JP2010138720A - Ignition control device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition control device for an engine capable of more precisely performing plasma jet ignition control, and capable of adequately enhancing combustion stability, durability, fuel consumption, and so forth. <P>SOLUTION: An ignition control device for an engine is provided with a plasma jet ignition device as a fuel/air mixture ignition means, and sensors 21 and 22 for detecting combustion stability of respective cylinders, calculates combustion stability factor for respective cylinders based on signals obtained from the sensors 21 and 22 during the plasma jet ignition control, and performs control to increase or decrease the number of ignition times per one combustion cycle by the plasma jet ignition device for respective cylinders, and/or ignition output energy of at least one time, based on the combustion stability factor. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ignition control device for an in-cylinder injection engine equipped with a plasma jet ignition device, and more particularly to an in-cylinder engine that contributes to improvement in combustion stability, durability, fuel consumption, etc. when the plasma jet ignition device is used. The present invention relates to an ignition control device for an injection engine.

  In the field of in-vehicle engines, it is known to perform stratified combustion operation in which fuel is injected in a compression stroke in order to improve fuel consumption and exhaust performance. When improving fuel efficiency and exhaust performance under stratified combustion operation, coexistence with combustion stability becomes an issue. Therefore, a method of adopting a plasma jet ignition system as an air-fuel mixture igniting means in the combustion chamber, giving a larger ignition energy to the air-fuel mixture than employing a currently generally used spark ignition system, and further improving combustion stability Is considered. However, the plasma jet ignition method has problems that the spark plug is consumed rapidly and the power consumption is large compared to the spark ignition method, and it is difficult to adopt it for a general vehicle-mounted engine at present.

  Therefore, as a solution to the above problem, conventionally, as seen in, for example, Patent Document 1 below, the energy applied to the spark plug is adjusted (the discharge current value and the discharge time are controlled) according to the operating state of the engine. At the time of difficult ignition operation such as during burn operation or when the engine coolant temperature is low, the plasma jet ignition method is used for ignition, and the spark ignition method is used for other ignition, so that the plasma jet ignition method (device) and spark ignition are used. It has been proposed to use a method (apparatus) together.

JP-A-6-66236

  However, in the ignition control device described in Patent Document 1, energy applied to the spark plug (hereinafter referred to as ignition output energy) is controlled by feedforward control, so that it is possible to perform so precise ignition control. However, there is a possibility that the adjustment of the ignition output energy may be excessive or insufficient, and there is a problem that the combustion stability, durability, fuel consumption, etc. cannot be sufficiently improved when using the plasma jet ignition device.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to enable more precise ignition control when using a plasma jet ignition device, such as combustion stability, durability, and fuel consumption. An object of the present invention is to provide an ignition control device for an engine that can be sufficiently improved.

  In order to achieve the above object, an engine ignition control device according to the present invention basically includes a fuel injection valve that directly injects fuel into a combustion chamber, and a plasma jet ignition device as a mixture ignition means in the combustion chamber. And a sensor for detecting the combustion stability of each cylinder.

  Then, when the plasma jet ignition device is used, a combustion stability index is calculated for each cylinder based on a signal obtained from the sensor, and based on the combustion stability index, one plasma jet ignition device is used for each cylinder. Control is performed to increase / decrease the number of ignitions and / or at least one ignition output energy for the combustion cycle.

  In a preferred embodiment, the mixture ignition means in the combustion chamber includes a spark ignition device in addition to the plasma jet ignition device.

  In a preferred specific aspect, a crank angle sensor and / or a cam angle sensor as a sensor for detecting the combustion stability is provided, and each cylinder with respect to the average crank angular speed of all the cylinders based on a signal obtained from the sensor. A deviation amount of the crank angular velocity or a correlation value thereof is obtained, and the combustion stability index is calculated for each cylinder based on the deviation amount or the correlation value.

  In another preferred specific aspect, an in-cylinder pressure sensor is provided as a sensor for detecting the combustion stability, and the in-cylinder pressure of each cylinder with respect to the average in-cylinder pressure of all cylinders is determined based on a signal obtained from the sensor. A deviation amount or a correlation value thereof is obtained, and the combustion stability index is calculated for each cylinder based on the deviation amount or the correlation value.

  In another preferred aspect, for each cylinder, it is determined whether or not the combustion stability index has deteriorated more than a set value, and for the cylinder that has deteriorated more than the set value, the number of ignitions is increased, or For a cylinder that has increased the ignition output energy and has not deteriorated more than the set value, the number of times of ignition is maintained or decreased, or the control of maintaining or decreasing the ignition output energy is performed. The

  In another preferred embodiment, a control for calculating a target combustion stability index based on the engine coolant temperature and increasing or decreasing the number of ignitions or ignition energy based on a comparison result between the combustion stability index and the target combustion stability index. To be done.

  In another preferred aspect, an upper limit is set for the number of ignitions and / or ignition output energy, and when the number of ignitions and / or ignition output energy reaches the upper limit, stratified charge combustion operation is prohibited. Is done.

  In another preferred embodiment, when the plasma jet ignition device is used, if there is a cylinder whose combustion stability index has deteriorated to a set value or more, the stratified charge combustion operation is prohibited.

  In another preferred embodiment, an operation region map divided into a plurality of blocks according to the engine speed and the intake air amount is provided for each cylinder, and each block in the map has the combustion stability index, the number of ignitions, and the ignition output. Store at least one of the energies and update it sequentially.

  The engine ignition control device according to the present invention calculates a combustion stability index (combustion stability) for each cylinder based on a signal obtained from a crank angle sensor, an in-cylinder pressure sensor, or the like when using a plasma jet ignition device. Based on the combustion stability index, feedback control is performed to increase / decrease the number of ignitions and / or at least one ignition output energy for one combustion cycle by the plasma jet ignition device. Ignition control can be performed more precisely than the conventional one, so that the combustion stability of each cylinder is improved and variation in crank angular speed among cylinders is reduced, and durability, fuel consumption, exhaust performance, etc. Improvement can be sufficiently achieved.

  Embodiments of an engine ignition control device according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an embodiment of an engine ignition control device according to the present invention together with an example of an in-vehicle engine to which the engine ignition control device is applied.

  In FIG. 1, an engine 10 to which the ignition control device 1 of the present embodiment is applied includes a spark ignition device having a spark plug 13 and an output circuit 15 and a plasma jet having a spark plug 14 and an output circuit 16 for each cylinder. An in-cylinder injection multi-cylinder gasoline engine having, for example, four cylinders, including an ignition device. The engine 10 includes a cylinder 10A including a cylinder head and a cylinder block, and a piston 17 that is slidably inserted into each cylinder of the cylinder 10A. A combustion chamber 20 having a roof portion is defined, and a fuel injection valve 12 for directly injecting fuel into the combustion chamber 20 is provided in the center of the ceiling portion of the combustion chamber 20 of each cylinder, and plasma is respectively provided on the left and right thereof. An ignition plug 14 for jet ignition and an ignition plug 13 for spark ignition are provided.

  The air used for the combustion of fuel is from an air cleaner (not shown), a hot-wire (H / W) type air flow sensor 4 and a tubular passage portion in which a throttle valve 5 is arranged, a collector 6, an intake manifold (Manifold), through an intake passage 2 including an intake port 2a and the like in which a TCV (tumble control valve) 18 is arranged, and through an intake valve 8 arranged in the downstream end (end of the intake port 2a) Distribution is supplied to the combustion chamber 20 of each cylinder.

  The air-fuel mixture of the air sucked into the combustion chamber 20 and the fuel injected from the fuel injection valve 12 is combusted by ignition by a spark ignition spark plug 13 or a plasma jet ignition spark plug 14, and the combustion waste gas ( Exhaust gas) is discharged from the combustion chamber 20 through the exhaust valve 9 to the outside (in the atmosphere) through the exhaust port 3a, the exhaust manifold, the exhaust purification catalyst, the exhaust pipe, and the like.

  Further, fuel (gasoline or the like) in the fuel tank is pressurized to about 3 to 20 MPa by a fuel pump and supplied through the common rail 11 to the fuel injection valve 12 provided for each cylinder. The fuel injection valve 12 is driven to open by a valve opening pulse signal that is supplied from an engine control unit (ECU) 100, which will be described later, and has a pulse width (corresponding to the valve opening time) according to the operation state at that time. An amount of fuel corresponding to the valve opening time is injected and supplied into the combustion chamber 20.

  Further, a spark ignition drive signal is sent from the spark ignition output circuit 15 to the spark ignition spark plug 13 so as to be ignited at the ignition timing calculated by the control unit 100, and for the plasma jet. A plasma jet ignition drive circuit 16 is sent from the plasma jet ignition output circuit 16 to the spark plug 14 so as to be ignited at the ignition timing and the number of ignition times calculated by the control unit 100. The one ignition time (discharge time) by the spark ignition spark plug 13 is on the order of milliseconds, whereas the one ignition time by the plasma jet spark plug 14 is on the order of microseconds, which is extremely short. When using the plasma jet ignition device, if necessary, the ignition (plasma discharge) may be continuously performed a plurality of times during one combustion cycle, that is, the number of times of ignition may be two or more. In order to improve the combustion stability of each cylinder, the number of ignitions is increased or decreased (detailed later). In place of the number of ignitions, the ignition output energy (electric power) applied to the plasma jet ignition plug 14 may be increased or decreased.

  And in the ignition control apparatus 1 of this embodiment, in order to perform various control of the engine 10, the control unit 100 incorporating a microcomputer is provided.

  The control unit 100 is well known per se and includes a CPU, an input circuit, an input / output port, a RAM, a ROM, and the like.

  As shown in FIG. 1 and FIG. 2, the control unit 100 includes an input signal corresponding to the intake air amount detected by the air flow sensor 4 and the opening of the throttle valve 5 detected by the throttle opening sensor 25. A signal corresponding to the degree, a signal representing the rotation (engine speed) and phase (crank angle) of the crankshaft obtained from the crank angle sensor 21 (a signal pulse is output from the crank angle sensor, for example, at every rotation angle) A signal representing the rotation and phase of the camshaft obtained from the cam angle sensor 22 (cylinder determination is performed based on the signal from the cam angle sensor 22 and the signal from the crank angle sensor 21), cylinder A signal corresponding to the engine coolant temperature detected by the water temperature sensor 19 disposed in 10A, the voltage of the in-vehicle battery 23, etc. It is supplied.

  The control unit 100 controls the fuel injection control, ignition control, and TCV (tumble control valve) 18 open / close control based on the various input signals as described above (for example, closes during stratified combustion operation to increase the intake air flow rate and tumble. And is opened during homogeneous combustion operation).

  Next, ignition control performed by the control unit 100 when using the plasma jet ignition device will be described mainly.

  FIG. 2 is a functional block diagram showing the processing content executed by the control unit 100 during ignition control when the plasma jet ignition device is used. The control unit 100 includes an engine speed calculation means 101 for calculating the engine speed based on signals obtained from the crank angle sensor 21 and the cam angle sensor 22, and the crank angular speed of each cylinder with respect to the average crank angular speed of all cylinders. Deviation amount calculating means 102 for calculating the deviation amount (or its correlation value), stratified combustion operation permission determining means 103, plasma jet ignition device use permission determining means 104, combustion stability index calculating means 105, target combustion stability A function indicator setting means 106, a combustion stability level calculation means 107, and an ignition frequency setting means 108 are functionally provided.

  More specifically, the deviation amount calculation means 102 obtains the crank angular speed (rotation angle per unit time of the crankshaft) in the explosion stroke in each cylinder. The crank angular velocity obtained here may be, for example, a value obtained by dividing the rotation angle (180 degrees) in the explosion stroke (from the top dead center to the bottom dead center) by the time required for the crank stroke. A value obtained by dividing a rotation angle from a predetermined crank angle position X (CA) to Y (CA) by a time required for the rotation angle may be used, or an instantaneous value at a predetermined crank angle position Z (CA) in an explosion stroke may be used. Good. The reason why the value in the explosion stroke of each cylinder is used as the crank angular velocity is that the variation in the crank angular velocity among the cylinders is the largest in the explosion stroke.

  Further, the deviation amount (or its correlation value) calculated by the deviation amount calculation means 102 is used by the combustion stability index calculation means 105.

  The stratified combustion operation permission determination means 103 determines whether or not the engine operating state is in the stratified combustion operation region based on the engine coolant temperature, the engine speed, the intake air amount, the throttle opening, and the like. In the stratified charge combustion operation region, the stratified charge combustion operation is permitted if the stratified charge combustion operation prohibition condition such as a sensor or component failure or various diagnostics NG is not satisfied.

  The plasma jet ignition device use permission determining means 104 determines whether or not to permit the use of the plasma jet ignition device based on various sensor signals and the like when the stratified charge combustion operation is permitted. As described above, the plasma jet ignition device has the problem that the spark plug is consumed quickly and consumes a large amount of power, and even if a spark ignition device is used, it is in an operating range where there is not much difference in combustion stability or the remaining battery capacity When (voltage) is lower than a predetermined value, use of the plasma jet ignition device is not permitted.

  The combustion stability index calculation means 105 calculates a combustion stability index for each cylinder based on the deviation amount (or its correlation value) for each cylinder calculated by the deviation amount calculation means 102. The combustion stability index is, for example, a value obtained by dividing the deviation amount by the average crank angular velocity, and is set to a smaller value as the deviation amount (or its correlation value) is smaller. The combustion stability index set here usually has a value in the range from 0 to about 0.5 as shown in FIG. 3, and the closer the combustion stability index is to 0, the better the combustion stability is. It shows that. The combustion stability index is calculated, for example, in units of 100 combustion cycles, and is updated sequentially.

  The target combustion stability index setting means 106 sets a target combustion stability index according to the engine coolant temperature (this is a water temperature table). Here, as shown by a thick solid line in FIG. 3, the target combustion stability index is 0.25 when the water temperature is 20 ° C. to 40 ° C., and the water temperature is 40 ° C. to 80 ° C. When the water temperature exceeds 80 ° C, it is set to 0.15. The reason why the target combustion stability index is set smaller as the water temperature is higher is that the higher the water temperature is, the better the combustion stability is. In addition, when the water temperature is low, in order to give priority to the exhaust performance, a large target combustion stability index is set.

  The combustion stability level setting means 107 uses the actual (current) combustion stability index calculated by the combustion stability index calculation means 105 and the target combustion stability index set by the target combustion stability index setting means 106. In comparison, the current combustion stability level is set in four stages for each cylinder. Specifically, as shown in FIG. 3, a region where the combustion stability index is less than 50% of the target combustion stability index is a “good” level region, and a region where the combustion stability index is 50% to less than 100% is a “normal” level region. The area of 100% to less than 150% is set as the “bad” level area, and the area of 150% or more is set as the “worst” level area.

  The number-of-ignitions setting means 108 is a combustion stability level for each cylinder set by the combustion stability level setting means 107 (any one of “good” level, “normal” level, “bad” level, and “worst” level). ), The number of times of ignition Nspk_n when using the plasma jet ignition device is set for each cylinder (n is 1 to 4 in the case of four cylinders). As for the number of times of ignition Nspk_n, the initial value and the lower limit value are 1 time, and the upper limit value is set to 5 times. That is, as shown in FIG. 4, the control unit 100 (the memory thereof) is provided with an operation region map divided into a plurality of blocks according to the engine speed and the intake air amount for each cylinder. The number of ignitions is stored in each block in the map, and is updated according to the combustion stability level, for example, every 100 combustion cycles. Specifically, the cylinder determined to be “good” level subtracts the number of ignition times Nspk_n once if the number of ignition times Nspk_n is two or more, and maintains the current state if the number of ignition times Nspk_n is one. The cylinder determined to be “bad” adds the number of ignition times Nspk_n only once.

  In addition, when the number of ignition times Nspk_n reaches the upper limit of 5, the stratified charge combustion operation is prohibited. Further, even if there is even one cylinder having the “worst” combustion stability level, the stratified charge combustion operation is prohibited. When the stratified charge combustion operation is prohibited, the operation is shifted to the homogeneous combustion operation, and the ignition method is changed from the plasma jet ignition method to the spark ignition method along with this shift.

  Next, an ignition control routine executed by the control unit 100 (processing of each of the means 103 to 108 and the like) will be described with reference to flowcharts shown in FIGS.

  This ignition control routine is repeatedly executed at a predetermined cycle. After the start, first, in step S1 (stratified combustion operation permission determination means 103), based on the engine coolant temperature, the engine speed, the intake air amount, the throttle opening, and the like. It is determined whether or not the engine operating state is in the stratified combustion operation region. In the stratified charge combustion operation region, as described above, the stratified charge combustion operation is permitted if the stratified charge combustion operation prohibition condition such as a sensor or component failure or various diagnoses NG is not satisfied.

  If the stratified charge combustion operation is not permitted in step S1, the process proceeds to step S10 to perform the homogeneous combustion operation. In principle, a spark ignition device is used during homogeneous combustion operation.

  If the stratified charge combustion operation is permitted in step S1, the process proceeds to step S2 (plasma jet ignition device use permission determining means 104), and whether or not the use of the plasma jet ignition device is permitted based on various sensor signals and the like. Determine whether. As described above, the plasma jet ignition device has the problem that the ignition plug is consumed quickly and the power consumption is large. Even if a spark ignition device is used, the operating range and the remaining battery capacity (voltage) are not greatly different in combustion stability. If is below a certain value, the use of a plasma jet ignition device is not permitted.

  When the use of the plasma jet ignition device is not permitted in step S2, the process proceeds to step S11, and the stratified combustion operation using the spark ignition device is performed.

  When the use of the plasma jet ignition device is permitted in step S2, the process proceeds to step S3, and fuel injection by the fuel injection valve 12 is performed during the compression stroke in order to execute the stratified combustion operation. Here, the fuel injection timing, the fuel pressure, the fuel injection amount, and the like are calculated, and the valve opening timing, the valve opening time, and the discharge pressure of the high-pressure fuel pump are controlled. Although fuel injection may be performed a plurality of times during one combustion cycle, at the time of stratified combustion operation, fuel is injected from the fuel injection valve at least once in the compression stroke (around 20 to 50 ° C. A BTDC of compression TDC). The

  In subsequent step S4, ignition by the plasma jet ignition device is performed for each cylinder. Here, the optimum value of the ignition timing is stored (mapped) in the memory for each operation region, and the ignition timing set for the current operation region is read from the ignition timing map. The number of ignitions is also calculated, for example, in units of 100 combustion cycles in accordance with the combustion stability level set by the combustion stability level setting unit 107 as described in the description of the ignition number setting unit 108 described above, and is sequentially updated. To be done.

  In step S5, a combustion stability index and a target combustion stability index are calculated. The combustion stability index is calculated as described in the combustion stability index calculation means 105, and the target combustion stability index is set as described in the target combustion stability index setting means 106. The combustion stability index is calculated, for example, in units of 100 combustion cycles and updated sequentially.

  In step S6 (combustion stability level setting means 107), the combustion stability level is set to 4 for each cylinder based on the comparison result between the combustion stability index for each cylinder calculated in step S5 and the target combustion stability index. Calculate by dividing into stages (good, normal, bad, worst).

  In step S7, it is determined whether or not there is at least one cylinder in which the combustion stable level calculated in step S5 is determined to be the “worst” level. If it is determined that there is a “worst” level cylinder, the process proceeds to step S14, and processing for prohibiting stratified charge combustion operation is executed next time, and it is determined that there is no “worst” level cylinder. In this case, the process proceeds to step S8, and it is determined whether or not the combustion stable level is the “normal” level for all cylinders.

  If it is determined in step S8 that all cylinders are not at the “normal” level, the process proceeds to step S12 to set the number of ignition times Nspk_n for each cylinder. The number of ignition times Nspk_n for each cylinder is set as described above for the ignition number setting means 108.

  In the subsequent step S13, it is determined whether or not there is a cylinder having an upper limit (5 times) for the number of ignitions Nspk_n. If it is determined that there is a cylinder having an upper limit (5) for the number of ignitions, the process proceeds to step S14. Next time, processing for prohibiting stratified charge combustion operation is executed.

  Further, if it is determined in step S8 that all cylinders are at the “normal” level, and if it is determined in step S13 that there is no cylinder whose ignition number Nspk_n is the upper limit (five times), the ignition number Nspk_n is set to the current state. Keep it and return.

  When the next stratified combustion operation prohibition process is executed in step S14, the process is shifted to the homogeneous combustion operation. During the homogeneous combustion operation, deposits accumulate on the tip of the fuel injection valve, and the direction of fuel injection and the fuel Since it is considered that the injection amount is different from the design value, a deposit removal measure such as increasing the fuel pressure than usual or using a deposit removing agent is executed. Further, when the deposit removal measures are completed, the stratified charge combustion operation prohibition is canceled.

  As understood from the above description, in the engine ignition control device 1 of the present embodiment, when using the plasma jet ignition device, each cylinder is determined based on signals obtained from the crank angle sensor 21, the cam angle sensor 22, and the like. Since a combustion stability index (combustion stability) is calculated and feedback control is performed to increase or decrease the number of ignitions for one combustion cycle by the plasma jet ignition apparatus based on the combustion stability index, the plasma jet ignition apparatus Ignition control at the time of use can be performed more precisely than the conventional one, so that the combustion stability of each cylinder is improved, the variation in crank angular speed among the cylinders is reduced, and the durability, fuel consumption, exhaust The performance and the like can be sufficiently improved.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram which shows one Embodiment of the ignition control apparatus of the engine which concerns on this invention with an example of the vehicle-mounted engine to which it is applied. The functional block diagram which shows the processing content which the control unit of FIG. 1 performs in the case of plasma jet ignition control. The figure used for description of a combustion stability parameter | index, a target combustion stability parameter | index, and a combustion stability level. The conceptual diagram which shows the driving | operation area | region map used for description of the setting of the frequency | count of ignition of each cylinder. The flowchart which shows the ignition control routine (the first half) which the control unit of FIG. 1 performs. The flowchart which shows the ignition control routine (the second half) which the control unit of FIG. 1 performs.

Explanation of symbols

1 Ignition control device 2 Intake passage 2a Intake port
3 Exhaust passage 3a Exhaust port 4 Air flow sensor 5 Throttle valve 6 Collector 8 Intake valve 9 Exhaust valve 10 Engine 10A Cylinder 11 Common rail
12 Fuel Injection Valve 13 Spark Plug for Spark Ignition 14 Spark Plug for Plasma Jet Ignition 15 Output Circuit for Spark Ignition 16 Output Circuit for Plasma Jet Ignition 17 Piston 18 TCV (Tumble Control Valve)
19 Water temperature sensor 20 Combustion chamber 21 Crank angle sensor 22 Cam angle sensor 23 Battery 25 Throttle opening sensor 100 ECU (Engine Control Unit)
DESCRIPTION OF SYMBOLS 101 Engine speed calculation means 102 Deviation amount calculation means 103 Stratified combustion operation permission determination means 104 Plasma jet ignition device use permission determination means 105 Combustion stability index calculation means 106 Target combustion stability index setting means 107 Combustion stability level setting means 108 Ignition Number setting means

Claims (9)

An engine ignition control device comprising a fuel injection valve for directly injecting fuel into a combustion chamber, a plasma jet ignition device as a mixture ignition means in the combustion chamber, and a sensor for detecting the combustion stability of each cylinder There,
When the plasma jet ignition device is used, a combustion stability index is calculated for each cylinder based on a signal obtained from the sensor, and one combustion cycle by the plasma jet ignition device is calculated for each cylinder based on the combustion stability index. An ignition control device for an engine, characterized by performing control to increase or decrease the number of ignitions and / or at least one ignition output energy.   2. The engine ignition control device according to claim 1, further comprising a spark ignition device in addition to the plasma jet ignition device as the air-fuel mixture ignition means in the combustion chamber.   A crank angle sensor and / or a cam angle sensor as a sensor for detecting the combustion stability, and based on a signal obtained from the sensor, a deviation amount of a crank angular speed of each cylinder from an average crank angular speed of all cylinders or 2. The engine ignition control device according to claim 1, wherein the correlation value is obtained, and the combustion stability index is calculated for each cylinder based on the deviation amount or the correlation value.   An in-cylinder pressure sensor is provided as a sensor for detecting the combustion stability, and based on a signal obtained from the sensor, a deviation amount of the in-cylinder pressure of each cylinder with respect to an average in-cylinder pressure of all cylinders or a correlation value thereof is obtained. 2. The engine ignition control device according to claim 1, wherein the combustion stability index is calculated for each cylinder based on the deviation amount or a correlation value thereof.   For each cylinder, it is determined whether or not the combustion stability index has deteriorated beyond a set value. For cylinders that have deteriorated beyond the set value, the number of times of ignition is increased or the ignition output energy is increased. 2. For a cylinder that has not deteriorated more than the set value, the number of times of ignition is maintained or reduced, or control for maintaining or reducing the ignition output energy is performed. The engine ignition control device described.   A target combustion stability index is calculated based on the engine coolant temperature, and control is performed to increase or decrease the number of times of ignition or ignition energy based on a comparison result between the combustion stability index and the target combustion stability index. The engine ignition control device according to claim 1.   2. An upper limit value is set for the number of ignition times and / or ignition output energy, and stratified combustion operation is prohibited when the number of ignition times and / or ignition output energy reaches the upper limit value. An engine ignition control device according to claim 1.   2. The engine ignition control device according to claim 1, wherein, when the plasma jet ignition device is used, the stratified combustion operation is prohibited when there is a cylinder whose combustion stability index has deteriorated to a set value or more.   An operation region map divided into a plurality of blocks according to the engine speed and the intake air amount is provided for each cylinder, and each block in the map has at least one of the combustion stability index, the number of ignitions, and the ignition output energy. The engine ignition control device according to claim 1, wherein the engine ignition control device is stored and updated sequentially.

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