JPH1113617A - Combustion state detecting device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability of decision without being influenced by noise when a combustion state is detected based on a current flowing between an ignition plug and a gland. SOLUTION: In this device, a current flowing between an ignition plug 12 and a gland is detected by the secondary winding 10b of an ignition coil 10, an ion current detecting resistor 17, and a computation amplifier 20, and from this current, a specified signal is picked up from the current by a BPF 22. By comparing the current with a given value preset by a noise mask circuit 24 and a deciding circuit 25, a combustion state is decided. By using a V/I conversion circuit 23, an output modulation circuit 30, a NOT gate 36, switching elements 37 and 39, and an offset current source 38, an output signal from the BPF 22 and an output signal from a decision circuit 25 are modulated and synthesized to generate a signal which is outputted through one and the same signal wire. This constitution forms signal wires from the cylinders into one signal wire and causes an influence to be hardly exercised by noise through signal-modulation, and improves reliability on decision.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion state detecting device for an internal combustion engine that detects a combustion state based on a current flowing between a spark plug disposed in a combustion chamber of the internal combustion engine and a ground.

[0002]

2. Description of the Related Art Conventionally, as a prior art document relating to a combustion state detecting device for an internal combustion engine, there is Japanese Patent Laid-Open No. 4-180774.
The one disclosed in Japanese Patent Application Publication No. HEI 10-203 (1995) is known. In this apparatus, an electronic control unit (computer unit) for an internal combustion engine and an igniter for driving an ignition coil for each cylinder are individually connected by wires, and a spark plug and a ground provided in a combustion chamber of the internal combustion engine are connected to each other. A technique is disclosed in which an internal control unit for an internal combustion engine detects a combustion state of each cylinder of the internal combustion engine based on an output signal from an igniter based on a current flowing between the cylinders.

[0003]

When misfire, pre-ignition (pre-ignition: pre-ignition), and knocking occur in the internal combustion engine, known processing is executed as abnormal combustion, and the combustion state of the internal combustion engine is determined. Is controlled to be optimal. Among them, particularly, the knock signal caused by the occurrence of the knocking state has an extremely small output, so that the knock signal is susceptible to the noise superimposed on the wire harness, and the reliability of the determination is low.

Accordingly, the present invention has been made to solve such a problem. When detecting a combustion state based on a current flowing between a spark plug provided in a combustion chamber of an internal combustion engine and a ground, noise is reduced. It is an object of the present invention to provide a combustion state detection device for an internal combustion engine that is highly reliable in determination without being affected by the above.

[0005]

According to the first aspect of the present invention, the current detecting means detects a current flowing between the spark plug and the ground, and from this current to the signal extracting means. Thus, a specific signal is extracted. Further, the combustion state is determined by comparing the current with a predetermined value set in advance by the output determination means, and the output signal from the signal extraction means and the output signal from the output determination means are modulated by the signal modulation means. -The combined signal is output via the same signal line. As a result, the number of signal lines for the ignition coil / igniter of each cylinder can be reduced to one, and the number of external connector pins can be minimized, so that an inexpensive configuration can be constructed.

According to a second aspect of the present invention, a current detecting means, a signal extracting means, an output judging means and a signal modulating means are arranged in an ignition coil / igniter of each of the cylinders which are driven by a built-in ignition coil. It is to establish. Thereby, the output signal from the external connection terminal of the ignition coil / igniter of each cylinder is simplified, and the influence of noise is suppressed.

According to a third aspect of the present invention, a timing for reading a signal from an external connection terminal of an ignition coil / igniter of each cylinder is generated based on an originally input ignition command signal. As a result, it is possible to minimize the number of input signals required for generating the read timing and to accurately generate the read timing.

According to a fourth aspect of the present invention, each output signal from the output modulation circuit in the ignition coil / igniter of each cylinder is input to the electronic control unit for the internal combustion engine as one signal by wire connection. doing. Thus, the output signal from the external connection terminal of the ignition coil / igniter of each cylinder is simplified, and the number of connector pins with the electronic control unit for the internal combustion engine can be reduced. For this reason, it is possible to adopt a configuration that is not easily affected by noise, and it is possible to improve the reliability of signal determination.

In the combustion state detecting device for an internal combustion engine according to the present invention, the output section signal from the electronic control unit for the internal combustion engine is branched into wires and input to the output modulation circuit 50 in the ignition coil / igniter of each cylinder. Thus, the electronic control unit for the internal combustion engine can accurately know the signal reading timing.

In the combustion state detecting apparatus for an internal combustion engine according to the present invention, the output value and the generation timing are changed and output in response to a signal specific at the time of misfire or occurrence of preignition by the signal modulation means. For this reason, the occurrence of misfire or preignition can be easily determined on the electronic control unit side for the internal combustion engine, and the reliability of the determination can be improved.

In the combustion state detecting device for an internal combustion engine according to the present invention, since the knock signal superimposed on the current detected by the current detecting means is originally a small signal, the occurrence of misfire and preignition is prevented by the signal extracting means. Are separately extracted and modulated. Thus, it is possible to prevent noise from being superimposed on the wire connection to the electronic control unit for the internal combustion engine.

In the combustion state detecting apparatus for an internal combustion engine according to the present invention, the determination result of the occurrence of misfire or preignition by the output determination means is generated based on the originally input ignition command signal. As a result, the determination result of misfire or occurrence of preignition is output at a predetermined timing synchronized with the ignition command signal, so that the reliability of the determination on the electronic control unit for the internal combustion engine can be improved.

In the combustion state detecting apparatus for an internal combustion engine according to the ninth aspect, knock determination is permitted by the signal modulation means depending on whether a modulated signal is generated during normal operation during normal combustion. Thus, the electronic control unit for the internal combustion engine is not affected by noise, so that the reliability of knock determination can be improved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples.

Embodiment 1 FIG. 1 is a block diagram showing a combustion state detecting device for an internal combustion engine according to a first embodiment of the present invention. Note that the internal combustion engine of this embodiment is # 1 cylinder to
Since the ignition coils / igniters 1 to 4 of the # 1 to # 4 cylinders have the same configuration, the ignition coil / igniter 1 of the # 1 cylinder will be mainly described below.

In FIG. 1, reference numeral 10 denotes an ignition coil;
10a is a primary winding of the ignition coil 10, and 10b is a secondary winding of the ignition coil 10. Reference numeral 12 denotes a spark plug provided in a combustion chamber of an internal combustion engine (not shown). Ignition coil 10
A switching element 11 is connected to the primary winding 10a, and the gate of the switching element 11 is connected to E (described later).
CU (Electronic Control Unit) 4
When the ignition command signal IGt1 from 0 is input from the external connection terminal 1a and the switching element 11 is turned on, the battery power supply +
A primary current I1 from B is supplied.

A current path in which the secondary current I2 circulates on the secondary winding 10b side of the ignition coil 10 is formed by the ignition plug 12, the secondary winding 10b of the ignition coil 10, the Zener diode 13 and the Zener diode 14. Have been. Here, the Zener diode 14 has a secondary current I2
It is connected in the forward direction with respect to the direction in which the (secondary circulating current) flows. The zener diode 13 is a diode for charging the capacitor 15 serving as an ion current detection power supply connected in parallel with the zener diode 13. Further, a resistor 16 is connected in parallel with the Zener diode 14.

At the time of detecting the ion current, the ion current IION flows from the capacitor 15 in the order of the secondary winding 10b of the ignition coil 10 and the ignition plug 12, and furthermore, the ion current detection resistor 17 from the inverting (-) terminal side of the operational amplifier 20. An ion current IION flows through the ion current detection resistor 17
As a result, an ion current IION is detected. The resistor 21 connected between the inverting (-) terminal and the output terminal of the operational amplifier 20 is an amplifying resistor for setting the gain of the operational amplifier 20.

The ion current signal S1 as an output signal from the operational amplifier 20 based on the ion current IION includes:
When the knocking state occurs, for example, 6KH
A characteristic knock signal waveform appears in a frequency band near z. Therefore, in order to extract this characteristic waveform from the ion current signal S1, a BPF (Band Pass Filte) of 6 kHz is used.
(r: specific frequency band-pass filter) 22 is converted into a current signal by a V / I conversion circuit 23. The output side of the V / I conversion circuit 23 is connected to the ECU 40
Connected to an external connection terminal 1b for connection to the terminal.

The ion current signal S1 is input to a noise mask circuit 24, and the signal passed through the noise mask circuit 24 is input to a determination circuit 25 for detecting the occurrence of a misfire or a knocking state. The signal S3 from the determination circuit 25 and the ignition command signal IGt1 from the ECU 40
Is input to the output modulation circuit 30. This output modulation circuit 30 is a NOT gate 3 for inverting the ignition command signal IGt1.
1. The signal S3 from the determination circuit 25 and the ignition command signal IGt
An OR gate 32 for inputting 1 and a flip-flop circuit 33 for generating a signal S4 which is set at the rising of the signal from the NOT gate 31 and reset at the rising of the signal from the OR gate 32, and the signal from the decision circuit 25 S
AND gate 3 for inputting an ignition command signal IGt1 and an ignition command signal IGt1
4. A one-shot circuit 35 which rises at the rise of the signal from the AND gate 34 to generate a signal S5 of a predetermined length.

The signal S4 from the flip-flop circuit 33 in the output modulation circuit 30 is input to the gate of the switching element 37 via the NOT gate 36. The collector of the switching element 37 is connected to the output side of the V / I conversion circuit 23 via the offset current source 38, and the emitter is connected to the ground. The signal S5 from the one-shot circuit 35 in the output modulation circuit 30 is input to the gate of the switching element 39. This switching element 3
9 is connected to the output side of the V / I conversion circuit 23, and the emitter is connected to the ground.

The external connection terminal 1b of the ignition coil / igniter 1 of the # 1 cylinder is connected to the external connection terminal 4 of the ECU 40.
0a, and the external connection terminal 1b is connected to a constant power supply 5 [V] via a pull-up resistor 41. The ignition coil / igniter 1 of the # 1 cylinder is driven by a constant power supply 5 [V] through an external connection terminal 40a of the ECU 40.
A voltage signal v based on a current i flowing to the external connection terminal 1b side of the microcomputer 45 is converted into a knock signal magnitude by a knock determination circuit 42 including a peak hold circuit and an A / D converter in the ECU 40, and then converted to a microcomputer 45. Is input to A timing signal is input from the microcomputer 45 to the knock determination circuit 42. The high-frequency component of the voltage signal v is removed through an LPF (Low Pass Filter) 43 in the ECU 40, and the A / D converter 44 performs A / D conversion (analog-digital conversion). Thereafter, it is input to the microcomputer 45.

The microcomputer 45 has a CP as a central processing unit for executing various known arithmetic processing.
U, a ROM storing a control program, a RAM storing various data, a B / U (backup) RAM, an input / output circuit, and a logical operation circuit including a bus line connecting them.

FIG. 2 is a time chart showing a transition state of each output signal in the internal combustion engine combustion state detecting apparatus according to the first embodiment of the present invention.

An ignition command signal IGt1 from the ECU 40 to the ignition coil / igniter 1 of the # 1 cylinder of the internal combustion engine.
Is turned on at time t1 and is ignition timing t
It is turned off at 3 (see FIG. 2A). First, FIG.
With reference to (b) to FIG. 2 (g), a transition state of each output signal when the combustion state of the internal combustion engine is normal or knock will be described. When the knocking state occurs, a knock signal is superimposed on the latter half of the ion current signal S1 shown in FIG. 2B, and a knock signal waveform appears in the signal S2 of the BPF 22 (see FIG. 2C).

On the other hand, the signal S3 in which the ionic current signal S1 has passed from the noise mask circuit 24 through the determination circuit 25 is turned on at time t4 when the ionic current signal S1 exceeds the threshold Vth, and at time t6 when the ionic current signal S1 falls below the threshold Vth. It is turned off (see FIG. 2D). Therefore, the signal S4 from the flip-flop circuit 33 of the output modulation circuit 30 is turned on at time t3 and turned off at time t4 (see FIG. 2 (e)).
The switching element 37 is inverted by the T gate 36.
Is turned off from time t3 to time t4. At this time, since the signal S5 from the one-shot circuit 35 of the output modulation circuit 30 does not turn on, the switching element 39 remains off.

Therefore, as shown in FIG. 2F, the current i lifted by the offset current source 38 at the time when the switching element 37 is turned on is supplied from the external connection terminal 40a of the ECU 40 to the # 1 cylinder. Flows to the side of the external connection terminal 1b of the ignition coil / igniter 1, and the voltage signal v at the external connection terminal 40a of the ECU 40 transitions as shown in FIG.

Next, FIGS. 2A and 2H to 2
With reference to (k), the transition state of each output signal at the time of misfire in the combustion state of the internal combustion engine will be described. In the event of a misfire,
Even if the ignition command signal IGt1 from the ECU 40 to the ignition coil / igniter 1 of the # 1 cylinder of the internal combustion engine is turned on / off as shown in FIG. 2A, nothing appears in the ion current signal S1. The signal S2 and the signal S3 from the determination circuit 25 also remain off. Therefore,
The signal S4 from the flip-flop circuit 33 of the output modulation circuit 30 is turned on at time t3 and turned off until time t7 (see FIG. 2 (i)), and is inverted by the NOT gate 36 to switch the switching element 37 at time t3. It is turned off from time t7. At this time, since the signal S5 from the one-shot circuit 35 of the output modulation circuit 30 does not turn on, the switching element 39 remains off.

Therefore, as shown in FIG. 2 (j), the current i lifted by the offset current source 38 at the time when the switching element 37 is turned on is supplied from the external connection terminal 40a of the ECU 40 to the # 1 cylinder. Flows to the side of the external connection terminal 1b of the ignition coil / igniter 1, and the voltage signal v at the external connection terminal 40a of the ECU 40 transitions as shown in FIG.

Next, FIGS. 2 (a) and 2 (l) to 2
With reference to (o), a transition state of each output signal when preignition occurs in a combustion state of the internal combustion engine will be described. When preignition occurs, the ignition command signal IGt1 from the ECU 40 to the ignition coil / igniter 1 of the # 1 cylinder of the internal combustion engine is turned on at time t1 as shown in FIG. 2A and turned off at time t3 which is the ignition timing. You. If preignition occurs in the internal combustion engine before time t3 of this ignition timing, the ion current signal S
1 shows a signal waveform as shown from time t2 to time t3 in FIG. At this time, the ion current signal S1
No knock signal is superimposed on.

Therefore, the signal S3 obtained by passing the ion current signal S1 from the noise mask circuit 24 through the determination circuit 25 is
It is turned on at time t2 when the ion current signal S1 becomes equal to or more than the threshold value Vth, and turned off at time t3 when it becomes equal to or less than the threshold value Vth.
Again, the time t when the ion current signal S1 becomes equal to or higher than the threshold value Vth
It is turned on at 4 and turned off at time t6 when it becomes equal to or lower than the threshold value Vth (see FIG. 2 (m)). Therefore, the signal S5 from the one-shot circuit 35 of the output modulation circuit 30 is turned on at time t2, and is turned off at time t5 after a predetermined time has elapsed (see FIG. 2 (n)). At this time, since the signal S4 from the flip-flop circuit 33 does not turn on, the switching element 37 is kept in the on state. And
EC corresponding to the time when the switching element 39 is turned on
Since the external connection terminal 40a of U40 is at the ground level, the voltage signal v at the external connection terminal 40a is
The transition is made as shown in FIG.

Next, the E used in the combustion state detecting device of the internal combustion engine according to the first embodiment of the present invention will be described.
FIG. 3 shows a processing procedure of misfire / preignition detection in the CPU of the microcomputer 45 in the CU 40.
2 will be described with reference to the above-described time chart of FIG. The misfire / preignition detection routine is executed at each timing when the voltage signal v is A / D converted by the A / D converter 44 through the LPF 43.

In FIG. 3, first, in step S101, 0.5 ms after ignition, that is, 0.5 ms from time t3 in FIG.
At the timing after s, the above-described voltage signal v is
A / D1 (indicated by an arrow in FIG. 2) as an A / D conversion value which is A / D converted by the A / D converter 44 through
TDC (After Top Dead Center: 60 ° CA)
(Crank Angle), that is, time t6 in FIG.
A little later, the above-mentioned voltage signal v becomes LP
A that is A / D converted by the A / D converter 44 through F43
A / D2 (indicated by an arrow in FIG. 2) as a / D conversion value is read. Next, the process proceeds to step S102, and it is determined whether A / D1 is less than 1 [V]. Here, the determination condition of step S102 is satisfied, and A / D1
Is less than 1 [V], the flow shifts to step S103, assuming that the voltage signal v is in the transition state at the time of preignition occurrence shown in FIG. 2 (o), and the flag XP indicating the occurrence of preignition is set to "1" ( After the pre-ignition has occurred and the flag XS representing ignition has been set to "1" (ignition), this routine ends.

On the other hand, if the condition for determination in step S102 is not satisfied and A / D1 is 1 [V] or more, the process proceeds to step S104, and it is determined whether A / D2 is less than 4.5 [V]. You. Here, when the determination condition of step S104 is satisfied and A / D2 is less than 4.5 [V], the process shifts to step S105, and the voltage signal v transitions between the normal state and the knocking state shown in FIG. In this state, the flag XP indicating the occurrence of pre-ignition is set to "0" (no pre-ignition occurs) and the flag XS indicating ignition is set to "1" (ignition), and then this routine ends.

On the other hand, when the determination condition of step S104 is not satisfied and A / D2 is equal to or more than 4.5 [V], the process shifts to step S106, and the voltage signal v changes at the time of misfire shown in FIG. In this state, the flag XP indicating the occurrence of pre-ignition is set to "0" (no pre-ignition occurs) and the flag XS indicating ignition is set to "0" (misfire), and then this routine ends.

Next, E used in the combustion state detecting device of the internal combustion engine according to the first embodiment of the present invention will be described.
A description will be given with reference to the above-described time chart of FIG. 2 based on the flowchart of FIG. 4 showing the processing procedure of permission / prohibition of knock determination in the CPU of the microcomputer 45 in the CU 40. The knock determination permission / prohibition routine is executed each time the above-described voltage signal v is read via knock determination circuit 42.

In FIG. 4, first, in step S201,
0.5 ms after the ignition, that is, from time t3 in FIG.
At a timing after 5 ms, the above-described voltage signal v becomes LPF
A / D converted by A / D converter 44 through A / D converter 43
It is determined whether A / D1 (indicated by an arrow in FIG. 2) as the D-converted value exceeds 4.5 [V]. Step S
When the determination condition of 201 is satisfied and A / D1 exceeds 4.5 [V], the voltage signal v is in the normal state or knock transition state shown in FIG. 2 (g) or shown in FIG. 2 (k). Assuming that the state is in any of the transition states at the time of misfire, step S202
Then, it is determined whether A / D2 is less than 4.5 [V]. If the determination condition of step S202 is satisfied,
/ D2 is less than 4.5 [V], the voltage signal v
Is determined to be in the normal state or the knock state transition state shown in FIG. 2 (g), the process proceeds to step S203, and after the knock determination permission process is executed, the present routine ends.

On the other hand, when the determination condition of step S201 is not satisfied and A / D1 is 4.5 [V] or less, or when the determination condition of step S202 is not satisfied and A / D2 is 4.5 [V]. If the above is the case, it is determined that the voltage signal v is in a state other than the transition state at the time of knocking, the flow proceeds to step S204, and after knocking determination prohibition processing is executed, this routine ends.

As described above, the apparatus for detecting the combustion state of an internal combustion engine according to the present embodiment has a secondary function of the ignition coil 10 for detecting the current flowing between the ignition plug 12 disposed in the combustion chamber of the internal combustion engine and the ground. Winding 10b, ion current detecting resistor 17,
A current detecting means comprising an operational amplifier 20 and the like, and a BP for extracting a specific signal from the current detected by the current detecting means
F22, a signal extracting means, and an output determining means including a noise mask circuit 24 and a determining circuit 25 for determining a combustion state based on a comparison between the current detected by the current detecting means and a predetermined value. V / V which outputs a signal obtained by modulating and synthesizing an output signal from the signal extracting means and an output signal from the output determining means via the same signal line.
I conversion circuit 23, output modulation circuit 30, NOT gate 3
6, signal modulation means including switching elements 37 and 39 and an offset current source 38.

Therefore, the secondary winding 10b of the ignition coil 10 as current detecting means, the ion current detecting resistor 17,
A current flowing between the spark plug 12 and the ground is detected by the operational amplifier 20 and the like, and a specific signal is extracted from the current by the BPF 22 as signal extracting means. Also,
This current is used as a noise mask circuit 24 as output determination means.
The combustion state is determined by comparison with a predetermined value set in advance by a determination circuit 25, and V / I as a signal modulating means is determined.
Conversion circuit 23, output modulation circuit 30, NOT gate 36,
Switching elements 37 and 39 and offset current source 38
, A signal obtained by modulating and combining the output signal from the BPF 22 and the output signal from the determination circuit 25 is output via the same signal line. As a result, the signal lines of the ignition coils / igniters 1 to 4 of the # 1 to # 4 cylinders can be made one,
The number of external connector pins can be minimized and an inexpensive configuration can be achieved.

In the combustion state detecting device for an internal combustion engine according to the present embodiment, the current detecting means, the signal extracting means, the output determining means and the signal modulating means are driven by a # 1 cylinder having an ignition coil 10 built therein. These are disposed in the ignition coils / igniters 1-4 of the # 4 cylinder. Therefore,
Output signals from the external connection terminals of the ignition coils / igniters 1 to 4 of the # 1 to # 4 cylinders are simplified. For this reason, the influence of noise is suppressed.

In the combustion state detecting device for an internal combustion engine according to this embodiment, the output modulating means receives an ignition command signal IGt from the internal combustion engine ECU 40 and outputs the ignition command signal IGt.
A signal is output in synchronization with t. That is, # 1
The timing of reading signals from the external connection terminals of the ignition coils / igniters 1 to 4 of the cylinders # 4 to # 4 can be generated based on the originally input ignition command signal IGt. As a result, it is possible to minimize the number of input signals required for generating the read timing and to accurately generate the read timing.

Further, in the combustion state detecting device for an internal combustion engine according to the present embodiment, the output modulating means may be a # 1 for each cylinder of the internal combustion engine.
An output modulation circuit 30 is provided in each of the ignition coils / igniters 1-4 of the cylinders # 4 to # 4, and each output signal from the output modulation circuit 30 is input to the ECU 40 for the internal combustion engine as one current i signal by wire connection. Is what you do. Therefore, the ignition coils / igniters 1 to 4 of the # 1 to # 4 cylinders
4, the output signal from the external connection terminal is simplified,
The number of connector pins with the 40 side can be reduced. For this reason, it is possible to adopt a configuration that is not easily affected by noise, and it is possible to improve the reliability of signal determination.

Further, in the combustion state detecting device for an internal combustion engine according to the present embodiment, the signal modulating means outputs an output signal based on the occurrence of misfire or preignition determined by the output determining means to a predetermined output value, a predetermined output value, and a predetermined output value. It changes the timing and outputs it. In other words, the output value and generation timing of the signal are changed and output in response to a signal specific to misfire or preignition at the signal modulating means. For this reason,
The misfire or the occurrence of preignition can be easily determined on the ECU 40 side, and the reliability of the determination can be improved.

In addition, in the combustion state detecting device for an internal combustion engine according to the present embodiment, the signal extracting means extracts an AC signal including a knock frequency in the current detected by the current detecting means. In other words, since the knock signal superimposed on the current detected by the current detection means is originally a small signal,
The signal is extracted and modulated by the signal extracting means separately from the occurrence of misfire and preignition. Thus, it is possible to prevent noise from being superimposed on the wire connection to the ECU 40 side.

In the combustion state detecting device for an internal combustion engine according to the present embodiment, the signal modulating means synchronizes with the ignition command signal IGt and modulates the judgment result by the output judging means at a predetermined timing. That is, the determination result of the occurrence of misfire or preignition by the output determination means is generated based on the originally input ignition command signal IGt.
As a result, the determination result of the misfire or the occurrence of the preignition is output at a predetermined timing synchronized with the ignition command signal IGt, so that the reliability of the determination on the ECU 40 side can be improved.

The apparatus for detecting a combustion state of an internal combustion engine according to the present embodiment permits knock determination based on a signal modulated when the signal modulation means is operating normally during normal combustion. In other words, the signal modulation means is permitted to make a knock determination depending on whether a modulated signal is generated during normal operation during normal combustion. Thus, since the ECU 40 is not affected by noise, the reliability of knock determination can be improved.

<Embodiment 2> FIG. 5 is a block diagram showing a combustion state detecting device for an internal combustion engine according to a second embodiment of the present invention. Note that the internal combustion engine of this embodiment is # 1 cylinder to
Since the ignition coils / igniters 1 'to 4' of the # 1 to # 4 cylinders have the same configuration, the ignition coil / igniter 1 'of the # 1 cylinder will be mainly described below. In the drawing, the same reference numerals and symbols are given to components having the same configuration or corresponding portions as those in the above-described embodiment, and detailed description thereof will be omitted.

The difference between FIG. 5 and FIG.
At 0, an output section signal generated as described later is output to the ignition coils / igniters 1 'to 4' of the # 1 to # 4 cylinders, and the output section signals are output to the ignition coils of the # 1 to # 4 cylinders. / Igniters 1 'to 4' are input to each output modulation circuit 50 from the external connection terminal 1c '. Further, the configuration of the output modulation circuit 50 and the output modulation circuit 50
Is input to the V / I conversion circuit 23, and the signal S7 from the output modulation circuit 50 is combined with the signal S8 from the V / I conversion circuit 23 via the V / I conversion circuit 63. is there.

Next, a detailed configuration of the output modulation circuit 50 in the combustion state detecting device for an internal combustion engine according to the second embodiment of the present invention will be described with reference to FIG.

The output modulation circuit 50 receives the signal S3 from the determination circuit 25, the ignition command signal IGt1 from the ECU 40, and the output section signal. This output modulation circuit 5
0 is set at the rising edge of the signal Sh1 from the AND gate 51, the NOT gate 52 inverting the output interval signal, and the AND gate 51 for inputting the ignition command signal IGt1 and the output interval signal, and at the rising edge of the signal from the NOT gate 52. A flip-flop circuit 53 that generates a signal Sh2 that is reset by resetting, an AND gate 54 that inputs the signal S3 from the determination circuit 25 and the ignition command signal IGt1,
One shot circuit 5 which rises at the fall of signal Sh3 from D gate 54 to generate signal Sh4 of a predetermined length
5, an AND gate 56 for inputting the signal Sh4 from the one-shot circuit 55 and the output section signal, and a NOT for inverting the signal S3 from the determination circuit 25 and the ignition command signal IGt1.
An AND gate 58 for inputting a signal from the gate 57;
One-shot circuit 59 which rises at the fall of signal Sh2 from flip-flop circuit 53 to generate signal Sh7 of a predetermined length, and signal S from flip-flop circuit 53
Flip-flop circuit 60 for generating signal Sh8 which is set at the rise of h2 and reset at the rise of signal Sh6 from AND gate 58, one-shot circuit 5
9 includes an AND gate 61 that inputs the signal Sh7 from the flip-flop circuit 60 and the signal Sh8 from the flip-flop circuit 60, and an OR gate 62 that inputs the signal Sh5 from the AND gate 56 and the signal Sh9 from the AND gate 61. The signal Sh2 from the flip-flop circuit 53 is output as a signal S6 from the terminal of the output modulation circuit 50, and the signal from the OR gate 62 is output as a signal S7 from the terminal of the output modulation circuit 50.

FIG. 7 shows an output modulation circuit 50 of a combustion state detecting device for an internal combustion engine according to a second embodiment of the present invention.
7 is a time chart showing a transition state of each output signal in FIG. 6, which will be described with reference to the output modulation circuit 50 of FIG.

An ignition command signal IGt1 from the ECU 40 to the ignition coil / igniter 1 'of the # 1 cylinder of the internal combustion engine.
Is turned on at time t11 and is the ignition timing t
It is turned off at 14 (see FIG. 7A). At this time, FIG.
As shown in (b), the signal becomes High at time t12 and becomes time t17.
, An output section signal which becomes Low is input. First, FIG.
With reference to (a), FIG. 7 (b) and FIGS. 7 (c) to 7 (i), the transition state of each output signal at the time of preignition occurrence or no preignition occurrence in the combustion state of the internal combustion engine will be described. . From the ignition command signal IGt1 shown in FIG. 7A and the output section signal shown in FIG.
The ND gate 51 generates a signal Sh1 as a detection section at the time of occurrence of preignition (see FIG. 7C).
A signal Sh2 that rises with this signal Sh1 and falls with a signal obtained by inverting the output section signal is generated by the flip-flop circuit 53 (see FIG. 7D).

Here, the ion current signal S1 is shown in FIG.
, The signal S3 from the determination circuit 25 becomes as shown in FIG. 7 (f). Therefore,
The signal Sh3 from the AND gate 54, which receives the ignition command signal IGt1 and the signal S3 from the determination circuit 25, is extracted from the signal S3 before the time t14, which is the ignition timing, that is, only the signal at the time of occurrence of preignition. The result is as shown in FIG. As described above, when the signal at the time of occurrence of preignition appears in the signal Sh3, the one-shot circuit 55 rises at the fall of the signal Sh3 to generate a signal Sh4 of a predetermined length (see FIG. 7 (h)). . Since this signal Sh4 overlaps with the output section signal, AN
It becomes equal to the signal Sh5 after passing through the D gate 56 (see FIG. 7 (h)). Therefore, after ignition 0.5
At the timing of reading A / D1 (indicated by an arrow in FIG. 7), which is the A / D converted value of ms, the signal Sh5 shown in FIG. 7H is High, and it can be determined that preignition has occurred. On the other hand, at the same read timing of A / D1 (indicated by an arrow in FIG. 7), FIG.
If the signal Sh5 remains Low as shown in (1), it can be determined that preignition does not occur.

Next, FIG. 7A, FIG. 7B, FIG.
With reference to (d) and FIGS. 7 (j) to 7 (n), the transition state of each output signal when the combustion state of the internal combustion engine is normal, that is, at the time of ignition will be described. In response to the ion current signal S1 in the transition state shown in FIG.
A signal Sh6 similar to the signal S3 from the AND gate 5
8 (see FIG. 7 (k)). Further, the signal Sh2 rises at the falling of the signal Sh2 from the flip-flop circuit 53 (time t17 shown in FIG. 7), and a signal Sh7 of a predetermined length is generated by the one-shot circuit 59 (see FIG. 7 (l)).
The signal Sh8 rises at the rise of the signal Sh2 from the flip-flop circuit 53 (time t12 shown in FIG. 7) and falls at the rise of the signal Sh6 from the AND gate 58 (time t15 shown in FIG. 7).
0 (see FIG. 7 (m)). For this reason, the signal Sh9 from the one-shot circuit 59 and the signal Sh8 from the flip-flop circuit 60 have no overlapping section, and the AND gate 61 outputs the signal Sh9 which remains Low (see FIG. 7 (n)). Therefore, A / D conversion value which is an A / D conversion value of 0.5 ms after the rise of an output section signal to be described later.
At the read timing 3 (indicated by the arrow in FIG. 7), the signal Sh9 is low as shown in FIG. 7 (n), so that it can be determined that ignition has occurred.

Next, FIG. 7A, FIG. 7B, FIG.
With reference to (d) and FIGS. 7 (o) to 7 (s), the transition state of each output signal at the time of misfire in the combustion state of the internal combustion engine will be described. At the time of misfire, as shown in FIG.
Since the ion current signal S1 does not change, the signal S3 from the determination circuit 25 remains Low, and a similar signal Sh6 is output from the AND gate 58 (see FIG. 7 (p)).
At this time, the signal Sh2 from the flip-flop circuit 53
Rise (time t17 shown in FIG. 7) and a signal Sh7 of a predetermined length is generated by the one-shot circuit 59 (see FIG. 7 (q)). And the flip-flop circuit 5
3 rise of signal Sh2 (time t12 shown in FIG. 7)
Is generated by the flip-flop circuit 60 (see FIG. 7 (r)). At this time, since the signal Sh6 from the AND gate 58 remains Low, the signal Sh8 becomes High at time t12 shown in FIG. 7 and the state is maintained. Therefore, the signal Sh7 from the one-shot circuit 59 and the signal Sh8 from the flip-flop circuit 60 are output.
From the AND gate 61 at time t17 to time t18.
The signal Sh9 that becomes high is output (see FIG. 7 (s)). Therefore, at the timing of reading A / D3 (indicated by an arrow in FIG. 7), which is an A / D converted value 0.5 ms after the rising of the output section signal described later, the signal Sh9 is output as shown in FIG. Since it is High, it can be determined that a misfire has occurred.

Next, the transition state of each output signal in the combustion state detecting device for an internal combustion engine according to the second embodiment of the present invention will be described with reference to the time chart of FIG. Note that the time chart of FIG. 8 shows a transition state in which knocking has occurred in cylinder # 1 and the other cylinders # 2 to # 4 are in normal ignition.

As shown in FIGS. 8 (a) to 8 (d), the ignition command signals IGt1 to IGt4 for the ignition coils / igniters 1 'to 4' of the # 1 to # 4 cylinders and FIG.
As shown in the figure, an output section signal is output. The ion current signal S1 in each cylinder is output from the operational amplifier 20 as shown in FIGS. 8 (f) to 8 (h). # 2
The ion current signal S1 of the cylinder is omitted. Therefore, the signal S3 from the determination circuit 25 in the ignition coil / igniter 1 'of the # 1 cylinder shown in FIG. 8J corresponding to the output section signal of the # 1 cylinder shown in FIG. Signal at the time of ignition appears as shown in FIG. When the # 1 cylinder is misfired, nothing appears in the signal S3 from the determination circuit 25 as shown by the broken line in FIG. 8 (j).

At the same time, the signal S2 from the BPF 22 in the ignition coil / igniter 1 'of the # 1 cylinder (FIG. 8 (k))
8) is subjected to voltage-current conversion by the V / I conversion circuit 23, and as shown in FIG. 8 (l), a knock signal superimposed in the latter half of the ignition section (see FIG. 8 (j)) largely appears. Therefore, the combined current i flowing to the side of each of the external connection terminals 1b 'of the ignition coils / igniters 1' to 4 'of the # 1 cylinder to # 4 cylinder by the constant power supply 5 [V] via the external connection terminal 40a of the ECU 40. Is as shown in FIG.
A signal representing ignition / knocking occurrence as the combustion state of cylinder # 1, a signal representing ignition as a combustion state of cylinder # 3, # 4
A signal indicating ignition as the combustion state of the cylinder will appear. In FIG. 8, the combustion state of the # 2 cylinder is omitted.

Next, the voltage signal v detected on the ECU 40 side with respect to the transition state of each output signal in the combustion state detecting apparatus for an internal combustion engine according to the second embodiment of the present invention.
9 showing FIG. 9 will be described with reference to FIG. 7 and FIG.

As shown in FIGS. 9 (a) to 9 (d), the ignition command signals IGt1 to IGt4 for the ignition coils / igniters 1 'to 4' of the # 1 to # 4 cylinders and FIG.
As shown in the figure, an output section signal is output. here,
If a misfire has occurred in the # 1 cylinder, at the timing of reading A / D3 (indicated by an arrow in FIG. 9) which is an A / D conversion value of 0.5 ms after the rise of the output section signal, FIG.
Based on the signal S7 from the output modulation circuit 50 by the signal Sh9 shown in (s), the combined current i flowing through the external connection terminal 40a of the ECU 40 increases as shown in FIG. 9 (f), and as a result, the voltage signal v Is reduced to near 0 [V] as shown in FIG.

If preignition has occurred in the # 3 cylinder, A / D conversion value 0.5 ms after ignition is obtained.
At the read timing of / D1 (indicated by the arrow in FIG. 9), the combined current i flowing through the external connection terminal 40a of the ECU 40 based on the signal S7 from the output modulation circuit 50 by the signal Sh5 shown in FIG. Becomes larger as shown in FIG. 9F, and as a result, the voltage signal v becomes
As shown in FIG. And #
When knocking occurs in the four cylinders, the signal S2 from the BPF 22 is transmitted to the V / I conversion circuit 2 as described with reference to FIG.
The knock signal superimposed in the latter half of the ignition section based on the signal S8 subjected to the voltage-current conversion in 3 appears as shown in FIG. 9 (g). It should be noted that normal ignition can be determined for the # 2 cylinder because there is no large change in the voltage signal v at the above-described read timing.

Next, the E used in the combustion state detecting device of the internal combustion engine according to the second embodiment of the present invention will be described.
A description will be given with reference to a time chart of FIG. 7 based on a flowchart of FIG. 10 showing a processing procedure of output section signal generation in the CPU of the microcomputer 45 in the CU 40.

Referring to FIG. 10, in step S301, 1 ms before ignition (time t12 shown in FIG. 7), the rise ATDC6
An output section signal that falls at 0 ° CA (time t17 shown in FIG. 7) is generated, and this routine ends. This output section signal is input from the ECU 40 to each output modulation circuit 50 in the ignition coils / igniters 1 'to 4' of the # 1 to # 4 cylinders.

Next, E used in the combustion state detecting device of the internal combustion engine according to the second example of the embodiment of the present invention.
FIG. 1 shows a processing procedure of misfire / preignition detection in the CPU of the microcomputer 45 in the CU 40.
1 will be described with reference to the time charts of FIGS. 7 and 9.

In FIG. 11, first, at step S401
0.5 ms after ignition, that is, 0.5 ms from time t14 in FIG.
At a timing after ms, the voltage signal v shown in FIG.
A / D1 (shown by an arrow in FIGS. 7 and 9) as an A / D converted value which is A / D-converted by the A / D converter 44 through the LPF 43 and after the fall of the output section signal. 5ms,
That is, at the timing 0.5 ms after the time t17 in FIG. 7, the A / D converted value obtained by A / D converting the voltage signal v shown in FIG. A / D3 (indicated by arrows in FIGS. 7 and 9) is read. Next, the process proceeds to step S402, where A /
It is determined whether D1 is less than 1 [V]. Here, the determination condition of step S402 is satisfied, and A / D1 is 1
If it is less than [V], the flow shifts to step S403, assuming that the voltage signal v is in the transition state at the time of occurrence of preignition as indicated by the # 3 cylinder in FIG. 9 (g), and the flag XP indicating the occurrence of preignition is set. It is set to "1" (preignition has occurred). On the other hand, the determination condition of step S402 is not satisfied, and A / D1 is 1 [V].
If so, the process proceeds to step S404, where it is determined that the voltage signal v is in the transition state when no pre-ignition occurs, and the flag XP indicating the occurrence of pre-ignition is set to "0" (no pre-ignition occurs).

Then, after the processing in step S403 or S404, the flow shifts to step S405, and it is determined whether A / D3 is less than 1 [V]. Here, the determination condition of step S402 is satisfied, and A / D3
Is less than 1 [V], the flow shifts to step S406, assuming that the voltage signal v is in the transition state at the time of misfire as shown by the # 1 cylinder in FIG. 9 (g), and the flag XS representing ignition is set to "0". "" (Misfire) and this routine ends. On the other hand, the determination condition of step S405 is not satisfied, and A
When / D3 is 1 [V] or more, step S407
Then, it is determined that the voltage signal v is in the transition state at the time of ignition, the flag XS representing ignition is set to "1" (ignition), and this routine ends.

As described above, the apparatus for detecting the combustion state of an internal combustion engine according to the present embodiment has a secondary function of the ignition coil 10 for detecting a current flowing between the ignition plug 12 disposed in the combustion chamber of the internal combustion engine and the ground. Winding 10b, ion current detecting resistor 17,
A current detecting means comprising an operational amplifier 20 and the like, and a BP for extracting a specific signal from the current detected by the current detecting means
F22, a signal extracting means, and an output determining means including a noise mask circuit 24 and a determining circuit 25 for determining a combustion state based on a comparison between the current detected by the current detecting means and a predetermined value. V / V which outputs a signal obtained by modulating and synthesizing an output signal from the signal extracting means and an output signal from the output determining means via the same signal line.
I conversion circuit 23, output modulation circuit 50, V / I conversion circuit 6
3 signal modulation means.

Therefore, the secondary winding 10b of the ignition coil 10 as current detecting means, the ion current detecting resistor 17,
A current flowing between the spark plug 12 and the ground is detected by the operational amplifier 20 and the like, and a specific signal is extracted from the current by the BPF 22 as signal extracting means. Also,
This current is used as a noise mask circuit 24 as output determination means.
The combustion state is determined by comparison with a predetermined value set in advance by a determination circuit 25, and V / I as a signal modulating means is determined.
Conversion circuit 23, output modulation circuit 50, V / I conversion circuit 63
, A signal obtained by modulating and combining the output signal from the BPF 22 and the output signal from the determination circuit 25 is output via the same signal line. As a result, the number of signal lines for the ignition coils / igniters 1 'to 4' of the # 1 to # 4 cylinders can be reduced to one, and the number of external connector pins can be minimized to achieve an inexpensive configuration.

In the combustion state detecting device for an internal combustion engine according to the present embodiment, the current detecting means, the signal extracting means, the output determining means and the signal modulating means are driven by a # 1 cylinder having an ignition coil 10 built therein. To # 4 cylinder ignition coils / igniters 1 'to 4'. Therefore, the ignition coil / igniter 1 'of the # 1 to # 4 cylinders
The output signals from the external connection terminals 〜4 ′ are simplified.
For this reason, the influence of noise is suppressed.

In the combustion state detecting device for an internal combustion engine according to the present embodiment, the output modulating means inputs an ignition command signal IGt from the internal combustion engine ECU 40, and outputs the ignition command signal IGt.
A signal is output in synchronization with t. That is, # 1
The timing of reading signals from the external connection terminals of the ignition coils / igniters 1 'to 4' of the cylinders # 4 to # 4 can be generated based on the originally input ignition command signal IGt. As a result, it is possible to minimize the number of input signals required for generating the read timing and to accurately generate the read timing.

Further, in the combustion state detecting device for an internal combustion engine according to the present embodiment, the output modulating means may be arranged so that the output modulating means # 1 for each cylinder of the internal combustion engine.
An output modulation circuit 50 is provided in each of the ignition coils / igniters 1 'to 4' of the cylinders # 4 to # 4.
Are input to the internal combustion engine ECU 40 as one current i signal by wire connection. Therefore, output signals from the external connection terminals of the ignition coils / igniters 1 'to 4' of the # 1 to # 4 cylinders are simplified, and the number of connector pins with the ECU 40 can be reduced. For this reason, it is possible to adopt a configuration that is not easily affected by noise, and it is possible to improve the reliability of signal determination.

Further, in the combustion state detecting apparatus for an internal combustion engine according to the present embodiment, the signal modulating means may be the ignition coil / igniter 1 'to # 1 cylinder to # 4 cylinder for each cylinder of the internal combustion engine.
4 'includes an output modulation circuit 50. The output modulation circuit 50 is provided for branching the output section signal from the internal combustion engine ECU 40 and inputting it to the output modulation circuit 50. That is, the predetermined timing is generated using the output section signal from the ECU 40 side. Thus, the ECU 40 can accurately know the signal reading timing.

In addition, in the combustion state detecting device for an internal combustion engine according to the present embodiment, the signal modulating means outputs an output signal based on the occurrence of misfire or preignition determined by the output determining means to a predetermined output value and a predetermined output value. It changes the timing and outputs it. In other words, the output value and generation timing of the signal are changed and output in response to a signal specific to misfire or preignition at the signal modulating means. Therefore, the occurrence of misfire or preignition can be easily determined on the ECU 40 side, and the reliability of the determination can be improved.

In the combustion state detecting device for an internal combustion engine according to the present embodiment, the signal extracting means extracts an AC signal including a knock frequency in the current detected by the current detecting means. That is, since the knock signal superimposed on the current detected by the current detecting means is originally a small signal, the knocking signal is extracted and modulated by the signal extracting means separately from the occurrence of misfire and preignition. Thus, it is possible to prevent noise from being superimposed on the wire connection to the ECU 40 side.

In the combustion state detecting device for an internal combustion engine according to the present embodiment, the signal modulating means synchronizes with the ignition command signal IGt and modulates the judgment result by the output judging means at a predetermined timing. That is, the determination result of the occurrence of misfire or preignition by the output determination means is generated based on the originally input ignition command signal IGt. As a result, the determination result of the misfire or the occurrence of the preignition is output at a predetermined timing synchronized with the ignition command signal IGt, so that the reliability of the determination on the ECU 40 side can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a combustion state detection device for an internal combustion engine according to a first example of an embodiment of the present invention.

FIG. 2 is a time chart showing a transition state of each output signal in a combustion state detection device for an internal combustion engine according to a first example of an embodiment of the present invention.

FIG. 3 is an EC used in a combustion state detection device for an internal combustion engine according to a first example of an embodiment of the present invention.
6 is a flowchart showing a processing procedure of misfire / preignition detection in the CPU of the microcomputer in U.

FIG. 4 is an EC used in a combustion state detection device for an internal combustion engine according to a first example of an embodiment of the present invention.
7 is a flowchart showing a procedure of knock determination permission / prohibition in the CPU of the microcomputer in U.

FIG. 5 is a configuration diagram showing a combustion state detection device for an internal combustion engine according to a second example of the embodiment of the present invention.

FIG. 6 is a configuration diagram showing details of an output modulation circuit in FIG. 5;

FIG. 7 is a time chart showing a transition state of each output signal in an output modulation circuit of a combustion state detection device for an internal combustion engine according to a second example of the embodiment of the present invention.

FIG. 8 is a time chart showing a transition state of each output signal in a combustion state detection device for an internal combustion engine according to a second example of the embodiment of the present invention.

FIG. 9 is a time chart showing a voltage signal detected on the ECU side with respect to a transition state of each output signal in the combustion state detection device for the internal combustion engine according to the second example of the embodiment of the present invention. .

FIG. 10 is a flowchart showing a processing procedure for generating an output section signal in a CPU of a microcomputer in an ECU used in a combustion state detection device for an internal combustion engine according to a second embodiment of the present invention. It is.

FIG. 11 shows a processing procedure of misfire / preignition detection in a CPU of a microcomputer in an ECU used in a combustion state detection device for an internal combustion engine according to a second embodiment of the present invention. It is a flowchart.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ignition coil / igniter (of 1 cylinder) 10 Ignition coil 10b Secondary winding (current detection means) 12 Spark plug (current detection means) 17 Ion current detection resistance (current detection means) 20 Operational amplifier (current detection means) 40 ECU (electronic control unit) 45 microcomputer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Eiji Takakuwa 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Co., Ltd. (72) Inventor Kazuhisa Mogi 1-Toyota-cho, Toyota-shi, Aichi Prefecture Toyota Motor Corporation (72) Inventor Hirohisa Kishi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (9)

[Claims] 1. A current detecting means for detecting a current flowing between an ignition plug disposed in a combustion chamber of an internal combustion engine and a ground, and a signal for extracting a specific signal from the current detected by the current detecting means. Extracting means, an output determining means for determining a combustion state based on a comparison between a current detected by the current detecting means and a predetermined value, and an output signal from the signal extracting means and the output determining means. And a signal modulating means for outputting a signal obtained by modulating and synthesizing the output signal of the internal combustion engine through the same signal line. 2. The current detection means, the signal extraction means,
The combustion state detection device for an internal combustion engine according to claim 1, wherein the output determination unit and the signal modulation unit are provided in an igniter that drives an ignition coil. 3. The signal modulating means inputs an ignition command signal and an output section signal from an electronic control unit for an internal combustion engine, and outputs a signal in synchronization with the ignition command signal or the output section signal. Claim 1 or Claim 2
A combustion state detection device for an internal combustion engine according to claim 1. 4. The signal modulating means has an output modulating circuit in each of the igniters for each cylinder of the internal combustion engine, and outputs each output signal from the output modulating circuit as one signal by wire connection. 4. An input to an electronic control unit for an engine.
A combustion state detection device for an internal combustion engine according to any one of the first to third aspects. 5. The signal modulation means has an output modulation circuit in each of the igniters for each cylinder of the internal combustion engine, and branches the output section signal from the electronic control unit for the internal combustion engine by wire. The combustion state detecting device for an internal combustion engine according to any one of claims 1 to 3, wherein the input is input to the internal combustion engine. 6. The signal modulating means outputs an output signal based on the occurrence of a misfire or a preignition determined by the output determining means by changing the output signal to a predetermined output value and a predetermined timing. The combustion state detecting device for an internal combustion engine according to any one of claims 1 to 5. 7. The apparatus according to claim 1, wherein the signal extracting unit extracts an AC signal including a knock frequency in the current detected by the current detecting unit. A combustion state detection device for an internal combustion engine of the present invention. 8. The apparatus according to claim 1, wherein the signal modulating means modulates a result of the determination by the output determining means at a predetermined timing in synchronization with the ignition command signal. A combustion state detection device for an internal combustion engine according to claim 1. 9. The apparatus according to claim 1, wherein the signal modulating unit permits knock determination based on a signal modulated when the engine is operating normally during normal combustion. A combustion state detection device for an internal combustion engine according to the above.