阅读说明：本技术 内燃机的控制装置 (Control device for internal combustion engine ) 是由 菅野翼 于 2019-06-24 设计创作，主要内容包括：一种内燃机的控制装置,抑制燃烧噪音的变化。内燃机(100)的控制装置(200)的燃烧控制部构成为,基于由振动传感器(210)检测出的振动加速度算出特定频带的2倍频的第1判定频带中的内燃机主体的第1振动等级,在第1振动等级小于根据内燃机运转状态预先设定的预定的第1基准振动等级时,以使得第1振动等级成为第1基准振动等级以上的方式修正目标喷射量和目标喷射正时中的一方或双方。(A control device for an internal combustion engine suppresses a change in combustion noise. A combustion control unit of a control device (200) of an internal combustion engine (100) is configured to calculate a1 st vibration level of an internal combustion engine body in a1 st determination frequency band of a2 nd harmonic of a specific frequency band based on vibration acceleration detected by a vibration sensor (210), and to correct one or both of a target injection amount and a target injection timing so that the 1 st vibration level becomes equal to or higher than a1 st reference vibration level preset in accordance with an engine operating state when the 1 st vibration level is lower than the 1 st reference vibration level.)

1. A control device for an internal combustion engine,

the control device controls an internal combustion engine, the internal combustion engine including:

an internal combustion engine main body;

a fuel injection valve that injects fuel for combustion in a combustion chamber of the internal combustion engine main body; and

a vibration sensor that detects a vibration acceleration of the engine main body,

the control device for an internal combustion engine includes a combustion control unit that controls an injection amount and an injection timing of fuel injected from the fuel injection valve so that the fuel is self-ignited and burned by controlling the injection amount and the injection timing of the fuel to a target injection amount and a target injection timing set based on an engine operating state, such that a pressure wave, which is generated 2 times in a stepwise manner in the combustion chamber and shows a change over time in a rate of increase in an in-cylinder pressure, is formed in a double-peak shape, and a peak interval, which is an interval from a1 st peak of a first peak of the pressure waveform formed by a1 st heat release to a2 nd peak of a second peak of the pressure waveform formed by a2 nd heat release, is a reference peak interval that suppresses a vibration acceleration of a specific frequency band in a vibration acceleration of the engine body,

the combustion control section is configured to control the combustion of the fuel,

calculating a1 st vibration level of the internal combustion engine main body in a1 st determination frequency band that is a frequency of 2 times the specific frequency band based on the vibration acceleration detected by the vibration sensor,

when the 1 st vibration level is lower than a predetermined 1 st reference vibration level set in advance in accordance with an engine operating state, one or both of the target injection amount and the target injection timing are corrected so that the 1 st vibration level becomes equal to or higher than the 1 st reference vibration level.

2. The control apparatus of an internal combustion engine according to claim 1,

the combustion control section is configured to control the combustion of the fuel,

at least the 1 st main fuel and the 2 nd main fuel are injected in sequence,

when the 1 st vibration level is lower than the 1 st reference vibration level, an estimated ignition timing of the fuel is calculated, and if the estimated ignition timing is later than a target ignition timing set according to an engine operating state, at least one or both of the target injection amount and the target injection timing of the 1 st main fuel is corrected so as to advance the ignition timing of the 1 st main fuel.

3. The control apparatus of an internal combustion engine according to claim 1 or 2,

the combustion control section is configured to control the combustion of the fuel,

at least the 1 st main fuel and the 2 nd main fuel are injected in sequence,

when the 1 st vibration level is lower than the 1 st reference vibration level, an estimated ignition timing of the fuel is calculated, and if the estimated ignition timing is earlier than a target ignition timing set according to an engine operating state, at least one or both of the target injection amount and the target injection timing of the 1 st main fuel is corrected so as to retard the ignition timing of the 1 st main fuel.

4. The control apparatus of an internal combustion engine according to claim 1,

the combustion control section is configured to control the combustion of the fuel,

calculating a2 nd vibration level of the engine body in a2 nd determination frequency band lower than the 1 st determination frequency band in the vicinity of the 1 st determination frequency band based on the vibration acceleration detected by the vibration sensor,

and correcting one or both of the target injection amount and the target injection timing so that the peak interval is narrowed when the 1 st vibration level is smaller than the 1 st reference vibration level and the 2 nd vibration level is equal to or greater than a predetermined 2 nd reference vibration level that is preset in accordance with an engine operating state.

5. The control apparatus of an internal combustion engine according to claim 4,

the combustion control section is configured to control the combustion of the fuel,

at least the 1 st main fuel and the 2 nd main fuel are injected in sequence,

one or both of the target injection amount and the target injection timing of the 1 st main fuel are corrected so that the ignition timing of the 1 st main fuel is retarded and the peak interval is narrowed.

6. The control apparatus of an internal combustion engine according to claim 1, 4 or 5,

the combustion control section is configured to control the combustion of the fuel,

calculating a 3 rd vibration level of the engine body in a 3 rd determination frequency band higher than the 1 st determination frequency band in the vicinity of the 1 st determination frequency band based on the vibration acceleration detected by the vibration sensor,

and correcting one or both of the target injection amount and the target injection timing so that the peak interval becomes wider when the 1 st vibration level is smaller than the 1 st reference vibration level and the 3 rd vibration level is equal to or greater than a predetermined 3 rd reference vibration level that is preset in accordance with an engine operating state.

7. The control apparatus of an internal combustion engine according to claim 6,

the combustion control section is configured to control the combustion of the fuel,

at least the 1 st main fuel and the 2 nd main fuel are injected in sequence,

one or both of the target injection amount and the target injection timing of the 1 st main fuel are corrected so that the ignition timing of the 1 st main fuel is advanced and the peak interval is widened.

Technical Field

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

Background

Patent document 1 discloses, as a conventional control device for an internal combustion engine, a device configured as follows: the main fuel injection is divided into the 1 st main fuel injection and the 2 nd main fuel injection to perform self-ignition combustion of the fuel so that the shape of a pressure waveform (in-cylinder pressure increase rate pattern) indicating a change over time in the in-cylinder pressure increase rate becomes a double peak shape and the interval between the peak timing of the first peak and the peak timing of the second peak of the pressure waveform becomes a predetermined interval. According to patent document 1, by controlling the peak interval between the peak timing of the first peak and the peak timing of the second peak of the pressure waveform to a predetermined interval in this manner, the vibration level of a predetermined frequency band can be reduced, and combustion noise can be reduced.

Disclosure of Invention

Problems to be solved by the invention

However, if the shape of the pressure waveform changes from the target two-peak shape due to, for example, deviation of the ignition timing from the target ignition timing due to some cause, the peak interval cannot be controlled to a predetermined interval any more, and therefore, there is a possibility that the combustion noise cannot be reduced any more.

The present invention has been made in view of such a problem, and an object of the present invention is to enable determination of whether or not the shape of a pressure waveform has changed from a target bimodal shape, and to correct the shape of the pressure waveform based on the determination result.

Means for solving the problems

In order to solve the above problem, according to an aspect of the present invention, there is provided a control device for an internal combustion engine, the control device controlling the internal combustion engine, the internal combustion engine including: an internal combustion engine main body; a fuel injection valve that injects fuel for combustion in a combustion chamber of an internal combustion engine main body; and a vibration sensor that detects a vibration acceleration of the engine body, wherein the control device of the internal combustion engine includes a combustion control unit that controls an injection amount and an injection timing of the fuel injected from the fuel injection valve to a target injection amount and a target injection timing set based on an engine operating state to perform self-ignition combustion of the fuel so that a pressure wave, which is generated 2 times in a stepwise manner in the combustion chamber and shows a temporal change in an in-cylinder pressure increase rate, is formed in a two-peak shape, and a peak interval, which is an interval from a1 st peak value of a first peak of a pressure waveform formed by a1 st heat release to a2 nd peak value of a second peak of a pressure waveform formed by a2 nd heat release, becomes a reference peak interval that suppresses a vibration acceleration of a specific frequency band in the vibration acceleration of the engine body. The combustion control unit is configured to calculate a1 st vibration level of the engine body in a1 st determination frequency band, which is a frequency of 2 times the specific frequency band, based on the vibration acceleration detected by the vibration sensor, and to correct one or both of the target injection amount and the target injection timing so that the 1 st vibration level is equal to or higher than a1 st reference vibration level, when the 1 st vibration level is lower than a predetermined 1 st reference vibration level set in advance in accordance with the engine operating state.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the aspect of the present invention, it is possible to determine whether or not the shape of the pressure waveform has changed from the target bimodal shape, and to correct the shape of the pressure waveform based on the determination result.

Drawings

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

Fig. 2 is a sectional view of an engine main body of an internal combustion engine according to embodiment 1 of the present invention.

Fig. 3 is a diagram showing a relationship between a crank angle and a heat generation rate when fuel is combusted in a combustion chamber by performing combustion control according to embodiment 1 of the present invention.

Fig. 4 is a diagram showing a relationship between a crank angle and a rate of increase in-cylinder pressure when fuel is combusted in a combustion chamber by performing combustion control according to embodiment 1 of the present invention.

Fig. 5 is a graph showing the vibration level of the engine body for each frequency calculated based on the output value of the knock sensor.

Fig. 6 is a flowchart illustrating combustion control according to embodiment 1 of the present invention.

Fig. 7 is a graph showing the vibration level of the engine body for each frequency calculated based on the output value of the knock sensor.

Fig. 8A is a flowchart illustrating combustion control according to embodiment 2 of the present invention.

Fig. 8B is a flowchart illustrating combustion control according to embodiment 2 of the present invention.

Description of the reference symbols

1: an internal combustion engine main body;

11: a combustion chamber;

20: a fuel injection valve;

100: an internal combustion engine;

200: an electronic control unit (control device);

210: a knock sensor (vibration sensor).

Detailed Description

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

(embodiment 1)

Fig. 1 is a schematic configuration diagram of an internal combustion engine 100 and an electronic control unit 200 for controlling the internal combustion engine 100 according to embodiment 1 of the present invention. Fig. 2 is a sectional view of the engine body 1 of the engine 100.

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

The engine body 1 burns fuel in a combustion chamber 11 (see fig. 2) formed in each cylinder 10 to generate power for driving a vehicle or the like, for example. The engine main 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 a vibration acceleration of the engine body 1 is mounted in the engine body 1. The knock sensor 210 is one of vibration sensors (acceleration sensors) provided with piezoelectric elements, and outputs a voltage value according to a vibration acceleration of the 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 pipe 24, and a fuel pressure sensor 211.

The fuel injection valve 20 is provided in 1 for each cylinder 10 so as to face the combustion chamber 11 of each cylinder 10, so that fuel can be directly injected into the combustion chamber 11. The opening time (injection amount) and the opening timing (injection timing) of the fuel injection valve 20 are changed in accordance with a control signal from the ecu 200, and fuel is directly injected from the fuel injection valve 20 into the combustion chamber 11 when the fuel injection valve 20 is opened.

The delivery pipe 21 is connected to a fuel tank 23 via a pressure pipe 24. A supply pump 22 for pressurizing the fuel stored in the fuel tank 23 and supplying the fuel to the delivery pipe 21 is provided in the middle of the pressure-feed pipe 24. The delivery pipe 21 temporarily stores the high-pressure fuel that is pressure-fed by the feed 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 11.

The discharge amount of the feed pump 22 can be changed, and the discharge amount of the feed pump 22 is changed in accordance with a control signal from the electronic control unit 200. The fuel pressure in the delivery pipe 21, that is, the injection pressure of the fuel injection valve 20 is controlled by controlling the discharge amount of the feed pump 22.

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

The intake device 3 is a device for introducing air into the combustion chamber 11, and is configured to be capable of changing the state of the air taken into the combustion chamber 11 (intake pressure (supercharging pressure), intake temperature, and EGR (Exhaust Gas Recirculation) Gas amount). That is, the intake device 3 is configured to be able to change the oxygen density in the combustion chamber 11. The intake device 3 includes an air cleaner 30, an intake pipe 31, a compressor 32a of a turbocharger 32, an intercooler 33, an intake manifold 34, an electronically controlled throttle valve 35, an air flow meter 212, an EGR passage 36, an EGR cooler 37, and an EGR valve 38.

The air cleaner 30 removes foreign matter such as sand contained in the air.

One end of the intake pipe 31 is connected to the air cleaner 30, and the other end is connected to a surge tank 34a of the intake manifold 34.

The turbocharger 32 is a type of supercharger, and forcibly compresses air using energy of exhaust gas, and supplies the compressed air to each combustion chamber 11. This improves the charging efficiency, and therefore increases the engine output. The compressor 32a is a member constituting a part of the turbocharger 32, and is provided in the intake pipe 31. The compressor 32a is rotated by a turbine 32b of a turbocharger 32, which will be described later, provided coaxially therewith, and forcibly compresses air. In addition, a Supercharger (Supercharger) mechanically driven by the rotational force of a crankshaft (not shown) may be used instead of the turbocharger 32.

The intercooler 33 is provided in the intake pipe 31 downstream of the compressor 32a, and cools the air compressed by the compressor 32a to have a high temperature.

The intake manifold 34 includes a surge tank 34a and a plurality of intake branch pipes 34b branched from the surge tank 34a and connected to openings of the intake ports 14 (see fig. 2) formed in the engine main body 1. The air introduced into the surge tank 34a is equally distributed into the combustion chambers 11 via the intake branch pipes 34b and the intake ports 14. In this way, the intake pipe 31, the intake manifold 34, and the intake ports 14 form an intake passage for introducing air into the combustion chambers 11. A pressure sensor 213 for detecting the pressure (intake air pressure) inside the surge tank 34a and a temperature sensor 214 for detecting the temperature (intake air temperature) inside the surge tank 34a are mounted to the surge tank 34 a.

The throttle valve 35 is provided in the intake pipe 31 between the intercooler 33 and the surge tank 34 a. The throttle valve 35 is driven by a throttle actuator 35a, and changes the passage cross-sectional area of the intake pipe 31 continuously or stepwise. The flow rate of air drawn into each combustion chamber 11 can be adjusted by adjusting the opening degree of the throttle valve 35 by the throttle actuator 35 a.

The airflow meter 212 is provided in the intake pipe 31 on the upstream side of the compressor 32 a. The airflow meter 212 detects the flow rate of air (hereinafter referred to as "intake air amount") that flows through the intake passage and is finally taken into each combustion chamber 11.

The EGR passage 36 is a passage for communicating an exhaust manifold 40, which will be described later, with the surge tank 34a of the intake manifold 34, and returning a part of the exhaust gas discharged from each combustion chamber 11 to the surge tank 34a by a pressure difference. Hereinafter, the exhaust gas flowing into the EGR passage 36 is referred to as "EGR gas", and the rate of the EGR gas amount to the cylinder interior gas amount, that is, the recirculation rate of the exhaust gas is referred to as "EGR rate". By returning the EGR gas to the surge tank 34a and to each combustion chamber 11, the combustion temperature can be lowered and the emission of nitrogen oxides (NOx) can be suppressed.

The EGR cooler 37 is provided in the EGR passage 36. The EGR cooler 37 is a heat exchanger for cooling the EGR gas by, for example, running wind, cooling water, or the like.

The EGR valve 38 is provided in the EGR passage 36 on the downstream side of the EGR cooler 37 in the EGR gas flow direction. The EGR valve 38 is a solenoid valve whose opening degree can be adjusted continuously or stepwise, and the opening degree is controlled by the electronic control unit 200. The flow rate of EGR gas recirculated to the surge tank 34a is adjusted by controlling the opening degree of the EGR valve 38. That is, the EGR rate can be controlled to an arbitrary value by controlling the opening degree of the EGR valve 38 to an appropriate opening degree based on the intake air amount, the intake pressure (supercharging pressure), and the like.

The exhaust device 4 is a device for purifying exhaust gas generated in each combustion chamber and discharging the exhaust gas to the outside, and includes an exhaust manifold 40, an exhaust pipe 41, a turbine 32b of the turbocharger 32, and an exhaust gas post-treatment device 42.

The exhaust manifold 40 includes a plurality of exhaust branch pipes connected to openings of the exhaust ports 15 (see fig. 2) formed in the engine body 1, and a collecting pipe for collecting the exhaust branch pipes into 1.

One end of the exhaust pipe 41 is connected to the manifold of the exhaust manifold 40, and the other end thereof is an open end. The exhaust gas discharged from each combustion chamber 11 to the exhaust manifold 40 through the exhaust port flows through the exhaust pipe 41 and is discharged to the outside.

The turbine 32b is a member constituting a part of the turbocharger 32, and is provided in the exhaust pipe 41. The turbine 32b is rotated by the energy of the exhaust gas, and drives the compressor 32a provided coaxially therewith.

A variable nozzle 32c is provided outside the turbine 32 b. The variable nozzle 32c functions as a throttle valve, and the nozzle opening degree (valve opening degree) of the variable nozzle 32c is controlled by the electronic control unit 200. By changing the nozzle opening of the variable nozzle 32c, the flow velocity of the exhaust gas that drives the turbine 32b can be changed. That is, by changing the nozzle opening degree of the variable nozzle 32c, the rotation speed of the turbine 32b can be changed to change the boost pressure. Specifically, when the nozzle opening degree of the variable nozzle 32c is decreased (the variable nozzle 32c is narrowed), the flow velocity of the exhaust gas increases, the rotation speed of the turbine 32b increases, and the boost pressure increases.

The exhaust gas post-treatment device 42 is provided in the exhaust pipe 41 on the downstream side of the turbine 32 b. The exhaust gas post-treatment device 42 is a device for purifying exhaust gas and then discharging the exhaust gas to the outside, and is a device in which various catalysts (for example, three-way catalysts) for purifying harmful substances are carried on a carrier.

The intake valve actuator 5 is a device for driving the intake valves 50 of the respective cylinders 10 to open and close, and is provided in the engine body 1. The intake valve actuator 5 of the present embodiment is configured to drive the intake valve 50 to open and close by an electromagnetic actuator, for example, so that the opening and closing timing of the intake valve 50 can be controlled.

The exhaust valve actuator 6 is a device for driving the opening and closing of the exhaust valves 60 of the respective cylinders 10, and is provided in the engine body 1. The exhaust valve transmission device 6 of the present embodiment is configured to drive the exhaust valve 60 to open and close by an electromagnetic actuator, for example, so that the opening and closing timing of the exhaust valve 60 can be controlled.

Further, the intake valve actuator 5 and the exhaust valve actuator 6 are not limited to electromagnetic actuators, and may be configured to drive the intake valve 50 or the exhaust valve 60 to open and close by a camshaft, for example, and a variable valve mechanism that changes a relative phase angle of the camshaft with respect to a crankshaft by hydraulic control may be provided at one end of the camshaft, thereby controlling the opening and closing timing of the intake valve 50 or the exhaust valve 60.

The electronic control unit 200 is constituted by a digital computer, and includes 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, which are connected to each other via a bidirectional bus 201.

The output signals of the knock sensor 210 and the like are input to the input port 205 via the corresponding AD converters 207. Further, as a signal for detecting the engine load, an output voltage of the load sensor 221 that generates an output voltage proportional to a depression amount of the accelerator pedal 221 (hereinafter referred to as an "accelerator depression amount") is input to the input port 205 via the corresponding AD converter 207. As a signal for calculating the engine speed or the like, an output signal of a crank angle sensor 222 that generates an output pulse every time the crankshaft of the engine body 1 rotates by, for example, 15 ° is input to the input port 205. As described above, the input port 205 receives output signals of various sensors required for controlling the internal combustion engine 100.

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

The electronic control unit 200 outputs control signals for controlling the respective control components from the output port 206 based on output signals of various sensors input to the input port 205 to control the internal combustion engine 100. The control of the internal combustion engine 100, particularly the combustion control of the fuel in the combustion chamber 11, by the electronic control unit 200 will be described below.

Fig. 3 is a diagram showing a relationship between a crank angle and a heat generation rate in the case where the combustion control of the present embodiment is performed and fuel is combusted in the combustion chamber 11 during a steady operation in which the engine operating state (the engine speed and the engine load) is constant. Fig. 4 is a diagram showing a relationship between the crank angle and the rate of increase in the in-cylinder pressure in this case.

The heat generation rate (dQ/d θ) [ J/deg.ca ] is the amount of heat generated per unit crank angle when the fuel is combusted, that is, the heat generation amount Q per unit crank angle. In the following description, a combustion waveform showing the relationship between the crank angle and the heat generation rate, that is, a combustion waveform showing a change in the heat generation rate with time is referred to as a "heat generation rate pattern". The in-cylinder pressure increase rate (dP/d θ) [ kPa/deg.CA ] is a crank angle differential value of the in-cylinder pressure P [ kPa ]. In the following description, a pressure waveform showing the relationship between the crank angle and the in-cylinder pressure increase rate, that is, a pressure waveform showing a temporal change in the in-cylinder pressure increase rate is referred to as an "in-cylinder pressure increase rate pattern".

As shown in fig. 3, the electronic control unit 200 divides the main fuel injection for outputting the required torque according to the engine load into the 1 st main fuel injection G1 and the 2 nd main fuel injection G2 and sequentially performs the operation of the engine main body 1 by auto-ignition combustion of the injected fuel.

In the present embodiment, the injection amount and the injection timing of each of the fuel injections G1 and G2 are controlled so that the fuel injected into the combustion chamber 11 by the 1 st main fuel injection G1 (hereinafter referred to as "1 st main fuel") and the fuel injected into the combustion chamber 11 by the 2 nd main fuel injection G2 (hereinafter referred to as "2 nd main fuel") are premixed compression ignited combustion in which combustion is performed with a premixed period of fuel and air being separated to some extent, and 2 times of heat release are generated in stages.

That is, as shown in fig. 3, the injection amounts and the injection timings of the respective fuel injections G1 and G2 are controlled so that the heat release when the 1 st main fuel is combusted forms the combustion waveform X1 of the first peak of the heat release rate pattern mainly, and thereafter, the heat release when the 2 nd main fuel is combusted forms the combustion waveform X2 of the second peak of the heat release rate pattern mainly, so that the heat release rate pattern has a two-peak shape.

As a result, as shown in fig. 4, the pressure waveform Y1 of the first peak of the in-cylinder pressure increase rate pattern is formed mainly by the heat release when the 1 st main fuel is combusted, and thereafter, the pressure waveform Y2 of the second peak of the in-cylinder pressure increase rate pattern is formed mainly by the heat release when the 2 nd main fuel is combusted, and the in-cylinder pressure increase rate pattern also has a two-peak shape together with the heat release rate pattern.

By generating the 2-time heat release in stages in this manner, the pressure wave generated by the 1 st-time heat release (mainly the pressure wave generated during combustion of the 1 st main fuel in the present embodiment) and the pressure wave generated by the 2 nd-time heat release (mainly the pressure wave generated during combustion of the 2 nd main fuel in the present embodiment) become pressure waves in a reverse phase in a specific frequency band and cancel each other out, and as a result, the vibration level [ dB ] of the engine body 1 in the specific frequency band can be reduced.

If the engine speed is the same, the frequency band in which the pressure wave generated by the 1 st heat release and the pressure wave generated by the 2 nd heat release cancel each other out (hereinafter referred to as "attenuation band") changes in accordance with the crank interval (hereinafter referred to as "peak interval") Δ θ (═ θ 2- θ 1) from the peak value (hereinafter referred to as "1 st peak") P1 of the pressure waveform Y1 to the peak value (hereinafter referred to as "2 nd peak") P2 of the pressure waveform Y2, and the attenuation band tends to move to the higher frequency side as the peak interval Δ θ becomes narrower, and to move to the lower frequency side as the peak interval becomes wider.

Therefore, in the present embodiment, the injection amount and the injection timing of each of the fuel injections G1 and G2 are controlled so that the heat release occurs 2 times in stages and the peak interval Δ θ becomes the peak interval (hereinafter referred to as "reference peak interval") Δ θ t in which the vibration level of the frequency band (hereinafter referred to as "target attenuation band". about.1.5 to 1.7[ kHz ] in the present embodiment) in which the noise generated from the engine body 1, which is considered to be particularly uncomfortable, can be reduced.

However, when the deviation between the ignition timing and the target ignition timing becomes large due to some factors such as a transient change in the in-cylinder environment (in-cylinder pressure, in-cylinder temperature, and in-cylinder oxygen density), the shape of the heat release rate pattern or the in-cylinder pressure increase rate pattern may change from the target shape (a shape capable of reducing the level of vibration of the target attenuation band).

For example, the deviation between the ignition timing and the target ignition timing may become large, the shape of the in-cylinder pressure increase rate pattern may change from the target shape, and the peak interval Δ θ may become narrower or wider than the reference peak interval Δ θ t. In this case, since the attenuation band deviates from the target attenuation band, the vibration level of the target attenuation band cannot be lowered any more, and the desired noise reduction effect cannot be obtained any more.

For example, the deviation between the ignition timing and the target ignition timing becomes large, the 1 st main fuel and the 2 nd main fuel are not combusted stepwise but are combusted integrally, the 2 nd heat release cannot be generated stepwise, and the shape of the heat release rate pattern or the in-cylinder pressure increase rate pattern becomes a single peak shape. In this case, the noise reduction effect itself of the engine body 1 in the specific frequency band based on the cancellation of the pressure wave generated by the 1 st heat release and the pressure wave generated by the 2 nd heat release can no longer be obtained.

Therefore, when the shape of the in-cylinder pressure increase rate pattern is changed from the target shape beyond the allowable range, it is preferable to correct the injection amount and the injection timing of each of the fuel injections G1 and G2 so that the shape of the in-cylinder pressure increase rate pattern approaches the target shape. Next, a method of determining whether or not the shape of the in-cylinder pressure increase rate pattern has changed from the target shape beyond the allowable range in the present embodiment will be described with reference to fig. 5.

Fig. 5 is a graph showing the vibration level of the engine body 1 for each frequency calculated based on the output value of the knock sensor 210. In fig. 5, the solid line indicates the vibration level of the engine body 1 for each frequency when the in-cylinder pressure increase rate pattern has a target shape, that is, when the heat release occurs 2 times in a stepwise manner, and the peak interval Δ θ is controlled to the reference peak interval Δ θ t. On the other hand, the broken line is a line shown for comparison, showing the vibration level of the engine body 1 for each frequency in the case where the amount of fuel injected from the fuel injection valve 20 and the injection timing are controlled so that the in-cylinder pressure increase rate pattern becomes a single peak shape.

As shown by the solid line in fig. 5, it can be seen that: when the in-cylinder pressure increase rate pattern has a target shape, the attenuation band can be made to coincide with the target attenuation band, and therefore the vibration level in the target attenuation band is lower than the vibration level indicated by the broken line.

Here, as a method of determining whether or not the shape of the in-cylinder pressure increase rate pattern has changed from the target shape beyond the allowable range, for example, the following method is given: if the vibration level of the target attenuation band is equal to or higher than a predetermined threshold value, it is determined that the shape of the in-cylinder pressure increase rate pattern has changed from the target shape beyond an allowable range. This is because: if the vibration level of the target attenuation band is above a predetermined threshold, it can be determined that: as a result of the peak interval Δ θ being shifted from the reference peak interval Δ θ t, the attenuation band is shifted from the target attenuation band, and the vibration level of the target attenuation band increases, or the in-cylinder pressure increase rate pattern has a unimodal shape, and the noise reduction effect by 2 pressure waves cannot be obtained, and the vibration level of the target attenuation band increases.

However, when the attenuation band matches the target attenuation band, the 2 pressure waves cancel each other and the vibration level decreases, so that the accuracy of calculating the vibration level in such a band tends to deteriorate, and erroneous determination may be caused.

Therefore, in the present embodiment, attention is paid to a frequency band that is 2-fold higher than the target attenuation frequency band (hereinafter referred to as "1 st determination frequency band"). As shown in fig. 5, when the attenuation band matches the target attenuation band, the vibration level indicated by the solid line is higher than the vibration level indicated by the broken line in the 1 st determination band.

That is, as a result of intensive studies by the inventors, it has been found that when the in-cylinder pressure increase rate pattern has a target shape and the peak interval Δ θ is controlled to be the reference peak interval Δ θ t, 2 pressure waves interfere with each other and increase in frequency band corresponding to 2 octaves of the attenuation frequency band, and the vibration level increases conversely.

When the in-cylinder pressure increase rate pattern has a target shape and the peak interval Δ θ is controlled to be the reference peak interval Δ θ t in this manner, the 1 st vibration level of the 1 st determination band increases. On the other hand, when the shape of the in-cylinder pressure increase rate pattern is changed from the target shape beyond the allowable range and the peak interval Δ θ cannot be controlled to the reference peak interval Δ θ t, the attenuation band deviates from the target attenuation band, and as a result, the frequency band of 2-fold frequency of the attenuation band deviates from the 1 st determination band, so the 1 st vibration level in the 1 st determination band is lower than the 1 st vibration level in the case where the peak interval Δ θ is controlled to the reference peak interval Δ θ t. In addition, since the 1 st determination frequency band is a frequency band in which 2 pressure waves interfere with each other and the vibration level increases, it is possible to suppress deterioration in the calculation accuracy of the vibration level.

Therefore, in the present embodiment, it is determined whether or not the 1 st vibration level of the 1 st determination frequency band is equal to or higher than the 1 st reference vibration level set in advance in accordance with the engine operating state, and if the 1 st vibration level of the 1 st determination frequency band is lower than the 1 st reference vibration level, it is determined that the shape of the in-cylinder pressure increase rate pattern has changed from the target shape beyond the allowable range. In this case, the target values of the fuel injection amount and the fuel injection timing set according to the engine operating state are corrected so that the in-cylinder pressure increase rate pattern has the target shape. The combustion control according to the present embodiment will be described below with reference to fig. 6.

Fig. 6 is a flowchart for explaining the combustion control according to the present embodiment. The electronic control unit 200 repeatedly executes the present routine at predetermined calculation cycles during the engine operation.

In step S1, the electronic control unit 200 reads the engine load detected by the load sensor 221 and the engine speed calculated based on the output signal of the crank angle sensor 222, and detects the engine operating state.

In step S2, the electronic control unit 200 sets a target injection amount Q1 of the 1 st main fuel injection G1 and a target injection amount Q2 of the 2 nd main fuel injection G2. In the present embodiment, the electronic control unit 200 refers to a map created in advance by experiments or the like, and sets the target injection amount Q1 and the target injection amount Q2 based on at least the engine load.

In step S3, the electronic control unit 200 sets the target injection timing a1 of the 1 st main fuel injection G1 and the target injection timing a2 of the 2 nd main fuel injection G2. In the present embodiment, the electronic control unit 200 refers to a map created in advance by an experiment or the like, and sets the target injection timing a1 and the target injection timing a2 based on the engine operating state.

In step S4, electronic control unit 200 calculates the 1 st vibration level in the 1 st determination frequency band by applying various processes (for example, a band pass filter process having the 1 st determination frequency band in the bandwidth, or the like) to the output value of knock sensor 210 in the combustion noise determination section acquired in the previous combustion cycle. In the present embodiment, the 1 st decision band is set to a band from 3.0[ kHz ] to 3.4[ kHz ]. The combustion noise determination section is a section corresponding to a crank angle range from the middle stage of the compression stroke to the middle stage of the expansion stroke of each cylinder 10.

In step S5, the electronic control unit 200 refers to a map created in advance by experiments or the like, and calculates the 1 st reference vibration level based on the engine operating state.

In step S6, the electronic control unit 200 determines whether or not the 1 st vibration level is equal to or greater than the 1 st reference vibration level. If the 1 st vibration level is the 1 st reference vibration level or more, the electronic control unit 200 proceeds to the process of step S7. On the other hand, if the 1 st vibration level is less than the 1 st reference vibration level, the electronic control unit 200 proceeds to the process of step S8.

In step S7, the electronic control unit 200 controls the injection amount and the injection timing of the 1 st main fuel injection G1 to the 1 st target injection amount Q1 and the 1 st target injection timing a1, respectively, and controls the injection amount and the injection timing of the 2 nd main fuel injection G2 to the 2 nd target injection amount Q2 and the 1 st target injection timing a2, respectively, to carry out fuel injection.

In step S8, the electronic control unit 200 calculates an estimated value of the ignition timing of the fuel in the previous combustion cycle (hereinafter referred to as "estimated ignition timing"). In the present embodiment, the electronic control unit 200 calculates the vibration level for each crank angle in the combustion noise determination section based on the output value of the knock sensor 210 in the combustion noise determination section acquired in the previous combustion cycle, and calculates the crank angle at which the vibration level becomes a predetermined ignition timing determination threshold value as the estimated ignition timing. The calculation of the estimated ignition timing is not limited to this method, and any known method may be used, and for example, when a cylinder pressure sensor is provided, the timing at which the cylinder pressure detected by the cylinder pressure sensor becomes equal to or greater than a predetermined value may be calculated as the estimated ignition timing.

In step S9, the electronic control unit 200 calculates the target ignition timing in the previous combustion cycle. The target ignition timing can be calculated by, for example, inputting the target injection amount in the previous combustion cycle to a prediction model of the ignition timing.

In step S10, the electronic control unit 200 determines whether the estimated ignition timing in the last combustion cycle is earlier or later than the target ignition timing. If the estimated ignition timing in the previous combustion cycle is earlier than the target ignition timing, the electronic control unit 200 proceeds to the process of step S11, and if delayed, the electronic control unit 200 proceeds to the process of step S12.

In step S11, the electronic control unit 200 corrects the target injection timing a1 of the 1 st main fuel injection G1 in such a manner that the ignition timing is retarded. Specifically, correction is performed to retard the target injection timing a1 of the 1 st main fuel injection G1 in accordance with the amount of advance of the estimated ignition timing from the target ignition timing.

In the present embodiment, the ignition timing is retarded by correcting the target injection timing a1 of the 1 st main fuel injection G1 to the retarded side in this way, but the ignition timing may be retarded by correcting the target injection amount Q1 to the reduced side instead of or in addition to the retard control of the target injection timing a1, for example. In this case, in order to satisfy the required torque, correction may be performed by increasing the target injection amount Q2 by the amount by which the target injection amount Q1 is decreased.

In step S12, the electronic control unit 200 corrects the target injection timing a1 of the 1 st main fuel injection G1 in such a manner that the ignition timing is advanced. Specifically, correction is performed to advance the target injection timing a1 of the 1 st main fuel injection G1 in accordance with the retard amount of the estimated ignition timing from the target ignition timing.

In the present embodiment, the ignition timing is advanced by correcting the target injection timing a1 of the 1 st main fuel injection G1 to the advance side in this way, but the ignition timing may be advanced by correcting the target injection amount Q1 to the increase side instead of or in addition to the advance control of the target injection timing a1, for example. In this case, correction may be performed by reducing the target injection amount Q2 by the amount of increase of the target injection amount Q1.

According to the present embodiment described above, the electronic control unit 200 (control device) for controlling the internal combustion engine 100 includes the combustion control unit, and the internal combustion engine 100 includes: an internal combustion engine main body 1; a fuel injection valve 20 that injects fuel for combustion in the combustion chamber 11 of the engine body 1; and a knock sensor (vibration sensor) 210 that detects a vibration acceleration of the engine body 1, the combustion control unit controls the injection amount and the injection timing of the fuel injected from the fuel injection valve 20 so that the fuel is self-ignited by controlling the injection amount and the injection timing of the fuel to be injected from the fuel injection valve 20 so that a pressure wave representing a change over time in the in-cylinder pressure increase rate occurs in stages 2 times in the combustion chamber 11 in a two-peak shape and a peak interval Δ θ, which is an interval from a1 st peak value of a first peak of a pressure waveform formed by a1 st heat release to a2 nd peak value of a second peak of a pressure waveform formed by a2 nd heat release, becomes a reference peak interval Δ θ t for suppressing a vibration acceleration of a target damping frequency band (specific frequency band) in the vibration acceleration of the engine body 1.

The combustion control unit is configured to calculate a1 st vibration level of the engine body 1 in a1 st determination frequency band that is a frequency of 2 times the target attenuation frequency band based on the vibration acceleration detected by the knock sensor 210, and to correct one or both of the target injection amount and the target injection timing so that the 1 st vibration level is equal to or higher than a1 st reference vibration level that is predetermined in accordance with the engine operating state when the 1 st vibration level is lower than the 1 st reference vibration level.

When the shape of the in-cylinder pressure increase rate pattern has a target double-peak shape, the 1 st vibration level in the 1 st determination frequency band in which the 2 pressure waves interfere with each other and the vibration level increases, so that it is possible to determine whether or not the shape of the in-cylinder pressure increase rate pattern has the target double-peak shape by comparing the 1 st vibration level with the 1 st reference vibration level as in the present embodiment. When the 1 st vibration level is lower than the 1 st reference vibration level, that is, when the shape of the in-cylinder pressure increase rate pattern does not have the target double-peak shape, the shape of the in-cylinder pressure increase rate pattern can be corrected toward the target double-peak shape by controlling the target injection amount and the target injection timing so that the 1 st vibration level becomes equal to or higher than the 1 st reference vibration level.

In addition, since the 1 st determination frequency band is a frequency band in which 2 pressure waves interfere with each other and the vibration level increases, the vibration level in the frequency band can be calculated with high accuracy. Therefore, it is possible to accurately determine whether or not the shape of the in-cylinder pressure increase rate pattern has changed from the target double-peak shape.

The combustion control unit of the present embodiment is configured to sequentially inject at least a1 st main fuel and a2 nd main fuel, calculate an estimated ignition timing of the fuel when the 1 st vibration level is lower than a1 st reference vibration level, correct at least one or both of the target injection amount and the target injection timing of the 1 st main fuel so as to advance the ignition timing of the 1 st main fuel if the estimated ignition timing is later than the target ignition timing set according to the engine operating state, and correct at least one or both of the target injection amount and the target injection timing of the 1 st main fuel so as to retard the ignition timing of the 1 st main fuel if the estimated ignition timing is earlier than the target ignition timing.

Thus, it is possible to determine whether the ignition timing is shifted from the target ignition timing to the advance side and the shape of the pressure increase rate pattern is changed from the target bimodal shape, or the ignition timing is shifted from the target ignition timing to the retard side and the shape of the pressure increase rate pattern is changed from the target bimodal shape. Therefore, according to the determination result, one or both of the target injection amount and the target injection timing of the 1 st main fuel can be appropriately corrected so that the 1 st vibration level becomes equal to or higher than the 1 st reference vibration level.

(embodiment 2)

Next, embodiment 2 of the present invention will be explained. The present embodiment is different from embodiment 1 in that it is further determined whether the peak interval Δ θ is narrower or wider than the reference peak interval Δ θ t. Hereinafter, the difference will be mainly described.

Fig. 7 is the same view as fig. 5.

In embodiment 1, it is determined whether or not the vibration level in the target attenuation band is reduced by comparing the 1 st vibration level in the 1 st determination band with the 1 st reference vibration level.

Here, as described above, the attenuation band tends to move to the lower frequency side as the peak interval Δ θ is wider, and the attenuation band tends to move to the higher frequency side as the peak interval Δ θ is narrower.

Therefore, when the peak interval Δ θ is wider than the reference peak interval Δ θ t, the attenuation band shifts to the lower frequency side, and as a result, the frequency band that is 2-fold higher in frequency shifts to the lower frequency side than the 1 st determination band. Therefore, the vibration level of the 2 nd determination band on the lower frequency side than the 1 st determination band shown in fig. 7 increases.

On the other hand, when the peak interval Δ θ is narrower than the reference peak interval Δ θ t, the attenuation band moves to the higher frequency side, and as a result, the frequency band that is 2-fold higher frequency than the 1 st determination band moves to the higher frequency side. Therefore, the vibration level of the 3 rd determination frequency band on the higher frequency side than the 1 st determination frequency band shown in fig. 7 increases.

Therefore, in the present embodiment, when it is determined that the 1 st vibration level of the 1 st determination frequency band is smaller than the 1 st reference vibration level and the shape of the in-cylinder pressure increase rate pattern has changed from the target shape beyond the allowable range, the vibration levels of the 2 nd determination frequency band and the 3 rd frequency band are further detected, and it is determined whether the peak interval Δ θ is wider or narrower than the reference peak interval Δ θ t. Then, the target values of the fuel injection amount and the fuel injection timing set according to the engine operating state are corrected based on the determination result. The combustion control according to the present embodiment will be described below with reference to fig. 8A and 8B.

Fig. 8A and 8B are flowcharts for explaining the combustion control according to the present embodiment. The electronic control unit 200 repeatedly executes the present routine at predetermined calculation cycles during the engine operation. In fig. 8A and 8B, the processing from step S1 to step S12 is the same as that in embodiment 1, and therefore, the description thereof is omitted.

In step S21, electronic control unit 200 calculates the 2 nd vibration level in the 2 nd determination frequency band by applying various processes (for example, a band pass filter process having the 2 nd determination frequency band in the bandwidth, or the like) to the output value of knock sensor 210 in the combustion noise determination section acquired in the previous combustion cycle. In the present embodiment, the 2 nd decision band is set to a band from 2.6[ kHz ] to 3.0[ kHz ].

In step S22, the electronic control unit 200 refers to a map created in advance by experiments or the like, and calculates the 2 nd reference vibration level based on the engine operating state.

In step S23, the electronic control unit 200 determines whether or not the 2 nd vibration level is equal to or greater than the 2 nd reference vibration level. If the 2 nd vibration level is not less than the 2 nd reference vibration level, the electronic control unit 200 determines that the peak interval Δ θ is wider than the reference peak interval Δ θ t and proceeds to the processing of step S24. On the other hand, if the 2 nd vibration level is less than the 2 nd reference vibration level, the electronic control unit 200 proceeds to the process of step S25.

In step S24, the electronic control unit 200 controls one or both of the amount of fuel injected from the fuel injection valve 20 and the injection timing so that the peak interval Δ θ wider than the reference peak interval Δ θ t becomes narrower toward the reference peak interval Δ θ t. In the case of the present embodiment, basically, it is considered that the ignition timing of the 1 st main fuel is advanced so that the 1 st peak P1 moves to the advance side, and the peak interval Δ θ is widened, so the electronic control unit 200 performs correction to retard the target injection timing a1 of the 1 st main fuel injection G1 by a predetermined crank angle.

In the present embodiment, the ignition timing of the 1 st main fuel is retarded by correcting the target injection timing a1 of the 1 st main fuel injection G1 to the retard side and the peak interval Δ θ is narrowed toward the reference peak interval Δ θ t, but the ignition timing may be retarded by correcting the target injection amount Q1 to the decrease side instead of or together with the retard control of the target injection timing a1, for example. In this case, in order to satisfy the required torque, correction may be performed by increasing the target injection amount Q2 by the amount by which the target injection amount Q1 is decreased.

In step S25, electronic control unit 200 calculates the vibration level in the 3 rd determination frequency band by applying various processes (for example, a band pass filter process having the 3 rd determination frequency band in the bandwidth, or the like) to the output value of knock sensor 210 in the combustion noise determination section acquired in the previous combustion cycle. In the present embodiment, the 3 rd decision band is set to a band from 3.4[ kHz ] to 3.8[ kHz ].

In step S26, the electronic control unit 200 refers to a map created in advance by experiments or the like, and calculates the 3 rd reference vibration level based on the engine operating state.

In step S27, the electronic control unit 200 determines whether or not the 3 rd vibration level is equal to or greater than the 3 rd reference vibration level. If the 3 rd vibration level is not less than the 3 rd reference vibration level, the electronic control unit 200 determines that the peak interval Δ θ is narrower than the reference peak interval Δ θ t and proceeds to the processing of step S28. On the other hand, if the 3 rd vibration level is lower than the 3 rd reference vibration level, electronic control unit 200 determines that the shape of the in-cylinder pressure increase rate pattern has not been a double peak shape but a single peak shape, and proceeds to the process of step S8.

In step S28, the electronic control unit 200 controls one or both of the amount of fuel injected from the fuel injection valve 20 and the injection timing so that the peak interval Δ θ narrower than the reference peak interval Δ θ t is expanded toward the reference peak interval Δ θ t. In the case of the present embodiment, basically, since it is considered that the ignition timing of the 1 st main fuel is retarded and the 1 st peak P1 is shifted to the retarded side and the peak interval Δ θ is narrowed, the electronic control unit 200 performs correction to advance the target injection timing a1 of the 1 st main fuel injection G1 by a predetermined crank angle.

In the present embodiment, the ignition timing is advanced by correcting the target injection timing a1 of the 1 st main fuel injection G1 to the advance side in this way, but the ignition timing may be advanced by correcting the target injection amount Q1 to the increase side instead of or in addition to the advance control of the target injection timing a1, for example. In this case, correction may be performed by reducing the target injection amount Q2 by the amount of increase of the target injection amount Q1.

The combustion control unit of the electronic control unit 200 (control device) according to the present embodiment described above is further configured to calculate the 2 nd vibration level of the engine body 1 in the 2 nd determination frequency band lower than the 1 st determination frequency band in the vicinity of the 1 st determination frequency band based on the vibration acceleration detected by the knock sensor 210 (vibration sensor), and to correct one or both of the target injection amount and the target injection timing so that the peak interval Δ θ t is narrowed when the 1 st vibration level is lower than the 1 st reference vibration level and the 2 nd vibration level is equal to or higher than the predetermined 2 nd reference vibration level set in advance in accordance with the engine operating state. More specifically, the combustion control unit is configured to correct one or both of the target injection amount and the target injection timing of the 1 st main fuel so that the ignition timing of the 1 st main fuel is retarded and the peak interval Δ θ t is narrowed.

Further, the combustion control unit is configured to calculate a 3 rd vibration level of the engine body 1 in a 3 rd determination frequency band higher than the 1 st determination frequency band in the vicinity of the 1 st determination frequency band based on the vibration acceleration detected by the knock sensor 210, and to correct one or both of the target injection amount and the target injection timing so that the peak interval Δ θ t becomes wider when the 1 st vibration level is lower than the 1 st reference vibration level and the 3 rd vibration level is equal to or higher than a predetermined 3 rd reference vibration level set in advance in accordance with the engine operating state. More specifically, the combustion control unit is configured to correct one or both of the target injection amount and the target injection timing of the 1 st main fuel so that the ignition timing of the 1 st main fuel is advanced and the peak interval Δ θ t is widened.

Thus, even when the change in the shape of the in-cylinder pressure increase rate pattern is small, such as when the peak interval Δ θ is shifted from the reference peak interval Δ θ t, although the bimodal shape can be maintained, the change can be accurately captured and the shape of the in-cylinder pressure increase rate pattern can be corrected toward the target bimodal shape.

While the embodiments of the present invention have been described above, the above embodiments are merely some of application examples of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configurations of the above embodiments.

For example, in the above-described embodiment, the injection amount and the injection timing of each of the fuel injections G1, G2 are controlled so that the 1 st main fuel and the 2 nd main fuel are premixed compression ignited to burn, and the 2 nd heat release is generated in stages, but the injection amount and the injection timing of each of the fuel injections G1, G2 may be controlled so that the 1 st main fuel and the 2 nd main fuel are diffusion burned, and the 2 nd heat release is generated in stages.