JP7699956B2 - Control device for compression ignition internal combustion engine - Google Patents

Description

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

In compression ignition internal combustion engines (such as a typical diesel engine), in which air is compressed and heated by a piston and then fuel is injected into the combustion chamber, where it ignites and burns, the noise generated during combustion is louder and more smoke is produced than in spark ignition internal combustion engines (such as a typical gasoline engine), in which air and fuel are mixed in the combustion chamber and ignited by a spark from a spark plug.

Conventionally, in compression ignition internal combustion engines, multiple pilot injections, which serve as pre-injections before the main injection, are performed in one combustion cycle, followed by a main injection, and various methods have been devised to reduce combustion noise by causing the pressure waves of the first combustion generated by the pilot injection and the second combustion generated mainly by the main injection to interfere with each other.

For example, in the fuel injection control method and fuel injection control device for a compression self-ignition engine described in Patent Document 1, a pre-injection (corresponding to a pilot injection) is performed before a main injection, and an after-injection is performed after the main injection. The time difference between the peak position of the heat release rate due to pre-combustion (corresponding to a first combustion) which is the combustion of the pre-injection in one combustion stroke and the peak position of the heat release rate due to the main combustion (corresponding to a second combustion) which is the combustion of the main injection, and the time difference between the peak position of the heat release rate due to the main combustion and the peak position of the heat release rate due to the after-injection are controlled so as to be a target interval even if the load and rotation speed of the internal combustion engine (operating state of the internal combustion engine) fluctuate. This control suppresses the resonance of the frequency band having a peak near 3500 [Hz], which is the highest frequency, among the multiple resonance frequency bands possessed by the structural system of the engine, and reduces the knock noise having peaks at 1300 [Hz], 1700 [Hz], and 2500 [Hz] on the low frequency side of the resonance frequency band.

Patent No. 6288066

In the following, unless otherwise specified, there will be no distinction between pilot injection, which is injected before the main injection, and pre-injection, and pilot injection, which is injected before the main injection, and pre-injection will be collectively referred to as "pilot injection." It is assumed that the pressure wave generated by the first combustion, which is combustion by pilot injection, and the pressure wave generated by the second combustion, which is combustion mainly by main injection, form a cancellation wave that cancels out and reduces combustion noise.

It should be noted that multiple combustions are generated during one combustion stroke , and these multiple combustions include pre-combustion, a first combustion that is generated following the pre-combustion so as to overlap with part of the pre-combustion, and a second combustion that is generated following the first combustion so as to overlap with part of the first combustion, and is generated mainly by main injection.

The inventors of the present application have found through various experiments and simulations that the offsetting wave for further reducing the combustion noise of a compression autoignition internal combustion engine is not limited to the resonant frequency specific to the compression autoignition internal combustion engine, but that there is an optimal offsetting frequency depending on the operating state of the compression autoignition internal combustion engine, and further that there is an optimal offsetting amplitude at the optimal offsetting frequency. In other words, the combustion noise of a compression autoignition internal combustion engine is greatly influenced by factors other than the specific resonant frequency, and it has been found that the overall combustion noise can be further reduced by forming an offsetting wave whose frequency and amplitude are adjusted according to the operating range, rather than forming an offsetting wave whose frequency is limited to the resonant frequency.

The inventors of the present application further discovered that in order to stably obtain optimal countervailing waves, it is necessary to more accurately target the start timing of the first combustion, and that to achieve this, it is necessary to appropriately control the pre-combustion that occurs immediately before the first combustion. The inventors discovered that pre-combustion requires a high amount of heat generation and a high rate of heat generation, and that if these requirements are not met, the start timing of the first combustion becomes unstable and the amount of smoke generated increases.

In Patent Document 1, the frequency of the offset wave is controlled to offset the knocking noises of the engine's inherent resonant frequencies of 1300 [Hz], 1700 [Hz], and 2500 [Hz] by controlling the time difference between the peak position of the heat release rate of the pre-combustion (corresponding to the first combustion) and the peak position of the heat release rate of the main combustion (corresponding to the second combustion), and the time difference between the peak position of the heat release rate of the main combustion and the peak position of the heat release rate of the after-combustion, to the targeted intervals. In other words, the focus is on the resonant frequency inherent to the compression self-ignition internal combustion engine, and not on the optimal offset frequency according to the operating state. In addition, the injection amount of the pre-injection (corresponding to the pilot injection) is increased according to the operating state of the compression self-ignition internal combustion engine, but this is an increase in the amount to generate pre-combustion (corresponding to the first combustion) at a targeted position in an operating region where combustion is difficult, and is not intended to achieve the optimal offset amplitude. Furthermore, Patent Document 1 does not mention or suggest the need for appropriate control of the combustion that occurs immediately before the first combustion, which occurs before the second combustion (main combustion) that corresponds to the main injection.

The present invention has been devised in consideration of the above points, and has an objective of providing a control device for a compression autoignition internal combustion engine that can more accurately and stably control the start timing of first combustion by appropriately controlling pre-combustion in multiple combustions that occur in one combustion stroke in a compression autoignition internal combustion engine, namely, pre-combustion, a first combustion that occurs following the pre-combustion so as to overlap with part of the pre-combustion, and a second combustion that occurs following the first combustion so as to overlap with part of the first combustion, thereby further reducing the amount of smoke generated and combustion noise.

In order to solve the above problems, a first aspect of the present invention is a control device for a compression autoignition internal combustion engine , which generates multiple combustions by injecting a main injection, which is a main fuel injection, and multiple pilot injections, which are multiple fuel injections that are pre-stage injections of the main injection, into a cylinder for one combustion stroke in the compression autoignition internal combustion engine. The multiple combustions for one combustion stroke include a pre-combustion, a first combustion that is generated following the pre-combustion so as to overlap with a portion of the pre-combustion, and a second combustion that is generated following the first combustion so as to overlap with a portion of the first combustion, the second combustion being generated mainly by the main injection. In a case where the amount of heat generation in the cylinder or the pressure in the cylinder changes with time for one combustion stroke , a time differential value of the amount of heat generation in the cylinder or a time differential value of the pressure in the cylinder corresponding to the first combustion is generated. Alternatively, in a case where the amount of heat generation in the cylinder or the pressure in the cylinder changes with a crank angle which is a rotation angle of a crankshaft, a time differential value of the amount of heat generation in the cylinder or a time differential value of the pressure in the cylinder corresponding to the pre-combustion is generated before a start time of the generation of the crank angle differential value of the amount of heat generation in the cylinder or the pressure in the cylinder corresponding to the first combustion. When a pre-combustion occurrence rate area surrounded by a time derivative value of the pressure, or a crank angle derivative value of the in-cylinder heat generation amount corresponding to the pre-combustion or a crank angle derivative value of the in-cylinder pressure is defined as Qp, the control device is a control device for a compression self-ignition internal combustion engine having a fuel injection adjustment unit that adjusts at least one of the injection timing and the injection amount in at least one pilot injection so that a pre-combustion occurrence rate area related amount based on Qp, which is the pre-combustion occurrence rate area, is equal to or less than a predetermined target pre-combustion area related amount upper limit.

Next, a second aspect of the present invention is a control device for a compression autoignition internal combustion engine, which generates multiple combustions by injecting a main injection , which is a main fuel injection, and multiple pilot injections, which are multiple fuel injections that are pre-stage injections of the main injection, into a cylinder for one combustion stroke in the compression autoignition internal combustion engine. The multiple combustions for one combustion stroke include a pre-combustion, a first combustion that is generated following the pre-combustion so as to overlap with a portion of the pre-combustion, and a second combustion that is generated following the first combustion so as to overlap with a portion of the first combustion, the second combustion being generated mainly by the main injection. In a case where the amount of heat generation in the cylinder or the pressure in the cylinder changes with time for one combustion stroke , a time differential value of the amount of heat generation in the cylinder or a time differential value of the pressure in the cylinder corresponding to the first combustion, or in a case where the amount of heat generation in the cylinder or the pressure in the cylinder changes with a crank angle which is a rotation angle of a crankshaft, a time differential value of the amount of heat generation in the cylinder or a time differential value of the pressure in the cylinder corresponding to the pre-combustion at a generation start time of the amount of heat generation in the cylinder or a time differential value of the pressure in the cylinder corresponding to the pre-combustion The control device is a control device for a compression self-ignition internal combustion engine having a fuel injection adjustment unit that adjusts at least one of the injection timing and the injection amount in at least one pilot injection so that a pre-combustion occurrence rate height related amount based on Hpre, which is the pre-combustion occurrence rate height, is equal to or less than a predetermined target pre-combustion height related amount upper limit, where Hpre is a pre-combustion occurrence rate height, which is the height of a crank angle differential value of the in-cylinder heat generation amount corresponding to the pre-combustion, or a crank angle differential value of the in-cylinder pressure corresponding to the pre-combustion.

Next, a third invention of the present invention is a control device for a compression autoignition internal combustion engine according to the first invention, in which, when a total input heat amount, which is a heat amount converted from a total injection amount, which is the amount of fuel injected by the pilot injection and the main injection in one combustion stroke , is Qall, the control device sets Qp/Qall as the pre-combustion occurrence rate area related amount in the fuel injection adjustment unit.

Next, a fourth invention of the present invention is a control device for a compression autoignition internal combustion engine related to the second invention described above, in which when a total injection amount , which is the amount of fuel injected by the pilot injection and the main injection for one combustion stroke, is Qv, the control device sets Hpre/Qv as the amount related to the pre-combustion occurrence rate height in the fuel injection adjustment unit.

The fifth aspect of the present invention is a control device for a compression autoignition internal combustion engine according to any one of the first to fourth aspects, in which the control device adjusts the injection amount of the pilot injection that is at least two injections before the main injection in the pre-stage injection by the fuel injection adjustment unit.

Next, a sixth aspect of the present invention is a control device for a compression autoignition type internal combustion engine according to any one of the first to fifth aspects of the present invention, wherein, in one combustion stroke , a time difference between a first peak time position which is a peak position corresponding to the first combustion among a plurality of peak positions of a time differential value of the in-cylinder heat generation amount or a time differential value of the in-cylinder pressure and a second peak time position which is a peak position corresponding to the second combustion among the plurality of peak positions is set to Δt, and a time differential value of the in-cylinder heat generation amount or the time differential value of the in-cylinder pressure at the first peak time position is set to Δt. a peak height ratio is Hp/Hm where Hp is the time differential value of the in-cylinder heat generation amount or the time differential value of the in-cylinder pressure at the second peak time position, and Hm is the time differential value of the in-cylinder heat generation amount or the time differential value of the in-cylinder pressure at the second peak time position , or a difference in crank angle between a first peak angle position which is a peak position corresponding to the first combustion among a plurality of peak positions due to the crank angle differential value of the in-cylinder heat generation amount or the crank angle differential value of the in-cylinder pressure in one combustion stroke and a second peak angle position which is a peak position corresponding to the second combustion among the plurality of peak positions is calculated based on the rotation speed of the crankshaft. a time difference converted into time based on the time difference calculated ... and a fuel injection calculation unit that calculates a ratio of Δt to the target time difference or a time difference-related amount based on Δt to the target time difference-related amount, and calculates the injection timing and injection amount of at least the pilot injection that is one injection before the main injection in the pre-stage injection, and the injection timing and injection amount of the main injection, so that Δt approaches the target time difference or so that a time difference-related amount based on Δt approaches the target time difference-related amount, and so that Hp/Hm approaches the target peak height ratio, and the injection timing and injection amount calculated by the fuel injection calculation unit are adjusted by the fuel injection adjustment unit.

According to the first aspect of the present invention, there is pre-combustion, first combustion, and second combustion, and when the pre-combustion occurrence rate area before the start of the first combustion for one combustion stroke is Qp (corresponding to the amount of heat generated (or amount of pressure generated) of pre-heat), at least one of the injection timing and the injection amount of at least one pilot injection is adjusted so that the amount related to the pre-combustion occurrence rate based on Qp is equal to or less than the upper limit of the amount related to the target pre-combustion area. In this way, by appropriately controlling the pre-combustion (in this case, the amount of heat generated (or amount of pressure generated) of pre-combustion), the start of the first combustion can be controlled more accurately and stably, and the amount of smoke generated and combustion noise can be further reduced.

According to the second aspect of the present invention, there is provided a combustion apparatus having pre-combustion, first combustion, and second combustion, and where the height of the pre-combustion occurrence rate at the start timing of the first combustion in one combustion stroke is denoted as Hpre, at least one of the injection timing and the injection amount of at least one pilot injection is adjusted so that the amount related to the pre-combustion occurrence rate height based on Hpre is equal to or less than the upper limit of the amount related to the target pre-combustion height. This makes it possible to more accurately and stably control the start timing of the first combustion by appropriately controlling the pre-combustion (in this case, the height of the heat release rate (or the height of the pressure release rate) of the pre-combustion), and to further reduce the amount of smoke generation and combustion noise.

According to the third aspect of the present invention, when the total input heat amount converted from the total injection amount in one combustion stroke is Qall, by setting Qp/Qall as the pre-combustion occurrence rate area related amount, it is possible to appropriately eliminate the influence of differences in the displacement of compression ignition internal combustion engines, and generalize the amount.

According to the fourth invention, when the total injection amount in one combustion stroke is Qv, by setting Hpre/Qv as the amount related to the height of the pre-combustion occurrence rate, it is possible to appropriately eliminate the influence of differences in the displacement of compression ignition internal combustion engines, and generalize the amount.

According to the fifth invention, pre-combustion (amount of heat generated (or amount of pressure generated) and rate of heat generation (or rate of pressure generation)) can be more easily and appropriately controlled by simply adjusting the injection amount of the pilot injection two injections before the main injection.

According to the sixth aspect of the present invention, the fuel injection calculation unit controls the injection timing and injection amount of at least the pilot injection immediately before the main injection and the injection timing and injection amount of the main injection so that the time difference Δt approaches the target time difference (or the target time difference related amount) corresponding to the operating state of the compression self-ignition internal combustion engine, thereby making it possible to make the frequency of the offsetting wave approach the optimal frequency corresponding to the operating state. In addition, the injection timing and injection amount of at least the pilot injection immediately before the main injection and the injection timing and injection amount of the main injection are controlled so that the peak height ratio Hp/Hm approaches the target peak height ratio corresponding to the operating state of the compression self-ignition internal combustion engine, thereby making it possible to make the amplitude of the offsetting wave approach the optimal amplitude corresponding to the operating state. Therefore, it is possible to appropriately reduce the overall combustion noise, not just the knock noise at the resonant frequency of the compression self-ignition internal combustion engine, for a wide range of operating states. The fuel injection adjustment unit then adjusts at least one of the injection timing and injection amount of at least one pilot injection to appropriately control pre-combustion, thereby more accurately controlling the start timing of the first combustion, and further reducing the amount of smoke generated and combustion noise.

1 is a diagram illustrating an example of a schematic configuration of an entire system of a compression ignition type internal combustion engine. FIG . 13 is a diagram for explaining an example of the relationship between the pilot injection, the main injection, the first combustion pressure, the second combustion pressure, the pressure development rate due to the first combustion, the pressure development rate due to the second combustion, and the crank angle in one combustion stroke. 3 is a diagram illustrating an example in which the pressure generation rate due to the first combustion and the pressure generation rate due to the second combustion shown in FIG. 2 are changed to a heat generation rate due to the first combustion and a heat generation rate due to the second combustion. FIG. FIG. 11 is a diagram for explaining an example of a simulation result when the rotation speed Ne of the compression ignition internal combustion engine is 1600 [rpm] and the (total) injection amount Qv is 30 [mm ³ /st]. FIG. 11 is a diagram for explaining an example of a simulation result when the rotation speed Ne of the compression ignition internal combustion engine is 1600 [rpm] and the (total) injection amount Qv is 55 [mm ³ /st]. FIG. 11 is a diagram illustrating an example of a simulation result when the rotation speed Ne of the compression ignition internal combustion engine is 2400 [rpm] and the (total) injection amount Qv is 30 [mm ³ /st]. FIG. 7 is a diagram for explaining the state in which the results of FIG. 4 to FIG. 6 are applied to positions during the operating state of a compression ignition type internal combustion engine, which are indicated by the rotation speed and the injection amount (load). FIG. 5 is a diagram for explaining the pressure generation rates of data S1 and S2 in FIG. 4 . FIG. 5 is a diagram for explaining the combustion noises of data S1 and S2 in FIG. 4 . FIG. 6 is a diagram for explaining the pressure generation rates of data S3 and S4 in FIG. 5 . FIG. 6 is a diagram for explaining the combustion noises of data S3 and S4 in FIG. 5 . FIG. 13 is a diagram illustrating an example of a target time-target peak height ratio characteristic. FIG. 13 is a diagram for explaining a tolerance of a target time-target peak height ratio characteristic. FIG. 16 is a diagram showing an example of experimental results of the heat release rate as a function of the crank angle when the injection timings and injection amounts of the first pilot injection (P1), the second pilot injection (P2), the third pilot injection (P3), and the main injection (M) are set as shown in FIG. FIG. 15 is a diagram showing the injection timing and injection amount of each pilot injection (P1, P2, P3) and main injection (M) for each heat generation rate (g1(θ), g2(θ), g3(θ), g4(θ), g5(θ)) according to the crank angle shown in FIG. FIG. 15 is a schematic diagram of g1(θ) shown in FIG. 14 . FIG. 11 is a diagram for explaining the relationship between Qp/Qall, which is the pre-combustion generation rate area (Qp) relative to the total input heat amount (Qall), which is the heat amount converted from the total injection amount, in one combustion stroke, and the amount of smoke generation. FIG. 11 is a diagram for explaining the relationship between Hpre/Qv, which is the pre-combustion occurrence rate height (Hpre) relative to the total injection amount (Qv) in one combustion stroke , and the amount of smoke generation. 10 is a flowchart illustrating an example of a processing procedure of a control device. 20 is a flowchart illustrating details (first embodiment) of [pre-combustion adjustment] in the flowchart shown in FIG. 19 . 21 is a flowchart illustrating another example of the flowchart shown in FIG. 20. 20 is a flowchart illustrating details of [pre-combustion adjustment] in the flowchart shown in FIG. 19 (second embodiment). 23 is a flowchart illustrating another example of the flowchart shown in FIG. 22.

[Example of schematic configuration of internal combustion engine system 1 (FIG. 1)]
An embodiment of the present invention will be described below with reference to the drawings. First, an example of a schematic configuration of an internal combustion engine system 1 will be described with reference to Fig. 1. In the description of the present embodiment, an internal combustion engine 10 (e.g., a diesel engine) mounted on a vehicle will be used as an example of a compression autoignition type combustion engine. Hereinafter, the internal combustion engine 10 refers to a compression autoignition type internal combustion engine.

The entire system will be described below, starting from the intake side and proceeding from the exhaust side. An air cleaner (not shown) and an intake air flow rate detection device 21 (e.g., an intake air flow rate sensor) are provided on the inlet side of the intake pipe 11A. The intake air flow rate detection device 21 outputs a detection signal corresponding to the flow rate of air taken in by the internal combustion engine 10 to the control device 50. The intake air flow rate detection device 21 is also provided with an intake air temperature detection device 28A (e.g., an intake air temperature sensor) and an atmospheric pressure detection device 23 (e.g., an atmospheric pressure sensor). The intake air temperature detection device 28A outputs a detection signal corresponding to the temperature of the intake air passing through the intake air flow rate detection device 21 to the control device 50. The atmospheric pressure detection device 23 outputs a detection signal corresponding to the surrounding atmospheric pressure to the control device 50.

The outlet side of the intake pipe 11A is connected to the inlet side of the compressor 35, and the outlet side of the compressor 35 is connected to the inlet side of the intake pipe 11B. The compressor 35 of the turbocharger 30 is driven to rotate by a turbine 36 that is driven to rotate by the energy of the exhaust gas, and supercharges the intake air that flows in from the intake pipe 11A by compressing it and sending it to the intake pipe 11B.

A compressor upstream pressure detection device 24A (e.g., a pressure sensor) is provided in the intake pipe 11A, which is upstream of the compressor 35. The compressor upstream pressure detection device 24A outputs a detection signal corresponding to the pressure in the intake pipe 11A to the control device 50. A compressor downstream pressure detection device 24B (e.g., a pressure sensor) is provided in the intake pipe 11B, which is downstream of the compressor 35 (a position in the intake pipe 11B between the compressor 35 and the intercooler 16). The compressor downstream pressure detection device 24B outputs a detection signal corresponding to the pressure in the intake pipe 11B to the control device 50.

An intercooler 16 is disposed upstream of the intake pipe 11B, and a throttle device 47 is disposed downstream of the intercooler 16. The intercooler 16 is disposed downstream of the compressor downstream pressure detection device 24B. An intake air temperature detection device 28B (e.g., an intake air temperature sensor) is provided between the intercooler 16 and the throttle device 47. The intake air temperature detection device 28B outputs a detection signal corresponding to the temperature of the intake air whose temperature has been reduced by the intercooler 16 to the control device 50.

The throttle device 47 drives a throttle valve 47V that adjusts the opening of the intake pipe 11B based on a control signal from the control device 50, and is capable of adjusting the intake flow rate. The control device 50 is capable of adjusting the opening of the throttle valve 47V by outputting a control signal to the throttle device 47 based on a detection signal from a throttle opening detection device 47S (e.g., a throttle opening sensor) and a target throttle opening. For example, the control device 50 determines the target throttle opening based on the amount of depression of the accelerator pedal detected based on the detection signal from the accelerator pedal depression amount detection device 25 and the operating state of the internal combustion engine 10, etc.

The accelerator pedal depression amount detection device 25 is, for example, an accelerator pedal depression angle sensor, and is provided on the accelerator pedal. The control device 50 can detect the amount of depression of the accelerator pedal by the driver based on the detection signal from the accelerator pedal depression amount detection device 25.

An intake manifold pressure detection device 24C (e.g., a pressure sensor) is provided downstream of the throttle device 47 in the intake pipe 11B, and the outlet side of the EGR pipe 13 is connected to it. The outlet side of the intake pipe 11B is connected to the inlet side of the intake manifold 11C, and the outlet side of the intake manifold 11C is connected to the inlet side of the internal combustion engine 10. The intake manifold pressure detection device 24C outputs a detection signal to the control device 50 according to the pressure of the intake air just before it flows into the intake manifold 11C. In addition, the EGR gas that flows in from the inlet side of the EGR pipe 13 (the connection with the intake pipe 11B) is discharged into the intake pipe 11B from the outlet side of the EGR pipe 13 (the connection with the intake pipe 11B).

The internal combustion engine 10 has multiple cylinders 45A-45D, and injectors 43A-43D are provided in each cylinder. Fuel is supplied to the injectors 43A-43D via a common rail 41 and fuel pipes 42A-42D, and the injectors 43A-43D are driven by control signals from the control device 50 to inject fuel into each cylinder 45A-45D.

The internal combustion engine 10 is provided with a rotation detection device 22, a coolant temperature detection device 28C, etc. The rotation detection device 22 is, for example, a rotation sensor, and outputs a detection signal corresponding to the rotation speed of the crankshaft of the internal combustion engine 10 (i.e., engine speed) to the control device 50. The coolant temperature detection device 28C is, for example, a temperature sensor, and outputs a detection signal corresponding to the temperature of the cooling coolant circulating within the internal combustion engine 10 to the control device 50.

The inlet side of the exhaust manifold 12A is connected to the exhaust side of the internal combustion engine 10, and the inlet side of the exhaust pipe 12B is connected to the outlet side of the exhaust manifold 12A. The outlet side of the exhaust pipe 12B is connected to the inlet side of the turbine 36, and the outlet side of the turbine 36 is connected to the inlet side of the exhaust pipe 12C.

The inlet side of the EGR pipe 13 is connected to the exhaust pipe 12B. The EGR pipe 13 connects the exhaust pipe 12B and the intake pipe 11B, and is capable of recirculating a portion of the exhaust gas in the exhaust pipe 12B (corresponding to the exhaust path) to the intake pipe 11B (corresponding to the intake path). The EGR pipe 13 is also provided with an EGR cooler 15 and an EGR valve 14. The EGR valve 14 adjusts the opening of the EGR pipe 13 based on a control signal from the control device 50, thereby adjusting the flow rate of EGR gas flowing through the EGR pipe 13.

An exhaust temperature detection device 29 is provided in the exhaust pipe 12B. The exhaust temperature detection device 29 is, for example, an exhaust temperature sensor, and outputs a detection signal corresponding to the exhaust temperature to the control device 50.

The outlet side of the exhaust pipe 12B is connected to the inlet side of the turbine 36, and the outlet side of the turbine 36 is connected to the inlet side of the exhaust pipe 12C. The turbine 36 is provided with a variable nozzle 33 that can control the flow rate of the exhaust gas led to the turbine 36 (the opening of the flow path leading to the exhaust gas to the turbine can be adjusted), and the opening of the variable nozzle 33 is adjusted by a nozzle driving device 31. The control device 50 can adjust the opening of the variable nozzle 33 by outputting a control signal to the nozzle driving device 31 based on a detection signal from a nozzle opening detection device 32 (e.g., a nozzle opening sensor) and a target nozzle opening.

A turbine upstream pressure detection device 26A (e.g., a pressure sensor) is provided in the exhaust pipe 12B upstream of the turbine 36. The turbine upstream pressure detection device 26A outputs a detection signal corresponding to the pressure in the exhaust pipe 12B to the control device 50. A turbine downstream pressure detection device 26B (e.g., a pressure sensor) is provided in the exhaust pipe 12C downstream of the turbine 36. The turbine downstream pressure detection device 26B outputs a detection signal corresponding to the pressure in the exhaust pipe 12C to the control device 50.

An exhaust purification device 61 is connected to the outlet side of the exhaust pipe 12C. For example, if the internal combustion engine 10 is a diesel engine, the exhaust purification device 61 includes an oxidation catalyst, a particulate filter, a selective reduction catalyst, etc.

The vehicle speed detection device 27 is, for example, a vehicle speed detection sensor, and is provided on the wheels of the vehicle. The vehicle speed detection device 27 outputs a detection signal corresponding to the rotation speed of the wheels of the vehicle to the control device 50.

The control device 50 has a CPU 51, a RAM 52, a storage device 53, a timer 54, etc. The control device 50 (CPU 51) receives detection signals from the various detection devices described above, and outputs control signals to the various actuators described above. The inputs and outputs of the control device 50 are not limited to the detection devices and actuators described above. The temperature and pressure of each part may be calculated by estimation without installing a sensor. The control device 50 detects the operating state of the internal combustion engine 10 based on detection signals from various detection devices including the above detection devices, and controls various actuators including the above actuators. The storage device 53 is a storage device such as a Flash-ROM, and stores programs and data for controlling the internal combustion engine and performing self-diagnosis. The control device 50 (CPU 51) also has an operating state detection unit 51A, a fuel injection calculation unit 51B, a fuel injection adjustment unit 51C, etc., the details of which will be described later.

The control device 50 injects the main injection, which is the main fuel injection , and one or more pilot injections, which are fuel injections prior to the main injection, into a cylinder in which air has been compressed and heated, for one combustion stroke, based on the operating state of the internal combustion engine 10. In the description of this embodiment, all injections prior to the main injection in one combustion stroke are collectively referred to as "pilot injections." The number and injection amount of pilot injections, the injection amount of main injection, etc. are calculated appropriately based on the total fuel injection amount in one combustion stroke and the operating state of the internal combustion engine, etc.

● [Pilot injection and main injection, pressure generation rate within the cylinder (Figure 2) and heat generation rate (Figure 3)]
Next, the pressure generation rate in the cylinder (e.g., cylinder No. 1) according to the crank angle (FIG. 2) and the heat generation rate in the cylinder (FIG. 3) will be described for pilot injection and main injection in one combustion stroke in a cylinder (e.g., cylinder No. 1) of the internal combustion engine 10. In the examples of FIGS. 2 and 3, the control device 50 performs three pilot injections slightly before the compression top dead center (position where crank angle = 0 [deg]) of the target cylinder, and performs one main injection slightly after the compression top dead center.

Figure 2 shows the results of an experiment or simulation in which the horizontal axis is the crank angle, which is the rotation angle of the crankshaft, and the vertical axis is the pressure generation rate in the cylinder. In the example of Figure 2, fuel is injected into the combustion chamber in which the intake air is compressed and heated by the piston in three pilot injections to cause self-ignition, and fuel is injected in the main injection to cause self-ignition. The three pilot injections cause one combustion, pilot combustion (corresponding to the first combustion), and the cylinder pressure due to this pilot combustion changes as shown by the pilot combustion pressure Pp indicated by the dotted line in Figure 2. The main injection also causes one combustion, main combustion (corresponding to the second combustion), and the cylinder pressure due to this main combustion overlaps with the pilot combustion pressure Pp and changes as shown by the main combustion pressure Pm indicated by the dashed line in Figure 2.

The pressure generation rate f(θ) shown by a solid line in FIG. 2 indicates the crank angle differential value of the in-cylinder pressure that changes according to the crank angle in one combustion stroke (the gradient of the change in the total in-cylinder pressure of the pilot combustion pressure Pp and the main combustion pressure Pm). As shown in FIG. 2, the peak position corresponding to the pilot combustion (corresponding to the first combustion) among the multiple peak positions in the pressure generation rate f(θ) in one combustion stroke is set as the pilot peak angle position Pap (corresponding to the first peak angle position). Similarly, the peak position corresponding to the main combustion (corresponding to the second combustion) among the multiple peak positions in the pressure generation rate f(θ) in one combustion stroke is set as the main peak angle position Pam (corresponding to the second peak angle position). As shown in FIG. 2, the crank angle of the pilot peak angle position Pap is set as θp, and the crank angle differential value of the in-cylinder pressure at the pilot peak angle position Pap is set as Hp. Similarly, the crank angle at the main peak angle position Pam is θm, and the crank angle differential of the in-cylinder pressure at the main peak angle position Pam is Hm. The crank angle difference Δθ (Δθ=θm-θp) between the main peak angle position Pam and the pilot peak angle position Pap is converted into time based on the difference in crank angle and the rotation speed of the crankshaft, and the time difference (the time difference corresponding to Δθ) is Δt. Furthermore, the crank angle differential of the in-cylinder pressure at the pilot peak angle position Pap (i.e., the value of the pressure generation rate) is Hp, the crank angle differential of the in-cylinder pressure at the main peak angle position Pam (i.e., the value of the pressure generation rate) is Hm, and the peak height ratio is Hp/Hm.

Although not shown, the horizontal axis in FIG. 2 may be changed from crank angle [deg] to time [sec], and the vertical axis may be changed from pressure development rate [MPa/deg] to pressure development rate [MPa/sec]. In this case, the pressure development rate (in this case, the time differential value of the cylinder pressure) is the same as the pressure development rate f(θ) in FIG. 2, and the peak positions corresponding to pilot combustion and main combustion among the multiple peak positions in the pressure development rate are respectively the pilot peak time position PtP (corresponding to the first peak time position) and the main peak time position Ptm (corresponding to the second peak time position). If the main peak time position Ptm (tm, Hm) and the pilot peak time position Ptp (tp, Hp) are used, the time difference Δt is expressed as tm-tp, and the peak height ratio is expressed as Hp/Hm.

Figure 3 shows a case where the focus is on heat inside the cylinder, as opposed to Figure 2, which focuses on pressure inside the cylinder. Figure 3 differs in that, when the same pilot injection and main injection as in Figure 2 are performed, the horizontal axis is the crank angle, just like in Figure 2, and the vertical axis is the heat release rate (the crank angle derivative of the amount of heat generated inside the cylinder). Figure 3 shows the results of an experiment or simulation where the horizontal axis is the crank angle, which is the rotation angle of the crankshaft, and the vertical axis is the heat release rate inside the cylinder.

The heat release rate g(θ) shown by a solid line in FIG. 3 indicates the crank angle differential value of the in-cylinder heat release amount that changes according to the crank angle in one combustion stroke (the gradient of the change in the total in-cylinder heat release amount of the pilot combustion heat Ep and the main combustion heat Em). As shown in FIG. 3, the peak position corresponding to the pilot combustion (corresponding to the first combustion) among the multiple peak positions in the heat release rate g(θ) in one combustion stroke is set as the pilot peak angle position Eap (corresponding to the first peak angle position). Similarly, the peak position corresponding to the main combustion (corresponding to the second combustion) among the multiple peak positions in the heat release rate g(θ) in one combustion stroke is set as the main peak angle position Eam (corresponding to the second peak angle position). As shown in FIG. 3, the crank angle of the pilot peak angle position Eap is set as θp, and the crank angle differential value of the in-cylinder heat release amount at the pilot peak angle position Eap is set as Hp. Similarly, the crank angle at the main peak angle position Eam is θm, and the crank angle differential of the in-cylinder heat generation amount at the main peak angle position Eam is Hm. The crank angle difference Δθ (Δθ=θm-θp) between the main peak angle position Eam and the pilot peak angle position Eap is converted into time based on the difference in crank angle and the rotation speed of the crankshaft, and the time difference (the time difference corresponding to Δθ) is Δt. Furthermore, the crank angle differential of the in-cylinder heat generation amount at the pilot peak angle position Eap (i.e., the value of the heat generation rate) is Hp, the crank angle differential of the in-cylinder heat generation amount at the main peak angle position Eam (i.e., the value of the heat generation rate) is Hm, and the peak height ratio is Hp/Hm.

Although not shown, the horizontal axis in FIG. 3 may be changed from crank angle [deg] to time [sec], and the vertical axis may be changed from heat release rate [J/deg] to heat release rate [J/sec]. In this case, the heat release rate (in this case, the time differential value of the amount of heat generated in the cylinder) is the same as the heat release rate g(θ) in FIG. 3, and the peak positions corresponding to pilot combustion and main combustion among the multiple peak positions in the heat release rate are respectively designated as pilot peak time position EtP (corresponding to the first peak time position) and main peak time position Etm (corresponding to the second peak time position). If the main peak time position Etm (tm, Hm) and the pilot peak time position Etp (tp, Hp) are used, the time difference Δt is expressed as tm-tp, and the peak height ratio is expressed as Hp/Hm.

The inventors have found through various experiments and simulations that there is an optimal time difference Δt and an optimal peak height ratio Hp/Hm for reducing the combustion noise of an internal combustion engine, depending on the operating state of the internal combustion engine. Note that the time difference Δt and the peak height ratio Hp/Hm may be based on the crank angle and pressure generation rate shown in FIG. 2, the crank angle and heat generation rate shown in FIG. 3, the time and pressure generation rate not shown, or the time and heat generation rate not shown, but the following description of this embodiment will be based on the crank angle and pressure generation rate shown in FIG. 2.

● [Simulation (or experimental) results for each operating condition (Figures 4 to 7)]
Next, using Figures 4 to 7, the results of a simulation (or experiment) in which the time difference Δt and the peak height ratio Hp/Hm are changed to various values in each operating state of the internal combustion engine are shown. The offset center frequency shown in Figures 4 to 6 is a time difference related amount based on the time difference Δt, a frequency calculated based on the time difference Δt, a frequency with the time difference Δt [sec] as 1/2 period, and f = 1/(2 * Δt). For example, when the time difference Δt = 0.26 [ms], the frequency = 1/(0.00026 [sec] * 2) ≒ 1.923 [KHz]. The offset center frequency is a frequency that is approximately the center of the offset frequency band (f = 0.3/Δt to f = 0.7/Δt) that offsets and reduces the combustion noise due to pilot combustion and main combustion.

FIG. 4 shows the results of a simulation (or experiment) in which the time difference Δt and the peak height ratio Hp/Hm are set to various values (circle positions in FIG. 4) when the internal combustion engine speed Ne is 1600 [rpm] and the injection amount (load) Qv injected in one combustion stroke is 30 [mm ³ /st]. The offset center frequency is a frequency converted from the time difference Δt, as described above. In the idling state of this internal combustion engine, the rotation speed Ne is about 700 [rpm] and the injection amount (load) Qv is about 5 [mm ³ /st]. The "injection amount (load) Qv" corresponds to the "total injection amount", which is the amount of fuel injected by pilot injection and main injection in one combustion stroke .

In Figure 4, the curves of combustion noise levels D1 to D5 shown by dashed lines indicate the overall combustion noise levels obtained by integrating the observed combustion noise in the range of 0.9 to 5.6 [KHz] as a result of simulation (or experiment), and the combustion noise levels are D5>D4>D3>D2>D1. Note that the region where the peak height ratio Hp/Hm exceeds 1.0 is not realistic because the peak position of the pilot combustion is higher than the peak position of the main combustion. Also, the peak height ratio Hp/Hm of less than 0.2 is not realistic because the pilot combustion is too small. Therefore, the peak height ratio Hp/Hm is considered to be 1.0 or less and 0.2 or more. Also, the region where the offset center frequency exceeds 2.2 [KHz] is the region where the time difference Δt becomes shorter than about 0.227 [msec], which is close to the limit of the injector and control, and is not realistic. In addition, in the region where the offset center frequency is less than 0.6 [KHz], the time difference Δt is longer than approximately 0.833 [msec], and the interval between the pilot injection and the main injection is too long, the offset frequency band width is short, and the offset effect cannot be obtained, so 0.6 [KHz] or more is considered. Therefore, the offset center frequency is considered to be 2.2 [KHz] or less and 0.6 [KHz] or more (same for Figures 5 and 6).

The operating state shown in Figure 4 (rotation speed = 1600 [rpm], fuel injection amount (load) = 30 [ ^mm3 /st]) is indicated as U1 in Figure 7, which shows operating states with rotation speed on the horizontal axis and fuel injection amount (load) on the vertical axis. In this operating state U1, as shown in Figure 4, it can be seen that in order to keep the combustion noise level below D1, the offset center frequency should be about 1.9 [KHz] to about 2.2 [KHz] (i.e., the time difference Δt should be about 0.227 [msec] to about 0.263 [msec]) and the peak height ratio Hp/Hm should be about 0.85 to about 1.0.

5 shows the results of a simulation (or experiment) in which the time difference Δt and the peak height ratio Hp/Hm are set to various values (circle positions in FIG. 5) when the internal combustion engine speed Ne is 1600 [rpm] and the injection amount (load) Qv injected in one combustion stroke is 55 [ ^mm3 /st]. Note that the cancellation center frequency is the frequency converted from the time difference Δt, as described above.

In Figure 5, the curves of combustion noise levels D1 to D5 shown by dashed lines indicate the observed overall combustion noise levels, as in Figure 4, with the combustion noise levels being D5>D4>D3>D2>D1. Also, the peak height ratio Hp/Hm is considered to be 1.0 or less and 0.2 or more, and the offset center frequency is considered to be 2.2 [KHz] or less and 0.6 [KHz] or more, which is also the same. However, the injection amount Qv is increased from the fuel injection amount in the operating state in Figure 4, and it is realistic to consider the offset center frequency to be approximately 0.9 [KHz] or less.

The operating state shown in Figure 5 (rotation speed = 1600 [rpm], fuel injection amount (load) = 55 [ ^mm3 /st]) is shown as U2 in Figure 7, which shows operating states with rotation speed on the horizontal axis and fuel injection amount (load) on the vertical axis. In this operating state U2, it can be seen that in order to achieve the combustion noise level D2 shown in Figure 5 and a realistic cancellation center frequency of approximately 0.9 [KHz] or less, the cancellation center frequency should be approximately 0.9 [KHz] or more (i.e., the time difference Δt should be approximately 0.556 [msec] or less) and the peak height ratio Hp/Hm should be approximately 0.2 to approximately 0.5.

6 shows the results of a simulation (or experiment) in which the time difference Δt and the peak height ratio Hp/Hm are set to various values (circle positions in FIG. 6) when the internal combustion engine speed Ne is 2400 [rpm] and the injection amount (load) Qv injected in one combustion stroke is 30 [ ^mm3 /st]. Note that the cancellation center frequency is the frequency converted from the time difference Δt, as described above.

In Figure 6, the curves of combustion noise levels D2 to D5 shown by dashed lines indicate the observed combustion noise levels, as in Figure 4, with the combustion noise levels being D5>D4>D3>D2. Also, the peak height ratio Hp/Hm is considered to be 1.0 or less and 0.2 or more, and the cancellation center frequency is considered to be 2.2 [KHz] or less and 0.6 [KHz] or more, which is also the same. However, the rotation speed Ne was increased from the rotation speed in the operating state in Figure 4, and did not decrease to the combustion noise level D1.

The operating state shown in Figure 6 (rotation speed = 2400 [rpm], fuel injection amount (load) = 30 [ ^mm3 /st]) is indicated as U3 in Figure 7, which shows operating states with the rotation speed on the horizontal axis and the fuel injection amount (load) on the vertical axis. In this operating state U3, as shown in Figure 6, it can be seen that in order to keep the combustion noise level below D2, the offset center frequency should be about 1.22 [KHz] to about 2.2 [KHz] (i.e., the time difference Δt should be about 0.227 [msec] to about 0.410 [msec]) and the peak height ratio Hp/Hm should be about 0.75 to about 1.0.

As shown in Figure 7, when the rotation speed is approximately constant and the load (fuel injection amount) increases from low to high, it can be seen that increasing the time difference Δt and decreasing the peak height ratio Hp/Hm is effective in reducing combustion noise. It can also be seen that when the load (fuel injection amount) is approximately constant and the rotation speed increases from low to high, the allowable range of the time difference Δt is expanded to a longer range and the allowable range of the peak height ratio Hp/Hm is expanded to a lower range.

As explained above, the time difference Δt (or the offset center frequency (time difference related quantity) converted from the time difference Δt) and the peak height ratio Hp/Hm have a significant effect on reducing combustion noise, and there is an optimal time difference Δt and an optimal peak height ratio Hp/Hm depending on the operating conditions.

[Optimal time difference Δt and optimal peak height ratio Hp/Hm in each operating state (Figures 8 to 11)]
FIG. 8 shows fs1(θ), which is the crank angle and pressure generation rate in the case of data S1 (1.9 [KHz], 0.88) in FIG. 4, and fs2(θ), which is the crank angle and pressure generation rate in the case of data S2 (1.9 [KHz], 0.58) in FIG. 4. Since the frequency converted from the time difference Δt is 1.9 [KHz] in both cases, the crank angle difference Δθ is the same. In addition, the peak height ratio Hp(H)/Hm(H) of fs1(θ) is 0.88, and the peak height ratio Hp(L)/Hm(L) of fs2(θ) is 0.58. The observation results of the frequency/combustion noise spectrum in this case are shown in FIG. 9.

As shown in Figure 9, for the same time difference Δt (converted frequency = 1.9 [KHz]), the peak height ratio Hp/Hm = 0.88 (combustion noise due to fs1(θ) (solid line graph in Figure 9)) shows a relatively large reduction in combustion noise in the frequency band from approximately 1.2 [KHz] to approximately 2.5 [KHz] compared to the peak height ratio Hp/Hm = 0.58 (combustion noise due to fs2(θ) (dotted line graph in Figure 9)).

Figure 10 shows fs3(θ), which is the crank angle and pressure generation rate in the case of data S3 (0.83 [KHz], 0.75) in Figure 5, and fs4(θ), which is the crank angle and pressure generation rate in the case of data S4 (0.83 [KHz], 0.26) in Figure 5. The frequencies converted from the time difference Δt are both 0.83 [KHz], so the crank angle difference Δθ is the same. In addition, the peak height ratio Hp(H)/Hm(H) of fs3(θ) is 0.75, and the peak height ratio Hp(L)/Hm(L) of fs4(θ) is 0.26. Since the main injection amount is larger than that in Figure 8, the time from the start of main injection to the main peak is longer, and it becomes difficult to shorten the time difference Δt (crank angle difference Δθ) with the pilot peak due to the constraint of the pilot and main injection interval. The observation results of the frequency and combustion noise spectrum in this case are shown in Figure 11.

As shown in Figure 11, for the same time difference Δt (converted frequency = 0.83 [KHz]), the peak height ratio Hp/Hm = 0.26 (combustion noise due to fs4 (θ) (solid line graph in Figure 11)) has less noise reduction effect in the cancellation frequency band of about 0.5 [KHz] to about 1.2 [KHz] compared to the peak height ratio Hp/Hm = 0.75 (combustion noise due to fs3 (θ) (dotted line graph in Figure 11)), but the noise increase effect in the amplification frequency band of about 1.2 [KHz] to about 2.2 [KHz] centered around about 1.7 [KHz] is suppressed, and the maximum value of the spectrum in the accumulation range of the overall combustion noise value from 0.9 [KHz] to 5.6 [KHz] is lower, indicating a relatively large reduction in combustion noise.

[Setting the target time/target peak height ratio characteristics (Figures 12 and 13)]
From the above results, a target time/target peak height ratio characteristic (see FIG. 12 ) is created in which an optimal target time difference (or an optimal target time difference related amount (target offset central frequency)) and an optimal target peak height ratio are set according to the operating state of the internal combustion engine (specifically, the rotation speed and load (injection amount)), and the target time/target peak height ratio is stored in the memory device 53 of the control device 50. The target time/target peak height ratio characteristic is set corresponding to each of a plurality of preset rotation speeds, with one of the target offset central frequency (or target time difference), which is the target time difference related amount calculated based on the target time difference, and the target peak height ratio on the vertical axis and the other on the horizontal axis.

The target time-target peak height ratio characteristic is expressed as a graph-like characteristic for each rotation speed, as shown in the example of Figure 12. In Figure 12, the characteristic when Ne = 1600 [rpm] is expressed by h (1600), the characteristic when Ne = 2000 [rpm] is expressed by h (2000), and the characteristic when Ne = 2400 [rpm] is expressed by h (2400).

Also, for example, in the characteristics of h(1600) (Ne=1600 [rpm]) in Figure 12, the position when the injection amount (load) Qv=30 [ ^mm3 /st] is represented by the position M11 (Ne1600, Qv30), the position when the injection amount (load) Qv=40 [ ^mm3 /st] is represented by the position M12 (Ne1600, Qv40), and the position when the injection amount (load) Qv=55 [ ^mm3 /st] is represented by the position M13 (Ne1600, Qv55). Similarly, in the characteristic of h(2000) (Ne=2000[rpm]) in Fig. 12, the position of the injection amount (load) Qv=40 [mm ³ /st] is represented by the position of M22 (Ne2000, Qv40), and the position of the injection amount (load) Qv=55 [mm ³ /st] is represented by the position of M23 (Ne2000, Qv55). Similarly, in the characteristic of h(2400) ⁽ Ne=2400[rpm]) in Fig. 12, the position of the injection amount (load) Qv=30 [mm ³ /st] is represented by the position of M31 (Ne2400, Qv30), and the position of the injection amount (load) Qv=40 [mm 3 /st] is represented by the position of M32 (Ne2400, Qv40). The dashed dotted lines in Fig. 12 indicate equal load lines passing through the same load positions. As shown in FIG. 12 , when the internal combustion engine speed is substantially constant and the load of the internal combustion engine increases from a low load to a high load, the target time difference-related quantity is changed so that the time difference (Δt) becomes longer (the target cancellation center frequency is changed so that it becomes lower), and the target peak height ratio (Hp/Hm) is changed so that it becomes smaller.

For example, the control device 50 can use the detected operating state (rpm, load) of the internal combustion engine and the target time/target peak height ratio characteristics (Figure 12) stored in the memory device 53 to determine the target time difference related quantity (in this case, the target offset center frequency) and the target peak height ratio according to the operating state (rpm, load) of the internal combustion engine.

Figure 13 shows an example of the allowable upper limit (Max) h (1600) and the allowable lower limit (Min) h (1600) in the characteristic of h (1600) in Figure 12. In the example of M11 in Figure 13, if ±0.15 for the target peak height ratio and ±0.2 [KHz] for the target cancellation center frequency are achieved based on data S1 in Figure 4, the target noise level can be kept within approximately ±1 [dBA]. As shown by the allowable upper limit (Max) h (1600) and allowable lower limit (Min) h (1600) in Figure 13, in the example of M11, even if the value is slightly larger than ±0.15 for the target peak height ratio or slightly larger than ±0.2 [KHz] for the target cancellation center frequency, the target noise level can be kept within approximately ±1 [dBA].

In addition, in the example of M12 in Fig. 13, which has a higher load than M11, if the target peak height ratio is ±0.15 and the target cancellation center frequency is ±0.2 [KHz], the target noise level can be kept within approximately ±1 [dBA]. In addition, in the example of M13 in Fig. 13, which has an even higher load than M12, the inventors have confirmed from the results of various simulations and experiments that if the target peak height ratio is slightly smaller than ±0.15 and the target cancellation center frequency is ±0.1 [KHz], the target noise level can be kept within approximately ±1 [dBA] based on the data S4 in Fig. 5. As shown in FIG. 13, the upper tolerance limit (Max) h (1600) and the lower tolerance limit (Min) h (1600) in the example of M13 can be kept within the target noise level of approximately ±1 dBA by setting the target peak height ratio to a value slightly smaller than ±0.15 and the target cancellation center frequency to ±0.1 [KHz], which is slightly smaller than ±0.2 [KHz].

In other words, it is preferable to control Hp/Hm so that the deviation amount falls within the allowable height ratio with respect to the target peak height ratio. The "allowable height ratio" is set to 0.15 (the allowable height ratio reference value) when the load (Qv) is close to a predetermined load (in this case, close to Qv = 40 [mm ³ /st]). Also, as the load (Qv) becomes smaller than the predetermined load (in this case, Qv = 40 [mm ³ /st]), the allowable height ratio is set to be larger than the allowable height ratio reference value (set to a value slightly larger than 0.15). Also, as the load (Qv) becomes larger than the predetermined load (in this case, Qv = 40 [mm ³ /st]), the allowable height ratio is set to be smaller than the allowable height ratio reference value (set to a value slightly smaller than 0.15). For this reason, in FIG. 13, the interval in the direction of the target peak height ratio at the allowable upper limit (Max) h (1600) and the allowable lower limit (Min) h (1600) is set to become narrower as the load (Qv) increases and to become wider as the load (Qv) decreases.

Similarly, it is preferable to control the target cancellation center frequency so that the deviation of the actual cancellation center frequency from the target cancellation center frequency falls within the allowable frequency. The "allowable frequency" is set to 0.2 [KHz] (allowable frequency reference value) when the load (Qv) is near the predetermined load (in this case, near Qv = 40 [mm ³ /st]). Also, as the load (Qv) becomes smaller than the predetermined load (in this case, Qv = 40 [mm ³ /st]), the allowable frequency is set to be larger than the allowable frequency reference value (set to a value slightly larger than 0.2 [KHz]). Also, as the load (Qv) becomes larger than the predetermined load (in this case, Qv = 40 [mm ³ /st]), the allowable frequency is set to be smaller than the allowable frequency reference value (set to a value slightly smaller than 0.2 [KHz]). For this reason, in FIG. 13, the interval in the direction of the target cancellation center frequency at the allowable upper limit (Max) h (1600) and the allowable lower limit (Min) h (1600) is set to become narrower as the load (Qv) increases, and to become wider as the load (Qv) decreases.

The above explanation has been about further reducing combustion noise based on the time difference Δt and the peak height ratio Hp/Hm. In the following, in addition to adjusting the time difference Δt and the peak height ratio Hp/Hm described above, we will further explain how the amount of smoke generated can be further reduced by appropriately controlling the pre-combustion that occurs before the above-mentioned pilot combustion (corresponding to the first combustion).

[Examples of differences in combustion due to differences in pre-combustion (Figures 14 to 16)]
FIG. 14 shows an example of experimental results of five types of combustion, g1(θ) to g5(θ), with the horizontal axis being the crank angle [deg] and the vertical axis being the heat release rate [J/deg] (crank angle derivative of the amount of heat generated in the cylinder). g1(θ) to g5(θ) are all obtained by performing three pilot injections indicated by "P1, P2, P3" and one main injection indicated by "M". Note that in g1(θ) to g5(θ), the injection timing (injection start crank angle position) and injection amount of each pilot injection (P1, P2, P3) and main injection (M) are as shown in FIG. 15, and only the injection amount of the pilot injection (second pilot injection P2) two injections before the main injection M is different. Note that the injection amount of the second pilot injection P2 is (Qb+β2)>(Qb+β1)>Qb>(Qb-α1)>(Qb-α2).

FIG. 16 is a diagram showing g1(θ) in FIG. 14 in a schematic diagram. As shown in FIG. 16, multiple combustions (pre-combustion, first combustion, second combustion) occur in one combustion stroke . The multiple combustions (combustion occurrence rates) have a pre-combustion occurrence rate (first, main pre-combustion occurrence rate), a first combustion occurrence rate, and a second combustion occurrence rate. In FIG. 16, the first pre-combustion (first pre-combustion occurrence rate in FIG. 16) occurs mainly by the first pilot injection P1, and the main pre-combustion (main pre-combustion occurrence rate in FIG. 16) occurs mainly by the second pilot injection P2. The first combustion (first combustion occurrence rate in FIG. 16) occurs mainly by the third pilot injection P3, and the second combustion (second combustion occurrence rate in FIG. 16) occurs mainly by the main injection M. The first combustion (first combustion occurrence rate) occurs following the pre-combustion (main pre-combustion occurrence rate) so as to overlap with a part of the pre-combustion (in this case, the main pre-combustion occurrence rate). The second combustion (second combustion occurrence rate) occurs subsequent to the first combustion (first combustion occurrence rate) so as to overlap with a part of the first combustion (first combustion occurrence rate). Note that in Fig. 14 and Fig. 16, the vertical axis is the "heat release rate" (crank angle derivative (or time derivative) of the amount of heat release in the cylinder), but the vertical axis may be the "pressure release rate" (crank angle derivative (or time derivative) of the pressure in the cylinder), and the name "combustion occurrence rate" is used as a name that can be used in either case.

In FIG. 16, the start time of the first combustion occurrence rate (in this case, the crank angle differential value of the in-cylinder heat generation amount that changes according to the crank angle) is the time (position) indicated by "θs1". Also, g1(θ) to g5(θ) in FIG. 14 are the time difference Δt converted from the angle difference and the rotation speed between the peak position (first peak angle position) of the first combustion occurrence rate (see FIG. 16) and the peak position (second peak angle position) of the second combustion occurrence rate (see FIG. 16), and Hp/Hm, which is the height Hp of the first peak angle position relative to the height Hm of the second peak angle position, are adjusted as described above to reduce the combustion noise. In addition, as described below, the amount of smoke generation can be reduced by appropriately adjusting the pre-combustion (the first pre-combustion occurrence rate and the main pre-combustion occurrence rate in FIG. 16). The adjustment of the pre-combustion occurrence rate to reduce the amount of smoke generation includes adjustment of the area of the pre-combustion occurrence rate and adjustment of the height of the pre-combustion occurrence rate, which will be described in order below.

[Adjustment of pre-combustion occurrence rate area Qp (FIGS. 16 and 17)]
16, the pre-combustion occurrence rate area Qp is an area surrounded by the pre-combustion occurrence rate (first pre-combustion occurrence rate, main pre-combustion occurrence rate) before the occurrence start time θs1 of the first combustion occurrence rate, and is an area indicated by the solid region "Qp." Note that the pre-combustion occurrence rate is a time differential value of the in-cylinder heat generation amount or in-cylinder pressure, or a crank angle differential value of the in-cylinder heat generation amount or in-cylinder pressure.

Since the pre-combustion occurrence rate area Qp (heat value) varies depending on the fuel injection amount, which corresponds to the displacement of the internal combustion engine, in order to generalize and eliminate these effects, Qp/Qall is calculated by dividing the pre-combustion occurrence rate area Qp by the total input heat value Qall, which is the heat value converted from the total injection amount Qv, which is the amount of fuel injected by the pilot injection and main injection in one combustion stroke. The total input heat value Qall can be calculated, for example, by the total injection amount Qv [ ^mm3 ] * fuel density [g/ ^mm3 ] * lower heating value [MJ/Kg].

Figure 17 is a plot of (Qp/Qall, smoke generation amount) for each of g1(θ) to g5(θ) shown in Figure 14, with Qp/Qall set on the horizontal axis and the smoke generation amount set on the vertical axis. In the example shown in Figure 17, g1(θ), g2(θ), and g3(θ) are below the allowable upper limit of the smoke generation amount, but g4(θ) and g5(θ) exceed the allowable upper limit. From Figure 17, in order to make the smoke generation amount below the allowable upper limit, Qp/Qall needs to be about 10.5 [%] or less (below the upper limit of the target pre-combustion area related amount). Note that g1(θ) to g5(θ) only differ in the injection amount of the second pilot injection, so by adjusting at least the injection amount of the second pilot injection, Qp/Qall can be relatively easily adjusted to about 10.5 [%] or less (below the upper limit of the target pre-combustion area related amount).

As shown in FIG. 14, the pre-combustion occurrence rate area Qp of g4(θ) and g5(θ) is much larger than the pre-combustion occurrence rate area Qp of g1(θ) to g3(θ), and the first combustion occurrence rate start time of g4(θ) and the first combustion occurrence rate start time of g5(θ) are more advanced than θs1 (the first combustion occurs earlier than the target). For this reason, in g4(θ) and g5(θ), the first combustion occurrence start time is unstable and advanced, so the time difference Δt is somewhat long, which is not very desirable in terms of suppressing combustion noise.

[Adjustment of pre-combustion occurrence rate height Hpre (Figures 16 and 18)]
16, the pre-combustion occurrence rate height Hpre is the height of the pre-combustion occurrence rate (main pre-combustion occurrence rate) at the occurrence start time θs1 of the first combustion occurrence rate, and is the height indicated by “Hpre.” The pre-combustion occurrence rate is the time differential value of the in-cylinder heat generation amount or the in-cylinder pressure, or the crank angle differential value of the in-cylinder heat generation amount or the in-cylinder pressure.

In addition, since the pre-combustion occurrence rate height Hpre (heat generation amount height) varies depending on the amount of fuel injection, which corresponds to the displacement of the internal combustion engine, in order to eliminate these effects and generalize the result, Hpre/Qv is calculated by dividing the pre-combustion occurrence rate height Hpre (heat generation amount height) by the total injection amount Qv, which is the amount of fuel injected by the pilot injection and main injection in one combustion stroke.

Figure 18 is a plot of (Hpre/Qv, smoke generation amount) for each of g1(θ) to g5(θ) shown in Figure 14, with Hpre/Qv on the horizontal axis and smoke generation amount on the vertical axis. In the example shown in Figure 18, g1(θ), g2(θ), and g3(θ) are below the allowable upper limit of smoke generation amount, but g4(θ) and g5(θ) exceed the allowable upper limit. From Figure 17, in order to make the smoke generation amount below the allowable upper limit, Hpre/Qv needs to be about 1.3 or less (below the upper limit of the target pre-combustion height related amount). Note that g1(θ) to g5(θ) only differ in the injection amount of the second pilot injection, so by adjusting at least the injection amount of the second pilot injection, Hpre/Qv can be relatively easily adjusted to about 1.3 or less (below the upper limit of the target pre-combustion height related amount).

As shown in FIG. 14, the pre-combustion occurrence rate height Hpre for g4(θ) and g5(θ) is much higher than the pre-combustion occurrence rate height Hpre for g1(θ) to g3(θ), and the first combustion occurrence rate start time for g4(θ) and the first combustion occurrence rate start time for g5(θ) are more advanced than θs1 (the first combustion occurs earlier than the target). For this reason, the first combustion occurrence start time for g4(θ) and g5(θ) is unstable and advanced, so the time difference Δt is somewhat longer, which is not very desirable in terms of suppressing combustion noise.

[Processing procedure of the control device 50 (FIGS. 19 to 23)]
Next, examples of processing procedures (first and second embodiments) by the control device 50 will be described with reference to the flowcharts shown in Figures 19 to 23. The first embodiment is a control using the above-mentioned "adjustment of the pre-combustion occurrence rate area Qp", and the second embodiment is a control using the above-mentioned "adjustment of the pre-combustion occurrence rate height Hpre".

[First embodiment (FIGS. 19 to 21)]
First, the processing procedure of the control device 50 in the first embodiment using "adjustment of the pre-combustion occurrence rate area Qp" will be described with reference to the flowcharts shown in Figures 19 to 21. The control device 50 (CPU 51) starts the processing shown in Figure 19, for example, at every predetermined crank angle (for example, every 180 [° CA] in the case of a four-cylinder engine), and proceeds to step S010.

In step S010, the control device 50 detects various operating conditions of the internal combustion engine, and the process proceeds to step S015. For example, the control device 50 detects the internal combustion engine speed, intake volume, intake manifold pressure, variable nozzle opening amount, accelerator pedal depression amount, fuel injection amount, etc. based on detection signals from various detection devices shown in FIG. 1 and the control amount of the injector (previous fuel injection amount). The control device 50 (CPU 51) that executes the process of step S010 corresponds to the operating condition detection unit 51A (see FIG. 1) that detects the operating condition of the internal combustion engine.

In step S015, the control device 50 calculates the torque required by the driver based on the detected driving state, and proceeds to step S020. For example, the control device 50 calculates the torque required based on the internal combustion engine speed and the accelerator pedal depression amount, using a map stored in the storage device, a formula, etc.

In step S020, the control device 50 calculates the (next) total injection amount (Qv) based on the calculated required torque and the operating state of the internal combustion engine, and proceeds to step S025. Note that the details of the calculation procedure for the total injection amount (Qv) will not be explained here.

In step S025, the control device 50 determines a target time difference related quantity (target offset central frequency) and a target peak height ratio based on the operating state of the internal combustion engine (revolutions per minute, load (total injection amount)) and the target time/target peak height ratio characteristic (see FIG. 12) stored in the storage device, and proceeds to step S030. For example, when the (revolutions per minute, load (injection amount)) is (1600 [rpm], 30 [ ^mm3 /st]), the control device 50 selects h(1600) from the target time/target peak height ratio characteristic shown in FIG. 12, and determines the target time difference related quantity (target offset central frequency) and the target peak height ratio from the position of M11 (Ne1600, Qv30) corresponding to the position of 30 [ ^mm3 /st] at the selected h(1600).

In step S030, the control device 50 determines the provisional number of pilot injections, the provisional injection timing and provisional injection amount of each pilot injection, and the provisional injection timing and provisional injection amount of the main injection for the next fuel injection based on the (next) total injection amount (Qv), the target time difference related amount (target offset center frequency), the target peak height ratio, and the operating state of the internal combustion engine, and proceeds to step S040. Note that in injections during one combustion stroke , the number of pilot injections is one or more, and the number of main injections is one.

At this time, the provisional injection timing of the main injection and the provisional injection timing of the pilot injection immediately before the main injection are set based on the target time difference related amount (target offset center frequency). For example, the memory device stores a target time interval according to the target time difference related amount (target offset center frequency) in the form of a map or the like, and the control device 50 uses the target time difference related amount and the map to determine the provisional injection timing of the main injection and the provisional injection timing of the pilot injection immediately before the main injection so that the target time interval is obtained. The above map is created using simulations, experiments, etc., and is stored in the memory device.

The provisional total pilot injection amount, which is the sum of the provisional injection amounts of the multiple pilot injections, and the provisional injection amount of the main injection are calculated using a predetermined calculation formula, map, etc. based on the target peak height ratio. For example, the control device 50 calculates the provisional total pilot injection amount and the provisional main injection amount by dividing the (next) total injection amount (Qv) into the provisional total pilot injection amount and the provisional main injection amount according to the target peak height ratio. The above-mentioned predetermined calculation formula and map are created using simulations, experiments, etc., and are stored in the storage device.

In step S040, the control device 50 executes "pre-combustion adjustment" and proceeds to step S050. Details of "pre-combustion adjustment" will be described later.

In step S050, the control device 50 calculates the final number of pilot injections, the final injection timing and final injection amount of each pilot injection, and the final injection timing and final injection amount of the main injection for the next fuel injection, and ends the process shown in Fig. 19. Note that in injection during one combustion stroke , the number of pilot injections is multiple (multiple to generate both pre-combustion and first combustion), and the number of main injections is one.

As described above, once the final number of pilot injections, the final injection timing and final injection amount of each pilot injection, and the final injection timing and final injection amount of the main injection are set, the control device 50 (not shown) executes the processing of each injection at the targeted timing using the existing pilot injection scheduling process and the existing main injection scheduling process.

The target time difference related quantity (target offset center frequency) in the above description may be changed to a target time difference. The target time difference is half the time (half wavelength) of one cycle at the target offset center frequency. For example, the horizontal axis of the target time/target peak height ratio characteristic shown in FIG. 12 is changed from the target offset center frequency (target time difference related quantity) to the target time difference, and the target time/target peak height ratio characteristic is stored in the storage device. Then, in step S025, the control device 50 calculates the target time difference and the target peak height ratio based on the operating state of the internal combustion engine (rotation speed, load (injection amount)) and the target time/target peak height ratio characteristic stored in the storage device. Then, in step S030, the control device 50 sets the injection timing of the main injection and the injection timing of the pilot injection immediately before the main injection based on the target time difference.

The control device 50 (CPU 51) which executes the processing of steps S025 and S030 described above corresponds to a fuel injection calculation unit 51B (see FIG. 1) which determines the target time difference or the target time difference related amount according to the operating state of the internal combustion engine and the target peak height ratio, and determines the injection timing and injection amount of at least the pilot injection immediately before the main injection in the pre-stage injection and the injection timing and injection amount of the main injection so that the time difference (Δt) approaches the target time difference (or the time difference related amount based on the time difference (Δt) approaches the target time difference related amount) and the peak height ratio (Hp/Hm) approaches the target peak height ratio.

● [Details of pre-combustion adjustment 1-1 (Figure 20) and 1-2 (Figure 21)]
Next, details (Details 1-1) of [Pre-combustion adjustment] in step S040 in Fig. 19 will be described with reference to Fig. 20. When the control device 50 advances the process to step S040 shown in Fig. 19, the control device 50 advances the process to step S110 shown in Fig. 20.

In step S110, the control device 50 predicts the state of each pre-combustion occurrence rate (first pre-combustion occurrence rate and main pre-combustion occurrence rate in FIG. 16) and proceeds to step S115. For example, the control device 50 predicts the occurrence position (crank angle) and magnitude (height) of the first pre-combustion occurrence rate, the occurrence position (crank angle) and magnitude (height) of the main pre-combustion occurrence rate, the occurrence position (crank angle) and magnitude (height) of the first combustion occurrence rate, etc., as shown in FIG. 16, based on the operating state of the internal combustion engine, the provisional number of pilot injections, and the provisional injection timing and amount of each pilot injection.

In step S115, the control device 50 predicts the occurrence start time θs1 of the first combustion rate (see FIG. 16) and proceeds to step S120. For example, the control device 50 predicts the occurrence start time θs1 of the first combustion rate based on the prediction performed in step S110.

In step S120, the control device 50 predicts the pre-combustion occurrence rate area Qp prior to the occurrence start time θs1, and proceeds to step S125. For example, the control device 50 calculates the pre-combustion occurrence rate area Qp based on the occurrence position and size (height) of the first pre-combustion occurrence rate predicted in step S110, the occurrence position and size (height) of the main pre-combustion occurrence rate, and the occurrence start time θs1.

In step S125, the control device 50 calculates the total input heat amount Qall from the (next) total injection amount Qv, and proceeds to step S130. As described above, for example, the control device 50 calculates the total input heat amount Qall using the total injection amount Qv [mm ³ ] * fuel density [g/mm ³ ] * lower heating value [MJ/Kg].

In step S130, the control device 50 determines whether or not Qp/Qall is equal to or less than the upper limit of the target pre-combustion area related quantity. If Qp/Qall is equal to or less than the upper limit of the target pre-combustion area related quantity (Yes), the control device 50 ends the process shown in FIG. 20 and returns to step S050 shown in FIG. 19, and if Qp/Qall is greater than the upper limit of the target pre-combustion area related quantity (No), the control device 50 proceeds to step S135.

When the process proceeds to step S135, the control device 50 reduces the provisional injection amount of the pilot injection two injections before the main injection, for example, according to the value of Qp/Qall, terminates the process shown in FIG. 20, and returns to step S050 shown in FIG. 19. For example, the memory device 53 stores a reduction map in which a reduction value (or reduction rate, etc.) according to Qp/Qall is set, and the control device 50 reduces the provisional injection amount of the pilot injection two injections before the main injection based on Qp/Qall and the reduction map. The reduction map is determined by various experiments, simulations, etc. The reduced injection amount may be allocated to the main injection and the pilot injection one injection before the main injection, according to the peak height ratio Hp/Hm.

In addition, instead of the [Pre-combustion adjustment] (Details 1-1) shown in FIG. 20, the [Pre-combustion adjustment] (Details 1-2) shown in FIG. 21 may be used. When the control device 50 advances the process to step S040 shown in FIG. 19, the control device 50 advances the process to step S110A shown in FIG. 21.

In step S110A, the control device 50 extracts an appropriate pattern from among previously prepared patterns according to the operating state of the internal combustion engine, the total injection amount Qv, the provisional number of pilot injections, the provisional injection timing and amount of each pilot injection, the provisional injection timing and amount of the main injection, etc., reads out the final number of pilot injections, the final injection timing and amount of each pilot injection, and the final injection timing and amount of the main injection, ends the process shown in FIG. 21, and returns to step S050 shown in FIG. 19. For example, the memory device 53 stores multiple patterns in which the final number of pilot injections, the final injection timing and amount of each pilot injection, and the final injection timing and amount of the main injection are set according to the operating state and a representative total injection amount Qv.

In addition, without being limited to the above example, the control device 50 may adjust at least one of the injection timing and injection amount in at least one pilot injection in [pre-combustion adjustment] so that the pre-combustion occurrence rate area related amount based on the pre-combustion occurrence rate area Qp (in the above example, Qp/Qall) is equal to or less than a preset target pre-combustion area related amount upper limit (in the above example, approximately 10.5% (see FIG. 17)). The control device 50 (CPU 51) that executes this [pre-combustion adjustment] process corresponds to the fuel injection adjustment unit 51C (see FIG. 1).

[Second embodiment (FIGS. 19, 22, and 23)]
Next, the processing procedure of the control device 50 in the second embodiment using "adjustment of the pre-combustion occurrence rate height Hpre" will be described with reference to the flowcharts shown in Figures 19, 22, and 23. The flowchart shown in Figure 19 is the same as that of the first embodiment, so the description will be omitted. The second embodiment differs in the details of [pre-combustion adjustment] in step S040 in the flowchart shown in Figure 19.

● [Details of pre-combustion adjustment 2-1 (Figure 22) and Details 2-2 (Figure 23)]
Next, details (Details 2-1) of the [pre-combustion adjustment] in step S040 in Fig. 19 will be described with reference to Fig. 22. When the control device 50 advances the process to step S040 shown in Fig. 19, the control device 50 advances the process to step S210 shown in Fig. 22.

In step S210, the control device 50 predicts the state of the main pre-combustion occurrence rate (the pre-combustion occurrence rate immediately preceding the first pre-combustion occurrence rate in FIG. 16), and proceeds to step S215. For example, the control device 50 predicts the occurrence position (crank angle) and magnitude (height) of the main pre-combustion occurrence rate, the occurrence position (crank angle) and magnitude (height) of the first combustion occurrence rate, etc., as shown in FIG. 16, based on the operating state of the internal combustion engine, the provisional number of pilot injections, and the provisional injection timing and amount of each pilot injection.

In step S215, the control device 50 predicts the occurrence start time θs1 of the first combustion rate (see FIG. 16) and proceeds to step S220. For example, the control device 50 predicts the occurrence start time θs1 of the first combustion rate based on the prediction performed in step S210.

In step S220, the control device 50 predicts the pre-combustion occurrence rate height Hpre at the occurrence start time θs1, and proceeds to step S230. For example, the control device 50 calculates the pre-combustion occurrence rate height Hpre based on the occurrence position and magnitude (height) of the first pre-combustion occurrence rate predicted in step S210, the occurrence position and magnitude (height) of the main pre-combustion occurrence rate, and the occurrence start time θs1.

In step S230, the control device 50 determines whether or not Hpre/Qv is equal to or less than the upper limit of the target pre-combustion height related quantity, where Qv is the total injection amount. If Hpre/Qv is equal to or less than the upper limit of the target pre-combustion height related quantity (Yes), the control device 50 ends the process shown in Fig. 22 and returns to step S050 shown in Fig. 19, whereas if Hpre/Qv is greater than the upper limit of the target pre-combustion height related quantity (No), the control device 50 proceeds to step S235.

When the process proceeds to step S235, the control device 50 reduces the provisional injection amount of the pilot injection two injections before the main injection, for example, according to the value of Hpre/Qv, terminates the process shown in FIG. 22, and returns to step S050 shown in FIG. 19. For example, the memory device 53 stores a reduction map in which a reduction value (or reduction rate, etc.) according to Hpre/Qv is set, and the control device 50 reduces the provisional injection amount of the pilot injection two injections before the main injection based on Hpre/Qv and the reduction map. The reduction map is determined by various experiments, simulations, etc. The reduced injection amount may be allocated to the main injection and the pilot injection one injection before the main injection, according to the peak height ratio Hp/Hm.

In addition, instead of the [Pre-combustion adjustment] (Details 2-1) shown in FIG. 22, the [Pre-combustion adjustment] (Details 2-2) shown in FIG. 23 may be used. When the control device 50 advances the process to step S040 shown in FIG. 19, the control device 50 advances the process to step S210A shown in FIG. 23.

In step S210A, the control device 50 extracts an appropriate pattern from among previously prepared patterns according to the operating state of the internal combustion engine, the total injection amount Qv, the provisional number of pilot injections, the provisional injection timing and amount of each pilot injection, the provisional injection timing and amount of the main injection, etc., reads out the final number of pilot injections, the final injection timing and amount of each pilot injection, and the final injection timing and amount of the main injection, ends the process shown in FIG. 23, and returns to step S050 shown in FIG. 19. For example, the memory device 53 stores multiple patterns in which the final number of pilot injections, the final injection timing and amount of each pilot injection, and the final injection timing and amount of the main injection are set according to the operating state and a representative total injection amount Qv.

In addition, without being limited to the above example, the control device 50 may adjust at least one of the injection timing and injection amount in at least one pilot injection in [pre-combustion adjustment] so that the pre-combustion occurrence rate height related amount based on the pre-combustion occurrence rate height Hpre (in the above example, Hpre/Qv) is equal to or less than a preset target pre-combustion height related amount upper limit (approximately 1.3 (see FIG. 18) in the above example). The control device 50 (CPU 51) that executes this [pre-combustion adjustment] process corresponds to the fuel injection adjustment unit 51C (see FIG. 1).

In the description of this embodiment, the time difference Δt and the peak height ratio Hp/Hm are adjusted to suppress combustion noise, and the pre-combustion generation rate area Qp or the pre-combustion generation rate height Hpre is adjusted to suppress the amount of smoke generated, but other methods may be used to suppress combustion noise.

The control device for a compression ignition internal combustion engine of the present invention is not limited to the configuration, structure, processing procedures, etc. described in this embodiment, and various modifications, additions, and deletions are possible without changing the gist of the present invention.

In the description of this embodiment, in Figs. 2, 3, 8, and 10, an example was described in which the horizontal axis represents the crank angle to determine the crank angle difference Δθ, but the horizontal axis may also represent time to determine the time difference Δt. Also, in Figs. 4, 5, 6, 12, and 13, an example was described in which the horizontal axis represents the offset center frequency f (amount related to time difference), but the horizontal axis of the figures may also represent the time difference Δt (f = 1/(Δt * 2)). Also, in Figs. 14 and 16, an example was described in which the horizontal axis represents the crank angle, but the horizontal axis may also represent time, and the vertical axis was the heat generation rate, but the vertical axis may also represent the pressure generation rate.

In addition, in the description of this embodiment, an example has been given in which the pre-combustion occurrence rate area-related quantity is Qp/Qall, but this is not limited thereto. For example, Qp or Qp/Qv (Qv = total injection amount) may be used as the pre-combustion occurrence rate area-related quantity. Similarly, in the description of this embodiment, an example has been given in which the pre-combustion occurrence rate height-related quantity is Hpre/Qv, but this is not limited thereto. For example, Hpre or Hpre/Qall may be used as the pre-combustion occurrence rate height-related quantity.

In addition, the control device for a compression ignition type internal combustion engine of the present invention is not limited to diesel engines, but can also be applied to compression ignition type gasoline engines.

In addition, terms such as "greater than or equal to" (≧), "less than or equal to" (≦), "greater than" (>), and "less than" (<) may or may not include an equal sign. In addition, the numerical values used in the explanation of this embodiment are merely examples, and the present invention is not limited to these numerical values.

REFERENCE SIGNS LIST 10 Internal combustion engine 11A, 11B Intake pipe 11C Intake manifold 12A Exhaust manifold 12B, 12C Exhaust pipe 13 EGR pipe 14 EGR valve 15 EGR cooler 21 Intake flow rate detection device 22 Revolution detection device 23 Atmospheric pressure detection device 24A Compressor upstream pressure detection device 24B Compressor downstream pressure detection device 24C Intake manifold pressure detection device 25 Accelerator pedal depression amount detection device 26A Turbine upstream pressure detection device 26B Turbine downstream pressure detection device 27 Vehicle speed detection device 28A, 28B Intake temperature detection device 28C Coolant temperature detection device 29 Exhaust temperature detection device 30 Turbocharger 31 Nozzle drive device 32 Nozzle opening detection device 33 Variable nozzle 35 Compressor 36 Turbine 41 common rail 43A to 43D injectors 45A to 45D cylinders 47 throttle device 47S throttle opening detection device 47V throttle valve 50 control device 51 CPU
51A Operating state detection unit 51B Fuel injection calculation unit 51C Fuel injection adjustment unit 53 Storage device 61 Exhaust gas purification device f(θ) Pressure generation rate Pam Main peak angle position (second peak angle position)
Pap Pilot peak angle position (first peak angle position)
Pm Main combustion pressure Pp Pilot combustion pressure g(θ) Heat release rate Eam Main peak angle position (second peak angle position)
Eap Pilot peak angle position (first peak angle position)
Em Main combustion heat Ep Pilot combustion heat Hp/Hm Peak height ratio Hpre Pre-combustion occurrence rate height Qall Total input heat Qp Pre-combustion occurrence rate area Qv Total injection amount θs1 Occurrence start time Δt Time difference Δθ Crank angle difference

Claims (6)

A control device for a compression autoignition type internal combustion engine, which injects a main injection, which is a main fuel injection, and a pilot injection, which is a plurality of fuel injections performed before the main injection, into a cylinder in one combustion stroke of the compression autoignition type internal combustion engine to generate a plurality of combustions,
The plurality of combustions for one combustion stroke are
Pre-combustion and
a first combustion occurring following the pre-combustion so as to overlap a portion of the pre-combustion;
A second combustion is generated following the first combustion so as to overlap a part of the first combustion, and the second combustion is generated mainly by the main injection;
It has
For one combustion stroke,
In a time-varying in-cylinder heat generation amount or in-cylinder pressure, a time differential value of the in-cylinder heat generation amount or a time differential value of the in-cylinder pressure corresponding to the first combustion;
Alternatively, in the in-cylinder heat generation amount or the in-cylinder pressure that changes depending on a crank angle that is a rotation angle of a crankshaft, a crank angle differential value of the in-cylinder heat generation amount or the crank angle differential value of the in-cylinder pressure that corresponds to the first combustion,
Before the start of the outbreak,
A time differential value of the in-cylinder heat generation amount corresponding to the pre-combustion or a time differential value of the in-cylinder pressure,
Alternatively, a crank angle differential value of the in-cylinder heat generation amount corresponding to the pre-combustion or a crank angle differential value of the in-cylinder pressure,
The pre-combustion occurrence rate area surrounded by Qp is
In this case,
The control device includes:
a fuel injection adjusting unit that adjusts at least one of an injection timing and an injection amount in at least one of the pilot injections so that a pre-combustion occurrence rate area related amount based on the pre-combustion occurrence rate area Qp becomes equal to or less than a target pre-combustion area related amount upper limit that is set so that an amount of smoke generation becomes equal to or less than an allowable upper limit,
Qv is the total injection amount, which is the amount of fuel injected by the pilot injection and the main injection in one combustion stroke; Qall is the total input heat amount, which is the amount of heat converted from the total injection amount;
In this case,
The control device includes:
The fuel injection adjusting unit sets Qp/Qall or Qp/Qv as the pre-combustion occurrence rate area related quantity.
A control device for a compression ignition type internal combustion engine. A control device for a compression autoignition type internal combustion engine, which injects a main injection, which is a main fuel injection, and a pilot injection, which is a plurality of fuel injections performed before the main injection, into a cylinder in one combustion stroke of the compression autoignition type internal combustion engine to generate a plurality of combustions,
The plurality of combustions for one combustion stroke are
Pre-combustion and
a first combustion occurring following the pre-combustion so as to overlap a portion of the pre-combustion;
A second combustion is generated following the first combustion so as to overlap a part of the first combustion, and the second combustion is generated mainly by the main injection;
It has
For one combustion stroke,
In a time-varying in-cylinder heat generation amount or in-cylinder pressure, a time differential value of the in-cylinder heat generation amount or a time differential value of the in-cylinder pressure corresponding to the first combustion;
Alternatively, in the in-cylinder heat generation amount or the in-cylinder pressure that changes depending on a crank angle that is a rotation angle of a crankshaft, a crank angle differential value of the in-cylinder heat generation amount or the crank angle differential value of the in-cylinder pressure that corresponds to the first combustion,
At the beginning of the outbreak,
A time differential value of the in-cylinder heat generation amount corresponding to the pre-combustion or a time differential value of the in-cylinder pressure,
Alternatively, a crank angle differential value of the in-cylinder heat generation amount corresponding to the pre-combustion or a crank angle differential value of the in-cylinder pressure,
The pre-combustion occurrence rate height, which is the height of
In this case,
The control device includes:
a fuel injection adjusting unit that adjusts at least one of an injection timing and an injection amount in at least one of the pilot injections so that a pre-combustion occurrence rate height related amount based on the pre-combustion occurrence rate height Hpre becomes equal to or less than a target pre-combustion height related amount upper limit that is set so that an amount of smoke generation becomes equal to or less than an allowable upper limit,
Qv is the total injection amount, which is the amount of fuel injected by the pilot injection and the main injection in one combustion stroke; Qall is the total input heat amount, which is the amount of heat converted from the total injection amount;
In this case,
The control device includes:
The fuel injection adjustment unit sets Hpre/Qv or Hpre/Qall as the pre-combustion occurrence rate height related amount.
A control device for a compression ignition type internal combustion engine. 2. A control device for a compression self-ignition type internal combustion engine according to claim 1,
When the pre-combustion occurrence rate area related amount is Qp/Qall, the value equal to or less than the upper limit of the target pre-combustion area related amount is set to 10.5 or less.
A control device for a compression ignition type internal combustion engine. The control device for a compression self-ignition type internal combustion engine according to claim 2,
When the pre-combustion occurrence rate height related amount is Hpre/Qv, the value equal to or less than the upper limit of the target pre-combustion height related amount is set to 1.3 or less.
A control device for a compression ignition type internal combustion engine. A control device for a compression self-ignition type internal combustion engine according to any one of claims 1 to 4,
The control device includes:
the fuel injection adjustment unit adjusts the injection amount of at least the pilot injection that is two injections before the main injection in the pre-stage injection.
A control device for a compression ignition type internal combustion engine. A control device for a compression self-ignition type internal combustion engine according to any one of claims 1 to 5,
In one combustion stroke, when a time difference between a first peak time position which is a peak position corresponding to the first combustion among a plurality of peak positions of the time differential value of the in-cylinder heat generation amount or the time differential value of the in-cylinder pressure and a second peak time position which is a peak position corresponding to the second combustion among the plurality of peak positions is Δt, a time differential value of the in-cylinder heat generation amount or the time differential value of the in-cylinder pressure at the first peak time position is Hp, and a time differential value of the in-cylinder heat generation amount or the time differential value of the in-cylinder pressure at the second peak time position is Hm, and a peak height ratio is Hp/Hm,
Alternatively, in one combustion stroke, a time difference obtained by converting the difference in crank angle between a first peak angle position, which is a peak position corresponding to the first combustion among a plurality of peak positions of the crank angle differential value of the in-cylinder heat generation amount or the crank angle differential value of the in-cylinder pressure, and a second peak angle position, which is a peak position corresponding to the second combustion among the plurality of peak positions, is Δt based on the rotation speed of the crankshaft, the crank angle differential value of the in-cylinder heat generation amount or the crank angle differential value of the in-cylinder pressure at the first peak angle position is Hp, and the crank angle differential value of the in-cylinder heat generation amount or the crank angle differential value of the in-cylinder pressure at the second peak angle position is Hm, and a peak height ratio is Hp/Hm:
The control device includes:
an operating state detection unit that detects an operating state of the compression ignition type internal combustion engine;
a fuel injection calculation unit that calculates a target time difference or a target time difference related amount according to the operating state of the compression ignition internal combustion engine, and a target peak height ratio, and calculates an injection timing and injection amount of at least the pilot injection that is one injection before the main injection in the pre-stage injection, and an injection timing and injection amount of the main injection, so that Δt approaches the target time difference or so that the time difference related amount based on Δt approaches the target time difference related amount and so that Hp/Hm approaches the target peak height ratio;
having
The injection timing and the injection amount calculated by the fuel injection calculation unit are adjusted by the fuel injection adjustment unit.
A control device for a compression ignition type internal combustion engine.

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