is opened when the combustion device 46 is operating (that is, when the catalytic activity is not sufficiently exhibited due to low temperature). The heating control is continued until the temperature Tc of the catalyst 24 becomes equal to or higher than a heating determination value Td ′ described later.

  As a result, the high-temperature exhaust gas discharged to the exhaust manifold 22 directly reaches the position of the combustion device 46 through the bypass passage 60 without passing through the turbocharger 28. Thus, according to the bypass passage 60, the burned fuel of the combustion device 46 and the deteriorated fuel supplied to the burner can be efficiently heated using the high-temperature exhaust gas.

  FIG. 6 is a characteristic diagram showing the relationship between the elapsed time after startup and the hydrocarbon (HC) in the exhaust gas flowing into the catalyst. In FIG. 6, the dotted line immediately after the start indicates the HC concentration when the heating control is performed. On the other hand, the solid line indicates the HC concentration when heating control is not performed. As shown in this figure, according to the heating control of the deteriorated fuel, the HC concentration immediately after start-up can be reduced for the reason described below.

  That is, when the deteriorated fuel is burned in a state where it is difficult to vaporize, such as at a low temperature start, a relatively large amount of HC is likely to be generated because the combustion state is poor. On the other hand, in the present embodiment, vaporization of the deteriorated fuel can be promoted by the high-temperature exhaust gas, and the deteriorated fuel can be burned in a good state. In this case, if the exhaust gas is supplied to the combustion device 46 through the normal exhaust path, the exhaust gas flows through the relatively long exhaust path or passes through the turbocharger 28. Therefore, the temperature of the exhaust gas is correspondingly increased. descend.

  However, in the present embodiment, since the bypass passage 60 is provided, it is possible to avoid the temperature reduction of the exhaust gas as described above. The high-temperature exhaust gas discharged from the internal combustion engine to the exhaust manifold 22 can be quickly supplied to the position of the combustion device 46 through the bypass passage 60. For this reason, for example, even immediately after startup, the deteriorated fuel can be efficiently vaporized using the exhaust gas having a high temperature.

  Therefore, according to the present embodiment, in addition to the effects of the first embodiment, it is possible to minimize HC generated during combustion of deteriorated fuel. Thereby, exhaust emission at the time of starting etc. can be improved. Further, by using the bypass passage 60, it is possible to easily heat the deteriorated fuel by using the heat of the exhaust gas without using a special heating device or heating energy. For this reason, the heating structure mounted on the system can be simplified, and the operating efficiency of the system can be increased.

  In the heating control of the deteriorated fuel, the bypass opening / closing valve 62 can be controlled according to the magnitude relationship between the catalyst temperature Tc and the heating determination value Td ′. As a result, the fuel can be heated accurately only at low temperatures when the deteriorated fuel is difficult to vaporize. In other cases, it is not necessary to perform the heating control, so that the exhaust can be performed through the normal exhaust path, and the influence on the supercharging operation or the like of the turbocharger 28 can be minimized.

[Specific Processing for Realizing Embodiment 2]
7 and 8 are flowcharts of control executed by the ECU 50 in the second embodiment of the present invention. Note that the routines shown in these figures are repeatedly executed during operation of the internal combustion engine.

  First, in the routine shown in FIG. 7, in steps 200 to 206, processing similar to that in steps 100 to 106 in the first embodiment is performed. That is, the biofuel is distributed to either the common rail 34 or the deteriorated fuel tank 44 in accordance with the magnitude relationship between the deterioration level Vfuel of the biofuel and the deterioration determination value Vd.

  Next, the temperature Tc of the catalyst 24 is detected by the catalyst temperature sensor 48 (step 208), and it is determined whether or not the catalyst temperature Tc is equal to or higher than the above-described combustion determination value Td (step 210). Then, when the determination in step 210 is established, the processing ends as it is in the same manner as in the first embodiment. Further, when the determination at step 210 is not established, the catalyst temperature increasing process shown in FIG. 8 is executed because the purification capability of the catalyst 24 is not sufficiently exhibited. In this case, the processing in steps 208 to 212 is repeated until the catalyst temperature Tc becomes equal to or higher than the combustion determination value Td.

  Next, in the catalyst temperature raising process shown in FIG. 8, first, as in the first embodiment, the combustion device 46 is operated to start the combustion control of the deteriorated fuel (step 300). Then, the catalyst temperature Tc is detected (step 302). Further, the bypass on-off valve (exhaust gas valve) 62 is opened, and the heating control of the deteriorated fuel is started (step 304). Thereby, the deteriorated fuel supplied to the combustion device 46 is heated by the high-temperature exhaust gas flowing from the bypass passage 60 and burned by the combustion device 46 in a vaporized state. As a result, the catalyst 24 is heated by the high-temperature combustion gas as in the first embodiment.

  Therefore, in step 306, it is determined whether or not the catalyst temperature Tc has risen above the heating determination value Td ′. The heating determination value Td ′ is a temperature set according to, for example, the temperature characteristics of the ease of vaporization of the deteriorated fuel, the activation temperature of the catalyst 24, and the like, and is stored in the ECU 50 in advance. That is, when the catalyst temperature Tc is equal to or higher than the heating determination value Td ′, sufficient catalyst performance can be obtained without heating the deteriorated fuel.

  For this reason, when the determination in step 306 is established, the bypass on-off valve 62 is closed, and the heating control of the deteriorated fuel is ended (step 308). In this case, the combustion control of the deteriorated fuel is also terminated. On the other hand, when the determination in step 306 is not satisfied, the processes of steps 302 to 306 are repeated, and the combustion control and heating control of the deteriorated fuel are continued until the determination is not satisfied. Thereby, even at the time of cold start etc., the catalyst 24 can be activated early, suppressing discharge | emission of HC.

  In the first and second embodiments, steps 110 and 112 in FIG. 4 and 210 and 212 in FIG. 7 show specific examples of the combustion control means. Steps 304 to 308 in FIG. 8 show a specific example of the heating control means.

  In the first and second embodiments, the deteriorated fuel is burned on the upstream side of the catalyst 24 by using the combustion device 46. However, the present invention does not necessarily require the use of the combustion device 46. For example, the deteriorated fuel may be combusted by the heat of the catalyst, thereby warming up the catalyst. In this configuration, for example, a fuel injection valve is disposed upstream of the catalyst 24 instead of the combustion device 46. The fuel injection valve injects the deteriorated fuel supplied from the branch fuel pipe 42 into the exhaust passage 14 on the upstream side of the catalyst 24. The injected deteriorated fuel flows into the catalyst 24 by the flow of exhaust gas and burns by the heat of the catalyst 24. Thereby, even if it does not use the combustion apparatus 46, catalyst temperature can be raised early.

  In the second embodiment, exhaust gas is supplied to the position of the combustion device 46 through the bypass passage 60 to heat the deteriorated fuel. However, the present invention is not limited to this, and instead of the bypass passage 60, the deteriorated fuel may be heated by, for example, an electric heater or the like.

  Further, in the second embodiment, the combustion determination value Td and the heating determination value Td ′ are used as the determination values for switching the control. In this case, in the present invention, these two determination values Td and Td ′ may be set to the same value or different values as necessary.

It is a whole block diagram for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a characteristic diagram which shows the relationship between the NOx occlusion amount of a catalyst, and catalyst temperature. It is a characteristic diagram which shows the relationship between the elapsed time after a starting, and the catalyst temperature about each when not decombusting when a deteriorated fuel is burned. In Embodiment 1 of this invention, it is a flowchart of the fuel pressure holding | maintenance control performed by ECU. It is a whole block diagram for demonstrating the system configuration | structure of Embodiment 2 of this invention. It is a characteristic diagram which shows the relationship between the elapsed time after starting, and the hydrocarbon in the exhaust gas which flows into a catalyst. In Embodiment 2 of this invention, it is a flowchart of the fuel pressure holding | maintenance control performed by ECU. In Embodiment 2 of this invention, it is a flowchart of the fuel pressure holding | maintenance control performed by ECU.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Intake passage 14 Exhaust passage 16 Intake manifold 18 Air flow meter 20 Throttle valve 22 Exhaust manifold 24 Catalyst 26 Exhaust addition valve 28 Turbocharger 30 Fuel tank 32 Fuel piping 34 Common rail 36 Fuel injection valve 38 Fuel deterioration sensor 40 Degraded fuel separation Equipment (Degraded fuel separation means)
42 Branch fuel piping (deteriorated fuel supply means)
44 Deteriorated fuel tank 46 Combustion device (Deteriorated fuel combustion means)
48 Catalyst temperature sensor (temperature detection means)
50 ECU
60 Bypass passage (degraded fuel heating means)
62 Bypass on-off valve (degraded fuel heating means)

Claims (8)

A deteriorated fuel separation means for separating deteriorated fuel from biofuel used as fuel for an internal combustion engine;
A catalyst for purifying unpurified components contained in the exhaust gas of the internal combustion engine;
A deteriorated fuel supply means for supplying deteriorated fuel separated from the biofuel to the upstream side of the catalyst;
A control device for an internal combustion engine, comprising:   The control apparatus for an internal combustion engine according to claim 1, further comprising a deteriorated fuel combustion means for burning the deteriorated fuel supplied to the upstream side of the catalyst. Temperature detecting means for detecting the temperature of the catalyst;
Combustion control means for burning the deteriorated fuel by the deteriorated fuel combustion means when the temperature of the catalyst is lower than a judgment value for combustion;
The control device for an internal combustion engine according to claim 2, comprising:   The control apparatus for an internal combustion engine according to any one of claims 1 to 3, further comprising deteriorated fuel heating means for heating the deteriorated fuel supplied to the upstream side of the catalyst.   The control apparatus for an internal combustion engine according to claim 4, wherein the deteriorated fuel heating means is configured to heat the deteriorated fuel using heat of exhaust gas. The deteriorated fuel heating means includes
A bypass passage connecting the exhaust port of the internal combustion engine and the upstream side of the catalyst at a shorter distance than the normal exhaust passage;
A bypass on-off valve for opening and closing the bypass passage;
The control apparatus for an internal combustion engine according to claim 4 or 5, further comprising: Temperature detecting means for detecting the temperature of the catalyst;
Heating control means for heating the deteriorated fuel by the deteriorated fuel heating means when the temperature of the catalyst is lower than a heating judgment value;
The control apparatus for an internal combustion engine according to any one of claims 4 to 6, further comprising:   The control device for an internal combustion engine according to any one of claims 1 to 7, further comprising a deteriorated fuel tank that stores the deteriorated fuel separated from the biofuel.

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