JP5525353B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a fuel injection control device that executes split fuel injection in which fuel injection in one cylinder is divided into a plurality of times.

  Patent Document 1 discloses a fuel injection control device that executes split fuel injection in a diesel engine. According to this device, it is estimated that the temperature in the combustion chamber is in a low temperature state after a predetermined time has elapsed since the complete explosion of the engine, and that the temperature in the combustion chamber is estimated to be in a high temperature state after the predetermined time has elapsed. When it is estimated that there is, the form of split fuel injection is changed. Specifically, the number of divisions is reduced or the injection suspension period is shortened, or a change is made to batch fuel injection instead of split fuel injection.

Japanese Patent No. 44033641

  The control method disclosed in Patent Document 1 solves the problem that if divided fuel injection is performed when the temperature in the combustion chamber is low, combustion becomes unstable and engine startability and exhaust characteristics may be deteriorated. It is intended. Therefore, the case where the temperature in the combustion chamber is too high is not taken into consideration. When the temperature in the combustion chamber is too high, there is a risk of increasing NOx emissions or combustion noise. However, the control method disclosed in Patent Document 1 cannot solve this problem.

  The present invention has been made paying attention to this point, and by performing divided fuel injection more appropriately, the internal combustion engine temperature can be maintained at an appropriate temperature, and deterioration of exhaust characteristics and combustion noise can be prevented. An object of the present invention is to provide a fuel injection control device.

In order to achieve the above object, a first aspect of the present invention provides a fuel injection control device for an internal combustion engine comprising fuel injection means (9) for injecting fuel into a combustion chamber of the internal combustion engine (1). Main fuel injection execution control means for executing main fuel injection for generating torque of the engine, and estimation for calculating an estimated combustion temperature (TME) that is an estimated value of the combustion chamber temperature when the main fuel injection is executed Combustion temperature calculation means, and the main fuel injection execution control means divides the main fuel injection into n when the estimated combustion temperature (TME) exceeds a predetermined temperature (TMTGT) (n is an integer of 2 or more) the estimated maximum value of the combustion temperature (TMEMAX) and the temperature difference between the predetermined temperature (TMTGT) (DTME) and the mass of the combustion chamber to the intake gas (MGAS) in based rather on the combustion temperature And have use suppression fuel quantity (DQIM), wherein as the estimated combustion temperature (TME) does not exceed a predetermined temperature (TMTGT), wherein in the divided fuel injection (n-1) th fuel injection quantity split injection (QIM (n-1)) and characterized by having a n th fuel injection amount of the split injection (QIM (n)) and the split injection control means for calculating.

  According to a second aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the first aspect, the divided injection control means performs the divided fuel injection execution timing (CAIM) based on the temperature difference (DTME). (j)) is calculated.

According to a third aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the first or second aspect, the split injection control means is a fuel injection amount (QIM () of the nth split injection in the split fuel injection. n )) is calculated according to the combustion temperature rise suppression fuel amount (DQIM) and the combustion efficiency (η I (n) ) at the execution time (CAIM ( n )) of the n-th divided injection. .

According to a fourth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to any one of the first to third aspects, the split injection control means is configured to execute the n-split main fuel injection. Estimated generated torque calculating means for calculating an estimated generated torque (TRQE) that is an estimated value of the generated torque, and when the estimated generated torque (TRQE) is smaller than the target torque (TRQD), the target torque (TRQD) and the estimated The advance angle correction means corrects the advance timing (CAIM ( n )) of the n-th split fuel injection based on the difference from the generated torque (TRQE), and the advance angle correction means includes the ( The execution interval (DCAIM) of the (n-1) th divided injection and the nth divided injection is the advance correction amount (DCAAD (n)) of the nth divided fuel injection at the predetermined minimum injection interval (DCAIMIN). Is smaller than the determination threshold value obtained by adding the execution timing of the (n−1) th divided injection (CAIM (n)) without correcting the advance angle of the nth divided fuel injection (CAIM (n)). n-1)) is advanced .

According to a fifth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the fourth aspect, the split injection control means is recalculated after executing the advance angle correction by the advance angle correction means. When the temperature (TME) exceeds the predetermined temperature (TMTGT), the division number n of the main fuel injection is increased .

According to a sixth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to any one of the first to fifth aspects, the split injection control means is configured to control a heat generation amount when the split injection is executed. Estimated heat generation amount calculation means for calculating an estimated heat generation amount (JME) which is an estimated value, and a gravity center angle position (CAGC) at which the integrated value of the estimated heat generation amount is 50% of the total estimated heat generation amount (JTOTAL) The center-of-gravity angle position calculation means for calculating the center-of-gravity angle is calculated, and the execution timing (CAIM (j)) of each divided injection is controlled so that the center-of-gravity angle position (CAGC) becomes a predetermined angle position (CAGCX) and is calculated again. When the estimated combustion temperature (TME) to be performed exceeds the predetermined temperature (TMTGT), the division number n of the main fuel injection is increased .

According to the first aspect of the present invention, the estimated combustion temperature when the main fuel injection is executed is calculated, and when the estimated combustion temperature exceeds the predetermined temperature, the main fuel injection is divided into n (n is an integer of 2 or more). ), and it has use the maximum value and the temperature difference and the combustion temperature rise suppressing fuel quantity rather based on the mass of the suction gas in the combustion chamber of a predetermined temperature estimation combustion temperature, so that the estimated combustion temperature does not exceed a predetermined temperature , in the divided fuel injection (n-1) th fuel injection quantity split injection and the fuel injection amount of n-th divided injection and are calculated. Therefore, by performing split fuel injection, the combustion temperature can be suppressed to a predetermined temperature or less, and deterioration of exhaust characteristics and combustion noise can be prevented.

  According to the second aspect of the invention, the execution timing of the divided fuel injection is calculated based on the temperature difference between the estimated combustion temperature and the predetermined temperature. Since the combustion temperature also depends on the fuel injection timing, the combustion temperature can be reliably suppressed by setting the divided injection execution timing according to the temperature difference.

According to the third aspect of the present invention, the fuel injection amount of the nth divided injection in the divided fuel injection is calculated according to the combustion temperature rise suppression fuel amount and the combustion efficiency at the execution timing of the nth divided injection. . Combustion efficiency changes depending on the execution timing of divisional injection, by calculating the fuel injection amount using the combustion efficiency corresponding to split injection execution timing, it is possible to perform the combustion temperature suppressed accurately.

According to the fourth aspect of the present invention, the estimated generated torque when the n-divided main fuel injection is executed is calculated, and when the estimated generated torque is smaller than the target torque, the difference between the target torque and the estimated generated torque is calculated. Based on this, the execution timing of the n-th split fuel injection is advanced. Further, when the execution interval between the (n-1) th divided injection and the nth divided injection is smaller than the determination threshold obtained by adding the advance correction amount of the nth divided fuel injection to the predetermined minimum injection interval, the nth The advance timing of the execution timing of the (n−1) th split injection is corrected without correcting the advance timing of the split fuel injection. Therefore, it is possible to prevent a decrease in generated torque caused by dividing the main fuel injection. When the execution interval between the (n-1) th divided injection and the nth divided injection is smaller than the determination threshold, the execution timing of the nth, that is, the last divided injection is advanced by an amount necessary for securing torque. Since the angle cannot be made, the generated torque is secured by advancing the execution timing of the (n-1) th divided injection.

According to the fifth aspect of the present invention, when the estimated combustion temperature calculated again after executing the advance correction of the divided injection timing exceeds a predetermined temperature, the division number n of the main fuel injection is increased. The temperature is suppressed below a predetermined temperature .

According to the sixth aspect of the present invention, the estimated heat generation amount when the divided injection is executed is calculated, the centroid angle position of the estimated heat generation amount is calculated, and the centroid angle position becomes the predetermined angle position. In addition, since the execution timing of each divided injection is controlled, the timing (angular position) at which the in-cylinder pressure is substantially maximized by combustion can be maintained at substantially the same position as when the main fuel injection is not divided. When the estimated combustion temperature calculated again exceeds the predetermined temperature, the division number n of the main fuel injection is increased, so that the combustion temperature is suppressed below the predetermined temperature.

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. It is a flowchart of the process which controls main fuel injection. It is a flowchart of the process which controls main fuel injection. It is a time chart for demonstrating the process of FIG.2 and FIG.3. It is a figure which shows the setting of the map for calculating combustion efficiency ((eta)).

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an internal combustion engine and a control device thereof according to an embodiment of the present invention. 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 9 is provided in each cylinder. The fuel injection valve 9 is electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 20, and the valve opening timing and valve opening time of the fuel injection valve 9, that is, the fuel injection timing and the fuel injection amount are determined by the ECU 20. Controlled by

  The engine 1 includes an intake passage 2, an exhaust passage 4, and a turbocharger 8. The turbocharger 8 includes a turbine 11 having a turbine wheel 10 that is rotationally driven by the kinetic energy of exhaust, and a compressor 16 having a compressor wheel 15 connected to the turbine wheel 10 via a shaft 14. The compressor wheel 15 pressurizes (compresses) air sucked into the engine 1.

  The turbine 11 includes a plurality of variable vanes 12 (only two are shown) that are driven to open and close to change the flow rate of exhaust gas blown to the turbine wheel 10 and an actuator (not shown) that drives the variable vanes to open and close. The flow rate of the exhaust gas blown to the turbine wheel 10 is changed by changing the opening degree of the variable vane 12, and the rotational speed of the turbine wheel 10 can be changed. The actuator that drives the variable vane 12 is connected to the ECU 20, and the opening degree of the variable vane 12 is controlled by the ECU 20. More specifically, the ECU 20 supplies a control signal with a variable duty ratio to the actuator, thereby controlling the vane opening. The configuration of a turbocharger having a variable vane is widely known, and is disclosed in, for example, Japanese Patent Laid-Open No. 1-208501.

  An intercooler 18 is provided downstream of the compressor 16 in the intake passage 2, and a throttle valve 3 is provided downstream of the intercooler 18. The throttle valve 3 is configured to be opened and closed by an actuator 19, and the actuator 19 is connected to the ECU 20. The ECU 20 controls the opening degree of the throttle valve 3 via the actuator 19.

  Between the exhaust passage 4 and the intake passage 2, an exhaust recirculation passage 5 that recirculates exhaust gas to the intake passage 2 is provided. The exhaust gas recirculation passage 5 is provided with an exhaust gas recirculation control valve (hereinafter referred to as “EGR valve”) 6 for controlling the exhaust gas recirculation amount (EGR amount) and an EGR cooler 7 for lowering the temperature of the recirculated exhaust gas. . The EGR valve 6 is an electromagnetic valve having a solenoid, and the valve opening degree is controlled by the ECU 20.

  In the intake passage 2, an intake air flow rate sensor 21 that detects the intake air flow rate GA, a boost pressure sensor 22 that detects an intake pressure (supercharge pressure) PB downstream of the compressor 16, and an intake air temperature that detects the intake air temperature TI. A sensor 23 and an intake pressure sensor 24 for detecting the intake pressure PI are provided. These sensors 21 to 24 are connected to the ECU 20, and detection signals from the sensors 21 to 24 are supplied to the ECU 20.

  An oxygen concentration sensor 26 for detecting the oxygen concentration in the exhaust gas is provided immediately downstream of the engine 1 in the exhaust passage 4, and the detection signal is supplied to the ECU 20. An oxidation catalyst 31 and a soot filter 32 to which a catalyst is added are provided downstream of the turbine 11 in the exhaust passage 4. The oxidation catalyst 30 promotes oxidation of hydrocarbons (unburned fuel components), CO, and NO contained in the exhaust.

  An accelerator sensor 27 that detects the amount of depression of an accelerator pedal (not shown) of a vehicle driven by the engine 1 (hereinafter referred to as “accelerator pedal operation amount”) AP, and an engine speed that detects an engine speed (rotation speed) NE. A sensor 28 and an atmospheric pressure sensor 29 for detecting the atmospheric pressure PA are connected to the ECU 20, and detection signals from these sensors are supplied to the ECU 20. The engine speed sensor 28 supplies the ECU 20 with a crank angle pulse generated at every predetermined crank angle (for example, 1 degree) and a TDC pulse generated in synchronization with the timing at which the piston of each cylinder of the engine 1 is located at the top dead center. To do.

  The ECU 20 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, a central processing unit (hereinafter referred to as “CPU”). A storage circuit for storing various calculation programs executed by the CPU and calculation results, an actuator for driving the variable vane 12 of the turbine 11, a fuel injection valve 9, an EGR valve 6, an actuator 19 for driving the throttle valve 3, etc. It comprises an output circuit for supplying a drive signal.

  The ECU 20 performs fuel injection control by the fuel injection valve 9, exhaust gas recirculation control by the EGR valve 6, supercharging pressure control by the variable vane 12, and the like according to the engine operating state (mainly the engine speed NE and the required torque TRQD). The required torque TRQD is calculated according to the accelerator pedal operation amount AP, and is set to increase as the accelerator pedal operation amount AP increases.

  In the present embodiment, when executing main injection, which is the main fuel injection for generating torque in the engine 1, the estimated combustion temperature TME is calculated, and the estimated combustion temperature TME does not exceed the predetermined temperature TMTGT. Control for dividing and executing injection is performed.

2 and 3 are flowcharts of processing for performing the main injection control, and this processing is executed by the CPU of the ECU 20 in synchronization with the generation of the TDC pulse.
In step S11, intake gas parameters such as intake air temperature TI, intake pressure PI, intake air flow rate GA, and exhaust gas recirculation rate are read. In step S12, injection control parameters, that is, main injection, are determined according to the engine speed NE and the required torque TRQD. The fuel injection amount (hereinafter referred to as “main injection amount”) QIM and the main injection execution timing (hereinafter referred to as “main injection timing”) CAIM are calculated.

In step S13, an estimated combustion temperature TME (i), which is an estimated value of the combustion chamber temperature in the compression stroke and the expansion stroke, is calculated for each predetermined crank angle DCA (for example, 1 degree) by the following equation (1). In equation (1), TI is the intake air temperature, ε is the compression ratio, κ is the specific heat ratio, “i” is an index parameter indicating the crank angle position for each predetermined crank angle DCA, and DTfuel (i) is the fuel injected This is the amount of temperature rise due to combustion, and is calculated by the following equation (2). In Equation (2), q is the fuel injection amount per predetermined crank angle DCA, η is the combustion efficiency, JL is the lower heating value of the fuel, R is the gas constant, and Mgas is the mass (in moles) of the gas sucked into the combustion chamber. Mfuel is a conversion value in terms of the number of moles of injected fuel (Σq). “Σ” means an integrated value from the fuel injection start time to the crank angle position corresponding to the index parameter i.

  The fuel injection amount q is calculated as follows. The main injection amount QIM is converted into a main fuel injection time TIM according to the injection characteristics and fuel pressure of the fuel injection valve 9, and the main fuel injection time TIM is converted into a main injection angle period DAIM according to the engine speed NE. Then, the fuel injection amount q per predetermined crank angle is obtained by multiplying the main injection amount QIM by (DCA / DAIM). After the time when the integrated value of the fuel injection amount q reaches QIM, q = 0.

  In step S14, it is determined whether or not the maximum value (hereinafter referred to as “maximum combustion temperature”) TMEMMAX of the estimated combustion temperature TME (i) calculated in step S13 is higher than a predetermined temperature TMTGT. If this answer is negative (NO), the process is immediately terminated. Therefore, one main injection is executed using the injection control parameter calculated in step S12.

If the answer to step S14 is affirmative (YES), a temperature difference DTME is calculated by subtracting the predetermined temperature TMTGT from the maximum combustion temperature TMEMAX (the following equation (3)) (step 15).
DTME = TMEMAX-TMTGT (3)

In step S16, the fuel subtraction amount DQIM is calculated by the following equation (4).
DQIM = DTME × R × Mgas / JL (4)

In step S15, the main injection is divided as described below. When this step is executed for the first time, the division number n is “2”. The fuel injection amount QIM (1) in the first main injection and the fuel injection amount QIM (2) in the second main injection are given by the following equations (5) and (6), respectively. In Equation (6), ηI (2) is the combustion efficiency at CAIM (2) when the second main injection is executed (hereinafter referred to as “second main injection timing”).
QIM (1) = QIM−DQIM (5)
QIM (2) = DQIM / ηI (2) (6)

  The second main injection timing CAIM (2) is set so that the maximum combustion temperature TMEMAX does not exceed the predetermined temperature TMTGT.

Next, the temperature rise amount DTM (2) due to the second fuel injection is calculated by the following equation (7). Mfuel2 in the equation (7) is a value converted into the number of moles of the injected fuel amount (QIM (1) + QIM (2)).
DTM (2) =
DQIM × JL / (R × (Mgas + Mfuel2)) (7)

Applying this temperature rise amount DTM (2) to the following equation (8), even if there is a temperature rise due to the execution of the second fuel injection, the compression rate at which the combustion temperature TME does not exceed the predetermined temperature TMTGT (hereinafter “ ΕLM (referred to as “limit compression rate”) is calculated, and a crank angle at which the compression rate ε becomes equal to the limit compression rate εLM is defined as a second main injection timing CAIM (2).

  Step S17 may be executed with the division number n increasing (becomes 3 or more) as described below. In this case, the (n-1) th injection is performed by the above-described method. By dividing into two, the fuel injection amount QIM (n−1) in the (n−1) th main injection is reduced, and the fuel injection amount QIM (n) in the nth main injection and the nth main injection are reduced. An injection timing CAIM (n) is calculated.

In step S18, the estimated combustion temperature TME (i) when the divided main injection is executed is calculated. In step S19, the estimated combustion temperature TME (i) is applied to the following equation (9) to calculate the estimated in-cylinder pressure PCE (i) in the compression stroke and the expansion stroke, and the estimated in-cylinder pressure PCE (i) is 10), the estimated torque TRQE is calculated. V (i) in the following formula is the combustion chamber volume. Further, iMAX in Expression (10) is the maximum value of the index parameter i, and is set to “359” when the predetermined crank angle DCA is 1 degree, for example.

  In step S20, it is determined whether or not the estimated torque TRQE is smaller than the required torque TRQD. If the answer is negative (NO), the heat generation gravity center position CAGC is calculated (step S21). Specifically, the estimated heat generation amount JME (i) is calculated using the estimated combustion temperature TME (i), and the estimated heat generation amount JME (i) is further integrated to obtain the total estimated heat generated by one combustion. The generated amount JTOTAL is calculated, and the crank angle position where the integrated value of the estimated heat generated amount JME (i) becomes JTOTAL / 2 is defined as the heat generating center of gravity position CAGC.

  In step S22, it is determined whether or not the heat generation gravity center position CAGC is equal to the predetermined position CAGCX. Specifically, it is determined whether or not the heat generation gravity center position CAGC is within a predetermined angle range centered on the predetermined position CAGCX. If this answer is affirmative (YES), the process is terminated.

  If the answer to step S22 is negative (NO), a total injection advance amount DCAADA is calculated according to the angular difference between the heat generation center of gravity position CAGC and the predetermined position CAGCX (step S23), and the divided main injections The timing CAIM (j) (j = 1 to n) is advanced by the total injection advance amount CAADA (step S24).

In step S25, the estimated combustion temperature TME (i) is calculated again using the advanced main injection timing CAIM (j). In step S26, it is determined whether or not the maximum combustion temperature TMEMAX obtained by the calculation in step S25 is higher than a predetermined temperature TMTGT. If this answer is negative (NO), the process is terminated.
If the answer to step S26 is affirmative (YES), the division number n is increased by “1” (step S27), and the process returns to step S15.

If the answer to step S20 is affirmative (YES), that is, if the estimated torque TRQE is smaller than the required torque TRQD, the process proceeds to step S31 in FIG. 3, and the (n-1) th injection timing CAIM (n-1) and the nth injection timing are reached. The final injection interval DCAIM, which is the difference between CAIM (n), is calculated by the following equation (11), and the torque deviation DTRQ is calculated by the following equation (12).
DCAIM = CAIM (n-1) -CAIM (n) (11)
DTRQ = TRQD-TRQE (12)

  In step S32, the advance amount DCAAD (n) of the nth injection timing CAIM (n-1) is calculated according to the torque deviation DTRQ. The advance amount DCAAD (n) is set so as to increase as the torque deviation DTRQ increases.

In step S33, it is determined whether or not the final injection interval DCAIM is equal to or less than a determination threshold value obtained by adding the advance angle amount DCAAD (n) to the minimum injection interval DCAIMIN. Since If the answer is affirmative (YES), it is impossible to n-th injection timing CAIM (n) is advanced by advancement amount DCAAD (n), (n-1) th injection timing CAIM (n-1 ) Is calculated in accordance with the torque deviation DTRQ (step S34). The advance amount DCAAD (n−1) is set so as to increase as the torque deviation DTRQ increases. In step S35, the (n-1) th injection timing CAIM (n-1) is advanced by the advance amount DCAAD (n-1) by the following equation (13).
CAIM (n-1) = CAIM (n-1) + DCAAD (n-1) (13)

If the answer to step S33 is negative (NO), the n-th injection timing CAIM (n) is advanced by the advance amount DCAAD (n) by the following equation (14) (step S36).
CAIM (n) = CAIM (n) + DCAAD (n) (14)

  In step S37, the estimated combustion temperature TME (i) is calculated again using the advanced injection timing. In step S38, it is determined whether or not the maximum combustion temperature TMEMAX obtained by the calculation in step S37 is higher than a predetermined temperature TMTGT. If this answer is negative (NO), the process returns to step S21 in FIG.

  If the answer to step S38 is affirmative (YES) and the estimated combustion temperature TME (i) exceeds the predetermined temperature TMTGT, the division number n is increased by “1” (step S39), and the process proceeds to step S15 in FIG. Return.

  2 (and FIG. 3), the fuel injection amount QIM (j) and the fuel injection timing CAIM (j) (j = 1 to n) corresponding to the single or plural main injections are calculated and calculated. The main injection is executed according to the fuel injection amount QIM (j) and the fuel injection timing CAIM (j).

  FIG. 4 is a time chart for explaining an example in which the division number n is “2”. The one-dot chain line L1 shown in this figure shows the transition of the estimated combustion temperature TME calculated first, and the solid line L2 shows the transition of the estimated combustion temperature TME after division. By dividing, the combustion temperature can be suppressed below the predetermined temperature TMTGT. In the present embodiment, when the estimated torque TRQE when the divided two main injections are executed is smaller than the required torque TRQD, the main injection timing is corrected to advance, so that the right-down hatching shown in FIG. The area of the region R1 marked with is substantially equal to the area of the region R2 hatched to the right, and the torque generated when the two divided main injections are performed and one main injection are performed. The generated torque can be made substantially equal.

  As described above, in the present embodiment, the estimated combustion temperature TME that is an estimated value of the combustion chamber temperature when the main injection is executed is calculated, and when the estimated combustion temperature TME exceeds the predetermined temperature TMTGT, the main injection is 2 or more. Based on the temperature difference DTME between the maximum combustion temperature TMEMMAX and the predetermined temperature TMTGT, the fuel injection amount QIM (j) in the divided fuel injection is calculated so that the estimated combustion temperature TME does not exceed the predetermined temperature TMTGT. Is done. Therefore, by performing the split fuel injection, the actual combustion temperature can be suppressed to the predetermined temperature TMTGT or less, and deterioration of exhaust characteristics and combustion noise can be prevented.

  Further, based on the temperature difference DTME between the estimated combustion temperature TME and the predetermined temperature TMTGT, the execution timing CAIM (j) (j ≧ 2) of the divided fuel injection is calculated. Since the combustion temperature also depends on the fuel injection timing, the combustion temperature can be reliably suppressed by setting the divided injection execution timing CAIM according to the temperature difference DTME.

  Further, the fuel injection amount QIM (j) (j ≧ 2) in the divided fuel injection is calculated according to the combustion efficiency η (j) (j ≧ 2) at the execution timing of each divided injection. The combustion efficiency η (j) is calculated by searching a η map set according to the estimated combustion temperature TME (j) and the oxygen concentration CONSO2. The oxygen concentration CONSO2 is calculated based on the output of the oxygen concentration sensor 26. As shown in FIG. 5A, the η map is set so that the combustion efficiency η increases as the estimated combustion temperature TME increases. Further, as shown in FIG. 5B, in the range where the oxygen concentration CONSO2 is lower than the predetermined concentration CONSO2X, the combustion efficiency η increases as the oxygen concentration CONSO2 increases, and in the range higher than the predetermined concentration CONSO2X, the oxygen concentration CONSO2 increases. The combustion efficiency η is set to decrease. Since the combustion efficiency η varies depending on the execution time of the divided injection, the combustion efficiency η (j) corresponding to each divided injection execution time calculated by searching a map set as shown in FIG. By using this to calculate the fuel injection amount QIM (j), the combustion temperature can be accurately controlled.

  An estimated torque TRQE, which is an estimated value of the generated torque when the divided main fuel injection is executed, is calculated. When the estimated torque TRQE is smaller than the required torque TRQD, the divided fuel injection execution timing CAIM (j) (j ≧ 2) is advanced. Therefore, it is possible to prevent a decrease in generated torque caused by dividing the main fuel injection.

  Further, when the execution interval between the (n−1) th divided injection and the nth divided injection, that is, the final injection interval DCAIM is smaller than the determination threshold value (DCAIMIN + DCAAD (n)), the (n−1) th injection timing CAIM (n -1) is advanced. When the execution interval between the (n-1) -th divided injection and the n-th divided injection is smaller than the determination threshold, the n-th injection timing CAIM (n) is advanced by the advance amount necessary for securing the torque. Therefore, the generated torque is secured by advancing the execution timing of the (n−1) th divided injection.

  In addition, the estimated heat generation amount JME when the divided injection is executed is calculated, and the heat generation center of gravity position CAGC at which the integrated value of the estimated heat generation amount JME is 50% of the total estimated heat generation amount JTOTAL is calculated. Since the execution timing CAIM (j) of each divided injection is controlled so that the center of gravity position CAGC becomes the predetermined position CAGCX, when the main fuel injection is not divided at the timing (angular position) at which the in-cylinder pressure becomes substantially maximum due to combustion And can be maintained at approximately the same position.

  In this embodiment, the fuel injection valve 9 corresponds to the fuel injection means, and the ECU 20 controls the main fuel injection execution control means, the estimated combustion temperature calculation means, the divided injection control means, the estimated generated torque calculation means, the advance angle correction means, and the estimation. A heat generation amount calculating means and a gravity center angle position calculating means are configured. Specifically, the processing shown in FIGS. 2 and 3 corresponds to main fuel injection execution control means, and steps S13, S18, S25 in FIG. 2 and step S37 in FIG. 3 correspond to estimated combustion temperature calculation means. Steps S14 to S27 and steps S31 to S39 in FIG. 3 correspond to the divided injection control means, and step S19 corresponds to the estimated generated torque calculation means. Further, step S21 in FIG. 2 corresponds to the estimated heat generation amount calculation means and the gravity center angle position calculation means, and steps S31 to S36 in FIG. 3 correspond to the advance angle correction 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, one main injection is first divided into two, and when the estimated torque TRQE is smaller than the required torque TRQD, or when the heat generation gravity center position CAGC does not coincide with the predetermined position CAGCX, the main injection timing is set. When the combustion angle TME is advanced and the estimated combustion temperature TME exceeds the predetermined temperature TMTGT, the division number n is increased. However, the process is terminated at the stage where the division is performed, and the divided main injection is performed. Also good. In that case, it is not necessary to calculate the estimated combustion temperature TME for each predetermined crank angle DCA, and the maximum combustion temperature TMEMAX is estimated according to the fuel injection amount QIM and the fuel injection timing CAIM, and the estimated maximum combustion temperature TMEMAX and the predetermined Based on the temperature difference from the temperature TMTGT, the fuel injection amount and fuel injection timing of the fuel injection divided into two can be calculated.

The present invention can be applied to fuel injection control of a spark ignition direct injection engine capable of multi-stage injection by adding an ignition timing parameter in addition to the injection timing.
The present invention can also be applied to fuel injection control of a marine vessel propulsion engine such as an outboard motor having a vertical crankshaft.

1 Internal combustion engine 9 Fuel injection valve (fuel injection means)
20 Electronic control unit (main fuel injection execution control means, estimated combustion temperature calculation means, split injection control means, estimated generated torque calculation means, advance angle correction means, estimated heat generation amount calculation means, center of gravity angle position calculation means)
21 Intake air flow sensor 23 Intake air temperature sensor 24 Intake air pressure sensor

Claims (6)

In a fuel injection control device for an internal combustion engine comprising fuel injection means for injecting fuel into a combustion chamber of the internal combustion engine,
Main fuel injection execution control means for executing main fuel injection for generating torque of the engine by the fuel injection means;
An estimated combustion temperature calculating means for calculating an estimated combustion temperature that is an estimated value of the temperature in the combustion chamber when the main fuel injection is performed,
The main fuel injection execution control means divides the main fuel injection into n when the estimated combustion temperature exceeds a predetermined temperature (n is an integer of 2 or more), and the maximum value of the estimated combustion temperature and the predetermined temperature temperature difference and have use of combustion temperature rise suppressing fuel quantity rather based on the mass of the combustion chamber to the intake gas, as the estimated combustion temperature does not exceed the predetermined temperature, in the divided fuel injection (n-1 ) th fuel injection quantity split injection and n-th divided calculate a fuel injection amount of the injection split injection control means fuel injection control device for an internal combustion engine and having a.   The fuel injection control device for an internal combustion engine according to claim 1, wherein the split injection control means calculates an execution timing of the split fuel injection based on the temperature difference. The split injection control means calculates the fuel injection amount of the nth split injection in the split fuel injection according to the combustion temperature rise suppression fuel amount and the combustion efficiency at the execution timing of the nth split injection. The fuel injection control device for an internal combustion engine according to claim 1 or 2. The divided injection control means includes
Estimated generated torque calculating means for calculating an estimated generated torque that is an estimated value of the generated torque when the n-divided main fuel injection is executed;
When the estimated generated torque is smaller than the target torque, the vehicle has an advance correction means for correcting the advance of the execution timing of the nth split fuel injection based on the difference between the target torque and the estimated generated torque .
The advance angle correction means is configured such that the execution interval between the (n-1) th divided injection and the nth divided injection is obtained by adding the advance angle correction amount of the nth divided fuel injection to a predetermined minimum injection interval. 2. If smaller, the execution timing of the (n-1) th divided injection is corrected to advance without correcting the execution timing of the nth divided fuel injection. 4. The fuel injection control device for an internal combustion engine according to any one of 3 above. The divided injection control means increases the division number n of the main fuel injection when the estimated combustion temperature calculated again after execution of the advance angle correction by the advance angle correction means exceeds the predetermined temperature. The fuel injection control device for an internal combustion engine according to claim 4. The divided injection control means includes an estimated heat generation amount calculating means for calculating an estimated heat generation amount that is an estimated value of the heat generation amount when the divided injection is executed,
Centroid angle position calculating means for calculating a centroid angle position at which the integrated value of the estimated heat generation amount is 50% of the total estimated heat generation amount;
The execution timing of each divided injection is controlled so that the center-of-gravity angle position becomes a predetermined angular position, and when the estimated combustion temperature calculated again exceeds the predetermined temperature, the division number n of the main fuel injection is increased. the fuel injection control apparatus for an internal combustion engine according to claim 1, any one of 5, characterized in that cause.

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