JP2008088973A - 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 accurately determining the cetane value of fuel in use in the idling state of the engine. <P>SOLUTION: Actual ignition timing CAFM is detected according to a pressure change rate dp/dθ which is the output of a cylinder internal pressure sensor 2, and the actual ignition timing CAFM is subtracted from target main injection ignition timing CAFMM to compute an ignition delay angle DCAM. A correction amount DC is computed according to a detected reflux exhaust temperature TEGR and an elapsed time TWAIT after shifting into the idling state, and the correction amount DC is added to the ignition delay angle DCAM to compute a corrected ignition delay angle DCAMC. A cetane value estimation value (a learning value) CETLRN is computed for fuel in use according to the corrected ignition delay angle DCAMC. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for a compression ignition internal combustion engine that burns by compressing an air-fuel mixture in a combustion chamber.

  Patent Document 1 discloses a control apparatus for a compression ignition internal combustion engine that performs premixed combustion. According to this apparatus, the actual ignition timing of the fuel is detected during the premixed combustion, and the ignition timing error that is a difference from the preset standard fuel ignition timing and the variation in the ignition timing error are detected. The property of the fuel is determined.

JP-A-2005-171818

  The engine operation region in which the premixed combustion is performed is, for example, a region indicated by hatching in FIG. 21, and is relatively narrow when viewed from the whole engine operation region. For this reason, the execution timing of the fuel property determination is delayed, the fuel injection timing is not suitable for the fuel property, and a misfire may occur.

  Therefore, the applicant of the present application has studied to determine the fuel property in the engine idle state, and as a result, the fuel property determination result, specifically the estimated cetane number, depending on the engine operating state immediately before shifting to the idle state. Was confirmed to fluctuate.

  The present invention has been made paying attention to this point, and an object of the present invention is to provide a control device for an internal combustion engine that can accurately determine the fuel property of the fuel in use in an idle state of the engine.

  In order to achieve the above object, the invention described in claim 1 is provided with fuel injection means (6) for injecting fuel into the combustion chamber of the internal combustion engine (1), and compressing the air-fuel mixture in the combustion chamber to compress the fuel. In the control apparatus for an internal combustion engine, the ignition delay detecting means for detecting the ignition delay (DCAM) of the fuel injected into the combustion chamber and the detected ignition delay (DCAM) in the predetermined operating state of the engine. Correction means for correcting according to temperature parameters (TEGR, TEX) indicating the temperature in the combustion chamber, and fuel property estimating means for estimating the property (CET) of the fuel according to the corrected ignition delay (DCAMC) It is characterized by providing.

  According to a second aspect of the present invention, in the control device for an internal combustion engine according to the first aspect, the engine has an exhaust gas recirculation mechanism (25, 26, 28, 29, 30) for recirculating a part of the exhaust gas to the intake system. The correction means uses the temperature (TEGR) of the exhaust gas recirculated by the exhaust gas recirculation mechanism as the temperature parameter.

  According to a third aspect of the present invention, in the control device for an internal combustion engine according to the second aspect of the present invention, the control apparatus for the internal combustion engine includes a recirculation exhaust temperature acquisition means for detecting or estimating a temperature (TEGR) of the exhaust recirculated by the exhaust recirculation mechanism, The correction means uses the exhaust temperature (TEGR) detected or estimated by the recirculation exhaust temperature acquisition means as the temperature parameter.

  According to a fourth aspect of the present invention, in the control device for an internal combustion engine according to the first aspect, the correction means determines the exhaust temperature (TEX) at a position close to the combustion chamber in the exhaust pipe of the engine as the temperature parameter. It is used as.

  According to a fifth aspect of the present invention, in the control device for an internal combustion engine according to the fourth aspect, the correction means estimates the exhaust gas temperature (TEX) according to a fuel injection amount (QINJ) by the fuel injection means. Exhaust temperature estimation means is provided, and the estimated exhaust temperature (TEX) is used as the temperature parameter.

  The correction means preferably corrects the actual ignition timing according to the temperature parameters (TEGR, TEX) and the elapsed time (TWAIT) from the time when the operating state of the engine shifts to an idle state.

  According to the first aspect of the present invention, the ignition delay of the injected fuel is detected based on the pressure change in the combustion chamber, and the ignition delay is corrected and corrected in accordance with the temperature parameter indicating the temperature in the combustion chamber. The fuel property of the fuel in use is estimated according to the ignition delay. In the idle operation state, the wall surface temperature in the combustion chamber changes depending on the engine operation state immediately before, and the ignition timing changes due to the influence of the wall surface temperature. Therefore, by correcting the ignition delay according to the temperature parameter indicating the temperature in the combustion chamber, and estimating the fuel property according to the corrected ignition delay, accurate fuel property estimation can be performed without the influence of the wall temperature of the combustion chamber. It can be performed.

  According to the second aspect of the invention, the ignition delay is corrected according to the temperature of the exhaust gas recirculated by the exhaust gas recirculation mechanism. Since the temperature of the recirculated exhaust gas reflects the temperature in the combustion chamber, accurate correction can be performed by using the recirculated exhaust gas temperature.

  According to the third aspect of the invention, the temperature of the exhaust gas recirculated by the exhaust gas recirculation mechanism is detected or estimated, and the ignition delay is corrected according to the detected or estimated recirculated exhaust gas temperature. The exhaust gas recirculation mechanism includes a recirculation exhaust cooler that cools the recirculated exhaust gas and a switching valve that switches whether to use the recirculation exhaust cooler, and a recirculation exhaust that detects the temperature of the recirculated exhaust gas in order to control the operation of the switching valve. Since a temperature sensor is often provided, accurate correction can be performed by using the detection value of the recirculation exhaust temperature sensor. Further, for example, when a catalyst temperature sensor for detecting the temperature of the exhaust purification catalyst provided in the exhaust system is provided, it depends on the catalyst temperature detected by the catalyst temperature sensor, the opening degree of the exhaust gas recirculation control valve, etc. Thus, the recirculation exhaust gas temperature can be estimated. By using the estimated exhaust gas temperature, correction can be performed even when there is no recirculation exhaust gas temperature sensor.

  According to the fourth aspect of the present invention, the ignition delay is corrected according to the exhaust temperature at a position close to the combustion chamber in the exhaust pipe of the engine. Since the temperature of the exhaust gas immediately after being discharged from the combustion chamber reflects the temperature in the combustion chamber, accurate correction can be performed by using this exhaust gas temperature.

  According to the fifth aspect of the present invention, since the exhaust gas temperature is estimated according to the fuel injection amount, it is not necessary to newly provide an exhaust gas temperature sensor, and the configuration can be simplified.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
1 and 2 are diagrams showing the configuration of an internal combustion engine and a control device therefor according to an embodiment of the present invention. The following description will be given with reference to both figures together. An internal combustion engine (hereinafter referred to as “engine”) 1 is a diesel engine that directly injects fuel into a cylinder, and a fuel injection valve 6 is provided in 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 timing and valve opening time of the fuel injection valve 6 are controlled by the ECU 4.

  The engine 1 includes an intake pipe 7, an exhaust pipe 8, and a turbocharger 9. The turbocharger 9 includes a turbine that is driven to rotate by exhaust kinetic energy, and a compressor that is connected to the turbine via a shaft. The turbocharger 9 pressurizes (compresses) air sucked into the engine 1.

  An intercooler 21 is provided on the downstream side of the compressor of the intake pipe 7, and a throttle valve 22 is provided on the downstream side of the intercooler 21. The throttle valve 22 is configured to be opened and closed by an actuator 23, and the actuator 23 is connected to the ECU 4. The ECU 4 controls the opening degree of the throttle valve 22 via the actuator 23.

  An exhaust gas recirculation passage 25 that recirculates exhaust gas to the intake pipe 7 is provided between the exhaust pipe 8 and the intake pipe 7. The exhaust gas recirculation passage 25 includes a recirculation exhaust cooler 30 that cools the recirculated exhaust gas, a bypass passage 29 that bypasses the recirculation exhaust cooler 30, and a switching valve 28 that switches between the recirculation exhaust cooler 30 side and the bypass passage 29 side. An exhaust gas recirculation control valve (hereinafter referred to as “EGR valve”) 26 for controlling the exhaust gas recirculation amount is provided. The EGR valve 26 is an electromagnetic valve having a solenoid, and the valve opening degree is controlled by the ECU 4. An exhaust gas recirculation mechanism is configured by the exhaust gas recirculation passage 25, the recirculation exhaust cooler 30, the bypass passage 29, the switching valve 28, and the EGR valve 26. The EGR valve 26 is provided with a lift sensor 27 for detecting the valve opening degree (valve lift amount) LACT, and the detection signal is supplied to the ECU 4.

  The intake pipe 7 includes an intake air amount sensor 33 that detects an intake air amount GA, a boost pressure sensor 34 that detects an intake pressure (supercharge pressure) PB downstream of the compressor, and an intake pressure that detects an intake pressure PI. A sensor 35 is provided, and a recirculation exhaust temperature sensor 36 for detecting the recirculation exhaust temperature TEGR is provided in the exhaust recirculation passage 25. These sensors 33 to 36 are connected to the ECU 4, and detection signals of the sensors 33 to 36 are supplied to the ECU 4.

  On the downstream side of the turbine of the exhaust pipe 8, a catalytic converter 31 that promotes oxidation of hydrocarbons and the like contained in the exhaust gas, and a particulate matter filter 32 that collects particulate matter (mainly composed of soot). Is provided.

  Each cylinder of the engine 1 is provided with an in-cylinder pressure sensor 2 that detects an in-cylinder pressure (combustion pressure). 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 (pressure fluctuation) with respect to the crank angle (time) of the in-cylinder pressure PCYL. The in-cylinder pressure PCYL integrates the output of the in-cylinder pressure sensor. Can be obtained.

  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 detects an accelerator sensor 37 that detects an operation amount AP of an accelerator pedal of a vehicle driven by the engine 1, a cooling water temperature sensor 38 that detects a cooling water temperature TW of the engine 1, and a temperature TOIL of the lubricating oil of the engine 1. An oil temperature sensor 39, an oxygen concentration sensor (not shown) for detecting the oxygen concentration in the exhaust, an intake air temperature sensor (not shown) for detecting the intake air temperature TA of the engine 1, and the like are connected. The detection signal is 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 The in-cylinder pressure PCYL is calculated by integrating the pressure change rate dp / dθ.

  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 26 according to the target exhaust gas recirculation amount GEGR to the EGR valve 26 via the output circuit 18. Supply. Further, the CPU 14 executes processing for estimating the cetane number of the fuel in use as described below, and performs fuel injection control according to the estimated cetane number.

  FIG. 3 is a block diagram showing a configuration of a module for calculating the main injection timing CAIM and the target exhaust gas recirculation amount GEGR by the fuel injection valve 6. The function of this module is realized by processing executed by the CPU 14.

  The module shown in FIG. 3 estimates the main injection timing calculation unit 40 that calculates the main injection timing CAIM, the target exhaust gas recirculation amount calculation unit 50 that calculates the target exhaust gas recirculation amount GEGR, and the cetane number CET of the fuel in use. The determination cetane number parameter generator 60 outputs a determination cetane number parameter CETD corresponding to the estimated cetane number. In the present embodiment, in consideration of the cetane number of the fuel distributed in the market, the cetane number of the fuel in use is set to the first cetane number CET1 (for example, 41), the second cetane number CET2 (for example, 47), or It is determined that it is one of the third cetane numbers CET3 (for example, 57), and fuel injection timing control and exhaust gas recirculation control according to the determined cetane numbers are performed. The determination cetane number parameter CETD takes values from “1” to “3” corresponding to the first to third cetane numbers CET1 to CET3. The second cetane number CET2 is an average cetane number of fuel that is distributed (available) in the market.

  The main injection timing calculation unit 40 includes a first main injection timing map value calculation unit 41, a second main injection timing map value calculation unit 42, a third main injection timing map value calculation unit 43, and a switch unit 44. .

  The first main injection timing map value calculation unit 41 searches a CAIMM1 map set in advance according to the engine speed NE and the required torque TRQ, and calculates the first main injection timing map value CAIMM1. The CAIMM1 map is set based on the fuel having the first cetane number CET1 described above. The second main injection timing map value calculation unit 42 searches a CAIMM2 map set in advance according to the engine speed NE and the required torque TRQ, and calculates a second main injection timing map value CAIMM2. The CAIMM2 map is set based on the fuel of the second cetane number CET2 described above. The third main injection timing map value calculation unit 43 searches a CAIMM3 map set in advance according to the engine speed NE and the required torque TRQ, and calculates a third main injection timing map value CAIMM3. The CAIMM3 map is set based on the fuel of the third cetane number CET3 described above.

  The switch unit 44 selects one of the first to third main injection timing map values CAIMM1 to CAIMM3 according to the determination cetane number parameter CETD. That is, when CETD = 1, the first main injection timing map value CAIMM1 is selected, when CETD = 2, the second main injection timing map value CAIMM2 is selected, and when CETD = 3, The third main injection timing map value CAIMM3 is selected. As the cetane number of the fuel decreases, the fuel injection timing is advanced, so that the relationship CAIMM1> CAIMM2> CAIMM3 is established when the operating state is the same.

  The target exhaust gas recirculation amount calculation unit 50 includes a first target EGR amount map value calculation unit 51, a second target EGR amount map value calculation unit 52, a third target EGR amount map value calculation unit 53, and a switch unit 54. Become.

  The first target EGR amount map value calculation unit 51 searches a GEGRM1 map set in advance according to the engine speed NE and the required torque TRQ, and calculates the first target EGR amount GEGRM1. The GEGRM1 map is set based on the fuel having the first cetane number CET1. The second target EGR amount map value calculation unit 52 searches a GEGRM2 map set in advance according to the engine speed NE and the required torque TRQ, and calculates a second target EGR amount GEGRM2. The GEGRM2 map is set based on the fuel having the second cetane number CET2. The third target EGR amount map value calculation unit 53 searches a GEGRM3 map set in advance according to the engine speed NE and the required torque TRQ, and calculates a third target EGR amount GEGRM3. The GEGRM3 map is set based on the fuel of the third cetane number CET3.

  The switch unit 54 selects one of the first to third target EGR amount map values GEGRM1 to GEGRM3 according to the determination cetane number parameter CETD. That is, when CETD = 1, the first target EGR amount map value GEGRM1 is selected, when CETD = 2, the second target EGR amount map value GEGRM2 is selected, and when CETD = 3, The third target EGR amount map value GEGRM3 is selected. As the cetane number of the fuel decreases, the target EGR amount decreases. Therefore, when the operating state is the same, the relationship of GEGRM1 <GEGRM2 <GEGRM3 is established.

  The determination cetane number parameter generation unit 60 includes a target main injection ignition timing calculation unit 61, an ignition timing detection unit 62, a subtraction unit 63, a correction coefficient calculation unit 64, a basic correction amount calculation unit 65, and a multiplication unit 66. , An adding unit 67, a switch unit 68, a cetane number estimating unit 69, and a determination parameter setting unit 70.

  The target main injection ignition timing calculation unit 61 searches a CAFMM map set in advance according to the engine speed NE and the required torque TRQ, and calculates the target main injection ignition timing CAFMM. The CAFMM map is set based on the fuel having the second cetane number CET2 (for example, 47).

  The ignition timing detection unit 62 detects the main injection ignition timing CAFM according to the pressure change rate dp / dθ obtained by converting the output signal of the in-cylinder pressure sensor 2 into a digital value. This detection method will be described later with reference to FIGS. The subtracting unit 63 calculates the ignition delay angle DCAM by subtracting the main injection ignition timing CAFM from the target main injection ignition timing CAFMM.

  In the present embodiment, the cetane number estimation process is executed in the idling state of the engine 1 in order to perform cetane number estimation immediately after refueling. In this case, the detected ignition timing CAFM changes depending on the engine operating state immediately before shifting to the idle state. Therefore, in the present embodiment, by correcting the ignition delay angle DCAM according to the recirculation exhaust gas temperature TEGR immediately before the start of the cetane number estimation process and the elapsed time TWAIT from the time when the engine operating state shifts to the idle state, Accurate cetane number estimation is performed regardless of the engine operating state immediately before shifting to the idle state. In the present embodiment, when the cetane number estimation process is executed, exhaust gas recirculation is stopped, but the temperature of the intake pipe and the intake valve is high depending on the immediately preceding engine operating state (vehicle running state). There is. In order to improve the accuracy of the estimated cetane number in such a case, correction according to the recirculation exhaust gas temperature TEGR is performed.

  The correction coefficient calculation unit 64 searches the KDC table shown in FIG. 4A according to the recirculation exhaust temperature TEGR, and calculates the correction coefficient KDC. The KDC table is set so that the correction coefficient KDC increases as the recirculation exhaust temperature TEGR increases. In FIG. 4A, temperatures TEGR1 and TEGR2 are, for example, 100 ° C. and 300 ° C., respectively.

  The basic correction amount calculation unit 65 searches the DCB table shown in FIG. 4B according to the elapsed time TWAIT from the time when the engine operating state shifts to the idle state, and calculates the basic correction amount DCB. The DCB table is set so that the basic correction amount DCB decreases as the elapsed time TWAIT increases. In FIG. 4B, the initial value DCB0 of the basic correction amount DCB is set to about 1.1 to 1.2 degrees, for example, and the predetermined time T0 is set to 250 to 300 seconds.

  The multiplication unit 66 calculates the correction amount DC by multiplying the basic correction amount DCB by the correction coefficient KDC. The adder 67 adds the correction amount DC to the ignition delay angle DCAM to calculate a corrected ignition delay angle DCAMC.

  The switch unit 68 is controlled to be switched by a switching control signal SCTL set in the process of FIG. 11 described later. The switching unit 68 is turned off when the switching control signal SCTL is “0” and turned on when “1”. The switching control signal SCTL is set to “1” when the cetane number estimation execution condition is satisfied.

The cetane number estimation unit 69 converts the corrected ignition delay angle DCAMC into the ignition delay time TDFM using the engine speed NE, searches the CET table shown in FIG. 7 according to the ignition delay time TDFM, and determines the cetane number CET. calculate. The cetane number estimation unit 69 further applies the cetane number CET to the following formula (1) to calculate a cetane number learning value CETLRN.
CETLRN = α × CET + (1−α) × CETLRN (1)
Here, α is an annealing coefficient set to a value between 0 and 1, and CETLRN on the right side is a previously calculated value.

  The cetane number learning value CETLRN described above is calculated using all the cylinder pressure sensor outputs of the four cylinders. Therefore, the cetane number CET detected for each cylinder and the cetane number CET with different detection timings are averaged by the above equation (1). When the cetane number estimation process is not executed, the latest stored cetane number learning value CETLRN is output from the cetane number estimation unit 69.

  The determination parameter setting unit 70 sets a determination cetane number parameter CETD according to the cetane number learning value CETLRN. Specifically, as shown in FIG. 8, a hysteresis characteristic is added, and the first threshold CETH1 and the second threshold CETH2 are compared with the cetane number learning value CETLRN. That is, if a parameter for adding hysteresis characteristics (hereinafter referred to as “hysteresis parameter”) is Δh, and the determination cetane number parameter CETD is “2”, the cetane number learning value CETLRN is set to the second threshold CETH2 as a hysteresis parameter. When the value obtained by adding Δh is exceeded, the determination cetane number parameter CETD is changed to “3”. Conversely, when the determination cetane number parameter CETD is “3”, the determination cetane number parameter CETD is changed to “2” when the cetane number learning value CETLRN falls below the value obtained by subtracting the hysteresis parameter Δh from the second threshold value CETH2. The A determination cetane number parameter CETD is set for the first threshold CETH1 by the same determination.

  FIG. 5 is a block diagram showing a configuration of an ignition timing calculation module that calculates (detects) the actual ignition timing CAFM. The function of the ignition timing calculation module is realized by arithmetic processing by the CPU 14. The ignition timing calculation module includes a band pass filter unit 71, a phase delay correction unit 72, and an ignition timing determination unit 73. The band change filter unit 71 receives the pressure change rate dp / dθ output from the in-cylinder pressure sensor 2. The bandpass filter unit 71 removes a noise component included in the pressure change rate dp / dθ. Since the phase delay occurs in the band pass filter unit 71, the phase delay correction unit 72 corrects this delay.

  The ignition timing determination unit 73 determines that the crank angle position at which the pressure change rate dp / dθ has a peak value corresponds to the fuel injection as the actual ignition timing CAFM. Specifically, as shown in FIG. 6B, the crank angle at which the pressure change rate dp / dθ output from the phase delay correction unit 72 exceeds the detection threshold DPP is determined as the actual ignition timing CAFM.

  FIG. 6A shows an injection pulse INJM starting from the crank angle CAIM, and FIG. 6B shows an angle range RDET (for example, 10 degrees) for detecting the actual ignition timing CAFM. Yes. Thus, by limiting the detection angle range RDET to a relatively narrow range, it is possible to accurately determine the ignition timing without increasing the calculation load on the CPU 14.

  FIG. 9 shows the transition of the estimated cetane number CET when the cetane number estimation process described above is executed from time t0 when the cetane number of the fuel is changed from the cetane number CETBF before refueling to the cetane number CETAF after refueling by refueling. Indicates. The solid line corresponds to the case where the wall surface temperature is low, not immediately after the high load operation, and the broken line corresponds to the case where the wall surface temperature is high immediately after the high load operation. As shown in this figure, the estimated cetane number CET gradually increases from the cetane number CETBF before refueling and almost coincides with the cetane number CETAF after refueling unless immediately after the high load operation. On the other hand, immediately after the high load operation, the fuel is easily ignited, so that the estimated cetane number CET is initially higher than the actual cetane number CETAF after refueling, and gradually converges to the cetane number CETAF after refueling. Go.

  FIG. 10 is a diagram showing the relationship between the elapsed time TWAIT and the ignition timing CAFM. The thin broken line L1 is an example in which the vehicle speed (hereinafter referred to as “immediately preceding vehicle speed”) VPB immediately before shifting to the idle state is 40 km / h. The thick broken line L2 corresponds to an example in which the immediately preceding vehicle speed VPB is 60 km / h, the thin solid line L3 corresponds to an example in which the immediately preceding vehicle speed VPB is 80 km / h, and the thick solid line L4 corresponds to the immediately preceding vehicle speed VPB. Corresponds to an example in which is 100 km / h. Regardless of the immediately preceding vehicle speed VPB, when the elapsed time TWAIT becomes about the time T0, the detected ignition timing CAFM becomes substantially the same value and becomes stable. That is, the time T0 is an elapsed time when the detected ignition timing is stabilized regardless of the immediately preceding driving state, and is, for example, about 250 to 300 seconds. Therefore, the DCB table shown in FIG. 4B is set such that the basic correction amount DCB becomes “0” when the elapsed time TWAIT reaches the time T0.

  FIG. 11 is a flowchart showing a procedure of processing for determining the execution condition of the cetane number estimation process, changing the engine operating parameter at the time of executing the cetane number estimation process, and setting the switching control signal SCTL. The process shown in FIG. 11 is executed at predetermined time intervals in the CPU 14.

In step S11, it is determined whether or not the engine 1 is in an idle state, and if the answer is affirmative (YES), whether or not a predetermined execution condition for stably executing the cetane number estimation is satisfied. Is determined. The predetermined execution condition is, for example, that the recirculation exhaust temperature TEGR is equal to or higher than the predetermined temperature TE0 (for example, about 90 ° C.), and the cooling water temperature TW or the oil temperature TOIL indicating the warm-up state of the engine 1 is the predetermined temperature TWUP (for example, 80 ° C.). It is established when it is above.
When the answer to step S11 or S12 is negative (NO), the switching control signal SCTL is set to “0” (step S17).

When the predetermined execution condition is satisfied in step S12, the pilot injection is stopped and single injection is performed (step S13). That is, the number of fuel injections NINJ per cylinder is set to 1, and the main injection timing is changed from the normal to the advance direction (step S14). In this way, the fuel injection is made as a single injection, and the fuel injection timing is advanced from the normal, so that the difference in ignition timing due to the difference in cetane number can be increased, and the accuracy of cetane number estimation based on the ignition timing can be improved. . In step S15, the EGR valve 26 is closed and exhaust gas recirculation is stopped. As a result, the ignition timing is prevented from changing due to the influence of the recirculated exhaust gas, and the estimation accuracy of the cetane number can be improved.
In step S16, the switching control signal SCTL is set to “1”, and this process is terminated.

  FIG. 12 is a diagram showing the transition of the heat release rate HRR in a specific cylinder of the engine 1, where the solid line corresponds to a high cetane number (for example, 57) fuel and the broken line represents a low cetane number (for example, 41) fuel Correspond. The horizontal axis is the crank angle CA (when the piston is at the compression top dead center, it is set to “0” degree). FIG. 6A corresponds to the case where pilot injection and main injection are performed. In this case, fuel injection is performed in the vicinity of a crank angle of 0 degrees (compression top dead center), and 5 to 10 after top dead center. The heat release rate HRR reaches a peak at a degree. The difference in peak position due to the difference in cetane number is about 1 degree. FIG. 6B corresponds to the case where only the main injection is executed by advancing the fuel injection timing. In this case, the fuel injection is performed near a crank angle of −20 degrees (20 degrees before compression top dead center). The heat release rate HRR reaches a peak at 5 to 10 degrees before top dead center. The difference in peak position due to the difference in cetane number is about 8 degrees. That is, by making the fuel injection only the main injection (single injection) and advancing the injection timing, the difference in the ignition timing due to the difference in cetane number becomes more remarkable, and the calculation accuracy of the cetane number CET can be improved. .

  FIG. 13 is a frequency distribution diagram of estimation results when a cetane number estimation process is executed using a cetane number 42.8 fuel. The black circle (●) shows the result when the correction with the correction amount DC is not performed, and the white circle (◯) shows the result when the correction with the correction amount DC is performed. As is apparent from FIG. 13, the estimation accuracy can be improved by correcting the ignition delay angle DCAM with the correction amount DC.

  In the present embodiment, the fuel injection valve 6 corresponds to the fuel injection means, the recirculation exhaust temperature sensor 36 corresponds to the recirculation exhaust temperature acquisition means, and the in-cylinder pressure sensor 3 constitutes a part of the ignition delay detection means. The ECU 4 constitutes part of the ignition delay detection means, correction means, and fuel property estimation means. Specifically, the target main injection timing calculation unit 61, the ignition timing detection unit 62, and the subtraction unit 63 correspond to an ignition delay detection unit, and include a correction coefficient calculation unit 64, a basic correction amount calculation unit 65, a multiplication unit 66, and The addition unit 67 corresponds to a correction unit, and the cetane number estimation unit 69 corresponds to a fuel property estimation unit.

[Second Embodiment]
In the present embodiment, in addition to the correction according to the above-described recirculation exhaust temperature TEGR, the ignition delay angle DCAM is corrected according to the exhaust temperature TEX in the vicinity of the combustion chamber immediately after being discharged from the combustion chamber of the engine 1. It is what I did. The second embodiment is the same as the first embodiment except for the points described below.

  FIG. 14 is a block diagram showing a configuration of a module for calculating the main injection timing CAIM and the target exhaust gas recirculation amount GEGR in the present embodiment. The module shown in FIG. 14 is obtained by changing the determination cetane number parameter generation unit 60 of the module shown in FIG. 3 to a determination cetane number parameter generation unit 60a. The determination cetane number parameter generation unit 60 a includes a correction coefficient calculation unit 81 and a multiplication unit 82 in addition to the components 61 to 70 illustrated in FIG. 3. The output of the multiplication unit 82 is input to the multiplication unit 66. Is done.

  The correction coefficient calculation unit 81 searches the KDCEX table shown in FIG. 15 according to the exhaust gas temperature TEX, and calculates the additional correction coefficient KDCEX. The KDCEX table indicates that the additional correction coefficient KDCEX is “1.0” when the exhaust temperature TEX is lower than a predetermined exhaust temperature TEX0 (for example, 250 ° C.), and that the higher the exhaust temperature TEX is higher when the exhaust temperature TEX0 is higher than the predetermined exhaust temperature TEX0. The correction coefficient KDCEX is set to increase. When the exhaust temperature TEX is lower than the predetermined exhaust temperature TEX0, the ignition timing is hardly affected by the exhaust temperature TEX, so the additional correction coefficient KDCEX is set to “1.0”.

The multiplier 82 multiplies the correction coefficient KDC by the additional correction coefficient KDCEX. The multiplier 66 multiplies the basic correction amount DCB by the product of the correction coefficient KDC and the additional correction coefficient KDCEX. Therefore, the correction amount DC is calculated by the following equation.
DC = DCB × KDC × KDCEX

  As described above, by performing the correction according to the exhaust gas temperature TEX as well as the correction according to the recirculation exhaust gas temperature TEGR, it is possible to reduce the estimated variation of the cetane number CET and improve the estimation accuracy.

  In the present embodiment, the exhaust temperature TEX is calculated according to the fuel injection amount QINJ per unit time. FIG. 16 is a block diagram showing a configuration of an exhaust temperature calculation module that estimates the exhaust temperature TEX. Actually, the exhaust temperature TEX is calculated by calculation in the CPU 14.

  The exhaust temperature calculation module includes a moving average calculation unit 91 and an exhaust temperature calculation unit 92. The moving average calculator 91 calculates and outputs a moving average value QIAVE of the fuel injection amount QINJ. The moving average value QIAVE is calculated, for example, by averaging the values of the fuel injection amount QINJ (the latest value and data for the previous 99 combustion cycles) during the most recent 100 combustion cycles (200 revolutions).

  The exhaust gas temperature calculation unit 92 searches the TEX table shown in FIG. 17 according to the moving average value QIAVE, and calculates the exhaust gas temperature TEX. The TEX table is obtained experimentally in advance. Although the exhaust temperature TEX actually varies depending on the fuel injection amount and the engine speed NE, in this embodiment, the cetane number estimation is executed in the idle state, and the engine speed NE is maintained at about 1000 rpm, for example. Therefore, the TEX table shown in FIG. 17 can be applied.

  FIG. 18 is a diagram showing the relationship between the exhaust gas temperature TEX calculated according to the moving average value QIAVE of the fuel injection amount QINJ and the actually measured exhaust gas temperature TEXA. The points plotted in the figure are actually measured. Data is shown. From the actual measurement data, it is confirmed that the calculated exhaust temperature TEX approximates the actual exhaust temperature TEXA with high accuracy.

  FIG. 19 is a time chart showing the transition of the exhaust gas temperature TEX. The solid line corresponds to the calculated exhaust gas temperature TEX, and the broken line corresponds to the measured value TEXA. From this figure, it is confirmed that the calculated exhaust temperature TEX closely approximates the actual exhaust temperature TEXA even when the engine operating state changes.

  FIG. 20 is a frequency distribution diagram of estimation results when a cetane number estimation process is executed using a cetane number 42.8 fuel. A black circle (●) shows the result when correction is performed with the correction amount DC in the first embodiment, and a white circle (◯) shows the result when correction is performed with the correction amount DC in the present embodiment. As is apparent from FIG. 20, the correction amount DC of the ignition delay angle DCAM is calculated not only according to the recirculation exhaust temperature TEGR but also according to the exhaust temperature TEX, thereby reducing the variation in the estimated cetane number and improving the estimation accuracy. Can be made.

  In this embodiment, the correction coefficient calculation unit 81, the multiplication unit 82, the moving average calculation unit 91, and the exhaust temperature calculation unit 92 correspond to correction means, and the moving average calculation unit 91 and the exhaust temperature calculation unit 92 estimate the exhaust temperature. Corresponds to means.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the embodiment described above, the ignition delay angle DCAM is corrected by the correction amount DC, but the detected ignition timing CAFM may be corrected. In that case, correction is performed by subtracting the correction amount DC from the detected ignition timing CAFM.

  In the embodiment described above, the recirculation exhaust temperature sensor 36 detects the recirculation exhaust temperature TEGR. However, for example, the temperature (catalyst temperature) TCAT of the catalytic converter 31 provided in the exhaust system is detected, and the catalyst temperature TCAT, The recirculation exhaust temperature TEGR may be estimated according to the lift amount of the EGR valve 26 or the like. When the estimated recirculation exhaust temperature TEGR is used, since the detection delay of the recirculation exhaust temperature sensor is eliminated, the initial value DCB0 of the basic correction amount DCB applied to the correction of the ignition delay angle DCAM is slightly increased, for example, 1 .It is set to about 3 degrees.

  In the second embodiment, the correction amount DC is calculated according to the recirculation exhaust temperature TEGR and the exhaust temperature TEX. However, the correction amount DC may be calculated only according to the exhaust temperature TEX.

  In the second embodiment, the exhaust temperature TEX is calculated (estimated) according to the fuel injection amount QINJ. However, an exhaust temperature sensor is provided near the combustion chamber of the exhaust pipe 8, and the exhaust temperature sensor The detected exhaust gas temperature may be used.

  In the above-described embodiment, the cylinder pressure sensors 2 are provided in all the cylinders of the engine 1 and the cetane number is estimated using all the detection signals of those sensors. However, only one specific cylinder is used. An in-cylinder pressure sensor may be provided, and the cetane number may be estimated based on the detection output of the in-cylinder pressure sensor. In this case, when the execution condition for cetane number estimation is satisfied, it is desirable to change to single injection (stop pilot injection) and advance the main injection timing only for that specific cylinder.

  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 more specifically showing a partial configuration of the control device shown in FIG. 1. It is a block diagram which shows the structure of the module which calculates main injection time (CAIM) and target exhaust gas recirculation amount (GEGR). It is a figure which shows the table referred by the correction coefficient calculation part and basic correction amount calculation part which are shown in FIG. It is a block diagram which shows the structure of the ignition timing detection part shown in FIG. It is a time chart for demonstrating the detection method of ignition timing. It is a figure which shows the table for calculating a cetane number (CET) from ignition delay time (TDFM). It is a figure for demonstrating the method of setting the determination cetane number parameter (CETD) according to a cetane number learning value (CETLRN). It is a time chart for demonstrating a problem when a high load driving | operation is performed immediately before idle state transfer. It is a figure which shows the relationship between the elapsed time (TWAIT) after idle state transfer, and a detection ignition timing (CAFM). It is a flowchart of the process which performs the setting of the switching control signal (SCTL) shown in FIG. It is a figure which shows transition of the heat release rate (HRR) in a specific cylinder. It is a figure which shows frequency distribution of an estimated cetane number (CET). It is a block diagram which shows the structure of the module (2nd Embodiment) which calculates main injection time (CAIM) and target exhaust gas recirculation amount (GEGR). It is a figure which shows the table for calculating a correction coefficient (KDCEX) according to exhaust temperature (TEX). It is a figure which shows the structure of the module which estimates exhaust temperature (TEX). It is a figure which shows the table for calculating exhaust temperature (TEX). It is a figure which shows the relationship between the exhaust-gas temperature (TEX) calculated according to the fuel injection quantity, and measured value (TEXA). It is a figure which shows transition of the estimated value of exhaust temperature, and a measured value. It is a figure which shows frequency distribution of an estimated cetane number (CET). It is a figure which shows a premix combustion area | region.

Explanation of symbols

1 Internal combustion engine 2 In-cylinder pressure sensor (ignition delay detection means)
4 Electronic control unit (ignition delay detection means, correction means, fuel property estimation means)
6 Fuel injection valve (fuel injection means)
36 Recirculation exhaust temperature sensor (recirculation exhaust temperature acquisition means)
62 Ignition timing detection unit (ignition delay detection means)
61 Target main injection ignition timing calculation unit (fuel property estimation means)
63 Subtraction unit (fuel property estimation means)
64 Correction coefficient calculation unit (correction means)
65 Basic correction amount calculation unit (correction means)
66 Multiplier (correction means)
67 Adder (Correction means)
69 Cetane number estimation part (Fuel property estimation means)
81 Correction coefficient calculation unit (correction means)
82 Multiplier (correction means)
91 Moving average calculation unit (correction means)
92 Exhaust temperature calculation unit (correction means)

Claims (5)

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, and combusting the fuel by compressing an air-fuel mixture in the combustion chamber,
An ignition delay detection means for detecting an ignition delay of the fuel injected into the combustion chamber in a predetermined operation state of the engine;
Correction means for correcting the detected ignition delay according to a temperature parameter indicating the temperature in the combustion chamber;
A control device for an internal combustion engine, comprising: fuel property estimation means for estimating the property of the fuel in accordance with the corrected ignition delay.   2. The engine according to claim 1, wherein the engine includes an exhaust gas recirculation mechanism that recirculates part of the exhaust gas to the intake system, and the correction unit uses the temperature of the exhaust gas recirculated by the exhaust gas recirculation mechanism as the temperature parameter. The internal combustion engine control device described. Recirculation exhaust gas temperature acquisition means for detecting or estimating the temperature of the exhaust gas recirculated by the exhaust gas recirculation mechanism;
3. The control apparatus for an internal combustion engine according to claim 2, wherein the correction means uses the exhaust temperature detected or estimated by the recirculation exhaust temperature acquisition means as the temperature parameter.   2. The control device for an internal combustion engine according to claim 1, wherein the correction unit uses an exhaust temperature at a position close to the combustion chamber in the exhaust pipe of the engine as the temperature parameter.   The said correction | amendment means has an exhaust temperature estimation means which estimates the said exhaust temperature according to the fuel injection quantity by the said fuel injection means, The estimated exhaust temperature is used as said temperature parameter. Control device for internal combustion engine.

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