JP2003184723A - Ignition device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition device for an internal combustion engine improving the detection accuracy of air-fuel mixture combustion state by suppressing the occurrence of electric re-discharge after the completion of spark electric discharge in detecting an air fuel mixture combustion state based on voltage between electrodes of a spark plug after the completion of spark electric discharge. <P>SOLUTION: In a third internal combustion engine ignition system 5, back electromotive force as electromotive force in reverse polarity of ignition voltage is generated in a secondary winding 27 by controlling a second transistor 79 to reenergize a primary winding 5 during spark electric discharge, and voltage subtracting voltage equivalent to the back electromotive force from residual induced voltage is generated at both ends of the secondary winding 27. Consequently, the occurrence of electric re-discharge due to the rise of voltage between electrodes at the spark plug 13 after the completion of spark electric discharge can be prevented. The misdetermination of combustion state due to the occurrence of electric re-discharge can be prevented and the detection accuracy of air fuel mixture combustion state based on voltage between electrodes of the spark plug after spark electric discharge can be improved. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generates a spark discharge between electrodes of a spark plug by applying a voltage for ignition generated in an ignition coil, and a voltage between electrodes of the spark plug after the end of the spark discharge. The present invention relates to an internal combustion engine ignition device having a function of detecting a combustion state of the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, it has been known that in an internal combustion engine used for an automobile engine or the like, when the air-fuel mixture burns due to spark discharge by a spark plug, ions are generated along with the combustion. Therefore, it is possible to determine that the air-fuel mixture has normally burned when the ions are present in the combustion chamber after the spark discharge is completed, and it is possible to determine that the misfire is caused when the ions are not present.

On the other hand, the ignition coil generates an ignition voltage at both ends of the secondary winding by the energy accumulated by energizing the primary winding, and applies this ignition voltage to the ignition plug to cause the ignition plug to operate. Sparks are being generated. The energy accumulated in the ignition coil is gradually consumed by the continuation of the spark discharge, but since the spark discharge naturally ends before it is completely consumed, the ignition coil remains in the ignition coil even after the spark discharge ends. Energy remains. In addition, the residual induction voltage generated in the ignition coil due to this residual energy is
It has the same polarity as the ignition voltage and is applied to the ignition plug in the same manner as the ignition voltage.

When ions are present in the combustion chamber when the residual induction voltage is generated, a current (ion current) flows between the electrodes of the spark plug through the ions, and the ion current causes residual energy in the ignition coil. Is consumed, the inter-electrode voltage of the spark plug rapidly drops. If no ions are present in the combustion chamber when the residual induction voltage is generated, no current flows between the electrodes of the spark plug, and the residual energy of the ignition coil is not consumed. Fall to.

From this, it is possible to judge the misfire by judging the combustion state of the air-fuel mixture based on the rate of decrease in the voltage between the electrodes with the passage of time after the end of the spark discharge. In other words, if the inter-electrode voltage of the spark plug drops rapidly after the end of the spark discharge, it can be determined that the combustion is normal, and if the inter-electrode voltage of the spark plug drops after the end of the spark discharge, Can be considered a misfire.

FIG. 8 is a time chart showing the state of each part (ignition command signal, inter-electrode voltage of the spark plug, and secondary current flowing in the secondary winding) in the conventional ignition device for an internal combustion engine. In FIG. 8, time t3 to time t5
The period from time t13 to time t15 represents the waveform at the time of normal combustion, while the period from time t13 to time t15 shows the waveform at time t13.
It can be seen that the inter-electrode voltage of the spark plug thereafter gradually decreases as compared with that after time t13. The ignition command signal is a signal for driving and controlling the ignition switching means for energizing / interrupting the primary winding. When the ignition command signal is at a high level, the primary winding is energized, and at a low level. Power to the primary winding is cut off.

In addition, when the inter-electrode voltage value within a certain period after the spark discharge is integrated, the inter-electrode voltage integrated value becomes a small value during normal combustion, and the inter-electrode voltage integrated value becomes a large value during misfire. Therefore, it is also possible to determine the combustion state of normal combustion or misfire based on the inter-electrode voltage integrated value.

[0008]

However, in the case of detecting a misfire based on the voltage across the electrodes of the spark plug after the spark discharge has ended, if the spark discharge ends early and the residual energy of the ignition coil becomes large, the residual energy remains. The energy causes a discharge to occur again between the electrodes of the spark plug, and there is a possibility that the combustion may be erroneously determined to be normal combustion despite the fact that misfire has occurred.

That is, the spark discharge may be interrupted by the turbulent flow of the air-fuel mixture (swirl flow or tumble flow), and the turbulent flow speed of the air-fuel mixture is high especially at high rotation speed, so that the spark discharge is relatively early timing. Therefore, the residual energy of the ignition coil becomes large. And
When a discharge occurs again due to this residual energy, the voltage between the electrodes of the spark plug may not be maintained and may drop.
When re-discharge occurs due to the residual energy of the ignition coil in this manner, the inter-electrode voltage of the spark plug after the end of the spark discharge is rapidly reduced regardless of the combustion state of the air-fuel mixture. It may not be possible to detect the condition accurately.

In FIG. 8, from time t23 to time 2
The period up to 5 represents the waveform at the time of re-discharge (breakdown), and the inter-electrode voltage of the spark plug after the end of the spark discharge (time t23), despite the occurrence of misfire,
It can be seen that the time of the same misfire falls more quickly than that after time t3. As a result, when the combustion state is detected based on the inter-electrode voltage after the spark discharge of the spark plug, if the re-discharge may occur even at the time of misfire, the inter-electrode voltage of the spark plug will be rapidly reduced. Therefore, the normal discharge is erroneously determined.

Particularly during high-speed operation, since the turbulent velocity of the air-fuel mixture in the combustion chamber is high, the spark discharge is interrupted at a relatively early timing, and the residual energy of the ignition coil becomes large, so that re-discharge occurs. It tends to occur, leading to a decrease in the misfire detection rate based on the voltage between the electrodes of the spark plug.

Therefore, the present invention has been made in view of these problems, and in detecting the combustion state of the air-fuel mixture based on the inter-electrode voltage of the spark plug after the end of the spark discharge, the present invention after the end of the spark discharge is detected. An object of the present invention is to provide an internal combustion engine ignition device that suppresses the occurrence of re-discharge and improves the detection accuracy of the combustion state of an air-fuel mixture.

[0013]

In order to achieve the above object, the present invention according to claim 1 has a primary winding and a secondary winding, and cuts off a primary current flowing through the primary winding. An ignition coil that generates an ignition voltage in the secondary winding, an ignition switching unit that turns on and off the primary current flowing in the primary winding of the ignition coil, and an ignition coil that is connected in series to the secondary winding. A spark plug that generates a spark discharge between its electrodes when a discharge current generated by a voltage flows,
Based on the inter-electrode voltage detection means for detecting the inter-electrode voltage generated between the electrodes of the spark plug and the inter-electrode voltage after the end of the spark discharge among the inter-electrode voltage detected by the inter-electrode voltage detection means, the internal combustion engine An ignition device for an internal combustion engine, comprising: a combustion state determining means for determining a combustion state of a reverse winding, which is an electromotive force having a polarity opposite to that of the ignition voltage in the secondary winding during spark discharge of the spark plug. It is characterized by comprising re-discharge preventing means for preventing re-discharge of the spark plug due to increase in inter-electrode voltage at the end of spark discharge by generating electromotive force.

That is, during spark discharge of the spark plug, a counter electromotive force, which is an electromotive force having a polarity opposite to that of the ignition voltage, is generated in the secondary winding, and the secondary winding is generated by the residual energy remaining in the ignition coil. A voltage obtained by subtracting the voltage corresponding to this counter electromotive force from the residual induction voltage induced in the secondary winding is generated at both ends of the secondary winding. As a result, the increase in the voltage across the secondary winding at the end of the spark discharge is suppressed, and the increase in the inter-electrode voltage in the spark plug is suppressed. In this way, it is possible to prevent the re-discharge between the electrodes of the spark plug due to the increase in the voltage between the electrodes at the end of the spark discharge.

Therefore, according to the ignition device for an internal combustion engine of the present invention (Claim 1), it is possible to suppress re-discharge from occurring in the spark plug at the end of the spark discharge, and despite the fact that a misfire has actually occurred, Since it is possible to prevent erroneous determination of normal combustion, it is possible to improve the accuracy of detecting the combustion state of the air-fuel mixture based on the voltage between the electrodes of the spark plug after the end of the spark discharge.

The end of the spark discharge is not limited to the natural end in which the spark discharge naturally ends when the energy accumulated in the ignition coil falls below the amount required to continue the spark discharge, but the ignition voltage is forcibly terminated. It also includes forced termination to shut off the spark discharge by lowering. Then, when the spark discharge is forcibly terminated, re-discharge easily occurs because the residual energy of the ignition coil increases, but by applying the present invention, the occurrence of re-discharge can be suppressed, and the combustion state The detection accuracy can be improved.

Further, the re-discharge preventing means in the above-mentioned ignition device for an internal combustion engine is not limited to the structure which is always driven in each combustion cycle after the operation of the internal combustion engine is started. In particular, the re-discharge prevention means is preferably driven at least when the engine speed of the internal combustion engine is high. The reason for this is that at high engine speeds, the turbulent velocity of the air-fuel mixture is high, so spark discharge tends to be interrupted at a relatively early timing, and residual energy in the ignition coil tends to become large, causing re-discharge. This is because it easily occurs.

Here, in the ignition device for an internal combustion engine according to the above-mentioned (claim 1), for example, the re-discharge preventing means generates a counter electromotive force in the secondary winding, so that the polarity is opposite to the ignition voltage. It is preferable that the external voltage applying unit externally applies an external voltage to the secondary winding. Then, after the spark discharge of the spark plug is started, the external voltage applying means,
By applying the external voltage to the secondary winding, the rise of the inter-electrode voltage at the end of the spark discharge is suppressed and the occurrence of re-discharge is prevented.

Further, in the ignition device for an internal combustion engine according to the above-mentioned (claim 1), for example, as described in claim 2, the re-discharge preventing means re-energizes the primary winding,
It may be provided as a re-energizing unit that generates a counter electromotive force in the secondary winding and forcibly interrupts the spark discharge of the spark plug.

That is, when the re-energizing means re-energizes the primary winding, an induced voltage (back electromotive force) having a polarity opposite to that of the ignition voltage is generated in the secondary winding. Further, the residual induced voltage is generated in the secondary winding with the same polarity as the ignition voltage, so by generating the counter electromotive force by re-energizing the primary winding,
A voltage obtained by subtracting the voltage due to the back electromotive force from the residual induced voltage is generated at both ends of the secondary winding. As a result, the spark discharge of the spark plug can be forcibly interrupted, and re-discharge due to the increase in the inter-electrode voltage at the end of the spark discharge (in this case, the forced end) can be prevented.

Therefore, according to the ignition device for an internal combustion engine of the present invention (claim 2), it is possible to suppress the occurrence of re-discharge at the end of the spark discharge, and it is based on the inter-electrode voltage of the spark plug after the end of the spark discharge. It is possible to improve the detection accuracy of the combustion state of the air-fuel mixture. The re-energizing means provided in the ignition device for an internal combustion engine according to (claim 2) drives the ignition switching means to re-energize the primary winding as described in claim 3, for example. It is preferable to include a first re-energization control means for controlling.

That is, by providing the first re-energization control means, the ignition switching means is also used for energization control of the primary winding for preventing re-discharge. And
During spark discharge, the ignition switching means is drive-controlled to re-energize the primary winding, and an induced voltage of the opposite polarity to the ignition voltage is generated in the secondary winding, thereby causing spark discharge of the spark plug. By forcibly shutting off, the degree of increase in the voltage between the electrodes at the end of the spark discharge is suppressed.

Therefore, according to the ignition device for an internal combustion engine of the present invention (Claim 3), by reenergizing the primary winding by the ignition switching means, the inter-electrode voltage at the end of the spark discharge is increased. Re-discharge can be prevented. As a result,
It is possible to improve the detection accuracy of the combustion state of the air-fuel mixture based on the voltage between the electrodes of the spark plug after the end of the spark discharge.

If one ignition switching means is used for both the purpose of generating an ignition voltage and preventing re-discharge, the energization time becomes long, and the temperature of the ignition switching means rises with the extension of the energization time. May rise. Then, when the ignition switching means is configured to be able to operate normally even in a high temperature environment, the temperature rise is not a problem, for example, when the ignition switching means is configured by a semiconductor element such as a transistor. It is possible that normal operation becomes impossible due to temperature rise. Further, if the energization time is excessively long, the temperature rise width becomes large, and in some cases, the high temperature may damage the ignition switching means.

Therefore, the re-energizing means provided in the ignition device for an internal combustion engine according to (claim 2) is connected in parallel to the ignition switching means as described in claim 4, for example, and the primary winding is connected. It is preferable to include a second switching unit that conducts and cuts off the primary current flowing through the second winding unit, and a second re-energization control unit that drives and controls the second switching unit to re-energize the primary winding.

That is, in addition to the ignition switching means, a second switching means is provided, and during the spark discharge, the second switching means is used to re-energize the primary winding to force the spark discharge of the spark plug. And shut off
This suppresses the re-discharge after the spark discharge is completed.

Thus, when re-energizing the primary winding, it is possible to prevent the energizing time of the ignition switching means from being lengthened and to suppress the temperature rise of the ignition switching means. As a result, the normal operation of the ignition switching means can be maintained and the ignition switching means can be prevented from being damaged.

Therefore, according to the ignition device for an internal combustion engine of the present invention (claim 4), it is possible to prevent the ignition switching means from being damaged by high temperature, and to continue the normal operation of the ignition switching means. It will be possible. Also, the second
By re-energizing the primary winding by the switching means, re-discharge after completion of spark discharge can be prevented, and detection accuracy of combustion state can be improved.

Further, in the ignition device for an internal combustion engine according to the above (claim 1), for example, as described in claim 5, the re-discharge preventing means short-circuits both ends of the primary winding, so that the secondary It may be provided as primary winding short-circuiting means for generating a counter electromotive force having a polarity opposite to that of the ignition voltage in the winding.

That is, when both ends of the primary winding are short-circuited during the spark discharge, the residual energy of the ignition coil causes a current to flow in a closed circuit composed of the primary winding short-circuiting means and the primary winding. Accordingly, an induced voltage (back electromotive force) having a polarity opposite to that of the residual induced voltage is generated in the secondary winding.
As a result, a voltage obtained by subtracting the back electromotive force from the residual induced voltage is generated at both ends of the secondary winding, so that it is possible to suppress an increase in the voltage value generated at both ends of the secondary winding, and spark discharge of the spark plug. Can be forcibly cut off, and the degree of increase in the inter-electrode voltage at the end of the spark discharge can be suppressed.

Therefore, according to the ignition device for an internal combustion engine of the present invention (Claim 5), it is possible to suppress the occurrence of re-discharge after the end of the spark discharge, and it is based on the voltage between the electrodes of the spark plug after the end of the spark discharge. It is possible to improve the detection accuracy of the combustion state of the air-fuel mixture. The primary winding short-circuit means provided in the internal combustion engine ignition device described above (claim 5) is, for example,
As described in claim 6, short-circuit switching means connected in parallel to the primary winding, and primary winding short-circuit control means for driving and controlling the short-circuit switching means to short-circuit both ends of the primary winding. You should be prepared.

As described above, by providing the short-circuit switching means and the primary winding short-circuit control means, both ends of the primary winding can be short-circuited during the spark discharge, and the spark discharge of the spark plug is forcibly cut off. At the same time, it is possible to suppress the degree of increase in the inter-electrode voltage after the end of the spark discharge. In addition,
The short-circuit switching means can be composed of, for example, a semiconductor element such as a transistor, a thyristor, a triac, or an FET.

Therefore, according to the ignition device for an internal combustion engine of the present invention (Claim 6), short-circuiting switching means short-circuits both ends of the primary winding to prevent re-discharge after the completion of spark discharge. . As a result, it is possible to improve the detection accuracy of the combustion state of the air-fuel mixture based on the voltage between the electrodes of the spark plug after the end of the spark discharge.

By the way, when the internal combustion engine is operated in an operating state in which the engine speed is high, the turbulent flow of the air-fuel mixture in the combustion chamber becomes fast, so that the probability of spark discharge being interrupted at an early stage becomes high. The engine rotation speed is the number of engine rotations per unit time.

For this reason, the higher the operating state of the internal combustion engine, the higher the probability that the residual energy will increase, and the re-discharge after the spark discharge is likely to occur. When the back electromotive force generation timing is constant regardless of the operating state of the internal combustion engine, if the interval from the start of spark discharge (ignition timing) to the back electromotive force generation timing is set to be long during high rotation operation, the back electromotive force is set. The spark discharge is interrupted before the ignition is generated, the residual energy existing in the ignition coil tends to increase, and the probability of occurrence of re-discharge increases.

Therefore, in the above-described ignition device for an internal combustion engine (any one of claims 1 to 6), as described in claim 7, the re-discharge preventing means of the internal combustion engine includes at least the engine rotation speed. Based on the operating state reading means for reading the operating state from the outside and the operating state read by the operating state reading means, the counter electromotive force generation timing for generating the counter electromotive force in the secondary winding is set, and at least the engine rotation speed is set. A counter electromotive force generation timing setting unit that sets the counter electromotive force generation timing earlier as the speed becomes higher may be provided.

That is, by setting the counter electromotive force generation timing earlier as the engine speed becomes higher, the spark discharge ends due to the turbulent flow of the air-fuel mixture,
Since the time from the start of spark discharge to the generation of back electromotive force can be shortened, back electromotive force is generated in the secondary winding before the spark discharge is interrupted, and the occurrence of re-discharge can be suppressed.

Therefore, according to the ignition device for an internal combustion engine of the present invention (claim 7), re-discharge can be suppressed even when the operating state of the internal combustion engine is high rotation.
It is possible to prevent an erroneous determination of the combustion state and improve the detection accuracy of the combustion state of the air-fuel mixture.

During high-speed operation, since the turbulent velocity of the air-fuel mixture is high and the fuel is agitated well, the air-fuel mixture is excellent in ignitability and even when the duration of spark discharge is short. It is possible to burn the air-fuel mixture. However, if you set an excessively short time as the duration of spark discharge,
There is a risk that the mixture will not be ignited and a misfire will result, making it impossible to operate the internal combustion engine normally.Therefore, the back electromotive force is generated at a spark discharge duration of 0.05 [mse
c] It is better to set it so that it is above. Further, the counter electromotive force generation timing setting means may set the counter electromotive force generation timing earlier at least as the engine rotation speed becomes higher, and set the counter electromotive force generation timing longer as the engine rotation speed becomes lower. In addition to this, under operating conditions that require a large amount of spark energy, such as during idle operation or immediately after the internal combustion engine is started and before the internal combustion engine is sufficiently warmed up, the spark discharge of the spark plug ends spontaneously. As described above, a configuration in which the back electromotive force generation time is not calculated may be incorporated. In addition to the engine rotation speed, the engine load may be used as the operating state.

The counter electromotive force generation timing setting means provided in the internal combustion engine ignition device of the above (claim 7) is, for example, as described in claim 8, the counter electromotive force generation according to the engine rotation speed. The back electromotive force generation timing setting information may be used to set the back electromotive force generation timing based on the engine speed.

In this way, the back electromotive force generation timing setting means sets the back electromotive force generation timing using the back electromotive force generation timing setting information, so that the back electromotive force generation timing is set according to the engine speed. can do. Note that the counter electromotive force generation timing setting information is, for example, an appropriate counter electromotive force according to the engine rotation speed based on the measurement result of measuring the natural end timing of spark discharge for each engine rotation speed using an actual internal combustion engine. It is preferable that the power generation timing can be set.
The back electromotive force generation timing setting information is provided in the internal combustion engine ignition device as a setting map, a setting table, or a setting calculation formula in which the back electromotive force generation timing corresponding to the engine speed is determined.

Therefore, according to the ignition device for an internal combustion engine of the present invention (claim 8), it is possible to set an appropriate counter electromotive force generation timing in accordance with the engine rotation speed of the internal combustion engine, and the operating state is high rotation. Even when it becomes, re-discharge can be suppressed,
It is possible to improve the detection accuracy of the combustion state of the air-fuel mixture.

By the way, the inter-electrode voltage of the spark plug can be detected, for example, by directly connecting the voltage detecting means, which is directly connected to the object to be measured and detects the voltage, to each electrode of the spark plug. However, in the case of directly detecting the inter-electrode voltage, it is necessary to use an expensive voltage detection means in which the inputtable voltage range is set to a wide range such that the voltage for ignition (about 40 [kV]) is included as the inputtable voltage range. However, the increase in cost becomes a problem.

Therefore, in the ignition device for an internal combustion engine according to any one of claims 1 to 8, as described in claim 9, the inter-electrode voltage detecting means includes the spark plug and the secondary winding. The capacitive coupling means for capacitively coupling between the ignition voltage generating end and the energizing path connecting the ignition voltage generating end, and the voltage dividing means serially connected to the capacitive coupling means, and the capacitive coupling means and the capacitive coupling means connected in series. The pressure means is connected in parallel to the ignition plug, and the divided voltage divided by the capacitive coupling means and the voltage dividing means may be detected as the inter-electrode voltage.

In the ignition device for an internal combustion engine thus configured, the divided voltage obtained by dividing the voltage between the electrodes of the spark plug by using the capacitive coupling means and the voltage dividing means connected in series is the electrode of the spark plug. The voltage value is proportional to the voltage.
Since the electrical characteristics (electrical resistance value, etc.) of each of the capacitive coupling means and the voltage dividing means are determined by the electric element to be used, the ratio (division ratio) of the voltage across each of the capacitive coupling means and the voltage dividing means. May be appropriately set according to the performance and design of the ignition coil and the ignition plug.

Further, since the capacitive coupling means and the voltage dividing means connected in series are connected in parallel to the spark plug, the voltage across the whole of the capacitive coupling means and the voltage dividing means connected in series is the spark plug. Becomes equal to the voltage between the electrodes.
Therefore, the inter-electrode voltage detecting means can detect the divided voltage divided by the capacitive coupling means and the voltage dividing means as the inter-electrode voltage of the spark plug.

Since the divided voltage is lower than the inter-electrode voltage of the spark plug, the inter-electrode voltage detecting means for detecting the inter-electrode voltage based on the divided voltage is the inter-electrode voltage of the spark plug. As compared with the case where the voltage is directly detected, it can be constituted by a low-priced voltage detection means in which the inputtable voltage range is set narrow.

Therefore, according to the ignition device for an internal combustion engine of the present invention (Claim 9), when detecting the inter-electrode voltage of the spark plug, it can be configured as a low-cost inter-electrode voltage detection means, and therefore, the manufacturing It is possible to suppress an increase in cost and improve the reliability of the device itself.

By the way, when a voltage is applied between the electrodes of the spark plug to generate an ionic current, compared with the case where the voltage is applied so that the center electrode has a negative polarity and the ground electrode has a positive polarity, It is known that a larger ion current can be generated when a voltage is applied so that the center electrode has a positive polarity and the ground electrode has a negative polarity. This is because when cations having a large volume are supplied with electrons, more electrons can be exchanged and moved by receiving the electrons supplied from the ground electrode having a larger surface area than the central electrode.

Therefore, in the ignition device for an internal combustion engine described above (any one of claims 1 to 9),
As described in (4) above, the center electrode of the spark plug may be connected to the ignition voltage generating end of the secondary winding so as to have a positive polarity. As a result, a larger ion current can be generated between the electrodes of the spark plug after the spark discharge, so that in the case of normal combustion, the inter-electrode voltage after the end of the spark discharge decreases more quickly. Therefore, the difference in the change rate of the inter-electrode voltage between the normal combustion and the misfire becomes clearer.

Therefore, according to the ignition device for an internal combustion engine of the present invention (Claim 10), the difference between the normal combustion and the misfire related to the inter-electrode voltage becomes clear, so that the normal combustion and the misfire can be easily determined. Therefore, the accuracy of the combustion state determination can be improved. The polarity of the ignition voltage of the secondary winding when the ignition voltage is generated can be set by adjusting the winding directions of the primary winding and the secondary winding of the ignition coil.

Here, in the spark plug, since the opposing electrodes function as a capacitance element and accumulate charges, a potential difference is generated between the electrodes. Therefore, after the spark discharge is completed, the secondary winding from the spark plug is terminated. If the charge moves (leaks) toward the ignition voltage generating end, the rate of decrease in the inter-electrode voltage will increase. In other words, when such charge transfer (leakage) occurs, the inter-electrode voltage after the end of the spark discharge decreases in a short time, so that it is considered that the combustion is normal despite the actual misfire. There is a risk of misjudgment.

Therefore, in the ignition device for an internal combustion engine described above (any one of claims 1 to 10),
As described in item 1, the secondary winding is connected in series on the energizing path connecting the ignition voltage generating end and the spark plug, allows the discharge current to flow, and allows the discharge current to flow in the opposite direction. It is preferable to provide a backflow prevention means for blocking energization.

That is, since the backflow preventing means is provided so as to prevent the current generated in the secondary winding from being energized when the primary winding is energized, the secondary winding from the spark plug after the spark discharge is completed. The movement (leakage) of electric charges toward the line is prevented, and erroneous determination of the combustion state due to electric charge leakage can be prevented.

Further, since the backflow preventing means allows the current (discharge current) generated in the secondary winding to be energized when the energization to the primary winding is interrupted, the backflow prevention means from the secondary winding when the ignition voltage is generated. Allows current to flow through the spark plug. That is, since the backflow prevention means does not prevent the energization when the ignition voltage is generated, the spark discharge cannot be generated due to the provision of the backflow prevention means.

Therefore, according to the ignition device for an internal combustion engine of the present invention (Claim 11), it is possible to prevent the leakage of charges from the spark plug to the secondary winding, and in spite of the fact that the engine is misfiring. Therefore, it is possible to prevent erroneous determination of normal combustion due to electric charge leakage, and it is possible to improve the determination accuracy of the combustion state.

[0057]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 is an electric circuit diagram showing a configuration of an internal combustion engine ignition device 1 as an embodiment. The internal combustion engine ignition device 1 is configured to generate a spark discharge between electrodes of an ignition plug 13. In addition, the inter-electrode voltage of the spark plug 13 can be detected.

In this embodiment, one cylinder is described, but the present invention can be applied to an internal combustion engine having a plurality of cylinders, and the basic structure of the internal combustion engine ignition device for each cylinder is the same. . As shown in FIG. 1, the ignition device 1 for an internal combustion engine according to the present embodiment has a constant voltage (for example, a voltage of 12
[V]) power supply device 11 (hereinafter referred to as battery 11)
(Also referred to as), a spark plug 13 provided in a cylinder of an internal combustion engine with a center electrode 21 and a ground electrode 23, and a primary winding 25 and a secondary winding 27 to generate ignition voltage. Np connected in series with coil 15 and primary winding 25
Ignition transistor 1 composed of n-type power transistor
7 and an electronic control unit 19 (hereinafter referred to as E, which outputs an ignition command signal 20 for driving and controlling the ignition transistor 17).
Also referred to as CU19).

Further, in the ignition device 1 for an internal combustion engine, the anode is the secondary winding 27 (the ignition voltage generating end 3 of the secondary winding 27).
5), a cathode 31 is connected to the center electrode 21 of the spark plug 13, and a backflow prevention diode 31 and a voltage detection circuit 51 for detecting the interelectrode voltage of the spark plug 13.

Of these, the ignition transistor 17
Is a switching element composed of a semiconductor element that performs a switching operation based on an ignition command signal 20 from the ECU 19 in order to energize / shut off the primary winding 25 of the ignition coil 15. The ignition device provided in the internal combustion engine of this embodiment is a full-transistor ignition device.

One end of the primary winding 25 is connected to the positive electrode of the power supply device 11, and the other end is connected to the ignition transistor 17.
Of the secondary winding 27, one end of the secondary winding 27 is connected to the ground of the same potential as the negative electrode of the power supply device 11, and the other end (that is, the ignition voltage generating end 35) of the backflow prevention diode 31. It is connected to the anode.

Further, the backflow prevention diode 31 has an anode connected to the secondary winding 27 and a cathode connected to the center electrode 21 of the ignition plug 13, so that the secondary winding 2
The current from 7 to the center electrode 21 of the spark plug 13 is allowed to flow, and the current from the center electrode 21 of the spark plug 13 to the secondary winding 27 is blocked.

Further, in the spark plug 13, the ground electrode 23 forming a spark discharge gap 24 facing the center electrode 21 to generate spark discharge is grounded to the ground having the same potential as the negative electrode of the power supply device 11. The base of the ignition transistor 17 is connected to the output terminal of the ignition command signal 20 of the ECU 19, and the emitter is grounded to the ground having the same potential as the negative electrode of the power supply device 11.

When the ignition command signal 20 output from the ECU 19 is at a low level (generally the ground potential), the base current does not flow and the ignition transistor 17 is not supplied.
Is turned off (cut-off state), and the ignition transistor 1
No current (primary current 26) flows through the primary winding 25 due to 7. Further, when the ignition command signal 20 output from the ECU 19 is at a high level (generally, the supply voltage 5 [V] from the constant voltage power source), the base current flows and the ignition transistor 17 is turned on (energized state). Next to
A current (primary current 26) flows through the primary winding 25 by the ignition transistor 17. When the primary winding 25 is energized, magnetic flux energy is accumulated in the ignition coil 15.

Therefore, when the ignition command signal 20 is at a high level and the primary current 26 is flowing through the primary winding 25 and the ignition command signal 20 is at a low level, the ignition transistor 17 is turned off and the primary transistor is turned off. The energization of the primary current 26 to the winding 25 is cut off (stopped). Then, the magnetic flux density in the ignition coil 15 suddenly changes, and an ignition voltage is generated in the secondary winding 27, which is applied to the spark plug 13 to cause a spark between the electrodes 21-23 of the spark plug 13. Electric discharge occurs.

The ignition coil 15 cuts off (stops) the energization of the primary winding 25 so that the center electrode 21 of the ignition plug 13 in the secondary winding 27 has a positive polarity higher than the ground potential. The ignition plug 13 is configured to generate a voltage, and when the ignition voltage is applied, the spark plug 13 generates a spark discharge between the electrodes 21-23. The secondary current 28 (discharge current 28) flowing in the secondary winding 27 due to the spark discharge is supplied from the secondary winding 27 by the backflow prevention diode 3
1, the center electrode 21 of the spark plug 13 and the ground electrode 23 in this order, and then flows in the direction of returning to the secondary winding 27 via the ground.

Then, as the spark discharge in the spark plug 13 continues, the energy accumulated in the ignition coil 15 is consumed, and when this energy falls below the amount required to continue the spark discharge, the spark in the spark plug 13 is reduced. The discharge ends naturally. Even when the spark discharge in the spark plug 13 naturally ends, residual energy remains in the ignition coil 15, and this residual energy causes
At both ends of the secondary winding 27, a residual induced voltage of approximately several kV is generated, which is not sufficient for the generation of spark discharge.

Since this residual induced voltage is generated in a state where the positive and negative polarities of the ends of the secondary winding have the same polarity as the ignition voltage, when the residual induced voltage is generated in the secondary winding, A voltage is applied to the spark plug 13 with the center electrode 21 having a positive polarity and the ground electrode 23 having a negative polarity.

Next, the voltage detection circuit 51 for detecting the inter-electrode voltage of the spark plug 13 will be described. First, the voltage detection circuit 51, as shown in FIG. 1, is a conductor that is capacitively coupled between the ignition voltage generating end 35 of the secondary winding 27 and the energization path that connects the center electrode 21 of the spark plug 13. 53,
Capacitor 6 connected between conductor 53 and ground
5 and a resistor 63 connected in parallel with the capacitor 65.

The conductor 53 is formed from an electrode plate arranged at a predetermined interval with respect to the energization path connecting the ignition voltage generating end 35 of the secondary winding 27 and the center electrode 21 of the ignition plug 13. And constitutes a capacitance element together with the energizing path. It should be noted that the electrostatic capacitance element formed by the conductor 53 and the energization path accumulates electric charge according to the inter-electrode voltage of the spark plug 13.

Further, the conductor 53 and the capacitor 65
Constitutes a voltage dividing circuit for dividing the voltage between the electrodes of the spark plug 13, and the voltage across the capacitor 65 is the voltage between the electrodes of the spark plug 13 and the conductor 53 and the capacitor 6.
The divided voltage is determined based on the voltage division ratio of 5. That is, the voltage across the capacitor 65 has a voltage value proportional to the inter-electrode voltage of the spark plug 13.

Further, the connection point between the conductor 53 and the capacitor 65 is connected to the input terminal of the discrimination circuit 67,
The divided voltage by the conductor 53 and the capacitor 65 is input to the determination circuit 67. Although not shown, the determination circuit 67 includes a filter circuit unit that extracts a predetermined component used for determining the combustion state from the inter-electrode voltage signal that changes according to the detected inter-electrode voltage and outputs it as a filtered voltage signal. Prepare The post-filter voltage signal is output from the filter circuit unit to each of a comparison circuit unit and a peak hold circuit unit, which will be described later. Further, the discrimination circuit 67 includes a post-filter voltage output from the filter circuit unit. A peak for obtaining the adjusted peak voltage signal by dividing the peak voltage signal output from the peak hold circuit section according to a predetermined voltage dividing ratio and the beak hold circuit section that holds the peak value of the voltage signal as the peak voltage signal. A voltage signal adjusting circuit section and a switch circuit section for switching control of the ON / OFF state of the peak hold circuit section based on a read command signal 72 from the ECU 19 are provided.

Further, the discrimination circuit 67 compares the adjusted peak voltage signal output from the peak voltage signal adjusting circuit section with the filtered voltage signal from the filter circuit section to adjust the filtered voltage signal. A comparison circuit unit that outputs the determination result signal 68 when the voltage is larger than the rear peak voltage signal is provided. Needless to say, each circuit unit included in the determination circuit 67 may have a known configuration.

The determination result signal 68 output from the determination circuit 67 having such a configuration is input to the ECU 19. Then, the ECU 19 detects the output time of the determination result signal 68, determines whether the output time of the determination result signal 68 is longer than a preset combustion state determination time, and outputs the determination result signal 68. It is determined that the combustion is normal when the output time is shorter than the combustion state determination time. vice versa,
When it is determined that the output time of the determination result signal 68 is longer than the combustion state determination time, it is determined that there is a misfire.

As described above, in the internal combustion engine ignition device 1, the ECU 19 determines normal combustion and misfire based on the output time of the determination result signal 68 output from the determination circuit 67. This corresponds to the determination of normal combustion and misfire by detecting the degree of decrease in the inter-electrode voltage with the lapse of time after the spark discharge at the spark plug 13 is completed. That is, the internal combustion engine ignition device 1 determines the combustion state of the internal combustion engine based on the inter-electrode voltage after the spark discharge of the spark plug 13 is completed.

When the high-level read command signal 72 is input from the ECU 19, the discriminating circuit 67 turns on the heat-hold circuit section to perform the combustion state discriminating process, and the low-level read command signal 72 is output. When input, the peak hold circuit unit is turned off, the held peak value of the filtered voltage signal is reset, and the combustion state determination process is not performed.

Next, the ECU 19 of the internal combustion engine ignition device 1
The combustion state determination process executed in step 3 will be described with reference to the flowchart shown in FIG. In addition, the state of each part (the ignition command signal 20, the inter-electrode voltage of the spark plug 13, and the secondary current 28 flowing through the secondary winding 27) in the internal combustion engine ignition device 1 when executing the combustion state determination process is represented. The time chart is shown in FIG.

The ECU 19 is for comprehensively controlling the spark discharge generation timing (ignition timing) of the internal combustion engine, the fuel injection amount, the idling speed, and the like, in addition to the combustion state determination processing described below. In addition, the operation state detection process to detect the operation state of each part of the engine, such as the intake air amount (intake pipe pressure), rotation speed (engine rotation speed), throttle opening, cooling water temperature, intake air temperature, etc., is separately executed. is doing.

In the combustion state determination process shown in FIG. 3, for example, the internal combustion engine detects intake, compression, combustion and exhaust based on a signal from a crank angle sensor that detects the rotation angle (crank angle) of the internal combustion engine. It is executed once in one combustion cycle to be performed, and further, processing for ignition control is also executed.

When the internal combustion engine is started and the combustion state determination process is started, first, in S310 (S represents a step), the operation of the internal combustion engine detected by the operation state detection process separately executed. The state is read, and at S320, based on the read operating state, the spark discharge occurrence time ts
(So-called ignition timing) and spark discharge duration Tt are set.

In the process of S310, information including the engine speed of the internal combustion engine and the engine load calculated using the throttle opening, the intake pipe negative pressure (intake air amount), etc. is read as the operating state. Perform processing. And S
In the process of 320, the spark discharge occurrence timing ts is obtained by obtaining a control reference value using a map, a table, or a calculation formula having the engine speed and the engine load as parameters, and correcting this based on the cooling water temperature, the intake air temperature, and the like. It is set by a conventionally known procedure such as "Yes".

Further, the spark discharge duration Tt is set based on the operating state including the engine speed and the engine load by using a map, a table or a calculation formula prepared in advance. It should be noted that the map, table, or calculation formula used to set the spark discharge duration Tt is set so that the spark discharge duration Tt increases as the operating condition (during low rotation speed) becomes slower because the turbulent flow of the air-fuel mixture is less likely to blow out the spark discharge. The spark discharge duration Tt is set to a shorter time as the turbulent flow of the air-fuel mixture becomes faster and the spark discharge is more likely to be blown out (in high rotation operation). There is.

Then, the setting map for setting the spark discharge duration Tt based on the engine speed and the engine load is constructed as shown in FIG. 10, for example. In addition, this setting map can set an appropriate spark discharge duration according to the engine speed based on the measurement result of measuring the natural end time of spark discharge for each engine speed using an actual internal combustion engine. Is configured.

By thus determining the spark discharge duration Tt, the counter electromotive force generation timing for generating the counter electromotive force in the secondary winding 27 is set. In the present embodiment, the optimum spark discharge duration Tt is set using a map, a table or a calculation formula with the engine speed and engine load as parameters. However, the spark discharge duration Tt is set based only on the engine speed. It is also possible to use a map, a table, or a calculation formula in which can be set.

Next, in S330, the spark discharge occurrence time t is set based on the spark discharge occurrence time ts set in S320.
For s, the energization start timing of the primary winding 25 that is earlier by a preset primary winding energization time is obtained, and at the time when the energization start timing is reached (time t1 shown in FIG. 2), the ignition command signal 20
Is changed from low level to high level (time t1 shown in FIG. 2).

When the ignition command signal 20 is switched from the low level to the high level by the process of S330, the ignition transistor 17 is turned on and the ignition coil 1
A primary current 26 flows through the primary winding 25 of the coil 5. Further, during the primary winding energization time until the spark discharge occurrence time ts, the energy accumulated in the ignition coil 15 by energizing the primary winding 25 can burn the air-fuel mixture under all operating conditions of the internal combustion engine. So that the maximum spark energy is
It is set in advance.

Then, in the following S340, it is judged based on the crank angle detection signal from the crank angle sensor whether or not the spark discharge occurrence timing ts set in S320 is reached.
When a negative determination is made, the same step is repeatedly executed to wait until the spark discharge occurrence timing ts.
When it is determined in S340 that the spark discharge occurrence time ts has been reached (time t2 shown in FIG. 2), the process proceeds to S350.

Then, in S350, the ignition command signal 20
Is inverted from the high level to the low level, and as a result, the ignition transistor 17 is turned off, the primary current 26 is cut off, the magnetic flux density of the ignition coil 15 is rapidly changed, and the ignition voltage is applied to the secondary winding 27. Then, a spark discharge is generated between the electrodes 21-23 of the spark plug 13.

From the time chart shown in FIG. 2, at the time t2 when the ignition command signal 20 is inverted from the high level to the low level, the inter-electrode voltage of the spark plug 13 becomes a large voltage value and the secondary current 28 becomes You can see that it is flowing. In the next S360, it is determined whether or not the spark discharge duration Tt set in S320 has elapsed, starting from the time point when the affirmative determination is made in S340. If the negative determination is made, the same step is repeatedly executed. By doing so, it waits until the spark discharge duration Tt elapses. And
When it is determined in S360 that the spark discharge duration time Tt has been reached (time t3 shown in FIG. 2), the process proceeds to S370.

Then, in S370, the ignition command signal 20
Is processed from low level to high level,
When the ignition command signal 20 switches from the low level to the high level, the ignition transistor 17 is turned on, and the primary current 26 flows through the primary winding 25 of the ignition coil 15,
A counter electromotive force, which is an electromotive force having a polarity opposite to that of the ignition voltage, is generated in the secondary winding 27. As a result, the spark discharge generated at the spark plug 13 is forcibly cut off. Further, from the time chart shown in FIG. 2, it can be seen that the secondary discharge is stopped by the spark discharge ending (cutting off) at time t3. The counter electromotive force has a polarity opposite to that of the residual induction voltage, and the voltage across the secondary winding 27 has a value obtained by subtracting the voltage value of the counter electromotive force from the residual induction voltage.

Since the voltage across the secondary winding 27 at this time has the same polarity as the ignition voltage, the reverse current prevention diode 3
It is applied between the electrodes of the spark plug 13 without being limited by 1. As a result, the electrodes of the spark plug 13 (the center electrode 21 and the ground electrode 23) function as electrostatic capacitance elements, so that charges are accumulated in each electrode and a potential difference is generated between the electrodes.

As described above, when the ions are present in the combustion chamber when the electric charge is accumulated in the electrodes of the spark plug 13, the electric charges are moved through the ions to cause a current to flow between the electrodes of the spark plug 13. Flows, and the inter-electrode voltage after the spark discharge of the spark plug 13 ends rapidly with the movement of the electric charge. Further, when there are no ions in the combustion chamber, the movement of charges via the ions does not occur, so that the inter-electrode voltage after the spark discharge of the spark plug 13 is gradually decreased. Even when there are no ions, a slight amount of electric charge leaks, and therefore the inter-electrode voltage of the spark plug 13 actually gradually decreases.

In FIG. 2, the time points from time t11 to time t15 are from time t1 to time t5, respectively.
It corresponds to each time until. Then, from time t3 to time t5, the waveform at the time of misfire is shown, and it can be seen that the inter-electrode voltage gradually decreases after the spark discharge of the spark plug 13 ends (time t3). Also, at time t1
From 3 to time t15, the waveform at the time of normal combustion is shown, and at the end of the spark discharge of the spark plug 13 (at time t1
It can be seen that the voltage between the electrodes after 3) is rapidly reduced.

Then, from time t3 to time t5,
In the period from time t13 to time t15, in the voltage detection circuit 51, the voltage across the capacitor 65 becomes a divided voltage according to the inter-electrode voltage of the spark plug 13, and the divided voltage is input to the determination circuit 67. ing.

Then, in synchronism with the processing of S370, in S380, the determination circuit 67 is used to make the spark plug 1
The process of reading the inter-electrode voltage (specifically, the divided voltage) of No. 3 is started. Specifically, the read command signal 72 output to the determination circuit 67 is changed to a high level, and when a predetermined combustion state determination period elapses, the read command signal 72.
Is changed to low level. The combustion state determination period is stored in the ECU 19 in advance.

In this embodiment, the combustion state determination period is set to a preset fixed value regardless of the operating state of the internal combustion engine, but an appropriate value may be set according to the operating state. In that case, the determination circuit 67 may be configured to set an appropriate value according to the operating state, and as the processing content of S390, a process of taking the combustion state determination period from the determination circuit 67 may be added.

Then, the discrimination circuit 67, to which the high level read command signal 72 is input, executes a process for reading the inter-electrode voltage of the spark plug 13 and outputs a determination result signal 68 to the ECU 19. In subsequent S390, the combustion state is determined based on the determination result signal 68 from the determination circuit 67, and a process of determining whether the combustion is normal combustion or misfire is performed.

In the next S400, it is determined whether or not the high level duration of the ignition command signal 20 has elapsed, starting from the time point when the affirmative determination is made in S360. If the negative determination is made, the same step is performed. By repeating the process, the process stands by, and if an affirmative determination is made, the process proceeds to S410. The high level duration of the ignition command signal 20 is E
It is stored in CU19. When it is determined in S400 that the high level duration of the ignition command signal 20 has elapsed (time t4 shown in FIG. 2), the process proceeds to S410. In the present embodiment, the high level duration of the ignition command signal 20 is set to a preset fixed value regardless of the operating state of the internal combustion engine, but an appropriate value may be set according to the operating state. Good.

Then, in S410, the ignition command signal 20
Is gradually reduced from a high level to a low level. The reason why the ignition command signal 20 is gradually decreased is to prevent the re-discharge from occurring. That is, when the ignition command signal 20 is rapidly changed from the high level to the low level, an ignition voltage is generated in the secondary winding 27 and re-discharge occurs, but the level of the ignition command signal 20 is gradually changed. By lowering it, the amount of change in current in the primary winding 25 per unit time can be reduced, and generation of ignition voltage in the secondary winding 27 can be prevented.

Then, when the processing in S410 ends, the combustion state determination processing ends. In FIG. 2, since the ignition command signal 20 gradually decreases from time t4 to time t5 and from time t14 to time t15, the inter-electrode voltage of the spark plug 13 does not become a high voltage. It can be seen that no discharge has occurred.

Here, in the above embodiment, the ignition transistor 17 corresponds to the ignition switching means described in the claims, the conductor 53 and the capacitor 65 correspond to the inter-electrode voltage detecting means, and the discriminating circuit 67. The filter circuit section, the peak hold circuit section, the peak voltage signal adjustment circuit section, the comparison circuit section, and the ECU 19 correspond to the combustion state determination means. Further, the conductor 53 corresponds to the capacitive coupling means,
The capacitor 65 corresponds to the voltage dividing means, and the backflow prevention diode 31 corresponds to the backflow prevention means.

Also, the ignition transistor 17 and S360, S370, S400, and S41 of the combustion state determination processing are performed.
0 corresponds to the re-energizing means (re-discharge preventing means), and particularly S360, S370, S400, S4 of the combustion state determination process.
10 corresponds to the first re-energization control means.

Further, S310 of the combustion state determination process corresponds to the operating state reading means, and S320 of the combustion state determination process.
Corresponds to the counter electromotive force generation timing setting means, and the map, table or calculation formula used in S320 of the combustion state determination process corresponds to the counter electromotive force generation timing setting information.

As described above, in the internal combustion engine ignition device 1 of the present embodiment, by re-energizing the primary winding 25 after the spark discharge ends, the electromotive force having the opposite polarity to the ignition voltage is generated. To generate a counter electromotive force in the secondary winding 27,
A voltage obtained by subtracting the voltage corresponding to this counter electromotive force from the residual induced voltage is generated at both ends of the secondary winding 27. As a result, it is possible to prevent the re-discharge due to the increase in the inter-electrode voltage of the spark plug 13 at the end of the spark discharge (in this case, at the time of forced shutoff).

Therefore, according to the ignition device for an internal combustion engine of the present embodiment, it is possible to suppress the occurrence of re-discharge after the completion of spark discharge, and it is erroneously determined that the combustion is normal despite the actual misfire. Can be prevented. Therefore, it is possible to improve the detection accuracy of the combustion state of the air-fuel mixture based on the voltage between the electrodes of the spark plug after the end of the spark discharge.

Further, the ignition device for the internal combustion engine of this embodiment is
In S310 of the combustion state determination process, a process of reading the operating state of the internal combustion engine including at least the engine speed is performed, and in S320, the spark discharge duration Tt is set based on the operating state read in S310. In addition, S
In 320, by setting the spark discharge duration Tt, the counter electromotive force generation timing for generating the counter electromotive force in the secondary winding 27 is set.

At this time, in S320, the spark discharge duration time Tt (in other words, the counter electromotive force generation time) is set based on at least the engine rotation speed using a map, a table, or a calculation formula. Then, by setting the spark discharge duration Tt to a longer time at lower rotation speeds, the back electromotive force generation timing is set to a later timing, and the spark discharge duration Tt is set to a shorter time at higher rotation speeds. Therefore, the back electromotive force generation time is set to an early time.

As described above, the counter electromotive force generation timing is set earlier as the engine speed becomes higher, so that the spark discharge ends at an earlier stage due to the interruption due to the turbulent flow of the air-fuel mixture. Also, since the time from the end of the spark discharge to the generation of the counter electromotive force can be shortened, the occurrence of re-discharge can be suppressed.

Therefore, according to the ignition device for an internal combustion engine of the present embodiment, re-discharge can be suppressed even when the operating condition of the internal combustion engine is high rotation, so that an erroneous determination of the combustion condition can be made. This can be prevented, and the accuracy of detecting the combustion state of the air-fuel mixture can be improved. Further, in the internal combustion engine ignition device of the present embodiment, the divided voltage obtained by dividing the inter-electrode voltage of the spark plug 13 is detected by using the conductor 53 and the capacitor 65 connected in series.

At this time, the divided voltage, which is the voltage across the capacitor 65, is lower than the interelectrode voltage of the spark plug. Therefore, the discrimination circuit 67 for detecting the interelectrode voltage based on the divided voltage As compared with a case where the voltage between the electrodes of the spark plug 13 is directly detected, it can be configured with a low-priced circuit in which the inputtable voltage range is set narrow. That is, the internal combustion engine ignition device of the present embodiment can detect the inter-electrode voltage of the spark plug 13 without using an expensive determination circuit having a wide inputtable voltage range as the determination circuit 67.

Therefore, according to the ignition device for an internal combustion engine of the present embodiment, the low-priced discriminating circuit 67 can be used in detecting the inter-electrode voltage of the spark plug 13.
It is possible to suppress an increase in manufacturing cost. Further, the internal combustion engine ignition device according to the present embodiment is provided with the backflow prevention diode 31 connected in series on the energizing path connecting the ignition voltage generating end 35 of the secondary winding 27 and the ignition plug 13. There is. The backflow prevention diode 31 allows the discharge current 28 to flow, and the discharge current 28
The current flowing in the opposite direction is blocked.

That is, the backflow prevention diode 31 blocks the current generated in the secondary winding 27 when the primary winding 25 is energized, so that the spark plug 13 and the secondary winding after the spark discharge ends. The movement (leakage) of the electric charge toward 27 is prevented, and the erroneous determination of the combustion state due to the leakage of the electric charge can be prevented. Further, since the backflow prevention diode 31 allows the discharge current 28 to pass therethrough,
The provision of the backflow prevention diode 31 does not prevent the generation of spark discharge.

Therefore, according to the ignition device for an internal combustion engine of the present embodiment, it is possible to prevent the leakage of charges from the spark plug to the secondary winding, and it is erroneously determined that the combustion is normal despite the misfire. This can be prevented, and the accuracy of determining the combustion state can be improved. Here, FIG. 9 shows the measurement results of measuring the inter-electrode voltage of the spark plug at the end of the spark discharge using the ignition device for an internal combustion engine of the present embodiment. This measurement is
The ignition device for an internal combustion engine according to the above-described embodiment is used to detect the peak value of the inter-electrode voltage of the spark plug when the spark discharge is forcibly interrupted, and the peak value is detected 100 times. The measurement results obtained by the execution are shown in FIG.

Further, as a comparative experiment, using the conventional ignition device for an internal combustion engine in which the primary winding is not re-energized during the spark discharge, the peak voltage of the interelectrode voltage of the spark plug when the spark discharge spontaneously ends. A measurement to detect the value was also performed. Both measurements were performed under the same operating conditions.

From the measurement results shown in FIG. 9, in the measurement using the conventional ignition device for the internal combustion engine, the peak value of the inter-electrode voltage after the spark discharge is in a wide range from about 1.1 to 3.7 [kV]. It can be seen that re-discharge occurs several times in the range of 2.3 [kV] or more. On the other hand, in the measurement using the ignition device for an internal combustion engine of the present invention, the peak value of the inter-electrode voltage is distributed in a narrow range of about 0.6 to 1.1 [kV], and re-discharge occurs. You can see that it has not occurred. The peak value of the inter-electrode voltage in the internal combustion engine ignition device of the present invention is lower than the peak value of the inter-electrode voltage in the conventional internal combustion engine ignition device. It can be seen that the electric ignition device is unlikely to cause re-discharge.

Therefore, according to the measurement results shown in FIG. 9, the internal combustion engine ignition device of the present invention is re-discharged as the inter-electrode voltage increases at the end of the spark discharge, as compared with the conventional internal combustion engine ignition device. It can be understood that this can be prevented, and erroneous determination in the combustion state determination processing can be prevented. Although the embodiment of the present invention (hereinafter referred to as the first embodiment) has been described above, the present invention is not limited to the above-described first embodiment, and various aspects can be adopted.

Therefore, as a second embodiment, by short-circuiting both ends of the primary winding during the spark discharge, the spark discharge is forcibly cut off and the second internal combustion engine configured to prevent re-discharge due to residual energy. The engine ignition device 3 will be described. First, FIG. 4 is an electric circuit diagram showing the configuration of the second internal combustion engine ignition device 3 as the second embodiment.

The second internal combustion engine ignition device 3 is different from the internal combustion engine ignition device 1 of the first embodiment shown in FIG.
Short-circuit switch 7 for short-circuiting both ends of the primary winding 25
5 is added and configured. The second internal combustion engine ignition device 3 is partially different in the processing content of the combustion state determination processing executed by the ECU 19.

Therefore, the second internal combustion engine ignition device 3 will be described, focusing on the differences from the internal combustion engine ignition device of the first embodiment. First, the short-circuit switch 75 includes the primary winding 2
5 are connected in parallel with each other and are configured so that the internal line is set to a short-circuited state based on the switch drive command signal 76 from the ECU 19. In the short-circuit switch 75, the internal line is normally open,
When the switch drive command signal 76 is input, the internal line is short-circuited, and when the current flowing through the internal line becomes a predetermined current value or less, the internal line shifts to an open state. It should be noted that such a short circuit switch 75 can be configured using, for example, a thyristor or a triac.

That is, the switch drive command signal 76 is input during the spark discharge, and the short-circuit switch 75 is turned on by the primary winding 2
When both ends of 5 are short-circuited, the residual energy of the ignition coil 15 causes a current to flow through the short-circuiting switch 75 to the primary winding 25. Then, an induced voltage (back electromotive force) having a polarity opposite to that of the residual induced voltage is generated in the secondary winding 27. As a result, a voltage obtained by subtracting the back electromotive force from the residual induction voltage is generated at both ends of the secondary winding 27, so that it is possible to suppress an increase in the voltage value generated at both ends of the secondary winding 27, and spark discharge is generated. It is possible to suppress the occurrence of re-discharge due to the increase in the voltage between the electrodes at the end.

Next, the ECU of the ignition device 3 for the second internal combustion engine
The combustion state determination process executed in 19 will be described with reference to the flowchart shown in FIG. Further, the second internal combustion engine ignition device 3 when executing the combustion state determination process
FIG. 5 is a time chart showing the states of the respective parts (the ignition command signal 20, the switch drive command signal 76, the inter-electrode voltage of the spark plug 13, and the secondary current 28 flowing in the secondary winding 27) in FIG.

Then, when the internal combustion engine is started and the combustion state determination process is started, first, in S610 (S represents a step), the operation of the internal combustion engine detected by the operation state detection process separately executed is performed. The state is read, and in S620, based on the read operating state, the spark discharge occurrence time ts
(So-called ignition timing) and spark discharge duration Tt are set.

The processing from S610 to S650 has the same contents as the processing from S310 to S350 in the combustion state determination processing of the first embodiment. That is, S6
In the processing from 10 to S650, the spark discharge generation timing ts and the spark discharge duration Tt are set based on the read operating state, and the ignition command signal 20 is output to drive and control the ignition transistor 17 to set the ignition coil. A voltage for ignition is generated in the secondary winding 27 of 15 and the spark plug 1
A series of treatments for generating a spark discharge between the electrodes of No. 3 is performed.

In the next step S660, the process of reading the inter-electrode voltage of the spark plug 13 using the discrimination circuit 67 is started. Specifically, the read command signal 72 output to the determination circuit 67 is changed to a high level, and when the predetermined combustion state determination period elapses, the read command signal 72 is changed to a low level. Then, in the discrimination circuit 67 that has received the high-level read command signal 72, the peak hold circuit section is turned on, and the comparison circuit section compares the filtered voltage signal with the adjusted peak voltage signal as described above. , And outputs the determination result signal 68 to the ECU 19.

In the combustion state determination period, the read command signal 7 is output before the ignition timing of the next combustion cycle in the same cylinder.
2 is set to output at a high level. Next S
In 670, it is determined whether or not the spark discharge duration Tt set in S620 has elapsed, starting from the point of time when the affirmative determination is made in S640. If the negative determination is made, the same step is repeatedly executed. Then, it waits until the spark discharge duration Tt elapses. Then, in S670,
When it is determined that the spark discharge duration time Tt has been reached (time t3 shown in FIG. 5), the process proceeds to S680.

Then, in S680, a process of outputting the switch drive command signal 76 as an instantaneous pulse signal is performed. When the switch drive command signal 76 is output, the short-circuit switch 75 is changed from the open state to the short-circuit state, Both ends of the primary winding 25 are short-circuited. Then, due to the residual energy, the primary current 26 flows in the primary winding 25 of the ignition coil 15, and a counter electromotive force having a polarity opposite to that of the ignition voltage is generated in the secondary winding 27. This back electromotive force has a polarity opposite to that of the residual induction voltage, and the voltage across the secondary winding 27 has a voltage value obtained by subtracting the voltage value of the back electromotive force from the residual induction voltage.

Since the voltage across the secondary winding 27 at this time has the same polarity as the ignition voltage, the reverse current prevention diode 3
It is applied between the electrodes of the spark plug 13 without being limited by 1. As a result, the electrodes of the spark plug 13 (the center electrode 21 and the ground electrode 23) function as electrostatic capacitance elements, so that charges are accumulated in each electrode and a potential difference is generated between the electrodes.

In this way, when electric charges are accumulated in the electrodes of the spark plug 13 and if ions are present in the combustion chamber, the electric charges move through the ions and a current flows between the electrodes of the spark plug 13. Will flow, and the voltage between the electrodes of the spark plug 13 will rapidly drop as the charge moves. If there are no ions in the combustion chamber,
Since the movement of charges via ions does not occur, the voltage between the electrodes of the spark plug 13 gradually decreases. Even when there are no ions, a slight amount of electric charge leaks, and therefore the inter-electrode voltage of the spark plug 13 actually gradually decreases.

In FIG. 5, the time points from time t11 to time t15 are from time t1 to time t5, respectively.
It corresponds to each time until. From time t3 to time t5, the waveform at the time of misfire is shown, and it can be seen that the inter-electrode voltage of the spark plug 13 is gradually decreasing. Further, from time t13 to time t15, the waveform at the time of normal combustion is shown, and it can be seen that the inter-electrode voltage of the spark plug 13 is rapidly lowered. Furthermore, time t
At 3 and time t13, re-energization to the primary winding is started before the spark discharge naturally ends, and the spark discharge is forcibly cut off.

Then, from time t3 to time t5,
In the period from time t13 to time t15, in the voltage detection circuit 51, the voltage across the capacitor 65 becomes a divided voltage according to the inter-electrode voltage of the spark plug 13, and the divided voltage is input to the determination circuit 67. ing.

In the following S690, the combustion state is determined based on the determination result signal 68 from the determination circuit 67, and the process of determining whether the combustion is normal combustion or misfire is performed. And
When the processing in S690 ends, the combustion state determination processing ends. The primary current 26 generated in the primary winding 25 due to the short-circuiting switch 75 being in the short-circuited state by the processing in S680 decreases with the passage of time, and when the primary current 26 becomes a predetermined current value or less, Short circuit switch 7
5 is open. Although the timing at which the short-circuit switch 75 is opened in this way changes depending on the amount of residual energy in the ignition coil 15 after the spark discharge ends, it is near time t5.

In the second embodiment, the short-circuit switch 7
5 and S670 and S680 of the combustion state determination processing correspond to the primary winding short-circuit means (re-discharge prevention means) described in the claims, and particularly, the short-circuit switch 75 corresponds to the short-circuit switching means, and the combustion state S670 of determination processing,
S680 corresponds to the primary winding short circuit control means.

Further, S610 of the combustion state determination processing corresponds to the operating state reading means, S620 of the combustion state determination processing corresponds to the back electromotive force generation timing setting means, and the map and table used in S620 of the combustion state determination processing. Alternatively, the calculation formula corresponds to the counter electromotive force generation timing setting information.

As described above, in the second internal combustion engine ignition device 3 of the second embodiment, by short-circuiting both ends of the primary winding 25 during spark discharge, the polarity opposite to the ignition voltage is obtained. The following electromotive force is generated in the secondary winding 27, and a voltage obtained by subtracting the voltage corresponding to this back electromotive force from the residual induced voltage is generated across the secondary winding 27. This allows
Since it is possible to suppress the degree of increase in the inter-electrode voltage in the spark plug 13 at the end of the spark discharge, it is possible to prevent re-discharge from occurring.

Therefore, according to the second internal combustion engine ignition device 3 of the second embodiment, it is possible to suppress the occurrence of re-discharge after the completion of the spark discharge, and the combustion is considered to be normal even though the actual misfire has occurred. It is possible to prevent erroneous determination. Therefore, it is possible to improve the detection accuracy of the combustion state of the air-fuel mixture based on the voltage between the electrodes of the spark plug after the end of the spark discharge.

In the second ignition device 3 for an internal combustion engine of the second embodiment, the short-circuit switch 75 is kept in a short-circuit state because the energizing current becomes a predetermined current value or less without receiving a command from the outside. Change to open state. That is, in the combustion state determination process, it is not necessary to execute the process for changing the short circuit switch 75 from the short circuit state to the open state.

Therefore, in the combustion state determination process of the second embodiment, S in the combustion state determination process of the first embodiment is used.
The processing corresponding to 400 and S410 can be omitted, and the processing content of the combustion state determination processing can be simplified. Further, by simplifying the processing content of the combustion state determination processing, the processing load of internal processing in the ECU 19 can be reduced.

Next, as a third embodiment, during spark discharge,
In addition to the ignition transistor, a second transistor 79 for energization / interruption of the primary winding is provided.
A third internal combustion engine ignition device 5 configured to forcibly interrupt the spark discharge and prevent re-discharge due to residual energy by re-energizing the primary winding by means of 9 will be described.

First, FIG. 7 is an electric circuit diagram showing a configuration of a third internal combustion engine ignition device 5 as a third embodiment. The third internal combustion engine ignition device 5 is configured by adding a second transistor 79 connected in parallel to the ignition transistor 17 to the internal combustion engine ignition device 1 of the first embodiment shown in FIG. ing. The third internal combustion engine ignition device 5 is partially different in the processing content of the combustion state determination processing executed by the ECU 19.

Therefore, the third internal combustion engine ignition device 5 will be described, focusing on the differences from the internal combustion engine ignition device of the first embodiment. First, the second transistor 79 is connected in parallel to the ignition transistor 17, and the ignition coil 1
In order to turn on / off the primary winding 25 of the ECU 5,
A semiconductor element (npn-type power transistor) that performs switching operation based on the second drive command signal 80 from 19
Is a switching element. The base of the second transistor 79 is connected to the output terminal of the second drive command signal 80 of the ECU 19, the collector is connected to the connection point between the primary winding 25 and the ignition transistor 17, and the emitter of the power supply device 11 is connected. It is grounded to the same ground as the negative electrode.

When the second drive command signal 80 is at a low level (generally, the ground potential), the second transistor 79 is in the off state (cutoff state) because the base current does not flow.
Then, when the second drive command signal 80 is at a high level (generally, the supply voltage 5 [V] from the constant voltage power supply), the base current flows to be in the ON state (energized state).

That is, when the second drive command signal 80 becomes high level and the second transistor 79 is turned on during the spark discharge, the residual energy of the ignition coil 15 causes a current to flow through the second transistor 79 to the primary winding 25. Along with this, an induced voltage (back electromotive force) having a polarity opposite to that of the residual induced voltage is generated in the secondary winding 27. As a result, the voltage obtained by subtracting the back electromotive force from the residual induced voltage becomes the secondary winding 2
Since it occurs at both ends of 7, the increase in the voltage value generated at both ends of the secondary winding 27 can be suppressed, and the increase in the inter-electrode voltage at the end of the spark discharge of the spark plug can be suppressed.

Next, the ECU of the ignition device 5 for the third internal combustion engine
The combustion state determination process executed in 19 will be described. The combustion state determination process of the third embodiment is configured by changing the processing contents of S370, S400 and S410 in the combustion state determination process of the first embodiment.

That is, in the combustion state determination process of the third embodiment, in S370, the process of changing the second drive command signal 80 from the low level to the high level is performed, and S40 is executed.
At 0, it is determined whether or not the high level duration of the second drive command signal 80 has elapsed, and at S410, processing for gently lowering the second drive command signal 80 from the high level to the low level is performed. The high-level duration of the second drive command signal 80 is stored in the ECU 19 in advance.

Therefore, by executing the combustion state determination process of the third embodiment, the ignition transistor 17 can be drive-controlled to generate the spark discharge, and the second transistor 79 is driven during the spark discharge. By controlling and re-energizing the primary winding 25, the spark discharge can be forcibly shut off and the spark plug 13 can be prevented from re-discharging.

In the third embodiment, the second transistor 79 and S360, S370, S of the combustion state determination process are performed.
400 and S410 correspond to the re-energizing means (re-discharge preventing means) described in the claims, particularly the second transistor 79 corresponds to the second switching means, and S360, S370 and S400 of the combustion state determination process. , S410 is second
It corresponds to re-energization control means.

As described above, in the third ignition device 5 for an internal combustion engine of the third embodiment, the second transistor 79 is drive-controlled to re-energize the primary winding 25 during the spark discharge. Then, a counter electromotive force, which is an electromotive force having a polarity opposite to that of the ignition voltage, is generated in the secondary winding 27, and a voltage obtained by subtracting a voltage corresponding to this counter electromotive force from the residual induced voltage is generated in the secondary winding 27. Are generated at both ends of. As a result, it is possible to prevent re-discharge due to the increase in the inter-electrode voltage in the spark plug 13 at the end of the spark discharge.

Therefore, according to the third internal combustion engine ignition device 5 of the third embodiment, it is possible to suppress the occurrence of re-discharge after the completion of the spark discharge, and the normal combustion is achieved despite the actual misfire. It is possible to prevent erroneous determination. Therefore, it is possible to improve the detection accuracy of the combustion state of the air-fuel mixture based on the voltage between the electrodes of the spark plug after the spark discharge is completed.

Further, the third internal combustion engine ignition device 5 is provided with the second transistor 79 in addition to the ignition transistor 17, and the second transistor 79 is used to re-energize the primary winding. The re-discharge of the spark plug 13 is suppressed. As a result, when re-energizing the primary winding, it is possible to prevent the energization time of the ignition transistor 17 from being lengthened, and it is possible to suppress the temperature rise of the ignition transistor 17. As a result, normal operation of the ignition transistor 17 can be maintained, and damage to the ignition transistor 17 due to temperature rise can be prevented.

Therefore, according to the third ignition device 5 for an internal combustion engine of the third embodiment, it is possible to improve the detection accuracy of the combustion state of the air-fuel mixture and prevent the spark discharge from being generated due to the damage of the ignition transistor 17. Can be prevented. that's all,
Although a plurality of embodiments of the present invention have been described, the present invention is not limited to the above embodiments, and various modes can be adopted.

For example, in the above embodiment, the discrimination circuit 67 performs the process of detecting the inter-electrode voltage of the spark plug 13 based on the divided voltage to determine the combustion state. It is also possible to directly take in and execute a process of determining the combustion state by an internal process of the ECU 19.

Further, in the above embodiment, the determination result signal 68 output from the determination circuit 67 is input to the ECU 19 and E
The CU 19 detects the output time of the determination result signal 68,
The determination circuit 67 determines whether misfire or normal combustion is performed by determining whether the output time of the determination result signal 68 is longer than a preset combustion state determination time. Inside, the output of the determination result signal output from the comparison circuit unit and the combustion state determination time are compared, and the misfire determination signal indicating that the misfire occurs when the output time is larger than the combustion state determination time. Is output to the ECU 19, and conversely, when the output time is shorter than the combustion state determination time, an output circuit section that outputs a normal determination signal indicating normal combustion is provided to perform the process of determining the combustion state. You can run it.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing a configuration of an internal combustion engine ignition device according to a first embodiment.

FIG. 2 is a time chart showing the state of each part in the internal combustion engine ignition device of the first embodiment.

FIG. 3 is a flowchart showing the processing content of a combustion state determination processing executed in the electronic control unit of the first embodiment.

FIG. 4 is an electric circuit diagram showing a configuration of a second ignition device for an internal combustion engine of a second embodiment.

FIG. 5 is a time chart showing the state of each part in the second ignition device for an internal combustion engine of the second embodiment.

FIG. 6 is a flowchart showing the processing contents of a combustion state determination process executed in the electronic control unit of the second embodiment.

FIG. 7 is an electric circuit diagram showing a configuration of a third ignition device for an internal combustion engine of a third embodiment.

FIG. 8 is a time chart showing the state of each part in the conventional ignition device for an internal combustion engine.

FIG. 9 is a measurement result of measuring the inter-electrode voltage of the spark plug after completion of the spark discharge by using the internal combustion engine ignition device of the present invention and the conventional internal combustion engine ignition device.

FIG. 10 is an explanatory diagram showing the configuration of a setting map for setting the spark discharge duration based on the engine rotation speed and the engine load.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine ignition device, 3 ... 2nd internal combustion engine ignition device, 5 ... 3rd internal combustion engine ignition device, 13 ... Spark plug,
15 ... Ignition coil, 17 ... Ignition transistor, 19 ...
Electronic control unit (ECU), 21 ... Central electrode, 23 ... Ground electrode, 25 ... Primary winding, 27 ... Secondary winding, 31 ... Backflow prevention diode, 51 ... Voltage detection circuit, 53 ... Conductor,
65 ... Capacitor, 67 ... Discrimination circuit, 75 ... Short circuit switch, 79 ... Second transistor.

Claims (11)

[Claims] 1. An ignition coil, which has a primary winding and a secondary winding, and which generates an ignition voltage in the secondary winding by interrupting a primary current flowing through the primary winding, and an ignition coil of the ignition coil. Ignition switching means for energizing and interrupting the primary current flowing through the primary winding, and a discharge current generated by the ignition voltage that is connected in series to the secondary winding and flows between itself electrodes. The spark plug that generates spark discharge, the inter-electrode voltage detection means that detects the inter-electrode voltage that occurs between the electrodes of the spark plug, and the spark among the inter-electrode voltage that is detected by the inter-electrode voltage detection means An ignition device for an internal combustion engine, comprising: a combustion state determination means for determining a combustion state of the internal combustion engine based on an inter-electrode voltage after the end of discharge, the secondary winding being provided during spark discharge of the spark plug. The point on the line By providing a back electromotive force which is an electromotive force having a polarity opposite to that of the fire voltage, there is provided a re-discharge preventing means for preventing re-discharge of the spark plug due to a rise in inter-electrode voltage at the end of the spark discharge. An ignition device for an internal combustion engine, comprising: 2. The re-discharge preventing unit re-energizes the primary winding to generate the counter electromotive force in the secondary winding and forcibly interrupt the spark discharge of the spark plug. The ignition device for an internal combustion engine according to claim 1, wherein the ignition device is provided as re-energizing means. 3. The re-energizing means comprises first re-energizing control means for driving and controlling the ignition switching means in order to re-energize the primary winding with electric current. An ignition device for an internal combustion engine according to item 1. 4. The second re-energizing means is connected in parallel to the ignition switching means, and energizes / disconnects the primary current flowing through the primary winding.
3. The internal combustion engine according to claim 2, further comprising switching means, and second re-energization control means for driving and controlling the second switching means to re-energize the primary winding. Ignition device. 5. The primary discharge short-circuiting unit that short-circuits both ends of the primary winding to generate a counter electromotive force having a polarity opposite to that of the ignition voltage in the secondary winding. The ignition device for an internal combustion engine according to claim 1, further comprising: 6. The primary winding short-circuiting means includes a short-circuiting switching means connected in parallel to the primary winding, and a primary drive controlling the short-circuiting switching means to short-circuit both ends of the primary winding. An ignition device for an internal combustion engine according to claim 5, further comprising: a winding short-circuit control means. 7. The re-discharge preventing means comprises: an operating state reading means for externally reading the operating state of the internal combustion engine including at least the engine speed; and the operating state read by the operating state reading means. A back electromotive force generation timing setting unit that sets a back electromotive force generation timing for generating the back electromotive force in the secondary winding and sets the back electromotive force generation timing earlier at least as the engine speed increases. The ignition device for an internal combustion engine according to any one of claims 1 to 6, further comprising: 8. The counter electromotive force generation timing setting means uses the counter electromotive force generation timing setting information in which the counter electromotive force generation timing according to the engine rotation speed is determined, and based on the engine rotation speed. The ignition device for an internal combustion engine according to claim 7, wherein a counter electromotive force generation timing is set. 9. The inter-electrode voltage detecting means is capacitive coupling means for capacitively coupling between the spark plug and an energization path connecting the ignition voltage generating end of the secondary winding, and the capacitive coupling means. And a voltage dividing means serially connected to the spark plug, the capacitive coupling means and the voltage dividing means connected in series are connected in parallel to the spark plug, and the capacitive coupling means and the voltage dividing means The divided voltage obtained by dividing the voltage is detected as the inter-electrode voltage. The ignition device for an internal combustion engine according to any one of claims 1 to 8, wherein: 10. The center electrode of the spark plug is connected to the ignition voltage generating end of the secondary winding so as to have a positive polarity, according to any one of claims 1 to 9. An ignition device for an internal combustion engine according to any one of claims. 11. A series connection is provided on an energization path connecting an ignition voltage generating end of the secondary winding and the spark plug,
11. A backflow prevention unit that allows the discharge current to flow and blocks the flow of a current that flows in the opposite direction to the discharge current. 11. Ignition device for internal combustion engine.