JP3565059B2 - Ignition control device for direct injection spark ignition type internal combustion engine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ignition control device for a direct-injection spark ignition type internal combustion engine, and more particularly, to a technique for recovering combustibility (ignition energy) by burning a deposit attached to a spark plug by air discharge.
[0002]
[Prior art]
Conventionally, in a direct-injection spark ignition type internal combustion engine, if insulation resistance is reduced due to adhesion of a deposit to a spark plug, ignition energy is reduced and a misfire occurs. When it is determined that the ignition control is performed, the ignition signal is simultaneously applied to the ignition coil units of the cylinders other than the ignition control target cylinder at the ignition timing of the ignition control target cylinder, so that the so-called idle air which does not participate in the ignition combustion of the air-fuel mixture is provided. There has been an ignition control device configured to cause discharge, thereby burning the deposit and recovering ignition energy (see Japanese Patent Application Laid-Open No. 9-303189).
[0003]
[Problems to be solved by the invention]
By the way, as described above, in the configuration in which the ignition signal is simultaneously applied to the ignition coil units of the cylinders other than the cylinder whose ignition is to be controlled at the ignition timing, the timing for performing the idle discharge in the case of the four-cylinder engine is determined by the ignition timing. After 180 ° CA (late stage of expansion stroke), after 360 ° CA of ignition timing (late stage of exhaust stroke), and after 540 ° CA of ignition timing (late stage of intake stroke). It has the common characteristic that it is a relatively low period.
[0004]
On the other hand, between the discharge voltage of the spark plug and the in-cylinder gas density, as shown in FIG. 4, the discharge voltage decreases as the in-cylinder gas density decreases, so that sparks can easily fly between regular gaps. Are known.
[0005]
That is, the conventional air discharge control for recovery of the ignition energy is to perform the air discharge under the condition that the spark is easy to fly between the regular gaps, and the deposit adheres to the insulator around the center electrode. Even if it is the case, sparks fly in the regular gap between the center electrode and the ground electrode, and the current flowing through the deposit and leaking to the ground electrode is small, so that the deposit is effectively burned. Therefore, there is a problem that the effect of recovering the ignition energy cannot be sufficiently obtained.
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a deposit adhered on an insulator around a center electrode of a spark plug is effectively burned by air discharge, so that a recovery of combustibility (ignition energy) can be reliably obtained. An object of the present invention is to provide an ignition control device for a direct injection spark ignition type internal combustion engine.
[0007]
[Means for Solving the Problems]
Therefore, according to the first aspect of the present invention, the ignition control of a direct injection spark ignition type internal combustion engine having an operating condition for performing fuel injection in a compression stroke is provided for each cylinder with a fuel injection valve having an injection port facing the cylinder. An apparatus which, in addition to the discharge of the spark plug at a normal ignition timing, is configured to perform an empty discharge of the spark plug when the deterioration of the flammability is determined, and to deposit around the center electrode of the spark plug. The configuration is such that the above-mentioned empty discharge is performed under the in-cylinder gas density condition in which a current flows along.
According to such a configuration, the discharge voltage of the ignition plug becomes higher as the in-cylinder gas density becomes higher, and the discharge spark becomes more difficult to fly between regular gaps as the discharge voltage becomes higher. Since the empty discharge below increases the leakage current flowing through the deposit around the center electrode, the effect of the deposit is made by performing the empty discharge under the in-cylinder gas density condition where the current flows along the deposit. Burn.
[0008]
According to the second aspect of the present invention, there is provided an ignition control device for a direct injection spark ignition type internal combustion engine having a fuel injection valve having an injection port facing a cylinder for each cylinder, and having operating conditions for performing fuel injection in a compression stroke. Therefore, in addition to the discharge of the ignition plug at the normal ignition timing, when the deterioration of the flammability is determined, the discharge of the ignition plug is performed so as to perform the idle discharge. The highest timing is detected based on engine operating conditions, and the idle discharge is performed at the detected timing.
According to such a configuration, by performing the idle discharge at the time when the in-cylinder gas density becomes the highest, the current flows reliably along the deposit around the center electrode, and the deposit burns effectively.
[0009]
According to the third aspect of the invention, the timing of the idle discharge is set to be immediately before the fuel injection in the compression stroke.
According to such a configuration, before the fuel injection during the compression stroke, the discharge is not involved in the ignition combustion of the fuel, and the discharge becomes an empty discharge. With such a configuration, the empty discharge is performed under the condition that the in-cylinder gas density is as high as possible.
[0011]
According to the fourth aspect of the present invention, the combustion period from the normal ignition operation is detected based on the engine operating conditions, and the idle discharge time is set immediately after the combustion period during the expansion stroke .
According to this configuration, the timing of the air discharge during the expansion stroke is controlled in response to the fact that the combustion period after the normal ignition operation changes according to the engine operating conditions (engine load, engine speed). The air discharge can be performed at a time when the in- cylinder gas density is as high as possible during the expansion stroke, and at a time when unburned components remaining until the latter stage of combustion adhere to the ignition plug to generate a deposit.
[0012]
According to a fifth aspect of the present invention, the idle discharge is performed only in an idle operation state of the engine.
According to this configuration, even when the idle discharge is performed immediately before the fuel injection during the compression stroke, the idle discharge is not performed when the engine is not in the idle operation state.
[0013]
The idle operation state of the engine is a condition in which the temperature of the ignition plug is low, and the discharge voltage becomes higher as the temperature of the ignition plug becomes lower, and the discharge spark becomes difficult to fly between the regular gaps. , The deposits are more effectively burned as compared with the operation state in which the temperature of the other ignition plugs is high.
[0014]
In the invention according to claim 6 , the timing of the idle discharge is set to be near the compression top dead center in the fuel cut state.
According to such a configuration, under the condition that fuel injection is stopped such as deceleration fuel cut, there is no fuel near the ignition plug near the compression top dead center where the in-cylinder gas density becomes highest, and there is no fuel near the compression top dead center. The discharge operation of the ignition plug in the above becomes idle discharge, and the idle discharge is performed under the condition that the in-cylinder gas density (discharge voltage) is the highest.
[0015]
【The invention's effect】
According to the first and second aspects of the present invention, there is an effect that the electric current flows reliably along the deposit around the center electrode of the ignition plug by the empty discharge, and the deposit can be effectively burned.
[0016]
According to the third aspect of the present invention, there is an effect that the air discharge can be performed during the compression stroke and as close to the top dead center as possible and under the condition that the in-cylinder gas density is maximized.
[0017]
According to the fourth aspect of the present invention, there is an effect that it is possible to perform the empty discharge under the condition where the in-cylinder gas density is the highest while avoiding the combustion period during the expansion stroke.
According to the fifth aspect of the present invention, the deposit can be more effectively burned by performing the idle discharge only under the condition that the temperature of the spark plug is low and the discharge voltage is high.
[0018]
According to the sixth aspect of the present invention, there is an effect that an empty discharge can be performed near the top dead center where the in-cylinder gas density becomes highest in the fuel cut state.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing a control system of a four-cycle type automobile gasoline engine which is a direct injection spark ignition type internal combustion engine.
[0020]
In FIG. 1, a high voltage is individually applied to a spark plug 1 provided for each cylinder from a secondary side of an ignition coil 2 provided for each spark plug 1. The energization of the primary side of each ignition coil 2 is controlled by an engine control unit (hereinafter referred to as ECU) 3.
[0021]
The ECU 3 receives detection signals from a crank angle sensor 4 for detecting a crank angle, a cylinder detection sensor for performing a cylinder determination, and a throttle sensor 6 for detecting the opening of a throttle valve (not shown). Although not shown, the ECU 3 includes an air-fuel ratio sensor for detecting the air-fuel ratio of the combustion mixture based on the oxygen concentration in the exhaust gas and an air flow meter for measuring the intake air amount of the engine, in addition to the various sensors. And a detection signal from a water temperature sensor or the like for detecting the temperature of the cooling water of the engine.
[0022]
The ECU 3 calculates the fuel injection timing and the fuel injection amount based on the detection signals from the various sensors, and according to the calculation result, the fuel provided for each cylinder with the injection port facing the cylinder. An injection valve drive signal is output to the injection valve 13 to control fuel injection.
[0023]
More specifically, the target air-fuel ratio is set based on the engine operating conditions such as the engine load, the engine speed, the water temperature, and the time after starting, and the homogeneous combustion by the fuel injection in the intake stroke and the fuel injection in the compression stroke are performed. And stratified combustion. Then, a fuel injection amount for controlling to the target air-fuel ratio is calculated, and an injection timing is calculated for each of the homogeneous combustion and the stratified combustion, and the injection timing has a pulse width corresponding to the fuel injection amount. A valve drive signal is output to the fuel injection valve 13 of the cylinder at the injection timing.
[0024]
Further, the ECU 3 calculates an ignition timing based on an engine load, an engine rotation speed, and the like, and discharges the calculated ignition timing to the ignition control target cylinder determined by the cylinder determination sensor 5. An ignition signal is output to the ignition coil 2 to control energization of the primary side of the ignition coil 2.
[0025]
By the way, when the fuel injection is performed in the compression stroke, the time from the fuel injection to the ignition timing is short, so that the fuel is insufficiently vaporized and incomplete combustion occurs. As a result, as shown in FIG. The combustion component may adhere to the insulator 8 around the center electrode 7 of the spark plug 1 to generate a deposit 10. The deposit 10 lowers the insulation resistance of the spark plug 1 and prevents discharge between the regular ignition gap between the center electrode 7 and the ground electrode 9, thereby lowering ignition energy and causing misfire. It becomes a factor.
[0026]
Therefore, the ECU 3 is configured to recover the ignition energy by causing the deposit 10 to burn by causing the discharge of the spark plug 1 that is not involved in the ignition combustion of the air-fuel mixture, that is, by causing the idle discharge.
[0027]
Here, a first embodiment of the idle discharge control will be described with reference to the flowchart of FIG.
In the flowchart of FIG. 2, first, in step S1, it is determined whether or not a stratified combustion condition under which fuel injection is performed in the compression stroke. If the stratified combustion condition, the process proceeds to step S2.
[0028]
In step S2, it is determined whether the combustion state has deteriorated.
The deterioration of the combustion state can be determined using various known means. For example, a state in which the misfire frequency is equal to or higher than a predetermined value can be determined as the deterioration state of the combustion state. Further, when the stratified combustion conditions have continued for a predetermined time or more, the deterioration of the combustion state due to the generation of the deposit 10 may be estimated. Further, as shown in FIG. 1, a spark plug resistance detecting means 12 for detecting the insulation resistance of the spark plug 1 may be provided to directly detect a decrease in the insulation resistance due to the generation of the deposit 10.
[0029]
If it is determined in step S2 that the combustion state has deteriorated, the process proceeds to step S3, and immediately before the fuel injection is performed in the compression stroke, the fuel injection is performed in the compression stroke in order to cause the spark plug 1 to discharge in the same cylinder. The ignition signal is output to the ignition coil 2 of the cylinder in which the operation is performed.
[0030]
If the discharge is performed by the spark plug 1 immediately before the fuel injection is performed, no fuel is present in the vicinity of the spark plug 1, so that the discharge is idle.
After the discharge immediately before the fuel injection is performed, the ignition signal is continuously output to the same ignition coil 2 so as to perform the discharge at the normal ignition timing. That is, as shown in FIG. 3, in the cylinder in the compression stroke in which the injection valve drive signal a is output, in the same compression stroke after the ignition signal c for the air discharge substantially synchronized with the injection valve drive signal a, An ignition signal b for igniting and burning the fuel is output.
[0031]
As described above, the timing of the idle discharge is arbitrarily controlled independently of the normal ignition timing, and the idle discharge is performed during the compression stroke and immediately before the fuel reaches the ignition plug 1. With this configuration, empty discharge can be performed under the condition that the in-cylinder gas density is as high as possible, whereby the deposit 10 around the center electrode 7 can be effectively burned.
[0032]
As shown in FIG. 4, when the in-cylinder gas density is high, the discharge voltage becomes high, making it difficult for sparks to fly between the regular gaps, and depositing on the insulator 8 around the center electrode 7 of the ignition plug 1. In this case, as shown in FIG. 5, the discharge current leaks to the ground electrode 9 via the conductive deposit 10 or does not fly through the regular gap, or After passing, sparks will fly in the interior of the housing pocket 11 where the gap is smaller than the regular gap. In other words, if an empty discharge is performed as much as possible during the compression stroke in which the in-cylinder gas density becomes high, current flows reliably along the deposit 10 around the center electrode 7 and the deposit 10 is effectively burned. Can be done.
[0033]
The idle discharge during the compression stroke may be performed at a fixed timing in the first half of the compression stroke in which fuel injection is not performed. However, if the discharge is synchronized with the injection valve drive signal as described above, the idle discharge is preferably performed. When the discharge timing is delayed, the idle discharge can be performed when the in-cylinder gas density is as high as possible, and the deposit 10 can be more reliably burned.
[0034]
By the way, as shown in FIG. 7, the lower the temperature of the electrode of the spark plug 9 is, the higher the discharge voltage is, the more difficult it is for a spark to fly between the gaps, and the easier it is for the current to flow along the deposit 10. As in the second embodiment shown in the flow chart, the air discharge immediately before the injection during the compression stroke shown in the flow chart of FIG. 2 is performed during the idling operation of the engine in which the electrode temperature of the ignition plug 1 becomes low (low load, low load). (During rotation).
[0035]
In the flowchart of FIG. 6, in step S11, it is determined whether or not the engine is in a predetermined idle operation state (low load, low rotation state), and only when the engine is in the idle operation state, the process proceeds to step S12 and thereafter.
[0036]
Then, when it is determined in step S12 that the stratified combustion condition is satisfied, and when it is determined in step S13 that the combustibility has deteriorated, the process proceeds to step S14, in which idle discharge is performed immediately before fuel injection in the compression stroke.
[0037]
If the idle discharge is performed during the idling operation and immediately before the fuel injection during the compression stroke in which the in-cylinder gas density is high, the discharge voltage increases due to the temperature condition of the ignition plug 1 and the in-cylinder Since the discharge voltage is increased due to the gas density condition, sparks are less likely to fly between the regular gaps, and the deposit can be more effectively burned by the empty discharge.
[0038]
In the above description, the air discharge is performed during the compression stroke under the stratified combustion condition and immediately before the fuel reaches the ignition plug 1. However, the condition that the in-cylinder gas density is high causes the air discharge during the expansion stroke. The discharge may be performed.
[0039]
In the flowchart of FIG. 8 showing the third embodiment, if it is determined in step S21 that the stratified combustion condition is satisfied, and if it is determined in step S22 that the combustibility has deteriorated, the process proceeds to step S23, in which the combustion in the expansion stroke is performed. An empty discharge is performed immediately after the period.
[0040]
Since the combustion period varies depending on the engine load and the engine rotation speed, the period d (see FIG. 9) from the normal ignition b to the idle discharge c depends on the engine load and the engine rotation speed as shown in FIG. What is necessary is just to determine as map data.
[0041]
As described above, if the idle discharge is performed immediately after the combustion period, independently of the ignition timing, as early as possible during the expansion stroke, that is, the in-cylinder gas density (discharge voltage) as much as possible during the expansion stroke Air discharge can be performed at a high time, and deposit combustion by air discharge can be performed effectively.
[0042]
It should be noted that the idle discharge in the above expansion stroke may be performed only during the idling operation.
By the way, in the first and second embodiments, the idle discharge is performed immediately before the fuel injection is performed by the output of the ignition signal synchronized with the injection valve drive signal. However, the condition for stopping the fuel injection is described. Even in the case of (fuel cut condition) and the injection valve drive signal is not output, the fourth embodiment shown in the flowchart of FIG. As shown in the figure, it is preferable to perform the idle discharge.
[0043]
In the flowchart of FIG. 11, in step S31, it is determined whether or not a deceleration fuel cut is performed on condition that the throttle valve is fully closed and the engine speed is equal to or higher than a predetermined speed. If it is the fuel cut condition, the process proceeds to step S32, where the injection timing during the compression stroke immediately before entering the fuel cut condition is stored, and in the next step S33, the fuel injection is stopped.
[0044]
In step S34, it is determined whether or not the flammability is deteriorated. If the flammability is deteriorated, the process proceeds to step S35, and the ignition coil 2 of the cylinder in the compression stroke is synchronized with the stored injection timing. , An idle signal is output to generate an idle discharge.
[0045]
Here, the discharge at the ignition timing after the idle discharge synchronized with the injection timing is also an idle discharge because the fuel is being cut and no fuel is present near the spark plug 1, and as a result, two discharges are performed during one cycle. An empty discharge will be performed.
[0046]
By the way, during the fuel cut as described above, the discharge is not limited by the injection timing and the combustion period and the discharge is performed at any timing, and the idle discharge is performed. Therefore, the fifth embodiment shown in the flowchart of FIG. As shown in the embodiment, when the fuel is being cut, an ignition signal is output in the vicinity of the compression top dead center so that the idle discharge can be performed under the condition of the highest in-cylinder gas density.
[0047]
In the flowchart of FIG. 12, in step S41, it is determined whether a fuel cut condition is satisfied. If so, the process proceeds to step S42 to stop fuel injection.
[0048]
Further, in step S43, it is determined whether the flammability has deteriorated. If the flammability has deteriorated, the process proceeds to step S44, in which the discharge at the normal ignition timing is stopped, and the ignition timing is reduced. An ignition signal is output to the corresponding cylinder in the vicinity of the compression top dead center, which is further delayed than it, to cause an idle discharge. Note that, at the time of fuel cut, an ignition timing for air discharge for burning the deposit may be set, and the air discharge may be performed near the compression top dead center by the output of an ignition signal according to the ignition timing.
[0049]
Although the compression top dead center is a timing after the normal injection timing, it is a condition under which the fuel cut is performed. Of course, the gas density in the cylinder is high near the compression top dead center, and the temperature of the spark plug 1 is low under the fuel cut condition. 7. The discharge current can be reliably applied to the deposits adhered to the surroundings, and the deposits can be burned effectively.
[0050]
It should be noted that the configuration may be such that the air discharge is performed near the compression top dead center as well as at the time near the compression top dead center as much as possible during the preceding compression stroke and / or expansion stroke.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a control system of a direct injection spark ignition type internal combustion engine according to an embodiment.
FIG. 2 is a flowchart showing a first embodiment of idle discharge control.
FIG. 3 is a time chart showing a state of discharge in the first embodiment.
FIG. 4 is a diagram showing a correlation between in-cylinder gas density and discharge voltage.
FIG. 5 is a partially enlarged view for explaining a detailed structure of a spark plug and a state of attachment of a deposit.
FIG. 6 is a flowchart illustrating a second embodiment of idle discharge control.
FIG. 7 is a diagram showing a correlation between an electrode temperature and a discharge voltage.
FIG. 8 is a flowchart showing a third embodiment of idle discharge control.
FIG. 9 is a time chart showing a state of discharge in the third embodiment.
FIG. 10 is a diagram showing a map for obtaining a period d for determining a timing of idle discharge in the third embodiment.
FIG. 11 is a flowchart illustrating a fourth embodiment of idle discharge control.
FIG. 12 is a flowchart showing a fifth embodiment of the idle discharge control.
[Explanation of symbols]
1 spark plug 2 ignition coil 3 engine control unit (ECU)
Reference Signs List 4 Crank angle sensor 5 Cylinder discrimination sensor 6 Throttle sensor 7 Center electrode 8 Insulator 9 Ground electrode 10 Deposit 11 Housing pocket 12 Spark plug resistance detecting means 13 Fuel injection valve

Claims (6)

An ignition control device for a direct-injection spark ignition type internal combustion engine having a fuel injection valve having an injection port facing a cylinder in each cylinder, and having operating conditions for performing fuel injection in a compression stroke,
In addition to the discharge of the ignition plug at the normal ignition timing, the configuration is such that the discharge of the ignition plug is performed when the deterioration of the flammability is determined,
An ignition control device for a direct-injection spark ignition type internal combustion engine , wherein the idle discharge is performed under an in-cylinder gas density condition in which a current flows along a deposit around a center electrode of the ignition plug . An ignition control device for a direct-injection spark ignition type internal combustion engine having a fuel injection valve having an injection port facing a cylinder in each cylinder, and having operating conditions for performing fuel injection in a compression stroke,
In addition to the discharge of the ignition plug at the normal ignition timing, the configuration is such that the discharge of the ignition plug is performed when the deterioration of the flammability is determined,
Ignition of a direct-injection spark-ignition type internal combustion engine , wherein a timing at which fuel is not ignited and burned and a gas density in a cylinder is the highest is detected based on engine operating conditions, and the idle discharge is performed at the detected timing. Control device. 3. The ignition control device for a direct injection spark ignition type internal combustion engine according to claim 2 , wherein the timing of the idle discharge is immediately before fuel injection in a compression stroke. 3. The direct injection spark according to claim 2 , wherein a combustion period from a normal ignition operation is detected based on an engine operating condition, and a time immediately after the combustion period during an expansion stroke elapses is set as the idle discharge timing. An ignition control device for an ignition type internal combustion engine. The ignition control device for a direct injection spark ignition type internal combustion engine according to any one of claims 1 to 4 , wherein the idle discharge is performed only in an idle operation state of the engine. 3. The ignition control device for a direct-injection spark ignition type internal combustion engine according to claim 2 , wherein the timing of the idle discharge is near a compression top dead center in a fuel cut state.

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