JP2003184635A - Engine misfire detecting device using ion current and recording medium recording program to be used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the accuracy of determining a misfire by preventing an determination error resulting from a change in parameter giving influences on the operating condition and combustion of an engine. <P>SOLUTION: A basic misfire determination level is set in accordance with an engine speed and an engine load (Step S102), a correction coefficient is set in accordance with an ignition timing, an air/fuel ratio, a temperature of engine cooling water and a fuel injection amount, as a parameter for giving influences on the combustion of the engine, and a misfire determination level is set by correcting the basic misfire determination level using the correction coefficient (Step S103). The misfire determination level is compared with a detected ion current value (Step S101) for determining the misfire (Step S104- Step S106). <P>COPYRIGHT: (C)2003,JPO

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, and thus 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 at the time of ignition and superposition of other electrical noises, for example, Japanese Patent Laid-Open No. 5-223
In Japanese Patent Laid-Open No. 002, for example, the detection timing of the ion current and the set value to be compared are varied according to the engine operating conditions such as the engine speed and the engine load to prevent this.

[0005]

However, in addition to the noise superposition described above, the detected ion current waveform changes the engine operating conditions such as the engine speed and the engine load, which causes the detected ion current value and It is also affected by changes in the generation area. That is, the ion current value changes such that the detected ion current waveform becomes large, becomes small, or changes in peak depending on the engine operating state. Further, the engine cooling water temperature, the air-fuel ratio, the fuel injection amount, the ignition timing, etc. affect the combustion state of the engine, and if these parameters change, the combustion state of the engine changes, so the detected ion current value changes. Under such circumstances, it is difficult to make a highly accurate misfire determination. The publications disclosed in the above-mentioned prior arts do not disclose any improvement for this.

In view of the above circumstances, the present invention provides an engine misfire detection device capable of improving the accuracy of misfire determination by preventing erroneous determinations due to changes in parameters that affect engine operating conditions and combustion. The purpose is to provide.

[0007]

According to a first aspect of the invention for achieving the above object, in an engine misfire detecting apparatus for determining whether or not there is a misfire in each cylinder by an ion current generated in each cylinder, Ion current detection means for detecting the ionic current generated in the cylinder, basic misfire determination level setting means for setting the basic misfire determination level based on the engine operating state, and based on the parameters affecting the combustion of the engine, the basic The correction coefficient setting means for setting a correction coefficient for correcting the misfire determination level, the misfire determination level setting means for correcting the basic misfire determination level with the correction coefficient to set the misfire determination level, and the ion current detection means And a determination means for determining misfire by comparing the ion current value and the misfire determination level.

That is, when the misfire in each cylinder is judged by the ion current generated in each cylinder, the basic misfire judgment level based on the engine operating condition is set and the combustion of the engine is set. The correction coefficient is set based on the parameter that affects the. Then, the detected ion current value is compared with the misfire determination level which is set by correcting the basic misfire determination level with a correction coefficient to determine misfire. Here, the combustion state changes due to changes in the engine operating state and parameters that affect combustion, which changes the ion current value.
A basic misfire determination level is set according to changes in engine operating conditions, a correction coefficient is set based on parameters that affect combustion, and a basic misfire determination level is corrected by the correction coefficient to determine a misfire. By setting the misfire determination level as the determination threshold, the misfire determination level can be set accurately in response to changes in the combustion state due to changes in engine operating conditions and parameters that affect combustion, that is, changes in the ion current value. Therefore, it is possible to prevent the erroneous determination due to the change in the parameter that affects the engine operating state and the combustion, and improve the misfire determination accuracy.

At this time, as in the second aspect of the present invention, the basic misfire determination level is set based on the engine speed and the engine load, and at least the engine cooling water temperature, the air-fuel ratio, the ignition timing, and the fuel injection amount are set. It is desirable to set the correction coefficient using one as a parameter.

According to a third aspect of the present invention, there is provided an ion current detection means for detecting an ion current generated in each cylinder, and a basic misfire determination level setting means for setting a basic misfire determination level based on an engine operating state. And a correction coefficient setting means for setting a correction coefficient for correcting the basic misfire determination level on the basis of the parameter affecting the combustion of the engine, and the basic misfire determination level is corrected by the correction coefficient to set the misfire determination level. The program for operating the electronic control device is recorded as a judgment means for judging misfire by comparing the misfire judgment level with the ion current value obtained by the ion current detection means. Characterize.

[0011]

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. 1B. 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, an ion current detection value according to the present invention) and the like, and the ROM 36 records a control program and preset fixed values and the like. Has been done. CPU34, based on the signals from various sensors,
Various types of engine control are performed by performing arithmetic processing using a fixed value and a control program stored in advance in the ROM 36.

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 smaller 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 interrupting 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.

After power is supplied for a predetermined time, that is, when the ignition timing is reached, the power transistor 27 is turned off by a 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 to ignite the spark plug 23, 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 due to 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 ion 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 ion 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 ionic 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.

Here, in the misfire determination by the ECU 20, the basic misfire determination level is set based on the engine speed and the engine load, and the ignition timing, the air-fuel ratio, the engine coolant temperature, and the parameters that affect the combustion of the engine are set. A correction coefficient is set based on the fuel injection amount, the basic misfire determination level is corrected by the correction coefficient, and the misfire determination level is set. Then, by determining the misfire by comparing the detected misfire determination level with the detected ion current value, it is possible to prevent misjudgment due to a change in parameters that affect the engine operating state and combustion, and improve the misfire detection accuracy. improves.

That is, the ECU 20 and the ion detection circuit 40 have the function of the ion current detection means according to the present invention, and the ECU 20 further includes the basic misfire determination level setting means, the correction coefficient setting means, and the misfire determination level according to the present invention. It has the functions of setting means and determining means, and specifically realizes the function of each means by the misfire determination routine shown in FIG.

The process relating to the misfire determination executed by the ECU 20 will be described below with reference to the flowchart shown in FIG.

FIG. 3 is a misfire determination routine executed for each cylinder with the combustion stroke as a sampling period of the ion current value. First, in step S101, the ion current value is detected. Then, in step S102, the basic misfire determination level table is referenced with interpolation calculation using the engine speed rpm as the engine operating state and the intake air amount gu per engine stroke representing the engine load as parameters to determine the misfire. A basic misfire determination level LVLB that is a basic value of the misfire determination level is set.

An example of the basic misfire determination level table is shown in FIG.
Shown in. The basic misfire determination level table is a proper misfire determination for determining a misfire in advance by simulation or experiment using the engine operating state based on the engine speed rpm and the intake air amount gu per one engine stroke as an example of the engine load as parameters. A threshold value is obtained, and this proper misfire determination threshold value is set as the basic value of the misfire determination level, that is, the basic misfire determination level LVLB, and the ROM 36 is used as a table.
It is stored in a series of addresses.

That is, the ion current waveform during combustion changes according to the engine speed and engine load, and the misfire determination is made by comparing the unique value of the misfire determination level (misfire determination level by a constant value) with the ion current value. If it is done, an incorrect determination will occur. The change characteristics of the ion current waveform depending on the engine operating state differ depending on the engine type and engine displacement,
Although it cannot be generally stated, FIG. 5 shows an ion current waveform at the time of combustion when the engine speed is fixed (2800 rpm) and the engine load is changed, as an example.

FIG. 5A shows a medium load (gu = 1.0), FIG. 5B shows a high load (gu = 2.2), and FIG. 5C shows a low load (gu = 0.2). The ionic current waveform in Fig. 2 shows a pattern of the ionic current waveform, a change in peak magnitude, and a phase change depending on the load. The ion current waveform also changes when the engine speed is changed.

Therefore, the engine speed and the engine load (in this embodiment, the intake air amount g per engine stroke)
By setting the basic misfire determination level LVLB as the basic value of the misfire determination threshold based on u), even if the ion current value changes due to a change in the engine operating state, the misfire determination level is compensated accordingly. This makes it possible to reliably prevent erroneous determination due to a change in ion current value due to a change in engine operating state.

The broken line in FIG. 5 indicates the basic misfire determination level LVLB, which is set to a value according to the engine speed and the engine load by the basic misfire determination table of FIG. 4 described above. The misfire determination level LVLB that is the basic value of the misfire determination level is appropriately set according to the change in the ion current waveform caused by the change in the operating state.

Next, in step S103, the basic misfire determination level LVLB is corrected by referring to a table or the like based on the ignition timing, the air-fuel ratio, the engine cooling water temperature, and the fuel injection amount as parameters affecting the combustion of the engine. Correction coefficient KADV, KA / F, KTW,
Set KINJ.

That is, the combustion state changes depending on whether the ignition timing is advanced or retarded, and the ion current value changes correspondingly. Also, the combustion state changes due to the difference in air-fuel ratio, the difference in engine cooling water temperature (combustion of the engine deteriorates at low temperature), and the difference in fuel injection amount, and the ion current value also changes correspondingly. To do.

Therefore, with the ignition timing, the air-fuel ratio, the engine cooling water temperature, and the fuel injection amount, which affect the combustion of the engine, as parameters, correction coefficients suitable for correcting the basic misfire determination level LVLB by simulation or experiment in advance. KADV, KA / F, KTW, and KINJ are obtained, and these are stored as a table at a series of addresses in the ROM 36. Incidentally, in the present embodiment, each correction coefficient KADV, KA / F, KTW, KI.
Since NJ is given to the basic misfire determination level LVLB as a multiplication term, each correction coefficient KADV, KA / F, KTW,
The KINJ base value (value corresponding to no correction) is 1.
It is 0.

The change characteristics of the ion current waveform due to changes in the ignition timing, the air-fuel ratio, the engine cooling water temperature, and the fuel injection amount, which affect the combustion, differ depending on the engine type and engine displacement, and cannot be generally stated. . However, in any case, these ignition timing, air-fuel ratio, engine cooling water temperature,
The basic misfire determination level LVLB is set in advance by simulation or experiment using the fuel injection amount as a parameter.
Each correction coefficient KADV, KA /
By obtaining F, KTW, and KINJ as respective tables, ignition timing, air-fuel ratio, engine cooling water temperature,
Even if the ion current value changes due to the change in the fuel injection amount, the correction coefficients KADV, KA / F, KTW,
It is possible to correct the basic misfire determination level LVLB by KINJ and appropriately set the misfire determination level LVL for determining misfire. As a result, it is possible to reliably prevent erroneous determination due to changes in the ion current value due to changes in the ignition timing, the air-fuel ratio, the engine cooling water temperature, and the fuel injection amount that affect the combustion state of the engine.

Here, FIG. 6A shows an example of the case where the parameter affecting the combustion state of the engine is changed and the combustion is disturbed. The solid line shows the ion current waveform when no turbulence occurs, and the waveforms other than the solid line show the ionic current waveform when combustion is disturbed due to changes in the parameters that affect the combustion state of the engine. As shown in the figure, when the combustion is disturbed by the change of the parameter that affects the combustion state of the engine, the ion current waveform is relatively lowered (at this time, it is burning and there is no misfire, so
It is necessary to determine "combustion"), each correction coefficient KAD
By correcting the basic misfire determination level LVLB by V, KA / F, KTW, and KINJ and setting the misfire determination level LVL, even if the ion current waveform relatively decreases, the corresponding misfire determination level LVL is set. It can be set appropriately.

FIG. 6 (b) shows the ion current waveform at the time of misfire. In FIGS. 6A and 6B, there is a trigger-like noise before and after the combustion section.
This is noise at the time of ignition discharge, and erroneous determination due to noise is prevented by stopping sampling of the ion current value in a predetermined crank angle section including the ignition timing or masking the ion current value detected in this section. be able to.

Then, in step S103, the basic misfire determination level LVLB is set to each correction coefficient KADV, KA /
Misfire judgment level L corrected by F, KTW, KINJ
Set VL (LVL ← LVLB × KADV × KA / F
(× KTW × KINJ), in the subsequent step S104, the ion current value and the misfire determination level LVL are compared, and when the ion current value is higher than the misfire determination level LVL, the process proceeds to step S105 and “combustion” (normal) If the ion current value is equal to or lower than the misfire determination level LVL, the process proceeds to step S106 to determine "misfire" and exit the routine.

When it is judged as "misfire", the warning lamp 2
Notify the driver of the occurrence of misfire by lighting or blinking 8
Misfire avoidance control is performed as necessary, and trouble data indicating the occurrence of misfire is stored in a predetermined address in the backup area of the RAM 35 of the ECU 20, and the ECU 20
By connecting an external device (fault diagnosis device) to the external device, reading to the external device becomes possible.

Each unit realized 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.

Needless to say, the present invention includes various modifications without departing from the scope of the present invention. For example, in the above-described embodiment, the intake air amount gu per engine stroke is used as the engine load, but any engine load may be used as long as it represents the engine load. Instead, for example, the throttle opening, intake air amount, throttle valve Downstream intake pipe pressure,
The basic fuel injection amount (basic fuel injection pulse width) or the fuel injection amount (fuel injection pulse width) may be used.

Further, in the above-described embodiment, in order to correct the basic misfire determination level LVLB, the ignition timing, the air-fuel ratio, the engine cooling water temperature, and the fuel injection amount, which affect the combustion of the engine, are used as parameters, and each correction coefficient is used. KADV, KA / F, KTW, and KINJ are set, and the basic misfire determination level LVLB is corrected by these correction coefficients KADV, KA / F, KTW, and KINJ to set the misfire determination level LVL. Instead, the correction coefficient may be set using at least one of the ignition timing, the air-fuel ratio, the engine cooling water temperature, and the fuel injection amount as a parameter, and the basic misfire determination level LVLB may be corrected to set the misfire determination level LVL.

[0045]

As described above, according to the present invention,
When determining the presence or absence of misfire in each cylinder by the ion current generated in the cylinder, the engine operating state, the combustion state is changed by a parameter affecting the combustion of the engine, thereby changing the ion current value, A basic misfire determination level is set according to changes in the engine operating state, a correction coefficient is set based on parameters that affect engine combustion, and a basic misfire determination level is corrected by the correction coefficient to determine misfire. Since the misfire determination level is set as a determination threshold for, the change in the combustion state caused by the change in the engine operating condition and the parameters that affect combustion, that is, the change in the ion current value, can be set appropriately for the misfire determination level. Can be set. Therefore, by comparing the misfire determination level with the ion current value to determine the misfire, it is possible to prevent erroneous determinations due to changes in the engine operating state and parameters that affect combustion, and to significantly improve the misfire determination accuracy. Can be improved.

[Brief description of drawings]

FIG. 1A is a schematic configuration diagram of a misfire detection device of the present invention,
(B) is a schematic block diagram of an electronic control unit.

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

FIG. 3 is a flowchart showing a misfire determination routine.

FIG. 4 is an explanatory diagram showing a basic misfire determination level table.

FIG. 5 is a timing chart showing an ion current waveform when the load is changed.

FIG. 6A is a timing chart of an ion current waveform when combustion is disturbed, and FIG. 6B is a timing chart of an ion current waveform when a misfire occurs.

[Explanation of symbols]

1 engine 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 by means of an ion current generated in each cylinder, comprising ion current detection means for detecting an ion current generated in each cylinder, Based on the basic misfire determination level setting means that sets the basic misfire determination level based on the engine operating state, and the parameters that affect the combustion of the engine,
Correction coefficient setting means for setting a correction coefficient for correcting the basic misfire determination level; misfire determination level setting means for correcting the basic misfire determination level by the correction coefficient to set a misfire determination level; and the ion current A misfire detecting device for an engine, comprising: a judging means for judging a misfire by comparing an ion current value obtained by a detecting means with the misfire judging level. 2. The basic misfire determination level setting means sets the basic misfire determination level based on engine speed and engine load, and the correction coefficient setting means sets the engine cooling water temperature, air-fuel ratio, ignition timing, The engine misfire detection device according to claim 1, wherein the correction coefficient is set by using at least one of the fuel injection amount and the fuel injection amount as a parameter. 3. An electronic control unit used in an engine misfire detection device for determining a misfire in each cylinder based on an ion current generated in each cylinder, the ion current detecting an ion current generated in each cylinder. Based on the detection means, the basic misfire determination level setting means for setting the basic misfire determination level based on the engine operating state, and the parameter affecting the combustion of the engine,
Correction coefficient setting means for setting a correction coefficient for correcting the basic misfire determination level; misfire determination level setting means for correcting the basic misfire determination level by the correction coefficient to set a misfire determination level; and the ion current A readable recording medium having a program recorded thereon for functioning as a determination unit for determining misfire by comparing the ion current value obtained by the detection unit with the misfire determination level.