JP3619073B2 - Combustion state detection device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combustion state detection device that detects a combustion state of an internal combustion engine by detecting, as an ionic current, ions generated when an air-fuel mixture burns in a combustion chamber of the internal combustion engine.
[0002]
[Prior art]
FIG. 4 is a circuit diagram showing a conventional combustion state detection device for an internal combustion engine. FIG. 5 is a timing chart showing operation waveforms of respective portions when the ignition operation is good in the circuit of FIG. On the other hand, FIG. 6 is a timing chart showing operation waveforms of respective portions when the ignition operation is defective in the circuit of FIG.
[0003]
In FIG. 4, the primary coil 2a of the ignition coil 2 has one end connected to the battery 1 and the other end connected to a switching element 6 that energizes / cuts off the current of the primary coil 2a. The crank angle sensor 3 detects the crank angle of the internal combustion engine and outputs the signal.
[0004]
The ECU 5 calculates the ignition timing from the signal of the crank angle sensor and the signals of various other sensors 4 and outputs a signal for driving the switching element 6. Based on the drive signal of the ECU 5, the switching element 6 is driven, and the current of the primary coil 2a of the ignition coil 2 is energized / interrupted.
[0005]
When the current of the primary coil 2a is cut off, a voltage of several hundred volts is generated on the terminal side connected to the switching element 6 of the primary coil 2a. This voltage generates a high voltage of several tens of kilovolts in the secondary coil 2b of the ignition coil 2, generates a discharge in the ignition plugs 14a and 14b connected to the secondary coil 2b, and the mixture in the combustion chamber of the internal combustion engine. To burn.
[0006]
In addition, the voltage of several hundred volts generated in the primary coil 2 a causes a current to flow through the path of the rectifying element 7 → the current limiting element 8 → the capacitor 13 → the rectifying element 12 to charge the capacitor 13. The voltage limiting element 11 limits the charging voltage of the capacitor 13.
[0007]
The voltage charged in the capacitor 13 is applied to the spark plug 14b via the current limiting element 10 and the rectifying element 9, and further to the spark plug 14a via the secondary coil 2b to flow an ionic current.
[0008]
In order to prevent a high voltage of several tens of kV generated at the time of ignition from being applied to the anode side of the rectifier element, a rectifier element having a peak reverse voltage higher than the generated voltage of the ignition coil is used as the rectifier element 9. Yes.
[0009]
The ionic current described above is converted into a voltage value by the current-voltage conversion circuit 15, further converted into a combustion state signal indicating the combustion state by the ion current signal processing circuit 16, and the combustion state signal is output to the ECU 5. The ECU 5 determines the combustion state based on the combustion state signal and reflects it in the ignition timing control and fuel injection control.
[0010]
In FIG. 4, the number of rectifying elements 9 is described as one, but actually, a plurality of rectifying elements having the same properties are connected in series so as to have a predetermined breakdown voltage.
[0011]
[Problems to be solved by the invention]
In a conventional combustion state detection device for an internal combustion engine having such a configuration, a voltage of about 30 kV is generally applied to the secondary coil 2b of the ignition coil 2 at the time of ignition, for example, when a large voltage is applied at the time of engine start. (V2 in FIG. 5). The place to be applied is a connection portion between the secondary coil 2 b and the rectifying element 9. Further, when the ignition operation is defective, that is, misfire occurs, the maximum voltage output from the secondary coil 2b is applied, which reaches 40 to 50 kV (V2 in FIG. 6).
[0012]
The rectifying element 9 needs to use an element with a very high peak reverse voltage for the purpose of preventing these high voltages. An element having a very high peak reverse voltage is expensive and has a large size. Therefore, downsizing is not easy and the cost is increased. Furthermore, when the rectifying element 9 is configured to be connected in series, it is necessary to connect a large number, and the circuit layout is not easy.
[0013]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a combustion state detection device for an internal combustion engine that can reduce the size and cost of the rectifying element.
[0014]
[Means for Solving the Problems]
In the combustion state detection apparatus for an internal combustion engine according to the present invention, a discharge is generated in an ignition plug disposed in the combustion chamber by a secondary voltage generated in the secondary coil of the ignition coil of the internal combustion engine, and the air-fuel mixture in the combustion chamber is discharged. Ions generated in the combustion chamber during combustion of an internal combustion engine by burning and charging a capacitor with a primary voltage generated in the primary coil of the ignition coil to generate a bias voltage and applying the bias voltage to the ignition plug via a rectifying element In the combustion state detection device for an internal combustion engine that detects current flowing from the capacitor to the ignition plug as an ionic current, the rectifying element is a rectifying element that breaks down when a voltage of a predetermined value or more is applied to the secondary coil side, and further the rectifying element There is a current path flowing a current to the ground from the secondary coil is provided when breakdown, the breakdown voltage of the rectifier element, the internal combustion engine A voltage higher than the required voltage.
[0015]
Furthermore, the breakdown voltage of the rectifying element is in the range of 30 kV to 40 kV, which is a voltage higher than the highest required voltage of the internal combustion engine.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a circuit configuration diagram showing a combustion state detection apparatus for an internal combustion engine according to the present invention. FIG. 2 is a timing chart showing operation waveforms of respective portions when the ignition operation is good in the circuit of FIG. On the other hand, FIG. 3 is a timing chart showing operation waveforms of respective portions when the ignition operation is defective in the circuit of FIG. Reference numerals 1 to 8 and 10 to 16 in FIG. 1 are the same as those in the conventional apparatus shown in FIG.
[0017]
That is, the primary coil 2a of the ignition coil 2 has one end connected to the battery 1 and the other end connected to the switching element 6 that energizes / cuts off the current of the primary coil 2a. The crank angle sensor 3 detects the crank angle of the internal combustion engine and outputs the signal.
[0018]
The ECU 5 calculates the ignition timing from the signal of the crank angle sensor and the signals of various other sensors 4 and outputs a signal for driving the switching element 6. Based on the drive signal of the ECU 5, the switching element 6 is driven, and the current of the primary coil 2a of the ignition coil 2 is energized / interrupted.
[0019]
When the current of the primary coil 2a is cut off, a voltage of several hundred volts is generated on the terminal side connected to the switching element 6 of the primary coil 2a. This voltage generates a high voltage of several tens of kilovolts in the secondary coil 2b of the ignition coil 2, generates a discharge in the ignition plugs 14a and 14b connected to the secondary coil 2b, and the mixture in the combustion chamber of the internal combustion engine. To burn.
[0020]
The voltage of several hundred volts generated in the primary coil 2a causes the current to flow through the path of the rectifying element 7 → the current limiting element 8 → the capacitor 13 → the rectifying element 12 to charge the capacitor 13. The voltage limiting element 11 limits the charging voltage of the capacitor 13.
[0021]
The voltage charged in the capacitor 13 is applied to the spark plug 14b via the current limiting element 10 and the rectifying element 19, and further to the spark plug 14a via the secondary coil 2b to flow an ionic current.
[0022]
The ionic current described above is converted into a voltage value by the current-voltage conversion circuit 15, further converted into a combustion state signal indicating the combustion state by the ion current signal processing circuit 16, and the combustion state signal is output to the ECU 5. The ECU 5 determines the combustion state based on the combustion state signal and reflects it in the ignition timing control and fuel injection control.
[0023]
In the present embodiment, the rectifying element 19 uses an avalanche diode that breaks down when a voltage of a predetermined value or higher is applied. The predetermined voltage value at this time is a voltage value exceeding the maximum required voltage of the internal combustion engine. When the internal combustion engine is normally ignited, the voltage applied to the rectifying element 19 is lower than the breakdown voltage, so that no current flows through the rectifying element 19 to the anode side.
[0024]
When the generated voltage of the ignition coil becomes higher than the maximum required voltage of the internal combustion engine in an abnormal state and exceeds the breakdown voltage of the rectifying element 19, the rectifying element 19 breaks down due to the avalanche effect, and is indicated by an arrow Ia in FIG. As described above, the current flows through the current limiting element 10 → the voltage limiting element 11 → the rectifying element 12 to the ground. This path constitutes a current path that releases current when the rectifying element 19 breaks down. The magnitude of the current Ia is as shown in FIG. At this time, the rectifying element 19 is not destroyed by the avalanche effect.
[0025]
Thus, since the current Ia flows to the ground when the breakdown voltage of the rectifying element 19 is exceeded, the voltage at the connection portion between the secondary coil 2b and the rectifying element 19 does not become larger (V2 in FIG. 3). ).
[0026]
Generally, for example, an avalanche diode that breaks down when a voltage higher than a predetermined value as used in the present embodiment is applied is smaller and less expensive than a rectifying element having a high peak reverse voltage that has been conventionally used. . And while the rectifying element having a high peak reverse voltage used in the past breaks down when a voltage exceeding the breakdown voltage is applied, the rectifying element 19 of the present embodiment does not break down.
[0027]
In FIG. 1, the number of rectifying elements 19 is described as one, but actually, a plurality of rectifying elements having the same properties are connected in series so as to have a predetermined breakdown voltage. However, since the predetermined withstand voltage may be smaller than that in the prior art, the number of elements connected to the series can be reduced and the circuit layout can be reduced.
[0028]
In the combustion state detection device for an internal combustion engine having such a configuration, as described above, when a voltage exceeding a predetermined value (a value higher than the maximum required voltage of the internal combustion engine) is applied to the rectifying element that blocks high voltage, breakdown occurs. The rectifying element 19 is used, and a current path flowing at that time is configured. By adopting such a configuration, the rectifier element may breakdown at a voltage higher than the maximum required voltage of the internal combustion engine, so that the breakdown voltage can be set low, and the rectifier element 19 can be made small and inexpensive. Therefore, it is possible to reduce the size and cost of the rectifying element.
[0029]
In the present embodiment, an avalanche diode is used for the rectifying element 19, but the same effect can be obtained with a Zener diode.
[0030]
Embodiment 2. FIG.
In the circuit having the configuration of the first embodiment, the maximum value of the required voltage of the internal combustion engine that performs spark discharge with the spark plugs 14a and 14b is in the range of 30 kV to 40 kV. At this time, by setting the breakdown voltage of the rectifying element 19 to a voltage higher than the maximum required voltage of the internal combustion engine, the operation can be guaranteed when the internal combustion engine is normal.
[0031]
【The invention's effect】
In the combustion state detection apparatus for an internal combustion engine according to the present invention, a discharge is generated in an ignition plug disposed in the combustion chamber by a secondary voltage generated in the secondary coil of the ignition coil of the internal combustion engine, and the air-fuel mixture in the combustion chamber is discharged. Ions generated in the combustion chamber during combustion of an internal combustion engine by burning and charging a capacitor with a primary voltage generated in the primary coil of the ignition coil to generate a bias voltage and applying the bias voltage to the ignition plug via a rectifying element In the combustion state detection device for an internal combustion engine that detects current flowing from the capacitor to the ignition plug as an ionic current, the rectifying element is a rectifying element that breaks down when a voltage of a predetermined value or more is applied to the secondary coil side, and further the rectifying element There is a current path flowing a current to the ground from the secondary coil is provided when breakdown, the breakdown voltage of the rectifier element, the internal combustion engine A voltage higher than the required voltage. Therefore, the breakdown voltage can be set low, and the size of the rectifying element can be reduced and the cost can be reduced.
[0032]
Furthermore, the breakdown voltage of the rectifying element is in the range of 30 kV to 40 kV, which is a voltage higher than the highest required voltage of the internal combustion engine. Therefore, it is possible to reduce the size of the rectifying element and reduce the cost, and to guarantee the operation when the internal combustion engine is normal.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram showing a combustion state detection apparatus for an internal combustion engine according to the present invention.
FIG. 2 is a timing chart showing operation waveforms of respective portions when the ignition operation is good in the circuit of FIG. 1;
FIG. 3 is a timing chart showing operation waveforms of respective parts when the ignition operation is defective in the circuit of FIG. 1;
FIG. 4 is a circuit configuration diagram showing a conventional combustion state detection device for an internal combustion engine.
5 is a timing chart showing operation waveforms of respective portions when the ignition operation is good in the circuit of FIG.
6 is a timing chart showing operation waveforms of respective portions when the ignition operation is defective in the circuit of FIG. 4;
[Explanation of symbols]
2 ignition coil, 2a primary coil, 13 capacitor, 14a, 14b spark plug, 19 rectifier.

Claims (2)

A primary voltage generated in a primary coil of the ignition coil by generating a discharge in an ignition plug disposed in a combustion chamber by a secondary voltage generated in a secondary coil of an ignition coil of an internal combustion engine and burning an air-fuel mixture in the combustion chamber A capacitor is charged with a voltage to generate a bias voltage, and the bias voltage is applied to the spark plug via a rectifying element, and flows from the capacitor to the spark plug by ions generated in the combustion chamber during combustion of the internal combustion engine. In a combustion state detection device for an internal combustion engine that detects current as ion current,
The rectifier element is a rectification element that breakdown voltage of a predetermined value or more to the secondary coil side is applied, a current path flowing a current to ground from the secondary coil is provided when the further rectifying elements surrendered And
A combustion state detecting device for an internal combustion engine, wherein the breakdown voltage of the rectifying element is higher than a required voltage of the internal combustion engine. 2. The combustion state detecting device for an internal combustion engine according to claim 1, wherein the breakdown voltage of the rectifying element is in a range of 30 kV to 40 kV which is a voltage higher than a maximum required voltage of the internal combustion engine.

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