JP2002213336A - Ion current detecting device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect the combustion ion current regardless of a certain amount of a lag in the detecting timing. SOLUTION: An ignition plug 10 is mounted in a combustion chamber of a first cylinder, and an ignition plug 20 is mounted in a combustion chamber of a fourth cylinder. An oscillator 33 generates a rectangular wave signal of a frequency of about 30 kHz, whereby the AC voltage is applied between the counter electrodes of the ignition plugs 10, 20. The electric current flowing between the counter electrodes of each of the ignition plugs 10, 20 is detected by current detecting resistors 16, 26. A differential amplifying circuit 40 takes the detected current of the cylinder (for example, first cylinder) in a combustion stroke and the detected current of the cylinder (for example, forth cylinder) not in a combustion stroke, and an absolute value circuit 50 takes the output of the differential amplifying circuit 40 to provide its absolute value. An S/H circuit 60 samples and holds the output of the absolute value circuit 50 with a phase to maximize the AC voltage, and outputs the same as a current signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion current detecting device for an internal combustion engine.

[0002]

2. Description of the Related Art Since the combustion state constantly changes depending on the running state of a vehicle, abnormal combustion such as misfire is detected, and the ignition timing and air-fuel ratio of a spark plug are controlled based on the detection result to improve the combustion state. It has been done to keep. here,
For the purpose of accurately detecting the combustion state of an internal combustion engine, a combustion state detection device disclosed in Japanese Patent Application Laid-Open No. 9-25867 has been proposed. In the device disclosed in the publication, an AC voltage is applied between the opposed electrodes of the ignition plug immediately after ignition, a current flowing through the opposed electrode is detected at that time, and a capacitive current component generated corresponding to the AC voltage is removed from the current. Then, only the combustion ion current component is extracted.

That is, when an AC voltage is applied to the ignition plug, in the phase where the AC voltage is maximum, the combustion ion current is maximum, while the capacity current is 0. Therefore, if the current detection value at the phase at which the AC voltage is maximized is obtained, only the combustion ion current component not including the capacity current component can be extracted.

[0004]

However, in the apparatus disclosed in the above-mentioned publication, if the current detection value can be obtained at the timing when the capacity current becomes 0 as described above, the combustion ion current can be detected with high accuracy. If the detection timing is shifted, the detection accuracy of the combustion ion current is greatly reduced under the influence of the capacitance current component.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an internal combustion system capable of accurately detecting a combustion ion current irrespective of a slight difference in detection timing. An engine ion current detection device is provided.

[0006]

According to the first aspect of the present invention, an AC voltage is applied to a pair of opposed electrodes in a combustion chamber of a multi-cylinder internal combustion engine, and accordingly, a current is applied between the opposed electrodes at the same frequency as the AC voltage. Flows. Then, this current is detected by the current detecting means. At this time, the current flowing between the opposed electrodes includes a combustion ion current component and a capacitance current component. In such a case, the current detected by the current detecting means for the cylinder in the combustion stroke and the current detected by the current detecting means for the cylinder not in the combustion stroke are simultaneously taken in by the ion current detecting means, and the current value of the current value is calculated. The combustion ion current is detected from the difference. In this case, the detected current in the combustion process includes the combustion ion current and the capacity current, whereas the detection current in the other than the combustion process includes only the capacity current without including the combustion ion current. Therefore, if the difference between these detected currents is taken, only the combustion ion current can be extracted for the cylinder in the combustion stroke.
That is, the capacitance current component included in each of the detected currents is canceled by the difference between the detected currents. As a result, the combustion ion current can be accurately detected irrespective of a slight shift in the detection timing.

According to the first aspect of the present invention, as described in the second aspect, the ion current detecting means has a combustion cycle of 3 times.
It is preferable that a detection current between cylinders shifted by 60 ° CA is taken in, and a combustion ion current is detected based on a difference between the current values. In other words, of the two cylinders that take the difference between the detected currents,
Preferably, one cylinder is in the intake stroke while the other cylinder is in the combustion stroke. In this case, the positions of the pistons (cylinder volumes) in the cylinders of the two cylinders that simultaneously take in the detected currents match, which means that the capacity currents in the respective cylinders substantially match. Therefore, according to the second aspect, the combustion ion current can be detected more accurately.

According to the third aspect of the present invention, the ionic current detecting means includes a differential amplifier circuit for receiving a detected current of a cylinder in a combustion stroke and a detected current of a cylinder not in a combustion stroke,
An absolute value circuit which takes in the output of the differential amplifier circuit and converts it to an absolute value. In this case, even if the combustion cylinders are exchanged and the magnitude of the detected current in each cylinder is reversed, the output of the differential amplifier circuit is converted into an absolute value by the absolute value circuit, so the level of the current signal is determined based on the same reference. be able to.

According to the present invention, the difference between the detected current of the cylinder in the combustion stroke and the detected current of the cylinder in the non-combustion stroke is taken at least in the same phase each time the AC voltage does not become 0, and the difference is taken. Output as a current signal (signal processing means). In this case, the combustion ion current can be detected each time the capacity current component is at a substantially constant level each time. If the current is detected at a phase where the AC voltage has a peak value, the capacity current becomes 0, and the influence of the capacity current can be further suppressed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The present embodiment is embodied as a combustion state detection device for a vehicle-mounted internal combustion engine, and the configuration is shown in FIG. In the present embodiment, as an example, the present invention is embodied as a four-cylinder internal combustion engine having one cycle and two revolutions (720 ° CA). FIG. 1 shows a configuration of all four cylinders from the first cylinder to the fourth cylinder. Only the configuration related to the first cylinder and the configuration related to the fourth cylinder are extracted and shown. In other words, the combustion order of each cylinder is the first cylinder → the third cylinder → the fourth cylinder → the second cylinder, and the combination of the first cylinder and the fourth cylinder whose combustion cycle is shifted by 360 ° CA is illustrated. Of course, the second cylinder and the third cylinder exist as different combinations, but the description is omitted here.

First, the configuration relating to the first cylinder will be described. The ignition plug 10 is provided in the combustion chamber of the first cylinder, and the ignition plug 10 is provided with opposed electrodes 11 and 12. One counter electrode (center electrode) 11 is connected to the secondary winding 13b of the ignition coil 13, and the other counter electrode (ground electrode) 12 is grounded.

The primary winding 13a of the ignition coil 13 has one end connected to the vehicle battery 31 and the other end connected to the transistor 1
4 collectors. An ignition signal IGT is input from the ECU 32 to the base of the transistor 14 via the OR gate circuit 15, and the transistor 14 is turned on while the ignition signal IGT is at the H level. Also,
The OR gate circuit 15 is connected to an oscillator 33 constituting an AC voltage applying means.
A rectangular wave signal of about 0 kHz is input.

The secondary winding 13b of the ignition coil 13
Is connected to the above-described ignition plug 10 and a current detection resistor 16 for detecting a current flowing between the opposed electrodes 11 and 12.

According to the above configuration, when the ECU 32 outputs an H level signal as the ignition signal IGT, the transistor 14 is turned on via the OR gate circuit 15 and the ignition energy is stored in the ignition coil 13 by the battery 31. You. Thereafter, when the ignition signal IGT changes from the H level to the L level, a high voltage is applied between the opposing electrodes 11 and 12 of the ignition plug 10 by electromagnetic induction, and the opposing electrodes 11 and 12 are applied.
A spark discharge occurs between 12. This spark discharge ignites the fuel mixture introduced into the combustion chamber, and is used for combustion.

The configuration of the fourth cylinder is the same. The ignition plug 20 provided in the combustion chamber of the fourth cylinder, the ignition coil 23 including the primary winding 23a and the secondary winding 23b, the transistor 24, and the OR It includes a gate circuit 25 and the like. The secondary winding 23b of the ignition coil 23 has:
A current detection resistor 26 for detecting a current flowing between the opposed electrodes 21 and 22 of the ignition plug 20 is connected. Then, when the ignition signal IGT from the ECU 32 becomes H level, the transistor 24 is turned on and the ignition energy is stored in the ignition coil 23. After that, the ignition signal IGT
Changes from the H level to the L level, a spark discharge is generated between the opposed electrodes 21 and 22 of the ignition plug 20, and the fuel mixture introduced into the combustion chamber is ignited.

The current signals detected by the current detection resistors 16 and 26 are input to a differential amplifier circuit 40, respectively. The differential amplifier circuit 40 outputs a signal corresponding to the potential difference between the current signals input from the input terminals 41 and 42, that is, the signal corresponding to the potential difference between the current signal in the first cylinder and the current signal in the fourth cylinder, to an output terminal 43.
Output more.

The absolute value circuit 50 converts the signal input from the input terminal 51 (the output of the differential amplifier circuit 40) into an absolute value,
It is output from the output terminal 52. The output of the absolute value circuit 50 is input to an S / H circuit (sample and hold circuit) 60. The S / H circuit 60 uses the rectangular wave signal from the oscillator 33 as a trigger and samples and holds the output of the absolute value circuit 50 at a predetermined timing. In the present embodiment, the differential amplifier circuit 40 and the absolute value circuit 50 correspond to “ion current detecting means” described in claims, and
The / H circuit 60 corresponds to the “signal processing means”.

Next, the operation of the above configuration will be described with reference to the waveform diagrams of FIGS. FIG. 2 shows the forms of various signals during the ignition operation for the first and fourth cylinders. As shown in (a) and (b) of FIG.
The ignition signals IGT # 1 and IGT # 4 for the cylinder No. are output in accordance with the ignition timing in each cylinder. Also, as shown in (c), the oscillator 33 outputs a rectangular wave signal for a certain period of time after several msec from the timing (ignition timing) when IGT # 1 and IGT # 4 change from H level to L level (ignition timing).
Then, the OR gate circuits 15 and 25 are (d) and (e)
Are output to the bases of the transistors 14 and 24. The transistors 14, 24 are periodically turned on / off by the outputs of the OR gate circuits 15, 25. By this series of operations, an AC voltage is applied to both the ignition plugs 10 and 20 after the ignition of the combustion mixture.

FIG. 3 shows the detailed operation when the first cylinder is in the combustion stroke and the fourth cylinder is in the intake stroke (not in the combustion stroke). In FIG. 3, an AC voltage (b) is applied to the ignition plugs 10 and 20 of the first and fourth cylinders by outputting a rectangular wave signal (a) from the oscillator 33. Note that the AC voltage has a waveform that is duller than that of the rectangular wave signal and has a constant phase and a delay of about 90 ° with respect to the rectangular wave signal due to the stray capacitance in the mounted state of the transistors 14 and 24 and the ignition coils 13 and 23. That is, at the falling edge of the rectangular wave signal, the AC voltage has a positive peak value (maximum value), and at the rising edge of the rectangular wave signal, the AC voltage has a negative peak value (minimum value).

At this time, the current (c) flows through the ignition plug 10 of the first cylinder at the same frequency as the AC voltage. The current (c) is obtained by combining the ion current accompanying the combustion with the capacitance current flowing through the capacitance of the ignition plug 10 and the ignition coil 13. Therefore, in order to obtain the combustion ion current, it is necessary to subtract the capacity current from the current (c). The current (d) flows through the ignition plug 20 of the fourth cylinder. The current of (d) does not include the combustion ion current because the fourth cylinder is in the intake stroke, but is only the capacity current.

The currents (c) and (d) are input to a differential amplifier circuit 40, and the difference between the two currents is obtained by the operation of the differential amplifier circuit 40. Is output as The current (e) is obtained by removing the capacity current component from the current (the current (c)) flowing through the spark plug 10, that is, becomes the combustion ion current of the first cylinder.
The current of (e) is taken into the S / H circuit 60 via the absolute value circuit 50. Then, the current (e) is sampled and held at the falling phase of the rectangular wave signal,
The signal is converted into a signal indicated by a two-dot chain line in FIG. The output level of the S / H circuit 60 corresponds to the combustion ion current itself, and abnormal combustion such as misfire can be detected by determining the signal level.

The case where the first cylinder is in the combustion stroke and the case where
When the cylinder number is in the combustion stroke, the magnitude of the current flowing through the ignition plugs 10 and 20 of each cylinder is reversed, and the sign of the output of the differential amplifier circuit 40 is inverted. The data is taken into the S / H circuit 60 via the absolute value circuit 50. Therefore, even if the magnitude of the current flowing through the ignition plugs 10 and 20 of each cylinder is reversed, the current level of the combustion ions can be determined based on the same reference.

According to the embodiment described in detail above, the following effects can be obtained. Cylinders in the combustion stroke (for example, 1
The detection current in the cylinder No.) and the detection current in the cylinder not in the combustion stroke (for example, the fourth cylinder) are taken in at the same time, and the combustion ion current is detected based on the difference between the current values. Only the combustion ion current can be extracted for the cylinder. In this case, the combustion ion current can be accurately detected irrespective of a slight shift in the detection timing.

Particularly, in the present embodiment, the combustion cycle is 3
The detected currents of the cylinders shifted by 60 ° CA (the first and fourth cylinders or the second and third cylinders) are taken in, and the combustion ion current is detected based on the difference between the current values. In this case, the positions (cylinder volumes) of the pistons in the cylinders of the cylinders for which the current detection is performed at the same time coincide, which means that the capacity currents of the cylinders substantially coincide. Therefore, the combustion ion current can be detected more accurately.

The differential amplifier circuit 40 calculates the difference between the detected currents of the cylinders, and outputs the output of the differential amplifier circuit 40 to the absolute value circuit 5.
Since the absolute value is set to 0, the level of the current signal can be determined based on the same reference even when the combustion cylinders are switched and the magnitude of the detected current in each cylinder is reversed.

In the S / H circuit 60, the difference between the detected current of the cylinder in the combustion stroke and the detected current of the cylinder not in the combustion stroke is taken in the phase at which the AC voltage is maximized. The combustion ion current can be detected each time it becomes 0, and the effect of the capacity current can be further suppressed.

The present invention can be embodied in the following forms other than the above. In the above embodiment, the combustion cycle is 36
Although the detection currents of the cylinders shifted by 0 ° CA are taken in at the same time, the combination of the cylinders may be other than that. For example, a combination of the first cylinder and the second cylinder may be used. The point is that any configuration may be adopted as long as the detection current in the cylinder in the combustion stroke and the detection current in the cylinder in the non-combustion stroke are simultaneously taken.

In the above embodiment, the output of the differential amplifier circuit 40 is taken into the S / H circuit 60 via the absolute value circuit 50, but this is changed. For example, a peak hold circuit is used instead of the S / H circuit 60. Also in this case, the increase or decrease of the combustion ion current can be suitably detected.

As described above, the configuration in which the output of the differential amplifier circuit 40 is extracted through the absolute value circuit 50 is convenient for signal processing convenience, but the absolute value circuit 50 is not always a requirement. The output of the differential amplifier circuit 40 is directly used as the S / H circuit 60
Alternatively, the configuration may be adopted.

In the above embodiment, the phase at which the AC voltage becomes the maximum, that is, the falling phase of the rectangular wave signal from the oscillator 33 (the phase at the time of change from H level to L level)
Although the detection current is taken in each cylinder, this is changed. For example, a configuration may be adopted in which the detected current in each cylinder is taken in at the rising phase of the rectangular wave signal (the phase when the level changes from L level to H level). The point is that the same phase may be used each time the AC voltage does not become zero.

In the above embodiment, the oscillator constituting the AC voltage applying means is provided on the primary side of the ignition coil. However, it may be provided on the secondary side of the ignition coil. Also in this case, an AC voltage can be applied between the opposed electrodes of the ignition plug, and the combustion ion current can be suitably detected. As a pair of counter electrodes for detecting the combustion ion current, a dedicated ion probe having a counter electrode may be used instead of the counter electrode of the ignition plug.

[Brief description of the drawings]

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

FIG. 2 is a waveform chart for explaining the operation of the combustion state detecting device.

FIG. 3 is a waveform chart for explaining the operation of the combustion state detecting device.

[Explanation of symbols]

10, 20: spark plug, 11, 12, 21, 22, ... counter electrode, 13, 23: ignition coil, 33: oscillator, 40
... a differential amplifier circuit, 50 ... an absolute value circuit, 60 ... an S / H circuit.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G01M 15/00 F02P 17/00 EF (72) Inventor Hiroshi Yorita 14 Iwatani, Shimowasukamachi, Nishio-shi, Aichi Pref. Within the Japan Automobile Parts Research Institute (72) Inventor Noboru Toriyama 1-1-1 Showa-cho, Kariya-shi, Aichi F-term in Denso Co., Ltd. (Reference) 2G087 AA13 BB14 CC35 EE24 FF08 3G019 AA05 BB08 CD01 CD03 DB07 EA14 GA16 HA07 KA25 KD16 LA05 3G084 AA03 BA16 DA04 FA24 3G301 HA01 HA06 JA20 JA23 LC10 NA08 NB20 PC09Z PE09Z

Claims (4)

[Claims] In a multi-cylinder internal combustion engine, a pair of opposed electrodes provided for each combustion chamber of each cylinder, AC voltage applying means for applying an AC voltage between the opposed electrodes of each combustion chamber, and an opposing electrode of each combustion chamber. A combustion state detection device for an internal combustion engine, comprising: a current detection means for detecting a current flowing between the electrodes; wherein a current detected by the current detection means for a cylinder in a combustion stroke, and a current detection for a cylinder not in a combustion stroke. An ion current detection device for an internal combustion engine, comprising: ion current detection means for simultaneously taking in the current detected by the means and detecting a combustion ion current based on a difference between the current values. 2. The ion current detecting means receives a detected current between cylinders whose combustion cycle is shifted by 360 ° CA,
2. The ion current detection device for an internal combustion engine according to claim 1, wherein a combustion ion current is detected based on a difference between the current values. 3. A differential amplifier circuit for taking in a detected current of a cylinder in a combustion stroke and a detected current of a cylinder in a non-combustion stroke, and an absolute value obtained by taking an output of the differential amplifier circuit. 3. The ion current detection device for an internal combustion engine according to claim 1, further comprising: 4. A signal processing for taking in a difference between a detected current of a cylinder in a combustion stroke and a detected current of a cylinder not in a combustion stroke at least in the same phase each time the AC voltage does not become 0, and outputting the difference as a current signal. The ion current detection device for an internal combustion engine according to claim 1, further comprising a unit.