JPH05223050A - Misfire detecting device for internal combustion engine - Google Patents

Abstract

PURPOSE:To suppress the adverse effect to the minimum when high leak voltage is applied and prevent the failure of an electronic circuit by independently and separately arranging a signal processing means and a judging means constituting the electronic circuit. CONSTITUTION:A detecting means l provided with a conductor 1A on the outer periphery of a high-voltage cord 2 to constitute a capacitor for detecting the secondary voltage is provided on the high-voltage cord 2 feeding the secondary voltage of an ignition coil to an ignition plug. A voltage dividing capacitor 1B is provided between this capacitor and the earth, the detection voltage capacitor-divided across the voltage diving capacitor 1B is inputted to a signal processing means 4, and it is converted into the signal configuration suitable for judging the misfire state. The output side of the signal processing means 4 is connected to a judging means 7 constituted of an amplifier 5, a comparator 9, and a microcomputer 10 provided separately and independently from the means 4, and the misfire state is judged by the judging means 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting a misfire during operation of a spark ignition type internal combustion engine such as a gasoline engine, and more particularly to a layout of electronic circuit parts thereof. Is.

[0002]

2. Description of the Related Art As is well known, in an internal combustion engine such as a gasoline engine, a high voltage generated by an ignition coil is distributed to each cylinder by a distribution means such as a distributor and applied to a spark plug of each cylinder. The sparks associated with the discharge between the electrodes ignite the fuel-air mixture drawn into the combustion chamber of each cylinder, causing combustion. In the ignition / combustion process of such an internal combustion engine,
For some reason, the combustion of the fuel mixture may not be performed normally, that is, misfire may occur. The causes of such misfire are roughly classified into those caused by the fuel system and those caused by the ignition system. The former misfire caused by the fuel system is caused by lean or rich fuel mixture, and is a phenomenon in which spark discharge occurs between the electrodes of the spark plug but the fuel mixture is not ignited.
On the other hand, the latter misfire caused by the ignition system is a phenomenon in which normal spark discharge does not occur due to fogging of the electrode of the spark plug or abnormality of the ignition circuit.

If a misfire occurs during operation of the internal combustion engine, not only the operating performance is deteriorated but also the fuel consumption is deteriorated, and further, the afterfire of unburned gas in the exhaust system passage adversely affects the exhaust gas purifying device and the like. And other problems occur. Further, once the misfire has occurred, it means that the fuel system or the ignition system has inconvenience such as misadjustment or failure, so it is necessary to avoid leaving the misfire. Therefore, recently, it has been strongly desired to develop a device that immediately detects a misfire when it occurs.

One type of misfire detection device that has been proposed in the past is the mis-spark detection device disclosed in Japanese Patent Laid-Open No. 52-118135. This miss spark detector
As shown in FIG. 9, a conductor 51 is wound around the outer periphery of a high-voltage cord 50 of the engine ignition system to form a detection capacitor (a kind of capacitance probe) 52 having the insulating coating 50A of the high-voltage cord 50 as a dielectric. In addition, the voltage dividing capacitor 53 is connected between the detecting capacitor 52 and the ground, and the detecting capacitor 52 is generated by the ignition voltage (secondary voltage of the ignition coil) applied to the conductive core wire 50B of the high voltage cord 50. A voltage is induced between both electrodes of the detection capacitor 52 by the electrostatic capacitance of
The induced voltage is electrostatically divided by the detection capacitor 52 and the voltage dividing capacitor 53, and the voltage across the voltage dividing capacitor 53 (divided voltage) is sent as a detection voltage to an electronic circuit 54 for signal processing and determination. Using the fact that the ignition voltage waveform is different between normal spark discharge and no spark discharge (mis spark),
The occurrence of miss sparks is determined. Therefore, the proposed device detects misfires, especially when no spark discharge is caused by the ignition system.

On the other hand, the applicant of the present application has already filed Japanese Patent Application No. 3-326.
No. 509 proposes a misfire detection device for an internal combustion engine. This misfire detection device detects the ignition voltage from the high voltage cord of the ignition system by electrostatic partial pressure as in the above, and even if spark discharge is performed, the ignition voltage waveform does not occur during normal combustion and normal combustion. Taking advantage of the fact that
This is to judge and detect misfire caused by the fuel system.

[0006]

As described above, as the conventional misfire detecting device, there are a device of a type for detecting the presence or absence of spark discharge of the spark plug and a device of a type for detecting the presence or absence of combustion. In both cases, it is common to detect the ignition voltage and compare the voltage value or voltage waveform with the ignition voltage value or voltage waveform in a normal state without misfire to determine misfire. Such a misfire detection device is basically a detection means for detecting the ignition voltage from a high voltage cord of the ignition system by a capacitance probe or the like, and an ignition voltage waveform detected by the detection means into a signal suitable for discrimination. A signal processing means for converting and an output signal from the signal processing means are compared and determined with a reference signal corresponding to an ignition voltage waveform in a normal state without misfire to determine a misfire state. And a judging means. The signal processing means and the determination means as the electronic circuit portion in such a conventional misfire detection device have a common substrate or are housed in at least a common housing, and are integrally assembled. It is normal.

By the way, the ignition voltage is generally a very high voltage of several tens of kV, and it is necessary to directly apply such a high voltage to an electronic circuit such as a signal processing circuit of a misfire detection device in view of insulation characteristics of the electronic circuit. Must be avoided. Therefore, generally, as described above, it is considered that the capacitance is divided into a detection voltage of about several tens of V and applied to an electronic circuit such as a signal processing circuit. However, in reality, a high voltage leak voltage may be applied to the electronic circuit due to deterioration of the insulator of the detection means such as the capacitance probe or other causes. There is a risk of causing an overall failure. In particular, it is convenient to use the determination circuit for determining the misfire state also as the microcomputer for controlling the engine. In this case, if the high voltage leak voltage as described above is applied, the microcomputer for controlling the engine, etc. May lead to failure.

Further, a high-frequency noise of several GHz is generated from a spark plug of an internal combustion engine, and this high-frequency noise often rides on a high-voltage cable, and such high-frequency noise is detected as a misfire. If the high-frequency noise is picked up by the detection means such as the capacitance probe of the device and the high-frequency noise is added to the judgment circuit from the signal processing circuit, malfunction of the circuit may occur and it may not be possible to correctly judge the misfire. Since the computer may be latched up, the engine control computer may malfunction if the engine control microcomputer is also used as the determination circuit microcomputer.

The present invention has been made in view of the above circumstances, and minimizes the adverse effects thereof even when a high-voltage leak voltage is applied to an electronic circuit portion or high frequency noise is picked up. It is an object of the present invention to provide a misfire detection device that suppresses the occurrence of a failure or malfunction of an electronic circuit, or at least suppresses it to a minimum.

[0010]

In order to solve the above-mentioned problems, according to the present invention, a detecting means for detecting the ignition voltage of the internal combustion engine and a voltage detected by the detecting means are processed. In a misfire detection device comprising a signal processing means for making a signal suitable for the determination of the misfire state, and a determination means for determining the misfire state according to the output signal of the signal processing means, basically, The signal processing means and the determination means are arranged separately so as to be independent from each other in terms of arrangement configuration, and these two means are coupled via a signal line.

[0011]

In the misfire detecting device of the present invention, the signal processing means and the judging means, which are electronic circuit parts, are separately arranged so as to be independent from each other in terms of arrangement configuration. The signal processing means is for converting the detection voltage from the detection means into a signal suitable for judging the misfire state, and is generally composed mainly of an analog circuit. On the other hand, the judging means is for judging the misfire state in accordance with the output signal from the signal processing means, and is composed of a digital circuit such as a microcomputer, or includes a part of an analog circuit and is mainly composed of a digital circuit. Configured as.

Since a digital circuit normally applies only a low signal voltage, it is generally designed to have a low withstand voltage, whereas an analog circuit is usually designed to have a high withstand voltage to some extent. In the case of the present invention, since the signal processing means and the determination means are separated, even if a high voltage leak voltage is applied from the detection means, the high voltage leak voltage is applied only to the signal processing means, and the determination means Does not join.

When the detecting means picks up the high frequency noise caused by the spark discharge of the spark plug, the high frequency noise is added to the signal processing means, but the determining means is separated from the signal processing means. Very unlikely to join. Since the signal processing means is mainly composed of an analog circuit, it is unlikely that high frequency noise will adversely affect the output waveform of the signal processing means. On the other hand, the judging means is mainly composed of a digital circuit, and if high frequency noise of several GHz is added, it may cause malfunction, but as described above, high frequency noise from the detecting means may be added to the judging means. Since the number is small, there is little possibility that the determination means will malfunction due to high frequency noise, resulting in an error in determining the misfire state.

[0014]

1 shows a basic embodiment of the misfire detection device of the present invention.

In FIG. 1, a high voltage cord 2 for sending a secondary side voltage of an ignition coil (not shown) to a spark plug through a distributor or without a distributor is used for detecting the secondary side voltage, that is, the ignition voltage. Detection means 1 is provided. This detecting means 1 can be constituted by a so-called capacitive probe in which a conductor 1A is provided on the outer circumference of a high voltage cord 2 to form a capacitor, as in the conventional example described above. It is desirable to provide a voltage dividing capacitor 1B between the two and to extract the detection voltage whose capacitance is divided from both ends of the voltage dividing capacitor 1B. Of course, other voltage sensors may be used as the detecting means 1. Further, the position at which the detection means 1 is provided may be any position from the secondary side of the ignition coil to the ignition plug, and is not limited to the middle of the high voltage cord 2. As described above, the detection means 1 only needs to be able to detect the ignition voltage, and its specific configuration and arrangement position are arbitrary, and this is the same in other embodiments described later.

The output side of the detection means 1 is electrically connected to the signal processing means 4 via a connection line 3. The signal processing means 4 is for converting the voltage value or the voltage waveform of the detected voltage by the detecting means 1 into a signal form suitable for discriminating the misfire state, and in the example shown in FIG.
However, it goes without saying that a filter or a protection circuit not shown may be included in addition to the above.

The output side of the signal processing means 4 has a signal line 6
, And is electrically connected to the determination means 7 provided separately and independently from the signal processing means 4. This judging means 7 is for judging the misfire state according to the output signal of the signal processing means 4, and in the example shown in FIG. 1, an amplifier 8 for amplifying the output signal of the signal processing means 4 and the amplifier. 8
And a comparator 9 for comparing the output of the
A microcomputer 10 having a function for determining whether or not a misfire has occurred based on a comparison signal of the output of
The D / A converter 11 is provided for converting the digital reference value output from the microcomputer 10 into an analog signal and applying it to the comparison circuit 9 as an analog reference signal. The microcomputer 10 may be an independent one, but it can also serve as an engine control microcomputer, and this point is the same in each of the following embodiments.

Here, the signal processing means 4 and the determination means 7 are not only spatially separated, but do not share a common circuit board, and have a separate housing for the circuit. In addition to being physically independent from each other, it is desirable that they are electrically separated / independent except for the signal line 6 for transmitting a minimum required signal. That is, for example, it is desirable to take measures such as connecting the ground lines to different places without making them common, and not directly connecting the power supply lines between the two, but drawing them out individually from the power supply unit.

In the embodiment shown in FIG. 1, the ignition voltage detected by the detection means 1 is impedance-converted by the amplifier 5 of the signal processing means 4 into a stable analog signal, and the determination means 7 is passed through the signal line 6. And is compared with a reference signal corresponding to a normal ignition voltage without a misfire or a normal ignition voltage waveform in the determination means 7,
A state where a normal ignition voltage (waveform) is obtained by the microcomputer 10 based on the reference signal, that is, a normal state without misfire, or an abnormal ignition voltage (waveform), that is, a misfire state Is determined.

Here, the output of the signal processing means 4 appearing on the signal line 6 is an analog signal, but since it is a stable impedance-converted signal, the high frequency noise picked up by the detecting means 1 is detected by the signal processing means 4. There is little risk that the output signal is applied to the determination means 7, and even if a high leak voltage is applied from the detection means 1, there is almost no possibility that it will be applied to the determination means 7.

FIG. 2 shows a second embodiment of the ignition detecting device of the present invention. 2 is different from the embodiment of FIG. 1 only in the configuration of the judging means 7, and other points are the same as the embodiment of FIG. That is, in FIG.
Is an amplifier 8 for amplifying a signal given from the signal processing means 4 through the signal line 6, and an A / D converter 12 for converting an analog signal output from the amplifier 8 into a digital signal.
The microcomputer 10 is provided with the output signal of the A / D converter 12. This Figure 2
In the above example, the signal is directly processed by the microcomputer 10 without performing comparison with the reference signal, and it is determined whether or not there is a misfire.

FIG. 3 shows a third embodiment in which the misfire detecting device shown in FIG. 1 is modified. The overall circuit configuration of the embodiment of FIG. 3 is substantially the same as that of the embodiment of FIG.
1 is different from the embodiment of FIG. 1 in that the comparator 9 is provided on the signal processing means 4 side in the embodiment of FIG. .. Along with this, as the signal line 6 connecting the signal processing means 4 and the judging means 7, the signal line 6A for transmitting the comparison signal representing the comparison result from the comparator 9 in the signal processing means 4 to the judging means 7. And the signal line 6B for transmitting the reference signal from the D / A converter 11 in the judging means 7 to the comparator 9 in the signal processing means 4 is required.

In the embodiment of FIG. 3, the output signal of the signal processing means 4, that is, the signal appearing on the signal line 6A is the comparator 9.
Is the signal of the comparison result, and this signal is generally a pulse train signal, that is, a kind of digital signal. The reference signal transmitted through the signal line 6B is an analog signal.

FIG. 4 shows a fourth embodiment in which the misfire detecting device shown in FIG. 3 is further modified. The overall circuit configuration of the embodiment of FIG. 4 is substantially the same as that of the embodiment of FIG. 3, but in the embodiment of FIG. 4, not only the comparator 9 but also the D / A converter 11 performs signal processing. It differs from the embodiment of FIG. 3 in that it is included in the means 4.

In the embodiment of FIG. 4, a digital signal from the microcomputer 10 for producing a reference signal appears on the signal line 6B for transmitting a signal from the judging means 7 to the signal processing means 4. Therefore, both of the two signal lines 6A and 6B transmit digital signals. If the configuration is such that the signal transmission between the signal processing means 4 and the judging means 7 is performed only by digital signals, as will be shown later in another embodiment, the signal lines 6 (6A, 6B) will be described again. It is possible to carry out the signal transmission in) by an optical signal.

FIG. 5 shows a fifth embodiment in which the misfire detection device of the embodiment of FIG. 4 is more concretely embodied. It should be noted that this embodiment is applied to a misfire detection device for detecting a misfire in the case where spark plug discharge is performed but normal combustion is not performed.

In FIG. 5, the signal processing means 4 for processing the detection voltage supplied from the detection means 1 is constructed as follows. That is, the detection voltage input terminal 20 is connected to the amplifier 21 for amplifying the detection voltage from the detection means 1, and the output side of the amplifier 21 is connected to the peak hold circuit 22. The output side of the peak hold circuit 22 is connected to one input terminal of a comparator 23 for comparing the output signal with a reference signal, and the output side of the comparator 23 goes to the judging means 7 and outputs a comparison signal. Is connected to the comparison signal output terminal 24 for outputting. The output side of the comparator 23 is connected to the reset terminal of the peak hold circuit 22 via a delay circuit 25 and a differentiating circuit 26 for delaying the signal by the time T _2, and resets a counter 28 described later. It is connected to the terminal. The pulse input terminal 27 to which the reference pulse signal from the determination means 7 is applied is connected to a counter 28, the output side of this counter 28 is connected to a D / A converter 29, and this D / A converter is further connected. The output side of 29 is connected to the other input terminal of the comparator 23 via an amplifier 30. The comparison signal output terminal 24 and the pulse input terminal 27 are connected to the determination means 7 via signal lines 6A and 6B, respectively. This judging means 7 is composed of a microcomputer 10 as in the case of FIG.

FIG. 6 shows the waveform of each part of the circuit shown in FIG. 5, and the operation of the apparatus of FIG. 5 will be described with reference to this FIG.

An ignition voltage is generated at timing t ₀ in response to the rising Ha of the ignition signal H from an ignition timing control device (not shown), and the ignition voltage is detected by the detecting means 1. The waveform of the detected voltage has a waveform as shown by a broken line B in a normal combustion state, but becomes a waveform as shown by a solid line A when normal combustion is not performed (at the time of misfire). That is, it is a characteristic at the time of misfire that an extremely high peak Pa is shown at the timing t ₂ in the latter stage of discharge. Even during normal combustion, a slight peak Pb is shown in the latter stage of discharge, but this peak value is significantly lower than the peak value during misfire. Therefore, the misfire is detected by using the peaks Pa and Pb in the latter period of the discharge.

That is, the detected voltage A or B is peak-held by the peak-hold circuit 22 to obtain a peak-hold output as indicated by C, and this peak-hold output C is applied to one input terminal of the comparator 23.
The maximum peak value of the peak hold output C becomes large due to the above-mentioned peak Pa in the latter stage of discharge at the time of misfire.
On the other hand, from the determination means 7, a serial reference pulse signal D having a predetermined pulse interval and the number of pulses is given to the counter 28 from the timing t ₁ delayed by the time T ₁ from the rising Ha of the ignition signal H, and this counter 28 is provided. D by the output of 28
A reference signal is output from the / A converter 29, and is applied to the other input terminal of the comparator 23 via the amplifier 30. This signal (reference signal) is indicated by a broken line E. The waveform of the reference signal E has a portion in which the voltage gradually increases with the passage of time from the timing t ₁ . The maximum voltage value of the reference signal E is set to sufficiently exceed the expected maximum value of the peak hold output C. Then, the voltage of the peak hold output C is compared with the voltage of the reference signal E in the comparator 23, and if the voltage of the reference signal E exceeds the voltage of the peak hold output C, the output of the comparator 23 rises at the timing t ₃ . The comparison signal F rises and is output, and this comparison signal F is sent from the comparison signal output terminal 24 to the determination means 7 (microcomputer 10) via the signal line 6A. On the other hand, the comparison signal F of the comparator 23
Is delayed by time T ₂ by the delay circuit 25, differentiated by the differentiating circuit 26, and given as a reset signal G to the peak hold circuit 22 and the counter 28, which are reset to reset the peak hold output C and the reference signal E. Simultaneously fall at the timing t ₄ , and the comparison signal F also falls accordingly. Therefore, the comparison signal F is always a pulse having a constant width.

As is clear from the above description, the higher the latter peak (Pa or Pb) of the discharge of the detection voltage (A or B), the higher the latter maximum hold voltage of the peak hold output C becomes. As a result, the timing t _{3 at} which the voltage of the reference value signal E exceeds the voltage of the peak hold output C is advanced, and the pulse timing of the comparison signal F is also advanced. Therefore, by determining the timing of the pulse of the comparison signal F by the determining means 7, it is possible to determine whether or not there is a misfire. That is, since the peak Pb of the detection voltage B in the latter period of discharge is low during normal combustion, the pulse timing of the comparison signal F is early, while when normal combustion is not performed (at the time of misfire), the latter period of discharge of the detection voltage A is late. Since the peak Pa of 1 is high, the pulse timing of the comparison signal F is delayed, and thus it is possible to discriminate between the two.

FIG. 7 shows a misfire detecting device according to a sixth embodiment of the present invention, that is, an embodiment in which signal transmission is performed by an optical signal.

In FIG. 7, the signal processing means 4 and the determination means 7 are arranged separately from each other so as to be independent from each other, as in the above-mentioned respective embodiments, and the signal line 6 between them is the same. An optical cable 31 capable of optical communication is used. The signal processing means 4 is configured to have an amplifier 5, a comparator 9 and a D / A converter 11 like the signal processing means 4 shown in FIG. 4, and further outputs the output signal (comparison signal) of the comparator 9 electrically. An electrical / optical converter 32 for converting the signal into an optical signal and sending it out to the optical cable 31, and an optical signal of the reference signal pulse from the judging means 7 is converted into an electrical signal and given to the comparator 9. And an optical / electrical converter 33 for On the other hand, the judging means 7 also has a microcomputer 10 as in the judging means 7 shown in FIG. Device 34 and microcomputer 10
And an electric / optical converter 35 for converting the electric pulse for the reference signal from the optical pulse signal into an optical pulse signal and sending the optical pulse signal to the optical cable 31.

If the signal transmission between the signal processing means 4 and the judging means 7 is performed by an optical signal as in the embodiment of FIG. 7, the signal processing means 4 and the judging means 7 are electrically connected. Therefore, even if high-frequency noise is picked up by the detection means 1 or a high-voltage leak voltage is applied, the influence of the detection means 1 on the determination means 7 is completely eliminated. To be prevented. In this case, in particular, since the destruction and latch-up of the microcomputer 10 of the determination means 7 is completely prevented, even if the microcomputer 10 is also used for engine control, the destruction and latch-up make it impossible to run. It is possible to effectively prevent the occurrence of such a situation.

In the embodiment of FIG. 7, as a specific example of the electric circuit configuration of the signal processing means 4, the same configuration as the signal processing means 4 of the embodiment shown in FIG. 5 can be applied.

FIG. 8 shows a seventh embodiment of the present invention, that is, another embodiment in which signal transmission is performed by an optical signal. This case is different from the embodiment of FIG. 7 in that the reference signal generating circuit 36 is built in the signal processing means 4. In this case, since it is not necessary to transmit the reference signal pulse from the determination means 7 to the signal processing means 4, the optical cable 31 which is the signal line 6 may be an optical cable capable of unidirectional optical communication. For the same reason, the signal processing means 4 does not require the optical / electrical converter 33 in FIG. 7, and the determining means 7 does not require the electrical / optical converter 35 in FIG.

In the present invention, it is essential that the signal processing means in the preceding stage changes the detected voltage waveform into a signal of an appropriate format according to the decision method and circuit configuration in the decision means in the subsequent stage. The target configuration may be determined according to the determination means in the latter stage, and is not limited to the configuration of each embodiment. Also, various determination methods in the determination means in the latter stage are conceivable, and the point is that the misfire state can be determined according to the value or waveform of the initial detection voltage, and the specific circuit configuration is also possible. It is not limited to each embodiment, but is arbitrary. For example, in the embodiment shown in FIG. 5, the misfire is determined to occur when combustion does not occur even if discharge occurs in the spark plug, but the presence or absence of discharge itself is determined by the ignition voltage. May be.

[0038]

According to the misfire detection device of the present invention, the signal processing means for processing the ignition voltage of the internal combustion engine detected by the detection means to generate a signal suitable for determining the misfire state, and the signal processing means of the signal processing means. Since the determination means for determining the misfire state according to the output signal and the determination means are arranged separately from each other in terms of arrangement configuration, even if a high voltage leak voltage is applied from the detection means, it is generally resistant. There is almost no risk that the high-voltage leak voltage will be applied to the determination means at the latter stage mainly composed of a digital circuit such as a low-voltage microcomputer, and therefore the determination means such as a microcomputer may be damaged by the high voltage. Since the number of signal processing means at the front stage is extremely small and generally an analog circuit having a high withstand voltage is used as a main component, the signal processing means is Fear less to fail even applied leak voltage pressure, and because fear very few break down until the subsequent determination means including a microcomputer or the like even if the front stage of the signal processing unit fails,
It is possible to minimize the damage due to the high voltage leak voltage. In particular, it is convenient to use the engine control microcomputer also as the determination means in the latter stage, but even in that case, the engine control microcomputer that also serves as the determination means may fail due to the high voltage leak voltage. Is extremely small.

Further, according to the misfire detection device of the present invention,
As described above, since the signal processing means at the front stage and the determination means at the rear stage are separated and independent, the high frequency noise associated with the dielectric breakdown during the spark discharge of the electrode of the spark plug is picked up near the detection means. In this case, the high frequency noise is extremely unlikely to be added to the determination means in the subsequent stage, and therefore the determination means mainly composed of the digital circuit which is apt to cause malfunction due to the high frequency noise malfunctions due to the high frequency noise, resulting in an incorrect misfire state. It is extremely unlikely that the engine control microcomputer will malfunction due to latch-up even when the engine control microcomputer also serves as the determination means. It can be effectively prevented.

Further, since a complete analog voltage is sent from the detecting means to the signal processing means, the cable between them can easily pick up external noise, but in the misfire detecting device of the present invention, the signal processing means is connected to the judging means in the subsequent stage. Since it can be placed in the vicinity of the detection means while being separated from each other, the length of the cable from the detection means to the signal processing means can be shortened, so that it can be less affected by external noise and the like. Since the means can determine its installation position almost independently of the position of the detecting means, it is mainly composed of a digital circuit such as a microcomputer that needs to be sufficiently considered for environmental conditions such as temperature, humidity and vibration. The determination means has a high degree of freedom in installation, and a position advantageous for environmental conditions such as temperature, humidity, and vibration can be easily selected.

Further, according to the misfire detecting device of the fourth aspect of the present invention, since the signal transmission between the signal processing means at the front stage and the determination means at the rear stage is performed by the optical signal, the signal processing means at the front stage and the rear stage are processed. Therefore, even if a high voltage leak voltage is applied from the detecting means as described above, the influence of the high voltage may not affect the judging means in the subsequent stage. Since there is nothing, it is possible to reliably prevent the failure of the judgment means including the microcomputer, and even if high frequency noise is picked up in the vicinity of the detection means, there is no possibility that it will be added to the judgment means in the subsequent stage. And latch-up can be reliably prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing a misfire detection device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a misfire detection device according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a misfire detection device according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing a misfire detection device according to a fourth embodiment of the present invention.

FIG. 5 is a fifth embodiment of the present invention that embodies the fourth embodiment.
It is a block diagram showing a misfire detection device of the embodiment of.

FIG. 6 is a waveform diagram showing voltage waveforms of various parts in the misfire detection device of the fifth embodiment shown in FIG.

FIG. 7 is a sixth example of the present invention in which an optical cable is used for signal transmission.
It is a block diagram showing a misfire detection device of the embodiment of.

FIG. 8 is a seventh view of the present invention in which an optical cable is used for signal transmission.
It is a block diagram showing a misfire detection device of the embodiment of.

FIG. 9 is a schematic diagram showing an example of a conventional misfire detection device.

[Explanation of symbols]

 1 detecting means 4 signal processing means 6 signal line 7 judging means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Maruyama 1-4-1, Chuo, Wako-shi, Saitama Honda R & D Co., Ltd. (72) Inventor Masaki Kanehiro 1-4-1, Wako-shi, Saitama Prefecture No. Incorporated in Honda R & D Co., Ltd. (72) Inventor Takuji Ishioka 1-4-1 Chuo, Wako, Saitama Incorporated in R & D Co., Ltd.

Claims (4)

[Claims] 1. A detection means for detecting an ignition voltage of an internal combustion engine, a signal processing means for processing the voltage detected by the detection means to obtain a signal suitable for discriminating a misfire state, and the signal thereof. The signal processing means and the judging means are arranged separately from each other so as to be independent from each other in the arrangement configuration. A misfire detection device for an internal combustion engine, characterized in that the means are coupled via a signal line. 2. The misfire detection device for an internal combustion engine according to claim 1, wherein the signal line is a path for transmitting a digital signal. 3. The misfire detection device for an internal combustion engine according to claim 1, wherein an electric signal is used as the digital signal. 4. The misfire detection device for an internal combustion engine according to claim 1, wherein an optical signal is used as the digital signal.