JP4675876B2 - 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 a control device having a function of estimating the fuel property of a fuel in use.

Patent Document 1 discloses a method for calculating a heat generation amount parameter that correlates with a heat generation amount in a combustion chamber of an internal combustion engine and measuring a fuel property of a fuel in use based on a change in the heat generation amount parameter. Has been. According to this method, PV ^κ (P: in-cylinder pressure, V: combustion chamber volume, κ: constant near the specific heat ratio of the air-fuel mixture) is used as a heat generation amount parameter, and the difference between the minimum value and the maximum value of PV ^κ is used. Based on ΔPV ^κ , the cetane number of the fuel in use is measured. At this time, the average value of the detected difference ΔPV ^κ is calculated, and the average value is converted into a cetane number by searching a map set in advance according to the average value.

JP 2005-344550 A

In the method shown in Patent Document 1, the map for converting the difference Pv ^kappa of heat production parameter to cetane number, a single one is used that has been set in advance. However, since the relationship between the amount of heat generated and the cetane number changes depending on the engine operating state and the cetane number of the fuel being used, the estimation accuracy decreases due to changes in the engine operating state and cetane number in a single map. There was a fear.

  The present invention has been made paying attention to this point, and provides a control device for an internal combustion engine that can more accurately estimate the fuel property of the fuel in use based on the amount of heat generated by the combustion of the fuel. With the goal.

In order to achieve the above object, a first aspect of the present invention is directed to a main injection for injecting fuel into a combustion chamber of an internal combustion engine, a fuel injection means for executing pilot injection preceding the main injection, and a combustion state of the injected fuel. and the control apparatus for an internal combustion engine and a fuel property estimating means, operating condition detecting means for detecting the rotational speed and the requested torque of the engine (NE, TRQ) for estimating the fuel property of the fuel based on the pilot injection Combustion state parameter calculation means for calculating a heat generation amount (IHR) due to combustion of the burned fuel as a combustion state parameter indicating the combustion state, and the fuel property estimation means includes the combustion state parameter (IHR) and , the relation between the fuel property parameter (CET) indicating the fuel property is approximated by the first and second straight lines, before using the first and second linear Combustion state parameter (IHR) has a conversion means for converting the fuel property parameter (CET), said conversion means, in accordance with the engine speed and the required torque is detected (NE, TRQ), the first and First and second conversion gains (A, B) indicating the slope of the second straight line, and a threshold value (IHR2) corresponding to the value of the combustion state parameter at the intersection of the first and second straight lines are set. When the combustion state parameter is equal to or lower than the threshold value (IHR2), the conversion is performed by applying the first conversion gain (A), and the combustion state parameter (IHR) exceeds the threshold value (IHR2). It said second applying a conversion gain (B) have the line the conversion, the first conversion gain (a) is characterized by being set to a value smaller than the second conversion gain (B) to And

According to a second aspect of the invention, the control apparatus for an internal combustion engine according to claim 1, wherein the conversion means, wherein the pre-Symbol first variant 換Ge in (A) the second variant 換Ge in (B when switching to) executes a transient control to gradually change the conversion gain, run immediately switching when switching to the first variant 換Ge in (a) from said second variable 換Ge in (B) It is characterized by doing.

The invention according to claim 3, in the control apparatus for an internal combustion engine according to claim 1 or 2, wherein the conversion means, estimated at the start of the fuel property, the first variant 換Ge in the (A) It is characterized by applying.

According to the first aspect of the present invention, the amount of heat generated by the combustion of the pilot- injected fuel is calculated as a combustion state parameter indicating the combustion state, and depends on the engine operating state, that is, the engine speed and the required torque. The fuel property is estimated by converting the combustion state parameter into the fuel property parameter using the set conversion gain. More specifically, the relationship between the combustion state parameter and the fuel property parameter is approximated by the first and second straight lines, and the slopes of the first and second straight lines are determined according to the detected engine speed and the required torque. And a threshold value corresponding to the value of the combustion state parameter at the intersection of the first and second straight lines, and the first conversion gain when the combustion state parameter is equal to or less than the threshold value. Since the conversion is performed by applying the second conversion gain when the combustion state parameter exceeds the threshold value, the accurate estimation can be performed regardless of the change in the engine operation state. As the combustion state parameter, the amount of heat generated by the combustion of the pilot- injected fuel is used, so that the fuel property can be accurately estimated in a relatively heavy engine operation state.

According to the second aspect of the present invention, when switching from the first conversion gain to the second conversion gain, the transient control for gradually changing the conversion gain is performed, and the first conversion gain is changed to the first conversion gain. When switching to gain, switching is performed immediately. Thereby, the calculation of the transient control can be simplified and the calculation load of the calculation device can be reduced. Further, by performing the transient control, when the calculated combustion state parameter fluctuates, the fluctuation of the fuel property parameter calculated according to the combustion state parameter can be suppressed, and a highly accurate fuel property parameter can be obtained. . Further, the heat generation amount of combustion corresponding to the pilot injection is used as a combustion state parameter, towards the first conversion gain, since the second smaller than conversion gain immediately performing a handover to the first conversion gain As a result, fluctuations in the calculated fuel property parameter can be suppressed.

According to the third aspect of the present invention, the first conversion gain is applied at the start of estimation of the fuel property. Heat generation amount of combustion corresponding to the pilot injection is used as a combustion state parameter, towards the first conversion gain is because less than the second conversion gain, suppress the variation of the fuel property parameter calculated in the estimation beginning 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 made 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.

  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 flow rate sensor 33 that detects an intake air flow rate GA, a boost pressure sensor 34 that detects an intake pressure (supercharge pressure) PB downstream of the compressor, and an intake pressure sensor that detects an intake pressure PI. 35, and an intake air temperature sensor 36 for detecting the intake air temperature TI. 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 includes an accelerator sensor 37 for detecting an operation amount AP of an accelerator pedal of a vehicle driven by the engine 1, a cooling water temperature sensor 38 for detecting a cooling water temperature TW of the engine 1, and a vehicle speed VP of the vehicle driven by the engine 1. A vehicle speed sensor 39 for detecting, 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. A detection signal from the sensor 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 ## EQU2 ## and converted into a digital value and stored in the buffer 12. 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 illustrating a configuration of a module that performs cetane number estimation. The function of this module is realized by processing executed by the CPU 14.

  The module shown in FIG. 3 includes a heat generation amount calculation unit 41, a first set value calculation unit 42, a second set value calculation unit 43, a third set value calculation unit 44, a conversion unit 45, and a learning unit 46. . The heat generation amount calculation unit 41 calculates a heat generation amount IHR of combustion corresponding to pilot injection. Specifically, the heat release rate HRR [J / deg] is calculated, for example, every crank angle by the following formula (1), and the heat release rate HRR is integrated over the angle range RINT shown in FIG. The generation amount IHR is calculated.

HRR = κ / (κ−1) × PCYL × dV / dθ
+ 1 / (κ−1) × VCYL × dp / dθ (1)
Where κ is the specific heat ratio of the air-fuel mixture, PCYL is the detected cylinder pressure, dV / dθ is the cylinder volume increase rate [m ³ / deg], VCYL is the cylinder volume, and dp / dθ is the pressure output from the cylinder pressure sensor. Change rate [kPa / deg].

  FIG. 4 is a diagram showing the transition of the heat generation rate HRR in order to explain the cetane number estimation method in the present embodiment, the solid line corresponds to the fuel having the cetane number of 42.8, and the broken line is the cetane number of 54.5. Corresponding to the fuel. The heat generation amount IHR of combustion corresponding to the pilot injection obtained by integrating the heat generation rate HRR in the angle range RINT shown in the figure (for example, a range of 10 degrees before top dead center to 6 degrees after top dead center) is Experiments have confirmed that the cetane number of fuel increases as the cetane number increases. For example, as shown in FIG. 5, the heat generation amount IHR increases almost linearly with increasing cetane number CET. In FIG. 5, CET1, CET2, and CET3 are, for example, 46, 50, and 55, respectively. Since the slope of the straight line (gains A and B) changes when the cetane number CET is about “50”, in this embodiment, the gain to be used is switched according to the calculated heat generation amount IHR, and the cetane number CET is changed. I am trying to calculate.

  Returning to FIG. 3, the first set value calculation unit 42 presets the first set heat generation amount IHR1 corresponding to the first cetane number CET1 shown in FIG. 5 according to the engine speed NE and the required torque TRQ. It is calculated by searching a map for the first cetane number. The second and third set value calculation units 43 and 44 search the map for the second cetane number and the map for the third cetane number in accordance with the engine speed NE and the required torque, respectively, and the second cetane number CET2 and Second and third set heat generation amounts IHR2 and IHR3 corresponding to the third cetane number CET3 are calculated.

  The first set heat generation amount IHR1 is set as shown in FIG. 6, for example. A broken line corresponds to the first predetermined torque TRQ1, a thin solid line corresponds to the second predetermined torque TRQ2, and a thick solid line corresponds to the third predetermined torque TRQ3. The first to third predetermined torques have a relationship of TRQ3> TRQ2> TRQ1, as shown in the figure. Although the setting tendency is not simple, it is generally set so as to increase as the engine speed NE increases and to decrease as the required torque TRQ increases. The second and third set heat generation amounts IHR2, IHR3 are also set with the same tendency. Further, if the operating state of the engine 1 (engine speed NE and required torque TRQ) is the same, a relationship of IHR1 <IHR2 <IHR3 is established as shown in FIG.

  The conversion unit 45 performs the process shown in FIG. 7 using the calculated heat generation amount IHR and the set heat generation amounts IHR1 to IHR3, and calculates the cetane number CET of the fuel in use. The process shown in FIG. 7 is executed in synchronization with the timing at which the piston of the engine 1 reaches top dead center, for example.

  In step S11, it is determined whether or not a predetermined execution condition for cetane number estimation is satisfied. This predetermined execution condition is satisfied when the following conditions 1) to 4) are all satisfied.

1) Change amount of supercharging pressure PB (difference between previous value and current value) The absolute value of DPB is less than or equal to a predetermined change amount DP0 (for example, 6.7 kPa (50 mmHg)).
2) The absolute value of the change amount DGA of the intake air flow rate GA is equal to or less than a predetermined change amount DG0 (for example, 15 g / sec).
3) The engine speed NE and the required torque TRQ are within predetermined ranges (for example, the engine speed NE is 1500 to 1900 rpm, and the required torque TRQ is 8 to 16 Nm).
4) The vehicle speed VP is within a predetermined range (for example, 50 to 150 km / h).

  If the answer to step S11 is negative (NO), the value of the upcount timer TWAIT is set to “0” (step S12), and the low cetane number flag FLC is set to “1” (step S14).

When the predetermined execution condition is satisfied, the process proceeds from step S11 to step S13, and it is determined whether or not the value of the timer TWAIT is equal to or longer than a predetermined time TST (for example, 10 seconds). Since this answer is negative (NO) at first, the process proceeds to step S14. In step S13, if TWAIT ≧ TST, the process proceeds to step S15, and the first gain A is calculated by the following equation (2).

In step S16, it is determined whether or not the heat generation amount IHR is equal to or less than the second set heat generation amount IHR2. When the answer to step S16 is affirmative (YES), the process proceeds to step S17, and the heat generation amount IHR is converted into a cetane number CET by the following equation (3) using the first gain A.
CET = A × (IHR−IHR1) + CET1 (3)

  In step S18, the low cetane number flag FLC is set to “1”, and this process ends.

When the heat generation amount IHR is larger than the second set heat generation amount IHR2 in step S16, the process proceeds to step S19, and it is determined whether or not the low cetane number flag FLC is “1”. Since FLC = 1 at first, the low cetane number flag FLC is set to “0” (step S20), and the transient gain b is set to the first gain A (step S21). Then, the heat generation amount IHR is converted into a cetane number CET by the following equation (4) using the transient gain b (step S25). Initially, since the transient gain b is equal to the first gain A, a calculation is performed based on the broken line conversion characteristic obtained by extending the straight line corresponding to the first gain A shown in FIG.
CET = b × (IHR−IHR2) + CET2 (4)

When the low cetane number flag FLC is “0” in step S19, the second gain B is calculated by the following equation (5).

In step S23, the transient gain b is updated by the following equation (6). In the equation (6), b ′ is the previous value of the transient gain b, and α is a transient coefficient (<1.0) set according to the number N0 (for example, 100 times) of transient control.
b = b ′ + α × B / A (6)

When the transient gain b is updated using the equation (6), the transient gain b (N0) after N0 operations is expressed by the following equation (7).
b (N0) = A + N0 × α × B / A (7)

Therefore, from the following equation (8) indicating that the transient gain b (N0) is equal to the second gain B, the transient coefficient α is given by the following equation (9).
B = A + N0 × α × B / A (8)
α = (B−A) × A / (N0 × B) (9)

In step S24, it is determined whether or not the transient gain b is greater than the second gain B. If the answer to step S24 is negative (NO), the process proceeds to step S25. When b> B in step S24, the heat generation amount IHR is converted into a cetane number CET by the following equation (10) using the gain B (step S26).
CET = B × (IHR−IHR2) + CET2 (10)

  According to the process of FIG. 7, when the heat generation amount IHR is equal to or less than the second set heat generation amount IHR2, conversion is performed using the first gain A, and the heat generation amount IHR is set to the second set heat generation amount IHR2. When it is larger, the transient gain b is first set to the first gain A and then set to gradually increase toward the second gain B. Then, conversion is performed using the transient gain b. When the transient gain b finally reaches the second gain B, conversion is performed using the second gain B.

Returning to FIG. 3, the learning unit 46 calculates the cetane number learned value CETLRN by applying the calculated cetane number CET to the following equation (11).
CETLRN = CAV × CET + (1−CAV) × CETLRN (11)
Here, CAV is an annealing coefficient set to a value between 0 and 1, and CETLRN on the right side is a previously calculated value.

  Fuel injection control is performed using the cetane number learning value CETLRN calculated in this way. Therefore, the smaller the variation of the cetane number CET before performing the smoothing calculation according to the equation (11), the faster the cetane number learned value CETLRN converges, and the accuracy of the fuel injection control can be increased earlier.

  In the process of FIG. 3, when the conversion gain applied when converting the heat generation amount IHR into the cetane number CET is switched from the first gain A to the second gain B, the second gain is gradually increased using the transient gain b. Set to be close to B. Thereby, the variation of the cetane number CET can be reduced, and the accurate cetane number learning value CETLRN can be obtained at an early stage.

  FIGS. 8A to 8C show frequency distribution diagrams of the cetane number CET calculated by the above method for fuels having cetane numbers of 55, 49, and 46, respectively. 4 is a time chart showing changes with time corresponding to fuels with cetane numbers 55, 49, and 46, respectively. In FIG. 8, the cetane number estimation process is executed immediately when the predetermined execution condition is satisfied, and the transient control is not performed (when the heat generation amount IHR exceeds the second set heat generation amount IHR2, the gain A immediately increases to the gain A). Corresponding to the example in which the thin solid line is subjected to the cetane number estimation process after a predetermined time TST has elapsed from the point in time when the predetermined execution condition is satisfied, and the transient control is not performed, and the thick solid line represents the present embodiment. This corresponds to the example in which the cetane number estimation process of the form is executed. As is clear from this figure, according to the present embodiment, it is possible to reduce the variation and temporal variation of the calculated cetane number CET and obtain a stable estimated value.

  Further, according to the processing of FIG. 7, when switching from the first gain A to the second gain B, the transient control by the transient gain b is performed, and when switching from the second gain B to the first gain A, the switching is performed immediately. . Thereby, the calculation of the transient gain b can be simplified and the calculation load of the CPU 14 can be reduced. Further, since the first gain A is smaller than the second gain B, the change to the calculated cetane number CET can be suppressed by immediately switching to the first gain A.

  At the start of estimation of the cetane number, the first gain A is used. Since the first gain A is smaller than the second gain B, fluctuations in the cetane number CET calculated at the beginning of estimation can be suppressed.

  In the present embodiment, the in-cylinder pressure sensor 2 and the ECU 4 constitute fuel property estimation means and combustion state parameter calculation means, and the ECU 4 constitutes conversion means. Specifically, the heat generation amount calculation unit 41 shown in FIG. 3 corresponds to combustion state parameter calculation means, and the first to third set value calculation units 42 to 44, the conversion unit 45, and the learning unit 46 estimate fuel properties. The conversion unit 45 corresponds to a conversion unit.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in-cylinder pressure sensors 2 are provided in all the cylinders of the engine 1 and the cetane number estimation processing is performed using the detected pressure change rate dp / dθ of all the cylinders. And the cetane number estimation process may be performed using the pressure change rate dp / dθ detected in the specific cylinder. Further, in-cylinder pressure sensors may be provided in two or three cylinders of the four cylinders, and cetane number estimation processing may be performed using the outputs of these sensors.

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

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. FIG. 2 is a diagram specifically illustrating a configuration of a part of the control device illustrated in FIG. 1. It is a figure which shows the structure of the module which performs cetane number estimation. It is a time chart which shows transition of a heat release rate (HRR). It is a figure which shows the change characteristic which changes a heat generation amount (IHR) into a cetane number (CET). It is a figure which shows the example of a setting of the map which calculates setting heat generation amount (IHR1-IHR3). It is a flowchart which shows the process in the conversion part shown in FIG. It is a figure which shows the dispersion | variation and time change of the estimated cetane number.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 In-cylinder pressure sensor (Fuel property estimation means, combustion state parameter calculation means)
4 Electronic control unit (fuel property estimation means, combustion state parameter calculation means)
41 Heat generation amount calculation unit (combustion state parameter calculation means)
42 1st setting calculation part (fuel property estimation means)
43 2nd setting calculation part (fuel property estimation means)
44 3rd setting calculation part (fuel property estimation means)
45 Conversion unit (conversion means)
46 Learning part (Fuel property estimation means)

Claims (3)

Fuel injection means for executing main injection for injecting fuel into the combustion chamber of the internal combustion engine and pilot injection preceding the main injection, and fuel property estimation means for estimating the fuel property of the fuel based on the combustion state of the injected fuel An internal combustion engine control device comprising:
Operating state detecting means for detecting the engine speed and required torque;
A combustion state parameter calculating means for calculating a heat generation amount due to combustion of the pilot injected fuel as a combustion state parameter indicating the combustion state;
The fuel property estimation means approximates the relationship between the combustion state parameter and the fuel property parameter indicating the fuel property with first and second straight lines, and uses the first and second straight lines to calculate the combustion state parameter. Conversion means for converting the parameter into the fuel property parameter ,
The conversion means, in accordance with the engine speed and the required torque is detected, the first and first and second conversion gain indicating the inclination of the second straight line, the intersection of the first and second linear A threshold value corresponding to the value of the combustion state parameter at
The conversion is performed by applying the first conversion gain when the combustion state parameter is less than or equal to the threshold, and the second conversion gain is applied when the combustion state parameter exceeds the threshold. There line,
The control apparatus for an internal combustion engine, wherein the first conversion gain is set to a value smaller than the second conversion gain .   The conversion means executes transient control for gradually changing the conversion gain when switching from the first conversion gain to the second conversion gain, and from the second conversion gain to the first conversion gain. 2. The control apparatus for an internal combustion engine according to claim 1, wherein the switching is performed immediately when switching.   3. The control device for an internal combustion engine according to claim 1, wherein the conversion unit applies the first conversion gain when the estimation of the fuel property is started. 4.

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