JP6354604B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device that controls combustion of an internal combustion engine.

  Conventionally, a technique is known in which fuel is divided into pilot injection and main injection and injected into the combustion chamber of the internal combustion engine, and the combustion noise of the internal combustion engine is reduced by adjusting the pilot injection amount (see, for example, Patent Document 1). ). In Patent Document 1, the maximum value of the change rate of the combustion pressure is calculated from the detection value of the in-cylinder pressure sensor for each of the pilot injection and the main injection, and the pilot injection amount is corrected based on the sum of both obtained maximum values. Techniques to do this are disclosed. According to this, it is supposed that the combustion noise can be reduced by accurately comprehending whether or not the correction of the pilot injection amount is necessary and correcting the pilot injection amount.

JP 2005-282441 A

  By the way, the sound that a vehicle occupant actually feels includes sound that is not caused by combustion of the internal combustion engine (for example, sound of a driving system such as a tire or wind noise generated by wind hitting a vehicle body). . In some cases, combustion noise generated in the internal combustion engine is greatly attenuated before being transmitted to the passenger compartment. Therefore, there is a correlation between an index correlating to the combustion noise obtained from the detection value of the in-cylinder pressure sensor (in the case of Patent Document 1, the sum of both maximum values of the change rate of the combustion pressure) and the combustion noise actually felt by the occupant. There are concerns. If the correlation is low, for example, even if control for reducing combustion noise is performed, the amount of control may be insufficient, and the passenger may still feel the combustion noise noisy. In addition, for example, when a sound that is not caused by combustion is dominant with respect to the vehicle interior sound, the passenger is less likely to experience the combustion noise. In this case, even if the combustion noise is large at the position of the combustion chamber of the internal combustion engine, the effect (effectiveness) of performing the control for reducing the combustion noise is low. If the combustion noise is strongly controlled when the effectiveness is low, the fuel consumption may be deteriorated.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device for an internal combustion engine that can reflect noise actually felt by an occupant in the control of combustion noise.

In order to solve the above problems, a control device for an internal combustion engine of the present invention includes a sound collector installed in a vehicle interior,
Noise control means for controlling combustion noise of an internal combustion engine mounted on the vehicle based on room sound which is sound obtained by the sound collector;
It is characterized by providing.

  According to the present invention, since the sound collecting device is installed in the vehicle interior, the vehicle interior sound of the vehicle can be obtained by the sound collecting device. This room sound correlates with the noise that the occupant actually feels. Therefore, by controlling the combustion noise based on this room sound, the noise that the occupant actually feels can be reflected in the control of the combustion noise. .

It is the figure which showed the structure relevant to engine schematic structure and engine control. It is the figure which showed pilot injection and main injection in the upper stage, and showed the change of the heat release rate in the lower stage. It is the figure which showed the relationship between the magnitude of a combustion noise, and the quality of a fuel consumption. It is the flowchart which showed the main process of the combustion noise control which ECU performs. It is a flowchart which shows the specific content of the process of S5 of FIG. It is a flowchart which shows the specific content of the process of S15 of FIG. It is the figure which illustrated the map where the volume change log | history was stored in association with engine operating conditions. It is the flowchart which showed the process which memorize | stores the log | history change history of an audio equipment. It is a flowchart which shows the specific content of the process of S17. It is the figure which illustrated the change between the microphone sound at the time of a fuel cut, and the microphone sound at the time of execution of fuel injection. It is a figure explaining the modification of the process of FIG. 9, and is the figure which illustrated the change of the microphone sound when fuel injection is performed on the 1st, 2nd injection conditions. It is a figure explaining the control method of the combustion noise in the embodiment of the present invention. It is the figure which illustrated the signal (time change) of the microphone sound in the upper stage, and illustrated the frequency spectrum of the microphone sound in the lower stage.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a diesel engine 1 (hereinafter simply referred to as an engine) as an internal combustion engine mounted on a vehicle and a configuration related to control of the engine 1.

  First, the outline of the engine 1 will be described with reference to FIG. The engine 1 (compression self-ignition internal combustion engine) is, for example, an in-line four-cylinder engine, and only one cylinder (cylinder) is shown in FIG. As shown in the figure, the engine 1 includes a cylinder block 2, a piston 3, a cylinder head 4, an intake passage 5, an exhaust passage 6, an intake valve 7, an injector 8, an exhaust valve 9, and the like.

  For example, four cylinders 2 a are formed in the cylinder block 2. Each cylinder 2a accommodates a piston 3 in a reciprocable manner. A cylinder head 4 is assembled to the cylinder block 2. A combustion chamber 16 is formed by the cylinder 2 a, the piston 3, and the cylinder head 4.

  An intake passage 5 is connected to the cylinder head 4. The intake passage 5 is connected to each cylinder 2 a via an intake manifold and an in-head passage 4 a in the cylinder head 4. The camshaft (not shown) is rotated by the rotation of the crankshaft (not shown) of the engine 1. Each intake valve 7 is driven based on the rotation of the camshaft, and each intake valve 7 opens and closes each in-head passage 4a.

  An exhaust passage 6 is connected to the cylinder head 4. The exhaust passage 6 is connected to each cylinder 2 a via an exhaust manifold and an in-head passage 4 b in the cylinder head 4. Each exhaust valve 9 is driven based on the rotation of the camshaft, and each exhaust passage 9 opens and closes each head passage 4b.

  Fuel (light oil) is pumped to the common rail 10 by a fuel pump (not shown). The common rail 10 (pressure accumulation container) holds the fuel in a pressure accumulation state. The injector 8 (fuel injection valve) injects the fuel held in the common rail 10 in a pressure accumulation state into the combustion chamber 16.

  In the intake stroke of the engine 1, air is sucked into the combustion chamber 16 through the intake passage 5, and the air is compressed by the piston 3 in the compression stroke. In the vicinity of the compression top dead center, fuel is injected into the combustion chamber 16 by the injector 8, and the fuel injected in the combustion stroke is self-ignited and burned. In the exhaust stroke, the exhaust in the combustion chamber 16 is exhausted through the exhaust passage 6.

  The engine 1 is provided with various sensors necessary for operation control of the engine 1. Specifically, for example, the engine 1 includes an in-cylinder pressure sensor 11 that detects pressure (in-cylinder pressure) in the combustion chamber 16 (in-cylinder), a common rail pressure sensor 12 that detects pressure in the common rail 10, and the engine 1. A rotation speed sensor 13 for detecting the rotation speed, an accelerator pedal sensor 14 for detecting an operation amount (depression amount) of an accelerator pedal for notifying the vehicle side of a required torque of the driver of the vehicle, and the like are provided. The rotation speed sensor 13 may be a crank angle sensor that detects a crank angle that is a rotation angle of the crankshaft. The in-cylinder pressure sensor 11 is attached to the cylinder head 4. The in-cylinder pressure signal detected by the in-cylinder pressure sensor 11 is input to the LPF 15 (low-pass filter), and noise included in the in-cylinder pressure signal is removed by the LPF 15. Signals from these sensors 11 to 14 are input to the ECU 20.

  A sound collecting device 23 (microphone) for detecting (sound collecting) the sound in the vehicle interior is provided in the vehicle interior. The room sound signal detected by the sound collector 23 is input to the ECCU 20. Furthermore, the vehicle is provided with an acoustic device 24 that outputs sound such as music and voice in the passenger compartment. The sound device 24 may be, for example, a radio device that outputs radio sound, or a playback device that reproduces music or movie sound stored on a CD, DVD, or the like. The acoustic device 24 includes a volume adjusting unit 25 that adjusts the intensity of the output sound, that is, the volume. The sound volume adjustment unit 25 is provided around the driver's seat and is configured as an operation unit (for example, a rotary button) that is operated by an occupant. The acoustic device 24 is connected to the ECU 20.

  An ECU (Electric Control Unit) 20 is provided in the vehicle. The ECU 20 has a normal computer structure, and includes a CPU (not shown) for performing various calculations and a memory 21 (ROM, RAM, storage device, etc.) for storing various information. The ECU 20 detects operating conditions of the engine 1 based on detection signals from sensors such as the rotational speed sensor 13 and the accelerator pedal sensor 14, and calculates an optimal fuel injection amount, injection timing, injection pressure, etc. according to the operating conditions. The fuel injection (injector 8) into the combustion chamber 16 is controlled. In the ECU 20, a sound intensity calculation unit 22 that calculates sound intensity (sound pressure level) is provided.

  Incidentally, the combustion process in the engine 1 is roughly divided into a premixed combustion period and a subsequent diffusion combustion period. In the premixed combustion period, the fuel injected into the combustion chamber 16 becomes a combustible air-fuel mixture and self-ignites, so that the fuel combustion proceeds rapidly. In the diffusion combustion period, the fuel is injected into the combustion gas generated in the combustion chamber 16 during the premixed combustion period, so that the fuel is continuously burned.

  Further, during the premixed combustion period, the combustion proceeds rapidly as described above, so that the rate of change (increase rate) of the combustion pressure in the combustion chamber 16 tends to increase. Therefore, if the premixed combustion period becomes longer, that is, if the proportion of fuel that burns rapidly by self-ignition increases, combustion noise increases.

  In order to suppress such an increase in combustion noise, in the present embodiment, divided injection is performed in which a required amount of fuel is divided into pilot injection and main injection when fuel is injected. Here, FIG. 2 is a diagram for explaining a difference in effect between split injection and normal injection in which a required amount of fuel is injected at once (that is, injection in which only main injection is performed without performing pilot injection). Specifically, the upper part of FIG. 2 schematically shows the timing and amount of pilot injection and main injection, with the horizontal axis representing the crank angle CA and the vertical axis representing the fuel injection rate. In the upper part of FIG. 2, pilot injection is performed at a crank angle before compression top dead center TDC (Top Dead Center). After the pilot injection, fuel injection is temporarily interrupted, and then at a crank angle that becomes compression top dead center TDC. It indicates that the main injection has started. In addition, the horizontal width of the figure indicating pilot injection and main injection in the figure indicates the injection period of pilot injection and main injection, and the area of the figure indicates the injection amount of pilot injection and main injection. This indicates the injection rate (injection amount per unit time) of pilot injection and main injection.

  2 shows the change in the heat generation rate (vertical axis) in the combustion chamber 16 with respect to the crank angle (horizontal axis), and the line 101 in FIG. 2 performs only main injection (normal injection). The line 102 shows the change in the heat generation rate when the pilot injection (split injection) is performed before the main injection.

  Comparing line 101 and line 102, the ignition delay period C2 of line 102 (the period from the start of main injection to the start of ignition) C2 is shorter than the ignition delay period C1 of line 101. In addition, the peak value (maximum value) B2 of the heat generation rate of the line 102 is smaller than the peak value B1 of the line 101. This means that when pilot injection is performed, the fuel of the main injection is ignited using the fuel of the pilot injection as a fire type, so the premixed combustion period is shortened and the proportion of fuel that burns rapidly by self-ignition decreases. Therefore, the increase in the combustion pressure is slow, that is, the peak value of the heat generation rate is reduced, indicating that the increase in combustion noise is suppressed.

  Considering the suppression of combustion noise from the viewpoint of the heat generation rate, the combustion noise is suppressed when the fuel injection conditions are set so as to lower the peak value of the heat generation rate. Further, from the viewpoint of improving fuel consumption (fuel consumption), the fuel efficiency improves as the injected fuel burns efficiently in a short period of time. On the other hand, since the fuel of pilot injection has a small contribution to the engine output, the fuel consumption tends to deteriorate when pilot injection is performed or when the injection amount of pilot injection is increased. That is, the fuel efficiency of the line 101 in FIG.

  From the above, the relationship between the magnitude of the combustion noise and the quality of fuel consumption tends to be shown in FIG. 3, that is, if the combustion noise is reduced, the fuel consumption becomes worse, and conversely, if the fuel efficiency is improved, the combustion noise tends to increase. There is.

  On the other hand, the combustion noise actually felt by a vehicle occupant (driver or the like) and the index (for example, the peak value of the heat generation rate) correlated with the combustion noise obtained from the in-cylinder pressure are not always highly correlated. Absent. This is because the sounds experienced by the occupant include sounds that are not caused by engine combustion in addition to the sounds that are caused by engine combustion. It is. Here, the noise (combustion noise) resulting from engine combustion includes, in addition to the direct sound in which noise generated by engine combustion directly enters the passenger's ear, the engine 1 vibrates due to engine combustion, and the vibration or combustion noise is A member other than the engine 1 (for example, a transmission, a drive shaft, a vehicle body, or the like) is vibrated, and an indirect sound that enters the occupant's ear is included. Further, examples of the sound not caused by engine combustion include a sound of a driving system such as a tire, a wind noise, a sound output from the acoustic device 24, and a sound from outside the vehicle.

  In addition, the combustion noise (feeling combustion noise) experienced by the occupant varies depending on the difference between the vehicle and the occupant. That is, sound generated by engine combustion is attenuated by a member such as rubber or damper in the process of being transmitted from the combustion chamber 16 to the vehicle interior. Even if the combustion noise at the position of the combustion chamber 16 has the same magnitude, the greater the amount of attenuation of the combustion noise until it is transmitted to the passenger compartment, the smaller the sensible combustion noise. The amount of attenuation varies from vehicle to vehicle. Further, the perception level of the combustion noise transmitted to the passenger compartment varies depending on the occupant, and even if the same level of combustion noise is transmitted to the passenger compartment, some occupants feel noisy and some occupants feel not noisy.

  Even if the control for reducing the combustion noise is performed strongly when the sensible combustion noise is small, the reduction effect (effectiveness) of the sensible combustion noise is small. Therefore, in the present invention, when the level of the sensible combustion noise is determined and the level is low, that is, when the occupant hardly senses the combustion noise, the target value D2 (see FIG. 3) of the combustion noise is set to a high level. The target value D1 (see FIG. 3) is suppressed to prevent the occupant from feeling that the combustion noise is noisy, and the deterioration of fuel consumption is suppressed (details will be described later). Conventionally, since the sensible combustion noise is not taken into account, when the combustion noise is controlled, a strong target value D1 is always set regardless of the magnitude of the sensible combustion noise, leading to deterioration of fuel consumption.

  Details of the combustion noise control in this embodiment will be described below. FIG. 4 is a flowchart showing a main process of the combustion noise control executed by the ECU 20. The process of FIG. 4 is started at the same time as the engine 1 is started, for example, and thereafter repeatedly executed at a predetermined cycle. In addition, ECU20 which performs the process of FIG. 4 is equivalent to the noise control means of this invention.

  When the processing of FIG. 4 is started, the ECU 20 determines the fuel injection conditions (pilot injection, injection timing of main injection, injection amount, injection pressure) based on, for example, the operating conditions of the engine 1 determined by the engine speed and the engine load (torque). Etc.) is set (S1). For example, a map that associates the operating conditions (engine speed, engine load) of the engine 1 with the injection conditions is stored in the memory 21. Then, the current injection condition is set based on the map and the current operation condition. The engine speed is obtained by the speed sensor 13. The engine load may be a detection signal of the accelerator pedal sensor 14, for example.

  Next, fuel is injected into the injector 8 under the injection conditions set in S1, and combustion is performed in the combustion chamber 16 (S2). Next, the in-cylinder pressure for each crank angle is acquired in association with the crank angle (S3). That is, the change in the in-cylinder pressure with respect to the crank angle is acquired. The in-cylinder pressure may be acquired from the in-cylinder pressure sensor 11, and the crank angle may be acquired from the rotation speed sensor 13 (crank angle sensor). Note that the in-cylinder pressure sensor 11 and the ECU 20 that executes the processes of S3 correspond to the acquisition means of the present invention.

Next, the heat generation amount dQ per unit angle dθ of the crank angle θ, that is, the heat generation rate dQ / dθ is calculated by the following equation (S4). In the equation, κ is a specific heat ratio (a ratio between a constant pressure specific heat Cp and a constant volume specific heat Cv), and a predetermined value may be used. P is the in-cylinder pressure, and the value obtained in S3 may be used. DV / dθ is a rate of change (volume change rate) of the volume V of the combustion chamber 16 per unit angle of the crank angle θ. The volume change rate dV / dθ and the volume V may be calculated based on the relationship between the crank angle θ and the volume V stored in advance in the memory 21. DP / dθ is the rate of change of the in-cylinder pressure P per unit angle of the crank angle θ (in-cylinder pressure change rate). The in-cylinder pressure change rate dP / dθ may be calculated based on the in-cylinder pressure P for each crank angle θ acquired in S3. In addition, ECU20 which performs the process of S4 corresponds to the calculation means of this invention.

  Next, the target value of the heat release rate in the combustion chamber 16 is set (S5). The process of S5 is a characteristic process of the present invention. FIG. 5 is a flowchart showing specific contents of the process of S5. When the process proceeds to the process of FIG. 5, the ECU 20 first sets a basic target value of the heat generation rate based on, for example, the operating conditions of the engine 1 determined by the engine speed and the engine load (S11). Specifically, the memory 21 stores a map of the basic target value of the heat generation rate that is adapted in consideration of combustion noise and the like for each operating condition of the engine 1. And the target value corresponding to this driving | running condition should just be acquired from the map. Further, as the basic target value, a waveform of a target heat generation rate with respect to the crank angle may be set, or only a target peak value of the heat generation rate may be set. As described with reference to FIG. 2, the heat generation rate (particularly the peak value of the heat generation rate) correlates with the combustion noise. The engine load may be a detection signal of the accelerator pedal sensor 14 or may be a fuel injection amount set in S1 of FIG. 4 based on the detection signal.

  Next, a signal of the vehicle interior sound (hereinafter referred to as a microphone sound) detected by the sound collecting device 23 is acquired (S12). Next, the sound intensity calculation unit 22 calculates the intensity S (sound pressure level) of the microphone sound signal acquired in S12 (S13). Here, the intensity S at the current time may be calculated, or the maximum value or the average value of the microphone sound during a period from a predetermined time before to the current time may be calculated as the intensity S.

  Next, it is determined whether the intensity S calculated in S13 is larger or smaller than a predetermined threshold value S0 (S14). This threshold value S0 is set to the sound intensity located at the boundary between whether the passenger feels noisy or not loud in the room. Note that the threshold value S0 corresponds to the second threshold value of the present invention. When the intensity S is smaller than the threshold value S0 (S14: No), the process of FIG. 5 is terminated and the process returns to the process of FIG. In this case, it is estimated that the occupant feels that room noise including combustion noise is noisy (quiet), and the basic target value set in S11 is not corrected. That is, the basic target value is set as the final target value of the heat generation rate.

  On the other hand, when the intensity S is larger than the threshold value S0 (S14: Yes), the passenger proceeds to the processing after S15 because there is a possibility that the passenger feels noisy indoor noise. Here, the ease of experiencing the combustion noise by the occupant varies depending on the operating conditions of the engine 1 (engine speed, engine load, etc.). This is because if the operating condition of the engine 1 changes, the fuel injection condition also changes, and if the injection condition changes, the combustion state of the engine 1 also changes. That is, even for the same occupant, there are operating conditions that make the combustion noise feel noisy, and other driving conditions that make it feel noisy. Further, even under the same operating conditions, there are some passengers who feel that combustion noise is noisy, and some passengers who feel that it is not noisy. Furthermore, even in the same occupant and the same driving conditions, the way in which combustion noise is transmitted to the passenger compartment changes depending on the vehicle on which the engine 1 is mounted, so the occupant may feel noisy combustion noise. And sometimes it feels noisy.

In view of these, in S15, the occupant's noise recognition level for the current operating condition of the engine 1 is determined (S15). FIG. 6 is a flowchart showing the specific contents of the process of S15. As a premise for performing the processing of FIG. 6, the ECU 20 creates the map 200 shown in FIG. 7 by the processing of the flowchart shown in FIG. 8 . Before explaining the processing of FIG. 6, the processing of FIG. 8 and the map 200 of FIG. 7 will be explained. The process of FIG. 8 is started at the same time as the engine 1 is started, for example, and thereafter repeatedly executed at a predetermined cycle. Further, the process of FIG. 8 is executed in parallel with the process of FIG.

When the processing of FIG. 8 is started, the ECU 20 determines whether or not the sound volume of the acoustic device 24 has been increased by the operation of the sound volume adjusting unit 25 by the occupant (S31). Specifically, for example, the operation signal of the volume adjusting unit 25 is input to the ECU 20 in a form that can be distinguished whether the operation signal is operated to increase or decrease the volume, and the ECU 20 is based on the operation signal, It is determined whether or not a volume increasing operation has been performed. Further, the sound device 24 may notify the ECU 20 that the volume increasing operation has been performed.

When the volume increasing operation is not performed (S31: No), the process of FIG. 8 is terminated. When the volume increasing operation is performed (S31: Yes), the change history indicating the frequency at which the volume increasing operation is performed, in other words, the frequency at which the volume of the sound device 24 is changed in the increasing direction is counted up by +1. Then, it is stored in the memory 21 in association with the current operating condition of the engine 1 (when the volume is changed) (S32). At this time, the change history deviating from the predetermined period may be deleted from the memory 21 each time so as to become the change history in a predetermined period (for example, a period from the present to one week before), or the condition of “predetermined period” The change history in all periods may be stored in the memory 21 without attaching.

FIG. 7 exemplifies the change history stored in the memory 21 in S32 . Specifically, the operating condition area determined by the engine speed and the engine load is divided into a plurality of areas and changed for each divided area. A map 200 storing a history (in FIG. 7 , the number of lines constituting a positive character) is shown. Note that the engine load in the map 200 may be, for example, a detection signal of the accelerator pedal sensor 14 or a command value for the fuel injection amount set based on the detection signal. After S32, and ends the process in FIG. The memory 21 corresponds to the storage means of the present invention. Moreover, ECU20 which performs the process of FIG. 8 is equivalent to the memory | storage control means of this invention.

  Next, the process of FIG. 6 will be described. If it transfers to the process of FIG. 6, ECU20 will specify the present engine speed and engine load, for example as a driving | running condition of the engine 1 of this time (this time) (S21). The engine speed can be specified from the detection signal of the rotation speed sensor 13, and the engine load can be specified from the detection signal of the accelerator pedal sensor 14.

Next, the volume change frequency E (current frequency) stored in the map 200 (see FIG. 7 ) in association with the driving condition specified in S21 is acquired (S22). Next, it is determined whether the change frequency E acquired in S22 is larger or smaller than a predetermined threshold E0 (S23). This threshold value E0 is set to a change frequency located at the boundary of whether the recognition level of indoor noise by the occupant is high or low. The threshold value E0 corresponds to the third threshold value of the present invention.

  When the change frequency E is larger than the threshold value E0 (S23: Yes), it is highly possible that the passenger feels noisy room noise including combustion noise under the current operating conditions of the engine 1, and the room noise is difficult to feel. Therefore, it is considered that the frequency of increasing the volume of the acoustic device 24 is increasing. That is, in this case, it is determined that the engine 1 is operating under an operating condition where the level of indoor noise recognition by the occupant is high (S24). In other words, under the current operating conditions of the engine 1, it is determined that the occupant is likely to feel noisy room noise including combustion noise, that is, the noise recognition level by the occupant is high. After S24, the process of FIG. 6 is terminated and the process returns to the process of FIG.

  On the other hand, when the change frequency E is smaller than the threshold value E0 (S23: No), it is highly possible that the occupant does not feel noisy room noise including combustion noise under the current operating conditions of the engine 1. It is considered that the frequency of increasing the volume of the acoustic device 24 is decreasing. That is, in this case, it is determined that the engine 1 is operating under an operating condition where the level of indoor noise recognition by the occupant is low (S25). In other words, under the current operating conditions of the engine 1, it is determined that the passenger is unlikely to feel noisy room noise including combustion noise, that is, the noise recognition level by the passenger is low. After S25, the process of FIG. 6 is terminated and the process returns to the process of FIG.

  Returning to the description of the process of FIG. 5, after the process of S15 is executed, it is next determined whether the recognition level of the room noise by the occupant is high or low based on the determination result of S15 (S16). When the recognition level of the room noise by the occupant is low, that is, when it is determined that the recognition level is low in S25 of FIG. 6 (S16: No), the process of FIG. 5 is terminated and the process returns to the process of FIG. In this case, although there is a certain level of intensity as a microphone sound, judging from past statistics (map 200), it is estimated that the occupant is unlikely to feel noisy room noise, and is set in S11. The basic target value is not corrected. That is, the basic target value is set as the final target value of the heat generation rate.

  On the other hand, if the recognition level of indoor noise by the occupant is high, that is, if it is determined that the recognition level is high in S24 of FIG. 6 (S16: Yes), the occupant is likely to feel noisy indoor noise. Next, the degree of influence of the engine combustion (combustion noise) on the microphone sound (room sound) is determined (S17). In other words, the microphone sound determines whether the sound caused by engine combustion is dominant or the sound not caused by engine combustion is dominant. Here, FIG. 9 shows a flowchart showing the specific contents of the processing of S17.

  9, the ECU 20 acquires the microphone sound S1 when the fuel injection by the injector 8 is stopped (fuel cut) (S41). This microphone sound S1 is a room sound when engine combustion is not being performed, and is a sound composed only of sound that is not caused by engine combustion.

Next, the microphone sound S2 when the fuel injection by the injector 8 is being executed is acquired (S42). In other words, the microphone sound S <b> 2 when the combustion is reliably performed in the combustion chamber 16 is acquired. The time when combustion is reliably performed in the combustion chamber 16 refers to the time when fuel of a predetermined value (for example, 10 mm ³ / st) or more is injected from the injector 8, for example. Further, the time when the amount of heat generation, which is an integrated value of the heat generation rate for each crank angle, is equal to or greater than a predetermined value may be a time when combustion is reliably performed in the combustion chamber 16.

  In S41 and S42, the engine speed is set to be the same. That is, the microphone sound S1 in the non-injection state and the microphone sound S2 in the injection execution state at the same engine speed are acquired (S41, S42). The “same engine speed” is intended to include not only the exact same engine speed but also some variation. For example, when two engine speeds NE1 and NE2 are assumed and the ratio NE1 / NE2 is 0.9 ≦ NE1 / NE2 ≦ 1.1, the speeds NE1 and NE2 are the same. And

  Thus, the engine speed is made the same for the following reason. That is, the combustion noise is generated every time combustion is performed in the combustion chamber 16, that is, is generated every time the engine rotates, and the combustion noise generated every time the engine rotates is transmitted to the vehicle interior. That is, the combustion noise transmitted to the vehicle interior correlates with the engine speed. More specifically, when the combustion noise is Fourier-transformed, the frequency determined by the engine speed becomes the fundamental frequency (primary component) of the combustion noise. Combustion noise can be expressed as a composite wave of a fundamental frequency component and a harmonic component. The harmonic component is inherently smaller than the fundamental frequency component and attenuates to a negligible level before being transmitted to the passenger compartment. Eventually, most of the combustion noise transmitted to the passenger compartment is a frequency component determined by the engine speed. Therefore, by making the engine speed the same and comparing the microphone sounds S1 and S2 in S43 and S44, which will be described later, it is possible to suppress a significant change in the frequency component due to combustion between the microphone sounds S1 and S2. As a result, it is possible to determine with high accuracy the degree of influence (dominance) of engine combustion on the room sound under the current engine operating conditions.

  On the other hand, comparing the microphone sound when the injection conditions are changed under different engine speed conditions, the microphone sound is compared when the engine operating conditions are completely different, and the engine combustion influence level is determined. Accuracy is reduced.

  Here, FIG. 10 illustrates the intensity of the microphone sounds S1 and S2 on a two-dimensional plane with the engine combustion intensity on the horizontal axis and the microphone sound intensity on the vertical axis. The engine combustion intensity on the horizontal axis can be replaced with the fuel injection amount.

  Next, an intensity difference ΔS (see also FIG. 10) between the microphone sounds S1 and S2 is calculated (S43). The intensities of the microphone sounds S1 and S2 are calculated by the sound intensity calculator 22 (see FIG. 1). This intensity difference ΔS correlates with the slope of the line 111 connecting the points S1 and S2 shown in FIG. In S43, the inclination of the line 111 itself may be calculated instead of the intensity difference ΔS. In this case, the difference ΔF (= F1) between the engine combustion intensity (= 0) in the microphone sound S1 and the engine combustion intensity F1 (fuel injection amount) in the microphone sound S2, and the intensity of the microphone sounds S1, S2 The difference ΔS is obtained, and the ratio ΔS / ΔF is obtained as the slope of the line 111. Thus, by obtaining the slope ΔS / ΔF, it is possible to obtain a highly accurate index indicating the influence degree of engine combustion excluding the influence of the engine combustion intensity F1 in the microphone sound S2. However, even when the intensity difference ΔS itself between the microphone sounds S1 and S2 is used as an index indicating the degree of influence of engine combustion, the acquisition condition (engine combustion intensity F1) of the microphone sound S2 is fixed. It is possible to suppress the difference ΔS from fluctuating due to the influence of the engine combustion strength F1.

  Next, it is determined whether the intensity difference ΔS is larger or smaller than a predetermined threshold value ΔS0 (S44). When the slope ΔS / ΔF is calculated in S43, it is determined in S44 whether the slope ΔS / ΔF is larger or smaller than a predetermined threshold. The threshold value ΔS0 corresponds to the first threshold value of the present invention.

  If the intensity difference ΔS or the slope ΔS / ΔF is larger than the threshold value (S44: Yes), it means that the intensity of the microphone sound changes greatly when the engine combustion state is changed. It is determined that the degree of influence of engine combustion is high (S45). That is, the microphone sound is determined to be dominant due to engine combustion.

  On the other hand, if the intensity difference ΔS or the slope ΔS / ΔF is smaller than the threshold value (S44: No), it means that the intensity of the microphone sound hardly changes even if the engine combustion state is changed. It is determined that the degree of influence of engine combustion on (room sound) is low (S46). That is, the microphone sound is determined to be dominant sound that is not caused by engine combustion. After S45 and S46, the process of FIG. 9 is terminated, and the process returns to the process of FIG.

  Returning to the description of the process of FIG. 5, after the process of S17 is executed, it is next determined based on the determination result of S17 whether the degree of influence of engine combustion on the room sound is high or low (S18). If it is determined in S45 of FIG. 9 that the degree of influence is high (S18: Yes), the basic target value of the heat generation rate is corrected so as to reduce the combustion noise (S19). As described with reference to FIG. 2, if the peak value of the heat generation rate decreases, the combustion noise decreases. Therefore, in S19, for example, the basic target value of the heat generation rate is corrected in a direction to decrease the peak value. The correction amount at this time may be a constant value regardless of the index indicating the degree of influence of engine combustion, that is, the value of the intensity difference ΔS or the inclination ΔS / ΔF, or the larger the intensity difference ΔS or the inclination ΔS / ΔF, the larger the correction amount. It may be set to a value. By changing the correction amount according to the intensity difference ΔS or the slope ΔS / ΔF, it is possible to set a target value of the optimum heat generation rate according to the degree of influence of engine combustion on the room sound, and as a result, suppression of the sensible combustion noise And better fuel economy can be realized more easily. Further, the target value may be reset based on the peak value of the actual heat generation rate obtained in S4 of FIG. In this case, a value (= B × K) obtained by multiplying the actual peak value B by a predetermined coefficient K smaller than 1 is set as a corrected target value. After S19, the process of FIG. 5 is terminated and the process returns to the process of FIG. In addition, ECU20 which performs the process of S19 is equivalent to the correction | amendment means of this invention.

  On the other hand, when the degree of influence of engine combustion on the room sound is low, that is, when it is determined that the degree of influence is low in S46 of FIG. 9 (S18: No), the process of FIG. 5 is terminated and the process of FIG. Return. In this case, the basic target value set in S11 is not corrected. That is, the basic target value is set as the final target value of the heat generation rate. In addition, ECU20 which performs the process of S17 and S18 corresponds to the determination means of this invention.

  Returning to the description of the process in FIG. 4, after the process of S5 is executed, the actual heat generation rate obtained in S4 is compared with the target value of the heat generation rate set in S5, and the actual heat generation is performed. It is determined whether the rate satisfies the target value (S6). For example, when the difference between the actual heat generation rate (peak value) and the target value (target peak value) is smaller than the threshold value, it is determined that the heat generation rate satisfies the target value, and the difference is larger than the threshold value. In this case, it is determined that the heat generation rate does not satisfy the target value.

  When the heat generation rate satisfies the target value, that is, when the peak value of the heat generation rate is equal to the target peak value (S6: Yes), the processing of FIG. In this case, combustion control (change of injection conditions) in a direction to reduce combustion noise is not performed.

  On the other hand, when the heat generation rate does not satisfy the target value, that is, when the peak value of the heat generation rate is larger than the target peak value (S6: No), the heat generation rate satisfies the target value. Thus, the injection condition is corrected (S7). That is, the injection condition is corrected in a direction that lowers combustion noise (for example, a direction that lowers the peak value of the heat generation rate). In addition, ECU20 which performs the process of S7 is equivalent to the adjustment means of this invention.

  The correction of the injection condition in the direction of reducing the combustion noise is known as described in Patent Document 1, but for example, when only the main injection is performed, the pilot injection is also performed, and the initial combustion is performed. Slows the increase in cylinder pressure. If pilot injection was originally performed, the pilot injection conditions (injection amount, injection timing, and injection pressure) are corrected in a direction that reduces combustion noise. At this time, the correction direction of whether to increase or decrease the injection amount, the correction direction to advance or retard the injection timing, and the correction direction to increase or decrease the injection pressure are the heat generation rate. It can be determined by feedback control that acts to reduce the difference between the target value and the target value. Similarly to Patent Document 1, when the maximum value of the change rate of the combustion pressure for pilot injection is larger than the target value, the pilot injection amount is corrected to decrease, and when the maximum value is less than the target value, pilot injection is performed. The amount may be corrected to increase.

  Further, in order to reduce the combustion noise, the injection conditions of the main injection may be corrected. For example, by correcting the injection timing of the main injection from the TDC to the retard side and separating the combustion from the TDC, the increase in the in-cylinder pressure at the initial stage of combustion can be slowed down, and as a result, the combustion noise can be reduced.

  If the target value of the heat generation rate is corrected in the process of S5, the actual heat generation rate does not satisfy the target value in S6, and the injection condition is corrected in S7. As a result, combustion noise can be reduced. On the other hand, when the target value is not corrected in the process of S5, it is easy to determine that the actual heat generation rate satisfies the target value in S6. In this case, since the injection condition is not corrected, the control for reducing the combustion noise is not performed. Further, when the target value is not corrected in the process of S5, even if control is performed to reduce the combustion noise because the actual heat generation rate does not satisfy the target value, the target value is corrected. In comparison, since the target value becomes loose, the degree of reducing the combustion noise can be suppressed. After S7, the process of FIG.

Here, FIG. 12 is a diagram for explaining a combustion noise control method in the present embodiment. As shown in FIG. 12 , the vehicle interior noise (T5) includes sounds (T4) that are not caused by engine combustion, such as running noise and wind noise, in addition to sounds caused by engine combustion (T1). . Therefore, in this embodiment, microphone sound level determination (T6, S14 in FIG. 5) as vehicle interior noise (T5), noise recognition level determination by the occupant (T7, S15 in FIG. 5), and engine for microphone sound Determination of the degree of influence of combustion (T8, S17 in FIG. 5) is performed. Then, the injection conditions are corrected based on not only the index value (peak value of the heat generation rate) correlated with the combustion noise obtained by processing the in-cylinder pressure signal (T2) but also the determination results of T6 to T8 ( T3).

  As a result, when the sensible combustion noise is low (when the microphone sound level is low, when the noise recognition level by the occupant is low, or when the influence of engine combustion is low), the target value of the combustion noise is set to improve fuel efficiency. Value D2 (see FIG. 3). Therefore, deterioration of fuel consumption can be suppressed while suppressing the passenger from feeling that the combustion noise is noisy.

  On the other hand, if the injection condition is corrected taking into consideration only the index (the peak value of the heat generation rate) that correlates with the combustion noise, the target value of the combustion noise (the peak value of the heat generation rate) Regardless, the high value D1 (see FIG. 3) is always set. In this case, the control for reducing the combustion noise is strongly executed even in a situation where the effectiveness of the control for reducing the combustion noise is low (for example, the situation where the room sound is dominated by the noise not caused by engine combustion). As a result, fuel consumption deteriorates.

  As described above, according to the present embodiment, the combustion noise is controlled based on the microphone sound (indoor sound) correlated with the combustion noise actually felt by the occupant, so that the occupant can hardly feel the combustion noise. At the same time, fuel consumption deterioration can be suppressed. Specifically, when the intensity of the room sound (microphone sound) is smaller than the threshold value (S14: No in FIG. 5), the target value of the heat generation rate is not corrected, so that it is more than necessary when the room sound is not noisy. In addition, the control of the combustion noise can be suppressed, and as a result, deterioration of fuel consumption can be suppressed.

  Further, even when the intensity of the room sound is greater than the threshold (S14: Yes), when the passenger is highly likely not to feel the room sound as noise (S16: No in FIG. 5), the rate of heat generation is increased. Since the target value is not corrected, it is possible to suppress the control of the combustion noise more than necessary when it is not felt as noise, and as a result, it is possible to suppress the deterioration of fuel consumption.

  In addition, even when the passenger is likely to feel the room sound as noise (S16: Yes), the sound that is not caused by engine combustion is the dominant sound (S18: No). ) Since the target value of the heat generation rate is not corrected, it is possible to suppress the control of the combustion noise more than necessary when the control of reducing the combustion noise is low, resulting in a deterioration in fuel consumption. Can be suppressed.

  In addition, the intensity of the room sound is large (S14: Yes), the passenger is highly likely to feel the room sound as noise (S16: Yes), and the room sound is dominated by the sound caused by engine combustion. If the noise is low (S18: Yes), the target value of the heat generation rate is corrected, so that the combustion noise can be reduced and the effectiveness of the control for reducing the combustion noise can be ensured.

  In addition, since it is determined whether or not there is a high possibility that the occupant feels the room sound as noise (determination in S15 in FIG. 5) based on the past behavior history (volume increase frequency) of the occupant, Differences in occupant personality, vehicle personality, and engine operating conditions can be reflected in the determination result.

  Further, in the determination of the degree of influence of engine combustion on the room sound (determination in S17 in FIG. 5), the conditions for fuel cut and the conditions for fuel injection are set. Is dominant, it is possible to increase the intensity change of the microphone sound between these conditions. As a result, the room sound can be determined with high accuracy whether or not the sound resulting from engine combustion is dominant.

In addition, this invention is not limited to the said embodiment, A various change is possible to the limit which does not deviate from description of a claim. For example, in the process of FIG. 9, the difference between the intensity of the microphone sound when the fuel injection is stopped and the intensity of the microphone sound when the fuel injection is performed is obtained. Instead, as shown in FIG. 11 , the microphone sound intensity S3 when the fuel is injected under the first injection condition F2 and the fuel under the second injection condition F3 different from the first injection condition. A difference ΔS1 from the microphone sound intensity S4 during the injection may be obtained, and the engine combustion influence degree may be determined based on the difference ΔS1. Even in this case, the engine speed is made the same when the strengths S3 and S4 are acquired.

  Further, as described above, the sound resulting from engine combustion is a sound having a frequency determined by the engine speed as a fundamental frequency (primary component). For example, when the engine speed of 1000 rpm (revolution per minute) is converted into the number of revolutions per second, it is about 17 rps (revolution per second), and this is expressed as 17 Hz. For example, when the engine speed of 4000 rpm is converted into the number of revolutions per second, it is about 67 Hz, and this is expressed as 67 Hz. Assuming that frequency components higher than the secondary component can be ignored, the sound resulting from engine combustion is a low frequency of a predetermined frequency (for example, 200 Hz) or less.

  Therefore, in order to determine whether the room sound is dominant due to engine combustion, the microphone sound signal (time change) is subjected to FFT analysis as shown in FIG. The degree of influence of engine combustion may be determined based on the ratio of the area (hatched portion in the lower diagram of FIG. 13) of the spectrum section below a predetermined frequency f0 (for example, 200 Hz) to the total section area of the obtained spectrum. For example, when the ratio is larger than the threshold value, it is determined that the room sound is dominant due to engine combustion (the degree of influence of engine combustion on the room sound is high). On the other hand, when the ratio is smaller than the threshold value, it is determined that the sound not caused by engine combustion is dominant (the degree of influence of engine combustion on the room sound is low). This makes it possible to determine the degree of influence of engine combustion on room noise without changing the state of engine combustion.

  Further, in S14 of FIG. 5, it was determined whether or not the intensity of the microphone sound is larger than the threshold. However, the intensity of the frequency component resulting from engine combustion by FFT analysis from the microphone sound acquired in S12, that is, FIG. The area of the hatched portion in the figure below may be obtained and it may be determined whether or not the area is larger than a threshold value. As a result, it can be determined whether the noise caused by engine combustion transmitted to the passenger compartment is loud or small, so that the combustion noise actually felt by the occupant can be more easily reflected in the combustion control.

  In the above embodiment, the combustion noise is controlled by controlling the peak value of the heat generation rate as an index correlated with the combustion noise. However, an index (for example, an in-cylinder pressure waveform) correlated with the combustion noise other than the peak value. The combustion noise may be controlled by controlling the peak value of the time differential value and the integrated value (heat generation amount) of the heat generation rate.

  Further, in the above embodiment, microphone sound level determination (S14 in FIG. 5), determination of noise recognition level by the occupant (S15, S16 in FIG. 5), and determination of the degree of influence of engine combustion on room sound (S17 in FIG. 5). However, only one or only two of these three determinations may be implemented. That is, in the process of FIG. 5, the process of S14 may be omitted, the processes of S15 and S16 may be omitted, the processes of S17 and S18 may be omitted, or the processes of S14 to S16. May be omitted, the processes of S14, S17, and S18 may be omitted, or the processes of S15 to S18 may be omitted. This also allows the body sensation to be reflected in the control of combustion noise.

  In the process of FIG. 5, when all of the processes of S14, S16, and S18 are affirmative determination, the target value of the heat generation rate is corrected, but either one or two of these processes are affirmed. In the case of determination, the correction may be performed. For example, if the determination in S16 is affirmative, that is, if the passenger's noise recognition level is high, the target value of the heat generation rate may be corrected regardless of the degree of influence of engine combustion on the room sound. As a result, the heat generation rate can be easily corrected, so that it is possible to further make the occupant less susceptible to combustion noise.

  Further, in the process of FIG. 5, when the intensity of the microphone sound is larger than the threshold value (S14: Yes) and the noise recognition level by the occupant is high (S16: Yes), the engine combustion influence degree is determined. Alternatively, if the intensity of the microphone sound is greater than the threshold, the degree of influence of engine combustion may be determined regardless of the noise recognition level by the occupant. If the noise recognition level by the occupant is high, the microphone sound You may determine the influence degree of engine combustion irrespective of intensity | strength. That is, the process of S17 may be executed when either the process of S14 or the process of S16 is affirmed.

1 Diesel engine (internal combustion engine)
20 ECU
23 Sound collector

Claims (10)

A sound collecting device (23) installed in a vehicle interior;
Noise control means (20, S1 to S7) for controlling the combustion noise of the internal combustion engine (1) mounted on the vehicle based on the room sound which is the sound obtained by the sound collector;
Equipped with a,
The noise control means includes determination means (S17, S18) for determining a change in the room sound when the combustion state of the internal combustion engine is changed as an influence degree of the combustion of the internal combustion engine on the room sound. And controlling the combustion noise of the internal combustion engine based on the degree of influence . The determination means determines, as the influence level, a change between the room sound when the fuel injection of the internal combustion engine is stopped and the room sound when the fuel injection of the internal combustion engine is executed. The control apparatus for an internal combustion engine according to claim 1 , wherein the control apparatus is an internal combustion engine. The determination means according to claim 1 or 2, characterized in that to determine the change in the indoor sound when the varying combustion state of the internal combustion engine the rotational speed as the same engine as the influence Control device for internal combustion engine. The noise control means is
Obtaining means (11, S3) for obtaining an in-cylinder pressure of the internal combustion engine;
Calculation means (S4) for calculating an index correlated with combustion noise of the internal combustion engine based on the in-cylinder pressure acquired by the acquisition means;
Adjusting means (S7) for adjusting an injection condition of fuel injected into the combustion chamber of the internal combustion engine so that the index becomes a target value;
Correcting means for correcting the target value in a direction to lower the combustion noise when the influence degree is larger than the first threshold value, and stopping the correction of the target value when the influence degree is smaller than the first threshold value. The control apparatus for an internal combustion engine according to any one of claims 1 to 3, further comprising (S19). The correction means corrects the target value when the intensity of the room sound is greater than a second threshold and the influence is greater than the first threshold, and the intensity of the room sound is less than the second threshold. 5. The control device for an internal combustion engine according to claim 4 , wherein the correction of the target value is stopped when the influence degree is smaller than the first threshold value. The noise control means stores a change history indicating the frequency of changing the volume of the acoustic device (24) installed in the vehicle room in the direction in which the volume is increased, in association with the operating condition of the internal combustion engine when the volume is changed. Storage control means (S31, S32) to be stored in the means (21),
The correction means is when the current frequency, which is the frequency stored in the storage means in association with the current operating condition of the internal combustion engine, is greater than a third threshold and the influence is greater than the first threshold. It corrects the target value, the in the case when the frequency is less than the third threshold value or the impact time is less than the first threshold value according to claim 4, characterized in that to stop the correction of the target value Control device for internal combustion engine. The noise control means is
Obtaining means (11, S3) for obtaining an in-cylinder pressure of the internal combustion engine;
Calculation means (S4) for calculating an index correlated with combustion noise of the internal combustion engine based on the in-cylinder pressure acquired by the acquisition means;
Adjusting means (S7) for adjusting an injection condition of fuel injected into the combustion chamber of the internal combustion engine so that the index becomes a target value;
When the intensity of the room sound is larger than the second threshold value, the target value is corrected so as to reduce the combustion noise, and when the intensity of the room sound is smaller than the second threshold value, the correction of the target value is stopped. The control device for an internal combustion engine according to claim 1, further comprising correction means (S19). A sound collecting device (23) installed in a vehicle interior;
Noise control means (20, S1 to S7) for controlling the combustion noise of the internal combustion engine (1) mounted on the vehicle based on the room sound which is the sound obtained by the sound collector;
With
The noise control means is
The noise control means includes determination means (S17, S18) for determining the degree of influence of combustion of the internal combustion engine on the room sound,
Obtaining means (11, S3) for obtaining an in-cylinder pressure of the internal combustion engine;
Calculation means (S4) for calculating an index correlated with combustion noise of the internal combustion engine based on the in-cylinder pressure acquired by the acquisition means;
Adjusting means (S7) for adjusting an injection condition of fuel injected into the combustion chamber of the internal combustion engine so that the index becomes a target value;
When the room sound intensity is greater than the second threshold and the influence is greater than the first threshold, the target value is corrected in a direction to reduce the combustion noise, and the room sound intensity is less than the second threshold. The control apparatus for an internal combustion engine, further comprising: correction means (S19) for stopping the correction of the target value when the influence or the influence degree is smaller than the first threshold value . A sound collecting device (23) installed in a vehicle interior;
Noise control means (20, S1 to S7) for controlling the combustion noise of the internal combustion engine (1) mounted on the vehicle based on the room sound which is the sound obtained by the sound collector;
With
The noise control means is
Determination means (S17, S18) for determining the degree of influence of combustion of the internal combustion engine on the room sound;
Obtaining means (11, S3) for obtaining an in-cylinder pressure of the internal combustion engine;
Calculation means (S4) for calculating an index correlated with combustion noise of the internal combustion engine based on the in-cylinder pressure acquired by the acquisition means;
Adjusting means (S7) for adjusting an injection condition of fuel injected into the combustion chamber of the internal combustion engine so that the index becomes a target value;
A change history indicating the frequency of changing the volume of the acoustic device (24) installed in the interior of the vehicle in the increasing direction is stored in the storage means (21) in association with the operating condition of the internal combustion engine when the volume is changed. Storage control means (S31, S32),
Correcting means for correcting the target value in a direction to lower the combustion noise when the influence degree is larger than the first threshold value, and stopping the correction of the target value when the influence degree is smaller than the first threshold value. (S19),
The target value is corrected when the current frequency, which is the frequency stored in the storage means in association with the current operating condition of the internal combustion engine, is greater than a third threshold and the influence is greater than the first threshold. And a correction means (S19) for stopping the correction of the target value when the current frequency is smaller than the third threshold or when the influence is smaller than the first threshold . Control device. A sound collecting device (23) installed in a vehicle interior;
Noise control means (20, S1 to S7) for controlling the combustion noise of the internal combustion engine (1) mounted on the vehicle based on the room sound which is the sound obtained by the sound collector;
With
The noise control means is
Obtaining means (11, S3) for obtaining an in-cylinder pressure of the internal combustion engine;
Calculation means (S4) for calculating an index correlated with combustion noise of the internal combustion engine based on the in-cylinder pressure acquired by the acquisition means;
Adjusting means (S7) for adjusting an injection condition of fuel injected into the combustion chamber of the internal combustion engine so that the index becomes a target value;
A change history indicating the frequency of changing the volume of the acoustic device (24) installed in the interior of the vehicle in the increasing direction is stored in the storage means (21) in association with the operating condition of the internal combustion engine when the volume is changed. Storage control means (S31, S32),
When the current frequency, which is the frequency stored in the storage means in association with the current operating condition of the internal combustion engine, is greater than a third threshold value, the target value is corrected in a direction to reduce the combustion noise, and the current time A control device for an internal combustion engine, comprising: correction means (S19) for stopping correction of the target value when the frequency is smaller than the third threshold value .

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