JP2014037811A - Combustion state determination method of internal combustion engine using ionic current - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem as to be erroneously determined as knock when noise occurring from an alternator is superimposed on an ion current wave form, upon the determining of occurrence of the knock in an internal combustion engine from an ionic current generated in a cylinder after combustion of the internal combustion engine.SOLUTION: In a combustion state determination method of an internal combustion engine for determining knock occurring in the internal combustion engine from an ionic current detected by an ionic current detection circuit 90, when wave forms of noise components produced in cylinders other than combustion stroke of the same time are equal to ion wave form when crank angle of the cylinder of the combustion stroke advances from the top dead point to 45° or more in the cylinder 10, it is determined that the noise component is superimposed on the ionic current wave form and the noise component is subtracted from the ionic current wave form to determine the presence or absence of knock occurrence of the cylinder 10.

Description

The present invention relates to a method for determining a combustion state of an internal combustion engine such as an automobile engine, and more particularly to a combustion state determination method using an ionic current.

Conventionally, in a spark ignition type internal combustion engine, a metallic noise or vibration phenomenon generated by the internal combustion engine is called knocking (hereinafter referred to as “knock”). The cause of knocking is that the ignition timing is too early or the compression ratio is If it is too high, combustion with an extremely thin air-fuel mixture, etc. may be raised, which may lead to engine blow. One method for detecting knock is to detect an ion current generated in the cylinder after combustion of the internal combustion engine and determine the occurrence of the knock from the waveform of the ion current.

However, if the noise component generated when knocking occurs or the noise component accompanying the operation of various parts that control the engine is superimposed on the ion current waveform, it becomes difficult to determine the occurrence of knock from the ion current waveform. occured. In order to solve such a problem, for example, Japanese Patent Laid-Open No. 9-228941 (hereinafter “Patent Document 1”) is known.

In Patent Document 1, the presence or absence of a knock component that is electrically connected to an ion current detection device that generates an ion current for each ignition in the combustion chamber of the internal combustion engine and is superimposed on the ion current when a knock occurs in the internal combustion engine Has been proposed that comprises a determination means for determining knock from the above and a determination invalidation means that invalidates the determination of the determination means in response to a noise component different from the knock component superimposed on the ionic current. Yes.

As another example, Japanese Patent Laid-Open No. 2008-267243 (hereinafter “Patent Document 2”) is known.

In the above-mentioned Patent Document 2, an ion current detecting means for detecting an ion current based on ions generated during combustion of the internal combustion engine, a knock signal detecting means for detecting a knock signal based on the ion current, and a rotational position of the internal combustion engine Crank angle detecting means for detecting the crank angle, window setting means for setting a window for noise detection after a predetermined crank angle corresponding to the end of the combustion stroke of the internal combustion engine, frequency component intensity and ion current of ion current in the window There has been proposed a knock detection device including a noise component detection unit that detects a noise component based on at least one of the generation amounts, and a knock determination unit that determines whether or not a knock has occurred based on a relationship between the noise component and the knock signal. ing.

JP-A-9-228941 JP 2008-267243 A

However, the above-described conventional knock detection device for an internal combustion engine has the following problems. That is, in Patent Document 1, when a noise component is superimposed on the ionic current, the determination invalidation means reacts to the noise component and invalidates the knock determination in the determination means, so that erroneous determination is reliably prevented. The In other words, even if the noise component includes a component equivalent to the knock component, if the noise component is included in the ionic current, the determination invalidating unit operates, so that the presence or absence of knocking due to the ionic current is not determined. Therefore, there is no erroneous determination that erroneously determines a noise component as a knock component and the reliability of knock detection is improved, but if knock determination is invalidated when the noise component is included, knocking actually occurs. Nevertheless, if noise continues continuously, there arises a problem that may lead to the damage of the worst engine.

Further, in Patent Document 2, based on the fact that almost no ion current signal is generated at the end of the combustion stroke when knocking occurs and no noise component is generated, a noise component having the same frequency as knock vibration is superimposed on the ion current signal. However, the noise component and the knock signal are discriminated with high accuracy and the presence / absence of knock occurrence is detected with high accuracy and high efficiency. However, if noise occurs after the desired crank angle, the reliability of the knock determination is improved. If it is determined that knocking has occurred and it is determined that knocking has not occurred, if the noise continues to be superimposed despite the fact that knocking has actually occurred, there arises a problem that may lead to damage to the worst engine.

Also, with these knock detection devices, it is difficult to distinguish between knock and noise for noise that fluctuates to various frequencies, even though it is possible to distinguish the noise component and knock having a regular frequency to some extent. Become. As a device that generates noise that fluctuates at various frequencies, there is an alternator that supplies power to automobile batteries and electrical components. The alternator rotates about 8 times the engine speed and always operates while the engine is running. Therefore, there is a concern about the influence of alternator noise (hereinafter referred to as “alternator noise”) superimposed on the knock determination.

FIG. 8A shows the rotation speed and noise frequency characteristics of the alternator. In FIG. 8A, the X axis indicates the engine speed, and the Y axis indicates the frequency of alternator noise. As the engine speed increases, the frequency of alternator noise also increases. That is, it is shown that the alternator noise is a noise having a great influence on the ion current as compared with other control components. FIG. 8B shows frequency characteristics of the noise band-pass filter and the knock band-pass filter. The X axis indicates the frequency of alternator noise, and the Y axis indicates the amplitude. Further, the frequency characteristic of the noise bandpass filter is indicated by a solid line, and the frequency characteristic of the knock bandpass filter is indicated by a broken line. In FIG. 8B, the frequency analysis of the noise bandpass filter (hereinafter referred to as “noise BPF”) reacts strongly with alternator noise at frequencies up to about 6800 Hz (X portion) and frequencies after about 11800 Hz (Z portion). On the other hand, the frequency analysis of the knock bandpass filter (hereinafter referred to as “knock BPF”) reacts strongly to the alternator noise of the frequency (Y part) of 6800 to 11800 Hz. Returning to FIG. 8A, the engine speed when generating alternator noise up to 6800 Hz is up to about 5000 rpm, and in such a low and medium speed range, noise BPF reacts strongly even if knocking occurs. There arises a problem that it is not determined to be knocked. The engine speed when generating 6800 to 11800 Hz alternator noise is up to 4800 to 8800 rpm. In such a high speed range, knock BPF reacts strongly even if noise occurs, so knock has occurred. Even if it does not, the problem of misjudging will occur.

The present invention has been made in view of the above problems, and noise generated from an alternator is superimposed on an ionic current waveform when determining whether knocking occurs in the internal combustion engine from an ionic current generated in the cylinder after combustion of the internal combustion engine. However, it is an object of the present invention to provide a combustion state determination method for an internal combustion engine that can accurately determine only the occurrence of knock.

In order to solve the above problems, the present invention is configured as follows. That is, according to the first aspect of the present invention, an internal combustion engine having a plurality of cylinders, a spark plug for igniting a mixture of fuel and air supplied into the cylinder of the cylinder, and supplying a high voltage to the spark plug An ignition coil composed of a primary coil, a secondary coil, and an iron core, and an ion current detection circuit that detects an ion current generated in the ignition plug by combustion of the internal combustion engine, and the ion current detection circuit detects the ion current detection circuit In the internal combustion engine combustion state determination method for determining knock generated in the internal combustion engine from an ion current, an ion current waveform detected from a cylinder in the combustion stroke among the cylinders is generated in a cylinder other than the combustion stroke in the same period. Determining whether or not knocking occurs in the cylinder from an ion current waveform obtained by subtracting a noise component from an alternator. The method.

In the above configuration, the waveform of the noise component generated in the cylinders other than the combustion stroke in the same period is equivalent to the time when the magnitude of the ion waveform of the cylinder in the combustion stroke of the cylinder is 0.2 V or less. In this case, assuming that a noise component is superimposed on the ion current waveform, the noise component may be subtracted from the ion current waveform, and the crank angle of the cylinder in the combustion stroke of the cylinder is 45 degrees from the top dead center. When the waveform of the noise component generated in the cylinders other than the combustion stroke at the same period is equivalent to the ion waveform when advanced, the noise component is superimposed on the ion current waveform. The noise component may be subtracted from the ion current waveform. Further, the noise component detected by the ion current detection circuit may be detected from the cylinder during the intake or exhaust stroke, and the noise component detected by the ion current detection circuit is detected by the cylinder during the combustion stroke. You may detect from the cylinder arrange | positioned in an adjacent position. Further, the noise component detected by the ion current detection circuit may be detected from a cylinder located at a distance from the alternator equivalent to a distance between the cylinder and the alternator in a combustion stroke.

As described above, in the combustion state determination method of the internal combustion engine that determines the knock generated in the internal combustion engine from the ion current detected by the ion current detection circuit 90, the crank angle of the cylinder in the combustion stroke of the cylinder 10 is 45 from the top dead center. If the waveform of the noise component generated in the cylinder other than the combustion stroke of the same period is equivalent to the ion waveform when the lead angle is advanced more than 15 degrees, the ion current waveform is assumed to be superimposed on the ion current waveform By subtracting the noise component from the cylinder 10 and determining the presence or absence of knock occurrence in the cylinder 10, even if the noise generated from the alternator is superimposed on the ion current waveform, only the occurrence of knock can be accurately determined. A combustion state determination method can be realized.

It is a figure which shows the structure of the internal combustion engine which is an Example of this invention. It is a circuit diagram of the ignition device of an internal combustion engine. It is a figure which shows the combustion stroke of a 3 cylinder engine. It is a time chart of the ion waveform detected from the 1st and 2nd cylinders of an internal combustion engine. It is the P section enlarged view of FIG. It is a time chart of the ion waveform (after noise subtraction) of the 1st cylinder of an internal-combustion engine. It is a flowchart which shows the combustion state determination method of the internal combustion engine using an ion waveform. (A) shows the number of rotations of the alternator and noise frequency characteristics, and (B) shows the frequency characteristics of the noise bandpass filter and the knock bandpass filter.

Hereinafter, an example showing the embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a diagram showing a configuration of an internal combustion engine according to an embodiment of the present invention, FIG. 2 is a circuit diagram of an ignition device for the internal combustion engine, FIG. 3 is a diagram showing a combustion stroke of a three-cylinder engine, and FIG. FIG. 4 is a time chart of ion waveforms detected from the first and second cylinders, FIG. 5 is an enlarged view of a portion P in FIG. 4, and FIG. 6 is a time chart of ion waveforms (after noise subtraction) of the first cylinder of the internal combustion engine. FIG. 7 is a flowchart showing a combustion state determination method for an internal combustion engine using an ion waveform.

In FIG. 1 to FIG. 3, the internal combustion engine is a three-cylinder engine including first, second, and third cylinders 10, and one cylinder 20 is formed for each cylinder 10. And a crank 32 for converting the vertical motion of the piston 30 into a rotational motion. Further, a crankshaft 34 for rotating the crank 32 of each cylinder 10 in an interlocking manner is provided. Further, an intake pipe 40 for supplying a mixture of fuel and air into the cylinder 20 and an exhaust pipe for exhausting exhaust gas from the cylinder 20 are provided above the cylinder 20 for each cylinder 10. And 60.

The intake pipe 40 is provided with an intake valve 42 for adjusting the amount of intake air into the cylinder 20, and the exhaust pipe 60 is provided with an exhaust valve 62 for adjusting the amount of exhaust gas from the cylinder 20. Yes. Further, an intake cam 44 for opening and closing the intake valve 42 and an exhaust cam 64 for opening and closing the exhaust valve 62 are provided above the cylinder 20 for each cylinder 10.

In addition, an intake cam shaft 46 for interlockingly rotating the intake cam 44 for each cylinder 10 and an exhaust cam shaft 66 for interlockingly rotating the exhaust cam 64 for each cylinder 10 are provided. ing. Further, the crankshaft 34, the intake camshaft 46, and the exhaust camshaft 66 are driven in conjunction by a timing belt.

The first, second, and third cylinders 10 perform an intake stroke, a compression stroke, a combustion stroke, or an exhaust stroke while the crankshaft 34 rotates twice (720 degrees), and the cylinder Each stroke is performed at intervals of 120 degrees every ten. Further, spark plugs 70 having electrodes for detecting sparks in the air-fuel mixture supplied to the cylinder 20 and detecting ionic current generated during combustion of the internal combustion engine are the same as the number of cylinders in the upper part of the cylinder 20. Number is provided.

Each ignition plug 70 is electrically connected to an ignition coil 80 for generating a voltage of several tens of kV necessary for ignition of the air-fuel mixture in the cylinder 20. Further, an ion current detection circuit 90 that detects an ion current generated in the spark plug 70 during combustion of the internal combustion engine is electrically connected to the ignition coil 80.

The ignition coil 80 and the ion current detection circuit 90 are electrically connected to an ECU 92 that performs electrical control of the internal combustion engine. Further, the internal combustion engine includes an alternator that supplies electric power to the vehicle battery 94 and the electric parts, and the alternator is connected by a harness to supply electric power to the battery 94 and the electric parts.

Returning to FIG. 2, the ignition coil 80 includes a primary coil 82 wound with a primary winding, a secondary coil 84 wound with a secondary winding, an iron core 86 made of a silicon steel plate, and a switching semiconductor. An igniter 88 consisting of The positive side of the battery 94 is connected to the low voltage side of the primary coil 82, and the negative side is connected to the body ground. Further, the high voltage side of the primary coil 82 is connected to the collector side of the igniter 88.

The emitter side of the igniter 88 is connected to the body ground, and the base side is connected to the ECU 92 to supply an ignition signal corresponding to the combustion cycle of the internal combustion engine. Further, the secondary coil 84 is disposed at a position where current is generated by electromagnetic induction between the primary coil 82 and the iron core 86, and the high voltage side of the secondary coil 84 is connected to the center electrode of the spark plug 70. ing.

Further, the spark plug 70 has a side electrode provided through a gap with a center electrode connected to the body ground. Further, the low voltage side of the secondary coil 84 is connected to the body ground via the ion current detection circuit 90.

Further, an ion current generated in the cylinder 20 during the combustion stroke of the internal combustion engine is detected by the ion current detection circuit 90 through the spark plug 70 and the secondary coil 84. Further, the ion current detection circuit 90 is connected to the ECU 92, and the ECU 92 calculates an ion current waveform from the magnitude of the ion current detected by the ion current detection circuit 90, and no knock is generated in the internal combustion engine. Judging. Thus, the ion current detection circuit 90 detects the ion current for the combustion stroke of each cylinder 10, and the ECU 92 determines the occurrence of knocking for each cylinder 10 from the ion current waveform for each cylinder 10. Yes.

Further, the noise from the alternator generates a turbulence in magnetic flux, particularly with respect to the secondary coil 84 of the ignition coil 80. Due to this influence, the ECU 92 detects a noise component by superimposing noise on an ion waveform that should not be input from the cylinders 10 other than the combustion stroke.

In FIG. 4, the X axis represents time and the Y axis represents the ion waveform. Further, the ion waveform detected by the ion current detection circuit 90 in the combustion of the first cylinder 10 is indicated by a solid line, and the noise component superimposed on the ion current detection circuit 90 of the second cylinder 10 generated at the same time is indicated. Shown in broken lines. FIG. 3 shows that the second cylinder 10 at a crank angle at which an ionic current is generated by combustion of the first cylinder 10 is in the exhaust stroke or the intake stroke, as shown by the solid line in FIG. In the first cylinder 10, the ion waveform rises to a peak value due to combustion and then decreases. However, when the alternator is driven, noise is superimposed on the ion waveform of the first cylinder 10. Such up and down fluctuations may be regarded as a knock waveform generated in an ion waveform when a knock occurs.

Further, since the noise generated from the alternator is superimposed on the ion waveform of the second cylinder 10 as shown by the broken line in FIG. 4, it is shown that the waveform that does not originally fluctuate up and down due to the alternator noise. Yes. Further, the alternator noise is emitted from the alternator main body and also from the alternator through the harness connecting the battery 94 and electrical components.

In FIG. 5, FIG. 5 shows the time on the X axis and the ion waveform on the Y axis, as in FIG. The ion waveform detected by the ion current detection circuit 90 during the combustion stroke of the first cylinder 10 is indicated by a solid line, and the noise component superimposed on the ion current detection circuit 90 of the second cylinder 10 generated simultaneously is indicated by a broken line. Show. Further, FIG. 5 shows that the noise components superimposed on the ion waveform generated in the first cylinder 10 and the ion current detection circuit 90 of the second cylinder 10 have the same shape and level. .

Returning to FIG. 4, the ion waveform generated in the first cylinder 10 ends after 28.0 ms, and the angle of the crank 32 at this time is 45 degrees from the top dead center with respect to the crank angle of the cylinder in the combustion stroke. It is more advanced. That is, the ion waveform generated in the first cylinder 10 is not generated when the crank angle of the cylinder in the combustion stroke is advanced to 45 degrees or more from the top dead center, and therefore is generated in the first cylinder 10 shown in FIG. Since the noise waveform superimposed on the ion current detection circuit 90 of the second cylinder 10 has the same shape and level, the ion waveform generated in the first cylinder 10 is affected by alternator noise. Can be determined.

In FIG. 6, FIG. 6 shows the time on the X-axis and the ion waveform on the Y-axis as in FIG. The ion waveform detected by the ion current detection circuit 90 during the combustion stroke of the first cylinder 10 is indicated by a solid line. Further, the ECU 92 detects the noise component detected by the ion current detection circuit 90 of the second cylinder 10 from the ion waveform generated in the first cylinder 10 received from the ion current detection circuit 90 shown in FIG. By subtracting, the ion waveform of the first cylinder 10 from which noise as shown in FIG. 6 is removed is calculated. Further, when a knock waveform as shown in the broken-line circle in FIG. 6 is generated from the corrected ion waveform of the first cylinder 10, the ECU 92 determines that knock has occurred in the internal combustion engine.

In addition, the ECU 92 controls the ignition signal to the igniter 88 and the fuel injection signal to the injector 50 based on the knock determination result to suppress the occurrence of knocking in the cylinder 10. Further, returning to FIG. 3, the ECU 92 detects the ion current because the third cylinder 10 at the crank angle at which an ion current is generated by the combustion of the second cylinder 10 is in the exhaust stroke or the intake stroke. By subtracting the noise component detected by the ion current detection circuit 90 of the third cylinder 10 from the ion waveform generated in the second cylinder 10 received from the circuit 90, the second noise is removed. The ion waveform of the cylinder 10 is calculated. Similarly, the ECU 92 receives from the ion current detection circuit 90 because the first cylinder 10 at a crank angle at which an ion current is generated by combustion of the third cylinder 10 is in the exhaust stroke or the intake stroke. Further, by subtracting the noise component detected by the ion current detection circuit 90 of the first cylinder 10 from the ion waveform generated in the third cylinder 10, the ions of the third cylinder 10 from which noise has been removed are subtracted. The waveform is calculated. Thus, the ECU 92 performs knock detection and knock suppression control for each cylinder 10 individually.

Next, operation | movement of the combustion state determination method of an internal combustion engine is demonstrated based on FIG.

In FIG. 7, the internal combustion engine starts a combustion cycle (S1), the ion current detection circuit 90 detects an ion current from the burned cylinder 10 through the secondary coil 84, and the ECU 92 detects the ion An ion waveform is calculated from the ion current detected by the current detection circuit 90 (S2). Further, the ECU 92 determines whether or not a noise component is detected in the waveform of the cylinder 10 during the exhaust or intake stroke at (S2) (S3), and the cylinder 10 at the exhaust or intake stroke at (S2) at (S3). When there is a noise component in the waveform, the ECU 92 subtracts the noise component detected in (S3) from the ion waveform calculated in (S2) (S4). Further, the ECU 92 determines whether or not the ion waveform corrected in (S4) has a knock component (S5). If the ion waveform corrected in (S4) in (S5) has a knock component, the ECU 92 It is determined that a knock has occurred in the combustion stroke of the internal combustion engine (S6), and the ECU 92 adjusts the ignition signal to the igniter 88 and the fuel injection signal to the injector 50, and knocks the cylinder 10. Is suppressed (S7).

If no noise component is generated in the waveform of the cylinder 10 during the exhaust or intake stroke at (S3) at (S3), the ECU 92 determines whether the ion waveform calculated at (S2) has a knock component ( S5). Further, when no knock component is generated in the ion waveform corrected in (S5) in (S5), the internal combustion engine proceeds to the next combustion stroke of the cylinder 10.

With the above configuration, the ECU 92 subtracts the noise component detected by the ion current detection circuit 90 of the cylinder 10 from the ion waveform generated by the combustion of the cylinder 10 received from the ion current detection circuit 90. The ion waveform of the cylinder 10 from which noise has been removed is calculated, and it is determined from this corrected ion waveform whether knock has occurred in the combustion stroke of the internal combustion engine. As a result, even if the alternator noise generated from the alternator main body or the alternator via the harness connecting the battery 94 and the electrical components is superimposed, only the occurrence of the knock is detected without erroneously extracting the alternator as a knock waveform. It can be determined accurately.

Further, in the ion waveform of the first cylinder 10 shown in FIG. 6, when the crank angle of the cylinder in the combustion stroke is advanced to 45 degrees or more from the top dead center, no ion current is generated. The ion waveform generated in the first cylinder 10 and the noise component superimposed on the ion current detection circuit 90 of the second cylinder 10 are generated in the first cylinder 10 when the shape and level are the same. The ion waveform to be detected is affected by alternator noise, and the noise component detected by the ion current detection circuit 90 of the second cylinder 10 is subtracted from the ion waveform generated in the first cylinder 10. It is proved that the ion waveform of the first cylinder 10 from which noise is removed is calculated.

As a modification of the above-described embodiment, the internal combustion engine of this embodiment is a three-cylinder engine including the first, second, and third cylinders 10, but the configuration may be changed to a configuration other than the three-cylinder engine. Similar effects can be obtained. The ECU 92 is a combination of cylinders that subtracts noise components detected by the ion current detection circuit 90 of the cylinder 10 from the ion waveform generated by the combustion of the cylinder 10 received from the ion current detection circuit 90. Since the influence of alternator noise differs depending on the position of each cylinder 10 or the like, for example, a noise component may be detected from the cylinder 10 during an intake or exhaust stroke, or arranged at a position adjacent to the cylinder 10 during a combustion stroke The noise component may be detected from the cylinder 10 to be detected, or may be detected from the cylinder 10 located at a distance from the alternator equivalent to the distance between the alternator and the cylinder 10 in the combustion stroke, or the alternator From the cylinder 10 positioned at a distance from the harness that is equivalent to the distance between the cylinder 94 and the harness connecting the battery 94 and electrical components.

Further, the ECU 92 subtracts the noise component detected by the ion current detection circuit 90 of the cylinder 10 from the ion waveform generated by the combustion of the cylinder 10 received from the ion current detection circuit 90, thereby reducing the noise. The occurrence of knock in the internal combustion engine is determined from the ion waveform of the cylinder 10 from which the gas is removed. For example, the ion waveform generated in the cylinder 10 after combustion and the other ions in the cylinder 10 are determined. A configuration may be adopted in which only the occurrence of a knock is accurately determined without comparing the shape or level of the waveform with the noise component detected by the current detection circuit 90 and extracting the alternator noise erroneously as a knock waveform. Further, a method for subtracting the noise component detected by the ion current detection circuit 90 of the cylinder 10 from the ion waveform generated by the combustion of the cylinder 10 received from the ion current detection circuit 90 is based on the crank angle. Alternatively, the ion waveform generated by the combustion of the cylinder 10 and other voltage values of noise components detected by the ion current detection circuit 90 of the cylinder 10 may be subtracted.

Further, the ECU 92 receives the ion waveform generated by the combustion of the cylinder 10 received from the ion current detection circuit 90 and the combustion stroke of the noise component detected by the ion current detection circuit 90 of the cylinder 10 other than the cylinder 10 with respect to the cylinder 10. When the angle and shape of the crank 32 are equal to or more than 45 degrees from the top dead center, it is determined that the ion waveform generated by the combustion of the cylinder 10 is affected by alternator noise, and the ion current detection circuit 90 The noise component detected by the ion current detection circuit 90 of the cylinder 10 may be subtracted from the ion waveform generated by the combustion of the cylinder 10 received from the cylinder 10. Further, the end of the ion waveform generated by the combustion of the cylinder 10 is when the angle of the crank 32 with respect to the cylinder 10 in the combustion stroke is advanced 45 degrees or more from the top dead center. Among them, the magnitude of the ion waveform of the cylinder in the combustion stroke may be 0.2 V or less.

10: Cylinder
20: Cylinder
30: Piston
32: Crank
34: Crankshaft
40: Intake pipe
42: Intake valve
44: Intake cam
46: intake camshaft
50: Injector
60: Exhaust pipe
62: Exhaust valve
64: Exhaust cam
66: Exhaust camshaft
70: Spark plug
80: Ignition coil
82: Primary coil
84: Secondary coil
86: Iron core
88: Igniter
90: Ion current detection circuit
92: ECU
94: Battery

Claims (6)

An internal combustion engine having a plurality of cylinders 10;
A spark plug 70 for igniting a mixture of fuel and air supplied into the cylinder 20 of the cylinder 10,
An ignition coil 80 comprising a primary coil 82, a secondary coil 84 and an iron core 86 for supplying a high voltage to the spark plug 70;
An ion current detection circuit 90 for detecting an ion current generated in the spark plug 70 by combustion of the internal combustion engine,
In the combustion state determination method of the internal combustion engine for determining knock generated in the internal combustion engine from the ion current detected by the ion current detection circuit 90,
Whether or not knocking occurs in the cylinder 10 from the ion current waveform obtained by subtracting the noise component from the alternator generated in the cylinders other than the combustion stroke of the same period from the ion current waveform detected from the cylinder in the combustion stroke of the cylinder 10 A method for determining a combustion state of an internal combustion engine, characterized by: determining. When the waveform of the noise component generated in the cylinders other than the combustion stroke in the same period is equivalent to the time when the magnitude of the ion waveform of the cylinder in the combustion stroke of the cylinder 10 is 0.2 V or less, the ion The combustion control method for an internal combustion engine according to claim 1, wherein the noise component is subtracted from the ion current waveform assuming that a noise component is superimposed on the current waveform. The waveform of the noise component generated in the cylinders other than the combustion stroke in the same period is equivalent to the ion waveform when the crank angle of the cylinder in the combustion stroke of the cylinder 10 is advanced 45 degrees or more from the top dead center. 2. The combustion control method for an internal combustion engine according to claim 1, wherein the noise component is subtracted from the ion current waveform on the assumption that a noise component is superimposed on the ion current waveform. 4. The combustion state of the internal combustion engine according to claim 1, wherein the noise component detected by the ion current detection circuit 90 is detected from a cylinder in the intake or exhaust stroke of the cylinder 10. Judgment method. 5. The noise component detected by the ion current detection circuit 90 is detected from a cylinder disposed in a position adjacent to a cylinder in a combustion stroke of the cylinder 10. A combustion state determination method for an internal combustion engine. 2. The noise component detected by the ion current detection circuit 90 is detected from a cylinder located at a distance from the alternator equal to a distance between a cylinder in a combustion stroke of the cylinder 10 and the alternator. 6. A combustion state determination method for an internal combustion engine according to any one of 1 to 5.

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