JP2024005027A - Control device for internal combustion engine - Google Patents

Abstract

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 and an ignition section for igniting an air-fuel mixture in the auxiliary combustion chamber includes: a cylinder pressure sensor 9 for detecting a pressure of the main combustion chamber; a BPF 53 that extracts pressure fluctuation data of a first frequency band; a BPF 54 that extracts pressure fluctuation data of a second frequency band lower than the first frequency band; an amplitude calculation section 55 that calculates first and second maximum amplitude included in the pressure fluctuation data of the first and second frequency bands in each combustion cycle of the internal combustion engine; a first determination section 56 that determines whether knocking is occurring in the main combustion chamber on the basis of the first maximum amplitude; a second determination section 57 that determines whether combustion noise is being generated in the main combustion chamber on the basis of the second maximum amplitude; and an ignition control section 58 that controls operation of the ignition section on the basis of an operating condition of the internal combustion engine and determination results.SELECTED DRAWING: Figure 4

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 a cylinder, a sub-combustion chamber that communicates with the main combustion chamber via a nozzle hole, and an ignition system that ignites the air-fuel mixture inside the sub-combustion chamber. A control device for an internal combustion engine, comprising: a pressure detection section that detects pressure in a main combustion chamber; and a pressure variation data in a first frequency band extracted from pressure variation data detected by the pressure detection section. a first extraction section; a second extraction section 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 section; and 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 second maximum amplitude included in the pressure fluctuation data in the second frequency band extracted by the second extraction section is calculated. An amplitude calculation unit that calculates the amplitude, a first determination unit that determines whether knocking has occurred in the main combustion chamber based on the first maximum amplitude calculated by the amplitude calculation unit, and an amplitude calculation unit that calculates the amplitude. a second determination unit that determines whether or not combustion noise is occurring in the main combustion chamber based on the second maximum amplitude determined by the second maximum amplitude; and a determination by the first determination unit and the second determination unit based on the operating conditions of the internal combustion engine. and an ignition control section that controls the operation of the ignition section based on the result.

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. 5 is a flowchart showing an example of a process executed by the controller in FIG. 4. FIG.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 7. 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). As shown in FIG. 2, an in-cylinder pressure sensor 9 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 9 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 CL1, 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 with respect to the axis CL1. The axis CL1 coincides with the center line of the cylinder 2 in FIG. 1, for example. The housing 45 may be provided so that the axis CL1 is offset from the center line of the cylinder 2, for example, to the opposite side of the injector 7.

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 around the axis CL1. The nozzle holes 47 are opened radially along an axis CL2 that extends obliquely from the axis CL1 toward the piston 3 and radially outward. Note that the angle α1 between the axis CL1 and the axis CL2 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° to 60°.

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 CL1. The spark plug 8 is arranged with its longitudinal center line along the axis CL1, 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.

When the flame jet 48 is ejected into the main combustion chamber 41 from the nozzle hole 47 of the auxiliary combustion chamber 42 in this way, the flame propagation in the main combustion chamber 41 is accelerated, which increases the thermal efficiency of the engine 1, but it also affects the presence or absence of knocking. Combustion noise may occur regardless. 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 9.

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 a spark plug 8, a cylinder pressure sensor 9, a crank angle sensor 51, an intake air amount sensor 52, and a band It has pass 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.

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. 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 torque sensor that detects 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 spark plug 8 (FIG. 3), a flame jet 48 is ejected into the main combustion chamber 41 from each nozzle hole 47 of the auxiliary combustion chamber 42, and the flame jet 48 ejects into the main combustion chamber 41 near the wall surface of the cylinder 2 where the flame jet 48 reaches. Pressure waves are generated by increasing internal pressure. 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 surface 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 plug 8 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 to 16kHz) and immediately adjust the ignition timing if pressure fluctuations exceeding the specified level are observed when knocking occurs. It is necessary to retard the timing and eliminate the knocking. In this case, it is necessary to ensure a sufficient retard amount (first predetermined amount) θ1 to eliminate knocking (for example, about 1.5 [deg]).

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. Just like knocking, combustion noise can also be alleviated by retarding the ignition timing. Combustion noise only needs to be reduced to the extent that it does not give the user a sense of discomfort, and the retardation amount (second predetermined amount) θ2 for reducing combustion noise is equal to the first predetermined amount θ1 necessary to eliminate knocking. (θ1>θ2) (for example, about 0.5 [deg]).

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 predetermined level that can be recognized as combustion noise are observed, and the observation frequency exceeds a predetermined frequency, the second frequency band (6 to 9 kHz) is monitored. By retarding the ignition timing by 2 predetermined amount θ2, combustion noise can be alleviated.

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 9, and the BPF 54 is configured to extract 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 9 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 55, a first determination unit 56, a second determination unit 57, and an ignition control unit 58.

The amplitude calculation unit 55 calculates, for each combustion cycle of the engine 1, the maximum amplitude PP1 included in the pressure fluctuation data in the first frequency band extracted by the BPF 53, 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 providing the cylinder pressure sensor 9 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 56 determines whether knocking is occurring in the main combustion chamber 41 based on the maximum amplitude PP1 calculated by the amplitude calculation unit 55. 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 56 is determined in advance through a test and stored in the storage unit 50B. The test for determining the first threshold value pp1 is performed while changing the operating conditions of the engine 1, that is, the engine speed and the engine load (intake air amount), and the first threshold value pp1 is determined in advance according to the engine speed and the load. It is stored in the storage unit 50B as a determined characteristic map. The first determination unit 56 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 57 determines whether the main combustion It is determined whether combustion noise is occurring in the chamber 41.

The second determination unit 57 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 57 is determined in advance by a test, and is determined in advance according to the engine speed and the engine load (intake amount). The map is stored in the storage unit 50B as a characteristic map. The second determination unit 57 determines the engine speed based on the engine 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 57 determines that the main It is determined that combustion noise is occurring in the combustion chamber 41.

Similarly to the first threshold value pp1 and the second threshold value pp2, the predetermined number of times c2 used for the determination of combustion noise by the second determination unit 57 is determined in advance by a test, and depends on the engine speed and the engine load (intake air amount). The map is stored in the storage unit 50B as a predetermined characteristic map. The second determination unit 57 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.

The ignition control unit 58 controls the operation of the spark plug 8 based on the operating conditions of the engine 1 and the determination results by the first determination unit 56 and the second determination unit 57. That is, when neither knocking nor combustion noise occurs, the ignition control unit 58 controls ignition at a reference ignition timing θ0 predetermined according to the operating conditions of the engine 1, for example, at the optimal ignition timing MBT that provides the maximum torque. The operation of the spark plug 8 is controlled so as to perform the following steps.

When the first determination unit 56 determines that knocking has occurred in the main combustion chamber 41, the ignition control unit 58 controls the operation of the spark plug 8 to retard the ignition timing by a first predetermined amount θ1. (θ0→θ0+θ1). Further, when the second determination unit 57 determines that combustion noise is occurring in the main combustion chamber 41, the operation of the spark plug 8 is controlled to retard the ignition timing by a second predetermined amount θ2 (θ0 →θ0+θ2). The first predetermined amount θ1 and the second predetermined amount θ2 are determined in advance through a test and stored in the storage unit 50B.

FIG. 7 is a flowchart showing an example of a process executed by the controller 50 of FIG. 4 according to a pre-stored program. The process shown in this flowchart is started after the engine is started, and is repeated at a predetermined period.

As shown in FIG. 7, first, in step S1, the signals from the crank angle sensor 51 and the intake air amount sensor 52, the cylinder pressure P1 in the first frequency band and the cylinder pressure P2 in the second frequency band extracted by the BPFs 53 and 54 are extracted. Load the fluctuation data. 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, the maximum amplitude PP1 for each combustion cycle of the engine 1 is calculated based on the fluctuation data of the cylinder pressure P1 in the first frequency band read in step S1. Next, in step S4, it is determined whether the maximum amplitude PP1 calculated in step S3 exceeds the first threshold value pp1 corresponding to the operating condition specified in step S2.

If the answer in step S4 is affirmative, the process proceeds to step S5, where it is determined that knocking has occurred in the main combustion chamber 41, and the process proceeds to step S6. In step S6, a control signal is output to the spark plug 8 to retard the reference ignition timing θ0 corresponding to the operating condition specified in step S2 by a first predetermined amount θ1 (θ0→θ0+θ1), and the process ends. .

On the other hand, if the result in step S4 is negative, it is determined that knocking has not occurred in the main combustion chamber 41, and the process proceeds to step S7. In step S7, 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 S8, it is determined whether the maximum amplitude PP2 calculated in step S7 exceeds a second threshold value pp2 corresponding to the operating condition specified in step S2.

If the result in step S8 is negative, it is determined that the combustion noise is below the standard and the process proceeds to step S9, and it is determined that neither knocking nor combustion noise is occurring in the main combustion chamber 41, and the process proceeds to step S10. In step S10, a control signal is output to the spark plug 8 to advance the spark plug 8 as necessary to the reference ignition timing θ0 (optimal ignition timing MBT) corresponding to the operating condition specified in step S2, and the process ends.

On the other hand, if the result in step S8 is affirmative, it is determined that the combustion sound is louder than the standard, and the process proceeds to step S11, 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 S12. In step S12, 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 S12 is affirmative, the process proceeds to step S13, where it is determined that only combustion noise is occurring in the main combustion chamber 41, and the process proceeds to step S14. In step S14, a control signal is output to the spark plug 8 to retard the reference ignition timing θ0 corresponding to the operating condition specified in step S2 by a second predetermined amount θ2 (θ0→θ0+θ2), and the process ends. . On the other hand, if the answer in step S12 is negative, the process ends without retarding or advancing the ignition timing.

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. (S3-S4, S7-S8). 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 (S4). 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. (S8, S11-S13).

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 sub-combustion chamber 42. 1 to 3).

The device 100 includes a cylinder pressure sensor 9 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 9. , 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 9, and a BPF 53 for each combustion cycle of the engine 1. an amplitude calculation unit 55 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 determination unit 56 that determines whether or not knocking has occurred in the main combustion chamber 41 based on the maximum amplitude PP1 calculated by the amplitude calculation unit 55; a second determination unit 57 that determines whether or not combustion noise is occurring in the main combustion chamber 41 based on the maximum amplitude PP2, the operating conditions of the engine 1, the first determination unit 56, and the second determination unit 57, and an ignition control section 58 that controls the operation of the spark plug 8 based on the determination result of the spark plug 57 (FIG. 4).

That is, the BPFs 53 and 54 are provided to monitor the first frequency band (10 to 16 kHz) where pressure fluctuations become large only when knocking occurs and the second frequency band (6 to 9 kHz) where pressure fluctuations become large when combustion noise occurs. . Thereby, the occurrence of knocking and the occurrence of combustion noise can be detected with high accuracy based on the single sensor value P0 from the single cylinder pressure sensor 9.

(2) The second determination unit 57 determines whether combustion noise is occurring in the main combustion chamber 41 on the condition that the first determination unit 56 determines that knocking is not occurring in the main combustion chamber 41. Determine. This makes it possible to preferentially detect the occurrence of knocking that could lead to damage to engine parts.

(3) When the first determination unit 56 determines that knocking has occurred in the main combustion chamber 41, the ignition control unit 58 operates the spark plug 8 to retard the ignition timing by a first predetermined amount θ1. When the second determination unit 57 determines that combustion noise is occurring in the main combustion chamber 41, the spark plug is retarded by a second predetermined amount θ2, which is smaller than the first predetermined amount θ1. Controls the operation of 8.

In other words, if knocking is occurring, knocking can be reliably eliminated by ensuring a sufficient retardation amount (first predetermined amount) θ1, and if combustion noise is occurring, a certain amount of retardation is ensured. Combustion noise is reduced by (second predetermined amount θ2). If the ignition timing is retarded from the optimum reference ignition timing θ0 that is predetermined according to the operating conditions of the engine 1, engine output and fuel efficiency will decrease. By determining the occurrence of knocking and the occurrence of combustion noise, and retarding the ignition timing appropriately according to the occurrence, it is possible to minimize the reduction in engine output and fuel efficiency due to ignition timing retardation.

(4) 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 56 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 57 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 a predetermined number of times c2 stored in the storage unit 50B, 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.

(5) 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.

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 spark plug, 9 cylinder pressure sensor, 41 main combustion chamber, 42 auxiliary combustion chamber, 47 nozzle hole, 50 controller, 50A calculation section, 50B storage section, 51 crank angle sensor, 52 intake air quantity sensor, 53, 54 BPF, 55 amplitude calculation section, 56 first judgment section, 57 second judgment section, 58 ignition control section, 100 control device (device)

Claims (5)

It has 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 an ignition section that ignites the air-fuel mixture inside the sub-combustion chamber. A control device for an internal combustion engine,
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;
a second determination unit that determines whether combustion noise is occurring in the main combustion chamber based on the second maximum amplitude calculated by the amplitude calculation unit;
An internal combustion engine comprising: an ignition control section that controls operation of the ignition section based on operating conditions of the internal combustion engine and determination results by the first determination section and the second determination section. control device. The control device for an internal combustion engine according to claim 1,
The second determination unit determines whether combustion noise is occurring in the main combustion chamber, on the condition that the first determination unit determines that knocking is not occurring in the main combustion chamber. A control device for an internal combustion engine characterized by: The control device for an internal combustion engine according to claim 2,
The ignition control unit controls the operation of the ignition unit 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; When the second determination section determines that combustion noise is occurring in the main combustion chamber, the ignition section is operated to retard the ignition timing by a second predetermined amount that is smaller than the first predetermined amount. A control device for an internal combustion engine. The control device for an internal combustion engine according to any one of claims 1 to 3,
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 any one of claims 1 to 3,
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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