JPH05312095A - Gasoline engine combustion condition detector - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a combustion state detection device for a gasoline engine, which is easy to install and maintain, has a compact configuration, and can accurately detect the combustion state of each cylinder. [Structure] A spark plug electrostatic that generates an electromotive force in the secondary circuit 12 by energizing the ignition coil 1 at a predetermined time after the completion of spark discharge due to induction discharge in the spark plug 3 and interrupting the energization for a predetermined time. Capacitance charging voltage generation means 4
A charging current limiting means 5 for limiting the current supplied to the spark plug electrostatic charging voltage generating means to a certain level or less; and a voltage divider for dividing the secondary voltage applied to the spark plug. 6, a secondary voltage detection circuit 7 for detecting the attenuation characteristic of the secondary voltage waveform after the time set after the spark discharge of the spark plug, and an ion density detection circuit 8 for detecting the ion density by the attenuation characteristic. Consists of.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention utilizes combustion in a gasoline engine utilizing the fact that the electric resistance value of the spark discharge gap of a spark plug is different between a normal ignition and a misfiring. The present invention relates to a state detection device.

[0002]

2. Description of the Related Art In gasoline engines such as automobile engines,
In order to purify exhaust gas and improve fuel efficiency, there is a demand for an apparatus that can detect the ignition state of each cylinder of an engine and can prevent misfires in all cylinders. Therefore, there is a method of detecting the combustion state from the decay characteristic of the charge charged in the electrostatic capacity of the spark plug after the spark discharge of the spark plug is completed.

[0003]

However, during the spark discharge of the spark plug or at an appropriate time after the spark discharge, the current of the primary coil is interrupted for a short time and then re-energized to generate the spark plug capacitance charging voltage. When the combustion state is detected by the re-energization for the charging voltage, the primary voltage of the ignition coil is lowered, so that the secondary voltage is lowered and the spark discharge is stopped. However, since the charging voltage is affected not only by the energization time of this voltage but also by the electric energy remaining in the ignition coil, when the spark discharge is limited to a short time, the charging voltage during re-energization after interruption is The voltage was so high that it could be re-discharged. In addition, since the secondary current may become too high to energize and discharge other cylinders, it is necessary to widen the electrodes between the cylinders in the distributor. Therefore, it is necessary to increase the size of the distributor itself by enlarging the cap of the distributor. An object of the present invention is to provide a combustion state detection device for a gasoline engine which is easy to install and maintain, has a compact structure, and can accurately detect the combustion state of each cylinder.

[0004]

A combustion state detecting apparatus for a gasoline engine according to the present invention comprises an ignition coil, a primary current interrupting means for the ignition coil, a distributor or a diode, and a spark plug mounted on a cylinder for spark discharge. A combustion state detection device mounted on an ignition device of a gasoline engine provided, wherein the ignition coil is energized at a predetermined time during or after a spark discharge due to an induction discharge in the spark plug, and the energization is performed after a predetermined time. Spark plug capacitance charging voltage generating means for shutting off and generating an electromotive force in the secondary circuit, and charging current for limiting the current supplied to the spark plug capacitance charging voltage generating means to a predetermined level or less. Limiting means, a voltage divider for dividing the secondary voltage applied to the spark plug, and a second voltage after the time set after the spark discharge of the spark plug is completed. A secondary voltage detector circuit for detecting the attenuation characteristics of the voltage waveform, by the attenuation characteristic, has a structure consisting of a misfire discrimination circuit for discriminating the misfire.

[0005]

In the ignition circuit of the present invention, during the spark discharge of the spark plug or at an appropriate time after the spark discharge, the primary current is supplied to the secondary circuit of the ignition coil for a short time to interrupt the current, and then the spark plug capacitance is set. The spark plug capacitance is charged by the charging voltage generating means. When the primary current is applied, the charging current limiting means is actuated to limit the current to a predetermined value or less, so that the voltage can be limited to a level that does not cause discharge in the spark discharge gap of the spark plug.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an ignition device for a gasoline engine, which is equipped with an ignition coil 1, a distributor (distributor) 2 and a spark plug 3. The primary circuit 11 of the ignition coil 1 is connected to the vehicle-mounted power source V, the primary current interrupting means 4 and the charging current limiting means 5, and the secondary circuit 12 is connected to the spark discharge gap of the spark plug 3 via the distributor 2. Secondary circuit 1 to 31
A voltage divider 6, a secondary voltage detection circuit 7, and a misfire determination circuit 8 are connected to 2.

The primary current interrupting means 4 comprises a switching element 41.
And a signal generator 42. The signal generator 42 inputs signals for the crank angle and throttle opening of the engine, and interrupts the primary current so that the spark discharge timing becomes an ignition advance angle adapted to the load and rotation speed of the engine. .. In this embodiment, the primary current interrupting means 4 also serves as the spark plug electrostatic charging voltage generating means.

The charging current limiting means 5 comprises a resistor 51 connected between the primary current connection / disconnection means 4 and the ground, and operates after completion of the spark discharge. By connecting the resistor 51, if the current value of the primary current supplied from the signal generator 42 to the ignition coil 1 is set to, for example, about 1/6 of the spark discharge voltage, the spark plug after the spark discharge is charged. Energization can be limited to 5-6 KV (kilovolts).

The voltage divider 6 is a secondary circuit 12 of the ignition coil 1.
And a low impedance element 62 connected between the high impedance element 61 and the ground. In this embodiment, a conductor arranged to generate a capacitance of 1 pF (picofarad) between the high impedance element 61 and the high voltage lead of the secondary circuit 12 is used, and the low impedance element 62 is 3000 pF. The secondary voltage generated in the secondary circuit 12 is reduced to 1/3000
Partial pressure is applied. In this case, when a 3 MΩ (mega ohm) resistor 63 forming a discharge circuit is connected in parallel to the capacitor (62), the time constant of the voltage divider 6 becomes 9 ms (milliseconds), and it is possible to reliably determine a relatively long decay time of 3 ms. it can. As a result, the secondary voltage of about 30,000 V (volt) at the maximum is divided into a level of 10 V and input to the secondary voltage detection circuit 7.

The secondary voltage detection circuit 7 is reset at the time set by the signal generator 42 as shown in FIG. 2, and a peak hold circuit 71 for holding the voltage division of the voltage divider 6 and the peak hold circuit 71.
The voltage dividing circuit 72 divides the output voltage of the voltage dividing circuit 72, and the voltage dividing circuit 72 compares the voltage dividing circuit 72 with the output of the voltage divider 6 and outputs a pulse. A microcomputer is used for the misfire determination circuit 8, and the combustion state is determined by comparing the output pulse of the secondary voltage detection circuit 7 with data obtained in advance by experiments or calculations. If a diode indicated by a chain double-dashed line is inserted in the secondary circuit 12 to prevent backflow, the combustion state detection accuracy can be increased.

The operation will be described with reference to FIG. The signal generator 42, which is the primary current interrupting means 4, outputs a pulse wave a for interrupting the primary current as indicated by. The pulse wave a is a signal for causing the spark plug 3 to generate a spark discharge. After the end of the pulse wave a, the pulse wave b from the spark plug capacitance charging voltage generating means (4) is
Since the charging current limiting means 5 is added, the magnitude is about 1/6 of the pulse wave a and is a signal for charging the floating electrostatic capacity of the spark plug 3 with the secondary voltage for combustion state detection.

Due to the interruption of the primary current, the secondary voltage shown in the ignition coil 1 of the secondary circuit 12 is generated. The high voltage p generated at the end of the pulse wave a causes a spark discharge. Next, during or after the spark discharge of the spark plug 3, the secondary voltage is charged by the pulse wave b, and electric energy is accumulated in the ignition coil 1 when the primary coil is energized, so that the spark discharge of the spark plug 3 is generated. It is cut off on the way, and a secondary voltage (waveform s) for detecting the combustion state is generated in the secondary circuit 12. At this time, the pulse wave b may be a pulse wave b ₁ that gradually decreases from the peak current value as indicated by. This is effective when the spark discharge of the spark plug 3 is forcibly stopped by the pulse wave b ₁ during the spark plug spark discharge.

With respect to the waveform s, there is a difference in the decay time depending on the presence / absence of ions existing in the air gap between the case of normal ignition and the case of misfire. That is, when the ignition is normal, the secondary voltage waveform has a sharp decay like the voltage waveform s ₁ , and when the ignition has failed, the secondary voltage waveform has a gentle drop like the voltage waveform s ₂ . However, an excessive current flows in the energization of the primary coil after the spark discharge, and the secondary voltage waveform is 10K as shown by the voltage waveform s ₃ indicated by the two-dot dashed line.
When the voltage is equal to or higher than V, the voltage is instantly stepped down, and the secondary voltage attenuation characteristics are similar when the ignition is normal and when the battery is discharged after the misfire, and the combustion state may not be detected. For this reason, in the present invention, the charging current limiting means 5 is added to the spark plug capacitance charging voltage generation means (4) to limit the primary current supplied to the ignition coil 1 for detecting the combustion state. To do. As a result, the spark plug capacitance charging voltage is limited, and as shown in the secondary voltage waveform s ₂ , the re-boosting immediately before the end of the induction discharge can be about 3 kilovolts at the maximum.

After that, in the secondary voltage detection circuit 6, the peak voltage value at an appropriate time after the completion of the step-down is held by the peak hold circuit 71 and divided by the voltage dividing circuit 72.
Is used as a reference voltage v and the output waveform of the voltage divider 6 is compared with the comparison circuit 73. This comparison circuit 73
3 outputs to the misfire discrimination circuit 8 a short pulse wave t ₂ shown in FIG. 3 when the ignition normally occurs, and a long pulse wave t ₄ when the misfire occurs. The misfire determination circuit 8 is
When the pulse waves t _{1 to} t ₄ are equal to or more than the specified value, it is determined that the misfire has occurred.

In the present invention, since the voltage waveform s ₁ and the voltage waveform s ₂ which are the secondary voltage waveforms for detecting the combustion state have their currents limited by the charging current limiting means 5,
The secondary voltage for detecting the combustion state can be generated at any time during the spark discharge. Therefore, the time from the start of spark discharge to the charging of the secondary voltage for combustion state detection can be limited,
As a result, there is no need to increase the width of the rotor electrode,
It is not necessary to unnecessarily widen the space between the electrodes 21 in the power distributor 2, and it is not necessary to increase the size of the cap 22 of the power distributor 2. This has the advantage that there is no need to increase the size of the power distributor 2.

The specifications of the ignition coil 1 and the on-vehicle power supply V
It is possible to prevent the detection voltage from becoming high and the ignition coil 1 from discharging, which makes it impossible to detect the combustion state due to variations such as the above. Therefore, it is possible to easily set the condition for determining the combustion state.

[0017]

According to the present invention, since the charging current limiting means is added so that the secondary voltage for detecting the combustion state is not discharged, the condition for determining the combustion state can be easily obtained, and the combustion is compact. It is possible to obtain a combustion state detection device for a gasoline engine with high state discrimination accuracy.

[Brief description of drawings]

FIG. 1 is an ignition circuit diagram of a gasoline engine equipped with a combustion state detecting device of the present invention.

FIG. 2 is a block diagram of a secondary voltage detection circuit.

FIG. 3 is a waveform diagram for explaining the operation of the combustion state detecting device of the present invention.

[Explanation of symbols]

1 Ignition Coil 2 Distributor 3 Spark Plug 4 Primary Voltage Interrupting Means (Spark Plug Capacitance Charging Voltage Generating Means) 5 Charging Current Limiting Means 6 Voltage Divider 7 Secondary Voltage Detection Circuit 8 Misfire Discrimination Circuit

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[Procedure amendment]

[Submission date] February 17, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

[0004]

A combustion state detecting apparatus for a gasoline engine according to the present invention comprises an ignition coil, a primary current interrupting means for the ignition coil, a distributor or a diode, and a spark plug mounted on a cylinder for spark discharge. A combustion state detection device mounted on an ignition device of a gasoline engine provided, wherein the ignition coil is energized at a predetermined time during or after a spark discharge due to an induction discharge in the spark plug, and the energization is performed after a predetermined time. Spark plug capacitance charging voltage generating means for shutting off and generating an electromotive force in the secondary circuit, and charging current for limiting the current supplied to the spark plug capacitance charging voltage generating means to a predetermined level or less. Limiting means, a voltage divider for dividing the secondary voltage applied to the spark plug, and a second voltage after the time set after the spark discharge of the spark plug is completed. A secondary voltage detector circuit for detecting the attenuation characteristics of the voltage waveform by the damping characteristics, detects the ion density
And an ion density detection circuit for outputting .

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an ignition device for a gasoline engine, which is equipped with an ignition coil 1, a distributor (distributor) 2 and a spark plug 3. The primary circuit 11 of the ignition coil 1 is connected to the vehicle-mounted power source V, the primary current interrupting means 4 and the charging current limiting means 5, and the secondary circuit 12 is connected to the spark discharge gap of the spark plug 3 via the distributor 2. Secondary circuit 1 to 31
2 includes a voltage divider 6, a secondary voltage detection circuit 7 and an ion density detector.
The output circuit 8 is connected.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

The voltage divider 6 is a secondary circuit 12 of the ignition coil 1.
And a low impedance element 62 connected between the high impedance element 61 and the ground. In this embodiment, a conductor arranged to generate a capacitance of 1 pF (picofarad) between the high impedance element 61 and the high voltage lead of the secondary circuit 12 is used, and the low impedance element 62 is 3000 pF. The secondary voltage generated in the secondary circuit 12 is reduced to 1/3000
Partial pressure is applied. In this case, when a 3 MΩ (mega ohm) resistor 63 forming a discharge circuit is connected in parallel to the capacitor (62), the time constant of the voltage divider 6 becomes 9 ms (millisecond), and a relatively long decay time of 3 ms can be reliably detected. it can. As a result, the secondary voltage of about 30,000 V (volt) at the maximum is divided into a level of 10 V and input to the secondary voltage detection circuit 7.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

The secondary voltage detection circuit 7 is reset at the time set by the signal generator 42 as shown in FIG. 2, and a peak hold circuit 71 for holding the voltage division of the voltage divider 6 and the peak hold circuit 71.
The voltage dividing circuit 72 divides the output voltage of the voltage dividing circuit 72, and the voltage dividing circuit 72 compares the voltage dividing circuit 72 with the output of the voltage divider 6 and outputs a pulse. A microcomputer is used as the ion density detection circuit 8, and the secondary voltage detection circuit 7 is used.
The output pulse of is compared with the data obtained in advance by experiments or calculations to detect the combustion state. If a diode indicated by a broken line is inserted in the secondary circuit 12 to prevent backflow,
The combustion state detection accuracy can be increased.

[Procedure Amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

After that, in the secondary voltage detection circuit 6, the peak voltage value at an appropriate time after the completion of the step-down is held by the peak hold circuit 71 and divided by the voltage dividing circuit 72.
Is used as a reference voltage v and the output waveform of the voltage divider 6 is compared with the comparison circuit 73. This comparison circuit 73
3 outputs to the ion density detection circuit 8 a short pulse wave t ₂ shown in FIG. 3 when ignition normally occurs, and a long pulse wave t ₄ when misfire occurs. Ion density test
The output circuit 8 detects a misfire when the pulse waves t _{1 to} t ₄ are equal to or more than a specified value.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

The specifications of the ignition coil 1 and the on-vehicle power supply V
It is possible to prevent the detection voltage from becoming higher and the ignition coil 1 from discharging, which makes it impossible to detect the combustion state.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

[0017]

According to the present invention, since the charging current limiting means is added so that the secondary voltage for detecting the combustion state is not discharged, the condition for detecting the combustion state can be easily obtained, and the combustion state is small. A combustion state detection device for a gasoline engine with high state detection accuracy can be obtained.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] Explanation of code

[Correction method] Change

[Correction content]

[Explanation of Codes] 1 Ignition coil 2 Distributor 3 Spark plug 4 Primary voltage interrupting means (spark plug capacitance charging voltage generating means) 5 Charging current limiting means 6 Voltage divider 7 Secondary voltage detection circuit 8 Ion density detection circuit

Claims (1)

[Claims] 1. A combustion state detecting device mounted on an ignition device of a gasoline engine, comprising an ignition coil, a primary current interrupting means thereof, a distributor or a diode, and a spark plug for spark discharge mounted on a cylinder. There is a spark plug electrostatic that generates an electromotive force in the secondary circuit by energizing the ignition coil and interrupting the energization for a certain period of time at a predetermined time after or during the spark discharge due to the induction discharge in the spark plug. Capacitance charging voltage generating means, charging current limiting means for limiting the current supplied to the spark plug electrostatic charging voltage generating means to a predetermined level or less, and a secondary voltage applied to the spark plug. A voltage divider for compressing, a secondary voltage detection circuit for detecting an attenuation characteristic of a secondary voltage waveform after a time set after the spark discharge of the spark plug, and the reduction circuit. Characteristics, the combustion state detecting apparatus of a gasoline engine comprising a misfire discriminating circuit for discriminating the misfire.