JP2000265934A - Ignition device for internal combustion engine - Google Patents

Abstract

(57) Abstract: In a full-transistor type ignition device, an ion current that changes according to an operating state of an internal combustion engine can always be accurately detected in an entire operating region. SOLUTION: The inductance of a secondary winding of an ignition coil is 4 to 1 smaller than that of a conventional one (20 to 30H).
By setting it within the range of 6H, the duration of the spark discharge when the spark plug is spark-discharged by energizing / disconnecting the primary winding and the voltage fluctuation time of the secondary winding generated at the end of the spark discharge are shortened. I do. As a result, after the start of spark discharge,
The time required until the ion current corresponding to the amount of ions generated due to the combustion of the air-fuel mixture can be detected is shortened, and the ion current can be accurately detected. Further, when the inductance of the secondary winding is reduced, the duration of the spark discharge is shortened, and the ignitability of the air-fuel mixture is reduced. Therefore, after the first spark discharge (time t1), the misfire is determined from the ion current ( At time t3), at the time of misfire, spark discharge is performed again by cutting off the current supply to the primary winding. As a result, the ignitability of the air-fuel mixture can be ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition device for an internal combustion engine having an ion current detection function for detecting, as a current value, ions generated by the ignition of a fuel mixture after spark discharge of a spark plug.

[0002]

2. Description of the Related Art Conventionally, in order to detect various operating states of an internal combustion engine (air-fuel ratio, lean limit of air-fuel ratio, limit of exhaust gas recirculation amount, etc.), in addition to misfire and knocking of the internal combustion engine, the internal combustion engine has been used. 2. Description of the Related Art There is known a technique that utilizes an ionic current flowing by ions existing near an electrode of a spark plug after spark discharge of the spark plug.

That is, in the cylinder of the internal combustion engine, ions are generated during combustion (flame propagation) after spark discharge by the spark plug, and the resistance value between the electrodes of the spark plug changes according to the amount of generated ions. The amount of generated ions varies depending on the combustion state of the internal combustion engine and the operation state of the internal combustion engine. For this reason, after a high voltage for ignition is applied to the ignition plug (that is, after spark discharge of the ignition plug), a voltage is externally applied to the ignition plug, and an ion current flowing thereby is detected, whereby the ignition plug is It is possible to detect a change in the resistance value between the electrodes (that is, a change in the operating state).

An ignition device having such an ion current detection function is disclosed in, for example, Japanese Patent Application Laid-Open No. 4-1914.
As disclosed in Japanese Patent Application Publication No. 65-65, etc., a so-called full-transistor type ignition in which a current flowing through a primary winding of an ignition coil is turned on / off by a switching element such as a power transistor connected in series to the primary winding. A device applied to an apparatus is known.

[0005]

However, in such a conventional full-transistor type ignition device, it takes a long time until the ion current can be accurately detected after spark discharge of the ignition plug. In some cases, the ionic current cannot be accurately detected depending on the operation state of the internal combustion engine.

That is, first, in the full transistor type ignition device, before the ignition timing at which the spark plug is spark-discharged, the power transistor is turned on and a current flows through the primary winding of the ignition coil. The power transistor is turned off, a high voltage for ignition is generated in the secondary winding of the ignition coil, and the high voltage for ignition is applied to the spark plug, thereby causing the spark plug to discharge.

[0007] The spark discharge of the spark plug is composed of a capacitive discharge that causes dielectric breakdown between the electrodes and an induced discharge (also referred to as an arc discharge) that occurs subsequently. The duration of the spark discharge including the induced discharge is as follows. The state of combustion in the cylinder,
It depends on the inductance of the ignition coil.

Further, when the internal combustion engine is operated at a low rotation speed and a low load, such as when the internal combustion engine is started or idling, it is difficult for the air-fuel mixture to ignite.
It is necessary to make the duration of the spark discharge sufficiently long (about 2 to 3 ms) as compared with the high load operation.

Therefore, in the conventional full-transistor type ignition device, the air-fuel mixture can be reliably ignited by the spark discharge even when the internal combustion engine is operated at a low speed and a low load (in other words, the spark discharge is performed). The self-inductance of the secondary winding of the ignition coil is set to a large value (about 20 to 30H) so that the duration time of the ignition coil can be made sufficiently long.

However, if the self-inductance of the secondary winding of the ignition coil is set to a sufficiently large value in consideration of the ignitability of the air-fuel mixture, the duration of the spark discharge becomes unnecessarily long. Under operating conditions in which the air-fuel mixture can be ignited and burned immediately after the spark discharge of the spark plug starts, such as during high-speed, high-load operation of the internal combustion engine, ions generated by the combustion of the air-fuel mixture cause ignition of the spark plug. It may disappear during spark discharge, and the ion current may not be detected. It is to be noted that ions generated due to the combustion of the air-fuel mixture after the spark discharge exist only for a short time after the ignition of the air-fuel mixture.

At the end of spark discharge of the ignition plug,
Due to the self-inductance of the secondary winding of the ignition coil (specifically, due to the self-inductance and the resonance characteristics generated by the capacitance component of the ignition system), voltage fluctuation (vibration) occurs on the secondary winding side. Then, when such a voltage fluctuation occurs, if a high voltage for ion current detection is applied to the ignition plug to detect the ion current, the detection signal (ion current) is the voltage of the secondary winding. It fluctuates greatly under the influence of the fluctuation, and an accurate ion current cannot be detected.

For this reason, in the conventional ignition device, the period from the time when the spark discharge is generated in the spark plug (ignition timing) to the time when the spark plug terminates the spark discharge and the voltage of the secondary winding is stabilized is determined. In some cases, a so-called masking process is performed in which the detection of an ion current is prohibited.

However, the voltage fluctuation of the secondary winding that occurs at the end of the spark discharge lasts longer as the self-inductance of the secondary winding is larger. In a conventional ignition device in which the self-inductance is set to a large value, the time until the ion current can be detected after the spark discharge of the spark plug starts becomes longer, and an operation region in which the ion current cannot be accurately detected is present. Will increase.

Further, if the ion current can be accurately detected, knocking of the internal combustion engine can be detected by extracting a signal of a specific frequency (knock frequency) superimposed on the detection signal. If the self-inductance of the next winding is large, the entire ignition system becomes a low-pass filter, and the knocking signal component superimposed on the ion current detection signal is attenuated.

For this reason, in the conventional full-transistor type ignition device, even if the ion current can be detected, there is a problem that knocking cannot be detected from the detected ion current. SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and in a full transistor type ignition device, an ion current that changes in accordance with an operation state of an internal combustion engine can be always accurately detected in an entire operation range of the internal combustion engine. The purpose is to:

[0016]

According to a first aspect of the present invention, there is provided an ignition coil in which one end of a secondary winding is connected to a spark plug, and a primary winding of the ignition coil. A switching element for energizing and interrupting a primary current flowing in accordance with an external command, and turning on and off the switching element to generate a high voltage for ignition in a secondary winding of the ignition coil, and An ignition device for an internal combustion engine, comprising: ignition control means for spark discharge of a plug; and ion current detection means for detecting an ion current flowing between electrodes of the ignition plug after spark discharge of the ignition plug. The self-inductance of the secondary winding of the coil is set in the range of 4H to 16H.

That is, in the ignition device for an internal combustion engine according to the present invention (claim 1), the ignition control means turns on and off a switching element such as a power transistor in synchronization with the rotation of the internal combustion engine. A high voltage for ignition is generated in the secondary winding of the spark plug to spark discharge the spark plug,
This is a so-called full-transistor type ignition device, and the ion current detection means detects the ion current flowing between the electrodes of the ignition plug after spark discharge of the ignition plug, as in the conventional ignition device described above.

In the present invention (claim 1), the self-inductance of the secondary winding of the ignition coil for generating a high ignition voltage applied to the ignition plug is used in a conventional full transistor type ignition device. Smaller than the self-inductance (20-30H) of the secondary winding of the ignition coil,
It is set in the range of 4H to 16H.

This is because if the self-inductance of the secondary winding is smaller than 4H, the duration of the spark discharge becomes too short, and an operation region in which the air-fuel mixture cannot be ignited surely occurs. The winding self inductance is 16
If it is larger than H, the period of occurrence of the voltage fluctuation occurring in the secondary winding after the end of the spark discharge becomes too long, and the amount of ions generated by the combustion of the air-fuel mixture (and This is because it becomes impossible to accurately detect the operating state of the internal combustion engine).

That is, the ignition device for an internal combustion engine of the present invention
Unlike the conventional ignition device, the self-inductance of the secondary winding of the ignition coil is set to a sufficiently large value so that the duration of the spark discharge is sufficiently long in consideration of only the ignitability of the air-fuel mixture. Instead, by performing various experiments exemplified in the examples described later, the self-inductance of the secondary winding capable of accurately detecting the ionic current in the entire operation region of the internal combustion engine while ensuring the ignitability of the air-fuel mixture is set. It is doing.

According to the ignition device for an internal combustion engine of the present invention thus constituted, the continuation of the spark discharge after the spark plug is caused to discharge by the operation of the ignition control means is different from the conventional device described above. Time can be shortened,
In addition, since the voltage fluctuation of the secondary winding generated at the end of the spark discharge can be quickly converged, the time from the ignition timing at which the spark plug starts the spark discharge to the time when the ion current detecting means starts the ion current detecting operation is started. Can be shortened.

Therefore, according to the present invention, even when the mixture is easily ignited, such as when the internal combustion engine is operating at a high speed and a high load, before the ions generated by the combustion of the mixture are exhausted, the ions are removed. It is possible to accurately detect an ion current corresponding to the amount of generation. Further, in the present invention, the self-inductance of the secondary winding of the ignition coil is set in the range of 4H to 16 which is smaller than that of the conventional one, so that the ignition Preventing the whole from becoming a low-pass filter that attenuates the knocking frequency component, extracting a signal component corresponding to knocking generated in the internal combustion engine from the ion current detected by the ion current detecting means, and determining knocking It is also possible.

Here, the ion current detecting means may be any as long as it can detect the ion current flowing between the electrodes of the spark plug after the spark discharge of the spark plug.
As described in 2, the ion current detecting means applies a high voltage for detection having a polarity opposite to the high voltage for ignition to the ignition plug after the spark discharge of the ignition plug, and the ion flowing between the electrodes of the ignition plug by applying the voltage. The current may be detected.

That is, in order to apply a detection high voltage having a polarity opposite to that of the ignition high voltage to the ignition plug,
As described in Examples below, the capacitor is charged with a discharge current that flows when the spark plug discharges by applying a high voltage for ignition to the spark plug, and the charged charge is used for detection. It is possible to generate a high voltage, and thus, it is not necessary to separately take in power for generating a high voltage for detection from a power supply device, and power consumption can be reduced.

On the other hand, according to the present invention (claims 1 and 2), the value of the self-inductance of the secondary winding of the ignition coil is 4H to 1H.
By setting it within the range of 6H, the duration of the spark discharge by the spark plug and the voltage fluctuation period of the secondary winding generated at the end of the spark discharge are shortened. In this way, the duration of the spark discharge is shortened. Then, under operating conditions where the air-fuel mixture is difficult to ignite, such as during low-speed, low-load operation of the internal combustion engine,
The mixture is easily misfired.

In order to solve such a problem,
According to a third aspect of the present invention, in the ignition device for an internal combustion engine according to the first or second aspect, the ignition of the air-fuel mixture is further performed based on the ion current detected by the ion current detection means.
It is preferable that a re-ignition control means is provided for driving the switching element again when the mis-fire is determined and for determining the mis-fire, and causing the spark plug to discharge again.

That is, in the ignition device for an internal combustion engine according to the third aspect, when the ignition control means causes a spark discharge of the spark plug, and thereafter, the ion current detection means detects the ion current, the re-ignition control means detects the ion current. Based on the ion current
When the ignition / misfire of the air-fuel mixture is determined and the misfire is determined, the spark plug is again subjected to spark discharge.

Therefore, according to the third aspect of the present invention,
Even if the air-fuel mixture cannot be ignited and burned by the first spark discharge by the ignition control means, the air-fuel mixture can be ignited and burned by the spark discharge by the re-ignition control means, It is possible to prevent a problem that misfiring easily occurs when the self-inductance of the winding is set to a value smaller than the conventional value.

Here, the reignition control means determines whether or not a misfire has occurred from the ionic current only once after the ignition control means has caused the spark plug to perform a spark discharge, and discharges the spark plug when the misfire is determined. For example, even after the second or subsequent spark discharge of the spark plug itself, the presence or absence of a misfire is determined from the ionic current, and the spark plug is spark-discharged at the time of the misfire determination. Alternatively, “misfire determination → spark discharge” may be repeatedly performed a plurality of times. If the re-ignition control means is configured to repeatedly perform “misfire determination → spark discharge” a plurality of times, misfire of the air-fuel mixture can be more reliably prevented and ignitability can be improved.

It should be noted that the reignition control means can be configured to repeatedly perform "misfire determination → spark discharge" a plurality of times in the present invention because of the self-inductance of the secondary winding of the ignition plug. Is set to 4H to 16H, which is smaller than the conventional value.

That is, the fact that the self-inductance of the secondary winding of the spark plug is small means that the self-inductance of the primary winding required to generate a high ignition voltage in the secondary winding is, of course, the conventional one. As a result, the energization time of the primary winding (in other words, the ON time of the switching element) required to generate the high voltage for ignition in the secondary winding is also shortened.

In the present invention, by reducing the self-inductance of the secondary winding of the ignition plug, the duration of the spark discharge of the ignition coil is shortened, and the ion current is reduced in a short time after the start of the spark discharge. We are trying to detect it accurately. Therefore, in the ignition device of the present invention, the time required for “energization of the primary winding → spark discharge → ion current detection” is extremely shorter than that of the conventional one, and for each ignition of the internal combustion engine, “misfire determination → The "spark discharge" can be repeated a plurality of times.

When the self-inductance of the secondary winding of the spark plug is set within the above range, misfiring easily occurs when the internal combustion engine is operated at a low rotation speed and a low load. At the time of rotation / high load operation, the air-fuel mixture is easily ignited and there is no risk of misfiring. Therefore, the operation of the re-ignition control means may be limited according to the operation state of the internal combustion engine.

Specifically, when the rotational speed of the internal combustion engine is equal to or lower than a predetermined rotational speed, the opening degree of the throttle valve, the ratio Q / N between the intake air amount Q and the rotational speed N, the intake pipe pressure, and the like are obtained. Only when the load of the internal combustion engine is equal to or lower than a predetermined level, the re-ignition control means is operated, and in the other operation region, the operation of `` misfire determination → spark discharge '' by the re-ignition control means is prohibited. Is also good.

According to this configuration, the time per one revolution of the internal combustion engine such as when the internal combustion engine is running at a high speed is shortened, and the engine control device that realizes the ignition control means and the re-ignition control means performs one ignition operation. When the time available for the winning process is reduced, the ignition control can be favorably executed without increasing the processing load on the engine control device side.

The lower the rotational speed of the internal combustion engine, the more difficult it is for the mixture to ignite. In addition, the number of times that the reignition control means can execute “misfire determination → spark discharge” per stroke of the internal combustion engine is as follows: As the rotation speed of the internal combustion engine becomes higher, it becomes smaller, so as described above, when the reignition control means is configured to execute the operation of “misfire determination → spark discharge” a plurality of times, the maximum number of executions is Depending on the rotation speed of the internal combustion engine, the setting may be made to increase as the rotation speed of the internal combustion engine decreases.

On the other hand, in order to more reliably ignite and burn the air-fuel mixture, the ignition control means may be provided by switching the switching element continuously a plurality of times during one combustion cycle of the internal combustion engine. By turning on and off the ignition plug, the spark plug is configured to continuously discharge sparks a plurality of times. The current may be detected.

That is, according to this configuration, the air-fuel mixture is more reliably ignited by a plurality of spark discharges of the ignition plug by the ignition control means, and then the misfire, The operating state of the internal combustion engine, such as knocking, can be detected well.

When the ignition control means is configured to continuously generate spark discharges of the spark plug a plurality of times as described above, the spark discharge is performed unnecessarily. It is desirable to limit the number of spark discharges generated by the ignition control means to the spark plug so that the current detection accuracy is not reduced and the life of the spark plug is not shortened.

Specifically, under operating conditions in which the mixture is unlikely to ignite (for example, during low-speed, low-load operation of the internal combustion engine),
The number of continuous spark discharges by the ignition control means is increased, and the number of continuous spark discharges by the ignition control means is reduced under operating conditions under which the mixture is likely to ignite (for example, during high-speed / high-load operation of the internal combustion engine). (In some cases, one spark discharge), and a spark discharge continuous number setting means for setting the number of spark discharges of the spark plug controlled by the ignition control means according to the operating state of the internal combustion engine. On the control means side, the switching element may be turned on / off in accordance with the set number of spark discharges, and the spark plug may be configured to perform spark discharge one or more times.

Since the spark discharge of the spark plug is continuously performed a plurality of times by the ignition control means in order to enhance the ignitability of the air-fuel mixture, if the duration of the spark discharge is reduced, the mixing time is reduced. The present invention may be applied to an internal combustion engine in which the ignitability of air is significantly reduced, specifically, a so-called direct injection type internal combustion engine in which a fuel injection valve (injector) directly injects fuel into a cylinder.

That is, in the direct injection type internal combustion engine, fuel is directly injected from the injector to the vicinity of the spark plug.
If the spark discharge period due to the spark plug is short, the fuel is likely to be smoldered, and in order to more reliably ignite the air-fuel mixture, another internal combustion engine (specifically, fuel is supplied at the intake pipe side, and fuel is supplied during the intake stroke). It is necessary to make the rise of the ignition high voltage steep and to make the duration of the spark discharge longer, as compared with the case of an internal combustion engine in which the air-fuel mixture is sucked into the cylinder.

In the ignition device according to the present invention, the self-inductance of the secondary winding of the ignition coil is set in the range of 4H to 16H, so that the impedance of the secondary winding is smaller than that of the conventional ignition device. And the rise of the ignition high voltage can be made steep. However, in this case, as described above, since the duration of the spark discharge is short, the spark discharge is suitable for detecting the ionic current.
The duration of the spark discharge becomes too short, and the ignitability may be reduced.

However, if the spark discharge before the detection of the ion current by the ignition control means is continuously performed a plurality of times, the duration of the spark discharge is increased. Is obtained, and the ignitability of the air-fuel mixture can be ensured. Therefore, the invention according to claim 4 can exert more effects particularly by applying a direct injection type internal combustion engine.

The invention according to claim 4 and the invention according to claim 3 can be combined with each other. If these inventions are combined, the number of times of performing spark discharge by the ignition control means a plurality of times can be increased. While minimizing
It is possible to reliably ignite and burn the air-fuel mixture, to prevent an unnecessary increase in the number of spark discharges of the spark plug, and to suppress a reduction in the life of the spark plug due to an increase in the number of spark discharges.

On the other hand, in the present invention, the self-inductance of the secondary winding of the ignition coil is set within the range of 4H to 16H. However, depending on the value of the set self-inductance, the duration of the spark discharge of the spark plug becomes longer. It is conceivable that the time may be longer than the minimum time required to ignite and burn the mixture.

Therefore, in order to shorten the duration of the spark discharge and improve the detection accuracy of the ion current, the spark discharge of the spark plug is stopped according to the operation state of the internal combustion engine. It is preferable to provide a spark discharge suspending means. That is, for example, when the self-inductance of the secondary winding is set to 16H, which is the maximum value in the present invention, the duration of the spark discharge is longer than necessary during high-speed / high-load operation of the internal combustion engine in which the air-fuel mixture easily ignites. It is thought that it becomes longer. On the other hand, in order to improve the detection accuracy of the ion current at the time of high rotation and high load operation of the internal combustion engine, it is desirable to minimize the time from the start of the spark discharge to the start of the ion current detection. Therefore, in the invention according to claim 5, for example, the higher the rotation speed and the higher the load of the internal combustion engine in which the air-fuel mixture easily ignites, the shorter the spark discharge duration of the spark plug becomes.
The spark discharge of the spark plug is stopped according to the operating state of the internal combustion engine. As a result, according to the invention as set forth in claim 5, it is possible to further shorten the duration of the spark discharge and improve the detection accuracy of the ion current.

To stop the spark discharge, the switching element is turned on during the spark discharge period of the spark plug,
What is necessary is just to restart the energization to the primary winding stage of the ignition coil. However, if the switching element is turned off after the resumption of energization, the spark plug again discharges sparks. Therefore, when it is not necessary to ignite the air-fuel mixture, the switching element is turned off after the internal combustion engine enters the exhaust stroke. It is good to do so.

[0049]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing a configuration (a) and an ionic current detection characteristic (b) of an ignition device for an internal combustion engine to which the present invention is applied.

As shown in FIG. 1A, the ignition device for an internal combustion engine according to this embodiment has an ignition plug 2 having an outer electrode 2a grounded, and an ignition plug 2 having one end of a secondary winding L2.
An ignition coil 4 connected to the center electrode 2b, a DC power source (battery) 6 having a positive pole connected to one end of a primary winding L1 of the ignition coil 4 and a negative pole grounded to ground, and a primary winding of the ignition coil 4 A switching element 8 provided on the side of the line L1 opposite to the battery 6 for conducting / cutting off an energizing path of the primary winding L1 extending to the negative electrode side of the battery 6 via the ground; and a secondary winding L2 of the ignition coil 4 Is provided on the opposite side of the ignition plug 2 and the ignition plug 2
An ion current detection circuit 10 for detecting an ion current flowing due to ions generated in the vicinity of the electrodes, and a switching element 8 are turned on and off to energize the primary winding of the ignition coil 4 and cut off the energization (switching element 8 at the time of turn-off), a high voltage for ignition is generated in the secondary winding L2 of the ignition coil 4 to cause the spark plug 2 to spark-discharge, and thereafter, the ion current detection circuit 10 is driven to detect the ion current. And a control device 12 composed of a microcomputer.

The switching element 8 has a collector connected to the primary winding L 1 of the ignition coil 4, an emitter grounded, and a base connected to the control device 12.
A PN-type power transistor is turned on when the ignition signal IG output from the control device 12 is at a high level, and the conduction path between the primary winding L1 of the ignition coil 4 and the battery 6 is conducted. Then, a current flows through the primary winding L1.

When the switching element 8 is turned off, the ignition coil 4 uses the energy stored in the primary winding L1 by energizing the primary winding L1 to turn on the ignition plug 2 of the secondary winding L2.
A negative high voltage for ignition lower than the ground potential is induced on the side of the center electrode 2b of the IGBT. A discharge current flows.

The self-inductance of the secondary winding L2 of the ignition coil 4 is 4H by applying the present invention.
１６16H (for example, 8H), and the turn ratio between the primary winding L1 and the secondary winding L2 (in other words, the self-inductance of the primary winding L1) is determined by the current flowing through the primary winding L1. The setting is made according to the ignition high voltage generated in the secondary winding L2 at the time of interruption.

Next, the ion current detection circuit 10 corresponds to the ion current detection means described in the claims, and has a resistor 20 having one end grounded, and a cathode connected to the resistor 20. A diode 22 connected in parallel to be on the ground side, and a resistor 24 and a Zener diode 2 also connected in parallel to the resistor 20
6 and a capacitor 28 connected in series on the side opposite to the ground side of the resistor 20.
(= Voltage across diode 22 = voltage across series circuit composed of resistor 24 and zener diode 26) is the ion current detection signal (ion current signal) Si
Is input to the control device 12.

The cathode of the charging diode 30 is connected to the opposite side of the capacitor 28 from the resistor 20. The charging diode 30 uses the discharge current flowing from the secondary winding L2 of the ignition coil 4 to the ion current detection circuit 10 side during the spark discharge of the ignition plug 2 to discharge the capacitor 2.
The anode is connected to the secondary winding L2 of the ignition coil 4 on the side opposite to the ignition plug 2. A discharging switch 32 whose both ends are short-circuited by a window signal IW (High level) indicating the ion current detection period output from the control device 12 is connected in parallel to the charging diode 30.

The ion current detection circuit 10 is provided with a Zener diode 34 having a cathode connected to the secondary winding L2 of the ignition coil 4 on the side opposite to the ignition plug 2 and an anode grounded to ground. ing. The Zener diode 34 forms a closed loop together with the secondary winding L2 and the spark plug 2 to allow a discharge current to flow at the time of spark discharge of the spark plug 2 and to establish a connection between the secondary winding L2 and the ground at the time of spark discharge. By maintaining the voltage at the Zener voltage, the charging diode 3
0, the capacitor 28 is connected to the Zener diode 3
4 is higher than the Zener voltage obtained by subtracting the forward voltage (2 × Vf = approximately 1.4 V) of the diodes 30 and 22 (a voltage at which the spark plug 2 does not spark discharge);
(About 0 V).

In the ion current detection circuit 10 configured as described above, when the discharge switch 32 is in the off state, the current flows only in the direction from the secondary winding L2 of the ignition coil 4 to the ground. At the time of spark discharge of the ignition plug 2, the discharge current is supplied to the charging diode 3
0, the capacitor 28 and the diode 22 are passed in a closed loop, and a discharge current is also supplied to the Zener diode 34 so that the voltage between both ends does not exceed the Zener voltage of the Zener diode 34.

At this time, the voltage between both ends of the capacitor 28 becomes a predetermined high voltage for detection determined by the Zener voltage of the Zener diode 34. When the discharge switch 32 is turned off, the high voltage for detection is applied to the capacitor 28. Can be applied to the center electrode 2b of the ignition plug 2 via the secondary winding L2 of the ignition coil 4.

Next, when the discharging switch 32 is closed in this state, the discharging switch 32
Through the secondary winding L2 and the center electrode 2 of the spark plug 2
A high voltage for detection is applied to b. At this time, if ions generated by the combustion of the air-fuel mixture are present in the vicinity of the electrodes of the spark plug 2, if the ions between the electrodes of the spark plug 2 and the resistance 20
The ion current flows through the path passing through. Also,
When the ion current flows in this manner, a voltage drop occurs in the resistor 20 depending on the magnitude of the ion current and the resistance value of the resistor 20, and the voltage across the resistor 20 has a value corresponding to the ion current.

Accordingly, as described above, the voltage across the resistor 20 (actually, a negative voltage lower than the ground potential generated at the connection point between the resistor 20 and the capacitor 28) is sent to the control device 12 as the ion current signal Si. By inputting, the control device 12 can detect the ion current.

The series circuit of the resistor 24 and the Zener diode 26 is for automatically changing the current measurement range (detection resistor). That is, for example, when the breakdown voltage of the Zener diode 26 is set to 3 V, the resistance of the resistor R20 is set to 100 kΩ, and the resistance of the resistor 24 is set to 10 kΩ, the current is 0 to 30 μA (in other words, the ion current signal Si is 3 V or less). , The ion current is equal to the resistance R20
However, when the ion current signal Si exceeds 3 V, the ion current flows through the Zener diode 26 to the resistor R24, so that the resistance value for detecting the ion current is a combination of the resistor R20 and the resistor R24. Resistance (about 10
kΩ).

As a result, the relationship between the ion current and the detection voltage (ion current signal Si) is as shown in FIG.
The ion current is equal to or less than a set value determined by the breakdown voltage of the Zener diode 26 and the resistance value of the resistor R20 (30 μA in the figure).
In the following case, the ion current signal Si changes greatly in response to the change in the ion current, but when the ion current exceeds its set value, the change (gradient) of the ion current signal Si with respect to the change in the ion current is obtained. Becomes smaller, and the change width of the detectable ion current (in other words, the ion current detection circuit 10
Dynamic range). Therefore, according to the ion current detection circuit 10 of the present embodiment, the ion current can be measured over a wide range and with high accuracy.

Next, the ignition control process executed by the control device 12 will be described with reference to the flowchart shown in FIG. The control device 12 is for comprehensively controlling the ignition timing, the fuel injection amount, the idling speed, and the like of the internal combustion engine, and is separately provided for an ignition control process described below.
An operating state detection process is performed to detect the operating state of each part of the internal combustion engine, such as the amount of intake air (intake pipe pressure), rotational speed, throttle opening, cooling water temperature, intake air temperature, and the like.

The ignition control process of this embodiment is performed in one cycle in which the internal combustion engine performs 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. Is executed once every two days. Then, as shown in FIG. 2, when the ignition control process is started, first, in S110 (S represents a step), the operation state (intake of the intake engine) detected in the operation state detection process executed separately is performed. The amount of air, the rotation speed, etc.) are read, and based on the operation state, the ignition timing at which the spark plug 2 is to be spark-discharged, the discharge time indicating the duration of the spark discharge, and the ion current after the end of the spark discharge are detected. Time (sampling time) for sampling ion current signal Si
Is calculated.

The ignition timing is obtained by, for example, obtaining a control reference value using a map or a formula using the intake air amount and the rotation speed of the internal combustion engine as parameters, and correcting the control reference value based on the cooling water temperature, the intake air temperature, and the like. It is calculated by such a procedure. Further, the discharge time is long during low-speed low-load operation of the internal combustion engine where the air-fuel mixture is difficult to ignite, for example, based on the rotation speed of the internal combustion engine and the throttle opening indicating the engine load. It is calculated by using a preset map or calculation formula so that it becomes shorter during high-load operation.

The sampling time is determined based on, for example, the rotational speed of the internal combustion engine and the throttle opening indicating the engine load. It is calculated using a preset map or formula so that it is long during operation and short during high-rotation high-load operation where the time required for the mixture to ignite and burn is short.

Next, in step S120, the power supply start timing for the primary winding L1 necessary for spark discharge of the spark plug 2 at the ignition timing calculated in step S110 is determined, and whether or not the power supply start time has been reached. Is determined, and if a negative determination is made, the same step is repeatedly executed to wait for the power supply start timing. Then, when it is determined in S120 that the energization start time has been reached, the process proceeds to S130,
Change the ignition signal IG from Low to High level (Fig. 3
(See time point t0). As a result, the switching element 8
Is turned on, and a primary current flows through the primary winding L1 of the ignition coil 4. Note that the energizing time of the primary winding L1 is set in advance, and in S120, a time earlier than the ignition timing calculated in S110 by the energizing time is determined by the primary winding L1.
1 is set as the energization start timing.

Next, in S140, it is determined whether or not the ignition timing obtained in S110 has been reached based on the detection signal from the crank angle sensor. If a negative determination is made, the same step is repeatedly executed. Therefore, it waits for the ignition timing. If it is determined in S140 that the ignition timing has been reached, the process proceeds to S150, where the ignition signal IG is set to Hi.
Change from gh to Low level (see time point t1 shown in FIG. 3).

As a result, the switching element 8 is turned off, the current supply to the primary winding L1 is cut off, and a high voltage for ignition (hereinafter referred to as secondary winding) is applied to the ignition plug 2 side of the secondary winding L2 of the ignition coil 4. The voltage on the spark plug 2 side of the line L2 is changed to the secondary voltage V2
) Occurs, and the spark plug 2 performs spark discharge.
At this time, the discharge switch 32 in the ion current detection circuit 10 is in the off state,
A charge for generating a high voltage for detection is accumulated in the capacitor 28 in the inside.

Next, in S160, after the power supply to the primary winding L1 is cut off in S150 (in other words, after the start of spark discharge), it is determined whether or not the discharge time obtained in S110 has elapsed. If it is determined, the same step is repeatedly executed to wait for the discharge time to elapse. Then, when it is determined in S160 that the discharge time has elapsed, the process proceeds to S170, and the ignition signal IG is again set to Lo.
w to a high level, and then at S180, the window signal I to be output to the ion current detection circuit 10
W is changed from Low to High level (see time point t2 shown in FIG. 3).

As a result, the switching element 8 is turned on again, the energization of the primary winding L1 is restarted, the spark discharge of the spark plug 2 is forcibly terminated, and the ion current detection circuit 10 The discharge switch 32 is turned on, and a high voltage for detection having a polarity opposite to that at the time of spark discharge is applied between the electrodes of the ignition plug 2 by the electric charge accumulated in the capacitor 28 in the ion current detection circuit 10. become.

By the operations of S170 and S180, the spark discharge of the spark plug is forcibly terminated, and at the same time immediately after the window signal IW is changed from Low to High level, as shown in FIG. The voltage fluctuation occurs in the winding L2, and the control device 12
Although the ion current signal Si input to the terminal fluctuates greatly,
In the present embodiment, since the self-inductance of the secondary winding L2 is set to a small value, for example, 8H, this fluctuation period is short, and thereafter, if the mixture is ignited and burns to generate ions, The current signal Si fluctuates according to the amount of generated ions, as indicated by the dotted line in FIG. 3. Conversely, if the mixture does not ignite and no ions are generated, the ion current signal Si is As shown by the solid line, the light level quickly converges to the reference level.

Next, in S190, the ion current signal Si output from the ion current detection circuit 10 is fetched,
After execution of the processing of S170 and S180 in S200, S1
It is determined whether or not the sampling time obtained in step 10 has elapsed. If the sampling time has not elapsed, step S19 is performed again.
In a procedure such as shifting to 0, the ion current signal Si output from the ion current detection circuit 10 within the sampling time is sampled.

If it is determined in S200 that the sampling time has elapsed, the flow shifts to S210, where the window signal IW to the ion current detection circuit 10 is set to High.
To a low level to temporarily stop the detection of the ion current (see time point t3 shown in FIG. 3). At S220, a misfire occurs based on the change of the ion current signal Si within the sampling time sampled at S190. Make a decision.

Next, if it is determined in S190 that no misfire has occurred and the air-fuel mixture is burning normally, the process proceeds to S23.
0, and determines whether or not the internal combustion engine has transitioned from the combustion stroke to the exhaust stroke, and waits for the exhaust stroke. When the internal combustion engine enters the exhaust stroke, the process proceeds to S240 and proceeds to ignition. Change the signal IG from High to Low level,
The energization of the primary winding L1 is cut off, and the process is temporarily terminated. This is because if the primary coil L1 is immediately cut off after the misfire determination even though the internal combustion engine is performing normal combustion, spark discharge occurs in the ignition plug 2 and adversely affects the combustion of the air-fuel mixture. This is because it is conceivable.

On the other hand, if it is determined in S190 that the ion current cannot be detected from the ion current signal Si sampled during the sampling time and that a misfire has occurred, the process proceeds to S250, where the ignition signal IG is changed from High to Low level. , The spark discharge for igniting the air-fuel mixture is executed again (see time point t3 shown in FIG. 3).

Then, in S260, the duration of the spark discharge is predicted based on the operation state (rotational speed, load, etc.) of the internal combustion engine, and the time when the duration has elapsed is set as the ion current detection start timing. And then S270
Then, it is determined whether or not the current time has reached the set detection timing, so that the detection timing is waited.

Next, when it is determined in S270 that the detection timing has been reached, the process proceeds to S280, where the window signal IW output to the ion current detection circuit 10 is set to Low, as in S180. To the High level (see time point t4 shown in FIG. 3).

Then, in S290, the ion current signal Si output from the ion current detection circuit 10 is fetched, and in S300, it is determined whether or not the sampling time obtained in S110 has elapsed after execution of the processing of S280. The ion current signal Si output from the ion current detection circuit 10 within the sampling time is sampled in such a procedure that the processing shifts to S290 again if the sampling time has not elapsed.

When it is determined in S300 that the sampling time has elapsed, the flow shifts to S310, where the window signal IW to the ion current detection circuit 10 is set to High.
, And the detection of the ion current is terminated (time t5 shown in FIG. 3). Then, in S320, misfire determination is performed based on the change in the ion current signal Si within the sampling time sampled in S190, the determination result is stored (or displayed), and the process ends.

As described above, the ignition device for an internal combustion engine according to the present embodiment turns the switching element 8 connected in series with the primary winding L1 of the ignition coil 4 on and off, so that the ignition plug 2 This is a full-transistor type ignition device that generates a spark discharge between its electrodes by applying a high voltage, and the self-inductance of the secondary winding L2 of the ignition coil 4 falls within a range of 4H to 16H (for example, 8H). Is set. For this reason, the impedance of the secondary winding L2 becomes extremely small as compared with the conventional ignition device in which the self-inductance of the secondary winding L2 is set to about 20H to 30H, and the duration of the spark discharge of the spark plug 2 is short. Become.

When the internal combustion engine is actually operated,
As shown in FIG. 3, first, during a period from time t0 to time t1 shown in FIG. 3, the spark plug 2 performs spark discharge at the ignition timing (time t1) obtained based on the operation state of the internal combustion engine.
The switching element 8 is turned on to energize the primary winding L1 of the ignition coil 4, and at time t1 when the switching element 8 is turned off, a high voltage for ignition is generated on the secondary winding L2 side of the ignition coil 4 to generate a high voltage for ignition. The spark plug 2 is spark-discharged at a high voltage for ignition.

If the spark discharge is left as it is, it continues until the energy stored in the ignition coil 4 is released by energizing the primary winding L1, but in this embodiment, the spark discharge is continued. A time is measured, and when this reaches a discharge time set based on the operation state of the internal combustion engine, t
2, the switching element 8 is turned on again, and the primary winding L1
To forcibly terminate the spark discharge. For this reason, the duration of the spark discharge of the ignition plug 2 is shorter than that of the conventional ignition device.

When the spark discharge is forcibly terminated, thereafter, the ion current signal Si output from the ion current detection circuit 10 is sampled until the time t3 when the sampling time set based on the operation state of the internal combustion engine elapses. I do. The signal waveform of the sampled ion current signal Si is affected by the voltage fluctuation (fluctuation of the secondary voltage V2) generated in the secondary winding L2 at the end of the spark discharge. Is smaller than that of the prior art, the fluctuation period of the secondary voltage V2 and, consequently, the fluctuation period of the ion current signal Si also become shorter.

For this reason, according to the present embodiment, the time from the start of the spark discharge until the ion current corresponding to the amount of ions generated due to the combustion of the air-fuel mixture can be detected is longer than that of the conventional ignition device. The mixture is easy to ignite, even under operating conditions where the time from the start of spark discharge to the generation of ions by combustion of the mixture is short (during high-speed, high-load operation of the internal combustion engine, etc.). Thus, the ion current can be accurately detected.

In this embodiment, the ion current signal Si
Is completed (time t3), a misfire determination is performed based on the sampled ion current signal Si. In this misfire determination, the signal waveform of the ion current signal Si excluding the fluctuation period of the secondary voltage V2 is used. Thus, misfire determination can always be made accurately regardless of the operating state of the internal combustion engine.

Further, in this embodiment, when a misfire is detected as a result of the misfire determination, the switching element 8 is turned off to cut off the current supply to the primary winding L1, thereby causing the spark plug 2 to discharge the spark again. Let it. Therefore, even if the air-fuel mixture cannot be ignited and burned by the first spark discharge, the air-fuel mixture is ignited and fired by the second spark discharge.
It becomes possible to burn.

In the present embodiment, among the ignition control processes executed by the control device 12, the processes of S120 to S150 function as the ignition control means of the present invention.
The process of 170 functions as the spark discharge suspending unit of the present invention, and the processes of S180 to S220 and S250 function as the re-ignition control unit of the present invention.

As described above, in the present embodiment, the self-inductance of the secondary winding L2 of the ignition coil 4 is set in the range of 4H to 16H, which is extremely smaller than that of the conventional one, so that the ignition plug 2 The duration of the spark discharge and the fluctuation period of the secondary voltage V2 generated at the end of the spark discharge are made shorter than before, and for the duration of the first spark discharge, the spark discharge is forcibly terminated. I try to keep it short.

This is because, as described above, the ion mixture can be easily ignited, and the ion current can be accurately detected even under an operating condition in which the time until the generation of ions after the start of spark discharge is short. Next, various experimental examples supporting these effects will be described. Experimental Example 1 First, FIG. 4 shows a measurement result obtained by measuring the effect of the self-inductance of the secondary winding of the ignition coil on the ionic current using a vehicle equipped with a 1.8-liter, four-cylinder internal combustion engine. Represent.

In FIG. 4, (a) shows a full-transistor type ignition device provided with the same ion current detection circuit as that of the above-described embodiment. (B) is a measurement result of the ion current signal Si, the secondary voltage V2, and the in-cylinder combustion pressure Pi when the vehicle is running at 100 km / h while the engine is operated at a lean air-fuel ratio. It is the measurement result which performed the same experiment using the self-inductance of the winding of 16H, and the same experiment was carried out using the self-inductance of the secondary winding using the ignition coil of 23H. It is a measurement result. The arrow ↑ below each measurement result indicates
Indicates the start timing (ignition timing) of spark discharge. From the measurement result, the self-inductance of the secondary winding is 23
When the ignition coil of H is used, the fluctuation of the secondary voltage V2 generated at the end of the spark discharge lasts long, and the ion current signal S
Since i also vibrates accordingly, it was found that the ion current waveform corresponding to the amount of ions generated due to the combustion of the air-fuel mixture was affected by the vibration. Further, when the self-inductance of the secondary winding is reduced to 16H and 8H, the fluctuation period of the secondary voltage V2 generated at the end of the spark discharge is shortened, and the ion current signal Si is less affected by the fluctuation of the secondary voltage V2. I also understood.

Therefore, in order to accurately detect the ion current from the measurement results of the first experimental example, the self-inductance of the secondary winding of the ignition coil must be set to 20H to 30H as in the conventional case.
It can be seen that it is better to set the value to a smaller value (4H to 16H) than in the related art, as in the above-described embodiment, instead of setting it to the degree.

[Experimental Example 2] Next, FIG. 5 shows a 1.8-liter, four-cylinder internal combustion engine using an ignition device similar to that of Experimental Example 1 using an ignition coil having a secondary winding having a self-inductance of 16H. And how the ion current signal Si changes when the spark discharge of the spark plug is continued to the end during the operation (a) and when the spark discharge is forcibly terminated (b). Shows the measurement results.

In FIG. 5, an arrow t1 below each measurement result indicates the start timing (ignition timing) of spark discharge, and an arrow t1 below (b) indicates that the switching element is re-energized. Represents the timing when the spark discharge is forcibly terminated. In this experiment, the internal combustion engine mounted on the vehicle was used, as in Experimental Example 1. The measurement results in FIG. 5 are values obtained when the vehicle is driven at 100 km / h while the internal combustion engine is operated at stoichiometric (stoichiometric air-fuel ratio).

From this measurement result, when the spark discharge is continued, not only the duration of the spark discharge but also the fluctuation period of the secondary voltage V2 generated at the end of the spark discharge becomes longer, and the ion current signal Si corresponding to the ion amount becomes longer. When the spark discharge is forcibly cut off, the duration of the spark discharge and the fluctuation period of the secondary voltage V2 at the end of the spark discharge are both shortened, and the ion current signal corresponding to the ion amount is reduced. It was found that Si could be obtained.

Therefore, in order to accurately detect the ion current from the measurement results obtained in Experimental Example 3, not only is the self-inductance of the secondary winding of the ignition coil set to a smaller value than in the past, As shown in the example, it can be seen that the spark discharge should be forcibly terminated so that the duration of the spark discharge is as short as possible within a range in which the air-fuel mixture can be ignited. [Experimental Example 3] Next, FIG. 6 shows an ignition device similar to Experimental Example 1 using an ignition coil having a secondary winding having a self inductance of 16H and an ignition coil having a self inductance of 23H, respectively. The 1.8-liter, four-cylinder internal combustion engine is operated while forcibly terminating the spark discharge of the spark plug. During the operation, the ion current signal Si is output when the air-fuel mixture burns normally (ignites) and when it misfires. Represents a measurement result of how the value changes.

In FIG. 6, (a) shows the measurement results when the self-inductance of the secondary winding is 16H and the self-inductance of the secondary winding is 23H. 4 shows the measurement results when the ignition coil was used. Arrows below each measurement result indicate the start timing (ignition timing) of spark discharge. In this experiment, the internal combustion engine mounted on the vehicle was used as in the first and second experimental examples. And the measurement result of FIG.
This is a value obtained when the vehicle is run at 75 km / h while the internal combustion engine is operated at stoichiometry (stoichiometric air-fuel ratio).

From this measurement result, when an ignition coil having a secondary winding of 23H in self-inductance is used, it is not possible to determine the misfire / ignition of the air-fuel mixture from the ion current signal Si due to the vibration generated after the end of the spark discharge. On the other hand, when an ignition coil having a secondary winding of 16H in self-inductance is used, since the period of occurrence of the vibration generated after the end of the spark discharge is short, the ion current signal S
It was found from the signal waveform of i that the misfire / ignition of the air-fuel mixture can be accurately determined.

Therefore, in order to accurately detect the ion current also from the measurement results obtained in Experimental Example 3, the self-inductance of the secondary winding of the ignition coil was set to a smaller value (4H to 16H) than in the past. It turns out that it is better. [Experimental Example 4] Next, FIG. 7 shows that ignition control of the following (1) to (3) is performed using the ignition coil of the above embodiment in which the self-inductance of the secondary winding is set to 23H. , 2
L, 6-cylinder internal combustion engine is operated, and the air-fuel ratio (A / F) of the air-fuel mixture that can operate the internal combustion engine in each ignition control is measured (a), and the combustion pressure in the cylinder in each ignition control 10B shows a measurement result (b) obtained by measuring the variation of Pi.

(1) Conventional ignition control in which spark discharge is executed only once without limiting the duration of spark discharge (the duration is 2.0 msec.). (2) Ignition control for limiting the duration of spark discharge to 1.5 msec. And 0.7 msec., Respectively, and executing the spark discharge only once.

(3) Spark discharge is performed while limiting the duration of spark discharge to 0.7 msec. After the first spark discharge, a misfire determination is made based on the ion current signal Si. The same ignition control as in the above embodiment for executing the discharge. The operating conditions of the internal combustion engine in this experiment were as follows:
Rotation speed: 2000 rpm, boost (negative suction pressure): 1
30 mmHg.

From the measurement result (a), in the ignition control in which the spark discharge is performed only once, if the duration of the spark discharge is too short (0.7 msec. In the present measurement result), the mixture is ignited. It has been found that the operating region in which the air-fuel ratio cannot be operated increases, and the upper limit of the air-fuel ratio of the air-fuel mixture that can be operated becomes low.
However, even if the duration of the spark discharge is similarly limited, if the misfire determination is performed and the spark discharge is executed again when the misfire is detected as in the above-described embodiment, the air-fuel mixture is generated in the second spark discharge. Ignited, and the upper limit of the air-fuel ratio of the operable mixture was found to be about the same as that of conventional ignition control.

On the other hand, from the measurement result (b), in the ignition control in which the spark discharge is performed only once, if the duration of the spark discharge is too short (in this measurement result, 0.7 msec.), The mixture is ignited. Because the operating area that can not do it increases,
It was found that the internal combustion engine could not be operated stably, and the variation in the in-cylinder combustion pressure Pi during the operation of the internal combustion engine became large. However, even if the duration of the spark discharge is similarly limited, if the misfire determination is performed as in the above-described embodiment and the spark discharge is executed again when the misfire is detected, the internal combustion engine can be stably operated. It has been found that the variation in the in-cylinder combustion pressure Pi during the operation of the internal combustion engine is almost the same as that of the conventional ignition control.

Therefore, based on the measurement results obtained in Experimental Example 4, the self-inductance of the secondary winding of the ignition coil was set to a small value (4H to 16H), and the duration of spark discharge of the ignition plug was changed according to the operating state. In this case, after the spark discharge, a misfire determination is performed using the ion current signal Si, and when the misfire is detected, the spark plug may be re-discharged. I understand. [Experimental example 5] Next, the knocking detection accuracy based on the ion current detected in the ignition device using the conventional ignition coil and the knocking detection based on the ion current detected in the ignition device using the ignition coil of the present invention. In order to compare the accuracy with the accuracy, a knocking signal component superimposed on the ion current signal Si when knocking occurred was measured (simulated) with the circuit configuration shown in FIG. FIG. 9 shows the simulation result.

In this simulation, as shown in FIG. 8, a battery 6 and a switching element 8 composed of an NPN power transistor are connected to both ends of a primary winding L1 of an ignition coil 4 respectively, and a secondary winding is formed. One end of L2 (the side opposite to the actual igniter shown in FIG. 1) has an outer electrode 2
a is the center electrode 2b of the spark plug 2 grounded to ground
And the other end of the secondary winding L2 is connected via a capacitor 28 to the other end of the resistor 20 whose one end is grounded, and the cathode is connected between the resistor 20 and the capacitor 28. An ignition circuit for simulation was used in which the anode of the diode 22 was connected, and the cathode of a Zener diode 34 whose anode was grounded was connected to the secondary winding side of the capacitor 28. Since these components are the same as those in the above embodiment, they are denoted by the same reference numerals.

A high resistance (1 MΩ) resistor 50 serving as an ion current path is connected in parallel to the ignition plug 2, and a circuit for superimposing a knocking signal component on the ion current is connected in parallel. Connected. The circuit for superimposing the knocking signal has an anode connected to the center electrode 2 of the spark plug 2.
A diode 52 connected to the b side and an emitter connected to a resistor 5
6, an NPN-type transistor 53 grounded to ground, one end connected to the cathode of the diode 52, the other end connected to the collector of the transistor 53, and a resistor connected to the base of the transistor 53. 58, and the transistor 5
By applying a drive signal having a frequency of 7 kHz or 14 kHz to the base of No. 3, a knocking signal component can be superimposed on the ion current.

In this simulation, the self-inductance of the secondary winding L2 is 4H, 8H, 16H,
Four types of ignition coils set at 23H were used. Then, for each ignition circuit having these ignition coils, the switching element 8 is turned on / off to generate a spark discharge between the electrodes of the ignition plug 2 and charge the capacitor 28. The leak current (ion current for simulation) is caused to flow through the resistor R50 by the detection high voltage charged to the transistor 28, and at the same time, the transistor 53 is switched by a drive signal having a frequency of 7 kHz or 14 kHz, whereby the electrode of the ignition plug 2 is switched. From the resistor R50, the equivalent resistance between the resistors R50, R54, and R56 is calculated as the combined resistance (= R50 × (R54 + R5
6) / (R50 + R54 + R56), and the voltage Vi generated at both ends of the ion current detection resistor 20 at that time was analyzed by FFT (Fast Fourier Transform). The analysis result is the simulation result shown in FIG.

As shown in FIG. 9, when the ignition coil 4 having a secondary winding L2 having a self-inductance of 4H is used, the detection signal Vi of the ionic current includes the same signal components as the switching frequencies 7kHz and 14kHz of the transistor 53. , And the harmonic components of these signals are superimposed. But,
The self-inductance of the secondary winding L2 of the ignition coil 4 is:
The levels of these signal components decrease as they increase to 8H, 16H, and 23H. In particular, when the self-inductance of the secondary winding L2 is 23H and the ignition coil 4 is used, harmonic components exceeding 14 kHz are generated. It turned out that it was buried in noise and could not be measured.

Therefore, from the simulation result of this experimental example 5, it is found that the knocking can be accurately detected from the ion current signal Si detected by using the ion current detection circuit, because the self inductance of the secondary winding L2 of the ignition coil 4 is required. Is set to a smaller value (4H to 16H) than before.

The level of the knocking signal component superimposed on the ionic current decreases as the self-inductance of the secondary winding L2 of the ignition coil 4 increases.
It is considered that this is because the entire ignition system becomes a low-pass filter due to the capacitance component of each part of the ignition system connected thereto, and the high-frequency knock signal component is attenuated. [Experimental Example 6] Next, FIGS. 10 to 14 show the effect of the self-inductance of the secondary winding of the ignition coil on the knocking detection accuracy based on the ionic current using a 2L, 4 cylinder internal combustion engine. Indicates the measurement result actually measured.

In Experimental Example 6, the internal combustion engine was operated without knocking and knocking using five types of ignition coils in which the self-inductance of the secondary winding was set to 4H, 8H, 12H, 16H, and 23H. Driving in the presence state. In addition, during this operation, in order to compare the detection accuracy of knocking based on ion current, the detection accuracy of knocking based on combustion pressure in the cylinder, and the detection accuracy of knocking using a knock sensor that detects vibration of the internal combustion engine, The rotation speed of the internal combustion engine is 1600 [rpm], 4000 [rp]
m.] and 6000 [rpm], the following measurements (1) to (3) were performed in accordance with each of these knocking detection methods.

(1) An ion current is detected using the same ion current detection circuit as in the above embodiment, and the obtained ion current signal Si is passed through a band-pass filter having a frequency band of 3 kHz to 20 kHz to obtain an ion current signal Si. Is extracted, and the extracted knocking signal component is integrated during a predetermined knock determination period.

(2) The detection signal from the pressure sensor for detecting the combustion pressure in the cylinder is converted into a frequency band of 3 kHz to 20 kHz.
The knocking signal component was extracted by passing through a band pass filter of No. 1, and the extracted knocking signal component was integrated during a predetermined knock determination period. (3) The detection signal from the knock sensor is converted to a frequency band of 3 kHz.
The knocking signal component was extracted through a bandpass filter of z to 20 kHz, and the extracted knocking signal component was integrated during a predetermined knock determination period.

Then, the integrated value of each signal obtained by the measuring methods (1) to (3) is calculated by using the integrated value obtained when knocking occurs in the internal combustion engine and the integrated value obtained when knocking occurs in the internal combustion engine. The ratio of the average value of each value was determined as the S / N ratio (= integral value when knocking occurred / integral value when knocking did not occur).

FIGS. 10 to 14 show the results (S / N ratio), and FIG. 10 shows the S / N ratio when the self-inductance of the secondary winding of the ignition coil is 4H.
Is the S / N ratio when the same is 8H, FIG. 12 is the S / N ratio when the same is 12H, FIG. 13 is the S / N ratio when the same is 16H, and FIG. Also 23
The S / N ratio when H is shown, respectively.

From the measurement result, the secondary winding L2
Has a self inductance of 4H to 8H, 12H, 1
6H, the detection accuracy (S / N ratio) of knocking based on the ion current decreases, and the secondary winding L
When the self-inductance of No. 2 was set to 23H, the knocking detection accuracy (S / N) based on the ion current was found to be worse than the detection accuracy (S / N) obtained by the knock sensor.

Therefore, also from this Experimental Example 6, it is desirable to minimize the self-inductance of the secondary winding of the ignition coil as much as possible in order to improve the knocking detection accuracy based on the ion current. It was found that the knocking detection accuracy could not be ensured.

In order to accurately detect the ionic current corresponding to the operating state of the internal combustion engine from the above various experimental examples, it is necessary to set the self-inductance of the secondary winding of the ignition coil to a value as small as 16H or less. I just found out. Therefore, in order to confirm the lower limit of the self-inductance, an ignition coil having a self-inductance of the secondary winding smaller than 4H was manufactured, and the same experiment as above was performed. Is also small,
It was found that the duration of spark discharge required for ignition of the air-fuel mixture could not be secured, and that the internal combustion engine could not be operated normally. Therefore, the self-inductance of the secondary winding of the ignition coil needs to be set to 4H or more.

The embodiments of the present invention and various experimental examples supporting the effects have been described above. However, the present invention is not limited to the above-described embodiments, and various embodiments can be adopted. For example, in the above embodiment, after the spark discharge of the spark plug, if a misfire is detected from the ionic current, the spark plug is again spark-discharged. The process as the re-ignition control means may be executed a plurality of times. Specifically, when misfire is detected in S220 of FIG. 2, the number of consecutive misfires is counted, and if the count value has reached a set value indicating the number of times reignition can be performed, the process proceeds to S25.
If the count value does not reach the set value indicating the number of times that re-ignition can be performed, the process may return to S150 to cause the spark plug to perform spark discharge. And
This makes it possible to more reliably ignite and burn the air-fuel mixture.

Further, in the above embodiment, the number of spark discharges of the ignition plug until the misfire is determined from the ion current is one. However, for example, as shown in FIG. The switching element 8 is continuously turned on and off a plurality of times by continuously inverting (three times in the figure), and the spark plug is continuously spark-discharged a plurality of times, and then the last spark discharge is completed. (forced termination)
After that, the misfire may be determined by detecting the ion current. And in this way, even in the case of an internal combustion engine having a long duration of spark discharge required to ignite and burn the air-fuel mixture, as in the above-described direct injection type internal combustion engine,
The mixture can be more reliably ignited.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration and an ion current detection characteristic of an ignition device for an internal combustion engine according to an embodiment.

FIG. 2 is a flowchart illustrating an ignition control process performed by a control device.

FIG. 3 is a time chart illustrating a signal waveform of each unit of the apparatus in accordance with an ignition control process.

FIG. 4 is a graph showing measurement results obtained in Experimental Example 1.

FIG. 5 is a graph showing measurement results obtained in Experimental Example 2.

FIG. 6 is a graph showing measurement results obtained in Experimental Example 3.

FIG. 7 is a graph showing measurement results obtained in Experimental Example 4.

FIG. 8 is an electric circuit diagram showing a simulation ignition circuit used in Experimental Example 5.

FIG. 9 is a graph showing a simulation result according to Experimental Example 5.

FIG. 10 is a graph showing measurement results when the self-inductance of the secondary winding is set to 4H in Experimental Example 6.

11 is a graph showing measurement results when the self-inductance of the secondary winding is set to 8H in Experimental Example 6. FIG.

FIG. 12 is a graph showing measurement results when the self-inductance of the secondary winding is set to 12H in Experimental Example 6.

FIG. 13 is a graph showing measurement results when the self-inductance of the secondary winding is set to 16H in Experimental Example 6.

FIG. 14 is a graph showing measurement results when the self-inductance of the secondary winding was set to 23H in Experimental Example 6.

FIG. 15 is a time chart for explaining another example of the ignition control process.

[Explanation of symbols]

2 ... spark plug, 2a ... outer electrode, 2b ... center electrode, 4
... Ignition coil, L1 ... Primary winding, L2 ... Secondary winding, 6 ...
Battery, 8 switching element, 10 ion current detection circuit, 12 controller, 20, 24 resistor, 22 diode, 26, 34 Zener diode, 28 capacitor, 30 charging diode, 32 discharging switch.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shigeru Miyata 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi F-term (reference) in Japan Special Ceramics Co., Ltd. 3G019 AA09 BB06 CD06 GA14 GA16 KC04 LA05 3G084 BA16 FA24 FA25

Claims (5)

[Claims] An ignition coil having one end of a secondary winding connected to an ignition plug; a switching element for energizing and interrupting a primary current flowing through the primary winding of the ignition coil in accordance with an external command; By turning on and off the element, a high voltage for ignition is generated in the secondary winding of the ignition coil,
An ignition device for an internal combustion engine, comprising: ignition control means for causing a spark discharge of the ignition plug; and ion current detection means for detecting an ion current flowing between the electrodes of the ignition plug after the spark discharge of the ignition plug. The ignition device for an internal combustion engine, wherein a self-inductance of the secondary winding of the ignition coil is set in a range of 4H to 16H. 2. The apparatus according to claim 1, wherein said ion current detection means applies a detection high voltage having a polarity opposite to that of the ignition high voltage to said ignition plug after spark discharge of said ignition plug. An ignition device for an internal combustion engine. 3. An ignition / misfire of the air-fuel mixture is determined based on the ion current detected by the ion current detection means. When the misfire is determined, the switching element is driven again to discharge the spark plug again. The ignition device for an internal combustion engine according to claim 1, further comprising a re-ignition control means. 4. The ignition control means continuously turns on and off the switching element a plurality of times at a combustion timing of one combustion cycle of the internal combustion engine, thereby causing the spark plug to discharge a plurality of sparks continuously. 2. The ignition device for an internal combustion engine according to claim 1, wherein said ion current detection means detects an ion current after said ignition control means makes a spark discharge of said ignition plug a plurality of times in succession. 5. An ignition device for an internal combustion engine according to claim 1, further comprising spark discharge stopping means for stopping spark discharge of said spark plug in accordance with an operation state of the internal combustion engine.