JPH1113620A - Ignition plug abnormality detecting device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly detect abnormality of an ignition plug due to smoldering during operation. SOLUTION: In this device, from the output voltage of a current detecting circuit to detect a leakage current between the electrode of an ignition plugs, a leakage resistance value Rn is calculated at a step 103 and a decision level correction factor C is set according to an engine operation state at steps 104-110. By multiplying the decision level correction factor C by the leakage resistance value Rn, the leakage resistance value Rn is corrected according to an engine operation state and a leakage resistance value RN after correction is determined at a step 111. When a state (a state that smoldering is detected) that the leakage resistance value RN is lower than a smoldering decision value R1 is continued, for example, 100 cycles, it is decided that abnormality of an ignition plug occurs, and an alarm lamp is lighted ON at steps 112 and 113. When a state of RN>R2 is continued, for example, 100 cycles during lightening ON of an alarm lamp, it is decided that a smoldering state is restored, the alarm lamp is lighted OFF at steps 114 and 115.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark plug abnormality detecting device for an internal combustion engine having a function of detecting "smoldering" of a spark plug.

[0002]

2. Description of the Related Art The term "smoldering" of a spark plug refers to a phenomenon in which carbon generated at the time of incomplete combustion of an internal combustion engine or the like adheres to the ignition portion insulator of the spark plug and the insulation resistance of the spark plug decreases. . When the degree of the smoldering progresses, a high current is applied during ignition, a leakage current flows between the electrodes of the ignition plug, and the voltage between the electrodes decreases, so that spark discharge is not generated and a fire may occur.

[0003]

Conventionally, as a countermeasure against smoldering, the insulation structure of the ignition plug has been improved, and the self-cleaning property of carbon (the property of burning off carbon at a certain temperature or higher) has been improved. ,Still, yet, furthermore,
Smoldering cannot be completely prevented. Therefore, when the degree of smoldering has advanced to some extent during driving, it is desirable to be able to detect it promptly.

However, to date, no method has been established for detecting smoldering as one of the failure modes of the spark plug during operation, and until the internal combustion engine malfunctions due to the smoldering degree, the smoldering degree is reduced. The reality was that they would continue driving without knowing the progress at all.

A system that detects ions generated when the air-fuel mixture burns in a cylinder of an internal combustion engine through an electrode of a spark plug and determines whether or not a misfire has occurred based on the ion current is disclosed in Japanese Patent Laid-Open No. 4-259671. As shown in the publication, attention is paid to the point that leakage current due to smoldering flows between the electrodes of the ignition plug even during the period in which ion current does not flow, and when a leakage current exceeding a reference value is detected during that period, misfire detection is performed. In some cases, erroneous detection of a misfire is prevented. However, in this case, the detection of leakage current due to smoldering is performed only to prevent erroneous detection of misfire, and does not detect the degree of smoldering itself.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a spark plug abnormality detection device for an internal combustion engine capable of quickly detecting an ignition plug abnormality due to smoldering during operation. Is to provide.

[0007]

According to a first aspect of the present invention, there is provided a spark plug abnormality detecting apparatus for an internal combustion engine, comprising the steps of: applying a voltage between the electrodes of a spark plug; (Leakage current) is detected by current detection means,
The degree of smoldering of the spark plug is determined by the degree of smoldering degree determination means based on the detected value. Then, the presence or absence of abnormality of the spark plug is determined by the ignition plug abnormality determination unit based on the determination result of the smoldering degree determination unit. With this configuration, during operation, abnormality of the ignition plug due to smoldering can be promptly detected from the current flowing between the electrodes of the ignition plug.

Incidentally, the degree of smoldering may change suddenly and transiently. For example, at the time of low temperature start, the degree of smoldering temporarily progresses suddenly due to fuel fogging of the spark plug (adhesion of unburned fuel). The attached carbon is burned and self-cleaned, and the smoldering degree is restored.
As described above, the smoldering degree may suddenly change suddenly depending on the operation state. Therefore, if the smoldering degree at the time of the transient sudden change is determined as it is by the same criterion as that in the normal operation, the smoldering is immediately recovered (self-cleaning). The progress of temporary smoldering that does not originally require smoldering detection is also detected as it is, resulting in excessive smoldering detection.

As a countermeasure, it is preferable that the determination level is corrected according to the operating state of the internal combustion engine. In this way, it is possible to determine the degree of smoldering at an optimum determination level according to the driving state,
It is possible to determine the degree of smoldering with high reliability while eliminating the influence of the driving state as much as possible.

Further, the determination of the degree of smoldering may be prohibited under specific operating conditions in which the degree of smoldering changes suddenly and transiently. If you do this,
It is not necessary to determine the smoldering degree in an unstable state in which the smoldering degree changes suddenly transiently, and then, after the smoldering degree is stabilized, the smoldering degree can be determined, and the smoldering degree determination accuracy can be improved. Can be improved.

Here, the specific operating condition is a transient increase correction of the fuel injection amount (claim 4). This is because if the fuel injection amount is transiently increased, the unburned fuel adhering to the spark plug will increase rapidly, and the smoldering degree will temporarily and abruptly advance.

In this case, it may be determined whether or not a specific operating condition is based on at least one of a cooling water temperature, an internal combustion engine speed, and a load change amount. Since the cooling water temperature, the internal combustion engine speed, and the load change amount are all parameters serving as criteria for determining whether to increase the fuel injection amount, at least one of them is used.
If it is determined whether the operating condition is a specific operating condition based on the above, it is possible to detect a transient increase in the fuel injection amount (hence, a transient sudden change in the degree of smoldering) as the specific operating condition.

On the other hand, the determination of the degree of smoldering may be made based on the magnitude of the current value (leakage current value) detected by the current detection means. The leakage resistance between the electrodes of the spark plug may be calculated, and the degree of smoldering of the ignition plug may be determined based on the leakage resistance. In this case, the smaller the leak resistance value, the more the smoldering degree is advanced,
The leakage resistance value is an index indicating the degree of smoldering.

Furthermore, the degree of smoldering of the spark plug is determined based on the output of the current detecting means during a period other than the period of generation of ions generated when the air-fuel mixture burns in the cylinder of the internal combustion engine. You may do it. With this configuration, only the leakage current can be accurately detected at a time when the ionic current does not flow between the electrodes of the ignition plug, and a stable smoldering degree that is not affected by the ionic current can be determined.

It is preferable that the driver warns the driver by the warning means when the spark plug abnormality determination means determines that the ignition plug is abnormal. Thus, when an abnormality occurs in the ignition plug due to smoldering, the driver can immediately know the abnormality by the warning operation of the warning means, and can quickly perform repair such as cleaning and replacement of the ignition plug.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. First, the circuit configuration of the ignition control system will be described with reference to FIG. Primary coil 2 of ignition coil 21
2 is connected to a battery 23 and the primary coil 22
Is connected to the collector of a power transistor 25 built in the igniter 24. Secondary coil 26
Of the secondary coil 26 is connected to a spark plug 27.
Is connected to ground via two Zener diodes 28 and 29.

The two Zener diodes 28 and 29 are connected in series in opposite directions, a capacitor 30 is connected in parallel to one Zener diode 28, and a current detecting resistor 31 is connected in parallel to the other Zener diode 29. . The potential Vin between the capacitor 30 and the current detection resistor 31 is input to the inverting input terminal (-) of the inverting amplifier circuit 33 via the resistor 32 and is inverted and amplified. The output voltage V of the inverting amplifier circuit 33 is used for current detection. The signal is input to the engine control circuit 34 as a signal. The current detection circuit 35 (current detection means) for detecting the ionic current and the leakage current includes zener diodes 28 and 29, a capacitor 30, and a current detection resistor 3.
1. It is composed of an inverting amplifier circuit 33 and the like.

During operation of the engine, the engine control circuit 34
The power transistor 25 is turned on / off at the rise / fall of the ignition command signal transmitted from the controller to the igniter 24. When the power transistor 25 is turned on, a primary current flows from the battery 23 to the primary coil 22, and thereafter,
When the power transistor 25 is turned off, the primary coil 22
Is interrupted, a high voltage is electromagnetically induced in the secondary coil 26, and a spark discharge is generated between the electrodes 36 and 37 of the ignition plug 27 by the high voltage. At this time, the discharge current flows from the ground electrode 37 of the ignition plug 27 to the center electrode 36, charges the capacitor 30 via the secondary coil 26, and flows to the ground via Zener diodes 28 and 29. After the capacitor 30 is charged, the current detection circuit 35 is driven by using the charging voltage (for example, 120 V) of the capacitor 30 regulated by the Zener voltage of the Zener diode 28 as a power source, and an ion current and a leakage current are detected as described later. You.

On the other hand, the ion current and the leakage current flow in the opposite direction to the discharge current. That is, after the end of ignition, the charging voltage of the capacitor 30 causes the electrode 3
Since a voltage is applied between the electrodes 36 and 37, an ion current flows between the electrodes 36 and 37 due to ions generated when the air-fuel mixture burns in the cylinder, and the ion current flows from the center electrode 27 to the ground electrode 28. To the capacitor 30 through the current detection resistor 31 from the ground side. At this time, the input potential Vin of the inverting amplifier circuit 33 changes in accordance with the change in the ionic current flowing through the current detecting resistor 31, and the voltage V corresponding to the ionic current from the output terminal of the inverting amplifier circuit 33 is used as a current detection signal as the engine control signal. Output to the circuit 34.
An ion current is detected from the output voltage V of the inverting amplifier 33, and misfire, preignition, knocking, and the like are detected from the ion current.

When the degree of smoldering of the ignition plug 27 advances, the insulation resistance between the electrodes 36 and 37 decreases.
A leakage current flows from the center electrode 27 to the ground electrode 28. This leakage current also flows along the same path as the ion current, and the input potential Vin of the inverting amplifier circuit 33 changes according to the leak current flowing through the current detection resistor 31, and a voltage corresponding to the leak current flows from the output terminal of the inverting amplifier circuit 33. V is output to the engine control circuit 34 as a current detection signal. However, when an ionic current is generated, the ionic current and the leakage current flow in a superimposed manner.

Next, the waveforms of the ion current and the leakage current appearing in the output (current detection signal) of the current detection circuit 35 will be described with reference to FIG. FIG. 2A shows a spark plug 27.
A waveform diagram when the air-fuel mixture ignites normally when there is no smoldering, a waveform diagram when (B) misfires when there is no smoldering in the spark plug 27, and (c) A misfire when there is smoldering in the spark plug 27. FIG. 7D is a waveform diagram in the case where the air-fuel mixture normally ignites when the ignition plug 27 has smoldering.

In any of the cases (a) to (d), the time t
When the ignition command signal rises at 1 and at the time t2, the ignition command signal falls.
A high voltage is applied between 6, 37. Thereby, (a)
In (d), during the period from time t2 to time t3, the spark discharge normally flies to the spark plug 27 and the mixture is ignited.
An ion current flows after time t4. This ionic current increases as the pressure in the cylinder increases, and decreases and disappears as the pressure in the cylinder decreases. During the period from the end of the spark discharge to the generation of the ion current (t3-t4), the high voltage cord or the like connected to the ignition plug 27 has a floating inductance or a floating capacitance. LC due to residual energy
Resonance occurs, and ion current starts flowing after this LC resonance. On the other hand, when a misfire occurs, as shown in (b) and (c), no ion current flows even after the LC resonance ends.

If smoldering occurs in the spark plug 27 and the insulation resistance between the electrodes 36 and 37 is reduced,
As shown in (c) and (d), when the primary current is applied to the ignition coil 21 (when the ignition command signal rises, t1), the ignition plug 27 is turned on by the voltage electromagnetically induced in the secondary coil 26.
Leakage current flows between the electrodes 36 and 37 in the same direction as the ion current. This leakage current flows immediately after the primary current application of the ignition coil 21 starts, and the time during which the leakage current flows tends to increase as the degree of smoldering increases.

Further, after the end of the ignition, a voltage is applied between the electrodes 36 and 37 of the ignition plug 27 by the charging voltage of the capacitor 30, so that the insulation resistance between the electrodes 36 and 37 is reduced by smoldering. (C) and (d), the leakage current flows between the electrodes 36 and 37 in the same direction as the ion current even after the LC resonance. Therefore, when normal ignition is performed with smoldering as shown in (d), the ionic current and the leakage current flow in a superimposed manner after LC resonance, but since the ionic current disappears in a short time, the leakage current thereafter. Only the current continues to flow. The leakage current increases as the degree of smoldering increases (in other words, as the insulation resistance value between the electrodes 36 and 37 decreases). Therefore, when the leakage current is detected at the time t5 after the extinction of the ionic current, only the leakage current can be accurately detected without being affected by the ionic current.

FIG. 3 shows an equivalent circuit when smoldering occurs in the spark plug 27. When smoldering occurs, the smoldering leakage resistance 41 is connected in parallel between the electrodes 36 and 37 of the ignition plug 27.

Here, the resistance value of the leakage resistance 41 is Rn, the resistance value of the current detection resistance 31 is Ro, the terminal voltage of the capacitor 30 is Vo, and the terminal voltage of the current detection resistance 31 (the input voltage of the inverting amplifier circuit 33). Assuming Vin as the leakage current and I as the leakage current, the following equation is established according to Ohm's law. Vin = I · Ro (1) Vo = I · (Rn + Ro) (2) By solving these equations (1) and (2) for Rn, the following equation (3) is obtained. Rn = Ro · (Vo / Vin-1) (3)

Here, the terminal voltage Vo of the capacitor 30 is regulated by the Zener voltage of the Zener diode 28 and may be considered as a constant voltage (constant). ), The leakage resistance Rn can be calculated, and the degree of smoldering of the spark plug 27 can be determined from the leakage resistance Rn. In the circuit shown in FIG. 1, the terminal voltage Vin of the current detection resistor 31 is inverted and amplified by the inverting amplifier circuit 33, and is taken into the engine control circuit 34 as a current detection signal.

On the other hand, the engine control circuit 34 is mainly composed of a microcomputer, and its ROM (storage medium) stores various engine control programs for controlling fuel injection and ignition timing. , The smoldering detection program shown in FIG. 4, and the maps and constants shown in FIGS. 5 and 6 used in the program are stored. The engine control circuit 34 detects a smolder by the above-described detection method by executing the smolder detection program, and is provided on an instrument panel (not shown) when the smolder state is continuously detected for a predetermined period. The warning lamp 38 (warning means) is turned on or blinks to warn the driver. Hereinafter, the processing content of the smoldering detection program of FIG. 4 will be described.

The smoldering detection program shown in FIG. 4 is started when the ignition command signal output from the engine control circuit 34 falls (time t2 in FIG. 2) and serves as a smoldering degree judging means in the claims. Fulfill. When the program is started, it is determined in step 101 whether a predetermined time T has elapsed, that is, whether a time t5 after the extinction of the ion current shown in FIG. 2 has elapsed. , And waits in step 101. Then, when the predetermined time T has elapsed, the process proceeds to step 102, where the output voltage V (current detection signal) of the current detection circuit 35 is read via an A / D converter (not shown), and then the process proceeds to step 103.
Then, the leakage resistance value Rn is calculated by the above equation (3).

Thereafter, in steps 104 to 106, the current engine operating state is determined. The engine operating state is
Judgment is made according to Is the engine speed less than or equal to, for example, 600 rpm, that is, before the start is completed? (Step 104) The throttle opening change amount ΔTA is equal to a predetermined amount A (for example, 3 °
/ Ms), that is, during rapid acceleration? (Step 105) Is the cooling water temperature THW lower than the predetermined temperature B (for example, 10 ° C.), that is, is the fuel increase when the engine is cold?
(Step 105)

In the determination of the current engine operation state, first, in step 104, it is determined whether or not the engine speed is equal to or less than 600 rpm (before the start is completed). Water temperature THW
The determination level correction coefficient map according to the current cooling water temperature THW is calculated by searching the determination level correction coefficient map of FIG. For example, when the cooling water temperature THW is 10 ° C.
At the time of the following starting (at the time of low temperature starting), the cooling water temperature THW
The determination level correction coefficient C is set in the range of 2.0 to 1.5 in accordance with the condition (1), and when the cooling water temperature THW is at the time of starting at 10 ° C. or higher (at the time of normal startup), the determination level correction coefficient C is set to 1.
Set to 5. Here, the determination level correction coefficient C is a correction coefficient that is multiplied by the leakage resistance value Rn calculated in step 103.

If the engine has been started, the routine proceeds from step 104 to step 105, where it is determined whether or not the throttle opening change amount ΔTA is larger than a predetermined amount A (that is, during rapid acceleration), and ΔTA> A If so, step 10
6, the cooling water temperature THW is set to a predetermined temperature B (for example, 10
° C), that is, whether the fuel is being increased when the engine is cold. Step 10 described above
When the determination results of steps 5 and 106 are both "Yes", that is, when both of the above conditions are satisfied after the engine is started, the fuel injection amount is transiently increased and the smoldering degree is transiently suddenly changed. It is determined that the driving condition is a specific driving condition, and the routine proceeds to step 109, where the determination level correction coefficient C is set to a value (for example, 100) for which a smoldering is not detected for a predetermined time (for example, one second). This prohibits the determination of the degree of smoldering.

On the other hand, if it is determined in step 105 that the throttle opening change amount ΔTA is equal to or smaller than the predetermined amount A (that is, not during rapid acceleration), the process proceeds to step 108, where the determination level correction coefficient C is set to 1.0. Set to. That is, the leakage resistance value Rn calculated in step 103 is used as it is as smoldering degree determination data without correction.

In step 106, the cooling water temperature T
If it is determined that the HW is equal to or higher than the predetermined temperature B (for example, 10 ° C.), the process proceeds to step 110, where the determination level correction coefficient map of FIG. The corresponding judgment level correction coefficient C is calculated. For example, the cooling water temperature THW is 10 to 60 ° C.
(That is, before the completion of warm-up), the determination level correction coefficient C is set to 2.0. If the cooling water temperature THW is 60 ° C. or higher (that is, after the completion of warm-up), the determination level correction coefficient C is set. Is set to 1.0.

As described above, after setting the judgment level correction coefficient C in any one of steps 107 and 108 to 110 according to the engine operating state, the routine proceeds to step 111, where the leakage resistance calculated in step 103 is set. By multiplying the value Rn by the judgment level correction coefficient C, the leakage resistance value Rn is corrected according to the engine operating state, and the corrected Rn is set as a new leakage resistance value RN.

Thereafter, in step 112, the corrected leakage resistance value RN is compared with the smoldering judgment value R1 (for example, 10 MΩ), and the state in which the leakage resistance value RN is smaller than the smoldering judgment value R1 (that is, smoldering is detected). It is determined whether or not (state) has continued for, for example, 100 cycles. If R
If the state of N <R1 continues for 100 cycles, it is determined that the spark plug 27 is abnormal, and the routine proceeds to step 113, where
The warning lamp 38 is turned on. The state of RN <R1 is 100
If the cycle does not continue, it is determined that there is no abnormality in the ignition plug 27, and the warning lamp 38 is not turned on. Note that the processing in step 112 functions as a spark plug abnormality determination unit described in the claims.

Then, at step 114, the leakage resistance value R
N is compared with a smoldering recovery determination value R2 (where R2>R1; R2 is, for example, 50 MΩ), and a state where the leakage resistance value RN is larger than the smoldering recovery determination value R2 (that is, a state in which the smoldering state is recovered) is continued for, for example, 100 cycles. It is determined whether or not. If the warning lamp 38 is on, RN>
If the state of R2 continues for 100 cycles, it is determined that the smoldering state has recovered, and the routine proceeds to step 115, where the warning lamp 38 is turned off. While the warning lamp 38 is on,
If the state of RN> R2 does not continue for 100 cycles, it is determined that the smoldering recovery state is still insufficient, and the warning lamp 38 continues to be lit.

According to the present embodiment described above, the degree of smoldering is determined by the number of cycles in which the smoldering state is continuously detected, and the abnormality of the ignition plug 27 is determined from the result of the determination of the degree of smoldering (number of smoldering detection cycles). Since the presence / absence of the ignition plug 27 is determined, an abnormality in the ignition plug 27 due to smoldering can be promptly detected from the current flowing between the electrodes 36 and 37 of the ignition plug 27 during operation. Etc. can be repaired at an early stage.

Further, the judgment level correction coefficient C is set according to the engine operating state (steps 104 to 110).
The leakage resistance value Rn is corrected according to the engine operating state by multiplying the leakage resistance value Rn by the determination level correction coefficient C. Therefore, the degree of smoldering is determined at an optimal determination level according to the engine operating state. This makes it possible to perform highly reliable smoldering determination while minimizing the influence of the engine operating state.

It should be noted that the judgment level correction coefficient C is defined as the leakage resistance value R
Instead of multiplying n, the smoldering judgment value R1 used in step 112 may be divided by the judgment level correction coefficient C to correct the smoldering judgment value R1 according to the engine operating state.

Also, in this embodiment, the specific operating condition (ΔTA> A and THW after the engine is started) in which the fuel injection amount is transiently increased and the smoldering degree transiently changes suddenly.
In the case of <B), since the determination of the smoldering degree is prohibited, it is not necessary to determine the smoldering degree in an unstable state in which the smoldering degree changes suddenly and transiently. After waiting, the smoldering degree can be determined, and the smoldering degree determination accuracy can be improved.

The criterion for determining the specific operating condition may be changed as appropriate. Whether the specific operating condition is satisfied or not is determined by at least the cooling water temperature, the engine speed, and the load change (throttle opening change). What is necessary is just to determine based on one. Since the cooling water temperature, the engine speed, and the load change amount are all parameters serving as a criterion for determining whether or not to increase the fuel injection amount, the specific operation conditions are based on at least one of them. If it is determined whether or not the fuel injection amount is transiently increased (and, consequently, the smoldering degree is transiently suddenly changed).
Can be detected as a specific operating condition.

In this embodiment, the current detection circuit 35
Although the smoldering degree is determined by calculating the leakage resistance value Rn from the output voltage of the above, the smoldering degree may be determined by comparing the output voltage of the current detection circuit 35 with the smoldering determination voltage. That is, as the degree of smoldering advances and the leakage resistance value Rn decreases, the leakage current I increases, the absolute value of the terminal voltage Vin of the current detection resistor 31 increases, and the output voltage of the current detection circuit 35 increases. Since there is a relationship, the degree of smoldering can be determined based on whether or not the output voltage of the current detection circuit 35 is equal to or higher than the smoldering determination voltage. Also in this case, if the output voltage of the current detection circuit 35 or the smoldering determination voltage is corrected according to the engine operating state, it is possible to perform highly reliable determination of the smoldering degree while eliminating the influence of the engine operating state as much as possible.

Also, in the present embodiment, in consideration of the possibility that the smoldering degree may be recovered, the smoldering state is recovered when the state where the leakage resistance value RN is larger than the smoldering recovery judgment value R2 is continued for, for example, 100 cycles. Is determined, the warning lamp 38 is turned off, so that the lighting period of the warning lamp 38 can be optimized in accordance with the change in the degree of smoldering during the operation of the engine.

Further, the smoldering recovery judgment value R2 is set to a value larger than the smoldering judgment value R1, and the warning lamp 3 is set.
Since the turning on / off of the lamp 8 has a hysteresis characteristic, it is possible to avoid a situation in which the turning on / off of the warning lamp 38 is frequently switched.

It should be noted that the smoldering recovery judgment value R2 may be the same value as the smoldering judgment value R1. Even in this case, the number of cycles in which the state of RN> R2 judged at step 114 is continued is judged at step 112. If the number of cycles in which the state of RN <R1 is set to be somewhat larger than the number of continuous cycles, the lighting / warning of the warning lamp 38 is performed as in the present embodiment.
Hysteresis characteristics can be provided for turning off the light.

In this embodiment, since the leakage current is detected at time t5 after the extinction of the ionic current, only the leakage current can be accurately detected, and the smoldering degree is not affected by the ionic current. Can be determined.

The detection timing of the leakage current is not limited to after the extinction of the ion current. As shown in FIGS. 2C and 2D, the leakage current flowing immediately after the rising of the ignition command signal (time t1) is determined. You may make it detect. The leakage current that flows immediately after the rise of the ignition command signal tends to increase the time during which the leakage current flows as the degree of smoldering increases, so that the rise of the ignition command signal (time t
The smoldering degree may be determined by measuring the time during which the leakage current flows from 1).

In addition, according to the present invention, when the progress of the smoldering degree is detected, the smoldering recovery control (for example, to increase the spark discharge of the spark plug 27 or to advance the ignition timing to increase the combustion temperature). Control to promote self-cleaning of the ignition plug 27).

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing a configuration of an ignition control system and a current detection circuit according to an embodiment of the present invention.

FIG. 2 is a waveform diagram of a current detection signal when the air-fuel mixture is normally ignited when there is no smoldering in the spark plug. FIG. (c) is a waveform diagram of a current detection signal when a misfire occurs when the ignition plug has smoldering, and (d) is a waveform diagram of a current detection signal when the air-fuel mixture normally ignites when the ignition plug has smoldering.

FIG. 3 is a circuit diagram showing an equivalent circuit of a current detection circuit when smoldering occurs.

FIG. 4 is a flowchart showing a processing flow of a smoldering detection program;

FIG. 5 is a diagram conceptually showing a determination level correction coefficient map when the engine is started.

FIG. 6 is a diagram conceptually showing a determination level correction coefficient map at the time of low water temperature and acceleration.

[Explanation of symbols]

Reference numeral 21: ignition coil, 22: primary coil, 23: battery, 24: igniter, 25: power transistor, 2
6 Secondary coil, 27 Spark plug, 28, 29 Zener diode, 31 Current detection resistor, 33 Inverting amplifier circuit, 34 Engine control circuit (smoldering degree determining means, spark plug abnormality determining means), 35 Current detection circuit (current detection means), 36: center electrode, 37: ground electrode,
38: warning lamp (warning means), 41: leakage resistance.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Eiji Takakuwa 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Co., Ltd. (72) Inventor Kazuhisa Mogi 1-Toyota-cho, Toyota-shi, Aichi Prefecture Toyota Motor Corporation (72) Inventor Hirohisa Kishi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (8)

[Claims] A current detecting means for applying a voltage between electrodes of a spark plug to detect a current flowing between the electrodes; and a smoldering degree judging for judging a smoldering degree of the spark plug based on an output of the current detecting means. And a spark plug abnormality determination unit for determining whether or not the ignition plug is abnormal based on the determination result of the smoldering degree determination unit. 2. The apparatus according to claim 1, wherein said smoldering degree determining means includes means for correcting a determination level in accordance with an operation state of the internal combustion engine. 3. The internal combustion engine according to claim 1, wherein said smoldering degree determination means includes means for prohibiting the determination of the smoldering degree under a specific operating condition in which the smoldering degree changes suddenly and transiently. Engine spark plug abnormality detection device. 4. The spark plug abnormality detection device for an internal combustion engine according to claim 3, wherein the specific operating condition is a transient increase correction of a fuel injection amount. 5. The smoldering degree determining means determines whether or not the specific operating condition is satisfied, based on at least one of a cooling water temperature, an internal combustion engine speed, and a load change amount. Item 5. The spark plug abnormality detection device for an internal combustion engine according to item 3 or 4. 6. The smoldering degree determining means calculates a leakage resistance value between the electrodes of the spark plug from a current value detected by the current detecting means, and determines a smoldering degree of the ignition plug based on the leakage resistance value. The spark plug abnormality detection device for an internal combustion engine according to any one of claims 1 to 5, wherein the determination is performed. 7. The degree of smoldering of the spark plug based on an output of the current detecting means during a period other than a period of generation of ions generated when the air-fuel mixture burns in a cylinder of the internal combustion engine. The spark plug abnormality detection device for an internal combustion engine according to any one of claims 1 to 6, wherein: 8. The internal combustion engine according to claim 1, further comprising a warning unit that warns a driver when the spark plug abnormality determination unit determines that the ignition plug is abnormal. Engine spark plug abnormality detection device.