JPH0826845B2 - Misfire detection device for gasoline engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misfire detection device for a gasoline engine, which detects whether or not a gasoline engine has misfired, based on a peak voltage of a voltage appearing between electrodes of a spark plug after completion of spark discharge.

[0002]

2. Description of the Related Art As a misfire detection device for a gasoline engine,
After the spark discharge, the voltage due to the residual energy of the secondary circuit of the ignition coil appears between the electrodes of the spark plug, and the voltage at this time varies depending on the ignition or misfire due to the ion density between the electrodes of the spark plug. Then, a misfire is detected by comparing the peak voltage after the spark discharge with a reference voltage.

In such a conventional device, the insulating coating of each plug cord connecting the distributor to each spark plug is used as a dielectric, and the static insulation between the conductor provided at the center conductor of each plug cord is established. The voltage between the electrodes of the spark plug is obtained as the voltage signal of the sensor by the capacitance, and the voltage is compared with the integral value of the integrator circuit that integrates within a predetermined period including the spark discharge period to prevent misfire. To detect.
Here, in the conventional device, the sensor for detecting the voltage appearing at the spark plug is not individually provided for the plurality of cylinders of the gasoline engine, and the signal of one sensor is
It is detected as a voltage signal corresponding to each cylinder in relation to the ignition timing for each cylinder, and the reference value determined based on the detected voltage value does not make a distinction for each cylinder, but only one reference value. The value is set.

[0004]

However, in the gasoline engine, the voltage appearing at the spark plug after the spark discharge is completed is not only different depending on the conditions such as the electrode shape of the spark plug and the gap length, but the spark plug is mounted. The inventor of the present application has found that it also varies depending on the relationship with the air flow in each combustion chamber for each cylinder. Therefore, in the misfire detection device in which the reference value for discriminating misfire is set uniformly regardless of each cylinder as in the conventional art, the misfire is erroneously detected with respect to the difference in the detection voltage for each cylinder. Since it is necessary to give a margin to the reference value to prevent it from happening,
There is a problem that accurate misfire detection cannot be performed.

According to the present invention, misfiring can be accurately detected without being affected by the spark plug electrode shape, the gap length, or the air flow in each combustion chamber of each cylinder in which the spark plug is mounted, which is different for each cylinder. An object is to provide a misfire detection device for a gasoline engine.

[0006]

According to the present invention, claim 1
A peak that detects the peak value of the voltage between the discharge electrodes of the spark plug after the spark discharge is completed, in the ignition device in which the spark plug is connected to the secondary circuit of the ignition coil that generates a high voltage for spark discharge by the interruption of the primary current. In a misfire detection device for a gasoline engine, which is provided with a voltage detection means and detects a misfire state of the gasoline engine based on the detected peak voltage,
Cylinder-specific peak voltage averaging means for obtaining a cylinder-specific average value of the peak voltage detected by the voltage detection means after completion of a plurality of spark discharges for each cylinder of the gasoline engine, and the cylinder-specific peak voltage averaging Cylinder reference value determination means for determining a cylinder reference value for each cylinder based on the cylinder average value of the means, and the peak voltage detected for each cylinder by the voltage detection means for the cylinder reference value determination The technical means is provided with the cylinder-by-cylinder reference value determined for each cylinder by means and the cylinder-by-cylinder comparison means for making a comparison for each cylinder, and determining misfire for each cylinder. Further, according to claim 2, for each cylinder, an average value averaging means for averaging the cylinder-specific average values of a plurality of cylinders other than the cylinder to calculate a cylinder comparison average value, and the cylinder-specific peak. Cylinder comparison means for respectively comparing the cylinder-by-cylinder average value of the corresponding cylinders obtained by the voltage averaging means with the cylinder comparison average value of the average value averaging means, and determining misfire for each cylinder To do this is a technical means.

[0007]

[Action]

<Regarding the operation of claim 1> The peak voltage detecting means holds the voltage between the electrodes of the spark plug after the spark discharge is finished for each cylinder, and the peak voltage after the spark discharge is finished a plurality of times for each cylinder. The average value is calculated. In this case, the peak voltage detecting means may directly detect the peak voltage on the secondary side of the ignition coil for each cylinder, or may detect the peak voltage on the primary side of the ignition coil. In that case, for example, the peak voltage Even if only one sensor is provided as the detection means, the detection voltage by that sensor can be set as the detection voltage for each cylinder of the gasoline engine by time division in synchronization with the ignition timing signal. Therefore, the peak voltage for each cylinder can be detected, and the average value of the peak voltage after completion of the spark discharge can be obtained for each cylinder. From the average value for each cylinder of the peak voltage obtained for each cylinder, for example, a value that is a constant multiple thereof is determined as the reference value for each cylinder, and the peak voltage detected after the spark discharge for each cylinder is The reference value for each cylinder determined for each cylinder is compared, and the presence or absence of misfire in that cylinder is determined based on the comparison result. <Regarding Operation of Claim 2> When only a certain cylinder is continuously misfired while a large number of spark discharges are repeatedly performed, that cylinder is detected by a sensor as peak voltage detecting means. Since the peak value itself of the detected voltage for the above will continuously increase, even if the peak voltage detected by the peak voltage detection means and the cylinder-by-cylinder reference value determined for each cylinder are compared, accurate misfire determination cannot be performed. There are cases. In such a case, the cylinder-by-cylinder average value of the peak voltage of the cylinder in the continuous misfire state becomes significantly higher than the cylinder-by-cylinder average value of the peak voltage of the other cylinders. In claim 2, the average value of the peak voltage for a certain cylinder for each cylinder is
In order to compare the average value for each cylinder of the peak voltage for other cylinders except that cylinder with the average value for cylinder comparison,
Since it is determined that the cylinder-by-cylinder average value of the misfired cylinder is different from the average of the cylinder-by-cylinder average values of the other cylinders, it is possible to determine the misfire of that cylinder. As a result, the cylinder that has misfired can be identified.

[0008]

According to the first aspect of the present invention, the cylinder-by-cylinder reference value is determined for each cylinder by obtaining the cylinder-by-cylinder average value of the peak voltage detected after the completion of the spark discharge for each cylinder of the gasoline engine. Therefore, for example, even if the electrode shape of the spark plug, the gap length, or the air flow in each combustion chamber of each cylinder in which the spark plug is mounted is different for each cylinder,
A cylinder-by-cylinder reference value considering these differences can be set for each cylinder. As a result, an appropriate cylinder-by-cylinder reference value is obtained for each cylinder. Therefore, by comparing the peak voltage detected for each cylinder with the cylinder-by-cylinder reference value, the presence or absence of misfire in that cylinder can be accurately detected. be able to. According to claim 2, even when only one cylinder continuously misfires and the cylinder reference value is not correctly determined, the cylinder reference value of that cylinder is compared with the average of the cylinder reference values of other cylinders. By doing so, the cylinder that misfired can be specified.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now 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 in-vehicle power supply, and each spark plug 3
A high voltage from the secondary circuit 11 of the ignition coil 1 is applied to.

The sensor 50 for detecting the voltage between the electrodes of each spark plug 3 has a plug cord insulation connecting the secondary circuit 11 of the ignition coil 1 and the distributor 2 as a dielectric, and a plug cord A high-voltage side capacitor 51 formed by an electrostatic capacity between the center conductor and a conductor provided corresponding to the center conductor, and the high-voltage side capacitor 51 are connected in series to divide the voltage between the electrodes of the ignition plug 3. And a resistor 53 provided in parallel with the low-voltage side capacitor 52 for discharging the low-voltage side capacitor 52.

Here, the high-voltage side capacitor 51 has an electrostatic capacity of, for example, 1 pF, and the low-voltage side capacitor 52 has an electrostatic capacity of 3000 pF. The voltage dividing circuit divides the voltage between the electrodes of the spark plug 3 into 1/3000, and converts a high voltage of up to 30,000 volts into the order of 10 volts. Further, the resistor 53 is provided for discharging the low-voltage side capacitor 52, but since the frequency component of the peak voltage is about 10 kHz, the impedance (about 5 ．
For example, a resistance value of 500 kΩ is set so that the peak voltage can be reliably detected for 3 kΩ).

The misfire detection circuit 20 is mainly composed of a microcomputer, and as its functional block is shown in FIG. 2, a peak voltage detection section 21, a peak average value calculation section 22, a discrimination level determination section 23, and a cylinder. Another comparison unit 24
And an average value averaging unit 25, a cylinder comparing unit 26, a misfire determining unit 30, and other auxiliary units. The peak voltage detection unit 21 detects the peak voltage after the spark discharge is completed by peak-holding the detection signal of the sensor 50 by the peak hold circuit that is reset immediately after the start of the spark discharge, and further detects the detected peak voltage. In order to obtain a signal for each cylinder, the number of cylinders (for example, the number of cylinders) is divided by time division corresponding to the timing signal for applying the spark discharge voltage from the signal generator 42 to each cylinder.
The four peak voltage signals for each cylinder are divided into four types.

The peak average value calculating section 22 calculates the peak voltage average value for each cylinder for the peak voltage signal for each cylinder divided by the peak voltage detecting section 21.
For the calculation of the peak voltage average value, a moving average obtained by sequentially adding a part of each, for example, 1/20 of the peak voltage signal after completion of the spark discharge of 20 times for each cylinder is used. Then, when the new peak voltage signal is given, the new peak voltage average value is sequentially obtained by deleting the value for the oldest peak voltage signal.

Based on the peak voltage average value for each cylinder calculated by the peak average value calculation unit 22, the determination level determination unit 23 determines a constant multiple of that value as the determination level for each cylinder. The cylinder-by-cylinder comparison unit 24 compares the peak voltage signal divided for each cylinder with the discrimination level of the discrimination level determination unit 23, and outputs a pulse signal according to the comparison result. Here, due to misfire, the peak voltage signal for each cylinder becomes a high level signal while the voltage is higher than the discrimination level, and ignition causes a low level signal while the sensor signal voltage is lower than the discrimination level. The pulse signal is sent in correspondence with the ignition timing of each cylinder.

The average value averaging unit 25 removes the peak voltage average value for each cylinder from the peak voltage average value for each cylinder calculated by the peak average value calculating unit 22, and determines the peaks for other cylinders. Further average the voltage average value,
A cylinder comparison average value for comparing the peak voltage average value of each cylinder with the peak voltage average value of another cylinder is calculated. For the cylinder comparison average value, for example, a constant multiple of the average of the sensor average values of cylinders other than the target cylinder is determined as the value.

The calculation operation of the average value averaging unit 25 is not performed sequentially according to the ignition timing, but is performed independently and arbitrarily. For example, the ignition discharge voltage is applied to each cylinder a large number of times. 1 for every 100 occurrences
It is done at a rate of times. The cylinder comparison unit 26 compares the peak voltage average value of the target cylinder with the cylinder comparison average value of the other cylinders, and outputs a pulse signal according to the comparison result. When the peak voltage average value for a certain cylinder greatly exceeds the average of the peak voltage average values for the other cylinders, it is determined that the cylinder is in continuous misfire. Therefore, in the cylinder comparison unit 26, when a divided peak voltage signal is applied to a certain cylinder,
When it is determined that the cylinder is misfiring, a pulse signal that makes it high level is sent.

The misfire discriminating section 30 discriminates in which cylinder the misfire has occurred from the high-level pulse signal based on the discrimination result of the cylinder-by-cylinder comparing section 24 or the cylinder comparing section 26. Or notify the driver by turning on a lamp. Here, the timing of the pulse signal of each determination unit,
Since it corresponds to each cylinder, the cylinder in which the misfire is detected can be specified from the timing when the high level is detected.

Next, the operation of the misfire detection device of the present embodiment having the above construction will be described together with the operation of the gasoline engine. 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, the secondary circuit 11 of the ignition coil 1
A secondary voltage is generated, and in the spark plug 3, spark discharge starts due to the high voltage generated at the end of the pulse current, and then inductive discharge occurs, and this spark discharge is generated only for a time corresponding to the rotational speed of the gasoline engine. It continues and ends with the reduction of the electrical energy of the ignition coil 1.

After completion of the spark discharge, the secondary voltage starts to be boosted by the electric energy remaining in the ignition coil 1, and the high voltage (2 to 3 in low speed operation) according to the rotational speed of the gasoline engine is started.
Kilovolt, 5 to 8 kilovolts at high speed operation) is boosted to a maximum value and then stepped down. In the misfire detection circuit 20,
After the detection voltage of the sensor 50 is peak-held after the spark discharge is completed, it is divided into peak voltage signals for each cylinder corresponding to the ignition timing signal, and the peak voltage average value is calculated for each cylinder by moving average. Based on that, the discrimination level for each cylinder is determined. The secondary voltage after completion of this spark discharge is longer in the case of normal ignition in the cylinder, the spark discharge time becomes longer, and as a result, the residual energy becomes smaller, so the peak voltage becomes lower, whereas in the case of misfire In this case, the spark discharge time becomes short, and as a result, the residual energy becomes large, so that the peak voltage becomes high.

When a misfire occurs in a cylinder and the voltage of the peak voltage signal is higher than the discrimination level, the cylinder-by-cylinder comparison unit 24 sends a high-level pulse signal at a timing corresponding to the cylinder to normally ignite. If so, a low level signal is transmitted. Therefore, a misfiring cylinder is specified by the timing of the pulse signal of the misfire determination unit.

On the other hand, when only a certain cylinder is continuously misfired while a large number of spark discharges are repeatedly performed, the voltage itself of the peak voltage signal continuously increases, so that In the determination based on the determination level determined based on the peak voltage signal, it may not be possible to accurately compare the peak voltage signals. When such a case occurs, the peak voltage average value of the cylinder in the state of continuous misfire is
Since it is significantly higher than the average of the peak voltage averages of the other cylinders, the cylinder comparison unit 26 determines that the peak voltage average value of the misfiring cylinder is different from the peak voltage average value of the other cylinders. Therefore, a high level pulse signal indicating misfire of the cylinder is transmitted. As a result, the misfire determination unit 30 can identify the cylinder that has misfired.

FIG. 3 shows an example of the frequency distributions at the time of ignition and misfire of the voltage value of the peak voltage signal for each cylinder after the end of spark discharge and an example of the discrimination level determined in each cylinder. Is shown by a broken line, the frequency distribution at the time of misfire is shown by a solid line, and the discrimination level is shown by a chain line, together with each frequency distribution in the entire gasoline engine. In the case of the example shown in FIG. 3, the ignition levels and misfires of each cylinder can be accurately (approximately 100%) determined by the determination levels a, b, c, d of the present invention determined for each cylinder. However, as in the conventional case, when the discrimination level is determined for the entire gasoline engine, the discrimination level as shown by the chain line A should be set so that misfire is not mistakenly discriminated at the time of ignition. Is required, so half of the case of misfire (about 50
It can be seen that misfire is only discriminated only for the (%) degree.

As described above, in the present invention, the discrimination level for discriminating misfire is determined for each cylinder. Therefore, the electrode shape of the spark plug, the gap length, or the inside of each combustion chamber of each cylinder to which the spark plug is mounted is determined. Even if there is a difference in the air flow and the like between the cylinders, it is possible to set a reference value for each cylinder in consideration of those differences. As a result, since an appropriate reference value is obtained for each cylinder, the presence or absence of misfire can be accurately detected by comparing the peak voltage detected for each cylinder with each reference value.

Although the sensor 50 for detecting the voltage between the electrodes of the ignition plug 3 is provided in the secondary circuit 11 of the ignition coil 1 in the embodiment shown in FIG. A voltage dividing circuit using a resistor may be provided on the primary circuit side instead of the sensor 50, and the voltage between the electrodes of the ignition plug 3 can be detected in the same manner as in the above case.

[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 functional block diagram showing a misfire detection device of the present invention.

FIG. 3 is a diagram showing a frequency distribution of a peak voltage signal and a discrimination level for explaining the operation of the misfire detection device of the present invention.

[Explanation of Codes] 1 Ignition coil 3 Spark plug 43 Diode 10 Ignition device 20 Misfire detection circuit (gasoline engine misfire detection device) 21 Peak voltage detection unit (peak voltage detection means) 22 Peak average value calculation unit (cylinder peak voltage) Averaging unit 23 Discrimination level determination unit (reference value determination unit) 24 Cylinder comparison unit (Cylinder comparison unit) 25 Average value averaging unit (Average value averaging unit) 26 Cylinder comparison unit (Cylinder comparison unit)

Claims (2)

[Claims] 1. A peak of the voltage between the discharge electrodes of the spark plug after the spark discharge is completed in an ignition device in which a spark plug is connected to a secondary circuit of an ignition coil that generates a high voltage for spark discharge by interrupting a primary current. Provided with a peak voltage detection means for detecting the value, in a misfire detection device of a gasoline engine for detecting the misfire state of the gasoline engine based on the detected peak voltage, after the spark discharge of a plurality of times for each cylinder of the gasoline engine For each cylinder for each cylinder based on the cylinder-specific peak voltage averaging means for obtaining the cylinder-specific average value of the peak voltage detected by the voltage detection means, and the cylinder-specific average value of the cylinder-specific peak voltage averaging means Cylinder reference value determining means for determining a cylinder reference value, and the peak voltage detected for each cylinder by the voltage detecting means to the cylinder reference value determining means. A misfire detection device for a gasoline engine, comprising: the cylinder-by-cylinder reference value determined for each cylinder; . 2. An average value averaging means for averaging the cylinder-specific average values of a plurality of cylinders other than the cylinder for each cylinder to calculate a cylinder comparison average value, and the cylinder-specific peak voltage average. And a cylinder comparing means for comparing the cylinder-by-cylinder average value of the corresponding cylinder obtained by the averaging means with the cylinder comparison average value of the average value averaging means, and determining misfire for each cylinder. The misfire detection device for a gasoline engine according to claim 1.