JPH0719153A - Misfire detecting device for gasoline engine - Google Patents

Abstract

PURPOSE:To judge misfire positively even in a gasoline engine with the peak voltage showing a damping characteristic corresponding to ignition and misfire by detecting spark discharge voltage after the start of spark discharge of a spark plug, and comparing the detected voltage with the reference value set to the value not more than twice the spark discharge voltage. CONSTITUTION:In an ignition device, a means for preventing the contraflow from a spark plug to a secondary circuit is provided between the spark plug and the secondary circuit in an ignition coil. A misfire detecting device 20 detects the misfire state of a gasoline engine on the basis of the detected voltage between discharge electrodes in the spark plug. In this case, the spark discharge voltage detected during the specified period after the start of spark discharge of the spark plug is memory-held by a sample holding circuit 22. On the basis of the stored spark discharge voltage, the value not more than twice the value of this voltage is set as the reference value by a voltage dividing circuit 23. The reference value and detection value of voltage are further compared by a comparing circuit 24, and a misfire judging part 26 judges the misfire of the gasoline engine according to the compared result.

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 a gasoline engine, which detects the presence or absence of a misfire in a gasoline engine based on a change in the voltage of the electric charge charged in the floating capacitance of the spark plug after the spark discharge is completed. Regarding

[0002]

2. Description of the Related Art In a gasoline engine, an electromotive force is generated in a secondary circuit of an ignition coil even after completion of spark discharge, and a floating capacitance of a spark plug is charged with a voltage corresponding to the electromotive force. Here, the ion density between the electrodes of the spark plug differs depending on ignition or misfire in the gasoline engine.
As a result, the attenuation characteristic of the voltage generated in the spark plug after the completion of the spark discharge depends on the ion density between the electrodes of the spark plug and changes differently depending on the presence or absence of ignition. For this reason,
Detects the change in the voltage of the spark plug after the spark discharge,
There is one that detects the presence or absence of a misfire based on the attenuation characteristic of the voltage. In the conventional misfire detection device based on the voltage decay characteristic of this spark plug, as a method of detecting the voltage decay characteristic, the insulation coating of each plug cord that connects the distributor and each spark plug is used as a dielectric, and each plug is The voltage between the electrodes of the spark plug is obtained as the voltage signal of the sensor by the electrostatic capacity between the conductor provided at the center of the cord and the peak voltage information of the sensor after the spark discharge is stored and retained. (Hold), and then the misfire detection is determined based on the time until the voltage drops to a reference value determined at a predetermined rate (for example, 1/3) based on the stored and held peak voltage. .

On the other hand, in high-speed, high-load operation of the engine, the voltage after the spark discharge is significantly increased, and the electric charges charged in the floating electrostatic capacity of the spark plug are spark-discharged in the spark discharge gap of the spark plug, The voltage may drop sharply (instantaneous breakdown) regardless of ignition or misfire. In such a case, in the misfire state, the voltage of the sensor after the end of the spark discharge does not drop gently, and the fall time of the voltage becomes extremely short. Therefore, the conventional misfire detection device cannot detect the misfire. Therefore, even if misfire cannot be detected in the determination based on the voltage decay characteristics due to an instantaneous breakdown, the peak voltage after the spark discharge is set to a predetermined voltage value in order to detect misfire. There is a type in which a peak voltage determination circuit for determining a misfire state when exceeding the above is added to the one for discriminating by the attenuation characteristic of the voltage and the misfire detection is performed by using two types of discrimination in combination.

[0004]

However, in a gasoline engine, when the voltage appearing at the sensor after the spark discharge has finished reaches a peak, the voltage is suddenly attenuated, and then the voltage that is abruptly attenuated is used to determine whether ignition has occurred. Some exhibit damping characteristics. In such a gasoline engine, since the attenuation characteristic of the sensor voltage depending on the presence or absence of ignition appears from the voltage at the time when it is significantly attenuated from the peak voltage, the misfire by the conventional misfire detection device that sets the reference value based on the peak voltage. In this determination, the peak voltage that appears in the sensor after the spark discharge ends changes according to the engine operating conditions and has different values depending on the sensor variations.Therefore, to prevent accidental misfire detection during ignition. It is necessary to give a margin to the reference value set based on the peak voltage. Therefore, even in the case of misfire, the decay time of the voltage is shortened in most cases, so that misfire cannot be detected correctly. In addition, as described above, in order to avoid the influence of sensor variation, in order to avoid the influence of sensor variation, in order to eliminate the false misfire detection, the method of comparing the peak voltage of the sensor with a predetermined voltage value is also used as a measure against the instantaneous breakdown. Similarly, it is necessary to set a sufficiently large reference value for discrimination. Therefore, even if two types of judgment, one for judging misfire based on the voltage decay characteristic and one for judging misfire by comparing the peak voltage with a predetermined voltage are used together, the misfire detection rate is significantly increased. There is a problem that it is difficult to improve.

The present invention relates to a sensor for detecting the voltage between the discharge electrodes of the spark plug even in a gasoline engine in which the peak voltage between the electrodes of the spark plug after the spark discharge has been drastically attenuated irrespective of the presence or absence of ignition. A misfire detection device for a gasoline engine that can detect misfires with certainty even if there are variations, and can reliably detect misfires even when an instantaneous breakdown occurs during misfires. The purpose is to provide.

[0006]

According to a first aspect of the present invention, an ignition plug is connected to a secondary circuit of an ignition coil that generates a high voltage for spark discharge by intermittently flowing a primary current, and the ignition plug and the ignition are connected. An ignition device having a backflow preventing means for preventing a backflow from the spark plug to the secondary circuit between the secondary circuit of the coil and a voltage detecting means for detecting a voltage between discharge electrodes of the spark plug. In a misfire detection device for a gasoline engine that detects a misfire state of the gasoline engine based on the detected voltage, the spark discharge voltage detected by the voltage detection means is stored and retained in a predetermined period after the spark discharge is started in the spark plug. Spark discharge voltage storage means, first reference value setting means for setting a first reference value based on the spark discharge voltage stored in the spark discharge voltage storage means, and the first base A technique including first voltage comparing means for comparing the first reference value of the value setting means with the detected voltage, and misfire determining means for determining misfire of the engine based on the comparison result of the first voltage comparing means. As a means.

According to a second aspect of the present invention, the misfire determination means further sets a second reference value larger than the spark discharge voltage based on the spark discharge voltage stored in the spark discharge voltage storage means. Reference value setting means, and the second
A charging / discharging circuit that compares a reference value with the detection voltage and charges the detection voltage and discharges the detection voltage with a predetermined time constant when the detection voltage is greater than the second reference value; and a voltage of the charging / discharging circuit as a fixed voltage. A technical means is provided with a second voltage comparing means for comparing, and discriminating misfire detection of the gasoline engine based on each comparison result of the first voltage comparing means and the second voltage comparing means.

[0008]

According to the present invention, in claim 1, when the spark discharge is started by the ignition device, the detection voltage of the voltage detection means is stored in the spark discharge voltage storage means as the spark discharge voltage, and based on the spark discharge voltage. The first reference value in the range of 2 times or less is set by voltage division or the like, and the first reference value of 2 times or less of the spark discharge voltage that is not too large with respect to the spark discharge voltage is set. The detected voltage is compared with this first reference value. Here, the voltage detected during the spark discharge is the voltage generated by the voltage drop due to the spark discharge current in the spark discharge between the spark discharge electrodes of the spark plug, which is determined by the specifications of the secondary circuit of the ignition device, the ignition system such as the spark plug, etc. Since the first reference value is determined based on this voltage, the first reference value is a value determined regardless of the variation of the sensor as the voltage detection unit that detects the voltage of the spark plug. As a result, the detection voltage of the voltage detection means after the spark discharge ends is significantly reduced (decreased) after once reaching the peak voltage.
Even in a gasoline engine that operates, the first reference value can be appropriately set by a partial pressure value, etc., and the detected voltage after being attenuated from the peak voltage by comparing the detected voltage with the first reference value , In the case of misfire, the duration of the state where the detected voltage is higher than the first reference value is long, and in the case of ignition, the duration is short, so until the detected voltage decays to the first reference value or less. Misfire can be detected based on the duration of. In this way, the first voltage determining means can detect misfire when the instantaneous breakdown in which the detected voltage sharply drops to 0 level does not occur.

According to a second aspect, based on the spark discharge voltage stored in the spark discharge voltage storage means as the spark discharge voltage,
A second reference value larger than the spark discharge voltage is set, and the detection voltage of the voltage detecting means is compared with this second reference value. Here, the second reference value is determined based on the voltage generated by the voltage drop due to the spark discharge current in the spark discharge between the spark discharge electrodes of the spark plug, which is determined by the specifications of the ignition system, as described above. The value is determined irrespective of the variation of the sensor as the voltage detecting means for detecting When the gasoline engine is operating at high speed and under high load, the detected voltage after the spark discharge is extremely high.However, when the ignition is normal, there are ions between the spark discharge gaps of the spark plug and the charge is discharged by the ions. Therefore, 3
In the case of a misfire, it rises to a voltage of more than 10 kilovolts, which is independent of any instantaneous breakdown that may occur thereafter. Therefore, when the detected voltage is larger than the second reference value which is determined to be larger than that based on the specifications of the ignition system, the detected voltage is charged in the charge / discharge circuit and discharged at a predetermined time constant, Even if charging is performed in the case of normal ignition, the voltage of the charging / discharging circuit quickly becomes lower than the fixed voltage because the voltage that is not so high with respect to the second reference value is charged. The voltage charged in the charging / discharging circuit exceeds the fixed voltage because it takes a long time until the voltage of the charging / discharging circuit becomes lower than the fixed voltage. By measuring the duration of this state, the misfire state can be detected without being affected by the variation of the sensor as the voltage detecting means.

As described above, in the cylinder, when the detection voltage breaks down from the peak voltage, even if the misfire cannot be detected depending on the comparison result of the first voltage comparison means, the second voltage is detected. In the comparison means, when the detected voltage rapidly falls below the second reference value, the voltage charged at the time of misfire increases, and the decay time until it decays to a fixed voltage or less becomes long. Can be detected.

[0011]

According to the first aspect of the present invention, the voltage between the discharge electrodes of the spark plug after completion of the spark discharge is compared with a first reference value which is set to be less than twice the spark discharge voltage. Since the misfire is detected based on the comparison result of the voltage comparison means, the voltage between the electrodes of the spark plug after the spark discharge is once abruptly attenuated (decreased) from the peak voltage, and then, depending on the presence or absence of ignition. Even in a gasoline engine exhibiting a damping characteristic, misfire can be detected by the comparison result of the first voltage comparison means. The first reference value, which serves as a reference for misfire detection by the first voltage comparison means, is set based on the voltage generated by the voltage drop due to the spark discharge current in the spark discharge between the spark discharge electrodes of the spark plug, which is determined by the specifications of the ignition system. Therefore, there is no influence of the variation of the sensor as the voltage detecting means for detecting the voltage between the spark discharge electrodes of the spark plug.

Further, in the invention of claim 2, the voltage between the discharge electrodes of the spark plug after the spark discharge is finished is compared with a second reference value which is set higher than that based on the discharge voltage,
When the detected voltage is higher than the second reference value, the voltage is charged, and the misfire is detected from the comparison result of the second voltage comparison means that compares the degree of decrease of the charged voltage with the fixed voltage.
Even if the misfire cannot be detected by the comparison result of the first voltage comparison means due to the instantaneous breakdown, the second voltage
The misfire can be reliably detected by the comparison result of the voltage comparing means. Each of the first and second reference values serving as a reference for misfire detection by each voltage comparison means is a voltage generated by a voltage drop due to a spark discharge current in a spark discharge between spark discharge electrodes of a spark plug which is determined by specifications of an ignition system. Since it is set based on the above, it is not affected by the variation of the sensor as the voltage detecting means for detecting the voltage between the spark discharge electrodes of the spark plug.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on the embodiments shown in the drawings. FIG. 1 shows one embodiment of a misfire device for a gasoline engine according to the present invention, which includes an ignition device 10 and a misfire detection circuit 20.
And a sensor 50. In the ignition device 10, 1
Is an ignition coil, 2 is a distributor, 3 is a spark plug having the number of cylinders,
41 is a switching element transistor, 42 is a signal generator, V is an on-vehicle power supply, and 43 is a backflow prevention diode. A high voltage from the secondary circuit of the ignition coil 1 is applied to each spark plug 3.

The sensor 50 for detecting the voltage between the electrodes of each spark plug 3 uses the insulating coating of each plug cord connecting the distributor 2 and each spark plug 3 as a dielectric, and the center of each plug cord. A sensor capacitor 51 formed by an electrostatic capacity between the conductor and a conductor provided corresponding to the conductor, and for connecting the sensor capacitor 51 in series and dividing the voltage between the electrodes of the ignition plug 3. A capacitor 52 for forming a voltage dividing circuit, and a capacitor 52
And a resistor 53 connected in parallel with the capacitor 52 for discharging the.

Here, each of the capacitors 51 has an electrostatic capacity of, for example, 1 pF, and the capacitor 52 has an electrostatic capacity of 3000 pF, and the voltage dividing circuit composed of these capacitors 51 and 52 is used. The voltage between the electrodes of the spark plug 3 is divided into 1/3000, and a high voltage of up to 30,000 volts is converted to the order of 10 volts. Further, the resistor 53 has a resistance value of 3 M ohms, whereby the time constant of the discharging circuit of the capacitor 52 is set to 9 ms (millisecond).

The misfire detection circuit 20, as shown in FIG.
The first voltage comparison unit 21, which is the center of misfire detection, and the sensor 5
A second voltage comparing section 30 that assists the first voltage comparing section 21 against an instantaneous breakdown of the output of 0, and a misfire determining section 26 that determines output signals of these voltage comparing sections via an OR circuit 25. And a zero potential setting circuit 20a for setting the potential of the output of the sensor 50 to zero potential according to the signal of the signal generator 42.

The first voltage comparison unit 21 samples and holds the output of the sensor 50 for a certain period (for example, 200 microseconds) immediately after the start of spark discharge in response to the ignition timing signal from the signal generator 42. A voltage dividing circuit 23 that divides the spark discharge voltage value held by the hold circuit 22 into a predetermined ratio (for example, 3/4) to obtain a divided voltage value, and the divided voltage value of the voltage dividing circuit 23 as a reference value It comprises a comparison circuit 24 which compares the output voltage of 50 and outputs a signal according to the comparison result of the output of the sensor 50 and the divided voltage value. When the output of the sensor 50 is higher than the voltage division value by the first voltage comparison unit 21 having these configurations, a high level signal is sent from the comparison circuit 24, and the output of the sensor 50 becomes lower than the voltage division value. , A low level signal is transmitted.

Here, the voltage division value of the voltage dividing circuit 23 is not a value based on the peak voltage of the sensor 50 after the spark discharge is completed, but is a voltage determined by the specifications of the ignition system in a predetermined period immediately after the spark discharge is started. Sample-held sensor 50
Since it is set based on the output voltage of the sensor 50, it can be set regardless of the variation in the capacitance of the spark plug 3 as the sensor 50. As a result, even after the output voltage of the sensor 50 after the spark discharge has reached the peak voltage and is significantly attenuated, even in an engine exhibiting an attenuation characteristic according to ignition and misfire, the voltage change after the peak is normally ignited. In this case, the decrease rate of the output voltage of the sensor 50 after the completion of the spark discharge is fast, so the high-level duration of the output of the comparison circuit 24 becomes short, and in the case of misfire, the decrease rate of the output of the sensor 50. Is high, the high-level duration of the output of the comparison circuit 24 is long. Therefore, misfire detection omission due to variations in the sensitivity of the sensor 50 can be eliminated, and highly accurate misfire detection can be performed. Here, in order to set the first reference value in the comparison circuit 24, the voltage dividing circuit 23
However, the first reference value is 2 with respect to the spark discharge voltage.
It does not have to be more than twice as large, and the spark discharge voltage held in the sample and hold circuit 22 is, for example, 0.5 to 1.
It may be set in a range up to 5 times.

The second voltage comparing section 30 detects the misfire in the engine so that the misfire can be detected even when an instantaneous breakdown occurs when the misfire occurs.
It is provided to compensate for misfire detection by the voltage comparison unit 21, and is set to a large value with respect to the value sampled and held at a predetermined time immediately after the start of spark discharge determined according to the ignition timing signal of the signal generator 42. When the output of the sensor 50 becomes larger than the reference value, the output voltage of the sensor 50 is charged, and the charging voltage is compared with a predetermined voltage while discharging with a predetermined time constant, and according to the comparison result. Emit a signal. Specifically, the first voltage comparison unit 2
The reference value setting circuit 31 that sets a constant multiple of the average value of the voltage sampled and held in the first sample and hold circuit 22 as the reference value, and the output of the sensor 50 is the reference value setting circuit 31.
Of the output voltage of the sensor 50 and the charge / discharge circuit 33 that discharges the charged electric charge with a predetermined time constant.
Switch circuit 3 for connecting the sensor 50 to the charge / discharge circuit 33 via the zero potential setting circuit 20a in order to charge the output voltage of the sensor 50 when the output voltage of the sensor becomes higher than the reference value.
4. A comparison circuit 35 that compares the charging voltage of the charging / discharging circuit 33 with a fixed reference voltage and outputs a signal according to the comparison result.
Consists of. In the charging / discharging circuit 33, 33a is a charging capacitor, 33b is a resistor for setting the discharging time constant, and in the comparison circuit 35, 35a, 35b.
Is a resistor for voltage division.

With these configurations, the second voltage comparison unit 30
Charges the charging / discharging circuit 33 as the peak voltage of the output of the sensor 50 when the output voltage of the sensor 50 becomes larger than a constant multiple of the voltage sampled and held at a predetermined time immediately after the spark discharge. The peak voltage charged in the charging / discharging circuit 33 does not become so high in the case of normal ignition, so in the comparison by the comparison circuit 35, the high level output ends in a short time and changes to the low level output. On the other hand, in the case of a misfire, the peak voltage of the sensor 50 to be charged is higher than that in the case of normal ignition at the time of charging, even if an instantaneous breakdown may occur thereafter. Since it takes a long time for the charge charge of the charge / discharge circuit 33 to decrease to a predetermined voltage value, the comparison circuit 35 makes a high-level output for a longer time than in the case of normal ignition.

The OR circuit 25 includes the first voltage comparison section 2 described above.
A logical sum signal of the outputs of the comparison circuits 24 and 35 of the first and second voltage comparison units 30 is obtained and used as a signal for misfire detection in the misfire determination unit 26 described later.

The misfire determination section 26 measures the duration of the sum of the respective high level signals of the first voltage comparison section 21 and the second voltage comparison section 30 obtained via the OR circuit 25 with a microcomputer, and the duration time. Is longer than the predetermined time, it is determined as misfire, and if shorter than the predetermined time is determined as normal ignition.

Next, the operation of the misfire detecting device of the present embodiment having the above construction will be explained together with the operation of the gasoline engine with reference to FIG. When the transistor 41 is turned on and off by the ignition timing signal of the signal generator 42, a pulse current flows in the primary circuit of the ignition coil 1. Due to this intermittent pulse current, a secondary voltage is generated in the secondary coil of the ignition coil 1, and the spark plug 3 starts spark discharge at time t1 due to the high voltage generated at the end of the pulse current. Induction discharge occurs, and this spark discharge lasts for a time corresponding to the rotational speed of the gasoline engine, and ends at time t2 as the electric energy of the ignition coil 1 decreases.

After the spark discharge is completed, the secondary voltage starts to be boosted by the electric energy remaining in the ignition coil 1, and a high voltage (2 to 3 at low speed operation) corresponding to the rotational speed of the gasoline engine is started.
The voltage is boosted to the maximum value p of kilovolts, 5 to 8 kilovolts at high speed operation, and then stepped down. The secondary voltage after the completion of this spark discharge shows the electric charge charged in the electrostatic capacitance (usually 10 to 20 pF) between the discharge electrodes of the spark plug 3, and the maximum value p
The secondary voltage waveform after the passage of the apex waveform including the is sharply decreased after the time t3 when it is significantly decreased from the maximum value p in the case of misfire, as shown by the solid line A, and when the ignition is normally performed. As shown by the solid line B, the value decreases rapidly as compared with the case of misfire.

On the other hand, in the misfire detection device 20 for detecting misfire based on the secondary voltage changing as described above, according to the ignition timing signal from the signal generator 42,
The zero potential setting circuit 20 at time t0 immediately before the generation of the spark discharge voltage.
The output voltage of the sensor 50 is set to zero potential by a, and thereafter, a predetermined period (time ta to t
In b), the output of the sensor 50 is sampled and held by the sample and hold circuit 22. As a result, the output voltage determined by the specifications of the ignition system is held in the sample hold circuit 22 regardless of the variation in the sensitivity of the sensor 50, and the divided voltage value and the reference value that is a constant multiple thereof are set.
After the spark discharge ends, the output signal of the comparison circuit 24 becomes a high level while the output voltage of the sensor 50 is larger than the divided voltage value, and becomes a low level signal when the output voltage of the sensor 50 becomes smaller than the divided voltage value. .

When the engine is normally ignited, the output voltage of the sensor 50 after the spark discharge is significantly reduced after the maximum value p after the spark discharge, regardless of whether the engine is operating at low speed or high speed. In the first voltage comparison circuit 24, the high level continues for a short period of time because it decays quickly, and when the misfire occurs, it takes time for the output voltage of the sensor 50 to decay, so the high level becomes long. Further, when the output voltage of the sensor 50 becomes larger than the reference value of the reference value setting circuit 31, the output voltage of the sensor 50 at that time is charged in the charge / discharge circuit 33, and the charge is discharged with a predetermined time constant, and the charge / discharge is performed. The voltage of the circuit 33 decreases in a time corresponding to the charged electric charge regardless of the presence or absence of the instantaneous breakdown in the spark plug 3 thereafter.

Here, in the case of a misfire during high-speed operation of the engine, the sensor 5 is activated after the spark discharge voltage for ignition ends.
After the output voltage of 0 becomes high and shows a maximum value p and drops significantly, an instantaneous breakdown may occur. In such a case, the output signal of the first voltage comparison unit 21 has a short high-level duration, and therefore misfire cannot be detected based on the signal. However, in the present embodiment, when the output voltage of the sensor 50 in the second voltage comparison unit 30 exceeds the reference value set based on the output voltage sampled and held in the fixed period immediately after the start of the spark discharge, The output voltage is charged into the charging / discharging circuit 33, and the time during which the voltage in the discharge is higher than a predetermined voltage is measured to detect a misfire. Misfires can be detected.

The misfire determination section 26 measures the duration of time when the sum of the output signals of the comparison circuit 24 and the comparison circuit 35 transmitted via the OR circuit 25 is high level, and when the duration is short, It is determined that the ignition is normal, and when the high level continues for a predetermined time or longer, it is determined as the engine misfire state.

Therefore, in the engine, the misfire when the instantaneous breakdown does not occur is output by the output signal of the first voltage comparison unit 21, and the misfire when the instantaneous breakdown occurs is output by the output signal of the second voltage comparison unit 30. Since it can be detected, misfire of the engine can be surely detected. Further, since the partial pressure value and the reference value of each voltage comparison unit are set as the voltage determined by the specifications of the ignition system based on the output voltage of the sensor 50 sampled and held in a predetermined period immediately after the start of the spark discharge, the sensor 50 Spark plug 3 as
It can be set regardless of the variation of the electrostatic capacitance. As a result, misfire detection omission due to variations in the sensitivity of the sensor 50 can be eliminated, and highly accurate misfire detection can be performed. As described above, in the present embodiment, after the spark discharge is completed, the output voltage of the sensor 50 is significantly reduced from the peak voltage, and even in the engine exhibiting the attenuation characteristic according to ignition and misfire, the spark plug 3 is also formed after the spark discharge is completed. It is possible to detect misfire based on the voltage between the electrodes due to the electrostatic capacitance of, and to reliably detect misfire accompanied by an instantaneous breakdown that tends to occur during high-speed operation of the engine without being affected by variations in the sensor 50. can do.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an ignition device to which a misfire detection device of the present invention is applied.

FIG. 2 is a block diagram showing a configuration of a misfire detection device of the present invention.

FIG. 3 is a time chart showing an output waveform of a sensor for explaining the operation of the misfire detection device of the present invention.

[Explanation of symbols]

 1 Ignition coil 3 Spark plug 10 Ignition device 20 Misfire detection circuit (gasoline engine misfire detection device) 22 Sample hold circuit (spark discharge voltage storage means) 23 Voltage dividing circuit (first reference value setting means) 24 Comparison circuit (first) Voltage comparison means) 26 misfire determination section (misfire determination means) 31 reference value setting circuit (second reference value setting means) 33 charge / discharge circuit 35 comparison circuit (second voltage comparison means) 43 diode (backflow prevention means) 50 Sensor (voltage detection means)

[Procedure amendment]

[Submission date] June 22, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F02P 15/00 302 Z G01M 15/00 Z 7324-2G

Claims (2)

[Claims] 1. A spark plug is connected to a secondary circuit of an ignition coil that generates a high voltage for spark discharge by intermittently flowing a primary current, and the spark plug is provided between the spark plug and the secondary circuit of the ignition coil. From the secondary circuit to the secondary circuit to prevent the backflow, the ignition device is provided with voltage detection means for detecting the voltage between the discharge electrodes of the spark plug, the misfire state of the gasoline engine based on the detected voltage. In a misfire detection device for a gasoline engine for detecting the spark discharge voltage storage means for storing and holding the spark discharge voltage detected by the voltage detection means during a predetermined period after the start of spark discharge in the spark plug, and the spark discharge voltage storage means. First reference value setting means for setting a value equal to or less than twice the spark discharge voltage stored in the means as the first reference value, and before the first reference value setting means Misfire detection of a gasoline engine comprising first voltage comparison means for comparing the first reference value with the detected voltage and misfire determination means for judging engine misfire based on the comparison result of the first voltage comparison means. apparatus. 2. The misfire determination means includes a second reference value setting means for setting a second reference value larger than the spark discharge voltage based on the spark discharge voltage stored in the spark discharge voltage storage means, and A charge / discharge circuit that compares a second reference value with the detection voltage, charges the detection voltage and discharges the detection voltage with a predetermined time constant when the detection voltage is greater than the second reference value, and a voltage of the charge / discharge circuit is fixed. A second voltage comparing means for comparing with a voltage, wherein the misfire detection of the gasoline engine is discriminated based on each comparison result of the first voltage comparing means and the second voltage comparing means. Engine misfire detection device.