JP2003286893A - Misfire detecting device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a misfire detecting device for an internal combustion engine by which misfire can be detected without being influenced by noise, and as a result, the reliability of misfire detection is improved. <P>SOLUTION: An ion current is detected as a voltage waveform at a current detecting part and high-frequency noise is attenuated (eliminated) (V2) by smoothing the detected voltage waveform by a low-pass filter (a smoothing part). Furthermore, a prescribed bias voltage (V3) is subtracted from the smoothed voltage waveform at a subtraction part and noise which is not processed (eliminated) by the low-pass filter 16c is eliminated (V4). Also, the prescribed bias voltage to be subtracted is set to a value which is larger than the voltage waveform formed by the noise. <P>COPYRIGHT: (C)2004,JPO

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 an internal combustion engine, which detects a misfire of the internal combustion engine based on an ion current generated when a mixture gas burns.

[0002]

2. Description of the Related Art In a spark ignition type internal combustion engine such as a gasoline engine, a high voltage generated by an ignition coil is applied to a spark plug arranged in each cylinder through a distributor or the like, and a gap between electrodes of the spark plug (gap). )
The air-fuel mixture in each cylinder is ignited by the spark discharge of, and combustion occurs. In such an ignition / combustion process of the internal combustion engine, a phenomenon that the ignition / combustion of the air-fuel mixture is not normally performed, that is, misfire may occur for some reason.

This misfire is roughly classified into two types, one caused by the fuel system and the other caused by the ignition system. The former misfire caused by the fuel system is caused by excessive leaning or enrichment of the air-fuel ratio, and spark discharge occurs between the electrodes of the spark plug, but it is a phenomenon that the mixture does not ignite. is there. On the other hand, the latter misfire caused by the ignition system is a phenomenon caused by so-called miss spark, in which normal spark discharge does not occur due to smoldering of the spark plug due to adhesion of unburned fuel or the like and abnormality of the ignition circuit.

When the air-fuel mixture normally burns, the air-fuel mixture (more precisely, the combustion gas generated by the combustion of the air-fuel mixture) is ionized (ionized) to generate an ion current. On the other hand, if a misfire occurs and the mixture is not burned,
No ion current is generated because the air-fuel mixture does not ionize.

Therefore, conventionally, for example, Japanese Patent Laid-Open No. 5-999.
As in the technique described in Japanese Patent Publication No. 56, by detecting the ion current generated in the combustion stroke and comparing the detected value, specifically the time integral value or the peak value, with a predetermined value, misfire of the internal combustion engine is performed. It is widely used to detect.

[0006]

When detecting an ion current, various noises, for example, noises generated by combustion in cylinders other than the detection target and noises generated by mutual induction or self-induction of ignition coils. Since it affects the detection accuracy, it is desirable to avoid those effects. Therefore, the above-mentioned Japanese Patent Laid-Open No. 5-99956
In the technique described in the publication, the influence is avoided by not detecting (masking) the ionic current when the induced noise occurs. However, if other noise generated outside the mask period is detected, the noise cannot be processed (removed) as an unnecessary input, and the generated voltage waveform may be erroneously detected as an ion current. However, the accuracy of misfire detection was not always satisfactory.

Therefore, an object of the present invention is to solve the above-mentioned problems and to enable misfire detection without being affected by noise, thereby improving the misfire detection accuracy of an internal combustion engine. To provide a device.

[0008]

In order to solve the above-mentioned problems, the present invention according to claim 1 applies a voltage to a spark plug arranged at a position facing a combustion chamber of an internal combustion engine,
In the misfire detection device of the internal combustion engine, which detects the ion current generated when the air-fuel mixture burns by the spark discharge between the electrodes by the current detection circuit, and detects the misfire of the internal combustion engine based on the detected ion current, The current detection circuit is a current detection unit that detects the ion current with a voltage waveform,
A smoothing processing unit that smoothes the detected voltage waveform, and a subtraction processing unit that subtracts the smoothed voltage waveform based on a predetermined bias voltage.

A current detection circuit for detecting an ionic current detects a current waveform of the ionic current by a current detecting section, and a detected voltage waveform is smoothed (averaged) to attenuate (remove) noise. Since the smoothing processing unit and the subtraction unit that removes the noise that could not be processed by the smoothing processing unit by performing the subtraction processing on the smoothed voltage waveform based on the predetermined bias voltage are configured, Misfires can be detected without being affected by noise, and thus misfire detection accuracy can be improved.

According to a second aspect of the present invention, the predetermined bias voltage is set to a value larger than the voltage waveform generated by noise.

Since the predetermined bias voltage for removing the noise is set to a value larger than the voltage waveform generated by the noise, the noise can be surely removed, and therefore the misfire detection accuracy can be improved. Can be further improved.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A misfire detecting device for an internal combustion engine according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic view showing an overall misfire detecting device for an internal combustion engine according to the embodiment.

In the figure, reference numeral 10 indicates a misfire detecting device according to the embodiment. The misfire detection device 10 includes an ignition plug 12, an ignition coil 14, a current detection circuit 16, an igniter 18, an ECU (electronic control unit) 20, a sensor group described later, and the like, and an internal combustion engine indicated by reference numeral 24 (hereinafter referred to as ""Engine". Only a part is shown), and detects whether or not the engine 24 is in a misfire state. The engine 24 is specifically a multi-cylinder spark ignition type engine, and the misfire detection device 10 is
Misfire detection is performed for each of the cylinders 26 (only one cylinder is shown in the figure).

The ignition plug 12 is arranged at a position facing the combustion chamber 28 of each cylinder 26, and ignites and burns the air-fuel mixture sucked into the combustion chamber 28 via the intake valve 30. The combustion gas generated by the combustion of the air-fuel mixture is discharged to the outside of the engine via the exhaust valve 32. Spark plug 12
Is connected to the ECU 20 via the ignition coil 14, the current detection circuit 16 and the igniter 18. Incidentally, the illustrated ignition coil 14 is a plug hole type, and the ignition plug 1
2, the ignition coil 14, the current detection circuit 16, the igniter 18, etc. are integrally built in the case 34.

The ECU 20 comprises a microcomputer having a ROM, a RAM and the like. The ECU 20 is provided with a crank angle sensor 3 which is arranged near a crank shaft or a cam shaft (both not shown) and outputs a signal corresponding to a TDC position of each cylinder and a crank angle obtained by subdividing the TDC position.
6, an absolute pressure sensor 38 that outputs a signal according to the absolute pressure in the intake pipe (PBA, which corresponds to the engine load) downstream of the throttle valve (not shown) of the intake pipe, according to the air-fuel ratio of the combustion gas (exhaust gas) Air-fuel ratio sensor (U
EGO (Universal Exhaust Gas Oxygen) sensor 4
0, and outputs of a sensor group (not shown) such as a water temperature sensor and an intake air temperature sensor are input.

Further, the ECU 20 is provided with a counter, and counts the output of the crank angle sensor 36 that has been input to calculate the engine speed NE. Also, based on the above-mentioned various input signals, the ignition timing θig1 is determined and the ignition plug 1
The air-fuel mixture is ignited via 2 and the target air-fuel ratio (A /
The fuel injection amount is determined so as to be F), and the injector (fuel injection valve) 42 is driven to open to inject gasoline fuel.

A warning light 4 is provided near the driver's seat (not shown).
4 is provided, is connected to the ECU 20, and is connected to the ECU.
It is lit when the engine 20 detects a misfire of the engine 24 (or a failure of the ignition system or the like).

FIG. 2 is an explanatory diagram showing a block diagram of the misfire detection device 10 according to this embodiment. The misfire detection device 10 detects the ion current generated by the combustion of the air-fuel mixture, and detects (determines) whether or not the engine 24 is in the misfire state based on the detected value.

The detection operation of the misfire detection device 10 will be briefly described below. The ECU 20 determines the ignition timing θig1.
The igniter 18 is operated at a crank angle corresponding to. When the current that flows through the ignition coil 14 (specifically, the primary coil 14a described later) and uses the vehicle-mounted power supply 46 as a voltage source is turned on and off by the operation of the igniter 18, the ignition coil 14 (specifically described later A high voltage is generated in the secondary coil 14b). The spark plug 12 is applied with this high voltage to generate a spark discharge between the electrodes, and ignites and burns the air-fuel mixture.

The above-mentioned respective currents are applied to the ignition coil 1
4 is input to the current detection circuit 16. Here, the current detection circuit 16 includes a current detection unit 16a, a first waveform conversion unit 16b, a low-pass filter 16c, a subtraction unit 16d, an amplification unit 16e, and a second waveform conversion unit 16f.

The operation of the current detection circuit 16 will be briefly described below. The current detection unit 16a detects the ion current as a voltage waveform, and the detected voltage waveform is the first waveform conversion unit 1.
6b, where the waveform is inverted.

The voltage waveform inverted in the waveform converter 16b is input to the low-pass filter 16c and smoothed (averaged), and the output (noise) in the frequency band other than the ion current is attenuated (or removed). .

The voltage waveform subjected to the smoothing processing is subtracted by the subtracting unit 16
It is input to d and is subtracted based on a predetermined bias voltage. As a result, noise that cannot be completely processed by the low-pass filter 16c is removed. The voltage waveform subjected to the subtraction processing by the subtraction unit 16d is amplified by the amplification unit 16e,
It is output to the ECU 20 via the second waveform conversion unit 16f.

Based on this output, the ECU 20 detects whether or not the engine 24 is in the misfire state, and when it is in the misfire state, the warning light 44 is turned on to notify the driver.

FIG. 3 is a circuit diagram showing in detail the configuration of the current detection circuit 16 and the like connected to the spark plug 12. 4 and 5 are time charts showing the output at each connection point of the circuit shown in FIG. 3. FIG. 4 shows the output at the time of combustion and FIG. 5 shows the output at the time of misfire.

The operation of the misfire detection device 10 according to this embodiment will be described in detail below with reference to FIGS. 3 to 5. The ECU 20 determines that the crank angle preceding the crank angle corresponding to the ignition timing θig by the energization time TON. The energizing pulse is turned on at, and turned off after a period corresponding to TON has passed, thereby operating the igniter 42 and the on-vehicle power supply 4
The current flowing from 6 to the primary coil 14a is turned on / off.

At the ignition timing θig, the primary coil 14
When the current flowing through a is cut off (energization pulse is turned off), a negative high voltage is generated in the secondary coil 14b, and a discharge current as shown in FIGS. 4 and 5 flows. Specifically, the spark plug 12 (center electrode 12a and ground electrode 12b) -secondary coil 14b-capacitor 16a.
1 (or Zener diode 16a2) -diode 16a4 flows between the electrodes of the spark plug 12 (center electrode 1
A spark discharge is generated between 2a and the ground electrode 12b) to ignite and burn the air-fuel mixture.

The discharge current charges the capacitor 16a1. The charged capacitor 16a1 functions as a current detection power supply having a bias voltage for detecting an ion current.

When the air-fuel mixture is burned by the spark discharge of the spark plug 12, the air-fuel mixture (more accurately, the combustion gas generated by the combustion of the air-fuel mixture) is ionized to generate ions. These ions intervene between the electrodes of the spark plug 12 and reduce the electrical resistance therebetween, thereby generating an ion current as shown in FIGS. 4 and 5 using the bias voltage of the capacitor 16a1 as a power source (see FIG. No ion current is generated at the time of the misfire shown in 5.). Specifically, the ion current is the capacitor 16a1-2 secondary coil 14b-spark plug 12-.
The current waveform (voltage waveform) flows through the detection resistor 16a4 and is input to the first waveform conversion unit 16b via the detection resistor 16a4.

The ion current waveform input to the first waveform converter 16b is inverted by the first transistor 16b1 (indicated by V1 in FIGS. 4 and 5). The inverted ion current waveform is input to the low-pass filter 16c, and high frequency components are attenuated (removed) and smoothed as shown in FIGS. 4 and 5 (shown by V2 in FIGS. 4 and 5). As a result, high frequency noise is attenuated (removed).

The voltage waveform smoothed by the low-pass filter 16c is input to the subtractor 16d, and is subtracted by the subtracting operational amplifier (operational amplifier) 16d1 based on a predetermined bias voltage. Specifically, in FIG. 4 and FIG. 5, the bias voltage (1 V) indicated by V3 is subtracted from the voltage waveform indicated by V2 (that is, the waveform of 1 V or less is removed) to obtain the waveform indicated by V4.

This makes it possible to remove noise that cannot be processed (removed) by the low-pass filter 16c. It should be noted that the voltage value generated by noise is previously obtained through experiments or the like, and the time constant of the low-pass filter 16c and the bias voltage of the subtraction unit 16d are set appropriately, that is, the noise smoothed by the low-pass filter 16c causes noise. Noise can be reliably removed by setting the bias voltage larger than the voltage waveform to be applied.

The voltage waveform generated in the subtracting section 16d is input to the amplifying section 16e and is doubled by the amplifying operational amplifier 16e1 (indicated by V5 in FIGS. 4 and 5). The amplified voltage waveform is input to the second waveform converter 16f.

The voltage waveform input to the second waveform converter 16f is converted by the second transistor 16f1 into a rectangular wave with an output of 5V having a threshold value of 0.6V (operating base voltage) (FIGS. 4 and 5). 5 in V6). The voltage waveform converted into the rectangular wave is further input to the NOT gate 16f.
After being inverted by 2 (indicated by V7 in FIGS. 4 and 5), it is output to the ECU 20.

The ECU 20 controls the engine 24 based on the voltage waveform (rectangular wave) input from the second waveform converter 16f.
Detect if the is in a misfire condition. Specifically, it is possible to detect whether or not the engine 24 is in the misfire state by determining the presence or absence of the rectangular wave indicated by V7 in FIGS. 4 and 5, that is, the presence or absence of the pulse output.

In this way, the ionic current is detected as a voltage waveform, smoothed by the low-pass filter 16c to attenuate (remove) high frequency noise, and the subtractor 16d subtracts the bias voltage from the smoothed voltage waveform. Since the low-pass filter 16c removes noise that cannot be completely processed (removed), misfire can be detected without being affected by noise, and thus misfire detection accuracy can be improved.

Further, since the bias voltage to be subtracted is set to a value larger than the voltage waveform generated by noise, the noise can be surely removed, thus further improving the accuracy of misfire detection. be able to.

As described above, in the misfire detection device for an internal combustion engine according to this embodiment, the internal combustion engine (engine)
Spark plug 1 arranged at a position facing 24 combustion chambers 28
2 is applied, and the current detection circuit 16 detects the ionic current generated when the air-fuel mixture burns due to the spark discharge between the electrodes (between the center electrode 12a and the ground electrode 12b),
In a misfire detection device 10 for an internal combustion engine, which detects a misfire of the internal combustion engine 24 based on the detected ion current,
The current detection circuit 16 includes a current detection unit 16a that detects the ion current as a voltage waveform, and a smoothing processing unit (low-pass filter) 1 that smoothes the detected voltage waveform.
6c, and a subtraction processing unit (subtraction unit) 16d that performs a subtraction process on the smoothed voltage waveform based on a predetermined bias voltage.

The predetermined bias voltage is set to a value larger than the voltage waveform generated by noise.

In the above description, the configuration for performing processing such as smoothing and subtraction is configured by hardware, but it may be configured by using a software method.

Further, the configurations of the low-pass filter 16c and the subtractor 16d are not limited to the above. For example,
Although the low-pass filter 16c is an RC filter using a resistor and a capacitor (capacitor), it may be an LC filter using a coil (inductor) and a capacitor. Further, in the subtracting unit 16d, the bias voltage may be variably set and the value to be subtracted may be changed according to the operating state of the engine 24. For example, when the amount of ion current generated is small, such as during lean combustion, set the bias voltage low to increase the extracted portion of ion current (that is, lower the minimum voltage value detected as ion current). Thereby, the detection accuracy of the ion current can be improved.

[0043]

According to the first aspect of the present invention, the current detection circuit for detecting the ionic current includes a current detecting section for detecting the ionic current as a voltage waveform and a smoothing process for the detected voltage waveform. A smoothing processing unit that attenuates (removes) noise and a subtraction unit that removes noise that could not be processed by the smoothing processing unit by performing a subtraction process on the smoothed voltage waveform based on a predetermined bias voltage. Since it is configured to be provided, misfire can be detected without being affected by noise, and thus misfire detection accuracy can be improved.

According to the second aspect of the present invention, the predetermined bias voltage for removing noise is set to a value larger than the voltage waveform generated by the noise, so that the noise is surely removed. Therefore, the accuracy of misfire detection can be further improved.

[Brief description of drawings]

FIG. 1 is an overall schematic view of an internal combustion engine misfire detection device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the device shown in FIG. 1 in blocks.

3 is a circuit diagram showing in detail the configuration of a current detection circuit and the like of the device shown in FIG.

FIG. 4 is a time chart for explaining the operation of the device shown in FIG. 1 through the output at the time of combustion at each connection point of the circuit shown in FIG.

5 is a time chart similar to FIG. 4, illustrating the operation of the device shown in FIG. 1 through the output at the time of misfire at each connection point of the circuit shown in FIG.

[Explanation of symbols]

10 Misfire detection device 12 Spark plug 12a center electrode 12b Ground electrode 16 Current detection circuit 16a Current detector 16b First waveform converter 16c low pass filter 16d Subtraction unit 16e amplifier 16f Second waveform converter 20 ECU (electronic control unit) 24 Internal combustion engine 28 Combustion chamber

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuyuki Kubo             1-4-1 Chuo Stock Market, Wako City, Saitama Prefecture             Inside Honda Research Laboratory (72) Inventor Moriya Gakuji             1-4-1 Chuo Stock Market, Wako City, Saitama Prefecture             Inside Honda Research Laboratory F-term (reference) 3G019 CD06 DB02 DB08 DC06 GA01                       GA08 GA11 GA13                 3G084 BA00 BA16 DA27 DA28 EA01                       EA02 EA09 EA11 EC02 FA02                       FA10 FA20 FA29 FA33 FA38

Claims (2)

[Claims] 1. A current detecting circuit detects an ionic current generated when a mixture is burned by a spark discharge between its electrodes, by applying a voltage to a spark plug arranged so as to face a combustion chamber of an internal combustion engine. In the internal combustion engine misfire detection device for detecting misfire of the internal combustion engine based on the detected ion current, the current detection circuit comprises: a. A current detector for detecting the ion current with a voltage waveform, b. A smoothing processing unit that smoothes the detected voltage waveform, and c. A misfire detection device for an internal combustion engine, comprising: a subtraction processing unit that performs a subtraction process on the smoothed voltage waveform based on a predetermined bias voltage. 2. The misfire detection device for an internal combustion engine according to claim 1, wherein the predetermined bias voltage is set to a value larger than a voltage waveform generated by noise.