JP2009203924A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately determine the concentration of biofuel in fuel, in an internal combustion engine using mixed fuel of the biofuel and hydrocarbon fuel, in relation to a control device of the internal combustion engine. <P>SOLUTION: This control device of the internal combustion engine has the internal combustion engine capable of using the fuel mixed with the biofuel and the hydrocarbon fuel produced from biomass, a parameter acquiring means for acquiring a combustion destabilizing parameter such as the EGR ratio of destabilizing combustion of the internal combustion engine, an ignition delay period measuring means for measuring an ignition delay period being a period until ignition is caused after injecting the fuel into a combustion chamber of the internal combustion chamber, and a biofuel concentration determining means for determining the concentration of the biofuel included in the fuel based on the relationship between the combustion destabilizing parameter and the ignition delay period measured by the ignition delay period measuring means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  There is known an internal combustion engine that uses a fuel obtained by mixing a biofuel produced from biomass and a fossil fuel-derived hydrocarbon fuel. For example, Japanese Unexamined Patent Application Publication No. 2005-171818 discloses a premixed compression ignition internal combustion engine that uses a fuel containing a fatty acid methyl ester produced from rapeseed oil, palm oil, waste cooking oil or the like. According to the publication, biofuel tends to have a high cetane number, so if a fuel with high biofuel concentration is subjected to premixed combustion, the ignitability of the premixed gas becomes high, and the ignition timing of the premixed gas is the standard ignition timing. It is stated that there is a possibility that it will be earlier than the season. On the premise of this, in the system described in the publication, the biofuel concentration is detected by a biofuel concentration sensor, and the higher the biofuel concentration, the smaller the operating region in which premixed combustion is performed, and normal combustion is performed. The operation area is expanded.

JP-A-2005-171818 JP 2007-64157 A JP 2006-242146 A

  However, the system described in the above publication has a problem that the manufacturing cost increases because an expensive biofuel concentration sensor needs to be provided. Further, the above publication describes that biofuel has a high cetane number, but according to the knowledge of the present inventors, it may not be said that the cetane number of a fuel containing biofuel is necessarily high. . That is, the cetane number of the fuel and the biofuel concentration may not necessarily be correlated.

  On the other hand, Japanese Patent Laid-Open No. 2007-64157 discloses a technique for estimating the cetane number of fuel based on an ignition delay correction amount in feedback control for making the actual ignition timing coincide with the target ignition timing. However, this publication does not disclose any method of using a mixed fuel of biofuel and hydrocarbon fuel, and further, a method for determining the concentration of biofuel in the fuel. Further, as described above, since the cetane number of the fuel and the biofuel concentration are not necessarily correlated, the biofuel concentration cannot be obtained from the cetane number.

  The present invention has been made in view of the above points, and in an internal combustion engine using a mixed fuel of a biofuel and a hydrocarbon fuel, the internal combustion engine capable of accurately determining the concentration of the biofuel in the fuel. An object of the present invention is to provide a control device.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
An internal combustion engine capable of using a mixture of biofuel produced from biomass and hydrocarbon fuel;
Parameter acquisition means for acquiring a combustion destabilization parameter that is a predetermined operating parameter that destabilizes the combustion of the internal combustion engine;
An ignition delay period measuring means for measuring an ignition delay period which is a period from when fuel is injected into the combustion chamber of the internal combustion engine until ignition occurs;
Biofuel concentration determination means for determining the concentration of biofuel contained in fuel based on the relationship between the combustion destabilization parameter and the ignition delay period measured by the ignition delay period measurement means;
It is characterized by providing.

The second invention is the first invention, wherein
Refueling detection means for detecting refueling;
Parameter control means for controlling the combustion destabilization parameter to temporarily match a predetermined value for biofuel concentration determination when refueling is detected;
With
The ignition delay period measuring means measures an ignition delay period when the combustion destabilization parameter matches the predetermined value.

The third invention is the first or second invention, wherein
The combustion destabilization parameter is an EGR rate or a fuel injection timing retardation amount.

According to a fourth invention, in any one of the first to third inventions,
The ignition delay period measuring means measures an ignition delay period under a plurality of operating states having different values of the combustion destabilization parameter,
The biofuel concentration determination means determines the biofuel concentration based on a relationship between an ignition delay period under the plurality of operation states and the combustion destabilization parameter.

According to a fifth invention, in any one of the first to fourth inventions,
The biofuel concentration determination means stores in advance a map showing the relationship between the combustion destabilization parameter and the ignition delay period for each biofuel concentration, and compares the measured ignition delay period with the map. Thus, the biofuel concentration is determined.

The sixth invention is the fifth invention, wherein
The map stipulates that the higher the biofuel concentration, the smaller the increase in the ignition delay period associated with the change in the combustion destabilization parameter in the direction of combustion destabilization.

The seventh invention is the fifth or sixth invention, wherein
The map is characterized in that the difference in the ignition delay period due to the difference in biofuel concentration increases as the combustion destabilization parameter changes in the direction of combustion destabilization.

Further, an eighth invention is any one of the first to seventh inventions,
The biofuel concentration determination means includes biofuel type determination means for determining the type of biofuel.

According to a ninth invention, in any one of the first to eighth inventions,
An EGR device for performing EGR in the internal combustion engine;
EGR control means for increasing the amount of EGR as the biofuel concentration value determined by the biofuel concentration determination means is higher,
It is characterized by providing.

According to a tenth invention, in any one of the first to ninth inventions,
An exhaust fuel addition device for adding fuel to the exhaust system of the internal combustion engine;
As the biofuel concentration value determined by the biofuel concentration determination means is higher, the fuel addition condition when adding fuel by the exhaust system fuel addition device is corrected so that the fuel is more easily vaporized. Fuel addition condition correction means for
It is characterized by providing.

  According to the first aspect, the concentration of biofuel contained in the fuel can be determined based on the relationship between the combustion destabilization parameter of the internal combustion engine and the measured ignition delay period. According to the knowledge of the present inventors, the difference in the biofuel concentration is less likely to appear in the difference in the ignition delay period in the operation state where the combustion is stable. There is a phenomenon in which a difference in concentration appears remarkably in a difference in the ignition delay period. According to the first invention, based on this phenomenon, the biofuel concentration is determined with high accuracy by detecting the relationship between the combustion destabilization parameter that destabilizes the combustion of the internal combustion engine and the ignition delay period. be able to.

  According to the second invention, when refueling is detected, the ignition instability parameter is positively controlled so as to become a predetermined value suitable for biofuel concentration determination, and the ignition delay period is measured. The biofuel concentration can be determined based on the measurement result. For this reason, when there is a possibility that the biofuel concentration has changed due to the refueling of new fuel, the biofuel concentration can be re-determined quickly and with high accuracy.

  According to the third invention, the biofuel concentration can be determined with higher accuracy by using the EGR rate or the fuel injection timing retard amount as the combustion destabilization parameter.

  According to the fourth invention, the ignition delay period is measured under a plurality of operating states having different values of the combustion instability parameter, and the ignition delay period and the combustion instability parameter under the plurality of operating states are determined. The biofuel concentration can be determined based on the relationship. Thereby, since the relationship between the ignition delay period and the combustion destabilization parameter can be grasped more accurately, the biofuel concentration can be determined with higher accuracy.

  According to the fifth aspect of the invention, a map showing the relationship between the combustion destabilization parameter and the ignition delay period for each biofuel concentration is stored in advance, and the biofuel concentration can be determined based on the map. Thereby, the biofuel concentration can be determined with high accuracy by a simple method.

  According to the sixth aspect of the invention, a map that defines that the increase in the ignition delay period associated with the change in the combustion destabilization parameter toward the combustion destabilization direction is smaller as the biofuel concentration is higher is used. Thus, the biofuel concentration can be determined with high accuracy.

  According to the seventh invention, by using a map that stipulates that the difference in the ignition delay period due to the difference in biofuel concentration increases as the combustion destabilization parameter changes in the combustion destabilization direction, The biofuel concentration can be determined with high accuracy.

  According to the eighth aspect, in addition to the biofuel concentration, the type of biofuel can be determined.

  According to the ninth aspect, the EGR amount can be increased as the determined biofuel concentration value is higher. The higher the biofuel concentration, the better the EGR limit because combustion is improved. Therefore, according to the ninth invention, when the biofuel concentration is high and it can be determined that the EGR limit is high, the NOx emission amount can be further reduced by increasing the EGR amount.

  According to the tenth invention, as the determined biofuel concentration value is higher, the fuel addition condition when the fuel is added by the exhaust system fuel addition device is corrected so that the fuel is more easily vaporized. can do. Accordingly, even when the biofuel concentration is high and difficult to vaporize, the vaporization of the exhaust added fuel can be promoted. Therefore, it is possible to reliably prevent the exhaust-added fuel from being clogged in the catalyst and the effects of rich spikes, S regeneration, and the like from being reduced.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes a diesel engine (compression ignition internal combustion engine) 10. It is assumed that the diesel engine 10 is mounted on a vehicle and used as a power source. Although the diesel engine 10 of the present embodiment is an in-line four-cylinder type, the number of cylinders and the cylinder arrangement are not limited to this in the present invention.

  Each cylinder of the diesel engine 10 is provided with an injector 11 that injects fuel directly into the cylinder. The injector 11 of each cylinder is connected to a common common rail 12. In the common rail 12, high-pressure fuel pressurized by the supply pump 13 is stored. Then, fuel is supplied from the common rail 12 to each injector 11.

  The injector 11 may be capable of injecting fuel into the cylinder at an arbitrary timing a plurality of times during one cycle. That is, during one cycle, in addition to the main injection that is the main fuel injection, a pilot injection prior to the main injection may be performed.

  Such a diesel engine 10 includes a fossil fuel-derived hydrocarbon fuel (light oil in this embodiment) and a biofuel produced from biomass such as rapeseed oil, soybean oil, palm oil, and waste cooking oil (this embodiment). In the form, it can be operated using a fuel mixed with fatty acid methyl ester).

  The fuel used in the diesel engine 10 is stored in the fuel tank 14. The fuel in the fuel tank 14 is supplied to the supply pump 13 through the fuel pipe 15. A fuel filter 16 is installed in the middle of the fuel pipe 15.

  The diesel engine 10 of this embodiment includes a turbocharger 17. The turbocharger 17 has an exhaust turbine 17a and an intake compressor 17b driven by the exhaust turbine 17a. The exhaust turbine 17 a is disposed in the middle of the exhaust passage 18. The intake air compressor 17 b is disposed in the intake passage 19.

  An exhaust purification device 20 is installed in the exhaust passage 18 on the downstream side of the exhaust turbine 17a. As the exhaust purification device 20, for example, a NOx occlusion reduction type catalyst, DPF (Diesel Particulate Filter), DPNR (Diesel Particulate-NOx-Reduction system) or the like can be used. An exhaust throttle valve 21 is installed in the exhaust passage 18 on the downstream side of the exhaust purification device 20.

  An air cleaner 22 is provided near the inlet of the intake passage 19 of the diesel engine 10. The air sucked through the air cleaner 22 is compressed by the intake compressor 17 b and then cooled by the intercooler 23. The cooled intake air passes through the intake manifold 24 and flows into each cylinder.

  An intake throttle valve 25 is installed in the intake passage 19 between the intercooler 23 and the intake manifold 24. An air flow meter 26 for detecting the amount of intake air is installed in the vicinity of the intake passage 19 downstream of the air cleaner 22.

  The diesel engine 10 is provided with an EGR device for performing a so-called external EGR (Exhaust Gas Recirculation) that recirculates a part of the exhaust gas to the intake passage 19. This EGR device has an EGR passage 27, an EGR valve 28, and an EGR cooler 29. The EGR passage 27 connects the exhaust manifold 30 and the intake passage 19 on the downstream side of the intake throttle valve 25. The amount of exhaust gas (that is, EGR gas) passing through the EGR passage 27 is adjusted by the opening degree of the EGR valve 28. The EGR cooler 29 cools the EGR gas passing through the EGR passage 27.

  Further, the diesel engine 10 is provided with a fuel addition injector 31 that adds fuel to the exhaust gas, and an in-cylinder pressure sensor (combustion pressure sensor) 32 that detects the pressure in the combustion chamber of the diesel engine 10. Fuel is supplied from the supply pump 13 to the fuel addition injector 31.

  In this system, a fuel addition injector is used when performing a rich spike for reducing and purifying NOx stored in the exhaust purification device 20, or when performing S regeneration for recovering sulfur poisoning of the exhaust purification device 20. Fuel is injected from 31 into the exhaust gas. The fuel injected from the fuel addition injector 31 is hereinafter referred to as “exhaust addition fuel”.

  The system of the present embodiment includes a crank angle sensor 34 that detects the crank angle of the diesel engine 10, an accelerator opening sensor 35 that detects the amount of depression of the accelerator pedal (accelerator opening) of the vehicle on which the diesel engine 10 is mounted, And an ECU (Electronic Control Unit) 50. The ECU 50 is electrically connected to the various sensors and actuators described above. The ECU 50 controls the operating state of the diesel engine 10 by operating each actuator according to a predetermined program based on the output of each sensor.

  As described above, the diesel engine 10 of the present embodiment can be operated by a mixed fuel of light oil and methyl ester which is a biofuel. The concentration of biofuel contained in the fuel supplied to the diesel engine 10, that is, the fuel in the fuel tank 14 varies depending on what biofuel concentration the user supplies. In order to optimally control the diesel engine 10, it is important to correct various control values according to the level of the biofuel concentration. As a method for obtaining the biofuel concentration in the fuel, it may be possible to directly measure by providing a fuel property sensor capable of detecting the biofuel concentration. However, such a fuel property sensor is expensive. For this reason, from the viewpoint of cost reduction, it is required to accurately determine the biofuel concentration without using a fuel property sensor.

  By the way, the ignition delay period of the diesel engine 10 correlates with the cetane number of the fuel. Therefore, conventionally, a technique is known in which the ignition delay period is measured based on the in-cylinder pressure detected by the in-cylinder pressure sensor 32, and the cetane number of the fuel is calculated from the ignition delay period. It is conceivable to apply this technique as a method for determining the biofuel concentration without using a fuel property sensor. However, according to the knowledge of the present inventors, the cetane number of the fuel and the biofuel concentration are not necessarily correlated. For example, about 30% of light oil mixed with 30% methyl ester (hereinafter referred to as “RME”) produced from rapeseed oil, that is, 30% of RME, the cetane number measured by the JIS (Japanese Industrial Standard) measurement method is almost equivalent to 100% It is. Therefore, the cetane number cannot be simply converted into the biofuel concentration.

  As a result of intensive studies while considering the above-described circumstances, the present inventors have found a phenomenon that the difference in the biofuel concentration appears more greatly in the difference in the ignition delay period as the operating state has a higher EGR rate. I found it. That is, the relationship between the EGR rate, the ignition delay period, and the biofuel concentration (RME concentration) can be expressed as shown in FIG. The horizontal axis in FIG. 2 is the EGR rate of the diesel engine 10, and the vertical axis is the ignition delay period represented by the crank angle.

  As shown in FIG. 2, in the operation state where the EGR rate is close to 0%, the ignition delay period is substantially the same regardless of the RME concentration. This indicates that the cetane number of the light oil RME mixed fuel is almost the same regardless of the RME concentration. And even if it is a case where any fuel is used, an ignition delay period increases as an EGR rate becomes high. However, the method of increasing the ignition delay period is more gradual as the fuel having a higher RME concentration. That is, in an operation state with a high EGR rate, the ignition delay period becomes shorter as the fuel with a higher RME concentration.

  The reason why the above phenomenon occurs is not necessarily clear, but can be considered as follows. Biofuel is an oxygen-containing fuel containing a large amount of oxygen atoms. On the other hand, light oil, which is a hydrocarbon fuel, does not contain oxygen. Therefore, the higher the biofuel concentration, the greater the amount of oxygen contained.

  On the other hand, when the EGR rate increases, the inert gas concentration in the combustion chamber increases and the oxygen concentration decreases. For this reason, it becomes the situation where fuel is hard to burn. Even under such circumstances, in the fuel having a high biofuel concentration, oxygen deficiency can be compensated for by oxygen in the fuel, and the oxidation reaction (that is, combustion) can be promoted. For this reason, in an operation state with a high EGR rate, it is considered that the higher the biofuel concentration, the shorter the ignition delay period.

  Based on the knowledge as described above, in the system of the present embodiment, the ignition delay period is measured under an operation state in which the EGR rate is relatively high, and the relationship between the ignition delay period and the EGR rate is shown in FIG. The biofuel concentration was determined by collating with such a map.

  In this embodiment, the ignition delay period is measured in each of a plurality of operating states with different EGR rates (for example, four EGR rates of 10%, 20%, 30%, and 40%), and the plurality of operating states are measured. The biofuel concentration was determined based on the relationship between the EGR rate and the ignition delay period below. Thereby, it can be determined with higher accuracy whether the relationship between the EGR rate and the ignition delay period corresponds to which biofuel concentration curve in the map as shown in FIG. That is, the biofuel concentration can be determined with higher accuracy.

  In addition, by grasping the relationship between the EGR rate and the ignition delay period under multiple operating conditions with different EGR rates, not only the biofuel concentration but also the type of biofuel (type due to differences in raw materials, manufacturing methods, etc.) is determined It is also possible to do. FIG. 3 shows the relationship between the EGR rate, the ignition delay period, and the biofuel concentration (SME concentration) when a mixed fuel of methyl ester (hereinafter referred to as “SME”) produced from soybean oil and light oil is used. FIG. As shown in FIGS. 2 and 3, the shape of the curve indicating the relationship between the EGR rate and the ignition delay period differs between the case of the RME light oil mixed fuel and the case of the SME light oil mixed fuel. Thus, the shape of the curve indicated by the relationship between the EGR rate, the ignition delay period, and the biofuel concentration changes according to the type of biofuel to be mixed. Therefore, in the present embodiment, maps such as those shown in FIGS. 2 and 3 are prepared for each type of biofuel, and data of ignition delay periods measured under a plurality of operating states having different EGR rates are used. By comparing with this map, it was decided to determine which curve the data corresponds to. Thereby, both the kind and density | concentration of biofuel can be determined accurately.

  The timing for determining the type and concentration of the biofuel contained in the fuel is not particularly limited, but it is preferably performed after the fuel tank 14 is refueled. This is because when the fuel tank 14 is refueled, the composition of the fuel in the fuel tank 14 changes depending on the type and concentration of biofuel in the newly fueled fuel. Therefore, in this embodiment, when refueling to the fuel tank 14 is detected, the type and concentration of the biofuel are subsequently determined. At this time, in this embodiment, the EGR rate is actively controlled so as to become a predetermined plurality of values (in this embodiment, 10%, 20%, 30%, and 40%), and those It was decided to measure the ignition delay period under each EGR rate.

  That is, in normal operation EGR control, the EGR rate is controlled to be an optimum EGR rate according to the engine speed, engine load, and the like. That is, the EGR rate changes according to changes in engine speed and engine load. For this reason, when the ignition delay period is measured after sequentially waiting for the EGR rate to become a plurality of predetermined values, the time required to complete the determination of the type and concentration of the biofuel increases, Various controls cannot be optimized. Therefore, in the present embodiment, when refueling is detected, the type and concentration of biofuel are determined by actively controlling the EGR rate to be a plurality of predetermined values and measuring the ignition delay period. Was completed quickly.

  In the present embodiment, after the determination of the type and concentration of biofuel is completed, it is preferable to perform, for example, the following control using the determination result.

(EGR control)
EGR is effective in reducing NOx emissions. As the EGR amount increases, the NOx emission amount can be reduced. However, when the EGR amount is increased, there is a problem that the emission amount of PM (Particulate Matter) is likely to increase. For this reason, there is a limit to the amount of EGR. In contrast, in a fuel having a high biofuel concentration, the oxidation reaction (combustion) is improved by the oxygen contained therein, so that the amount of PM emission is reduced. As a result, there is room for the PM regulation value, and the EGR amount can be increased by that amount. Therefore, in this embodiment, control is performed so that the EGR amount increases as the biofuel concentration increases. As a result, when a fuel with a high biofuel concentration is used, the EGR amount can be increased more than usual, so that the NOx emission amount can be further reduced.

(Exhaust fuel addition control)
As described above, when the rich spike or the S regeneration of the exhaust purification device 20 is performed, the fuel is injected from the fuel addition injector 31 into the exhaust gas. When such exhaust fuel addition is performed, it is important that the exhaust addition fuel injected from the fuel addition injector 31 is sufficiently vaporized. This is because if the fuel added to the exhaust gas is not sufficiently vaporized, the effects such as rich spike and S regeneration may not be sufficiently exerted, or the fuel inside the exhaust purification device 20 may be clogged. Therefore, usually, a predetermined amount of fuel is injected from the fuel addition injector 31 at predetermined intervals.

  Biofuels generally have the characteristics of high kinematic viscosity and poor evaporation. When exhaust fuel is added, both the injection pressure and the ambient temperature are low. For this reason, in the case of a fuel with a high biofuel concentration, vaporization tends to be insufficient. As a result, the effects such as rich spike and S regeneration are reduced and clogging in the exhaust purification device 20 is likely to occur. Therefore, in the present embodiment, as the biofuel concentration is higher, the injection amount per one time of the fuel addition injector 31 is reduced. Thereby, vaporization of the exhaust gas added fuel can be promoted, and it is possible to reliably avoid the occurrence of the inconvenience as described above. Further, when the injection amount per one injection of the fuel addition injector 31 is reduced, the total addition amount of the exhaust additive fuel reaches the required amount by shortening the injection interval.

[Specific Processing in Embodiment 1]
FIG. 4 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. This routine is repeatedly executed every predetermined time. Note that this routine is executed after the diesel engine 10 is started. According to the routine shown in FIG. 4, first, it is determined whether or not there is a refueling history in the fuel tank 14 (step 100). The method of detecting refueling is not particularly limited. For example, a sender gauge (level gauge) provided in the fuel tank 14, a fuel lid of a vehicle equipped with the diesel engine 10, an ORVR (Onboard Refueling Vapor Recovery) system (whichever It is possible to detect that refueling has been performed based on a state such as (not shown). When it is detected that refueling has been performed, it is assumed that there is a refueling history.

  If it is determined in step 100 that there is no refueling history, it can be determined that the type and concentration of the biofuel in the fuel tank 14 is the same as that in the previous operation and has not changed. . In this case, since it is not necessary to re-determine the type and concentration of biofuel, the execution of this routine is terminated as it is.

  On the other hand, if it is determined in step 100 that there is a refueling history, it can be determined that the biofuel concentration or type of fuel in the fuel tank 14 may change. Therefore, in this case, the type and concentration of the biofuel are determined as follows. First, it is determined whether or not the measurement of the ignition delay period is completed for each of a plurality of predetermined EGR rates (step 102). In the present embodiment, the ignition delay period is measured in each operation state in which the EGR rate is 10%, 20%, 30%, and 40%. Therefore, in step 102, it is determined whether or not the measurement of the ignition delay period is completed for each of the four EGR rates.

  If it is determined in step 102 that the ignition delay period in at least one of the EGR rates of 10%, 20%, 30%, and 40% is unmeasured, the ignition delay in the unmeasured EGR rate In order to measure the period, the EGR rate is controlled to be the value (step 104). The actual EGR rate can be calculated based on the engine speed, the engine load, the intake air amount, and the like. In step 104, the opening degree of the EGR valve 28 and the opening degree of the intake throttle valve 25 are controlled as necessary so that the actual EGR rate becomes the predetermined value.

  If the actual EGR rate is controlled to coincide with the predetermined value, then the ignition delay period is measured (step 106). In the present embodiment, the ignition delay period is measured based on the in-cylinder pressure detected by the in-cylinder pressure sensor 32. When the fuel injected into the combustion chamber is ignited and combustion starts, the in-cylinder pressure starts to rise rapidly. For this reason, the actual ignition timing can be detected by detecting the in-cylinder pressure with the in-cylinder pressure sensor 32. Therefore, in step 106, the difference between the actual ignition timing and the fuel injection timing (main injection timing) is measured as the ignition delay period.

  In the present invention, the method for measuring the ignition delay period is not limited to the above method. For example, it is possible to measure the ignition delay period based on the signal of the crank angle sensor 34. That is, when the fuel in the combustion chamber is ignited and combustion is started, thermal energy is generated and the piston is pushed down, so that the rotation of the crankshaft of the diesel engine 10 detected by the crank angle sensor 34 changes sharply. By detecting this variation, the actual ignition timing can be detected, and therefore the ignition delay period can be measured. As described above, the method for measuring the ignition delay period based on the signal of the crank angle sensor 34 is described in detail in Japanese Patent Application Laid-Open No. 61-197742, and is well known, so further explanation is omitted here. To do.

  After the ignition delay period is measured in step 106, the processing in step 102 and subsequent steps is executed again. That is, it is determined again whether or not the measurement of the ignition delay period at each EGR rate of 10%, 20%, 30%, and 40% is completed, and the measurement of the ignition delay period is not completed at any EGR rate. If there is, the processes of steps 104 and 106 are executed again. In this way, by repeatedly executing the processing of steps 104 and 106, the measurement of the ignition delay period in each operation state in which the EGR rate is 10%, 20%, 30%, and 40% is sequentially executed.

  When the measurement of the ignition delay period at the four EGR rates of 10%, 20%, 30%, and 40% is completed and the determination in step 102 is affirmed, the type of biofuel is determined based on the measurement result. The density is determined as follows (step 108). As described above, the ECU 50 stores in advance maps such as those shown in FIGS. 2 and 3 for each type of biofuel assumed to be used. That is, in these maps, curve data indicating the relationship between the EGR rate and the ignition delay period is defined for each type and concentration of biofuel. In step 108, the curve closest to the curve composed of the data of the ignition delay period at the four EGR rates measured by the above processing is selected from the curve group of such a map. And the kind and density | concentration (for example, RME30% etc.) of the biofuel which the curve shows are made into a determination result.

  Once the type and concentration of the biofuel are determined, a process for optimizing the EGR control is executed based on the determination result (step 110). FIG. 5 is a diagram illustrating an example of a map used for optimizing EGR control. The top column of the map of FIG. 5 is the EGR valve opening when the fuel is 100% light oil. On the other hand, the column that follows is the EGR valve opening degree in the case of fuel mixed with biofuel. In step 110, the EGR valve opening is corrected using the values in the column corresponding to the type and concentration of the biofuel determined in step 108 in each column of the map shown in FIG. According to the map shown in FIG. 5, as the biofuel concentration is higher, the EGR valve opening is corrected in the expansion direction, and the EGR amount is increased. As described above, the higher the biofuel concentration, the more difficult the PM is discharged, and there is a margin for the regulation value. Therefore, the EGR amount can be increased by that amount. For this reason, the NOx emission amount can be further reduced by increasing the EGR amount.

Subsequently, a process for optimizing the exhaust addition control is executed (step 112). FIG. 6 is a diagram showing an example of an exhaust addition coefficient map used for optimizing the exhaust addition control. In the present embodiment, when fuel is added to the exhaust gas from the fuel addition injector 31 in rich spike or S regeneration, the injection amount per injection and the injection interval are multiplied by the exhaust addition coefficient shown in FIG. It shall be corrected. For example, according to the example shown in FIG. 6, when it is determined that the RME is 20% in the exhaust fuel addition condition in which the injection amount per normal time and the injection interval are 50 mm ³ / time and 25 seconds. Then, 45 mm ³ / time obtained by multiplying this by 0.9 and 22.5 seconds are set as the injection amount and injection interval per time.

  According to the process of step 112, the added fuel from the fuel addition injector 31 can be injected in small portions as the biofuel concentration is high, that is, the case where the exhaust addition fuel is less likely to vaporize. For this reason, vaporization of the exhaust gas added fuel can be promoted. Therefore, it is possible to reliably prevent adverse effects such as a decrease in the effect such as rich spike and S regeneration, and fuel clogging in the exhaust purification device 20.

  In the present invention, the method for optimizing the exhaust gas addition control is not limited to the above method. For example, instead of the above method, vaporization may be promoted by correcting the injection pressure from the fuel addition injector 31 to be higher as the biofuel concentration is higher.

  As described above, according to the system of the present embodiment, the biofuel concentration in the fuel can be determined without using an expensive fuel property sensor. In particular, the biofuel concentration is determined by utilizing the phenomenon that the difference in the biofuel concentration appears more prominently as the difference in the ignition delay period when the EGR rate is relatively high and the combustion state is likely to become unstable. Therefore, the biofuel concentration can be determined with high accuracy.

  In addition to the case where the EGR rate is relatively high, if the operation state is such that the combustion is likely to become unstable, a phenomenon in which the difference in the biofuel concentration appears significantly as the difference in the ignition delay period occurs. For example, if the fuel injection timing from the injector 11 is retarded from the normal timing, the combustion is likely to become unstable, and in such a state, a difference in biofuel concentration appears significantly as a difference in ignition delay period. Therefore, in the present invention, even if the fuel injection timing retardation amount (retard amount from the normal timing) of the injector 11 is used as the combustion destabilization parameter instead of the EGR rate, the above-described embodiment. Similar to 1, it is possible to determine the concentration and type of biofuel.

  In the first embodiment described above, the EGR rate is the “combustion destabilization parameter” in the first invention, and the fuel addition injector 31 is the “exhaust system fuel addition device” in the tenth invention. It corresponds. Further, the ECU 50 calculates the actual EGR rate by a known method based on the signal of each sensor, so that the “parameter acquisition unit” in the first invention executes the processing of step 106 to execute the first step. When the “ignition delay period measuring means” in the invention of the first aspect executes the process of step 108, the “biofuel concentration determination means” of the first aspect of the invention executes the process of step 100 to execute the second step. When the “oil supply detecting means” in the invention of the second aspect executes the process of step 104, the “parameter control means” in the second aspect of the invention executes the process of step 108, and “ In the ninth aspect of the present invention, the “biofuel species discriminating means” "EGR control means", "fuel addition condition correcting means" in the invention of claim 10 by performing the process of step 112 is implemented, respectively.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure which shows the relationship between an EGR rate, an ignition delay period, and biofuel concentration (RME concentration). It is a figure which shows the relationship between an EGR rate, an ignition delay period, and biofuel concentration (SME concentration). It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure which shows the example of the map used in order to optimize EGR control. It is a figure which shows the example of the map of the exhaust gas addition coefficient used in order to optimize exhaust gas addition control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Diesel engine 11 Injector 12 Common rail 14 Fuel tank 17 Turbo supercharger 18 Exhaust passage 19 Intake passage 20 Exhaust purification device 21 Exhaust throttle valve 24 Intake manifold 25 Intake throttle valve 26 Air flow meter 27 EGR passage 28 EGR valve 30 Exhaust manifold 31 Fuel Additive injector 32 In-cylinder pressure sensor 50 ECU

Claims (10)

An internal combustion engine capable of using a mixture of biofuel produced from biomass and hydrocarbon fuel;
Parameter acquisition means for acquiring a combustion destabilization parameter that is a predetermined operating parameter that destabilizes the combustion of the internal combustion engine;
An ignition delay period measuring means for measuring an ignition delay period which is a period from when fuel is injected into the combustion chamber of the internal combustion engine until ignition occurs;
Biofuel concentration determination means for determining the concentration of biofuel contained in fuel based on the relationship between the combustion destabilization parameter and the ignition delay period measured by the ignition delay period measurement means;
A control device for an internal combustion engine, comprising: Refueling detection means for detecting refueling;
Parameter control means for controlling the combustion destabilization parameter to temporarily match a predetermined value for biofuel concentration determination when refueling is detected;
With
2. The control apparatus for an internal combustion engine according to claim 1, wherein the ignition delay period measuring means measures an ignition delay period when the combustion destabilization parameter coincides with the predetermined value.   3. The control apparatus for an internal combustion engine according to claim 1, wherein the combustion destabilization parameter is an EGR rate or a fuel injection timing retardation amount. The ignition delay period measuring means measures an ignition delay period under a plurality of operating states having different values of the combustion destabilization parameter,
The biofuel concentration determination means determines the biofuel concentration based on a relationship between an ignition delay period under the plurality of operating states and the combustion destabilization parameter. The control device for an internal combustion engine according to any one of the preceding claims.   The biofuel concentration determination means stores in advance a map showing the relationship between the combustion destabilization parameter and the ignition delay period for each biofuel concentration, and compares the measured ignition delay period with the map. 5. The control apparatus for an internal combustion engine according to claim 1, wherein the biofuel concentration is determined by the determination.   The map stipulates that, as the biofuel concentration is higher, the increase width of the ignition delay period associated with the change in the combustion destabilization parameter in the direction of combustion destabilization is smaller. 6. The control device for an internal combustion engine according to 5.   The map defines that the difference in the ignition delay period due to the difference in biofuel concentration increases as the combustion destabilization parameter changes in the direction of combustion destabilization. 6. The control apparatus for an internal combustion engine according to 6.   The control device for an internal combustion engine according to any one of claims 1 to 7, wherein the biofuel concentration determination means includes biofuel type determination means for determining the type of biofuel. An EGR device for performing EGR in the internal combustion engine;
EGR control means for increasing the amount of EGR as the biofuel concentration value determined by the biofuel concentration determination means is higher,
The control apparatus for an internal combustion engine according to any one of claims 1 to 8, further comprising: An exhaust fuel addition device for adding fuel to the exhaust system of the internal combustion engine;
As the biofuel concentration value determined by the biofuel concentration determination means is higher, the fuel addition condition when adding fuel by the exhaust system fuel addition device is corrected so that the fuel is more easily vaporized. Fuel addition condition correction means for
The control device for an internal combustion engine according to any one of claims 1 to 9, further comprising:

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