JP7123476B2 - Control device for internal combustion engine - Google Patents

Description

The present invention relates to a control device for controlling a spark ignition internal combustion engine mounted on a vehicle or the like.

In a spark ignition type internal combustion engine, a spark plug for igniting an air-fuel mixture filled in a cylinder receives an induced voltage generated by an ignition coil, and a dielectric breakdown occurs between the center electrode and the ground electrode. cause an electric discharge.

An igniter having a semiconductor switching element is provided on an electric circuit that energizes the ignition coil. When the semiconductor switch of the igniter is ignited (turned on), current flows through the primary side of the ignition coil. The primary current through the primary coil increases during firing of the semiconductor switch. After that, when the semiconductor switch is extinguished (turned OFF (non-conducting state)) at an appropriate spark ignition timing, a high voltage is generated on the primary side of the ignition coil due to self-induction at the moment the primary current is cut off. do. Further, a higher induced voltage is generated in the secondary side coil that shares the magnetic circuit and magnetic flux with the primary side. When this high induced voltage is applied to the center electrode of the spark plug, discharge occurs between the center electrode and the ground electrode (see, for example, the following patent documents).

JP 2016-089631 A

Recently, during one cycle of one cylinder (in a 4-stroke engine, a series of intake stroke - compression stroke - expansion stroke - exhaust stroke is regarded as one cycle), discharge is performed twice or more for the purpose of ignition. Implementation of multi-ignition (multi-spark, multi-discharge) is under consideration. Multi-ignition is intended to perform additional ignition immediately after the main ignition to reinforce the ignition combustion of the fuel or air-fuel mixture in the cylinder, thereby preventing misfires or destabilizing combustion. is doing.

However, simply increasing the number of spark ignitions in the same cycle is not enough. As the number of ignitions increases, the final ignition timing is retarded accordingly. Retarding the ignition timing causes afterfire, in which the fuel or air-fuel mixture burns in the exhaust port or exhaust passage, or backfire, in which the fuel or air-fuel mixture burns in the intake port or intake passage. Inappropriate after-fire and back-fire are never preferable because they lead to the generation of loud abnormal noises, damage to constituent members and sensors of the internal combustion engine, and the like.

SUMMARY OF THE INVENTION It is an object of the present invention to realize good ignition combustion while suppressing inappropriate afterfire or backfire by optimizing the number of discharge executions in multi-ignition.

In the present invention, a control device for controlling a spark ignition type internal combustion engine that applies an induced voltage generated by interrupting the energization of an ignition coil after energizing it to the electrodes of a spark plug to cause discharge between the electrodes, Two or more discharges are performed for the purpose of ignition during one cycle of one cylinder. The slowest ignition timing that does not cause inappropriate after-fire or back-fire by setting before the crank angle such that it becomes possible and setting it according to the current operating range of the internal combustion engine among the two or more discharges. A control device for an internal combustion engine is configured to cancel discharge without executing discharge when the timing is retarded from the threshold value of the crank angle .

In determining the spark ignition timing for the second and subsequent times, the energization time and the duration of spark discharge, which are preparations for spark discharge at each time, are determined according to the current operating range of the internal combustion engine, and based on this, each time It is conceivable to determine ignition timing. On top of that, if the ignition coil is not energized before the discharge to prepare for the discharge to be canceled because the timing is retarded from the threshold value, wasteful power consumption can be avoided. It is also useful for preventing heat damage due to temperature rise of the ignition coil.

According to the present invention, it is possible to optimize the number of times discharge is performed in multi-ignition, thereby realizing good ignition combustion while suppressing inappropriate afterfire or backfire.

1 is a diagram showing a schematic configuration of a spark ignition internal combustion engine and its control device according to an embodiment of the present invention; FIG. FIG. 2 is a circuit diagram of the ignition device for the internal combustion engine of the same embodiment; 4 is a diagram showing an example of spark ignition timing in multi-ignition performed by the control device of the embodiment; FIG. FIG. 4 is a diagram showing the relationship between the operating range of the internal combustion engine of the embodiment and whether or not multi-ignition is required; The figure which shows transition of the primary current and secondary current in the multi-ignition which the control apparatus of the same embodiment implements. The figure which shows the procedure example of the process which the control apparatus of the same embodiment performs according to a program. FIG. 4 is a diagram showing firing/extinguishing of a semiconductor switch in multi-ignition performed by the control device of the embodiment;

One embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of a vehicle internal combustion engine. The internal combustion engine in this embodiment is a port-injection, four-stroke, spark-ignited engine having a plurality of cylinders 1 (eg, three cylinders, one of which is shown in FIG. 1). An injector 11 for injecting fuel toward the intake port is provided near the intake port of each cylinder 1 . A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1, respectively.

An intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1 . An air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order on the intake passage 3 from upstream.

An exhaust passage 4 for exhausting exhaust guides the exhaust generated as a result of burning fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and a three-way catalyst 41 for purifying exhaust gas are arranged on the exhaust passage 4 .

Air-fuel ratio sensors 43 and 44 for detecting the air-fuel ratio of the exhaust gas flowing through the exhaust passage 4 are installed upstream and/or downstream of the catalyst 41 in the exhaust passage 4 . Each of the air-fuel ratio sensors 43 and 44 may be an _O2 sensor having a nonlinear output characteristic with respect to the air-fuel ratio of the exhaust gas, or a linear A/F sensor having an output characteristic proportional to the air-fuel ratio of the exhaust gas. may be The output characteristics of the _O2 sensors 43 and 44 show a sharp slope with a large rate of change in output with respect to the air-fuel ratio in a certain range (window) near the stoichiometric air-fuel ratio. , and in a rich region where the air-fuel ratio is smaller than that, it asymptotically approaches a high-level saturation value, drawing a so-called Z characteristic curve.

The exhaust gas recirculation device 2 realizes external EGR (Exhaust Gas Recirculation) in which part of the exhaust gas flowing through the exhaust passage 4 is recirculated to the intake passage 3 and mixed with intake air. The external EGR device 2 includes an external EGR passage 21 that communicates the upstream side of the catalyst 41 in the exhaust passage 4 and the downstream side of the throttle valve 32 in the intake passage 3, an EGR cooler 22 provided on the EGR passage 21, and an EGR An EGR valve 23 that opens and closes the passage 21 and controls the flow rate of the EGR gas flowing through the EGR passage 21 is an element. The inlet of the EGR passage 21 is connected to the exhaust manifold 42 in the exhaust passage 4 or a predetermined location downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3, especially to the surge tank 33 .

The internal combustion engine may be accompanied by a VVT (Variable Valve Timing) mechanism 5 capable of variably controlling at least the opening/closing timing of the intake valve of each cylinder 1 . The VVT mechanism 5 for adjusting the intake valve timing is, for example, a vane type that changes the rotation phase of the camshaft that drives the intake valve of each cylinder 1 with respect to the crankshaft by hydraulic pressure (lubricating oil pressure), or by an electric motor. It is an electric type that changes (motor drive VVT). As is well known, the camshaft receives rotational driving force from the crankshaft, which is the output shaft of the internal combustion engine, and rotates following the crankshaft. A winding transmission device (not shown) for transmitting rotational driving force is interposed between the crankshaft and the camshaft. The winding transmission device consists of a crank sprocket (or pulley) provided on the crankshaft side, a cam sprocket (or pulley) provided on the camshaft side, and a timing chain (or , timing belt). The VVT mechanism 5 changes the rotation phase of the camshaft with respect to the crankshaft by rotating the camshaft relative to the cam sprocket, thereby changing the opening/closing timing of the intake valve.

The VVT mechanism for adjusting the opening/closing timing of the exhaust valves changes, for example, the rotation phase of the camshaft that drives the exhaust valves of each cylinder 1 with respect to the crankshaft by hydraulic pressure or an electric motor. Note that this VVT mechanism may not be present, in which case the exhaust valve timing remains unchanged.

The VVT mechanism 5 described above is used to improve the charging efficiency of intake air into the cylinder 1 and to extend or shorten the valve overlap period during which both the intake valve and the exhaust valve are opened. By manipulating the valve overlap period, it is possible to increase or decrease the amount of internal EGR gas remaining in cylinder 1 without being discharged from cylinder 1 .

A specific aspect of the VVT mechanism 5 is arbitrary and not uniquely limited. In addition to advancing/retarding the rotation phase of the camshaft with respect to the crankshaft, there are several cams that drive the opening of the intake valves or exhaust valves, and these cams are used appropriately. There are known systems in which the pressure is changed via an electric motor, systems in which intake valves or exhaust valves are electromagnetic solenoid valves, and the like, and it is permitted to select and employ from among these various mechanisms.

FIG. 2 illustrates an electric circuit of an ignition device for a spark ignition type internal combustion engine. The spark plug 12 receives an induced voltage generated by the ignition coil 14 and induces discharge between the center electrode and the ground electrode. The ignition coil 14 is integrally built in a coil case together with an igniter 13 having a semiconductor switching element 131 such as an IGBT (Insulated Gate Bipolar Transistor).

When the igniter 13 receives an ignition signal i from an ECU (Electronic Control Unit) 0, which is a control device for the internal combustion engine of the present embodiment, the semiconductor switch 131 of the igniter 13 is first ignited, and a current is supplied to the primary side 141 of the ignition coil 14. flows, and the semiconductor switch 131 extinguishes the arc at the timing of spark ignition immediately after that, cutting off this current. A self-inductive action then occurs and a high voltage is generated on the primary side 141 . Since the primary side 141 and the secondary side 142 share a magnetic circuit and magnetic flux, a higher induced voltage is generated on the secondary side 142 . The induced voltage on the secondary side 142 reaches 10 kV to 30 kV. This high induced voltage is applied to the center electrode of the spark plug 12, and discharge occurs between the center electrode and the ground electrode.

A primary side coil 141 of the ignition coil 14 is connected to the power storage device 16 mounted on the vehicle via the semiconductor switch 131 . The power storage device 16 is a battery (lead battery, lithium ion battery, nickel metal hydride battery, etc.), a capacitor, or the like. A vehicle may be equipped with a combination of power storage devices 16 of a plurality of types.

When the semiconductor switch 131 is ignited and the DC voltage supplied from the power storage device 16 is applied to the primary coil 141 to start energization, the primary current flowing through the primary side (low voltage system) circuit including the primary coil 141 is Gradually increase. Assuming that the electric circuit on the primary side including the power storage device 16 and the primary side coil 141 is an RL series circuit, the primary current I(t) when the application of the DC voltage E is started at t=0 is
I(t)≈{1−e− ^(R/L)t }E/R
becomes. That is, the primary current gradually increases as a transient phenomenon, but the speed of increase gradually declines. The primary current saturates at E/R after a long period of time from the start of energization. However, in reality, the saturation value E/R is not necessarily reached because the primary current does not increase further even if the primary coil 141 continues to be energized due to the operation of the current limiting function, which will be described later.

In a state where the primary current is sufficiently large, the ECU 0 extinguishes the semiconductor switch 131 of the igniter 13 associated with the cylinder 1 in accordance with the ignition timing of the cylinder 1, and turns off the ignition coil 14 associated with the cylinder 1. cut off the energization to the primary coil 141 of As a result, the induced voltage generated by the ignition coil 14 is applied to the center electrode of the spark plug 12 of the cylinder 1, thereby causing discharge due to dielectric breakdown between the center electrode of the spark plug 12 and the ground electrode. provoke

Incidentally, the igniter 13 has a current limiting function for suppressing excessive primary current. This current limiting feature is similar to that of today's popular off-the-shelf igniters. Specifically, the control circuit 132 constantly measures the primary current in the form of voltage across the resistor 133 via the detection resistor 133 . While the magnitude of the primary current (the voltage across the resistor 133) is below a specified value, the semiconductor switch 131 is turned on, and when it exceeds the specified value, the semiconductor switch 131 is turned off. This clips the magnitude of the primary current to a specified value.

Further, the igniter 13 is provided with a primary voltage setting section using a Zener diode 134, for example. This primary voltage setting unit serves to suppress the magnitude of the primary voltage induced in the primary side coil 141 of the ignition coil 14 to a predetermined value for the purpose of protecting the semiconductor switch 131 from high voltage. If the semiconductor switch 131 is an IGBT, a voltage clamping Zener diode 134 is interposed between the collector and gate of the IGBT 131, with its anode connected to the IGBT 131 gate and its cathode connected to the IGBT 131 collector. The Zener diode 134 clips the magnitude of the primary voltage induced in the primary coil 141 of the ignition coil 14 by extinguishing the IGBT 131 to a value within the range of, for example, 350V to 500V, and the primary voltage exceeds that value. It works to prevent it from rising too much.

In addition, the igniter 13 also has a function of forcibly cutting off the current to the primary side coil 141 when abnormal heat generation is detected such that the temperature of the ignition coil 14 or the igniter 13 itself exceeds the upper limit value. there is

The ignition device for an internal combustion engine of this embodiment has an ignition coil 14 for supplying a high voltage for spark ignition to the spark plug 12 of each cylinder 1 for each cylinder 1 . Each of the ignition coils 14 for each cylinder 1 is composed of one primary side coil 141 and one secondary side coil 142 forming a pair. The primary side coil 141 and the secondary side coil 142 are connected via the diode 15 . The diode 15 is for noise prevention to prevent backflow from the secondary side 142 .

A generator 17, which is a power supply source for energizing the ignition coil 14, driving the valves 23 and 32, the motor, and other electrical systems mounted on the vehicle, receives engine torque from the crankshaft, which is the output shaft of the internal combustion engine. Electric power is generated by receiving the supply, and the generated electric power is stored in the power storage device 16 mounted on the vehicle.

The generator 17 may be an alternator that has been conventionally used as a generator for automobiles, or may be a motor generator or a motor generator that also functions as an electric motor that drives the crankshaft of an internal combustion engine or the axle of a vehicle (and the driving wheels). It may be an ISG (Integrated Starter Generator). The internal combustion engine and the generator 17 are connected to each other through, for example, a winding transmission device having belts and pulleys as elements.

An IC regulator or controller 171 associated with the generator 17 receives a control signal m that commands a target value for the output voltage of the generator 17, issued from the ECU0. Then, in order to cause the terminal voltage of the storage device 16 (or the power supply voltage supplied to the electrical system) to follow the instructed target voltage, the semiconductor switching element is switched to apply excitation to the excitation (field) winding. PWM (Pulse Width Modulation) control is performed to adjust the magnitude of the current. The output voltage of the generator 17 increases as the excitation current flowing through the excitation winding increases.

In addition, the generator 17 can perform regenerative braking when the vehicle decelerates and recover the kinetic energy of the vehicle as electrical energy. The ECU 0 controls the excitation current flowing through the excitation winding of the generator 17 when the amount of depression of the accelerator pedal by the driver becomes 0 or less than a predetermined value close to 0, that is, when deceleration of the internal combustion engine and the vehicle is required. A control signal m is applied to the IC regulator or controller 171 to raise the upper limit of current and the output voltage of the generator 17 .

The ECU0, which controls the operation of the internal combustion engine, is a microcomputer system having a processor, memory, input interface, output interface, and the like.

The input interface of the ECU 0 receives a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed, a crank angle signal b output from a crank angle sensor that detects the rotation angle of the crankshaft of the internal combustion engine and the engine speed. , an accelerator opening signal c output from a sensor that detects the amount of depression of the accelerator pedal or the opening of the throttle valve 32 as the accelerator opening (so to speak, the required engine load factor or engine torque), the intake passage 3 (particularly, Intake air temperature/intake pressure signal d output from a temperature/pressure sensor that detects the intake air temperature and intake pressure in the surge tank 33), terminal voltage and/or terminal current (in particular, battery voltage and/or or battery current), a coolant temperature signal f output from a coolant temperature sensor that detects the coolant temperature indicating the temperature of the internal combustion engine, and a plurality of cam angles of the intake camshaft. A cam angle signal g output from a cam angle sensor, an air-fuel ratio signal h output from air-fuel ratio sensors 43 and 44 for detecting the air-fuel ratio of the exhaust gas flowing through the exhaust passage 4, and the like are input.

From the output interface of the ECU 0, an ignition signal i to the igniter 13, a fuel injection signal j to the injector 11, an opening operation signal k to the throttle valve 32, an opening operation signal l to the EGR valve 23, A control signal m for controlling the generator 17 is output to the IC regulator or controller 171 of the generator 17 , a valve timing control signal n is output to the VVT mechanism 5 , and the like.

The processor of the ECU0 interprets and executes programs stored in the memory, calculates operating parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various types of information a, b, c, d, e, f, g, and h necessary for controlling the operation of the internal combustion engine through an input interface, learns the engine speed, and fills the cylinder 1. Estimate the amount of intake air, the partial pressure of fresh air and the partial pressure of EGR gas. Then, based on them, the required fuel injection amount corresponding to the intake air amount (fresh air amount), fuel injection timing (including the number of fuel injections for one combustion), fuel injection pressure, ignition timing, required EGR rate (or EGR gas amount), power generation amount (output voltage) of the generator 17, opening/closing timing of the intake valve and/or the exhaust valve, etc. are determined. The ECU 0 applies various control signals i, j, k, l, m, and n corresponding to the operating parameters through the output interface.

During operation of the internal combustion engine, the ECU 0 feedback-controls the air-fuel ratio of the air-fuel mixture that fills the cylinder 1 and, in turn, the air-fuel ratio of the exhaust gas that is discharged from the cylinder 1 and led to the catalyst 41 . The ECU 0 first calculates the amount of intake air charged into the cylinder 1 from the intake pressure, the intake air temperature, the engine speed, the required EGR rate, etc., and the ratio of this to the target air-fuel ratio (normally, the theoretical air-fuel ratio is 14.0). 6 or its vicinity) is determined.

Next, this basic injection amount TP is corrected with a feedback correction coefficient FAF that is determined according to the air-fuel ratio on the upstream side and/or downstream side of the catalyst 41 . The feedback correction coefficient FAF is adjusted according to the deviation between the target air-fuel ratio and the air-fuel ratio of the gas actually measured via the air-fuel ratio sensors 43, 44, and is increased when the actually measured air-fuel ratio is leaner than the target air-fuel ratio. and decreases when the measured air-fuel ratio is rich with respect to the target air-fuel ratio.

Then, the final fuel injection time (energization time for the injector 11) T is calculated in consideration of various correction coefficients K determined depending on the situation and the invalid injection time TAUV of the injector 11. The fuel injection time T is
T = TP x FAF x K + TAUV
becomes. The ECU 0 inputs a signal j to the injector 11 for the fuel injection time T, and opens the injector 11 to inject fuel.

The external EGR rate, which is the ratio of the external EGR gas to the intake air charged into the cylinder 1 in the intake stroke, in other words, the opening of the EGR valve 23, is determined by the operating range of the internal combustion engine at that time [engine speed, surge tank 33 internal intake pressure (or accelerator opening, engine load factor, engine torque, partial pressure of fresh air in intake charged into cylinder 1, intake amount charged into cylinder 1 or fuel injection amount)] adjust. Basically, the external EGR rate is maximized in a medium load region where the accelerator opening is moderate, and then decreases as the accelerator opening decreases, and further decreases as the accelerator opening increases. In the idling or low load operating range where the accelerator opening is 0 or close to 0, or in the full load (Wide Open Throttle) or high load operating range where the accelerator opening is fully open or close to full open, the required external EGR rate is 0, and the EGR valve 23 is fully closed.

The valve timing realized by the VVT mechanism 5 is also adjusted according to the operating range of the internal combustion engine at that time [engine speed, intake pressure in surge tank 33 (or accelerator opening, etc.)]. As a specific example of the opening and closing timing of the intake valve, when the engine is idling or in a low-load operating range, or when the coolant temperature of the internal combustion engine is low, the intake valve timing is most retarded to minimize or zero the valve overlap period. and eliminate blow-back of exhaust to the intake port. In the medium load operating region, the intake valve timing is advanced more than in the low load operating region, and the valve overlap period is extended. When the valve overlap period is lengthened, the internal EGR rate, which is the ratio of the internal EGR gas to the air-fuel mixture charged in the cylinder 1, increases, and the pumping loss of the internal combustion engine can be reduced. In operating regions where the engine load is higher or the engine speed is higher, the intake valve timing is further advanced to effectively utilize the inertial force of the intake air, and the intake air once drawn into cylinder 1 is blown back to the intake port. Reduce volume and improve volumetric efficiency to increase engine torque and power.

The ECU 0 of this embodiment performs multi-ignition in which spark ignition is performed two or more times during one cycle of one cylinder 1, in other words, during the period from the compression stroke to the expansion stroke in the cylinder 1. can be done. Each discharge induced between the electrodes of the spark plug 12 in the multi-ignition aims at igniting the air-fuel mixture charged in the cylinder 1, that is, the fuel present in the cylinder 1. FIG. Multi-ignition is intended to reinforce the ignition combustion of the air-fuel mixture by performing additional ignition immediately after the main ignition, and to prevent misfires or destabilization of combustion. The multi-ignition makes it possible to increase the EGR rate of the intake air and/or allows EGR to be performed even in an operating region where EGR could not be performed conventionally, thereby improving the fuel efficiency of the internal combustion engine. Further improvements and improved emissions can be expected.

In order to realize multiple ignitions in the same cycle, the rate of increase of the primary current flowing through the primary coil 141 of the ignition coil 14 should be increased as much as possible, that is, the required amount of electric energy to be stored in the ignition coil 14 should be increased. It is required to shorten the time as much as possible. The ignition coil 14 of the ignition device for the internal combustion engine of the present embodiment adjusts the number of turns, the size of the core, etc., so that the rate of increase of the primary current can be changed to the conventional one in which spark ignition is performed once per cycle. faster than that in the ignition system. On the other hand, the trade-off is that the secondary voltage generated in the secondary coil 142, which depends on the difference in the number of turns between the primary coil 141 and the secondary coil 142, may decrease. Therefore, the induced electromotive force (induced electromotive force) of the primary coil 141 is made larger than that of the conventional ignition device.

In this embodiment, it is assumed that three ignitions are added at maximum after the first main ignition. FIG. 3 illustrates the timing of spark ignition in multi-ignition. In this illustrated example, during the same cycle of cylinder 1, one additional ignition is performed after the main ignition, for a total of two ignitions. In FIG. 3, the time when the crank angle is 0°CA is the compression top dead center of cylinder 1, and the time when the crank angle is a negative value is during the compression stroke before the compression top dead center (BTDC) of cylinder 1. The value is during the expansion stroke after compression top dead center (ATDC). Time S1 represents the timing of the first main ignition, and time S2 represents the timing of the additional second ignition. The first ignition timing can be determined in the same manner as in the control of a conventional spark ignition internal combustion engine. In addition, it is desirable to set the timing of the second ignition following the first ignition before the crank angle at which the mass fraction burnt in cylinder 1 becomes a predetermined value, for example, 5%. MFB is the ratio of the mass of fuel burned to the mass of fuel supplied into cylinder 1 per cycle. MFB is expressed by the following equation as a function of crank angle θ, for example.
MFB=[1−cos{π(θ−θ ₀ )/θ _b }]/2
where θ ₀ is the crank angle at the beginning of combustion and θ _b is the crank angle at the end of combustion. In FIG. 3, A1 represents the time when MFB reaches 5%, and A2 represents the time when MFB reaches 50%. The crank angle at the second ignition timing does not fluctuate much and is generally constant.

Whether or not to perform multi-ignition is determined according to the operating range of the internal combustion engine [engine speed, intake pressure in surge tank 33 (or accelerator opening, etc.)]. FIG. 4 shows the relationship between the operating range of the internal combustion engine and whether or not multi-ignition is performed. In a region R1 where the engine speed is relatively low and the accelerator opening is relatively small, multi-ignition is performed.

On the other hand, in the region R2 where the accelerator opening is larger than that, the amount of intake air and the amount of combustion injection charged to the cylinder 1 are large (especially in the high load region, a large amount of fresh air flows into the cylinder 1 and relatively The amount of EGR gas is reduced), and the combustion is originally less likely to become unstable, so there is little need to implement multi-ignition. Therefore, by not implementing multi-ignition, that is, by performing spark ignition only once during one cycle of one cylinder 1, electric power consumption and temperature rise of the ignition coil 14, and furthermore, the electrode of the spark plug 12 will be reduced. Reduce wear and tear. Further, in the region R3 where the engine speed is relatively high, the spark ignition execution frequency per unit time inevitably increases, and there is concern that the temperature of the ignition coil 14 may rise excessively and cause heat damage. do not implement

FIG. 5 illustrates the ignition/extinguishing of the semiconductor switch 131 in the spark ignition device and the transition of the current flowing through the primary coil 141 and the secondary coil 142 of the ignition coil 14 when multi-ignition is performed. In this illustrated example, a total of two ignitions are performed during the same cycle of cylinder 1 . In FIG. 5, time T0 represents the time at which the semiconductor switch 131 is ignited in preparation for the first ignition and energization of the primary coil 141 is started, and time T1 is the time at which the semiconductor switch 131 is turned off for the first ignition. It represents the point in time at which the energization of 141 to the primary side coil is interrupted. Time T1 coincides with the start of the first discharge between the electrodes of the spark plug 12, that is, the first ignition timing in cylinder 1.

A subsequent time point T3 represents a time point at which the semiconductor switch 131 is ignited in preparation for the second ignition and energization of the primary coil 141 is restarted, and a time point T4 indicates the time point at which the semiconductor switch 131 is turned off for the second ignition. It represents the point in time at which the energization of 141 to the primary side coil is interrupted. Time T4 coincides with the start of the second discharge between the electrodes of spark plug 12, that is, the second ignition timing in cylinder 1.

In this embodiment, the time T3 at which the semiconductor switch 131 is re-ignited in preparation for the second ignition is earlier than the time T2 at which the last discharge for the first ignition ends. If the semiconductor switch 131 were not re-ignited at time T3, the first discharge would continue and the electrodes of the secondary side coil 142 and the spark plug 12 would be discharged as indicated by the dashed lines in FIG. The amount of current flowing through the discharge path in between should decrease over time, resulting in a local minimum value of 0 or near 0 at some point T2. However, the latter half of the discharge when the current amount is reduced does not necessarily contribute to the ignition combustion of the fuel in the cylinder 1, so it is a waste of electric power. can also be depleted.

Therefore, in the present embodiment, the semiconductor switch 131 is re-ignited at time T3 when the magnitude of the current flowing through the discharge path between the electrodes of the secondary coil 142 or the spark plug 12 becomes equal to or less than a certain amount. When the semiconductor switch 131 is ignited during the discharge between the electrodes of the spark plug 12, the energization of the primary side 141 of the ignition coil 14 is resumed, the voltage applied to the center electrode of the spark plug 12 drops, and the electrode Discharge between is forcibly interrupted. At this time, in the ignition coil 14, surplus magnetic flux induced due to the previously interrupted discharge remains. In other words, a certain amount of energy is already stored in the ignition coil 14 at time T3 when energization of the ignition coil 14 is resumed to trigger the next discharge, and this energy can be used for the next discharge. Therefore, the time required for energizing the ignition coil 14 for triggering the next discharge, that is, the time required for increasing the primary current flowing through the primary coil 141 to the magnitude necessary for spark ignition, is shortened. The time interval between the discharge and the second discharge is not extended, and the next discharge can be induced at a suitable timing. After all, the energy spent in the later stages of the discharge, which does not necessarily contribute to ignition combustion, can be used for the next discharge.

Hereinafter, a method for determining the ignition timing by the ECU 0 of this embodiment will be described in detail. FIG. 6 shows an example of the procedure of processing executed by the ECU according to the program. In determining the timing of spark ignition in the expansion stroke or compression stroke of each cylinder 1, the ECU 0 first determines the timing of the first ignition, that is, discharge (step S1). In step S1, the first ignition timing is adjusted in accordance with the operating range of the internal combustion engine, as in the control of the conventional spark ignition internal combustion engine. The memory of the ECU 0 stores in advance map data defining the relationship between the parameters representing the operating range of the internal combustion engine [engine speed, intake pressure in surge tank 33 (or accelerator opening, etc.)] and the first ignition timing. is stored. The ECU 0 searches the map using the current operating range of the internal combustion engine as a key, and obtains the first ignition timing.

Next, the ECU 0 determines whether or not to carry out multi-ignition in which additional ignition or discharge is performed immediately after the first ignition or discharge (step S2). When the coolant temperature of the internal combustion engine is higher than a predetermined temperature, when the intake air temperature is higher than a predetermined temperature, or when the outside air temperature is higher than a predetermined temperature, an excessive temperature rise of the ignition coil 14 is avoided. Do not carry out multi-ignition. Also, if it is within a predetermined period of time after the internal combustion engine has been cold-started and the amount of electricity stored in the power storage device 16, especially the battery voltage is less than or equal to a predetermined amount, the multi-ignition is not performed. This is because when the voltage applied to the primary side 141 of the ignition coil 14 is low, the primary current increases at a slow rate. The current storage amount of the power storage device 16 can be known or estimated by referring to the voltage/current signal e.

In addition, as already mentioned, whether or not to implement multi-ignition depends on the operating range of the internal combustion engine. The ECU 0 determines that multi-ignition is to be performed only when the current operating range of the internal combustion engine is in a range R1 in which the engine speed is relatively low and the intake pressure in the surge tank 33 is relatively low. Decide not to ignite. Exceptionally, when the cooling water temperature of the internal combustion engine is extremely low below a predetermined temperature, or when the internal combustion engine is just after a cold start, the first ignition timing is adjusted more than usual in order to promote the temperature rise of the catalyst 41 for purifying exhaust gas. When the engine is also retarded, multi-ignition may be performed. If the temperature in the combustion chamber of cylinder 1 is remarkably low or the spark ignition timing is remarkably late, ignition combustion of fuel or air-fuel mixture in cylinder 1 becomes unstable. Moreover, at extremely low temperatures, the fuel injected from the injector 11 becomes liquid and adheres to the electrode of the spark plug 12, which is a so-called plug fogging. Plug fogging is a factor that destabilizes ignition combustion. Therefore, regardless of the current operating range of the internal combustion engine, when the temperature of the internal combustion engine is extremely low or the ignition timing is greatly retarded, multi-ignition is performed to stabilize the ignition combustion.

In step S2, the ECU 0, which has decided to carry out the multi-ignition, determines the length of the energization time of the primary coil 141 of the ignition coil 14 in preparation for inducing the second and subsequent ignitions, i.e., the discharge. is determined (step S3). The energization time of each time means the time from when the semiconductor switch 131 is ignited before the ignition timing of each time until it is extinguished. Needless to say, the extinguishing of the semiconductor switch 131 coincides with the timing of the ignition in question. In this embodiment, three ignitions are added at maximum after the main ignition. Therefore, in step S3, as shown in FIG. 7, the energization time to prepare for each of these additional ignitions, that is, the energization time tonmulti1 before the second ignition, the energization time tonmulti2 before the third ignition, and the fourth time. An energization time tonmulti3 before the first ignition is set respectively. However, as will be described later, it is not always necessary to add three ignitions after the main ignition. The energization times tonmulti1, tonmulti2, and tonmulti3 of each time may have the same value or may have different values. Note that ton in FIG. 7 is the energization time before the first main ignition, and the necessary primary current is secured at the first ignition timing, as in the control of the conventional spark ignition internal combustion engine. It should be set to a length long enough to be Each energization time tonmulti1, tonmulti2, tonmulti3 for the additional ignitions is often shorter than the energization time ton for the main ignition.

The memory of the ECU 0 stores in advance the relationship between the parameters representing the operating range of the internal combustion engine [engine speed, intake pressure in surge tank 33 (or accelerator opening, etc.)] and the basic value of the energization time before each ignition. Stores map data that defines The ECU 0 searches the map using the current operating range of the internal combustion engine as a key, and obtains the basic value of the energization time before each ignition. The length of the energization time tends to be shorter as the engine speed is higher. This is because the higher the engine speed, the higher the angular velocity of the crankshaft of the internal combustion engine, and because the number of times of ignition per unit time increases and the amount of heat generated by the ignition coil 14 increases.

On the other hand, the length of the energization time before each ignition is expanded or reduced according to the magnitude of the electrical resistance between the electrodes of the spark plug 12 at the time of ignition. This is because the greater the resistance between the electrodes, the more energy is required to cause dielectric breakdown between the electrodes to initiate discharge. The electrical resistance between the electrodes of the spark plug 12 increases as the amount of fresh air charged in the cylinder 1 increases and as the partial pressure of the fresh air increases. Under the condition that the engine speed is the same, the energization time before each ignition set in step S3 is the surge in the intake stroke of the same cycle as the ignition (that is, the most recent before ignition). The higher the intake pressure in the tank 33, the longer it is, the greater the intake air amount (or fresh air amount) flowing into the cylinder 1 in the intake stroke of the same cycle, the longer it is, or the larger the accelerator opening, the longer it is.

In step S3, the ECU 0 corrects the basic value of the energization time according to the current operating range of the internal combustion engine according to the current amount of electricity stored in the power storage device 16 or the battery voltage. The rate of increase of the primary current flowing through the primary side of the ignition coil 14 depends on the voltage applied to the primary side coil 141. The higher the applied voltage, the faster the rate of increase of the primary current. Conversely, the lower the applied voltage, the faster the primary current. Increase speed slows down. That is, when the applied voltage is low, it is necessary to energize the primary coil 141 for a longer time before spark ignition. For this reason, the lower the current storage amount of the power storage device 16 or the battery voltage, the longer the energizing time before each ignition is corrected.

However, an upper limit value and/or a lower limit value are set in advance for the energization time of the primary coil 141 before each ignition. If the power-on time exceeds the upper limit value after adding the correction to the basic value, the power-on time is clipped to the upper limit value. Clip the energization time to the lower limit. Setting the upper limit for the energization time is intended to suppress the amount of heat generated by the ignition coil 14 to prevent heat damage. The reason why the lower limit is set for the energization time is that the secondary voltage flowing through the primary side coil 141 is induced in the secondary side coil 142 in order to induce the minimum required secondary voltage to cause discharge between the electrodes of the spark plug 12. The intention is to secure the energization time for increasing the primary current. The magnitude of the voltage that can be applied from the secondary coil 142 to the center electrode of the spark plug 12 is determined by the magnitude of the primary current immediately before the energization of the primary coil 141 is interrupted. If the primary current is small, the secondary voltage will also be small, and the dielectric breakdown between the electrodes of the spark plug 12 will not occur, resulting in no discharge.

Subsequently, the ECU 0 determines the length of time to sustain the discharge for the first main ignition, and the length of time to sustain the discharge for the second and subsequent ignitions added to this ( step S4). The discharge duration of each time means the time from extinguishing the semiconductor switch 131 at each ignition timing to igniting it again. If the discharge duration is shortened and the semiconductor switch 131 is re-ignited at a point when the discharge has not yet ended, the current discharge will be interrupted. In this embodiment, a maximum of three ignitions are added after the main ignition. Therefore, in step S4, as shown in FIG. 7, the discharge duration of each ignition performed before these additional ignitions, that is, the discharge duration tonintm of the first ignition, the discharge duration of the second ignition Tonint1 and discharge duration tonint2 for the third ignition are set respectively. Of course, it is not always necessary to add three ignitions after the main ignition. The energization times tonintm, toninto1, and tonint2 of each time may be the same value or may be mutually different values. The discharge durations tonint1, tonint2 of the additional ignitions are often shorter than the discharge duration tonintom of the main ignitions. Note that tonint3 in FIG. 7 is the discharge duration of the third additional ignition, which is the final of the additional ignitions, and the fourth ignition in total including the main ignition. The control may be continued until the discharge ends as in the control of the engine, or the semiconductor switch 131 may be re-ignited before the discharge ends to suppress wear of the electrode of the spark plug 12 as much as possible. good.

The relationship between the parameters representing the operating range of the internal combustion engine [engine speed, the intake pressure in the surge tank 33 (or accelerator opening, etc.)] and the basic value of the discharge duration of each ignition is stored in the memory of the ECU 0 in advance. Stores map data that defines The ECU 0 searches the map using the current operating range of the internal combustion engine as a key, and obtains the basic value of the discharge duration of each ignition. The length of the discharge duration tends to be shorter as the engine speed is higher. This is because the higher the engine speed, the higher the angular velocity of the crankshaft of the internal combustion engine.

Also, the length of the discharge duration scales according to the speed at which the amount of current flowing through the discharge path between the electrodes of the secondary coil 142 and the spark plug 12 decreases after the start of the discharge for spark ignition. . Since the latter period of the discharge when the amount of current decreases does not necessarily contribute to the ignition combustion of the fuel in the cylinder 1, the discharge in the latter period may be terminated without being continued. Therefore, the faster the rate of decrease of the discharge current, the shorter the discharge duration.

The speed at which the amount of current decreases during discharge depends on the electrical resistance between the electrodes of the spark plug 12 . The energy consumed by the discharge between the electrodes is the time integral of the product of the secondary voltage applied to the electrodes of the spark plug 12 and the secondary current flowing through the electrodes. The magnitude of the secondary current when the discharge starts between the electrodes depends on the characteristics of the ignition coil 14, and the magnitude of the secondary voltage when the discharge starts increases as the resistance between the electrodes increases. The greater the resistance between the electrodes, the faster the energy stored in the ignition coil 14 is consumed, and the faster the secondary current and secondary voltage decrease. Moreover, the greater the resistance between the electrodes, the more energy is required to cause dielectric breakdown between the electrodes to initiate discharge, and the secondary current will decrease accordingly.

The electrical resistance between the electrodes of the spark plug 12 increases as the amount of fresh air charged in the cylinder 1 increases and as the partial pressure of the fresh air increases. Under the condition that the engine speed is the same, the discharge duration of the ignition set in step S4 is the surge tank 33 in the intake stroke of the same cycle as the ignition (that is, the latest before ignition). The higher the internal intake pressure, the shorter it is.

Furthermore, the electrical resistance between the electrodes of the spark plug 12 increases as the amount of fuel present in the cylinder 1 decreases and as the partial pressure of the EGR gas decreases. One reason for this is that ions are contained in the components of unburned fuel or burned fuel. The discharge duration of ignition set in step S4 is the same as that of cylinder 1 in the same cycle in which ignition is performed under the condition that the engine speed and the above-mentioned intake pressure, intake amount, or accelerator opening are equivalent. The smaller the amount of fuel supplied to the engine or the larger the air-fuel ratio of the intake air charged to cylinder 1, the shorter it is, or the EGR rate, which is the ratio of EGR gas to the intake gas charged to cylinder 1 in the intake stroke of the same cycle. becomes shorter as .

Based on the same idea, under the same other conditions, the lower the temperature of the intake air charged to cylinder 1 in the intake stroke of the same cycle as the ignition is performed, the shorter the discharge duration is. The discharge duration can be shortened as the cooling water temperature is lowered. Also, under the same other conditions, the discharge duration may be shortened as the humidity of the intake air charged into the cylinder 1 is lower in the intake stroke of the same cycle. However, if the humidity of the intake air increases, the temperature of the electrode of the ignition plug 12 decreases and the secondary voltage at the start of discharge increases. Therefore, it is not necessary to adjust the discharge duration according to the humidity of the intake air. Maybe.

As a result of determining the energization time of each time in step S3 and determining the discharge duration of each time in step S4, the ignition timing of each time is determined. However, the energization time and discharge duration values obtained through steps S3 and S4 are both in units of time (milliseconds or microseconds), not crank angle (° CA). Needless to say, the angular speed of rotation of the crankshaft of the internal combustion engine, in other words, the speed of reciprocating motion of the piston in cylinder 1, varies according to the engine speed. Therefore, even if the energization time and discharge duration are the same each time, the crank angle of the spark ignition timing each time differs according to the engine speed. Therefore, the ECU 0 converts the energization time and discharge duration of each time into a crank angle from the current engine speed, and calculates the crank angle of each ignition timing (step S5).

Then, the ECU 0 determines how many additional ignitions are to be performed after the first main ignition according to the current situation (step S6). Specifically, the EGR valve 23 in the EGR device 2 is opened to perform external EGR, or the engine speed has increased to a certain level (for example, 1000 rpm to 1200 rpm) and the VVT mechanism 5 opens and closes the intake valve. When the timing is advanced to provide a valve overlap period and internal EGR is performed, additional ignition is performed a predetermined number of times (for example, twice. In that case, the fourth ignition is canceled). do. Even if this is not the case, when the cooling water temperature of the internal combustion engine is extremely low, the maximum number of additional ignitions (three times) is performed. Incidentally, when the temperature of the internal combustion engine is extremely low, normally EGR is not performed and the EGR valve 23 is fully closed. Alternatively, when the first ignition timing is retarded from normal in order to accelerate the temperature rise of the catalyst 41 immediately after the cold start of the internal combustion engine, additional ignition is performed a predetermined number of times (for example, twice). It is assumed that If none of these apply, either a minimum number of additional ignitions (eg, once) or no additional ignitions are performed.

In addition, the ECU 0 sets a crank angle threshold for the slowest ignition timing that does not cause inappropriate afterfire or backfire in order to prevent inappropriate afterfire or backfire due to additional ignition. Then, the ignition is canceled when the timing is retarded from the threshold (step S7). The memory of the ECU 0 stores in advance the relationship between the parameters representing the operating range of the internal combustion engine [engine speed, the partial pressure of fresh air in the intake air (or accelerator opening, etc.)] and the crank angle threshold for ignition timing. Prescribed map data is stored. The ECU 0 searches the map using the current operating range of the internal combustion engine as a key, and obtains the threshold value of the crank angle of the ignition timing. Then, the crank angle of each ignition timing calculated in step S5 is compared with a threshold value, and it is determined to cancel the ignition in which the ignition timing is later than the threshold value.

Through this step S7, the number of ignitions to be added to the main ignition is finally determined. The number of times may be less than the number of ignitions determined in step S6. For example, when the external EGR rate is set to a predetermined value or more, or the opening degree of the EGR valve 23 is set to a predetermined value or more, additional discharge is performed twice in addition to the main discharge. Suppose you run a discharge. However, the crank angle at the timing of the second additional discharge, that is, the third discharge as a whole (calculated in step S5) is the crank angle at the latest ignition timing according to the current operating range of the internal combustion engine. , the second additional discharge is canceled without being executed. On the other hand, the crank angle at the timing of the first additional discharge, that is, the second discharge as a whole (also calculated in step S5) is the latest ignition timing according to the current operating range of the internal combustion engine. If the crank angle is more advanced than the threshold, the first additional discharge is executed without being cancelled.

The ECU 0 performs a process of energizing the primary coil 141 of the ignition coil 14 before the discharge in preparation for the discharge that is to be canceled because the timing is delayed from the crank angle threshold of the latest ignition timing. Not performed. Then, the discharge to be executed in the cycle immediately preceding the one to be canceled is continued without interruption until the discharge to be executed ends. In accordance with the above example, when the first additional discharge is executed but the second additional discharge is canceled without being executed, the semiconductor switch 131 is extinguished at the timing of the first additional discharge. After the energization to the primary side coil 141 is interrupted by , the semiconductor switch 131 is not ignited again and the energization to the primary side coil 141 is not restarted until the first additional discharge ends. As a result, the duration of the first additional discharge is longer than when performing the second additional discharge. The same semiconductor switch 131 is ignited again to energize the same secondary coil 141 during the intake stroke or compression stroke of the next cycle of the same cylinder 1, that is, during the main spark ignition of the current cycle of the same cylinder 1. Before, in the preparatory period for inducing the main discharge.

When multi-ignition is not performed, only the first main spark ignition is performed during one cycle of one cylinder 1, as in the control of the conventional spark ignition type internal combustion engine.

In this embodiment, when the ignition coil 14 (primary side 141) is energized and then de-energized, an induced voltage (on the secondary side 142) is applied to the electrodes of the spark plug 12 to cause discharge between the electrodes. A control device 0 for controlling a spark-ignited internal combustion engine, which discharges two or more times for the purpose of ignition during one cycle of one cylinder 1, and the first discharge lasts During this time, energization of the ignition coil 14 (primary side 141) is resumed to interrupt the first discharge and prepare for the execution of the second discharge, under the condition that the engine speed is the same, The duration from the start to the discontinuation of the first discharge in a certain cycle is shortened as the intake pressure in the intake stroke of the cycle is higher, and is shortened as the amount of intake air flowing into cylinder 1 is increased in the intake stroke of the cycle. Alternatively, a control device 0 for an internal combustion engine is constructed in which the greater the opening of the accelerator, the shorter it is.

According to this embodiment, the fuel or air-fuel mixture in the cylinder 1 is ignited by the main spark ignition of the first time, and furthermore the second and subsequent spark ignitions are additionally carried out to achieve combustion in the conventional manner. can be stabilized more. Such multi-ignition reduces the risk of misfiring, that is, improves resistance to misfiring, making it possible to increase the EGR rate of the intake air more than before, and/or where EGR could not be performed in the past. Since EGR is permitted even in the operating range, it is expected that the fuel consumption performance of the internal combustion engine will be further improved and the emissions will be improved.

Moreover, according to this embodiment, it is possible to use the energy spent in the later stage of the discharge, which does not necessarily contribute to the ignition combustion, for the discharge of the next ignition, so that the energy can be used efficiently. In addition, the length of time during which the ignition coil 14 (primary side 141) is energized for inducing the second and subsequent discharges is shortened, and the time interval between the first discharge and the second and subsequent discharges is not lengthened. , the second and subsequent discharges can be induced at suitable timing, and the thermomechanical conversion efficiency of the internal combustion engine is improved.

The speed at which the amount of current flowing through the discharge path between the electrodes of the ignition coil 14 (secondary side 142 of it) and the spark plug 12 during discharge decreases depends on the intake pressure in the cylinder 1 and the amount of intake air charged in the cylinder 1. Varies depending on That is, the higher the intake pressure and the higher the intake air volume, the faster the decrease in the current amount. Therefore, the higher the intake pressure, the higher the intake air volume, or the greater the accelerator opening, the shorter the duration from the start of the discharge to the interruption of the previous discharge, and the timing to interrupt the discharge of the previous discharge is shortened. expedite.

In addition, the speed at which the amount of current flowing through the discharge path between the electrodes of the ignition coil 14 and the spark plug 12 decreases during discharge also varies depending on the air-fuel ratio of the air-fuel mixture charged in the cylinder 1 and the amount of EGR gas. . These affect the amount of ions present in the cylinder 1 and increase or decrease the electrical resistance between the spark plug 12 electrodes. In principle, the smaller the amount of fuel or EGR gas present in cylinder 1, the faster the amount of current decreases. Therefore, the duration from the start of the previous discharge to the interruption is shortened as the amount of fuel supplied to the cylinder 1 is smaller or the air-fuel ratio of the intake air charged in the cylinder 1 is larger, and/or The smaller the EGR rate, which is the proportion of EGR gas in the intake air, the shorter it is, and the earlier the timing of interrupting the previous discharge.

Further, in the present embodiment, a control device for controlling a spark ignition type internal combustion engine that applies an induced voltage generated by interrupting the energization of the ignition coil 14 after energizing it to the electrodes of the spark plug 12 to cause discharge between the electrodes. The length of the energization time of the ignition coil 14 in preparation for the second and subsequent discharges. is extended as the intake pressure in the intake stroke of the cycle is higher, or as the amount of intake air flowing into cylinder 1 is greater in the intake stroke of the cycle, under the condition that the engine speed is the same. A control device 0 for an internal combustion engine is configured in which the longer the opening, the longer it is, and the higher the engine speed, the shorter it is under the condition that the intake pressure, the intake air amount, or the accelerator opening is equal.

According to this embodiment, when performing multi-ignition, the length of time during which the primary side coil 141 of the ignition coil 14 is energized before the second and subsequent ignitions, that is, discharge, can be optimized. . The control device 0 for an internal combustion engine according to the present embodiment extends the energization time of the ignition coil 14 before ignition as the electrical resistance between the electrodes of the spark plug 12 at the time of ignition increases, thereby ensuring the second and subsequent discharges. provoke At the same time, the higher the engine speed, the shorter the energization time to the ignition coil 14 before ignition. It becomes possible to execute ignition each time. As a result, the second and subsequent ignitions contribute to the ignition combustion of the fuel or air-fuel mixture in the cylinder 1, avoiding waste of electrical energy, and further improving the thermomechanical conversion efficiency of the internal combustion engine.

Moreover, the control device 0 for an internal combustion engine according to the present embodiment can set the length of the energization time to the ignition coil 14 in preparation for the second and subsequent discharges at the same engine speed, intake pressure, intake amount, or accelerator opening. Under the condition that there is, the lower the voltage applied to the ignition coil 14 when the ignition coil 14 is energized, the longer it is. More specifically, the energization time is extended as the current storage amount of the power storage device 16 serving as the power source or the battery voltage is lower. Therefore, it is possible to absorb the influence of the amount of electricity stored in the electricity storage device 16 that fluctuates from moment to moment during the operation of the internal combustion engine and the vehicle, and to charge the ignition coil 14 with the necessary energy before ignition. It is possible to prevent the resulting ignition failure and deterioration of ignition combustion.

In addition, in the present embodiment, a control device for controlling a spark ignition type internal combustion engine that applies an induced voltage generated by interrupting the energization of the ignition coil 14 after energizing it to the electrodes of the spark plug 12 to cause discharge between the electrodes. 0, and two or more discharges are performed for the purpose of ignition during one cycle of one cylinder 1, and the number of discharges for the purpose of ignition during the same cycle is defined as the intake of the cycle. A control device 0 for an internal combustion engine is configured to change the length of a valve overlap period during which both the intake valve and the exhaust valve of cylinder 1 open during a stroke.

In particular, in the present embodiment, the number of discharges for the purpose of ignition during one cycle of one cylinder 1 is defined as the period of valve overlap in which both the intake and exhaust valves of cylinder 1 open during the intake stroke of the cycle. , the ratio of EGR gas to the intake air charged into cylinder 1 during the same cycle intake stroke, the timing of ignition during the same cycle expansion stroke, and the temperature of the internal combustion engine.

That is, in step S6, the control device 0 of the present embodiment sets other conditions such as the external EGR rate or the opening of the EGR valve 23, the timing of the first main spark ignition, the cooling water temperature of the internal combustion engine, etc. , the VVT mechanism 5 is operated to lengthen the valve overlap period (the valve overlap period is set to a predetermined value or more, or the amount of advance of the intake valve timing from the most retarded position is set to a predetermined value or more). The number of discharges in the case (e.g., two additional discharges, totaling three discharges combined with the main discharge), the shorter the valve overlap period (less than the specified valve overlap period, or the intake valve timing) than the number of discharges when the advance angle from the most retarded position is set to less than a predetermined value (e.g., one additional discharge or less, two times in total with the main discharge, or one time with the main discharge only) do more As a result, in a situation where the internal EGR rate is high and the ignition combustion of the fuel or air-fuel mixture in the cylinder 1 is likely to become unstable or the combustion may become slow, the number of times of spark ignition is increased to stabilize combustion. can be done. On the other hand, when the internal EGR rate is low and the ignition combustion of the fuel or air-fuel mixture is relatively stable, the number of times of spark ignition can be reduced to suppress energy consumption and electrode wear of the spark plug 12 .

In addition, under the same other conditions, the control device 0 of the present embodiment increases the opening degree of the EGR valve 23 to increase the external EGR rate (the external EGR rate is set to a predetermined value or more, or When the opening of the EGR valve 23 is set to a predetermined value or more, the number of discharges (for example, two discharges are added, and a total of three discharges are combined with the main discharge) is reduced by lowering the external EGR rate (external EGR rate is less than a predetermined value, or the degree of opening of the EGR valve 23 is less than a predetermined value), the number of discharges (for example, one additional discharge or less, two times in total with the main discharge, or only the main discharge). more than once). As a result, in a situation where the external EGR rate is high and the ignition combustion of the fuel or air-fuel mixture in the cylinder 1 is likely to become unstable or the combustion may become slow, the number of times of spark ignition is increased to stabilize combustion. can be done. On the other hand, when the external EGR rate is low and the ignition combustion of the fuel or air-fuel mixture is relatively stable, the number of times of spark ignition can be reduced to suppress energy consumption and electrode wear of the spark plug 12 .

The control device 0 of the present embodiment controls the number of discharges (for example, two additional discharges, total three times together with the main discharge), otherwise the number of discharges Main discharge only once) or higher. As a result, it is possible to effectively avoid unstable ignition and combustion of the fuel or air-fuel mixture in the cylinder 1 due to retardation of the ignition timing. On the other hand, when retardation correction control of ignition timing is not performed for the purpose of increasing the temperature of the catalyst 41, the number of times of spark ignition can be reduced to suppress energy consumption and electrode wear of the spark plug 12.例文帳に追加

Furthermore, the control device 0 of the present embodiment adds the number of discharges (for example, three discharges) when the cooling water temperature, which indicates the temperature of the internal combustion engine, is a predetermined or lower cryogenic temperature, and together with the main discharge 4 times in total) than the number of discharges in the other case (eg, no more than 2 additional discharges, 3 times in total with the main discharge, 2 times, or 1 time with the main discharge only). The maximum number of times of discharge when the temperature of the internal combustion engine is below a predetermined value is the maximum number of times of discharge when internal EGR and/or external EGR is performed (maximum of three times), or delay of ignition timing. It is larger than the maximum number of discharges (three times at maximum) when angle correction control is being performed. As a result, under extremely low temperatures where the ignition combustion of the fuel or air-fuel mixture in the cylinder 1 becomes unstable and the risk of misfire is high, the number of times of spark ignition is sufficiently increased to stabilize the combustion and avoid the occurrence of misfire. It becomes possible. On the other hand, if the temperature of the internal combustion engine is not extremely low, the number of spark ignitions can be reduced to reduce energy consumption and electrode wear of the spark plug 12 .

Further, in the present embodiment, a control device for controlling a spark ignition type internal combustion engine that applies an induced voltage generated by interrupting the energization of the ignition coil 14 after energizing it to the electrodes of the spark plug 12 to cause discharge between the electrodes. 0 and two or more discharges are performed for the purpose of ignition during one cycle of one cylinder 1, and among the two or more discharges, the current operating range of the internal combustion engine [engine number, partial pressure of fresh air in intake air charged into cylinder 1 (or intake pressure in surge tank 33, accelerator opening, engine load factor, engine torque, amount of intake air charged into cylinder 1 or fuel injection amount) ], the controller 0 for an internal combustion engine is configured to cancel the discharge without executing the discharge when the timing is retarded more than the threshold value set according to the above.

The control device 0 of the present embodiment determines the energization time to the primary coil 141 for preparation of each time of main ignition and additional ignition, and the discharge duration of each time, and based on them, the current The crank angle for each ignition or discharge timing is calculated with reference to the engine speed of . Then, if the calculated crank angle falls below a limit threshold that does not cause improper afterfire or backfire (no such danger), the ignition or discharge is canceled rather than performed. According to the present embodiment, it is possible to optimize the number of discharge executions in multi-ignition, thereby realizing good ignition combustion while suppressing inappropriate afterfire or backfire.

The control device 0 of the present embodiment does not energize the ignition coil 14 before the discharge to prepare for the discharge to be canceled because the timing is retarded more than the threshold value. Therefore, it is possible to avoid unnecessary power consumption associated with energization of the ignition coil 14, which also leads to suppression of heat damage due to temperature rise of the ignition coil 14.

The present invention is not limited to the embodiments detailed above. For example, if an airflow meter capable of detecting the flow rate of intake air (or fresh air) flowing through the intake passage of the internal combustion engine toward the cylinder is mounted, the amount of intake air (fresh air) measured via this airflow meter amount), the duration from the start to the interruption of discharge for the first ignition in a certain cycle, the length of the energization time of the ignition coil 14 before the second and subsequent ignitions, and the inappropriate The slowest ignition timing threshold that does not cause afterfire or backfire can be adjusted.

In addition, the specific configuration of each part, the procedure of processing, etc. can be modified in various ways without departing from the scope of the present invention.

INDUSTRIAL APPLICABILITY The present invention can be applied to control of a spark ignition internal combustion engine mounted on a vehicle or the like.

0... Control unit (ECU)
REFERENCE SIGNS LIST 1 cylinder 12 spark plug 13 igniter 131 semiconductor switch 14 ignition coil 141 primary coil 142 secondary coil 2 external EGR device 23 EGR valve 3 intake passage 32 throttle valve 33 surge tank 5 VVT mechanism b crank angle signal c accelerator opening signal d intake air temperature/intake pressure signal e voltage/current signal f cooling water temperature signal i ignition signal j fuel injection signal k throttle valve opening Operation signal l... EGR valve opening operation signal n... Valve timing control signal

Claims (2)

A control device for controlling a spark ignition type internal combustion engine that applies an induced voltage generated by interrupting the energization of an ignition coil after energizing it to the electrodes of a spark plug to cause discharge between the electrodes,
Two or more discharges are performed for the purpose of ignition during one cycle of one cylinder. While setting before the crank angle such that
Of the two or more discharges, the timing is retarded from the crank angle threshold of the latest ignition timing that does not cause inappropriate afterfire or backfire, which is set according to the current operating range of the internal combustion engine. A control device for an internal combustion engine that cancels discharge without executing it. In determining the spark ignition timing for the second and subsequent times, the energization time and the duration of spark discharge, which are preparations for spark discharge in each time, are determined according to the current operating range of the internal combustion engine, and each ignition is performed based on this. to determine the timing of
2. The control device for an internal combustion engine according to claim 1, wherein the ignition coil is not energized before the discharge to prepare for the discharge to be canceled because the timing is retarded from the threshold value.

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