JP6477619B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device applied to a compression ignition type internal combustion engine.

  As an internal combustion engine mounted on a vehicle or the like, a compression ignition type internal combustion engine having a fuel injection valve for injecting fuel into a cylinder is known. In a compression ignition type internal combustion engine, an amount of fuel smaller than that of main injection is injected from the fuel injection valve immediately before fuel is injected from the fuel injection valve (hereinafter referred to as “main injection”) at a timing that contributes to engine output. (Hereinafter referred to as “pre-injection”) to shorten the ignition delay period of the main injected fuel is known.

  As described above, in an internal combustion engine in which pre-injection is performed immediately before main injection, the second-order differential value (hereinafter referred to as “secondary change rate”) with respect to the crank angle of the pressure in the cylinder (hereinafter referred to as “in-cylinder pressure”). A technique for feedback-controlling the fuel injection amount and the injection timing of the pre-injection based on the peak value and the timing at which the peak value occurs has also been proposed (see, for example, Patent Document 1).

JP 2004-1000055 A JP-A-11-247703

  By the way, in the conventional technique described above, the secondary change rate of the in-cylinder pressure due to the combustion of the pre-injected fuel is a predetermined reference value (when the fuel is not injected from the fuel injection valve into the cylinder (the fuel in the cylinder (Secondary change rate of in-cylinder pressure) when the operating state is the same except that fuel is not injected from the fuel injection valve into the cylinder) (hereinafter referred to as “pre-combustion”). And the period during which the secondary change rate of the in-cylinder pressure is greater than the predetermined reference value due to the combustion of the fuel injected by the main injection (hereinafter referred to as “main fluctuation period”). (Hereinafter, referred to as “variation interval”) is not taken into consideration, and thus the variation interval may be increased. Here, as a result of intensive experiments and verifications by the inventor of the present application, it was found that the noise level of the combustion noise increases as the fluctuation interval increases. Therefore, if the fluctuation interval increases, the noise level of the combustion noise may increase.

  The present invention has been made in view of the above circumstances, and an object thereof is to reduce the noise level of combustion noise in an internal combustion engine in which pre-injection is performed immediately before main injection.

  The present invention employs the following means in order to solve the above-described problems. That is, the present invention is a control device applied to a compression ignition type internal combustion engine having a fuel injection valve for injecting fuel into a cylinder, and performs pre-injection from the fuel injection valve immediately before main injection. It is a control device. And the said control apparatus performed pre-injection so that the above-mentioned fluctuation | variation space | interval might become below a predetermined value.

Specifically, the present invention is a control device applied to a compression ignition type internal combustion engine having a fuel injection valve for injecting fuel into a cylinder. The control device is configured to inject fuel from the fuel injection valve at a timing that contributes to the output of the internal combustion engine, and to inject a smaller amount of fuel from the fuel injection valve at a time earlier than the main injection. Perform pre-injection. At that time, the control device is a pre-prevention period in which the secondary change rate, which is a value obtained by second-order differentiation of the in-cylinder pressure of the internal combustion engine with respect to the crank angle, is larger than a predetermined reference value due to combustion of the pre-injected fuel. In each operating state of the internal combustion engine, there is a fluctuation interval that is an interval between the fluctuation period and the main fluctuation period in which the secondary change rate is larger than a predetermined reference value due to combustion of the fuel injected by the main injection. Pre-injection is executed in accordance with the pre-injection execution time (hereinafter referred to as “pre-injection time”) determined to be equal to or less than a predetermined value.

  The “predetermined reference value” here is the case where fuel is not injected into the cylinder from the fuel injection valve as described above (when no fuel combustion occurs in the cylinder), and from the fuel injection valve to the cylinder. This is the secondary change rate when the operating state (for example, intake air amount, engine rotational speed, coolant temperature, crank angle, etc.) other than that the fuel is not injected into the engine is the same. Such a predetermined reference value is obtained in advance for each operating state of the internal combustion engine.

  As described above, the inventor of the present application has found that the noise level of the combustion noise increases as the fluctuation interval, which is the interval between the pre-variation period and the main fluctuation period, increases as a result of intensive experiments and verifications. Got. This is because the secondary change rate of the in-cylinder pressure has a high correlation with the high-frequency component of the combustion noise, so when the fluctuation interval increases, the high-frequency combustion noise is generated in two parts, thereby causing the noise of the combustion noise. The level is estimated to increase.

  According to the above knowledge, the noise level of the combustion noise can be reduced by reducing the fluctuation interval. Therefore, in the present invention, the pre-injection timing at which the fluctuation interval is equal to or less than the predetermined value is determined for each operation state of the internal combustion engine, and the relationship between the pre-injection timing and the operation state of the internal combustion engine is determined by a map, a calculation model, or the like. It shall be memorize | stored in a control apparatus with the form. The pre-injection timing at that time is determined based on the execution time of the main injection (hereinafter referred to as “main injection time”). That is, the time interval between the end timing of the pre-injection and the start timing of the main injection is determined to be constant. And a control apparatus performs the pre-injection from a fuel injection valve according to the pre-injection time defined as mentioned above. The “predetermined value” here is a value that is considered that the noise level of the combustion noise exceeds a presumed allowable range when the fluctuation interval becomes larger than the predetermined value. Based on the results of experiments, simulations, and the like in advance. It is a defined value.

  As described above, when the pre-injection is executed according to the pre-injection timing determined so that the fluctuation interval is equal to or less than the predetermined value, the noise level of the combustion noise can be suppressed to an allowable range.

  Note that the intake air caused by the temperature in the cylinder (in-cylinder temperature) at the time of execution of pre-injection deviating from the temperature assumed when the pre-injection time is determined, or deposits are accumulated in the intake ports of the internal combustion engine. If a change in characteristics occurs, or a change in fuel injection characteristics due to changes in the fuel injection valve over time occurs, even if pre-injection is executed according to the pre-injection timing determined as described above, the actual fluctuation interval will be There is a possibility of becoming larger than a predetermined value.

  Therefore, the internal combustion engine to which the control device of the present invention is applied may be provided with an in-cylinder pressure sensor for detecting the in-cylinder pressure of the internal combustion engine. Then, the control device calculates an actual secondary change rate, which is an actual secondary change rate of the in-cylinder pressure, based on a detection value of the in-cylinder pressure sensor, and an actual secondary change rate calculated by the calculation unit. And determining means for determining whether or not the actual fluctuation interval is less than or equal to a predetermined value, and when the determination means determines that the actual fluctuation interval is greater than the predetermined value, Feedback means for executing injection timing feedback control for correcting the execution timing (pre-injection timing) in the retard direction may be provided.

  When the injection timing feedback control as described above is executed, the in-cylinder temperature or the like deviates from the assumed temperature, or changes over time such as changes in intake characteristics or fuel injection characteristics occur. When a situation occurs in which the fluctuation interval becomes larger than a predetermined value, the pre-injection timing after the next cycle is corrected in the retarding direction. In that case, since the time when the pre-injected fuel is ignited and burned approaches the time when the main injected fuel is ignited and combusted, the pre-variation period and the main fluctuation period become closer accordingly. As a result, the actual fluctuation interval can be set to a predetermined value or less, or can be close to a predetermined value.

  Note that the feedback means is operated when the determination means determines that the actual fluctuation interval is larger than the predetermined value, among the pre-injection timings stored in the control device in the form of a map or a calculation model as described above. Only the pre-injection timing corresponding to the state may be corrected. Further, the feedback means may uniformly correct the pre-injection timing derived from the above-described map or calculation model regardless of the operating state of the internal combustion engine.

  By the way, when the fuel injection characteristic changes with time as described above, the amount of fuel actually pre-injected from the fuel injection valve (hereinafter referred to as “pre-injection amount”) may deviate from the target pre-injection amount. There is sex. Further, when the internal combustion engine has a plurality of cylinders, a pressure fluctuation occurs in a delivery pipe such as a common rail every time fuel injection is performed from the fuel injection valve of each cylinder. Thus, when the pressure fluctuation in the delivery pipe occurs, the fuel pressure acting on the fuel injection valve varies from time to time. Therefore, when the pre-injection timing is corrected by executing the injection timing feedback control described above, the fuel pressure acting on the fuel injection valve at the pre-injection pre-injection timing and the fuel injection valve at the corrected pre-injection timing There is a possibility that the fuel pressure acting on In such a case, the fuel amount actually injected from the fuel injection valve at the corrected pre-injection timing may deviate from the target pre-injection amount.

  For various reasons as described above, if the actual pre-injection amount deviates from the target pre-injection amount, the noise level of the combustion noise may increase even if the actual fluctuation interval is less than or equal to the predetermined value. . For example, if the actual pre-injection amount becomes larger than the target pre-injection amount, the maximum value of the actual secondary change rate during the pre-variation period increases, so that the noise of combustion noise generated when the pre-injected fuel burns The level increases. On the other hand, when the actual pre-injection amount becomes smaller than the target pre-injection amount, the heat field formed when the pre-injected fuel burns becomes small. Therefore, although a part of the fuel injected from the fuel injection valve at the beginning of the main injection period ignites and burns quickly using the heat field, the ignition delay period of the remaining fuel becomes longer, and the fuel is There is a possibility of burning all together with the fuel injected from the injection valve. In this case, since the maximum value of the actual secondary change rate during the main fluctuation period is increased, the noise level of the combustion noise generated when the main injected fuel is burned is increased.

  Here, the actual pre-injection amount correlates with the difference between the maximum value (peak value) of the actual secondary change rate during the pre-variation period and a predetermined reference value (hereinafter referred to as “maximum variation amount”). In other words, the maximum fluctuation amount increases as the actual pre-injection amount increases.

  Therefore, in addition to the injection timing feedback control, the feedback means performs fuel injection so that the maximum fluctuation amount, which is the difference between the maximum value of the actual secondary change rate during the pre-variation period and the predetermined reference value, matches the target fluctuation amount. Injection amount feedback control for feedback control of the fuel amount pre-injected from the valve (pre-injection amount) may be executed. The “target fluctuation amount” here corresponds to the maximum fluctuation amount corresponding to the target value of the pre-injection amount.

When the injection amount feedback control as described above is executed, even if a situation occurs in which the actual pre-injection amount deviates from the target value, the actual pre-injection amount after the next cycle is made equal to the target value, or the next cycle The actual pre-injection amount thereafter can be brought close to the target value. As a result, the noise level of the combustion noise can be suppressed more reliably.

  According to the present invention, in an internal combustion engine in which pre-injection is performed immediately before main injection, the noise level of combustion noise can be reduced.

1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. It is a figure which shows transition of the fuel-injection timing and secondary change rate in case a fluctuation interval is larger than predetermined value (= 0). It is a figure which shows transition of the injection timing and secondary change rate in case a fluctuation interval is a predetermined value (= 0). It is a figure which shows the relationship with the maximum value (dB) of the noise level in each frequency (Hz) of the combustion noise which generate | occur | produced in the period from the start of the pre-injected fuel to the end of the main injected fuel. . 4 is a flowchart illustrating a processing routine executed by an ECU when determining a fuel injection amount and a fuel injection timing in the first embodiment. In 2nd Embodiment, it is a flowchart which shows the process routine which ECU performs when determining a fuel injection quantity and fuel injection timing. It is a flowchart which shows the processing routine which ECU performs when determining the correction coefficient k. It is a figure which shows transition of the injection timing and secondary change rate in case a fluctuation interval is smaller than predetermined value (= 0). It is a figure which shows the relationship between difference (DELTA) di (difference between the actual fluctuation interval di and predetermined value (= 0)), and update amount (DELTA) k. In a 3rd Example, it is a flowchart which shows the process routine which ECU performs when determining fuel injection quantity and fuel injection timing. It is a flowchart which shows the process routine which ECU performs when determining the correction | amendment term C. FIG. It is a figure which shows the relationship between difference (DELTA) V (difference of the largest fluctuation amount Vmax and the target fluctuation amount Vtrg), and the update amount (DELTA) C.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

<Embodiment 1>
First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. An internal combustion engine 1 shown in FIG. 1 is a four-stroke cycle compression ignition type internal combustion engine (diesel engine) having a plurality of cylinders 2. In FIG. 1, only one cylinder 2 among the plurality of cylinders 2 is shown.

The internal combustion engine 1 includes a piston 3 that is slidably inserted into each cylinder 2. The internal combustion engine 1 has an intake port 5 for guiding intake air to a combustion chamber 4 formed above the piston 3 in each cylinder 2 and an exhaust port 6 for discharging burned gas in the combustion chamber 4. I have. The intake port 5 is connected to the intake passage 50. The exhaust port 6 is connected to the exhaust passage 60. The opening end of the intake port 5 and the opening end of the exhaust port 6 in the combustion chamber 4 are opened and closed by an intake valve 7 and an exhaust valve 8, respectively.

  The internal combustion engine 1 includes a fuel injection valve 9 that injects fuel into the combustion chamber 4 of each cylinder 2 and an in-cylinder pressure sensor 10 that measures the pressure (in-cylinder pressure) in each cylinder 2. The in-cylinder pressure sensor 10 does not need to be provided in all the cylinders 2 and may be provided in at least one cylinder 2.

  The internal combustion engine 1 includes a water temperature sensor 11 that measures the temperature of cooling water circulating through the internal combustion engine 1, a crank position sensor 12 that measures the rotational position of a crankshaft (not shown), and an operation amount (accelerator opening) of an accelerator pedal (not shown). Various sensors such as an accelerator position sensor 13 for measuring the air flow and an air flow meter 14 for measuring the intake air amount of the internal combustion engine 1 are mounted.

  The internal combustion engine 1 configured as described above is provided with an ECU 15 as a “control device” according to the present invention. The ECU 15 is an electronic control unit that includes a CPU, ROM, RAM, backup RAM, and the like. The ECU 15 is input with the measurement values of the various sensors described above. Moreover, ECU15 is electrically connected with various apparatuses, such as the fuel injection valve 9, and can control those various apparatuses electrically.

  In the present embodiment, the ECU 15 is configured such that the engine rotational speed calculated from the measured value of the crank position sensor 12, the engine load calculated from the measured value of the accelerator position sensor 13, the measured value (intake air amount) of the air flow meter 14, and the water temperature. Using a measured value (cooling water temperature) of the sensor 11 as a parameter, a fuel amount (target fuel injection amount) injected from the fuel injection valve 9 per cycle and a target fuel injection timing are calculated, and these target fuel injection amount and The fuel injection valve 9 is controlled according to the target fuel injection timing.

Here, in the combustion of fuel injected from the fuel injection valve 9 (main injection) at a timing that contributes to the output of the internal combustion engine 1 (for example, near the top dead center of the compression stroke), the fuel is first mixed with air and combustible. The period during which the mixture is formed (ignition delay period), the period during which the combustible mixture formed during the ignition delay period ignites and burns (premix combustion period or explosive combustion period), and fuel injection after the explosive combustion period This is realized sequentially through a period (diffusion combustion period) in which fuel continuously injected from the valve 9 burns while being mixed with air. In an operation region where the amount of main injected fuel is relatively large and the oxygen concentration in the combustion chamber 4 is relatively large, the amount of combustible air-fuel mixture that is formed during the ignition delay period increases, which is explosive. The amount of fuel combusted all at once during the combustion period increases. As a result, there is a problem that may become a number generation amount of NO _X, or combustion noise may become large.

To problems described above, an increasing number of the amount of fuel burned simultaneously in explosive combustion period, or greater than the upper limit amount generation amount of NO _X, and or noise level of combustion noise in the explosive combustion period is the upper limit value In an operation region estimated to exceed (hereinafter referred to as “pre-injection execution region”), pre-injection that causes fuel to be injected from the fuel injection valve 9 at a time earlier than the main injection is performed at an earlier time than the main injection. A method is conceivable. According to such a method, the pre-injected fuel is ignited and burned before the start of the main injection to form a heat field, so that the ignition delay period of the main injected fuel is shortened. As a result, since the amount of fuel to be combusted simultaneously in explosive combustion period as described above is reduced, the NO _X generation amount exceeds the upper limit amount, and the noise level of combustion noise can be prevented from exceeding the upper limit value .

Here, when the pre-injection is executed immediately before the main injection, first, the total fuel injection amount is calculated using the engine speed, the engine load, the intake air amount, the cooling water temperature, and the like as parameters. The relationship between the operating state specified by the parameters described above and the total fuel injection amount suitable for the operating state is determined in advance based on the results of experiments and simulations. Next, the amount of fuel injected from the fuel injection valve 9 (hereinafter referred to as “main injection amount”) is calculated using the engine speed, the total fuel injection amount, and the like as parameters. The relationship between the operating state specified by the parameters described above and the main injection amount suitable for the operating state is determined in advance based on the results of experiments and simulations. Then, the main injection execution timing (main injection timing) is calculated using the engine speed, the main injection amount, and the like as parameters. The relationship between the operating state specified by the above parameters and the main injection timing suitable for the operating state is determined in advance based on the results of experiments and simulations. The main injection amount is calculated using the engine speed and the total fuel injection amount as parameters as described above. Therefore, the total fuel injection amount may be used instead of the main injection amount as one of the parameters when calculating the main injection timing. Further, the amount of fuel pre-injected from the fuel injection valve 9 (pre-injection amount) is calculated using the engine speed, the total fuel injection amount, and the like as parameters. The relationship between the operating state specified by the above parameters and the pre-injection amount suitable for the operating state is determined in advance based on the results of experiments and simulations. Further, an interval between the pre-injection start timing and the main injection start timing (hereinafter referred to as “injection interval”) is calculated using the engine speed, the pre-injection amount, and the like as parameters. The relationship between the operating state specified by the above parameters and the injection interval suitable for the operating state is determined in advance based on the results of experiments and simulations. The pre-injection amount is calculated using the engine speed and the total fuel injection amount as parameters as described above. Therefore, the total fuel injection amount may be used instead of the pre-injection amount as one of the parameters when calculating the injection interval. Next, the pre-injection time is set based on the injection interval and the main injection time. Specifically, a time that is earlier than the main injection time by the injection interval is set as the pre-injection time.

  By the way, when the pre-injection time set by the above procedure is too early with respect to the main injection time (that is, when the injection interval is too large), the second-order differential value with respect to the crank angle of the pressure in the cylinder 2 (in-cylinder pressure). (Secondary change rate) due to the combustion of pre-injected fuel (pre-fluctuation period) and secondary change rate of in-cylinder pressure due to combustion of the main-burned fuel As a result, the interval (variation interval) with the period (main variation period) larger than the predetermined reference value increases. The “predetermined reference value” here is a case where fuel is not injected into the cylinder 2 from the fuel injection valve 9 (when no fuel combustion occurs in the cylinder 2), and from the fuel injection valve 9 to the cylinder 2 This is the secondary change rate when the operating state (for example, intake air amount, engine rotational speed, coolant temperature, crank angle, etc.) other than that the fuel is not injected into the engine is the same.

  As a result of the inventor's earnest experiment and verification, as described above, the knowledge that the noise level of combustion noise increases when the fluctuation interval, which is the interval between the pre-variation period and the main fluctuation period, increases. Obtained. According to this knowledge, if the pre-injection time is too early with respect to the main injection time, the fluctuation interval increases, and the noise level of the combustion noise may increase accordingly.

  Here, FIG. 2 shows the transition of the fuel injection timing and the secondary change rate with respect to the crank angle of the in-cylinder pressure when the pre-injection timing is too early with respect to the main injection timing (when the fluctuation interval is large). A one-dot chain line in the lower diagram in FIG. 2 indicates the predetermined reference value described above. A period dp between t1 and t2 in FIG. 2 indicates a pre-variation period. A period di from t2 to t3 in FIG. 2 indicates a fluctuation interval. A period dm between t3 and t4 in FIG. 2 indicates a main fluctuation period. Iint in FIG. 2 indicates an injection interval.

Since the secondary change rate of the in-cylinder pressure indicates the change rate (acceleration) of the change rate of the in-cylinder pressure, it rapidly rises at the early stage of combustion immediately after the pre-injected fuel is ignited and becomes larger than a predetermined reference value. (Immediately after t1 in FIG. 2). Then, when the rate of change of the in-cylinder pressure decreases from the middle combustion stage to the end of fuel of the pre-injected fuel, the secondary change rate of the in-cylinder pressure changes from an increasing tendency to a decreasing tendency. Thereafter, when the pre-injected fuel finishes burning and the in-cylinder pressure changes from an increasing tendency to a decreasing tendency, the secondary change rate of the in-cylinder pressure rapidly decreases. As described above, when the secondary change rate of the in-cylinder pressure shows a decreasing tendency, when the main injected fuel is ignited, the secondary change rate of the in-cylinder pressure starts to increase again from the decreasing tendency. At this time, if the pre-injection timing is too early with respect to the main injection timing, the ignition delay period of the main injected fuel becomes longer, so that the secondary change rate of the in-cylinder pressure decreases to a value smaller than a predetermined reference value. Then, the main injected fuel is ignited and burned, and the secondary change rate of the in-cylinder pressure changes from a decreasing tendency to an increasing tendency. As a result, a period (a period from t2 to t3 in FIG. 2) in which the secondary change rate is equal to or less than a predetermined reference value occurs between the pre-variation period dp and the main fluctuation period dm. That is, a variation interval di larger than “0” is formed between the end timing t2 of the pre-variation period dp and the start timing t3 of the main variation period dm. Here, the secondary change rate of the in-cylinder pressure is highly correlated with the high-frequency component of the combustion noise. Therefore, as shown in FIG. 2, if a variation interval di larger than “0” is formed between the pre-variation period dp and the main variation period dm, high-frequency combustion noise is generated twice. Therefore, it is estimated that the noise level of the combustion noise increases.

  Therefore, in the present embodiment, the pre-injection timing is controlled by paying attention to the above-described fluctuation interval di. That is, the pre-injection timing is controlled so that the fluctuation interval di is not more than a predetermined value. Specifically, an injection interval at which the fluctuation interval di is equal to or less than a predetermined value is determined in advance for each operating state of the internal combustion engine 1. In other words, an operating state determined from the engine speed and the pre-injection amount, and an injection interval (for example, a time interval between the pre-injection end timing and the main injection start timing) in which the fluctuation interval di is equal to or smaller than a predetermined value. The relationship with a constant (for example, 200 μs or less) is obtained in advance based on the results of experiments and simulations, and the relationship is stored in the ROM or backup RAM of the ECU 15 in the form of a map or calculation model. Shall be kept. Note that the “predetermined value” here is preliminarily assumed to be a noise level of combustion noise generated when the pre-injected fuel and the main-injected fuel are combusted when the fluctuation interval di becomes larger than the predetermined value. The value is considered to exceed the allowable range, and is, for example, “0” or a value approximated to “0”. Hereinafter, a case where the predetermined value is “0” will be described.

  Here, FIG. 3 shows the transition of the fuel injection timing and the secondary change rate when the pre-injection is executed according to the injection interval determined so that the fluctuation interval di becomes “0”. When the pre-injection is executed in accordance with the injection interval determined so that the injection interval becomes “0”, the fluctuation interval di becomes “0”, so the end timing of the pre-variation period dp (t2 ′ in FIG. 3) ) And the start time of the main fluctuation period dm (t3 ′ in FIG. 3) are the same period. As a result, the noise level of the combustion noise generated when the pre-injected fuel and the main-injected fuel are combusted can be suppressed within the allowable range.

  FIG. 4 is a diagram showing the maximum value (dB) of the noise level at each frequency (Hz) of the combustion noise generated during the period from when the pre-injected fuel starts to burn until the main injected fuel finishes burning. is there. 4 indicates a case where the fluctuation interval di is larger than “0” as shown in FIG. 2, and the solid line in FIG. 4 indicates that the fluctuation interval di is as shown in FIG. The case of “0” is shown.

  In the high frequency band of about 1000 Hz or more in FIG. 4, when the fluctuation interval di is larger than “0” (one-dot chain line in FIG. 4), the maximum noise level between about 1000 Hz to 2000 Hz and about 6000 Hz is other than that. It is larger than the frequency band. On the other hand, when the fluctuation interval di is “0” (solid line in FIG. 4), it is about 1000 Hz to about 2000 Hz, compared to when the fluctuation interval di is larger than “0” (one-dot chain line in FIG. 4). The maximum noise level around 6000 Hz is small.

  Therefore, as described above, by performing the pre-injection according to the pre-injection timing determined so that the fluctuation interval di becomes “0”, the noise level of the combustion noise in the high frequency band can be reduced.

  Hereinafter, a procedure for determining the fuel injection amount and the fuel injection timing in the present embodiment will be described with reference to FIG. FIG. 5 is a processing routine executed by the ECU 15 when determining the fuel injection amount and the fuel injection timing. This processing routine is stored in advance in the ROM of the ECU 15, and is executed every cycle.

  In the processing routine of FIG. 5, the ECU 15 first calculates the total fuel injection amount Qt in the processing of S101. As described above, the total fuel injection amount Qt includes the engine speed calculated from the measured value of the crank position sensor 12, the engine load calculated from the measured value of the accelerator position sensor 13, and the measured value of the air flow meter 14 (intake air). Amount), a measured value of the water temperature sensor 11 (cooling water temperature), and the like are calculated as parameters.

In the process of S102, the ECU 15 determines whether or not the operating state of the internal combustion engine 1 belongs to the pre-injection execution region. Here, the "pre-injection execution region", as described above, increasingly fuel burning simultaneously the explosive combustion period, or greater than the upper limit amount generation amount of NO _X, and or in explosive combustion period This is the operating region where the noise level of combustion noise is estimated to exceed the upper limit. At this time, whether the operation state of the internal combustion engine 1 belongs to the pre-injection execution region by predetermining the relationship between the operation state of the internal combustion engine 1 and the pre-injection execution region based on the results of experiments and simulations. What is necessary is just to discriminate | determine. The operating state of the internal combustion engine 1 here is an operating state determined from the engine speed, the oxygen concentration of the intake air, and the total fuel injection amount Qt calculated in the processing of S101. The oxygen concentration of the intake air may be measured by attaching an oxygen concentration sensor to the intake passage 50, or may be estimated from the operating state of the internal combustion engine 1 (for example, the engine rotational speed or the total fuel injection amount Qt). .

As another method for determining whether or not the operating state of the internal combustion engine 1 belongs to the pre-injection execution region, the secondary change rate in the main fluctuation period dm is based on the measured value of the in-cylinder pressure sensor 10 in the previous cycle. A method of calculating the maximum value and determining that the operating state of the internal combustion engine 1 belongs to the pre-injection execution region may be used if the difference between the maximum value and the predetermined reference value is larger than a predetermined threshold. . As described above, the predetermined reference value here is an operating state (intake air amount, engine rotational speed, coolant temperature, crank angle, etc.) other than that fuel is not injected into the cylinder 2 from the fuel injection valve 9. ) Is the same as the secondary change rate of the in-cylinder pressure. The relationship between the secondary change rate of the in-cylinder pressure and the operating state of the internal combustion engine 1 when fuel is not injected into the cylinder 2 from the fuel injection valve 9 is obtained in advance based on the results of experiments or simulations. The relationship is stored in the ROM or backup RAM of the ECU 15 in the form of a map or a calculation model. The predetermined threshold value here is exceeded or when the difference between the maximum value of the secondary rate of change in the main variation period dm and said predetermined threshold is greater than the predetermined threshold value, the amount of the NO _X is the upper limit amount , And / or the noise level of the combustion noise during the explosive combustion period is assumed to exceed the upper limit value, and is determined in advance based on the results of experiments and simulations.

If an affirmative determination is made in the process of S102, it is necessary to execute the pre-injection immediately before the main injection. Therefore, in the processes of S103 to S106, the ECU 15 performs the main injection amount Qm, the main injection timing Tm, and the pre-injection amount Qp. , And the pre-injection time Tp are determined. First, in the process of S103, the ECU 15 calculates the main injection amount Qm and the main injection timing Tm. Specifically, as described above, the ECU 15 calculates the main injection amount Qm and the main injection timing Tm by using the engine speed and the total fuel injection amount Qt calculated in the process of S101 as parameters.

  In the process of S104, the ECU 15 calculates the pre-injection amount Qp. Specifically, as described above, the ECU 15 calculates the pre-injection amount Qp using the engine speed and the total fuel injection amount Qt calculated in the processing of S101 as parameters.

  In the process of S105, the ECU 15 calculates the injection interval Iint. Specifically, as described above, the ECU 15 calculates the injection interval Iint based on a map or calculation model using the engine speed and the total fuel injection amount Qt as arguments. The map or calculation model at that time is configured such that the injection interval Iint determined so that the fluctuation interval di is “0” as described above.

  In the process of S106, the ECU 15 calculates the pre-injection time Tp based on the main injection time Tm calculated in the process of S103 and the injection interval Iint calculated in the process of S105. Specifically, the ECU 15 calculates a time earlier than the main injection time Tm calculated in the process of S103 by the injection interval Iint calculated in the process of S105, and uses that time as the pre-injection time. Set to Tp.

  If a negative determination is made in the process of S102, it is not necessary to execute pre-injection immediately before the main injection, so the ECU 15 determines the main injection amount Qm and the main injection timing Tm in the processes of S107 and S108. decide. First, in the process of S107, the ECU 15 sets the total fuel injection amount Qt calculated in the process of S101 to the main injection amount Qm. Subsequently, the ECU 15 calculates the main injection timing Tm using the main injection amount Qm set in the processing of S108 and the engine speed as parameters.

  As described above, when the fuel injection from the fuel injection valve 9 is performed according to the fuel injection amount and the fuel injection timing determined based on the processing routine of FIG. 2, the operating state of the internal combustion engine 1 is changed to the pre-injection execution. When belonging to a region, the above-described variation interval di can be set to “0”. As a result, the noise level of the combustion noise can be reduced as described above with reference to FIG.

<Embodiment 2>
Next, a second embodiment of the present invention will be described with reference to FIGS. Here, a configuration different from the above-described first embodiment will be described, and description of the same configuration will be omitted.

  The difference between the first embodiment described above and the present embodiment is that the pre-injection is executed according to the injection interval determined so that the fluctuation interval becomes a predetermined value (= 0) in each operation state of the internal combustion engine 1. In this case, if the actual fluctuation interval is larger than the predetermined value (= 0), the pre-injection timing is corrected in the retarding direction so that the actual fluctuation interval in the next cycle or less is equal to or less than the predetermined value (= 0). The feedback control is executed.

  Here, as described in the first embodiment, the pre-injection is executed in accordance with the injection interval (hereinafter, referred to as “basic injection interval”) determined so that the fluctuation interval becomes a predetermined value (= 0). Even when the pre-injection is performed, the in-cylinder temperature is deviated from the temperature assumed when the basic injection interval is determined, or deposits are accumulated on the intake port or the like of the internal combustion engine 1. If there is a change in the intake characteristic that occurs, or a change in the fuel injection characteristic due to a change in the fuel injection valve 9 over time, the actual fluctuation interval may become larger than the predetermined value (= 0).

  Therefore, in the present embodiment, an actual secondary change rate that is the actual secondary change rate of the in-cylinder pressure is calculated based on the measured value of the in-cylinder pressure sensor 10, and the actual fluctuation is calculated based on the actual secondary change rate. It is determined whether or not the interval is equal to or less than a predetermined value (= 0). If it is determined that the actual fluctuation interval is greater than the predetermined value (= 0), the pre-injection timing is retarded so that the actual fluctuation interval in the next cycle and after is less than the predetermined value (= 0). The injection timing feedback control for correcting to is performed. Note that the injection timing feedback control of the present embodiment performs pre-injection timing by correcting the injection interval in the subsequent cycle in the shortening direction when it is determined that the actual fluctuation interval is greater than a predetermined value (= 0). Is a process of correcting in the retard direction.

  Hereinafter, the procedure for determining the fuel injection amount and the fuel injection timing in the present embodiment will be described with reference to FIG. In the processing routine of FIG. 6, the same reference numerals are given to the same processing as the processing routine of FIG. The difference between the processing routine of FIG. 6 and the processing routine of FIG. 5 described above is that the processing of S201 to S202 is executed instead of the processing of S105.

  In the process of S201 of the process routine of FIG. 6, the ECU 15 calculates a basic injection interval Iintbase. The basic injection interval Iintbase here is an injection interval determined so that the fluctuation interval di becomes a predetermined value (= 0) as described above. Therefore, ECU15 should just set the injection interval calculated in the procedure similar to the process of S105 of the processing routine of FIG. 5 mentioned above to the basic injection interval Iintbase.

In the process of S202, the ECU 15 calculates the injection interval Iint by substituting the basic injection interval Iintbase calculated in the process of S201 into the following equation (1).
Iint = Iintbase * k (1)
K in the above equation (1) is a correction coefficient determined based on the difference between the actual fluctuation interval and the predetermined value (= 0) when the actual fluctuation interval is larger than the predetermined value (= 0). is there. The correction coefficient k is a positive number larger than “0” and equal to or smaller than “1”, and “1” is set as an initial value thereof. A method for determining the correction coefficient k will be described later.

  When the ECU 15 finishes executing the process of S202, the ECU 15 proceeds to the process of S106, and calculates the pre-injection timing Tp based on the injection interval Iint calculated in the process of S202.

  Next, the procedure for determining the correction coefficient k will be described with reference to FIG. FIG. 7 is a processing routine executed by the ECU 15 when determining the correction coefficient k. This processing routine is stored in advance in the ROM of the ECU 15, and is executed with the start of pre-injection in the cylinder 2 to which the in-cylinder pressure sensor 10 is attached as a trigger.

In the processing routine of FIG. 7, the ECU 15 first calculates the actual secondary change rate by differentiating the measured value of the in-cylinder pressure sensor 10 in the processing of S301. The calculation of the actual secondary change rate is repeatedly executed for each unit crank angle in a period from the start of pre-injection to a predetermined time tn after the start of main injection. The predetermined time tn here is a time when it is estimated that the secondary change rate is larger than a predetermined reference value due to combustion of the main injected fuel, and t3 and t4 in FIG. 2 described above. (Or any time between t3 ′ and t4 in FIG. 3). Such a predetermined time tn is determined in advance based on the results of experiments or simulations. At this time, the predetermined time tn is determined on the assumption that the ignition delay period of the main injected fuel is the longest. Note that the “calculation means” according to the present invention is realized by the ECU 15 executing the processing of S301.

  In the process of S302, the ECU 15 is based on the actual secondary change rate calculated in the process of S301 in a period from the start of the pre-variation period dp to the predetermined time tn (hereinafter referred to as “determination period”). It is determined whether or not the actual secondary change rate has decreased to a predetermined reference value or less. Here, as shown in FIG. 2 or FIG. 3 described above, when the actual fluctuation interval is “0”, or when the actual fluctuation interval is larger than “0”, an affirmative determination is made in the processing of S302. . On the other hand, as shown in FIG. 8, when the actual fluctuation interval is smaller than “0”, the actual secondary change rate does not decrease to a predetermined reference value or less during the determination period, so a negative determination is made in the process of S302. The

  If an affirmative determination is made in the process of S302, the ECU 15 proceeds to the process of S303 and calculates the actual fluctuation interval dir. Subsequently, the ECU 15 proceeds to the process of S304, and determines whether or not the actual fluctuation interval dir calculated in the process of S303 is greater than “0”. Here, as shown in FIG. 2 described above, when the actual fluctuation interval is larger than “0”, an affirmative determination is made in the process of S304. On the other hand, as shown in FIG. 3 described above, when the actual fluctuation interval is “0”, a negative determination is made in the process of S304.

  Note that the “determination means” according to the present invention is realized by the ECU 15 executing the processing of S302 to S304.

  If an affirmative determination is made in the process of S304, the ECU 15 proceeds to the process of S305, and calculates a new correction coefficient k by subtracting a predetermined update amount Δk from the previous value kold of the correction coefficient. The predetermined update amount Δk is a value determined according to a difference Δdi between the actual fluctuation interval dir and a predetermined value (= 0). Specifically, as shown in FIG. 9, the predetermined update amount Δk is a positive number sufficiently smaller than “1”, and is set to a larger value as the difference Δdi increases. When the correction coefficient k is determined in this way, the injection interval Iint calculated based on the above-described equation (1) in the next cycle and thereafter is corrected in the shortening direction. Then, the pre-injection timing Tp determined based on the corrected injection interval Iint is corrected in the retarding direction with respect to the pre-injection timing determined based on the pre-correction injection interval. As a result, even when the actual fluctuation interval dir becomes larger than “0”, the actual fluctuation interval dir in the next cycle and thereafter can be made “0” or less, or close to “0”.

  Further, when a negative determination is made in the process of S302 and a negative determination is made in the process of S304, since the actual fluctuation interval dir is “0” or less, the pre-injection timing is corrected in the retard direction. There is no need. Therefore, the ECU 15 proceeds to the process of S306, and sets the correction coefficient k to a value equivalent to the previous value kold.

  Here, the “feedback means” according to the present invention is realized when the ECU 15 executes the processing of S201 to S202 of the processing routine of FIG. 2 and the processing of S305 to S306 of the processing routine of FIG.

  Therefore, according to the control device of the present embodiment, the actual fluctuation interval is set to a predetermined value because the in-cylinder temperature or the like deviates from the assumed temperature or a change with time such as a change in intake characteristics or fuel injection characteristics occurs. Even if the situation becomes larger than the value (= 0), the actual fluctuation interval after the next cycle is set to a predetermined value (= 0) or less, or the actual fluctuation interval is made closer to the predetermined value (= 0). Can do. As a result, the noise level of the combustion noise when pre-injection is executed immediately before main injection can be more reliably suppressed.

  In this embodiment, the basic injection interval Iintbase derived from the above-described map or calculation model is exemplified as a case where it is uniformly corrected regardless of the operating state of the internal combustion engine 1, but the above-described map or calculation is described above. Of the basic injection intervals Iintbase stored in the ECU 15 in the form of a model or the like, only the basic injection interval Iintbase corresponding to the operating state when it is determined that the actual fluctuation interval is larger than the predetermined value (= 0) is corrected. May be.

<Embodiment 3>
Next, a third embodiment of the present invention will be described with reference to FIGS. Here, a configuration different from the above-described second embodiment will be described, and description of the same configuration will be omitted.

  The difference between the second embodiment and the present embodiment is that fuel injection amount feedback control for feedback control of the pre-injected fuel amount (pre-injection amount) is performed in addition to the above-described injection timing feedback control. There is in point to be called.

  Here, if the fuel injection characteristic changes with time as described above, the actual pre-injection amount may deviate from the target pre-injection amount. Further, as described in the description of FIG. 1 described above, when the internal combustion engine 1 has a plurality of cylinders 2, a delivery pipe such as a common rail is used every time fuel is injected from the fuel injection valve 9 of each cylinder 2. Pressure fluctuations occur inside. Thus, when the pressure fluctuation in the delivery pipe occurs, the fuel pressure acting on the fuel injection valve 9 varies from time to time. Therefore, when the pre-injection timing is corrected by the injection timing feedback control described above, the fuel pressure acting on the fuel injection valve 9 at the pre-injection timing before correction and the fuel injection valve 9 at the pre-injection time after correction are corrected. There is a possibility that the fuel pressure acting on the fuel is different. Even in such a case, the actual pre-injection amount may deviate from the target pre-injection amount. For these reasons, if the actual pre-injection amount deviates from the target pre-injection amount, even if the actual fluctuation interval is a predetermined value (= 0), the combustion in the case where the pre-injection is executed immediately before the main injection The noise level of noise may increase.

  For example, when the actual pre-injection amount is larger than the target pre-injection amount, the maximum value of the actual secondary change rate during the pre-variation period dp increases, so that the noise of combustion noise generated when the pre-injected fuel burns The level increases. On the other hand, when the actual pre-injection amount becomes smaller than the target pre-injection amount, the heat field formed when the pre-injected fuel burns becomes small. Therefore, although a part of the fuel injected from the fuel injection valve 9 at the initial stage of the main injection period is ignited and burned quickly using the heat field, the ignition delay period of the remaining fuel becomes longer and thereafter There is a possibility of simultaneous combustion with the fuel injected from the fuel injection valve 9. In this case, since the maximum value of the actual secondary change rate during the main fluctuation period is increased, the noise level of the combustion noise generated when the main injected fuel is burned is increased.

  Here, the actual pre-injection amount correlates with the difference (maximum variation amount) between the maximum value of the actual secondary change rate and the predetermined reference value in the pre-variation period dp. In other words, the maximum fluctuation amount increases as the actual pre-injection amount increases.

  Therefore, in this embodiment, the maximum fluctuation amount is calculated based on the actual secondary change rate calculated from the measured value of the in-cylinder pressure sensor 10, and the maximum fluctuation amount corresponds to the target fluctuation amount (the target value of the pre-injection amount). Injection amount feedback control for performing feedback control of the pre-injection amount is executed so that the maximum variation amount after the next cycle becomes the target variation amount.

Hereinafter, in this embodiment, the procedure for determining the fuel injection amount and the fuel injection timing will be described with reference to FIG.
A description will be given along 0. In the processing routine of FIG. 10, the same reference numerals are given to the same processes as those of the processing routine of FIG. The difference between the processing routine of FIG. 10 and the processing routine of FIG. 6 described above is that the processing of S401 to S403 is executed instead of the processing of S104 to S201.

  In the process of S401 of the process routine of FIG. 10, the ECU 15 calculates the basic pre-injection amount Qpbase. The basic pre-injection amount Qpbase here corresponds to the pre-injection amount calculated in the processing of S104 of the processing routine of FIGS. 5 and 6 described above, and corresponds to the target pre-injection amount. Therefore, the ECU 15 sets the pre-injection amount calculated in the same procedure as the process of S104 to the basic pre-injection amount Qpbase.

In the process of S402, the ECU 15 calculates the pre-injection quantity Qp by substituting the basic pre-injection quantity Qpbase calculated in the process of S401 into the following equation (2).
Qp = Qpbase + C (2)
C in the above equation (2) is a correction term determined based on the difference between the maximum fluctuation amount and the target fluctuation amount when the maximum fluctuation amount deviates from the target fluctuation amount. “0” is set. A method for determining the correction term C will be described later.

  When the ECU 15 finishes executing the process of S402, the ECU 15 proceeds to the process of S403, and calculates the basic injection interval Iintbase based on the basic pre-injection amount Qpbase calculated in the process of S401. Thereafter, the ECU 15 proceeds to the process of S202, and calculates the injection interval Iint based on the basic injection interval Iintbase calculated in the process of S403.

  Next, the procedure for determining the correction term C will be described with reference to FIG. FIG. 11 is a processing routine executed by the ECU 15 when the correction term C is determined. This processing routine is stored in advance in the ROM of the ECU 15 and is executed by the ECU 15 when pre-injection is started in the cylinder 2 to which the in-cylinder pressure sensor 10 is attached.

  In the processing routine of FIG. 11, the ECU 15 first calculates the actual secondary change rate by differentiating the measured value of the in-cylinder pressure sensor 10 in the processing of S501. The calculation of the actual secondary change rate is repeatedly executed for each unit crank angle in the period from the start of pre-injection to the start of main injection.

  In the process of S502, the ECU 15 calculates the maximum fluctuation amount Vmax. Specifically, the maximum actual secondary change rate is extracted from the actual secondary change rates calculated in the process of S501, and the actual secondary change rate is calculated as the real secondary change rate in the pre-variation period dp. Set as the maximum value. Subsequently, the ECU 15 calculates a predetermined reference value corresponding to the crank angle at which the actual secondary change rate indicates the maximum value. Then, the ECU 15 calculates the maximum fluctuation amount Vmax by subtracting the predetermined reference value from the maximum value.

  In the process of S503, the ECU 15 calculates the target fluctuation amount Vtrg using the pre-injection amount Qp in the cycle for which the maximum fluctuation amount Vmax is calculated as a parameter. At this time, the relationship between the pre-injection amount Qp and the target fluctuation amount Vtrg is obtained in advance based on the results of experiments or simulations, and the relationship is stored in the ROM of the ECU 15 in the form of a map or a calculation model. And

In the process of S504, the ECU 15 calculates the difference between the maximum fluctuation amount Vmax calculated in the process of S502 and the target fluctuation amount Vtrg calculated in the process of S503, and whether or not the absolute value of the difference is greater than zero. Is determined. That is, in the process of S504, it is determined whether or not the maximum fluctuation amount Vmax is deviated from the target fluctuation amount Vtrg.

  If an affirmative determination is made in step S504, the maximum fluctuation amount Vmax is deviated from the target fluctuation amount Vtrg. Therefore, the actual pre-injection amount is calculated according to the target pre-injection amount (the processing routine of FIG. 10 described above). It is estimated that there is a deviation from the basic pre-injection amount Qpbase). Therefore, the ECU 15 proceeds to the processing of S505, and calculates a new correction term C by adding a predetermined update amount ΔC to the previous value Cold of the correction term. The predetermined update amount ΔC is a value determined according to a difference ΔV (= Vmax−Vtrg) between the maximum fluctuation amount Vmax and the target fluctuation amount Vtrg. Specifically, as shown in FIG. 12, when the maximum fluctuation amount Vmax is larger than the target fluctuation amount Vtrg (when ΔV is a positive number), the predetermined update amount ΔC is a value larger than 0, The larger the difference ΔV, the larger the value. On the other hand, when the maximum fluctuation amount Vmax is smaller than the target fluctuation amount Vtrg (when ΔV is a negative number), the predetermined update amount ΔC is set to a value smaller than 0 and smaller as the difference ΔV becomes smaller. Is done.

  When the correction term C is determined in this way, the pre-injection amount Qp calculated based on the above-described equation (2) after the next cycle reduces the difference between the maximum fluctuation amount Vmax and the target fluctuation amount Vtrg. Will be corrected in the direction. In other words, the pre-injection amount Qp calculated based on the above equation (2) after the next cycle is in a direction to reduce the difference between the actual pre-injection amount and the target pre-injection amount (basic pre-injection amount Qpbase). It will be corrected. When the pre-injection is executed according to the pre-injection amount Qp, the actual pre-injection amount is made to coincide with the target pre-injection amount (basic pre-injection amount Qpbase), or the actual pre-injection amount is set to the target pre-injection. The amount (basic pre-injection amount Qpbase) can be approached.

  If the determination in S504 is negative, the maximum fluctuation amount Vmax is not deviated from the target fluctuation amount Vtrg, so the actual pre-injection amount is determined from the target pre-injection amount (basic pre-injection amount Qpbase). It is estimated that there is no deviation. Therefore, the ECU 15 proceeds to the process of S506 and sets the previous value Cold of the correction term to a new correction term C.

  As described above, according to the control device of the present embodiment, even if the actual pre-injection amount deviates from the target pre-injection amount (basic pre-injection amount Qpbase), the actual pre-injection after the next cycle The amount can be matched with the target pre-injection amount (basic pre-injection amount Qpbase), or the actual pre-injection amount can be brought close to the target pre-injection amount (basic pre-injection amount Qpbase). As a result, the noise level of the combustion noise when pre-injection is executed immediately before main injection can be more reliably suppressed.

  In the first to third embodiments described above, an example in which fuel injection per cycle is divided into pre-injection and main injection has been described, but in addition to pre-injection and main injection, pilot injection and The present invention can be applied even when at least one of after-injection and post-injection is performed. In short, the present invention can be applied to any internal combustion engine in which at least pre-injection and main injection are executed.

1 Internal combustion engine 2 Cylinder 9 Fuel injection valve 10 In-cylinder pressure sensor 12 Crank position sensor 13 Accelerator position sensor 14 Air flow meter 15 ECU

Claims (3)

A control device applied to a compression ignition type internal combustion engine having a fuel injection valve for injecting fuel into a cylinder,
The control device includes:
Main injection for injecting fuel from the fuel injection valve at a timing that contributes to the output of the internal combustion engine, and injection of a smaller amount of fuel than the main injection from the fuel injection valve at an earlier time than the main injection Perform pre-injection,
A pre-variation period in which a secondary change rate, which is a value obtained by second-order differentiation of the in-cylinder pressure of the internal combustion engine with respect to a crank angle, is greater than a predetermined reference value due to combustion of the pre-injected fuel; The fluctuation interval, which is the interval between the main fluctuation period, which is a period during which the next change rate is greater than the predetermined reference value due to the combustion of the main injected fuel, is less than or equal to the predetermined value in each operating state of the internal combustion engine. The control apparatus for an internal combustion engine, wherein the pre-injection is executed according to the execution time of the pre-injection determined to be The internal combustion engine further includes an in-cylinder pressure sensor for detecting an in-cylinder pressure of the internal combustion engine,
The control device includes:
Calculation means for calculating an actual secondary change rate that is a secondary change rate of the actual in-cylinder pressure based on a detection value of the in-cylinder pressure sensor;
Discrimination means for discriminating whether or not the actual fluctuation interval is equal to or less than the predetermined value based on the actual secondary change rate calculated by the calculation means;
Feedback means for executing injection timing feedback control for correcting the execution timing of the pre-injection in the subsequent cycle in the retard direction when the determination means determines that the actual fluctuation interval is greater than the predetermined value; ,
The control device for an internal combustion engine according to claim 1, comprising:   In addition to the injection timing feedback control, the feedback means is configured so that the maximum fluctuation amount, which is the difference between the maximum value of the actual secondary change rate in the pre-variation period and the predetermined reference value, matches the target fluctuation amount. 3. The control apparatus for an internal combustion engine according to claim 2, wherein injection amount feedback control is performed to feedback control the amount of fuel pre-injected from the fuel injection valve.

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