JP2689361B2 - Misfire detection device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting a misfire in an internal combustion engine, and more particularly to a device for detecting a misfire related to a fuel system.

[0002]

2. Description of the Related Art An ignition plug is provided for each cylinder for igniting a fuel-air mixture taken into a cylinder of an internal combustion engine. Normally, a high voltage generated in an ignition coil of an internal combustion engine is sequentially distributed to a spark plug of each cylinder via a power distribution device to ignite the fuel mixture. In this case, if ignition by the ignition plug is not performed normally, that is, if misfire occurs, various adverse effects occur. For example, the driving performance is deteriorated, the fuel efficiency is deteriorated, and furthermore, the unburned gas is post-burned in the exhaust system, resulting in an increase in the catalyst temperature in the exhaust gas purification device. Therefore, misfires that cause such adverse effects must be absolutely prevented. The causes of this misfire can be roughly classified into those related to the fuel system and those related to the ignition system. The former related to the fuel system is caused by lean or rich fuel mixture, and the latter related to the ignition system is caused by so-called miss spark. Miss spark means that a normal spark discharge does not occur in the spark plug. For example, this is a case where normal spark discharge is not performed due to smoldering of an ignition plug due to adhesion of unburned fuel or an abnormality in an ignition circuit.

The applicant of the present invention detects an ignition voltage as a misfire detection device for detecting a misfire related to the cause of the fuel system, and detects a period during which the ignition voltage exceeds a predetermined voltage value and / or an ignition voltage. When the area of the portion exceeding the predetermined voltage value exceeds the reference value, it has been proposed that the engine be misfired (patent application dated November 14, 1991, serial number JP2793). .

[0004]

However, although there is a high possibility that a misfire may be erroneously determined depending on the engine operating state, such as when the engine is started or immediately after the engine is started, the conventional device has this problem. Points were not taken into account. That is, when the engine starts or immediately after starting (especially engine temperature
Is low), the air-fuel ratio tends to fluctuate.
The frequency of misfires is higher than that of
But the combustion is unstable, i.e. the flame is
The way it burns, like propagating crab
It is often not normal. Ignition, like the conventional device above
For the period when the voltage value exceeds the specified voltage value or the area of the part where it exceeds
Therefore, in the method of determining misfire, there is no misfire
If the firing state is abnormal, the ignition voltage value
The period of crossing or the area of the crossing exceeds the specified threshold.
There is a case of accidental misfire
There was a risk of being set. For example, if the air-fuel ratio is too lean
Looking at the ignition voltage characteristics when there is a misfire,
The mixture has a high insulating power and the mixture is ionized
Not done Increased electrical resistance between plug gaps
The breakdown voltage value immediately after the ignition command is
Greater than normal. Also, the value of the induced discharge voltage after that,
Since the resistance during discharge is higher than in the normal combustion state
large. Furthermore, the capacity discharge immediately after the last stage of the inductive discharge state
As for the electric voltage value, the insulation power of the air-fuel mixture is large and
Whether the discharge state ends early and the residual energy increases
From the normal combustion state. In this case, the above
A misfire is determined by the determination method. Then start the engine
When the air-fuel ratio is unstable immediately after starting or when starting,
Even if a flame kernel is formed, the combustion is slow, so the mixture is
Since it is not quickly ionized, the
The ignition voltage waveform fluctuates greatly. Therefore, ignition
When the voltage value exceeds the specified voltage value
Even though the specified threshold value has been exceeded and there is no misfire
Regardless, it is easy to be mistakenly determined to have misfired. like this
In addition, in the above conventional device, the
As a result, there is no misfire depending on engine operating conditions such as combustion conditions.
However, there is a high possibility that the
There was room for improvement in the accuracy of fire judgment.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a misfire detection device capable of more accurately detecting a misfire related to the cause of a fuel system.

[0006]

To achieve the above object, the present invention provides an engine operating condition detecting means for detecting the value of an engine operating parameter, and an ignition timing determining ignition timing based on the value of the engine operating parameter. A signal generating means for generating a command signal, an ignition means for generating a high voltage for discharging an ignition plug provided in the engine based on the ignition command signal, and a high voltage for the ignition means Voltage value detecting means for detecting the voltage value of, and at least one of a period during which the ignition voltage value after the ignition command signal exceeds a predetermined voltage value and an area of a portion where the ignition voltage value exceeds the predetermined voltage value is a reference value. When exceeding, in the misfire detection device of the internal combustion engine having a misfire determination means for determining the misfire state of the engine,
During the start of the engine and / or within a predetermined period after the start, a prohibiting means for prohibiting the determination by the misfire determining means is provided.

Further, it is preferable that the prohibiting means sets the predetermined period according to the engine temperature.

[0008]

Operation: The misfire determination is prohibited during the start of the engine and within a predetermined period after the start.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the construction of an embodiment of a misfire detecting device for an internal combustion engine according to the present invention. A power supply terminal T1 to which a power supply voltage VB is supplied has a primary side coil 2 and a secondary side coil 3. Is connected to an ignition coil (ignition means) 1. The primary coil 2 and the secondary coil 3 are connected to each other at one end thereof, the other end of the primary coil 2 is connected to the collector of the transistor 4, and the base of the transistor 4 is connected to the CPU 11 via the drive circuit 16. , Its emitter is grounded. The base of the transistor 4 is C
The ignition command signal A is supplied from the PU 11. The other end of the secondary coil 3 is connected to the center electrode 5a of the spark plug 5 via a distributor 6. The ground electrode 5b of the spark plug 5 is grounded.

An ignition voltage sensor 10 which is electrostatically coupled to the connecting line connecting the distributor 6 and the ignition plug 5 (which forms a capacitor of several pF with the connecting line) is provided in the middle of the connecting line. ing. Ignition voltage sensor 10
Is connected to the A / D converter 17 via the input circuit 12, and the output of the A / D converter 17 is connected to the CPU 11. The output voltage (ignition voltage) V of the first input circuit 12 is converted into a digital value by the A / D converter 17, and CP
Supplied to U11.

Various engine operating parameter sensors (engine operating conditions) for detecting the values of engine operating parameters such as engine speed, engine load, engine cooling water temperature, engine oil temperature, etc., via the second input circuit 13 are provided to the CPU 11. (Detection means) 9 is connected, and the detected value of the engine operation parameter is input. Further, the CPU 11 is connected to the base of the transistor 4 via the drive circuit 16, and supplies the ignition command signal A to the transistor 4.

In the present embodiment, the ECU 8 constitutes a signal generating means, a prohibiting means, and a misfire determining means.

FIG. 2 is a circuit diagram showing a specific configuration of the first input circuit 12, in which the input terminal T2 is
It is connected to a non-inverting input of an operational amplifier (hereinafter referred to as “op amp”) 416 via a resistor 415. The input terminal T2 is connected to the ground via a circuit in which a capacitor 411, a resistor 412 and a diode 414 are connected in parallel, and is connected to a power supply line VBS via a diode 413. As the capacitor 411, for example, a capacitor of about 10 ⁴ pF is used, and the ignition voltage sensor 1
It serves to divide the voltage detected by 7 into thousands. The resistance 412 is, for example, about 500 KΩ. The diodes 413 and 414 are provided so that the input voltage of the operational amplifier 416 falls within the range of approximately 0 to VBS. The inverting input of the operational amplifier 416 is connected to the output of the operational amplifier 416,
Operates as a buffer amplifier (impedance conversion circuit). The output of the operational amplifier 416 is A as the ignition voltage V.
It is supplied to the / D converter 45.

FIG. 3 is a time chart showing the transition of the ignition voltage V when the ignition command signal is generated. The solid line shows the ignition voltage at the normal combustion of the fuel mixture, and the broken line shows the misfire due to the cause of the fuel system. The ignition voltage at the time of "FI misfire" is shown.

First, the ignition voltage characteristic (characteristic indicated by the solid line) during normal combustion will be described with reference to FIG. Immediately after the ignition command signal A generation time t0, the ignition voltage rises to a value at which the insulation of the fuel mixture (between the discharge gaps of the spark plugs) is destroyed (curve a). For example, as shown in FIG. 3, the value of the ignition voltage V is the FI misfire determination reference voltage (predetermined voltage).
When Vmis ₁ is exceeded (when V> Vmis ₁ ), the insulation of the fuel mixture is destroyed, and discharge occurs from the capacity discharge state (a discharge state of a very short time due to a current of several hundred amperes) before the insulation breakdown. The voltage shifts to an inductive discharge state where the voltage is substantially constant (curve b) (a discharge period of about several milliseconds by a current of about several tens of milliamperes). The induction discharge voltage increases as the pressure in the cylinder increases during the compression stroke after time t0. This is because the higher the pressure, the higher the voltage required for the induction discharge. In the last stage of the induction discharge, the voltage between the spark plug electrodes becomes lower than the voltage for maintaining the induction discharge due to the decrease in the induction energy of the ignition coil, the induction discharge disappears, and a transition is made to the capacity discharge state. In the capacity discharge state, the voltage between the spark plug electrodes rises because the insulation of the fuel mixture is destroyed again, but the remaining energy of the ignition coil 1 is small and the voltage rise is slight (curve c). This is because when combustion occurs, the electric resistance between the plug gaps is low, and the fuel mixture during combustion is ionized.

Next, the ignition voltage characteristic (characteristic indicated by the dotted line) when the FI misfire occurs (when combustion does not occur) due to the fuel mixture becoming lean or cut due to an abnormality in the fuel supply system or the like will be described. To do. Immediately after the ignition command signal A generation time t0, the ignition voltage V rises to a value that breaks the insulation of the fuel mixture between the spark plug electrodes. At this time, the value of the insulation breakdown voltage depends on the air occupying the fuel mixture. Is higher than normal, the dielectric strength of the fuel mixture increases, and since no combustion occurs, the fuel mixture does not ionize and the electrical resistance between the plug gaps decreases. Since it becomes higher, it becomes higher than the voltage value during normal combustion (curve a ′). Thereafter, the state shifts to the induction discharge state as in the normal combustion (curve b ′). However, since the resistance during the discharge also becomes larger than that in the normal combustion, the induction discharge voltage becomes higher than that in the normal combustion, and the induction discharge voltage becomes higher. The state shifts from the discharge state to the capacity discharge state (curve c ′). The value of the capacity discharge voltage generated at the time of the transition from the last stage of the induction discharge to the capacity discharge is due to the fact that the dielectric breakdown voltage of the fuel mixture is higher than that during normal combustion, and that the induction discharge ends earlier (discharge duration Since the residual energy also increases, it becomes much larger than that during normal combustion as shown in FIG. 3 (curve c ′). Therefore, immediately after this capacity discharge, the residual energy of the ignition coil sharply decreases, so that the ignition voltage drops sharply to substantially zero (curve c ′).

FIG. 4 is a flow chart of a program for determining misfire. This program is executed by the CPU 11 at regular intervals.

First, it is determined whether or not the monitor condition is satisfied (step S1). Here, the monitor condition is a condition that is satisfied when the engine is in an operating state in which the misfire determination should be executed, and is determined by the program of FIG. 5 described later. If this condition is not satisfied (the answer to step S1 is negative (No)), this program is immediately terminated.

When the answer to step S1 is affirmative (Yes), that is, when the monitor condition is satisfied, whether or not "1" is set in the IG flag (FlagIG) showing whether or not the ignition command signal A is generated. Is determined (step S
2). “1” indicates that the ignition command signal A has been generated.
This IG flag is set to “1” when the ignition command signal A is generated.
And is set to "0" after a lapse of a predetermined time. Since "1" has not risen before the generation of the ignition command signal A, the determination in step S2 is negative, and the process proceeds to steps S3, S4, and S5, and the timer (the timer for measuring the time after the generation of the ignition command signal A) ), A predetermined time Tmis ₁ is set, the value of the area S is initialized to zero, and stored in the memory.
The flag is set to "0" and the program ends. IG
The process of setting the flag to "1" is performed by a routine different from the routine of FIG. 5, for example, an ignition timing calculation processing routine.

It should be noted that the value of the predetermined time Tmis ₁ is set to a time slightly larger than the time from the generation of the ignition command signal A to the generation of the capacity discharge at the final stage of the induction discharge during normal combustion. It is a value read from the map or table according to the state (engine operation parameter value). The same applies to Vmis ₁ and Smis described later.

Next, when the ignition command signal A is generated and the IG flag is set to "1", the process proceeds from step S2 to S6 and the timer determines whether or not a predetermined time Tmis ₁ has passed ( (See FIG. 3). Since the predetermined time Tmis ₁ has not elapsed immediately after the ignition command signal A is generated, it is determined whether the value of the ignition voltage V exceeds the value of the predetermined voltage Vmis ₁ (step S7) (see FIG. 3). The predetermined voltage VMIS ₁ is always set to exceed the value ignition voltage V is in the capacitive discharge following the capacitive discharge during and after induction discharge immediately after generation of the ignition command signal A when the time for example normal combustion. If V ≦ Vmis ₁ ,
Terminate this program immediately. If V> Vmis ₁ , then
In the ignition voltage characteristic curve shown in FIG. 3, the area of the part where V> Vmis ₁ is obtained (step S8), the value of this area is added to the memory in which the value of the area S is stored, and the new area S is added.
Value. Next, the value of the new area S is equal to the predetermined area S
judge whether the value of mis is exceeded (step S
9) If it exceeds, it is determined that FI misfire has occurred (step S1).
0) If not, it is determined that there is no FI misfire, and this program ends. It performed until a predetermined time TMIS ₁ has elapsed by the timer of the processing ECU 8 (step S6).
The value of the predetermined area Smis is set to be smaller than the value of the area S integrated at the time of the FI misfire.

An example of the value of the area S is shown in FIG. In FIG. 3, the area S ₁ indicated by a downward slanting line indicates the area S during normal combustion, and the sum of the areas S ₂ and S ₃ indicated by a downward slanting line indicates the area S during FI misfire. Area S at FI misfire
Is much larger than the area S during normal combustion and definitely exceeds the predetermined area Smis.

In FIG. 4, S ₁ and S ₂ are areas during capacitive discharge immediately after the ignition command signal is generated, and S ₃ is area during capacitive discharge following the subsequent induction discharge. , S is the sum of S ₂ and S ₃ .

FIG. 5 is a flow chart of a program for determining the monitor condition.

This program is executed in synchronization with the generation of each TDC signal pulse generated each time the crankshaft of the engine rotates by a predetermined angle.

In step S21, it is determined whether the engine is in the starting mode. This determination is performed, for example, based on whether the starter switch is on or off, whether the engine speed is equal to or higher than a predetermined speed, or the like. The answer in step S21 is affirmative (Yes
s), that is, in the start mode, the monitor prohibition period TMF is calculated by searching the TMF table according to the detected engine cooling water temperature TW (step S2).
2). The TMF table is a table in which the monitor prohibition period TMF is set corresponding to the period cooling water temperature TW, and is set so that the TMF value decreases as the TW value increases as shown in FIG. 6, for example.

In the following step S23, the timer tTMF is set.
The monitor prohibition period TMF is set to and started, and it is determined that the monitor condition is not satisfied (step S2).
6) End this program.

If the answer to step S21 is negative (No), that is, if the engine is not in the starting mode, it is determined that the engine is in a rotating state after starting, and it is determined whether or not the count value of the timer tTMF is 0 ( Step S24). This answer is negative (No), that is, the monitor prohibition period TMF after the start mode is finished.
If it is within the range, it is determined that the monitor condition is not satisfied (step S26). The answer in step S24 is affirmative (Yes),
That is, after the monitor prohibition period TMF has elapsed from the end of the start mode, it is determined that the monitor condition is satisfied (step S2).
5), this program ends.

According to this program, it is determined that the monitor condition is not satisfied during the start mode and during the monitor prohibition period TMF after the start mode is completed. This is because combustion is unstable and accurate misfire determination cannot be performed during the start mode and during the monitor prohibition period TMF after the end of the start mode. Further, the monitoring prohibition period TMF is set to be shorter as the engine cooling water temperature TW becomes higher, because combustion becomes stable earlier as the engine temperature becomes higher. Normally, the engine temperature in the start mode is low, but in the case of restarting immediately after the engine is stopped, it is considered that the engine temperature changes depending on the immediately preceding engine operating state and the operation stop period. Further, when the engine temperature at the time of starting is substantially a value like the warm-up temperature, the monitor prohibition period TMF may be set to 0 to prohibit only at the time of starting.

By the monitor condition judgment by the program of FIG. 4, the misfire judgment by the program of FIG. 5 is executed only when the monitor condition where combustion is stable is established, so that a more accurate judgment can be made.

In this embodiment, the cooling water temperature TW is used as a parameter representing the engine temperature, but the present invention is not limited to this, and the temperature of the lubricating oil may be used, for example.

FIG. 7 is a diagram showing a circuit configuration for misfire determination according to the second embodiment of the present invention. The output of the first input circuit 12 is the non-inverting input of the peak hold circuit 13 and the comparator 15. It is connected to the. The output of the peak hold circuit 13 is connected to the inverting input of the comparator 15 via the comparison level setting circuit 14. Also, the peak hold circuit 1
To the reset input of 3, the CPU 11 is connected,
A reset signal for resetting the peak hold value is supplied from the CPU 11 at an appropriate timing. The output of the comparator 15 is input to the CPU 11. Further, a diode 7 is provided between the secondary coil 3 and the distributor 6. Except for the above points, the circuit is the same as that of FIG.

FIG. 8 is a circuit diagram showing a specific configuration of the first input circuit 12, the peak hold circuit 13, and the comparison level setting circuit 14 of FIG. 7. The first input circuit 12 is
It is the same as FIG.

In FIG. 8, the output of the operational amplifier 416 of the first input circuit 12 is connected to the non-inverting input of the comparator 15 and the non-inverting input of the operational amplifier 421. The output of the operational amplifier 421 is connected to the non-inverting input of the operational amplifier 427 via the diode 422, and the inverting inputs of the operational amplifiers 421 and 427 are both connected to the output of the operational amplifier 427. Therefore, these operational amplifiers also operate as buffer amplifiers.

The non-inverting input of the operational amplifier 427 is a resistor 42.
3 and the capacitor 426, and the resistor 423
The connection point between the capacitor 426 and the capacitor 426 is connected to the collector of the transistor 425 via the resistor 424. The emitter of the transistor 425 is grounded, and a reset signal that is high level at reset is input from the CPU 11 to the base.

The output of the operational amplifier 427 is grounded through the resistors 431 and 432 which constitute the comparison level setting circuit 14, and the connection point of the resistors 431 and 432 is connected to the inverting input of the comparator 15.

According to the circuit of FIG. 8, the peak value of the detected ignition voltage V (the output of the operational amplifier 416) is held by the peak hold circuit 13, and the peak hold value is set to 1 by the comparison level setting circuit 14. It is multiplied by a small predetermined number and supplied to the comparator 15 as the comparison level VCOMP. Accordingly, a pulse signal (comparison determination pulse) which becomes a high level when V> VCOMP is established at the terminal T4.
Is output.

The operation of the misfire detection circuit configured as described above will be described with reference to the time chart shown in FIG.
9 (b) to 9 (e), a solid line indicates an operation at the time of combustion, and a broken line indicates an operation at the time of occurrence of FI misfire.

Further, FIG. 7A shows an ignition command signal.

FIG. 6B shows the detected ignition voltage V (B,
B ′) and the comparison level VCOMP (C, C ′), and the curve B during combustion changes in the same manner as in FIG. 3 described above. On the other hand, the curve B ′ at the time of occurrence of misfire differs from the case of FIG. This is because the diode 7 is provided between the secondary coil 3 and the distributor 6 as shown in FIG. Hereinafter, this point will be described in detail.

The electric energy generated by the ignition coil 1 is
It is supplied to the spark plug 5 through the diode 7 and the distributor 6 and discharged between the electrodes of the spark plug 5. At this time, the electric charge that could not be discharged is the diode 7
It is stored in the floating capacitance between the spark plug 5 and the spark plug 5, but at the time of combustion, this charge is neutralized by the ions existing in the vicinity of the electrode of the spark plug 5, so that the ignition voltage V (FIG. B) of b) is rapidly reduced as in the case without the diode 7.

On the other hand, at the time of misfire, there are almost no ions near the electrodes of the spark plug 5, so that the diode 7
The electric charge stored between the ignition plug 5 and the spark plug 5 is not neutralized by the ions and cannot be back-flowed to the ignition coil 1 by the diode 7, so that the electric charge is retained as it is, and the pressure in the cylinder decreases and the required discharge voltage is reduced. When it becomes equal to the voltage applied by this electric charge, it is discharged in the electrode of the spark plug 5 (FIG. 9 (b), time t5). Therefore, the ignition voltage V continues to be in the high voltage state for a relatively long time (compared to the time of normal combustion) even after the end of the capacity discharge.

Curves C and C'in FIG. 9B indicate the ignition voltage V
Comparison level VCOMP obtained from the peak hold value of
, And is reset between times t2 and t3. Therefore, before the time t2, the comparison level VCOMP of the previously ignited cylinder is shown. In addition, FIG.
FIG. 9C shows the output of the comparator 15, and as is clear from FIGS. 9B and 9C, the time t at the time of combustion is shown.
V> VCOMP from 2 to t4 and V> VCOMP from time t1 to t5 at the time of misfire, during which the output of the comparator 15 becomes high level.

Therefore, the misfire can be determined by measuring the pulse width of the comparison determination pulse output from the comparator 15 and comparing it with the reference value. FIG. 10 is a flowchart of a program for performing misfire determination based on the comparison determination pulse, and this program is executed by the CPU 11 at regular time intervals.

In step S41, it is determined whether or not the above-mentioned monitor condition is satisfied, and the answer is negative (No).
In this case, the program is immediately terminated. When the answer to step S41 is affirmative (Yes), it is determined whether or not the IG flag (FlagIG) is "1" (step S42), and the answer is negative (No), that is, when the IG flag is "0". At this time, the measured value tR of the reset timer is set to a value of 0 (step S43), and this program is ended.
If the answer to step S42 is affirmative (Yes), that is, if the IG flag is "1", it is determined whether or not the measured value tR of the reset timer is smaller than a predetermined time tRESET (step S44). Immediately after the IG flag changes from "0" to "1", the answer is affirmative (Yes), and it is determined whether or not there is a comparison determination pulse, that is, whether there is an output pulse of the comparator 44 (step S47). If the answer is negative (No), the program is immediately terminated. If the answer is yes (Yes), the count value CP of the counter is incremented by 1 (step S48), and the count value CP becomes larger than the reference value CPREF. It is determined whether or not it is smaller (step S4
9).

When the answer to step S49 is affirmative (Yes), that is, when CP <CPREF, it is determined that the combustion is normal and the flag FMIS is set to "0" (step S50).
The answer to step S49 is negative (No), that is, CP ≧ CPR.
In the case of EF, FI misfire is determined, the flag FMIS is set to "1" (step S51), and this program ends.

If the answer to step S44 is negative (No),
That is, when tR> tRESET, the count value CP and the IG flag of the counter are reset to 0 (steps S45 and S46), and the process proceeds to step S50.

According to the program of FIG. 10, FIG.
As shown in (d) and (e), at the time of combustion, the count value CP does not exceed the reference value CPREF, but at the time of misfire, the count value CP exceeds the reference value CPREF, so misfire is detected (FMIS is Change from 0 to 1.) Further, based on the monitor condition determined by the program of FIG. 5, the misfire determination is performed only when the combustion is stable, so the accurate misfire determination can be performed.

The peak hold circuit 22 shown in FIG.
An averaging circuit (integrating circuit) may be used instead.

Further, in the second embodiment, the area of the portion where the detected ignition voltage V exceeds the comparison level VCOMP ((V-
VCOMP) may be used to detect a misfire in the same manner as in the first embodiment. Further, the first embodiment and the second embodiment may be combined to determine that a misfire has occurred only when the detection result of both is misfire.

The comparison determination pulse width in the second embodiment may be measured only within a predetermined gate period (for example, the latter half of the discharge period).

[0053]

As described above, according to the misfire detection device of the present invention, the misfire determination is prohibited during the engine start and / or within a predetermined period after the start, and the misfire determination is performed only when the combustion is stable. Therefore, accurate misfire determination can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit configuration of a misfire detection device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a specific configuration of a part of the circuit of FIG.

FIG. 3 is a time chart showing changes in ignition voltage.

FIG. 4 is a flowchart of a program for performing misfire determination.

FIG. 5 is a flowchart of a program for determining a monitor condition.

FIG. 6 is a diagram showing a table for calculating a monitor prohibition period (TMF).

FIG. 7 is a diagram showing a circuit configuration of a misfire detection device according to another embodiment of the present invention.

8 is a circuit diagram showing a specific configuration of a part of the circuit of FIG. 7;

FIG. 9 is a time chart for explaining the operation of the circuit of FIG. 7;

FIG. 10 is a flowchart of a program for performing misfire determination.

[Explanation of symbols]

 1 Ignition coil 2 Primary side coil 3 Secondary side coil 5 Spark plug 8 Electronic control unit (ECU) 9 Operating parameter sensor 10 Ignition voltage sensor 11 CPU

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shigeki Baba 1-4-1 Chuo, Wako-shi, Saitama Pref. Inside the Honda R & D Co., Ltd. (72) Takashi Hisagi 1-4-1 Chuo, Wako-shi, Saitama Inside the Honda R & D Co., Ltd. (72) Inventor Shigeru Maruyama 1-4-1, Chuo, Wako-shi, Saitama Prefecture Incorporated Honda R & D Co., Ltd. (72) Masataka Chikamatsu 1-4-1, Chuo, Wako-shi, Saitama Co., Ltd. Inside the Technical Research Institute (72) Inventor Norihiro Terada 1-4-1 Chuo, Wako-shi, Saitama Pref. Inside Honda Technical Research Institute (72) Inventor Kenichi Maeda 1-4-1 Chuo, Wako-shi, Saitama Pref. In the laboratory (72) Inventor Kazuhito Kakimoto 1-4-1 Chuo, Wako-shi, Saitama Pref. In Honda R & D Co., Ltd. 118135 (JP, A) JP Akira 50-43334 (JP, A) JP Akira 64-77758 (JP, A)

Claims (2)

(57) [Claims] 1. An engine operating state detecting means for detecting a value of an engine operating parameter, a signal generating means for determining an ignition timing based on the value of the engine operating parameter to generate an ignition command signal, and the ignition command signal. Ignition means for generating a high voltage for discharging an ignition plug provided in the engine, voltage value detection means for detecting a voltage value when the high voltage is generated in the ignition means, and the ignition A misfire determination means for determining an engine misfire state when at least one of a period during which the ignition voltage value after the generation of the command signal exceeds a predetermined voltage value and an area of a portion where the ignition voltage value exceeds the predetermined voltage value exceeds a reference value. In the misfire detection device for an internal combustion engine having, during the start of the engine and / or within a predetermined period after the start,
A misfire detecting device for an internal combustion engine, which is provided with a prohibiting means for prohibiting the judgment by the misfire judging means. 2. The misfire detecting device for an internal combustion engine according to claim 1, wherein the prohibiting unit sets the predetermined period according to an engine temperature.