JP2018003635A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize the period of energization of an ignition coil in a spark ignition type internal combustion engine to achieve both good ignition combustion of an air-fuel mixture and improvement of energy efficiency. SOLUTION: An induction voltage generated by energizing an ignition coil and then shutting off the energization is applied to an electrode of a spark plug to induce a spark discharge and control a spark ignition type internal combustion engine that ignites an air-fuel mixture in a cylinder. Therefore, the length of the period during which spark discharge occurs between the electrodes of the spark plug is measured, and the average of the length of the spark discharge period at the predetermined number of ignition opportunities in the past is calculated, and the average is more than the target. If it is short, a correction is added to extend the energization period to the ignition coil, and an internal combustion engine control device is configured in which the predetermined number of times is set to a smaller number as the load on the internal combustion engine increases. [Selection diagram] Fig. 4

Description

  The present invention relates to a control device that controls operation of 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 a voltage induced by an ignition coil and causes a spark discharge between a center electrode and a ground electrode. To do.

  An igniter having a semiconductor switching element is provided on an electric circuit for energizing the ignition coil. When the igniter semiconductor switch is ignited, a current flows to the primary side of the ignition coil. The primary current flowing through the primary coil increases while firing the semiconductor switch. Thereafter, when the semiconductor switch is extinguished at an appropriate spark ignition timing, a high voltage is generated on the primary side of the ignition coil by the self-induction action at the moment when the primary current is cut off. Then, a higher induced voltage is generated in the secondary side coil sharing the magnetic circuit and magnetic flux with the primary side. By applying this high induced voltage to the center electrode of the spark plug, a spark discharge is generated between the center electrode and the ground electrode.

  The magnitude of the electric energy input to the spark plug for spark ignition depends on the magnitude of the primary current flowing through the primary coil of the ignition coil when the semiconductor switch is extinguished. That is, the longer the energization period for the primary side coil, the greater the electrical energy input to the secondary side coil and hence the spark plug. Increasing the electric energy input to the spark plug, that is, the energy of spark discharge, is expected to improve the ignitability of the air-fuel mixture in the cylinder and improve the combustion (see the following patent document).

  On the other hand, lengthening the energization period to the ignition coil leads to an increase in power consumption and deterioration in energy efficiency. Furthermore, there is a concern that excessive heat generation of the ignition coil may be caused. Therefore, it is required to optimize the energization period to the ignition coil.

Japanese Patent Laid-Open No. 2006-089659

  An object of the present invention is to optimize the energization period of an ignition coil in a spark ignition type internal combustion engine and to achieve both good ignition and combustion of an air-fuel mixture and improvement in energy efficiency.

  In order to solve the above-described problems, in the present invention, a spark that ignites an air-fuel mixture in a cylinder by applying an induced voltage generated by cutting off the current supplied to the ignition coil to the electrode of the spark plug to cause a spark discharge. Controls an ignition type internal combustion engine, measures the length of the period during which spark discharge occurs between the electrodes of the spark plug, and calculates the average of the length of the spark discharge period in the past predetermined number of ignition opportunities. If the average is shorter than the target, a correction for extending the energization period to the ignition coil is added, and the control device for the internal combustion engine is configured so that the predetermined number of times is set to a smaller number as the load of the internal combustion engine is larger. .

  In addition, a minimum energization period is set according to the rotational speed of the internal combustion engine, the load of the internal combustion engine, and the voltage of the power storage device that is a power source for applying a voltage to the ignition coil. The maximum energization period is set according to the voltage, and if the average length of the spark discharge period in the predetermined number of ignition opportunities is shorter than the target, the energization period to the ignition coil is brought close to the maximum energization period, and the average is If it is longer than the target, the energization period to the ignition coil is brought close to the minimum energization period, and the difference between the current energization period and the minimum energization period is determined as the learned value of the energization period to the ignition coil, and the current energization period If the ratio between the period and the difference between the maximum energization period is learned and stored, the learned value learned in one operation region can be used in another operation region.

  ADVANTAGE OF THE INVENTION According to this invention, the electricity supply period to the ignition coil in a spark ignition type internal combustion engine can be optimized, and it can aim at coexistence with favorable ignition combustion of an air-fuel | gaseous mixture, and an energy efficiency improvement.

The figure which shows schematic structure of the internal combustion engine in one Embodiment of this invention. The circuit diagram of the ignition device of the internal combustion engine of the same embodiment, and an ionic current detection circuit. The figure which illustrates transition of the primary current which flows through the primary side coil of an ignition coil in the period from ignition of an igniter to spark ignition. The figure which illustrates each transition of the current signal detected via an ion current detection circuit, and the combustion chamber pressure of a cylinder. The figure which illustrates the relationship between the operation area | region of an internal combustion engine, and the length of a target discharge period. The figure which illustrates the relationship between the length of the electricity supply period to an ignition coil, and the length of the generation | occurrence | production period of the spark discharge which occurs between the electrodes of a spark plug.

  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 in the present embodiment. The internal combustion engine in the present embodiment is a spark ignition type four-stroke engine and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel is provided. 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. On the intake passage 3, 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.

  The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4.

  The exhaust gas recirculation device 2 realizes a so-called high-pressure loop EGR 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 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 passage 21. And an EGR valve 23 that 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 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, particularly to the surge tank 33.

  FIG. 2 shows an electric circuit of an ignition device for an internal combustion engine. The spark plug 12 receives spark voltage generated by the ignition coil 14 and causes spark 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 an ignition signal i from an ECU (Electronic Control Unit) 0 which is a control device of the internal combustion engine of the present embodiment, first, the semiconductor switch 131 of the igniter 13 is ignited, and a current is supplied to the primary side of the ignition coil 14. The semiconductor switch 131 extinguishes 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. Since the primary side and the secondary side share the magnetic circuit and the magnetic flux, a higher induced voltage is generated on the secondary side. The induced voltage on the secondary side reaches 10 kV to 30 kV. This high induction voltage is applied to the center electrode of the spark plug 12, and a spark discharge occurs between the center electrode and the ground electrode.

  The primary coil of the ignition coil 14 is connected to the in-vehicle power storage device 17 via the semiconductor switch 131. The power storage device 17 is a battery (lead battery, lithium ion battery, nickel metal hydride battery, or the like), a capacitor, or the like. A plurality of types of power storage devices 17 may be combined and mounted on the vehicle.

  When the semiconductor switch 131 is ignited and a DC voltage supplied from the power storage device 17 is applied to the primary side coil to start energization, the primary current flowing through the primary side (low voltage system) circuit including the primary side coil increases. .

FIG. 3 illustrates the transition of the primary current after the start of energization of the primary coil. Assuming that the electric circuit on the primary side including the power storage device 17 and the primary side coil is an RL series circuit, the primary current I (t) when the DC voltage E is applied at time t = 0 is
I (t) ≈ {1-e- ^{(R / L) t} } E / R
It becomes. That is, the primary current increases as a transient phenomenon, but the rate of increase gradually decreases. When a sufficiently long time elapses, the primary current is saturated to E / R as indicated by the broken line in FIG. 3 unless the current limiting function described later works.

In FIG. 3, the time point t ₁ is the ignition timing of the cylinder 1. At this time t ₁ , the semiconductor switch 131 of the igniter 13 associated with the cylinder 1 is extinguished, the energization of the primary coil of the ignition coil 14 associated with the cylinder 1 is cut off, and the ignition coil 14 generates The induced voltage is applied to the center electrode of the spark plug 12 of the cylinder 1.

The time point t ₀ or the time point t ₀ ′ is a start point of energization of the primary coil of the ignition coil 14. That is, the period from time t ₀ to time t ₁ , or the period from time t ₀ ′ to time t ₁ is the energization period to the primary coil of the ignition coil 14. The time point t ₀ is a start point of energization when the energization period to the ignition coil 14 is relatively short, and the transition of the primary current in this case is drawn by a solid line in FIG. On the other hand, the time point t ₀ ′ is an energization start time when the energization period to the ignition coil 14 is relatively long, and the transition of the primary current in this case is drawn by a one-dot chain line in FIG. The latter energization start time t ₀ ′ is earlier than the former energization start time t ₀ .

As already described, the primary current flowing through the primary coil of the ignition coil 14 increases after the ignition of the semiconductor switch 131 (time t ₀ or time t ₀ ′). Therefore, the primary current flowing through the primary coil at the ignition timing t ₁ becomes larger as the energization start time t ₀ , t ₀ ′ is advanced. An increase in the primary current means an increase in electrical energy applied to the ignition coil 14. As a result, the primary current is induced by the extinction of the semiconductor switch 131 (time t ₁ ) and applied to the center electrode of the ignition plug 12. This means that the induced voltage increases.

In short, as the energization start time points t ₀ and t ₀ ′ are advanced (the primary current flowing through the primary coil at the ignition timing t ₁ is increased), the electric energy input to the spark plug 12 is increased. As a result, the voltage of the spark discharge generated between the center electrode of the spark plug 12 and the ground electrode is increased, and the duration of the spark discharge is also increased.

  The igniter 13 has a current limiting function that suppresses excessive primary current. This current limiting function is similar to that of off-the-shelf igniters that are popular 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. The semiconductor switch 131 is ignited while the magnitude of the primary current (voltage across the resistor 133) is equal to or less than a specified value, while the semiconductor switch 131 is extinguished when the magnitude exceeds the specified value. As a result, the primary current is clipped to the specified value as indicated by the alternate long and short dash line in FIG. In FIG. 3, the case where the current limiting function does not work is drawn by a broken line, and the case where the current limiting function works is drawn by a one-dot chain line.

  The igniter 13 is provided with a primary voltage setting unit using a Zener diode 134, for example. The primary voltage setting unit plays a role of suppressing the primary voltage induced in the primary coil 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 voltage clamp Zener diode 134 is interposed between the collector and gate of the IGBT 131, the 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 of the ignition coil 14 by extinguishing the IGBT 131 to a certain value within a range of 350 V to 500 V, for example, and the primary voltage is further increased. It works to prevent the increase.

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

  The ECU 0 of the present embodiment can detect an ionic current generated in the combustion chamber of the cylinder 1 during the combustion of the air-fuel mixture, and can determine the combustion state with reference to the ionic current.

  As shown in FIG. 2, in this embodiment, a circuit for detecting an ionic current is added to the electric circuit for spark ignition. This detection circuit includes a bias power supply unit 15 for effectively detecting an ionic current and an amplification unit 16 that amplifies and outputs a detection voltage corresponding to the amount of the ionic current. The bias power supply unit 15 includes a capacitor 151 that stores a bias voltage, a Zener diode 152 for increasing the voltage of the capacitor 151 to a predetermined voltage, current blocking diodes 153 and 154, and a load that outputs a voltage corresponding to the ion current. A resistor 155. The amplifying unit 16 includes a voltage amplifier 161 typified by an operational amplifier.

  The capacitor 151 is charged during arc discharge between the center electrode and the ground electrode of the spark plug 12, and then an ion current flows through the load resistor 155 by the bias voltage charged in the capacitor 151. The voltage between both ends of the resistor 155 generated by the flow of the ionic current is amplified by the amplifying unit 16 and received by the ECU 0 as the ionic current signal h.

  FIG. 4 illustrates respective transitions of the current signal h detected through the ion current detection circuit and the pressure in the combustion chamber (combustion pressure) of the cylinder 1 in normal combustion. In FIG. 4, the ionic current is drawn with a broken line, and the combustion pressure is drawn with a solid line. In the case of normal combustion, the ionic current decreases after the end of the spark discharge by a chemical reaction and before the compression top dead center, and then increases again by thermal dissociation. In addition, the ionic current reaches a maximum almost simultaneously with the peak of the combustion pressure.

  A generator 18 serving as a power supply source for energizing the ignition coil 14, opening / closing driving of the valves 23 and 32, and an electrical system mounted on the vehicle, etc., generates engine torque from a crankshaft that is an output shaft of the internal combustion engine. The supplied power is generated and the generated power is stored in the in-vehicle power storage device 17.

  The generator 18 may be an alternator conventionally used as a generator for automobiles, or may be a motor generator having a function as an electric motor for driving a crankshaft of an internal combustion engine or an axle (and drive wheels) of a vehicle. It may be an ISG (Integrated Starter Generator). The internal combustion engine and the generator 18 are connected via, for example, a winding transmission device having a belt and a pulley as elements.

  The IC regulator or controller 181 attached to the generator 18 receives a control signal m issued from the ECU 0 and commanding a target value of the output voltage of the generator 18. Then, in order to make the terminal voltage of the power storage device 17 (or the power supply voltage supplied to the electrical system) follow the commanded target voltage, the semiconductor switching element is switched and applied to the excitation (field) winding. PWM (Pulse Width Modulation) control for adjusting the magnitude of the current is performed. The output voltage of the generator 18 increases as the excitation current flowing through the excitation winding increases.

  Further, the generator 18 can perform regenerative braking when the vehicle is decelerated, and can recover the kinetic energy of the vehicle as electric energy. The ECU 0 performs excitation that flows through the excitation winding of the generator 18 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 requested. A control signal m for raising the upper limit value of the current and the output voltage of the generator 18 is supplied to the IC regulator or controller 181.

  The ECU 0 that controls 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 includes 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 an engine rotation sensor that detects the rotation angle and engine speed of the crankshaft, and depression of an accelerator pedal. An accelerator opening signal c output from a sensor that detects the amount or the opening of the throttle valve 32 as an accelerator opening, and a temperature / pressure sensor that detects the intake air temperature and intake pressure in the intake passage 3 (especially the surge tank 33). An intake air temperature / intake pressure signal d output from the vehicle, a voltage / current signal e output from a sensor that detects a terminal voltage and / or terminal current (particularly, battery voltage and / or battery current) of the in-vehicle power storage device 17, The coolant temperature signal f output from the coolant temperature sensor that detects the coolant temperature indicating the temperature of the internal combustion engine, and the brake pedal Or a brake signal g output from a sensor (such as a brake switch or a master cylinder pressure sensor) that detects whether the brake pedal is depressed, or an ionic current generated with combustion of the air-fuel mixture in the combustion chamber of the cylinder 1 A current signal h or the like output from the circuit to be detected is input.

  From the output interface, 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, the opening operation signal l for the EGR valve 23, the generator A control signal m or the like for controlling the generator 18 is output to an IC regulator or controller 181 attached to 18.

  The processor of the 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, and h necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the intake volume. Based on the engine speed, the intake air amount, etc., the required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, ignition timing, required EGR rate (or EGR rate) Amount), the power generation amount (output voltage) of the generator 18 and the like, and various operation parameters are determined. The ECU 0 applies various control signals i, j, k, l and m corresponding to the operation parameters via the output interface.

  The ECU 0 of the present embodiment determines the length of the period during which the primary coil of the ignition coil 14 is energized based on the operating range of the internal combustion engine and the length of the spark discharge generated in the spark plug 12 of the cylinder 1. By making adjustments, it is possible to achieve both reliable ignition and combustion of the air-fuel mixture and improved energy efficiency.

  First, the ECU 0 sets a minimum energization period for the primary coil of the ignition coil 14 according to the current operation region of the internal combustion engine [engine speed, engine load] and the voltage of the power storage device 17 (particularly, battery voltage). To do. As specific parameters representing the engine load, for example, the intake pressure in the surge tank 33, the accelerator opening, the intake amount charged in the cylinder 1, or the fuel injection amount can be used. The minimum energization period means the lower limit of the length of the energization period for the primary coil, which is the minimum required to cause a spark discharge that can ignite the air-fuel mixture in the combustion chamber of the cylinder 1 (does not misfire). .

  The memory of the ECU 0 stores in advance map data that defines the relationship between the engine speed, the engine load, and the minimum energization period. The ECU 0 searches the map using the current engine speed and engine load (intake pressure in the surge tank 33, etc.) as keys, and obtains the basic value of the minimum energization period. Furthermore, the length of the minimum energization period is determined by adding a correction corresponding to the current voltage of the power storage device 17 to the basic value. In principle, the minimum energization period is corrected to be shorter as the voltage of the power storage device 17 is higher, that is, as the voltage applied to the primary coil of the ignition coil 14 is higher. However, the map data defining the relationship between the engine speed, the engine load, the voltage of the power storage device 17 and the minimum energization period is stored in the memory of the ECU 0, and the current engine speed, the engine load, and the power storage device 17 are stored. The map may be searched using the voltage as a key to obtain the minimum energization period.

  In addition, the ECU 0 sets the maximum energization period for the primary coil of the ignition coil 14 according to the current engine speed and the voltage of the power storage device 17. The maximum energization period is an energization period for the primary side coil that does not consume excessive electrical energy unnecessarily to ignite the air-fuel mixture in the combustion chamber of the cylinder 1 or that the ignition coil 14 does not overheat. It means the upper limit of length.

  In the memory of the ECU 0, map data defining the relationship between the engine speed, the voltage of the power storage device 17 and the maximum energization period is stored in advance. The ECU 0 searches the map using the current engine speed and the voltage of the power storage device 17 as keys, and obtains the maximum energization period.

  Further, the ECU 0 refers to the current signal h detected via the ion current detection circuit, and measures the length of the period during which spark discharge is occurring between the electrodes of the spark plug 12 installed in the cylinder 1. Specifically, a period from when the semiconductor switch 131 of the igniter 13 associated with the ignition coil 14 is extinguished until the magnitude of the current signal h exceeds a predetermined threshold value for the first time is regarded as a spark discharge period. Measure the length.

  And the average of the length of the spark discharge period measured in the last predetermined number of ignition opportunities in the past is obtained. In calculating the average, the number of measurement values of the spark discharge period used for the above-mentioned predetermined number of times, in other words, the average calculation, is reduced as the engine load increases. In the memory of the ECU 0, map data defining the relationship between the engine load and the predetermined number of times is stored in advance. The ECU 0 obtains the predetermined number of times by searching the map using the current engine load as a key, and calculates the average length of the spark discharge period for the predetermined number of times.

  Thus, the ECU 0 has a case where the average of the length of the past spark discharge period is shorter than the target discharge period, that is, when there is a possibility that the spark discharge has not occurred for a period sufficient for the ignition combustion of the air-fuel mixture. Then, a correction for extending the energization period to the ignition coil 14 is added, and the electric energy input to the spark plug 12 is increased more than before. As a result, the generation period of spark discharge caused between the electrodes of the spark plug 12 is lengthened, the certainty of spark ignition for the air-fuel mixture is increased, and the risk of misfire is reduced. On the other hand, when the average length of the past spark discharge period is longer than the target discharge period, that is, there is a possibility that the spark discharge has occurred for a longer period than necessary and sufficient for the ignition and combustion of the mixture. For this, a correction for shortening the energization period to the ignition coil 14 is added, and the electric energy input to the spark plug 12 is reduced more than before. As a result, power consumption is reduced and energy efficiency is improved.

  The length of the target discharge period varies depending on the operating region of the internal combustion engine at that time. In particular, as shown in FIG. 5, the longer the engine load, the shorter the target discharge period is set. This is because as the combustion chamber pressure (compression pressure) of the cylinder 1 at the ignition timing is larger, the spark discharge is less likely to occur between the electrodes of the spark plug 12, and the duration of the spark discharge is also shortened. In the memory of the ECU 0, map data that defines the relationship between the engine speed and the engine load and the target discharge period is stored in advance. The ECU 0 obtains the target discharge period by searching the map using the current engine speed and engine load as keys, and compares the target discharge period with the average of the lengths of the past spark discharge periods.

ECU0 of this embodiment determines the length of the period which supplies with electricity to the primary side coil of the ignition coil 14 according to the following Formula;
Energization period = {minimum energization period × learning value} + {maximum energization period × (1−learning value)}
However, 0 ≦ learning value ≦ 1. As the learning value approaches 1, the energization period to the ignition coil 14 becomes shorter and approaches the minimum energization period. On the contrary, as the learning value approaches 0, the energization period to the ignition coil 14 becomes longer and approaches the maximum energization period. If the average of the length of the past spark discharge period is shorter than the target discharge period, the ECU 0 calculates a new learning value by subtracting the correction amount KTONLRRNDEC from the current learning value, and stores it in the memory. On the other hand, if the average of the length of the past spark discharge period is longer than the target discharge period, a new learning value is calculated by adding the correction amount KTONLRNADD to the current learning value, and stored in the memory. As a result, feedback control for converging the length (average) of the spark discharge period to the target discharge period is realized.

  The correction value KTONLRRNDEC and / or KTONLRNADD of the learning value is preferably variable according to the operating region of the internal combustion engine. For example, map data defining the relationship between the engine speed and the engine load and the correction amount KTONLRRNDEC and / or KTONLRNADD is stored in the memory of the ECU 0 in advance. Then, the ECU 0 searches the map using the current engine speed and engine load as a key to obtain the correction amount KTONLRRNDEC and / or KTONLRNADD, and uses the correction amount KTONLRRNDEC and / or KTONLRNADD to update the learning value. Use.

  The number of measurement values, target discharge period, and learning value correction amounts KTONLRRNDEC and KTONLRNADD used for obtaining the average of the minimum energization period, maximum energization period, and spark discharge period are the effects of the current operating range of the internal combustion engine. Receive. However, the learning value can be shared regardless of the current operating region of the internal combustion engine. It is freed from the need to learn and update learning values individually for various driving areas, and learning values learned in driving areas with high transition frequency are used for control even in driving areas with low switching frequency As a result, it is possible to optimize the length of the period during which the primary coil of the ignition coil 14 is energized in a wide range of operation.

  In the present embodiment, a spark ignition type internal combustion engine that applies an induced voltage generated by cutting off the power supply to the ignition coil 14 after applying current to the ignition coil 14 to cause spark discharge to ignite the air-fuel mixture in the cylinder 1. And measuring the length of the period during which spark discharge is occurring between the electrodes of the spark plug 12, and calculating the average of the length of the spark discharge period in the past predetermined number of ignition opportunities, If the average is shorter than the target, a correction for extending the energization period to the ignition coil 14 is added, and the control device 0 for the internal combustion engine is configured such that the predetermined number of times is set to a smaller number as the load of the internal combustion engine is larger.

  According to the present embodiment, it is possible to optimize the length of the period in which the ignition coil 14 is energized prior to the spark ignition of the air-fuel mixture in the cylinder 1, and to improve the ignition and combustion of the air-fuel mixture and the improvement in energy efficiency. A balance can be achieved. Further, it is possible to cope with the secular change of the spark plug 12, the ignition coil 14, and the like.

FIG. 6 schematically shows a correlation between the length of the energization period to the primary coil of the ignition coil 14 and the length of the generation period of the spark discharge that occurs between the electrodes of the spark plug 12. In FIG. 6, the correlation in the high load operation region where the engine load is large (the intake air amount charged into the cylinder 1 is large) is drawn with a solid line, and the low load where the engine load is small (the intake amount charged into the cylinder 1 is small). The correlation in the operation region is drawn with a one-dot chain line. T _L is the maximum energization period, T _S ′ is the minimum energization period in the high load operation area, and T _S is the minimum energization period in the low load operation area. T _A ′ is the target discharge period in the high load operation region, T _A is the target discharge period in the low load operation region, and T _X is the misfire limit, that is, the lower limit of the length of the spark discharge period that does not cause misfire. .

In the high-load operation region, the range of the energization period to the ignition coil 14 that is unlikely to cause spark discharge originally and can appropriately ignite the air-fuel mixture (from the minimum energization period T _S ′ to the maximum energization period T _L). And the energization period of the ignition coil 14 is required to be precisely controlled. In the high load operation region, the ECU 0 of the present embodiment reduces the number of measurement values of the predetermined number of times, that is, the length of the last past spark discharge period used for calculating the average, The average change rate of the length is increased, and thus the length of the spark discharge period is made to follow the target discharge period at high speed.

On the other hand, in the low load operation region, the S / N ratio of the current signal h detected through the ion current detection circuit tends to decrease. In addition, in the low load operation region, the range of the energization period of the ignition coil 14 that is easy to cause spark discharge originally and can appropriately ignite the mixture (from the minimum energization period T _S to the maximum energization period T _L). The range between) becomes wider. In other words, the margin for misfire is large compared to the high load operation region. Therefore, by increasing the number of measurements of the length of the last past spark discharge period used for calculating the average, it is possible to prevent the average of the length of the spark discharge period from deviating from the actual situation due to noise, Avoid false learning. This contributes to further shortening the energization period to the primary coil of the ignition coil 14, improving energy efficiency, and improving fuel efficiency.

  The control device 0 of the present embodiment sets the minimum energization period according to the rotational speed of the internal combustion engine, the load of the internal combustion engine, and the voltage of the power storage device 17 serving as a power source for applying a voltage to the ignition coil 14, and the internal combustion engine The maximum energization period is set according to the number of rotations and the voltage of the power storage device 17, and if the average length of the spark discharge period in a predetermined number of ignition opportunities is shorter than the target, the energization period to the ignition coil 14 is If the average is longer than the target, the energization period of the ignition coil 14 is brought closer to the minimum energization period. As a learning value of the energization period of the ignition coil 14, the current energization period and The ratio between the difference between the minimum energization period and the difference between the current energization period and the maximum energization period is learned and stored. A learned value learned in a certain operation region can also be used to control the energization period of the ignition coil 14 in a different operation region.

  The present invention is not limited to the embodiment described in detail above. For example, when the length of the spark discharge period measured with reference to the current signal h detected through the ion current detection circuit is shorter than a predetermined warning value, the average value of the latest past spark discharge periods Regardless of the above, it is conceivable to execute fail-safe control for extending the energization period to the ignition coil 14 than before.

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be used for an ignition device of a spark ignition type internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 12 ... Spark plug 13 ... Igniter 131 ... Semiconductor switch 14 ... Ignition coil b ... Crank angle signal d ... Intake air temperature / intake pressure signal e ... Voltage / current signal h ... Current signal i ... Ignition signal

Claims (2)

A spark ignition type internal combustion engine that applies an induced voltage generated by cutting off the energization of the ignition coil to the electrode of the spark plug to cause a spark discharge to ignite an air-fuel mixture in the cylinder,
Measure the length of the period during which spark discharge occurs between the electrodes of the spark plug and determine the average of the length of the spark discharge period in the past predetermined number of ignition opportunities. If the average is shorter than the target, ignite We will add a correction to extend the energization period of the coil,
A control device for an internal combustion engine, wherein the predetermined number of times is set to a smaller number as the load of the internal combustion engine is larger. The minimum energization period is set according to the rotational speed of the internal combustion engine, the load of the internal combustion engine, and the voltage of the power storage device as a power source for applying a voltage to the ignition coil,
Set the maximum energization period according to the rotational speed of the internal combustion engine and the voltage of the power storage device,
If the average of the length of the spark discharge period in the predetermined number of ignition opportunities is shorter than the target, the energization period to the ignition coil is brought close to the maximum energization period, and if the average is longer than the target, the energization period to the ignition coil Is close to the minimum energization period,
The learned value of the energization period to the ignition coil is learned and stored as a learning value of the difference between the current energization period and the minimum energization period and the difference between the current energization period and the maximum energization period. Control device for internal combustion engine.

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