JPH10300634A - Burning state detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a burning state detector in which failure due to the charge movement of the insulator surface of a firing plug can be canceled. SOLUTION: Ion currents generated accompanied with voltage application to a firing plug 2 in a capacitor 23 are detected by a current detecting resistance 24. The firing plug 2 is provided with electrodes 18 and 19 for detecting an insulator potential for detecting the potential of an insulator, and the generation of a noise is judged from the change of the potential detected by the electrodes 18 and 19 by a judging circuit 37, and when the noise is generated, digital, switches 27 and 33 are opened. A burning state by a burning ion which is present in a burning chamber during burning is detected from ion currents detected by the current detecting resistance 24 in the post-stages of the digital switches 27 and 33.

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 detecting a combustion state of an internal combustion engine, and more particularly to a combustion state detecting device for detecting a combustion state by an ionic current.

[0002]

2. Description of the Related Art It has been studied to detect ions generated at the time of combustion by using a voltage applied to an electrode of a spark plug to grasp a combustion state. U.S. Pat. No. 4,491,110 discloses an example of detecting an ion current with a spark plug for knock detection of an internal combustion engine. this is,
A positive voltage is applied to the ignition plug, and the knock intensity is measured from the amplitude of the knock frequency component of the ion current flowing through the ignition plug. This technique will be described in more detail with reference to FIG.
02 and the housing 103 are insulated, and the housing 10
3, a voltage is applied between the electrodes 102 and 104 after the discharge for ignition is completed, and the current flowing at this time (ion current generated by combustion) is detected by the ion current detection circuit 105. The detection is performed using the ion current detection resistor 106.

When the ion current is measured by the ignition plug 100 as described above, electric charges remain on the surface of the ignition plug insulator 101 even after discharging for ignition as shown in FIG. For some reason, it may flow out at once. That is, when the ignition plug 100 is used,
Charges are parasitic on the surface of the plug insulator due to the high voltage applied at the time of ignition, and the charges move at random times to generate electric signals. This electric signal has the same direct current component as the combustion signal, contains the same frequency component as the knock, and it is difficult to remove the influence only by the electric circuit (105). This has caused a decrease in reliability.

[0004]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a combustion state detecting device which can solve the problem caused by the charge transfer on the insulator surface of the ignition plug.

[0005]

According to the first aspect of the present invention, there are provided (1) an insulator potential detecting means for detecting a potential of an insulator of a spark plug, and (2) a potential of the insulator detected by the insulator potential detecting means. Determining means for determining the occurrence of noise from the change.

[0006] By adopting such a configuration, an ion current generated when the voltage is applied to the ignition plug by the voltage applying means is detected by the ion current detecting means.
Further, the occurrence of noise is determined from the change in the potential detected by the insulator potential detecting means by the determining means. Then, based on the result of the determination by the determination means, the combustion state by the combustion ions present in the combustion chamber during combustion is detected from the ion current detected by the ion current detection means by the combustion state detection means.

[0007] In this manner, the combustion state can be detected in consideration of the noise due to the charge transfer on the insulator surface of the ignition plug. According to a second aspect of the present invention, there is provided (1) an insulator potential detecting electrode which is attached to the insulator of the spark plug and takes out the movement of the electric charge on the insulator surface as an electric signal;
AC noise detecting means for detecting the occurrence of AC noise due to the movement of electric charges on the insulator surface at the spark plug from the electric signal from the insulator potential detecting electrode; and (3) detecting the occurrence of AC noise by the AC noise detecting means. And a mask means for interrupting the input of the ionic current to the combustion state detection means during the noise generation period or prohibiting the combustion state detection processing by the combustion state detection means.

By employing such a configuration, the ion current detecting means detects the ion current generated when the voltage applying means applies the voltage to the ignition plug. The combustion state detection means detects a combustion state due to the combustion ions present in the combustion chamber during combustion based on the ion current detected by the ion current detection means. On the other hand, the insulator of the spark plug is equipped with an insulator potential detection electrode for extracting the movement of the electric charge on the insulator surface as an electric signal, and the AC noise detection means converts the electric signal from the insulator potential detection electrode into a spark plug. Of the AC noise caused by the movement of the electric charge on the surface of the insulator is detected. When the AC noise detection unit detects the occurrence of the AC noise, the mask unit shuts off the input of the ionic current to the combustion state detection unit during the noise generation period, or executes the combustion state detection processing by the combustion state detection unit. Ban.

Therefore, the movement of the electric charge on the surface of the insulator of the ignition plug tends to act as noise on the combustion state detection system. However, when the noise is generated, the processing of the combustion state detection system is interrupted and the accuracy is not affected by the noise. High measurement can be performed, and problems caused by charge transfer on the insulator surface of the ignition plug can be eliminated.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a combustion state detection device for an internal combustion engine (engine) according to the present embodiment.

Secondary winding 1 of transformer (ignition coil) 1
The b is provided with an ignition plug 2 for detecting an ion current, and the tip of the plug 2 projects from the combustion chamber Rc of the engine as shown in FIG. The combustion state detecting device detects the combustion state by igniting with the ion current detection spark plug 2 and applying a voltage to the plug 2 after the discharge for ignition to detect an ion current generated by combustion. Is what you do.

In the longitudinal sectional view of the ion current detecting spark plug 2 shown in FIG. 2, the plug 2 mainly includes a housing 3, an insulator 4, and electrodes (center electrode 5, ground electrode 6). Support of insulator 4 and plug 2
Is mounted on the engine, and the center electrode 5 and the housing 3 are insulated by the insulator 4.

The insulator 4 is made of alumina porcelain, and has a shaft hole 7 at the center thereof. A metal middle shaft 8 is inserted into an upper portion of the shaft hole 7 of the insulator 4. A terminal 9 is screwed and fixed to the head of the center shaft 8. The cylindrical housing 3 is made of a metal having heat resistance, corrosion resistance, and conductivity, and the insulator 4 is provided inside the housing 3 through a ring-shaped airtight packing 10 and a caulking ring 11.
Has been fixed. The housing 3 is provided with a screw portion 12, and the plug 2 is fixed to the cylinder head CH of the engine by the screw portion 12. More specifically, it is screwed into a spark plug mounting hole provided in the cylinder head CH.

The center electrode 5 has a cylindrical casing 13.
And a chip 14 provided at a lower end portion in the casing 13.
And a heat value adjusting core rod 15 provided in the casing 13.
It is composed of The casing 13 is made of a Ni alloy, the tip 14 is made of a conductive ceramic made of TiO and Al ₂ O ₃ , and the core rod 15 for adjusting heat value is made of Cu having good heat conductivity. The cylindrical casing 13 has a bulge 16 near its upper end. The tip 14 is stored in the casing 13 and slightly protrudes from its tip.

The core rod 15 is made of a powdery Cu
The chip 3 is filled so as to press the bottom surface of the chip 14, pressed, melted, then solidified and fixed. The center electrode 5 is inserted into the lower portion of the shaft hole 7 of the insulator 4, and the core rod 15 improves heat dissipation.

A conductive glass seal layer 17 is sealed in the shaft hole 7 of the insulator 4, and the conductive glass seal layer 17 is made of copper powder and low-melting glass. The center shaft 8 and the center electrode 5 are electrically connected by the seal layer 17, and both are fixed to the shaft hole 7 of the insulator 4 immovably.

A ground electrode 6 is fixed to the lower end surface of the housing 3 by welding. The ground electrode 6 is bent in a J-shape and is made of a metal having heat resistance, corrosion, and conductivity. The gap between the center electrode 5 and the ground electrode 6 becomes a spark discharge gap (spark gap). Then, when a high voltage is applied to the center electrode 5 at the time of ignition, spark discharge is started, the spark flies, and the mixture is ignited.

As described above, the spark plug 2 has the center electrode 5 and the housing 3 insulated by the insulator 4 and the housing 3 to which the ground electrode 6 is fixed.
Attached to.

Further, the spark plug 2 according to the present embodiment
A ring-shaped insulator potential detecting electrode 18 is formed on the outer surface of the insulator 4 at a position slightly above the upper end of the housing 3. The insulator potential detecting electrode 18 is made of Ag.
(Silver) thick film. A ring-shaped insulator potential detecting electrode 19 is formed on the outer surface of the lower end of the insulator 4. The insulator potential detecting electrode 19 is made of a thick film of Ag (silver). As described above, the electrodes (probes) 18 and 19 are mounted on the insulator surface of the ignition plug 2, and the potential on the insulator surface can be detected by the electrodes (insulator potential detecting means) 18 and 19. That is, the movement of the charge on the insulator surface can be extracted as an electric signal (AC noise signal) at the electrodes 18 and 19.

The configuration of the combustion state detecting device for an internal combustion engine shown in FIG. 1 using the ignition plug 2 having such a configuration will be described. In FIG. 1, a secondary winding 1b of the transformer 1 is connected to a terminal 9 (center electrode 5) of the ignition plug 2. A battery 20 is connected to one terminal of the primary winding 1a of the transformer 1, and a switching transistor 21 for turning on / off the application of voltage by the battery 20 is connected to the other terminal of the primary winding 1a. Collector is connected. An engine control ECU (engine control electronic control unit) mainly composed of a microcomputer is provided on the basis of the switching transistor 21.
22 are connected. The engine control ECU 22 includes:
An ignition signal IGT is generated based on the engine operating state at that time, and the ignition signal IGT is output to the base of the switching transistor 21.

In such a case, the mixture of fuel and air introduced into the combustion chamber of the engine is ignited by the ignition plug 2, the transformer 1, and the like. That is, the engine control ECU 22
Outputs an H level signal as an ignition signal IGT, the switching transistor 21 is turned on, and ignition energy is accumulated from the battery 20 in the transformer 1 serving as an ignition coil. After that, the ignition signal IGT
Changes from the H level to the L level, a high voltage is applied between the electrodes 5 and 6 of the ignition plug 2 by electromagnetic induction,
A spark discharge occurs between the six. The mixture is ignited by the spark discharge and provided for combustion.

On the other hand, a capacitor 23 and a current detecting resistor 24 are connected in series between the secondary winding 1b of the transformer 1 and the ground. The current detection resistor 24 serving as an ion current detection means is provided with
This is for detecting an ion current flowing therebetween. Further, a zener diode 25 is connected in parallel to the capacitor 23, and a diode 26 is connected in parallel to the current detection resistor 24. Then, as described above, a high voltage is generated in the secondary winding 1b of the transformer 1 by the ignition signal IGT from the engine control ECU 22.
After ignition, a voltage is applied to the center electrode 5 of the spark plug 2. Note that the capacitor 23 accumulates charges corresponding to the voltage of the Zener diode 25.

As described above, in this embodiment, the capacitor 2
Reference numeral 3 functions as voltage applying means for applying a voltage to the ignition plug 2. If ions generated by combustion are present in the cylinder, a current (ion current) flows between the electrodes 5 and 6 with application of a voltage by the capacitor 23 after ignition.
This current can be taken out from the connection point a between the capacitor 23 and the current detection resistor 24 as a voltage change by the current detection resistor 24 to the outside. The signal from point a includes a combustion signal flowing during combustion (or a misfire signal during misfire).
And a high-frequency vibration component generated at the time of knocking.

A connection point a between the capacitor 23 and the current detection resistor 24 is connected via a digital switch 27 to the integration circuit 2.
8 is connected. The engine control ECU 22 generates a reset signal SG1 after a lapse of a predetermined time after the output of the ignition signal IGT, and outputs the reset signal SG1 to the integration circuit 28. The integration circuit 28 performs integration processing until reset by the reset signal SG1. That is, the total (integral value Ip) of the combustion ion current corresponding to the total amount of combustion ions is measured for each combustion cycle.

The output (integral value Ip) of the integrating circuit 28 is input to the + input terminal of the comparator 29. The negative input terminal of the comparator 29 is connected to a slide contact of the variable resistor 30. The reference voltage determined by the position of the slide contact is adjusted in advance so that the voltage drop of the battery 31 corresponds to the lower limit Imin of the predetermined integral value Ip of the combustion ion current. That is, the comparator 29
Is for comparing the integral value Ip of the combustion ion current with the lower limit value Imin. If the integral value Ip is equal to or more than the lower limit value Imin, the output is set to the H level, and the integral value Ip is set to the lower limit value Imi.
If it is less than n, the output is set to L level. The output of the comparator 29 is the misfire indicator 32 and the engine control E
It is input to the CU 22. If the output of the comparator 29 is at the L level, the misfire indicator 32 is lit to indicate that the current engine is in a "misfire state". When the output of the comparator 29 is at the L level, the engine control ECU 22 determines that the current engine is in the “misfire state” and reflects the result in the engine control.

On the other hand, the capacitor 23 and the current detecting resistor 24
Is connected to a band-pass filter 34 via a digital switch 33, and the band-pass filter 3
4 is connected to an A / D converter 36 via a peak hold circuit 35. After generating the above-described reset signal SG1, the engine control ECU 22 outputs a reset signal SG2 to the peak hold circuit 35 after a predetermined period. The peak hold circuit 35 holds the peak value of the high-frequency component (for example, 6 to 8 kHz) of the ion current signal that has passed through the band-pass filter 34 until reset by the reset signal SG2. That is, the peak value ΔIp at which the amplitude of the output of the band-pass filter 34 becomes maximum is held. The A / D converter 36 converts the output (peak value ΔIp) of the peak hold circuit 35 into a digital signal and outputs the digital signal to the engine control ECU 22. The engine control ECU 22 compares the peak value ΔIp of the knocking frequency component with the knocking determination level ΔImax, and determines that the current engine is in the “knocking state” if the peak value ΔIp is equal to or greater than the knocking determination level ΔImax. .

As described above, in this embodiment, the members indicated by reference numerals 28 to 31 and 34 to 36, 22 constitute two systems (misfire detection system, knock detection system) of combustion state detecting means.

Although the reset signal SG2 is generated after a predetermined period after the generation of the reset signal SG1, the reset signal SG2 and the reset signal SG1 may be generated simultaneously.

The insulator potential detecting electrodes 18 and 19 provided on the surface of the insulator 4 of the ignition plug 2 are connected to a judging circuit 37. The judging circuit 37 receives the insulator potential signal V1 from the insulator potential detecting electrode 18, and An insulator potential signal V2 is input from the insulator potential detection electrode 19. A determination circuit 37 as a determination means and an AC noise detection means determines the occurrence of AC noise from the insulator potential signal, and
Control.

FIG. 3 shows a specific configuration diagram of the determination circuit 37. The insulator potential signal V1 from the insulator potential detection electrode 18
And an insulator potential signal V2 from the insulator potential detecting electrode 19 are added at point b through buffer circuits 38 and 39, input to a bandpass filter 41 via an operational amplifier 40 and the like, and furthermore, a half-wave from the bandpass filter 41. The signal is input to the rectifier circuit 42. That is, when the potential signal on the insulator surface of the ignition plug 2 is passed through the band-pass filter 41, FIG.
When a specific waveform is generated at the time of noise generation as shown in (c), a component of a specific frequency band (for example, 200 kHz) included in this signal appears as shown in FIG. The half-wave rectification circuit 42 performs half-wave rectification.

Further, the output signal of the half-wave rectifier circuit 42 shown in FIG. 3 passes through a low-pass filter 43, and its absolute amount is detected by the low-pass filter 43 as shown in FIG. Further, it is input to the + input terminal of the comparator 44. A variable resistor 45 is connected to a negative input terminal of the comparator 44.
Are connected. The reference voltage determined by the position of the slide contact is adjusted in advance so that the voltage drop of the battery 46 corresponds to a predetermined upper limit value Vmax of the absolute value of the insulator potential. That is, the comparator 4
Reference numeral 4 compares the absolute value V of the insulator potential with the upper limit value Vmax. If the absolute value V of the insulator potential is equal to or more than the upper limit value Vmax, the output is set to the H level, and the absolute value V of the insulator potential is less than the upper limit value Vmax. If so, the output is set to L level. In this way, the magnitudes of the components of the specific frequency band (the waveform peculiar to the occurrence of noise) included in the signal shown in FIG. 4D are compared by the comparator 44, and are shown in FIG. As described above, when the level exceeds a certain fixed level (threshold), this is determined as the occurrence of noise, and an H level signal is output.

The output of the comparator 44 shown in FIG. 3 becomes a drive signal for the digital switches 27 and 33 via the driver circuit 47. When the output is at the H level, noise affects the ion current as shown in FIG. After delaying the time τ, the contacts of the digital switches 27 and 33 are opened. That is, when an abnormality occurs in the insulator potential, a misfire detection system,
The signal line to the knock detection system is opened to interrupt the transmission of the abnormal signal included in the ion current signal, and the adverse effect due to the charge transfer on the insulator surface of the ignition plug 2 is eliminated. In this manner, the digital switches 27 and 33 are opened for a period T corresponding to the magnitude of noise after delaying the time τ from the change in the insulator potential of the ignition plug 2 to mask the ion current signal. The measurement by the ion current is interrupted only during the period T. In this way, the effects of noise are eliminated and a highly accurate combustion measurement can be maintained.

In this embodiment, the digital switches 27 and 33 constitute a mask means for cutting off the input of the ionic current to the combustion state detecting means at the subsequent stage due to the occurrence of AC noise.

The delay τ in FIG. 4F includes the delay due to the circuit such as the band-pass filter 41. Further, the open period T may be a constant value. Next, the operation of the combustion state detecting device configured as described above will be described with reference to the time charts of FIGS.

First, the overall outline will be described with reference to FIG. As shown in FIG. 4A, at time t1, the ignition signal I
GT rises to H level, and thereafter, at time t2, the ignition signal IGT falls to L level. At this time, capacitive discharge is observed by the electrostatic energy of the ignition plug 2, and subsequently, induction discharge by the electromagnetic energy stored in the transformer 1 is observed. Then, when the air-fuel mixture in the combustion chamber is ignited by the spark ignition of the spark plug 2, the in-cylinder pressure starts to increase.

Further, as shown in FIG.
Thereafter, the output of the current detection resistor 24 becomes an AC signal for noise and an AC signal of an ion current knock component, and the signals are output from the point a in FIG.

On the other hand, while the insulator potential changes as shown in FIG. 4C, the insulator potential signals V1 and V2 from the insulator potential detecting electrodes 18 and 19 are added at point b in FIG. After passing through the filter 41, only a predetermined AC component is extracted as shown in FIG. Then, this signal is half-wave rectified by the half-wave rectifier circuit 42 in FIG. 3 and passes through the low-pass filter 43 to obtain an envelope of a peak value as shown in FIG. This output value is compared with the upper limit value Vmax by the comparator 44. When the output value is higher than the upper limit value Vmax, the comparator 44 outputs an H level signal. The driver circuit 47 opens the contacts of the digital switches 27 and 33 when the signal from the comparator 44 is at the H level. That is, the digital switch 27,
The contact point 33 is opened, and the ion current by the current detection resistor 24 shown in FIG. 4 (g) is masked. As a result, the passing signal of the digital switches 27 and 33 is
(H) is obtained. The vibration component in the signal is
As shown in FIG. 4 (j), the AC signal corresponding to the noise is removed, and the AC signal includes only the ion current knock component.

On the other hand, the passing signal of the digital switch 27 in FIG. 1 is integrated by an integrating circuit 28, and further, the integrated value Ip and the lower limit value I
When the integral value Ip is less than the lower limit value Imin, the output thereof is set to the L level, the misfire indicator 32 is lit as the current engine is in the "misfire state", and the engine control ECU 22 This is reflected in engine control.

The signal passed through the digital switch 33 is passed through a band pass filter 34 to the peak hold circuit 3.
5, the peak value ΔIp at which the amplitude becomes maximum is held, and the A / D converter 36 converts the peak value ΔIp into a digital signal. The engine control ECU 22 compares the peak value ΔIp of the knocking frequency component with the knocking determination level ΔImax. If the peak value ΔIp is equal to or greater than the knocking determination level ΔImax, it is determined that the current engine is in the “knocking state”. Reflect on control.

Next, as described above, the digital switch 27,
The procedure for detecting the combustion state of the engine from the passing signal 33 will be described with reference to the time chart of FIG. Time t11 in the figure indicates the ignition timing, and time t12 indicates the end time of the induction discharge after the ignition.

FIG. 5 (c) shows the change over time in the in-cylinder pressure of the combustion chamber during one combustion cycle. In the figure, three cases of "normal combustion", "knocking" and "misfire" are shown. 5 shows a change state of the internal pressure. In all combustions, the in-cylinder pressure increases after ignition and tends to attenuate after reaching the maximum value.However, when compared with normal combustion, when knocking, pressure oscillation occurs in the combustion chamber due to pressure waves in the combustion chamber. A vibration component appears. In the case of a misfire, no combustion ions are generated, so that a waveform similar to that of motoring (for example, a waveform at the time of cranking driving) is obtained.

FIG. 5D shows the change over time in the combustion ion current during the combustion cycle, which appears as the output of the digital switches 27 and 33. The ion current waveform during normal combustion is a waveform corresponding to the in-cylinder pressure. When a misfire occurs, no ion current is output because no combustion ions are generated. When knocking occurs, knocking oscillation also appears in the ion current waveform.

FIG. 5E shows an integrating circuit 2 for detecting misfire.
8 shows the output. In the case of normal combustion, since the integrated value of the combustion ions is output, a value corresponding to the amount of combustion is obtained. If the integral value Ip of the ion current waveform is equal to or less than the lower limit value Imin, the engine control ECU 22 determines that a misfire has occurred. By performing the misfire detection using the output of the integration circuit 28 in this manner, the influence of the variation in combustion is small and the misfire detection accuracy is improved as compared with the method of detecting the ion current value at a predetermined timing. As shown in FIG. 5E, by performing the masking process, it is possible to prevent erroneous detection of misfire.

FIG. 5F shows an output of the band-pass filter 34 for detecting knocking. Only the vibration component of the ion current waveform when knocking occurs is extracted. In the case of normal combustion, there is no vibration and there is no output. If the amplitude value ΔIp of the ion current waveform is equal to or larger than the vibration amplitude ΔImax, the occurrence of knocking is determined by the engine control ECU 22.

As described above, this embodiment has the following features. (A) Insulator potential detecting electrodes 18 and 19 for detecting the potential of the insulator 4 of the ignition plug 2 are provided, and the occurrence of noise is determined based on a change in the potential detected by the insulator potential detecting electrodes 18 and 19. The circuit 37 is provided and the capacitor 23 is provided.
The current detection resistor 24 detects an ionic current generated by the application of a voltage to the ignition plug 2 by the current detection resistor 24, and the determination circuit 37 determines the occurrence of noise from the change in the potential detected by the insulator potential detection electrodes 18 and 19. And a combustion state detecting means (28-31, 34-36, 22) based on the determination result.
In the above, the combustion state due to the combustion ions present in the combustion chamber during combustion is detected from the ion current detected by the current detection resistor 24. Therefore, it is possible to detect the combustion state in consideration of the noise due to the charge transfer on the insulator surface of the ignition plug 2. (B) More specifically, when the determination circuit 37 detects the occurrence of AC noise, a digital switch that cuts off the input of the ion current to the combustion state detection system (28 to 31, 34 to 36, 22) during the noise generation period 27, 33,
When the movement of the electric charge on the insulator surface of the ignition plug 2 attempts to act as noise for the two combustion state detection systems,
Interrupt the processing of the combustion state detection system so that it is not affected by noise. Therefore, highly accurate measurement can be performed, and problems caused by charge transfer on the insulator surface of the ignition plug 2 can be eliminated.

In the example described so far, when the occurrence of AC noise is detected, the input of the ionic current to the combustion state detection system (28-31, 34-36, 22) during the noise occurrence period is cut off. However, the detection process of the combustion state by the combustion state detection system may be prohibited. Specifically, for example, as shown in FIG. 6, the digital switch 27 is arranged downstream of the integration circuit 28, and the digital switch 33 is arranged downstream of the bandpass filter 34. Alternatively, a noise generation detection signal from the determination circuit 37 in FIG. 1 is sent to the comparator 29 and the engine control ECU 22 to force the output of the comparator 29 to the H level and to output the signal to the engine control ECU 2.
In step 2, even when the peak value ΔIp of the knocking frequency component is input from the A / D converter 36, the comparison with the knocking determination level ΔImax is not performed. In short, at the time of noise detection, the processing in the misfire detection system and the knock determination system is masked, and the combustion state is detected by the ionic current during periods other than the noise generation period.

Further, in the example described so far, a case has been described in which there are two combustion state detection systems, a misfire detection system and a knock detection system. However, only one of the misfire detection system and the knock detection system is provided. The present invention may be embodied in a combustion state detecting device.

In this case, it is preferable that the insulator potential detecting electrode 19 provided in the combustion chamber Rc in FIG. 2 is used for misfire detection, and the insulator potential detecting electrode 18 provided outside the combustion chamber Rc is used for knock detection.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a combustion state detection device according to an embodiment.

FIG. 2 is a longitudinal sectional view of the ignition plug for detecting an ion current in the embodiment.

FIG. 3 is a configuration diagram of a determination circuit.

FIG. 4 is a time chart showing an outline of the operation of the combustion state detecting device.

FIG. 5 is a time chart for explaining a procedure for detecting a combustion state.

FIG. 6 is a configuration diagram of a combustion state detection device in another example.

FIG. 7 is a configuration diagram of a conventional combustion state detection device.

[Explanation of symbols]

2 ... Ignition plug for ion current detection, 3 ... Housing, 4
... Insulator, 5 ... Center electrode, 6 ... Ground electrode, 18 ... Insulator potential detection electrode, 19 ... Insulator potential detection electrode, 22 ... Engine control ECU, 23 ... Capacitor, 24 ... Current detection resistor, 27 ... Digital Switch, 28 integration circuit, 2
9 Comparator, 30 Variable resistor, 31 Battery, 32 Misfire indicator, 33 Digital switch, 34
... bandpass filter, 35 ... peak hold circuit, 3
6. A / D converter, 37 ... Judgment circuit.

Continued on the front page (72) Inventor, Atsushi Yoshinaga, 14 Iwatani, Shimowasukamachi, Nishio, Aichi Prefecture Inside the Japan Automobile Parts Research Institute (72) Inventor, Hiroshi Yorida 14 Iwatani, Shimotsukamachi, Nishio, Aichi, Japan (72) Inventor Koji Sakakibara 1-1-1, Showa-cho, Kariya-shi, Aichi Pref.

Claims (2)

[Claims] 1. An ignition plug attached to an internal combustion engine, voltage applying means for applying a voltage to the ignition plug, and an ion current for detecting an ion current generated when the voltage applying means applies a voltage to the ignition plug. Detecting means; insulator potential detecting means for detecting the potential of the insulator of the spark plug; determining means for determining the occurrence of noise from a change in the potential detected by the insulator potential detecting means; determination results of the determining means Combustion state detection means for detecting a combustion state due to combustion ions present in the combustion chamber during combustion from the ion current detected by the ion current detection means based on the above. 2. An ignition plug attached to an internal combustion engine, voltage applying means for applying a voltage to the ignition plug, and an ion current for detecting an ion current generated by applying a voltage to the ignition plug by the voltage applying means. Detection means; combustion state detection means for detecting a combustion state due to combustion ions present in the combustion chamber during combustion based on the ion current detected by the ion current detection means; and an insulator mounted on the insulator of the spark plug, An insulator potential detecting electrode for extracting the movement of the electric charge on the surface as an electric signal; and detecting the occurrence of AC noise caused by the movement of the electric charge on the insulator surface at the ignition plug from the electric signal from the insulator potential detecting electrode. AC noise detection means, and when the AC noise detection means detects the occurrence of AC noise, A combustion state detection device, comprising: mask means for interrupting the input of ion current to the combustion state detection means, or inhibiting the combustion state detection processing by the combustion state detection means.