JP2003184725A - Misfire detection device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a misfire detection device for an internal combustion engine capable of improving the accuracy and reliability of misfire detection by considering changes of ion current waveforms corresponding to changes of operating conditions of the internal combustion engine. <P>SOLUTION: Thresholds #S1, #S2 for determining the existence of misfire are exchanged (ECU24, from S10 to S24) according to changes of operating conditions of the internal combustion engine, for example, an air-fuel ratio A/F (or engine speed NE). In the case of the engine provided with two spark plugs in a cylinder, output characteristics of a detection circuit connected to each plug are different and one of those is selected and used according to operating conditions. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misfire detection device for an internal combustion engine, which detects a misfire of the internal combustion engine based on an ion current generated by combustion of a mixture.

[0002]

2. Description of the Related Art In a spark ignition type internal combustion engine such as a gasoline engine, a high voltage generated by an ignition coil is applied to a spark plug arranged in each cylinder through a distributor or the like, and a gap between electrodes of the spark plug (gap). )
The air-fuel mixture in each cylinder is ignited by the spark discharge of, and combustion occurs. In such an ignition / combustion stroke of the internal combustion engine, a phenomenon that combustion of the air-fuel mixture is not normally performed, that is, misfire may occur for some reason.

The causes of this misfire are roughly classified into those caused by the fuel system and those caused by the ignition system. The former misfire caused by the fuel system is caused by excessive leanness or enrichment of the air-fuel mixture, and spark discharge occurs between the electrodes of the spark plug, but it is a phenomenon that is not ignited by the air-fuel mixture. . On the other hand, the latter misfire caused by the ignition system is a phenomenon caused by so-called miss spark, in which normal spark discharge does not occur due to smoldering of the spark plug due to adhesion of unburned fuel or the like and abnormality of the ignition circuit.

When the air-fuel mixture normally burns, the air-fuel mixture (more precisely, the combustion gas generated by the combustion of the air-fuel mixture) is ionized (ionized) to generate an ion current. On the other hand, if a misfire occurs and the mixture is not burned,
No ion current is generated because the air-fuel mixture does not ionize.

FIG. 21 shows the waveform of the ion current during misfire and during normal combustion. As shown in the same figure, when the normal combustion is performed, that is, when ions are generated, the ion current waveform rises momentarily and greatly immediately after the discharge between the spark plug electrodes (in the figure, at A1). After that, the current continues to flow according to the amount of generated ions, and eventually returns to a predetermined level. On the other hand, when a misfire has occurred, that is, when no ions are generated, a large instantaneous rise (immediately indicated by A2 in the figure) immediately after the end of the discharge and then immediately returns to a predetermined level.

Therefore, in the past, for example, Japanese Unexamined Patent Publication No. 5-999
As in the technique described in Japanese Patent Publication No. 56, a spark plug, more specifically, its electrode is used as a probe for detecting an ionic current, and an ionic current (current waveform) generated in a combustion process is detected. It is widely practiced to detect misfire of an internal combustion engine by comparing the detected value with a predetermined value.

The above-mentioned A1 and A2 and B1 and B2 shown in the figure are large instantaneous rises caused by induction noise due to electromagnetic induction of the ignition coil.

Further, conventionally, there is known an internal combustion engine in which two ignition plugs are provided in one cylinder (for example, Japanese Patent Laid-Open No. 2001-28943 previously proposed by the applicant). As a misfire detecting device for an internal combustion engine in which two spark plugs are provided in one cylinder as described above, for example, Japanese Patent Laid-Open No. 11-141
There is a technique described in Japanese Patent No. 448. In this technique, an integrator for detecting an ionic current is separately connected to the two spark plugs, and the detected value of the ionic current is integrated over the entire combustion cycle. Then, the integrated values are compared with each other or with a preset value, and if one is extremely small, it is determined that the spark plug connected to the integrator is abnormal, and both are preset. If it is smaller than the specified value, it will be judged as a misfire.

[0009]

It is known that the amount of ions generated by the combustion of air-fuel mixture changes depending on the operating condition. For example, as the air-fuel ratio (A / F) increases, that is, when the ratio of fuel in the air-fuel mixture decreases (becomes lean), the amount of ions generated by combustion decreases, so that FIG. Thus, as the amplitude of the ion current waveform becomes smaller, the generation time becomes shorter.
Therefore, when the air-fuel ratio is large, the detection value (integral value) S is smaller than when it is small. In the figure, the waveform indicated by the thick line is during normal combustion, and the waveform indicated by the thin line is during misfire. Further, v indicates a reference voltage for determining whether or not to execute integration, t1 indicates a mask period (non-integration period) for avoiding the influence of the above-mentioned induction noise, and t2 indicates an integration period.

The ion current waveform also changes depending on the number of revolutions of the internal combustion engine. Specifically, the higher the engine speed, the shorter the exhaust stroke time, that is, the shorter the time the ions stay in the combustion chamber.
As shown in, the generation time of the ion current waveform is shortened. Therefore, when the engine speed is high, the detected value (integral value) S is smaller than when it is low.

As described above, the detected value of the ionic current greatly changes depending on the operating state of the internal combustion engine. However,
In the above-mentioned conventional technology, this point is not taken into consideration, and there is room for improvement in the accuracy and reliability of misfire detection.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems and improve the accuracy and reliability of misfire detection by taking into consideration the change of the ion current waveform according to the change of the operating state of the internal combustion engine. It is an object of the present invention to provide a misfire detection device for an internal combustion engine, which enables the above.

[0013]

In order to solve the above-mentioned problems, according to the present invention, at least one spark plug is arranged in a cylinder of an internal combustion engine mounted in a vehicle, and the spark plug is provided in the cylinder. A voltage is applied to ignite and burn the air-fuel mixture in the internal combustion engine by spark discharge between the electrodes, and an ion current generated by the combustion of the air-fuel mixture is detected by a detection circuit, and the detected value and the In the misfire detection device for an internal combustion engine that detects the presence or absence of misfire of the internal combustion engine by comparing the set threshold values, the threshold value is switched depending on the operating state of the internal combustion engine.

By changing the threshold value for judging the presence or absence of misfire in accordance with the change of the operating state of the internal combustion engine, the misfire can be accurately detected in any operating state, so that the reliability of misfire detection can be improved. Can be improved.

More specifically, when the operating state includes an air-fuel ratio and the air-fuel ratio is larger than a predetermined value, the threshold value is changed to a small value. As configured.

Further, as described in claim 3,
The threshold value is changed to a small value when the operating state includes the engine speed and the engine speed is equal to or higher than a predetermined speed.

As a result, even if the ion current waveform changes according to the change in the operating state of the internal combustion engine, more specifically, even if the detected value becomes small, the misfire can be accurately detected, and the reliability of misfire detection can be improved. The property can be further improved.

Further, as described in claim 4, two spark plugs are arranged in the cylinder, the first detection circuit is connected to the first spark plug, and the second spark plug is connected to the second spark plug. A second detection circuit different from the first detection circuit is connected, and when the operating state is a predetermined operating state, the sum of detection values of the first and second detection circuits and the threshold value are set. It was configured to detect the presence or absence of the misfire by comparing.

Two ignition plugs are arranged in the cylinder, the first detection circuit is connected to the first ignition plug, and the second ignition plug is provided with a second detection circuit different from the first detection circuit. When a detection circuit is connected and the operating state of the internal combustion engine is a predetermined operating state, specifically, when the detected value of the ion current is small, that is, when the air-fuel ratio is a predetermined value or more, or the engine speed is a predetermined value. When the number of revolutions is equal to or higher than the rotation speed, the presence or absence of misfire is detected by comparing the sum of the detection values of the first and second detection circuits with the threshold value. Therefore, the detection value of the ion current is sufficiently large. Since it becomes a value, it is possible to prevent erroneous detection of a misfire due to a decrease in the ion current due to an increase in the air-fuel ratio or the engine speed, thereby further improving the accuracy and reliability of misfire detection. .

According to a fifth aspect of the present invention, a first spark plug and a second spark plug are arranged in a cylinder of an internal combustion engine mounted on a vehicle, and a voltage is applied to each of the spark plugs to cause spark discharge between electrodes. While igniting and burning the air-fuel mixture in the internal combustion engine, the ion current generated by the combustion of the air-fuel mixture is detected by a detection circuit, and the presence or absence of misfire of the internal combustion engine is detected based on the detected value. In a misfire detection device for an internal combustion engine, a first detection circuit is connected to the first spark plug, and a second detection circuit different from the first detection circuit is connected to the second spark plug. At least one of the detection values of the first and second detection circuits is selected according to the operating state of the internal combustion engine, and the presence or absence of the misfire is detected based on the selected detection value.

A first detection circuit is connected to the first spark plug, and a second detection circuit different from the first detection circuit is connected to the second spark plug to set the operating state of the internal combustion engine. Accordingly, at least one of the detection values of the first and second detection circuits is selected, and the presence or absence of the misfire is detected based on the selected detection value, in other words, in response to a change in the operating state of the internal combustion engine. By selecting the most optimal detection circuit for detecting the ion current at that time, the misfire can be accurately detected in any operating state, and the reliability of misfire detection can be improved.

In the sixth aspect of the invention, the operating state is configured to include the air-fuel ratio, and more specifically, the detection circuit is selected according to the change in the air-fuel ratio that greatly affects the generation of ions. Since it did so, the above-mentioned effect can be acquired more reliably.

Further, in claim 7, the output characteristics of the first and second detection circuits are set so that one of the detection values of the first and second detection circuits becomes larger than the other detection value. And the presence or absence of the misfire is detected based on the detection value of the detection circuit set so that the detection value becomes large when the air-fuel ratio is larger than a predetermined value.

As a result, it is possible to prevent erroneous detection of a misfire due to a decrease in the ion current due to an increase in the air-fuel ratio, and thus to further improve the accuracy and reliability of misfire detection.

Further, in the present invention, the operating state is configured to include the engine speed. Specifically, in accordance with a change in the engine speed that greatly affects the generation time of the ion current waveform. Since I chose the detection circuit,
The above effect can be obtained more reliably.

In the ninth aspect, the output characteristics of the first and second detection circuits are set so that one of the detection values of the first and second detection circuits becomes larger than the other detection value. And the presence or absence of the misfire is detected based on the detection value of the detection circuit set so that the detection value becomes large when the engine rotation speed is equal to or higher than the predetermined rotation speed.

This makes it possible to prevent erroneous detection of a misfire due to a decrease in the ion current due to an increase in the engine speed, thereby further improving the accuracy and reliability of misfire detection. .

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION A misfire detecting device for an internal combustion engine according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic view showing an overall misfire detecting device for an internal combustion engine according to this embodiment.

The structure will be described below with reference to FIG. 1. An internal combustion engine (only a part is shown; specifically, a 4-cylinder gasoline engine) 1 mounted on a vehicle (not shown) 1
In each cylinder 12 of 0, the combustion chamber 16 near the exhaust valve 14
The exhaust side spark plug 18E is arranged at a position facing the combustion chamber 16, and the intake side spark plug 18I is arranged at a position facing the combustion chamber 16 near the intake valve 20. That is, the internal combustion engine 1
Reference numeral 0 is a two-plug ignition type internal combustion engine having a total of two spark plugs.

The exhaust side spark plug 18E and the intake side spark plug 18I are both plug hole type ignition coils 22.
It is connected to an ECU (electronic control unit) 24 via (described later).

The ECU 24 is composed of a microcomputer provided with ROM, RAM and the like. The ECU 24 is provided with a crank angle sensor s which is arranged near a crank shaft or a cam shaft (neither is shown) and which outputs a signal according to a TDC position of each cylinder and a crank angle obtained by subdividing the TDC position.
1, the output of an absolute pressure sensor s2 that outputs a signal according to the intake pipe absolute pressure (PBA), an air-fuel ratio sensor s3 (UEGO sensor), and a sensor group (not shown) such as a water temperature sensor and an intake temperature sensor are input.

Further, the ECU 24 calculates the engine speed NE based on the input output of the crank angle sensor s1. Also, based on the various input signals described above, the ignition timing θ
ig is determined to ignite the exhaust side spark plug 18E and the intake side spark plug 18I, and the desired air-fuel ratio (A
/ F), and determines the combustion injection amount to drive the injector (combustion injection valve) 26. Further, as will be described later, the presence or absence of misfire of the internal combustion engine 10 is detected (determined).

Here, the plug-hole type ignition coil 22 will be described in detail. Fig. 2 shows a plug-hole type ignition coil 2
2 is a side sectional view of the plug hole type coil 22a connected to the exhaust side ignition plug 18E. FIG.

As shown in the figure, the plug hole type coil 22a is inserted into a cylindrical plug hole 28 bored in the cylinder head of the internal combustion engine 10 while connecting the exhaust side ignition plug 18E to the tip thereof. The electrodes of the connected exhaust side spark plug 18E, specifically, the center electrode 18Ea and the ground electrode 18Eb are housed so as to be arranged at a position facing the combustion chamber 16.

Further, the plug-hole type ignition coil 22a
Is a case 30, an ignition coil unit including a primary coil 32a and a secondary coil 32b, and an ion current detection circuit for detecting an ion current (hereinafter simply referred to as "detection circuit").
34) and an igniter 36 that sends out a signal for supplying a high voltage to the primary coil 32a.

Further, the plug-hole type ignition coil 22a
A connector 40 including a plurality of connector pins 38 is formed on the upper part of the. One end of the connector pin 38 is connected to the detection circuit 34 and the igniter 36, and the other end thereof is connected to the ECU (not shown in the figure) 24 and a voltage power source (vehicle-mounted power source. Not shown in the figure). ) Is connected with.

The voltage power supply is boosted to a high voltage by the ignition coil section through the igniter 36, and then the exhaust side ignition plug 18E is connected through the conductive shaft 42 and the conductive spring 44.
To ignite the exhaust side spark plug 18E. Further, the ionic current generated by the ignition / combustion of the air-fuel mixture is the exhaust side spark plug 18E (more specifically, the center electrode 18Ea and the ground electrode 18Eb), the conductive spring 4
4, the conductive shaft 42, and the secondary side coil 32b, and is detected in the detection circuit 34.

FIG. 3 is a circuit diagram composed of an exhaust side ignition plug 18E and a plug hole type ignition coil 22 including a detection circuit 34E.

Before explaining FIG. 3, the operation of the detection circuit 34 will be outlined with reference to FIG. FIG. 4 shows the detection circuit 3
FIG. 4 is a block diagram showing 4 as a block. As shown in the figure, the detection circuit 34 includes an ion current detection unit 34a, a waveform conversion unit 34b, an integration unit 34c, and an integration period setting unit 34.
d, integration start delay unit 34e, integration ON / OFF (ON.
An off) unit 34f and an integrated value reset unit 34g.

The operation will be outlined below. The ion current waveform detected by the ion current detector 34a is output to the waveform converter 34b, where the sign inversion of the waveform and the pressure reduction process are performed.

The sign-inverted and low-voltage ionic current waveform in the waveform converting section 34b is input to the integrating section 34c, where integration processing is performed to detect the ionic current as an integrated value. In other words, an output signal proportional to time integration is obtained.

Further, the sign-inverted and low-voltage ion current waveforms in the waveform conversion section 34b are also input to the integration period width setting section 34d, and output through a low-pass filter inside thereof in a frequency band other than the ion current ( Noise) etc. is attenuated, and an integration period, specifically, a period during which integration processing is performed by the integration unit 34c is set (determined) according to the generation period of the ion current.

Further, the start timing of the integration processing period set by the integration period setting unit 34d is delayed (masked) by the integration start delay unit 34e until the time when it is not affected by the above-mentioned induction noise. These integration period setting section 34
d and the integration ON / OF based on the integration processing period and the integration start time determined by the integration start delay unit 34e.
By operating the F section 34f, the input of the ion current waveform to the integrating section 34c is turned on / off, and the integration processing in the integrating section 34c is performed for a desired period, specifically, a period corresponding to the generation period of the ion current. Limit to only.

The integrated output accumulated by the integrating section 34c over the above-described integration period is the integrated value resetting section 34g.
In, the reset is performed every time the energizing pulse is transmitted to the ignition coil.

Returning to FIG. 3, the above description will be made in detail. From the voltage power supply 46, a connector pin (not shown) 38, etc.
The current flowing through the secondary coil 32a is energized / interrupted by the operation of the igniter 36 according to the ignition signal (ignition command) from the ECU 24.

When the current flowing through the primary coil 32a is cut off, a negative high voltage is generated in the secondary coil 32b, and a discharge current flows. Specifically, the exhaust side spark plug 18E (the center electrode 18Ea and the ground electrode 1
8Eb)-(conductive spring 44, conductive shaft 42 (neither shown in the figure))-secondary coil 32b-capacitor 34a1 (or Zener diode 34b2)-
Flowing with the diode 34a3, spark discharge is generated between the electrodes of the exhaust side spark plug 18 (between the center electrode 18Ea and the ground electrode 18Eb) to ignite and burn the air-fuel mixture. Also,
The discharge current charges the capacitor 34a1 to the polarity shown. The charged capacitor 34a1 functions as a current detection power supply having a bias voltage for detecting an ion current.

When the air-fuel mixture is burned by the spark discharge of the exhaust side spark plug 18E, the air-fuel mixture (more accurately, the combustion gas generated by the combustion of the air-fuel mixture) is ionized to generate ions.
When the ions move due to the action of the bias voltage of the capacitor 34a1, in other words, the ions intervene between the electrodes of the spark plug 24 and the electrical resistance therebetween decreases, so that the secondary coil of the capacitor 34a1-2. 32b- (conductive shaft 42, conductive spring 44) -Ion current flowing through the exhaust side ignition plug 18E is generated. At this time, the detection resistance 34a is dragged by the generated ion current.
The voltage value at 4 changes. Ion current detector 34a
Outputs the change in the voltage value, that is, the ion current waveform, to the waveform conversion unit 34b.

FIG. 5 is a time chart showing the output (detection current waveform or pulse) at each point of the circuit shown in FIG. Note that FIG. 5 is a time chart when normal combustion is performed, and FIG. 6 shows that at the time of misfire. Also, in FIGS. 5 and 6, a, b, c, ..., H
Shows the output at the locations indicated by a, b, c, ..., H in FIG.

The ion current waveform detected by the ion current detector 34a, that is, the current waveform at the portion indicated by a in FIG. 3, is input to the waveform converter 34b as described above, and is subjected to sign conversion and low pressure processing. , And is input to the integration unit 34c.

Further, the ion current waveform that has been sign-converted and reduced in voltage in the waveform conversion section 34b is also input to the integration period setting section 34d, and the low-pass filter therein attenuates frequency components other than the ion current. . Further, the output thereof, specifically, the current waveform at the portion indicated by b in FIG. 3 (indicated by b in FIGS. 5 and 6) is input to the minus side of the integration period setting comparator 34d1.

Also, the integration period setting comparator 34d
The first reference voltage (denoted by c in FIGS. 5 and 6) is always input to the positive side of 1, and these are compared and the output (ion current waveform) after passing through the low-pass filter is used. Is high, the output of the integration period setting comparator 34d1, that is, the output pulse (shown as d in FIGS. 5 and 6) at the portion indicated by d in FIG. 3 is Lo.
Let w.

Here, the integration period setting comparator 34
The Low pulse output period of d1 becomes the integration period in the integration unit 34c, that is, the ion current detection period for detecting misfire. For this reason, the integration period naturally becomes zero at the time of misfire.

It should be noted that the first portion shown as c in FIGS.
The reference voltage v1 can be set to an appropriate value by changing the resistance values of the first reference voltage setting resistors 34d2 and 34d3. In other words, the first reference voltage setting resistor 3
The integration period can be adjusted by setting 4d2 and 34d3.

The output pulse of the integration period setting unit 34d is further input to the integration start delay unit 34e, and the integration period setting unit 34d is charged and discharged by the integration start delay capacitor 34e1.
By delaying the inversion timing of the output pulse of d (the timing at which the Low pulse is output), the current waveform shown by e in FIGS. 5 and 6 is obtained at the location indicated by e in FIG.

The current waveform thus obtained is input to the plus side of the integration start delay comparator 34e2, and the second reference voltage (denoted by f in FIGS. 5 and 6) v2 is input to the minus side thereof. To do. Then, an output pulse corresponding to the comparison result, that is, an output pulse in g of FIG. 3 (indicated by g in FIGS. 5 and 6) is obtained.

As is apparent from FIGS. 5 and 6, the output pulse finally obtained through the integration start delay unit 34e has its inversion timing delayed from the ion current generation start timing by a predetermined period. In other words, the mask period t1 in which the integration process is not executed is set to avoid the detection of the above-mentioned induced noise, and the final integration period t2 is set (t1 and t2 are not set at the time of misfire). (It becomes zero)). Based on the output pulse whose inversion timing is delayed, the FET of the integration ON / OFF section 34f
The field effect transistor 34f1 is turned on / off to turn on / off the input of the ion current waveform output from the waveform converter 34b to the integrator 34c.

The second portion indicated by f in FIGS. 5 and 6 is used.
The reference voltage v2 can be set to an appropriate value by changing the resistance values of the second reference voltage setting resistors 34e3 and 34e4. Therefore, the mask period t1 can be set by setting the second reference voltage setting resistors 34e3 and 34e4. It can be adjusted. In other words, the final integration period t2 can be adjusted. As is apparent from the above, the first reference voltage v1 and the second reference voltage v2 are reference voltages for determining the integration period, more specifically, the final integration period t2, and have been described in the related art. Equivalent to v.

The integrator 34c outputs an output signal proportional to the time integration of the ion current input as described above, specifically, the voltage value of the integrating capacitor 34c1 (indicated by h in FIGS. 5 and 6). Is output to the ECU 24 as the detected value S of the ion current. The ECU 24 detects (determines) the presence or absence of misfire of the internal combustion engine based on the detected value (voltage value. Integrated value) S, specifically by comparing with a threshold value #S. In this specification, all values with # are E
The setting values preset and stored in the ROM or the like of the CU 24 are shown.

The increase in the output indicated by h at the time of misfire shown in FIG. 6 is due to the output amplifying action of the operational amplifier. Therefore, it is preferable that the slope of this output increase is as small as possible, that is, it is preferable to set the amplification factor to a small value, but if it is set too small, the detection sensitivity of the ion current will decrease, so this point must be kept in mind. . It goes without saying that the amplification factor can be adjusted by appropriately setting the integration capacitor 34c1 and the amplification factor setting resistor 34c2.

The voltage value of the integrating capacitor 34c1 is reset by turning on the switch 34c3 and discharging the integrating capacitor 34c1 by a signal from the integral value resetting unit 34g sent every time the energizing pulse is transmitted. To be done.

Next, referring to FIG. 7, the intake side spark plug 1
The plug-hole type ignition coil 22b to which 8I is connected will be described. The figure shows a plug-hole type ignition coil 22.
It is a sectional side view of b. The difference from the plug-hole ignition coil 22a shown in FIG. 2 will be mainly described. The plug-hole ignition coil 22b shown in FIG. 7 does not include the detection circuit 34. FIG. 8 shows the intake side spark plug 18I.
The circuit diagram which consists of and the plug-hole type ignition coil 22b is shown. The other structure is the same as that of the plug-hole type ignition coil 22a shown in FIG.

Therefore, in this embodiment, the ion current is detected by using the exhaust side spark plug 18E.

As described above, of the two spark plugs, the one to which the detection circuit 34 is connected is the one spark plug (exhaust side spark plug 18E). Therefore, in this embodiment, the cost is reduced. The effect can be obtained.

Next, referring to the flow chart of FIG.
The operation of detecting the presence or absence of misfire in the ECU 24 will be described. The illustrated program is executed for each predetermined crank angle.

First, in S10, the detected value S of the ion current and the air-fuel ratio (detection value detected by the air-fuel ratio sensor s3) A / F are read, and in S12 the air-fuel ratio A / F.
Is greater than or equal to a predetermined value # A / F (for example, 23) or not.
The air-fuel ratio A / F may be a target value calculated by the ECU 24.

When the result in S12 is negative and it is determined that the air-fuel ratio A / F is smaller than the predetermined value # A / F, that is, when it is determined that the amount of ions generated by combustion is large, then the routine proceeds to S14. Then, it is determined whether or not the detected value S of the ionic current is greater than or equal to the first threshold value # S1.

When the determination is affirmative and it is determined that a sufficient ion current is generated, the routine proceeds to S16, where it is determined to be combustion, and when the determination is negative, the routine proceeds to S18, where it is determined to be misfire.

On the other hand, if the result in S12 is affirmative and it is determined that the amount of ions generated by combustion is small, then S20
And the detected value S of the ion current is the second threshold value # S2.
It is determined whether or not the above.

Here, the second threshold value # S2 is set smaller than the first threshold value # S1. Air-fuel ratio A / F
As described above, the ion generation amount decreases as the value becomes larger, and the detected value of the ion current decreases despite the normal combustion (as shown in FIG. 10, the air-fuel ratio A / F is a predetermined value). # A / F (23) or more (solid line) and less than (dashed line) the ion current waveform and the detected value of the ion current are shown in comparison). Therefore, in this embodiment, as shown in FIG. 10, the threshold value (first threshold value # S1) when the air-fuel ratio A / F is less than a predetermined value and the air-fuel ratio A / F Is set to a value equal to or larger than a predetermined value (a second threshold value # S2 smaller than the first threshold value # S1), and the threshold value is changed according to the air-fuel ratio A / F.

Returning to the explanation of the flow chart of FIG. 9, S
When the result in 20 is affirmative, the routine proceeds to S22, where it is determined that combustion is normal, and when the result is negative, the routine proceeds to S24 where it is determined that there is a misfire.

As described above, in this embodiment,
Since the threshold for judging the presence or absence of misfire is changed depending on the change of the operating state of the internal combustion engine, more specifically, the change of the air-fuel ratio, the ion current waveform changes according to the operating state. Even if the detected value becomes small, it is possible to prevent the misjudgment of misfire. Therefore, it is possible to accurately detect the presence or absence of misfire in any operating state, and thus improve the reliability of misfire detection.

Next, a misfire detecting device for an internal combustion engine according to a second embodiment of the present invention will be described.

The difference from the first embodiment is that the threshold value for judging the presence or absence of misfire is changed depending on the change of the engine speed NE.

Referring to FIG. 11, first, S10
At 0, the detected value S of the ion current and the engine speed NE
Is read and it is determined in S102 whether the engine speed NE is equal to or higher than a predetermined speed #NE (eg, 4000 rpm).

When it is denied here and it is judged that the engine speed NE is less than the predetermined speed #NE, that is, when it is judged that the ion current waveform is generated for a time sufficient to detect the ion current, Next, in S104, it is determined whether the detected value S of the ion current is equal to or larger than the third threshold value # S3.

When the result in S104 is affirmative and it is determined that a sufficient ion current is generated, the routine proceeds to S106, in which it is determined that combustion, and when it is not, it is determined in S108 that misfiring has occurred.

On the other hand, when the result in S102 is affirmative and it is determined that the ion current waveform does not occur for a sufficient time, the process proceeds to S110, in which it is determined whether the detected value S of the ion current is the fourth threshold value # S4 or more. To determine.

Here, the fourth threshold value # S4 is set smaller than the third threshold value # S3. Engine speed N
As described above, when the E becomes large, the generation time of the ion current waveform becomes short, and the detected value of the ion current decreases despite the normal combustion (the engine speed NE is shown in FIG. 12). The ion current waveform and the detected value of the ion current when the value is equal to or more than a predetermined value #NE (4000 rpm) (broken line) and when it is less than that (solid line) are shown in comparison).
Therefore, in the second embodiment, as shown in FIG. 12, the threshold value (third threshold value # S3) when the engine speed NE is less than the predetermined value and the engine speed NE Is greater than or equal to a predetermined value (a fourth threshold value # S4 smaller than the third threshold value # S3), and the engine speed NE is set.
I decided to change it according to.

Returning to the explanation of the flow chart of FIG.
When the result in S110 is affirmative, the routine proceeds to S112, where it is determined that combustion is normal, and when the result is negative, the routine proceeds to S114, where it is determined that a misfire has occurred.

As described above, in the second embodiment, the threshold value for judging the presence or absence of misfire in accordance with the change in the operating state of the internal combustion engine, more specifically, the change in the engine speed. Since it is configured to change over, it is possible to accurately detect the presence or absence of a misfire in any operating state, and thus improve the reliability of misfire detection.

The rest of the configuration is the same as that of the above-mentioned embodiment, so the explanation is omitted. Further, the configuration in which the threshold value is changed depending on the air-fuel ratio described in the above embodiment may be added to this embodiment. For example, when the air-fuel ratio is equal to or higher than the predetermined value and the engine speed is also equal to or higher than the predetermined speed, a threshold value smaller than the threshold values # S2 and # S4 is selected. The presence or absence of misfire can be detected more accurately.

Next, a misfire detecting device for an internal combustion engine according to a third embodiment of the present invention will be described.

Focusing on the difference from the first and second embodiments described above, in this embodiment, as shown in FIG. 13, a plug connected to the intake side ignition plug 18I. The hall-type ignition coil is the same as that connected to the exhaust-side ignition plug 18E, that is, the plug-hole-type ignition coil 22 also provided with the detection circuit 34 on the intake side.
a. Hereinafter, the detection circuit 34 in the plug-hole type ignition coil 22a connected to the exhaust side ignition plug 18E is referred to as an exhaust side detection circuit 34E, and the intake side thereof is referred to as an intake side detection circuit 34I. Further, the detection value of the exhaust side detection circuit 34E is SE and the detection value of the intake side detection circuit 34I is SI.

A further characteristic feature of this embodiment is that the detected value SE of the exhaust side detection circuit 34E is normally detected.
The presence or absence of misfire is detected based on the above, and when the abnormality of at least one of the exhaust side spark plug 18E and the exhaust side detection circuit 34E is confirmed, the intake side detection circuit 34
The presence or absence of the misfire is detected based on the detected value SI of I.

Explaining with reference to the flow chart of FIG. 14, in S200, it is determined by an appropriate method whether or not there is an abnormality in at least one of the exhaust side spark plug 18E and the exhaust side detection circuit 34E. For example, the output of the integrator 34c is read at a timing when the ion current should not be generated (after the exhaust stroke is finished and before the next combustion (explosion) stroke is started), and whether or not a leak current is generated, etc. Judge by checking.

When the result is negative, the routine proceeds to S202, where the detection value SE of the exhaust side detection circuit 34E is read, and S20
In step 4, it is determined whether the exhaust side detected value SE is greater than or equal to the threshold value #S. When the determination is affirmative and it is determined that sufficient ion current is generated, the routine proceeds to S206, where it is determined to be combustion, and when the determination is negative, it is determined to be misfire in S208.

On the other hand, when the result in S200 is affirmative, S21
In step S212, the detection value SI of the intake side detection circuit 34I is read, and in step S212, the intake side detection value SI is the threshold value #S.
It is determined whether or not the above. If the result is affirmative, it is determined in S214 that combustion has occurred, and if the result is negative, it is determined that there is misfire in S216.

As described above, the intake side detection circuit 34I is connected to the intake side ignition plug 18I, and the exhaust side ignition plug 18E and the exhaust side detection circuit 34E connected thereto are connected.
When at least one of them is abnormal, the presence or absence of misfire is alternatively detected based on the detection value SI of the intake side detection circuit 34I, so that the accuracy and reliability of misfire detection can be further improved. it can.

It should be noted that a structure for changing the threshold value according to the change in the operating state (air-fuel ratio A / F, engine speed NE) of the internal combustion engine described in the above-described embodiment should be added to this embodiment. You can For example, S202 and S2
After 10 the operating condition (air-fuel ratio A / F, engine speed N
A step for determining the size of E) is added, and the air-fuel ratio A /
When F is equal to or higher than a predetermined value, or when the engine speed NE is higher than or equal to a predetermined speed, a threshold value smaller than that in the other cases may be selected.

Further, normally, the presence or absence of misfire is detected based on the detection value SI of the intake side detection circuit 34I, and when it is abnormal (when the ion current cannot be accurately detected due to disconnection, etc.), the detection by the exhaust side detection circuit 34E is performed. It may be based on the value SI.

Next, a misfire detecting device for an internal combustion engine according to a fourth embodiment of the present invention will be described.

In the fourth embodiment, the presence or absence of misfire is detected based on each of the detection value SE of the exhaust side detection circuit 34E and the detection value SI of the intake side detection circuit 34I,
It is determined that a misfire has occurred only when both are detected as misfire, and in either case, an abnormality in the spark plug on the side where misfire is detected, specifically, smoldering of the spark plug or disconnection of the ignition circuit, etc. It is configured to judge that normal ignition (ignition) cannot be performed due to the above.

This will be described with reference to the flow chart of FIG. 15. In S300, it is determined which of the misfire detection results is based on the detection value SE of the exhaust side detection circuit 34E.

When it is determined in S300 that combustion (no misfire) is present, the process proceeds to S302, in which it is determined that combustion has occurred based on the detection value SI of the intake side detection circuit 34I, and it is determined that combustion has occurred. At this time, the routine proceeds to S304, where it is judged that the internal combustion engine 10 (more specifically, its cylinder 12) is in the combustion state, and both the exhaust side ignition plug 18E and the intake side ignition plug 18I are normal.

On the other hand, if it is determined in S302 that a misfire has occurred, the process proceeds to S306, in which it is determined that the internal combustion engine 10 is in a combustion state and the intake side spark plug 18I is abnormal. That is, the generation of ions is not confirmed near the intake side spark plug 18I, whereas the generation of ions is confirmed near the exhaust side spark plug 18E, so that combustion by the intake side spark plug 18I is not performed. If so, the intake side spark plug 18I is not ignited normally,
It can be determined that the spark plug is smoldering or that the ignition circuit has an abnormality such as a disconnection. On the other hand,
Since the air-fuel mixture is burned by the ignition of the exhaust side spark plug 18E, the presence / absence of misfire can be determined to be no misfire, that is, combustion.

When it is judged in S300 that there is a misfire, S30
8, the detection value S of the intake side detection circuit 34I is the same as S302.
It is determined which of the detection results of the presence or absence of misfire is based on I. When it is determined that combustion is occurring, the process proceeds to S310, and for the same reason as in S306, it is determined that the internal combustion engine 10 is in a combustion state and the exhaust side spark plug 18E is abnormal. Further, when it is determined that there is a misfire in S308, S312
Proceed to and judge that there was a misfire and end.

As described above, in the fourth embodiment, the presence or absence of misfire is detected based on each of the detected value SE of the exhaust side detection circuit 34E and the detected value SI of the intake side detection circuit 34I, and both are detected. Only when the misfire is detected, it is determined that the misfire has occurred, and when it is either one, it is judged that it is an abnormality of the spark plug on the side where the misfire is detected. It is possible to make a judgment, and further improve the accuracy and reliability of misfire detection.

Further, before the complete misfire state (abnormality such as two ignition plugs smoldering together or two ignition circuits breaking together) occurs, the driver replaces the ignition plugs. It is possible to obtain a secondary effect that it becomes possible to promote measures such as taking action.

In order to improve accuracy, it is possible to judge that the spark plug on the side where the misfire is detected is abnormal only when the difference in the detection result occurs a plurality of times in succession.

Next, a misfire detecting device for an internal combustion engine according to a fifth embodiment of the present invention will be described.

In the fifth embodiment, the presence or absence of misfire is detected by comparing the sum of the detection value SI of the intake side detection circuit 34I and the detection value SE of the exhaust side detection circuit 34E with the threshold value #S. I decided to do it.

Explaining with reference to the flow chart of FIG. 16, first, in S400, the detection value SE of the exhaust side detection circuit 34E and the detection value SI of the intake side detection circuit 34I are read, and the sum thereof is a threshold value. #S
It is determined whether or not the above.

If the result in S402 is affirmative, then S4
If NO in step 04, it is determined that combustion has occurred. If NO, step S406 is performed and it is determined that misfire has occurred.

As described above, since the presence or absence of misfire is detected based on the sum of the detected value SI of the intake side detection circuit 34I and the detected value SE of the exhaust side detection circuit 34E, the change in the operating state of the internal combustion engine is performed. Even if the amount of generated ions is reduced or the generation time of the ion current waveform is shortened, it is possible to obtain a sufficient detection value sufficient to determine the presence or absence of misfire.
Therefore, it is possible to accurately detect the presence or absence of misfire in any operating condition.

Incidentally, when the operating state of the internal combustion engine 10 is a predetermined operating state, specifically, when the detected value of the ion current is small, that is, when the air-fuel ratio A / F is a predetermined value or more, The detected value SI of the intake side detection circuit 34I and the detected value S of the exhaust side detection circuit 34E only when the number of revolutions is equal to or higher than the predetermined number of revolutions.
The presence / absence of misfire may be detected based on the sum of E, and the other cases may detect the presence / absence of misfire based on only one detection result.

Next, a misfire detecting device for an internal combustion engine according to a sixth embodiment of the present invention will be described.

The characteristic feature of the sixth embodiment is that the output of the intake side detection circuit 34I changes because the amount of ions generated with the combustion of the air-fuel mixture changes depending on the operating state as described above. This is because the characteristics and the output characteristics of the exhaust side detection circuit 34E are made different, and the optimum detection circuit is selected according to the operating state.

More specifically, since the detected value decreases as the air-fuel ratio (A / F) increases, either one of the intake side detection circuit 34I and the exhaust side detection circuit 34 is used in this embodiment. 1 in the intake side detection circuit 34I.
7 and FIG. 18, a first reference voltage v1 and a second reference voltage v2 that determine the final integration period t2.
Is set appropriately to extend the integration period t2 (indicated by a broken line in both figures), and further, to increase the amplification factor of the operational amplifier described above to detect the output characteristic of the intake side detection circuit 34I. The output is set to increase in comparison with that of the circuit 34E. Note that the first reference voltage v1 is the first reference voltage setting resistors 34d2 and 3
4d3, the second reference voltage v2 is the resistance value of the second reference voltage setting resistors 34e3 and 34e4, and the amplification factor is the integration capacitor 34c1 and the amplification factor setting resistor 3.
As described above, the value can be adjusted by appropriately setting 4c2.

The selection operation of the detection circuit and the detection operation of the presence or absence of misfire will be described with reference to the flow chart of FIG. 19. First, in S500, the air-fuel ratio A / F is a predetermined value #A.
/ F or more is judged.

If the answer is NO here, the program proceeds to S502 where the detection value SE of the exhaust side detection circuit 34E is read and S50
In step 4, it is determined whether the exhaust side detected value SE is greater than or equal to the threshold value #S. When the determination is affirmative and it is determined that a sufficient ion current is generated, the routine proceeds to S506, where it is determined to be combustion, and when the determination is negative, it is determined to be misfire in S508.

On the other hand, when the result in S500 is affirmative, S51
In step S512, the detection value SI of the intake side detection circuit 34I is read, and in step S512, the intake side detection value SI is the threshold value #S.
It is determined whether or not the above. If the result is affirmative, it is determined in S514 that combustion has occurred, and if the result is negative, it is determined that there is misfire in S516.

As described above, in the sixth embodiment, the output characteristic of the intake side detection circuit 34I is set in the output increasing direction as compared with that of the exhaust side detection circuit 34E, in other words, the air-fuel ratio is large. A detection circuit used when the air-fuel ratio is small and a detection circuit used when the air-fuel ratio is small are provided.When the air-fuel ratio is above a predetermined value, that is, when the amount of generated ions decreases, By detecting the presence or absence of misfire based on the detection value SI of the detection circuit 34I used for the above, it is possible to prevent a decrease in ion current due to an increase in the air-fuel ratio from being mistakenly detected as misfire. The accuracy and reliability of misfire detection can be further improved.

In the sixth embodiment, the threshold value may be changed depending on the engine speed. For example, a step of determining the magnitude of the engine speed NE is added after S502 and S510, and when the engine speed NE is equal to or higher than a predetermined speed, a threshold value smaller than that when it is not selected is selected. Is also good.

Next, a misfire detecting device for an internal combustion engine according to a seventh embodiment of the present invention will be described.

The difference from the sixth embodiment is that in this embodiment, the detection circuit is selected according to the engine speed NE instead of the air-fuel ratio A / F. is there.

Specifically, as the engine speed increases, the exhaust stroke time becomes shorter, the ion current waveform generation time becomes shorter, and the ion current detection value becomes smaller. Intake side detection circuit 3 as in the embodiment
4I or the exhaust side detection circuit 34, in this embodiment, the output characteristic of the intake side detection circuit 34I is set in the output increasing direction as compared with that of the exhaust side detection circuit 34E.

The selection operation of the detection circuit and the detection operation of the presence or absence of misfire will be described with reference to the flow chart of FIG. 20. First, in S600, it is determined whether the engine speed NE is equal to or higher than a predetermined speed #NE.

When the determination is negative, the routine proceeds to S602, where the detection value SE of the exhaust side detection circuit 34E is read, and S60
In step 4, it is determined whether the exhaust side detected value SE is greater than or equal to the threshold value #S. When the determination is affirmative and it is determined that a sufficient ion current is generated, the routine proceeds to S606, where it is determined that combustion, and when the determination is negative, it is determined at S608 that there is a misfire.

On the other hand, when the result in S600 is affirmative, S61
0, the detection value SI of the intake side detection circuit 34I is read, and the process proceeds to S612, where the intake side detection value SI is the threshold value #S.
It is determined whether or not the above. If the result is affirmative, it is determined in S614 that combustion has occurred, and if the result is negative, it is determined that there is misfire in S616.

As described above, in the seventh embodiment, the output characteristic of the intake side detection circuit 34I is set in the output increasing direction as compared with that of the exhaust side detection circuit 34E, in other words, the engine speed is changed. A detection circuit used at high rotation speed and a detection circuit used at low rotation speed are provided, and when the engine rotation speed is equal to or higher than a predetermined rotation speed, that is, when the detected value of the ion current becomes small, the intake side detection circuit ( By detecting the presence or absence of misfire based on the detection value SI of the detection circuit 34I used at the time of high rotation, it is possible to prevent the decrease of the ion current due to the increase of the engine speed from being mistakenly detected as misfire. Therefore, the accuracy and reliability of misfire detection can be further improved.

Incidentally, in the seventh embodiment, a configuration may be added in which the threshold value is changed depending on the air-fuel ratio described in the sixth embodiment. For example, S602
And a step of determining the magnitude of the air-fuel ratio A / F after S610, and when the air-fuel ratio A / F is equal to or more than a predetermined value,
It is possible to select a threshold value that is smaller than when there is no such situation.

As described above, in the misfire detection device for an internal combustion engine according to the first to seventh embodiments of the present invention,
At least one spark plug (exhaust side spark plug 18E) is arranged in a cylinder 12 of an internal combustion engine 10 mounted on a vehicle, and a voltage is applied to the (exhaust side) spark plug 18E to apply electrodes (center electrode 18Ea, ground electrode). 18Eb), the air-fuel mixture in the internal combustion engine 10 is ignited and burned by the spark discharge, and the detection circuit 34 detects the ion current generated by the combustion of the air-fuel mixture, and the detected value S
In a misfire detection device for an internal combustion engine, which detects the presence or absence of a misfire of the internal combustion engine 10 by comparing the threshold value #S with a preset threshold value #S, Configured to change.

More specifically, the operating state is the air-fuel ratio A.
/ F, the air-fuel ratio A / F has a predetermined value # A / F.
Is larger than the above, the threshold value is set to a small value (# S2).
(ECU 24, S10 to S24).

Further, the operating state is the engine speed NE.
And the engine speed NE is equal to the predetermined speed #NE.
In the above case, the threshold value is changed to a small value (# S4) (ECU 24, S100 to S114).

Further, two spark plugs (exhaust side spark plug 18E and intake side spark plug 18 are provided in the cylinder 12.
I) is arranged, and the first spark plug (exhaust side spark plug 1
8E) is connected to the first detection circuit 34E and
A second detection circuit 34I different from the first detection circuit 34E is connected to the ignition plug (intake-side spark plug 18I), and the operating state is a predetermined operating state (specifically, the air-fuel ratio A / F). Is equal to or greater than a predetermined value # A / F, or engine speed NE
Is equal to or higher than a predetermined rotation speed #NE), the first and second
Sum of detection values SE and SI of the detection circuits 34E and 34I (S
The presence or absence of the misfire is detected by comparing (E + SI) with the threshold value (ECU 24, S400 to S4).
06).

Further, a first spark plug (exhaust side spark plug 18E) is attached to the cylinder 12 of the internal combustion engine 10 mounted on the vehicle.
And a second spark plug (intake-side spark plug 18I) are arranged, and a voltage is applied to each of them and an electrode (center electrode 18E)
a, 18Ia, ground electrodes 18Eb, 18Ib) ignites and burns the air-fuel mixture in the internal combustion engine 10 by the spark discharge, and the detection circuit 34 detects the ion current generated by the combustion of the air-fuel mixture. , Its detected value S
In the misfire detection device for an internal combustion engine that detects the presence or absence of misfire of the internal combustion engine 10 based on the above, while connecting a first detection circuit (exhaust side detection circuit 34E) to the first spark plug, A second detection circuit (intake-side detection circuit 34I) different from the first detection circuit is connected to the spark plug, and the first and second detection circuits 34E, 34E, according to the operating state of the internal combustion engine 10. At least one of the detection values SE and SI of 34I is selected, and the presence or absence of the misfire is detected based on the selected detection value (ECU 24, S500 to S516, S600 to S616).

Further, the operating state is configured to include the air-fuel ratio A / F, and more specifically, the detection circuit is selected in accordance with the change in the air-fuel ratio that greatly affects the generation of ions ( ECU 24, S500 to S516).

In addition, the first and second detection circuits 34
The output characteristics of the first and second detection circuits are set such that one of the detected values SE and SI of E and 34I is larger than the other detected value, and the air-fuel ratio A / F is set to a predetermined value #. When it is larger than A / F, the presence or absence of the misfire is detected based on the detection value SI of the detection circuit (intake side detection circuit 34I) set so that the detection value becomes large (EC
U24, S500 to S516).

Further, the operating state is constituted so as to include the engine speed NE, specifically, the detection circuit is selected in accordance with the change of the engine speed which greatly affects the generation time of the ion current waveform ( ECU 24, S600 to S61
6) I did. .

In addition, the first and second detection circuits 34
The output characteristics of the first and second detection circuits 34E and 34 are set so that one of the detected values SE and SI of E and 34I is larger than the other detected value, and the engine speed NE is predetermined. When the engine speed is equal to or higher than the rotational speed #NE, the presence or absence of the misfire is detected based on the detection value SI of the detection circuit (intake side detection circuit 34I) set so that the detection value becomes large (ECU 24, S600 to S616). Configured to.

In the above description, the configuration up to obtaining the integrated output is shown in hardware by an electric circuit diagram, but it may be configured in software.

[0133]

According to the first aspect of the present invention, the misfire is accurately detected in any operating condition by changing the threshold value for judging the presence or absence of the misfire in accordance with the change in the operating condition of the internal combustion engine. Therefore, the reliability of misfire detection can be improved.

The claim 1 is, more specifically, the claim 2.
As described in the section, the operation state includes an air-fuel ratio, and when the air-fuel ratio is larger than a predetermined value, the threshold value is changed to a small value.

Further, as described in claim 3,
The threshold value is changed to a small value when the operating state includes the engine speed and the engine speed is equal to or higher than a predetermined speed.

As a result, even when the ion current waveform changes according to the change in the operating state of the internal combustion engine, more specifically, even when the detected value becomes small, misfire can be accurately detected, and the reliability of misfire detection can be improved. The property can be further improved.

According to the present invention, two spark plugs are arranged in the cylinder, the first detection circuit is connected to the first spark plug, and the first spark plug is connected to the first spark plug. A second detection circuit different from the detection circuit is connected, and when the operating state of the internal combustion engine is a predetermined operating state, specifically, when the detected value of the ionic current is small, that is, the air-fuel ratio is a predetermined value or more. When the engine speed is equal to or higher than a predetermined speed, the presence or absence of misfire is detected by comparing the sum of the detection values of the first and second detection circuits with the threshold value. The detected value of the ion current becomes sufficiently large, and it is possible to prevent the decrease of the ion current due to the increase of the air-fuel ratio or the engine speed from being mistakenly detected as a misfire. Therefore, the accuracy and reliability of misfire detection can be improved. The property can be further improved.

According to the present invention, the first detection circuit is connected to the first spark plug, and the second detection circuit different from the first detection circuit is connected to the second spark plug. However, at least one of the detection values of the first and second detection circuits is selected according to the operating state of the internal combustion engine, and the presence or absence of the misfire is detected based on the selected detection value, in other words, According to the change of the operating state of the internal combustion engine, by selecting the most optimal detection circuit for detecting the ion current at that time, it is possible to accurately detect the misfire in any operating state, and therefore the misfire detection The reliability can be improved.

According to a sixth aspect of the present invention, the operating state is configured to include the air-fuel ratio. Specifically, the detection circuit is selected in accordance with the change in the air-fuel ratio that greatly affects the generation of ions. Since it did so, the above-mentioned effect can be acquired more reliably.

According to another aspect of the present invention, the output characteristics of the first and second detection circuits are set so that one of the detection values of the first and second detection circuits becomes larger than the other detection value. Along with setting, when the air-fuel ratio is larger than a predetermined value, by detecting the presence or absence of the misfire based on the detection value of the detection circuit is set to increase the detection value, to increase the air-fuel ratio It is possible to prevent the accompanying decrease in the ion current from being erroneously detected as misfire, and thus it is possible to further improve the accuracy and reliability of misfire detection.

According to the eighth aspect of the present invention, the operating state is configured to include the engine speed. Specifically, in response to a change in the engine speed that greatly affects the generation time of the ion current waveform. Since the detection circuit is selected, the above effect can be obtained more reliably.

According to the ninth aspect, it is possible to prevent erroneous detection of a decrease in ion current due to an increase in engine speed as a misfire, and thus to improve the accuracy and reliability of misfire detection. It can be further improved.

[Brief description of drawings]

FIG. 1 is an overall schematic view of an internal combustion engine misfire detection device according to an embodiment of the present invention.

FIG. 2 is a side sectional view of a plug-hole type ignition coil connected to the exhaust side ignition plug shown in FIG.

FIG. 3 is a circuit diagram including the exhaust side ignition plug shown in FIG. 1 and a plug hole type ignition coil including an exhaust side detection circuit.

FIG. 4 is a block diagram showing the circuit shown in FIG. 3 as a block.

5 is a time chart showing the output at the time of combustion at each point of the circuit shown in FIG.

6 is a time chart similar to FIG. 5, showing the output at the time of misfire at each point of the circuit shown in FIG.

FIG. 7 is a side sectional view of a plug-hole type ignition coil connected to the intake-side spark plug shown in FIG.

8 is a circuit diagram including the intake-side spark plug shown in FIG. 1 and a plug-hole type ignition coil including an intake-side detection circuit.

9 is a flow chart showing a detection operation of presence / absence of misfire of the device shown in FIG.

FIG. 10 is a time chart similar to FIG. 5, showing the output during combustion when the air-fuel ratio is not less than a predetermined value and when it is not.

FIG. 11 is a flow chart showing a misfire detection operation of the misfire detection device for an internal combustion engine according to the second embodiment of the present invention.
It is a chart.

FIG. 12 is a time chart similar to FIG. 5, showing the output during combustion when the engine speed is equal to or higher than a predetermined speed and when it is not.

FIG. 13 is a schematic view similar to FIG. 1, generally showing a misfire detection device for an internal combustion engine according to a third embodiment of the present invention.

FIG. 14 is a flow chart showing the operation of detecting the presence or absence of misfire of the misfire detection device for an internal combustion engine according to the third embodiment of the present invention.
It is a chart.

FIG. 15 is a flow chart showing a misfire detection operation of the misfire detection device for an internal combustion engine according to the fourth embodiment of the present invention;
It is a chart.

FIG. 16 is a flowchart showing the operation of detecting the presence or absence of misfire of the misfire detection device for an internal combustion engine according to the fifth embodiment of the present invention.
It is a chart.

FIG. 17 is a time chart similar to FIG. 5, for explaining the adjustment of the integration period by changing the first reference voltage.

FIG. 18 is a time chart similar to FIG. 5, for explaining the adjustment of the integration period by changing the second reference voltage.

FIG. 19 is a flowchart showing a misfire detection operation of the misfire detection device for an internal combustion engine according to the sixth embodiment of the present invention;
It is a chart.

FIG. 20 is a flow chart showing a misfire detection operation of the misfire detection device for an internal combustion engine according to the seventh embodiment of the present invention;
It is a chart.

FIG. 21 is a time chart showing ion current waveforms at the time of combustion and at the time of misfire.

FIG. 22 is a time chart showing the detected value (integrated value) of the ionic current according to the related art in comparison between a case where the air-fuel ratio is large and a case where the air-fuel ratio is small.

FIG. 23 is a time chart showing the detected value (integrated value) of the ionic current according to the conventional technique in comparison between the case where the engine speed is high and the case where the engine speed is low.

[Explanation of symbols]

10 Internal combustion engine 12 cylinder 14 Exhaust valve 16 Combustion chamber 18E Exhaust spark plug 18I Intake side spark plug 20 intake valve 22a Plug-hole type ignition coil with detection circuit 22b Plug-hole type ignition coil without detection circuit 24 ECU 34E Exhaust side detection circuit 34I Intake side detection circuit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshihiro Ogama             1-4-1 Chuo Stock Market, Wako City, Saitama Prefecture             Inside Honda Research Laboratory (72) Inventor Kenichi Ishida             1-4-1 Chuo Stock Market, Wako City, Saitama Prefecture             Inside Honda Research Laboratory F term (reference) 2G087 AA13 BB14 CC35 DD17 FF23                 3G019 CD00 CD01 DB04 DB06 DB07                       DB19 FA19 GA05 KA25

Claims (9)

[Claims] 1. At least one spark plug is arranged in a cylinder of an internal combustion engine mounted on a vehicle, and a voltage is applied to the spark plug to ignite a mixture in the internal combustion engine by spark discharge between electrodes. An internal combustion engine which detects the presence or absence of misfire of the internal combustion engine by burning and detecting an ion current generated by the combustion of the air-fuel mixture by a detection circuit, and comparing the detected value with a preset threshold value. A misfire detection device for an internal combustion engine, wherein the threshold value is switched depending on an operating state of the internal combustion engine. 2. The misfire of an internal combustion engine according to claim 1, wherein the operating state includes an air-fuel ratio, and when the air-fuel ratio is larger than a predetermined value, the threshold value is changed to a small value. Detection device. 3. The threshold value is changed to a small value when the operating state includes an engine speed and the engine speed is equal to or higher than a predetermined speed.
Item 3. A misfire detection device for an internal combustion engine according to item 2 or 3. 4. Arranging two spark plugs in the cylinder,
While connecting the first detection circuit to the first spark plug,
A second detection circuit different from the first detection circuit is connected to the second spark plug, and when the operating state is a predetermined operating state, the sum of the detected values of the first and second detecting circuits. 2. The misfire detection device for an internal combustion engine according to claim 1, wherein the presence or absence of the misfire is detected by comparing the threshold value with the threshold value. 5. A first cylinder in an internal combustion engine mounted on a vehicle.
A spark plug and a second spark plug are provided, and a voltage is applied to each of them to ignite and burn the air-fuel mixture in the internal combustion engine by spark discharge between the electrodes, and is generated along with the combustion of the air-fuel mixture. In the misfire detection device for an internal combustion engine, the ionic current is detected by a detection circuit, and the presence or absence of misfire of the internal combustion engine is detected based on the detected value.
And a second detection circuit different from the first detection circuit is connected to the second ignition plug, and the second detection circuit different from the first detection circuit is connected to the second ignition plug according to the operating state of the internal combustion engine. A misfire detection device for an internal combustion engine, wherein at least one of the detection values of the first and second detection circuits is selected, and the presence or absence of the misfire is detected based on the selected detection value. 6. The misfire detection device for an internal combustion engine according to claim 5, wherein the operating state includes an air-fuel ratio. 7. The output characteristics of the first and second detection circuits are set such that one of the detection values of the first and second detection circuits is larger than the other detection value, and
The internal combustion engine according to claim 6, wherein when the air-fuel ratio is larger than a predetermined value, the presence or absence of the misfire is detected based on a detection value of a detection circuit set to increase the detection value. Misfire detection device. 8. The misfire detection device for an internal combustion engine according to claim 5, wherein the operating state includes an engine speed. 9. The output characteristics of the first and second detection circuits are set such that one of the detection values of the first and second detection circuits is larger than the other detection value.
The presence or absence of the misfire is detected based on a detection value of a detection circuit set so that the detection value becomes large when the engine speed is equal to or higher than a predetermined speed.
A misfire detection device for an internal combustion engine according to the above item.