JP2024005028A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect occurrence of knocking and generation of combustion noise.

SOLUTION: A control device 100 for an internal combustion engine having a main combustion chamber, an auxiliary combustion chamber, a main chamber ignition section and an auxiliary chamber ignition section includes: a cylinder pressure sensor 10; BPFs 53, 54 that extract pressure fluctuation data of first and second frequency bands; an amplitude calculation section 57 that calculates first and second maximum amplitudes included in the pressure fluctuation data of the first and second frequency bands in each combustion cycle; a first determination section 58 that determines whether knocking is occurring on the basis of the first maximum amplitude; a second determination section 59 that determines whether combustion noise is being generated on the basis of the second maximum amplitude on a condition that determination that knocking is not occurring is made; and an ignition plug control section 56 that controls operation of the ignition section so as to expand a phase difference between ignition timing of the main chamber ignition section and ignition timing of the auxiliary chamber ignition section when determination that combustion noise is being generated is made on the basis of an operating condition and determination results.

SELECTED DRAWING: Figure 4

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a control device for an internal combustion engine having a sub-combustion chamber.

BACKGROUND ART Conventionally, a device for detecting knocking of an internal combustion engine is known (for example, see Patent Document 1). In the device described in Patent Document 1, a signal in a predetermined frequency band including the knocking frequency is extracted from the cylinder pressure signal obtained through the output of the cylinder pressure sensor, and based on the extracted signal, it is determined that knocking has occurred. It is determined whether or not.

Japanese Patent Application Publication No. 2008-157087

By the way, in an internal combustion engine that has a main combustion chamber and a sub-combustion chamber, flame propagation is accelerated by ejecting flame from the sub-combustion chamber into the main combustion chamber, so while the thermal efficiency is high, combustion noise is also low regardless of the presence or absence of knocking. This may occur. For this reason, it is preferable to detect not only the occurrence of knocking but also the occurrence of combustion noise.

One aspect of the present invention includes a main combustion chamber facing a piston that reciprocates within the cylinder, a sub-combustion chamber that communicates with the main combustion chamber via a nozzle hole, and a main combustion chamber that ignites the air-fuel mixture inside the main combustion chamber. A control device for an internal combustion engine having a chamber ignition section and an auxiliary chamber ignition section that ignites the air-fuel mixture inside the auxiliary combustion chamber, the control device comprising a pressure detection section that detects the pressure in the main combustion chamber, and a pressure detection section. A first extractor extracts pressure fluctuation data in a first frequency band from the detected pressure fluctuation data, and extracts pressure in a second frequency band lower than the first frequency band from the pressure fluctuation data detected by the pressure detection section. a second extraction unit that extracts fluctuation data; and a second extraction unit that calculates, for each combustion cycle of the internal combustion engine, a first maximum amplitude included in the pressure fluctuation data in the first frequency band extracted by the first extraction unit; Knocking occurs in the main combustion chamber based on the amplitude calculation section that calculates the second maximum amplitude included in the pressure fluctuation data in the second frequency band extracted by the section, and the first maximum amplitude calculated by the amplitude calculation section. a first determination unit that determines whether knocking is occurring in the main combustion chamber; and a second maximum amplitude calculated by an amplitude calculation unit, provided that the first determination unit determines that knocking has not occurred in the main combustion chamber. a second determination unit that determines whether combustion noise is occurring in the main combustion chamber based on the operating conditions of the internal combustion engine, and determination results by the first determination unit and the second determination unit, An ignition control section that controls operations of the main chamber ignition section and the sub-chamber ignition section. When the second determination unit determines that combustion noise is occurring in the main combustion chamber, the ignition control unit increases the phase difference between the ignition timing of the main chamber ignition unit and the ignition timing of the pre-chamber ignition unit. The operation of the main chamber ignition section and the sub-chamber ignition section is controlled so as to

According to the present invention, occurrence of knocking and combustion noise can be detected.

1 is a diagram schematically showing a main part configuration of an engine as an internal combustion engine to which a control device for an internal combustion engine according to an embodiment of the present invention is applied. FIG. 2 is a diagram showing the main parts of the engine when cut along the arrow II-II line in FIG. 1; An enlarged view of the main part of FIG. 1. FIG. 1 is a block diagram showing the main configuration of a control device for an internal combustion engine according to an embodiment of the present invention. 2 is a diagram for explaining resonance frequencies when knocking and combustion noise occur in the main combustion chamber of FIG. 1. FIG. 5 is a diagram showing an example of cylinder pressure fluctuation data detected by the cylinder pressure sensor of FIG. 4 and cylinder pressure fluctuation data extracted by BPF. FIG. FIG. 3 is a diagram for explaining reduction in combustion noise and reduction in engine output by adjusting ignition timing. 5 is a flowchart showing an example of processing in main chamber ignition mode executed by the controller of FIG. 4. FIG. 5 is a flowchart showing an example of processing in the pre-chamber ignition mode executed by the controller of FIG. 4. FIG. 5 is a flowchart showing an example of processing in phase difference ignition mode executed by the controller of FIG. 4. FIG.

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 8C. FIG. 1 is a diagram schematically showing the configuration of main parts of an engine 1, which is an example of an internal combustion engine to which the present invention is applied. The engine 1 is, for example, a gasoline engine that burns an air-fuel mixture by spark ignition using gasoline as fuel, and is a four-stroke engine that undergoes four strokes of intake, expansion, compression, and exhaust during an operating cycle. For convenience, the period from the start of the intake stroke to the end of the exhaust stroke is referred to as one combustion stroke cycle or combustion cycle of the engine 1. Although the engine 1 has a plurality of cylinders, such as 4 cylinders, 6 cylinders, and 8 cylinders, FIG. 1 shows the configuration of a single cylinder. Note that the configuration of each cylinder is the same. The fuel may include alcohol.

As shown in FIG. 1, the engine 1 includes a substantially cylindrical cylinder 2 formed in a cylinder block 11, a piston 3 slidably disposed along the inner wall of the cylinder 2, and a piston 3 and a cylinder head 12. A combustion chamber 4 is formed between the combustion chamber 4 and the combustion chamber 4. The piston 3 is connected to a crankshaft 6 via a connecting rod 5, and as the piston 3 reciprocates within the cylinder 2, the crankshaft 6 rotates. Although the upper surface of the piston 3 is formed, for example, in an uneven shape, it is shown as a flat surface in FIG. 1 for convenience.

The cylinder head 12 is provided with an intake port 13 and an exhaust port 14. An intake passage 15 communicates with the combustion chamber 4 via an intake port 13 , and an exhaust passage 16 communicates with the combustion chamber 4 via an exhaust port 14 . The intake port 13 is opened and closed by an intake valve 17, and the exhaust port 14 is opened and closed by an exhaust valve 18. A throttle valve 19 is provided in the intake passage 15 on the upstream side of the intake valve 17, and the amount of intake air flowing into the combustion chamber 4 is adjusted by the throttle valve 19. The intake valve 17 and the exhaust valve 18 are opened and closed at predetermined timings synchronized with the rotation of the crankshaft 6 by a valve mechanism (not shown).

The injector 7 is mounted on the cylinder head 12 so as to face the combustion chamber 4. The injector 7 is arranged, for example, on the side of the cylinder block 11 and near the intake valve 17, with the fuel injection port at the tip facing diagonally downward. The injector 7 injects fuel into the combustion chamber 4 once or multiple times within the range from the intake stroke to the compression stroke according to a command from the controller (FIG. 4). That is, the injector 7 is configured as a direct injection type fuel injection valve. Note that the arrangement of the injector 7 is not limited to this, and for example, the injector 7 may be arranged facing the intake port 13 and configured as a port injection type fuel injection valve.

FIG. 2 is a view of the cylinder 2 viewed from below (a view cut along the arrow II-II line in FIG. 1). FIG. 2 shows a pair of reference lines L1 and L2 that pass through the center of the cylinder 2 and are orthogonal to each other, and an axis CL1 that passes through the intersection of the reference lines L1 and L2 and is orthogonal to the reference lines L1 and L2. . Further, on the reference line L1, an axis line CL2 is shown parallel to the axis line CL1, which is the center line of the cylinder 2.

As shown in FIG. 2, a pair of intake valves 17 are provided on one side of the reference line L2 with the reference line L1 in between. A pair of exhaust valves 18 are provided on the other side of the reference line L2 with the reference line L1 in between. Note that a pair of intake ports 13 and an exhaust port 14 are also provided corresponding to the intake valve 17 and the exhaust valve 18, respectively. The distance between the pair of exhaust valves 18 is longer than the distance between the pair of intake valves 17. The injector 7 in FIG. 1 is arranged on the reference line L1 (area A1 in FIG. 2), and injects fuel from the intake port side to the exhaust port side along the reference line L1.

An in-cylinder pressure sensor 10 is provided near the wall surface of the cylinder 2 between the pair of intake valves 17 and the pair of exhaust valves 18 . The cylinder pressure sensor 10 is provided in the cylinder head 12 so as to face the combustion chamber 4 (main combustion chamber 41), and measures the cylinder pressure which is the pressure of the combustion chamber 4 (main combustion chamber 41), more specifically, the cylinder pressure of the cylinder 2. Detects cylinder pressure near the wall.

As shown in FIGS. 1 and 2, a housing 45 is provided at the center of the cylinder head 12, protruding toward the piston 3 between the intake port 13 and the exhaust port 14. FIG. 3 is an enlarged view of the main part of FIG. 1 showing the surrounding structure of the housing 45 in an enlarged manner. As shown in FIG. 3, the housing 45 has a substantially U-shaped cross section centered on the axis CL2, and more specifically, the tip 46 on the protruding side is formed in a substantially arc shape (for example, semicircular or dome shape). The distal end portion 46 has a symmetrical shape about the axis CL2. Although the axis CL2 is offset from the center line (axis CL1) of the cylinder 2 in FIG. 1 to the opposite side of the injector 7 (FIG. 2), the housing 45 may be provided so that the axis CL2 coincides with the axis CL1. good.

A plurality of circumferential through holes, that is, nozzle holes 47, are opened in the distal end portion 46 of the housing 45 at equal intervals in the circumferential direction about the axis CL2. The nozzle holes 47 are opened radially along an axis CL3 that extends obliquely from the axis CL2 toward the piston 3 and radially outward. Note that the angle α1 between the axis CL2 and the axis CL3 is preferably set to an angle that prevents the flame jet from touching the combustion chamber wall, and is, for example, in the range of 30 degrees to 60 degrees.

The combustion chamber 4 is divided by the housing 45 into a main combustion chamber 41 outside the housing 45 and a sub-combustion chamber 42 inside the housing 45. As shown in FIG. 1, the injector 7 is arranged facing the main combustion chamber 41, and fuel is injected into the main combustion chamber 41. A spark plug 8 is provided in the center of the cylinder head 12 between the intake port 13 and the exhaust port 14, more specifically, on the axis CL2. The spark plug 8 is arranged with its longitudinal center line along the axis CL2, for example, so that the ignition part at the tip faces the auxiliary combustion chamber 42, and is ignited by electric energy in accordance with a command from the controller (FIG. 4). is configured to generate a spark at the

When fuel is injected from the injector 7 into the main combustion chamber 41, a mixture of air and fuel is generated in the main combustion chamber 41. A portion of this air-fuel mixture flows into the sub-combustion chamber 42 through a plurality of circumferential nozzle holes 47, is ignited by the spark plug 8, and is combusted. The combustion gas generated in the auxiliary combustion chamber 42 drives the air-fuel mixture near the nozzle holes into the main combustion chamber 41 as unburned gas jets, and then ejects radially from the plurality of nozzle holes 47 as torch-shaped flame jets 48. , the air-fuel mixture in the main combustion chamber 41 is combusted. During the expansion stroke, the piston 3 is pushed down by the high-temperature, high-pressure combustion gas burned in the main combustion chamber 41, and the crankshaft 6 is rotated.

As shown in FIG. 2, the cylinder head 12 is further provided with a spark plug 9 between the pair of exhaust valves 18, more specifically on the reference line L1. The ignition part at the tip of the spark plug 9 faces the main combustion chamber 41 at an intermediate point (1/2 point of the cylinder radius) or approximately the intermediate point from the center line (axis line CL1) of the cylinder 2 to the cylinder wall. The center line in the longitudinal direction is arranged parallel to the axis CL2, and the ignition section is configured to generate sparks using electrical energy in response to commands from the controller (FIG. 4). Note that the spark plug 9 may be arranged closer to the center or closer to the cylinder wall than a point that is 1/2 of the cylinder radius. After fuel is injected into the main combustion chamber 41 from the injector 7, when the spark plug 9 is ignited, the air-fuel mixture is combusted in the main combustion chamber 41, the piston 3 is pushed down, and the crankshaft 6 is rotated.

Thus, in this embodiment, the spark plugs 8 and 9 are provided in the main combustion chamber 41 and the auxiliary combustion chamber 42, respectively. Hereinafter, the spark plug 9 provided in the main combustion chamber 41 may be referred to as a main chamber spark plug, and the spark plug 8 provided in the auxiliary combustion chamber 42 may be referred to as an auxiliary chamber spark plug. The operation of the spark plugs 8, 9 is controlled by a controller (FIG. 4). The ignition modes include a main chamber ignition mode in which only the main chamber ignition plug 9 is ignited in the combustion cycle, a sub-chamber ignition mode in which only the sub-chamber ignition plug 8 is ignited, and a main-chamber ignition mode in which only the sub-chamber ignition plug 8 is ignited, and a main-chamber ignition plug 9 and a sub-chamber ignition plug 8. includes a phase difference ignition mode in which both of the

In the phase difference ignition mode, in the same combustion cycle, after the main chamber ignition plug 9 is ignited, when the crank angle changes by a predetermined crank angle (predetermined phase difference), the pre-chamber ignition plug 8 is ignited. The difference between the ignition timing of the main chamber ignition plug 9 and the ignition timing of the pre-chamber ignition plug 8 at this time is represented by the difference in rotation angle of the crankshaft 6 (crank angle difference). Note that the crank angle difference is also called a phase difference.

Since combustion by the pre-chamber spark plug 8 is rapid combustion by a flame jet, the combustion speed of the air-fuel mixture by the pre-chamber spark plug 8 is faster than the combustion speed by the main chamber spark plug 9. Therefore, if the phase difference is too small, the flame propagation caused by the ignition of the main chamber ignition plug 9 in the main combustion chamber 41 will be overtaken by the flame propagation caused by the ignition of the pre-chamber ignition plug 8, resulting in the effect of ignition of the main chamber ignition plug 9. is not obtained. On the other hand, if the phase difference is too large, the air-fuel mixture will be sufficiently combusted by the ignition of the main chamber ignition plug 9, so that when the flame caused by the ignition of the pre-chamber ignition plug 8 reaches the main combustion chamber 41, In this case, no unburned portion of the air-fuel mixture remains, and the effect of rapid combustion by the pre-chamber spark plug 8 cannot be produced. Considering this point, in order to obtain the combustion effect due to the ignition of the main chamber spark plug 9 and the combustion effect due to the ignition of the pre-chamber spark plug 8 in the phase difference ignition mode, the reference phase difference of the phase difference ignition mode is set. is set.

The controller determines the ignition mode according to the operating state of the engine 1 such as the engine speed and the load acting on the engine 1, and outputs a control signal to the spark plugs 8 and 9 according to the ignition mode. Thereby, the ignition mode is switched between the main chamber ignition mode, the sub-chamber ignition mode, and the phase difference ignition mode depending on the operating state. More specifically, a plurality of characteristic maps indicating reference ignition timing according to engine speed and engine load are stored in advance in the controller, and the ignition mode is switched using these characteristic maps.

In the pre-chamber ignition mode and the phase-difference ignition mode, flame propagation in the main combustion chamber 41 is accelerated by ejecting the flame jet 48 from the sub-combustion chamber 42 into the main combustion chamber 41, so that the thermal efficiency of the engine 1 is increased. Combustion noise may occur with or without knocking. Therefore, in this embodiment, a control device for an internal combustion engine is configured as follows so that the occurrence of knocking and combustion noise can be detected based on the in-cylinder pressure detected by the in-cylinder pressure sensor 10.

FIG. 4 is a block diagram showing a main part configuration of an internal combustion engine control device (hereinafter referred to as the device) 100 according to an embodiment of the present invention. As shown in FIG. 4, the device 100 is configured around a controller 50, and includes spark plugs 8 and 9, a cylinder pressure sensor 10, a crank angle sensor 51, and an intake air amount sensor 52, which are connected to the controller 50, respectively. , bandpass filters (BPF) 53 and 54.

The crank angle sensor 51 is provided on the crankshaft 6 and is configured to output a pulse signal as the crankshaft 6 rotates. Based on the pulse signal from the crank angle sensor 51, the controller 50 specifies the rotation angle (crank angle) of the crankshaft 6 based on the position of top dead center TDC at the start of the intake stroke of the piston 3, and Calculate the rotation speed. Therefore, the crank angle sensor 51 also functions as an engine rotation speed sensor. In the following, for convenience, it is assumed that the crank angle sensor 51 detects the engine rotation speed.

The intake air amount sensor 52 is a sensor that detects the amount of intake air into the cylinder 2, and is configured by, for example, an air flow meter disposed in the intake passage 15 (more specifically, upstream of the throttle valve). The controller 50 calculates the target injection amount of the injector 7 based on the signal from the intake air amount sensor 52, and controls the injector 7 to inject the target injection amount of fuel. The intake air amount detected by the intake air amount sensor 52 has a correlation with the output torque of the engine 1. Therefore, the intake air amount sensor 52 also functions as a sensor for detecting engine load. Although the engine load (engine output torque) is calculated by the controller 50, in the following, for convenience, it is assumed that the intake air amount sensor 52 detects the engine load.

FIG. 5 is a diagram for explaining the resonance frequency when knocking or combustion noise occurs in the main combustion chamber 41. The inventors used Wavelet transformation to analyze fluctuations in cylinder pressure (changes over time) for each frequency, and found that the frequency bands in which pressure fluctuations become large are different when knocking occurs and when combustion noise occurs. That is, when knocking occurs, the pressure fluctuation becomes large in the first frequency band (10 to 16 kHz) and the second frequency band (6 to 9 kHz), which is lower than the first frequency band, and when combustion noise occurs, the pressure fluctuation increases in the second frequency band (6 to 9 kHz). It was found that pressure fluctuations were large only in the belt.

When ignition is performed by the pre-chamber spark plug 8 (FIG. 3), a flame jet 48 is ejected from each nozzle hole 47 of the sub-combustion chamber 42 into the main combustion chamber 41, and the flame jet 48 reaches the vicinity of the wall surface of the cylinder 2. As the cylinder pressure increases, a pressure wave is generated. Furthermore, when knocking occurs, the air-fuel mixture self-ignites at a plurality of ignition points near the wall surface of the cylinder 2, and pressure waves are also generated starting at each ignition point. The pressure waves generated in this way interfere with the reflected waves reflected from the opposite wall of the cylinder 2, thereby causing a resonance phenomenon within the main combustion chamber 41.

At a crank angle near top dead center TDC where ignition by the spark plugs 8 and 9 occurs, the main combustion chamber 41 forms a cylindrical space whose height is sufficiently small relative to its diameter. In such a cylindrical space, a plurality of resonance modes having spatial distributions of amplitude and phase are generated in the circumferential direction and the radial direction. FIG. 5 shows the mode shape of the resonance mode generated in the cylindrical space. The broken lines represent the nodal lines of resonance vibration, and ± represents the phase of resonance vibration. The circumferential order m corresponds to the number of nodal lines in the circumferential direction of the cylindrical space, and the radial order n corresponds to the number of nodal lines in the radial direction of the cylindrical space.

The frequency of such resonance mode (resonance frequency) f _m,n,0 [Hz] can be estimated based on Draper's equation. ρ _m,n,0 is the mode constant, κ is the specific heat ratio, R is the gas constant [J/kgK], T is the representative temperature of the main combustion chamber 41 [K], and B is the diameter of the cylindrical space (i.e., the diameter of the cylinder 2). diameter) [m].
f _1,0,0 = ρ _1,0,0 (κRT) ^1/2 /πB

In Fig. 5, as an example, the diameter B of the cylindrical space is 0.073 [m], the specific heat ratio κ is 1.3, the gas constant R is 287 [J/kgK], and the representative temperature T is 2424 [K]. The resonant frequency f _m,n,0 is shown. The first frequency band (10 to 16 kHz) where the pressure fluctuation increases only when knocking occurs is a frequency band near the resonance frequency f _2,0,0 (12.6 [kHz]) of the (2,0,0) mode. be. The second frequency band (6 to 9 kHz), where pressure fluctuations are large both when knocking occurs and when combustion noise occurs, is the resonant frequency f _1,0,0 (7.63 [kHz) of the (1,0,0) mode. ]) is a frequency band nearby.

When knocking occurs, self-ignition occurs simultaneously near the wall surface of the cylinder 2 where the flame jet 48 reaches and near the wall surface on the opposite side, and pressure waves and reflected waves originating from each ignition point interfere with each other. As a result, (1,0,0) mode resonance and (2,0,0) mode resonance occur simultaneously. Knocking can lead to damage to engine parts, so monitor the magnitude of pressure fluctuations in the first frequency band (10-16kHz) and take immediate action if pressure fluctuations exceeding the specified level are observed when knocking occurs. There is a need.

On the other hand, if knocking does not occur, engine parts will not be damaged even if combustion noise occurs, that is, even if the combustion noise becomes loud enough to give a user a sense of discomfort. However, if a state where the sound volume (size of pressure fluctuation) is large occurs more than a certain frequency, it may give a sense of discomfort to the user and may reduce the marketability of the engine 1.

Pressure fluctuations in the second frequency band (6-9kHz) due to (1,0,0) mode resonance can be recognized as combustion noise, but pressure fluctuations in the first frequency band (10kHz) due to (2,0,0) mode resonance can be recognized as combustion noise. Pressure fluctuations (~16kHz) are difficult to recognize as combustion noise due to their high frequency. The magnitude of pressure fluctuations in the second frequency band (6 to 9 kHz) is monitored, and if pressure fluctuations exceeding a certain level that can be recognized as combustion noise are observed, and the observation frequency exceeds the specified frequency, measures will be taken. It is preferable to do so.

The BPF 53 in FIG. 4 is configured to extract pressure fluctuation data in a first frequency band from the cylinder pressure fluctuation data detected by the cylinder pressure sensor 10, and the BPF 54 extracts pressure fluctuation data in a second frequency band. It is configured as follows.

FIG. 6 is a diagram showing an example of fluctuation data of the cylinder pressure (sensor value) P0 detected by the cylinder pressure sensor 10 and fluctuation data of the cylinder pressures P1, P2 extracted by the BPFs 53, 54, with respect to the crank angle θ. An example of fluctuation data of cylinder pressures P0 to P2 is shown.

The controller 50 in FIG. 4 is configured by an electronic control unit (ECU), and includes a computer having a calculation unit 50A such as a CPU, a storage unit 50B such as ROM and RAM, and other peripheral circuits. The calculation unit 50A of the controller 50 functions as an amplitude calculation unit 57, a first determination unit 58, a second determination unit 59, an ignition mode determination unit 55, and a spark plug control unit 56.

The storage unit 50B stores a pair of characteristic maps predetermined according to the engine rotation speed and engine load as characteristic maps for determining the reference ignition timing. More specifically, a preceding ignition map indicating the reference ignition timing of the preceding spark plug (for example, the optimum ignition timing MBT that yields the maximum torque) of the spark plugs 8 and 9, and the ignition timing of the spark plugs 8 and 9 are used. A phase difference map indicating a reference phase difference is stored.

The preceding spark plug is the spark plug that is lit first in the combustion cycle, and in the pre-chamber ignition mode, the pre-chamber spark plug 8 is the pre-chamber spark plug, in the main chamber spark plug, the main chamber spark plug 9 is the main chamber spark plug, and in the phase difference ignition mode, the main chamber spark plug is the main chamber spark plug 9. Spark plug 9 becomes a leading spark plug. The phase difference map includes at least a range of phase differences that is greater than or equal to a predetermined value (lower limit value) and less than or equal to a predetermined value (upper limit value). The lower limit value is a phase difference when the phase difference is too small to provide the ignition effect of the main chamber ignition plug 9, and is, for example, 0 degrees. The upper limit value is a phase difference when the phase difference is too large and the ignition effect of the pre-chamber spark plug 8 cannot be obtained, and is, for example, 15 degrees. The phase difference between the spark plugs 8 and 9 in the phase difference ignition mode is larger than the lower limit value and smaller than the upper limit value.

The ignition mode determining unit 55 selects a main chamber ignition mode, a pre-chamber ignition mode, and a phase difference ignition mode according to the engine speed detected by the crank angle sensor 51 and the engine load detected by the intake air amount sensor 52. Decide the target ignition mode from among them. Specifically, first, a reference phase difference is calculated using a phase difference map. Then, when the reference phase difference is less than the lower limit value, the combustion effect due to ignition of the main chamber ignition plug 9 cannot be obtained, so the target ignition mode is determined to be the pre-chamber ignition mode. Furthermore, when the reference phase difference is greater than or equal to the upper limit value, the combustion effect due to ignition of the pre-chamber ignition plug 8 cannot be obtained, so the target ignition mode is determined to be the main-chamber ignition mode. On the other hand, when the reference phase difference is larger than the lower limit value and smaller than the upper limit value, the target ignition mode is determined to be the phase difference ignition mode.

When the main chamber ignition mode is determined to be the target ignition mode by the ignition mode determining section 55, the spark plug control section 56 uses the preceding ignition map stored in the storage section 50B to select the preceding spark plug (in this case, the main chamber ignition mode). Calculate the reference ignition timing θa of the spark plug 9). Then, a control signal is output to the spark plugs 8 and 9 so that the main chamber spark plug 9 fires at the reference ignition timing θa without the sub chamber spark plug 8 firing. This causes the ignition mode to become the main chamber ignition mode.

When the pre-chamber ignition mode is determined to be the target ignition mode by the ignition mode determining section 55, the spark plug control section 56 uses the pre-chamber ignition map stored in the storage section 50B to select the pre-chamber ignition mode (in this case, the pre-chamber ignition mode). Calculate the reference ignition timing θa of the spark plug 8). Then, a control signal is output to the spark plugs 8 and 9 so that the sub chamber spark plug 8 fires at the reference ignition timing θa without the main chamber spark plug 9 igniting. As a result, the ignition mode becomes the pre-chamber ignition mode.

When the ignition mode determining unit 55 determines the phase difference ignition mode as the target ignition mode, the spark plug control unit 56 uses the preceding ignition map to set the reference ignition of the preceding spark plug (in this case, the main chamber spark plug 9). Calculate the time θa. Next, using the phase difference map, a reference phase difference θb between the main chamber spark plug 9 and the pre-chamber spark plug 8 according to the engine speed and the engine load is calculated. After the main chamber ignition plug 9 ignites at the reference ignition timing θa, the ignition plugs 8 and 9 are set so that the pre-chamber ignition plug 8 ignites at the ignition timing θa+θb delayed by the reference phase difference θb from the reference ignition timing θa. Outputs a control signal. As a result, the ignition mode becomes the phase difference ignition mode.

The amplitude calculation unit 57 calculates the maximum amplitude PP1 included in the pressure fluctuation data in the first frequency band extracted by the BPF 53 for each combustion cycle of the engine 1, and also calculates the maximum amplitude PP1 included in the pressure fluctuation data in the second frequency band extracted by the BPF 54. The maximum amplitude PP2 included in the data is calculated. More specifically, as shown in FIG. 6, from the fluctuation data of the cylinder pressure P1 in the first frequency band and the cylinder pressure P2 in the second frequency band, the point where the amplitude is maximum is detected for each combustion cycle, and the maximum amplitude is detected. Amplitudes (PP (Peak to Peak) values) PP1 and PP2 are calculated.

As shown in FIG. 5, in both the (2, 0, 0) mode corresponding to the first frequency band and the (1, 0, 0) mode corresponding to the second frequency band, the amplitude near the wall surface of the cylinder 2 is Becomes the belly of. As shown in FIG. 2, by installing the cylinder pressure sensor 10 near the wall surface of the cylinder 2 and detecting the cylinder pressure P0 near the wall surface of the cylinder 2, it is possible to accurately detect the maximum amplitudes PP1 and PP2 of pressure fluctuations. can.

The first determination unit 58 determines whether knocking is occurring in the main combustion chamber 41 based on the maximum amplitude PP1 calculated by the amplitude calculation unit 57. More specifically, it is determined whether the maximum amplitude PP1 exceeds a first threshold value pp1 predetermined according to the operating conditions of the engine 1. When the maximum amplitude PP1 exceeds the first threshold pp1 (PP1>pp1), it is determined that knocking has occurred, and when it is below the first threshold pp1 (PP1≦pp1), it is determined that knocking has not occurred. do.

The first threshold value pp1 used in the knocking determination by the first determination unit 58 is determined in advance through a test and stored in the storage unit 50B. The test for determining the first threshold pp1 is performed while changing the operating conditions of the engine 1, that is, the engine speed and the engine load, and the first threshold pp1 is predetermined according to the engine speed and the engine load. The map is stored in the storage unit 50B as a characteristic map. The first determination unit 58 determines the first determination based on the characteristic map stored in the storage unit 50B based on the engine speed detected by the crank angle sensor 51 and the engine load detected by the intake air amount sensor 52. 1 threshold pp1 is searched and used for knocking determination.

The second determination unit 59 determines whether the main combustion It is determined whether combustion noise is occurring in the chamber 41.

The second determination unit 59 first determines whether the combustion sound is louder than a reference. More specifically, it is determined whether the maximum amplitude PP2 exceeds a second threshold value pp2 predetermined according to the operating conditions of the engine 1. When the maximum amplitude PP2 exceeds the second threshold pp2 (PP2>pp1), it is determined that the combustion sound is larger than the standard, and when it is less than the second threshold pp2 (PP2≦pp2), the combustion sound is determined to be less than the standard. judge.

Similarly to the first threshold value pp1, the second threshold value pp2 used in the determination of combustion noise by the second determination unit 59 is determined in advance by a test, and is set as a characteristic map determined in advance according to the engine speed and the engine load. It is stored in the storage unit 50B. The second determination unit 59 determines the engine rotation speed detected by the crank angle sensor 51 and the engine load detected by the intake air amount sensor 52, based on the characteristic map stored in the storage unit 50B. 2 threshold value pp2 is searched and used for determination of combustion sound.

In determining the combustion sound for each combustion cycle, the second determination unit 59 determines that the main It is determined that combustion noise is occurring in the combustion chamber 41.

The predetermined number of times c2 used for the determination of combustion noise by the second determination unit 59 is also determined in advance by a test, similarly to the first threshold value pp1 and the second threshold value pp2, and is determined in advance according to the engine speed and the engine load. The map is stored in the storage unit 50B as a characteristic map. The second determination unit 59 determines a predetermined value based on the characteristic map stored in the storage unit 50B based on the engine speed detected by the crank angle sensor 51 and the engine load detected by the intake air amount sensor 52. The number of times c2 is retrieved and used for determining combustion noise.

<Adjustment of ignition timing in main compartment ignition mode>
Adjustment of the ignition timing in the main chamber ignition mode will be explained. When the first determination unit 58 determines that knocking has occurred in the main combustion chamber 41, the spark plug control unit 56 controls the preceding spark plug (in this case, the main spark plug) to retard the ignition timing by a predetermined amount θ1. The operation of the indoor spark plug 9) is controlled (θa→θa+θ1). The predetermined amount θ1 is determined in advance through testing as a sufficient retard amount (for example, about 1.5 degrees) to eliminate knocking, and is stored in the storage unit 50B.

When it is determined that knocking has not occurred in the main combustion chamber 41, the spark plug control unit 56 controls the preceding spark plug (main chamber spark plug 9) to gradually advance the ignition timing with the optimum ignition timing MBT as the upper limit. ). In the main chamber ignition mode, there is no rapid combustion caused by the flame jet from the pre-chamber spark plug 8, and no combustion noise without knocking occurs, so the second determination section 59 does not determine the combustion noise.

<Adjustment of ignition timing in pre-chamber ignition mode>
Adjustment of ignition timing in pre-chamber ignition mode will be explained. When the first determination unit 58 determines that knocking has occurred in the main combustion chamber 41, the spark plug control unit 56 controls the preceding spark plug (in this case, the secondary spark plug) to retard the ignition timing by a predetermined amount θ1. The operation of the indoor spark plug 8) is controlled (θa→θa+θ1).

When the second determination unit 59 determines that combustion noise is occurring in the main combustion chamber 41, the spark plug control unit 56 controls the preceding spark plug (pre-chamber ignition) to retard the ignition timing by a predetermined amount θ2. The operation of the plug 8) is controlled (θa→θa+θ2). The predetermined amount θ2 is determined in advance through testing as a sufficient retardation amount (for example, about 0.5 degrees) to reduce combustion noise, and is stored in the storage unit 50B. The predetermined amount θ2 for reducing combustion noise is smaller than the predetermined amount θ1 for eliminating knocking (θ1>θ2).

When it is determined that neither knocking nor combustion noise is occurring in the main combustion chamber 41, the spark plug control unit 56 controls the preceding spark plug (main chamber 41) to gradually advance the ignition timing with the optimum ignition timing MBT as the upper limit. Controls the operation of the spark plug 9).

<Adjustment of ignition timing in phase difference ignition mode>
Adjustment of ignition timing in phase difference ignition mode will be explained. When the first determination unit 58 determines that knocking has occurred in the main combustion chamber 41, the spark plug control unit 56 controls the preceding spark plug (in this case, the main spark plug) to retard the ignition timing by a predetermined amount θ1. The operation of the indoor spark plug 9) is controlled (θa→θa+θ1).

When the second determination unit 59 determines that combustion noise is occurring in the main combustion chamber 41, the spark plug control unit 56 increases the phase difference between the ignition timings of the spark plugs 8 and 9 by a predetermined amount θ3. The operation of the spark plugs 8 and 9 is controlled (θb→θb+θ3). Since the pre-chamber spark plug 8 is ignited with a delay of the phase difference from the ignition timing of the main-chamber spark plug 9, the amount of expansion of the phase difference (predetermined amount θ3) is the amount of retardation of the ignition timing of the pre-chamber spark plug 8. (predetermined amount θ3).

Such a predetermined amount θ3 is determined in advance through tests as an amount of expansion of the phase difference or a retardation amount of the ignition timing of the pre-chamber spark plug 8 (for example, about 0.5 degrees) to reduce combustion noise. , are stored in the storage unit 50B. The predetermined amount θ3 for reducing combustion noise is smaller than the predetermined amount θ1 for eliminating knocking (θ1>θ3). Note that when the phase difference θb+θ3 after expansion becomes 15 degrees or more, the ignition mode determining unit 55 determines (changes) the target ignition mode to the main chamber ignition mode.

When it is determined that neither knocking nor combustion noise is occurring in the main combustion chamber 41, the spark plug control unit 56 controls the spark plugs 8, 9 so as to gradually reduce the phase difference between the ignition timings of the spark plugs 8, 9. control the behavior of Note that when the phase difference after reduction becomes 0 degrees or less, the ignition mode determining section 55 determines (changes) the target ignition mode to the pre-chamber ignition mode.

FIG. 7 is a diagram for explaining the reduction in combustion noise and the reduction in engine output by adjusting the ignition timing, and shows the change in the maximum amplitude PP2 of pressure fluctuation in the second frequency band and the engine output when adjusting the ignition timing. An example is shown below. State A in FIG. 7 is a state in which the maximum amplitude PP2 exceeds the second threshold pp2, that is, a state in which the combustion sound is larger than the reference, and states B and C are states in which the maximum amplitude PP2 is the second threshold value pp2, i.e. Indicates the standard combustion sound condition.

As shown by the dashed line in FIG. 7, when the ignition timing of the spark plugs 8 and 9 is retarded while maintaining the phase difference, the engine output is significantly reduced as the combustion noise is reduced (state A→state B). On the other hand, as shown by the two-dot chain line, if the ignition timing of the pre-chamber ignition plug 8 is retarded while maintaining the ignition timing of the main-chamber ignition plug 9, which is the preceding spark plug, and the phase difference is expanded, the combustion noise is reduced. It is possible to suppress a decrease in engine output accompanying this (state A→state C).

8A to 8C are flowcharts showing an example of processing executed by the controller 50 of FIG. 4 according to a pre-stored program. FIG. 8A shows an example of the process in the main chamber ignition mode, FIG. 8B shows an example of the process in the sub-chamber ignition mode, and FIG. 8C shows an example of the process in the phase difference ignition mode. The processes shown in these flowcharts are started after the engine is started, and are repeated at predetermined intervals.

As shown in FIG. 8A, in the process in the main chamber ignition mode, first, in step S1, the signals from the crank angle sensor 51 and the intake air amount sensor 52 and the in-cylinder pressure P1 in the first frequency band extracted by the BPFs 53 and 54 are and fluctuation data of cylinder pressure P2 in the second frequency band. Next, in step S2, the operating conditions of the engine 1 are specified based on the signal read in step S1. Next, in step S3, it is determined whether the target ignition mode corresponding to the operating condition specified in step S2 is the main compartment ignition mode. If the result in step S3 is affirmative, the process proceeds to step S4, and if the result in step S3 is negative, the process ends.

In step S4, the maximum amplitude PP1 for each combustion cycle of the engine 1 is calculated based on the fluctuation data of the in-cylinder pressure P1 in the first frequency band read in step S1. Next, in step S5, it is determined whether the maximum amplitude PP1 calculated in step S4 exceeds the first threshold pp1 corresponding to the operating condition specified in step S2.

If the result in step S5 is affirmative, the process proceeds to step S6, where it is determined that knocking has occurred in the main combustion chamber 41, and the process proceeds to step S7. In step S7, a control signal is output to the preceding spark plug (main chamber spark plug 9) so as to retard the reference ignition timing θa by a predetermined amount θ1 (θa→θa+θ1) corresponding to the operating condition specified in step S2. , ends the process.

On the other hand, if the result in step S5 is negative, the process proceeds to step S8, where it is determined that knocking has not occurred in the main combustion chamber 41, and the process proceeds to step S9. In step S9, a control signal is output to the preceding spark plug (main chamber spark plug 9) to gradually advance the ignition timing with the optimum ignition timing MBT corresponding to the operating condition specified in step S2 as the upper limit, and processing is performed. end.

As shown in FIG. 8B, in the process in the pre-chamber ignition mode, first, in step S1, signals from the crank angle sensor 51 and intake air amount sensor 52 and the cylinder pressure P1 in the first frequency band extracted by the BPFs 53 and 54 are used. and fluctuation data of cylinder pressure P2 in the second frequency band. Next, in step S2, the operating conditions of the engine 1 are specified based on the signal read in step S1. Next, in step S10, it is determined whether the target ignition mode corresponding to the operating condition specified in step S2 is the pre-chamber ignition mode. If the result in step S10 is affirmative, the process proceeds to step S4, and if the result in step S10 is negative, the process ends.

In step S4, the maximum amplitude PP1 for each combustion cycle of the engine 1 is calculated based on the fluctuation data of the in-cylinder pressure P1 in the first frequency band read in step S1. Next, in step S5, it is determined whether the maximum amplitude PP1 calculated in step S4 exceeds the first threshold pp1 corresponding to the operating condition specified in step S2.

If the result in step S5 is affirmative, the process proceeds to step S6, where it is determined that knocking has occurred in the main combustion chamber 41, and the process proceeds to step S7. In step S7, a control signal is output to the preceding spark plug (pre-chamber spark plug 8) to retard the reference ignition timing θa corresponding to the operating condition specified in step S2 by a predetermined amount θ1 (θa→θa+θ1). , ends the process.

On the other hand, if the result in step S5 is negative, the process proceeds to step S8, where it is determined that knocking has not occurred in the main combustion chamber 41, and the process proceeds to step S11. In step S11, the maximum amplitude PP2 for each combustion cycle of the engine 1 is calculated based on the fluctuation data of the in-cylinder pressure P2 in the second frequency band read in step S1. Next, in step S12, it is determined whether the maximum amplitude PP2 calculated in step S11 exceeds a second threshold value pp2 corresponding to the operating condition specified in step S2.

If the result in step S12 is negative, it is determined that the combustion noise is below the standard and the process proceeds to step S13, and it is determined that neither knocking nor combustion noise is occurring in the main combustion chamber 41, and the process proceeds to step S9. In step S9, a control signal is output to the preceding spark plug (pre-chamber spark plug 8) to gradually advance the ignition timing with the optimum ignition timing MBT corresponding to the operating condition specified in step S2 as the upper limit, and processing is performed. end.

On the other hand, if the result in step S12 is affirmative, it is determined that the combustion sound is louder than the standard, and the process proceeds to step S14, where the number of times C2 is determined to be that the combustion sound is louder than the standard is counted up (C2 (current value) = C2 (previous value). value)+1), the process proceeds to step S15. In step S15, it is determined whether the number of times C2 in which the combustion noise is determined to be louder than the reference exceeds a predetermined number of times c2 corresponding to the operating condition specified in step S2.

If the result in step S15 is affirmative, the process proceeds to step S16, where it is determined that only combustion noise is occurring in the main combustion chamber 41, and the process proceeds to step S17. In step S17, a control signal is output to the preceding spark plug (pre-chamber spark plug 8) so as to retard the reference ignition timing θa corresponding to the operating condition specified in step S2 by a predetermined amount θ2 (θa→θa+θ2). , ends the process. On the other hand, if the answer in step S15 is negative, the process ends without retarding or advancing the ignition timing.

As shown in FIG. 8C, in the process in the phase difference ignition mode, first in step S1, the signals from the crank angle sensor 51 and the intake air amount sensor 52 and the in-cylinder pressure P1 in the first frequency band extracted by the BPFs 53 and 54 are and fluctuation data of cylinder pressure P2 in the second frequency band. Next, in step S2, the operating conditions of the engine 1 are specified based on the signal read in step S1. Next, in step S20, it is determined whether the target ignition mode corresponding to the operating condition specified in step S2 is the phase difference ignition mode. If the result in step S20 is affirmative, the process proceeds to step S4, and if the result in step S20 is negative, the process ends.

In step S4, the maximum amplitude PP1 for each combustion cycle of the engine 1 is calculated based on the fluctuation data of the in-cylinder pressure P1 in the first frequency band read in step S1. Next, in step S5, it is determined whether the maximum amplitude PP1 calculated in step S4 exceeds the first threshold value pp1 corresponding to the operating condition specified in step S2.

If the result in step S5 is affirmative, the process proceeds to step S6, where it is determined that knocking has occurred in the main combustion chamber 41, and the process proceeds to step S7. In step S7, a control signal is output to the preceding spark plug (main chamber spark plug 9) so as to retard the reference ignition timing θa by a predetermined amount θ1 (θa→θa+θ1) corresponding to the operating condition specified in step S2. , ends the process.

On the other hand, if the result in step S5 is negative, the process proceeds to step S8, where it is determined that knocking has not occurred in the main combustion chamber 41, and the process proceeds to step S9. In step S9, a control signal is output to the preceding spark plug (main chamber spark plug 9) to gradually advance the ignition timing with the optimum ignition timing MBT corresponding to the operating condition specified in step S2 as the upper limit.

Next, in step S11, the maximum amplitude PP2 for each combustion cycle of the engine 1 is calculated based on the fluctuation data of the in-cylinder pressure P2 in the second frequency band read in step S1. Next, in step S12, it is determined whether the maximum amplitude PP2 calculated in step S11 exceeds a second threshold value pp2 corresponding to the operating condition specified in step S2.

If the result in step S12 is negative, it is determined that the combustion noise is below the standard and the process proceeds to step S13, and it is determined that neither knocking nor combustion noise is occurring in the main combustion chamber 41, and the process proceeds to step S21. In step S21, a control signal is output to the spark plugs 8 and 9 so as to gradually reduce the phase difference, and the process ends.

On the other hand, if the result in step S12 is affirmative, it is determined that the combustion sound is louder than the standard, and the process proceeds to step S14, where the number of times C2 is determined to be that the combustion sound is louder than the standard is counted up (C2 (current value) = C2 (previous value). value)+1), the process proceeds to step S15. In step S15, it is determined whether the number of times C2 in which the combustion noise is determined to be louder than the reference exceeds a predetermined number of times c2 corresponding to the operating condition specified in step S2.

If the answer in step S15 is affirmative, the process proceeds to step S16, where it is determined that only combustion noise is occurring in the main combustion chamber 41, and the process proceeds to step S22. In step S22, a control signal is output to the spark plugs 8 and 9 so as to expand the reference phase difference θb corresponding to the operating condition specified in step S2 by a predetermined amount θ3 (θb→θb+θ3), and the process ends. On the other hand, if the result in step S15 is negative, the process ends without retarding or advancing the ignition timing or expanding the phase difference.

The occurrence of knocking and the occurrence of combustion noise can be detected separately by monitoring a first frequency band in which pressure fluctuations become large only when knocking occurs and a second frequency band in which pressure fluctuations become large only when combustion noise occurs. (S4-S5, S11-S12). Furthermore, by preferentially detecting the occurrence of knocking that could lead to damage to engine parts, even if knocking occurs, it can be immediately resolved (S5). In addition, since the occurrence of combustion noise is detected only when the combustion noise continues to be louder than the standard, it is possible to suppress excessive retardation of ignition timing and minimize the decline in engine output and fuel efficiency. (S12, S15 to S17, S22).

According to this embodiment, the following effects can be achieved.
(1) The device 100 includes a main combustion chamber 41 facing the piston 3 reciprocating within the cylinder 2, a sub-combustion chamber 42 communicating with the main combustion chamber 41 via the nozzle hole 47, and an interior of the main combustion chamber 41. The engine 1 has a main chamber spark plug 9 that ignites the air-fuel mixture in the sub-combustion chamber 42, and an auxiliary chamber spark plug 8 that ignites the air-fuel mixture inside the sub-combustion chamber 42 (FIGS. 1 to 3).

The device 100 includes a cylinder pressure sensor 10 that detects the pressure in the main combustion chamber 41, a BPF 53 that extracts pressure fluctuation data in a first frequency band (10 to 16 kHz) from pressure fluctuation data detected by the cylinder pressure sensor 10. , a BPF 54 that extracts pressure fluctuation data in a second frequency band (6 to 9 kHz) lower than the first frequency band from pressure fluctuation data detected by the cylinder pressure sensor 10, and a BPF 53 for each combustion cycle of the engine 1. An amplitude calculation unit 57 that calculates the maximum amplitude PP1 included in the pressure fluctuation data of the extracted first frequency band, and also calculates the maximum amplitude PP2 contained in the pressure fluctuation data of the second frequency band extracted by the BPF 54. Prepare (Figure 4).

The device 100 further includes a first determining unit 58 that determines whether knocking is occurring in the main combustion chamber 41 based on the maximum amplitude PP1 calculated by the amplitude calculating unit 57; On the condition that it is determined that knocking is not occurring in the main combustion chamber 41, it is determined whether or not combustion noise is occurring in the main combustion chamber 41 based on the maximum amplitude PP2 calculated by the amplitude calculation unit 57. a second determination unit 59 that makes a determination; a spark plug control unit that controls the operation of the spark plugs 8 and 9 based on the operating conditions of the engine 1; and the determination results by the first determination unit 58 and the second determination unit 59; 56 (FIG. 4).

When the second determination unit 59 determines that combustion noise is occurring in the main combustion chamber 41, the spark plug control unit 56 adjusts the ignition timing of the main chamber ignition plug 9 and the ignition timing of the pre-chamber spark plug 8. The operation of the spark plugs 8 and 9 is controlled to increase the phase difference between them (FIG. 8C).

In this way, the BPFs 53 and 54 are provided, and the first frequency band (10 to 16 kHz) where the pressure fluctuation becomes large only when knocking occurs and the second frequency band (6 to 9 kHz) where the pressure fluctuation becomes large when combustion noise occurs, respectively. By monitoring, the single in-cylinder pressure sensor 10 can accurately detect the occurrence of knocking and the occurrence of combustion noise. In addition, if knocking does not occur and only combustion noise occurs, the phase difference between the ignition timings of the spark plugs 8 and 9 can be expanded to minimize the decrease in engine output and fuel efficiency, and improve efficiency. Combustion noise can be effectively eliminated (Figure 7).

(2) When the first determination unit 58 determines that knocking has occurred in the main combustion chamber 41, the spark plug control unit 56 controls the preceding spark plug (main The operation of the chamber spark plug 9) is controlled, and when the second determination unit 59 determines that combustion noise is occurring in the main combustion chamber 41, the phase difference is expanded by a predetermined amount θ3, which is smaller than the predetermined amount θ1. The operation of the spark plugs 8 and 9 is controlled (FIG. 8C).

That is, if knocking is occurring, the knocking can be reliably eliminated by sufficiently retarding the ignition timing of the main chamber ignition plug 9, and if combustion noise is occurring, the phase difference can be expanded. By retarding the ignition timing of the pre-chamber spark plug 8 to some extent, combustion noise is reduced. By determining the occurrence of knocking and the occurrence of combustion noise, and correcting the ignition timing of the spark plugs 8 and 9 in an appropriate manner according to the occurrence event, it is possible to prevent a decrease in engine output and fuel efficiency due to a retardation of the ignition timing. can be minimized.

(3) The device 100 sets the first threshold pp1 corresponding to the maximum amplitude PP1 when knocking occurs in the main combustion chamber 41, and the maximum amplitude PP2 when combustion noise occurs in the main combustion chamber 41. It further includes a storage unit 50B that stores a corresponding second threshold value pp2 and a predetermined number of times c2 (FIG. 4). The first determination unit 58 determines that knocking is occurring in the main combustion chamber 41 when the maximum amplitude PP1 exceeds the first threshold pp1 stored in the storage unit 50B. The second determination unit 59 determines that when the number of times C2 that the maximum amplitude PP2 exceeds the second threshold value pp2 stored in the storage unit 50B exceeds the predetermined number of times c2 stored in the storage unit 50B, the combustion noise is generated in the main combustion chamber 41. It is determined that this has occurred. The first threshold value pp1, the second threshold value pp2, and the predetermined number of times c2 are determined in advance according to the operating conditions of the engine 1.

More specifically, the first threshold pp1, the second threshold pp2, and the predetermined number of times c2 are each stored in the storage unit 50B as a characteristic map predetermined according to the engine speed and the engine load. In this way, by carefully setting the threshold values used for determining knocking, combustion noise, and combustion noise according to the operating conditions of the engine 1, it is possible to detect the occurrence of knocking and combustion noise with higher accuracy. can. Further, it is possible to prevent excessive determination of the occurrence of knocking and the occurrence of combustion noise, and it is possible to minimize the reduction in engine output and fuel efficiency due to retardation of ignition timing.

(4) The first frequency band and the second frequency band are determined in advance according to the diameter B of the cylinder 2. That is, if the engine 1 has a main combustion chamber 41 and a sub-combustion chamber 42, an appropriate first frequency band and second frequency band are determined according to the diameter B of the cylinder 2, and the generation of knocking and combustion noise is determined. can be detected with high accuracy.

In the above embodiment, the injector 7, the subchamber ignition plug 8, and the main chamber ignition plug 9 are arranged on the same straight line (reference line L1), but the arrangement of the main chamber ignition section and the subchamber ignition section is as described above. Not limited to things. In the above embodiment, the pre-chamber spark plug 8 is arranged offset from the center line (axis CL1) of the cylinder 2, but it may be arranged on the center line of the cylinder 2. That is, the position of the pre-chamber ignition part is not limited to the above-mentioned position as long as it is disposed approximately at the center of the cylinder 2.

In the above embodiment, depending on the operating conditions of the engine 1, there is a main chamber ignition mode in which only the main chamber ignition plug 9 ignites, a sub chamber ignition mode in which only the sub chamber ignition plug 8 ignites, and a main chamber ignition mode in which only the sub chamber ignition plug 8 ignites. Although the present embodiment is configured to switch between the phase difference ignition mode in which both of the pre-chamber spark plugs 8 fire, only the phase difference ignition mode may be performed regardless of the operating conditions of the engine 1.

In the above embodiment, the ignition mode determining unit 55 switches between the main chamber ignition mode, the pre-chamber ignition mode, and the phase difference ignition mode according to the engine speed and the engine load. The ignition mode may be switched in consideration of the temperature (temperature). That is, when the engine 1 is started at a low temperature, the wall surface temperature of the sub-combustion chamber 42 is decreasing, and combustion is not stable. Therefore, the temperature of the engine 1 (for example, the temperature of the cylinder block) may be detected, and if the detected temperature is below a predetermined value, the ignition mode may be determined to be the main chamber ignition mode.

The above description is merely an example, and the present invention is not limited to the above-described embodiments and modifications as long as the characteristics of the present invention are not impaired. It is also possible to arbitrarily combine the above embodiment and one or more of the modifications, and it is also possible to combine the modifications.

1 engine, 2 cylinder, 3 piston, 8 pre-chamber spark plug, 9 main chamber spark plug, 10 cylinder pressure sensor, 41 main combustion chamber, 42 sub-combustion chamber, 47 nozzle hole, 50 controller, 50A calculation section, 50B storage section , 51 crank angle sensor, 52 intake air amount sensor, 53, 54 BPF, 55 ignition mode determination section, 56 spark plug control section, 57 amplitude calculation section, 58 first determination section, 59 second determination section, 100 control device (device )

Claims (4)

a main combustion chamber facing a piston that reciprocates within the cylinder, a sub-combustion chamber communicating with the main combustion chamber via a nozzle hole, a main combustion chamber igniting the air-fuel mixture inside the main combustion chamber; A control device for an internal combustion engine, comprising: a sub-chamber ignition section that ignites the air-fuel mixture inside the sub-combustion chamber;
a pressure detection unit that detects the pressure in the main combustion chamber;
a first extraction unit that extracts pressure fluctuation data in a first frequency band from pressure fluctuation data detected by the pressure detection unit;
a second extraction unit that extracts pressure fluctuation data in a second frequency band lower than the first frequency band from the pressure fluctuation data detected by the pressure detection unit;
For each combustion cycle of the internal combustion engine, the first maximum amplitude included in the pressure fluctuation data in the first frequency band extracted by the first extraction section is calculated, and the first maximum amplitude included in the pressure fluctuation data in the first frequency band extracted by the first extraction section is calculated. an amplitude calculation unit that calculates a second maximum amplitude included in the pressure fluctuation data of two frequency bands;
a first determination unit that determines whether knocking is occurring in the main combustion chamber based on the first maximum amplitude calculated by the amplitude calculation unit;
Based on the second maximum amplitude calculated by the amplitude calculation unit, on the condition that the first determination unit determines that knocking is not occurring in the main combustion chamber, the combustion noise is determined in the main combustion chamber based on the second maximum amplitude calculated by the amplitude calculation unit. a second determination unit that determines whether or not is occurring;
an ignition control section that controls operations of the main chamber ignition section and the sub-chamber ignition section based on operating conditions of the internal combustion engine and judgment results by the first judgment section and the second judgment section; Prepare,
When the second determination unit determines that combustion noise is occurring in the main combustion chamber, the ignition control unit controls the ignition timing between the ignition timing of the main chamber ignition unit and the ignition timing of the sub-chamber ignition unit. A control device for an internal combustion engine, characterized in that the operation of the main chamber ignition section and the sub-chamber ignition section is controlled so as to increase a phase difference between the main chamber ignition section and the sub-chamber ignition section. The control device for an internal combustion engine according to claim 1,
The ignition control unit controls the main chamber ignition unit and the sub-combustion chamber to retard the ignition timing by a first predetermined amount when the first determination unit determines that knocking has occurred in the main combustion chamber. controlling the operation of a chamber ignition unit, and when the second determination unit determines that combustion noise is occurring in the main combustion chamber, increasing the phase difference by a second predetermined amount that is smaller than the first predetermined amount; A control device for an internal combustion engine, characterized in that the operation of the main chamber ignition section and the sub-chamber ignition section is controlled so as to. The control device for an internal combustion engine according to claim 1 or 2,
a first threshold corresponding to the first maximum amplitude when knocking is occurring in the main combustion chamber; and a second threshold corresponding to the second maximum amplitude when combustion noise is occurring in the main combustion chamber. further comprising a storage unit that stores the threshold value and the predetermined frequency;
The first determination unit determines that knocking is occurring in the main combustion chamber when the first maximum amplitude exceeds the first threshold stored in the storage unit,
The second determination unit is configured to determine whether combustion noise occurs in the main combustion chamber when the frequency at which the second maximum amplitude exceeds the second threshold value stored in the storage unit exceeds the predetermined frequency stored in the storage unit. It is determined that this has occurred,
A control device for an internal combustion engine, wherein the first threshold value, the second threshold value, and the predetermined frequency are determined in advance according to operating conditions of the internal combustion engine. The control device for an internal combustion engine according to claim 1 or 2,
A control device for an internal combustion engine, wherein the first frequency band and the second frequency band are determined in advance according to a diameter of the cylinder.

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