JP4974630B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control device for an internal combustion engine.

  As a technique for reducing combustion noise of a diesel internal combustion engine, a technique for performing pilot injection prior to main injection, which is main fuel injection, is known. By performing pilot injection, preliminary combustion with pilot injected fuel is performed prior to main injection, and main injection is performed there. Therefore, the main injected fuel burns in a state with little ignition delay, and is moderately overall. Combustion is achieved. As a result, the change in the in-cylinder pressure (combustion chamber pressure) accompanying the combustion of the main injected fuel becomes slow, so that the combustion noise due to the combustion of the main injected fuel is reduced.

Patent Document 1 includes a sensor for measuring combustion noise in an internal combustion engine that performs pilot injection. When the measured combustion noise deviates from a predetermined target noise, a pilot injection amount or a pilot interval (pilot injection) A technique is disclosed in which feedback control is performed so as to make combustion noise coincide with target noise by manipulating fuel injection parameters related to pilot injection, such as an interval between timing and main injection timing.
Japanese Patent Publication No. 7-78376 JP 2001-227393 A JP 2000-120487 A JP 2005-282441 A JP 2002-276444 A JP 2003-286876 A

  By the way, the actual fuel injection amount may deviate from the fuel injection command value for the fuel injection valve due to deterioration of the fuel injection valve over time, variation in fuel injection characteristics, or the like. In this case, the pilot injection amount is too small to sufficiently obtain the effect of slowing down the combustion of the main injection fuel, or conversely, the pilot injection amount is excessive and the combustion noise caused by the combustion of the pilot injection fuel is not obtained. There is a risk of becoming larger.

  Even if the pilot injection amount is appropriate, for example, when the temperature of the internal combustion engine is low such as during cold start, the ignitability of the fuel is reduced, so that the pilot injected fuel does not burn well and the main injected fuel There is a possibility that the effect of slowing down combustion cannot be obtained.

  As described above, even if pilot injection is performed, it is difficult to accurately control combustion noise unless combustion with the pilot injected fuel is actually performed appropriately.

  However, in the above prior art, since there is no means for acquiring the combustion state in the actual internal combustion engine, when the measured combustion noise deviates from the target noise, it is caused by excessive or insufficient pilot injection amount. It was not possible to determine whether this was due to poor combustion of the pilot injected fuel or due to other factors.

  For this reason, it is difficult to select the optimal fuel injection parameter to match the combustion noise with the target noise, and to determine the operation direction and operation amount of the selected fuel injection parameter. There was a possibility that I could not.

  The present invention has been made in view of such problems, and provides a technique that enables combustion noise to be controlled with higher accuracy in an internal combustion engine that controls combustion noise by performing pilot injection. Objective.

In order to achieve the above object, a fuel injection control device for an internal combustion engine according to the present invention can perform pilot injection prior to main injection, which is main fuel injection, and noise detection means for estimating or detecting combustion noise of the internal combustion engine. Fuel injection means, combustion state detection means for estimating or detecting the combustion state of the actual pilot injection fuel of the internal combustion engine, and combustion noise due to combustion of the main injection fuel estimated or detected by the noise detection means is a predetermined target to match the noise, the pilot injection quantity based on the combustion state of the pilot injection fuel in the internal combustion engine which is estimated or detected by said combustion state detecting means, the interval between the pilot injection timing and main injection timing, and the pilot injection frequency and operating at this priority, the operation of the fuel injection parameters according to the pilot injection to a predetermined operation limit If still the combustion noise and cracking does not match the target noise is characterized by comprising control means for operating the fuel injection parameters according to the main injection, the.

  Here, the “predetermined target noise” is a target value of the combustion noise of the internal combustion engine, and is determined in advance by experiments or the like. Further, “the combustion noise matches the target noise” means that the absolute value of the difference between the combustion noise and the target noise is a value within a predetermined allowable range. The “fuel injection parameter related to pilot injection and / or main injection” is a fuel injection command value for the fuel injection means. For example, the pilot injection amount, the pilot injection timing, the number of pilot injections, and the pilot injection are performed a plurality of times. In this case, the pilot injection interval, the interval between the pilot injection timing and the main injection timing (hereinafter referred to as “pilot interval”), the main injection amount, the main injection timing, and the like can be exemplified.

  According to the above configuration, the combustion state detection means can estimate or detect (hereinafter simply referred to as “detection”) the actual combustion state of the fuel injected by the fuel injection means in the internal combustion engine. When the combustion noise estimated or detected by the engine (hereinafter simply referred to as “detection”) deviates from the target noise, the deviation is caused by any combustion state of the pilot injected fuel or the main injected fuel. It can be determined whether there is.

  Thereby, in order to make the combustion noise coincide with the target noise, it is possible to select an optimal fuel injection parameter as an operation target, and to determine an optimal operation direction and operation amount of the selected fuel injection parameter. As a result, the combustion noise can be controlled with higher accuracy.

  For example, it is assumed that when combustion noise larger than the target noise is detected by the noise detection means, the combustion state detection means detects that the combustion by the pilot injected fuel is in a predetermined poor combustion state.

  Here, the “predetermined defective combustion state” is a combustion state in which the pilot injected fuel does not burn well and the combustion of the main injected fuel cannot be sufficiently slowed down, and is determined in advance by experiments or the like. . The poor combustion state includes a case where the pilot injection fuel is misfired and not combusting.

  When a poor combustion state of the pilot injected fuel is detected, it can be determined that the detection of the combustion noise larger than the target noise is caused by at least the pilot injection amount being too small. Therefore, it is possible to select to increase the pilot injection amount from the previous pilot injection amount as the optimum fuel injection parameter operation for matching the combustion noise with the target noise (in this case, reducing the combustion noise). .

By increasing the pilot injection amount in the next cycle, the pilot injected fuel will burn well, so the change in in-cylinder pressure accompanying the combustion of the main injected fuel will be slowed down and the combustion noise will be reduced Can do.

  On the other hand, it is assumed that when the combustion noise larger than the target noise is detected by the noise detection means, the combustion state detection means detects that the combustion by the pilot injected fuel is in a predetermined excessive combustion state.

  Here, the “predetermined excessive combustion state” is a state in which the pilot injected fuel burns abruptly and combustion noise due to the combustion of the pilot injected fuel increases beyond an allowable range. The permissible range of the combustion noise due to the combustion of the pilot injected fuel is determined in advance by experiments or the like.

  When the excessive combustion state of the pilot injected fuel is detected, it can be determined that the detection of the combustion noise larger than the target noise is caused by at least the pilot injection amount being excessive. Therefore, it is possible to select to reduce the pilot injection amount from the previous pilot injection amount as the optimum fuel injection parameter operation for making the combustion noise coincide with the target noise (in this case, reducing the combustion noise). .

  By reducing the pilot injection amount in the next cycle, the pilot injected fuel is appropriately combusted, so that the combustion noise caused by the combustion of the pilot injected fuel is within the allowable range, and the combustion of the pilot injected fuel The change in the in-cylinder pressure accompanying the combustion of the main injection fuel is moderated, and the combustion noise can be reduced.

  Further, although the combustion state detection means detects that the combustion by the pilot injection fuel is a good combustion state that is neither the poor combustion state nor the excessive combustion state, the combustion noise larger than the target noise is still noise. Suppose that it was detected by the detection means.

  Here, “a good combustion state that is neither a poor combustion state nor an excessive combustion state” means that combustion of the main injected fuel is suitably slowed by the combustion of the pilot injected fuel, and combustion noise caused by the combustion of the pilot injected fuel Is in an acceptable range. In other words, the fuel injection is performed in accordance with the fuel injection parameters including the pilot injection amount that makes the combustion noise as a function of the pilot injection amount a value near the minimum value, and is determined in advance by experiments or the like.

  When a good combustion state of the pilot injected fuel is detected, it can be determined that the detection of the combustion noise larger than the target noise is not caused by excess or deficiency of the pilot injection amount. That is, it can be determined that the combustion noise is controlled to a minimum value with respect to the control of the combustion noise by manipulating the pilot injection amount.

  Therefore, in this case, if the pilot injection amount is increased as an operation of the fuel injection parameter, the pilot injection amount becomes excessive and combustion noise may increase. Similarly, if the pilot injection amount is reduced, the pilot injection amount may become too small, and combustion noise may also increase.

  That is, it is difficult to further reduce the combustion noise by manipulating the pilot injection amount. Therefore, in this case, the present invention selects to shorten the pilot interval as the operation of the optimum fuel injection parameter for making the combustion noise coincide with the target noise (in this case, reducing the combustion noise).

By shortening the pilot interval in the next cycle, the combustion of the pilot injected fuel comes close to the main injection timing, so that the main injected fuel is burned with little ignition delay. Thereby, the change of the in-cylinder pressure accompanying the combustion of the main injection fuel is slowed down, and the combustion noise can be reduced.

  Further, although the combustion state detecting means detects that the interval between the combustion by the pilot injected fuel and the combustion by the main injected fuel is a value within a predetermined range, the combustion noise that is still larger than the target noise Is detected by the noise detection means.

  Here, “the state where the interval between the combustion by the pilot injected fuel and the combustion by the main injected fuel is a value within a predetermined range” means that the combustion of the pilot injected fuel is too far from the main injection timing and the ignition delay of the main injected fuel is delayed. Is not sufficiently reduced, or the combustion of pilot injected fuel is too close to the main injection timing and integrated with the combustion of main injected fuel. This is a state in which the pilot-injected fuel is burned at a timing such that the initial combustion is suitably slowed down. In other words, a pilot injection amount that makes the combustion noise as a function of the pilot injection amount a value near the minimum value, a pilot interval that makes the combustion noise as a function of the pilot interval a value near the minimum value, and Is in a state in which fuel injection is performed according to fuel injection parameters including, and is determined in advance by experiments or the like.

  When it is detected that the interval between the combustion by the pilot injected fuel and the combustion by the main injected fuel is a value within a predetermined range, it is detected that the combustion noise larger than the target noise is detected. It can be determined that it is not caused by a shortage or a pilot interval being too long or too short. That is, regarding the control of the combustion noise by the operation of the pilot injection amount and the operation of the pilot interval, it can be determined that the combustion noise is controlled to a minimum value.

  Therefore, in this case, if the pilot injection amount is increased or decreased as the operation of the fuel injection parameter, there is a possibility that the pilot injection amount becomes excessive or excessive and combustion noise increases. Similarly, if the pilot interval is shortened or extended, the combustion by the pilot injected fuel and the main injection timing will be too close or too far apart, which may also increase the combustion noise.

  That is, it is difficult to further reduce the combustion noise by operating the pilot injection amount or the pilot interval. Therefore, in this case, the present invention selects to increase the number of pilot injections as the optimum fuel injection parameter operation for making the combustion noise coincide with the target noise (in this case, reducing the combustion noise).

  By increasing the number of pilot injections in the next cycle, the change in the in-cylinder pressure associated with the combustion of the main injected fuel is further slowed down, and the combustion noise can be reduced.

  Further, it is assumed that the combustion noise larger than the target noise is detected by the noise detection means even though the number of pilot injections is equal to or greater than the predetermined upper limit number.

  Here, the “predetermined upper limit number of times” is the number of times of combustion of pilot injected fuel that cannot effectively slow down the change in in-cylinder pressure due to combustion of the main injected fuel by combustion of pilot injected fuel beyond that. Therefore, it is obtained in advance by experiments or the like.

  In this case, regarding the control of the combustion noise by manipulating the number of pilot injections, it is considered that the combustion noise is controlled to a minimum value.

Therefore, it is difficult to further reduce the combustion noise by operating the number of pilot injections. Therefore, in this case, in the present invention, the operation of the fuel injection parameter related to the main injection is selected as the operation of the optimal fuel injection parameter for matching the combustion noise with the target noise (in this case, reducing the combustion noise).

  The case where the fuel injection parameter is manipulated to reduce the combustion noise when the combustion noise detected by the noise detection means is larger than the target noise has been described. In order to increase the combustion noise when the combustion noise is smaller than the target noise. It is also conceivable to manipulate the fuel injection parameters.

  For example, if the combustion state of the fuel in the internal combustion engine is poor and the combustion noise is excessively low, the combustion noise will fluctuate greatly when the combustion noise becomes the target noise in the next and subsequent cycles, and the combustion noise Even if the noise itself matches the target noise, there is a possibility that the noise around the vehicle and the audible noise for the passenger may be felt greatly. In such a case, the operation of the fuel injection parameter for increasing the combustion noise is performed in order to make the combustion noise coincide with the target noise.

  Even when the combustion noise is increased, the combustion noise can be controlled with higher accuracy by manipulating the fuel injection parameter based on the actual combustion state of the fuel in the internal combustion engine.

  For example, when combustion noise smaller than the target noise is detected by the noise detection means, it is detected by the combustion state detection means that the combustion by the pilot injected fuel is in a good combustion state that is neither the poor combustion state nor the excessive combustion state. In this case, select the operation to increase or decrease the pilot injection amount from the previous pilot injection amount as the optimal fuel injection parameter operation to match the combustion noise to the target noise (in this case, increase the combustion noise) can do.

  When the pilot injection amount is increased in the next cycle, the combustion by the pilot injected fuel becomes the excessive combustion state, and the combustion noise increases. Further, when the pilot injection amount is reduced in the next cycle, the combustion by the pilot injection fuel becomes the combustion failure state, so that the combustion noise due to the combustion of the main injection fuel becomes large.

  Further, when the combustion state detection means detects that the combustion by the pilot injection fuel is in the excessive combustion state, but the combustion noise smaller than the target noise is detected by the noise detection means, the combustion is detected. As an operation of the optimal fuel injection parameter for matching the noise to the target noise (in this case increasing the combustion noise), it is possible to choose to extend the pilot interval.

  When the pilot interval is extended in the next cycle, the combustion of the pilot injected fuel departs from the main injection timing, so that the effect of slowing the initial combustion of the main injected fuel by the combustion of the pilot injected fuel is weakened, and the combustion noise increases. .

  Further, although the combustion state detecting means detects that the combustion state in which the interval between the combustion with the pilot injected fuel and the combustion with the main injected fuel is a value exceeding the predetermined range, the target noise is still exceeded. If small combustion noise is detected by the noise detection means, reduce the number of pilot injections as the optimal fuel injection parameter operation to match the combustion noise to the target noise (in this case increase the combustion noise) Can be selected.

By reducing the number of pilot injections in the next cycle, the effect of slowing down the initial combustion of the main injected fuel by the combustion of the pilot injected fuel is weakened, and the combustion noise is increased.

  Further, when the number of pilot injections is zero, that is, when combustion noise smaller than the target noise is detected by the noise detection means even though the pilot injection is stopped, the combustion noise is matched with the target noise. As the operation of the optimal fuel injection parameter for increasing the combustion noise in this case, the operation of the fuel injection parameter related to the main injection can be selected.

  The present invention relates to an internal combustion engine capable of switching the combustion mode of the internal combustion engine to the diffusion combustion mode or the premixed combustion mode by changing the fuel injection parameter in accordance with the operating state of the internal combustion engine. It can be applied to control of combustion noise.

  In general, in the diffusion combustion mode, main injection is performed near the compression top dead center, and pilot injection is performed earlier than the main injection. On the other hand, in the premixed combustion mode, only main injection is performed earlier than the compression top dead center, and a larger amount of EGR gas is introduced than in the diffusion combustion mode. Thus, not only the fuel injection parameters but also the EGR gas amount greatly differs between the diffusion combustion mode and the premixed combustion mode.

  Here, the amount of EGR gas is generally regulated by adjusting the opening degree of a flow rate adjusting valve (hereinafter referred to as “EGR valve”) provided in the EGR passage. Since the EGR passage is provided outside the intake / exhaust system so as to connect the intake pipe and the exhaust pipe, the path length of the EGR gas flow path from the EGR valve to the cylinder (combustion chamber) of the internal combustion engine is relatively long. Therefore, the amount of EGR gas actually flowing into the cylinder after the EGR valve opening is changed to the target opening corresponding to the switching destination combustion mode in accordance with the switching of the combustion mode is the target EGR gas of the switching destination combustion mode. There is a delay before changing to a quantity.

  On the other hand, the actual fuel injection parameter value becomes the target value of the switching destination combustion mode after the injection command value for the fuel injection valve is changed to the target value corresponding to the switching destination combustion mode with the switching of the combustion mode. The response time when changing is very short.

  Therefore, at the time of transition when the combustion mode is switched, the fuel injection parameter is not appropriate for the amount of EGR gas recirculated in the cylinder, the combustion noise becomes excessive due to rapid combustion, or combustion failure occurs, resulting in combustion noise. There is a possibility that the fluctuation range of will become large.

  In contrast, by applying the present invention, the combustion state detection means detects that the combustion noise detected by the noise detection means coincides with a predetermined target noise during a transition in which the internal combustion engine shifts to a different combustion mode. Based on the actual engine combustion state, the change of the fuel injection parameters related to the pilot injection and / or the main injection when the combustion mode is switched can be controlled.

  As a result, the optimum operation target of the fuel injection parameter for controlling the combustion noise to the target noise is selected, and the operation direction and operation amount thereof are determined based on the change in the combustion state due to the change in the fuel injection parameter and the EGR gas amount. can do. As a result, it is possible to more accurately control the combustion noise in the transition period in which the combustion mode is switched.

  The present invention makes it possible to control combustion noise of an internal combustion engine with higher accuracy.

  The best mode for carrying out the present invention will be exemplarily described in detail below 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.

<Configuration of internal combustion engine>
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the fuel injection control device for an internal combustion engine according to this embodiment is applied, and its intake and exhaust systems. The internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine. A piston 3 is slidably inserted into the cylinder 5 of the internal combustion engine 1, and a combustion chamber 2 is defined and formed by the upper surface of the piston 3 and the inner wall of the cylinder 5. A fuel injection valve 6 that directly injects fuel into the combustion chamber 2 is provided at the upper portion of the combustion chamber 2.

  The combustion chamber 2 communicates with the intake pipe 22 via the intake port 20. Further, the combustion chamber 2 communicates with an exhaust pipe 32 via an exhaust port 30. The cylinder 5 is provided with an intake valve 23 that opens and closes an opening at a connection point between the combustion chamber 2 and the intake port 20, and an exhaust valve 33 that opens and closes an opening at a connection point between the combustion chamber 2 and the exhaust port 30. It has been.

  The internal combustion engine 1 is provided with an EGR device 40 that recirculates part of the exhaust gas to the combustion chamber 2. The EGR device 40 includes an EGR passage 41 and an EGR valve 42. The EGR passage 41 is a passage connecting the exhaust pipe 32 and the intake pipe 22, and part of the exhaust gas flowing through the exhaust pipe 32 through the EGR passage 41 flows into the intake pipe 22 and passes through the intake port 20 to the combustion chamber. 2 is inhaled. In this embodiment, the exhaust gas recirculated to the combustion chamber 2 by the EGR device 40 is referred to as EGR gas. The EGR valve 42 is a flow rate adjustment valve that can change the amount of EGR gas flowing through the EGR passage 41 by changing the flow passage cross-sectional area of the EGR passage 41. The amount of EGR gas can be adjusted by adjusting the opening degree of the EGR valve 42.

  In addition to adjusting the opening degree of the EGR valve 42 as a method for adjusting the EGR gas amount, the opening degree of the nozzle vane for changing the flow rate characteristic of the turbine in the configuration having the variable displacement turbocharger is adjusted. Or a method of adjusting the opening of the exhaust throttle valve or the intake throttle valve in the configuration having the exhaust throttle valve in the exhaust pipe 32 or the configuration having the intake throttle valve in the intake pipe 22.

  The internal combustion engine 1 is provided with an electronic control unit (ECU) 8 that controls the engine. The ECU 8 is a bidirectional bus for read only memory (ROM), random access memory (RAM), central processing unit (CPU), input / output port, digital / analog converter (DA converter), analog / digital converter (AD converter), etc. It is configured as a microcomputer having a known configuration connected in the above.

The ECU 8 performs various basic controls known in the diesel engine, such as controlling the fuel injection amount and fuel injection timing by the fuel injection valve 6 in accordance with the operating state of the internal combustion engine 1 and the request from the driver. Therefore, the internal combustion engine 1 in this embodiment includes a water temperature sensor 70 that detects the coolant temperature Tw of the internal combustion engine 1, a crank position sensor 71 that detects the rotational phase (crank angle) θ of the crankshaft of the internal combustion engine 1, An accelerator opening sensor 72 that detects the amount of depression of the accelerator pedal 7 (accelerator opening) Accp by the driver, an intake air temperature sensor 73 that detects the temperature Tin of fresh air flowing into the intake pipe 22, and a new that flows into the intake pipe 22 An air flow meter 75 for detecting the air flow rate Min, an in-cylinder pressure sensor 74 for detecting the pressure P of the gas in the combustion chamber 2 (hereinafter also referred to as “in-cylinder pressure”), and an oxygen concentration Ro (hereinafter referred to as “gas concentration”) of the gas in the combustion chamber 2. In-cylinder oxygen concentration sensor 76 for detecting the in-cylinder oxygen concentration), combustion noise sensor 77 for detecting the combustion noise CN of the internal combustion engine 1 Speed sensor 78 for detecting a rotational speed Ne, is provided. In addition, although illustration and description are omitted in particular, sensors that are generally provided in a diesel engine are provided.

  These sensors are connected to the ECU 8 through electrical wiring, and output signals from the sensors are input to the ECU 8.

  The ECU 8 is connected to devices such as a drive device for driving the fuel injection valve 6, the EGR valve 42, the intake valve 23, and the exhaust valve 33 through electric wiring, and these devices are controlled according to control signals output from the ECU 8. Are controlled.

  ECU8 grasps | ascertains the driving | running state of the internal combustion engine 1, and a driver | operator's request | requirement based on the detection value by each sensor. For example, the ECU 8 detects the operating state of the internal combustion engine 1 based on the engine speed Ne input from the speed sensor 78 and the engine load calculated from the accelerator opening Accp input from the accelerator opening sensor 72. Then, the combustion mode and combustion noise of the internal combustion engine 1 are controlled by controlling the fuel injection valve 6, the EGR valve 42, and the like based on the detected engine operating state, the driver's request, and the like.

<Combustion noise and multi-injection>
Here, the fuel injection valve 6 provided in the internal combustion engine 1 of the present embodiment is capable of performing a plurality of fuel injections (hereinafter also referred to as “multi-injection”) during one cycle. In this embodiment, in order to control the combustion noise of the internal combustion engine 1 to a predetermined target noise, in addition to the main injection that is the main fuel injection, one or more pilot injections are performed prior to the main injection. 6 is performed.

  By performing pilot injection, preliminary combustion with pilot injected fuel is performed prior to main injection, and the state in the combustion chamber (in-cylinder temperature and in-cylinder pressure) becomes a state suitable for combustion of the main injected fuel. Therefore, the main injection fuel burns in a state with little ignition delay, and gentle combustion is performed as a whole. As a result, the change in the in-cylinder pressure accompanying the combustion of the main injected fuel becomes slow, so that the combustion noise due to the combustion of the main injected fuel is reduced.

  On the other hand, when the pilot injection amount is decreased or pilot injection is not performed, the change in the in-cylinder pressure accompanying the combustion of the main injected fuel becomes steep, and the combustion noise due to the combustion of the main injected fuel increases.

  Thus, the internal combustion engine is operated by manipulating the fuel injection parameters (pilot injection amount, pilot injection timing, pilot interval, pilot injection frequency, pilot injection interval, main injection amount, main injection timing, etc.) relating to pilot injection and main injection. The combustion noise of the engine 1 can be controlled to a desired target noise.

  In this embodiment, the ECU 8 sets the target value of the fuel injection parameter according to the operating state of the internal combustion engine 1, and controls the fuel injection valve 6 according to the set fuel injection parameter, thereby executing multi-injection and combustion. Control the noise.

<Conventional problems>
By the way, the actual fuel injection amount may deviate from the fuel injection command value to the fuel injection valve 6 by the ECU 8 due to deterioration with time of the fuel injection valve 6 or variations in fuel injection characteristics. In this case, the actual pilot injection amount is less than the target pilot injection amount, so that the effect of slowing down the combustion of the main injected fuel cannot be obtained sufficiently, or conversely, the actual pilot injection amount is the target pilot injection amount. There is a possibility that the combustion noise resulting from the combustion of the pilot injected fuel becomes larger than that.

  Further, even if the pilot injection amount is appropriate, when the temperature of the internal combustion engine 1 is low, such as during cold start, the ignitability of the fuel decreases, so the pilot injected fuel does not burn well and the main There may be a case where the effect of slowing the combustion of the injected fuel is not obtained. In this case, although only the fuel injected by the main injection is actually burned even though the pilot injection is being performed, the in-cylinder pressure suddenly changes and combustion larger than the target noise occurs. Noise may be generated.

  As described above, even if pilot injection is performed, it is difficult to accurately control the combustion noise to the target noise unless the combustion by the pilot injected fuel is actually performed suitably.

<Example>
Therefore, in this embodiment, the actual combustion state in the combustion chamber 2 of the fuel injected by the fuel injection valve 6 is detected, and the fuel injection parameter is operated based on the detected combustion state. Thereby, when the combustion noise deviates from the target noise, it is possible to determine what combustion state of the pilot injection fuel or the main injection fuel caused the deviation. Thereby, in order to control the combustion noise to the target noise, it is possible to select an optimal fuel injection parameter as an operation target, and to determine an optimal operation direction and operation amount of the selected fuel injection parameter. As a result, the combustion noise can be controlled with higher accuracy.

  Hereinafter, the combustion noise control in the present embodiment will be described in detail.

<Detection of combustion state>
First, a method for detecting the actual combustion state of combustion in the combustion chamber 2 of the internal combustion engine 1 will be described. In this embodiment, the combustion state of the fuel is estimated based on the in-cylinder pressure detected by the in-cylinder pressure sensor 74.

  FIG. 2 is a diagram showing temporal changes in the compression stroke and the expansion stroke of the in-cylinder pressure. FIG. 3 is a diagram showing a time change in the compression stroke and the expansion stroke in the increment of the in-cylinder pressure. 4 and 5 are diagrams showing temporal changes in the compression stroke and the expansion stroke in time differentiation of the increment of the in-cylinder pressure.

  The vertical axis in FIG. 2 represents the in-cylinder pressure P, and the horizontal axis represents the crank angle θ. A solid line L <b> 1 in FIG. 2 represents a change in the in-cylinder pressure when the fuel burns in the combustion chamber 2. 2 represents a change in the in-cylinder pressure when the gas sucked into the combustion chamber 2 is simply compressed by the movement of the piston 3 (that is, when combustion is not accompanied). Psub represents the peak value of the in-cylinder pressure accompanying the combustion of the pilot injected fuel, and Pmain represents the peak value of the in-cylinder pressure accompanying the combustion of the main injected fuel.

  The vertical axis in FIG. 3 represents the increase ΔP of the in-cylinder pressure due to fuel combustion, and the horizontal axis represents the crank angle θ. Here, “increase in in-cylinder pressure” is a difference in in-cylinder pressure between when the fuel does not combust in the combustion chamber 2 and when the fuel combusts. From the pressure change represented by the solid line L1 in FIG. It is obtained as a value obtained by subtracting the pressure change represented by the one-dot chain line L2 in FIG. ΔPsub represents the peak value of the in-cylinder pressure increment accompanying the combustion of the pilot injected fuel, and ΔPmain represents the peak value of the increment of the in-cylinder pressure accompanying the combustion of the main injected fuel.

4 and 5, the vertical axis represents the time differential dΔP / dt (hereinafter referred to as “in-cylinder pressure change rate”) of the in-cylinder pressure increment ΔP due to fuel combustion, and the horizontal axis represents the crank angle θ. (DΔP /
dt) sub represents the peak value of the in-cylinder pressure change rate associated with the combustion of the pilot injected fuel, and (dΔP / dt) main represents the peak value of the in-cylinder pressure change rate associated with the combustion of the main injected fuel. In this embodiment, the crank angle at which the rate of change in the in-cylinder pressure accompanying the combustion of the pilot injected fuel is maximized is the combustion timing θsub of the pilot injected fuel. Similarly, the crank angle at which the in-cylinder pressure change rate associated with the combustion of the main injected fuel is maximized is defined as the combustion timing θmain of the main injected fuel.

<Combustion judgment of pilot injection fuel>
In the present embodiment, when the peak value (dΔP / dt) sub of the in-cylinder pressure change rate accompanying the combustion of the pilot injected fuel is equal to or greater than the predetermined reference value Assubmin and equal to or less than the predetermined reference value Assubmax, Is actually combusting properly. The reference value Assubmin is hereinafter referred to as “pilot combustion lower limit value”. The reference value Assubmax is hereinafter referred to as “pilot combustion upper limit value”.

  In the example shown in FIG. 4, the peak value of the in-cylinder pressure change rate accompanying the combustion of the pilot injected fuel is between the pilot combustion lower limit value Submmin and the pilot combustion upper limit value Submax, so that the pilot injected fuel is in a good combustion state. It is determined.

  The pilot combustion lower limit value Asubmin can sufficiently slow down the change in the in-cylinder pressure accompanying the combustion of the main injection fuel by the combustion of the pilot injection fuel, and the pilot injection that can suitably reduce the combustion noise due to the combustion of the main injection fuel The lower limit value of the fuel combustion state is obtained in advance by experiments.

  In other words, when the peak value of the in-cylinder pressure change rate accompanying the combustion of the pilot injected fuel is smaller than the pilot combustion lower limit value Submmin, the pilot injected fuel is misfired and not combusting or is not combusting sufficiently. Thus, the effect of slowing the change in the in-cylinder pressure in the initial combustion of the main injection fuel cannot be sufficiently obtained.

  That is, in the present embodiment, the combustion state in which the peak value of the in-cylinder pressure change rate accompanying the combustion of the pilot injected fuel is smaller than the pilot combustion lower limit value Submin corresponds to the “combustion failure state” in the present invention.

  The pilot combustion upper limit value Submax is obtained in advance by experiments as an upper limit value of the combustion state of the pilot injected fuel such that the combustion noise due to the combustion of the pilot injected fuel falls within the allowable range.

  In other words, when the peak value of the in-cylinder pressure change rate due to the combustion of the pilot injected fuel is larger than the pilot combustion upper limit value Submax, the combustion noise due to the combustion of the pilot injected fuel becomes too large, and on the contrary, the effect of reducing the combustion noise as a whole Cannot be obtained.

  That is, in the present embodiment, the combustion state in which the peak value of the in-cylinder pressure change rate accompanying the combustion of the pilot injected fuel is greater than the pilot combustion upper limit value Submax corresponds to the “excessive combustion state” in the present invention.

  Therefore, in this embodiment, the combustion state in which the peak value of the in-cylinder pressure change rate accompanying the combustion of the pilot injected fuel is not less than the pilot combustion lower limit value Subbmin and not more than the pilot combustion upper limit value Subbmax is the This corresponds to “a good combustion state that is not a combustion state”. In the present embodiment, this combustion state is hereinafter referred to as “minimum pilot combustion state”.

<Pilot interval judgment>
Further, in this embodiment, the peak value (dΔP / dt) sub of the in-cylinder pressure change rate accompanying combustion of pilot injected fuel (here, expressed as Bsubmax for convenience) and the in-cylinder pressure change rate accompanying combustion of pilot injected fuel are calculated. A difference ΔBsub (= Bsubmax−Bsubmin) (hereinafter referred to as “post-combustion drop”) between the minimum value Bsubmin of the in-cylinder pressure change rate between the peak and the peak of the in-cylinder pressure change rate accompanying the combustion of the main injected fuel is When the predetermined reference value ΔBsubmin is equal to or greater than the predetermined reference value ΔBsubmax, it is determined that the interval between the combustion by the pilot injected fuel and the combustion by the main injected fuel is a suitable combustion state. The reference value ΔBsubmax is hereinafter referred to as “pilot suspension limit value”. Further, the reference value ΔBsubmin is hereinafter referred to as “pilot proximity limit value”.

  The pilot suspension limit value ΔBsubmax is such that the combustion chamber temperature at the main injection timing, the pressure, etc. are suitable for the combustion of the main injection fuel due to the combustion of the pilot injection fuel, and the combustion of the main injection fuel is sufficiently slowed down. The upper limit of the drop after the pilot combustion that can suitably reduce the combustion noise due to the combustion of is determined in advance through experiments.

  In other words, if the drop ΔBsub after pilot combustion is larger than the pilot suspension limit value ΔBsubmax, the pressure or temperature in the combustion chamber increased by the combustion of the pilot injected fuel returns to a condition that is not significantly different from that before the pilot injected fuel is burned. The effect of slowing down the change in the in-cylinder pressure in the initial combustion of the main injection fuel is not sufficiently obtained, and as a result, combustion noise similar to that in the case where pilot injection is not performed occurs.

  That is, in the present embodiment, the case where the drop ΔBsub after pilot combustion becomes larger than the pilot suspension limit value ΔBsubmax corresponds to the case where the pilot interval is too long in the present invention.

In addition, the pilot proximity limit value ΔBsubmin is such that the combustion chamber temperature at the main injection timing, the pressure and the like are suitable for combustion of the main injection fuel due to the combustion of the pilot injection fuel, and the combustion of the main injection fuel is sufficiently slowed down. The lower limit value of the drop after the pilot combustion that can suitably reduce the combustion noise due to the combustion of the injection combustion is obtained in advance by experiments.

  In other words, when the drop ΔBsub after pilot combustion is smaller than the pilot proximity limit value ΔBsubmin, the combustion of the pilot injected fuel is too close to the main injection timing and integrated with the combustion of the main injected fuel, so that the pilot injection is substantially performed. Since it is not performed, the effect of slowing down the in-cylinder pressure change in the initial combustion of the main injected fuel is not sufficiently obtained, resulting in the same combustion noise as when pilot injection is not performed To do.

  That is, in the present embodiment, the case where the drop ΔBsub after pilot combustion is smaller than the pilot proximity limit value ΔBsubmin corresponds to the case where the pilot interval is too short in the present invention.

  Therefore, in the present embodiment, the combustion state in which the post-pilot combustion drop ΔBsub is equal to or greater than the pilot proximity limit value ΔBsubmin and equal to or less than the pilot suspension limit value ΔBsubmax is the “interval between combustion by pilot injected fuel and combustion by main injected fuel” in the present invention. Corresponds to a “combustion state” with a value within a predetermined range. In the present embodiment, this combustion state is hereinafter referred to as “optimum interval combustion state”.

<Combustion noise detection>
Incidentally, the in-cylinder pressure change rate represents the intensity of change in the in-cylinder pressure. Therefore, the in-cylinder pressure change rate correlates with the combustion noise. That is, the greater the in-cylinder pressure change rate, the steeper change in the in-cylinder pressure, and the greater the combustion noise. In addition, the smaller the in-cylinder pressure change rate, the slower the in-cylinder pressure changes, and thus the lower the combustion noise.

  In this embodiment, the combustion noise is directly detected by the combustion noise sensor 77, but the in-cylinder pressure change rate is calculated based on the in-cylinder pressure detected by the in-cylinder pressure sensor 74, and the combustion noise is estimated from this value. You can also The method for detecting or estimating the actual combustion state of the fuel is not limited to the method described above.

<Operation of fuel injection parameters>
Next, the operation of the fuel injection parameter based on the actual combustion state of the fuel detected as described above will be described.

  In this embodiment, when the combustion noise is deviated from the target noise, first, the fuel injection parameters related to pilot injection are operated in order to make the combustion noise coincide with the target noise. If the combustion noise does not coincide with the target noise even when the operation of the fuel injection parameter related to the pilot injection is performed up to the predetermined operation limit value, the operation of the fuel injection parameter related to the main injection is operated.

  Here, the operation of the fuel injection parameter related to the pilot injection is given priority over the operation of the fuel injection parameter related to the main injection, so that the influence on the torque and emission resulting from the operation of the fuel injection parameter can be reduced. Because.

  In this embodiment, (1) pilot injection amount, (2) pilot interval, and (3) pilot injection frequency are operated in this priority order as fuel injection parameters related to pilot injection.

Note that the operation direction and the operation amount for the fuel injection parameter to be operated are calculated based on the following formula 1.

<In case of excessive noise>
Next, the operation of the fuel injection parameters when combustion noise larger than the target noise is detected by the combustion noise sensor 77 will be described with reference to FIGS. Graphs (A) drawn in the upper part of FIGS. 6 to 11 each show the time change of the in-cylinder pressure change rate, the vertical axis represents the in-cylinder pressure change rate, and the horizontal axis represents the crank angle. Further, the graph (B) drawn in the lower part shows the fuel injection pattern by the fuel injection valve 6, the vertical axis represents the fuel injection amount, and the horizontal axis represents the crank angle.

  When the combustion noise sensor 77 detects combustion noise larger than the target noise, the in-cylinder pressure sensor 74 detects the time variation of the in-cylinder pressure change rate dΔP / dt as shown by the solid line J1 in FIG. . Assume that the fuel injection parameters at this time are pilot injection timing θP1, pilot injection amount QP1, main injection timing θM1, and main injection amount QM1, as shown in FIG. 6B.

  As shown by a solid line J1 in FIG. 6A, at this time, the peak value of the in-cylinder pressure change rate accompanying the combustion of the pilot injected fuel is smaller than the pilot combustion lower limit value Submin. Therefore, it can be seen that the pilot injection fuel is misfired and not combusting or is not combusting sufficiently.

  Therefore, it can be determined that the detection of combustion noise larger than the target noise is caused by at least the pilot injection amount being insufficient. Therefore, in the present embodiment, as the operation of the optimum fuel injection parameter for reducing the combustion noise to coincide with the target noise, the pilot injection amount is selected to be increased from the previous pilot injection amount.

  By increasing the pilot injection amount in the next cycle, the pilot injected fuel burns well, and the change in the in-cylinder pressure accompanying the combustion of the main injected fuel is more moderated, and the combustion noise is reduced.

  FIG. 7 shows the time variation of the in-cylinder pressure change rate when the pilot injection amount is increased to QP2 (> QP1) in this way. Assume that the fuel injection parameters at this time are pilot injection timing θP1, pilot injection amount QP2, main injection timing θM1, and main injection amount QM1, as shown in FIG. 7B.

  The broken line J1 in FIG. 7A indicates the change in the in-cylinder pressure in the case of FIG. 6, that is, when the fuel injection parameters are the pilot injection timing θP1, the pilot injection amount QP1, the main injection timing θM1, and the main injection amount QM1. It shows the time change of the rate.

  As indicated by the solid line J2 in FIG. 7A, at this time, the peak value of the in-cylinder pressure change rate accompanying the combustion of the pilot injected fuel is larger than the pilot combustion lower limit value Submin, and the combustion failure of the pilot injected fuel is eliminated. It is understood that it was done. Further, the peak value of the in-cylinder pressure change rate accompanying the combustion of the main injected fuel is smaller than that in the case of FIG. 6 (broken line J1), and it can be seen that the combustion noise due to the combustion of the main injected fuel is reduced. .

  However, even though the pilot injection amount is increased to QP2 (> QP1) in this way, it is assumed that combustion noise larger than the target noise is still detected.

  As shown by the solid line J2 in FIG. 7A, it can be seen that the peak value of the in-cylinder pressure change rate accompanying the combustion of the pilot injected fuel is larger than the pilot combustion upper limit value Submax. Therefore, it can be seen that the combustion noise caused by the combustion of the pilot injection fuel is an excessive combustion state in which the noise exceeds the allowable range.

  Therefore, it can be determined that the fact that the combustion noise larger than the target noise is detected is caused by at least the pilot injection amount being excessive. Therefore, in the present embodiment, as the operation of the optimum fuel injection parameter for reducing the combustion noise to match the target noise, it is selected to reduce the pilot injection amount from the previous pilot injection amount QP2.

By reducing the pilot injection amount in the next cycle, the pilot injected fuel burns well, more suitably the change in the in-cylinder pressure accompanying the combustion of the main injected fuel is slowed down, and the combustion noise is reduced.

  FIG. 8 shows the change over time in the in-cylinder pressure change rate when the pilot injection amount is reduced to QP3 (QP1 <QP3 <QP2) in this way. Assume that the fuel injection parameters at this time are pilot injection timing θP1, pilot injection amount QP3, main injection timing θM1, and main injection amount QM1, as shown in FIG. 8B.

  The broken line J2 in FIG. 8A indicates the change in the in-cylinder pressure in the case of FIG. 7, that is, when the fuel injection parameters are the pilot injection timing θP1, the pilot injection amount QP2, the main injection timing θM1, and the main injection amount QM1. It shows the time change of the rate.

  As shown by the solid line J3 in FIG. 8A, at this time, the peak value of the in-cylinder pressure change rate accompanying the combustion of the pilot injected fuel is larger than the pilot combustion lower limit value Submin and smaller than the pilot combustion upper limit value Submax. It has become. Accordingly, in this case, it is understood that the combustion state of the pilot injected fuel is the “minimum pilot combustion state”. The peak value of the in-cylinder pressure change rate due to the combustion of the main injected fuel is larger than that in the case of FIG. 7 (broken line J2), but the peak value of the in-cylinder pressure change rate due to the combustion of the pilot injected fuel is Compared with the case of FIG. 7 (broken line J2), it is greatly reduced, and it can be seen that the combustion noise is reduced as a whole.

  Here, it is assumed that the combustion noise larger than the target noise is detected even though the pilot injection amount is set to QP3 and it is detected that the combustion state of the pilot injected fuel has become the minimum pilot combustion state.

  In this case, fuel injection is performed in accordance with fuel injection parameters including a pilot injection amount that makes the combustion noise as a function of the pilot injection amount a substantially minimum value. In other words, regarding the control of the combustion noise by manipulating the pilot injection amount, it can be determined that the combustion noise is controlled to a minimum value.

  Therefore, in this case, it can be determined that the detection of combustion noise larger than the target noise is not due to excess or deficiency of the pilot injection amount.

  Therefore, in this case, if the pilot injection amount is increased as an operation of the fuel injection parameter, the pilot injection amount becomes excessive and combustion noise may increase. Similarly, if the pilot injection amount is reduced, the pilot injection amount may become too small, and combustion noise may also increase. That is, it is difficult to further reduce the fuel noise by operating the pilot injection amount.

  In such a case, in this embodiment, it is determined whether or not the combustion state of the pilot injected fuel is the “optimum interval combustion state”. That is, as shown in FIG. 9A, after the pilot combustion drop ΔBsub3 (the peak value Bsubmax3 of the in-cylinder pressure change rate accompanying the combustion of the pilot injected fuel, the peak of the in-cylinder change rate accompanying the combustion of the pilot injected fuel, and the main A difference Bsubmax3−Bsubmin3) between the minimum value Bsubmin3 of the in-cylinder pressure change rate with respect to the peak of the in-cylinder change rate due to the combustion of the injected fuel is obtained, and this value is obtained from the pilot proximity limit value ΔBsubmin and the pilot suspension limit value ΔBsubmax. It is determined whether or not the value is between.

Here, it is assumed that the drop ΔBsub3 after pilot combustion is larger than the pilot suspension limit value ΔBsubmax. In this case, the combustion of the pilot injected fuel is too far from the main injection timing, and the combustion of the pilot injected fuel cannot make the conditions such as pressure and temperature in the combustion chamber suitable for the combustion of the main injected fuel, It can be seen that the effect of slowing down the initial combustion of the main injection fuel was not sufficiently obtained.

  Therefore, it can be determined that the detection of combustion noise larger than the target noise is caused by at least the pilot interval being too long. Therefore, in the present embodiment, the pilot interval is selected to be shorter than the previous pilot interval as the optimum fuel injection parameter operation for reducing the combustion noise to match the target noise. In the present embodiment, the pilot interval is shortened by retarding the pilot injection timing to approach the main injection timing.

  By shortening the pilot interval in the next cycle, the combustion of the pilot injected fuel comes close to the main injection timing, so the main injected fuel burns in a state with less ignition delay. As a result, it can be expected that the change in the in-cylinder pressure accompanying the initial combustion of the main injected fuel is further slowed and the combustion noise is reduced.

  In this way, when the pilot interval is shortened and combustion noise larger than the target noise is detected, the pilot interval is shortened until the drop after pilot combustion ΔBsub reaches the pilot proximity limit value ΔBsubmin.

  FIG. 10 shows the time change rate of the in-cylinder pressure change rate when the pilot interval is shortened until the drop after pilot combustion ΔBsub becomes substantially equal to the pilot proximity limit value ΔBsubmin. Assume that the fuel injection parameters at this time are pilot injection timing θP4, pilot injection amount QP3, main injection timing θM1, and main injection amount QM1, as shown in FIG.

  The broken line J3 in FIG. 10A indicates the in-cylinder pressure in the case of FIG. 9, that is, when the fuel injection parameters are the pilot injection timing θP1, the pilot injection amount QP3, the main injection timing θM1, and the actual garden injection amount QM1. The time change of the change rate is shown.

  As shown by the solid line J4 in FIG. 10A, at this time, the drop after the pilot combustion becomes ΔBsub4 (≈ΔBsubmin <ΔBsub3), which is smaller than that in the case of FIG. 9 (broken line J3). The peak value of the in-cylinder pressure change rate accompanying the combustion of the main injected fuel is smaller than that in the case of FIG. 9 (broken line J3), and it can be seen that the combustion noise is reduced.

  Here, it is assumed that combustion noise larger than the target noise is detected even though the pilot interval is shortened until the drop ΔBsub after pilot combustion becomes substantially equal to the pilot proximity limit value ΔBsubmin.

  In this case, a fuel including a pilot injection amount having a combustion noise as a function of the pilot injection amount as a value in the vicinity of the minimum value and a pilot interval having a combustion noise as a function of the pilot interval as a value in the vicinity of the minimum value. Fuel injection is performed according to the injection parameters. In other words, regarding the control of the combustion noise by the operation of the pilot injection amount and the operation of the pilot interval, it can be determined that the combustion noise is controlled to a substantially minimum value.

  Therefore, in this case, it can be determined that the detection of combustion noise larger than the target noise is not caused by excessive or insufficient pilot injection amount or too long pilot interval.

Therefore, in this case, if the pilot injection amount is increased or decreased as the operation of the fuel injection parameter, there is a possibility that the pilot injection amount becomes excessive or excessive and combustion noise increases. Similarly, if the pilot interval is shortened, the combustion by the pilot injected fuel and the main injection timing are too close, and the combustion noise may also increase. That is, it is difficult to further reduce the combustion noise by operating the pilot injection amount and the pilot interval.

  Therefore, in this case, as an operation of the optimal fuel injection parameter for reducing the combustion noise to match the target noise, in this embodiment, it is selected to increase the number of pilot injections from the previous number of pilot injections. To do.

  By increasing the number of pilot injections in the next cycle, the change in the in-cylinder pressure accompanying the combustion of the main injected fuel is further slowed down and the combustion noise is reduced.

  FIG. 11 shows the change over time in the in-cylinder pressure change rate when the number of pilot injections is increased to 2 in this way. As shown in FIG. 11B, the fuel injection parameters at this time are assumed to be pilot injection timings θP5 and θP4, and the pilot injection amounts are equal QP3, main injection timing θM1, and main injection amount QM1.

  The broken line J4 in FIG. 11A indicates the change in the in-cylinder pressure in the case of FIG. 10, that is, when the fuel injection parameters are the pilot injection timing θP4, the pilot injection amount QP3, the main injection timing θM1, and the main injection amount QM1. It shows the time change of the rate.

  As indicated by the solid line J5 in FIG. 11A, at this time, the peak value of the rate of change in the in-cylinder pressure accompanying the combustion of the main injected fuel is significantly lower than that in the case of FIG. 10 (broken line J4). It can be seen that the combustion noise due to the combustion of the main injection fuel is reduced.

  Here, the pilot injection amounts are set equal to QP3, but the pilot injection amounts may be different. Fuel injection parameters (each pilot injection amount, pilot injection timing, pilot injection interval, etc.) related to pilot injection when performing multiple pilot injections are related to the effect of reducing combustion noise due to combustion of main injected fuel, torque and emissions, respectively. The optimum value is obtained in advance by experiment in consideration of the influence of the above.

  If combustion noise larger than the target noise is detected, the number of pilot injections is increased until the number of pilot injections reaches a predetermined upper limit pilot injection number. Then, it is assumed that combustion noise larger than the target noise is detected even though the number of pilot injections becomes the upper limit pilot injection number.

  Here, the upper limit number of pilot injections is the number of pilot injections that cannot effectively slow down the change in the in-cylinder pressure accompanying the initial combustion of the main injected fuel even if pilot injection is performed more than that. It is obtained in advance by experiment in consideration of emissions.

  In this case, the pilot injection amount that makes the combustion noise as a function of the pilot injection amount a substantially minimum value, the pilot interval that makes the combustion noise as a function of the pilot interval a substantially minimum value, and the combustion noise as a function of the number of pilot injections The fuel injection is performed in accordance with the fuel injection parameters including the number of pilot injections with the substantially minimum value. In other words, regarding the control of the combustion noise by operating the pilot injection amount, the pilot interval, and the number of pilot injections, it can be determined that the combustion noise is controlled to a substantially minimum value.

Therefore, in this case, it can be determined that the detection of combustion noise larger than the target noise is not caused by excessive or insufficient pilot injection amount, excessive pilot interval, or insufficient number of pilot injections.

  Therefore, in this case, if the pilot injection amount is increased or decreased as the operation of the fuel injection parameter, there is a possibility that the pilot injection amount becomes excessive or excessive and combustion noise increases. Similarly, if the pilot interval is shortened, combustion by pilot injected fuel and the main injection timing are too close, and combustion noise may increase. Further, even if the number of pilot injections is increased, combustion noise may increase in the same manner. Therefore, in this case, it is difficult to further reduce the combustion noise by operating the fuel injection parameters.

  Therefore, in this embodiment, the operation of the fuel injection parameter related to the main injection is selected as the operation of the optimum fuel injection parameter for reducing the combustion noise to match the target noise.

  As the operation of the fuel injection parameter related to the main injection, for example, increase / decrease of the main injection amount, advance angle or delay angle of the main injection timing, and the like can be considered. The optimum operation of the main injection parameter in this case is obtained in advance by experiments.

  The combustion noise is reduced by operating the fuel injection parameters related to the main injection in the next cycle.

<In case of excessive noise>
Next, the operation of the fuel injection parameters when combustion noise smaller than the target noise is detected by the combustion noise sensor 77 will be described with reference to FIGS. The graphs (A) drawn in the upper part of FIGS. 12 to 17 each show the time change of the in-cylinder pressure change rate, the vertical axis represents the in-cylinder pressure change rate, and the horizontal axis represents the crank angle. Further, the graph (B) drawn in the lower part shows the fuel injection pattern by the fuel injection valve 6, the vertical axis represents the fuel injection amount, and the horizontal axis represents the crank angle.

  As a case where the combustion noise is increased when the combustion noise is smaller than the target noise, for example, a case where a sudden change in the combustion noise is suppressed can be exemplified. For example, if the combustion state of the fuel in the internal combustion engine becomes a poor combustion state and the combustion noise is excessively low, the combustion noise will fluctuate greatly when the combustion noise becomes the target noise in the next and subsequent cycles. . In this case, even if the combustion noise itself coincides with the target noise, there is a possibility that generation of loud noise is felt for the surrounding environment of the vehicle and the passenger. Therefore, there are cases where the operation of the fuel injection parameter for increasing the combustion noise is performed in order to suppress such a rapid fluctuation of the combustion noise.

  Even when the combustion noise is increased, the combustion noise can be controlled with higher accuracy by manipulating the fuel injection parameter based on the actual combustion state of the fuel in the internal combustion engine.

  For example, it is assumed that when the combustion noise sensor 77 detects combustion noise smaller than the target noise, the in-cylinder pressure sensor 74 detects a time change in the in-cylinder pressure change rate as indicated by the solid line J6 in FIG. Assume that the fuel injection parameters at this time are pilot injection timing θP6, pilot injection amount QP6, main injection timing θM6, and main injection amount QM6, as shown in FIG.

  As shown by a solid line J6 in FIG. 12A, at this time, the peak value of the in-cylinder pressure change rate due to the combustion of the pilot injected fuel is larger than the pilot combustion lower limit value Submin and smaller than the pilot combustion upper limit value Submax. Yes. Therefore, it can be seen that the pilot injected fuel is in the minimum pilot combustion state.

  Therefore, in the present embodiment, as the operation of the optimum fuel injection parameter for increasing the combustion noise to match the target noise, the pilot injection amount is selected to be increased or decreased from the previous pilot injection amount QP6.

  By increasing the pilot injection amount in the next cycle, the combustion by the pilot injected fuel becomes an excessive combustion state, and the combustion noise increases. Further, by reducing the pilot injection amount in the next cycle, the combustion by the pilot injected fuel becomes in a poor combustion state, so that the combustion noise due to the combustion of the main injected fuel increases.

  FIG. 13 shows the time variation of the in-cylinder pressure change rate when the pilot injection amount is increased to QP7 (> QP6) in this way. Assume that the fuel injection parameters at this time are pilot injection timing θP6, pilot injection amount QP7, main injection timing θM6, and main injection amount QM6, as shown in FIG. 13B.

  The broken line J6 in FIG. 13A indicates the change in the in-cylinder pressure in the case of FIG. 12, that is, when the fuel injection parameters are the pilot injection timing θP6, the pilot injection amount QP6, the main injection timing θM6, and the main injection amount QM6. It shows the time change of the rate.

  As shown by a solid line J7 in FIG. 13A, at this time, the peak value of the in-cylinder pressure change rate accompanying the combustion of the pilot injected fuel is larger than the pilot combustion upper limit value Submax. Therefore, in this case, it is understood that the combustion state of the pilot injection fuel is the “excess combustion state”. Therefore, the peak value of the in-cylinder pressure change rate due to the combustion of the main injected fuel is smaller than that in FIG. 12 (broken line J6), but the peak value of the in-cylinder pressure change rate due to the combustion of the pilot injected fuel is shown in FIG. Compared with the case of 12 (broken line J6), the combustion noise is greatly increased as a whole.

  In this way, the pilot injection amount is increased, and when a combustion noise smaller than the target noise is detected, the pilot injection amount is increased to a predetermined upper limit value. Here, the predetermined upper limit value is obtained in advance through experiments or the like, for example, as a pilot injection amount at which the post-combustion drop ΔBsub is approximately equal to the pilot suspension limit value ΔBsubmax. Hereinafter, this upper limit value is referred to as a “pilot increase upper limit value”. The method for determining the pilot increase upper limit is not limited to the above.

  FIG. 14 shows the change over time in the in-cylinder pressure change rate when the pilot injection amount is increased until the pilot injection amount becomes substantially equal to the pilot increase upper limit value. Assume that the fuel injection parameters at this time are pilot injection timing θP6, pilot injection amount QP8, main injection timing θM6, and main injection amount QM6, as shown in FIG.

  As shown by the solid line J8 in FIG. 14A, at this time, it is found that the drop after pilot combustion is ΔBsub8 (≈ΔBsubmax).

  Here, it is assumed that the combustion noise smaller than the target noise is detected even though the pilot injection amount is increased until the trailing drop of the pilot injected fuel becomes substantially equal to the pilot suspension limit value.

  In this case, in the present embodiment, it is selected to extend the pilot interval from the previous pilot interval as the operation of the optimum fuel injection parameter for increasing the combustion noise to match the target noise. In this embodiment, the pilot interval is extended by advancing the pilot injection timing.

  By extending the pilot interval in the next cycle, the combustion of the pilot injected fuel moves away from the main injection timing, so that the effect of slowing the initial combustion of the main injected fuel by the combustion of the pilot injected fuel is weakened, and the combustion noise is increased. Become.

  FIG. 15 shows the change over time in the in-cylinder pressure change rate when the pilot interval is thus extended. Assume that the fuel injection parameters at this time are pilot injection timing θP9, pilot injection amount QP8, main injection timing θM6, and main injection amount QM6, as shown in FIG.

  The broken line J8 in FIG. 15A indicates the change in the in-cylinder pressure in the case of FIG. 14, that is, when the fuel injection parameters are the pilot injection timing θP6, the pilot injection amount QP8, the main injection timing θM6, and the main injection amount QM6. It shows the time change of the rate.

  As shown by a solid line J9 in FIG. 15A, at this time, the post-pilot combustion drop ΔBsub9 is further larger than the post-pilot combustion drop ΔBsub8 in the case of FIG. 14 and exceeds the pilot suspension limit value ΔBsubmax. . Then, the peak value of the in-cylinder pressure change rate due to the combustion of the main injected fuel is larger than that in the case of FIG. 14 (broken line J8), and it can be seen that the combustion noise due to the combustion of the main injected fuel is increased.

  In this way, the pilot interval is extended, and when the combustion noise smaller than the target noise is detected, the pilot interval is extended to a predetermined upper limit value. Here, the predetermined upper limit value is determined in advance by experiments or the like in consideration of the influence on the slowing effect of combustion of the main injection fuel, torque, emission and the like. Hereinafter, this upper limit value is referred to as “pilot interval extension upper limit value”.

  FIG. 16 shows the change over time in the in-cylinder pressure change rate when the pilot interval is extended until the pilot interval becomes substantially equal to the pilot interval extension upper limit value. Assume that the fuel injection parameters at this time are pilot injection timing θP10, pilot injection amount QP8, main injection timing θM6, and main injection amount QM6, as shown in FIG.

  As shown by the solid line J10 in FIG. 16A, at this time, the drop after the pilot combustion becomes larger, and the peak value of the rate of change in the in-cylinder pressure due to the combustion of the main injected fuel is compared with the case of FIG. It can be seen that the combustion noise due to the combustion of the main injection fuel is increased.

  Here, it is assumed that combustion noise smaller than the target noise is detected even though the pilot interval is extended until the pilot interval becomes substantially equal to the pilot interval extension upper limit value.

  In this case, as the operation of the minimum fuel injection parameter for increasing the combustion noise to match the target noise, in this embodiment, it is selected to reduce the number of pilot injections from the previous number of pilot injections.

  By reducing the number of pilot injections in the next cycle, the effect of slowing down the initial combustion of the main injected fuel by the combustion of the pilot injected fuel is weakened, and the combustion noise is increased.

FIG. 17 shows the change over time in the in-cylinder pressure change rate when the number of pilot injections is reduced in this way. The fuel injection parameters at this time are as shown in FIG.
It is assumed that the pilot injection is not executed and the main injection timing θM6 and the main injection amount QM6 are obtained.

  The broken line J10 in FIG. 17A indicates the change in the in-cylinder pressure in the case of FIG. 16, that is, when the fuel injection parameters are the pilot injection timing θP9, the pilot injection amount QP8, the main injection timing θM6, and the main injection amount QM6. It shows the time change of the rate.

  As shown by the solid line J11 in FIG. 17A, at this time, the peak value of the rate of change in the in-cylinder pressure due to the combustion of the main injected fuel is larger than that in the case of FIG. 16 (broken line J10), and the main injected fuel It can be seen that the combustion noise due to the combustion of is increased.

  In the above case, since the number of pilot injections is reduced from the case where the number of pilot injections is 1, the number of pilot injections becomes zero when the fuel injection parameter operation for reducing the number of pilot injections is performed once. However, if the above fuel injection parameter is operated from a state in which pilot injection is performed a plurality of times, and combustion noise smaller than the target noise is detected, the number of pilot injections is zero, that is, pilot injection The number of pilot injections is decreased until no longer occurs.

  It is assumed that combustion noise smaller than the target noise is detected even though the number of pilot injections becomes zero. In this case, in this embodiment, the operation of the fuel injection parameter related to the main injection is selected as the optimal operation of the fuel injection parameter for increasing the combustion noise to match the target noise.

  As the operation of the fuel injection parameter related to the main injection, for example, increase / decrease of the main injection amount, advance angle or delay angle of the main injection timing, and the like can be considered. The optimum operation of the main injection parameter in this case is obtained in advance by experiments.

  Combustion noise is increased by operating the fuel injection parameters related to the main injection in the next cycle.

<Combustion noise control main routine>
Next, a specific execution procedure when the combustion noise control in the present embodiment described above is performed during the operation of the internal combustion engine 1 will be described. FIG. 18 is a flowchart showing a combustion noise control routine of the present embodiment performed during operation of the internal combustion engine 1. This routine is repeatedly executed by the ECU 8 at regular intervals during the operation of the internal combustion engine 1.

  First, in step S101, the ECU 8 detects the operating state of the internal combustion engine 1. Specifically, the engine load is calculated based on the engine rotational speed Ne detected by the rotational speed sensor 78 and the accelerator opening degree Accp input from the accelerator opening degree sensor 72 to the ECU 8.

  In step S102, the ECU 8 determines whether or not the operating state of the internal combustion engine 1 is a steady state. If an affirmative determination is made in step S102, the ECU 8 executes step S103. On the other hand, when a negative determination is made in step S102, the ECU 8 executes step S104.

  In step S103, the ECU 8 executes combustion noise control when the internal combustion engine 1 described later is in a steady operation state.

In step S104, the ECU 8 executes combustion noise control when the internal combustion engine 1 described later is in a transient operation state.

  After executing step S103 or step S104, the ECU 8 once ends the execution of this routine.

<Stationary control subroutine>
Next, combustion noise control performed when the operation state of the internal combustion engine 1 is in a steady operation state, that is, combustion noise control executed in step S103 will be described with reference to FIG. FIG. 19 is a flowchart showing a combustion noise control routine performed when the internal combustion engine 1 is in a steady operation state.

  First, in step S201, the ECU 8 reads the target noise corresponding to the operating state of the internal combustion engine 1 detected in step S101. The target noise is obtained in advance by experiments or the like and stored in the ROM of the ECU 8.

  In step S202, the ECU 8 detects combustion noise. Specifically, the detection value of the combustion noise sensor 77 is read.

  In step S203, the ECU 8 determines whether or not the combustion noise detected in step S202 matches the target noise read in step S201. In this embodiment, when the absolute value of the difference between the combustion noise and the target noise is less than a predetermined value, it is determined that the combustion noise and the target noise match. If an affirmative determination is made in step S203, the ECU 8 once ends the execution of this routine. On the other hand, if a negative determination is made in step S203, the ECU 8 executes step S204.

  In step S <b> 204, the ECU 8 detects the actual combustion state of the fuel in the combustion chamber 2. Specifically, the in-cylinder pressure change rate is calculated based on the in-cylinder pressure detected by the in-cylinder pressure sensor 74, and the actual fuel combustion state is estimated by the above-described method based on the obtained in-cylinder pressure change rate. .

  In step S205, the ECU 8 determines whether or not to operate the fuel injection parameter related to pilot injection as the operation of the fuel injection parameter in the next cycle. As described above, in the combustion noise control of the present embodiment, basically, the fuel injection parameter related to the pilot injection is preferentially operated over the fuel injection parameter related to the main injection to control the combustion noise. For example, when reducing the combustion noise, if the number of pilot injections reaches a predetermined upper limit pilot injection number, the fuel injection parameter related to the main injection is operated in the next cycle.

  If an affirmative determination is made in step S205, the ECU 8 executes step S206. On the other hand, if a negative determination is made in step S205, the ECU 8 executes step S207.

  In step S206, the ECU 8 operates fuel injection parameters related to pilot injection. Specifically, it is determined whether the combustion noise should be reduced or increased in the next cycle based on the combustion noise detected in step S202 and the target noise read in step S201, and according to the above-described priority order. The pilot injection amount, the pilot interval, and the number of pilot injections are executed.

In step S207, the ECU 8 operates fuel injection parameters related to main injection. Specifically, it is determined whether the combustion noise should be reduced or increased in the next cycle based on the combustion noise detected in step S202 and the target noise read in step S201. The operation of the fuel injection parameter is executed.

  After controlling the fuel injection valve 6 according to the fuel injection parameters determined in step S206 or step S207, the ECU 8 returns to step S202, detects combustion noise again, and in step S203, the combustion noise and the target noise are equal. Determine whether you are doing it. If it is determined that the combustion noise and the target noise match, the ECU 8 once ends the execution of this routine.

  By executing the routine described above, the ECU 8 can control the combustion noise when the operation state of the internal combustion engine 1 is in the steady operation state to the target noise.

<Combustion noise control for pilot combustion failure>
For example, even when the fuel injection valve 6 is controlled in accordance with a fuel injection parameter capable of controlling combustion noise to target noise in a normal operation state, the internal combustion engine 1 in an idle operation state during cold start or the like. When the temperature of the pilot fuel is low, the pilot injected fuel does not burn properly, and the combustion noise reduction effect by the pilot injection may not be obtained as expected.

  FIG. 20 is a diagram showing the change over time in the in-cylinder pressure change rate in such a case. FIG. 20A shows the change over time of the in-cylinder pressure change rate calculated from the value detected by the in-cylinder pressure sensor 74, where the vertical axis represents the in-cylinder pressure change rate and the horizontal axis represents the crank angle. FIG. 20B shows a fuel injection pattern by the fuel injection valve 6. The vertical axis represents the fuel injection amount, and the horizontal axis represents the crank angle.

  By performing fuel injection by the fuel injection valve 6 according to the fuel injection parameters (pilot injection timing θP1, pilot injection amount QP1, main injection timing θM1, main injection amount QM1) as shown in FIG. It is assumed that the combustion noise at the time of steady operation when the temperature is sufficiently high can be controlled to the target noise (80 dB).

  However, it is assumed that combustion noise (88 dB) larger than the target noise is generated even though the fuel is injected according to the same fuel injection parameter in the cold state.

  In this case, in order to reduce the combustion noise and match the target noise, the above-described fuel injection parameter operation is performed. In the conventional combustion noise control that does not consider the actual combustion state of the fuel, It was difficult to accurately determine what factors caused the difference in combustion noise from that in cold weather. Therefore, it has been difficult to select an optimal fuel injection parameter to be operated in order to reduce combustion noise and to appropriately determine the operation direction and the operation amount.

  On the other hand, in this embodiment, since the actual fuel combustion state can be detected based on the in-cylinder pressure detected by the in-cylinder pressure sensor 74, there is a difference in combustion noise between the warm time and the cold time. It can be determined based on the detection result of the combustion state what kind of difference is caused by the combustion state.

  For example, if the change in the cylinder pressure change rate in the idling operation in the cold state is detected as indicated by the solid line J2 in FIG. 20A, the pilot injection fuel is not burned as the actual combustion state of the fuel. I understand. Based on the detection result of the combustion state, it can be determined that the fact that the combustion noise larger than the target noise is detected in the cold state is caused by the poor combustion of the pilot injected fuel.

  Therefore, it is possible to select to increase the pilot injection amount as the operation of the optimal fuel injection parameter for reducing the combustion noise.

  FIG. 21 shows the change over time in the in-cylinder pressure change rate when the pilot injection amount is increased to QP3 (> QP1) in the next cycle. The solid line J3 in FIG. 21A shows the change over time of the in-cylinder pressure change rate when the pilot injection amount is QP3, and the broken line J2 is the in-cylinder pressure before the pilot injection amount is increased, that is, when the pilot injection amount is QP1. The time change of the change rate is shown.

  As shown in FIG. 21 (A), by increasing the pilot injection amount to QP3, the peak value of the in-cylinder pressure change rate accompanying the combustion of the pilot injected fuel is between the pilot combustion lower limit value Subbmin and the pilot combustion upper limit value Submax. It can be seen that the pilot-injected fuel burns well. As a result, it can be seen that the combustion noise is reduced from 88 dB (broken line J2) to 84 dB (solid line J3).

  However, although the combustion noise has decreased to 84 dB, this combustion noise is still larger than the target noise (80 dB). Therefore, it is necessary to further operate the fuel injection parameters in order to further reduce the combustion noise and bring it closer to the target noise.

  Here, based on the actual combustion state detected as indicated by the solid line J3 in FIG. 21A, it can be determined that the pilot-injected fuel is combusting well as described above. It can be determined that the increase in the pilot injection amount beyond this is not effective as the injection parameter.

  Therefore, it is possible to select to shorten the pilot interval as the operation of the optimal fuel injection parameter for reducing the combustion noise.

  FIG. 22 shows the change over time in the in-cylinder pressure change rate when the pilot interval is shortened by retarding the pilot injection timing to θP4 (> θP1) in the next cycle. The solid line J4 in FIG. 22A shows the change over time in the in-cylinder pressure change rate when the pilot injection timing is θP4, and the broken line J3 shows the change in the in-cylinder pressure before shortening the pilot interval, that is, when the pilot injection timing is θP1. It shows the time change of the rate.

  As shown in FIG. 22 (A), by reducing the pilot interval, the drop after pilot combustion has decreased from ΔBsub3 to ΔBsub4, and the change over time in the in-cylinder pressure change rate accompanying the combustion of the main injected fuel is slower. It can be seen that As a result, it can be seen that the combustion noise is reduced from 84 dB (broken line J3) to the target noise of 80 dB (solid line J4).

  As described above, the operation of the fuel injection parameter is finished when the combustion noise coincides with the target noise.

<Combustion noise control in the case of excessive pilot combustion>
Further, for example, even when the fuel injection valve 6 is controlled in accordance with a fuel injection parameter capable of controlling the combustion noise to the target noise if the fuel injection valve 6 is normal, the fuel injection valve 6 is caused by deterioration over time, injection variation, or the like. Thus, the actual fuel injection amount may deviate from the injection command value for the fuel injection valve 6.

In this case, the pilot injection amount becomes too small with respect to the target value, so that the effect of slowing down the combustion of the main injected fuel cannot be obtained sufficiently. There is a possibility that the combustion noise due to the combustion of the injected fuel becomes excessively large.

  FIG. 23 is a diagram showing the change over time in the in-cylinder pressure change rate when the pilot injection amount is excessive with respect to the target value. FIG. 23A shows the change over time in the in-cylinder pressure change rate calculated from the value detected by the in-cylinder pressure sensor 74. The vertical axis represents the in-cylinder pressure change rate, and the horizontal axis represents the crank angle. FIG. 23B shows a fuel injection pattern by the fuel injection valve 6. The vertical axis represents the fuel injection amount, and the horizontal axis represents the crank angle.

  The fuel injection valve 6 performs fuel injection according to the fuel injection parameters (pilot injection timing θP1, pilot injection amount QP1, main injection timing θM1, main injection amount QM1) as shown in FIG. It is assumed that the combustion noise during steady operation when 6 is normal can be controlled to the target noise (80 dB).

  However, it is assumed that a combustion noise (88 dB) larger than the target noise is actually generated even though the fuel is injected according to the fuel injection parameters.

  In this case, in order to reduce the combustion noise and match the target noise, the above-described fuel injection parameter is operated. In this embodiment, based on the in-cylinder pressure detected by the in-cylinder pressure sensor 74. Since the actual combustion state of the fuel can be detected, it is possible to determine on the basis of the detection result of the combustion state whether a large combustion noise that should not be generated due to the cause is generated.

  For example, assuming that the actual change in the in-cylinder pressure change with time is detected as indicated by the solid line J2 in FIG. 23A, the peak value of the in-cylinder pressure change rate accompanying the combustion of the pilot injected fuel is larger than the pilot combustion upper limit value Submax. You can see that

  Based on the detection result of the combustion state, it can be determined that the fact that the combustion noise larger than the target noise is detected is due to the fact that the pilot injected fuel is in the excessive combustion state.

  Accordingly, it is possible to select to reduce the pilot injection amount as the operation of the optimal fuel injection parameter for reducing the combustion noise.

  FIG. 24 shows the change over time in the in-cylinder pressure change rate when the pilot injection amount is reduced to QP3 (<QP1) in the next cycle. The solid line J3 in FIG. 24A shows the change over time in the in-cylinder pressure change rate when the pilot injection amount is QP3, and the broken line J2 is the in-cylinder pressure before the pilot injection amount is reduced, that is, when the pilot injection amount is QP1. The time change of the change rate is shown.

  As shown in FIG. 24A, by reducing the pilot injection amount to QP3, the peak value of the rate of change in in-cylinder pressure due to combustion of pilot injected fuel is smaller than before the pilot injection amount is reduced. You can see that As a result, the peak value of the in-cylinder pressure change rate accompanying the combustion of the main injection fuel is slightly increased, but it is understood that the combustion noise is reduced from 88 dB to 82 dB as a whole.

  However, although the combustion noise has decreased to 82 dB, this combustion noise is still larger than the target noise (80 dB). Therefore, it is necessary to further operate the fuel injection parameters in order to further reduce the combustion noise and bring it closer to the target noise.

  Here, based on the actual combustion state detected as indicated by the solid line J3 in FIG. 24A, the peak value of the in-cylinder pressure change rate associated with the combustion of the pilot injected fuel is still slightly larger than the pilot combustion upper limit value Submax. Therefore, it is possible to select to reduce the pilot injection amount again as the optimum operation of the fuel injection parameter for reducing the combustion noise.

  FIG. 25 shows the time variation of the in-cylinder pressure change rate when the pilot injection amount is reduced to QP4 (<QP3) in the next cycle. The solid line J4 in FIG. 25A shows the change over time of the in-cylinder pressure change rate when the pilot injection amount is QP4, and the broken line J3 is the in-cylinder pressure before the pilot injection amount is reduced, that is, when the pilot injection amount is QP3. The time change of the change rate is shown.

  As shown in FIG. 25 (B), by further reducing the pilot injection amount, the peak value of the in-cylinder pressure change rate associated with the combustion of the pilot injected fuel is further reduced, which is smaller than the pilot combustion upper limit value Submax and pilot combustion. It can be seen that the value is larger than the lower limit value Submin. As a result, it can be seen that the combustion noise is reduced from 82 dB (broken line J3) to the target noise of 80 dB (solid line J4).

  As described above, the operation of the fuel injection parameter is finished when the combustion noise coincides with the target noise.

  As described above, according to the present embodiment, the optimum fuel injection parameter to be operated in order to bring the combustion noise close to the target noise can be determined based on the actual combustion state of the fuel. In addition, combustion noise can be controlled.

  Next, combustion noise control performed when the operation state of the internal combustion engine 1 is in a transient operation state, that is, combustion noise control executed in step S104 will be described.

<Diffusion combustion mode and premixed combustion mode>
First, the transient operation state of the internal combustion engine 1 in the present embodiment will be described. The internal combustion engine 1 of the present embodiment changes various fuel injection parameters such as fuel injection amount, fuel injection timing, number of fuel injections, pilot interval (interval between pilot injection timing and main injection timing) related to main injection and pilot injection. By doing so, it is possible to operate by appropriately switching between the diffusion combustion mode and the premixed combustion mode.

  When the internal combustion engine 1 is operated in the premixed combustion mode, as shown in FIG. 26, only the main injection is performed at a time earlier than the compression top dead center (the intake stroke or the initial or middle of the compression stroke) Pilot injection is not performed (that is, the pilot injection amount is set to 0). On the other hand, when the internal combustion engine 1 is operated in the diffusion combustion mode, as shown in FIG. 27, main injection is performed near the compression top dead center, and a small amount of pilot injection is performed earlier than the main injection. .

  The ECU 8 switches the combustion mode according to the operating state of the internal combustion engine 1. FIG. 28 is a map that defines the relationship between the operating state of the internal combustion engine 1 and the combustion mode. The horizontal axis in FIG. 28 represents the engine speed of the internal combustion engine 1, and the vertical axis represents the engine load of the internal combustion engine 1. The ECU 8 detects the operating state of the internal combustion engine 1 based on the engine rotational speed Ne detected by the rotational speed sensor 78 and the engine load calculated from the accelerator opening degree Accp detected by the accelerator opening degree sensor 72. When the detected operation state is in the premixed combustion operation region of FIG. 28, the internal combustion engine 1 is operated in the premixed combustion mode, and when the detected operation state is in the diffusion combustion operation region of FIG. Is operated in diffusion combustion mode.

  Further, when the internal combustion engine 1 is operated in the premixed combustion mode, the fuel injected by the main injection is operated in the diffusion combustion mode in order to suppress premature ignition before the compression top dead center. Compared to the case, a larger amount of EGR gas is introduced into the combustion chamber 2. In the case of the present embodiment, when the diffusion combustion mode is switched to the premixed combustion mode, the amount of EGR gas recirculated to the combustion chamber 2 is increased by increasing the opening of the EGR valve 42.

<Noise caused by EGR gas response delay when switching combustion mode>
Thus, when the combustion mode is switched in the internal combustion engine 1, the fuel injection parameter and the EGR valve opening are changed.

  The fuel injection amount, fuel injection timing, etc. from the fuel injection valve 6 after the injection command value for the fuel injection valve 6 is changed to the target value of the fuel injection parameter corresponding to the switching destination combustion mode in accordance with the switching of the combustion mode. Is very short in response time until it actually changes to the target value of the fuel injection parameter corresponding to the combustion mode of the switching destination.

  On the other hand, since the EGR gas flows into the EGR passage 41 from the exhaust pipe 32 and is recirculated to the combustion chamber 2 through the EGR valve 42, the intake pipe 22, and the intake port 20, the EGR gas circulation path is long. Response from when the target opening degree is changed to the EGR valve opening degree corresponding to the switching destination combustion mode until the EGR gas amount actually flowing into the combustion chamber 2 changes to the target EGR gas amount of the switching destination combustion mode Delay time is relatively long.

  That is, after the opening degree of the EGR valve 42 is changed, the EGR gas amount sucked into the combustion chamber 2 gradually approaches the target EGR gas amount in the switching destination combustion mode.

  Therefore, when the combustion mode of the internal combustion engine 1 is switched, there exists a transient state in which the EGR rate of the gas sucked into the combustion chamber 2 and thus the in-cylinder oxygen concentration gradually changes.

  Therefore, when the operating state of the internal combustion engine 1 satisfies the combustion mode switching condition, the EGR valve 42 is controlled to the target EGR valve opening degree of the switching destination combustion mode and at the same time, the fuel injection parameter is set to the target value of the switching destination combustion mode. If this is the case, the fuel injection parameter will not be an appropriate value for the in-cylinder oxygen concentration in this transient state, the combustion noise will become excessive due to rapid combustion, or a combustion failure will occur, resulting in a fluctuation range of the combustion noise. May become larger.

  For example, when the combustion mode of the internal combustion engine 1 is switched from the diffusion combustion mode to the premixed combustion mode, it is necessary to stop the pilot injection and greatly advance the main injection timing. However, when the pilot injection is stopped when the in-cylinder oxygen concentration is not sufficiently reduced and the main injection timing is advanced to the target main injection timing for the premixed combustion mode, the fuel is ignited prematurely and burned. Noise tends to increase.

  Further, when the combustion mode of the internal combustion engine 1 is switched from the premixed combustion mode to the diffusion combustion mode, it is necessary to start the pilot injection and greatly retard the main injection timing. However, if the pilot injection is started when the in-cylinder oxygen concentration is not sufficiently increased and the main injection timing is retarded to the target main injection timing for the diffusion combustion mode, the pilot injection fuel or the main injection fuel is misfired. Because the combustion noise is excessively smaller than the target noise, the in-cylinder oxygen concentration is sufficiently increased and diffusion combustion is suitably performed. When the combustion noise matches the target noise, the combustion noise changes rapidly. This may cause a sense of loud combustion noise to the passengers and the surrounding environment of the vehicle.

Therefore, in this embodiment, the fuel injection parameter is changed in stages so as to suppress rapid fluctuations in combustion noise at the time of transition in which the diffusion combustion mode and the premixed combustion mode are switched.

<When shifting from diffusion combustion mode to premixed combustion mode>
FIG. 29 is a procedure for changing the in-cylinder oxygen concentration and the combustion noise over time when the combustion mode of the internal combustion engine 1 is switched from the diffusion combustion mode to the premixed combustion mode, and changing the fuel injection parameters for pilot injection and main injection. It is a timing chart which shows.

  When the operating state of the internal combustion engine 1 shifts from the diffusion combustion operation region of FIG. 28 to the premixed combustion operation region at time t1, a condition for switching the combustion mode of the internal combustion engine 1 from the diffusion combustion mode to the premixed combustion mode is established. The internal combustion engine 1 enters a transient operation state.

  At this time, the ECU 8 increases the amount of EGR gas recirculated to the combustion chamber 2 to reduce the in-cylinder oxygen concentration Ro to the target in-cylinder oxygen concentration Roh for the predetermined premixed combustion mode. The opening degree Oegr is increased from the target EGR valve opening degree Oegrd for the diffusion combustion mode to the target EGR valve opening degree Oeghr for the premixed combustion mode. Thereby, the in-cylinder oxygen concentration Ro begins to gradually decrease.

  Here, the ECU 8 gradually advances the pilot injection timing θp and gradually increases the pilot injection amount Qp. At this time, in order to suppress the torque fluctuation, the fuel amount corresponding to the increased amount of the pilot injection amount Qp is decreased from the main injection amount Qm.

  When the pilot injection amount Qp increases to a predetermined transition period upper limit value Qpt at time t2, the ECU 8 stops increasing the pilot injection amount Qp and decreasing the main injection amount Qm.

  When the pilot injection timing Cp is advanced to a predetermined transient advance limit Cpt at time t3, the advance of the pilot injection timing Cp is stopped and the main injection timing Cm is gradually advanced.

  The advance angle of the main injection timing Cm is advanced to the target main injection timing Cmh for the premixed combustion mode when the in-cylinder oxygen concentration Ro decreases to the target in-cylinder oxygen concentration Roh for the premixed combustion mode. Gradually.

  At time t4, when the in-cylinder oxygen concentration Ro decreases to the target in-cylinder oxygen concentration Roh for the premixed combustion mode, various fuel injection parameters are set to the target values for the premixed combustion mode. That is, the pilot injection amount Qp is set to 0 to stop the pilot injection, and the main injection is performed at the main injection amount Qmh.

  FIG. 30 shows the transition of the fuel injection pattern when the fuel injection parameters related to pilot injection and main injection are changed as described above. The horizontal axis of each graph in FIG. 30 represents the crank angle. Further, the place where the graph stands indicates that the fuel injection valve 6 is opened and fuel injection is being performed. Also, time t flows from top to bottom.

  As shown in FIG. 30, fuel injection parameters mainly related to pilot injection are operated from time t1 to time t3. From time t3 to time t4, the fuel injection parameters mainly related to main injection are operated.

  Thus, by changing the fuel injection pattern stepwise, the combustion noise CN in the transition period when the internal combustion engine 1 is switched from the diffusion combustion mode to the premixed combustion mode can be controlled to the target noise CNtrg.

<When shifting from premixed combustion mode to diffusion combustion mode>
FIG. 31 is a procedure for changing the fuel injection parameters relating to the pilot injection and the main injection, and the time variation of the in-cylinder oxygen concentration and the combustion noise when the combustion mode of the internal combustion engine 1 is switched from the premixed combustion mode to the diffusion combustion mode. It is a timing chart which shows.

  When the operation state of the internal combustion engine 1 shifts from the premixed combustion operation region of FIG. 28 to the diffusion combustion operation region at time t5, a condition for switching the combustion mode of the internal combustion engine 1 from the premixed combustion mode to the diffusion combustion mode is established, The internal combustion engine 1 enters a transient operation state.

  At this time, the ECU 8 opens the EGR valve 42 in order to reduce the amount of EGR gas recirculated to the combustion chamber 2 and increase the in-cylinder oxygen concentration Ro to the target in-cylinder oxygen concentration Rod for the predetermined diffusion combustion mode. The degree Oegr is decreased from the target EGR valve opening degree Oeghr for the premixed combustion mode to the target EGR valve opening degree Oegrd for the diffusion combustion mode. Thereby, the in-cylinder oxygen concentration Ro begins to gradually increase.

  Here, the ECU 8 gradually retards the main injection timing θm.

  When the main injection timing θm is retarded to the target main injection timing θmd for the diffusion combustion mode at time t6, the delay of the main injection timing θm is stopped and pilot injection is started. Then, the pilot injection amount Qp is gradually increased, and the pilot injection timing θp is gradually advanced. At this time, in order to suppress the torque fluctuation, the fuel amount corresponding to the increase in the pilot injection amount Qp is decreased from the main injection amount Qm.

  When the pilot injection amount Qp increases to a predetermined transitional period upper limit value Qpt at time t7, the increase in the pilot injection amount Qp and the decrease in the main injection amount Qm are stopped.

  At time t8, when the pilot injection timing θp is advanced to the predetermined transient advance limit θpt, the advance of the pilot injection timing θp is stopped, and the pilot injection amount Qp is decreased and the main injection amount Qm is increased. To do. Here, the decrease in the pilot injection amount Qp and the increase in the main injection amount Qm are performed when the in-cylinder oxygen concentration Ro rises to the target in-cylinder oxygen concentration Rod for the diffusion combustion mode. The process is gradually performed so as to obtain the amount Qpd and the target main injection amount Qpm.

  When the in-cylinder oxygen concentration Ro increases to the target in-cylinder oxygen concentration Rod for the diffusion combustion mode at time t9, various fuel injection parameters are set to the target values for the diffusion combustion mode. That is, pilot injection of pilot injection amount Qpd is performed at pilot injection timing θpd, and main injection of main injection amount Qmd is performed at main injection timing θmd.

  FIG. 32 shows the transition of the fuel injection pattern when the fuel injection parameters related to pilot injection and main injection are changed as described above. The horizontal axis of each graph in FIG. 32 represents the crank angle. Further, the place where the graph stands indicates that the fuel injection valve 6 is opened and fuel injection is being performed. Also, time t flows from top to bottom.

  As shown in FIG. 32, fuel injection parameters mainly related to main injection are operated from time t5 to time t6. From time t5 to time t9, fuel injection parameters mainly related to pilot injection are operated.

Thus, by changing the fuel injection pattern stepwise, the combustion noise CN in the transition period when the internal combustion engine 1 is switched from the premixed combustion mode to the diffusion combustion mode is changed to the target noise CN.
It can be controlled to trg.

  As described above, the in-cylinder oxygen concentration that gradually changes by operating the fuel injection parameters related to the pilot injection and the main injection in a stepwise manner at the time when the combustion mode of the internal combustion engine 1 is switched. Therefore, it is possible to perform appropriate fuel injection, and it is possible to suitably suppress combustion noise in a transient state when switching the combustion mode.

  By the way, even if the operation of the fuel injection parameter is performed during the transition in which the combustion mode of the internal combustion engine 1 is switched as described above, the actual combustion state of the fuel injected by the fuel injection valve 6 for some reason is desired. If it deviates from the combustion state, the combustion noise may not match the target noise. In the same manner as in the steady operation state, for example, the actual fuel injection amount and the target may be caused by, for example, the pilot-injected fuel not combusting, the deterioration of the fuel injection valve 6 over time, manufacturing variations, and the like. This occurs when the fuel injection amount deviates.

  Therefore, in the present embodiment, as in the steady operation state, the actual combustion state of the fuel injected by the fuel injection valve 6 in the combustion chamber 2 is detected, and the fuel injection parameter is determined based on the detected combustion state. Perform the operation. As a result, the optimum fuel injection parameter operation for controlling the combustion noise to the desired target noise can be selected based on the actual combustion state of the fuel.

<Transient control subroutine>
Hereinafter, the combustion noise control that is performed when the operation state of the internal combustion engine 1 is in the transient operation state, that is, the combustion noise control that is executed in step S104 will be described with reference to FIG. FIG. 33 is a flowchart showing a combustion noise control routine performed when the internal combustion engine 1 is in a transient operation state.

  In step S301, the ECU 8 determines whether the operation state detected in step S101 belongs to the diffusion combustion operation region or the premixed combustion operation region based on the combustion mode switching map of FIG. The target fuel injection parameters for mode (target main injection amount, target main injection timing, target pilot injection amount, target pilot injection timing, target pilot interval, etc.), target noise, and target in-cylinder oxygen concentration are read. These target fuel injection parameters are obtained in advance by experiments or the like and stored in the ROM of the ECU 8.

  In step S302, the ECU 8 detects combustion noise and in-cylinder oxygen concentration. Specifically, the detection value of the combustion noise sensor 77 is read, and the detection value of the in-cylinder oxygen concentration sensor 76 is read.

  In step S303, the ECU 8 determines whether or not the combustion noise detected in step S302 matches the target noise read in step S301. In this embodiment, when the absolute value of the difference between the combustion noise and the target noise is less than a predetermined value, it is determined that the combustion noise and the target noise match. If an affirmative determination is made in step S303, the ECU 8 executes step S308. On the other hand, if a negative determination is made in step S303, the ECU 8 executes step S304.

  In step S <b> 304, the ECU 8 detects the actual combustion state of the fuel in the combustion chamber 2. Specifically, the in-cylinder pressure change rate is calculated based on the in-cylinder pressure detected by the in-cylinder pressure sensor 74, and the actual fuel combustion state is estimated by the above-described method based on the obtained in-cylinder pressure change rate. .

  In step S305, the ECU 8 determines whether or not to operate the fuel injection parameter related to the pilot injection as the operation of the fuel injection parameter in the next cycle. If an affirmative determination is made in step S305, the ECU 8 executes step S306. On the other hand, if a negative determination is made in step S305, the ECU 8 executes step S307.

  In step S306, the ECU 8 operates fuel injection parameters related to pilot injection. Specifically, it is determined whether the combustion noise should be reduced or increased in the next cycle based on the combustion noise detected in step S302 and the target noise read in step S301. The operation such as the number of pilot injections is executed.

  In step S307, the ECU 8 operates fuel injection parameters related to main injection. Specifically, it is determined whether the combustion noise should be reduced or increased in the next cycle based on the combustion noise detected in step S302 and the target noise read in step S301. Perform fuel injection parameter operations.

  After controlling the fuel injection valve 6 in accordance with the fuel injection parameter determined in step S306 or step S307, the ECU 8 returns to step S302, detects combustion noise again, and in step S303, the combustion noise and the target noise match. Determine whether you are doing it. If it is determined that the combustion noise and the target noise match, the ECU 8 executes step S308.

  In step S308, the ECU 8 determines whether or not the in-cylinder oxygen concentration matches the target in-cylinder oxygen concentration. If a negative determination is made in step S308, the ECU 8 determines that the internal combustion engine 1 is in a transient operation state, and returns to step S302 to continue control of combustion noise. On the other hand, if an affirmative determination is made in step S308, the ECU 8 determines that the switching of the combustion mode of the internal combustion engine 1 has been completed, and proceeds to step S309.

  In step S309, the ECU 8 sets the fuel injection parameter to the target fuel injection parameter of the switching destination combustion mode, and once ends the execution of this routine.

  By executing the routine described above, the ECU 8 can accurately control the combustion noise at the time of transition in which the combustion mode is switched in the internal combustion engine 1 to the target noise.

  The above-described embodiment is an example for explaining the present invention, and various modifications can be made to the above-described embodiment without departing from the spirit of the present invention.

1 is a diagram illustrating a schematic configuration of an intake system and an exhaust system of an internal combustion engine according to a first embodiment. The time change of the in-cylinder pressure in the compression stroke and the expansion stroke when the fuel is combusted in the internal combustion engine of the first embodiment, and the time change of the cylinder pressure in the compression stroke and the expansion stroke when the fuel is not burned are represented. FIG. It is a figure showing the time change of the increment of the in-cylinder pressure in the compression stroke and the expansion stroke when fuel burns in the internal combustion engine of the first embodiment. It is a figure showing the time change of the time differential (cylinder pressure change rate) of the increment of the in-cylinder pressure in the compression stroke and the expansion stroke when the fuel is combusted in the internal combustion engine of the first embodiment. It is a figure showing the time change of the time differential (cylinder pressure change rate) of the increment of the in-cylinder pressure in the compression stroke and the expansion stroke when the fuel is combusted in the internal combustion engine of the first embodiment. FIG. 6A shows the change over time in the in-cylinder pressure change rate when combustion noise larger than the target noise is detected in the internal combustion engine of the first embodiment. In particular, the combustion state of the pilot injected fuel is in a poor combustion state. It is a figure showing the time change of the cylinder pressure change rate detected sometimes. FIG. 6B shows the fuel injection parameters at that time. FIG. 7A shows the change over time in the in-cylinder pressure change rate when combustion noise larger than the target noise is detected in the internal combustion engine of the first embodiment. In particular, the combustion state of the pilot injected fuel is an excessive combustion state. It is a figure showing the time change of the cylinder pressure change rate detected sometimes. FIG. 7B shows the fuel injection parameters at that time. FIG. 8 (A) shows the change over time in the in-cylinder pressure change rate when combustion noise larger than the target noise is detected in the internal combustion engine of the first embodiment, and particularly the state where the combustion state of the pilot injected fuel is well burned. It is a figure showing the time change of the cylinder pressure change rate detected at the time. FIG. 8B shows the fuel injection parameters at that time. FIG. 9A shows the change over time in the in-cylinder pressure change rate when combustion noise larger than the target noise is detected in the internal combustion engine of the first embodiment, and particularly when the combustion state of the pilot injected fuel is good, the pilot interval. It is a figure showing the time change of the in-cylinder pressure change rate detected when is longer than a predetermined allowable upper limit value. FIG. 9B shows the fuel injection parameters at that time. FIG. 10A shows the change over time in the in-cylinder pressure change rate when combustion noise larger than the target noise is detected in the internal combustion engine of the first embodiment, and particularly detected when the pilot interval is shortened to a predetermined shortening limit value. It is a figure showing the time change of the cylinder pressure change rate to be performed. FIG. 10B shows the fuel injection parameters at that time. FIG. 11A shows the change over time in the in-cylinder pressure change rate when combustion noise larger than the target noise is detected in the internal combustion engine of the first embodiment, and particularly when the pilot interval is shortened to a predetermined shortening limit value. It is a figure showing the time change of the in-cylinder pressure change rate detected when the number of times of pilot injection is increased. FIG. 11B shows the fuel injection parameters at that time. FIG. 12 (A) shows the change over time in the in-cylinder pressure change rate when combustion noise smaller than the target noise is detected in the internal combustion engine of the first embodiment, and particularly the state where the combustion state of the pilot injected fuel is well burned. It is a figure showing the time change of the cylinder pressure change rate detected at the time. FIG. 12B is a diagram showing the fuel injection parameters at that time. FIG. 13A shows the change over time in the in-cylinder pressure change rate when combustion noise smaller than the target noise is detected in the internal combustion engine of the first embodiment, and particularly when the combustion state of the pilot injected fuel is burning well. It is a figure showing the time change of the in-cylinder pressure change rate detected when the pilot injection amount is increased. FIG. 13B shows the fuel injection parameters at that time. FIG. 14A shows the change over time in the in-cylinder pressure change rate when combustion noise smaller than the target noise is detected in the internal combustion engine of the first embodiment, and is detected particularly when the pilot injection amount is increased to a predetermined increase upper limit value. It is a figure showing the time change of the cylinder pressure change rate to be performed. FIG. 14B shows the fuel injection parameters at that time. FIG. 15A shows the change over time in the in-cylinder pressure change rate when combustion noise smaller than the target noise is detected in the internal combustion engine of the first embodiment. In particular, the pilot injection amount is increased to a predetermined increase upper limit value. It is a figure showing the time change of the in-cylinder pressure change rate detected when a pilot interval is extended in the case. FIG. 15B shows the fuel injection parameters at that time. FIG. 16A shows the change over time in the in-cylinder pressure change rate when combustion noise smaller than the target noise is detected in the internal combustion engine of the first embodiment, and is detected particularly when the pilot interval is extended to a predetermined extension upper limit value. It is a figure showing the time change of the cylinder pressure change rate. FIG. 16B shows the fuel injection parameters at that time. FIG. 17A shows the change over time in the in-cylinder pressure change rate when combustion noise smaller than the target noise is detected in the internal combustion engine of the first embodiment, and particularly when the pilot interval is extended to a predetermined extension upper limit value. It is a figure showing the time change of the in-cylinder pressure change rate detected when the frequency | count of pilot injection is decreased. FIG. 17B shows the fuel injection parameters at that time. 3 is a flowchart illustrating a combustion noise control routine in the first embodiment. 3 is a flowchart illustrating a combustion noise control subroutine that is executed when the operation state of the internal combustion engine of the first embodiment is a steady operation state. FIG. 20A shows the change over time in the in-cylinder pressure change rate when combustion noise larger than the target noise is detected when the internal combustion engine of the first embodiment is in a low temperature state after cold start, and in particular, the pilot injection fuel It is a figure showing the time change of the in-cylinder pressure change rate detected when a combustion state is a combustion failure state. FIG. 20B shows the fuel injection parameters at that time. FIG. 21 (A) shows the change over time in the in-cylinder pressure change rate when combustion noise larger than the target noise is detected when the internal combustion engine of the first embodiment is in a low temperature state after cold start. It is a figure showing the time change of the in-cylinder pressure change rate detected when the pilot injection amount is increased when the combustion state is a poor combustion state. FIG. 21B shows the fuel injection parameters at that time. FIG. 22 (A) shows the change over time in the in-cylinder pressure change rate when combustion noise that matches the target noise is detected when the internal combustion engine of the first embodiment is in a low temperature state after cold start. It is a figure showing the time change of the in-cylinder pressure change rate detected when a pilot interval is shortened when the combustion state of this is burning favorably. FIG. 22B shows the fuel injection parameters at that time. FIG. 23 (A) shows the change over time in the in-cylinder pressure change rate when combustion noise larger than the target noise is detected in the internal combustion engine of the first embodiment, and in particular, the combustion state of the pilot injected fuel is an excessive combustion state. It is a figure showing the time change of the cylinder pressure change rate detected sometimes. FIG. 23B shows the fuel injection parameters at that time. FIG. 24A shows the change over time in the in-cylinder pressure change rate when combustion noise larger than the target noise is detected in the internal combustion engine of the first embodiment, particularly when the combustion state of the pilot injected fuel is an excessive combustion state. It is a figure showing the time change of the cylinder pressure change rate detected when pilot injection quantity is reduced. FIG. 24B is a diagram showing the fuel injection parameters at that time. FIG. 25A shows the change over time in the in-cylinder pressure change rate when combustion noise that matches the target noise is detected in the internal combustion engine of the first embodiment, and particularly when the combustion state of the pilot injected fuel is an excessive combustion state. It is a figure showing the time change of the cylinder pressure change rate detected when the pilot injection quantity is reduced. FIG. 25B shows the fuel injection parameters at that time. 3 is a time chart showing a fuel injection pattern when the combustion mode of the internal combustion engine of the first embodiment is a premixed combustion mode. 3 is a time chart showing a fuel injection pattern when the combustion mode of the internal combustion engine of the first embodiment is a diffusion combustion mode. 3 is a map that defines the relationship between the operating state of the internal combustion engine and the switching of the combustion mode according to the first embodiment. In-cylinder oxygen concentration, EGR valve opening, pilot injection timing, pilot injection amount, main injection timing, main injection amount, during transition when the combustion mode of the internal combustion engine of the first embodiment is switched from the diffusion combustion mode to the premixed combustion mode, It is a time chart which shows the time change of combustion noise. It is a figure which shows transition of the fuel-injection pattern at the time of the transition in which the combustion mode of the internal combustion engine of Example 1 is switched from a diffusion combustion mode to the premixed combustion mode. In-cylinder oxygen concentration, EGR valve opening, pilot injection timing, pilot injection amount, main injection timing, main injection amount, during transition when the combustion mode of the internal combustion engine of the first embodiment is switched from the premixed combustion mode to the diffusion combustion mode, It is a time chart which shows the time change of combustion noise. It is a figure which shows transition of the fuel-injection pattern at the time of the transition in which the combustion mode of the internal combustion engine of Example 1 is switched from the premix combustion mode to the diffusion combustion mode. 3 is a flowchart illustrating a combustion noise control subroutine that is executed when the operation state of the internal combustion engine of the first embodiment is a transient operation state.

Explanation of symbols

1 internal combustion engine 2 combustion chamber 3 piston 5 cylinder 6 combustion injection valve 7 accelerator pedal 8 ECU
20 Intake port 22 Intake pipe 23 Intake valve 30 Exhaust port 32 Exhaust pipe 33 Exhaust valve 40 EGR device 41 EGR passage 42 EGR valve 70 Water temperature sensor 71 Crank position sensor 72 Accelerator opening sensor 73 Intake temperature sensor 74 In-cylinder pressure sensor 75 Air flow meter 76 In-cylinder oxygen concentration sensor 77 Combustion noise sensor 78 Rotation speed sensor

Claims (11)

Noise detection means for estimating or detecting combustion noise of the internal combustion engine;
Fuel injection means capable of executing pilot injection prior to main injection which is main fuel injection;
Combustion state detection means for estimating or detecting the combustion state of the actual pilot injection fuel of the internal combustion engine;
The combustion state of pilot injected fuel of the internal combustion engine estimated or detected by the combustion state detecting means so that the combustion noise due to the combustion of the main injected fuel estimated or detected by the noise detecting means coincides with a predetermined target noise pilot injection amount based on the distance between the pilot injection timing and main injection timing, and the pilot injection number, operating in this priority, the operation of the fuel injection parameters according to the pilot injection is performed up to a predetermined operation limit If the combustion noise still does not match the target noise, the control means for operating the fuel injection parameters related to the main injection ,
A fuel injection control device for an internal combustion engine, comprising: In claim 1,
The combustion noise estimated or detected by the noise detection means is larger than the target noise, and the combustion by the pilot injected fuel does not burn the pilot injected fuel well, and the combustion of the main injected fuel is sufficiently slowed down. The fuel injection of the internal combustion engine, wherein the control means increases the pilot injection amount when the combustion state detection means estimates or detects that the predetermined combustion failure state is a combustion state that cannot be performed. Control device. In claim 1,
The combustion noise estimated or detected by the noise detection means is larger than the target noise, the combustion by the pilot injected fuel is abruptly burned, and the combustion noise by the combustion of the pilot injected fuel falls within an allowable range. The internal combustion engine is characterized in that the control means reduces the pilot injection amount when the combustion state detecting means estimates or detects that the engine is in a predetermined excessive combustion state that is larger than Fuel injection control device. In any one of Claims 1-3,
Combustion noise estimated or detected by the noise detection means is larger than the target noise, combustion by pilot injected fuel is suitably slowed down by combustion of pilot injected fuel, and pilot injected fuel When it is estimated or detected by the combustion state detection means that the combustion noise resulting from the combustion of the engine is within a permissible range, the control means detects the pilot injection timing and the main injection timing. A fuel injection control device for an internal combustion engine, characterized in that the interval between and is shortened. In claim 4,
The combustion noise estimated or detected by the noise detection means is greater than the target noise and the interval between the combustion by the pilot injected fuel and the combustion by the main injected fuel is a value within a predetermined range. The fuel injection control device for an internal combustion engine, wherein the control means increases the number of pilot injections when estimated or detected by the state detection means. In claim 5,
When the combustion noise estimated or detected by the noise detection means is larger than the target noise and the number of pilot injections is equal to or greater than a predetermined upper limit number, the control means changes a fuel injection parameter related to main injection. A fuel injection control device for an internal combustion engine. In claim 4,
When the combustion noise estimated or detected by the noise detection means is smaller than the target noise and the combustion state detection means estimates or detects that the combustion by the pilot injected fuel is in the good combustion state, The fuel injection control device for an internal combustion engine, wherein the control means changes a pilot injection amount. In claim 7,
When the combustion noise estimated or detected by the noise detecting means is smaller than the target noise and the combustion state detecting means estimates or detects that the combustion by the pilot injected fuel is in the excessive combustion state, The fuel injection control device for an internal combustion engine, wherein the control means extends an interval between the pilot injection timing and the main injection timing. In claim 8,
The combustion noise estimated or detected by the noise detection means is smaller than the target noise, and the interval between the combustion by the pilot injected fuel and the combustion by the main injected fuel is not a value within a predetermined range. The fuel injection control device for an internal combustion engine, wherein the control means reduces the number of pilot injections when estimated or detected by the state detection means. In claim 9,
When the combustion noise estimated or detected by the noise detection means is smaller than the target noise and the number of pilot injections is zero, the control means changes a fuel injection parameter related to main injection. A fuel injection control device for an internal combustion engine. In any one of Claims 1-10,
Switching means for switching the combustion mode of the internal combustion engine to the diffusion combustion mode or the premixed combustion mode by changing fuel injection parameters related to main injection and / or pilot injection by the fuel injection means in accordance with the operating state of the internal combustion engine. Prepared,
The control means detects the combustion state detection means so that the combustion noise estimated or detected by the noise detection means coincides with the predetermined target noise during a transition in which the combustion mode of the internal combustion engine is switched by the switching means. A fuel injection control device for an internal combustion engine, which controls a change in injection parameters related to main injection and / or pilot injection by the switching means based on a combustion state of the internal combustion engine estimated or detected by

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