JP2003184636A - Engine misfire detection device using ionic current and recording medium recording program used in the device - Google Patents

Abstract

(57) [Problem] To improve the misfire determination accuracy in an engine misfire detection device using ion current. SOLUTION: An ion current value at the time of fuel supply under various operation states is detected (S101), and an ion current value learned at the time of fuel cut is read out from an area corresponding to a corresponding operation state in a learning value table (S102). Then, a difference between the ion current value during fuel supply and the ion current value during fuel cut corresponding to the operating state is calculated (S103), and misfire is determined by comparing the difference value with the misfire determination level (S103).
104 to S106).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine misfire detection device for determining whether or not misfire occurs in each cylinder based on a detected value of an ion current generated in each cylinder.

[0002]

2. Description of the Related Art In an engine using a catalyst for exhaust gas treatment, when a misfire occurs in a cylinder, unburned gas is discharged, which may deteriorate the function of the catalyst and deteriorate the exhaust gas. Therefore, when a misfire has occurred, it is extremely important to notify the driver or perform misfire avoidance control to protect the engine, so that it is extremely important to determine whether or not a misfire has occurred.

As one of such misfire determinations, there is one that determines the misfire based on the ion current generated in each cylinder during combustion. This misfire determination is more advantageous than the case of utilizing the rotational behavior of the engine in an engine equipped with a recent variable valve mechanism, but noise is generated when a coil is driven during ignition, for example. There is a risk of being superimposed on the detected current value. Under such an environment, there is a disadvantage that misfire cannot be detected at the time of misfire, or combustion is erroneously determined as misfire.

In order to prevent misjudgment due to superimposition of electric noise at the time of ignition and other factors, for example, Japanese Patent No. 284
No. 3221 discloses an erroneous determination by reading an ion current value at a predetermined time, comparing it with a threshold value, converting it into a pulse, and removing a high-frequency component of the pulse with a low-pass filter.

[0005]

However, when factors such as engine-to-product variations, plug aging, or high altitude operation are added, the reference ion current detection value changes, and accurate misfire determination is performed. I can't do it.
Moreover, when the ion current waveform is actually measured at the time of misfire, some detected values are seen, and it is necessary to prevent this from being erroneously determined as combustion. No improvement over these can be found in the prior art mentioned above.

The present invention has been made in view of the above points, and an object thereof is to provide an engine misfire detection device capable of making an accurate misfire determination by an ion current even under the above-mentioned circumstances.

[0007]

The invention of an engine misfire detection device using an ion current according to claim 1 for achieving the above object is an ion for detecting an ion current value when fuel is supplied under various operating conditions. Current value detection means, learning means for learning the ion current value at the time of fuel cut in the operating state for each cylinder and recording it as the ion current value, learning corresponding to the ion current value during fuel supply and the operating state It is provided with a calculating means for calculating a difference from the ion current value at the time of fuel cut, and a judging means for comparing the difference value and the misfire judgment level to judge a misfire.

According to this, the ion current value to be actually compared is the difference value between the ion current value during fuel supply under operating conditions and the ion current value learned during fuel cut, which is the noise level. . Therefore, even if a factor such as the secular change of the plug as described in the subject is added, accurate misfire determination can be performed. That is, the noise detection value, which appears as the ion current value detected at the time of misfire, is not erroneously recognized as the combustion state detection value by subtracting the waveform level detection value at the time of fuel cut. The erroneous determination that a small increase in the ion current value of the noise level is determined as the combustion state will not occur.

According to a second aspect of the present invention, there is provided an engine misfire detection device using an ionic current, wherein the ionic current value as a learning value in the learning means is recorded as an ionic current value at the time of fuel cut under various operating conditions. The preset smolder determination value of the plug is compared, and if the ion current value is larger than the smolder determination value, it is determined to be plug smolder and the ion current value is not recorded.

This is because the ion current value at the time of fuel cut is not appropriate when the plug smoldering state occurs in the cylinder despite the fuel cut.
This cannot be recorded as a learning value. Therefore,
This smoldering state of the plug is detected and only the proper value is learned. As a result, it is possible to eliminate a factor that causes an erroneous determination by not recording the detected value of the smoldering state of the plug, so that more accurate misfire determination can be performed.

Incidentally, such a smoldering state of the plug is
This occurs because of the inconvenience caused either in the plug itself or in the ignition system. Therefore, if this can be detected, it is possible to detect and diagnose the failure of the plug and the like.

According to a third aspect of the present invention, there are provided an ionic current value detecting means for detecting an ionic current value at the time of fuel supply under various operating conditions, and an ionic current value at the time of fuel cut in the operating condition. Learning means for learning for each cylinder and recording as an ion current value, calculating means for calculating the difference between the ion current value at the time of fuel supply and the learned ion current value at the time of fuel cut corresponding to the operating state, and the difference value And a misfire determination level are compared with each other, and a program for causing the electronic control unit to function as a determination unit for determining a misfire is recorded.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1A is a schematic configuration diagram for explaining a misfire detection device by an ion current, and FIG. 1B is an electronic control device 20 (hereinafter, simply referred to as “EC
FIG. 4 is a schematic configuration diagram of “U”). In the present embodiment, since each cylinder has the same structure, only one of the cylinders will be described below, and the other cylinders will be omitted.

Reference numeral 1 denotes an engine, and a mixture of air and fuel is supplied to a combustion chamber 5 composed of a piston 2, an intake valve 3, an exhaust valve 4 and the like. When the supplied air-fuel mixture is compressed by the piston 2, in the vicinity of its top dead center, based on an ignition signal from the ECU 20 via the power transistor 27 (see FIG. 2), the ignition plug 23 attached to the cylinder head 23. It is ignited by spark discharge from and causes explosive combustion. Due to the explosive combustion, ions due to ionization are generated in the combustion chamber 5, and the ion current is detected via the plug 23.

As a result, the ion current flowing through the gap of the spark plug 23 is detected by the ion detection circuit 40 via the ion detection line L1 and further output as an analog signal, which will be described later with reference to the microcomputer 30 of the ECU 20 (see FIG. b)) is input. The details of the ion detection circuit 40 will be described later.

The ECU 20 is a device for controlling the engine based on signals from various sensors. The structure of the ECU 20 will be described with reference to FIG. 1 (b). Has an input circuit 31a to which is input, an A / D converter 32 that converts the input signal into a digital signal, and an input circuit 31b to which digital signals from various sensors are input. Then, the microcomputer 30 receives signals from the A / D converter 32 and the digital signal input circuit 31b, and outputs a control signal to various actuators 38 such as a power transistor 27 forming an injector or an igniter via an output circuit 37. It has an input / output port 33 (I / O port) which plays a role of outputting. The microcomputer 30 mainly includes a CPU 34 and a RAM.
35, ROM 36, and I / O port 33 mutually connect to bus 3
9 connected.

RA constituting the microcomputer 30
The M35 and the ROM 36 may be collectively referred to as a memory, and the RAM 35 stores various values (for example, a learning value according to the present invention, an ion current detection value) and the like, and the ROM 3
6 is a control program or a preset fixed value (for example,
The misfire determination level, which will be described later) and the like are recorded. CPU
34 is a ROM 36 based on signals from various sensors
Various types of engine control are performed by performing arithmetic processing according to fixed values and control programs stored in advance.

The analog signal of the ion current output from the ion detection circuit 40 is A / D via the input circuit 31a.
When it is digitally converted by the converter 32 and input through the I / O port 33 of the microcomputer 30, it is arithmetically processed by the CPU 34 and a misfire determination threshold value (hereinafter, referred to as a misfire determination threshold value for determining whether or not a misfire has occurred.
It is referred to as "misfire determination level"). That is,
Here, the misfire determination according to the present invention is performed.

When the detected value of the ion current to be compared does not reach the predetermined level, that is, when it is lower than the misfire determination level, such a state is judged as "misfire" and the warning lamp 28 is operated. Notifying a person of occurrence of misfire, the CPU 34 causes the I / O port 33,
A control signal for avoiding misfire is output to the various actuators 38 via the output circuit 37, and necessary misfire avoidance control is performed.

Next, the structure of the ignition system including the above-mentioned misfire detection device will be described with reference to FIG. The configuration of the ECU 20 in the figure is the same as that described in FIG. 1, and the description thereof is omitted.

The microcomputer 30 of the ECU 20 controls the timing for starting and stopping the energization of the primary coil 22a of the ignition coil 22, that is, the ignition timing based on the engine operating state detected by various sensors. A power transistor 27 forming an igniter is provided between the ECU 20 and the primary coil 22a.
Are arranged, and the power transistor 27 is connected to the ECU 2
Based on the ignition signal from 0, the current to the primary coil 22a is turned on and off. When the power transistor 27 is turned on, a primary current is passed from the battery 21 to the primary coil 22a side. The magnitude of this primary current depends on the battery 21.
It depends on the voltage, energizing time, etc.

Then, after a predetermined time of energization, that is, when the ignition timing is reached, the power transistor 27 is turned off by the signal from the ECU 20, and the primary coil 22a side is shut off. As a result, a counter electromotive force corresponding to the magnitude of this primary current is generated, and thereby a high voltage corresponding to the number of turns of the secondary coil 22b is generated between the terminals on the secondary coil 22b side. By applying this high voltage to the spark plug 23, the plug 2
Spark discharge is generated between the electrodes of No. 3, and the air-fuel mixture is ignited as described above, and explosive combustion is performed.

That is, at the ignition timing when the power transistor 27 is turned off, a high voltage is generated on the side of the secondary coil 22b and the spark plug 23 is ignited, and the secondary coil 22 is ignited.
A discharge current flows through b, the diode (b) and the spark plug 23, and the counter electromotive force in the primary coil 22a causes the capacitor 2 to pass through the diode (c) and the resistor 24.
5 is charged.

After that, as described above, since ions are generated in the combustion chamber 5 by the explosive combustion, the ion current is captured through the spark plug 23, and when the ion current flows between the electrodes, it is sent to the ion detection circuit 40. To detect. The ion detection circuit 40 is connected in parallel to the secondary coil 22b side and the spark plug 23, and has an ion current detection resistor 24,
It is composed of a capacitor 25 and an ion waveform processing circuit 26. Ion current detection resistor 24 and capacitor 25
Are connected in series, and have the role of detecting the ion current flowing through the spark plug 23.

That is, at the time of explosive combustion, an ionic current flows through the resistor 24, the diode (a) and the ignition plug 23 due to the charging voltage charged in the capacitor 25, and a voltage corresponding to the ionic current is generated in the resistor 24. Further, an ion waveform processing circuit 26 is connected in parallel with these, and the voltage generated in the resistor 24 due to the ion current flowing is
Final processing for input to U20 is being performed.

The detected ion current value thus processed is input to the microcomputer 30 of the ECU 20 and the misfire determination according to the present invention is performed. As described above, in the misfire determination based on the ion current, misfire / combustion is determined by comparing the detected value by this and the misfire determination level preset in the ECU 20. When the ECU 20 determines that a misfire has occurred, the ECU 20 turns on or blinks the warning lamp 28 to notify the driver of the occurrence of a misfire, and executes misfire avoidance control as necessary.

A specific procedure for carrying out the misfire determination performed in the ECU 20 for controlling the misfire detecting device of the present invention having the above-described structure, particularly the ignition system including this misfire detecting device, will be described below with reference to FIG. And it demonstrates based on the flowchart of FIG.

First, in step S101 of FIG. 3, the ion current at the time of fuel supply under a predetermined operating condition is detected, and the detection value obtained by this is set as the ion current value Z. FIG. 5A shows an ion current waveform of one cylinder at this time. For example, the first peak (Z = 3.0 V) that appears in the initial combustion period in one combustion period.
And 2 of the second peak (Z = 3.5V) that appears during the heat generation period
It has a mountain-shaped waveform with two local maxima. The increase in the output of the ion current seen on both sides of this mountain-shaped waveform is noise.

Based on the obtained ion current value Z, the following steps S102 to S104 are performed to determine whether or not a misfire has occurred in the cylinder.

In step S102, step S1
The ion Lo value (ion current value X) at the time of fuel cut in the operating state corresponding to the operating state when the ion current value Z is obtained in 01 is called from the learning value table stored in the backup area of the RAM 35.

The learning procedure of the ion Lo value (ion current value X) called from the learning value table in step S102 will be described in detail with reference to FIG.

In the first step S201 of FIG. 4, it is determined whether fuel is being injected in the cylinder, that is, whether the fuel has been cut. If the fuel is cut (YES in step S201), the ion current at the time of fuel cut is detected in step S202. In the present embodiment, the detected value thus obtained is used as the ion current value X. If the fuel cut is not performed in step S201 (in the case of NO),
The following actions are not performed.

As shown in FIG. 5B, the ion current waveform obtained when the fuel is cut is different from the ion current waveform at the time of fuel supply shown in FIG. 5A, and its output is, for example, X = There are only two small rises due to noise on the order of 0.5V.

The ion current value X was obtained (step S20).
2) After that, in step S203, the smolder determination value Y preset in the ROM 36 is compared. The smoldering determination value Y is a reference value provided for determining the smoldering of the plug 23, that is, a reference for detecting that the smoldering state of the plug 23 has occurred even during fuel cut. It is a value. When the ionic current value X is smaller than the smolder determination value Y, it is determined that the smoldering state of the plug 23 has not occurred, and when it is larger, the plug 2
It is determined that the smoldering state of 3 has occurred.

Therefore, when the ion current value X is smaller than the smolder determination value Y (YES in step S203), the process proceeds to step S204, and the ion is assigned to the corresponding address in the learning value table corresponding to the operating state at this time. The current value X is learned and recorded as the ion Lo value. The ion Lo value is the basic fuel injection pulse width Tp (= K × Q / N, where K is the engine operating state, as an example of the engine load, where K
Is a constant and Q is an intake air amount) and the engine speed N are used as parameters in the learning value table divided into a plurality of regions and corresponding to the corresponding operating state, and this is used for misfire determination.

In step S203, if the ion current value X is large (NO), it is determined that the smoldering of the plug has occurred, and the process proceeds to step S205. The ion current value X obtained in this case is not recorded in the learning value table of the RAM 35. As a result, it is possible to prevent the ionic current value X of the smoldered state of the plug 23, which cannot obtain the ionic current waveform normally observed at the time of fuel cut, from being recorded as a learning value in the learning value table. The erroneous determination can be eliminated.

The smoldering of the plug is caused by the addition of some factor such as carbon adhesion to the plug 23 itself, or the defective state of the ignition system. By detecting this smolder, it is possible to detect a defective state of the plug 23 itself and diagnose a defective state of the ignition system, so that the failure factor can be removed early and it can contribute to the prevention of misfire.

Each step from step S201 to step S205 is performed by the microcomputer 30 of the ECU 20.
In the above, the process is performed every predetermined period, for example, every constant time or every constant crank angle. As a result, even if a factor such as secular change of the spark plug 23 is added, the latest ion Lo value is always recorded in each area of the learning value table, which can lead to accurate misfire determination.

As described above, in step S102 of FIG.
Although the ion Lo value (ion current value X) called from the learning value table has been described, the description returns to step S102 of FIG. 3 below.

As described above, after obtaining the ion current value Z at the time of fuel supply under the predetermined operating condition in step S101, the ion Lo value at the time of fuel cut corresponding to the operating condition is learned as the learning value in step S102. Get from the table. In the present embodiment, since the basic fuel injection pulse width Tp and the engine speed N are used as parameters indicating the operating state, the basic fuel injection pulse width Tp at the time of fuel cut and the engine corresponding to these parameters at the time of fuel supply and the engine The ion Lo value with the rotation speed N as a parameter is stored in the RAM 35.
It is obtained by calling from the learning value table recorded in.

Subsequently, in step S103, the ion Lo value is subtracted from the ion current value Z to obtain a difference value S. This is to subtract the ion current waveform at the time of fuel cut, which is the noise level shown in FIG. 5 (b), from the ion current waveform at the time of fuel supply shown in FIG. 5 (a). An ion current waveform as shown is obtained. That is, FIG.
The two peaks shown in (a) (Z = 3.0 V and 3.5)
The portion V) corresponds to the two peaks (Z) shown in FIG. 6A by subtracting the ion current value (about 0.5 V) of the noise level, which is the corresponding portion shown in FIG. 5B.
= 3.0V and 2.5V). These difference values S are used for misfire determination.

Thus, even if the ion current waveforms obtained in FIGS. 5 (a) and 5 (b) change due to the addition of factors such as secular change of the plug 23 or traveling in high altitude, under the same conditions as the base. Since the ion current waveform level at the time of fuel cut is subtracted, it is possible to obtain an accurate value for performing misfire determination without being affected by such factors.

The difference value S is thus obtained (step S1
03) After that, in step S104, a comparison is made with the misfire determination level (misfire determination threshold value) preset in the ROM 36. Note that the misfire determination level is an engine operation state such as the engine speed and engine load as a parameter, and a suitable misfire determination threshold value is determined in advance to determine a misfire by simulation or experiment etc., and the table is used as the misfire determination level. You may give it.

If the difference value S is larger than the misfire determination level (YES in step S104), step S1
If it is determined to be "combustion" (normal) and is lower than the misfire determination level (NO in step S104),
Proceed to step S106, and recognize as "misfire".

If it is determined in step S106 that a misfire has occurred, as described above, the warning lamp 28 is turned on or blinks to notify the driver of the occurrence of a misfire, and if necessary, misfire avoidance control is performed and a trouble indicating a misfire occurs. Data is stored in a predetermined address in the backup area of the RAM 35 of the ECU 20, and the external device (fault diagnosis device) is connected to the ECU 20 so that the external device can read the data.

Since the difference value S is used for the determination,
The ion current waveform to be judged when it is judged as misfire in step S106 has a difference value S as close to 0V as shown in FIG. 6B, and the peaks of the two peaks caused by noise are observed only slightly. It is something that is done. Therefore, an erroneous determination that misfire is determined to be a combustion state is reliably prevented. When step S105 or step S106 ends, this routine ends.

These steps S101 to S1
Each step from 06 to step S201 to step S201
As in the case up to 205, the microcomputer 30 of the ECU 20 performs the process at a predetermined cycle, for example, a constant time or a constant crank angle. As a result, the difference value S can be obtained based on the latest ion current value, and accurate misfire determination can be performed.

Each means implemented in the ECU 20 which constitutes the engine misfire detection device of the present invention described in the above embodiment functions by the control program recorded in the ROM 36, and is a recording medium. Are included in the present invention.

[0049]

As described above, according to the present invention,
Under various operating conditions, the difference between the ion current value at the time of fuel supply and the ion current value at the time of fuel cut is calculated, and this difference value is compared with the misfire determination level to determine the presence or absence of misfire in each cylinder. The highly accurate and reliable misfire determination can be performed.

[Brief description of drawings]

1A is a schematic configuration diagram of a misfire detection device according to the present invention, and FIG. 1B is a schematic configuration diagram of an electronic control device.

FIG. 2 is a schematic configuration diagram of an ignition system including a misfire detection device according to the present invention.

FIG. 3 is a flowchart illustrating a misfire determination routine according to the present invention.

FIG. 4 is a flowchart illustrating a procedure for learning an ion Lo value.

FIG. 5 is an ion current waveform diagram during (a) fuel supply and (b) fuel cut.

FIG. 6 is an ion current waveform diagram after (a) fuel supply and (b) misfire after taking the difference.

[Explanation of symbols]

1 engine 5 Combustion chamber 20 Electronic control unit 23 Spark plug 40 ion detection circuit

Claims (3)

[Claims] 1. An engine misfire detection device for determining the presence or absence of a misfire in each cylinder based on an ion current generated in each cylinder, wherein an ion current value at the time of fuel supply under various operating conditions is detected. Current value detection means, learning means for learning the ion current value at the time of fuel cut in the operating state for each cylinder and recording it as the ion current value, and ion current value at the time of fuel supply and corresponding to the operating state An engine comprising: a calculating unit that calculates a difference between the learned ion current value at the time of fuel cut and a determining unit that compares the difference value and a misfire determination level to determine a misfire. Misfire detection device. 2. The learning means compares the ionic current value at the time of fuel cut under various operating conditions with a preset smolder determination value of the plug, and the ionic current value is larger than the smolder determination value. 2. The engine misfire detection device according to claim 1, wherein the smoldering of the plug is determined and the ion current value is not recorded. 3. An electronic control unit used in an engine misfire detection device for determining the presence or absence of a misfire in each cylinder by an ion current generated in each cylinder, and an ion control unit for supplying fuel under various operating conditions. Ion current value detecting means for detecting a current value, learning means for learning the ion current at the time of fuel cut in the operating state for each cylinder, and recording as an ion current value, and the ion current value at the time of fuel supply And a program that functions as a determination unit that determines the misfire by comparing the difference value and the misfire determination level with a calculation unit that calculates the difference between the learned ion current value at the time of fuel cut corresponding to the operating state. A readable recording medium on which is recorded.