JP2019138292A - Control device of internal combustion engine - Google Patents

Abstract

To suppress the lowering of the detection accuracy of fuel ignition timing.SOLUTION: A control device 200 of an internal combustion engine 100 comprises: a combustion control part for combusting fuel by controlling an injection amount and the injection timing of the fuel which is injected from a fuel injection valve 20 to a target injection amount and target injection timing which are set on the basis of an engine operation state; an amplitude value calculation part for calculating an amplitude value of vibration acceleration in an arbitrary frequency band area from 5 kHz up to 10 kHz; and a combustion form discrimination part for discriminating a combustion form of the fuel. When a maximum value or an average value of the amplitude value in a prescribed ignition determination zone is not smaller than a prescribed value, the combustion form discrimination part discriminates that the combustion form of the fuel is diffusion combustion, and when the maximum value or the average value is smaller than the prescribed value, determines that the combustion form of the fuel is premixed combustion.SELECTED DRAWING: Figure 1

Description

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

  In Patent Document 1, as a conventional control device for an internal combustion engine, an amplitude corresponding to an amplitude of a vibration acceleration in a range of about 5 [kHz] to 7 [kHz] among vibration accelerations of the engine body detected by a knock sensor. An apparatus configured to detect an ignition timing by comparing an equivalent value with a predetermined ignition timing determination level is disclosed.

JP 2010-216264 A

  In an internal combustion engine that premixes and burns fuel in part or all of the engine operating range, it is premixed due to some factors such as transient changes in the cylinder environment (cylinder pressure, cylinder temperature, cylinder oxygen density) If the ignition delay time is shorter than expected, the combustion mode of the fuel may become a combustion mode closer to diffusion combustion than premixed combustion. Conversely, even in an internal combustion engine in which fuel is diffusely burned in part or all of the engine operating region, it is also conceivable that for some reason, the fuel combustion mode is closer to premixed combustion than diffusion combustion. .

  Here, the horizontal axis indicates the crank angle or time, and the vertical axis indicates the amplitude value of the vibration acceleration detected by the knock sensor. It changes with use. At this time, since the frequency band of vibration acceleration from which an amplitude value waveform correlated with the actual in-cylinder pressure waveform is obtained differs depending on the combustion mode, to detect the ignition timing based on the amplitude value of vibration acceleration It is necessary to determine the combustion form in advance.

  The present invention has been made paying attention to such problems, and an object of the present invention is to determine the combustion mode in advance in detecting the ignition timing.

  In order to solve the above problems, according to an aspect of the present invention, an engine body, a fuel injection valve that injects fuel into a combustion chamber of the engine body, and a vibration sensor that detects vibration acceleration of the engine body are provided. A control device for an internal combustion engine for controlling the internal combustion engine controls the injection amount and injection timing of fuel injected from the fuel injection valve to a target injection amount and a target injection timing set based on the engine operating state. A combustion control unit that burns the fuel, an amplitude value calculation unit that calculates an amplitude value of vibration acceleration in an arbitrary frequency band from 5 kHz to 10 kHz, and a combustion mode determination unit that determines the combustion mode of the fuel. The combustion form determination unit determines that the combustion form of the fuel is diffusion combustion if the maximum value or average value of the amplitude value in the predetermined ignition determination section is equal to or greater than the predetermined value, and the maximum value or average value is predetermined. If it is less than the value, it is determined that the combustion mode of combustion is premixed combustion.

  According to this aspect of the present invention, the combustion mode can be determined in advance when detecting the ignition timing.

FIG. 1 is a schematic configuration diagram of an internal combustion engine and an electronic control unit for controlling the internal combustion engine according to an embodiment of the present invention. FIG. 2 is a diagram showing an operation region of the internal combustion engine. FIG. 3A is a diagram showing an amplitude value waveform of vibration acceleration in the entire frequency band when the combustion mode is diffusion combustion. FIG. 3B is a diagram illustrating an amplitude value waveform of vibration acceleration in a frequency band from 0 [kHz] to 2.5 [kHz] when the combustion mode is diffusion combustion. FIG. 3C is a diagram illustrating an amplitude value waveform of vibration acceleration in a frequency band from 2.5 [kHz] to 5 [kHz] when the combustion mode is diffusion combustion. FIG. 3D is a diagram illustrating an amplitude value waveform of vibration acceleration in a frequency band from 5 [kHz] to 7.5 [kHz] when the combustion mode is diffusion combustion. FIG. 3E is a diagram illustrating an amplitude value waveform of vibration acceleration in a frequency band from 7.5 [kHz] to 10 [kHz] when the combustion mode is diffusion combustion. FIG. 3F is a diagram illustrating an amplitude value waveform of vibration acceleration in a frequency band from 10 [kHz] to 12.5 [kHz] when the combustion mode is diffusion combustion. FIG. 4A is a diagram showing an amplitude value waveform of vibration acceleration in the entire frequency band when the combustion mode is premixed combustion. FIG. 4B is a diagram illustrating an amplitude value waveform of vibration acceleration in a frequency band from 0 [kHz] to 2.5 [kHz] when the combustion mode is premixed combustion. FIG. 4C is a diagram illustrating an amplitude value waveform of vibration acceleration in a frequency band from 2.5 [kHz] to 5 [kHz] when the combustion mode is premixed combustion. FIG. 4D is a diagram illustrating an amplitude value waveform of vibration acceleration in a frequency band from 5 [kHz] to 7.5 [kHz] when the combustion mode is premixed combustion. FIG. 4E is a diagram illustrating an amplitude value waveform of vibration acceleration in a frequency band from 7.5 [kHz] to 10 [kHz] when the combustion mode is premixed combustion. FIG. 4F is a diagram illustrating an amplitude value waveform of vibration acceleration in a frequency band from 10 [kHz] to 12.5 [kHz] when the combustion mode is premixed combustion. FIG. 5 is a flowchart illustrating ignition timing detection control including combustion mode discrimination control according to an embodiment of the present invention. FIG. 6 is a flowchart illustrating combustion control according to an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are assigned to similar components.

  FIG. 1 is a schematic configuration diagram of an internal combustion engine 100 and an electronic control unit 200 that controls the internal combustion engine 100 according to an embodiment of the present invention.

  As shown in FIG. 1, an internal combustion engine 100 includes an engine body 1 having a plurality of cylinders 10, a fuel supply device 2, an intake device 3, an exhaust device 4, an intake valve device 5, and an exhaust valve device. 6.

  The engine body 1 is configured so that fuel can be ignited and combusted in a combustion chamber formed in each cylinder 10 to generate power for driving a vehicle, for example. The engine body 1 is provided with a pair of intake valves 50 and a pair of exhaust valves 60 for each cylinder. Further, a knock sensor 210 for detecting vibration of the engine body 1 is attached to the engine body 1. Knock sensor 210 is a type of vibration sensor (acceleration sensor) including a piezoelectric element, and outputs a voltage value corresponding to the vibration of engine body 1.

  The fuel supply device 2 includes an electronically controlled fuel injection valve 20, a delivery pipe 21, a supply pump 22, a fuel tank 23, a pressure feed pipe 24, and a fuel pressure sensor 211.

  One fuel injection valve 20 is provided in each cylinder 10 so as to face the combustion chamber of each cylinder 10 so that fuel can be directly injected into the combustion chamber. The valve opening time (injection amount) and the valve opening timing (injection timing) of the fuel injection valve 20 are changed by a control signal from the electronic control unit 200, and when the fuel injection valve 20 is opened, the fuel injection valve 20 opens to the combustion chamber. The fuel is directly injected into the tank.

  The delivery pipe 21 is connected to the fuel tank 23 via a pressure feed pipe 24. A supply pump 22 for pressurizing the fuel stored in the fuel tank 23 and supplying it to the delivery pipe 21 is provided in the middle of the pressure feeding pipe 24. The delivery pipe 21 temporarily stores the high-pressure fuel pumped from the supply pump 22. When the fuel injection valve 20 is opened, the high-pressure fuel stored in the delivery pipe 21 is directly injected from the fuel injection valve 20 into the combustion chamber.

  The supply pump 22 is configured to be able to change the discharge amount, and the discharge amount of the supply pump 22 is changed by a control signal from the electronic control unit 200. By controlling the discharge amount of the supply pump 22, the fuel pressure in the delivery pipe 21, that is, the injection pressure of the fuel injection valve 20 is controlled.

  The fuel pressure sensor 211 is provided on the delivery pipe 21. The fuel pressure sensor 211 detects the fuel pressure in the delivery pipe 21, that is, the pressure (injection pressure) of fuel injected from each fuel injection valve 20 into each cylinder 10.

  The intake device 3 is a device for guiding intake air into the combustion chamber, and changes the state of intake air (intake pressure (supercharging pressure), intake air temperature, EGR (Exhaust Gas Recirculation) gas amount) taken into the combustion chamber. It is configured to be able to. The intake device 3 includes an intake pipe 30 and an intake manifold 31 serving as an intake passage, and an EGR passage 32.

  The intake pipe 30 has one end connected to the air cleaner 34 and the other end connected to the intake collector 31 a of the intake manifold 31. The intake pipe 30 is provided with an air flow meter 212, a compressor 71 of the exhaust turbocharger 7, an intercooler 35, and a throttle valve 36 in order from the upstream.

  The air flow meter 212 detects the flow rate of air that flows through the intake pipe 30 and is finally sucked into the cylinder 10.

  The compressor 71 includes a compressor housing 71a and a compressor wheel 71b disposed in the compressor housing 71a. The compressor wheel 71b is rotationally driven by the turbine wheel 72b of the exhaust turbocharger 7 mounted on the same axis, and compresses and discharges the intake air flowing into the compressor housing 71a. The turbine 72 of the exhaust turbocharger 7 is provided with a variable nozzle 72c for controlling the rotational speed of the turbine wheel 72b. By controlling the rotational speed of the turbine wheel 72b by the variable nozzle 72c, the compressor housing 71a. The pressure (supercharging pressure) of the intake air discharged from the inside is controlled.

  The intercooler 35 is a heat exchanger for cooling the intake air that has been compressed by the compressor 71 to a high temperature, for example, with traveling wind, cooling water, or the like.

  The throttle valve 36 adjusts the intake air amount introduced into the intake manifold 31 by changing the passage cross-sectional area of the intake pipe 30. The throttle valve 36 is driven to open and close by a throttle actuator 36a, and its opening (throttle opening) is detected by a throttle sensor 213.

  The intake manifold 31 is connected to an intake port 14 formed in the engine body 1, and distributes the intake air flowing in from the intake pipe 30 to each cylinder 10 evenly through the intake port 14. An intake collector 31a of the intake manifold 31 detects an intake pressure sensor 214 for detecting the pressure of intake air (intake pressure) sucked into the cylinder and a temperature of intake air (intake air temperature) sucked into the cylinder. An intake air temperature sensor 215 is provided.

  The EGR passage 32 communicates the exhaust manifold 41 and the intake collector 31a of the intake manifold 31, and is a passage for returning a part of the exhaust discharged from each cylinder 10 to the intake collector 31a by a pressure difference. Hereinafter, the exhaust gas flowing into the EGR passage 32 is referred to as “EGR gas”, and the ratio of the EGR gas amount to the in-cylinder gas amount, that is, the exhaust gas recirculation rate is referred to as the “EGR rate”. By recirculating the EGR gas to the intake collector 31a and thus to each cylinder 10, the combustion temperature can be reduced and the emission of nitrogen oxides (NOx) can be suppressed. The EGR passage 32 is provided with an EGR cooler 37 and an EGR valve 38 in order from the upstream.

  The EGR cooler 37 is a heat exchanger for cooling the EGR gas with, for example, traveling wind or cooling water.

  The EGR valve 38 is an electromagnetic valve whose opening degree can be adjusted continuously or stepwise, and the opening degree is controlled by the electronic control unit 200 according to the engine operating state. By controlling the opening degree of the EGR valve 38, the flow rate of the EGR gas to be recirculated to the intake collector 31a is adjusted.

  The exhaust device 4 is a device for discharging exhaust gas from the inside of the cylinder, and includes an exhaust manifold 41 and an exhaust passage 42.

  The exhaust manifold 41 is connected to an exhaust port 15 formed in the engine body 1, and exhausts exhausted from the cylinders 10 are collectively introduced into the exhaust passage 42.

  The exhaust passage 42 is provided with a turbine 72 of the exhaust turbocharger 7 and an exhaust aftertreatment device 43 in order from the upstream.

  The turbine 72 includes a turbine housing 72a and a turbine wheel 72b disposed in the turbine housing 72a. The turbine wheel 72b is rotationally driven by the energy of the exhaust gas flowing into the turbine housing 72a, and drives the compressor wheel 71b mounted coaxially.

  The variable nozzle 72c described above is provided outside the turbine wheel 72b. The variable nozzle 72 c functions as a throttle valve, and the nozzle opening (valve opening) of the variable nozzle 72 c is controlled by the electronic control unit 200. By changing the nozzle opening degree of the variable nozzle 72c, the flow rate of the exhaust for driving the turbine wheel 72b can be changed in the turbine housing 72a. That is, by changing the nozzle opening degree of the variable nozzle 72c, the supercharging pressure can be changed by changing the rotational speed of the turbine wheel 72b. Specifically, when the nozzle opening of the variable nozzle 72c is reduced (the variable nozzle 72c is throttled), the exhaust flow rate increases, the rotational speed of the turbine wheel 72b increases, and the supercharging pressure increases.

  The exhaust aftertreatment device 43 is a device for purifying exhaust gas and discharging it to the outside air, and includes various exhaust purification catalysts for purifying harmful substances, filters for collecting harmful substances, and the like.

  The intake valve operating device 5 is a device for opening and closing the intake valve 50 of each cylinder 10 and is provided in the engine body 1. The intake valve operating device 5 according to the present embodiment is configured to open and close the intake valve 50 by, for example, an electromagnetic actuator so that the opening and closing timing of the intake valve 50 can be controlled. However, the present invention is not limited to this, and the intake valve 50 is configured to open and close by the intake camshaft, and a variable valve that changes the relative phase angle of the intake camshaft with respect to the crankshaft by hydraulic control at one end of the intake camshaft. By providing a mechanism, the opening / closing timing of the intake valve 50 may be controlled.

  The exhaust valve device 6 is a device for opening and closing the exhaust valve 60 of each cylinder 10 and is provided in the engine body 1. The exhaust valve device 6 according to the present embodiment is configured to open and close the exhaust valve 60 by, for example, an electromagnetic actuator so that the opening and closing timing of the exhaust valve 60 can be controlled. However, the present invention is not limited to this, and the exhaust valve 60 is configured to open and close by an exhaust camshaft, and a variable valve that changes the relative phase angle of the exhaust camshaft with respect to the crankshaft by hydraulic control at one end of the exhaust camshaft. By providing a mechanism, the opening / closing timing of the exhaust valve 60 may be controlled. Further, for example, the opening / closing timing and the lift amount of the exhaust valve 60 may be changed by changing the cam profile by hydraulic pressure or the like.

  The electronic control unit 200 is composed of a digital computer and is connected to each other by a bi-directional bus 201. A ROM (read only memory) 202, a RAM (random access memory) 203, a CPU (microprocessor) 204, an input port 205, and an output port 206.

  Output signals such as the knock sensor 210 and the fuel pressure sensor 211 described above are input to the input port 205 via the corresponding AD converters 207. Also, the output voltage of the load sensor 217 that generates an output voltage proportional to the amount of depression of the accelerator pedal 220 (hereinafter referred to as “accelerator depression amount”) as a signal for detecting the engine load corresponds to the input port 205. Is input via the AD converter 207. The input port 205 is supplied with an output signal of a crank angle sensor 218 that generates an output pulse every time the crankshaft of the engine body 1 rotates, for example, 15 °, as a signal for calculating the engine rotational speed and the like. As described above, output signals of various sensors necessary for controlling the internal combustion engine 100 are input to the input port 205.

  The output port 206 is connected to each control component such as the fuel injection valve 20 via a corresponding drive circuit 208.

  The electronic control unit 200 controls the internal combustion engine 100 by outputting a control signal for controlling each control component from the output port 206 based on the output signals of various sensors input to the input port 205. Hereinafter, control of the internal combustion engine 100 performed by the electronic control unit 200 will be described.

  The electronic control unit 200 switches the operation mode of the engine body 1 to either the premixed combustion mode or the diffusion combustion mode based on the engine operation state (engine rotation speed and engine load).

  As shown in FIG. 2, the electronic control unit 200 switches the operation mode to the premixed combustion mode if the engine operation state is within the first operation region on the low rotation and low load side. The electronic control unit 200 switches the operation mode to the diffusion combustion mode if the engine operation state is within the second operation region on the high rotation high load side. The electronic control unit 200 controls the injection amount and injection timing of the fuel injected from the fuel injection valve 20 to the target injection amount and target injection timing corresponding to each operation mode set based on the engine operating state. Combustion control is performed to burn the fuel.

  Specifically, when the operation mode is the premixed combustion mode, the electronic control unit 200 injects fuel into the combustion chamber 11 once or a plurality of times at an arbitrary time from the intake stroke to the compression stroke. An air / fuel ratio leaner than the stoichiometric air / fuel ratio (for example, about 30 to 40) is formed inside, and the premixed gas is combusted by compression self-ignition to operate the engine body 1.

  Further, when the operation mode is the diffusion combustion mode, the electronic control unit 200 injects fuel into the combustion chamber 11 that has become high temperature and high pressure near the compression top dead center, and diffuses and burns the fuel to operate the engine body 1. I do. In the present embodiment, pilot injection is performed during the compression stroke prior to fuel injection (main fuel injection) performed near the compression top dead center.

  Here, if the ignition timing deviates from the target ignition timing, various problems may occur, such as exhaust emission deterioration or a decrease in output of the engine body 1 to cause torque fluctuation. Therefore, the self-ignition timing of the fuel is detected, and if there is a deviation of a predetermined value or more between the detected self-ignition timing and the target self-ignition timing, the fuel injected from the fuel injection valve 20 to correct the deviation It is desirable to correct one or both of the target injection amount and the target injection timing.

  As a method for detecting the ignition timing, for example, an in-cylinder pressure sensor is attached to the engine body 1, and the in-cylinder pressure at each crank angle detected by the in-cylinder pressure sensor is used as a predetermined in-cylinder pressure value for determining the ignition timing. The method of detecting by comparing is mentioned. According to this method, since the pressure fluctuation in each cylinder can be directly detected, the ignition timing can be accurately detected. However, in-cylinder pressure sensors are required for the number of cylinders, and the unit price of the in-cylinder pressure sensor itself is high, which increases the cost.

  On the other hand, if the ignition timing can be accurately detected based on the output value of knock sensor 210, that is, the vibration acceleration of engine body 1 detected by knock sensor 210 (hereinafter referred to as "detected vibration acceleration"), knock sensor 210 will be unit priced. Is cheap and can be attached to the engine body 1 at least one, so that an increase in cost can be suppressed. When the fuel is combusted, the vibration acceleration of the engine body 1 increases as the fuel is combusted. Therefore, as a method for detecting the ignition timing based on the detected vibration acceleration, various processes are performed on the detected vibration acceleration to obtain a predetermined value. A method of calculating the amplitude value of the detected vibration acceleration in the ignition determination section (section corresponding to a predetermined crank angle range before and after the ignition timing) and comparing the amplitude value with a predetermined ignition timing determination threshold. It is done.

  However, the magnitude of the amplitude value of the detected vibration acceleration calculated by performing various processes on the detected vibration acceleration is the frequency band of the bandpass filter process that is one of the processes performed when calculating the amplitude value. Varies with (bandwidth). That is, the magnitude of the calculated amplitude value changes depending on which frequency band of the detected vibration acceleration is used to calculate the amplitude value.

  Therefore, the shape of the amplitude value waveform with the crank angle or time on the horizontal axis and the amplitude value of the detected vibration acceleration on the vertical axis is the detected vibration acceleration in which frequency band of the detected vibration acceleration in calculating the amplitude value. It depends on whether you use As a result of the inventors' diligent research, it has been found that the frequency band in which the amplitude value waveform correlated with the actual in-cylinder pressure waveform is obtained differs depending on the combustion mode. Hereinafter, this point will be described with reference to FIGS. 3A to 4F.

  FIGS. 3A to 3F are diagrams each showing an amplitude value waveform when the combustion mode is diffusion combustion, and the shape of the amplitude value waveform depends on the frequency band of the detected vibration acceleration used for calculating the amplitude value. It is the figure shown in comparison. 4A to 4F are diagrams each showing an amplitude value waveform when the combustion mode is premixed combustion, and the shape of the amplitude value waveform is set to the frequency band of the detected vibration acceleration used for calculating the amplitude value. It is the figure shown in comparison accordingly.

  3A and 4A are diagrams showing amplitude value waveforms when the amplitude value is calculated using the detected vibration acceleration in the entire frequency band. 3B and 4B are diagrams showing amplitude value waveforms when the amplitude value is calculated using the detected vibration acceleration in the frequency band from 0 [kHz] to 2.5 [kHz]. 3C and 4C are diagrams illustrating amplitude value waveforms when the amplitude value is calculated using the detected vibration acceleration in the frequency band from 2.5 [kHz] to 5 [kHz]. 3D and 4D are diagrams illustrating amplitude value waveforms when the amplitude value is calculated using the detected vibration acceleration in the frequency band from 5 [kHz] to 7.5 [kHz]. 3E and 4E are diagrams illustrating amplitude value waveforms when the amplitude value is calculated using the detected vibration acceleration in the frequency band from 7.5 [kHz] to 10 [kHz]. 3F and 4F are diagrams illustrating amplitude value waveforms when the amplitude value is calculated using the detected vibration acceleration in the frequency band from 10 [kHz] to 12.5 [kHz].

  As shown in FIGS. 3A to 3F, when the combustion form is diffusion combustion, the amplitude value waveform when the amplitude value is calculated using the detected vibration acceleration in the frequency band from 5 [kHz] to 10 [kHz] ( FIGS. 3D and 3E) show an amplitude close to an actual in-cylinder pressure waveform in which an increase in amplitude value due to fuel combustion by pilot injection and an increase in amplitude value due to fuel combustion by main injection appear. It turns out that it becomes a value waveform.

  On the other hand, as shown in FIGS. 4A to 4F, when the combustion mode is premixed combustion, the amplitude value is calculated using the detected vibration acceleration in the frequency band from 2.5 [kHz] to 12.5 [kHz]. It was found that the amplitude value waveform (FIG. 4C to FIG. 4F) at that time hardly increased in amplitude value due to premixed combustion. The amplitude value waveform (FIG. 4B) when the amplitude value is calculated using the detected vibration acceleration in the frequency band from 0 [kHz] to 2.5 [kHz] is an increase in the amplitude value due to the premixed combustion. It turned out that it became an amplitude value waveform close | similar to the actual in-cylinder pressure waveform which appeared.

  Therefore, when detecting the ignition timing based on the detected vibration acceleration, when the operation mode is the premixed combustion mode, the detected vibration acceleration in an arbitrary frequency band from 0 [kHz] to 2.5 [kHz] is used. It is desirable to compare the calculated amplitude value with, for example, an ignition timing determination threshold value V1 for premixed combustion. When the operation mode is the diffusion combustion mode, the amplitude value calculated using the detected vibration acceleration in an arbitrary frequency band from 5 [kHz] to 10 [kHz], for example, the ignition timing determination threshold V2 for diffusion combustion. It is desirable to compare with

  However, even when the operation mode is the premixed combustion mode, the ignition delay of the premixed gas is delayed due to some factors such as a transient change in the in-cylinder environment (in-cylinder pressure, in-cylinder temperature, in-cylinder oxygen density). If the time is shorter than expected, the combustion mode of the fuel may become a combustion mode closer to diffusion combustion than premixed combustion. Conversely, even when the operation mode is the diffusion combustion mode, it is conceivable that the combustion mode of the fuel becomes a combustion mode closer to the premixed combustion than the diffusion combustion for some reason.

  Therefore, just because the operation mode is the premixed combustion mode, based on the amplitude value calculated using the detected vibration acceleration in an arbitrary frequency band from 0 [kHz] to 2.5 [kHz] without determining the combustion mode. When the ignition timing is detected, there is a possibility that the detection accuracy of the ignition timing is lowered or the ignition timing is erroneously detected when the combustion mode is close to diffusion combustion. On the other hand, the ignition mode is ignited based on the amplitude value calculated using the detected vibration acceleration in an arbitrary frequency band from 5 [kHz] to 10 [kHz] without discriminating the combustion mode just because the operation mode is the diffusion combustion mode. When the timing is detected, there is a possibility that the detection accuracy of the ignition timing is lowered or the ignition timing is erroneously detected when the combustion mode is close to premixed combustion.

  Therefore, in order to suppress such deterioration in detection accuracy of the ignition timing and false detection, the actual combustion mode is diffusion combustion (or combustion mode close to diffusion combustion), or premixed combustion (or pre-mixed combustion). It is desirable to confirm whether the combustion mode is close to mixed combustion.

  Therefore, in the present embodiment, the maximum value or the average value of the amplitude values calculated using the detected vibration acceleration in the frequency band from 5 [kHz] to 10 [kHz] in the ignition determination section is used as a predetermined combustion form determination threshold value. Compared with V3, if the maximum value or average value of the amplitude value is equal to or greater than the combustion mode determination threshold V3, it is determined that the actual combustion mode is diffusion combustion, and the maximum value or average value of the amplitude value is the combustion mode If it is less than the determination threshold value V3, it is determined that the actual combustion mode is premixed combustion. Then, after determining the combustion mode, the ignition timing is detected.

  Hereinafter, the ignition timing detection control including the combustion mode discrimination control according to the present embodiment will be described with reference to FIG.

  FIG. 5 is a flowchart illustrating the ignition timing detection control according to the present embodiment.

  In step S1, the electronic control unit 200 reads the output value (detected vibration acceleration) of the knock sensor 210 in the ignition determination section. In this embodiment, the ignition determination section is a section corresponding to the crank angle range from the middle of the compression stroke to the middle of the expansion stroke of each cylinder 10, but can be changed as appropriate.

  In step S2, the electronic control unit 200 filters the detected vibration acceleration with a bandpass filter having a frequency band from 0 [kHz] to 2.5 [kHz] in the ignition determination section. The detected vibration acceleration in the frequency band is extracted.

  In the present embodiment, the filtering process is performed by the band pass filter having the frequency band from 0 [kHz] to 2.5 [kHz] in step S2, but from 0 [kHz] to 2.5 [kHz]. Filter processing may be performed by a bandpass filter having a bandwidth of an arbitrary frequency band up to [kHz] (for example, a frequency band from 1 [kHz] to 2.5 [kHz]).

  In step S3, the electronic control unit 200 performs a filtering process on the detected vibration acceleration with a bandpass filter having a frequency band from 5 [kHz] to 10 [kHz], and the frequency in the ignition determination section. The detected vibration acceleration of the band is extracted.

  In the present embodiment, in step S3, the filter processing is performed by a bandpass filter having a frequency band from 5 [kHz] to 10 [kHz], but from 5 [kHz] to 10 [kHz]. Filtering is performed by a band pass filter having an arbitrary frequency band (for example, a frequency band from 5 [kHz] to 7.5 [kHz] or a frequency band from 7.5 [kHz] to 10 [kHz]). May be.

  In step S4, the electronic control unit 200 takes each crank or time on the horizontal axis, creates a detected vibration acceleration waveform with the detected vibration acceleration in the ignition determination section extracted in step S3 on the vertical axis, and detects the detected vibration. By performing envelope processing (envelope processing) on the acceleration waveform, the amplitude value waveform (hereinafter referred to as “first amplitude value”) of the detected vibration acceleration in the frequency band from 5 [kHz] to 10 [kHz] in the ignition determination section. Create a waveform.)

  In step S5, the electronic control unit 200 calculates the maximum value Vmax of the amplitude value of the detected vibration acceleration in the ignition determination section based on the first amplitude value waveform, and whether the maximum value Vmax is equal to or greater than the combustion form determination threshold V3. Determine whether or not. If the maximum value Vmax of the detected vibration acceleration amplitude value in the ignition determination section is equal to or greater than the combustion mode determination threshold value V3, the electronic control unit 200 proceeds to the process of step S6. On the other hand, if the maximum value Vmax of the amplitude value of the detected vibration acceleration in the ignition determination section is equal to or greater than the combustion mode determination threshold V3, the electronic control unit 200 proceeds to the process of step S8.

  In this embodiment, the maximum value Vmax of the amplitude value in the ignition determination section is compared with the combustion mode determination threshold value V3 in this way, but may be compared with the average value of the amplitude value in the ignition determination section.

  In step S6, the electronic control unit 200 determines that the combustion mode of the fuel is diffusion combustion.

  In step S7, the electronic control unit 200 detects the ignition timing based on the first amplitude value waveform, that is, the amplitude value of the detected vibration acceleration in the frequency band from 5 [kHz] to 10 [kHz] in the ignition determination section. . In the present embodiment, when the electronic control unit 200 detects that the amplitude value of the detected vibration acceleration in the frequency band from 5 [kHz] to 10 [kHz] in the ignition determination section is equal to or greater than the ignition timing determination threshold V2 for diffusion combustion. Is detected as the ignition timing.

  Here, as in this embodiment, when the fuel is burned by performing multistage injection (in this embodiment, pilot injection and main injection) in the diffusion combustion mode, combustion of the main injection fuel for generating the required torque Although it is necessary to detect the time as the ignition timing, the vibration acceleration also increases during the combustion of the pilot injected fuel. Therefore, when performing multistage injection, it is desirable to set the ignition timing determination threshold value V2 for diffusion combustion so as to be larger than the amplitude value of the vibration acceleration generated when the fuel other than the main injection fuel is combusted. In addition to such a method, in order to detect the time of combustion of the main injected fuel as the ignition timing when detecting the ignition timing, for example, where the increased portion of the amplitude value is based on the first amplitude value waveform, It is possible to detect the ignition timing after judging whether it is caused by combustion. In this way, the set value of the ignition timing determination threshold value V2 can be lowered.

  In step S8, the electronic control unit 200 determines that the combustion mode of combustion is premixed combustion.

  In step S9, the electronic control unit 200 takes each crank or time on the horizontal axis, creates a detected vibration acceleration waveform with the detected vibration acceleration in the ignition determination section extracted in step S2 on the vertical axis, and detects the detected vibration. By performing envelope processing (envelope processing) on the acceleration waveform, the amplitude value waveform (hereinafter referred to as “second”) of the detected vibration acceleration in the frequency band from 0 [kHz] to 2.5 [kHz] in the ignition determination section. Amplitude value waveform ").

  In step S10, the electronic control unit 200 sets the ignition timing based on the second amplitude value waveform, that is, the amplitude value of the detected vibration acceleration in the frequency band from 0 [kHz] to 2.5 [kHz] in the ignition determination section. To detect. In the present embodiment, the electronic control unit 200 determines that the amplitude value of the detected vibration acceleration in the frequency band from 0 [kHz] to 2.5 [kHz] in the ignition determination section is equal to or higher than the ignition timing determination threshold V1 for premixed combustion. Is detected as the ignition timing.

  FIG. 6 is a flowchart illustrating the combustion control according to the present embodiment.

  In step S11, the electronic control unit 200 reads the engine load detected by the load sensor 217 and the engine rotation speed calculated based on the output signal of the crank angle sensor 218, and detects the engine operating state.

  In step S12, the electronic control unit 200 refers to a map prepared in advance, and determines the target injection amount and target injection timing of the fuel injected from the fuel injection valve 20 corresponding to each operation mode based on the engine operating state. calculate.

  In step S13, the electronic control unit 200 reads the ignition timing detected by the ignition timing detection control in the previous combustion cycle, and according to the detected ignition timing and each operation mode set in advance for each engine operating state. The deviation from the target ignition timing is calculated as an ignition timing deviation ΔC.

  In step S14, the electronic control unit 200 determines whether or not the absolute value of the ignition timing deviation ΔC is less than a predetermined deviation. If the absolute value of the ignition timing deviation ΔC is less than the predetermined deviation, the electronic control unit 200 proceeds to the process of step S15. On the other hand, if the absolute value of the ignition timing deviation ΔC is greater than or equal to the predetermined deviation, the electronic control unit 200 proceeds to the process of step S16.

  In step S15, the electronic control unit 200 controls the fuel supply device so that a target injection amount of fuel is injected from the fuel injection valve 20 at the target injection timing.

  In step S16, the electronic control unit 200 corrects one or both of the target injection amount and the target injection timing so that the detected self-ignition timing becomes the target ignition timing.

  According to the present embodiment described above, the engine body 1, the fuel injection valve 20 that injects fuel into the combustion chamber of the engine body 1, the knock sensor 210 (vibration sensor) that detects the vibration acceleration of the engine body 1, and An electronic control unit 200 (control device) that controls the internal combustion engine 100 with the fuel injection amount and the injection timing injected from the fuel injection valve 20 is set based on the target injection amount and the target set based on the engine operating state A combustion control unit that controls the injection timing to burn fuel, an amplitude value calculation unit that calculates an amplitude value of vibration acceleration in an arbitrary frequency band from 5 [kHz] to 10 [kHz], and a combustion mode of the fuel A combustion form determining unit for determining.

  The combustion mode determination unit determines that the combustion mode of the fuel is diffusion combustion if the maximum value or the average value of the amplitude values in the predetermined ignition determination section is equal to or greater than the combustion mode determination threshold V3 (predetermined value). If the maximum value or the average value is less than the combustion mode determination threshold value V3, the combustion mode of combustion is determined to be premixed combustion.

  Thus, according to the present embodiment, the combustion mode of the fuel can be determined in advance when detecting the ignition timing. Therefore, for example, when premixed combustion is performed, when the combustion mode of the fuel is a combustion mode close to diffusion combustion rather than premixed combustion, or conversely, when performing diffusion combustion, Even when the fuel combustion mode is closer to premixed combustion than diffusion combustion, the ignition timing is detected based on the amplitude value of vibration acceleration in the frequency band corresponding to the actual combustion mode can do. For this reason, it is possible to suppress the detection accuracy of the ignition timing from being lowered or erroneously detecting the ignition timing.

  The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

DESCRIPTION OF SYMBOLS 1 Engine main body 20 Fuel injection valve 100 Internal combustion engine 200 Electronic control unit (control apparatus)
210 Knock sensor (vibration sensor)

Claims (1)

The engine body,
A fuel injection valve for injecting fuel into the combustion chamber of the engine body;
A vibration sensor for detecting vibration acceleration of the engine body;
An internal combustion engine control apparatus for controlling an internal combustion engine comprising:
A combustion control section for controlling the injection amount and injection timing of the fuel injected from the fuel injection valve to a target injection amount and a target injection timing set based on the engine operating state, and burning the fuel;
An amplitude value calculation unit for calculating an amplitude value of the vibration acceleration in an arbitrary frequency band from 5 kHz to 10 kHz;
A combustion mode discriminating unit for discriminating the combustion mode of fuel;
With
The combustion form discrimination unit
If the maximum value or the average value of the amplitude value in a predetermined ignition determination section is equal to or greater than the predetermined value, it is determined that the combustion mode of the fuel is diffusion combustion, and the maximum value or the average value is less than the predetermined value. If there is, it is determined that the combustion mode of combustion is premixed combustion.
Control device for internal combustion engine.

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