JP5688683B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine that ignites an air-fuel mixture in a cylinder of the internal combustion engine with a discharge spark of a spark plug.

  Some internal combustion engines mounted on vehicles are equipped with an EGR device that recirculates a part of exhaust gas to an intake passage as EGR gas for the purpose of improving fuel consumption or suppressing knocking (knocking). In addition, as a countermeasure against knocking due to the increase in the frequency of high-load operation and the change in fuel properties due to downsizing (smaller displacement) of internal combustion engines in recent years, the EGR amount (the flow rate of EGR gas recirculated to the intake passage) has been conventionally increased. There is a growing demand to increase the amount of money.

  However, when the amount of EGR is increased, the ratio of air (fresh air) sucked into the cylinder is decreased, so that the ignitability of the air-fuel mixture is lowered and the combustion state may be deteriorated. Therefore, in order to respond to a request for increasing the EGR amount, it is necessary to increase the EGR limit (the upper limit value of the EGR amount that can ensure a good combustion state).

  As a combustion improvement technique for an internal combustion engine equipped with an EGR device, for example, as described in Japanese Patent Application Laid-Open No. 2000-291519, the discharge time of the ignition coil is increased as the EGR rate increases. There are things that ensure flammability.

  Further, as described in Patent Document 2 (Japanese Patent Application Laid-Open No. 2010-1790), the ignitability is improved by increasing the magnetic field applied to the electric spark gap of the spark plug as the EGR amount increases. There are also things.

JP 2000-291519 A JP 2010-1790 A

  By the way, in order to increase the EGR limit (the upper limit value of the EGR amount that can ensure a good combustion state), the applicant of the present invention has performed an in-cylinder airflow strength (e.g. By strengthening the airflow to increase the strength of the flow and extending the discharge spark generated between the electrodes of the spark plug (see FIG. 2), the contact area between the discharge spark and the mixture is increased to ignite the mixture. We are researching a system to improve the performance, but the following new problems were found in the research process.

  In general, when a high voltage generated by an ignition device is applied to a spark plug, a discharge spark is generated between the electrodes and a discharge current flows, and then the discharge voltage gradually decreases to maintain the discharge spark. The discharge spark is maintained until it falls below the required discharge sustaining voltage (or the discharge spark is maintained until the discharge current gradually decreases and falls below the discharge sustaining current necessary to maintain the discharge spark).

  However, when the discharge spark is extended due to airflow enhancement, the discharge sustaining voltage (discharge sustaining current) increases accordingly, so the time until the discharge voltage falls below the discharge sustaining voltage (the time until the discharge current falls below the discharge sustaining current) ) Becomes shorter, and a phenomenon in which the discharge spark cannot be maintained at an early stage (hereinafter, this phenomenon is referred to as “discharging of the discharge spark”) may occur. For this reason, even if an attempt is made to improve the ignitability of the air-fuel mixture by extending the discharge spark by airflow enhancement, if the discharge spark blows out, the period during which the discharge spark can be maintained (actual discharge time) will be shortened, and mixing There is a problem that the ignitability of qi cannot be sufficiently improved.

In the above-described conventional techniques (the techniques of Patent Documents 1 and 2), since the blowout of the discharge spark is not considered at all, the problem of the blowout of the discharge spark cannot be solved.
Therefore, the problem to be solved by the present invention is that, when performing airflow enhancement during the execution of EGR control, it is possible to suppress blowout of the discharge spark, and to effectively improve the ignitability of the air-fuel mixture. An object of the present invention is to provide a control device for an internal combustion engine.

In order to solve the above-mentioned problems, an invention according to claim 1 is directed to an internal combustion engine control device for igniting an air-fuel mixture in a cylinder of an internal combustion engine with a discharge spark of an ignition plug. Based on the airflow control means for strengthening the airflow in the cylinder during the execution of the EGR control for returning to the intake passage as gas, and the airflow intensity and the ignition timing of the spark plug during the execution of the EGR control, It is determined whether or not there is a phenomenon in which the discharge spark of the spark plug cannot be maintained at an early stage (hereinafter, this phenomenon is referred to as “discharge spark blowout”), and the discharge spark is blown out. and if it is determined to increase the discharge current of the spark plug and a blow out suppression control means for suppressing the blow out of the discharge sparks, blow out suppression control means, as the discharge current ignition timing becomes the advance-side It is obtained by a configuration to increase the amount of increase.

  Depending on the airflow strength and the ignition timing, the flow velocity of the airflow near the electrode of the spark plug at the ignition timing changes, and the discharge spark elongation changes accordingly and the discharge sustaining voltage (discharge sustaining current) changes. If the airflow intensity and the ignition timing are used, it can be determined whether or not the discharge spark is blown out.

Then, when it is determined that the discharge spark is blown out, if the discharge current of the spark plug is increased, the time until the discharge current falls below the discharge sustaining current (the discharge voltage falls below the discharge sustaining voltage) Time) and the blowout of the discharge spark can be suppressed. This makes it possible to lengthen the period during which the discharge spark can be extended by increasing the airflow (the state in which the contact area between the discharge spark and the mixture is increased), thus effectively improving the ignitability of the mixture. Therefore, the EGR limit (the upper limit value of the EGR amount that can ensure a good combustion state) can be increased, and an increase in the EGR amount can be met.
In addition, within the general correction range of the ignition timing, the flow rate of the air current near the spark plug electrode at the ignition timing increases as the ignition timing advances, so the discharge spark increases as the ignition timing advances. The amount tends to increase and the discharge sustaining voltage tends to increase.
Therefore, in the invention according to claim 1, the amount of increase in the discharge current is increased as the ignition timing is advanced by the blow-out suppression control means. In this way, the amount of increase in the discharge current can be increased in response to the increase in the discharge sustaining voltage and the increase in the discharge sustaining current as the ignition timing is advanced, so that the discharge current can be increased. It is possible to set to an appropriate value necessary for suppressing the blow-off.

  Generally, the stronger the airflow strength, the faster the flow velocity of the airflow near the electrode of the spark plug at the ignition timing. Therefore, the stronger the airflow strength, the greater the discharge spark elongation and the higher the discharge sustaining voltage.

  Therefore, as described in claim 2, it is preferable that the blow-out suppression control means increase the increase amount of the discharge current as the airflow strength increases. In this way, as the airflow strength increases, the discharge sustain voltage increases and the discharge sustain current increases, so that the amount of increase in the discharge current can be increased, and the discharge current is blown out by the discharge spark. It is possible to set an appropriate value necessary for suppressing the noise.

FIG. 1 is a diagram showing a schematic configuration of an engine control system in Embodiment 1 of the present invention. FIG. 2 is a view showing a state in which the discharge spark of the spark plug is extended. FIG. 3 is a diagram showing the relationship between the airflow intensity, the ignition timing, and the airflow velocity near the electrode of the ignition plug. FIG. 4 is a flowchart showing the flow of processing of the blow-off suppression control routine of the first embodiment. FIG. 5 is a diagram for explaining a blowout occurrence region. FIG. 6 is a diagram conceptually showing an example of a map of the airflow intensity correction coefficient Kt. FIG. 7 is a diagram conceptually showing an example of a map of the ignition timing correction coefficient Ksa. FIG. 8 is a time chart illustrating an execution example of blow-off suppression control according to the first embodiment. FIG. 9A is a diagram showing the behavior of the discharge current when the discharge current is increased, and FIG. 9B is a diagram showing the behavior of the discharge current when the discharge time is increased. FIG. 10 is a diagram for explaining a method for determining the blowout of the discharge spark according to the second embodiment as a reference example related to the present invention . FIG. 11 is a flowchart showing the flow of processing of the blow-off suppression control routine of the second embodiment.

  Hereinafter, some embodiments embodying the mode for carrying out the present invention will be described.

A first embodiment of the present invention will be described with reference to FIGS.
First, the overall configuration of the engine control system will be schematically described with reference to FIG.
An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 (intake passage) of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. On the other hand, the exhaust pipe 15 (exhaust passage) of the engine 11 is provided with a catalyst 16 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas.

  The engine 11 is equipped with an exhaust turbine driven supercharger 17 that supercharges intake air. In the supercharger 17, an exhaust turbine 18 is disposed on the upstream side of the catalyst 16 in the exhaust pipe 15, and a compressor 19 is disposed on the downstream side of the air flow meter 14 in the intake pipe 12. The supercharger 17 is connected so that the exhaust turbine 18 and the compressor 19 rotate integrally, and the exhaust turbine 18 is rotationally driven by the kinetic energy of the exhaust gas, so that the compressor 19 is rotationally driven to suck the intake air. It is supposed to supercharge.

  An intercooler 20 for cooling the intake air is provided downstream of the compressor 19 in the intake pipe 12. A throttle valve 21 whose opening is adjusted by a motor (not shown) is provided downstream of the intercooler 20. Is provided. In addition, an air flow control valve 23 is provided in each intake manifold 22 (or intake port) that introduces air into each cylinder of the engine 11 to adjust the air flow strength in the cylinder (for example, the strength of the tumble flow). The air flow control valve 23 is adjusted in opening degree by an actuator such as a motor (not shown).

  Furthermore, each cylinder of the engine 11 is provided with a fuel injection valve 24 that directly injects fuel into the cylinder, and a spark plug 25 is attached to each cylinder head of the engine 11 for each cylinder. A high voltage generated by the ignition device 26 is applied to the spark plug 25 to generate a discharge spark, and the air-fuel mixture in the cylinder is ignited by the discharge spark of each spark plug 25.

  The engine 11 is provided with an LPL type (low pressure loop type) EGR device 27 that recirculates a part of the exhaust gas from the exhaust pipe 15 to the intake pipe 12 as EGR gas. In the EGR device 27, an EGR pipe 28 is connected between the downstream side of the exhaust turbine 18 in the exhaust pipe 15 (for example, the downstream side of the catalyst 16) and the upstream side of the compressor 19 in the intake pipe 12. The EGR pipe 28 is provided with an EGR cooler 29 for cooling the EGR gas, and an EGR valve 30 for adjusting the EGR amount (the flow rate of the EGR gas recirculated to the intake pipe 12).

  In addition, the engine 11 is provided with a coolant temperature sensor 31 that detects the coolant temperature, a crank angle sensor 32 that outputs a pulse signal each time a crankshaft (not shown) rotates a predetermined crank angle, and the like. Based on the 32 output signals, the crank angle and the engine speed are detected.

  Outputs of these various sensors are input to an electronic control unit (hereinafter referred to as “ECU”) 33. The ECU 33 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), thereby depending on the engine operating state, the fuel injection amount, the ignition timing. The throttle opening (intake air amount) and the like are controlled.

  In addition, the ECU 33 calculates a target EGR amount (or target EGR rate) according to an engine operating state (for example, engine rotation speed and load) by executing an EGR control routine (not shown), and this target EGR amount (or The opening degree of the EGR valve 31 is controlled so as to realize the target EGR rate), and the EGR control for returning the EGR gas cooled by the EGR cooler 29 to the intake pipe 12 is executed.

  Further, the ECU 33 functions as an air flow control means by executing an air flow control routine (not shown), and controls the opening degree of the air flow control valve 23 in accordance with the engine operating state (for example, the engine speed and load). The airflow strength (for example, the strength of the tumble flow) is controlled. As a result, during the execution of the EGR control for recirculating the EGR gas to the intake pipe 12, the airflow is strengthened to increase the airflow intensity, and the discharge spark generated between the electrodes 34 and 35 of the spark plug 25 is extended (FIG. 2). See), increasing the contact area between the discharge spark and the mixture to improve the ignitability of the mixture.

  In general, when a high voltage generated by the ignition device 26 is applied to the spark plug 25, a discharge spark is generated between the electrodes 34 and 35, a discharge current flows, and then the discharge voltage is gradually decreased to cause a discharge spark. The discharge spark is maintained until the discharge sustain voltage is lower than the discharge sustain voltage necessary to maintain the discharge spark (or the discharge spark is maintained until the discharge current gradually decreases and falls below the discharge sustain current required to maintain the discharge spark. ).

  However, when the discharge spark is extended due to airflow enhancement, the discharge sustaining voltage (discharge sustaining current) increases accordingly, so the time until the discharge voltage falls below the discharge sustaining voltage (the time until the discharge current falls below the discharge sustaining current) ) Becomes shorter, and a phenomenon in which the discharge spark cannot be maintained at an early stage (hereinafter, this phenomenon is referred to as “discharging of the discharge spark”) may occur. For this reason, even if an attempt is made to improve the ignitability of the air-fuel mixture by extending the discharge spark by airflow enhancement, if the discharge spark blows out, the period during which the discharge spark can be maintained (actual discharge time) will be shortened, and mixing Qi ignitability cannot be improved sufficiently.

  Therefore, in the first embodiment, the blowout suppression control routine of FIG. 4 to be described later is executed so that the discharge sparks are blown out based on the airflow intensity and the ignition timing of the spark plug 25 during execution of the EGR control. It was determined whether or not it was a state in which the discharge spark of the spark plug 25 could not be maintained earlier than in the case of no airflow enhancement, and it was determined that the discharge spark was blown out. In such a case, blowout suppression control for increasing the discharge current of the spark plug 25 to suppress blowout of the discharge spark is executed.

  As shown in FIG. 3, generally, as the airflow strength increases, the airflow velocity in the vicinity of the electrode of the spark plug 25 at the ignition timing tends to increase. Further, within the general correction range of the ignition timing, the flow velocity of the airflow near the electrode of the spark plug 25 at the ignition timing tends to increase as the ignition timing becomes the advance side. As described above, the flow velocity of the airflow near the electrode of the spark plug 25 at the ignition timing changes according to the airflow intensity and the ignition timing, and the extension amount of the discharge spark changes accordingly, and the discharge sustaining voltage (discharge sustaining current). Therefore, if the airflow intensity and the ignition timing are used, it can be determined whether or not the discharge spark is blown out.

  Then, when it is determined that the discharge spark is blown out, if the discharge current of the spark plug 25 is increased, the time until the discharge current falls below the discharge sustaining current (the discharge voltage becomes the discharge sustaining voltage). (Time until it falls) can be lengthened, and the blowout of the discharge spark can be suppressed.

Hereinafter, the processing content of the blowout suppression control routine of FIG. 4 executed by the ECU 33 in the first embodiment will be described.
The blow-out suppression control routine shown in FIG. 4 is repeatedly executed at a predetermined period during the power-on period of the ECU 33 (while the ignition switch is on), and plays a role as blow-out suppression control means in the claims. When this routine is started, first, at step 101, it is determined whether or not EGR control for returning the EGR gas cooled by the EGR cooler 29 to the intake pipe 12 is being executed (during opening control of the EGR valve 30). If it is determined that the EGR control is not being executed, this routine is terminated without executing the processing from step 102 onward.

  On the other hand, if it is determined in step 101 that the EGR control is being executed, the processing after step 102 is executed as follows. First, in step 102, the current opening degree of the airflow control valve 23 (for example, the opening degree command value or the opening degree detection value of the airflow control valve 23) is read, and then the process proceeds to step 103 where the opening degree of the airflow control valve 23 is set. On the basis of this, the airflow intensity (for example, the tumble ratio) is calculated by a map or a mathematical formula. Here, a map or a mathematical expression used for calculating the airflow intensity (eg, tumble ratio) is created in advance based on test data, design data, and the like, and stored in the ROM of the ECU 33. The tumble ratio is an index indicating the strength of the tumble flow. For example, the tumble ratio is the ratio of the rotational speed of the tumble flow to the rotational speed of the engine 11 (the rotational speed of the tumble flow per one rotation of the engine 11).

  Thereafter, the process proceeds to step 104, and whether or not the airflow intensity (for example, the tumble ratio) is equal to or greater than a predetermined value (for example, 0.7) and the ignition timing is on the advance side of the predetermined value (for example, 25CA before top dead center). Thus, it is determined whether or not the discharge spark is blown out.

  Note that the method for determining whether or not the discharge spark is blown out is not limited to this. For example, as shown in FIG. 5, the airflow intensity (for example, the tumble ratio) is a predetermined value (for example, 0). .7) An engine operating region in which the ignition timing is more advanced than a predetermined value (for example, 25CA before top dead center) is set as the “blow-out occurrence region” and the current engine operating state (for example, the engine It may be determined whether or not the discharge spark is blown out depending on whether or not the rotation speed and load) are in the blowout occurrence region.

  If it is determined in step 104 that the discharge sparks are blown out, the process proceeds to step 105, where the basic discharge current Ibase is mapped or expressed according to the current engine speed and battery voltage. Calculated by

  Thereafter, the process proceeds to step 106, where an airflow intensity correction coefficient Kt corresponding to the current airflow intensity (eg, tumble ratio) is calculated with reference to the map of the airflow intensity correction coefficient Kt shown in FIG. In general, the stronger the air flow strength is, the faster the flow velocity of the air current near the electrode of the spark plug 25 at the ignition timing is. Therefore, the stronger the air flow strength is, the more the discharge spark elongation increases and the discharge sustaining voltage tends to increase.

  Therefore, the map of the airflow intensity correction coefficient Kt shown in FIG. 6 is set so that the airflow intensity correction coefficient Kt increases as the airflow intensity increases (for example, the tumble ratio increases) and the amount of increase in the discharge current increases. ing. Thereby, the increase amount of the discharge current is increased in response to the increase in the discharge sustaining voltage and the increase in the sustaining current as the airflow strength increases.

  Thereafter, the routine proceeds to step 107, where the ignition timing correction coefficient Ksa corresponding to the current ignition timing is calculated with reference to the map of the ignition timing correction coefficient Ksa shown in FIG. Within the general correction range of the ignition timing, the flow rate of the airflow near the electrode of the spark plug 25 at the ignition timing increases as the ignition timing advances, so the discharge spark elongation increases as the ignition timing advances. Tends to increase and the discharge sustaining voltage tends to increase.

  Therefore, the map of the ignition timing correction coefficient Ksa shown in FIG. 7 is set so that the ignition timing correction coefficient Ksa increases as the ignition timing advances, and the amount of increase in the discharge current increases. As a result, the amount of increase in the discharge current is increased in response to the increase in the discharge sustaining voltage and the increase in the discharge sustaining current as the ignition timing is advanced.

Thereafter, the routine proceeds to step 108, where the target discharge current Is is calculated from the following equation using the basic discharge current Ibase, the airflow intensity correction coefficient Kt, and the ignition timing correction coefficient Ksa.
Is = Ibase x Kt x Ksa

  The ECU 33 controls the ignition device 26 so that the discharge current (maximum value) of the spark plug 25 becomes the target discharge current Is, thereby increasing the discharge current of the spark plug 25 and suppressing the discharge spark from being blown out. Execute cut suppression control.

Next, an execution example of blow-out suppression control of the first embodiment will be described with reference to FIG. 8 (a dotted line in FIG. 8 shows a comparative example in which blow-off suppression control is not executed).
In the example of FIG. 8, when the throttle opening increases due to the driver's accelerator depression and the engine speed increases, at the time t1 when the throttle opening increases, the EGR valve 30 is opened to intake the EGR gas. EGR control for refluxing the pipe 12 is executed. Further, along with the execution of this EGR control, the ignition timing is advanced, and the airflow reinforcement is executed to increase the airflow intensity.

  During execution of EGR control, whether or not the airflow intensity (for example, the tumble ratio) is equal to or greater than a predetermined value (for example, 0.7) and the ignition timing is on the more advanced side than the predetermined value (for example, 25 CA before top dead center). Therefore, it is determined whether or not the discharge spark is blown out. At the time t2 when it is determined that the discharge spark is blown out, the discharge current of the spark plug 25 is increased. Blow-out suppression control is performed to suppress blow-off of the discharge spark.

  Thereafter, at the time t3 when the throttle opening is decreased, the EGR valve 30 is closed to complete the EGR control, and accordingly, the ignition timing advance and the air flow enhancement are terminated, and the discharge current of the spark plug 25 is decreased. The blow-out suppression control is terminated.

  In the first embodiment described above, during the execution of EGR control, it is determined whether or not the discharge spark is blown out based on the airflow intensity and the ignition timing of the spark plug 25, and the discharge spark is determined. When it is determined that a blow-off occurs, the time until the discharge current of the spark plug 25 is increased and the discharge current falls below the discharge sustain current (the time until the discharge voltage falls below the discharge sustain voltage) is determined. Since the blowout suppression control that suppresses the blowout of the discharge spark is executed by increasing the length, the discharge spark is extended by increasing the airflow (the state in which the contact area between the discharge spark and the mixture is increased) The period that can be maintained can be lengthened. Moreover, when the discharge current is increased [see FIG. 9A], the ignition energy can be used more efficiently and energy loss can be reduced than when the discharge time is increased [see FIG. 9B]. it can. As a result, the ignitability of the air-fuel mixture can be improved effectively, and the EGR limit (the upper limit value of the EGR amount that can ensure a good combustion state) can be increased. Compared to the dotted line in FIG. 8), the EGR amount can be increased, whereby the knocking suppression effect can be enhanced and the pumping loss can be reduced to improve the fuel efficiency.

  Further, in the first embodiment, in the blowout suppression control, the increase amount of the discharge current is increased as the airflow strength is increased, and the increase amount of the discharge current is increased as the ignition timing is advanced. Therefore, the amount of increase in the discharge current can be increased corresponding to the increase in the discharge sustain voltage (the discharge sustain current increases) as the airflow strength increases, and the discharge sustain voltage as the ignition timing is advanced. The increase amount of the discharge current can be increased corresponding to the increase in the discharge current (the discharge sustaining current increases). As a result, the discharge current can be set to an appropriate value necessary for suppressing the blowout of the discharge spark, and the discharge current can be prevented from being increased more than necessary.

  In the first embodiment, the tumble ratio is used as the airflow strength. However, the present invention is not limited to this. For example, the opening degree of the airflow control valve 23, the swirl ratio, or the like may be used as the airflow strength. good.

Next, Example 2 as a reference example related to the present invention will be described with reference to FIGS. However, description of substantially the same parts as those in the first embodiment will be omitted or simplified, and different parts from the first embodiment will be mainly described.

  In the second embodiment, the ECU 33 executes a blowout suppression control routine shown in FIG. 11 to be described later, so that the discharge is performed based on the difference between the ideal discharge time and the actual discharge time of the spark plug 25 during the EGR control. It is determined whether or not a spark is blown out (a phenomenon in which the discharge spark of the spark plug 25 cannot be maintained earlier than when the air current is not strengthened). When it is determined that there is, blowout suppression control for increasing the discharge current of the spark plug 25 to suppress blowout of the discharge spark is executed.

  As shown in FIG. 10, when the discharge spark is blown out, the actual discharge time T2 (period during which the discharge spark can be maintained) is shortened, and the ideal discharge time T1 (for example, set according to the engine operating state, battery voltage, etc.). The difference ΔT (= T1−T2) between the ideal discharge time and the actual discharge time T2 becomes large. Therefore, if the difference ΔT between the ideal discharge time T1 and the actual discharge time T2 is used, the discharge spark is blown out. It is possible to determine whether or not a state occurs.

In the blow-off suppression control routine of FIG. 11, first, in step 201, is the EGR control in which the EGR gas cooled by the EGR cooler 29 is recirculated to the intake pipe 12 being performed (the valve opening control of the EGR valve 30 is being performed). If it is determined that the EGR control is being executed, the process proceeds to step 202, and a difference ΔT between the ideal discharge time T1 and the actual discharge time T2 is calculated.
ΔT = T1-T2

  Thereafter, the process proceeds to step 203, where it is determined whether or not the discharge spark is blown out depending on whether or not the difference ΔT between the ideal discharge time T1 and the actual discharge time T2 is larger than a predetermined determination value. To do.

  If it is determined in step 203 that the discharge sparks are blown out, the process proceeds to step 204 where the basic discharge current Ibase is mapped or represented by a formula or the like according to the current engine speed and battery voltage. Calculated by

  Thereafter, the process proceeds to step 205, and a correction coefficient K corresponding to the difference ΔT between the ideal discharge time T1 and the actual discharge time T2 is calculated with reference to a map of the correction coefficient K (not shown). The map of the correction coefficient K is set so that the correction coefficient K increases and the amount of increase in the discharge current increases as the difference ΔT between the ideal discharge time T1 and the actual discharge time T2 increases. As a result, the amount of increase in the discharge current is increased corresponding to the difference between the ideal discharge time and the actual discharge time becoming larger as the discharge sustaining voltage becomes higher and the period during which the discharge spark can be maintained (actual discharge time) becomes shorter. It's getting bigger.

Thereafter, the process proceeds to step 206, and the target discharge current Is is calculated from the following equation using the basic discharge current Ibase and the correction coefficient K.
Is = Ibase x K

  The ECU 33 controls the ignition device 26 so that the discharge current (maximum value) of the spark plug 25 becomes the target discharge current Is, thereby increasing the discharge current of the spark plug 25 and suppressing the discharge spark from being blown out. Execute cut suppression control.

  In the second embodiment described above, it is determined whether or not the discharge spark is blown out based on the difference between the ideal discharge time and the actual discharge time of the spark plug 25 during execution of the EGR control. When it is determined that the discharge spark is blown out, the blowout suppression control for increasing the discharge current of the spark plug 25 to suppress the discharge spark is performed. The substantially same effect as Example 1 can be acquired.

  Further, in the second embodiment, in the blowout suppression control, the increase amount of the discharge current is increased as the difference between the ideal discharge time and the actual discharge time is increased. As the period during which the spark can be maintained (actual discharge time) is shortened, the increase amount of the discharge current can be increased corresponding to the difference between the ideal discharge time and the actual discharge time. As a result, the discharge current can be set to an appropriate value necessary for suppressing the blowout of the discharge spark, and the discharge current can be prevented from being increased more than necessary.

  In the second embodiment, during the blowout suppression control, the discharge current of the spark plug 25 is increased in accordance with the difference between the ideal discharge time and the actual discharge time. However, the present invention is not limited to this. The discharge current of the spark plug 25 may be increased according to the ratio between the ideal discharge time and the actual discharge time. Alternatively, the discharge current of the spark plug 25 may be increased by a predetermined value set in advance.

  In the first and second embodiments, the discharge current of the spark plug 25 is increased by correcting the target discharge current in the blowout suppression control. However, the present invention is not limited to this. The discharge current of the spark plug 25 can be increased by changing the map of the energization time of the coil, or the inductance of the ignition coil can be changed by switching the circuit of the ignition device. The current may be increased.

  In the first and second embodiments, the LPL that recirculates EGR gas from the downstream side of the exhaust turbine 18 in the exhaust pipe 15 (for example, the downstream side of the catalyst 16) to the upstream side of the compressor 19 in the intake pipe 12. Although the present invention is applied to an engine with a supercharger that employs a system (low pressure loop system) EGR device 27, the present invention is not limited to this. For example, an exhaust pipe from an upstream side of an exhaust turbine in an exhaust pipe The present invention may be applied to an engine with a supercharger that employs an HPL system (high-pressure loop system) EGR device that recirculates EGR gas to the downstream side of the compressor (for example, downstream of the throttle valve). Further, the EGR cooler 29 may be omitted.

  Further, the present invention is not limited to an engine equipped with an exhaust turbine-driven supercharger (so-called turbocharger), but is equipped with a machine-driven supercharger (so-called supercharger) or an electric supercharger. It may be applied to the engine.

  In addition, the present invention is not limited to an engine with a supercharger, and may be applied to a naturally aspirated engine (NA engine) not equipped with a supercharger. Further, the present invention is not limited to the in-cylinder injection engine as shown in FIG. 1, but is a dual injection type equipped with both an intake port injection type engine and a fuel injection valve for intake port injection and a fuel injection valve for in-cylinder injection. It can also be applied to other engines.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe (intake passage), 14 ... Air flow meter, 15 ... Exhaust pipe, 21 ... Throttle valve, 23 ... Air flow control valve, 24 ... Fuel injection valve, 25 ... Spark plug, 26 ... Ignition device, 27 ... EGR device, 28 ... EGR piping, 30 ... EGR valve, 32 ... Crank angle sensor, 33 ... ECU (airflow control means, blow-out suppression control means)

Claims (2)

In a control device for an internal combustion engine that ignites an air-fuel mixture in a cylinder of the internal combustion engine with a discharge spark of a spark plug,
Airflow control means for performing airflow enhancement to increase the airflow intensity in the cylinder during execution of EGR control for returning a part of the exhaust gas of the internal combustion engine as EGR gas to the intake passage;
A phenomenon in which the discharge spark of the spark plug cannot be maintained at an early stage based on the airflow intensity and the ignition timing of the spark plug during the execution of the EGR control (this phenomenon is hereinafter referred to as “discharge spark blowout”). When the discharge spark is blown out, the discharge current of the spark plug is increased to suppress the discharge spark from being blown out. Blowout suppression control means ,
The blowout suppression control means increases the amount of increase in the discharge current as the ignition timing is advanced .   2. The control device for an internal combustion engine according to claim 1, wherein the blow-out suppression control unit increases the increase amount of the discharge current as the airflow intensity increases.

Images