JPH0552176A - Misfire detecting device for gasoline engine - Google Patents

Abstract

PURPOSE:To provide a misfire detecting device whereby a misfire can be accurately detected with constitution of facilitating mounting and maintenance. CONSTITUTION:A DLI(distributorless igniter) type ignition device comprises a secondary voltage detecting circuit 6 for detecting secondary divided voltage 5 applied to a spark plug 3 and a damping characteristic of a secondary voltage waveform, peak voltage detecting circuit 8 of the secondary voltage waveform after ending a spark discharge and a misfire detecting and discriminating circuit 7, 8 for discriminating a misfire by a level of the peak voltage value or the above-mentioned damping characteristic of secondary voltage. An ignition circuit having a distributor comprises a spark plug electrostatic capacity charging voltage generating means, voltage divider 5, secondary voltage detecting circuit 6 for detecting a damping characteristic of the secondary voltage waveform, peak voltage detecting circuit 8 of the secondary voltage waveform after ending a spark discharge and misfire detecting and discriminating circuits 7, 9 for discriminating a misfire by a level of the peak voltage value or the above- mentioned damping characteristic of the secondary voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gasoline engine (engine) in which the electric resistance value of the spark discharge gap of the spark plug is different when the ignition is normally performed and when an ignition error (misfire) occurs. The present invention relates to a misfire 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. As a misfire detecting device, conventionally, a method of making a hole in a cylinder block and mounting a combustion optical sensor, mounting a pressure sensor on a mounting seat of a spark plug, and measuring an ionic current of an ignition circuit are known.

[0003]

The conventional method is suitable for experimental use such as engine test, but it is troublesome to install the sensor on all cylinders of an actual vehicle engine, and the sensor is troublesome for constant use. There are drawbacks such as the need for a high-voltage diode to detect the current and the need for maintenance. An object of the present invention is to provide a misfire detection device that is easy to implement and maintain and that can accurately detect misfire.

[0004]

DISCLOSURE OF THE INVENTION The misfire detection device of the present invention is mainly used in a gasoline engine equipped with a distributor-less igniter (hereinafter referred to as DLI) type ignition device to detect a secondary voltage applied to a spark plug. A voltage divider to detect the partial pressure, a secondary voltage detection circuit that detects the attenuation characteristics of the secondary voltage after the time set before and after the spark discharge, and the peak voltage of the secondary voltage waveform after the spark discharge. It comprises a peak voltage detection circuit for detecting a value and a misfire discrimination circuit for discriminating a misfire based on the level of the peak voltage value or the attenuation characteristic of the secondary voltage.

Further, in a gasoline engine mainly equipped with an ignition circuit having a distributor, an ignition coil is provided at a predetermined time after completion of spark discharge due to induction discharge in a spark plug during low-speed low-load operation of the engine. The primary circuit is energized and the energization is cut off after a certain period of time to generate an electromotive force in the secondary circuit. A spark plug capacitance charging voltage generating means and a partial voltage of the secondary voltage applied to the spark plug are provided. The voltage divider for detection and the high-speed operation of the engine detect the attenuation characteristics of the secondary voltage waveform after the time set before and after the end of the spark discharge, and during low-speed low-load operation of the engine, the spark plug capacitance A secondary voltage detection circuit that detects the attenuation characteristic of the secondary voltage waveform generated by the charging voltage generation means, and a peak voltage value that detects the peak voltage value of the secondary voltage waveform after the spark discharge is completed. And click voltage detecting circuit, the attenuation characteristic of the level or the secondary voltage of the peak voltage value, and a misfire determining circuit for determining a misfire.

[0006]

The invention described in claim 1 is mainly applied to a DLI type ignition device. In this ignition device, the electric energy remaining in the ignition coil immediately after the completion of the spark discharge is charged mainly in the floating capacitance of the spark plug through the backflow prevention diode. This charge has a secondary voltage of 5 to 8 kilovolts when the engine rotates at high speed and 2-3 kilovolts when the engine rotates at low speed. This secondary voltage becomes an ionic current from the spark discharge gap of the spark plug after the spark discharge is completed, and is discharged rapidly (normal ignition), or it leaks from the secondary circuit and slowly discharges (misfire), and is stepped down. To do. Therefore, after monitoring the voltage between the backflow prevention diode and the spark plug, for example, the time until the secondary voltage drops to a certain level with respect to the peak value that is peak-held at an appropriate setting time (decay time). The misfire can be accurately determined by detecting the attenuation characteristic such as, and detecting the peak level itself.

The invention described in claim 2 is mainly applied to an ignition device having a distributor. In this ignition device, there is an air gap such as a rotor gap between the ignition coil and the spark plug. During low-speed operation of the engine, the electric energy remaining in the ignition coil after spark discharge is small and the voltage boost is small, so the level of the secondary voltage is low, and it may be difficult to accurately determine the damping characteristics. Therefore, only during low-speed rotation, the primary current is caused to flow in the primary circuit of the ignition coil for a short time to be interrupted and the secondary voltage is boosted during or after the induction discharge period of the spark discharge period. The level of this boosted secondary voltage (secondary voltage for detecting misfire) is such that the breakdown of the series gap such as the rotor gap of the distributor is possible and the breakdown of the spark plug gap is not possible at the time of misfire (for example, 5 Control to ~ 7 kV). As a result, a voltage is applied to the spark plug, and the electrostatic capacitance of the spark plug is charged. The decay characteristic of the charged electric charge and the level of the peak value are detected in the same manner as above.

During high-speed operation of the engine, the boosting level of the secondary voltage after the spark discharge is high, and the series gap can be broken down. Therefore, the spark plug capacitance charging voltage generation circuit is not operated. It is unnecessary. The peak level is detected for the following reason. When the engine is operating at high speed and under high load, the secondary voltage after the spark discharge ends may become too high and spark discharge may occur in the spark discharge gap of the spark plug. In this case, since the electric charge charged in the floating capacitance of the spark plug is released at one time, the secondary voltage is rapidly lowered even if misfire occurs. Therefore, in the detection of only the secondary voltage drop characteristic,
It is difficult to distinguish from normal ignition. However, in this high-speed and high-load operation, the boosting level of the secondary voltage after the end of the spark discharge is significantly different between normal ignition and misfire. That is, when ions are present normally in the spark discharge gap of the spark plug and the charged charge of the spark plug is discharged as an ionic current, the voltage rises only up to about 3 to 5 kilovolts, whereas spark discharge due to misfire. When you do 10
Step up to a voltage in excess of kilovolts. Therefore, by detecting the secondary voltage after completion of the spark discharge and discriminating the level thereof, it is possible to accurately discriminate the misfire during the high speed and high load operation.

[0009]

As described above, in the misfire detection device of the present invention, the combustion light sensor, the pressure sensor, and the high voltage diode connected in parallel to the rotor gap of the distributor for detecting the ion current are not necessary, and the structure is simple and the automobile is simple. It is possible to obtain a misfire detection device which is excellent in mountability on an engine, easy to maintain, and highly practical.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a DLI type ignition device 100 of a gasoline engine having ignition coils 1 and spark plugs 3 as many as the number of cylinders. The primary circuit 11 of each ignition coil 1 is
The secondary circuit 12 is connected to the vehicle-mounted power source V and the primary current interrupting means 4, and is connected to the spark plug 3 via the backflow prevention diode 13. The voltage divider 5, the secondary voltage detection circuit 6, and the misfire detection circuit 7 are connected to the secondary circuit 12 between the backflow prevention diode 13 and the spark discharge gap 31 of the spark plug 3. In addition, the secondary voltage detection circuit 6
Is provided with a peak voltage detection circuit 8, and its output is input to a misfire determination circuit 9 including the misfire detection circuit 7.

The primary current interrupting means 4 comprises a switching element 41.
And a signal generator 42, which detects 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 voltage divider 5 comprises a secondary circuit 1
A sensor 5 made of a conductor arranged to generate a capacitance of 1 pF (picofarad) between the high voltage lead 2 and the high voltage lead 2.
1 is used, 3000p as a low impedance element
The secondary voltage generated in the secondary circuit 12 is divided into about 1/3000 by using the capacitor 52 having the capacitance of F. In this case, if the 3 megohm resistor 53 forming the discharge circuit of the capacitor 52 is connected in parallel, the time constant of the voltage divider 5 is 9 m.
Since it becomes s (millisecond), the decay time of the secondary voltage waveform, which will be described later and is relatively long such as 2 to 3 ms, can be reliably determined. As a result, the high voltage waveform of about 30,000 volts at the maximum is lowered to the level of 10 volts and is input to the secondary voltage detection circuit 6.

The secondary voltage detection circuit 6 is, as shown in FIG.
The peak hold circuit 61 and the peak hold circuit 61, which are reset at the time set by the signal generator 42 and hold the partial pressure of the voltage divider 5,
The voltage dividing circuit 62 divides the output voltage of the voltage dividing circuit 62, and the comparison circuit 63 that compares the voltage dividing of the voltage dividing circuit 62 with the output of the voltage divider 5 and outputs a pulse output. A microcomputer is used for the misfire detection circuit 7, and the misfire is discriminated by comparing the output pulse of the secondary detection circuit 6 with data obtained in advance by experiments or calculations. The secondary voltage detection circuit 6 is additionally provided with a peak voltage detection circuit 8 for detecting a misfire according to the boosting level of the secondary voltage after the spark discharge is completed. ,
The set reference voltage is compared and output to the misfire determination circuit 9 including the misfire detection circuit 7.

The operation will be described with reference to FIG. The signal generator 42 turns on and off the switch element 41,
The primary circuit 11 generates a primary current such as the pulse wave a. Due to the interruption of the primary current, the secondary voltage shown in the secondary coil L2 of the ignition coil 1 is generated. The high voltage p generated at the end of the pulse wave a starts the spark discharge, which is followed by a gentle secondary voltage waveform q due to the inductive discharge. With respect to the secondary voltage waveform q, the spark discharge lasts for about 2 milliseconds during the low speed operation of the engine, and ends with the reduction of the electric energy of the ignition coil 1. Immediately before this end, the secondary voltage starts to be boosted by the electric energy remaining in the ignition coil 1. Immediately after the end, the secondary voltage is boosted to 2-3 kilovolts and then lowered. Further, during high-speed operation of the engine, the spark discharge lasts for about 1 millisecond, after which the voltage is increased to 5-8 kilovolts and then reduced.

The secondary voltage waveform between the backflow prevention diode 13 and the spark plug 3 after completion of the spark discharge is mainly the electrostatic capacitance of the spark plug 3 (usually 10 to 20 pF).
The discharge state of the charged electric charge is shown in FIG. 6, and as shown in (4), there is a difference in the decay time between normal ignition (solid line) and misfiring (two-dot chain line). That is, when normally ignited, the charged electric charge is discharged as an ionic current through the ions existing in the spark discharge gap 31 of the spark plug 3, and is rapidly attenuated as q ₁ . On the other hand, when there is a misfire, the current leaks through the insulator of the spark plug, the plug cap, etc., so the voltage is gently reduced like q ₂ .

The signal generator 42 is, for example,
Depending on the rotation speed, load, and ignition system specifications, experiment or measurement
Average spark discharge duration under various operating conditions
After 0.5 ms from the time, reset and peak
The peak hold circuit 61 is activated.
Let The charging voltage value at this time is set to the peak hold circuit 61.
Hold and then divide by 1/3 of the voltage divided by the voltage dividing circuit 62.
With the bell as the reference voltage v, the output waveform of the voltage divider 5,
The comparison is made in the comparison circuit 63. The output of this comparison circuit 63
The force pulse is shown in Fig. 3 when the ignition normally occurs.
Short pulse wave t ₁Is output, and when there is a misfire
Long pulse wave t₂Is output to the misfire detection circuit 7.

The misfire detection circuit 7 has a decay time of 3 ms when the engine speed is 1000 rpm, for example.
It was determined that there was a misfire, and at 6000 rpm, 1 ms
It is determined that the misfire has occurred, and in the case of an intermediate operating condition, it is determined that the misfire has occurred when the proportional value is exceeded. In addition, when the center electrode of the spark plug 3 has a positive potential, the ionic current flows more smoothly than when it has a negative potential. It is desirable to set it to a positive potential.

FIG. 4 shows, for example, an engine of 5000 rp.
The secondary voltage waveform during high speed and high load operation such as m and full throttle is shown. Secondary voltage after the spark discharge ended, normal ignition is not boosted only up to about 3-5 kV as q _3, becomes 10 kV or more, as shown in q ₄ at the time of misfire, spark discharge as shown in order q ₅ May instantly reduce the voltage. Therefore, the decay characteristics of the secondary voltage after the end of the peak-holding spark discharge are similar when the ignition is normal, when there is a misfire, and then when the voltage drops due to the spark discharge. Will be difficult. However, as in this embodiment, the level of the secondary voltage after the completion of the spark discharge is detected, and the set level (for example, 10 above) is detected.
It is possible to accurately detect misfires even at high speed and high load operation by distinguishing normal ignition if it is less than or equal to kilovolts and misfire if it is more than that.

FIG. 5 shows an embodiment of the invention according to claim 2. The same reference numerals as in FIG. 1 indicate the same items. This ignition device
A power distributor 2 is provided. In this embodiment, the primary current connecting / disconnecting means 4 comprises a spark plug electrostatic capacity charging voltage generating means which also has the function thereof. When the engine is operated at a low speed of 3000 rpm or less, the boosting level of the secondary voltage after the spark discharge is low. Therefore, the voltage level with which the electrostatic capacitance of the spark plug 3 is charged through the air gap is low, and it is difficult to accurately determine the attenuation characteristic. In this case, separately generating a high level secondary voltage is advantageous for accurate determination of the attenuation characteristic.

Therefore, the spark plug capacitance charging voltage generating means (4) is, for example, 3000 rpm by the engine.
The spark plug capacitance charging voltage is generated only during the following low speed rotation. When the engine is rotating at a high speed of 3000 rpm or higher, the boosting level of the secondary voltage is as high as 5 to 8 kilovolts, and the dielectric breakdown of the air gap is ensured, so that it is not necessary to operate it. The operating range of the spark plug capacitance charging voltage generating means 4 is appropriately determined according to the model of the engine and can be adjusted according to operating conditions such as the engine load, cooling water temperature, and battery voltage.

The action of the engine during the high speed rotation is defined by the above-mentioned claim 1.
The invention is the same as that of the above-mentioned invention, and the operation during low speed rotation will be described with reference to FIG. The signal generator 42 outputs a pulse signal for interrupting the primary current, and causes the primary circuit 11 to generate such a primary current. The pulse wave a having a large width is a signal for generating a spark discharge in the spark plug 3, and the pulse wave having a small width delayed by a delay time i of about 1.5 to 2.0 ms after the end of the pulse wave a. b is a signal for generating a spark plug electrostatic charging voltage (ion detection voltage). In the rotor gap 21 of the power distributor 2, the proximity time between the rotor and the side electrode changes depending on the engine speed, so during medium speed operation of the engine,
It is desirable to set the delay time i as short as about 1.5 ms.

Due to the interruption of the primary current, the secondary circuit 12
In the ignition coil 1, the secondary voltage shown in is generated. The spark discharge is started by the high voltage p generated at the end of the pulse wave a, and then a gentle secondary voltage waveform q due to the inductive discharge is generated and the spark discharge is ended. Next, in response to the rising of the pulse wave b, a positive waveform r due to the back electromotive force is generated in the secondary circuit 12, and electric energy is accumulated in the ignition coil 1 when the primary coil is energized. After the stop, the secondary voltage is boosted again, and the waveform s appears. The re-boosting level of the secondary voltage can be set as desired by the delay time i and the width of the pulse wave b. In the present invention, the level of the waveform s is set so that the dielectric breakdown of the rotor gap 21 is possible, and the discharge becomes impossible if the burning fuel ions do not exist in the spark discharge gap 31 of the spark plug 3. Set to 7 kilovolts.

As a result, between the rotor gap 21 of the distributor 2 and the spark discharge gap 31 of the spark plug 3,
Mainly the capacitance of the spark plug 3 (usually 10-20p
As shown in, the secondary voltage charged in F) has a difference in the decay time between when it normally ignites and when it misfires.
That is, when the ignition is normal, the voltage waveform is a voltage that rapidly drops like a solid line waveform s ₁ , and when the ignition is misfire, a secondary voltage waveform that is gradually attenuated like a two-dot chain line waveform s ₂ . The misfire is determined by reset and peak hold at the set time, detection of the decay time to the level of 1/3 of the peak hold voltage, and determination of the absolute level of the peak value, as in the first aspect of the invention. ..

If a backflow prevention diode is inserted between the ignition coil 1 and the distributor 2, the voltage of 5 to 7 kilovolts charged in the electrostatic capacity of the spark plug 1 will be applied to the rotor gap 21. It is possible to prevent the phenomenon of jumping over and returning to the ignition coil 1 and instantaneously reducing the voltage to 3 to 4 kilovolts, and improving the accuracy of misfire detection. In each of the above embodiments, the secondary voltage of the secondary voltage waveform divided by the voltage divider 5 is held at the set time and the decay time thereof is used as the reference for misfire detection. The secondary voltage level may be detected.

[Brief description of drawings]

FIG. 1 is an ignition circuit diagram of a gasoline engine equipped with the misfire detection device of claim 1.

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

FIG. 3 is a waveform diagram for explaining the operation of the misfire detection device of claim 1.

FIG. 4 is a waveform diagram for explaining the operation of the misfire detection device of claim 1.

FIG. 5 is an ignition circuit diagram of a gasoline engine equipped with the misfire detection device of claim 2.

FIG. 6 is a waveform diagram for explaining the operation of the misfire detection device according to claim 2;

[Explanation of symbols]

 1 Ignition coil 2 Distributor 3 Spark plug 4 Primary current interruption means 5 Voltage divider 6 Secondary voltage detection circuit 7 Misfire detection circuit 8 Peak voltage detection circuit 9 Misfire determination circuit

Front page continuation (72) Inventor Yasushi Ito 14-18 Takatsuji-cho, Mizuho-ku, Nagoya City Nippon Special Ceramics Co., Ltd.

Claims (2)

[Claims] 1. A gasoline engine equipped with an ignition device having an ignition coil, a primary current connection / disconnection means for connecting / disconnecting a current flowing through a primary circuit thereof, a backflow prevention diode provided in a secondary circuit of the ignition coil, and a spark plug. A misfire detection device for detecting the partial voltage of the secondary voltage applied to the spark plug, and a secondary voltage detection device for detecting the secondary voltage attenuation characteristic after the time set before and after the end of the spark discharge. Secondary voltage detection circuit, peak voltage detection circuit for detecting the peak voltage value of the secondary voltage waveform after the end of spark discharge, and misfire discrimination for determining misfire by the level of the peak voltage value or the attenuation characteristic of the secondary voltage. Misfire detection device for gasoline engine consisting of a circuit. 2. A spark ignition engine including an ignition circuit having an ignition coil, a primary current connection / disconnection means for connecting / disconnecting a current flowing through a primary circuit thereof, a distributor provided in a secondary circuit of the ignition coil, and a spark plug. In the misfire detection device of the above, at the low speed and low load operation of the engine, the primary circuit of the ignition coil is energized and the energization is cut off after a predetermined time at a predetermined time after the spark discharge due to the inductive discharge in the spark plug is completed. , A voltage generator for spark plug capacitance charging that generates an electromotive force in the secondary circuit, a voltage divider that detects the partial voltage of the secondary voltage applied to the spark plug, and a spark discharge during high-speed operation of the engine. Attenuation characteristics of the secondary voltage waveform after the time set before and after the end are detected, and during the low speed low load operation of the engine, the secondary voltage generated by the spark plug electrostatic capacity charging voltage generating means. A secondary voltage detection circuit that detects the waveform attenuation characteristic, a peak voltage detection circuit that detects the peak voltage value of the secondary voltage waveform after the end of spark discharge, a level of the peak voltage value or the attenuation characteristic of the secondary voltage. A misfire detection device for a gasoline engine, which comprises a misfire determination circuit for determining a misfire.