JP7102061B2 - Internal combustion engine control device - Google Patents

Description

The present invention relates to a control device for controlling a spark ignition type 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 induction voltage generated by an ignition coil and undergoes dielectric breakdown between the center electrode and the ground electrode. Causes a discharge.

An igniter having a semiconductor switching element is provided on the electric circuit that energizes the ignition coil. When the semiconductor switch of the igniter is ignited (set to the ON state (conducting state)), a current flows to the primary side of the ignition coil. The primary current flowing through the primary coil increases gradually while the semiconductor switch is ignited. After that, when the semiconductor switch is extinguished at the appropriate spark ignition timing (OFF state (non-conducting state)), a high voltage is generated on the primary side of the ignition coil due to the self-induction action at the moment when the primary current is cut off. do. Then, 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, a discharge is generated between the center electrode and the ground electrode (see, for example, the following patent documents).

Japanese Unexamined Patent Publication No. 2016-089631

Recently, during one cycle of one cylinder (in a 4-stroke engine, the series of intake stroke-compression stroke-expansion stroke-exhaust stroke is one cycle), two or more discharges are executed for the purpose of ignition. It is being considered to carry out multi-ignition (multi-spark, multiple discharge). 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 and thus prevent misfire or combustion instability. is doing.

However, by implementing multi-ignition, the time that the ignition coil is energized is inevitably longer than that of the conventional ignition device that ignites sparks once in one cycle, and as a result, the ignition coil The calorific value increases. Therefore, if the energization time of the ignition coil is set as in the conventional ignition device, the ignition coil may be damaged by heat damage.

An object of the present invention is to optimize the number of times of discharge in multi-ignition to realize good ignition combustion while suppressing damage to the ignition coil.

The present invention is a control device for controlling a spark ignition type internal combustion engine that applies an induced voltage generated by energizing an ignition coil and then shutting off the energization to an electrode of a spark plug to induce a discharge between the electrodes. Two or more discharges are performed for the purpose of ignition in one cycle of one cylinder, and the number of discharges for the purpose of ignition in the same cycle is the ambient temperature that affects the temperature of the ignition coil. In addition, a control device for an internal combustion engine that changes according to the length of the energization time of the ignition coil per predetermined time is configured.

More specifically, if the length of the energization time to the ignition coil per predetermined time exceeds the threshold value, the number of discharges for the purpose of ignition in one cycle of one cylinder is reduced, and the internal combustion engine is used. It is preferable to set the threshold value when the engine temperature, intake air temperature or outside air temperature is high to be lower than the threshold value when the engine temperature, intake air temperature or outside air temperature is lower. It should be noted that the length of the energization time to the ignition coil before the second and subsequent ignitions in a certain cycle is adjusted according to the measured value of the flow rate of the intake air or fresh air flowing toward the cylinder in the intake passage of the internal combustion engine. There can be.

According to the present invention, it is possible to optimize the number of times of execution of discharge in multi-ignition and realize good ignition combustion while suppressing damage to the ignition coil.

The figure which shows the schematic structure of the spark ignition type internal combustion engine and the control device thereof in one Embodiment of this invention. The circuit diagram of the ignition device of the internal combustion engine of the same embodiment. The figure which shows an example of the timing of the spark ignition in the multi-ignition carried out by the control device of the same embodiment. The figure which shows the relationship between the operating area of the internal combustion engine of the same embodiment, and the necessity of carrying out multi-ignition. The figure which shows the transition of the primary current and the secondary current in the multi-ignition carried out by the control device of the same embodiment. The figure which shows the procedure example of the process which the control device of the same embodiment executes according to a program. The figure which shows the firing / extinguishing of the semiconductor switch in the multi-ignition carried out by the control device of the same embodiment.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle. The internal combustion engine of the present embodiment is a port injection type 4-stroke spark ignition engine, and includes a plurality of cylinders 1 (for example, three cylinders, one of which is illustrated in FIG. 1). An injector 11 for injecting fuel toward the intake port is provided in the vicinity of the intake port of each cylinder 1. Further, a spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1.

The 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 from the upstream on the intake passage 3.

The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 to the outside from the exhaust port of each cylinder 1. 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 O ₂ sensor having a non-linear 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. It may be. The output characteristics of the _O2 sensors 43 and 44 show a steep 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 a low saturation value in the lean region where the air-fuel ratio is larger than that. In the rich region where the air-fuel ratio is smaller than that, a so-called Z characteristic curve is drawn, which asymptotes to the high saturation value.

The exhaust gas recirculation device 2 realizes an external EGR (Exhaust Gas Recirculation) in which a part of the exhaust gas flowing through the exhaust passage 4 is returned to the intake passage 3 and mixed with the intake air. The external EGR device 2 includes an external EGR passage 21 that connects 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. The element is 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. The inlet of the EGR passage 21 is connected to the exhaust manifold 42 in the exhaust passage 4 or a predetermined position downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined position downstream of the throttle valve 32 in the intake passage 3, particularly a 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 hydraulic pressure), or a motor. It is an electric type (motor drive VVT) that can be changed. As is well known, the camshaft receives a rotational driving force from the crankshaft, which is the output shaft of the internal combustion engine, and rotates in accordance with 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 includes 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 pulley) to be wound around these sprockets (or pulleys). , Timing belt) and as an element. The VVT mechanism 5 changes the rotation phase of the camshaft with respect to the crankshaft by rotating the camshaft relative to the camsprocket, thereby changing the opening / closing timing of the intake valve.

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

The above-mentioned VVT mechanism 5 is used to increase the filling efficiency of the intake air into the cylinder 1 and to expand or contract the valve overlap period in which both the intake valve and the exhaust valve open. By operating the valve overlap period, it is possible to increase or decrease the amount of internal EGR gas remaining in the cylinder 1 without being discharged from the cylinder 1.

The specific embodiment of the VVT mechanism 5 is arbitrary and is not uniquely limited. In addition to the one that advances / retards the rotation phase of the camshaft with respect to the crankshaft, the one that prepares multiple cams that open and drive the intake valve or exhaust valve and use those cams appropriately, the lever ratio of the rocker arm Those that change via an electric motor, those that use an intake valve or an exhaust valve as an electromagnetic solenoid valve, and the like are known, and it is permitted to select and adopt from these various mechanisms.

FIG. 2 illustrates an electric circuit of an ignition device of a spark-ignition type internal combustion engine. The spark plug 12 receives the application of the induced voltage generated by the ignition coil 14 and induces an electric discharge between the center electrode and the ground electrode. The ignition coil 14 is integrally incorporated 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 the ignition signal i from the ECU (Electronic Control Unit) 0 which is the control device of the internal combustion engine of the present embodiment, the semiconductor switch 131 of the igniter 13 first ignites and a current is applied to the primary side 141 of the ignition coil 14. The semiconductor switch 131 is extinguished at the timing of spark ignition immediately after that, and this current is cut off. Then, a self-induction action occurs, and a high voltage is generated on the primary side 141. Since the primary side 141 and the secondary side 142 share the magnetic circuit and the magnetic flux, a higher induced voltage is generated on the secondary side 142. The induced voltage of 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 a discharge occurs between the center electrode and the ground electrode.

The primary coil 141 of the ignition coil 14 is connected to the in-vehicle power storage device 16 via the semiconductor switch 131. The power storage device 16 is a battery (lead battery, lithium ion battery, nickel hydrogen battery, etc.), a capacitor, or the like. A plurality of types of power storage devices 16 may be combined and mounted on a vehicle.

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 circuit on the primary side (low voltage system) including the primary coil 141 is changed. Gradually increase. Assuming that the primary side electric circuit 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 the time of t = 0 is
I (t) ≒ {1-e- ^{(R / L) t} } E / R
Will be. That is, the primary current gradually increases as a transient phenomenon, but the rate of increase gradually decreases. When a long time has passed from the start of energization, the primary current saturates in E / R. However, in reality, since the current limiting function described later works, the primary current does not increase any more even if the primary coil 141 is continuously energized, so that the saturation value E / R is not always reached.

In a state where the primary current is sufficiently large, the ECU 0 extinguishes the semiconductor switch 131 of the igniter 13 attached to the cylinder 1 in accordance with the ignition timing of the cylinder 1, and the ignition coil 14 attached to the cylinder 1 is used. The energization to the primary coil 141 is cut off. 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 a discharge due to dielectric breakdown between the center electrode of the spark plug 12 and the ground electrode. Raise.

Incidentally, the igniter 13 has a current limiting function that suppresses an excessive primary current. This current limiting feature is similar to that of off-the-shelf igniters in widespread use today. Specifically, the control circuit 132 constantly measures the primary current in the form of the voltage across the resistor 133 via the detection resistor 133. Then, while the magnitude of the primary current (voltage between both ends of the resistor 133) is equal to or less than the specified value, the semiconductor switch 131 is ignited, and when the magnitude exceeds the specified value, the semiconductor switch 131 is extinguished. As a result, the magnitude of the primary current is clipped to the specified value.

Further, the igniter 13 is provided with a primary voltage setting unit using, for example, a Zener diode 134. The primary voltage setting unit plays a role of suppressing 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 a high voltage. When the semiconductor switch 131 is an IGBT, the Zener diode 134 for voltage clamping is interposed between the collector and the gate of the IGBT 131, its anode is connected to the gate of the IGBT 131, and the cathode is connected to the collector of the IGBT 131. 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 in the range of, for example, 350V to 500V, and the primary voltage is higher than that. It works to prevent a large increase.

In addition, the igniter 13 also has a function of forcibly shutting off the energization of the primary coil 141 when an 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 of the internal combustion engine of the present embodiment has one ignition coil 14 for supplying a high voltage for spark ignition to the spark plug 12 of the cylinder 1 for each cylinder 1. The ignition coil 14 for each cylinder 1 is a pair of one primary coil 141 and one secondary coil 142, respectively. The primary coil 141 and the secondary coil 142 are connected to each other via a diode 15. The diode 15 is for noise prevention to prevent backflow from the secondary side 142.

The generator 17, which serves as an electric power 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 crank shaft, which is the output shaft of the internal combustion engine. It receives the supply and generates electric power, and the generated electric power is stored in the in-vehicle power storage device 16.

The generator 17 may be an alternator that has been used as an automobile generator for a long time, or a motor generator or a motor generator that also functions as an electric motor for driving a crankshaft of an internal combustion engine or an axle (and a driving wheel) of a vehicle. It may be an ISG (Integrated Starter Generator). The internal combustion engine and the generator 17 are connected via, for example, a winding transmission device having a belt and a pulley as elements.

The IC regulator or controller 171 attached to the generator 17 receives the control signal m that commands the target value of the output voltage of the generator 17 emitted from the ECU 0. Then, in order to make the terminal voltage of the power storage device 16 (or the power supply voltage supplied to the electrical system) follow the commanded target voltage, the semiconductor switching element is operated by a switch to apply excitation to the exciting (field) winding. PWM (Pulse Width Modulation) control for adjusting the magnitude of the current is performed. The output voltage of the generator 17 increases as the exciting current flowing through the exciting winding increases.

Further, the generator 17 can perform regenerative braking when the vehicle is decelerated, and recover the kinetic energy of the vehicle as electrical energy. The ECU 0 excites the excitation winding of the generator 17 when the amount of depression of the accelerator pedal by the driver becomes 0 or a predetermined value close to 0, that is, when deceleration of the internal combustion engine and the vehicle is required. A control signal m for raising the upper limit of the current and the output voltage of the generator 17 is given to the IC regulator or the controller 171.

The ECU 0 that controls the operation of the internal combustion engine is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

The input interface of ECU 0 has a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from a crank angle sensor that detects the rotation angle of the crank shaft of the internal combustion engine and the engine rotation speed. , 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), intake passage 3 (particularly, The intake temperature / intake pressure signal d output from the temperature / pressure sensor that detects the intake temperature and intake pressure in the surge tank 33), the terminal voltage and / or the terminal current (particularly, the battery voltage and /) of the in-vehicle power storage device 16. Or the voltage / current signal e output from the sensor that detects the battery current), the cooling water temperature signal f that is output from the water temperature sensor that detects the cooling water temperature that suggests the temperature of the internal combustion engine, and the multiple cam angles of the intake cam shaft. From the cam angle signal g output from the cam angle sensor, the air fuel ratio signal h output from the air fuel ratio sensors 43 and 44 that detect the air fuel ratio of the exhaust gas flowing through the exhaust passage 4, and the outside temperature sensor that detects the outside temperature. The output outside temperature signal o or the like is input.

From the output interface of the ECU 0, the ignition signal i for the igniter 13, the fuel injection signal j for the injector 11, the opening operation signal k for the throttle valve 32, and the opening operation signal l for 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 and the like are output to the VVT mechanism 5.

The processor of ECU 0 interprets and executes a program stored in the memory, calculates an operation parameter, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, h, o necessary for the operation control of the internal combustion engine via the input interface, obtains the engine rotation 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 these, the required fuel injection amount, fuel injection timing (including the number of fuel injections for one combustion), fuel injection pressure, ignition timing, required EGR rate (or) corresponding to the intake amount (fresh air amount). Various operating parameters such as the amount of EGR gas), the amount of power generated by the generator 17 (output voltage), the opening / closing timing of the intake valve and / or the exhaust valve, and the like are determined. The ECU 0 applies various control signals i, j, k, l, m, and n corresponding to the operation parameters via the output interface.

During the operation of the internal combustion engine, the ECU 0 feedback-controls the air-fuel ratio of the air-fuel mixture filled in the cylinder 1, and eventually the air-fuel ratio of the exhaust gas discharged from the cylinder 1 and led to the catalyst 41. The ECU 0 first calculates the amount of intake air filled in the cylinder 1 from the intake pressure and intake temperature, the engine speed, the required EGR rate, etc., and the ratio with this is the target air-fuel ratio (normally, the theoretical air-fuel ratio 14. 6 or its vicinity) The basic injection amount TP of the fuel is determined.

Next, the basic injection amount TP is corrected by a feedback correction coefficient FAF determined according to the air-fuel ratio on the upstream side and / or the downstream side of the catalyst 41. The feedback correction coefficient FAF is adjusted according to the deviation between the air-fuel ratio of the gas measured via the air-fuel ratio sensors 43 and 44 and the target air-fuel ratio, and increases when the measured air-fuel ratio is lean with respect to the target air-fuel ratio. However, it 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 by taking into consideration various correction coefficients K determined according to 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
Will be. The ECU 0 inputs a signal j to the injector 11 for the fuel injection time T, opens the injector 11 to inject fuel.

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

The valve timing embodied 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 the surge tank 33 (or accelerator opening, etc.)]. To give a specific example of the opening / closing timing of the intake valve, when the operating region is idling or has a low load, or when the cooling water temperature of the internal combustion engine is low, the intake valve timing is most retarded to minimize or 0 the valve overlap period. And eliminate the blowback of the exhaust to the intake port. In the medium load operating region, the intake valve timing is advanced more and the valve overlap period is extended as compared with the low load operating region. When the valve overlap period is long, the internal EGR ratio, which is the ratio of the internal EGR gas to the air-fuel mixture filled in the cylinder 1, can be increased, and the pumping loss of the internal combustion engine can be reduced. In the operating region 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 sucked into the cylinder 1 is blown back to the intake port. The amount is suppressed to improve volumetric efficiency and increase engine torque and output.

The ECU 0 of the present embodiment performs multi-ignition that executes spark ignition 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. In multi-ignition, each discharge evoked between the electrodes of the spark plug 12 is intended to ignite the air-fuel mixture filled in the cylinder 1, that is, the fuel existing in the cylinder 1. Multi-ignition is intended to reinforce the ignition combustion of the air-fuel mixture and prevent the occurrence of misfire or destabilization of combustion by executing additional ignition immediately after the main ignition. Multi-ignition makes it possible to increase the EGR rate of intake air more than before, and / or allows EGR to be performed even in the operating range where EGR could not be performed in the past, and the fuel efficiency of the internal combustion engine is improved. Further improvement and improvement of emissions can be expected.

In order to realize multi-ignition in the same cycle, it is necessary to increase the rate of increase of the primary current flowing through the primary coil 141 of the ignition coil 14 as much as possible, that is, to store the electric energy required for the ignition coil 14. It is required to shorten the time as much as possible. The ignition coil 14 of the ignition device of the internal combustion engine of the present embodiment is a conventional one that executes spark ignition once in one cycle by adjusting the number of turns, the size of the core, and the like to increase the primary current. It is faster than that in the igniter. On the other hand, as a trade-off, 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 a maximum of three ignitions are added after the main first ignition. FIG. 3 illustrates the timing of spark ignition in multi-ignition. In this illustrated example, in the same cycle of the cylinder 1, one ignition is added after the main ignition, and a total of two ignitions are executed. In FIG. 3, the time when the crank angle is 0 ° CA is the compression top dead center of the cylinder 1, and the time when the crank angle is a negative value is positive during the compression stroke before the compression top dead center (BTDC) of the same cylinder 1. The value period is during the expansion stroke after compression top dead center (ATDC). The time point S1 represents the timing of the first main ignition, and the time point S2 represents the timing of the additional second ignition. The first ignition timing can be determined in the same manner as the control of a conventional spark-ignition type internal combustion engine. On top of that, it is desirable that the timing of the second ignition following the first ignition is set before the crank angle such that the mass fraction burnt in the cylinder 1 becomes a predetermined value, for example, 5%. The MFB is the ratio of the mass of the burned fuel to the mass of the fuel supplied into the cylinder 1 per cycle. The MFB is expressed by the following equation as a function of the crank angle θ, for example.
MFB = [1-cos {π (θ-θ ₀ ) / θ _b }] / 2
Here, 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 a time point when MFB reaches 5%, and A2 represents a time point when MFB reaches 50%. The crank angle of the second ignition timing does not fluctuate so much and is almost always constant.

Whether or not to carry out multi-ignition is determined according to the operating range of the internal combustion engine [engine speed, intake pressure in the surge tank 33 (or accelerator opening, etc.)]. FIG. 4 shows the relationship between the operating region of the internal combustion engine and the presence / absence of implementation of multi-ignition. In the 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 filled in the cylinder 1 are large (especially in the high load region, a large amount of fresh air flows into the cylinder 1 and is relatively relative. Since EGR gas is reduced) and combustion is inherently less likely to become unstable, there is little need to carry out multi-ignition. Therefore, multi-ignition is not performed, that is, spark ignition is performed only once in one cycle of one cylinder 1, and power consumption, temperature rise of the ignition coil 14, and further, electrode of the spark plug 12 are performed. Suppress wear. Further, in the region R3 where the engine speed is relatively high, the frequency of spark ignition per unit time is inevitably high, and there is a concern that the ignition coil 14 will be excessively heated and suffer heat damage. Therefore, multi-ignition Do not carry out.

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 executed in the same cycle of the cylinder 1. In FIG. 5, the time point T0 represents the time point in which the semiconductor switch 131 is ignited in preparation for the first ignition and the energization of the primary coil 141 is started, and the time point T1 is the time point in which the semiconductor switch 131 is extinguished for the first ignition. It represents the time point when the current of 141 is cut off to the primary coil by arcing. The time point T1 coincides with the start time of the first discharge between the electrodes of the spark plug 12, that is, the first ignition timing in the cylinder 1.

A subsequent time point T3 represents a time point in 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 is a time point in which the semiconductor switch 131 is extinguished for the second ignition. It represents the time point when the current of 141 is cut off to the primary coil by arcing. The time point T4 coincides with the start time of the second discharge between the electrodes of the spark plug 12, that is, the second ignition timing in the cylinder 1.

In the present embodiment, the time point T3 at which the semiconductor switch 131 is re-ignited in preparation for the second ignition is earlier than the time point T2 at which the discharge for the most recent first ignition ends. Assuming that the semiconductor switch 131 is not re-ignited at the time point T3, the first discharge is continued, and the electrodes of the secondary coil 142 and the spark plug 12 are shown as shown by the broken lines in FIG. The amount of current flowing through the discharge path between them will decrease over time, resulting in a minimum value of 0 or close to 0 at some point in time T2. However, in the latter half of the discharge in which the amount of current is reduced, it does not necessarily contribute to the ignition and combustion of the fuel in the cylinder 1, so that it is a waste of electric power. Can also wear out.

Therefore, in the present embodiment, the semiconductor switch 131 is re-ignited at the time point 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 discharge between the electrodes of the spark plug 12, the energization of the primary side 141 of the ignition coil 14 is restarted, the voltage applied to the center electrode of the spark plug 12 drops, and the electrodes The discharge between them is forcibly interrupted. At this time, the excess magnetic flux induced by the interrupted discharge remains in the ignition coil 14. So to speak, at the time T3 when the energization of the ignition coil 14 is restarted to induce the next discharge, a certain amount of energy is already stored in the ignition coil 14, and this can be used for the next discharge. Therefore, the time required to energize the ignition coil 14 to induce the next discharge, that is, the time required to increase the primary current flowing through the primary coil 141 to the size required for spark ignition is shortened, so that the first time is required. The time interval between the discharge and the second discharge is not extended, and the next discharge can be triggered at a suitable timing. After all, the energy consumed in the latter half of the discharge, which does not necessarily contribute to ignition combustion, can be applied to the next discharge.

Hereinafter, the method by which the ECU 0 of the present embodiment determines the ignition timing will be described in detail. FIG. 6 shows an example of the procedure of the process 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, the discharge (step S1). In step S1, the first ignition timing is adjusted according to the operating range of the internal combustion engine, as in the control of the conventional spark ignition type internal combustion engine. Map data that defines in advance the relationship between the parameters [engine speed, intake pressure in the surge tank 33 (or accelerator opening, etc.)] representing the operating region of the internal combustion engine and the first ignition timing in the memory of ECU 0. Is stored. The ECU 0 searches the map using the current operating area of the internal combustion engine as a key, and knows the first ignition timing.

Next, ECU 0 determines whether or not to carry out multi-ignition that performs additional ignition, that is, discharge immediately after the first ignition, that is, discharge (step S2). For example, when the cooling water temperature of the internal combustion engine is higher than a predetermined temperature, the intake air temperature is higher than a predetermined temperature, or the outside air temperature is higher than a predetermined temperature, the ignition coil 14 is excessively heated. Do not carry out multi-ignition to avoid. Further, even if it is within a predetermined time after the cold start of the internal combustion engine and the amount of electricity stored in the power storage device 16, particularly the battery voltage, is not more than the predetermined time, the multi-ignition is not performed. This is because if the voltage applied to the primary side 141 of the ignition coil 14 is low, the rate of increase of the primary current becomes slow. The current amount of electricity stored in the electricity storage device 16 can be known or estimated with reference to the voltage / current signal e.

In addition, as already mentioned, whether or not multi-ignition should be carried out depends on the operating range of the internal combustion engine. The ECU 0 determines that the multi-ignition is performed only when the current operating region of the internal combustion engine is in the region R1 where the engine speed is relatively low and the intake pressure in the surge tank 33 is relatively low, otherwise the multi-ignition is performed. Judge that ignition will not be carried out. Exceptionally, when the cooling water temperature of the internal combustion engine is extremely low below the specified temperature, or immediately after the cold start of the internal combustion engine, the first ignition timing is set to promote the temperature rise of the catalyst 41 for exhaust gas purification. When the angle is retarded, multi-ignition may be performed. If the temperature in the combustion chamber of the cylinder 1 is remarkably low or the timing of spark ignition is remarkably delayed, the ignition combustion of the fuel or the air-fuel mixture in the cylinder 1 becomes unstable. Moreover, at extremely low temperatures, so-called plug fog, in which the fuel injected from the injector 11 becomes liquid and adheres to the electrodes of the spark plug 12, is likely to occur. Spark plug fog is a factor that destabilizes ignition combustion. Therefore, regardless of the current operating range of the internal combustion engine, when the internal combustion engine has an extremely low temperature or the ignition timing is greatly retarded, multi-ignition is performed to stabilize ignition combustion.

The ECU 0, which has determined to perform multi-ignition in step S2, energizes the primary coil 141 of the ignition coil 14 as a preparation for inducing each ignition, that is, discharge from the second time onward. Is determined (step S3). The energization time of each time means the time from when the semiconductor switch 131 is ignited before the timing of each ignition to when the semiconductor switch 131 is extinguished. Needless to say, the extinguishing of the semiconductor switch 131 coincides with the timing of ignition at that time. In this embodiment, a maximum of three ignitions will be added 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 before the second ignition tonmulti1, the energization time before the third ignition tonmulti2, and four. The energization time tonmulti3 before the second ignition is set respectively. However, as will be described later, it is not always the case that three ignitions are added after the main ignition. The energization time of each time tonmulti1, tonmulti2, and tonmulti3 may be the same value or different values from each other. The ton in FIG. 7 is the energization time before the first ignition, which is the main, and the required primary current is secured at the time of the first ignition timing as in the control of the conventional spark-ignition type internal combustion engine. It should be set long enough to be used. Each energization time for additional ignition tonmulti1, tonmulti2, tonmulti3 is often shorter than the energization time ton for the main ignition.

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

On the other hand, the length of the energizing time before each ignition expands or contracts according to the magnitude of the electric resistance between the electrodes of the spark plug 12 at the time of ignition. This is because the larger the resistance between the electrodes, the more energy is required to cause dielectric breakdown between the electrodes in order to start the discharge. The electrical resistance between the electrodes of the spark plug 12 increases as the amount of fresh air filled in the cylinder 1 increases and as the partial pressure of the fresh air increases. The energization time before each ignition set in step S3 is a surge in the intake stroke of the same cycle (that is, immediately before ignition) as the ignition is executed under the condition that the engine speeds are the same. The higher the intake pressure in the tank 33, the longer it becomes, the larger the intake amount (or fresh air amount) flowing into the cylinder 1 in the intake stroke of the same cycle, the longer it becomes, or the larger the accelerator opening, the longer it becomes.

In step S3, the ECU 0 adds a correction according to the current storage amount of the power storage device 16 or the battery voltage to the basic value of the energization time according to the current operating region of the internal combustion engine. 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 coil 141. The higher the applied voltage, the faster the rate of increase of the primary current, and conversely, the lower the applied voltage, the higher the rate of increase of the primary current. The rate of increase slows down. That is, when the applied voltage is low, it becomes necessary to energize the primary coil 141 for a longer period of time before spark ignition. From this, the lower the current storage amount or battery voltage of the power storage device 16, the longer the energization time before each ignition is corrected.

However, an upper limit value and / or a lower limit value is set in advance for the energization time of 141 to the primary coil before each ignition. Then, when the energization time as a result of correcting the basic value exceeds the upper limit value, the energization time is clipped to the upper limit value, and when the energization time as a result of correcting the basic value is less than the lower limit value, the energization time is clipped to the upper limit value. Clip the energizing time to the lower limit. The purpose of setting the upper limit value for the energizing time is to suppress the heat generation amount of the ignition coil 14 and prevent the heat damage. The lower limit of the energization time is set to flow through the primary coil 141 in order to induce a secondary voltage having a minimum magnitude required to induce a discharge between the electrodes of the spark plug 12 in the secondary coil 142. The intention is to secure an energization time that increases 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 cut off. If the primary current is small, the secondary voltage is also small, and the insulation between the electrodes of the spark plug 12 is not broken, resulting in no discharge.

Subsequently, ECU 0 determines the length of time to sustain the main discharge for the first ignition and the length of time to sustain the discharge for the second and subsequent ignitions added thereto (). Step S4). The discharge duration of each time means the time from extinguishing the semiconductor switch 131 at the timing of each ignition to reigniting the semiconductor switch 131. If the discharge duration is shortened and the semiconductor switch 131 is re-ignited when the discharge has not yet ended, the discharge at that time is terminated halfway. 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 executed before the additional ignition, that is, the discharge duration of the first ignition, tonintm, and the discharge duration of the second ignition. Tonint1 and the discharge duration of the third ignition tonint2 are set respectively. However, it is not always the case that three ignitions are added after the main ignition. The energization time tonintm, tonint1 and tonint2 of each time may be the same value or different values from each other. The discharge durations of additional ignitions tont1 and tont2 are often shorter than the discharge duration of the main ignition. Note that tont3 in FIG. 7 is the discharge duration of the fourth ignition as a whole including the additional third ignition and the main ignition, which are the final of the additional ignitions, and is the conventional spark ignition type internal combustion engine. Similar to the control of the engine, the discharge may be continued until the end of the discharge, or the semiconductor switch 131 may be re-ignited and interrupted before the end in order to suppress the wear of the electrode of the spark plug 12 as much as possible. good.

In the memory of ECU0, the relationship between the parameters [engine speed, intake pressure in surge tank 33 (or accelerator opening, etc.)] representing the operating area of the internal combustion engine and the basic value of the discharge duration of each ignition in advance. The map data that specifies is stored. The ECU 0 searches the map using the current operating area 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 become shorter as the engine speed increases. This is because the higher the engine speed, the faster the angular velocity of the crankshaft of the internal combustion engine.

Further, the length of the discharge duration expands or contracts according to the speed at which the amount of current flowing in 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 half of the discharge in which the amount of current is reduced does not necessarily contribute to the ignition and combustion of the fuel in the cylinder 1, the later discharge may be terminated without being sustained. Therefore, the faster the rate of decrease in the amount of discharge current, the shorter the discharge duration.

The rate 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 is started between the electrodes depends on the characteristics of the ignition coil 14, and the magnitude of the secondary voltage when the discharge is started 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 the secondary voltage decrease. Moreover, the greater the resistance between the electrodes, the more energy is required to cause dielectric breakdown between the electrodes in order to start the discharge, and the secondary current is reduced accordingly.

The electrical resistance between the electrodes of the spark plug 12 increases as the amount of fresh air filled in the cylinder 1 increases and as the partial pressure of the fresh air increases. The discharge duration of ignition set in step S4 is the surge tank 33 in the intake stroke of the same cycle as executing ignition (that is, immediately before ignition) under the condition that the engine speeds are the same. The higher the internal intake pressure, the shorter the length, the larger the intake amount (or fresh air amount) flowing into the cylinder 1 in the intake stroke of the same cycle, the shorter the length, or the larger the accelerator opening, the shorter the length.

Further, the electric resistance between the electrodes of the spark plug 12 increases as the amount of fuel present in the cylinder 1 decreases and the partial pressure of the EGR gas decreases. This is partly due to the inclusion of ions in the components of the unburned or burned fuel. The discharge duration of ignition set in step S4 is the cylinder 1 in the same cycle as executing ignition under the condition that the engine speed and the above-mentioned intake pressure, intake amount or accelerator opening are equal. The smaller the amount of fuel supplied to the cylinder 1 or the larger the air-fuel ratio of the intake air charged in the cylinder 1, the shorter the EGR ratio, which is the ratio of the EGR gas to the intake air charged in the cylinder 1 in the intake stroke of the same cycle. The smaller the value, the shorter the length.

Based on the same idea, under the same other conditions, the lower the temperature of the intake air filled in the cylinder 1 in the intake stroke of the same cycle as the ignition, the shorter the discharge duration, or the shorter the discharge duration of the internal combustion engine. The lower the cooling water temperature, the shorter the discharge duration. Further, under the same conditions as other conditions, the lower the humidity of the intake air charged in the cylinder 1 in the intake stroke of the same cycle, the shorter the discharge duration may be. However, considering that the temperature of the electrode of the spark plug 12 decreases and the secondary voltage at the start of discharge increases as the humidity of the intake air increases, 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 time (milliseconds or microseconds) units, not crank angle (° CA) units. Needless to say, the angular velocity of rotation of the crankshaft of the internal combustion engine, in other words, the speed of reciprocating movement of the piston in the cylinder 1, fluctuates according to the engine rotation speed. Therefore, even if the energization time and the discharge duration of each time are the same, the crank angle at the timing of each spark ignition differs depending on the engine speed. Therefore, the ECU 0 converts the energization time and the discharge duration of each time from the current engine speed into a crank angle, and calculates the crank angle of the ignition timing of each time (step S5).

Then, the ECU 0 determines how many times of ignition is additionally executed after the first main ignition according to the current situation (step S6). For example, the EGR valve 23 in the EGR device 2 is opened to perform external EGR, or the engine rotation speed is increased to some extent (for example, 1000 rpm to 1200 rpm) or more, and the VVT mechanism 5 advances the opening / closing timing of the intake valve. When the internal EGR is performed with an angled valve overlap period, additional ignition is performed a predetermined number of times (eg, twice, in which case the fourth ignition is cancelled). Even if this is not the case, when the cooling water temperature of the internal combustion engine is extremely low below a predetermined value, additional ignition is performed a maximum number of times (three times). Incidentally, when the internal combustion engine is extremely low temperature, EGR is not normally performed and the EGR valve 23 is fully closed. Alternatively, immediately after the cold start of the internal combustion engine and when the first ignition timing is delayed from normal in order to promote the temperature rise of the catalyst 41, additional ignition is executed a predetermined number of times (for example, twice). I will do it. If none of these are true, then the additional ignition is performed a minimum number of times (eg, once) or no additional ignition is performed.

However, the ECU 0 of the present embodiment may limit the number of ignitions, that is, discharges, in one cycle of one cylinder 1 in order to prevent the ignition coil 14 from being damaged due to excessive temperature rise (). Step S7). Specifically, the purpose is to ignite one cylinder 1 in the same cycle according to the ambient temperature that affects the temperature of the ignition coil 14 and the length of the energization time of the ignition coil 14 per predetermined time. Adjust the number of discharges. Examples of the ambient temperature that affects the temperature of the ignition coil 14 include the temperature of the internal combustion engine itself, the temperature of the intake air flowing through the intake passage 3 of the internal combustion engine toward the cylinder 1, the temperature of the outside air, and the like. The higher the temperature of the current internal combustion engine, the higher the temperature of the intake air, and the higher the temperature of the outside air, the easier it is for the temperature of the ignition coil 14 to rise and the less likely it is to fall. Further, when the temperature of the internal combustion engine is high, the ignition coil 14 receives heat from the internal combustion engine and raises the temperature.

As a matter of course, the degree of temperature rise of the ignition coil 14 depends on the length of time that the ignition coil 14 is energized. When the temperature around the ignition coil 14 is high and there is a concern that the ignition coil 14 is excessively heated, the ECU 0 has one cycle of one cylinder 1 in order to suppress an increase in the energization time of the ignition coil 14. Reduce the number of discharges inside.

In step S7, the ECU 0 energizes the primary coil 141 in preparation for each discharge calculated in step S3 in the cycle in which the target cylinder 1 is about to be spark-ignited (not yet ignited). And the time when the primary coil 141 was energized before each discharge in the most recent past (already ignited) one or multiple cycles of the same cylinder 1 are added up. In addition, the sum of the energization time and non-energization time of the primary side coil 141 in the cycle in which the spark discharge of the same cylinder 1 is about to occur, and the sum of the energization time and the non-energization time of the primary side coil 141 and the primary side coil 141 in the most recent past one-time or multiple-degree cycle of the same cylinder 1. Add up the sum of the energized time and the non-energized time. Then, the ratio of the total value of the former energization time to the total value of the latter energization time and non-energization time, so to speak, the duty ratio of energization to the primary coil 141 through the latest past cycle and the next cycle is obtained. At the same time, the ratio is compared with a given threshold. If the ratio is within the threshold value, the number of discharges determined in step S6 is adopted as the number of discharges for the purpose of ignition in the cycle in which the spark ignition of the same cylinder 1 is about to occur.

On the other hand, if the ratio exceeds the threshold value, the number of discharges for the purpose of ignition in the cycle in which the spark ignition of the same cylinder 1 is about to occur is determined in step S6 (adopted when the ratio is below the threshold value). Reduce to less than the number of times you did. In particular, it is preferable to reduce the number of discharges so that the ratio falls below the threshold value. At this time, it is possible to cancel all the additional ignition and use only the main ignition. However, if the number of additional ignitions determined in step S6 is originally small or zero, the number of additional ignitions may not be further reduced.

In step S7, the threshold value to be compared with the above ratio is set to a value lower as the temperature around the ignition coil 14 is higher. That is, the threshold value when the cooling water temperature, which suggests the temperature of the internal combustion engine, is higher is set to a lower value than the threshold value when the cooling water temperature is lower, and the threshold value when the intake air temperature is higher is set to the threshold value when the intake air temperature is lower. The value is lower than the threshold value, and / or the threshold value when the outside air temperature is higher is set to a lower value than the threshold value when the outside air temperature is lower. As a result, the number of discharges for ignition in one cycle of one cylinder 1 when the temperature around the ignition coil 14 is high is larger than that when the temperature around the ignition coil 14 is lower. Can be reduced.

Moreover, ECU 0 sets the threshold value of the crank angle of the latest ignition timing that does not cause inappropriate afterfire or backfire in order to prevent the generation of inappropriate afterfire or backfire due to the additional ignition. Then, the ignition is canceled at a timing retarded from this threshold value (step S8). In the memory of ECU0, the relationship between the parameter [engine speed, partial pressure of fresh air in intake (or accelerator opening, etc.)] representing the operating area of the internal combustion engine and the threshold of the crank angle of ignition timing is stored in advance. The specified map data is stored. The ECU 0 searches the map using the current operating area 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 the threshold value, and it is determined to cancel the ignition of the times such that the ignition timing is later than the threshold value.

Through steps S6 to S8 described above, 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 times of ignition determined in steps S6 and S7. For example, when the external EGR rate is set to a predetermined value or higher, or the opening degree of the EGR valve 23 is set to a predetermined value or higher, two additional discharges are applied to the main discharge, for a total of three times in the same cycle of the same cylinder 1. It is assumed that the discharge is executed (the number of discharges is not reduced by step S7). However, the crank angle of the timing of the second additional discharge, that is, the third discharge as a whole (calculated in step S5) is the crank angle of the latest ignition timing according to the operating region of the current internal combustion engine. If the angle is retarded from the threshold value of (the one set in step S8), the second additional discharge is canceled without being executed. On the other hand, the crank angle of the timing of the first additional discharge, that is, the timing of 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 it is advanced above the crank angle threshold, the first additional discharge is performed without cancellation.

ECU 0 cancels because the DUTY ratio of the energization time to the primary coil 141 is reduced because it exceeds the threshold (step S7), and the timing is delayed from the threshold of the crank angle of the latest ignition timing. (Step S8) With respect to the discharge of the number of times, the process of energizing the primary coil 141 of the ignition coil 14 is not performed before the discharge in preparation for the discharge. Then, with respect to the discharge to be executed in the most recent round of the reduction or cancellation, the discharge to be executed is continued without interruption until the discharge to be executed is completed. According to the above example, when the first additional discharge is executed but the second additional discharge is not executed and canceled, the semiconductor switch 131 is extinguished at the timing of the first additional discharge. After shutting off the energization of the primary coil 141, the semiconductor switch 131 is not re-ignited and the energization of the primary coil 141 is not resumed until the first additional discharge is completed. As a result, the duration of the first additional discharge will be longer than when the second additional discharge is performed. The semiconductor switch 131 is re-ignited to energize the same-order coil 141 during the intake stroke or compression stroke of the next cycle of the same cylinder 1, that is, the main spark ignition of the cycle of the same cylinder 1. Before, in the preparatory period to provoke that main discharge.

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

In the present embodiment, an induced voltage generated by energizing the ignition coil 14 (primary side 141) and then shutting off the energization (on the secondary side 142) is applied to the electrodes of the spark plug 12 to induce a discharge between the electrodes. It is a control device 0 that controls a spark-ignition type internal combustion engine, and executes two or more discharges for the purpose of ignition during one cycle of one cylinder 1, and the first discharge is sustained. While the ignition coil 14 (primary side 141) is re-energized to interrupt the first discharge and prepare for the execution of the second discharge, under the condition that the engine speeds are the same. The duration from the start to the interruption of the first discharge in a certain cycle is shortened as the intake pressure in the intake stroke of the cycle is higher, and as the amount of intake air flowing into the cylinder 1 in the intake stroke of the cycle is larger. Or, the control device 0 of the internal combustion engine, which shortens as the accelerator opening increases, is configured.

According to the present embodiment, the fuel or the air-fuel mixture in the cylinder 1 is ignited by the first spark ignition, which is the main engine, and the second and subsequent spark ignitions are additionally executed on the fuel or the air-fuel mixture, whereby combustion is conventionally performed. Can be more stable than. By such multi-ignition, the risk of misfire is reduced, that is, the proof stress against misfire is improved, so that the EGR rate of the intake air can be increased more than before, and / or EGR cannot be performed in the conventional case. It is permissible to perform EGR even in the operating range, and it is expected that the fuel efficiency performance of the internal combustion engine will be further improved and the emission will be improved.

Moreover, according to the present embodiment, the energy consumed in the latter stage of the discharge, which does not necessarily contribute to the ignition combustion, can be applied to the discharge of the next ignition, and the energy can be efficiently used. Then, the length of time for energizing the ignition coil 14 (primary side 141) is shortened to induce the second and subsequent discharges, and the time interval between the first discharge and the second and subsequent discharges is not extended. It becomes possible to induce the second and subsequent discharges at an appropriate 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) and the spark plug 12 decreases during discharge is the intake pressure in the cylinder 1 or the intake amount filled in the cylinder 1. It fluctuates according to. That is, the higher the intake pressure and the larger the intake amount, the faster the decrease in the current amount becomes. Therefore, the duration from the start to the interruption of the previous discharge is shortened as the intake pressure is higher, the intake amount is larger, or the accelerator opening is larger, and the timing for interrupting the previous discharge is set. Hurry up.

In addition, the rate 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 varies depending on the air-fuel ratio of the air-fuel mixture filled 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 electrodes of the spark plug 12. In principle, the smaller the amount of fuel or EGR gas present in the cylinder 1, the faster the amount of current decreases. Therefore, the duration from the start to the interruption of the previous discharge 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 ratio, which is the ratio of the EGR gas to the intake air, the shorter the EGR ratio, 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 energizing the ignition coil 14 and then shutting off the energization to the electrodes of the spark plug 12 to cause a discharge between the electrodes. 0, which executes two or more discharges for the purpose of ignition during one cycle of one cylinder 1, and the length of the energization time to 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, and is extended as the intake amount flowing into the cylinder 1 is larger in the intake stroke of the cycle, or the accelerator is provided, under the condition that the engine speeds are the same. The internal combustion engine control device 0 is configured to extend as the opening degree increases and shorten as the engine speed increases under the condition that the intake pressure, the intake amount, or the accelerator opening degree are the same.

According to the present embodiment, in carrying out the multi-ignition, it is possible to optimize or optimize the length of time for energizing the primary coil 141 of the ignition coil 14 before each ignition, that is, discharge, after the second ignition. .. In the control device 0 of the internal combustion engine of the present embodiment, as the electric resistance between the electrodes of the spark plug 12 at the time of ignition increases, the energization time of the ignition coil 14 before ignition is extended, and the second and subsequent discharges are surely performed. To evoke. At the same time, the higher the engine speed, the shorter the energization time to the ignition coil 14 before ignition is adjusted, so that the timing of the second and subsequent ignitions is prevented from being delayed unnecessarily, and at the optimum timing. It is possible to carry out each ignition. As a result, the second and subsequent ignitions contribute to the ignition and combustion of the fuel or the air-fuel mixture in the cylinder 1, waste of electric energy can be avoided, and further improvement in the thermomechanical conversion efficiency of the internal combustion engine can be expected.

Moreover, in the control device 0 of the internal combustion engine of the present embodiment, the length of the energization time to the ignition coil 14 in preparation for the second and subsequent discharges is the same as the engine rotation speed, the intake pressure, the intake amount, or the accelerator opening. Under certain conditions, the lower the voltage applied to the ignition coil 14 when the ignition coil 14 is energized, the longer the voltage is extended. More specifically, the lower the current storage amount or battery voltage of the power storage device 16 as a power source, the longer the energization time. Therefore, it is possible to absorb the influence of the amount of electricity stored in the power 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 energy required before ignition, resulting in a decrease in battery voltage. It is possible to prevent the ignition failure due to the ignition and the deterioration of the ignition combustion.

Further, in the present embodiment, a control device for controlling a spark-ignition internal combustion engine in which an induced voltage generated by energizing the ignition coil 14 and then shutting off the energization is applied to the electrodes of the spark plug 12 to cause a discharge between the electrodes. It is 0, and two or more discharges are executed for the purpose of ignition in one cycle of one cylinder 1, and the number of discharges for the purpose of ignition in the same cycle is the number of times of discharge for the purpose of ignition in the cycle. The control device 0 of the internal combustion engine is configured to be changed according to the length of the valve overlap period in which both the intake valve and the exhaust valve of the cylinder 1 are opened during the stroke.

In particular, in the present embodiment, the number of discharges for the purpose of ignition in one cycle of one cylinder 1 is the period of valve overlap in which both the intake valve and the exhaust valve of the cylinder 1 open during the intake stroke of the cycle. It is decided to change according to the length of the above, the ratio of EGR gas to the intake air filled in the cylinder 1 in the intake stroke of the same cycle, the ignition timing in the expansion stroke of the same cycle, and the temperature of the internal combustion engine.

That is, in step S6, the control device 0 of the present embodiment has the same other conditions as the external EGR rate or the opening degree of the EGR valve 23, the timing of the main first spark ignition, the cooling water temperature of the internal combustion engine, and the like. Under the above, the VVT mechanism 5 was operated to lengthen the valve overlap period (the valve overlap period was set to a predetermined value or longer, or the amount of advance of the intake valve timing from the latest retarded angle position was set to a predetermined value or longer). The number of discharges in the case (for example, two additional discharges and three times in total with the main discharge) has a shorter valve overlap period (valve overlap period less than specified, or intake valve timing). From the number of discharges (for example, one additional discharge or less, two times in total with the main discharge, or one time only in the main discharge) when the amount of advance angle from the latest retarded angle position is less than the specified value. Also many. As a result, in a situation where the internal EGR rate is high, the ignition combustion of the fuel or the air-fuel mixture in the cylinder 1 tends to be unstable, and the combustion can be slow, the number of spark ignitions is increased to stabilize the combustion. Can be done. On the other hand, in a situation where the internal EGR rate is low and the ignition combustion of the fuel or the air-fuel mixture is relatively stable, the number of spark ignitions can be reduced to suppress energy consumption and wear of the electrodes of the spark plug 12.

On that basis, the control device 0 of the present embodiment expands the opening degree of the EGR valve 23 to make the external EGR rate higher (the external EGR rate is set to a predetermined value or higher, or the external EGR rate is set to a predetermined value or higher) under the same conditions as other conditions. The number of discharges (for example, two discharges were added and three times in total with the main discharge) when the opening degree of the EGR valve 23 was set to a predetermined value or more was reduced to a lower external EGR rate (external EGR). The number of discharges when the rate is less than the specified value or the opening degree of the EGR valve 23 is less than the specified value (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, the ignition combustion of the fuel or the air-fuel mixture in the cylinder 1 tends to be unstable, and the combustion can be slow, the number of spark ignitions is increased to stabilize the combustion. Can be done. On the other hand, in a situation where the external EGR rate is low and the ignition combustion of the fuel or the air-fuel mixture is relatively stable, the number of spark ignitions can be reduced to suppress energy consumption and wear of the electrodes of the spark plug 12.

The control device 0 of the present embodiment is the number of discharges (for example, two) when the first ignition timing is delayed from the normal in order to promote the temperature rise of the catalyst 41 immediately after the cold start of the internal combustion engine. Add one discharge and combine it with the main discharge three times, otherwise the number of discharges (eg, additional discharge less than two times, combined with the main discharge three times, twice or Set to 1 time or more only for the main discharge). Thereby, instability of ignition combustion of the fuel or the air-fuel mixture in the cylinder 1 due to the retardation of the ignition timing can be effectively avoided. On the other hand, when the retard correction control of the ignition timing for the purpose of raising the temperature of the catalyst 41 is not performed, the number of spark ignitions can be reduced to suppress energy consumption and wear of the electrodes of the spark plug 12.

In the control device 0 of the present embodiment, the number of discharges (for example, three discharges are added and combined with the main discharge) when the cooling water temperature suggesting the temperature of the internal combustion engine is an extremely low temperature of a predetermined value or less is convenient. (Times) is greater than the number of discharges otherwise (eg, no more than two additional discharges, three times for convenience combined with the main discharge, two times, or one for the main discharge only). The maximum number of discharges when the temperature of the internal combustion engine is below a predetermined value is the maximum number of discharges (up to three times) when the above-mentioned internal EGR and / or external EGR is performed, and the delay in ignition timing. This is more than the maximum number of discharges (up to three times) when angle correction control is performed. As a result, the ignition combustion of the fuel or the air-fuel mixture in the cylinder 1 becomes unstable, and in an extremely low temperature where there is a high risk of misfire, the number of spark ignitions can be sufficiently increased to stabilize the combustion and avoid the occurrence of misfire. It will be 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 suppress energy consumption and wear of the electrodes 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 energizing the ignition coil 14 and then shutting off the energization to the electrodes of the spark plug 12 to cause a discharge between the electrodes. It is 0, and two or more discharges are executed for the purpose of ignition during one cycle of one cylinder 1. Of the two or more discharges, the current operating range of the internal combustion engine [engine rotation] Number, partial pressure of fresh air in the intake air charged in cylinder 1 (or intake pressure in surge tank 33, accelerator opening, engine load factor, engine torque, intake amount or fuel injection amount filled in cylinder 1) ], The internal combustion engine control device 0 is configured to cancel without executing the discharge if the timing is retarded from 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 each preparation of the main ignition and the additional ignition, and the discharge duration of each time, and based on these, is currently present. The crank angle at the timing of each ignition or discharge is calculated with reference to the engine speed of. Then, when the calculated crank angle becomes slower than the threshold value of the limit that does not cause inappropriate afterfire or backfire (without such danger), the ignition or discharge is canceled without being executed. According to this embodiment, it is possible to optimize the number of times of discharge in multi-ignition and to realize 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 in preparation for the discharge to be canceled because the timing is retarded from the threshold value. Therefore, wasteful power consumption due to energization of the ignition coil 14 can be avoided, and heat damage due to the temperature rise of the ignition coil 14 can be suppressed.

Further, in the present embodiment, a control device for controlling a spark ignition type internal combustion engine that applies an induced voltage generated by energizing the ignition coil 14 and then shutting off the energization to the electrodes of the spark plug 14 to cause a discharge between the electrodes. It is 0, and two or more discharges are executed for the purpose of ignition in one cycle of one cylinder 1, and the number of discharges for the purpose of ignition in the same cycle is set to the number of discharges of the ignition coil 14. The control device 0 of the internal combustion engine is configured to be changed according to the ambient temperature that affects the temperature and the length of the energization time to the ignition coil 14 per predetermined time.

The control device 0 of the present embodiment reduces the number of discharges for ignition in one cycle of one cylinder 1 if the length of the energization time to the ignition coil 14 per predetermined time exceeds the threshold value. The threshold value when the temperature, intake air temperature or outside air temperature of the internal combustion engine is high is set lower than the threshold value when the temperature, intake air temperature or outside air temperature of the internal combustion engine is lower.

According to the present embodiment, in a situation where the temperature around the ignition coil 14 is relatively low, or the energization time to the ignition coil 14 is relatively short, and there is a margin for the temperature rise of the ignition coil 14, the number of spark ignitions is increased. The amount can be increased as necessary and sufficient to improve the ignitability and combustion efficiency of the fuel or the air-fuel mixture. On the other hand, when the temperature around the ignition coil 14 is high or the energization time of the ignition coil 14 is long and there is a concern that the ignition coil 14 may be damaged due to excessive temperature rise, the number of spark ignitions is limited to ignite. The coil 14 can be protected and its damage can be prevented.

The present invention is not limited to the embodiment described in detail above. For example, if an air flow meter capable of detecting the flow rate of the intake air (or fresh air) flowing through the intake passage of the internal combustion engine toward the cylinder is installed, the intake air amount (fresh air) measured through this air flow meter is installed. Depending on the amount), the duration from the start to the interruption of the discharge for the first ignition in a cycle, the length of the energization time to the ignition coil 14 before the second and subsequent ignitions, is inappropriate. The latest ignition timing threshold can be adjusted so as not to cause after-fire or back-fire.

In addition, the specific configuration of each part, the processing procedure, and the like can be variously modified without departing from the spirit of the present invention.

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

0 ... Control unit (ECU)
1 ... Cylinder 12 ... Ignition plug 13 ... Ignite 131 ... Semiconductor switch 14 ... Ignition coil 141 ... Primary side coil 142 ... Secondary side 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 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 that controls a spark-ignition internal combustion engine that applies an induced voltage generated by energizing an ignition coil and then shutting off the energization to the electrodes of a spark plug to cause a discharge between the electrodes.
It executes two or more discharges for the purpose of ignition during one cycle of one cylinder.
The number of discharges for the purpose of ignition in the same cycle is changed according to the ambient temperature that affects the temperature of the ignition coil and the length of the energization time to the ignition coil per predetermined time .
If the length of the energization time to the ignition coil per predetermined time exceeds the threshold value, the number of discharges for the purpose of ignition in one cycle of one cylinder is reduced.
A control device for an internal combustion engine that sets the threshold value when the temperature, intake air temperature, or outside air temperature of the internal combustion engine is high to be lower than the threshold value when the temperature, intake air temperature, or outside air temperature of the internal combustion engine is lower. Claim 1 that adjusts the length of energization time to the ignition coil before ignition from the second time onward in a certain cycle according to the measured value of the flow rate of intake air or fresh air flowing toward the cylinder in the intake passage of the internal combustion engine. The control device for an internal combustion engine according to the description.

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