JP4694465B2 - Control device for internal combustion engine - Google Patents

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 fuel properties of a fuel in use.

  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. 15 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.

  Accordingly, the applicant of the present application has studied not only the engine operating region in which premixed combustion is performed, but also the determination of the fuel properties in the low load operation state including the engine idle state, and as a result, immediately before shifting to the low load operation state. It was confirmed that the fuel property judgment result, specifically the estimated value of cetane number, fluctuates depending on the engine operating condition.

  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 properties of the fuel in use in a low-load operating state of the engine. To do.

In order to achieve the above object, the invention described in claim 1 includes a fuel injection means (6) for injecting fuel into the combustion chamber of the internal combustion engine (1), and an exhaust gas recirculation means for returning a part of the exhaust gas to the intake system ( 25, 26, 28 to 30), a recirculation exhaust gas temperature detecting means for detecting a temperature (TEGR) of exhaust gas recirculated by the exhaust gas recirculation means in a predetermined operation state of the engine, Cooling water temperature detecting means for detecting the cooling water temperature (TW) of the engine, rotational speed detecting means for detecting the rotational speed (NE) of the engine, and ignition timing of fuel injected into the combustion chamber of the engine ( Ignition timing detection means for detecting CAFM, DCAM), the engine is in an idle state, the recirculation exhaust temperature (TEGR) is equal to or higher than a predetermined exhaust temperature (TE0), and the cooling water temperature (TW) is In the predetermined operating state is constant coolant temperature (TWUP) above, wherein the stop exhaust gas recirculation, in the state in which stop exhaust reflux, detected ignition timing (CAFM, DCAM) the property of the fuel in accordance with the A fuel property estimation means for estimating the fuel property estimation means, wherein the fuel property estimation means is the recirculation exhaust gas temperature (TEGR), the engine speed (NE), and the elapsed time (TM) from the start of the fuel property estimation. depending on the ignition timing (CAFM, DCAM) has a correction means for correcting the, and performs estimation of the fuel property in accordance with the corrected ignition timing by the previous SL correcting means (DCAMC).

According to the first aspect of the present invention, the temperature of the exhaust gas recirculated by the exhaust gas recirculation means, the cooling water temperature, and the engine speed are detected, and the ignition timing of the fuel injected into the combustion chamber is detected. Is in the idle state, the reflux exhaust temperature is equal to or higher than the predetermined exhaust temperature, and the exhaust gas recirculation is stopped and the exhaust gas recirculation is stopped in the predetermined operation state in which the cooling water temperature is equal to or higher than the predetermined cooling water temperature. The fuel property is estimated according to the detected ignition timing. Specifically, the detected ignition timing is corrected according to the recirculation exhaust temperature, the engine speed, and the elapsed time from the start of fuel property estimation , and the fuel property is estimated according to the corrected ignition timing. Is done. Ignition timing of fuel in the combustion chamber conditions vary depending on (e.g. temperature, etc. of the gas (fresh air + recirculated exhaust gas) introduced into the temperature and combustion chamber of the combustion chamber wall), the fuel property in a predetermined operating condition The state of the combustion chamber immediately after the start of estimation largely depends on the temperature of the recirculated exhaust immediately before the exhaust gas recirculation stop , and thereafter the time when the fuel property estimation is started , that is, the elapsed time from the exhaust recirculation stop time and the engine speed. It changes depending on. Therefore, by correcting the detected ignition timing in accordance with these parameters, not only immediately after starting the Oite fuel property estimating a predetermined operating condition, to perform the accurate estimation of fuel property even after the lapse of some time Can do.

Embodiments of the present invention will be described below with reference to the drawings.
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 rotationally driven by the kinetic energy of the exhaust, 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.

  The intake pipe 7 branches to intake pipes 7A and 7B on the downstream side of the throttle valve 22, and further branches corresponding to each cylinder. FIG. 1 shows only the configuration corresponding to one cylinder. Each cylinder of the engine 1 is provided with two intake valves (not shown) and two exhaust valves (not shown). Intake ports (not shown) that are opened and closed by two intake valves are connected to intake pipes 7A and 7B, respectively.

  In addition, a swirl control valve (hereinafter referred to as “SCV”) 19 that generates a swirl in the combustion chamber of the engine 1 by limiting the amount of air sucked through the intake pipe 7B is provided in the intake pipe 7B. Yes. The SCV 19 is a butterfly valve driven by an actuator (not shown), and the valve opening degree is controlled by the ECU 4.

  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 is provided with an intake air amount sensor 33 for detecting the intake air amount GA, an intake air temperature sensor 34 for detecting the intake air temperature TA, and an intake air pressure sensor 35 for detecting the intake air pressure PI. Is provided with a recirculation exhaust temperature sensor 36 for detecting the recirculation exhaust temperature TEGR. 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 and an oxygen concentration sensor (not shown) for detecting the oxygen concentration in the exhaust are 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 converter 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 amount calculation unit 64, an addition unit 67, a switch unit 68, a cetane number. An estimation unit 69 and a determination parameter setting unit 70 are included.

  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. Specifically, the heat generation rate HRR [J / deg] is calculated by the following formula (1), and the integrated value IHRR of the heat generation rate HRR is calculated from the fuel injection timing CAIM. Then, the time when the integrated value IHRR reaches the ignition determination threshold value IHRRTH is determined as the main injection ignition timing CAFM.
HRR = κ / (κ−1) × PCYL × dV / dθ
+ 1 / (κ−1) × VCYL × dp / dθ (3)
Here, κ is the specific heat ratio of the air-fuel mixture, PCYL is the detection cylinder pressure, dV / dθ is the cylinder volume increase rate [m ³ / deg], VCYL is the cylinder volume, dp / dθ is the pressure change rate [kPa / deg]. It is.

  FIG. 7 is a time chart showing the transition of the heat release rate HRR. In this figure, the solid line corresponds to an example in which additional fuel injection described later is executed, and the broken line corresponds to an example in which additional fuel injection is not executed. Part A of FIG. 7 shows an increase in the heat release rate HRR due to the ignition of the fuel injected for cetane number estimation (pilot injection is not executed but only main injection is executed). Therefore, by appropriately setting the ignition determination threshold value IHRRTH, the ignition timing CAFM is determined as shown in FIG.

  7 shows an increase in the heat generation rate HRR due to the combustion of the additionally injected fuel. By executing the additional fuel injection, it is possible to increase the torque generated in the corresponding cylinder without changing the ignition timing CAFM applied to the cetane number estimation. As a result, the torque difference between the torque generated in the cylinder that performs cetane number estimation and the torque generated in the other cylinders can be reduced, and unpleasant engine vibration can be prevented.

  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 ignition timing CAFM changes depending on the engine operating state immediately before shifting to the idle state. Therefore, in the present embodiment, the ignition delay angle DCAM is corrected according to the recirculation exhaust temperature TEGR, the estimated exhaust temperature TEX, the cooling water temperature TW, the intake air temperature TA, and the engine speed NE immediately before starting the cetane number estimation process. Thus, 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. Further, correction is performed in consideration of the fact that the degree of influence of the recirculation exhaust gas temperature TEGR immediately before the start of the cetane number estimation process decreases as the elapsed time TM from the start of the cetane number estimation process increases.

  Returning to FIG. 3, the correction amount calculation unit 64 includes a coolant temperature TW, an intake air temperature TA, a recirculation exhaust temperature TEGR, a fuel injection amount QINJ per injection, an engine speed NE, and a cetane number learning value CETLRN and switching control described later. A correction amount DC is calculated according to the signal SCTL. 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 switch-controlled by a switch control signal SCTL set in the process of FIG. 13 described later, and is in an off state when the switch control signal SCTL is “0”, and is in an on state 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. 8 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 (2) to calculate the cetane number learning value CETLRN.
CETLRN = α × CET + (1−α) × CETLRN (2)
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.
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. 9, 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, assuming that a parameter for adding hysteresis characteristics (hereinafter referred to as “hysteresis parameter”) is Δh, when 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.

  As shown in FIG. 4, the correction amount calculation unit 64 includes an elapsed time correction amount calculation unit 80, a cooling water temperature correction amount calculation unit 81, an intake air temperature correction amount calculation unit 82, a moving average calculation unit 83, and a recirculation exhaust gas temperature correction amount. A calculation unit 84, a correction coefficient calculation unit 85, a moving average calculation unit 87, an exhaust temperature estimation unit 88, an exhaust temperature correction amount calculation unit 89, addition units 90, 91, 92, and a multiplication unit 93 are provided.

The elapsed time correction amount calculation unit 80 calculates the elapsed time correction amount DTM by applying the elapsed time TM from the cetane number estimation process start time to the following equation (3).
DTM = A × (B ^−TM −1) (3)
Here, A is a coefficient calculated by searching the A table shown in FIG. 5A according to the recirculation exhaust temperature TEGR. The A table is set so that the coefficient A increases as the recirculation exhaust temperature TEGR increases. B is a speed parameter that determines the speed at which the elapsed time correction amount DTM decreases according to the elapsed time TM, and is calculated by searching the B table shown in FIG. 5B according to the engine speed NE. . The B table is set so that the speed parameter B increases as the engine speed NE increases. Since the minimum value of the speed parameter B is set to about 1.005, for example, the elapsed time correction amount DTM always takes a negative value.

  The cooling water temperature correction amount calculation unit 81 searches the DTW table shown in FIG. 5C according to the cooling water temperature TW, and calculates the cooling water temperature correction amount DTW. The DTW table is set so that the correction amount DTW increases as the coolant temperature TW increases. The intake air temperature correction amount calculation unit 82 searches the DTA table shown in FIG. 5D and calculates the intake air temperature correction amount DTA. The DTA table is set so that the correction amount DTA increases as the intake air temperature TA increases.

  The moving average calculator 83 calculates and outputs a moving average value TEGRA of the detected recirculation exhaust temperature TEGR. The moving average value TEGRA is, for example, an average of the values of the recirculated exhaust gas temperature TEGR (the latest value and the data for the previous 99 combustion cycles) detected during the period of 100 combustion cycles (200 revolutions) immediately before the start of the cetane number estimation process. To calculate.

  The recirculation exhaust temperature correction amount calculation unit 84 searches the DTEGR table shown in FIG. 5E according to the moving average value TEGRA of the recirculation exhaust temperature, and calculates the recirculation exhaust temperature correction amount DTEGR. The DTEGR table is set so that the correction amount DTEGR increases as the moving average value TEGRA increases. The correction coefficient calculation unit 85 searches the KCET table shown in FIG. 6A according to the cetane number learned value CETLRN, and calculates the correction coefficient KCET. The KCET table is set so that the correction coefficient KCET decreases as the cetane number learned value CETLRN increases (for example, when the cetane number learned value CETLRN is “55”, the correction amount is greater than when “46”). DC is set to decrease by about 50%). This is because the higher the cetane number of the fuel, the smaller the change in the ignition timing due to the influence of the recirculation exhaust temperature TEGR, the cooling water temperature TW, the intake air temperature TA, and the like.

  The moving average calculator 87 calculates and outputs a moving average value QINJA of the fuel injection amount QINJ. The moving average value QINJA is calculated, for example, by averaging the values of the fuel injection amount QINJ during the most recent 100 combustion cycles (200 revolutions) (the latest value and the data for the previous 99 combustion cycles). The exhaust temperature estimating unit 88 searches the TEX table shown in FIG. 6B according to the moving average value QINJA of the fuel injection amount, and calculates the estimated exhaust temperature TEX. The exhaust temperature correction amount calculation unit 89 searches the DTEX table shown in FIG. 6C according to the estimated exhaust temperature TEX, and calculates the exhaust temperature correction amount DTEX. The DTEX table is set so that the exhaust temperature correction amount DTEX increases as the estimated exhaust temperature TEX increases.

  The TEX table is obtained experimentally in advance. Although the exhaust temperature 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. The TEX table shown in FIG. 6B can be applied.

The adders 90 to 92 perform calculation of the following formula (4). That is, the elapsed time correction amount DTM, the cooling water temperature correction amount DTW, the intake air temperature correction amount DTA, the recirculation exhaust temperature correction amount DTEGR, and the exhaust temperature correction amount DTEX are added to calculate the basic correction amount DCB.
DCB = DTM + DTW + DTA + DTEGRC + DTEX (4)

  The multiplier 93 calculates the correction amount DC by multiplying the basic correction amount DCB by the correction coefficient KCET.

  By adding the correction amount DC to the ignition delay angle DCAM, it is possible to accurately estimate the cetane number regardless of the operation state immediately before shifting to the idle state.

  FIG. 10A is a diagram showing changes in the ignition timing CAFM and the engine speed NE before and after the time t0 when the cetane number estimation process starts. Before time t0, normal operation that is not idle operation is performed and exhaust gas recirculation is performed. However, after time t0, exhaust gas recirculation is stopped, and in fact, several seconds until the operation state is stabilized after shifting to the idle operation state. After waiting, the cetane number estimation process is started. In the present embodiment, the specific one-cylinder fuel injection mode is changed to main injection only, and the main injection timing CAIM is advanced to detect the ignition timing CAFM. However, in order to prevent a decrease in torque generated by the cylinder that executes the ignition timing detection process, additional injection is executed as necessary, as will be described later.

  FIG. 10B shows a transition of the recirculation exhaust gas temperature TEGR before and after time t0 (L12) and a transition of the ignition timing CAFM detected after time t0 (L11). The time t1 in this figure is the time when about 7 seconds have elapsed from the time t0, and the time t2 is the time when 60 seconds have elapsed from the time t0.

  FIGS. 11A and 11B are diagrams showing the correlation between the detected ignition timing CAFM and the recirculation exhaust temperature TEGR, and FIG. 11A corresponds to the detection data at time t1 in FIG. 10B. FIG. 6B corresponds to the detection data at time t2. The correlation coefficient obtained from the data in FIG. 11 (a) is 0.942, whereas the correlation coefficient obtained from the data in FIG. 11 (b) is 0.726, and from time t0 when exhaust gas recirculation is stopped. It can be seen that the correlation between the recirculation exhaust temperature TEGR and the ignition timing CAFM decreases with time. Therefore, by using the elapsed time correction amount DTM corresponding to the elapsed time TM from the time when the exhaust gas recirculation is stopped and the cetane number estimation process is started, accurate estimation of the cetane number is performed regardless of the detection timing of the ignition timing CAFM. It can be performed.

  FIG. 12 is a diagram showing the relationship between the elapsed time TM from time t0 and the ignition timing CAFM, and the thin broken line L1 indicates that the vehicle speed immediately before shifting to the idle state (hereinafter referred to as “immediately preceding vehicle speed”) VPB is 40 km / The thick broken line L2 corresponds to the example in which the immediately preceding vehicle speed VPB is 60 km / h, the thin solid line L3 corresponds to the example in which the immediately preceding vehicle speed VPB is 80 km / h, and the thick solid line L4 corresponds to the example in which h is thick. This corresponds to an example in which the immediately preceding vehicle speed VPB is 100 km / h. Since the effect of the immediately preceding vehicle speed VPB is reflected in the recirculation exhaust temperature TEGR immediately before time t0, the coefficient A of the equation (3) is calculated according to the recirculation exhaust temperature TEGR, and immediately before the cetane number estimation is started. Accurate correction can be performed by eliminating the influence of the operating state.

  FIG. 13 is a flowchart showing a processing procedure for determining the execution condition of the cetane number estimation process and setting the switching control signal SCTL. The process shown in FIG. 13 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. 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 a 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. The time point when the predetermined execution condition is satisfied corresponds to “the time point when the state shifts to the predetermined operation state”.

If the answer to step S11 or S12 is negative (NO), the switching control signal SCTL is set to “0” (step S15).
When the predetermined execution condition is satisfied in step S12, the EGR valve 26 is closed and exhaust gas recirculation is stopped (step S13). 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 S14, the switching control signal SCTL is set to “1”, and this process is terminated.

  FIG. 14 is a flowchart showing the procedure of the fuel injection control process. This process is executed by the CPU 14 every crank angle of 180 degrees corresponding to the fuel injection of each cylinder. In the present embodiment, the cetane number is estimated based on the ignition timing CAFM detected in the cylinder # 1 among the four cylinders # 1 to # 4. Therefore, when estimating the cetane number, the fuel injection amount of the cylinder # 1 is fixed to a constant value, and the fuel injection amounts of the other cylinders # 2 to # 4 are equal to the target engine speed NEIDL. To be controlled.

  In step S21, it is determined whether or not the switching control signal SCTL is “1”, and if the answer is negative (NO), normal control is executed (step S22). That is, the main injection amount, the pilot injection amount, the main injection timing, and the pilot injection timing are calculated according to the engine speed NE and the required torque TRQ.

  When SCTL = 1 in step S21 and the cetane number estimation process is executed, it is determined whether or not the current control target cylinder is cylinder # 1 (step S23). When the target cylinder is not cylinder # 1, the main injection amount QINJM # n (n = 2 to 4) and the pilot injection amount QINJP # n (n = 2 to 4) so that the engine speed NE matches the target speed NEIDL. ) Is calculated (step S24). In the idle state, the main injection timing CAIM and the pilot injection timing CAIP are set, for example, at about 7 degrees before top dead center and about 3 degrees before top dead center, respectively.

  In step S25, the fuel injection amount QINJ is calculated by adding the main injection amount QINJM # n and the pilot injection amount QINJP # n. In step S26, it is determined whether or not the fuel injection amount QINJ is equal to or greater than a predetermined injection amount QINJTH (for example, 10 mg). If the answer is negative (NO), the additional injection flag FADD is set to “0”. (Step S31), this process is terminated. When QINJ ≧ QINJTH and the difference between the fuel injection amount of cylinder #n and the fuel injection amount of cylinder # 1 is large, the additional injection flag FADD is set to “1” (step S27).

  When the target cylinder is cylinder # 1 in step S23, the process proceeds to step S28, the main injection amount QINJM # 1 is set to the fixed injection amount QFIX (for example, 6 mg), and the pilot injection amount QINJP # 1 is set to “0”. The main injection only. Further, the main injection timing CAIM is advanced by a predetermined angle DEST (for example, 20 degrees before top dead center). As described above, only the main injection is executed and the main injection timing is advanced from the normal time, so that the difference in the ignition timing due to the difference in the cetane number can be increased and the accuracy of the cetane number estimation based on the ignition timing can be improved. .

  In step S29, it is determined whether or not the additional injection flag FADD is “1”. If the answer to step S29 is negative (NO), the process immediately ends. When FADD = 1, the difference between the generated torque of cylinder # 1 and the generated torque of the other cylinders is large, so that additional fuel injection is executed after main injection, for example, at a timing of 10 degrees after top dead center. (Step S30). The additional fuel injection amount QIADD at this time is set to, for example, a difference (QINJ−QFIX) between the fixed injection amount QFIX and the fuel injection amount QINJ of other cylinders.

  By executing the additional fuel injection, the heat generation rate HRR changes as shown by the solid line in FIG. 7, and fluctuations in the engine speed NE can be suppressed.

  In the idling state, the SCV 19 is normally fully closed, but it is desirable to open the SCV 19 when performing additional fuel injection. In that case, the opening degree of the SCV 19 is controlled to increase as the additional fuel injection amount QIADD increases.

  As described above in detail, in the present embodiment, the ignition delay angle DCAM of the injected fuel is calculated in the idling state of the engine 1, and the ignition delay angle DCAM is calculated based on the recirculation exhaust gas temperature TEGR, the engine speed NE, and the cetane number. The elapsed time correction amount DTM is calculated by applying the elapsed time TM from the start time of the estimation process to Equation (3). Then, the cetane number of the fuel is estimated according to the ignition delay angle DCAMC corrected by the elapsed time correction amount DTM. Thus, accurate estimation can be performed not only immediately after starting the cetane number estimation process but also when a certain amount of time has passed.

In this embodiment, the fuel injection valve 6 corresponds to the fuel injection means, and the exhaust gas recirculation passage 25, the EGR valve 26, the switching valve 28, the bypass passage 29, and the recirculation exhaust cooler 30 constitute the exhaust gas recirculation means, and the recirculation exhaust temperature sensor. 36, the cooling water temperature sensor 38, and the crank angle position sensor 3 correspond to the recirculation exhaust temperature detection means, the cooling water temperature detection means, and the rotation speed detection means, respectively, and the in- cylinder pressure sensor 2 and the crank angle position sensor 3 correspond to the ignition timing. It constitutes a part of the detection means, E CU4 some ignition timing detection means, the correction manual stage, and the fuel property estimating means. Specifically, the ignition timing detector 62 shown in FIG. 3 corresponds to the ignition timing detector, and the target main injection ignition timing calculator 61, the subtractor 63, the correction amount calculator 64, and the adder 67 serve as the corrector. Correspondingly, the cetaneization estimation unit 69 corresponds to fuel property estimation 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.

  Further, in the above-described embodiment, the cetane number estimation process is executed in the idling state of the engine 1, but it may be performed in the premixed combustion region illustrated in FIG. In that case, in step S24 of FIG. 14, the main injection amount QINJM # n, the pilot injection amount QINJP # n, the main injection timing CAIM, and the pilot injection timing CAIP are calculated according to the engine speed NE and the required torque TRQ. To do. In this case, additional fuel injection may be performed in the cylinder # 1 when the required torque TRQ is equal to or greater than the predetermined torque TRQTH.

  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 block diagram which shows the structure of the correction amount calculation part shown in FIG. It is a figure which shows the table used for the calculation in each block shown in FIG. It is a figure which shows the table used for the calculation in each block shown in FIG. It is a time chart which shows transition of a heat release rate (HRR). 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 transition of the ignition timing detected from the start time of a cetane number estimation process. It is a figure which shows the correlation with recirculation | reflux exhaust gas temperature (TEGR) and ignition timing (CAFM). It is a time chart which shows transition of 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 flowchart which shows the procedure of a fuel-injection control process. It is a figure which shows a premix combustion area | region.

Explanation of symbols

1 Internal combustion engine 2 In-cylinder pressure sensor (ignition timing detection means)
3 Crank angle position sensor (ignition timing detection means, rotation speed means)
4 Electronic control unit (ignition timing detection means, correction means, fuel property estimation means)
6 Fuel injection valve (fuel injection means)
36 Recirculation exhaust temperature sensor ( recirculation exhaust temperature detection means)
38 Cooling water temperature sensor (cooling water temperature detection means)
61 Target main injection ignition timing calculation unit (correction means)
62 Ignition timing detector (Ignition timing detection means)
63 Subtraction unit (correction means)
64 Correction amount calculation unit (correction means)
67 Adder (Correction means)
69 Cetane number estimation part (Fuel property estimation means)

Claims (1)

In a control apparatus for an internal combustion engine, comprising: fuel injection means for injecting fuel into a combustion chamber of the internal combustion engine; and exhaust gas recirculation means for returning a part of exhaust gas to the intake system.
Recirculation exhaust gas temperature detection means for detecting the temperature of the exhaust gas recirculated by the exhaust gas recirculation means;
Cooling water temperature detection means for detecting the cooling water temperature of the engine;
A rotational speed detecting means for detecting the rotational speed of the engine;
Ignition timing detection means for detecting the ignition timing of the fuel injected into the combustion chamber of the engine;
The exhaust gas recirculation is stopped and the exhaust gas recirculation is stopped in a predetermined operation state in which the engine is in an idle state, the recirculated exhaust gas temperature is equal to or higher than a predetermined exhaust gas temperature, and the cooling water temperature is equal to or higher than a predetermined cooling water temperature. A fuel property estimating means for estimating the property of the fuel according to the detected ignition timing in a stopped state ,
The fuel property estimating means includes
Correction means for correcting the ignition timing according to the elapsed time from the time when the reflux exhaust temperature, the engine speed, and the fuel property estimation start ,
Control apparatus for an internal combustion engine, characterized in that an estimate of the fuel property in accordance with the ignition timing corrected by the previous SL correction means.

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