JP5493585B2 - Control device for internal combustion engine - Google Patents

Description

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

  In recent years, it has become necessary to use alternative fuels for internal combustion engines from the viewpoints of oil depletion and global environmental problems. Therefore, it is desired to develop an internal combustion engine that can handle a wide variety of fuels. In order to deal with a wide variety of fuels, it is desirable to accurately detect the cetane number of the fuel in an actual vehicle. This is because it is necessary to perform engine control in accordance with the cetane number of the fuel in order to properly control the combustion.

  As a method for detecting a cetane number on a vehicle, conventionally, a method is known in which an in-cylinder pressure sensor is provided to detect an in-cylinder pressure to detect an ignition delay period and to estimate the cetane number from the ignition delay period. (For example, refer to Patent Document 1).

JP 2009-46989 A JP 2005-344557 A JP 2009-36027 A JP 2008-208773 A

  However, since the in-cylinder pressure sensor is expensive, it may be difficult to install the in-cylinder pressure sensor from the viewpoint of cost.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine that can accurately determine the cetane number of fuel with a low-cost configuration.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
Pilot injection means for performing pilot injection prior to main fuel injection in the cylinder of the internal combustion engine;
First operating means for operating the internal combustion engine with the amount of pilot injection as a first amount;
Second operating means for operating the internal combustion engine with the amount of pilot injection as a second amount different from the first amount;
Regarding the amount of at least one of CO and HC discharged from the internal combustion engine, when the internal combustion engine is operated by the first operating means, and when the internal combustion engine is operated by the second operating means Change detecting means for detecting changes between
Cetane number determination means for determining the cetane number of the fuel based on the change detected by the change detection means ,
The first operating means includes means for controlling the pilot injection amount per unit air amount to be a first predetermined amount,
The second operating means includes means for controlling the amount of the pilot injection per unit air amount to be a second predetermined amount different from the first predetermined amount.

The second invention is a control device for an internal combustion engine,
  Pilot injection means for performing pilot injection prior to main fuel injection in the cylinder of the internal combustion engine;
  First operating means for operating the internal combustion engine with the amount of pilot injection as a first amount;
  Second operating means for operating the internal combustion engine with the amount of pilot injection as a second amount different from the first amount;
  Regarding the amount of at least one of CO and HC discharged from the internal combustion engine, when the internal combustion engine is operated by the first operating means, and when the internal combustion engine is operated by the second operating means Change detecting means for detecting changes between
  Cetane number determination means for determining the cetane number of the fuel based on the change detected by the change detection means,
  The cetane number determining means includes cetane number calculating means for calculating the cetane number of the fuel based on the amount of change detected by the change detecting means.

The third invention is a control device for an internal combustion engine,
  Pilot injection means for performing pilot injection prior to main fuel injection in the cylinder of the internal combustion engine;
  First operating means for operating the internal combustion engine with the amount of pilot injection as a first amount;
  Second operating means for operating the internal combustion engine with the amount of pilot injection as a second amount different from the first amount;
  Regarding the amount of at least one of CO and HC discharged from the internal combustion engine, when the internal combustion engine is operated by the first operating means, and when the internal combustion engine is operated by the second operating means Change detecting means for detecting changes between
  Cetane number determination means for determining the cetane number of the fuel based on the change detected by the change detection means,
  The cetane number determining means includes means for determining the level of the cetane number of the fuel based on the sign of the amount of change detected by the change detecting means.

  The fourth invention is a control device for an internal combustion engine,
  A catalyst disposed in the exhaust passage of the internal combustion engine and having a function of oxidizing harmful components;
  Pilot injection means for performing pilot injection prior to main fuel injection in the cylinder of the internal combustion engine;
  First operating means for operating the internal combustion engine with the amount of pilot injection as a first amount;
  Second operating means for operating the internal combustion engine with the amount of pilot injection as a second amount different from the first amount;
  Regarding the amount of at least one of CO and HC discharged from the internal combustion engine, when the internal combustion engine is operated by the first operating means, and when the internal combustion engine is operated by the second operating means Change detecting means for detecting changes between
  Cetane number determination means for determining the cetane number of the fuel based on the change detected by the change detection means;
  Temperature detection means for detecting the bed temperature of the catalyst or the exhaust gas temperature downstream of the catalyst;
  Correction means for correcting the second amount based on the temperature detected by the temperature detection means when the internal combustion engine is operated by the first operation means;
  The change detecting means includes a temperature detected by the temperature detecting means when the internal combustion engine is operated by the first operating means, and a change detected when the internal combustion engine is operated by the second operating means. A difference from the temperature detected by the temperature detecting means is detected as the change.

  The fifth invention is a control device for an internal combustion engine,
  Pilot injection means for performing pilot injection prior to main fuel injection in the cylinder of the internal combustion engine;
  First operating means for operating the internal combustion engine with the amount of pilot injection as a first amount;
  Second operating means for operating the internal combustion engine with the amount of pilot injection as a second amount different from the first amount;
  Regarding the amount of at least one of CO and HC discharged from the internal combustion engine, when the internal combustion engine is operated by the first operating means, and when the internal combustion engine is operated by the second operating means Change detecting means for detecting changes between
  Cetane number determination means for determining the cetane number of the fuel based on the change detected by the change detection means;
  When the magnitude of the change detected by the change detecting means is smaller than a predetermined threshold, the amount of the pilot injection is set as a third amount farther than the second amount when viewed from the first amount. Third operating means for operating the internal combustion engine;
  Regarding the amount of at least one of CO and HC discharged from the internal combustion engine, when the internal combustion engine is operated by the first operating means, and when the internal combustion engine is operated by the third operating means And a second change detecting means for detecting a change between
  The cetane number determining means includes means for determining the cetane number of the fuel based on the change detected by the second change detecting means.

According to the first invention, when the internal combustion engine is operated with the amount of pilot injection as the first amount, and when the internal combustion engine is operated with the amount of pilot injection as the second amount different from the first amount By detecting the change in the emission amount of at least one of CO and HC for each, the cetane number of the fuel can be accurately determined. For this reason, since an expensive sensor such as an in-cylinder pressure sensor is not required, an increase in cost can be prevented. By controlling the amount of pilot injection per unit air amount, the influence of fluctuations in the intake air amount can be more reliably eliminated, so that the cetane number of fuel can be determined with higher accuracy.

According to the second invention, since a specific value of cetane number can be calculated, the cetane number can be determined with higher accuracy.

According to the third aspect of the present invention, the level of the cetane number of the fuel can be determined with high accuracy with a simple configuration.

According to the fourth aspect of the invention, it is possible to detect a change in the CO and HC emissions based on the bed temperature of the exhaust purification catalyst or the exhaust gas temperature downstream of the catalyst. For this reason, it is possible to accurately detect changes in CO and HC emissions with a simple configuration. The second amount can be corrected based on the catalyst bed temperature or the catalyst downstream exhaust gas temperature when the pilot injection amount is the first amount. For this reason, when the pilot injection amount is set to the second amount, for example, it is possible to more reliably prevent the occurrence of adverse effects such as the smoke emission amount exceeding the reference.

According to the fifth aspect, when the internal combustion engine is operated with the pilot injection amount being the first amount, and when the internal combustion engine is operated with the pilot injection amount being the second amount different from the first amount When the change in the emission amount of at least one of CO and HC is small, the internal combustion engine is operated with the pilot injection amount as the third amount so that the change is enlarged. The emission of at least one of CO and HC between when the internal combustion engine is operated with the pilot injection amount as the first amount and when the internal combustion engine is operated with the pilot injection amount as the third amount The cetane number of the fuel can be determined based on the change in the amount. For this reason, the fall of the cetane number determination accuracy can be prevented reliably, and the cetane number can be determined with higher accuracy.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure which shows the drive signal with respect to a fuel injector. It is a graph which shows the CO emission curve when ambient temperature is high, and the CO emission curve (fuel is the same) when ambient temperature is low. It is a graph which shows the CO discharge curve when the amount of intake air is large, and the CO discharge curve when the amount of intake air is small (the fuel is the same). It is the graph which expressed the pilot injection quantity per unit air quantity on the horizontal axis, and expressed CO emission amount on the vertical axis. It is the graph which expressed the pilot injection quantity per unit air quantity on the horizontal axis for the CO emission curve (the fuel is the same) when the ambient environment temperature is high and low. It is a figure which shows the relationship between CO emission amount of an internal combustion engine, and the bed temperature of an oxidation catalyst. 6 is a graph showing the pilot injection amount per unit air amount on the horizontal axis and the exhaust temperature after catalyst on the vertical axis. 6 is a graph showing the pilot injection amount per unit air amount on the horizontal axis and the exhaust temperature after catalyst on the vertical axis. It is a map which shows the correspondence of the difference of exhaust gas temperature after catalyst, and the cetane number of fuel. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure which shows the relationship between the pilot injection quantity per unit air quantity in case the high cetane number fuel is used, and a smoke discharge amount. It is a figure which shows the relationship between the cetane number of a fuel, the area | region (smoke increase area | region) where smoke emission exceeds a reference value, and the area | region (misfire area | region) where a misfire occurs. It is a figure which shows the CO emission curve of a high cetane number fuel. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a figure which shows the same cetane number calculation map as FIG. It is a figure which shows the CO discharge | emission curve in case of CN = 75. It is a map which shows the correspondence between the value of ( _Tγ - _Tα ) and the cetane number of fuel. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a figure which shows the relationship between HC discharge | emission amount from an internal combustion engine, sensor output A / F, and calculation A / F. Is a diagram illustrating the value of (E ₂ -E _1), the relationship between the cetane number of the fuel. It is a flowchart of the routine performed in Embodiment 4 of this invention.

Embodiment 1 FIG.
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 compression ignition type internal combustion engine (diesel engine) 10. The internal combustion engine 10 is preferably used as a power source for a vehicle or the like. The illustrated internal combustion engine 10 is an in-line four-cylinder type, but the number of cylinders and the cylinder arrangement are not particularly limited.

  Each cylinder of the internal combustion engine 10 is provided with a fuel injector 12 that injects fuel directly into the cylinder. The fuel injector 12 of each cylinder is connected to a common rail 14. The fuel sent from the fuel tank 40 is pressurized by the supply pump 16 and stored in the common rail 14. Then, the high-pressure fuel stored in the common rail 14 is supplied to the fuel injector 12 of each cylinder.

  The exhaust gas discharged from each cylinder of the internal combustion engine 10 is collected by the exhaust manifold 18 and then flows into the turbine of the turbocharger 20. An oxidation catalyst 26 for purifying exhaust gas is provided in the exhaust passage 22 on the downstream side of the turbocharger 20.

  An air cleaner 30 is provided near the inlet of the intake passage 28 of the internal combustion engine 10. The air sucked through the air cleaner 30 is compressed by the compressor of the turbocharger 20 and then cooled by the intercooler 32. The intake air that has passed through the intercooler 32 branches at the intake manifold 34 and flows into each cylinder.

  An intake throttle valve 36 is installed between the intercooler 32 and the intake manifold 34 in the intake passage 28. Further, an air flow meter 38 for detecting the amount of intake air is installed in the vicinity of the intake passage 28 downstream of the air cleaner 30.

  The system of this embodiment further includes an exhaust temperature sensor 42 that detects the temperature of the exhaust gas that exits the oxidation catalyst 26, an air-fuel ratio sensor 44 that is installed upstream of the oxidation catalyst 26 and detects the air-fuel ratio of the exhaust gas. A crank angle sensor 46 for detecting the rotation angle of the crankshaft (output shaft) of the internal combustion engine 10, an accelerator position sensor 48 for detecting the accelerator pedal position of the driver's seat of the vehicle, and an ECU (Electronic Control Unit) 50. ing.

  The ECU 50 is electrically connected to the various sensors and actuators described above. The ECU 50 controls the operation of the internal combustion engine 10 by operating each actuator according to a predetermined program based on the output of each sensor.

  The fuel injector 12 can inject fuel into the cylinder a plurality of times during one cycle. FIG. 2 is a diagram showing a drive signal for the fuel injector 12. As shown in FIG. 2, in the internal combustion engine 10, pilot injection prior to the main injection (main fuel injection) can be performed as fuel injection from the fuel injector 12. As shown in FIG. 2, the pilot injection can be performed a plurality of times. In the following description, the amount of fuel injected by pilot injection is referred to as “pilot injection amount”. When pilot injection is performed a plurality of times, the pilot injection amount is the total amount. In the internal combustion engine 10, fuel injection other than pilot injection and main injection may be further performed. For example, after the main injection, after injection, post injection, or the like may be performed.

  When the pilot injection amount is changed, the amount of CO (carbon monoxide) discharged from the internal combustion engine 10 (hereinafter referred to as “CO emission amount”) changes. When a graph is drawn with the pilot injection amount on the horizontal axis and the CO emission amount on the vertical axis, the graph becomes a curve having a minimum value (hereinafter referred to as a “CO emission curve”). That is, there is a pilot injection amount that minimizes the CO emission amount. This is considered to be due to the following reasons. If the pilot injection amount is too small, the combustion temperature decreases, and as a result, the amount of CO generated increases. Conversely, if the pilot injection amount is too large, the amount of oxygen in the cylinder that is consumed before the main injection is increased by the combustion of fuel in the pilot injection. As a result, oxygen becomes deficient in the combustion of the fuel of the main injection, and the amount of CO generated increases. For this reason, there exists an optimum pilot injection amount value at which the generation of CO is most suppressed.

  The shape of the CO emission curve varies depending on the cetane number of the fuel. Therefore, if the relationship between the shape of the CO emission curve and the cetane number of the fuel is examined by experiment and the information is stored in the ECU 50 in advance, the cetane number of the fuel can be determined by detecting the CO emission characteristics. There is sex. However, when determining the cetane number of the fuel in this way, there are the following problems.

  The amount of CO emissions also changes depending on the ambient temperature. FIG. 3 is a graph showing a CO emission curve when the ambient temperature is high and a CO emission curve (the fuel is the same) when the ambient temperature is low. As shown in FIG. 3, when the ambient temperature is high, the CO emission curve shifts in the negative direction of the vertical axis as compared to the case where the ambient temperature is low. This is because the higher the ambient temperature, the higher the intake air temperature, and the reactivity in the cylinder is improved, resulting in a decrease in the amount of CO generated. For this reason, even if the cetane number of the fuel is the same, the CO emission amount changes under the influence of the ambient environment temperature. Therefore, in order to accurately determine the cetane number of the fuel from the CO emission characteristics, it is necessary to eliminate the influence of the ambient environment temperature.

  There are also the following problems. The CO emission amount also varies depending on the intake air amount. FIG. 4 is a graph showing a CO discharge curve when the intake air amount is large and a CO discharge curve when the intake air amount is small (the fuel is the same). As shown in FIG. 4, when the intake air amount is large, the CO emission curve shifts in the positive direction of the horizontal axis as compared with the case where the intake air amount is small. This is because the larger the intake air amount, the smaller the pilot injection amount per unit air amount, which is substantially the same as reducing the pilot injection amount and increases the amount of CO generated. For this reason, even if the cetane number of the fuel is the same, the CO emission amount changes under the influence of the intake air amount. Therefore, in order to accurately determine the cetane number of the fuel from the CO emission characteristics, it is necessary to eliminate the influence of the intake air amount.

  In this embodiment, in order to eliminate the influence of the intake air amount, a value obtained by dividing the pilot injection amount by the intake air amount, that is, the pilot injection amount per unit air amount is used as a parameter. FIG. 5 is a graph showing the pilot injection amount per unit air amount on the horizontal axis and the CO emission amount on the vertical axis. In the following description, this graph is also referred to as a “CO emission curve”. The pilot injection amount per unit air amount is represented by the symbol Q. As shown in FIG. 5, if the pilot injection amount per unit air amount is used as a parameter, it is possible to avoid the CO discharge curve from moving in the horizontal axis direction even if the intake air amount changes.

Further, in this embodiment, in order to eliminate the influence of the ambient environment temperature, the internal combustion engine 10 is operated under two operating conditions with different pilot injection amounts per unit air amount, and the CO emission amount between the two points It was decided to detect changes. FIG. 6 is a graph showing a CO emission curve (the fuel is the same) when the ambient temperature is high and low with the pilot injection amount per unit air amount as the horizontal axis. As shown in FIG. 6, the internal combustion engine has two points, that is, a pilot injection amount per unit air amount is a first predetermined amount Q ₁ and a second predetermined amount Q ₂ (Q ₁ ≠ Q ₂ ). 10 is operated, and the difference in CO emission amount between the two points is set to ΔE. The graph of the CO emission curve translates in the direction of the vertical axis in accordance with changes in the ambient environment temperature. For this reason, the difference ΔE in the CO emission amount between the two points Q ₁ and Q ₂ is constant regardless of the ambient environment temperature. Therefore, if the cetane number is determined based on this ΔE, the influence of the ambient environment temperature can be eliminated.

  Incidentally, the CO discharged from the internal combustion engine 10 is oxidized in the oxidation catalyst 26. FIG. 7 is a diagram showing the relationship between the CO emission amount of the internal combustion engine 10 and the bed temperature of the oxidation catalyst 26. The oxidation reaction of CO is an exothermic reaction. For this reason, the amount of heat generated increases as the amount of CO flowing into the oxidation catalyst 26 increases. For this reason, as shown in FIG. 7, as the CO emission amount increases, the bed temperature of the oxidation catalyst 26 increases. The exhaust gas temperature downstream of the oxidation catalyst 26 (hereinafter referred to as “post-catalyst exhaust temperature”) also shows the same tendency. In the system shown in FIG. 1, the exhaust temperature after the catalyst can be detected by the exhaust temperature sensor 42.

  In the present embodiment, the cetane number of the fuel is determined as follows based on the principle described above. FIG. 8 and FIG. 9 are diagrams for explaining a method for determining the cetane number of fuel in the present embodiment, respectively.

  8 and 9 show graphs in which the pilot injection amount per unit air amount is plotted on the horizontal axis and the exhaust temperature after the catalyst is plotted on the vertical axis. As described above, the post-catalyst exhaust temperature increases as the amount of CO emission from the internal combustion engine 10 increases. Therefore, the post-catalyst exhaust temperature can be used as an index of the CO emission amount instead of the CO emission amount. Therefore, as shown in FIGS. 8 and 9, the shape of the graph with the post-catalyst exhaust temperature on the vertical axis is the same as the above-described CO emission curve. Hereinafter, such a graph is also referred to as a “CO emission curve”. The cetane number is represented by the symbol CN.

  The internal combustion engine 10 also discharges HC as an unburned fuel component together with CO. Since this HC is also oxidized by the oxidation catalyst 26, the oxidation reaction heat of the HC also contributes to an increase in the bed temperature of the oxidation catalyst 26 and the exhaust temperature after the catalyst. Therefore, the bed temperature of the oxidation catalyst 26 or the exhaust temperature after the catalyst is actually an indicator of the combined emission amount of CO and HC. However, the emission characteristics of HC are the same as the emission characteristics of CO, and HC increases and decreases with the same tendency as CO. Accordingly, the bed temperature of the oxidation catalyst 26 or the exhaust temperature after the catalyst is actually an indicator of the combined emission amount of CO and HC, but changes in the same tendency as the emission amount of CO alone. Therefore, in this embodiment, the bed temperature of the oxidation catalyst 26 or the exhaust temperature after the catalyst is used as an index of the CO emission amount.

FIG. 8 shows a CO emission curve with CN = 75 and a CO emission curve with CN = 50. When determining the cetane number, the pilot injection amount per unit air amount is a first predetermined amount Q ₁ and a second predetermined amount Q ₂ (Q ₁ <Q ₂ ). The internal combustion engine 10 is operated, and the difference in the exhaust gas temperature after the catalyst between the two points (represented by the symbol ΔT) is detected. As shown in FIG. 8, when CN = 75, ΔT (75) = T2−T1, and when CN = 50, ΔT (50) = T4−T3. In the case of CN = 50, ΔT (50) <0 since the slope of the CO emission curve is negative between Q ₁ and Q ₂ . On the other hand, in the case of CN = 75, since the slope of the CO emission curve is positive between Q ₁ and Q ₂ , ΔT (75)> 0.

On the other hand, FIG. 9 shows a CO emission curve with CN = 75 and a CO emission curve with CN = 90. As shown in this figure, when CN = 90, ΔT (90) = T6-T5. When CN = 90, the slope of the CO emission curve between Q ₁ and Q ₂ is larger than when CN = 75. Therefore, ΔT (90)> ΔT (75).

  Thus, there is a one-to-one correspondence between the post-catalyst exhaust temperature difference ΔT and the cetane number of the fuel. FIG. 10 is a map showing the correspondence. In this embodiment, according to this map, the cetane number of the fuel can be calculated based on the difference ΔT in the exhaust temperature after the catalyst.

For the purpose of accurate determination of the cetane number, the first predetermined amount Q ₁ and the second predetermined amount Q ₂ are, as shown in FIGS. 8 and 9, the slope of the CO emission curve due to the difference in cetane number. It is desirable to set the range so that the difference between the two appears remarkably.

  FIG. 11 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. According to the routine shown in FIG. 11, first, it is determined whether or not a predetermined cetane number determination condition is satisfied (step 100). For example, when the cetane number determination condition is that the internal combustion engine 10 is in the idle state, it is determined in this step 100 whether or not the internal combustion engine 10 is in the idle state. Moreover, you may make it include in the cetane number determination conditions that the fuel supply to the fuel tank 40 was detected. When fuel is newly supplied to the fuel tank 40, there is a possibility that the cetane number of the fuel supplied to the internal combustion engine 10 may change. Therefore, after the fuel is supplied, the cetane number may be determined. Because it is appropriate.

If the cetane number determination condition is not satisfied in step 100, the routine is terminated here. On the other hand, when the cetane number determination condition is satisfied in step 100, the following cetane number determination control is executed. First, the pilot injection amount is set to the first amount (step 102). In step 102, the unit amount of air per pilot injection amount is such that the first predetermined amount Q _1, the pilot injection amount from the fuel injector 12 is set. That is, an air amount calculated based on the output of the air flow meter 38 is read, and an amount obtained by multiplying the air amount by the first predetermined amount Q ₁ is set as a pilot injection amount from the fuel injector 12. .

Subsequent to the processing in step 102, the exhaust temperature after the catalyst is measured using the exhaust temperature sensor 42 (step 104). This measurement value and T _α. The process of step 104 is preferably executed after a predetermined time has elapsed so that the post-catalyst exhaust temperature converges after the process of step 102 is executed.

Subsequently, the pilot injection amount is set to the second amount (step 106). In step 106, the unit amount of air per pilot injection amount such that the second predetermined amount Q _2, the pilot injection amount from the fuel injector 12 is set. That is, the air amount calculated based on the output of the air flow meter 38 is read, and the amount obtained by multiplying the air amount by the second predetermined amount Q ₂ is set as the pilot injection amount from the fuel injector 12. .

Subsequent to the processing in step 106, the post-catalyst exhaust temperature is measured using the exhaust temperature sensor 42 (step 108). This measured value is _Tβ . The process of step 108 is desirably executed after a predetermined time has elapsed so that the post-catalyst exhaust temperature converges after the process of step 106 is executed.

Next, a process for calculating the cetane number of the fuel is executed (step 110). In step 110, first, the difference between the T _alpha obtained in after-catalyst exhaust temperature T _beta and the step 104 obtained in the above step 108 _(T β -T _α) is calculated. Then, the cetane number of the fuel is calculated based on the value of the post-catalyst exhaust temperature difference ( _Tβ − _Tα ) and the map shown in FIG.

  After the cetane number of the fuel is calculated, a process of reflecting the value of the cetane number in the contents of the engine control is executed in order to optimize the engine control according to the cetane number (step 112). That is, the ECU 50 is a map for correcting and optimizing various control parameters (for example, fuel injection timing, fuel injection pressure, number of times of fuel injection, EGR rate, etc.) of the internal combustion engine 10 according to the cetane number of the fuel. Is stored in advance. In step 112, the control parameters are corrected according to the cetane number of the fuel according to the maps.

  As described above, according to the present embodiment, the cetane number of the fuel supplied to the internal combustion engine 10 can be detected with high accuracy. This makes it possible to perform optimal engine control according to the cetane number of the fuel, so that even when a wide variety of fuels such as alternative fuels are used, the emission characteristics and fuel consumption characteristics are deteriorated. Can be reliably suppressed.

  Further, according to this embodiment, the cetane number of the fuel can be determined with high accuracy using the output of the exhaust temperature sensor 42. For this reason, since an expensive sensor such as an in-cylinder pressure sensor is not required, the cost can be reduced.

  In this embodiment, the post-catalyst exhaust temperature detected by the exhaust temperature sensor 42 is used as an index of the CO emission amount. However, in the present invention, means (sensor) for detecting the bed temperature of the oxidation catalyst 26 is used. And the bed temperature of the oxidation catalyst 26 may be used as an index of the CO emission amount.

  In the present embodiment, the CO exhaust amount is indirectly detected using the post-catalyst exhaust temperature detected by the exhaust temperature sensor 42 as an index of the CO exhaust amount. However, in the present invention, the CO sensor or the HC is detected. A sensor may be provided to directly detect the CO emission amount or the HC emission amount.

As described above, in this embodiment, the cetane number of the fuel is calculated based on the value of the post-catalyst exhaust temperature difference ( _Tβ − _Tα ) and the map shown in FIG. On the other hand, as can be seen from the map shown in FIG. 10, if the value of the post-catalyst exhaust temperature difference (T _β -T _α ) is positive, it can be determined that the fuel has a relatively high cetane number, and the post-catalyst exhaust When the temperature difference ( _Tβ − _Tα ) is negative, it can be determined that the fuel has a relatively low cetane number. The present invention may thus only roughly determine whether the cetane number is high or low. That is, in the present invention, it is not always necessary to calculate a specific value of the cetane number.

  In the first embodiment described above, the ECU 50 executes the process of step 102, whereby the “first driving means” in the first and second inventions executes the process of step 104. The “second detecting means” in the first and second inventions executes the processing of the steps 104, 108 and 110, whereby the “change detecting means” in the first and fifth inventions is the above step. By executing the process 110, the “cetane number determining means” in the first invention and the “cetane number calculating means” in the third invention perform the pilot injection as shown in FIG. Each of the “pilot injection means” in the present invention is realized. The oxidation catalyst 26 corresponds to the “catalyst” in the fifth aspect of the invention, and the exhaust temperature sensor 42 corresponds to the “temperature detection means” in the fifth aspect of the invention.

Embodiment 2. FIG.
Next, the second embodiment of the present invention will be described with reference to FIG. 12 to FIG. 16. The description will focus on the differences from the first embodiment described above, and the same matters will be described. Simplify or omit.

  The present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 16 to be described later using the hardware configuration shown in FIG.

  In the internal combustion engine 10, generally, if the pilot injection amount is too large, the smoke emission amount increases. In addition, the higher the cetane number of the fuel, the more easily smoke is emitted. For this reason, when a fuel having a very high cetane number (hereinafter referred to as “high cetane number fuel”) is used, when the pilot injection amount is increased, the smoke emission amount may exceed the reference value.

FIG. 12 is a diagram showing a relationship between the pilot injection amount per unit air amount and the smoke emission amount when a high cetane number fuel is used. In the first embodiment described above, the pilot injection amount per unit air amount is increased from the first predetermined amount Q ₁ to the second predetermined amount Q ₂ in the cetane number determination control. As shown in FIG. 12, when high cetane fuel is used, the smoke emission increases from S ₁ to S ₂ with this increase. As a result, the smoke emission amount may exceed the reference value.

In the present embodiment, in order to reliably avoid the above problem, when there is a possibility that the high-octane fuel is used, in the cetane number determination control, by correcting the second predetermined amount Q ₂ Q ₂ 'And. The corrected second predetermined amount Q ₂ ′ is smaller than the first predetermined amount Q ₁ . That is, in the present embodiment, when there is a possibility that high cetane number fuel is used, the pilot injection amount per unit air amount is reduced from the first predetermined amount Q ₁ to the second predetermined amount Q ₂ ′. As shown in FIG. 12, the smoke emission amount decreases from S ₁ to S ₂ ′ with this reduction. Therefore, the smoke discharge amount can be reliably suppressed to a reference value or less.

On the other hand, when a fuel having a very low cetane number (hereinafter referred to as “low cetane number fuel”) is used, if the pilot injection amount is too small, there is a risk of misfire. FIG. 13 is a diagram showing the relationship between the cetane number of fuel, the region where the smoke emission exceeds the reference value (smoke increase region), and the region where misfire occurs (misfire region). As shown in FIG. 13, when the low cetane number fuel is used, unlike the case where the high cetane number fuel is used, the pilot injection amount per unit air amount is changed from the first predetermined amount Q ₁ to the _first amount. 2 Even if the amount is increased to the predetermined amount Q ₂ , there is no possibility of entering the smoke increasing region. However, when a low cetane number fuel is used, if the pilot injection amount per unit air amount is reduced from the first predetermined amount Q ₁ to the second predetermined amount Q ₂ ′, there is a risk of entering a misfire region. Therefore, in the present embodiment, only when there is a possibility that the high-octane fuel is used, the second predetermined amount and to correct the Q ₂ to Q ₂ '.

The possibility of using high cetane number fuel is determined based on the post-catalyst exhaust temperature T _α when the pilot injection amount per unit air amount is operated as the first predetermined amount Q _1. Can do. As can be seen from the graphs of the CO emission curves in the case of CN = 50, 75, and 90 shown in FIGS. 8 and 9, the pilot injection amount per unit air amount becomes the first predetermined amount as the cetane number of the fuel increases. it is lower exhaust temperature T _alpha after catalyst when it is Q _1. As described above, the graph of the CO emission curve moves in the vertical axis direction according to the ambient environment temperature. For this reason, an accurate cetane number value cannot be determined from the post-catalyst exhaust temperature T _α when the pilot injection amount per unit air amount is the first predetermined amount Q ₁ , but a rough determination of the cetane number is possible. Is possible. That is, if the post-catalyst exhaust temperature T _α when the pilot injection amount per unit air amount is the first predetermined amount Q ₁ is lower than the predetermined determination value T ₀ , there is a possibility that the fuel is a high cetane number fuel. Otherwise, it can be determined that there is no possibility of high cetane number fuel.

FIG. 14 is a diagram showing a CO emission curve of a high cetane fuel. As shown in FIG. 14, when the second predetermined amount is corrected from Q ₂ to Q ₂ ′, the post-catalyst exhaust temperature becomes T _β ′. Therefore, the difference in the exhaust gas temperature after the catalyst compared to when the pilot injection amount per unit air amount is the first predetermined amount Q ₁ is (T _β ′ −T _α ). Map indicating the value of the (T β _{'-T α),} the relationship between the cetane number of the fuel, but the shape is different from the map of FIG. 10, can be created in a similar manner. Therefore, such a map (hereinafter referred to as “the cetane number calculation map when the second predetermined amount is corrected”) is stored in advance in the ECU 50, so that it is based on the value of (T _β ′ −T _α ). Thus, the cetane number of the fuel can be calculated.

  FIG. 15 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. In FIG. 15, the same steps as those in the routine shown in FIG. 11 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

According to the routine shown in FIG. 15, when the establishment of the cetane number determination condition is recognized in step 100, the following cetane number determination control is executed. First, the pilot injection amount from the fuel injector 12 is set so that the pilot injection amount per unit air amount becomes the first predetermined amount Q ₁ (step 102). Next, the post-catalyst exhaust temperature is measured using the exhaust temperature sensor 42 (step 104). This measurement value and T _α.

Then, after the catalyst has been obtained in step 104 exhaust temperature T _alpha whether less than the determination value T ₀ is determined (step 114). As a result, if T _α ≧ T ₀ , it can be determined that there is no possibility that the current fuel is a high cetane number fuel. In this case, it is not necessary to correct the second predetermined amount Q _2. Therefore, in this case, the remaining processing of the cetane number determination control is executed in the same manner as in the first embodiment (steps 106 to 112).

On the other hand, if T _α <T ₀ in step 114, it can be determined that the current fuel may be a high cetane number fuel. In this case, the second predetermined amount Q ₂ is corrected to Q ₂ ′, which is a predetermined value smaller than the first predetermined amount Q ₁ (step 116). Next, the pilot injection amount is set to the second amount (step 118). In step 118, the pilot injection amount from the fuel injector 12 is set so that the pilot injection amount per unit air amount becomes the corrected second predetermined amount Q ₂ '. That is, an air amount calculated based on the output of the air flow meter 38 is read, and an amount obtained by multiplying the air amount by the corrected second predetermined amount Q ₂ ′ is a pilot injection amount from the fuel injector 12. Set as

Subsequent to the processing in step 118, the post-catalyst exhaust temperature is measured using the exhaust temperature sensor 42 (step 120). This measured value is defined as T _β ′. The process of step 120 is preferably executed after a predetermined time has elapsed so that the post-catalyst exhaust temperature converges after the process of step 116 is executed.

Next, a process for calculating the cetane number of the fuel is executed (step 122). In step 122, first, 'the difference between the T _alpha obtained in the above step 104 (T _beta' after-catalyst exhaust temperature T _beta obtained in the above step 120 -T _alpha) is calculated. Then, the cetane number of the fuel is calculated based on the difference in the exhaust gas temperature after the catalyst (T _β ′ −T _α ) and the cetane number calculation map (not shown) when the second predetermined amount is corrected. Is done. After the cetane number of the fuel is calculated, a process of reflecting the value of the cetane number in the contents of the engine control is executed in order to optimize the engine control according to the cetane number (step 112).

  According to the second embodiment described above, even when a high cetane number fuel is used, it is more reliably prevented that smoke exceeding the reference amount is discharged when the cetane number determination control is executed. be able to. In the second embodiment described above, the “correction means” in the sixth aspect of the present invention is realized by the ECU 50 executing the processing of steps 116 and 118 described above.

Embodiment 3 FIG.
Next, the third embodiment of the present invention will be described with reference to FIG. 16 to FIG. 19. The description will focus on the differences from the above-described embodiment, and the description of the same matters will be simplified. Or omit.

  The present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 19 to be described later using the hardware configuration shown in FIG.

As described above, in the first embodiment, in the cetane number determination control, the after-catalyst exhaust temperature T _α when the pilot injection amount per unit air amount is the first predetermined amount Q ₁ and the pilot injection amount per unit air amount. The cetane number is calculated by fitting the difference (T _β -T _α ) from the post-catalyst exhaust temperature T _β when is the second predetermined amount Q ₂ to the map shown in FIG. The absolute value of _(T β -T _α) increases as the inclination of the CO emissions curve between the first predetermined amount Q ₁ and the second predetermined amount Q ₂ is steep, big. As can be seen from FIGS. 8 and 9, in the case of CN = 75, compared with the case of CN = 50 and the case of CN = 90, it is between the first predetermined amount Q ₁ and the second predetermined amount Q _2. The CO emission curve has a gentle slope. Therefore, when CN = 75, the absolute value of ( _Tβ − _Tα ) is smaller than when CN = 50 or CN = 90. As in the case of CN = 75, when the cetane number is in a specific range, the absolute value of ( _Tβ − _Tα ) is small. In the following description, a specific cetane number range having a small absolute value of (T _β -T _α ) is referred to as a “specific cetane number range”. In the case of this embodiment, the specific cetane number range is a range from approximately 55 to 75.

FIG. 16 is a diagram showing the same cetane number calculation map as FIG. As shown in FIG. 16, in the specific cetane number range, since the absolute value of ( _Tβ − _Tα ) is small, the slope of the cetane number calculation map becomes gentle. For this reason, when a fuel having a specific cetane number range is used, when an error occurs in the detected value of ( _Tβ - _Tα ), the calculated value of the cetane number is likely to change greatly. Therefore, there is a concern that it is somewhat difficult to determine the cetane number with high accuracy.

In the present embodiment, the following control is performed in order to eliminate the above-mentioned concerns. FIG. 17 is a diagram showing a CO emission curve when CN = 75. First, ( _Tβ − _Tα ) is detected in the same manner as in the first embodiment. Next, the detected absolute value of ( _Tβ − _Tα ) is compared with a predetermined threshold Th. As a result, when the absolute value of (T _β −T _α ) is smaller than the threshold value Th, the pilot injection amount per unit air amount is set to the second farther than the second predetermined amount Q _{2 when} viewed from the first predetermined amount Q ₁ . 3. The internal combustion engine 10 is operated with the predetermined amount Q ₃ set. Then, the exhaust temperature after the catalyst is detected again. _Let this detected value be _Tγ . As shown in FIG. 17, Q ₃ > Q ₂ . Therefore, since (Q ₃ -Q ₁ )> (Q ₂ -Q ₁ ), the absolute value of (T _γ -T _α ) is larger than the absolute value of (T _β -T _α ).

FIG. 18 is a map showing the correspondence between the value of ( _Tγ − _Tα ) and the cetane number of the fuel. When ( _Tγ − _Tα ) is detected, the cetane number is calculated based on this map. As described above, the absolute value of (T _γ -T _α ) is larger than the absolute value of (T _β -T _α ). Accordingly, the cetane number calculation map shown in FIG. 18 has a larger slope than the cetane number calculation map shown in FIG. Therefore, when the used fuel is in the specific cetane number range, even if an error occurs in the detected value of (T _γ -T _α ), the change in the calculated cetane number is small. For this reason, even if it is a case where the fuel currently used exists in a specific cetane number range, a cetane number can be determined with high precision.

  FIG. 19 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. In FIG. 19, the same steps as those in the routine shown in FIG. 11 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

According to the routine shown in FIG. 19, when the establishment of the cetane number determination condition is recognized in step 100, the following cetane number determination control is executed. First, the pilot injection amount from the fuel injector 12 is set so that the pilot injection amount per unit air amount becomes the first predetermined amount Q ₁ (step 102). After the post-catalyst exhaust temperature converges, the post-catalyst exhaust temperature is measured using the exhaust temperature sensor 42 (step 104). This measurement value and T _α.

Subsequently, the pilot injection amount from the fuel injector 12 is set so that the pilot injection amount per unit air amount becomes the second predetermined amount Q ₂ (step 106). After the post-catalyst exhaust temperature converges, the post-catalyst exhaust temperature is measured using the exhaust temperature sensor 42 (step 108). This measured value is _Tβ .

Next, it is determined whether or not the absolute value of ( _Tβ − _Tα ) is smaller than a predetermined threshold Th (step 124). When the absolute value of ( _Tβ − _Tα ) is greater than or equal to the threshold Th, it can be determined that the specific cetane number range does not fall within the range. That is, it can be determined that the cetane number can be determined with high accuracy based on the value of ( _Tβ − _Tα ). Therefore, in this case, the cetane number is calculated by applying the value of ( _Tβ − _Tα ) to the map shown in FIG. 16 (step 110).

On the other hand, when the absolute value of ( _Tβ − _Tα ) is smaller than the threshold value Th in step 124, it can be determined that the specific cetane number range is satisfied. In this case, since the inclination of the cetane number calculation map shown in FIG. 16 is small, there is a concern that the cetane number determination accuracy is lowered. Therefore, in this case, the following processing is executed to use the cetane number calculation map shown in FIG. First, the pilot injection amount is set to the third amount (step 126). In step 126, the unit amount of air per pilot injection amount such that the third predetermined quantity Q _3, the pilot injection amount from the fuel injector 12 is set. That is, the air amount calculated based on the output of the air flow meter 38 is read, and an amount obtained by multiplying the air amount by the third predetermined amount Q ₃ is set as the pilot injection amount from the fuel injector 12. . Subsequently, after the post-catalyst exhaust temperature converges, the post-catalyst exhaust temperature is measured using the exhaust temperature sensor 42 (step 128). This measured value is defined as _Tγ . Then, a difference (T _γ -T _α ) between this T _γ and T _α obtained in step 104 is calculated, and the value of (T _γ -T _α ) is applied to the map shown in FIG. The cetane number is calculated (step 130).

  After the cetane number of the fuel is calculated in step 110 or 130, processing for reflecting the value of the cetane number in the contents of the engine control is executed in order to optimize the engine control according to the cetane number ( Step 112).

  As described above, according to the above-described third embodiment, the determination accuracy of the cetane number can be further improved, and a more accurate cetane number can be calculated. In the present embodiment, when the ECU 50 executes the processes of steps 124 and 126 described above, the “third driving means” in the eighth invention executes the processes of steps 128 and 130 described above. The “second change detecting means” and the “cetane number determining means” in the eighth invention are realized.

Embodiment 4 FIG.
Next, the fourth embodiment of the present invention will be described with reference to FIG. 20 to FIG. 22. The difference from the above-described embodiment will be mainly described, and the description of the same matters will be simplified. Or omit.

  The present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 22, which will be described later, using the hardware configuration shown in FIG.

  As described above, the system shown in FIG. 1 includes the air-fuel ratio sensor 44 that detects the air-fuel ratio (A / F) of the exhaust gas. In the following description, the air-fuel ratio calculated based on the output of the air-fuel ratio sensor 44 is referred to as “sensor output A / F”, and the calculated air-fuel ratio calculated based on the fuel injection amount and the intake air amount is This is referred to as “calculation A / F”.

  FIG. 20 is a diagram showing the relationship between the HC emission amount from the internal combustion engine 10, the sensor output A / F, and the calculation A / F. As shown in the figure, when the HC emission amount is small, the sensor output A / F coincides with the calculation A / F, but when the HC emission amount is large, the sensor output A / F is the calculation A / F. Smaller than. The deviation between the sensor output A / F and the calculation A / F increases as the HC emission amount increases. This is because when the amount of HC emission is large, it is recognized that the amount of oxygen to be sensed has decreased due to HC adhering to the sensor portion of the air-fuel ratio sensor 44.

  In the present embodiment, the HC emission amount is detected based on the deviation amount between the sensor output A / F and the calculation A / F using the characteristics shown in FIG. The rate of decrease in sensor output A / F with respect to calculation A / F varies depending on parameters such as engine load. For this reason, when detecting HC discharge | emission amount by said method, it is preferable to correct | amend according to those parameters as needed.

As described above, the HC emission amount shows the same change tendency as the CO emission amount with respect to the change of the pilot injection amount and the cetane number of the fuel. Therefore, even if the CO emission amount in the above-described embodiment is replaced with the HC emission amount, the cetane number can be determined based on the same concept. Therefore, in the present embodiment, the HC emission amount is detected by the above-described method when the pilot injection amount per unit air amount is set to the first predetermined amount Q ₁ and when the pilot injection amount is set to the second predetermined amount Q _2. Thus, the cetane number of the fuel is calculated.

The HC emission amount when the pilot injection amount per unit air amount is the first predetermined amount Q ₁ is E _1, and the HC emission amount when the pilot injection amount per unit air amount is the second predetermined amount Q ₂ is E _2. And FIG. 21 is a diagram showing the relationship between the value of (E ₂ −E ₁ ) and the cetane number of the fuel. Since the HC emission amount exhibits the same characteristics as the CO emission amount, the graph of FIG. 21 has the same tendency as the graph of FIG. In the present embodiment, the cetane number of the fuel can be calculated from the value of (E ₂ −E ₁ ) based on the relationship shown in FIG.

  FIG. 22 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. In FIG. 22, the same steps as those in the routine shown in FIG. 11 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

According to the routine shown in FIG. 22, when the establishment of the cetane number determination condition is recognized in step 100, the following cetane number determination control is executed. First, the pilot injection amount from the fuel injector 12 is set so that the pilot injection amount per unit air amount becomes the first predetermined amount Q ₁ (step 102). Then, the HC emission amount is measured based on the deviation amount between the sensor output A / F and the calculation A / F (step 132). The measured value and E _1.

Next, the pilot injection amount from the fuel injector 12 is set so that the pilot injection amount per unit air amount becomes the second predetermined amount Q ₂ (step 106). Then, the HC emission amount is measured based on the deviation amount between the sensor output A / F and the calculation A / F (step 134). This measurement value E _2.

Subsequently, a process for calculating the cetane number is executed (step 136). In this step 136, first, the value of (E ₂ −E ₁ ) is calculated, and then the cetane number is calculated by applying the value to the map of FIG. After the cetane number of the fuel is calculated in this way, a process for reflecting the value of the cetane number in the contents of the engine control is executed in order to optimize the engine control according to the cetane number (step 112). ).

  According to the fourth embodiment as described above, the same effect as in the first embodiment described above can be obtained. Further, according to this embodiment, the cetane number of the fuel can be determined with high accuracy using the output of the air-fuel ratio sensor 44. For this reason, since an expensive sensor such as an in-cylinder pressure sensor is not required, the cost can be reduced.

  In the above-described fourth embodiment, the ECU 50 calculates the calculation A / F, so that the “air-fuel ratio calculation means” in the seventh invention executes the processing of steps 132 and 134 to execute the seventh The “HC detection means” in the invention executes the processing of step 136, whereby the “change detection means” in the seventh invention is realized.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Fuel injector 14 Common rail 18 Exhaust manifold 20 Turbocharger 22 Exhaust passage 26 Oxidation catalyst 28 Intake passage 34 Intake manifold 36 Intake throttle valve 38 Air flow meter 42 Exhaust temperature sensor 44 Air fuel ratio sensor 50 ECU

Claims (5)

Pilot injection means for performing pilot injection prior to main fuel injection in the cylinder of the internal combustion engine;
First operating means for operating the internal combustion engine with the amount of pilot injection as a first amount;
Second operating means for operating the internal combustion engine with the amount of pilot injection as a second amount different from the first amount;
Regarding the amount of at least one of CO and HC discharged from the internal combustion engine, when the internal combustion engine is operated by the first operating means, and when the internal combustion engine is operated by the second operating means Change detecting means for detecting changes between
Cetane number determination means for determining the cetane number of the fuel based on the change detected by the change detection means ,
The first operating means includes means for controlling the pilot injection amount per unit air amount to be a first predetermined amount,
The control device for an internal combustion engine, wherein the second operating means includes means for controlling the pilot injection amount per unit air amount to be a second predetermined amount different from the first predetermined amount. Pilot injection means for performing pilot injection prior to main fuel injection in the cylinder of the internal combustion engine;
First operating means for operating the internal combustion engine with the amount of pilot injection as a first amount;
Second operating means for operating the internal combustion engine with the amount of pilot injection as a second amount different from the first amount;
Regarding the amount of at least one of CO and HC discharged from the internal combustion engine, when the internal combustion engine is operated by the first operating means, and when the internal combustion engine is operated by the second operating means Change detecting means for detecting changes between
Cetane number determination means for determining the cetane number of the fuel based on the change detected by the change detection means ,
The control device for an internal combustion engine, wherein the cetane number determination means includes a cetane number calculation means for calculating a cetane number of the fuel based on a change amount detected by the change detection means. Pilot injection means for performing pilot injection prior to main fuel injection in the cylinder of the internal combustion engine;
First operating means for operating the internal combustion engine with the amount of pilot injection as a first amount;
Second operating means for operating the internal combustion engine with the amount of pilot injection as a second amount different from the first amount;
Regarding the amount of at least one of CO and HC discharged from the internal combustion engine, when the internal combustion engine is operated by the first operating means, and when the internal combustion engine is operated by the second operating means Change detecting means for detecting changes between
Cetane number determination means for determining the cetane number of the fuel based on the change detected by the change detection means ,
The control device for an internal combustion engine, wherein the cetane number determination means includes means for determining the level of the cetane number of the fuel based on the sign of the amount of change detected by the change detection means. A catalyst disposed in the exhaust passage of the internal combustion engine and having a function of oxidizing harmful components;
Pilot injection means for performing pilot injection prior to main fuel injection in the cylinder of the internal combustion engine;
First operating means for operating the internal combustion engine with the amount of pilot injection as a first amount;
Second operating means for operating the internal combustion engine with the amount of pilot injection as a second amount different from the first amount;
Regarding the amount of at least one of CO and HC discharged from the internal combustion engine, when the internal combustion engine is operated by the first operating means, and when the internal combustion engine is operated by the second operating means Change detecting means for detecting changes between
Cetane number determination means for determining the cetane number of the fuel based on the change detected by the change detection means;
Temperature detection means for detecting the bed temperature of the catalyst or the exhaust gas temperature downstream of the catalyst;
Correction means for correcting the second amount based on the temperature detected by the temperature detection means when the internal combustion engine is operated by the first operation means;
The change detecting means includes a temperature detected by the temperature detecting means when the internal combustion engine is operated by the first operating means, and a change detected when the internal combustion engine is operated by the second operating means. A control device for an internal combustion engine, wherein a difference from a temperature detected by a temperature detecting means is detected as the change. Pilot injection means for performing pilot injection prior to main fuel injection in the cylinder of the internal combustion engine;
First operating means for operating the internal combustion engine with the amount of pilot injection as a first amount;
Second operating means for operating the internal combustion engine with the amount of pilot injection as a second amount different from the first amount;
Regarding the amount of at least one of CO and HC discharged from the internal combustion engine, when the internal combustion engine is operated by the first operating means, and when the internal combustion engine is operated by the second operating means Change detecting means for detecting changes between
Cetane number determination means for determining the cetane number of the fuel based on the change detected by the change detection means;
When the magnitude of the change detected by the change detecting means is smaller than a predetermined threshold, the amount of the pilot injection is set as a third amount farther than the second amount when viewed from the first amount. Third operating means for operating the internal combustion engine;
Regarding the amount of at least one of CO and HC discharged from the internal combustion engine, when the internal combustion engine is operated by the first operating means, and when the internal combustion engine is operated by the third operating means And a second change detecting means for detecting a change between
The control device for an internal combustion engine, wherein the cetane number determination means includes means for determining a cetane number of fuel based on a change detected by the second change detection means.

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