JP2008064045A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of executing estimating processing of a cetane number, and accurately carrying out cetane estimation for a long period, while monitoring a deterioration state of a fuel injection valve. <P>SOLUTION: A pilot injection is executed during fuel cut operation. At that time, a pilot injection amount QINJP is set to be a predetermined misfire injection amount QIP0 which does not ignite (S12), and gradually increased (S13). A deterioration correcting coefficient KIVD is calculated according to a total increasing amount DQIPI at the time of ignition (S15). In an idle operation state of an engine, fuel injection is carried out by fuel injection amount corrected by the deterioration correcting coefficient KIVD, and the cetane number CET of fuel during using is estimated according to the ignition time of injected fuel. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to an apparatus having a function of estimating the cetane number of fuel used in an internal combustion engine.

  Patent Document 1 discloses a control device for an internal combustion engine having a function of estimating a cetane number of a fuel in use. According to this apparatus, during the fuel supply cutoff operation of the internal combustion engine, a specified amount of fuel is injected, and the cetane number of the fuel in use is estimated based on the ignition timing of the injected fuel.

JP 2005-344557 A

  When the characteristic of the fuel injection valve that injects fuel into the combustion chamber of the internal combustion engine changes with time, the amount of fuel actually injected changes even if the injection control signal that drives the fuel injection valve is the same. Therefore, even if fuel injection is performed to inject a specified amount of fuel in the conventional control device, the actual fuel injection amount may change and the detected ignition timing may change. In addition, during the fuel supply cutoff operation, there is a possibility that the torque fluctuation becomes large due to a slight change in the fuel amount.

  The present invention has been made paying attention to this point, and can perform cetane number estimation processing while monitoring the deterioration state of the fuel injection valve, and can perform accurate cetane number estimation over a long period of time. An object of the present invention is to provide a control device for an internal combustion engine.

  In order to achieve the above object, a first aspect of the present invention provides a control device for an internal combustion engine comprising fuel injection means (6) for injecting fuel into a combustion chamber of the internal combustion engine (1), wherein the fuel injection means (6). The fuel injection control means for controlling the fuel injection by the fuel, the combustion state detection means (2) for detecting the combustion state in the combustion chamber of the engine, and the fuel injection control means for the fuel injection by the fuel injection means (6) A cetane number estimating means for estimating a cetane number (CET) of fuel in use based on the output of the combustion state detecting means (2) when the timing (CAINJ) is changed, and the fuel injection control means, Deterioration state determination for determining the deterioration state of the fuel injection means (6) based on the output of the combustion state detection means (2) when the fuel injection amount (QINJP) by the fuel injection means (2) is changed The fuel injection control means has a fuel injection timing (CAIFC) when the deterioration state determination of the fuel injection means (6) is different from a fuel injection timing when the cetane number is estimated. It is characterized by setting to.

  According to a second aspect of the present invention, in the control device for an internal combustion engine according to the first aspect, the cetane number estimating means executes the cetane number estimation in an idle operation state of the engine, and the deterioration state determining means is The deterioration state determination is performed in a fuel supply cutoff operation state of the engine.

  According to a third aspect of the present invention, in the control device for an internal combustion engine according to the first or second aspect, the fuel injection control means is configured to change the fuel injection means according to the deterioration state determined by the deterioration state determination means. The fuel injection control amount (TIM, TIP) is corrected.

  According to the first aspect of the present invention, since the cetane number estimation of the fuel being used and the deterioration state determination of the fuel injection means are performed, the determination result of the deterioration state of the fuel injection means can be used to obtain a more accurate Cetane number estimation can be performed. In addition, since the fuel injection timing at which it is easy to detect the effect of changes in the fuel injection amount and the fuel injection timing at which the difference in ignition timing due to the difference in cetane number is easy to detect are different, the fuel injection timing at which the deterioration state determination is performed is By setting the timing different from the fuel injection timing when estimating the cetane number, it is possible to improve the accuracy of the deterioration state determination and the cetane number estimation.

  According to the second aspect of the present invention, the cetane number estimation is performed in the engine idle operation state, and the deterioration state determination of the fuel injection means is performed in the engine fuel supply cutoff operation state. Cetane number estimation can be performed accurately in the idling state where the engine operating state is stable, and the deterioration state determination of the fuel injection means is performed in the fuel supply cutoff operation state, so that the normal operation of the engine is performed. It is possible to prevent the drivability or exhaust characteristics from deteriorating.

  According to the third aspect of the invention, since the fuel injection control amount of the fuel injection means is corrected according to the deterioration state of the fuel injection valve, the actual fuel injection amount is reduced regardless of the deterioration state of the fuel injection valve. It can be controlled accurately.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 and FIG. 2 are diagrams showing the configuration of an internal combustion engine and its control device according to one embodiment of the present invention. The following description will be given with reference to both figures together. An internal combustion engine (hereinafter simply referred to as “engine”) 1 having four cylinders is a diesel engine that directly injects fuel into a combustion chamber, and a fuel injection valve 6 is provided in the combustion chamber of each cylinder. The fuel injection valve 6 is electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 4, and the valve opening time and valve opening timing of the fuel injection valve 6, that is, the fuel injection time and fuel injection timing are determined by the ECU 4. Controlled by

  The engine 1 includes an intake pipe 7 and an exhaust pipe 8. An exhaust gas recirculation passage 9 is provided between the exhaust pipe 8 and the intake pipe 7 to recirculate part of the exhaust gas to the intake pipe 7. The exhaust gas recirculation passage 9 is provided with an exhaust gas recirculation control valve (hereinafter referred to as “EGR valve”) 20 for controlling the exhaust gas recirculation amount. The EGR valve 20 is an electromagnetic valve having a solenoid, and the valve opening degree is controlled by the ECU 4. The exhaust gas recirculation passage 9 and the EGR valve 20 constitute an exhaust gas recirculation mechanism.

  Each cylinder of the engine 1 is provided with an in-cylinder pressure sensor 2 for detecting in-cylinder pressure (combustion chamber pressure of the engine 1) as combustion state means for detecting the combustion state in the combustion chamber. In the present embodiment, the in-cylinder pressure sensor 2 is configured integrally with a glow plug provided in each cylinder. A detection signal from the in-cylinder pressure sensor 2 is supplied to the ECU 4. The detection signal of the in-cylinder pressure sensor 2 actually corresponds to a differential signal with respect to the crank angle (time) of the in-cylinder pressure PCYL, and the in-cylinder pressure PCYL is obtained by integrating the in-cylinder pressure sensor output. .

  The engine 1 is provided with a crank angle position sensor 3 that detects a rotation angle of a crankshaft (not shown). The crank angle position sensor 3 generates a pulse every crank angle, and the pulse signal is supplied to the ECU 4. The crank angle position sensor 3 further generates a cylinder identification pulse at a predetermined crank angle position of the specific cylinder and supplies it to the ECU 4.

  The ECU 4 includes an accelerator sensor 21 that detects an operation amount AP of an accelerator pedal of a vehicle driven by the engine 1, a cooling water temperature sensor 22 that detects a cooling water temperature TW of the engine 1, and an intake air that detects an intake air temperature TA of the engine 1. An air temperature sensor 23 is connected, and detection signals from these sensors are supplied to the ECU 4.

  The ECU 4 supplies a control signal for the fuel injection valve 6 provided in the combustion chamber of each cylinder of the engine 1 to the drive circuit 5. The drive circuit 5 is connected to the fuel injection valve 6, and supplies a drive signal corresponding to the control signal supplied from the ECU 4 to the fuel injection valve 6. Thus, at the fuel injection timing corresponding to the control signal output from the ECU 4, fuel is injected into the combustion chamber of each cylinder by the fuel injection amount corresponding to the control signal. The ECU 4 normally executes pilot injection and main injection for one cylinder.

  The ECU 4 includes an amplifier 10, an A / D converter 11, a pulse generator 13, a CPU (Central Processing Unit) 14, a ROM (Read Only Memory) 15 that stores a program executed by the CPU 14, and a CPU 14. A RAM (Random Access Memory) 16 for storing calculation results and the like, an input circuit 17, and an output circuit 18 are provided. A detection signal of the in-cylinder pressure sensor 2 is input to the amplifier 10. The amplifier 10 amplifies an input signal. The signal amplified by the amplifier 10 is input to the A / D converter 11. The pulse signal output from the crank angle position sensor 3 is input to the pulse generator 13.

  The A / D conversion unit 11 includes a buffer 12, converts the in-cylinder pressure sensor output input from the amplifier 10 into a digital value (hereinafter referred to as “pressure change rate”) dp / dθ, and stores the converted value in the buffer 12. More specifically, the A / D converter 11 is supplied with a pulse signal PLS1 (hereinafter referred to as “1 degree pulse”) PLS1 having a crank angle of 1 degree from the pulse generator 13, and this 1 degree pulse PLS1. The in-cylinder pressure sensor output is sampled at a period of

  On the other hand, the pulse signal PLS6 with a crank angle of 6 degrees is supplied from the pulse generator 13 to the CPU 14, and the CPU 14 performs a process of reading the digital value stored in the buffer 12 with the period of the 6 degrees pulse PLS6. . That is, in this embodiment, the A / D conversion unit 11 does not issue an interrupt request to the CPU 14, but the CPU 14 performs a reading process at a cycle of the 6-degree pulse PLS6.

  The input circuit 17 converts detection signals from various sensors into digital values and supplies them to the CPU 14. The engine speed NE is calculated from the cycle of the 6-degree pulse PLS. Further, the required torque TRQ of the engine 1 is calculated according to the accelerator pedal operation amount AP.

  The CPU 14 calculates the target exhaust gas recirculation amount GEGR according to the engine operating state, and sends a duty control signal for controlling the opening degree of the EGR valve 20 according to the target exhaust gas recirculation amount GEGR to the EGR valve 20 via the output circuit 18. Supply.

  FIG. 3 is a flowchart of a process for determining the deterioration state of the fuel injection valve 6. This process is executed by the CPU 14. In the present embodiment, only the pilot injection is executed during the fuel cut operation for shutting off the fuel supply to the engine 1, and the injection amount is gradually increased from the pilot injection amount that does not ignite, and based on the ignited injection amount. Then, the deterioration state of the fuel injection valve 6 is determined.

  In step S11, it is determined whether or not the fuel cut operation for shutting off the fuel supply to the engine 1 is in progress. When the fuel cut operation is not being performed, this processing is immediately terminated.

  When the fuel cut operation is being performed, the pilot injection amount QINJP is set to a predetermined misfire injection amount QIP0 (for example, 1 mg) (step S12). The predetermined misfire injection amount QIP0 is set to a value that ensures a misfire during use regardless of the cetane number of the fuel.

  In step S13, the pilot injection amount QINJP is increased by a predetermined amount ΔQIP (for example, 0.1 mg). In step S14, it is determined whether or not the injected fuel has ignited. Specifically, it is determined whether or not the pressure change rate dp / dθ detected by the in-cylinder pressure sensor 2 exceeds a predetermined threshold value DPTH, and it is determined that ignition has occurred when the pressure change rate dp / dθ exceeds the predetermined threshold value DPTH. To do.

  If the answer to step S14 is negative (NO), that is, if ignition has not occurred, the process returns to step S13 to increase the pilot injection amount QINJP by a predetermined amount ΔQIP. When steps S13 and S14 are repeatedly executed and the injected fuel is ignited, the process proceeds to step S15, and according to the total increase amount DQIPI (= ΔQIP × NINC, NINC is the number of executions of step S13), the KIVD shown in FIG. The table is searched and the deterioration correction coefficient KIVD is calculated.

  The KIVD table is set so that the deterioration correction coefficient KIVD increases as the total increase amount DQPI increases. 4 is an initial total increase amount when the fuel injection valve 6 is not deteriorated. When the total increase amount DQIPI is equal to the initial total increase amount DQI0, the deterioration correction coefficient KIVD is “1.0”. Set to Depending on the mode of deterioration of the fuel injection valve, the fuel injection amount when the same drive pulse is supplied may increase or decrease from the initial state. When the fuel injection amount decreases, the deterioration correction coefficient KIVD is “1”. The value is set to a value larger than “.0”, and when it increases, the value is set to a value smaller than “1.0”. The deterioration correction coefficient KIVD is applied to the correction of the fuel injection amount in the fuel injection control (FIG. 10) described above.

The fuel injection timing CAIFC for determining deterioration when the processing of FIG. 3 is executed is a crank angle position at which the influence of the fuel injection amount on the ignitability becomes large, for example, about 10 degrees before top dead center.
The deterioration state determination of the fuel injection valve 6 is performed for each cylinder, and the deterioration correction coefficient KIVD is calculated for each cylinder.

FIG. 5 is a flowchart of a process for estimating the cetane number of the fuel in use. This process is executed by the CPU 14.
In step S21, it is determined whether or not the engine 1 is in an idle operation state. If the engine 1 is not in an idle operation state, the present process is immediately terminated. When the engine is in the idle state, premixed combustion control is executed (step S22). Specifically, only main injection is performed without performing pilot injection, and the injection timing is advanced from the normal injection timing. The fuel injection timing CAINJ is set to a predetermined initial injection timing CAI0 (for example, 30 degrees before the top dead center), and the fuel injection amount QINJM is slightly larger than the minimum injection amount QIMIN or the minimum injection amount QIMIN that can be ignited even with a low cetane number fuel. Set to value. At this time, the fuel injection amount QINJM is calculated by applying the deterioration correction coefficient KIVD.

  In step S23, the fuel injection timing CAINJ is retarded by a predetermined crank angle ΔCA (for example, 0.1 degree). In step S24, it is determined whether or not the injected fuel has ignited. This determination is performed based on the pressure change rate dp / dθ, as in step S14 of FIG.

If the answer to step S24 is negative (NO), that is, if ignition has not occurred, the process returns to step S23 to retard the fuel injection timing CAINJ by a predetermined crank angle ΔCA. When steps S23 and S24 are repeatedly executed and ignited, the process proceeds to step S25, and the CET table shown in FIG. 6 is searched according to the total retard amount CARTD (= ΔCA × NRTD, NRTD is the number of executions of step S23). The estimated cetane number CET is calculated. The larger the total retard amount CARTD until ignition is, the more difficult it is to ignite. Therefore, the CET table is set so that the cetane number CET decreases as the total retard amount CARTD increases.
In step S26, the fuel injection timing CAINJ is returned to the original, and this process is terminated.

  Next, the fuel injection timing suitable for cetane number estimation will be described. FIG. 7 is a diagram showing the relationship between the fuel injection timing (main injection timing) CAINJM and the HC (hydrocarbon) emission amount THC in single injection. As is clear from FIG. 6A, as the fuel injection timing CAIM is advanced, the HC emission amount THC increases. Therefore, the fuel injection timing CAIM is larger than −25 degrees (more retarded). It is desirable to set it to a value.

  As is clear from FIG. 6B, the HC emission amount THC increases when the fuel injection timing CAINJM is further retarded from the top dead center (0 degree), so the fuel injection timing CAINJM is more than 2 degrees. It is desirable to set a smaller (more advanced side) value.

  FIG. 8 is a diagram showing the relationship between the fuel injection timing CAINJM and the actual ignition timing CAFM. The actual ignition timing CAFM is an actual ignition timing when the crank angle is defined so that the angle at which the piston is located at the top dead center is 0 degree and the advance direction is positive. Also, the circular points in the figure correspond to fuels with a cetane number of 54.5, and the rectangular points correspond to fuels with a cetane number of 40.5.

  The difference in actual ignition timing CAFM due to the difference in cetane number becomes larger on the advance side than −20 degrees shown in FIG. 11A, and the cetane number can be accurately estimated. However, referring also to FIG. 5B, in the range of -20 degrees to 2 degrees, the difference in actual ignition timing CAFM due to the difference in cetane number becomes small, and it is difficult to estimate the cetane number accurately.

  From the above, the fuel injection timing CAINJM when estimating the cetane number is, as shown in FIG. 9, the HC emission amount THC is equal to or less than a predetermined amount THCLH (for example, 5 mg / sec) and actual ignition due to the difference in cetane number It is desirable to set in a range R0 (−25 to −20 degrees) that is equal to or greater than the timing CAFM difference ΔCACET predetermined value ΔCATH (for example, 0.14 degrees / cetane number). Ranges R1 and R2 shown in FIG. 9 correspond to a range where the HC emission amount THC increases, and range R3 corresponds to a range where the difference in actual ignition timing CAFM due to the difference in cetane number decreases.

By setting the fuel injection timing CAINJM within the range R0 and performing cetane number estimation, it is possible to perform accurate estimation while suppressing the HC emission amount THC to be equal to or less than the predetermined amount THCLH.
Since the range R0 is a range of the injection timing at which the injected fuel is surely ignited, the predetermined initial injection timing CAI0 in the present embodiment is 30 degrees before top dead center.

FIG. 10 is a flowchart of the fuel injection control process executed by the CPU 14.
In step S71, a main injection amount map, a pilot injection amount map, a main injection timing map, and a pilot interval map (not shown) are searched according to the engine speed NE and the required torque TRQ, and the basic main injection amount QIMMAP, Basic pilot injection amount QIPMAP, basic main injection timing CAIMMAP (defined as an advance amount from the crank angle position corresponding to the top dead center), and basic pilot interval ICPMAP (defined as an advance amount from the main injection timing) ) Is calculated. The main injection amount map, the pilot injection amount map, the main injection timing map, and the pilot interval map are set based on the average cetane number fuel.

  In step S72, the main injection amount correction value QIMC, the pilot injection amount correction value QIPC, the main injection timing correction value CAIMC, and the pilot interval correction value ICPC are calculated according to the cetane number CET estimated in the process of FIG. Step S73). The main injection timing correction value CAIMC is set to decrease as the cetane number CET increases.

In step S73, the main injection amount QINJM, the pilot injection amount QINJP, the main injection timing CAINJM, and the pilot interval ICAINJP are calculated by the following formulas (1) to (4).
QINJM = (QIMMAP + QIMC) × KIVD (1)
QINJP = (QIPMAP + QIPC) × KIVD (2)
CAINJM = CAIMMAP + CAIMC (3)
ICAINJP = ICPMAP + ICPC (4)

  The CPU 14 drives the fuel injection valve 6 according to the calculated main injection amount QINJM, pilot injection amount QINJP, main injection timing CAINJM, and pilot interval ICAINJP. That is, the main injection amount QINJM and the pilot injection amount QINJP are converted into the valve opening times TIM and TIP of the fuel injection valve 6, and the fuel injection valve 6 is opened at the pilot injection timing determined by the main injection timing CAINJM and the pilot interval ICAINJP. The valve is opened for valve times TIM and TIP.

  As described above in detail, in the present embodiment, the deterioration correction coefficient KIVD indicating the deterioration state of the fuel injection valve 6 is calculated, and the cetane number estimation process during use is performed. Therefore, the fuel injection amount is calculated using the deterioration correction coefficient KIVD. Is corrected, and cetane number estimation is performed using the corrected fuel injection amount, so that accurate cetane number estimation can be performed. In addition, taking into account that the difference between the fuel injection timing at which it is easy to detect the effect of changes in the fuel injection amount and the fuel injection timing at which the difference in ignition timing due to the difference in cetane numbers is easy to detect, the fuel used when determining the deterioration state The injection timing is set to about 10 degrees before top dead center, and the fuel injection timing for estimating the cetane number is set to a range of about 30 degrees to 20 degrees before top dead center. Can be increased.

  Further, since the cetane number estimation is performed in the idling state where the engine operation state is stable, accurate estimation is possible, while the deterioration state determination of the fuel injection valve 6 is performed in the fuel cut operation state. Therefore, it is possible to prevent deterioration of operability or exhaust characteristics during normal operation of the engine.

  Further, the actual fuel injection amount can be accurately controlled regardless of the deterioration state of the fuel injection valve 6 by calculating the fuel injection amounts QINJM and QINJP by performing correction using the deterioration correction coefficient KIVD.

  In the present embodiment, the fuel injection valve 6 corresponds to the fuel injection means, and the in-cylinder pressure sensor 2 corresponds to the combustion state detection means. The ECU 4 constitutes fuel injection control means, cetane number estimation means, and deterioration state determination means. Specifically, the process in FIG. 10 corresponds to the fuel injection control means, the process in FIG. 3 corresponds to the deterioration state determination means, and the process in FIG. 5 corresponds to the cetane number estimation means.

The present invention is not limited to the embodiment described above, and various modifications can be made. For example, instead of the process shown in FIG. 3, the deterioration state of the fuel injection valve 6 may be determined by the process shown in FIG.
Step S31 is the same as step S11 of FIG. When the fuel cut operation is being performed, the pilot injection amount QINJP is set to a predetermined ignition injection amount QIP1 (for example, 2 mg) (step S32). The predetermined ignition injection amount QIP1 is set to a value that ensures ignition regardless of the cetane number of the fuel.

  In step S33, the pilot injection amount QINJP is decreased by a predetermined amount ΔQIP (for example, 0.1 mg). In step S34, it is determined whether or not the injected fuel has misfired. Specifically, it is determined whether or not the pressure change rate dp / dθ detected by the in-cylinder pressure sensor 2 has exceeded a predetermined threshold value DPTH. If the pressure change rate dp / dθ does not exceed the predetermined threshold value DPTH, a misfire has occurred. Is determined.

  If the answer to step S34 is negative (NO), that is, if no misfire has occurred, the process returns to step S33 to decrease the pilot injection amount QINJP by a predetermined amount ΔQIP. When steps S33 and S34 are repeatedly executed and a misfire occurs, the process proceeds to step S35, and the KIVD table shown in FIG. 12 is displayed according to the total decrease amount DQIPD (= ΔQIP × NDEC, NDEC is the number of executions of step S33). Search and calculate the degradation correction coefficient KIVD.

  The KIVD table shown in FIG. 12 is set so that the deterioration correction coefficient KIVD decreases as the total decrease amount DQIPD increases. DQD0 in FIG. 12 is an initial total decrease amount when the fuel injection valve 6 is not deteriorated. When the total decrease amount DQIPD is equal to the initial total decrease amount DQD0, the deterioration correction coefficient KIVD is “1.0”. Set to When the fuel injection amount when the same drive pulse is supplied decreases due to the deterioration of the fuel injection valve, the total decrease amount DQIPD decreases from the initial state, and the deterioration correction coefficient KIVD is less than “1.0”. Set to a large value. On the other hand, when the fuel injection amount when the same drive pulse is supplied increases, the total decrease amount DQIPD increases from the initial state, and the deterioration correction coefficient KIVD is set to a value smaller than “1.0”.

  In the above-described embodiment, the example in which the in-cylinder pressure sensor is used as the combustion state detection unit has been described. However, the present invention is not limited to this, and the crank angle position sensor, A method for detecting the peak position of the rate of change dp / dθ, a method for calculating the integral value of the knock sensor output, and the like can also be used.

  The present invention can also be applied to control of a marine vessel propulsion engine such as an outboard motor having a crankshaft as a vertical direction.

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. FIG. 2 is a diagram specifically illustrating a configuration of a part of the control device illustrated in FIG. 1. It is a flowchart of the process which determines the deterioration state of a fuel injection valve. It is a figure which shows the table referred by the process of FIG. It is a flowchart of the process which estimates the cetane number of the fuel in use. It is a figure which shows the table referred by the process of FIG. It is a figure which shows the relationship between fuel-injection time (CAINJM) and HC discharge | emission amount (THC). It is a figure which shows the relationship between fuel-injection time (CAINJM) and actual ignition timing (CAFM). It is a figure for demonstrating the setting range (R0) of the fuel injection time suitable for cetane number estimation. It is a flowchart of the process which performs fuel-injection control. It is a flowchart which shows the modification of the process shown in FIG. It is a figure which shows the table referred by the process of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 In-cylinder pressure sensor (combustion state detection means)
4 Electronic control unit (fuel injection control means, cetane number estimation means, deterioration state determination means)
6 Fuel injection valve (fuel injection means)

Claims (3)

In a control device for an internal combustion engine comprising fuel injection means for injecting fuel into a combustion chamber of the internal combustion engine,
Fuel injection control means for controlling fuel injection by the fuel injection means;
Combustion state detection means for detecting the combustion state in the combustion chamber of the engine;
A cetane number estimating means for estimating the cetane number of the fuel in use based on the output of the combustion state detecting means when the fuel injection control means changes the fuel injection timing by the fuel injection means;
The fuel injection control means comprises a deterioration state determination means for determining a deterioration state of the fuel injection means based on an output of the combustion state detection means when the fuel injection amount by the fuel injection means is changed;
The fuel injection control means sets the fuel injection timing when the deterioration state determination of the fuel injection means is performed to a timing different from the fuel injection timing when the cetane number is estimated. Control device.   The cetane number estimating means performs the cetane number estimation in an idle operation state of the engine, and the deterioration state determination means executes the deterioration state determination in a fuel supply cutoff operation state of the engine. The control apparatus for an internal combustion engine according to claim 1.   The internal combustion engine according to claim 1 or 2, wherein the fuel injection control means corrects a fuel injection control amount of the fuel injection means in accordance with the deterioration state determined by the deterioration state determination means. Control device.

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